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mechanism of growth inhibition by methotrexate.the effect of methotrexate on the growth of chinese hamster cells was examined under a variety of conditions. the experiments suggest that the important biological effects of methotrexate are the result of direct inhibition of thymidylate synthetase and one or both of the folate-dependent enzymes involved in a purine biosynthesis. in addition, analysis of the distribution of intracellular folate derivatives following methotrexate treatment gives no indication of accumulation of dihydrofolate, an ...19751167807
cycloheximide resistance in chinese hamster cells. i. spontaneous mutagenesis.resistance to cycloheximide (chm) was studied in cultured chinese hamster cells. concentrations of chm above 5-10-7 m were toxic for the cells. at concentrations above 9-10-7 m no colonies were recovered in selective medium. 15 resistant clones of independent origin were isolated in selective medium containing 7-10-7 m chm. resistance was stable when the cells were cultured under non-selective conditions. the spontaneous mutation rate was determined by the fluctuation test. mutations to chm resi ...19751117878
studies on recovery from chemically induced damage in mammalian cells.the survival of plateau-phase or nondividing chinese hamster ovary cells (in vitro) is reduced to a greater extent by treatments with nitrosourea compounds than are cells treated in the exponential phase of growth. the greatest decrease in the survival fraction occurred following treatments with 1-trans-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea where approximately 128 times more cells were killed in plateau phase than in the dividing state (at the 10 mug/ml-for-1-hr dose). only 5 time ...197547265
length distributions of single-stranded dna in chinese hamster ovary cells. 1975239245
[the effect of 0-methylhydroxylamine on the chromosomes of chinese hamster cells].0-methylhydroxylamine increases the frequency of all kinds of aberrations in chinese hamster cells, except chromatid exchange. the percentage of aberrant metaphases and the average number of breakages per cell increases by 5,5-6 times as compared with the control. omha proves to be very effective inducer of chromosome aberrations. since omha induces, except gene mutations, also chromosome aberrations, there are reasons to suppose that its effect is connected not only with transitions, but also w ...19751241684
[development of 0-methylhydroxylamine induced mutations causing resistance to 8-azaguanine in chinese hamster cells].the dependence of the yield of mutations of the resistance to 8-azaguanine induced with 0-methylhydroxylamine on the number of cell generations that have passed by the time of the creation of selective conditions and the existence of a phenotypic lag period is established. the highest rate of mutations is found after 8-azaguanine treatment in two generations. as the number of generations increased, the number of detectable mutations decreased. a dependence is observed between the induced mutatio ...19751241683
the dna polymerases of chinese hamster cells. subcellular distribution and properties of two dna polymerases. 19751168446
the effect of potassium on the cell membrane potential and the passage of synchronized cells through the cell cycle.the cell membrane potential of cultured chinese hamster cells is known to increase at the start of the s phase. the putative role of the cell membrane potential as a regulator of cell proliferation was examined by following the cell cycle traverse of synchronized chinese hamster cells in the presence or absence of high exogenous levels of potassium. an increase in external potassium levels results in a depressed membrane potential and a reduced rate of cell proliferation. a potassium concentrati ...19751168203
effect of leucine on the temperature sensitive phenotype of a mammalian leucyl-trna synthetase mutant.the concentration of leucine in the growth medium has been found to influence the expression of the temperature sensitive phenotype of a mutant of chinese hamster ovary cells with an altered leucyl-trna synthetase. plating efficiency and growth studies showed that increasing the leucine concentration allows cells to survive at normally non-permissive high temperatures and conversely decreasing the leucine concentration enhances the adverse effectsof high temperature. a similar but smaller effect ...19751168198
purine mutants of mammalian cell lines. ii. identification of a phosphoribosylpyrophosphate amidotransferase-deficient mutant of chinese hamster lung cells.a class of purine auxotrophs blocked early in the purine biosynthetic pathway was examined. the inability of these mutants to accumulate formylglycinamide ribotide (fgar) in the presence of azaserine suggested that one or more of the first three enzymes of the pathway were either missing or defective. by direct enzyme assay, phosphoribosylpyrophosphate (prpp) amidotransferase (e.c. 2.4.2.14) was found to be absent in extracts of mutant cells. thus these cells were unable to convert prpp to phosp ...19751147888
[simultaneous effect of 5-bromodeoxyuridine and cysteamine on x-irradiated diploid cells of chinese hamster, cricetulus griseus, in vitro].cells of the chinese hamster line b 14 faf 28 were treated with budr and irradiated with x-rays under the presence of cysteamine. the dose-dependent inactivation rates could be determined rather precisely by marking single cells. daily cell counts in the growing colonies made it possible to establish individual colony growth curves. the results of both analyses show for untreated and treated cells a nearly equal factor with respect to the protecting effect of cysteamine. also in the "macrocoloni ...19751135897
the dna polymerases of chinese hamster cells. the products specified by salmon sperm dna template. 19751124932
conditionally lethal mutations in chinese hamster cells. characterization of a cell line with a possible defect in the krebs cycle.a variant chinese hamster cell line has been isolated from a mutagenized population that has a markedly reduced ability to oxidize a variety of substrates via the krebs cycle. the production of 14co2 from 14c-labeled compounds was measured using pyruvate, acetate, beta-hydroxybutyrate, palmitate and glutamate, and in all cases it was neglibible in the mutant. in contrast to this, significant amounts of 14co2 were produced from 14c-aspartate and 14c-succinate which suggest that some reactions of ...19751123408
