Salmonella typhimurium

J Dairy Sci, 1989 Dec, 72(12), 3166 - 75
Lactoferrin and lysozyme in milk during acute mastitis and their inhibitory effect in Delvotest P; Carlsson A et al.; Microbiological methods for detection of antibiotic residues in milk give no explanations regarding the identity of the inhibitory substance(s) . Natural antibacterial substances, present at higher concentrations in mastitic milk and in colostrum, occasionally cause false positive results in antibiotic assays . In an earlier investigation, lysozyme and lactoferrin were shown to inhibit the growth of Bacillus stearothermophilus var . calidolactis spores, used as test organism in Delvotest P . To study the effect of high lysozyme and lactoferrin concentrations in milk on the Delvotest P, cows were subjected to acute experimental mastitis by infusion of Salmonella typhimurium SH 4809 endotoxin . Milk samples were collected up to 11 h postinfusion . Concentrations of lactoferrin and lysozyme, somatic cell count, and effect on Delvotest P were determined . A positive reaction in the Delvotest correlated well with an increase in lactoferrin and lysozyme concentrations . The nature of the inhibitory effect is briefly discussed.

FEMS Microbiol Immunol, 1989 Dec, 1(8-9), 485 - 90
Immunogenic endotoxin associated protein from a rough strain of Salmonella; Phillips M et al.; A multimolecular complex of polypeptides found associated with the lipopolysaccharide endotoxin in Salmonella, referred to as endotoxin-associated protein (EP), has been extracted from a rough strain of Salmonella typhimurium which does not synthesize 0 antigens . Since standard methods of extraction applicable to smooth strains of Salmonella were not successful for this rough strain, two modified procedures were developed . The resulting products were similar to smooth EP in terms of their biochemical, physical and mitogenic properties . When the immunogenicity of the rough EP was characterized by a protection assay in mice challenged with virulent Salmonella, it was found that the rough EP preparations were protective; however, they were not as active as the EP from a smooth strain of S . typhimurium.

APMIS, 1989 Dec, 97(12), 1114 - 20
Protective properties of a human IgG preparation rich in antibodies to a wide spectrum of lipopolysaccharides; Fomsgaard A et al.; Naturally occurring human IgG, rich in antibodies to different lipopolysaccharides was investigated for possible protective effects against lethal endotoxin shock and lethal gram-negative infection in mice . The IgG preparation was obtained from pooled serum of selected blood donors with high concentrations of antibodies to 11 different LPS as measured by ELISA . The human IgG (5 mg/mouse) protected C3H/TifF mice against an otherwise lethal infection with Salmonella typhimurium . The human IgG also inhibited the lethality induced by purified LPS in D-galactosamine sensitized C57B1/6 mice . The protection was dependent on the IgG dose given . However, protection was not obtained against all the LPS preparations tested . Absorption of the IgG with different LPS, showed the protection to be caused by serotype-specific anti-LPS antibodies . Protection against a given LPS was not related directly to the corresponding anti-LPS titer as measured by ELISA and passive hemolysis . The interpretation of these results is discussed.

J Immunol, 1989 Dec 1, 143(11), 3703 - 7
Regulated expression of proenkephalin A in normal lymphocytes; Rosen H et al.; The expression of proenkephalin A (PEA), a neuropeptide-encoding gene, was examined in normal rat lymphocytes . With the use of Northern blot hybridization analysis of total RNA, PEA mRNA was found in normal cells derived from spleen, lymph nodes, and bone marrow . Cell sorting of the two main fractions of B and T cells derived from the spleen revealed that PEA is expressed in normal B cells (sIg+) . The expression of PEA mRNA was markedly enhanced after a short incubation (3 h) of cells with LPS or Salmonella typhimurium . This was not the case when these cells were incubated with Con A during the same period of time; whereas, in thymocytes the presence of PEA mRNA was exclusively dependent upon mitogenic stimulus (Con A) and could be detected after 24 h of in vitro incubation . Extracts of cells were also found to contain immune reactive enkephalins, indicating that the PEA mRNA is translated . These results support the concept that neuropeptides, such as enkephalins, have a role in the modulation of the immune response and may participate in the bidirectional communication between the nervous and immune systems.

Genetics, 1989 Dec, 123(4), 625 - 33
Genetic analysis of temperature-sensitive lethal mutants of Salmonella typhimurium; Schmid MB et al.; We have isolated 440 mutants of Salmonella typhimurium that show temperature-sensitive growth on complex medium at 44 degrees . Approximately 16% of the mutations in these strains have been mapped to 17 chromosomal locations; two of these chromosomal locations seem to include several essential genes . Genetic analysis of the mutations suggests that the collection saturates the genes readily mutable to a ts lethal phenotype in S . typhimurium . Physiological characteristics of the ts lethal mutants were tested: 6% of the mutants can grow at high temperature under anaerobic conditions, 17% can grow when the medium includes 0.5 M KCl, and 9% of the mutants die after a 2-hr incubation at the nonpermissive temperature . Most ts lethal mutations in this collection probably affect genes required for growth at all temperatures (not merely during high temperature growth) since Tn10 insertions that cause a temperature-sensitive lethal phenotype are rare.

FASEB J, 1989 Dec, 3(14), 2574 - 82
Bacterial adaptation to oxidative stress: implications for pathogenesis and interaction with phagocytic cells; Hassett DJ et al.; During phagocytosis, phagocytic cells generate superoxide and other reactive oxygen species, which are involved in antibacterial activity . However, many bacteria possess antioxidant defenses that may explain their survival in inflammatory foci . These defenses include antioxidant enzymes such as superoxide dismutase and catalase, DNA repair systems, scavenging substrates, and competition with phagocytes for molecular oxygen . These defenses are probably coordinated, and different responses occur with different reactive oxygen species . Escherichia coli and Salmonella typhimurium mutants have allowed the demonstration of a variety of critical genes for enzymatic defense and DNA repair, as well as an oxyR regulon system . In more complex systems, the conditions found in inflammatory foci, such as decreasing glucose and the production of lactate, enhance bacterial catalase production and resistance to hydrogen peroxide . Resistance and adaptation to phagocyte-derived oxidant stress are critical aspects of bacterial pathogenesis.

Immunol Lett, 1989 Dec, 23(2), 125 - 32
Immunological functions in food-restricted rats: enhanced expression of high-affinity interleukin-2 receptors on splenic T cells; Iwai H et al.; Several immunological functions of B and T cells including IL-2 receptor expression on T cells were measured in 12-month-old Fisher-344 male rats maintained from 6 weeks of age on an ad libitum (AL) or a 40% food-restricted (FR) diet . Direct anti-SRBC plaque-forming cell (PFC) assays revealed a higher response in FR rats than in AL rats when splenocytes were cultured with or without recombinant interleukin-2 (rIL-2) . B cell functions were studied by using nylon wool-purified splenic B cells stimulated either with rIL-2, lipopolysaccharide (LPS), or Salmonella typhimurium mitogen (STM) as a thymus-independent antigen . Reserve plaque assay showed no difference between FR and AL rats in the secretion of anti-IgM and anti-IgG antibodies . In addition, no difference was found in proliferation of B cells stimulated by LPS, STM mitogens or rIL-2 . Although purified splenic T cells demonstrated an equally proliferative response in FR and AL rats when cultured with concanavalin A (Con A) or phytohemagglutinin (PHA), T cells in FR rats developed higher responses when stimulated with an alloantigen and rIL-2 . Time-course studies carried out to measure high-affinity (HA) IL-2 receptor (R) molecules by using purified T cells with rIL-2 and 125I-labeled IL-2 revealed a higher expression of IL-2R molecules on T cells of FR rats than on T cells of AL rats at 72 h after culturing with Con A.(ABSTRACT TRUNCATED AT 250 WORDS)

J Cell Biol, 1989 Dec, 109(6 Pt 1), 2771 - 82
The opsonizing ligand on Salmonella typhimurium influences incorporation of specific, but not azurophil, granule constituents into neutrophil phagosomes; Joiner KA et al.; Phagosomes were purified from human neutrophils ingesting Salmonella typhimurium opsonized with adsorbed normal human serum or with rabbit IgG . Constituents within the phagosome were endogenously labeled by supplying the cells with 125INa during phagocytosis . Lactoferrin and vitamin B12 binding protein (TC1 and TC3), markers for specific granules, were present in the phagosomes from neutrophils ingesting S . typhimurium opsonized with IgG but were 3.5- to 5-fold less prominent in phagosomes from cells phagocytosing Salmonella bearing C3 fragments only . In contrast, iodinated azurophilic granule components, most prominently defensins, were the major constituents in phagosomes prepared under both opsonization conditions . Furthermore, labeled complement (CR1 and CR3) and immunoglobulin (Fc gamma RIII) receptors were incorporated in the phagosome regardless of the ligand mediating phagocytosis . These results suggest that the ligand-receptor interactions mediating phagocytosis influence incorporation of neutrophil-specific granule contents into phagosomes.

Infect Immun, 1989 Dec, 57(12), 3894 - 900
O antigen and lipid A phosphoryl groups in resistance of Salmonella typhimurium LT-2 to nonoxidative killing in human polymorphonuclear neutrophils; Stinavage P et al.; We have compared the intraleukocytic survival of isogenic strains of Salmonella typhimurium, whose outer membrane lipopolysaccharide differed in O antigen and lipid A composition and whose susceptibility to nonoxidative antimicrobial granule proteins of human polymorphonuclear neutrophilis (PMN) could be established . We found that the order of resistance to the bactericidal activity of intact PMN of the three bacterial strains utilized closely resembled their ordered resistance to the purified human cationic antimicrobial 57,000-dalton protein (CAP57) . LT-2, a smooth wild-type strain, was far more resistant than SH9178, its rough (Rb LPS) mutant . It was most significant that SH7426, a polymyxin B-resistant pmrA mutant of SH9178, not only was substantially more resistant to CAP57 and to intraphagocytic killing than SH9178 but also came close to being as resistant as LT-2 . These experiments confirm earlier work that showed the importance of the glycosyl groups of O antigens of S . typhimurium for their resistance to O2-independent antimicrobial phagocytosis by PMN . The surprising result was that a rough strain, very susceptible to bactericide, became substantially more resistant when a mutation led to its lipid A phosphoryl groups being 100% substituted with amino pentoses . Yet unresolved is whether the protection is due to the loss of negative charges on the lipid A, the substitution of sugar molecules in vulnerable loci in the outer membrane, or both.

Gene, 1989 Nov 30, 83(2), 197 - 206
Comparative analysis of the Salmonella typhi and Escherichia coli ompC genes; Puente JL et al.; The nucleotide (nt) sequence of the gene encoding the Salmonella typhi OmpC outer membrane protein, and its deduced amino acid (aa) sequence are presented here . The S . typhi ompC gene consists of an open reading frame of 1134 nt, corresponding to a protein of 378 aa; with a 21-aa signal peptide . This protein is 11 aa longer than Escherichia coli OmpC, but it has an identical leader peptide . The mature OmpC sequence shows 79% similarity for both bacteria at the aa level, and 77% similarity at the nt level . Seven main variable regions in the OmpC protein were identified . Five of them correspond to hydrophilic regions and contain aa observed most frequently in turn configurations in soluble proteins . This suggests that these aa stretches could be located on the exterior of the outer membrane . To probe into the genus and species specificity of the main variable regions, we have constructed complementary oligodeoxyribonucleotides . The use of one of them with a small number of DNA samples is illustrated here; no restriction fragment length polymorphism or nt sequence heterogeneity could be found between S . typhi and Salmonella typhimurium.

J Immunol Methods, 1989 Nov 30, 124(2), 267 - 75
Oxygen-independent antimicrobial action in sphingosine-treated neutrophils; Stinavage P et al.; Sphingosine is reported to inhibit the oxidative burst and superoxide anion production of human polymorphonuclear neutrophils (PMN) phagocytosing in atmospheric oxygen (Wilson et al., 1986) . We have confirmed its effect on superoxide production and examined the antimicrobial phagocytic capacity of PMN treated with sphingosine, comparing them with PMN, untreated but phagocytosing either under anaerobic conditions or in atmospheric oxygen . Sphingosine just like anaerobiosis partially inhibited, but did not eliminate, the bactericidal activity of PMN when compared to non-treated aerobic cells . In fact, sphingosine-treated PMN mimicked killing of Staphylococcus aureus (S . aureus) and Serratia marcescens (S . marcescens) due to anaerobic PMN . Moreover, our results with Salmonella typhimurium and sphingosine-treated cells duplicated results this laboratory published previously about comparative killing of Salmonella in aerobic versus anaerobic neutrophils . In these studies sphingosine-treated PMN took up bacteria as avidly as untreated PMN and retained their viability, as assessed by trypan blue exclusion . While sphingosine should not be completely substituted for anaerobic studies, it is a convenient screening reagent for the study of non-oxidative killing mechanisms of PMN . Results achieved with anaerobic and with sphingosine-treated cells suggest that O2-independent antimicrobial action is substantially more powerful than has been generally acknowledged.

J Biol Chem, 1989 Nov 25, 264(33), 20112 - 9
Characterization of bacteriophage P22 tailspike mutant proteins with altered endorhamnosidase and capsid assembly activities; Schwarz JJ et al.; The tailspike protein of Salmonella typhimurium phage P22 is a multifunctional homotrimer which is involved in the terminal reaction of phage assembly, the adsorption of the phage to susceptible cells, and the hydrolysis of the Salmonella O-antigen during the first steps of phage infection . The proteins made from 15 mutant tailspike structural genes carried on high level expression plasmids have been analyzed with respect to their in vivo stability, quaternary structure, capsid assembly activity, and enzymatic activity . Nine mutants synthesize tailspike proteins which fail to accumulate to any appreciable level in vivo, and thus these proteins are probably degraded . Four other altered proteins accumulate in vivo as soluble monomers . The remaining two altered proteins accumulate in vivo as stable trimers . Each of these two proteins is defective for at least one of the known functions of the tailspike protein . One is defective in the capsid assembly reaction and shows an unusual quaternary structural defect but is normal with respect to the enzymatic hydrolysis of O-antigen . The other is defective in the enzymatic hydrolysis of O-antigen but is normal with respect to its capsid assembly activity and quaternary structure . The known sequence changes which give rise to these altered proteins and those of previously identified mutants allow the description of possible functional and structural "domains" of this multifunctional protein.

Nature, 1989 Nov 23, 342(6248), 396 - 401
The barrier to recombination between Escherichia coli and Salmonella typhimurium is disrupted in mismatch-repair mutants; Rayssiguier C et al.; The requirement for DNA sequence homology in generalized genetic recombination is greatly relaxed in bacterial mutL, mutS and mutH mutants deficient in mismatch repair . In such mutants, intergeneric recombination occurs efficiently between Escherichia coli and Salmonella typhimurium, which are approximately 20% divergent in DNA sequence . This finding has implications for speciation, for regulating recombination between diverged repeated sequences, and for hitherto difficult interspecies hybridizations.

Eur J Biochem, 1989 Nov 20, 185(3), 541 - 6
rfaP mutants of Salmonella typhimurium; Helander IM et al.; Salmonella typhimurium rfaP mutants were isolated and characterised with respect to their sensitivity towards hydrophobic antibiotics and detergents, and their lipopolysaccharides were chemically analysed . The rfaP mutants were selected after diethylsulfate mutagenesis or as spontaneous mutants . The mutation in two independent mutants SH7770 (line LT2) and SH8551 (line TML) was mapped by cotransduction with cysE to the rfa locus . The mutants were sensitive to hydrophobic antibiotics (clindamycin, erythromycin and novobiocin) and detergents (benzalkoniumchloride and sodium dodecyl sulfate) . Analysis of their lipopolysaccharides by chemical methods and by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed that their saccharide portion was, to a large extent, of chemotype Rc with small proportions of material containing a more complete core oligosaccharide and O-specific chains . Only 2.5 mol phosphate/mol lipopolysaccharide was found whereas the phosphate content of the lipopolysaccharide of a galE mutant strain was 4.8 mol . Thus the rfaP mutant lipopolysaccharides lacked more than two phosphate residues . Assessment of the location of phosphate groups in rfaP lipopolysaccharides revealed the presence of at least 2 mol phosphate in lipid A, indicating that the core oligosaccharide was almost devoid of phosphate . The chemical, physiological and genetic data obtained for these mutants are in full agreement with those reported earlier for rfaP mutants of Salmonella minnesota.

Gene, 1989 Nov 15, 83(1), 95 - 103
Human metallothionein-II is synthesized as a stable membrane-localized fusion protein in Escherichia coli; Jacobs FA et al.; A synthetic gene encoding human metallothionein-II (HMT) was cloned into the specially constructed high-copy-number expression vector, pUA7, and expressed in Escherichia coli . The plasmid construct includes the promoter/operator and regulatory sequences of the Salmonella typhimurium ara operon and part of the 5'-coding and all of the 3'-noncoding regions of the E . coli lpp . Upon induction with arabinose, the resulting Lpp::HMT fusion protein was produced 75,000-fold over uninduced cells, with a relatively stable mRNA (T1/2 of 8.3 min) and a completely stable protein . In addition, over 95% of the final fusion protein was localized in the outer membrane and was capable of binding heavy metals (especially cadmium) in vitro . Cells producing Lpp::HMT bioaccumulated heavy metals (e.g., cadmium) 66-fold over nonproducing cells.

J Natl Cancer Inst, 1989 Nov 15, 81(22), 1743 - 7
Inhibition by diacylmethane derivatives of mutagenicity and nucleic acid binding of 2-aminofluorene derivatives; Wang CY et al.; The active methylene compounds acetylacetone, 1,1,1-trifluoroacetylacetone, benzoylacetone, dibenzoylmethane, and 1,3-indandione inhibited the mutagenicity of 2-nitrofluorene in Salmonella typhimurium . They also inhibited the N,O-acetyltransferase-catalyzed transfer RNA binding of N-hydroxy-2-acetylaminofluorene, but they did not inhibit N,O-acetyltransferase . However, only 1,3-indandione and 1,1,1-trifluoroacetylacetone significantly inhibited the binding of N-acetoxy-2-acetylaminofluorene to transfer RNA . Reaction of the trifluoro compound with the acetoxy compound yielded 1-(N-2-fluorenylacetamido)acetone . These results demonstrate that active methylene compounds can inhibit mutagenicity and nucleic acid binding of chemical carcinogens.

Cancer Res, 1989 Nov 15, 49(22), 6304 - 12
Roles of individual human cytochrome P-450 enzymes in the bioactivation of benzo(a)pyrene, 7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene, and other dihydrodiol derivatives of polycyclic aromatic hydrocarbons; Shimada T et al.; Human liver microsomes oxidized 7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene {B(a)P-7,8-diol} to products that yield DNA adduct formation and umu gene expression in the tester system Salmonella typhimurium TA1535/pSK1002 . The umu response is correlated to levels of microsomal cytochrome P-450NF (P-450NF) and nifedipine oxidation in different human liver samples used for activation, and both the (+)- and (-)-enantiomers of B(a)P-7,8-diol gave similar results in these and other assays . The microsomal umu response was inhibited by antibodies raised against P-450NF . 7,8-Benzoflavone stimulated the B(a)P-7,8-diol-dependent umu response observed with purified P-450NF and human liver and lung microsomes . Thus, P-450NF appears to be the major enzyme involved in the activation of B(a)P-7,8-diol in human liver and possibly lung . Similar results were obtained for the activation of trans-9,10-dihydroxy-9,10-dihydrobenzo(b)fluoranthene and trans-3,4-dihydroxy-3,4-dihydro-7,12-dimethylbenz(a)anthracene, compounds that are known to form highly tumorigenic diol-epoxides . The major product of the oxidation of (+)-B(a)P-7,8-diol was the cis-syn isomer of benzo(a)pyrene-7,8,9,10-tetraol{7 beta, 8 alpha, 9 beta, 10 beta-tetrahydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene} . Studies on the nature of the human liver enzymes involved in the formation of B(a)P-7,8-diol {from benzo(a)pyrene} indicate that neither P-450NF, P-450PA, P-450j, P-450DB, nor P-450MP is involved . The correlation of 7,8-diol formation with phenacetin O-deethylation in a set of liver samples and the partial inhibition of the reaction by 7,8-benzoflavone and anti-rat P-450 beta NF-B suggest that the enzyme involved may be P1-450, the human ortholog of rat P-450 beta NF-B, which catalyzes both the formation of B(a)P-7,8-diol and its subsequent oxidation in tissues of polycyclic hydrocarbon-treated rats . The differential effects of inhibitors indicate that benzo(a)pyrene 3-hydroxylation, 4,5-epoxidation, and 9,10-epoxidation are catalyzed by an enzyme(s) distinct from that which forms the 7,8-epoxide . The roles of the human P-450 enzymes differ from the rodent orthologs in the paradigm for bioactivation of polycyclic hydrocarbons; further, flavones appear to have opposing effects on diol formation and further epoxidation in both human liver and lung.

FEBS Lett, 1989 Nov 6, 257(2), 274 - 8
Molecular organization of genes constituting the virulence determinant on the Salmonella typhimurium 96 kilobase pair plasmid; Taira S et al.; The ability of intracellular growth is plasmid-dependent in Salmonella typhimurium . Only a small portion of this 96 kilobase pair plasmid appears essential for intracellular growth . The genetic organization of this region (the essential virulence determinant) was resolved . Fragments of the virulence determinant were cloned from the 96-kb plasmid pEX102 and transformed into minicell-producing E . coli . Plasmid-directed protein synthesis was investigated in metabolically labeled minicells . This analysis indicated the presence of at least four genes, mkaA, mkaB, mkaC and mkaD, within the virulence determinant encoding proteins of 70, 31, 30 and 29 kDa, respectively . The genes were positioned on the restriction map of the 96-kb virulence plasmid and the map locations confirmed by nucleotide sequence analysis of two new virulence genes (mkaB and mkaC).

Eur J Biochem, 1989 Nov 6, 185(2), 319 - 25
Studies on the domain structure of the Salmonella typhimurium AraC protein; Lauble H et al.; The Salmonella typhimurium araC gene product is known to be susceptible to proteolytic degradation . Limited cleavage by trypsin, kallikrein, elastase and pronase E yields stable fragments comprising approximately the N-terminal two thirds of the AraC protein . These fragments have in common the ability to dimerize in solution and to bind L-arabinose and D-fucose . Under appropriate conditions, hydrolysis of the AraC protein with Staphylococcus aureus V8 protease leads to a small C-terminal fragment which is able to bind specifically to a synthetic ara consensus sequence . These results indicate that, as with several other prokaryotic gene regulatory proteins, the basic functions of effector binding, subunit interaction and specific DNA binding are segregated into distinct domains of the AraC protein.

Photochem Photobiol, 1989 Nov, 50(5), 625 - 32
Singlet oxygen induced mutagenesis of benzo{a}pyrene derivatives; Seed JL et al.; Singlet oxygen activates the mutagenicity of several benzo{a}pyrene (BP) derivatives in the absence of mammalian metabolic action . This has been demonstrated using a separated-surface-sensitizer system for generating chemically pure singlet oxygen, eliminating most of the complications that arise with singlet oxygen generation by conventional photosensitization . Salmonella typhimurium bacteria were exposed to singlet oxygen in the presence of certain BP derivatives and the mutation frequency determined with an azaguanine forward mutation assay . The mutation frequency was increased by exposure to singlet oxygen compared to light-only controls for those BP derivatives that were saturated at either the 7,8 or 9,10 positions but not both . The increase in mutation frequency depends on both the concentration of BP derivative and on the dose of singlet oxygen . Mutation frequency was also significantly increased when bacteria were treated with a solution of trans-7,8-dihydrodiol-BP that had been separately exposed to singlet oxygen, unequivocally demonstrating that the mutagenicity is due to the formation of a product of BP derivative oxidation by singlet oxygen and that this product has a lifetime at least on the order of minutes in acetonitrile . The requirement for singlet oxygen rather than some other form of reactive oxygen was confirmed by determination of the gas phase lifetime of the intermediate responsible for activating mutagenicity . This was performed by measuring the dependence of the mutation frequency on the distance separating the sensitizer from the target . This gives a value of 88 +/- 35 ms, which is in excellent agreement with the mean value of 89 ms calculated from previous independent determinations of the gas phase lifetime of singlet oxygen reported in the literature.

Mutagenesis, 1989 Nov, 4(6), 453 - 5
Re-evaluation of the effect of ellagic acid on dimethylnitrosamine mutagenicity; Lord HL et al.; Dimethylnitrosamine (DMN) is activated to mutagenic species in the Ames test (Salmonella typhimurium strain TA100) by hamster hepatic S9 preparation . This S9 activity is induced by administration of ethanol to the animals . The organic solvents dimethylsulphoxide (DMSO) and N-methyl-2-pyrrolidinone (MP) inhibit this mutagenicity, apparently because they inhibit DMN demethylase activity (assayed as formaldehyde production) . Ellagic acid, dissolved in DMSO or MP, had no inhibitory effect on DMN mutagenicity, beyond the effect of the solvent vehicle.

Mutagenesis, 1989 Nov, 4(6), 446 - 52
Mutagenic nitrenes/nitrenium ions from azido-imidazoarenes and their structure-activity relationships; Wild D et al.; New heterocyclic arylazides (azido-imidazoarenes) structurally related to the food mutagen/carcinogen 2-amino-3-methyl-imidazo{4,5-f}quinoline (IQ) have been prepared . Their photolysis yields nitrenes and/or nitrenium ions which induce mutations in Salmonella typhimurium . The relationships between the chemical structure and mutagenic activity of these species are the same as those found in our previous studies of the amino- and nitro-imidazoarenes . Therefore the efficiency of the reaction with DNA of the ultimate metabolite, the nitrene/nitrenium ion, is the critical step governing the mutagenic potency of the amino- and nitro-imidazoarenes . The efficiency of DNA-binding depends on the delocalization of the positive charge of the nitrenium ion or of the electron deficiency of the nitrene . It is typical of the N-1-substituted and N-3-substituted arenimidazolyl-nitrenium ions that they can form another nitrenium resonance structure very similar to the parent nitrenium ion structure . We suggest that this property of the nitrene/nitrenium ion, in combination with its aromatic structure facilitating carbonium ion resonance structures, is the basic reason for the extremely potent mutagenic activity of IQ and related food mutagens/carcinogens.

Food Chem Toxicol, 1989 Nov, 27(11), 723 - 30
The stability of the nitrosated products of indole, indole-3-acetonitrile, indole-3-carbinol and 4-chloroindole; Tiedink HG et al.; The nitrosation rates of indole-3-acetonitrile, indole-3-carbinol, indole and 4-chloroindole and the stability of their nitrosated products were investigated . Each of the nitrosated indole compounds was directly mutagenic to Salmonella typhimurium TA100 in the following order of potency: 4-chloroindole much greater than indole-3-carbinol greater than or equal to indole greater than indole-3-acetonitrile . Total N-nitroso determinations, carried out according to a modified method of Walters et al . (Analyst, Lond . 1978, 103, 1127), and Ames test results revealed that each of the indole compounds immediately formed mutagenic N-nitroso products upon nitrite treatment under acidic conditions . However, the nitrosation rates of indole and 4-chloroindole were higher than those of indole-3-acetonitrile and indole-3-carbinol . For indole-3-carbinol, indole-3-acetonitrile and indole, no change in the amount of nitrosated products was observed at increasing incubation times from about 15 up to 60 min . For 4-chloroindole the amount of nitrosated products decreased with increasing incubation times . In all cases the responses in the Ames test paralleled the amounts of nitrosated products . The stabilities of the nitrosated products of the indole compounds were investigated at pH 2 and 8 . Both mutagenicity data and measurements by high-performance liquid chromatography using a photohydrolysis detector indicated that the nitrosation products of indole-3-acetonitrile, indole-3-carbinol and indole were more stable at pH 8 than at pH 2 . Conversely, nitrosated 4-chloroindole was stable at pH 2 but not at pH 8 . The pH 8 chromatograms showed a large nitrite peak . From this we hypothesized that the presence of free nitrite might be responsible for the stability of nitrosated indole-3-acetonitrile, indole-3-carbinol and indole at pH 8 . Experiments confirmed the existence of an equilibrium between the nitrosated indole compound and the free indole compound plus nitrite.

Poult Sci, 1989 Nov, 68(11), 1454 - 60
Age-related changes in the persistence and pathogenicity of Salmonella typhimurium in chicks; Gast RK et al.; Effects of age at exposure on the persistence of Salmonella in various tissues of chicks were assessed in two experiments . Broiler chicks, housed on wire floors in isolation cabinets, were orally inoculated with S . typhimurium at various ages (1 to 8 days after hatching) . The postinoculation mortality of chicks declined significantly (P less than .05) as the age at inoculation increased . One experiment investigated the effect of age at inoculation on the persistence of S . typhimurium in the cecum . Salmonella persisted for 7 wk after inoculation in 81.3% of the chicks inoculated at 1 day of age and in 62.5% of the chicks inoculated at 8 days of age . The mean number of cecal Salmonella at 7 wk postinoculation was also greater for chicks inoculated on Day 1 than for those inoculated on Day 8 . The second experiment examined the effect of age at inoculation on the adherence of S . typhimurium to and penetration through the cecal epithelium . The ceca of chicks inoculated at 1 day of age were colonized by significantly more adhering Salmonella at 2 days postinoculation (1.4 x 10(8)/g) than were those of chicks inoculated at 3, 5, or 7 days of age (8.0 x 16(6)/g or less), but age did not affect the recovery of S . typhimurium from livers or spleens.

J Med Microbiol, 1989 Nov, 30(3), 213 - 7
The influence of cultural conditions on the expression in Salmonella typhimurium of an antigen related to cholera toxin; Qi GM et al.; The choice of strain, culture conditions, composition of medium and size of inoculum all affected the expression of a cholera-toxin-related antigen (CTRA) in Salmonella typhimurium . A previous study had shown that the number of organisms expressing CTRA in Casamino acid Yeast Extract (CYE) medium decreased between 4 h and 6 h in uninterrupted culture . In the present experiments, organisms harvested at 4-5 h were subcultured into fresh CYE medium and incubated for a further 2 h; the total number of organisms increased, and the decrease in the proportion of organisms expressing CTRA was reduced . Use of Hartley Digest Broth in place of CYE medium increased the proportion of organisms expressing CTRA in all strains tested, in both the uninterrupted and the subculture procedures . The higher the initial inoculum, the lower was the proportion of organisms expressing CTRA . The presence of the antigen in cells remained constant for about 18 h after transfer from 37 degrees C to 4 degrees C . These data have important implications for the production and purification of CTRA: they show that it was expressed during log-phase of growth, and they suggest that expression was regulated by a non-growth-limiting factor . Moreover, some avirulent strains were better producers of the antigen than virulent ones . The significance of the data is discussed in relation to the in-vivo situation.

Mutat Res, 1989 Nov, 227(3), 135 - 45
Phenazine derivatives as the mutagenic reaction product from o- or m-phenylenediamine derivatives with hydrogen peroxide; Watanabe T et al.; 8 Kinds of o- and m-phenylenediamine (PD) derivatives, which are used as oxidative-type hair dyes, were treated with hydrogen peroxide (H2O2) . Both before and after H2O2 treatment, their mutagenicity was tested by using Salmonella typhimurium TA98 in the presence or absence of a mammalian metabolic activation system (S9 mix) . After H2O2 treatment, the mutagenic potencies of p-nitro-o-phenylenediamine, 3,4-diaminotoluene, p-nitro-m-phenylenediamine and 2,4-diaminophenol did not vary or slightly increased in comparison with those of the starting materials . The mutagenicity of o-PD, p-chloro-o-phenylenediamine (p-Cl-o-PD), m-PD and 2,4-diaminoanisole (p-OMe-m-PD) was enhanced remarkably by treatment with H2O2 and all the oxidation products required metabolic activation by S9 mix for their mutagenesis . In a gas chromatography/mass spectrometric study, 2,3-diaminophenazine and 2,7-diaminophenazine were identified with authentic samples in o-PD and m-PD oxidation mixture, respectively . The oxidation mixture obtained from p-Cl-o-PD and p-OMe-m-PD was separated into several fractions by repeated column chromatography . Brownish yellow crystals were isolated from oxidized p-Cl-o-PD and the structure of the compound was determined to be 2,3-diamino-7-chlorophenazine from physicochemical and chemical evidence . Two reddish yellow crystals, obtained from oxidized p-OMe-m-PD, were 2,7-diamino-3,8-dimethoxyphenazine and 2,7-diamino-3-methoxyphenazine . The number of revertants induced by 1 nmole of phenazines detected from oxidized PD derivatives was as follows; 2,3-diaminophenazine: 349 rev.; 2,3-diamino-7-chlorophenazine; 406 rev.: 2,7-diaminophenazine: 12 110 rev.; 2,7-diamino-3,8-dimethoxyphenazine: 4229 rev.; 2,7-diamino-3-methoxyphenazine: 24 640 rev . in S . typhimurium TA98 strain with 25 microliters S9 per plate.

J Bacteriol, 1989 Nov, 171(11), 5776 - 82
Cloning of Salmonella typhimurium DNA encoding mutagenic DNA repair; Thomas SM et al.; Mutagenic DNA repair in Escherichia coli is encoded by the umuDC operon . Salmonella typhimurium DNA which has homology with E . coli umuC and is able to complement E . coli umuC122::Tn5 and umuC36 mutations has been cloned . Complementation of umuD44 mutants and hybridization with E . coli umuD also occurred, but these activities were much weaker than with umuC . Restriction enzyme mapping indicated that the composition of the cloned fragment is different from the E . coli umuDC operon . Therefore, a umu-like function of S . typhimurium has been found; the phenotype of this function is weaker than that of its E . coli counterpart, which is consistent with the weak mutagenic response of S . typhimurium to UV compared with the response in E . coli.

Infect Immun, 1989 Nov, 57(11), 3276 - 80
A Salmonella typhimurium virulence gene linked to flg; Carsiotis M et al.; Isogenic pairs of strains of Salmonella typhimurium which differed only in whether or not they were flagellate were found to be equally virulent in C57BL/6J mice infected orally, intravenously, or intraperitoneally . Therefore, we investigated the genetic basis for our previous observation that in this mouse model, nonflagellate delta flagABCDE25 strains were reduced in virulence compared with isogenic wild-type flagellate strains . The recombinant plasmid pMH6, which contains several flg+ genes and a segment of the S . typhimurium chromosome adjacent to the flg genes, was introduced into a delta flgABCDE25 mutant . This restored virulence in mice challenged intraperitoneally, which suggested that a virulence gene occurs adjacent to the flg genes . When plasmid pMH64, which lacks the chromosomal segment adjacent to the flg genes, was introduced into the same delta flgABCDE25 mutant, virulence was not restored . In contrast, the introduction of pMH71, a plasmid which retains the chromosomal segment adjacent to the flg genes, restored virulence . We concluded that a hitherto unknown virulence gene, which we have named mviS, occurs adjacent to the flg genes and that its absence in delta flgABCDE25 mutants, rather than the nonflagellate phenotype of the delta flgABCDE25 mutants, caused the previously reported attenuation of such mutants.

Carcinogenesis, 1989 Nov, 10(11), 2119 - 22
Genotoxicity and effects on rat liver drug-metabolizing enzymes by possible substitutes for 4,4'-methylene bis(2-chloroaniline); Wu K et al.; The mutagenic properties of Ethacure 300, Cyanacure and Polacure 740M, all possible substitutes for the industrial carcinogen, 4,4'-methylene bis(2-chloroaniline), have been determined in Salmonella typhimurium strains TA100, TA98, TA1535 and TA1537 . These data have been compared with the effects of these chemicals on ethoxyresorufin O-deethylase (EROD) activity and aldrin epoxidase (AE) activity in rat liver . Ethacure 300 was clearly positive in both TA100 and TA98 bacterial strains, while Cyanacure was positive only in TA100 . Polacure 740M was negative in all strains . Ethacure 300 caused a 28-fold induction of EROD while Cyanacure caused a doubling . Polacure 740M was without effect . Neither Ethacure 300 nor Cyanacure affected AE, while Polacure 740M caused an increase at only the lower dose tested . Thus there was excellent correlation between mutagenicity and EROD induction . A similar correlation was noted for six other structurally related compounds giving support to the contention that the ability of a chemical to induce EROD bears some relationship to its carcinogenic potential.

Carcinogenesis, 1989 Nov, 10(11), 2019 - 24
Singlet oxygen as an ultimately reactive species in Salmonella typhimurium DNA damage induced by methylene blue/visible light; Epe B et al.; The specific recognition of various DNA modifications by repair enzymes is exploited for the analysis of DNA damage induced by visible light in the presence of methylene blue in Salmonella typhimurium . The relative frequencies of various endonuclease-sensitive sites and strand breaks are determined in the plasmid pAQ1 of the treated bacteria and are compared with those observed after exposure of isolated DNA to various conditions . This comparison of damage profiles indicates that the cellular DNA damage by illumination in the presence of methylene blue is caused predominantly by the direct action of singlet oxygen . Indirect mechanisms, e.g . involving a generation of superoxide and hydroxyl radicals or the activation of cellular nucleases, do not contribute very much . The damage is dominated by base modifications . These are subject to an efficient repair that is not mediated by uvrABC proteins and therefore most probably involves recognition by specific glycosylases . Revertant frequencies observed under these conditions in the strains TA1535, TA100, TA2638 and TA104 indicate a pronounced mutagenicity of the lesions induced . On the other hand, the DNA damage does not contribute significantly to the cytotoxicity caused by the treatment as an excision repair deficiency (uvrB) has no influence on cell killing.

Arch Exp Veterinarmed, 1989 Nov, 43(6), 849 - 54
{The secondary microbial colonization of organ samples for bacterial meat examination}; Schuppel H et al.; The capability of bacteria to penetrate liver, spleen, and kidney samples was investigated, using one strain each of Salmonella typhimurium . Serratia marcescens, and Micrococcus luteus . The intact organ capsule was found to be an effective barrier to bacterial invasion, even at room temperature and with high contamination doses . Injuries to or absence of the organ capsule led to massive secondary germ colonisation of samples within 5 hours, even under conditions of cool storage . Germ colonisation of the sample interior will inevitably start from cut surfaces and cannot be prevented, if samples have to be stored several hours or transported, since sterile sampling is not possible under slaughterhouse conditions . Hence, new approaches have to be found to bacteriological carcass inspection.

