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aconitase (e.c. 4.2.1.3) mitochondrial locus mapped to human chromosome 22: studies with chinese hamster--human somatic cell hybrids.three separate somatic cell fusions were made between chinese hamster lines and human lymphocytes containing (1) a 3/4 translocation, (2) an x/9 translocation, and (3) a 17/9 translocation. eleven independently derived hybrids showed that only human chromosome 22 was consistently present when human aconm was expressed and absent when human aconm was not expressed. these studies assign a gene for human aconm to chromosome 22, and are consistent with prior gene-mapping results.1978728065
genetic analysis of cell malignancy--evidence from somatic cell genetics.when normal nontumorigenic cells are fused with tumorigenic cells some of the resulting hybrids are nontumorigenic in respect to their ability to grow in immune-deficient nude mice. comparison of the chromosome content of nontumorigenic with tumorigenic hybrids, as well as with the cells of tumors which develop from the latter, reveals that in normal human x tumorigenic chinese hamster hybrid crosses, two specific human chromosomes of the nontumorigenic parental line are very likely responsible ...1978728675
effect of caffeine on ultraviolet mutagenesis in v79 chinese hamster cells. 1978729970
bromodeoxyuridine-induced mutations in synchronous chinese hamster cells: temporal induction of 6-thioguanine and ouabain resistance during dna replication.mutations were induced in synchronous chinese hamster cells by bromodeoxyuridine (budr) incorporated into cells for one-hour periods in the cell cycle. there was a very pronounced temporal dependence during the first half of the dna synthesis period for the induction of damage leading to 6-thioguanine (6tg) and ouabain resistance. no mutants above background were induced by exposure to budr in g1 and g2 cells, and very few mutants were induced in the latter part of the dna synthesis period. the ...1978730050
suppression of the frequencies of sister chromatid exchanges in bloom's syndrome fibroblasts by co-cultivation with chinese hamster cells.the effect of co-cultivation of bloom's syndrome fibroblasts with chinese hamster ovary cells (cho) on the incidence of sister chromatid exchanges (sces) was studied. the results show that suppression of the frequency of sces in bloom's syndrome cells occurs only if cell to cell contact is present with cho cells, without any effect on the sce frequency in the latter. it is suggested that possible genetic heterogeneity between different bloom's syndrome patients can be studied using the method of ...1978730162
isolation of mutant mammalian cells altered in polyamine transport.chinese hamster ovary and rat myoblast cells resistant to the toxic action of methylglyoxal bis guanylhydrazone (mgbg), an antimitotic agent and inhibitor of polyamine synthesis, have been isolated by single step selection. mutagenesis with ethyl methanesulfonate increases the recovery of the variants at least 30-fold. intracellular accumulation of mgbg is greatly reduced in resistant cells. this property is accompanied by a 99% decrease in the uptake of all three naturally occurring polyamines. ...1978730773
evidence for variation in the number of functional gene copies at the amar locus in chinese hamster cell lines.the hypothesis of functional hemizygosity has been examined for the alpha-amanitin resistant (amar, a codominant marker) locus in a series of chinese hamster cell lines. amar mutants were obtained from different cell lines, e.g., cho, dhw, m3- 1 and cho-kl, at similar frequencies. after fractionation of different rna polymerase activities in the extracts by chromatographic procedures, the sensitivity of the mutant rna polymerase ii towards alpha-amanitin was determined. while all of the rna poly ...1978730780
studies of the diphtheria toxin receptor on chinese hamster cells.concanavalin a, wheat germ agglutinin and the ovalbumin glycopeptide are all inhibitors of the cytotoxic effect of diphtheria toxin on chinese hamster cells. ovalbumin glycopeptide loses its inhibitory property after treatment with beta-n-acetylglucosaminidase. this demonstrates the importance of the glycopeptide structure for the mechanism of inhibition. the glycopeptide may be a toxin cell-surface receptor analogue. diphtheria toxin-resistant mutants were isolated in order to search for cells ...1978732311
excorporation efficacy with ca-dtpa of 241am and 252cf in the skeleton, liver, and kidney of the rat and syrian and chinese hamsters: lack of correlation with the biological half-times. 1978734050
[electron microscopic study of mammalian somatic cell fusion under the action of polyethylene glycol].an electron microscope study of heterokaryons and synkaryons, obtained after the treatment of suspension of human embryonic fibroblasts and cultured fibroblasts of chinese hamster (clone m151) with polyethylene glycol (pec, m. v. 6000) has shown that in 15 minutes after the administration of peg, the cell agglutination and disappearance of plasma membranes between cells takes place. it is not obvious, however, how per is passing through the cell envelope, but the similar action of pef towards th ...1978734774
