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[identification of l. donovani promastigotes from phlebotomus by monoclonal antibody].it has been reported by the authors that monoclonal antibody l12g9 produced from target antigens of l. donovani promastigotes, was very useful for detecting promastigotes from artificially infected sandflies. in the present study, detection of promastigotes from artificially infected sandflies by mcab showed that the positive rate correlated with the infection duration of sandflies. 4 days after feeding on infected chinese hamsters, the sandflies were lightly infected with l. donovani promastigo ...19902099257
biological and immunological characterization of a cloned cholera toxin-like enterotoxin from salmonella typhimurium.a chromosomal dna fragment, encoding an enterotoxin gene of salmonella typhimurium q1, was cloned into bacteriophage embl3 and plasmid vector pbr322. the recombinant clones lambda b8 and pc1 were identified using a synthetic oligonucleotide probe made to the b subunit region of the cholera toxin gene (ctx). cell lysates of escherichia coli vcs257 [lambda b8] induced fluid secretion in rabbit intestinal loops, while lysates of e. coli dh5 alpha [pc1] failed to elicit an enterotoxic response in th ...19902099384
[effects of 10-hydroxycamptothecin on induced chromosome aberrations in chinese hamster ovary cells and micronuclei in mouse bone marrow and fetal liver].10-hydroxycamptothecin (hc) is a new antitumor principle isolated from camptotheca acuminata indigenous to china. the genetic toxicity of hc was assessed by mouse bone marrow and transplacental micronucleus test as well as chinese hamster ovary cell chromosomal aberrations. all of these tests showed positive results. the highest rate of chromosomal aberrations was 83% at 0.125 microgram/ml for 48 h. the number of micronucleated polychromatic erythrocytes in bone marrow of mice was remarkably inc ...19902104494
characterization of a transferrin-independent uptake system for iron in hela cells.hela cells incubated in serum-free medium accumulated 59fe ("non-transferrin iron") when incubated with either 59fe-citrate, 59fe-nitrilotriacetate, or 59fe dissolved in tricine ascorbate. accumulation of iron was time-, concentration-, and ca2+-dependent and was saturable. uptake of non-transferrin (non-tf) iron was transferrin-independent because of the fact that uptake occurred at ph 5.5, a ph at which transferrin binds iron poorly and at which transferrin is not internalized by cells. uptake ...19902105943
multisite phosphorylation of the epidermal growth factor receptor. use of site-directed mutagenesis to examine the role of serine/threonine phosphorylation.the major sites of serine and threonine phosphorylation of the human epidermal growth factor (egf) receptor observed in intact cells are thr654, thr669, ser1046, and ser1047. phosphorylation of the egf receptor is increased at these sites in cells treated with platelet-derived growth factor or phorbol ester. this increase in egf receptor phosphorylation is associated with an inhibition of the high affinity binding of egf to cell surface receptors and an inhibition of the receptor tyrosine protei ...19902105948
aflatoxin b1-specific cytochrome p-450 isozyme (p-450-afb) inducible by 3-methylcholanthrene in golden hamsters.hepatic microsomes of polychlorinated biphenyl (pcb)-treated syrian golden hamsters possessed a higher potency toward aflatoxin b1 activation, based on the ames test, than other animal species. this activity was induced in hamsters preferentially by treatment with 3-methylcholanthrene rather than phenobarbital. the contribution of an isozyme of cytochrome p-450 (p-450-afb) to the activity of hamster livers for aflatoxin b1 was studied. p-450-afb, purified from 3-methylcholanthrene-treated hamste ...19902106321
the cdna sequence of the alpha-subunit of the chinese hamster adenylate cyclase-stimulatory g-protein. 19902106672
induction of hsp27 phosphorylation and thermoresistance in chinese hamster cells by arsenite, cycloheximide, a23187, and egta.incorporation of [3h]leucine, immunochemical analyses with a specific hamster hsp27 rabbit immunoserum, and [32p]orthophosphate labeling were used to monitor synthesis, accumulation, and phosphorylation of hsp27 in chinese hamster cells after induction of thermoresistance by arsenite, cycloheximide, a23187, and egta. in contrast to arsenite-induced thermotolerance, which develops in parallel to synthesis and accumulation of hsp27, enhanced thermoresistance observed immediately after incubating c ...19902107559
