decreased autophosphorylation and kinase activity of insulin receptors in diabetic chinese clarify the role of the insulin receptor in diabetes, the hepatic insulin receptor was investigated in the spontaneously diabetic chinese hamsters, which are the animal models for insulin-deficient diabetes. insulin binding in the diabetic animals increased mainly due to an increase in the number of receptors. it was also observed that both the autophosphorylation and kinase activity of the hepatic insulin receptor were decreased in the diabetic animals compared to the control animals. these ...19902174332
entry of pseudorabies virus into cho cells is blocked at the level of penetration.replication of pseudorabies virus (prv) in chinese hamster ovary (cho) cells, a cell line naturally resistant to infection by herpesviruses, is blocked at the level of penetration. virions bound to the surface of cho cells are taken up into cytoplasmic vesicles and degraded.19902175593
muscarinic acetylcholine receptor subtypes which selectively couple to phospholipase c: pharmacological and biochemical properties.the pharmacological and biochemical properties of rat m1 and m3 muscarinic acetylcholine receptors (machr) stably transfected into chinese hamster ovary-k1 (cho) cells were characterized with ligand binding, affinity labeling and biochemical assays. both machr subtypes display saturable, high affinity binding of [3h]-quinuclidinyl benzilate (qnb) and a rank order of antagonist potency of qnb greater than atropine greater than pirenzepine greater than af-dx 116. carbachol displacement of [3h]-qnb ...19902175603
strong and persistent activation of inositol lipid breakdown induces early mitogenic events but not go to s phase progression in hamster fibroblasts. comparison of thrombin and carbachol action in cells expressing m1 muscarinic acetylcholine order to evaluate the role of phosphoinositide turnover in growth factor action, we expressed human m1 muscarinic acetylcholine (hm1) receptors in chinese hamster lung fibroblasts (ccl39 cell line). in the transfected cells (39m1-81 clone), but not in wild type fibroblasts, the muscarinic agonist carbachol induced a release of inositol phosphates as strong as alpha-thrombin, a very potent growth factor and activator of phosphoinositide-specific phospholipase c (plc) in this cell system. in co ...19902176213
extracellular domain chimeras of the tsh and lh/cg receptors reveal the mid-region (amino acids 171-260) to play a vital role in high affinity tsh binding.we constructed a series of tsh-lh/cg receptor chimeras by homologous substitution of relatively small regions of the tsh receptor extracellular domain for the corresponding region of the extracellular domain of the lh/cg receptor. constructs were stably expressed in chinese hamster ovary cells. of the five chimeric receptors, only tsh-lhr-14, which contains mid-region domain c (amino acid residues 171-260) of the extracellular component of the tsh receptor, exhibited tsh binding of relatively hi ...19902176485
a combination of h2o2 and vanadate concomitantly stimulates protein tyrosine phosphorylation and polyphosphoinositide breakdown in different cell lines.treatment of four cell lines [rat hepatoma (fao), murine muscle (bc3h-1), chinese hamster ovary (cho), and rat basophilic leukemia (rbl)] with a combination of 3 mm h2o2 and 1 mm sodium orthovanadate markedly stimulates protein tyrosine phosphorylation, which is accompanied by a dramatic increase (5-15-fold) in inositol phosphate (insp) formation. h2o2/vanadate stimulate best formation of inositol triphosphate while their effects on the mono and di derivatives are more moderate. in the presence ...19902176864
construction of cell lines that express high levels of the human estrogen receptor and are killed by prepare large amounts of the human estrogen receptor (er) for biochemical and biophysical studies we have employed the cloned er sequences to construct chinese hamster ovary (cho) cell line derivatives that overexpress the receptor. we have employed an efficient expression vector (sv40 enhancer, human metallothionein iia promoter) and a new system of gene amplification based on the human metallothionein iia gene and stepwise selection in cadmium. cells from the initial transfected pools, befo ...19902178215
isolation and characterization of chinese hamster ovary cell mutants defective in glucose transport.cultured chinese hamster ovary (cho) cells possess an insulin-sensitive facilitated diffusion system for glucose transport. mutant clones of cho cells defective in glucose transport were obtained by repeating the selection procedure, which involved mutagenesis with ethyl methanesulfonate, radiation suicide with tritiated 2-deoxy-d-glucose, the polyester replica technique and in situ autoradiographic assaying for glucose accumulation. on the first selection, we obtained mutants exhibiting about h ...19902178689
studies on the genotoxicity of beryllium sulphate in vitro and in vivo.there is limited evidence that beryllium is a lung carcinogen to man, and several compounds of beryllium are carcinogenic to the lungs of the rat, rabbit and monkey. one such compound is beryllium sulphate (beso4.4h2o). this soluble salt has been evaluated in a range of genotoxicity tests. it was non-mutagenic to salmonella typhimurium (strains ta1535, 1537, 1538, 98 and 100) when evaluated in the plate-incorporation assay at dose levels up to 5 mg/plate (+/- induced rat-liver s9 mix). it was al ...19902179717
tetra-amidines exhibiting anti-proteinase activity: effects on oriented migration and in vitro invasiveness of a chinese hamster cell line transfected with the activated human t24-ha-ras-1 the present paper we have investigated the effects of aromatic tetra-amidines on attachment, oriented migration and in vitro invasiveness of the chinese hamster fh06t1-1 fibroblast lung cell line, transformed with the activated human t24-ha-ras-1 oncogene. the fh06t1-1 cell line is tumorigenic in nude mice and displays growth properties and biological features clearly distinct from those of the fh06n1-1 cell line, obtained after transfection of the same fibroblast cells with the normal ha-ras ...19902183928
ercc2: cdna cloning and molecular characterization of a human nucleotide excision repair gene with high homology to yeast rad3.human ercc2 genomic clones give efficient, stable correction of the nucleotide excision repair defect in uv5 chinese hamster ovary cells. one clone having a breakpoint just 5' of classical promoter elements corrects only transiently, implicating further flanking sequences in stable gene expression. the nucleotide sequences of a cdna clone and genomic flanking regions were determined. the ercc2 translated amino acid sequence has 52% identity (73% homology) with the yeast nucleotide excision repai ...19902184031
dna alkylations and mutation after exposure to ethyl methanesulphonate in mammalian cell lines routinely used in mutagenicity testing.dna ethylations were measured in four mammalian cell lines, chinese hamster ovary cho, mouse lymphoma l5178y t k+/-, human lymphoblastoid tk6 and chinese hamster v79, following exposure to [3h]ethyl methanesulphonate. concurrent estimates of cytotoxicity and gene mutation were also carried out. total dna-binding and relative levels of ethylation at n-7 guanine (n-7g), o6 guanine (o6g) and n-3 adenine (n-3a) were essentially the same in all four cell lines. differences in response to ems between ...19902184323
