PMID(sorted ascending)
regional asssignments of the loci ak3, acons, and ass on human chromosome 9.experiments are described in which human cells carrying balanced reciprocal translocations involving four different regions of chromosome 9 were fused with a chinese hamster cell line and the resulting hybrids used to obtain subchromosomal assignments of the loci ass, ak3, and acons. ass was localized on the distal portion of the long arm of chromosome 9, in the region 9q34 leads to 9qter, and ak3 and acons on the short arm, in the region 9pter leads to 9p13.1979219990
calcium-mediated cell surface changes in chinese hamster cells. 1979220066
coordinate overproduction of orotate phosphoribosyltransferase and orotidine-5'-phosphate decarboxylase in hamster cells resistant to pyrazofurin and 6-azauridine.cells resistant to pyrazofurin and 6-azauridine have been selected from a simian virus 40-transformed syrian hamster line and from a chinese hamster lung line. by increasing the concentrations of inhibitors in several steps, mutant cells from both lines have been obtained which resist high concentrations (1 to 5 mm) of the two inhibitors separately or together. orotidine-5'-phosphate decarboxylase (ec, the sixth and last enzyme in ump biosynthesis, is inhibited by the nucleoside monoph ...1979220255
karyology and tumorigenicity of a simian virus 40-transformed chinese hamster cell clone.a pseudodiploid clone of chinese hamster cells tranformed in vitro with simian virus 40 (sv40) was isolated from soft agar and injected into nude mice through three successive passages with a short in vitro cultivation between each animal inoculation. the original clone and the three subsequent tumor populations were characterized in regard to sv40 t antigen staining, modal chromosome number, and giemsa-banded karyotype. all tumor cell lines maintained the pseudodiploid mode, as well as the posi ...1979220269
biochemical genetic analysis of pyrimidine biosynthesis in mammalian cells. ii. isolation and characterization of a mutant of chinese hamster ovary cells with defective dihydroorotate dehydrogenase (e.c. activity.a mutant (a204) of chinese hamster ovary cells (cho-k1), which is deficient in dihydroorotate (dho) dehydrogenase (e.c. 1.3,3.1) activity, has been isolated by a replica plating procedure. the mutant does not show a requirement for exogenously added pyrimidines. examination of intact cells shows that the mutant accumulates a large amount of carbamyl aspartate and is markedly but not totally deficient in biosynthesis of orotate from earlier precursors of pyrimidine biosynthesis, including asparta ...1979220270
diethyldithiocarbamate enhancement of radiation and hyperthermic effects on chinese hamster cells in vitro. 1979220663
gonadotropin stimulation of cyclic amp levels in chinese hamster ovary cells in culture.when chinese hamster ovary (cho) cells, incubated in serum-free medium, are exposed to gonadotropins a transient increase in the intracellular concentration of cyclic amp is observed. maximum accumulation of cyclic amp is noted 30 minutes after addition of either human chorionic gonadotropin (hcg) or follicle stimulating hormone (fsh). within one to two hours after hormone addition, the intracellular concentrations of cyclic amp have returned to basal levels. the enhancement of intracellular cyc ...1979222777
organotropic mutagenesis in tissues of chinese hamsters induced by chemical order to investigate the relationship between mutation and carcinogenesis in vivo, a method has been developed in which somatic mutation can be studied in specific organs of chinese hamsters after acute dosing with chemical carcinogens. in preliminary experiments an increase in mutation was detected in cultures derived from lung tissue of hamsters after intraperitoneal dosing with the direct-acting mutagen and weak carcinogen, ethyl methanesulphonate, or with diethylnitrosamine, a carcinogen ...1979223525
the roles of the simian virus 40 tumor antigens in transformation of chinese hamster lung cells.simian virus 40 mutants and deletions between 0.54 and 0.59 map units direct the synthesis of defective 20k t antigens (crawford et al., 1978). these deletion mutants transformed actively growing chl cells nearly as efficently as did wild-type virus, in either the focus formation assay or the growth in soft agar assay. in contrast, when chl cells were in a resting state during infection, the transformation frequency of the mutants relative to wild-type dropped approximately 50 fold. the presence ...1979225037
extension of branching processes from hybrids of brain and chinese hamster ovary cells. 1979225185
loss of epidermal growth factor requirement and malignant transformation.serum provides growth factors that regulate and limit the growth of normal cells in tissue culture. animal cells that are malignantly transformed usually exhibit diminished serum requirements for growth in culture. we have used a defined, serum-free medium to determine which of these growth factors becomes dispensable for the growth of transformed syrian and chinese hamster fibroblast cells. the medium's four growth factors-epidermal growth factor (egf), insulin, fibroblast growth factor, and tr ...1979226990
chinese hamster ovary cell population density affects intracellular concentrations of calcium-dependent regulator and ability of regulator to inhibit adenylate cyclase activity.the adenylate cyclase activity [atp pyrophosphate-lyase (cyclizing), ec] of crude chinese hamster ovary cell membranes was inhibited 30-40% by low concentrations (6-600 ng/ml) of calcium-dependent regulator (cdr). this inhibitory effect was lost at concentrations of cdr above 600 ng/ml. the adenylate cyclase activity of membranes prepared from low population density chinese hamster ovary cells was not appreciably altered by cdr. however, with increasing cell population density there was ...1979226991
a nutritional test for the low density lipoprotein receptor in chinese hamster fibroblasts. 1979227721
enhanced proliferation of endogenous virus in chinese hamster cells associated with microtubules and the mitotic apparatus of the host cell.chinese hamster ovary cells harbour intracytoplasmic virus-like particles of type a which are closely associated with sites of microtubule formation. we report here the enhanced proliferation of these particles and their release at the cell membrane by using either 5-bromodeoxyuridine or dibutyryl cyclic amp. the extracellular mature particles are similar in morphology to retroviruses of type b. close association of the type a virus precursors with microtubule organizing centres, i.e. kinetochor ...1979228000
