Publications

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 ...	1975	1168095
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 ...	1975	1168203
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 ...	1975	1168198
[the effect of cysteamine on x-ray induction of mutations resulting in resistance to 8-azaguanine in chinese hamster cells in vitro].	the survival of chinese hamster cell was increased after the administration of cisteamine (at doses of 1,25; 2,5 and 5,0 mm/ml) in the culture for 15--20 min. before x-irradiation (600r). in the same experiment the protector decreased the rate of induced ag-resistance gene mutations.	1975	1241544
[a further study of the mutation process in chinese hamster cells in vitro].	spontaneous mutagenesis and mutagenesis induced by chemical mutagens in culture chinese hamster cells were investigated. appearance of mutations controlling the resistance to 6-mercaptopurine (6m) and reverse mutations to sensitivity was studied. the rate of spontaneous mutations of 6m resistance in cells studied was found to be sufficiently stable: it was independent on the repeated freezing of these cells and the duration of their cultivation. 5-bromodeoxyuridine (budr) has been shown to induc ...	1975	1241539
biochemical genetics of chinese hamster cell mutants with deviant purine metabolism: biochemical analysis of eight mutants.	purine biosynthesis was studied in 8 mutants of chinese hamster cells which require purines for growth and in wild-type cells which do not show this nutritional requirement. of these, 6 mutants, ade-b, ade-d, ade-e, ade-f, gat-, and at-, were shown to accumulate metabolic intermediates not accumulated by wild-type cells. these intermediates were shown to be compounds unique to the adenylic acid biosynthetic pathway by the following criteria: (a) their radioisotopic labeling properties, (b) their ...	1975	1235902
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 ...	1975	1147888
[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 ...	1975	1135897
the dna polymerases of chinese hamster cells. the products specified by salmon sperm dna template.		1975	1124932
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 ...	1975	1123408
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 ...	1975	1120998
chromosome measurement and sorting by flow systems.	a flow microfluorometer was used to measure metaphase chromosomes in suspension at rates up to 100,000 per min. chromosomes from cells of the chinese hamster m3-1 cell line were isolated, stained for dna with the fluorescent dye ethidium bromide, and analyzed for dna content. nine distinct peaks were resolved that correspond well with independent chromosomal dna measurements made with a high-resolution scanning cytophotometer. chromosomes were sorted from each peak by an electronic cell sorter. ...	1975	1055399
cell cycle specific fluctuations in adenosine 3':5'-cyclic monophosphate and polyamines of chinese hamster cells.	chinese hamster v79 cells were synchronized by mitotic selection, which resulted in approximately 95% synchrony. the adenosine 3':5'-cyclic monophosphate level was elevated within 3 hr (g1 phase) and reached a level 2-fold higher than in early g1 within 6 hr (early s phase). an increase in ornithine decarboxylase activity (6-ornithine carboxy-lyase, ec 4.1.1.17), the initial enzyme in the polyamine biosynthetic pathway, was detected within 4 hr and was maximal at 8 hr. since about 20% of the cel ...	1975	165512
[2-colored fluorescence of differentially condensed chromosomes stained with acridine orange].	metaphase chromosomes of the chinese hamster differentially-condensed under the influence of a) 5-bromdeoxyuridine, b) colcemide, and c) cold, were stained with acridine-orange (ao) in concentrations of 1.5 x 10(-7) to 3 x 10(-5) g/ml at ph 4.1 to 8.5. it was found that stretched chromosomal segments fluoresced in the orange/red part of the spectrum, whereas normally condensed ones--were green. the colour distribution along the chromosome depended mainly on the ao concentration and the exposure ...	1975	53076
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.	1975	1167702
relationship between cyclic amp microtubule organization, and mammalian cell shape. studies on chinese hamster ovary cells and their variants.		1975	165090
cell-cycle-dependent phosphorylation of serine and threonine in chinese hamster cell f1 histones.		1975	235918
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 ...	1975	1167807
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 ...	1975	1117878
radiosensitization of cultured mammalian cells by 5-iodouridine.	radiosensitization of cultured mammalian cells was studied with halogenated pyrimidines, such as 5-iodouridine or 6-chloropurine, which have been shown to promote bacterial cell lethality when combined with gamma-irradiation. when chinese hamster cells were exposed to gamma-rays to acidic ph values and the number of colonies was scored after 6 to 11 days of incubation, many more cells were inactivated in the presence of the drug than in its absence. this may be due to radiation-induced cytotoxic ...	1975	236986
