PMID(sorted ascending)
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 ...1977863895
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.1977864264
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.1977864278
chromosome aberrations and sister chromatid exchanges in chinese hamster cells exposed to various 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 ...1977864744
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 ...1977865486
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 ...1977865492
structural repeat units of chinese hamster ovary chromatin. evidence for variations in repeat unit dna size in higher eukaryotes.dna lengths in the structural repeat units of chinese hamster ovary (cho) and chicken erythrocyte chromatin were compared by analyzing the sizes of dna fragments produced after treatment of nuclei with staphylococcal nuclease. the repeat length of cho chromatin (173 +- 4 bp) is about 20 base pairs (bp) smaller than that of chicken erythrocyte chromatin (194 +- 8 bp). repeat lengths of rat liver and calf thymus chromatin were found to be about 10 bp shorter than that of chicken erythrocyte chroma ...1977866190
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 ...1977870291
the units of dna replication in the mammalian chromosomes: evidence for a large size of replication units.the replication of chromosomal dna in human and chinese hamster cell populations has been studied by means of the dna fiber autoradiography. it was found that the rate of dna replication for one fork in human cells varies from 0.2 to 0.9 micron/min, the average being 0.6 micron/min. in the chinese hamster cells the rate dna replication is greater, varying from 0.3 to 1.2 micron/min, the average being 0.8 micron/min. there are no clusters containing a great number of replication units in human an ...1977870295
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 ...1977870297
quantitative analysis of biological marker synthesis in tumor cell cycle.a quantitative relationship between tumor cell number and biologic marker concentration has been investigated and characterized by the previously developed discrete-time kinetic model for the study of cell kinetics. here, this model is further expanded to cope with both cell cycle kinetics and biologic marker synthesis. a synchronized tumor-cell population is examined to determine the time course of the synthesis of markers in relation to cell cycle. the dna content distributions, measured by fl ...1977872404
the metabolic activation of 7-methylbenz(a)anthracene: the induction of malignant transformation and mutation in mammalian cells by non-k-region dihydrodiols.four different dihydrodiols derived from 7-methylbenz(a)anthracene have been tested, together with the parent hydrocarbon, for their ability to induce the in vitro malignant transformation of mouse m2 fibroblasts and mutations in v79 chinese hamster cells. in the transformation tests withe the non-k-region dihydrodiols, the 3,4-diol was the most active dihydrodiol tested and the 8,9-diol was also more active than 7-methylbenz(a)anthracene itself; the 1,2-diol showed only slight activity. the k-r ...1977873646
rapid assays for evaluating the drug sensitivity of tumor cells.assays that assess the ability of cells to incorporate labeled precursors into acid-precipitable material in the presence of adriamycin, daunorubicin, puromycin, vinblastine, melphalan, or methotrexate were investigated as an approach to the detection of resistant cells in human tumor samples. each assay was evaluated with suitable drug-resistant chinese hamster ovary cell lines and normal human fibroblasts to determine whether the assays reflected the drug sensitivity of these lines. moreover, ...1977875055
reverse transformation of chinese hamster ovary cells by a factor produced by vibrio parahaemolyticus. 1977875243
pre-implantation embryos of chinese hamster. i. incidence of karyotype anomalies in 226 control embryos.karyotyes were determined in 226 pre-implantation embryos (4--8-cell stages) of chinese hamster. the study was carried out under controlled natural breeding conditions, without superovulation and with the embryos developing in their mothers. a total of 5.3% karyotypically abnormal embryos were found. over half, 3.1%, were due to ploidy mutations, 5 cases of triploidy and 2 cases of haploidy. only 0.9% genome mutations were present, consisting of one autosomal trisomy and one autosomal monosomy. ...1977876265
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. ...1977876266
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 ...1977876270
l-dopa: selective toxicity for melanoma cells in a study of the effect of l-dopa, an intermediate in the biosynthesis of the pigment melanin, on the growth of human and murine melanoma cells a highly selective inhibition of growth was observed for pigmented cell lines (s91a and human melanoma) as compared to the nonpigmented control cells (amelanotic melanoma s91b, mouse fibroblast l929, and chinese hamster ovary). there was a correlation between toxicity and the extent of incorporation of radioactively labeled l-dopa by each line.1977877570
