Publications

newly synthesized hypoxia-mediated drugs as radiosensitizers and cytotoxic agents.	chinese hamster cells in culture were used to compare the radiosensitizing efficiency and cytotoxicity of misonidazole with several 2, 4 and 5 substituted nitroimidazoles. the two substituted compounds (sr 2508 and sr 2555) are similar to misonidazole in radiosensitizing effectiveness, but are significantly less toxic to hypoxic cells. this reduced cytotoxicity may result from either slower drug penetration or slower removal of non-protein sulfhydryl compounds (npsh). the compound mjl-1-191-vii ...	1982	7061257
the chinese hamster as a model for the study of diabetes mellitus.	selection for and against diabetes and subsequent inbreeding of chinese hamsters started in 1963. currently there are six inbred sublines that have greater than 85% incidence of glycosuria and two control inbred nondiabetic sublines that are essentially free of glycosuria. at birth, hamsters from inbred sublines are considered prediabetic. there is phenotypic variation between diabetic sublines. onset time, incidence of ketonuria, blood glucose, plasma insulin, glucagon and glycohydrolase levels ...	1982	6761191
effect of high concentrations of camp on proliferative activity of v79-1a cells.	we studied the mechanisms of the inhibitory effect of high camp concentrations on growth of chinese hamster v79-1a cells. high camp concentrations inhibit growth of v79-1a cells in the s phase of the cell cycle. the inhibition is probably due to some effect on the metabolism of dna precursors. we suggest that this inhibition is not induced by the cyclic nucleotide itself, but by amp as a degradation product of camp.	1982	6293894
intracellular levels of cyclic nucleotides and proliferative activity of v79-1a cells.	we studied intracellular levels of camp and cgmp in relation to the proliferative activity of chinese hamster v79-1a cells. in the course of population growth the intracellular level of camp correlated with cell growth activity. the intracellular level of cgmp rather correlated with population density. stimulation of stationary cells with fresh medium was accompanied by a surge of camp level while cgmp level was not affected.	1982	6293893
radiation-dose dependence of the formation of micronuclei in misonidazole treated cell cultures.	the effect of misonidazole at different concentrations on the anoxic radiation sensitivity of chinese hamster cells was investigated using the frequency of radiation induced micronuclei as criterion. the result indicates that, in a high radiation dose region, sensitization with a dose modifying factor of about 1.9 and 1.3 occurs after treatment with the substance at a concentration of 8 and 0.2 mmol/l, respectively. in a low dose region the corresponding values were 1.7 and 0.8. it was concluded ...	1982	6289614
direct demonstration of genetic alterations at the dihydrofolate reductase locus after gamma irradiation.	gamma ray-induced mutants of chinese hamster ovary cells lacking dihydrofolate reductase activity were screened for dna sequence changes at the locus specifying this activity by using a cloned cdna probe. two of nine mutants screened displayed an altered restriction fragment pattern suggesting the occurrence of dna deletions or rearrangements.	1982	6287224
localization of sces and their possible relationship to da . dt- or dg . dc-clusters, respectively, in chinese hamster v79-e chromosomes.		1982	6286538
inhibition of metabolic cooperation in chinese hamster v79 cells in culture by various polybrominated biphenyl (pbb) congeners.	using an in vitro assay system to measure a form of cell-cell communication in chinese hamster v79 cells, several purified polybrominated biphenyl (pbb) congeners were analyzed for their ability to affect colony-forming ability and "metabolic cooperation" in these cells. results clearly demonstrate the assay's ability to distinguish differences in the cytotoxic and metabolic cooperation-inhibiting properties of these congeners related to their structure. it appears that if a carbon ortho to the ...	1982	6279328
modification of radiation-induced division delay by caffeine analogues and dibutyryl cyclic amp.	the mitotic selection procedure for cell cycle analysis was utilized to investigate the concentration-dependent modification of radiation-induced division delay in chinese hamster ovary (cho) cells by methyl xanthines (caffeine, theophylline, and theobromine) and by dibutyryl cyclic amp. the methyl xanthines (concentrations from 0.5 to 1000 micrograms/ml) all reduced radiation-induced division delay with the effect being linear between approximately 100 and 1000 micrograms/ml. after doses of 100 ...	1982	6277814
dense bodies in silver-stained spermatocytes of the chinese hamster: behavior and cytochemical nature.	from the silver staining behavior of various organelles in the nucleus we have divided meiotic prophase (leptotene to the diffuse stage) of the male chinese hamster into five stages. components within the nucleus, such as synaptonemal complex (sc), sex bivalent (sb), nucleolus organizer regions (nors), chromatin and the dense bodies, showed a characteristic feature in each stage of meiotic prophase. the lampbrush chromosome stage was found to be followed by the diffuse stage. the chromatin aroun ...	1982	6217037
flow cytometric analysis of chromosomes and cells using a modified brdu-hoechst method.	chromosomes and interphase cells were harvested from cultures of the chinese hamster line b14 f28 grown in medium containing brdu up to four cell cycles and stained with the fluorescent dye 33342 hoechst for flow cytometry. the newly synthetized brdu-dna is not stainable by the hoechst dye which is highly specific for thymidine. the temporal development of the dna fluorescence after addition of brdu to the growth medium has been investigated. the chromosomal fluorescence intensity is reduced one ...	1982	6184345
the structure of partly decondensed metaphase chromosomes.	the technique of freeze-drying was applied to examine the submicroscopic organisation of metaphase chromosomes from chinese hamster after removal of bivalent cations with edta and removal of histone hi with 0,6 m nacl. treated chromosomes increased in size, and nucleosomal filaments appeared at the periphery of the chromosomes. removal of bivalent cations is accompanied with the appearance of regularly organized structures of the "beads-on-a-string" type. the regular organization of the fibers i ...	1982	6183061
