the role of o6-alkylguanine in cell killing and mutagenesis in chinese hamster ovary cells.chinese hamster ovary cells with no detectable (less than 200 molecules/cell) o6-methylguanine-dna methyltransferase (ec were transfected with human cell dna and psv2neo plasmid by electroporation. two stable transformant clones, gc-1 and gc-2, containing 4 x 10(4) and 4-6 x 10(3) methyltransferase molecules/cell respectively were isolated by successive screening in the presence of g418 and 2-chloroethyl-n-nitrosourea (cnu). only three or four copies of psv2neo dna and no repetitive hu ...19911988186
clastogenicity of 1-nitropyrene, dinitropyrenes, fluorene and mononitrofluorenes in cultured chinese hamster cells.the chromosomal aberration test using a chinese hamster lung cell line (chl) was carried out on 1-nitropyrene (np), 3 dinitropyrenes (dnps), fluorene and 4 mononitrofluorenes with and without metabolic activation (rat s9 mix). the 3 dnps (1,3-, 1,6- and 1,8-dnp) induced chromosomal aberrations in the absence of s9 mix. the frequencies of cells with aberrations after treatment for 48 h were 43% at 2 micrograms/ml of 1,3-dnp, 55% at 0.1 microgram/ml of 1,6-dnp and 45% at 0.025 microgram/ml of 1,8- ...19911988818
genotoxicity of 1-nitronaphthalene in chinese hamster v79 cells.1-nitronaphthalene (1-nn) has been identified in the u.s. national toxicology program as a non-carcinogen showing some evidence of in vitro genotoxicity. we tested this compound in chinese hamster v79 cells at 20-80 micrograms/ml with two endpoints: sister-chromatid exchange (sce) and thioguanine resistance (tgr), with 5 repeat experiments. the sce values in the presence of rat or hamster hepatocytes were consistently above the 95% and usually the 99% upper confidence limits for the correspondin ...19911988819
pertactin, an arg-gly-asp-containing bordetella pertussis surface protein that promotes adherence of mammalian cells.a 69-kda protein has been identified on the surface of the gram-negative pathogen bordetella pertussis that can elicit a protective immune response in animal models. this protein is associated with virulent strains of b. pertussis but its function has remained unclear. in this report we demonstrate that purified preparations of the 69-kda outer membrane protein can promote the attachment of chinese hamster ovary (cho) cells. the interaction between the mammalian cells and this protein can be spe ...19911988935
structure-function studies of human aromatase by site-directed mutagenesis: kinetic properties of mutants pro-308----phe, tyr-361----phe, tyr-361----leu, and phe-406----arg.aromatase, a cytochrome p450, catalyzes the formation of aromatic c-18 estrogenic steroids from c-19 androgens. four mutants of human aromatase have been expressed in chinese hamster ovary cells using a stable expression method. the activities of these mutants were determined using [1 beta,2 beta-3h]androstenedione, [19-14c]androstenedione, and [1 beta,2 beta-3h]testosterone as substrates. the mutant phe-406----arg was completely inactive. since there were only small changes in the km and vmax v ...19911988941
senescence of nickel-transformed cells by an x chromosome: possible epigenetic control.transfer of a normal chinese hamster x chromosome (carried in a mouse a9 donor cell line) to a nickel-transformed chinese hamster cell line with an xq chromosome deletion resulted in senescense of these previously immortal cells. at early passages of the a9/cx donor cells, the hamster x chromosome was highly active, inducing senescence in 100% of the colonies obtained after its transfer into the nickel-transformed cells. however, senescence was reduced to 50% when chinese hamster x chromosomes w ...19911990442
reproductive integrity of mammalian cells exposed to power frequency electromagnetic fields.human lymphocytes and chinese hamster ovary (cho) fibroblasts were analyzed for cytogenetic and cytotoxic endpoints to determine whether exposure to power frequency (60 hz) electromagnetic fields (emf) interferes with normal cell growth and reproduction. an exposure chamber was built to apply variable electric current densities of 3, 30, 300, and 3,000 microa/cm2, simultaneously with a fixed magnetic field of 2.2 g to proliferating cells. the current densities were chosen to bracket those that m ...19911991460
thyrotropin-luteinizing hormone/chorionic gonadotropin receptor extracellular domain chimeras as probes for thyrotropin receptor define the sites in the extracellular domain of the human thyrotropin (tsh) receptor that are involved in tsh binding and signal transduction we constructed chimeric thyrotropin-luteinizing hormone/chorionic gonadotropin (tsh-lh/cg) receptors. the extracellular domain of the human tsh receptor was divided into five regions that were replaced, either singly or in various combinations, with homologous regions of the rat lh/cg receptor. the chimeric receptors were stably expressed in chinese ham ...19911992482
stable expression of rabies virus glycoprotein in chinese hamster ovary cells.the rabies virus glycoprotein (g protein) has several important functions and is a major antigenic stimulus of the host immune system following rabies virus infection or vaccination. we developed a model system for studying the role of n-linked glycosylation in the intracellular transport and antigenicity of this molecule. the full-length cdna of the g protein of the era strain of rabies virus was inserted into the eukaryotic shuttle vector psg5 and then stably transfected into wild-type chinese ...19911993876
allosteric interactions at the m1, m2 and m3 muscarinic receptor subtypes.the purpose of our study was to investigate the interactions of allosteric antagonists at the individual m1, m2 and m3 muscarinic receptor subtypes. this was achieved through the use of transformed chinese hamster ovary cells stably expressing the rat m1 or m3 receptor genes. a homogeneous population of the m2 subtype was obtained from rat heart tissue. our data indicate that the cardioselective antagonists (gallamine, methoctramine, af-dx 116 and himbacine) display the following rank order of p ...19911993991
antagonist binding profiles of five cloned human muscarinic receptor subtypes.a variety of muscarinic antagonists are currently used as tools to pharmacologically subclassify muscarinic receptors into m1, m2 and m3 subtypes. in the present study, we have determined the affinity profiles of several of these antagonists at five cloned human muscarinic receptors (m1-m5) stably expressed in chinese hamster ovary cells (cho-k1). at all five receptors, the (r)-enantiomers of trihexyphenidyl and hexbutinol displayed considerably higher affinities (up to 525-fold) than their corr ...19911994002
mycoplasma oxoniensis, a new species isolated from chinese hamster conjunctivas.mycoplasmas which were distinct from mycoplasma cricetuli were isolated from the conjunctivas of chinese hamsters. two clones, which were derived from a single colony and were obtained on separate occasions, were examined in detail for morphology, growth, and biochemical characteristics. these clones were indistinguishable from each other and had the following properties: guanine-plus-cytosine content of 29 mol%, requirement for sterol, facultatively anaerobic, and positive for glucose metabolis ...19911995033
adp-ribosylation in clostridium difficile toxin-treated cells is not related to cytopathogenicity of toxin b.adp-ribosylation of a protein in human fibroblasts treated with partially purified clostridium difficile toxin b was previously reported. here we show that the same protein was adp-ribosylated also in human fibroblasts exposed to supernatant from a c. difficile strain producing neither toxin a nor toxin b. furthermore, in chinese hamster ovary and in vero cells, showing toxin b-induced cytopathogenic effect, the protein was not significantly adp-ribosylated. the results indicate that the adp-rib ...19911995067