the organization of repeated nucleotide sequences in the replicons of mammalian dna.chinese hamster ovary cells were irradiated with 100-5,000 rads of x-rays and inhibition of the initiation of replicons after irradiation was demonstrated by analyzing nascent dna sedimented in alkaline sucrose gradients. the renaturation kinetics of dna synthesized during 60 min of incubation after irradiation was compared with that of dna synthesized during the 60 min after sham irradiation and with that of parental dna. nascent dna from cells whose replicon initiation was inhibited renatured ...1977880330
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. 1977880697
the adhension of chinese hamster cells. i. effects of temperature, metabolic inhibitors and proteolytic dissection of cell surface macromolecules. 1977881433
a reduction in the degree of h4 acetylation during mitosis in chinese hamster cells. 1977883971
action of heparin on mammalian nuclei. i. differential extraction of histone h1 and cooperative removal of histones from chromatin.heparin interacts strongly with the histone component of chromatin, forming heparin-histone complexes which resist dissociation by 0.2 m h2so4. heparin treatment of unfractionated histones isolated from nuclei of chinese hamster cells indicates that the affinities of the histone classes for heparin appear in the order from greatest to least: (h3, h4) greater than (h2a, h2b) greater than h1. however, when isolated nuclei are treated with heparin, h1 is released from the chromatin more readily tha ...1977884118
[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 ...1977884267
repair following combined x-ray and heat at 41 degrees in plateau-phase mammalian cells.plateau-phase v79 chinese hamster cells maintained at 37 degrees following x-irradiation demonstrated both sublethal damage repair and potentially lethal damage repair. when cells were kept at 41 degrees for 1 hr following irradiation, no sublethal damage repair was seen. in contrast, irradiated cells maintained at 41 degrees for 1 hr and then returned to 37 degrees were capable of repairing both sublethal and potentially lethal radiation damage; hyperthermic (41 degrees) inhibition of radiation ...1977884682
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 ...1977884704
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 ...1977885285
regional chromosomal localization of the human gene for galactose-1-phosphate the progeny of somatic cell hybrids formed by fusion of human lymphocytes and chinese hamster mutant cells, a single human chromosome a2 was selectively retained when grown in appropriate medium. spontaneous breakage of this chromosome in different hybrid subclones led to the assignment of the gene for galactose-1-phosphate uridyltransferase to the centromeric region of this chromosome (2q11 leads to 2q14). this gene is shown to be syntenic to the previously mapped genes for acid phosphatase ...1977885547
synteny between glycinamide ribonucleotide synthetase and superoxide dismutase (soluble).the auxotrophic mutant ade -c derived from chinese hamster ovary cell cho-k1 lacks the enzyme glycinamide ribonucleotide synthetase and requires exogenous supplement of purines for growth. cells from this mutant were fused with normal human lymphocytes, and the resulting hybrids were isolated in purine-deficient medium. a total of 32 primary clones and 49 secondary clones were analyzed for various isozyme markers. cytogenetic analysis with chromosome banding was also performed in some hybrid clo ...1977889603
no mutagenic effect of enflurane on cultured cells.enflurane was tested by the 8-azaguanine system for any evidence of mutagenic effects. no significant increase in the number of mutant colonies compared with controls was found after 24 h of exposure of chinese hamster cells to 1.5-6.5% enflurane and no damaged chromosomes were seen in metaphase cells on slides. studies of inhibition of growth rate by enflurane show that in this respect its effects were similar in magnitude to other commonly used inhalation anaesthetic agents, but with regard to ...1977889666
a radioprotective effect of vitamin c observed in chinese hamster ovary cells.vitamin c at high concentrations was found to inhibit the growth of cho clone a cells in culture. it had a radioprotective effect, giving a maximum increase in cell survival of a factor of seven under the experimental conditions used. the protective effect was mainly but not exclusively attributable to an increase in the do, the maximum increase observed being the order of 1.4.1977890235
malignant transformation and mutagenesis in mammalian cells induced by vicinal diol-epoxides derived from benzo(a)pyrene.benzo[a] pyrene and the syn- and anti-isomers of the 7,8-diol 9,10-oxide and of the 9,10-diol 7,8-oxide derived from this hydrocarbon have been tested for their abilities to induce malignant transformation in m2 mouse fibroblasts and mutagenesis in v79 chinese hamster cells. the anti-isomer of the 7,8-diol 9,10-oxide induced more mutations and transformation than did the other three vicinal diol-epoxides. the two 9,10-diol 7,8-oxides were moderately mutagenic but did not induce any transformatio ...1977890685