radiosensitization of cultured mammalian cells by 5-iodouridine.radiosensitization of cultured mammalian cells was studied with halogenated pyrimidines, such as 5-iodouridine or 6-chloropurine, which have been shown to promote bacterial cell lethality when combined with gamma-irradiation. when chinese hamster cells were exposed to gamma-rays to acidic ph values and the number of colonies was scored after 6 to 11 days of incubation, many more cells were inactivated in the presence of the drug than in its absence. this may be due to radiation-induced cytotoxic ...1975236986
[dependence of heterochromatin differential staining on the time of its reduplication and the degree of condensation].a comparison of the chromosomes banding pattern after g-and c-staining with the time of dna reduplication and the degree of chromosome condensation, was carried out using chinese hamster metaphase chromosomes. chromosome condensation was studied under 5-bromodeoxyuridine and 5-bromodeoxycytidine treatment. all the chromosomal segments stained with c-technique are also stainable with g-technique, while only some g-positive segments are capable to be c-bands. c-bands are heterochromatic segments c ...197549115
possible role of adenosine cyclic 3':5'-monophosphate phosphodiesterase in the morphological transformation of chinese hamster ovary cells mediated by n6,o2-dibutyryl adenosine cyclic 3':5"-monophosphate.we have demonstrated that in chinese hamster ovary (cho) cells, n6,o2'-dibutyryl adenosine cyclic 3':5'-monophosphate (dibutyryl cyclic amp) has a remarkable morphogenetic effect in converting cells of a compact, epithelial-like morphology into a spindle-shaped, fibroblast-like form. homogenates of cho cells were found to contain two adenosine cyclic 3':5'-monophosphate (cyclic amp) phosphodiesterase (ec 3.1.4.c) activities, which differ in apparent km with respect to their substrate, cyclic amp ...1975164438
comparative effects of three nitrosourea derivatives on mammalian cell cycle progression.three nitrosourea analogs, 1,3-bis(2-chloroethyl)-1-nitrosourea, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, and 1-trans-(2-chloroethyl)-3-cyclohexyl-1-(4-methylcyclohexyl)-1-nitrosourea, were examined for effects on survival and cell cycle traverse capacity in exponentially growing (cycling) populations of line cho chinese hamster cells and in cultures arrested in g1 by isoleucine deprivation during treatment with drugs, then returned to the cycling mode by restoration of isoleucine (noncycli ...19751167349
isolation of hydroxyurea-resistant cho cells with altered levels of ribonucleotide reductase.a chinese hamster ovary cell line selected for resistance to hydroxyurea was serially cultivated in the absence of a selective agent, and cells with decreased resistance to the cytotoxic effects of hydroxyurea gradually accumulated in the population. three stable subclones with differing drug sensitivities were isolated from this mixed population and were found to contain intracellular levels of drug-sensitive ribonucleotide reductase which correlated with the degree of cellular resistance to hy ...1975432759
identification of interspecific translocation chromosomes in human-chinese hamster hybrid cells.chromosome material of human and chinese hamster origin can be stained differentially in human-chinese hamster translocation chromosomes by use of the giemsa-11 staining technique.197551825
sister chromatid exchange in human chromosomes from normal individuals and patients with ataxia telangiectasia.a new fluorescence plus giemsa staining technique now makes the detection of sister-chromatid exchange (sce) a relatively easy matter in cells containing 5-brdu-substituted dna. the technique has been applied to human cells to examine the distribution of sce between different people and within different chromosomes. the results show: (1) that there were no large differences in the incidence of sce between blood leukocyte chromosomes from male and female adults and newborn, and that similar frequ ...197552431
visualization of nucleolar organizer regions im mammalian chromosomes using silver staining.a simple ammoniacal silver staining procedure, designated ag-as, differentially stains the chromosomal locations of ribosomal dna in certain mammalian species. this was critically demonstrated by ag-as staining of the nucleolus organizer regions in karyotypes of the same species and cell lines used for locating the ribosomal cistrons by dna/rna in situ hybridization. with ag-as, silver stained nors (ag-nors) are visualized as black spherical bodies on yellow-brown chromosome arms. ag-nors were v ...197553131
enterotoxigenic escherichia coli and idiopathic diarrhoea in bangladesh.faecal escherichia coli from bangalee patients with idiopathic diarrhoea were tested in the chinese hamster ovary cell (c.h.o.) assay to detect production of thermolabile enterotoxin (l.t.). c.h.o-positive e. coli produce both l.t. and a thermostable toxin (s.t.). c.h.o.-positive strains were found in 19.2% of all cases and in 70% of the most severely ill patients with non-vibrio cholera. e. coli which produce s.t. alone were identified in a third of the c.h.o.-negative cases. enterotoxigenic e. ...197553601
expression of differentiated functions in hepatoma cell hybrids: ix extinction and reexpression of liver-specific enzymes in rat hepatoma-chinese hamster fibroblast hybrids.most of the hybrid clones derived from a cross of chinese hamster fibroblasts (don) with rat hepatoma cells (faza 967) showed preferential loss of rat chromosomes. two of the hybrid clones retained the rat chromosomes, and both showed extinction of 4 liver-specific enzymes: aldolase b, liver alcohol dehydrogenase, and the inducible enzymes tyrosine aminotransferase and alanine aminotransferase. subcloning of 1 of these hybrids, which contained 2 sets of hepatoma chromosomes and 1 set of hamster ...197517164
diabetogenic effects of n-nitrosomethylurea in the chinese hamster.to evaluate the role of the glucose residue of the diabetogenic substance streptozotocin, the effect of its aglucone derivate n-nitrosomethylurea was tested in chinese hamsters. at a dose of 50 mg/kg body weight of n-nitrosomethylurea a triphasic blood glucose curve was recorded with an initial hyperglycaemic peak after 3 hours followed by a decrease at 6 hours. after 24 hours and during the following days the values were moderately elevated. there was a high mortality in the diabetic animals, a ...1975125026
