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the effect of respiratory carcinogenesis on systemic humoral and cell-mediated immunity of syrian golden hamsters.the effect of intratracheal instillation of benzo(a)pyrene and its noncarcinogenic analog benzo(a)pyrene on the systemic humoral and cell-mediated immune response of syrian golden hamsters was evaluated. hamsters treated with the carcinogen had a transient suppression of the splenic plaque-forming cell response to sheep erythrocytes, compared with analog-treated controls. the numbers of direct (immunoglobulin m) and indirect (immunoglobulin g) plaque-forming cells were suppressed at the 9th week ...1977318605
enterotoxigenic escherichia coli isolated from patients at a hospital in dacca.enterotoxigenic strains of escherichia coli, a significant cause of acute, watery, cholera-like diarrhea, were isolated from 23 of 65 patients with diarrhea in whom no other enteric pathogens were found during one week (november 1974) at the cholera research hospital, dacca, bangladesh. diarrhea associated with enterotoxigenic strains of e. coli occurred primarily in adults but affected persons of all age groups and could not be distinguished from cholera or from other cholera-like diarrhea on c ...1977320276
microsome-mediated mutagenesis in v79 chinese hamster cells by various nitrosamines.a microsome-mediated mutagenesis system has been established with the v79 chinese hamster cell line. the cells, grown in monolayer, were treated with various nitrosamines in the presence of a postmitochondrial fraction ((s15) from rat liver and a reduced nicotinamide adenine dinucleotide-generating system for 1 hr, washed and incubated for 2 to 3 hr in fresh culture medium, and then plated for toxicity and mutagenicity assays. mutation was determined by resistance to 20mug 8-azaguanine per ml. i ...1977321116
diarrhea due to escherichia coli in the rabbit: a novel mechanism.a strain of escherichia coli o15 (rdec-1) isolated from several rabbits with diarrhea was examined to determine (1) whether the strain could produce diarrhea when administered by the orogastric route to other rabbits and (2) whether this strain was invasive or enterotoxigenic. strain rdec-1 produced diarrhea in 48 of 62 rabbits when given by the orogastric route in doses that ranged from 1.5 x 10(2) to 4 x 10(10) bacteria. the organism did not give a positive result in the 18-hr ileal loop or se ...1977321703
characterization of the chinese hamster ovary cell assay for the enterotoxins of vibrio cholerae and escherichia coli and for specific antisera, and toxoid.the morphologic change in chinese hamster ovary (cho) cells that is associated with increased intracellular concentrations of adenosine 3':5'-cyclic phosphate (cyclic amp) provided a highly sensitive assay for the heat-liable enterotoxins of vibrio cholerae and escherichia coli. the similarity between the responses of cho cells and those of intestinal mucosa to enterotoxins was demonstrated by the inhibition of these effects by the ganglioside galactosyl-n-acetylgalactosaminyl [sialosyl] lactosy ...1977323378
mutagenicity of polycyclic hydrocarbons. ii. monitoring genetical hazards of chrysene in vitro and vivo.mutagenicity tests were performed with chrysene in the salmonella/microsome test, nmri-mice oocytes, bone-marrow cells and spermatogonia of chinese hamsters. only in mice oocytes was a weak but significant increase of structural chromosome aberrations observed. correlations were found between weak carcinogenic and observed weak mutagenic activities of chrysene in vitro and in vivo.1977327309
mutagenicity and cytotoxicity of benz[alpha]anthracene diol epoxides and tetrahydro-epoxides: exceptional activity of the bay region 1,2-epoxides.three diastereomeric pairs of diol epoxides, two tetrahydro-epoxides, and the k-region oxide of the polycyclic aromatic hydrocarbon benz[a]anthracene were evaluated for mutagenic activity in strain ta 100 of salmonella typhimurium and in line v79-6 of chinese hamster lung cells. the two diastereomeric 1,2-epoxides of the trans-3,4-dihydrodiol of benz[a]anthracene are 15 to 35 times more mutagenic to the bacteria and 65 to 125 times more mutagenic to the mammalian cells than are the diastereomeri ...1977331315
mutagenicity of isomeric diol-epoxides of benzo[a]pyrene and benz[a]anthracene in s. typhimurium ta98 and ta100 and in v79 chinese hamster cells.pairs of isomeric vicinal diol-epoxides derived from benzo[a]pyrene 7,8- and 9,10-dihydrodiols and from benz[a]anthracene 8,9-dihydrodiol were tested for their abilities to revert salmonella typhimurium strains ta98 and ta100 to histidine prototrophy and to induce the formation of 8-azaguanine- or of ouabain-resistant v79 chinese hamster cells. all six diol-epoxides were active in both bacterial strains, but 7beta,8alpha-dihydroxy-9beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (the syn iso ...1977333280