assignment of the gene for enolase to mouse chromosome 4 using somatic cell hybrids.somatic cell hybrids between mouse peritoneal macrophages (mpm) and human fibrosarcoma cells (ht-1080) or chinese hamster cells (a3) were analyzed by starch-gel electrophoresis for the expression of murine enolase. data obtained indicate that the locus for enolase is on chromosome 4 in the mouse.1977891258
metabolic behaviour of nonhistone chromosomal proteins in proliferating and in resting fibroblasts.the metabolism of nonhistone chromosomal proteins was studied in two lines of cells showing a different degree of contact inhibition: human diploid fibroblasts, which are easily contact-inhibited, and chinese hamster fibroblasts, which had been made to stop proliferating by fasting. by following the 3h414c ratio of [3h]tryptophan-labelled nonhistone chromosomal proteins and [14c]thymidine-labelled dna in chase experiments three main groups of these proteins could be detected with respect to thei ...1977891550
distribution of uv-induced unscheduled dna synthesis in metaphase chromosomes of chinese hamster cells. 1977891651
the deposition of 241am and 252cf in the skeleton of chinese hamster, syrian hamster and the rat. 1977893106
the recovery of normal dna replication kinetics in ultraviolet-irradiated chinese hamster cells. 1977895752
dna replication kinetics in x-irradiated chinese hamster ovary cells. 1977897075
repair of potentially lethal damage in chinese hamster cells after x and alpha irradiation. 1977897087
the pineal complex and its relationship to other epithalamic structures.the pineal complex of rodents is made up of a pineal gland which developmentally always originates from the area between the habenular and posterior commissure and a pineal sac which is continuous with the choroid plexus of the third ventricle. at the light-microscopic level, this sac appears to be identical to the choroid plexus. the pineal sac abuts the deep and superficial pineal glands of the golden hamster. in the pet mouse, gerbil, kangaroo rat, and chinese hamster, the sac is contiguous w ...1977899706
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 ...1977899949
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 ...1977899950
abnormalities in pelvic visceral nerves. a basis for neurogenic bladder in the diabetic chinese order to determine whether bladder dysfunction and hydronephrosis in diabetic chinese hamsters are associated with nerve pathology, the pelvic visceral nerves of diabetic and normal hamsters were examined with histochemical and electron microscopic techniques. acetylcholinesterase activity was reduced in the nerves and on smooth muscle fibers in the urinary bladder of diabetic hamsters when compared to controls. depression of enzyme staining was most marked in those hamsters with the most sev ...1977903213
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.1977906893
somatostatin in the pancreas, stomach and hypothalamus of the diabetic chinese hamster. 1977908469
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.1977911573
histone composition of nucleosomes isolated from cultured chinese hamster cells.nuclei isolated from cultured chinese hamster cells were treated with micrococcal nuclease and lysed, and the resulting chromatin subunit classes (nucleosomes) were purified by sedimentation and resedimentation through isokinetic sucrose gradients. nucleosomes isolated from [3h]thymidine-labeled cells were analyzed for dna size using both polyacrylamide gel and electron microscopic techniques. nucleosomes isolated from [14c]lysine-labeled cells were analyzed for protein content using a sodium do ...1977911804
discrete electrophoretic products of mitochondrial protein synthesis in the chinese hamster ovary cell line.mitochondrial proteins labelled with [35s]methionine for 1 h in whole chinese hamster ovary (cho) cells in the presence of cycloheximide or emetine, known inhibitors of cytosolic protein synthesis, have been enumerated and characterized by their electrophoretic mobility in sodium dodecyl sulfate slab gel electrophoresis. ten distinct electrophoretic bands were observed. the components were relatively stable during a 2 h postlabelling period. the same 10 bands were also seen with the cho cell lin ...1977912598
forward and reverse mutations affecting the kinetics and apparent molecular weight of mammalian hgprt.chinese hamster cells selected for resistance to 8-azaguanine following mutagenesis have hypoxanthine-guanine phosphoribosyltransferase (hgprt; e.c. with characteristics compatible with different mutations in the structural gene for that enzyme. using immunopurification and sds-polyacrylamide electrophoresis, mutants producing antigenically active forms of the enzyme can be analyzed for changes in the molecular weight of hgprt. enzyme subunits from mutants rjk3 and rjk39 are reduced in ...1977912745
nucleolar chromatin in chinese hamster ovary cells. topographical distribution of ribosomal dna sequences and isolation of ribosomal transcription complexes. 1977913418
cell cycle variation associated with feeder effects in cultures of chinese hamster fibroblasts. 1977913497
