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reexpression of hprt activity following cell fusion with polyethylene glycol.polyethylene glycol-1000 (peg-1000) induced fusion of hprt (e.c. 2.4.2.8) deficient chinese hamster cells with alpha-galactosidase a (e.c. 2.3.1.22) deficient cells from a patient with fabry's disease yielded hybrids which contained both human and hamster hprt, g6pd (e.c. 1.1.1.49), and aprt (e.c. 2.4.2.7) and chinese hamster alpha-galactosidase b. thus peg-1000 mediated somatic cell fusion led to reexpression of chinese hamster hprt. it did not restore the expression of human alpha-galactosidas ...1978209782
study on the mutagenicity of conjugated estrogens in human, animal and bacterial systems.conjugated estrogens were studied for mutagenicity (and implied carcinogenicity) in two strains of s. typhimurium, two normal and three neoplastic human lymphoid cell lines (the latter from burkitt's lymphoma patients) in cell culture and a chinese hamster cell line in diffusion chambers implanted into mice. no significant increase in mutation rate or chromosome aberrations were noticed after exposure to conjugated estrogens.1978217940
persistence of the fc cytophilic antibody receptor in macrophage hybrid cells.hybrid cell clones were obtained from mouse macrophase/ehrlich ascites cell fusions which showed the 'fc' cytophilic antibody receptor site, phagocytosis and motility typical of macrophages. with continued growth of the clones for 11 weeks, the receptor became undetectable but could be unmasked by dilute trypsin treatment; subsequent remasking of the receptor could be prevented with cycloheximide treatment of the hybrid cells. these hybrids produced cystic anaplastic tumours in neonatal irradiat ...1978400978
brefeldin a-induced increase of sphingomyelin synthesis. assay for the action of the antibiotic in mammalian cells.brefeldin a leads to an increase of sphingomyelin in chinese hamster ovary cells. the antibiotic is known to cause a dramatic morphological change of the endomembrane system in various mammalian cells resulting in a redistribution of golgi resident proteins to the endoplasmic reticulum (lippincott-schwartz, j., donaldson, j. g., schweizer, a., berger, e. g., hauri, h. p., yuan, l. c., and klausner, r. d. (1990) cell 60, 821-836). a strict correlation was found between the brefeldin a-induced inc ...19781544889
an analysis of concanavalin a-mediated agglutination in two chinese hamster ovary subclones whose surface phenotypes respond to maintenance in medium supplemented with dibutyryl cyclic amp. v. biochemical composition of the plasma membrane.we have used two chinese hamster ovary subclones whose surface phenotype has been extensively investigated with regard concanavalin a-mediated cell-cell agglutination and concanavalin a-induced receptor site clustering to investigate what changes in membrane composition, if any, can be correlated with the concanavalin a-detected changes in surface phenotype. these cell clones are uniquely disposed for this purpose since maintenance of the cells under different growth conditions produces changes ...1978218629
kinetics of dna repair in ultraviolet-irradiated and n-acetoxy-2-acetylaminofluorene-treated mammalian cells.repair kinetics after saturating doses of ultraviolet radiation (uv), n-acetoxy-2-acetylaminofluorene (aaaf), and combinations of both agents were studied in human fibroblasts proficient and deficient in excision repair, and in chinese hamster cells (v-79) deficient in excision repair. three techniques were used: unscheduled dna synthesis, photolysis of dna repaired in the presence of bromodeoxyuridine (brdurd), and measurements of sites sensitive to a uv-endonuclease. the repair rate appears to ...197819431355
responses of proliferating and non-proliferating chinese hamster cells to cytotoxic agents.the effects of various cytotoxic chemicals, as measured by viable cell counts, colony-forming ability and proliferative capacity, have been studied using chinese hamster cells in exponential and plateau (stationary) phases of growth. the proliferating cells were altogether more sensitive to the action of the drugs than non-proliferating cells. however, imuran (azathioprine) a purine antimetabolite, was more effective against the plateau-phase cells. the observed response of cells to imuran could ...1978638016
the aggregation of chinese hamster cells. aggregate size distributions and temperature dependence. 1978631210
the distribution of moderately repeated dna sequences among chinese hamster chromosomes. 1978631209
cytological effects of 1-(2-nitro-1-imidazolyl)-3-methoxy-2-propanol (misonidazole) on hypoxic mammalian cells in vitro.hypoxic chinese hamster v-79 cells were examined for light-microscope morphology, progression through the cell cycle, chromosomal aberrations, and viability, after incubation with the 2-nitroimidazole, misonidazole [1-(2-nitro-1-imidazolyl)-3 methoxy-2-propanol]. cytological examination of cells up to 42 hr after incubation with the drug at 37 degrees indicated that increasing contact time and increasing drug concentrations interfered with cell attachment and progressively slowed cell progressio ...1978626969
induction of thermotolerance in chinese hamster ovary cells by high (45 degrees) or low (40 degrees) hyperthermia. 1978626962
mutagenicity of heterocyclic nitrogen mustards (icr compounds) in cultured mammalian cells.the mutagenicity of six heterocylic nitrogen mustards (icr compounds) has been determined in a cultured mammalian cell system by use of resistance to the purine analog 6-thioguanine to select for mutation induction at the hypoxanthine-guanine phosphoribosyltransferase locus in chinese hamster ovary cells. the six compounds tested are icr 191, 170, 292, 372, 191-oh, and 170-oh. the first four contain a single 2-chloroethyl group (nitrogen half-mustard) on the side chain and are mutagenic, with th ...1978626955