rate and time of dna synthesis of individual chinese hamster cells.the duration of dna synthesis of a diploid cell line of chinese hamster fibroblasts was determined in a comparative study by the flm technique, and also by a new technique for measuring the rate of dna synthesis of individual cells. these methods produced comparable results when applied during exponential growth of the cells. the rate of dna synthesis was measured by means of quantitative autoradiography following a short-term incubation of the cells with 5 x 10(-6) m fudr and 10(-5) m 14c-tdr. ...1975126804
simian virus 40 functions required for the establishment and maintenance of malignant transformation.members of the five classes of temperature-sensitive simian virus 40 mutants were tested for their ability to transform chinese hamster lung cells. two criteria for transformation were used: the ability to form clones in medium with low serum concentrations and the ability to overgrow a monolayer. only a mutants failed to transform at the restrictive temperature when subconfluent chinese hamster lung monolayers were used. however, both a and d mutants failed to transform at the restrictive tempe ...1975163374
detection by means of cell fusion of macromolecular synthesis involved in the reconstruction of the nuclear envelope in mitosis.using the cultured chinese hamster cell line don, g1 or s or a mixture of late-s/g2 cells were prepared by release from metaphase arrest. metaphase (m) cells were also obtained by mitotic arrest of log-phase cultures with colcemid and held in metaphase; such m cells remained untreated with any other compound and were termed standard m cells. when interphase (i) cells were fused at ph 8.0 and 37 degrees c with standard cells in the presence of colcemid by means of uv-inactivated sendai virus, bin ...1975163831
cellular adsorption function of the sialoglycoprotein of vesicular stomatitis virus and its neuraminic acid.exposure of vesicular stomatitis (vs) virions to neuraminidase resulted in loss of their ability to agglutinate goose erythrocytes and to attach to l cells concomitant with hydrolysis of sialic acid. these viral adsorptive functions were also destroyed by tryspsinization. sialyl transferase resialylation in vitro of neuraminidase-treated vs virions restored their hamagglutinating and adsorptive functions almost to original levels. erythrocyte and l cell receptors for attachment of vs virions wer ...1975163924
hudrolysis of butyryl derivatives of adenosine cyclic 3':5'-monophosphate by chinese hamster ovary cell extracts and characterization fo the products. 1975164439
mutant hamster cells exhibiting a pleiotropic effect on carbohydrate metabolism.sixty-seven galactose negative (gal minus) clones were established from survivors after treatment of chinese hamster lung (v79) cells with 5-bromodeoxyuridine and black light. the mutational origin of these clonal isolates was inferred on the basis of the previously demonstrated mutagenic action of the combined treatment, persistence of the gal minus phenotype in cell progeny in the absence of selection, conditional lethality of three isolates, interallelic complementation, and assignment of a h ...1975164654
changes in lactate dehydrogenase enzyme pattern in chinese hamster cells infected and transformed with simian virus 40.the lactate dehydrogenase (ldh) isozyme patterns of consecutive passages of chinese hamster embryo cultures were monitored. at early passages the population displayed two ldh bands, m4 and m3h; however, at higher passages the cultures exhibited m2h2, m2h, and m4. when primary cultures of chinese hamster embryo cells were infected with simian virus 40 (sv40), no change in the ldh pattern was observed; however, the total activity of ldh increased. twenty-three of 25 transformed colonies isolated f ...1975167939
the effects of several croton oil constituents on two types of dna repair and cyclic nucleotide levels in mammalian cells in vitro.the purpose of the present study was to determine the effects of two potent tumor-promoting agents on two dna repair mechanisms and cyclic nucleotide levels in mammalian cells. human amnion (av3) cells were treated with low dose levels of either uv of n-acetoxy-acetylaminofluorene. subsequently, dna excision repair as measured by unscheduled dna synthesis was followed in the absence or presence of non-toxic levels of either 12-o-tetradecanoylphorbol-13-acetate (tpa), phorbol-12,13-dibenzoate (pd ...1975168978
site of synthesis of membrane and nonmembrane proteins of vesicular stomatitis virus.upon infection of chinese hamster ovary cells (cho), vesicular stomatitis (vsv) virus synthesizes two membrane proteins (the vsv glycoprotein and the vsv matrix or membrane (m) protein) and three nonmembrane proteins (the vsv nucleocapsid, the viral transcriptase, and an ns protein). we have used the vsv-infected cell as a model system for the study of the site of synthesis of these membrane and nonmembrane proteins. we have isolated vsv mrna from free polyribosomes, membrane-bound polyribosomes ...1975169263
a rapid electrophoretic technique for human and chinese hamster galactokinase. 1975170194
induction of gene mutations and chromosomal aberrations by simian virus 40 in cultured mammalian cells.induction of gene mutations by sv40 was studied in aneuploid human and chinese hamster cells. in chinese hamster cells sv40-induced chromosome aberrations were also studied. sv40 penetrated into the cells of both lines and induced synthesis of the t antigen. the efficiency of infection in chinese hamster cells was tested additionally by their ability to form colonies in medium lacking the serum growth factor. the maximal number of cells with serum growth factor independence was observed on the f ...1975172787
thermolabile t (tumor) antigen from cells transformed by a temperature-sensitive mutant of simian virus 40.partially purified tumor (t) antigen from a strain of chinese hamster lung cells transformed by wild-type simian virus 40 (sv 40) and either of two temperature-sensitive sv 40 mutants has been studied as a dna binding protein. the dna binding activity present in the t-antigen-containing fractions is inhibited by purified hamster anti-t igg but not by equivalent amounts of nonimmune hamster igg. t from either wild-type- or tsc219-transformed cells is relatively stable during heating at 44 degrees ...1975172906
growth of enveloped rna viruses in a line of chinese hamster ovary cells with deficient n-acetylglucosaminyltransferase activity.sindbis and vesicular stomatitis viruses were grown in a line (termed 15b) of chinese hamster ovary (cho) cells that is deficient in a specific udp-n-acetyl-glucosamine:glycoprotein n-acetylglucosaminyltransferase. both viruses replicated normally in the cell line, but the glycoproteins of the released virus migrated faster on sodium didecyl sulfate-polyacrylamide gels than did glycoproteins of virus grown in parent cho cells. digestion of the viral glycoproteins with pronase followed by gel fil ...1975173886
