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radiation-induced cytogenetic damage in relation to changes in interphase chromosome conformation.the premature chromosome condensation (pcc) technique was used to study several factors that determine the yield of chromosome fragments as observed in interphase cells after irradiation. in addition to absorbed dose and the extent of chromosome condensation at the time of irradiation, changes in chromosome conformation as cells progressed through the cell cycle after irradiation affected dramatically the yield of chromosome fragments observed. as a test of the effect of chromosome decondensatio ...19863515397
bradykinin induces a rapid release of inositol trisphosphate from a neuroblastoma hybrid cell line ncb-20 that is not antagonized by enkephalin.in mouse neuroblastoma x chinese hamster brain clonal cell line ncb-20, bradykinin (bk) receptor stimulation causes phosphoinositide hydrolysis and release of inositol phosphates. maximum stimulation (4-fold) of [2-3h]inositol trisphosphate (ip3) release in the absence of li+ from ncb-20's prelabelled for 20-24 hours with [2-3h]myo-inositol (15 microci/confluent 60mm dish) occurred after 5-10 seconds of bradykinin exposure, with an ec50 of approximately 100nm. inositol bisphosphate (ip2) and ino ...19863516143
bacterial and mammalian cell mutagenicity of four optically active bay-region 3,4-diol-1,2-epoxides and other derivatives of the nitrogen heterocycle dibenz[c,h]acridine.the mutagenic activities of the enantiomers of the diastereomeric pair of bay-region 3,4-diol-1,2-epoxides of the nitrogen heterocycle, dibenz[c,h]acridine, have been evaluated in histidine-dependent strains of salmonella typhimurium and in an 8-azaguanine-sensitive line of chinese hamster cells. in strains ta 98 and ta 100 of s. typhimurium the pair of enantiomers with [1r,2s,3s,4r] and [1s,2r,3r,4s] absolute configuration and the benzylic hydroxyl group trans to the epoxide oxygen are 2 to 4 t ...19863516386
ascorbate enhances u.v.-mutagenesis in e. coli but inhibits it in chinese hamster cells.ascorbic acid (vitamin c) causes an increase in the mutation frequency of u.v.-irradiated escherichia coli wp2. the enhancement occurs at all u.v. fluences, and is dependent upon the ascorbate concentration in the medium. a maximum effect (approximately 8- to 13-fold) is seen at 100-150 micrograms/ml, although some enhancement can be seen even at 10 micrograms/ml. the comutagenic effect of ascorbate with u.v. in e. coli is dependent upon peptone, a constituent of nutrient broth. the enhancement ...19863516435
inhibition of mammalian cell dna synthesis by ionizing radiation.a semi-log plot of the inhibitory effect of ionizing radiation on the rate of dna synthesis in normal mammalian cells yields a two-component curve. the steep component, at low doses, has a d0 of about 5 gy and is the result of blocks to initiation of dna replicons. the shallow component, at high doses, has a d0 of greater than or equal to 100 gy and is the result of blocks to dna chain elongation. the target size for the inhibition of dna replicon initiation is about 1000 kb, and the target size ...19863516900
unusual forms of low density lipoprotein receptors in hamster cell mutants with defects in the receptor structural gene.the structure and processing of low density lipoprotein (ldl) receptors in wild-type and ldl receptor-deficient mutant chinese hamster ovary cells was examined using polyclonal anti-receptor antibodies. as previously reported for human ldl receptors, the ldl receptors in wild-type chinese hamster ovary cells were synthesized as precursors which were extensively processed by glycosylation to a mature form. in the course of normal receptor turnover, an apparently unglycosylated portion of the cyst ...19863517003
[experimental induction and cytogenetic study of yolk sac tumors in chinese hamsters].the development of teratomas and yolk sac tumors from displaced yolk sac is well documented in rats and mice. however, the precise mechanisms of induction and pathogeneses of these tumors still remain unknown. the present study was undertaken in order 1) to elucidate whether this phenomenon is common to all rodents, 2) to identify the origin of these tumors and 3) to explore specific chromosomal changes in yolk sac tumors. ten benign teratomas and two malignant tumors with teratomatous elements ...19863517196
intracellular assembly and packaging of hepatitis b surface antigen particles occur in the endoplasmic reticulum.hepatitis b surface antigen (hbsag) particles are secreted by chinese hamster ovary cells that are stably transfected with the s gene of hepatitis b virus. the assembly of hbsag into cylindrical and spherical particles occurred intracellularly within the endoplasmic reticulum. hbsag particles accumulated within large dilated areas of the endoplasmic reticulum and remained within these structures for most of the time prior to secretion from the cells. once the particles were formed, the hbsag pol ...19863517385
mutagenic and comutagenic action of 5'-deoxy-5'-(methylthio)adenosine.5'-deoxy-5'-(methylthio)adenosine (mta) alone and in combination with methionine was found to increase frequencies of background hgprt mutation and sce in v79 chinese hamster cells. the same agents exert a comutagenic action on these effects as well as upon mutation induction in escherichia coli stain ab1157 (but not in its non-adaptable derivative ada-6) following treatment with n-methyl-n-nitrosourea (mnu). mta plus methionine also enhanced the lethal action of mnu on hamster cells. the effect ...19863517630
aneuploidy-inducing chemicals in yeast evaluated by the micronucleus test.chinese hamsters were exposed to acetone, methyl ethyl ketone, ethyl acetate and 2-methoxy ethyl acetate, known to be strong inducers of aneuploidy in the yeast saccharomyces cerevisiae. all solvents yielded negative results in the micronucleus test, whereas the vinca alkaloid vindesine--used as a positive control substance--proved to act as a spindle poison in mammals in vivo.19863517637
actively transcribed genes in the raf oncogene group, located on the x chromosome in mouse and human.murine and human cdnas, related to but distinct from c-raf-1, have been isolated and designated ma-raf and ha-raf, respectively. the ma-raf and ha-raf cdnas detect the same murine and human fragments in southern blots of restriction enzyme-cleaved murine and human cellular dna. the murine restriction enzyme fragments homologous to ma-raf cdna cosegregate with mouse chromosome x in a panel of chinese hamster-mouse hybrid cells, thus localizing the ma-raf locus to mouse chromosome x. two independe ...19863520560
characterization of human prorenin expressed in mammalian cells from cloned cdna.human preprorenin was synthesized in chinese hamster ovary (cho) cells transfected with an expression vector containing renin cdna sequences. these cells secrete an inactive form of renin (ec 3.4.23.15) that can be activated by trypsin. this inactive renin is precipitable by antibody generated against purified human renal renin and also by antisera generated to a synthetic peptide derived from the amino acid sequence of the pro segment of preprorenin (anti-propeptide), indicating that the secret ...19863520565
production of extracellular enzymes and cytotoxicity by vibrio vulnificus.thirty-three strains of vibrio vulnificus of clinical and environmental origin were examined for production of 12 extracellular enzymes of potential importance to the virulence of this bacterium. strains of vibrio vulnificus were consistent in their production of protease, mucinase, lipase, chondroitinase, hyaluronidase, dnase, sulfatase, and hemolysin. no differences between clinical and environmental isolates were noted. although none of the enzymes appeared to correlate with the ability of th ...19863522090