zinc and manganese contents of micro-dissected pancreatic islets of some rodents. a microchemical study in adult and newborn guinea pigs, rats, chinese hamsters and spiny mice.by a flameless atomic absorption spectrophotometry procedure, using a graphite furnace, it was possible to assay the contents of zinc and managanese in micro-dissected pancreatic islets of several rodents. interest was focused upon the islets of guinea-pigs, due to the fact that guinea-pig insulin lacks a histidine residue in the b10 position of the molecule which normally binds zinc (or other heavy metals) in the hexamer formation, probably involved in the storage of insulin. both the zinc and ...1977335757
escherichia coli heat-labile enterotoxin: comparison of antitoxin assays and serum antitoxin levels.the mouse adrenal tumor cells (y-1 strain) and the chinese hamster ovary cells, two routinely used tissue culture assays for escherichia coli heat-labile enterotoxin (lt), were used to detect serum antitoxin responses in culture-positive patients from several well-defined sources. there was no correlation between a significant antitoxin response and isolation of lt-producing e. coli in two "domestic" diarrheal outbreaks. serum samples from a third group of individuals in a rural cholera-endemic ...1977336543
toxin from the culture filtrate of shigella dysenteriae that causes morphological changes in chinese hamster ovary cells and is distinct from the neurotoxin.a toxin that causes morphological changes in chinese hamster ovary cells was isolated from a culture filtrate of shigella dysenteriae 1. it was partially purified by successive column chromatography on diethylaminoethyl-cellulose, bio-gel a-5m, and hydroxylapatite. the toxin was separated from neurotoxin by diethylaminoethyl-cellulose column chromatography and was not lethal for mice.1977336549
inhibition of mammalian ribonucleotide reductase by a dinucleotide produced in eucaryotic cells.hs3, a highly phosphorylated dinucleoside originally purified from the fungus achlya, has been isolated from chinese hamster ovary cells undergoing glutamine starvation. the hs3 compounds obtained from the fungal and mammalian sources exhibited similar physical and chemical properties. this unusual dinucleotide may be an important regulator of eucaryotic ribonucleoside diphosphate reductase activity; for 50 micrometer hs3, isolated from either mammalian or fungal cells, significantly inhibited c ...1977338619
assignment of the structural genes for the alpha subunit of hexosaminidase a, mannosephosphate isomerase, and pyruvate kinase to the region q22-qter of human chromosome 15.concordant segregation of the expression of the alpha subunit of human hexosaminidase a, human mannosephosphate isomerase, and pyruvate kinase was observed in somatic cell hybrids between either thymidine kinase-deficient mouse cells or thymidine kinase-deficient chinese hamster cells and human white blood cells carrying a translocation of the distal half (q 22-qter) of the long arm of chromosome 15 to chromosome 17. a positive correlation was established between the expression of these human ph ...1977341373
characterization of alpha-galactosidase isoenzymes in normal and fabry human-chinese hamster somatic cell hybrids.the alpha-galactosidases in normal man-chinese hamster somatic cell hybrids were investigation with antibodies specific for human alpha-galactosidase a and antibodies specific for chinese hamster alpha-galactosidase. it was found that an isoenzyme in hybrid cells, which has an electrophoretic mobility between that of human alpha-galactosidase a and chinese hamster alpha-galactosidase, contains immunologic determinants of both human and chinese hamster origin, suggesting that it is a heteropolyme ...1977404232
assay of escherichia coli heat-labile enterotoxin with vero cells.the continuous cell line of african green monkey kidney, vero, showed characteristic morphological changes in response to culture filtrates from toxigenic strains of escherichia coli. the response compared favorably with that of y-1 (mouse adrenal) and cho (chinese hamster ovary) cells. vero cells were the simplest and most economical to maintain in the laboratory.1977405326
selection and characterization of cells resistant to diphtheria toxin and pseudomonas exotoxin a: presumptive translational mutants.two classes of diphtheria toxin-resistant variants were selected from chinese hamster ovary (cho-k1) cells: permeability variants, in which uptake of toxin was impaired, and a new class of cytoplasmic variants, which were cross-resistant to pseudomonas exotoxin. ef-2 prepared from the cytoplasmic variants was resistant to adp-ribosylation by either toxin. the evidence presented suggests that these are translational variants possessing a mutationally altered ef-2 gene product. these studies also ...1977408012
localization of neurotensin-immunoreactive cells in the small intestine of man and various mammals.antibodies against synthetic bovine neurotensin were raised in rabbits and used to demonstrate neurotensin-immunreactive cells by immunohistochemical methods. in the jejunum and ileum of all species investigated (man, dog, monkey, cat, rabbit, sheep, rat, mouse, hamster, chinese hamster, gerbil, pig and guinea pig) cells were present in the mucosa, which reacted specifically with antineurotensin serum using the indirect immunofluorescence and peroxidase-antiperoxidase methods. in the monkey tupa ...1977409699