[dependence of dna synthesis in chinese hamster cells on the culture growth conditions]. 1978734783
growth retardation in chinese hamster v-79 cells exposed to 1 mhz ultrasound. 1978734793
organization of mammalian chromosomal dna: supercoiled and folded circular dna subunits from interphase cell nuclei.chinese hamster cells (line v79/4) in the g2 phase of the mitotic cycle were lysed onto neutral sucrose gradients and the released chromosomal dna was characterized according to its size and shape by sedimentation velocity studies. using the intercalating agent, ethidium bromide, in the gradients and the induction of dna single- and double-strand breaks by irradiation, the dna was proved to be released into the gradient in supercoiled circular subunits whose homogenous size corresponds to 2.8 . ...1978735613
assignment of the gene for dipeptidase 2 to mus musculus chromosome 18 by somatic cell hybridization.evidence is presented for the assignment of the gene for dipeptidase 2 to mus musculus chromosome 18 by synteny testing and karyotypic analysis of chinese hamster x mouse somatic cell hybrid clones. dip-2 and chromosome 18 were expressed concordantly in 24/24 clones examined (ten primary clones and 14 secondary clones). synteny testing indicated that dip-2 was not expressed concordantly with the expression of any marker enzymes.1978736882
modification of uv-induced mutation frequencies in chinese hamster cells by dose fractionation, cycloheximide and caffeine treatments.chinese hamster (v79) cells were irradiated with a fractionated regime of ultraviolet light (uv1 + uv2). the fractionation of a uv dose always increased the colony-forming ability but reduced (or it did not change) the mutation frequencies. treatment with cycloheximide between the two uv irradiations resulted in two types of effects, depending on the protocols used. long exposures to cycloheximide (i.e., greater than 6 h) for the entire period between uv1 and uv2 or partial treatment of cyclohex ...1978740008
absence of interaction between x-rays and uv light in inducing ouabain- and thioguanine-resistant mutants in chinese hamster cells.chinese hamster ovary cells were irradiated with x-rays at times from 0 to 17 h before being irradiated with ultraviolet (uv) light. no synergism was observed between the two radiations for the production of mutants resistant to either ouabain or 6-thioguanine. these experiments were designed to test whether x-rays induced an error-prone repair system that would increase the frequency of mutations produced by uv light, but no such system was detected.1978740009
enhancement of repair replication in mammalian cells by hydroxyurea.the effect of hydroxyurea on dna repair replication has been studied in chinese hamster ovary cells. mitotic cells were treated with uv irradiation, methyl methanesulfonate or nitrogen mustard and incuated in the presence of each of the 4 [3h] deoxyribonucleosides plus brdurd and fdurd for 2 h. the amount of repair replication was quantitated on cscl gradients and similar values were obtained for each nucleoside. in all cases addition of hu during the incubation period increased these values app ...1978740011
[effect of natural and synthetic acid polypeptides on normal and gamma-irradiated cells of the chinese hamster]. 2014740860
inverse relationship between galactokinase activity and 2-deoxygalactose resistance in chinese hamster ovary cells.galactokinase activity is reduced in 12 independent clones of chinese hamster ovary cells resistant to 2-deoxygalactose. the frequency of resistant colonies is increased with chemical mutagens. the resistant phenotype is stable in the absence of selection. there is an inverse correlation between the levels of galactokinase activity and the cloning efficiency in deoxygalactose. cells with high resistance have 1% or less of the enzyme activity observed in the parental cells; while cells with low r ...1978741353
role of adenine phosphoribosyltransferase in adenine uptake in wild-type and aprt- mutants of cho.adenine uptake in cultured chinese hamster fibroblasts showed biphasic saturation kinetics. the transport system was highly specific for adenine and was competitively inhibited by adenosine. utilizing mutant clones of chinese hamster fibroblasts that have either reduced or negligible adenine phosphoribosyltransferase (aprt) activity, we found that (1) adenine was not accumulated against a concentration gradient in the absence of aprt activity and (2) after rapid initial uptake equal to that of t ...1978743195
"carrier activation" and glucose transport in chinese hamster fibroblasts. 1978743314
responses of mammalian metaphase chromosomes to endonuclease digestion.digestion of fixed metaphase chromosomes by endonucleases (micrococcal nuclease and dnase ii) under optimal digestion conditions followed by giemsa staining produces sharp banding patterns identical to g-bands. in 3h-thymidine labeled, synchronized metaphase cells of the chinese hamster (cho line), the band induction is accompanied by the removal of dna. the single strand specific nuclease s1 and dnase i do not produce such banding patterns.1978743903
