Proc Natl Acad Sci U S A, 1980 Jan, 77(1), 457 - 61 Growth and differentiation of embryonal carcinoma cell line F9 in defined media; Rizzino A et al.; This paper reports the growth and differentiation of the mouse embryonal carcinoma cell line F9 in completely defined culture media . The defined growth medium, referred to as EM-3, contains plasma fibronectin, insulin, and transferrin in place of serum . F9 cells cultured in EM-3 for over 15 generations retain their ability to form tumors and to differentiate . Fibronectin is essential for the attachment of F9 cells in defined media and its effect can be blocked with affinity-purified anti-fibronectin . When retinoic acid was added to EM-3, the F9 cells differentiated . The majority of the the newly formed cells differed from patient F9 cell two major respects: (i) they were morphologically different; and (ii) they secreted plasminogen activator, and the secretion was stimulated by dibutyrlyl adenosine cyclic monophosphate. J Biochem (Tokyo), 1980 Jan, 87(1), 333 - 8 Effect of different growth media on the synthesis of carbohydrate-Binding protein from Dictyostelium discoideum NC-4; Yamada H et al.; The carbohydrate-binding protein, discoidin, was synthesized from Dictyostelium discoideum NC-4 grown on a Bacto peptone (Difco) containing medium together with bacteria . When the cells were transferred by serial passage to a Proteose peptone (Daigo)-containing medium, the productivity of discoidin was reduced to a negligible amount, but the cells formed aggregates, and another protein which binds with Sepharose 4B was detected by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate . We conclude that discoidin synthesis is already regulated during growth, and even when the amount of this protein is nil or negligible, the cells still retain aggregate-forming ability. Z Mikrosk Anat Forsch, 1980, 94(4), 661 - 8 {Effect of substance P on nerve fiber regeneration in tissue culture}; Lindner G et al.; Explants of the ganglion trigeminale from chick embryos (PNS) and of the hippocampus from fetal rats (CNS) were cultivated in maximow chambers with growth medium or maintanance medium . Varied concentrations of substance P (SP . 3 CH3COOH . 4 H2O) were added . 1 . The effect of substance P (SP) is related to concentration . In the presence of 10(-7)M SP in the growth medium and of 10(-4)M SP in the maintanance medium the cultivation of PNS cultures indicates positive results . These doses are suitable . 2 . Within the first 24 hours in vitro SP stimulates the index of area in PNS cultures . The index of characterizes the relation of the outgrowth zone to the explant . In CNS cultures a significant difference of this effect was not observed . 3 . The index of growth of nerve fibers may compare the test cultures with the control cultures . SP significantly increases the index of fiber growth in PNS cultures . A stimulation of CNS cultures was observed, significance was not found . 4 . From the beginning of the cultivation with SP up to 48 hours in vitro the growth of nerve fibers significantly increases in the treated cultures in comparison with the control cultures . After this time the growth of nerve fibers decreased and a morphological conformity of test cultures and controls was observed . 5 . The role of SP is discussed in specific activity on PNS tissue in vitro . The reactive neurons may be from the medio dorsal group of cells of the sensible ganglion. Ciba Found Symp, 1980, 79, 163 - 82 Copper and the synthesis of elastin and collagen; Harris ED et al.; Copper's role in connective tissue is linked to the enzyme lysyl oxidase . From a biochemical perspective, copper is a cofactor for the enzyme and a determinant of its activity in connective tissues . Lysyl oxidase catalyses a post-translational oxidation of certain lysine and hydroxylysine residues . The peptidyl aldehydes so formed become active centres for the formation of cross-links in collagen and elastin . Less well understood is how copper controls the steady-state activity of lysyl oxidase; the enzyme fails in copper deficiency . Giving copper to a deprived animal increases lysyl oxidase activity in aortic tissue . Such activation in vivo appears to require caeruloplasmin . Suspending aortic tissue in a copper-enriched growth medium also activates lysyl oxidase provided that tissue structure is kept intact . Activation in vitro occurs with the binding of copper to a large-molecular-weight component, presumably the enzyme . Binding will not occur if protein synthesis is blocked . These studies clearly show that the synthesis of mature elastin and collagen can be controlled by the availability of copper . They further suggest that transport of copper to aortic tissue and its engagement to lysyl oxidase are linked to the synthesis or lysyl oxidase, an extracellular carrier, or both. J Gen Virol, 1979 Dec, 45(3), 599 - 610 The influence of arginine starvation on the synthesis of virus high molecular weight DNA in HeLa cells productively infected by adenovirus type 5; Kumel G et al.; In culture cells productively infected by adenovirus a high mol . wt . form of DNA is synthesized which is known to represent, at least in part, virus DNA integrated into cellular DNA . We found that the synthesis of this high mol . wt . DNA and the other DNA size classes can strongly and differentially be influenced by altering the metabolic state of the cells . The effects of different rates of cell growth were tested in this respect as well as arginine deprivation as opposed to application of complete growth medium . Synthesis of virus high mol . wt . DNA and unit genome length DNA is enhanced in actively growing as compared to resting Ad5-infected HeLa cells . Under arginine deficiency, in resting Ad5-infected HeLa cells, integration of virus DNA sequences into cellular DNA is almost totally suppressed whereas virus unit genome length DNA is still synthesized . This differential effect is interpreted by the hypothesis that the formation of virus high mol . wt . DNA is a synthetic process that is independent of the unit size virus DNA replication, but coupled to the synthesis of a special form of a special form of cellular DNA that is less effectively shut off by the infection than cellular DNA in general. J Cell Sci, 1979 Dec, 40, 125 - 44 Quantitative replicon analysis of DNA synthesis in cancer-prone conditions and the defects in Bloom's syndrome; Ockey CH; A quantitative method of replicon analysis of DNA fibre autoradiographs has been used to study the relationship between mean rate of DNA chain growth (R) and distance between adjacent replicons (ID) in fibroblasts from cancer-prone conditions . Results are expressed in terms of the mean linear regression R = delta +(K.ID)10-2 . When replicon behaviour was examined in cells from patients with ataxia telangiectasia, basal cell naevus and Bloom's syndromes grown at high density after 48 h in culture, no significant differences could be found in replicon behaviour between these syndromes and normal cultures . However when Bloom's cells were grown at low density and examined 24 h earlier, the mean rate of chain growth R was reduced compared to normal cells at the same density . Both cell types at high densities at 24 h showed equal but lower R values than at 48 h after plating the cultures . The lower rate of chain growth in Bloom's was accompanied by a longer S-period and cell cycle . Studies of cell proliferation kinetics using consecutive mitoses after bromodeoxyuridine (BUdR) incorporation and harlequin banding showed that Bloom's cells at low cell density require a longer period to recover a normal cell cycle length after plating than do normal cells at the same density . Plating densities and using conditioned media shorten the recovery period in Bloom's cells, and when foetal calf serum/MEM is replaced by human AB serum/McCoy 5a medium as the growth media, cell cycle behaviour of low density Bloom's and normal cells are equal at a much earlier time . It is concluded that the slow rate of DNA chain growth in Bloom's cells is an artefact introduced by culture conditions and also may be present in normal cells at an earlier period . The behaviour of replicons during this recovery period appears to be similar in Bloom's and normal cells except for the time lag . As recovery proceeds, the DNA chain growth in the associated replicon pairs recover progressively . This alters both the mean R value from 0.4 to 0.8 micron/min, the slope of the regression K from less than 1.0 to approximately 1.0 while the distance between initiation sites (ID) remains constant throughout . Pretreatment of all cultures with fluorodeoxyuridine (FUdR) produced the same differential effect on release from DNA synthesis inhibition, that is a similar increase in the activation of normally inactive replicons and a slightly slower rate of chain growth over all replicons . No evidence of a substance released by Bloom's cells in culture capable of increasing the sister-chromatid frequency in normal cells could be found . Since SCE frequencies were found to increase with fixation time after BUdR introduction it is concluded that some of the reported changes could be due to differences in cell cycle kinetics brought about by the different media conditions. J Bacteriol, 1979 Dec, 140(3), 843 - 7 Influence of molecular size and osmolarity of sugars and dextrans on the synthesis of outer membrane proteins O-8 and O-9 of Escherichia coli K-12; Kawaji H et al.; Supplementation of the growth medium with high concentrations of sugars or low-molecular-weight dextrans results in a drastic change in the ratio of outer membrane proteins O-8 and O-9, due to induction of O-8 synthesis and suppression of O-9 synthesis . Sugars and dextrans of molecular weights greater than 600 to 700 switched the synthesis of O-9 to that of O-8 more effectively than those of lower molecular weight, although the effect was almost the same within each of the two groups irrespective of the differences in molecular weight within the group . Proteins O-8 or O-9, or both, are responsible for the formation of pores that allow the passive diffusion of hydrophilic molecules whose molecular weights are smaller than about 600 (T . Nakae, Biochem . Biophys . Res . Commun . 71:877-884, 1976) . The results indicate that substances that cannot pass through the outer membrane switch the synthesis of O-9 to that of O-8 more effectively than those that can penetrate this membrane with the aid of O-8, O-9, or both . It is suggested that the osmotic pressure exerted on the outer membrane plays an important role in the regulation of synthesis of the two proteins. Z Naturforsch {C}, 1979 Dec, 34(12), 1177 - 85 Expression of aspartokinase, dihydrodipicolinic acid synthase and homoserine dehydrogenase during growth of carrot cell suspension cultures on lysine- and threonine-supplemented media; Matthews BF et al.; Reduction in the amounts of activity of the first enzyme, aspartokinase (EC 2.7.2.4) and two branch-point enzymes, dihydrodipicolinic acid synthase (EC 4.2.1.52) and homoserine dehydrogenase (EC 1.1.1.3), located in the pathway for the synthesis of aspartate-family amino acids, occurred when cell suspension cultures of Daucus carota L . var . Danvers were grown in media containing 2 mM threonine or 2 mM lysine, endproducts of the pathway . Activity of the lysine-sensitive form of aspartokinase was decreased when cells were grown in medium containing lysine and the activity of the threonine-sensitive form was decreased when cells were grown in medium containing threonine . Activity of the branch-point enzyme leading to threonine synthesis, homoserine dehydrogenase, was decreased up to 70% in specific activity (units/mg protein) and relative activity (units/g fresh weight) when cells were grown in media containing lysine or threonine . Threonine had no effect on the relative activity of dihydrodipicolinic acid synthase, but decreased its specific activity . Lysine decreased the relative activity of the synthase by up to 40%, but had little effect on its specific activity . The decreased activities of the enzymes were apparently not due to binding of the inhibitory amino acids to the enzymes since homogenization of cells in buffer with 2 mM lysine and threonine did not decrease the measurable enzyme activities . These and other results presented suggest that both forms of the aspartokinase activity and homoserine dehydrogenase activity can be altered by supplementing the growth medium with lysine or threonine. Infect Immun, 1979 Dec, 26(3), 925 - 32 Novel iron uptake system specified by ColV plasmids: an important component in the virulence of invasive strains of Escherichia coli; Williams PH; The enhanced virulence of invasive strains of Escherichia coli carrying ColV plasmids was shown to be due to a novel plasmid-mediated iron uptake system . Possession of a ColV plasmid conferred strong selective advantage on the host bacterial strain in experimental infections unless excess iron was administered in the inoculum . Moreover, supplementation of defined minimal medium with transferrin to complex available iron caused marked limitation of the growth of plasmid-free strains but had no effect on strains carrying a ColV plasmid . The activity of an efficient iron uptake process was clearly shown by experiments with a mutant of E . coli deficient in enterochelin biosynthesis . Although the mutant was dependent on the presence of citrate in the growth medium to facilitate iron transport, colicinogenic derivatives did not require added citrate for growth . Radioactive iron was shown to be taken up rapidly by nongrowing cells of the plasmid-carrying strain . Furthermore, it was observed that repression of the synthesis of specific outer membrane proteins normally induced by conditions of iron deficit was maintained after a shift of the colicinogenic strains from a rich medium to a medium low in iron . The ColV plasmid-mediated iron uptake system was independent of the active iron transport mechanisms known in E . coli, but