determination of benzidine--dna adduct formation in cho, hela, l5178y, tk6 and v79 cells.using 32p-postlabelling, evidence of dna adduct formation was sought in six mammalian cell lines, namely chinese hamster ovary (cho), human cervical carcinoma (hela s3), mouse lymphoma l5178y tk +/- and l5178y wild-type, human lymphoblastoid tk6 and chinese hamster v79, following treatment with benzidine (bzd) in the presence of s-9. adduct formation was also determined in calf thymus dna reacted in vitro with n-hydroxy-n'-acetyl-bzd, and in liver dna from mice given a single intraperitoneal inj ...19902184324
mutation assays of ethyl methanesulphonate, benzidine and benzo[a]pyrene using chinese hamster v79 a contribution to the third ukems collaborative trial, ethyl methanesulphonate (ems), benzo[a]pyrene (b[a]p) and benzidine (bzd) were examined for mutagenicity at the hprt locus in chinese hamster v79 cells, as assessed by 6-thioguanine (6tg) resistance. ems was examined in the absence of any exogenous metabolic activation system, and the mutagenic dose-response obtained served to calibrate the assay. b[a]p and bzd were examined using three levels of aroclor 1254-induced rat liver s9 suppleme ...19902184328
mutation of tyrosine residues 1162 and 1163 of the insulin receptor affects hormone and receptor internalization.insulin internalization and degradation, insulin receptor internalization and recycling, as well as long term receptor down-regulation were comparatively studied in chinese hamster ovary (cho) cell lines, either parental or expressing the wild-type human insulin receptor (cho.r) or a mutated receptor in which the tyrosine residues in positions 1162 and 1163 were replaced by phenylalanines (cho.y2). the two transfected cell lines presented very similar binding characteristics, and their pulse lab ...19902184349
genetic toxicity of the benzene metabolite trans, trans-muconaldehyde in mammalian and bacterial cells.previous studies in our laboratory identified trans,trans-muconaldehyde (muc), a six-carbon diene dialdehyde, as a microsomal metabolite of benzene. this ring-opened metabolite of benzene was also shown to be hematotoxic in mice in a manner similar to benzene. to further explore the role of muc in relation to benzene toxicity, a number of test systems were utilized to determine its genotoxic potential. in b6c3f1 mice, muc induced a highly significant increase in sister-chromatid exchange (sce), ...19902184354
metallothioneins with interdomain hinges expanded by insertion mutagenesis.specific peptides of varying lengths were inserted between the two metal cluster domains of metallothionein (mt), which normally are spanned by only three amino acids, lys-lys-ser. these interdomain expansions were made to test if such structural alterations would affect mt function. these constructs were engineered by inserting defined oligonucleotides of up to four tandem repeats of dodecanucleotides and hexanucleotides into an alu-1 endonuclease cleavage site, which separates the two exonic r ...19902184435
substrate specificity and inhibitor structure-activity relationships of recombinant human renin: implications in the in vivo evaluation of renin inhibitors.homogeneous, active recombinant human renin obtained from chinese hamster ovary (cho) cells was characterized in vitro by (i) determination of its relative rates of hydrolysis of plasma angiotensinogens (angs) from human, monkey, baboon, rat, pig, rabbit, hamster, and dog and (ii) analysis of several synthetic ang-based, inhibitors ranging in ic50 from 10(-10) to 10(-6) m. comparison of the recombinant human renin with human kidney renin showed that these enzymes were indistinguishable from each ...19902184838
an insulin-induced dna-binding protein for the human growth hormone gene.the control of gene transcription is usually mediated by transacting transcriptional factors that bind to upstream regulatory elements. as insulin regulates transcription of the growth hormone (gh) gene, we tested nuclear extracts from unstimulated and insulin-stimulated chinese hamster ovarian (cho) cells for binding to four human gh (hgh) gene promoter oligonucleotide fragments identified as target-binding sequences by dnase i footprinting. using a mobility shift assay, an insulin-induced dna- ...19902185279
inhibition of p34cdc2 kinase activity by etoposide or irradiation as a mechanism of g2 arrest in chinese hamster ovary cells.the mammalian homologue of the yeast cdc2 gene product, p34cdc2, is a cell cycle-regulated protein essential for mitosis. we have used polyclonal antisera raised against a peptide corresponding to the carboxyl terminus of the sequence of human cdc2 to study p34cdc2 in chinese hamster ovary (cho) cells. major bands are immunoprecipitated at a molecular weight of 34,000, although not in the presence of competing antigenic peptide. p34cdc2 is coimmunoprecipitated with proteins of molecular weights ...19902187601
evaluation of olestra in short-term genotoxicity assays.olestra, a mixture of hexa-, hepta- and octa-esters formed from the reaction of sucrose with long-chain fatty acids, was evaluated for its genotoxic potential in the salmonella/mammalian microsome test, the l5178y thymidine kinase (tk+/-) mouse lymphoma assay, an unscheduled dna synthesis assay in primary rat hepatocytes, and an in vitro cytogenetic assay in chinese hamster ovary cells. the results indicated that olestra was non-genotoxic in these assays.19902187775
characterization of an insulin receptor mutant lacking the subunit processing insulin receptor mutant was constructed utilizing site-directed mutagenesis to delete the arg-lys-arg-arg basic amino acid cleavage site (positions 720-723) from the cdna encoding the human insulin proreceptor. this mutant was transfected into chinese hamster ovary cells. immunoprecipitation of metabolically labeled cells revealed a 205-kda proreceptor which bound to wheat germ agglutinin. processed 130-kda alpha and 95-kda beta subunits were also observed and contained approximately 20% as m ...19902187866
mutagenicity of oxidized microsomal metabolites of 1-nitropyrene in chinese hamster ovary cells.1-nitropyrene, a tumorigenic environmental pollutant, is mutagenic in chinese hamster ovary (cho) cells in the presence of a liver homogenate 9000 g supernatant fraction (s9). the metabolic pathways involved in this response were studied by comparing the mutagenicities at the hypoxanthine-guanine phosphoribosyl transferase locus of 1-nitropyrene, some oxidized microsomal metabolites of 1-nitropyrene, and related compounds. in the absence of s9, pyrene 4,5-oxide and 6-hydroxy-1-nitropyrene displa ...19902188067
chromosomal destabilization during gene amplification.acentric extrachromosomal elements, such as submicroscopic autonomously replicating circular molecules (episomes) and double minute chromosomes, are common early, and in some cases initial, intermediates of gene amplification in many drug-resistant and tumor cell lines. in order to gain a more complete understanding of the amplification process, we investigated the molecular mechanisms by which such extrachromosomal elements are generated and we traced the fate of these amplification intermediat ...19902188107
endogenous mutagens derived from amino acids.l-cysteine, glutathione and the therapeutically used l-cysteine precursor, n-acetyl-l-cysteine, induced strong mutagenic effects in salmonella typhimurium (reversion of the his- strains ta97, ta92 and ta104), when tested in the presence of subcellular kidney preparations. the tyrosine metabolites, levodopa (an ortho-hydroquinone) and homogentisic acid (a para-hydroquinone) reverted various his- strains as well. this mutagenicity did not require the presence of mammalian enzymes, and was relative ...19902188121