comparison of highly inbred diabetic and nondiabetic lines in the upjohn colony of chinese hamsters. 1977913895
induction of thioguanine- and ouabain-resistant mutants and single-strand breaks in the dna of chinese hamster ovary cells by 3h-thymidine.cultured chinese hamster cells were labeled with 6-3h-thymidine or 5-methyl-3h-thymidine and allowed to accumulate damage from 3h decays for various periods of time while frozen. the frequencies of cells resistant to 6-thioguanine or ouabain and the amount of dna damage (i.e., number of single-strand breaks) were determined and compared with the mutation frequencies resulting from x and ultraviolet light irradiation. whereas 3h decays and x rays made only 6-thioguanine-resistant mutants, ultravi ...1977914028
two-step chromosomal control of tumorigenicity of chinese hamster cells in nude mice.a simple method for microinjecting isolated chromosomes into a single living cell under an inverted microscope has been developed. of the 368 injected cells, 85 were able to form a colony and could be cloned. clones of chinese hamster v79 cells microinjected with chromosomes isolated from murine d56 cells [v79 (d56) cells] were tested for tumorigenicity in immunodeficient nude mice and for colony-forming ability in soft agar. untreated recipient v79 cells were highly tumorigenic and had a high c ...1977914396
a role for aminoacyl-trna synthetases in the regulation of amino acid transport in mammalian cell lines.the regulation of neutral amino acid transport was examined utilizing two temperature-sensitive aminoacyl-trna synthetase mutants, by comparison of their transport activities at permissive and marginally permissive temperatures. when the temperature-sensitive leucyl-trna -synthetase mutant tsh1 was shifted from a normal growth temperature of 34 degrees to a marginally permissive temperature for growth of 38%, a significant enhancement in the initial rate of uptake of leucine and other l system a ...1977914817
a quantitative assay of mutation induction at the hypoxanthine-guanine phosphoribosyl transferase locus in chinese hamster ovary cells (cho/hgprt system): utilization with a variety of mutagenic agents.the induction of mutation by a variety of mutagens has been measured utilizing the hypoxanthine-guanine phosphoribosyl transferase (hgprt) locus in chinese hamster ovary (cho) cells (cho/hgprt) system). these mutagens include physical agents such as uv light and x-rays, and chemicals such as alkylating agents, icr-191, and metallic compounds. this system can also be modified for study of the mutagenicity of promutagens such as dimethylnitrosamine (dmn) which require biotransformation for mutagen ...1977917031
mutagenic and epigenetic influence of caffeine on the frequencies of uv-induced ouabain-resistant chinese hamster cells.caffeine, given as a post-treatment to uv-irradiated chinese hamster cells in vitro, modified the frequency were increased when caffeine was added only for the dna repair and mutation fixation period. when caffeine was added after the dna repair and mutation fixation period, or immediately after dna damage and for the entire repair and selection period, mutation frequencies were reduced. a hypothesis, given to explain both results, is that caffeine, by blocking a constitutive "error-free" postre ...1977917032
effect of tumor promoting agents on mutation frequencies in cultured v79 chinese hamster cells. 1977917033
effect of caffeine on sister chromatid exchanges and chromosomal aberrations induced by mutagens in chinese hamster cells. 1977917034
a quantitative assay of mutation induction at the hypoxanthine-guanine phosphoribosyl transferase locus in chinese hamster ovary cells (cho/hgprt system): development and definition of the assay is described for the measurement of mutation induction at the hypoxanthine-guanine phosphoribosyl transferase (hgprt) locus in chinese hamster ovary (cho) cells utilizing resistance to 6-thioguanine (tg). optimal selection conditions are defined for such parameters as phenotypic expression time prior to selection, and tg concentration and cell density which permits maximum mutant recovery. the nature of the tg-resistant mutants is characterized by several physiological and biochemical m ...1977917038
spontaneous lesions in chinese hundred and fifty-seven chinese hamsters (cricetulus griseus) from the lovelace foundation inhalation toxicology research institute colony had pulmonary granulomas, nodular hyperplasia of the liver, granulocytic bone marrow hyperplasias and myelogenous leukemia, nephrosclerosis and uterine adenocarcinomas. these chinese hamsters had a median life span of 1 075 days. the long life span and information on naturally-occurring diseases suggest that this species might be more widely used for toxi ...1977919235
analysis of karyotype variation following carcinogen treatment of chinese hamster primary cell lines.chinese hamster primary fibroblasts derived from several embryos were treated with the carcinogens benzo(a)pyrene, 7,12-dimethylbenz(a)anthracene or n-methyl-n'-nitro-n-nitrosoguanidine. karyotype analysis, sister chromatid exchange frequency, evidence of transformation by growth in agar, cell morphology and reaction to cytocholasin b were tested at regular intervals over many culture passages. carcinogen treatment was found to shorten the time period before onset of permanent karyotypically cha ...1977924693