like them it required tonB activity as a source of energy. J Gen Microbiol, 1979 Dec, 115(2), 517 - 21 Preparation of protoplasts and whole cell ghosts from Mycobacterium smegmatis; Rastogi N et al.; Cell wall-deficient forms of Mycobacterium smegmatis were produced in growth medium containing D-cycloserine and horse serum . These cells were transformed into protoplasts with EDTA and lysozyme . Subsequent lysis by nucleases followed by osmotic shock produced membrane vesicles (whole cell ghosts). Antimicrob Agents Chemother, 1979 Dec, 16(6), 838 - 48 Triggering of autolytic cell wall degradation in Escherichia coli by beta-lactam antibiotics; Kitano K et al.; A biochemical method was developed to quantitatively compare the effectiveness of beta-lactams in triggering murein degradation (autolysin activity) in Escherichia coli . Bacteria prelabeled in their cell walls with radioactive diaminopimelic acid in growth medium were exposed for 10 min to the antibiotics at the appropriate minimal growth inhibitory concentrations and at multiples of these values, and the rate of cell wall degradation was followed during subsequent penicillin-binding protein (PBP)-1 were the most effective triggers of autolytic wall degradation; beta-lactams selective for PBP-2 were the poorest; and antibiotics preferentially binding to PBP-3 showed intermediate activities . The relative effectiveness of beta-lactams in autolysin triggering was found to parallel the effectiveness of the same drugs in causing rapid loss of viability, culture lysis, and spheroplast formation . Autolysin triggering was suppressed by inhibitors of protein and ribonucleic acid biosynthesis but not by inhibitors of deoxyribonucleic acid synthesis . The beta-lactam-induced cell wall degradation did not seem to involve a direct stimulation of enzyme activity or synthesis of new enzyme molecules, and murein sacculi isolated from cells that had been preexposed to a triggering dose of beta-lactam treatment exhibited the same sensitivity to crude, homologous autolysins as sacculi prepared from untreated control bacteria . On the basis of these observations, mechanisms are considered for the triggering of E . coli autolysins and for the role of autolytic activity in bacterial spheroplast formation, lysis, and death. Virchows Arch B Cell Pathol Incl Mol Pathol, 1979 Dec, 32(1), 47 - 56 Lowered resistance to lytic agents in sucrose vacuolation; Benassi G et al.; Vacuolation in fibroblasts cultivated in the presence of sucrose is associated with progressive accumulation of the undigestible sugar . In radioisotope experiments the process lasted several days, and when the cells were subcultured back into a medium devoid of sucrose the label was also lost after several days . This type of vacuolated cells is more fragile when it is challenged with lytic agents . 51Cr-labelled LS fibroblasts released more radioactivity when they had been growing in the presence of sucrose, whether they were suspended in media of decreasing osmolarity, in dilutions of various surfactants, exposed to high temperatures, or subjected to mechanical stress . It is concluded that these cells exhibit a lower resistance when exposed to unfavourable environments, but retain their viability in growth media despite some morphological and biochemical alterations. Biochem J, 1979 Nov 15, 184(2), 409 - 19 Two forms of 'malic' enzyme with different regulatory properties in Trypanosoma cruzi; Cannata JJ et al.; 1 . Cell-free extracts from culture epimastigotes of Trypanosoma cruzi contained two forms of NADP+-linked 'malic' enzyme (EC 1.1.1.40), I and II, with the same molecular weight but different electrophoretic mobilities and kinetic and regulatory properties . 2 . The apparent Km for L-malate was lower for 'malic' enzyme I, with hyperbolic kinetics, whereas the kinetic pattern for 'malic' enzyme II was slightly sigmoidal (h 1.4) . The kinetics for NADPH were hyperbolic for 'malic' enzyme I, and very complex for 'malic' enzyme II, suggesting both positive and negative co-operativity . 3 . 'Malic' enzyme II was markedly inhibited by adenine nucleotides; AMP was the the most effective, at least in the presence of an excess of MnCl2 . 'Malic' enzyme I was much less affected by the nucleotides . Both enzyme forms were inhibited by oxaloacetate, competitively towards L-malate, but the apparent Ki for 'malic' enzyme I (9 microM) was 10-fold lower than the value for 'malic' enzyme II . 'Malic' enzyme II, but not 'malic' enzyme I, was activated by L-aspartate and succinate (apparent Ka of 0.12 and 0.5 mM respectively); the activators caused a decrease in the apparent Km for L-malate and, to a lesser extent, in the apparent Km for NADP+ . L-Aspartate, but not succinate, increased the apparent Vmax . 4 . The inhibition by AMP suggests regulation by energy charge, with the L-malate-decarboxylation reaction catalysed by 'malic' enzyme II fulfilling a biosynthetic role . The inhibition by oxaloacetate and the activation by succinate are probably involved in the regulation of the 'partial aerobic fermentation' of glucose which yields succinate as final product . The activation by L-aspartate would facilitate the catabolism of this amino acid, when present in excess in the growth medium. Mutat Res, 1979 Nov, 63(1), 21 - 34 Effects of spermine on the detection of induced forward mutation at the Can1 locus in yeast: evidence for selection against canavanine-resistant mutants; McDougall KJ et al.; The effect of exogenous spermine tetrahydrochloride (0.5 mg/ml) on hydrazine- and nitrous acid-induced forward mutation to canavanine resistance (CAN1 leads to can1, normal to defective arginine permease) was examined in stationary-phase haploid Saccharomyces cerevisiae . Post-treatment cell division (specifically DNA replication) is required for hydrazine mutagenesis at this locus, whereas nitrous acid mutagenesis exhibits, in addition, a significant post-treatment-independent component . Spermine addition only during mutagenic treatments in buffer did not affect mutagen cytotoxicity, but did result in a slight yet consistent decrease in induced mutation frequencies . Addition of spermine to the yeast extract--peptone--dextrose (YEPD) post-treatment growth medium resulted in dramatic reductions of induced mutation frequencies, which could be alleviated by pregrowth in spermine-containing YEPD . Such a medium was found to cause an apparent temporary growth inhibition for almost 40 h, after which the growth rate of the culture increased rapidly . Cultures "recovering" from spermine inhibition were no longer inhibitable by spermine in fresh medium, suggesting an outgrowth of spontaneous and/or induced spermine-resistant derivatives . Genetic analysis of one isolate revealed a single dominant nuclear gene conferring resistance by some means other than defective spermine uptake . Growth of this mutant was only slightly inhibited by spermine (20% increase in doubling time), while mutation expression remained high . Results of competitive growth experiments indicated that spermine-containing YEPD exerted a selection pressure against canavanine-resistant cells, while YEPD by itself did not . The mechanism for this selection is not presently understood . With respect to replication-dependent induced mutation at CAN1, our initial observation of a strong apparent antimutagenic action of spermine was found to be best explained by this specific selection against can1 mutants . This underscores the need for caution in the interpretation of experiments designed to study physiological modification of mutagenic potential. Proc Natl Acad Sci U S A, 1979 Nov, 76(11), 5992 - 6 Migration of Schwann cells and wrapping of neurites in vitro: a function of protease activity (plasmin) in the growth medium; Kalderon N; In vitro conditions were defined under which Schwann cells, from a population of dissociated embryonic chicken spinal cord cells, migrate along the growing neuronal fibers and wrap bundles as well as individual axons, in a pattern similar to that found in a developing peripheral nervous system in vivo . The migration of Schwann cells and their wrapping of nerve fibers was found to be a function of plasmin activity in the growth medium . It was determined that at least one cell type among the spinal cord cells is producing plasminogen activator, the enzyme that activates the plasminogen that is a constituent of any serum . It is concluded that, to achieve wrapping of neurons by Schwann cells in culture, it is essential to have an active plasmin-generating system in the medium . It is hypothesized that the Schwann cell produces plasminogen activator . The possible role of both the Schwann cell and the plasminogen possible role of both the Schwann cell and the plasminogen activator in the formation of the neuromuscular junction is discussed. J Protozool, 1979 Nov, 26(4), 586 - 8 Extrusion of DNA from the macronucleus of Tetrahymena pyriformis GL; Lykkesfeldt AE; Administration of the thymidine analog 5-bromodeoxyuridine to exponentially growing cultures of Tetrahymena pyriformis GL in chemically defined medium results in inhibition of cell multiplication by at least one generation before DNA synthesis stops . Cell multiplication can be restored in these cultures, if they are transferred to fresh growth medium, but although most of the cells in the culture contain close to a G2-amount of DNA, a full DNA replication round is a prerequisite for renewed cell multiplication . Large extrusion bodies are found at the first division after transfer to fresh growth medium . Autoradiographic analysis has revealed that the DNA in the extrusion body is a representative of the DNA in the macronucleus indicating a random distribution of DNA between daughter nuclei and extrusion body. Biochem J, 1979 Oct 15, 184(1), 45 - 50 Synthesis of cytoplasmic membrane during growth and division of Escherichia coli . Dispersive behaviour of respiratory nitrate reductase; Cadenas E et al.; We have used the penicillin selection method of Autissier & Kepes {(1972) Biochimie 54, 93--101} to study the segregation of membrane-bound respiratory nitrate reductase (EC 1.9.6.1) in Escherichia coli for the three generations after cessation of nitrate reductase synthesis caused by withdrawal of nitrate from the growth medium . We also included a physical separation procedure that permitted direct assay for nitrate reductase activity among all fractions produced by the penicillin selection method . We conclude that the segregation of nitrate reductase after cell division is dispersive, and not semi-conservative as proposed by Autissier & Kepes (1972). Nucleic Acids Res, 1979 Oct 10, 7(3), 765 - 79 Production of specific site probes of tRNA structure by enrichment with carbon 13 at particular locations; Tompson JG et al.; Escherichia coli C6 rel met cys was cultured in a stringently defined minimal medium containing 13C-enriched metabolites in order to (1) achieve maximal 13C isotopic enrichment of tRNA; and (2) produce site specific but natural, non-perturbing NMR probes of tRNA structure and function . Growth conditions were manipulated to achieve optimal culture growth concomitant with maximal in vivo incorporation of various 13C-enriched nucleic acid precursors, including L-{methyl-13C} methionine, {2-(13)C} adenine, and {2-(13)C} uracil . Effective blockage of purine biosynthesis de novo was accomplished with the addition of the antimetabolite 6-mercaptopurine to the growth medium . Transfer RNAs specifically 13C-enriched in all methyl groups (57 atom %), C2 of adenine (60 atom %), and C2 of uracil (82 atom %) and C2 of cytosine (73 atom %) have been produced. J Cell Physiol, 1979 Oct, 101(1), 57 - 65 Trace element uptake by L-cells as a function of trace elements in a synthetic growth medium; Zombola R et al.; The concentration of trace elements in L-cells has been studied as a function of the trace metal content of the growth medium . Cells were cultured in synthetic media which contained varying trace amounts of the elements manganese, iron, cobalt, copper, zinc and molybdenum . The cellular concentration of the of the elements potassium, iron, copper and zinc were then determined . It was found that the cell accumulates trace metals at a different rate than they are made available . Deficiencies in zinc could be "induced" in the cell by increasing the concentration of iron, manganese and cobalt; cellular iron deficiencies were observed at larger medium concentrations of zinc, manganese, copper and cobalt . Trace metal uptake by the cell was seen to parallel the utilization by multicellular organisms. Cornell Vet, 1979 Oct, 69(4), 411 - 25 Trypanosoma theileri: a literature review and report of incidence in New York cattle; Schlafer DH; The incidence of infection in adult dairy cattle in New York State with Trypanosoma (Megatrypanum) theileri (Laveran 1902) was determined by culturing buffy coats of peripheral blood samples in tissue culture growth media . Three sample groups of cattle were studied and revealed an overall rate of trypanosome infection of 44.4% (67 of 151) as determined by a single culture . Fifty-seven cows, representing four herds from three different geographic locations in the Southern-tier region of the state, comprised the first group . The infection rates of these herds ranged from 56.5 to 100% . The second group consisted of 81 cows randomly selected from animals admitted to the Large Animal Clinic of the New York State College of Veterinary Medicine . Trypanosoma theileri was cultured from 25.9% (21 of 81) of these animals . Repeated blood cultures from a third group of thirteen yearling heifers during the spring and summer revealed an increase in the infection rate from 0% in May, to 66.7% (8 of 12) in September, with 76.9% (10 of 13) positive at least once during this period . These findings are compared with the reported incidence of bovine T . theileri infections in other areas of the United States and in other countries. Arch Biol Med Exp (Santiago), 1979 Oct, 12(3), 359 - 66 Regulation of collagen synthesis and