cloning of the genes for t84.66, an antibody that has a high specificity and affinity for carcinoembryonic antigen, and expression of chimeric human/mouse t84.66 genes in myeloma and chinese hamster ovary cells.carcinoembryonic antigen (cea) is one of the best characterized tumor-associated antigens and is extensively used in the in vitro immunodiagnosis of human colon adenocarcinomas. among a number of anti-cea monoclonal antibodies, the murine monoclonal antibody t84.66 shows the highest specificity and affinity for cea and has been used successfully for in vivo tumor imaging in mice and humans. we report here the cloning and sequencing of the genes coding for monoclonal antibody t84.66 and the amino ...19902107969
biochemical and biological activities of recombinant s1 subunit of pertussis toxin.degp-deficient strains of escherichia coli grown in m-9 medium supplemented with zncl2 expressed the recombinant s1 subunit of pertussis toxin (rs1) in a form electrophoretically identical to the authentic s1 subunit. subcellular fractionation showed that the full-length form of rs1 was membrane associated, while proteolytic fragments of rs1 were present in the periplasm. rs1 was extracted from outer membrane preparations with 8 m urea and purified by gel filtration chromatography. purified rs1 ...19902108094
rhodopsin expressed in chinese hamster ovary cells regulates adenylyl cyclase activity.the cdna encoding bovine opsin was transfected into chinese hamster ovary (cho) cells to generate stable clones expressing the rod cell photoreceptor protein. cells expressing opsin, when incubated in 11-cis retinal and exposed to light, inhibited forskolin-stimulated adenylyl cyclase activity. rhodopsin-mediated inhibition of adenylyl cyclase was prevented by treatment of cells with pertussis toxin. in the same cells, thrombin stimulated phosphatidylinositol hydrolysis through g protein-mediate ...19902108693
the thyroglobulin gene is syntenic with the myc and mos protooncogenes and carbonic anhydrase ii and maps to chromosome 14 in cattle.using a panel of bovine x chinese hamster hybrid somatic cells, sequences homologous to genes spanning human chromosome arm 8q have been syntenically assigned in cattle. thyroglobulin (tg), carbonic anhydrase ii (ca2), and the protooncogenes myc and mos were assigned to a newly identified bovine syntenic group, u23. additionally, in situ hybridization of the thyroglobulin probe to bovine metaphase chromosomes revealed this syntenic group to be on bovine chromosome 14 and the bovine thyroglobulin ...19902108842
presence and transcription of intracisternal a-particle-related sequences in cho cells.we have characterized sequences expressed in chinese hamster ovary (cho) cells which are related to the intracisternal a-particle (iap) genes of mice and syrian hamsters. several cdna clones homologous to syrian hamster iap probes have been isolated and used to evaluate the abundance and expression of these retroviruslike sequences. dna blot analysis with homologous chinese hamster iap probes revealed that iap-related sequences are present in cho cell dna at moderately repetitive levels (approxi ...19902109099
closely related glycosylation patterns of recombinant human il-2 expressed in a cho cell line and natural il-2.we report here the study of the glycosylation pattern of human recombinant (r) il2 expressed in a chinese hamster ovary (cho) cell line. the human ril2 secreted by this high-producing recombinant cho cell line was metabolically radiolabelled with [35s]-methionine, or with [3h]-glucosamine and [3h]-galactose, purified to homogeneity, and then characterized. the electrophoretic analysis of the [35s]-methionine-labelled proteins present in the culture medium of the cho cell line showed that the ril ...19902109157
induction of aldose reductase expression in rat kidney mesangial cells and chinese hamster ovary cells under hypertonic conditions.rat kidney cortex mesangial cells (mes) and chinese hamster ovary cells (cho) responded to hypertonicity (600 mosmol/kg) in culture by accumulating sorbitol. the accumulation of sorbitol was due to increased aldose reductase (ar) activity, apparently brought about by increased levels of ar mrna and protein. the levels of ar mrna increased approximately 60-fold in mes cells and 30-fold in cho cells by 24 h in culture media (300 mosmol/kg supplemented with 150 mm nacl, 600 mosmol/kg total). ar act ...19902109701
