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the effect of repeated small doses of radiation on recovery from sub-lethal damage by chinese hamster cells irradiated in the plateau phase of growth.unfed plateau-phase cells have been irradiated with either single doses or up to ten fractions of x-rays 6 hours apart. the single-dose survival curve had an extrapolation number of 11-4, and the oxygen-enhancement ratio (o.e.r.) was 3-1. cells were exposed to multiple fractions of 200 rad or 150 rad in air and 600 rad or 450 rad in hypoxia. the resulting survival curves did not fit a multi-target, single-hit model of cell survival, being much steeper than that would predict. the curves were exp ...20011083845
negative pion irradiation of mammalian cells. 1. survival characteristics of monolayers and spheroids of chinese hamster lung cells.monolayers and spheroids of chinese hamster cells (v79) were subjected to negative pion irradiation under aerobic conditions. r.b.e. values in the pion peak of 1-8 and 1-5 were obtained for monolayers and spheroids, respectively, whereas the r.b.e. for the plateau was found to be slightly higher than 1. in addition, it was observed that the higher resistance of the v79 spheroid cells than the monolayers to gamma-irradiation is not diminished in the pion peak, suggesting that the underlying pheno ...19761083848
the effect of nitroimidazole and nitroxyl radiosensitizers on the post-irradiation synthesis of dna.the modification of dna damage by three radiosensitizing drugs, present during gamma-irradiation of hypoxic chinese hamster cells, was investigated. both 2-methyl-5-nitroimidazole-1-ethanol (metronidazole) and 1-(2-nitro-1-imidazole)-3-methoxy-2-propranol (ro-07-0582) were found to cause large increases in the yield of dna single-strand breaks (ssb); triacetoneamine-n-oxyl (tan) was found to have only a small effect on ssb production. the three drugs tested did not inhibit the rejoining of ssb. ...19761086839
the ultra-fast repair of single-strand breaks in dna of gamma-irradiated chinese hamster cells. 19761087297
sub-unit structure of soluble and mitochondrial malic enzyme: demonstration of human mitochondrial enzyme in human-mouse hybrids.1. malic enzyme has been examined by starch-gel electrophoresis in human cultured fibroblasts and in 60 brain samples. the polymorphism of mem has been confirmed and the electrophoretic pattern suggests that this enzyme, like mes, is a tetramer. 2. the appearance of the soluble and mitochondrial malic enzymes in mouse and chinese hamster is described, and the identity of the enzymes in man, mouse and hamster has been established from a study of interspecific somatic cell hybrids. in man and in h ...19751088824
mutagenicity of the food additive af-2, a nitrofuran, in escherichia coli and chinese hamster cells in culture. 19751093019
requirement for cell dispersion prior to selection of induced azaguanine-resistant colonies of chinese hamster cells.with v79 chinese hamster cell cultures treated with a mutagen, the maximum frequency of colonies resistant to 8-azaguanine (azg) was attained when the cells were dispersed after a suitable expression time before adding the selection medium. v79-4 cells were exposed to 500 mum mms, 7 mum afaa, or 10 mum mnng and allowed to multiply before being reseeded at 4 times 10-4 cells/60 mm dish and selected with 10 mu-g/ml azg. maximum frequencies of 4 times 10-5, 4 times 10-4, and 2.4 times 10-3 were obt ...19751093934
studies of the mechanisms of radiosensitization of bacterial and mammalian cells by diamide.diamide sensitizes bacterial and mammalian cells to radiation by at least two mechanisms. sensitization of v79-gl1 chinese hamster cells is due mainly to a reduction of a reduction of the survival-curve shoulder, is observed both in oxygen and in hypoxia,and is additive to the sensitization of hypoxic cells by some nitroimidazoles. in contrast, sensitization of the radioresistant organism, micrococcus sodonensis, which has apronounced shoulder, is entirely dose-modifying. in a rapid-mix study us ...19751093986
a technic for the collection of peritoneal cells from laboratory animals.a simple method was devised for the collection of peritoneal cells from rats, chinese hamsters, and mice using a special glass pipette. cell collection was performed by lavage on the intact unanesthetized animal within 30-60 sec, and it yielded 5-20 million cells per rat and 0.3-2.5 million cells per mouse or chinese hamster. the procedure can be repeated on different occasions in the same animal without apparent adverse effects.19751094186
the mutagenicity of saccharin.seventeen different reports are available dealing with the mutagenic effects of saccharin. many of these are short abstracts, carrying incomplete information. mainly tested as its sodium salt, saccharin has been found to be weakly mutagenic in salmonella at very high doses, in drosophila at moderate doses, and in mice at moderate to high doses. the compound is a weak chromosome breaker in onion root tips and in chinese hamster cells. for most of these, and for other test systems as well, a numbe ...19751095924
an ultrastructural study of pancreatic islet cell destruction by n-nitrosomethylurea.an ultrastructural study of the early effects of intraperitoneal injection of 50 mg/kg body weight of n-nitrosomethylurea on the pancreatic islet tissue in chinese hamsters was performed. thirty minutes after injection there was slight dilatation of the endoplasmic reticulum and mitochondrial swelling in a few peripheral alpha2-cells near to capillaries and also in some beta-cells. after 1 hour these changes were more pronounced. after 3 hours, distinct nuclear pyknosis was seen in endocrine isl ...19751096530
non-random chromosome distribution in radial metaphases from the chinese hamster. i. uncultured cells.chromosome distribution was analyzed in uncultured radial metaphase cells (corneal epithelium, testicular mitotic cells, cells in the diakinesis, and cells in metaphase ii) from the chinese hamster. the hypothesis of random distribution was rejected at the 0.001 level (chi 2/3 = 31.6).--homologous association was observed for two pairs of chromosomes (3 and 10) in corneal epithelial cells. it was observed for all four cell types. the chromosomes associated in four groups of similarly sized and s ...19751097212
