J Biol Chem, 1976 Jan 25, 251(2), 503 - 9 Effect of L-3,4-dehydroproline on collagen synthesis and prolyl hydroxylase activity in mammalian cell cultures; Kerwar SS et al.; The incorporation of DL-3,4-dehydro{14C}proline into collagen and total protein of 3T3 cells occurred at approximately one-fifth the rate observed for L-{14C}proline . Addition of L-3,4-dehydroproline to the culture medium inhibited markedly the incorporation of {14C}glycine and L-{3H}lysine into the collagen of 3T3 cells, but there was only slight inhibition of the incorporation of the radiolabeled amino acids into total cellular proteins, indicating that the action of L-3,4-dehydroproline is specific for collagen . When 1 mM L-3,4-dehydroproline was added to the culture medium the {14C}hydroxyproline content was reduced 40% in the cell layer and 70% in the medium . The D isomer of 3,4-dehydroproline did not inhibit {14C}hydroxyproline formation . These findings indicate that L-3,4-dehydroline reduced the hydroxylation of the susceptible prolyl residues in the collagen molecule and the secretion of collagen from the cell . The reduction in the hydroxyproline content is probably related in part to a reduction in the activity of prolyl hydroxylase; when various mammalian cell cultures were exposed to 0.2 mM L-3,4-dehydroproline, the specific activity of prolyl hydroxylase was reduced markedly, while that of lysyl hydroproline, the specific activity of prolyl hydroxylase was reduced markedly, while that of lysyl hydroxylase was not affected . Under these conditions, cell growth and lactic dehydrogenase required protein synthesis . Removal of L-3,4-dehydroproline from the growth medium resulted in a time-dependent increase in the specific activity of prolyl hydroxylase. Biochim Biophys Acta, 1976 Jan 14, 421(1), 106 - 14 Differential inhibition of branching enzyme in a morphological mutant and in wild type Neurospora . Influence of carbon source in the growth medium; Abramsky T et al.; 1 . A morphological mutant of Neurospora crassa, smco 9, (R2508) that exhibits colonial morphology when grown on sucrose or on maltose, showed a partial reversal of this morphology toward that of the wild type when it was grown on potato starch or on isomaltose . 2 . A common feature of both potato starch and isomaltose is the presence of alpha-1, 6 glucosidic linkages . This suggested that these morphological effects might be due to differences in alpha-1,4 glucan: alpha-1,4 glucan 6 glycosyltransferase, (EC 2.4.1.18) commonly known as "the branching enzyme" . 3 . The branching enzyme was purified from wild type, Neurospora crassa, and from the semicolonial mutant, R2508, both grown on sucrose or on potato starch . It has a molecular weight of 140,000 as estimated by gel filtration on a Bio Gel A 1.5 m column . This enzyme plus phosphorylase a in an unprimed reaction catalyzes the synthesis of a branched polysaccharide in vitro . 4 . No branching enzyme activity was apparent in extracts of the mutant R2508, grown on potato starch until a thermolabile inhibitor was removed by fractionation on a DEAE column . 5 . This inhibitor has a molecular weight greater than 100,000 as estimated on a P-100 polyacrylamide gel column . The specificity of the inhibitor is not absolute in that it inhibits glycogen synthetase in addition to the branching enzyme in Neurospora. Biochemistry, 1976 Jan 13, 15(1), 125 - 31 Purification and properties of gentamicin acetyltransferase I; Williams JW et al.; Gentamicin acetyltransferase I is induced 13-fold in R factor resistant Escherichia coli by high concentrations (1 mg/ml) of gentamicin in the growth medium . The enzyme is maximally released from bacteria by osmotic shock in late-log phase, unlike previously studied periplasmic enzymes . Streptomycin sulfate and ammonium sulfate precipitations of shockate followed by affinity and ion-exchange chromatography recover 51% of the induced enzyme with a 360-fold increase in purity (12% of 4400-fold, uninduced) . The purified enzyme appears homogeneous by six criteria, the first aminoglycoside inactivating enzyme so purified . Sodium dodecyl sulfate electrophoresis, amino acid analysis, and sedimentation analyses indicate a tetrameric protein of 63000 molecular weight . The protein does not contain tryptophan . Kinetic analyses yield apparent values of: Vmax = 3.4 +/- 0.2 mumol per min mg at pH 8 (optimum), Km (acetyl-CoA) = 3.9 +/- 0.2 muM, Km (gentamicin Cla) = 0.3 +/- 0.08 muM, KI (gentamicin substrate inhibition) = 160 +/- 29 muM . The activity of the enzyme is stable to a variety of conditions, including lyophilization and prolonged storage, and can be monitored by two convenient spectrophotometric assays. Proc Soc Exp Biol Med, 1976 Jan, 151(1), 221 - 4 The serial cultivation of suspended BHK-21/13 cells in serum-free Waymouth medium; Guskey LE et al.; A simple medium system was developed to obtain growth of BHK-21 cells in shaker cultures in the absence of serum . These cells have now undergone over 80 serial passages in serum-free Waymouth medium and have been recovered from the frozen state after storage for over 1 month in medium containing 10% dimethyl sulfoxide (DMSO) and 1% bovine serum albumin (BSA) . Various amounts of exogenous lipid in the form of sodium oleate were added to cultures of cells growing in serum-free Waymouth medium . Concentrations of 10-50 mug of sodium oleate/ml had no detrimental effects on the cells as measured by trypan blue uptake . Furthermore, the cells were serially passed ten times in the presence of 10 mug sodium oleate/ml . Depletion of calf serum from the growth medium and addition of known quantities of lipids to the system provides a means of revealing subtle changes in lipid synthesis and lipid turnover during cellular growth. J Dairy Sci, 1976 Jan, 59(1), 68 - 79 Rumen microbial growth rates and yields: effect of amino acids and protein; Maeng WJ et al.; Effects of amino acids upon microbial growth, optimum ratio of nonprotein to amino acid nitrogen for microbial growth, and incorporation of amino acids into microbial cells were determined with washed cell suspension in vitro as were rumen microbial cells . Rumen microbial dry matter, nitrogen, ribonucleic acid, deoxyribonucleic acid, and substrate disappearance was greatest when a mixture of 18 amino acids was substituted for urea . Substitutions of mixtures of 10 essential amino acids, 8 nonessential amino acids, and sulfur containing amino acids and glutamate also stimulated microbial growth . Acid hydrolyzed casein markedly improved microbial growth . Branched amino acid addition did not affect growth . The optimum ratio of nonprotein to amino acid nitrogen for microbial growth was 75% urea nitrogen and 25% amino acid nitrogen . With this amount of amino acids, an average of 53% of added amino acid was incorporated into microbial cells, 14% was fermented to carbon dioxide and volatile fatty acids, and 33% remained in the supernatant . Both 100% urea and 100% amino acid in growth media were unfavorable for maximal microbial growth . With all carbohydrate substrates, 100% urea nitrogen supported the growth of 9 mg bacterial dry matter per 100 mg of substrate . Substitutions of amino acids for urea increased yields to over 20 mg/100 mg . Microbial growth yields in incubations under carbon dioxide were less than when flasks were flushed with nitrogen . However, yield of bacterial dry matter per unit of substrate was less under nitrogen than under carbon dioxide. J Exp Med, 1976 Jan 1, 143(1), 64 - 72 A common cell-type specific surface antigen in cultured human glial cells and fibroblasts: loss in malignant cells; Vaheri A et al.; Fibroblast surface antigen (SFA) is a high molecular weight protein antigen, first shown on the surface of cultured fibroblasts in fibrillar structures . It is shed to the extracellular medium and also present in the circulation (serum and plasma) . Fibroblasts transformed by tumor viruses produce SFA but do not retain it on cell surface . In this report we show that SFA is also present in cultured nonestablished astroglial cells . The glial and fibroblast SFAs are immunologically indistinguishable . Glial cells (three different nonestablished lines) contain more SFA per milligram cellular protein than fibroblasts . SFA was located on cell surface in fibrillar striae that frequently extended out from the cell body . Fluorescence was also found intracellularly in the cytoplasm . Malignant gliomas (astrocytomas) established to grow in culture from human tumor material produced SFA into the growth medium but had very little (lines U-105 MG and U-343 MG) or no detectable (lines U-118 MG, U-251 MG, and U-343 MG-a) cell surface SFA . In cultures of the glioma cells many cells, in particular those that appeared to be in the telophase stage, stained strongly positive for intracellular cytoplasmic SFA . These data demonstrate that similar to fibroblasts transformed experimentally by oncogenic viruses, cells grown from naturally occurring human tumors (glioblastomas) produce SFA but lose ability to retain it on cell surface. Acta Odontol Scand, 1976, 34(1), 33 - 41 An in vitro method for toxicity evaluation of water-soluble substances; Wennberg A; The purpose of the present investigation was to develop a simple method for the evaluation of reversible and irreversible toxic influences in a cell culture system . A cell monolayer established on the bottom of glass scintillation vials was exposed to a toxic substance (phenol) . Changes in the DNA synthesis of the cells were utilized as a criterion of toxic influence, and were measured by recording the incorporation of tritium labelled thymidine using a liquid scintillation technique . The exposure of the cells to phenol caused a marked decrease in the rate of DNA synthesis when the phenol concentration was increased from 0.01 to 0.1% . The decrease in the DNA synthesis could be reversed by maintaining the cells in growth medium for 4 hours after the cell-phenol contact . The degree of reversibility was dependent on the cell-phenol contact time, the phenol concentration, and the cell line used . The simple test procedures and the quick and convenient obtainment of results simplify the assay of large test series and make the method particularly useful for screening tests. Zentralbl Bakteriol Parasitenkd Infektionskr Hyg, 1976, 131(3), 512 - 6 Production of Candida utilis on slop by-product of fermentation industries; Foda MS et al.; The slop (vinas) liquor, a major by-product a alcohol fermentation industries, has been used as growth medium for production of the torula yeast, Candida utilis . Supplementation of the slop with 0.2% ammonium sulphate and 1% to 5% molasses improved the cell yield significantly . The crude slop gave better results than the diluted or centrifuged liquors . Under optimal conditions, more than 15 grams of yeast were obtained on dry weight basis . The application feasibility of these results is presented. J Supramol Struct, 1976, 5(4), 475 - 95 Comparison of the structural and chemical composition of giant T-even phage heads; Aebi U et al.; A study has been made of the structure of the capsids of T4D giant phage produced from mutants in gene 23 and temperature-sensitive mutants in gene 24, and T4D and T2L giant phage formed by the addition of L-canavanine followed by an Larginine chase in the growth medium . All the giant phage capsids have been shown to be built according to the same geometrical architecture . This consists of a near-hexagonal surface net, lattice constant 129.5 A, folded into a left-handed T = 13 prolate icosahedron elongated along one of its fivefold symmetry axes . Their only apparent difference from wild-type T-even phage capsids is their abnormally elongated tubular part . A comparison of the capsomere morphologies and protein compositions of the giant phage capsids showed that all T4D giants are identical but differ from T2L: The T4D capsomere has a complex (6 + 6 + 1)-type morphology, whereas the T2L has a simple 6-type . T2L phage, however, lack two capsid proteins, "soc" and "hoc", present in T4D . The difference in capsomere morphology can therefore be related to the difference in the protein compositions of these two phage . Possible differences between the initiation and means of length regulation of giant phage heads and the aberrant polyheads are discussed. Cytogenet Cell Genet, 1976, 17(1), 1 - 8 Pachytene mapping of the male Chinese hamster; Pathak S et al.; Minced seminiferous tubules of male Chinese hamsters when treated with a mixture of trypsin (one part) and McCoy's 5a growth medium with 20% fetal calf serum (nine parts) at 4 degrees C, washed twice with the regular growth medium, incubated at 37 degrees C in growth medium for 4 h, and harvested without Colcemid and hypotonic pretreatments, gave excellent pachytene morphology for studies on chromomere patterns . The Giemsa banding patterns of all somatic metaphase chromosomes except the sex chromosomes of the hamster cells correspond well to the chromomere patterns of meiotic pachytene bivalents. Cell, 1976 Jan, 7(1), 97 - 103 Modifications of mammalian cell surfaces induced by sugars: scanning electron microscopy; Amos H et al.; Substitution of galactose, xylose, or mannose for glucose in the growth medium of L cells or the addition of equal concentrations of the alternate sugars to glucose-containing medium results in marked morphologic changes . The changes are revealed by conventional staining for light microscopy and by scanning electron microscopy . L cells grow indefinitely on combinations of equal concentrations of glucose and galactose, xylose, or mannose . There appear to be no significant differences in growth rate on glucose compared to the combinations of sugars cited . Cells subcultured from glucose to the combinations while undergoing rapid multiplication show marked morphologic changes by light and scanning electron microscopy within 36 hr . Of particular note are the loss of microvilli; flattening of the cells; assumption of polygonal shape; prominence of nuclei and nucleoli; and changes in the structure and distribution of filopodia . Virtually all cells in the population exhibit the changes noted. Mikrobiologiia, 1976 Jan-Feb, 45(1), 67 - 72 {The effect of carbon dioxide gas on the growth of Candida utilis yeasts during continuous cultivation in a chemostat}; Shkidchenko AN; The cells of Candida utilis were cultivated in the conditions of chemostat, and the growth was limited by a nitrogen source . Accumulation in the medium of carbon dioxide inhibited the growth of the microbial population . The growth was now limited not by a source of nitrogen but by an excess of one of the forms of carbon dioxide--hydrocarbonate . This inhibition was reversible and could be eliminated either by intensifying ventilation of the apparatus or by varying pH of the medium within the range optimal for the growth, which changed the ratio between free and hydrocarbonate forms of carbon dioxide in the growth medium. Zentralbl Bakteriol Parasitenkd Infektionskr Hyg, 1976, 131(3), 497 - 500 The stimulatory effect of kojic acid on the production of aflatoxin by isolates of Aspergillus flavus Link; El-Khadem M et al.; Kojic acid at the levels of 0.01, 0.1, and 1.0% (w/v) was incorporated in the growth media of Aspergillus flavus . In the presence of 0.01% of kojic acid, isolates I, II, and III produced 157, 113, and 135% aflatoxin, respectively, as compared to the control . At the highest level of kojic acid, i.e . 