[dependence of heterochromatin differential staining on the time of its reduplication and the degree of condensation].	a comparison of the chromosomes banding pattern after g-and c-staining with the time of dna reduplication and the degree of chromosome condensation, was carried out using chinese hamster metaphase chromosomes. chromosome condensation was studied under 5-bromodeoxyuridine and 5-bromodeoxycytidine treatment. all the chromosomal segments stained with c-technique are also stainable with g-technique, while only some g-positive segments are capable to be c-bands. c-bands are heterochromatic segments c ...	1975	49115
possible role of adenosine cyclic 3':5'-monophosphate phosphodiesterase in the morphological transformation of chinese hamster ovary cells mediated by n6,o2-dibutyryl adenosine cyclic 3':5"-monophosphate.	we have demonstrated that in chinese hamster ovary (cho) cells, n6,o2'-dibutyryl adenosine cyclic 3':5'-monophosphate (dibutyryl cyclic amp) has a remarkable morphogenetic effect in converting cells of a compact, epithelial-like morphology into a spindle-shaped, fibroblast-like form. homogenates of cho cells were found to contain two adenosine cyclic 3':5'-monophosphate (cyclic amp) phosphodiesterase (ec 3.1.4.c) activities, which differ in apparent km with respect to their substrate, cyclic amp ...	1975	164438
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.	1975	1168346
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 ...	1975	1167349
survival of synchronized chinese hamster cells exposed to radiation of different linear-energy transfer.	chinese hamster v79 cells were exposed to ionizing radiations of a wide range of linear-energy transfer (let), including 145kv x-rays and six different heavy ions accelerated in the berkeley heavy-ion linear accelerator. the let of the ions ranged from 19 kev/um to 2000 kev/um. survival curves were determined for both synchronized and asynchronous cells, using survival of colony-forming capacity as the end-point. results with asynchronous cultures were similar to results reported previously for ...	1975	1079018
isolation of mammalian cell mutants deficient in glucose-6-phosphate dehydrogenase activity: linkage to hypoxanthine phosphoribosyl transferase.	mutants of chinese hamster ovary cells deficient in glucose-6-phosphate dehydrogenase (d-glucose-6-phosphate: nadp 1-oxidoreducatse, ec 1.1.1.49) activity were isolated after mutagenesis with ethyl methane sulfonate. the mutants were induced at frequencies of about 10-4 and do not differ in growth properties from wild-type cells. they were isolated by means of a sib selection technique coupled with a histochemical stain of colonies for enzyme activity. the lack of enzyme activity is not due to a ...	1975	1054832
premature chromosme condensation in the bone marrow of chinese hamster after application of bleomycin in vivo.	the chinese hamster bone marrow was used as a test system in vivo to analyse the chromosome-danaging effect of bleomycin. both chromosome and chromatid aberrations were found. mitoses with aberrations (ma) show a linear dose-effect relationship after a recovery time of 24 h, the same hold true for cells with micronuclei (cm) and for mitoses with premature chromosome condensation (pcc). the dose-effect relationships for ma, cm and pcc run parallel to each other with ma at the highest and pcc at t ...	1975	48189
method for testing mutagenic effects of chemicals on spermatogonia of the chinese hamster: results obtained with cyclophosphamide, saccharin, and cyclamate.	the action of different cyclophosphamide doses on spermatogonia of the chinese hamster was examined. two oral treatments at an interval of 24 h were carried out and spermatogonia were prepared for examination 24 or 48 h after the second dose. accordingly the effects of 5 oral cyclophosphamide doses given on five consecutive days were tested on spermatogonia and preparations were made 24 or 72 h after the last treatment. the results so obtained form the basis of reference for findings following o ...	1975	1243659
[dna replication and the development of spontaneous mutations in the somatic cells of mammals. i. the relationship between the outcome of gene mutations and the duration of cell life].	the reduction of serum concentration in culture medium to 0,1% was proposed as a method of slowing division and dna replication in chinese hamster cells in vitro. under these conditions the rate of dna replication was reduced by more than one order of magnitude, while cell viability remained high enough (about 10%) for a long period up to 30 days. the spontaneous mutation rate to 6-mercaptopurine resistance, as calculated per day in cells with reduced dna replication rate, was comparable to that ...	1975	1241543