specific uptake of labelled n-nitrosomethylurea in the pancreatic islets of chinese hamsters. 19751100425
in vivo chromosome-damaging effect of cyclohexylamine in the chinese hamster. 19751100496
mutagenic and cytotoxic activity of benzol[a]pyrene 4,5-, 7,8-, and 9,10-oxides and the six corresponding phenols.the benzo[a]pyrene 4,5-, 7,8-, and 9,10-oxides and the six corresponding phenols (4-, 5-, 7-, 8-, 9-, and 10-hydroxybenzo[a]pyrene) have been tested for mutagenic and cytotoxic activity in bacteria and in a mammalian cell culture system. benzo[a]pyrene 4,5-oxide (k-region) was highly mutagenic in two histidine-dependent strains (ta1537 and ta1538) of salmonella typhimurium which detect frameshift mutagens. in contrast, benzo[a]pyrene 7,8- and 9,10-oxides were less than 1% as mutagenic as the 4,5 ...19751103140
excision-repair of gamma-ray-damaged thymine in bacterial and and mammalian systems.the selective excision of products of the 5,6-dihydroxy-dihydrothymine type (t') from gamma-irradiated or oso4-oxidized dna or synthetic poly[d(a-t)] was observed with crude extracts of escherichia coli and isolated nuclei from human carcinoma hela s-3 and chinese hamster ovary cells. the results with e. coli extracts allow the following conclusion: (1) the uvra-gene product is not required for t' excision. (2) radiation-induced strand breakage is not required for product excision. (3) experimen ...19751103854
distribution of 18+28s ribosomal genes in mammalian genomes.in situ hybridization with 3h 18s and 28s ribosomal rna from xenopus laevis has been used to study the distribution of dna sequences coding for these rnas (the nucleolus organizing regions) in the genomes of six mammals. several patterns of distribution have been found: 1) a single major site (rat kangaroo, seba's fruit bat), 2) two major sites (indian muntjac), 3) multiple sites in centromeric heterochromatin (field vole), 4) multiple sites in heterochromatic short arms (peromyscus eremicus), 5 ...19751104290
selection of chinese hamster somatic cell mutants after irradiation of budr-labelled cells.the selection of somatic cell mutants after irradiation of budr-labelled cells is improved with the use of a mercury lamp combined with a plastic sheet which filters the unwanted wave lengths below 303 nm. new somatic cell mutants defective for galactose metabolism or auxotrophe for fetal calf serum were thus isolated.19761107336
cell surface structure of rodent sperm heads.replicas of critical point dried rodent sperm were examined by transmission electron microscopy. the surface of rat sperm heads appeared to be coated with regularly spaced 90a lamellar material. the plasma membrane overlying the acrosomal region of guinea pig spermatozoa displayed a regular scalloped array of lamellar structures. in replicas, the surface of chinese hamster spermatozoa appeared coated by an array of small tubles and vesicles in the region overlaying the acrosome. it was possible ...19751110344
responses to arginine of the perfused pancreas of the genetically diabetic chinese hamster.nonketotic, genetically diabetic cinese hamsters show subnormal pancreatic insulin release and impaired suppression of glucagon in response to glucose. to study the pancreatic effects of other agents, dynamic insulin and glucagon release was measured from the in vitro perfused pancreases of normal and diabetic chinese hamsters in response to various combinations of arginine (20mm), glucose (100 or 150 mg. per 100 ml.), and theophylline (10 mm). theophylline alone caused identical insulin and glu ...19751116650
quantitative comparison of techniques used to measure complement-mediated cytotoxicity of nucleated cells.?the cytotoxicity of nucleated cells by specific antibody and complement can be guantitated in vitro by several methods. trypan blue exclusion, 51-cr release, inhibition of uptake of 3-h-thymidine, and inhibition of colony formation are the four assays that we used to guantitatively compare the c-mediated cytotoxicity of chinese hamster lung (chl) cells. chl cells were sensitized with either guinea pig or rabbit anti-chl antisera, and exposed to guinea pig, human, or rabbit c. we found that the ...19751117130
cycloheximide resistance in chinese hamster cells. i. spontaneous mutagenesis.resistance to cycloheximide (chm) was studied in cultured chinese hamster cells. concentrations of chm above 5-10-7 m were toxic for the cells. at concentrations above 9-10-7 m no colonies were recovered in selective medium. 15 resistant clones of independent origin were isolated in selective medium containing 7-10-7 m chm. resistance was stable when the cells were cultured under non-selective conditions. the spontaneous mutation rate was determined by the fluctuation test. mutations to chm resi ...19751117878
a radioprotective stereostructure-activity study of cis- and trans-2-mercaptocyclobutylamine analogs and homologs of 2-mercaptoethylamine.for purposes of studying stereostructure-activity relationships at the molecular, cellular, and animal levels and probing the mechanism of 2-mercaptoethylamine (mea) radioprotection we synthesized several conformationally constrained cyclobutyl analogs. the comparative radioprotective properties for mea, cis- and trans-2-mercaptocyclobutylamine (2), cis- and trans-2-mercaptocyclobutylmethylamine (3), and trans-2-mercaptomethylcyclobutylamine (4) are discussed in terms of their ability to chemica ...19751120998
conditionally lethal mutations in chinese hamster cells. characterization of a cell line with a possible defect in the krebs cycle.a variant chinese hamster cell line has been isolated from a mutagenized population that has a markedly reduced ability to oxidize a variety of substrates via the krebs cycle. the production of 14co2 from 14c-labeled compounds was measured using pyruvate, acetate, beta-hydroxybutyrate, palmitate and glutamate, and in all cases it was neglibible in the mutant. in contrast to this, significant amounts of 14co2 were produced from 14c-aspartate and 14c-succinate which suggest that some reactions of ...19751123408
the dna polymerases of chinese hamster cells. the products specified by salmon sperm dna template. 19751124932