escherichia coli heat-labile enterotoxin: dna-directed in vitro synthesis and structure.escherichia coli heat-labile enterotoxin was synthesized in a cell-free system directed by dna of the plasmid p307. synthesis of the toxin, assayed by the elongation induced in chinese hamster ovary cells, was strongly stimulated by cyclic amp and occurred at physiological levels of mg2+ only when the polyamine spermidine was present. activity was abolished by heat and antisera prepared against the enterotoxins of both e. coli p263 and vibrio cholera. tritium-labeled enterotoxin was purified by ...1979228267
rate limitation of (na+ + k+)-stimulated adenosinetriphosphatase by membrane acyl chain ordering.a somatic cell mutant (cr1) of the chinese hamster ovary cell line (cho-k1) that is defective in the regulation of cholesterol biosynthesis can be grown under conditions in which plasma membranes from these cells display various cholesterol contents and acyl chain order parameters. the (na+ + k+)-stimulated adenosinetriphosphatase (atp phosphohydrolase, ec from these cells was shown to vary in activity by a factor of 10 as the order parameter was varied, and the activity exhibited an ex ...1995228269
roles of the simian virus 40 tumor antigens in transformation of chinese hamster lung cells: studies with simian virus 40 double mutants.simian virus 40 mutants containing both a tsa mutation (rendering the 90,000 molecular weight [90k] t-antigen thermolabile) and a deletion between 0.54 and 0.59 map units (reducing the size and the amount of the 20k t-antigen) were used to transform chinese hamster lung cells. the frequencies of transformation by the double mutants were comparable to that of the tsa mutant alone by both the focus and agar assays except when the cells were serum depleted before infection. growth-arrested cells we ...1979229242
endogenous cyclic amp does not modulate transport of hexoses, nucleosides, or nucleobases in chinese hamster ovary a previous study we have demonstrated that neither extracellular nor intracellular cyclic adenosine monophosphate (amp) levels directly affect the uptake of nucleosides, nucleobases, or hexoses by various types of cultured mammalian cells. uptake of these nutrients into cells, however, involves two processes operating in tandem: facilitated transport across the membrane and intracellular phosphorylation; and uptake rates generally reflect the rates of substrate phosphorylation rather than of ...1979230391
enhancement of oxygen toxicity by diethyldithiocarbamate on chinese hamster and mouse cells. 1979231599
expression of galactose-1-p-uridyltransferase in chinese hamster x human galactosemia somatic cell hybrids.lymphocytes from a patient with classic galactosemia (galt deficiency) were hybridized with a chinese hamster cell line. electrophoretic valuation of galt in 31 independently derived interspecific hybrid clones failed to demonstrate expression of the human galt gene even when human chromosome 9 was present. possible mechanisms for this lack of expression are presented.1979231967
quantitative electron microscopy of intracytoplasmic type a particles at kinetochores of metaphase chromosomes isolated from chinese hamster and murine cell lines.we have successfully isolated and spread individual chromosomes of cho-ki cells for electron microscopic karyotyping. controlled preparation permitted a quantitative evaluation of the association between endogenous intracytoplasmic type a virus precursor particles and the centromeric region (kinetochores) of isolated chromosomes at prophase and metaphase. our results suggest the transfer of type a particles from the cytoplasmic to the centromeric regions during early metaphase in conjunction wit ...1979232135
expression of simian virus 40 gene a affects tubulin stability.the stability of tubulins present in crude extracts of untransformed balb/c-3t3 mouse fibroblasts, chinese hamster lung cells, and various of their simian virus 40 transformants was assessed by measurement of their individual colchicine-binding decay rates. in all cases studied the decays followed the kinetics of first-order reactions, and rates were reduced at low temperatures and by vinblastine sulfate. under all assay conditions, including different temperatures and protein concentrations, t ...1979232186
in vitro transformation of primary chinese hamster cells by minichromosomes from simian virus 40.purified sv 40 dna and sv 40 minichromosomes, either isolated from sv 40 infected cells (nami) or reconstituted from viral dna and the h1 depleted calf thymus histone fraction (remi), were tested for their ability to transform primary chinese hamster lung (chl) cells. using the agar suspension technique as the transformation assay, an approximately 200 fold increase in transformation activity for nami in comparison with the sv 40 dna and an approximately 50 fold increased activity in comparison ...1979232409
increased mutation rates in doubly viral transformed chinese hamster untransformed parental chinese hamster cell line, one polyoma transformed clone, and two clones containing both sv40 and polyoma dna were tested for the appearance of variants resistant to 6-thioguanine or oubain. the frequency of such variants was found to be highest in doubly transformed cells. the mutation rate at these loci was correlated with the level of transformation. the mutants observed were stable and had low reversion frequencies with no gross cytogenetic changes. these results es ...1979232576
difference in renal alpha-galactosidase levels in male and female chinese hamsters (cricetulus griseus).1. the activity of alpha-galactosidase was found to be significantly higher in the kidney of female than that of male chinese hamsters in a highly inbred colony but its activity in liver, heart and spleen remained similar between female and male animals. 2. partially purified renal alpha-galactosidase by sequential column chromatography on sepharose 6b and deae-sepharose cl-6b showed identical elution profiles, ph optima (4.5), kms (4.4 mm) and heat-inactivation curves between enzymes of male an ...1978233797
acid glycohydrolase in chinese hamster (cricetulus griseus) with spontaneous diabetes--v. subcellular distribution in the kidney.1. seven renal glycohydrolases were measured in four subcellular fractions prepared from highly inbred aglycosuric (av-line) and glycosuric (xa-line) chinese hamsters. 2. alpha-d-galactosidase and beta-d-galactosidase were highest in the nuclear (n) and supernatant (s) fractions; both fractions showed reduced activities in the xa animals. 3. alpha-d-mannosidase was chiefly a particulate enzyme and its decrease in xa animals was evident in n, lysosomal-mitochondrial (lm) and mitochondrial-microso ...1979233812
effects of asbestos on epithelioid cell lines.the in vitro effects of asbestos fibers on the growth and viability of cho cells, an epithelioid cell line derived from chinese hamster ovary, and on k-22 cells, an epithelial cell line derived from rat liver, have been studied. relatively low concentrations of asbestos (10 micrograms/ml) were quite cytotoxic to both cell types. a sample of chrysotile asbestos was more toxic than samples of crocidolite or amosite. the toxic factor could not be extracted from the asbestos and toxicity occurred on ...1978233816
