Contrib Microbiol Immunol, 1979, 6, 100 - 10 Structure and function of plasmid ColE1 and related plasmids; Sherratt DJ et al.; Analysis of plasmid ColE1, its naturally occurring relatives ColK and CloDF13, and a wide range of ColE1 derivatives containing either insertions or deletions of genetic material has allowed localization on the ColE1 genome of DNA sequences responsible for colicin E1 synthesis, immunity to colicin killing, conjugal mobility and incompatibility . We have examined incompatibility between pairs of ColE1 derivatives ranging in size from 2.6 to 13.8 Md . Though all the plasmids tested exerted ColE1 incompatibility, a definite pattern was observed regarding the dominant plasmid in any pair tested (i.e . the plasmid that displaces the other from a heterozygote) . Usually the larger plasmid is displaced . We conclude that loci for incompatibility reside within 0.7 kb of the ColE1 replication region . A model is presented to explain both the incompatibility data and the observation that the fraction of total DNA occurring as ColE1-like plasmid in a cell is approximately constant . Transposons Tn1 and Tn3 (3.2 Md; Apr and approximately 85% homologous), Tn501 (5.5 Md; Hgr), and Tn7 (9.3 Md; Tpr Smr) can all be transposed into ColE1 . Though all have closely related . Tn501 and Tn7 do not complement transposition of Tn3 transposition defective deletions . A Tn3-specified 19,000 dalton protein is absent in one particular class of transposition-defective deletion. Neoplasma, 1979, 26(3), 281 - 5 Peripheral blood lymphocyte nucleoi of rats with Yoshida ascitic sarcoma and the effect of endotoxin; Likovsky Z et al.; Nucleoli of lymphocytes were studied in the peripheral blood of male Wistar rats bearing Yoshida ascitic tumor untreated and treated with Escherichia coli endotoxin . Both the neoplastic process and the endotoxin produced an increase of peripheral lymphocytes with "active" nucleoli in number . The treatment of experimental animals bearing the tumor with the endotoxin decreased their mortality and enhanced the increase of the lymphocytes with "active" nucleoli in their peripheral blood. Microbiol Immunol, 1979, 23(11), 1077 - 83 "Pseudolysogenization" by RNA phage Q beta; Watanabe I et al.; We isolated fairly stable lysogenic-like bacteria from a lysogenic state established between an amber mutant for the maturation protein gene of RNA phage Q beta (Q beta am 205) and its nonpermissive host BE110 . These bacteria contained few mature phages intracellularly (less than 10(-3) plaque forming unit per cell), continued to grow with a potentiality to produce Q beta am 205 spontaneously, and showed an immunity-like response against homologous phage infection . These characteristics were maintained by growth in liquid medium containing anti-Q beta serum . We designated these cells as pseudolysogenic bacteria . The relative amounts of RNA genomes in these pseudolysogenic cells (about 10(2) infectious RNA strands per cell) indicated that the RNA genomes could replicate in nonpermissive cells and be distributed in daughter cells synchronizing well with cell division. Genetika, 1979, 15(2), 209 - 19 {Incorporation of the ampicillin resistance transposon into the Escherichia coli K-12 chromosome and into plasmids}; Volozhantsev NV et al.; The mutant pEG1 of R-factor RP4 with temperature-sensitive defect in replication, carrying a transposable ampicillin resistance element Tn1 was used to define the frequency of insertion of this element into Escherichia coli K-12 chromosome and some other plasmids . Our results indicate that the frequency of colony forming by bacteria with pEG1-factor on ampicillin medium in non-permissive conditions corresponds to the frequency of Tn1 insertion into bacterial chromosome or some other plasmid (in case when the strains are carrying a second plasmid) . The frequency of Tn1 insertion into the chromosome is about 4.10(-4) . The defect in recA gene produce no serious change in the frequency of Tn1 insertion into the bacterial chromosome . The translocation of Tn1 element from pEG1-factor to R483, R6 and ColE1 plasmids occurs at 10 to 100-fold-higher frequency than from the plasmid to the chromosome . The insertion of Tn1 into the F'-factor KLF10 and R-factor R64-11 occurs at far lower frequency than that to plasmids R6, R483, or ColE1. Genetika, 1979, 15(2), 200 - 8 {Asymmetry in the frequencies of reciprocal recombinants in crosses of T4 phage rIIB mutants}; Shcherbakov VP et al.; The frequencies of reciprocal recombinants in crosses between rIIB mutants of T4 phage were shown to differ from each other . In terms of the correction model, this asymmetry of genetic recombination was used to measure the comparative correctability of the mismatched regions to the wild type and to the mutant alleles . The data obtained are in quantitative agreement with the analogous values for the same mismatched regions determined by comparison of the markers located at the same site . This strongly suggests that the asymmetry of genetic recombination in T4 reflects the corresponding difference in rates of correction of the mismatched regions in heteroduplexes in opposite directions. Enzyme, 1979, 24(6), 353 - 7 Escherichia coli tRNA (uracil-5-)-methyltransferase: Inhibition by analogues of adenosylhomocysteine; Shugart L et al.; Structural analogues of adenosylhomocysteine (AdoHcy) have been tested as inhibitors of a tRNA(uracil-5-)-methyltransferase preparation obtained from Escherichia coli . All analogues tested gave linear competitive inhibition kinetics with adenosylmethionine (AdoMet) as the variable substrate . Comparison of the Ki values obtained leads to the following conclusions concerning the specificity of the AdoMet-AdoHcy binding site on the enzyme: (i) the terminal amino group of the amino acid moiety is necessary for activity; (ii) both a chiral change of the asymmetric carbon atom of homocysteine and the presence of the terminal carboxyl group contribute little towards inhibitory activity; (iii) analogues in which the amino function of the adenyl moiety is modified or substituted are still potent inhibitors; (iv) inhibitor specificity is considerably reduced when adenine is replaced by a pyrimidine base. Adv Exp Med Biol, 1979, 123, 59 - 78 L-Glutamate decarboxylase; Sze PY; Much progress has been made in recent years regarding enzymological aspects of mammalian brain GAD, such as its purification and characterization, but some uncertainty still remains concerning its molecular weight and forms, and its subunit structure . The availability of antibodies to this enzyme has allowed immunocytochemical studies which have provided important information on the intrinsic organization of GABA-ergic neurones in the CNS, particularly in the cerebellum and nigrostriatal pathway . With the increased understanding of the enzymology of GAD and the distribution of central GABA-ergic neurones, it is becoming feasible to study the regulatory biochemistry of GAD in terms of control and adaptive mechanisms at the cellular level . In our own laboratory, as well as in others, initial approaches have already begun . Obviously, cellular regulation of this phenotypic enzyme is an important issue for the understanding of GABA-ergic neurones and their functions. Infection, 1979, 7 Suppl 5, S443 - 5 Efficacy of bacampicillin and ampicillin in experimental pyelonephritis in the rat; Ritzerfeld W; Bacampicillin and ampicillin were tested and compared with each other in a model of acute, obstructive pyelonephritis in the rat . The compounds were administered orally at five dose levels ranging from 50 mg/kg to 150 mg/kg . Bacampicillin was found to have a greater therapeutic activity than ampicillin, particulary at the higher doses, indicating that its improved absorption properties make it a therapeutically more effective compound than ampicillin. Arch Exp Veterinarmed, 1979, 33(2), 237 - 46 {Effect of reduced gastrointestinal motility on the regulation of gastrointestinal flora and the pathogenesis of coli enterotoxinemia in market swine}; Schulze F; Opium tincture and Spasmentral were applied to piglets early after weaning and reduced their gastro-intestinal motility, which, however, caused only very minor changes in quantitative germ flora composition in those first days . Short-time suppression of gastro-intestinal motility obviously does not result in detrimental consequences to the organism as a whole, since there seem to be several factors which are involved in the control and regulation of the intestinal germ flora . Impairment of gastro-intestinal motility appeared to be of no importance to the pathogenesis of coli-enterotoxaemia, as it was not followed by higher incidence of the disease. Acta Biochim Pol, 1979, 26(1-2), 29 - 38 Effect of temperature and 4,6'-diamidine-2-phenylindole on restriction of supercoiled Col E1 DNA by Eco RI endonuclease; Stepien E et al.; Supercoiled Col E1 DNA is split by Eco RI endonuclease at 37 degrees C without intermediate formation of open circular DNA . Accumulation of this restriction product is observed at low temperature . The fluorescent dye, 4,6'-diamidine-2-phenylindole (DAPI) inhibits restriction by Eco RI endonuclease . This effect is due to the DAPI:DNA rather than to the DAPI:Eco RI interactions. Vet Med Nauki, 1979, 16(1), 28 - 32 {Immunostimulating activity of certain subcellular fractions of Escherichia coli O138:K81:H19}; Ruskova M; A 24-hour culture of Escherichia coli 0138:K81:H19 was used to isolate a soluble cytoplasmic fraction, an O antigen, and an unsolube cell ingredient . Their immunogenic action was followed up through subcutaneous vaccination of mice and the production of humoral antibodies in rabbits . It was found that the cytoplasmic ingredient was a slightly toxic protective antigen forming considerable immunity in mice and a comparatively high titer of antibodies in rabbit sera . The unsoluble cell ingredient and the O antigen proved comparatively toxic and did not produce favourable immune response . Discussed in the use of the cytoplasmic ingredient as a vaccine as well as the type of the immunoglobulins produced. Microbiol Immunol, 1979, 23(7), 569 - 80 Integration of temperature-sensitive nonconjugative plasmid carrying kanamycin gene into conjugative R plasmids; Katsumata R et al.; A nonconjugative R plasmid, rMS3, whose molecular weight was 2.4 X 10(7) daltons, possessed a kanamycin resistance gene and was thermosensitive in its maintenance in Escherichia coli strains . We mobilized rMS3 with a conjugative R plasmid, R100 or T-tet, and obtained cointegrates carrying all the parental resistance markers . Various markers of the cointegrates were frequently deleted by P1 transduction and the deletion patterns among the different cointegrates were differed from each other . The cointegrates were thermoresistant, but the thermosensitive replicon could be segregated from the thermoresistant cointegrate by deletion . Some cointegrates between rMS3 and T-tet showed a derepressed state of transferability because of the integration of rMS3 and T-tet showed a derepressed state of transferability because of the integration of rMS3 into the regulator gene of the transfer loci . The genome size of the cointegrate so far tested was the sum of the sizes of the parental plasmids, indicating that the whole genome of rMS3 could integrate into various sites of the conjugative plasmids R100 and T-tet. Biochimie, 1979, 61(5-6), 671 - 9 Methylated amino acids in ribosomal proteins from Escherichia coli treated with ethionine and from a mutant lacking methylation of protein L11; Alix JH et al.; In the present study, the nature, proportions and distribution of methylated amino acids in ribosomal proteins from Escherichia coli grown in the presence of ethionine and from mutant prm 1 were studied . The undermethylated ribosomes had been labeled by addition in vitro or in vivo of radioactive methyl groups from S-adenosylmethionine or from methionine . The following compounds were identified : N alpha-mono-, di- and trimethylalanines, N epsilon-mono-, di- and trimethyllysines, methylamine and N alpha-trimethylalanyllysine . Except for the latter compound and N-alpha-dimethylalanine, all other derivatives had been previously identified in the literature . It is shown that the dipeptide had been in the past mistaken for N epsilon-monomethyllysine, and arises through incomplete hydrolysis in 24 hrs of the N-terminal peptide bond of protein L11 . The results of the present study are discussed in the light of previous work on ribosomal protein methylation by the authors and other workers in the field. Arzneimittelforschung, 1979, 29(7), 1062 - 4 Endotoxin, fever and anomalies of development in rabbits . Short communication; Hellmann W; E . coli endotoxin was injected i.v . in rabbits (White New Zealands) on day 9 of gestation . The rise of temperatures was examined by thermoelectric recording . On day 29 of pregnancy the rabbits were killed, the uteri examined for resorptions and the fetuses inspected for malformations . The results were compared with those of control animals . The group treated with E . coli endotoxin showed a significant higher resorption and malformation rate . On the basis of the slight increase of temperatures (up to 1.1 degrees C above normal value), it is supposed that the endotoxin-induced fever did not participate in the teratogenic effects observed. Arzneimittelforschung, 1979, 29(5), 804 - 7 Ontogenic drug studies in calves . II . Changes in salicylate levels and metabolism in calves with diarrhoea; Sechserova M et al.; Acetylsalicylic acid (ASA) was administered by oral route to calves and mice . A comparison of plasma levels of salicylates and salicyluric acid was performed in healthy and diarrhoic calves . The calves were infected with E . coli enterotoxin producing strains . During the 6 h observation period increased levels of salicylates were found in all age groups