cytotoxicity of diesel exhaust particle extract--a comparison among five diesel passenger cars of different manufactures.	the cytotoxicity of the dichloromethane extracts of diesel exhaust particles from passenger cars of different manufactures was studied in cultured chinese hamster ovary cells. while exhaust particles from diesel cars of the same make and model yielded extracts of similar cytotoxicity, those from cars of different manufactures yielded extracts with a 3-fold difference in cytotoxicity. using data on the percentages of extractable organic chemicals and total exhaust particulate emission rates, the ...	1982	6182643
electron microscopy of silver-stained core-like structures in metaphase chromosomes.	chinese hamster metaphase chromosomes, stained with ammoniacal silver and examined by electron microscopy, were covered with fine silver grains of variable size. in addition, many chromosomes contained linear aggregates of silver grains running continuously from one end of each chromatid to the other, forming a core-like structure. extensive deposits of silver were observed over the nucleolar organizers and the centromeric regions, and the silver precipitate in the latter region appeared to be a ...	1982	6181857
pre-adipocyte determination either by insulin or by 5-azacytidine.	chef/18 is a diploid chinese hamster cell line of embryonic origin, which is fibroblastic in structure, but behaves like a mesenchymal stem cell line in its ability to differentiate into adipocytes, myoblasts, and chondrocytes. with these cells, adipocyte formation has been divided experimentally into two stages: (i) determination of pre-adipocytes, which have lost the ability to form other cell types while retaining their fibroblast structure; and (ii) commitment or terminal differentiation, in ...	1982	6176995
chromosomal aberrations in chinese hamster cells exposed in vitro to tritium-labelled thymidine or x-rays at--196 degrees c.	a comparison was made between the incidence of chromosomal aberrations in g2-phase first division chinese hamster cells exposed to tritium labelled thymidine (dose range 54-522 rad) or to 250 kv x-rays (dose range 98-711 rad) at--196 degrees c. the dose-response relationship for chromatid aberrations, expressed as breaks per cell, appeared to be linear for intranuclear tritium whereas that for x-rays was curvilinear. for the dose range studied, cells exposed to x-rays were markedly less sensitiv ...	1982	7128208
isolation, purification and partial characterization of galactokinase from chinese hamster liver.	1. galactokinase was purified from chinese hamster liver. the purification process consisted of an initial biphasic partition separation followed by column chromatography on deae-cellulose. deae-sephadex, sephacryl s-200 and hydroxyapatite. 2. the enzyme was stabilized during the purification procedure by the inclusion of 10% glycerol, 1 mm phosphate and 20 mm beta-mercaptoethanol in all the buffer solutions. 3. chromatography on hydroxyapatite separated two forms of galactokinase, one of which ...	1982	7117670
cytotoxic and mutagenic properties of shale oil byproducts ii. comparison of mutagenic effects at five genetic markers induced by retort process water plus near ultraviolet light in chinese hamster ovary cells.	a chinese hamster ovary (cho) cell line heterozygous at the adenine phosphoribosyl transferase (aprt) locus was used for selection of induced mutants resistant to 8-azaadenine (8aa), 6-thioguanine (6tg), ouabain (oua), emetine (emt) and diphtheria toxin (dip). the expression times necessary for optimizing the number of mutants recovered at the different loci have been determined using the know direct acting mutagen, far ultraviolet light (fuv), and a complex aqueous organic mixture (shale oil pr ...	1982	7117215
evidence that sister chromatid exchanges and chromatid breaks are two independent events.	the relative frequencies of sister chromatid exchanges (sce) and chromatid breaks in brdu (5-bromodeoxyuridine) - sensitive site (lq22 leads to lq23) in chinese hamster cells after brdu incorporation were studied. the results show that chromatid breaks do not follow the "exchange hypothesis" and provide evidence that chromatid breaks and sces are two independent events despite some common features.	1982	7117032
meiotic chromosomal radiosensitivity in primary oocytes of the chinese hamster.		1982	7116943
strand breakage and decreased molecular weight of dna induced by specific metal compounds.	the effect of various metal compounds on the dna of chinese hamster ovary (cho) cells was studied. both nicl2 and crystalline nis caused dna strand breaks in cultured cho cells, whereas amorphous nis did not. strand breaks were quantitated by determining the number of average molecular weight of dna following treatment with the metal compounds. exposure of cells to crystalline nis, cos, cds, ags, cus and ni3s2 at 10 micrograms/ml for 24 h also induced dna strand breaks. similar exposure to activ ...	1982	7116559
fractionated low-level gamma irradiation of chinese hamster cells: cellular and biochemical effects.	chinese hamster v79 cells in log-phase were exposed daily to 0.6 gy of gamma radiation for 3-6 months. after such an exposure the population doubling time increased from 10 to 15 h. when irradiation was discontinued doubling time gradually decreased. cell survival following acute radiation dose of the low-level irradiated cells remained the same as that of untreated cells. the fractionated irradiation did not affect the capacity of the cells to perform dna repair synthesis. likewise, the sensiti ...	1982	7111682
the induction of sce and chromosomal aberrations with relation to specific base methylation of dna in chinese hamster cells by n-methyl-n-nitrosourea and dimethyl sulphate.	chinese hamster cells (v79) were treated, either as exponentially proliferating cultures or under conditions where they were density-inhibited, with various doses of the potent carcinogen n-methyl-n-nitrosourea (mnu) or the relatively weak carcinogen dimethylsulphate (dms). the colony forming ability of these cells and the induced frequencies of sister chromatid exchanges (sces) and chromosomal aberrations were assayed. following the exposure of density-inhibited cells to radio-labelled methylat ...	1982	7094205
ultrastructural observations on the pineal gland of the chinese hamster, cricetulus griseus. i. the superficial pineal.	the ultrastructure of the pineal parenchymal cells, pinealocytes and glia-like cells, of the chinese hamster (cricetulus griseus) is described. pinealocyte nuclei contain spindle-shaped inclusions consisting of bundles of closely packed parallel filaments of about 8 nm in thickness. mitochondria contain lamellar and tubular cristae. smaller and larger mitochondria are usually localized separately in individual pinealocytes. flattened mitochondria contain two to four closely arranged, unusual lam ...	1982	7060102
