Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| modification of the response to actinomycin d-induced sublethal damage by simultaneous recovery from potentially lethal damage in mammalian cells. | exponentially growing cells and cells that were allowed to enter a plateau or nondividing state of growth by depleting the medium of growth-essential nutrients were used in these studies. nondividing chinese hamster ovary cells in vitro are less sensitive to actinomycin d (amd) than are exponentially growing cells. the cells were tested for their ability to recover from amd-induced potentially lethal damage (pld) or sublethal damage. the proliferating and the nonproliferating cells do not recove ... | 1976 | 1268824 |
| formation of thymidine kinase and deoxycytidylate deaminase in synchronized cultures of chinese hamster cells temperature-sensitive for dna synthesis. | cytosol thymidine kinase (tk) and deoxycytidylate (dcmp) deaminase formation was investigated in synchronized cultures of k12 chinese hamster cells which have a temperature-sensitive lesion affecting the initiation of dna synthesis. enzyme formation was found to be cycloheximide-sensitive and also temperature-dependent. beginning at about six hours after addition of medium with 10% calf serum to serum-depleted k12 cultures, cytosol tk and dcmp deaminase activities increased when the cultures wer ... | 1976 | 1262406 |
| isolation and partial characterization of three methotrexate-resistant phenotypes from chinese hamster ovary cells. | three mechanisms for resistance to methotrexate (mtx) have been identified in chinese hamster ovary (cho) cells selected from resistance to this drug. first-step selections produce cells with either an apparent structural alteration in the enzyme dihydrofolate reductase (class i), or a decreased permeability to the drug (class ii). mutagenesis with ethyl methanesulfonate increases the proportion of mtx-resistant cells 5-10-fold. second-step selections to higher resistance using class i resistant ... | 1976 | 1028172 |
| isolation of mutants lacking branched-chain amino acid transaminase. | variants of the chinese hamster ovary cell have been isolated which can no longer grow when valine, leucine, or isoleucine is replaced in the culture medium by its respective alpha-keto acid: alpha-ketoisovaleric acid, alpha-ketoisocaproic acid, or alpha-keto-beta-methylvaleric acid. these variants lack branched-chain amino acid transaminase activity. evidence is presented indicating these variants to be single gene mutants. genetic evidence is also presented confirming previous biochemical evid ... | 1976 | 1028171 |
| biochemical genetics of chinese hamster cell mutants with deviant purine metabolism. iv. isolation of a mutant which accumulates adenylosuccinic acid and succinylaminoimidazole carboxamide ribotide. | the production, isolation, and characterization of a new complementation group (ade-i) of adenine-requiring mutant of chinese hamster cells (cho-k1) is described. this mutant accumulates two intermediates of purine biosynthesis, both of which contain an aspartate moiety. one of these is shown to be adenylosuccinic acid (amps) by chromatographic analysis, while evidence is presented that strongly suggests the other intermediate is succinylaminoimidazole carboxamide ribotide (saicar). thus, ade-i ... | 1976 | 1028168 |
| biochemical characterization of azetidine carboxylic acid-resistant chinese hamster cells. | we have isolated variants of chinese hamster lung (chl) fibroblasts with decreased sensitivity to the toxic proline analog, l-azetidine-2-carboxylic acid (azca). resistance to azca is a stable characteristic of these cell lines since it is maintained after 40 generations in nonselective medium. two azca-resistant cell lines overproduce and excrete more proline than wild-type cells. furthermore, azca rapidly inhibits the synthesis of proline from glutamic acid in wild-type but not the resistant c ... | 1976 | 954094 |
| the rna polymerase ii of an alpha-amanitin-resistant chinese hamster ovary cell line. | amal, an alpha-amanitin-resistant mutant of the chinese hamster ovary cell line, contains an rna polymerase activity which elutes from deae-sephadex at a salt concentration characteristic of an rna polymerase ii, but which is not sensitive to alpha-amanitin at levels where the polymerase ii of wild-type cells is strongly inhibited. this result suggests that amal owes its amanitin-resistant phenotype to a mutation affecting one of its genes for rna polymerase ii. to test this hypothesis, we purif ... | 1976 | 954093 |
| cytotoxicity, mutations and dna damage produced in chinese hamster cells treated with streptozotocin, its analogs, and n-methyl-n'-nitro-n-nitrosoguanidine. | the activities of streptozotocin (sz), three structural analogs of sz, and n-methyl-n'-nitro-n-nitrosoguanidine (mnng) in producing cytotoxicity, mutations to 8-azaguanine (8-azg) resistance, and dna damage (single-strand breaks) in v79 chinese hamster cells have been examined. these three biological processes appear to be associated. mnng was about 10(3) times more active on a molar basis than sz, and the activities of the analogs fell within these extremes. | 1976 | 130988 |
| induction of stable protein-deoxyribonucleic acid adducts in chinese hamster cell chromatin by ultraviolet light. | ultraviolet (uv)-light-mediated formation of protein-dna adducts in chinese hamster cell chromatin was investigated in an attempt to compare chromatin alterations induced in vitro with those observed in vivo. three independent methods of analysis indicated stable protein-dna associations: (1) a membrane filter assay which retained dna on the filter in the presence of high salt-detergent; (2) a sepharose 4b column assay in which protein eluted cincident with dna; and (3) a cscl density gradient e ... | 1976 | 5110 |