replacement of the human insulin receptor transmembrane and cytoplasmic domains by corresponding domains of the oncogene product v-ros leads to accelerated internalization, degradation, and down-regulation.internalization, degradation, and insulin-induced down-regulation of insulin receptors were studied comparatively in transformed chinese hamster ovary (cho) cell lines, cho.t and, respectively expressing either the wild-type human insulin receptor (hir) or a mutated hybrid receptor in which the transmembrane and cytoplasmic domains of hir were replaced by corresponding domains of the transforming protein p68gag-ros (v-ros) of avian sarcoma virus ur2. at 37 degrees c, degradation of in ...19902188977
protection of chimpanzees from infection by hiv-1 after vaccination with recombinant glycoprotein gp120 but not gp160.the development of a vaccine to provide protective immunity to human immunodeficiency virus type 1 (hiv-1), the virus causing aids, would be the most practical method to control its spread. subunit vaccines consisting of virus envelope glycoproteins, produced by recombinant dna technology, are effective in preventing viral infections. we have now used this approach in the development of a candidate aids vaccine. chimpanzees were immunized with recombinant forms of the hiv-1 glycoproteins gp120 a ...19902190095
characterization of recombinant gp120 and gp160 from hiv-1: binding to monoclonal antibodies and soluble cd4.we compared four preparations of recombinant hiv-1 envelope glycoprotein: mammalian (chinese hamster ovary cells) gp120 (celltech); baculovirus gp120 from american biotechnologies inc. (abt) and from microgenesys (mgs); and baculovirus gp160 (institute of virology, oxford, uk). each envelope glycoprotein binds to a neutralizing monoclonal antibody (mab) directed against the v3 loop, confirming the integrity of this type-specific neutralization epitope. mgs gp120 binds abnormally well to a mab wh ...19902190605
transgenic chinese hamster v79 cell lines which exhibit variable levels of gpt mutagenesis.the escherichia coli gpt gene coding for xanthine-guanine phosphoribosyl transferase has been stably transfected into hprt- chinese hamster v79 cells. several gpt- cell lines have been established, which retain the sequence(s) even after long-term culture without selection for gpt. each cell line exhibits a characteristic spontaneous mutation frequency (10(-5) to 10(-2)) in 6-thioguanine (6tg) selection. while spontaneous mutagenesis to gpt- occurs rather frequently for most cell lines, it canno ...19902197084
insulin activates the kinase activity of the raf-1 proto-oncogene by increasing its serine phosphorylation.insulin was found to stimulate the serine/threonine kinase activity of the proto-oncogene product raf-1. this stimulation was observed in hela, nih 3t3, and chinese hamster ovary cells, all overexpressing the human insulin receptor. in the hela cells, 100 pm insulin gave a significant increase in raf-1 kinase activity, and 100 nm insulin caused a maximal 2-5-fold increase in activity. the increase in activity was detected after 2 min of insulin treatment and peaked after 5 min. in addition to st ...19902197270
isolation, characterization, and host-cell-binding properties of a cytotoxin from campylobacter jejuni.a 68,000-molecular-weight protein was isolated by polyacrylamide gel electrophoresis from the organism-free filtrate of a fully virulent clinical strain of campylobacter jejuni. the eluted protein was heat labile, was inactivated at either ph 3.0 or 9.0, was sensitive to trypsin, and was lethal for fertile chicken eggs. it also had toxic effects on chicken embryo fibroblast, chinese hamster ovary (cho), and intestinal 407 (int407) cells. a monoclonal antibody (cetpmab4) raised to this eluted tox ...19902199497
toxoplasma gondii: fusion competence of parasitophorous vacuoles in fc receptor-transfected fibroblasts.after actively entering its host cells, the protozoan parasite toxoplasma gondii resides in an intracellular vacuole that is completely unable to fuse with other endocytic or biosynthetic organelles. the fusion blocking requires entry of viable organisms but is irreversible: fusion competence of the vacuole is not restored if the parasite is killed after entry. the fusion block can be overcome, however, by altering the parasite's route of entry. thus, phagocytosis of viable antibody-coated t. go ...19902200126
studies on the induction of gene mutations in bacterial and mammalian cells by the ring-opened benzene metabolites trans,trans-muconaldehyde and trans,trans-muconic acid.t,t-muconaldehyde and t,t-muconic acid have been investigated for the induction of gene mutations in salmonella typhimurium (reversion of the his- strains ta97, ta98, ta100, ta102, ta104 and ta1535), escherichia coli (reversion of the trp- strain wp2 uvra) and chinese hamster v79 cells (acquisition of resistance toward 6-thioguanine). t,t-muconaldehyde proved weakly mutagenic in strain ta104 in the presence and absence of nadph-fortified postmitochondrial fraction from rat liver homogenate (s9 m ...19902200946
isolation and characterization of a chinese hamster ovary cell line deficient in fatty alcohol:nad+ oxidoreductase activity.we have isolated a mutant chinese hamster ovary cell line that is defective in long-chain fatty alcohol oxidation. the ability of the mutant cells to convert labeled hexadecanol to the corresponding fatty acid in vivo was reduced to 5% of the parent strain. whole-cell homogenates from the mutant strain, faa.1, were deficient in long-chain fatty alcohol:nad+ oxidoreductase (fao; ec activity, which catalyzes the oxidation of hexadecanol to hexadecanoic acid, although the intermediate fa ...19902201021
expression of atypical and classical insulin receptors in chinese hamster ovary cells transfected with cloned cdna for the human insulin receptor.human placenta and im-9 lymphocytes contain subpopulations of atypical insulin receptors which differ from classical insulin receptors in their higher binding affinity for insulin-like growth factors i and ii (igf-i and igf-ii). both types of insulin receptors may be derived from different but related genes, or may represent alternative post-translational modifications of the same gene product. to test these possibilities, we have examined the igf binding characteristics of the human insulin rec ...19902201534
binding of proteolytically-degraded human colonic mucin glycoproteins to the gal/galnac adherence lectin of entamoeba histolytica.rat and human colonic mucin glycoproteins bind to the gal/galnac adherence lectin on the surface of entamoeba histolytica in vitro, thus inhibiting the organism from adhering to and lysing the target cells. human colonic mucin glycoproteins were isolated by sepharose 4b gel filtration chromatography, they were proteolytically degraded with trypsin, pronase, and papain, and the glycoprotein fractions were reisolated by sephacryl s-200 gel filtration chromatography. binding of the mucin glycoprote ...19902201583
the saccharomyces cerevisiae dpm1 gene encoding dolichol-phosphate-mannose synthase is able to complement a glycosylation-defective mammalian cell line.the saccharomyces cerevisiae dpm1 gene product, dolichol-phosphate-mannose (dol-p-man) synthase, is involved in the coupled processes of synthesis and membrane translocation of dol-p-man. dol-p-man is the lipid-linked sugar donor of the last four mannose residues that are added to the core oligosaccharide transferred to protein during n-linked glycosylation in the endoplasmic reticulum. we present evidence that the s. cerevisiae gene dpm1, when stably transfected into a mutant chinese hamster ov ...19902201896
purification of mouse ren 2 prorenin produced in chinese hamster ovary cells.renin is produced from a larger, inactive precursor, prorenin, by endoproteolytic removal of the amino-terminal prosegment. in this study, we have transfected chinese hamster ovary cells with the expression plasmid of mouse ren 2 preprorenin, and have purified mouse ren 2 prorenin from the incubation medium of these cells by deae-toyopearl chromatography, blue-toyopearl chromatography, and isoelectric focusing. prorenin thus purified has a molecular mass of 42 kda as determined by sds-page and a ...19902202716
