[characteristics of somatic cell hybrids (mouse x chinese hamster) with ratios of chromosome sets different from the parent species. iv. an electrophoretic analysis of several enzymes of the dehydrogenase class].electrophoretic mobilities in polyacrylamide gel of five dehydrogenases: nadp-dependent malate dehydrogenase (nadp-mdh), 6-phosphogluconate dehydrogenase (6pgd), alcohol dehydrogenase (adh), glucose-6-phosphate dehydrogenase (g6pd) and glutamate dehydrogenase (gdh) were investigated in a series of mouse x chinese hamster somatic cell hybrids. seven hybrid lines with different ratio of chromosome sets of hamster and mouse: 1 : 1, 2 : 1, 3 : 1 and 1 : 2 respectively were studied. nadp-mdh and 6pgd ...19751241545
acrylonitrile biotransformation in rats, mice, and chinese hamsters as influenced by the route of administration and by phenobarbital, skf 525-a, cysteine, dimercaprol, or thiosulfate.female wistar rats, conventional albino mice, and chinese hamsters were given a single dose of acrylonitrile, 0.5 or 0.75 mm/kg body weight. the elimination in the urine of thiocyanate, which is the main metabolite of acrylonitrile, indicated a decreasing proportion of biotransformation after oral (over 20%), intraperitoneal, or subcutaneous (2 to 5%), and intravenous (1%) administration in rats. oral administration of acrylonitrile in hamsters and mice was also followed by higher biotransformat ...19751242300
effect of room fluorescent light on the deterioration of tissue culture medium.a major cause of tissue culture medium deterioration is exposure to room fluorescent light. riboflavin and tryptophan present in dulbecco's modified eagle's minimum essential medium, when exposed to light, yield toxic photoproducts responsible for loss of the ability of the medium to support clonal growth of human, mouse and chinese hamster cell lines. procedures for minimizing medium deterioration are discussed.19761244326
lack of synergistic effect between x-ray and uv irradiation on the frequency of chromosome aberrations in pha-stimulated human lymphocytes in the g1 stage.pha-stimulated human lymphocytes in the g1 stage were irradiated with uv radiation and x-rays, and the cells were analyzed for chromosomal aberrations in the first mitotic division. the frequency of dicentric chromosomes after single x-irradiation in the g1 stage was about twice the yield in the g0 stage. no increase in the yield of dicentrics was observed after combined irradiation with uv and x-rays. this is contrary to the finding for g0 lymphocytes, where a 2-fold increase of chromosome aber ...19761250244
organisation of the genes coding for 5s rna in the chinese hamster.hybridisation of iodinated mouse 5s rna with chinese hamster dna fractionated on a cscl gradient, identifies two separate dna components that hybridise with the labelled probe. one component is slightly, and one considerably heavier than the main band dna. this suggests that the gene coding for 5s rna in the chinese hamster may constitute two distinct populations differing in g + c content of their adjacent spacer regions.19761250414
selective modification of cell surface proteins and thymidine transport in hamster cells exposed to cholera toxin.the increased adherence and morphological response which occurs in chinese hamster ovary cells as a result of exposure to cholera toxin is paralleled by modification in the relative exposure of outer proteins. mild proteolysis treatment of the cells prelabeled with [3h] glucosamine reveals a markedly different kinetics of release of external glycopeptides as a result of exposure to cholera toxin. selective alterations in external tyrosyl-rich proteins can also be detected by lactoperoxidase-cata ...19761256059
a comparative analysis of the karyotypes of cricetus cricetus and cricetulus griseus.this study presents a comparison of the mitotic chromosomes of the two species of hamsters cricetus cricetus (european hamster) and cricetulus griseus (chinese hamster), which have the same chromosome number of 2n=22.--g-banding procedure reveals striking similarities in both karyotypes and gives the possibility to analyse structural changes so that two examples for robertsonian rearrangement can be observed.--a remarkable kind of difference between the two karyotypes becomes obvious after c-ban ...19761269344
amino terminus of the interleukin-8 receptor is a major determinant of receptor subtype specificity.interleukin-8 (il-8) is a key mediator in the migration of neutrophils from the circulation to the site of inflammation in the tissue. il-8 is secreted by many cell types in response to proinflammatory stimuli such as interleukin 1, tumor necrosis factor, and lipopolysaccharide and is a potent chemoattractant and activator of neutrophils. neutrophil activating peptide-2 (nap-2) and melanoma growth-stimulatory activity (mgsa/gro) are structurally and functionally related to il-8 and, like il-8, b ...19921281158
detection of somatic mutations in vivo in lung fibroblasts, i. spontaneous frequencies in chinese hamsters and f344 rats.the frequency of mutant cells observed in a series of experiments in which primary cells were isolated from untreated or solvent control animals are reported. the mutants detected are thioguanine-resistant lung fibroblasts isolated de novo from chinese hamsters or fischer 344 rats. the results in the two species were very similar. the distribution of mutant colonies in cells isolated from untreated animals is not random (poissonian) but rather shows an excess of mutant clusters. no significant d ...19921281265
mutagenesis and comutagenesis by lead compounds.we have previously reported that lead(ii) is weakly mutagenic to chinese hamster v79 cells. a transgenic cell line g12 containing a single copy of the e. coli gpt gene was developed in this laboratory from chinese hamster v79 cells. the gpt locus in the g12 cells is more mutable by radiation and oxidative agents compared with the endogenous hprt locus of wild-type v79 cells. we have investigated the mutagenicity of two lead compounds at the gpt locus in g12 cells. only at a toxic dose is lead ac ...19921282217
characterization of the glutamine synthetase amplifiable eukaryotic expression system applied to an integral membrane protein--the human thyrotropin amplifiable eukaryotic expression system, based upon glutamine synthetase, has been applied to the production of a complex integral membrane glycoprotein, the human receptor for the polypeptide hormone thyrotropin (tsh). production of recombinant protein was achieved in chinese hamster ovary (cho) cells at levels at least 10-fold higher than has been achieved in any other system. after amplification of the inserted gene, the gene copy number was found to be increased in most (but not all) sub ...19921283293
clastogenicity of aporphine alkaloids in vitro.the chromosomal aberration test using a chinese hamster lung cell line (chl) was carried out on 19 aporphine alkaloids including apomorphine with and without rat liver homogenates (s9) mix. eighteen of 19 alkaloids tested induced chromosomal aberration in the presence or absence of s9 mix. among the alkaloids tested, anolobine, liriodenine and 4,5-dioxodehydrocrebanine induced chromosomal aberrations at relatively low concentrations and as low as 2.5, 5 and 3.13 micrograms/ml, respectively. dice ...19921287184
[mutagenicity studies of prednisolone farnesylate (pnf)].prednisolone farnesylate (pnf) was tested for mutagenicity by ames test using salmonella typhimurium (ta100, ta1535, ta98, ta1537) and escherichia coli (wp2 uvra), for clastogenic activity in vitro by the chromosomal aberration test in a chinese hamster fibroblast cell line (chl), and for induction of micronuclei by the micronucleus test in male icr mice. 1) in ames test, pnf with and without metabolic activation showed no mutagenicity in any strains at any dose levels (312-5,000 micrograms/plat ...19921293327