of calves (1-60 days) . There were no significant differences in salicyluric acid plasma levels between controls and diarrhoic animals . Intravenous injection of cholera toxin in mice caused lower levels of total salicylates, but increased levels of salicylic acid and salicyluric acid . The importance of adequate animal model is discussed. Antonie Van Leeuwenhoek, 1979, 45(2), 253 - 63 Competition between an Escherichia coli tyrosine auxotroph and a prototrophic revertant in glucose- and tyrosine-limited chemostats; Mason TG et al.; A tyrosine-requiring strain of Escherichia coli was grown in tyrosine-limited chemostats at a range of dilution rates between 0.08 h-1 and 0.42 h-1, conditions which always resulted in the selection of a prototrophic revertant population able to synthesise tyrosine . Analysis of the two-membered mixed cultures which arose showed that the prototrophic population outgrew the auxotroph since its growth rate was not restricted by the growth-limiting concentrations of exogenous tyrosine . During the take-over of the culture, the prototroph population grew exponentially but the specific growth rate increased with decreasing dilution rate of the competition experiments . In glucose-limited chemostats (in the presence of non-growth-limiting concentrations of tyrosine) of the tyrosine-requiring strain, prototrophs were never detected . Constructed two-membered mixed cultures with both populations competing for limiting amounts of glucose, showed that the prototroph was less competitive than the auxotroph. Agents Actions Suppl, 1979, (4), 147 - 55 The role of thromboxane A2 in endotoxin-induced aggregation of guinea-pig platelets in vitro; Bult H et al.; Large concentrations of endotoxin lipopolysaccharides (LPS) E . coli O127:B8 and E . coli O26:B6 were needed for induction of platelet aggregation in citrated platelet rich plasma (PRP) from normal guinea-pigs . When guinea-pigs were actively immunized with LPS E . coli O127:B8 their PRP became more sensitive to the aggregatory effects of this type of LPS . The increase in sensitivity was rather selective since the responses to ADP and LPS E . coli O26:B6 remained unchanged . In endotoxin-stimulated PRP from normal guinea-pigs thromboxane A2 (TXA2) was not detectable by bioassay . Thus biosynthesis of TXA2 seemed to be of little importance in endotoxin-induced platelet responses in normal citrate PRP . LPS E . coli O127:B8, but not LPS E . coli O26:B6, was a potent inducer of the biosynthesis of TXA2 in sensitized PRP . Under those conditions endotoxin-induced aggregation seemed to be dependent on the endogenous biosynthesis of TXA2 by the platelets. Vopr Onkol, 1979, 25(7), 64 - 7 {Ultraviolet-induced effect of N-nitrosamines on the in vitro parameters of DNA fusion}; Iamshanov VA; The results of studies have shown the UV-induced decrease of melting temperatures of the DNA of E . coli and chick erythrocytes under the influence of simple N-nitrosamines (NDMA, NDEA, NDPA) . Either UV or nitrosoamines separately failed to effect the DNA, or their action was insignificant . It is suggested that this effect may be partly due to the action of UV on DNA. Scand J Urol Nephrol, 1979, 13(2), 155 - 60 Continued experimental study on the pathogenesis of sporadic bacteriuria in the rat; Hjort EF; An experimental model implying ligature of the left ureter in the rat has previously (1977) been described by the author . The same model has been used in the experiments which are presented in this paper . The aim has been to study further the hematogenous seeding of bacteria to the hydronephrotic left kidney . The experiments seem to confirm the author's view that sporadic hematogenous infection with intestinal bacteria occasionally takes place and can be demonstrated by this method . Intravenous injection of E . coli showed that the minimal kidney infecting dose amounted to 0.5 ml E . coli 10(6) bacteria per ml . The author found considerable increase of sporadic infection after splenectomy and partial liver resection. Genetika, 1979, 15(8), 1522 - 4 {Enhanced UV sensitivity of Escherichia coli strain uvrA crp}; Skavronskaia AG et al.; UV-sensitivity and UV-induced mutability to tryptophan independence has been studied in isogenic crp, cya, crp+, uvrA crp and uvrA crp+ strains of Escherichia coli . crp and cya strains are found to have the same UV-sensitivity as an isogenic wild type strain . UV-sensitivity of uvrA crp strain seems to be one-two orders increased as compared with the sensitivity exhibited by the uvrA - crp+ strain . The yield of UV-induced revertants is slightly higher in crp, cya and uvrA crp strains than in the wild type cells . The existence of cap-dependent inducible error-free repair pathway is supposed due to the data obtained. Genetika, 1979, 15(7), 1206 - 20 {Genetic control of the formation of plasmid F' . I . Effect of recA- and seg-2 mutations in an Hfr donor strain on the character of plasmid F' formation}; Gorelov VN et al.; Assuming the similarity of the processes of illegitimate recombination, such as deletion formation, with the process of F' plasmid formation, we have undertaken the study of the influence of recA- and seg- alleles of Hfr donor on the F' plasmid formation . The data obtained demonstrate the strong influence of donor genotype on the frequency of F' plasmid formation and on the nature of F' plasmids formed, thus demonstrating that the most of F' plasmids have been formed via recombination in Hfr donor cells . The recA- mutation decreased the total yield of F' plasmids selected using both proximal and distal Hfr markers and affected drastically the distribution of the F' plasmids inheriting different proximal unselected markers . The existence of recA-dependent and recA-independent modes of F' plasmid formation was demonstrated . The Escherichia coli chromosome contains regions which involve preferentially in recA-dependent (between proA and gal, and clockwise from gal) or recA-independent (between leu and proA, and the region counterclockwise from argE) recombination . The seg-2 mutation causes only partial block of both recA-dependent and recA-independent recombination pathways, however it causes dramatic decrease of genetic exchanges leading to the formation of the type II F' plasmids . Both seg- and recA- mutations decrease the frequency of the formation of Tra+ F' transconjugants . The percent of Tra- transconjugants, which remain sensitive to MS2 and Q beta donor specific phages, also drops significantly under the influence of the recA- and seg- alleles . Thus, the recombination involving the F structure in wild type strains and seg- mutants occures preferentially in the points of F outside the regions essential for transfer and sensitivity to male specific phages, while in recA- and recA-ges- strains the points inside these regions (tra operon) frequently involved in F' plasmid looping out . There exist more strict correlation between the fertility and sensitivity to phage Q beta than to phage MS2. Res Vet Sci, 1979 Jan, 26(1), 97 - 101 The pathogenesis of experimental Escherichia coli mastitis in newly calved dairy cows; Hill AW et al.; Experimental infections of the mammary gland of newly calved cows with 500 serum resistant Escherichia coli produced a very severe form of mastitis when compared with animals in mid-lactation . Ten hours after infection the bacteria had multiplied in the milk to very high numbers (10(6)--10(7)/ml) and the animals showed signs of pyrexia, anorexia and diarrhoea . Initially the gland and milk showed little or no clinical signs of mastitis, but later the secretion became a viscous, serous fluid with little or no casein or fat . A delay in diapedesis of neutrophils into the gland appears to be the reason for the peracute state and lack of clinical signs . This form of pathogenesis may produce a paradoxical situation where the most severe cases of E coli mastitis cannot be diagnosed at a stage early enough for the animal to respond to therapy. Folia Microbiol (Praha), 1979, 24(3), 224 - 7 A comparison of UV-induction in exponentially growing and resting Escherichia coli B/r Hcr+; Slezarikova V et al.; Using the method of two separate UV exposures the increase of UV resistance after various induction fluences in growing and resting Escherichia coli B/r Hcr+ was followed . In resting cells, the optimum induction energy fluence was found to be 30 J/m2 . In exponentially growing cells testing of induction has proved to be possible only under conditions of postincubation of cells with chloramphenicol after the second fluence . Under these conditions the induction energy fluence up to the observed 50 J/m2 resulted in an increased survival. Exp Cell Biol, 1979, 47(3), 218 - 25 Particular RNA fragments as promoters of leukocyte and platelet formation in rabbits; Beljanski M et al.; Under well-defined conditions, ribosomal RNA from Escherichia coli is fragmented by pancreatic ribonuclease, leading to the appearance of particular RNA fragments . Some of these fragments act as primers for in vitro replication of DNA extracted from blood-cell and platelet-forming tissues . In experimental rabbits they restore in a rapid and harmless way normal circulating leukocyte and platelet levels when these have been drastically decreased by various chemotherapeutic agents mainly used in anticancer therapy . Imbalance between polynuclear and lymphocyte count provoked in rabbits by cyclophosphamide can be rapidly corrected by treating the animal with active RNA fragments. Eksp Med Morfol, 1979, 18(2), 76 - 81 {Changes in the motor activity of an isolated intestinal loop from the jejunum of dogs exposed to an endotoxin}; Tsafarov M; The author examined the motor activity of an isolated Loop in vivo of founonnarcotised dogs under the conditions of chronic experiments before and after administration of E . coli in dose of 0.1, 0.5, 1.0, and 2.0 mg/body weight . There was inhibition of the movements of the intestinal loop, which was manifested by a reduction of the frequency and amplitude of the intestinal contractions . The inhibition of the motor activity was explained by the disturbances in the circulation and neuro-bunoral control of the intestinal smooth muscle. Contrib Nephrol, 1979, 16, 16 - 21 Immunological aspects of pyelonephritis; Hanson LA et al.; Several virulence factors, such as O and K antigens and capacity to attach to uroepithelial cells, seem to be required for Escheria coli to cause acute pyelonephritis . These factors induce an immune response, however, which can modify the course and clinical expression of the infection . During acute pyelonephritis, autoantibodies to the Tamm-Horsfall protein increase . These antibodies, which probably are evoked by a cross-reaction noted between structures of E . coli LPS and the Tamm-Horsfall protein, may add to the renal tissue engagement in interstitial nephritis caused by bacterial pyelonephritis. Circ Shock Suppl, 1979, 1, 69 - 79 Lipid metabolism in endotoxic shock; Spitzer JJ; A brief overview of the alterations in the control of free fatty acid (FFA) and triglyceride (TG) turnover following the administration of Escherichia coli endotoxin is presented . Hormone-sensitive lipase activity was increased following either in vivo or in vitro administration of endotoxin . In conscious dogs, the rate of appearance of glycerol was also increased while that of FFA was not changed, indicating that in addition to increased lipolysis, increased reesterification in the adipose tissue may also be present . Myocardial utilization of FFA was decreased and that of lactate increased following endotoxin both in vivo and in vitro using isolated myocytes . Both myocardial and adipose tissue lipoprotein lipase activity were decreased following endotoxin, indicating a possible decrease in TG removal by these tissues . Additional studies are warranted to further elucidate the interrelation between the changes of lipid and carbohydrate metabolism and those of hemodynamics in shock. Nucleic Acids Res, 1979, 6(6), 2363 - 79 Segmental flexibility in Escherichia coli ribosomal protein S1 as studied by fluorescence polarization; Chu YG et al.; Ribosomal protein S1 covalently reacts with approximately one equivalent of iodoacetylethylenediamine (1,5-napthol sulfonate (IAEDANS) or iodoacetylaminofluorescein (IAAF) . The product AEDANS-S1 can bind to 30S ribosomal subunits lacking S1 as shown by polyacrylamide-agarose gel electrophoresis AEDANS-S1 and AAF-S1 when added back to S1-depleted 30S subunits modulate poly(U)-dependent polyphenylalanine synthesis in the presence of IF3 in a very similar way to unmodified S1 . AEDANS-S1 also stimulates RI7-dependent fMet-tRNA binding to 1.0M NH4C1 washed ribosomes whereas AAF-S1 does not . Both static and nanosecond fluorescence polarization techniques were used to study the rotational motions of AEDANS-S1 . Several previous studies had indicated that S1 is a highly extended protein which can be modeled by a prolate ellipsoid with an axial ratio of 10 to 1 . However, the rotational correlation time we find is about half that expected for such a particle . This suggests that S1 is a flexible protein with at least two domains that can rotate independently. Mol Biol (Mosk), 1979 Jan-Feb, 13(1), 216 - 27 {Unprimed synthesis of poly (d(A-T)), catalyzed by a preparation of Escherichia coli DNA polymerase I}; Nazarenko IA et al.; The initial events of the de novo synthesis of poly{d(A-T)}, catalyzed by preparations of E . coli DNA-polymerase I, were investigated . The data provide evidence that deoxynucleoside diphosphate: oligonucleotide deoxynucleotidyl transferase (dNDP-transferase), the enzyme which is able to catalyze unprimed polymerization of dNDP, participates in the process of initiation . This conclusion is based on the following data: 1) preincubation of E . coli DNA-polymerase I preparation with dADP and dTDT abolishes a lag-period in the poly{d(A-T)} synthesis; 