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protective effect of two sunscreens against lethal and genotoxic effects of uvb in v79 chinese hamster cells and saccharomyces cerevisiae strains xv185-14c and d5.effects of p-aminobenzoic acid (paba) and of 4-[(2-oxo-3-bornylidene)methyl]-phenyl trimethylammonium methylsulfate (omm), two components used in sunscreen formulations, on the mutagenicity of uvb irradiation are compared in three genetic assay systems. a haploid strain of saccharomyces cerevisiae xv185-14c was used to measure reverse mutations at three loci. the diploid strain d5 of saccharomyces cerevisiae was used to screen for reciprocal mitotic recombination. the induction of forward mutati ...19921375337
cytotoxicity of 5-aza-2'-deoxycytidine in a mammalian cell system.after the addition of 5-aza-2'-deoxycytidine, a potent inhibitor of dna methylation and s-phase-specific cytotoxic agent, metaphase chromosomes of chinese hamster ovary (cho) cells exhibited a highly decondensed and extended morphology (numerous "fragile sites") at the first mitotic division. however, when a lethal dose of this drug was added in early g1 phase to cells synchronised by mitotic selection, the majority subsequently divided at the same time as an untreated control cell population wi ...19921375483
p-selectin and e-selectin. distinct but overlapping leukocyte ligand specificities.p-selectin on platelets and endothelial cells and e-selectin on endothelial cells are leukocyte receptors that recognize lineage-specific carbohydrates on neutrophils and monocytes. the proposed ligands for these receptors contain the le(x) core and sialic acid. since other investigators have shown that both e-selectin and p-selectin bind to sialylated le(x), we evaluated whether e-selectin and p-selectin recognize the same counter-receptor on leukocytes. the interaction of hl60 cells with chine ...19921375936
high cell density-dependent resistance and p-glycoprotein-mediated multidrug resistance in mitoxantrone-selected chinese hamster cells.mitoxantrone (mit) resistance has been studied in a colony selected from the cho aa8 parental line in one step under a low degree of selective pressure (9 nm). the cells of the clonal isolate aa8/mit c1(0) were sensitive to 9 nm mit at low cell density but able to grow at high density. parental aa8 cells were not able to grow under the latter condition. decreased mit accumulation (-20%) was observed at this step (step 0) in the absence of overexpression of mdr rna coding for the drug efflux pump ...19921376119
stable and functional expression of the calcium channel alpha 1 subunit from smooth muscle in somatic cell lines.voltage-activated calcium channels are membrane spanning proteins that allow the controlled entry of ca2+ into the cytoplasm of cells. the principal channel forming subunit of an l-type calcium channel is the alpha 1 subunit. transfection of chinese hamster ovary (cho) cells with complementary dna encoding the calcium channel alpha 1 subunit from smooth muscle led to the expression of functional calcium channels which bind calcium channel blockers and show the voltage-dependent activation and sl ...19921376244
(6-4) photoproducts and not cyclobutane pyrimidine dimers are the main uv-induced mutagenic lesions in chinese hamster cells.a partial revertant (rh1-26) of the uv-sensitive chinese hamster v79 cell mutant v-h1 (complementation group 2) was isolated and characterized. it was used to analyze the mutagenic potency of the 2 major uv-induced lesions, cyclobutane pyrimidine dimers and (6-4) photoproducts. both v-h1 and rh1-26 did not repair pyrimidine dimers measured in the genome overall as well as in the active hprt gene. repair of (6-4) photoproducts from the genome overall was slower in v-h1 than in wild-type v79 cells ...19921376437
sulfated polymers inhibit the interaction of human cytomegalovirus with cell surface heparan sulfate.several sulfated polysaccharides (dextran sulfate, pentosan polysulfate, heparin) and copolymers of acrylic acid with vinylalcohol sulfate have proved to be potent inhibitors of human cytomegalovirus (cmv) infectivity in vitro. sulfated alpha-cyclodextrins are only weak inhibitors of cmv. a close correlation was found between the 50% inhibitory concentrations of the sulfated polymers for cmv cytopathogenicity, virus-cell binding, and expression of immediate early antigens (iea) in human embryoni ...19921376540
dna double labelling with idurd and cldurd for spatial and temporal analysis of cell proliferation and dna replication.a procedure was developed that very effectively distinguishes between idurd and cldurd incorporated in the dna of cell nuclei and chromosomes. for double staining we used the rat anti-brdurd monoclonal antibody from sera-lab that binds specifically to cldurd and brdurd but not to idurd, in combination with the mouse anti-brdurd monoclonal antibody from becton dickinson. this antibody binds to all three halogenated deoxyuridines, but when the nuclei are washed in tris buffer with a high salt conc ...19921376726
expression and chromosome localization of the murine cystic fibrosis transmembrane conductance regulator.a 13.5-kb genomic fragment of the mouse cystic fibrosis transmembrane conductance regulator (cftr) gene was isolated from a c57bl/6j liver dna library, using a human cftr exon 10 probe. this region of the human gene includes the most common cystic fibrosis mutation (deletion of the phe508 residue) in the first nucleotide binding domain of cftr. sequence analysis demonstrated 87% identity between the predicted mouse and the normal human cftr exon 10 sequences, including conservation of the phe508 ...19921377165
determination of the amino acid residues in substance p conferring selectivity and specificity for the rat neurokinin receptors.we have measured the affinity of various analogs and fragments of the tachykinin substance p for the cloned rat nk1, nk2, and nk3 receptors heterologously expressed in chinese hamster ovary cells. the hydrophobic carboxyl-terminal pentapeptide sequence substance p-(7-11) binds with similar affinity (2-20 microm) to all three receptors. our data suggest that addition of one to three amino-terminal residues to this sequence results in the optimization of its interaction within the binding pocket o ...19921377326
mutation induction and dna adduct formation in chinese hamster ovary cells treated with 6-nitrochrysene, 6-aminochrysene and their metabolites.6-nitrochrysene, 6-aminochrysene and several of their metabolites were assayed for mutagenic activity at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus in dna-repair-proficient chinese hamster ovary (cho-k1) cells and excision-repair-deficient cho-uv5 cells. mutagen-dna adducts were analyzed by 32p-postlabeling in cells treated under the conditions of the mutagenicity assay and compared with the adduct patterns produced from the in vitro reaction of metabolites of 6-nitrochryse ...19921377330
induction of micronuclei in v79 chinese hamster cells by tetrachlorohydroquinone, a metabolite of pentachlorophenol.tetrachlorohydroquinone, a metabolite of the fungicide pentachlorophenol, induced significant dose-related increases in micronuclei in v79 chinese hamster cells without exogenous metabolic activation. the lowest observed effective dose was 10 microm, where the relative survival was about 62%. at the highest dose tested, 20 microm, the relative survival was about 8% and the frequency of cells with micronuclei was about 6 times the solvent control frequency. the induction of micronuclei by tetrach ...19921377336
