Publications

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
evaluation of the mutagenic potential of cyclohexylamine on spermatogonia of the chinese hamster.	in a cytogenetic study on the spermatogonia of chinese hamster, cyclohexylamine (neutral sulphate) was evaluated for mutagenic effects in comparison with an untreated control group and a group treated with the mutagenic compound cyclophosphamide, by assessing spermatogonial metaphases of treated chinese hamster for chromosomal structural changes. each test group comprised 8 male hamsters selected at random. approximately 100 metaphases from each animal were assessed. the doses were 5 x 150 mg cy ...	1976	958236
effects of actinomycin d and puromycin on colchicine-induced endoreduplication in chinese hamster cells in vitro.	experiments were carried out to study the events through which the process of endoreduplication occurs after treatment with colchicine in chinese hamster cells cultivated in vitro, and to analyse the differences between the processes leading to normal mitosis and those leading to endoreduplication. chinese hamster cells (line c-125) were treated with colchicine (10(-4) m) for 1 h, in order to induce endoreduplication. before and after colchicine treatment the cultures were treated at various int ...	1976	954141
cell volume growth after cell cycle block with chemotherapeutic agents.	the effects of various chemotherapeutic agents on the volume of chinese hamster v79 fibroblasts and murine lymphoma l5178y cells were studied by electronic volume spectroscopy. cells arrested in the division cycle by a chemotherapeutic block continued to grow in volume resulting in abnormally large cells unable to reduce their volume by cell division. this was observed in cells treated with colcemid, vinblastine, excess thymidine, hydroxyurea, ara-c, 5-fluorouracil, actinomycin-d and bleomycin, ...	1976	58726
the significance of dna damage in the cell cycle sensitivity of chinese hamster ovary cells to bleomycin.	chinese hamster ovary cells have been treated with bleomycin at various stages in the cell cycle. mitotic cells, which exhibit least survival, show the greatest amount of dna strand breakage and a marked inhibition of dna replication in the subsequent s phase. strand-rejoining experiments suggest that this is primarily due to differences in the amount of damage produced in the dna but does not exclude the possibility that cells at the various cell stages also differ in their ability to repair th ...	1976	58718
configurational changes in chromatids from helical to banded structures.	induction of configurational changes in the helical chromatids of air dried chromosomes was used to explore the mechanism of g-banding. from the water-giemsa stained metaphase spreads of chinese hamster cells, chromosomes having clearly helical chromatids were selected and photographed. then the chromosomes were decolorized, treated with trypsin, and restained with saline-giemsa (1x ssc). such procedures were repeatedly carried out upon the same chromosomes. subsequent examination of the chromos ...	1976	976013
effect of hoechst 33258 on chinese hamster chromosomes.	cells of the chinese hamster strain c-125 were treated for different time intervals with h 33258, a bibenzimidazole derivative. the same compound was used to stain fixed cells of the same strain. h 33258 induced in cells in culture specific areas of reduced spiralization on the metaphase chromosomes of some cells. these probably correspond to dna segments rich in a-t bases interspersed along the chromosomes. probably h 33258 acts during s period of cell cycle. the banding obtained by staining wi ...	1976	61845
isolation of mammalian cell mutants deficient in glucose 6-phosphate dehydrogenase by means of a replica-plating technique.	a replica-plating technique is described which was used for the isolation of g-6-pd-deficient mutants in cultures of mutagen-treated chinese hamster cells. mutants were recognized by their failure to stain in a histochemical g-6-pd-specific staining reaction. four mutants were isolated and characterized by growth properties, stability of their variant phenotypes, and reduced g-6-pd activity. one of these mutants on electrophoresis exhibited a variant g-6-pd and thus is very likely the result of ...	1976	59685