variations in chromosome numbers and their possible relationship to the development of 8-azaguanine resistance in v79 chinese hamster cells.		1982	7055844
rabl's model of the interphase chromosome arrangement tested in chinese hamster cells by premature chromosome condensation and laser-uv-microbeam experiments.		1982	7076247
the induction of dna strand breakage by nickel compounds in cultured chinese hamster ovary cells.	both nicl2 and crystalline alphanis induced dna strand breaks in cultured chinese hamster ovary (cho) cells. alkaline sucrose gradient analysis of [3h]thymidine radiolabelled dna isolated from cells exposed to nicl2 at 1 microgram/ml for only 2 h indicated a high degree of dna strand breakage. similarly crystalline alphanis caused substantial strand breakage at 1 microgram/ml following a 24-h treatment interval. these nickel compounds caused dna strand breaks at concentrations which did not sign ...	1982	7059962
dose-response relationship for induction of structural chromosome aberrations in chinese hamster oocytes after x-irradiation.		1982	7057780
characterization of sister chromatid exchange induction by hydrogen peroxide.	hydrogen peroxide (h2o2) induces sces in v-79 chinese hamster cells. the incorporation of brdurd sensitizes the cells to the action of h2o2, but damage leading to the formation of sces can also be induced in dna not substitued with brdurd. catalase leads to a complete reduction of the sce-producing as well as the toxic effect. the amino acid l-cysteine does not reduce the h2o2-induced sce-frequencies. the results yield information about the relevance of sce investigations in vitro for the determ ...	1982	7075578
the effects of methylated thymidines upon cultures of v79 cells and the mechanism of incorporation of o4-methylthymidine into their dna.	high concentrations of o2-methylthymidine, 3-methylthymidine and o4-methylthymidine (o4-medt) have little effect on the colony forming ability of cultured chinese hamster (v79) cells. however, the methylated derivatives enhance the toxic effects of thymidine (dt) at concentrations at which the modified nucleosides alone show no toxicity. o4-medt was the only modified nucleoside which is incorporated into v79 cell dna at a detectable level. in the presence of added dt there is an increase in the ...	1982	7067049
depopulation of the ventromedial hypothalamic nucleus in the diabetic chinese hamster.	the relationship between diabetes and the size, density and area of the ventromedial hypothalamic nucleus (vmh) was studied in the genetically diabetic chinese hamster. matched diabetic and non-diabetic control chinese hamsters were perfused, the hypothalamus collected, sectioned and stained for light microscopy. the mid-point of each vmh nucleus was located, photographed and enlarged for morphometric analysis. each neuron that possessed a nucleolus and was located within the confines of a vmh w ...	1982	7064660
role of dna repair in mutagenesis of chinese hamster ovary cells by 7-bromomethylbenz[a]anthracene.	the role of dna repair in mutagenesis was studied in normal, repair-proficient chinese hamster ovary cells and in two mutant strains that are deficient in excision repair. by using the mutagen 7-bromomethylbenz[a]anthracene (7-brmeba) and the technique of alkaline elution of dna, the mutants were found to be defective at or before the incision step of excision repair. dose--responses were determined for cell killing, mutation induction at three loci, and sister chromatid exchanges over a surviva ...	1982	6952204
the longevity of chemically induced sister chromatid exchanges in chinese hamster ovary cells.	the persistence of the lesions leading to sister chromatid exchanges (sces) following acute exposure of chinese hamster ovary (cho) cells to direct-acting chemical mutagens was measured. the results revealed that these lesions (and consequently sces) are rapidly eliminated from cells. sce levels fell to near control values by the third or fourth day (six and eight cell cycles, respectively) following exposure of cho cells to quinacrine mustard (qm) and mitomycin c (mmc). in contrast, cells expos ...	1982	6891633
induction of sister chromatid exchanges by 5-fluorodeoxycytidine: correlation with dna methylation.	chinese hamster ovary cells grown in medium containing 10 microm 5-fluorodeoxycytidine for forty-eight hours were found to have up to 5% of the deoxycytidine residues of the dna substituted by this analog. cytological studies of these cells showed that the incorporated 5-fdc caused a two-fold increase of sister chromatid exchanges (sce) over the control level. however, 5-fdc was capable of inducing sce only after it had been present in the cell for at least two cycles of dna synthesis. this is i ...	1982	6889952
sister chromatid exchange and gene mutation.	the parallel induction of sister chromatid exchange (sce) and single-gene mutation was quantified in chinese hamster ovary cells following exposure to nine different physical or chemical agents representing a wide variety of inducing lesions. for each agent, the frequency of induced sce was linearly related to the induction of mutation, but the efficiency of sce formation relative to mutation induction differed for each. studies in repair deficient cells suggested that unrepaired lesions enhance ...	1982	6889483
biochemical and immunological characterisation of mutants induced in v79 chinese hamster cells by a benzo[a]pyrene diolepoxide.	a series of 8-azaguanine resistant mutants was induced by treatment of v79 chinese hamster cells with either r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (antibpde) or methylnitrosourea (mnu). hypoxanthine phosphoribosyltransferase (hprt) activity in the mutants was determined for both hypoxanthine and azaguanine as substrates. with antiserum to purified brain hprt, cross-reacting material was also determined and analysed by two dimensional polyacrylamide gel electrophoresis. b ...	1982	6811144
sister chromatid exchange induced by short-lived monoadducts produced by the bifunctional agents mitomycin c and 8-methoxypsoralen.	to see if dna crosslinks are involved in the induction of sister chromatid exchange (sce), chinese hamster ovary cells were exposed to two bifunctional alkylating agents, mitomycin c and 8-methoxypsoralen, and their monofunctional derivatives, decarbamoyl mitomycin c and angelicin. the data indicate that monoadducts, rather than crosslinks, are responsible for sce formation. furthermore, all agents but angelicin produced short-lived lesions that led to sces in the first period of dna replication ...	1982	6807672