immunochemical evidence for glutamine-mediated degradation of glutamine synthetase in cultured chinese hamster cells.the specific activity of glutamine synthetase in cultured chinese hamster cells is inversely related to the concentration of glutamine in the surrounding solution. enzyme specific activity increases 8- to 10-fold when glutamine is removed from serum-free f12 growth media. the induction of glutamine synthetase activity occurs only after glutamine removal and not after the removal of other amino acids (methionine, leucine, or isoleucine). the analysis of the glutamine-mediated decrease in glutamin ...1975234454
cell-cycle-dependent phosphorylation of serine and threonine in chinese hamster cell f1 histones. 1975235918
radiosensitization of cultured mammalian cells by 5-iodouridine.radiosensitization of cultured mammalian cells was studied with halogenated pyrimidines, such as 5-iodouridine or 6-chloropurine, which have been shown to promote bacterial cell lethality when combined with gamma-irradiation. when chinese hamster cells were exposed to gamma-rays to acidic ph values and the number of colonies was scored after 6 to 11 days of incubation, many more cells were inactivated in the presence of the drug than in its absence. this may be due to radiation-induced cytotoxic ...1975236986
length distributions of single-stranded dna in chinese hamster ovary cells. 1975239245
interaction of phospholipid vesicles with cultured mammalial cells. i. characteristics of uptake.the interaction of monolayer cultures of chinese hamster v79 cells with artificially generated, unilamellar lipid vesicles (approximately 500 a diameter) was examined. vesicles prepared from a variety of natural and synthetic radiolabeled phosphatidyl cholines (lecithins) were incubated with v79 cells bathed in a simple balanced salt solution. after incubation, the cells were analyzed for exogenous lipid incorporation. large quantities (approximately 10(8) molecules/cell/h) of lecithin became ce ...1975240860
a system for studying effects of microwaves on cells in improved design of the fluid-filled waveguide-exposure chamber is described for studying effects of microwave radiation on cells in vitro. the system with a micropipette sample holder may be used as a prototype to isolate the apparent nonthermal factor of microwave radiation on cells in culture from those effects resulting from cell temperature rise. this system also allows more precise calibration of incident and absorbed microwave energies. compared with control, somatic cells of the chines ...1978255162
transfer rna isoacceptors in cultured chinese hamster ovary cells. 1979255210
relationship between histidyl-trna level and protein synthesis rate in wild-type and mutant chinese hamster ovary cells.a preliminary investigation was carried out to determine how conditional lethal mutants affected in particular aminoacyl-trna synthetases may be used to study the role of trna charging levels in protein synthesis. the relationship between rate of protein synthesis and level of histidyl-trna in wild-type cultured chinese hamster ovary cells was determined using the analogue histidinol to inhibit histidyl-trna synthetase activity. this response was compared with that obtained using a mutant strain ...1979256567
human gene mapping and cancer biology.the topics covered in this paper include: (i) a somatic cell genetics approach for measuring the individual variability in the susceptibility to dna damage/repair at the level of specific chromosomal sites; (ii) a rationale for a selective chemotherapy and/or immunotherapy of chromosomally unbalanced tumours; and (iii) studies on complementation for sister chromatid exchange (sce) in roden-human hybrids. preliminary studies indicate that the 'radiation co-transfer method' for gene mapping can be ...1979258171
changes in repair competency after 5-bromodeoxyuridine pulse labeling and near-ultraviolet light.synchronized v79 chinese hamster cells, pulse-labeled with 5-bromodeoxyuridine (brdurd), show marked changes in the sensitivity to near-ultraviolet light during the cell cycle. cells are least sensitive during the remainder of the s-phase after the brdurd pulse. they become maximally sensitive in the next cell cycle when the brdurd-labeled dna presumably serves as the template for replication. this is followed by a return to relative insensitivity during the remainder of the s-phase, the increas ...1979262378
x-ray response of chinese hamster ovary cells during the latter part of g2.the ability of chinese hamster ovary (cho) cells to repair x-radiation damage during the transit from the late g2 to early m cell cycle stages was investigated by conventional dose-fractionation techniques. despite their relatively high radiation sensitivity, cho cells positioned in late g2 exhibit increased survival when a given dose of ionizing radiation is administered as two fractions (separated by 40-50 min) instead of as a single fraction. this increased survival apparently represents repa ...2003262563
functional correlation between cell adhesive properties and some cell surface proteins.the adhesive properties of chinese hamster v79 cells were analyzed and characterized by various cell dissociation treatments. the comparisons of aggregability among cells dissociated with edta, trypsin + ca2+, and trypsin + edta, revealed that these cells have two adhesion mechanisms, a ca2+-independent and a ca2+-dependent one. the former did not depend on temperature, whereas the latter occurred only at physiological temperatures. both mechanisms were trypsin sensitive, but the ca2+-dependent ...1994264120
microcell-mediated transfer of murine chromosomes into mouse, chinese hamster, and human somatic this report, we describe the production and characterization of proliferating hybrid cell populations generated by fusion of murine microcells with intact mouse, chinese hamster, and human recipient cells. the microcell hybrids so produced contained one to five intact murine chromosomes derived from the microcell donor. these transferred chromosomes were maintained as functioning genetic elements in the hybrid cells. our results firmly establish subnuclear particle-mediated chromosome transfe ...1977264685
assignment of the major histocompatibility complex to a region of the short arm of human chromosome 6.interspecific cell hybrids containing defined parts of human chromosome 6 were used for regional mapping of gene loci previously assigned to chromosome 6: the human leukocyte antigens (hla) region, phosphoglucomutase-3 (pgm3; alpha-d-glucose-1,6-bisphosphate:alpha-d-glucose-1-phosphate phosphotransferase, ec and malic enzyme-1 [malic dehydrogenase(decarboxylating) (nadp+), l-malate:nadp+ oxidoreductase (oxaloacetate-decarboxylating), ec]. human fibroblasts containing a balanced ...1977265561