phosphorylation of distinct regions of f1 histone. relationship to the cell cycle.	the phosphorylation of different amino acids in distinct regions of f1 histone was studied in highly synchronized chinese hamster cell populations (line cho). the purified, 32p-labeled f1 histone was bisected into nh2-terminal and cooh-terminal fragments with n-bromosuccinimide. tryptic phosphopeptides from these fragments were resolved using sequential high voltage electrophoretic steps on paper. no phosphorylation was observed in early g1-arrested cells. interphase phosphorylation began in lat ...	1976	180006
cyclic amp phosphodiesterase inhibitors depress production of plasminogen activator by chinese hamster ovary cells.		1976	182161
biological and biochemical characterisation of purine analogue resistant clones of v79 chinese hamster cells.	purine analogue resistant clones have been selected from the closely related chinese hamster lines v79a and v79s. clones were of either spontaneous origin or induced by ems or ultraviolet light. the majority of clones selected in 8-azaguanine showed stable cross resistance to 6-thioguanine. clones derived from v79a and selected for 6-thioguanine resistance were cross resistant to 8-azaguanine: however a group of 6-thioguanine resistant mutants selected from v79s cells were 8-azaguanine sensitive ...	1976	14997605
the relative effectiveness of 6-thioguanine and 8-azaguanine in selecting resistant mutants from two v79 chinese hamster cells in vitro.	the frequency of surviving colonies in two v79 cell lines exposed to either 6-thioguanine or 8-azaguanine was dependent on initial plating density. different degrees of metabolic-co-operation were found to occur in the two cell lines and the loss of both spontaneous and added mutants occurred at a lower cell density when 6tg was used for selection than when 8 az was used in both cell lines. both analogues were degraded on incubation in medium plus serum in the absence of added cells. variation i ...	1976	14997604
proceedings: cytotoxic effects of electromagnetic radiation on chinese hamster cells in culture.		1976	1047668
interaction between radiation and drug damage in mammalian cells. ii. the effect of actinomycin-d on the repair of the sublethal radiation damage in plateau phase cells.	the effect of actinomycin-d (amd) on radiation damage repair was studied in plateau phase v79 chinese hamster cells. sublethal radiation damage repair, as demonstrated by survival fluctuations following two x-ray exposures separted by time, was observed in our plateau phase cells. plateau phase cells exposed to 0.01-0.04 mug/ml amd (a nontoxic regimen to 8 hours) between x-ray exposures were less able to repair sublethal damage. if plateau phase cells were plated at low dilutions into fresh medi ...	1976	985734
characterisation of the lysosomal heterogeneity in chinese-hamster fibroblasts.	1. homogenates of chinese hamster fibroblasts have been fractionated by analytical centrifugation techniques. lysosomes have been characterised and identified by the distinctive behaviour of specific marker constituents. 2. the acid hydrolases of hamster fibroblasts were located in two distinct organelles, characterised by differences in their equilibrium densities and rates of sedimentation. the lighter population of lysosomes with a modal density of 1.10 g cm-3, contained glycosidases, nucleas ...	1976	949969
mammalian cell survival response following irradiation with 4 mev x rays or accelerated helium ions combined with hyperthermia.	the effects of hyperthermia on chinese hamster ovary cell radioresponse were studied using either 4 mev x rays or accelerated helium ions. both pre-and postirradiation hyperthermic doses act to decrease the slope of the x-irradiation survival curve in a temperature-dependent manner, while the extrapolation number does not change appreciably. pre-irradiation hyperthermic treatment has only a slightly greater dose-modifying effect than similar postirradiation hyperthermia. for cells irradiated wit ...	1976	935413