no adaptive response of chinese hamster ovary cells to low doses of ionizing radiation.chinese hamster ovary (cho) cells that had been exposed to very low doses of ionizing radiation from incorporated tritiated thymidine or x-rays were shown not to be more resistant to the induction of chromatid aberrations by a subsequent higher dose of ionizing radiation than previously untreated cells. the adaptive response to ionizing radiation was absent both in cells challenged with high doses of x-rays (1.25 gy) and in cells post-treated with thermal neutrons (0.5-1 x 10(12) n/cm2). in agre ...19921295849
inhibition of target cell adhesion by monoclonal antibody to the 66 kd surface antigen of entamoeba histolytica.the adherence of entamoeba histolytica trophozoites to target cells was studied using a monoclonal antibody to a major surface antigen of 66 kd. preincubation of trophozoites with monoclonal antibody decreased their ability to adhere to and engulf erythrocytes and to destroy chinese hamster ovary cells. the monoclonal antibody was specific for the 66 kd antigen, which is possibly a major participant in the adhesion that precedes phagocytosis and cytopathic effects.19921296611
[effect of elastin peptides on cell proliferation].elastin peptides were shown to act on a cell membrane receptor coupled to a g-protein, phospholipase c, and its activation increases ip3 and dag and opens receptor-dependent ca(++)-channels. as some growth factors also produce similar modifications in intracellular ca++, we wanted to explore the effect of elastin peptides on cell proliferation using 3h-thymidine incorporation and cell counting. the concentration of peptides needed for the stimulation of cell proliferation varied between large li ...19921297524
coexpression of the cys e and cys m genes of salmonella typhimurium in mammalian cells: a step towards establishing cysteine biosynthesis in sheep by transgenesis.the salmonella typhimurium genes for serine acetyltransferase (cys e) and o-acetylserine sulphydrylase b (cys m) were isolated and characterized in order to express these as transgenes in sheep to establish a cysteine biosynthesis pathway and, thereby, to achieve an increased rate of wool growth. comparison of the s. typhimurium and escherichia coli genes showed considerable homology, both at the nucleotide and amino acid sequence levels. the in vitro and in vivo expression studies showed that b ...19921301209
incidence of aeromonas isolated from diarrhoeal children and study of some virulence factors in the isolates.stool samples from 305 children with diarrhoea and equal number of age and sex matched non-diarrhoeal control children, less than 5 years of age, were examined during the period from sept 1988 to april 1989. aeromonas spp. were isolated from 37 (12.1%) diarrhoeal and 05 (1.6%) control cases. out of 37 diarrhoeal isolates 13 (35.1%) were a. hydrophila, 19 (51.1%) a. sobria and 05 (13.5%) a. caviae. all the isolated strains were tested for haem agglutination property and haemolysin production. sev ...19921303082
in vivo biological activities of recombinant human erythropoietin analogues produced by cho cells, bhk cells and c127 cells.the in vivo biological activity of four pharmaceutical preparations of recombinant human erythropoietin was compared. two of the erythropoietins were produced by chinese hamster ovary cells, cho-k1, and the others were produced by mouse mammary cells, c127, and baby hamster kidney cells, bhk-21. the activities of the analogues were estimated by a simple cell counting method with conventional automated microcell counters. the amounts of these analogues gave straight logarithmic dose-response curv ...19921305401
firefly luciferase gene transmission and expression in transgenic medaka (oryzias latipes).plasmids containing the luciferase gene from the firefly (photinus pyralis) fused to the chinese hamster metallothioneine i promoter (chmti) were microinjected into the pronuclei of medaka (oryzias latipes) eggs, which were then artificially inseminated. evidence of integration into the genome was gained from observation of germ-line transmission in a mendelian fashion from the f1 to the f2 generation. however, gene expression (light emission) could not be demonstrated in the established transge ...19921308822
cell-specific posttranslational events affect functional expression at the plasma membrane but not tetrodotoxin sensitivity of the rat brain iia sodium channel alpha-subunit expressed in mammalian cells.the rat brain iia na+ channel alpha-subunit was expressed and studied in mammalian cells. cells were infected with a recombinant vaccinia virus (vv) carrying the bacteriophage t7 rna polymerase gene and were transfected with cdna encoding the iia na+ channel alpha-subunit under control of a t7 promoter. whole-cell patch-clamp recording showed that functional iia channels were expressed efficiently (approximately 10 channels/microns2 in approximately 60% of cells) in chinese hamster ovary (cho) c ...19921309573
insulin stimulation of phosphatidylinositol 3-kinase activity maps to insulin receptor regions required for endogenous substrate phosphorylation.we have studied the phosphatidylinositol 3-kinase (ptdins 3-kinase) in insulin-stimulated chinese hamster ovary (cho) cells expressing normal (cho/ir) and mutant human insulin receptors. insulin stimulation of cho/ir cells results in an increase in ptdins 3-kinase activity associated with anti-phosphotyrosine (alpha py) immunoprecipitates, which has been previously shown to correlate with the in vivo production of ptdins(3,4)p2, and ptdins(3,4,5)p3 (ruderman, n., kapeller, r., white, m.f., and c ...19921309768
regulated and constitutive secretion. differential effects of protein synthesis arrest on transport of glycosaminoglycan chains to the two secretory pathways.many neural and endocrine cells possess two pathways of secretion: a regulated pathway and a constitutive pathway. peptide hormones are stored in granules which undergo regulated release whereas other surface-bound proteins are externalized constitutively via a distinct set of vesicles. an important issue is whether proper function of these pathways requires continuous protein synthesis. wieland et al. (wieland, f.t., gleason, m.l., serafini, t.a., and rothman, j.e. (1987) cell 50, 289-300) have ...19921309785
phosphatidylinositol-3-kinase in isolated rat adipocytes. activation by insulin and subcellular distribution.insulin increases phosphatidylinositol-3-kinase (pi-3-kinase) activity in chinese hamster ovary cells transfected with human insulin receptor (ruderman, n. b., kapeller, r., white, m. f., and cantley, l. c. (1990) proc. natl. acad. sci. u.s.a. 87, 1411-1415). the subcellular distribution of pi-3-kinase has not been investigated, and it is unclear if insulin has a stimulatory effect on pi-3-kinase in a nonproliferating target tissue, and, if so, whether this effect is subject to counter-regulatio ...19921310686
nitrobenzo[a]pyrene-induced dna amplification in sv40-transformed chinese hamster embryo cells.nitrobenzo[a]pyrenes (nbaps) are ubiquitous environmental pollutants that produce mutations in salmonella typhimurium and chinese hamster ovary cells. in this study, 1-, 3-, and 6-nbap induced amplification of sv40 dna sequences in an sv40-transformed chinese hamster embryo cell line which is sensitive to dna amplification by various known carcinogens. of the three isomers, 3-nbap produced the highest level of gene amplification, which was 4.8 relative to untreated controls at a dose of 5 microg ...19921311674