characterization of residual hexosaminidase activity in sandhoff's disease using man-chinese hamster cell hybrids.to obtain information about the nature of the residual hexosaminidase activity in sandhoff's disease, hybrid cell lines between fibroblasts from a patient with sandhoff's disease and chinese hamster cells were isolated. in these hybrid cell lines, a heteropolymeric isoenzyme was detected that is composed of human alpha- and chinese hamster hexosaminidase subunits. due to the electrophoretic and immunological behavior of the heteropolymeric molecules in interspecies hybrids with normal fibroblast ...1977413781
regional localization of a beta-galactosidase locus on human chromosome 22.human white blood cells with an x/22 translocation [46, xx, t(x;22)(q23;q13)] were fused with chinese hamster cells. the isolated hybrids were analyzed for human chromosomes and 21 enzyme markers. an electrophoretic technique for studying the beta-galactosidase isoenzymes in man-chinese hamster hybrid cells was developed. immunological studies showed that the beta-galactosidase marker studied in these hybrids did contain immunological determinants of human origin. furthermore the results provide ...1977414365
the effect of adriamycin on cell cycle progression and dna replication in chinese hamster ovary cells.administration of[3h]aflatoxin b2 (2,3-dihydroaflatoxin b1)(afb2) to male rats resulted in levels of hepatic dna- and ribosomal (r)rna-aflatoxin adducts that were about 1% of those for rats given [3h]aflatoxin b1(afb1). the levels of hepatic protein-aflatoxin adducts were 35 to70% as great for afb2-treated as compared to afb1-treated rats...1977830405
chromosome replication in somatic hybrids of mouse and temperature sensitive chinese hamster cells. 1977833213
characterization of beta-d-n-acetylhexosaminidase isoenzymes in man-chinese hamster somatic cell hybrids.a series of man-chinese hamster hybrids were investigated with the use of an anti-chinese hamster hexosaminidase serum, a specific anti-human hex a serum and an anti-human hex b serum. the expression of human hex a was found to be dependent on the presence of hex b. a heteropolymeric molecule is formed independently of hex b, which consists of chinese hamster and specific hex a moieties. it has an electrophoretic mobility nearly identical to hex a. a relationship between the absence and presence ...1977835571
th induction of thioguanine-resistant mutants of chinese hamster cells by gamma-rays.the induction of mutation to purine analogue resistance was assessed in chinese hamster v79-4 cells exposed to gamma-radiation. after irradiation, the cells were grown in non-selective medium for different time intervals before respreading into medium containing 0.5-0.7 mug/ml thioguanine. in some experiments colonies arising in thioguanine-medium were counter-selected in medium containing the glutamine analogue azaserine, which distinguishes mutants with very little activity of the enzyme hypox ...1977840237
liver homogenate-mediated mutagenesis in chinese hamster v79 cells by polycyclic aromatic hydrocarbons and aflatoxins.several chemical carcinogens that require metabolic activation have been examined for their cytotoxic and mutagenic activity in chinese hamster v79 cells. mutagenic activity was measured as the induced frequency of 6-thioguanine-resistant colonies. metabolic activation was provided by the 9000 g supernatant fraction of rat liver plus cofactors. the cytotoxicity and mutagenicity of aflatoxin b1 and b2, benzo(a)pyrene, 3-methylcholanthrene, 7,12-dimethylbenz(a)anthracene, dibenz(a,h)-anthracene, d ...1977840239
single strand breakage and repair in eukaryotic dna as assayed by s1 nuclease.a sensitive new approach for measuring the repair of single strand breaks in dna induced by low doses of gamma irradiation was tested in cultured fibroblasts from chinese hamster lung, human afflicted with ataxia telangiectasia or fanconi's anemia and in normal cells of early and late passages. the assay is based on the increasing rate of strand separation of dna duplexes in alkali for molecules with increasing numbers of single strand scissions. dna strand separation is shown to follow the rela ...1977840643
study on cytological effects of carofur -- a new mutagen.chinese hamster cells (line v-79) and human leukocytes in vitro and mice of the cba strain were treated with carofur (also called nifurprazinum), an antibacterial agent of pharmaceutical importance. at concentrations as low as 20 ppm, the in vitro treatments of cells of chinese hamster and human lymphocytes expressed chromosome aberrations, almost exclusively of deletion type. this effect resembles that of fluorodeoxyuridine but may not necessarily reflect the same basic mechanism involved. when ...1977846486