| independent fluctuations of cytidine and adenosine diphosphate reductase activities in cultured chinese hamster fibroblasts. | the activities of cdp and adp reductases were determined throughout the cell cycle of chinese hamster fibroblasts synchronized by partial deprivation of isoleucine. both enzyme activities were increased in s phase as compared to g1 phase. cdp reductase increased about 8-fold while adp reductase increased about 2.5-fold. the ratio of cdp to adp reductase was 0.26 at the g1 and early s phases of the cell cycle; the ratio was increased to 0.83 by late s phase. addition of actinomycin d or cyclohexi ... | 1976 | 1260052 |
| carcinogenic effects of different nitroso-compounds in chinese hamsters. i. dimethylnitrosamine and n-diethylnitrosamine. | three hundred and twenty chinese hamsters (cricetulus griseus) (ch) were treated (s.c.) with 1/5, 1/10 or 1/20 ld50 of dimethylnitrosamine (dmn) or n-diethylnitrosamine (den). these substances, in several respects, showed a different organotropy in this species than in both the syrian golden (sgh) and the european hamster (eh). in ch, den produced up to 100% squamous cell papillomata and occasionally also carcinomata of the cheek pouch, tongue, pharynix, oesophagus and forestomach. with den a hi ... | 1976 | 1268032 |
| quantification of mitochondria during the cell cycle of chinese hamster cells. | 1976 | 1261614 | |
| effects of laser uv-microirradiation (lambda = 2573 a) on proliferation of chinese hamster cells. | 1976 | 1257404 | |
| the effect of combined treatment with a platinum complex and ionizing radiation on chinese hamster ovary cells in vitro. | cis-dichlorobis(cyclopentylamine)platinum ii (dbcp) belongs to the group of platinum complexes which have recently been reported to have anti-tumour activity. its cytotoxic activity in cho cells is not cell-age-dependent, but enhancement of the effect of ionizing radiation is both dose-and cell cycle phase-dependent. in asynchronous cell populations dbcp acts as a dose-modifying factor for ionizing radiation. doses of dbcp reducing survival of cho cells to 26% and 4% applied 1 h before irradiati ... | 1976 | 944586 |
| chromosome analyses in cell cultures of the chinese hamster after application of cadmiumsulphate. | cell cultures of a chinese hamster cell line were treated with cdso4 in concentrations of between 10(-4) and 10(-8) mol/l for different time periods. after a treatment of 16 h the mitotic index was reduced. strong stickiness and pycnosis of chromosomes occurred at the highest concentrations. a treatment period of 3 h with concentrations of 10(-5) and 10(-4) mol/l without additional application of colcemid and hypotonic solution yielded a stathmokinetic effect. the mitotic index increased, mitose ... | 1976 | 934175 |
| sequence of centromere separation of mitotic chromosomes in chinese hamster. | chromosome preparation in late metaphase cells from bone marrow of colcemid treated male chinese hamsters were used to analyse the sequence of separation of sister centromeres. chromatids of chromosomes 2 and 1 are the first ones to separate at centromeres, followed by members of group b, d and c. some acrocentric chromosome is always the last one to separate at the centromere. the data point to a possible correlation between the position of a centromere in the separation sequence in the genome ... | 1976 | 1253649 |
| hydroxyurea does not prevent synchronized g1 chinese hamster cells from entering the dna synthetic period. | 1976 | 1259759 | |
| g2 block in chinese hamster cells induced by x-irradiation, hyperthermia, cycloheximide, or actinomycin-d. | 1976 | 1265214 | |
| x-ray-induced mutants resistant to 8-azaguanine. ii. cell cycle dose response. | synchronous chinese hamster ovary cells were irradiated in g1 or s phase. colony survival in alpha mem medium with dialyzed serum was determined with or without 15 mug/ml 8-azaguanine (ag). an expression period of over three generations (multiplicity of 20) was utilized, with expression times ranging from 58 to 114 h. both g1 and s phase were practically identical in sensitivity to x-ray-induced mutations, with mutant frequency/viable cell/rad ranging from 1 x 10(-7) (75-100 rad) to 8 x 10(-7) ( ... | 1976 | 1264111 |
| x-ray-induced mutants resistant to 8-azaguanine. i. effects of cell density and expression time. | asynchronous chinese hamster ovary cells were irradiated and colony survival in alpha mem medium with dialyzed serum was determined with or without 15 mug/ml 8-azaguanine (ag). data indicated that a reproducible assay for the system was dependent upon controlling cell density at least two days prior to induction as well as throughout the expression period. generally, spontaneous and radiation-induced mutant frequencies decreased when cell densities exceeded a critical density of 3-6 x 10(4) cell ... | 1976 | 1264110 |
| selection and characterization of chinese hamster ovary cells resistant to the cytotoxicity of lectins. | chinese hamster ovary (cho) cells selected in a single step for resistance to the cytotoxicity of the lectin from red kidney beans (pha) behave as authentic somatic cell mutants. the pha-resistant (phar) phenotype is stable in the absence of selection; its frequency in a sensitive-population is increased several-fold by mutagenesis; and it behaves recessively in somatic cell hybrids. the activity of a specific glycosyl transferase which transfers n-acetylglucosamine (glcnac) to terminal alpha-ma ... | 1976 | 1262042 |
| non-histone protein synthesis during g1 phase and its relation to dna replication. | the kinetics of non-histone chromosomal protein (nhcp) synthesis were studied in chinese hamster ovary (cho) plateau phase cells stimulated to proliferate and were compared to nhcp synthesis kinetics in two populations of synchronous g1 traversing cells. in all cases, nhcp synthesis rates increase 3- to 5-fold as cells traversed g1 and attained maximum values one hour before semi-conservative dna replication began. similar to results in synchronous g1 cells, the molecular weight distributions of ... | 1976 | 1254652 |