2) dithiothreitol and N-ethylmaleinide, inhibitors of dNDP-transferase, inhibit de novo synthesis of {d(A-T)}-copolymer by preparations of E . coli DNA-polymerase I but do not effect primed synthesis ensured by this enzyme . High concentration of the substrate have similar effect . Using two-dimentional thin-layer chromatography and microcolumn chromatography on TEAE-cellulose we have shown that preliminary incubation of DNA-polymerase I preparations with dADP and dTDP results in the synthesis of short oligonucleotides (from di- to decanucleotides) . Hydrolysis of these oligonucleotides with dilute sulfuric acid demonstrates that among the reaction products prevail oligoadenylates and oligothymidylates, but an appreciable amounts of heterooligomers including oligo{d(A-T)} were revealed as well . The model of so called de novo synthesis of regular polynucleotides is proposed, according to which dNDP-transferase, an accompanying enzyme in the preparations of DNA-polymerase I E . coli, is carrying out the synthesis of short oligonucleotides which form template-primer complexes repeatedly replicated by the DNA-polymerase I E . coli. Genetika, 1979, 15(5), 823 - 30 {Comparative study of mutator-gene prv and several other mutator-genes of Escherichia coli K-12}; Khmel'nitskii MI et al.; Mutations prv1, prv2 and mutR34, increasing frequencies of intragenic recombinations, are found not to complement and therefore to be alleles of one gene . Checking for the influence of mutator genes mutS3, mutT1 and uvrE502 on the intragenic recombination in conjugational crossings has shown that mutators mutS3 and uvrE502 increase the frequency of intragenic recombinations while mutT1 does not change it . None of the examined mutator genes influence the conjugational frequencies of recombination . A supplementary analysis for the mutability of the mutant prv1 has been carried out . The prv1 mutation can induce mutations of the frameshift type . Mutations uvrA6, recB21, recC22 and lexA produce no influence on the display of a mutator effect of the prv1 mutation. Chir Forum Exp Klin Forsch . 1979;:261-4. Enhancement of local immune response in the treatment of experimental peritonitis; Hau T et al.; We conclude from these experiments that the host defense in peritoneal infections rests largely on the phagocytic cells attracted into the peritoneal cavity by the offending organism, and that an increase in the number of available phagocytes by pretreatment with chemotactic substances protects against lethal peritoneal infections . There seems to be a direct relationship between the number of available phagocytes in the peritoneal cavity at the time of inoculation and the reduction of mortality in experimental peritonitis (Fig . 1). Circ Shock, 1979, 6(1), 13 - 21 Pulmonary vascular response to endotoxin in normal and lymphocyte depleted sheep; Bohs CT et al.; The cardiopulmonary effects of intravenously administered Escherichia coli endotoxin were studied in unanesthetized sheep . One group of animals was depleted of circulating T-lymphocytes while a non-depleted group served as control . T-lymphocyte depletion was accomplished by chronic thoracic duct drainage of lymph, removal of lymphocytes by continuous flow centrifugation and return of the cell free lymph intravenously . The T-lymphocyte depleted sheep demonstrated markedly obtunded increases in pulmonary arterial pressure and pulmonary vascular resistance following endotoxin when compared to the effects of the lipopolysaccharide in control animals . additionally, the lymphocyte depleted group showed a significant augmentation of myocardial contractility which occurred at the same time as marked systemic hypotension . This period of extreme hypotension following endotoxin is presumed to be accompanied by a reflex increase in the activity of the sympathetic nervous system . The control sheep, although equally hypotensive at this time, did not demonstrate a significant increase in myocardial contractility from the preendotoxin value . The results of these experiments indicate that T-lymphocytes may mediate some of the pathophysiological effects of bacterial endotoxin on the cardiovascular system. Nucleic Acids Res, 1979, 6(5), 1831 - 41 DNA sequences of the integration sites and inverted repeated structure of transposon Tn3; Takeya T et al.; The nucleotide sequence of the "inverted repeat" structure of the transposon Tn3 was determined by the DNA sequencing procedure developed by Maxam and Gilbert(1) . The sequence, 38 base pairs long, is as follows: 5'-GGGGTCTGACGCTCAGTGGAACGAAAACTCACGTTAAG..(Tn3) 3'-CCCCAGACTGCGAGTCACCTTGCTTTTGAGTGCAATTC. . The integration of Tn3 is associated with a directly repeated sequence of 5 nucleotides appearing at each end of Tn3 . The two directly repeated sequences so far determined are not the same . Furthermore, there is no homologous structure around the integration point of Tn3. Nucleic Acids Res, 1979, 6(5), 1817 - 30 Physical map of the seven ribosomal RNA genes of Escherichia coli; Boros I et al.; Escherichia coli DNA was digested with restriction endonucleases BamHI, PstI, EcoRI, SalI, HindIII, XhoI, BglII, SmaI, HpaI and with selected double and triple combinations of the same enzymes . The digests were electrophoresed and hybridized with 32P-labelled ribosomal RNA by using the Southern blotting technique . The resulting bands could be arranged into seven groups, and it was possible to construct a unique physical map of the seven rRNA genes (operons) of the bacterial chromosome . Mapping information obtained on several transducing phages and recombinant plasmids carrying rRNA genes, and mapping data published in the literature helped to determine the final map . The results suggest that phage lambda daroE152 carries a "hybrid" rRNA gene which was probably formed by recombination between two different chromosomal rRNA genes. Nucleic Acids Res, 1979, 6(5), 1775 - 90 Max-Planck-Institut für Molekulare Genetik, Abteilung Wittmann, Berlin-Dahlem, GFR; Zwieb C et al.; It is well established that when E . coli 30S ribosomal subunits are irradiated with ultraviolet light under mild conditions a specific cross-link is formed between protein S7 and the 16S RNA . Methodology is presented for the analysis of the single nucleotide residue concerned in this cross-link . Firstly, the identity of the ribonuclease T1 octanucleotide attached to S7 is confirmed by a new method, which involves isolation and analysis of S7-polynucleotide complexes containing 30 -- 40 nucleotides . Secondly, the isolated S7-octanucleotide complex is digested successively with ribonuclease A, proteinase K and ribonuclease T2, and the nucleotides liberated are identified . The results show unambiguously that uridine residue number 1239 in the 16S RNA sequence is cross-linked to protein S7. Nucleic Acids Res, 1979, 6(5), 1761 - 74 The regulatory region of MS2 phage RNA replicase cistron . IV . Functional activity of specific MS2 RNA fragments in formation of the 70 S initiation complex of protein biosynthesis; Borisova GP et al.; The initiation region of the MS2 replicase cistron can be isolated as a fragment 59 bases in length protected from RNAase by the binding of the coat protein which serves as a translational repressor . This fragment MS2 R(-53 leads to 6) starts 53 bases before the initiation codon and retains full activity in binding ribosomes . We have investigated the functional activity in initiation of a series of fragments from this region variously shortened from the 5'-end . Ribosome protected fragments starting 17 or 21 bases before the AUG are unable to rebind to ribosomes . The shortest fragment which has this activity was produced by partial S1 nuclease digestion and starts 33 to 35 bases before the AUG . The initiation signal comprises some nucleotides between 21 and 33 bases before the initiation codon and the regulatory region responsible for initiation is longer than that protected by the ribosome in the final initiation complex. Infection, 1979, 7(2), 64 - 6 Effect of in vitro treatment with reducing drugs on structure and function of human secretory immunoglobulin A; Plebani A et al.; Samples of unstimulated whole saliva from 15 healthy children with 0.5--6 mg/100 ml of secretory IgA and from 10 healthy adults with 4--18 mg/100 ml of secretory IgA were pooled and treated in vitro with dithiothreitol and alpha-mercaptopropionylglycine . The effect of these reducing drugs on the immunochemical properties of secretory IgA was evaluated . Dithiothreitol induced depolymerization of secretory IgA and splitting of the secretory piece from the IgA molecule; furthermore it strongly reduced the titer of secretory antibodies to Escherichia coli antigens . The drug alpha-mercaptopropionylglycine apparently did not affect either the polymeric structure of secretory IgA or the titer of secretory anti-E . coli antibodies; however it induced splitting of the secretory piece . On the whole it appers that drugs with reducing properties, currently employed for liquifying mucous secretions in clinical practice, should be carefully evaluated for possible depressive side-effects on local immunity. Mutat Res, 1979 Jan, 59(1), 15 - 26 Effect of mutagens, chemotherapeutic agents and defects in DNA repair genes on recombination in F' partial diploid Escherichia coli; Norin AJ et al.; The ability of mutagenic agents, nonmutagenic substances and defects in DNA repair to alter the genotype of F' partial diploid (F30) Escherichia coli was determined . The frequency of auxotrophic mutants and histidine requiring (His-) haploid colonies was increased by mutagen treatment but Hfr colonies were not detected in F30 E . coli even with specific selection techniques . Genotype changes due to nonreciprocal recombination were determined by measuring the frequency of His- homogenotes, eg . F' hisC780, hisI+/hisC780, hisI+, arising from a His+ heterogenote, F' hisC780 hisI+/hisC+, his1903 . At least 75% of the recombinants were homozygous for histidine alleles which were present on the F' plasmid (exogenote) of the parental hetergenote rather than for histidine alleles on the chromosome . Mutagens, chemotherapeutic agents which histidine alleles on the chromosome . Mutagens, chemotherapeutic agents which block DNA synthesis and a defective DNA polymerase I gene, polA1, were found to increase the frequency of nonreciprocal recombination . A defect in the ability to excise thymine dimers, uvrC34, did not increase spontaneous nonreciprocal recombination . However, UV irradiation but not methyl methanesulfonate (MMS) induced greater recombination in this excision-repair defective mutant than in DNA-repair-proficient strains . Mutagenic agents, with the exception of ethyl methanesulfonate (EMS), induced greater increases in recombination than the chemotherapeutic agents or the polA1 mutation . EMS, which causes relatively little degradation of DNA, was more mutagenic but less recombinogenic than MMS, a homologous compound ths that inhibition of DNA occurring single-stranded regions in replicative intermediates of the DNA . Mutagens which cause the rapid breakdown of DNA may, in addition, introduce lesions into the genome that increase the number of single-stranded regions thus inducing even higher frequencies of recombination. J Gen Microbiol, 1979 Jan, 110(1), 61 - 6 Uroporphyrin- and coproporphyrin I-accumulating mutant of Escherichia coli K12; Chartrand P et al.; A new type of haem-deficient mutant was isolated in Escherichia coli K12 by neomycin selection . The mutant was deficient in uroporphyrinogen III cosynthase activity as indicated by the accumulation of uroporphyrin I and coproporphyrin . The mapping of the corresponding hemD gene by P1-mediated transduction showed that the new gene was located between ilv and cya, at min 83 on the chromosomal map of Escherichia coli K12. J Gen Microbiol, 1979 Jan, 110(1), 47 - 59 Transfer of a gene for sucrose utilization into Escherichia coli K12, and consequent failure of expression of genes for D-serine utilization; Alaeddinoglu NG et al.; As the first stage in investigating the genetic basis of natural variation in Escherichia coli, the gene(s) conferring the ability to use sucrose as a carbon and energy source (given the symbol sac+) was transferred from a wild strain to K12, which does not use sucrose . The sac+ region was transferred by two different methods . On both occasions it took a chromosomal location at minute 50.5 on the linkage map, between aroC and supN, in the region of the dsd genes, which confer the ability to use D-serine as a carbon and energy source . When the sac+ region was present in the K12 chromosome the bacteria were unable to use D-serine as a carbon and energy source . In F' sac+/dsd+ diploids, the dsd+ genes were similarly not expressed . Strain K12(sac+) bacteria were sensitive to inhibition by D-serine; they mutated to D-serine resistance with much greater frequency than did a dsd mutant of K12 . Such bacteria also mutated frequently to use raffinose . Strain K12(sac+) bacteria did not utilize sucrose when they carried a mutation affecting the phosphotransferase system. J Gen Microbiol, 1979 Jan, 110(1), 211 - 20 Protein II influences ferrichrome-iron transport in Escherichia coli K12; Coulton JW et al.; Ferrichrome-promoted iron uptake in Escherichia coli K12 is strictly dependent upon the tonA gene product, a 'minor' outer membrane protein . By selection for mutants of E . coli resistant to phages which require 'major' outer membrane proteins as receptors, strains with pronounced protein deficiencies were constructed . Such strains were tested for anomalous behaviour of ferrichrome transport . No significant differences in iron uptake were detected in E . coli K12 strains with markedly reduced amounts of protein I . However, a reduction in the initial velocity (up to 40%) was observed in E . coli deficient in outer membrane protein II . This difference was only