insulin-degrading enzyme: stable expression of the human complementary dna, characterization of its protein product, and chromosomal mapping of the human and mouse genes.we have recently described the isolation of a cdna encoding an enzyme thought to be involved in the degradation of insulin by insulin-responsive tissues. this enzyme, referred to as insulin-degrading enzyme (ide), is a cytosolic proteinase of 110,000 mol wt which shares structural and functional homology with bacterial protease iii. the enzyme may function in the termination of the insulin response. we report here the mapping of the human and mouse ide genes to human chromosome 10 and mouse chro ...19902293021
the biological role of the carboxyl-terminal extension of human chorionic gonadotropin [corrected] beta-subunit.hcg is a member of a family of glycoprotein hormones which share a common alpha-subunit, but differ in their hormone-specific beta-subunits. the cg beta-subunit is unique in that it contains a hydrophilic carboxyl-terminal extension with four serine o-linked oligosaccharides. to examine the role of the o-linked oligosaccharides and the carboxyl-terminal extension of hcg beta on receptor binding, steroidogenesis in vitro, and ovulation induction in vivo, site-directed mutagenesis and gene transfe ...19902293995
the sialylated oligosaccharides of recombinant bovine lutropin modulate hormone bioactivity.the asn-linked oligosaccharides from bovine lutropin (blh(pit] are predominantly dibranched complex-type structures with the terminal sequence so4-4galnac beta 1,4glcnac beta 1,2man alpha. recombinant blh expressed in chinese hamster ovary cells (blh(cho] bears di- (60%) and tribranched (30%) complex-type oligosaccharides; however, these terminate in the sequence sia alpha 2,3gal beta 1,4glcnac beta 1,2man alpha. in contrast to the limited spectrum of oligosaccharide structures present on recomb ...19902295623
transfection of a human alpha-(1,3)fucosyltransferase gene into chinese hamster ovary cells. complications arise from activation of endogenous alpha-(1,3) order to isolate a human gene encoding an alpha-(1,3)fucosyltransferase (alpha-(1,3)fuc-t), genomic dna from hl-60 cells was transfected by several methods into chinese hamster ovary (cho) cells. colonies expressing alpha-(1,3)fuc-t activity were identified by their ability to bind a monoclonal antibody (anti-ssea-1) that recognizes the carbohydrate product of alpha-(1,3)fuc-t action. cho cells do not express alpha-(1,3)fuc-t activity but contain at least two, silent alpha-(1,3)fuc-t genes pr ...19902295646
tumor necrosis factor-alpha inhibits albumin gene expression in a murine model of cachexia.the mechanisms responsible for decreased serum albumin levels in patients with cachexia-associated infection, inflammation, and cancer are unknown. since tumor necrosis factor-alpha (tnf alpha) is elevated in cachexia-associated diseases, and chronic administration of tnf alpha induces cachexia in animal models, we assessed the regulation of albumin gene expression by tnf alpha in vivo. in this animal model of cachexia, chinese hamster ovary cells transfected with the functional gene for human t ...19902295699
mutagenicity in v79 cells does not correlate with carcinogenity in small rodents for 12 aromatic amines.the aim of this investigation was to study the correlation between carcinogenicity in small rodents and mutagenic potency of aromatic amines, as measured by the induction of 6-thioguanine resistance in v79 chinese hamster cells. it has been previously shown that the carcinogenic potency of these compounds is not correlated to their ability to induce dna breakage, sces, or point mutations in bacteria, but a correlation exists with autoradiographic dna repair test (in primary hepatocyte cultures). ...19902299684
genotoxicity of 1-nitropyrene and 2,4,7-trinitro-9-fluorenone to mammalian cells.nitroarenes are ubiquitous environmental pollutants displaying potent genotoxicity in bacterial and mammalian cells. in this study, 2,4,7-trinitro-9-fluorenone (tnf) was more potent than 1-nitropyrene (1-np) in eliciting genotoxic responses in 4 mammalian cell lines. all 4 cell types were capable of activating the nitroarenes, since no special incubation conditions were required. inhibition of normal dna synthesis and cytotoxicity were significantly increased with tnf in a dose range of 0.2-5 mi ...19902300077
growth of cells superinoculated onto irradiated and nonirradiated confluent monolayers.we prepared confluent monolayers of normal balb/c 3t3 cells and compared differences in the growth of four types of cells superinoculated onto these nonirradiated and irradiated monolayers. the test cells were normal balb/c 3t3 a31 cells, a squamous cell carcinoma from a human esophageal cancer (kse-1), human fetal fibroblasts, and v-79 cells from chinese hamster lung fibroblasts. cell growth was checked by counting the cell number, determining [3h]thymidine incorporation and assessing colony fo ...19902300732
characterization of phosphatidylinositol-specific phospholipase c defects associated with thrombin-induced a previous paper (rath, h. m., doyle, g. a. r., and silbert, d. f. (1989) j. biol. chem. 264, 13387-13390), we reported a selection for the isolation of chinese hamster lung fibroblasts (ccl39) defective in thrombin-induced mitogenesis. one mutant, d1-6b, had decreased production of inositol phosphates when challenged with activators of phosphatidylinositol turnover and extracts of this mutant showed a marked decrease in phospholipase c (plc) activity toward phosphatidylinositol. in the curre ...19902303441
chinese hamster ovary cells deficient in peroxisomes lack the nonspecific lipid transfer protein (sterol carrier protein 2).chinese hamster ovary cells deficient in intact peroxisomes were compared with wild type cells for the presence of the nonspecific lipid transfer protein (nsl-tp; sterol carrier protein 2). with the immunoblotting technique using the affinity purified antibody against rat liver nsl-tp, this protein was shown to be present in the homogenates from wild type cells, but could not be detected in mutant cells. in agreement with a previous study using livers from zellweger patients it appears that ther ...19902303496
effect of exposure to calcium entry blockers on doxorubicin accumulation and cytotoxicity in multidrug-resistant cells.flow cytometry has been used to measure doxorubicin (dox) retention in several pairs of drug-sensitive and multidrug-resistant (mdr) cell lines and in unselected human tumor cell lines. co-exposure to several agents that have been reported to reverse multidrug resistance, particularly calcium entry blockers (cebs), produced a dose-dependent increase in dox accumulation in mdr cell lines. in mdr chinese hamster ovary cells (chrc5), dox levels declined rapidly following removal of cebs, reaching a ...19902304090
suppression of 6-tg-resistant mutations in v79 cells and recessive spot formations in mice by vanillin.the antimutagenic effects of vanillin, anisaldehyde, cinnamaldehyde and coumarin were investigated in cultured chinese hamster v79 cells in vitro. the frequencies of 6-tg-resistant mutations induced by uv or x-rays were decreased by treatment with each compound during the expression time. these decreases were not due to cytotoxic effects on cellular growth or killing effects on damaged cells. the antimutagenic effect of vanillin was also investigated in vivo in the mouse spot test using male pw ...19902304483
protective immunogenicity of two synthetic peptides selected from the amino acid sequence of bordetella pertussis toxin subunit s1.two peptides, corresponding to amino acids 1-17 and 169-186 of the amino acid sequence of pertussis toxin (pt) subunit s1, were synthesized and coupled to the diphtheria toxin cross-reactive mutant protein crm 197 and evaluated for immunogenicity and protective capacity against pt challenge in vivo. the peptide-crm conjugates induced high antibody titers against native toxin in mice (balb/c, c57/black, and outbred nmri) as measured by elisa. upon pt challenge (0.5 microgram of toxin) of the nmri ...19902304902