simian virus 40-chinese hamster kidney cell interaction. i. relationship of chromosome changes to transformation.after approximately 20 in vitro passages, chinese hamster kidney (chk) cell cultures transformed upon exposure to different strains of sv 40 can show a diploid modal chromosome number of 22 with chromosome counts exclusively or essentially in the diploid range (20-25). in primary culture and at the 5th-7th subculture, tumors produced in nude mice by such cells can display a diploid modal value of 22 chromosomes. numerical chromosome variations and karyotype abnormalities observed in chk cells tr ...1975174521
[stimulation of sv40 virus replication in chinese hamster kidney cells by treatment of the cells with mitomycin c].the production of virions by chinese hamster kidney cells infected with sv 40 dna is increased 10 to 100 fold by mitomycin c treatment. this observation has been confirmed for different cell clones. the optimum concentration of mitomycin c has been determined.1975174828
[mutagenesis under the influence of simian vacuolating virus 40 (sv40). i. induction of chromosome aberrations in chinese hamster cells during the first days following infection].chromosome aberrations were studied in cultured chinese hamster cells on the 1--4th days after infection with simian virus 40. in the first and second mitoses after infection a statistically significant increase of the percentage of aberrant metaphases was observed (up to 22% as compared to 8--10% in intact cells). already after 3 days following treatment the percentage of aberrant metaphases decreased sharply, reaching the control level. the virus induced a significant increase of the frequency ...1975178571
[mutagenesis under the influence of simian virus 40 (sv40). ii. induct?ion of mutations resulting in resistance to purine base analogs in human and chinese hamster cells].induction of gene mutations by sv40 was studied in aneuploid human and chinese hamster cell lines. it is shown that sv40 penetrates into the cells studied and induces the t-antigen synthesis. the efficiency of the infection in chinese hamster cells was tested additionally by the ability of infected cells to form colonies in the medium lacking serum growth factor. the maximal number of colony-forming cells was detected 24 hours after the infection. by culturing cells in factor-free medium a chine ...1975178572
the induction of sv40-transformed chinese hamster and mouse kidney cells by mitomycin c.the induction by mitomycin c (mc) of sv40 production in three lines of semi- or nonpermissive sv40-transformed cells is described. the production of virions by a line of semipermissive, virus-shedding chinese hamster kidney cells is increased 1,000-fold by mc treatment; the proportion of infectious centers and v-antigen-containing cells is increased to a lesser degree, suggesting that both the burst per cell and the number of virus-producing cells are increased. mc treatment induces the producti ...1975178625
[protective effect of thymidine in relation to the cytostatic action of cyclic adenosine-3', 5'-monophosphate in mammalian cell cultures].under the action of lmm of cyclic adenosine-3',5'-monophosphate (camp) the survival and the rate of reproduction of the cells of chinese hamster in the culture decreased in comparison with control to 27 and 42%, respectively. addition of 0.02 mm thymidine together with camp almost completely eliminated the cytostatic action of the latter. thymidine also prevented the cytostatic effect of noncyclic 5'-amr, but failed to influence the death of the cells with the action of dibutyril camp and theoph ...1975179557
[mutagenesis under the influence of simian virus 40 (sv40). ii. induction of mutations for resistance to analogs of purine bases in human and chinese hamster cells].induction of gene mutations by sv40 was studied in aneuploid human and chinese hamster cell lines. it is shown that sv40 penetrates into the cells studied and induces the t-antigen synthesis. the efficiency of the infection in chinese hamster cells was tested additionally by the ability of infected cells to form colonies in the medium lacking serum growth factor. the maximal number of colony-forming cells was detected 24 hours after the infection. by culturing cells in factor-free medium a chine ...1975182615
immunochemical evidence for glutamine-mediated degradation of glutamine synthetase in cultured chinese hamster cells.the specific activity of glutamine synthetase in cultured chinese hamster cells is inversely related to the concentration of glutamine in the surrounding solution. enzyme specific activity increases 8- to 10-fold when glutamine is removed from serum-free f12 growth media. the induction of glutamine synthetase activity occurs only after glutamine removal and not after the removal of other amino acids (methionine, leucine, or isoleucine). the analysis of the glutamine-mediated decrease in glutamin ...1975234454
carcinogenesis in tissue culture 25: reduced tumorigenicity of alkaline phosphatase-constitutive variants from chinese hamster ovary cells.several subclones with high alkaline phosphatase (alp) activity were isolated from alp-negative chinese hamster ovary cells (cho-k1). when inoculated into cheek pouch membranes of syrian golden hamsters treated with anti-hamster thymocyte serum (ats), alp-negative cho-k1 cells produced progressively growing tumors, whereas the cells of alp-positive subclones did not, although small nodules were formed temporarily. the animals injected cho-k1 cells died of tumor by 35 days after grafting, and met ...19751083437
sub-unit structure of soluble and mitochondrial malic enzyme: demonstration of human mitochondrial enzyme in human-mouse hybrids.1. malic enzyme has been examined by starch-gel electrophoresis in human cultured fibroblasts and in 60 brain samples. the polymorphism of mem has been confirmed and the electrophoretic pattern suggests that this enzyme, like mes, is a tetramer. 2. the appearance of the soluble and mitochondrial malic enzymes in mouse and chinese hamster is described, and the identity of the enzymes in man, mouse and hamster has been established from a study of interspecific somatic cell hybrids. in man and in h ...19751088824