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 ...1977929628
drug-resistant mutants of chinese hamster ovary cells possess an altered cell surface carbohydrate component.surface label experiments using the galactose oxidase-]3h]-borohydride technique reveal that cells from drug-resistant chinese hamster ovary clones possess a surface carbohydrate component of apparent molecular weight 165,000 which is absent from wild-type cells. the component may also be demonstrated by [14c]glucosamine incorporation but not by [3h]leucine incorporation or by the lactoperoxidase surface labeling reaction.1976933538
factors affecting the growth of chinese hamster cells in hat selection media.factors affecting the efficiency of selection of "revertants" of salvage pathway mutants in media containing amethopterin have been examined. our v79 chinese hamster cell line was found to require a significantly higher level of thymidine for optimal growth in such media than has been reported for other cell lines. hypoxanthine (but not glycine) was also required for reversal of amethopterin toxicity, but levels did not differ significantly from those reported elsewhere. growth in hat was also d ...1976934167
factors affecting the efficiency of purine analogues as selective agents for mutants of mammalian cells induced by ionising the chinese hamster cell line v79-4, the frequencies of the cells selected for their resistance to purine analogues do not always reflect the true frequencies of resistant mutants. the frequency of cells resistant to 8-azaguanine varied widely, especially when different sources of serum were used in the selective medium. even with the more efficient analogue, 6-thioguanine, small colonies arose in the selective medium at a frequency which was strongly dependent upon analogue concentration and ...1976934168
the effect of insecticides on chinese hamster cell cultures.the effect of p,p'-isomers of ddt and its derivatives ddd, dde and dda on chinese hamster cells in culture was studied. at different concentrations and various times of treatment the proliferation rate was inhibited most strongly by ddd and ddt, whereas dde exhibited a markedly weaker influence. dda was the least toxic compound of the four. the cytogenetic effects were also different. again, dda induced the least damage. only enhanced gap rates but no chromosome breaks were observed. dde was mor ...1976934173
chromosome analyses in cell cultures of the chinese hamster after application of cadmiumsulphate.cell cultures of a chinese hamster cell line were treated with cdso4 in concentrations of between 10(-4) and 10(-8) mol/l for different time periods. after a treatment of 16 h the mitotic index was reduced. strong stickiness and pycnosis of chromosomes occurred at the highest concentrations. a treatment period of 3 h with concentrations of 10(-5) and 10(-4) mol/l without additional application of colcemid and hypotonic solution yielded a stathmokinetic effect. the mitotic index increased, mitose ...1976934175
mammalian cell survival response following irradiation with 4 mev x rays or accelerated helium ions combined with hyperthermia.the effects of hyperthermia on chinese hamster ovary cell radioresponse were studied using either 4 mev x rays or accelerated helium ions. both pre-and postirradiation hyperthermic doses act to decrease the slope of the x-irradiation survival curve in a temperature-dependent manner, while the extrapolation number does not change appreciably. pre-irradiation hyperthermic treatment has only a slightly greater dose-modifying effect than similar postirradiation hyperthermia. for cells irradiated wit ...1976935413
investigations on the frequency of chromosome aberrations in bone marrow cells of chinese hamsters after simultaneous application of caffeine and cyclophosphamide.the potentiating effect of caffeine (1,3,7-trimethylxanthine) on chemically induced chromosome aberrations was studied in bone marrow cells of chinese hamsters, exposed to the alkylating agent cyclophosphamide. four experimental series were performed: in the first two tests caffeine (200 mg/kg) or cyclophosphamide (40 mg/kg), respectively, were administered. a third and fourth test was performed with caffeine plus cyclophosphamide (200 + 40 mg/kg and 35 + 40 mg/kg, respectively) simultaneously. ...1976939563
the human gene for beta glucuronidase is on chromosome 7.inconsistent assignments of the human gene for beta glucuronidase (gus) to chromosomes 7 and 9 have previously been reported. in this study, we have correlated the expression of human gus in 22 primary chinese hamster/human hybrid lines with quantitative cytogenetic analysis. eight hybrids were positive for human gus as manifested by a five-band pattern on electrophoresis. all of them contained a human chromosome 7 in 34% or more of cells, and seven of them had not retained chromosome 9. one hyb ...1976941903
initiation and elongation of protein synthesis: their relative rates and sensitivities to inhibition in chinese hamster ovary cells determined by a modified edman procedure. 1976942107