a single amino acid residue replacement in the beta subunit of human chorionic gonadotrophin results in the loss of biological activity.the heterodimer, human chorionic gonadotrophin (hcg), contains an alpha subunit that is common to the glycoprotein hormones and a hormone-specific beta subunit. a comparison of all known beta amino acid sequences shows that an aspartic acid at position 99 (with the numbering scheme for hcg-beta) is one of the seven non-cys invariant residues. using site-directed mutagenesis we have replaced hcg-beta asp99 with arg. chinese hamster ovary cells, containing a stably integrated gene for bovine alpha ...19921311931
immunolocalization of membrane-associated ctp:phosphocholine cytidylyltransferase in phosphatidylcholine-deficient chinese hamster ovary cells.the location of ctp:phosphocholine cytidylyltransferase in chinese hamster ovary (cho) cells made deficient in phosphatidylcholine was determined by immunofluorescence techniques. a rabbit polyclonal antibody was raised against a synthetic peptide corresponding to the amino-terminal 17 amino acid residues of rat liver cytidylyltransferase. the antibody recognized both native and denatured cytidylyltransferase from both rat liver and cho cells. cho cells were treated with phospholipase c to alter ...19921312094
upregulation of o6-alkylguanine-dna-alkyltransferase expression and the presence of double minute chromosomes in alkylating agent selected chinese hamster cells.chinese hamster v79 lung fibroblasts are sensitive to the toxic effects of chloroethylating agents such as mitozolomide (mz) and express very low levels (less than 2 fmol/mg) of the dna repair enzyme o6-alkylguanine-dna-alkyltransferase (atase). these cells were subjected to selection by treatment with serially increasing doses of mz. after each dose, the surviving population was expanded and atase activity was determined in cell extracts. atase specific activity increased stepwise and in cells ...19921312399
the use of the amplifiable high-expression vector pee14 to study the interactions of autoantibodies with recombinant human thyrotrophin order to produce significant quantities of the human thyrotrophin (tsh) receptor we have investigated the use of two eukaryotic high expression systems. dna encoding the receptor was obtained by the polymerase chain reaction (pcr) applied to thyroid cdna. receptor dna was inserted into the baculovirus system; despite high mrna levels there was little or no demonstrable protein production. however, using a novel amplifiable glutamine synthetase system, clones of transfected chinese hamster ova ...19921312488
detection of receptor-specific murine leukemia virus binding to cells by immunofluorescence analysis.four classes of murine leukemia virus (mulv) which display distinct cellular tropisms and bind to different retrovirus receptors to initiate virus infection have been described. in the present study, we describe a rapid, sensitive immunofluorescence assay useful for characterizing the initial binding of mulv to cells. by using the rat monoclonal antibody 83a25 (l. h. evans, r. p. morrison, f. g. malik, j. portis, and w. j. britt, j. virol. 64:6176-6183, 1990), which recognizes an epitope of the ...19921312632
characterization of a recombinant chimeric plasminogen activator composed of a fibrin fragment-d-dimer-specific humanized monoclonal antibody and a truncated single-chain urokinase.a recombinant chimeric plasminogen activator, ma-15c5hu/scu-pa-32k, composed of a humanized fibrin fragment-d-dimer-specific monoclonal antibody (ma-15c5hu) and a recombinant low-molecular-mass single-chain urokinase-type plasminogen activator, comprising amino acids leu144-leu411 (scu-pa-32k), was produced by cotransfecting chinese hamster ovary (cho) cells with the cdna encoding the ma-15c5hu light-chain sequence and the cdna encoding the ma-15c5hu heavy-chain sequence fused with the cdna enco ...19921313361
characterization of the endogenous adp-ribosylation of wild-type and mutant elongation factor 2 in eukaryotic cells.anti-[adp-ribosylated elongation factor 2 (ef-2)] antiserum has been used to immunoprecipitate the modified form of ef-2 from polyoma-virus-transformed baby hamster kidney (pybhk) cells [fendrick, j. l. & iglewski, w. j. (1989) proc. natl acad. sci. usa 86, 554-557]. this antiserum also immunoprecipitates a 32p-labelled protein of similar size to ef-2 from a variety of primary and continuous cell lines derived from many species of animals. one of these cell lines, chinese hamster ovary cho-k1 ce ...19921313365
expression of a cloned rat histamine h2 receptor mediating inhibition of arachidonate release and activation of camp accumulation.a dna, cloned after screening a rat genomic bank with probes derived from the sequence of a putative dog histamine h2 receptor [gantz, i., schäffer, m., delvalle, j., logsdon, c., campbell, v., uhler, m. & yamada, t. (1991) proc. natl. acad. sci. usa 88, 429-433], was used to prepare a probe for northern blot analysis and to transfect chinese hamster ovary (cho) cells. distribution of the gene transcripts in guinea pig tissues was consistent with that of h2 receptors. transfected cho cells expre ...19921313563
suramin is an inhibitor of dna topoisomerase ii in vitro and in chinese hamster fibrosarcoma cells.the antitrypanosomal and antifiliarial drug suramin is currently under investigation for treatment of advanced malignancies including prostatic cancer, adrenocortical cancer, and some lymphomas and sarcomas. here we show that suramin is a potent inhibitor of the nuclear enzyme dna topoisomerase ii. suramin inhibited purified yeast topoisomerase ii with an ic50 of about 5 microm, as measured by decatenation or relaxation assays. suramin did not stabilize the covalent dna-topoisomerase ii reaction ...19921313577
liver-specific expression of the gene coding for human factor x, a blood coagulation factor.factor x is a vitamin k-dependent glycoprotein that plays an essential role in both the intrinsic and extrinsic pathways of blood coagulation. studies on a recombinant lambda phage containing the 5'-flanking region of the human factor x gene showed that the factor x gene was linked to and was located at the 3' end of the factor vii gene: the initiation codon of the factor x gene was 2823 base pairs (bp) downstream from the polyadenylation site of the factor vii gene. this 2.8-kilobase intergenic ...19921313796
expression of a gene encoding a rabbit sperm membrane protein in mammalian cells.a general mammalian expression vector designated psv2-ep was reconstructed by inserting an oligonucleotide fragment into psv2-dhfr. this vector allowed insertion of cdnas with ecori cohesive ends. the psv2-ep contains a simian virus 40 (sv40) early promoter, origin for dna replication, sv40 poly-a site, splicing site, an initiator atg downstream from the promoter and an ecori site for the insertion of cdna fragment screened from lambda gt11 expression libraries. a recombinant plasmid (ps-vrs-1) ...19921314063
evolutionarily conserved structure of the 3' non-translated region of a chinese hamster polyubiquitin gene.from a v79 chinese hamster genomic library, we isolated a clone containing a polyubiquitin gene (designated as chub1), and determined its nucleotide sequence. the coding region of the chub1 gene consisted of five direct repeats of the ubiquitin unit with no spacer, followed by a single tyrosine residue. northern hybridization analysis with a synthesized probe specific to the 3' non-translated region of the chub1 gene revealed that it codes for a 1.8 kb mrna. an evident homology to the human poly ...19921314094
the use of chimeric gene constructs to express a bacterial endoglucanase in mammalian cells.the synthesis and secretion of a truncated clostridium thermocellum endoglucanase (ege') encoded by the cele' gene was investigated in chinese hamster ovary (cho) cells. fusion genes consisting of the human growth hormone (hgh) gene and cele', transcribed from the sv40 early enhancer/promoter, were constructed and stably transfected into cho cells. a gene consisting of cele' inserted into the first exon of the hgh gene resulted in the synthesis of truncated proteins (less than or equal to 22 kda ...19921314095