on the sequence homology of the ribosomal proteins, escherichia coli s11, yeast rp59 and chinese hamster s14.a strong sequence homology was found among the ribosomal proteins of the different species, s11 of escherichia coli, rp59 of saccharomyces cerevisiae and s14 of chinese hamster ovary cell. the significance of this series of highly conserved proteins is discussed.19863522274
mutagenic and cell-transforming activities of triol-epoxides as compared to other chrysene metabolites.the syn- and anti-isomers of the bay-region diol-epoxides of chrysene and of 3-hydroxychrysene and their metabolic precursors have been investigated for mutagenicity in salmonella typhimurium (reversion to histidine prototrophy) and v79 chinese hamster cells (acquirement of resistance to 6-thioguanine) and for transforming activity in m2 mouse prostate cells. other known and potential chrysene metabolites have been included in mutagenicity experiments. direct mutagenic activity in s. typhimurium ...19863524815
immunochemical and ultrastructural mapping of the gelatin-binding and cell-attachment regions of human plasma fibronectin with monoclonal antibodies.monoclonal antibodies against fibronectin were used to locate the gelatin-binding and cell-attachment regions of plasma fibronectin at an ultrastructural level. a total of 23 hybridomas were generated using mice immunized with either intact fibronectin or a 40 000 mr gelatin-binding fibronectin fragment. one of these antibodies (d9b) strongly inhibited the interaction of radio-labelled fibronectin with gelatin. another antibody (ib10) inhibited the attachment of chinese hamster ovary (cho) cells ...19863525581
inducible overproduction of the mouse c-myc protein in mammalian cells.we have made chinese hamster ovary (cho) cell lines that contain up to 2000 copies of the coding region of the mouse c-myc gene fused to the promoter of the drosophila gene (hsp70) encoding a mr 70,000 heat shock protein. incubation of these cells at 43 degrees c results in an estimated 100-fold induction of c-myc mrna. translation of this mrna occurs when the cells are returned to 37 degrees c, and during the first 3 hr of recovery at 37 degrees c, the c-myc protein is one of the most abundantl ...19863526329
reduction of the toxicity and mutagenicity of alkylating agents in mammalian cells harboring the escherichia coli alkyltransferase gene.the toxic, mutagenic, and carcinogenic effects of alkylating agents have been attributed to their ability to damage dna. reaction at the o6 position of guanine results in miscoding during dna replication, has been shown to be mutagenic in both bacteriophage and bacteria, and may be responsible for malignant transformation. in common with many other prokaryotes and eukaryotes the escherichia coli b strain contains a protein that repairs o6-alkylation damage in dna by transferring the alkyl group ...19863529080
homologous ribosomal proteins in bacteria, yeast, and humans.we describe sequences of two human ribosomal proteins, s14 and s17, and messenger rnas that encode them. cdnas were used as molecular hybridization probes to recognize complementary genes in rodent, drosophila, and yeast chromosomal dnas. human ribosomal protein sequences are compared to analogous chinese hamster, yeast, and bacterial genes. our observations suggest that some ribosomal protein genes have been conserved stringently in the several phylogenetic lines examined. these genes apparentl ...19863529092
comutagens in e. coli and chinese hamster cells with special attention to arsenite. 19863529106
elimination of metabolic cooperation by glycyrrhetinic acid, an anti-tumor promoter, in cultured chinese hamster cells.the effect of glycyrrhetinic acid (ga) on the metabolic cooperation between 6-thioguanine-resistant (6tgr) and sensitive (6tgs) chinese hamster v79 h3 cells, was investigated. because ga has been reported to inhibit strongly tumor formation in mouse skin induced by 7,12-dimethylbenz[a]anthracene (dmba) plus teleocidin or dmba plus 12-o-tetradecanoylphorbol-13-acetate (tpa), we expected that ga might restore the metabolic cooperation inhibited by tpa. the results were contrary to our expectations ...19863533303
glycosylation defects alter insulin but not insulin-like growth factor i binding to chinese hamster ovary cells.insulin binding to two chinese hamster ovary cell lines with well-defined defects in their glycosylation pathway has been characterized and compared to insulin-like growth factor i (igf-i) binding in the same cell lines. insulin competition curves indicate that b4-2-1 cells, which transfer co-translationally to proteins an endoglycosidase h insensitive, truncated lipid-linked oligosaccharide, bind insulin with higher than normal affinity. lec 1 cells, which fail to process oligosaccharide side c ...19863533914
chinese hamster cells harbouring the escherichia coli o6-alkylguanine alkyltransferase gene are less susceptible to sister chromatid exchange induction and chromosome damage by methylating agents.clones of chinese hamster v79 cells harbouring the escherichia coli o6-alkylguanine (o6-ag) alkylphosphotriester (ap) alkyltransferase (atase) gene (clone 8) or a subclone of it that codes only for o6-ag atase activity (clone sb) have been exposed to increasing doses of n-methyl-n-nitrosourea (mnu) or methylmethanesulphonate (mms) and the frequencies of induced sister chromatid exchanges (sces) measured. in control (clone 2) cells, sce induction was almost linearly proportional to dose of mnu or ...19863536142
expression in mammalian cells of a truncated escherichia coli gene coding for o6-alkylguanine alkyltransferase reduces the toxic effects of alkylating agents.the lesion o6-alkylguanine (o6-ag) is produced in cellular dna following exposure to monofunctional alkylating agents and its miscoding and mutagenic properties have been demonstrated in specific in vitro systems. in order to examine whether this lesion could be responsible for any of the biological effects of alkylating agents in mammalian cells, we have constructed a plasmid containing the o6-ag alkyltransferase (atase) region of the gene from escherichia coli, the product of which normally re ...19863536143
mutagenicity of n-substituted phenanthrene 9,10-imines in salmonella typhimurium and chinese hamster v79 cells.we previously showed that some (nonsubstituted) aziridines derived from polycyclic aromatic hydrocarbons (arene imines) elicit various mutagenic and genotoxic effects in bacteria and mammalian cells and that these arene imines are active at much lower concentrations than the corresponding epoxide analogues. in the present study, n-substituted derivatives of phenanthrene 9,10-imine were investigated. all 10 derivatives studied showed direct mutagenicity in salmonella typhimurium ta100. some of th ...19863536471
escherichia coli aspartate transcarbamylase: a novel marker for studies of gene amplification and expression in mammalian cells.eucaryotic expression vectors containing the escherichia coli pyrb gene (pyrb encodes the catalytic subunit of aspartate transcarbamylase [atcase]) and the tn5 phosphotransferase gene (g418 resistance module) were transfected into a mutant chinese hamster ovary cell line possessing a cad multifunctional protein lacking atcase activity. g418-resistant transformants were isolated and analyzed for atcase activity, the ability to complement the cad atcase defect, and the ability to resist high conce ...19863537729