pharmacokinetics in chimpanzees of recombinant human tissue-type plasminogen activator produced in mouse c127 and chinese hamster ovary cells.pharmacokinetics of recombinant tissue-type plasminogen activator (rt-pa) produced in mouse c127 cells (t-pa(c127] and chinese hamster ovary cells (t-pa(cho] was investigated in chimpanzees. rt-pa was administered via a constant rate i.v. infusion for 60 min, and t-pa concentration and activity in plasma were measured during and after infusion. the noncompartmental parameters were calculated according to the moment analysis method, and a population pharmacokinetic analysis was performed to obtai ...19902110870
localization of the murine leukemia inhibitory factor gene near the centromere on chromosome 11.leukemia inhibitory factor (lif) is a glycoprotein with divergent activities: it induces the differentiation of certain myeloid leukemic cells, inhibits the differentiation of embryonic stem cells, and promotes bone remodelling in vivo and in vitro. the murine lif gene has been assigned to the proximal region of chromosome 11 at sub-bands a1-a2, by analysis of a panel of mouse x chinese hamster somatic cell hybrids and by in situ hybridization. interestingly, the proximal portion of chromosome 1 ...19902111155
molecular cloning and biological characterization of the human excision repair gene ercc-3.in this report we present the cloning, partial characterization, and preliminary studies of the biological activity of a human gene, designated ercc-3, involved in early steps of the nucleotide excision repair pathway. the gene was cloned after genomic dna transfection of human (hela) chromosomal dna together with dominant marker psv3gpth to the uv-sensitive, incision-defective chinese hamster ovary (cho) mutant 27-1. this mutant belongs to complementation group 3 of repair-deficient rodent muta ...19902111438
specificity of human natural antibody to recombinant tissue-type plasminogen activator (t-pa) expressed in mouse c127 cells.a natural antibody with binding specificity for recombinant tissue-type plasminogen activator (t-pa) expressed in mouse c127 cells was present in almost all disease-free humans and patients with thrombotic disease examined. this antibody was specific for a carbohydrate, alpha 1-3-linked galactose residue, and was isolated by affinity chromatography using synsorb 90 coupled with the glycosidic epitope gal alpha 1-3gal beta 1-4glc-r as an immunoadsorbent. the evaluation of various glycoproteins fo ...19902112046
introduction of stable high-copy-number dna into chinese hamster ovary cells by electroporation.a new gene transfer protocol has been developed that introduces up to 800 copies of an expression vector into chinese hamster ovary cells in a single step by electroporation. the dna typically integrates in tandem repeats so that the restriction endonuclease site used to linearize the input dna remains intact. this is likely due to ligation of vector dna via cohesive ends prior to integration. this high-copy-number procedure is far more rapid than the conventional stepwise gene amplification met ...19902112395
measurement of beta-galactosyltransferase activity in cell extracts with an elisa-based assay.an enzyme-linked immunosorbent assay (elisa)-based glycosyltransferase assay has been used to measure udp-gal:n-acetylglucosamine beta-1,4-galactosyl-transferase (ec 2.4.1.38) activity in detergent extracts of chinese hamster ovary (cho) cells. lec11 cells (a mutant of the cho cell line, pro -5), which are known to express a complex array of carbohydrate structures, were used to develop the assay for use with whole cell extracts. a detergent-solubilized preparation of the enzyme from whole cells ...19902112899
high level expression in chinese hamster ovary cells of soluble forms of cd4 t lymphocyte glycoprotein including glycosylation variants.the cd4 cell surface antigen is of interest as a marker of t lymphocytes that recognize foreign antigens in the context of mhc class ii antigen, as a receptor for the human immunodeficiency virus (hiv) and as a member of the immunoglobulin superfamily (igsf) with four ig-like domains present in the extracellular domain. in order to produce large amounts of soluble cd4 for x-ray crystallography and other molecular studies, a recently developed expression system based on selection via glutamine sy ...19902113054