separation of linked markers in chinese hamster cell hybrids: mitotic recombination is not involved.a search for mitotic recombination was carried out using mutant subclones of cultured chinese hamster ovary cells. recombination events were sought between the linked loci specifying the enzymes hypoxanthine phosphoribosyl tranferase and glucose-6-phosphate dehydrogenase. it was shown by fluctuation analysis that markers at these two loci co-segregate from doubly heterozygous pseudotetraploid hybrid cells more than 90% of the time. the minority class of segregants, which had lost one marker with ...1978744475
unusually thick filaments in intrafusal muscle fibers of the chinese hamster. 1978744920
cytogenetic toxicity of gentian violet and crystal violet on mammalian cells in vitro.the cytogenetic toxicity of gentian violet in chinese hamster cho cells in vitro has been studied by analyzing (1) squash preparations from direct fixation for recording mitotic anomalies and (2) air-dried preparations (with colcemid--hypotonic pretreatments) for recording metaphase chromosome aberrations. it was concluded that this compound is a mitotic poison as well as a clastogen in vitro. its clastogenic property was confirmed in 5 other different mammalian cel types. 10 samples of differen ...1978745616
cytogenetic effects of inhaled ozone.we have repeated as closely as possible the experiments of zelac et al., who observed significantly elevated levels of chromosome aberrations in short-term cultures of peripheral lymphocytes from chinese hamsters that had inhaled ozone. unlike zelac et al., we observed no increase in chromosome-type aberration levels, though a small increase in chromatid-aberration levels similar to that reported for exposed human subjects by merz et al. was seen. no increase in the levels of any chromosomal abe ...1978745619
sister-chromatid exchanges induced in rabbit lymphocytes by 2-aminofluorene and 2-acetylaminofluorene after in vitro and in vivo metabolic activation.because short in vitro treatments of chinese hamster cells with 2-aminofluorene and 2-acetylaminofluorene did not increase sces even in the presence of a metabolic activation system, experiments were carried out with rabbits to see if in vivo activation occurred. rabbits injected with 2-af could activate the compound and a transient dose-dependent increase in sces was found in peripheral lymphocytes cultured at various times after the injection. with 2-aaf, however, the response was more variabl ...1978745622
caffeine inhibits excision of 7-bromomethylbenz (a) anthracene-dna adducts from exponentially growing but not from stationary phase chinese hamster cells.excision of 7-bromomethylbenz(a)anthracene (7-bmba)-dna adducts from exponentially growing cultures of chinese hamster v79-379a cells followed logarithmic kinetics with a half of approximately 20 hrs. post-treatment incubation in the presence of a sub-toxic concentration of caffeine markedly reduced this loss. caffeine brought about a concomitant increase in overall dna synthetic rate in treated exponential cultures. excision in stationary, non-dna-replicating cultures, was slower and caffeine d ...1978745993
inhibitory effects of d-mannosamine and reversal of the d-mannosamine inhibition by d-glucosamine on growth of a glucosamine-requiring mutant of chinese hamster lung cells. 1978748281
lipopolysaccharide effects on sensitive and resistant variant chinese hamster ovary cell lines.chinese hamster ovary (cho . k1 . pro) cell growth was inhibited by addition of a gram-negative bacterial lipopolysaccharide (lps) to the cell culture medium. growth inhibition began after three or four days of incubation, was dose-dependent up to a maximum at an lps concentration of 500 microgram/ml and was accompanied by cell shape changes and enhanced cytoplasmic vacuolization. formation of bizarre cho . k1 . pro cell shapes and vacuole formation were most pronounced after seven days of incub ...1978748676
plasma membrane proteins and glycoproteins from chinese hamster cells sensitive and resistant to actinomycin d.plasma membrane proteins and glycoproteins have been isolated from chinese hamster cells of the spontaneously transformed dc-3f parental cell line and the dc-3f/ad x line with a high level of acquired resistance to actinomycin d. plasma membrane preparations from both cell lines band at 1.16 g/ml after isopycnic centrifugation. we present evidence to indicate differences in the leucylpeptide backbones of the antibiotic-sensitive cells and the drug-resistant dc-3f/ad x cells. in addition, there a ...1978748679
cellular and molecular studies on globin gene expression.globin gene expression has been studied with the use of a combination of cell and molecular biology techniques. with a somatic cell hybrid between mouse erythroleukemia (mel) and human erythroid cells, human and mouse globin genes can be coexpressed in the same hybrid cell. somatic cell hybridization between mel cells and nonerythroid cells (e.g., human fibroblasts) results in hybrid cells that cannot be induced to produce hemoglobin of any type. molecular hybridization of cellular dna and rna w ...1978748760