methylglyoxal in beverages and foods: its mutagenicity and carcinogenicity.methylglyoxal was found to induce mutations in salmonella typhimurium strains ta100, ta102 and ta104, gene conversion in saccharomyces cerevisiae strain d7, and diphtheria toxin resistance mutation in chinese hamster lung cells. methylglyoxal was detected in coffee, whiskey, a soft drink, toasted bread and soy sauce. the mutagenicity of methylglyoxal was suppressed by sulfite, cysteine, glutathione and dithiothreitol, and enhanced by hydrogen peroxide. methylglyoxal induced sarcomas in rats at t ...19863539787
genetic effects of dna mono- and diadducts photoinduced by furocoumarins in eukaryotic cells.the genotoxic activity of two bifunctional furocoumarins, 8- and 5-methoxypsoralen (8-mop and 5-mop), and the newly developed monofunctional furocoumarin, 7-methyl-pyrido(3,4-c)psoralen (mepyps), was determined in diploid yeast. in parallel experiments, the dna photobinding capacity of the compounds was estimated. this capacity was, in decreasing order, mepyps greater than 5-mop greater than 8-mop. the lesions induced by 8- and 5-mop, which consist of a mixture of mono- and diadducts, were found ...19863539789
role of the a subunit of pertussis toxin in alteration of chinese hamster ovary cell morphology.the mechanism by which pertussis toxin induces morphological changes in chinese hamster ovary cells was studied to determine whether the resulting clustered growth pattern is due to toxin-catalyzed adp-ribosylation of a cellular substrate. while pertussis toxin was extremely potent in inducing morphological changes in chinese hamster ovary cells, preparations of isolated a subunit or b oligomer exhibited greatly reduced activity. the clustered growth response of these cells correlated with adp-r ...19873539804
acute insulin action requires insulin receptor kinase activity: introduction of an inhibitory monoclonal antibody into mammalian cells blocks the rapid effects of insulin.the role of the insulin receptor tyrosine kinase (protein-tyrosine kinase, ec 2.7.1.112) in various rapid insulin effects was studied by injecting four different cell types (by osmotic lysis of pinocytotic vesicles) with a monoclonal antibody that specifically inhibits the kinase activity of the insulin receptor and the closely related receptor for insulin-like growth factor (igf)-i. injection of this inhibitory antibody resulted in a decreased ability of insulin to stimulate the uptake of 2-deo ...19873540958
genotoxicity studies of methyl isocyanate in salmonella, drosophila, and cultured chinese hamster ovary cells.the genotoxic effects of methyl isocyanate (mic) were investigated using four short-term tests: the salmonella reversion assay (ames test), the drosophila sex-linked recessive lethal assay, and the sister chromatid exchange (sce) and chromosomal aberration assays in cultured chinese hamster ovary (cho) cells. no evidence was found for the induction of mutations in either salmonella or drosophila. mic did, however, induce sces and chromosomal aberrations in cho cells both in the presence and abse ...19873542520
pre-screening of carcinogens by studying of dna synthesis inhibition and gene mutations in mammalian cells.the ability to induce gene mutations at the hgprt locus in chinese hamster v79 cells and to inhibit dna synthesis in human eue cells has been followed in eighteen chemical substances and ultraviolet light. the aim was to determine whether following of inhibition of dna synthesis in impaired human cells may serve as an indicator of the mutagenicity of the relevant chemical substance. the results permit us to assume that following of dna synthesis, the so-called dna-inhibition test provides a prel ...19863543704
complementation of sensitivity to alkylating agents in escherichia coli and chinese hamster ovary cells by expression of a cloned bacterial dna repair gene.dual expression vectors derived from psv2gpt and encoding all or part of the escherichia coli ada+ gene have been constructed. following transformation into an e. coli ada strain or transfection and stable integration into the genome of chinese hamster ovary (cho) cells, plasmid vectors containing the whole ada+ gene conferred resistance to both killing and mutagenesis by n-methyl-n'-nitro-n-nitrosoguanidine (mnng). thus, the bacterial dna repair gene was functionally expressed in the mammalian ...19863545815
[experimental therapy in chinese hamsters and rats infected with larval echinococcus multilocularis by using mebendazole, albendazole and ivermectin with brief review of chemotherapy of human multilocular echinococcosis].the effects of the mebendazole, albendazole and ivermectin on secondary multilocular echinococcosis in chinese hamsters infected with intraperitoneal inoculation of protoscolices and in rats infected with transportal inoculation of protoscolices were investigated. a reduction in weight of the hydatids greater than 95% was recorded in chinese hamsters intraperitoneally injected with mebendazole suspension. oral administration of mebendazole moderately inhibited the development of the hydatids. al ...19873546045
retinol (vitamin a) inhibition of dimethylnitrosamine (dmn) and diethylnitrosamine (den) induced sister-chromatid exchanges in v79 cells and mutations in salmonella/microsome assays.when the chinese hamster cell line v79 and the tester strain of salmonella typhimurium ta100 were treated with the precarcinogens dimethylnitrosamine (dmn) or diethylnitrosamine (den) in the presence of s9 mix, a dose-dependent increase of sister-chromatid exchanges (sce) in v79 cells and his+ revertants in ta100 resulted. dmn was a far more efficient sce inducer than den, while den was a more efficient inducer of his+ revertants than dmn. retinol (rol) effectively inhibited dmn and den induced ...19873547112
the 32p-post-labeling method in quantitative dna adduct dosimetry of 2-acetylaminofluorene-induced mutagenicity in chinese hamster ovary cells and salmonella typhimurium ta1538.the usefulness of the 32p-post-labeling/t.l.c. method for quantitative dna adduct dosimetry was evaluated. 2-acetylaminofluorene (2-aaf)-dna adducts from three systems were characterized qualitatively and quantitatively by the 3h-radiolabeled technique with subsequent analysis by h.p.l.c. (pre-labeling method) and by the 32p-post-labeling method. both methods showed n-acetoxyacetylaminofluorene (n-oac-aaf) reaction products with calf thymus dna were predominantly n-(deoxyguanosin-8-yl)-2-acetyla ...19873549038
buoyant density variation during the cell cycle in microorganisms.the behavior of cell buoyant density during the cell cycle has been determined for a number of different cell types, including bacteria, yeast, and mammalian cells. mean buoyant density was extremely constant and independent of cell age during the cell cycle of the bacterium escherichia coli, the fission yeast schizosaccharomyces cerevisiae, the protozoan amoebae proteus, cells from suspension cell cultures of mouse lymphoma and myeloma, and chinese hamster ovary cells. in all of these cases, th ...19873549158
clonogenic assay combined with flow cytometric cell sorting for cell-cycle analysis of human leukemic colony-forming cells.the purpose of this study is to develop a method combining clonogenic assay and flow cytometric cell sorting based on dna content for determination of percentage distribution of human malignant clonogenic cells over cell-cycle phases. flow cytometric cell sorting was carried out for chinese hamster ovary (cho) and human leukemic bone marrow cells under sterile conditions using a supravital dye for dna, 4',6-diamidino-2-phenylindole dihydrochloride (dapi). the fraction sorted for g0/g1 cho cells ...19873551785
