Publications

immunological detection of cell surface components related with aggregation of chinese hamster and chick embryonic cells.		1979	110634
two-dimensional electrophoretic analysis of concanavalin-a binding components in the plasma membranes of chinese hamster fibroblasts.		1979	456578
neurogenesis in the amygdaloid nuclear complex in a rodent (the chinese hamster).		1979	421144
higher order structure of chromosomes.	isolated chinese hamster metaphase chromosomes were resuspended in 4 m ammonium acetate and spread on a surface of distilled water or 0.15 to 0.5 m ammonium acetate. the dna was released in the form of a regular series of rosettes connected by interrossette dna. the mean length of the rosette dna was 14 micron, similar to the mean length of 10 micron for chromomere dna of drosophila polytene chromosomes. the mean interrosette dna was 4.2 micron. sds gel electrophoresis of the chromosomal nonhist ...	1979	456198
mutagenesis of chinese hamster cells is facilitated by thymidine and deoxycytidine.		1979	431725
cytotoxic effects of procaine, lignocaine and bupivacaine.	cytotoxic effects of procaine, lignocaine and bupivacaine were investigated on cultures of chinese hamster lung fibroblasts. cell growth was inhibited over 24 h exposures with an ed50 of 0.17% for procaine, 0.07% for lignocaine and 0.02% for bupivacaine. cell survival (measured as colony-forming ability) was reduced over 24 h exposure with an ed50 of 0.21% for procaine, 0.09% for lignocaine and 0.06% for bupivacaine. morphological changes included vacuolation, cell rounding and retraction from t ...	1979	465252
effect of cell growth rate and dose fractionation on chemically-induced ouabain-resistant mutations in chinese hamster v79 cells.	chinese hamster v79 cells were grown in medium containing either 10% or 2% fcs during the expression time following exposure to mnng. the lower serum concentration was used to reduce the rate of cell replication, thereby allowing more time for dna repair prior to "fixation" of the mutagenic lesion. in addition, fractionated and continuous exposures to mnng and mam, respectively, were carried out to determine their effect on the number of induced ouabain-resistant mutants. the results indicated t ...	1979	460287
growth and morphology of colonies of chinese hamster ovary cells growing on agar is affected by insulin.	as a model for the effect of hormones and growth factors on three-dimensional growth of mammalian cells, we have analyzed the effect of insulin on the three-dimensional growth and morphology of chinese hamster ovary (cho) colonies grown on the surface of agar. sequential photographs in dark-field illumination of growing colonies have been analyzed with computer-assisted techniques. in this analysis the entire shape of each colony in a sizeable population (up to 10(5) colonies per experiment) can ...	1979	287027
calcium-mediated cell surface changes in chinese hamster cells.		1979	220066
rapid isolation of metaphase chromosomes containing high molecular weight dna.	metaphase chromosomes with high molecular weight dna were isolated from chinese hamster ovary (cho) cells in a neutral buffer containing polyamines and chelators. the individual, unfixed chromosomes retained their centromeric and secondary constrictions, distinct sister chromatids, and complex banding patterns. the dna from these chromosomes was 100-fold larger (2 x 10(8) daltons) than dna from chromosomes isolated by other procedures. these characteristics indicate preservation during isolation ...	1979	39081
alteration in structure of multifunctional protein from chinese hamster ovary cells defective in pyrimidine biosynthesis.	a combined genetic, biochemical, and immunological approach has clarified structural relationships involving the first three enzymes of de novo pyrimidine biosynthesis. a procedure involving antibody and protein a-sepharose was used to isolate the enzymes carbamoyl-phosphate synthase [atp:carbamate phosphotransferase (dephosphorylating, amido-transferring), ec 2.7.2.9], aspartate transcarbamoyltransferase (carbamoylphosphate:l-aspartate carbamoyltransferase, ec 2.1.3.2), and dihydro-orotase (l-5 ...	1979	36610
quantitation of antibody binding to cell surface antigens by x-ray fluorescence spectrometry.	an x-ray spectrometric method has been developed to quantitate antibody bindng to whole cell surfaces in order to obtain a distribution of binding within a population of cells. the method involves incubation of target cells with ferritin-labeled antibody. analysis of prepared samples in a modified transmission electron microscope with an x-ray detector and data analysis equipment, yields quantitative results on the binding of labeled antibody to individual cells. the binding of anti-2,4-dinitrop ...	1979	435491
circular dichroic and sedimentation studies of phosphorylated h1 from chinese hamster cells.		1979	427101
detachment variants of chinese hamster cells. hyaluronic acid as a modulator of cell detachment.		1979	218830
characterization of naturally occurring auxotrophic mammalian cells.	in a previous study, several cultured cell lines were detected which are naturally occurring auxotrophs. in this investigation, the enzyme deficienceis involved are described. it is demonstrated that the chinese hamster cell lines cho(k1), yh21, rjk-36, and chw-1102 are deficient in cystathionase and argininosuccinate synthetase. in addition, cho (k1) and chw-1102 were found to lack argininosuccinate lyase. chw-1102 cells were also found to be unable to proliferate in medium containing branched- ...	1979	483124
respiration-deficient chinese hamster cell mutants: genetic characterization.	we present here genetic experiments with a series of chinese hamster cell mutants defective in oxidative energy metabolism. the mutations were all shown to be recessive in intraspecies hybrids. thirty-five mutants were sorted into eight complementation groups, but one of these mutants failed to complement representatives of two distinct complementation groups. the possibility was raised that this is a cell carrying two mutations or a deletion. because of the greatly different frequencies with wh ...	1979	483122