isolation and partial characterization of a cholesterol-requiring mutant of chinese hamster ovary cells.a sterol-requiring mutant has been isolated from mutagenized chinese hamster ovary cells. this mutant grows normally only when cholesterol is present in the medium. cell lysis occurs within 3 days in the absence of cholesterol. the frequency of reversion of this mutant to prototrophic growth is low (less than or equal to 10(-6). whole cell pulse experiments with [14c]acetate or [3h]mevalonate indicate that the rate of synthesis of digitonin-precipitable material is greatly diminished in the muta ...1993265577
absence of a measurable g2 phase in two chinese hamster cell lines.evidence is presented that demonstrates the absence of a measurable g2 phase in the cell cycles of two sublines of the chinese hamster lung fibroblast v79. one of the sublines, in addition, lacks a detectable g1 phase, thereby possessing a cell cycle comprised of simply two phases, dna synthesis (s) and mitosis (m).1977266201
microvascular lesions of gingival and cheek pouch tissue in the diabetic chinese hamster. 1977266583
serial transfer of a human gene to rodent cells by sequential chromosome-mediated gene transfer.the human hypoxanthine phosphoribosyl-transferase (imp:pyrophosphate phosphoribosyltransferase, ec gene (hprt) has been serially transferred to mouse cells and then to chinese hamster fibroblasts by two cycles of metaphase chromosome isolation and incubation with recipient cells. human metaphase chromosomes were incubated with mouse a9 cells deficient in hypoxanthine phosphoribosyltransferase, and independent colonies expressing the human species form of this gene were isolated in a sel ...1977268645
transfer of codominant markers by isolated metaphase chromosomes in chinese hamster ovary cells.codominant mutations to methotrexate and ouabain resistance in chinese hamster ovary cells can be transferred to recipient chinese hamster ovary cells by isolated metaphase chromosomes. for methotrexate, both the structural change and the increased activity of dihydrofolate reductase (5,6,7,8-tetrahydrofolate:nadp+ oxidoreductase ec, characteristic of the donor cells, are observed in the transferents (cells that carry and express functions derived by chromosome transfer). the transferen ...1977269408
stable association of the human transgenome and host murine chromosomes demonstrated with trispecific microcell hybrids.trispecific microcell hybrids were prepared by transferring limited numbers of chromosomes from a human/mouse gene-transfer cell line to a chinese hamster recipient line. the donor cells employed were murine l-cells that stably expressed the human form of the enzyme hypoxanthine phosphoribosyltransferase. karyotypic, zymographic, and back-selection tests of the resulting human/mouse/chinese hamster microcell hybrids provided strong genetic evidence for a stable association of the human transgeno ...1977269444
selective loss of wheat germ agglutinin binding to agglutinin-resistant mutants of chinese hamster ovary cells.the binding of 125i-labeled wheat germ agglutinin (wga) to parental and three distinct wga-resistant chinese hamster ovary cell lines possessing modified cell surface carbohydrate structures has been examined over a 10(6)-fold range of wga concentrations. the scatchard plot for wga binding to parental cells was complex and exhibited positively cooperative binding at the high affinity sites. one of the wga-resistant mutants (wgariii) was apparently not altered in its wga-binding ability compared ...1977270740
assignment of the human gene for galactose-1-phosphate uridyltransferase to chromosome 9: studies with chinese hamster-human somatic cell hybrids.chinese hamster-human somatic cell hybrids were analyzed for the expression of human galactose-1-phosphate uridyltransferase (galt; udpglucose:alpha-d-galactose-1-phosphate uridyltransferase, ec by electrophoresis and for the presence of human chromosomes cytogenetically with the aid of q-banding. three of the 10 randomly chosen independently derived primary hybrid lines showed the presence of human galt. human chromosome 9 was consistently present in the hybrid lines expressing human ...1977271990
diphtheria toxin has the properties of a lectin.the inhibition of protein synthesis in chinese hamster v79 cells by diphtheria toxin is antagonized by the lectins concanavalin a, succinylated concanavalin a, and wheat germ agglutinin but not by proteus vulgaris phytohemagglutinin or abrus agglutinin. the effects of concanavalin a and wheat germ agglutinin are reversed by methyl alpha-mannoside and n-acetylglucosamine, respectively. the inhibition of diphtheria toxin as a function of concanavalin a concentration fits a model of competitive inh ...1978272642
temperature-sensitive rna polymerase ii mutations in chinese hamster ovary cells.mutant chinese hamster ovary cell lines temperature-sensitive (ts) for growth and containing ts mutations in rna polymerase ii (nucleosidetriphosphate:rna nucleotidyltransferase, ec have been isolated. wild-type cells were treated with the mutagen n-methyl-n'-nitro-n-nitrosoguanidine and a population of cells possessing mutations in rna polymerase ii was initially selected by isolating alpha-amanitin-resistant clones at 34 degrees . of 168 such alpha-amanitin-resistant isolates screened ...1983272657
electrophoretic shift mutants in chinese hamster ovary cells: evidence for genetic diploidy.electrophoretic shift mutants induced in chinese hamster ovary (cho) cells indicate that these cells not extensively functionally hemizygotic. therefore, effective haploidy is unsatisfactory as a general theory to explain the frequency of recessive mutants in this cell line. cho cells were screened for electrophoretic shift variants of enzymes coded by approximately 40 genetic loci. clones isolated after exposure to ultraviolet radiation were examined by starch gel and cellogel electrophoresis. ...1981273919
defective regulation of cholesterol biosynthesis and plasma membrane fluidity in a chinese hamster ovary cell mutant.a chinese hamster ovary cell mutant resistant to killing by 25-hydroxycholesterol is shown to be defective in the regulation of cholesterol synthesis by exogenous cholesterol. when grown with various cholesterol supplements in delipidized serum, the mutant cell exhibits a variation in cholesterol content and plasma membrane fluidity that is not observed in the parental cell type.1978274716