structural determinants of the noncatalytic chain of tissue-type plasminogen activator that modulate its association rate with plasminogen activator inhibitor-1.in order to identify the regions of recombinant (r) tissue plasminogen activator (tpa) that mediate its kinetically relevant interaction with r-plasminogen activator inhibitor-1 (rpai-1), we have determined the second-order association rate (k1) constants of domain-altered variants of tpa with rpai-1, at 10 degrees c. with two-chain, wild-type recombinant tpa (tcwt-rtpa), obtained by expression of the human cdna for tpa in five different cell systems (viz. insect cells, human kidney 293 cells, c ...19902113057
source of heterogeneity in secreted interferon-gamma. a study on products of translation in vitro.a cdna clone coding for human interferon-gamma (ifn-gamma) was subcloned into a transcription-translation vector. when the mrna transcribed in vitro was added to a rabbit reticulocyte-lysate system, two polypeptides were synthesized: one corresponding in mr to pre-ifn-gamma (18,000) and one with a lower mr (12,000) which corresponds to a polypeptide arising from incorrect initiation of translation. when microsomal vesicles isolated from dog pancreas or chinese-hamster ovary (cho) cells were adde ...19902114101
biochemical and functional characterization of human tissue-type plasminogen activator variants with mutagenized kringle domains.the cdna encoding full-length human tissue-type plasminogen activator (t-pa) and five variant cdnas, constructed by in vitro site-directed mutagenesis, were cloned and expressed in chinese hamster ovary cells. the variant cdnas were designed to increase the fibrin affinity of t-pa by mutagenesis in the kringle domains of specific amino acids which are assumed to constitute the lysine-binding site. these amino acids were replaced with the corresponding amino acids present in kringle 1 of plasmino ...19902115513
bis(benzyl)polyamine analogues are substrates for a mammalian cell-transport system which is distinct from the polyamine-transport system.bis(benzyl)polyamine analogues (e.g. nn'-bis(3-[(phenylmethyl)amino]propyl)-1,8-diamino-octane [c6h5ch2nh-(ch2)3nh(ch2)8nh(ch2)3nhch2c6h5]) have previously been shown to regulate polyamine biosynthesis and growth of rat hepatoma (htc) cells. saturable uptake of the analogues, the ability of other bis(benzyl)polyamine analogues to compete for this uptake and the trans-acceleration of this uptake in pre-loaded cells indicate that these novel compounds are accumulated through the action of a transp ...19902115774
binding of tissue plasminogen activator to human aortic endothelial cells.the experiments described in this paper were designed to examine the specific binding of tissue plasminogen activator (tpa) to cultured human aortic endothelial (hae) cells. when 125i-labelled tpa was incubated with the cells at 4 degrees c, binding was found to plateau within 90 min after incubations were begun. binding was saturable and the bound enzyme dissociated from the sites with a half-time of approx. 48 min. scatchard analyses were performed using tpa molecules isolated from human melan ...19902117440
inhibition of arachidonic acid release by nordihydroguaiaretic acid and its antioxidant action in rat alveolar macrophages and chinese hamster lung fibroblasts.the ability of nordihydroguaiaretic acid (ndga) to inhibit arachidonic acid (aa) release from rat alveolar macrophages treated with t-butyl hydroperoxide (tbooh) or from chinese hamster lung fibroblasts (v79 cells) treated with linoleic acid hydroperoxide (looh) was examined. treatment of alveolar macrophages with 100 microm tbooh significantly increased arachidonic acid release and its conversion to metabolites. pretreatment of macrophages with ndga (greater than or equal to 2.5 microm) inhibit ...19902118282
(difluoromethylene)phosphates of guanine nucleosides as probes of dna polymerases and g proteins.5'-polyphosphates of n2-(p-n-butylphenyl)-2'-deoxyguanosine and -guanosine which contain a difluoromethylene group in place of a phosphoanhydride oxygen have been synthesized. 5'-[beta,gamma-(difluoromethylene)triphosphates], including that of 2'-deoxyguanosine, were prepared by reaction of the corresponding 5'-phosphates, activated by 1,1'-carbonyldiimidazole, with difluoromethanediphosphonate. the 5'-[(difluoromethylene)diphosphate] of n2-(p-n-butylphenyl)guanosine was prepared by treatment of ...19902118802
acquisition of polyamines by the obligate intracytoplasmic bacterium rickettsia prowazekii.both the polyamine content and the route of acquisition of polyamines by rickettsia prowazekii, an obligate intracellular parasitic bacterium, were determined. the rickettsiae grew normally in an ornithine decarboxylase mutant of the chinese hamster ovary (c55.7) cell line whether or not putrescine, which this host cell required in order to grow, was present. the rickettsiae contained approximately 6 mm putrescine, 5 mm spermidine, and 3 mm spermine when cultured in the presence or absence of pu ...19902120188