assay of ribonucleotide reduction in nucleotide-permeable hamster cells.ribonucleotide reduction was measured in chinese hamster ovary cells made permeable to nucleotides by treatment with the detergent tween-80. when compared to the respective ribonucleotide reductase activity in partially purified cell extracts, cdp and gdp reductase activities in permeabilized cells responded in a similar fashion to dithiothreitol, ph, mgcl2, fecl3, substrate concentration and the presence of positive or negative allosteric effectors. at low protein concentrations both cdp and gd ...1978621224
dominance of colchicine resistance in hybrid cho cells.intraspecific hybrids of colchicine-sensitive with colchicine-resistant (chr) chinese hamster ovary cells were constructed, using six different colchicine-resistant clones from two independent series. in each instance, colchicine resistance was expressed in an incompletely dominant manner. some hybrid clones were examined further for the expression of the pleiotropic chr phenotype and for the cell surface p glycoprotein. these features of the colchicine-resistant phenotype were also expressed co ...1978566474
the selection of wild-type revertants from methotrexate permeability mutants.in a previous report, we described the selection and partial characterization of three distinct classes of methotrexate (mtx)-resistant chinese hamster ovary cells (cho) (1). class i cells contained a structural alteration in dihydrofolate reductase. class ii cells showed a alteration affecting the permeability of the drug. class iii cells, selected from class i cells, had an increased activity of the altered enzyme. in the work described here, the sensitivity of these lines to the diaminopyrimi ...1978566473
long-term culture of chinese hamster kupffer cell lines isolated by a primary cloning step. 1978564778
reduction of beta-galactosidase in the ketotic chinese hamster kidney.kidneys from normal, diabetic-nonketotic and ketotic chinese hamsters were homogenized, fractionated and assayed for beta-glucosidase, and beta-galactosidase activities. the kidneys of the ketotic animals were enlarged but the protein content in each subcellular fraction was similar in all three groups of animals. beta-glucosidase was found chiefly in the soluble fraction and no difference was observed in these animals. beta-galactosidase was distributed in both cytoplasmic and particulate fract ...1978417989
preparation and identification of partially fractionated chinese hamster chromosomes. 1978344049
defective regulation of cholesterol biosynthesis and plasma membrane fluidity in a chinese hamster ovary cell mutant.a chinese hamster ovary cell mutant resistant to killing by 25-hydroxycholesterol is shown to be defective in the regulation of cholesterol synthesis by exogenous cholesterol. when grown with various cholesterol supplements in delipidized serum, the mutant cell exhibits a variation in cholesterol content and plasma membrane fluidity that is not observed in the parental cell type.1978274716
histone phosphorylation and chromatin structure during mitosis in chinese hamster cells. 1978206429
the effect of bleomycin and its combined effect with radiation on cultured chinese hamster cells v-79. 197875797
toxicity, radiation sensitivity modification, and metabolic effects of dehydroascorbate and ascorbate in mammalian cells.dehydroascorbate, an electron affinic metabolite of vitamin c, sensitized ehrlich ascites tumor cells, in vivo, to radiation and was selectively toxic to v79 chinese hamster lung cells under hypoxic conditions (without radiation). the radiosensitization may involve both the electron affinic nature of dehydroascorbate as well as its ability to oxidize the intracellular nad(p)h and non-protein sulfhydryl. dehydroascorbate's oxidation of nad(p)h required higher concentrations than other sulfhydryl ...197823385
action of heparin on mammalian nuclei. ii. cell-cycle-specific changes in chromatin organization correlate temporally with histone h1 phosphorylation.the interaction of the polyanion heparin with the inner histones of chromatin has been used to detect changes in chromatin organization associated with cell-cycle traverse. synchronized populations of chinese hamster cells were obtained either in early g1 or near the g1/s boundary. the rate of interaction of heparin with chromatin-associated inner histones was measured using nuclei isolated from synchronized cell populations in different phases of the cell cycle. a g1-specific decrease in rate o ...1978626747
acid glycohydrolase in chinese hamster with spontaneous diabetes ii. n-acetyl-beta-d-hexosaminidase in plasma and tissues.excessively high activity of n-acetyl-beta-d-hexosaminidase (2-acetamido-2-deoxy-beta-d-glucoside acetamidodeoxy-glucohydrolase, ec 3.2.1.30) was found in the plasma of hereditary diabetic xa line animals, which however showed similar activity of this enzyme in both 12 00 x g supernatant and precipitate fractions of kidney homogenates as the nondiabetic m line animals. 0.1% triton x-100 extracts of kidney, spleen, hind leg muscle, cheek pouch and spinal cord of xa and m line animals also showed ...1978623771
alcohol dehydrogenase mutants of chinese hamster somatic cells resistant to allyl alcohol.alcohol dehydrogenase (alcohol: nad oxidoreductase, e.c. 1.1.1.1.) mutants of chinese hamster somatic cells were isolated as resistant to allyl alcohol (allr). the allr phenotypes of the mutant clones were reproducible with high fidelity and stable over long intervals of growth in the absence of the selecting drug. several mutants, adh-1, adh-2, adh-9 and adh-13, resistant to allyl alcohol were characterized. they have between 15 and 40% of the alcohol dehydrogenase activity of the wild-type cel ...1978640376