maturation by 3,4-dehydroproline; Kerwar SS; Proline analogs are readily incorporated into collagen and noncollagen proteins . Since the imino acid content of collagen is greater than other proteins, it is suggested that the incorporation of a proline analog into cellular protein would have a maximal effect on collagen metabolism . Using a partially purified amino acyl tRNA synthetase preparation, various proline analogs were tested for their ability to inhibit Pro-tRNA synthesis . Amongst those tested, dehydroproline was the preferred inhibitor . Dehydroproline was also a substrate for amino acyl tRNA synthetase . When dehydroproline was added in vitro to membrane bound polysomes, the synthesis of collagenous proteins was preferentially inhibited . The addition of dehydroproline to mammalian cell cultures caused a marked reduction in prolyl hydroxylase activity . Under these conditions growth of cells, activities of lysyl; hydroxylase or lactic dehydrogenase were not affected . Reduction of prolyl hydroxylase activity by dehydroproline required protein synthesis . Removal of dehydroproline from the growth medium resulted in an increase in prolylhydroxylase activity . Hepatic fibrosis can be induced in rats by chronic administration of carbon tetrachloride . Under these conditions, the collagen content and prolyl hydroxylase activity of the liver is enhanced . Treatment of these fibrotic animals with dehydroproline results in a reduction of prolyl hydroxylase activity of the liver . A mechanism by which dehydroproline reduces prolyl hydroxylase activity will be discussed . Since prolyl hydroxylase plays a key role in the maturation and deposition of collagen, specific inhibitors of this enzyme are potentially useful in controlling collagen deposition in various pathological conditions. J Cell Sci, 1979 Oct, 39, 383 - 96 Intracellular distribution of lead in Tetrahymena during continuous exposure to the metal; Nilsson JR; Lead acetate (0.1--0.2%) forms a precipitate with the organic growth medium . The Tetrahymena cells ingest this lead-containing precipitate and cell growth is resumed after a variable lag period . Ingested lead is observed as electron-dense material in food vacuoles . Soon after exposure, cytoplasmic lead (preserved with certain fixation only) is revealed as electron-dense particles in cilia and in a halo around digestive vacuoles . Later the lead particles pervade the entire cell but after the lag period they are confined to membrane-bound spaces . In dilute growth medium, high concentrations of lead inhibit food-vacuole formation and cell growth . Under these conditions lead is deposited in alveoli of the pellicle and is also found in autophagic vacuoles and other membrane-limited structures . The study has revealed that lead enters Tetrahymena through the membrane of digestive vacuoles and through the cell surface . The change in distribution of lead during the lag period indicates that a mechanism is activated for removal of lead into membrane-bound spaces . The final storage of lead seems to be in lysosomes. Infect Immun, 1979 Oct, 26(1), 70 - 5 Adherence of Mycoplasma pneumoniae to glass surfaces; Feldner J et al.; Attachment of M . pneumoniae to glass was quantitated in an experimental system enabling the settling down of {3H}palmitic acid-labeled cells onto glass cover slips . Attachment of mycoplasmas suspended in buffer increased with temperature, decreased with higher ionic strength, and showed a maximum at about pH 5.5 . The findings suggest a participation of ionic bonds in the attachment process . Trypsin did not detach glass-bound mycoplasmas, and treatment of the cells with glutaraldehyde did not reduce their attachment to glass, suggesting that membrane components other than proteins may be involved in the attachment . Low concentrations (up to 20 mg/ml) of bovine serum albumin buffer . However, during the next few hours, attachment increased far above the bovine serum albumin control . This marked increase was reduced by more than half in the presence of chloramphenicol . Increased attachment was also observed when glucose (0.1 to 2 mg/ml) was added to the bovine serum albumin-containing buffer . The findings suggest different mechanisms for the attachment in protein-free buffer and in growth medium or glucose-containing bovine serum albumin buffer, respectively . The latter apparently requires metabolic activity of the mycoplasmas. Biochem J, 1979 Sep 15, 182(3), 847 - 59 Mechanisms of protein degradation in growing and non-growing L-cell cultures; Amenta JS et al.; L-cells prelabelled with {14C}leucine and {3H}thymidine were placed in either fresh growth medium (minimal essential medium with 10% serum) or stepdown medium (minimal essential medium) for 3 days . The 14C/3H ratio remained constant in the growing cultures and decreased in the stationary-phase cultures, indicating no protein turnover in growing cultures and a degradative rate of 0.6%/h in the stationary-phase cultures . Media analysis, however, indicated that 14C-labelled proteins were being degraded at approx . 1.2%/h in growing cultures and 1.7%/h in stationary-phase cultures . Additional studies indicated that a subpopulation of L-cells in the monolayer, comprising approx . 20--30% of the total, were lost in the original processing procedure . Experiments in which recoveries approached 100% by fixation of the monolayer in situ indicated that a protein-degrading subpopulation accounted for all the observed proteolysis in the growing cultures . Proteolysis in these cultures was only partially inhibited with NH4Cl, indicating that only a small part of the protein degradation was occurring in an activated lysosomal-autophagic system . NaF produced a more effective inhibition of proteolysis, but we were not able to distinguish whether this effect was on an ATP-requiring basal-turnover mechanism or a direct effect on unregulated activity of proteinases in the cell hyaloplasm . However, NH4Cl inhibited the proteolysis induced when cells were placed in stepdown medium, suggesting that the induced proteolysis was occurring via the autophagic system . We conclude that L-cells exist in at least two states with respect to protein degradation: (a) a subpopulation that is actively replicating and does not degrade cellular proteins, and (b) a second subpopulation of cells, derived from the preceding one, which degraded most of their labelled proteins, are not capable of further replication, and are not sedimented in an iso-osmotic EDTA buffer solution . In addition, proliferating L-cells, when placed in stepdown medium, begin to degrade cell protein through a mechanism involving autophagolysosomes. Int J Cancer, 1979 Sep 15, 24(3), 336 - 40 Transformation of feline embryo cells in culture by a chemical carcinogen; Rhim JS et al.; A feline embryo cell line was treated in vitro with various levels of 7,12-dimethylbenz{a}anthracene (DMBA) or dimethyl sulfoxide (control) . Repeat treatment of DMBA only induced in vitro transformation of feline embryo cells following clonal growth and selection . The morphologically altered cells formed large cell aggregates and grew in this aggregate form when suspended in liquid growth medium above an agar base, formed colonies in soft agar, and grew to high saturation densities . However, no progressively growing tumors were produced when cells were inoculated into nude athymic mice . The transformed lines were negative for feline oncornavirus-associated cell membrane antigen (FOCMA). J Cancer Res Clin Oncol, 1979 Sep, 95(1), 29 - 37 Control of in vitro cytotoxicity of positively charged liposomes; Panzner EA et al.; The parameters which influence the in vitro cytotoxicity of positively charged liposomes for L 1210 cells were analyzed . The cytotoxicity was liposome/cell ratio-dependent . It also depended upon the mole fractions of stearylamine (SA) to phosphatidylcholine (PC) . There was no difference between the cytotoxicity of unilamellar and multilamellar vesicles but the cytotoxic effect of free SA was about 4 times greater than that of liposome incorporated SA at a molar ratio of 1:4, SA:PC, respectively . The process which resulted in cell death was irreversible after 60 min of cell-liposome contact . The simultaneous presence of neutral liposomes or of positively charged liposomes with a lesser charge density decreased the cytotoxic effect of liposomes with a higher SA content . The cytotoxicity could be decreased by trypsinization of cells following exposure to liposomes while treatment of cells with trypsin prior to the exposure to positively charged liposomes had no effect on the subsequent cytotoxicity . The cytotoxicity was also decreased if cells were incubated in the presence of sodium azide . The usual concentration of serum (10%) present in the growth medium had no effect on the cytotoxicity while preincubation of cells with liposomes in 80% serum resulted in full protection . The protective effect of serum could be replaced by the albumin fraction. Cancer Res, 1979 Sep, 39(9), 3661 - 72 Quantitative models for growth inhibition of human leukemia cells by antitumor anthracycline derivatives; Kanter PM et al.; A batch elution method with hydroxylapatite was developed to assay DNA damage by a set of antitumor anthracycline derivatives and was standardized with respect to the kinetics of unwinding, size of the alkaline unwinding unit, and fidelity of selective elution of single and double-stranded DNA . The method was applied to a study of a set of 10 antitumor anthracycline derivatives which inhibit growth of CCRF-CEM human leukemia cells over a range of potencies exceeding four orders of magnitude . The derivatives, including Adriamycin, daunorubicin, and carminomycin, vary in structure at C-4 and C-13, with substitutions at C-14 and N and stereochemical differences at C-4' . In a static model (fixed drug concentrations and incubation times), the potency {1/ID37 (concentration of agent that inhibits cell growth by 37%)} of nine of the ten derivatives may be expressed as functions of DNA damage (n), inhibition of thymidine incorporation (l), and drug retention (r): ID37 = Ka(r/l . n)kb, with a coefficient of correlation of greater than 0.99 . A kinetic model with 4-demethoxydaunorubicin (varying concentrations and incubation times) was also described . Following initial uptake and a period of rapid loss after cells are washed free of excess drug, the change in agent concentration in the cells follows first-order kinetics . The cell index (cell number after 50 hr in drug-free growth medium/cell number after initial 2-hr exposure with drug) may be expressed linearly in terms of the kinetics of drug loss (coefficient of correlation, greater than 0.98), or as functions of 1/n (coefficient of correlation, greater than 0.958), 1/l . n (coefficient of correlation, greater than 0.963, or r/l . n (coefficient of correlation, greater than 0.963) . These studies may be used to define a class of similarly acting anthracycline agents and to give some insight into the mechanism of action of the agents that fall within the class. J Med Chem, 1979 Sep, 22(9), 1104 - 9 Anticandidal activity of 5-fluorocytosine-peptide conjugates; Steinfeld AS et al.; An approach to the development of new anticandidal drugs is described that employs peptides as carriers of toxic agents into cells . 5-Flurorcytosine (5-FC) was chosen as a toxic agent with which to prepare 5-FC-peptide conjugates as models to test the carrier proposal . Model compounds were synthesized and then tested for antiyeast activity against S . Cerevisiae 9763, C . albicans 1-V, C . albicans WD 18-4, and C . Krusei 1-T . The 5-FC derivatives showed antiyeast activity comparable to 5-FC in all strains except C . krusei 1-T, in which case the compounds were less active . The solution stabilities of 5-FC conjugates at 37 degrees C were tested in the same growth medium used for susceptibility testing . The results indicated a range of stabilities where the half-life (t1/2) = 0.3--17.6 h . These results and those obtained in the susceptibility testing suggest extracellular hydrolysis and indicate that the type of linkage used to conjugate 5-FC to peptides will not provide appropriate compounds to evaluate the peptide-carrier concept. J Biol Chem, 1979 Aug 25, 254(16), 8067 - 73 The isolation and amino acid/sugar composition of human fibroblastoid interferon; Tan YH et al.; Human fibroblastoid interferon produced from an established human cell line was purified by controlled-pore glass and concanavalin A-Sepharose column chromatography followed by preparative two-dimensional gel electrophoresis . The purification procedure provided a 10% recovery of pure interferon with good reproducibility . The purified protein was homogeneous with respect to its molecular weight of 20,000 and net electrical charge at pH 2.5 . Interferon of high specific activity of 5 x 10(8) units/mg of protein was directly demonstrated in the polyacrylamide gel before staining with Coomassie brilliant blue . Parallel purification of a sham-induced interferon preparation did not yield an equivalent product indicating the purified interferon is not derived from uninduced cells or from the fetal calf serum of the tissue culture growth medium . Pure interferon was radioiodinated by Bolton-Hunter reagent . Amino acid analysis of the pure preparation shows interferon to be a leucine-rich glycoprotein containing a high percentage of glutamic/glutamine residues and that disulfide bridges(s) are important for its biological activity. Eur J Biochem, 1979 Aug 15, 99(1), 1 - 7 Level and turnover of polyadenylate-containing ribonucleic acid in Neurospora crassa in different steady states of growth; Sturani E et al.; Mycelia of Neurospora crassa in a steady state of growth in different media have a ribosomal content proportional to the rate of growth . Moreover, both the percentage of polysomes and the average ribosomal activity are about the same at all different growth rates . The content of polyadenylated RNA was determined in three different