Publications

cell cycle time determinations based on liquid scintillation counting of 3h-tdr labeled mitotic cells.	following a 10 min pulse labeling with 3h-tdr, flasks of asynchronous monolayer cultures of chinese hamster ovary cells were subjected to mitotic selection at 2 hr intervals. the mitotic index of the selected populations was always greater than 90%. counts per min per cell obtained by liquid scintillation counting were plotted versus time after the pulse label. comparisons were made between cycle times obtained by the mitotic-scintillation counting method and by the standard per cent labeled mit ...	1977	884704
chromosome tests with 134 compounds on chinese hamster cells in vitro--a screening for chemical carcinogens.	chromosomal aberration tests in vitro were carried out on chinese hamster cells grown in culture with various chemicals, including carcinogenic n-nitroso compounds and their related derivatives, food additives, medical drugs, pesticides and other chemicals commonly used in laboratories or industries. sixty-three of the 134 chemicals gave negative results in our test system even with doses at which the cell growth was markedly inhibited. nearly all compounds known to be mutagenic in bacteria were ...	1977	876270
complementation between mutants of cho cells resistant to a variety of plant lectins.	chinese hamster cell mutants resistant to the lectins pha, wga, ric, lca, and con a were previously grouped into 8--10 distinct phenotypes on the basis of their unique patterns of lectin resistance and lectin-binding properties. all but one of these classes of lectin-resistant (lecr) mutants behave recessively in somatic cell hybrids. one ricin-resistant class (ricrii) behaves dominantly. tests for complementation, by measuring the lectin-resistant properties of appropriate hybrids, show that se ...	1977	601679
n-ethylmaleimide sensitization of x-irradiated hypoxic chinese hamster cells.		1977	560026
sister chromatid exchange and chromosome aberration analysis with the use of several carcinogens and noncarcinogens.	several chemical carcinogens and noncarcinogens were tested for their ability to induce sister chromatid exchanges (sce) and structural chromosome aberrations in cultured v79-4 chinese hamster cells. all of the direct-acting carcinogens induced a large increase in sce frequency. two chemicals, which are mutagenic in microorganisms but whose carcinogenicity is poorly documented, also increased the frequency of sce. carcinogenic polycyclic hydrocarbons caused an increased incidence of sce only whe ...	1977	406414
isolation of uv-sensitive variants of cho-k1 by nylon cloth replica plating.	techinques are described which permit the identification and isolation of uv-sensitive variants from mutagenized populations of chinese hamster ovary (cho) cells. identification is based on the observation that within two days after receiving a dose of approximately 240 ergs/mm2 of uv irradiation most of the cells in a colony of cho detach from the surface of a plastic tissue culture dish. at a lower dose of uv, which does not kill or detach a significant number of parental cells, uv-sensitive c ...	1977	341370
dilution of hypoxanthine-guanine phosphoribosyl transferase and other factors affecting the frequency of 6-thioguanine resistance in chinese hamster lung cells.		1977	331095
effect of salt solutions on radiosensitivity of mammalian cells. ii. treatment with hypotonic solutions.	chinese hamster (v79) cells were treated with hypotonic nacl, nacl-ouabain, kcl, licl, nh4cl, nano3 or sucrose solutions and irradiated at various times during exposure to the solution. the extreme increase in the radiosensitivity of these cells, mainly characterized by changes in do, could be attributed to increases in the cell water-content and possibly the decrease in total cell water structure. the various ions may exert their specific effects on radiosensitivity by influencing the above wat ...	1977	301872
flow cytometric analysis of bromodeoxyuridine-substituted cells stained with 33258 hoechst.	this paper describes a flow-cytometric application of the quenching of fluorescence from 33258 hoechst stained chinese hamster ovary-line cells due to the incorporation of 5-bromo-deoxyuridine (brdu) into the cellular deoxyribonucleic acid. cells were grown for 24 hr in medium containing brdu in concentrations ranging from 1 x 10(-8) to 1 x 10(-4) m. for each concentration we measured the average fluorescence as determined by flow cytometry, the extent of brdu substitution and the effect of the ...	1977	70460
control of glycoprotein synthesis. lectin-resistant mutant containing only one of two distinct n-acetylglucosaminyltransferase activities present in wild type chinese hamster ovary cells.		1977	558978
effect of radioprotective aminothiols on the induction and repair of single-strand breaks in the dna of irradiated mammalian cells.	the effect of cysteamine and 2-mercapto-propionyl-glycine on the induction and repair of single-strand breaks in the dna of chinese hamster cells by irradiation in vitro in the presence of oxygen or in anoxia was investigated. the substances protected against the formation of breaks by irradiation both under oxic and anoxic conditions. the substances also exhibited a toxic effect which resulted in degradation of dna. cysteamine inhibited the rejoining of breaks after radiation exposure.	1977	906893
inhibition by caffeine of post-replication repair in chinese hamster cells treated with 7-bromomethylbenz(a)anthracene: enhancement of toxicity, chromosome damage and inhibition of ligation of newly-synthesized dna.		1977	880697
chromosome aberrations and sister chromatid exchanges in chinese hamster cells exposed to various chemicals.	to evaluate its usefulness for detection of mutagenicity and oncogenicity of chemicals, the frequency of chromosome aberrations and sister chromatid exchanges (sce) was examined in cultured chinese hamster cells exposed to 33 kinds of chemical agents, including 2 aromatic hydrocarbons, 7 amine derivatives, 3 phenols, 6 carboxylic acid derivatives, 4 azo compounds, 7 heterocyclic compounds, and 4 other types of agents. among them, 7 chemicals, including 5 known oncogens (n-n-butyl-n-nitrosouretha ...	1977	864744