lamins a and c bind and assemble at the surface of mitotic study a possible interaction of nuclear lamins with chromatin, we examined assembly of lamins a and c at mitotic chromosome surfaces in vitro. when a postmicrosomal supernatant of metaphase cho cells containing disassembled lamins a and c is incubated with chromosomes isolated from mitotic chinese hamster ovary cells, lamins a and c undergo dephosphorylation and uniformly coat the chromosome surfaces. furthermore, when purified rat liver lamins a and c are dialyzed with mitotic chromosomes in ...19902202732
comparative genotoxicity testing of mainstream whole smoke from cigarettes which burn or heat tobacco.the genotoxic potential of mainstream whole smoke (mws) from cigarettes which heat tobacco (test) was compared to the genotoxic potential of mws from a cigarette which burns tobacco (reference). mws was collected from a university of kentucky 1r4f cigarette (reference) and two, test cigarettes, one with regular flavor and the other with menthol flavor. all cigarettes were smoked on a smoking machine and the particulate phase was collected on cambridge filter pads. the vapor phase, which passed t ...19902202896
phosphorylation state and biological function of a mutant human insulin receptor val996.chinese hamster ovary (cho) cell transfectants that expressed human insulin receptors whose glycine 996 was substituted by valine were studied. receptor processing and insulin binding were unaffected by this mutation; however, this mutant insulin receptor had little or no tyrosine kinase activity. nevertheless, the val996 mutant exhibited seryl and threonyl phosphorylation in both the basal and insulin-stimulated state in intact cells. this is in contrast to the lys----ala1018 tyrosine kinase de ...19902203761
dna sequence analysis of gamma radiation-induced deletions and insertions at the aprt locus of hamster cells.gamma radiation-induced gene rearrangements at the chinese hamster ovary cell locus coding for the purine salvage enzyme adenine phosphoribosyl transferase (aprt) consist of both simple deletions and more complex alterations that are presumably the result of multiple strand breaks. to characterize these mutations at the dna sequence level, fragments altered by deletion and insertion mutations were obtained by cloning in lambda phage vectors or by using the polymerase chain reaction. the radiatio ...19902206285
assessment of genotoxicity of nicotine employing in vitro mammalian test system.genotoxicity of nicotine was evaluated employing chinese hamster ovary (cho) cells. two cytogenetic endpoints, viz. frequency of sister chromatid exchange (sce) and chromosome aberration (ca) were considered. nicotine was found to induce ca and sce frequency in a dose and duration dependent manner. statistically significant elevations in ca frequency were observed only with higher concentrations of nicotine, whereas, sce frequencies were increased significantly by all the doses utilized. it was ...19902208095
stable expression of human aromatase complementary dna in mammalian cells: a useful system for aromatase inhibitor screening.a mammalian cell expression plasmid, ph beta-aro, containing the human placenta aromatase complementary dna was constructed. the prepared plasmid was used to transfect breast cancer cells (mcf-7), noncancerous breast cells (hbl-100), and chinese hamster ovary cells by a stable expression method. while the maximum velocities for aromatase expressed in three types of cells were different (10-201 pmol of [3h2o] formed/h/mg) using [1 beta, 2 beta-3h]androst-4-ene-3,17-dione as the substrate, the app ...19902208160
significant differences in the structural basis of the induction of sister chromatid exchanges and chromosomal aberrations in chinese hamster ovary cells.the structural basis of the induction of sister chromatid exchanges (sce) and chromosomal aberrations (cvt) in chinese hamster ovary cells was investigated by the case (computer automated structure evaluation) method, an artificial-intelligence-based system. using the relevant national toxicology program data bases case identified a set of structural determinants responsible for the induction of sce and another one for cvt. a comparison between the structural determinants associated with sce and ...19902209572
the spectrum of n-linked oligosaccharide structures detected by enzymic microsequencing on a recombinant soluble cd4 glycoprotein from chinese hamster ovary cells.structures of the n-linked oligosaccharides of a recombinant soluble form of human cd4 glycoprotein (scd4) have been investigated by enzymic microsequencing. the glycoprotein has two n-glycosylation sites, asn271 and asn300, at both of which evidence for the presence of complex type biantennary sialo-oligosaccharides has been obtained previously by mass spectrometric analyses [carr, s.a., hemling, m.e., folena-wasserman, g., sweet, r.w., anumula, k., barr, j.r., huddleston, m.j. & taylor, p. (19 ...19902209609
construction and characterization of a recombinant murine monoclonal antibody directed against human fibrin fragment-d dimer.cdna libraries in lambda phage were generated from the murine hybridoma secreting mab-15c5, a monoclonal antibody directed against fragment-d dimer of crosslinked human fibrin [holvoet et al. (1989) thromb. haemostasis 61, 307-313], and clones encoding fragments of the heavy (gamma 1) and the light (kappa) chain were isolated. the kappa-chain cdna was reconstructed from two overlapping clones encoding 20 amino acids of signal sequence and the 214 amino acids of the mature protein chain. the gamm ...19902209622
re-examination of potassium sorbate and sodium sorbate for possible genotoxic potential.potassium sorbate and sodium sorbate were investigated for possible genotoxic actions using the salmonella/mammalian-microsome test, hgprt and sister chromatid exchange (sce) test with chinese hamster ovary cells, the micronucleus test on bone marrow cells of mice and chinese hamsters, and the chromosome aberration and sce test on chinese hamsters. in all the in vitro tests no signs of genotoxicity were detected. whereas no in vivo mutagenicity of potassium sorbate and sodium sorbate with freshl ...19902210512
effects of amino acid replacements within the tetrabasic cleavage site on the processing of the human insulin receptor precursor expressed in chinese hamster ovary cells.we have studied the specificity requirements for processing of the human insulin proreceptor by successively replacing each basic amino acid in the tetrabasic cleavage site with alanine. these mutated receptor cdnas have then been overexpressed in chinese hamster ovary cells, using vectors containing the mouse dihydrofolate reductase gene to amplify the transfected cdnas in the presence of increasing concentrations of methotrexate. high levels of expression, ranging up to 6 x 10(7) receptors/cel ...19902211623
differential effects of brefeldin a on sialylation of n- and o-linked oligosaccharides in low density lipoprotein receptor and epidermal growth factor receptor.low density lipoprotein receptor (ldl-r) is a membrane glycoprotein carrying both n- and o-linked oligosaccharides, processing of which is reflected in conversion from a precursor to mature form during its synthesis and intracellular transport. treatment with brefeldin a (bfa) of mouse macrophage-like j774 cells, chinese hamster ovary cells, and two human cancer cell lines (a431 and imc-2) resulted in production of ldl-r with a molecular size 5-10 kda smaller than that of the mature form in the ...19902211629