inverted repeated dna from chinese hamster ovary cells studied with cloned dna fragments.fragments from the dna of chinese hamster ovary cells produced by restriction endonuclease ecori were cloned in charon 16a lambda bacteriophage and examined for the ability to hybridize in situ with 32p-labeled double-stranded regions from heterogeneous nuclear rna (hnrna). of 235 clones tested, 87 (37%) contained sequences that hybridized with the double-stranded hnrna. nine of these were examined for the presence of inverted repeat dna structures (ir-dna) by electron microscopy. all nine conta ...1978275835
genetic analysis of the g1 period: isolation of mutants (or variants) with a g1 perior from a chinese hamster cell line lacking g1.cells of the chinese hamster line v79-8 multiply without a g1 period (i.e., they are g1(-)) and have an average generation time of 9.5 hr. after mutagenesis and selection we have derived five stable mutants (or variants) of this line that have longer generation times. in each case the increase in generation time is due solely to the introduction of a g1 period into the cell cycle, with no measurable effect on s, g2, or m. fusions among these five g1(+) mutant lines and another presumably nonmuta ...1978275858
ultrastructural study of the mitochondria in the skeletal muscle fibers in the diabetic chinese ultrastructural study of skeletal muscle fiber biopsies from the tongue and soleus muscle of diabetic chinese hamsters revealed the presence of lipid droplets within the muscle fibers. these droplets often were found in the cyptoplasm near mitochondira, sometimes inside or surrounded by one or more mitochondria. glycogen granules were found in great quantities in the cytoplasm of the tongue and soleus muscle. granules which appeared to be glycogen were also found within the mitochondria of th ...1967276592
tumorigenicity and its suppression in cybrids of mouse and chinese hamster cell lines.the effect of cytoplasm upon the expression of tumorigenicity was examined with a pair of mouse and a pair of chinese hamster cell lines, in intraspecies cybrids formed by reciprocal fusions between either tumorigenic or nontumorigenic cells and cytoplasms derived from them. with the mouse cells, 3t3 and the simian virus 40-transformed line svt2, the cybrid clones were tumorigenic when svt2 cells were fused with 3t3 cytoplasts, but not in the reciprocal fusion. with the hamster cells, chef/18 an ...1978276880
cytotoxic effect of 5-thio-d-glucose on chronically hypoxic cells in multicell spheroids.the effect of 5-thio-d-glucose on chronically hypoxic cells in the multicell spheroids of chinese hamster v79 cells was investigated. the radiation survival curves of spheroid cells indicated that most of the chronically hypoxic cells in the spheroids could be eliminated by incubating the spheroids with 5-20 mm of 5-thio-d-glucose or 17 hours. histological studies also demonstrated that 5-thio-d-glucose preferentially kills the hypoxic cells located in the inner part of the spheroids.1978277213
hypoxic cell sensitizers and heavy charged-particle radiations.stationary-phase populations of chinese hamster v-79 cells were irradiated with 250 kv x-rays and the bragg peaks (spread to a width of 4 cm) of energetic he-, c-, ne-, and a-ion beams produced at the 184-inch cyclotron and bevalac at lawrence berkeley laboratory. survival curves were generated with each radiation for cells suspended in air-saturated and nitrogen-saturated medium with and without sensitizer present. the oxygen enhancement ratios (oers) measured for x-rays with 1mm metronidazole ...1964277223
rapid-mixing studies of the mechanisms of chemical radiosensitization and protection in mammalial cells.a continuous flow, rapid-mixing system has been constructed to measure the degree of radiosensitization or protection observable after incubation of chinese hamster ovary cells at room temperature for periods from about 5 to 1000 ms with a number of radiation modifiers. in agreement with adams et al. (1975) full sensitization by oxygen is obtained in only a few tens of milliseconds. misonidazole (10 mm) sensitizes at very nearly the steady-state level (e.r. approximately 2.3) in about 300 ms. si ...1978277254
polyfunctional radiosensitizers iv. the effect of contact time and temperature on sensitization of hypoxic chinese hamster cells in vitro by bifunctional nitroxyl compounds.three biradical nitroxyl compounds have been shown to modify the slope and shoulder region of the hypoxic cell survival curve of v79 cells to different degrees. the amount of sensitization produced by these compounds is dependent on the cell-drug contact time at both 20 degree and 37 degree c whereas sensitization by the monoradical nitroxyl, nppn, is independent of these factors. the results suggest that biradicals may modify cellular biochemistry in such a way as to change the repair capacity ...1978277261
late s phase cells (chinese hamster ovary) induce early s phase dna labeling patterns in g1 phase nuclei.cells (chinese hamster ovary) in g1 phase were fused with cells in late s phase to determine if a cell in late s phase can induce dna synthesis in the nucleus of a g1 cell and, if so, to determine if the dna synthesis so induced in a g1 phase nucleus has an autoradiographic pattern characteristic of early or of late s phase synthesis. the results indicate (i) that 89% of the g1 nuclei in late-s/g1 binucleates synthesized dna, while only 2% of the control unfused g1 cells synthesized dna, and (ii ...1978277928
conjugation of methotrexate to poly(l-lysine) increases drug transport and overcomes drug resistance in cultured cells.methotrexate and [(3)h]methotrexate were conjugated through a carbodiimide-catalyzed reaction to a 70,000 molecular weight poly(l-lysine) in molar ratios of approximately 13 to 1. the cellular uptake of labeled conjugate was far in excess of the uptake of free drug in cells that were either proficient or deficient in methotrexate transport. the conjugate markedly inhibited the growth of pro(-)3 mtx(rii) 5-3 chinese hamster ovary cells, which are known to be drug resistant by virtue of a deficien ...1978279001
cell killing and kinetic effects of diglycolaldehyde on dividing and nondividing mammalian cells in vitro.the effects of the anticancer drug diglycolaldehyde (nsc-118994) were studied on chinese hamster ovary cells growing in vitro. dividing cells, specifically those in s-phase, were more sensitive to the drug than were nondividing cells, although a large fraction of nondividing cells was also killed by doses up to 800 microgram/ml. dose-dependent effects on cell progression kinetics were observed in all phases of the cell cycle except in mitosis, during which treated cells progressed at control rat ...1978280715
chimeric toxins: toxic, disulfide-linked conjugate of concanavalin a with fragment a from diphtheria toxin.a disulfide-linked conjugate of concanavalin a (con a) and fragment a from diphtheria toxin has been synthesized and shown to be toxic for hela (human), chinese hamster ovary (cho), and sv3t3 (murine) cells. the conjugate was constructed by first coupling cystamine to con a with a carbodiimide reagent and then reacting the modified con a with reduced fragment a under conditions promoting disulfide interchange. the desired conjugate, obtained in nearly 50% yield relative to input of fragment a, w ...1978281682