mutagenicity of the food additive af-2, a nitrofuran, in escherichia coli and chinese hamster cells in culture. 19751093019
requirement for cell dispersion prior to selection of induced azaguanine-resistant colonies of chinese hamster cells.with v79 chinese hamster cell cultures treated with a mutagen, the maximum frequency of colonies resistant to 8-azaguanine (azg) was attained when the cells were dispersed after a suitable expression time before adding the selection medium. v79-4 cells were exposed to 500 mum mms, 7 mum afaa, or 10 mum mnng and allowed to multiply before being reseeded at 4 times 10-4 cells/60 mm dish and selected with 10 mu-g/ml azg. maximum frequencies of 4 times 10-5, 4 times 10-4, and 2.4 times 10-3 were obt ...19751093934
studies of the mechanisms of radiosensitization of bacterial and mammalian cells by diamide.diamide sensitizes bacterial and mammalian cells to radiation by at least two mechanisms. sensitization of v79-gl1 chinese hamster cells is due mainly to a reduction of a reduction of the survival-curve shoulder, is observed both in oxygen and in hypoxia,and is additive to the sensitization of hypoxic cells by some nitroimidazoles. in contrast, sensitization of the radioresistant organism, micrococcus sodonensis, which has apronounced shoulder, is entirely dose-modifying. in a rapid-mix study us ...19751093986
a technic for the collection of peritoneal cells from laboratory animals.a simple method was devised for the collection of peritoneal cells from rats, chinese hamsters, and mice using a special glass pipette. cell collection was performed by lavage on the intact unanesthetized animal within 30-60 sec, and it yielded 5-20 million cells per rat and 0.3-2.5 million cells per mouse or chinese hamster. the procedure can be repeated on different occasions in the same animal without apparent adverse effects.19751094186
the mutagenicity of saccharin.seventeen different reports are available dealing with the mutagenic effects of saccharin. many of these are short abstracts, carrying incomplete information. mainly tested as its sodium salt, saccharin has been found to be weakly mutagenic in salmonella at very high doses, in drosophila at moderate doses, and in mice at moderate to high doses. the compound is a weak chromosome breaker in onion root tips and in chinese hamster cells. for most of these, and for other test systems as well, a numbe ...19751095924
mutagenic and cytotoxic activity of benzol[a]pyrene 4,5-, 7,8-, and 9,10-oxides and the six corresponding phenols.the benzo[a]pyrene 4,5-, 7,8-, and 9,10-oxides and the six corresponding phenols (4-, 5-, 7-, 8-, 9-, and 10-hydroxybenzo[a]pyrene) have been tested for mutagenic and cytotoxic activity in bacteria and in a mammalian cell culture system. benzo[a]pyrene 4,5-oxide (k-region) was highly mutagenic in two histidine-dependent strains (ta1537 and ta1538) of salmonella typhimurium which detect frameshift mutagens. in contrast, benzo[a]pyrene 7,8- and 9,10-oxides were less than 1% as mutagenic as the 4,5 ...19751103140
excision-repair of gamma-ray-damaged thymine in bacterial and and mammalian systems.the selective excision of products of the 5,6-dihydroxy-dihydrothymine type (t') from gamma-irradiated or oso4-oxidized dna or synthetic poly[d(a-t)] was observed with crude extracts of escherichia coli and isolated nuclei from human carcinoma hela s-3 and chinese hamster ovary cells. the results with e. coli extracts allow the following conclusion: (1) the uvra-gene product is not required for t' excision. (2) radiation-induced strand breakage is not required for product excision. (3) experimen ...19751103854
distribution of 18+28s ribosomal genes in mammalian genomes.in situ hybridization with 3h 18s and 28s ribosomal rna from xenopus laevis has been used to study the distribution of dna sequences coding for these rnas (the nucleolus organizing regions) in the genomes of six mammals. several patterns of distribution have been found: 1) a single major site (rat kangaroo, seba's fruit bat), 2) two major sites (indian muntjac), 3) multiple sites in centromeric heterochromatin (field vole), 4) multiple sites in heterochromatic short arms (peromyscus eremicus), 5 ...19751104290
cell surface structure of rodent sperm heads.replicas of critical point dried rodent sperm were examined by transmission electron microscopy. the surface of rat sperm heads appeared to be coated with regularly spaced 90a lamellar material. the plasma membrane overlying the acrosomal region of guinea pig spermatozoa displayed a regular scalloped array of lamellar structures. in replicas, the surface of chinese hamster spermatozoa appeared coated by an array of small tubles and vesicles in the region overlaying the acrosome. it was possible ...19751110344
responses to arginine of the perfused pancreas of the genetically diabetic chinese hamster.nonketotic, genetically diabetic cinese hamsters show subnormal pancreatic insulin release and impaired suppression of glucagon in response to glucose. to study the pancreatic effects of other agents, dynamic insulin and glucagon release was measured from the in vitro perfused pancreases of normal and diabetic chinese hamsters in response to various combinations of arginine (20mm), glucose (100 or 150 mg. per 100 ml.), and theophylline (10 mm). theophylline alone caused identical insulin and glu ...19751116650
quantitative comparison of techniques used to measure complement-mediated cytotoxicity of nucleated cells.?the cytotoxicity of nucleated cells by specific antibody and complement can be guantitated in vitro by several methods. trypan blue exclusion, 51-cr release, inhibition of uptake of 3-h-thymidine, and inhibition of colony formation are the four assays that we used to guantitatively compare the c-mediated cytotoxicity of chinese hamster lung (chl) cells. chl cells were sensitized with either guinea pig or rabbit anti-chl antisera, and exposed to guinea pig, human, or rabbit c. we found that the ...19751117130
[some patterns of rna synthesis in the proliferation induction process in a stationary culture of chinese hamster cells].an increase in the incorporation of eh-uridine into rna and in the cell membrane permeability for 3h-uridine in stationary culture cells after medium replenishment were found to be parallel. increase in the rna synthesis occurs practically in all cells stimulated to proliferate and is not accompanied by swelling nucleii, as demonstrated by measuring the projected areas of nucle on fixed cells. the rise in rna synthesis as a response to proliferative stimulus is pronounced at every cell density b ...19751135947