a procedure for selecting mammalian cells with an impairment in oxidative phosphorylation.the mitochondrial encephalomyopathies in man are characterized by heterogeneous defects leading to an impairment in the pathway of aerobic energy production. as a means of investigating the molecular and genetic mechanisms underlying these disorders we have developed a procedure for selecting mammalian cell lines with features resembling the human pathological phenotypes. the principle of the selection is the use of a fluorescent amphiphilic dye, 2,4-(dimethylamino)-1-styrylmethylpyridiniumiodin ...19921314097
glut4 facilitates insulin stimulation and camp-mediated inhibition of glucose transport.the glucose transporter isoform glut4 is found only in cells that exhibit insulin-sensitive glucose transport. to investigate the function of this transporter, l6 myoblasts were stably transfected with glut4 cdna. glut4 underwent insulin-dependent movement to the cell surface in myoblasts overexpressing the transporter. one cell line (243-6) expressed sufficient levels of the glut4 protein to study insulin-dependent glucose transport. unlike wild-type l6 cells, 243-6 myoblasts exhibited two feat ...19921314390
[the characteristics of the realization of cytogenetic damage in mammalian and plant cells exposed to low doses of radiation].a complicated character of the cytogenetic injury dependence upon radiation dose was revealed after low-level gamma irradiation of vicia faba seedlings and chinese hamster fibroblasts. the dependence was linear with low-level secondary exposure to 70 gev protons. the authors discuss a threshold nature of induction of the cytogenetic damage repair responsible for a high outcome of damages under the effect of low-level gamma radiation.19921314399
analysis of sequence specificity of 5-bromodeoxyuridine-induced reversion in cells containing multiple copies of a mutant gpt gene.for studies on molecular mechanisms of mutagenesis, it would be advantageous to transfer mutant genes with specific alterations into mammalian cells and use the transformed cells in reversion analyses. in the present paper, we describe an efficient method for analyzing reversion events occurring in cells that possess multiple copies of a mutational target gene. this method involves amplification of the chromosomally integrated target genes with the polymerase chain reaction (pcr) and restriction ...19921315457
subcellular distribution of beta 2-adrenergic receptors delineated with quantitative ultrastructural autoradiography of radioligand binding sites.beta-adrenergic receptors play a critical role in signal transduction in the cardiovascular system. regulation of beta-adrenergic receptor expression depends on multiple factors, including rates of synthesis and degradation of receptor protein and trafficking of receptors between the cell surface and putative intracellular compartments. to characterize the subcellular distribution of beta-adrenergic receptors and to delineate the ultrastructure of intracellular compartments in which adrenergic r ...19921315641
mechanism of action of a cytotonic enterotoxin produced by aeromonas this study, we describe the mechanism of action of a cytotonic enterotoxin produced by two isolates of aeromonas hydrophila. isolates ssu and ah65 are of different origin and both are capable of producing either a cytotoxic enterotoxin or aerolysin. a cytotonic enterotoxin produced by diarrheal isolate ssu, which was purified and characterized in our laboratory, elevated intracellular camp and pge2 levels in cultured chinese hamster ovary (cho) cells. likewise, enterotoxic activity expressed ...19921315703
the role of the c-terminal domain in collagenase and stromelysin specificity.recombinant human interstitial collagenase, an n-terminal truncated form, delta 243-450 collagenase, recombinant human stromelysin-1, and an n-terminal truncated form, delta 248-460 stromelysin, have been stably expressed in myeloma cells and purified. the truncated enzymes were similar in properties to their wild-type counterparts with respect to activation requirements and the ability to degrade casein, gelatin, and a peptide substrate, but truncated collagenase failed to cleave native collage ...19921315762
human chorionic gonadotropin (hcg) interacts directly with recombinant human tsh receptors.we have previously shown that highly purified urinary hcg has the potential to both stimulate the intracellular accumulation of cyclic amp and induce growth of immortalized rat thyroid cells. we have now compared the ability of recombinant human tsh and purified urinary hcg preparations to stimulate chinese hamster ovary (cho) cells which have been transfected with the human tsh receptor. only transfected cho cells expressing recombinant tsh receptors, but not control cho cells, were stimulated ...19921317388
site-directed mutagenesis of the rat m1 muscarinic acetylcholine receptor. role of conserved cysteines in receptor function.there are 9 cysteine residues in the rat m1 muscarinic acetylcholine receptor (machr) that are conserved among all five mammalian machr subtypes sequenced to date. to study the role of these cysteines in rat m1 machr function, site-directed mutagenesis was used to convert each cys residue to ser, and the mutant receptor genes were transfected into machr-deficient chinese hamster ovary (cho) cells. substitution of cys391 (extracellular loop iii) or cys421 and cys435 (carboxyl terminus) produces r ...19921317867
activation of g proteins by (rp) and (sp) diastereomers of guanosine 5'-[beta-thio]triphosphate in hamster fibroblasts. differential stereospecificity of gi, gs and gp.the effects of guanosine 5'-[beta-thio]triphosphate (gtp beta[s]) on g proteins have been examined in chinese hamster lung fibroblasts (ccl39 line) permeabilized with alpha-toxin from staphylococcus aureus. although much less effective than guanosine 5'-[gamma-thio]triphosphate (gtp gamma[s]), both (rp) and (sp) diastereomers of gtp beta[s] were found to activate three g protein-mediated pathways: inhibition of forskolin-stimulated adenylate cyclase (mediated by gi), potentiation of receptor-med ...19921318029
chromosomal localization of human glutamate receptor genes.the chromosomal localization of human glutamate receptor genes (glur1-4) has been established using pcr with dna isolated from mapping panels of chinese hamster-human hybrid cell lines and high-resolution fluorescent in situ suppression hybridization. this was accomplished with genomic clones containing putative human homologs of rat glur 1-4 isolated by high-stringency screening of a cosmid library with the rat cdnas encoding glur1-4. the locations of glur1-4, respectively, are 5q32-33, 4q32-33 ...19921319477
modulation of the cell cycle-dependent cytotoxicity of adriamycin and 4-hydroperoxycyclophosphamide by novobiocin, an inhibitor of mammalian topoisomerase ii.centrifugal elutriation was used to obtain synchronized cell populations in various cell cycle phases without prior growth-perturbing manipulation. treatment of these subpopulations with novobiocin (novo), a putative inhibitor of the mammalian topoisomerase ii enzyme, revealed a unique cell cycle phase-dependent cytotoxicity for this agent. at a concentration of 0.3 mm, novo was cytotoxic only to a specific cell subpopulation in the g1-s phase boundary. cells in other cell cycle phases were comp ...19921319822
coupling of two endothelin receptor subtypes to differing signal transduction in transfected chinese hamster ovary cells.we examined the intracellular signal transduction of two endothelin receptor subtypes (eta and etb) by transfection and stable expression of individual receptor cdnas in chinese hamster ovary cells. both receptors showed a rapid and marked stimulation of phosphatidylinositol hydrolysis and arachidonic acid release in response to agonist interaction. the two receptors, however, exhibited different responses in the cyclic amp transduction cascades. eta mediated the accumulation of cyclic amp forma ...19921319997