[cytotoxicity test on medical drugs--chromosome aberration tests with chinese hamster cells in vitro (author's transl)]. 1978750044
the response of chinese hamster ovary cells to fast neutron radiotherapy beams. iii. variation in biological effectiveness with position in the cell cycle. 1978752158
assignment of a human galactose-1-phosphate uridylyltransferase gene (galt1) to chromosome 9 in human-chinese hamster somatic cell hybrids. 1978752475
toward the development of a standard reference cholera antitoxin.the need for a reference cholera antitoxin to serve as a standard for the calibration of cholera enterotoxin and toxoid as well as for measurement of the antitoxin response in animals and patients was recognized by the nih cholera advisory committee, niaid, dhew, usa. two cholera antitoxins have been used for several years as provisional references, but neither was considered to embody all of the properties of an ideal standard. accordingly, a lot of cholera antitoxin was prepared by immunizatio ...1978753669
microwave radiation-induced chromosomal aberrations in corneal epithelium of chinese hamsters.a microwave diathermy machine was used to irradiate the eyes of 5-month-old female chinese hamsters. the right eye of each of seven animals was irradiated with 75 mw/cm2 radiation density for 10 minutes. after one month, slit-lamp examinations revealed lens opacities in the exposed eyes of two animals. next, the right eye of each of 32 animals was irradiated with 100 mw/cm2 radiation density for 30, 20, 10, or 5 minutes. epithelial cells of the cornea were collected to make chromosomal preparati ...2005753878
[in vitro effect of asbestos fibers on short-term cultures of human lymphocytes].the endocellular incorporation of asbestos fibres seems to be capable to induce on chinese hamster cell cultures numerical and structural chromosome aberrations. in the present study asbestos fibres have been added at different concentrations to human cultured lymphocytes which have been harvested at 48 and 72 h, respectively. the results do not show significant difference in the distribution of chromatid and chromosome-type aberrations between the control cultures and the cultures treated with ...1978755418
absence of povidone-iodine-induced mutagenicity in mice and hamsters.povidone-iodine usp was tested for mutagenicity in mice by the dominant lethal assay or micronucleus test and in chinese hamsters by the bone marrow test. none of the three tests revealed any evidence of mutagenic effect.1979758440
the effect of lucanthone on the radiation response of intestinal stem cells in chinese hamsters.crypt microcolony assay was used to determine the effect of lucanthone on the radiation response of intestinal stem cells in chinese hamsters . the dq of the crypt microcolony radiation--survival curve was maximally reduced by 205 rads when lucanthone injection preceded irradiation by 10 hours and was reduced by 140 rads when injection followed irradiation by 5 hours. on simultaneous injection and irradiation, dq was reduced by only 20 rads; when injection and irradiation were separated by appro ...1979760168
chromosomal imbalance in ovulated oocytes from syrian hamsters (mesocricetus auratus) and chinese hamsters (cricetulus griseus).chromosomes were studied in ovulated oocytes from syrian hamsters (mesocricetus auratus) and chinese hamster (cricetulus griseus) to assess the degree of chromosomal imbalance after first meiotic division of oogenesis. only one hyperploid oocyte among 307 studied was detected in the former, and none in oocytes from the latter species. structural chromosome alterations, single chromatids due to presegregation, and diploid chromosome sets resulting from meiotic blockage were not observed. the horm ...1979761487
emetine resistance in chinese hamster cells. analysis of ribosomal proteins prepared from mutant cells. 1979762080
sterol synthesis in variant chinese hamster lung cells selected for resistance to 25-hydroxycholesterol. cross-resistance to 7-ketocholesterol, 20alpha-hydroxycholesterol, and serum.two lines of chinese hamster lung (dede) cells which are resistant to the killing effect of 25-hydroxycholesterol, and which grow to confluence in its presence, have been isolated. one of the resistant lines exhibited a high to normal growth rate and normal levels of 3-hydroxy-3-methylglutaryl coenzyme a (hmg-coa) reductase (mevalonate:nadp+ oxidoreductase (coa-acylating), ec 1.1.1.34) activity and sterol synthesis in the presence of concentrations of 25-hydroxycholesterol that caused nearly com ...1979762093
structural studies of the major high mannose oligosaccharide units from chinese hamster ovary cell glycoproteins.the major high mannose-type glycopeptides present in chinese hamster ovary cells have the compositions (man)9(glcnac)2-asn, (man)8(glcnac)2-asn, and (man)6(glcnac)2-asn. the structures of these glycopeptides were determined by the combination of methylation analysis, acetolysis, smith periodate degradation, and alpha- and beta-mannosidase digestion. their complete structures are: manalpha1 leads to 2manaalpha1 leads to 6(manalpha1 leads to 2manalpha1 leads to 3)manalpha1 leads to 6(manalpha1 lea ...1979762159