evaluation of genotoxicity of tert.-butylhydroquinone in an hepatocyte-mediated assay with v79 chinese hamster lung cells and in strain d7 of saccharomyces cerevisiae.tert.-butylhydroquinone (tbhq) has been reported to be genotoxic in some short-term assays but non-genotoxic in others. we have examined cytotoxicity and genotoxicity of tbhq, a principal metabolite of the phenolic antioxidant 2(3)-tert.-butyl-4-hydroxyanisole (bha), in an hepatocyte-mediated assay with v79 chinese hamster lung cells including both sister-chromatid exchange (sce) and thioguanine-resistance (tgr) endpoints. the ability of bha and of tbhq to elicit a genotoxic response in saccharo ...19921377341
simultaneous analysis of chromosome damage and aneuploidy in cytokinesis-blocked v79 chinese hamster lung cells using an antikinetochore antibody.a modified antikinetochore antibody technique was established in the v79 chinese hamster lung cells to simultaneously analyze chromosome damage and aneuploidy induced by various agents. the method involved sequential treatment of slides with crest serum, fluoresceinated goat-antihuman and swine-antigoat antibodies, and propidium iodide. in this method, cytoplasm (green), nuclei or micronuclei (red), and kinetochores (yellow), are identified using the same filter setting under blue excitation (44 ...19921377355
genotoxicity of n-acryloyl-n'-phenylpiperazine, a redox activator for acrylic resin polymerization.n-acryloyl-n'-phenylpiperazine is a promoter of redox reactions synthesized recently, and proposed as an activator for the polymerization of acrylic resins for biomedical use. the chemical was analyzed for different genotoxicity endpoints, to obtain both information on its possible mutagenic/carcinogenic potential and a model analysis of a tertiary arylamine, which belongs to a class of chemicals commonly used as polymerization accelerators in the biomaterial field. the genotoxicity endpoints co ...19921377358
epitopes predominantly retained on the carcinoembryonic antigen molecules in plasma of patients with malignant tumors but not on those in plasma of normal individuals.we have previously reported that a group of monoclonal antibodies (mabs) to carcinoembryonic antigen (cea), designated group f mabs, are able to discriminate cea in tumor tissues from normal fecal antigen-2, a soluble form cea-counterpart in normal adult feces, and that the protein epitopes recognized by them are present on the domain a3-b3 of the cea molecule. in this study, we further investigated the molecular localization of the epitopes recognized by the group f mabs using three new recombi ...19921377668
spectrum of sialylated and nonsialylated fuco-oligosaccharides bound by the endothelial-leukocyte adhesion molecule e-selectin. dependence of the carbohydrate binding activity on e-selectin density.carbohydrate recognition by the human endothelial-leukocyte adhesion molecule, e-selectin, has been investigated by binding studies using 3h-labeled chinese hamster ovary cells expressing different levels of the transfected full-length adhesion molecule and a series of structurally defined oligosaccharides linked to the lipid phosphatidylethanolamine dipalmitoate (neoglycolipids) and synthetic glycolipids chromatographed on silica gel plates or immobilized on plastic wells. evidence is presented ...19921377689
the hinge region of the cd8 alpha chain: structure, antigenicity, and utility in expression of immunoglobulin superfamily domains.the lymphocyte surface cd8 antigen is a heterodimer with each chain containing a single ig-related domain, a hinge-like sequence, a transmembrane segment, and a short cytoplasmic sequence. a soluble form of the rat cd8 alpha chain was produced by introducing a stop codon into the cdna at the end of the region encoding the extracellular sequence and expressed in chinese hamster ovary cells. scd8 alpha was produced at 20 mg/l, and consisted of monomers, dimers, and higher aggregates. the latter co ...19921377946
species-specific restriction of complement by hrf20 (cd59) generated by cdna transfection.the 20-kda homologous restriction factor (hrf20, cd59) is a phosphatidyl inositol-anchored membrane glycoprotein that inhibits the formation of human complement membrane attack complexes. the cdna of hrf20 was transfected into chinese hamster ovary (cho) cells resulting in expression of human hrf20 protein on the cell surface anchored via glycosylphosphatidyl inositol. the transfected cho cells were resistant to human complement-mediated cell killing. however, the cells remained sensitive to rat ...19921378024
highly sensitive enzyme-linked immunosorbent assay for marograstim (kw-2228), a mutant of human granulocyte colony-stimulating factor.an enzyme-linked immunosorbent assay (elisa) for marograstim (kw-2228) was established. this elisa proved to be highly sensitive with the detection limit of 0.01 ng/ml (about 0.5 fmol/ml) of kw-2228 and the assay range between 0.01 and 2 ng/ml. when 0.02 to 2 ng/ml of kw-2228 added to human plasma was determined, the variation coefficiencies of intra-day and inter-day assays were 0.4 to 7.6% and 5.2 to 15.8%, respectively, with good recoveries. these results indicate that this elisa will be appl ...19921378090
radiation-sensitive irs mutants rejoin dna double-strand breaks with efficiency similar to that of parental v79 cells but show altered response to radiation-induced g2 delay.induction and repair of dna double-strand breaks (dsb) was investigated in plateau phase chinese hamster v79 cells and three radiosensitive mutant cell lines derived from them, irs-1, irs-2 and irs-3, using a pulsed-field gel electrophoresis assay, asymmetric field inversion gel electrophoresis (afige). there was no difference in the induction of dna dsb per gy and dalton between the radiosensitive mutant cells and wild-type v79 cells despite the wide differences in their radiosensitivity. also, ...19921378203
uv-induced hprt mutations in a uv-sensitive hamster cell line from complementation group 3 are biased towards the transcribed strand.the molecular nature of 254 nm ultraviolet light (uv)-induced mutations at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in uv24 chinese hamster ovary (cho) cells, which are defective in nucleotide excision repair, was determined. sequence analysis of 19 hprt mutants showed that single base substitutions (9 mutants) and tandem base changes (7 mutants) dominated the uv mutation spectrum in this cell line. sixty-five percent of the base substitutions were gc greater than at trans ...19921378206
inhibition of transcription and strand-specific dna repair by alpha-amanitin in chinese hamster ovary cells.recent studies have shown preferential repair of uv-induced cyclobutane pyrimidine dimers (cpd) in the transcribed strand of the expressed dihydrofolate reductase (dhfr) gene in human and rodent cells. we have tested the hypothesis that the strand-specific repair of such transcription-blocking lesions is dependent upon concurrent transcription. chinese hamster ovary (cho) b11 cells with an amplified dhfr gene were treated with alpha-amanitin before irradiation with uv (254 nm) and during post-ir ...19921378211
genotoxic potential of crown ethers in mammalian cells: induction of sister-chromatid exchanges.crown ethers are macrocyclic polyethers which possess ionophoric properties. these compounds are currently being studied for potential use as pharmaceutical agents as well as antibacterials. though crown ethers have been shown to be highly toxic in prokaryotes and eukaryotes, there have been few investigations into the potential genotoxicity of these compounds. when sister-chromatid exchanges (sces) were quantitated after exposure to crown ethers, the results reflected no significant genotoxic e ...19901378535
expression of soluble isoforms of rat cd45. analysis by electron microscopy and use in epitope mapping of anti-cd45r monoclonal antibodies.the cd45 or leucocyte-common antigens are encoded by a single gene but can be found in various forms due to alternative splicing of three exons near the 5' end of the gene. the cd45 antigens are major glycoproteins of all types of leucocytes. monoclonal antibodies recognizing restricted epitopes of cd45 have been used to distinguish phenotypic and functional subsets of lymphocytes. to facilitate epitope mapping and biochemical studies, we have expressed the extracellular portions for four differ ...19921378817