| inhibition by caffeine of post-replication repair in chinese hamster cells treated with cis platinum (ii) diamminedichloride: the extent of platinum binding to template dna in relation to the size of low molecular weight nascent dna. | treatment of chinese hamster lung v79-379a cells with the anti-tumour agent cis platinum (ii) diamminedichloride, (cis pt(ii)), resulted in an immediate recuction in the rate of dna synthesis. sedimentation of newly synthesised dna through alkaline sucrose gradients revealed it to be approximately the same size as that obtained from untreated cells. in contrast, in the presence of 0.75 mm caffeine, the rate of dna synthesis rapidly returned to control levels, although sedimentation analysis show ... | 1976 | 1253338 |
| increased cell killing by metronidazole and nitrofurazone of hypoxic compared to aerobic mammalian cells. | nitromidazole and nitrofuran derivatives comprise a large family of compounds, some of which have been shown to be hypoxic cell specific radiosensitizers in vivo and in vitro. the effects of metronidazole (2-methyl-5-nitroimidazole-1-ethanol) and nitrofurazone (5-nitro-2-furaldehyde semicarbazone) were studied on cell viability in vitro in the presence of air or nitrogen in the absence of radiation. exponential-phase chinese hamster ovary cells were placed in suspension culture in complete mediu ... | 1976 | 1253180 |
| negative pion irradiation of mammalian cells. 1. survival characteristics of monolayers and spheroids of chinese hamster lung cells. | monolayers and spheroids of chinese hamster cells (v79) were subjected to negative pion irradiation under aerobic conditions. r.b.e. values in the pion peak of 1-8 and 1-5 were obtained for monolayers and spheroids, respectively, whereas the r.b.e. for the plateau was found to be slightly higher than 1. in addition, it was observed that the higher resistance of the v79 spheroid cells than the monolayers to gamma-irradiation is not diminished in the pion peak, suggesting that the underlying pheno ... | 1976 | 1083848 |
| cytological evidence for switches in polarity of chromosomal dna. | from the types of ring chromosomes induced in x-irradiated chinese hamster ovary (cho) cells, we deduce the existence of switches in the polarity of chromosomal dna; if there is a continuous dna double helix along the full length of the chromosome then the polarity switches imply 3'-3' and 5'-5' phosphodiester linkages. the resolution of the method is such that we estimate that there is one polarity switch for every 10(9) normal 3'-5' phosphodiester bonds. | 1976 | 1062800 |
| dna strand breaks, repair, and survival in x-irradiated mammalian cells. | the yields of unrepairable single-and double-strand breaks in the dna of x-irradiated chinese hamster cells were measured by low-speed neutral and alkaline sucrose density gradient sedimentation in order to investigate the relation between these lesions and reproductive death. after maximal single-strand remoining, at all doses, the number of residual single-strand breaks was twice the number of residual double-strand breaks. both double-strand and unrepairable single-strand breaks were proporti ... | 1976 | 1062792 |
| biochemical selection systems for mammalian cells: the essential amino acids. | the essential amino acid requirement of cultured mammalian cells can be satisfied by 19 amino acid derivatives. this finding (a) confirms the results of animal nutritional studies and (b) identifies 19 essential amino acid derivatives and should permit the isolation of a new class of auxotrophic mutants. five naturally occurring auxotrophic markers have been detected in this survey; namely, inability to utilize cystathionine and citrulline in chinese hamster ovary (cho) cells, inability to metab ... | 1976 | 1028167 |
| isolation and characterization of temperature-sensitive mutants of chinese hamster ovary cells after treatment with uv and x-irradiation. | the isolation of ten conditionally lethal temperature-sensitive mutants of the chinese hamster ovary cell (cho-kl, pro-) by the budr-visible light selection procedure described. treatment with radiation at doses known to cause single gene mutation in mammalian cells increases the mutation frequency by a factor of at least 14. these mutants will grow with normal plating efficiency at 34.5 degrees but will not grow at 39.5 degrees. complementation analysis by two independent methods indicates that ... | 1976 | 1028162 |
| carcinogenic effects of different nitroso-compounds in chinese hamsters: n-dibutylnitrosamine and n-nitrosomethylurea. | three hundred and twenty chinese hamsters (cricetulus griseus) (ch) were subcutaneously (s.c.) treated with 1/5, 1/10 or 1/20 the mean lethal dose (ld50) of n-dibutylnitrosamine (dbn) or n-nitrosomethylurea (nmu). in several respects these two substances produced the same organotropy in the ch as in the syrian golden (sgh) and european hamsters (eh). dbn prolonged lung tumours and neoplasms of the injection site. nmu induced tumours of the injection site only. | 1976 | 1016942 |
| isolation and characterisation of chinese hamster cells resistant to 5-fluorodeoxyuridine. | 1976 | 130246 | |
| the cytogenetic effect of an x-ray contrast medium in chinese hamster cell cultures. | chinese hamster cell cultures were treated with different concentrations of joduron, a water-soluble iodized x-ray contrast medium. the cytogenetic effect was analysed for a treatment period of 2 or 16 h. jorudron primarily acts on the mitotic apparatus of the cell. the type of damage ranges from different forms of initial "c-mitosis" to unpolarized stathmokinesis. additionally, structural chromosome damage, mainly of the chromatid type, was observed, especially after a joduron treatment for 2 h ... | 1976 | 1250248 |
| phosphorylation of ribosome-associated proteins during the mammalian cell cycle. unique phosphorylation of a specific protein during mitosis. | chinese hamster ovary cells in monolayer culture were incubated with [32p] phosphate. ribosome-associated proteins, including both structural proteins and those tightly bound to washed, centrifuged ribosomes, were isolated and separated by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels. the electrophoretic pattern showed five major regions or peaks of 32p radioactivity which represented phosphorylated ribosome-associated proteins with molecular weights of 17 500, 23 000, 30 000, 3 ... | 1976 | 1244853 |
| diet-induced hypercholesterolemia in the diabetic and non-diabetic chinese hamster. | 1976 | 1274792 | |