mechanisms by which lipoprotein lipase alters cellular metabolism of lipoprotein(a), low density lipoprotein, and nascent lipoproteins. roles for low density lipoprotein receptors and heparan sulfate proteoglycans.we sought to investigate effects of lipoprotein lipase (lpl) on cellular catabolism of lipoproteins rich in apolipoprotein b-100. lpl increased cellular degradation of lipoprotein(a) (lp(a)) and low density lipoprotein (ldl) by 277% +/- 3.8% and 32.5% +/- 4.1%, respectively, and cell association by 509% +/- 8.7% and 83.9% +/- 4.0%. the enhanced degradation was entirely lysosomal. enhanced degradation of lp(a) had at least two components, one ldl receptor-dependent and unaffected by heparitinase ...19921320015
molecular characterization of a novel metabotropic glutamate receptor mglur5 coupled to inositol phosphate/ca2+ signal transduction.a cdna clone for a new metabotropic glutamate receptor, mglur5, was isolated through polymerase chain reaction-mediated dna amplification by using primer sequences conserved among the metabotropic glutamate receptor (mglur) family and by the subsequent screening of a rat brain cdna library. the cloned receptor consists of 1171 amino acid residues and exhibits a structural architecture common to the mglur family, possessing a large extracellular domain preceding the seven putative membrane-spanni ...19921320017
the role of insulin receptor kinase domain autophosphorylation in receptor-mediated activities. analysis with insulin and anti-receptor antibodies.the role of specific tyrosine autophosphorylation sites in the human insulin receptor kinase domain (tyr1158, tyr1162, and tyr1163) was analyzed using in vitro mutagenesis to replace tyrosine residues individually or in combination. each of the three single-phe, the three possible double-phe a triple-phe and a triple-ser mutant receptors, stably expressed in chinese hamster ovary cells, were compared with the wild-type receptor in their ability to mediate stimulation of receptor kinase activity, ...19921320027
purification and quantification of recombinant epstein-barr viral glycoproteins gp350/220 from chinese hamster ovary cells.truncated epstein-barr virus (ebv) membrane antigen gp350/220 (ebv-ma) lacking the membrane anchor was expressed and secreted into the medium of recombinant chinese hamster ovary cells that had been cultured in plasmapur hollow-fibre modules using defined serum-free medium. the ebv-ma in the medium was concentrated by 70% (w/v) ammonium sulphate precipitation and subsequently purified by immunoaffinity chromatography using an anti-ebv-ma (ebv.0t6) monoclonal antibody (mab) column. adsorbed antig ...19921320046
stable overexpression of human beta 2-adrenergic receptors in mammalian cells.human beta 2-adrenergic receptors were overexpressed in chinese hamster ovary (cho) and human epitheloid carcinoma (hela) cells. stable expression in these cells was achieved by transfection of a vector containing the cdnas for the human beta 2-adrenergic receptor as well as for dihydrofolate reductase. by stepwise increases of the concentration of methotrexate - an inhibitor of dihydrofolate reductase - the expression in cho cells could be increased to levels of almost 200 pmol/mg membrane prot ...19921320210
non-random chromosome rearrangements in herpes simplex virus type 1 transformed diploid chef cells.the effects of herpes simplex virus type 1 (hsv-1) on diploid, non-tumourigenic chinese hamster embryo fibroblasts (chef/18-1d-3) were studied. six independent lines transformed by hsv-1 alone or by hsv-1 in combination with acyclovir or aqueous tobacco extract were isolated. in contrast to uninfected chef/18-1d-3 cells, all transformants grew in soft agar and were tumourigenic in nude mice. neither infectious virus nor viral antigens could be detected in any of the lines. cytogenetic analysis r ...19921320359
molecular cloning and promoter analysis of the rat liver farnesyl diphosphate synthase gene.the isolation and characterization of the rat genomic clone encoding the cholesterogenic enzyme farnesyl diphosphate (fpp) synthase is reported. the gene is localized on a 15-kilobase (kb) genomic fragment, spans approximately 12 kb and contains eight exons. sequences containing from 3.9 kb to 132 base pairs (bp) of the putative promoter were joined to the coding region of the bacterial reporter gene chloramphenicol acetyltransferase (cat). the cat activities or cat mrna levels of the hybrid gen ...19921321149
[mutagenicity tests of suplatast tosilate (ipd-1151t)].1. the reverse mutation test was carried out on suplatast tosilate (ipd-1151t) at dose range of 50-5000 micrograms/plate using salmonella typhimurium strains ta100, ta1535, ta98 ta1538 and ta1537, and escherichia coli strains wp2, wp2uvra. in all tester strains no significant differences 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 ipd-1151t was carried ...19921321262
cloned human neuropeptide y receptor couples to two different second messenger systems.neuropeptide y (npy) is one of the most abundant neuropeptides in the mammalian nervous system and exhibits a diverse range of important physiological activities, including effects on psychomotor activity, food intake, regulation of central endocrine secretion, and potent vasoactive effects on the cardiovascular system. two major subtypes of npy receptor (y1 and y2) have been defined by pharmacological criteria. we report here the molecular cloning of a cdna sequence encoding a human npy recepto ...19921321422
site-directed mutants of human myeloperoxidase. a topological approach to the heme-binding site.two site-directed mutants of human promyeloperoxidase, mpo(his416----ala) and mpo(his502----ala), have been expressed in chinese hamster ovary cells and purified. overall purification yields and apparent molecular masses of the mutant proteins were similar to those of the wild-type enzyme. both mutant species were analyzed spectroscopically to check the presence of the hemic iron in the proteins and were assayed for peroxidase activity. the data show that substitution of his502 leads to the loss ...19921321726
role of the carboxyl-terminal half of the extracellular domain of the human thyrotropin receptor in signal transduction.we studied the role of the carboxyl-terminus of the extracellular region of the human tsh receptor in signal transduction (camp generation). for this purpose, we introduced homologous substitutions of smaller segments within amino acids 261-418 (domains d and e) of the tsh receptor with the corresponding amino acids of the rat lh/cg receptor. amino acids 317-366 were not investigated in view of previous data indicating their noninvolvement. mutant tsh receptor cdnas, in a eukaryotic expression v ...19921322272
the glycosaminoglycan of recombinant human soluble thrombomodulin affects antithrombotic activity in a rat model of tissue factor-induced disseminated intravascular coagulation.previous studies on recombinant human soluble thrombomodulin (rstm) from chinese hamster ovary cells revealed that rstm was expressed as two proteins that differed functionally in vitro due to the presence (rstm beta) or absence (rstm alpha) of chondroitin-4-sulfate. the current study evaluates the in vivo behavior of rstm in rats and in a rat model of tissue factor-induced disseminated intravascular coagulation (dic). rstm beta was more potent than rstm alpha for prolongation of the activated p ...19921322570