biochemical genetics of chinese hamster cell mutants with deviant purine metabolism: isolation and characterization of a mutant deficient in the activity of phosphoribosylaminoimidazole synthetase.	a new purine-requiring mutant of chinese hamster ovary cells (cho-kl) is described. this mutant, ade-g, grows on aminoimidazole carboxamide, hypoxanthine, or adenine. it complements all eight of our other previously described ade- mutants. biochemical analysis of de novo purine synthesis in whole cells suggests that ade-g is capable of the first four reactions of de novo purine biosynthesis and that it synthesizes and accumulates phosphoribosylformylglycinamidine (fgam). direct enzyme assay in c ...	1979	483121
effects of hyperthermia and x irradiation on sister chromatid exchange (sce) frequency in chinese hamster ovary (cho) cells.		1979	441255
the effect of hexose on chloramphenicol sensitivity and resistance in chinese hamster cells.		1979	438306
characterization of cell lines showing growth control isolated from both the wild type and a leucyl-trna synthetase mutant of chinese hamster ovary cells.	the genetic approach to the problem of cellular growth control is limited by the availability of recessive mutations in cell lines which are capable of growth control in vitro. the cho cell line has yielded many recessive mutations including, for example, tsh1, a temperature sensitive leucyl-trna synthetase mutant, which under non-permissive conditions rapidly shuts down protein synthesis and generates uncharged trna. both cho and tsh1 are transformed, however, and do not respond to environmenta ...	1979	438301
the importance of ornithine as a precursor for proline in mammalian cells.	ornithine aminotransferase catalyzes the reversible transamination of l-ornithine to delta1-pyrroline-5-carboxylate, the immediate precursor of proline. the direction and flux through this pathway in mammalian cells has not been established. glutamate has generally been considered to be the most important precursor for proline biosynthesis, but recent studies in xiphoid cartilage indicate that a significant fraction of cellular proline is derived from ornithine. using newly isolated mutant chine ...	1979	438294
failure of caffeine to influence induced mutation frequencies and the independence of cell killing and mutation induction in v79 chinese hamster cells.	using v79 chinese hamster cells and a replating assay, no effect of caffeine post-treatment on spontaneous or uv- or ems-induced mutation frequencies to 8-azaguanine resistance was demonstrable. however, considerable potentiation of cell killing was observed. previous reports that caffeine enhances induced mutation frequencies are explained by an artefact in the situ method used; a similar artefact may also explain the cumulative in situ mutation dose-response curves. furthermore, the relationsh ...	1979	431556
[effect of the inhibition of a synthesis processes in the s-period on the subsequent course of mitosis in a synchronized chinese hamster cell culture].	the transcription of all nuclear rna and rrna was inhibited in the synchronized chinese hamster cell culture by actinomycin d and protein synthesis was suppressed by pyromycin during the first and the second parts of the s period of the mitotic cycle. a decrease of the mitotic cell activity was revealed during the first and second waves of cell proliferation after the synchronization irrespective of the time of the antibiotic administration. at the same time there was noticed an increase of such ...	1979	427282
the discrete-time kinetic model analysis of dna content distributions in experimental tumour cells.	a method was developed to analyse and characterize fmf measurements of dna content distribution, utilizing the discrete time kinetic (dtk) model for cell kinetics analysis. the dtk model determines the time sequence of the cell age distribution during the proliferation of a tumor cell population and simulates the distribution pattern of the dna content of cells in each age compartment of the cell cycle. the cells in one age compartment are distributed and spread into several compartments of the ...	1979	371812
karyotype and tumorigenicity of 1-methylguanine-transformed chinese hamster cells.	chinese hamster embryo cells transformed with the trna catabolite 1-methylguanine were characterized by giemsa-banded karyotyping and by their tumorigenic potency in athymic nude mice. all seven 1-methylguanine-transformed cell lines were hyperdiploid with a modal chromosome number of 23. three of these lines had an additional marker chromosome derived from the long (q) arm of chromosome no. 4, and they had alterations of chromosome no. 5 as well. two of these three cell lines were tumorigenic. ...	1979	283292
diethyldithiocarbamate enhancement of radiation and hyperthermic effects on chinese hamster cells in vitro.		1979	220663
biochemical genetic analysis of pyrimidine biosynthesis in mammalian cells. ii. isolation and characterization of a mutant of chinese hamster ovary cells with defective dihydroorotate dehydrogenase (e.c. 1.3.3.1) activity.	a mutant (a204) of chinese hamster ovary cells (cho-k1), which is deficient in dihydroorotate (dho) dehydrogenase (e.c. 1.3,3.1) activity, has been isolated by a replica plating procedure. the mutant does not show a requirement for exogenously added pyrimidines. examination of intact cells shows that the mutant accumulates a large amount of carbamyl aspartate and is markedly but not totally deficient in biosynthesis of orotate from earlier precursors of pyrimidine biosynthesis, including asparta ...	1979	220270