Immunopharmacology, 1989 Nov-Dec, 18(3), 157 - 66
Suppression of avidin processing and presentation by mouse macrophages after sublethal exposure to dieldrin; Krzystyniak K et al.; The molecular events in macrophage antigen processing and presentation were examined to determine the possible site(s) of cell-xenobiotic interaction . Antigenic processing by mouse peritoneal macrophages of a single protein antigen, avidin, was significantly suppressed following sublethal exposure of animals to an organochlorine pesticide, dieldrin . Exposure of C57B1/6 female mice to dieldrin affected the in vitro uptake of {methyl-14C}avidin by peritoneal macrophages and markedly decreased phagocytosis of fluorescein-labelled microspheres and Salmonella typhimurium . Release of the processed avidin, determined by immunochemical quantification of immunogenic avidin and by bioassay of immunogenicity of the released antigen, was also markedly affected . Dieldrin markedly affected presentation of avidin on the macrophage surface, observed by cytoimmunochemical staining of the antigen with fluorescent antibody and flow cytometry . Inhibition of the release of processed avidin was dieldrin dose- and time-dependent, following single sublethal intraperitoneal (ip) exposure to the pesticide . The antigenic properties of processed avidin, determined by biological assay using lymphocyte cultures of normal C57B1/6 mice primed with avidin, were proportional to the antigen concentration in supernatants of macrophage cultures, for both vehicle controls and dieldrin-exposed animals . This observation and analysis of the kinetics of release of processed avidin by macrophages from control and dieldrin-exposed animals suggested that the release of processed avidin, but not the immunogenicity of the antigen itself, was affected by the pesticide exposure . Generally, impairment of avidin processing and presentation appeared to be more dramatic than other pesticide-related injuries to macrophages, such as the uptake of the antigen . In conclusion, antigen processing could be a sensitive target for dieldrin-related injury of macrophage functional activities, which, in consequence, could produce suppression of the humoral immune response.

Plasmid, 1989 Nov, 22(3), 256 - 9
Tn4527, a Tp Sp/Sm transposon related to Tn7 and flanked by IS1; Dumans AT et al.; Tn4527 was isolated from a Salmonella typhimurium strain obtained in Brazil . Its size is 19.6 kb and it carries resistance to trimethoprim, spectinomycin, and streptomycin, as in the case of Tn7 (14 kb) . A restriction analysis of the transposon shows regions of similarity to Tn7 mixed with extra DNA . The 2.6-kb and 2.2-kb HindIII fragments of Tn7, which encode transposition-related proteins, show homology to Tn4527 . In contrast to Tn7, Tn4527 is flanked by direct repeats, which seem to be IS1's, as they have appropriate restriction sites and hybridize both to IS1 and to internal IS1 oligonucleotides.

Microb Pathog, 1989 Nov, 7(5), 337 - 46
Effect of Salmonella typhimurium porins on biological activities of human polymorphonuclear leukocytes; Tufano MA et al.; The effect of Salmonella typhimurium porins on human polymorphonuclear leukocytes (PMNs) was studied . Labeled porins were shown to bind to the PMNs, and could be completely displaced by unlabeled porins . The binding caused modifications of membrane integrity and of the physico-chemical characteristics of the PMN surface, e.g . decreased oxidative burst, decreased hydrophobicity and altered cell morphology . The porins acted as both chemotaxins and chemotaxinogens . When PMNs were preincubated with porins their migration in the presence of commonly used chemoattractants (serum activated by zymosan or N-formyl-L-methionyl-L-leucyl-L-phenylalanine) was inhibited.

J Bacteriol, 1989 Nov, 171(11), 6330 - 7
Mutational analysis of the histidine operon promoter of Salmonella typhimurium; Shand RF et al.; We isolated a collection of 67 independent, spontaneous Salmonella typhimurium his operon promoter mutants with decreased his expression . The mutants were isolated by selecting for resistance to the toxic lactose analog o-nitrophenyl-beta-D-thiogalactoside in a his-lac fusion strain . The collection included base pair substitutions . small insertions, a deletion, and one large insertion identified as IS30 (IS121), which is resident on the Mu d1 cts(Apr lac) phage used to construct the his-lac fusion . Of the 37 mutations that were sequenced, 14 were unique . Six of the 14 were isolated more than once, with the IS30 insertion occurring 16 times . The mutations were located throughout the his promoter region, with two in the conserved - 35 hexamer sequence, four in the conserved - 10 hexamer sequence (Pribnow box), seven in the spacer between the - 10 and -35 hexamer sequences, and the IS30 insertions just upstream of the -35 hexamer sequence . Four of the five substitution mutations changed a consensus base pair recognized by E sigma 70 RNA polymerase in the -10 or -35 hexamer . Decreased his expression caused by the 14 different his promoter mutations was measured in vivo . Relative to the wild-type promoter, the mutations resulted in as little as a 4-fold decrease to as much as a 357-fold decrease in his expression, with the largest decreases resulting from changes in the most highly conserved features of E sigma 70 promoters.

J Bacteriol, 1989 Nov, 171(11), 5860 - 5
Fine-structure genetic map of the maltose transport operon of Salmonella typhimurium; Schneider E et al.; We have constructed a fine-structure genetic map of the maltose transport operon in Salmonella typhimurium . We have isolated mal mutants by using indicator plates, penicillin selection, or a proton suicide technique . Mutants were obtained as spontaneous events or were induced by chemical mutagenesis and transposon insertion . Tn10 and Mu d(lac Ap)1 insertion mutations were used to create deletions . Mutations were also obtained in a gene that is equivalent to lamB in Escherichia coli, which codes for the lambda bacteriophage receptor . The gene products in the mutants were characterized by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis and immunoblotting . Our data indicate that the location of this operon on the Salmonella chromosome as well as the gene order and its orientation are the same as those in E . coli . This map will be useful in studying the mechanism of periplasmic transport in S . typhimurium.

Mutagenesis, 1989 Nov, 4(6), 437 - 8
Genotoxic potential of crown ethers in Salmonella typhimurium; Arenaz P et al.; Macrocyclic polyethers (crown ethers) are a family of compounds which possess the ability to transport ionic species across natural and artificial membranes . Because of this characteristic, they have wide applications in industry and are being investigated for their potential as pharmacologic agents . However, these compounds are highly cytotoxic in both prokaryotes and eukaryotes . Because of the cytotoxicity of crown ethers, an investigation of the potential genotoxicity of these compounds in Salmonella typhimurium was initiated . Several unsubstituted and substituted crown ethers did not induce a genotoxic response in S . typhimurium strains TA100, TA1530, TA98 and TA1537 either with or without rat liver S9 mixture . The data support the conclusion that the toxicity of these compounds is probably not due to an interaction with nucleic acid to induce premutagenic lesions and they do not appear to be genotoxic in prokaryotes.

Food Chem Toxicol, 1989 Nov, 27(11), 715 - 21
Non-clastogenicity in mouse bone marrow of fructose/lysine and other sugar/amino acid browning products with in vitro genotoxicity; MacGregor JT et al.; Heated sugar/amino acid reaction mixtures, known to contain products that are clastogenic and/or mutagenic to cells in vitro, were evaluated for clastogenic activity in mouse bone marrow using the erythrocyte micronucleus assay . Heated (i.e . browned) fructose/lysine reaction mixtures were also evaluated in the Salmonella his-reversion assay and the Chinese hamster ovary (CHO) cell chromosomal aberration assay to confirm and extend previous in vitro observations . Significant mutagenicity of fructose/lysine mixtures was observed in Salmonella typhimurium strains TA100, TA2637, TA98 and TA102, with greater activity in mixtures heated at pH 10 than at pH 7 . S-9 decreased the activity in strains TA100, TA2637 and TA98, but increased the activity in strain TA102 . Both pH 7 and pH 10 reaction mixtures of the fructose/lysine browning reaction were highly clastogenic in CHO cells . Heated mixtures of fructose and lysine, and of glucose or ribose with lysine, histidine, tryptophan or cysteine, did not increase the frequency of micronucleated erythrocytes in mice when administered by the oral route . This indicates the absence of chromosomal aberrations in erythrocyte precursor cells, and indicates that the genotoxic components of the browned mixtures are not absorbed and distributed to bone marrow cells in amounts sufficient to induce micronuclei when given orally . Because sugar/amino acid browning reactions occur commonly in heated foods, it is important to evaluate further the in vivo genotoxicity of browning products in cell populations other than bone marrow.

Zentralbl Veterinarmed A, 1989 Nov, 36(9), 664 - 75
Clinical, endocrinological and spermatological studies after endotoxin injection in the boar; Wallgren M; Three adult boars were injected intravenously with endotoxin from Salmonella typhimurium . Blood plasma was analysed for the contents of 15-ketodihydro-PGF2 alpha, LH and testosterone . Total amount of white blood cells and differential counts were determined in whole blood . Semen was examined for concentration, motility, volume and morphological appearance of the spermatozoa . The boars were slaughtered three months after the endotoxin injection and the testes were examined . The total number of white blood cells decreased and the levels of 15-ketodihydro-PGF2 alpha rose immediately after the endotoxin administration . An initial increase in LH was seen in two out of the three boars . The increase in LH was followed by a testosterone increase in one boar and a testosterone decrease in the other . The third boar showed no initial increase in LH but an increase in testosterone . Semen examination demonstrated various morphological changes of the spermatozoa in all boars . The changes started to appear at about the same time after the endotoxin injection, but differed among the individuals . The examination of the testes depicted no changes from what is seen in normal animals . The present results indicate that the boar responds to endotoxin similar to what is seen in the ram . The endocrine changes, e.g . in LH and testosterone, are similar to those seen after termination of heat stress . The seminal changes indicate a disturbance located in the epididymis as well as a short-term, mild degeneration in the seminiferous epithelium.

Jpn J Cancer Res, 1989 Nov, 80(11), 1021 - 3
Mutagenicity arising from boiled rice on treatment with nitrous acid; Hayatsu H et al.; When an aqueous homogenate of boiled rice was treated with nitrous acid at pH 3, direct-acting mutagens were formed . The presence of the mutagens was demonstrated by isolating the mutagenic fractions through blue-rayon adsorption, a method used to extract polycyclic compounds, and subsequent high-performance liquid chromatography (HPLC) . The mutagens were active in Salmonella typhimurium TA100 and TA98 without metabolic activation . Several different mutagens were formed, as judged from the HPLC profile.

Biochem Pharmacol, 1989 Nov 1, 38(21), 3811 - 7
Metabolism of fusarin C by rat liver microsomes . Role of esterase and cytochrome P-450 enzymes with respect to the mutagenicity of fusarin C in Salmonella typhimurium; Lu SJ et al.; Fusarin C (FC) is a potent mutagen present on Fusarium moniliforme contaminated corn . This compound requires metabolic activation for which microsomes from phenobarbital-induced rats are most effective . Inhibition of the simultaneously induced esterase activity, which produced a less mutagenic metabolite, doubled the mutagenicity of FC . Carbon monoxide inhibited the mutagenicity of FC, suggesting the involvement of a heme containing enzyme . However, monoclonal antibodies specific for the phenobarbital-induced cytochrome P-450 enzymes PB-4 and PB-5, while inhibiting O-demethylation of p-nitroanisole and aflatoxin B1 mutagenicity, had not effect on FC mutagenicity . This implies that either these enzymes are not involved in the activation of FC or FC competes well with the antibodies for binding to the cytochrome P-450 enzymes . Two additional metabolites of FC were detected . One had an ultraviolet spectrum similar to FC: the other had a lambda max at 326 nm, and its retention time on reverse phase HPLC was very sensitive to changes in pH.

J Photochem Photobiol B, 1989 Nov, 4(2), 171 - 84
Partition of rose bengal anion from aqueous medium into a lipophilic environment in the cell envelope of Salmonella typhimurium: implications for cell-type targeting in photodynamic therapy; Dahl TA et al.; Photodynamic therapy employs photosensitizers for the selective destruction of tumor tissue while sparing the surrounding healthy tissue . Photosensitization may also be applied to the selective eradication of microorganisms . Photosensitized inactivation requires that the sensitizer bind to the target and therefore the factors that determine photosensitizer binding are critical to photosensitization selectivity . This paper reports the determination of some features of the binding site of the potent photosensitizer, Rose Bengal, in Salmonella bacteria and describes some of the factors that affect this binding . The shift in the wavelength of maximum fluorescence and experiments with the fluorescence quencher TNBS indicate that Rose Bengal is located in a non-aqueous compartment such as the outer membrane . The dye does not seem to significantly accumulate inside the cell, but rather to accumulate in the outer membrane . Time-dependent changes in sensitizer localization in two strains of Salmonella typhimurium that differ in cell wall formation, LT-2 and TA1975, correspond to their differences in susceptibility to photosensitized killing . Therefore these results provide clues to the factors that determine photosensitization selectivity . Understanding this phenomenon is essential for the efficient design of selective photosensitizers and for optimizing antitumor and antiviral photodynamic therapy.

Ann Ig, 1989 Nov-Dec, 1(6), 1445 - 58
{Antimicrobial activity exerted by sodium dichloroisocyanurate}; D'Auria FD et al.; Sodium dichloroisocyanurate is a chlorinated cleaner . It was used for swimming pool sanitation and for the sterilisation of linen . Not recently ago sodium dichloroisocyanurate has substituted hypochlorite for the sterilisation of infant feeding bottles and teats . Sodium dichloroisocyanurate is soluble in water; this condition causes the hydrolysis of sodium dichloroisocyanurate in hypochlorous acid, that is the active agent, isocyanurate and isocyanurate chlorine . These compounds form a chlorine protein that carry out microbicidal activity . In a toxicology study has been shown that no severe changes in the normal metabolic function occurred, furthermore sodium dichloroisocyanurate has not shown teratogenic effects at the concentration of 200 mg/kg . The antimicrobial activity of sodium dichloroisocyanurate was evaluated against Gram negative bacteria such as E . coli or Salmonella typhimurium and against some fungi . This study illustrates a rapid antimicrobial activity using concentrations . Our study concentrated on the antimicrobial activity of sodium dichloroisocyanurate in some experimental conditions . We tested 66 strains of fungi, 28 Gram positive bacteria and 29 Gram negative bacteria . We also evaluated the antimicrobial activity of sodium dichloroisocyanurate against protozoa such as Trichomonas vaginalis . The antimicrobial activity was evaluated in cultural conditions and non cultural conditions; in these experiments we observed similar action in both the commercial product and pure substance . In cultural conditions sodium dichloroisocyanurate shows a good activity against fungi and bacteria, moreover it can be observed that the serum didn't interfere with its activity . In a non cultural condition the Candida was killed rapidly by the sodium dichloroisocyanurate but this activity is influenced by the growth phase of the yeast . Against mycelial form such as Penicillium and Aspergillus the sodium dichloroisocyanurate needs a longer contact time than yeast form for its activity . It is interesting to note that well known bacteria, that are resistant to the common antimicrobial agents, such as Pseudomonas aeruginosa, were inhibited by sodium dichloroisocyanurate in a rapid bactericidal action . Our data demonstrates that no significant adverse influence on the activity of sodium dichloroisocyanurate was shown by pH and by temperature even if in some experimental conditions increased activity was noticed at pH = 6.6 . The sodium dichloroisocyanurate has demonstrated good activity against Trichomonas vaginalis . This fact extends the broad-spectrum activity of sodium dichloroisocyanurate to the protozoa . In conclusion, sodium dichloroisocyanurate has demonstrated a good activity against all tested strains, furthermore its activity did not decrease in the presence of 1% of organic substance (serum etc.).(ABSTRACT TRUNCATED AT 400 WORDS)

J Biol Chem, 1989 Oct 25, 264(30), 17681 - 90
Refined atomic model of glutamine synthetase at 3.5 A resolution; Yamashita MM et al.; An atomic model of 43,692 non-hydrogen atoms has been determined for the 12-subunit enzyme glutamine synthetase from Salmonella typhimurium, by methods of x-ray diffraction including restrained least-squares atomic refinement against 65,223 unique reflections . At 3.5 A resolution the crystallographic R-factor (on 2 sigma data) is 25.8% . As reported earlier for the unrefined structure, the 12 subunits are arranged in two layers of six; at the interface of pairs of subunits within each layer, cylindrical active sites are formed by six anti-parallel beta strands contributed by one subunit and two strands by the neighboring subunit . This interpretation of the electron density map has now been supported by comparison with glutamine synthetase from Escherichia coli by the Fourier difference method . Each active site cylinder holds two Mn2+ ions, with each ion having as ligands three protein side chains and two water molecules (one water shared by both metals), as well as a histidyl side chain just beyond liganding distance . The protein ligands to Mn2+ 469 are Glu-131, Glu-212, and Glu-220; those to Mn2+ 470 are Glu-129, His-269, and Glu-357 . The two layers of subunits are held together largely by the apolar COOH terminus, a helical thong, which inserts into a hydrophobic pocket formed by two neighboring subunits on the opposite ring . Also between layers, there is a hydrogen-bonded beta sheet interaction, as there is between subunits within a ring, but hydrophobic interactions account for most of the intersubunit stability . The central loop, which extends into the central aqueous channel, is subject to attack by at least five enzymes and is discussed as an enzyme "passive site."

FEBS Lett, 1989 Oct 9, 256(1-2), 155 - 8
Lipopolysaccharide toxin can directly stimulate the intracellular accumulation of lipids and their secretion into medium in the primary culture of rabbit hepatocytes; Victorov AV et al.; Low doses (0.1-0.3 micrograms/ml per 10(6) cells) of the lipopolysaccharide toxin (LPS) from Salmonella typhimurium were shown to increase (after an 18 h incubation) the intracellular content of free cholesterol (CH), esterified cholesterol (EC) and triglycerides (TG) by 30-40% in the primary culture of rabbit hepatocytes . A similar increase was found for the incorporation of {14C}acetate into these lipids . The concentration of lipids in cultural medium, under these conditions, was also augmented: by 30-40% for CH; by 50-60% for TG and by 60-80% for EC . Higher doses (up to 50 micrograms/ml) of LPS hardly affected the lipid content in hepatocytes but strongly (by two-fold) inhibited the secretion of lipids . It is suggested that in vivo low concentrations of LPS in bloodstream (in the absence of conspicuous pathology) might induce hyperlipidemia directly influencing on hepatic cells, while, under the higher concentrations of LPS, hyperlipidemia caused by cachectin (or tumor necrosis factor) is probably observed.

Biochemistry, 1989 Oct 3, 28(20), 8174 - 80
Salmonella typhimurium histidinol dehydrogenase: complete reaction stereochemistry and active site mapping; Grubmeyer CT et al.; The stereochemistry of the L-histidinol dehydrogenase reaction was determined to be R at NAD for both steps, confirming previous results with a fungal extract {Davies, D., Teixeira, A., & Kenworthy, P . (1972) Biochem . J . 127, 335-343} . NMR analysis of monodeuteriohistidinols produced by histidinol/NADH exchange reactions arising via reversal of the alcohol oxidation reaction indicated a single stereochemistry at histidinol for that step . Comparison of vicinal coupling values of the exchange products with those of L-alaninol and a series of (S)-2-amino-1-alcohols allowed identification of the absolute stereochemistry of monodeuteriohistidinols and showed that histidinol dehydrogenase removes first the pro-S then the pro-R hydrogens of substrate histidinol . The enzyme stereochemistry was confirmed by isotope effects for monodeuteriohistidinols as substrates for the pro-R-specific dehydrogenation catalyzed by liver alcohol dehydrogenase . Active site mapping was undertaken to investigate substrate-protein interactions elsewhere in the histidinol binding site . Critical binding regions are the side-chain amino group and the imidazole ring, whose methylation at the 1- or 2-position caused severe decreases in binding affinity . Use of alternative substrates further clarified active site interactions with the substrate . Compounds in which the alpha-amino group was replaced by chloro, bromo, or hydrogen substituents were not substrates of the overall reaction at 1/10,000 the normal rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetika, 1989 Oct, 25(10), 1740 - 6
{A comparative analysis of mutagenic and SOS-induced activity in three classes of chemical compounds}; Vasil'eva SV et al.; Mutagenic and SOS-inducing potential of 23 derivatives of fluorenone, phenanthrenequinone and biphenyl have been studied in tester strains of Salmonella typhimurium and in Escherichia coli strain PQ 37 . 14 of these compounds revert the mutation hisD3052 (much less than -1 much greater than type), but none of them induce mutations in the strain TA 1535 . Maximal mutagenic activity has been shown in strain TA 1538 for amide of 2,7-dinitrofluorenone-4-carbonic acid (580 revertants per nmol), 2,7-dinitrophenanthrenequinone (308 revertants per nmol), 2,4,7-trinitrophenanthrenequinone (306 revertants per nmol) and 2',4,4'-trinitrobiphenyl-2-carbonic acid (251 revertants per nmol) . In plasmid-containing strain TA 98 the mutagenic potential of the compounds tested is lower than in the TA 1538 strain . It has been suggested that mutagenic activity of these compounds can be attributed to their acceptor properties, namely, the ability to form charge transfer complexes with DNA . SOS-inducing activity has been shown for 5 compounds, also positive in mutation induction . Mutagenic and SOS-inducing activities positively correlate in fluorenone derivatives . Among phenanthrenequinone derivatives, compounds with high mutagenic activity only can induce SOS response . None of the biphenyls tested induce SOS functions . The compounds giving the positive result in the SOS-chromotest have rigid co-planar structure.

Klin Med (Mosk), 1989 Oct, 67(10), 108 - 11
{Immunologic status of patients with Salmonella infections}; Frolov VM et al.; Salmonella typhimurium infection was diagnosed in 186 patients aged 18-56 . The clinical picture was that of gastroenteritis (73.1%), enteritis (14.0%), gastritis (6.45%), gastroenterocolitis (6.45%) . Salmonellosis of moderate severity presented in 88.7% of patients, a severe course occurred in 11.3% . Concomitant disorders arose in 22.6% of cases . Immunological investigation disclosed T-lymphopenia, reduced number of multireceptor RFC, both T-helpers and T-suppressors . The levels of 0-lymphocytes and CIC were on the increase . Salmonellosis of long duration was characterized by hyperactivity of autoimmune reactions.

Chem Pharm Bull (Tokyo), 1989 Oct, 37(10), 2838 - 40
A mutagenic new iridoid in the water extract of catalpae fructus; Nozaka T et al.; A mutagenic principle in the water extract from Catalpae Fructus (originated from Catalpa ovata G . DON) (Bignoniaceae) was isolated and characterized as a new iridoid named catalpin . The iridoid exhibited mutagenic activity towards Salmonella typhimurium strain TA100 in the presence and absence of rat liver homogenate (S9) mix in Ames' test.

Can J Vet Res, 1989 Oct, 53(4), 378 - 84
Hybridization studies with a DNA probe derived from the virulence region of the 60 Mdal plasmid of Salmonella typhimurium; Poppe C et al.; Plasmid DNA of 68 strains of Salmonella that belonged to 18 serovars and exhibited 48 different plasmid profiles was examined for hybridization with a 32P-labelled DNA probe which consisted of a 3750 base pairs (bp) HindIII-HindIII fragment derived from the virulence region of the 60 megadalton (Mdal) plasmid of Salmonella typhimurium . The 32 Mdal plasmid of S . cholerae-suis, the 50 Mdal plasmid of S . dublin, the 36 Mdal plasmid of S . enteritidis, the 60 Mdal plasmid of S . gallinarum, the 60 Mdal plasmid of S . pullorum, and the 60 Mdal plasmid of S . typhimurium, plasmids that have been associated with virulence, all hybridized with the probe . Digestion of plasmid DNA of these strains with PvuII and hybridization with the probe revealed that the plasmids of strains of all six serovars contained fragments of approximately 2520 and 1520 bp that hybridized with the probe . Similarly, hybridization with BglI digests of DNA of the virulence-associated plasmids of strains of these six serovars showed that all six plasmids contained a fragment of approximately 3690 bp that hybridized with the probe . No other plasmids of these strains nor any plasmids of 12 other Salmonella serovars hybridized with the probe . Chromosomal DNA did not hybridize with the probe . The 60 Mdal plasmids of S . gallinarum and S . pullorum showed similar digestion patterns with restriction endonucleases BglI, BglII and PvuII.

Poult Sci, 1989 Oct, 68(10), 1357 - 60
Prevention of Salmonella typhimurium colonization of broilers with D-mannose; Oyofo BA et al.; Broiler chickens can be contaminated by Salmonella typhimurium, which is a food safety concern . It has been previously shown that D-mannose blocks S . typhimurium adherence to chicken intestine in vitro . One-day-old broiler chickens were fed normal drinking water or drinking water supplemented with 2.5% mannose for 10 days . On Day 3, both groups were challenged orally with 1 x 10(8) S . typhimurium {ST-10 (Animal Diagnostics Laboratory, Ames, IA)} resistant to Nal and Nov (Sigma, St . Louis, MO) . On Day 10 the birds' caecal contents were examined for the antibiotic-marked S . typhimurium . Two additional groups of birds were provided normal drinking water or mannose but were not challenged with the bacteria . Salmonella-challenged control chickens were 78, 82, and 93% colonized whereas Salmonella-challenged mannose-treated chickens were only 28, 21, and 43% colonized . Moreover, the mean log10 counts of control and mannose groups were significantly (P less than .001) reduced by at least 99% . Mannose-supplemented drinking water had no effect on weight gains . Certain carbohydrates may provide a means to reduce S . typhimurium contamination in broilers.

Poult Sci, 1989 Oct, 68(10), 1351 - 6
Inhibition by mannose of in vitro colonization of chicken small intestine by Salmonella typhimurium; Oyofo BA et al.; The in vitro adherence of {3H}thymidine-labeled Salmonella typhimurium isolates to the small intestine of one-day-old chickens was investigated . Bacteria were screened for mannose sensitivity and mannose-resistance binding properties . Type 1 fimbriae positive strains adhered significantly better than Type 2 fimbriae-negative strains . Adherence was significantly (P less than .05) inhibited by D-mannose, methyl-alpha-D-mannoside, arabinose, and galactose . Adherence was both time and temperature dependent . These findings suggest that the small intestine of the chicken has receptors for bacteria with Type 1 fimbriae . The function of the receptors is dependent on a mannose moiety . Bacteria adhered better to fresh intestine cells than to cells held overnight at 4 C . Thus, adherence was dependent upon a metabolically active host cell . The in vitro adherence assay may further be used to study the interaction of bacteria with chicken enterocytes.

Zentralbl Bakteriol, 1989 Oct, 271(4), 493 - 500
Enhancement of protection against Salmonella infection in mice mediated by a synthetic lipopeptide analogue of bacterial lipoprotein in S . typhimurium vaccines; Schlecht S et al.; Vaccines consisting of acetone-killed Salmonella typhimurium were supplemented with a synthetically prepared lipopeptide derivative of bacterial lipoprotein, Pam3Cys-Ser-Ser-Asn-Ala . NMRI mice were immunized with these vaccines, receiving two intraperitoneal injections and were challenged intraperitoneally with graded doses of S . typhimurium C5 . The protective capacity of the supplemented vaccines was compared with that of the unsupplemented bacterial vaccine, and with the effectiveness of the supplementing component alone . The LD50 served as a criterion for protective capacity . The results showed that 90% of the S . typhimurium S-form vaccine could be replaced by the adjuvant lipopeptide without a recognizable decrease in protective immunizing capacity . A similar but less pronounced enhancement of protection was obtained with a R-mutant vaccine supplemented with the lipopeptide; by supplementing the standard vaccine dose with lipopeptide an increase in protection was also achieved . Lipopeptide alone was not effective in protecting mice from infection with S . typhimurium.

Toxicol Lett, 1989 Oct, 49(1), 1 - 13
Protein A protects mice from depletion of biotransformation enzymes and mortality induced by Salmonella typhimurium endotoxin; Dwivedi PD et al.; Changes in hepatic microsomal mixed-function oxidase enzyme levels (aniline hydroxylase, aminopyrine demethylase, glutathione S-transferase), glutathione content, total sulphydryl content, and plasma enzyme levels of aspartate transaminase, alanine transaminase and alkaline phosphatase were studied in male Swiss albino mice exposed to Salmonella typhimurium endotoxin (50-150 micrograms per mouse, LC50 141.82 micrograms) . Animals exposed to the same dose of endotoxin but pretreated with protein A of Staphylococcus aureus (5 micrograms/per mouse) protected the animals from both mortality and depletion of biotransformation enzymes.

Epidemiol Infect, 1989 Oct, 103(2), 235 - 41
Persistence of S . typhimurium in a large dairy herd; Giles N et al.; Salmonella typhimurium 49a infection in a large dairy herd persisted for 3.5 years . Illness initially occurred in cows and calves but latterly although there were fewer clinical cases milk filters were culturally positive on 26 out of 73 samplings . Three associated human disease incidents occurred . Individual milk samples identified one cow as an excreter and the organism was recovered from the mammary gland of this animal at slaughter . Correlation between calving pattern, the times of calving and the occurrence of positive milk filters suggest that the cow may have been excreting the organism intermittently from the udder for 2.5 years.

Epidemiol Infect, 1989 Oct, 103(2), 219 - 25
A national outbreak of Salmonella typhimurium DT 124 caused by contaminated salami sticks; Cowden JM et al.; An outbreak of Salmonella typhimurium DT 124 infection which affected 101 people in England in December 1987 and January 1988 was detected through surveillance of laboratory reports from medical microbiology laboratories of the NHS and PHLS . Within 1 week of noting the increase in reports, epidemiological and microbiological investigations identified a small German salami stick as the vehicle of infection and the product was withdrawn from sale . The epidemiological investigation highlighted the occurrence of a long incubation period, bloody diarrhoea . Prompt recognition and investigation of the outbreak prevented further cases of severe infection.

Anticancer Drug Des, 1989 Oct, 4(3), 209 - 19
Bacterial mutagenicity studies of DNA-intercalating aniline mustards: an insight into the mode of action of a novel class of anti-tumour drugs; Ferguson LR et al.; Bifunctional alkylating agents are reactive compounds which work by crosslinking DNA, but which have no special affinity for it . A series of acridine-linked aniline mustards of widely-varying alkylator reactivity (5-11), designed as DNA-directed alkylating agents, have been evaluated in various strains of Salmonella typhimurium with differing DNA repair capabilities to obtain information about their mechanism of action . The compounds showed greatly increased potency (determined as D37 values) compared with the corresponding untargeted mustards, in the repair-proficient strain TA1978+ . All but the most unreactive mustards were considerably more potent (greater than 10-fold) in the corresponding repair-deficient strain TA98, indicating that DNA-crosslinking is the major cytotoxic mechanism . However, the mutagenic profile of the compounds in four Salmonella strains, particularly in the excision repair-deficient strains TA98 and TA100, suggest the compounds also form substantial levels of mutagenic monoadducts . The possibility that intercalative binding by the acridine chromophore provides an additional geometrical restraint on cross-linking by the mustard is an important facet of design which needs further study.

Proc Soc Exp Biol Med, 1989 Oct, 192(1), 81 - 6
Concanavalin A promotes adherence of Salmonella typhimurium to small intestinal mucosa of rats; Abud RL et al.; A number of dietary lectins have been shown to resist proteolytic digestion . These lectins interact with the small intestinal mucosa causing structural and functional changes . Concomitant to these changes, bacterial overgrowth was reported and a possible interaction between lectins and bacteria in the small intestine was postulated . The aim of this study was to investigate the effect of various lectins on adherence of Salmonella typhimurium to both isolated small intestinal enterocytes and ligated intestinal loops . Isolated intestinal cells or ligated intestinal loops were incubated with {3H} adenine-S . typhimurium in the presence or absence of concanavalin A, phytohemagglutinin, peanut agglutinin, and wheat germ agglutinin . Only concanavalin A promoted the adherence of various strains of nonfimbriated S . typhimurium to isolated viable intestinal cells . Other lectins showed no effect on the adherence . In situ studies showed that bacterial binding was increased in concanavalin A-treated intestinal loops, supporting the significance of the experiments in vitro . These data suggest that lectins may act by promoting bacterial adherence to the small intestine, thereby facilitating colonization and infection, and leading to bacterial overgrowth.

Mutat Res, 1989 Oct, 224(2), 219 - 27
The mutagenic activity of sodium perborate; Seiler JP; Sodium perborate (CAS No . 1333-73-9, 10486-00-7, or 13517-20-9, depending on the structural formula given) is produced in huge amounts mainly for its use as a bleaching agent in laundry detergents . Its action involves the liberation of active oxygen species at elevated temperatures . In view of the widespread use of this compound it is surprising to note that no mutagenicity test data yet exist . The investigations reported in this paper have shown that sodium perborate is indeed capable of producing mutagenic changes in a number of in vitro test systems . Its potential for inflicting damage to DNA could be demonstrated in an assay which is tailored to probe for oxidative damage induced by a chemical agent . As expected, sodium perborate proved to be able to oxidize thymidine to an appreciable extent at an incubation temperature of 80 degrees C, but even at 40 degrees C thymidine oxidation was measurable . The compound induced point mutations in the Salmonella typhimurium strains TA100 and TA102, while TA98 did not respond . Also, incubation in the presence of a mammalian auxiliary metabolic system (rat liver S9) abolished the mutagenic activity completely . Finally, Chinese hamster ovary cells (strain CHO-K1) were shown to undergo extensive chromosomal damage when treated with sodium perborate . The rather unusual prevalence of chromosome rearrangements was especially noted . Sodium perborate is thus to be regarded as a direct-acting in vitro mutagen.

J Med Microbiol, 1989 Oct, 30(2), 149 - 56
Quantification of the leucocyte influx into rabbit ileal loops induced by strains of Salmonella typhimurium of different virulence; Wallis TS et al.; Leucocyte influx into rabbit ileal loops, induced by strains of Salmonella typhimurium of different virulence, was assessed with 111Indium-labelled leucocytes . Strains fell into two groups on the basis of their leucotactic potential: "virulent" strains (which induced fluid secretion) caused a dose-dependent leucocyte influx; strains which did not induce fluid secretion failed to induce a significant leucocyte influx . Fluid secretion was never observed in the absence of leucocyte influx, but leucocyte influx per se did not induce fluid secretion . The phenotype of the challenge inoculum influenced fluid secretion; young log-phase organisms induced fluid secretion with a higher frequency than overnight cultures . These findings support earlier evidence implicating leucocytes in an interactive but not exclusive role in the genesis of salmonella-induced fluid secretion . They suggest, though do not prove, that interaction of leucocytes with the appropriate phenotype of organisms results in the release of a host-derived or bacterial secretagogue, or both . The bacterial factor may or may not be the antigen related to cholera toxin, described previously.

J Bacteriol, 1989 Oct, 171(10), 5620 - 9
Genetic and biochemical analysis of the MetR activator-binding site in the metE metR control region of Salmonella typhimurium; Urbanowski ML et al.; The Salmonella typhimurium metE and metR genes share a common control region, with overlapping, divergently transcribed promoters . A double gene fusion was constructed in which the metE promoter directs expression of the Escherichia coli lacZ gene and the metR promoter directs expression of the E . coli galK gene . By using an E . coli strain lysogenized with a lambda bacteriophage carrying the metE-lacZ metR-galK double fusion (lambda Elac.Rgal), two classes of cis-acting mutations were isolated that increase metR-galK expression . The first class of mutations causes a simultaneous decrease in metE-lacZ expression by disrupting the normal MetR-mediated activation of the metE promoter . The mutations are located within a region extending from 17 to 34 base pairs upstream of the -35 region of the metE promoter . Gel mobility shift assays and DNaseI protection experiments demonstrated that the MetR protein specifically binds to a 24-base-pair region encompassing these mutations . The second class of mutations increases metR-galK expression by directly altering the promoter consensus sequences of the metE and metR promoters.

J Bacteriol, 1989 Oct, 171(10), 5581 - 6
Nucleotide sequences of dnaE, the gene for the polymerase subunit of DNA polymerase III in Salmonella typhimurium, and a variant that facilitates growth in the absence of another polymerase subunit; Lancy ED et al.; The dnaE gene of Salmonella typhimurium, like that of Escherichia coli, encodes the alpha subunit containing the polymerase activity of the principal replicative enzyme, DNA polymerase III . This gene, or one nearby, has been identified as the locus of suppressor mutations that promote growth by cells deleted for dnaQ, the gene for the editing subunit of this enzyme complex . Using a combination of nucleotide sequencing and marker rescue experiments, the alteration in one such suppressor was identified as a valine-to-glycine substitution at amino acid 832 of the 1,160-amino-acid alpha polypeptide . The alpha polypeptides of E . coli and S . typhimurium are identical in size and in 97% of their amino acid residues . Their identity includes the valine residue that was changed in the suppressor allele of S . typhimurium . We also localized a temperature-sensitive dnaE mutation to the 3' half of dnaE.

J Bacteriol, 1989 Oct, 171(10), 5436 - 42
Pyrimidine regulation of tandem promoters for carAB in Salmonella typhimurium; Lu CD et al.; The carAB operon of Salmonella typhimurium encodes the two subunits of the enzyme carbamoylphosphate synthetase . Transcription of the operon is initiated at tandem promoters that are subject to control by pyrimidines and arginine . Pyrimidine regulation was examined by quantitative primer extension experiments under conditions in which densitometric measurements of the transcripts were linear with the amount of RNA . RNA was obtained from mutant strains that permit manipulations of pyrimidine nucleotide pools . The data showed that a uridine nucleotide repressed the upstream promoter (Pl), whereas arginine repressed the downstream promoter (P2) . Exogenous cytidine, which increased the intracellular CTP pool in certain mutant strains, did not affect either promoter . However, CTP limitation resulted in derepression of the pyrimidine-specific promoter as well as the downstream arginine-specific promoter . The effect of pyrimidines on P2 was confirmed in a carA::lacZ transcriptional fusion in which the activity of the pyrimidine-specific promoter was abolished . Primer extension experiments with an argR::Tn10 derivative showed that repression of Pl by uridine nucleotides did not require a functional arginine repressor and that repression of P2 by arginine did not interfere with elongation of transcripts initiated at the upstream Pl promoter.

J Bacteriol, 1989 Oct, 171(10), 5339 - 46
Cloning and nucleotide sequence of DNA mismatch repair gene PMS1 from Saccharomyces cerevisiae: homology of PMS1 to procaryotic MutL and HexB; Kramer W et al.; The PMS1 gene from Saccharomyces cerevisiae, implicated in DNA mismatch repair in yeast cells (M . S . Williamson, J . C . Game, and S . Fogel, Genetics 110:609-646, 1985), was cloned, and the nucleotide sequence was determined . The nucleotide sequence showed a 2,712-base-pair open reading frame; the predicted molecular mass of the deduced protein is 103 kilodaltons . Deletion mutants of the open reading frame were constructed and genetically characterized . The deduced amino acid sequence of the PMS1 gene exhibited homology to those of the mutL gene from Salmonella typhimurium and the hexB gene from Streptococcus pneumoniae, genes required for DNA mismatch repair in these organisms . The homology suggests an evolutionary relationship of DNA mismatch repair in procaryotes and eucaryotes.