identification of three related human gro genes encoding cytokine functions.the product of the human gro gene is a cytokine with inflammatory and growth-regulatory properties; gro is also called mgsa for melanoma growth-stimulatory activity. we have identified two additional genes, gro beta and gro gamma, that share 90% and 86% identity at the deduced amino acid level with the original gro alpha isolate. one amino acid substitution of proline in gro alpha by leucine in gro beta and gro gamma leads to a large predicted change in protein conformation. significant differen ...19902217207
direct interaction of a ligand for the erbb2 oncogene product with the egf receptor and p185erbb2.the erbb2 oncogene encodes a 185-kilodalton transmembrane protein whose sequence is similar to the epidermal growth factor receptor (egfr). a 30-kilodalton factor (gp30) secreted from mda-mb-231 human breast cancer cells was shown to be a ligand for p185erbb2. an antibody to egfr abolished the tyrosine phosphorylation induced by egf and transforming growth factor-alpha (tgf-alpha) but only partially blocked that produced by gp30 in sk-br-3 breast cancer cells. in two cell lines that overexpress ...19902218496
synthesis and secretion of active lipoprotein lipase in chinese-hamster ovary (cho) cells.cultured chinese-hamster ovary cells (cho cells) were found to produce and secrete a lipase, which was identified as a lipoprotein lipase by the following criteria. its activity was stimulated by serum and apolipoprotein cii, and was inhibited by high salt concentration. the lipase bound to heparin-agarose and co-eluted with 125i-labelled bovine lipoprotein lipase in a salt gradient. a chicken antiserum to bovine lipoprotein lipase inhibited the activity and precipitated a labelled protein of th ...19902222404
characterization of na(+)-dependent, active nucleoside transport in rat and mouse peritoneal macrophages, a mouse macrophage cell line and normal rat kidney cells.peritoneal rat macrophages expressed solely an na(+)-dependent, concentrative nucleoside transporter, which possesses a single na(+)-binding site and transports purine nucleosides and uridine but not thymidine or deoxycytidine. the michaelis-menten constants for formycin b and na+ were about 6 microns and 14 mm, respectively, and the estimated na+:formycin b stoichiometry was 1:1. rat macrophages accumulated 5 microm formycin b to a steady-state level exceeding that in the medium by about 500-fo ...19902223800
cross-resistance pattern of cell lines selected for resistance towards different cytotoxic drugs to membrane-toxic phospholipids in vitro.the synthetic ether lipids et-18-och3 and bm41.440 and a derivative, hexadecylphosphocholine, were tested for inhibition of [3h]-thymidine uptake into a chinese hamster ovarian cell line (auxbl) and its multidrug-resistant subline selected for colchicine resistance (chrc5). the activity of all three compounds against the multidrug-resistant subline was equal to or higher than that against the parent line. the same result was found for their activity against a human leukemic lymphoblastic cell li ...19902225315
formation of cyclic deoxyguanosine adducts in chinese hamster ovary cells by acrolein and crotonaldehyde.acrolein and crotonaldehyde are alpha,beta-unsaturated carbonyl compounds that form 1,n2-propanodeoxyguanosine adducts when reacted with dna in vitro. these compounds are mutagenic in salmonella, and crotonaldehyde is tumorigenic in rats. this study used immunoassay and 32p-postlabeling methods to determine if acrolein and crotonaldehyde form these adducts in cultured mammalian cells. adduct levels were highest in chinese hamster ovary cells exposed to acrolein (1 mm) with 162 mumol adduct/mol d ...19902225341
carbohydrate structures of a human tissue plasminogen activator variant expressed in recombinant chinese hamster ovary cells.the carbohydrate structures of a genetically engineered human tissue plasminogen activator variant bearing a single n-glycosylation site at asn 448 are reported. after isolation of the tryptic glycopeptide and liberation of the n-linked carbohydrates by polypeptide:n-glycosidase f, 6 major oligosaccharide fractions were separated by hplc on nh2-bonded phase. their structures were determined by compositional and methylation analyses combined with fast atom bombardment mass spectrometry. seventy p ...19902226797
evaluation of cytotoxic activity in fecal filtrates from patients with campylobacter jejuni or campylobacter coli enteritis.we sought to determine the prevalence of cytotoxic activity in fecal filtrates from persons with c. jejuni or c. coli enteritis. stool specimens were collected from 20 persons with c. jejuni or c. coli enteritis, 20 persons with acute diarrheal illnesses of other causes, and 9 healthy, asymptomatic persons. fecal filtrates were then incubated with chinese hamster ovary (cho) or hela cells. the fecal filtrate from 1 of the 20 (5%) persons with campylobacter enteritis was cytotoxic for hela cells ...19902227365
isolation and characterization of the gene encoding bovine adenylate kinase isozyme 2.mitochondrial adenylate kinase isozyme 2 (ak2) exists in two isoforms, ak2a and ak2b, which have the same amino-acid sequence except for the c-terminal portion. we have isolated the gene encoding ak2 from a bovine genomic library. the gene covers about 25 kb and consists of seven exons and six introns. the nucleotide sequences from exon 1 to the 5' half of exon 6 encode the portion common to ak2a and ak2b, while the sequences of the 3' half of exon 6 and exon 7 direct the unique portions of ak2a ...19902227435
mutagenicity tests of mofezolac (n-22).1. the reverse mutation test was carried out on mofezolac (n-22) at dose range of 50-5000 micrograms/plate using salmonella typhimurium strains, ta100, ta98, ta1535 and ta1537, and escherichia coli strain wp2uvra. in all tester strains no significant increases were observed in the number of revertant colonies as compared with solvent control in the absence or presence of mammalian metabolic activation system. 2. the chromosomal aberration test on n-22 was carried out using cultured chinese hamst ...19902231792
increased production of tumor necrosis factor by normal immune cells in a model of the humoral hypercalcemia of malignancy.the rat leydig cell tumor is a well characterized model of the humoral hypercalcemia of malignancy. the studies reported here were provoked by the observation that tumor-bearing rats become extremely cachectic and develop hypertriglyceridemia as they become hypercalcemic. since the bone resorbing cytokine tumor necrosis factor (tnf)/cachectin is associated with cachexia and hypertriglyceridemia, we examined hypercalcemic tumor-bearing rats for evidence of increased tnf production using a tnf rad ...19902232714
temperature-sensitive dna mutant of chinese hamster ovary cells with a thermolabile ribonucleotide reductase activity.jb3-b is a chinese hamster ovary cell mutant previously shown to be temperature sensitive for dna replication (j. j. dermody, b. e. wojcik, h. du, and h. l. ozer, mol. cell. biol. 6:4594-4601, 1986). it was chosen for detailed study because of its novel property of inhibiting both polyomavirus and adenovirus dna synthesis in a temperature-dependent manner. pulse-labeling studies demonstrated a defect in the rate of adenovirus dna synthesis. measurement of deoxyribonucleoside triphosphate (dntp) ...19902233712