stable alterations at the cell membrane of chinese hamster ovary cells resistant to the cytotoxicity of phytohemagglutinin.	chinese hamster ovary (cho) cells selected for resistance to the cytotoxicity of phytohemagglutin (pha) have been found to exhibit stable alterations at their plasma membranes. the pha-resistant (phar) cells bind markedly less 125i-pha than do sensitive cho cells and also exhibit an increased sensitivity to the cytotoxicity of concanavalin a, a lectin of different receptor specificity. mutagenesis with ethylmethanesulfonate increases the proportion of phar cells 20- to 100-fold. pha-resistant ce ...	1975	1235899
detection of possible heteroduplexes in somatic chinese hamster cells dna by molecular autoradiography.		1975	1227397
[hereditary infertility in male white chinese hamsters (cricetulus griseus milne edwards 1867)].	in the chinese hamster (cricetulus griseus) a white mutant (ws) with a dark dorsal stripe was observed. while the white females reproduced normally, the white males were always found to be infertile. the testicular weight of the white chinese hamster was approximately a quarter of that of the normal grey animals. in the seminiferous tubules of sexually mature white animals, spermatogenic cells were practically always absent. the tubules were lined with sertoli cells and contained foamy cytoplasm ...	1975	1224832
proceedings: cytogenetic analysis of 3-chinuclidylbenzilate, 3-chinuclidinol and benactyzine in bone marrow of chinese hamster.		1975	1221784
variations in sensitivity of synchronized chinese hamster cells to oxic and anoxic x-ray exposures.	v-79 chinese hamster cells in monolayer cultures on glass surfaces were synchronized by treatment with hydroxyurea and exposed at different times thereafter to x-rays in the air or in oxygen-free argon. survival determinations indicated that the oxygen enhancement ratio oer as expressed by the ratio of the respective d0 values varied over a narrow range in the different phases of the cell cycle. these changes resulted from cyclic alterations in both aerobic and anaerobic d0 values, and perhaps i ...	1975	1214926
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 ...	1975	1132285
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 ...	1975	1097212
interaction of gamma-ray and neutron effects on the proliferative capacity of chinese hamster cells.	the loss of reproductive capacity of chinese hamster cells has been studied using 60co gamma-rays and dt neutrons singly or combined in fixed proportions. surviving fractions were measured down to 2 times 10-4. interaction between the effects produced by neutrons and gamma-rays in the mixed irradiations has been demonstrated. the results are compared with those predicted by the cellular inactivation model developed by katz and co-workers from their delta-ray theory of track structure.	1975	1078820
direct biochemical measurements of microtubule assembly and disassembly in chinese hamster ovary cells. the effect of intercellular contact, cold, d2o, and n6,o2'-dibutyryl cyclic adenosine monophosphate.	a study was undertaken to develop a means of quantitating the amount of tubulin present as a soluble pool and as intact microtubules in cultured chinese hamster ovary cells. a procedure was developed in which these cells grown on monolayer culture in petri dishes were placed in a "microtubule stabilizing medium" (mtm) consisting of 50% glycerol, 10% dimethylsulfoxide and sodium phosphate magnesium buffer, as described previously by filner and behnke. these cells then were homogenized and the hom ...	1975	162792
repair (or recovery) effects in quiescent chinese hamster cells: an attempt at classification.	increased survival of density-inhibited chinese hamster cells after a variety of treatments is analyzed in terms of half-time of "repair," magnitude of repair, and dependence upon nutrient medium during the repair interval. at least three different systems are identified: x-ray-like, uv-like, and an entirely different system after heat shock. repair after methyl methanesulfonate and after visible light (in bromodeoxyuridine-substituted cells) may be interpreted as a superposition of the x-ray an ...	1975	53050
a high resolution study of the dna replication patterns of chinese hamster chromosomes using sister chromatid differential staining technique.	chinese hamster cells were grown for 1+ and 2+ cell cycles in the presence of brdu and then treated by the sister chromatid differential staining technique (scd). those regions of a chromosome which had replicated twice in the presence of brdu were pale staining and by selecting appropriate metaphase cells an accurate reconstruction of the dna synthetic patterns was possible. a direct correlation between the staining intensity of the g bands and the order in which they replicate was found. dark ...	1975	53130