antioxidant-mediated reversal of ultraviolet light cytotoxicity.	several antioxidants were tested for their protective effect in chinese hamster embryo cell against ultraviolet light (uvl)-irradiation. ascorbic acid, dl-alpha-tocopherol, butylated hydroxytoluene, and reduced glutathione were all shown to reverse uvl-induced cytotoxicity. at concentrations tested, no protective effect was detected when any of these antioxidants were added prior to uvl irradiation.	1977	864278
chromosome damage in chinese hamster cells sensitized to near-ultraviolet light by psoralen and angelicin.	the clastogenic effect of furocoumarins psoralen and angelicin in the presence of near-uv (320-380 nm) differs greatly, as do their modes of interaction with dna. psoralen, which requires only one-fifth as much light energy to produce the same lethal effect as angelicin at equimolar concentrations, is able to cross-link dna whereas angelicin cannot. the frequency of micronuclei which arise from chromosomal fragments shows the same differential effect as lethality. indeed aberrations account for ...	1977	561302
the pericentriolar material in chinese hamster ovary cells nucleates microtubule formation.	the structure and function of the centrosomes from chinese hamster ovary (cho) cells were investigated by electron microscopy of negatively stained wholemount preparations of cell lysates. cells were trypsinized from culture dishes, lysed with triton x-100, sedimented onto ionized, carbon-coated grids, and negatively stained with phosphotungstate. the centrosomes from both interphase and dividing cells consisted of pairs of centrioles, a fibrous pericentriolar material, and a group of virus-like ...	1977	559676
cell cycle dependent changes in morphology. studied with a cold-sensitive mutant of chinese hamster ovary cells.		1977	558900
inactivation and mutation of cultured mammalian cells by aluminium characteristic ultrasoft x-rays. i. properties of aluminium x-rays and preliminary experiments with chinese hamster cells.	irradiation with ultrasoft x-rays produces electron tracks of short defined lengths in the irradiated material. this property is of particular interest in distinguishing between different models of radiation action on living organisms. the production, absorption and dosimetry of aluminium k characteristic x-rays of energy 1.5 kev are described. quantitative experiments on mammalian cells with these x-rays are possible, and they were found to be considerably more effective than gamma-rays in inac ...	1977	301864
microvascular lesions of gingival and cheek pouch tissue in the diabetic chinese hamster.		1977	266583
cyclic amp-protein-dna complex formation in mammalian cell-free systems.	a cytoplasmic protein fraction from kb and chinese hamster ovary cells (cho-kl) was shown to bind in vitro to camp and subsequently to dna-cellulose. this protein complex was not found in de-52 purified cho-k1 camp-dependent protein kinases. the complex appeared to exist as a small fraction of the total camp binding proteins, preferred native to denatured dna and exhibited multiple sedimentation coefficients in glycerol gradients. this complex, after elution from the dna cellulose column, was sh ...	1977	198443
a role for asparaginyl-trna in the regulation of asparagine synthetase in a mammalian cell line.	the expression of asparagine synthetase activity [l-aspartate:ammonia ligase (amp-forming), ec 6.3.1.1] in cultured chinese hamster ovary (cho) cells is regulated by asparagine. after transfer of cho cells from an asparagine-supplemented medium to a medium lacking asparagine, activity increases 1.5- to 2-fold. if asparagine is added back to the medium, activity returns to control levels. to test the possible involvement of asn-trnaasn in regulating the levels of asparagine synthetase, we have ex ...	1977	18735
effect of ph on hyperthermic cell survival.	chinese hamster ovary cells incubated with various concentrations of co2, to obtain extracellular ph values in the range of 6.40-7.85, were heated at 45.5c for 5, 10, or 20 minutes. thermal sensitivity increased sharply from ph 7.35 to 6.65 (i.e., survival decreased from 1 x 10(-2) to 3 x 10(-5) for 20 minutes of heating), but remained constant from ph 7.35 to 7.85. the enhanced thermal sensitivity at ph values below pth 7.35 suggested that tumors should be preferentially destroyed by heat relat ...	1977	17014
reduced synthesis of [14c]mannosyl oligosaccharide-lipid by membranes prepared from concanavalin a-resistant chinese hamster ovary cells.	we compared the synthesis of mannosyl oligosaccharide-lipid by membranes of wild type and concanavalin a-resistant chinese hamster ovary cells during incubations with gdp-[14c]mannose and udp-n-acetylglucosamine. the membranes prepared from exponentially growing mutant cells incorporated 10- to 70-fold less [14c]mannose into oligosaccharide-lipid than did membranes of wild type cells. the lectin-resistant cells are temperature-sensitive for growth. using temperature-resistant revertants, we show ...	1977	863895
cellular inactivation by ultrasound.	the lethal effect of ultrasound (us) on mammalian cells has received relatively little attention. understandably, potential genetic aspects of us have been of prime concern to physicians who use us as a diagnostic tool; at the average power densities involved (<1 w cm(-2)) little, if any cell killing is to be expected. there have been sporadic attempts to use higher intensities ( approximately 1 w cm(-2)) as a treatment modality in cancer therapy, but those experiments seem to have been based on ...	1977	16073431
nonrandom distribution of chromosomal proteins during cell replication.	the distribution of chromatin-associated proteins in replicating chinese hamster ovary cells has been examined using the method described by taichman and freedlender (taichman, l., and freedlender, e.f. (1976), biochemistry 15, 447). cells are grown for several generations in [14c]lysine and thymidine, and then for one generation in the presence of [3h]lysine and 5-bromodeoxyuridine (brudrib) and a further generation in cold amino acid and brudrib. this protocol produces equal amounts of unifila ...	1977	557988
[protein synthesis during the period of mitotic recovery following exposure to colchicine and colcemide].	autoradiographic study with leucine-3h showed the restoration of normal mitosis course after the action of colchicine on the culture of chinese hamster cells to be accompanied by a marked activation of the protein synthesis exceeding the initial level. this intensification of protein synthesis precedes complete normalization of the mitotic activity in the cell culture. the course of normalization under the influence of colcemide is characterized only by the stabilization of the protein synthesis ...	1977	884267