actinomycin d effects on mitosis and chromosomes: sticky chromatids and localized lesions.when indian muntjac and chinese hamster cells in culture were treated with actinomycin d (1 micron/ml) for 1-2 hours, the sister chromatids, especially the distal segments, appeared to have difficulty separating in anaphase. the separated proximal segments progressively became stretched. the nucleolus organizer regions seemed to be most susceptible to stretching, and breaks in these regions were frequently observed. electron microscopic observations showed that the sticky chromatids (and less fr ...19751132285
saccharin: lack of chromosome-damaging activity in chinese hamsters in vivo. 19751132847
x-ray and uv-induced chromatid aberrations: evidence for polynemic chromosomes?ikushima and wolff have recently interpreted both their observation of chromatid aberrations in second and third mitoses following x-irradiation and the production of chromatid type chromosomal aberrations by uv light administered during the g1 phase of the cell cycle in terms of a polyneme model of eukaryote chromosome structure. they were led to do so, however, largely because of their x-ray data, which the interpreted as evidence for the induction of sub-chromosomal lesions (by g1 irradiation ...19751134507
ploidy level and mutation to hypoxanthine-guanine-phosphoribosyl-transferase (hgprt) deficiency in chinese hamster cells.the x-ray induction of 8-azaguanine (ag) resistent mutants in two sets of diploid and tetraploid chinese hamster cells (don and v79) was investigated. it was found that (i) the induced mutant frequencies in diploid and tetraploid cells appeared to be of the same order of magnitude and (ii) all mutants showed almost complete loss of hypoxanthine-guanine-phosphoribosyl-transferase (hgprt) activity except that in the tetraploid v79 cells 50--100% of activity was retained. the gene--dosage effect fo ...19751134510
[simultaneous effect of 5-bromodeoxyuridine and cysteamine on x-irradiated diploid cells of chinese hamster, cricetulus griseus, in vitro].cells of the chinese hamster line b 14 faf 28 were treated with budr and irradiated with x-rays under the presence of cysteamine. the dose-dependent inactivation rates could be determined rather precisely by marking single cells. daily cell counts in the growing colonies made it possible to establish individual colony growth curves. the results of both analyses show for untreated and treated cells a nearly equal factor with respect to the protecting effect of cysteamine. also in the "macrocoloni ...19751135897
[some patterns of rna synthesis in the proliferation induction process in a stationary culture of chinese hamster cells].an increase in the incorporation of eh-uridine into rna and in the cell membrane permeability for 3h-uridine in stationary culture cells after medium replenishment were found to be parallel. increase in the rna synthesis occurs practically in all cells stimulated to proliferate and is not accompanied by swelling nucleii, as demonstrated by measuring the projected areas of nucle on fixed cells. the rise in rna synthesis as a response to proliferative stimulus is pronounced at every cell density b ...19751135947
the action of hexyl mercury bromide on chinese hamster cells in vitro. 20131137322
the action of hexyl mercury bromide on chinese hamster cells in vitro. 19751141008
correlation between resistance to actinomycin d, karyology, agglutination by concanavalin a and tumorigenicity in chinese hamster hybrid cells.subclones isolated from a chinese hamster hybrid line, derived from fusion of an actinomycin d-resistant and an actinomycin d-sensitive strain, were studied with respect to their resistance to actinomycin d, karyology, transplantability and agglutination by concanavalin a. statistical analysis of the results allowed the establishment of a classification of the strains based on increasing resistance to actinomycin d. there appeared to be an inverse correlation between actinomycin d-resistance and ...19751141394
relationship between experimental results in mammals and man. i. cytogenetic analysis of bone marrow injury induced by a single dose of cyclophosphamide.the extrapolation of experimental results to man was studied by cytogenetic bone marrow analysis and micronucleus test in mice, rats and chinese hamsters. furthermore, the frequency of chromosomal aberrations was compared with the frequencies of polychromatic erythrocytes containing micronuclei. cyclophosphamide (cy) was given intraperitoneally at the doses of 5, 10, 20, 40 and 80 mg/kg b.w. to icr mice and wistar rats and at the doses of 10, 20, 40, 80, 120 and 160 mg/kg b.w. to chinese hamster ...19751143298
[differential reaction of condensed and diffuse chromatin to polyamines. i. reaction of interphase nuclei chromatin to putrescine].condensation of the interphase nuclei chromatin under putrescine treatment was studied in cultured human fibroblasts 46, xx: 47, xxx: 49, xxxxy, and aneuploid cells of the chinese hamster. the effect was tested separately for diffuse and condensed chromatin. putrescine treatment did not affect the percentage of cell nuclei with x-chromatin bodies in the human cell strains while significantly increasing the percentage of nuclei with coarse chromatin network and chromocenters. in cultured chinese ...19751145759
mitosis in mammalian cells during exposure to anesthetics.the effects of methoxflurane, trichloroethylene, chloroform, halothane and diethyl ether on the division of chinese hamster fibroblasts in spinner culture have been studied. all agents caused dose-dependent inhibition of cell multiplication. halothane increased the cell cycle time roughly in accordance with its effect on multiplication rate. there was no evidence that mitosis was greatly prolonged, and only small numbers of "c-metaphases" were seen. however, exposure to halothane resulted in a m ...19751147307
purine mutants of mammalian cell lines. ii. identification of a phosphoribosylpyrophosphate amidotransferase-deficient mutant of chinese hamster lung cells.a class of purine auxotrophs blocked early in the purine biosynthetic pathway was examined. the inability of these mutants to accumulate formylglycinamide ribotide (fgar) in the presence of azaserine suggested that one or more of the first three enzymes of the pathway were either missing or defective. by direct enzyme assay, phosphoribosylpyrophosphate (prpp) amidotransferase (e.c. 2.4.2.14) was found to be absent in extracts of mutant cells. thus these cells were unable to convert prpp to phosp ...19751147888