[effect of temperature on the duration of mitosis in mammalian cells cultivated outside the body].nine cell strains of different origin were cultivated at 28--36 degrees with the interval of 2 degrees. during the phase of logarithmic culture growth, the duration of mitosis (tm) was determined by means of colchicine method. a strict temperatural dependence tm, obeyed to arrenius' law was revealed. temperature range within which arreinius' law is valid in different cell strains is not alike. cultivation of l cells and connective tissue cells from chinese hamster to 39, 41and 42 degrees demonst ...1978565630
effects of hyperthermia on survival and progression of chinese hamster ovary cells. 1978563767
the radiation response of cultured mammalian v79-s171 cells exposed to a wide concentration range of sulphate salt solutions.the radiation response of chinese hamster cells (v79) exposed to a wide concentration range of li2so4, na2so4 or k2so4 has been examined and compared with the radiation response of cells treated in an identical manner with licl, nacl, or kcl solutions. at hypotonic salt concentrations, cells were radiosensitized by both the chloride and sulphate salts. at high salt concentrations, approximately greater than 0.9 m, a radioprotective effect was observed with both chloride and sulphate salts. at in ...1978305425
studies with bleomycin and misonidazole on aerated and hypoxic cells.bleomycin is a chemotherapuetic drug used primarily in the treatment of squamous-cell carcinoma, while misonidazole is an effective radiosensitizer and potent cytotoxic agent selectively affecting hypoxic cells. v79 chinese hamster cells were used to investigate the cytotoxicity of bleomycin (blm) under aerated and hypoxic conditions as a function of drug concentration. at a lowered temperature of 17.5 degrees c, or at an elevated temperature of 42.5 degrees c, hypoxic cells are more sensitive t ...197875740
heterogeneity in chinese hamster ribosomal dna.a discrete heterogeneity has been detected in chinese hamster ribosomal dna after eco r1 digestion of total dna followed by a southern transfer and hybridization with [125i]18s or [125i]28s ribosomal rna. digestion with eco r1 produces three fragments, 4.3, 6.0 and 9.5 x 10(6) daltons respectively, which hybridize with 18s rna. the smallest fragment also hybridizes with 28s rna. either length heterogeneity or sequence heterogeneity (i.e. presence of an additional eco r1 site in some of the rdna ...1978624239
biochemical characterization of a mutant asparaginyl-trna synthetase from chinese hamster ovary cells.the biochemical and physical properties of asparaginyl-trna synthetase from wild type chinese hamster ovary cells and a temperature sensitive mutant strain (lys 65a) are compared. the asparaginyl-trna synthetase in the mutant strain exhibits a greater temperature lability in vitro, a higher temperature-independent km for asparagine, and a lower temperature-dependent catalytic capacity than the enzyme from the wild type strain. the mutant enzyme shows no differences in its molecular weight, its k ...1978618867
cyclic amp levels and types i and ii cyclic amp-dependent protein kinase activity in synchronized cells and in quiescent cultures stimulated to proliferate.cyclic amp as well as the specific activity of cyclic amp-dependent protein kinase decreased from the first two hours after chinese hamster ovary cells in plateau phase were stimulated to proliferate by tripsinization of confluent cultures and dilution in fresh media. from two to five hours after this stimulation, the cyclic amp level and the specific activity of cyclic amp-dependent protein kinase increased two-fold. there was a 40--50% increase in the degree of activation of cyclic amp-depende ...1978202331
[cytotoxicity test on medical drugs--chromosome aberration tests with chinese hamster cells in vitro (author's transl)]. 1978750044
plasma membrane proteins and glycoproteins from chinese hamster cells sensitive and resistant to actinomycin d.plasma membrane proteins and glycoproteins have been isolated from chinese hamster cells of the spontaneously transformed dc-3f parental cell line and the dc-3f/ad x line with a high level of acquired resistance to actinomycin d. plasma membrane preparations from both cell lines band at 1.16 g/ml after isopycnic centrifugation. we present evidence to indicate differences in the leucylpeptide backbones of the antibiotic-sensitive cells and the drug-resistant dc-3f/ad x cells. in addition, there a ...1978748679
lipopolysaccharide effects on sensitive and resistant variant chinese hamster ovary cell lines.chinese hamster ovary (cho . k1 . pro) cell growth was inhibited by addition of a gram-negative bacterial lipopolysaccharide (lps) to the cell culture medium. growth inhibition began after three or four days of incubation, was dose-dependent up to a maximum at an lps concentration of 500 microgram/ml and was accompanied by cell shape changes and enhanced cytoplasmic vacuolization. formation of bizarre cho . k1 . pro cell shapes and vacuole formation were most pronounced after seven days of incub ...1978748676
unusually thick filaments in intrafusal muscle fibers of the chinese hamster. 1978744920