carcinogen-induced activation of sv40 gene expression in a semi-permissive environment.carcinogen-induced expression of the integrated viral genome was examined on sv40-transformed chinese hamster cells. carcinogen treatment markedly increased the transcription rate and the steady state mrna level of both early and late viral transcripts. carcinogen-induced transcription was mediated by rna polymerase ii. the increase in viral gene expression was also detected at the protein level, although at a reduced amplitude. enhanced transcription was apparent as early as 12 hr postexposure ...19921322584
the gene for the dihydropyridine-sensitive calcium channel alpha 2 subunit (cchl2a) maps to the proximal region of mouse chromosome 5.a rat brain cdna probe for the gene encoding the alpha 2 subunit of the dihydropyridine-sensitive l-type calcium channel was used as a hybridization probe for the southern blot analysis of chinese hamster x mouse somatic cell hybrids and the progeny of an intersubspecies backcross. this gene, termed cchl2a, was mapped near the centromeric end of the chromosome 5 linkage group with gene order: centromere-pgy-1-cchl2a-il-6-pgm-1.19921324224
comparison of recombinant tissue factor pathway inhibitors expressed in human sk hepatoma, mouse c127, baby hamster kidney, and chinese hamster ovary cells.recombinant tissue factor pathway inhibitor (rtfpi) has been expressed in four mammalian expression systems using human sk hepatoma, mouse c127, baby hamster kidney (bhk), and chinese hamster ovary (cho) cells as hosts. on sodium dodecyl sulfate polyacrylamide gel electrophoresis, the immunoaffinity purified rtfpis all show broad bands and the mean molecular weight of sk hepatoma and c127 rtfpis (m(r) approximately 38,000) appear larger than those of bhk and cho rtfpis (m(r) approximately 35,000 ...19921325078
molecular cloning and expression of an adenosine a2b receptor from human brain.a novel receptor cdna was isolated from a human hippocampal cdna library. the encoded polypeptide contains structural features consistent with its classification as a g protein-coupled receptor and shares 45% homology with the human a1 and a2a adenosine receptors. chinese hamster ovary k1 cells expressing this receptor showed marked stimulation of adenylate cyclase when treated with 1mm adenosine. there was no response to ligands selective for a1 and a2a receptors but the general adenosine agoni ...19921325798
the insulin receptor-related receptor. tissue expression, ligand binding specificity, and signaling 1989, shier and watt identified a gene which was predicted to encode a new member of the insulin receptor (ir) family, and they called it the insulin receptor-related receptor (irr) (shier, p., and watt, v. m. (1989) j. biol. chem. 264, 14605-14608). however, the tissues expressing this receptor, its ligand binding specificity and its signaling capability have remained unknown. in the present studies we report northern blot analyses and polymerase chain reaction data, which indicate that the ...19921326521
interaction of the frog brain kainate receptor expressed in chinese hamster ovary cells with a gtp-binding protein.a protein that binds kainate with high affinity has been purified and cloned from frog brain (rana pipiens) and has approximately 35% sequence homology with mammalian non-n-methyl-d-aspartate glutamate receptors, some of which have been shown to be ligand-gated ion channels. frog brain membranes and membranes from chinese hamster ovary (cho) cells transfected with the cdna coding for the frog kainate-binding protein (cho-4 cells) bound kainate with essentially identical affinity (kd values of 1. ...19921326545
modulation of the cellular phenotype by integrated adeno-associated virus.the adeno-associated virus (aav) rep gene encodes a series of overlapping, multifunctional, nonstructural proteins (rep proteins) which regulate the viral life cycle and which are also capable of trans-regulating nonviral gene expressions (reviewed in berns, 1990, microbiol. rev. 54, 316-329). to investigate the expression of the aav rep gene in a cellular chromosomal context, sv40-transformed chinese hamster embryo (od4) cells were infected with an aav/neo hybrid virus and progeny resistant to ...19921326806
the rat neurotensin receptor expressed in chinese hamster ovary cells mediates the release of inositol study second messenger synthesis mediated by the cloned rat neurotensin receptor, we derived a cell line stably expressing this receptor. the cdna clone of this receptor was subcloned into the pcdna1neo expression vector. this construct was then used to transfect chinese hamster ovary (cho)-k1 cells. colony clones, selected for resistance to antibiotic g-418 sulfate, were isolated and grown separately. nineteen individual clones were screened for total [3h]neurotensin binding as an indication ...19921328536
cloning and pharmacological characterization of a novel human 5-hydroxytryptamine1d receptor subtype.the canine rdc4 gene was used to isolate two distinct human serotonin receptor genes. the receptor encoded by clone rh-6 was the species homolog of rdc4 and was identical to a human serotonin 5-hydroxytryptamine1d (5-ht1d) receptor that was recently reported [mol. pharmacol. 40:143-148 (1991)]. the receptor encoded by rh-2 was a novel 5-ht receptor that was 61% identical to rh-6 and showed the greatest homology with the rat 5-ht1b receptor sequence (94%). the rh-2 gene contained an intronless, 1 ...19921328844
expression cloning of a cdna encoding udp-glcnac:gal beta 1-3-galnac-r (glcnac to galnac) beta 1-6glcnac transferase by gene transfer into cho cells expressing polyoma large tumor antigen.a cdna encoding udp-glcnac:gal beta 1-3galnac-r (glcnac to galnac) beta 1-6glcnac transferase (ec, which forms critical branches in o-glycans, has been isolated by an expression cloning approach using chinese hamster ovary (cho) cells. increased activity of this enzyme and the concomitant occurrence of the o-glycan core 2 structure [gal beta 1-3(glcnac beta 1-6)galnac] has been observed in a variety of biological processes, such as t-cell activation and immunodeficiency due to the wis ...19921329093
human cytomegalovirus penetrates host cells by ph-independent fusion at the cell surface.biochemical, genetic, and morphological criteria were used to demonstrate that human cytomegalovirus penetrates permissive fibroblasts and nonpermissive chinese hamster ovary (cho) cells by ph-independent fusion between the virus envelope and the host cell plasma membrane and not by low ph-induced fusion within endosomes. viral immediate early (ie) gene expression and infectivity were unaffected by conditions which block various stages of endocytosis or agents that alter the acidic ph of the end ...19921329327
characterization of human tissue-type plasminogen activator variants with amino acid mutations in the kringle 1 domain.recombinant variants of tissue-type plasminogen activator (t-pa) were constructed by site-directed mutagenesis and expressed in chinese hamster ovary cells. five variants were designed to improve the function of t-pa by mutagenesis in the kringle 1 (k1) domain. the amino acids were replaced with the corresponding residues present in the kringle 2 (k2) domain of native t-pa. the t-pa mutants expressed were as follows: variant e94v.d95g with point mutations in glu94----val and asp95----gly; varian ...19921330023
studies on glutathione transferases belonging to class pi in cell lines with different capacities for conjugating (+)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene.the glutathione transferases (gst) belonging to class pi are primarily responsible for the intracellular detoxification of the highly mutagenic and carcinogenic compound (+)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (bpde). the aim of the present investigation was to study the nature and function of the gst pi gene in relation to the mutagenicity of bpde in different cell lines. the studies were performed on three cell lines commonly used in toxicological ...19921330340