| the response of chinese hamster ovary cells to fast neutron radiotherapy beams. i. relative biological effectiveness and oxygen enhancement ratio. | 1976 | 1246571 | |
| selection of chinese hamster somatic cell mutants after irradiation of budr-labelled cells. | the selection of somatic cell mutants after irradiation of budr-labelled cells is improved with the use of a mercury lamp combined with a plastic sheet which filters the unwanted wave lengths below 303 nm. new somatic cell mutants defective for galactose metabolism or auxotrophe for fetal calf serum were thus isolated. | 1976 | 1107336 |
| mutability of different genetic loci in mammalian cells by metabolically activated carcinogenic polycyclic hydrocarbons. | the relationship between carcinogenesis and mutagenesis in mammalian cells has been determined with 10 polycyclic hydrocarbons with different degrees of carcinogenicity. mutagenesis was determined in chinese hamster cells with genetic markers that affect the surface membrane, nucleic-acid synthesis, and protein synthesis. the mutations were characterized by resistance to ouabain, 8-azaguanine, and temperature. mutagenesis by the carcinogens required metabolic activation and this was provided by ... | 1976 | 1061115 |
| [damaging effect of 3h-uridine on tissue culture cells during the logarithmic and stationary phases of growth]. | the chinese hamster fibroblasts entered the stationary phase of growth after 5.5 days of cultivation. the induction of the culture proliferation occurred within the first 4 hrs of cultivation in the fresh nutrient medium. after addition of 3h-uridine in high concentration and with high specific activity (75 micron cu/m and 23 cu/mm), in the stationary phase a lesser number of cells with aberrations and a higher mitotic index were noted than in the logarithmic phase. 3h-uridine injured the cells ... | 1976 | 1036114 |
| [development of spontaneous mutations in somatic mamalian cells and dna replication. ii. expression of gene mutations in cultured cells]. | the dependence of spontaneous rate and phenotypic expression of 6-mercaptopurine resistance mutations of dna replication synthesis was studied in cultured chinese hamster cells. spontaneous mutations arising with a constant rate per cell per time unit independently on dna replication rate were shown to be expressed only in the course of subsequent cell divisions. the frequency of n-nitrosomethylurea induced mutations in cells with reduced and normal dna replication rate is approximately the same ... | 1976 | 1034583 |
| biochemical genetics of chinese hamster cell mutants with deviant purine metabolism iii. isolation and characterization of a mutant unable to convert imp to amp. | the isolation and characterization of a new mutant of chinese ovary cells (cho-k1) is described. this mutant, ade-h, has the following properties: (1) it forms a new genetic complementation group; (2) it specifically requires adenine for growth and will not grow on aminoimidazole carboxamide (aic) or hypoxanthine; (3) it accumulates imp; (4) it cannot synthesize adenine nucleotides; (5) its phenotype can be mimicked by treatment of cho-k1 (the wild type parental strain) with hadacidin, an inhibi ... | 1976 | 1028159 |
| proposed banding nomenclature for the chinese hamster chromosomes (cricetulus grises). | 1976 | 1024658 | |
| enhance anchorage independence and tumorigenicity of aneuploid chinese hamster cells with nearly doubled chromosome complements. | the role of a cell's chromosome complement in its tumorigenic and anchorage-independent growth properties in vitro was investigated by injecting a chinese hamster cell line and its subclones into immunodeficient nude mice and by plating the cells in a semisolid medium containing methylcellulose. the parental wor-6 cell clone originally consisted of 89% 1s cells and 11% cells with a nearly double (2s) complement. tumors that developed from wor-6 were found to consis entirely or primarily of cells ... | 1976 | 1022225 |
| induction and isolation of cold-sensitive lines of chinese hamster cells. | 1976 | 1004229 | |
| short-term microcultures of lymphocytes from chinese hamster peripheral blood. | a microtechnique for the culture of chinese hamster lymphocytes is described using cooke microtiter plates with 100,000 leucocytes in a culture volume of 0.1 ml and a culture time of three days. the culture media used were rpmi 1640 and trowell t8 supplemented with 20% foetal calf serum (fcs) and 2 mu pha. the cells were harvested with a skatron cell culture harvester using glass fibre filters. various technical aspects of the lymphocyte cultures from the chinese hamster are described. the relev ... | 1976 | 993605 |
| [spontaneous and induced mutagenesis in a culture of chinese hamster cells]. | spontaneous and nitrosoguanidine (ng)-induced rate of reversions to glutamine independence was studied in cultured temperature-sensitive glutamine auxotrophs of chinese hamster cells. in 3 experiments the spontaneous rate of reversions varied from 0.8-10(-6) to 3.84-10(-6) per cell per generation. a dependence of the yield of ng-induced back mutations upon the time interval between the mutagenic treatment and the transfer to selective conditions (glutamine deficient medium, 40 degrees c) was est ... | 1976 | 986338 |
| relevance of dimethylamine to mechanism studies of dic (dtic, nsc 45388). | monolayer cultures of chinese hamster ovary (cho) cells take up the photo-decomposition products of dic more readily than dic itself. dimethylamine, an immediate product of this degradative pathway, can ultimately become associated with the dna, rna, and protein of the cells as demonstrated by selective enzymatic degradation of macromolecules and isopycnic centrifugation. the relevance of these observations to mechanism studies of dic is discussed. | 1976 | 979914 |
| proposed banding nomenclature for the chinese hamster chromosomes (cricetulus griseus). | 1976 | 975930 | |
| [combined effect of n-nitroso-n-methylurea and actinomycin d on chinese hamster cell chromosomes]. | 1976 | 955409 | |