the cystic fibrosis transmembrane regulator is present and functional in endosomes. role as a determinant of endosomal ph.cystic fibrosis is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (cftr), which lead to defective cl- conductance in epithelial cells. while the cftr gene product has been detected in the plasma membrane, its presence and functional role in the membranes of intracellular compartments remain to be established. the purpose of the present experiments was to functionally localize cftr in the endosomal membrane and to test the role of the associated c ...19921378835
reversion of radiosensitivity in azacytidine-treated xrs5 cells does not result in full radioprotection by wr-1065.a series of cell lines were previously generated from the radiation sensitive chinese hamster ovary line xrs5 after treatment with azacytidine. six of these lines have been examined for their resistance to killing by 0 to 20 gray of 60co gamma rays and the amount of radioprotection afforded by treatment with the drug 2-[(aminopropyl)amino]ethanethiol (wr-1065). as xrs5 cells have lost the ability to be protected by wr-1065, studies were performed to determine whether reversion to radio-resistanc ...19921379219
in vitro and in vivo mutagenicity studies on sporidesmin, the toxin associated with facial eczema in ruminants.sporidesmin, a fungal toxin with widespread distribution within new zealand, is thought to exert toxic effects through oxidative damage. the purified chemical was tested for its ability to cause point mutations in four strains of salmonella typhimurium (ta98, ta100, ta102 and ta1537), in the presence and absence of exogenous metabolic activation. although toxic effects were seen at concentrations exceeding 400 mu gl/plate, there were no significant increases in revertant colonies. in strain ta10 ...19921379325
comparative investigation of cyclophosphamide action on bone marrow cells of the armenian hamster and 4 other species of rodents.we studied the clastogenic action of cyclophosphamide (cp) on bone marrow cells of the armenian hamster (ah), cricetulus migratorius. cp induced a dose-dependent linear increase in aberrant cells. the maximal cytogenetic action was observed 12 h after cp treatment. male and female ahs were similarly sensitive to the clastogenic action of cp. we compared cp clastogenicity at a dose of 25 mg/kg on bone marrow cells of ahs, mice, rats, guinea pigs and chinese hamsters 24 h after treatment. we obser ...19921379326
different modifications by vanillin in cytotoxicity and genetic changes induced by ems and h2o2 in cultured chinese hamster cells.the modifying effects of vanillin on the cytotoxicity and 6-thioguanine (6tg)-resistant mutations induced by two different types of chemical mutagens, ethyl methanesulfonate (ems) and hydrogen peroxide (h2o2), were examined using cultured chinese hamster v79 cells. the effects of vanillin on h2o2-induced chromosome aberrations were also examined. vanillin had a dose-dependent enhancing effect on ems-induced cytotoxicity and 6tg-resistant mutations, when cells were simultaneously treated with van ...19921379329
an inhibitor of potentially lethal damage (pld) repair reduces the frequency of gamma-ray-induced mutations in cultured chinese hamster v79 cells.cordycepin (3'-deoxyadenosine, 3'-da) is an rna antimetabolite and a radiosensitizer in cultured mammalian cells. in the present paper, the effects of 3'-da on gamma-ray-induced lethality and 6-thioguanine (6tg)-resistant mutations in cultured chinese hamster v79 cells were examined. 3'-da had the effect of sensitizing the lethality induced by gamma-rays. the potentially lethal damage (pld) repair produced by post-incubation of cells in hanks' solution after gamma-irradiation was almost complete ...19921379331
clastogenicity of low ph to various cultured mammalian cells.it has been reported that low ph itself can be clastogenic to chinese hamster ovary cells or mouse lymphoma l5178y cells. on the other hand, there was no indication that low ph is clastogenic to rat or human lymphocytes. therefore, in order to evaluate the generality of clastogenicity of low ph conditions, chromosomal aberration tests were carried out on chinese hamster cell line cells (cho-k1, chl, don and v79 379a) and human cells (hela and peripheral lymphocytes used as whole-blood cultures). ...19921379335
monoclonal antibodies against defined epitopes of the human transferrin receptor cytoplasmic tail.three murine monoclonal antibodies (mabs) against the 61-residue amino-terminal cytoplasmic tail of the human transferrin receptor (tr) have been produced by immunization of mice with recombinant human tr produced in a baculovirus expression system. mutant human trs expressed in chick embryo fibroblasts (cefs) with point mutations or deletions in their cytoplasmic tails have been used to map the epitopes defined by each of the mabs. one mab, h68.4, previously shown to block receptor internalizat ...19921379471
a naturally occurring secreted form of fibroblast growth factor (fgf) receptor 1 binds basic fgf in preference over acidic fgf.alternatively spliced variants of fibroblast growth factor receptor 1 mrna are predicted to encode secreted forms and membrane-bound forms of receptors. the predicted amino acid sequences of these receptor variants differ in a portion of the extracellular region. in this study, we characterized the function of one of these splice variants which was predicted by its cdna to be a secreted fgf receptor. we expressed this secreted form of the human fgfr1 (sfgfr1) in chinese hamster ovary cells. the ...19921379591
clastogenicity of 2-chlorobenzylidene malonitrile (cs) in v79 chinese hamster cells.the clastogenicity of the sensory irritant 2-chlorobenzylidene malonitrile (cs) to v79 chinese hamster cells was investigated at various exposure conditions. cs efficiently induced chromatid-type aberrations in a dose-dependent manner provided the cells could run through at least one or two s-phases during a 20-h exposure over a 3-h exposure followed by a 20-h recovery period (cell cycle time 8-10 h). the induction of sces indicates an s-dependent mechanism. the hydrolysis products o-chlorobenza ...19921379683
chromosomal analysis of chinese hamster v79 cells exposed to multiple gamma-ray fractions: induction of adaptive response to mitomycin c.chinese hamster v79 cells were irradiated daily with 0.3 gy of gamma-rays 5 times per week for 12 weeks (total 18 gy). these cells were challenged with an additional dose of 15. gy gamma-rays or treated with 5 micrograms/ml of mitomycin c (mmc) for 2 h. in spite of the high total accumulated dose of gamma-rays, the number of chromosomal aberrations and sister-chromatid exchanges (sces) did not significantly increase in the preirradiated cells, as compared to control cells. if preirradiated cells ...19921379688
the rat angiotensin ii at1a receptor couples with three different signal transduction pathways.to examine whether the subpopulation of the rat type 1 angiotensin ii (aii) receptor (at1a) couples with a single or multiple signal transduction pathways, we constructed chinese hamster ovary (cho) cell lines producing the recombinant receptor. the expressed at1a receptor exhibits typical pharmacological characteristics of the at1 receptor, known to mediate the main physiological function of aii. addition of aii to the cho cells induced a rapid, transient increase in intracellular free ca2+ con ...19921379799