metaphase chromosome anomaly: association with drug resistance and cell-specific products.large, homogeneously staining chromosome regions which lack the longitudinal differentiation ordinarily revealed by cytogenetic "banding" methods have been found in antifolate-resistant chinese hamster cells and also in human neuroblastoma cells established in vitro. the drug-resistant cells are characterized by excessive production of the target enzyme, dihydrofolate reducatase, while the human neuroblastoma cells have phenotypes of normal neuronal cells. the homogeneously staining region appea ...1976942798
profiles of brain glycosidase activity in cuprizone-fed syrian hamsters and in scrapie-affected mice, rats, chinese hamsters and syrian hamsters. 1976943426
surface polypeptides of the chinese hamster ovary cell; an immunochemical study.antibodies elicited by the injection of live chinese hamster ovary cells (cho) into rabbits precipitated four major components from detergent extracts of cho membranes. the four components, of molecular weights 200000, 125000, 95000 and 41000 daltons, corresponded to cell surface components identified by the lactoperoxide surface label technique.1976944075
the effect of combined treatment with a platinum complex and ionizing radiation on chinese hamster ovary cells in vitro.cis-dichlorobis(cyclopentylamine)platinum ii (dbcp) belongs to the group of platinum complexes which have recently been reported to have anti-tumour activity. its cytotoxic activity in cho cells is not cell-age-dependent, but enhancement of the effect of ionizing radiation is both dose-and cell cycle phase-dependent. in asynchronous cell populations dbcp acts as a dose-modifying factor for ionizing radiation. doses of dbcp reducing survival of cho cells to 26% and 4% applied 1 h before irradiati ...1976944586
somatic cell chromosome interconnections in trypan preparations of chinese hamster testicular cells. 1976944637
[isolation and characteristics of temperature sensitive mutants in a culture of chinese hamster cells].the treatment of a temperature-resistant glutamine-independent clone of chinese hamster cells (237 glu+ tr) with 5-bromodeoxyuridine (budr) for 48 or 72 hours at 40 degrees c and subsequent illumination with visible light was used for selection of spontaneous and n-methyl-n'-nitro-n-nitrosoguanidein-induced ts mutants. 30 clones were isolated. their temperature-sensitivity was studied at two cell densities: 500 and 10000 (or 15 000) cells per dish. 21 clones proved to be temperature-sensitive. t ...1976944672
articular cartilage of diabetic chinese hamsters.investigations were carried out in order to determine whether animals with spontaneous diabetes are prone to develop skeletal lesions comparable to those found in diabetic human subjects. the present report deals with the ultrastructure of the cartilage of the hip joint of diabetic chinese hamsters and nondiabetic control animals. in the diabetic animals, chondrocytes of the femoral head showed atrophy of the endoplasmic reticulum, bizarre mitodhoncria, and huge lipid inclusions, which are chang ...1976946390
a respiration-deficient chinese hamster cell line with a defect in nadh-coenzyme q reductase.we have recently described a chinese hamster cell line with a greatly reduced rate of respiration. in this report we conclude that the defects is in nadh-coenzyme q reductase (nadh oxidase), the first part of the electron transport chain. the conclusion is based on the following observations. (a) in this and in the earlier report we determined that the relevant enzymes of the krebs cycle are present and active. (b) oxygen consumption by isolated mitochondria is normal when driven by succinate an ...1976947896
pachytene mapping of the male chinese hamster.minced seminiferous tubules of male chinese hamsters when treated with a mixture of trypsin (one part) and mccoy's 5a growth medium with 20% fetal calf serum (nine parts) at 4 degrees c, washed twice with the regular growth medium, incubated at 37 degrees c in growth medium for 4 h, and harvested without colcemid and hypotonic pretreatments, gave excellent pachytene morphology for studies on chromomere patterns. the giemsa banding patterns of all somatic metaphase chromosomes except the sex chro ...1976949904
the in vitro isolation and characterization of monosomic sublines derived from a colcemid-treated chinese hamster cell population.a series of 18 sublines deficient for one or two chromosomes was isolated in vitro from a pseudodiploid chinese hamster cell population treated appropriately with colcemid to obtain maximal induction of aneuploidy. chromosomes 10 and 11 were the most frequently involved and, to a lesser extent, chromosome 9 and the partially deleted 6. since analysis of chromosome banding patterns did not reveal any evidence of chromosome rearrangement, it was concluded that entire chromosomes were absent, and t ...1976949905