| the in vitro isolation and characterization of monosomic sublines derived from a colcemid-treated chinese hamster cell population. | a series of 18 sublines deficient for one or two chromosomes was isolated in vitro from a pseudodiploid chinese hamster cell population treated appropriately with colcemid to obtain maximal induction of aneuploidy. chromosomes 10 and 11 were the most frequently involved and, to a lesser extent, chromosome 9 and the partially deleted 6. since analysis of chromosome banding patterns did not reveal any evidence of chromosome rearrangement, it was concluded that entire chromosomes were absent, and t ... | 1976 | 949905 |
| pachytene mapping of the male chinese hamster. | minced seminiferous tubules of male chinese hamsters when treated with a mixture of trypsin (one part) and mccoy's 5a growth medium with 20% fetal calf serum (nine parts) at 4 degrees c, washed twice with the regular growth medium, incubated at 37 degrees c in growth medium for 4 h, and harvested without colcemid and hypotonic pretreatments, gave excellent pachytene morphology for studies on chromomere patterns. the giemsa banding patterns of all somatic metaphase chromosomes except the sex chro ... | 1976 | 949904 |
| [isolation and characteristics of temperature sensitive mutants in a culture of chinese hamster cells]. | the treatment of a temperature-resistant glutamine-independent clone of chinese hamster cells (237 glu+ tr) with 5-bromodeoxyuridine (budr) for 48 or 72 hours at 40 degrees c and subsequent illumination with visible light was used for selection of spontaneous and n-methyl-n'-nitro-n-nitrosoguanidein-induced ts mutants. 30 clones were isolated. their temperature-sensitivity was studied at two cell densities: 500 and 10000 (or 15 000) cells per dish. 21 clones proved to be temperature-sensitive. t ... | 1976 | 944672 |
| drug-resistant mutants of chinese hamster ovary cells possess an altered cell surface carbohydrate component. | surface label experiments using the galactose oxidase-]3h]-borohydride technique reveal that cells from drug-resistant chinese hamster ovary clones possess a surface carbohydrate component of apparent molecular weight 165,000 which is absent from wild-type cells. the component may also be demonstrated by [14c]glucosamine incorporation but not by [3h]leucine incorporation or by the lactoperoxidase surface labeling reaction. | 1976 | 933538 |
| control effects of cyclic nucleotides on the proliferation activity of the bone marrow cells of the chinese hamster in vivo and their relation to the radiosensitivity. | 1976 | 199053 | |
| [role of oncogenic viruses in the formation of dna provirus during acute infection of chinese hamster cells by tick-borne encephalitis viruses]. | 1976 | 187396 | |
| the cell cycle specificity of the morphological conversion of chinese hamster ovary cells by n6, o2'-dibutyryl cyclic adenosine 3',5'-phosphate. | 1976 | 173560 | |
| radiation response of multicell spheroids--an in vitro tumour model. | multicell spheroids provide an in vitro tumour model of intermediate complexity between tumours and standard cell cultures. spheroids of several varieties of normal and tumour cells have been grown and chinese hamster v79-171b cells have been studied in detail. spheroids simulate conditions in those solid tumours which contain nodular areas with necrosis at a distance from blood vessels and show a decrease in growth fraction as they increase in size. they contain radiation resistant chronically ... | 1976 | 128440 |
| isolation and characterization of an unsaturated fatty acid-requiring mutant of cultured mammalian cells. | an unsaturated fatty acid-requiring mutant derived from chinese hamster ovary (cho) cells has been isolated and characterized. this mutant grows normally when oleate or other unsaturated fatty acids are supplemented in the growth medium. unlike the wild-type cho cells, growth stops when medium is deprived of unsaturated fatty acid. whole cell pulse experiments with [14c]acetate or [14c]stearate indicate that the mutant is defective in unsaturated fatty acid synthesis. enzyme assays in vitro show ... | 1976 | 1750 |
| selenium is an essential trace nutrient for growth of wi-38 diploid human fibroblasts. | the trace element selenium is essential for clonal growth of diploid fibroblasts from human fetal lung (wi-38) in media containing small amounts of serum protein. maximum growth stimulation is obtained when 30 nm neutralized selenious acid is added to a synthetic medium containing 1.5 mg/ml of dialyzed fetal bovine serum protein (equivalent to a 3% serum concentration). serum appears to be a source of selenium in most culture media, since higher concentrations of serum protein or whole serum mas ... | 1976 | 1064872 |
| study of markers of human erythroid differentiation in hybrid cells. | somatic cell hybrids exhibiting co-expression of the globin genes of two species were generated by fusion of mouse erythroleukemia cells with chinese hamster or human marrow erythroid cells. in contrast, extinction of the mouse globin genes occurred in hybrids formed between the erythroleukemia cells and human fibroblasts. direct detection of the human globin genes in human x mouse fibroblast hybrids was achieved by annealing of dna from these cells to human globin complementary dna. this method ... | 1976 | 1071439 |
| genetics of somatic mammalian cells: genetic, immunologic, and biochemical analysis with chinese hamster cell hybrids containing selected human chromosomes. | through hybridization of specific chinese hamster cell auxotrophs with human cells and selection in media lacking the nutritional supplements required by the former cells, a series of stable hybrid clones can be prepared. these hybrids have genomes consisting of a common part--the complete or almost complete set of chinese hamster chromosomes, plus a variable part--one or a few human chromosomes. the identity of the human chromosomes can be varied by utilizing different chinese hamster auxotroph ... | 1976 | 1061117 |