human recombinant soluble decay accelerating factor inhibits complement activation in vitro and in vivo.complement plays a role in activating the inflammatory response and has been implicated in the pathogenesis of some inflammatory diseases. with a view toward controlling unwanted c activation, we evaluated the c regulator, human decay accelerating factor (daf). three forms of recombinant daf were purified from transfected chinese hamster ovary cells: glycophosphatidylinositol (gpi)-linked membrane daf (mdaf) extracted from cell membranes; spontaneously shed soluble daf (sdaf) derived from mdaf; ...19921380537
increased sensitivity of a chinese hamster ovary cell line to alkylating agents after overexpression of the human metallothionein ii-a gene.the elevation of intracellular levels of metallothionein has been associated with the development of resistance to the cytotoxic effects of some alkylating agents. in order to study the mechanisms underlying metallothionein associated drug resistance we transfected the alkylating agent sensitive cho cell line mmc-1 (robson et al., 1985) with an episomally replicating plasmid coding for the human metallothionein ii-a gene. two transfectants were isolated which carried about 10 copies of the plasm ...19921380651
homologous recombination of adenovirus dna in mammalian cells: enhanced recombination following uv-irradiation of the virus.we have used adenovirus as a molecular probe to examine the recombination of viral dna following infection of mammalian cells. the technique gives a quantitative measure of homologous recombination between adenovirus type 2 (ad2) and ad5pymtr3. ad5pymtr3 is an insertion mutant of ad5 containing polyoma virus (py) dna inserted into a deleted e1 region of the ad5 genome. cells were coinfected with ad2 and ad5pymtr3 and at an appropriate time after infection, viral dna was extracted from the infect ...19921380653
differential gene expression in wild-type and x-ray-sensitive mutants of chinese hamster ovary cell lines.complementary dna cloning, differential screening and northern hybridization techniques were used to study differential gene expression in the wild-type chinese hamster ovary (cho) k1 cell line and its two x-ray sensitive mutants, xrs-5 and xrs-6. 11 species of mrnas were found underexpressed in the two independently isolated mutants. the steady-state levels of those mrnas are 3-26-fold less in the two mutants, depending on the particular species. 6 of the underexpressed mrnas have been identifi ...19921380656
induction of chromosomal damage in mammalian cells in vitro and in vivo by sulfapyridine or 5-aminosalicylic acid.sulfapyridine (sp) and 5-aminosalicylic acid (5-asa) are the two primary metabolites of the anti-inflammatory drug salicylazosulfapyridine (sasp). these two metabolites were studied for induction of chromosomal damage in mammalian cells, in vitro and in vivo, in an attempt to understand better the genetic effects produced by sasp in humans and laboratory mice. to this end, sp and 5-asa were tested for induction of sister-chromatid exchanges (sce) and chromosomal aberrations (abs) in chinese hams ...19921380664
review of the genotoxicity of ozone.ozone is a powerful oxidant, reactive to biomolecules. in aqueous solution it decomposes to give hydrogen peroxide, superoxide and hydroxy radicals which can take part in secondary reactions. ozone is a disinfectant that inactivates both viruses and bacteria. although other reactions are primarily responsible for the inactivation, cellular dna is also damaged. ozone is genotoxic to microorganisms, plants and cell cultures in vitro. the results from in vivo cytogenetic studies with laboratory ani ...19921381051
right-angle light scattering to assay basal and regulated plasma membrane cl- conductances.we describe a simple and rapid technique for assaying both constitutive and regulated plasma membrane cl- conductances. the method uses right-angle light scattering to measure the rate of swelling of cells in suspension, in which the anion conductance is rate limiting for swelling, due to introduction of high plasma membrane cation conductance using gramicidin. the technique was verified using chinese hamster ovary cells and mouse l cells, both stably transfected with the cystic fibrosis transme ...19921381149
sequences and expression of alleles of polymorphic arylamine n-acetyltransferase of human liver.fifty human livers obtained at autopsy were analyzed for n-acetyltransferase and classified into six genotypes. determination of n-acetyltransferase activity and proteins from supernatants of liver homogenates indicate that genotype i corresponds to rapid acetylator, genotypes ii and iii to intermediate acetylator, and genotypes iv, v, and vi to slow acetylator phenotypes. northern blot analysis shows that levels of mrna for n-acetyltransferase in the livers do not markedly differ among the six ...19921381364
forward mutations and dna-protein crosslinks induced by ammonium metavanadate in cultured mammalian cells.ammonium metavanadate yielded a dose-dependent increase in mutation frequency at the v79 hprt locus following a 24-h exposure period in serum-free f12 medium. vanadate also increased the mutation frequency of v79 cells by exposure of cells in salts-glucose medium, but these effects were not as striking, or as dose-dependent as they were in serum-free f12 medium. ammonium metavanadate enhanced the mutation frequency in a v79 variant containing a transfected bacterial gpt gene. these cells are kno ...19921381466
enhancing effects of heterocyclic amines and beta-carbolines on the induction of chromosome aberrations in cultured mammalian cells.the effects of post-treatment with heterocyclic amines and beta-carbolines on the induction of chromosome aberrations were studied in chinese hamster cho k-1 cells and sv40-transformed excision repair-deficient human xp2ossv cells. the number of chromosome aberrations induced by uv and mmc were increased by post-treatment with trp-p-1 and trp-p-2, in both the presence and the absence of s9 mix. a alpha c, mea alpha c, glu-p-1, glu-p-2, iq, meiq, harman and harmine increased chromosome aberration ...19921381474
genotoxicity of 2,4,6-trichlorophenol in v79 chinese hamster cells.the genotoxicity of the rodent carcinogen 2,4,6-trichlorophenol (tcp) was studied without exogenous metabolic activation in v79 chinese hamster cells. tcp did not induce mutation at the hprt locus to 6-thioguanine resistance or structural chromosome aberrations. however, it produced statistically significant, dose-related increases in hyperdiploidy and micronuclei. from these results it appears that tcp causes chromosome malsegregation as its major mode of genotoxic action.19921381480
detection of vincristine-induced hyperploidy in meiotic ii metaphases of male chinese hamsters.induction of hyperploidy in germ cells of male chinese hamsters treated with vincristine at dose levels of 0.25, 0.50 or 0.75 mg/kg of body weight was investigated. animals were killed at 6, 24, 48, 72 and 96 h after administration of the chemical by a single intraperitoneal injection. the testes were removed and processed for spermatogonial, meiotic i, and meiotic ii metaphases. significantly increased frequencies of hyperploidy were obtained in meiotic ii cells harvested 6, 24 and 48 h but not ...19921381481
the effect of gamma-irradiation on the toxicity of malathion in v79 chinese hamster cells and molt-4 human lymphocytes.there is growing interest in the irradiation of food and agricultural products for insect disinfestation, sprout inhibition, delayed ripening and the reduction of microbiological loads. extensive research has been done on this process, and irradiation to a maximum dose of 10 kgy is recognized as safe by national and international regulatory agencies. the question has been raised, however, whether irradiation of pesticide residues might produce radiation products that were more toxic or less toxi ...19921381482