J Bacteriol, 1989 Oct, 171(10), 5332 - 8
Nucleotide sequence of the Streptococcus pneumoniae hexB mismatch repair gene: homology of HexB to MutL of Salmonella typhimurium and to PMS1 of Saccharomyces cerevisiae; Prudhomme M et al.; The Hex mismatch repair system of Streptococcus pneumoniae acts both during transformation (a recombination process that directly produces heteroduplex DNA) to correct donor strands and after DNA replication to remove misincorporated nucleotides . The hexB gene product is one of at least two proteins required for mismatch repair in this organism . The nucleotide sequence of a 2.7-kilobase segment from the S . pneumoniae chromosome that includes the 1.95-kilobase hexB gene was determined . The gene encodes a 73.5-kilodalton protein (649 residues) . The spontaneous hex Rx chromosomal mutant allele with which a mutator phenotype has been associated is shown to result from a single base substitution (TAC to TAA) leading to a truncated HexB polypeptide (484 residues) . The HexB protein is homologous to the MutL protein, which is required for methyl-directed mismatch repair in Salmonella typhimurium and Escherichia coli, and to the PMS1 gene product, which is likely to be involved in a mismatch correction system in Saccharomyces cerevisiae . The conservation of HexB-like proteins among procaryotic and eucaryotic organisms indicates that these proteins play an important common role in the repair process . This finding also suggests that the Hex, Mut, and PMS systems evolved from a common ancestor and that functionally similar mismatch repair systems could be widespread among procaryotic as well as eucaryotic organisms.

J Bacteriol, 1989 Oct, 171(10), 5325 - 31
Nucleotide sequence of the Salmonella typhimurium mutL gene required for mismatch repair: homology of MutL to HexB of Streptococcus pneumoniae and to PMS1 of the yeast Saccharomyces cerevisiae; Mankovich JA et al.; The mutL gene of Salmonella typhimurium LT2 is required for dam-dependent methyl-directed DNA mismatch repair . We have cloned and sequenced the mutL gene of S . typhimurium LT2 and compared its sequence with those of the hexB gene product of the gram-positive bacterium Streptococcus pneumoniae and the PMS1 gene product of the yeast Saccharomyces cerevisiae . MutL was found to be quite similar to the HexB mismatch repair protein of S . pneumoniae and to the mismatch repair protein PMS1 of the yeast S . cerevisiae . The significant similarities among these proteins were confined to their amino-terminal regions and suggest common evolution of the mismatch repair machinery in those organisms . The DNA sequence for mutL predicted a gene encoding a protein of 618 amino acid residues with a molecular weight of 67,761 . The assignment of reading frame was confirmed by the construction of a chimeric protein consisting of the first 30 amino acids of LacZ fused to residues 53 through 618 of MutL . Interestingly, the presence of excess amounts of this fusion protein in wild-type mutL+ cells resulted in a trans-dominant effect causing the cell to exhibit a high spontaneous mutation frequency.

Carcinogenesis, 1989 Oct, 10(10), 1953 - 5
Modulating effect of plant flavonoids on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine; Francis AR et al.; Tests have been carried out with several plant flavonoids to detect their ability to suppress mutagenesis in Salmonella typhimurium strain TA100 NR induced by the direct-acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine . Among the most effective flavonoids are the isoflavone, biochanin A, the flavanone glycoside, naringin, and its aglycone, naringenin, and several flavonols, e.g . morin, fisetin, kaempferol, gossypetin and quercetin, including a flavonol glycoside, rutin . In particular, naringin possesses exceptional antimutagenic activity, in as much as, less than half the equimolar amount can reduce the mutagenic potency of this carcinogen by 50% . These flavonoids appear to act either by preventing passage of the carcinogen into bacterial cells or by altering some cellular processes.

Mutat Res, 1989 Oct, 224(2), 229 - 33
Evaluation of the mutagenicity and the tumor-promoting activity of parasite extracts: Schistosoma japonicum and Clonorchis sinensis; Ishii A et al.; In relation to the observed association of carcinogenesis with parasitic infections, the mutagenicity of extracts of Schistosoma japonicum and Clonorchis sinensis was examined . In the bacterial mutagenicity tests using the Ames Salmonella typhimurium strains TA98, TA100, TA97 and TA102, and Escherichia coli WP2 and WP2 uvrA pKM101 Schistosoma soluble egg antigen and a homogenate of adult Schistosoma worms showed no positive responses either in the presence or in the absence of S9 mix . Likewise, adult worm extracts of Clonorchis showed no mutagenicity . The Schistosoma soluble egg antigen showed a weak but significant activity for the induction of Epstein-Barr virus expression in viral genome-carrying human lymphoblastoid cells in culture . This phenomenon suggests that the soluble egg antigen possesses tumor-promoting activity.

J Bacteriol, 1989 Oct, 171(10), 5572 - 80
Isolation and characterization of mutants with deletions in dnaQ, the gene for the editing subunit of DNA polymerase III in Salmonella typhimurium; Lancy ED et al.; dnaQ (mutD) encodes the editing exonuclease subunit (epsilon) of DNA polymerase III . Previously described mutations in dnaQ include dominant and recessive mutator alleles as well as leaky temperature-sensitive alleles . We describe the properties of strains bearing null mutations (deletion-substitution alleles) of this gene . Null mutants exhibited a growth defect as well as elevated spontaneous mutation . As a consequence of the poor growth of dnaQ mutants and their high mutation rate, these strains were replaced within single colonies by derivatives carrying an extragenic suppressor mutation that compensated the growth defect but apparently not the mutator effect . Sixteen independently derived suppressors mapped in the vicinity of dnaE, the gene for the polymerization subunit (alpha) of DNA polymerase III, and one suppressor that was sequenced encoded an altered alpha polypeptide . Partially purified DNA polymerase III containing this altered alpha subunit was active in polymerization assays . In addition to their dependence on a suppressor mutation affecting alpha, dnaQ mutants strictly required DNA polymerase I for viability . We argue from these data that in the absence of epsilon, DNA replication falters unless secondary mechanisms, including genetically coded alteration in the intrinsic replication capacity of alpha and increased use of DNA polymerase I, come into play . Thus, epsilon plays a role in DNA replication distinct from its known role in controlling spontaneous mutation frequency.

Bioorg Khim, 1989 Oct, 15(10), 1375 - 83
{Synthesis of cytidine diphosphate-3,6-dideoxyhexoses--donors of glycosyl residues in the biosynthesis of O-specific polysaccharides of Salmonella of serogroups A, B and C}; Utkina NS et al.; Interaction of lithium alcoholates of 2,4-di-O-benzoates of paratose and abequose with tetrabenzyl pyrophosphate gave alpha-phosphates of the 3,6-dideoxyhexoses, further converted into the corresponding cytidine-5'-diphosphate derivatives . These synthetic nucleotides were shown to participate in the biosynthesis of the O-specific polysaccharides for Salmonella typhimurium and S . nitra.

J Biol Chem, 1989 Sep 25, 264(27), 15796 - 808
Characterization of the flavoprotein moieties of NADPH-sulfite reductase from Salmonella typhimurium and Escherichia coli . Physicochemical and catalytic properties, amino acid sequence deduced from DNA sequence of cysJ, and comparison with NADPH-cytochrome P-450 reductase; Ostrowski J et al.; NADPH-sulfite reductase flavoprotein (SiR-FP) was purified from a Salmonella typhimurium cysG strain that does not synthesize the hemoprotein component of the sulfite reductase holoenzyme . cysJ, which codes for SiR-FP, was cloned from S . typhimurium LT7 and Escherichia coli B, and both genes were sequenced . Physicochemical analyses and deduced amino acid sequences indicate that SiR-FP is an octamer of identical 66-kDa peptides and contains 4 FAD and 4 FMN per octamer . Potentiometric titrations of SiR holoenzyme, SiR-FP, and FMN-depleted SiR-FP yielded the following redox potentials for the prosthetic groups at pH 7.7: E'1 (FMNH./FMN) = -152 mV; E'2 (FMNH2/FMNH.) = -327 mV; E'3 (FADH./FAD) = -382 mV; E'4 (FADH2/FADH.) = -322 mV . Microcoulometric titration of SiR-FP at 25 degrees C yielded data which were in full agreement with these potentials . Spectroscopic and catalytic studies of native SiR-FP and of SiR-FP depleted of FMN support the following electron flow sequence: NADPH----FAD----FMN . FMN can then contribute electrons to the hemoprotein component of sulfite reductase, as well as to cytochrome c and various diaphorase acceptors . The FMN is postulated to cycle between the FMNH2 and FMNH . oxidation states during catalysis; in this sense SiR-FP shares a catalytic mechanism with NADPH-cytochrome P-450 oxidoreductase . SiR-FP domains involved in binding FMN, FAD, and NADPH are proposed from amino acid sequence homologies with Desulfovibrio vulgaris flavodoxin (Dubourdieu, M., and Fox, J.L . (1977) J . Biol . Chem . 252, 1453-1463) and spinach ferredoxin-NADP+ oxidoreductase (Karplus, P.A., Walsh, K.A., and Herriott, J . R . (1984) Biochemistry 23, 6576-6583) . Comparison of the deduced amino acid sequences of SiR-FP and NADPH-cytochrome P-450 oxidoreductase (Porter, T . D., and Kasper, C.B . (1985) Proc . Natl . Acad . Sci . U . S.A . 82, 973-977) also showed identities that suggest these two proteins are descended from a common precursor, which contained binding regions for both FMN and FAD.

J Biol Chem, 1989 Sep 25, 264(27), 15774 - 80
Microspectrophotometric studies on single crystals of the tryptophan synthase alpha 2 beta 2 complex demonstrate formation of enzyme-substrate intermediates; Mozzarelli A et al.; Microspectrophotometry of single crystals of the tryptophan synthase alpha 2 beta 2 complex from Salmonella typhimurium is used to compare the catalytic and regulatory properties of the enzyme in the soluble and crystalline states . Polarized absorption spectra demonstrate that chromophoric intermediates are formed between pyridoxal phosphate at the active site of the beta subunit and added substrates, substrate analogs, and reaction intermediate analogs . Although the crystalline and soluble forms of the enzyme produce some of the same enzyme-substrate intermediates, including Schiff base and quinonoid intermediates, in some cases the equilibrium distribution of these intermediates differs in the two states of the enzyme . Ligands which bind to the active site of the alpha subunit alter the distribution of intermediates formed at the active site of the beta subunit in both the crystalline and soluble states . The three-dimensional structures of the tryptophan synthase alpha 2 beta 2 complex and of a derivative with indole-3-propanol phosphate bound at the active site of the alpha subunit have recently been reported (Hyde, C . C., Ahmed, S . A., Padlan, E . A., Miles, E . W., and Davies, D . R . (1988) J . Biol . Chem . 264, 17857-17871) . Our present findings help to establish experimental conditions for selecting defined intermediates for future x-ray crystallographic analysis of the alpha 2 beta 2 complex with ligands bound at the active sites of both alpha and beta subunits . These crystallographic studies should explain how catalysis occurs at the active site of the beta subunit and how the binding of a ligand to one active site affects the binding of a ligand to the other active site which is 25 A away.

Nature, 1989 Sep 21, 341(6239), 245 - 8
Adaptive eradication of methionine and cysteine from cyanobacterial light-harvesting proteins; Mazel D et al.; Sulphur is unique among the main elements of living cells in that it is covalently bound to biopolymers but does not occur in the biopolymer backbone . Indeed, most of the bacterial sulphur content resides in the methionine and cysteine side-chains of proteins . The growth yield of an organism under conditions of sulphur limitation could therefore be greatly enhanced by mutations that substitute Met and Cys in the organism's proteins for sulphur-free amino acids . Because the saving in sulphur would increase with such accumulating mutations, Met and Cys changes could be progressively selected . Abundant proteins should be the prime targets of such a selection . A few published observations give credence to this scenario . Sulphate permease, which is abundantly produced by sulphur-starved Salmonella typhimurium, lacks Met and Cys residues . Also, two species of marine purple bacteria synthesize more protein than can be expected from a limited sulphate supply . We now report that the cyanobacterium Calothrix sp . PCC 7601 (referred to here as Calothrix) encodes sulphur-depleted versions of its most abundant proteins--phycocyanin and its auxiliary polypeptides--which it specifically expresses under conditions of sulphur limitation . Although these proteins do not take part in the fixation of sulphur, their elevated synthesis affects the sulphur budget of cyanobacterial cells . Direct evidence is thus provided that the structure of macromolecules can be subject to metabolic optimization.

J Biol Chem, 1989 Sep 15, 264(26), 15726 - 37
Characterization of the cysJIH regions of Salmonella typhimurium and Escherichia coli B . DNA sequences of cysI and cysH and a model for the siroheme-Fe4S4 active center of sulfite reductase hemoprotein based on amino acid homology with spinach nitrite reductase; Ostrowski J et al.; The hemoprotein component of Salmonella typhimurium sulfite reductase (NADPH) (EC 1.8.1.2) was purified to homogeneity from cysJ266, a mutant strain lacking sulfite reductase flavoprotein . The siroheme- and Fe4S4-containing enzyme was isolated as a monomeric 63-kDa polypeptide and consisted of a mixture of unligated enzyme and a complex with sulfite . Following reduction with 5'-deazaflavin-EDTA and reoxidation, the complex was converted to the uncomplexed, high spin ferri-siroheme state seen previously with Escherichia coli sulfite reductase hemoprotein preparations . The S . typhimurium hemoprotein exhibited catalytic and physical properties identical to the hemoprotein prepared by urea dissociation of E . coli sulfite reductase holoenzyme and was fully competent in reconstituting NADPH-sulfite reductase activity when combined with excess purified sulfite reductase flavoprotein . The DNA sequences of cysI and cysH from S . typhimurium and E . coli B were determined and, together with previously reported data, confirmed the organization of this region as promoter-cysJ-cysI-cysH with all three genes oriented in the same direction from the promoter . Molecular weights deduced for the cysI-encoded sulfite reductase hemoprotein and for the cysH-encoded 3'-phosphoadenosine 5'-phosphosulfate sulfotransferase were approximately 64,000 and 28,000, respectively . Comparison of the deduced amino acid sequence of sulfite reductase hemoprotein with that of spinach nitrite reductase (Back, E., Burkhart, W., Moyer, M., Privalle, L., and Rothstein, S . (1988) Mol . Gen . Genet . 212, 20-26), which also contains siroheme and an Fe4S4 cluster, showed two groups of cysteine-containing sequences with the structures Cys-(X)3-Cys and Cys-(X)5-Cys, which are homologous in the two enzymes and are postulated to provide the ligands of the Fe4S4 cluster in both proteins . From these sequences and from crystallographic (McRee, D . E., Richardson, D . C., Richardson, J . S., and Siegel, L . M . (1986) J . Biol . Chem . 261, 10277-10281) and spectroscopic data in the literature, a model is proposed for the structure of the active center of these two enzymes.

Cancer Lett, 1989 Sep 15, 47(1-2), 37 - 44
Effect of tannic acid on rat liver S9 mediated mutagenesis, metabolism and DNA binding of benzo{a}pyrene; Vance RE et al.; Tannic acid, a naturally occurring plant phenol, inhibited rat liver S9 mediated mutagenesis of benzo{a}pyrene in Salmonella typhimurium by 32-77% at concentrations of 5-50 micrograms/mutagenesis plate . Tannic acid (10-40 microM) had no affect on the formation of organosoluble metabolites of benzo{a}pyrene or of its water-soluble conjugates . It did, however, inhibit benzo{a}pyrene (B{a}P) metabolite binding to calf thymus DNA by 40% at a concentration of 40 microM and inhibited benzo{a}pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE): deoxyguanosine adduct formation in calf thymus DNA by 12-54% at concentrations of 10-40 microM . These results suggest that the antimutagenic effect of tannic acid and inhibition of B{a}P metabolite binding to DNA is by a previously described scavenging mechanism and/or by a DNA-affinity binding mechanism that prevents BPDE interaction with DNA as previously described for ellagic acid.

J Mol Biol, 1989 Sep 5, 209(1), 127 - 33
Terminal regions of flagellin are disordered in solution; Vonderviszt F et al.; Limited proteolysis of flagellin from Salmonella typhimurium SJW1103 by subtilisin, trypsin and thermolysin results in homologous degradation patterns . The terminal regions of flagellin are very sensitive to proteolysis . These parts are degraded into small oligopeptides at the very early stage of a mild digestion that yields a relatively stable fragment with a molecular weight of 40,000 . Further proteolytic degradation results in a stable 27,000 Mr fragment . The 40,000 Mr tryptic fragment has been identified as residues 67 to 446 of the flagellin sequence, while the 27,000 Mr fragment involves the 179 to 418 segment . The NH2-terminal sequence positions for the corresponding fragments produced by subtilisin are 60 and 174 for the 40,000 Mr and 27,000 Mr fragments, respectively . The fragments lost their polymerizing ability . Structural properties of flagellin and its 40,000 Mr tryptic fragment were compared by circular dichroism spectroscopy and differential scanning calorimetry . Analysis of the calorimetric melting profiles suggests that terminal parts of flagellin have no significant internal stability and they are in extensive contact with water . However, these regions contain some secondary structure, probably alpha-helices, as revealed by comparison of the circular dichroic spectra in the far-ultraviolet region . Our results indicate that, although the terminal regions of flagellin may contain some alpha-helical secondary structure of marginal stability, they have no compact ordered tertiary structure in solution . On the contrary, the central region of the molecule involves at least two compact structural units.

J Biol Chem, 1989 Sep 5, 264(25), 14716 - 22
Inhibition of lipopolysaccharide O-antigen synthesis by colicin M; Harkness RE et al.; Colicin M inhibits peptidoglycan biosynthesis at the level of the bactoprenyl carrier lipid . Since the synthesis of O-antigen also requires bactoprenyl carrier lipid, the effect of colicin M on O-antigen biosynthesis was studied using a colicin-sensitive strain of Salmonella typhimurium . Determination of O-antigen intermediates by two different methods showed that bactoprenyl-dependent O-antigen biosynthesis was inhibited by colicin M . Synthesis of both O-antigen and peptidoglycan was almost immediately inhibited following colicin addition . This was followed some 20 min later by cell lysis . The only known common step between O-antigen and peptidoglycan synthesis is formation of bactoprenyl phosphate by dephosphorylation of bactoprenyl pyrophosphate . Determination of bactoprenyl phosphates showed an accumulation of bactoprenyl pyrophosphate in colicin-treated cultures . It was concluded that dephosphorylation of the bactoprenyl lipid carrier was inhibited by colicin M, and this in turn prevented both O-antigen and peptidoglycan synthesis.

Immunol Lett, 1989 Sep, 22(3), 195 - 8
The absence of direct antimicrobial activity in extracts of cytotoxic lymphocytes; Joag S et al.; An important mechanism used by the immune system in resisting infections by intracellular pathogens is the destruction of host cells by cytolytic lymphocytes . Whether these lymphocytes display a more direct antimicrobial action remains unclear . We have attempted to answer this question by testing extracts of cytolytic lymphocytes, prepared by cell fractionation, against three bacterial species - Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes . We also tested these extracts against two viruses - pseudorabies virus and vesicular stomatitis virus . The extracts showed negligible activity against the test organisms under the conditions used.

Gene, 1989 Sep 1, 81(1), 73 - 82
Molecular characterization of TRP1, a gene coding for tryptophan synthetase in the basidiomycete Coprinus cinereus; Skrzynia C et al.; We utilized a cloned gene (TRP5) encoding tryptophan synthetase (TSase) from Saccharomyces cerevisiae to identify and clone the corresponding gene (TRP1) from the basidiomycete Coprinus cinereus . The primary nucleotide (nt) sequence of this gene was determined and compared to sequences from other filamentous fungi, as well as to other genes coding for TSase . A transformation assay was used to demonstrate that 321 nt, which do not include CAAT or TATAAA elements and precede the translation initiation codon, are sufficient for expression in a variety of chromosomal locations . The coding region (2584 nt) is interrupted at nine positions, and putative splicing signals (5'-GTRNGT...YAG-3') are present in each case . The predicted translation product contains 702 amino acids (aa) and is very similar to other TSases, except in the region of aa 257-296 that connects the alpha and beta functional domains . Both the number and the identity of the aa differ in this region between C . cinereus . S . cerevisiae, and Neurospora crassa . Comparison of exon boundaries in the C . cinereus sequence to the three-dimensional structure of Salmonella typhimurium TSase indicates that there is no simple correlation between exons and major functional domains in this protein.

FEMS Microbiol Rev, 1989 Sep, 5(3), 265 - 76
Peptidases and proteases of Escherichia coli and Salmonella typhimurium; Lazdunski AM; A number of peptidases and proteases have been identified in Escherichia coli . Although their specific physiological roles are often not known, some of them have been shown to be involved in: the maturation of nascent polypeptide chains; the maturation of protein precursors; the signal peptide processing of exported proteins; the degradation of abnormal proteins; the use of small peptides as nutrients; the degradation of colicins; viral morphogenesis; the inactivation of some regulatory proteins for which a limited lifetime is a physiological necessity . Some of these enzymes act in concert to carry out specific functions . At present, twelve peptidases and seventeen proteases have been characterized . The specificity for only a few of them is known . The possible roles and the properties of these enzymes are discussed in this review.

J Gen Microbiol, 1989 Sep, 135 ( Pt 9), 2561 - 7
Transformation in restriction-deficient Salmonella typhimurium LT2; Tsai SP et al.; Stable restriction-deficient, modification-proficient galE (JR501) and F'galE+ (JR502) strains of Salmonella typhimurium were constructed and the effects of restriction on transformation by plasmid pBR322 were tested . Several factors which affect transformation efficiency were systematically examined to determine optimum transformation conditions and a simplified method is presented.

Microb Pathog, 1989 Sep, 7(3), 165 - 73
Identification and genetic analysis of mkaA--a gene of the Salmonella typhimurium virulence plasmid necessary for intracellular growth; Taira S et al.; Salmonella typhimurium, like many other Salmonella serovars, harbours a large plasmid required for mouse virulence and growth of bacteria in host cells . The nature of one virulence-abolishing Tn5 insertion (zzx-2556::Tn5) in the plasmid was characterized . A 3.7 kb insert harbouring this region was cloned in pBR325 . Plasmid-directed protein synthesis in minicells indicated that the transposon had eliminated the expression of a 70 kDa protein encoded by the virulence plasmid . Nucleotide sequence analysis of the corresponding wild type DNA region showed a 1773 bp open reading frame (mkaA), encoding a protein of 591 amino acid residues and a predicted molecular mass of 60.6 kDa; zzx-2556::Tn5 was situated within mkaA.

J Nat Prod, 1989 Sep-Oct, 52(5), 1118 - 27
Abrusosides A-D, four novel sweet-tasting triterpene glycosides from the leaves of Abrus precatorius; Choi YH et al.; In addition to abrusoside A {1}, abrusosides B {2}, C {3}, and D {4}, three further sweet glycosides based on the novel cycloartane-type aglycone, abrusogenin {5}, were isolated from an n-BuOH-soluble extract of the leaves of Abrus precatorius . Using a combination of spectral methods, the structures of compounds 1-4 were assigned, respectively, as the 3-O-beta-D-glucopyranosyl, the 3-O-beta-D-glucopyranosyl-(1----2)-beta-D-6-methylglucuronopyranosyl+ ++, the 3-O-beta-D-glucopyranosyl-(1----2)-beta-D-glucopyranosyl, and the 3-O-beta-D-glucopyranosyl-(1----2)-beta-D-glucuronopyranosyl derivatives of compound 5 . After it established that compounds 1-4 were neither acutely toxic with mice nor mutagenic with Salmonella typhimurium strain TM677, they were found by a human taste panel to exhibit sweetness potencies in the range 30-100 times greater than sucrose.

J Nat Prod, 1989 Sep-Oct, 52(5), 1092 - 9
Plant antimutagenic agents, 7 . Structure and antimutagenic properties of cymobarbatol and 4-isocymobarbatol, new cymopols from green alga (Cymopolia barbata); Wall ME et al.; Two new compounds, cymobarbatol and 4-isocymobarbatol, were isolated from the marine alga Cymopolia barbata . The complete structures and absolute stereochemistries of these compounds were elucidated by a variety of spectroscopic techniques and X-ray crystallography . Both compounds were found to be nontoxic over a broad concentration range to Salmonella typhimurium strains T-98 and T-100 . Both compounds exhibited strong inhibition of the mutagenicity of 2-aminoanthracene and ethyl methanesulfonate toward, respectively, the T-98 strain plus a metabolic activator and T-100.

Infection, 1989 Sep-Oct, 17(5), 306 - 8
Salmonella typhimurium infection of thoracic aorta aneurysm in immunocompetent subject . Case report and literature review; Gabbi E et al.; The authors describe a Salmonella typhimurium infection of thoracic aorta aneurysm in an immunocompetent subject . The patient, a 62-year-old male, was found to have recurrent S . typhimurium bacteremia despite multiple antibiotic treatments . A roentgenogram of the chest, which was normal on admission, revealed the presence of a first arch enlargement of the heart shadow . A computed tomography confirmed the diagnosis . Surgical resection of the aneurysm was carried out with in situ prosthetic graft interposition . The surgical specimen culture yielded S . typhimurium . The postoperative course was uneventful . Twenty-four months after discharge the patient remained well . A review of English language literature is presented.

Mutagenesis, 1989 Sep, 4(5), 371 - 6
Relevance of plasmid pKM101-mediated mutagenicity in bacteria to genotoxicity in mammalian cells; Little CA et al.; Three structurally related compounds, 4-acetoxy-3-acetoxy-methyl-acetophenone (AAMAP), 1-{4'-hydroxy-3'-hydroxy-methylphenyl}-2-{benzyl-t-butylamino} ethanone hydrochloride (HHBEH) and 1-{4'-hydroxy-3'-hydroxymethyl-phenyl}-2-{benzyl-t-butylamino} ethanol (HHBE), gave positive dose-related mutagenic responses in the Ames test when Salmonella typhimurium strain TA100 was used as the test organism . Strain TA100 carries the hisG46 allele, which is revertable by base changes, together with plasmid pKM101, which encodes mucAB genes that are analogous to umuDC, the chromosomal SOS-repair genes of Escherichia coli K-12 . None of the compounds was mutagenic in Ames strain TA1535, which is the plasmid-free derivative of strain TA100 . Only AAMAP, and that at only the highest concentration tested, was mutagenic in strain TA98, which detects frameshift mutations and carries plasmid pKM101 . No compound was significantly mutagenic in strain TA1538, which is the plasmid-free derivative of strain TA98 . When the three compounds were tested for the induction of sister-chromatid exchanges (SCEs) in Chinese hamster cells, the two more potent mutagens, AAMAP and HHBEH were found to increase SCEs, whereas HHBE did not give a significant response at any concentration tested . Ames test data showing plasmid pK101-dependent mutagenesis are therefore, at least for these compounds, relevant indicators of eukaryotic genotoxicity.

Mutagenesis, 1989 Sep, 4(5), 355 - 60
Comparative genotoxicities of procarbazine and two deuterated analogs in mammalian cells in vitro and in vivo; Holme JA et al.; N-isopropyl-alpha-(2-methylhydrazino)-p-toluamide hydrochloride (procarbazine; 50-1000 micrograms/ml) induced DNA damage in hepatocytes measured by an automated alkaline elution method, whereas no significant increase in unscheduled DNA synthesis was seen . In hepatocytes isolated from PCB-treated rats, DNA damage was detected in both test systems at concentrations as low as 1-10 micrograms/ml . DNA damage, as measured by alkaline elution and sister-chromatid exchange(s), was observed also in V79 cells incubated with PCB-hepatocytes . In contrast, no mutagenic activity was observed in the Salmonella typhimurium strain TA1530 co-incubated with the hepatocytes . Exposure of rats to low doses of procarbazine (25-50 mg/kg) caused DNA damage measured by alkaline elution in liver and testis, with the liver being somewhat more sensitive . The genotoxicity caused by procarbazine was increased by a factor of 2-3 in both organs by PCB-treatment of the rats . N-isopropyl-alpha-(2-methyl-hydrazino)-p-{alpha,alpha-2H2}toluamide (d2-procarbazine), was found to cause significantly less genotoxicity in control rats than either procarbazine itself, or N-isopropyl-alpha-(2-{alpha,alpha,alpha-2H3}methylhydrazino)-p-tol uamide (d3-procarbazine) . This indicates that benzylic C-H oxidation of procarbazine is an important step in the activation of procarbazine to genotoxic metabolites in uninduced rats.

Mutagenesis, 1989 Sep, 4(5), 335 - 42
Optimization of metabolic activation for four mutagens in a bacterial, fungal and two mammalian cell mutagenesis assays; Rees RW et al.; The optimum concentrations of Aroclor-induced rat liver S9 microsomal fraction for the mutagenic activity of the four standard mutagens 2-aminofluorene (2-AF), acriflavine (ACR), benzo{a}pyrene (BP) and cyclophosphamide (CP) were determined in four mutation assays . The four assays were the Ames test using Salmonella typhimurium strain TA100, cycloheximide resistance in the yeast Saccharomyces cerevisiae, the mouse lymphoma TK assay and the human peripheral lymphocyte cytogenetic assay . BP was the only mutagen to be most active at comparable S9 concentrations, of approximately 1%, for all four assays . The optimum S9 concentrations for each of the remaining three mutagens varied substantially between the four assays . ACR was a potent direct-acting mutagen in both mammalian cell assays . The mouse lymphoma TK assay results showed similar optimal values of 1.5% S9 or below for each of the four test agents . The assay with the largest variation of optimal S9 values for the four mutagens was the Ames test in strain TA100, although it also had the widest peaks of activity over the range of S9 concentrations tested . It is likely that the diversity of findings is due to a variety of metabolites affecting the different genetic endpoints that are measured in these assays . Thus from these results it is not possible for bacterial optimization data to be related to other routine in vitro systems . The use of more than one concentration of S9 would contribute useful information.

Antimicrob Agents Chemother, 1989 Sep, 33(9), 1549 - 52
Aminoglycoside uptake increased by tet gene expression; Merlin TL et al.; The expression of extrachromosomal tet genes not only confers tetracycline resistance but also increases the susceptibilities of gram-negative bacteria to commonly used aminoglycoside antibiotics . We investigated the possibility that tet expression increases aminoglycoside susceptibility by increasing bacterial uptake of aminoglycoside . Studies of {3H}gentamicin uptake in paired sets of Escherichia coli HB101 and Salmonella typhimurium LT2 expressing and not expressing tet showed that tet expression accelerates energy-dependent {3H}gentamicin uptake . Increased {3H}gentamicin uptake was accompanied by decreased bacterial protein synthesis and bacterial growth . Increased aminoglycoside uptake occurred whether tet expression was constitutive or induced, whether the tet gene was class B or C, and whether the tet gene was plasmid borne or integrated into the bacterial chromosome . tet expression produced no measurable change in membrane potential, suggesting that tet expression increases aminoglycoside uptake either by increasing the availability of specific carriers or by lowering the minimum membrane potential that is necessary for uptake.

Antimicrob Agents Chemother, 1989 Sep, 33(9), 1540 - 3
Treatment of experimental salmonellosis in mice with ampicillin-bound nanoparticles; Fattal E et al.; We tested the effectiveness of ampicillin bound to nanoparticles of polyisohexylcyanoacrylate (PIHCA) in treating C57BL/6 mice experimentally infected with Salmonella typhimurium C5 . The diameter of the nanoparticles was 187 +/- 13 nm, and the ampicillin/PIHCA ratio was 0.2/1 . The proportion of ampicillin bound was 90 +/- 3% . All control mice and all those treated with nonloaded nanoparticles died within 10 days of infection . By contrast, all mice treated with a single injection of 0.8 mg of nanoparticle-bound ampicillin survived . With free ampicillin, a similar curative effect required three doses of 32 mg each . Lower doses delayed but did not reduce mortality . The sharp increase in the therapeutic index of ampicillin after linkage to PIHCA nanoparticles was explained by studies of the distribution of ampicillin, which showed that when bound to nanoparticles, the ampicillin was concentrated mainly in the liver and spleen, the primary foci of infection in the experimental model that we used . These findings warrant further development of intracellular targeting of antibiotics on biodegradable polymeric carriers such as PIHCA.

Vet Immunol Immunopathol, 1989 Sep, 22(2), 135 - 44
Comparison of Mycoplasma gallisepticum subunit and whole organism vaccines containing different adjuvants by western immunoblotting; Barbour EK et al.; Chickens were vaccinated with subunit (adhesin protein) or whole organisms of Mycoplasma gallisepticum (MG) adjuvanted with multilamellar positively charged liposomes or oil-emulsion . Sera were collected before and following the first (13 weeks of age) and second (17 weeks of age) vaccination . The chicken sera were used in western immunoblotting against whole MG polypeptides . Vaccination with the subunit (MG-adhesin) bacterin containing positively charged liposomes resulted in antibody response specific to adhesin band (75 kD) at 3 weeks post the first and second vaccination; however, crossreactions of the same antibodies occurred to MG proteins of 85 kD (3 weeks after the first vaccination) and 56 kD (3 weeks after the second vaccination) . Vaccination with whole MG proteins containing positively charged liposomes resulted in significant immunopotentiation of antibodies against low molecular weight polypeptides of MG (less than 48.0 kD) . The addition of Salmonella typhimurium cell wall proteins mitogens (STP) to the different bacterins suppressed the antibody responses to some MG polypeptides.

Genetics, 1989 Sep, 123(1), 19 - 28
Role of gene duplications in the adaptation of Salmonella typhimurium to growth on limiting carbon sources; Sonti RV et al.; Duplication-containing cells are selected when growth of Salmonella typhimurium is limited by the availability of any one of several carbon and energy sources . Under conditions of extreme starvation, growth occurs almost exclusively in the duplication-containing fraction of the population . Cells with duplications of one large segment of the chromosome are repeatedly selected regardless of which of these carbon sources limits growth . The duplicated chromosomal segment encodes the transport systems for all of these carbon sources . This duplication is not selected during growth on a carbon source for which the permease is not included within the duplication segment . This suggests that the growth advantage conferred by the duplication may be due to increased transport of the limiting carbon source . Inclusion of the permease alone is not sufficient to explain the growth advantage of the duplications, since other common duplications that include the permease are not selected.

Clin Ther, 1989 Sep-Oct, 11(5), 701 - 4
Investigation of 11 strains of Salmonella typhimurium on plasmids by agarose gel electrophoresis; Cosar G; Gel electrophoresis of deoxyribonucleic acid from 11 clinical isolates of Salmonella typhimurium resistant to antibiotics revealed plasmids of different sizes . Most of the plasmids ranging in size from 13 kilobase pairs to 4.360 base pairs were present (1,500 base pairs = 1 megadalton) . Some of the plasmids were smaller than 4.360 base pairs.

Appl Environ Microbiol, 1989 Sep, 55(9), 2344 - 8
Preliminary characterization of a food-borne multiple-antibiotic-resistant Salmonella typhimurium strain; Schuman JD et al.; Plasmid characterization studies were conducted on a Salmonella typhimurium strain isolated from pasteurized milk and from a symptomatic patient during the 1985 Illinois salmonellosis outbreak . This strain (Hf) was reported to possess an unusual plasmid profile which distinguished it from all Salmonella strains isolated in the United States prior to 1984 . Antibiotic susceptibility testing revealed that the strain was resistant to tetracycline, erythromycin, clindamycin, sulfisoxazole, sulfadiazene, triple sulfa, cefoperazone, streptomycin, mezlocillin, piperacillin, carbenicillin, penicillin, ampicillin, and kanamycin . Plasmid analysis revealed that the strain possessed four plasmids with sizes of approximately 158, 98, 10.2, and 6.0 kilobase pairs (kb) . Successive transfer at 43 degrees C led to increased antibiotic sensitivity in 75.5% of the isolates screened . Electroporation and calcium chloride treatment were each used to transform plasmid-free Escherichia coli strains with the plasmid pool from S . typhimurium Hf . Plasmids introduced by transformation ranged in size from 4.4 to 23.2 kb and correlated with resistance to penicillin G, ampicillin, carbenicillin, cephalothin, cefoperazone, cefamandole, mezlocillin, piperacillin, and in some cases, tetracycline and kanamycin . DNA-DNA hybridization experiments localized these resistance genes to a highly duplicated 6.3-kb fragment of the total EcoRI restriction digest of the S . typhimurium Hf plasmid pool.

APMIS, 1989 Sep, 97(9), 825 - 32
Experimental Salmonella typhimurium infections in rats . I: Influence of thymus on the course of infection; Hougen HP et al.; The course of experimentally induced Salmonella typhimurium infection was studied in three groups of inbred LEW rats: homozygous +/+, athymic rnu/rnu and isogeneic thymus-grafted rnu/rnu rats . In the first experiment the animals were inoculated intraperitoneally with 10(8) bacteria and all animals became severely septicemic and died within a week of inoculation, irrespective of presence or absence of thymus . In the second experiment the animals were inoculated with 10(6) bacteria, and both euthymic and thymus-grafted animals responded with high titres of anti bacterial antibodies while these were very low in the athymic nude animals . Polyclonal antibody production was only observed in the euthymic animals and only regarding IgG . Athymic rats were not able to clear the infection, while the thymus-grafted animals reacted like euthymic rats: Very few animals housed the bacteria four weeks after inoculation, and no bacteria could be detected after four months . Immunohistochemical studies of lymphoid organs revealed that the infection caused a drop in the percentages of T non-helper cells, indicating low suppressor activity . The study shows that athymic nude rats are well suited for studies of infectious diseases in immune deficient hosts, and that whole neonatally isogeneic thymus grafting is a good way of reconstituting these animals immunologically.

Proc Natl Acad Sci U S A, 1989 Sep, 86(18), 7077 - 81
Salmonella typhimurium phoP virulence gene is a transcriptional regulator; Groisman EA et al.; Salmonella typhimurium is a facultative intracellular pathogen capable of surviving within host phagocytic cells . Salmonella strains carrying phoP mutations are avirulent, unable to survive in macrophages, and extremely sensitive to peptides having antimicrobial activity such as the host-derived defensins . We present here the DNA sequence of the phoP gene and show that the deduced amino acid sequence of phoP has extensive homology with the Escherichia coli transcriptional regulators PhoB and OmpR, which control the expression of loci in response to different environmental stimuli . The psiD locus, which is regulated by phosphate availability, was found to be under the control of the phoP gene product . Sequences homologous to phoP were found in several Gram-negative species and in the yeast Saccharomyces cerevisiae.

Proc Natl Acad Sci U S A, 1989 Sep, 86(18), 6953 - 7
Reconstitution of a bacterial periplasmic permease in proteoliposomes and demonstration of ATP hydrolysis concomitant with transport; Bishop L et al.; The histidine periplasmic permease of Salmonella typhimurium has been partially purified and reconstituted into proteoliposomes . In this in vitro preparation, transport activity is completely dependent on the presence of all four permease proteins (HisJ, HisQ, HisM, and HisP) and on internal ATP . The reconstituted system shows initial rates of transport that are comparable to those obtained with right-side-out membrane vesicles and it establishes a 100-fold concentration gradient for histidine . Proteoliposomes also transport histidine when GTP replaces ATP . Proteoliposomes do not catalyze significant ATP hydrolysis until histidine transport is initiated by addition of substrate along with HisJ, the water-soluble histidine-binding protein . Both initially and throughout the course of substrate transport there is a concomitant hydrolysis of ATP, with an apparent stoichiometry (ATP/histidine) of 5:1 . These experiments demonstrate directly that ATP is the source of energy for periplasmic permeases, thus resolving previous controversies on this topic.