defective transport of sindbis virus glycoproteins in end4 mutant chinese hamster ovary cells.mutant v.24.1, a temperature-sensitive derivative of chinese hamster ovary cells, defines the end4 complementation group of mutants selected for resistance to protein toxins and has defective lysosomes at the restrictive temperature (p. a. colbaugh, m. stookey, and r. k. draper, j. cell biol. 108:2211-2219, 1989). we have investigated the biosynthesis of sindbis virus envelope glycoproteins in v.24.1 cells. when the cells were infected at the restrictive temperature, the envelope glycoproteins e ...19911995947
recommended protocols based on a survey of current practice in genotoxicity testing laboratories: ii. mutation in chinese hamster ovary, v79 chinese hamster lung and l5178y mouse lymphoma cells.laboratory protocols and guidelines have been developed for the performance of point mutation assays using chinese hamster ovary (cho) cells, v79 cells, and l5178y mouse lymphoma cells. since only minor differences in the treatment of cho and v79 cells exist, these two assays could be combined in one procedural guideline. a second protocol was developed for the mouse lymphoma assay in order to incorporate concerns and methods specific to that cell type and genetic locus. the protocols were based ...19911996124
recommended protocols based on a survey of current practice in genotoxicity testing laboratories, iv. chromosome aberration and sister-chromatid exchange in chinese hamster ovary, v79 chinese hamster lung and human lymphocyte cultures.a recommended protocol has been developed for chromosomal aberration and sister-chromatid exchange assays in cho, v79 and human lymphocyte cultures. the protocol was based on the responses to a detailed questionnaire completed by north-american and european governmental, university, and contract laboratories using these tests. this report identifies those modifications to previously described methods that are used on a regular basis and clarifies confusing or inconsistent practices. these protoc ...19911996126
human interleukin 1 beta fused to the human growth hormone signal peptide is n-glycosylated and secreted by chinese hamster ovary cells.a hybrid gene consisting of the sequences coding for the signal peptide of human growth hormone and the mature form of interleukin-1 beta (il-1 beta) was chemically synthesized. this sequence was inserted into a eukaryotic expression vector and introduced into chinese hamster ovary cells. the resulting stably transformed cell lines produced large amounts of recombinant il-1 beta, which was secreted into the culture medium mainly as a 22-kda form. expression in the presence of tunicamycin, an inh ...19911999289
characterization of binding proteins from ovarian carcinoma and kidney tubule cells that are specific for cisplatin modified dna.we have detected proteins in nuclear extracts from ovarian carcinoma cells and kidney tubule cells that bind specifically to platinated dna. a 123-bp restriction fragment was platinated with cisplatin (ddp) to a formal molar platinum to nucleotide ratio of 0.05 and end-labeled with [32p]-dctp. incubation with nuclear extracts from 2008 human ovarian carcinoma cells caused shifts in the mobility of this probe in non-denaturing polyacrylamide gels. proteinase k, but not ribonuclease a, destroyed t ...19912001331
carbohydrate structures of recombinant soluble human cd4 expressed in chinese hamster ovary cells.infection of t-lymphocytes and macrophages by human immunodeficiency virus (hiv) is mediated by the binding of the hiv envelope glycoprotein to the cell-surface receptor glycoprotein cd4. a soluble, recombinant cd4 molecule (rcd4), produced by expression of a truncated cd4 gene in chinese hamster ovary (cho) cells [smith et al. (1987) science 238, 1704-1707], is in clinical trials as a potential therapeutic agent in the treatment of acquired immunodeficiency syndrome (aids). in the present study ...19912001369
isolation and characterization of a human cdna encoding uracil-dna glycosylase.dna repair of genetic information is an essential defense mechanism, which protects cells against mutation and transformation. the biochemistry of human dna repair is in its beginning stages. our research has concentrated on the enzymes involved in the removal of atypical bases from dna. we present information on the identification and characterization of a cdna isolate encoding uracil-dna glycosylase. uracil-dna glycosylase was purified to homogeneity from hela s3 cells and used to generate pol ...19912001396
posttranslational modifications of rat proenkephalin overexpressed in chinese hamster ovary cells.rat proenkephalin was overexpressed in chinese hamster ovary cells using the dihydrofolate reductase-coupled genetic amplification method. about 2 mg purified protein could be obtained from 250 ml conditioned medium; multiple successive harvests could be obtained from the same roller bottle. degradation of proenkephalin released into the conditioned medium was reduced significantly in the presence of 2% fetal bovine serum. forty-eight percent of recombinant proenkephalin was glycosylated; glycos ...19912004604
the chinese hamster hprt gene: restriction map, sequence analysis, and multiplex pcr deletion screen.the fine structure of the chinese hamster hypoxanthine guanine phosphoribosyltransferase (hprt) gene has been determined; the gene has nine exons and is dispersed over 36 kb dna. exons 2-9 are contained within overlapping lambda bacteriophage clones and exon 1 was obtained by an inverse polymerase chain reaction (pcr). all the exons have been sequenced, together with their immediate flanking regions, and these sequences compared to those of the mouse and human hprt genes. sequences immediately f ...19912004774
mapping of a locus correcting lack of phosphoribosylaminoimidazole carboxylase activity in chinese hamster ovary cell ade-d mutants to human chromosome 4.the human phosphoribosylaminoimidazole (air) carboxylase locus has been until this report one of the genes encoding purine biosynthetic enzymes that had not been assigned to an individual human chromosome. characterization of chinese hamster ovary (cho) cell mutant ade-d showed that the cell line was unable to produce imp and accumulated air. cho ade-d cells were fused with normal human lymphocytes utilizing inactivated sendai virus and the resulting hybrid cell lines were selected for purine pr ...19912004782
a gene correcting the defect in the cho mutant ade -h, deficient in a branch point enzyme (adenylosuccinate synthetase) of de novo purine biosynthesis, is located on the long arm of chromosome 1.somatic hybrids between human cells and the chinese hamster ovary (cho) k1 mutant, ade -h cells, were selected for purine prototrophy by growth in adenine-free medium. the ade -h mutant is defective in the enzyme adenylosuccinate (amps) synthetase (adss; ec, which carries out the first of a two-step sequence in the biosynthesis of amp from imp, and therefore requires exogenous adenine for growth. the presence of the long arm of human chromosome 1 in the hybrids is 100% concordant for th ...19912004783
isolation of 37 single-copy dna probes from human chromosome 6 and physical mapping of 11 probes by in situ hybridization.fifty-five single-copy dna probes were isolated from the library ll06ns01, which was constructed from a complete hindiii digest of a flow-sorted human chromosome 6. because chromosomes from a human x chinese hamster somatic cell hybrid were used as the starting material for the flow-sorting, the library could be expected to contain some contaminating chinese hamster dna as well as dna from human chromosomes other than 6. thirty-seven of the 55 probes, however, were shown to map to human chromoso ...19912004785