certain tryptophan photoproducts are inhibitors of cytochrome p450-dependent mutagenicity.two photoproducts, derived from uv-irradiation of the amino acid l-tryptophan and with high ah (tcdd) receptor binding affinity, were tested for genotoxic and antimutagenic effects. the two indolo[3,2-b]carbazole derivatives, with the molecular weights of 284 and 312, respectively, were tested in saccharomyces cerevisiae strain d7 for mitotic gene conversion and reverse mutation and in strain rs112 for sister chromatid conversion and gene conversion. no significant (p > 0.05) genotoxic effects w ...19921330548
involvement of an asn/val cleavage site in the production of a soluble form of a human tumor necrosis factor (tnf) receptor. site-directed mutagenesis of a putative cleavage site in the p55 tnf receptor chain.soluble forms of receptors for tumor necrosis factor (tnf) might be important for regulating the actions of tnf. site-directed in vitro mutagenesis was employed to examine the processing of the p55 tumor necrosis factor receptor chain (tnf-r55) into soluble tnf-binding protein (tnf-r55-bp). an asn/val sequence close to the transmembrane region in tnf-r55 was indicated as a putative cleavage site for proteolytic processing. by mutagenesis, asn and val were replaced with gly and ala, respectively. ...19921330568
lack of intrinsic activity and significant subtype selectivity of sr 95639a at muscarinic receptors.we assessed the intrinsic activity of the purported selective muscarinic m1 receptor agonist sr 95639a (morpholinoethylamino-3-benzocyclohepta-(5,6-c)-pyridazine) in inducing several receptor-mediated signals. our results indicate that sr 95639a lacks the ability to activate phosphoinositide hydrolysis in rat cerebral cortex or in chinese hamster ovary cells transfected with the genes of the muscarinic m1 and m3 receptors. similarly, this compound did not exhibit intrinsic activity in stimulatin ...19921330650
stimulation of phosphatidylcholine breakdown by thrombin and carbachol but not by tyrosine kinase receptor ligands in cells transfected with m1 muscarinic receptors. rapid desensitization of phosphocholine-specific (pc) phospholipase d but sustained activity of pc-phospholipase order to evaluate the possible contribution of phospholipase d (pld) stimulation to the mitogenic response, a screening of a variety of different compounds, some of which are known to be potent mitogens, was performed using the well characterized chinese hamster lung fibroblast (ccl39) cell line. in wild type ccl39 cells, or derivatives expressing high levels of either the human m1 muscarinic receptor (hm1) or the human epidermal growth factor (egf) receptor (39m1-81 and 39er22 clones, respec ...19921331066
activation of the na+/h+ antiporter during cell volume regulation. evidence for a phosphorylation-independent mechanism.a variety of cell types regulate their volume in anisotonic media by stimulating na+/h+ exchange. like growth factors, osmotic challenge activates the na+/h+ antiport by increasing its sensitivity to intracellular [h+]. to investigate the molecular mechanism underlying this shift in ph sensitivity, the antiporter of 32p-labeled human bladder carcinoma cells and of chinese hamster ovary cells was immunoprecipitated using antibodies raised against the cytosolic domain of the nhe-1 isoform of the n ...19921331102
binding and functional selectivity of himbacine for cloned and neuronal muscarinic receptors.the binding potencies for the putative m2-selective antagonist himbacine were determined in radioligand binding and in functional response assays in neuronal tissue and chinese hamster ovary cells containing transfected muscarinic receptors. himbacine was shown to bind to all five cloned muscarinic receptor subtypes in the order of potencies: hm2 = hm4 > hm3 > hm1 > hm5 (kd values were 4, 7, 59, 83 and 296 nm, respectively). himbacine was shown to bind to m2 receptors in rat heart and brain stem ...19921331410
phospholipase c activation by neurotensin and neuromedin n in chinese hamster ovary cells expressing the rat neurotensin receptor.the rat neurotensin receptor cdna sequence was transfected in chinese hamster ovary cells and cellular clones which stably express the corresponding protein were isolated and characterized. the scatchard analysis of the specific binding of [3h]neurotensin indicated a kd value of 0.45 +/- 0.08 nm and a bmax value of 3.27 +/- 0.29 pmol/mg of protein. displacement experiments using peptidic analogs of neurotensin and levocabastine confirmed that the transfected receptor exhibits the binding propert ...19921331689
functional properties of the rat and human beta 3-adrenergic receptors: differential agonist activation of recombinant receptors in chinese hamster ovary cells.beta 3-adrenergic receptors (beta 3ar) mediate lipolytic and thermogenic responses in rodent adipose tissues in vitro, and "atypical" beta ar agonists that active these receptors have potent therapeutic effects in in vivo rodent models of adult-onset diabetes and obesity. however, experiments with rodent cells that natively express the beta 3ar, as well as those with cells that express cloned rodent beta 3ar, have suggested that the pharmacological properties of the rodent and human beta 3ar dif ...19921331754
kinetic properties of alpha 1 beta 1 gamma-aminobutyric acida receptor channels expressed in chinese hamster ovary cells: regulation by pentobarbital and picrotoxin.single-channel recordings from excised outside-out patches were obtained from chinese hamster ovary cells stably transfected with plasmids containing bovine gamma-aminobutyric acid (gaba) type a (gabaa) receptor channel alpha 1 and beta 1 subunit cdnas. the predominant or main conductance level recorded had a 17-ps chord conductance. there were minor contributions made from 25-ps and 11-ps conductance levels. average open duration, burst duration, and openings/burst did not change as the gaba co ...19921331767
chromosomal assignments of mouse connexin genes, coding for gap junctional proteins, by somatic cell hybridization.the connexin genes cx31 and cx45 coding for proteins of gap junctional subunits have been assigned to mouse chromosomes 4 and 11 by southern blot hybridization of specific gene probes to dna from mouse x chinese hamster somatic cell hybrids. in addition, our results confirm the recent assignment of mouse connexin genes cx26, cx32, cx37, cx40, cx43, and cx46 to mouse chromosomes 14, x, 4, 3, 10, and 14, respectively, by analysis of interspecific backcrosses and by somatic cell hybridization. our ...19921332196
characterization of a minimal promoter element required for transcription of the mouse type ii beta regulatory subunit (rii beta) of camp-dependent protein kinase.the 5'-flanking dna of the mouse rii beta subunit of the camp-dependent protein kinase gene was characterized by transient transfection of rii beta-cat constructs into mouse neuroblastoma cells (nb2a) and chinese hamster ovary (cho) cells and by gel mobility shift and footprinting assays. the minimal promoter of the rii beta gene was composed of two adjacent functional elements. a 3'-element which supported enhanced cat activity was located between base pairs (bp) -267/-168 from the translation ...19921332964
transcription enhances intrachromosomal homologous recombination in mammalian cells.the influence of transcription on homologous intrachromosomal recombination between direct and inverted repeats has been examined by using chinese hamster ovary cells. recombination was monitored between two integrated neomycin (neo) genes, including one silent allele and a second allele regulated by the inducible mouse mammary tumor virus promoter. transcription of mouse mammary tumor virus neo alleles was regulated with the glucocorticoid hormone dexamethasone. alleles transcribed at high leve ...19921333040