conditions of exponential growth, which allowed growth rates that ranged from 0.26 to 0.51 duplications/h, and was found to constitute about the same fraction of total RNA (4.5--5.2%) . Using a kinetic approach, an equation was derived which allowed determination of the average half-lives of polyadenylated RNA: in each medium the cultures were labeled from the moment of the inoculation with {32P}orthophosphate and were then given a 10-min pulse with {5-3H}uridine when they were in the exponential phase . It was found that the determined half-lives of polyadenylated RNA vary, depending on the growth medium, between 30 and 60 min, but with no direct correlation with the growth rate . Moreover, the rate of synthesis of polyadenylated RNA relative to that of stable RNA decreased with the growth rate . On the basis of previous data on the rates of synthesis of stable RNA, it was possible to make an evaluation of the absolute rate of synthesis of polyadenylated RNA . Whereas the rate of synthesis of stable ribosomal RNA increases as a function of the square of the number of duplications per hour, the increase in the rate of synthesis of polyadenylated RNA with the growth rate is much less consistent . It is concluded that in Neurospora the growth rate does not depend on the rate of synthesis of mRNA but rather on the rate of synthesis of rRNA, which sets both the ribosomal level and the steady-state level of mRNA. Int J Cancer, 1979 Aug, 24(2), 225 - 34 Importance of a collagen substratum for stimulation of capillary endothelial cell proliferation by tumour angiogenesis factor; Schor AM et al.; Tumour extracts were obtained from rat Walker 256 carcinoma and examined for the presence of tumour angiogenesis factor (TAF) in vivo before being used in tissue culture experiments . Capillary endothelial cells derived from cow brain white matter were used to study the effects of TAF-containing tumour extracts on cell proliferation in vitro . The cells were grown on two types of substrata: (1) plastic tissue culture dishes and (2) hydrated gels made of rat tail tendon type I collagen . Human platelets or platelet-released factors were introduced into the system because of the many inter-relationships known to exist between platelets, collagen and endothelial cells . If trypsin was used during the preparation of TAT, the resulting batches stimulated endothelial cell proliferation only when the cells were growing on a collagen substratum and either platelets or platelet-released factors were present in the growth medium . If incubation with trypsin was omitted from the TAF extraction procedure, the resulting batches stimulated cell growth both on plastic and on collagen . A synergistic interaction also occurred between these TAF-containing tumour extracts and platelet-released factors . This effect was always more marked when the cells were growing on collagen than when on plastic . These data suggest that the nature of the substratum affects the response of the endothelial cells to TAF and to platelet-released factors. Cancer Res, 1979 Aug, 39(8), 3194 - 8 Toxicity of metabolic benzo(a)pyrenediones to cultured cells and the dependence upon molecular oxygen; Lorentzen RJ et al.; The three quinone metabolites of carcinogenic benzo(a)pyrene, the isomeric benzo(a)pyrenediones (6, 12; 1,6; 3,6), are toxic to cultured hamster cells at low concentrations . The reduction in cell number, observed after treatment with these metabolites, is the result of both direct cell killing and the inhibition of growth, since DNA synthesis is inhibited very early after treatment with benzo(a)pyrene 1,6-dione when little cell death has occurred . The rate of RNA synthesis was also inhibited by treatment of cells with benzo(a)pyrene 3,6-dione . These actions of the benzo(a)pyrenediones toward hamster cells can be eliminated or substantially reduced by the removal of oxygen from the growth medium and atmosphere in which the cells are incubated . In contrast, anaerobic conditions do not reduce the cytotoxicity observed with the alkylating agent ethyl methanesulfonate . These results support the hypothesis that benzo(a)pyrenediones, and other biologically active quinones, owe their activity to oxidation-reduction cycles involving quinone, hydroquinone, and molecular oxygen; the reactive reduced oxygen radicals and semiquinone radical formed during these cycles may be responsible for the observed cellular injury and inhibition of cellular processes. Mutat Res, 1979 Aug, 62(1), 35 - 42 Antagonism by propidium of petite induction by ethidium and ethidium azide in Saccharomyces cerevisiae; Fukunaga M et al.; Propidium, a phenanthridinium dye similar to ethidium, did not induce petite mutations in non-growing yeast cells in contrast to ethidium . Combined exposure to ethidium and an excess of propidium for periods up to 2 h resulted in the expected petite induction expressed after subsequent plating on growth medium . As incubation was continued with propidium, the numbers of petites declined on subsequent plating whether the drug had been added before, during, or after the mutagenic treatment by ethidium . Propidium decreased petite induction by the monoazide analog of ethidium when applied before but not after photolytic attachment of the drug. Proc Natl Acad Sci U S A, 1979 Aug, 76(8), 3670 - 2 Adenine aminohydrolase: occurrence and possible significance in trypanosomid flagellates; Kidder GW et al.; Adenine aminohydrolase (EC 3.5.4.2) from four species of Leishmania and from Crithidia fasciculata was examined for specific activities, affinity for substrate (adenine), and stability to heat . All were found to be strongly and non-competitively inhibited by both coformycin and deoxycoformycin, two tight-binding inhibitors of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) . Deoxycoformycin is the more potent inhibitor of the two . Neither inhibitor was active against the purine phosphoribosyltransferases . When deoxycoformycin was added to the defined growth medium containing hypoxanthine as the purine source, the growth of C . fasciculata was unaffected, but when adenine was the purine source for the organism, severe inhibition resulted . This implies that hypoxanthine is the obligatory base for nucleotide synthesis and that the adenine phosphoribosyltransferase (AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7) is, in some manner,idenied access to exogenous substrate. J Protozool, 1979 Aug, 26(3), 510 - 8 Secretion of hexosaminidase isozymes by Tetrahymena; Vick GW 3rd et al.; Tetrahymena pyriformis strain HSM secrete large quantities of lysosomal acid hydrolases into the medium . The finding that 2 isozymes of beta-N-acetylhexosaminidase (2-acetamido-2-deoxy-beta-D-glucoside acetamidodeoxyglucohydrolase; EC 3.2.1.30) could be resolved by DEAE ion exchange chromatography and of possible differences between the secreted mixture and the intralysosomal hexosaminidase activity suggested that Tetrahymena might prove useful for studies of the control of lysosomal hydrolase isozyme secretion . In the present paper, we report a considerable purification of these isozymes and describe a number of their kinetic properties . Four isozymes were isolated into 2 major forms, A1 and B1, and 2 minor forms, A2 and B2, which were similar to the respective major forms in all kinetic properties tested . Hexosaminidase B1 has a molecular weight of approximately 93,000 daltons and is inhibited by high concentrations of p-nitrophenyl-N-acetyl-beta-D-glucosaminide . The inhibition is reversed by ethanol . Hexosaminidase B1 has a molecular weight of approximately 93,000 daltons and is inhibited by high concentrations of p-nitrophenyl-N-acetyl-beta-D-glucosaminide . The inhibition is reversed by ethanol . Hexosaminidase A1 has a molecular weight of approximately 170,000 and is not inhibited by high concentrations of substrate . The A forms are relatively less active against p-nitrophenyl-N-acetyl-beta-D-galactosaminide than the B forms . Neither hexosaminidases A1 or B1 has any endo-beta-N-acetylhexosaminidase activity . Comparison of the properties of the 2 major isozymes suggested that measurements of activity obtained under different assay conditions could be used to quantitate the amount of each isozyme in a mixture of the two . Log- and early stationary-phase cells secrete approximately 20% of isozyme A and 80% of isozyme B into the medium or into a dilute salt solution . With increasing culture age the fraction of isozyme A secreted rises to over 90% . Supplementation of the proteose-peptone growth medium with glucose causes a decrease in total hexosaminidase subsequently secreted but with no change in proportion of each isozyme . Cells suspended in a dilute salt solution containing 0.1 mM L-propranolol secrete slightly more isozyme A than do control cells suspended without L-propranolol . Phenoxybenzamine (0.2 mM) causes a slight decrease in the proportion of isozyme A released. Biochim Biophys Acta, 1979 Jul 27, 574(1), 39 - 47 Plasma membrane lipids of human diploid fibroblasts from normal individuals and patients with cystic fibrosis; Riordan JR et al.; The lipid composition of isolated plasma membranes of human skin fibroblasts is described for the first time . Plasma membranes from a number of strains of fibroblasts from patients with cystic fibrosis and matched normals were isolated by a recently described procedure and analysed for major phospholipid classes, cholesterol and fatty acids . No differences in the quantities of these compounds were detected between cells of the two different origins . The fetal calf serum used to supplement the growth medium contained relatively more palmitoleate and oleate but less stearate than the membranes . There were also no consistent differences between cystic fibrosis and normal membranes in terms of the fatty acid compositions of their individual phospholipid classes . Consistent with this lack of chemical change in the lipids of membranes of cystic fibrosis cells, the degree of fluorescence polarization of diphenylhexatriene, an index of fluidity, was also unchanged. Mol Gen Genet, 1979 Jul 2, 174(1), 33 - 8 Regulation of s-amino acids biosynthesis in Saccharomycopsis lipolytica; Morzycka E et al.; ATP-sulfurylase, cysteine synthase, homocysteine synthase, arylsulfatase and beta-cystathionase in Saccharomycopsis lipolytica are repressed on the addition of methionine, homocysteine or cysteine to the growth medium . The use of appropriate mutants enabled us to demonstrate that the synthesis of these enzymes is regulated by the system involving at least two low-molecular weight effectors--most likely cysteine and methionine (or their close derivatives). Mikrobiologiia, 1979 Jul-Aug, 48(4), 738 - 44 {Microbial cenosis in the initial stage of spruce needle decomposition}; Zaitsev SA et al.; The formation of saprophytic microbial cenosis at the primary stage of decomposition of spruce needles was studied by the method of scanning electron microscopy with parallel inoculations into growth media . The composition of the cenosis was found to differ depending on whether the needles were decomposed on the surface of the forest floor or on the soil without any flooring . The characteristics of the formation of the saprophytic microbial cenosis are described . The cenosis is formed from individual species of the soil microbial complex and from some representatives of the epiphytic microbial cenosis which change here becoming saprophytes instead of biotrophs . Yeasts and yeast-like organisms predominate at the primary stage of decomposition of spruce needles. J Natl Cancer Inst, 1979 Jul, 63(1), 29 - 41 Growth of normal and malignant human mammary epithelial cells in culture; Kirkland WL et al.; Normal and malignant human mammary epithelial cells were placed in culture . Normal cells were recovered from late-lactation milk and breast fluids, and malignant cells were isolated from primary breast tumors by collagenase digestion . The concentration of cells obtained from breast fluid samples was inversely proportional to the volume of fluid secreted . Most of these cells adhered rapidly to the substrate, did not replicate, displayed Fc receptor-dependent phagocytic activity, and were thus identified as macrophages . The remaining cells grew out into large islands comprised of one or two distinct morphologic types of mammary epithelial cells . Optimum growth of these cells was obtained in medium buffered to pH 6.8, and the epidermal growth factor markedly prolonged the exponential growth phase of the cells . Two morphologically distinct populations of epithelial cells were also observed in cultures established from individual breast tumors . Growth of the malignant cells was relatively unaffected by the pH of the culture medium, and the cells were unresponsive to exogenously added hormones . Overgrowth of malignant epithelial cells in primary cultures by stromal fibroblasts was retarded by replacement of standard growth medium with fresh medium containing a serum substitute; growth of the malignant epithelial cells was unaffected . A feeder layer of mitomycin C-treated human fibroblasts increased the plating efficiency of both normal and malignant cells in primary culture and also facilitated passage of these cells to secondary and tertiary cultures. Biull Eksp Biol Med, 1979 Jul, 88(7), 76 - 8 {Synthesis of alpha-fetoprotein, albumin and transferrin by long-term cultured cells of murine hepatoma}; Aleksanian IuT; The capacity of continuous cell of XXIIa mouse hepatoma (strain MHXXIIa) to synthesize alpha-fetoprotein, albumin and transferrin was studied by immunoautoradiography . Albumin and transferrin were detected in the polyethylene glycol concentrated growth medium of hepatoma cells on the 5th year (the 55th month) of their cultivation . alpha-fetoprotein was not found . Only transferrin was revealed in the growth medium of hepa toma cells of the 8th year (the 92d month) of cultivation . Two clonal cultures obtained on the 8th year of hepatoma cell cultivation were also characterized by the