| identification of mutagenic metabolites of benzo(a)pyrene in mammalian cells. | the mutagenicity of benzo[a]pyrene and 15 of its derivatives, which included phenols, the benzo[a]yrene-4,5-epoxide (the k-region epoxide), dihydrodiols, two isomeric 7,8-diol-9,10-epoxides, a 6-methyl derivative, and a 6-hydroxymethyl derivative, were tested with chinese hamster v79 cells in order to identify the mutagenic metabolites of benzo[a]pyrene. mutations were characterized by resistance to ouabain or 8-azaguanine. since v79 cells do not metabolize polycyclic hydrocarbons, mutagenesis w ... | 1976 | 1061161 |
| the effect of insecticides on chinese hamster cell cultures. | the effect of p,p'-isomers of ddt and its derivatives ddd, dde and dda on chinese hamster cells in culture was studied. at different concentrations and various times of treatment the proliferation rate was inhibited most strongly by ddd and ddt, whereas dde exhibited a markedly weaker influence. dda was the least toxic compound of the four. the cytogenetic effects were also different. again, dda induced the least damage. only enhanced gap rates but no chromosome breaks were observed. dde was mor ... | 1976 | 934173 |
| the human gene for beta glucuronidase is on chromosome 7. | inconsistent assignments of the human gene for beta glucuronidase (gus) to chromosomes 7 and 9 have previously been reported. in this study, we have correlated the expression of human gus in 22 primary chinese hamster/human hybrid lines with quantitative cytogenetic analysis. eight hybrids were positive for human gus as manifested by a five-band pattern on electrophoresis. all of them contained a human chromosome 7 in 34% or more of cells, and seven of them had not retained chromosome 9. one hyb ... | 1976 | 941903 |
| metaphase chromosome anomaly: association with drug resistance and cell-specific products. | large, homogeneously staining chromosome regions which lack the longitudinal differentiation ordinarily revealed by cytogenetic "banding" methods have been found in antifolate-resistant chinese hamster cells and also in human neuroblastoma cells established in vitro. the drug-resistant cells are characterized by excessive production of the target enzyme, dihydrofolate reducatase, while the human neuroblastoma cells have phenotypes of normal neuronal cells. the homogeneously staining region appea ... | 1976 | 942798 |
| profiles of brain glycosidase activity in cuprizone-fed syrian hamsters and in scrapie-affected mice, rats, chinese hamsters and syrian hamsters. | 1976 | 943426 | |
| surface polypeptides of the chinese hamster ovary cell; an immunochemical study. | antibodies elicited by the injection of live chinese hamster ovary cells (cho) into rabbits precipitated four major components from detergent extracts of cho membranes. the four components, of molecular weights 200000, 125000, 95000 and 41000 daltons, corresponded to cell surface components identified by the lactoperoxide surface label technique. | 1976 | 944075 |
| somatic cell chromosome interconnections in trypan preparations of chinese hamster testicular cells. | 1976 | 944637 | |
| articular cartilage of diabetic chinese hamsters. | investigations were carried out in order to determine whether animals with spontaneous diabetes are prone to develop skeletal lesions comparable to those found in diabetic human subjects. the present report deals with the ultrastructure of the cartilage of the hip joint of diabetic chinese hamsters and nondiabetic control animals. in the diabetic animals, chondrocytes of the femoral head showed atrophy of the endoplasmic reticulum, bizarre mitodhoncria, and huge lipid inclusions, which are chang ... | 1976 | 946390 |
| behavioral development in three hamster species. | the preweaning behavioral development was compared in 3 hamster species: the golden (mesocricetus auratus), chinese (cricetulus griseus), and djungarian (phodopus sungorus). differences in the age of appearance of action patterns could not be summarized by simply ranking species on either precocity or developmental speed, nor were they eliminated by measuring age from conception. problems in the interpretation of species differences in the age of appearance of action patterns are discussed. | 1976 | 955290 |
| selective isolation of reversible cold sensitive variants from chinese hamster ovary cell cultures. | variants of the chinese hamster ovary cell line cho-ki (attcccl61)which grow almost normally at 38.5c but very poorly or not at all at 30c were obtained after treatment with mutagens and application of an indirect selection procedure. two kinds of variants were recovered. in the first of these, the cold sensitive phenotypw is expressed completely only at low cell densities. at higher cell desity, growth continues at the nonpermissive temperature, but at a reduced rate. in the second class, t ... | 1976 | 956283 |
| significance of dimers to the size of newly synthesized dna in uv-irradiated chinese hamster ovary cells. | dna synthesized after uv irradiation is smaller than that in unirradiated cells even when pulse-labeling times are increased to compensate for the overall reduction in the rate of dna replication. by isolating newly replicated dna, incubating it with dimer-specific endonuclease from micrococcus luteus, and analyzing it on alkaline sucrose gradients, we have been able to demonstrate that this dna is synthesized in segments corresponding in size to the interdimer distance on the parental strand. i ... | 1976 | 963196 |
| cytogenetic effects of mutagens/carcinogens after activation in a microsomal system in vitro i. induction of chromosome aberrations and sister chromatid exchanges by diethylnitrosamine (den) and dimethylnitrosamine (dmn) in cho cells in the presence of rat-liver microsomes. | a rat-liver microsomal system in vitro has been used to activate two indirectly acting carcinogens, dmn and den. on activation, both compounds were extremely potent in inducing chromosomal aberrations as well as sister chromatid exchanges in chinese hamster cells. the implications of these findings and the potential utility of this technique to detect mutagens/carcinogens are discussed. | 1976 | 967188 |