J Med Microbiol, 1989 Sep, 30(1), 79 - 87
Intracellular destruction of salmonellae in genetically resistant mice; Lin FR et al.; Virulent Salmonella typhimurium, 2000 LD50, were injected intraperitoneally into inbred male A/J mice, genetically resistant to salmonella infection . Peritoneal exudate cells were harvested between 5 and 54 h after infection and examined by electronmicroscopy . Polymorphs were seen ingesting as well as digesting the pathogens as early as 5 h after infection . Macrophages were equally active in destroying the phagocytosed organisms throughout this period . In the meantime, the proliferation of salmonellae appeared to occur extracellularly in the peritoneal cavity as evidenced by their division.

J Clin Microbiol, 1989 Sep, 27(9), 2019 - 24
Comparison of epidemiological marker methods for identification of Salmonella typhimurium isolates from an outbreak caused by contaminated chocolate; Kapperud G et al.; Plasmid profile analysis, restriction endonuclease analysis, and multilocus enzyme electrophoresis were used in conjunction with serotyping, bacteriophage typing, and biochemical fingerprinting to trace epidemiologically related isolates of Salmonella typhimurium from an outbreak caused by contaminated chocolate products in Norway and Finland . To evaluate the efficiency of the epidemiological marker methods, isolates from the outbreak were compared with five groups of control isolates not known to be associated with the outbreak . Both plasmid profile analysis and phage typing provided further discrimination over that produced by serotyping and biochemical fingerprinting . Plasmid profile analysis and phage typing were equally reliable in differentiating the outbreak isolates from the epidemiologically unrelated controls and were significantly more effective than multilocus enzyme electrophoresis and restriction enzyme analysis of total DNA . The greatest differentiation was achieved when plasmid profile analysis and phage typing were combined to complement serotyping and biochemical fingerprinting . However, none of the methods employed, including restriction enzyme analysis of plasmid DNA, were able to distinguish the outbreak isolates from five isolates recovered in Norway and Finland over a period of years from dead passerine birds and a calf.

Mutat Res, 1989 Sep, 227(1), 13 - 6
Genotoxicity of nitrosated ranitidine; Franekic J et al.; The genotoxicity of ranitidine, widely used in the therapy of peptic ulcers, and of nitrosated ranitidine was examined in test systems with the bacteria Salmonella typhimurium for gene mutations, and with the yeast Saccharomyces cerevisiae D7 for reverse mutations and gene conversion . Under the experimental conditions applied, ranitidine was negative in both systems, while the product obtained by nitrosation in vitro was mutagenic for Salmonella strains TA100 and TA98 with and without metabolic activation . The largest increase of his+ revertants, 3 times greater than the control, was obtained in strain TA100 in the absence of S9 fraction . Nitrosated ranitidine was also recombinogenic for the yeast S . cerevisiae.

Mutat Res, 1989 Sep, 224(1), 95 - 104
Relationships between structure, toxicity and genetic effects in Salmonella typhimurium and Saccharomyces cerevisiae for substituted aniline mustards; Ferguson LR et al.; A series of 4-substituted aniline mustards of widely varying reactivities have been evaluated for their mutagenic effects in Salmonella typhimurium strains of varying uvrB gene and plasmid status, and for their ability to cause mitotic crossing-over in Saccharomyces cerevisiae . The 4-methyl aniline mustard N,N-bis(2-chloroethyl)-4-methylaniline and its corresponding half-mustard N-(2-chloroethyl)-4-methylaniline showed widely different effects in the various bacterial strains, with the half-mustard being much less toxic than the full mustard in the uvrB- strain TA100 . However, in the uvrB+ strain TA1978+, possessing an intact excision repair system, both compounds were equally toxic and the full mustard was the more mutagenic . Both compounds were equally effective in promoting mitotic crossing-over in yeast . For a series of 4-substituted full mustards, the toxicity in S . typhimurium strain TA100 correlated with substituent electronic parameters in the same way as does mammalian cell toxicity, supporting the view that the primary mode of toxicity is via DNA cross-linking, even for unreactive analogues . However, there were no obvious correlations between substituent physiochemical properties and mutagenic potential in bacteria, suggesting that mutagenic events are subject to a variety of influences other than the reactivity of the mustard group . In contrast, the most chemically reactive compounds were the most toxic and most recombinogenic in yeast.

Mutat Res, 1989 Sep, 224(1), 89 - 94
Effect of pH on mutagenesis by thiols in Salmonella typhimurium TA102; Stark AA et al.; The mutagenicity of thiol (SH)-containing compounds was tested in Salmonella typhimurium TA102 in the liquid preincubation method . Cysteinyl-glycine (CG), cysteine ethyl ester (CEE), L- and D-penicillamine (PA), cysteine (Cys) and glutathione (GSH) were mutagenic to strain TA102 without metabolic activation . On a molar basis, CG was the most potent mutagen . The mutagenicity of the remaining compounds decreased in the order specified above . The mutagenic response of each thiol-containing compound was a function of the pKa of the thiol group and the pH of the preincubation mixture . This indicates that a thiolate anion, rather than a free thiol, is required for mutagenesis.

Mutat Res, 1989 Sep, 224(1), 127 - 34
Genotoxicity of coal fly ash, assessed in vitro in Salmonella typhimurium and human lymphocytes, and in vivo in an occupationally exposed population; Kleinjans JC et al.; Fly ash as a product of coal combustion is known to contain various mutagenic substances, but genotoxic properties, especially of the particular (larger-size) fly ash fraction which is electrostatically precipitated (ESP) in the energy plant, have hardly been investigated . While smaller-size fly ash particles escape through the stack during powder coal combustion, the ESP fraction is collected and used for the manufacturing, for instance according to the Lytag process, of secondary products which can serve several construction purposes . Since fly ash as well as fly ash products are generally introduced into the human environment, a study of possible genotoxic effects to human DNA is indicated . Mutagenic properties of ESP fly ash, as well as of the Lytag product, were investigated by means of the Salmonella microsome assay . The capacity to cause human chromosome damage of both ESP fly ash and Lytag dust was studied in vitro by application of the sister-chromatid exchange (SCE) test using human lymphocytes . Furthermore, effects of ESP fly ash/Lytag dust on the incidence of SCE in peripheral lymphocytes in vivo were measured in an occupationally exposed, male population, using individually matched employees from a flour-processing industry as the control population . It is demonstrated that ultrasonically treated DMSO extracts of ESP fly ash are slightly mutagenic to Salmonella tester strains TA97 and TA102 . Lytag dust is effective in inducing reversions in all tester strains . Furthermore, it appeared that both compounds significantly increase the SCE frequency of human lymphocytes after incubation in vitro in comparison to non-exposed cells . Also, peripheral lymphocytes of the occupationally exposed population show a considerably higher incidence of SCE than the control population . Major disturbing factors in assessing the effects of occupational exposure to fly ash/Lytag dust on lymphocyte SCE frequency appeared to be smoking behavior and alcohol consumption . It is concluded that exposure to fly ash from powder coal combustion implies a moderate genotoxic risk to man.

Mutat Res, 1989 Sep, 224(1), 115 - 25
Bacterial mutagenicity of new cyclopenta-fused cata-annelated polycyclic aromatic hydrocarbons, and identification of the major metabolites of benz{j}acephenanthrylene formed by Aroclor-treated rat liver microsomes; Ball LM et al.; Three novel cyclopenta-fused polycyclic aromatic hydrocarbons were synthesized, benz{d}aceanthrylene, benz{k}aceanthrylene, and benz{j}acephenanthrylene, and evaluated for mutagenic activity in the Ames Salmonella typhimurium plate incorporation assay . The two benzaceanthrylene derivatives were active at low S9 concentrations in strain TA98 (4 and 27 rev/nmole respectively), as had been predicted from the calculated delta Edeloc/beta values of the carbocations derived from opening of the cyclopenta-fused epoxide rings, but the majority of this mutagenicity appeared to be due to free-radical decomposition products of spontaneous endo-peroxide formation . These compounds were therefore not further investigated . Benz{j}acephenanthrylene was also an indirect-acting frameshift mutagen (8-12 rev/nmole in strain TA98), but unlike most of the previously assayed cyclopenta-fused polycyclic aromatic hydrocarbons exhibited no peak of activity at low S9 protein concentration . The principal metabolites formed from this compound by microsomes from Aroclor-treated rat liver were benz{j}acephenanthrylene-4,5-dihydro-4,5-diol (necessarily derived from hydration of benz{j}acephenanthrylene 4,5-oxide) and benz{j}acephenanthrylene-9,10-dihydro-9,10-diol (precursor to benz{j}acephenanthrylene-9,10-dihydrodiol 7,8-oxide, the bay-region diol-epoxide) . Consideration of the reduced activity of this compound compared to the related structure chrysene, the S9 dependence curves, and the predicted delta Edeloc/beta values of the postulate active species, suggests that in contrast to most other cyclopenta-fused polycyclic aromatic hydrocarbons, bay-region diol-epoxide formation plays a greater role than epoxidation of the cyclopenta-fused ring in the metabolic activation of benz{j}acephenanthrylene.

J Bacteriol, 1989 Sep, 171(9), 5215 - 7
pepM is an essential gene in Salmonella typhimurium; Miller CG et al.; The pepM gene of Salmonella typhimurium codes for a methionine-specific aminopeptidase that removes N-terminal methionine residues from proteins . This gene was inactivated in vitro by the insertion of a DNA fragment coding for kanamycin resistance . The inactivated gene could not replace the wild-type chromosomal pepM gene unless another functional copy was present in the cell . The lethal effect of the pepM insertion was not a result of polarity on any gene downstream, nor was it affected by the presence or absence of other peptidases.

J Bacteriol, 1989 Sep, 171(9), 4761 - 6
Magnesium transport in Salmonella typhimurium: 28Mg2+ transport by the CorA, MgtA, and MgtB systems; Snavely MD et al.; Three loci in Salmonella typhimurium (corA, mgtA, and mgtB) code for components of distinct Mg2+ transport systems (S . P . Hmiel, M . D . Snavely, J . B . Florer, M . E . Maguire, and C . G . Miller, J . Bacteriol . 171:4742-4751, 1989) . Strains carrying one wild-type and two mutant alleles of the three loci were constructed to study the kinetics and specificity of ion transport of each system in isolation . The transport systems had different Km and Vmax values for Mg2+ uptake, and each was inhibited by other divalent cations in a distinct rank order of potency: for CorA, Mg2+ greater than Mn2+ greater than Co2+ greater than Ni2+ greater than Ca2+; for MgtA, Zn2+ greater than or equal to Mg2+ greater than Ni2+ approximately Co2+ greater than Ca2+; and for MgtB, Mg2+ approximately Ni2+ approximately Ni2+ greater than Mn2+ much greater than Ca2+ . Other differences among the three systems were apparent . The CorA transport system functioned as a Mg2+-Mg2+ exchange system, mediating both efflux and influx of Mg2+ . Neither the MgtA nor the MgtB system could mediate Mg2+ efflux . Transport via the MgtB system was very temperature sensitive; Mg2+ was transported at 37 degrees C but not at 20 degrees C . The MgtA and the MgtB transport systems were found to be regulated by the extracellular concentration of Mg2+.

J Bacteriol, 1989 Sep, 171(9), 4563 - 8
Characterization of the major DNA repair methyltransferase activity in unadapted Escherichia coli and identification of a similar activity in Salmonella typhimurium; Rebeck GW et al.; Escherichia coli has two DNA repair methyltransferases (MTases): the 39-kilodalton (kDa) Ada protein, which can undergo proteolysis to an active 19-kDa fragment, and the 19-kDa DNA MTase II . We characterized DNA MTase II in cell extracts of an ada deletion mutant and compared it with the purified 19-kDa Ada fragment . Like Ada, DNA MTase II repaired O6-methylguanine (O6MeG) lesions via transfer of the methyl group from DNA to a cysteine residue in the MTase . Substrate competition experiments indicated that DNA MTase II repaired O4-methylthymine lesions by transfer of the methyl group to the same active site within the DNA MTase II molecule . The repair kinetics of DNA MTase II were similar to those of Ada; both repaired O6MeG in double-stranded DNA much more efficiently than O6MeG in single-stranded DNA . Chronic pretreatment of ada deletion mutants with sublethal (adapting) levels of two alkylating agents resulted in the depletion of DNA MTase II . Thus, unlike Ada, DNA MTase II did not appear to be induced in response to chronic DNA alkylation at least in this ada deletion strain . DNA MTase II was much more heat labile than Ada . Heat lability studies indicated that more than 95% of the MTase in unadapted E . coli was DNA MTase II . We discuss the possible implications of these results for the mechanism of induction of the adaptive response . A similarly active 19-kDa O6MeG-O4-methylthymine DNA MTase was identified in Salmonella typhimurium.

Carcinogenesis, 1989 Sep, 10(9), 1685 - 9
The effects of bay-region methyl substitution on 6-nitrochrysene mutagenicity in Salmonella typhimurium and tumorigenicity in newborn mice; el-Bayoumy K et al.; The mutagenic activities in Salmonella typhimurium and tumorigenic activities in newborn mice of 6-nitrochrysene (6-NC), 5-methyl-6-nitrochrysene (5-Me-6-NC), 11-methyl-6-nitrochrysene (11-Me-6-NC) and 5-methylchrysene (5-MeC) were compared . In S . typhimurium TA100 in the absence of rat liver 9000 g supernatant, 11-Me-6-NC was the most active compound followed by 6-NC; 5-Me-6-NC and 5-MeC were inactive . In the assays conducted in the presence of rat liver 9000 g supernatant, the order of activity was 11-Me-6-NC greater than 6-NC greater than 5-Me-6-NC approximately 5-MeC . In S . typhimurium TA98 a similar trend was observed . For the tumorigenicity studies, groups of mice were treated with the appropriate compounds in DMSO by i.p . injections on the 1st, 8th and 15th day of life . At a dose of 100 nmol/mouse 6-NC induced significantly more lung tumors than 5-MeC, which in turn was more active than 11-Me-6-NC and 5-Me-6-NC . All compounds induced significant numbers of liver tumors in treated males compared to controls; the order of activity was the same as that observed for lung tumor induction . The results of this study clearly indicate that bay region methyl substitution can either inhibit (5-position) or enhance (11-position) the mutagenic activity of 6-NC . In contrast, bay region methyl substitution (5- and 11-positions) inhibited the tumorigenic activity of 6-NC in newborn mice . Since ring oxidation and nitroreduction are involved in the metabolic activation of 6-NC in newborn mice, bay region methyl substitution may either inhibit the nitroreduction pathway or hinder the formation of the appropriate bay region diol epoxide . Steric factors may be important in determining the tumorigenicity of methylated nitrochrysenes.

Carcinogenesis, 1989 Sep, 10(9), 1675 - 9
Enzymatic acetylation and sulfation of N-hydroxyarylamines in bacteria and rat livers; Yamazoe Y et al.; In mammalian hepatic cytosol both acetyltransferase and sulfotransferase are involved in the activation of N-hydroxy derivatives of arylamines and arylamides . The role of acetyltransferase is also shown in Salmonella, whereas no rigid evidence is provided on the role of sulfotransferase in Salmonella . In Ames mutagenesis test without S9-mix, the number of revertants of Salmonella typhimurium TA98 induced was 10-fold higher with 2-hydroxyamino-3-methylimidazo{4,5-f} quinoline (N-hydroxy-IQ) than with 2-hydroxyamino-6-methyldipyrido{1,2-a:3',2'-d}imidazole (N-hydroxy-Glu-P-1) . The extents of the binding to calf thymus DNA of N-hydroxy-Glu-P-1 were, however, 3.9 to 8.6-fold higher than that of N-hydroxy-IQ in both acetyl CoA- and PAPS-fortified rat hepatic cytosol systems . To understand the mechanism causing the apparent discrepancy between the results of the mutation and DNA binding, the activating capacities of cytosols of S . typhimurium TA98 and TA98/1,8-DNP6 strains on the binding of N-hydroxy-Glu-P-1 and N-hydroxy-IQ have been examined in comparison with those of rat livers . Although both N-hydroxyarylamines were activated by hepatic cytosols in the presence of PAPS, no significant DNA binding of these N-hydroxyarylamines was detected in the presence of PAPS and either one of the two strains of bacterial cytosols . In addition, both cytosols of TA98 and TA98/1,8-DNP6 strains showed no measurable activity on the sulfation of p-nitrophenol, suggesting no capacity for sulfotransferase-mediated activation of N-hydroxyarylamines in Salmonella . On the contrary, the extents of the acetyl CoA-dependent binding of N-hydroxy-IQ in cytosols of TA98, but not of TA98/1,8-DNP6, were respectively 6- and 9-fold higher than those in hepatic cytosols of male and female rats, although the extents of the binding of N-hydroxy-Glu-P-1 were rather higher in hepatic than in bacterial cytosols . In addition, the covalent binding of N-hydroxy-2-acetylaminofluorene to DNA was detected in hepatic, but not in bacterial cytosols, although the binding of N-hydroxy-2-aminofluorene was detectable in both hepatic and bacterial cytosols in the presence of acetyl CoA . These results indicate that the metabolic activating capacities of Salmonella and rat liver cytosols differ qualitatively, and the difference in the substrate specificity of acetyltransferase between Salmonella and rat livers may be involved, in part, in the difference of their DNA damage in bacteria and mammals.

Infect Immun, 1989 Sep, 57(9), 2842 - 6
Salmonella typhimurium virulence in a burned-mouse model; Carsiotis M et al.; Various features of salmonellosis were examined in a burned-mouse model . In this model, which uses an outbred mouse strain, a challenge dose of ca . 100 CFU with any of several strains of Salmonella typhimurium caused a fatal infection . A variety of mutated strains attenuated for virulence in Salmonella-susceptible parenterally infected mice were also attenuated in the burned-mouse model . When administered as live vaccines injected intraperitoneally the same attenuated strains provided between slight and complete protection against subsequent lethal challenge subcutaneously at the site of a burn . The correspondence of results obtained in the burned-mouse model with those seen in other mouse models coupled with the unique advantages of the burned-mouse model argue for the usefulness of the model in studies of salmonellosis and in testing of strains constructed for use as live vaccines.

Infect Immun, 1989 Sep, 57(9), 2758 - 63
Isolation of orally attenuated Salmonella typhimurium following TnphoA mutagenesis; Miller I et al.; One hundred fifty Tn5 IS50L::phoA (TnphoA) mutants of a mouse-virulent, nalidixic acid-resistant (Nalr), prototrophic Salmonella typhimurium strain, C5 Nalr, were isolated . None of the mutants were auxotrophs . Groups of 8 to 10 BALB/c mice were infected orally with each of 95 mutants with a dose equivalent to 20-fold the 50% lethal dose of the wild-type C5 Nalr strain, and deaths were counted over the next 28 days . Fifteen of the mutants failed to kill any mice, whereas all mice died following challenge with the other mutants . Nine of the 15 attenuated mutants exhibited a defect in lipopolysaccharide biosynthesis . The remaining six mutants were smooth . The TnphoA transposon of each of the smooth attenuated mutants was moved, using P22-mediated transduction, into a fresh C5 background, and all retransductants were still attenuated . Analysis of the membrane proteins of the attenuated mutants failed to reveal any alterations in detectable major outer membrane proteins, although colonies of two of the mutants exhibited a mucoid phenotype following growth on L-agar plates . Individual attenuated mutants differed in their abilities to translocate to livers and spleens of mice following oral infection . All of the smooth TnphoA mutants exhibited increased 50% lethal doses with respect to the wild type following intravenous infection of BALB/c mice . Southern analysis of DNA prepared from each of the mutants suggested that TnphoA had inserted into a number of different sites in the S . typhimurium genome . None of the TnphoA mutants had inserts in the virulence-associated plasmid.

Mol Microbiol, 1989 Sep, 3(9), 1287 - 94
Osmotic regulation of porin expression: a role for DNA supercoiling; Graeme-Cook KA et al.; The OmpC and OmpF porins are major outer membrane proteins of Escherichia coli and Salmonella typhimurium . Their expression is affected by many environmental factors and by mutations in a variety of independent genes . The pair of regulatory proteins, OmpR and EnvZ, are required for normal porin expression . Despite intensive investigation, the mechanisms by which porin expression is regulated remain unclear . Mutations which alter supercoiling, as well as inhibitors of DNA gyrase, show that porin expression is extremely and specifically sensitive to the level of DNA supercoiling . Our data lead us to suggest that environmentally induced changes in DNA supercoiling may play a role in determining the level of porin expression . These findings have implications for current models of porin regulation.

Mutat Res, 1989 Sep, 227(1), 53 - 8
Mutagenic activation of aflatoxin B1 by P-450 HFLa in human fetal livers; Kitada M et al.; The genotoxic and mutagenic activation of promutagens by human fetal livers was measured by the induction of umu gene expression in Salmonella typhimurium TA1535/pSk1002 . Liver homogenates of human fetuses were the most active for the mutagenic activation of aflatoxin B1 (AFB1), followed by 2-amino-3-methylimidazo(4,5-f)quinoline (IQ), and to a lesser extent by 2-amino-6-methyldipyrido(1,2-a:3',2'-d)imidazole (Glu-P-1) . The amounts of P-450 HFLa immunochemically determined in human fetal livers correlated highly with the induction of umu gene expression by AFB1 (r = 0.98, n = 5) . P-450 HFLa catalyzed the mutagenic activation of AFB1 in a reconstituted system: cytochrome b5 markedly stimulated the activation . Anti-P-450 HFLa antibodies inhibited the mutagenic activation of AFB1 in a dose-dependent manner . These results strongly support the idea that P-450 HFLa is responsible for the mutagenic activation of AFB1 in human fetal livers.

J Bacteriol, 1989 Sep, 171(9), 4900 - 5
Transcription of pfl is regulated by anaerobiosis, catabolite repression, pyruvate, and oxrA: pfl::Mu dA operon fusions of Salmonella typhimurium; Wong KK et al.; Pyruvate formate-lyase (EC 2.3.1.54), a key enzyme in the anaerobic metabolism of Salmonella typhimurium, catalyzes the conversion of pyruvate to acetyl coenzyme A and formate . pfl::Mu dA operon fusions were isolated for the study of transcriptional regulation . pfl was transcribed both aerobically and anaerobically, but the activity increased about sixfold under anaerobic conditions . The addition of pyruvate, formate, and acetate in nutrient broth did not have any effect on the anaerobic expression of pfl . However, the addition of pyruvate to minimal glucose medium increased the anaerobic expression of pfl . The expression of pfl varied in different growth media . Anaerobic expression of pfl was lower when the culture was grown in minimal glucose medium than when it was grown in nutrient broth . When Casamino Acids (Difco Laboratories, Detroit, Mich.) were added to minimal glucose medium, the expression of pfl increased proportionally with the amount of Casamino Acids added . The transcription of pfl was positively controlled by the oxrA gene product and was affected by both the cya and crp mutations . However, mutations in genes affecting the cyclic AMP-cyclic AMP receptor protein complex or oxrA could not completely abolish the anaerobic derepression of pfl . In merodiploid strains, pfl::Mu dA/F' pfl+, the beta-galactosidase activities were decreased . The mutations gyrA, oxrC, and oxrE, which affected anaerobic metabolism, did not affect anaerobic expression of pfl.

J Bacteriol, 1989 Sep, 171(9), 4752 - 60
Magnesium transport in Salmonella typhimurium: expression of cloned genes for three distinct Mg2+ transport systems; Snavely MD et al.; In Salmonella typhimurium, the corA, mgtA, and mgtB loci are involved in active transport of Mg2+ (S . P . Hmiel, M . D . Snavely, C . G . Miller, and M . E . Maguire, J . Bacteriol . 168:1444-1450, 1988; S . P . Hmiel, M . D . Snavely, J . B . Florer, M . E . Maguire, and C . G . Miller, J . Bacteriol . 171:4742-4751, 1989) . In this study, the gene products coded for by the corA, mgtA, and mgtB genes were identified by using plasmid expression in Escherichia coli maxicells . Complementation was assessed by introducing plasmids into a Mg2+-dependent corA mgtA mgtB strain and determining the ability of the plasmid to restore growth on medium without a Mg2+ supplement . Complementing plasmids containing corA expressed a 42-kilodalton (kDa) protein . This protein was not expressed by plasmids containing insertions or deletions that eliminated complementation . A plasmid containing mgtA expressed 37- and 91-kDa gene products . Data obtained with subclones and insertions in this plasmid indicated that plasmids expressing only the 91-kDa polypeptide complemented; plasmids that did not express this protein did not complement regardless of whether they expressed the 37-kDa protein . Plasmids carrying mgtB expressed a single protein of 102 kDa whose presence or absence correlated with the ability of the plasmid to complement the Mg2+-dependent triple mutant . Fractionation of labeled maxicells demonstrated that the 42-kDa corA, the 91-kDa mgtA, and the 102-kDa mgtB gene products are all tightly associated with the membrane, a location consistent with involvement in a transport process . These data provide further support the for existence of three distinct systems for Mg2+ transport in S . typhimurium.

J Bacteriol, 1989 Sep, 171(9), 4742 - 51
Magnesium transport in Salmonella typhimurium: genetic characterization and cloning of three magnesium transport loci; Hmiel SP et al.; Salmonella typhimurium strains lacking the CorA Mg2+ transport system retain Mg2+ transport and the ability to grow in medium containing a low concentration of Mg2+ . Mutagenesis of a corA strain followed by ampicillin selection allowed isolation of a strain that required Mg2+-supplemented media for growth . This strain contained mutations in at least two loci in addition to corA, designated mgtA and mgtB (for magnesium transport) . Strains with mutations at all three loci (corA, mgtA, and mgtB) exhibited no detectable Mg2+ uptake and required 10 mM Mg2+ in the medium for growth at the wild-type rate . A wild-type allele at any one of the three loci was sufficient to restore both Mg2+ transport and growth on 50 microM Mg2+ . P22 transduction was used to map the mgt loci . The mgtA mutation was located to approximately 98 map units (cotransducible with pyrB), and mgtB mapped at about 80.5 map units (near gltC) . A chromosomal library from S . typhimurium was screened for clones that complemented the Mg2+ requirement of a corA mgtA mgtB mutant . The three classes of plasmids obtained could each independently restore Mg2+ transport to this strain and corresponded to the corA, mgtA, and mgtB loci . Whereas the corA locus of S . typhimurium is analogous to the corA locus previously described for Escherichia coli, neither of the mgt loci described in this report appears analogous to the single mgt locus described in E . coli . Our data in this and the accompanying papers (M . D . Snavely, J . B . Florer, C . G . Miller, and M . E . Maguire, J . Bacteriol . 171:4752-4760, 4761-4766, 1989) indicate that the corA, mgtA, and mgtB loci of S . typhimurium represent three distinct systems that transport Mg2+.

J Bacteriol, 1989 Sep, 171(9), 4728 - 35
Isolation, nucleotide sequence, and preliminary characterization of the Escherichia coli K-12 hemA gene; Verkamp E et al.; The Escherichia coli hemA gene, essential for the synthesis of 5-aminolevulinic acid (ALA), was isolated and sequenced . The following criteria identified the cloned gene as hemA . (i) The gene complemented a hemA mutation of E . coli . (ii) The gene was localized to approximately 26.7 min on the E . coli chromosomal linkage map, consistent with the location of the mapped hemA locus . Furthermore, DNA sequence analysis established that the cloned gene lay directly upstream of prfA, which encodes polypeptide chain release factor 1 . (iii) Deletion of the gene resulted in a concomitant requirement for ALA . The hemA gene directed the synthesis of a 46-kilodalton polypeptide in maxicell experiments, as predicted by the coding sequence . The DNA and deduced amino acid sequences of the E . coli hemA gene displayed no detectable similarity to the ALA synthase sequences which have been characterized from a variety of organisms, but are very similar to the cloned Salmonella typhimurium hemA sequences (T . Elliott, personal communication) . Results of S1 nuclease protection experiments showed that the hemA mRNA appeared to have two different 5' ends and that a nonoverlapping divergent transcript was present upstream of the putative distal hemA transcriptional start site.

J Bacteriol, 1989 Sep, 171(9), 4694 - 706
Nucleotide sequence of the transcriptional control region of the osmotically regulated proU operon of Salmonella typhimurium and identification of the 5' endpoint of the proU mRNA; Overdier DG et al.; Southern blot analysis of 15 proU transposon insertions in Salmonella typhimurium indicated that this operon is at least 3 kilobase pairs in length . The nucleotide sequence of 1.5-kilobase-pair fragment that contains the transcriptional control region of the proU operon and the coding sequences specifying 290 amino acids of the first structural gene of the operon was determined . The predicted amino acid sequence of the product of this gene shows extensive similarity to the HisP, MalK, and other proteins that are inner membrane-associated components of binding protein-dependent transport systems . S1 mapping and primer extension analysis of the proU mRNAs revealed several species with different 5' ends . Two of these endpoints are sufficiently close to sequences that have weak similarities to the consensus -35 and -10 promoter sequences that they are likely to define two transcription start sites . However, we cannot rule out the possibility that some or all of the 5' endpoints detected arose as a result of the degradation of a longer mRNA . The expression of proU-lacZ operon fusions located on plasmids was normal in S . typhimurium regardless of the plasmid copy number . The sequences mediating normal, osmoregulated expression of the proU operon were shown by subcloning to be contained on an 815-base-pair fragment . A 350-base-pair subclone of this fragment placed onto a lacZ expression vector directed a high-level constitutive expression of beta-galactosidase, suggesting that there is a site for negative regulation in the proU transcriptional control region which has been deleted in the construction of this plasmid.

Mol Gen Genet, 1989 Sep, 218(3), 371 - 6
Molecular cloning and nucleotide sequencing of oxyR, the positive regulatory gene of a regulon for an adaptive response to oxidative stress in Escherichia coli: homologies between OxyR protein and a family of bacterial activator proteins; Tao K et al.; Treatment of Escherichia coli and Salmonella typhimurium cells with a low dose of hydrogen peroxide induces expression of a large number of genes, and confers resistance to oxidative stresses . The oxyR gene encodes a positive regulatory protein for a subset of these genes involved in the defense against oxidative damage . We cloned a DNA fragment that contains the E . coli oxyR region on a plasmid vector, and analyzed the nucleotide sequence of the gene . The amino acid sequence of OxyR protein, deduced from the nucleotide sequence, shows a high degree of homology to the sequences of a number of bacterial activator proteins including LysR, CysB, IlvY, MetR and NodD . The product of the oxyR gene identified by the maxicell procedure was a 34 kDa protein, which agrees with the size predicted from the nucleotide sequence of the gene.

Mol Gen Genet, 1989 Sep, 218(3), 377 - 83
Induction of genetic duplications and frameshift mutations in Salmonella typhimurium by acridines and acridine mustards: dependence on covalent binding of the mutagen to DNA; Hoffmann GR et al.; The aroC321 allele permits positive selection for the detection of a large genetic duplication that arises in the Salmonella typhimurium chromosome by homologous recombination . Strains that contain both aroC321 and the hisC3076 allele were constructed so that the induction of genetic duplications and frameshift mutations in a run of GC base pairs could be studied simultaneously by selecting for tryptophan and histidine prototrophy, respectively . Using these strains, we examined the ability of 9-aminoacridine, quinacrine, four acridine mustards (ICR-170, ICR-191, ICR-372, and quinacrine mustard) and the nitroacridine Entozon to induce genetic duplications and frameshift mutations . Although all these compounds induce reversion of hisC3076, only the four mustards and Entozon are effective as inducers of genetic duplications under identical treatment conditions . The induction of genetic duplications by acridine mustards, like the toxic and mutagenic effects of these compounds, is enhanced by a deficiency for excision repair caused by a deletion through the uvr B gene . The ineffectiveness of 9-aminoacridine and quinacrine in the test for genetic duplications indicates that simple intercalation is sufficient for the mutagenic effect measured with the hisC3076 allele but that the induction of duplications by the acridine mustards and Entozon requires covalent binding of the chemical to DNA.

Biochim Biophys Acta, 1989 Aug 21, 984(1), 119 - 27
Composition and structure of lipopolysaccharide-human plasma low density lipoprotein complex . Analytical ultracentrifugation, 31P-NMR, ESR and fluorescence spectroscopy studies; Victorov AV et al.; Complexes of Salmonella typhimurium lipopolysaccharide toxin (LPS) with low density lipoproteins (LDL) prepared in vitro have been analyzed . LPS-LDL complexes were found to comprise approx . 0.24 mg LPS/mg LDL protein . The major protein of complexes was apolipoprotein apoB-100 (greater than or equal to 90-95%) . Incorporation of LPS molecules into LDL was accompanied by small changes in lipid composition, i.e . the phosphatidylcholine content was diminished by approx . 11% and the free fatty acid concentration was raised 2-fold . Analytical ultracentrifugation showed that insertion of LPS into LDL results in the increase of a portion of particles with higher density (lower flotation coefficient) compared to initial LDL . As was evidenced by ESR, in LPS-LDL complexes, the phospholipid hydrocarbon chains are more ordered than in LDL . 31P-NMR spectra indicated that in LPS-LDL complexes the mobility of phospholipid polar headgroups is restricted in comparison with LDL . Application of the shift reagent (Pr3+) revealed that phospholipid molecules form a monolayer structure on the surface of complexes . Upon binding of LPS to LDL, a maximum of the apoB intrinsic fluorescence was slightly red-shifted (1-2 nm) which may testify that the localization of apoB remains nearly unchanged . For LPS-LDL complexes, the accessibility of apoB fluorophores to quenchers (I-, Cs+, acrylamide) did not dramatically differ from that of LDL . It is concluded that rather large amounts of LPS (about 9-10 molecules) can accommodate in one LDL particle without severely perturbing its original composition and structure . Moreover, in the LPS-LDL complexes, oligosaccharide chains of LPS screen notably neither phospholipid polar headgroups nor, what is very important, apoB . LPS-LDL complexes are suggested to be able in vivo to bind to cellular apoB/E receptors, possible LPS receptors and scavenger-receptors of macrophages (monocytes).

J Mol Biol, 1989 Aug 5, 208(3), 477 - 89
Formation of intermolecular and intramolecular hydrogen bonds in histidine-binding protein J of Salmonella typhimurium upon binding L-histidine . A proton nuclear magnetic resonance study; Buckel SD et al.; Histidine-binding protein J of Salmonella typhimurium has been chosen as a model system for a proton nuclear magnetic resonance spectroscopic investigation of binding protein-ligand interaction . This interaction is involved in the recognition step of the osmotic shock-sensitive active transport systems . When J protein binds L-histidine, four new, low-field, exchangeable proton resonances appear in the region +7 to +12 parts per million downfield from the water proton resonance (or +11.7 to +16.7 parts per million downfield from the methyl proton resonance of 2,2-dimethyl-2-silapentane-5-sulfonate) . Due to their chemical shift range and other properties, they indicate the formation of both intra- and intermolecular hydrogen bonds . Experiments with 15N-labeled compounds confirm this conclusion . The specificity of the hydrogen-bond formation is demonstrated by observing the effects of substrate analogs, temperature, pH, and mutations on the exchangeable proton resonances . Proton-proton nuclear Overhauser effect measurements suggest that two of these exchangeable proton resonances (at +7.2 and +10.6 parts per million from H2O) are most likely from intramolecular hydrogen-bonded protons, while the other two (at +7.1 and +9.5 parts per million from H2O) are intermolecular hydrogen bonds . Our finding of L-histidine-induced hydrogen-bond formation in histidine-binding protein J in the solution state is an excellent demonstration of the production of specific conformational changes in a periplasmic binding protein upon binding of ligand.

J Gen Microbiol, 1989 Aug, 135 ( Pt 8), 2209 - 22
Leaky pantothenate and thiamin mutations of Salmonella typhimurium conferring suphometuron methyl sensitivity; LaRossa RA et al.; The herbicide suphometuron methyl inhibits the utilization of pyruvate and 2-ketobutyrate by the branched-chain amino acid biosynthetic enzyme acetolactate synthase . Eighteen insertions of the transposon Tn10 into the genome of Salmonella typhimurium LT2 caused hypersensitivity to this herbicide . Five of these insertions conferred a partial auxotrophic requirement . Concurrent herbicide sensitivity and heat-labile pantothenate auxotrophy was due to panD::Tn10 mutations, while coincident sulphometuron methyl sensitivity and thiamin auxotrophy was attributable to thiA::Tn10 mutations . The phenotypes of these mutations suggested that coenzyme A and thiamin pyrophosphate availability modulated the cells' response to sulphometuron methyl . A model suggesting a key role for 2-ketobutyrate accumulation in herbicide action is supported by the function of thiamin pyrophosphate in 2-ketoacid metabolism and the known role of a 2-ketoacid in coenzyme A synthesis.

Mol Microbiol, 1989 Aug, 3(8), 1039 - 51
Transcriptional polarity enhances the contribution of the internal promoter, ilvEp, in the expression of the ilvGMEDA operon in wild-type Escherichia coli K12; Lopes JM et al.; The ilvG gene of Escherichia coli K12 produces a cryptic peptide as a result of a frameshift mutation located approximately halfway through the coding sequence of the gene . This mutation is polar on expression of the downstream genes (ilvEDA) because transcription terminates within the translationally barren region that results from the mutation . Contrary to this, Salmonella typhimurium produces a full-length functional ilvG protein and is therefore unlikely to manifest this polarity event . E . coli K12 strains with mutations either in the ilvG gene (which restores a full-length protein) or in the rho gene, relieve this polarity suggesting that this event couples transcription and translation in a manner analogous to attenuation . This paper describes experiments designed to determine the molecular nature and location of the polarity event . Most significantly, this work establishes the contribution of the internal promoter (ilvEp, located downstream of the polar site) to the expression of the downstream genes in E . coli K12 wild-type and mutant strains (ilvG) and by extension to the role of this promoter in S . typhimurium . This analysis suggests that ilvEp contributes as much as 90% of ilvEDA expression in wild-type E . coli K12 and only 15% in wild-type S . typhimurium when grown under non-repressing conditions.