organization of mammalian chromosomal dna: supercoiled and folded circular dna subunits from interphase cell nuclei.chinese hamster cells (line v79/4) in the g2 phase of the mitotic cycle were lysed onto neutral sucrose gradients and the released chromosomal dna was characterized according to its size and shape by sedimentation velocity studies. using the intercalating agent, ethidium bromide, in the gradients and the induction of dna single- and double-strand breaks by irradiation, the dna was proved to be released into the gradient in supercoiled circular subunits whose homogenous size corresponds to 2.8 . ...1978735613
growth retardation in chinese hamster v-79 cells exposed to 1 mhz ultrasound. 1978734793
studies of the diphtheria toxin receptor on chinese hamster cells.concanavalin a, wheat germ agglutinin and the ovalbumin glycopeptide are all inhibitors of the cytotoxic effect of diphtheria toxin on chinese hamster cells. ovalbumin glycopeptide loses its inhibitory property after treatment with beta-n-acetylglucosaminidase. this demonstrates the importance of the glycopeptide structure for the mechanism of inhibition. the glycopeptide may be a toxin cell-surface receptor analogue. diphtheria toxin-resistant mutants were isolated in order to search for cells ...1978732311
effect of weak magnetic fields on growth of cells in tissue culture.normal chinese hamster v79 cells were grown in vitro for more than one year in a magnetic field of 10(-7) tesla to test recently hypothesized effects of weak magnetic fields on biological systems. no significant difference was observed between growth rate in such fields and that in the ambient geomagnetic field.1978724808
use of a chinese hamster ovary cell line with a temperature sensitive defect in cytoplasmic protein synthesis to examine protein synthesis associated with cell nuclei. 1978710698
characterization of sister chromatid exchange induction by 8-methoxypsoralen plus near uv light.the combination of 8-methoxypsoralen and near uv light is highly effective in inducing sister chromatid exchanges (sces) in chinese hamster ovary cells. appreciable increases in sces can be effected by treatments compatible with cell survival, and effects of a single dose of alkylation persist over multiple generations. both the frequency and location of sces induced at different times within the dna synthesis period varies in a manner indicating that exchange induction is restricted to regions ...1978668416
biological toxicity of auger emitters: molecular fragmentation versus electron irradiation.two hypotheses have been advanced to explain the extreme biological toxicity of dna associated 125i: (a) high local concentrations of radiation energy from low energy auger electron; (b) charge-induced molecular fragmentations in the dna. to distinguish between these two hypotheses an attempt was made to evaluate the molecular events associated with electron capture decay, to calculate the microdistribution of radiation energy after 125i decay, and to relate the microdosimetry data to the biolog ...1978639556
mutants of cho cells resistant to the protein synthesis inhibitor emetine: genetic and biochemical characterization of second-step mutants.second-step mutants highly resistant to the protein synthesis inhibitor emetine (emt(rii) have been selected from emetine resistant (emt(ri)) chinese hamster ovary cells described earlier. the frequency of the emt(rii) mutants was increased 50- to 75-fold after mutagenesis, and none of these highly resistant mutants could be selected in one step using wild-type cells. like the emt(ri) mutants, the increased resistance of emt(rii) mutants results from another lesion in the polyribosomal fraction, ...1978628886
six complementation classes of conditionally lethal protein synthesis mutants of cho cells selected by 3h-amino acid.using a tritiated amino acid suicide procedure designed specifically to select conditional protein synthesis mutants, we have isolated and characterized a large number of such mutants of chinese hamster ovary cells. all of the mutants are genetically stable and behave as recessives in somatic cell hybrids. most of the new mutants are phenotypically dependent on the concentration of a specific amino acid as well as on temperature. in addition to identifying many additional leucyl- and asparagyl-t ...1978628883
comparative effects of adenine analogs upon metabolic cooperation between chinese hamster cells with different levels of adenine phosphoribosyltransferase activity. 1978622085
alpha-amanithin-resistant mutants of chinese hamster ovary (cho) cells.spontaneous and ems-induced alpha-amanitin-resistant cho cells have been isolated and characterized. dna-dependent rna polymerase ii in cell-free extracts from a mutant (arm-1) was partially resistant to alpha-amanitin. growing mutants for several generations in the presence or absence of alpha-amanitin did not change the pattern of inhibition. the mutants grew with a lag following transfer to medium with or without alpha-amanitin. the mutants have an altered rna polymerase ii, and possibly an a ...1978622084
a possible difference in the mechanism of replication of moderately repeated nucleotide sequences in chinese hamster ovary cells. 1978620691
adhesion and detachment characteristics of chinese hamster cell membrane mutants.we have investigated the adhesion and detachment properties of wild-type chinese hamster cells and of variant lines, which possess altered cell surface glycoproteins as detected by galactose oxidase-[3h]borohydride labeling. the wild-type and variant lines tested all adhered to protein-coated glass surfaces at the same rate; however, the variant cells differed from wild type and from each other in terms of the ease with which they were detached by trypsinization. morphological differences betwee ...1978618896
[repair of dna--protein cross-links in a culture of chinese hamster cells. possible molecular mechanisms]. 1978569570