cure, regression and cell survival: a comparison of common radiobiological endpoints using an in vitro tumour model.multicell spheroids of chinese hamster v79-171 cells grown in suspension culture display many of the characteristics of solid tumours in vivo, and can be used as an in vitro tumour model. two populations of spheroids differing in age and radiosensitivity were exposed to single doses of gamma-radiation and their response assayed by several techniques: (1) spheroids were reduced to single cells by trypsinization at various times post-irradiation, and viability of the single cells determined by col ...19751148588
temperature-sensitive hypoxanthine-guanine phosphoribosyltransferase in mutant chinese hamster cells.by selecting variants of chinese hamster cells that were resistant to 6tg at 39 degrees c, but which would continue to grow in hat medium at 33 degrees c, we have isolated cell lines with thermosensitive phenotypes for hgprt controlled properties. the hgprt produced by those clones is temperature sensitive. these results indicate that the selected clones carry missense mutations in the structural gene for the enzyme.20131149068
premature chromosome condensation in the bone marrow of chinese hamsters after whole body irradiation with co-60 gamma rays in vivo.in the chinese hamster bone marrow chromosomal aberrations were induced after whole body irradiation with co-60 gamma rays in vivo. aberrant mitoses give rise to lagging chromatin that forms micronuclei. eventually the micronuclei are slowed down in their cell cycles in comparison to the main nuclei. the mitotic chromatin of the main nuclei induces premature chromosome condensation (pcc) in the micronuclei that are still in the interphase state of their cell cycles.19751150276
reversion of the 8-azaguanine resistant phenotype of variant chinese hamster cells treated with alkylating agents and 5-brono-2'-deoxyuridine.from cultures of v79 chinese hamster cells, 10 independent clones of 8-azaguanine resistant cells were isolated and subcultured. cells from all ten clones were resistant to 1 mg/ml levels of 8-azaguanine (8-azg), contained less than 3% of the wild type levels of the enzyme, hypoxanthine guanine phosphoribosyl transferase (hgprt), and were unable to grow in hat medium. the ten clones were classified according to the conditions under which they reverted to the wild type phenotype. clones in classe ...19751152855
membrane-mediated drug resistance and phenotypic reversion to normal growth behavior of chinese hamster cells.development of resistance to actinomycin d, daunomycin, or vincristine in chinese hamster cells growing in vitro resulted in reversion to or retention of normal phenotypes in comparison to spontaneously transformed drug-sensitive parent populations. sublines resistant or cross-resistant to actinomycin d showed reduced uptake of antibiotic in proportion to degree of resistance. the cells with acquired resistance were either weakly tumorigenic or nontumorigenic when tested in the cheek pouches of ...19751159844
induction of chromosome changes in chinese hamster cells by exposure to asbestos fibres. 19751161005
age response for line cho chinese hamster cells exposed to x-irradiation and alpha particles from plutonium. 19751162031
laboratory studies of a lymphocytic choriomeningitis virus outbreak in man and laboratory animals.investigation of an outbreak of prolonged febrile illness in medical center personnel at the university of rochester school of medicine and dentistry revealed lymphocytic choriomeningitis (lcm) virus to be the causative agent. syrian or golden hamsters (mesocricetus auratus) were found to be the only animals involved in maintaining the virus and were the source of human infections. isolations of lcm virus were made from autopsy specimens of 13 of 46 (28%) golden hamsters. virus isolations were m ...19751163529
membrane effects of cytochalasin b. competitive inhibition of facilitated diffusion processes in rat hepatoma cells and other cell lines and effect on formation of functional transport sites.cytochalasin b competitively inhibits the transport of 2-deoxy-d-glucose and thymidine in a number of different cell lines (novikoff rat hepatoma cells, mouse l, s180 and ki-msv-transformed balb/3t3 cells, and human hela cells). the apparent km values for the transport of these substrates as well as the apparent ki values for the inhibition by cytochalasin b are very similar for the various cell lines, and the effect is readily and completely reversed by removal of the chemical. thymidine trans ...19751165581
hyperplasia in chinese hamster livers after chronic hepatic beta-irradiation. 20051166578
comparative effects of three nitrosourea derivatives on mammalian cell cycle progression.three nitrosourea analogs, 1,3-bis(2-chloroethyl)-1-nitrosourea, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, and 1-trans-(2-chloroethyl)-3-cyclohexyl-1-(4-methylcyclohexyl)-1-nitrosourea, were examined for effects on survival and cell cycle traverse capacity in exponentially growing (cycling) populations of line cho chinese hamster cells and in cultures arrested in g1 by isoleucine deprivation during treatment with drugs, then returned to the cycling mode by restoration of isoleucine (noncycli ...19751167349
heavy-ion irradiation of human and chinese hamster cells in vitro. 19751167420
chromosome-wide event accompanies the expression of recessive mutations in tetraploid cells.mutants resistant to 6-thioguanine were induced in pseudotetraploid hybrid chinese hamster cells homozygous wild-type at the locus for hypoxanthine phophoribosyl transferase but heterozygous for the linked marker glucose-6-phosphate dehydrogenase. about half of these mutants had concomitantly lost the wild-type allele for glucose-6-phosphate dehydrogenase, as expected if mutation plus chromosome segregation had occurred.19751167702