1%, aflatoxin production was inhibited to 74% in isolate I, but was little affected in isolate II (104%) and strongly inhibited in isolate III (54%) . Kojic acid, at a concentration of 0.1%, was still stimulatory to isolate II, while it was inhibitory to isolates I and III . The dry weight of mycelia of the three isolates was not affected by kojic acid addition. Experientia, 1976, 32(7), 852 - 3 Repressible alkaline phosphatase in Aspergillus niger; Ramaswamy V et al.; ALP from A . niger is a) P1 repressible enzyme; b) stimulated by addition of Zn++ to the growth medium, and c) that EDTA inhibits the enzyme reversibly, which could be restored by addition of Zn++ and perhaps Mg++ . This property is in contrast to the enzyme from N . crassa, which is independent of any metal requirement. Int J Radiat Biol Relat Stud Phys Chem Med, 1976 Jan, 29(1), 37 - 50 DNA breakage, repair and lethality after 125I decay in rec+ and recA strains of Escherichia coli; Krisch RE et al.; Iodine-125 decays by electron capture and is known to cause extensive molecular fragmentation via the Augur effect . 125I was incorporated into the DNA of exponentially-growing E . coli K12 AB2487, a recA mutant, and E . coli K12 AB2497, the corresponding rec+ strain, as 5-iododeoxyuridine (IUdR), an analogue of thymidine . Radioactive bacteria were stored at - 196 degrees C, and samples were periodically assayed for loss of viability and for the induction of double-strand breaks (DSBs) in DNA . Each 125I decay in the DNA of either strain induces one DSB, i.e . alpha(DSB) = 1.0 . For the recA strain, alpha(lethal) = 0.9 and for the rec+ strain, 0.4 . Assays for biological repair of DSBs, involving incubation of thawed samples in growth-medium at 37 degrees C before the extraction of DNA, demonstrate significant repair of 125I-induced DSBs by rec+ cells but none by recA cells . For small numbers of decays, there is approximately a 1:1 correlation, for either strain, between lethal decays and post-incubation residual DSBs . Comparison with data for larger numbers of decays indicates that a typical rec+ cell can repair no more than three to four DSBs per completed genome (2.5 x 10(9) daltons). Dev Biol Stand, 1976, 35, 45 - 53 One year experience on the Lindholm B medium used in large--scale FMD virus production on BHK cells in suspension; Jensen MH et al.; The propagation of FMD virus on BHK 21 clone 13 suspension cells was based on the Lindholm B medium during the production period August 1975 to June 1976 . The medium was used in connection with a production cycle including decreasing amounts of serum in the cell growth medium and inoculation of the cells while they were still in growth . This method of virus production, compared with the traditional method, is cheaper due to the lowered medium cost . The improved utilization of the fermenter capacity and the decreased consumption of serum have practical as well as economic aspects . The results obtained during the period indicate that virus production by this method is reliable and at least on the same level as by traditional methods. Hamatol Bluttransfus, 1976, 19, 541 - 55 Control of peptide chain initiation in uninfected and virus infected cells by membrane mediated events; Koch G et al.; Initiation of protein synthesis in tissue culture cells is rapidly inhibited or blocked by addition of either DMSO, ethanol, TPCK, cytochalasin B, or sucrose to the growth medium . In contrast, these agents do not interfere with the initiation of protein synthesis in cell-free extracts to a comparable extent . These results support the hypothesis that protein synthesis in tissue culture cells can be influenced by membrane mediated events . Translation of viral mRNA in RNA virus infected cells is resistant to a number of these inhibitors of peptide chain initiation and proceeds under conditions where translation of host mRNA is almost completely suppressed . It appears that viral mRNA possesses a greater ability than host mRNA to form mRNA-ribosome initiation complexes when the overall rate of peptide chain initiation is reduced . This observation has led to a number of predictions concerning the strategy of virus directed suppression of host mRNA translation . Under optimal growth conditions protein synthesis appears to be regulated mainly, but not exclusively, by the amount of the mRNA available for translation . However, when cellular growth and/or the overall rate of peptide chain initiation is restricted, control of protein synthesis at the translational level becomes decisive with the translation of each mRNA species proceeding with its own characteristic efficiency most probably as a result of inherent differential affinities of individual mRNA species for ribosomes. Arch Virol, 1976, 52(1-2), 123 - 34 Individual translational efficiencies of SV40 and cellular mRNAs; Oppermann H et al.; The technique of selective inhibition of peptide chain initiation by growth medium hypertonicity was adapted for cell monolayer cultures and applied to a study of protein synthesis in SV40 infected BSC-1 cells . The translational efficiences for individual peptide chain initiation sites on SV40 mRNAs were determined and compared to those for cellular mRNA species under conditions of a reduced rate of peptide chain initiation . The SV40 mRNAs show different translational efficiences . The results indicate that the synthesis of the SV40 proteins VP1, 2 and 3 are initiated independently and with different rates on viral mRNA(s) . It is proposed, therefore, that VP2 is not a precursor for VP3. J Cell Sci, 1976 Jan, 20(1), 47 - 55 The influence of gibberellic acid and abscisic acid on cell and tissue differentiation of bean callus; Haddon L et al.; Bean callus was induced to form roots (tissue differentiation) and vascular nodules (cell differentiation) by lowering the ratio of auxin to cytokinin in the growth medium . Both types of differentiation were inhibited by the addition of abscisic acid (at concentrations greater than I muM) to induction medium . Initiation of differentiation was inhibited, but its subsequent development was not, and the inhibition was not affected by the addition of gibberellic acid . Addition of gibberellic acid (GA) alone to induction medium stimulated tissue differentiation, although cell differentiation was unaffected (30 muM GA) or inhibited (45 muM GA) and its onset was delayed at both concentrations . Root initiation was also stimulated by gibberellic acid (0.I-45 muM) at an auxin-to-kinin ratio 10 times that normally optimal for cell differentiation . The phenylalanine ammonia lyase (PAL) activity of the calluses was closely correlated with the amount of cell differentiation which had occurred, and measurement of this confirmed that gibberellic acid delayed the initiation of cell differentiation . The increase and subsequent decline of PAL and betaI leads to 3 glucan synthetase activities, normally induced by transfer to induction medium, was abolished by abscisic acid . Addition of gibberellic acid did not affect the betaI leads to 3 glucan synthetase activity. Zentralbl Bakteriol Parasitenkd Infektionskr Hyg, 1976, 131(3), 489 - 96 Kinetics and properties of L-glutaminase and L-asparaginase activities of Pseudomonas ovalis; Badr El-Din SM et al.; Pseudomonas ovalis produces L-glutaminase and L-asparaginase activities simultaneously upon induction by L-glutamine or L-asparagin in the growth medium . Both activities are confined to the cell during active growth and are not released into the medium . The apparent Km values are 1.4 X 10(-2) M and 6 X 10(-3) M for L-glutamine and L-asparagine substrates, respectively . Induction of both activities is substantially favoured in media with initial pH values higher than 7 . In buffered yeast extract L-asparagine medium, significant amounts of L-glutaminase and L-asparaginase activities appeared towards the end of the exponential phase and along the stationary phase . The process of enzyme formation showed a firm link to the cell active growth, as evidenced by the use of growth inhibitors. Biotechnol Bioeng Symp, 1976, (6), 35 - 53 Production of cellulase by Trichoderma; Sternberg D; The cellulase complex in T . viride is inducible . For large-scale enzyme production the fungus should be cultured on media containing cellulose . The cellulase enzymes are respressible . To produce and maintain best cellulase yields cultural conditions which lead to carbohydrate consumption in excess of cellular needs should be avoided . With the present mutant (QM9414) extracellular enzyme preparations having 1.6 FP units/ml and 1.6 mg protein/ml have been obtained within four to five days in submerged fermentation . Such preparations are capable of producing a 5% sugar solution when mixed with 10% ball milled cellulose and incubated 24 hr at 50 degrees C . Further improvements of cellulase yields are being sought by continued mutagenesis and increased nutrient levels in the growth medium. Biokhimiia, 1976, 41(7), 1306 - 12 {Regulation of glutamine metabolism in Chlorella pyrenoidosa . Mechanisms of regulating the activity of glutamine synthetase during ammonia assimilation}; Akimova NI et al.; Glutamine synthetase (GS) (E.C.6.3.1.2) activity in Chlorella cells decreased when NH4+ was added to nitrogen-free growth medium . This GS inactivation had such a rate, that it could not be due to the repression of enzyme synthesis: the GS activity decreased by 20% within 5 minutes of NH4+ assimilation . Glutamine content in cell increased in 2.5 times for this period . In vitro experiments have shown that glutamine is a strong inhibitor of GS from Chlorella grown in the presence of NO3-, and in a less degree--an inhibitor of GS from cells grown in ammonium-containing medium . The data obtained are negative with respect to possible mechanisms of GS activity regulation via adenylation and ATP-dependent destruction of glutamine synthetase. Connect Tissue Res, 1976, 4(4), 211 - 8 Effect of ascorbic acid on arylsulfatase A and B activities in human chondrocyte cultures; Schwartz ER et al.; Cultured normal human articular cartilage chondrocytes exhibited decreasing levels of arylsulfatase A and B activities when grown in the presence of increasing levels of ascorbic acid (0 to 90 mug/ml) in the media . That this was not a general effect on all lysosomal enzymes was supported by the increase in acid phosphatase activity and no change in beta-glucuronidase activity observed with increasing levels of vitamin C under identical culture conditions . No decrease in either arylsulfatase activity was observed when ascorbic acid was replaced by ascorbate-2-sulfate . Ascorbic acid did not inhibit either arylsulfatase activity when added directly to the assay mixture . These data, combined with results of mixing experiments, suggest that the effect of vitamin C is mediated through cellular factors produced in response to its inclusion in the growth media. Microbios, 1976, 15(59), 49 - 56 Effect of hydrogen ion buffers on photosynthetic oxygen evolution in the blue-green alga, Agmenellum quadruplicatum; Bridges S et al.; The photosynthetic oxygen evolution capacity of Agmenelium quadruplication suspended in four hydrogen ion buffers (pH 7.4, 0.05 M) and its synthetic marine growth medium was measured with an oxygen electrode . High rates of oxygen evolution were obtained in the growth medium and N-tris(hydroxymethyl)-methylglycine (Tricine) buffer . Compared to oxygen evolution in the growth medium, rates in phosphate buffer and N-tris(hydroxymethyl)-2-aminoethanesulphonic acid (TES) buffer were sometimes reduced by up to 30% and rates in tris (hydroxymethyl) amino-methane (Tris) were consistently reduced by 50% . An incubation-rinsing procedure caused inhibition of oxygen evolution in TES, phosphate, and Tris by 50 to 100% . Oxygen evolution could be restored to cells rinsed in TES or phosphate by resuspension in growth medium or in buffer plus magnesium and calcium ions . Bezoquinone-supported oxygen evolution was not affected by rinsing with any buffer tested except Tris . Ferricyanide was photoreduced at a low rate by cells rinsed in Tes but at a high rate in TES plus magnesium and calcium ions . We interpreted our results to mean that, in Agmenellum quadruplicatum, inhibition of photosynthetic oxygen evolution by Tris occurs at the level of photosystem 2 while the effects of TES and phosphate are on electron-transport occurring