characterization of the mechanism of endocytic vesicle fusion in vitro.a cell-free assay to monitor receptor-mediated endocytic processes has been developed that uses biotinylated transferrin and avidin-linked beta-galactosidase as receptor-associated and fluid-phase probes, respectively (wessling-resnick, m., and braell, w. a. (1990) j. biol. chem. 265, 690-699). the fusion of vesicles from heterologous sources can be detected in this assay: endocytic vesicles from k562 cells (a human cell line) will fuse with vesicles from chinese hamster ovary cells. fusion betw ...19902120206
isolation and structure determination of the intact sialylated n-linked carbohydrate chains of recombinant human follitropin expressed in chinese hamster ovary cells.biologically active recombinant human follitropin has been expressed in chinese hamster ovary cells. the carbohydrate chains of the recombinant glycoprotein hormone were enzymatically released by peptide-n4-(n-acetyl-beta-glucosaminyl)asparagine amidase f. the oligosaccharides were separated from the n-deglycosylated protein by gel-permeation chromatography on bio-gel p-100, and fractionated by a combination of fplc on mono q and hplc on lichrosorb-nh2. the structures of the carbohydrate chains ...19902121479
a specific effect of muscle cells on the distribution of presynaptic proteins in neurites and its absence in a c2 muscle cell variant.the distribution of neurofilament (nf) and synaptic vesicle (sv) proteins in neurites cultured in vitro was visualized with immunocytochemical methods. nf and sv proteins were detected in neurites from both embryonic mouse spinal cord and chick ciliary ganglion neurons. nf proteins generally occupied more proximal, unbranched neurite segments while sv proteins were most often found in highly branched terminal segments. neurites from mouse spinal cord cells showed a striking segregation of the nf ...19902121566
impaired secretion and fluid-phase endocytosis in the end4 mutant of chinese hamster ovary cells.mutant v.24.1 defines the end4 complementation group of temperature-sensitive chinese hamster ovary cell mutants selected for resistance to protein toxins. we investigated the secretory pathway in the mutant cells and found: 1) the hemagglutinin of influenza virus failed to reach the plasma membrane and was retained in a form sensitive to endoglycosidase h at the restrictive temperature. 2) transferrin receptors synthesized at the restrictive temperature remained sensitive to endoglycosidase h. ...19902122970
physical and chemical characteristics of apolipoprotein a-i-lipid complexes produced by chinese hamster ovary cells transfected with the human apolipoprotein a-i gene.chinese hamster ovary cells transfected with the human apolipoprotein a-i gene linked to the human metallothionein gene promoter region secrete large quantities of apolipoprotein a-i (7.1 +/- 0.4% total secreted protein) in the presence of zinc. approx. 16% of the secreted apolipoprotein a-i is complexed with lipid and can be isolated ultracentrifugally at d less than or equal to 1.21 g/ml. the latter complexes are composed of discs and vesicles as judged by electron microscopy and can be furthe ...19902123400
cloning and expression of avian glutamine phosphoribosylpyrophosphate amidotransferase. conservation of a bacterial propeptide sequence supports a role for posttranslational processing.the cdna for glutamine phosphoribosylpyrophosphate amidotransferase, the regulatory enzyme of de novo purine nucleotide biosynthesis, has been cloned for the first time from an animal. the derived amino acid sequence of the avian amidotransferase is homologous with amidotransferase sequences from bacteria and yeast. an 11-amino acid propeptide in bacillus subtilis amidotransferase is conserved in the avian enzyme. expression in chinese hamster ovary (cho) cells and escherichia coli provides evid ...19902123487
endocytic membrane traffic to the golgi apparatus in a regulated secretory cell line.we have established a ricin-resistant glycosylation-defective pc12 pheochromocytoma cell line to study biochemically glycoprotein traffic from the cell surface to the golgi apparatus in regulated secretory cells. the strategy employed in this study is a modification of that used previously (duncan, j. r., and kornfeld, s. (1988) j. cell biol. 106, 617-628) to demonstrate transport of the cation-independent and -dependent mannose 6-phosphate receptors from the cell surface to the trans-golgi netw ...19902123489