the effect of methylated oxypurines on the size of newly-synthesized dna and on the production of chromosome aberrations after uv irradiation in chinese hamster cells.	a comparison has been made, in chinese hamster cells, of the ability of various methylated oxypurines to inhibit post-replication repair of dna after uv irradiation and to potentiate uv-induced chromosome aberrations. dna synthesized in uv-irradiated cells contains gaps, which are subsequently sealed by a process termed post-replication repair. in rodent cells this process is inhibited by caffeine and its analogues. this has been quantitated by measuring the molecular weight of the dna synthesiz ...	1975	1207709
mitochondrial protein synthesis in a mammalian cell-line with a temperature-sensitive leucyl-trna synthetase.	the temperature-sensitive chinese hamster ovary cell mutant tsh1, has been shown previously to contain a temperature-sensitive leucyl-trna synthetase. at the non-permissive temperature of 40 degrees c cytosolic protein synthesis is rapidly inhibited. the protein synthesis which continues at 40 degrees c appears to be mitochondrial, since: (a) whole-cell protein synthesis at the permissive temperature of 34 degrees c is not inhibied by tevenel, the sulfamoyl analogue of chloramphenicol and a spec ...	1975	1204605
the inactivation of chinese hamster cells by x rays: the effects of chemical modifiers on single- and double-events.		1975	1197646
the inactivation of chinese hamster cells by x rays: synchronized and exponential cell populations.		1975	1197645
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 ...	1975	1182695
lack of specific correlation of the deoxycytidine triphosphate pool level with rate of dna synthesis.	the levels of the four deoxyribonucleoside triphosphate pools and the distribution of cells in the various phases of the cell cycle have been examined in chinese hamster cells as thymidine, present as a regular constituent in the growth medium, was removed in stages. the results indicate that: 1. duration of the dna synthetic phase was lengthened when thymidine was removed from the growth medium. 2. temporally correlated with lengthening of the dna synthetic phase upon thymidine removal was a 7- ...	1975	1203255
[conformational changes before and after dna synthesis increase cytogenetically lethal radiation damage].	chinese hamster ovary fibroblasts were synchronized by mitotic selection and showed cytogenetic lethally acting radiation damages, which depended on age at irradiation time. the development of cell cultures was followed by counting of the killed cells in the 3rd daughter generation of the irradiated ones and by evaluation of the colony size spectra 73.5 h after innoculation. at a dose of 300 rads two narrow but high peaks of radiation sensitivity were induced, which appeared at the beginning and ...	1975	1227981
analysis of the replication pattern of chinese hamster chromosomes using 5-bromodeoxyuridine suppression of 33258 hoechst fluorescence.	chinese hamster fibroblasts were synchronized and given 5-bromodeoxyuridine for dna synthesis except during one hour of the s phase when thymidine was present in the medium. in the next mitosis, chromosomes stained with 33258 hoechst were banded in appearance when photographed by fluorescence microscopy. the bright regions corresponded to the chromosome segments replicated during the thymidine exposure in the s phase. the segments replicated together during any one hour produced three distinct p ...	1975	53132
isolation and characterization of variant clones of chinese hamster cells after treatment with irradiated 5-iodouridine.	variant clones were isolated from cultured chinese hamster don cells after treatment with irradiated 5-iodouridine. the following characters of a primary variant clone, c-11 and a secondary variant clone, c-24 were compared with those of the original clone c-1: colony-forming activity, growth rate in the presence of irradiated and unirradiated 5-iodouridine, distribution of chromosome numbers and cell cohesion. the variant clones c-11 and c-24 were partially resistant to unirradiated 5-iodouridi ...	1975	1240593
post-replication repair of dna in chinese hamster cells treated with cis platinum (ii) diamine dichloride. enhancement of toxicity and chromosome damage by caffeine.	the anti-tumor agent cis platinum (ii) diammine dichloride (cis pt(ii)) caused chromosomal abnormalities in chinese hamster v79-379a cells. the time of appearance of these abnormalities suggested that they arise as a consequence of dna synthesis on a damaged template. the yield and severity of chromosomal abnormalities was greatly enhanced by a non-toxic concentration of caffeine, and this enhancement was associated with a potentiation of cis pt(ii) induced cell death. these results suggest that ...	1975	1240592