mutagenicity testing of 5-(4-nitrophenyl)-2,4-pentadien-1-al (spy dust) and its metabolites in vitro and in vivo.5-(4-nitrophenyl)-2,4-pentadien-1-al (nppd; spy dust) was tested for mutagenicity in salmonella and for its ability to induce chromosome aberrations and sister chromatid exchanges (sce) in cultured chinese hamster ovary (cho) cells and mouse bone marrow. two metabolites of nppd produced by the rat, 4-nitrobenzoic acid (nba) and 4-nitrohippuric acid (nha), were also tested in salmonella and cho cells. nppd was mutagenic in salmonella, and induced low-level increases in chromosome aberrations and ...19873552647
abnormalities in glucose-stimulated insulin release, 45ca uptake, and 86rb efflux in diabetic chinese hamster islets.we loaded islets from normal and diabetic chinese hamsters with 86rb (an analogue for k+) and measured 86rb efflux during stimulation with 20 mm d-glucose. genetically diabetic chinese hamsters were selected from a subline (l) known for subnormal pancreatic insulin release and excessive pancreatic glucagon release in vitro. 86rb accumulation in 1 mm glucose was normal in the diabetic islets. similar to the pattern of 86rb efflux previously seen from normal rat and mouse islets, 20 mm glucose sup ...19873552797
prediction of chemical carcinogenicity in rodents from in vitro genetic toxicity assays.four widely used in vitro assays for genetic toxicity were evaluated for their ability to predict the carcinogenicity of selected chemicals in rodents. these assays were mutagenesis in salmonella and mouse lymphoma cells and chromosome aberrations and sister chromatid exchanges in chinese hamster ovary cells. seventy-three chemicals recently tested in 2-year carcinogenicity studies conducted by the national cancer institute and the national toxicology program were used in this evaluation. test r ...19873554512
localization of a gene involved in complementation of the defect in xeroderma pigmentosum group a cells on human chromosome 1.human, chinese hamster or chinese hamster/human hybrid cytoplasts were fused with uv-irradiated xeroderma pigmentosum group a (xp-a) cells. unscheduled dna synthesis (uds) of the xp-a nucleus was measured 0-2 and 2-4 h after seeding of the fused population. human cytoplasts did correct the defect in the xp-a nucleus immediately after fusion, whereas the chinese hamster cytoplasts did not show this rapid increase in excision repair. the results obtained after fusion of cytoplasts isolated from a ...19873556430
species-specific differences in the toxicity of rhodamine 123 towards cultured mammalian cells.the toxicity of cationic fluorescent dye, rhodamine 123, towards a number of independently established cell lines from three different species, namely human, mouse, and chinese hamster, has been examined. all of the cell lines from any one species that were examined were found to exhibit similar sensitivities towards rhodamine 123 and no appreciable differences were observed between the normal and transformed cell types. however, in comparison to the cells of human origin, mouse and chinese hams ...19873558490
[mutagenicity tests for isepamicin (hapa-b)].to detect mutagenic activity of isepamicin (hapa-b), a new aminoglycoside antibiotic, we carried out several mutagenicity tests using microorganisms and cultured mammalian cells. effects of the antibiotic on dna-lesion induction and repair were examined using the rec-assay with bacillus subtilis and a sister-chromatid exchange test with cultured chinese hamster cells. the drug caused no increase of mutagenicity indices in both tests, suggesting that the antibiotic has no dna-damaging effect. to ...19863560443
a procedure for the cho/hgprt mutation assay involving treatment of cells in suspension culture and selection of mutants in soft-agar.a procedure involving treatment of cells in suspension culture and soft-agar cloning was developed for measuring mutation of chinese hamster ovary (cho) cells to 6-thioguanine (6tg) resistance. the use of suspension cultures precluded the need for trypsinization and also permitted a 5-fold increase in cell population for compound exposure and mutant selection as compared to former monolayer techniques. soft-agar cloning reduced the opportunity for metabolic cooperation and permitted the use of n ...19873561430
measurement of dna damage in mammalian cells using flow cytometry.a technique for the detection of dna damage induced by radiation insult has been developed. cells were lysed with a buffer containing 2 m sodium chloride to release the dna in a supercoiled form, the nucleoid. these were stained with the dna intercalating dye, ethidium bromide, and exposed to laser light within a flow cytometer. scattered and fluorescent light was analyzed from the laser/nucleoid interaction following irradiation of viable cells with gamma rays. the addition of ethidium bromide ...19873562788
binding and internalization of recombinant human erythropoietin in murine erythroid precursor cells.erythropoietin (epo) biosynthetically labelled with [35s]cysteine was produced from chinese hamster ovary (cho) cells containing amplified copies of human epo cdna. the glycosylated recombinant [35s]epo, purified to virtual radiochemical homogeneity, was biologically active. we studied the interaction of this labeled recombinant epo with erythroid precursor cells from mice made anemic with phenylhydrazine. the [35s]-labeled molecule bound to erythroid precursors in a time- and temperature-depend ...19873567362
enhancement of the chemical transformation of chinese hamster embryo cells in vitro by 7-methylguanine.the rna catabolite 7-methylguanine has been shown to inhibit queuine modification of trna in chinese hamster embryo cells under conditions leading to in vitro transformation. phorbol ester tumor promoters also induce queuine hypomodification of trna in normal human cells, and this effect was reported to be correlated directly to the appearance of an altered (transformed) cell phenotype. based on this common macromolecular alteration, 7-methylguanine was evaluated for its ability to enhance the c ...19873567929
a somatic cell hybrid with a single human chromosome 22 corrects the defect in the cho mutant (ade-i) lacking adenylosuccinase activity.adenine-requiring chinese hamster ovary (cho-k1) auxotrophs of the complementation group ade-i were hybridized with various human cells, and hybrids were isolated under selective conditions in which retention of the complementing gene on the human chromosome is necessary for survival. ade-i cells are deficient in adenylosuccinase activity. this enzyme carries out two independent, but similar, steps of purine biosynthesis: the removal of a fumarate from succinylaminoimidazole carboxamide ribotide ...19873568763
immune response to the b oligomer of pertussis toxin.immunization of mice with the b oligomer of pertussis toxin induced antibodies to the native toxin as measured by an enzyme-linked immunosorbent assay. these antibodies neutralized the ability of pertussis toxin to alter the morphology of chinese hamster ovary cells. furthermore, mice immunized with the b oligomer, when challenged with pertussis toxin, did not exhibit the leukocytosis normally associated with exposure to the toxin. these results demonstrate that the b oligomer, which does not co ...19873570457