activation of mitomycin c by nadph:cytochrome p-450 reductase.mitomycin c is an alkylating agent used in cancer chemotherapy that shows some specificity towards hypoxic cells. the therapeutic effects of this compound are thought to result from its metabolic activation by enzymes such as nadph:cytochrome p-450 reductase. in a previous report we described a chinese hamster ovary cell line resistant to mitomycin c, which had a decreased nadph:cytochrome p-450 reductase activity coupled with a lower rate of mitomycin c metabolism. in order to provide further e ...19902123741
sialylated carbohydrate chains of recombinant human glycoproteins expressed in chinese hamster ovary cells contain traces of n-glycolylneuraminic acid.hplc analysis of sialic acids released from recombinant variants of human tissue plasminogen activator, human chimeric plasminogen activator, human erythropoietin, and human follitropin, expressed in chinese hamster ovary cells, demonstrates for each glycoprotein the presence of n-acetylneuraminic acid and n-glycolylneuraminic acid in a ratio of 97:3. structural analysis by 500 mhz1h-nmr spectroscopy, of the enzymatically released n-linked carbohydrate chains of chimeric plasminogen activator an ...19902124546
[studies on acetylspiramycin. ii. biological activities of spiramycin components].acetylspiramycin (aspm) was fractionated using high performance liquid chromatography (hplc). the peak fractions were named f1 to f7 successively in order of increasing retention times (rt), i.e., increasing hydrophobicity, and studied for 1) antibacterial activities (mic), 2) antibacterial potency against bacillus subtilis atcc 6633, 3) therapeutic effect on mice infected with streptococcus pneumoniae iii, staphylococcus aureus smith, 4) acute toxicity by i.p. administration to mice (ld50) and ...19902124632
recombinant human interferon-gamma. differences in glycosylation and proteolytic processing lead to heterogeneity in batch culture.recombinant human interferon-gamma (hu-ifn-gamma) produced by chinese-hamster ovary (cho) cells was analysed by immunoprecipitation and sds/page. up to twelve molecular-mass variants were secreted by this cell line. three variants were recovered after enzymic removal of all n-linked oligosaccharides or when glycosylation was inhibited by tunicamycin. the presence of three polypeptide forms rather than a single form suggested that proteolytic cleavage had occurred at two sites in both the glycosy ...19902125204
molecular cloning and characterization of retrovirus-like intracisternal type a particle genes (iap) present in the chinese hamster genome.endogenous retrovirus-like sequences that are homologous to the multigenic murine and syrian hamster intracisternal type a particle (iap) genes can be detected in very few copies in the chinese hamster (ch) genome. they were cloned from a cho gene library and two recombinants, harboring the major iap-like dna genes characterized by southern blot hybridization after dna digestion with several restriction enzymes. the iap dna inserts of the two clones analyzed were 4.70 and 8.04 kb respectively, a ...19902126900
mutagenicity studies on dihydroergocristine.dihydroergocristine (dhec) is an ergot derivative used for the therapy of patients with cerebrovascular insufficiency. it was tested for mutagenicity by means of four tests. in the mutagenicity in vitro assay on salmonella typhimurium, dhec was checked at 10,000 micrograms/plate on ta98 and ta1538 strains and at 3000 micrograms/plate on ta1535, ta1537 and ta100 strains with and without metabolic activation. in a quantitative in vitro test for mutagenicity in v79 chinese hamster cells, dhec was s ...19902128268
comparison of the antiviral activity and toxicity of a protein magnesium ammonium phospholinoleate anhydride polymer with other antiviral drugs.1. sb-73, a magnesium ammonium phospholinoleate anhydride aggregate, exhibited antiviral action in vitro in the concentration range of 50 to 100 micrograms/ml against herpes simplex type 1, stomatitis vesicular virus, adenovirus type 5, and in vivo in the dose range of 0.7 to 1.3 mg/kg against canine parvovirus and distemper virus. 2. the lethal dose (ld50) was 2.71 +/- 1.55 g/kg body weight in mice inoculated intraperitoneally. oral ingestion of the aggregate up to 30 g/kg body weight by mice h ...19902136564