Mol Microbiol, 1989 Aug, 3(8), 1025 - 38
Molecular characterization of the proU loci of Salmonella typhimurium and Escherichia coli encoding osmoregulated glycine betaine transport systems; Stirling DA et al.; The proU loci of Salmonella typhimurium and Escherichia coli encode high-affinity glycine betaine transport systems which play an important role in survival under osmotic stress . Transcription of the proU locus is tightly regulated by osmolarity and this regulation appears to be mediated by osmotically induced changes in DNA supercoiling . In order to study the regulatory mechanisms involved we have cloned and characterized the proU locus of S . typhimurium by an in vivo transductional procedure . The locus is shown to consist of at least three genes, designated proVWX, cotranscribed as a single operon . The first gene in the operon encodes a protein sharing considerable sequence identity with ATP-binding proteins from other periplasmic transport systems . Unexpectedly, the highly expressed periplasmic glycine betaine binding protein was found to be encoded by a distal gene, proX, in the operon . The operon has no significant internal promoters but is expressed from a single osmoregulated promoter whose transcription start site has been mapped . The proU promoter of E . coli has also been sequenced and the transcription start site shown to be similar to that of S . typhimurium . Evidence is presented which suggests that, besides de novo glycine betaine uptake, an important function of ProU may be the recapture and recycling of other osmolytes that leak from the cell.

Microb Pathog, 1989 Aug, 7(2), 111 - 20
The induction of interferon production in fibroblasts by invasive bacteria: a comparison of Salmonella and Shigella species; Hess CB et al.; As the role of interferon (IFN) in host defense against facultative intracellular bacterial infections continues to expand, it has become increasingly important to understand what cell types can produce IFN following infection and/or interaction with these invasive bacteria . We have demonstrated previously that Shigella flexneri was able to induce high levels of IFN in primary cultures of human and murine fibroblasts following bacterial invasion . In this study, we examined the ability of Salmonella typhimurium to induce IFN production in different cell lines . S . typhimurium-infected primary cell cultures of mouse embryo-fibroblasts (MEF) were shown to produce high levels of IFN following bacterial challenge . In contrast to Shigella, Salmonella required a much lower multiplicity of infection for optimal IFN induction . Examination at the RNA level of IFN production by MEF following challenge with either bacteria revealed that the IFN produced was a mixture of IFN alpha and IFN beta (IFN alpha/beta), with IFN beta 1 as the predominant species . As previously demonstrated for Shigella, bacterial invasion of cells appeared to be required for the induction of IFN production by S . typhimurium . Salmonella rendered non-invasive by UV-treatment failed to induce IFN production in MEF . Furthermore, Salmonella LPS, when tested over a wide range of concentrations, was unable to induce IFN production in these cells . In contrast to MEF, human and murine continuous cell lines did not produce IFN following Salmonella challenge . These results taken together suggest that IFN may be a common factor involved in Salmonella and Shigella infections . Furthermore, IFN may play an important role in the front line host defense against these types of infections.

Fundam Appl Toxicol, 1989 Aug, 13(2), 341 - 8
Comparison of the hepatotoxicity in mice and the mutagenicity of three nitroalkanes; Dayal R et al.; The hepatotoxic and mutagenic potentials of 2-nitropropane, nitromethane, and nitroethane were compared . Hepatotoxicity was assessed biochemically and histopathologically in BALB/c mice . In male mice, plasma activities of the hepatic enzymes sorbitol dehydrogenase, alanine aminotransferase, and aspartate aminotransferase were significantly elevated 48, 72, and 96 hr after ip administration of 9 mmol/kg 2-nitropropane, but not at 24 hr and not after administration of smaller doses of 2-nitropropane nor after nitromethane or nitroethane (9 mmol/kg) . In female mice a dose of 6.7 mmol/kg of 2-nitropropane was sufficient to cause hepatotoxicity . The histopathological evaluation supported the biochemical results, and livers of mice that had received 2-nitropropane (9 mmol/kg) showed damage, particularly in the periportal region . Mutagenicity was tested in Salmonella typhimurium tester strains TA98, TA100, and TA102 . Both 2-nitropropane and its anionic form, propane-2-nitronate, were mutagenic but the nitronate was the more powerful mutagen . Nitromethane, nitroethane, nor their nitronates caused an increase in the number of revertant colonies over those seen in control plates . The results suggest that the primary nitroalkanes are much less hepatotoxic and mutagenic than 2-nitropropane.

Mol Gen Genet, 1989 Aug, 218(2), 348 - 52
The repressor of the PEP:fructose phosphotransferase system is required for the transcription of the pps gene of Escherichia coli; Geerse RH et al.; We have cloned the pps gene, coding for PEP synthase, of Escherichia coli . PEP synthase catalyses the ATP-dependent conversion of pyruvate into phosphoenol-pyruvate and is required for gluconeogenesis . The pps gene was cloned by an in vivo cloning method using a mini-Mulac bacteriophage containing a plasmid replicon . Upon expression of the cloned pps gene in the maxicell system a protein with an apparent molecular weight of 84 kDa was synthesized . The position of the pps gene of the plasmid was localized by restriction analysis of isolated transposon insertions and the determination of the PEP synthase activities of the different clones . An operon fusion between the pps gene and the galK gene was constructed . Measurements of the galactokinase activity in Salmonella typhimurium galK and galK fruR mutants showed that the transcription of the pps gene requires the presence of FruR, the repressor of the PEP: fructose phosphotransferase system (PTS) in E . coli and S . typhimurium . To test whether the components of the Fructose PTS, in particular FPr, are involved in the expression of the pps gene, we investigated a S . typhimurium galK strain, containing the fusion plasmid, in which the chromosomal fru operon was inactivated by a transposon insertion . Measurements of the galactokinase activity showed that the absence of the Fructose PTS proteins has no significant influence on the regulation of the pps gene.

Mutat Res, 1989 Aug, 216(4), 211 - 20
A sensitive method for the detection of mutagenic nitroarenes: construction of nitroreductase-overproducing derivatives of Salmonella typhimurium strains TA98 and TA100; Watanabe M et al.; 'Classical nitroreductase' is an enzyme involved in the intracellular metabolic activation of mutagenic nitroarenes . The nitroreductase gene of Salmonella typhimurium TA1538 was cloned into pBR322 and the plasmids harboring the gene were introduced into TA98 and TA100 . The resulting strains (YG1021 and YG1026) had more than 50 times higher nitrofurazone-reductase activity than TA1538 containing pBR322, and were extremely sensitive to the mutagenic action of 2-nitrofluorene, 1-nitropyrene and 2-nitronaphthalene . These results indicate that the new strains permit the efficient detection of mutagenic nitroarenes.

Mutat Res, 1989 Aug, 213(2), 217 - 26
Role of hemin in the inhibition of mutagenic activity of 3-amino-1-methyl-5H-pyrido{4,3-b}indole (Trp-P-2) and other aminoazaarenes; Arimoto S et al.; The mechanism of inhibition by hemin of the mutagenic activities of food pyrolysate aminoazaarenes, particularly that of Trp-P-2 (3-amino-1-methyl-5H-pyrido{4,3-b}indole), was investigated . Hemin efficiently inhibited the metabolic activation by S9 of Trp-P-2, as demonstrated by high-performance liquid chromatographic analysis of the reaction mixtures in which Trp-P-2 had been treated with S9 in the presence or absence of hemin . N-Hydroxy-Trp-P-2, an activated form of Trp-P-2 having direct mutagenicity on Salmonella typhimurium TA98, undergoes spontaneous oxidative degradation in its aqueous solution, and the presence of hemin in the solution accelerated the degradation significantly . The presence of excess hemin with N-hydroxy-Trp-P-2 completely abolished the mutagenic activity of this mutagen towards Salmonella . A UV-visible spectroscopic study has suggested the formation of a complex between hemin and N-hydroxy-Trp-P-2/Trp-P-2 . In support of this view, the fluorescence spectrum of a Trp-P-2 solution was quenched efficiently by the addition of hemin . These observations indicate that this complex formation plays a role in the observed multiple actions of hemin . Similar inhibitory actions of hemin on several other direct-acting aminoazaarene mutagens are also described, as well as the inhibition activities of protoporphyrin, chlorophyllin, biliverdin and bilirubin.

J Med Microbiol, 1989 Aug, 29(4), 283 - 94
Studies on early association of Salmonella typhimurium with intestinal mucosa in vivo and in vitro: relationship to virulence; Worton KJ et al.; The abilities of six strains of Salmonella typhimurium to associate with rabbit ileal mucosa have been measured in vitro . Two were "virulent" strains (TML and W118 which are invasive and inducers of fluid secretion in rabbit ileal loops); four were "avirulent" (LT7, M206 and SL1027 which are invasive but induce negligible fluid secretion, and Thax-1 which is neither invasive nor an inducer of fluid secretion) . A special organ-culture apparatus was designed to expose only the luminal surface of the mucosa to organisms . Viable counts of washed homogenised tissue taken 30 min after challenge showed that virulent strains TML and W118 and avirulent strains LT7 and M206 could not be distinguished from each other . Avirulent strain SL1027 associated less well than the other four strains, and Thax-1 associated less well than SL1027; both these strains were non-motile whereas the other four were motile . Thus, early association with gut mucosa did not discriminate all avirulent strains from the virulent strains . Qualitative examination of tissues by scanning electronmicroscopy did not detect strains LT7 and M206 on the mucosal surface whereas strains TML and W118 were readily seen, suggesting that the nature of association of virulent and avirulent strains was different . Qualitative examination by transmission electronmicroscopy of tissues challenged in vivo for 120 min showed virulent strains TML and W118 invading epithelial cells; similar events were reproduced after 120-min challenge in vitro . In contrast, invasion by avirulent strains was observed only very rarely.

J Bacteriol, 1989 Aug, 171(8), 4472 - 8
Features of the rho-dependent transcription termination polar element within the hisG cistron of Salmonella typhimurium; Ciampi MS et al.; Previous genetic analysis showed that the polar effects of mutations in the hisG cistron of Salmonella typhimurium are dependent on the presence of a single putative transcription termination element within the hisG gene . In fact, all proximal mutations causing translation termination are strongly polar, whereas distal ones are not . The element was mapped by isolating mutations able to relieve the polar phenotype, and they were found to be small deletions in the region downstream of the translational stop codon (M . S . Ciampi and J . R . Roth, Genetics 118:193-202, 1988) . In this study, we analyzed the his-specific RNAs synthesized in vivo in different strains harboring the polar frameshift hisG2148 mutation . The nature of the polarity effects is clearly transcriptional, since shorter RNA molecules were produced . When the hisG2148 mutation was transferred in a rho background or in strains harboring the small distal deletions, an increase in readthrough transcription was observed . The transcriptional termination element was characterized in more detail by performing high-resolution S1 nuclease mapping experiments . This analysis showed that (i) termination or exonucleolytic degradation following termination produced transcripts with heterogeneous 3' ends; (ii) this process is dependent on the transcription termination factor Rho, since relief of termination occurs in a rho background; and (iii) the element appears to function as a transcription terminator, at least to some extent, even in the course of active translation of the hisG cistron.

J Bacteriol, 1989 Aug, 171(8), 4436 - 41
Genetic regulation of the tricarboxylate transport operon (tctI) of Salmonella typhimurium; Widenhorn KA et al.; Tricarboxylates are transported into Salmonella typhimurium by a binding protein-dependent transport system known as TctI . Genetically, it comprises three structural genes, tctCBA, as well as a fourth gene of unknown function (tctD), which is transcribed divergently from tctC (K . A . Widenhorn, J . M . Somers, and W . W . Kay, J . Bacteriol . 170:3223-3227, 1988) . Deletions in tctD strongly reduced expression of tctC or of tctC-lacZ transcriptional fusions; however, expression was restored when tctD was present in trans . Expression of tctD-lacZ transcriptional fusions was strongly repressed in the presence of D-glucose but could be alleviated by the addition of cyclic AMP . Furthermore, transcription of tctD was found not to be autogenously regulated . Thus, tctD is considered to be regulated by catabolite repression and encodes a transcriptional activator of tctCBA expression . From the DNA sequence of tctD, the predicted gene product was hydrophilic and shared distinct homologies with other globally regulated transcriptional activators such as OmpR and NtrC.

Environ Res, 1989 Aug, 49(2), 271 - 82
Mutagenic activity of ultraviolet-irradiated mixtures of nitrogen dioxide and propene or butadiene; Victorin K et al.; The mutagenic activities of mixtures of nitrogen dioxide and 1,3-butadiene or propene were investigated after uv-irradiation in a small, laboratory-bench scale flow-through gas exposure system . The tester organism was Salmonella typhimurium, principally strain TA100 . The photoreaction products from 1,3-butadiene and nitrogen dioxide were more mutagenic than those from propene and nitrogen dioxide . Approximately 0.25 ppm butadiene, compared to 100 ppm propene, was needed to give a significant mutagenic effect with 0.25 ppm NO2 after 6 hr exposure . The influence of different experimental conditions on mutagenic activity was studied using propene plus nitrogen dioxide . Increasing the mean reaction time from 40 min to 1 hr 20 min or 3 hr 20 min by reduction of the flow rate through the 20-liter reaction vessel did not appreciably increase the sensitivity of the system, nor did humidification of the air, omission of the metabolic system (S9 mix), or spreading of the bacteria on the agar surface . Prolongation of the exposure time from 6 to 16 or 24 hr did, however, give an increased mutagenic response . With prolonged exposure, a slight mutagenic effect could also be detected with ethene + NO2 + uv . Ozone addition did not appreciably enhance the mutagenic response.

Carcinogenesis, 1989 Aug, 10(8), 1445 - 55
Carcinogens induce intrachromosomal recombination in yeast; Schiestl RH et al.; To identify environmental carcinogens there is a need for inexpensive and reliable short-term tests that can be used to predict the carcinogenic potential of any given substance with high accuracy . The Ames assay, which is based on the induction of mutations in Salmonella typhimurium, is the most extensively used short-term test but certain human or animal carcinogens exist that are persistently undetectable as mutagens with the Ames assay or with other short-term tests . There is a need for a short-term test to detect those carcinogens that are missed by the Ames assay . Carcinogenesis is in many cases associated with genome rearrangement . Because of this association a system screening for intrachromosomal recombination that results in genome rearrangement has been constructed for potential use as a short-term test in the yeast Saccharomyces cerevisiae . Evaluation of this recombination system shows that it is readily inducible by a variety of mutagenic as well as non-readily inducible by a variety of mutagenic as well as non-mutagenic carcinogens, including carcinogens that are not detectable by the Ames assay or by various other short-term tests, such as safrole, urethane, ethionine, auramine, methylene chloride, carbon tetrachloride, cadmium sulfate, aniline, dimethylhydrazine, aminotriazole, acetamide, thiourea and DDE . The present report shows the data for these as well as for additional agents, their response profiles with different concentrations of the agents and the protocol for the DEL system.

Carcinogenesis, 1989 Aug, 10(8), 1403 - 7
A rationale for the non-mutagenicity of 2- and 3-aminobiphenyls; Ioannides C et al.; Of the three isomeric forms of aminobiphenyl, only 4-aminobiphenyl is an established carcinogen while the 2-isomer is considered as a non-carcinogen and 3-aminobiphenyl is at best described as a weak carcinogen . In the present studies we investigated the mutagenicity of these three compounds, their N-hydroxy derivatives and their nitrosoderivatives in the Ames test using the Salmonella typhimurium strains TA98 and TA100 . The studies were performed both in the absence and presence of an activation system derived from the liver of rats pretreated with Aroclor 1254 . Of the three isomers only 4-aminobiphenyl exhibited mutagenicity and only in the presence of an activation system . N-Hydroxy-4-aminobiphenyl was a potent direct mutagen in both bacterial strains, N-hydroxy-2-aminobiphenyl was mutagenic in only TA100 while N-hydroxy-3-aminobiphenyl displayed mutagenicity in neither strain . Both 2- and 3-nitrosobiphenyls were direct mutagens in strain TA100 . These findings suggest that the weak carcinogenicity of 3-aminobiphenyl may be attributed to the lack of genotoxicity of its N-hydroxyderivative, whereas in the case of 2-aminobiphenyl it may be due to the inability of the hepatic preparations to catalyse its N-hydroxylation, which is in agreement with published in vivo metabolic studies . It is interesting that of the three isomers only 2-aminobiphenyl is non-planar, forming a dihedral angle of 40 degrees, and this may preclude it from acting as a substrate of the P-450I family of haemoproteins, which selectively catalyses the N-hydroxylation of many aromatic amines including 4-aminobiphenyl.

Carcinogenesis, 1989 Aug, 10(8), 1389 - 96
Genotoxicity of the food mutagen 2-amino-1-methyl-6-phenylimidazo{4,5-b}pyridine (PhIP): formation of 2-hydroxamino-PhIP, a directly acting genotoxic metabolite; Holme JA et al.; Hepatocytes isolated from Aroclor 1254 (PCB) pretreated rats metabolized 2-amino-1-methyl-6-phenylimidazo{4,5-b}pyridine (PhIP) to a reactive metabolite that induced DNA damage measured by alkaline elution or as increased unscheduled DNA synthesis . PhIP induced mutations in Salmonella typhimurium TA98 and DNA strand breaks and sister chromatid exchange(s) in Chinese hamster V79 cells co-incubated with PCB-hepatocytes . No, or only minor genotoxic, effects were observed when hepatocytes from non-induced rats were used . The bacterial mutagenicity could be inhibited by alpha-naphthoflavone, indicating a role of P-450 in the activation of PhIP . At least eight different metabolites could be separated on HPLC after PhIP had been incubated with PCB-hepatocytes . All of the directly acting mutagenicity towards S.typhimurium TA98 co-eluted with one of the metabolites . The identity of this metabolite was concluded to be 2-hydroxamino-PhIP based on the following evidence: (i) it reduced ferric ion to ferrous ion as hydroxylamines do, (ii) it had an identical UV spectrum and chromatographic properties as a species formed upon reduction of 2-nitro-PhIP by NADPH P-450 reductase . This product displayed a major peak at m/z 241 during thermospray mass spectrometry in the positive-ion mode as would be expected from 2-hydroxamino-PhIP . 2-Hydroxamino-PhIP was directly genotoxic both to TA98 and V79 cells . The genotoxic activity of the medium after removing the hepatocytes remained stable for several hours . Compared to 2-amino-3,4-dimethylimidazo{4,5-f}quinolone (MeIQ), PhIP caused a much larger increase in DNA damage in V79 cells (with hepatocyte activation), whereas MeIQ was more potent with respect to DNA damage induced in hepatocytes and bacteria.

Arch Biochem Biophys, 1989 Aug 1, 272(2), 311 - 7
L-histidinol dehydrogenase, a Zn2+-metalloenzyme; Grubmeyer C et al.; The enzymatic activity of L-histidinol dehydrogenase from Salmonella typhimurium was stimulated by the inclusion of 0.5 mM MnCl2 in the assay medium . At pH 9.2 the stimulation was correlated with binding of 1 g-atom of 54Mn2+/mol dimer, KD = 37 microM . ZnCl2, which prevented the MnCl2 stimulation, also bound to the enzyme, 1.2 g-atom/mol dimer, KD = 51 microM, and prevented Mn2+ binding . Enzyme activity was lost when histidinol dehydrogenase was incubated in 8 M urea . Reactivation was observed when urea-denatured enzyme was diluted into buffer containing 2-mercaptoethanol but required either MnCl2 or ZnCl2 . Histidinol dehydrogenase was inactivated by the transition metal chelator 1,10-phenanthroline or by high levels of 2-mercaptoethanol . The nonchelating 1,7-phenanthroline was not an inactivator, and inactivation by either 1,10-phenanthroline or 2-mercaptoethanol was prevented by MnCl2 . Enzyme inactivated by 1,10-phenanthroline could be reactivated by addition of MnCl2 or ZnCl2 in the presence of 2-mercaptoethanol . Reactivation was correlated with the binding of 1.5 g-atom 54Mn2+/mol dimer . Atomic absorption analysis of the native enzyme indicated the presence of 1.65 g-atom Zn/mol dimer, and no Mn was detected . The results demonstrate, therefore, that histidinol dehydrogenase contains two metal binding sites per enzyme dimer, which normally bind Zn2+, but which may bind Mn2+ while retaining enzyme function . Histidinol dehydrogenase is thus the third NAD-linked oxidoreductase in which Zn2+ fulfills an essential structural and/or catalytic role.

Infect Immun, 1989 Aug, 57(8), 2566 - 8
Evidence of coordinate regulation of virulence in Salmonella typhimurium involving the rsk element of the 95-kilobase plasmid; Vandenbosch JL et al.; Integration of the Salmonella typhimurium virulence plasmid into the chromosome reduces mouse virulence, serum resistance, and HeLa cell adhesion-invasion while prolonging lag time in minimal medium . The proposed virulence plasmid regulatory element, rsk, partially restores virulence and fully restores the other three phenotypes to wild-type levels . Plasmid curing reduces virulence without affecting the other phenotypes . rsk has no apparent effect on the cured strain.

Microb Pathog, 1989 Aug, 7(2), 85 - 99
Molecular cloning and analysis of the incompatibility and partition functions of the virulence plasmid of Salmonella typhimurium; Cerin H et al.; The incompatibility functions (inc) of the virulence plasmid of Salmonella typhimurium LT2 were initially located in a 4.3 kb region near the repA locus of the plasmid . Expression of inc required the presence, in cis or in trans, of two distinct DNA regions of the fragment . These regions, maximally 0.3 kb and 0.6 kb in size, were separated in the fragment by c . 3.0 kb . This intervening DNA encoded two proteins, of Mr values 37 kDa and 40 kDa . The promoter for the 37 kDa protein lay in or near one of the inc regions (incL) . No function was assigned to this protein, however, it may be the product of a rep gene . The 40 kDa protein may have a partition (par) function, and may bind to a centromeric site in or near the other inc region (incR) . An inc+ par- derivative of the original plasmid clone was used in a simple method, not involving the use of curing agents/mutagens, to eliminate virulence plasmid DNA from Salmonella typhimurium, Salmonella dublin, Salmonella enteritidis, and Salmonella cholerae-suis . The par function served to stabilise pJRD158B-based plasmid greater than 10(6)-fold in Escherichia coli and the virulence plasmid-cured Salmonella strains.

Proc Natl Acad Sci U S A, 1989 Aug, 86(16), 6383 - 7
Cloning and molecular characterization of genes whose products allow Salmonella typhimurium to penetrate tissue culture cells; Galan JE et al.; Invasion of the intestinal epithelium is thought to be an important step in the pathogenesis of Salmonella infections . Using an in vitro system, we have isolated a genetic locus, inv, that confers to a noninvasive strain of Salmonella typhimurium the ability to penetrate tissue culture cells . Highly virulent S . typhimurium strains carrying inv mutations were defective for entry into Henle-407 cells while remaining unaffected in their ability to attach to cultured cells . When administered perorally to BALB/c mice, inv mutants of S . typhimurium had higher 50% lethal doses (LD50) than their wild-type parent strains . To the contrary, there were no differences in the observed LD50 when strains were administered intraperitoneally . In addition, inv mutants presented decreased ability to colonize the Peyer's patches, the small intestinal wall, and the spleen when administered perorally, although when administered intraperitoneally, they showed no difference in their ability to colonize the spleen compared to the wild-type parent strain.

J Bacteriol, 1989 Aug, 171(8), 4402 - 9
Genetic characterization of the pnuC gene, which encodes a component of the nicotinamide mononucleotide transport system in Salmonella typhimurium; Zhu N et al.; The pnuC gene, which encodes a component of the nicotinamide mononucleotide transport system, has been mapped and oriented . The gene order of the pnuC region, which is at min 17 of the Salmonella chromosome, is nadA-pnuC-aroG-gal . Polarity tests, with pnuC::Mu d-lac operon fusions, reveal that the pnuC gene is the promoter distal gene in an operon with the nadA gene, which encodes the second enzyme of the pyridine biosynthetic pathway . The nadA pnuC operon is regulated by the NadI repressor . The pnuC gene also has its own promoter, since strains with a nadA::Tn10d(Tc) insertion still express the pnuC gene at a low, unregulated level.

Int J Food Microbiol, 1989 Aug, 9(1), 63 - 71
Extraction of Salmonella antigens in non-sedimentable forms for enzyme immunoassay; Blais BW et al.; Heating Salmonella typhimurium in ethylenediaminetetraacetate was found to dissociate its antigens into forms that are non-sedimentable at 10,000 x g . The treatment caused a marked increase in the rate of immunoreaction and the sensitivity in an enzyme immunoassay for the detection of Salmonella antigens . The method permits the extraction of Salmonella antigens from solid-rich samples and the preparation of solid-free samples by means of centrifugation . When the level of the antigens in the supernatant was too low for the immunoassay, the antigens were readily concentrated by passing a large volume of the supernatant through a macroporous hydrophobic cloth coated with anti-Salmonella antibody . Using this method, the detection of as few as 10 Salmonella cells per gram of chicken meat was possible within a total of 18 h, which included 16 h of enrichment in either tetrathionate, selenite cystine, or nutrient broths.

Eur J Clin Microbiol Infect Dis, 1989 Aug, 8(8), 737 - 41
Conditions required for the antibacterial activity of zidovudine; Lewin CS et al.; In a study to determine the conditions required for its antibacterial activity, zidovudine was found to be bactericidal against Escherichia coli and Salmonella typhimurium in nutrient broth over 6 h . Zidovudine was also found to be active against ten clinical isolates of Salmonella and Escherichia coli at 1 mg/l, which is a clinically achievable concentration of the drug . Bacterial protein synthesis was required for the bactericidal activity of zidovudine against both Escherichia coli and Salmonella typhimurium . Zidovudine was found to be inactive against non-dividing bacteria, as it was unable to kill bacteria of either species when they were suspended in PBS.

Nucleic Acids Res, 1989 Jul 25, 17(14), 5547 - 63
The sequence asymmetry of the Escherichia coli chromosome appears to be independent of strand or function and may be evolutionarily conserved; Rogerson AC; I have examined potential determinants of the asymmetric distribution of nucleotide sequences in the genome of Escherichia coli as cataloged in GenBank release 44 . I have used the frequency of occurrence of all possible tetranucleotides in a given sequence catalog or derivative as a comparative measure of asymmetry . The GenBank-cataloged strand and its complement show statistically similar (not complementary) distributions . The distribution is statistically similar in comparisons between the protein coding subset and the total genome, the coding subset and selected non-coding genes, the coding subset and the remainder of the DNA, and the coding subset and stable RNA sequences . I have compared the distribution in the genome of E . coli with the distributions found in the cataloged genomes of Salmonella typhimurium, Bacillus subtilis, and of coliphages lambda and T7 . The distribution summed in both strands of the cataloged DNA differs statistically only in comparisons with lytic bacteriophage T7 because only the two strands of T7 show statistically dissimilar distributions . Despite similarities in tetranucleotide distribution, the pattern of codon complementarity in B . subtilis is different than that documented for E . coli . Thus, sequence asymmetry does not seem related to specific DNA function or to documented similarities or differences in codon bias . The sequence asymmetry of the E . coli genome may thus reflect a hitherto unsuspected pattern impressed on both strands of DNA which is or can be packaged into bacterial genomes.

FEMS Microbiol Lett, 1989 Jul 15, 51(1), 137 - 41
Salmonella typhimurium metC operator-constitutive mutations; Park YM et al.; We used an Escherichia coli lac deletion strain lysogenized with a metC-lacZ fusion phage (lambda Clac) to select operator-constitutive mutations in the Salmonella typhimurium metC gene control region . The mutations were located in a region containing 2 tandemly repeated 8 bp palindromes previously proposed to be the MetJ repressor binding site . Lysogens carrying lambda Clac mutant phage exhibit high beta-galactosidase levels that are only partially repressible by methionine . The results suggest that the mutations disrupt the methionine control system mediated by the metJ gene product.

FEBS Lett, 1989 Jul 3, 250(2), 565 - 9
Cleavage of the O antigen 4, 5, 12 of Salmonella typhimurium by hydrofluoric acid; Helander IM et al.; The effect of hydrofluoric acid (aqueous 48% HF) upon different lipopolysaccharides (LPS) was studied, employing conditions (48 h at +4 degrees C) that are commonly used to dephosphorylate LPS . From the LPS of Salmonella typhimurium having the O antigen 4,5,12 almost all of the O-antigenic sugars (Abe, Gal, Glc, Man, Rha) were liberated in dialysable form, whereas the saccharide chains of Salmonella LPS with O antigen 6,7 (Man, Glc, GlcNAc) were resistant to HF . The lability towards HF was shown to be due to the presence of the deoxysugar L-rhamnose in the saccharide backbone of the O antigen 4,5,12, since only Rha was found as the terminal sugar in the corresponding dialysable material . Hydrofluoric acid can thus be used to specifically cleave Rha-containing polysaccharides.

Int J Food Microbiol, 1989 Jul, 8(4), 351 - 61
Effect of accelerated natural lactic fermentation of infant food ingredients on some pathogenic microorganisms; Nout MJ et al.; Accelerated natural lactic fermentation in mixtures of water and ground sorghum, millet and pigeon pea was obtained by gradual selection of lactic acid bacteria, through inoculum recycling . Weaning food prepared from ingredients fermented this way, contained approx . 0.7% lactic and 0.05% acetic acids and had a pH of about 3.8 . In porridges, a pH of less than or equal to 4.0 was required to cause death of Salmonella typhimurium and Staphylococcus aureus . Several intestinal pathogenic bacteria were inoculated into sour porridge . The most resistant Salmonella sp . died at a rate of 1.2 log cycle/h; the most resistant Shigella sp . at 0.9 log cycle/h; and the most resistant Escherichia coli strain at 0.6 log cycle/h . A yeast, Candida albicans, could grow well in the sour product, whereas a bacteriophage (MS-2) was inactivated at a rate of 0.1 log cycle/h . In the acid-sensitive bacterial cultures, no gradual adaptation to acid environments could be observed . The survival studies were carried out at 30 degrees C.

Int J Food Microbiol, 1989 Jul, 8(4), 321 - 33
Utilization of two improved enzyme immunoassays based on avidin-biotin interaction for the detection of Salmonella; Prusak-Sochaczewski E et al.; Based on a strong interaction between avidin and biotin, two enzyme immunoassays have been modified and tested for the detection of Salmonella typhimurium in foodstuffs . In both assays, the antigen containing sample was first reacted with antibody to Salmonella which was precoated on a polystyrene microtiter plate . The bound antigen was then allowed to react with an appropriate amount of biotinylated antibody . In the first procedure, the presence of Salmonella was quantified by using peroxidase-labeled avidin . In the latter, avidin acted as a bridge between the biotinylated antibody and the biotinylated peroxidase . Samples containing 10(3) and 10(4) cells/ml of the Salmonella virulent strain, respectively, were detectable by these two methods . The results thus compared favorably with the detection limit of the standard ELISA (10(5) cells/ml) . The superiority of the modified ELISA's utilizing biotin/avidin interactions was also demonstrated for the detection of Salmonella in artificially contaminated food samples inoculated with only 2-5 Salmonella cells followed by two incubation steps . No significant interference of E . coli (up to 5 x 10(6) cells/ml) was observed in the quantification of Salmonella cells.

J Mol Recognit, 1989 Jul, 2(1), 18 - 24
Interaction between phage G13 and its oligosaccharide receptor studied by equilibrium dialysis; Bruse GW et al.; The reversible binding of phage G13, a phi X174-like single-strand DNA phage, to a 3H-labelled nonasaccharide from the lipopolysaccharide of its natural host Escherichia coli C was studied with equilibrium dialysis . The binding constant (Ka) was determined to 1.3 x 10(7) M-1 in Scatchard and Lineweaver-Burk plots . Approximately one saccharide bound per G13 phage particle which suggests that only one of the 12 spikes in each G13 virion was engaged in the phage/receptor saccharide interaction . Equilibrium dialysis inhibition experiments with saccharides from lipopolysaccharides of an isogenic series of Salmonella typhimurium mutants showed that hepta- and pentasaccharides from two G13-sensitive bacteria, i.e., with efficiencies of plating of 0.1-1.0 compared to E . coli C, were efficient inhibitors with Ka-values greater than or equal to 1.2 x 10(7) M-1 . The octa- and hexasaccharides from two G13 resistant strains, with efficiency of plating less than or equal to x 10(-4), were either greater than 1000-fold or greater than 15-fold less efficient as inhibitors with Ka-values less than or equal to 8.8 x 10(5) M-1 . The results show that phage G13 binds in a specific and reversible way to penta-, hepta-, and nonasaccharides from G13 sensitive bacteria with the specificity residing in the hexose and heptose region of the core lipopolysaccharide.

East Afr Med J, 1989 Jul, 66(7), 453 - 7
Salmonella typhimurium outbreak at Kenyatta National Hospital (1985); Mirza NB et al.; A total of 560 Salmonellae species were isolated from Jan-Dec 1985 . Of these, 347 (62%) were from blood cultures, 180 (32%) from stools and 33 (6%) were from cerebrospinal fluid (CSF) and other body aspirates . S . typhimurium were the highest isolated . These were, 291 (52%) from blood cultures, 94 (17%) from stool cultures and 32 (6%) from CSF . S . typhimurium was also multi-drug resistant . More than 50% strains of S . typhimurium were resistant to ampicillin, tetracycline, kanamycin and chloramphenicol . The need for coordination between the laboratory and clinical staff to prevent the spill-over of infection with S . typhimurium and its epidemic spread is discussed.

J Nat Prod, 1989 Jul-Aug, 52(4), 774 - 8
Plant antimutagens, 6 . Intricatin and intricatinol, new antimutagenic homoisoflavonoids from Hoffmanosseggia intricata; Wall ME et al.; Intricatin {1} and intricatinol {2} are new homoisoflavonoids isolated from a desert plant Hoffmanosseggia intricata, which was collected in Baja California, Mexico . The structures of the compounds were elucidated using a variety of spectroscopic techniques . The structure of 1 was shown to be 7,4'-dimethoxy-8-hydroxyhomoisoflavone, and 2 was shown to be 4'-methoxy-7,8-dihydroxyhomoisoflavone . Both compounds 1 and 2 displayed activity in the inhibition of the mutagenicity of 2AN toward Salmonella typhimurium (T98) . Compound 2 was much more active than 1 in the case of the inhibition of the mutagenicity of AAF toward S . typhimurium (T98) and the inhibition of EMS towards S . typhimurium (T100) . Compounds 1 and 2 are the first examples of antimutagenic activity in homoisoflavones.

J Nat Prod, 1989 Jul-Aug, 52(4), 769 - 73
Plant antimutagenic agents, 5 . Isolation and structure of two new isoflavones, fremontin and fremontone from Psorothamnus fremontii; Manikumar G et al.; Two new isoflavones, fremontin and fremontone, were isolated from roots of Psorothamnus fremontii (Fabaceae), a desert plant . Compound 1 has the structure 5'-(alpha, alpha-dimethylallyl)-5,7,2',4'-tetrahydroxyisoflavone; compound 2 is similar but also contains the 3'-(gamma,gamma-dimethylallyl) substituent . The alpha,alpha-dimethylallyl substituent is rarely observed, and the combination of the alpha,alpha- and gamma,gamma-dimethylallyl substituents is unprecedented . Both 1 and 2 were nontoxic toward Salmonella typhimurium and were both highly active in the inhibition of mutagenicity of ethyl methanesulfonate (EMS) at all concentrations tested . Compound 2 was more active than 1 in the inhibition of mutagenicity of 2-aminoanthracene (2AN) and acetylaminofluorene (AAF) toward S . typhimurium.

Environ Health Perspect, 1989 Jul, 82, 81 - 9
Multiple activation pathways of benzene leading to products with varying genotoxic characteristics; Glatt H et al.; Benzene and 13 potential metabolites were investigated for genotoxicity in Salmonella typhimurium and V79 Chinese hamster cells . In the presence of NADPH-fortified hepatic postmitochondrial fraction (S9 mix), benzene reverted his- S . typhimurium strains . The effect was strongest in strain TA1535 . Among the potential metabolites, only the trans-1,2-dihydrodiol, in the presence of S9 mix, and the diol epoxides, in the presence and absence of S9 mix, proved mutagenic in this strain . The anti-diol epoxide was more potent than the syn-diastereomer . Both enantiomers of the anti-diastereomer showed similar activities . S9 mix did not appreciably affect the mutagenicity of the anti-diol epoxide . However, detoxification was observed when purified rat liver dihydrodiol dehydrogenase (EC 1.3.1.20) was used at concentrations comparable to that present in the liver . The (1S)-anti-diol epoxide was a much better substrate than the (1R)-enantiomer, as was true also for (1S)-versus (1R)-trans-1,2-dihydrodiol . The anti-diol epoxide reverted all six strains of S . typhimurium used and induced all four genotoxic effects studied in V79 cells (sister chromatid exchange greater than acquisition of 6-thioguanine resistance, acquisition of ouabain resistance, micronuclei) . However, other potential benzene metabolites showed genotoxic effects in V79 cells, as well: sister chromatid exchange was induced by the syn-diol epoxide, 1,2,4-trihydroxybenzene, hydroquinone, catechol, and 1,2,3-trihydroxybenzene . Elevated frequencies of micronucleated cells were observed after treatment with hydroquinone, 1,2,4-trihydroxybenzene, catechol, phenol, 1,2,3-trihydroxybenzene, and quinone . Mutations to 6-thioguanine resistance were induced by quinone, hydroquinone, 1,2,4-trihydroxybenzene, catechol, and the trans-1,2-dihydrodiol.(ABSTRACT TRUNCATED AT 250 WORDS)

Indian J Pathol Microbiol, 1989 Jul, 32(3), 213 - 5
Multiple drug resistant untypable Salmonella typhimurium infection in children & neonates; Shetty M et al.; Salmonella typhimurium infection in children and neonates is reported . Out of 21 cases, 6 were new-born and 13 were below one year of age . Clinical manifestations included fever, abdominal pain and diarrhoea . All the isolates were from stool, out of the total 21 cases, 4 expired . This study was done at Microbiology Department of Kasturba Medical College over a period of seven months.

Avian Dis, 1989 Jul-Sep, 33(3), 531 - 4
Effect of carbohydrates on Salmonella typhimurium colonization in broiler chickens; Oyofo BA et al.; The effect of carbohydrates in the drinking water of broiler chickens on Salmonella typhimurium colonization was evaluated . Results indicate that mannose and lactose (2.5%) significantly (P less than 0.05) reduced intestinal colonization of S . typhimurium by at least one-half, as compared with dextrose, maltose, and sucrose . Lactose and mannose also significantly reduced (P less than 0.01) the mean log10 number of S . typhimurium in the cecal contents . Although mannose was the most effective sugar at blocking colonization, lactose may be more practical because it is effective and costs much less than mannose . Provision of carbohydrates in the drinking water had no significant effect on weight gain.

Lab Anim, 1989 Jul, 23(3), 275 - 7
Uterine involvement in guineapig salmonellosis; Okewole PA et al.; Of 334 mature breeding guineapigs, 53 (15.9%) died in a disease outbreak involving Salmonella typhimurium serotypes 1, 4, 5 and 12 : i : 1,2 . The uterus was consistently involved . Nine other Salmonella-free mature female guineapigs when inoculated with a pure isolate from the outbreak, using the subcutaneous, intramuscular or per os route, succumbed to salmonellosis, reproducing signs and lesions observed during the outbreak . Abortion was not recorded during the outbreak despite many pregnant sows being affected . The isolate was sensitive to gentamicin, tetracycline, ampicillin and cefuroxime but resistant to co-trimoxazole, erythromycin and penicillin.