genotoxicity assessment of pirmenol, a new antiarrhythmic drug.the genotoxicity of pirmenol was tested in the e. coli and s. typhimurium mutagenesis assay, an in vitro mammalian cell chromosome-aberration assay and an in vivo mouse micronucleus assay. the e. coli tester strain wp2s was exposed to concentrations of pirmenol as high as 10,000 micrograms/plate both in the absence (s9-) and presence (s9+) of metabolic activation. five strains of s. typhimurium (ta98, ta100, ta1535, ta1537, ta1538) were exposed to concentrations of pirmenol as high as 5000 micro ...19921381484
chinese hamster ovary cells deficient or proficient in o6-alkylguanine-dna alkyltransferase activity are equally sensitive to x-rays.in mammalian cells, under aerobic conditions, ionizing radiations and radiomimetic chemical agents can induce an enzymatic activity involved in dna repair, o6-alkylguanine-dna alkyltransferase (o6-at). this catalytic protein is active against alkyl-radical-induced dna damages. this induction was proposed to be linked to the formation of hydroxyl radicals. the possible involvement of o6-at in the defense mechanism of the cell against aerobic radiation damage was investigated by comparing the x-ra ...19921381489
molecular weights of glycosylated and nonglycosylated forms of recombinant human stem cell factor determined by low-angle laser light scattering.the molecular weight of recombinant human stem cell factor (scf) was determined using a low-angle laser light scattering combined with a differential refractometer and a uv detector. the protein samples were applied to these detectors through a gel filtration column by a high-performance liquid chromatographic pump. the chinese hamster ovary (cho) cell-derived scf gave a molecular weight of 53,000 for the entire molecule and 35,000 for the protein moiety only at ph 7.0, indicating that the cho c ...19921381876
post-translational processing of membrane-associated recombinant human stem cell factor expressed in chinese hamster ovary cells.this report describes the structure of soluble human stem cell factor isolated from the conditioned medium of chinese hamster ovary (cho) cells transfected with stem cell factor (scf) cdna, which encodes a leader sequence plus 248 additional amino acids. the 248 amino acids include a hydrophobic transmembrane region at positions 190-212. the isolated material is glycosylated and three bands (apparent m(r) 28,000, m(r) 35,000, and m(r) 40,000) are evident by sodium dodecyl sulfate (sds)-polyacryl ...19921381905
induction of resistance to 6-thioguanine and cytarabine by a range of anticancer drugs in chinese hamster aa8 cells.a mutagenicity assay using aa8 chinese hamster cells has been used to explore the potential of some currently used clinical anticancer drugs to induce cells resistant to 6-thioguanine and cytarabine. preliminary experiments gave evidence of a "low dose" and "high dose" resistance to cytarabine, and subsequent work considered only the latter of these events. when ethyl methane sulphonate was used as a reference mutagen, induced resistance to cytarabine developed substantially later and at a lower ...19921381928
high level expression on a chimeric anti-ganglioside gd2 antibody: genomic kappa sequences improve expression in cos and cho cells.we report a flexible strategy for the high level expression of a recombinant human monoclonal antibody (mab) in chinese hamster ovary (cho) cells, initially using cos monkey kidney cell transfections to evaluate rapidly modifications to immunoglobulin (ig) dna constructs. using sequential transfections with two amplifiable markers, we generated cho cell lines and clones that secrete 80-110 micrograms/10(6) cells/24 hours of a mouse-human chimeric igg1 kappa mab. this cellular productivity is con ...19921382457
novel sulfated ligands for the cell adhesion molecule e-selectin revealed by the neoglycolipid technology among o-linked oligosaccharides on an ovarian cystadenoma glycoprotein.e-selectin is the inducible adhesion protein on the surface of endothelial cells which has a crucial role in the initial stages of recruitment of leucocytes to sites of inflammation. in addition, it is almost certainly involved in tumor cell adhesion and metastasis. this report is concerned with identification of a new class of oligosaccharide ligand--sulfate-containing--for the human e-selectin molecule from among oligosaccharides on an ovarian cystadenoma glycoprotein. this has been achieved b ...19921382586
normal human erythrocytes express cd36, an adhesion molecule of monocytes, platelets, and endothelial cells.we have recently shown that rosetting of plasmodium falciparum (mc r+ line)-infected erythrocytes (parasitized red blood cells [prbcs]) with uninfected erythrocytes (rbcs) is blocked by coating of the rbcs with anti-cd36 monoclonal antibodies (moabs; handunnetti et al, blood 80:2097, 1992). adult rbcs have previously been considered negative for cd36. however, using fluorescence-activated cell sorter analysis with the anti-cd36 moabs 8a6, okm5, and okm8, which reverse rosetting, we consistently ...19921382721
expression of carcinoembryonic antigen and its predicted immunoglobulin-like domains in hela cells for epitope analysis.carcinoembryonic antigen (cea) is a member of the immunoglobulin gene superfamily with one predicted variable domain-like region (n domain; 108 amino acids) and three sets of constant domain-like regions (a1b1, a2b2, and a3b3; 92 amino acids for a domains and 86 amino acids for b domains). in addition, cea possesses two signal peptides, one at the amino terminus and one at the carboxyl terminus. both are removed during posttranslational processing, with the one at the carboxyl terminus being rep ...19921382844
the thermoresistant state: protection from initial damage or better repair?the induction of and recovery from heat-induced perturbations in several cellular parameters were examined in normal, transiently thermotolerant, and permanently heat-resistant ha-1 chinese hamster fibroblasts. the initial heat-induced perturbations in total cellular protein synthesis, rna synthesis, vimentin-containing intermediate filaments, and nuclear protein mass were similar in the three different cell types which display various levels of thermal resistance as determined by clonogenic sur ...19921383016
production and secretion in cho cells of the extracellular domain of amog/beta 2, a type-ii membrane protein.a hybrid gene consisting of the sequences coding for the signal peptide and n terminus of a type-i membrane protein, the neural cell adhesion molecule (n-cam), and the extracellular domain of the adhesion molecule on glia (amog/beta 2), a type-ii membrane protein, was constructed. the sequence was inserted into a eukaryotic expression vector containing the human cytomegalovirus promoter and the glutamine synthetase selection marker, and used to transfect chinese hamster ovary cells. the resultin ...19921383096
biochemical characterization of 25 distinct carcinoembryonic antigen (cea) epitopes recognized by 57 monoclonal antibodies and categorized into seven groups in terms of domain structure of the cea molecule.the chemical nature of 25 distinct carcinoembryonic antigen (cea) epitopes, which were recognized by 57 different monoclonal antibodies and categorized into 7 groups (groups a to g) in terms of domain structure of the cea molecule, was analyzed and the findings obtained were compared with the results of our previous studies using recombinant cea proteins. all 21 epitopes of groups a to f defined by 48 mabs were resistant to periodate oxidation and were to a greater or lesser extent retained afte ...19921383122