the peripherin gene maps to mouse chromosome 15.we have mapped the mouse peripherin gene, prph, to chromosome 15 by means of southern analysis of a panel of chinese hamster/mouse somatic cell hybrids using a rat peripherin cdna probe. peripherin is a recently characterized type iii intermediate filament expressed in the peripheral and the central nervous system. although its exact function is not known, peripherin is likely to be involved in the neuronal cytoskeleton, a role it shares with other intermediate filaments, such as the neurofilame ...19912004788
structural analysis of the transmembrane domain of the epidermal growth factor receptor.the ligand-binding domain of the epidermal growth factor (egf) receptor is separated from the cytoplasmic protein tyrosine kinase domain by a predicted single transmembrane segment. antipeptide antibodies prepared against the outer portion of the predicted transmembrane segment confirmed this area was exposed only when cells were treated with permeabilizing agents. to investigate structural requirements for signal transduction by the transmembrane domain, three types of mutant egf receptor were ...19912005111
a novel suicide inhibitor strategy for antiparasitic drug development.dl-alpha-difluoromethylornithine (dfmo), a suicide inhibitor of eukaryotic ornithine decarboxylase (odc), has therapeutic activities against african trypanosomiasis. the ki value of dfmo for odc of trypanosoma brucei is somewhat higher than that for mouse odc. the therapeutic efficacy of dfmo cannot therefore be attributed to a preferential inhibition of the parasite enzyme. the t. brucei gene encoding odc was cloned and sequenced, and the derived amino acid sequence has 61.5% homology with that ...19912005184
differential introduction of dna damage and repair in mammalian genes transcribed by rna polymerases i and ii.we have developed a general quantitative method for comparing the levels of drug-induced dna crosslinking in specific mammalian genes. we observed a dramatic difference between the efficiency of the removal of both psoralen monoadducts and interstrand crosslinks from the rrna genes and the efficiency of their removal from the dihydrofolate reductase (dhfr) gene in cultured human and hamster cells. while 90% of the interstand crosslinks were removed from the human dhfr gene in 48 h, less than 25% ...19912005908
a cloned gene encoding phosphatidylserine decarboxylase complements the phosphatidylserine biosynthetic defect of a chinese hamster ovary cell mutant.a phosphatidylserine-auxotrophic mutant of cultured chinese hamster ovary cells, psa-3, manifests a defect in phosphatidylserine synthase i activity (kuge, o., nishijima, m., and akamatsu, y. (1986) j. biol. chem. 261, 5790-5794). we cloned a chinese hamster gene, designated pssc, which was able to transform the psa-3 cell line to a phosphatidylserine prototroph. the resultant transformant contained phosphatidylserine in normal amounts but remained defective in phosphatidylserine synthase i acti ...19912007589
studies on the immunogenicity of chinese hamster ovary cell-derived recombinant gp120 (hiv-1iiib).recombinant dna-derived gp120 (hiv-1iiib) expressed in chinese hamster ovary cells elicited specific humoral and cell-mediated immune responses in a variety of mammals. antisera from immunized rabbits, sheep and goats recognized virus-derived gp120 and its precursor (gp160). neutralizing antibodies were also elicited, but only in a few animals, and this may be related to the protein's susceptibility to cleavage through the neutralizing domain. however, in rabbits the degree of cleavage of gp120 ...19912008801
a method for determination of iododeoxyuridine substitution of thymidine using reversed-phase high-performance liquid assay for thymidine substitution by iododeoxyuridine (idurd) using reversed-phase high-performance liquid chromatography (hplc) has been developed. three principal steps in this procedure are: extraction of dna from cell or tissues, hydrolysis of dna into deoxynucleosides and separation using hplc. approximately 1 microgram of dna was recovered from 10(5) cells by phenol extraction, and subjected to hydrolysis into deoxynucleosides which required a three-stage dna digestion using enzymes dnas ...19912009316
human müllerian inhibiting substance inhibits tumor growth in vitro and in vivo.müllerian inhibiting substance (mis) causes regression of the müllerian duct in the male fetus. bovine mis has been reported to inhibit the growth of some gynecological tumors. recombinant human mis (rhmis) produced in transfected chinese hamster ovary cells has been highly purified by immunoaffinity chromatography. the introduction of a salt wash prior to elution of mis from the affinity column removes a growth-stimulating factor(s) derived from chinese hamster ovary cells. this immunopurified ...19912009529
inhibition of tumor invasion of smooth muscle cell layers by recombinant human metalloproteinase inhibitor.matrix metalloproteinases secreted by tumor cells play an important role in the proteolytic degradation of the extracellular matrix during invasion. in a previous study, we showed that the degradation of extra-cellular matrices by human ht 1080 fibrosarcoma cells is suppressed by endothelial cells. the identification of inhibitors of metalloproteinases secreted by endothelial cells led us to postulate that these inhibitors were responsible for the suppressive effect (cancer res., 46: 3580-3586, ...19912009533
polyoma and hamster papovavirus large t antigen-mediated replication of expression shuttle vectors in chinese hamster ovary cells.eukaryotic expression vectors have been used successfully in viral lt-expressing cell lines (ie. cos) to clone cdnas encoding proteins that can be detected through their bio-activity or reactivity with specific antibodies. since chinese hamster ovary cells (cho) have been used extensively for the isolation and characterization of somatic cell mutants, we felt it would be an advantage to develop an expression cloning system in cho cells. we have modified the eukaryotic expression vector cdm8 by r ...19912011514
detection of direct mutagenicity of cigarette smoke condensate in mammalian cells.mutagenicity of cigarette smoke condensate (csc) and the acidic, basic and neutral fractions of csc was examined in the al hybrid cell, a chinese hamster ovary cell containing one human chromosome 11. since the human chromosome 11 is not necessary for survival of the al cells, mutations involving large deletions and chromosomal loss by non-dysjunction are non-lethal events that are detectable by loss of human cell surface antigens (a1, a2 and a3) encoded by genes on chromosome 11p (a1 and a3) an ...19912013132
genetic mapping of the gene for androgen-binding protein/sex hormone-binding globulin to mouse chromosome 11.southern blot analysis of dnas from chinese hamster x mouse and rat x mouse somatic cell hybrids showed that the mouse gene encoding androgen-binding protein/sex hormone-binding globulin (abp-shbg) is on chromosome 11. progeny from an intersubspecies backcross were analyzed to position this locus, termed shbg, between il-3 and int-4 in the middle of this chromosome. shbg is thus closely linked to several neurological mutations, one of which, tr, is also associated with male sterility. the recent ...19912013230
differential effect of cysteine-to-serine substitutions in metallothionein on cadmium resistance.a set of mutant coding sequences for chinese hamster metallothionein (mt) 2 in which codons for individual cysteines were replaced by serine codons was cloned into a yeast expression system. mt gene expression was placed under control of a constitutive promoter on a multicopy escherichia coli-yeast shuttle vector. mts were expressed in a metal-sensitive host that lacks the endogenous mt gene. the expressed mts conferred increased metal resistance to the yeast host. a sensitive assay for cadmium ...19912014225