Immunology, 1989 Jul, 67(3), 394 - 400
Confirmation of destruction of salmonellae within murine peritoneal exudate cells by immunocytochemical technique; Lin FR et al.; A procedure was developed with which peritoneal exudate cell (PEC) preparations were fixed in a glutaraldehyde-picric acid mixture, post-fixed with osmium tetroxide, embedded in LR White resin and then stained with immunogold probe . It provided tissue sections showing both well-defined ultrastructures as well as specifically labelled Salmonella O antigens by electron microscopy . Inbred, male C57BL/6 mice were injected intraperitoneally with 2 x 10(7) virulent Salmonella typhimurium . Peritoneal exudate cells were harvested at 16 and 20 hr after infection . Disintegrating intracellular bacteria were identified as salmonellae by the immunogold markers . Deposition of gold particles in the cytoplasm of phagocytes also indicated that intracellular debris contained digested pathogen . This investigation therefore confirms previous findings of the destruction of salmonellae within inflammatory polymorphs and macrophages.

Mutat Res, 1989 Jul, 226(3), 181 - 4
Mutagenicity of 2,6-dinitrotoluene and its metabolites, and their related compounds in Salmonella typhimurium; Sayama M et al.; The mutagenic activities of 2,6-dinitrotoluene (2,6-DNT) and its 6 metabolites, and their 8 related compounds were examined using Salmonella typhimurium strains TA98 and TA100 in the absence or presence of S9 mix . 2,6-DNT itself showed no mutagenicity toward either strain, but 2,6-dinitrobenzaldehyde (2,6-DNBAl), one of the metabolites of 2,6-DNT, showed the highest mutagenic activity in strain TA100 . 2,6-DNBAl was a direct-acting mutagen, not requiring metabolic activation . The other compounds containing nitro groups showed weak or no mutagenic activity . This result suggests that the direct-acting mutagenicity of 2,6-DNBAl is mainly due to the aldehyde group of the 2,6-DNBAl molecule.

Mutat Res, 1989 Jul, 226(3), 175 - 80
Simple method for precise determination of chemical lethality in the L-arabinose resistance test of Salmonella typhimurium; Roldan-Arjona T et al.; A simple method is described for the determination of the lethal effects of chemicals assayed with the L-arabinose resistance test of Salmonella typhimurium . The method uses a mixed culture of 2 isogenic bacterial strains which are distinguished on the basis of their different nutritional requirements: sensitivity or resistance to L-arabinose, auxotrophy or prototrophy to histidine and leucine . BA13 (the mutation indicator strain) is the strain for routine screening of mutagens and allows the selection of forward mutation from L-arabinose sensitivity to L-arabinose resistance . BAL13 (the survival indicator strain) is a derivative of BA13 . Both bacterial strains are found to be equally sensitive to the lethal effects of mutagens . The method described permits the measurement of cell survival at the same high cell concentration as used in the measurement of the mutant yield and in the same type of minimal medium with L-arabinose and glycerol, except for the histidine supplement in the mutant plates or the leucine in the survival plates.

Mutat Res, 1989 Jul, 226(3), 169 - 74
7-Amino-2,4,6-trimethylquinoline as a mutagenic pyrolysate compound of polyurethane foam; Hirayama T et al.; Commercial polyurethane foam was pyrolyzed by gas burners at 600-700 degrees C for 2 h with introduction of air (200 ml/min) . Gaseous pyrolysate was trapped in water and 10% hydrochloric acid . Basic and neutral pyrolysates have a mutagenic activity (447 revertants/10 micrograms) in Salmonella typhimurium TA98 in the presence of a mammalian metabolic activation system . These pyrolysates contained 12.32 mg of amino compounds as diaminotoluene per g polyurethane foam, amounts which are 120 times higher than those in unpyrolysed polyurethane foam . Basic and neutral pyrolysates were subjected to silica gel column chromatography, and 6 fractions having mutagenic potency were obtained . The colorless needles (m.p . 200.5-202 degrees C) were separated from fraction 4 . These needles have the most potent mutagenicity (678 revertants/2 micrograms) in basic and neutral pyrolysates in Salmonella typhimurium TA98 with 10% S9 mix . From the physicochemical data, the structure of the compound was estimated to be an aminoquinoline derivative, and was identified using synthesized 7-amino-2,4,6-trimethylquinoline by mixed melting point, thin-layer co-chromatography and gas chromatography-mass spectrometry.

Mutat Res, 1989 Jul, 226(3), 151 - 5
Mutagenicity on chlorination of products formed by ozonation of naphthoresorcinol in water; Sayato Y et al.; The mutagenicity of products formed by chlorination after ozonation of naphthoresorcinol in aqueous solution was assayed with Salmonella typhimurium strains TA98 and TA100 in the presence and absence of S9 mix from phenobarbital- and 5,6-benzoflavone-induced rat liver . Ozonated and subsequently chlorinated naphthoresorcinol was directly mutagenic, as was ozonated naphthoresorcinol, in both strains tested . The mutagenic activity at chlorination with 8 equivalents of chlorine per mole of naphthoresorcinol after ozonation was markedly higher than that at only ozonation . Of the identified ozonation products of naphthoresorcinol, muconic acid, after chlorination with 2 or 4 equivalents of chlorine per mole of the compound, induced direct mutagenicity against TA98 and TA100 . The chlorination of glyoxal with 0.5 and 1 chlorine equivalents per mole of the compound was shown to produce direct mutagenicity toward TA98 . The identification of the chlorination products of these compounds is also discussed.

Proc Natl Acad Sci U S A, 1989 Jul, 86(13), 5173 - 7
Penetration of human intestinal epithelial cells by Salmonella: molecular cloning and expression of Salmonella typhi invasion determinants in Escherichia coli; Elsinghorst EA et al.; Salmonella typhi, the causative agent of typhoid fever, must invade the human gastrointestinal tract and multiply within the host to cause disease . We have cloned from S . typhi Ty2 a chromosomal region that confers upon Escherichia coli HB101 the ability to invade cultured human intestinal epithelial cells . Three invasion-positive recombinant cosmids were isolated and restriction endonuclease analyses of the inserts showed a 33-kilobase region of identity . Transmission electron microscopy of epithelial cells invaded by S . typhi Ty2 or E . coli HB101 carrying an invasion cosmid showed intracellular bacteria contained within endocytic vacuoles . One of the invasion cosmids was mutagenized with transposon Tn5 to identify the cloned sequences that are required for the invasive phenotype . Seven of 92 independent Tn5 insertions within the common 33-kilobase region eliminated invasive ability and revealed at least four separate loci that are required for invasion . Penetration of epithelial cells by Ty2 and HB101 carrying the cloned invasion determinants was inhibited by cytochalasin B and D, indicating that epithelial cell endocytosis of S . typhi is a microfilament-dependent event . The invasion cosmids were found to carry the recA and srlC genes indicating that the cloned invasion determinants are located at about 58 minutes on the S . typhi chromosome . With a segment of the cloned S . typhi invasion region used as a probe, homologous sequences were isolated from Salmonella typhimurium . Two independent S . typhimurium recombinant cosmids containing the entire 33-kilobase common region identified in S . typhi were isolated, but these cosmids did not confer upon HB101 the ability to invade epithelial cells.

J Bacteriol, 1989 Jul, 171(7), 3860 - 5
Identification of a umuDC locus in Salmonella typhimurium LT2; Smith CM et al.; The umuDC operon of Escherichia coli is required for efficient mutagenesis by UV light and many other DNA-damaging agents . The existence of a umuDC analog in Salmonella typhimurium has been questioned . With DNA probes to the E . coli umuD and umuC genes, we detected, by Southern blot hybridization, sequences similar to both of these genes in S . typhimurium LT2 . We also confirmed that the presence of cloned E . coli umuD enhances the UV mutability and resistance of S . typhimurium . Our data strongly suggest that S . typhimurium contains a functional umuDC operon.

J Bacteriol, 1989 Jul, 171(7), 3597 - 602
Accumulation of 3-(N-morpholino)propanesulfonate by osmotically stressed Escherichia coli K-12; Cayley S et al.; We found that exogenous morpholinopropanesulfonate (MOPS) is concentrated approximately fivefold in the free volume of the cytoplasm of Escherichia coli K-12 (strain MG1665) when grown at high osmolarity (1.1 OsM) in two different media containing 40 mM MOPS . MOPS was not accumulated by E . coli grown in low-osmolarity MOPS-buffered medium or in 1.1 OsM MOPS-buffered medium containing the osmoprotectant glycine betaine . Salmonella typhimurium LT2 did not accumulate MOPS under any condition examined . We infer that accumulation of MOPS by E . coli K-12 is not due to passive equilibration but rather to transport, possibly involving an as yet uncharacterized porter not present in S . typhimurium . Glutamate and MOPS were the only anionic osmolytes we observed by 13C nuclear magnetic resonance in E . coli K-12 grown in MOPS-buffered medium . The increase in positive charge accompanying the increase in the steady-state amount of K+ in cells shifted from low to high external osmolarity appeared to be compensated for by changes in the amounts of putrescine, glutamate, and MOPS . MOPS is not an osmoprotectant, because its accumulation did not increase cell growth rate.

Proc Natl Acad Sci U S A, 1989 Jul, 86(13), 5054 - 8
A two-component regulatory system (phoP phoQ) controls Salmonella typhimurium virulence; Miller SI et al.; We have determined that Salmonella typhimurium strains with mutations in the positive regulatory locus phoP are markedly attenuated in virulence for BALB/c mice . The DNA sequence for the phoP locus indicates that it is composed of two genes present in an operon, termed phoP and phoQ . The deduced amino acid sequence of the phoP and phoQ gene products are highly similar to other members of bacterial two-component transcriptional regulators that respond to environmental stimuli . S . typhimurium strains with transposon insertions that create transcriptional and translational gene fusions that require phoP and phoQ for expression have been isolated and have different chromosomal locations, indicating that this system is a regulon . One of these fusion strains, containing a mutation in a gene termed pagC, has a virulence defect . Other strains, including those containing mutations in the phoN gene, encoding an acid phosphatase, have wild-type virulence . Strains with pagC, phoP, or phoQ mutations have decreased survival in cultured mouse macrophages . When used as live vaccines in mice, strains with phoP or phoQ mutations afford partial protection to subsequent challenge by wild-type S . typhimurium.

J Bacteriol, 1989 Jul, 171(7), 3948 - 60
Cloning, genetic characterization, and nucleotide sequence of the hemA-prfA operon of Salmonella typhimurium; Elliott T; The first step in heme biosynthesis is the formation of 5-aminolevulinic acid (ALA) . Mutations in two genes, hemA and hemL, result in auxotrophy for ALA in Salmonella typhimurium, but the roles played by these genes and the mechanism of ALA synthesis are not understood . I have cloned and sequenced the S . typhimurium hemA gene . The predicted polypeptide sequence for the HemA protein shows no similarity to known ALA synthases, and no ALA synthase activity was detected in extracts prepared from strains carrying the cloned hemA gene . Genetic analysis, DNA sequencing of amber mutations, and maxicell studies proved that the open reading frame identified in the DNA sequence encodes HemA . Another surprising finding of this study is that hemA lies directly upstream of prfA, which encodes peptide chain release factor 1 (RF-1) . A hemA::Kan insertion mutation, constructed in vitro, was transferred to the chromosome and used to show that these two genes form an operon . The hemA gene ends with an amber codon, recognized by RF-1 . I suggest a model for autogenous control of prfA expression by translation reinitiation.

J Bacteriol, 1989 Jul, 171(7), 3890 - 900
L-, P-, and M-ring proteins of the flagellar basal body of Salmonella typhimurium: gene sequences and deduced protein sequences; Jones CJ et al.; The flgH, flgI, and fliF genes of Salmonella typhimurium encode the major proteins for the L, P, and M rings of the flagellar basal body . We have determined the sequences of these genes and the flgJ gene and examined the deduced amino acid sequences of their products . FlgH and FlgI, which are exported across the cell membrane to their destinations in the outer membrane and periplasmic space, respectively, both had typical N-terminal cleaved signal-peptide sequences . FlgH is predicted to have a considerable amount of beta-sheet structure, as has been noted for other outer membrane proteins . FlgI is predicted to have an even greater amount of beta-structure . FliF, as is usual for a cytoplasmic membrane protein of a procaryote, lacked a signal peptide; it is predicted to have considerable alpha-helical structure, including an N-terminal sequence that is likely to be membrane-spanning . However, it had overall a quite hydrophilic sequence with a high charge density, especially towards its C terminus . The flgJ gene, immediately adjacent to flgI and the last gene of the flgB operon, encodes a flagellar protein of unknown function whose deduced sequence was hydrophilic and may correspond to a cytoplasmic protein . Several aspects of the DNA sequence of these genes and their surrounds suggest complex regulation of the flagellar gene system . A notable example occurs within the flgB operon, where between the end of flgG (encoding the distal rod protein of the basal body) and the start of flgH (encoding the L-ring protein) there was an unusually long noncoding region containing a potential stem-loop sequence, which could attenuate termination of transcription or stabilize part of the transcript against degradation . Another example is the interface between the flgB and flgK operons, where transcription termination of the former may occur within the coding region of the latter.

Infect Immun, 1989 Jul, 57(7), 2136 - 40
Characterization of porin and ompR mutants of a virulent strain of Salmonella typhimurium: ompR mutants are attenuated in vivo; Dorman CJ et al.; The ompC, ompD, and ompF genes encode the three major porins of Salmonella typhimurium . ompR encodes a positive regulator required for the expression of ompC and ompF . Transposon-generated mutations in ompC, ompD, ompF, and ompR were introduced into the S . typhimurium mouse virulent strain SL1344 by P22-mediated transduction . Following preliminary characterization in vitro, the strains were used to challenge BALB/c mice by using the oral or intravenous route . Strains harboring ompC or ompF mutations were as virulent as SL1344 after oral challenge . Strains harboring ompD mutations had a slight reduction in virulence . In contrast, ompR mutants failed to kill BALB/c mice after oral challenge and the intravenous 50% lethal dose was reduced by approximately 10(5) . The ompR mutants persisted in murine tissues for several weeks following oral or intravenous challenge . Furthermore, mice orally immunized with these ompR mutant strains were well protected against challenge with virulent SL1344.

J Clin Pathol, 1989 Jul, 42(7), 677 - 81
Infections in British clinical laboratories, 1986-87; Grist NR et al.; During 1986-87 this continuing survey showed 15 specific infections in the staff of 235 laboratories, representing 28,524 person years of exposure . The community was the probable source of four of the five cases of tuberculosis and one of the five cases of salmonellosis . Occupational exposure was the probable cause of four infections by Shigella flexneri, three by Salmonella typhimurium, and one by S typhi, all affecting medical laboratory scientific officers (MLSOs) in microbiology . Occupational exposure was also the probable cause of one case of tuberculosis in a mortuary technician and one of probable non-A, non-B hepatitis in a medical laboratory scientific officer haematology worker . The overall incidence of reported infections was 52.6/100,000 person years (35/100,000 for infections of probable occupational origin) . The highest rates of laboratory acquired infections related to MLSO microbiology workers and mortuary technicians . No additional infections were seen as a result of extending the survey to forensic laboratories.

Mutat Res, 1989 Jul, 223(3), 273 - 85
Antimutagenic activity of green tea polyphenols; Wang ZY et al.; For centuries green tea has been a widely consumed beverage throughout the world . It is known to contain a number of pharmacologically active compounds . In this study water extracts of green tea (WEGT) and their major constituents, green tea polyphenols (GTP), were examined for antimutagenic activity . WEGT and GTP were found to significantly inhibit the reverse mutation induced by benzo{alpha}pyrene (BP), aflatoxin B1 (AFB1), 2-aminofluorene, and methanol extracts of coal tar pitch in Salmonella typhimurium TA100 and/or TA98 in the presence of a rat-liver microsomal activation system . GTP also inhibited gene forward mutation in V79 cells treated with AFB1 and BP, and also decreased the frequency of sister-chromatid exchanges and chromosomal aberrations in V79 cells treated with AFB1 . The addition of GTP during and after nitrosation of methylurea resulted in a dose-dependent inhibition of mutagenicity . Studies to define the mechanism of the antimutagenic activity of GTP suggest that it may affect carcinogen metabolism, DNA adduct formation, the interaction of ultimate carcinogen or the scavenging of free radicals.

Infect Immun, 1989 Jul, 57(7), 2260 - 4
In vitro and in vivo toxicity of T-2 toxin, a Fusarium mycotoxin, to mouse peritoneal macrophages; Vidal D et al.; The effects of T-2 toxin on mouse peritoneal macrophages were investigated . Scanning electron microscopy of macrophages treated in vitro with T-2 toxin revealed retraction of pseudopodia . Protein synthesis was inhibited after in vitro contact with T-2 toxin but was not affected 24 h after injection of a sublethal dose of toxin into mice . There was reduction in the phagocytosis of Pseudomonas aeruginosa when macrophages were exposed in vitro to T-2 toxin and when mice were injected with T-2 toxin . Clearance of colloidal carbon was not modified after T-2 toxin injection, whereas spleen weight was decreased 24 h after T-2 injection . T-2 toxin enhanced the mortality of mice infected with Salmonella typhimurium C5S when it was administered 24 h prior to oral challenge with the bacterium.

J Appl Bacteriol, 1989 Jul, 67(1), 53 - 9
Inhibition by antibiotics of the bacterial response to long-term starvation of Salmonella typhimurium and the colon microbiota of mice; Stenstrom TA et al.; The number of viable cells of two strains of Salmonella typhimurium and the number of viable cells and the cell size of the colon microbiota of mice were examined during non-growing conditions after exposure to antibiotics with known modes of action . Salmonella typhimurium starved for 1, 2, 4, 5, 12 and 20 d in a phosphate buffer saline solution and subsequently exposed for 2 and 6 h showed the following characteristics . The protein synthesis inhibitors gentamicin and tetracycline, the RNA synthesis inhibitor rifampicin and the membrane potential inhibitor polymyxin all impaired survival of starved cells . The reduction in the number of viable cells caused by the addition of gentamicin, rifampicin and polymyxin was generally more pronounced with extended exposure to energy and nutrient deprivation . Both 2- and 6-h exposure of tetracycline, however, had diminishing inhibitory effects after 20 d compared with 5 d of starvation . Control experiments to verify non-growing conditions in the starvation regime showed that DNA and cell wall synthesis inhibitors had no inhibitory effect after 24-h starvation . The rough mutant strain displayed a lower sensitivity to a hydrophobic rather than a hydrophilic inhibitor as compared to the smooth wild-type strain . The cell size reduction but not viability was partly prevented by protein synthesis inhibitors as seen for both in vivo and in vitro colon microbiota studies.

J Bacteriol, 1989 Jul, 171(7), 3824 - 30
Suppression of a -1 frameshift mutation by a recessive tRNA suppressor which causes doublet decoding; O'Mahony DJ et al.; sufS was found to suppress the only known suppressible-1 frameshift mutation, trpE91, at a site identified as GGA and mapped within the single gene of the only tRNA that can decode GGA in Escherichia coli . It mapped to the same gene in Salmonella typhimurium . sufS alleles were recessive, and dominant alleles could not be isolated . This is in contrast to all other tRNA structural gene mutations identified thus far that cause frameshift suppression . The recessiveness implies that all sufS alleles are poor competitors against their wild-type tRNA(Gly2) counterparts . The base G immediately 5' of the GGA suppression site influenced the level but was not critical for suppression by sufS601 . From this result, it is inferred that sufS601 causes frameshifting by doublet decoding.

Tidsskr Nor Laegeforen, 1989 Jun 30, 109(19-21), 1982 - 5
{The contaminated chocolate epidemic of 1987}; Kapperud G et al.; The article describes a nationwide outbreak of Salmonella typhimurium infection in 1987 caused by contaminated chocolate products from one particular factory . A total of 349 bacteriologically verified cases were recorded . It was estimated, however, that 20,000-40,000 persons became ill during the outbreak . We describe the epidemiological and bacteriological investigations which led to identification of the source of infection, and discuss two epidemiological models for investigation of food-borne outbreaks . The article emphasizes the importance of collaboration between the community health service and the local food inspection laboratories during investigation of foodborne outbreaks.

Lancet, 1989 Jun 24, 1(8652), 1411 - 4
Serological diagnosis of salmonella infections by enzyme immunoassay; Isomaki O et al.; An enzyme immunoassay (EIA) for the detection and measurement of serum IgM, IgG, and IgA antibodies to salmonella was developed with commercially available lipopolysaccharides (LPSs) of Salmonella typhimurium and S enteritidis combined as antigen . Of 130 sera from patients with culture-confirmed salmonella infections, 115 (88.5%) were positive in this assay . The classic Widal agglutination test was positive in only 50 (38.5%) cases . This EIA method offers a substantial advance in the serological diagnosis of acute salmonella infections; it detects antibodies to the salmonellae of groups B and D, which constitute about 70% of culture-positive cases of human salmonellosis . Antibodies to other salmonellae are also detected . This EIA is particularly valuable for the detection of salmonella antibodies during post-infectious complications when isolation of the organism is often no longer possible.

Biochem Biophys Res Commun, 1989 Jun 15, 161(2), 923 - 30
Abortive infection of the virulent phage 9NA in a fatty acid auxotroph of Salmonella typhimurium: effect of fatty acid supplementation; Goyal R et al.; A conditional (temperature sensitive) fatty acid biosynthetic mutant (fabB2) of Salmonella typhimurium does not support the development of the virulent bacteriophage 9NA even at permissive temperature (30 degrees C) . A limited amount of phage DNA synthesis takes place at this temperature . When the fatty acid composition of the host membrane is altered by growing the cells at 37 degrees C in the presence of exogenous unsaturated fatty acid, differential expression of phage genes was observed . Phage specific lysozyme is induced when the cultures are supplemented with elaidic, palmitelaidic, linoleic and linolelaidic acids but not with oleic and plamitoleic acids . However, in no case were infective particles produced . Under conditions where no lysozyme is synthesized the infected cells increase in length and become filamentous.

J Immunol, 1989 Jun 15, 142(12), 4450 - 7
Multimeric C9 within C5b-9 deposits in unique locations in the cell wall of Salmonella typhimurium; Joiner KA et al.; We have shown previously that multimeric C9 within C5b-9 (C9:C5b-8 greater than 3:1) is needed for killing of a rough strain of Escherichia coli . We now extend these studies using serum sensitive, rough (R) and serum resistant, wild type (WT) strains of Salmonella typhimurium as well as a mutant S . typhimurium strain (TS) with a temperature sensitive mutation in synthesis of keto-deoxy-octulosonate, a constituent within the deep core structure of Salmonella LPS . Both R and TS required multimeric C9 within C5b-9 to be killed . Addition at 37 degrees C of increasing inputs of C9 to TS or R bearing C5b-9 led to a dose-related increase in C9 binding and killing . In contrast, addition of high inputs of C9 to the same strains at 4 degrees C, a procedure that limits the C9:C5b-8 ratio to 1:1, resulted in low C9 binding and minimal killing . Bactericidal C5b-9 formed at 37 degrees C on R and TS with high inputs of C9 co-sedimented with the bacterial outer membrane on sucrose density gradient analysis . Non-bactericidal C5b-9 on R, WT, and TS co-sedimented near the inner membrane, despite the presumed lack of association between these constituents . Whereas 125I C9 within the non-bactericidal pools immunoprecipitate with anti-C5, 125I C9 within bactericidal pools did not immunoprecipitate with anti-C5, anti-C7, or anti-C9 . These findings suggest that bactericidal C5b-9 may be deposited in a unique location or configuration within the bacterial cell wall.

J Immunol, 1989 Jun 15, 142(12), 4256 - 60
HLA class I-related impairment in IL-2 production and lymphocyte response to microbial antigens in reactive arthritis; Inman RD et al.; The contribution of certain Gram-negative bacteria and host HLA class I Ag to the development of reactive arthritis (ReA)3 has strong epidemiologic support but the pathogenesis of the arthritis is unknown . An outbreak of Salmonella typhimurium afforded the opportunity to compare the immune response to the organism between those who developed ReA (ReA+, n = 11) with those who did not (ReA-, n = 12) . Of the 11 ReA+ patients, 4 were B27-positive and 6 were B7-positive; of the ReA- patients none was B27- or B7-positive . The causative pathogen S . typhimurium phage 22 was used to examine PBL proliferation by {3H}thymidine incorporation . Impairment in lymphocyte response to S . typhimurium in ReA+ compared with ReA- was demonstrated by: i) lower stimulation index (1.9 +/- 0.3 for ReA+, 5.7 +/- 0.6 for ReA-, p less than 0.01); ii) lower in vitro Ig production; and iii) lower Ag-induced IL-2 production . Mixing experiments did not demonstrate a soluble suppressor factor in ReA+ supernatants . Thus, after infection with S . typhimurium there is an impairment in cellular immunity that has correlates in immunogenetic and clinical features of the infected population.

J Biol Chem, 1989 Jun 15, 264(17), 9827 - 35
Affinity labeling of a glutamyl peptide in the coenzyme binding site of NADP+-specific glutamate dehydrogenase of Salmonella typhimurium by 2-{(4-bromo-2,3-dioxobutyl)thio}-1,N6-ethenoadenosine 2',5'-bisphosphate; Bansal A et al.; NADP+-specific glutamate dehydrogenase from Salmonella typhimurium, cloned and expressed in Escherichia coli, has been purified to homogeneity . The nucleotide sequence of S . typhimurium gdhA was determined and the amino acid sequence derived . The nucleotide analogue 2-{(4-bromo-2,3-dioxobutyl)thio}-1,N6-ethenoadenosine 2',5'-bisphosphate (2-BDB-T epsilon A-2',5'-DP) reacts irreversibly with the enzyme to yield a partially inactive enzyme . After about 60% loss of activity, no further inactivation is observed . The rate of inactivation exhibits a nonlinear dependence on 2-BDB-T epsilon A-2',5'-DP concentration with kmax = 0.160 min-1 and KI = 300 microM . Reaction of 200 microM 2-BDB-T epsilon A-2',5'-DP with glutamate dehydrogenase for 120 min results in the incorporation of 0.94 mol of reagent/mol of enzyme subunit . The coenzymes, NADPH and NADP+, completely protect the enzyme against inactivation by the reagent and decrease the reagent incorporation from 0.94 to 0.5 mol of reagent/mol enzyme subunit, while the substrate alpha-ketoglutarate offers only partial protection . These results indicate that 2-BDB-T epsilon A-2',5'-DP functions as an affinity label of the coenzyme binding site and that specific reaction occurs at only about 0.5 sites/enzyme subunit or 3 sites/hexamer . Glutamate dehydrogenase modified with 200 microM 2-BDB-T epsilon A-2',5'-DP in the absence and presence of coenzyme was reduced with NaB3H4, carboxymethylated, and digested with trypsin . Labeled peptides were purified by high performance liquid chromatography and characterized by gas phase sequencing . Two peptides modified by the reagent were isolated and identified as follows: Phe-Cys(CM)-Gln-Ala-Leu-Met-Thr-Glu-Leu-Tyr-Arg and Leu-Cys(CM)-Glu-Ile-Lys . These two peptides were located within the derived amino acid sequence as residues 146-156 and 282-286 . In the presence of NADPH, which completely prevents inactivation, only peptide 146-156 was labeled . This result indicates that modification of the pentapeptide causes loss of activity . Glutamate 284 in this peptide is the probable reaction target and is located within the coenzyme binding site.

Cancer Res, 1989 Jun 15, 49(12), 3218 - 28
Human liver microsomal cytochrome P-450 enzymes involved in the bioactivation of procarcinogens detected by umu gene response in Salmonella typhimurium TA 1535/pSK1002; Shimada T et al.; A total of 57 procarcinogens was examined for induction of umu gene response in the chimeric plasmid pSK1002, carried in Salmonella typhimurium TA 1535, after incubation with a series of human liver microsomal preparations which had been selected on the basis of characteristic levels of individual cytochrome P-450 (P-450) enzymes . The 18 most active compounds were selected and further analyzed using the umu gene response and correlative studies with a larger number of microsomal preparations, enzyme reconstitution studies involving purified enzymes, immunochemical inhibition, and patterns of stimulation and inhibition of catalytic activity by 7,8-benzoflavone . The results collectively indicate that 16 of these 18 most potent genotoxins examined are activated primarily either by P-450NF (the nifedipine oxidase) or P-450PA (the phenacetin O-deethylase) . P-450NF appears to be the major enzyme involved in the bioactivation of aflatoxin B1, aflatoxin G1, sterigmatocystin, trans-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene, 6-aminochrysene, and tris-(2,3-dibromopropyl)phosphate in human liver . P-450PA appears to be the major enzyme involved in the bioactivation of 2-amino-3-methylimidazo{4,5-f}quinoline, 2-amino-3,5-dimethylimidazo{4, 5-f}quinoline, 2-amino-3,8-dimethylimidazo{4,5-f}quinoxaline, 2-aminoanthracene, 2-amino-6-methyldipyrido{1,2-a:3',2'-d}imidazole, 2-aminofluorene, 2-acetylaminofluorene, 4-aminobiphenyl, 3-amino-1-methyl-5H-pyrido{4,3-b} indole, and 2-aminodipyrido{1,2-a:3',2'-d}imidazole . More than one enzyme appears to contribute significantly to the bioactivation of the other two compounds examined, 3-amino-1,4-dimethyl-5H-pyrido{4,3-b} indole and 6-nitrochrysene . The literature suggests that the two human liver P-450s involved in activation of these 16 procarcinogens are highly inducible by barbiturates, macrolide antibodies, and certain steroids (P-450NF) and by smoking and ingestion of charcoal-containing food (P-450PA); noninvasive assays are available to monitor the function of both P-450NF and P-450PA.

Biochemistry, 1989 Jun 13, 28(12), 5306 - 10
Amino acid sequence of Salmonella typhimurium branched-chain amino acid aminotransferase; Feild MJ et al.; The complete amino acid sequence of the subunit of branched-chain amino acid aminotransferase (transaminase B, EC 2.6.1.42) of Salmonella typhimurium was determined . An Escherichia coli recombinant containing the ilvGEDAY gene cluster of Salmonella was used as the source of the hexameric enzyme . The peptide fragments used for sequencing were generated by treatment with trypsin, Staphylococcus aureus V8 protease, endoproteinase Lys-C, and cyanogen bromide . The enzyme subunit contains 308 residues and has a molecular weight of 33,920 . To determine the coenzyme-binding site, the pyridoxal 5-phosphate containing enzyme was treated with tritiated sodium borohydride prior to trypsin digestion . Peptide map comparisons with an apoenzyme tryptic digest and monitoring radioactivity incorporation allowed identification of the pyridoxylated peptide, which was then isolated and sequenced . The coenzyme-binding site is the lysyl residue at position 159 . The amino acid sequence of Salmonella transaminase B is 97.4% identical with that of Escherichia coli, differing in only eight amino acid positions . Sequence comparisons of transaminase B to other known aminotransferase sequences revealed limited sequence similarity (24-33%) when conserved amino acid substitutions are allowed and alignments were forced to occur on the coenzyme-binding site.

J Mol Biol, 1989 Jun 5, 207(3), 643 - 4
Crystallization and preliminary X-ray studies of HisJ and LAO periplasmic proteins from Salmonella typhimurium; Kang CH et al.; Two periplasmic binding proteins, HisJ and LAO, which are involved in histidine and arginine transport, respectively, have been crystallized . Preliminary X-ray diffraction studies of the HisJ and LAO crystals show that both belong to the orthorhombic space group P2(1)2(1)2(1) and have unit cell dimensions of a = 39.26 A, b = 66.17 A, c = 88.33 A and a = 36.08 A, b = 78.34 A, c = 102.02 A, respectively . Both HisJ and LAO crystals diffract beyond 2.0 A resolution.

Kokubyo Gakkai Zasshi, 1989 Jun, 56(2), 263 - 88
{Study on biocompatibility of titanium alloys}; Kodama T; The biocompatibility of two different titanium alloys, Ti-6Al-4V ELI and Ti-5Al-2, 5Fe, and pure titanium were evaluated . The results were as follows: 1) Titanium alloys were implanted into the dorsal subcutaneous tissues of the Hartley guinea-pig for 12 weeks, immersed in calf serum or in Ringer's solution for 8 weeks . The surface changes of the titanium alloys were observed by SEM and the chemical composition was analyzed by XMA . No evident surface changes were found . 2) Three hundred mg, 200 mg and 100 mg of the powders of the tested materials were immersed in 2ml of Eagle's MEM, incubated for 1-7 days, 8-21 days and 22-70 days at 37 C degrees . The amount of metallic elements dissolved in the solutions was measured by ICP and AAS . The detected corrosion rates of V and Al contained in the solution, in which Ti-6Al-4V ELI 100 mg was immersed for 1-7 days, were 194.3 +/- 17.6 and 73.0 +/- 28, 1 pg/mg alloy/day, respectively . V was released more than Al . The amount of Ti was below the detectable limit . The solution Ti-5Al-2.5 Fe 100 mg immersed for 1-7 days contained 31.9 +/- 34.4 pg/mg alloy/day Fe and 25.7 +/- 6.3 pg/mg alloy/day Al . Only in the solution 300 mg immersed for 1-7 days was Ti detected at 1.4 pg/mg alloy/day . 3) By the bacterial mutation assay of Salmonella typhimurium TA 98, Salmonella typhimurium TA 100 and Escherichia coli WP2 uvrA, the solutions, in which the tested materials were immersed, were not found to be mutagenic . 4) By the UDS assay, the grain counts on autoradiography with the solutions, in which the tested materials were immersed, were not greater than the negative control . The results suggest an excellent corrosion resistance of the titanium alloys . Mutagenicity was negative by these mutation assays, indicating that the tested alloys and pure titanium are safe for humans and animals.

Arzneimittelforschung, 1989 Jun, 39(6), 706 - 9
Assessment of the preclinical activity of budotitane in three different transplantable tumor systems, its lack of mutagenicity, and first results of clinical phase I studies; Keppler BK et al.; The antitumor activity of budotitane was investigated in three different tumor systems--the transplantable murine ascitic-colon-adenocarcinoma MAC 15A, the TD-osteosarcoma of the rat, and the intramuscularly transplanted murine sarcoma 180 . Marked inhibition of tumor growth was observed in the intramuscularly transplanted sarcoma 180, and cure rates of 50-80% were achieved in the colon adenocarcinoma MAC 15A . In contrast to these findings, bulotitane was inactive in the transplantable TD-osteosarcoma of the rat . Preliminary mutagenicity studies with the Salmonella typhimurium/mammalian microsome assay of Ames did not show any evidence of mutagenicity for the compound . The first results of the phase I clinical trials showed mild hepatotoxicity at a dose level of 15 mg/kg, dose-limiting nephrotoxicity at 21 mg/kg, and a reversible impairment of the sense of taste, beginning at a dose of 9 mg/kg.

Appl Environ Microbiol, 1989 Jun, 55(6), 1329 - 33
Effects of nisin on growth of bacteria attached to meat; Chung KT et al.; Nisin had an inhibitory effect on gram-positive bacteria (Listeria monocytogenes, Staphylococcus aureus, and Streptococcus lactis) but did not have an inhibitory effect on gram-negative bacteria (Serratia marcescens, Salmonella typhimurium, and Pseudomonas aeruginosa) attached to meat . Nisin delayed bacterial growth on meats which were artificially inoculated with L . monocytogenes or Staphylococcus aureus for at least 1 day at room temperature . If the incubation temperature was 5 degrees C, growth of L . monocytogenes was delayed for more than 2 weeks, and growth of Staphylococcus aureus did not occur . We also found that the extractable activity of nisin decreased rapidly when the meats were incubated at ambient temperatures and that this decrease was inversely related to the observed inhibitory effect . These findings disclosed that nisin delays the growth of some gram-positive bacteria attached to meat . However, nisin alone may not be sufficient to prevent meat spoilage because of the presence of gram-negative and other nisin-resistant gram-positive bacteria.

Am J Infect Control, 1989 Jun, 17(3), 159 - 61
Activities of infection control practitioners during an outbreak of Salmonella typhimurium . Task Force of Association for Practitioners in Infection Control; Jarosch MJ et al.; ICPs played an invaluable role, and their activities resulted in minimal nosocomial incidence . The survey reported two cases of nosocomial infection in patients, one in the medical service and one in the pediatric unit, as well as the reported employee cases . Two nosocomial employee cases were reported, a laboratory technologist and medical student . Implementation of these recommendations will make the job of the ICP easier during any outbreak . We believe that our interventions, interactions, and assistance positively affected the course of the epidemic . In the final analysis the activities of surveillance, supervision of isolation, education and consultation, employee health, and public relations served to strengthen the positive image of ICPs.

Zh Mikrobiol Epidemiol Immunobiol, 1989 Jun, (6), 52 - 7
{Interaction of T-activin with peritoneal macrophages}; Korotkova MN et al.; The action of T-activin on peritoneal macrophages of CBA mice after its introduction into the animals has been studied . In intact mice the phagocytic activity of macrophages and their resistance to the cytopathogenic action of Salmonella typhimurium live cells remains unchanged . The injection of corpuscular pertussis vaccine into mice leads to a decrease in the resistance of macrophages to the action of salmonellae . The simultaneous injection of T-activin into mice in doses of 0.1 and 1.0 microgram per animal abolishes the damaging action of the vaccine . The analysis of the in vitro action of T-activin on macrophages of intact mice revealed that the preliminary incubation of cells with the preparation sharply increases their resistance to the action of salmonellae, while its introduction simultaneously with bacteria or after them rapidly leads to the death of macrophages . The action of T-activin is supposed to be linked with triggering the biosynthetic processes mediating the resistance of macrophages to the cytopathogenic action of salmonellae.

J Pharmacobiodyn, 1989 Jun, 12(6), 345 - 51
Comparative studies on the metabolism and mutagenicity of vinyl ethers; Sone T et al.; 4-Nitrophenyl vinyl ether (1), umbelliferyl vinyl ether (2), 4-cyanophenyl vinyl ether (3), and 4-acetylphenyl vinyl ether (4) were mutagenic toward Salmonella typhimurium TA100 and TA100NR in the presence of the hepatic 9000 x g supernatant fraction fortified with a reduced nicotinamide adenine dinucleotide phosphate generating system (S9mix), but no significant mutagenicity of 4-chlorophenyl vinyl ether (5), phenyl vinyl ether (6), n-butyl vinyl ether (7), and ethyl vinyl ether (8) was found . The epoxides of 1-4 were highly mutagenic toward the bacteria without the S9mix . Also, epoxides of 5 and 6 showed relatively weak mutagenicity . Studies on the metabolism of 1 showed that the epoxide (1a) formed from 1 by microsomes behaved as a labile intermediate in the incubation mixture . Untreated rat hepatic microsomes accumulated 1a and induced mutagenicity of 1 most effectively among the activation systems used . Mutagenic activities of vinyl ethers in the presence of the S9mix were correlated with stabilities of their epoxides . From these results, it is suggested that the critical factor for the mutagenicity of vinyl ethers is the formation and stability of epoxide intermediate in the biological system.