retinol (vitamin a) inhibits sister chromatid exchanges and cell cycle delay induced by cyclophosphamide and aflatoxin b1 in chinese hamster v79 cells.	retinol (vitamin a alcohol) at the doses tested neither induced an increase of frequency of sister chromatid exchanges (sce) nor cell cycle delay in chinese hamster v79 cells with or without the metabolic activation of s-9 mix. however, it inhibited sce frequencies and cell cycle delay in v79 cells induced by the indirect mutagen cyclophosphamide or aflatoxin b1. the inhibition was found to be dose and time dependent. these results suggest that retinol itself may have no direct effect on the gen ...	1982	6802508
isolation by a replica-plating technique of chinese hamster temperature-sensitive cell cycle mutants.	isolation of a wide variety of temperature-sensitive (ts) cell cycle mutants in mammalian cells has previously proved to be a very difficult task. the various procedures used for the isolation of such mutants included a mutant enrichment step based on exposure of the cells to the restrictive temperatures in order to kill the growing wild-type cells with agents that kill dna-synthesizing cells. hence, these methods favored the isolation of ts mutants that do not lose viability rapidly at the rest ...	1982	6752155
syntheses and modulations in the chromatin contents of histones h1 degrees and h1 during g1 and s phases in chinese hamster cells.		1982	7126528
interaction of razoxane and radiation on cultured chinese hamster cells.	razoxane [(+/-)-1,2-bis(3,5-dioxopiperazine-1-yl)propane] was investigated for its effects on the survival of irradiated chinese hamster fibroblasts in vitro. razoxane alone produced cytotoxicity that was dependent upon drug concentration and pulse exposure time, with a preferential lethality for cells treated while in the dna-synthetic phase. razoxane enhanced radiation-induced cell killing when used as either a pulse exposure or a continuous treatment. in asynchronous populations of cells, thi ...	1982	7141912
development of tetraploidy in v79 spheroids.	chinese hamster v-79-171 cells, when placed in suspension culture, spontaneously form multicell spheroids. as the spheroids enlarge the fraction of polyploid (predominantly tetraploid) cells increases and can approach 100% in very large spheroids. spheroid size, rather than age, seems to be a major determinant for increased ploidy. when cell separation techniques were used to select enriched populations of diploid and tetraploid cells, the growth rate and plating efficiency of the diploid cells ...	1982	7129485
increase of a surface glycoprotein by cyclic amp in chinese hamster ovary cells. dependence on cell-cell interaction.	cell surface proteins and glycoproteins of the cho-k1 clone of chinese hamster ovary cells were radiolabeled by surface-specific reactions as well as by metabolic incorporation of glycoprotein precursors. after the proteins were separated by two-dimensional gel electrophoresis, they were quantified according to the amount of radioactivity which was associated with individual proteins spots. a glycoprotein of 133,000 daltons (p133-11) wa found to increase severalfold by the elevation of the cytop ...	1982	6284757
characterization of the collagens synthesized by chinese hamster ovary cells. effect of colcemid and dibutyryladenosine cyclic monophosphate.	the collagens synthesized by chinese hamster ovary cells have been isolated and characterized. although these cells produce very small amounts of collagen, at least five distinct collagenous chains could be identified from radiolabeled media and cell extracts after limited pepsin digestion. two chains were characterized as alpha 1(v) and alpha 2(v), based on electrophoretic mobility, resistance to vertebrate collagenase, chromatographic properties on carboxymethylcellulose, and cyanogen bromide ...	1982	6291590
gene amplification accompanies low level increases in the activity of dihydrofolate reductase in antifolate-resistant chinese hamster lung cells containing abnormally banding chromosomes.	three independently-derived, antifolate-resistant chinese hamster lung cell lines that exhibit low level increases in dihydrofolate reductase (dhfr) activity, i.e., three- to fivefold vs. controls, have been compared with drug-sensitive cells to determine relative dhfr gene content. with a solution hybridization technique that makes use of genomic dna and a cloned double-stranded chinese hamster dhfr cdna probe, it has been found that the enzyme activity increases are associated with an approxim ...	1982	7107708
demonstration of recovery from the potentially mutagenic effects of ultraviolet light by replication-inhibited chinese hamster v79 cells.	the effects of replication-inhibiting conditions on the ability of chinese hamster (v79) cells to recover from the potentially mutagenic effects of ultraviolet (uv) light were investigated. v79 cells were synchronized by a new technique using a low concentration of hydroxyurea (0.2 mm), which provided a mildly-toxic, nonmutagenic method for producing large quantities of synchronized cells needed for these studies. the protocol developed for this study involved uv-irradiation of synchronized v79 ...	1982	6956805
repair capability and the cellular age response for killing and mutation induction after uv.	the cell-cycle response for killing and mutation induction by ultraviolet irradiation was measured in synchronous chinese hamster ovary cells (cho wild-type) and in a uv-hypersensitive mutant (43-3b) derived from this line. the cho 43-3b line shows a greatly enhanced sensitivity to killing (d0 of 0.3 as compared to 3.2 j/m2 for the wild-type), is hypermutable, and deficient in dna repair. for the wild-type, a characteristic age response is seen for killing by uv, with maximum sensitivity in earl ...	1982	6889678
defective removal of dna cross-links in a repair-deficient mutant of chinese hamster cells.	to further understand the relationships between dna damage, dna repair, and cellular end points such as survival and mutation, the repair capacity of a dna repair-deficient mutant (strain uv-20) of chinese hamster ovary cells was characterized in response to dna cross-linking agents. this mutant, previously shown to be hypersensitive to killing by both ultraviolet light and the cross-linking agent mitomycin c, was also found to be extremely sensitive to cis-diamminedichloroplatinum, another dna ...	1982	6807537