mutagenicity studies by co-cultivation of bronchoalveolar cells and blood lymphocytes with v79 chinese hamster cells.human bronchoalveolar cells, consisting of approximately 85% pulmonary alveolar macrophages (pams), and peripheral blood lymphocytes isolated from healthy volunteers were investigated for their ability to metabolize 7,8-diol of benzo[a]pyrene (b(a)p). the mutagenicity of reactive metabolites was analyzed by employing a co-cultivation system using v79 chinese hamster cells for the detection of mutations. the metabolic activity of the human cells was compared to pams isolated from rabbits. the num ...19873574323
comparison of s9 fractions from rats, mice, and chinese hamsters to metabolize dimethylnitrosamine and diethylnitrosamine to intermediates that induce sister-chromatid exchanges in v79 cells.this study was designed to compare the ability of hepatic s9 preparations from rats, mice and chinese hamsters to activate dimethylnitrosamine (dmn) and diethylnitrosamine (den) into intermediates capable of causing sister-chromatid exchanges (sces) in v79 cells. the results indicated that the hepatic preparations from the species studied differed in their ability to activate dmn while in the case of den no species difference in bioactivation was observed. for dmn, a dose-dependent increase of s ...19873574338
effect of cycloheximide on the development of thermotolerance and the synthesis of 68-kilodalton heat shock protein in chinese hamster v79 and mouse l cells in vitro. 19863580037
relationships between benzo(a)pyrene-dna adduct levels and genotoxic effects in mammalian cells.the effectiveness of benzo(a)pyrene [b(a)p]-dna binding as an internal dosimeter was evaluated. data were obtained from concurrent studies, measuring b(a)p induced genotoxic effects and dna adducts in several short-term bioassay systems: cytotoxicity, gene mutation, and sister chromatid exchange in chinese hamster v79 cells; cytotoxicity, gene mutation, and chromosome aberrations in mouse lymphoma l5178y tk+/-; cytotoxicity and enhanced virus transformation in syrian hamster embryo cells; and cy ...19873581076
natural size classes in dna from chinese hamster metaphase chromosomes.dna from isolated chinese hamster ovary (cho) metaphase chromosomes can be obtained in three different molecular weight classes. the two largest forms have sedimentation coefficients of 80 and 120 s at 7,500 rpm. based on sedimentation and speed dependence analysis these have molecular weights of 220 million and above 5,000 million, and are thought to be analogs of dna classes observed in a prior study of human metaphase chromosomes. an extract can be converted to primarily the 80 s form through ...19873581998
[mutagenicity of gastric juice in patients with chronic gastritis].mutagenicity of fasting gastric juice from 108 chronic gastritis patients in high- and low-risk areas of stomach cancer was assayed using in vitro sce test in cultured human lymphocytes and micronucleus test in cultured chinese hamster v79 cell. the results showed that mutagenicity could be found in this gastric juice. the positive rate of these two tests, sce/cell, micronucleated cell rate and micronucleus rate were significantly higher in high-risk area than in low-risk area (p less than 0.01) ...19863582108
translational efficiency of polycistronic mrnas and their utilization to express heterologous genes in mammalian cells.the translation of polycistronic mrnas in mammalian cells was studied. transcription units, constructed to contain one, two or three open reading frames (orfs), were introduced stably into chinese hamster ovary cells and transiently into cos monkey cells. the analysis of mrna levels and protein synthesis in these cells demonstrated that the mrnas transcribed were translated to generate multiple proteins. the efficiency of translation was reduced approximately 40- to 300-fold by the insertion of ...19873582359
thyroglobulin, the major and obligatory exportable protein of thyroid follicle cells, carries the lysosomal recognition marker mannose-6-phosphate.thyroglobulin (tg), the major exportable protein of thyroid follicle cells, is conveyed to lysosomes on a complex secretion, storage and recapture pathway by as yet unknown transport mechanisms. this report establishes that the dimeric porcine tg-molecule carries an average of six phosphate residues. endoglycosidase digestion showed that two phosphate residues are bound to the high-mannose carbohydrate side chains (cho), while two others are linked to the complex cho. these four residues are als ...19873582367
safety issues related to the use of recombinant dna-derived cell culture products. i. cellular components.anti-thymocyte serum (ats) treated newborn rats were used to assess the tumorigenic potential of mammalian cell and mammalian cell culture derived substances. injection of as much as 100 micrograms of chinese hamster ovary (cho) dna, an amount in excess of 10(8) fold more than might be present in one dose of a typical final product derived from mammalian cell cultures, failed to initiate a tumor in immunosuppressed animals. in addition, injection of 10 micrograms of activated oncogene cloned fro ...19873582742
suppression of tumorigenicity in somatic cell hybrids does not involve quantitative changes in transcription of cellular ha-ras, ki-ras, myc, and fos oncogenes.the transcriptional activity of ten cellular oncogenes was analyzed in somatic cell hybrids that had been obtained after fusion of tumorigenic chinese hamster cells and normal mouse fibroblasts. the hybrids showed either the tumorigenic or the nontumorigenic phenotype (suppression of tumorigenicity). out of ten c-onc genes analyzed, four (c-ha-ras, c-ki-ras, c-myc, and c-fos) were found to be transcriptionally active at similar levels in tumorigenic as well as in nontumorigenic (suppressed) hybr ...19873584261
modulation of the cytotoxicity and mutagenicity of benzo[a]pyrene and benzo[a]pyrene 7,8-diol by glutathione and glutathione s-transferases in mammalian cells (cho/hgprt assay).biologically reactive metabolites of benzo[a]pyrene (bp) and benzo[a]-pyrene 7,8-diol (bp-diol), formed by the mixed-function oxidase (mfo) system, are substrates for conjugation and detoxication by glutathione (gsh) when catalyzed by glutathione s-transferases (gsht). we have investigated the detoxication of bp- and bp-diol-induced cytotoxicity and mutagenicity with gsh by supplementing the s9 mix used in the chinese hamster ovary cells/hypoxanthine-guanine phosphoribosyltransferase (cho/hgprt) ...19873587256
[analysis of the kinetic growth patterns of cultured cells. iii. the effect of inoculation density, of a geroprotector-antioxidant and of stationary-phase aging].with the help of a previously devised model of cultured cell growth kinetics it was shown that the "plateau" level on the growth curve of human embryo diploid fibroblasts increased, if the cells were grown with epigid geroprotector-antioxidant (equal results with two drug concentrations: 10(-5) and 10(-7) m, resp.). it was also found that the "plateau" level on the growth curve of cultured "3 days aged" chinese hamster cells (subcultivated to a fresh medium 3 days after a 1:6 subcultivation) lay ...19873590315