the control of o6-methylguanine-dna methyltransferase (mgmt) activity in mammalian cells: a pre-molecular view.human peripheral blood lymphocytes (pbls) can have a range of o6-methylguanine-dna methyltransferase (mgmt) activities. pbls from some individuals may have almost no mgmt activity. such individuals have most often been subject to malignancy or to immunodeficiency disease. long-term lymphoblastoid lines (lcls) prepared from pbls of normal subjects by epstein-barr virus (ebv) transformation have mgmt activities which are in general somewhat higher than the pbls from which they derive. such culture ...19902233795
monochromosomal mouse microcell hybrids containing inserted selectable neo genes.normal mouse fibroblasts at early passage levels were used as a starting material to construct mouse-hamster microcell hybrids (mch). the neor gene, carried on the psv2neo and pzip-neosv(x)1 plasmids, was introduced into the mouse fibroblasts by gene transfection and retroviral infection, respectively, prior to microcell hybridization into the e36 chinese hamster cell line. in total about 180 mch clones were isolated and their amount of mouse dna was estimated by dot-blot analysis. about 50% of ...19902237638
[genotoxicity of a standardized hypericum extract].st. john's wort (hypercum perforatum) contains hypericin and hypericin-like substances as well as flavonoids, of which particularly quercetin has generated a wide-spread controversial discussion with respect to mutagenic action. the genotoxicity of a standardized aqueous ethanolic hypericum extract (hypericum extract steigerwald, psychotonin m) was verified in different in-vivo and in-vitro testsystems with mammalian cells. the in-vitro investigations were performed with the hgprt (hypoxanthine ...19902242075
hormone-free mouse glucocorticoid receptors overexpressed in chinese hamster ovary cells are localized to the nucleus and are associated with both hsp70 and this work, we examine the cellular localization and protein interactions of mouse glucocorticoid receptors that have been overexpressed in chinese hamster ovary (cho) cells (hirst, m. a., northrop, j. p., danielsen, m., and ringold, g. m. (1990) mol. endocrinol. 4, 162-170). we demonstrate that wild-type unliganded mouse glucocorticoid receptor, which is expressed in cho cells to a level approximately 10 times that of l cells, is localized entirely to the nucleus by indirect immunofluorescenc ...19902243084
cd4-pseudomonas exotoxin conjugates delay but do not fully inhibit human immunodeficiency virus replication in lymphocytes in vitro.the cd4 molecule is a high affinity receptor for the human immunodeficiency virus (hiv) envelope glycoprotein (gp160 or gp120). this glycoprotein is expressed on the surface membrane of cells infected with hiv. it has, therefore, been suggested that a soluble form of cd4 might be used as a targeting agent to deliver toxins selectively to cells infected with hiv. we demonstrate that cd4-pseudomonas exotoxin a (pe) conjugates inhibit the proliferation of gp160-transfected chinese hamster ovary cel ...19902243139
low density lipoprotein for delivery of a water-insoluble alkylating agent to malignant cells. in vitro and in vivo studies of a drug-lipoprotein complex.previous studies have shown that human leukaemic cells and certain tumour tissues have a higher receptor-mediated uptake of low density lipoprotein (ldl) than the corresponding normal cells or tissues. ldl has therefore been proposed as a carrier for anti-cancer agents. in the current study, a water-insoluble mitoclomine derivative (wb 4291) was incorporated into ldl. the wb 4291-ldl complex contained about 1,500 drug molecules per ldl particle and showed receptor-mediated toxicity in vitro as j ...19902245164
eukaryotic and prokaryotic signal peptides direct secretion of a bacterial endoglucanase by mammalian is well established that hydrophobic signal sequences direct proteins into or across the endoplasmic reticulum membrane in eukaryotes and cell membranes in prokaryotes. although it is recognized that eukaryote proteins are efficiently secreted by bacterial systems, the export of bacterial proteins by eukaryotes has received little attention. to investigate membrane translocation of bacterial proteins by mammalian cells, the secretion of a bacterial endoglucanase (endoglucanase e) from stably ...19902246276
reconstitution of steps in the constitutive secretory pathway in permeabilized cells. secretion of glycosylated tripeptide and truncated sphingomyelin.the constitutive secretory pathway has been reconstituted in mechanically permeabilized chinese hamster ovary cells using two secretory markers, an acyltripeptide (n-octanoyl-asn-tyr-thr-nh2) that is glycosylated at asn in the endoplasmic reticulum and a truncated ceramide that is converted to sphingomyelin. secretion of these bulk phase markers is dependent on cytosolic proteins and atp. secretion of both the glycosylated tripeptide and truncated sphingomyelin was inhibited at 15 degrees c. the ...19902246279
isolation and characterization of cell hybrids containing human xp-chromosome fragments.we have subjected c12d, a chinese hamster hybrid containing only the human x chromosome, to 6-thioguanine selection. the majority of the derivative clones retained rearranged xp-fragments, which were characterized by using a combination of enzyme markers, dna probes, and in situ hybridization. two of these, tg2 and tg5sc9.1, contained only an xpter----p21 fragment and should be an ideal resource for directed cloning from this region. a possible mechanism for the specific retention of xp-fragment ...19902249469
organization of the beta-galactoside alpha 2,6-sialyltransferase gene. evidence for the transcriptional regulation of terminal glycosylation.little is currently known about the mechanisms by which the cellular glycosylation machinery is regulated to produce cell type-specific glycosylation sequences on glycoprotein and glycolipid sugar chains. previously, we have shown that one enzyme involved in terminal glycosylation, beta-galactoside alpha 2,6-sialyltransferase, is expressed in a tissue-specific fashion, with the highest enzyme activity as well as mrna levels being found in the liver. in addition, the liver mrna was found to be 4. ...19902249992
insulin receptor tyrosine residues 1162 and 1163 control insulin stimulation of myristoyl-diacylglycerol generation and subsequent activation of glucose transport.chinese hamster ovary (cho) transfectants expressing human insulin receptors that were mutated at tyrosines 1162 and 1163 (cho-y2 cells) exhibit decreased insulin stimulation of both receptor tyrosine kinase and 2-deoxyglucose uptake compared with transfectants expressing wild-type human insulin receptors (cho-r cells). we now provide evidence that insulin stimulation of myristoyl-diacylglycerol (dag) production is also markedly impaired in cho-y2 cells; this is manifested as a decreased respons ...19902250023
chromosome aberration and sister chromatid exchange tests in chinese hamster ovary cells in vitro. v: results with 46 chemicals.forty-six coded chemicals were tested for their ability to induce sister chromatid exchanges (sces) and chromosomal aberrations (abs) in cultured chinese hamster ovary (cho) cells using a standard protocol with and without exogenous metabolic activation. sixteen chemicals were negative and 15 were positive in both assays; 15 were positive for sces only (one chemical that was positive for sces was equivocal for abs), and no chemicals induced abs only. the effect of cell harvest time on the abilit ...19902253606
the regulated degradation of 3-hydroxy-3-methylglutaryl-coa reductase requires a short-lived protein and occurs in the endoplasmic reticulum.a chimeric gene consisting of the coding sequence for the membrane domain of the endoplasmic reticulum protein, 3-hydroxy-3-methylglutaryl-coenzyme a (hmg-coa) reductase, fused to the coding sequence for the soluble enzyme, beta-galactosidase of escherichia coli, has been previously constructed. this fusion protein, hmgal, has been localized to the membrane of the endoplasmic reticulum of chinese hamster ovary cells transfected with this chimeric gene, and its beta-galactosidase activity has dec ...19902254343