a potent enhancer made of clustered liver-specific elements in the transcription control sequences of human alpha 1-microglobulin/bikunin gene.alpha 1-microglobulin (a1m) and bikunin are plasma proteins which are present both as free molecules and as complexes with either iga heavy chains for a1m or the h1, h2, and h3 heavy chains of the inter-alpha-inhibitor family for bikunin. mature a1m and bikunin originate from the cleavage of an a1m/bikunin precursor (abp) synthesized from a single gene with liver-specific expression. five kilobases of the 5'-flanking region of the human abp gene were sequenced. deletion mutants of this region su ...19921383209
mapping of epitopes, glycosylation sites, and complement regulatory domains in human decay accelerating factor.decay accelerating factor (daf, cd55) is a glycophospholipid-anchored membrane protein that protects cells from complement-mediated damage by inhibiting the formation and accelerating the decay of c3/c5 convertases. daf deletion mutants lacking each of the four short consensus repeats (scr) or the serine/threonine-rich region (s/t) were created by site-directed mutagenesis. these deletion mutants were expressed by stable transfection in chinese hamster ovary cells for the purpose of mapping impo ...19921383332
interaction between the kinetics of thermotolerance and effect of cis-diamminedichloroplatinum(ii) or bleomycin given at 37 or 43 degrees c.the interaction between the cytotoxic effect of bleomycin (blm) or cis-diamminedichloroplatinum(ii) (cis-ddp) and the kinetics of thermotolerance was studied in cultured chinese hamster ovary (cho) cells. pre-heated cells were treated with cis-ddp or blm at 37 or 43 degrees c for various times after heating. pre-heating enhanced cis-ddp cytotoxicity given immediately after heating, but this enhancement decreased within 24 h to an additive level. cell survival following the initial heating and th ...20131383358
characterization of the binding of a potent, selective, radioiodinated antagonist to the human neurokinin-1 receptor.we have synthesized a potent, selective, radioiodinated antagonist of the human neurokinin-1 (nk1) receptor and have characterized its binding to the cloned receptor expressed in chinese hamster ovary cells. (cis)-2-(diphenylmethyl)-n-[(2-iodophenyl)-methyl]-1- azabicyclo[2.2.2]octan-3-amine (l-703606) inhibits binding of 125i-tyr8-substance p to the human nk1 receptor with an ic50 of 2 nm. this compound is a competitive antagonist of substance p-induced inositol phosphate generation, with a kb ...19921383685
analysis of x-ray-induced hprt mutations in cho cells: insertion and deletions.molecular alterations were examined in the hypoxanthine guanine phosphoribosyltransferase (hprt) gene of 41 independent x-ray-induced thioguanine-resistant (tgr) chinese hamster ovary (cho) cell clones. rapid screening of the clones by multiplex polymerase chain reaction (pcr) for the presence or absence of exons revealed that the causes of the mutant phenotype were total gene deletion (26/41), partial gene deletion (4/41), and an insertion (1/41). no alterations of exon number or sizes were app ...20051383700
nalidixic acid-resistant v79 cells with reduced dna topoisomerase ii activity and amplification prone phenotype.spontaneously nalidixic acid-resistant lines (nar lines) were selected from a v79 chinese hamster cell line and phenotypically characterized. nar lines showed an increased doubling time, a higher number of spontaneous sce, and more interestingly, decreased dna topoisomerase ii activity. these lines were also cross-resistant to the eukaryotic topoisomerase ii inhibitors etoposide and adriamycin, but showed the same level of sensitivity as the parental line to the dna topoisomerase i inhibitor cam ...20061383716
dna base sequence changes in spontaneous and ethyl methanesulfonate-induced mutations of a chromosomally-integrated gene in chinese hamster ovary cells.a series of spontaneous and ethyl methanesulfonate-induced 6-thioguanine-resistant mutants were isolated in the cho-10t5 cell line. this cell line was constructed by the introduction of a shuttle vector containing the escherichia coli gpt gene into a hypoxanthine-guanine phosphoribosyltransferase deficient derivative of the chinese hamster cell line cho-k1. shuttle vector sequences were recovered from many of the mutant cell lines by the cos cell fusion technique and the dna base sequence of the ...19921383728
effects of an inhibitor and a mimic of superoxide dismutase on bleomycin mutagenesis in chinese hamster ovary cells.we have investigated the roles of reactive oxygen species (ros) in bleomycin (blm)-induced gene mutations in chinese hamster ovary (cho) cells using a superoxide dismutase (sod) inhibitor, triethylenetetramine (trien), and a sod mimic, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tem-pol), to lower and increase intracellular 'sod activity', respectively. pretreatment of cho cells with trien (1 mm) for 1 h enhanced the mutagenic response of blm (5-50 micrograms/ml, 1 h treatment) in the hypoxa ...20021383733
persistently elevated frequency of spontaneous mutations in progeny of cho clones surviving x-irradiation: association with delayed reproductive death phenotype.certain clonal progeny of chinese hamster ovary (cho) cells surviving x-irradiation demonstrate pleomorphic changes including a persistently decreased cloning efficiency, a dominant phenotype we have termed delayed reproductive death (chang and little, 1991, 1992b). we now report that cells from these progeny clones show a persistently elevated frequency of spontaneous mutations at the hprt locus for up to 95-100 population doublings post-irradiation. mutant fractions as high as 10(-3) were scor ...19921383736
genotoxicities of nitropyrenes and their modulation by apigenin, tannic acid, ellagic acid and indole-3-carbinol in the salmonella and cho systems.four naturally occurring compounds, indole-3-carbinol (i3c), apigenin (api), ellagic acid (ea) and tannic acid (ta), were tested for their inhibitory effects against 1-nitropyrene- (1-np) or 1,6-dinitropyrene (1,6-dnp)-induced genotoxicity in salmonella tester strains and chinese hamster ovary (cho) cells. api and ta strongly inhibited the bacterial mutagenesis induced by nitropyrenes, while i3c and ea had little or no effect. for example, in ta98, 0.2 mumole api resulted in 48% and 56% inhibiti ...19921383740
bombesin impairs spindle function in mitotic v79 chinese hamster cells by a receptor-dependent mechanism.bombesin belongs to a family of peptides acting as local hormones with roles in growth regulation, neural function and secretion. upon binding to its receptor bombesin primarily elicits an increase of inositolphosphates and diacylglycerol, events leading to increased [ca2+]i and activation of protein kinase c. when asynchronously growing v79 chinese hamster cells were treated with bombesin in the 10(-9)-10(-7) m concentration range their content of inositolphosphates increased and so did the fre ...19921383741
cell culture models for oxidative stress: superoxide and hydrogen peroxide versus normobaric hyperoxia.according to the free radical theory of aging, loss of cellular function during aging is a consequence of accumulating subcellular damage inflicted by activated oxygen species. in cells, the deleterious effects of activated oxygen species may become manifest when the balance between radical formation and destruction (removal) is disturbed creating a situation denoted as 'oxidative stress'. cell culture systems are especially useful to study the effects of oxidative stress, in terms of both toxic ...19921383781
potentiation of sodium chromate(vi)-induced chromosomal aberrations and mutation by vitamin b2 in chinese hamster v79 cells.the effect of vitamin b2, which is capable of reducing chromium(vi) to chromium(v), on chromosomal aberrations and mutation caused by na2cro4 was investigated in chinese hamster v79 cells. pretreatment with 200 microm vitamin b2 (riboflavin) for 24 h prior to exposure to na2cro4 (2.5-5 microm) resulted in an increase of metal-induced chromosomal aberrations and mutation at the hgprt locus. these and other previous studies suggest that vitamin b2 enhances the clastogenic and mutagenic action of c ...19921383790