drug resistance to cis-diamminedichloroplatinum (ii) in chinese hamster ovary cell lines transfected with glutathione s-transferase pi gene.establishment of chinese hamster ovary (cho) cell lines expressing human glutathione s-transferase-pi (gst-pi) was performed after cotransfection of psv2-neo and human gst-pi cdna-carrying plasmid p beta actgpi-2. about 30 g418-resistant clones were tested for their expression of gst-pi by northern blot analysis. two clones, beta 2-3 and beta 2-5, expressed a significant amount of gst-pi mrna; and one clone, beta 1-1, that did not was also used for further study. western blot analysis with anti- ...19902306248
genotoxic effects of five polycyclic aromatic hydrocarbons in human and rat mammary epithelial cells.five polycyclic aromatic hydrocarbons (pahs) of different carcinogenic activities were evaluated for their effects on dna synthesis (3htdr labeling index (l.i.] of rat and human mammary epithelial cells (mec) and for their effects on chromosomes in mec-mediated sister chromatid exchange (sce) assays. when compared with dmso-treated cells, exposures of rat mec to the two most potent carcinogens (5 micrograms/ml for 24 hr), i.e., 7,12-dimethylbenz(a)anthracene (dmba) and benzo(a)pyrene (b[a]p), re ...19902307152
lack of covalent binding to dna of di-n-octyltin dichloride (dotc) in vivo and in vitro.[14c]di-n-octyltin dichloride ([14c]dotc) was administered by oral gavage to male and female rats. after 96 h hepatic and thymic dna was isolated. all dna fractions were radioactive, but analysis of dna hydrolysates by hplc revealed that the radioactivity was incorporated via biosynthesis and was not due to adduct formation. the limit of detection for adduct formation, expressed in units of the covalent binding index (cbi = mumol chemical bound per mol nucleotides/mmol chemical applied per kg bo ...19902309236
an assessment of the genotoxicity of vanadium.the activities of vanadium oxide (v2o3), vanadyl sulfate (voso4) and ammonium metavanadate (nh4vo3) in inducing sister chromatid exchange (sce) and chromosomal aberrations (cab) were assayed in chinese hamster ovary cells. the toxic concentrations (tc50) for these compounds were found to be 25, 23 and 16 micrograms elemental vanadium/ml, respectively. at does 1/50-1/4 tc50, vanadium compounds were able to induce significant increases (p less than 0.01) in the sce frequency with or without the ad ...19902309250
resorthiomycin, a novel antitumor antibiotic. iii. potentiation of antitumor drugs and its mechanism of action.resorthiomycin suppressed the clonogenic activity of a multidrug-resistant mutant cell line of chinese hamster v79 cells more potently than its parental cells. moreover, resorthiomycin at 40 micrograms/ml potentiated the cytotoxic activity of vincristine and actinomycin d on v79 cells over 3-fold. uptake of [3h]actinomycin d into v79 cells was stimulated 2-fold by 40 micrograms/ml of resorthiomycin during 2 hours incubation. on the other hand, incorporation of [3h]thymidine and [3h]uridine into ...19902312403
uptake of the cation hexakis(2-methoxyisobutylisonitrile)-technetium-99m by human carcinoma cell lines in vitro.uptake of the cationic compound hexakis(2-methoxyisobutylisonitrile)-technetium-99m ([99mtc]mibi) was examined in nine human tumor cell lines. the concentration of [99mtc]mibi after a 1-h incubation with the compound varies from 5 to 28% of the activity in the external medium. in contrast, normal v79 cells (chinese hamster lung fibroblasts) and human peripheral blood mononuclear cells exhibit a minimal uptake of less than 2% of the activity in the medium. kinetic experiments with sw-13 cells ind ...19902317808
expression of human chromosome 2 ornithine decarboxylase gene in ornithine decarboxylase-deficient chinese hamster ovary cells.ornithine decarboxylase (odc) belongs to a multigene family and some of these may very well be nonfunctional (pseudogenes). we isolated an odc gene from a human chromosome 2-specific library and transfected the gene into odc-deficient chinese hamster ovary cells to directly demonstrate that this odc gene is functional and odc is essential for cell proliferation. after screening 2.5 x 10(5) plaques using a human odc complementary dna probe, a typical clone with a 5.4-kilobase insert was isolated ...19902317811
genetic and biochemical characterization of the cho-uv-1 mutant defective in postreplication recovery of dna.the cho-uv-1 mutant, a chinese hamster ovary cell with defective postreplication recovery of dna, is 2- to 4-fold more sensitive than its wild-type counterpart (cho-77256) to the lethal effects of ethylating agents and uv radiation; it is also hypersensitive (10- to 20-fold) to some dna-methylating and -cross-linking agents. we studied the cho-uv-1 mutant further to define its phenotype in terms of dna damage induction and repair, methyltransferase activity, and effects of caffeine on mutational ...19902317821
expression of complementary dna and genomic clones for carcinoembryonic antigen and nonspecific cross-reacting antigen in chinese hamster ovary and mouse fibroblast cells and characterization of the membrane-expressed products.complementary dna clones coding for both carcinoembryonic antigen (cea), a well characterized colonic tumor marker, and nonspecific cross-reacting antigen (nca), a related antigen, were expressed in chinese hamster ovary (cho) cells and l-cells (mouse fibroblasts). a genomic clone coding for cea was also expressed in cho cells. positive clones were identified by fluorescence flow cytometry and enzyme-linked immunosorbent assay. membrane location of the recombinant cea and nca was confirmed by in ...19902317824
characterization of a soluble form of human cd4. peptide analyses confirm the expected amino acid sequence, identify glycosylation sites and demonstrate the presence of three disulfide bonds.cd4 is a glycoprotein that is expressed on the surface of a variety of cells of the immune system and is believed to participate in the interactions of these cells with antigen-presenting cells bearing the class ii major histocompatibility (mhc) antigens. cd4 also acts as the receptor for the human immunodeficiency virus (hiv) by binding to the viral glycoprotein gp120. recombinant soluble cd4 (rcd4) is a truncated form of human cd4 that is secreted from transfected chinese hamster ovary cells. ...19902318210
generation of transforming growth factor-alpha from the cell surface by an o-glycosylation-independent multistep process.the precursor for transforming growth factor-alpha (tgf-alpha) is a membrane glycoprotein that can establish contact with epidermal growth factor/tgf-alpha receptors on adjacent cells or can be cleaved to release tgf-alpha that diffuses into the medium. cleavage of pro-tgf-alpha occurs at ala/leu-ala/leu-ala-val-val sites located at each end of the mature tgf-alpha sequence. to characterize the cleavage process of pro-tgf-alpha and the role of glycosylation in this process, we have introduced a ...19902318860
isolation and expression of a human ornithine decarboxylase gene.we have isolated a human ornithine decarboxylase (odc) gene from a leukocyte genomic dna library in order to examine the mechanisms involved in the regulation of odc gene expression in normal and neoplastic cell growth. nucleotide sequence analysis shows that the human odc gene in clone odc709-a2 consists of 12 exons which encode a protein identical to that inferred from a human odc cdna sequence. the 5' end of the gene was determined by s1 nuclease and primer extension mapping. the high g + c c ...19902318872