experimental study of the functional morphology of the kinetochore in mitosis.chinese hamster cells in culture were blocked in prometaphase by the addition of chloral hydrate. after 2 h the chloral hydrate was removed and the ultrastructural changes in the kinetochore studied during recovery of mitosis. the kinetochore in the blocked cells is a disc measuring 300-350 nm in diameter and 30-35 nm in thickness. imediately after recovery of mitosis the disc begins to break up and fuse with the inner nucleus of the kinetochore, when it acquires a spherical organization. on com ...19751167800
mechanism of growth inhibition by methotrexate.the effect of methotrexate on the growth of chinese hamster cells was examined under a variety of conditions. the experiments suggest that the important biological effects of methotrexate are the result of direct inhibition of thymidylate synthetase and one or both of the folate-dependent enzymes involved in a purine biosynthesis. in addition, analysis of the distribution of intracellular folate derivatives following methotrexate treatment gives no indication of accumulation of dihydrofolate, an ...19751167807
isolation of cell subpopulations from in vitro tumor models according to sedimentation velocity.chinese hamster v79-171 cells grown in vitro as asynchronous single cells, as plateau-phase cultures, and as multicell spheroids contianed subpopulations that differed in cell volume. these subpopulations could be isolated according to their sedimentation velocity at unit gravity. asynchronous cells were found to sediment at a modal velocity of 17.7 mm/hr, whereas the modal sedimentation velocities of plateau and spheroid cells were found to be 16.0 and 15.1 mm/hr, respectively. when the composi ...19751168095
distribution of repetitious dna in randomly growing and synchronized chinese hamster cells. 19751168140
deficient uridine diphosphate-n-acetylglucosamine:glycoprotein n-acetylglucosaminyltransferase activity in a clone of chinese hamster ovary cells with altered surface glycoproteins.we have reported the isolation of a clone (termed 15b) of chinese hamster ovary (cho) cells which are deficient in certain plant lectin-binding sites and have decreased amounts of sialic acid, galactose, and n-acetylglucosamine in its membranes (gottlieb et al. (1974) proc. natl. acad. sci. u.s.a. 71, 1078-1082). this study demonstrates that extracts of 15b cells, in contrast to the parent cell line, do not transfer n-acetylglucosamine residues from udp-glcnac to certain glycopeptide and glycopr ...19751168193
effect of leucine on the temperature sensitive phenotype of a mammalian leucyl-trna synthetase mutant.the concentration of leucine in the growth medium has been found to influence the expression of the temperature sensitive phenotype of a mutant of chinese hamster ovary cells with an altered leucyl-trna synthetase. plating efficiency and growth studies showed that increasing the leucine concentration allows cells to survive at normally non-permissive high temperatures and conversely decreasing the leucine concentration enhances the adverse effectsof high temperature. a similar but smaller effect ...19751168198
the effect of potassium on the cell membrane potential and the passage of synchronized cells through the cell cycle.the cell membrane potential of cultured chinese hamster cells is known to increase at the start of the s phase. the putative role of the cell membrane potential as a regulator of cell proliferation was examined by following the cell cycle traverse of synchronized chinese hamster cells in the presence or absence of high exogenous levels of potassium. an increase in external potassium levels results in a depressed membrane potential and a reduced rate of cell proliferation. a potassium concentrati ...19751168203
alterations in the growth rate and metabolism of chinese hamster cells in vitro (38530).chinese hamster (don) lung cells undergo a gradual decline in proliferation (phase iii) during their lifespan in culture. in addition, cells in phase iii utilize more glucose per 10-4 cells and produce more lactic acid per 10-4 cells than do phase ii cell cultures.19751168346
the dna polymerases of chinese hamster cells. subcellular distribution and properties of two dna polymerases. 19751168446
optimal conditions for uptake of exogenous dna by chinese hamster lung cells deficient in hypoxanthine-guanine phosphoribosyltransferase.conditions were characterized for maximizing the uptake of exogenous mammalian cell dna by hypoxanthine-guanine phosphoribosyltransferase-deficient chinese hamster lung cells. recipient cell cultures in an exponential growth phase were found to be more competent in taking up dna than stationary cultures. polyornithine enhanced the uptake of exogenous dna more reproducibly and to a greater extent than did any of the other facilitators tested (deae-dextran, cacl2, latex spheres, spermine, polylysi ...19751168508
sequential phsophorylation of histone subfractions in the chinese hamster cell cycle.ion exchange chromatography and preparative electrophoresis were used to examine the phosphorylation of histone f1 and f3 subfractions in synchronized chinese hamster cells (line cho). three discrete f1 phosphorylation events were demonstrated to occur in sequence during the cell cycle. the first event (f1g1) commenced in g1 2 hours prior to entry of cells into s phase; the second event (f1s) commenced simultaneously with initiation of dna synthesis; and the third event (f1m) commenced when cell ...20051168641
caffeine-mediated changes of sex ratio in chinese hamsters, cricetulus griseus.sixty 6- to 10-week-old male chinese hamsters were assigned to two groups. in one, the animals were untreated and in the other, they were treated with 0.02 g caffeine/100 ml water orally for 60 days. the sex ratio of the resulting litters showed a significant (p smaller than 0.025) skewing towards females (61.4%) when compared to that of the controls (49.2%).20051168707
mutant chinese hamster cells with a thermosensitive hypoxanthine-guanine phosphoribosyltransferase.by selecting variants of chinese hamster cells that were resistant to 6-thioguanine at 39 degrees c, but which would continue to grow in hat medium at 33 degrees c, we have isolated cell lines with thermosensitive phenotypes. these clones form colonies in hat medium and incorporate 14-c-hypoxanthine much more efficiently at 33 degrees c than at 39 degrees c. the specific activity of hypoxanthine-guanine phosphoribo-syltransferase is at least 10 times higher in variant cells grown at 33 degrees c ...19751170021