mutation induction by 5-fluorodeoxyuridine in synchronous chinese hamster cells.	chinese hamster ovary cells synchronized by mitotic detachment were treated with 5-fluorodeoxyuridine (fdurd), 0.2 micrograms/ml, at various times in the cell cycle. fdurd treatment in the early s period induced resistance to 6-thioguanine. treatment of asynchronous cells with fdurd caused little increase in 6-thioguanine resistance over the spontaneous frequency. mitotic selection thus enhances the probability of a cell being in the portion of s period receptive to mutation. these observations ...	1979	154970
biochemical genetic analysis of pyrimidine biosynthesis in mammalian cells: iii. association of carbamyl phosphate synthetase, aspartate transcarbamylase, and dihydroorotase in mutants of cultured chinese hamster cells.	carbamyl phosphate synthetase (ec 2.7.2.9), aspartate transcarbamylase (ec 2.1.3.2), and dihydroorotase (ec 3.5.2.3), the first three enzymes in de novo pyrimidine synthesis in chinese hamster ovary cell strain kl (cho-kl), cose diment through a glycerol gradient. when an extract from urd- a, a pyrimidine-requiring auxotroph reduced in all three activities, is run on a glycerol gradient, the enzyme activities appear in two peaks higher in the gradient, a peak of aspartate transcarbamylase separa ...	1979	39353
response of cells to hyperthermia under acute and chronic hypoxic conditions.	the lethal response of chinese hamster cells heated to 42 degrees was determined following 0 to 30 hr culturing under hypoxic conditions. oxygenated and acutely hypoxic cells were equally sensitive to hyperthermia; however, sensitivity increased with the time of culturing under hypoxic conditions prior to treatment. three hr at 42 degrees resulted in a surviving fraction of approximately or equal to 0.1 under acute hypoxic conditions and less than 0.001 for cells cultured for 30 hr under oxygen- ...	1979	34477
radioprotection by dmso of mammalian cells exposed to x-rays and to heavy charged-particle beams.	populations of g1-phase chinese hamster cells in stirred suspensions containing various concentrations of dmso were irradiated with 250 kv x-rays or various heavy charged-particle beams. chemical radioprotection of cell inactivation was observed for all let values studied. when cell survival data were resolved into linear and quadratic components, the extent and concentration dependence of dmso protection were found to be different for the two mechanisms. the chemical kinetics of radioprotection ...	1979	572979
sterol synthesis in variant chinese hamster lung cells selected for resistance to 25-hydroxycholesterol. cross-resistance to 7-ketocholesterol, 20alpha-hydroxycholesterol, and serum.	two lines of chinese hamster lung (dede) cells which are resistant to the killing effect of 25-hydroxycholesterol, and which grow to confluence in its presence, have been isolated. one of the resistant lines exhibited a high to normal growth rate and normal levels of 3-hydroxy-3-methylglutaryl coenzyme a (hmg-coa) reductase (mevalonate:nadp+ oxidoreductase (coa-acylating), ec 1.1.1.34) activity and sterol synthesis in the presence of concentrations of 25-hydroxycholesterol that caused nearly com ...	1979	762093
potentially lethal damage versus sublethal damage: independent repair processes in actively growing chinese hamster cells.		1979	441249
a study of the repair of potentially lethal and sublethal radiation damage in chinese hamster cells exposed to extremely hypo- or hypertonic nacl solutions.		1979	441248
ribosomal transcriptional complexes in subnuclear fractions of chinese hamster ovary cells after short-term actinomycin d treatment.		1979	430587
the effect of amino acids on the temperature sensitive phenotype of the mammalian leucyl-trna synthetase mutant tshl and its revertants.	the temperature sensitive leucyl-trna synthetase mutant tshl and two revertants have been compared to the parental chinese hamster ovary cells with respect to the effects of amino acid concentrations in the medium on growth. elevating the leucine concentration 30- or 100-fold allowed tshl to grow exponentially at 38.5 degrees c, normally the nonpermissive temperature. partial revertants that had recovered some enzyme activity required smaller supplements for growth. measurements of the leucine p ...	1979	422660
structure-activity relationships in the development of hypoxic cell radiosensitizers. ii. cytotoxicity and therapeutic ratio.	this paper describes measurements of the aerobic cytotoxicity of 42 nitroaromatic and nitroheterocyclic compounds towards chinese hamster cells in vitro. the results of acute and chronic exposure were quantified, and the concentration c required to achieve a standard response estimated. fitting the data to an equation of the form - log c = b0 + b1e, where e is the one-electron reduction potential, explained 47 and 71 per cent of the variance in the acute and chronic aerobic cytotoxicity respecti ...	1979	312784
structure-activity relationships in the development of hypoxic cell radiosensitizers. i. sensitization efficiency.	the efficiency of 35 nitroaromatic and nitroheterocyclic compounds in radiosensitizing hypoxic chinese hamster cells in vitro was determined. the concentration c of the compound required to achieve an enhancement ratio of 1.6 was measured, and the redox and partition properties were quantified as the one-electron reduction potential at ph 7, e, and the octanol: water partition coefficient, p, respectively. most of the compounds studied were 2-nitroimidazoles, but some 4- and 5-nitromidazoles, 5- ...	1979	312783
emetine resistance in chinese hamster cells. analysis of ribosomal proteins prepared from mutant cells.		1979	762080
the initiation and elongation steps in protein synthesis: relative rates in chinese hamster ovary cells during and after hyperthermic and hypothermic shocks.	the relative rates of the initiation and elongation phases of protein synthesis have been determined in heat- and cold-shocked cho cells from measurements of the incorporation of 35s-methionine into n-terminal and internal positions of growing peptides by a modified edman degradation. when the cells are shifted from 37 degrees c to temperatures between 10 degrees c and 34 degrees c, the rate of initiation is at first reduced more extensively than that of elongation. after 20 to 30 minutes at the ...	1979	762195