alpha-naphthoflavone metabolized by 2,3,7,8-tetrachlorodibenzo(p)dioxin-induced rat liver microsomes: a potent clastogen in chinese hamster ovary cells.alpha-naphthoflavone (anf) is a widely used inhibitor of p-450-mediated metabolism. previously, we have demonstrated that in vitro addition of anf to human lymphocytes produced significantly greater numbers of sister chromatid exchanges (sces) in samples from smokers compared to nonsmokers. in order to study the mechanism of this differential induction, we investigated the clastogenic activity of anf as a consequence of metabolism by induced and uninduced rat liver microsomes. exponentially grow ...19873594431
transfer of human genes conferring resistance to methylating mutagens, but not to uv irradiation and cross-linking agents, into chinese hamster ovary cells.chinese hamster ovary cells were transfected by human dna ligated to the bacterial gpt (xanthine-guanine-phosphoribosyltransferase) gene which was used either in its native form or after partial inactivation with methylnitrosourea. the gpt+ transfectants were screened for resistance to high doses of n-methyl-n'-nitro-n-nitrosoguanidine. using this approach, we showed that chinese hamster ovary cells can acquire n-methyl-n'-nitro-n-nitrosoguanidine resistance upon transfection with dna from diplo ...19873600657
involvement of dna polymerases in the repair of dna damage by benzo[a]pyrene in cultured chinese hamster cells.mechanisms for induction of single-strand scissions in dna by s9-activated benzo[a]pyrene (b[a]p) and their repair in cultured chinese hamster v79 cells were investigated with inhibitors of dna-repair synthesis using alkaline sucrose gradient sedimentation analysis. the marked induction of single-strand scissions in dna was observed following 3 h treatment of v79 cells with 5 micrograms/ml of b[a]p. these dna lesions were repaired to the control level within 4 h after removal of b[a]p. the simul ...19873600683
pesticide clastogenicity in chinese hamster ovary cells.paraquat, alachlor, butachlor, phorate and monocrotophos, several of the most extensively used pesticides in taiwan, were investigated for their clastogenicity using chromosome aberration (cab) induction in chinese hamster ovary (cho) cells. significance levels of the binomial trend analysis and binomial mutagenicity data test were two criteria for the summary judgement of the pesticide clastogenicity. except for phorate, all pesticides tested were clastogenic to cho cells in the absence of in v ...19873600690
action of calcium antagonists on multidrug resistant cells. specific cytotoxicity independent of increased cancer drug accumulation.previous studies have shown that calcium channel blockers can overcome, at least partially, multidrug resistance (mdr). this study was undertaken to attempt to determine the mechanisms whereby these agents bring about this effect. their influence on the uptake and retention of several cancer drugs and on the toxic actions of these compounds was assessed employing mdr cell lines from several species. the wild-type drug sensitive parent cells proved to be more susceptible than the multidrug resist ...19873606629
effect of cholesterol alpha and beta epoxides on cell killing and transformation.v-79 chinese hamster lung fibroblasts and c3h-10t1/2 mouse embryo cells were used to study the toxicity and transformation effects of the 5 alpha,6 alpha, and 5 beta,6 beta-epoxy derivatives of cholesterol. both epoxides were found to be carcinogenic, and the transformation frequency increased with epoxide concentration and exposure time. the 5 beta,6 beta-epoxide caused a higher level of transformation than the alpha-isomer, and this is consistent with its greater toxicity.19873606646
sorcin (v19), a soluble acidic calcium-binding protein overproduced in multidrug-resistant cells. identification of the protein by anti-sorcin antibody.sorcin (soluble resistance-related calcium-binding protein), an acidic (pi = 5.7) protein (mr approximately 20 kda) previously designated v19, was originally identified in cells selected for high levels of resistance to vincristine. two-dimensional gel electrophoresis and/or western blot techniques now show sorcin to be overproduced in cells selected for resistance to actinomycin d (qua/adj), colchicine (chrc5), and adriamycin (be(2)-c/adr). not all cell lines selected for resistance to these dr ...19873606647
antibody-induced down-regulation of a mutated insulin receptor lacking an intact cytoplasmic domain.insulin receptor down-regulation was studied in various chinese hamster ovary (cho) cell lines expressing transfected human insulin receptor cdnas. in addition to a cell line expressing the normal receptor (cho.t line), three lines expressing mutated receptors were studied: the cho.t-t line, which expresses a receptor with a degraded cytoplasmic domain due to the removal of the c-terminal 112 amino acids, and the cho.yf1 and cho.yf3 lines, in which important autophosphorylation sites of the rece ...19873607002
characterization of recombinant human erythropoietin produced in chinese hamster ovary cells.physicochemical properties of recombinant human erythropoietin were examined. this protein, produced in chinese hamster ovary cells, showed a conformation apparently identical with the natural product isolated from human urine when examined by circular dichroism, uv absorbance, and fluorescence spectroscopy. sedimentation equilibrium experiments showed the recombinant erythropoietin preparation to be essentially a single macromolecular component with a molecular weight of 30,400 and a carbohydra ...19873607040
mechanism of inhibition of junctional communication between animal cells by phorbol ester.the tumour promotor 4 beta-phorbol 12-myristate 13-acetate (tpa) reduces the rate of junction formation between v79 chinese hamster lung cells in culture but not between bhk21/13 syrian hamster fibroblasts. tpa may act on all cells but only affect junction formation in those situations where the rate of junction formation is already low.19873607839
failure of the tumor promoter 12-o-tetradecanoylphorbol-13-acetate (tpa) to inhibit cell-cell coupling in newborn mouse epidermal cells and chinese hamster v79 cells under non-standard culture conditions.the function of the skin tumor promoter 12-o-tetradecanoyl-phorbol-13-acetate (tpa) during two-stage carcinogenesis in mice remains obscure because of tpa's numerous phenotypic effects. in vitro studies under established conditions have generated substantial interest in tpa's ability to inhibit, although transiently in some cases, direct cell-cell coupling in several permanent cell lines, by analogy allowing latent 'initiated cells' to escape homeostatic controls in vivo. using different culture ...19873608083
evolutionary relationships of the chinese hamster x chromosome and autosomes: a comparison using solution hybridization techniques.the evolutionary relationships of chinese hamster x chromosome and autosome dna sequences were compared by solution hybridization techniques. chinese hamster x chromosome tracer was prepared by radiolabeling dna from chromosomes isolated by fluorescence-activated sorting. radiolabeled chinese hamster total genomic dna, approximately 90% of which is of autosome origin, was used as autosome tracer. each tracer was mixed with excess driver dna of chinese hamster, syrian hamster, rat, rabbit, cat, c ...19873608718
functional expression of the human transferrin receptor cdna in chinese hamster ovary cells deficient in endogenous transferrin receptor.transferrin (tf) receptor-variant chinese hamster ovary cells have been isolated by selection for resistance to two tf-toxin conjugates. the hybrid toxins contain tf covalently linked to ricin a chain or a genetically engineered diphtheria toxin fragment. the tf-receptor-variant (trv) cells do not have detectable cell-surface tf receptor; they do not bind fluorescein-tf or 125i-tf. trv cells are at least 100-fold more resistant to the tf-diphtheria toxin conjugate than are the parent cells. the ...19873611186