mammalian cell mutant requiring cholesterol and unsaturated fatty acid for growth.a mutant requiring both cholesterol and oleate for growth has been isolated from mutagenized chinese hamster ovary cells. by comparison with wild-type cells, sterol and unsaturated fatty acid biosynthetic activities in the mutant cells grown in fetal calf serum medium appear to be nearly intact. however, whole-cell radioactive acetate, mevalonate, dihydrolanosterol, and stearate incorporation studies show that sterol synthesis from acetate, lanosterol demethylation, and fatty acid desaturation a ...1978281693
amplified dihydrofolate reductase genes are localized to a homogeneously staining region of a single chromosome in a methotrexate-resistant chinese hamster ovary cell line.methotrexate-resistant chinese hamster ovary cells selected for high resistance by progressive increments of methotrexate in the culture medium have levels of dihydrofolate reductase (tetrahydrofolate dehydrogenase, 7,8-dihydrofolate: nadp+ oxidoreductase, ec 200 times that of sensitive cells and a corresponding increase in the number of copies of the dihydrofolate reductase gene. the resistant cells contain an expanded region on the second chromosome (homogeneously staining region) tha ...1978281704
cytoplasmic transfer of resistance to antimycin a in chinese hamster cells.a mutant subline of v79 chinese hamster cells resistant to antimycin a (ant) was obtained by treatment with ethyl methanesulfonate followed by serial selection in ant-containing medium. clonal derivatives of the resistant line are less susceptible than parent cells to growth inhibition by ant in mass populations and show a higher plating efficiency in graded levels of inhibitor. resistance to ant is stable in drug-free medium and follows a pattern of incomplete dominance in hybrids between resis ...1978281710
actinomycin d inhibits initiation of dna replication in mammalian cells.mammalian (chinese hamster ovary) cells were synchronized in the division cycle and blocked at the beginning of s phase with fluorodeoxyuridine. traces of thymidine in the medium allowed cells to enter s phase and initiate dna replication at some origins. for many hours after the traces of thymidine were depleted new sites for dna replication accumulated in a small fraction of the dna. however, these potential origins became active in bidirectional replication only when cells were released by ad ...1978282626
karyotype and tumorigenicity of 1-methylguanine-transformed chinese hamster cells.chinese hamster embryo cells transformed with the trna catabolite 1-methylguanine were characterized by giemsa-banded karyotyping and by their tumorigenic potency in athymic nude mice. all seven 1-methylguanine-transformed cell lines were hyperdiploid with a modal chromosome number of 23. three of these lines had an additional marker chromosome derived from the long (q) arm of chromosome no. 4, and they had alterations of chromosome no. 5 as well. two of these three cell lines were tumorigenic. ...1979283292
induction of ornithine decarboxylase activity in a temperature-sensitive cell cycle mutant of chinese hamster cells.we have investigated the induction of ornithine decarboxylase (l-ornithine carboxy-lyase, ec activity in a temperature-sensitive cell cycle mutant of chinese hamster fibroblasts. this activity is not induced at the nonpermissive temperature, although the synthesis of the majority of proteins is normal. from a combination of studies with inhibitors of mrna synthesis and maturation (alpha-amanitin, and cordycepin) and of proteins synthesis (cycloheximide, diphtheria toxin, and emetine), ...1978283409
inducers of dna synthesis present during mitosis of mammalian cells lacking g1 and g2 phases.the cell cycle analysis of chinese hamster lung fibroblast v79-8 line by the premature chromosome condensation method has confirmed the absence of measurable g1 and g2 periods. sendai virus-mediated fusion of mitotic v79-8 cells with g1 phase hela cells resulted in the induction of both dna synthesis and premature chromosome condensation in the latter, indicating the presence of the inducers of dna synthesis above the critical level not only throughout s phase, as it is in hela, but also during ...1978283413
emetine resistance in chinese hamster cells is linked genetically with an altered 40s ribosomal subunit protein, s20.emr-2 is an emetine-resistant (emr) chinese hamster ovary cell mutant that contains a single electrophoretically altered ribosomal protein, a component of its 40s ribosomal subunit [boersma, d., mcgill, s., mollenkamp, j. & roufa, d.j. (1979) j. biol. chem. 254, in press]. this report describes a genetic experiment designed to test linkage between the genes that specify the altered ribosomal protein, s20*, and emetine resistance in emr clones that segregated from cultures of emr-2 cells hybridiz ...1979284357
measurement of mutagenesis in mammalian cells.a method using mammalian cells in vitro for detection and quantitation of mutagenic actions that appears to be useful for screening for carcinogenesis and genetic damage by environmental agents is presented. the method involves use of stable human--chinese hamster ovary hybrid cells that have retained a single human chromosome not necessary for cell reproduction. forward mutations are detected in genes necessary for production of specific human cell surface antigens. such mutants form colonies i ...1979286318
dna-mediated transfer of the adenine phosphoribosyltransferase locus into mammalian this report, we demonstrate the feasibility of transforming mouse cells deficient in adenine phosphoribosyltransferase (aprt; amp:pyrophosphate phosphoribosyltransferase, ec to the aprt+ phenotype by means of dna-mediated gene transfer. transformation was effected by using unfractionated high molecular weight genomic dna from chinese hamster, human, and mouse cells and restriction endonuclease-digested dna from rabbit liver. the transformation frequency observed was between 1 and 10 ...1979286319
growth and morphology of colonies of chinese hamster ovary cells growing on agar is affected by a model for the effect of hormones and growth factors on three-dimensional growth of mammalian cells, we have analyzed the effect of insulin on the three-dimensional growth and morphology of chinese hamster ovary (cho) colonies grown on the surface of agar. sequential photographs in dark-field illumination of growing colonies have been analyzed with computer-assisted techniques. in this analysis the entire shape of each colony in a sizeable population (up to 10(5) colonies per experiment) can ...1979287027