study of trans-cyclopropylbis (diketopiperazine) and chelating agents related to icrf 159. cytotoxicity, mutagenicity, and effects on scheduled and unscheduled dna synthesis.	the cytotoxicity, mutagenicity, and dna damaging potential of trans-cyclopropylbis (diketopiperazine) (3) and chelating agents related to icrf 159 (1) were examined as a function of concentration and duration of exposure in the chinese hamster cell line v79a. at a concentration of 10(-3) m, 1 and the trans-cyclopropanediamine tetraacid 8 and ester 7 proved to be cytotoxic and mutagenic. the trans-cyclopropyl analogue 3 of icrf 159 and acyclic tetraacid 6 were less cytotoxic at all concentrations ...	1977	857019
hyperthermic effects on dna repair mechanisms.	studies have been carried out using neutral and alkaline sucrose density gradients to investigate the effect of 41 degree-43 degree c on the ability of chinese hamster ovary cells to repair single (ssb) and double stranded dna breaks (dsb) caused by exposure to ionizing radiation. the authors found that when hyperthermia exists prior to irradiation significant inhibition occurs. the data support the conclusion that unrepaired dna damage may be lethal to the cell. though no increase in radiation- ...	1977	847220
mutants of chinese hamster ovary cells with altered glucose-6-phosphate dehydrogenase activity.	two mutant clones of a chinese hamster ovary cell line deficient in glucose-6-phosphate dehydrogenase (g6pd) activity have been characterized. in each case, there is evidence that a structural gene mutation has taken place. the first mutant produces 11% specific enzyme activity compared to wild-type parental cells, but this residual activity is much more heat sensitive than that of the wild type. the second mutant contains no residual activity, but a revertant was isolated that exhibits a partia ...	1977	605387
variant chinese hamster cells resistant to the proline analog l-azetidine 2-carboxylic acid.	variants resistant to the toxic effects of the proline analog l-azetidine 2-carboxylic acid (azca) have been isolated from the chinese hamster tissue culture line g3 by a three-step selection procedure using increasing concentrations of azca. cells surviving each of the three selective steps have been examined for azca resistance and for proline uptake, biosynthesis, and degradation. the largest increment in azca resistance is acquired in the third step and is due to overproduction of proline as ...	1977	605386
spontaneous, chemical and viral mutagenesis in temperature-sensitive glutamine-requiring chinese hamster cells.		1977	194150
synaptonemal complex karyotyping in spermatocytes of the chinese hamster (cricetulus griseus). iii. quantitative evaluation.	relative length is a constant and distinctive characteristic for each autosomal sc, despite variations in absolute length from cell to cell. arm ratio is distinctive for each sc except for two of the three sub-acrocentrics, and serves, together with relative length, for identification. the constancy of relative length and arm ratios indicates biological stability and lack of physical distortion in these spread preparations. there is a 1:1 relationship between relative lengths of autosomal scs an ...	1977	870297
regulation of hypoxanthine transport by cyclic nucleotides in cultured chinese hamster lung fibroblasts.		1977	193444
excision of 7-bromomethylbenz[a]anthracene--dna adducts in replicating mammalian cells.	the excision of 7-bromomethylbenz[a]anthracene--dna adducts was studied in two cell lines (hela s-3 and chinese hamster v-79379a). in both cell lines, carcinogen-modified adenine residues were excised more readily than the modified guanine residues and the percentage of the total products excised decreased after treatment with higher concentrations of carcinogen. at the highest concentrations used in the chinese hamster cells, neither dna synthesis nor excision was detected. the lowest concentra ...	1977	849427
the synthesis of polyadenylated rna and other rna species in synchronised chk cells.	chinese hamster kidney cells have been synchronised by the double thymidine block technique. the rate of incorporation of [5-3h]uridine into the polyadenylated rna fraction has been analysed throughout two complete cell cycles and compared with the rate of incorporation into other rna species and the utp pool. in contrast with other reports, we have found that synthesis of 18 s rrna continues steadily throughout the cell cycle, as does synthesis of 5 s rna and trna. in the case of the polyadenyl ...	1977	851534
pre-implantation embryos of chinese hamster. ii incidence and type of karyotype anomalies after treatment of the paternal post-meiotic germ cells with an alkylating mutagen.	ninety-two male chinese hamsters were treated with a single, sub-lethal dose of the alkylating cytostatic drug trenimon. after 3--23 days they were mated with untreated females. the great majority of the male germ cells had been exposed to the mutagen while they were in the highly sensitive post-meiotic spermatid stage. the karyotypes of the resulting embryos were studied in the 4--8-cell stage. out of 221 analysable embryos, 24.4% had aberrant karyotypes. ploidy and genome mutations were, at 0. ...	1977	876266
the effect of dose fractionation on gamma-radiation induced mutations in mammalian cells.	the lethal and mutagenic effects of single and fractionated doses of gamma-radiation were studied in v79-4 chinese hamster cells, as dose fractionation is of interest in radiation protection studies. the results show that the induction of 8-azaguanine resistant (agr) mutants has a non-linear dose response curve following single doses of radiation. the lethal and mutagenic effects of fractionated doses were always less than if the radiation was given in a single dose. any change in treatment whic ...	1977	865492