the action of the tumour promoter, tpa, on mutagenesis induced by different agents (uv light, chemical and viral mutagens).the present paper deals with effects of 12-o-tetradecanoylphorbol-13-acetate (tpa) on the frequency of induced mutations to 6-mercaptopurine (6mp) and ouabain resistance in chinese hamster and mouse cells. uv light, bovine adenovirus 3(bav-3) and 5-bromodeoxyuridine (brdu) were used as mutagens. tpa was shown to raise the frequency of gene mutations induced by uv light and bav-3 but it did not enhance the mutagenic effect of brdu. we also examined the ability of bav-3 and brdu to induce tumours ...19873614245
induction of sister-chromatid exchanges by pesticides in primary rat tracheal epithelial cells and chinese hamster ovary cells.possible induction of sister-chromatid exchanges by butachlor, paraquat, phorate and monocrotophos was examined in primary rat tracheal epithelial (rte) and chinese hamster ovary (cho) cells. at dose levels that killed less than 50% of the cell population, monocrotophos induced sces positively in cho and rte cells, while paraquat was positive only in rte cells. in two trials of the same experiment, paraquat and butachlor in cho cells, and phorate in either rte or cho cells failed to induce a sig ...19873614248
enzymatic denitrosation of diphenylnitrosamine: activation or inactivation?nitrosodiphenylamine was tested for induction of dna single strand breaks in rat hepatocytes and chinese hamster v 79 cells with the alkaline filter elution assay. while in rat hepatocytes dna damage could be observed, negative results were obtained in v 79 cells. in view of the metabolic capacity of hepatocytes and the chemical structure of nitrosodiphenylamine, it seems likely that cytochrome p-450-dependent, reductive denitrosation might be necessary for exerting this effect. therefore the me ...19873619641
cytochrome p-450-mediated o-demethylation: a route in the metabolic activation of etoposide (vp-16-213).the antitumor agent vp-16-213 is oxidatively o-demethylated by rat liver microsomes and purified rat liver microsomal cytochrome p-450. 3-methylcholanthrene can quantitatively induce o-demethylation of vp-16-213. the km and vmax values for o-demethylation by noninduced, phenobarbital-, and 3-methylcholanthrene-induced rat liver microsomes were found to be 130, 600, and 160 microm and 8.5, 11.8, and 15.6 nmol h2co/min x mg protein, respectively. mass spectrometric comparison of the product of o-d ...19873621161
comparison of melphalan toxicity in human lymphocytic cells and chinese hamster cells in vitro: the relationship between dna-dna cross-link formation and clonogenic survival.human ccrf-cem ('t' cell), eb3p ('b' cell) and rpmi-8226 (myeloma cell) lymphocytic cell lines were an order of magnitude more sensitive to melphalan (mel) than chinese hamster, v-79-753b, cells even though the amount of [14c]mel they incorporated was less than 50% of that incorporated into the rodent cells: the d0 values were 0.16, 0.20 and 0.30 microgram/ml respectively compared with 1.6 micrograms/ml. furthermore, mel sensitivity was not related to the total thiol content of the cells. dna-dn ...19873621462
enhanced repair of pyrimidine dimers in coding and non-coding genomic sequences in cho cells expressing a prokaryotic dna repair gene.we have previously demonstrated that the active dihydrofolate reductase (dhfr) gene is efficiently repaired in chinese hamster ovary (cho) cells which remove only a small fraction of u.v.-induced pyrimidine dimers from the overall genome. preferential dna repair of essential genes may explain why the u.v. resistance of normal cho cells is as high as that of fully repair-proficient normal human cells. in this report, we have studied the removal of pyrimidine dimers in a cho cell line expressing t ...19873621470
toxicity and mutagenicity of 6 anti-cancer drugs in chinese hamster cells co-cultured with rat hepatocytes. 19873623237
carbohydrate structure of erythropoietin expressed in chinese hamster ovary cells by a human erythropoietin cdna.the proper glycosylation of erythropoietin is essential for its function in vivo. human erythropoietins were isolated from chinese hamster ovary cells transfected with a human erythropoietin cdna and from human urine. carbohydrate chains attached to these proteins were isolated and fractionated by anion-exchange high performance liquid chromatography (hplc) and hplc employing a lichrosorb-nh2 column. the structures of fractionated saccharides were analyzed by fast atom bombardment-mass spectrome ...19873624248
dominant white spotting in the chinese hamster.an autosomal dominant white spotting mutant is described for the chinese hamster. the mutant gene is designated as dominant spot (symbol ds). the homozygote dsds is a prenatal lethal while the heterozygote ds + displays white spotting. the expression of white is variable, ranging from a white forehead spot to extensive white on the body. the venter is invariably white. growth appears to be normal and the fertility of both sizes shows no impairment.19873624848
[excision of the plasmid containing the inserted human satellite dna from chinese hamster chromosomes after fusion of hamster and human cells].fusion of the chinese hamster stably transformed tk+ cells containing chromosomally integrated plasmid with a fragment of human satellite iii dna (hs3), with mitomycin c-treated human cells (b-lymphoma, line raji) results in amplification and excision of heterogeneous plasmid material from hamster chromosomes. some of these plasmids contain hs3. functional activity of hs3 in the initiation of dna replication is shown in transient transfection experiments. the results indicate that mitomycin c in ...19873627135
[trial of pertussis toxin activity in vitro on cho cells].the activity of b. pertussis toxin has been tested in the continuous culture of cho (chinese hamster ovary) cells. the in vitro method of testing b. pertussis toxin is rapid, highly sensitive and specific. the unit of activity of b. pertussis toxin is higher than in mouse tests by several orders. the specificity of the action of b. pertussis toxin on cho cells has been confirmed by the test of the neutralization of the toxicity effect with antiserum.19873630484
growth-promoting activity in serum-free medium of kallikreinlike arginylesteropeptidases from rat submaxillary gland.the characterization and purification of the growth-promoting activity present in rat submaxillary gland extracts, known to be required for the proliferation of adipose precursor cells in serum-free medium, have been undertaken. fractionation of the extracts by ion-exchange chromatography, gel filtration, and affinity chromatography on immobilized benzamidine allowed the copurification of the mitogenic activity with two distinct arginylesteropeptidases of apparent molecular weight 25,000; one of ...19873644823
mutant with diphtheria toxin receptor and acidification function but defective in entry of toxin.a mutant of chinese hamster ovary cells, ge1, that is highly resistant to diphtheria toxin was isolated. the mutant contains 50% adp-ribosylatable elongation factor 2, but its protein synthesis was not inhibited by the toxin even at concentrations above 100 micrograms/ml. 125i-labeled diphtheria toxin was associated with ge1 cells as well as with the parent cells but did not block protein synthesis of ge1 cells even when the cells were exposed to low ph in the presence or absence of nh4cl. the i ...19873653257