rabbit very low density lipoprotein receptor: a low density lipoprotein receptor-like protein with distinct ligand specificity.a cdna that expresses a receptor for very low density lipoprotein (vldl) was isolated from a rabbit heart cdna library and characterized. the deduced amino acid sequence of the cdna revealed that the cdna encodes a protein with striking homology to the low density lipoprotein (ldl) receptor. like the ldl receptor, the mature protein consists of the following five domains spanning 846 amino acids: 328 n-terminal amino acids including an 8-fold repeat of 40 amino acids homologous to the ligand bin ...19921384047
transfection of the escherichia coli nth gene into radiosensitive chinese hamster cells: effects on sensitivity to radiation, hydrogen peroxide, and bleomycin sulfate.the escherichia coli nth gene encodes endonuclease iii, which catalyses the glycolytic removal of various oxidized thymine residues from dna. a truncated version of nth, with the prokaryotic regulatory sequences removed, was ligated into the retrovirus-based vector pzipneosv(x)1 and transfected into the radiosensitive chinese hamster ovary cell line, xrs7. following selection with g418, two clones (x7nth1 and x7nth6) were shown by southern analysis to contain the nth gene. no substantial differe ...19921384080
small linear chloride channels are endogenous to nonepithelial cells.we used both single-channel and whole cell patch-clamp techniques to characterize chloride channels and currents endogenous to sf9 cells, 3t3 fibroblasts, and chinese hamster ovary cells. in cell-attached patches from these cell types, anion channels were observed with low ohmic conductance (4-11 ps), linear current-voltage relationships, and little time- or voltage-dependent behavior. these channels are very similar to the cl- channels reported to appear concomitant with the expression of cysti ...19921384347
characterization of a bifunctional peptidylglycine alpha-amidating enzyme expressed in chinese hamster ovary cells.peptidylglycine alpha-amidating enzyme (alpha-ae) catalyzes the conversion of glycine-extended prohormones to their biologically active alpha-amidated forms. we have derived a clonal chinese hamster ovary cell line that secretes significant quantities of active alpha-ae. enzyme production was increased by selection for methotrexate-resistant cells expressing a dicistronic message. amplification of the alpha-ae gene was monitored by southern blot analysis, enzyme activity, and immunoreactive prot ...19921384431
rat cystathionine beta-synthase: expression of four alternatively spliced isoforms in transfected cultured cells.the gene for rat cystathionine beta-synthase consists of 17 exons. its transcripts are alternatively spliced, forming four distinct mrna species. type iii consists of exons 1 through 12, 14, 15, and 17; type i also contains exon 16. the open reading frame of type iv spans exons 1-->13; type ii, 3-->13. we cloned the corresponding cdnas into appropriate expression vectors and inserted the constructs into escherichia coli (i, iii, and iv) and chinese hamster (ch) cells (i through iv); all sequence ...19921384433
hexachlorocyclohexane pesticides reduce survival and alter plasma membrane structure of chinese hamster v79 cells.we studied the cytotoxic effects of alpha-, beta-, gamma-, and delta-hexachlorocyclohexanes (hcch) on the survival of chinese hamster v79 cells using clonogenic assays. lethal dose yielding 50% cell survival (ld50) suggests the following order of cytotoxicity: delta-(+)gamma-hcch (ld50 4 micrograms/ml) (1:1, w/w, mixture) > delta-hcch (ld50 6 micrograms/ml) > gamma-hcch (ld50 13 micrograms/ml) > alpha-hcch (ld50 approx. 35 micrograms/ml) > beta-hcch. structural changes in plasma membranes prepar ...19921384434
excessive production of transforming growth-factor beta 1 can play an important role in the development of tumorigenesis by its action for angiogenesis: validity of neutralizing antibodies to block tumor growth.angiogenesis is an important part of tumor growth in vivo. we used the transfected chinese hamster ovary (cho) cells that overproduced recombinant transforming growth-factor beta 1 (tgf-beta 1) to examine the possible role of this factor in tumor growth and angiogenesis in a nude mouse model. the in-vitro proliferation of tgf-beta 1-transfected cho cells was unaffected by the treatment of either recombinant tgf-beta 1 or an anti-tgf-beta 1 antibody. the tgf-beta 1-transfected cells grew more rap ...19921384712
cd59 molecule: a second ligand for cd2 in t cell adhesion.the t cell surface molecule cd2 forms, with its counter-receptor cd58 (lfa-3), a powerful adhesion/activation pathway. there is some evidence that cd2 might bind more than a single ligand. chinese hamster ovary cells (cho) expressing human cd59 after cdna transfection (cd59+cho) form rosettes with human t cells; these rosettes are inhibited in a dose-dependent fashion by the cd59 monoclonal antibody (mab) h19 and by the cd2 mab o275 known to block natural rosettes, but not by the cd2r mab d66, a ...19921385156
genotoxicity studies in vitro and in vivo on carminic acid (natural red 4).the potential genotoxic activity of carminic acid (cas no. 1260-17-9; einecs no. 215-023-3; c.i. no. 75410), a component of natural red colouring products (cochineal: cas no. 1343-78-8; einecs no. 215-680-6; c.i. no. 75470), used in food, cosmetics and drugs, has been evaluated by means of a series of short-term tests in vitro and in vivo, namely salmonella reverse mutation, chromosome aberrations and sister chromatid exchanges in vitro on chinese hamster ovary cells, and the mouse micronucleus ...19921385283
n-glycosylation is required for human cd2 immunoadhesion functions.the t-lymphocyte glycoprotein receptor, cd2, mediates cell-cell adhesion by binding to the surface molecule cd58 (lfa-3) on many cell types including antigen presenting cells. two domains comprise the cd2 extracellular segment, with all adhesion functions localized to the amino-terminal domain that contains a single n-glycosylation site at asn65. we have defined an important role for the n-linked glycans attached to asn65 of this domain in mediating cd2-cd58 interactions and also characterize it ...19921385399
expression and function of irs-1 in insulin signal transmission.irs-1 is a major insulin receptor substrate which may play an important role in insulin signal transmission. the mrna for irs-1 in rat cells and tissues is about 9.5 kilobases (kb). rat liver irs-1 was stably expressed in chinese hamster ovary (cho) cells (cho/irs-1). although its calculated molecular mass is 131 kda, irs-1 from quiescent cells migrated between 165 and 170 kda during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. irs-1 was phosphorylated strongly on serine residues a ...19921385403
growth hormone (gh) induction of tyrosine phosphorylation and activation of mitogen-activated protein kinases in cells transfected with rat gh receptor cdna.the mechanism of growth hormone (gh) action was studied in chinese hamster ovary (cho) cells transfected with gh receptor cdna. cytosolic extracts from gh- or phorbol ester (12-o-tetradecanoyl 4 beta-phorbol 13-acetate)-treated cells, transfected with full-length gh receptor cdna, had an enhanced ability to phosphorylate myelin basic protein. myelin basic protein, a substrate for mitogen-activated protein (map) kinase, was maximally phosphorylated using extracts from cells treated with 50 nm bov ...19921385420