cell-mediated mutagenesis in cultured chinese hamster cells by carcinogenic polycyclic hydrocarbons: nature and extent of the associated hydrocarbon-dna reaction.	a system of cell-mediated mutagenesis is described for the study of compounds which require metabolic activation to exert their cytotoxic and mutagenic effects. this system combines bhk21 cells for metabolism of the compounds and v79 cells as targets for mutagenesis. using the two polycyclic hydrocarbon carcinogens benzo(a)pyrene and 7-methylbenz(a)anthracene we have shown that the hydrocarbon-dna reaction which accompanies mutagenesis in the target cell is indistinguishable from that reported t ...	1977	865486
continued initiation of dna synthesis in arginine-deprived chinese hamster ovary cells.	when exponentially growing cho cells were deprived of arginine (arg), cell multiplication ceased after 12 h, but initiation of dna synthesis continued: after 48 h of starvation with continuous [3h]thymidine exposure, 85% of the population had incorporated label, as detected autoradiographically. consideration of the distribution of exponential cells in the various cell cycle phases leads to a calculation that most cells in g1 at the time that arg was removed, as well as those in s, engaged in so ...	1977	853059
an ultrastructural study of the recovery of chinese hamster ovary cells after freezing and thawing.		1977	558864
mammalian cells with defective mitochondrial functions: a chinese hamster mutant cell line lacking succinate dehydrogenase activity.	a mutant cell line derived from chinese hamster fibroblasts is described which is defective in oxidative energy metabolism. glucose is continuously required in the medium. as a result of a block in the krebs cycle, these cells are auxotrophs for carbon dioxide and asparagine. several experiments support our conclusion that the mutant cells lack appreciable levels of succinate dehydorgenase activity. other components of the electron transport chain appear to be fully functional, although there is ...	1977	558831
absence of a measurable g2 phase in two chinese hamster cell lines.	evidence is presented that demonstrates the absence of a measurable g2 phase in the cell cycles of two sublines of the chinese hamster lung fibroblast v79. one of the sublines, in addition, lacks a detectable g1 phase, thereby possessing a cell cycle comprised of simply two phases, dna synthesis (s) and mitosis (m).	1977	266201
purification and properties of dihydrofolate reductase from methotrexate-sensitive and methotrexate-resistant chinese hamster ovary cells.	we have previously described methotrexate-resistant chinese hamster ovary cells which appear to contain normal levls of a structurally altered dihydrofolate reductase (ec 1.5.1.3) (flintoff, w.f., davidson, s.v., and siminovitch, l. (1976) somatic cell genet.2,245-261). by selecting for increased resistance form these class i cells, class iii resistant cells were isolated which appeared to possess an increased activity of the altered enzyme. in the report, we describe the purification and severa ...	1977	15711
action of cyclic nucleotide analogues in chinese hamster ovary cells.	cyclic nucleotide analogues have been tested for their ability to cause the morphological conversion of chinese hamster ovary cells in culture, as well as for effects on cyclic amp-related enzymes. the ability of the analogues to inhibit the cyclic amp phosphodiesterase activity and to activate the cyclic amp-dependent protein kinase activity in cell extracts has been measured. cell cultures were incubated with the analogues and the effects on morphology, intracellular level of cyclic amp, and i ...	1977	191090
synaptonemal complex karyotyping in spermatocytes of the chinese hamster (cricetulus griseus). ii. morphology of the xy pair in spread preparations.	the x and y chromosome axes have a distinctive morphology at pachytene and are clearly distinguishable from autosomal scs. the x and y are totally unpaired at late zygotene when most of the autosomes are synapsed; however, their attachment points at the presumptive sc end are closely apposed. the x and y axes pair to form a length of sc that is somewhat shorter than the unpaired portion of the y. unpaired axes may appear thin and sometimes double, or may thicken to form fusiform bulges that are ...	1977	870291
synaptonemal complex karyotyping in spermatocytes of the chinese hamster (cricetulus griseus). i. morphology of the autosomal complement in spread preparations.	using the counce-meyer spreading technique, in over 70 spermatocytes it was possible consistently to obtain whole, flattened nuclei containing complete sets of pachytene scs. the scs are visible in both the phase and electron microscopes. each sc is morphologically intact, preferentially stained, and attached to the nuclear envelope by a dense, terminal plaque. it is thus possible to trace each sc for its entire length. also, a structure representing the kinetochore is clearly visible in each au ...	1977	858262
lack of mutagenic effect of halothane or chloroform on cultured cells using the azaguanine test system.	halothane with and without nitrous oxide and chloroform alone were tested for mutagenic effects at the 8-azaguanine locus on the chromosomes of chinese hamster lung fibroblast cells in culture. no significant numbers of mutations were found after 24 h exposures to 1-3% of these anaesthetics, or to 75% nitrous oxide.	1977	911573
culture of pre-implantation chinese hamster (cricetulus griseus) embryos in vitro.	pre-implantation embryos from chinese hamsters (cricetulus griseus) were cultivated under completely defined conditions. the embryos were placed in drops of chemically defined medium under liquid paraffin and cultured in an atmosphere of 10% co2 in air. by this method, development will proceed in vitro from the two-cell stage up to the blastula within 72 h. it is possible to stop the cultivation at different stages of development, to fix the embryos and analyse the chromosomes. the method descri ...	1977	857153
segregation studies in cho hybrid cells: i. spontaneous and mutagen-induced segregation events of two recessive drug-resistant loci.	the process of segreation or phenotypic expression of two recessive drug-resistant loci from heterozygous chinese hamster ovary hybrid lines is examined. the spontaneous segregation rates of phytohaemagglutinin resistance (phar) and a temperature-dependent 8-azaguanine-resistant locus (azarts) from heterozygous quasitetraploid lines using luria-delbruck fluctuation analysis were 5 x 10(-5) and 10(-5) events/cell/generation, respectively. in quasihexaploid lines, the latter rates increased 40- an ...	1977	605380