isolation and characterization of recombinant human prorenin in chinese hamster ovary cells.recombinant human prorenin (rh-prorenin) was purified from supernatants of chinese hamster ovary (cho) cell line transfected with the cdna for rh-prorenin by employing a simple two-step procedure which consisted of ammonium sulfate precipitation and immunoaffinity chromatography using a monoclonal antibody specific for the profragment of human prorenin. about 100-fold purification with 35% recovery was achieved after the two steps. purified rh-prorenin migrated as a single protein band with appa ...19912016271
estradiol beta-d-xyloside, an efficient primer for heparan sulfate biosynthesis.animal cells utilize beta-d-xylosides as primers for glycosaminoglycan synthesis. however, most xylosides preferentially stimulate chondroitin sulfate synthesis and only weakly prime heparan sulfate synthesis. to test if the structure of the aglycone determines the type of glycosaminoglycan made, the priming activity of methyl, n-octyl, p-nitrophenyl, 4-methylumbelliferyl, trans,trans-farnesyl, cholesteryl, and estradiol beta-d-xylosides was compared. their potency was tested in pgsa-745 cells, ...19912016281
synthesis of potential dual-acting radiation sensitizer antineoplastic agents: 2,2-dimethylphosphoraziridines containing 2-nitroimidazoles or other electron-affinic view of the in vivo demonstrated radiation-potentiating activities of several previously studied 2,2-dimethylphosphoraziridines, six new compounds incorporating the bis(2,2-dimethyl-1-aziridinyl)phosphinyl moiety, together with an electron-affinic group such as 2-nitroimidazole or nitrobenzyl, have been synthesized and tested (1) in vitro for ability to increase the effect of x-irradiation under hypoxic conditions on v-79 chinese hamster lung fibroblast cells, (2) in vivo for antitumor activi ...19912016716
site-directed mutagenesis of the human thyrotropin receptor: role of asparagine-linked oligosaccharides in the expression of a functional receptor.we studied the role of glycosylation in the expression of a functional human tsh receptor. oligonucleotide-directed mutagenesis was used to replace, separately or together, the asn codons with gln in each of the six potential glycosylation sites in the receptor. recombinant wild-type and mutated tsh receptors were stably expressed in chinese hamster ovary cells. high affinity tsh binding and the camp response to tsh stimulation were abolished in the receptor mutated at asn77 as well as in the re ...19912017190
genotoxicity studies of the reaction of chlorine or chlorine dioxide with l-tryptophan.non-volatile reaction products generated from the reactions of 70 mm aqueous chlorine or chlorine dioxide with 10 mm l-tryptophan were shown to be direct-acting mutagens to salmonella typhimurium ta100 and ta98. several of the fluorescent bands obtained after thin-layer chromatographic fractionation of the xad-2/8 resin concentrates of the reaction mixtures were shown to be more mutagenic than the reaction mixtures using the ames salmonella/microsome assay. in addition, these fractions were show ...19912017781
the protective activity of tea against infection by vibrio cholerae o1.extracts of black tea exhibited bactericidal activity against vibrio cholerae o1. the tea extract inhibited the haemolysin activity of v. cholerae o1, el tor and the morphological changes of chinese hamster ovary cells induced by cholera toxin. tea extract also reduced fluid accumulation induced by cholera toxin in sealed adult mice and by v. cholerae o1 in ligated intestinal loops of rabbits. these findings suggest that tea has protective activity against v. cholerae o1.19912019547
identification of phosphorylated sites in the mouse glucocorticoid receptor.glucocorticoid receptors in vivo are phosphorylated in the absence of hormone and become hyperphosphorylated in the presence of glucocorticoid agonist but not antagonists (ortí, e., mendel, d.b., smith, l.i., and munck, a. (1989) j. biol. chem. 264, 9728-9731). as a preliminary step to elucidating the functional significance of receptor phosphorylation, we have identified seven phosphorylated sites on the mouse receptor. tryptic phosphopeptides from 32p-labeled receptors were purified from gluco ...19912019585
substitution of leucine for tryptophan 412 does not abolish cytochalasin b labeling but markedly decreases the intrinsic activity of glut1 glucose transporter.glut1 glucose transporter cdna was modified to introduce a single amino acid substitution of leucine for tryptophan 412, a putative cytochalasin b photo-affinity labeling site. although the mutated transporter was expressed into plasma membranes of chinese hamster ovary cells, glucose transport activity of the mutated transporter was observed to be only 15-30% of that of the wild-type glut1 when glucose transport activity was assessed by 2-deoxyglucose uptake at 0.1-10 mm concentrations. analysi ...19912019601
characterization of tissue-specific enhancer elements in the second intron of the human apolipoprotein b gene.we report the identification and characterization of tissue-specific transcriptional enhancer elements that influence the expression of the human apolipoprotein b gene. a 704-base pair psti fragment comprising sequences from the first and second introns of the human apolipoprotein b gene (positions +360 to +1064) possesses tissue-specific transcriptional enhancer elements when assayed in transient transfection experiments using either the apolipoprotein b or thymidine kinase promoter. the majori ...19912019605
six chains of the human t cell antigen receptor.cd3 complex are necessary and sufficient for processing the receptor heterodimer to the cell surface.the t cell antigen receptor (tcr) plays a key role in the process of antigen recognition. it is a complex of at least seven peptide chains (alpha beta gamma delta epsilon zeta-zeta). it is found on the surface of mature t cells and functions in antigen binding in the presence of the major histocompatibility complex. it has been known for some time that physical associations between the cd3 proteins and the tcr chains are essential for efficient transport of either component to the surface of t c ...19912019606
loss of the intrinsic heat resistance of human cells and changes in mr 70,000 heat shock protein expression in human x hamster hybrids.since mammalian cells vary widely in their intrinsic thermoresistance, we have investigated the genetic basis underlying this phenomenon in human and rodent cell lines. typically, human cells are considerably more resistant to killing by heat than rodent cell lines. to determine whether the heat-resistant phenotype is dominant or recessive and to locate the chromosome(s) bearing determinants for heat resistance, we have prepared hybrids of heat-resistant human ht1080 cells and heat-sensitive chi ...19912021941
effects of tamoxifen and protein kinase c inhibitors on hyperthermic cell killing.the effects of the anti-estrogen, tamoxifen, and the protein kinase c inhibitor, 1-(5-isoquinolinylsulfonyl)2-methylpiperazine (h7), on hyperthermic cytotoxicity were studied. three cell lines were used, a human colon cancer cell line (ht-29), a human mammary carcinoma cell line (mcf-7), and chinese hamster v79 lung fibroblasts. with all three cell lines, tamoxifen at concentrations greater than 7.5 microm during heating or with a 3-hr exposure prior to heating significantly sensitized cells to ...19912022504