factors affecting the efficiency of purine analogues as selective agents for mutants of mammalian cells induced by ionising radiation.	in the chinese hamster cell line v79-4, the frequencies of the cells selected for their resistance to purine analogues do not always reflect the true frequencies of resistant mutants. the frequency of cells resistant to 8-azaguanine varied widely, especially when different sources of serum were used in the selective medium. even with the more efficient analogue, 6-thioguanine, small colonies arose in the selective medium at a frequency which was strongly dependent upon analogue concentration and ...	1976	934168
factors affecting the growth of chinese hamster cells in hat selection media.	factors affecting the efficiency of selection of "revertants" of salvage pathway mutants in media containing amethopterin have been examined. our v79 chinese hamster cell line was found to require a significantly higher level of thymidine for optimal growth in such media than has been reported for other cell lines. hypoxanthine (but not glycine) was also required for reversal of amethopterin toxicity, but levels did not differ significantly from those reported elsewhere. growth in hat was also d ...	1976	934167
initiation and elongation of protein synthesis: their relative rates and sensitivities to inhibition in chinese hamster ovary cells determined by a modified edman procedure.		1976	942107
alpha-amanitin resistance of rna polymerase ii in mutant chinese hamster ovary cell lines.	a number of mutant chinese hamster ovary (cho) cell lines resistant to the cytotoxic action of alpha-amanitin have been isolated. the alpha-amanitin sensitivity of the different mutant cell lines varied widely, but correlated well with the alpha-amanitin sensitivity of the rna polymerase ii activity in each of these mutant cell lines. in comparison with the rna polymerase ii of wild-type cells, three mutants, ama39, ama6, and amal, required respectively 2- to 3-fold, 8- to 10-fold, and about 800 ...	1976	1262341
carcinogenic effects of different nitroso-compounds in chinese hamsters. ii. n-nitrosomorpholine and n-nitrosopiperidine.	a total of 320 chinese hamsters (cricetulus griseus) (ch) were subcutaneously (s.c.) treated with 1/5, 1/10, or 1/20 ld50 of n-nitrosomorpholine (nm) or n-nitrosopiperidine (np). in the ch, nm and np both produced up to a 100% rate of papillomas of the cheek pouch, tongue, pharynx, esophagus and forestomach. occasionally squamous cell carcinomas also developed in these organs. a high rate of hepatomas was realized by np.	1976	132034
effects of ultraviolet irradiation on the rate and sequence of dna replication in synchronized chinese hamster cells.	the effects of ultraviolet light (uv) irradiation on the rate of dna replication in synchronized chinese hamster ovary (cho) cells were investigated. a technique for measuring semiconservative dna replication was employed that involved growing the cells in medium containing 5-bromodeoxyuridine and subsequently determining the amount of dna that acquired hybrid buoyant density in cscl density gradients. one of the advantages of this technique was that it allowed a characterization of the extent o ...	1976	1276380
galactokinase mutants of chinese hamster somatic cells resistant to 2-deoxygalactose.	the growth of chinese hamster somatic cells was inhibited by 0.2 mg/cc of 2-deoxygalactose. mutants partially or fully resistant to 2-deoxygalactose were isolated in a single-step or two-step selection. some of them did not grow as well as the wild type; one of them which lacked galactokinase(ec.2.7.1.6) activity did not grow at all in galactose medium. the galactokinase kinetic properties (vmax & kmax of the other mutants and of the wild type were different. therefore resistance resulted either ...	1976	1269916
a study of the morphological changes in the small intestine of the spontaneously diabetic chinese hamster.	several morphological changes were observed microscopically in the small intestine of some diabetic chinese hamsters. although some alterations lacked statistical significance due to variation, most diabetics displayed a greater incidence and severity compared with nondiabetic controls. the following structural deviations were seen in the small intestines of some diabetics: increased surface area, elevated number of goblet cells per villus, decreased muscle thickness with connective tissue infil ...	1976	1269845
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