use of a cell hybrid test system to demonstrate that benomyl induces aneuploidy and polyploidy.we have monitored the segregation of a single human chromosome in a human-chinese hamster hybrid cell line, eubi, following exposure to benomyl. we found a dose-dependent increase in frequency of aneuploidy, but a much more marked induction of polyploidy was noted at the highest benomyl concentration. we confirm the usefulness of this assay for determining genetic risk associated with human exposure to environmental chemicals.19902255326
sensitization of multidrug-resistant mouse ascites hd33 and chinese hamster ovary chrc5s3 cells by a photoreactive vinblastine derivative, napavin.we have synthesized a new photoreactive vinblastine derivative, 3-[[[2-amino(4-azido-2-nitrophenyl)ethyl]amino] carbonyl]-o4-deacetyl-3-de-(methoxycarbonyl)-vincaleukoblastine (napavin), which absorbs light at around 450 nm. we report here its effects in vitro on multidrug-resistant mouse hd33 ehrlich-lettré ascites cells, on chinese hamster ovary chrc5s3 cells, on the corresponding drug-sensitive cells, on chemosensitive rat tma1 mammary carcinoma, and on human sw48 colon carcinoma cells. cells ...19902257016
recognition of 29 kda surface-associated adhesive molecule of entamoeba histolytica by monoclonal antibodies.monoclonal antibodies have been developed and used as specific probe to locate and identify a 29-kda molecule of axenic entamoeba histolytica trophozoites. monoclonal antibody produced by clone c8 (moab c8) strongly agglutinated the amoebic trophozoites. the immunofluorescence of live e. histolytica trophozoites and surface fluorescence of acetone-fixed trophozoites by moab c8 indicated existence of a 29-kda molecule on surface-associated plasma membrane of e. histolytica. the monoclonal antibod ...19902257172
use of a selectable reporter for the isolation of mammalian regulatory genes.a general method is described for isolating the genes encoding differentiation-specific activators of transcription using genetic selection. employing regulation of the prolactin encoding gene (prl) as a model, we have shown that the hamster dihydrofolate reductase-encoding gene (dhfr) is an effective dominant selectable reporter in this methodology. the dhfr coding region was ligated to the rat prl promoter, and the resultant construct was stably transfected into dhfr- chinese hamster ovary (ch ...19902258059
immunoregulatory role of transforming growth factor beta (tgf-beta) in development of killer cells: comparison of active and latent tgf-beta 1.using recombinant dna technology, we have generated chinese hamster ovary (cho) cell lines that synthesize latent transforming growth factor beta 1 (tgf-beta 1) to study immune regulation by tgf-beta 1. in vitro, latent tgf-beta 1 synthesized by transfectants or added exogenously as a purified complex after activation inhibited ctl generation to a similar extent as seen with acid-activated recombinant human (rhu) tgf-beta 1. in vivo, serum from nu/nu mice bearing cho/tgf-beta 1 tumors contained ...19902258706
comparison of radiation sensitivity for three cell lines as measured by the cloning assay and the micro-nucleus test.the correlation between cell killing and the induction of micro-nuclei was studied for three cell lines after treatment with gamma radiation to investigate whether the frequency of micro-nucleated cells can be used to determine the radiation sensitivity of a cell type. r1 rat rhabdomyosarcoma cells showed a higher sensitivity for the induction of proliferative death than ruc rat ureter carcinoma cells and v79 chinese hamster cells which had a similar radiation sensitivity. the frequencies of mic ...19902260014
biological activities and endotoxic activities of protective antigens (pags) of leptospira interrogans.the biological and endotoxic activities of protective antigens (pags) prepared by the chloroform-methanol-water method from leptospira interrogans serovars lai, copenhageni and canicola were examined. the pag preparations did not show a local shwartzman reaction in the rabbits at doses of 100 micrograms and 50 micrograms/site and lethal toxicity to galactosamine-sensitized mice at the dose of 12.5 micrograms to 50 micrograms/mouse. pags exhibited a weak cytotoxic action on peritoneal exudate mac ...19902261063
isolation and characterization of a variant dihydrofolate reductase cdna from methotrexate-resistant murine l5178y cells.dihydrofolate reductase (dhfr) cdna sequences were isolated from a methotrexate-resistant mouse l5178y cell line previously shown to contain methotrexate-resistant dihydrofolate reductase enzyme activity. specifically-primed reverse transcription products were amplified using the polymerase chain reaction and then cloned into a mammalian expression plasmid. candidate clones were identified by restriction analysis and then functionally tested by transfection into mouse 3t3 fibroblasts, selecting ...19902263462
cell line-specific differences in the control of cell cycle progression in the absence of mitosis.this paper reports that there are major differences between mammalian cell lines in the propensity to progress into subsequent cell cycles when mitosis is inhibited with agents that disrupt the assembly of the mitotic spindle apparatus (colcemid, nocodazole, and taxol). human hela s3 cells, which represent one extreme, remain arrested in mitosis, with elevated levels of cyclin b and p34cdc2 kinase activity. in chinese hamster ovary cells, at the other extreme, the periodic rise and fall of cycli ...19902263610
cell proliferation in chorionic villi at different gestational ages, as analyzed by premature chromosome condensation.the technique of premature chromosome condensation (pcc) was adapted to human first-trimester chorionic villi cells to analyze the cell-cycle kinetics of interphase chromatin. uncultured cells of the cytotrophoblast (ct) and the mesenchymal core (mc) were obtained by a two-step digestion. pcc was induced by fusion of the chorionic interphase cells with mitotic chinese hamster ovary or hela cells. cells showing pcc in g1 (classes 1-6), s, and g2 were found. to analyze further the proliferation st ...19902265555
agonist-induced down-regulation of m1 muscarinic receptors and reduction of their mrna level in a transfected cell line.agonist-induced reduction in both the number of m1 muscarinic receptors and the mrna coding for the receptor protein was investigated in chinese hamster ovary (cho) cells which were transfected with the m1 muscarinic receptor gene. receptor concentration was measured by the specific binding of the muscarinic ligand, [3h]quinuclidinyl benzilate ([3h]qnb), and northern blot hybridization analysis was used to evaluate the levels of receptor mrna. incubation of cells with 1 mm of the muscarinic agon ...19902265699
molecular cloning and chromosomal localization of a gene coding for human cardiac myosin heavy-chain.alpha- and beta-human cardiac myosin heavy-chain (mhc) genes, which correspond to myh6 and myh7, respectively, according to human gene mapping nomenclature, were isolated from human genomic and cdna clones, using two rat cardiac pcmhc26: alpha-mhc type; and pcmhc5: beta-mhc type as probes, and characterized. the alpha-mhc type cardiac genomic dna clone and the beta-mhc type cardiac cdna clone were used as probes in the southern analysis of human genomic dna from human-chinese hamster or human-mo ...19902266579