isolation of lysosomal alpha-mannosidase mutants of chinese hamster ovary cells.a method is presented for detection of lysosomal hydrolase activity in situ in colonies of chinese hamster ovary cells. this method was used to screen for mutants deficient in lysosomal alpha-mannosidase. mutagenized cells were replicated onto filter papers [esko, j. d. & raetz, c. r. h. (1978) proc. natl. acad. sci. usa 75, 1190-1193] and allowed to divide for 11-14 days; cells on the filter replicas were lysed, and the filters were incubated with 4-methylumbelliferyl-alpha-d-mannopyranoside at ...1979287030
germ line integration of moloney leukemia virus: identification of the chromosomal integration site.the chromosomal integration site of the structural gene of moloney murine leukemia virus (m-mulv) in the genome of balb/mo mice was mapped genetically. these mice transmit the exogenous m-mulv as an endogenous virus at a single mendelian locus. two independent experimental approaches were used: (i) non-virus-producing fibroblasts prepared from homozygous balb/mo embryos were fused to chinese hamster wg3-h-o cells. in an analysis of 30 independent mouse-chinese hamster cell hybrid clones, the seg ...1979287034
codominant translational mutants of chinese hamster ovary cells selected with diphtheria toxin.diphtheria toxin-resistance markers in two translational mutants, ch-re1.22c, possessing no toxin-sensitive ef-2 (class iia), and ch-re1.32, with 50% toxin-sensitive and 50% toxin-resistant ef-2 (class iib), behaved codominantly in somatic cell hybrids. there was no complementation in hybrids formed between the two resistant mutants. the mutant parents and their hybrids, except those formed by fusion of ch-re1.32 and wild-type cells, grew in the presence of toxin. to explain these results we sug ...1979291128
genetic analysis of tumorigenesis: iv. chromosome reduction and marker segregation in progeny clones from chinese hamster cell hybrids.hybrid cells produced by the fusion of pairs of cells, one a tumorigenic derivative of chef/16 and the other a nontumorigenic derivative of chef/18, give rise to clones which are largely tetraploid, but rare reduced hybrids with chromosome counts in the diploid range have been recovered from tumors of hybrid origin. this paper describes the recovery in cell culture of reduced hybrids in the diploid range by selection with 5-bromodeoxyuridine (brdu) or methylcellulose as well as by growth in cult ...1979291130
assignment of the gene for cytoplasmic superoxide dismutase (sod-1) to a region of chromosome 16 and of hprt to a region of the x chromosome in the the search for homologous chromosome regions in man and mouse, the locus for cytoplasmic superoxide dismutase (sod-1; superoxide:superoxide oxidoreductase, ec is of particular interest. in man, the sod-1 gene occupies the same subregion of chromosome 21 that causes down syndrome when present in triplicate. although not obviously implicated in the pathogenesis, sod-1 is considered to be a biochemical marker for this aneuploid condition. using a set of 29 mouse-chinese hamster somatic ...1979291939
regional localization of human gene loci on chromosome 9: studies of somatic cell hybrids containing human translocations.somatic cell hybrids were derived from the fusion of (1) chinese hamster cells deficient in hypoxanthine guanine phosphoribosyltransferase (hprt) and human cells carrying an x/9 translocation and (2) chinese hamster cells deficient in thymidine kinase (tk) and human cells carrying a 17/9 translocation. several independent primary hybrid clones from these two series of cell hybrids were analyzed cytogenitically for human chromosome content and electrophoretically for the expression of human marke ...1979292306
resistance against cycloheximide in cell lines from chinese hamster and human cells is conferred by the large subunit of cytoplasmic ribosomes.cell lines from chinese hamster ovary [cho-k1-d3] and human fibroblast cells [46, xx, 18p-] were mutagenized with n-nitrosomethylurea followed by a selection for cycloheximide resistance. two mutants resistant against the drug were selected from either wildtype. 80s ribosomes and their ribosomal subunits were isolated from all mutant and wildtype cells. 80s ribosomes reassociated from the isolated subunits were as active as isolated 80s couples in the poly (u) dependent poly (phe) synthesis. hyb ...1979292826
organ-specific mutations in chinese hamsters induced by chemical carcinogens. 1979293496
hybrid mammalian cells assemble hybrid ribosomes.hybrid cell lines formed by fusion of mouse 3t3 cells and chinese hamster ovary (cho) cells resistant to emetine, which have an altered 40s ribosomal protein, are generally sensitive to emetine. from most hybrid lines it was possible to select sublines resistant to emetine. the ribosomal components of three lines were studied: a34, an emetine-sensitive hybrid; a34/r3, an emetine-resistant derivative of a34; and a72, an emetine-sensitive hybrid that did not give rise to emetine-resistant sublines ...1979293661
amplified dihydrofolate reductase genes in unstably methotrexate-resistant cells are associated with double minute chromosomes.selection of mammalian cells in progressively increasing concentrations of methotrexate results in selective amplification of dna sequences coding for dihydrofolate reductase (tetrahydrofolate dehydrogenase, 5,6,7,8-tetrahydrofolate:nadp+ oxidoreductase, ec in some cell variants the amplified genes are stable with growth in the absence of methotrexate, whereas in other variants the amplified genes are lost from the population. we have previously reported that in a stably amplified vari ...1979293670
disappearance of a structural chromatin protein a24 in mitosis: implications for molecular basis of chromatin condensation.a chromatin protein, a24, a conjugate of histone h2a and evolutionally conserved ubiquitin, was virtually the only structural polypeptide that was present in interphase but missing in mitosis of a chinese hamster cell line (don). because a 10% increase in the h2a/dna ratio observed in interphase-mitosis transition explained the stoichiometric conversion of a24 to h2a, it appears that ubiquitin bound to h2a of nucleosomal surfaces in interphase is released at mitosis whereas the total h2a remains ...1980293727
genetic and biochemical analysis of the a1 cell-surface antigen associated with human chromosome 11.a highly versatile system for genetic, biochemical, and immunological analysis of human cell surface components has been developed using a human-chinese hamster somatic cell hybrid containing chromosome 11 as its only human chromosome. this system lends itself to studies such as identification of human cell surface antigens and other genetic markers, regional gene mapping of these markers on chromosome 11, mutational analysis of these markers, and exploration of distribution of these antigens in ...1979293736