investigations into the mechanism of action of anti-tumour platinum compounds: time- and dose-dependent changes in the alkaline sucrose gradient sedimentation profiles of dna from hamster cells treated with cis-platinum (ii) diamminedichloride.	under the conditions of low speed centrifugation used in this study, the proportion of radioactively labelled dna from chinese hamster v79-379a cells sedimenting to the 700s region of an alkaline sucrose gradient was increased in a dose-dependent manner by prior treatment of the cells for 2 h with cis-platinum (ii) diamminedichloride [cis-pt(ii)]. this increase was at the expense of material sedimenting in the 400-650s region. this profile was not modified by a 2-h post-treatment incubation prio ...	1975	1238177
proceedings: different radiosensitivity of chinese hamster fibroblasts for chromatid breaks in g2/prophase. dependence on let.		1975	1220789
drug resistance and membrane alteration in mutants of mammalian cells.	independent colchicine-resistant (chr) mutants of chinese hamster ovary cells displaying reduced permeability to colchicine have been isolated. a distinguishing feature of these membrane-altered mutants is their pleiotropic cross-resistance to a variety of unrelated compounds. genetic characterization of the chr lines indicate that colchicine resistance and cross-resistance to other drugs are of a dominant nature in somatic cell hybrids. revertants of chr have been isolated which display decreas ...	1975	1203765
folate-dependent enzymes in cultured chinese hamster ovary cells: induction of 5-methyltetrahydrofolate homocysteine cobalamin methyltransferase by folate and methionine.		1975	1200638
effect of heat and radiation on synchronous chinese hamster cells: killing and repair.		1975	1197661
cytological detection of mutagen-carcinogen exposure by sister chromatid exchange.	a staining technique that detects sister chromatid exchanges (sces) has been used to examine the response of chromosomes in cultured chinese hamster cells to a wide variety of mutagens-carcinogens. the test gives a very sensitive and rapid method for detecting chromosome mutagenicity of chemical agents and provides a powerful new method for detecting environmental mutagens.	1975	52847
proceedings: interaction of ionizing radiation with a platinum complex in chinese hamster cells.		1975	1220777
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 + ...	1975	1182694
dip and dip+2 as glutathione oxidants and radiation sensitizers in cultured chinese hamster cells.	two diamide analogues, diazene dicarboxylic acid bis (n'-methylpiperazide) or dip, and its bis-n'-methyl iodide salt, or dip + 2, were tested for their ability to penetrate cultured chinese hamster cells and oxidize intracellular glutathione. dip penetrated the cells at a reasonable rate at 18 degrees c, 160 nmoles being required to oxidize the endogenous glutathione of 2 x 10(6) cells, but it penetrated very slowly at 0 degrees c. dip +2 did not effectively oxidize glutathione in chinese hamste ...	1975	1081977
the oxygen-enhancement ratio for reproductive death induced by 3h or 125i damage in mammalian cells.	the oxygen-enhancement ratio (o.e.r.) for 3h- and 125i-induced cell death at 4 degrees c was determined in cultured chinese hamster cells. the o.e.r. for cell death induced by 3h-thymidine was 3-2, essentially the same value as that previously reported for x-ray induced cell death. for cell death induced by 125i-iododeoxyuridine (125idurd), the o.e.r. was less than 1-4. the lower o.e.r. for 125i-induced death was not due to the presence of the base analogue itself, since cells that had incorpora ...	1975	1081976
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 ...	1975	1174506
proceedings: types of chromosome aberration in pre-implementation embryos of chinese hamster after treatment of the sires with trenimon.		1975	1186732
proceedings: comparative mutagenicity test of three cyclophosphamides in the bone marrow of chinese hamsters (cricetulus griseus).		1975	1186726
in vivo chromosome-damaging effect of cyclohexylamine in the chinese hamster.		1975	1100496
appearance of cytoplasmic informosomes in cultured chinese hamster cells in the absence of protein synthesis.		1975	1170098
[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.	1975	1170089
evidence that x-irradiation inhibits dna replicon initiation in chinese hamster cells.		1975	1170863
effect of volatile anaesthetics on cell survival as measured by colony forming ability.	chinese hamster fibroblast cells in stirred suspension cultures were exposed to volatile anaesthetic agents for 3 hr or for 24 hr. cell viability was measured as colony forming ability and was found to be reduced, in a dose related manner, by halothane, chloroform, methoxyflurane, trichloroetheylene and diethyl ether.	1975	1201160