[phenomenon of premature chromatin condensation following fusion of chinese hamster cells using polyethyleneglycol]. 1978567115
[remote changes in the course of mitosis in synchronized cultures of chinese hamster cells following inhibition of rna and protein synthesis].the effect of inhibition of the synthesis of some types of rna and proteins was determined in the synchronized culture of chinese hamster cells at various stages of the interphase on the course of remote mitosis. analysis of mi and some forms of pathological cell division showed that the action of different doses of amd and pyromycin during the first part of the interphase provoked an identical effect--c-mitosis at the immediate and remote waves of cell division. suppression of the synthesis of ...1978567074
chromosome damage in chinese hamster cells produced by 125i-udr at the site of its incorporation.metaphase chromosomal aberrations were produced by 125i-labeled iododeoxyuridine (125i-udr) incorporated into chinese hamster don cells at the end of the s-period of the cell cycle. chromosome damage and the number of autoradiographic silver grains were recorded for whole cells, for chromosome pairs no. 4 and no. 5, and for the x and the y chromosomes. the x and the y chromosomes, which label late in s, were at least twice as heavily labeled as chromosome pairs no. 4 and no. 5--two readily recog ...1978565274
cell survival and cytogenetic responses to 125i-udr in cultured mammalian cells.the relative toxicity of dna precursors labeled with iodine-125, iodine-131, or hydrogen-3 was studied in exponentially growing chinese hamster cells. per decay, iodine-125 was found to be approximately 12 times as lethal as iodine-131 and 16 times as lethal as hydrogen-3. chromosomal aberrations induced in these cells by the three radionuclides occurred with the same relative efficacy as their lethal effects.1978565273
molecular suicide studies of 125i and 3h disintegration in the dna of chinese hamster cells.the shape of the survival curve for cells inactivated by tritium decay in dna is modified by the presence of halogenated pyrimidines in the dna in a manner analogous to their effect on x-ray induced reproductive death. the large shoulder found for tritium suicide is removed completely by coincorporation of 10(-6) m iudr. the oxygen enhancement ratio for 125i and tritium disintegrations in unsynchronized chinese hamster cells was determined for cells permitted to accumulate damage from these even ...1978565272
radionuclide toxicity in cultured mammalian cells: elucidation of the primary site of radiation damage.synchronized suspension cultures of chinese hamster ovary cells (cho) were labeled with various doses of 3h-thymidine or 125i-iododeoxyuridine to evaluate the cytocidal effects of intranuclear radionuclide decay. damage produced by radionuclide decay outside the cell nucleus was studied on cells exposed to 125i labeled, monovalent concanavalin a. after labeling, the cells were resynchronized in g1-phase and incubated for 36 h at 4 degrees c to permit dose accumulation. cell lethality was evaluat ...1978565271
the in vivo induction of sister chromatid exchanges in the bone marrow of the chinese hamster. ii.n-nitrosodiethylamine (den) and n-isopropyl-alpha-(2-methyl-hydrazino)-p-toluamide (natulan), two carcinogenic compounds with specific mutagenicity problems.n-nitrosodiethylamine (den) and n-isopropyl-alpha-(2-methylhyadrazino)-p-toluamide (natulan) were examined with the in vivo sce method of vogel and bauknecht. only natulan showed a positive effect with a significant increase of induced sce between 10 and 25 mg/kg b.w. the six-point curve of the dose effect was of the plateau type. with den only a slight increase with high doses could be obtained, which was not significant when 50 or 100 cells were counted. compared with the results of other test ...1978342947
the effects of ultra-high dose rates on survival and sublethal repair in chinese-hamster cells. 1978304852
lethality in mammalian cells due to hyperthermia under oxic and hypoxic conditions.from several studies of hyperthermia there have been reports that hypoxic cells are more sensitive to heat than their oxic counterparts. experimental techniques in this investigation eliminate the effect of ph, trypsinization and cell attachment, when assaying the effects of hyperthermia on cells. under hypoxic conditions, hela s3 and chinese hamster cell-lines do not have an increased sensitivity to heat compared with oxic cells. hela s3 cells are protected against heat by hypoxia. light-micros ...1978304850
difference in renal alpha-galactosidase levels in male and female chinese hamsters (cricetulus griseus).1. the activity of alpha-galactosidase was found to be significantly higher in the kidney of female than that of male chinese hamsters in a highly inbred colony but its activity in liver, heart and spleen remained similar between female and male animals. 2. partially purified renal alpha-galactosidase by sequential column chromatography on sepharose 6b and deae-sepharose cl-6b showed identical elution profiles, ph optima (4.5), kms (4.4 mm) and heat-inactivation curves between enzymes of male an ...1978233797
the role of butyrate in the reverse transformation reaction in mammalian cells.the reverse transformation reaction of chinese hamster ovary cells from compact, epithelial-like, randomly growing, heavily knobbed, lectin reactive cells into stretched, tighly adherent, smooth-surfaced, lectin resistant, fibroblast-like cells normally elicited by dibutyryl camp can be produced to its complete extent by n6-monobutyryl camp or 8-bromo-camp, o2'-monobutyryl camp is ineffective as is camp itself in the absence of an inhibitor of phosphodiesterase activity. in the presence of a pho ...1978201654