overexpressed human metallothionein iia gene protects chinese hamster ovary cells from killing by alkylating agents.experiments were designed to detect survival advantages that cells gain by overexpressing metallothionein (mt). chinese hamster ovary k1-2 cells and an x-ray-sensitive derivative were transfected with a bovine papillomavirus (bpv)-linked construct carrying the human metallothionein iia (hmt-iia) gene. transfectants survived 40-fold higher levels of cadmium chloride, harbored at least 30 copies of hmt-iia, and contained 25- to 166-fold more mt than the parent cells. even under conditions of reduc ...19902320583
heterogeneity in radiation-induced dna damage and repair in tumor and normal cells measured using the "comet" assay.a method for measuring dna damage to individual cells, based on the technique of microelectrophoresis, was described by ostling and johanson in 1984 (biochem. biophys. res. commun. 123, 291-298). cells embedded in agarose are lysed, subjected briefly to an electric field, stained with a fluorescent dna-binding stain, and viewed using a fluorescence microscope. broken dna migrates farther in the electric field, and the cell then resembles a "comet" with a brightly fluorescent head and a tail regi ...19902320728
differential regulation of low density lipoprotein suppression of hmg-coa reductase activity in cultured cells by inhibitors of cholesterol biosynthesis.treatment of rat intestinal epithelial cells (iec-6 cells) with lanosterol 14 alpha-demethylase inhibitors, ketoconazole and miconazole, had similar effects on 3-hydroxy-3-methylglutaryl coenzyme a (hmg-coa) reductase activity and cholesterol biosynthesis but the drugs differed in their ability to prevent the low density lipoprotein (ldl) suppression of reductase activity. miconazole, at concentrations that inhibited the metabolism of lanosterol and epoxylanosterol to the same degree as ketocona ...19902324644
sequence of the chinese hamster small heat shock protein hsp27. 19902326203
a point mutation in the cytoplasmic domain of the transferrin receptor inhibits endocytosis.the rate of receptor-mediated endocytosis of diferric 125i-transferrin by chinese-hamster ovary cells expressing human transferrin receptors was compared with the rate measured for cells expressing hamster transferrin receptors. it was observed that the rate of endocytosis of the human transferrin receptor was significantly higher than that for the hamster receptor. in order to examine the molecular basis for the difference between the observed rates of endocytosis, a cdna clone corresponding to ...19902327986
effect of iron on production of a possible virulence factor by plesiomonas shigelloides.plesiomonas shigelloides, when grown in an iron-poor medium (syncase), produces a substances that causes elongation of chinese hamster ovary (cho) cells similar to that produced by cholera toxin. when syncase is supplemented with iron, the ability of p. shigelloides (but not of vibrio cholerae) to produce this elongation of cho cells is lost. iron depletion of the growth medium appears to be essential for the cho cell elongation produced by p. shigelloides but is not essential for the production ...19902332475
induction of spermidine/spermine n1-acetyltransferase activity in chinese-hamster ovary cells by n1n11-bis(ethyl)norspermine (corrected) and related compounds.treatment of chinese-hamster ovary (cho) cells with n1n11-bis(ethyl)norspermine (bensm) led to a very large increase in the activity of spermidine/spermine n1-acetyltransferase (sat), which rose by about 600-fold within 48 h. smaller, but still very large increases, were also produced in decreasing order of potency by 3,7,11,15,19-penta-azaheneicosane, n1n12-bis(ethyl)spermine and by n1n14-bis(ethyl)homospermine. the rise in acetyltransferase activity was due to an increase in enzyme protein, as ...19902334396
structure and chromosomal location of the rat ribophorin i gene.ribophorin i is a type i transmembrane glycoprotein characteristic of the rough portions of the endoplasmic reticulum where it is thought to play a role in the cotranslational insertion of nascent polypeptides. a rat ribophorin i cdna was used to isolate four overlapping genomic clones from a rat embl3 genomic library. restriction mapping, southern blotting, and dna sequencing showed that these clones, spanning approximately 21 kilobases of chromosomal dna, include the entire ribophorin i gene, ...19902335524
erythropoietin fails to reverse the anemia in mice continuously exposed to tumor necrosis factor-alpha in vivo.tumor necrosis factor-alpha (tnf) is a monokine produced by activated macrophages that has cytotoxic and cytostatic effects on erythroid progenitor cells. we have recently shown that chinese hamster ovary cells transfected with the human tnf gene and which constitutively express tnf induced a hypoproliferative anemia, mild thrombocytopenia, and mild leukocytosis when injected into nude mice. we have used this murine model to determine if treatment with recombinant human erythropoietin can preven ...19902338132
localization of the adenosine deaminase, transferrin, and ump synthetase genes on chinese hamster chromosomes 4 and 6 by in situ hybridization.careful analysis of g-band patterns in various rodent families allows identification of homology and thus accurate prediction of gene map positions. however, conclusions based on the synteny of genes without a careful study of chromosome evolution and g-band homology can be misleading. we tested these generalizations by means of g-band analysis and in situ hybridization with three genes in chinese hamster (cricetulus griseus, cgr) chromosomes. the location of the adenosine deaminase gene, previo ...19902338490
concanavalin a-induced receptor aggregation stimulates the tyrosine kinase activity of the insulin receptor in intact cells.concanavalin a (cona) stimulated the phosphorylation of the beta-subunit of the insulin receptor and an mr-185,000 protein on serine and tyrosine residues in intact h-35 rat hepatoma cells. this mr-185,000 protein whose phosphorylation was stimulated by cona was identical to pp185, a protein reported previously to be a putative endogenous substrate for the insulin receptor tyrosine kinase in rat hepatoma cells. in chinese hamster ovary (cho) cells transfected with cdna of the human insulin recep ...19902339989
correlation between cell killing by cis-diamminedichloroplatinum(ii) in six mammalian cell lines and binding of a cis-diamminedichloroplatinum(ii)-dna antiserum.the relationship between cell killing and the binding of the anticancer drug cis-diamminedichloroplatinum(ii) (cis-ddp) to dna was studied in six mammalian cell lines. two of the human cell lines (cov413b) were of the same origin, comprising one sensitive to cis-ddp and the other with induced resistance to the drug. the four other lines, two rodent (rif-1, chinese hamster ovary) and two human (a2780, a1847), were unrelated. the cell lines differed in their sensitivity to cis-ddp, as tested in a ...19902340504
the gene for the ubiquitous octamer-binding protein oct-1 is on human chromosome 1, region cen-q32, and near ly-22 and ltw-4 on mouse chromosome 1.oct-1 is a sequence-specific transcription and dna replication factor that recognizes the octameric sequence atgcaaat. this protein shares an extended region of sequence similarity, called the pou domain, with the lymphoid-specific transcription factor oct-2, the pituitary-specific transcription factor pit-1, and the caenorhabditis elegans cell lineage gene product unc-86. two subdomains, pou-related homeobox and pou-specific box, lie within the pou domain. unlike other pou or homeodomain protei ...19902341156