characterisation of the lysosomal heterogeneity in chinese-hamster fibroblasts.1. homogenates of chinese hamster fibroblasts have been fractionated by analytical centrifugation techniques. lysosomes have been characterised and identified by the distinctive behaviour of specific marker constituents. 2. the acid hydrolases of hamster fibroblasts were located in two distinct organelles, characterised by differences in their equilibrium densities and rates of sedimentation. the lighter population of lysosomes with a modal density of 1.10 g cm-3, contained glycosidases, nucleas ...1976949969
the rna polymerase ii of an alpha-amanitin-resistant chinese hamster ovary cell line.amal, an alpha-amanitin-resistant mutant of the chinese hamster ovary cell line, contains an rna polymerase activity which elutes from deae-sephadex at a salt concentration characteristic of an rna polymerase ii, but which is not sensitive to alpha-amanitin at levels where the polymerase ii of wild-type cells is strongly inhibited. this result suggests that amal owes its amanitin-resistant phenotype to a mutation affecting one of its genes for rna polymerase ii. to test this hypothesis, we purif ...1976954093
biochemical characterization of azetidine carboxylic acid-resistant chinese hamster cells.we have isolated variants of chinese hamster lung (chl) fibroblasts with decreased sensitivity to the toxic proline analog, l-azetidine-2-carboxylic acid (azca). resistance to azca is a stable characteristic of these cell lines since it is maintained after 40 generations in nonselective medium. two azca-resistant cell lines overproduce and excrete more proline than wild-type cells. furthermore, azca rapidly inhibits the synthesis of proline from glutamic acid in wild-type but not the resistant c ...1976954094
evidence for the formation of hybrid dna during mitotic recombination in chinese hamster evidence is provided for the formation of hybrid dna during mitotic recombination in cho cells. the cells were labeled for one round of replication in medium containing budr, so that the density of the dna was heavy light (hl) and then returned to light medium. further dna synthesis, during either repair or chromosome replication, can only result in hl or fully light (ll) dna; however, the formation of hybrid dna as part of the process of recombinational repair will produce some fully hea ...1976954106
effects of actinomycin d and puromycin on colchicine-induced endoreduplication in chinese hamster cells in vitro.experiments were carried out to study the events through which the process of endoreduplication occurs after treatment with colchicine in chinese hamster cells cultivated in vitro, and to analyse the differences between the processes leading to normal mitosis and those leading to endoreduplication. chinese hamster cells (line c-125) were treated with colchicine (10(-4) m) for 1 h, in order to induce endoreduplication. before and after colchicine treatment the cultures were treated at various int ...1976954141
action of a platinum complex [cis-dichlorobis (cyclopentylamine)-platinum (ii)] on chinese hamster ovary cells in vitro.cis-dichlorobis(cyclopentylamine)platinum (ii) (dbcp) treatment of chinese hamster ovary (cho) monolayer cell cultures was found to cause: (1) growth inhibition due to an impaired g1 leads to s transition and formation of a non-cycling compartment; (2) delayed cell death (with a maximum at 72 h after treatment); (3) decrease of [14c] tdr incorporation into dna. part of the surviving cell population was subject to non-lethal damage. the do values of the dose--survival curves were 9.2 and 14 mug/m ...1976954143
behavioral development in three hamster species.the preweaning behavioral development was compared in 3 hamster species: the golden (mesocricetus auratus), chinese (cricetulus griseus), and djungarian (phodopus sungorus). differences in the age of appearance of action patterns could not be summarized by simply ranking species on either precocity or developmental speed, nor were they eliminated by measuring age from conception. problems in the interpretation of species differences in the age of appearance of action patterns are discussed.1976955290
[combined effect of n-nitroso-n-methylurea and actinomycin d on chinese hamster cell chromosomes]. 1976955409
selective isolation of reversible cold sensitive variants from chinese hamster ovary cell cultures.variants of the chinese hamster ovary cell line cho-ki (attcccl61)which grow almost normally at 38.5c but very poorly or not at all at 30c were obtained after treatment with mutagens and application of an indirect selection procedure. two kinds of variants were recovered. in the first of these, the cold sensitive phenotypw is expressed completely only at low cell densities. at higher cell desity, growth continues at the nonpermissive temperature, but at a reduced rate. in the second class, t ...1976956283
the influence of serum components on the growth and mutation of chinese hamster cells in medium containing 8-azaguanine.low concentrations (less than or equal 20 mug/ml) of 8-azaguanine are 1000 fold more toxic to v79 chinese hamster cells in medium containing 10% dialyzed fetal calf serum than in medium containing 10% undialyzed serum. serum enzyme activity that converts ag to nontoxic 8-azaxanthine degrades ag at the same rate, whether or not the serum is dialyzed. however, cytotoxicity results similar to those obtained with us were produced in medium containing ds and 2.5 mug of hypoxanthine (hx)/ml (dsh). the ...1976958230