sexually differentiated activity and isozymes of renal beta-galactosidase in the chinese hamster. 197830661
inhibitory effect of d-mannosamine on the growth of d-glucosamine-requiring mutant strain of chinese hamster lung cells. 1978669979
chinese hamster cell lines resistant to the cytotoxic action of fluoride.the proliferation and efficiency of colony formation of a chinese hamster ovary cell line, cho, was found to be inhibited by concentrations of fluoride greater than or equal to 10(-3) m. from mutagenized populations of cho cells, clones were isolated that were from 1.6 to 13 times more resistant than the wild-type to the cytotoxic action of fluoride. the resistant clones were found to be stable in the absence of selection. the fluoride sensitivity of wild-type and fluoride resistant clones was n ...1978657004
cytological effects of microwave radiation in chinese hamster cells in vitro.cytological effects were investigated in the chinese hamster cell line (cho-k1) exposed to microwave radiation of 2450 mhz frequency and incident power of 25 to 200 w for a period of 30 min. nuclear vacuoles, pycnotic and decondensed chromosomes were observed in cells exposed to 25 w under elevated temperature conditions (uncontrolled temp). in addition a significant increase in chromosomal breakages/cell was observed. cells exposed to relatively higher power, 75-200 w, under hypothermic conditi ...1978657002
chromosomal damage and mutations after exposure of chinese hamster cells to high concentrations of oxygen. 1978642965
"carrier activation" and glucose transport in chinese hamster fibroblasts. 1978743314
calcium, asparagine and camp are required for ornithine decarboxylase activation in intact chinese hamster ovary cells. 197883867
inhibitory effects of d-mannosamine and reversal of the d-mannosamine inhibition by d-glucosamine on growth of a glucosamine-requiring mutant of chinese hamster lung cells. 1978748281
caffeine inhibits excision of 7-bromomethylbenz (a) anthracene-dna adducts from exponentially growing but not from stationary phase chinese hamster cells.excision of 7-bromomethylbenz(a)anthracene (7-bmba)-dna adducts from exponentially growing cultures of chinese hamster v79-379a cells followed logarithmic kinetics with a half of approximately 20 hrs. post-treatment incubation in the presence of a sub-toxic concentration of caffeine markedly reduced this loss. caffeine brought about a concomitant increase in overall dna synthetic rate in treated exponential cultures. excision in stationary, non-dna-replicating cultures, was slower and caffeine d ...1978745993
separation of linked markers in chinese hamster cell hybrids: mitotic recombination is not involved.a search for mitotic recombination was carried out using mutant subclones of cultured chinese hamster ovary cells. recombination events were sought between the linked loci specifying the enzymes hypoxanthine phosphoribosyl tranferase and glucose-6-phosphate dehydrogenase. it was shown by fluctuation analysis that markers at these two loci co-segregate from doubly heterozygous pseudotetraploid hybrid cells more than 90% of the time. the minority class of segregants, which had lost one marker with ...1978744475
[dependence of dna synthesis in chinese hamster cells on the culture growth conditions]. 1978734783
evidence for variation in the number of functional gene copies at the amar locus in chinese hamster cell lines.the hypothesis of functional hemizygosity has been examined for the alpha-amanitin resistant (amar, a codominant marker) locus in a series of chinese hamster cell lines. amar mutants were obtained from different cell lines, e.g., cho, dhw, m3- 1 and cho-kl, at similar frequencies. after fractionation of different rna polymerase activities in the extracts by chromatographic procedures, the sensitivity of the mutant rna polymerase ii towards alpha-amanitin was determined. while all of the rna poly ...1978730780
an effect of cell-cycle position on ultraviolet-light-induced mutagenesis in chinese hamster ovary cells.using synchronous populations obtained by selectively detaching mitotic cells from cultures grown in monolayer, we demonstrate here that chinese hamster ovary (cho) cells exhibit a differential sensitivity to mutation induction by uv as a function of position in the cell cycle. when mutation induction to 6-thioguanine (tg) resistance is monitored, several maxima and minima are displayed during cell-cycle traverse, with a major maximum occurring in early s phase. although cells in s phase are mor ...1978723911
effects of harman and norharman on spontaneous and ultraviolet light-induced mutagenesis in cultured chinese hamster cells.nontoxic concentrations of harman and norharman were tested in cultured chinese hamster cells for their effects on dna repair and mutagenesis. the following effects of harman were observed: (a) the survival of ultraviolet light- or x-ray-damaged cells was reduced; (b) the ultraviolet light-induced unscheduled dna synthesis was slightly inhibited; and (c) the frequency of spontaneous or ultraviolet light-induced ouabain-resistant (ouar) or 6-thioguanine-resistant (6-tgr) mutations was reduced. fu ...1978719638
elimination of hypoxic protection by 5-thio-d-glucose in multicell spheroids.the effect of 5-thio-d-glucose on oxic and hypoxic v79-171 chinese hamster cells was studied in vitro with single cells and multicell spheroids. at concentrations that were not toxic to oxic cells, this compound killed hypoxic cells with a d0 of 1 hr with a 5 mm concentration and more rapidly at 10 mm beginning 2 hr after incubation at 37 degrees. 5-thio-d-glucose also sensitized hypoxic cells to radiation and protected oxic cells from radiation damage. multicell spheroids irradiated after incub ...1978719634