reduction of benzo(a)pyrene induced chromosomal aberrations by dl-alpha-tocopherol.	the antioxidant, dl-alpha-tocopherol (vitamin e), has been demonstrated to significantly reduce the percentage of benzo(a)pyrene (bp) induced chromosomal aberrations in vitro. chinese hamster lung (don) and chinese hamster ovary (cho) cells were treated with either 1 microgram/ml or 5 micrograms/ml bp for 4 to 28 h; some cultures were treated with s9 mix activated bp. additional cultures of don and cho were treated simultaneously with 100 micrograms/ml of dl-alpha-tocopherol and bp. in cho cells ...	1982	6290222
a chinese hamster ovary cell mutant deficient in glucosylation of lipid-linked oligosaccharide synthesizes lysosomal enzymes of altered structure and function.		1982	7085675
respiration-defective chinese hamster cell mutants containing low levels of nadh-ubiquinone reductase and cytochrome c oxidase.		1982	6282874
selection of temperature-resistant mutants of chinese hamster cells for growth on d-galactose.	somatic cell variants of chinese hamster v79 were selected for rapid growth on d-galactose at high temperatures. their phenotypes are stable after many generations in the absence of selection pressure. they clone in d-galactose at temperatures at which the wild type cannot, while in d-glucose, the variants and the wild type appear to have the same growth properties. the use of such variants should be very important for the study of gene regulation of carbohydrate metabolism in mammalian cells.	1982	7200825
sister-chromatid exchange and chromosomal aberrations by dhaq and related anthraquinone derivatives in chinese hamster ovary cells.	the induction of sister-chromatid exchanges (sces) and chromosomal aberrations in chinese hamster ovary cells by doxorubicin (adriamycin), dhaq and several related anthraquinone derivatives was investigated. doxorubicin, dhaq and some of its analogues exhibited genotoxic effects at 1 nm concentration. among them, dhaq possessed the strongest activity. the dna-damaging action of these substituted anthraquinone compounds correlated well with their antiproliferative effect on cells, and this action ...	1982	7200569
effects of hyperthermia on dividing chinese hamster ovary cells and on microtubules in vitro.	the ultrastructure of chinese hamster ovary cells was examined immediately after heating cells in mitosis, and the findings were compared with (a) the behavior of heated cells monitored with time lapse cinematography following heat shocks and (b) proliferative survival of individual cells followed for 7 days after heating. treatment of dividing cells at 45.5 degrees (5 to 15 min) disassembled the spindle and disrupted both the contractile ring and the midbody-cytoplasmic bridge complex to varyin ...	1982	7199378
insulin and glucagon release in the diabetic chinese hamster: differences among inbred sublines.	release of insulin and glucagon from perfused pancreases in vitro of 40 normal male and female chinese hamsters (from one inbred subline) and 110 male and female diabetic hamsters (from three inbred sublines) was measured in response to glucose plus arginine, theophylline alone, or potassium alone, in order to determine if differences in hormone secretion exist among different diabetic sublines. glucose plus arginine and potassium produced subnormal insulin responses in all three diabetic sublin ...	1982	7047274
mutant of chinese hamster ovary cells with altered mannose 6-phosphate receptor activity is unable to synthesize mannosylphosphoryldolichol.	b4-2-1 is a chinese hamster ovary cell mutant previously isolated and characterized as deficient in mannose 6-phosphate receptor activity. we show here that b4-2-1 is a pleiotropic mutant, defective in biosynthesis of asparagine-linked oligosaccharides, b4-2-1 is unable to synthesize mannosylphosphoryldolichol; the consequences of this defect on glycosylation are (i) biosynthesis of one major lipid-linked oligosaccharide, characterized by its resistance to endoglycosidase h and decreased size; t ...	1982	6954541
on the contribution of the mitochondrial genome to the growth of chinese hamster embryo cells in culture.	the present results demonstrate that chinese hamster embryo cell populations in culture can be adapted to grow in the presence of chloramphenicol. it is shown that tryptose phosphate broth and uridine, one of its components, prevent the growth inhibitory effect of the drug. study of some respiratory parameters (cytochrome c oxidase, cytochrome spectra, oxygen consumption) indicated that neither the broth nor uridine prevented the inhibitory effect of chloramphenicol on mitoribosomal protein synt ...	1982	6282420
reversible differential decondensation of unfixed chinese hamster chromosomes induced by change in calcium ion concentration of the medium.	differential decondensation of isolated unfixed chinese hamster metaphase chromosomes was obtained by decreasing the calcium ion concentration in the surrounding medium. a banded appearance of the swollen chromosomes could be observed either directly by phase contrast microscopy or after glutaraldehyde fixation and staining. there was a gradual transition from homogeneously dense to banded and finally to extensively decondensed chromosomes. the patterns induced at different stages were similar t ...	1982	7042235
mutagenic response to ultraviolet light and x-rays at five independent genetic loci in chinese hamster ovary cells.	the mutagenic response to ultraviolet light and x-irradiation at a number of well characterized independent genetic loci, viz those conferring resistance to 6-thioguanine, ouabain, emetine, methylglyoxal (bis) guanylhydrazone (mgbg), and 5, 6-dichlororibofuranosyl benzimidazole (drb), has been determined. upon exposure of cells to uv light in the range of 70 to 180 ergs/mm2, the frequency of mutants at all of the above genetic loci increased in a linear dose-dependent manner. however, some genet ...	1982	7140673
temperature-sensitive chinese hamster fibroblast mutant with a defect in rna metabolism.	we describe a new temperature-sensitive mutant of chinese hamster cell fibroblasts. after a shift to the nonpermissive temperature of 40.5 degrees c, the rates of dna, rna, and protein synthesis declined rapidly (to < or = 50% within 12 h) and the progression of unsynchronized cells through the cell cycle was affected. we believe that dna synthesis came to a halt after a short time, because cells no longer entered the s phase. the decrease in protein synthesis at 40.5 degrees c was shown to be a ...	1982	14582197
test for induction of chromosomal aberrations in chinese hamster ovary cells (in vitro) by 2-(2',4'-diaminophenoxy)ethanol.		1982	7177148
thermal tolerance and specific protein synthesis in chinese hamster fibroblasts exposed to prolonged hypoxia.		1982	7173335