after the rate-limiting reaction. Proc Natl Acad Sci U S A, 1976 Jan, 73(1), 24 - 8 Isolation and characterization of an unsaturated fatty acid-requiring mutant of cultured mammalian cells; Chang TY et al.; An unsaturated fatty acid-requiring mutant derived from Chinese hamster ovary (CHO) cells has been isolated and characterized . This mutant grows normally when oleate or other unsaturated fatty acids are supplemented in the growth medium . Unlike the wild-type CHO cells, growth stops when medium is deprived of unsaturated fatty acid . Whole cell pulse experiments with {14C}acetate or {14C}stearate indicate that the mutant is defective in unsaturated fatty acid synthesis . Enzyme assays in vitro show that the enzymatic defect of the mutant is localized to the microsomal stearoyl-CoA desaturase. Mol Gen Genet, 1975 Dec 30, 143(1), 113 - 8 Nucleic acid metabolism in yeast . I . Inhibition of RNA and DNA synthesis by high concentrations of exogenous deoxythymidine 5'-monophosphate in 5'-dTMP low requiring strains; Langjahr UG et al.; The three haploid yeast strains T2tmpl1-3, T2tmp1-1, and T6tmp1-51 auxotrophic for 5'-dTMP differ in their requirement for thymidylate: 72, 16, and 3 mug 5'-dTMP/ml will restore optimal growth, respectively . Thymidylate low requirement in strain T2tmp1-1 and T6tmp1-51 is termed tlrA and tlrC, respectively . When the growth medium is made 5 x 10(-4) M for 5'-dTMP only strain T6tmp1-51 is severely inhibited in RNA and DNA synthesis . This inhibition is reversible after removal of excessive 5'-dTMP . The inhibitory characteristic is in marked contrast to "thymineless death" due to the lack of 5'-dTMP in strain T6tmp1-51 where only DNA synthesis stops while RNA synthesis continues . The inhibitory effect of 5 x 10(-4) M 5'-dTMP is not due to the 5'-dTMP auxotrophy but to the thymidylate low requiring character (tlrC) in strain T6tmp1-51 . The arrest of RNA and DNA synthesis by high concentrations of exogenous 5'-dTMP suggests a regulatory role of either the mono- or triphosphate on nucleoside or nucleotide biosynthesis in yeast. Biochim Biophys Acta, 1975 Dec 19, 414(3), 221 - 30 Lack of specific correlation of the deoxycytidine triphosphate pool level with rate of DNA synthesis; Walters RA et al.; The levels of the four deoxyribonucleoside triphosphate pools and the distribution of cells in the various phases of the cell cycle have been examined in Chinese hamster cells as thymidine, present as a regular constituent in the growth medium, was removed in stages . The results indicate that: 1 . Duration of the DNA synthetic phase was lengthened when thymidine was removed from the growth medium . 2.Temporally correlated with lengthening of the DNA synthetic phase upon thymidine removal was a 7-fold increase in level of the dCTP pool, reduction in the dGTP pools, and little or no change in dATP pool . 3.Radioactive labeling procedures indicated that expansion of the dCTP pool could be completely accounted for by increased ribonucleotide reductase activity and that the dTTP pool switched from a largely exogenous thymidine source to endogenous dTTP synthesis as the extracellular thymidine concentration was reduced . 4.Deoxyuridine and thymidine were apparently transported by the same system in Chinese hamster cells, while deoxycytidine was transported by a different system . Although deoxycytidine transport was unaffected by thymidine, phosphorylation of intracellular deoxycytidine compounds to the triphosphate level was stimulated by thymidine . Cytidine transport was not significantly affected by thymidine. Eur J Biochem, 1975 Dec 15, 60(2), 357 - 62 Regulation of Escherichia coli K10 aminoendopeptidase synthesis . Effects of mutations involved in the regulation of alkaline phosphatase; Lazdunski A et al.; The synthesis of alkaline phosphatase in Escherichia coli is controlled by the action of at least four genes denoted phoS, phoT, phoR and phoB . The effect of mutations in the first three of these genes on the synthesis of periplasmic aminoendopeptidase of E . coli K 10 have been investigated . phoR gene product does not seem to be involved either in the constitutive or in the derepressed synthesis of this enzyme . Mutations in phoS or phoT influence the intracellular level of Pi in much the same way as depletion of Pi from the growth medium, and only as a consequence influence the synthesis of aminoendopeptidase and alkaline phosphatase . Point, amber or deletion mutations in the alkaline phosphatase structural gene do not affect aminoendopeptidase synthesis . Thus, alkaline phosphatase and 'derepressed' aminoendopeptidase synthesis are co-regulated by the endogenous level of inorganic phosphate . The way by which this regulation operates is discussed. J Biol Chem, 1975 Dec 10, 250(23), 9090 - 8 Regulation of mitochondrial biogenesis: enzymatic changes in cytochrome-deficient yeast mutants requiring delta-aminolevulinic acid; Woods RA et al.; Yeast cells almost completely deficient in all cytochromes were obtained by introducing two defective nuclear genes, cyd1 and cyc4, into the same haploid strain . The action of the two mutant genes is synergistic, since either gene acting singly results in only partial cytochrome deficiency . Normal synthesis of all cytochromes can be restored in the double mutant by adding delta-aminolevulinic acid to the growth medium . The optimum concentration of delta-aminolevulinate for restoration of cytochrome synthesis is about 40 muM; when higher concentrations are used, synthesis of cytochromes is partially suppressed, particularly that of cytochrome a.a3 . Growth yield of the double mutant is stimulated by ergosterol and Tween 80, a source of unsaturated fatty acid . Methionine stimulates further . None of these nutrients is required for growth when sufficient delta-aminolevulinic acid is present in the growth medium . With respect to nutritional responses, the single-gene, cytochrome-deficient mutant, ole3, behaves like the double mutant . The frequency of the p-mutation in the double mutant grown in the absence of ergosterol, Tween 80, and delta-aminolevulinic acid is at least 15% . The frequency can be reduced to less than 1% by either delta-aminolevulinic acid or Tween 80 . Ergosterol alone does not decrease the p- frequency . The ole3 mutant does not exhibit increased p-frequency under similar conditions of unsaturated fatty acid deficiency. Biochim Biophys Acta, 1975 Dec 5, 411(2), 263 - 81 Effects of external osmolality on polyamine metabolism in HeLa cells; Munro GF et al.; The polyamine content of Escherichia coli is inversely related to the osmolality of the growth medium . The experiments described here demonstrate that a similar phenomenon occurs in mammalian cells . When grown in media of low NaCl concentration, HeLa cells and human fibroblasts were found to contain high levels of putrescine, spermidine, and spermine . The putrescine content of HeLa cells was a function of the osmolality of the medium, as shown by growing cells in media containing mannitol or additional glucose . External osmolality per se had no effect on the contents of spermidine and spermine . For all media, the total cellular polyamine content could be correlated with the activity of ornithine decarboxylase, the first enzyme in polyamine biosynthesis . Different levels of enzyme activity appear to result solely from variations in the rate of enzyme degradation . A sudden increase in a NaCl concentration produced rapid loss of ornithine decarboxylase activity and a gradual loss of putrescine and spermidine . A sudden decrease in NaCl concentration led to rapid and substantial increases in ornithine decarboxylase activity and putrescine. Radiat Environ Biophys, 1975 Dec 4, 12(4), 315 - 20 Influence of energy metabolism on the repair of x-ray damage in living cells . IV . Effects of 2-deoxy-D-glucose on the repair phenomena during fractionated irradiation of yeast; Jain VK et al.; Inhibition of repair of sublethal and potentially lethal damage was observed in respiratory-deficient mutants of yeast during fractionated X-irradiation in the presence of equimolar concentrations of 2-deoxy-D-glucose and glucose in the growth medium . In the wild-type cells, on the other hand, an enhancement of repair of the potentially lethal damage was obtained under similar conditions . These results suggest, by analogy, that in higher organisms also, 2-deoxy-D-glucose may differentially inhibit the repair of radiation damage in hypoxic tumor cells while enhancement of repair processes could be expected in normal tissues. Tsitologiia, 1975 Dec, 17(12), 1415 - 20 {The effect of hydroxymethyl derivatives of 7,12-dimethylbenz(a)anthracene on its metabolism and toxic action in tissue culture}; Belitskii GA et al.; The naturally occurring hydroxymethyl derivatives of the carcinogen 7,12-dimethylbenz(a)anthracene was found to inhibit the metabolic hydroxylation and toxic effect of this carcinogen in mouse embryo fibroblast-like cell culture . The greatest reduction of both effects was obtained when 12-hydroxymethyl-7-methylbenz(a)anthracene was added to the growth medium, less effective were, resp., 7,12-dihydroxymethylbenz(a)-anthracene and 7-hydroxymethyl-12-methylbenz(a)anthracene . The data obtained are discussed in terms of the intracellular regulation of carcinogenic hydrocarbon metabolism. Lipids, 1975 Dec, 10(12), 726 - 31 Uptake and metabolism of exogenous eicosa-8,11,14-trienoic acid in minimal deviation hepatoma 7288 C cells; Gaspar G et al.; Minimal deviation hepatoma 7288 C cells were cultured in Swim's medium containing 10% serum for 48 hr . The growth medium was replaced with serum free media containing different concentrations of {1-14C} eicosa-8,11,14-trienoic acid and the cells were incubated for 24 hr . Incorporation into cell lipids, oxidation to CO2, and desaturation to arachidonic acid were studied . The oxidation of the acid was very low . It was preferentially incorporated into the polar lipids of the cell . The incorporation depended on the number of cells and fatty acid concentration . Saturation of the cells with the acid was reached when 144.7 nmoles per mg of cellular protein were incorporated . The acid was desaturated readily to arachidonic acid . The nmoles of eicosatrienoic acid converted to arachidonic acid per mg of cellular protein were hyperbolic function of the acid incorporated . Maximal desaturation, 23 nmoles per mg of cellular protein, was reached when the cells were saturated with the acid . The calculations of the desaturation capacity and of the endogenous pool of eicosatrienoic acid available for desaturation in the cell are discussed. Mikrobiologiia, 1975 Nov-Dec, 44(6), 1034 - 40 {Effect of the composition of the medium and magnesium and calcium ions on the germination of spores of Thermoactinomyces vulgaris}; Kirillova IP et al.; The germination of the spores of Thermoactinomyces vulgaris formed on a complex medium is stimulated by suspending them in solutions containing Mg2+ and Ca2+ ions . The stimulation is not the result of the initiation of the spores in the presence of the ions since the experiments were carried out at a temperature of 20 degrees C at which the initiation did not virtually take place . The ions of Na+ and K+ have almost no effect on the germination of the spores . The fraction of the resting spores of Thermoactinomyces vulgaris depends on the composition of the growth medium, especially on its amino acid composition . The addition of Mg2+ and Ca2+ ions to a minimal synthetic growth medium stimulates the growth of the cultures and decreases the dormancy of the spores . The spores formed on the synthetic medium are less thermostable than the spores formed on the complex medium . Thermostability of the spores increases upon the addition of Mg2+ to the synthetic medium . Spore suspensions obtained on the synthetic medium with Mg2+ or Ca2+ are initiated more completely than spore suspensions obtained on the complex medium. Mikrobiologiia, 1975 Nov-Dec, 44(6), 1030 - 3 {Determination of optical activity of the growth medium as a method for detection of extraterrestrial life}; Imshenetskii AA et al.; Determination of optical activity of the cultural medium can be used for detection of extraterrestrial life . The composition of the growth medium depends on the duration of the experiment . Automatic biological stations are sent to planets for a short time, and the best components of the growth medium are D-glucose and D-maltose; optical activity of the cultural broth disappears upon assimilation of these compounds . Tartaric acid is less suitable since the duration of the experiment increases several times and desert soils do not always contain microorganisms assimilating tartaric acid. Mutat Res, 1975 Nov, 30(2), 209 - 18 Repair of UV-induced DNA damage and survival in yeast . I . Dimer excision; Wheatcroft R et al.; The amount of pyrimidine dimer UV photoproduct lost from the DNA of irradiated yeast cells during dark incubation has been measured in various conditions . It was found that no dimers were lost when cells were incubated in saline . When the cells were incubated, with aeration, in a full growth medium, dimers were lost, most excision being complete within 4 h . Not all dimers were lost and the number lost was a function of UV dose . Maximum loss, amounting to 50 000 dimers per genome was observed after 4000 or 6000 erg/mm2 of UV . At higher doses, the number excised declined . Making the assumptions that dimers are the principal lethal product of UV, that a single dimer remaining in its genome is enough to prevent a cell from multiplying and that excision is the principal dark-repair process in yeast, these data were incorporated into the repair term of an expression relating survival to repair8 and it was found that the survival of yeast at doses up to 2000 erg/mm2 of UV could be quite accurately predicted . This is the first time it has been possible to account for survival in