| replicative bypass repair of ultraviolet damage to dna of mammalian cells: caffeine sensitive and caffeine resistant mechanisms. | replicative bypass repair of uv damage to dna was studied in a wide variety of human, mouse and hamster cells in culture. survival curve analysis revealed that in established cell lines (mouse l, chinese hamster v79, hela s3 and sv40-transformed xeroderma pigmentosum (xp)), post-uv caffeine treatment potentiated cell killing by reducing the extrapolation number and mean lethal uv fluence (do). in the do reduction as the result of random inactivation by caffeine of sensitive repair there were mar ... | 1976 | 967189 |
| human gene locations achieved by means of human-chinese hamster (cho-k1) auxotrophic cell hybridization. | 1976 | 975914 | |
| expression of human x-chromosomal markers in man-chinese hamster hybrids treated with isolated human chromosomes. | 1976 | 975919 | |
| effects of actinomycin d on cell cycle kinetics and the dna of chinese hamster and mouse mammary tumor cells cultivated in vitro. | actinomycin d produces changes in the cell cycle kinetics of chinese hamster (ha1) and mouse mammary tumor cells (emt6) cultivated in vitro. there was a reduced rate of progression of the cells through s phase and a g2 arrest, the duration and degree of which were drug dose dependent. the lethal effects of the drug on the two cell lines were comparable. at the molecular level, dna single-strand breaks (true breaks and/or alkali-labile bonds) appear initially. after drug removal, the extent of di ... | 1976 | 986240 |
| hypoxia-dependent reduction of 1-(2-nitro-1-imidazolyl)-3-methoxy-2-propanol by chinese hamster ovary cells and kht tumor cells in vitro and in vivo. | incubation of chinese hamster ovary cells and kht murine fibrosarcoma tumor cells in the absence of oxygen with 1-[2-14c]nitro-1-imidazolyl)-3-methoxy-2-propanol, one of the most effective radiation sensitizers of hypoxic cells, results in the preferential reduction of 1-[2-14c]nitro-1-imidazolyl)-3-methoxy-2-propanol. the radioactivity associated with the acid-insoluble precipitate from cells incubated in nitrogen is about four times higher than that of cells incubated in air. when aqueous extr ... | 1976 | 986241 |
| chromosome distribution in a23 chinese hamster fibroblasts. | this study deals with a systematic chromosome position analysis of 116 anti-mitotic and hypotonic treated a23 chinese hamster cells. no chromosome or pair of chromosomes was found to be located nearer the center or the periphery of the metaphase plate than would be expected by the reference distribution. the homologous chromosomes of pair 2 lie nearer to each other but they do not form a specific angle. the same relative position was shown for the chromosome groups 1-2, 1-e1 and 2-e5 (e standing ... | 1976 | 1001138 |
| biochemical and electron-microscopic evidence that the subunit structure of chinese-hamster-ovary interphase chromatin is conserved in mitotic chromosomes. | biochemical and electron microscopic studies demonstrate that the subunit structure of chinese hamster ovary cell interphase chromatin is conserved in mititic chromosomes. digestion of purified chromosomes or nuclei with micrococcal nuclease produces dna in discrete size classes, as visualized by polyacrylamide gel electrophoresis, which are common to the two materials. early in digestion the dna fragments are integral multiples of a monomer approximately 177 base pairs in length, whereas after ... | 1976 | 1009941 |
| human gene locations achieved by means of human-chinese hamster (cho-k1) auxotrophic cell hybridization. | 1976 | 1024644 | |
| expression of human x-chromosomal markers in man-chinese hamster hybrids treated with isolated human chromosomes. | 1976 | 1024646 | |
| transfer of the human x chromosome to human--chinese hamster cell hybrids via isolated hela metaphase chromosomes. | evidence is presented for the uptake of the human x chromosome by human-chinese hamster cell hybrids which lack h p r t activity, following incubation with isolated human hela s3 chromosomes. sixteen independent clonal cell lines were isolated in h a t medium, all of which contained a human x chromosome as determined by trypsin-giemsa staining. the frequency of h a t-resistant clones was 32 x 10(-6) when 10(7) cells were incubated with 10(8) hela chromosomes. potential reversion of the hybrid ce ... | 1976 | 1027148 |
| asynchronous dna replication and asymmetrical chromosome loss in chinese hamster-mouse somatic cell hybrids. | a number of parameters were measured in a series of 12 hybrid cell clones from chinese hamster and mouse cells to test the hypothesis that asymmetrical chromosome loss may result from asynchrony in the replication of the two parental sets of chromosomes. all clones tended to lose telocentric (mouse) chromosomes with culture time, irrespective of the starting ratio of parental chromosomes, and in all clones, biarmed (hamster) chromosomes appeared to complete dna replication slightly earlier than ... | 1976 | 1028157 |
| reactivation of chick erythrocyte nuclei in heterokaryons with temperature-sensitive chinese hamster cells. | chinese hamster cell line k12 is temperature-sensitive for the initiation of dna synthesis. k12 cells synchronized by serum deprivation were collected in early g1(g0). heterokaryons were formed by fusing chick erythrocytes with serum-starved k12 cells through the use of uv-irradiated sendai virus. at the permissive temperature (36.5 degrees c), erythrocyte nuclei in heterokaryons enlarged, the chromatin dispersed, and erythrocyte nuclei synthesized dna at about the same time as the k12 nuclei. a ... | 1976 | 1028158 |
| expression of human hypoxanthine phosphoribosyl transferase in chinese hamster cells treated with isolated human chromosomes. | chinese hamster cells deficient for the enzyme hypoxanthine phosphoribosyl transferase (hprt) were incubated with isolated human metaphase chromosomes and 21 colonies were isolated in hat medium. three different types of cell lines were established from these clones. first, 4 cell lines had 10-30% of normal chinese hamster hprt activity with the same electrophoretic mobility as human hprt. this hprt activity remains detectable during at least 8 weeks of growth of the cells in nonselective medium ... | 1976 | 1028163 |