isolation and cell cycle analysis of temperature-sensitive mutants from chinese hamster cells.mutants temperature-sensitive for growth have been isolated from the established line of chinese hamster fibroblasts wg1a. these mutants, together with the ones previously isolated by roscoe et al. ('73), have been characterized with regard to their cell cycle properties. most of them become arrested in the g1 phase of the cell cycle when incubated under restrictive conditions. by performing temperature shift experiments with synchronous cultures, the execution steps of most of the mutated funct ...1979762193
the initiation and elongation steps in protein synthesis: relative rates in chinese hamster ovary cells during and after hyperthermic and hypothermic shocks.the relative rates of the initiation and elongation phases of protein synthesis have been determined in heat- and cold-shocked cho cells from measurements of the incorporation of 35s-methionine into n-terminal and internal positions of growing peptides by a modified edman degradation. when the cells are shifted from 37 degrees c to temperatures between 10 degrees c and 34 degrees c, the rate of initiation is at first reduced more extensively than that of elongation. after 20 to 30 minutes at the ...1979762195
pancreaticoduodenal transplantation in juvenile syrian and chinese hamsters. 1975766272
isolation and properties of heat-labile enterotoxin(s) from enterotoxigenic escherichia coli.various techniques have been applied to the detection of skin reactivity associated with heat-labile escherichia coli enterotoxin in fermenter-grown cultures of enterotoxigenic strains in syncase medium and in trypticase soy broth. isolated products that were homogeneous, as determined by disc electrophoresis and sodium dodecyl sulfate gel electrophoresis, differed immunologically and in physicochemical characteristics depending on the strain and medium used, even though the products had similar ...1976768386
animal models of diabetes and obesity, including the pbb/ld mouse.diabetes mellitus occurs in many animals species. however, only a few have been utilized in systematic studies designed to answer unsolved problems associated with the disorder in man such as molecular basis, pathogenesis of the vascular and neural lesions, and the roles of diet, exercise and obesity. among the animal models available, rodents have been studied most thoroughly for a number of reasons: a) short generation time (sexually mature at about 3 mo of age, gestation time 21 days) and lif ...1976770197
inhibition of human lymphoma cell-line colony formation by lymphocytes from patients with lymphoma and cancer hospital employees.inhibition of human lymphoma cell-line colony formation (icf) was induced by peripheral blood lymphocytes (pbl) from patients with lymphoma and apparently healthy cancer hospital personnel. pbl from patients with non-lymphoma neoplasms and from normal blood bank donors did not elicit icf. icf was most marked when pbl were cocultivated for 24 hours in a ratio of 1000:i with target lymphoma cells that had been cultured for 24 hours before exposure. no significant icf was observed when target cells ...1976779948
mutagenicity and cytotoxicity of benzo(a)pyrene arene oxides, phenols, quinones, and dihydrodiols in bacterial and mammalian cells.twenty-nine benzo(a)pyrene derivatives were tested for mutagenic acitivity without metabolic activation in salmonella typhimurium strains ta98, ta100, and ta1538 and in chinese hamster v79 cells. the compounds studied included 4 arene oxides, all 12 isomeric phenols, 5 quinones, and 8 dihydrodiols. benzo(a)pyrene 4,5-oxide was the most mutagenic of the compounds tested in both the bacterial and mammalian systems. the other arene oxides [benzo(a)pyrene 7,8-, 9,10-, and 11,12-oxides] were only wea ...1976788898
mutagenicity and cytotoxicity of benzo(a)pyrene benzo-ring epoxides.four benzo-ring epoxides of the environmental carcinogen benzo(a)pyrene (bp) were tested for mutagenic and cytotoxic activity in 3 strains of salmonella typhimurium (ta1538, ta98, and ta100) and in chinese hamster v79 cells. although very unstable in aqueous solution, 7beta,8alpha-dihydroxy-0beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (diol epoxide 1), with the 7-hydroxyl group on the same face of the molecule as the epoxide oxygen, was 1.5 to 4 times as mutagenic in the bacterial strain ...1976788899
differential rates of sister chromatid exchanges between euchromatin and heterochromatin.in two rodent species, the chinese hamster and the montane vole (microtus montanus), the rate of sister chromatid exchange was lower in constitutive heterochromatin than in euchromatin.1976793794
a comparative study of different experimental protocols for mutagenesis assays with the 9-azaguanine resistance system in cultured chinese hamster cells.both spontaneous and ems-induced mutant frequencies were determined in cultured cells from v79 chinese hamsters using three different experimental protocols. after optimal expression time was attained, mutation frequencies only remained constant when a protocol was used in whcih the cell density was maintained below critical values both before and during mutant selection. the identification of such a plateau allows, besides more reliable and reproducible estimates of mutation frequency, reductio ...1976794707