ability to synthesize transferrin . The continuous mouse hepatoma cells retained their malignancy . The agar micro-precipitation reaction showed the presence of alpha-fetofetoprotein in lyfogel concentrated serum of mice with tumors formed after inoculation of the hepatoma cells of the 5th year of cultivation . However, alpha-fetoprotein was not detected in the serum of mice with tumors induced by inoculation of the hepatoma cells of the 8th year of cultivation. Mikrobiologiia, 1979 Jul-Aug, 48(4), 711 - 5 {Candida mycoderma growth inhibition with phenol and the autoselection of resistent forms under continuous pH-stat cultivation}; Bril'kov AV et al.; The effect of phenol on the growth rate and respiration was studied with the yeast Candida mycoderma cultivated in the pH-static conditions with continuous recording of the principal kinetic parameters of the population . The kinetics of growth inhibition with phenol was studied . Adaptation of the culture in terms of the growth rate and the rate of oxygen uptake was detected within 10--15 hours of cultivation . A new strain of C . mycoderma Phen . R . isolated using the technique of autoselection upon continuous cultivation for a long period of time, at a phenol concentration of 1.5 g/l in the growth medium, had an elevated growth rate (2.2 times higher) in these conditions as compared with the parent culture and required less oxygen. Biochim Biophys Acta, 1979 Jun 13, 554(1), 156 - 67 Active K+ transport in Mycoplasma mycoides var . Capri . Net and unidirectional K+ movements; Leblanc G et al.; Analysis of the cation composition of growing Mycoplasma mycoides var . Capri indicates that these organisms have a high intracellular K+ concentration (Ki: 200--300 mM) which greatly exceeds that of the growth medium, and a low Na+ concentration (Na+i: 20 mM) . Unlike Na+i,K+i varies with cell aging . The K+ transport properties studied in washed organisms resuspended in buffered saline solution show that cells maintain a steady and large K+ concentration gradient across their membrane at the expense of metabolic energy mainly derived from glycolysis . In starved cells, K+i decreases and is partially compensated by a gain in Na+ . This substitution completely reverses when metabolic substrate is added (K+ reaccumulation process) . Kinetic analysis of K+ movement in cells with steady K+ level shows that most of K+ influx is mediated by an autologous K+-K+ exchange mechanism . On the other hand, during K+ reaccumulation by K+-depleted cells, a different mechanism (a K+ uptake mechanism) with higher transport capacity and affinity drives the net K+ influx . Both mechanisms are energy-dependent . Ouabain and anoxia have no effect on K+ transport mechanisms; in contrast, both processes are completely blocked by dicyclohexylcarbodiimide, an inhibitor of the Mg2+ -dependent ATPase activity. Biochim Biophys Acta, 1979 Jun 12, 585(2), 210 - 9 Epoxide hydrase in Trypanosoma cruzi epimastigotes; Yawetz A et al.; 1 . Microsomal fractions from Trypanosoma cruzi epimastigotes catalyze the hydration of styrene oxide to styrene glycol . The activity is linear up to 45 min of incubation, is proportional to microsomal protein concentration within certain range, and has an optimum pH of 8.5 . 2 . Double-reciprocal plots indicate a Km value of 5.3 . 10(-4) M for styrene oxide and a V of 29.6 pmol of styrene glycol formed/min per mg protein at 37 degrees C . 4-Chlorophenyl-2,3-epoxypropyl either (Ki = 2.08 . 10(-4) M) and juvenile hormone I (Ki = 2.7 . 10(-4) M) are competitive inhibitors; whereas, 1-chloro-2,3-epoxypropane is a non-competitive inhibitor . The enzyme is induced about three-fold by 5 mM phenobarbital in the growth medium . 3 . The epoxide hydrase is not activated by detergents but rather inhibited by concentrations of Tween-80 and Lubrol as low as 0.025% . 4 . Experiments with intact cells indicate that about 3% of {8-14C}styrene oxide penetrates after 90 min of incubation; whereas, over 30% of juvenile hormone I is found intracellularly after the same incubation period . Intracellular styrene oxide is hydrated to styrene glycol to a significant extent and the in vivo hydration is increased by pretreatment with phenobarbital and inhibited upon the addition of 4-chlorophenyl-2,3-epoxypropyl ether . Only a small amount of the intracellular juvenile hormone I is recovered as the corresponding diol ester. Parasitology, 1979 Jun, 78(3), 343 - 54 The uptake in vitro of dyes, monosaccharides and amino acids by the filarial worm Brugia pahangi; Chen SN et al.; The uptake in vitro of various substances by Brugia pahangi was investigated using infective larvae obtained from Aedes aegypti and worms removed from Meriones unguiculatus at 2, 3, 10, 20 and 90 days post-infection . Worms incubated in growth medium 199 containing 1% Trypan blue possessed demonstrable dye in the oral orifice, the anterior oesophageal lumen and the external openings of the vulva and the cloaca or anus but the dye was not found in the gut lumen even after incubation for 24 h . No uptake of ferritin particles into the intestine of the worms was found and no fluorescence could be demonstrated in the gut lumen of worms incubated in medium containing 50% (v/v) fluorescein isothiocyanate-conjugated calf serum for up to 24 h . Trypan blue uptake by the gut of Aspiculuris tetraptera was clearly observed after incubation for several hours . The uptake of D-glucose and L-leucine by B . pahangi was demonstrated using autoradiographic and scintillation counting techniques and incorporation into worm tissues was detected . Glucose was found to be readily incorporated in the apical, glycogen-rich areas of the myocytes of worms of all ages studied and in the uterine epithelium of the adult female . In contrast, a lower incorporation of D-glucose was found in the eggs, embryos and vas deferens and especially in the gut . The incorporation of L-leucine occurred throughout the tissue of the worms during a 30 min incubation . Labelling was also located over the surface of the cuticle of the worms, when incubated for a period of 15 to 60 min in L-{H}leucine . Scintillation counting techniques demonstrated that there was no uptake of 14C-labelled L-glucose or sucrose by B . pahangi . The data presented on the uptake in vitro of nutrients or other compounds by infective larvae and adult stages of B . pahangi did not demonstrate an intestinal route of uptake but indicated that the transcuticular route of uptake may be employed. J Gen Microbiol, 1979 Jun, 112(2), 389 - 92 The components of Mycoplasma salivarium and its growth medium that are responsible for film formation; Ichimaru H et al.; Studies on film production by mycoplasmas revealed that film was produced by completely disintegrated mycoplasma cells on Noble agar in the presence of horse serum . Film production was due to an enzymic reaction between mycoplasma lipase, possibly phospholipase A, and phospholipid in serum. J Cell Physiol, 1979 Jun, 99(3), 319 - 26 Production of factors required for cell attachment and spreading is a constitutive property in mouse A9 cells; Dairkee SH et al.; It is demonstrated here that cells in a suspension culture of an established mammalian cell line release non-dialyzable factors into their growth medium . These factors are capable of promoting the adhesion and spreading of these cells on a generally non-attachable substratum and also promote spreading on an adhering substrate . Evidence is presented which demonstrates that the spreading promotion activity of the condition medium is dependent on the cell density of the culture from which it was derived . Dilution of the conditioned medium results in a proportionate dilution of the spreading promotion activity . The results clearly demonstrate that the production of this spreading promotion factor is continued even in the absence of cell to substrate attachment. Biochim Biophys Acta, 1979 Jun 1, 585(1), 94 - 9 Transport of L-carnitine induced by prednisolone in an established cell line (CCL 27) . A possible explanation of the therapeutic effect of glucocorticoids in muscular carnitine deficiency syndrome; Molstad P et al.; Prednisolone (10(-8)--10(-5) mol/l) in the growth medium for 24 h increased the rate of uptake of L-{3H}carnitine in an established cell line (CCL 27) to 164 +/- 6% (mean +/-S.E.) of the rate observed in untreated cells . At the same time the intracellular content of free L-carnitine increased about 20% . The simultaneous addition of prednisolone (10(-6) mol/l for 24 h) and L-carnitine (10(-4) mol/l for 96 h) to the growth medium increased the rate of uptake to 225 +/- 8% (mean +/-S.E.) of that in untreated cells . The increase seemed to be mediated through an increase in number of carriers, as judged by the increase in V of the transport process with unchanged Km . Phosphodiesterase I, an enzyme mainly localized in the plasma membrane, increased its activity about 3.5 times when cells were stimulated with prednisolone . Thus, it seems that the increase in the rate of uptake of L-carnitine mediated by glucocorticoids, is part of a more general effect on the plasma membrane . The observations offer an explanation to the observed clinical improvement in patients with muscular carnitine deficiency treated with glucocorticoids and/or L-carnitine. J Cell Physiol, 1979 Jun, 99(3), 303 - 12 Relationship between histidyl-tRNA level and protein synthesis rate in wild-type and mutant Chinese hamster ovary cells; Lofgren DJ et al.; A preliminary investigation was carried out to determine how conditional lethal mutants affected in particular aminoacyl-tRNA synthetases may be used to study the role of tRNA charging levels in protein synthesis . The relationship between rate of protein synthesis and level of histidyl-tRNA in wild-type cultured Chinese hamster ovary cells was determined using the analogue histidinol to inhibit histidyl-tRNA synthetase activity . This response was compared with that obtained using a mutant strain with a defective histidyl-tRNA synthetase that phenotypically shows decreased rates of protein synthesis at reduced concentrations of histidine in the growth medium . The approach used was based on measuring the histidyl-tRNA levels in live cells . The percentage charging was estimated by comparing {14C}histidine incorporated into alkali-labile material in paired samples, one of which was treated with cycloheximide, five minutes before terminating during the incubation, to produce maximal aminoacylation . Wild-type cells under histidinol inhibition exhibited a sensitive, sigmoidal relationship between the level of histidyl-tRNA and the rate of protein synthesis . A decrease in the relative percentage of acylated tRNA (His) from 46% to 35% elicited a large reduction in the rate of protein synthesis from 90% to 30% relative to untreated cells . An unpredicted result was that the relationship between protein synthesis and histidyl-tRNA in the mutant was essentially linear . High acylation values for tRNA (His) were associated with rates of protein synthesis that were not nearly as high as in wild-type cells . These findings suggest that the charging charging levels of tRNA (His) isoacceptors could play a regulatory role in determining the rate of protein synthesis under conditions of histidine starvation in normal cells . The mutant appears to be a potentially useful system for studying the pivotal role of tRNA charging in protein synthesis, assuming that the altered response in the mutant is caused by its altered synthetase. J Cell Sci, 1979 Jun, 37, 157 - 67 A ligand-receptor model for the cohesive behaviour of Dictyostelium discoideum axenic cells; Jaffe AR et al.; Axenically grown cells of D . discoideum Ax-2 harvested in the log phase of growth, cohere rapidly when shaken in phosphate buffer . After 3.5 days in the stationary phase of growth, cells become completely non-cohesive . Although they do not stick to each other, stationary phase cells do stick to both log phase cells and aggregation-competent cells . The cohesion of stationary phase cells with these other 2 cell types is inhibited by both EDTA and the low-molecular-weight factor which we have previously demonstrated in stationary-phase growth medium . There is a decline in the sensitivity of slime mould cell cohesion to the low-molecular-weight inhibitory factor as the cells become aggregation-competent . This effect parallels the developmentally-regulated decline in sensitivity to EDTA . The low-molecular-weight inhibitor is not a chelating agent, however . The effect of the inhibitor seems to be specifically against contact sites-B mediated cohesion . We suggest that the simplest cohesive mechanism which can explain our results, is that the EDTA-sensitive cohesion of log phase cells could be dependent on a ligand-receptor system. J Immunol, 1979 Jun, 122(6), 2516 - 20 In search of alpha 1-microglobulin on the lymphocyte surface; Akerstrom B et al.; alpha 1-Microglobulin was found by immunofluorescence not to be associated with human lymphoid and nonlymphoid cell lines . No accumulation of alpha 1-microglobulin was detected in culture media of these cell lines . A weak membrane fluorescence with anti-alpha 1-microglobulin on peripheral lymphocytes could not be blocked by the purified protein . No release of alpha 1-microglobulin into the growth medium was seen by normal cultured leukocytes . Treatment of normal lymphocytes, erythrocytes, and various cell lines with solubilization techniques did not yield any alpha 1-microglobulin . alpha 1-Microglobulin and protein HC display immunologic and biochemical identity . However, anti-protein HC stained almost all of the tested cell lines and normal lymphocytes . Blocking experiments with the purified protein were not successful . Antibodies reacting with a minor impurity (50,000 d) in the alpha 1-microglobulin or protein HC preparations could be absorbed from anti-alpha 1-microglobulin with normal leukocytes and a lymphoid cell line. Mol Gen Genet, 1979 May 23, 173(1), 71 - 84 Chromosomal and extrachromosomal control of senescence in the ascomycete Podospora anserina; Tudzynski P et al.; In Podospora anserina senescence leading to cellular death occurs regularly after prolonged vegetative propagation . However, the life span of this ascomycete may be extended by various means: 1 . Mutations in a least 8 morphogenetic genes belonging to 4 linkage groups postpone drastically or even prevent in certain pairwise combinations (e.g . i viv) the onset of senescence . 