proceedings: chromosome aberrations in metaphase ii oocytes of chinese hamsters (cricetulus griseus).		1975	1186737
colchicine permeation is required for inhibition of concanavalin a capping in chinese hamster ovary cells.	several antimitotic, tubulin-binding agents, such as colchicine, colcemid, and podophyllotoxin, inhibit the capping of fluorescent-labeled concanavalin a in chinese hamster ovary cells. by comparing the effects of these agents on parental cell lines on several independently selected colchicine-resistant mutants with decreased drug permeability, we have demonstrated that permeation of these drugs in required for inhibition of capping. these data support the hypothesis that these antimitotic agent ...	1975	1060133
enhanced cell killing by bleomycin and 43 degrees hyperthermia and the inhibition of recovery from potentially lethal damage.	the effect of hyperthermia on bleomycin (bleo) toxicity and repair was studied in "unfed" monolayer cultures of chinese hamster cells. synergy of toxicities was observed with simultaneous exposure to bleo and 43 degrees. for example, when cells were exposed for 1 hr to bleo (40 mug/ml) at 43 degrees, survival was reduced to 4 x 10(-5); separately, hyperthermia and 37 degrees bleo exposure each resulted in a survival of 20%. heating at 43 degrees prior to drug exposure at 37 degrees also produced ...	1975	52401
cell cycle-dependent surface changes in chinese hamster cells grown in suspension culture.		1975	1193160
concanavalin a as a selective agent in tissue culture for temperature-sensitive hamster cell lines.	a novel method for isolating chinese hamster cell cultures with temperature-sensitive growth properties is described. concanavalin a can be used as a selective agent in tissue culture to isolate lectin-resistant cell lines which exhibit colony-forming abilities at the nonpermissive temperature relative to the permissive temperature as low as 10(-4) to 10(-6). a general correlation exists between resistance to the lectin and temperature sensitivity.	1975	1238161
the dose-response relationship for ultraviolet-light-induced mutations at the hypoxanthine-guanine phosphoribosyltransferase locus in chinese hamster ovary cells.	exposure of chinese hamster ovary (cho) cells clone k1bh4 to ultraviolet (uv) light at doses up to 86 ergs/mm2 did not significantly reduce cell survival, but uv doses of 86-648 ergs/mm2 produced an exponential cell killing. observed mutation frequency ro 6-thioguannine resistance induced by uv increases approximately in proportion to increasing doses up to 260 ergs/mm2 in a range of 5-648 ergs/mm2 examined. the pooled data of mutation frequency f(x) as a function of dose x from 0-260 ergs/mm2 i ...	1975	1235913
non-mendelian segregation in hybrids between chinese hamster cells.	mechanisms of segregation have been examined in hybrids between chinese hamster cells, where chromosome loss in comparison to other systems is minimal. hybrid cells were grown in hat medium and subjected to back selection with bromodeoxyuridine (budr) or azaguanine (azg). in azg or budr at 30 mug/ml, segregation began with a random high frequency event that gave rise to cells capable of growth in both hat and back selection medium, unlike the precursor hybrid or original parental cell types. bud ...	1975	1194375
a comparative study of the effects of lucanthone (miracil d) and actinomycin d on the chinese hamster cells grown in cultures.	chinese hamster cells of an established clone line grown in monolayers were incubated for up to two hours with either lucanthone (0.3-30 mug/ml) or actinomycin d (0.06-0.10 mug/ml) and subjected to radioautographic investigations with 3h-uridine during the period of treatment. at concentration of 9 mug/ml lucanthone selectively inhibited the synthesis of nucleolar (ribosomal) rna while the extranucleolar rna synthesis proceeded at a high level. similar results were obtained with 0.08 mug/ml acti ...	1975	1194365
isolation and characterization of alkaline phosphatase-constitutive variants from chinese hamster ovary cells (cho-k1).	pure clones with high alkaline phosphatase (alp) activity were isolated from chinese hamster ovary (cho-k1) cells which showed no detectable alp activity. alp-positive cells appeared at the frequency of 10(-4) in the n-methyl-n'-nitrosoguanidine-treated cell population. with respect for cellular morphology, plating efficiency and several other enzymatic activities, no distinct difference was found between the original cho-k1 cells and its alp-positive variants, although some alterations in karyo ...	1975	1194364
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 ...	1975	1182798
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.	1975	1177963
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 ...	1975	1176535