isolation and cell cycle analysis of temperature-sensitive mutants from chinese hamster cells.	mutants temperature-sensitive for growth have been isolated from the established line of chinese hamster fibroblasts wg1a. these mutants, together with the ones previously isolated by roscoe et al. ('73), have been characterized with regard to their cell cycle properties. most of them become arrested in the g1 phase of the cell cycle when incubated under restrictive conditions. by performing temperature shift experiments with synchronous cultures, the execution steps of most of the mutated funct ...	1979	762193
[effect of polyethyelene glycol on proliferation of cultured chinese hamster cells].	chinese hamster cells in suspension were treated with peg 4000 for 20 min. it was found that cell size began to diminish already when a 5% peg solution was used, and reached the minimal value in a 20% peg solution. a pronounced cell death was observed when peg concentration exceeded 20%, but cells that survived retained their proliferation potential. it is concluded that the cell death results from hypoosmotic shock when cell suspension in peg solution is diluted.	1979	571153
a simple method for producing different growth fractions in vitro for use in anti-cancer drug studies.	a simple technique has been used experimentally to produce in vitro chinese hamster ovary cells with growth fractions ranging from 0 to 100%. known numbers of exponentially growing and plateau-phase tissue culture cells were mixed in various proportions to yield the desired final growth fraction. cells attach to the culture flask surface within 1 hr of mixing. treatment at that time with the nitrosourea compounds, ccnu and meccnu, resulted in differential drug survival sensitivities that were de ...	1979	570456
gene mutation and sister chromatid exchange in chinese hamster cells.	the mutation in hypoxanthine phosphoribosyl transferase gene and the induction of sister chromatid exchange (sce) were comparatively studied treating chinese hamster ovary cells with the mutagens ethylmethanesulphonate. n-methyl-n'-nitro-n-nitrosoguanidine, mitomycin c and x-ray. all the agents exerted strong mutagenic effects and showed a dose-dependent relationship for the induction of sces.	1979	555171
the effect of hydroxyurea on synchronized chinese hamster ovary cells irradiated by ultraviolet light.		1979	550666
nucleolar organizing regions of normal chinese hamster and chw cell line chromosomes.	the chromosome preparations from fibroblasts of normal male and female chinese hamsters and the cell line chw were stained with agno3. the silver stain was usually localized at the telomeres of autosomes. the marker chromosome m1 in the chw cell line has ag-nor near the centre of the long arm, which indicates that either the long arms of two number 5 chromosomes fused at the telomeres or the intact telomeric region of one chromosome fused with one with a deleted telomere. the variation of ag-nor ...	1979	527380
enhancement of thermal killing by polyamines. iv. effects of heat and spermine on protein synthesis and ornithine decarboxylase activity.	protein synthesis is shown to be very heat-sensitive in chinese hamster cells. it is shut off completely following 15-20 min at 42 degrees c whereas rna and dna syntheses are affected only after much longer exposure times. cells recover from inhibition of protein synthesis upon transfer to 37 degrees c. the degree of recovery is inversely related to the duration of heat exposure and it fits cell survival quantitatively. cells which become temporarily heat-resistant by prior heat-treatment, are a ...	1979	498061
an ultrastructural study of morphogenesis of fibrogranular complex and centriole in ductuli efferentes of chinese hamster.	an ultrastructural study of ciliated epithelial cells in the ductuli efferentes of young and adult hamsters has revealed that these cells possess dense granules, dense granule clusters, dense bodies and fibrogranular complexes as reservoirs or precursors for ciliogenesis. the dense granules are first seen in the centrosomal region. later, many dense granules and dense granule clusters appear in the apical portion of the epithelial cells where, subsequently, dense bodies are also found. finally, ...	1979	494233
sister chromatid exchanges in vivo in chinese hamster embryonic liver cells exposed transplacentally to brdu.		1979	477415
microspectrofluorometric analysis of surface antigens of murine melanoma and hamster peritoneal cell hybrids: comparisons of species antigenicity, chromosome number, and tumorigenicity.	somatic cell hybrids from viral fusions of murine melanoma (pazg) x chinese hamster peritoneal cells (ch) were compared with respect to surface antigenicity, karyotype and tumorigenicity. one line, f57-(9), which arose from the hybridization of two ch cells and one pazg cell, had slight (6%) ch chromosome loss but 80%pazg chromosome loss after 10 months in culture. these cells expressed ch antigens strongly and pazg antigens weakly. in comparison, another hybrid, f57-(7), formed from one ch and ...	1979	471422
cytogenetic properties of chinese hamster v79-e cells: g-banding, c-banding, nucleolar organizer regions, and sister chromatid exchanges.	a line of the chinese hamster v79 strain, denominated as v79-e, is cytogenetically characterized. it has a modal chromosome number of 22. chromosome morphology, g- and c-banding reveal strong differences from the normal complement of the chinese hamster presumably caused by rearrangements of chromosome segments during the past 20 years of in vitro culture. 4 chromosomes possess terminal nucleolar organizer regions. spontaneous sister chromatid exchanges occur with a frequency of 0.38 sister chro ...	1979	446595