a specific heterotypic cell adhesion activity between members of carcinoembryonic antigen family, w272 and nca, is mediated by n-domains.the ca(2+)-independent homotypic and heterotypic cell adhesion activities of a carcinoembryonic antigen (cea) family member, w272 (cgm6), whose cdna has recently been isolated from libraries of human peripheral leukocytes of apparently normal subjects (arakawa, f., kuroki, mo., misumi, y., oikawa, s., nakazato, h., and matsuoka, y. (1990) biochem. biophys. res. commun. 166, 1063-1071) and spleen of chronic myelogenous leukemia patients (berling, b., kolbinger, f., grunert, f., thompson, j. a., b ...19912022629
choriocarcinoma cells increase the number of differentiating human cytotrophoblasts through an in vitro interaction.the human placenta arises from the zygote through single cell intermediates called cytotrophoblasts that in turn give rise to a syncytium. in culture, mononucleated cytotrophoblasts exhibit little, if any, cell division but are converted to multinucleated cells. choriocarcinoma, the malignant tumor of placenta trophoblast, comprises a mixed population of dividing cellular intermediates that resemble cytotrophoblasts but are less differentiated. because the choriocarcinoma intermediates arise fro ...19912022665
recombinant human thyrotropin (tsh) receptor in a radioreceptor assay for the measurement of tsh receptor autoantibodies.we studied the suitability of using the recombinant human tsh receptor expressed in chinese hamster ovary cells in a tsh binding inhibition (tbi) assay for autoantibodies against the tsh receptor. purified immunoglobulin g (igg) containing potent thyroid-stimulating immunoglobulin bioactivity competed for radiolabeled tsh binding to recombinant tsh receptor in parallel to inhibition by unlabeled tsh. using polyethylene glycol-prepared igg, this assay discriminated very well between sera from nor ...19912022709
ionizing radiation and genetic risks. iii. nature of spontaneous and radiation-induced mutations in mammalian in vitro systems and mechanisms of induction of mutations by radiation.this paper (1) presents an analysis of published data on the molecular nature of spontaneously arising and radiation-induced mutations in mammalian somatic cell systems and (2) examines whether the molecular nature and mechanisms of origin of radiation-induced mutations, in mammalian in vivo and in vitro systems, as currently understood, are consistent with expectations based on the biophysical and microdosimetric properties of ionizing radiation. depending on the test system (cho cells, human t ...19912023601
sindbis virus infection of a chinese hamster ovary cell mutant defective in the acidification of endosomes.sindbis virus infection of a chinese hamster ovary temperature-sensitive mutant cell line defective in its ability to acidify endosomes was examined to evaluate the importance of this step in the process of alphavirus penetration of host cells by measuring the time at which viral rna synthesis was initiated. we found that rna synthesis was initiated in these mutant cells at the same time after addition of virus at either permissive or nonpermissive temperature. we conclude that exposure to the a ...19912024467
the pathway mediating insulin's effects on pyruvate dehydrogenase bypasses the insulin receptor tyrosine kinase.the effect of insulin on pyruvate dehydrogenase activity was examined in two different cell types that over expressed either normal or defective human insulin receptors, rat 1 embryonic fibroblasts and chinese hamster ovary (cho) cells. insulin stimulated pyruvate dehydrogenase activity in cells that expressed normal insulin receptors (rat 1 hirc, and cho-wt and cho-t cells), or receptors in which lysine 1018 in the atp-binding site of the tyrosine kinase domain was exchanged for alanine (rat 1 ...19912026596
induction of chromosomal aberrations and sce by chloramphenicol.the induction of chromosomal aberrations and sister-chromatid exchanges (sce) was studied in human lymphocyte cultures treated with chloramphenicol (cap), an antimicrobial agent acting by inhibiting protein synthesis. moreover chromosomal aberrations and sister-chromatid exchanges were studied in bone marrow cells of treated mice and in chinese hamster cell cultures (v79) respectively. while no aberrations were induced by short treatments in human lymphocytes exposed in g1 and g2 phases, high fr ...19912030703
evidence supporting a passive role for the insulin receptor transmembrane domain in insulin-dependent signal transduction.we previously have demonstrated that intramolecular interactions between alpha beta-alpha beta subunits are necessary for insulin-dependent activation of the protein kinase domain within a single alpha 2 beta 2 heterotetrameric insulin-receptor complex (wilden, p. a., morrison, b. d., and pessin, j. e. (1989) biochemistry 28, 785-792). to evaluate the role of the beta subunit transmembrane domain in the insulin-dependent signalling mechanism, mutant human insulin receptors containing a series of ...19912033070
production of antisera selective for m1 muscarinic receptors using fusion proteins: distribution of m1 receptors in rat brain.a fragment of the cdna encoding the third intracellular loop of the rat m1 muscarinic receptor was cloned, and the dna was expressed in escherichia coli as a fusion protein. the fusion protein was purified and utilized as an antigen to raise a polyclonal antiserum in rabbits. chinese hamster ovary cells stably transfected with the cdna encoding each of the five known subtypes of muscarinic receptor were used as tissue sources to test the antiserum. the antiserum was found to quantitatively immun ...19912034236
mapping of human chromosome 22 with a panel of somatic cell hybrids.the adenylosuccinate lyase (adsl) which is essential for generating adenylate, maps to the long arm of chromosome 22. by using a chinese hamster ovary cell line deficient in adsl activity, we have constructed a set of 17 somatic cell hybrids containing defined regions of human chromosome 22. this panel was extended with six additional hybrids, obtained in other laboratories using various methods of selection. southern analysis of the hybrids with 38 chromosome 22 probes defined 14 different subr ...19912037296
high level expression of functional full length and truncated glucocorticoid receptor in chinese hamster ovary cells. demonstration of ligand-induced down-regulation of expressed receptor mrna and protein.full length human glucocorticoid receptor and truncated receptor derivatives lacking the major amino-terminal trans-activating domain were expressed in stably transfected chinese hamster ovary (cho) cells. the receptors were co-expressed together with human metallothionein iia, and the expression levels were amplified in the presence of increasing concentrations of metal. in amplified cells, both synthesized receptor forms showed the expected molecular weights, as assayed by affinity labeling an ...19912037566
cdna cloning and expression of platelet p24/cd9. evidence for a new family of multiple membrane-spanning proteins.this study was designed to clone, sequence, and express the full-length cdna for the human platelet p24/cd9 antigen. a 1.3-kilobase cdna clone was identified that has an open reading frame encoding a mature protein of 228 amino acids (approximately 25,400 da) containing 10 cysteine residues and four putative transmembrane domains. the identity of the clone was confirmed by: (i) its predicted size, (ii) identity to four peptide sequences from the isolated protein including the nh2 terminus, and ( ...19912037603