comparative investigations on cytogenetic effects of x-irradiation on the germinal epithelium of male mice and chinese hamsters.	in one short-term-experiment and one long-term-experiment spermatogonia of mice and chinese hamsters were compared for their sensitivity of x-ray induced chromosome aberrations. short-term-experiment: six hours after varying doses of x-rays the spermatogonia of both species were analysed and the number of induced chromatid breaks determined. at the dose range from 25-125 r the number of induced chromatid breaks per cell per roentgen is 0.01 in mice. in chinese hamsters this value is 0.0072. the ...	1976	1002141
quantitative evaluation of somatotrophic cells (sc) in the adenohypophysis of normal and diabetic male chinese hamsters.	the pituitary of genetically diabetic chinese hamsters contains significantly (p less than 0.001) greater numbers of somatotrophes than pituitary of non-diabetics. this may play a role in the aetiopathology of diabetes in this species or at least contribute to the maintenance of hyperglycaemia.	1976	976637
investigations on the frequency of chromosome aberrations in bone marrow cells of chinese hamsters after simultaneous application of caffeine and cyclophosphamide.	the potentiating effect of caffeine (1,3,7-trimethylxanthine) on chemically induced chromosome aberrations was studied in bone marrow cells of chinese hamsters, exposed to the alkylating agent cyclophosphamide. four experimental series were performed: in the first two tests caffeine (200 mg/kg) or cyclophosphamide (40 mg/kg), respectively, were administered. a third and fourth test was performed with caffeine plus cyclophosphamide (200 + 40 mg/kg and 35 + 40 mg/kg, respectively) simultaneously. ...	1976	939563
the effect of hyperthermia on the repair of radiation damage in plateau phase cells.	hyperthermia (41 degrees c for 1 hr.) completely inhibited both sublethal and potentially lethal radiation damage repair by plateau phase cells taken from v79 chinese hamsters. this suggests that there may be disadvantages in combining x-ray and heat therapies for the treatment of tumors.	1976	1257447
metabolic effects and mortality rate in diabetic chinese hamsters after long-term treatment with 5-methoxyindole-2-carboxylic acid (mica).	chronic oral treatment of male diabetic chinese hamsters with 100 mg/kg/day 5-methoxyindole-2-carboxylic acid (mica) causes a depression of blood glucose in fasted animals and an improvement in the glucose profile in fed animals. glycogen levels in the liver and body weight are decreased. treated animals die at a higher rate than do controls. it is concluded that treatment with a potent inhibitor of gluconeogenesis like mica will not provide a useful tool in managing diabetes.	1976	989012
failure to detect chromosome damage in bone-marrow cells of mice and chinese hamsters exposed in vivo to some ergot derivatives.	a known chemical mutagen (trenimon, bayer), and three ergot derivatives (ergotamine tartrate, dihydroergotoxine mesylate, and methysergide hydrogen maleate) were tested in mice and chinese hamsters for mutagenic effects by means of the micronucleus test and the conventional chromosome method. in contrast to trenimon, which proved to be a powerful mutagen in these test systems, neither of the ergot derivatives showed an effect. it is concluded that these compounds, at subtoxic or therapeutic dose ...	1976	800380
the effects of serum concentration on the level of integration of simian virus (sv40) genome and the transformation frequency in sv40-infected chinese hamster cells.		1976	174291
induction by short-chain fatty acids of alkaline phosphatase activity in cultured mammalian cells.	short-chain fatty acids, such as propionic, n-butyric, n-butyric, n-valeric, isovaleric, n-caproic, and n-caprylic acids, induce alkaline phosphatase activity in cultured mammalian cells. long-chain fatty acids have no similar effects. with b-6 cells (mouse x chinese hamster cell hybrids), n-butyrate at 2 to 5 mm exhibits the greatest activity. induction begins exponentially about 24 hours after addition of the fatty acid and continues over 48 hours. studies on the inducing activity-structure r ...	1976	177433
enhanced sv 40-virus replication in chinese hamster kidney cells pretreated with 5-iodo-2'-deoxyuridine.	sv40 virion production was enhanced when semipermissive chinese hamster kidney cells were treated with 5-iodo-2'-deoxyuridine (iudr), prior to infection either with virus or viral-dna. pretreatment did not increase sv40 replication in fully permissive monkey kidney and nonpermissive syrian hamster or mouse embryo cells.	1976	176975