studies on 1-beta-d-arabinofuranosyl cytosine-resistant mutants of chinese hamster fibroblasts: iii. joint resistance to arabinofuranosyl cytosine and to excess thymidine--a semidominant manifestation of deoxycytidine triphosphate pool expansion.	variants isolated from mutagenized chinese hamster fibroblasts by a single cycle of exposure to ara-c distributed into two classes: (1) deoxycytidine (dc) kinase deficient clones with a high level of resistance, this phenotype was recessive in hybrids; and (2) clones exhibiting joint resistance to thymidine (dt) and to "low" ara-c concentration, this phenotype was accounted for by an increased dctp pool. the incorporation of exogenous dc into macromolecules was markedly altered in these variants ...	1979	432758
[vaginal smear cycle in 4-day cyclic chinese hamsters, cricetulus griseus].	the contents of vaginal smear of 4-day cyclic chinese hamster (cricetulus griseus) was investigated every 3 hours for 5 days. a light-dark cycle of 14--10 hr was used with the lights turned on at 6 : 00 a.m. estrous cycle of the chinese hamster determined by vaginal smears can be divided into 6 periods. the proestrous phase started at about 0 : 00 of day 1, the day of the proestrous phase was designated as day 1 of the estrous cycle. in the afternoon of the same day 1, nucleated epithelial cells ...	1979	428430
synthesis of low molecular weight rna components a, c and d by polymerase ii in alpha-amanitin-resistant hamster cells.	in an attempt to establish which rna polymerase catalyzes the synthesis of the low molecular weight rna components a, c and d, ama 1 cells (mutant chinese hamster cells) were used in experiments with addition of alpha-amanitin. ama 1 cells contain an altered rna polymerase ii which is 800 times more resistant towards inhibition by alpha-amanitin than the wild type enzyme. alpha-amanitin (up to 200 microgram/ml) added to these cells does not affect the synthesis of the low molecular weight rnas a ...	1979	424295
chromosomal aberrations of don lung cells of chinese hamster after exposure to vinblastine in vitro.		1979	423909
purification of p-glycoprotein from plasma membrane vesicles of chinese hamster ovary cell mutants with reduced colchicine permeability.		1979	500733
86rb+ fluxes in chinese hamster ovary cells as a function of membrane cholesterol content.	steady-state fluxes of 86rb+ (as a tracer for k+) were measured in chinese hamster ovary cells (cho-k1) and a mutant (cr1) defective in the regulation of cholesterol biosynthesis; the membrane cholesterol content of this mutant was varied by growing it on a range of cholesterol supplements to lipid-free medium (sinensky, m. (1978) proc. natl. acad. sci. u.s. 75, 1247--1249). analogous to previous findings in ascites tumor cells, 86rb+ influx in the parent strain was differentiated into a ouabain ...	1979	508750
effects of heat shock on gene expression and subcellular protein distribution in chinese hamster ovary cells.	incubation of chinese hamster ovary (cho) cells for one hour at 43 degrees c results in several obvious changes in protein distribution and protein synthesis. one major protein of the cytoplasm (molecular weight 45,000 daltions), also present as a minor component in the nucleus, rapidly disappeared while several proteins, especially high molecular weight peptides, were induced by heat shock. localization of the proteins in the cytoplasm, extra-nucleolar chromatin and nucleolar bodies has been ca ...	1979	537909
cytogenetic effects of antituberculosis antibiotic rifampin on chinese hamster ovary cells.		1979	540994
induction of sister-chromatid exchanges in chinese hamster ovary cells by thiol and hydrazine compoudns.	cysteine, cysteamine and glutathione all induce sister-chromatid exchanges (sces) in chinese hamster ovary (cho) cells when applied to cell cultures at concentrations between 10(-4) and 10(-2) m. acute exposure of cells th thiol compound for a period of 2--3 h resulted in a unique dose--response relationship in each instance. this consisted of two peak sce frequencies, one at either extreme of the concentration range. each peak corresponded to a 2--3-fold increase over the spontaneous level. a c ...	1979	522883
the effect of caffeine on cytotoxicity, mutagenesis, and sister-chromatid exchanges in chinese hamster cells treated with dihydrodiol epoxide derivatives of benzo[a]pyrene.	the effect of caffeine on chinese hamster v79 cells after treatment with the highly mutagenic (+/-)-7 beta,8 alpha-dihydroxy-9 alpha, 10 alpha-7,8,9,10-tetrahydrobenzo[a]pyrene, and the weaker mutagen (+/-)-7 beta,8 alpha-dihydroxy-9 beta,10 beta-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, b[a]p-deiol-epoxide ii, was studied at both the biological and molecular levels. caffeine, at nontoxic dose levels, caused a synergistic reduction in cell survival induced by both isomers and also inhibited dna e ...	1979	522876
a comparison of cytotoxicity, ouabain-resistant mutation, sister-chromatid exchanges, and nascent dna synthesis in chinese hamster cells treated with dihydrodiol epoxide derivatives of benzo[a]pyrene.	chinese hamster v79 cells were treated with either (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (b[a]p-diol epoxide i) or (+/-)-7 beta,8 alpha-dihydroxy-9 beta,10 beta-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (b[a]p-diol epoxide ii) and the nascent dna was labeled with [me-3h]thymidine. the cells were harvested for determination of cytotoxicity, sister-chromatid exchanges (sce), ouabain-resistant (or) mutations and the size of newly synthesized daughte ...	1979	522875
modification by cysteamine of ultrasound lethality to chinese hamster v-79 cells.		1979	515353
a cadmium-resistant variant of the chinese hamster (cho) cell with increased metallothionein induction capacity.		1979	510415
effects of caffeine on purine metabolism and ultraviolet light-induced lethality in cultured mammalian cells.	caffeine, at doses which enhance the killing action of ultraviolet light, inhibits both de novo synthesis and the utilization of exogenous purines in cultured cho-k1, a chinese hamster ovary cell line. the decrease in synthesis was measured as inhibition by caffeine of the accumulation of phosphoribosylformylglycineamide or of phosphoribosylaminoimidazolecarboxamide, the fourth and ninth intermediates, respectively, in the de novo biosynthetic pathway. the effect is dose dependent, with a caffei ...	1979	498124