Microb Pathog, 1989 Jun, 6(6), 433 - 43
Virulence and vaccine potential of phoP mutants of Salmonella typhimurium; Galan JE et al.; We have constructed Salmonella typhimurium phoP mutants and found them to be avirulent and able to induce a protective immune response . BALB/c mice survived challenge with phoP derivatives of the highly virulent S . typhimurium strains SR-11 and SL1344 when inoculated intraperitoneally and per oral with doses equivalent to 10(4) 50% lethal doses (LD50) of the parent virulent strains . The avirulent mutants were able to establish an infection of the Peyer's patches of orally infected animals for up to 10 days after inoculation but were very inefficient at reaching the spleens . Despite the low level of infectivity of these mutants, immunized animals developed a delayed-type hypersensitivity (DTH) response to Salmonella antigens and resisted challenge with up to 10(4) LD50 of the virulent parent strain 30 days after immunization.

Zentralbl Hyg Umweltmed, 1989 Jun, 188(3-4), 271 - 83
{Effect of high frequency treatment on several microorganisms important to food health}; Rosenberg U et al.; There is an increasing consumer interest in the microwave oven as a more convenient and quicker means of meal preparation . This study investigated whether growth or inactivation of microorganisms in the microwave field follows the same dynamics as conventional heat processing . Product safety during microwave treatment of food products is of special interest . As parameters D-values of Escherichia coli, Salmonella typhimurium and Staphylococcus aureus were calculated after microwave exposure and conventional heat treatment at +55 degrees C and +60 degrees C respectively . The irradiation frequency was 2450 MHz; the microwave power ranged from 0 to 1037 W . Furthermore an assessment was made on the growth rates of E . coli at +37 degrees C and on the influence of microwaves on lyophilized E . coli-cells . With a special temperature measurement system (Luxtron 1000 A) which used nonmetallic and microwave transparent fiber optic probes, the temperature was recorded during each experiment . At certain temperatures some of the strains showed slight although significant differences depending on which of the abovementioned techniques had been applied . However there was no particular trend evident from the results . D-values of E . coli at +55 degrees C and S . typhimurium at +55 degrees C and +60 degrees C obtained from both heat sources were coincided . Microwave reduction of S . aureus at +55 degrees C was more rapid than conventional heat inactivation; on the other hand a slower inactivation rate of S . aureus and E . coli at +60 degrees C was observed . Growth of E . coli was slightly delayed during microwave incubation . There are no effects concerning microwave-treated E . coli-cells . The hypothesis positing the existence of so called "athermal effects" was neither proved nor rejected on the basis of the experiments . In terms of product safety, it must be taken into account that microwave heat processing in general use may result in a markedly uneven distribution of temperature within the product . Adequate means should be provided for heat conduction so as to allow temperatures of "hot" and "cold" spots to be sufficiently equilibrated.

Am J Infect Control, 1989 Jun, 17(3), 141 - 7
Investigation of a food-borne outbreak of salmonellosis among hospital employees; Opal SM et al.; An explosive outbreak of Salmonella enterocolitis developed in 27 hospital employees in an acute-care community hospital in Rhode Island in 1987 . Salmonella typhimurium was isolated from the stools of 19 employees during the outbreak . In each patient the implicated organism had an identical antibiotic susceptibility pattern, biotype, plasmid profile, and restriction endonuclease digestion pattern . The outbreak was limited to health care workers and other hospital employees; there were no cases in hospitalized patients . Of the afflicted employees 96% ate in the hospital cafeteria on July 11 or 12, 1987 . Food-specific attack rates, based on the dietary histories of ill employees and 50 healthy employees who ate in the cafeteria that weekend, indicated an association between the ingestion of salads and illness (p less than 0.01) . One food service employee, in whom symptoms of abdominal cramping and diarrhea had developed 6 days earlier, had prepared the implicated foods . S . typhimurium with the identical characteristics of the outbreak strain was isolated from the stools of this food service employee . Environmental cultures and cultures of meat, poultry, and dairy sources for the cafeteria all showed negative results . Food service employees need to be counseled against working during any symptomatic enteric illness and require thorough instruction on hygienic food handling.

Mutat Res, 1989 Jun, 223(2), 205 - 12
The distribution of mutagenic activity in red, rose and white wines; Nguyen T et al.; Using a modified Salmonella typhimurium TA98 Ames-test system, more than 150 red, white and rose wines were analyzed for direct-acting and microsomal enzyme-enhanced mutagenic activity . The following conclusions were reached from analysis of this wine mutagenicity data base . White and rose wines, as well as grape juices, exhibited little or no detectable direct-acting or microsomal enzyme-enhanced mutagenic activity . However, red wine samples contained highly variable amounts of mutagens, ranging from undetectable to levels 30-fold above the sensitivity limit of the assay system . The variations in red wine mutagenicity were unrelated to grape variety, vintage, aging methods or production region . Hence, individual winery production practices must represent the most significant contribution to the variations observed.

Mutat Res, 1989 Jun, 212(2), 275 - 84
Preferential activation of 6-aminochrysene and 2-aminoanthracene to mutagenic moieties by different forms of cytochrome P450 in hepatic 9000 X g supernatants from the rat; Lubet RA et al.; 6-Aminochrysene and 2-aminoanthracene were activated to metabolites which were mutagenic to Salmonella typhimurium TA98 by hepatocytes or hepatic 9000 X g supernatants (S9s) from control or xenobiotic-treated rats . Hepatocytes from Aroclor-1254-treated rats were more efficient than hepatocytes from untreated rats at activating these aromatic amines . When plate-incorporation and liquid-incubation bacterial mutagenesis assays were performed in the presence of limiting amounts of rat hepatic S9, 2-aminoanthracene was activated to a greater extent in both cases, as judged by his+ revertant formation, by 3-methylcholanthrene-induced hepatic S9 than by phenobarbital-induced or control S9s . In contrast, 6-aminochrysene was activated more efficiently by phenobarbital-induced S9 than by 3-methylcholanthrene-induced or control S9s . This unexpected finding was confirmed employing polyclonal antibodies directed against specific forms of rat cytochrome P450 . Thus, when employing Aroclor-1254-induced S9 as a source of metabolic activation, antibody directed against cytochrome P450IA1 inhibited the activation of 2-aminoanthracene but not of 6-aminochrysene . In contrast, antibody directed against cytochrome P450IIB1 inhibited the activation of 6-aminochrysene but not of 2-aminoanthracene . These results suggest that under conditions in which the amounts of S9 added are rate-limiting, the two aromatic amines are preferentially activated by different induced forms of cytochrome P-450.

J Bacteriol, 1989 Jun, 171(6), 3553 - 6
Unusual nucleotide arrangement with repeated sequences in the Escherichia coli K-12 chromosome; Nakata A et al.; Between 59 and 60 min on the Escherichia coli genetic map, there is a highly conserved sequence of 29 base pairs, containing an inverted repeat of seven base pairs that appears 14 times, 32 or 33 base pairs apart, downstream of the iap gene coding region . About 24 kilobase pairs downstream of the 14 repeats, a similar 29-base-pair sequence with a spacing of 32 base pairs appears seven times . Nucleotide sequences hybridizing with the 29-base-pair fragment were also detected in Shigella dysenteriae and Salmonella typhimurium but not in Klebsiella pneumoniae or Pseudomonas aeruginosa.

J Bacteriol, 1989 Jun, 171(6), 3316 - 23
Functions required for vitamin B12-dependent ethanolamine utilization in Salmonella typhimurium; Roof DM et al.; When B12 is available, Salmonella typhimurium can degrade ethanolamine to provide a source of carbon and nitrogen . B12 is essential since it is a cofactor for ethanolamine ammonia-lyase, the first enzyme in ethanolamine breakdown . S . typhimurium makes B12 only under anaerobic conditions; in the presence of oxygen, exogenous B12 must be provided to permit ethanolamine utilization . Genes required for ethanolamine utilization are encoded in the eut operon . For complementation testing, an F' plasmid containing the eut genes was constructed by transposition of the eut operon (flanked by two Tn10 elements) to an existing F plasmid . Complementation tests defined six genes in the eut operon . Three of these genes encode enzymes known to be involved in degradation of ethanolamine: ethanolamine ammonia-lyase (eutB and eutC) and acetaldehyde dehydrogenase (eutE) . One gene (eutR) seems to encode a positive regulatory protein required for induction of transcription of eut . The function of one of the remaining two genes (eutA) was shown to be required for ethanolamine utilization only when cyano-B12 or hydroxy-B12 were the precursors of the adenosyl-B12 cofactor of ethanolamine ammonia-lyase; eutA mutants could use ethanolamine as the nitrogen source only when adenosyl-B12 was provided . No function has been assigned to the eutD gene, which is required for use of ethanolamine as a carbon source . Ethanolamine uptake assays of eut mutants suggest that no ethanolamine permease is encoded in the eut operon.

J Bacteriol, 1989 Jun, 171(6), 3277 - 81
Role of homocysteine in metR-mediated activation of the metE and metH genes in Salmonella typhimurium and Escherichia coli; Urbanowski ML et al.; The metR-mediated activation of the Salmonella typhimurium metE and metH genes was shown to be modulated by homocysteine, an intermediate in the methionine biosynthetic pathway . Homocysteine stimulates expression of a metE-lacZ gene fusion four- to fivefold by increasing transcription from the metE promoter . In contrast, homocysteine plays an inhibitory role in the metR-mediated activation of the metH gene, decreasing expression of a metH-lacZ gene fusion threefold.

J Bacteriol, 1989 Jun, 171(6), 3247 - 57
Flagellar switch of Salmonella typhimurium: gene sequences and deduced protein sequences; Kihara M et al.; The fliG, fliM, and fliN genes of Salmonella typhimurium encode flagellar components that participate in energy transduction and switching . We have cloned these genes and determined their sequences . The deduced amino acid sequences correspond to proteins with molecular masses of 36,809, 37,815, and 14,772 daltons, respectively . None of the protein sequences are especially hydrophobic or look as though they correspond to integral membrane proteins, a result consistent with other evidence suggesting that the proteins may be peripheral to the membrane, possibly mounted onto the basal body M ring . The fliL gene, which immediately precedes fliM, is of unknown function; it encodes a protein with a deduced molecular mass of 17,082 daltons . The hydropathy profile of FliL indicates that it is likely to be an integral membrane protein with at least one spanning segment, near its N terminus . None of the four proteins exhibit consensus N-terminal signal sequences . Comparison of the fliL, fliM, and fliN sequences with the homologous ones in Escherichia coli reveals ranges of similarities of 77 to 95% at the amino acid level and 75 to 86% at the nucleotide level, with the majority (58 to 89%) of codon changes being synonymous ones.

J Bacteriol, 1989 Jun, 171(6), 3008 - 15
Characterization of anaerobic sulfite reduction by Salmonella typhimurium and purification of the anaerobically induced sulfite reductase; Hallenbeck PC et al.; Mutants of Salmonella typhimurium that lack the biosynthetic sulfite reductase (cysI and cysJ mutants) retain the ability to reduce sulfite for growth under anaerobic conditions (E . L . Barrett and G . W . Chang, J . Gen . Microbiol., 115:513-516, 1979) . Here we report studies of sulfite reduction by a cysI mutant of S . typhimurium and purification of the associated anaerobic sulfite reductase . Sulfite reduction for anaerobic growth did not require a reducing atmosphere but was prevented by an argon atmosphere contaminated with air (less than 0.33%) . It was also prevented by the presence of 0.1 mM nitrate, which argues against a strictly biosynthetic role for anaerobic sulfite reduction . Anaerobic growth in liquid minimal medium, but not on agar, was found to require additions of trace amounts (10(-7)M) of cysteine . Spontaneous mutants that grew under the argon contaminated with air also lost the requirement for 10(-7)M cysteine for anaerobic growth in liquid . A role for sulfite reduction in anaerobic energy generation was contraindicated by the findings that sulfite reduction did not improve cell yields, and anaerobic sulfite reductase activity was greatest during the stationary phase of growth . Sulfite reductase was purified from the cytoplasmic fraction of the anaerobically grown cysI mutant and was purified 190-fold . The most effective donor in crude extracts was NADH . NADPH and methyl viologen were, respectively, 40 and 30% as effective as NADH . Oxygen reversibly inhibited the enzyme . Two high-molecular-weight proteins separated by gel filtration (Mr 360,000 and 490,000, respectively) were required for maximal activity with NADH . Indirect evidence, including in vitro complementation experiments with a cysG mutant extract, suggested that the 360,000-Mr component contains siroheme and is the terminal reductase . This component was further purified to near homogeneity and was found to consist of a single subunit of molecular weight 67,500 . The anaerobic sulfite reductase showed some resemblance to the biosynthetic sulfite reductase, but apparently it has a unique, as yet unidentified function.

J Bacteriol, 1989 Jun, 171(6), 2986 - 93
Two outer membrane transport systems for vitamin B12 in Salmonella typhimurium; Rioux CR et al.; The involvement of an outer membrane transport component for vitamin B12 uptake in Salmonella typhimurium, analogous to the btuB product in Escherichia coli, was investigated . Mutants of S . typhimurium selected for resistance to bacteriophage BF23 carried mutations at the btuB locus (butBS) (formerly called bfe, at the analogous map position as the E . coli homolog) and were defective in high-affinity vitamin B12 uptake . The cloned E . coli btuB gene (btuBE) hybridized to S . typhimurium genomic DNA and restored vitamin B12 transport activity to S . typhimurium btuBS mutants . An Mr-60,000 protein in the S . typhimurium outer membrane was repressed by growth with vitamin B12 and was eliminated in a btuBS mutant . The btuBS product thus appears to play the same role in vitamin B12 transport by S . typhimurium as does the E . coli btuBE product . A second vitamin B12 transport system that is not present in E . coli was found by cloning a fragment of S . typhimurium DNA that complemented btuB mutants for vitamin B12 utilization . In addition to this plasmid with a 6-kilobase insert of S . typhimurium DNA, vitamin B12 utilization by E . coli btuB strains required the btuC and btuD products, necessary for transport across the cytoplasmic membrane, but not the btuE or tonB product . The plasmid conferred low levels of vitamin B12-binding and energy-dependent transport activity but not susceptibility to phage BF23 or utilization of dicyanocobinamide . The cloned S . typhimurium DNA encoding this new transport system did not hybridize to the btuBE gene or to E . coli chromosomal DNA and therefore does not carry the S . typhimurium btuBS locus . Increased production of an Mr -84,000 polypeptide associated with the outer membrane was seen . The new locus appears to be carried on the large plasmid in most S . typhimurium strains . Thus S . typhimurium possesses both high- and low-affinity systems for uptake of cobalamins across the outer membrane.

Carcinogenesis, 1989 Jun, 10(6), 1089 - 97
Photoactivation of mutagens; De Flora S et al.; Solutions of several promutagens or of non-genotoxic carcinogens were exposed to sunlight or to artificial sources of UV or fluorescent light, under various experimental conditions . Irradiation resulted in the oxygen-mediated formation of direct-acting mutagenic and DNA-damaging photoproducts in bacteria, with evident structure-activity relationship . Of the aromatic amines tested, 2-aminofluorene and, with lower efficiency, 2-acetylaminofluorene were photoactivated, whereas irradiation of 4-acetylaminofluorene and of the 1- and 2-amino substitutes of anthracene and naphthalene did not produce mutagenic derivatives in Salmonella typhimurium . Of the heterocyclic amines, 2-amino-3-methylimidazo{4,5-f}quinoline and 2-amino-3,4-dimethylimidazo{4,5-f}quinoline were extraordinarily sensitive to activation by sunlight and fluorescent light, which contrasted with the insensitivity of the tryptophan pyrolysis products . Use of optical and interference filters showed that near-UV light is the main component of solar radiation responsible for the formation of highly stable mutagenic derivatives . The mutagenicity of 2-aminofluorene and of the aminoimidazoquinoline compounds, following both metabolic and light activation, was lost in nitroreductase- and O-acetyltransferase-dificient bacteria . Benzo{alpha}pyrene was better activated by 254- than by 365-nm UV light . Sunlight did not affect the lack of mutagenicity of carcinogenic organochlorine pesticides, but exposure to 254-nm UV light selectively resulted in the formation of weak mutagens from dieldrin and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene, but not from 4,4'-dichlorodiphenyltrichloroethane, lacking carbon-carbon double bonds.

Carcinogenesis, 1989 Jun, 10(6), 1079 - 84
The mutagenicity of dibenz{a,j}acridine, some metabolites and other derivatives in bacteria and mammalian cells; Bonin AM et al.; Dibenz{a,j}acridine (DBAJAC) was studied because of its close structural relationship with a number of important carcinogenic polycyclic and azaaromatic hydrocarbons . It was of particular relevance to examine the mutagenicity of known or proposed 'bay-region' metabolites, which may be proximate or ultimate carcinogenic derivatives of DBAJAC . Trans-1,2-, 3,4- and 5,6-dihydrodiols, the 4- and 6-phenols, the 5,6-oxide and N-oxide derivatives, and anti- and syn-3,4-diol 1,2-epoxides of DBAJAC were examined for their mutagenicity in Salmonella typhimurium TA98 and TA100 and in V79 Chinese hamster lung cells . Of all the compounds studied which require metabolic activation, the 3,4-dihydrodiol was the most active in both TA100 and in V79 cells . The activity of the 3,4-dihydrodiol enantiomers was also tested in strain TA100 where no difference was observed from that of the racemic mixture . In V79 cells only the 3R,4R-dihydrodiol was active, the activity being about three times that of the racemic material . Salmonella strains TA98 and TA100 also differed in their sensitivity towards DBAJAC dihydrodiols, the 1,2-isomer being of greatest activity in TA98 . The most mutagenic compounds in both mammalian and bacterial cells were the 'bay-region' diol epoxides of DBAJAC which did not require metabolic activation by S9 mix . The anti-DBAJAC 3,4-diol 1,2-epoxide was more mutagenic than the syn form in V79, TA98 and TA100 cells . Overall these results suggest that the in vivo biological activity of DBAJAC metabolites is likely to reflect previous findings with other similar polycyclic aromatic hydrocarbons.

Chem Pharm Bull (Tokyo), 1989 Jun, 37(6), 1600 - 3
Formation of a direct mutagen, diazo-N-nitrosoetilefrin, by interaction of etilefrin with nitrite; Kikugawa K et al.; Reaction of an antihypotensive drug, etilefrin {alpha-{(ethylamino)methyl}-m-hydroxybenzyl alcohol}, with nitrite under mildly acidic conditions produced N-nitrosoetilefrin {alpha-{(N-nitrosoethylamino)methyl}-m-hydroxybenzyl alcohol} (a mixture of syn and anti forms) (Iab) and diazo-N-nitrosoetilefrin {1-(4-diazo-3-oxo-1,5-cyclohexadienyl-2-(N-nitrosoethylamino )ethanol} (a mixture of syn and anti forms) (IIab) . Treatment of etilefrin with an equivalent amount of nitrite at pH 3 and 37 degrees C for 4 h gave Iab (yield, 30%) and IIab (yield, 5%) . Treatment of etilefrin with 4 eq of nitrite under the same conditions gave Iab (23%) and IIab (53%) . Compounds Iab and IIab were each composed of two isomers due to the configuration of the N-nitroso group . While compound Iab was not mutagenic, compound IIab showed mutagenicity to Salmonella typhimurium TA98 and TA100 strains without metabolic activation . Specific mutagenic activity of IIab was 300 his+ revertant colonies for both TA98 and TA100 strains with a dose of 0.1 mumol . Addition of a microsomal activation system little affected the activity . It is noteworthy that this orally administered drug can produce a direct-acting mutagen by reaction with nitrite, which is present in the digestive tract.

J Bacteriol, 1989 Jun, 171(6), 3572 - 4
Glutamine auxotrophs of Bacillus subtilis that overproduce glutamine synthetase antigen have altered conserved amino acids in or near the active site; Zhang J et al.; A number of mutations within the Bacillus subtilis glutamine synthetase (GS) gene result in altered catalytic properties and overproduction of the GS antigen . The restriction fragments containing mutations from three such mutants were sequenced, and they all had amino acid changes in conserved residues found either within or near sequences contributing to the active site of the Salmonella typhimurium GS.

Can J Microbiol, 1989 Jun, 35(6), 646 - 50
Accumulation of incomplete metabolic side products of lipid A in Salmonella typhimurium during inhibition of 3-deoxy-D-manno-octulosonate incorporation by a new class of antibacterial agents; Kadam SK et al.; A new class of antibacterial agents for Gram-negative bacteria, rationally designed to inhibit the incorporation of 3-deoxy-D-manno-octulosonate into lipopolysaccharide (LPS), was recently reported . In Salmonella typhimurium, where the lipid A species are well characterised, it was previously demonstrated that the addition of a compound which inhibits the enzyme 3-deoxy-manno-octulosonate cytidylytransferase (CMP-KDO synthetase; EC 2.7.7.38) leads to rapid accumulation of lipid A derivatives . The major lipid A species, IVA (O-(2-amino-2-deoxy-beta-D-glucopyranosyl)-(1-6)-2-amino-2-deoxy-alpha-D - glucose, acylated at positions 2, 3, 2', 3' with beta-hydroxymyristoyl groups and bearing phosphates at positions 1 and 4'), was shown to be converted mainly to LPS by pulse-chase experiments in the absence of inhibitor . Labelled precursor (IVA) was also chased to other more polar lipid A derivatives . During chase in the presence of inhibitor, there was no conversion to LPS, while the major lipid A species was converted to the same polar lipid A derivatives as in chase without inhibitor . Our data indicate that despite the accumulation of several species of lipid A derivatives during inhibition of LPS synthesis, only IVA is destined for synthesis of mature LPS when LPS synthesis resumes . The more polar lipid A derivatives would thus represent aberrant side reaction products which occur when the pathway is inhibited.

Cancer Lett, 1989 Jun, 45(3), 177 - 82
Modification of the mutagenicity of aflatoxin B1 and N-methyl-N'-nitro-N-nitrosoguanidine by certain phenolic compounds; Francis AR et al.; Five natural and two synthetic phenolic compounds were tested for their ability to suppress mutagenicity of aflatoxin B1 (AFB1) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Salmonella typhimurium tester strain TA100 . Caffeic acid and eugenol were observed to inhibit mutagenicity of both the carcinogens, while chlorogenic acid was effective in the case of AFB1 alone and ellagic acid and butylated hydroxytoluene were found to be antimutagenic only for MNNG . These differential activities of the phenolic compounds appeared to be due to their different modes of action towards direct and indirect acting carcinogens.

Toxicol Ind Health, 1989 May, 5(3), 451 - 61
Effects of inhaled hexachlorobenzene aerosols on rat pulmonary host defenses; Sherwood RL et al.; Pulmonary bactericidal activity, macrophage phagocytic activity, alveolar macrophage (AM) enzyme activity, and T- and B-cell mitogenesis of lymphocytes from lung associated lymph nodes (LALN) or mesenteric lymph nodes (MESLN) were assessed in Sprague-Dawley rats exposed 4 hr/d, 4 days/wk for 1, 4, or 16 days to hexachlorobenzene (HCB) aerosols . Pulmonary bactericidal activity was depressed after 1 or 4 but not 16 exposures to 35 mg/m3 of HCB . AM phagocytosis of 51Cr-RBC in vitro was increased after 4 but not 1 or 16 exposures to HCB, and no effect was observed in peritoneal macrophages . HCB significantly enhanced mitogenesis in MESLN to the B-cell mitogen Salmonella typhimurium lipopolysaccharide (STM) after 4 exposures; LALN STM mitogenesis and LALN and MESLN mitogenesis to phytohemagglutinin (PHA) were not affected . After 16 exposures, however, the PHA responses in LALN and MESLN were significantly increased and decreased, respectively.

J Toxicol Sci, 1989 May, 14(2), 131 - 41
Mutagenicity tests on propiverine hydrochloride; Ohuchida A et al.; 1 . The reverse mutation test was carried out on propiverine hydrochloride (P-4) at dose range of 5-500 micrograms/plate use Salmonella typhimurium strains, TA100, TA98, TA1535 and TA1537, and Escherichia coli strain WP2uvrA . As compared with solvent-treated control, no significant increases were observed in the number of revertant colonies in all tester strains in both systems with and without mammalian metabolic activation (S9 Mix) . 2 . The chromosomal aberration test was also carried out on P-4 using cultured Chinese hamster lung cells (CHL) . The cells were treated with P-4 at the doses of 5, 10, 20 and 40 microM without S9 Mix and at 62.5, 125, 250 and 500 microM with S9 Mix . No significant differences were found in the incidence of structural- and numeral-aberrations of chromosomes in both systems with and without S9 Mix . 3 . These results indicate that P-4 has no mutagenic activity.

Dig Dis Sci, 1989 May, 34(5), 773 - 80
Intestinal infections in patients with acquired immunodeficiency syndrome . A prospective study in 132 patients; Rene E et al.; We studied prospectively 132 patients with acquired immunodeficiency syndrome to define the spectrum of enteric pathogens during this disease, with special reference to the correlation between the lesions, the infections, and the symptoms . Forty-four percent of the patients harbored at least one enteric pathogen: the most frequently recovered were Cryptosporidium (28), cytomegalovirus (16), Entamoeba histolytica (13), Giardia lamblia (9), and Mycobacterium avium intracellulare (7) . Patients harboring pathogens were more likely to be diarrheics (69%) than patients without a pathogen (38%; P = 0.01) and more likely to have endoscopic lesions (29%) than patients without a pathogen (4%; P less than 0.001) . The most common pathogen associated with diarrhea was Cryptosporidium . Cytomegalovirus, Entamoeba histolytica, and Salmonella typhimurium were each significantly associated with endoscopic lesions . Patients with cytomegalovirus infection tended to have a greater incidence of ulcer than patients without cytomegalovirus infection . Stool analysis diagnosed 61% of the infections, while endoscopy diagnosed 44% . Seven percent were recognized by stool analysis and endoscopy . When considering the 24 patients in whom accurate diagnosis warranted endoscopic biopsies, stool examination alone would have given an incomplete diagnosis in 14 patients (due to the presence of polyinfection) . The frequency of inaccurate diagnosis of infection by stool determination alone, plus the development of new antiviral agents that suppress cytomegalovirus, may favor the earlier application of endoscopic evaluation in these patients.

J Bacteriol, 1989 May, 171(5), 2803 - 10
Basal-body-associated disks are additional structural elements of the flagellar apparatus isolated from Wolinella succinogenes; Kupper J et al.; The intact flagella of Wolinella succinogenes, a gram-negative, anaerobic bacterium with a single polar flagellum, were obtained by an improved procedure, introduced recently by Aizawa et al . (S.-J . Aizawa, G . E . Dean, C . J . Jones, R . M . Macnab, and S . Yamaguchi, J . Bacteriol . 161:836-849, 1985) for the flagellum of Salmonella typhimurium . Disks with a diameter of 130 +/- 30 nm, which were attached to the basal body of the isolated intact flagella, could be identified by electron microscopy as additional structural elements of the bacterial flagellar apparatus . In freeze-dried and metal-shadowed samples, two rings of the basal body were detected on one side and a terminal knob was located on the other side of the disks . Suspension of the flagellar apparatus in acidic solution dissociated the flagellar filaments, yielding hook-basal body complexes with and without the associated disks . If whole cells were subjected to low pH, double disks of the same diameter and with a central hole of about 13 nm could be isolated . Similar parallel disks could be seen also in negatively stained whole cells . When uranyl acetate was used for negative staining of the intact flagella, concentric rings were detected on the disks, similar to the concentric membrane rings found by Coulton and Murray (J . W . Coulton and R . G . E . Murray, J . Bacteriol . 136:1037-1049, 1978) on platelike arrays of proteins in outer membrane preparations of Aquaspirillum serpens . Because the disks of W . succinogenes can be isolated together with the flagellar hook-basal body complex, they appear to be basal-body-rather than secondary membrane-associated structures . It is possible that these disks are the bearing or stator of this rotary device.

Infect Immun, 1989 May, 57(5), 1483 - 90
Immunomodulatory activity of monophosphoryl lipid A in C3H/HeJ and C3H/HeSnJ mice; Hiernaux JR et al.; Treatment with nontoxic monophosphoryl lipid A (MPL) derived from a polysaccharide-deficient, heptoseless Re mutant of either Salmonella typhimurium or Salmonella minnesota R595 enhanced the immunoglobulin M (IgM) anti-type III pneumococcal polysaccharide (SSS-III) antibody response of C3H/HeSnJ mice . Such an adjuvant effect was not observed in lipopolysaccharide-nonresponder C3H/HeJ mice . Nevertheless, C3H/HeJ spleen cells produced a weak mitogenic response to both preparations of MPL in vitro, and C3H/HeJ mice showed a significant increase in serum IgM levels without an increase in numbers of splenic IgM-secreting plaque-forming cells after in vivo treatment with MPL . A significant increase in serum IgG3 levels was accompanied by a transient decrease in serum IgG1 levels in C3H/HeSnJ mice given MPL; such non-antigen-specific polyclonal effects were not observed in C3H/HeJ or in athymic nu/nu mice . Since the enhanced antibody response to SSS-III has been attributed to the inactivation of suppressor T cells by MPL and since suppressor-T-cell activity is demonstrable in both C3H/HeSnJ and C3H/HeJ mice, these findings imply that (i) the suppressor T cells of C3H/HeJ mice are refractory to inactivation by MPL and (ii) some of the polyclonal and mitogenic effects produced in C3H/HeJ mice are due to the direct action of MPL on B lymphocytes.

Rev Inst Med Trop Sao Paulo, 1989 May-Jun, 31(3), 135 - 8
Labeling of Salmonella typhimurium with iodine-131 to study phagocytic function in rats; Sato MK et al.; The present study describes a method for labeling Salmonella typhymurium with iodine-131 to evaluate both the morphological and the functional characteristics of the reticulo-endothelial system . A suspension containing 2 x 10(9) bacteria per ml was labeled with carrier-free Na131I without reductor, with a labeling yield of 46.5 +/- 3% and 3.5 +/- 1.3% of free Iodine-131 . The biodistribution of the labeled bacteria in rats was studied with a large-field-of-view scintillation camera equiped with a pinhole collimator . Whole body images were obtained 15 and 30 minutes after intravenous injection of the labeled microorganisms . Images showed accumulation of bacteria in the liver and both normal and transplanted spleens of the animals . Autoradiographs of liver and spleen demonstrated labeled bacteria within the cells of the reticulo-endothelial system . The method described is easy to perform, has a good labeling yield and allows the functional evaluation of the reticulo-monophagocytic system, including transplanted spleens.

Zh Mikrobiol Epidemiol Immunobiol, 1989 May, (5), 8 - 12
{Effect of the immune system functioning of the body on the structure of Salmonella typhimurium populations according to the traits of antibiotic resistance and virulence}; Kalutskii PV et al.; The passage of salmonellae through mice with different immune status (intact, immunosuppressed and immunized) has been found to lead to the multidirectional selection of the animals . Passages through intact and immunosuppressed mice lead mainly to the selection of the animals with the minimal number of resistance markers, while passages through immunized mice result in the selection of the animals with the maximal number of the markers of resistance to antibiotics . The ratio of these kinds of cells coincides with the degree of the virulence of the population: salmonellae isolated from immunosuppressed mice have the highest virulence and those isolated from immunized mice have the lowest virulence.

Mol Gen Genet, 1989 May, 217(1), 182 - 4
Cloning and nucleotide sequence of the Salmonella typhimurium LT2 gnd gene and its homology with the corresponding sequence of Escherichia coli K12; Reeves P et al.; The complete nucleotide sequence of the Salmonella strain LT2 gnd gene for 6-phosphogluconate dehydrogenase was determined . The gene contains 1404 bases and encodes a 468 amino acid polypeptide, which is the same as for Escherichia coli K12 . The DNA sequence shows 14.8% difference between the two and the amino acid sequence 3.6% difference . Changes are mostly in the third codon base and most of the amino acid changes are conservative.

Mutagenesis, 1989 May, 4(3), 235 - 40
Mutagenicity, metabolism and DNA adduct formation of 6-nitrochrysene in Salmonella typhimurium; el-Bayoumy K et al.; The mutagenic activities of 6-nitrochrysene (6-NC) and its previously identified metabolites were evaluated in Salmonella typhimurium TA100 and TA98 in the presence and absence of metabolic activation by 9000 g supernatant from the livers of rats treated with Aroclor . 6-Aminochrysene (6-AC) and trans-1,2-dihydro-1,2-dihydroxy-6-aminochrysene (1,2-DHD-6-AC) were the most active mutagens in TA100 upon metabolic activation . 6-NC and 6-AC were the most active mutagens in TA100 in the absence of metabolic activation . Upon metabolic activation, 6-AC was the most active in TA98; the other compounds were weak or inactive depending on the conditions of the assay . In the absence of metabolic activation, the mutagenic activities of 6-NC and its metabolites in TA98 were comparable to those observed in TA100 . The major metabolite formed upon incubation of {3H}6-NC with S.typhimurium TA100 and 9000 g supernatant from the livers of Aroclor-induced rats was identified as trans-1,2-dihydro-1,2-dihydroxy-6-nitrochrysene (1,2-DHD-6-NC); trans-9,10-dihydro-9,10-dihydroxy-6-nitrochrysene and 1,2-dihydroxy-6-nitrochrysene were also identified . The major DNA adduct formed in TA100 under these conditions was chromatographically identical to that previously detected in vivo in the liver and lungs of newborn mice treated with 6-NC, as well as to that obtained upon incubation of 1,2-DHD-6-AC with calf thymus DNA in the presence of rat liver microsomes . The DNA adducts derived from 6-NC in S.typhimurium TA100 without activation were identical to those adducts previously identified after incubation of 6-hydroxylaminochrysene with calf thymus DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Mutagenesis, 1989 May, 4(3), 228 - 9
Temperature and time effects on mutagen production in cooked lamb meat; Sflomos C et al.; Basic extracts isolated from lamb meat treated at various temperatures were tested for mutagenicity in Salmonella typhimurium strain TA98 in the presence of S9 mix . Samples of ground lamb patties were cooked for 10 min per side at 100, 150, 200, 250 and 300 degrees C . Low cooking temperatures resulted in products with low levels of mutagenicity . At temperatures greater than 150 degrees C the mutagenic activity of the cooked meat increased to reach a maximum at 300 degrees C . In another series of experiments, lamb patties were cooked at 250 degrees C for 2, 4, 6, 8, 10 and 12 min . Short cooking times (rare products) caused no mutagenic activity and uncooked ground meat showed no activity . Prolonged cooking appeared to increase the mutagenicity of the products with a maximum value at 10 min . The results indicate that the formation of mutagens depends on both cooking temperature and cooking time . The level of mutagenicity tends to increase with the degree of charring.

Mutagenesis, 1989 May, 4(3), 200 - 4
Hydroxychavicol: a new anti-nitrosating phenolic compound from betel leaf; Nagabhushan M et al.; Hydroxychavicol and eugenol are the phenolic compounds isolated from betel leaf (piper betel) . The modulation of nitrosation of methylurea by sodium nitrite at pH 3.6 and 30 degrees C was studied . The formation of mutagenic N-nitrosomethylurea was monitored by checking the mutagenicity of reaction mixture in Salmonella typhimurium strain TA100 and TA1535 without S9 mix . Hydroxychavicol and eugenol exhibit dose-dependent suppression of nitrosation in vitro without affecting the survival of the bacteria . Pre- or post-treatment of bacterial cells from S . typhimurium strains TA100 and TA1535 with phenolics did not modify the mutagenicity of nitrosomethylurea . The blocking of hydroxy group(s) in the benzene ring by acetylation abolishes the anti-nitrosating activity of the molecule(s) . The nitrosation inhibition by hydroxychavicol is through scavenging of nitrite ions in the media, thus making them non-available for the nitrosation of methylurea.

Proc Soc Exp Biol Med, 1989 May, 191(1), 47 - 54
Vitamin A supplementation improves macrophage function and bacterial clearance during experimental salmonella infection; Hatchigian EA et al.; The effects of additional but nontoxic amounts of vitamin A on susceptibility to salmonella infection was studied by comparing rates of bacterial clearance and phagocytosis . Forty-eight male Lewis rats were divided into a treatment group receiving a total of 6000 units of vitamin A palmitate weekly for 5 weeks and a control group was given an equal volume of saline . After completion of the treatment regimen, one-half from each group were infected intraperitoneally with 10(5) Salmonella typhimurium; the other half received intraperitoneal injection of saline . At this time no differences in weight gain were noted and all animals were sacrificed within 2 weeks . At 72 hr after bacterial challenge, all saline-treated control animals displayed bacteremia . Cultures of liver and splenic homogenates were positive in 89 and 100% of infected control animals vs 0 and 44% for treated animals during the first week of infection . Kupffer cell, peritoneal, and splenic macrophages of the vitamin A-treated group had greater phagocytic activity than controls as assessed by the percentage of cells ingesting yeast particles and by the number of particles ingested (phagocytic index) . These results suggest that vitamin A in moderate amounts may benefit the host's response to infection by enhancing phagocytic cell function.

Mutat Res, 1989 May, 226(1), 55 - 9
Mutagenicity of the reaction products of carbazole in the presence of nitrogen dioxide and nitrocarbazole; Hisamatsu Y et al.; The mutagenicity of the photochemical reaction products of carbazole in the presence of nitrogen dioxide (NO2) and nitrocarbazole was investigated using a high-pressure mercury lamp (100 W) . Samples extracted from the photochemical reaction products of carbazole with NO2 were more mutagenic than those of acridine and phenazine with NO2 for Salmonella typhimurium strain TA98 in the absence of S9 mix with a trend toward detoxification in the presence of the metabolic system . The mutagenicity of the photochemical reaction products of carbazole with NO2 were higher than those of the reaction products of carbazole with a mixture of NO2 and sulfur dioxide (SO2) and no irradiation . Mononitro- and dinitro-carbazole in the samples extracted from the reaction products were analyzed by mass spectrometry . It was suggested that mononitrocarbazole, which seemed to be weakly mutagenic, and dinitrocarbazole were readily formed by the reaction of carbazole with NO2, and that the other high-potency mutagens were formed by the photochemical reaction of carbazole with NO2 with irradiation by light.