neutral amino acid transport systems of tissue culture cells.we have studied the interactions among a varied group of neutral amino acids for uptake into two different animal tissue culture cell lines. 3t3 mouse cells and chinese hamster ovary cells were used in these studies. the results showed that the affinities of the amino acids clustered into two groups, one including amino acids such as glycine, alanine, and alpha-aminoisobutyric acid and the other group included amino acids such as leucine and phenylalanine. the specificities and properties of the ...1977853037
synthesis of newcastle disease virus polypeptides in a wheat germ cell-free system.we have isolated 18s rna from cytoplasmic extracts of newcastle disease virus-infected chinese hamster ovary cells and tested its ability to direct protein synthesis in extracts derived from wheat germ. the products of the cell-free reaction directed by this rna contain polypeptides that comigrate with np, m,f, and 47k roteins from virions. in addition, the products contain a polypeptide (67k) that migrates on polyacrylamide gels slightly faster than the hn protein from virions. tryptic peptide ...1977853567
response of extremely hypoxic cells to hyperthermia: survival and oxygen enhancement ratios.chinese hamster v79 cells and mouse emt6 cells were made extremely hypoxic with a chamber technique that relies upon gas exchange rather than respiration-assisted oxygen depletion. cells in these chambers were treated with heat (43degrees c) or heat plus x-irradiation, and colony-forming ability was determined. hyperthermia: (a) kills exponentially growing v79 cells more efficiently than plateau-phase cells; (b) kills euoxic and extremely hypoxic cells equally; and (c) radiosensitizes euoxic and ...1977860045
selective incorporation of l-3,4-dihydroxyphenylalanine by s-91 cloudman melanoma in vitro.the incorporation of precursors of the biopigment melanin into melanotic and amelanotic s-91 cloudman melanoma, mouse fibroblast l-929, and chinese hamster ovary cells was studied. tyrosine did not selectively accumulate in pigmented cells compared to that in nonpigmented control cells. inhibition of protein synthesis with cycloheximide provided an estimate of the partition of tyrosine between protein (95%) and pigment biosynthesis (5%). l-3,4-dihydroxyphenylalanine, a more proximal precursor of ...1977861938
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
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
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
l-dopa: selective toxicity for melanoma cells in vitro.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
regional chromosomal localization of the human gene for galactose-1-phosphate uridyltransferase.in 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
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
the deposition of 241am and 252cf in the skeleton of chinese hamster, syrian hamster and the rat. 1977893106
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
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 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
detection of chemically induced somatic mutation in chinese hamsters. 1977593291
comparison of highly inbred diabetic and nondiabetic lines in the upjohn colony of chinese hamsters. 1977913895
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
the dose-dependence of sister chromatid exchanges induced by 3 hydrocarbons, in the in vivo bone marrow test with chinese hamsters. 1977401744
coordinate regulation of protein synthesis and messenger rna content during growth arrest of suspension chinese hamster ovary cells.we have found chinese hamster ovary cells, cultured in suspension, are subject to growth control by serum. when suspended in medium containing 0.5% serum the cells becomes reversibly arrested in the beginning of the g1 phase of the cell cycle and can be maintained in this viable, nonproliferating state for several days. this system was used to examine the regulation of protein synthesis with growth rate. in particular, the experiments addressed the question whether mrna content is the principal ...1977558201
the kinetics of contact inhibition in mammalian cells.to elucidate the process of contact inhibition in mammalian cells, we investigated the kinetics of growth arrest in [3h]thymidine labelled embryonic chinese hamster (cricetulus griseus l.) cells after the addition of various concentrations of unlabelled cells. it was observed that after the contact inhibition concentration had been reached, the cells grew undisturbed for one more generation. in the following 24 hr the concentration fell back to the level at the beginning of the experiment and st ...1977558054
rapid cell cycle analysis by measurement of the radioactivity per cell in a narrow window in s phase (rcsi).a new rapid method for the cell cycle analysis of asynchronously growing cells is presented. the new method is an alternative to the more time consuming and subjective fraction of labeled mitoses (flm) method. like the flm method, all cells in the s phase of the cell cycle are marked by pulse labeling with a radioactive dna precursor. the subsequent progress of the cohort of cells thus labeled is monitored through a narrow window in the cell cycle. the window is defined by a narrow range of dna ...1977322870