retinol inhibition of ornithine decarboxylase induction and g1 progression in chinese hamster ovary cells.		1979	498118
elimination of metabolic cooperation in chinese hamster cells by a tumor promoter.	wild-type chinese hamster v79 cells (6-thioguanine-sensitive) reduce the recovery of 6-thioguanine-resistant cells when they are cultured together at high densities, through a form of intercellular communication (metabolic cooperation). cooperation is inhibited by 12-o-tetradecanoyl phorbol-13-acetate, rescuing the 6-thioguanine-resistant cells. these results may be useful in the study of an aspect of the mechanism of tumor promotion and in assaying for promoters.	1979	493994
precursor-product relationships between thymidine nucleotides and dna in mammalian cells. ii. studies with dtdp and dttp on cells partially lysed by brij-58.	cells from chinese hamster ovary cell cultures were partially lysed with brij-58 and incubated in a reaction mixture containing deoxyribonucleoside triphosphates and permitting semiconservative dna replication. the reaction mixture was supplemented with [3h]dttp and [14c]dtdp or, alternatively, with [14c]dttp and [3h]dtdp, and at different times, 3h and 14c specific activities of dttp and dtdp, as well as 3h/14c ratios in dna were determined. isotope ratios in dna were in good agreement with tho ...	1979	508757
effects of various oxygenated sterols on cellular sterol biosynthesis in chinese hamster lung cells resistant to 25-hydroxycholesterol.	the effects of a wide variety of oxygenated sterols upon sterol biosynthesis and hydroxymethylglutaryl-coa reductase (mevalonate: nadp+ oxidoreductase (coa-acylating), ec 1.1.1.34) activity in a wild-type clone and in a 25-hydroxycholesterol-resistant clone of chinese hamster lung (dede) cells are described. derivatives of cholesterol which were oxygenated in the 6, 7 or 15 positions of the sterol nucleus or in the 20, 22, 24 or 25 positions of the sterol side chain were shown to be potent inhib ...	1979	508785
asparaginyl-trna aminoacylation levels and asparagine synthetase expression in cultured chinese hamster ovary cells.		1979	40971
dna crosslinking, sister-chromatid exchange and specific-locus mutations.	chinese hamster ovary cells were treated with the dna-crosslinking chemicals, mitomycin c (mmc) and porfiromycin (por), and their monofunctional derivative decarbamoyl mitomycin c (dcmmc). after exposure, the cells were studied for the induction of sister-chromatid exchanges (sces) and mutations at the hypoxanthine phosphoribosyltransferase and adenine phosphoribosyltransferase loci. the frequency of sces varied significantly in successive sampling intervals, requiring the weighting of each inte ...	1979	522865
mutagenicity of metal cations in cultured cells from chinese hamster.	the mutations at the hypoxanthine-guanine phosphoribosyl transferase (hgprtase) locus in chinese hamster v79 cells induced by metal cations were examined by the development of resistance to 8-azaguanine (8ag). the spontaneous frequency of 8ag resistance was 5.8 per 10(6) cells, and the frequency was enhanced to 2-6 times that of the control by treatment of cells with the chlorides of beryllium and manganese. about 75% of 8ag-resistant colonies were sensitive to amethopterin, and 86% of the resis ...	1979	514305
reversible inactivation of autosomal alleles in chinese hamster cells.	evidence is presented which suggests that a cho-derived thymidine kinase (tk) heterozygote, ts201, can reversibly inactivate the wild type tk allele, and that this event may result in simultaneous inactivation of a linked allele, galactokinase (glk). the clone ts201 was isolated as a revertant of a stable tk- 5-bromodeoxyuridine (brdu)-resistant mutant of cho. the reacquired tk activity differed from that of the wild type with respect to km and heat resistance, supporting the contention that ts2 ...	1979	511955
relationship between sister chromatid exchange and mutagenicity, toxicity and dna damage.	reciprocal exchanges of dna in sister chromatids (sces) are induced by various carcinogens and mutagens, although the quantitative relationship between the number of mutations and sces induced varies among chemicals. nevertheless, the analysis of sce production by various agents is often proposed as a sensitive and quantitative assay for genetic damage of the sort leading to mutation and cancer. in v-79 chinese hamster cells we have been measuring dna damage by alkaline elution, mutation inducti ...	1979	503206
thermosensitization by sulfhydryl compounds of exponentially growing chinese hamster cells.	the effect of various sulfhydryl compounds on the survival of exponentially growing monolayer cultures of chinese hamster cells (ha1) heated to temperatures of 37-43 degrees was examined. concentrations of cysteamine which were nontoxic or minimally toxic at room temperature or 37 degrees became increasingly toxic at elevated temperatures, greatly potentiating the killing produced by heat alone in the absence of cysteamine. this enhancement of hyperthermia-induced cell killing increased with inc ...	1979	498092
effect of salt solutions on the radiosensitivity of mammalian cells as a function of the state of adhesion and the water structure.	the radiation isodose survival curve of attached chinese hamster (v79) cells, subjected to a wide concentration range of salt or sucrose solutions, is characterized by two maxima separated by a minimum. cells are radioprotected at the maxima (high and low hypertonic salt concentrations) while they are radiosensitized at the minimum (intermediate hypertonic salt concentrations). both cations and anions can alter the cellular radiosensitivity above and beyond the (osmotic) effect observed for cell ...	1979	397199