2 . Inhibitors of mt DNA and of mitochondrial protein synthesis show a life prolonging effect when added in low concentrations to the growth medium . 3 . A similar effect was found when mycelia were fed exclusively on non repressive carbon sources . Whereas the anti-aging effect of specific mutated genes is rather permanent, the life prolonging action of the inhibitors and carbon sources is restricted and temporary . These substances have no long lasting effect, since after their removal from the medium aging proceeds . Physiological experiments have further shown the existence of three phases in the life span of Podospora anserina . During the juvenile phase aging is prevented by all of these compounds; during the presenescent phase aging is prevented by inhibitors of mt DNA only, and during the senescent phase aging is irreversible . Senescence may be induced in juvenile protoplasts by DNA extracted from senescent mycelia . This, together with the well known fact that senescence is extrachromosomically inherited, points to extrachromosomal DNA as the causative agent of senescence . This kind of DNA may be connected with or perhaps located in the mitochondria . Collectively, the data are consistent in showing that the syndrome of senescence in Podospora anserina is controlled by a chromosomal-extrachromosomal interaction . In this system, extrachromosomal DNA, perhaps a mt DNA, is identical with the infectious principle initiating the decay of the cell, and nuclear genes supervise its expression. J Gen Microbiol, 1979 May, 112(1), 15 - 27 Characteristics of a lipolytic and fatty acid-requiring Butyrivibrio sp . isolated from the ovine rumen; Hazlewood G et al.; A naturally occurring fatty acid-requiring Butyrivibrio sp . (strain S2), isolated from the ovine rumen, deacylates plant galactolipids, phospholipids and sulpholipids to obtain sufficient fatty acid for growth . Growth in vitro was promoted by adding to the growth medium a single straight-chain saturated fatty acid (C13 to C18) or vaccenic acid . Palmitoleic and oleic acids also supported growth but gave lengthy lag phases probably due to their toxicity . Linolenic and linoleic acids supported good growth but they were completely hydrogenated to trans-11-octadecenoic acid which was incorporated into the bacterial complex lipids . No chain elongation, chain shortening or desaturation of the added fatty acids occurred and all were substantially incorporated into bacterial lipids of the plasmalogen type, partially as a new type of hydrophobic grouping derived from two molecules of fatty acid . The absence of fatty acid unsaturation poses the question of the maintenance of membrane fluidity within this bacterium. Mikrobiologiia, 1979 May-Jun, 48(3), 400 - 5 {Efficiency of glucose utilization by Gluconobacter oxydans}; Uspenskaia SN et al.; The dynamics of growth and acid production in Gluconobacter oxydans cultures at various glucose concentrations has been investigated . Dinitrophenol (10-4 M) was shown to have effect on hexonic acids formation by the growing culture and resting cells of G . oxydans, as well as on the values of Y0 . G . oxydans molar growth yield for glucose have been calculated . Oxidative transformation of glucose was shown to be not involved in energy supply of processes connected with the reproduction of G . oxydans . Glucose concentration in the growth medium determines the efficiency of utilization of this carbon and energy source. J Cell Physiol, 1979 May, 99(2), 239 - 46 Selection and characterization of a varient of murine L5178Y lymphoma resistant to local anesthetics; Yau TM et al.; A varient of murine L5178Y lymphoma resistant to procaine hydrochloride (PH) was selected by exposing the cells to gradual increments of PH in the growth medium until the cell grew exponentially in the presence of 1.5 mM PH . Using cinephotomicrography, it was observed that the majority of cells that initially succumbed to PH failed to undergo successful mitosis . With respect ot chromosomal, cell size distribution and flow microfluorometric analyses, the PH-resistant cells are very similar to a spontaneous tetraploid cell line (R1T) previously cloned . The isolated cells, designated R1/P, were also found to be cross-resistant to analogues of PH, namely, lidocaine, tetracaine and dibucaine . The naturally-occurring tetraploid cell line (R1T) was also found to be more resistant to local anesthetics, although not to the same extent as R1/P cells . Since the enzyme that hydrolyzes procaine appears to be absent in all these lymphoid cell lines, the difference in resistance does not appear to depend on differences in the ability of these cells to remove the agent . It is suggested that an alteration in the structure and/or function of the plasma membrane in R1/P cells have rendered them either less sensitive to the membrane-perturbing effects of the local anesthetics or less permeable to local anesthetics molecules . The ability of local anesthetics to affect membranes and cytoskeleton structures may play a role in the genesis and/or selection of these cell variants. Prikl Biokhim Mikrobiol, 1979 May-Jun, 15(3), 475 - 7 {Effect of a deficiency of carbon, nitrogen, phosphorus and magnesium in the growth medium on the mechanical properties of Escherichia coli cell walls}; Chemeris NA et al.; Values of modulus of elasticity of cell walls and strength level of cells Escherichia coli cultivated in the carbon, nitrogen and phosphorus deficient media or incubated in the magnesium-free medium were determined . Elastic modulus of cells grown in the magnesium-free medium was by two order of magnitude lower than that of the control cells . Elastic modulus of cells cultivated in the nitrogen and carbon deficient media was by one and two orders of magnitude lower than in the control cells whereas strength level was by 1.15 and 1.39 times higher, respectively . Elastic modulus of cells grown in the phosphorus deficient medium remained undetermined and strength level of those cells proved to be the lowest (0.9 of the control). J Med Chem, 1979 May, 22(5), 592 - 4 Synthesis and biological activity of 5-fluoro- and 5-methyl-1,3-oxazine-2,6(3H)-dione; Bobek M et al.; 5-Fluoro-1,3-oxazine-2,6(3H)-dione (3-oxa-FU) was synthesized by reacting 3-oxauracil with fluoroxytrifluoromethane and decomposing the adduct in the presence of a catalytic amount of Et3N . 5-Methyl-1,3-oxazine-2,6(3H)-dione (3-oxathymine) was prepared by polyphosphoric acid catalyzed ring closure of beta-(N-ethoxycarbonylamino)-2-methacrylic acid and by treatment of citraconimide with sodium hypochlorite . As determined in vitro, 3-oxa-FU was markedly inhibitory to S . faecium (ID50 = 9 X 10(-8) M) and E . coli (ID50 = 1 X 10(-7) M) but was less active against leukemia L-1210 cells (ID50 = 1 X 10(-5) M) . At 1 x 10(-4) M, 3-oxathymine was inactive in these cell systems . Inhibition of the growth of S . faecium by 3-oxa-FU was reversed competitively by the natural pyrimidines . The relatively rapid hydrolysis of the compounds in the growth media is a major factor in determining their biological effectiveness. J Bacteriol, 1979 May, 138(2), 492 - 8 Protein and ribonucleic acid syntheses in heat-damaged and heat-killed Escherichia coli; Dean RG et al.; Protein and ribonucleic acid (RNA) syntheses were measured in both lethally injured and thermally damaged viable cells after heating at lethal temperatures . Immediately after heating, cells were incubated in growth media containing either {14C}leucine or {3H}uracil . The labeled cells were subsequently treated with penicillin . Viable cells were shown to lyse, and the intact nonviable cells were collected by centrifugation . The results showed that after heating, protein and RNA synthesis were reinitiated in the penicillin-sensitive cell population, but there was no detectable protein or RNA synthesis in the heat-killed cells which were resistant to penicillin . The lack of protein or RNA synthesis in lethally damaged cells during the entire recovery period may be interpreted to reflect the lethal thermal damage. J Biochem (Tokyo), 1979 May, 85(5), 1367 - 75 Comparison of inducible and constitutive kynureninases of Neurospora crassa; Tanizawa K et al.; Two types of kynureninase were isolated from Neurospora crassa IFO 6068 . The formation of one of them, which was separated from the inducible kynureninase by DEAE-cellulose chromatography, was independent of the presence of tryptophan in the growth medium . Ouchterlony double-diffusion analysis and immunochemical titration indicated that the constitutive-type enzyme is immunologically different from the inducible enzyme . We confirmed by a selective assay method with antiserum that the addition of tryptophan to the medium does not affect the formation of one of the enzymes (constitutive-type) . The constitutive kynureninase was purified approximately 650-fold and was free of the inducible enzyme as judged by analytical gel electrophoresis . The molecular weight and optimum pH values of both enzymes are very similar . However, the constitutive enzyme shows much higher activity and affinity for L-3-hydroxykynurenine than for L-kynurenine, suggesting that the enzyme functions biosynthetically as a 3-hydroxykynureninase . Constitutive kynureninase activities were widely found in all the fungi tested, whereas the inducible enzyme activity was not present in Mucor or Rhizopus species . The inducible enzymes of all the Neurospora strains examined were shown to be immunologically identical. Eur J Biochem, 1979 Apr 2, 95(2), 287 - 93 Demonstration by membrane reconstitution of a butanol-soluble intermediate in the biosynthesis of the O9 antigen of Escherichia coli; Kanegasaki S et al.; The activity in vitro of the mannan-synthesizing system of Escherichia coli O9 depends on the presence of glucose in the growth medium of the bacteria . Inactive membranes of E . coli strain F988 grown without gain mannan-synthesizing activity by reconstitution with a butanol extract obtained from the same bacteria grown with glucose . Inactive membranes could also be restored to biosynthetic activity by incubation with UDP-glucose in the presence of magnesium chloride . In this magnesium-ion-dependent reaction, a glucolipid was formed which was extractable with butanol . It could be used for the reconstitution of inactive membranes . The products of incubations with GDP-mannose of reconstituted and active membranes were analysed for electrophoretic mobility in sodium dodecylsulfate/polyacrylamide gel electrophoresis, molecular weight and composition . In all cases they proved to be the mannan attached to a hydrophobic mannose carrier, presumably a glucolipid . These results suggest that a glucolipid is the intermediary mannose acceptor in the biosynthesis of the O9 antigen. Appl Environ Microbiol, 1979 Apr, 37(4), 670 - 5 Effect of inorganic sulfide on the growth and metabolism of Methanosarcina barkeri strain DM; Mountfort DO et al.; Minimal growth of Methanosarcina barkeri strain DM occurred when sulfide was omitted fromthe growth medium, and addition of either sodium sulfate or coenzyme M to sulfide-depleted media failed to restore growth . Optimal growth occurred in the presence of 1.25 mM added sulfide, giving a molar growth yield (YCH4) of 4.4 mg (dry weight) of cells per mmol of CH4 produced . Increasing sulfide to 12.5 mM led to decrease in YCH4 (1.9 mg {dry weight}/mmol of CH4), in the specific growth rate and in be intracellular levels of adenosine triphosphate . However, the specific rate of methane production increased . The data suggested that at elevated sulfide levels (12.5 mM) the decrease in YCH4 might be a result of an increase in the relative energy needed for maintnenace and of uncoupling of growth from energy production. J Cell Biol, 1979 Apr, 81(1), 1 - 9 On the mechanism of 5-bromodeoxyuridine induction of prolactin synthesis in rat pituitary tumor cells; Biswas DK et al.; GH12C1, a clonal strain of rat pituitary tumor cells in culture (GH cells), does not produce detectable amounts of prolactin . 