synthesis and biological activity of the intercalating agent 3-acetamido-5-[123/125i]iodo-6-aminoacridine.3-acetamido-5-iodo-6-aminoacridine (3), a derivative of the known intercalating agent proflavine (3,6-diaminoacridine) (1) was synthesized, and no-carrier-added 123i and 125i labeled compounds prepared. compound 3 was taken up by live cells and localized in the nucleus. the intracellular concentration of [125i]3 was 7-fold greater in human prostate carcinoma (pc-3) cells than in normal chinese hamster lung fibroblast (v-79) cells.19902341291
physicochemical and biological comparison of recombinant human erythropoietin with human urinary erythropoietin.physicochemical and biological properties of recombinant human erythropoietin (rhepo) were compared with human urinary erythropoietin (uepo). uepo and rhepo were purified to apparent homogeneity from the urine of patients with aplastic anemia and from the conditioned medium of chinese hamster ovary (cho) cells transfected with a cdna clone for human epo, respectively. the microheterogeneous nature of both factors, observed on isoelectric focusing, is derived from the difference of the number of ...19902341370
diversity of oligosaccharide structures on the envelope glycoprotein gp 120 of human immunodeficiency virus 1 from the lymphoblastoid cell line h9. presence of complex-type oligosaccharides with bisecting n-acetylglucosamine residues.the n-linked oligosaccharide structures on the envelope glycoprotein gp120 of human immunodeficiency virus 1 derived from chronically infected lymphoblastoid (h9) cells have been investigated by enzymatic microsequencing after release from protein by hydrazinolysis, labeling with nab3h4, and chromatography on adsorbent columns of phaseolus vulgaris erythrophytohemagglutinin and ricinus communis agglutinin (mr 120,000) and on bio-gel p-4. a substantially greater diversity of oligosaccharide struc ...19902341393
separation by cation-exchange high-performance liquid chromatography of three forms of chinese hamster ovary cell-derived recombinant human interleukin-2.purified recombinant (r) interleukin 2 (il-2) produced by a transformed chinese hamster ovary cell line shows a single peak when analysed by reversed-phase high-performance liquid chromatography, but it can be resolved into three forms by sodium dodecyl sulphate polyacrylamide gel electrophoresis. these three forms were successfully isolated by narrow-bore ion-exchange chromatography through optimization of the elution conditions. the addition of n-propanol as an organic modifier to the mobile p ...19902341521
a truncated, secreted form of the epidermal growth factor receptor is encoded by an alternatively spliced transcript in normal rat tissue.two independent cdna clones corresponding to a 2.7-kilobase (kb) epidermal growth factor receptor (egf-r) mrna were isolated from a rat liver cdna library. sequence analysis revealed 100% homology in the external domain when compared with the full-length rat egf-r nucleotide sequence and 80 to 90% similarity relative to the human egf-r. however, the 3'-terminal sequence of these clones did not match egf-r or any other known sequence(s) and was distinct from the 3' end of the 2.8-kb mrna, which e ...19902342466
comparative induction of gene mutations and chromosome damage by 1-methoxy-1,3,5-cycloheptatriene (mcht), 1. results from a battery of standard tests.the ability of 1-methoxy-1,3,5-cycloheptatriene (mcht) to induce gene mutations and chromosome breaks has been examined in a battery of standard assays. mcht was not mutagenic to 5 strains of salmonella, with or without s9 fraction. in l5178y tk+/- mouse lymphoma cells, mcht induced tk-/- mutants in the presence but not in the absence of s9 fraction. in v79 chinese hamster cells, mcht induced azaguanine-resistant mutants in the presence and absence of s9 but the effect was considerably reduced i ...19902342499
cyclobutane-pyrimidine dimer excision in uv-sensitive cho mutants and the effect of the human ercc2 repair gene.using a radiochromatographic assay, we have examined cis-syn cyclobutane-pyrimidine dimer removal after ultraviolet irradiation in cell lines representative of the first 6 complementation groups of chinese hamster ovary dna nucleotide excision repair mutants. aa8, the cho cell line from which these mutants were derived, consistently showed normal dimer excision for a rodent cell. the mutants uniformly exhibited no significant dimer excision within the limits of determination. additionally, v-h1, ...19902342503
induction of sister-chromatid exchanges by polycyclic aromatic hydrocarbons following metabolic activation with phorbol ester-stimulated human polymorphonuclear leukocytes.we have previously observed that the interaction of an oxidant generated by polymorphonuclear leukocytes (pmns) with (+-)-trans benzo[a]pyrene-7,8-dihydrodiol (bp-7,8-diol) resulted in covalent binding to dna and elicited bacterial mutagenesis (pnas 82:5194, 1985). we now report that this interaction also induces sister chromatid exchanges (sces) in chinese hamster v-79 cells. this genotoxic response required stimulation of the pmns by phorbol ester as no effect was observed with unstimulated ce ...19902343183
in vitro fertilization of siberian hamster oocytes.siberian hamsters were superovulated and various media were tested in an effort to fertilize the recovered oocytes in vitro. the highest percentage of fertilized ova was achieved by using a modified tyrode's medium, designated mt (bavister, j. reprod. fertil., 18:544-545, '69), previously formulated to fertilize syrian hamster ova in vitro. spermatozoa incubated in this medium in a concentrated state overnight (14 hr) and then diluted (1 hr) fertilized 39% of the ova. similar results (40%) were ...19902345347
effect of a preparation from viscum album on tumor development in vitro and in mice.the effect of iscador, a commercial preparation made from viscum album was studied on several cell lines using in vitro tissue culture as well as tumor-bearing animals. iscador was found to be cytotoxic to animal tumor cells such as dalton's lymphoma ascites cells (dla cells) and ehrlich ascites cells in vitro and inhibited the growth of lung fibroblasts (lb cells), chinese hamster ovary cells (cho cells) and human nasopharyngeal carcinoma cells (kb cells) at very low concentrations. moreover, a ...19902345458
mutagenicity of 3-tert-butyl-4-hydroxyanisole (bha) and its metabolites in short-term tests in vitro.the mutagenicity of 3-tert-butyl-4-hydroxyanisole (bha) and its metabolites was investigated in the reverse mutation assay using s. typhimurium strains and the chromosomal aberration test in vitro using a chinese hamster fibroblast cell line, chl. bha, tert-butylhydroquinone (bhq), tert-butylquinone (bq) and bha dimer (dibha) did not show any mutagenic potential with and without s9 mix in the reverse mutation assay. in addition to the above 4 chemicals, 3-tert-butyl-4,5-dihydroxyanisole (bha-oh) ...19902345551
a comparison of chromosome aberration induction by 25 compounds tested by two chinese hamster cell (chl and cho) systems in culture.twenty-five chemicals were tested for the induction of chromosomal aberrations in 2 cultured mammalian cell systems, chinese hamster lung cells (chl) and chinese hamster ovary cells (cho). this study was carried out to provide a data set that would permit an assessment of the extent to which the 2 systems agree in the results produced. results presented for the 2 systems in this paper are not based on the same criteria but rather on the criteria standardly used in each of the systems. in tests c ...19902345556