evident when cells were grown under iron-starvation conditions; it was abolished when cells were grown in rich medium . Kinetic parameters for ferrichrome transport were determined for maximum velocity but for Km; double reciprocal plots showed a biphasic nature, probably attributable to a limited number of outer membrane binding sites and to the multi-component nature of the ferrichrome-iron transport system. Gene, 1979 Jan, 5(1), 45 - 58 The physical localization of the gene for ribosomal protein S20; Mackie GA; As a prerequisite to the examination of the structure and properties of the promoter for ribosomal protein S20 of Escherichia coli, I have determined the cleavage sites in lambdadapB2cI857S7 DNA for four restriction endonucleases . Subsequently, purified fragments obtained after digestion of this DNA with BamI or HindIII have served as templates for coupled transcription and translation . This has permitted the localization of the structural gene for S20 within a 1000 base pair segment of lambdadapB2cIB57S7 DNA . Cleavage of this DNA with HindIII partially inactivates the expression of S20 in vitro, implying that one HindIII site lies in or near a region essential for the expression of S20. Gene, 1979 Jan, 5(1), 19 - 43 Restriction map of the region surrounding the EcoRI site in the pCR1 plasmid and analysis of an inserted ovalbumin gene; Wickens MP et al.; We have determined a restriction map of a 1650 base pair region surrounding the EcoRI site of the bacterial plasmid, pCR1 . We have used pCR1 as a vector in cloning synthetic ovalbumin double-stranded cDNA . Using the pCR1 restriction map, we have characterized the ovalbumin sequences inserted in one recombinant plasmid, pOvE12 . POvE12 appears to contain all, or nearly all, of the sequences found in full length, double-stranded cDNA synthesized in vitro. Can J Comp Med, 1979 Jan, 43(1), 44 - 9 Permeability properties of swine small intestine: effect of a heat stable Escherichia coli enterotoxin; Presnell KR et al.; The permeability of weanling swine small intestine was estimated using measurements of filtration coefficients and equivalent pore size . Hypertonic solutions of mannitol, erythritol and urea were used to calculate reflection coefficients in the duodenum, mid jejunum and distal jejunum . Estimated effective pore radius was 6.4-7.4, 5.6-7.2 and 4.7-4.9A degrees in the three respective regions . Similarly the filtration coefficient induced by hypertonic solutions of mannitol decreased significantly in the distal jejunal segments . The results show an aboral gradient of decreasing permeability along the small intestine of the weanling pig . In situ incubation of loops in the proximal jejunum with a heat stable Escherichia coli enterotoxin for one hour did not significantly change the effective pore size as calculated from reflection coefficients of hypertonic solutions of erythritol and urea . However, the filtration coefficients of loops exposed to the enterotoxin were significantly greater than control loops with hypertonic solutions of erythritol and urea but not mannitol . This suggests the occurrence of a slight reduction in epithelial porosity . The results support the hypothesis that intestinal secretion induced by heat stable E . coli enterotoxin is not the result of an increased mucosal permeability. Biochem J, 1979 Jan 1, 177(1), 129 - 36 Polypeptide-chain stoicheiometry and lipoic acid content of the pyruvate dehydrogenase complex of Escherichia coli; Hale G et al.; The pyruvate dehydrogenase multienzyme complex was isolated from Escherichia coli grown in the presence of {35S}sulphate . The three component enzymes were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and the molar ratios of the three polypeptide chains were determined by measurement of the radioactivity in each band . The chain ratio of lipoamide dehydrogenase to lipoate acetyltransferase approached unity, but there was a molar excess of chains of the pyruvate decarboxylase component . The 35S-labelled complex was also used in a new determination of the total lipoic acid content . It was found that each polypeptide chain of the lipoate acetyltransferase component appears to bear at least three lipoyl groups. Proc Natl Acad Sci U S A, 1979 Jan, 76(1), 91 - 5 Thermosensory transduction in Escherichia coli: inhibition of the thermoresponse by L-serine; Maeda K et al.; Information processing of the thermoresponse in Escherichia coli was compared with that of the chemoresponse . Competition experiments between various chemical stimuli and the thermal stimulus showed that only L-serine was a potent inhibitor of the thermosensory transduction . The concentration of L-serine necessary for complete inhibition of the thermoresponse was about 0.1 mM . L-Serine at this concentration did not inhibit chemoresponses to many amino acids . Pleiotropic aspartate-taxis mutants (tar) showed normal thermoresponse but pleiotropic serine-taxis mutants (tsr) showed decreased or almost no thermoresponse . These results suggest that the thermosensory transducing system in E . coli has an intimate interaction with the chemosensory transducing pathway specific for L-serine . A simple model for the thermosensory transduction is discussed. Proc Natl Acad Sci U S A, 1979 Jan, 76(1), 386 - 90 Evidence for transcriptional regulation of orotidine-5'-phosphate decarboxylase in yeast by hybridization of mRNA to the yeast structural gene cloned in Escherichia coli; Bach ML et al.; From a large population of strains of Escherichia coli carrying shear fragments of yeast (Saccharomyces cerevisiae) DNA attached by in vitro recombination to the plasmid vector pMB9, two hybrid plasmids were selected that relieve the pyrimidine requirement of nonreverting pyrF mutants of E . coli . An 1100-base-pair DNA fragment common to the two complementing plasmids was recloned into another plasmid vector, pBR322; these new hybrids retained the ability to specify orotidine-5'-phosphate decarboxylase (orotidine-5'-phosphate carboxy-lyase, EC 4.1.1.23) synthesis in E . coli . Evidence is presented that this common fragment is yeast DNA and thus apparently carried the structural information for yeast orotidine-5'-phosphate decarboxylase, the product of yeast gene ura3 . A hybrid plasmid containing the 1100-base-pair fragment was used to measure levels of putative ura3 mRNA from yeast cultures labeled with {3H}adenine, ura3 mRNA was unstable with an apparent half-life of 10.5 min . Under different circumstances previously shown to alter the level of orotidine-5'-phosphate decarboxylase in yeast, a coordinate variation in proportion of labeled RNA complementary to the hybrid plasmid was found . These data support the hypothesis that regulation of the ura3 gene in yeast is at the level of transcription. Proc Natl Acad Sci U S A, 1979 Jan, 76(1), 260 - 4 Identification of a methyl-accepting chemotaxis protein for the ribose and galactose chemoreceptors of Escherichia coli; Kondoh H et al.; The ribose and galactose chemoreceptors of Escherichia coli have previously been identified as the ribose- and galactose-binding proteins . We now report the discovery of a methyl-accepting chemotaxis protein that functions in the transfer of receptor signals from these two binding proteins to the flagella . This protein is distinct from previously described methyl-accepting chemotaxis proteins . Its level of methylation is influenced by D-ribose, D-galactose, and certain structural analogues of them . This methyl-accepting protein is required for chemotaxis toward those attractants; mutants in the trg gene, which do not methylate this protein, are devoid of taxis toward D-ribose, D-galactose, and their analogues . In addition, methylation of the methyl-accepting protein in response to each of these attractants requires the appropriate binding protein . The binding protein's chemoreceptor function is required for such methylation, but its transport activity is not . Because the function of this methyl-accepting chemotaxis protein involves two of the best-characterized chemoreceptors, the discovery of this protein represents a promising base for further study of the linkage between chemoreceptors and flagella in bacteria. Proc Natl Acad Sci U S A, 1979 Jan, 76(1), 236 - 40 Translational and post-translational cleavage of M13 procoat protein: extracts of both the cytoplasmic and outer membranes of Escherichia coli contain leader peptidase activity; Mandel G et al.; The coat protein of coliphage M13 is an integral protein of the host cytoplasmic membrane at all stages of the infectious cycle . Both in in vivo and DNA-directed in vitro synthesis, it is initially made with an NH2-terminal "leader peptide" of 23 amino acids and is termed procoat . We now report that leader peptidase, and activity which removes the leader peptide and converts procoat to coat, is found in both the inner (cytoplasmic) and outer membrane of Escherichia coli . However, only cytoplasmic membranes will catalyze cleavage of procoat in the absence of detergent . Leader peptidase will cleave procoat either during translation or after protein synthesis is complete. Proc Natl Acad Sci U S A, 1979 Jan, 76(1), 189 - 93 Interaction of Escherichia coli RNA polymerase with promoters of several coliphage and plasmid DNAs; von Gabain A et al.; The interaction of Escherichia coli RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) with restriction fragments obtained from various E . coli related DNAs was studied in vitro . The DNAs investigated included several coliphage genomes (T5, lambda, T7, fd) and plasmid DNAs (pML 21, pSC101) . By using the nitrocellulose filter binding of the enzyme-DNA complexes, fragment-specific relative rates of complex formation as well as complex stabilities were determined . Promoter-specific relative rates of polymerase binding were derived from fragment-specific rates by taking into account the number of major binding sites for RNA polymerase within several DNAs . Estimates of the stability of complexes formed between some major binding sites and the enzyme were obtained by studying the rate of complex decay . Both characteristics--rate of complex formation and rate of decay--varied widely and independently of each other . The promoters reacting most efficiently with E . coli RNA polymerase were found in the early region of coliphage T5 whereas some promoters in pML 21, or for example, the lambda promoter PI, belong to signals binding the enzyme most slowly . Based on the second-order rate constant determined for the interaction of E . coli RNA polymerase with promoters of phage fd, the fastest promoters characterized so far reacted with rates in the order of 10(8) M-1s-1 . The hierarchy of promoters established here is of interest from the viewpoint that promoter strength correlates with the rate of polymerase binding . Among the promoters studied here this rate spans a range of 2 orders of magnitude. Proc Natl Acad Sci U S A, 1979 Jan, 76(1), 126 - 30 ATP-dependent renaturation of DNA catalyzed by the recA protein of Escherichia coli; Weinstock GM et al.; The product of the recA gene of Escherichia coli has been purified to near-homogeneity by a simple three-step procedure . Incubation of the recA protein with complementary single strands of DNA, Mg2+, and ATP results in the rapid formation of large DNA aggregates containing many branched structures . As judged by resistance to S1 nuclease and by electron microscopy, these aggregates contain both duplex and single-stranded regions . The renaturation and aggregation of DNA catalyzed by the recA protein is coupled to the hydrolysis of ATP . The recA protein purified from a cold-sensitive recA mutant does not catalyze DNA renaturation or aggregation at 28 degrees C, but does so at 37 degrees C, a finding which correlates with the recombination defect observed in vivo and indicates that this activity is an intrinsic function of the recA protein . These results suggest that the recA protein plays a specific role in strand transfer during recombination and possibly in postreplication repair of damaged DNA. Nucleic Acids Res, 1979 Jan, 6(1), 71 - 80 Origin and direction of replication of the bacteriocinogenic plasmid Clo DF13; Stuitje AR et al.; Cairn's type replicative intermediates of both the wildtype Clo DF13 plasmid and the copy mutant CLO DF13 cop3 were isolated by dye-buoyant density centrifugation . Replicative intermediates were linearized at the HpaI or Sa1I cleavage site, and examined with the electron-microscope . The data show that replication of both the Clo DF13 wild type plasmid and the Clo DF13 cop3 plasmid, initiates at about 2.8% on the physical map . Replication proceeds unindirectionally and counterclockwise on this map. Nucleic Acids Res, 1979 Jan, 6(1), 371 - 83 The specificity of in vitro chromatin transcription; Crouse GF et al.; The in vitro transcription of chicken reticulocyte chromatin with E . coli RNA polymerase has been studied in several different ways . The amount of globin RNA sequences has been measured by hybridizing the transcript with globin cDNA; we show that under the proper conditions mercurated transcript RNA can be separated from endogenous RNA on sulfhydryl affinity columns . The amount of globin RNA in the transcript is approximately 20 fold greater than that from erythrocyte chromatin or reticulocyte DNA . Although these data could be used to support the hypothesis of specific transcription, we show by RNA/RNA self hybridization of the transcript (which is at least 50% symmetric) and by hybridization of the transcript to unique DNA in vast RNA excess that the bulk of the chromatin transcript differs little from the transcript of naked DNA . Several explanations for these apparently contradictory results are offered with the most likely one being compatible with random transcription of at least most of the sequences in the chromatin. Nucleic Acids Res, 1979 Jan, 6(1), 181 - 93 Fluorescence