additive action of ionizing and non-ionizing radiations throughout the chinese hamster cell-cycle. 1977300730
growth and biochemical characteristics of a detachment variant of cho cells.a variant subline of chinese hamster cells (line cho) was isolated that had increased resistance to detachment from the substratum. comparisons between parental and variant cells of the complex carbohydrates liberated during trypsin detachment showed that the variant cells synthesized little or no hyaluronic acid. these cells also had reduced amounts of other complex carbohydrates in the cell periphery. however, parental and variant cells did not differ in morphology, growth control, or cyclic a ...1977192736
mutations affecting the antigenic properties of hypoxanthine-guanine phosphoribosyl transferase in cultured chinese hamster cells.cells of the mutant chinese hamster strain rjk10 do not contain either hypoxanthine-guanine phosphoribosyl transferase activity (hgprt) or protein that cross-reacts immunologically with hgprt. hgprt+ revertants have been isolated from rjk10 and those strains produce hgprt with altered antigenic properties. hgprt from the revertant cells is less reactive with anti-hgprt serum than enzyme from the wild-type cells, and enzymes from the two sources are immunoprecipitated independently from mixtures ...197775576
isolation of wheat germ agglutinin-resistant clones of chinese hamster ovary cells deficient in membrane sialic acid and galactose.several clones of chinese hamster ovary cells have been selected for their resistance to the toxic effects of wheat germ agglutinin. the clones do not bind wheat germ agglutinin as well as parent cells and are 5- to 250-fold more resistant to the toxic effects of the lectin. of three clones studied in detail, all exhibit a decrease in wheat germ agglutinin binding affinity. two have normal numbers of wheat germ agglutinin binding sites, while one (clone 13) has a 65% decrease in binding sites. c ...1977320201
mechanisms for sister chromatid exchanges and their relation to the production of chromosomal aberrations.by taking advantage of the fact that fluorescent light (fl) induces strand breaks only in bromodeoxyuridine(brduy-substituted dna, and that those breaks eventually lead to the formation of sister chromatid exchanges (sces), the response of sces to fl was studied carefully in chinese hamster chromosomes in which, out of four dna strands, brdu-substitution had occurred either in one or three strands. the fl-induced sce frequency did not differ greatly between these two types of chromosomes. howeve ...1977837800
enhancement by caffeine of cell killing and chromosome damage in chinese hamster cells treated with thiotepa. 1977402344
biochemical genetics of chinese hamster cell mutants with deviant purine metabolism. vi. enzymatic studies of two mutants unable to convert inosinic acid to adenylic acid.ade-h and ade-i are two auxotrophic mutants of chinese hamster ovary (cho-k1) cells which specifically require adenine as the purine source to grow. the enzymatic defects of these mutants were examined in cell-free extracts. it was found that ade-h did not have any detectable adenylosuccinate synthetase activity and ade-i was defective in the adenylosuccinate lyase enzyme. the relevance of adenine-requiring mutants to the study of the regulation of purine metabolism in mammalian cells is discuss ...1977849250
clonal variation in colony morphology and growth of cho cells cultured on agar.single chinese hamster ovary (cho) cells plated on agar form macroscopic colonies with high efficiency. colonies produced by cells from the uncloned cell line increase in diameter continuously for 10-12 days after plating to form mounds of cells about 1 mm in diameter. with further incubation, some of these colonies do not increase in diameter (arrested dome), some form an expanding annular monolayer of cells around the central mount (fried egg), and some grow by enlarging the central mound into ...1977837451
125i-udr induced division delay.mitotic selection for cell cycle analysis was used to investigate the effects of (3)h and (125)i, incorporated into dna, on the cell cycle progression of chinese hamster ovary (cho) cells. the results indicate that s-phase cells were delayed and g(2) cells were not.1977836938
the relationship between polyamine accumulation and dna replication in synchronized chinese hamster ovary cells after heat shock.the relationship of polyamine accumulation and semiconservative dna replication was studied in synchronous chinese hamster ovary cultures, progressing through the cell cycle either normally at 37 degrees or after hyperthermic exposure (43 degrees for 1 hr) during g1 or s phase. in control cultures, intracellular polyamine levels decreased as cells divided and then reaccumulated as cells exited g1 and proceeded through the s and g2 phases. immediately after cultures were exposed to 43 degrees hea ...1977832272