the cloning and production of recombinant human erythropoietin.the production of recombinant human erythropoietin (r-huepo) began with a search for the gene coding for human erythropoietin (epo). two radiolabeled pools of oligonucleotide probes were designed, based on amino acid sequence information obtained from human urinary epo. each probe, consisting of complex mixtures of 128 short synthetic sequences of dna, was used to search a human genomic library for clones containing the human epo gene sequence. to verify that the isolated clones contained the co ...19902345709
nucleolin gene organization in rodents: highly conserved sequences within three of the 13 introns.the complete nucleotide (nt) sequence of the rat nuc gene encoding nucleolin, the major nucleolar-specific protein in eukaryotic exponentially growing cells, is compared with the corresponding locus recently characterized in mouse. [bourbon et al., j. mol. biol. 200 (1988) 627-638]. in both murine species the genomic organization has been strikingly conserved during evolution, i.e., the coding region extends over 9 kb and is split into 14 exons, encoding a 712-amino acid protein. moreover, all t ...19902347493
c-terminal truncated glucose transporter is locked into an inward-facing form without transport activity.the facilitated glucose transporters comprise a structurally related family of proteins predicted to have 12 membrane-spanning domains, with the amino terminus, a relatively large middle loop and the carboxy-terminus all oriented towards the cytoplasm. an alternating conformation model has been proposed to explain the mechanism of facilitated glucose transport. to understand the structure-function relationships, especially the role of the intracellular c-terminal domain, we have modified the rab ...19902348864
purification of the il-2 receptor (tac) by ligand-affinity chromatography and utilization of the immobilized receptor for receptor-affinity chromatography (rac) purification of il-2, mutant il-2, and il-2 fusion proteins.recombinant technology has facilitated the production of two soluble forms of human p55 interleukin-2 receptor (il-2r) in chinese hamster ovary cells. we have developed a ligand-affinity method for the medium-scale purification of these two soluble forms of the il-2r, based on the biochemical interactions between the matrix-bound ligand (interleukin-2) and its soluble receptor. the affinity-purified il-2r is further purified by anion-exchange chromatography followed by gel filtration. this metho ...19902351848
development of a retroviral vector for inducible expression of transforming growth factor beta 1.a retroviral vector system for the expression of exogenous genes under the control of an inducible promoter was developed. by utilizing this system, the cdna for human transforming growth factor beta 1 (tgf-beta 1) was inserted into a retroviral vector under the control of an internal mouse metallothionein promoter and introduced via infection into normal rat kidney fibroblasts (nrk-49f) and epithelial cells (nrk-52e), chinese hamster ovary cells (cho), and the human monocytic cell line u937. co ...19902352331
transforming growth factor alpha-pseudomonas exotoxin fusion protein prolongs survival of nude mice bearing tumor xenografts.transforming growth factor alpha (tgf alpha)-pseudomonas exotoxin 40 (pe40) is a chimeric protein consisting of an n-terminal tgf alpha domain fused to a c-terminal 40-kda segment of the pseudomonas exotoxin a protein. tgf alpha-pe40 exhibits the receptor-binding activity of tgf alpha and the cell-killing activity of pe40. these properties make tgf alpha-pe40 an effective cytotoxic agent for cells that possess epidermal growth factor receptors (egfr). however, the utility of this protein as an a ...19902352944
assignment of intrachain disulfide bonds and characterization of potential glycosylation sites of the type 1 recombinant human immunodeficiency virus envelope glycoprotein (gp120) expressed in chinese hamster ovary cells.this report describes the structural characterization of the recombinant envelope glycoprotein (rgp120) of human immunodeficiency virus type 1 produced by expression in chinese hamster ovary cells. enzymatic cleavage of rgp120 and reversed-phase high performance liquid chromatography were used to confirm the primary structure of the protein, to assign intrachain disulfide bonds, and to characterize potential sites for n-glycosylation. all of the tryptic peptides identified were consistent with t ...19902355006
iron-supplemented bovine serum as an alternative to fetal bovine serum in the cho/hgprt mutation assay.iron-supplemented bovine calf serum (ics) was found to be a viable alternative to fetal bovine serum (fbs) in the growth promotion and cloning efficiency of chinese hamster ovary (cho) cells that are used in the hgprt mutation assay. suspension cultures of cho cells had an average generation time of 11.5 h in ics and 13.6 h for cells maintained in fbs. this slight difference was due to lot variability on the part of fbs and could be eliminated by routine quality control measures. the average clo ...19902355932
introns in histone genes alter the distribution of 3' ends.chimeric genes were constructed which contained either a histone or globin promoter, a human alpha-globin coding region as a cdna or containing one or both intervening sequences, and the 3' end of a mouse histone h2a gene. the genes were introduced into mouse l cells or chinese hamster ovary cells. the genes containing at least one intervening sequence produced two mrnas in about equal amounts, one which ended at a cryptic polyadenylation site 33 nucleotides 3' to the normal histone mrna 3' end ...19902356116
spontaneous frequency of 6-thioguanine resistant mutants in cho-as52 cells after prolonged culturing in the absence of selective agents.the escherichia coli xanthine-guanine phosphoribosyl transferase (xpt) containing chinese hamster ovary (cho-as52) cells were studied in our laboratory to evaluate its general applicability in genotoxicity testing of industrial chemicals. our initial effort was to evaluate the stability of the 6-thioguanine sensitive phenotype. the cho-as52 cells were cloned and cultured continuously for over 600 days in the absence of any selective agents. the spontaneous 6-thioguanine resistant mutant frequenc ...19902357973
structure of recombinant human interleukin 5 produced by chinese hamster ovary cells.the complete peptide map of purified recombinant human interleukin 5 (rhil-5) was determined to verify its primary structure, glycosylation sites, and disulfide bonding structure. each peptide fragment generated by achromobacter protease i (api) digestion was purified and characterized by amino acid analysis and amino acid sequence analysis. after digestion with api, we could identify all the peptides which were expected from human il-5 cdna sequence. the analyses of sulfhydryl content in rhil-5 ...19902361960
the role of sphingomyelin in phosphatidylcholine metabolism in cultured human fibroblasts from control and sphingomyelin lipidosis patients and in chinese hamster ovary cells.human fibroblasts in culture take up exogenous [choline-me-3h,32p]sphingomyelin (sm) from the medium and incorporate it into cellular sm and phosphatidylcholine [spence, clarke & cook (1983) j. biol. chem. 258, 8595-8600]. the ratio of [3h]choline/[32p]pi is similar in sm and phosphatidylcholine, indicating that the phosphocholine (p-cho) moiety is transferred intact. similar results are obtained with niemann-pick (np) cells which are deficient in lysosomal sphingomyelinase activity, suggesting ...19902363706
prolactin stimulates milk protein promoter in cho cells cotransfected with prolactin receptor cdna.a functional biological system was developed by cotransfecting mammalian cell lines with the cdna of the prolactin receptor (prl-r) and a fusion gene containing the promoter of the milk protein, ovine beta-lactoglobulin linked to the coding sequence of the chloramphenicol acetyltransferase (cat) gene. surprisingly, this system is effective even if a non-mammary cell line is used, since chinese hamster ovary (cho) cells transfected both transiently and stably with prl-r cdna respond to prl, as ob ...19902365131