phosphorylation of hsp27 during development and decay of thermotolerance in chinese hamster cells.the small molecular weight heat shock protein hsp27 was recently shown to confer a stable thermoresistant phenotype when expressed constitutively in mammalian cells after structural gene transfection. these results suggested that hsp27 may also play an important role in the development of thermotolerance, the transient ability to survive otherwise lethal heat exposure after a mild heat shock. in chinese hamster o23 cells increased thermoresistance is first detected at 2 h after a triggering trea ...19912037626
co-culture systems for assessing the stability and genotoxicity of reactive 1,2-dibromo-3-chloropropane (dbcp) metabolites.1,2-dibromo-3-chloropropane (dbcp) induced dna damage, measured by alkaline elution, at low concentrations (5-10 microm) in suspensions of hepatocytes and testicular cells isolated from rats. at higher concentrations (greater than or equal to 100 microm) dbcp caused dna damage and increased the frequency of sister chromatid exchanges in chinese hamster v79 cells. when dbcp (2.5-10 microm) was tested for its ability to cause unscheduled dna synthesis (uds) in monolayers of liver cells isolated fr ...19912038269
nitroreduction is not involved in the genotoxicity of 2-nitropropane in cultured mammalian cells.we have investigated the importance of nitroreduction for the genotoxicity of the carcinogen 2-nitropropane (2-np) in primary cultures of rat hepatocytes and in v79 chinese hamster cells. induction of dna repair synthesis was used as an indicator of genotoxic effects in hepatocytes. genotoxicity in v79 cells was determined as induction of dna repair, micronuclei and mutations to 6-thioguanine (tg) resistance. both hepatocytes and v79 cells were found capable of reducing and oxidizing 2-np. reduc ...19912038276
suppression of tumor formation in vivo by expression of the je gene in malignant cells.the early growth response gene je encodes a monocyte chemoattractant, mcp-1. the je/mcp-1 protein attracts and stimulates human monocytes and induces monocyte-mediated inhibition of tumor cell growth in vitro. expression of human or murine je/mcp-1 in chinese hamster ovary (cho) cells completely suppressed their ability to form tumors in nude mice. coinjection of je/mcp-1-expressing cells with nonexpressing cho cells or with hela cells also prevented tumor formation. since je/mcp-1 expression ha ...19912038321
demonstration by confocal microscopy that unliganded overexpressed glucocorticoid receptors are distributed in a nonrandom manner throughout all planes of the nucleus.mouse glucocorticoid receptors (gr) that are over-expressed in chinese hamster ovary (cho) cells behave like progesterone receptors, in that the unliganded receptor localizes to the nucleus where it resides in a loosely bound docking complex, probably in association with the 90-kda heat shock protein (hsp90) and hsp70. in this paper we examine the localization of the overexpressed gr within the cho cell nucleus by confocal microscopy. in hormone-free cells the receptor distributes in a mottled p ...19912038343
similarity between physicochemical properties of recombinant rat prorenin and native inactive renin.rat prorenin was synthesized by chinese-hamster ovary cells transfected with an expression vector containing rat preprorenin cdna sequences, then purified by concanavalin a-sepharose chromatography and h.p.l.c. on g3000sw. the molecular mass of purified prorenin was 46,000 da, as determined by h.p.l.c. on g3000sw. immunoblot analysis indicated that recombinant prorenin cross-reacted with anti-(mature renin) antibody and two kinds of antibodies recognizing the n-terminus and c-terminus of the pro ...19912039449
mutagenesis of cysteines in the hormone binding domain of the human estrogen receptor. alterations in binding and transcriptional activation by covalently and reversibly attaching ligands.we have carried out experiments to determine the role of the cysteines in the hormone-binding domain (hbd) of the human estrogen receptor (er) in receptor function. in each mutant receptor, 1 of the 4 cysteines in the hbd (cysteines 381, 417, 447, and 530) was changed by in vitro mutagenesis of the er cdna (containing gly400) from cysteine to alanine; cys530 was also mutated to a serine. the mutant and wild-type receptor cdnas were expressed in chinese hamster ovary cells using an expression vec ...19912040605
the importance of n- and o-linked oligosaccharides for the biosynthesis and in vitro and in vivo biologic activities of erythropoietin.erythropoietin (epo) plays a critical role in stimulating the proliferation and differentiation of erythroid precursor cells. epo is heavily glycosylated with three asparagine (n)-linked tetraantennary oligosaccharides that may contain n-acetyl-lactosamine repeats and a single serine (o)-linked oligosaccharide. epo expressed in chinese hamster ovary cells exhibits biologic properties and amino acid and carbohydrate composition similar to natural urinary epo. the importance of the complex n-linke ...19912043765
a new system for high-resolution dna sequence mapping interphase pronuclei.cosmid clones containing human or hamster inserts have been hybridized in situ and localized with fluorescent reporter molecules in interphase nuclei (pronuclei) obtained after fusion of hamster eggs with either human or hamster sperm. hamster egg cytoplasm processes the tightly packaged sperm dna into large diffuse networks of chromatin fiber bundles, providing hybridization targets more extended than those available in somatic interphase cell nuclei. pronuclear physical distances between hybri ...19912045112
chromosomal mapping of glutamate dehydrogenase gene sequences to mouse chromosomes 7 and 14.glutamate dehydrogenase (glud) plays an important role in mammalian neuronal transmission. in human, glud is encoded by a small gene family. to determine whether defects in glud genes are associated with known neurological mutations in the mouse and to contribute to the comparative mapping of homologous genes in man and mouse, the chromosomal location of genes reactive with a mouse brain glud cdna were determined. genomic southern analysis of a well-characterized panel of chinese hamster x mouse ...19912045113
isolation of a human cdna encoding amidophosphoribosyltransferase and functional complementation of a cho ade-a mutant deficient in this activity.we report here the isolation of a human cdna encoding the first step in de novo purine biosynthesis, amidophosphoribosyltransferase (prat). the human prat cdna was isolated by complementation of a saccharomyces cerevisiae ade4 mutant deficient in prat enzymatic activity. the identity of the isolated cdna, designated padea-3, was confirmed by several independent methods. genomic dna sequences homologous to padea-3 show coordinate segregation with the hypoxanthine nutritional requirement in chines ...19912047942
an approach to imaging of living cell surface topography by scanning tunneling microscopy.since a scanning tunneling microscope (stm) was developed, an observation of living cell surface has been one of the final aims in the biological application of stm. by developing a new style of stm which was combined with an optical microscope and with a novel system for the centering of both images, we successfully got the stm images of living cell surface of t24 cells (human bladder cancer cell line) and cho cells (chinese hamster ovary fibroblast) cultured on highly oriented pyrolytic graphi ...19912049086
a sensitive method for measuring neutralizing antibodies to bordetella pertussis toxin: optimized adp-ribosylation of transducin.pertussis toxin (pt), preactivated with 20 mm dithiothreitol (dtt), was incubated with different serum dilutions (1/10-1/200) before addition to the reaction mixture. final concentrations of the reagents were: pt (50 ng/ml), dithiothreitol (dtt)(less than or equal to 0.3 mm), bovine transducin (2 micrograms/ml), atp (1 mm). gtp (1 mm), lysophosphatidylcholine (ltc) (0.1 mg/ml), sodium acetate (naac) (0.1 m), tris-hcl, ph 7.1 (0.06 m) and 32p-nad+ (10 microci 28 ci/mm). the reaction was stopped b ...19912049177