quinacrine-enhanced killing response of cultured chinese hamster cells by x-rays. 1978569894
effects of bouvardin (nsc 259968), a cyclic hexapeptide from bouvardia ternifolia, on the progression capacity of cultured chinese hamster. 1978569011
actinomycin d inhibits initiation of dna replication in mammalian cells.mammalian (chinese hamster ovary) cells were synchronized in the division cycle and blocked at the beginning of s phase with fluorodeoxyuridine. traces of thymidine in the medium allowed cells to enter s phase and initiate dna replication at some origins. for many hours after the traces of thymidine were depleted new sites for dna replication accumulated in a small fraction of the dna. however, these potential origins became active in bidirectional replication only when cells were released by ad ...1978282626
differential control of synergistic effect with polyene macrolide antibiotics upon chinese hamster cells in vitro.an amphotericin b-resistant cell (ambr-1), which was isolated from aneuploid chinese hamster cells (v79), was found to show much higher resistance than the parent v79 cells to other polyene antibiotics, such as pentamycin and filipin. to obtain the 50 to 60% inhibition of the control protein synthesis activity by a synergistic combination of fusidic acid and amphotericin b, 50 microgram fusidic acid per ml were combined with 10 microgram amphotericin b in v79 cells, whereas in ambr cells 50 micr ...197882481
mutagenesis of chinese hamster cells is facilitated by thymidine and deoxycytidine. 1978723933
enhancement of thermal killing by polyamines. ii. uptake and metabolism of exogenous polyamines in hyperthermic chinese hamster cells.the uptake and metabolism of the polyamines spermine, spermidine, cadaverine and putrescine, previously shown to potentiate heat sensitivity, were studied in cultured chinese hamster cells. heat (42 degrees c) causes enhanced uptake of exogenously supplied polyamines into the acid-soluble fraction of the cells. putrescine is taken up exceptionally fast at 37 degrees c, about 10 times faster than its homologue, cadaverine. this uptake is slower at 42 degrees c. the polyamines taken up were metabo ...1978721321
enhancement of thermal killing by polyamines. i. survival of chinese hamster cells.exposure of chinese hamster cells to polyamines at an elevated temperature (42 degrees c) results in synergistic cell killing. the effectiveness of polyamines in potentiating thermal killing decreases in the following order: spermine greater than spermidine greater than cadaverine greater than putrescine. the magnitude of the synergism increases with exposure time. the survival curves, when plotted as a function of polyamine concentration, display a shoulder during 1 h exposure at 42 degrees c, ...1978721320
the response of chinese hamster ovary cells to fast neutron radiotherapy beams. iii. variation in biological effectiveness with position in the cell cycle. 1978752158
cytogenetic toxicity of gentian violet and crystal violet on mammalian cells in vitro.the cytogenetic toxicity of gentian violet in chinese hamster cho cells in vitro has been studied by analyzing (1) squash preparations from direct fixation for recording mitotic anomalies and (2) air-dried preparations (with colcemid--hypotonic pretreatments) for recording metaphase chromosome aberrations. it was concluded that this compound is a mitotic poison as well as a clastogen in vitro. its clastogenic property was confirmed in 5 other different mammalian cel types. 10 samples of differen ...1978745616
inverse relationship between galactokinase activity and 2-deoxygalactose resistance in chinese hamster ovary cells.galactokinase activity is reduced in 12 independent clones of chinese hamster ovary cells resistant to 2-deoxygalactose. the frequency of resistant colonies is increased with chemical mutagens. the resistant phenotype is stable in the absence of selection. there is an inverse correlation between the levels of galactokinase activity and the cloning efficiency in deoxygalactose. cells with high resistance have 1% or less of the enzyme activity observed in the parental cells; while cells with low r ...1978741353
enhancement of repair replication in mammalian cells by hydroxyurea.the effect of hydroxyurea on dna repair replication has been studied in chinese hamster ovary cells. mitotic cells were treated with uv irradiation, methyl methanesulfonate or nitrogen mustard and incuated in the presence of each of the 4 [3h] deoxyribonucleosides plus brdurd and fdurd for 2 h. the amount of repair replication was quantitated on cscl gradients and similar values were obtained for each nucleoside. in all cases addition of hu during the incubation period increased these values app ...1978740011
absence of interaction between x-rays and uv light in inducing ouabain- and thioguanine-resistant mutants in chinese hamster cells.chinese hamster ovary cells were irradiated with x-rays at times from 0 to 17 h before being irradiated with ultraviolet (uv) light. no synergism was observed between the two radiations for the production of mutants resistant to either ouabain or 6-thioguanine. these experiments were designed to test whether x-rays induced an error-prone repair system that would increase the frequency of mutations produced by uv light, but no such system was detected.1978740009