terms of measured repair . It is suggested that the divergence of the predicted and observed curves at higher doses is due to other processes known to exist in yeast. J Bacteriol, 1975 Nov, 124(2), 985 - 96 Serine transhydroxymethylase isoenzymes from a facultative methylotroph; O'Connor ML et al.; Two serine transhydroxymethylase activities have been purified from a facultative methylotrophic bacterium . One enzyme predominates when the organism is grown on methane or methanol as the sole carbon and energy source, whereas the second enzyme is the major isoenzyme found when succinate is used as the sole carbon and energy source . The enzyme from methanol-grown cells is activated by glyoxylate, is not stimulated by Mg2+, Mn2+, or Zn2+, and has four subunits of 50,000 molecular weight each . The enzyme from succinate-grown cells is not activated by glyoxylate and is stimulated by Mg2+, Mn2+, and Zn2+, and sodium dodecyl sulfate-acrylamide gel electrophoresis indicates that this enzyme has subunit molecular weight of 100,000, the same as the molecular weight obtained for the active enzyme . Cells grown in the presence of both methanol and succinate incorporate less methanol carbon per unit time than cells grown on methanol and have a lower specific activity of the glyoxylate-activated enzyme than methanol-grown cells . Adenine, glyoxylate, or trimethoprim in the growth medium causes an increased level of serine transhydroxymethylase in both methanol- and succinate-grown cells by stimulating the synthesis of the glyoxylate-activated enzyme. J Biochem (Tokyo), 1975 Nov, 78(5), 1079 - 85 Biochemical studies on sulfate-reducing bacteria . XIV . Enzyme levels of adenylylsulfate reductase, inorganic pyrophosphatase, sulfite reductase, hydrogenase, and adenosine triphosphatase in cells grown on sulfate, sulfite, and thiosulfate; Kobayashi K et al.; Sulfate-reducing bacteria, Desulfovibrio vulgaris, strain Miyazaki, were grown on either sulfate, sulfite, or thiosulfate as the terminal electron acceptor . Better growth was observed on sulfite and less growth on thiosulfate than on sulfate . Enzyme levels of adenylylsulfate (APS) reductase {EC 1.8.99.2}, reductant-activated inorganic pyrophosphatase {EC 3.6.1.1}, sulfite reductase {EC 1.8.99.1} (desulfoviridin), hydrogenase {EC 1.12.2.1}, and Mg2+-activated ATPase {EC 3.6.1.3} were compared in crude extracts of these cells at various stages of growth . 1) The specific activity of APS reductase in sulfite-grown cells was only one-fourth that in sulfate-grown cells throughout growth . Thiosulfate-grown cells had an activity intermediate between those of sulfate- and sulfite-grown cells . 2) Cells grown on sulfite had lower specific activity of reductant-activated inorganic pyrophosphatase than cells grown on sulfate or thiosulfate . 3) The specific activity of sulfite reductase (desulfoviridin) was highest in sulfite-grown cells . The sulfite medium gave the enzyme in high yield as well as with high specific activity . 4) The specific activities of hydrogenase and Mg2+-ATPase were not significantly altered by electron acceptors in the growth medium. Proc Natl Acad Sci U S A, 1975 Nov, 72(11), 4337 - 40 Requirement for cellular protein synthesis in reversal of ethidium-bormide-induced inhibition of cell transformation by murine sarcoma virus; Roa RC et al.; Cultures of mouse Balb 3T3 fibroblasts exposed to a noncytotoxic dose of ethidium bromide for 16-18 hr are unable to produce foci after infection with murine sarcoma virus . Such cultures regain susceptibility to infection when incubated for 6-8 hr in drug-free growth medium . Pretreated but not untreated cultures exhibit sensitivity toward brief (6 hr) exposure to cycloheximide, chloramphenicol, and actinomycin D before infection . Pretreatment with cordy-cepin inhibits the ability of cultures to produce foci after infection . The recovery of ethidium-bromide-treated cultures requires the synthesis of cellular proteins which may have some important role in the establishment of RNA tumor virus infection. Science, 1975 Oct 31, 190(4213), 464 - 5 Tetrahymena: growth without phagocytosis; Basmussen L et al.; We have succeeded in growing a Tetrahymena mutant without food vacuoles in growth media supplemented with vitamins and heavy-metal salts . This finding implies the existence of adequate alternative routes of entry for every required nutrient, and clearly indicates that the food vacuole in Tetrahymena is a dispensable cellular organelle . The growth of the mutant without food vacuoles makes available a valuable experimental tool. Can J Microbiol, 1975 Oct, 21(10), 1541 - 7 Specific inhibition of sclerotium formation by 2-mercaptoethanol and related sulfhydryl compounds in Sclerotium rolfsii; Christias C; Sclerotium formation in Sclerotium rolfsii was completely inhibited by 2-mercaptoethanol at a concentration of 2-4 mM without any adverse effect on mycelial growth . Concentrations lower than 2 mM had no effect on mycelial growth and sclerotium formation, whereas both were inhibited at concentrations higher than 4 mM . Complete inhibition of sclerotium formation with no effect on mycelial growth was also obtained by propyl mercaptan, 1-butyl mercaptan and 2-butyl mercaptan at a concentration of 0.10 mM . Sclerotium formation was also inhibited by benzyl mercaptan and thioglycolic acid at 0.15 mM and 2-4 mM concentration respectively, whereas it was only partially inhibited by L-cysteine and glutathione at 20 mM . Mycelium grown for 21 days in nutrient medium supplemented with mercaptoethanol at a concentration of 3 mM, when transferred into fresh medium without the chemical, grew normally and produced abundant mature sclerotia . Mercaptoethanol inhibited the initiation as well as the further development of young, unpigmented sclerotia . The mechanism of sclerotium formation was arrested completely when mercaptoethanol was added to the growth medium at any time between inoculation and the appearance of sclerotia of the "development" stage . It is suggested that the specific inhibitory action of mercaptoethanol could be used to study the mechanism of sclerotium formation J Cell Physiol, 1975 Oct, 86(2 PT 2 SUPPL 1), 321 - 6 Growth enhancement of myogenic tumor cells by conditioned medium from embryo fibroblasts; Baker RS et al.; Growth medium was conditioned by incubation on mouse embryo cells in vitro . Supplementation of agar suspension cultures with conditioned medium from primary cells, but not from established lines, readily enhanced colony development by mouse tumor cells . Only cells with the properties of myoblasts responded to conditioned medium . Other fibroblastoid cells and virus-transformed cell lines were not affected . Myogenic cells in agar cultures grew in the presence of conditioned medium but did not differentiate . Soluble collagen at 400 mug/ml possessed little colony-stimulating activity by comparison with fresh conditioned medium. J Bacteriol, 1975 Oct, 124(1), 269 - 78 Role of methionine in the regulation of serine hydroxymethyltransferase in Eschericia coli; Greene RC et al.; Significant derepression of serine hydroxymethyltransferase is observed when metE or metF mutants of Escherichia coli K-12 are grown on D-methionine sulfoxide instead of L-methionine . The derepression is not prevented by addition of glycine, adenosine, guanosine, guanosine, and thymidine to the growth medium of methionine-limited metF cells showing that the effect is not due to a secondary deficiency of these nutrients . On the other hand, methionine-limited growth of a metA mutant leads to derepression of met regulon enzymes, but only a marginal increase in serine hydroxymethyltransferase activity . A prototrophic metJ strain grown on minimal medium has about the same serine hydroxymethyltransferase as the wild type . The enzyme activity of the metJ strain is not influenced by methionine, but it is partially repressed by glycine, adenosine, and thymidine . metK strains have about twice as much serine hydroxymethyltransferase activity as wild-type cells when grown on minimal medium; but when both types of cells are grown on medium supplemented with glycine, adenosine, guanosine, and thymidine, their enzyme activities are about the same . The results show that methionine limitation can lead to depression of serine hydroxymethyltransferase, but that the regulatory system is different from the one which controls the methionine regulon. Proc Natl Acad Sci U S A, 1975 Oct, 72(10), 4162 - 6 Mechanism of action of penicillin: triggering of the pneumococcal autolytic enzyme by inhibitors of cell wall synthesis; Tomasz A et al.; During penicillin treatment of an autolysin defective mutant pneumococcus we have observed three novel phenomena: (i) Growth of the mutant cultures is inhibited by the same concentrations of penicillin that induce lysis in the wild type . (ii) Mutant bacteria treated with the minimum growth inhibitory concentration of penicillin will lyse upon the addition of wild-type autolysin to the growth medium . Chloramphenicol and other inhibitors of protein synthesis protect the cells against lysis by exogenous enzyme . Sensitivity of the cells to exogenous autolysin requires treatment with penicillin or other inhibitors of cell wall synthesis (e.g., D-cycloserine or fosfonomycin) since exogenous autolysin alone has no effect on bacterial growth . (iii) Treatment with penicillin (or other inhibitors of cell wall synthesis) causes the escape into the medium of a choline-containing macromolecule that has properties suggesting that it contains pneumococcal lipoteichoic acid (Forssman antigen) . Each one of these three phenomena (growth inhibition, sensitization to exogenous autolysin, and leakage of lipoteichoic acid) shows the same dose response as that of the penicillin-induced lysis of wild-type pneumococci . On the basis of these findings we propose a new hypothesis for the mechanism of penicillin-induced lysis of bacteria . It is suggested that inhibition of cell wall synthesis by any means triggers bacterial autolytic enzymes by destabilizing the endogenous complex of an autolysin inhibitor (lipoteichoic acid) and autolytic enzyme . Escape of lipoteichoic acid-like material to the growth medium is a consequence of this labilization . Chloramphenicol protects bacteria against penicillin-induced lysis by interfering with the activity of the autolytic enzyme, rather than by depleting the concentration of the enzyme at the cell surface. Biochim Biophys Acta, 1975 Sep 8, 404(1), 1 - 6 Wall mannan of Saccharomyces cerevisiae . Metabolic stability and release into growth medium; Kratky Z et al.; Selective labelling of cell wall mannan with radioactive precursors in growing Saccharomyces cerevisiae showed that this polysaccharide is metabolically stable during exponential growth . Mannan once inserted into the wall is not subject to turnover or release into the growth medium . However, about 10% of the amount of mannan incorporated into the cell wall fraction can be recovered in the non-dialyzable material isolated from the growth medium . Therefore, the mannan escaping from the cell must be either a mannan de novo synthesized, not trapped in the growing wall structure, or a mannan with a non-structural role . Radioactivity was also retained in the wall fraction of cells pre-labelled with {14C} glucose which pointed to metabolic stability of all cell wall polysaccharides in growing S . cerevisiae. Mikrobiologiia, 1975 Sep-Oct, 44(5), 808 - 12 {Extracellular polysaccharides in yeasts of the genus Sporobolomyces Kluyver et van Niel}; Elinov NP et al.; Nineteen yeast strains belonging to the genus Sporobolomyces were tested for the ability to produce extracellular polysaccharides during submerged cultivation in a defined growth medium . These polysaccharides, accumulated by the yeast Sporobolomyces in the cultural broth, are a heterogeneous group of polymers. J Virol, 1975 Sep, 16(3), 634 - 41 Biochemical studies on bovine adenovirus type 3 . II . Incomplete virus; Igarashi K et al.; Incomplete virus of oncogenic bovine adenovirus type 3 (BAV3) was highly purified and its biological activity was studied . The production of incomplete virus was found to increase with a high multiplicity of infection and with a large amount of arginine in the growth medium . On infection of contact-inhibited mouse cells, incomplete virus induced cellular DNA synthesis and focus formation . Moreover, this virus was oncogenic to newborn hamsters . On infection of calf kidney cells, a permissive cell line, viral early and late RNA, viral DNA, and almost all the viral late proteins were produced, but no mature progeny virus was detected . It is, therefore, suggested that incomplete virus of BAV3 may be unable to synthesize a protein(s) (perhaps a kind of maturation protein{s}) essential for assembly of viral macromolecules for maturation. Mikrobiologiia, 1975 Sep-Oct, 44(5), 863 - 9 {Irregular growth of Escherichia coli under periodic cultivation conditions}; Shaforostova LD et al.; Uneven growth of Escherichia coli ML 30 was found in periodic conditions of cultivation on a defined medium containing maltose or glucose as a source of carbon . This is demonstrated by changes in the slope of the logarithmic curve expressed in units of optical density, and the curve of the specific growth rate plotted against time . The uneven pattern of growth can be revealed only if samples are taken every 15 min . Variations in the growth rate are accompanied with irregular utilization of carbon sources, acidification of the medium, accumulation of organic acids in the cultural broth, deviations in the enzyme activity and the content of polymers in the cells . According to the dynamics of the aforementioned parameters, the growth phase of E . coli is complex and can be subdivided into five different cycles . Such a synchronization of growth is presumed to be due to changes in the composition of the growth medium. Scand J Dent Res, 1975 Sep, 83(5), 274 - 8 Comparison of five growth media and two anaerobic techniques for isolating bacteria from dental plaque; Slots J; Five agar media in combination with the Hungate roll tube technique and conventional anaerobic jar technique (Baird & Tatlock inverted question mark jars) were evaluated to determine the most suitable medium for non-selective isolation of the viable microorganisms in dental plaque . The highest colony count was obtained by using "Modified Medium 10" with the roll tube technique . About twice as many plaque colonies were recovered by roll tube technique as by the conventional anaerobic technique . With the MM 10 roll tube technique, 7 d of incubation revealed only 93% of the colonies that could be detected after 14 d of incubation. J Biochem (Tokyo), 1975 Sep, 78(3), 537 - 45 Studies on phospholipases from Streptomyces . III . Purification and properties of Streptomyces hachijoensis phospholipase C; Okawa Y et al.; 1 . Phospholipase C {EC 3.1.4.3} found in the growth medium of Streptomyces hachijoensis was purified about sixty-fold by dialysis and column chromatography on Sephadex G-50 . 