[electron microscopic study of interphase in a culture of fibroblast-like cells].	the analysis of the ultrastructural changes of fibroblast-like cells of chinese hamster at different periods of the cell cycle demonstrates that the most reliable morphological criteria for identification of different periods of the interphase are changes of the nuclear chromatin and nucleolus and the dynamics of development of the daughter centrioles. no prominent changes of the morphology of the protein-synthesizing apparatus during interphase were noted.	1977	560735
coordinate regulation of protein synthesis and messenger rna content during growth arrest of suspension chinese hamster ovary cells.	we have found chinese hamster ovary cells, cultured in suspension, are subject to growth control by serum. when suspended in medium containing 0.5% serum the cells becomes reversibly arrested in the beginning of the g1 phase of the cell cycle and can be maintained in this viable, nonproliferating state for several days. this system was used to examine the regulation of protein synthesis with growth rate. in particular, the experiments addressed the question whether mrna content is the principal ...	1977	558201
the kinetics of contact inhibition in mammalian cells.	to elucidate the process of contact inhibition in mammalian cells, we investigated the kinetics of growth arrest in [3h]thymidine labelled embryonic chinese hamster (cricetulus griseus l.) cells after the addition of various concentrations of unlabelled cells. it was observed that after the contact inhibition concentration had been reached, the cells grew undisturbed for one more generation. in the following 24 hr the concentration fell back to the level at the beginning of the experiment and st ...	1977	558054
rapid cell cycle analysis by measurement of the radioactivity per cell in a narrow window in s phase (rcsi).	a new rapid method for the cell cycle analysis of asynchronously growing cells is presented. the new method is an alternative to the more time consuming and subjective fraction of labeled mitoses (flm) method. like the flm method, all cells in the s phase of the cell cycle are marked by pulse labeling with a radioactive dna precursor. the subsequent progress of the cohort of cells thus labeled is monitored through a narrow window in the cell cycle. the window is defined by a narrow range of dna ...	1977	322870
additive action of ionizing and non-ionizing radiations throughout the chinese hamster cell-cycle.		1977	300730
growth and biochemical characteristics of a detachment variant of cho cells.	a variant subline of chinese hamster cells (line cho) was isolated that had increased resistance to detachment from the substratum. comparisons between parental and variant cells of the complex carbohydrates liberated during trypsin detachment showed that the variant cells synthesized little or no hyaluronic acid. these cells also had reduced amounts of other complex carbohydrates in the cell periphery. however, parental and variant cells did not differ in morphology, growth control, or cyclic a ...	1977	192736
mutations affecting the antigenic properties of hypoxanthine-guanine phosphoribosyl transferase in cultured chinese hamster cells.	cells of the mutant chinese hamster strain rjk10 do not contain either hypoxanthine-guanine phosphoribosyl transferase activity (hgprt) or protein that cross-reacts immunologically with hgprt. hgprt+ revertants have been isolated from rjk10 and those strains produce hgprt with altered antigenic properties. hgprt from the revertant cells is less reactive with anti-hgprt serum than enzyme from the wild-type cells, and enzymes from the two sources are immunoprecipitated independently from mixtures ...	1977	75576
isolation of wheat germ agglutinin-resistant clones of chinese hamster ovary cells deficient in membrane sialic acid and galactose.	several clones of chinese hamster ovary cells have been selected for their resistance to the toxic effects of wheat germ agglutinin. the clones do not bind wheat germ agglutinin as well as parent cells and are 5- to 250-fold more resistant to the toxic effects of the lectin. of three clones studied in detail, all exhibit a decrease in wheat germ agglutinin binding affinity. two have normal numbers of wheat germ agglutinin binding sites, while one (clone 13) has a 65% decrease in binding sites. c ...	1977	320201
mechanisms for sister chromatid exchanges and their relation to the production of chromosomal aberrations.	by taking advantage of the fact that fluorescent light (fl) induces strand breaks only in bromodeoxyuridine(brduy-substituted dna, and that those breaks eventually lead to the formation of sister chromatid exchanges (sces), the response of sces to fl was studied carefully in chinese hamster chromosomes in which, out of four dna strands, brdu-substitution had occurred either in one or three strands. the fl-induced sce frequency did not differ greatly between these two types of chromosomes. howeve ...	1977	837800
enhancement by caffeine of cell killing and chromosome damage in chinese hamster cells treated with thiotepa.		1977	402344
biochemical genetics of chinese hamster cell mutants with deviant purine metabolism. vi. enzymatic studies of two mutants unable to convert inosinic acid to adenylic acid.	ade-h and ade-i are two auxotrophic mutants of chinese hamster ovary (cho-k1) cells which specifically require adenine as the purine source to grow. the enzymatic defects of these mutants were examined in cell-free extracts. it was found that ade-h did not have any detectable adenylosuccinate synthetase activity and ade-i was defective in the adenylosuccinate lyase enzyme. the relevance of adenine-requiring mutants to the study of the regulation of purine metabolism in mammalian cells is discuss ...	1977	849250
clonal variation in colony morphology and growth of cho cells cultured on agar.	single chinese hamster ovary (cho) cells plated on agar form macroscopic colonies with high efficiency. colonies produced by cells from the uncloned cell line increase in diameter continuously for 10-12 days after plating to form mounds of cells about 1 mm in diameter. with further incubation, some of these colonies do not increase in diameter (arrested dome), some form an expanding annular monolayer of cells around the central mount (fried egg), and some grow by enlarging the central mound into ...	1977	837451