mutagenicity of industrial compounds: styrene and its possible metabolite styrene oxide.styrene and its presumed metabolite, styrene oxide, were tested for their mutagenic effect on a forward mutation system of yeast and of chinese hamster cells, and on a gene-conversion system of yeast. experiments with liver microsomal preparations and host-mediated assay with yeast were also carried out. styrene oxide was mutagenic in all test systems. styrene was mutagenic only in the host-mediated assay.1976796697
the mutagenicity of benzimidazole and benzimidazole derivatives. vi. cytogenetic effects of benzimidazole derivatives in the bone marrow of the mouse and the chinese hamster.methyl benzimidazole-2-ylcarbamate (mbc) was mutagenic in mice by the micro-nucleus test. other benzimidazole derivatives, with the exception of the parent compound of mbc, benomyl, and the very closely related substance 2-benzimidazolylurea, did not produce micro-nuclei in mouse bone marrow. evidence is presented that mbc acts through inhibition of mitosis and that for this action the carbamoyl group is a necessary but not a sufficient condition. it is also demonstrated that for this particular ...1976796698
sister chromatid exchange as an assay for genetic damage induced by mutagen-carcinogens. ii. in vitro test for compounds requiring metabolic activation.sister chromatid exchanges (sce's) which are easily seen by "harlequin chromosome" techniques can be readily induced in cultured chinese hamster ovary (cho) cells by low concentrations of mutagen-carcinogens that do not require metabolic activation. if the cells are simultaneously treated with cyclophosphamide which does require metabolic activation before it becomes mutagenic, and an activating system consisting of an extract of rat liver containing microsomes (s-9 mix) then numerous sce's are ...1976796721
mutagenicity and metabolism of vinyl chloride and related compounds.the various adverse biological effects of vinyl chloride appear to be dependent upon the metabolic conversion of this compound into chemically reactive metabolites. the metabolism of vinyl chloride in mammals and in man, including the formation of monochloroacetic acid and some identified sulfur conjugates is reviewed. hepatic microsomal mixed function oxidases from rats, mice, and humans were equally effective in transforming vinyl chloride into alkylating agents in vitro. two of the enzyme rea ...1976799962
biochemical genetics of chinese hamster cell mutants with deviant purine metabolism: isolation, selection, and characterization of a mutant lacking hypoxanthine-guanine phosphoribosyltransferase activity by nutritional means.mutants of the chinese hamster ovary cell derived from cho-k1 have been selected for lack of hypoxanthine-guanine phosphoribosyltransferase (ec 2.4.2.8) (hgprt) without the use of a drug-resistance protocol. the procedure depends on the use of a parental strain carrying a mutation making it unable to synthetize purines and thus dependent upon exogenously added purines for growth. the standard "budr-visible-light" procedure is then used to select those cells which can use adenine but cannot use h ...1976800293
failure to detect chromosome damage in bone-marrow cells of mice and chinese hamsters exposed in vivo to some ergot derivatives.a known chemical mutagen (trenimon, bayer), and three ergot derivatives (ergotamine tartrate, dihydroergotoxine mesylate, and methysergide hydrogen maleate) were tested in mice and chinese hamsters for mutagenic effects by means of the micronucleus test and the conventional chromosome method. in contrast to trenimon, which proved to be a powerful mutagen in these test systems, neither of the ergot derivatives showed an effect. it is concluded that these compounds, at subtoxic or therapeutic dose ...1976800380
absence of ultrafast processes of repair of single-strand breaks in mammalian dna.town, smith and kaplan (1972) reported that the yield of dna single-strand breaks (ssb) in e. coli is largely independent of the presence of molecular oxygen during irradiation. they suggested that the oxygen enhancement ratio (o.e.r.) normally observed is due to the presence of an ultrafast repair mechanism acting (in bacterial cells) mainly on anoxically-produced breaks. to determine whether similar mechanisms exist in mammalian cells, we carried out comparable experiments on two cell-lines, o ...1975804459
identification of hamster thymus-derived lymphocytes employing rabbit anti-hamster brain serum.rabbit anti-hamster brain sera prepared from the brains of syrian and chinese hamsters were evaluated for their potential to identify thymus-derived lymphocytes present in these animals. the unabsorbed antisera were cytotoxic in vitro for both homologous and heterologous thymocytes and splenocytes. following absorption with hamster liver and erythrocytes, the antisera remained toxic for thymocytes, but were less toxic for splenocytes. comparative testing of both the rabbit anti-syrian and anti-c ...1975807688