[effect of suboptimal temperature on the mitotic regime].a two-hour treatment of chinese hamster cells with a suboptimal temperature of 21 degrees c leads to a decrease of the mitotic index and to a delay in division at the metaphase. cooling causes a sharp rise of the pathological mitosis, represented mainly by the forms of pathology connected with the disorganization of the mitotic apparatus, such as c-mitosis and dispersion of chromosomes in the metaphase. after being transferred to the optimal temperature conditions the cells completely restored t ...1977558014
altered morphology and increased cell adhesiveness of chinese hamster ovary cells cultured on fibrin.chinese hamster ovary cells cultivated on fibrin exhibited different characteristic from cells growing on plastic. while sparsely plated cells on plastic dishes had an epithelioid morphology, cells on fibrin assumed a round shape and then converted to a stretched form with protruded processes that increased with cell density. within a few days, cells fibrinolysed adjacent fibrin and returned to the morphology seen in plastic dishes. when fibrinolysis was inhibited by epsilon-aminocaproic acid (e ...1977557051
glycoprotein synthesis in a temperature-sensitive chinese hamster cell cycle mutant.a temperature-sensitive mutant of chinese hamster cells is described which has two interesting properties: (1) it is a cell cycle mutant and (2) glycoprotein synthesis appears to be affected at the at the non-permissive temerature (40degreesc). synchronized cells shifed to 40degreesc in the beginning of their g1 phase do not incorporate [3h]-thymidine into dna during the expected s-phase, but once dna synthesis has been initiated ( approximately 10 hours after termination of serum starvation) a ...1977557044
action of fdurd and dcyd on the incorporation of brdurd in chinese hamster somatic cell dna and the isolation of auxotrophic mutants.chinese hamster somatic cells grown in the presence of bromodeoxyuridine, deoxycytidine and fluorodeoxyuridine incorporate more bromodeoxyuridine in the dna than cells grown in the presence of bromodeoxyuridine alone. thus they become more sensitive to light irradiation. our data suggest that 0.05 mm--0.2 mm bromodeoxyuridine, 0.05 mm deoxyctidine and 10 mmug/ml fluorodeoxyuridine is one of the best possible combinations for the selection of chinese hamster somatic cells mutants. auxotrophs for ...1977138686
the isolation and characterization of asparagine-requiring mutants of chinese hamster cells. 197714014
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
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
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
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
the molecular basis of emetine resistance in chinese hamster ovary cells: alteration in the 40s ribosomal subunit.the molecular basis of resistance to the protein synthesis inhibitor emetine has been examined in cell-free, protein-synthesizing extracts derived from normal and emetine-resistant (emtr) mutants. we had earlier shown that protein synthesis in extracts of the mutant cells was resistant to the inhibitory action of emetin. when extracts from a wild-type and mutant cell line were fractionated into supernatant (s-100) and polyribosome fractions and mixed in different combinations, resistance to emet ...1977837444
protease activation of g1 nuclei isolated from chinese hamster fibroblasts. 1977836402
spermatogenesis in the chinese hamster.in this article a description of the process of spermatogenesis in the chinese hamster is given. spermiogenesis could be divided into 16 steps. the cycle of the seminferous epithelium was divided into 12 stages, coinciding with the first 12 steps of spermiogenesis. the relative and absolute duration of the stages was determined. the duration of the cycle of the seminiferous epithelium was found to be 17.0 days. the morphology of the spermatogonia was studied in seminiferous tubules mounted "in t ...1977835840
ultrasonic treatment of chinese hamster cells at high intensities and long exposure times.monolayers of single chinese hamster cells growing on 0.036 mm melinex film in specially constructed irradiation vessels were treated to continuous 990.5 khz focused ultrasound. after treatment, cells were incubated until they formed small microcolonies (48 h) or until confluent growth was obtained (96 h). damage was assessed by scoring a focal area of 5 mm2 for a reduction in colony number or multiplcity after three generations or for a cell-free area after seven generations. the results showed ...1977831919
effect of phorbol myristate acetate on the recovery of spontaneous and ultraviolet light-induced 6-thioguanine and ouabain-resistant chinese hamster cells.12-0-tetradecanoyl-phorbol-13-acetate (tpa) and phorbol were tested in chinese hamster cells for their effects on mutagenesis (resistance to 6-thioguanine and to ouabain), dna repair, and survival after ultraviolet (uv) irradiation. recovery of 6-thioguanine- and ouabain-resistant colonies was significantly increased by tpa treatment and, to a lesser extent, by phorbol in uv-irradiated cells. moreover, maximum enhancement of recoverable uv-induced 6-thioguanine- and ouabain-resistant mutants occ ...1977830404