assignment of the ak1:np:abo linkage group to human chromosome 9.	in man-chinese hamster somatic cell hybrids the segregation patterns of the loci for 25 human enzyme markers and human chromosomes were studied. the results provide evidence for the localization of the gene for adenylate kinase-1 (ak1) on chromosome 9. since the loci for the abo blood group (abo), nail-patella syndrome (np), and ak1 are known to be linked in man, the abo:np:ak1 linkage group may be assigned to chromosome 9.	1976	176661
chromosomally depleted interspecific hybrid cell clones selected with cytotoxic antisera: utilization in the study of control of murine leukemia virus host-range.	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 ...	1976	176536
persistent reovirus infection of cho cells resulting in virus resistance.	we obtained a persistently infected line of chinese hamster ovary cells by selection for resistance to reovirus infection. the cells were persistently infected by a population of viruses that were (i) cytopathic for parental chinese hamster ovary cells and (ii) similar to wild-type reovirus in molecular characteristics. the growth rate, plating efficiency, and morphology of the cells were altered. a large majority of the cells in the population were infected. there was no detectable interferon p ...	1976	176428
a novel chromosome abnormality in human neuroblastoma and antifolate-resistant chinese hamster cell lives in culture.	four cell lines, sk-n-sh, sk-n-mc, sk-n-be(2), and imr-32, established in vitro from tumor tissue of patients with neuroblastoma were analyzed by trypsin-giemsa banding methods. in two of the lines a large, abnormally staining chromosome region was observed. this "homogeneously staining region" (hsr) was considerably longer than any of the bands present in normal human cells and, as revealed by both g- and q-banding, stained with an intermediate intensity. it was located on chromosomes no 6, 10, ...	1976	62055
streptozotocin and renal amyloidosis in the syrian hamster.	in the syrian hamster, administration of the drug streptozotocin was associated with an increased incidence and severity of renal amyloidosis. some of the more severely affected animals showed a frankly nephrotic picture. although some of the diseased animals showed decreased levels of serum albumin, no other definite changes in serum proteins were noted, nor was there any evidence of glomerular immunoglobulin or immune complex deposition. none of the lesions previously found after administratio ...	1976	59551
antisera against electrophoretically purified tubulin stimulate colchicine-binding activity.	several rabbit antisera have been prepared against reduced and alkylated, electrophoretically purified tubulin isolated from chick brain. these antisera give a single precipitin line in ouchterlony double diffusion plates when tested against partially purified tubulin, and label specifically microtubule- and tubulin-containing structures, such as mitotic spindles, cilia, and vinblastine-induced crystals, in a variety of cells. the same antisera also display the unique ability to stimulate the co ...	1976	57619
chromosomal assignment of the gene for human red cell adenylate kinase (ak1) in man-chinese hamster somatic cell hybrids.		1976	192371
laboratory investigation of diarrhea in travelers to mexico: evaluation of methods for detecting enterotoxigenic echerichia coli.	a laboratory investigation was conducted on cultures collected from travelers before, during, and after a trip to mexico to characterize the etiology of traveler's diarrhea. four laboratory methods for detecting enterotoxigenicity of escherichia coli were evaluated: the infant mouse assay, the chinese hamster ovary (cho) cell assay, the y1 adrenal cell assay, and the rabbit ileal loop. although a number of common enteric pathogens were identified as a cause of traveler's diarrhea, including six ...	1976	180047