epidermal growth factor stimulation of dna synthesis is potentiated by compounds that inhibit its clustering in coated pits.	we have used inhibitors of receptor-mediated endocytosis to investigate the mechanism and function of epidermal growth factor uptake by cultured cells. when rhodamine-labeled epidermal growth factor is bound to cell surface receptors on confluent monolayers of balb/c 3t3 cells, it rapidly collects in cell surface clusters and is internalized. the clustering of occupied receptors requires ca(2+) and is inhibited by primary alkylamines; both of these properties are shared by the enzyme transglutam ...	1979	42903
the biosynthesis of the major lipid-linked oligosaccharide of chinese hamster ovary cells occurs by the ordered addition of mannose residues.		1979	489594
deficiency of arginine and lysine causes increase in the frequency of sister chromatid exchanges.	an increase in the rate of sister chromatid exchanges (sce) was found when v79 chinese hamster cells were exposed to increasingly severe degrees of arginine and lysine deficiency. the data suggest a possible function of chromosomal proteins, and of histones in particular, in the maintenance of the low normal rate of sce.	1979	511161
initiation of dna replication in chromosomes of chinese hamster ovary cells.	the initiation of dna replication and the subsequent chain elongation were studied using chinese hamster ovary cells synchronized at the beginning of s phase. the cells were synchronized by a combination of mitotic selection and treatment with 5-fluorodeoxyuridine (fdu). the use of this drug at a concentration of 10(-5) m was found to effectively prevent the leakage of cells into s phase. reversal of the fdu block by supplying thymidine resulted in the synchronous onset of initiation at multiple ...	1979	160308
folate-dependent enzymes in cultured chinese hamster ovary cells: evidence for mutant forms of folylpolyglutamate synthetase.		1979	583488
hypoxanthine transport by chinese hamster lung fibroblasts: kinetics and inhibition of nucleosides.		1979	543723
inhibition by trioxalen (psoralen) plus near-ultraviolet light of the induction of ornithine decarboxylase in chinese-hamster cells.	trioxalen (trimethylpsoralen) plus near-u.v. light, a potent inhibitor of dna and rna synthesis, inhibits the induction of ornithine decarboxylase in stationary-phase v79 fibroblasts. it does not affect the translation of pre-existing mrna. the method, in view of its high degree of specificity and precise timing, is a better choice for inhibiting rna synthesis than the commonly used chemical inhibitors and precursor analogues.	1979	534483
enhancement of the chromosome-damaging action of ascorbate by transition metals.	freshly prepared ascorbate inhibited mitosis and induced chromosome aberrations in cultured chinese hamster ovary cells. cu(ii) and mn(ii) (10(-4) or 10(-5) m) enhanced both actions. fe(ii) and fe(iii) (10(-4) or 10(-5) m) reduced or abolished the mitosis-inhibiting action of ascorbate. at 10(-4) m, fe(ii) and fe(iii) strongly enhanced the chromosome-damaging capacity of ascorbate. up to 100% of all examined metaphase plates had multiple chromosome exchanges or breaks. since the cytostatic and c ...	1979	476651
radiolysis of chromatin extracted from cultured mammalian cells: formation of dna-protein cross links.	chromatin extracted from chinese hamster lung fibroblasts has been examined for the formation of radiation-induced dna-protein cross links, using a membrane filter assay. the relative efficiencies of the aqueous radical intermediates, oh., eaq- and o2-, were investigated. cross links were found in gamma-irradiated isolated chromatin and in chromatin irradiated in the cell before isolation. when isolated chromatin was irradiated under conditions in which the chromosomal proteins were dissociated ...	1979	317599
fixation of potentially lethal radiation damage by post-irradiation exposure of chinese hamster cells to 0.5 m or 1.5 m nacl solutions.	the effect of 0.05 m and 1.5 m nacl treatments on cho cells during and after irradiation has been examined. treatment with either hypotonic or hypertonic salt solutions during and after irradiation resulted in the fixation of radiation damage which would otherwise not be expressed. the half time for fixation was 4 to 5 min, and the increased expression of the potentially lethal damage by anisotonic solutions was mainly characterized by large decreases in the shoulder of the survival curve, as we ...	1979	317597
a nutritional test for the low density lipoprotein receptor in chinese hamster fibroblasts.		1979	227721
comparison of the properties of the alcohol dehydrogenases from wild-type and mutant chinese hamster somatic cells.	alcohol dehydrogenases (alcohol: nad oxidoreductase, e.c. 1.1.1.1.) from allyl alcohol-resistant and wild-type chinese hamster cells were purified using gel filtration, ion-exchange, and affinity-column chromatography. both enzymes exhibited the same isozyme band patterns on electrophoresis and isoelectric focusing. physicochemical properties of the two enzymes such as ph and temperature optima, km values, and temperature stability were found to be the same within the experimental errors. the ge ...	1979	44189
adaptation of thymidine utilization to changing rates of dna synthesis in the cell cycle.	in synchronous cultures of p-815 murine mastocytoma and of chinese hamster ovary (cho) cells, the relative contribution of exogenous thymidine to dna synthesis was studied by comparing rates of (3h)thymidine incorporation with the rate of dna synthesis as derived from incorporation of (3h)thymidine (10(-5) m) in the presence of amethopterin. in synchronous p-815 cultures, time-dependent variations of dna synthesis rates were in close agreement with those of (3h)thymidine incorporation rates at c ...	1979	117296