125i-udr induced division delay.	mitotic selection for cell cycle analysis was used to investigate the effects of (3)h and (125)i, incorporated into dna, on the cell cycle progression of chinese hamster ovary (cho) cells. the results indicate that s-phase cells were delayed and g(2) cells were not.	1977	836938
the relationship between polyamine accumulation and dna replication in synchronized chinese hamster ovary cells after heat shock.	the relationship of polyamine accumulation and semiconservative dna replication was studied in synchronous chinese hamster ovary cultures, progressing through the cell cycle either normally at 37 degrees or after hyperthermic exposure (43 degrees for 1 hr) during g1 or s phase. in control cultures, intracellular polyamine levels decreased as cells divided and then reaccumulated as cells exited g1 and proceeded through the s and g2 phases. immediately after cultures were exposed to 43 degrees hea ...	1977	832272
[effect of suboptimal temperature on the mitotic regime].	a two-hour treatment of chinese hamster cells with a suboptimal temperature of 21 degrees c leads to a decrease of the mitotic index and to a delay in division at the metaphase. cooling causes a sharp rise of the pathological mitosis, represented mainly by the forms of pathology connected with the disorganization of the mitotic apparatus, such as c-mitosis and dispersion of chromosomes in the metaphase. after being transferred to the optimal temperature conditions the cells completely restored t ...	1977	558014
altered morphology and increased cell adhesiveness of chinese hamster ovary cells cultured on fibrin.	chinese hamster ovary cells cultivated on fibrin exhibited different characteristic from cells growing on plastic. while sparsely plated cells on plastic dishes had an epithelioid morphology, cells on fibrin assumed a round shape and then converted to a stretched form with protruded processes that increased with cell density. within a few days, cells fibrinolysed adjacent fibrin and returned to the morphology seen in plastic dishes. when fibrinolysis was inhibited by epsilon-aminocaproic acid (e ...	1977	557051
glycoprotein synthesis in a temperature-sensitive chinese hamster cell cycle mutant.	a temperature-sensitive mutant of chinese hamster cells is described which has two interesting properties: (1) it is a cell cycle mutant and (2) glycoprotein synthesis appears to be affected at the at the non-permissive temerature (40degreesc). synchronized cells shifed to 40degreesc in the beginning of their g1 phase do not incorporate [3h]-thymidine into dna during the expected s-phase, but once dna synthesis has been initiated ( approximately 10 hours after termination of serum starvation) a ...	1977	557044
action of fdurd and dcyd on the incorporation of brdurd in chinese hamster somatic cell dna and the isolation of auxotrophic mutants.	chinese hamster somatic cells grown in the presence of bromodeoxyuridine, deoxycytidine and fluorodeoxyuridine incorporate more bromodeoxyuridine in the dna than cells grown in the presence of bromodeoxyuridine alone. thus they become more sensitive to light irradiation. our data suggest that 0.05 mm--0.2 mm bromodeoxyuridine, 0.05 mm deoxyctidine and 10 mmug/ml fluorodeoxyuridine is one of the best possible combinations for the selection of chinese hamster somatic cells mutants. auxotrophs for ...	1977	138686
the isolation and characterization of asparagine-requiring mutants of chinese hamster cells.		1977	14014
lectin receptors and lectin resistance in chinese hamster ovary cells.	chinese hamster ovary (cho) cells previously selected in a single-step for resistance to one or two different lectins and assigned to individual phenotypic groups on the basis of their unique patterns of lectin resistance, have been examined for their lectin-binding abilites. the lectin-binding parameters of cho cells were shown to be very complex in a detailes study of the binding of 125i-wga to wild-type (wt) cells. on the basis of these results, standard assay conditions were established and ...	1977	899950
altered drug permeability in mammalian cell mutants.	the properties of colchicine uptake into chinese hamster ovary cells were examined and found to be consistent with an unmediated diffusion mode. this uptake was stimulated several fold by metabolic inhibitors. the activation energy of colchicine uptake was found to be 19 kcal per mole; a similar value was obtained in cells stimulated by cyanide. drug resistant mutants with greatly reduced colchicine permeability have been isolated. they displayed a pleiotropic phenotype, being cross-resistant to ...	1977	899949
chromosomal characteristic of chinese hamster cells and their hgprt-deficient mutant line.	chinese hamster cell line (line k 431, hgprt+) and its mutant (line k ii, hgprt-) are similar in the numberical composition of the karyotype (modal number 22 chromosomes), but differ in its structureal constitution (occurrence of trisomy, breaks in the centromeric region, chromosome losses and others). deletion and rearrangement of some heterochromatic segments of the x chromosome appeared with a higher frequency in hgprt- line and can constitute one of the conceivable causes of the hgprt activi ...	1977	885285
the influence of the serum/pha ratio, microplate well shape and 2-mercaptoethanol on the stimulation of different numbers of cells in lymphocyte cultures from the chinese hamster.	conditions for microculture of chinese hamster lymphocytes are described which allow measurement of thymidine uptake with 6000 to 1000 lymphocytes per culture. the relationship between degree of cell stimulation, pha concentration culture surface and cell concentration is described, as well as the influence of addition of 2-mercaptoethanol to the cultures.	1977	864264
the molecular basis of emetine resistance in chinese hamster ovary cells: alteration in the 40s ribosomal subunit.	the molecular basis of resistance to the protein synthesis inhibitor emetine has been examined in cell-free, protein-synthesizing extracts derived from normal and emetine-resistant (emtr) mutants. we had earlier shown that protein synthesis in extracts of the mutant cells was resistant to the inhibitory action of emetin. when extracts from a wild-type and mutant cell line were fractionated into supernatant (s-100) and polyribosome fractions and mixed in different combinations, resistance to emet ...	1977	837444