cloning and in vivo expression of the human gart gene using yeast artificial chromosomes.two yeast artificial chromosomes (yacs) were isolated each with a full-length copy of the human gene that encodes the trifunctional protein containing phosphoribosylglycinamide synthetase (gars), phosphoribosylglycinamide formyltransferase (gart) and phosphoribosylaminoimidazole synthetase (airs). the yacs were characterized by restriction mapping and by in situ hybridization of cosmid subclones containing the yac ends to human metaphase chromosomes. one of the yacs contains co-cloned non-contig ...19912050105
identification of human hookworm in failed-treatment cases using chinese hamsters (cricetulus griseus) and scanning electron attempt was made to identify the human hookworm involved in failed-treatment cases using abnormal hosts and scanning electron microscopy. thirty-seven, 2 to 6 month old chinese hamsters (cricetulus griseus) from a closed, outbred, conventional colony, were each given between 20 and 120 filariform larvae per os. the larvae were cultured from faeces from mebendazole (vermox) 500 mg single-dose, failed-treatment cases living in the lowveld farming area of the transvaal province, south africa. ab ...19912050988
preparation of soluble murine il-6 receptor and anti-murine il-6 receptor antibodies.starting with a previously isolated cdna clone encoding murine il-6r, a stable transformed chinese hamster ovary cell line constitutively expressing soluble murine il-6r (smil-6r) has been established. the smil-6r was purified to homogeneity by sequential filtration and chromatography of culture medium. the smil-6r augmented the sensitivity of m1 cells to il-6 in their growth inhibition in a dose-response manner. rat hybridomas producing mab specific to murine il-6r were also established. one of ...19912051018
division-associated and division-independent hyperthermic cell death: comparison with other cytotoxic agents.we have heated chinese hamster ovary (cho) cells in g1 phase, and followed them by microscopic observation for 8 days. non-clonogenic cells were monitored with regard to when they died, and whether death was preceded by cell division. such cells underwent either a division-independent or division-associated mode of death. at high survival levels most cells died a division-associated death, while at low survival levels division-independent death predominated. mouse 10t1/2 cells died primarily acc ...19912051076
study on the pathogenicity of campylobacter jejuni by modifying the medium.campylobacter jejuni has been documented as one of the major aetiological agents of diarrhoeal illness all over the world. studies revealed its pathogenicity by different assay methods, but none could be strongly recommended as a tool for differentiating toxigenic strains of c. jejuni. this study was an attempt to demonstrate better its pathogenicity by media modification. fifteen isolates of c. jejuni recovered from diarrhoeal patients at the international centre for diarrhoeal disease research ...19912051523
expression of type i and type ii bovine scavenger receptors in chinese hamster ovary cells: lipid droplet accumulation and nonreciprocal cross competition by acetylated and oxidized low density lipoprotein.type i and type ii scavenger receptors, which have been implicated in the development of atherosclerosis and other macrophage-associated functions, differ only by the presence in the type i receptor of an extracellular cysteine-rich c-terminal domain. stable chinese hamster ovary (cho) cell transfectants expressing high levels of either the type i or type ii bovine scavenger receptors have been generated. type i and type ii receptors in these cells mediated high-affinity saturable endocytosis of ...19912052575
effect of cysteine replacements at positions 13 and 50 on metallothionein structure.recombinant wild-type and mutant chinese hamster metallothioneins, purified from the yeast saccharomyces cerevisiae, were analyzed for their chemical and spectroscopic properties. the mutant proteins contain cysteine to tyrosine replacements at positions 13 and 50. wild-type and mutant metallothioneins, in their cadmium-bound forms, all showed characteristic ultraviolet absorption spectra with shoulders at 245-250 nm due to cadmium-thiolate charge transfer. upon acidification, these absorption s ...19912054361
effects of ca2+ channel ligands on [3h]qnb binding at m1 and m3 muscarinic receptors.1. the effects of ca2+ channel ligands on [3h]qnb binding in m1- or m3-transfected chinese hamster ovary (cho) cells have been studied. 2. the ic50 values of ca2+ channel ligands for the inhibition of [3h]qnb binding were between 10(-6) and 10(-4) m and the rank order of potency was hoe 166 greater than mcn 6186 greater than nicardipine greater than tiamdipine greater than verapamil greater than diltiazem greater than bay k 8644 greater than nifedipine at m1 and m3 receptors. 3. the results indi ...19912055419
mutagenic specificity of n-methyl-n'-nitro-n-nitrosoguanidine in the gpt gene on a chromosome of chinese hamster ovary cells and of escherichia coli cells.dna base sequence changes induced by n-methyl-n'-nitro-n-nitrosoguanidine (mnng) mutagenesis have been determined for the escherichia coli gpt gene stably incorporated in a chromosome of chinese hamster ovary cells and in the chromosome of both growing and starving e. coli cells, instead of on a plasmid as in most previous studies. in the three cases, nearly all mutations were g:c to a:t transitions, with a 2- to 4-fold higher mutation rate, compared to other sites, at guanines flanked on the 5' ...19912062306
human spermidine synthase gene: structure and chromosomal localization.the human spermidine synthase (ec gene was isolated from a genomic library constructed with dna obtained from a human immunoglobulin g (igg) myeloma cell line. subsequent sequence analyses revealed that the gene comprised of 5,818 nucleotides from the cap site to the last a of the putative polyadenylation signal with 8 exons and 7 intervening sequences. the 5'-flanking region of the gene was extremely gc rich, lacking any tata box but containing ccaat consensus sequences. no perfect co ...19912069720
molecular cloning, sequence analyses, and expression of complementary dna encoding murine progesterone receptor.progesterone receptors exist in two molecular forms commonly designated as "a" and "b" forms, the relative proportion of which can vary among species. in murine tissues, progesterone receptor exists predominantly as the "a" form which, in mammary glands, is also under developmental regulation [shyamala et al. (1990) endocrinology 126, 2882-2889]. therefore, toward resolving the molecular mechanisms responsible for the predominance of the "a" form of progesterone receptor in murine tissues and it ...19912069958
platelet glycoprotein iib-iiia (alpha iib beta 3 integrin) confers fibrinogen- and activation-dependent aggregation on heterologous analyze molecular mechanisms of platelet aggregation, we have studied the aggregation of chinese hamster ovary (cho) cells expressing between 1 and 4 x 10(5) recombinant human glycoprotein (gp) iib-iiia molecules per cell (a5 cells). these cells aggregated as measured by the disappearance of single cells during rotary agitation. aggregation was dependent on the presence of extracellular fibrinogen (approximately 500 nmol/l) and divalent cations, and required prior activation of the gpiib-iiia ...19912070074