effects of colchicine, colcemid and vincristine on ethyl methanesulfonate-induced sister chromatid exchanges and chromosomal aberrations in chinese hamster cells.	the effect of colchicine, colcemid and vincristine on ethyl methanesulfonate-induced sister chromatid exchanges and chromosomal aberrations was studied in chinese hamster cells. the number of ethyl methanesulfonate-induced sister chromatid exchanges was markedly decreased with increasing doses of colchicine and vincristine. in the presence of colchicine, ethyl methanesulfonate-induced chromosomal aberrations increased; these were mainly breaks and fragmentations. the effects were most prominent ...	1982	7160582
patterns of histone variant synthesis can distinguish g0 from g1 cells.	quiescent chinese hamster ovary cells, as well as three other types of quiescent cells, synthesize histone at a reduced but significant rate. the variant patterns of the histone synthesis in quiescent, s-phase and g1-phase and g2-phase cells ali differed from each other. h3.3 was the only h3 variant synthesized in quiescent and in g1 and g2 cells. all four h2a variants were synthesized in quiescent and s-phase cells, but only h2a.x and h2a.z were synthesized in g1 and g2 cells. no part of g1 or ...	1982	7159927
enhanced mutagenic response of mnu by post-treatment with methylmercury, caffeine or thymidine in v79 chinese hamster cells.	post-treatment with a non-toxic dose of thymidine, caffeine or methylmercury-hydroxide enhanced the mutagenic response from mnu at high doses, whereas no enhancement was observed with low doses of mnu. no mutagenic effects were found with thymidine, caffeine or methylmercury alone at the doses used. quantitatively, the modifying effects observed were similar for the 3 agents which indicates the possibility of a similar way of action.	1982	7155170
time-lapse cinemicrographic observations of heated g1-phase chinese hamster ovary cells ii. cell death, fusion, and multipolar divisions.		1982	7163483
time-lapse cinemicrographic observations of heated g1-phase chinese hamster ovary cells. i. division probabilities and generation times.		1982	7163482
survival and mutation of chinese hamster cells after ultraviolet irradiation and caffeine treatment.	uv-irradiated chinese hamster cells on post-irradiation treatment with caffeine in growth medium for 24 h gave rise to biphasic uv-survival curves. at caffeine concentrations between 0.001 and 0.1 mm, control and caffeine-grown cells had similar survival curves initially from 0 to 30 j/m2. at fluences greater than 30 j/m2, there was effectively only little further killing of caffeine-grown cells beyond that observed at 30 j/m2. at concentrations of caffeine greater than 0.5 mm, there was a gradu ...	1982	7162526
stepwise isolation and properties of unstable chinese hamster cell variants that overproduce adenylate deaminase.	addition of coformycin (0.5 microgram/ml) to a culture medium containing adenine causes in chinese hamster fibroblasts a lethal depletion of imp. resistant variants have been recovered, some of which exhibit increased adenylate deaminase activity. (debatisse et al., j. cell. physiol., 106:1-11, 1981). the selective medium was made more specific for the isolation of this class of variants by supplementation with azaserine. the hyperactive variants remained sensitive to coformycin concentrations a ...	1982	7162515
elimination of mnu-induced mutational lesions in v79 chinese hamster cells.	studies were performed on the non-linear dose response for gene mutations induced by low doses of monofunctional methylating agents in v79 chinese hamster cells. when treatment with methylnitrosourea was applied at the beginning of the s phase in synchronized cells, a linear dose-response curve was obtained, whereas application of the dose after gene replication resulted in a strong reduction of the number of induced mutations. additional time for repair resulted in reduced dose response of mnu, ...	1982	7155169
enhancement of the cytotoxicity of radiosensitizers by modest hyperthermia: the electron-affinity relationship.	the cytotoxicity of 3 electron-affinic radiosensitizers has been studied in chinese hamster v-79 cells as a function of ph and modest hyperthermia. when equitoxic concentrations were used and temperature was increased from 34 to 41 degrees c metronidazole, the compound with the lowest electron affinity showed the greatest enhancement of hypoxic-cell toxicity, and nitrofurantoin, the compound with the highest electron affinity, the least. the results can be explained if the mechanisms of toxicity ...	1982	7150485
molecular cloning of 3-hydroxy-3-methylglutaryl coenzyme a reductase and evidence for regulation of its mrna.	a recombinant plasmid containing a 1.2-kilobase cdna for 3-hydroxy-3-methylglutaryl coenzyme a reductase was isolated from a cdna library prepared from ut-1 cells, a clone of chinese hamster ovary cells that has markedly elevated reductase activity. this plasmid, designated pred-10, was identified by differential colony hybridization and hybrid-selected mrna translation. the mrna that hybridized to pred-10 directed the synthesis in vitro of a 90,000-dalton protein that was immunoprecipitated by ...	1982	6961444
antagonization by cycloheximide of ethyl methanesulfonate-induced 6-thioguanine-resistant mutation and sister-chromatid exchanges.	we studied the effect of cycloheximide (ch) on the induction of mutation and sister-chromatid exchanges (sces) in ethyl methanesulfonate (ems)-treated chinese hamster cells. at 10(-6)m, ch strongly antagonized the induction of mutation and sces and cell survival increased. this suggests that protein synthesis is essential for the induction of mutation as well as sces. results of experiments in which ch treatment preceded or followed exposure to mutagens were similar with respect to the response ...	1982	6891437
dansyl chloride-stained nucleolar organizers and core-like structures in chinese hamster metaphase chromosomes.		1982	6890902
hypermutability of a uv-sensitive aphidicolin-resistant mutant of chinese hamster fibroblasts.	an ultraviolet light (uv)-sensitive thymidine auxotroph of chinese hamster v79 cells that exhibits pleiotropic effects such as a high level of deoxycytidine triphosphate, slow growth, sensitivity to cytidine, and high frequencies of site-specific bromodeoxyuridine-dependent chromosomal aberrations was selected by its resistance to aphidicolin. the uv-induced mutability of this mutant and one of its revertants, which retains some of the phenotypes listed above, was studied in 3 mutation assay sys ...	1982	6818477