b7 costimulates proliferation of cd4-8+ t lymphocytes but is not required for the deletion of immature cd4+8+ thymocytes.in addition to tcr-derived signals, costimulatory signals derived from stimulation of the cd28 molecule by its natural ligand, b7, have been shown to be required for cd4+8- t cell activation. we investigate the ability of b7 to provide costimulatory signals necessary to drive proliferation and differentiation of virgin cd4-8+ t-cells that express a transgenic tcr specific for the male (h-y) ag presented by h-2db class i mhc molecules. virgin male-specific cd4-8+ t cells can be activated either w ...19921385518
superantigen and hla-dr ligation induce phospholipase-c gamma 1 activation in class ii+ t cells.bacterial enterotoxin superantigens bind directly to hla class ii molecules (hla-dr) expressed on both apc and activated human t cells, and simultaneously bind to certain v beta chains of the tcr. in this report, we compared early t cell signaling events in human alloantigen-stimulated t cells when activated by hla-dr ligation through antibody cross-linking or by direct enterotoxin superantigen binding. both types of stimuli induced tyrosine phosphorylation of phosphatidylinositol-specific phosp ...19921385526
coupled expression of ca2+ transport atpase and a dihydrofolate reductase selectable marker in a mammalian cell system.stable expression of a full-length cdna encoding chicken fast muscle ca2+ transport atpase was obtained in a chinese hamster lung cell line (dc-3f), using a dual-promoter expression vector (ph beta fcaa3) in which the atpase was cloned downstream of a human beta-actin gene promoter, and a mutant dihydrofolate reductase cdna (a3/dhfr) was cloned downstream of an sv40 promoter-enhancer. owing to its essentially normal catalytic activity and modest (20-fold) resistance to the antifolate methotrexat ...19921385939
human cyclin b1 gene (ccnb1) assigned to chromosome 5 (q13-qter).cyclins play an important role in cell cycle regulation. at least five classes of cyclins have been identified--a, b, c, d, and e. b cyclins are generally of two types in most organisms--b1 and b2. we have mapped the gene for human cyclin b1 (ccnb1) to human chromosome 5 (region q13-qter) by southern blot analysis of human x chinese hamster somatic cell hybrid panels. many more cyclin b-related sequences have been identified in the mouse (cycb-1 to cycb-10) and have been mapped to chromosomes 4, ...19921386686
high-level stable expression of recombinant 5-ht1a 5-hydroxytryptamine receptors in chinese hamster ovary cells.the human 5-hydroxytryptamine 5-ht1a receptor gene was transfected into chinese hamster ovary cells. a series of recombinant monoclonal cell lines expressing the receptor were isolated and the properties of one cell line that expressed receptors at a high level (2.8 pmol/mg) were studied in detail. in ligand binding assays with the selective 5-ht1a receptor agonist 2-(nn-di[3h]propylamino)-8-hydroxy-1,2,3,4-tetrahydronaphthalene ([3h]8-oh-dpat) only a single class of saturable high-affinity bind ...19921386736
the asparagine-linked oligosaccharides on tissue factor pathway inhibitor terminate with so4-4galnac beta 1, 4glcnac beta 1,2 mana alpha.tissue factor pathway inhibitor (tfpi) produced by endothelial cells contains sulfated asn-linked oligosaccharides. we have determined that greater than 70% of the oligosaccharides on recombinant tfpi expressed in 293 cells terminate with the sequence so4-4galnac beta 1, 4glcnac beta 1, 2man alpha. oligosaccharides terminating with this sequence have previously been described on lutropin, thyrotropin, and pro-opiomelanocortin: glycoproteins synthesized in the anterior pituitary. a galnac-transfe ...19921388166
evidence that the scavenger receptor is not involved in the uptake of negatively charged liposomes by cells.scavenger receptors have a broad ligand specificity, ranging from modified low-density lipoproteins to a variety of high-molecular-weight poly-anions. a recent report by nishikawa et al. (j. biol. chem. (1990) 265, 5226-5231) suggested that this receptor is also involved in the binding and endocytosis of liposomes containing negatively charged phospholipids. the mechanism by which liposomes are taken up by cells is of interest because liposomes are promising versatile carriers for macromolecules ...19921390854
experimental evidence for the involvement of the cytoskeleton in mammalian cell electropermeabilization.chinese hamster ovary (cho) cells and human erythrocytes were pulsed by using square-wave electric-field pulses. this treatment induced their permeabilization. this phenomenon appears to be a three-step process of creation, expansion and annihilation of permeated structures. altering the cell cytoskeleton, either with drugs, such as colchicine, known to depolymerise the microtubules in cho cells, or by high temperature shock to affect the spectrin-actin network in erythrocytes, induced no modifi ...19921390863
biochemical properties of recombinant mutants of nonglycosylated single chain urokinase-type plasminogen activator.the role of glycosylation on the enzymatic properties of single chain urokinase-type plasminogen activator (scu-pa) was investigated by site-specific mutagenesis of the glycosylated asn-302 residu to gln. in addition, the role of the nh2-terminal polypeptide chain and of the cys-148 to cys-279 interchain disulphide bond on the activity of non-glycosylated scu-pa was investigated. therefore, variants of recombinant scu-pa (rscu-pa) were produced by transfecting chinese hamster ovary cells with cd ...19921390910
lethality, dna alkylation, and cell cycle effects of adozelesin (u-73975) on rodent and human cells.adozelesin (u-73975) is an extremely potent cytotoxic agent which causes 90% lethality, after 2 h exposure in vitro, of chinese hamster ovary and lung (cho and v79), mouse melanoma (b16), and human ovarian carcinoma (a2780) cells at 0.33, 0.19, 0.2, and 0.025 ng/ml, respectively. under similar conditions, adriamycin and cisplatin had 90% lethality values in cho cells of 150 ng/ml (= 249 nm) and 6800 ng/ml (= 2266 nm), respectively. the relative drug sensitivity of the cell lines (a2780 > v79, b1 ...19921394193
estrogen receptor-directed radiotoxicity with auger electrons: specificity and mean lethal dose.to assess the feasibility of using estrogen receptor-directed therapy with auger electron-emitting ligands for therapy of estrogen receptor (er)-containing cancers, we synthesized and evaluated the radiotoxicity of several 123i-labeled estrogens to specifically kill er+ cells in culture. auger electrons have been previously shown to be of short range, generally less than the dimensions of a cell, so that to use them therapeutically a mechanism is needed to deliver the auger electron-emitting nuc ...19921394199
posttreatment with sodium arsenite alters the mutational spectrum induced by ultraviolet light irradiation in chinese hamster ovary cells.arsenic, a potent carcinogen, fails to induce gene mutations in mammalian cells. however, posttreatment of ultraviolet light (uv) irradiated cells with sodium arsenite synergistically enhances the mutation frequency on the hypoxanthine (guanine) phosphoribosyltransferase locus. to investigate the molecular mechanism of the comutagenic effects of sodium arsenite, we characterized the alterations of nucleotide sequences in 30 uv-induced and 39 sodium arsenite enhanced hprt mutants from chinese ham ...19921396606
chromosomal breakage following treatment of cho-k1 cells in vitro with u-68,553b is due to induction of undercondensation of heterochromatin.preferential breakage of chromosomes at specific sites (so-called "fragile sites") has been observed to occur spontaneously, and has been induced by some metal salts and chemicals. furthermore, a heterochromatic region of the long arm of the chinese hamster ovary (cho) x-chromosome is known to be susceptible to a disproportionately high frequency of spontaneous breakage; unless there is physical displacement of chromatin the resulting achromatic lesions are not scored as structural aberrations. ...19921396608
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