Mutat Res, 1989 May, 223(1), 13 - 22
Mutagenic activity of nitracrine derivatives in Salmonella typhimurium: relationship to drug physicochemical parameters, and to bacterial uvrB and recA genes and plasmid pKM101; Ferguson LR et al.; To determine whether it is possible to separate antitumour and mutagenic properties in the nitracrine series, a number of 4-substituted derivatives of the hypoxia-selective drug nitracrine have been evaluated for their mutagenic effects at three loci in several strains of Salmonella typhimurium differing in DNA-repair capacity (uvrB, recA, plasmid pKM101) . The drugs divided into two series in terms of their biological effects . Group A compounds (nitracrine and its Cl, F, Me and OMe derivatives) were very toxic to bacteria, and uvrB and recA deletions enhanced toxicity by 10-80-fold . Mutagenic potency was high, being slightly enhanced by uvrB and reduced by recA deletions . In contrast the toxicities and mutagenic potentials of Group B compounds (COOMe, NMe2, and two other bulky amine derivatives) were reduced by at least an order of magnitude, with uvrB and recA deletions showing lesser influence . The COOMe derivative was the only compound showing greater effects at the hisC3076 locus than the hisD3052 or hisG46 loci . The data suggest that all the compounds cause mutations through intercalation and/or monoadduct formation, but only for the COOMe derivative is intercalation the dominant mode of action . Group A compounds appear to have the additional ability to cross-link DNA, a property which amounts for their high potency but which is not compatible with bulky 4-substituents . Apart from these generalizations, there was considerable variation in mutagenic efficiency (as measured by the maximum numbers of revertant colonies) within each series . Of the compounds studied, the 4-OMe derivative appears to best retain the desirable antitumour properties of nitracrine while showing greatly-reduced mutagenic potential, and is an interesting lead for further development.

Mutat Res, 1989 May, 217(3), 203 - 9
Genotoxicity of quinoxaline 1,4-dioxide derivatives in Escherichia coli and Salmonella typhimurium; Nunoshiba T et al.; The mutagenicities of 5 quinoxaline 1,4-dioxide (QdO) derivatives were tested by 2 bacterial assays using forward mutation with Escherichia coli WP2uvrA/pKM101 and reverse mutation with Salmonella typhimurium TA100 and TA98 . Potent mutagenic activities of all QdOs tested were observed in both mutation assays . Mutagenicities of these compounds were varied by addition of S9 mix . Their SOS-inducing activities were examined with a 'Rec-lac test' that has been newly developed by us for detecting genotoxins . A high level of SOS-inducing activity was observed in all samples tested . These results suggest that the mutagenicity of QdOs results from the error-prone repair involved in SOS responses.

J Bacteriol, 1989 May, 171(5), 2903 - 5
Comparison of Escherichia coli K-12 outer membrane protease OmpT and Salmonella typhimurium E protein; Grodberg J et al.; The predicted amino acid sequence of OmpT, an Escherichia coli outer membrane protease, was found to be highly homologous to that predicted for the pgtE gene product of Salmonella typhimurium . In this paper, it is shown that pgtE codes for a protein functionally homologous to OmpT as judged by its ability to proteolyze T7 RNA polymerase and to localize in the outer membrane of E . coli.

Infect Immun, 1989 May, 57(5), 1517 - 23
Nucleotide sequence of the plasminogen activator gene of Yersinia pestis: relationship to ompT of Escherichia coli and gene E of Salmonella typhimurium; Sodeinde OA et al.; We have determined the nucleotide sequence of the 1.4-kilobase DNA fragment containing the plasminogen activator gene (pla) of Yersinia pestis, which determines both plasminogen activator and coagulase activities of the species . The sequence revealed the presence of a 936-base-pair open reading frame that constitutes the pla gene . This reading frame encodes a 312-amino-acid protein of 34.6 kilodaltons and containing a putative 20-amino-acid signal sequence . The presence of a single large open reading frame is consistent with our previous conclusion that the two Pla proteins which appear in the outer membrane of pla+ Y . pestis are derived from a common precursor . The deduced amino acid sequence of Pla revealed that it possesses a high degree of homology to the products of gene E of Salmonella typhimurium and ompT of Escherichia coli but does not possess significant homology to other plasminogen activators of known sequence . We also identified a transcription unit that resides on the complimentary strand and overlaps the pla gene.

Infect Immun, 1989 May, 57(5), 1399 - 404
Isolation and immunological characterization of a 55-kilodalton surface protein from Salmonella typhimurium; Foulaki K et al.; Surface proteins of different Salmonella R mutants were labeled selectively by treating live bacteria with cycloheptaamylose-dansylchloride . The labeled proteins were extracted from the cells with 6 M urea and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis . From the urea extract a 55-kilodalton protein common to numerous Salmonella strains could be isolated by ion-exchange chromatography and gel filtration free of lipopolysaccharide . Immunization of rabbits with isolated protein led to the formation of specific antibodies . Such antiprotein antisera could be employed in Western blots for the specific identification of the 55-kilodalton protein in bacterial extracts containing mixtures of different Salmonella proteins . The importance of this antigen is emphasized by antisera against acetone-killed Salmonella bacteria, showing a preferential interaction with the 55-kilodalton protein in Western blots . Active immunization of mice with the 55-kilodalton protein afforded significant protection against experimental infection with S . typhimurium.

Am J Vet Res, 1989 May, 50(5), 662 - 70
Virulence determinants of Salmonella typhimurium from animal sources; McDonough PL et al.; Two hundred seventy-eight strains of Salmonella typhimurium isolated from 1973 to 1981 from animal sources in New York State were studied for possible virulence determinants and for a serotype-specific plasmid possibly linked with virulence . Of the strains, 98% possessed type-1 fimbriae . All strains possessed flagella and were motile . One hundred twenty-three strains (44%) treated with mitomycin C tested positive for the cholera-Escherichia coli heat labile family of toxins by a kinetics-based ELISA; when treated with mitomycin C and extracted with polymyxin B, 249 (90%) were positive in the kinetics-based ELISA . All strains were negative in the Biken test . A smooth cell wall was found in 99% of the strains . Sixty-one percent (169) of the strains had a 62-Md plasmid . Seventy-six (27%) of the strains had detectable plasmids ranging in size from 1 to 124 Md.

Indian J Med Res, 1989 May, 89, 121 - 7
Protective immunity induced by porin against Salmonella infection in mice; Udhayakumar V et al.; Porin, a major outer membrane protein was purified from Salmonella typhimurium and its immune potential was studied in mice . Active immunization with porin induced about 45 per cent protection to an intravenous challenge with 10LD50 of S . typhimurium . Further, in porin immunized mice significant level of anti-porin antibodies and DTH reaction were detected . Attempts were also made to improve the immune potential of porin . Freund's complete adjuvant when mixed with immunogenic doses of porin enhanced the anti-porin antibody titre . However, it could not improve the protective ability of porin . On the other hand, porin when injected along with lipopolysaccharide (LPS) induced a higher level (55% survival with 50LD50) of protection than porin or LPS alone . This finding was also substantiated by the significantly reduced in vivo growth of challenge organisms in mice immunized with porin plus LPS . These results indicate that porin is a protective antigen and LPS significantly enhances the protective ability of porin.

Mutagenesis, 1989 May, 4(3), 221 - 7
Mutagenicity spectra in Salmonella typhimurium strains of glutathione, L-cysteine and active oxygen species; Glatt H; Glutathione and L-cysteine, in the presence of rat kidney post-mitochondrial supernatant (S9) fraction, and various forms of active oxygen were investigated for mutagenicity in seven his- strains of Salmonella typhimurium . Glutathione and L-cysteine showed qualitatively and quantitatively virtually identical mutagenic activities . The number of mutants induced in strain TA97 was 3-4 times higher than in TA100, the strain in which the mutagenicity was originally detected . Mutagenic effects were also observed in strains TA92, TA102 and TA104, but not in TA1535 and TA1537 . Hydrogen peroxide, superoxide and glucose/glucose oxidase in the presence and absence of kidney S9 fraction showed pronounced mutagenic effects in strains TA104 and TA102 . Additionally, weak mutagenic effects were observed in TA100, while the remaining strains, including TA97, were not responsive . These mutagenicity spectra suggest that the mutagenic species formed from glutathione and L-cysteine are similar, if not identical, and are different from hydrogen peroxide, superoxide and other oxygen species derived from them . Further support for this notion was given when it was observed that catalase did not affect the mutagenicity of glutathione and that superoxide dismutase showed a significant effect only when used in milligram quantities . This study shows that mutagenicity spectra may be useful in the elucidation of activation pathways . Furthermore, it is interesting to note that all the compounds and preparations showing a positive response in the Ames test in the present study occur endogenously in organisms: glutathione, L-cysteine, hydrogen peroxide, superoxide, glucose, glucose oxidase and kidney S9 fraction (which was mutagenic in several strains).

Mutagenesis, 1989 May, 4(3), 179 - 86
Induction of SOS repair by monofunctional methanesulphonates in various Escherichia coli strains . Structure-activity relationships in comparison with mutagenicity in Salmonella typhimurium; Eder E et al.; Seventeen monofunctional alkylmethanesulphonates of widely varying structures were investigated in the SOS Chromotest using the Escherichia coli strains PM21, PQ37 and GC4798 . As a measure of the SOS-inducing activity, the beta-galactosidase enzyme units (Up/mumol) were determined . Strains PM21 and PQ37 gave similar results in spite of the presence of different genetic markers . In general, the SN1 type secondary compounds (O-alkylation) induced higher SOS repair than the SN2 type primary compounds (N-alkylation) . However, methylmethanesulphonate exerted the highest SOS induction of all tested strains, presumably due to its extremely high SN2 reactivity . In general, strain GC4798, which lacks 3-alkyladenine-DNA glycosylases I and II, was more sensitive towards monofunctional alkylating compounds and in particular towards the SN2 type compounds . A good correlation was found between the SOS repair response in the E . coli strains PM21 and PQ37 and the mutagenicity in Salmonella typhimurium TA100 . There was, however, little correspondence when comparing the two measures used for the SOS-inducing activity in this work, the SOSIP (SOS-inducing potency) and the specific beta-galactosidase activity (Up/mumol) . This effect was explained by the different toxicity corrections used for the calculation of the two measures . Whereas for the SOSIP value the single constitutive enzyme alkaline phosphatase is used, for the Up/mumol the absorbance at 600 nm, which indicates the growth delay (overall toxicity), is utilized . The influence of the toxicity corrections is discussed in more detail.

J Med Chem, 1989 May, 32(5), 1069 - 74
Synthesis of 8-substituted derivatives of the 2-deoxy analogue of 3-deoxy-beta-D-manno-2-octulopyranosonic acid (2-deoxy-beta-KDO) as inhibitors of 3-deoxy-D-manno-octulosonate cytidylyltransferase; Pring BG et al.; The 2-deoxy analogue of 3-deoxy-beta-D-manno-2-octulopyranosonic acid (2-deoxy-beta-KDO, 2) is a potent inhibitor of the enzyme 3-deoxy-D-manno-octulosonate cytidylyltransferase, which is involved in the biosynthesis of lipopolysaccharide, an essential component of the outer membrane of Gram-negative bacteria . Since compound 2 lacks antibacterial activity, a series of 8-substituted derivatives of 2 has been synthesized in an attempt to find enzyme inhibitors suitable for modification as antibacterials . Compounds 9, 11, and 13, in which the 8-hydroxy group of 2 is replaced by F, H, and NH2, respectively, were as potent inhibitors of the enzyme as 2, but were devoid of antibacterial activity, with the exception of the amino acid 13, which showed weak activity against some strains of Salmonella typhimurium.

J Immunol, 1989 May 1, 142(9), 3164 - 70
Halogenation and proteolysis of complement component C3 on Salmonella typhimurium during phagocytosis by human neutrophils; Joiner KA et al.; We examined the fate of C component C3 on the surface of Salmonella typhimurium during ingestion by human neutrophils . Initial experiments showed that C3 fragments and C3-acceptor complexes were the major serum ligands which were surface iodinated by canine myeloperoxidase on serum-incubated rough and smooth isolates of S . typhimurium . In contrast, labeled C3 was not identified when the same organisms were ingested by neutrophils in the presence of 125I-Na, a situation previously shown to iodinate particulate targets via the neutrophil myeloperoxidase-halide-H2O2 system . Pretreatment of neutrophils before phagocytosis with the lipid-soluble protease inhibitor diisopropylfluorophosphate (DFP), but not with other protease inhibitors (p-nitrophenylguanidinobenzoate, leupeptin, pepstatin), substantially blocked proteolysis of 125I-C3 on S . typhimurium strain RG108 during ingestion by neutrophils . Purification of neutrophil phagosomes containing S . typhimurium-bearing 125I-C3 showed that DFP but no other protease inhibitors blocked proteolysis of 125I-C3 within phagosomes . Iodinated C3-acceptor complexes were identified by immunoprecipitation from the detergent-insoluble fraction of phagosomes prepared from DFP-treated cells ingesting S . typhimurium in the presence of 125I-Na . These results show that C3 fragments on the surface of S . typhimurium are the major serum ligands which are halogenated and degraded by proteolysis during phagocytosis by human neutrophils, and suggest that the majority of proteolysis on the ingested target occurs within the neutrophil phagosome.

J Bacteriol, 1989 May, 171(5), 2811 - 8
Analysis of ferrichrome biosynthesis in the phytopathogenic fungus Ustilago maydis: cloning of an ornithine-N5-oxygenase gene; Wang J et al.; By using a non-enterobactin-producing enb-7 mutant of Salmonella typhimurium LT2 as a biological indicator, a novel screening method was developed for identifying mutants of Ustilago maydis defective in the biosynthesis of the siderophores ferrichrome and ferrichrome A . Two classes of siderophore mutations, both recessive, were isolated after mutagenesis of haploid cells of the corn smut fungus . Class I mutants no longer produced ferrichrome while retaining the ability to produce ferrichrome A; class II mutants were defective in the production of both ferrichrome and ferrichrome A . Genetic and biochemical data suggest that class II mutants are defective in the ability to hydroxylate L-ornithine to delta-N-hydroxyornithine, the first step in the biosynthesis of these siderophores . A genomic library of wild-type U . maydis DNA was constructed in the cosmid transformation vector pCU3, which contains a dominant selectable marker for hygromycin B resistance . Two cosmids, pSid1 and pSid2, were identified in this library by their ability to complement class II siderophore auxotrophs . The production of both siderophores was concomitantly restored in the majority of the resultant transformants . Transforming DNA could be recovered from the fungal, cosmid-containing transformants by in vitro packaging with lambda bacteriophage extracts . Alternatively, the clones could be identified by a sib selection procedure . Cotransformation was found to occur at a high frequency in the fungus and was used to determine that a 2.5-kilobase HindIII-NruI fragment in pSid1 was responsible for complementing the class II siderophore biosynthetic mutation.

Chem Res Toxicol, 1989 May-Jun, 2(3), 162 - 8
Decomposition and quality control considerations in biological work with fecapentaene preparations; Streeter AJ et al.; Solutions of synthetic fecapentaene 12 (FP-12) intended for carcinogenicity studies were found to decompose extremely rapidly during customary dosage procedures . Apparent half-lives as short as 15 min were observed . While rates and even the qualitative course of decomposition were surprisingly variable in replicate experiments, high concentration and exposure to air were confirmed to be especially important destabilizing influences . The results suggested a primary role for a radical decomposition mechanism in the presence of atmospheric oxygen . Consistent with this hypothesis, FP-12 solutions were significantly stabilized by the radical chain-breaking antioxidant vitamin E . On the other hand, dithiothreitol greatly destabilized FP-12, presumably because of its nucleophilicity . The diacetyl diester of FP-12 was more soluble than the parent diol, but its decomposition rates in the presence and absence of vitamin E were similar to those of unesterified FP-12 . Ultraviolet irradiation of an all-trans-FP-12 solution decreased its concentration by 70% in 0.5 min . The mutagenicities of the decomposition/isomerization products of FP-12, as studied in Salmonella typhimurium tester strain TA 100, ranged from negligible to comparable with all-trans-FP-12 itself . It is concluded that unchecked decomposition of fecapentaene preparations can profoundly affect biological tests therewith . While this can be largely controlled through the use of rigorous precautions, including protection from air, light, nucleophiles, and acids as well as selection of the lowest concentration compatible with the application at hand, the data argue strongly for inclusion of appropriate quality control measures in all future dosing operations to prove that the biological activity reported is that of the fecapentaene itself rather than that of a decomposed dosing solution.

J Bacteriol, 1989 May, 171(5), 2424 - 34
Altered transcriptional patterns affecting several metabolic pathways in strains of Salmonella typhimurium which overexpress the fructose regulon; Chin AM et al.; Expression of beta-galactosidase in transcriptional fusions with the pps gene (encoding phosphoenolpyruvate {PEP} synthase), the aceBAK operon (encoding malate synthase, isocitrate lyase, and isocitrate dehydrogenase kinase, respectively), and the phs operon (encoding either thiosulfate reductase or a regulatory protein controlling its expression) was studied in Salmonella typhimurium . beta-Galactosidase synthesis in these strains was repressible either by growth in the presence of glucose or by the presence of a fruR mutation, which resulted in the constitutive expression of the fructose (fru) regulon . Five enzymes of gluconeogenesis (PEP synthase, PEP carboxykinase, isocitrate lyase, malate synthase, and fructose-1,6-diphosphatase) were shown to be repressed either by growth in the presence of glucose or the fruR mutation, while the glycolytic enzymes, enzyme I and enzymes II of the phosphotransferase system as well as phosphofructokinase, were induced either by growth in the presence of glucose or the fruR mutation . Overexpression of the cloned fru regulon genes (not including fruR) resulted in parallel repression of representative gluconeogenic, Krebs cycle, and glyoxylate shunt enzymes . Studies with temperature-sensitive mutants of S . typhimurium which synthesized heat-labile IIIFru proteins provided evidence that this protein plays a role in the regulation of gluconeogenic substrate utilization . Other mutant analyses revealed a complex relationship between fru gene expression and the expression of genes encoding gluconeogenic enzymes . Taken together, the results suggest that a number of genes encoding catabolic, biosynthetic, and amphibolic enzymes in enteric bacteria are transcriptionally regulated by a complex catabolite repression/activation mechanism which may involve enzyme IIIFru of the phosphotransferase system as one component of the regulatory system.

Biochemistry, 1989 Apr 18, 28(8), 3541 - 9
(1-Aminoethyl)boronic acid: a novel inhibitor for Bacillus stearothermophilus alanine racemase and Salmonella typhimurium D-alanine:D-alanine ligase (ADP-forming); Duncan K et al.; (1-Aminoethyl)boronic acid (Ala-B), an analogue of alanine in which a boronic acid group replaces the carboxyl group, has been synthesized and found to inhibit the first two enzymes, alanine racemase (from Bacillus stearothermophilus, EC 5.1.1.1) and D-alanine:D-alanine ligase (ADP-forming) (from Salmonella typhimurium, EC 6.3.2.4), of the D-alanine branch of bacterial peptidoglycan biosynthesis . In both cases, time-dependent, slow binding inhibition is observed due to the generation of long-lived, slowly dissociating complexes . Ala-B inhibits alanine racemase with a Ki of 20 mM and a kappa inact of 0.15-0.35 min-1 . Time-dependent loss of activity is paralleled by conversion of the 420-nm chromophore of initial bound PLP aldimine to a 324-nm absorbing species . On dilution of Ala-B, racemase activity is regained with a t1/2 of ca . 1 h . The D-Ala-D-Ala ligase also shows progressive inhibition by Ala-B provided ATP (but not AMP-PNP or AMP-PCP) is present . The presence of D-alanine along with ATP also leads to Ala-B-induced inactivation . Kinetic analysis suggests Ala-B can compete with D-alanine at either of the two D-alanine binding sites, and on inactivation with Ala-B, labeled D-alanine, and labeled ATP, the inactive enzyme has stoichiometric amounts of D-alanine, ADP, Pi, and Ala-B bound . The half-life of inactive enzyme complexes varied from approximately 2 h (without D-alanine) to 4.5 days (with D-alanine) . No D-Ala-D-Ala-B dipeptide was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

J Biol Chem, 1989 Apr 15, 264(11), 6288 - 96
The alpha subunit of tryptophan synthase . Evidence that aspartic acid 60 is a catalytic residue and that the double alteration of residues 175 and 211 in a second-site revertant restores the proper geometry of the substrate binding site; Nagata S et al.; Our studies, which are aimed at understanding the catalytic mechanism of the alpha subunit of tryptophan synthase from Salmonella typhimurium, use site-directed mutagenesis to explore the functional roles of aspartic acid 60, tyrosine 175, and glycine 211 . These residues are located close to the substrate binding site of the alpha subunit in the three-dimensional structure of the tryptophan synthase alpha 2 beta 2 complex . Our finding that replacement of aspartic acid 60 by asparagine, alanine, or tyrosine results in complete loss of activity in the reaction catalyzed by the alpha subunit supports a catalytic role for aspartic acid 60 . Since the mutant form with glutamic acid at position 60 has partial activity, glutamic acid 60 may serve as an alternative catalytic base . The mutant form in which tyrosine 175 is replaced by phenylalanine has substantial activity; thus the phenolic hydroxyl of tyrosine 175 is not essential for catalysis or substrate binding . Yanofsky and colleagues have identified many missense mutant forms of the alpha subunit of tryptophan synthase from Escherichia coli . Two of these inactive mutant forms had either tyrosine 175 replaced by cysteine or glycine 211 replaced by glutamic acid . Surprisingly, a second-site revertant which contained both of these amino acid changes was partially active . These results indicated that the second mutation must compensate in some way for the first . We now extend the studies of the effects of specific amino acid replacements at positions 175 and 211 by two techniques: 1) characterization of several mutant forms of the alpha subunit from S . typhimurium prepared by site-directed mutagenesis and 2) computer graphics modeling of the substrate binding site of the alpha subunit using the x-ray coordinates of the wild type alpha 2 beta 2 complex from S . typhimurium . We conclude that the restoration of alpha subunit activity in the doubly altered second-site revertant results from restoration of the proper geometry of the substrate binding site.

J Biol Chem, 1989 Apr 15, 264(11), 6280 - 7
The beta subunit of tryptophan synthase . Clarification of the roles of histidine 86, lysine 87, arginine 148, cysteine 170, and cysteine 230; Miles EW et al.; Our studies, which are aimed at understanding the catalytic mechanism of the beta subunit of tryptophan synthase from Salmonella typhimurium, use site-directed mutagenesis to clarify the functional roles of several putative active site residues . Although previous chemical modification studies have suggested that histidine 86, arginine 148, and cysteine 230 are essential residues in the beta subunit, our present findings that beta subunits with single amino acid replacements at these positions have partial activity show that these 3 residues are not essential for catalysis or substrate binding . These conclusions are consistent with the recently determined three-dimensional structure of the tryptophan synthase alpha 2 beta 2 complex . Amino acid substitution of lysine 87, which forms a Schiff base with pyridoxal phosphate in the wild type beta subunit, yields an inactive form of the beta subunit which binds alpha subunit, pyridoxal phosphate, and L-serine . We also report a rapid and efficient method for purifying wild type and mutant forms of the alpha 2 beta 2 complex from S . typhimurium from an improved enzyme source . The enzyme, which is produced by a multicopy plasmid encoding the trpA and trpB genes of S . typhimurium expressed in Escherichia coli, is crystallized from crude extracts by the addition of 6% poly(ethylene glycol) 8000 and 5 mM spermine . This new method is also used in the accompanying paper to purify nine alpha 2 beta 2 complexes containing mutant forms of the alpha subunit.

Infect Immun, 1989 Apr, 57(4), 1011 - 7
Resistance to infection in murine beta-thalassemia; Ampel NM et al.; Clinical evidence suggests that individuals with chronic iron overload may be at increased risk of bacterial infection . We studied this question by using a unique model in which mice homozygous for a deletion in the gene encoding for the beta-major globin develop moderate anemia, splenomegaly, and tissue iron overload, a syndrome similar to beta-thalassemia in humans . Mice heterozygous for the gene deletion were phenotypically normal . Homozygous mice were significantly more susceptible to infection with Listeria monocytogenes than were heterozygous mice (P less than 0.01) . This increased susceptibility was associated with a greater number of organisms in the liver and spleen than was found in heterozygous mice (P less than 0.05) . However, histologic studies demonstrated similar inflammatory responses within these organs in homozygous and heterozygous mice . The increased susceptibility of homozygous mice to infection with L . monocytogenes was not seen when homozygotes were immunized with a low dose of L . monocytogenes . Although the results were not as striking as with L . monocytogenes, homozygous mice were also found to be more susceptible to infection with Salmonella typhimurium than were heterozygous mice (P less than 0.05) . Splenic mononuclear cells from homozygous mice demonstrated less responsiveness in vitro to the mitogens concanavalin A and phytohemagglutinin than did those from heterozygotes (P less than 0.05) . These data suggest that there is a generalized defect in innate immunity in homozygous mice which makes them more susceptible to infection by L . monocytogenes and S . typhimurium . The site of this immunological defect is not known but is most likely in the mononuclear phagocyte and may be due to tissue iron overload.

Rev Soc Bras Med Trop, 1989 Apr-Jun, 22(2), 81 - 3
{Genetic analysis of lactose-fermenting Salmonella typhimurium isolated in Rio de Janeiro}; Camara FP et al.; Lactose fermenting Salmonella typhimurium are endemic in Sao Paulo, but not in Rio de Janeiro Two isolations are described from the latter city . These Rio de Janeiro strains have a plasmid of 7.4 megadaltons . These plasmids were not auto-transferable, were thermostable and were not eliminated by acridine orange . One of these strains arose from a plasmid that had the lactose operon repressed, leading us to speculate about the evolution of the lactose fermenting character in Brazilian Salmonella.

J Gen Microbiol, 1989 Apr, 135 ( Pt 4), 805 - 15
Regulation of Salmonella typhimurium pyr gene expression: effect of changing both purine and pyrimidine nucleotide pools; Jensen KF; The synthesis of the pyrimidine biosynthetic enzymes is repressed by the pyrimidine nucleotide end-products of the pathway . However, purine nucleotides also play a role . In this study, I have measured expression of the pyr genes (pyrA-E) in Salmonella typhimurium strains harbouring mutations that permit manipulation of the intracellular pools of both pyrimidine and purine nucleotides . The results identify the effectory purine compound as being a guanine nucleotide; it is probably GTP, but it may be GDP or GMP . The synthesis of carbamoylphosphate synthase, encoded by pyrA, and particularly dihydroorotase, encoded by pyrC, and dihydroorotate dehydrogenase, encoded by pyrD, is stimulated by the guanine nucleotide, while the synthesis of aspartate transcarbamoylase, encoded by pyrBI, and orotate phosphoribosyltransferase, encoded by pyrE, is inhibited by guanine nucleotides . The regulatory pattern of each pyr gene is discussed in relation to present knowledge on gene structure and regulatory mechanism.

Proc Natl Sci Counc Repub China B, 1989 Apr, 13(2), 109 - 18
Characterization and cloning of enterotoxin genes of Salmonella typhimurium; Yang MK et al.; Five of fifty five strains of Salmonella typhimurium of human origin was hybridized with both the LT-A and LT-B gene of Escherichia coli . The remarkably erythromatous and indurated response on rabbit skin and significant elongation of Chinese Hamster Ovary (CHO) cells indicated the production of enterotoxin of these isolates . The Salmonella enterotoxin is heat-labile and is not a secretory product . The LT gene of E . coli was used to analyze the chromosome and plasmid DNA from Salmonella typhimurium strains for toxin gene sequences . Southern blot analysis demonstrated that the toxin gene was located on the plasmid but not on the chromosome . Restriction enzymes BamHI, EcoRI, HindIII and PstI were used to analyze the DNA isolated from salmonella strains Nos.22, 52, 55 and 59 . Three DNA fragments with size of 5.2 Kb of strain 22, 5.0 Kb of strain 52 and 8.6 Kb of strain 59 were identified as containing the enterotoxin gene . Plasmid pUC19 was used as the vector to clone these DNA fragments in E . coli . The rabbit skin permeability test indicated that Salmonella enterotoxin could be synthesized at readily detectable levels in these transformed E . coli.

Rev Ig Bacteriol Virusol Parazitol Epidemiol Pneumoftiziol Bacteriol Virusol Parazitol Epidemiol, 1989 Apr-Jun, 34(2), 123 - 31
{Hospital strains of Salmonella serotype typhimurium with particular biological properties}; Lucinescu S et al.; 93 cultures of Salmonella typhimurium (STm) were isolated from the infants (under one year old) admitted into a pediatrics ward . All the cultures had only flagellation antigens in phase I, a common sensitivity spectrum to antibiotics and the same sensitivity to the sets of bacteriophages for typing of this serotype . Of these, 10 strains were negative H2S and 6 immobile . Using as carrier a strain of E . coli, K12Nxr, an experimental transfer of multiple resistance to the antibiotics obtained from strains of Salmonella, agona serotype (with special resistance markers) to STm strains was made . The transfer was equally possible to monophasic and diphasic strains of STm . In the transfer to the diphasic strains, the modification of the phage type was noticed . The results suggest the possibility of the in vivo transfer of R plasmids from the agona serum to the typhimurium serum of Salmonella.

Biokhimiia, 1989 Apr, 54(4), 549 - 58
{Structure of the lipopolysaccharide/human plasma low density lipoprotein complex . 31P-NMR and fluorescence spectroscopy studies}; Viktorov AV et al.; Complexes of Salmonella typhimurium lipopolysaccharide toxin (LPS) with low density lipoproteins (LDL) containing various amounts of LPS were prepared in vitro . The 31P-NMR spectra showed that in the LDL-LPS complexes as well as in native LDL all phosphate groups of phospholipids are accessible to the paramagnetic shift reagent, Pr3+ . Besides, the low frequency mobility of phospholipid phosphates in the complex is diminished . It was supposed that the phospholipid molecules in the LDL/LPS complex as in native LDL form a monolayer structure on the surface of LDL . The intrinsic fluorescence spectra of tryptophan residues of the apoprotein (apo B-100) revealed that the incorporation of LPS molecules into LDL particles is accompanied by minor changes in the conformation and orientation of the apo B molecule . As a result of these changes, certain fragments become exposed to a more hydrophilic environment and become more accessible to fluorescence quenchers . The use of charged (I-, Cs+) and uncharged (acrylamide) quenchers permitted to identify in the apo B molecule different tryptophan residues, some of which are localized in the vicinity of negatively charged groups, whereas others are neighbouring positively charged groups . It is suggested that the LPS molecules incorporated into LDL particle do not screen the apo B molecule to such an extent that it would hinder the LDL/LPS complex binding to apo B/E cellular receptors.

Microb Pathog, 1989 Apr, 6(4), 265 - 76
Reduced proliferative response of mouse spleen cells to mitogens during infection with Salmonella typhimurium or Listeria monocytogenes; Brunner H et al.; A significant reduction in the mitogenic responsiveness (uptake of 3H-thymidine) of murine spleen cells to concanavalin A, phytohemagglutinin or lipopolysaccharide was observed during infection with virulent Salmonella typhimurium . The decreased response to mitogens could be observed independent of the immunity to typhimurium (Ity) genotype, i.e . in CBA/J mice and C3H/HeJ mice (Ityr) as well as in C57BL/6 mice (Itys) . Because reduced responsiveness was demonstrated in C3H/HeJ mice, which are susceptible to S . typhimurium infection but are unresponsive to lipopolysaccharide, it is concluded that the two phenomena are not correlated with one another . A similar decrease in response to mitogens was shown in mice infected with Listeria monocytogenes . Reduction in mitogenic responsiveness was directly correlated with the number of viable bacteria detected in the spleen cell suspension . Decreased lymphoproliferation could be observed as early as 2 days after infection and lasted 3 weeks in sublethally infected mice . The question remains whether or not the reduced responsiveness indicates an enhanced susceptibility to infection or merely represents a high degree of activation of defense mechanisms.

Avian Dis, 1989 Apr-Jun, 33(2), 340 - 4
In vitro attachment of Salmonella typhimurium to chick ceca exposed to selected carbohydrates; McHan F et al.; This investigation was designed to study the effect of selected carbohydrates on the in vitro attachment of Salmonella typhimurium to the ceca of chickens 1 and 2 weeks of age . Ceca were surgically removed from chickens immediately after euthanasia, inverted on glass rods, and then rinsed with sterile saline before being exposed to S . typhimurium in a solution of saline containing the carbohydrate to be evaluated . Attachment of S . typhimurium to ceca was reduced in 1-week-old chicks in the presence of N-acetyl-D-galactosamine, L-fucose, D-galactose, L+arabinose, and D+mannose . Minimal or no reduction in attachment of S . typhimurium was noted when ceca from 2-week-old chicks were exposed to the same compounds . Carbohydrates investigated and found to be ineffective for reduction of S . typhimurium attachment to chick ceca were D+fucose and N-acetyl-D-glucosamine.

Mol Gen Genet, 1989 Apr, 216(2-3), 303 - 14
Heme-deficient mutants of Salmonella typhimurium: two genes required for ALA synthesis; Elliott T et al.; The first step in heme biosynthesis is the formation of 5-aminolevulinic acid (ALA) . We have isolated, mapped and characterized a large number of Salmonella typhimurium mutants auxotrophic for ALA . These mutants carry defects in either one of two genes, both required for ALA synthesis . The previously identified hemA gene maps at 35 min, and the hemL gene maps at 5 min on the S . typhimurium genetic map . Mutants in hemA and hemL are defective for aerobic and anaerobic respiration, and appear to be oxygen sensitive . The Hem- phenotype of hemL mutants is less severe than that of hemA mutants . Although hemA and hemL mutants are deficient in heme synthesis, genetic tests indicate that they still synthesize two minor products of the heme pathway, siroheme and cobalamin (vitamin B12), under anaerobic conditions . In contrast, hemB, hemC and cysG mutants, blocked after ALA synthesis, make neither siroheme nor vitamin B12 . Double mutants defective in both hemA and hemL also make siroheme . We suggest that hemA and hemL are required for one route of ALA synthesis and that a second, minor route of ALA synthesis may operate in S . typhimurium; this second pathway would be independent of the hemA and hemL functions.

J Clin Microbiol, 1989 Apr, 27(4), 622 - 7
Clonal groups of Salmonella typhimurium in New York State; McDonough PL et al.; The epidemiology of 278 strains of Salmonella typhimurium isolated from 1973 to 1981 from animals in New York State was studied by using four "fingerprinting" techniques, bacteriophage type (B.R . Callow, J . Hyg . 57:346-359, 1959), biotype (J . P . Duguid, E . S . Anderson, G . A . Alfredsson, R . Barker, and D . C . Old, J . Med . Microbiol . 8:149-166, 1975), plasmid profile, and antibiogram . Phage type with biotype was the most useful marker for distinguishing clonal groups of S . typhimurium . Four clones of S . typhimurium predominated, i.e., phage type/biotypes U275/26, 49/26, 10/3, and 2/3 . U275/26 and 49/26 were commonly found until 1976, but clones 10/3 and 2/3 were predominant after 1976 . Comparison of results with data from Canada suggested a dissemination of strains of S . typhimurium between Canada and New York . Cattle were a common source of phage type 49, as has been observed in other countries.

Tijdschr Diergeneeskd, 1989 Apr 1, 114(7), 381 - 3
{A trial with attenuated live Salmonella typhimurium vaccine for protection against an experimental Salmonella infection in pigeons}; Uyttebroek E et al.; A live, attenuated Salmonella typhimurium vaccine, available on the market, was administered to six pigeons . The strain of vaccine could not be identified in the droppings of pigeons up to ten days after administration . The pigeons as well as controls were experimentally infected with a Salmonella typhimurium var . copenhagen pigeon strain four weeks after vaccination . Differences in excretion of the var . copenhagen strain and in the appearance of diarrhoea and polyuria between the vaccinated and non-vaccinated pigeons were not detected.

Mutat Res, 1989 Apr, 222(4), 337 - 41
Genotoxic effects of niclosamide in Aspergillus nidulans; de la Torre RA et al.; A 2-5-month treatment with niclosamide, a widely used drug in developing countries, has been reported to induce lymphosarcomas in toad liver and kidney . The genotoxic effects of this drug have also been evaluated in Salmonella typhimurium, in somatic and germinal cells of mice and in human lymphocytes exposed in vitro and in vivo . The present study shows that niclosamide is also capable of inducing mitotic crossing-over and non-disjunction in Aspergillus nidulans, which points to the wide potential of this drug as a genotoxic agent.

J Bacteriol, 1989 Apr, 171(4), 2173 - 80
DNA ligase and the pyridine nucleotide cycle in Salmonella typhimurium; Park UE et al.; Bacterial DNA ligases use NAD as an energy source . In this study we addressed two questions about these enzymes . First, what is the physiological consequence of completely removing the NAD-dependent enzyme and replacing it with an ATP-dependent DNA ligase? We constructed Salmonella typhimurium strains in which the endogenous NAD-dependent DNA ligase activity was inactivated by an insertion mutation and the ATP-dependent enzyme from bacteriophage T4 was provided by a cloned phage gene . Such strains were physiologically indistinguishable from the wild type, even under conditions of UV irradiation or treatment with alkylating agents . These results suggest that specific functional interactions between DNA ligase and other replication and repair enzymes may be unimportant under the conditions tested . Second, the importance of DNA ligation as the initiating event of the bacterial pyridine nucleotide cycle was critically assessed in these mutant strains . Surprisingly, our results indicate that DNA ligation makes a minimal contribution to the pyridine nucleotide cycle; the Salmonella strains with only an ATP-dependent ligase had the same NAD turnover rates as the wild-type strain with an NAD-dependent ligase . However, we found that NAD turnover was significantly decreased under anaerobic conditions . We suggest that most intracellular pyridine nucleotide breakdown occurs in a process that protects the cell against oxygen damage but involves a biochemical mechanism other than DNA ligation.

J Bacteriol, 1989 Apr, 171(4), 2075 - 82
Release of flagellar filament-hook-rod complex by a Salmonella typhimurium mutant defective in the M ring of the basal body; Okino H et al.; A Salmonella typhimurium strain possessing a mutation in the fliF gene (coding for the component protein of the M ring of the flagellar basal body) swarmed poorly on a semisolid plate . However, cells grown in liquid medium swam normally and did not show any differences from wild-type cells in terms of swimming speed or tumbling frequency . When mutant cells were grown in a viscous medium, detached bundles of flagellar filaments as long as 100 microns were formed and the cells had impaired motility . Electron microscopy and immunoelectron microscopy revealed that the filaments released from the cells had the hook and a part of the rod of the flagellar basal body still attached . Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis showed that the rod portion of the released structures consisted of the 30-kilodalton FlgG protein . Double mutants containing this fliF mutation and various che mutations were constructed, and their behavior in viscous media was analyzed . When the flagellar rotation of the mutants was strongly biased to either a counterclockwise or a clockwise direction, detached bundles were not formed . The formation of large bundles was most extreme in mutants weakly biased to clockwise rotation.

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