2 . The active fraction was separated by isoelectric focusing into two fractions, phospholipase C-I (pI 6.0) and phospholipase C-II (pI 5.6) . 3 . Both purified phospholipases C were homogeneous by immunodiffusion and were not differentiated as regards antigencity . 4 . Phospholipase C-I had maximal activity at pH 8.0 and the optimal temperature was 50degree . Phospholipase C-I was stable at 50degrees for 30 min and was stable at neutral pH . 5 . The activity of phospholipase C-I was inhibited by high concentrations of various detergents such as Triton X-100, sodium, cholate, SDS and was also inhibited by Ca2+, Ba2+, Al3+, and EDTA, but was stimulated by Mg2+, and ethyl ether . 6 . The Km value of phospholipase C-I was 0.9 mM, using phosphatidylcholine as a substrate . 7 . By the gel filtration procedure, the molecular weights of phospholipase C-I and -II were both determined to be 18,000 . 8 . Phosphatidylcholine, phosphatidylinositol, cardiolipin, sphingomyelin, and lysophosphatidylcholine were hydrolyzed by phospholipase C-I, but phosphatidylethanolamine and phosphatidylserine were hydrolyzed with difficulty under the same conditions, Phospholipase C-I also hydrolyzed phosphatidic acid. J Biol Chem, 1975 Aug 10, 250(15), 5852 - 8 Regulation of mitochondrial membrane assembly in Neurospora crassa . Transient expression of a respiratory mutant phenotype; Klein JL et al.; Cultures of mutant cni-1, a chromosomal mutant of Neurospora crassa, undergo a marked change in respiratory properties as the age of the culture increases . Early log phase cultures have a high level of respiration that is insensitive to inhibition by cyanide or antimycin A . Late log and stationary phase cultures have reduced rates of respiration . A high percentage of this respiration is inhibited by cyanide . Mitochondria from early log phase cni-1 have an excess of cytochrome c and little or no detectable cytochrome aa3 . Mitochondria from late log and stationary phase cultures have levels of c-, b-, and a-type cytochromes that are not significantly different in concentration from those found in wild type cells . The cytochrome aa3 content and the cytochrome oxidase activity of cni-1 mitochondria increase 5- to 10-fold as the age of the culture increases . Mitochondria from early log phase cells of cni-1 synthesize only polypeptides of apparent molecular weights 7,000 to 10,000 and donot synthesize any of the mitochondrial components of cytochrome oxidase . Mitochondria from late log and stationary phase cells synthesize the normal complement of mitochondrial translation products including the mitochondrial components of cytochrome oxidase . The assembly of cytochrome oxidase is likely due to the availability of the mitochondrially synthesized components of the enzyme . The regulation of mitochondrial translation in the cni-1 mutant is independent of the nutrient content of the growth medium and is due to the accumulation or depletion of some component within the cell. J Natl Cancer Inst, 1975 Aug, 55(2), 375 - 84 Properties and malignant transformation of established rat liver parenchymal cells in culture; Borenfreund E et al.; Epithelioid cells from the livers of normal and genetically impaired (Gunn) rats were established in long-term cultures in vitro . These cells grew as flat, epithelioid cobble-stone-type monolayers and showed a diploid karyotype . They secreted rat serum albumin and proteins into their growth media and contained aryl hydrocarbon hydroxylase . Such cells were transformed by treatment with methylazoxymethanol acetate; they then exhibited an irregular, piling growth pattern, acquired the ability to grow in soft agar, and thereafter grew as tumors in hamsters given cortisone and in nude mice . These malignant spindle-cell tumors were reestablished in culture and still secreted serum albumin . The transformed cells became highly multinucleate when exposed to cytochalasin B and thus behaved like tumor cells . This behavior was not shown by the original cells . Cells transformed by benzo{a}pyrene failed to grow in soft agar culture or as tumor in animals . Cells were not affected by diethylnitrosamine. J Med Microbiol, 1975 Aug, 8(3), 397 - 404 Complement-dependent and complement-independent interactions between Mycoplasma hominis and antibodies in vitro; Lin JS et al.; Several in vitro reactions between a strain of M . hominis (no . 4195) and homologous antiserum have been delineated and compared . One complement-dependent and four complement-independent activities of antibody have been studied . The complement-dependent activity was mycoplasmacidal and was inhibited by the presence of arginine in the test medium . The complement-independent antibody-mediated reactions were not mycoplasmacidal and were four in number: (a) agglutination, which was manifested in buffered saline after incubation for 24-48 h at 36 degrees C, and in which the end-points were dependent upon the concentration of antigen; (b) metabolic inhibition, in which antiserum added to liquid growth medium produced slowing of the rate at which the pH rises during growth; (c) agglutination during growth, which occurred in liquid growth medium after the addition of antiserum and coincided with, but generally preceded, metabolic inhibition; and (d) inhibition of multiplication in which high concentrations of antiserum led to inhibition of multiplication or metabolic activity, with persistence of viable mycoplasmas, under otherwise favourable conditions of growth . The end-points for each of the above methods of detecting antibody are not identical. J Cell Physiol, 1975 Aug, 86(1), 9 - 13 Glutamine synthetase activity in WI-38 cells; Viceps D et al.; In the presence of complete growth media (Eagle's MEM), human diploid WI-38 cells have a low level of glutamine synthetase activity . The activity could be increased by depriving the cells of exogenous glutamine; addition of hydrocortisone to either glutamine-deficient or complete medium had no effect on the acitivty of the enzyme . Cell growth ceased under conditions that enhanced glutamine synthetase activity, and hydrocortisone could not reverse this inhibition. Can J Microbiol, 1975 Aug, 21(8), 1287 - 90 Assembly of the enveloped bacteriophage phi 6 in environments which perturb the host cell membranes; Sands JA et al.; The effects of known membrane-perturbing agents (pH, Na+, Ca2+, and a small lipid-soluble molecule) on the enveloped bacteriophage phi 6 host cell system were investigated at the levels of cellular growth, virus assembly and stability, and the physical and chemical properties of host cell membranes . Spin-label probes of cellular membranes indicate that growth in high levels of Na+ or the small spherical hydrophobic molecule adamantanone results in membranes having increased "fluidity," while growth in high levels of Ca2+ results in slightly greater rigidity of the membranes . In addition, the phospholipid composition of the cellular membranes is dependent on the NaCl concentration in the growth medium . None of these membrane alterations, however, prevent the production of infectious phi 6 virus particles. Can J Microbiol, 1975 Aug, 21(8), 1211 - 6 The development of an increased rate of Cl- uptake in the ascomycete Neocosmospora vasinfecta; Miller AG et al.; Freshly harvested mycelium of the filamentous ascomycete Neocosmospora vasinfecta accumulated C1- against a concentration gradient by a process probably requiring the expenditure of metabolic energy . When mycelium, washed free of growth medium, was incubated in deionized water or tris (hydroxymethyl) aminomethane sulfate at pH 7.5 for 4 h and then transferred to K36C1 solutions, the C1- uptake rate was, on the average, 3.77 +/- 0.26 (+/-SE, N = 20) times the uptake rate exhibited by freshly harvested mycelium . This development of an increased rate of Cl- uptake could be blocked by the presence of an inhibitor of ribonucleic acid synthesis (azaguanine) or of protein synthesis (cycloheximide, fluorophenylalanine, or puromycin) . The combined presence of glucose and a potassium salt in the preincubation solution virtually arrested the development of enhanced Cl- uptake . The rate of Cl- uptake by freshly harvested mycelium did not vary greatly with the age of the culture on harvest but the ability to develop an increased rate declined with age . The fact that it is possible to obtain mycelium possessing widely different capacities for Cl- uptake should assist in biochemical characterization of the Cl- uptake system. J Gen Microbiol, 1975 Aug, 89(2), 221 - 8 The synthesis of beta-galactosidase by constitutive and other regulatory mutants of Escherichia coli in chemostat culture; Macleod CJ et al.; The synthesis of beta-galactosidase by an E . coli constitutive mutant was examined in a chemostat using glucose-, glycerol-, succinate- or N-limited growth media . Except for glucose-grown bacteria, the steady-state intracellular level of beta-galactosidase was maximal at dilution rates between 0-2 and 0-3 h-1 . At higher dilution rates enzyme synthesis was reduced by catabolite repression, which could be relieved by the addition of cyclic AMP . With a catabolite-resistant mutant (UV5c), no decrease in enzyme level at high dilution rates were observed . All mutants examined were constitutive and gave decreased enzyme levels at low dilution rates, with the exception of lac-/F'lac UV5c mutants where the enzyme levels rose at low dilution rates . Hyper-producing mutants were isolated but were unstable . A constitutive mutant growing on glycerol-limited media was considered the most suitable for large-scale production of beta-galactosidase in a chemostat. Biochim Biophys Acta, 1975 Jul 14, 399(1), 203 - 12 Mossbauer effect studies in the fungus Phycomyces; Spartalian K et al.; Mossbauer spectra of 57- Fe have been observed from different parts (mycelia, spores, sporangiophores) of the fungus Phycomyces blakesleeanus grown in an agar medium isotopically enriched with 57- Fe . The spectra indicate that the iron within Phycomyces exists primarily in two chemical states: one which is the same as that of the iron in the growth medium and the other in the form of ferritin, an iron-storage protein . The amount of iron in the former state is observed to decrease relative to the amount of iron in the latter state in going from mycelia to the sporangiophores to the sporangia themselves . Thus, the conversion of iron from the chemical state of the nutrient to ferritin has been monitored for different parts of the phycomyces . In addition, our spectra indicate that at low temperatures the iron atoms clustered within a ferritin molecule are antiferromagnetically coupled . The size of these clusters is inferred from their superparamagnetic behavior at low tempertures and comparison with horse ferritin indicates that the phycomyces ferritin iron clusters are smaller by a factor of two. Mikrobiologiia, 1975 Jul-Aug, 44(4), 759 - 61 {Development of Thermoactinomyces vulgaris on a synthetic medium}; Kirillova IP et al.; A synthetic medium was used to obtain the dormant spores of Thermoactinomyces vulgaris . The fraction of the dormant spores depended on the amino acid composition of the growth medium . The rate of growth and development of the organism on the synthetic medium is lower as compared to the routinely employed complex medium. Nucleic Acids Res, 1975 Jul, 2(7), 1111 - 21 Ribosomal RNA metabolism in cucumber leaf mesophyll protoplasts; Coutts RH et al.; Aspects of the metabolism of RNA have been studied in enzymatically isolated protoplasts from cotyledon and first leaf mesophyll tissue of two cultivars of cucumber . The first leaf mesophyll protoplasts incorporated (3H)-uridine into ribosomal RNA at a constant rate for up to 25 hr in a simple salts medium and for up to 45 hr in a growth medium . Pulse-chase labelling experiments on such preparations showed a rapid dilution of the intracellular (3H)-uridine pool(s) and a high metabolic rate in the cells in one cultivar but not in another . Gel electrophoretic analysis of the RNA from both cotyledon and first leaf protoplasts showed that both protoplast types incorporated either (14C)- or (3H)-uridine into ribosomal RNA species . Incorporation of (3H)-uridine into chloroplasts RNA was minimal in cotyledon protoplasts, but significant in leaf protoplasts . Greater incorporation into the chloroplast RNA species could be achieved by longer pulses . Synthesis of all of the ribosomal RNA species was sensitive to actinomycin D at 10 and 25 mug/ml concentrations in all protoplasts tested. Mikrobiologiia, 1975 Jul-Aug, 44(4), 676 - 81 {Autoselection in Candida utilis yeasts in a chemostat culture}; Shkidchenko AN et al.; Long-term continuous cultivation of Candida utilis in the conditions of chemostat, with the growth rate being limited with phosphates, was