studies of the accessibility of the 3' ends of the ribosomal RNAs in Escherichia coli ribosomes and subunits; Schreiber JP et al.; The accessibility of the 3'-ends of E . coli in various states has been probed by reaction, after periodate oxidation, with the fluorescent dye proflavine semicarbazide . Free oxidized 16S and 23S rRNAs each react with 2 equivalents of dye . The 23S rRNA is equally reactive in the 50S subunit and the 70S ribosome . The 16S RRNA 3'-end is accessible in the 30S subunit . In the intact 70S particle, periodate can reach the 3'-end of the 16S rRNA but the dye cannot . The 5S rRNA is relatively inaccessible to periodate oxidation or dye reaction in the 70S particle . Dye-labelled 16S rRNA will reconstitute into 30S particles but they are inactive in polypeptide synthesis . This is apparently due to the inability of the 30S particles to form tight complexes with 50S subunits . Iodide quenching studies indicate that the environment of the 3'-end of 16S rRNA in the 30S particle is different from that of the free rRNA. Nucleic Acids Res, 1979 Jan, 6(1), 111 - 37 The interaction of RNA polymerase and lac repressor with the lac control region; Schmitz A et al.; We have examined the interactions of lac repressor and RNA polymerase with the DNA of the lac control region, using a method for direct visualization of the regions of DNA protected by proteins from DNAase attack . The repressor protects the operator essentially as reported by Gilbert and Maxam (1) with some small modifications . However, the evidence reported here concerning the binding of RNA polymerase to the DNA of the promoter mutant UV5 indicates that : 1) the RNA polymerase molecule binds asymmetrically to the promoter DNA, 2) RNA polymerase protects DNA sequences to within a few bases of the CAP binding site, suggesting direct interaction between polymerase and the CAP protein at this site, 3) RNA polymerase still binds to the promoter when repressor is bound to the operator, but fails to form the same extensive complex. Mikrobiologiia, 1979 Jan-Feb, 48(1), 149 - 52 {Effect of temperature on the viability of Escherichia coli strains in seawater}; Alton LV et al.; The survival and growth of E . coli strains were studied at different temperatures of sea water . The bacterial number for serotypes 055 and 078 was found to increase with a decrease in temperatue of sea water to 5 degrees C . The bacteria of serotype 015 did not grow in sea water whereas those of serotype 0115 were capable of growth only at 20 and 15 degrees C . The bacteria were able to survive from 4 to 98 days depending on the temperature of water and the strain of E . coli. J Environ Pathol Toxicol, 1979 Jan-Feb, 2(3), 751 - 65 Toxicity studies with decamethrin, a synthetic pyrethroid insecticide; Kavlock R et al.; Decamethrin is a synthetic pyrethroid insecticide that has been under investigation by the World Health Organization for use in some vector control programs . Decamethrin proved to be a highly toxic pyrethroid ester . The acute LD50 for adult female rats was 31 mg/kg by the oral route and 4 mg/kg by the intravenous route of administration . The LD50 was observed to be sex and age dependent, with higher values recorded for weanlings and males . Initial signs of decamethrin poisoning include profuse salivation and convulsive movements . Weakness, dyspnea, anorexia and staining of the fur were observed beyond the first day following compound administration . Absorption of decamethrin was rapid by the inhalation route and minimal by the dermal route of administration . No evidence of teratogenic activity was found in rats or mice at dose levels that produced marked maternal toxicity, and no persistent toxicity was observed in neonatal rats that received perinatal exposure to decamethrin . No mutagenic activity was detected in three different in vitro assays, with or without metabolic activation. J Int Med Res, 1979, 7(1), 100 - 5 Multicentre study of 'Flagyl' in the prevention of post-operative anaerobic infection; Goulton J et al.; In a study carried out with 565 patients undergoing gynaecological and general surgical procedures, metronidazole ('Flagyl') was used pre- and post-operatively and the incidence of post-operative infection, particularly that due to anaerobic organisms, was recorded . This was not a controlled study but, by comparison with other series, it would appear that the use of oral metronidazole had substantially reduced the likelihood of supervention of anaerobic sepsis . It is probable that the use of intravenous metronidazole therapy would have reduced the incidence of anaerobic sepsis still further had this preparation been available at the time. Chemotherapy, 1979, 25(1), 5 - 8 In vitro activity of sulphonamides as a function of their molar refractivity; Kaliszan R et al.; A significnat correlation has been found between the in vitro activity of 16 commonly employed sulphonamides and their molar refractivity . The molar refractivity has been shown to be a superior parameter for the description of the activity of sulphonamides than the sum of electronegativities of atoms making up a heterocyclic substituent in the sulphonamide molecule and molecular weight of the substituent. Cell, 1979 Jan, 16(1), 191 - 200 Length-independent separation of DNA restriction fragments in two-dimensional gel electrophoresis; Fischer SG et al.; When double helical DNA is exposed to conditions favoring partial melting in polyacrylamide gels, its electrophoretic mobility undergoes a sharp cooperative transition, resulting in a large reduction in mobility . In the present experiments, where the transition is effected at a uniform temperature of 60 degrees C in a concentration gradient of a urea-formamide mixture, each Eco RI fragment of lambda or E . coli DNA exhibits the mobility transition at a characteristic concentration of the denaturant . The sudden retardation of fragments moving toward higher denaturant concentration in the gradient results in a pattern of sharpened zones in order depending upon nucleotide sequence, rather than size, and only very slightly dependent upon the time after the last fragment has been retarded . When combined with length-dependent electrophoresis in agarose in the perpendicular direction, this system provides a two-dimensional separation of fragments . The resolving power of the system is demonstrated by the clear resolution of over 250 fragments of the Eco RI digest of E . coli DNA . Corresponding fragments from an isogenic lambda lysogen of E . coli are found in the same positions, and additional fragments unique to the lysogen are evident. Cell, 1979 Jan, 16(1), 123 - 9 Mu insertion duplicates a 5 base pair sequence at the host inserted site; Allet B; Nucleotide sequences were analyzed across the two ends of lysogenic Mu DNA . These ends were cloned separately in lambdapMu hybrid particles that derived from a single Mu lysogen in the lac Z part of lambdaplac5 . The obtained data imply that Mu lysogenization was associated with the duplication of 5 base pairs present in lac DNA at the Mu insertion site . As a result of this duplication, Mu DNA is flanked by two copies of five identical base pairs oriented as direct repeats . A similar conclusion has been obtained independently by other investigators with the use of a different Mu lysogen (D . Kamp and R . Kahmann, personal communication) . Thus Mu insertion seems to have a striking similarity to typical IS-mediated insertions that were found to be associated with a short DNA duplication at the target site. Cell, 1979 Jan, 16(1), 111 - 21 In vitro transcripts from the rrn B ribosomal RNA cistron originate from two tandem promoters; Glaser G et al.; The functional structure of the promoter region of a bacterial ribosomal operon is analyzed by in vitro transcription of linear DNA fragments derived from the hybrid Col EI plasmid pGG1 . This plasmid contains the promoter region of the rrn B ribosomal cistron present in the lambdarifd18 . When transcripts arising from this promoter region are terminated by restriction endonuclease cleavage of DNA, two RNA chains are resolved by gel electrophoresis that differ in length by about 100 bases . Evidence is presented indicating that these two transcripts arise from different initiation sites, each directing tandem transcription on the sense strand of the early portion of the ribosomal cistron. Biokhimiia, 1979 Jan, 44(1), 130 - 41 {Isolation and properties of DNA-cytosine-methylase I from Escherichia coli MRE 600}; Nesterenko VF et al.; DNA-cytosine-methylase I was isolated and purified to homogeneity . The yield made up to about 30% of total activity . The enzyme molecular weight as determined by centrifugation in a sucrose gradient, by gel filtration and by electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate was found to be 45,000 . The Michaelis constant was 1,8 . 10(-6) M for SAM and 2 . 10(-4) M for DNA . DNA-cytosine-methylase I modifies phage lambda DNA in 60 sites . This modification does not protect DNA from the effects of restriction endonucleases HpaII and BsuRI . The enzyme methylates DNA in the nucleotide sequence: 5'...Pur-MC-C-G-G-Pyr...3'. J Bacteriol, 1979 Jan, 137(1), 92 - 104 Structural and functional analysis of cloned DNA segments containing the replication and incompatibility regions of a miniplasmid derived from a copy number mutant of NR1; Taylor DP et al.; A 1.45-megadalton segment of DNA cloned from a miniplasmid derived in vivo from a copy number mutant of the R plasmid NR1 has been shown to contain all functions essential for incompatibility and autonomous plasmid replication in Escherichia coli . Specific endonuclease cleavage sites within this DNA segment that localize functions required for replication have been mapped . A 0.45-megadalton fragment that specifies the FII incompatibility of NR1 has been identified within the replication region, and DNA fragments containing this incompatibility region, but lacking other functions required for replication, have been cloned. J Bacteriol, 1979 Jan, 137(1), 694 - 6 Accumulation of peptidyl tRNA is lethal to Escherichia coli; Menninger JR; A mutant strain of Escherichia coli with temperature-sensitive peptidyl-tRNA hydrolase grows at 30 degrees C but, when shifted to 40 degrees C, dies at rates affected by physiological, pharmacological, and genetical perturbations . The rate of killing correlates with the relative accumulation of peptidyl-tRNA, suggesting that it is responsible for the death of the cells. J Bacteriol, 1979 Jan, 137(1), 692 - 3 Simple method for identification of plasmid-coded proteins; Sancar A et al.; Proteins encoded by plasmid DNA are specifically labeled in UV-irradiated cells of Escherichia coli carrying recA and uvrA mutations because extensive degradation of the chromosome DNA occurs concurrently with amplification of plasmid DNA. J Bacteriol, 1979 Jan, 137(1), 673 - 6 Method for isolating restriction- and modificationless mutants of Escherichia coli K-12; Del Giudice L; A simple method is described for the selection and isolation of restriction- and modificationless mutants in Escherichia coli K-12 by using the following properties: (i) the temperature-sensitive repressor activity of phage lambdacI857; (ii) a mutant of lambda phage defective in integration and the establishment of repression (lambdab2cI); (iii) a virulent lambda phage insensitive to the repressor activity . The final yield of spontaneously arising rk-mk+ and rk-mk- mutants from stationary-phase cultures was about 5% of the surviving cells. J Bacteriol, 1979 Jan, 137(1), 658 - 60 rorA mutation of Escherichia coli K-12 affects the recB subunit of exonuclease V; Glickman BW; The ATP-dependent nuclease, exonuclease V, of Escherichia coli plays an important role in repair and recombination . The enzyme is composed of two subunits, one of which is the product of the recB and recC genes . In this communication it is shown by mapping and complementation experiments that the rorA mutation, which results in radiation sensitivity but not the loss of recombination ability, is an allele of the recB gene. J Bacteriol, 1979 Jan, 137(1), 584 - 94 Organization of genes for transcription and translation in the rif region of the Escherichia coli chromosome; Yamamoto M et al.; The lambdarifd18 transducing phage is known to carry several genes for components of transcriptional and translational machineries; these genes are clustered in the rif region at 88 min on the Escherichia coli genetic map . They include a set of genes for rRNA's (rrnB), a gene for spacer tRNA, tRNA2Glu (tgtB), one of the two genes for EF-Tu (tufB), genes for four ribosomal proteins (rplK, A, J, and L), genes for the beta and beta' subunits of RNA polymerase (rpoB and rpoC), and genes for three tRNA's (tyrU, gluT, and thrT) . An additional tRNA gene (subsequently identified as thrU by Landy and his co-workers) and a gene for a protein (protein U) with unknown functions were found to be carried by lambdarif d18 . We analyzed the organization of these genes by using various deletion and hybrid phages derived from lambdarif d18 and lambdarif d12, a phage related to lambdarif d18 . The expression of various genes was examined in UV-irradiated cells infected with these transducing phages . Two main conclusions were obtained . First, the four tRNA genes are not cotranscribed with the genes in rrnB, even though these tRNA genes are located close to the distal end of rrnB . Second, the four ribosomal protein genes are organized into two separate transcriptional units; rplK and A are in one unit and rplJ and L are in the second unit . The first group of genes was shown to have a promoter separate from that for tufB or protein U . The second group of genes shares the promoter with rpoB and C, as described in a separate paper (M . Yamamoto and M . Nomura, Proc . Natl . Acad . Sci . U.S.A., 75:3891--3895) . These and other results described in this paper