temperature-sensitive cell cycle mutants: a chinese hamster cell line with a reversible block in cytokinesis.a thermosensitive line (ts 111) was isolated from a suspension culture of chinese hamster fibroblasts, using a budr suicide selection technique. in this line, cytokinesis is blocked at 39 degrees c. dna and protein synthesis are not arrested but keep on at a steady rate. giant cells are produced which accumulate either numerous nuclei or one big nucleus with several nucleoli and more than a hundred chromosomes. at each nuclear cycle, all the chromosomes in the cell appear to condense in a synchr ...19751170022
isolation of heat- and cold-sensitive mutants of chinese hamster lung cells affected in their ability to express the transformed state.a clone of spontaneously transformed chinese hamster lung cells was exposed to n-methyl-n'-nitro-n-nitroso-guanidine (mnng), and six heat-sensitive and three cold-sensitive mutants were isolated after selection for inability to form colonies in soft agar at 39.5 degrees c and 34.5 degrees c, respectively. the heat-sensitive mutants had growth characteristics of transformed cells at 34.5 degrees c, but exhibited a normal phenotype at 39.5 degrees c. by contrast, cold-sensitive mutants displayed t ...19751170023
the temporal structure of s phase.dna synthesis in the s phase of v79 and cho chinese hamster cells was examined in detail using an automated system for selection and subculturing of mitotic cells and four different assays for dna synthesis. flow microfluorometric (fmf) analysis showed that the selected populations were highly synchronous with few noncycling cells. in cho cells changes in mean and modal fluorescence in the fmf suggested that dna content increased in a saltatory fashion with 10-20% of the dna replicated in early ...19751170024
the interactions of benzo(a)pyrene with cell membranes: uptake into chinese hamster ovary (cho) cells and fluorescence studies with isolated membranes.the interactions of benzo(a)pyrene (b(a)p) with the cell surface membrane were studied by measuring b(a)p uptake into intact mammalian cells and by determining b(a)p fluorescence in the presence of isolated cell surface membranes. it was found that 0.19 mu-g b(a)p were taken up by 10-6 chinese hamster ovary (cho) cells after 30 min exposure to a solution containing 0.59 mu-g/ml. culture conditions were found to markedly alter b(a)p uptake. low cell culture densities resulted in a four-fold incre ...19751170030
[induced radiation resistance in cell cultures of chinese hamster cells: induction and manner of resistance (author's transl)].mutations-induction followed by selection is a suitable method for developing a cell line with resistance to low doses of x-rays. in comparison with the original cell line, the derived resistant line is characterized by an enhanced variability of the chromosome number, and no higher level of cellular repair, limited to the two repair types described.19751170089
appearance of cytoplasmic informosomes in cultured chinese hamster cells in the absence of protein synthesis. 19751170098
detection of g1 proteins in chinese hamster cells synchronized by isoleucine deprivation or mitotic selection.examination of labeling patterns of proteins in chinese hamster cells(line cho) revealed the presence of a class of protein(s) that is synthesized during g1 phase of the cell cycle. cells arrested in g1 by isoleucine (ile) deprivation were prelabeded with [14-c]ile, induced to traverse g1 by addition of unlabeled ile, and labeled with [3-h]ile at hourly intervals. cells were fractionated into neclear and cytoplasmic portions, and proteins were separated by sodium dodecyl sulfate-polyacrylamide g ...19751170176
the kinetics of in situ hybridization.the kinetics of the cytological or in situ dna-rna hybridization reaction between 125-i hela cell 18s and 28s rrna and the interphase nuclei of chinese hamster cells were studied. the reaction is consistent with the expected first order kinetics, and the value of the rate constant was very similar to the value obtained from analogous filter disc dna-rna hybridization experiments. this similarity in the rate constants and the known relationship between the rate constant and the complexity of the ...19751170554
evidence that x-irradiation inhibits dna replicon initiation in chinese hamster cells. 19751170863
metabolism of the polyadenylate sequence of nuclear rna and messenger rna in mammalian cells.the poly(a) sequences at the 3' end of mrna and nuclear rna molecules of mouse sarcoma and chinese hamster cells are subject to an elongation process distinct from de novo synthesis. this process continues in cells treated with a high level of actinomycin d to block transcription. this results in the labeling of the steady-state poly(a) population in the cytoplasm and of unusually long poly(a) segments in the nucleus. in cells incubated with 3h-adenosine in the absence of drug treatment, cytopla ...19751170955
high-speed quantitative karyotyping by flow microfluorometry.we describe a new flow-system technique for high-speed quantitative karyotyping. metaphase chromosomes are isolated from cells, stained with a dna-specific fluorochrome, and individually measured for stain content at rates up to 10(5)/min in a flow microfluorometer. the resulting distribution contains quantitative information about the relative frequency of occurrence and the chromosomal dna content of the measured chromosomes. such analyses of chinese hamster chromosomes are in good agreement ...19751170959
mutagenesis and genetic analysis with chinese hamster auxotrophic cell markers.chinese hamster ovary cells were treated with various physical and chemical mutagens and subject to the bromodeoxyuridine plus visible light procedure for isolation of auxotrophic mutants. more than 200 auxotrophs have been isolated which require exogenous supplement of various nutrilites for growth, such as glycine, adenine, thymidine, inositol, etc. fifty-five of these have been characterized by complementation tests and were shown to constitute 15 different loci. all these auxotrophs are high ...19751171046