association of mutator activity with uv sensitivity in an aphidicolin-resistant mutant of chinese hamster v79 cells.	the spontaneous mutation rates of an ultraviolet light (uv)-sensitive aphidicolin-resistant mutant (aphr-4-2) and its revertants have been determined by 2 techniques. by using the fluctuation analysis, the mutant and its thymidine (tdr)-prototrophic 'revertant' were found to exhibit elevated spontaneous mutation rates at the 6-thioguanine- and diphtheria-toxin-resistant loci. in contrast, the tdr-auxotrophic 'revertant' did not show this property. similar results were obtained by the multiple re ...	1982	6818476
regulation of folylpoly-gamma-glutamate synthesis in mammalian cells. in vivo and in vitro synthesis of pteroylpoly-gamma-glutamates by chinese hamster ovary cells.	cultured chinese hamster ovary cells accumulated labeled folate and 5-methyltetrahydrofolate and metabolized these compounds to polyglutamates of chain length up to 10, with hexa-, hepta-, and octaglutamates predominating. intracellular vitamin was concentrated up to 50-fold, although the intracellular pteroylmonoglutamate concentration did not exceed that in the medium. folylpolyglutamate levels in mutant cells (auxb1), which are defective in the enzyme folylpolyglutamate synthetase, were less ...	1982	7142166
detection and localization of a class of proteins immunologically related to a 100-kda nucleolar protein.	a high-molecular-mass nucleolar protein (100-kda protein) is associated with nascent pre-rrna and pre-ribosomes in chinese hamster ovary cells. we have prepared antiserum against the 100-kda protein and we have used it to study the intracellular localization and the possible processing of this protein. serologically related proteins were detected in the nucleolus and in ribosomes. proteins of various subcellular fractions were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresi ...	1982	7151790
antifolate-resistant chinese hamster cells. mrna directed overproduction of multiple dihydrofolate reductases from a series of independently derived sublines containing amplified dihydrofolate reductase genes.	purification of the dihydrofolate reductases overproduced by 16 independently-derived antifolate-resistant sublines of chinese hamster lung cells and their drug-sensitive parental cell line, dc-3f, has confirmed our original observation that two molecular weight classes of this enzyme, viz. mr = 21,000 can be overproduced by drug-resistant cells (melera, p. w., wolgemuth, d., biedler, j. l., and hession, c. (1980) j. biol. chem. 255, 319-322). of the 16 drug-resistant sublines analyzed, 12 overp ...	1982	7130188
coupled ribonucleoside diphosphate reduction, channeling, and incorporation into dna of mammalian cells.	there is rapid and specific channeling of ribonucleoside diphosphates into dna through reactions beginning with ribonucleotide reductase and terminating with dna polymerase. lysolecithin-permeabilized chinese hamster embryo fibroblasts in culture rapidly reduced ribonucleoside diphosphates by ribonucleotide reductase action when dithiothreitol was provided as a reducing agent and incorporated these deoxynucleotides into dna. the radioactive label provided in ribo-cdp was not diluted by added deo ...	1982	6752137
potential radiosensitizing agents iii: 2-nitro-4-acetylimidazole analogs.	new analogs of 2-nitroimidazole have been synthesized in an effort to minimize the toxicity and increase selective sensitization of hypoxic mammalian cells toward lethal effects of ionizing radiation. 2-nitro-4(5)-acetyl-5(4)-methylimidazole was synthesized from the corresponding 2-amino analog and then reacted with oxiranes to produce the corresponding 1-substituted 2-propanol and 3-methoxy-2-propanol derivatives. the biological results of radiosensitizing activity of these agents against chine ...	1982	7175708
mutation-induced instability of antibiotic-resistant mammalian ribosomes.	emetine is an antibiotic which inhibits the activity of the 40-s subunits of eukaryotic ribosomes. a number of emetine-resistant mutants of chinese hamster cells have been isolated. we have studied the ribosomes isolated from strains carrying either of two alleles of an emetine resistance locus, one of which leads to an alteration in the electrophoretic mobility of ribosomal protein s14. both mutations lead to a loss of specific proteins, including s14, from 40-s subunits isolated in 0.5 m kcl, ...	1982	7173205
genetic analysis of tumorigenesis: xii. genetic control of the anchorage requirement in chef cells.	chinese hamster somatic cell hybrids between diploid anchorage-independent chef/204bu50 cells and diploid anchorage dependent chef/205-30 cells are anchorage dependent but can segregate subclones at low frequency which reexpress anchorage independence. thus, anchorage independence, like other characteristics of the transformed phenotype, is suppressed in these hybrids. anchorage-independent subclones were recovered from the anchorage-dependent hybrids under conditions which favored the retention ...	1982	7163952
molecular studies on the hyperthermic inhibition of dna synthesis in chinese hamster ovary cells.		1982	7163486
induction of sister chromatid exchanges in chinese hamster ovary cells by 5-bromodeoxyuridine.	sister chromatid exchange (sce) induction in established cell lines has become a widely used criterion for the assessment of genotoxicity. detection of sce is only possible if a base-analogue such as bromodeoxyuridine (brdu) is incorporated into the dna; it is not known to what extent the observed background level of sce is a consequence of the presence of the base-analogue, and to what extent it represents a 'natural' background. in this paper, experiments are described in which a number of dif ...	1982	7151225
potential radiosensitizing agents. 5. 2-substituted benzimidazole derivatives.	a series of 2-substituted benzimidazoles and their derivatives have been synthesized and tested for their ability to selectively sensitize hypoxic chinese hamster cells (v-79) toward the lethal effect of ionizing radiation. these compounds were prepared by reacting the 2-substituted benzimidazoles with 1,2-epoxy-3-methoxypropane in the presence of potassium carbonate. reaction of the 2-nitro and 2-methylfonyl analogue with the epoxide also yielded a cyclized material, which was confirmed to be a ...	1982	7143372
characterization of giemsa dark- and light-band dna.	using synchronized cultures of v79-8 chinese hamster lung fibroblasts, we either alternately labeled early- and late-replicating dna, or substituted one of these with bromodeoxyuridine to separate them in cscl density gradients or to identify the bromodeoxyuridine-containing chromosome bands by fluorescence microscopy. the giemsa light r bands were shown to replicate in the first half of s phase, and the dark g bands were shown to replicate in the last half of s phase. s phase was bimodal, with ...	1982	7159923