show that the genes are organized in the following order: promoter, genes in rrnB; promoter, thrU, tyrU, (promoter?) glyT, thrT; (promoter?) tufB; promoter, a gene for protein U; promoter, rplK, rplA; promoter, rplJ, rplL, rpoB, rpoC. J Bacteriol, 1979 Jan, 137(1), 574 - 83 Localization of proteolytic activity in the outer membrane of Escherichia coli; MacGregor CH et al.; An enzyme in the cytoplasmic membrane, nitrate reductase, can be solubilized by heating membranes to 60 degrees C for 10 min at alkaline pH . A protease in the cell envelope has been shown to be responsible for this solubilization . The localization of this protease in the outer membrane was demonstrated by separating the outer membrane from the cytoplasmic membrane, adding back various forms of outer membrane protein to the cytoplasmic membrane, and following the increase in nitrate reductase solubilization with increasing amounts of outer membrane proteins . This solubilization is accompanied by the cleavage of one of the subunits of nitrate reductase and is inhibited by the protease inhibitor p-aminobenzamidine . Analysis of membrane proteins synthesized by cells grown in the presence of various amounts of p-aminobenzamidine revealed that p-aminobenzamidine affects the synthesis of the major outer membrane proteins but has little effect on the synthesis of cytoplasmic membrane proteins . When outer membrane is reacted with the protease inhibitor {3H}diisopropylfluorophosphate, a single protein in the outer membrane is labeled . Since the interaction with diisopropylfluorophosphate is inhibited by p-aminobenzamidine, it is suggested that this single outer membrane protein is responsible for the in vitro solubilization of nitrate reductase and the in vivo processing of the major outer membrane proteins. J Bacteriol, 1979 Jan, 137(1), 568 - 73 Isolation and characterization of amber mutations in the lexA gene of Escherichia coli K-12; Pacelli LZ et al.; We describe the isolation and characterization of amber mutations in the lexA gene of Escherichia coli K-12 . These mutations, designated spr(Am), were isolated and characterized in a lexA tif sfi genetic background . They abolished the sensitivity of the strain to UV light and resulted in high rates of synthesis of recA protein . Phage lambda+ failed to lysogenize the strains as observed with similar strains carrying non-amber spr mutations described previously, thereby indicating a constitutive expression of the phage induction pathway . Introduction of an amber suppressor mutation into a strain bearing the spr(Am) mutation restored expression of the LexA mutant phenotype . We conclude that spr mutations either inactivate or prevent synthesis of the lexA gene product and that loss of this product results in constitutive expression of the E . coli induction system in the tif sfi genetic background. J Bacteriol, 1979 Jan, 137(1), 502 - 6 ColE1 hybrid plasmids for Escherichia coli genes of glycolysis and the hexose monophosphate shunt; Thomson J et al.; The Clarke-Carbon clone bank carrying ColE1-Escherichia coli DNA has been screened by conjugation for complementation of glycolysis and hexose monophosphate shunt mutations . Plasmids were identified for phosphofructokinase (pfkA), triose phosphate isomerase (tpi), phosphoglucose isomerase (pgi), glucose-6-phosphate dehydrogenase (zwf), gluconate-6-phosphate dehydrogenase (gnd), enolase (eno), phosphoglycerate kinase (pgk), and fructose-1,6-P2 aldolase (fda) . Enzyme levels for the plasmid-carried gene ranged, for the various plasmids, from 4- to 25-fold the normal level. J Bacteriol, 1979 Jan, 137(1), 469 - 73 Five different enzymatic activities are associated with the multienzyme complex of fatty acid oxidation from Escherichia coli; Pramanik A et al.; The purified multienzyme complex of fatty acid oxidation from Escherichia coli was found to possess 3-hydroxyacyl-coenzyme A (CoA) epimerase and cis-delta3-trans-delta2-enoyl-CoA isomerase activities in addition to the previously identified enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and 3-ketoactyl-CoA thiolase activities . Evidence is presented in support of the proposed association of all five enzyme activities with one protein which apparently is composed of two types of subunits and which can exist in several aggregated forms . The five component enzymes of the complex were rapidly inactivated by tris(hydroxymethyl)aminomethane, whereas they remained active in the presence of potassium phosphate. J Bacteriol, 1979 Jan, 137(1), 447 - 55 Direct determination of the properties of peptide transport systems in Escherichia coli, using a fluorescent-labeling procedure; Payne JW et al.; A direct study of peptide uptake by Escherichia coli was made using a fluorescent procedure . After incubation with the bacteria, peptides remaining in the medium were dansylated, separated chromatographically, and quantitated from their fluorescent intensities and/or from their incorporated radioactivity when tritiated dansyl derivatives were prepared . Peptide uptake was apparently not regulated and proceeded continuously until complete, with the absorbed peptides undergoing rapid intracellular hydrolysis and the excess amino acid residues leaving the cell . Thus, peptide uptake and amino acid exodus occur concurrently . However, peptidase-resistant substrates, e.g . triornithine and glycylsarcosine, which can be similarly estimated in cell extracts, were accumulated about 1,000-fold . The influence of amino acid composition and chain length on rates of transport was assessed . Different strains of E . coli showed variability in their rates of di- and oligopeptide transport . With respect to energy coupling, both the di- and oligopeptide permeases behaved like shock-sensitive transport systems. J Bacteriol, 1979 Jan, 137(1), 44 - 50 Methylation-dependent DNA synthesis in Escherichia coli mediated by DNA polymerase I; Lark C; An in vitro system was used to study DNA synthesis in lysates of Escherichia coli cells which had been grown in the presence of ethionine . Such lysates showed a reduced capacity to incorporate {3H}TTP into high-molecular-weight material . Activity could be restored by incubation with S-adenosyl methionine and ATP . S-adenosyl methionine-reactivated TTP incorporation required the presence of DNA polymerase I, ATP, and all four deoxyribonucleotide triphosphates . DNA polymerase III was not required. J Bacteriol, 1979 Jan, 137(1), 365 - 73 Escherichia coli K-12 mutants that allow transport of maltose via the beta-galactoside transport system; Shuman HA et al.; We have isolated mutants of Escherichia coli that have an altered beta-galactoside transport system . This altered transport system is able to transport a sugar, maltose, that the wild-type beta-galactoside transport system is unable to transport . The mutation that alters the specificity of the transport system is in the lacY gene, and we refer to the allele as lacYmal . The lacYmal allele was detected originally in strains in which the lac genes were fused to the malF gene . Thus, as a result of gene fusion and isolation of the lacYmal mutation, a new transport system was evolved with regulatory properties and specificity similar to those of the original maltose transport system . Maltose transport via the lacYmal gene product is independent of all of the normal maltose transport system components . The altered transport system shows a higher affinity than the wild-type transport system for two normal substrates of the beta-galactoside transport system, thiomethyl-beta-D-galactoside and o-nitrophenyl-beta-D-galactoside. J Bacteriol, 1979 Jan, 137(1), 281 - 4 Recipient competence in F'lac matings of Escherichia coli K-12; Cullum J et al.; We studied recipient mating ability in the presence of excess F'lac donors . Ninety-five percent of recipients were able to receive F'lac in 30-min matings . Competition between an F'-lac donor and an F'lac traI donor, which mobilized a ColE1 derivative (pML2), showed that each recipient mated with an average of two to three donors in 30 min . Experiments in which the competing donor was added at different times showed that some competition occurred throughout the 30-min mating period, which suggested that aggregate formation was spread over this time. J Bacteriol, 1979 Jan, 137(1), 234 - 42 Pyrimidine dimer excision in Escherichia coli strains deficient in exonucleases V and VII and in the 5' leads to 3' exonuclease of DNA polymerase I; Chase JW et al.; An isogenic series of Escherichia coli strains deficient in various combinations of three 5' leads to 3' exonucleases (exonuclease V, exonuclease VII, and the 5' leads to 3' exonuclease of DNA polymerase I) was constructed and examined for the ability to excise pyrimidine dimers after UV irradiation . Although the recB and recC mutations (deficient in exonuclease V) proved to be incompatible with the polA(Ex) mutation (deficient in the 5' leads to 3' exonuclease of DNA polymerase I), it was possible to reduce the level of the recB,C exonuclease by the use of temperature-sensitive recB270 recC271 mutants . It was found that, by employing strains deficient in exonuclease V, postirradiation DNA degradation could be reduced and dimer excision measurements could be facilitated . Mutants deficient in exonuclease V were found to excise dimers at a rate comparable to that of the wild type . Mutants deficient in exonuclease V and the 5' leads to 3' exonuclease of DNA polymerase I are slightly slower than the wild type at removing dimers accumulated after doses in excess of 40 J/m2 . However, although strains with reduced levels of exonuclease VII excised dimers at the same rate as the wild type, the addition of an exonuclease VII deficiency to a strain with reduced levels of exonuclease V and the 5' leads to 3' exonuclease of DNA polymerase I caused a marked decrease in the rate and extent of dimer excision . These observations support previous indications that the 5' leads to 3' exonuclease of DNA polymerase I is important in dimer removal and also suggest a role for exonuclease VII in the excision repair process. J Bacteriol, 1979 Jan, 137(1), 129 - 36 Characterization of mutationally altered dihydropteroate synthase and its ability to form a sulfonamide-containing dihydrofolate analog; Swedberg G et al.; Among spontaneous mutants of Escherichia coli selected for resistance against sulfonamides, thermosensitive strains were found . These were shown to possess a changed dihydropteroate synthase (EC 2.5.1.15), which had a substantially higher Km value for its normal substrate, p-aminobenzoic acid, and an about 150-fold higher Km for sulfonamides . The mutationally changed dihydropteroate synthase was found to be thermosensitive by in vitro assays . The thermosensitivity was used as an enzyme marker to demonstrate the complex formation between 2-amino-4-hydroxy-6-pyrophosphorylmethyl pteridine and sulfonamides by partially purified dihydropteroate synthase . The formation of folate from 2-amino-4-hydroxy-6-pyrophosphorylmethyl pteridine and p-aminobenzoylglutamic acid by dihydropteroate synthase was found to be very sensitive to inhibition by sulfonamides and very inefficient with the mutationally changed enzyme. J Bacteriol, 1979 Jan, 137(1), 115 - 23 Expression of RNA polymerase and ribosome component genes in Escherichia coli mutants having conditionally defective RNA polymerases; Little R et al.; The expression of the genes coding for the beta and beta' subunits of RNA polymerase, ribosomal RNA, ribosomal proteins, and beta-galactosidase was investigated in strains carrying conditionally lethal mutations affecting either RNA polymerase core assembly or RNA polymerase enzyme activity . The mutant strain XH56 produces a temperature-sensitive beta' subunit and at 42 degrees C is defective in RNA chain initiation; consequently, little or no transcription occurs at the restrictive temperature . A partial restriction, produced by shifting the strain to 39 degrees C, resulted in a rapid fivefold increase in the transcription of the rpoB and C genes and in the synthesis of the beta- and beta'-subunit proteins for which they code . The RNA polymerase assembly-defective strains A2R7 and TS4 exhibited a 1.5- to 2-fold increase in the transcription of the rpoB and C genes and in the synthesis of beta- and beta-subunit proteins after prolonged restriction . These results demonstrate (i) that regulation of the synthesis of the beta- and beta-RNA polymerase subunits is under these conditions primarily transcriptional rather than translational, and (ii) that a stimulation of rpoB and C gene expression results from a restriction on RNA synthesis caused by either RNA polymerase inactivation or inhibition of its assembly . During restriction of the mutant strains, the transcription of the ribosome component genes exhibited patterns which were similar to transcription of the rpoB and C genes, supporting the evidence that genes coding for RNA polymerase are cotranscribed with ribosomal protein genes; transcription of the lacZ gene was observed to decrease concomitant with the stimulation of the rpoB and C genes. Nutr Metab, 1979, 23(1), 26 - 37 Transcription of rat liver chromatin by Escherichia coli RNA polymerase: template properties after protein restriction; Andersson GM et al.; Transcription was determined in liver chromatin from rats fed for 6 days, an optimal (20%) or suboptimal (3%) amount of high-quality protein . Transcription by Escherichia coli RNA polymerase (EC 2.7.7.6) was lower after prolonged incubation with chromatin from rats fed 3% as compared with 20% protein . Differences were detected in the transcripts of the two types of chromatin after analysis by sucrose density gradient centrifugation . But no measurable differences were found in the melting profiles at low ionic strength of the two chromatin preparations . Transcription per milligram chromatin DNA was 25-fold higher using E . coli RNA polymerase instead of rat liver RNA polymerase II . The use of UTP as radioactive precursor in the absence of ATP, GTP and CTP resulted in a low labelling of RNA . One {lambda32P}UTP nucleotide was incorporated/8 UMP nucleotides . The product obtained was sensitive to ribonuclease treatment . In the presence of ATP, GTP and CTP {lambda-32P}UTP nucleotide incorporation was reduced and that of UMP nucleotide was increased giving a ratio of 1:188. J Urol, 1979 Jan, 121(1), 129 - 30 Transrectal seminal vesiculography; Meyer JJ et al.; Lesions of the seminal vesicle can be evaluated by the transrectal needle approach . Biopsy, aspiration of contents for culture and cytology, injection of contrast medium for x-ray and drainage of cysts or abscesses can be done with this approach. Adv Shock Res, 1979, 2, 219 - 32 Lidocaine treatment following baboon endotoxin shock improves survival; Fletcher JR et al.; Baboons treated with lidocaine (2 mg/kg/hr) after shock from endotoxin were compared to untreated controls in an LD70 E coli endotoxin (4 mg/kg) model . Survival, systemic and pulmonary arterial pressures, cardiac output, white blood cell and platelet counts, blood gases and arterial and mixed venous PGE and PGF 2 alpha levels were determined . Baboons receiving lidocaine had a better (P less than 0.05) survival at 72 hours than the controls . Circulatory function was improved with lidocaine; however, white blood cell and platelet counts, blood gases, and the prostaglandin release were similar in both groups . The mechanism by which lidocaine improves survival in baboon endotoxin shock appears to be unrelated to its effects on white blood cells, platelets, or the prostaglandin release. Nucleic Acids Res, 1979 Jan, 6(1), 275 - 87 In vitro DNA dependent synthesis of globin RNA sequences from erythroleukemic cell chromatin; Reff ME et al.; Murine erythroleukemic cells in culture accumulate cytoplasmic globin mRNA during differentiation induced by dimethyl sulfoxide (DMSO)1 . Chromatin was prepared from DMSO induced erythroleukemic cells that were transcribing globin RNA in order to determine whether in vitro synthesis of globin RNA sequences was possible from chromatin . RNA was synthesized in vitro using 5-mercuriuridine triphosphate and exogenous Escheria coli RNA polymerase . Newly synthesized mercurated RNA was purified from endogenous chromatin associated RNA by affinity chromatography on a sepharose sulfhydryl column, and the globin RNA sequence content of the mercurated RNA was assayed by hybridization to cDNA globin . The synthesis of globin RNA sequences was shown to occur and to be sensitive to actinomycin and rifampicin and insensitive to alpha-amanitin . In contrast, synthesis of globin RNA sequence synthesis was not detected in significant amounts from chromatin prepared from uninduced erythroleukemic cells, nor from uninduced cell chromatin to which globin RNA was added prior to transcription . Isolated RNA:cDNA globin hybrids were shown to contain mercurated RNA by affinity chromatography . These results indicated that synthesis of globin RNA sequences from chromatin can be performed by E . coli RNA polymerase. Acta Physiol Lat Am, 1979, 29(1), 81 - 5 Transcriptional features of fractionated human breast tumor chromatin; Thierbach LI et al.; By means of controlled mechanical shearing it was possible to fractionate human breast tumor chromatin in "active" and "inactive" species, according to their in vitro template activity, using Escherichia coli RNA polymerase . The "active" molecules can be resolved in three well defined regions in an exponential sucrose gradient, showing approximately 300 times the efficiency for synthesizing ribonucleic acid, relative to the chromatin which migrated fastest . This technique could provide the initial tool to isolate eu-and heterochromatin from native human chromatin. Acta Physiol Acad Sci Hung, 1979, 54(3), 257 - 63 Central and peripheral adrenergic mechanisms in endotoxin fever and newborn guinea pigs; Szekely M; In 0--3 day-old guinea pigs cerebroventricular pretreatment with alpha-methyl-p-tyrosine failed to modify the course of fever induced by E . coli endotoxin administration into the cerebral ventricles . Central or intraperitoneal administration of phentolamine or central administration of propranolol were also ineffective . Intraperitoneal propranolol, however, prevented both the first and the second temperature rise after endotoxin, while the transient fall in temperature that usually occurs between them still ensued . Central noradrenergic mechanisms seem to play, at most, a minor role in the mediation of endotoxin fever, while the integrity of peripheral beta adrenergic receptors is indispensable for the febrile response to occur. Environ Mutagen, 1979, 1(4), 347 - 52 Substrate-specificity of uvr excision repair; Murray ML; The substrate specificity of the uvr endonuclease, the product of the uvrA, uvrB, and uvrC genes is reviewed . It is suggested that the relatively well-defined substrate specificity of this repair enzyme is useful as a guide in determining the nature of the DNA-lesion caused by a given mutagen. Ann Biol Clin (Paris), 1979, 37(5), 259 - 70 {Hereditary abnormalities of galactose metabolism: diagnosis and biochemical supervision (author's transl)}; Brivet M et al.; The authors define the main stages of the biochemical study of hereditary abnormalities of galactose metabolism . They review laboratory examinations for detection, enzyme examinations which provide the diagnostic proof, further examinations which permit one to follow the course and efficacy of a galactose-free diet, the demonstration of genetic variants, the technics of antenatal diagnosis and routine neonatal detection. Mol Gen Genet, 1979, 177(1), 65 - 72 A restriction enzyme cleavage map of Tn5 and location of a region encoding neomycin resistance; Jorgensen RA et al.; This paper reports a cleavage site map of Tn5 for restriction enzymes BamHI, Bg/I, Bg/II, Hind II, HindIII, HpaI, Sa/I, Aval, SmaI, XhoI, PstI, PvuII, HaeII and HaeIII that was determined by the analysis of restriction enzyme cleavage patterns of ColEl, two independent ColEl::Tn5 plasmids, and a ColEl::Tn5 deletion derivative . Ba/I, EcoRI, KpnI, and PvuI do not cleave Tn5 . Construction and analysis of in vitro-generated deletions of a ColEl::Tn5 plasmid limit the sequences encoding neomycin resistance to a 1500-base-pair-long segment of Tn5 . Insertion of DNA at a Bg/II site within this segment results in loss of the neomycin resistance phenotype . Since this Bg/II site lies in an inverted repeat region, sequences within this repeat seem to be involved in the expression of neomycin resistance. Mol Gen Genet, 1979, 177(1), 169 - 75 DNA supercoiling and transcription in Escherichia coli: influence of RNA polymerase mutations; Mirkin SM et al.; Coumermycin A1, a specific inhibitor of DNA gyrase, differentially changes the spectrum of proteins synthesized in wild type E . coli cells but has no effect on the protein spectrum in mutant cells with coumermycin-resistant DNA gyrase . The rpoB265 mutation affecting RNA polymerase decreases the coumermycin A1-sensitivity of bacteria while the rpoC3 mutation increases it . The interaction of wild type and mutant RpoB265 RNA polymerases with ColEl plasmid DNA in vitro is differently affected by DNA supercoiling . No such differences are observed in the case of RpoC3 RNA polymerase . The results suggest that template supercoiling may have a substantial effect on transcription in vivo, an effect which, in some cases, depends on the properties of RNA polymerase. Mol Gen Genet, 1979, 177(1), 163 - 8 In vitro insertion of the lambda attachment site into the plasmid RP4; Pastrana R et al.; The region of the phage lambda chromosome containing the attachment site (P.P') and the genes int and xis, excised by the action of endonuclease R.EcoRI, has been inserted into the unique site for that enzyme on the promiscuous conjugative plasmid, RP4, generating the recombinant plasmid RP4att lambda . Transformants containing the hybrid plasmid were recognised by their ability to allow efficient lysogenization by phage lambda b2 (Weil and Signer, 1968; Echols et al., 1968) containing the mutant attachment site delta . P' . The construction and properties of the hybrid plasmid RP4att lambda are described. Mol Gen Genet, 1979, 177(1), 113 - 20 Replication of the colicin E1 plasmid in extracts of Escherichia coli: uncoupling of leading strand from lagging strand synthesis; Staudenbauer WL et al.; The replication of the ColEl plasmid was studied in extracts from E . coli dnaG mutants . It was found that the synthesis of the complementary strands of ColEl DNA can be carried out in these extracts in two consecutive steps: (1) synthesis of the leading L strand independent of the dnaG function, and (2) synthesis of the lagging H strand depending upon addition of wild-type dnaG protein . In contrast to L strand synthesis, the latter reaction is insensitive to rifampicin and novobiocin . Both synthetic pathways are however blocked by antiserum directed against dnaB protein . This indicates an additional role of the dnaB protein in duplex DNA replication besides assisting the dnaG protein in the priming of lagging strand synthesis . The T7 gene-4 protein acting in conjunction with T7 DNA polymerase can substitute for both the function of the dnaB and dnaG protein . It is concluded that plasmid replication proceeds by a semi-discontinuous mechanism. Biochimie, 1979, 61(10), 1151 - 60 Isolation and identification of mutants constitutive for aspartokinase III synthesis in Escherichia coli K 12; Boy E et al.; We devised a procedure in order to isolate, in Escherichia coli, constitutive mutants for aspartokinase III synthesis, the first enzyme of the lysine regulon . It consists of the introduction of a limiting step in lysine biosynthesis, by the use of the partial suppression of a nonsense mutation . For the first time we could isolate many constitutive mutants . Their characteristics (cotransduction with the lysC structural gene; no effect on the synthesis of other enzymes of the regulon; cis-dominance) lead to classify these mutations as operator-type . The fact that no repressor mutations could be isolated is discussed. Cold Spring Harb Symp Quant Biol, 1979, 43 Pt 1, 63 - 7 DNA helicases; Kuhn B et al.; In summary, we postulate that DNA unwinding and ATP dephosphorylation are coupled in different ways, depending on whether the fibrous ATPase or one of the globular ATPases provides the catalytic agent . Unanswered is the question of whether there is stoichiometry of ATP utilization during the unwinding of a duplex, and unsolved is the role of the individual enzyme in the cell. Cold Spring Harb Symp Quant Biol, 1979, 43 Pt 1, 345 - 8 DNA-dependent ATPases from Escherichia coli K12; Richet E et al.; Four DNA-dependent ATPases have been isolated from E . coli extracts . ATPases I and III, both sensitive to NEM, require denatured DNA but differ in their heat sensitivity, elution from DEAE-cellulose, and sedimentation coefficient . ATPases II and IV are both resistant to NEM . ATPase II requires partially denatured DNA, whereas ATPase IV can be stimulated by SS DNA . ATPase I is a DNA-unwinding enzyme; ATPase II may be involved in recombination. Nucleic Acids Res, 1979, 6(5), 1863 - 7 Genome organization of retroviruses . III . Restriction endonuclease cleavage maps of mouse sarcoma virus double-stranded DNA synthesized in vitro; Verma IM; Genome length complementary DNA (cDNA) transcripts were synthesized in vitro by using purified virions of a cloned isolate of mouse sarcoma virus (MSV Clone 124) . The cDNA transcripts were converted to double-stranded form by utilizing DNase-digested calf thymus DNA primers and E . coli DNA polymerase I . Restriction endonucleases Sal I, Hind III, Hpa I, Bgl II and Xba I were found to cleave the MSV double-stranded DNA once to generate two fragments, whereas restriction endonucleases Bgl I and Hae II cleaved twice to generate three fragments . Restriction endonucleases E . coli RI and Bam HI did not cleave MSV double-stranded DNA . The order of the restriction fragments was determined in relation to the 5' and 3' ends of the genomic RNA. J Lab Clin Med, 1979 Jan, 93(1), 25 - 31 Evidence that endotoxin is the cyclic 3':5'-GMP--promoting factor in erythropoietin preparations; Graber SE et al.; Since Ep preparations are contaminated with endotoxin, the possibility that the latter might be the factor in crude Ep which increases cGMP levels in rat fetal liver cells was examined . Endotoxin produced a striking elevation of cGMP in rat fetal liver cells without affecting cAMP levels or heme synthesis . Absorption with Limulus lysate of more than 99% of the endotoxin in a crude Ep preparation caused a parallel decrease in the cGMP-promoting activity without reduction of heme synthetic potency . It is concluded that endotoxin is the component of crude Ep which increases cGMP levels in rat fetal liver . The precise role of elevated cGMP in the action of endotoxin on cells and the universality of this effect remain to be determined. Acta Physiol Acad Sci Hung, 1979, 54(3), 265 - 76 Endotoxin fever in the newborn kitten . The role of prostaglandins and monoamines; Szekely M; In 5--10 day-old kittens at thermoneutral environmental temperature cerebroventricular injections of 10 microgram serotonin or noradrenaline caused hyperthermia and hypothermia, respectively . Central injections of 20 and 200 ng prostaglandin E1 induced hyperthermia . Monophasic fever followed the cerebroventricular injections of 0.2 or 0.002 microgram E . coli endotoxin, both in thermoneutral and moderately cool environments . In kittens pretreated with para-chlorophenylalanine (PCPA) the endotoxin induced rise in body temperature was attenuated within 60 to 90 min after the endotoxin . Indomethacin pretreatment prevented the first part of the febrile response and only a slight temperature rise occurred after a long latency . Central injections of phentolamine did not modify the fever response, while centrally applied propranolol modified the fever course so that it resembled that seen in PCPA treated kittens . The central mediation of endotoxin fever in the kitten is complex, despite that the pattern of the temperature change is simple (monophasic) . Arachidonic acid metabolites and serotonin of the central nervous system may be involved in the reaction, while the activation of central noradrenergic mechanisms does not seem to be indispensable for the response . The changes in mediators are similar to those in newborn guinea pigs, although the fever course is different in the two species. Environ Mutagen, 1979, 1(1), 65 - 78 A colorimetric assay of lysogenic induction designed for screening potential carcinogenic and carcinostatic agents; Elespuru RK et al.; Simple, rapid colorimetric tests for lysogenic induction (the derepression of a latent bacterial virus) are described . A quantitative test and a more rapid semiquantitative test are based on the assay of the beta-galactosidase synthesized from lacZ gene fused to an operon under lambda repressor control . These biochemical "inductests" are suitable for screening programs designed to detect agents that damage DNA and that are of potential interest in carcinogenesis and cancer chemotherapy. J Hyg Epidemiol Microbiol Immunol, 1979, 23(3), 261 - 5 Effect of experimental magnetic storm on the production of lambda phage; Chervinets VM; 1 . Sharp fluctuation of the intensity of the vertical component of the MF amounting to +/- 0.1 Oe changing the sign over each 3 min causes variability of both lysogenic and indicator strains of E . coli . This testifies to an extremely low threshold of their magnetic susceptibility and to biological importance of fluctuations of natural parameters of the geomagnetic field as an ecological factor of the environment . 