protease activation of g1 nuclei isolated from chinese hamster fibroblasts.		1977	836402
spermatogenesis in the chinese hamster.	in this article a description of the process of spermatogenesis in the chinese hamster is given. spermiogenesis could be divided into 16 steps. the cycle of the seminferous epithelium was divided into 12 stages, coinciding with the first 12 steps of spermiogenesis. the relative and absolute duration of the stages was determined. the duration of the cycle of the seminiferous epithelium was found to be 17.0 days. the morphology of the spermatogonia was studied in seminiferous tubules mounted "in t ...	1977	835840
ultrasonic treatment of chinese hamster cells at high intensities and long exposure times.	monolayers of single chinese hamster cells growing on 0.036 mm melinex film in specially constructed irradiation vessels were treated to continuous 990.5 khz focused ultrasound. after treatment, cells were incubated until they formed small microcolonies (48 h) or until confluent growth was obtained (96 h). damage was assessed by scoring a focal area of 5 mm2 for a reduction in colony number or multiplcity after three generations or for a cell-free area after seven generations. the results showed ...	1977	831919
effect of phorbol myristate acetate on the recovery of spontaneous and ultraviolet light-induced 6-thioguanine and ouabain-resistant chinese hamster cells.	12-0-tetradecanoyl-phorbol-13-acetate (tpa) and phorbol were tested in chinese hamster cells for their effects on mutagenesis (resistance to 6-thioguanine and to ouabain), dna repair, and survival after ultraviolet (uv) irradiation. recovery of 6-thioguanine- and ouabain-resistant colonies was significantly increased by tpa treatment and, to a lesser extent, by phorbol in uv-irradiated cells. moreover, maximum enhancement of recoverable uv-induced 6-thioguanine- and ouabain-resistant mutants occ ...	1977	830404
[rate of spontaneous chromosome aberration occurrence in cultured chinese hamster cells].	the spontaneous chromosome mutation rate was studied in cultured aneuploid chinese hamster cells (clone 237(1)) using the method of slowing down the rate of cell division in a limiting medium containing 0.1% of serum. it was shown that during one cell generation (which lasted 14 days in limiting medium) the accumulation of chromosome aberrations with time took place. the data obtained are in keeping with the assumption of a linear dependence of this accumulation on time. the spontaneous chromoso ...	1977	612482
[induction of gene mutations and the lethal action of ultraviolet rays in synchronized chinese hamster cells].	lethal and mutagenic effects of uv light were studied in two synchronized uv-sensitive chinese hamster cell clones differing in the degree of sensitivity (chs1, chs2). it is shown that the phase of mitosis is most resistant to the lethal effect of uv. the sensitivity of both cell clones increases in the pre-synthetic phase and reaches its maximum during the phase of dna synthesis. positive correlation of cell sensitivity to mutagenic and lethal action of uv was observed when studying induced mut ...	1977	612481
chromosome replication patterns in an established cell line (cho).	the chromosome replication patterns of the established cell line cho have been examined and compared with those of normal primary chinese hamster cells, using the budr-hoechst fluorescence technique developed by latt (1973). the results of this study indicate that the majority of cho chromosomes replicate normally. there are four clear-cut exceptions to this rule, three of which are most easily explained as undetected or misinterpreted structural rearrangements ot the cho genome. several other r ...	1977	606507
hyperthermic treatment (43 degrees c) rapidly impedes attachment of fibroblasts to culture substrates.	hyperthermic (43 degrees c) exposure of chinese hamster fibroblasts for more than 30 min, either in suspension or as a monolayer, significantly inhibits their ability to attach to the culture substrate. this finding as well as the effect of hyperthermia on membrane proteins and on surface topology are rapidly expressed and differ from the inhibition of colony formation which is a later effect of hyperthermia on reproductive ability.	1977	565256
[hybridization of chinese hamster cells sensitive to ultraviolet irradiation].	resistance to uv-light was studied in two uv-sensitive aneuploid chinese hamster cell clones to different origin and degree of sensitivity, their respective polyploids and somatic cell hybrids. the karyotype of the parental clones, cell hybrids and polyploids was analyzed in parallel. a great variability of karyotypes was detected in hybrid cells. serial cultivation of hybrids was accompanied by chromosome loss. soon after fusion the hybrid clones proved to be more resistant to uv than the paren ...	1977	561015
a simple method for cloning and replica plating of mammalian cells using multicellular spheroids.	v 79/4 chinese hamster cells or hela cells grow in eagle's mem supplemented with 25 microgram/ml dextran sulphate to form clonal multicellular spheroids. these cell clones, consisting of 5-10(2) cells, are easy to separate, to transfer from one culture vessel into another and grow as normal monolayer colonies on dederon cloth circles after subculture in eagle's mem without dextran sulphate. a simple replica technique is described by which 500 clones can be transfered onto at least 3 replica clot ...	1977	356496
variance in ldh isozyme patterns in a chinese hamster (cricetulus griseus) colony.	1. ldh activity and isozyme pattern were examined in the liver and epididymal fat pad of animals in 12 different sublines of the upjohn chinese hamster colony, which was established to produce animals with spontaneous diabetes. 2. considerable divergence was observed and the animals could be divided into 3 groups according to ldh-h activity. each group was significantly different from the other in epididymal fat pad ldh-1, 2,3 and 5 and liver ldh-3, 4 and 5. 3. the variance in ldh isozyme patter ...	1977	318257