regulation of endogenous virus production by bromodeoxyuridine and dibutyryl cyclic amp in chinese hamster ovary cells.	either dibutyryl cyclic amp or bromodeoxyuridine can enhance rna type-c virus production in chinese hamster ovary cells. the resultant effect of simultaneous treatment of cells with 1 mm cyclic amp and 65 mum bromodeoxyuridine is greater than their additive effects when used separately. the increase in virus production does not seem to involve viral gene amplification, but correlates with an increase in viral rna transcription. the virus is also shown immunologically to be unique to the chinese ...	1979	90523
a concanavalin a-resistant chinese hamster ovary cell line is deficient in the synthesis of [3h]glucosyl oligosaccharide-lipid.	in this report we present an initial determination of the biochemical defect present in a chinese hamster ovary cell line selected for resistance to concanavalin a. membranes of this mutant, b211, incorporated at least 10-fold less mannose from gdp-[14c]mannose into oligosaccharide-lipid than membranes of the wild type. in the presence of dolichol phosphate, membranes of the mutant and wild type exhibited similar rates of synthesis of number of early intermediates, namely, mannosylphosphoryldoli ...	1979	479186
inhibitory effect of guanyl nucleotides toward adenylate cyclase activity of chinese hamster ovary cell membranes activated in vitro by cholera toxin.		1979	479151
comparison of complexity and diversity of polyadenylated polysomal and informosomal messenger ribonucleic acid from chinese hamster cells.	the sequence complexity and relative abundance of cytoplasmic polyadenylated polysomal (ribosome-bound) mrna and cytoplasmic polyadenylated informosomal (ribosome-free) mrna were analyzed in exponentially growing chinese hamster cells (line cho) using the technique of cdna hybridization to excess poly(a)+ mrna. polysomal and informosomal mrnas had similar complexities ( approximately 8300 mrna species), but both the fraction of mrna and the number of sequences comprising the mrna abundance class ...	1979	486422
a partial characterization of dna fragments protected from nuclease degradation in histone depleted metaphase chromosomes of the chinese hamster.	a small proportion (0.1-0.5%) of the total dna content of native chinese hamster metaphase chromosomes is protected from nucleolytic degradation following the removal of histones by extraction with either 0.2 n hcl or 2 m nacl, and remains attached to the nonhistone protein core. acid extraction followed by dnase i digestion leads to small fragments of 10-30 bases. salt extraction followed by micrococcal nuclease digestion gives approx. 140 b.p. fragments which are undistinguishable in size from ...	1979	493144
different chinese hamster cell lines express a g1 period for different reasons.	previous studies from our laboratory have shown that the absence of g1(g1-condition) in two lines of chinese hamster cells is dominant over the presence of g1(g1+condition) in a variety of intraspecific cell hybrids. g1+ mutants or variants cna be isolated from g1- cells following mutagenesis and selection. these g1+ mutants fall into multiple complementation groups based on their abilities to form g1- cell hybrids with one another. this is evidence that different mutants have g1 intervals for d ...	1979	531733
intercellular adhesion as a function of the cell cycle traverse.	intercellular adhesion is assumed to play an important role in a multitude of biological phenomena governing cellular behavior. the rate of intercellular adhesion as a function of the cell cycle traverse has been investigated using, in the monolayer assay, synchronized chinese hamster ovary-k1 cells. results obtained demonstrate that cells in g1 adhere to g1 cells at twice the rate that s cells adhere to each other. g1 cells adhere to s cells at an intermediate rate. the additive adhesiveness se ...	1979	511931
differential radiosensitivity of two mammalian cell lines after hyperthermic pretreatment.	hyperthermia in combination with 60co-gamma-therapy not only increases the radiosensitivity of mammalian cells, it also can create a greater selectivity between individual cell populations. tw established chinese hamster cell lines (v79 and b14f28) showed a similar radiosensitivity at 37 degrees c, but exhibited a marked difference in their response to 60co-gamma-rays when they were pretreated with mild hyperthermia (1 hour at 42 degrees c): about 50% of each cell type survived a dose of 400 rad ...	1979	505472
enhancement of excision-repair efficiency by conditioned medium from density-inhibited cultures in v79 chinese hamster cells: evidence for excision repair as an error-free repair process.	conditioned medium from density-inhibited v79 chinese hamster cell cultures, given as a post-treatment to uv-irradiated homologous cells, was demonstrated to reduce the lethal action of ultraviolet light by temporarily blocking dna replication. since the increased survival was not affected by various non-toxic concentrations of caffeine, such protective effect would be attributable to the prolonged intervention of excision repair before dna replication during the post-treatment period. the influ ...	1979	503101
synergistic biological effects of ultrasound and ionizing radiations evaluated in vitro.	the effects of diagnostic ultrasound on growing asynchronous cultures of chinese hamster ovarian cells were evaluated, with particular attention to possible synergism with ionizing radiations. measurements of cellular growth rate/survival and changes in morphology indicated that synergistic biological effects were absent.	1979	472256
isolation and characterization of cho cell mutants with altered asparagine synthetase.	two asparagine auxotrophic mutants (n3, n4) were isolated from the gat- strain of chinese hamster ovary cells, using a selection procedure modified from that of goldfarb et al. (1). the defect in these mutants is due to a deficiency in asparagine synthetase activity. n3, in particular, had no measurable enzyme activity. complementation analysis by peg-mediated cell fusion showed that the auxotrophic phenotype behaved as a recessive trait; complementation was obtained between n3 or n4 and the pse ...	1979	43600