| differential staining of interspecific chromosomes in somatic cell hybrids by alkaline giemsa stain. | staining of chromosome preparations of chinese hamster-human hybrid cells and mouse-chimpanzee hybrids with alkaline giemsa has yielded color differentiation of the interspecific chromosomes. bicolor chromosomes, indicating apparent translocations also are observed for each of these hybrids. the specific color differences observed provide a rapid means of recognizing and aiding in the identification of the interspecific chromosomes and apparent translocations in these somatic cell hybrids. | 1976 | 1028166 |
| isolation of a factor causing morphological changes of chinese hamster ovary cells from the culture filtrate of vibrio parahaemolyticus. | a factor changing chinese hamster ovary cells from an oval to a spindle shape was isolated from the culture filtrate of vibrio parahaemolyticus. it was partially purified by successive column chromatographies on diethylaminoethylcellulose, diethylaminoethyl-sephadex a-25, hydroxylapatite, and sephadex g-200. this factor was separated from thermostabl direct hemolysin and was heat labile. | 1976 | 1033156 |
| the production and action of interferon in chinese hamster cells. | the interferon system has been investigated in primary cell cultures established from chinese hamster embryos and new born pups. interferon synthesis was induced with sindbis virus, ultraviolet inrradiated newcastle disease virus (u.v.-ndv) and with polyriboinosine acid-polyribocytidylic acid complex [poly (ri). poly (rc)]. only u.v.-ndv induced significant production of interferon, maximum amounts being produced in 'aged' cells. its apparent mol. wt. was 25000. cho-ki cells, an established line ... | 1976 | 1033270 |
| [protein sh-group concentration and rna synthesis during the process of induction of proliferation in the stationary phase of cell culture growth]. | the dynamics of intracellular protein sh-group (psh) content was studied cytochemically in the course of stimulation of cell proliferation in stationary cultures of an established chinese hamster cell line and of human diploid embryo fibroblasts. the results were compared with the pattern of rna synthesis during the prereplicative period. in chinese hamster cells immediately after medium changing in stationary cultures there is an augmentation of psh content in parallel withe the increase in rna ... | 1976 | 1034987 |
| [duration of the mitotic cycle of chinese hamster cells cultured at 30--39 degrees]. | the duration of the mitotic cycle (t) at temperatures of 30, 33, 36 and 39 degrees c was studied in subline 237 of chinese hamster cells with the aid of the radioautographic method. t was the least at 39 degrees c and increased with reduction of the cultivation temperature. at the temperature range of 33--39 degrees c prolongation of t and its periods was "proportional" to the temperature under study. the characteristic curve gradient of t dependence on the temperature showed a sharp change in t ... | 1976 | 1035117 |
| [on the simultaneous effects of ionising radiation and chemical agents on animal cells. 1st communication. cytogenetic studies on x-rays and isonicotinic acid hydrazide in the chinese hamster, cricetulus griseus (author's transl)]. | in bone marrow cells of chinese hamsters enhanced chromosome damage is observed after 48 h treatment of the animals with isoniazid (inh) combined with x-rays only at much higher doses than normally applied in human therapy. compared to x-ray-induced aberration levels, 125 mg/kg inh and 50 r given simultaneously increase the number of gaps and breaks, the latter being increased over-additively. this points to an interaction between both agents. the combined treatment changes the mitotic rate of t ... | 1976 | 1036915 |
| relationship between experimental results in mammals and man. ii. cytogenetic analysis of bone-marrow cells after treatment of cytembena and cyclophosphamide- cytembena combination. | cytogenetic analysis and the micronucleus test of bone-marrow cells was used to study the possible extrapolation of results from experimental animals to man. cytembena was given i.p. in doses of 5, 10, 20, 40 and 80 mg/kg body wt. to wistar rats and in doses of 20, 40 and 80 mg/kg body wt. to icr mice and to chinese hamsters. five patients with various types of malignancy, so far medically untreated, received 20 mg cytembena/kg body wt i.v. a combination of cytembena and cylophosphamide was appl ... | 1976 | 1037016 |
| 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 ... | 1976 | 819318 |
| 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 ... | 1976 | 819823 |
| 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 ... | 1976 | 826906 |
| 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. | 1976 | 828861 | |
| 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 ... | 1976 | 829289 |
| 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 ... | 1976 | 829598 |
| effect of room fluorescent light on the deterioration of tissue culture medium. | a major cause of tissue culture medium deterioration is exposure to room fluorescent light. riboflavin and tryptophan present in dulbecco's modified eagle's minimum essential medium, when exposed to light, yield toxic photoproducts responsible for loss of the ability of the medium to support clonal growth of human, mouse and chinese hamster cell lines. procedures for minimizing medium deterioration are discussed. | 1976 | 1244326 |
| lack of synergistic effect between x-ray and uv irradiation on the frequency of chromosome aberrations in pha-stimulated human lymphocytes in the g1 stage. | pha-stimulated human lymphocytes in the g1 stage were irradiated with uv radiation and x-rays, and the cells were analyzed for chromosomal aberrations in the first mitotic division. the frequency of dicentric chromosomes after single x-irradiation in the g1 stage was about twice the yield in the g0 stage. no increase in the yield of dicentrics was observed after combined irradiation with uv and x-rays. this is contrary to the finding for g0 lymphocytes, where a 2-fold increase of chromosome aber ... | 1976 | 1250244 |