[rate of spontaneous chromosome aberration occurrence in cultured chinese hamster cells].the spontaneous chromosome mutation rate was studied in cultured aneuploid chinese hamster cells (clone 237(1)) using the method of slowing down the rate of cell division in a limiting medium containing 0.1% of serum. it was shown that during one cell generation (which lasted 14 days in limiting medium) the accumulation of chromosome aberrations with time took place. the data obtained are in keeping with the assumption of a linear dependence of this accumulation on time. the spontaneous chromoso ...1977612482
[induction of gene mutations and the lethal action of ultraviolet rays in synchronized chinese hamster cells].lethal and mutagenic effects of uv light were studied in two synchronized uv-sensitive chinese hamster cell clones differing in the degree of sensitivity (chs1, chs2). it is shown that the phase of mitosis is most resistant to the lethal effect of uv. the sensitivity of both cell clones increases in the pre-synthetic phase and reaches its maximum during the phase of dna synthesis. positive correlation of cell sensitivity to mutagenic and lethal action of uv was observed when studying induced mut ...1977612481
chromosome replication patterns in an established cell line (cho).the chromosome replication patterns of the established cell line cho have been examined and compared with those of normal primary chinese hamster cells, using the budr-hoechst fluorescence technique developed by latt (1973). the results of this study indicate that the majority of cho chromosomes replicate normally. there are four clear-cut exceptions to this rule, three of which are most easily explained as undetected or misinterpreted structural rearrangements ot the cho genome. several other r ...1977606507
hyperthermic treatment (43 degrees c) rapidly impedes attachment of fibroblasts to culture substrates.hyperthermic (43 degrees c) exposure of chinese hamster fibroblasts for more than 30 min, either in suspension or as a monolayer, significantly inhibits their ability to attach to the culture substrate. this finding as well as the effect of hyperthermia on membrane proteins and on surface topology are rapidly expressed and differ from the inhibition of colony formation which is a later effect of hyperthermia on reproductive ability.1977565256
[hybridization of chinese hamster cells sensitive to ultraviolet irradiation].resistance to uv-light was studied in two uv-sensitive aneuploid chinese hamster cell clones to different origin and degree of sensitivity, their respective polyploids and somatic cell hybrids. the karyotype of the parental clones, cell hybrids and polyploids was analyzed in parallel. a great variability of karyotypes was detected in hybrid cells. serial cultivation of hybrids was accompanied by chromosome loss. soon after fusion the hybrid clones proved to be more resistant to uv than the paren ...1977561015
a simple method for cloning and replica plating of mammalian cells using multicellular spheroids.v 79/4 chinese hamster cells or hela cells grow in eagle's mem supplemented with 25 microgram/ml dextran sulphate to form clonal multicellular spheroids. these cell clones, consisting of 5-10(2) cells, are easy to separate, to transfer from one culture vessel into another and grow as normal monolayer colonies on dederon cloth circles after subculture in eagle's mem without dextran sulphate. a simple replica technique is described by which 500 clones can be transfered onto at least 3 replica clot ...1977356496
variance in ldh isozyme patterns in a chinese hamster (cricetulus griseus) colony.1. ldh activity and isozyme pattern were examined in the liver and epididymal fat pad of animals in 12 different sublines of the upjohn chinese hamster colony, which was established to produce animals with spontaneous diabetes. 2. considerable divergence was observed and the animals could be divided into 3 groups according to ldh-h activity. each group was significantly different from the other in epididymal fat pad ldh-1, 2,3 and 5 and liver ldh-3, 4 and 5. 3. the variance in ldh isozyme patter ...1977318257
survival of synchronized v79 cells treated with x-rays and cordycepin.the survival of v79 chinese hamster lung cells exposed to x-irradiation is reduced by co-treatment with cordycepin (3'-deoxyadenosine). this reduction is manifested principally by a decrease in the d0 of the x-ray survival curve from 199 rad in untreated cells to 106 rad in cordycepin-treated cells. reduced survival is seen throughout the life-cycle when synchronized cell populations are exposed to both agents with cells in mid-s being especially sensitive.1977300368
control of cell shape by adenosine 3' : 5' - phosphate in chinese hamster ovary cells: studies of cyclic nucleotide analogue action, protein kinase activation, and microtubule organization. 1977197834
sequence programming of dna replication over the s phase of chinese hamster cells. 1977137816