molecular and genetic analyses of arylamine n-acetyltransferase polymorphism of rabbit liver.a cdna clone encoding the full coding region of polymorphic arylamine n-acetyltransferase was isolated from rabbit liver and expressed in chinese hamster ovary cells. the expressed enzyme acetylated 2-aminofluorene, procainamide, sulfamethazine, and p-aminobenzoic acid at equivalent rates. n-acetyltransferase activity was measured in 17 rabbits from an inbred colony which were classified into rapid, intermediate, and slow acetylators. the livers of the rapid and intermediate acetylators efficien ...19912071601
[mapping of the silver fox genome. iii. determination of the chromosomal localization of the got2, ak1, aldoc, acp1, itpa, pgp and blvr genes].evidence is presented for the chromosome localization of seven silver fox genes obtained with the help of panel of fox x chinese hamster somatic cell hybrids. thus, the ak1, got2 and aldoc are assigned to chromosome vfu2, pgp to chromosome vfu3, blvr to chromosome vfu5, acp1 to chromosome vfu8 and itpa to chromosome vfu14. the genetic map of 29 fox genes is compared with those reported for man and other animals. the results obtained support and extend our previous suggestion that formation of th ...19902074010
in vivo discrimination among beta-tubulin isotypes: selective degradation of a type iv beta-tubulin isotype following overexpression in cultured animal cells.preceding efforts have revealed that tubulin synthesis in animal cells is regulated both by selective expression of individual members of the tubulin multigene families and by a post-transcriptional control pathway that cotranslationally degrades tubulin mrnas when the concentrations of unassembled subunits are increased. to test the effect of forced expression of a specific beta-tubulin, we constructed chinese hamster ovary (cho) cell lines that stably express the chicken class iv (c-iv) beta-t ...19902078553
growth hormone (gh) stimulates protein synthesis in cells transfected with gh receptor complementary expression vector containing a rat gh receptor cdna was transfected into chinese hamster ovary (cho) cells, and stable cell lines expressing gh receptors were established. in contrast to nontransfected cho cells, expression of gh receptors in transfected cells resulted in the appearance of high affinity (kd = 1.53 nm) specific binding of gh. cross-linking of [125i]hgh to the receptors and subsequent sodium dodecyl sulfate (sds)-electrophoresis gave an estimated receptor mol wt of 84,000. gh t ...19902082195
actin and lamin comprised filaments in the nuclei of chinese hamster ovary cells affected with clostridium difficile enterotoxin a.the major change in the ultrastructure of chinese hamster ovary (cho) cells treated with clostridium difficile enterotoxin a was the formation of bundles of filaments in the nucleoplasm. the filaments appeared after 2.5 h and disappeared by the fourth hour of incubation with the toxin. to partially characterize these filaments, laser diffractometry and ultrastructural immunocytochemistry were employed. the bundles consist of coiled filaments of about 11 nm and 16 nm diameter and a main long axia ...19902090392
post-transcriptional regulation of retroviral vector-transduced low density lipoprotein receptor activity.we have reported the use of a retroviral vector to introduce the low density lipoprotein (ldl) receptor gene into receptor-deficient watanabe heritable hyperlipidemic (whhl) rabbit fibroblasts (miyanohara, a., m. f. sharkey, d. steinberg, j. l. witztum, and t. friedmann. 1988. proc. natl. acad. sci. usa. 85: 6538-6542). because the cdna for the ldl receptor did not contain the 5' sterol regulatory element that confers sterol-mediated inhibition of ldl receptor transcription, we did not anticipat ...19902090710
oxygenation of desmosterol and cholesterol in cell order to determine whether hydration of the delta 24 bond of desmosterol contributes to the formation of the regulatory oxysterol, 25-hydroxycholesterol, [3h]desmosterol was incubated with two cultured cell lines and the labeled products were analyzed. small amounts of 25-hydroxycholesterol were formed with chinese hamster lung (dede) cell cultures, but not with mouse fibroblast (l) cell cultures. apparently, desmosterol was converted into cholesterol, a process that does not occur in l cells ...19902090711
[a novel group of nucleolar organizer region associating proteins].with the scleroderma autoantinucleolar antiserum which was discribed in our previous paper, we identified a novel group of nucleolar organizer associating proteins, anop. by means of immunoblotting, it was found that anop mainly consists of three polypeptides with molecular weights of 65, 76, and 78 kd respectively. immunoelectron microscopy demonstrated that anop is localized in the shells of dense fibril components surrounding fibrillar centers of nucleolus. moreover, indirect immunofluorescen ...19902091420
evaluation of four in vitro genetic toxicity tests for predicting rodent carcinogenicity: confirmation of earlier results with 41 additional chemicals.the effectiveness of four in vitro short-term tests (stt) for genetic toxicity, induction of mutations in salmonella (sal) and mouse lymphoma l5178y cells (mla), and induction of sister chromatid exchanges (sce) and chromosome aberrations (abs) in chinese hamster ovary cells that are used for predicting rodent carcinogenicity were examined. the in vitro results were compared with the results from 41 rodent carcinogenicity studies performed by the national toxicology program. the predictive value ...19902091921
selective dna repair in active colleagues and i have discovered intragenomic heterogeneity in dna repair in mammalian cells. consequences of unrepaired dna damage depend upon the precise location of the damage with respect to relevant genes. it is therefore important to understand rules governing accessibility of specific dna sequences in chromatin to damage and repair. the efficiency of removal of pyrimidine dimers has been mapped in the active dihydrofolate reductase (dhfr) gene in chinese hamster ovary (cho) cells. repa ...19902094132
[studies on the toxicity of a new synthetic drug sc1001-aminum].sc1001a is a new sedative, hypnotic and anti-epileptic drug. screening for possible mutagenicity of the agent consisted of a battery scheme of short-term mutagenic tests with different hereditary detecting end points. three assays were with in the scheme: ames test (for detecting gene mutation in vitro), micronucleus test (for detecting chromosomal aberration in vivo) and chl (chinese hamster lung cell line) test (for detecting chromosomal aberration in vitro). in addition, a routine teratogenic ...19902094640
detection of autoantibodies to recombinant human thyroid peroxidase by sensitive enzyme immunoassay.autoantibodies to thyroid peroxidase (tpo), the thyroid 'microsomal' antigen, are widely utilized in the diagnosis of human autoimmune thyroid disease. crude human thyroid preparations of tpo are of differing potency, contain residual thyroglobulin (tg) and other human membrane antigens, and are available in only limited amounts. hence, immunoassays for anti-tpo are unstandardized and of variable sensitivity and specificity. we co-transfected the chinese hamster ovary (cho) cell line with a full ...19902096010
membrane traffic between secretory compartments is differentially affected during mitosis.membrane traffic has been shown to be regulated during cell division. in particular, with the use of viral membrane proteins as markers, endoplasmic reticulum (er)-to-golgi transport in mitotic cells has been shown to be essentially blocked. however, the effect of mitosis on other steps in the secretory pathway is less clear, because an early block makes examination of following steps difficult. here, we report studies on the functional characteristics of secretory pathways in mitotic mammalian ...19902099191
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