binding of recombinant variants of human tissue-type plasminogen activator (t-pa) to human umbilical vein endothelial cells.endothelial cells synthesize and secrete hemostatic components like tissue-type plasminogen activator (t-pa) which is thought to be the major determinant of fibrinolytic activity in the blood. most recently, a receptor protein for t-pa on human umbilical vein endothelial cells (huvec) in culture has been described (1); there are, however, in addition low affinity binding sites for t-pa on huvec. the sites of binding are of particular interest, because they are potential regulators of t-pa activi ...19921333104
dissociation of cytotoxicity and dna cleavage activity induced by topoisomerase ii-reactive intercalating agents in hamster-human somatic cell hybrids.previous studies using the mutant chinese hamster ovary cell line vpmr-5 indicate that its resistance to epipodophyllotoxins and intercalating agents is likely to be mediated through a qualitative change in type ii topoisomerase that confers resistance to drug-stimulated dna cleavage activity. in a further investigation of the genetic basis of drug resistance in vpmr-5 cells, we fused a hypoxanthine-guanine phosphoribosyl transferase-deficient subline of vpmr-5 (vtgm-6) with normal human lymphoc ...19921333369
endotoxin transduces ca2+ signaling via platelet-activating factor receptor.lipopolysaccharide (lps) is a pathogenic substance causing severe multiple organ failures and high mortality. although several lps binding proteins have been identified, the molecular mechanism underlying the lps signaling pathway still remains obscure. we have found that the lps-induced ca2+ increase in platelets and platelet aggregation is blocked by selective platelet-activating factor (paf) receptor antagonists, thus suggesting a cross-talk between lps and the paf receptor. next, we confirme ...19921333988
testosterone and 5 alpha-dihydrotestosterone interact differently with the androgen receptor to enhance transcription of the mmtv-cat reporter gene.testosterone and its 5 alpha-reduced derivative 5 alpha-dihydrotestosterone exert different actions in the male during embryogenesis and in postnatal life. nevertheless the two hormones bind to the same intracellular androgen receptor, and genetic and endocrinological studies in the tfm mouse suggest that the actions of both hormones are mediated by this single receptor. previous studies indicate that dihydrotestosterone binds more tightly to the androgen receptor but that the bmax of binding of ...19921334007
subtype-selective desensitization of alpha 2-adrenergic receptors. different mechanisms control short and long term agonist-promoted desensitization of alpha 2c10, alpha 2c4, and alpha 2c2.we have recently shown that the alpha 2c10 adrenergic receptor (ar) undergoes short term agonist-promoted desensitization, mediated by phosphorylation of sites in the third intracellular loop. there is significant divergence in the third loop amino acid sequences between alpha 2c10 and the other subtypes, alpha 2c4 and alpha 2c2. we therefore explored the mechanisms of alpha 2ar subtype desensitization by expressing each human subtype in chinese hamster ovary cells and subjecting them to short a ...19921334095
cells transfected with human interleukin 6 cdna acquire binding sites for the hepatitis b virus envelope protein.earlier studies revealed that human interleukin 6 (il-6) contains recognition sites for the hepatitis b virus (hbv) envelope (env) protein, and that il-6 and anti-il-6 antibodies, respectively, inhibited the interaction of cells expressing a receptor for hbv with the pres(21-47) segment of the hbv env protein, encompassing the complementary attachment site for il-6. this suggested that il-6 mediates hbv-cell interactions. we report that: (a) chinese hamster ovary cells transfected with human il- ...19921334115
insulin-dependent formation of a complex containing an 85-kda subunit of phosphatidylinositol 3-kinase and tyrosine-phosphorylated insulin receptor substrate 1.monoclonal antibodies raised against the 85-kda subunit (p85) of bovine phosphatidylinositol (pi) 3-kinase were found to recognize uncomplexed p85 or p85 in the active pi 3-kinase. immunoprecipitation studies of chinese hamster ovary cells, which overexpress the human insulin receptor when treated with insulin, showed increased amounts of p85 and pi 3-kinase activity immunoprecipitable with monoclonal anti-p85 antibody and no increase in the tyrosine phosphorylation of p85. insulin also induced ...19921334490
the gene for the alpha 1 subunit of the skeletal muscle dihydropyridine-sensitive calcium channel (cchl1a3) maps to mouse chromosome 1.cchl1a3 encodes the dihydropyridine-sensitive calcium channel alpha 1 subunit isoform predominantly expressed in skeletal muscle. mdg (muscular dysgenesis) has previously been implicated as a mutant allele of this gene. hybridization of a rat brain cdna probe for cchl1a3 to southern blots of dnas from a panel of chinese hamster x mouse somatic cell hybrids suggested that this gene maps to mouse chromosome 1. analysis of the progeny of an inbred strain cross-positioned cchl1a3 1.3 cm proximal to ...19921335956
analysis of the acp1 gene product: classification as an fmn phosphatase.the relationship between the acp1 gene product, an 18kda acid phosphatase (e.c. postulated to function as a protein tyrosyl phosphatase, and the cellular flavin mononucleotide (fmn) phosphatase has been examined in vitro and by using cultured chinese hamster ovary (cho) cells. kinetic analysis indicated that at ph 6 the acid phosphatase utilized a variety of phosphate monoesters as substrates. while small molecules such as fmn were effectively utilized as substrates (kcat/km = 7.3 x 10( ...19921336375
expression of ca(2+)-induced ca2+ release channel activity from cardiac ryanodine receptor cdna in chinese hamster ovary cells.we constructed an expression plasmid (pmamcrr51) that carried the entire protein-coding sequence of the rabbit cardiac ryanodine receptor cdna, linked to the dexamethasone-inducible mouse mammary tumor virus promoter and escherichia coli xanthine-guanine phosphoribosyltransferase (gpt). chinese hamster ovary (cho) cells were transfected with pmamcrr51 and mycophenolic acid-resistant cells showing caffeine-induced intracellular ca2+ transients were selected. immunoprecipitation with a monoclonal ...19921337083
a complementary dna for human choline acetyltransferase induces two forms of enzyme with different molecular weights in cultured cells.complementary dna (cdna) clones containing the entire coding region of human choline acetyltransferase (chat) were isolated from cdna libraries prepared from the autopsied spinal cord. in the human cdna, the atg codon assigned to the putative initiation codon for pig, rat and mouse chat cdnas was replaced by acg. the human cdna contained an in-frame atg codon 324 nucleotides upstream of the acg codon. therefore, human chat cdna should code for a 748 amino acid polypeptide of 82.6 kda. this deduc ...19921337937
humanized monoclonal antibody campath-1h: myeloma cell expression of genomic constructs, nucleotide sequence of cdna constructs and comparison of effector mechanisms of myeloma and chinese hamster ovary cell-derived material.expression of campath-1h, a humanized moab directed against an abundant surface antigen on human lymphocytes, has been studied using transfected myeloma cells. as the site of chromosome integration of dna transfected into a cell is random we investigated the feasibility and frequency of hitting a 'jackpot' site for expression after co-transfection with campath-1h heavy and light chain constructs in genomic context. a cell line generating 40 micrograms/ml of campath-1h in spent culture supernatan ...19921339322
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