production of a unique cytotoxin by campylobacter jejuni.campylobacter jejuni is an important diarrheal pathogen worldwide; the mechanisms by which it causes disease remain unclear. because of its association with inflammatory diarrhea, we postulated that c. jejuni might produce a cytotoxin similar to that produced by shigella sp., enterohemorrhagic escherichia coli o157, or clostridium difficile. filtrates of 12 polymyxin-treated isolates of c. jejuni were placed on hela cells (sensitive to shiga toxin cytotoxicity) and chinese hamster ovary (cho) ce ...19873653987
perturbation of n-linked oligosaccharide structure results in an altered incorporation of [3h]palmitate into specific proteins in chinese hamster ovary cells.increased [3h]palmitate incorporation into specific cellular proteins has been reported to occur in chinese hamster ovary (wellner, r. b., ray, b., ghosh, p. c., and wu, h. c. (1984) j. biol. chem. 259, 12788-12793) and yeast (wen, d., and schlesinger, m. j. (1984) mol. cell. biol. 4, 688-694) mutant cells. in this paper we report studies concerning the relationship between n-linked oligosaccharide structure and [3h]palmitate incorporation into proteins of chinese hamster ovary (cho) cells. we h ...19873654608
in vitro production of cholera toxin-like activity by plesiomonas shigelloides.although plesiomonas shigelloides is considered to cause diarrhea in humans, the mechanisms by which it might do so are not known. enteric pathogens such as vibrio cholerae and some strains of escherichia coli produce enterotoxins that activate adenylate cyclase, increase production of cyclic amp, and thereby cause elongation of chinese hamster ovary (cho) cells in tissue culture. we grew 28 strains of p. shigelloides and the type strain in an iron-depleted medium, and sterile filtrates were exa ...19873655401
rodent fibroblast tumours expressing human myc and ras genes: growth, metastasis and endogenous oncogene expression.the effects of expression of human c-myc and both mutated (t24) and normal forms of human ha-ras-1 were studied in an aneuploid rat fibroblast line (208f). mutated t24 ha-ras was also studied in a near-diploid cell derived from early passage chinese hamster lung fibroblasts (chl). in contrast to the parental fibroblasts, cells expressing any of the human oncogenes engendered rapidly growing tumours in immune-suppressed animals. blood- and lymph-borne metastases were observed from both ras- and m ...19873663473
altered function and structure of low-density lipoprotein receptor in compactin (ml236b)-resistant mutants of chinese hamster cells.mutants resistant to compactin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme a reductase, have been previously isolated from the chinese hamster v79 cell line. two compactin-resistant mutants, mf-1 and mf-2, show altered responses to human low-density lipoprotein (ldl). accumulation of fluorescent-labeled ldl was much reduced. ligand blotting showed ldl receptor activity in mf-1 and mf-2 cells of about one half to one third that of v79. internalization and degradation of ldl in mf-1 or mf ...19873663697
inhibition of phorbol ester-mediated phenotypic changes in cultured cells by hypoxanthine.hypoxanthine induces the differentiation of certain transformed cells in vitro, so analyses were undertaken to determine whether this purine metabolite might influence the expression of transformed phenotypes induced in normal cells by chemical agents. chinese hamster embryo cells and human skin fibroblasts in culture were treated with the promoting agent phorbol-12,13-didecanoate (pdd) with or without prior treatment with 3-methylcholanthrene (mca), and various phenotypic effects were monitored ...19873664954
chromosome segregation from cell hybrids. iii. segregation is independent of spindle constitution.hamster beta-tubulin (detected as a mutant subunit that confers colcemid resistance) is either not expressed or is underexpressed in chinese hamster-mouse somatic cell hybrids. this selectivity of tubulin expression suggests that a uniparental mouse spindle might preferentially engage mouse chromosomes and lead to loss of hamster chromosomes. however, the repression of hamster tubulin was found to have no bearing on the direction of chromosome segregation occurring in eight hybrids studied, some ...19873666450
structure of the carbohydrate moiety of human interferon-beta secreted by a recombinant chinese hamster ovary cell line.the carbohydrate structure of the major oligosaccharide of human interferon-beta (ifn-beta) synthesized by a genetically engineered chinese hamster ovary cell line has been determined. analysis of the glycopeptidase f-released carbohydrates by sequential exoglycosidase treatment, methylation analysis, and fast atom bombardment-mass spectrometry revealed that 95% of the ifn-beta oligosaccharides had the following structure: (formula: see text). the remaining 5% of the carbohydrates are probably t ...19873667593
expression and characterization of human antithrombin iii synthesized in mammalian cells.antithrombin iii (atiii) has been expressed in transiently transfected cos-1 monkey cells and in stably transformed chinese hamster ovary cells, and the resultant protein has been characterized for biological activity. both cell types efficiently secrete high levels of heterogeneous molecular weight forms of atiii antigen. the heterogeneity results from differences in post-translational modifications. however, only a small percentage (5-10%) of the total antigen expressed is biologically active. ...19873667601
effect of propeptide mutations on post-translational processing of factor ix. evidence that beta-hydroxylation and gamma-carboxylation are independent events.post-translational processing of factor ix includes glycosylation, cleavage of the signal peptide and propeptide, vitamin k-dependent carboxylation of specific glutamic acid residues to form gamma-carboxyglutamic acid, and beta-hydroxylation of aspartic acid at residue 64 to form beta-hydroxyaspartic acid. the human factor ix cdna coding sequence was modified in the propeptide region (residue -18 to -1) using oligonucleotide-directed site-specific mutagenesis, and the altered factor ix cdna was ...19873667614
a monoclonal antibody recognizes a human nuclear protein resembling xenopus oocyte nucleoplasmin.the monoclonal antibody 10bg2 (igg3) was derived from a mouse immunized with human pre b cells. in immunofluorescence studies the antibody revealed a human nuclear-associated determinant, which in interphase cells was entirely restricted to the nucleus. in metaphase cells 10bg2 antigen was detected throughout the cytoplasm with intensified staining at the periphery of chromosomes. 10bg2 antibody stained all human normal and transformed cells tested. in contrast, the antibody did not stain mouse ...19873667726
interaction of [3h]dipyridamole with the nucleoside transporters of human erythrocytes and cultured animal cells.equilibrium binding of [3h]dipyridamole identified high-affinity (kd approximately 10 nm) binding sites on human erythrocytes (approximately 5 x 10(5) sites/cell) and on hela cells (approximately 5 x 10(6) sites/cell). the equilibration of dipyridamole with these sites on human erythrocytes was compatible with a second-order process which proceeded at 22 degrees c with a rate constant of about 6 x 10(6) m-1 sec-1. binding of dipyridamole to these sites correlated kinetically with the inhibition ...19873669065
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