survival of synchronized v79 cells treated with x-rays and cordycepin.	the survival of v79 chinese hamster lung cells exposed to x-irradiation is reduced by co-treatment with cordycepin (3'-deoxyadenosine). this reduction is manifested principally by a decrease in the d0 of the x-ray survival curve from 199 rad in untreated cells to 106 rad in cordycepin-treated cells. reduced survival is seen throughout the life-cycle when synchronized cell populations are exposed to both agents with cells in mid-s being especially sensitive.	1977	300368
control of cell shape by adenosine 3' : 5' - phosphate in chinese hamster ovary cells: studies of cyclic nucleotide analogue action, protein kinase activation, and microtubule organization.		1977	197834
sequence programming of dna replication over the s phase of chinese hamster cells.		1977	137816
potential genetic risks from stationary magnetic field.	cytogenetic analysis of dede cell lines (chinese hamster) was used to study the mutagenic effect of stationary magnetic field (smf) and the combined effect of smf and tepa. cytogenetic analysis showed a moderate mutagenic effect after exposure to smf. in combination with tepa, only the additive effect of the two mutagens was observed.	1977	76658
[occurrence of pseudoisocyanine-positive endocrine cells in the midgut of the hamster (cricelulus griseus) (author's transl)].	pseudoisocyanine-reacting cells could be identified in the intestinal glands of the upper duodenum of the hamster (cricetulus griseus). these cells contain numerous granules as carrier substances of the colouring pigments. presumable these cells are insulin-producing cells.	1977	72477
detection of chemically induced somatic mutation in chinese hamsters.		1977	593291
comparison of highly inbred diabetic and nondiabetic lines in the upjohn colony of chinese hamsters.		1977	913895
chromosome studies on bone marrow cells of chinese hamsters fed a radiosterilized diet.	metaphase preparations of chromosomes from bone marrow cells of chinese hamsters were examined for mutagenic effects following the feeding of a radiosterilized diet. no increase in the incidence of structural chromosomal aberrations was observed. as far as numerical aberrrations were concerned, the proportion of cells with polyploidy increased to between 4 to 5 times the control level, irrespective of the moisture content of the diet. this polyploidy effect occurred very early, being detectable ...	1977	929628
the dose-dependence of sister chromatid exchanges induced by 3 hydrocarbons, in the in vivo bone marrow test with chinese hamsters.		1977	401744
heterogeneity of karyotype and growth potential in simian virus 40-transformed chinese hamster cell clones.	five clones of chinese hamster cells transformed with simian virus 40 (sv40) were isolated from methylcellulose and characterized as to giemsa-banded karyotype, dna content, saturation density, agglutination with concanavalin a, and tumorigenicity. chromosome analysis and dna content studies at early passage revealed that the genetic complement for all clones was predominantly near tetraploid. all cultures examined contained a proportion of hypertetraploid cells. nonrandom chromosome changes inc ...	1977	192902
mechanism of action of inosine dialdehyde (nsc 118994) in the inhibition of proliferation of tumor cells in culture.	inosine dialdehyde (inox), the periodate oxidation product of inosine, inhibited the proliferation of various tumor cell lines in suspension culture in a concentration-dependent manner. a concentration of about 1 mm was required to completely inhibit the proliferation of novikoff rat hepatoma and mouse l-cells, whereas about 0.1 mm completely inhibited the proliferation of l1210 and p388 mouse leukemia and chinese hamster ovary cells. inox inhibited in a similar time- and concentration-dependent ...	1977	193637
purineless death: ribosomal rna turnover in a purine-starved ade- mutant of chinese hamster cells.	when v79 pur 1, a purine-requiring auxotroph of a chinese hamster cell line, is deprived of adenine, nucleic acid and protein synthesis decline rapidly. however, on continuous starvation rna and dna synthesis recommences to reach approximately 30% of the normal level between 12 to 24 h starvation. this is accompanied by a rise in the intracellular nucleotide pool. utilizing mengovirus, which gives a productive infection in v79 pur 1 cells even under conditions of starvation, we can show that rrn ...	1977	195948
simian virus 40-chinese hamster kidney cell interaction. iii. characteristics of chemical induction in a clone of virogenic transformed cells.	a number of chemical and physical agents were screened to determine their effectiveness in inducing simian virus (sv40) production in a virogenic clone of sv40-transformed chinese hamster cells. mitomycin c (mc) was the most effective inducing agent, and mc induction was further characterized. it was found that levels of infectious sv40 dna were increased above control levels as early as 6 h after addition of mc to the culture medium and reached maximum levels by 48 h. virus capsid (v) antigen a ...	1977	196036
simian virus 40-chinese hamster kidney cell interaction. iv. enhanced virus replication in infected cells upon treatment with mitomycin c.	chinese hamster kidney cells are semi-permissive to simian virus 40 (sv40). exposure to mitomycin c (mc) of chinese hamster kidney cells infected with sv40 dna enhanced the yield of infectious virus 10- to 100-fold. this stimulation occurred whether the treatment was performed before or after infection. a simultaneous increase in the number of v antigen-synthesizing cells and virus-producing cells, as well as the virus burst size, was observed upon mc pretreatment, whereas the proportion of t an ...	1977	196038
correlation between changes in intracellular level of cyclic amp, activation of cyclic amp-dependent protein kinase, and the morphology of chinese hamster ovary cells in culture.		1977	196552
initiation points for dna replication in nontransformed and simian virus 40-transformed chinese hamster lung cells.	randomly growing chinese hamster lung cells were pulse-labeled with 3h-thymidine, and the replicating forks of individual dna fibers were visualized by autoradiography. when grown in complete medium, wild-type sv40-transformed cells had more forks per unit length of dna than nontransformed cells. in isoleucine-depleted medium, wild-type sv40-transformed cells had fewer forks per unit length than those few nontransformed cells (1-3% of the population) which continued dna replication. cells transf ...	1977	196764