5-Bromodeoxyuridine (BrdUrd), the thymidine analogue, at sublethal concentrations (3-5 microgram/ml) induces prolactin synthesis in these cells . BrdUrd also induces prolactin synthesis in F1BGH12C1 cells, a BrdUrd resistant (BrdUrdr) substrain isolated from GH12C1 cells . The F1BGH12C1 strain is not drug dependent, but its resistance to BrdUrd is a stable phenotype . The significant features of the induction of prolactin synthesis in the BrdUrdr strain are the increased net synthesis of prolactin and the shortening of the lag period of prolactin induction . As BrdUrd concentration in the growth medium is increased, the rise in prolactin synthesis parallels the increased incorporation of BrdUrd into DNA . Prolactin synthesis is first detected when BrdUrd replaces 20-25% of the thymidine in DNA . BrdUrd can replace up to 75-80% of the thymidine within 2 d of treatment . Partial starvation of these cells under specified growth conditions does not affect the general growth pattern of the cells, general protein synthesis, and thymidine uptake, but does affect DNA synthesis . When cells are cultured under conditions in which DNA synthesis is preferentially inhibited, BrdUrd does not induce prolactin synthesis, suggestive of a DNA-mediated mechanism of action for the drug. Mol Cell Endocrinol, 1979 Apr, 14(1), 81 - 97 Prolactin receptors in primary cultures of carcinogen-induced rat-mammary tumors; Costlow ME et al.; 7,12-Dimethylbenz{alpha}anthracene-induced rat mammary tumors were dissociated with collagenase and hyaluronidase and placed into primary culture . In most cultures, specific binding of 125I-labeled ovine prolactin was (i) lower than that for the original tumors unless bovine prolactin (1 microgram/ml) had been added to the dissociation medium, and (ii) varied with the type of growth medium used . The level of prolactin binding in cultured cells was relatively constant for the first 7-10 days . Prolactin binding in cultured cell homogenates was maximal at pH 7.0, proportional to cell protein, specific for prolactin, and reached a steady state by 12 h at 22 degrees C . The half-maximum inhibition of 125I-labeled prolactin binding by unlabeled prolactin was 100 ng/ml for cells grown in 5-1000 ng of prolactin/ml . After prolactin was removed from the growth medium, the level of available binding sites progressively increased, reached a maximum at 48 h and then declined . At 48 h, the dissociation constant for prolactin binding (Kd approximately 1 x 10(-10) M) was comparable to that in tumors . In some cultured tumors, a 48-h treatment with 0.5 or 1.0 ng of prolactin/ml caused an apparent increase in the level of prolactin binding . Prolactin increased DNA synthesis and its removal caused a reduction in {3H}estradiol and {3H}-R5020 binding to cultured cell cytosols. Cancer Treat Rep, 1979 Apr, 63(4), 587 - 90 In vitro growth of cutaneous T-cell lymphomas; Gazdar AF et al.; It is relatively easy to propagate EB virus-transformed normal and malignant B lymphocytes in vitro . Normal T lymphocytes divide for short periods of time after exposure to many mitogens . Exposure of normal T lymphocytes to lymphocyte-conditioned medium (LCM) permits them to divide for longer periods of time, but permanent cell lines cannot be established . Intial attempts to grow malignant T cells from patients with cutaneous T-cell lymphomas (CTCL) in unsupplemented growth medium resulted in the establishment of four EB virus-transformed B-lymphoblastoid lines . The responses of CTCL cells to mitogens and LCM varied from unresponsive to near normal . Subsequent attempts to grow CTCL cells in medium supplemented with mitogens or LCM resulted in the establishment of two cell lines lacking B-cell markers or EB virus . The cells of both lines initially had the ability to form E rosettes, although one of the lines has lost this ability with passage . The two lines can be distinguished from normal T cells by having some or all of the following properties: long-term proliferation, tumorigenecity in nude mice, gradual loss of dependence on mitogen or LCM, and convoluted nuclear morphology. Cell, 1979 Apr, 16(4), 885 - 93 Transformed mammalian cells secrete specific proteins and phosphoproteins; Senger DR et al.; We have examined the proteins secreted into the growth medium by normal and transformed cells . Transformed cell lines from several mammalian species all secrete proteins in the 58,000 dalton molecular weight range . These proteins are all immunologically related and are secreted at low levels or not at all by the parental normal cell lines . Secretion of the 58K proteins occurs with either DNA or RNA virus transformation and with spontaneous transformation . The transformed cells also secrete phosphoproteins in the same size range, but these are immunologically distinct from the 58K proteins mentioned above . The sizes of the phosphoproteins are species-specific and unrelated to the transforming virus . Incubation of conditioned media from transformed cell cultures with gamma-32P-ATP labels phosphoproteins of the same sizes, indicating the presence in the media of both protein kinase and substrate . All three properties (58K protein, phosphoprotein, in vitro phosphorylation) are closely correlated with transformation in cells transformed by temperature-sensitive viruses . The biological implications of these results remain unknown, but the results may be relevant to recent data on the (phospho)proteins and protein kinase encoded by RNA tumor viruses and the molecular basis of the transformed phenotype. Biochim Biophys Acta, 1979 Mar 28, 562(1), 162 - 76 Regulation of purine de novo synthesis in cultured human fibroblasts: the role of P-ribose-PP; Gordon RB et al.; Procedures for assaying the rate of purine de novo synthesis in cultured fibroblast cells have been compared . These were (i) the incorporation of {(14)C}-glycine or {(14)C}formate in alpha-N-formylglycinamide ribonucleotide (an intermediate in the purine synthetic pathway) and (ii) the incorporation of {(14)C}-formate into newly synthesised cellular purines and purines excreted by the cell into the medium . Fibroblast cells, derived from patients with a deficiency of hypoxanthine phosphoribosyltransferase (HPRT-) (EC 2.4.2.8) and increased rates of purine de novo synthesis, were compared with fibroblasts from healthy subjects (HPRT+) . Fetal calf serum, which was used to supplement the assay and cell growth medium, was found to contain sufficient quantities of the purine base hypoxanthine to inhibit purine de novo synthesis in HPRT+ cells . This inhibition was the basis of differentiation between HPRT- and HPRT+ cells . In the absence of added purine base, both cell types had similar capacities for purine de novo synthesis . This result contrasts with the increased rates of purine de novo synthesis reported for a number of human HPRT- cells in culture but conforms recent studies made on human HPRT- lymphoblast cells . The intracellular concentration and utilisation of 5-phosphoribosyl-1-pyrophosphate (P-Rib-PP), a substrate and potential controlling factor for purine de novo synthesis, were determined in HPRT- and HPRT+ cells . The rate of utilisation of P-Rib-PP in the salvage of free purine bases was far greater than that in purine de novo synthesis . Although HPRT- cells had a 3-fold increase in P-Rib-PP content, the rate of P-Rib-PP generation was similar to HPRT+ cells . Thus, in fibroblasts, the concentration of P-Rib-PP appears to be critical in the control of de novo purine synthesis and its preferential utilisation in the HPRT reaction limits its availability for purine de novo synthesis . In vivo, HPRT+ cells, in contrast to HPRT- cells, may be operating purine de novo synthesis at a reduced rate because of their ability to reutilise hypoxanthine. J Biol Chem, 1979 Mar 25, 254(6), 1944 - 50 Regulation of hydroxydocosanoic acid sophoroside production in Candida bogoriensis by the levels of glucose and yeast extract in the growth medium; Cutler AJ et al.; Cells of Candida bogoriensis produce as a major extracellular lipid 13-{(2'-O-beta-D-glucopyranosyl-beta-D-glucopyranosyl)oxy}docosanoic acid 6',6''-diacetate (Ac2Glc2HDA), the diacetylated sophoroside of 13-hydroxydocosanoic acid (HDA), along with mono- and unacetylated derivatives . The HDA glycolipid production is greater than 2 g/liter when cells are grown on a "standard" medium of 3% glucose and 0.15% yeast extract . Either lowering the glucose concentration (0.5 to 2.0% glucose, at 0.2% yeast extract) or raising the yeast extract concentration (2 to 4% yeast extract at 3% glucose) greatly decreased the yield of this glycolipid, as well as its rate of synthesis measured by {14C}acetate incorporation . Total HDA production was also depressed on the low glucose medium, as was the activity of UDP-glucose:HDA glucosyltransferase, the first enzyme involved in the synthesis of Ac2Glc2HDA from HDA . Levels of acetyl-CoA:Glc2HDA acetyltransferase were not decreased by growth on a low glucose medium, however, even under conditions in which glycolipid production was less than 4% of that found in the standard medium . Low levels of the HDA glycolipids were monitored by high pressure liquid chromatography of their p-bromophenacyl esters, formed by the action of alpha,beta-dibromoacetophenone on the sodium salt of the lipid in the presence of a crown reagent catalyst . This regulation of extracellular Ac2Glc2HDA production by the nutrient composition of the growth medium may represent an important property in the adaptation of C . bogoriensis to its natural environment, the phyllosphere. Biochim Biophys Acta, 1979 Mar 22, 583(3), 394 - 402 Inhibition of cell-substratum attachment of cultured rat heart cells by protein synthesis inhibitors; Speicher DW et al.; Addition of cycloheximide to growth medium of neonatal rat heart cell cultures prevented cell-substratum attachment . Even concentrations of cycloheximide which inhibited only 50% of normal protein synthesis prevented some cells from attaching . Cells which required the longest time to attach were not dependent on protein synthesis . The kinetics of cell-substratum adhesion in the presence of various concentrations of cycloheximide supported the hypothesis that repair of damaged cell membranes was required prior to attachment . An alternate hypothesis that protein synthesis was required for substratum attachment either to synthesize new unique proteins or higher concentrations of existing proteins not damaged by enzymes was not supported by experimentally obtained data . If the second hypothesis were true, no cells would have attached when protein synthesis was completely inhibited (greater than 95%) and all cells should have been equally affected by protein synthesis inhibition; such was not the case . Inhibition of mRNA formation by actinomycin D also should have inhibited attachment completely and this was not observed . Since attachment was minimally affected by actinomycin D, protein synthesis on long-lived mRNA was apparently sufficient for cell-substratum adhesion. Mol Gen Genet, 1979 Mar 5, 170(3), 309 - 17 Relaxation of stable RNA synthesis by a plasmid-borne locus; Yarus M; The plasmid pMY3, which was constructed so as to express the Su+7 amber suppressor tRNA gene, also relaxes control of stable RNA synthesis in stringent cells . The relaxation is not growth medium or strain-dependent and does not occur in the presence of the vehicle alone . When expression of the effective sequence is diminished, in a lysogen of phi 80d3 ilv+Su+7, the sequence no longer affects RNA synthesis . The relaxation is general, extending to all or almost all tRNA loci, including tRNAs located in the ribosomal spacer regions, and to all ribosomal RNAs . Relaxed plasmid-carrying strains are still able to elevate guanosine tetra- and penta-phosphate levels in response to amino acid starvation, but steady state levels are somewhat diminished . Aminoacyl-tRNA falls to control levels when the plasmid-carrying strain is deprived of amino acid . Therefore, the relaxed strain perceives amino acid starvation, but does not respond normally . These properties define a novel locus which relaxes stringent control. Am J Vet Res, 1979 Mar, 40(3), 387 - 92 Production of labile Newcastle disease virus progeny after infection of chicken embryo cells in the presence of caffeine; Olson NJ et al.; A study was undertaken to examine the effects of caffeine on Newcastle disease virus (NDV) infection of chicken embryo cells . Addition of 10 mM caffeine to the growth medium produced 95% reduction in progeny synthesis, 63% reduction in RNA synthesis, 45% reduction in protein synthesis, and 25% reduction in hemadsorption ability in NDV-infected cultures when compared with untreated, infected cultures . Purified NDV obtained from caffeine-treated, infected cultures was more sensitive to ultraviolet irradiation and to damage by freezing and thawing than was observed in untreated virus cultures . The SDS-polyacrylamide gel electrophoresis revealed that purified virions contained the same complement of polypeptides, but there was a significant variation in the quantities of several of the NDV polypeptides. Cancer Res, 1979 Mar, 39(3), 1051 - 5 Comparative studies of glucose metabolism in HTC, RLC, MH1C1, and Reuber H35 rat hepatoma cells; Schamhart DH et al.; Carbohydrate metabolism by four rat hepatoma cell lines in culture, namely, Reuber H35, MH1C1, RLC, and HTC, has been investigated . Glucose utilization by H35 and MH1C1 cells is lower than that by RLC and HTC cells . The four cell lines also differ with respect to the accumulation of lactic acid in the growth medium; in particular, H35 cells show uptake of lactic acid, rather than accumulation in the medium . Specific activities of a number of enzymes involved in glycolysis, gluconeogenesis, pentose phosphate pathway, and glycogen formation were determined in the four cell lines . A direct relationship between the differences was found for the activities of some enzymes belonging to carbohydrate metabolism, namely, hexokinase, pyruvate kinase, aldolases A and B, glucose-6-phosphate dehydrogenase, and phosphogluconate dehydrogenase and the differences found for glucose utilization by the different cell lines. Appl Environ Microbiol, 1979 Mar, 37(3), 471 - 9 Evidence for the subcellular localization and specificity of chlordane inhibition in the marine bacterium Aeromonas proteolytica; Nakas JP et al.; Sublethal levels (10 to 100 micrograms/ml) of the chlorinated insecticide chlordane (1,2,4,5,6,7,8,8-octachloro-3a,4,7,7a-tetrahydro-4,7-methanoindan) were introduced into the growth medium of the marine bacterium, Aeromonas proteolytica . Chlordane inhibited the synthesis of an extracellular endopeptidase by almost 40% but exhibited no such inhibition of the extracellular aminopeptidase also produced during the growth cycle . Studied with 14C-labeled chlordane demonstrated that the insecticide was not biologically degraded under the test conditions used and that up to 75% of the recoverable chlordane was cell associated within 48 h . Studied with uniformly labeled L{14C}valine and {2-14C}uracil established that neither the transport nor the incorporation of these protein and ribonucleic acid precursors was inhibited by chlordane . Separation of the membrane fractions using isopycnic centrifugation localized 14C-labeled chlordane in the cytoplasmic membrane . Also, chlordane inhibited the membrane-bound adenosine 5'-triphosphatase while the soluble (released) form of this enzyme remained unaffected . These data indicate that chlordane resides in the cytoplasmic