uptake of labelled-n-nitrosomethylurea in the pancreatic islets.labelled n-nitrosomethylurea was injected intravenously into mice (c57/bi strain) and chinese hamsters. in whole-body autoradiograms the isotope was found to accumulate heavily in the islet tissue of the chinese hamsters but not in that of the mice. the selective uptake in the islet of chinese hamsters was most pronounced after one hour. a dose of 50 mg/kg body weight of non-labelled n-nitrosomethylurea caused hyperglycemia in the chinese hamsters while no hyperglycemia occurred in the mice at a ...1975809906
distribution of 2,2(1),4,4(1),5,5(1)-hexachlorobiphenyl in mice and chinese hamsters: dose dependent accumulation in the mouse bronchial mucosa.the distribution of 2,2(1),4,4(1),5,5(1)-hexachlorobiphenyl-14c was studied in mice and chinese hamsters using whole body autoradiography and liquid scintillation counting. the mice exhibited a strong and persistent accumulation of radioactivity in the bronchial mucosa, and this accumulation was not fully developed until about 24 hours after an intravenous injection. the labelled substance passed to the fetuses of pregnant mice and was also concentrated in the fetal bronchi. mice pretreated with ...1975812457
alpha-galactosidase in man-chinese hamster somatic cell hybrids. 1975812566
aging changes in intervertebral discs and spondylosis in chinese hamsters.vertebrae and intervertebral discs of chinese hamsters, a species of rodents that develop spontaneous diabetes, were investigated for age-linked changes and for the occurrence of spondylosis. aging changes in the intervertebral discs were similar in diabetic and nondiabetic animals. the incidence of spondylosis was significantly increased and its onset was accelerated in the diabetic animals. the mechanisms operative in the pathogenesis of the lesions and their relation to the human disease are ...1976819318
evaluation and re-evaluation of genetic radiation hazards in man. ii. the arm number hypothesis and the induction of reciprocal translocations in man.the arm number hypothesis proposed by brewen and collagues in 1973 has been examined in the light of information thus far available from mammalian studies. in experiments with peripheral blood lymphocytes (radiation in vitro), a linear relationship between dicentric yield and the effective chromosome arm number of the species was obtained in the mouse, chinese hamster, goat, sheep, pig, wallaby and man. however, the data are not consistent with such a relationship in several primate species (ma ...1976819823
chinese hamster purine-nucleoside phosphorylase: purification, structural, and catalytic properties.purine-nucleoside phosphorylase (ec 2.4.2.1; purine-nucleosideorthophosphate ribosyltransferase) was purified to apparent homogeneity from chinese hamster liver and kidneys and from v79 tissue culture cells. the enzymes from both sources appear to have identical structural and catalytic properties. a simple rapid radioisotope assay capable of detecting 0.1 nmol of product for both directions of the purine-nucleoside phosphorylase reaction is described using bio-rad cu2+ chelex in pasteur pipet c ...1976825137
biochemical evidence of variability in the dna repeat length in the chromatin of higher eukaryotes.biochemical evidence is presented which confirms that the dna repeat length in micrococcal nuclease (spleen endonuclease, nucleate 3'-oligonucleotidohydrolase, ec 3-1-4-7) digests of chinese hamster ovary chromatin is shorter than that of rat liver chromatin [j.l. compton, r. hancock, p. oudet, and p. chambon (1976) eur. j. biochem., in press]. a survey of available cells has shown that the dna repeat length of the chromatin of higher eukaryotes varies widely. a value of 196 base pairs was found ...1976826906
confirmation of the assignment of the locus determining ada to chromosome 20 in man: data on possible synteny of ada and itp in human-chinese hamster somatic cell hybrids. 1976828861
intrachromosomal gene mapping in man: assignment of nucleoside phosphorylase to region 14cen leads to 14q21 by interspecific hybridization of cells with a t(x;14) (p22;q21) translocation.the structural gene for purine-nucleoside phosphorylase (np) has been assigned to a subregion of chromosome 14 by somatic cell hybridization of male and female cells containing the balanced translocation t(x;14) (p22;q21). peripheral lymphocytes were fused to a pseudodiploid hprt-deficient established chinese hamster cell line. 23 primary hybrid clones (10 derived from male and 13 from female cells) were isolated and maintained in hat selective medium. parallel subcultures from generations 16, 2 ...1976829289
interpretative differences in cytogenetic analyses: preliminary results of a collaborative study.in an effort to establish some of the parameters which influence differences in interpretation of chromosome aberrations, we initiated a collaborative study with 26 different laboratories located in the u.s., canada and europe. they include government, private industry, and academic institutions. three species were selected for study which vary in chromosome number and complexity of the karyotype. these were the chinese hamster, human, and african green monkey. each metaphase was preselected and ...1976829598
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