trypanosome ornithine decarboxylase is stable because it lacks sequences found in the carboxyl terminus of the mouse enzyme which target the latter for intracellular degradation.ornithine decarboxylase (odc) is a key enzyme in polyamine biosynthesis. mouse odc is rapidly degraded in mouse cells, whereas odc within trypanosoma brucei, a protozoan parasite infesting cattle, is stable. we have expressed cloned odc genes of both t. brucei and mouse in odc-deficient chinese hamster ovary (cho) cells. the t. brucei enzyme is stable, whereas the mouse odc similarly expressed in cho cells is unstable. this shows that the observed difference in intracellular stability is a prope ...19902365702
stable expression of functional mitochondrial uncoupling protein in chinese hamster ovary cells.the mitochondrial uncoupling protein (ucp) is a membranous proton carrier exclusively synthesized in brown adipocytes. the cdna for the rat ucp was placed in an expression vector and transfected into mammalian cells. its expression was tested in transiently transfected cho cells. in these cells the ucp was detected in mitochondria by using antibodies. permanent expression of the ucp was achieved in stable transformed cho cell lines. in these cells the ucp was characterized in mitochondrial membr ...19902367527
pharmacological inhibition of the intracellular transport of low-density lipoprotein-derived cholesterol in chinese hamster ovary cells.mammalian cells, cultured in the presence of serum lipoproteins, acquire cholesterol necessary for growth from the uptake and lysosomal hydrolysis of low-density lipoproteins (ldl). the mechanism(s) of intracellular transport of ldl-derived cholesterol from lysosomes to other cellular sites is unknown. in this study, various pharmacological agents were assessed for their ability to inhibit the movement of ldl-cholesterol from lysosomes to the plasma membrane. the only pharmacological agent teste ...19902369585
regional assignment of the mouse alpha a2-crystallin gene (crya-1) to chromosome 17a3----b by in situ hybridization.previously, we assigned the alpha a2-crystallin (crya-1) structural gene to mouse chromosome 17 via southern blot hybridization analysis of mouse x chinese hamster somatic cell hybrids. using in situ hybridization, we have now localized this gene to 17a3----b, a subchromosomal region containing several genes whose linkage relationships have been shown to be conserved on human chromosome 6. in man, however, the homologous gene (crya1) is located on human chromosome 21, indicating that internal re ...19902369847
synaptonemal complex analysis of spermatocytes of talpa occidentalis (insectivora, mammalia): autosomal synapsis and substaging of zygonema and pachynema.spermatocytes from the mole, talpa occidentalis, a species that includes both xx males and intersexes, were surface-spread and silver-stained to substage meiotic prophase from early zygonema through pachynema. in zygonema, only the z2 and z3 substages were found. this stage differed in comparison with such species as the chinese hamster, laboratory mouse, and deer mouse, which belong to orders other than insectivora. pachynema, in which five substages were established (p1-p5), seems to be a more ...19902369848
boron neutron capture enhancement of 252cf brachytherapy.dosimetric and radiobiological studies were undertaken to investigate the potential enhancement in dose, dose distribution and cell killing effectiveness of 252cf brachytherapy achievable when boron-10 enriched compounds are incorporated into simulated 252cf brain implants. thermal neutron distributions in a human head phantom containing a 252cf source were measured by gold foil activation and calculated using a 1-dimensional transport code. this information was then used to modify measured even ...19902370192
the human cell-surface glycoproteins huly-m5, membrane co-factor protein (mcp) of the complement system, and trophoblast leucocyte-common (tlx) antigen, are cd46.the non-lineage restricted human cd46 antigen, with two glycoproteins of 56,000 molecular weight (mw) and 66,000 mw, was defined using a panel of monoclonal antibodies (mab) that included the e4.3 mab to the huly-m5 antigen. here the e4.3 mab is used to show that two other human cell-surface molecules, membrane co-factor protein (mcp) of the complement system and trophoblast leucocyte-common antigen (tlx), are the same as huly-m5; thus, these three independently identified molecules are equivale ...19902373515
role of sugar chains in the in vitro biological activity of human erythropoietin produced in recombinant chinese hamster ovary cells.human erythropoietin contains three asn-type and one mucin-type sugar chains. that the branching structure of the outer portion of asn-type sugar chains is correlated to its biological activity in vivo has been reported recently (takeuchi, m., inoue, n., strickland, t. w., kubota, m., wada, m., shimizu, r., hoshi, s., kozutsumi, h., takasaki, s., and kobata, a. (1989) proc. natl. acad. sci. u. s. a. 86, 7819-7822). in this study, the effect of trimming of sugar chains on the biological activity ...19902373681
identification of amino acids in the gamma-carboxylation recognition site on the propeptide of prothrombin.a gamma-carboxylation recognition site on the propeptide of the vitamin k-dependent blood coagulation proteins directs the carboxylation of glutamic acid residues by binding to the vitamin k-dependent carboxylase. to determine residues that define this site, we evaluated the effect of mutation of certain residues in the prothrombin propeptide on the extent of carboxylation. the prothrombin cdna modified by site-specific mutagenesis was expressed in chinese hamster ovary cells using a system that ...19902373701
hypoxanthine enhances hydroxyurea-induced sister-chromatid exchanges in chinese hamster ovary cells.treatment with 1 mm hydroxyurea (hu) for 12 h induced sister-chromatid exchange (sce) in cho-k1 cells. the induced sce frequency was always higher in cells grown in ham's f12 medium than in those grown in rpmi 1640 medium. it was shown that hypoxanthine (hyp), a component of ham's f12, was to a great extent responsible for producing a higher level of hu-induced sces: hu-induced sces were synergistically enhanced when hyp was added to rpmi 1640 medium supplemented with dialyzed fetal bovine serum ...19902374560
negative regulation of transforming growth factor-beta by the proteoglycan decorin.decorin is a small chondroitin-dermatan sulphate proteoglycan consisting of a core protein and a single glycosaminoglycan chain. eighty per cent of the core protein consists of 10 repeats of a leucin-rich sequence of 24 amino acids. similar repeats have been found in two other proteoglycans, biglycan and fibromodulin, and in several other proteins including drosophila morphogenetic proteins. expression of high levels of decorin in chinese hamster ovary cells has a dramatic effect on their morpho ...19902374594
[the induction of specific dicentric chromosomes in cho-6 chinese hamster ovary cells].under a long treatment of cells cho-6 with 5-bromodeoxyuridine and colcemid it was discovered that dicentric chromosomes in metaphases of the first division of polykaryocytes contained micronuclei. when the cells were treated with colcemid only, the number of dicentrics was less. this phenomenon was described earlier in the chinese hamster cell line b11d-ii faf28. under the similar testing of continuous cell lines of human, swine, african green monkey and syrian hamster origin this result failed ...19902375062