membrane and may cause specific alterations in membrane-associated activities. J Antibiot (Tokyo), 1979 Mar, 32(3), 205 - 11 Purification and partial characterization of an antibiotic produced by Myxococcus coralloides; Arias JM et al.; A strain of Myxococcus coralloides producing an antibiotic capable of inhibiting growth of Gram-positive bacteria was isolated . Antibiotic production occurred during vegetative growth but not during myxospore formation . The antibiotic was extracted from the growth medium with chloroform and purified by adsorption on silicic acid and by preparative silica gel thin-layer chromatography . The purified antibiotic showed a resistance to heat, acid, alkali and proteolytic enzymes . Chromatographic and electrophoretic behavior as well as infrared, ultraviolet and mass spectra are presented. Biochim Biophys Acta, 1979 Feb 26, 572(2), 352 - 62 Mutant and immunochemical studies on the involvement of cytochrome b5 in fatty acid desaturation by yeast microsomes; Ohba M et al.; The involvement of cytochrome b5 in palmitoyl-CoA desaturation by yeast microsomes was studied by using yeast mutants requiring unsaturated fatty acids and an antibody to yeast cytochrome b5 . The mutants used were an unsaturated fatty acid auxotroph (strain E5) and a pleiotropic mutant (strain Ole 3) which requires either Tween 80 and ergosterol or delta-aminolevulinic acid for growth . Microsomes from the wild-type strain possessed both the desaturase activity and cytochrome b5, whereas those from mutant E5 contained the cytochrome but lacked the desaturase activity . Microsomes from mutant Ole 3 grown with Tween 80 plus ergosterol were devoid of both the desaturase activity and cytochrome b5, but those from delta-aminolevulinic acid-grown mutant Ole 3 contained cytochrome b5 and catalyzed the desaturation . The cytochrome b5 content in microsomes from mutant Ole 3 could be varied by changing the delta-aminolevulinic acid concentration in the growth medium, and the desaturase activity of the microsomes increased as their cytochrome b5 content was increased . The antibody to yeast cytochrome b5, but not the control gamma-globulin fraction, inhibited the NADH-cytochrome c reductase and NADH-dependent desaturase activities of the wild-type microsomes . It is concluded that cytochrome b5 is actually involved in the desaturase system of yeast microsomes . The lack of desaturase activity in mutant Ole 3 grown with Tween 80 plus ergosterol seems to be due to the absence of cytochrome b5 in microsomes, whereas the genetic lesion in mutant E5 appears to be located at ther terminal desaturase. Biochim Biophys Acta, 1979 Feb 19, 583(1), 55 - 62 4-Hydroxybenzyl alcohol . A metabolite produced during the biosynthesis of thiamine in Escherichia coli; White RH; 4-Hydroxybenzyl alcohol was identified by gas chromatography-mass spectrometry as a metabolite of Escherichia coli when it is grown on a medium containing no thiamine or 4-methyl-5-beta-hydroxyethyl thiazole . 4-Hydroxybenzyl alcohol was found to be derived from L-tyrosine and the amount produced was found to be inhibited by the addition of thiamine to the growth medium . The amount of 4-hydroxybenzyl alcohol produced, as measured by isotopic dilution, was shown to be equivalent to the amount of thiamine formed . Based on these observations, it was concluded that 4-hydroxybenzyl alcohol is the cleavage product produced during the biosynthesis of the thiazole moiety of thiamine from tyrosine. Appl Environ Microbiol, 1979 Feb, 37(2), 208 - 12 Convenient procedures for the biosynthesis, isolation, and isotope labeling of cytochalasins; Zabel RA et al.; Efforts to improve small-scale yields of useful cytochalasins by fermentation resulted in selection of an enriched aflatoxin medium which increased yields by fivefold over those reported in the literature . With Helminthosporium dematoideum and Zygosporium masonii in stationary culture for 3 weeks, cytochalasins B and D were obtained in quantities approaching 700 and 500 mg/liter, respectively . It appears that the critical component in this growth medium is factors associated with whole wheat . By using these procedures, coupled with improvements in isolation, supplementation with two radioactive phenylalanine species readily produced {14C}- or {3H}cytochalasin B . Oxidation of carrier-free radioactive cytochalasin B to cytochasasin A readily provided this labeled congener as well . The isotopic ocnversion of precursor to crystalline products that met analytical criteria ranged from 2 to 4% of the administered radioactivity. J Bacteriol, 1979 Feb, 137(2), 1031 - 4 Effect of growth medium on the relative polypeptide composition of cellular outer membrane and released outer membrane material in Escherichia coli; Loeb MR et al.; When ratios of the major polypeptides of the outer membrane isolated from cells of Escherichia coli B grown in minimal medium containing either a single amino acid or several amino acids were compared, no difference was observed . However, the ratio of these polypeptides in outer membrane material released into the medium during logarithmic phase growth on these two media was markedly different. Proc Natl Acad Sci U S A, 1979 Feb, 76(2), 833 - 6 Heme biosynthesis in Friend erythroleukemia cells: control by ferrochelatase; Rutherford T et al.; The activities of the enzymes of heme biosynthesis (except protoporphyrin oxidase) have been followed during the induction of Friend cells in culture . All the enzyme activities increased after induction with dimethyl sulfoxide . The activities of the intermediate enzymes were much higher than those of delta-aminolevulinate synthase {succinyl-CoA:glycine C-succinyltransferase (decarboxylating), EC 2.3.1.37}, the initial enzyme, or ferrochelatase (protoheme ferro-lyase, EC 4.99.1.1), the final enzyme of the pathway . Ferrochelatase activity was not detectable in the uninduced cell . delta-Aminolevulinate synthase activity increased during the first 24 hr of induction; porphobilinogen deaminase activity began to increase after 48 hr and ferrochelatase activity, after 72 hr . However, the induction of heme synthesis followed the same time course as that of ferrochelatase activity, not that of delta-aminolevulinate synthase activity . The cellular growth medium was found to contain traces of protoporphyrins . Thus, ferrochelatase is shown to be rate limiting for heme synthesis during early stages of Friend cell induction . A Friend cell variant (Fw), which is not inducible except in the presence of exogenous hemin, was also studied . All the enzymes of heme synthesis except ferrochelatase were inducible by butyric acid . Ferrochelatase was not inducible by butyric acid or hemin plus butyric acid . These cells also excrete protoporphyrin, The failure to induce ferrochelatase activity is believed to be the cause of, not a consequence of, the noninducibility of this cell line. J Gen Virol, 1979 Feb, 42(2), 265 - 78 Stimulation of ornithine decarboxylase by human cytomegalovirus; Isom HC; Human cytomegalovirus (HCMV) infection of low serum-arrested confluent whole human embryo (Flow 5000) cells markedly stimulated ornithine decarboxylase (ODC) activity . Increased ODC activity was apparent by 12 h post-infection . The capacity of HCMV to stimulate ODC was: (1) dependent upon multiplicity of infection; (2) eliminated when the virus was neutralized with specific antiserum; and (3) sensitive to ultraviolet irradiation . Virus-mediated induction, in contrast to high serum induction of ODC, was not subject to inhibition by polyamines added to the growth medium . Phosphonoacetic acid (PAA) which blocks HCMV replication by inhibiting the activity of HCMV-specific DNA polymerase and which does not prevent HCMV induced stimulation of cell DNA synthesis, reversibly inhibited HCMV-induced stimulation of ODC activity by 74% . Studies with PAA indicated that HCMV-induced stimulation of ODC activity is independent of cell DNA synthesis and that the mechanism regulating virus-induced stimulation may be related to the HCMV-specific DNA polymerase. J Cell Sci, 1979 Feb, 35, 307 - 20 On the reduced intercellular adhesiveness of virally transformed BHK21 cells; Edwards JG et al.; Baby hamster kidney fibroblasts (BHK21 cells) transformed by polyoma or Rous sarcoma viruses aggregate less than the untransformed parental cells when incubated in growth medium in a gyratory shaker for 18-24 h . This difference can be measured by electronic particle counting, or by filtering aggregated suspensions of 32P-labelled cells through bolting fabric . The aggregation of transformed derivatives is not enhanced by the presence, during aggregation of epsilon-amino caproic acid, an inhibitor of plasmin activation . Some lines of transformed BHK21 cells do not appear less adhesive than untransformed cells in a short-term aggregation assay, and none adheres markedly less well when seeded onto homotypic cell sheets . The decreased aggregation of transformed cells is consistent with suggestions that LETS protein is involved in intercellular adhesion of fibroblasts as well as in attachment of cells to non-cellular substrates . If so, the short-term aggregation of freshly trypsinized cells may depend on secretion of LETS from an intracellular pool. Eur J Clin Invest, 1979 Feb, 9(1), 5 - 10 The effects of albumin bound fatty acids on the platelet inhibitory function of human endothelial cells; Nordoy A et al.; This study was carried out to evaluate the effects of albumin-bound fatty acids on the anti-platelet effects of endothelial cells . Primary cultures of human endothelial cells (ECM), grown in confluent monolayers, were incubated with plasma or growth medium enriched with albumin-bound fatty acids (FA) for 2-20 h . The effects of ECM on ADP-induced platelet aggregation (PA) and collagen-induced PA and prostaglandin synthesis in platelet-rich plasma were tested . ECM released an inhibitor of platelet reactions which resembled the activity of PGI2 (prostacyclin) . The inhibitory activity was increased by preincubation of ECM with arachidonic acid (AA) . A moderate decrease of the activity was obtained by incubation with long-chain saturated, monoenoic and dienoic unsaturated fatty acids . A pronounced decrease of the inhibitor was obtained by incubation with di-homo-gamma-linolenic acid (DHLA) . Paired combinations of AA with the other fatty acids in the incubation medium partially restored the inhibitory activity obtained by the separate FA . The stimulation of the inhibitor by AA was dose dependent and high concentrations of AA reduced this activity . The present study indicates that the quantity and quality of the plasma free fatty acids can affect the endothelial cells' ability to act as a non-thrombogenic surface. J Biochem (Tokyo), 1979 Feb, 85(2), 591 - 9 Studies on cellulases of a phytopathogenic fungus, Pyricularia oryzae Cavara . III . Multiplicity of beta-glucosidase, and purification and properties of a second component; Hirayama T et al.; To determine the relationship between the induction patterns of three components of beta-glucosidase of Pyricularia oryzae and carbon sources in the growth medium, various culture conditions were examined . Avicel, hydroxyethylcellulose and methyl-beta-D-glucoside as the carbon source induced both beta-glucosidase components, GB-1 and GB-2, whereas cellobiose and gentiobiose induced only one component, GB-1 . Thus, these two components were induced independently and hence thought to be isozymes . The GB-2 was purified to homogeneity by ion exchange and gel filtration chromatographies from two different cultures on methyl-beta-D-glucoside and Avicel . The specific activity of GB-2 when salicin was used as substrate was approximately 5.9 mg glucose/min/mg protein . GB-2 was found to be an oligomeric glycoprotein, which consisted of two subunits with molecular weight of approximately 120,000, comprising a relatively large number of acidic amino acids and mannose, as is the case with GB-1 . These two isozymes were clearly different in thermostability, GB-2 being more thermolabile than GB-1 . However, the same carboxyl group (pKa 4.2--4.8) was found to be strongly implicated in the formation and dissociation of the enzyme-substrate complex for both of the enzymes, from the analysis of kinetic parameters as a function of pH. Biochem Genet, 1979 Feb, 17(1-2), 57 - 75 Inborn errors of cobalamin metabolism: effect of cobalamin supplementation in culture on methylmalonyl CoA mutase activity in normal and mutant human fibroblasts; Willard HF et al.; We have examined the effect of addition of hydroxocobalamin to growth medium on the activity of the adenosylcobalamin-requiring enzyme methylmalonyl CoA mutase in normal human fibroblasts and in mutant human fibroblasts derived from patients with inherited methylmalonicacidemia . The mutant cell lines were assigned to four distinct genetic complementation groups (cbl A, cbl B, cbl C, and cbl D), each deficient in some step in the synthesis of adenosylcobalamin from hydroxocobalamin . After control cells were grown in cobalamin-supplemented medium, mutase holoenzyme activitiy increased markedly in a time- and concentration-dependent fashion . Growth in cobalamin-supplemented medium had no effect on mutase activity in some mutant lines belonging to the cbl B group, while activity increased severalfold in other cbl B mutants and in all cbl A, cbl C, and cbl D mutants examined, although mutase activity was still less than 10% of control . Comparison of mutase holoenzyme activity and total propionate pathway activity suggests that enhancement of mutase activity in mutant cells after cobalamin supplementation to values 5--10% of control may be sufficient to overcome the inherited metabolic block and to restore total pathway activity to normal. Mol Gen Genet, 1979 Jan 16, 169(1), 63 - 6 Reversal of protection by light of the ethidium bromide induced petite mutation in yeast; Hixon SC et al.; An intermediate in the ethidium bromide (EB) induced petite mutation pathway may be destabilized by daylight light to