relationship between experimental results in mammals and man. i. cytogenetic analysis of bone marrow injury induced by a single dose of cyclophosphamide.the extrapolation of experimental results to man was studied by cytogenetic bone marrow analysis and micronucleus test in mice, rats and chinese hamsters. furthermore, the frequency of chromosomal aberrations was compared with the frequencies of polychromatic erythrocytes containing micronuclei. cyclophosphamide (cy) was given intraperitoneally at the doses of 5, 10, 20, 40 and 80 mg/kg b.w. to icr mice and wistar rats and at the doses of 10, 20, 40, 80, 120 and 160 mg/kg b.w. to chinese hamster ...19751143298
[differential reaction of condensed and diffuse chromatin to polyamines. i. reaction of interphase nuclei chromatin to putrescine].condensation of the interphase nuclei chromatin under putrescine treatment was studied in cultured human fibroblasts 46, xx: 47, xxx: 49, xxxxy, and aneuploid cells of the chinese hamster. the effect was tested separately for diffuse and condensed chromatin. putrescine treatment did not affect the percentage of cell nuclei with x-chromatin bodies in the human cell strains while significantly increasing the percentage of nuclei with coarse chromatin network and chromocenters. in cultured chinese ...19751145759
membrane-mediated drug resistance and phenotypic reversion to normal growth behavior of chinese hamster cells.development of resistance to actinomycin d, daunomycin, or vincristine in chinese hamster cells growing in vitro resulted in reversion to or retention of normal phenotypes in comparison to spontaneously transformed drug-sensitive parent populations. sublines resistant or cross-resistant to actinomycin d showed reduced uptake of antibiotic in proportion to degree of resistance. the cells with acquired resistance were either weakly tumorigenic or nontumorigenic when tested in the cheek pouches of ...19751159844
laboratory studies of a lymphocytic choriomeningitis virus outbreak in man and laboratory animals.investigation of an outbreak of prolonged febrile illness in medical center personnel at the university of rochester school of medicine and dentistry revealed lymphocytic choriomeningitis (lcm) virus to be the causative agent. syrian or golden hamsters (mesocricetus auratus) were found to be the only animals involved in maintaining the virus and were the source of human infections. isolations of lcm virus were made from autopsy specimens of 13 of 46 (28%) golden hamsters. virus isolations were m ...19751163529
membrane effects of cytochalasin b. competitive inhibition of facilitated diffusion processes in rat hepatoma cells and other cell lines and effect on formation of functional transport sites.cytochalasin b competitively inhibits the transport of 2-deoxy-d-glucose and thymidine in a number of different cell lines (novikoff rat hepatoma cells, mouse l, s180 and ki-msv-transformed balb/3t3 cells, and human hela cells). the apparent km values for the transport of these substrates as well as the apparent ki values for the inhibition by cytochalasin b are very similar for the various cell lines, and the effect is readily and completely reversed by removal of the chemical. thymidine trans ...19751165581
heavy-ion irradiation of human and chinese hamster cells in vitro. 19751167420
the interactions of benzo(a)pyrene with cell membranes: uptake into chinese hamster ovary (cho) cells and fluorescence studies with isolated membranes.the interactions of benzo(a)pyrene (b(a)p) with the cell surface membrane were studied by measuring b(a)p uptake into intact mammalian cells and by determining b(a)p fluorescence in the presence of isolated cell surface membranes. it was found that 0.19 mu-g b(a)p were taken up by 10-6 chinese hamster ovary (cho) cells after 30 min exposure to a solution containing 0.59 mu-g/ml. culture conditions were found to markedly alter b(a)p uptake. low cell culture densities resulted in a four-fold incre ...19751170030
metabolism of the polyadenylate sequence of nuclear rna and messenger rna in mammalian cells.the poly(a) sequences at the 3' end of mrna and nuclear rna molecules of mouse sarcoma and chinese hamster cells are subject to an elongation process distinct from de novo synthesis. this process continues in cells treated with a high level of actinomycin d to block transcription. this results in the labeling of the steady-state poly(a) population in the cytoplasm and of unusually long poly(a) segments in the nucleus. in cells incubated with 3h-adenosine in the absence of drug treatment, cytopla ...19751170955
high-speed quantitative karyotyping by flow microfluorometry.we describe a new flow-system technique for high-speed quantitative karyotyping. metaphase chromosomes are isolated from cells, stained with a dna-specific fluorochrome, and individually measured for stain content at rates up to 10(5)/min in a flow microfluorometer. the resulting distribution contains quantitative information about the relative frequency of occurrence and the chromosomal dna content of the measured chromosomes. such analyses of chinese hamster chromosomes are in good agreement ...19751170959
mutagenesis and genetic analysis with chinese hamster auxotrophic cell markers.chinese hamster ovary cells were treated with various physical and chemical mutagens and subject to the bromodeoxyuridine plus visible light procedure for isolation of auxotrophic mutants. more than 200 auxotrophs have been isolated which require exogenous supplement of various nutrilites for growth, such as glycine, adenine, thymidine, inositol, etc. fifty-five of these have been characterized by complementation tests and were shown to constitute 15 different loci. all these auxotrophs are high ...19751171046
differential potentiation by nystatin of the effect of antibiotics on yeast and mammalian cells.the effect of the polyene antibiotic nystatin, used in combination with several other antibiotics, on the membranes of candida albicans sc#8169 (yeast) cells and of chinese hamster ovary and 3t3 (mammalian) cells was investigated. it was concluded from determinations of the viability of the yeast cells and from measurements of deoxyribonucleic acid synthesis by the mammalian cells that nystatin acts synergistically with several antibiotics on yeast cells, but not on cho and 3t3 cells. this selec ...19751171651