accompanied by autoselection . The culture obtained had a higher growth rate and differed by some physiological characteristics from the parent culture . The content of intracellular phosphates varied from 1.9 to 0.55% per dry weight, depending on the concentration of phosphates in the growth medium . At the threshold concentration (0.007 g/litre), phosphates were not virtually utilized by the culture . Specific time of transitional processes depends on the value of interfering effect. Infect Immun, 1975 Jul, 12(1), 211 - 20 Competition between Chlamydia psittaci and L cells for host isoleucine pools: a limiting factor in chlamydial multiplication; Hatch TP; L cells (mouse fibroblasts) supported the multiplication of the obligately intracellular parasitic bacterium Chlamydia psittaci (strain 6BC) when incubated in fresh growth medium (medium 199 + 5% fetal calf serum) . When incubated in the medium supernatant from a 24-h-old culture of uninfected L cells (24-h used medium), uninfected cells did not divide and infected cells did not provide an adequate environment for the multiplication of C . psittaci, which persisted in a noninfectious latent state within the host cells . The failure of both L cells and chlamydiae to divide resulted from an overall reduction in the rate of protein synthesis by both host and parasite brought about by an insufficiency of the essential amino acid isoleucine in 24-h used medium . The concentration of isoleucine required to activate minimal growth of C . psittaci also minimally stimulated uninfected L cells to divide . The addition of cycloheximide to 24-h used medium also activated the latent chlamydial infection because it stimulated the incorporation of host protein-derived isoleucine into chlamydial protein . The results suggest that the chlamydial parasite and the L-cell host compete for the isoleucine in the soluble pool of the host cell and that the parasite is capable of sequestering isoleucine for its own biosynthetic needs only when the concentration of isoleucine in the host pool rises above the level required to maintain the hose in the stationary state . Extrapolation of the results obtained with the L cell-C . psittaci model system to natural latent chlamydial infections is discussed. Int J Radiat Biol Relat Stud Phys Chem Med, 1975 Jul, 28(1), 45 - 51 Influence of rat blood on radiation protection of mammalian cells by cysteamine and cystamine in vitro; Grant GA et al.; The protective effect of cystamine and cystamine on T-cells in normal growth-medium was studied in the presence of whole rate blood (WRB) . The protective effectiveness of both agents was increased by the addition of WRB, but much less so on the activity of cystamine . In the presence of WRB a dose-reduction factor of 1-5 was obtained at the low concentration of 0-05 mM cysteamine . The increase in protection was not due to induction of anoxia or to a release of glutathione from the rat red cell . The increase in protection may be due to protector RS radicals reacting with rat red cells. J Clin Microbiol, 1975 Jul, 2(1), 11 - 3 Pluronic polyols in human lymphocyte cell line cultures; Mizrahi A; Pluronic polyols markedly improved the growth of two human lymphocyte cell lines when added to the growth medium in concentrations of 0.05 to 0.1% . The results of the current studies suggest that, in addition to the protective effect of polyols against mechanical damage of mammalian cells in submerged cultures, the pluronic compounds may also, by lowering surface tension, facilitate transport of metabolites into cells and thus increase the growth rate. Proc Natl Acad Sci U S A, 1975 Jul, 72(7), 2635 - 9 Isolation of a cationic polypeptide from human serum that stimulates proliferation of 3T3 cells; Antoniades HN et al.; A basic polypeptide that stimulates DNA synthesis and cell division in confluent populations of mouse Balb/c-3T3 cells has been isolated from whole human serum, and has been separated from the heterogenous group of molecules with insulin-like activity . This highly purified basic polypeptide has a molecular weight of 1.3 x 10(4) and an isoelectric point of 9.7 . Approximately 10(7) polypeptide molecules in the growth medium allow the replication of one density-inhibited cell. Mikrobiologiia, 1975 Jul-Aug, 44(4), 742 - 8 {Purity criteria for Bdellovibrio bacteriovorus cultures}; Lambina VA et al.; Two-component cultures of Bdellovibrio bacteriovorus, a bacterial parasite, are not always pure; sometimes they contain microbial forms, different from the host and parasite, which cannot be isolated by conventional techniques of inoculation on solid growth media . The only way to isolate them is to apply techniques used for the reversion of L-forms of bacteria . The isolated microorganisms have been identified . The criteria of purity were established for two-component cultures consisting of the host and parasite. Avian Dis, 1975 Jul-Sep, 19(3), 544 - 55 Growth of Mycoplasma synoviae in a medium supplemented with nicotinamide instead of B-nicotinamide adenine dinucleotide; DaMassa AJ et al.; The cultivation of Mycoplasma synoviae (MS) on growth medium requires supplementation with B-nicotinamide adenine dinucleotide (NAD), an expensive and relatively unstable compound . Strains of MS were adapted (selected) to grow in a medium supplemented instead with nicotinamide, a stable and inexpensive substance that can be heat-sterilized in the medium without impairing its growth-promoting properties . MS plate agglutinating antigens grown in nicotinamide-enriched media were comparable in yield and serological reaction to antigens grown with NAD supplementation. Cell, 1975 Jul, 5(3), 311 - 8 Effects of cycloheximide on virus RNA replication in an inducible line of polyoma-transformed rat cells; Manor H et al.; In this article, we describe two distinct effects of cycloheximide (CH), a potent inhibitior of protein synthesis, on the replication of polyoma virus (PV) DNA in an inducible line of PV-transformed rat cells (LPT cells) . Exposure of LPT cells to CH causes up to an 8 fold increase in the cellular concentration of PV DNA determined by molecular hybridization . The same treatment inhibits cell division and chromosomal DNA replication . However, the amount of chromosomal DNA per cell is not affected by the drug . In LPT cells treated with mitomycin C (MMC), PV DNA replication is enhanced after 7 hr . During the period extending from 7 hr to 24 hr, the concentration of virus DNA increases at least 100 fold . CH added to the cells 0-7 hr after treatment with MMC inhibits the replication of PV DNA by 90-100% . The inhibition is less effective in cells exposed to CH from 7 hr and on . The inhibitory effect is reversible: virus DNA synthesis is resumed after removal of CH from the growth medium . Thus CH acts as an inducer of virus DNA synthesis in cells whose resident viral genome is repressed, but inhibits the autonomous replication of the activated genome following induction with MMC. Z Immunitatsforsch Exp Klin Immunol, 1975 Jul, 149(2-4), 104 - 17 Chemical structure of the peptidoglycan, its modifiability and relation to the biological activity; Schleifer KH; The peptidoglycan is a heteropolymer composed of polysaccharide chains which are cross-linked through short peptides . The polysaccharide moiety (glycan) is made up of beta-1,4 glycosidically linked N-acetylglucosamine and N-acylmuramic acid residues . The carboxyl group of muramic acid is usually substituted by a peptide which consists of alternating L- and D-amino acids . These peptide subunits are cross-linked between the diamino acid in position 3 and the C-terminal D-alanine in position 4 of an adjacent peptide subunit either in a direct way or via an interpeptide bridge (Group A) . In some coryneform bacteria the cross-linkage extends from the alpha-carboxyl group of D-glutamic acid in position 2 to D-alanine of a neighbouring peptide subunit (Group B) . In the latter case a diamino acid is always found in the interpeptide bridge . A chemical modification of the peptidoglycan may occur in some bacteria due to growth in a quite unbalanced medium . The influence of glycine-rich and glycine-deficient growth medium on the chemical structure of the peptidoglycan of S . aureus will be discussed . Inhibiting concentrations of penicillin, glycine or D-amino acids can also modify the peptidoglycan . Further modification can occur through different extraction procedures which are used to obtain a clean peptidoglycan free of non-peptidoglycan cell wall material . Little is known about the molecular basis of the biological activity . The chemical composition is at least important for the antigenic determinants . The lysozyme susceptibility and the size of the preparation may be other crucial points for the biological activity of the peptidoglycan. Cancer Res, 1975 Jul, 35(7), 1865 - 72 The effect of flavonoids on aerobic glycolysis and growth of tumor cells; Suolinna EM et al.; Certain bioflavonoids inhibit the glycolysis of variety of tumor cells by interfering with the generation of adenosine diphosphate and inorganic phosphate which are required for glycolysis . Tetra- and pentahydroxy flavones with hydroxyl groups as 3, 3', 4', 5, and 7 (e.g., quercetin) are the most active . They inhibit the activity of isolated Na+-K+-adenosinetriphosphatase of the plasma membrane and of mitochondrial adenosinetriphosphatase, but under appropriate conditions do not interfere with the ion transport increase the the translocation efficiency of the ion pump . It was shown that in several tumor cells loosely coupled ion pumps are responsible for the high rate of aerobic glycolysis, the effect of quercetin on the growth of several cell lines was examined . Since bicarbonate and serum albumin were found to counteract the effect of quercetin, the cells were grown in tissue cultures at low concentrations of these compounds . Pronounced inhibition of growth was observed at 5 to 20 mug of quercetin per ml of growth medium. Ann N Y Acad Sci, 1975 Jun 30, 253, 318 - 32 Programmed synthesis of flagellar tubulin during cell differentiation in Naegleria; Fulton C et al.; Amebae of Naegleria gruberi differentiate into flagellates when transferred from growth medium to non-nutrient buffer . This differentiation, which requires 48 min at 28 degrees C, is dependent on transcription and translation . Tubulin of the flagellar outer doublets comprises about 0.15% of the protein of flagellate, and only about 1-2% of the total tubulin . An antiserum to flagellar (outer-doublet) tubulin contains antibodies that react selectively with flagellar tubulin . Measurements using this antiserum have shown that 97-98% of the flagellar tubulin antigen appears during differentiation . The appearance of tubulin antigen is sensitive to actinomycin D and cycloheximide . Isotope dilution experiments using {35S}methione demonstrated that at least 70% of the flagellar tubulin is synthesized from amino acids during differentiation . Experiments using both the specific antiserum and isotopes have shown that flagellar tubulin synthesis begins about one-third of the way through differentiation, before any morphological change has occurred . These experiments demonstrate that most, if not all, of the flagellar tubulin is synthesized de novo during differentiation, and that cells selectively use a specific subpopulation of tubulin in assembling the outer doub)lets . The results bring into focus major unsolved questions about the synthesis and assembly of flagellar tubulin. Arch Microbiol, 1975 Jun 22, 104(2), 101 - 4 In vivo biosynthesis of peptidophosphogalactomannan in Penicillium charlesii; Drewes LR et al.; The major exocellular glycopeptide (peptidophosphogalactomannan) produced by Penicillum charlesii first appears in the culture filtrate when the growth medium is nearly depleted of NH4+ . The extent of incorporation of exogenously supplied radioactive precursors (D-{U-14C} GLUCOSE, L-{U-14C}threonine and NaH2(32)PO4) into peptidophosphogalactomannan suggests that approximately 20% of the total quantity of peptidophosphogalactomannan is assembled from constituents taken from the growth medium before NH4+ starvation and that the remainder is assembled from constituents in the medium during NH4" starvation . In the absence of NH4+, an increase in dry weight continues until the medium is depleted of glucose . However, peptidophosphogalactomannan accumulation proceeds until after glucose is depleted and growth is halted . These data suggest that peptidophosphogalactomannan is a product of cellular turnover. Arch Microbiol, 1975 Jun 20, 104(1), 89 - 94 Studies on an unstable phenotype induced by UV irradiation: the lysine excreting (lex(-)) phenotype of the yeast Saccharomycosis lipolytica; Gaillardin CM et al.; Unstable clones excreting L-lysine into their growth medium are obtained at a very high frequency following UV irradiation in both haploid and diploid strains of Saccharomycopsis lipolytica, provided they carry a mutation affecting the first enzyme of the lysine pathway and confering resistance to end product inhibition . The phenotype can be stabilized in some sublines; it appears as dominant and coupled with a decrease in spore viability . Excretion in batch cultures is confined to the end of the exponential phase, and seems not to consist in a simple release of the lysine pool content. Arch Microbiol, 1975 Jun 20, 104(1), 51 - 6 {The development and the reversion of spheroplasts of a diaminopimelic acid-auxotrophic mutant of Escherichia coli}; Maurer M et al.; 1 . The formation and reversion of spheroplasts of the diaminopimelic acid-auxotrophic mutant Escherichia coli K 12, 335, DAP-, R+TEM in a medium lacking diaminopimelic acid have been investigated by microphotography: During their development from rod form cells to spheroplasts cells on slide-surface-agar preparations underwent two successive cell divisions in the course of which the cells retained their rod form . The cells formed by these divisions partitioned into a varying number of spheroplasts of different size . The reversion of spheroplasts to rod form cells, started by the addition of diaminopimelic acid showed two characteristic steps: Each spheroplast partitioned again into several spheroplast-like cell bodies; most of them reverted directly to rod form cells . 