[chromosome mutagenicity of a 193 nm excimer laser].considering the fundamental role somatic mutations play in carcinogenesis, inducing mutations by any form of therapy should be avoided as far as possible. the mutagenicity of uv irradiation in the wavelength range of 248 to 310 nm is well established. the data on shorter wavelengths, e.g. 193 nm, however, are so far not clear-cut. therefore, the potential chromosome-damaging effect of a 193 nm excimer laser was examined in the present study. cultures of primary human fibroblasts and the chinese ...19902376370
evaluation of genotoxicity of n-nitrosodibenzylamine in chinese hamster v79 cells and in concerns have arisen due to the formation of n-nitrosodibenzylamine (ndbza; cas no. 5336-53-8) in pork processed in a new type of rubber netting. in view of the potent carcinogenicity of related nitrosamines (e.g. n-nitroso-n-dibutylamine and n-nitrosodiethylamine), ndbza was evaluated for genotoxicity in vitro in both chinese hamster v79 cells and in salmonella. in v79 cells, concentrations up to 25 micrograms/ml were tested with and without activation by rat or hamster hepatocytes. sign ...19902377174
expression of the mammalian system a neutral amino acid transporter in xenopus this report, we demonstrate the expression of the mammalian system a neutral amino acid transporter in xenopus laevis oocytes following microinjection of mrna from rat liver, chinese hamster ovary (cho) cells, and human placenta. stage 6 oocytes were injected with poly(a+) mrna from one of these three sources and incubated for 24 h prior to assaying na(+)-dependent 2-aminoisobutyric acid transport to monitor the increase in system a activity. the endogenous 2-aminoisobutyric acid uptake rates ...19902380194
differential repair and replication of damaged dna in ribosomal rna genes in different cho cell lines.we studied the repair of psoralen adducts in the pol i-transcribed ribosomal rna (rrna) genes of excision repair competent chinese hamster ovary (cho) cell lines, their uv sensitive mutant derivatives, and their uv resistant transformants, which express a human excision repair gene. in the parental cell line cho-aa8, both monoadducts and interstrand crosslinks are removed efficiently from the rrna genes, whereas neither adduct is removed in the uv sensitive derivative uv5; removal of both adduct ...19902380262
in vitro drug sensitivity testing with agar-containing glass capillaries.capillary cloning has been shown to have advantages over conventional cloning of human tumor cells in petri dishes. we have recently published in this journal an optimization of the capillary method towards homogeneous colony distribution and high cloning efficiency. in the present study this modified capillary cloning system was investigated for its feasibility for drug sensitivity testing. for the human breast cancer cell line mda-231 and the drug sensitive chinese hamster ovary cell line cho- ...19902382979
lonidamine can enhance the cytotoxic effect of cisplatin in human tumour cells and rodent cells.lonidamine combined with cisplatin treatment was tested in human glioma (u87mg) human squamous cell carcinoma (umsccl) and chinese hamster (ha1) cells. the order of sensitivity to cisplatin was ha1 greater than u87mg greater than umsccl. lonidamine caused little sensitization in u87mg cells, moderate sensitization in ha1 cells and large sensitization in umsccl cells. the degree of sensitization was correlated to the effect of lonidamine on cell growth. the degree of sensitization to cisplatin by ...19902382989
promotion of altered hepatic foci development in rat liver, cytochrome p450 enzyme induction and inhibition of cell-cell communication by ddt and some structurally related organohalogen pesticides.the organochlorine pesticide 1,1'-(2,2,2-trichloroethylidene) bis(4-chlorobenzene) (ddt) and four structural analogues (bromopropylate, chlorobenzilate, dicofol and fenarimol) were investigated for their ability to inhibit gap junctional intercellular communication both in the chinese hamster v79 metabolic co-operation assay and in the scrape-loading/dye-transfer assay in wb-f344 rat liver epithelial cells. the pesticides were also studied for their ability to enhance the development of gamma-gl ...19902387028
isolation and characterization of a rat delta-aminolevulinate dehydratase processed pseudogene.southern blot analysis of genomic dna from different strains of rat indicated that there were multiple copies of the gene encoding the second enzyme of the heme biosynthetic pathway, delta-aminolevulinate dehydratase (ala-d). two types of genomic clones were isolated from a sprague-dawley rat library. one appears to be the expressed gene, whereas the nucleotide sequence of the other suggests that it contains an ala-d processed pseudogene because (1) there are no introns, (2) there are multiple m ...19902387590
expression of functional mouse muscle acetylcholine receptors in chinese hamster ovary cells.cho cells were transfected with cdnas for all 4 subunits of the mouse muscle acetylcholine receptor (achr) to obtain a stable cell line (cho-ar) expressing the achr on its surface. immunoprecipitation experiments established that the achr contained alpha- and beta-subunits assembled with gamma- and/or delta-subunits. in addition, one of the toxin-binding sites of the achr was blocked by a myasthenic serum that specifically recognizes achr containing the gamma-subunit. achr from the cho-ar cells ...19902388086
mapping an origin of dna replication at a single-copy locus in exponentially proliferating mammalian cells.a general method for determining the physical location of an origin of bidirectional dna replication has been developed recently and shown to be capable of correctly identifying the simian virus 40 origin of replication (l. vassilev and e. m. johnson, nucleic acids res. 17:7693-7705, 1989). the advantage of this method over others previously reported is that it avoids the use of metabolic inhibitors, the requirement for cell synchronization, and the need for multiple copies of the origin sequenc ...19902388621
dna damage induced by n-nitrosodibenzylamine and n-nitroso-alpha-acetoxybenzyl-benzylamine in mammalian cell systems and in vivo.n-nitrosodibenzylamine (ndbza) and n-nitroso-alpha-acetoxybenzyl-benzylamine (alpha-acetoxy-ndbza) were tested for induction of dna single-strand breaks (ssbs) in v 79 chinese hamster cells (v 79 cells) and isolated rat hepatocytes. the alkaline elution assay was used for the detection of dna strand breaks. treatment of v 79 cells with alpha-acetoxy-ndbza effectively increased the rate of dna ssbs, while with ndbza, no dna-damaging activity was detectable. both substances produced significant dn ...19902389257
preparation and use of lipid microemulsions as nutritional supplements for culturing mammalian cells.cells grown in vitro generally have a requirement for an exogenous source of lipid. this requirement is often met by the addition of serum, lipoproteins, or lipids complexed to albumin. to overcome the disadvantages of using lipoproteins or albumin for culturing cells in serum-free media, a method has been devised to provide necessary lipids. this report describes the preparation and use of protein-free lipid microemulsions suitable for use in tissue culture. the microemulsions are prepared from ...19902394672
molecular structure, chromosome assignment, and promoter organization of the human matrix gla protein gene.matrix gla protein (mgp) is an 84-residue vitamin k-dependent protein initially isolated from bovine bone. mgp is also expressed at high levels in heart, kidney, and lung and is up-regulated by vitamin d in bone cells. to characterize the genomic sequences responsible for the regulated expression of this gene, we screened a human genomic library using a mgp cdna probe and obtained two clones containing the mgp locus. the human mgp gene spans 3.9 kilobases of chromosomal dna and consists of four ...19902394711