the selection of virus-resistant chinese hamster ovary cells.	we have selected chinese hamster ovary (cho) cells resistant to infection by encephalomycarditis (emc) virus. thus far, we have obtained five lines resistant to emc, all of which manifest different phenotypes. three of the five are not persistently infected with virus, while two lines produce infectious virus and grow in its presence. the nonpersistently infected lines exhibit different resistance profiles to the other viruses we have tested, and they are stable in nonselective growth conditions ...	1976	182382
simian virus 40-chinese hamster kidney cell interaction. ii. the semipermissivity of the cell system.	throughout in vitro passages, chinese hamster kidney (chk) cells progressively lost susceptibility to sv 40 virus infection while remaining continuously susceptible to viral dna infection. upon infection with sv 40 virus or viral dna, the chk cell line supported viral dna and virus replication at a low level. sv 40 transformed chk cell lines spontaneously produced small amounts of viral dna and virions. the percentage of virus-producing cells was low. various clones derived from each of these li ...	1976	176967
resting state in normal and simian virus 40 transformed chinese hamster lung cells.	normal cell deprived of amino acids or serum factors enter a resting state, whereas cells transformed by wild-type simian virus 40 do not. the ability to enter a resting state is temperature-sensitive (ts) in cells transformed by a tsa mutant of simian virus 40. we shown further: (i) that when complete medium is added to resting cells, the length of time until the onset of dna synthesis often exceeds the length of g1 in growing cells; (ii) that the length of this interval depends upon the condit ...	1976	179093
mutagenesis by simian virus 40. i. detection of mutations in chinese hamster cell lines using different resistance markers.	the mutagenic action of sv40 in permanent lines of chinese hamster cells (cho-k1 and v79) was investigated with the aid of different resistance markers. the markers studied had resistance to 8-azaguanine (25 and 30 mug/ml), aminopterin (3.3--5.5x10(-3) mug/ml), colchicine (6.5 and 7.0x10(-2) mug/ml) and 5-bromodeoxyuridine (50--120 mug/ml), respectively. after virus infection the mutation frequencies were increased by one (azaguanine, aminopterin) and two (colchicine) orders of magnitude as comp ...	1976	184380
ultrastructural study of the adenohypophysis of the chinese hamster.	the adenohypophysis of normal chinese hamsters of both sexes was examined ultrastructurally. organs were fixed by intravascular perfusion with s-collidine-buffered glutaraldehyde solution. seven types of cells were differentiated and, according to morphological characteristics, classified as (1) mammotropes, with very large (400-800 nm) polymorphous secretory granules; (2) somatotropes, either in the storage phase with numerous large, dense granules (average 300 nm), or in the hormone synthesis ...	1976	184639
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	185012
chromosomal assignment of the gene for human red cell adenylate kinase (ak1) in man-chinese hamster somatic cell hybrids.		1976	185020
simian virus 40 mutants carrying two temperature-sensitive mutations.	five temperature-sensitive mutants of simian virus 40 containing two temperature-sensitive mutations were isolated. the double mutant of the a and d complementation groups, like the d mutants, failed to complement by conventional complementation analysis and did not induce host dna synthesis at 40 degrees c. however, under conditions that suppressed the d defect, the a:d double mutant expressed only the a defect. thus, viral dna replication dropped rapidly after this mutant was shifted from perm ...	1976	185417
[transmission and expression of malignancy in somatic hybrid cell lines (hamster/hamster, mouse/mouse, hamster/mouse)].	various characteristics of transformation were studied in subclones isolated from a hybrid cell line obtained by fusion of two chinese hamster sub-lines having the same origin but presenting different properties, particularly in respect to heterotransplantability. different subclones were obtained by cloning on semisoft agar. transplantability, plating efficiency, agglutinability by concanavalin a and actinomycin d resistance were studied in parallel with the evolution of the karyotype to try to ...	1976	186142