potential genetic risks from stationary magnetic field.cytogenetic analysis of dede cell lines (chinese hamster) was used to study the mutagenic effect of stationary magnetic field (smf) and the combined effect of smf and tepa. cytogenetic analysis showed a moderate mutagenic effect after exposure to smf. in combination with tepa, only the additive effect of the two mutagens was observed.197776658
[occurrence of pseudoisocyanine-positive endocrine cells in the midgut of the hamster (cricelulus griseus) (author's transl)].pseudoisocyanine-reacting cells could be identified in the intestinal glands of the upper duodenum of the hamster (cricetulus griseus). these cells contain numerous granules as carrier substances of the colouring pigments. presumable these cells are insulin-producing cells.197772477
the effect of cyclophosphamide on the centromere separation sequence in chinese hamster spermatogonia.the sequence of centromere separation in spermatogonial chromosomes of untreated and cyclophosphamide-treated chinese hamsters is described. centromeres of chromosome 1 and 2 separated much earlier than all other chromosomes, especially 6-8. cyclophosphamide significantly inhibits the centromere separation in all chromosome groups but does not alter the sequence of separation.1977598845
tyzzer's disease in the chinese hamster (cricetulus griseus). 1977599880
effects of ultraviolet light on synchronized chinese hamster ovary cells; potentiation by hydroxyurea.we have examined the effects of hydroxyurea on u.v.-irradiated chinese hamster cho-ki cells. ultraviolet irradiation followed by incubation with hydroxyurea causes only slight disruption of dna and chromosome structure in cho-ki cells compared with hela cells. there is, however, a clear potentiation by hydroxyurea of the u.v. killing of cho-ki cells, which is most pronounced at those points in the cycle which are reported to have small dna precursor pools. this potentiation is reduced when dna p ...1977599176
pesticide induced ouabain resistant mutants in chinese hamster v79 cells.the effect of 3 insecticides (chlordane, dieldrin and carbaryl) and one herbicide (2,4-d-fluid) was studied on the induction of ouabain-resistant mutants in chinese hamster v79 cells at concentrations approaching the environmental protection agency (epa) tolerance limits. the kinetics and dose range for cytotoxicity were determined by colony formation assay. results showed that these compounds enhanced the number of ouabain-resistant mutants and acted as weak mutagens.1977413633
retention of the glycocalyx after cell detachment by egta.chinese hamster ovary cells were examined ultrastructurally following several detachment procedures. alterations in the surface glycoproteins were observed by using ruthenium red in the fixation procedure. trypsin removed a major portion of the cells glycocalyx and formed spherical cellular configurations. egta detached cells were also spherical, however, their glycocalyx appeared to remain although redistributed over the cell surface. kinetic studies showed no alterations in subsequent populati ...1977411829
a search for allelic recombination in chinese hamster cell hybrids.mutants resistant to 6-thioguanine were selected from cho cells which were either temperature sensitive or proline requiring. these mutants were stable and had low levels of hypoxanthine guanine phosphoribosyl transferase (hgprt). hybrids were selected which were heteroallelic at the hgprt locus and complementation between the mutants used was not observed. interallelic recombination at this locus would generate hgprt+ cells which could be selected in littlefield's hat medium. selection experime ...1977600266
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
differential giemsa staining of sister chromatids after extraction with acids.chromosomes of chinese hamster strain cells were air-dried on slides after brdu substitution for two or three rounds of replication. the preparations were treated with 20% pca at 55 degrees c for 20-30 min, or 5n hcl at 55 degrees c for 15-20 min. after staining with giemsa, unifilarly brdu-substituted chromatids stained faintly and bifilarly substituted chromatids stained darkly. such a pattern of sister chromatid differential staining was confirmed by the examination of metaphase cells grown w ...197772637
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
studies on adenosine 3',5'-phosphate-binding and adenosine 3',5-phosphate-dependent protein kinase activities associated with subcellular fractions of chinese hamster ovary cells.both cyclic amp-binding and cyclic amp-dependent protein kinase activities exist in chinese hamster ovary cell extract. competition experiments demonstrate that the binding is specific for cyclic amp. all cellular elements including nucleus, mitochondria, plasma membrane, microsome, ribosome and cytosol contain both activities. binding activity is highest in the cytosol and lowest in the nucleus. each fraction contains endogenous protein kinase activity which is insensitive to cyclic amp activat ...1977200277
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
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