isolation and characterization of the hamster gadd153 gene. activation of promoter activity by agents that damage dna.a group of five cdna clones, representing the gadd genes, were recently isolated from chinese hamster ovary (cho) cells as genes induced upon growth arrest and after dna damage (fornace, a. j., jr., nebert, d. w., hollander, m. c., luethy, j. d., papathanasiou, m., fargnoli, j., and holbrook, n. j. (1989) mol. cell. biol. 9, 4196-4203). we have isolated and characterized one of these genes, gadd153. the gene spans five kilobases and contains four exons. the 5'-flanking region of the gene, within ...19902398062
inhibition of the receptor-mediated endocytosis of diferric transferrin is associated with the covalent modification of the transferrin receptor with palmitic acid.the human transferrin receptor is post-translationally modified by the covalent attachment of palmitic acid to cys62 and cys67 via a thio-ester bond. to investigate the role of the acylation of the transferrin receptor, cys62 and cys67 were substituted with serine and alanine residues. the properties of the mutant receptors were compared with wild-type receptors after expression in chinese hamster ovary cells that lack endogenous transferrin receptors. rapid incorporation of [3h]palmitate into t ...19902398066
involvement of different pathways in the genotoxicity of nitropropanes in cultured mammalian cells.the metabolic pathways leading to genotoxicity of nitropropanes in mammalian cells were investigated by measuring the effects of 2-nitropropane (2-np) and 1-nitropropane (1-np) on various cell lines characterized for their expression of cytochrome p450-dependent mono-oxygenases. cells used were the rat hepatoma cell lines 2sfou, h4iiec3/g- and c2rev7, which express various forms of cytochrome p450-dependent mono-oxygenases, and v79 chinese hamster cells which lack these enzyme activities. induct ...19902398819
molecular dosimetry of dna adducts in chinese hamster ovary cells and c3h10t1/2 mouse embryo fibroblast cells treated with benzo[a]pyrene.chromatographic profiles of dna adducts formed following treatment of chinese hamster ovary (cho) cells or c3h10t1/2 mouse embryo fibroblast cells with benzo[a]pyrene (bp), in the presence or absence of rat liver s9 fraction, have been obtained by both direct labelling ([3h]bp) and 32p-post-labelling methods. the principal adduct formed in both cell lines was (+)-n2-(7r,8s,9r-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene- 10s-yl) 2'-deoxyguanosine (detected as its 3',5'-bisphosphate by 32p-post-l ...19902398820
ordered splicing of thymidine kinase pre-mrna during the s phase of the cell cycle.concomitant with the onset of s phase, a series of thymidine kinase (tk) splicing intermediates as well as mature tk mrna accumulates in the nucleus of balb/c 3t3 cells. most of the tk splicing intermediates are retained by oligo(dt)-cellulose chromatography, and, therefore, 3' end formation and polyadenylation probably precede the splicing of tk pre-mrnas. we have further characterized the tk pre-mrnas that are present in the nuclei of s-phase cells by using specific probes derived from each of ...19902398906
effect of purified recombinant human erythropoietin on anemia in rats with experimental renal failure induced by five-sixth nephrectomy.recombinant human erythropoietin (rhuepo) was purified from the conditioned media of chinese hamster ovary cells with a transfected human erythropoietin gene. we investigated the effects of the rhuepo in rats with renal anemia induced by partial nephrectomy. five-sixth nephrectomy resulted in renal failure with anemia. twenty-five days after the operation plasma urea nitrogen was increased about 2.5 times, and the red blood cell count, hematocrit, and hemoglobin concentration fell to 85% of norm ...19902400629
use of a chinese hamster ovary cell cytotoxicity assay for the rapid diagnosis of pertussis.a cytotoxicity assay with chinese hamster ovary cells (cho) capable of detecting 750 pg of pertussis toxin was assessed for use as a rapid test for the diagnosis of pertussis and compared with direct immunofluorescence (dfa). with pure bacterial cultures and simulated clinical specimens, the cho assay detected as few as two colonies of bordetella pertussis; no cytotoxicity occurred with other respiratory tract microorganisms. next, nasopharyngeal aspirate secretions and nasopharyngeal cultures h ...19902405012
mutagenicity experiments on l-cysteine and d-penicillamine using v79 cells as indicators and for metabolic activation.previous studies have shown that cysteine and penicillamine induce gene mutations in salmonella typhimurium, the effect being strongly potentiated in the presence of mammalian tissue preparations. it has now been demonstrated that homogenate of v79 chinese hamster cells is an efficient activator of thiol amino acids as well. nevertheless, l-cysteine and d-penicillamine did not induce gene mutations (acquisition of resistance towards 6-thioguanine) in v79 cells. this was true even in the presence ...19902407952
isolation of a novel cell-attachment and spreading-promoting protein from human serum.a protein with potent cell-attachment and spreading-promoting activity was isolated from fibronectin-free human serum. the purification steps included affinity chromatography on heparin-agarose and preparative isoelectric focusing. the purified protein was homogeneous as judged from dodecyl sulphate/polyacrylamide-gel electrophoresis. it had an isoelectric point of 5.0 and an mr of 52 000. the protein promoted the spreading of chinese-hamster ovary cells to plastic in a manner similar to that ob ...19852408601
[expression in chinese hamster transformant tk+-cells of the bacterial gene for beta-lactamase].using monospecific immune antiserum the expression of beta-lactamase bacterial gene (from the plasmid pbr322) in transformed tk+ chinese hamster cells was studied. it is shown that in some tk+-clones the beta-lactamase gene is expressed and this expression is stimulated by an inhibitor of dna methylation-5-azacytidine. two physically linked genes (the herpes simplex thymidine kinase gene, and the beta-lactamase gene) introduced into the chinese hamster cells on the same plasmid are found to be e ...19852411034
role of mevalonate in regulation of cholesterol synthesis and 3-hydroxy-3-methylglutaryl coenzyme a reductase in cultured cells and their cytoplasts.h4-ii-e-c3 hepatoma cells in culture respond to lipid-depleted media and to mevinolin with increased sterol synthesis from [14c]acetate and rise of 3-hydroxy-3-methylglutaryl coenzyme a reductase levels. mevalonate at 4 mm concentration represses sterol synthesis and the reductase, and completely abolishes the effects of mevinolin. mevalonate has little or no effect on sterol synthesis or reductase in enucleated hepatoma cells (cytoplasts) or on reductase in cytoplasts of cultured chinese hamste ...19852411835
[genetic transformation of somatic cells. viii. the effect of the dna methylation inhibitor 5-azacytidine on the stability of thymidine kinase-negative and -positive phenotypes of transformant clone cells].a study was made of the effect of an dna methylation inhibitor 5-azacytidine (azac) on the frequency of reversion to a thymidine kinase-positive (tk+) phenotype in 5-bromodeoxy-uridine (brdu)-resistant subclones obtained from clones of chinese hamster cells transformed by thymidine kinase gene (tk-gene) of herpes simplex virus type 1 (hsv1). it is shown that in 8 of 15 brdu-resistant subclones azac increases 2-1000-fold the frequency of reversion to tk+ phenotype. variations in the inducibility ...19852413597
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