characterization of a mutator gene in chinese hamster ovary cells.we have recently reported the isolation of a class of mutants (called thy-) that is both resistant to arabinosyl cytosine and auxotrophic for thymidine. thy- mutants have a 5- to 10-fold elevated pool of dctp and are deficient in the synthesis of dttp as an apparent consequence of a single mutation in the gene for ribonucleoside-diphosphate reductase (2'-deoxyribonucleoside-diphosphate:oxidized-thioredoxin 2'-oxidoreductase, ec here we show that three independent thy- lines have a 5- ...1980293738
influence of crystallization habit of minerals on in vitro cytotoxicity.four samples of cummingtonite-grunerite series in various crystallization habits were tested in vitro. the cytotoxicity to chinese hamster ovary cells and hemolysis to sheep erythrocytes were inversely proportional to the structural faults and surface defects of the minerals. at a comparable surface area, asbestiform grunerite (uicc amosite), semi-asbestiform cummingtonite, acicular cummingtonite, and acicular grunerite were found to be cytotoxic and hemolytic in a decreasing order. the influenc ...1979294214
high frequency of mutation to tubercidin resistance in cho cells.the acquisition of high-level resistance to tubercidin (an adenosine analog) in cho cells occurs in a single step at high frequency (10(-3) to 10(-4)) without mutagenesis. analysis of a large number of independent mutants by a fluctuation test (luria and delbruk, 1943) indicates that they arise independently of the selection medium and all fall into the same complementation group. all mutants tested lack detectable adenosine kinase activity. an analysis of hybrids between mutant and wild-type ce ...1980294700
the effect of bromodeoxyuridine on the segregation of the chicken-specific hprt gene from chinese hamster-chick red blood cell somatic hybrids.the segregation of the chick-specific hprt gene was studied in three chinese hamster-chick red blood cell hybrid lines. the three lines showed individual segregation kinetics, the segregation taking place in an exponential-like fashion. bromodeoxyuridine becomes incorporated into the nuclear dna and increases the spontaneous segregation rate.1978299650
quantitative initiation of microtubule assembly by chromosomes from chinese hamster ovary cells.the microtubule nucleating capacity of chromosomes was tested in vitro in lysates of chinese hamster ovary cells. colcemid-blocked mitotic cells were lysed with the detergent triton x-100, incubated with exogenous porcine brain tubulin, attached to electron microscope grids and observed as whole-mounts. under suitable conditions, greater than 98% of the chromosomes gave rise to microtubules at their kinetochore regions, thus unequivocally demonstrating that chromosomes are competent to initiate ...1978299651
survival of synchronized v79 cells treated with x-rays and cordycepin.the survival of v79 chinese hamster lung cells exposed to x-irradiation is reduced by co-treatment with cordycepin (3'-deoxyadenosine). this reduction is manifested principally by a decrease in the d0 of the x-ray survival curve from 199 rad in untreated cells to 106 rad in cordycepin-treated cells. reduced survival is seen throughout the life-cycle when synchronized cell populations are exposed to both agents with cells in mid-s being especially sensitive.1977300368
rescue of marker phenotypes mediated by somatic cell hybridization.the effect of irradiation prior to virus-induced cell fusion on the frequency of hybrid production has been measured as a function of radiation dose. the chinese hamster line wg3h (hgprt-) was crossed with the tk- mutants; chinese hamster a23 or mouse 3t34e, and hybrids were selected in hat medium. irradiation of one (marker rescue) or both (mutual rescue) partners before fusion yielded qualitatively different results. after x-irradiation marker rescue curves were of single-hit type, with d0 val ...1977300369
additive action of ionizing and non-ionizing radiations throughout the chinese hamster cell-cycle. 1977300730
comparison of three mammalian cell-lines with respect to their sensitivities to hyperthermia, gamma-rays and u.v.-radiation.three types of cultured mammalian cells, from a rat ureter carcinoma (ruc-2), from a mouse mammary carcinoma (m8013), and from a chinese hamster lung cell-line (ch-v79), have been compared with respect to various treatments. using cloning assay, the sensitivity of these cell-lines was measured for ionizing radiation, u.v.-light and for temperatures of 41 degrees, 42 degrees, 43 degrees, 44 degrees and 45 degrees c. ruc-2 cells are the least sensitive to these treatments, except for 45 degrees c. ...1977301514
inactivation and mutation of cultured mammalian cells by aluminium characteristic ultrasoft x-rays. i. properties of aluminium x-rays and preliminary experiments with chinese hamster cells.irradiation with ultrasoft x-rays produces electron tracks of short defined lengths in the irradiated material. this property is of particular interest in distinguishing between different models of radiation action on living organisms. the production, absorption and dosimetry of aluminium k characteristic x-rays of energy 1.5 kev are described. quantitative experiments on mammalian cells with these x-rays are possible, and they were found to be considerably more effective than gamma-rays in inac ...1977301864
inactivation and mutation of cultured mammalian cells by aluminium characteristic ultrasoft x-rays. ii. dose-responses of chinese hamster and human diploid cells to aluminium x-rays and radiations of different let.the induction of inactivation and mutation to thioguanine-resistance of two types of cultured mammalian cells, v79 chinese hamster and hf19 human diploid, was studied after irradiation with aluminium k characteristic ultrasoft x-rays, helium ion track intersections of different let, 42 mev d-be neutrons, and hard x- or gamma-rays. the form of the dose-response curves was different for the two cell-types, and there was an overall difference in radiosensitivity, the human cells being the more sens ...1977301865
inactivation and mutation of cultured mammalian cells by aluminium characteristic ultrasoft x-rays. iii. implication for theory of dual radiation action.microdosimetric distributions for aluminium k characteristic ultrasoft x-rays and 4he ion tract intersections are calculated and used to analyse recent biological results obtained with these radiations. results on inactivation and mutation-induction to thioguanine resistance of both v79 chinese hamster cells and hf19 human diploid fibroblasts in vitro are analysed in terms of the kellerer-rossi "theory of dual radiation action". the small quantum energy of the aluminium x-ray photons and the ver ...1977301870
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