[increased cytotoxicity of misonidazole by ph reduction and 41 degrees c hyperthermia in chinese hamster cells].		1982	7157431
delayed sensitization to heat by inhibitors of polyamine-biosynthetic enzymes.	exposure of chinese hamster ovary cells to the enzyme inhibitors methylglyoxal bis(guanylhydrazone and alpha-difluoromethylornithine (dfmo) results in increased sensitivity to hyperthermia. while methylglyoxal bis(guanylhydrazone) demonstrates pronounced cytotoxicity at moderate extracellular concentrations, dfmo is tolerated well by this cell line at concentrations of up to 10 mm, as assayed by clonogenic survival after treatments at 37 degrees. an 8-hr preincubation at 37 degrees with either d ...	1982	6814750
genetic evidence that a phorbol ester tumor promoter stimulates ornithine decarboxylase activity by a pathway that is independent of cyclic amp-dependent protein kinases in cho cells.	ornithine decarboxylase (odc) inductions by cholera toxin and by the phorbol ester tumor promoter, tpa, were compared in wild-type chinese hamster ovary (cho) cells and in mutant cells having altered cyclic amp-dependent protein kinase activity. the aim of these studies was to determine whether cyclic amp-dependent protein kinase is involved in these inductions. the time course and the magnitude of odc inductions by either 100 ng/ml cholera toxin or 100 ng/ml tpa were similar in wild-type cells ...	1982	6294128
isolation by tritium suicide of uridine-cytidine kinase-defective mutants in chinese hamster v79 cells.		1982	6293853
beta-adrenergic mechanism of mammalian cells radioprotection by isoproterenol.	in experiments on fibroblasts of chinese hamster (b ii d ii faf-28, clone 431) it is shown that the specific beta-agonist isoproterenol causes an increase in the intracellular content of camp and a decrease in radiosensitivity of the cells. the beta-antagonist propranolol blocks the appearance of the above effects due to isoproterenol. isoproterenol fails to affect either the intracellular camp level or radiosensitivity of mice fibroblasts l, clone b-82, endowed with a functioning adenylate cycl ...	1982	6131549
enhanced survival of adriamycin-treated chinese hamster cells by 2-deoxy-d-glucose and 2,4-dinitrophenol.		1982	7104992
identification of a cholesterol-regulated 53,000-dalton cytosolic protein in ut-1 cells and cloning of its cdna.	ut-1 cells, a clone of chinese hamster ovary (cho) cells, have a 100- to 1,000-fold elevation in the amount of 3-hydroxy-3-methylglutaryl coa reductase and therefore grow in the presence of compactin, an inhibitor of reductase. in this paper, we report that ut-1 cells also have a markedly increased amount of another protein with a mr of 53,000 and an isoelectric point of approximately equal to 6. whereas the reductase is an enzyme of the endoplasmic reticulum, the 53,000-dalton protein (termed t ...	1982	6959111
relationship between aberrant dna replication and loss of cell viability in chinese hamster ovary cho-k1 cells.	we have previously presented evidence that a transient block to dna replication induces an aberrant form of dna synthesis. the most feasible explanation for this data is that the block to dna replication results in some segments of the chromosomal dna being replicated more than once in a single cell cycle. this form of aberrant dna synthesis was demonstrated to occur following direct inhibition of dna replication by 1-beta-d-arabinofuranosylcytosine or 9-beta-d-arabinofuranosyladenine or after i ...	1982	7127310
dna degradation in chinese hamster ovary cells after exposure to hyperthermia.	chinese hamster ovary cells grown in suspension showed a progressive reduction in the size of their nuclear dna to 50 to 60s fragments after hyperthermia (43-48 degrees). this dna degradation was not a homogeneous response but was observed only in cells incapable of attaching to a substratum after acute heating. the dna degradation was associated with the inability of cells to exclude the vital stain, trypan blue. the degradation process appeared to be a result of nucleolytic enzyme digestion wh ...	1982	7127283
cell-cycle kinetics and ultraviolet light survival in uv-1, a chinese hamster ovary cell mutant defective in post-replication recovery.	uv-i, an ultraviolet-sensitive mutant of cho-ki, is abnormally slow to recover from the inhibition of dna synthesis caused by u.v. irradiation. when synchronized uv-i cells are irradiated in g1, their movement into s phase is unaltered, but thymidine incorporation is depressed (compared with that in the parent cell similarly treated). when irradiated in s phase, again incorporation is more depressed, and s phase suffers a greater delay in uv-i than in the parent cell. uv-i and its parent have si ...	1982	6891386
modification of mutation frequency in plateau phase chinese hamster ovary cells exposed to gamma radiation during recovery from potentially lethal damage.	induction of forward mutations leading to 8-azaguanine resistance was studied in plateau phase chinese hamster ovary cells exposed to gamma-radiation. survival and mutation frequency were assessed immediately after irradiation or after 6 hours of post-irradiation recovery at 37 degrees c. cells exposed to doses above 4gy showed appreciable increase in the survival level as a result of recovery from potentially lethal damage. the mutation frequency response curve for cells plated immediately afte ...	1982	6984033
dimethyl sulfoxide affects colony morphology on agar and alters distribution of glycosaminoglycans and fibronectin.	we have found striking changes in the morphology of colonies of chinese hamster ovary cells grown on agar containing low doses of dimethyl sulfoxide. effects on morphology of cells grown on plastic at the same dimethyl sulfoxide concentrations were not as pronounced. computer-assisted analysis of darkfield photographs of growing colonies proved very useful in measuring the magnitude of morphological changes at various doses. a large decrease in total cell-bound and released glycosaminoglycans (g ...	1982	6960355
induction of mutations and sister-chromatid exchanges in chinese hamster ovary cells by ethylating agents.	chinese hamster ovary (cho) cells were exposed to [3h]ethyl nitrosourea (enu) or [3h]ethyl methanesulfonate (ems) and the following dna ethylation products were quantitated: 3- and 7-ethyladenine, o2-ethylcytosine, 3-, 7- and o6-ethylguanine, o2- and o4-ethyldeoxythymidine and the representative ethylated phosphodiester, deoxythymidylyl (3'-5')ethyl-deoxythymidine. when mutations at the hypoxanthine-guanine phosphoribosyl transferase (hgprt) locus induced by these same treatments were compared w ...	1982	6891748