mutagenic mechanism of 5-bromodeoxyuridine in chinese hamster cells.resistance to 6-thioguanine was induced by 5-bromodeoxyuridine (budr) in synchronous chinese hamster cells. the yield of mutant colonies was not proportional to the amount of budr incorporated into dna; thus mutants were not due to mispairing of budr with guanine during replication. few mutants were induced until budr concentrations exceeded that of the intracellular thymidine triphosphate pool and mutant yield was depressed by addition of thymidine to the medium. these data suggest that budr ex ...1976958231
evaluation of the mutagenic potential of cyclohexylamine on spermatogonia of the chinese a cytogenetic study on the spermatogonia of chinese hamster, cyclohexylamine (neutral sulphate) was evaluated for mutagenic effects in comparison with an untreated control group and a group treated with the mutagenic compound cyclophosphamide, by assessing spermatogonial metaphases of treated chinese hamster for chromosomal structural changes. each test group comprised 8 male hamsters selected at random. approximately 100 metaphases from each animal were assessed. the doses were 5 x 150 mg cy ...1976958236
chemical transformation of chinese hamster cells. i. a comparison of some properties of transformed cells.fifty-one subclones from carcinogen-treated cells of 3 tissues (kidney, liver and prostate) of the male chinese hamster have been studied to determine the relationships of 3 criteria of in vitro transformation: morphological change, increased plating efficiency and growth in soft agar. there was no correlation between increased plating efficiency and the other 2 parameters. morphological change was not always easily recognisable, particularly in cells derived from liver, and was not always a sta ...1976962992
effects of ionizing radiation of rna metabolism in cultured mammalian cells. iii. specific reduction in mrna synthesis during resumed division and plateau phases following exposure to 800 rads of x irradiation.the cell growth response of cultured chinese hamster ovary cells, line cho, to 800 rads of x irradiation involves a period of division delay, followed by a period of resumed division which terminates in a plateau phase. over 95% of the cells die eventually. no direct effects of rna or protein metabolism are evident during the delay period. during the resumed division and beginning of plateau phases, however, a specific and relatively constant reduction in mrna synthesis relative to messenger-lik ...1976963053
chain elongation and joining of dna synthesized during hydroxyurea treatment of chinese hamster cells.we have previously presented evidence that hydroxyurea treatment of synchronized g1 chinese hamster cells did not prevent the entry of cells into the dna synthetic period but that the dna synthesized during this period (in which total dna synthesis was severely depressed) was quite small (walters, r.a., tobey, r.a. and hildebrand, c.e. (1976) biochem. biophys. res. com. 69, 212-217). in view of the reported effects of hydroxyurea on deoxyribonucleoside metabolism and possible relationship to con ...1976963081
significance of dimers to the size of newly synthesized dna in uv-irradiated chinese hamster ovary cells.dna synthesized after uv irradiation is smaller than that in unirradiated cells even when pulse-labeling times are increased to compensate for the overall reduction in the rate of dna replication. by isolating newly replicated dna, incubating it with dimer-specific endonuclease from micrococcus luteus, and analyzing it on alkaline sucrose gradients, we have been able to demonstrate that this dna is synthesized in segments corresponding in size to the interdimer distance on the parental strand. i ...1976963196
fragmentation of chromatin with 125i radioactive disintegrations.the dna in chinese hamster cells was labeled first for 3 h with [3h]tdr and then for 3 h with [125i]udr. chromatin was extracted, frozen, and stored at -30 degrees c until 1.0 x 10(17) and 1.25 x 10(17) disintegrations/g of labeled dna occurred for 125i and 3h respectively. velocity sedimentation of chromatin (dna with associated chromosomal proteins) in neutral sucrose gradients indicated that the localized energy from the 125i disintegrations, which gave about 1 double-strand break/disintegrat ...1976963201
cytogenetic effects of mutagens/carcinogens after activation in a microsomal system in vitro i. induction of chromosome aberrations and sister chromatid exchanges by diethylnitrosamine (den) and dimethylnitrosamine (dmn) in cho cells in the presence of rat-liver microsomes.a rat-liver microsomal system in vitro has been used to activate two indirectly acting carcinogens, dmn and den. on activation, both compounds were extremely potent in inducing chromosomal aberrations as well as sister chromatid exchanges in chinese hamster cells. the implications of these findings and the potential utility of this technique to detect mutagens/carcinogens are discussed.1976967188
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