differential potentiation by nystatin of the effect of antibiotics on yeast and mammalian cells.the effect of the polyene antibiotic nystatin, used in combination with several other antibiotics, on the membranes of candida albicans sc#8169 (yeast) cells and of chinese hamster ovary and 3t3 (mammalian) cells was investigated. it was concluded from determinations of the viability of the yeast cells and from measurements of deoxyribonucleic acid synthesis by the mammalian cells that nystatin acts synergistically with several antibiotics on yeast cells, but not on cho and 3t3 cells. this selec ...19751171651
rna synthesis in chinese hamster cells. iii. non-coordinate increases during interphase in synthesis rates for informosomal, polysomal and heterogeneous nuclear rnas.cultured chinese hamster ovary cells were synchronized by mitotic selection. relative synthesis rates for informosomal messenger-like rna (mlrna), polysomal messenger rna (mrna), and heterogeneous nuclear rna (hnrna) were estimated from the amount of labeled adenosine or uridine incorporated into these species in early and late interphase. the amounts of uridine incorporated into hnrna, mrna, and mlrna during a pulse administered 9.75-10.75 h post-mitosis were 3.48 4.64, and 2.82 times the amoun ...19751171696
rna synthesis in the ultrastructural and biochemical components of the nucleolus of chinese hamster ovary cells.a correlated autoradiographic and biochemical study of rna synthesis in the nucleoli of chinese hamster ovary cells has been made. quantitative analysis of the labeling indicates that the fibrillar ribonucleoprotein (rnp) component is labeled faster than 80s rnp and 45s rna molecules, but approaches simultaneously a steady-state 3h to 14c ratio or grains/mum2 after 30 min of [3h]uridine incorporation. on the other hand, the 55s rnp, the 36s + 32s rna, and the granular rnp components have the sam ...19751171872
[effect of actinomycin d on rna synthesis in a stationary culture of chinese hamster cells stimulated to proliferate].the study of the effects of actinomycin d on stationary cultures of chinese hamster cells and those stimulated by medium changing has revealed that rna synthesis is more sensitive in the latter, the difference in the first place being attributed to the rate of labeled uridine incorporation into cell nucleoli. there is no significant difference in h3-actinomycin d uptake between stationary and stimulated cells, but the latter incorporate more labeled actinomycin d into their nuclei. a pronounced ...19751172310
[inhibition by actinomycin d of ribosomal rna synthesis in the presynthesis period of the mitotic cycle of chinese hamster cell cultures].using radioautographic technique actinomycin d at a concentration of 0.08 mug/ml was shown to inhibit selectively ribosomal rna (rrna) synthesis in monolayer cultures of chinese hamster cells. the treatment with actinomycin d of cells synchronized by mitotic selection in the beginning of the g1 period causes a delay in the onset of dna synthesis. however, a similar treatment in the late g1 period does not prevent cells from entering the s-period. the same effect has been produced by 9 mug/ml luc ...19751172311
localization of human gene loci using spontaneous chromosome rearrangements in human-chinese hamster somatic cell hybrids.analysis of human-chinese hamster somatic cell hybrids with spontaneously derived chromosome structural changes has provided data for the regional and subregional localization of gene loci which have previously been assigned to human chromosomes 2, 12, and x. correlation of the expression of human gene loci with the human chromosome complements present in somatic cell hybrids indicates that the cytoplasmic malate dehydrogenase (mdh1) locus is in the 2p23yields2pter region, and red cell acid phos ...19751172370
in vivo cytogenetic investigations in bone marrow cells of rats, chinese hamsters and mice treated with 6-mercaptopurine.the chromosome-damaging effect of 6-mercaptopurine (6-mp) was investigated in bone marrow cells of rats, chinese hamsters, and mice after single intraperitoneal injections of doses from 3.125 to 250 mg/kg, and after multiple applications of 10, 25, 50, and 125 mg/kg. the optimal time of investigation after single administration in these studies was 48 hrs after treatment for all 3 species. a nearly linear dose-response relationship with a low quadratic component was observed. the "critical dose" ...19751173752
surface polypeptides of the cultured chinese hamster ovary cell.the organization of the plasma membrane of logarithmically growing chinese hamster ovary (cho) suspension cells has been probed using surface label techniques in conjunction with subcellular fractionation and sodium dodecyl sulfate gel electrophoresis. five components of apparent molecular weights 137,000, 121,000, 97,000, 67,000, and 57,000 have been shown to be exposed at the outer surface of the cell. these components fully meet the criteria of being (a) reactive with two or more surface labe ...19751174506
lack of effect of blood sampling-induced haematopoiesis on in vivo chromosome damage by cyclohexylamine in chinese hamsters. 19751176074
mutation induction in chinese hamster v79 cells by two vinyl chloride metabolites, chloroethylene oxide and 2-chloroacetaldehyde.chloroethylene oxide and 2-chloroacetaldehyde, two possibly carcinogenic metabolities of vinyl chloride in mammals, caused a dose-dependent induction of 8-azaguanine- and ouabain-resistant mutants in chinese hamster v79 cells in vitro. up to one-hundred-fold higher concentrations of 2-chloroethanol or monochloroacetic acid, a urinary vinyl chloride metabolite in rats and man, were inactive.19751176210
biochemical and immunological studies of purified mouse beta-galactosidase.beta-galactosidase (ec 3.2.1.23) has been purified from the livers of c57bl/6j mice. the enzyme migrated as a single band of protein on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. the molecular weight of the denatured and reduced enzyme was 63,000. the native form of beta-galactosidase appeared to be a tetramer of 240,000 at ph 5.0, which was reversibly dissociated at alkaline ph to a dimer with apparent molecular weight of 113,000. multiple charge isomers of be ...19751176446