2 . The release of the R-factor mediated periplasmic TEM-beta-lactamase, E . C . 3.4.2.6., into the growth medium during the development of spheroplasts attained more than 50% of the entire TEM-beta=lactamase activity . The spheroplasts showed a multiple enhancement of TEM-beta-lactamase activity per mg cell protein compared with rod form cells. Br J Exp Pathol, 1975 Jun, 56(3), 223 - 30 The effect of normal spleen cells on 3H-thymidine uptake by target cells in vitro; Nyssen J et al.; When tumour cells (line L cells) were grown in culture with syngeneic normal non-immune C3H/He mouse spleen cells or in the cell free supernatant of these spleen cells they incorporated less tritiated thymidine (3H-Tdr) than when grown by themselves . Despite this effect there was no depression in either cell growth or DNA synthesis . Autoradiographic studies revealed that the decrease of 3H-Tdr incorporation into tumour cells in the presence of spleen cells was not due to inhibition of cell entry into S phase but due to the amount of 3H-Tdr the tumour cells incorporated . Since the medium of spleen cell cultures was found to contain DNA and the addition of calf thymus DNA to fresh growth medium also resulted in decreased 3H-Tdr uptake by the tumour cells, it was concluded that line L cells utilize DNA released by spleen cells into the medium for de novo DNA synthesis . On the basis of these findings, it is suggested that caution be used in interpreting decreased 3H-Tdr uptake as determined by scintillation counting as evidence for a cytostatic effect exerted by lymphoid cells or their supernatants in vitro. Proc Soc Exp Biol Med, 1975 Jun, 149(2), 530 - 3 Amino acid uptake in growing and arrested human diploid cell populations; Birckbichler PJ et al.; Human diploid fibroblasts cultured in vitro weremonitored for amino acid uptake in preconfluent and confluent cultures under conditions amenable to growth and in confluent cultures arrested in an essentially nonmitotic state . Preconfluent and confluent cultures in growth medium showed similar uptake patterns for leucine and alpha-aminoisobutyrate; arrested cultures exhibited a reduced uptake of both amino acids . Kinetic measurements revealed a 4-fold reduction in apparent Vmax for alpha-aminoisobutyrate influx in arrested cultures . These results suggest that the culture conditions used in this study to produce restrictions in mitotic activity likewise influence amino acid accumulation. J Gen Microbiol, 1975 Jun, 88(2), 329 - 38 Modification of the membrane composition of Mycoplasma mycoides subsp . capri by the growth medium; Archer DB; Mycoplasma mycoides subsp . capri was grown in different media . The amounts of the lipids in these media were varied, resulting in altered lipid compositions of the cells . Lowering the amounts of cholesterol in the media resulted in less cholesterol incorporation into the cell lipid, with a concomitant decrease in the amount of phospholipid . The changes in the phospholipid/cholesterol ratio in the mycoplasmas were very small compared with the large changes in the amounts of cholesterol which occurred when the cholesterol content in the medium was altered . Changes in the amounts of glycolipid and glyceride in the cell lipid also resulted from alterations of the cholesterol concentration in the media . Under these conditions cell with reduced cholesterol contents were more sensitive to lysis by digitonin . No changes were observed in the polyacrylamide gel electrophoretic pattern of cellular or membrane proteins when the cholesterol was replaced by other sterols. J Bacteriol, 1975 Jun, 122(3), 931 - 42 Relationship between chromosome replication and cell division in a thymineless mutant of Escherichia coli B/r; Meacock PA et al.; The relationship between chromosome replication and cell division was investigated in a thymineless mutant of Escherichia coli B/r . Examination of the changes in average cell mass and DNA content of exponential cultures resulting from changes in the thymine concentration in the growth medium suggested that as the replication time (C) is increased there is a decrease in the period between termination of a round of replication and the subsequent cell division (D) . Observations on the pattern of DNA synthesis during the division cycle were consistent with this relationship . Nevertheless, the kinetics of transition of exponential cultures moving between steady states of growth with differing replication velocities provided evidence to support the view that the time of cell division is determined by termination of rounds of replication under steady-state conditions. J Bacteriol, 1975 Jun, 122(3), 1230 - 8 chlD gene function in molybdate activation of nitrate reductase; Sperl GT et al.; chlD mutants of Escherichia coli lack active nitrate reductase but form normal levels of this enzyme when the medium is supplemented with 10-3 M molybdate . When chlD mutants were grown in unsupplemented medium and then incubated with molybdate in the presence of chloramphenicol, they formed about 5% the normal level of nitrate reductase . Some chlD mutants or the wild type grown in medium supplemented with tungstate accumulated an inactive protein which was electrophoretically identical to active nitrate reductase . Addition of molybdate to those cells in the presence of chloramphenicol resulted in the formation of fully induced levels of nitrate reductase . Two chlD mutants, including a deletion mutant, failed to accumulate the inactive protein and to form active enzyme under the same conditions . Insertion of 99-Mo into the enzyme protein paralleled activation; 185-W could not be demonstrated to be associated with the accumulated inactive protein . The rates of activation of nitrate reductase at varying molybdate concentrations indicated that the chlD gene product facilitates the activation of nitrate reductase at concentrations of molybdate found in normal growth media . At high concentrations, molybdate circumvented this function in chlD mutants and appeared to activate nitrate reductase by a mass action process . We conclude that the chlD gene plays two distinguishable roles in the formation of nitrate reductase in E . coli . It is involved in the accumulation of fully induced levels of the nitrate reductase protein in the cell membrane and it facilitates the insertion of molybdenum to form the active enzyme. J Bacteriol, 1975 Jun, 122(3), 1301 - 9 Gas vesicle assembly in Microcyclus aquaticus; Konopka AE et al.; When observed in the electron microscope intact gas vesicles appeared as transparent areas in whole cells of Microcylus aquaticus, whereas vesicles collapsed by centrifugation were not discernible . Within 5 min of suspending cells containing collapsed vesicles in growth medium, small transparent vesicles were detected . By 15 min the average number of vesicles per cell was 15 . This number remained relatively constant while the size of the vesicles increased until they attained their maximum diamtere of 100 nm . At this time the vesicles, interpreted as biconical structures, began to elongate presumably due to the synthesis of the cylindrical midsection . Closely correlated with the time at which vesicles began to elongate was the initiation of smaller vesicles which resulted in a doubling of the number of vesicles per cell by 90 min . This evidence coupled with the isolation of a mutant which assembles only the conical portions of the vesicle suggests that assembly occurs in two distinct stages subject to genetic mutation . Protein and ribonucleic acid synthesis, and presumably adenosine triphosphate formation, were required for gas vesicle assembly . In addition, inhibition of protein or ribonucleic acid synthesis resulted in a loss of extant gas vesicles . Over the time course of our study, deoxyribonucleic acid synthesis was not required for gas vesicle assembly or stability. J Bacteriol, 1975 Jun, 122(3), 1339 - 50 Cell surface-located deoxyribonucleic acid receptors in transformable pneumococci; Seto H et al.; We studied deoxyribonucleic acid (DNA) binding in transformable pneumococci . The relevant findings are as follows . (i) At least half of the DNA Molecules adsorbed to competent cells in the growth medium are attached to sites on the protoplast membrane . (ii) Most of the DNA bound to live competent cells in the presence of glucose is not released by moderate shear or by autolysin treatment . In contrast, most of the DNA adsorbed to competent cells in the absence of glucose is shear and autolysin sensitive . (iii) The presence of binding sites resembling in properties the sites in live competent cells can be demonstrated in wall-membrane complexes . Most of these sites are lost during preparation of cell walls and protoplasts . It is suggested that the DNA-binding site is a membrane component (protein?) Stabilized by polysaccharide (cell Wall) material . (IV) Mechanical or enzymatic damage to the cell wall or change in the ionic conditions can induce DNA binding (and surface-nuclease activity) in the incompetent pneumococci . However, such cells still show neither genetic transformation nor extensive nuclease-resistant binding of DNA . It is suggested that both competent and incompetent cells contain a large number of sequestered DNA-binding sites that can be unmasked by several experimental conditions . Induction of the competent state by the competence activator protein may involve an endogenous unmasking process. Cancer Res, 1975 Jun, 35(6), 1559 - 62 Transcription of the repetitive DNA sequences in polyoma-transformed and nontransformed mouse cells in culture; Grady LJ et al.; RNA-DNA saturation hybridization experiments were used to estimate the extent of transcription of repetitive DNA sequences in polyoma-transformed and nontransformed mouse cells in culture . Measurements were made with RNA from nontransformed cells in both the subconfluent and confluent stages of growth, transformed cells in normal growth medium, and transformed cells grown in medium containing 5-bromodeoxyuridine, 3 mu-g/ml, a treatment which reduces their tumorigenic potential . No differences were observed in the amount of repetitive DNA transcribed or in the families of sequences expressed, except in transformed cells grown in the presence of 5-bromodeoxyuridine, in which case the extent of transcription was reduced. J Bacteriol, 1975 Jun, 122(3), 1062 - 70 Changes in glucosamine and galactosamine levels during conidial germination in Neurospora crassa; Schmit JC et al.; The levels of glucosamine and galactosamine were determined in conidia, germinating conidia, and vegetative mycelia of Neurospora crassa . In the vegetative mycelia about 90% of the amino sugars were shown to be components of the cell wall . The remaining 10% of the amino sugars were tentatively identified as the nucleotide sugars uridine diphospho-2-acetamido-2-deoxy-D-glucose and uridine diphospho-2-acetamido-2-deoxy-D-galactose . Conidia and vegetative mycelia contained about the same levels of glucosamine . During the first 9 h after the initiation of germination, the total glucosamine content had increased 3.1-fold, whereas the residual dry weight of the culture had increased 7.7-fold . This led to a drop in the glucosamine concentration from 100 mumol/g of residual dry weight to 42 mumol/g . During this time, all of the conidia had germinated and the surface area of the new germ tubes had increased to 10 times that of the conidia . Either germ tubes were initially produced without glucosamine-containing polymers, or these polymers (probably chitin) were deposited only at low densities in the germ tube cell walls . The chitin precursor uridine diphospho-2-acetamido-2-deoxy-D-glucose was present at all times during conidial germination . Conida contained very low levels of galactosamine . During germination, galactosamine could not be detected until the culture had reached a cell density of about 0.6 mg of residual dry weight per ml of growth medium . This was observed regardless of the time required to reach this cell density or the fold increase in dry weight . The accumulation of galactosamine-containing polymers does not appear to be necessary for germ tube formation . The levels of soluble galactosamine (uridine diphospho-2-actamido-2-deoxy-D-galatose) were very low in conidia and increased during germination at the same time that galactosamine appeared in the cellular polymers . In addition, under certain culture conditions, the appearance of galactosamine and the increase in the glucosamine concentration occurred simultaneously. Arch Microbiol, 1975 May 5, 103(3), 259 - 70 The regreening of nitrogen-deficient Chlorella fusca II . Structural changes during synchronous regreening; Pyliotis NA et al.; Chlorella fusca, strain 211-15, cells degreened in a nitrogen-deficient mineral growth medium in the light for 4-6 weeks were regreened for up to 24 hrs in a nitrogen rich medium that leads to synchronous cell division at 24-26 hrs . Structural changes in the plastid membranes during the regreening period were observed by thin section and freeze-fracture electron microscopy . Nitrogen-deficient plastids were found to have non-appressed lamellae, prolamellar body-like membrane aggregations, and only 2 types of freeze-fracture face . At this time no photosynthetic oxygen evolution could be demonstrated . After 6 hrs regreening the plastid lamellae had fused to form bands of appressed lamellae and the four types of freeze-fracture face, described previously, were visible . At this time photosynthetic oxygen evolution could be demonstrated . After 24 hrs regreening the plastids had an appearance typical of normally grown Chlorella and had commenced to divide . Supporting evidence for these developmental stages is presented from isolated chloroplast particle fractions . An unusual type of cell wall proliferation was observed in the nitrogen-deficient Chlorella cells that resulted in the laying down of several walls, each with a trilaminar component. C R Acad Sci Hebd Seances Acad Sci D, 1975 May 5, 280(17), 2041 - 3 {Regulation of lysyl-tRNA synthetase of Escherichia coli K12}; Reinisch F et al.; In Escherichia coli K 12, addition of lysine to the growth medium does not lead to a repression of the synthesis of the lysyl-tRNA synthetase . On the contrary, by use of a strain bradytrophic for one of the lysine biosynthetic enzymes, a shift from a medium containing lysine to minimal medium leads to an increase in the specific activity for this enzyme . This increase is discrete (1.5 fold) but reproducible . Thus it may be assumed that lysyl-tRNA synthetase belongs to the lysine regulon. Biochem J, 1975 May, 148(2), 169 - 77 Rates of degradation and synthesis of glycosidases de novo during growth and differentiation of Dictyostelium discoideum; Every D et al.; 1 . Injection of a purified preparation of beta-N-acetylglucosaminidase from the spent growth medium of myxamoebae of Dictyostelium discoideum into rabbits gave rise to an antibody preparation containing both anti-alpha-glucosidase and anti-beta-acetylglucosaminidase activities . 