2 . A change in the intensity of the vertical component of the MF, not any higher than +/-0.1 Oe, inhibits phage production in the lysogenic system of E . coli K = 12 lambda and is also reflected in the morphological peculiarities of negative phage colonies as well as in the phage-susceptibility of the E . coli indicator strain. Genetika, 1979, 15(1), 32 - 40 {Effect of the dose of ptsI- and ptsH-genes on carbohydrate transport and regulation of lac-operon activity in Escherichia coli K-12}; Gershanovich VN et al.; Phage Mu-1 cts61 was used for transposition of pts1 and ptsH genes . The received F'-factors AUF2 and AUF3 carry short fragments of the bacterial chromosome . Merodiploid strains with double pts genes were selected in sexduction crosses with the appropriate recA recipients . Effect of the gene dose was not registered in pts+/pts+ strains in the case of accumulation of the substrates of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) and in the case of bacterial growth in the presence of these carbohydrates . This indicates that the enzyme (enzymes) II of the PTS is the limiting step in the transpost process . Induction of beta-galactosidase and the growth on carbohydrates not transported via the PTS (maltose, lactose) were greatly reduced in pts mutant . Introduction of the pts+ allele with episome lead to the restoration of the two above processes . These data show that the phospho approximately HPr generating system of the PTS is directly (or in indirect manner) involved in the regulation of catabolite-sensitive operons . Glucose repression was markedly increased in pts+/pts+ merodiploids as compared with pts+/pts- ones and with pts+ bacteria . Possible mechanisms of this effect are discussed. J Bacteriol, 1979 Jan, 137(1), 653 - 7 Genetic and physiological studies on the relationship between colicin B resistance and ferrienterochelin uptake in Escherichia coli K-12; McIntosh MA et al.; The Escherichia coli gene for the ferrienterochelin uptake and colicins B and D receptor protein is located at approximately 13 min, adjacent to or among genes for enterochelin biosynthetic enzymes . The two receptor functions (colicin and siderophore) are separable by mutation. J Bacteriol, 1979 Jan, 137(1), 221 - 5 Requirement for membrane potential in active transport of glutamine by Escherichia coli; Plate CA; The effect of reducing the membrane potential on glutamine transport in cells of Escherichia coli has been investigated . Addition of valinomycin to tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid-treated E . coli cells in the presence of 20 mM exogenous potassium reduced the membrane potential, as measured by the uptake of the lipophilic cation triphenylmethylphosphonium, and caused a complete inhibition of glutamine transport . Valinomycin plus potassium also caused a rapid decrease in the intracellular levels of ATP of normal E . coli cells, but had little if any effect on the ATP levels of two mutants of E . coli carrying lesions in the energy-transducing ATP complex (unc mutants) . Yet both the membrane potential and the capacity to transport glutamine were depressed in the unc mutants by valinomycin and potassium . These findings are consistent with the hypothesis that both ATP and a membrane potential are essential to the active transport of glutamine by E . coli cells. Arch Exp Veterinarmed, 1979, 33(4), 489 - 94 {Preliminary results of an atiepizootic field test using EDTA-Na extract vaccine from Escherichia coli strains pathogenic to swine in swine production industrial units}; Mochmann H et al.; An anti-epizootic field test was applied to industrialised pig farms in the region of Wroclaw, Poland, to test the effectiveness of a pentavalent EDTA (calcium disodium edetate)--sodium vaccine extracted from Escherichia coli strains with pathogenicity to swine . The vaccine had been received from a centre in Berlin-Buch, GDR . The vaccine failed to provide any protection, when orally applied to nursed piglets . However, both morbidity and mortality were reduced and, thus, an anti-epizootic effect on nursed piglets produced, when the vaccine had been injected intramuscularly to the pregnant mother animals, prior to farrowing . In weaned piglets morbidity was sucessfully reduced by both oral as well as intramuscular administration. Nucleic Acids Symp Ser, 1979, (6), s47 - 50 Evolutionary considerations of DNA repair in relation to mutagenesis, teratogenesis and carcinogenesis; Kondo S; Living organisms have various mechanisms for repairing spontaneous and mutagen-induced damage in DNA . Mutagenesis, teratogenesis, and carcinogenesis are discussed in relation to DNA misrepair . The existence of highly efficient genetic mechanisms for tolerating environmental threats is argued from evolutionary viewpoints. Vet Med Nauki, 1979, 16(6), 35 - 41 {Suitability of chemical neutralizers applied for disinfection control on commercial animal husbandry objects}; Bineva I et al.; A study on the effect of various neutralizers of the most widely spread means of disinfection applied in animal rearing was made . For that purpose twin lecytine was tested for quadruple ammonium compounds: twin--for phenolic compounds, natrium thiosulfate--for iodoformium and chlor-containing compounds, as well as natrium sulfite--for formalin . As test micro-organisms were used Staph . aureus Sg 511, E . coli 078, and Ps . aeruginosa . The investigations were performed after the suspension method with dilutions in geometrical progressions . It was established that for the disinfection by quadruple ammonium compounds 3% twin-80 plus 0.3% lecytine is suitable as neutralizer . In disinfection with phenolic compounds the 1% twin-80 solution gives good results . As neutralizer of formalin disinfection 2% natrium sulfite solution can be successfully used . For iodoformium disinfection or disinfection with chlor-containing compounds good neutralizing effect can be achieved by 1% solution of natrium thiosulfate. Am J Pediatr Hematol Oncol, 1979 Fall, 1(3), 245 - 9 Activation of coagulation and disseminated intravascular coagulation in the newborn; Corrigan JJ Jr; Human newborns have certain hemostatic "deficiencies" which seem to be peculiar to this period of life, such as reduced factors II, VII, IX, X, XI, and XII, reduced antithrombin III levels, and reduced plasminogen levels . However, they are capable of activating the coagulation mechanism to elicit either the entity of disseminated intravascular coagulation or the occurrence of localized and diffuse thrombotic events . The mechanisms involved have yet to be defined . Evidence has been presented to suggest that preterm infants may manifest a variant form of disseminated intravascular coagulation in which thrombocytopenia is not present. Scand J Immunol, 1979, 10(1), 81 - 6 Efficient conjugation of rabbit Fab' with beta-D-galactosidase from Escherichia coli; Yoshitake S et al.; An efficient procedure for the conjugation of rabbit Fab' with beta-D-galactosidase from Escherichia coli using N,N-o-phenylenedimaleimide is described . Thiol groups of Fab' were stabilized by the presence of ethylenediaminetetraacetate, and malemide groups were shown to be stable at pH 5 at 4 degrees C . The stability of thiol and maleimide groups enabled an efficient introduction of maleimide groups into Fab' and the average number of maleimide groups introduced into Fab' was 0.76 (range 0.73-0.79; n = 10) per molecule . As a result, 43.4% (range 41.3-46.9%; n = 6) of Fab' used could be conjugated with most of beta-D-galactosidase used . The average number of Fab' molecules conjugated per enzyme molecule was calculated to be 4.2 (range 4.0-4.6; n = 6) . Both the enzyme and antibody activities were well preserved in the conjugate . There was no self-coupling of Fab', although the enzyme was polymerized to some extent during the conjugation reaction . The enzyme activity and cross-link in the conjugate was stable at pH 6.0-7.0 at 4 degrees C for at least 3 months. Nucleic Acids Res, 1979, 6(6), 2355 - 61 The conformational properties of ribosomal protein S1; Moore PB et al.; The proton NMR spectrum of S1 reveals that S1 has considerable tertiary structure in physiological buffers, but more structural flexibility than normal for globular proteins . S1's NMR spectrum is independent of the method of preparation. Arch Exp Veterinarmed, 1979 Jan, 33(1), 47 - 52 {Preparation and testing of polyvalent EDTA-Na-extract vaccine from Escherichia coli strains pathogenic to Swine}; Austenat L et al.; Monovalent vaccines were prepared of E . coli strains with pathogenicity to swine by means of a technique described elsewhere . A polyvalent vaccine was obtained by mixing the monovalent vaccines . This polyvalent vaccine was tested by criteria usually applied to vaccine of E . coli strains with pathogenicity to man, and it exhibited the same quality characteristics. Biophys Chem, 1979 Jan, 9(2), 121 - 31 Interaction of phenosafranine with nucleic acids and model polyphosphates . III . Heterogeneity in phenosafranine interactions with DNA base pairs; Balcarova Z et al.; Fluorescence and circular dichroism spectral measurements, thermal denaturation studies and binding competition experiments with netropsin and actinomycin D were carried out in systems containing phenosafranine bound to DNA's differing in base composition . The investigated properties exhibit a heterogeneity related to the content of A.T and G.C pairs in DNA and to the nature of phenosafranine binding modes . At low level of saturation of binding sites (r less than 0.1) phenosafranine does not show strong preference for any of the DNA base pairs in the overall binding . However, the strong monomer non-cooperative binding outside the helix (mode I1) occurs predominantly, even though not exclusively in G.C rich regions . The strong binding modes involving intercalated dye molecules (mode I2 and eventually mode II1) prevail in A.T rich regions . These binding modes become the principal types of strong phenosafranine interaction with DNA when the level of saturation of binding sites increases, i.e . at r greater than 0.1.20 J Bacteriol, 1979 Jan, 137(1), 340 - 9 Isolation and characterization of an endogenous inhibitor of protein synthesis in Escherichia coli K-12; Clark VL; A low-molecular-weight factor was isolated from cell extracts of Escherichia coli K-12 . The concentration of the factor in cells was dependent upon nutritional conditions, the concentration being higher in faster growing cells . Treatment of cells with colicin K caused an increase in concentration of the factor . The factor inhibited protein synthesis in E . coli . This inhibition was reversible, apparently because of metabolism of the factor . The inhibition of synthesis of beta-galactosidase lasted longer than the inhibition of protein synthesis; cyclic AMP eliminated this difference . The factor inhibited the synthesis of beta-galactosidase from preformed lac mRNA, indicating an inhibition of translation . Kinetic studies of the onset of inhibition of beta-galactosidase synthesis by the factor suggested that the factor may inhibit protein synthesis at the initiation of translation. J Bacteriol, 1979 Jan, 137(1), 137 - 45 Tight-binding repressors of the lac operon: selection system and in vitro analysis; Pfahl M; The isolation and characterization of altered repressors of the lac operon which have an increased affinity for an operator should give useful clues about the molecular basis for the very tight and specific interaction between repressor and operator . A selection system has been devised which allows the isolation of such repressor mutants . This system selects for mutant repressors which can overcome lac operator-constitutive (Oc) mutations . By using in vivo assays, 24 candidates were obtained which, compared with wild type, have an increased trans effect of their repressor on one or several Oc operators . Three of these candidates have been investiga