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
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
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
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
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
protease activation of g1 nuclei isolated from chinese hamster fibroblasts. 1977836402
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 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
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
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
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
hyperthermic effects on dna repair mechanisms.studies have been carried out using neutral and alkaline sucrose density gradients to investigate the effect of 41 degree-43 degree c on the ability of chinese hamster ovary cells to repair single (ssb) and double stranded dna breaks (dsb) caused by exposure to ionizing radiation. the authors found that when hyperthermia exists prior to irradiation significant inhibition occurs. the data support the conclusion that unrepaired dna damage may be lethal to the cell. though no increase in radiation- ...1977847220
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
excision of 7-bromomethylbenz[a]anthracene--dna adducts in replicating mammalian cells.the excision of 7-bromomethylbenz[a]anthracene--dna adducts was studied in two cell lines (hela s-3 and chinese hamster v-79379a). in both cell lines, carcinogen-modified adenine residues were excised more readily than the modified guanine residues and the percentage of the total products excised decreased after treatment with higher concentrations of carcinogen. at the highest concentrations used in the chinese hamster cells, neither dna synthesis nor excision was detected. the lowest concentra ...1977849427
the synthesis of polyadenylated rna and other rna species in synchronised chk cells.chinese hamster kidney cells have been synchronised by the double thymidine block technique. the rate of incorporation of [5-3h]uridine into the polyadenylated rna fraction has been analysed throughout two complete cell cycles and compared with the rate of incorporation into other rna species and the utp pool. in contrast with other reports, we have found that synthesis of 18 s rrna continues steadily throughout the cell cycle, as does synthesis of 5 s rna and trna. in the case of the polyadenyl ...1977851534
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
continued initiation of dna synthesis in arginine-deprived chinese hamster ovary cells.when exponentially growing cho cells were deprived of arginine (arg), cell multiplication ceased after 12 h, but initiation of dna synthesis continued: after 48 h of starvation with continuous [3h]thymidine exposure, 85% of the population had incorporated label, as detected autoradiographically. consideration of the distribution of exponential cells in the various cell cycle phases leads to a calculation that most cells in g1 at the time that arg was removed, as well as those in s, engaged in so ...1977853059
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
study of trans-cyclopropylbis (diketopiperazine) and chelating agents related to icrf 159. cytotoxicity, mutagenicity, and effects on scheduled and unscheduled dna synthesis.the cytotoxicity, mutagenicity, and dna damaging potential of trans-cyclopropylbis (diketopiperazine) (3) and chelating agents related to icrf 159 (1) were examined as a function of concentration and duration of exposure in the chinese hamster cell line v79a. at a concentration of 10(-3) m, 1 and the trans-cyclopropanediamine tetraacid 8 and ester 7 proved to be cytotoxic and mutagenic. the trans-cyclopropyl analogue 3 of icrf 159 and acyclic tetraacid 6 were less cytotoxic at all concentrations ...1977857019
culture of pre-implantation chinese hamster (cricetulus griseus) embryos in vitro.pre-implantation embryos from chinese hamsters (cricetulus griseus) were cultivated under completely defined conditions. the embryos were placed in drops of chemically defined medium under liquid paraffin and cultured in an atmosphere of 10% co2 in air. by this method, development will proceed in vitro from the two-cell stage up to the blastula within 72 h. it is possible to stop the cultivation at different stages of development, to fix the embryos and analyse the chromosomes. the method descri ...1977857153
synaptonemal complex karyotyping in spermatocytes of the chinese hamster (cricetulus griseus). i. morphology of the autosomal complement in spread preparations.using the counce-meyer spreading technique, in over 70 spermatocytes it was possible consistently to obtain whole, flattened nuclei containing complete sets of pachytene scs. the scs are visible in both the phase and electron microscopes. each sc is morphologically intact, preferentially stained, and attached to the nuclear envelope by a dense, terminal plaque. it is thus possible to trace each sc for its entire length. also, a structure representing the kinetochore is clearly visible in each au ...1977858262
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
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