the chinese hamster v79 cell mutant v-h4 is phenotypically like fanconi anemia has been shown by genetic complementation analysis that a mitomycin c-sensitive mutant (v-h4) of chinese hamster v79 cells is the first rodent equivalent of fanconi anemia (fa) group a. the v-h4 mutant shows many typical characteristics of cells derived from fa patients. v-h4 cells exhibit increased sensitivity towards cross-linking agents as mmc (approximately 30-fold), cis-ddp (approximately 10-fold), deb (approximately 10-fold), and puva (approximately 1.6-fold), but an only slightly incre ...19902267631
gene mapping of mouse laminin a and b2 subunits using mouse-chinese hamster somatic cell hybrids.laminin is a multichain extracellular matrix glycoprotein found primarily in basement membranes. the molecule is made up of three subunits, designated as a, b1, and b2. using an 850-base cdna probe for the mouse laminin a-chain and a 1000-base cdna probe for the mouse laminin b2 chain, we have screened mouse-chinese hamster somatic cell hybrids in order to assign the genes for each of these polypeptides to their respective mouse chromosome. we have determined that the mouse laminin b2-chain gene ...19902267633
radiation effect of gadolinium-neutron capture reactions on the survival of chinese hamster gadolinium-neutron capture reactions, prompt gamma rays with an energy spectrum of up to 7 mev, x-rays and electrons are released. we measured the effect of radiation as a result of capture reactions on cultured chinese hamster cells. cells in the medium containing 5000 ppm gadolinium were exposed to thermal neutrons from a nuclear reactor. the survival curve for those cells exhibited a shoulder in the low neutron fluence region. the survival curve for cells exposed to thermal neutrons in the ...19902267661
generation of a biologically active, secreted form of human thyroid peroxidase by site-directed mutagenesis.using site-directed mutagenesis, we introduced two stop codons immediately upstream of the putative transmembrane domain in human thyroid peroxidase (htpo) cdna, truncating the carboxyl terminus of htpo (933 amino acids) by 85 residues. mutated htpo cdna, inserted into a eukaryotic expression vector, was stably transfected into chinese hamster ovary (cho) cells. immunoprecipitation of cellular 35s-methionine-labeled proteins with hashimoto's serum revealed a 105-101 kilodalton doublet. in contra ...19902274058
genotoxicity evaluation of lithium hypochlorite.lithium hypochlorite (liocl), the pool and spa sanitizer/algicide, was evaluated for genotoxicity in a battery of studies designed to evaluate potential mutagenicity, dna damage and chromosome aberrations. liocl was not mutagenic in the ames test when tested in salmonella typhimurium strains ta98, ta100, ta1535, ta1537, ta1538 or in the hypoxanthine-guanine phosphoribosyl transferase (hgprt) mutation assay in chinese hamster ovary (cho) cells without metabolic activation. liocl did not induce dn ...19902274961
[the identification of kinetochore proteins by using the sera of patients with collagenoses].sera of rheumatology patients with antikinetochore autoantibodies are identified. immunoblot of human cell proteins showed that all the sera contained autoantibodies to kinetochore proteins a and b. in chinese hamster cells proteins with m. m. 45 kd, 100 kd and 110 kd are presumably kinetochore proteins, whereas in murine cells these are proteins with m. m. 45 kd 85 kd and 100 kd.19902275018
effects of antimitotic and antimitochondrial agents on the cellular distribution of microtubules and mitochondria.using antibodies to a mitochondrial molecular chaperone class of protein, which is specifically altered in mutants resistant to microtubule (mt) inhibitors, the effect of a number of mt and mitochondrial inhibitors on the cellular distribution of mitochondria and various cytoskeletal filaments was examined. treatment of chinese hamster ovary (cho) or chicken embryo fibroblast (cef) cells with the mt inhibitors podophyllotoxin, colchicine, nocodazole and vinblastine caused depolymerization of cel ...19902276284
cytolethal distending toxin (cldt) production by enteropathogenic escherichia coli (epec).culture supernates of 16 strains of epec belonging to 6 different serogroups, when assayed on chinese hamster ovary (cho) cells up to 96-120 h, induced distinct morphological changes. the supernate activities were heat-labile, unrelated to heat-labile enterotoxin (lt), verotoxin (vt), or hemolysin, did not show necrosis in rabbit skin and caused no fluid secretion in the rabbit ileal loop assay (rila). simultaneous production of cldt and heat-stable enterotoxin (st) were detected in four epec st ...19902276608
toxicity studies of butylated hydroxyanisole and butylated hydroxytoluene. i. genetic and cellular effects.the cellular effects of the antioxidants butylated hydroxyanisole and butylated hydroxytoluene were studied in a battery of in vitro tests. no evidence of genotoxicity was obtained for either compound in the hepatocyte primary culture/dna repair test, the salmonella/microsome mutagenesis test, the adult rat liver epithelial cell/hypoxanthine guanine phosphoribosyl transferase test, or for butylated hydroxyanisole in the chinese hamster ovary cell/sister chromatid exchange test. both compounds in ...19902276702
isolation of the functional human excision repair gene ercc5 by intercosmid recombination.the complete human nucleotide exicision repair gene ercc5 was isolated as a functional gene on overlapping cosmids. ercc5 corrects the excision repair deficiency of chinese hamster ovary cell line uv135, of complementation group 5. cosmids that contained human sequences were obtained from a uv-resistant cell line derived from uv135 cells transformed with human genomic dna. individually, none of the cosmids complemented the uv135 repair defect; cosmid groups were formed to represent putative huma ...19902276736
[identification of genotoxic compounds used in leather processing industry].the release of mutagens from 7 carbon black-based leather dyes and from leather samples at various stages of finishing was determined. after vigorous treatment with toluene, 4 commercial dyes yelded mutagenic extracts on salmonella typhimurium in the presence of microsomal enzymes. only in one case were the responsible chemicals identified as polycyclic aromatic hydrocarbons. the low bioavailability of mutagens contained in carbon black and their low mutagenic activity suggest that the risk asso ...19902277596
[isolation and mapping of arbitrary single copy dna fragment located on human chromosome 11p11-q11].a library of genomic dna has been constructed in embl3 lambda phage, from a chinese hamster/human lymphocytes somatic cell hybrid carrying human chromosome 11 and 20. recombinants containing human genomic dna origin can be isolated from the hybrid cell genomic library by using species-specific probe. 8 single copy fragments have been isolated from 13 recombinants. one of them designated as fd11-1 has been identified on chromosome 11 by hybridized it with hybrid cell clone panel and mapped on chr ...19902288761
purification and characterization of soluble human il-6 receptor expressed in cho immunosorbent assay system to detect genetically engineered il-6 receptor (il-6r) was established, whereby soluble il-6 receptor (sil-6r) was detected in the culture medium when sil-6r cdna was transfected into cos1 cells. a stably transformed chinese hamster ovary (cho) cell line constitutively expressing sil-6r has been established. the recombinant sil-6r was purified to homogeneity by sequential filtration and chromatography of the culture medium. the recombinant sil-6r augmented the sensi ...19902292596
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