transformation of chinese hamster embryo cells with an avian sarcoma virus ts mutant.	chinese hamster embryo cells were transformed with temperature-sensitive mutant of the schmidt-ruppin strain of rous sarcoma virus-subgroup a (ts ny68s ra-a). the developed cell line elicited the morphological transformation at a permissive temperature of 35 degrees c, whereas after a shift to a non-permissive temperature of 40 degrees c the cells reverted to a normal phenotype. tests for the presence of avian sarcoma group-specific antigen showed that the antigen was not expressed both at permi ...	1976	186335
evolutionary trends in 18s ribosomal rna nucleotide sequences of rat, mouse, hamster and man.	the large t1 ribonuclease fragments of 18s ribosomal rna from four mammalian species, rat, mouse, hamster and man, were compared by two-dimensional homochromatography fingerprinting. the nucleotide sequences of the large t1 ribonuclease fragments, polypyrimidines and polypurines which were different among the four mammalian species were determined and compared. the method used for determining nucleotide sequences utilizes 32p-labeling of oligonucleotides at their 5'-termini by polynucleotide kin ...	1976	188015
enterotoxin testing of escherichia coli causing epidemic infantile enteritis in the u.k.	three test systems were used to study enterotoxin production by epidemic strains of escherichia coli from cases of infantile enteritis in well-documented outbreaks in the u.k. the tests used were the y1-mouse-adrenal-cell test and the chinese-hamster-ovary-cell (c.h.o.) test for the detection of heat-labile enterotoxin and the infant-mouse test for the detection of heat-stable enterotoxin. all 6 outbreaks had been studied using full serotyping techniques and the results had been published. in ea ...	1976	55904
cell surface antigens. iv. immunological coorespondence between glycophorin and the a1 human cell surface antigen.	a stable human-chinese hamster ovary cell hybrid has been produced which, in addition to the complement of chinese hamster ovary (cho-k1) chromosomes, contains only one human chromosome, no. 11. the human cell-surface antigens whose expression is controlled by human chromosome 11, and are expressed by this hybrid, have been defined as the al immunogenetic complex. although one component of this immunogenetic complex (a1) is also expressed by human red blood cells, a second component (a2) is not. ...	1976	61843
ten model mutagens evaluated by the micronucleus test.	the following ten mutagenic compounds were subjected to the micronucleus bone marrow test (mnt) in the mouse: cyclophosphamide (ctx), thiotepa (tt), vincristin (vcr), colcemid (colc), adriamycin (am), bleomycin (bm), cytosin arabinoside (ara c), 6-mercaptopurine (6-mp), methotrexate (mtx) and 5-fluorouracil (5-fu). dose-effect curves were established for all compounds. with the exception of ctx, colc and am, the drugs also were subjected to chromosome analyses on chinese hamster fibroblasts in v ...	1976	64925
modified 5'-nucleotides resistant to 5'-nucleotidase: isolation of 3-(3-amino-3-carboxypropyl) uridine 5'-phosphate and n2, n2-dimethylguanosine 5'-phosphate from snake venom hydrolysates of transfer rna.	a procedure for the quantitative measurement of the o2'-methylnucleoside constitutents of rna has recently been developed in this laboratory (gray, m.w. can. j. biochem. 53, 735-746 (1975)). this assay method is based on the resistance of o2'-methylnucleoside 5'-phosphates (pnm) (generated by phosphodiesterase hydrolysis of rna) to subsequent dephosphorylation by venom 5'-nucleotidase (ec 3.1.3.5). in the present investigation, two base-modified 5'-nucleotides, each displaying an unusual resista ...	1976	6133
the production of chinese hamster interferon.		1976	11678
the electrophoretic properties and aggregation of mouse lymphoma cells, chinese-hamster fibroblasts and a somatic-cell hybrid.	1. the electrophoretic mobilities of a mouse lymphoma cell, a chinese-hamster fibroblast and a somatic-cell hybrid (also fibroblastic), produced by fusion of the hamster cell and a mouse lymphoma cell, were measured at 25 degrees c over a range of ph, concentration of ca2+ ions and concentration of la3+ ions. 2. all the cells have pi at ph3.5. 3. ca2+ ions decrease the mobilities and zeta potentials of the cells to zero in the range 1-100mm. 4. la3+ ions lower the mobilities and zeta potentials ...	1976	12752
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