modification of uv-induced mutation frequencies in chinese hamster cells by dose fractionation, cycloheximide and caffeine treatments.chinese hamster (v79) cells were irradiated with a fractionated regime of ultraviolet light (uv1 + uv2). the fractionation of a uv dose always increased the colony-forming ability but reduced (or it did not change) the mutation frequencies. treatment with cycloheximide between the two uv irradiations resulted in two types of effects, depending on the protocols used. long exposures to cycloheximide (i.e., greater than 6 h) for the entire period between uv1 and uv2 or partial treatment of cyclohex ...1978740008
search for dna interchange corresponding to sister chromatid exchanges in chinese hamster ovary cells.chinese hamster ovary cells (cho) grown for one cycle in bromodeoxyuridine (brdu) contain a small amount (0.5%) of unusually dense double stranded dna. this dense dna has been previously interpreted as being bifilarly substituted with brdu and hence evidence that sister chromatid exchange (sce) formation proceeds via the holliday model of recombination. however, the amount of this dense dna is 100 times greater than that expected based on the sce frequency in similarly cultured cho cells, and it ...1978724509
ultrastructural study of virus-like particles in chinese hamster lung cells.virus-like particles were found in the e36 cells. one type, associated with centrioles, consisted of two concentric shells with a diam. of 50 to 60 nm. some of these particles were seen budding through the plasma membrane giving rise to a free immature particle showing two concentric shells and an outer envelope. concentration of the inner shell into a nucleoid results in a mature particle characterized by a nucleoid, mainly eccentrically located, surrounded by an intermediate layer and wrapped ...1978569185
synthesis of poly(adenosine diphosphate ribose) in synchronized chinese hamster cells. 1978363436
cytoplasmic transfer of resistance to antimycin a in chinese hamster cells.a mutant subline of v79 chinese hamster cells resistant to antimycin a (ant) was obtained by treatment with ethyl methanesulfonate followed by serial selection in ant-containing medium. clonal derivatives of the resistant line are less susceptible than parent cells to growth inhibition by ant in mass populations and show a higher plating efficiency in graded levels of inhibitor. resistance to ant is stable in drug-free medium and follows a pattern of incomplete dominance in hybrids between resis ...1978281710
amplified dihydrofolate reductase genes are localized to a homogeneously staining region of a single chromosome in a methotrexate-resistant chinese hamster ovary cell line.methotrexate-resistant chinese hamster ovary cells selected for high resistance by progressive increments of methotrexate in the culture medium have levels of dihydrofolate reductase (tetrahydrofolate dehydrogenase, 7,8-dihydrofolate: nadp+ oxidoreductase, ec 1.5.1.3) 200 times that of sensitive cells and a corresponding increase in the number of copies of the dihydrofolate reductase gene. the resistant cells contain an expanded region on the second chromosome (homogeneously staining region) tha ...1978281704
mammalian cell mutant requiring cholesterol and unsaturated fatty acid for growth.a mutant requiring both cholesterol and oleate for growth has been isolated from mutagenized chinese hamster ovary cells. by comparison with wild-type cells, sterol and unsaturated fatty acid biosynthetic activities in the mutant cells grown in fetal calf serum medium appear to be nearly intact. however, whole-cell radioactive acetate, mevalonate, dihydrolanosterol, and stearate incorporation studies show that sterol synthesis from acetate, lanosterol demethylation, and fatty acid desaturation a ...1978281693
cell killing and kinetic effects of diglycolaldehyde on dividing and nondividing mammalian cells in vitro.the effects of the anticancer drug diglycolaldehyde (nsc-118994) were studied on chinese hamster ovary cells growing in vitro. dividing cells, specifically those in s-phase, were more sensitive to the drug than were nondividing cells, although a large fraction of nondividing cells was also killed by doses up to 800 microgram/ml. dose-dependent effects on cell progression kinetics were observed in all phases of the cell cycle except in mitosis, during which treated cells progressed at control rat ...1978280715
suppression of the frequencies of sister chromatid exchanges in bloom's syndrome fibroblasts by co-cultivation with chinese hamster cells.the effect of co-cultivation of bloom's syndrome fibroblasts with chinese hamster ovary cells (cho) on the incidence of sister chromatid exchanges (sces) was studied. the results show that suppression of the frequency of sces in bloom's syndrome cells occurs only if cell to cell contact is present with cho cells, without any effect on the sce frequency in the latter. it is suggested that possible genetic heterogeneity between different bloom's syndrome patients can be studied using the method of ...1978730162
membrane lipid modification of chinese hamster ovary cells. thermal properties of membrane phospholipids. 1978701264
hybridization of cultured chinese hamster kupffer cells possessing quantitative differences in enzyme activities. 1978568558
role of adenine phosphoribosyltransferase in adenine uptake in wild-type and aprt- mutants of cho.adenine uptake in cultured chinese hamster fibroblasts showed biphasic saturation kinetics. the transport system was highly specific for adenine and was competitively inhibited by adenosine. utilizing mutant clones of chinese hamster fibroblasts that have either reduced or negligible adenine phosphoribosyltransferase (aprt) activity, we found that (1) adenine was not accumulated against a concentration gradient in the absence of aprt activity and (2) after rapid initial uptake equal to that of t ...1978743195
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