interaction of phospholipid vesicles with cultured mammalian cells. ii. studies of mechanism.the mechanism of interaction of artificially generated lipid vesicles (approximately 500 a diameter) with chinese hamster v79 cells bathed in a simple balanced salt solution was investigated. the major pathways of exogenous lipid incorporation in vesicle-treated cells are vesicle-cell fusion and vesicle-cell lipid exchange. at 37 degrees c, the fusion process is dominant, while at 2 degrees c or with energy depleted cells, exchange of lipids between vesicles and cells is important. the fusion me ...19751176535
factors affecting the quantitation of dose-response curves for mutation induction in v79 chinese hamster cells after exposure to chemical and physical mutagens.using four common mutagens, ethyl methanesulphonate (ems), methyl methanesulphonate (mms), uv, and x-irradiation, the relationship between dose of mutagen, cellular lethality and frequency of 8-azaguanine resistant colonies in v79 chinese hamster cells has been examined. several factors affecting the recovery of mutants including inter and intra-clone metabolic co-operation have been quantitated and their influence on survival response curves examined. induced mutant frequencies were assayed by ...19751177958
cycloheximide resistance in chinese hamster cells. ii. induction of chm resistance in chinese hamster cells by n-nitrosomethylurea.mutant chinese hamster ovarian (cho) cells with a resistance to 7-10(-7) and 8-10(-7) m cycloheximide (chm) were induced at mutation rates of 1.9-5.2-10(-3) and 1.6-1.8-10(-3) respectively after treatment with n-nitrosomethylurea (nmu) at 100 mug/ml. the induced mutation rates differed by two orders of magnitude from the spontaneous rate of mutation to chm resistance.19751177963
schedule-dependent synergistic cytotoxicity of arabinofuranosylcytosine with adriamycin or 3,6-bis(5-chloro-2-piperidinyl)-2,5-piperazinedione in cultured cells.the purpose of this study was to demonstrate that in vitro cell culture systems could serve a useful purpose in providing some guidelines in formulating drug schedules for combination cancer chemotherapy in the clinic. using monolayer cultures of chinese hamster ovary cells as the test system, we screened the combinations of 1-beta-d-arabinofuranosylcytosine (ara-c) + adriamycin, ara-c + 3,6 - bis(5 - chloro - 2 - piperidinyl) - 2,5 - piperazinedione, melphalan + 5-fluorouracil, and melphalan + ...19751182694
the nature of adriamycin-induced cytotoxicity in chinese hamster cells as revealed by premature chromosome condensation.the short- and long-term effects of adriamycin treatment on the cell cycle kinetics and chromosome structure of chinese hamster ovary cells were investigated. adriamycin treatment, either pulse or continuous, did not delay the progression of g1 cells into s phase but did prolong the duration of s and g2 phases. this effect was dose dependent, and the prolongation of g2 period was greater than that of s. the frequency of chromosomal aberrations induced by adriamycin was studied in the mitotic as ...19751182695
cholera toxin effects on cell growth accompanied by selective alterations in metabolite uptake and modification of cell surface proteins.exposure of chinese hamster ovary cells to cholera toxin at or below mug levels causes a marked morphological changes and increased adhesion and orientation of the cells. such changes are paralleled by alterations in surface proteins as indicated by the cholera toxin-mediated modifications detectable by lactoperoxidase-catalyzed radioiodination of outer proteins. mild tryptic treatment of cells prelabeled with [3h]glucosamine revealed a different kinetics of release of external glycoproteins in ...19751182696
selection and characterization of eight phenotypically distinct lines of lectin-resistant chinese hamster ovary cell.clones resistant to the lectins phytohemagglutinin (pha), wheat germ agglutinin (wga), the agglutinin(s) from lens culinaris (lca), and ricin (ric) have been selected from parental auxotrophic chinese hamster ovary (cho) cells. the sensitivity to other lectins of these cells and of cho cells resistant to concanavalin a (cona) has been determined, and their activity of udp-n-acetyl-glucosamine glycoprotein n-acetyl-glucosaminyltransferase (glcnac-t) has been measured. at least 8 different phenoty ...19751182798
adenine phosphoribosyltransferase and hypoxanthine-guanine phosphoribosyltransferase immunoprecipitation reactions in human-mouse and human-hamster cell hybrids.male new zealand white rabbits were immunized with human adenine phosphoribosyltransferase (aprt) and hypoxanthine-guanine phosphoribosyltransferase (hgprt), which were purified about 2000-fold and 800-fold, respectively, from erythrocytes by deae-cellulose chromatography, ammonium sulfate precipitation and preparative polyacrylamide gel electrophoresis. specific immunoprecipitations of aprt and hgprt were achieved with the antisera that were obtained and by using polyethylene glycol as a substi ...19751184004
a temperature-sensitive mutation affecting the mammalian 60 s ribosome.a temperature-sensitive chinese hamster cell mutant, ts14, is unable to synthesize protein in tissue culture at 39 degrees. that mutant's protein biosynthetic machinery has been characterized in cell-free, biologically active extracts. similar to the mutant's phenotype in tissue culture, ts14 extracts cease protein synthesis in vitro within 15 min at 40 degrees. in contrast, at 25 degrees both ts14 and wild type extracts synthesize protein for more than 2 hours. fractionation of mutant extracts ...20051184581
proceedings: a correlated study in lymphocytes and bone marrow cells of chinese hamsters after nbu treatment. 19751186718
proceedings: frequency of chromosome aberrations in bone marrow cells of chinese hamsters after treatment with cyclophosphamide or caffeine alone or together. 19751186722
proceedings: comparative mutagenicity test of three cyclophosphamides in the bone marrow of chinese hamsters (cricetulus griseus). 19751186726
proceedings: types of chromosome aberration in pre-implementation embryos of chinese hamster after treatment of the sires with trenimon. 19751186732
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