2 . These two activities were shown to reside in different immunoglobulin molecules and it was concluded that the beta-N-acetylglucosaminidase preparation contained trace amounts of highly antigenic alpha-glucosidase . 3 . A single precipitin band having beta-N-acetylglucosaminidase activity was formed in Ouchterlony plates when this antibody preparation was tested against extracts obtained from differentiated cells or from myxamoebae grown either axenically or on bacteria . 4 . The antibody preparation was used to show that both beta-N-acetylglucosaminidase and alpha-glucosidase molecules are synthesized de novo from isotopically labelled amino acids during both the growth and differentiation phases of the life cycle and to show that neither of these proteins is significantly degraded during the growth phase or during the first 9h of differentiation . 5 . The rates of accumulation of these assayable enzyme activities are thus equal to their rates of synthesis during growth and early differentiation . 6 . The factors regulating cellular enzyme activity during the life cycle of D . discoideum are discussed. Biochem J, 1975 May, 148(2), 161 - 7 Rates of accumulation of glycosidase activities during growth and differentiation of Dictyostelium discoideum; Every D et al.; 1 . The rates of accumulation (enzyme units/h per 10(8) cells) of a number of glycosidase activities were studied in Dictyostelium discoideum cells during the growth and differentiation phases of this organism's life cycle . 2 . The rates of accumulation of the enzymes beta-N-acetylglucosaminidase, alpha-glucosidase and beta-galactosidase remain unchanged during the growth and early differentiation phases . 3 . The considerable changes in specific activity of the enzymes which occur in the early differentiation phase are due to the massive loss of total cellular protein which occurs at this time . 4 . Significant alterations can occur in the rates of accumulation of alpha-mannosidase during both the growth and differentiation phases, and since, on the onset of differentiation, beta-glucosidase activity is excreted and degraded, the rate of accumulation of this enzyme differs in the growth and differentiation phases . 5 . The characteristic rates of accumulation of all these glycosidases change markedly with changes in the growth conditions of the myxamoebae, and thus these rates of synthesis must be regulated independently; however, addition of cyclic AMP to the growth medium has no effect on them. Zentralbl Bakteriol {Orig B}, 1975 May, 160(3), 191 - 211 {Studies on the metabolism of benzo(a)pyren in alveolar-macrophages . I . Uptake of benzo(a)pyrene and induction of benzo(a)pyrene hydroxylase (author's transl)}; Dehnen W; Alveolar macrophages play a significant role in the elimination of inhaled foreign compounds and particles from the lung . The question arises, if alveolar macrophages participate in the detoxification or activation of environmental carcinogenic compounds . In the first communication on this subject we describe experiments concerning the uptake of benzo(a)pyrene and the activity of the metobolizing enzymes . The alveolar macrophages are obtained by lung lavage from guinea pigs (Fig . 1,2,3) . The cells are grown in monolayers in petri dishes or on the surface of cover slips or glass-vials . The uptake of benzo(a)pyrene in alveolar macrophages is measured by a microfluorimetric method in single cells and by using labelled substrate . The results obtained by both methods indicate that the uptake is terminated between 1-2 h (Fig . 4, 5) . The kinetics of uptake and elimination (Fig . 8, 9) . are influenced by the concentration of serum (Fig . 6) and benzo(a) pyrene (Fig . 7) in the medium . Two mechanism for the uptake in the alveolar macrophages are discussed: diffusion and pinocytose . The activity of the metabolizing enzymes (benzo(a)pyrene hydroxylase, aryl hydrocarbon hydroxylase)increases during incubation with benzo(a)pyrene (Fig . 10, 11) and is dependant on the concentration of benzo(a)pyrene in the growth medium (Fig . 12) . The enzyme activity is inducible also by other polycyclic hydrocarbons (Tab . 1) . The induction is inhibited by actinomycin D and cycloheximid (Tab . 2) . The activity of the enzymes in guinea pig alveolar macrophages is comparable to the activity in leucocytes and alveolar-macrophages from humans (Tab . 3, 4). Mikrobiologiia, 1975 May-Jun, 44(3), 408 - 13 {Radiometric study of the decarboxylating activity of desert soil microflora}; Imsenecki AA et al.; Employment of growth media containing salts of organic acids, labelled with 14C, gave a rapid and intensive signal concerning the decarboxylating activity of microorganisms from desert soils . The value of the signal was higher than that during the decomposition of uniformly labelled glucose . The results of these studies would help to select the optimal growth medium for carrying out exobiological experiments. Mikrobiologiia, 1975 May-Jun, 44(3), 395 - 9 {Mechanism of action of beta-ionone on the carotene-synthesizing enzymes of Blakeslea trispora}; Feofilova EP et al.; The addition of beta-ionone to the growing culture of Blakeslea trispora stimulates the synthesis of carotene, protein, and RNA . The experiments with the addition to the growth medium of an inhibitor of translation (cycloheximide) and an inhibitor of transcription (actinomycin D), in the presence of beta-ionone, suggest that beta-ionone stimulates the synthesis of carotene-forming enzymes de novo in B1 . trispora, this effect being manifested at the level of translation of the templates in the ribosomes. J Gen Microbiol, 1975 May, 88(1), 20 - 6 Missense suppression in Coprinus lagopus associated wtih a chromosome duplication; Lewis D et al.; Amongst some 70 recessive suppressors of a met-I mutation in Coprinus lagopus, one unstable suppressor was identified . The unstable suppressor, designated sup-6plus, could be maintained on minimal medium, but was lost within 24h on minimal medium containing more than 1-7 p.p.m . DL-methionine or 0-75 p.p.m . L-methionine . Isolation of hyphal tips from the monokaryotic strain carrying sup-6plus yielded three types of colony: the unstable parental type, the stable met-I auxotroph and a stable prototroph which was slow-growing and inhibited by methionine in the growth medium . This stable sup-6plus type was recovered with difficulty by resolving dikaryons formed between the unstable sup-6plus strain and strains carring the wild-type allele of the suppressor gene . From sexual crosses, neither the unstable nor stable sup-6plus type segregated, only the met-I auxotrophic revertant . The unstable sup-6plus strain is thought to have an extra chromosome carrying the sup-6plus mutation . For vigorous growth the wild-type allele, sup-6, is indispensable and would be carried on the homologous chromosome . The selective pressures on different media account for loss of the duplicated chromosomes . The results are interpreted as missense suppression by a mutant of an indispensable tRNA. Appl Microbiol, 1975 May, 29(5), 615 - 20 Inhibition of microbial growth by fatty amine catalysts from polyurethane foam test tube plugs; Bach JA et al.; When polyurethane foam test tube plugs are autoclaved, they release volatile fatty amines that inhibit the growth of some microorganisms . The chemical structures of these amines were determined by the use of a gas chromatograph-mass spectrometer . They are catalysts used to produce the foam . The problem of contaminating growth media with toxic substances released from polymeric materials is discussed. Genetics, 1975 May, 80(1), 61 - 76 Mating type and sporulation in yeast . II . Meiosis, recombination, and radiation sensitivity in an alpha-alpha diploid with altered sporulation control; Hopper AK et al.; In wild-type S . cerevisiae, diploid cells must be heterozygous at the mating-type locus in order to sporulate . In the preceding paper, we described a number of mutants (CSP mutants), isolated from nonsporulating aa and alpha-alpha parent strains, in which sporulation appeared to be uncoupled from control by mating type . The characterization of one of these mutants (CSP1) is now extended to other processes controlled by mating type . This mutant is indistinguishable from alpha-alpha cells and unlike aalpha cells for mating factor production and response, zygote formation, intragenic mitotic recombination, and for X-ray sensitivity . The mutant apparently undergoes a full round of DNA synthesis in sporulation medium, but with delayed kinetics . Only 20% of the cells complete sporulation . Among spores in completed asci, the frequency of both intra- and intergenic recombination is the same as it is for spores produced by aalpha cells . However, experiments in which cells were shifted from sporulation medium back to minimal growth medium gave a frequency of meiotic recombination between ade2 or leu2 heteroalleles only 25% to 29% as high for CSP1 alpha-alpha diploid or CSP1 aa disomic cells as for aalpha diploid or disomic cells . Because the latter result, indicating recombination defectiveness, measured recombinant production in the entire cell population, whereas the result indicating normal recombination sampled only completed spores, we infer that all meiotic recombination events occuring in the population of CSP1 alpha-alpha cells are concentrated in those few cells which complete sporulation . This high degree of correlation between meiotic recombination and the completion of meiosis and sporulation suggests that recombination may be required for proper meiotic chromosome segregation in yeast just as it appears to be in maize and in Drosophila. J Bacteriol, 1975 May, 122(2), 585 - 91 Simple downshift and resulting lack of correlation between ppGpp pool size and ribonucleic acid accumulation; Hansen MT et al.; The growth rate of Escherichia coli can be limited by the availability of carbon and energy . To impose such a limitation, alpha-methylglucoside (alpha MG), a non-metabolizable analogue, can be used to decrease uptake of glucose by competition for the transport of this sugar . Varying the ratio of glucose to alphaMG allowed shifts in growth rate without simultaneous qualitative changes in the growth medium and permitted examination of the immediate changes accompanying such shifts . Stringent (rel+) as well as relaxed (rel minus) strains were able to rapidly curtail their accumulation of ribonculeic acid (RNA) after a downshift imposed by decreasing glucose transport into the cell . Guanosine 5'-diphosphate 3'-diphosphate (ppGpp) accumulated in both rel+ and rel minus strains after a degrease in growth rate . However, the accumulation of ppGpp in relaxed derivatives was very slow, and there was no direct or obligatory correlation between the level of ppGpp and the rate of RNA accumulation . This latter conclusion is supported by measurements of ppGpp levels and rates of RNA accumulation after restoration of maximal growth rates by addition of excess glucose. J Bacteriol, 1975 May, 122(2), 367 - 74 Existence of two levels of repression in the biosynthesis of methionine in Saccharomyces cerevisiae: effect of lomofungin on enzyme synthesis; Surdin-Kerjan Y et al.; Derepression of a methionine biosynthetic enzyme (homocysteine synthase) has been studied after repression either by exogenous methionine or by exogenous S-adenosylmethionine (SAM) . Lomofungin, which inhibits the synthesis of ribosomal precursor and messenger ribonucleic acid but not of protein in Saccharomyces cerevisiae, has been used in this system . It has been shown that the addition of this antibiotic prevents the derepression of homocysteine synthase after repression by exogenous methionine but not after repression by exogenous SAM . These experiments with lomofungin and the kinetics of repression after addition of methionine or SAM to the growth medium provide evidence that the repression induced by exogenous methionine acts at the transcriptional level whereas the repression induced by exogenous SAM acts at the translational level. J Gen Microbiol, 1975 May, 88(1), 153 - 8 Synchronous cultures of micro-organisms: large-scale preparation by continuous-flow size selection; LLoyd D et al.; The separation of the smallest cells from an exponentially growing culture by passage through a continuous flow centrifuge rotor under controlled conditions of rotor speed and flow rate, provides a simple method for the rapid production of large-scale synchronou