interaction of phospholipid vesicles with cultured mammalial cells. i. characteristics of uptake.	the interaction of monolayer cultures of chinese hamster v79 cells with artificially generated, unilamellar lipid vesicles (approximately 500 a diameter) was examined. vesicles prepared from a variety of natural and synthetic radiolabeled phosphatidyl cholines (lecithins) were incubated with v79 cells bathed in a simple balanced salt solution. after incubation, the cells were analyzed for exogenous lipid incorporation. large quantities (approximately 10(8) molecules/cell/h) of lecithin became ce ...	1975	240860
induction of chromosome changes in chinese hamster cells by exposure to asbestos fibres.		1975	1161005
the carcinogenic effect of dimethylnitrosamine on the chinese hamster (cricetulus griseus).	three groups of chinese hamsters (20 males, 20 females/group) received weekly subcutaneous injections for life of dimethylnitrosamine (dmn) at dose levels 0.20, 0.10 and 0.05 of the ld50. eighty-two to 100% of the animals developed tumors of vascular origin. the neoplasms were primarily hepatic hemangioendotheliomas and their incidence was unrelated to dose or sex. although animals in the low dose group received a total dose which was one-third that of the highest dose group, their survival time ...	1975	1235055
a glucosamine-requiring mutant of chinese hamster lung cells.		1975	1230461
effect of carbohydrates on the growth of d-glucosamine-requiring mutant cells of chinese hamster lung cells.		1975	1230456
flow microfluorometric analysis of isolated chinese hamster chromosomes.		1975	1193141
sister chromatid exchanges and lack of isolabeling in chinese hamster chromosomes.		1975	1193131
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 ...	1975	1177958
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 ...	1975	1171872
age response for line cho chinese hamster cells exposed to x-irradiation and alpha particles from plutonium.		1975	1162031
chinese hamster ovary cells selected for resistance to the cytotoxicity of phytohemagglutinin are deficient in a udp-n-acetylglucosamine--glycoprotein n-acetylglucosaminyltransferase activity.	several clones of chinese hamster ovary cells resistant to the cytotoxicity of the phytohemagglutinin from phaseolus vulgaris show decreased binding of 125i-labeled phytohemagglutinin and contain decreased levels of a udp-n-acetylglucosamine--glycoprotein n-acetylglucosaminyltransferase (ec 2.4.1.51; udp-2-acetamido-2-deoxy-d-glucose:glycoprotein 2-acetamido-2-deoxy-d-glucosyltransferase) activity when compared to wild-type cells. the decrease in transferase activity varies from 45% to 96%, depe ...	1975	1059116
temperature-sensitive mutants of a chinese hamster cell line. i. selection of clones with defective macromolecular biosynthesis.	temperature-sensitive clones have been selected from a mutagenized culture of chinese hamster lung cells by a procedure involving bromodeoxyuridine (brdu) incorporation and irradiation with black light. the selection procedure used in these studies was adapted from methods developed by others to yield mutants that cease dna replication within a short time after they are transferred to nonpermissive temperature. after mutagenesis with ethyl methanosulfonate ten clones survived the selection proce ...	1975	1232024
[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 ...	1975	1172311
[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 ...	1975	1172310
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 ...	1975	1134510
length distributions of single-stranded dna in chinese hamster ovary cells.		1975	239245
[the effect of 0-methylhydroxylamine on the chromosomes of chinese hamster cells].	0-methylhydroxylamine increases the frequency of all kinds of aberrations in chinese hamster cells, except chromatid exchange. the percentage of aberrant metaphases and the average number of breakages per cell increases by 5,5-6 times as compared with the control. omha proves to be very effective inducer of chromosome aberrations. since omha induces, except gene mutations, also chromosome aberrations, there are reasons to suppose that its effect is connected not only with transitions, but also w ...	1975	1241684
[development of 0-methylhydroxylamine induced mutations causing resistance to 8-azaguanine in chinese hamster cells].	the dependence of the yield of mutations of the resistance to 8-azaguanine induced with 0-methylhydroxylamine on the number of cell generations that have passed by the time of the creation of selective conditions and the existence of a phenotypic lag period is established. the highest rate of mutations is found after 8-azaguanine treatment in two generations. as the number of generations increased, the number of detectable mutations decreased. a dependence is observed between the induced mutatio ...	1975	1241683
the dna polymerases of chinese hamster cells. subcellular distribution and properties of two dna polymerases.		1975	1168446
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 ...	1975	1134507