localization of human gene loci using spontaneous chromosome rearrangements in human-chinese hamster somatic cell hybrids.analysis of human-chinese hamster somatic cell hybrids with spontaneously derived chromosome structural changes has provided data for the regional and subregional localization of gene loci which have previously been assigned to human chromosomes 2, 12, and x. correlation of the expression of human gene loci with the human chromosome complements present in somatic cell hybrids indicates that the cytoplasmic malate dehydrogenase (mdh1) locus is in the 2p23yields2pter region, and red cell acid phos ...19751172370
in vivo cytogenetic investigations in bone marrow cells of rats, chinese hamsters and mice treated with 6-mercaptopurine.the chromosome-damaging effect of 6-mercaptopurine (6-mp) was investigated in bone marrow cells of rats, chinese hamsters, and mice after single intraperitoneal injections of doses from 3.125 to 250 mg/kg, and after multiple applications of 10, 25, 50, and 125 mg/kg. the optimal time of investigation after single administration in these studies was 48 hrs after treatment for all 3 species. a nearly linear dose-response relationship with a low quadratic component was observed. the "critical dose" ...19751173752
mutation induction in chinese hamster v79 cells by two vinyl chloride metabolites, chloroethylene oxide and 2-chloroacetaldehyde.chloroethylene oxide and 2-chloroacetaldehyde, two possibly carcinogenic metabolities of vinyl chloride in mammals, caused a dose-dependent induction of 8-azaguanine- and ouabain-resistant mutants in chinese hamster v79 cells in vitro. up to one-hundred-fold higher concentrations of 2-chloroethanol or monochloroacetic acid, a urinary vinyl chloride metabolite in rats and man, were inactive.19751176210
biochemical and immunological studies of purified mouse beta-galactosidase.beta-galactosidase (ec 3.2.1.23) has been purified from the livers of c57bl/6j mice. the enzyme migrated as a single band of protein on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. the molecular weight of the denatured and reduced enzyme was 63,000. the native form of beta-galactosidase appeared to be a tetramer of 240,000 at ph 5.0, which was reversibly dissociated at alkaline ph to a dimer with apparent molecular weight of 113,000. multiple charge isomers of be ...19751176446
cholera toxin effects on cell growth accompanied by selective alterations in metabolite uptake and modification of cell surface proteins.exposure of chinese hamster ovary cells to cholera toxin at or below mug levels causes a marked morphological changes and increased adhesion and orientation of the cells. such changes are paralleled by alterations in surface proteins as indicated by the cholera toxin-mediated modifications detectable by lactoperoxidase-catalyzed radioiodination of outer proteins. mild tryptic treatment of cells prelabeled with [3h]glucosamine revealed a different kinetics of release of external glycoproteins in ...19751182696
adenine phosphoribosyltransferase and hypoxanthine-guanine phosphoribosyltransferase immunoprecipitation reactions in human-mouse and human-hamster cell hybrids.male new zealand white rabbits were immunized with human adenine phosphoribosyltransferase (aprt) and hypoxanthine-guanine phosphoribosyltransferase (hgprt), which were purified about 2000-fold and 800-fold, respectively, from erythrocytes by deae-cellulose chromatography, ammonium sulfate precipitation and preparative polyacrylamide gel electrophoresis. specific immunoprecipitations of aprt and hgprt were achieved with the antisera that were obtained and by using polyethylene glycol as a substi ...19751184004
mammalian cell transformation and cell-mediated mutagenesis by carcinogenic polycyclic hydrocarbons.the introduction of a polycyclic hydrocarbon such as benzo(alpha)pyrene (bp) into normal golden hamster embryo cell cultures results, in addition to cytotoxicity, in malignant cell transformation. studies on the effect of different doses of bp on the normal cells showed that the frequency of transformed colonies was directly related to the dose of the carcinogen. analysis of this dose-response curve suggests a one-event ("one-hit") response for transformation by this carcinogen. the one-event re ...19751186764
turnover of plasma membrane polypeptides in nonproliferating cultures of chinese hamster ovary cells and human skin fibroblasts. 19751190794
mapping the xga red blood cell antigen in human-chinese hamster cell hybrids. the xg locus is possibly located on the short arm of the x chromosome. 19751192805
alpha-galactosidase in man-chinese hamster somatic cell hybrids. 19751192822
evidence for synteny between the human loci for galactose-1-phosphate uridyl transferase and aconitase in man-chinese hamster somatic cell hybrids. 19751192837
synteny relationship between the human loci for hexosaminidase-a, mannose phosphate isomerase, and pyruvate kinase-3 studied in man-chinese hamster somatic cell hybrids. 19751192838
electrophoretic pattern of hypoxanthine phosphoribosyltransferase produced in chinese hamster cells following incorporation of human chromosomes. 19751192840
cycloheximide resistance in chinese hamster cells. iii. characterization of cell-free protein synthesis by polysomes.two clones were selected for mass cultivation from 18 phenotypically stable chm-resistant cho clones. the polysomes isolated from these two clones were compared with cho wildtype polysomes and rat liver polysomes in a cell-free protein synthesis system for their ability to incorporate amino acids. chm had an inhibitory effect on the protein synthesis activity of cho wildtype and rat liver polysomes, but had no effect on the polysomes obtained from either of the mutant cho clones.19751196299
x-ray-induced inhibition of dna synthesis in chinese hamster ovary, human hela, and mouse l cells. 19751197664
selective depletion of chromosomes in a stable mouse-chinese hamster hybrid cell line using antisera directed against species-specific cell surface antigens.a chromosomally-stable mouse-chinese hamster hybrid cell line was subjected to five rounds of selection with cytotoxic antisera raised in rabbits against either the parental mouse 3t3 cells or the parental chinese hamster wg-1 cells. routine karyological analysis of clones isolated at each stage of serum selection revealed that treatment with either serum resulted in a limited loss of chromosomes (compared to the untreated hybrid cell cultured in parallel) and that the pattern of chromosome loss ...19751202037
preparation of peritoneal cell metaphases of rats, mice and chinese hamsters after mitogenic stimulation with magnesium sulfate and/or aluminum hydroxide.a new cytogenetic system in vivo is presented using peritoneal cells, collected from unanesthetized rats, mice and chinese hamsters, 48 h after an i.p. injection of a mitogen. the test is useful for periodic monitoring of chromosome aberration rates in the investigation of such problems as aging and chronic effects of mutagens and carcinogens. among the 2 mitogens tested, aluminum hydroxyde was more efficient than magnesium sulfate in all 3 species. the rat is considered to be the most suitable ...19751202331
mapping the xga red blood cell antigen in human-chinese hamster cell hybrids. the xg locus is possibly located on the short arm of the x chromosome. 19751203469
evidence for synteny between the human loci for galactose-1-phosphate uridyl transferase and aconitase in man-chinese hamster somatic cell hybrids. 19751203497
synteny relationship between the human loci for hexosaminidase-a, mannose phosphate isomerase, and pyruvate kinase-3 studied in man-chinese hamster somatic cell hybrids. 19751203498
electrophoretic pattern of hypoxanthine phosphoribosyltransferase produced in chinese hamster cells following incorporation of human chromosomes. 19751203500
[characteristics of structural chromosome aberrations induced by type 1 adenovirus in human and chinese hamster cells in vitro].adenovirus multiplies in both studied cultures. in the chinese hamster cells infection is of slowed down, cyclic character. in this case a short subcultivation of cells infected with the virus and the study of the damage distribution in groups of chromosomes are possible. no selectivity was found with respect to the damage of certain group chromosomes.19751221572
[presence of biologically active glutamyl peptide in rabbit bone marrow].the presence of chromatographically pure and biologically active glutamylpeptide in the rabbit bone marrow was shown and methods of its isolation were given. the substances had an unusual circular dichroism contrary to that of the natural proteins. in a concentration of 10(-5) m the isolated peptide decreased the survival of the chinese hamster culture cells to 30%. it was analogous to the peptide isolated formerly from plants by a number of physical and chemical characteristics; the latter poss ...19751225406
[characteristics of somatic cell hybrids (mouse x chinese hamster) with different ratios of parental species chromosome sets. iv. electrophoretic analysis of several enzymes of the dehydrogenase class].electrophoretic mobilities in polyacrylamide gel of five dehydrogenases: nadp-dependent malate dehydrogenase (nadp-mdh), 6-phosphogluconate dehydrogenase (6pgd), alcohol dehydrogenase (adh), glucose-6-phosphate dehydrogenase (g6pd) and glutamate dehydrogenase (gdh) were investigated in a series of mouse x chinese hamster somatic cell hybrids. seven hybrid lines with different ratio of chromosome sets of hamster and mouse: 1:1, 2:1, 3:1 and 1:2 respectively were studied. nadp-mdh and 6pgd of both ...19751232030
diabetogenic effects of n-nitrosomethylurea with special regard to species variations.the effect of n-nitrosomethylurea on the blood-glucose and the pancreatic islet light microscopic picture was studied in the chinese hamsters, golden hamsters, guinea pigs, mice, rats and sand rats. the chinese hamsters were most susceptible. only in this species did a dose of 50 mg/kg body weight cause blood-glucose elevations and pancreatic islet damage. at a dose of 100 mg/kg body weight of n-nitrosomethylurea, blood-glucose elevations were recorded in the golden hamster together with damage ...19751233304
incorporation of isolated chromosomes and induction of hypoxanthine phosphoribosyltransferase in chinese hamster cells.evidence is presented for the uptake of radioactive-labeled isolated chinese hamster chromosomes following incubation with chinese hamster cells. metaphases were found which contained radioactive labeled chromosomes in a very low frequency, and in some of the labeled chromosomes only one chromatid was labeled. incubation of hypoxanthine phosphoribosyltransferas (hprt)-deficient chinese hamster cells with chromosomes isolated from hprt+ chinese hamster or human cells resulted in the appearance of ...19751235904
genetics of somatic cell surface antigens. iii. further analysis of the al marker.the al antigen present on the surface of various human somatic cells, and on those hybrids of human and chinese hamster ovary cells which have retained human chromosome number 11, has been resolved into at least two separate antigenic activities, a1 and a2. specific antisera active against each antigen separately have been prepared. by treatment of the original al+ hybrid with mutagenic agents and selection in particular antisera, stable clones are preparable whose phenotypic behavior correspond ...19751235908
synteny between the pro+ marker and human glutamate oxaloacetate transaminase.chinese hamster ovary cells with a specific auxotrophy for proline were fused with human cells from a variety of sources and the resulting hybrids analyzed for human genetic markers. of 63 hybrid clones examined, 27 possessed both proline and cytoplasmic glutamate oxaloacetate transaminase markers; 36 had neither; and no clones were found possessing one and not the other. these results constitute evidence that the proline and glutamate oxalocetate transaminase markers are syntenic. evidence for ...19751235910
chinese hamster x mouse hybrid cells segregating mouse chromosomes and isozymes.hybrid cells are readily formed by fusing clonal chinese hamster cells to fresh, noncultured, adult mouse spleen cells followed by isolation in selective medium. the vast majority of such hybrids retain chinese hamster chromosomes and isozymes while segregating mouse chromosomes and isozymes. the growth, plating efficiency, ease of karyology, and rapid segregation of mouse markers allows linkage tests in primary clones. analysis of 13 isozymes showed 12 to be asyntenic and on epair (pgd-pgm2) to ...19751235911
gene linkage analysis in the mouse by somatic cell hybridization: assignment of adenine phosphoribosyltransferase to chromosome 8 and alpha-galactosidase to the x chromosome.somatic cell hybridization techniques were applied to gene linkage analysis in the laboratory mouse. cells of an established line of chinese hamster lung fibroblasts were fused with mouse embryo fibroblasts and with mouse peritoneal macrophages obtained from different inbred strains. from 3 hybridization experiments, 123 primary and secondary clones were isolated in hat selective medium and 24 were back-selected in 8-azaguanine. hybrid clones were characterized for the expression of 16 murine is ...19751235912
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