misonidazole hypoxic cytotoxicity and chemosensitization in two cell lines with different intracellular glutathione levels.nitroimidazoles such as misonidazole (miso) or sr-2508 are known to be cytotoxic to hypoxic cells and, with preincubation under hypoxic conditions, to sensitize cells to certain chemotherapy drugs, notably melphalan. in addition, these nitroimidazoles afford hypoxic radiosensitization; however, high intracellular glutathione (gsh) levels have been shown to significantly reduce radiosensitization by some nitroimidazoles. using two cell lines that have an 8-fold difference in cellular gsh content, ...19902138473
co-transformation of lec 1 cho cells with n-acetylglucosaminyltransferase 1 activity and a selectable marker.in animal cells, the enzyme alpha(1,3)-mannoside-beta(1,2)-n-acetylglucosaminyltransferase i (glcnac-ti, ec.2.4.1.101) catalyzes the addition of n-acetylglucosamine to the asn-linked man glcnac oligosaccharide. the chinese hamster ovary (cho) mutant cell line lec1 is deficient in this enzyme activity and, therefore, accumulates mannose-terminating cell surface asn-linked oligosaccharides. consequently, lec1 cells are sensitive to the cytotoxic effects of the mannose-binding lectin concanavalin a ...19902138626
[the establishment of pathogen-free colonies of chinese and syrian hamsters (cricetulus griseus and mesocricetus auratus) by foster rearing].naturally born (less than 5 d old) or hysterectomy-derived litters from 7 mice, 90 chinese and 19 syrian hamsters were fostered to conventional or gnotobiotic mouse, chinese hamster or rat dams. generally, chinese hamsters and mice are able to serve mutually as foster mothers without special manipulations of dams or pups. chinese hamsters adopted suckling mice with less problems than mice when fostering young hamsters. in correlation with sucking activity the growth of most of the mouse-fostered ...19902138838
plasminogen activator activities of equimolar complexes of streptokinase with variant recombinant plasminogens.the steady-state kinetic characteristics of the amidolytic and plasminogen activator activities of equimolar streptokinase (sk)-human plasminogen (hpg) and sk-human plasmin (hpm) complexes have been determined, exploiting the generation and use of cleavage site resistant mutants of hpg to stabilize plasminogen within the complex. whereas amidolytic kinetic constants for equimolar complexes of sk with the following proteins, viz., plasma hpm, insect (i) cell-expressed wild-type (wt) recombinant ( ...19902141279
enhancement of adriamycin cytotoxicity in a multidrug resistant chinese hamster ovary (cho) subline, cho-adrr, by toremifene and its modulation by alpha 1 acid glycoprotein.the effects of a new antioestrogen, toremifene, on multidrug resistance have been studied in a chinese hamster ovary parental line, cho-k1, and in a multidrug resistance subline, cho-adrr. toremifene at subinhibitory concentrations increased the cytotoxic effectiveness of adriamycin in both cell lines. the degree of potentiation was greater in the cho-adrr lines for any given concentration of toremifene. toremifene is 99.7% bound to human serum proteins (sipila et al. pharmacol toxicol 1988, 63, ...19902141509
in vitro and in vivo bioactivity of recombinant human follicle-stimulating hormone and partially deglycosylated variants secreted by transfected eukaryotic cell lines.recent studies have shown that chinese hamster ovary (cho) cells transfected with the fsh subunit genes secrete bioactive fsh. here, we determined the in vitro and in vivo bioactivity of recombinant fsh produced by cho mutant cells deficient in the glycosylation enzyme n-acetylglucosamine transferase-i (nagt-), resulting in glycoproteins with asparagine-linked (glcnac)2(mannose)5 oligosaccharides, or mutant cells defective in sialic acid transport into the golgi (st-). in the latter, glycoprotei ...19902141816
regulation of epidermal growth factor receptor signal transduction. role of gangliosides.the addition of gangliosides to tissue culture cells causes a decrease in the tyrosine protein kinase activity of the epidermal growth factor (egf) receptor and an inhibition of egf-stimulated growth. based on these data, the hypothesis that the egf receptor is physiologically regulated by gangliosides has been proposed by e.g. bremer, j. schlessinger, and s. hakomori (j. biol. chem. (1986) 261, 2434-2440). to test this hypothesis, a mutant chinese hamster ovary cell line (clone idl d) that has ...19902142159
porphyrin photosensitivity in cell lines expressing a heat-resistant phenotype.in vitro sensitivity to porphyrin-mediated photodynamic therapy (pdt) has been examined in cell lines resistant to hyperthermia. parental (ha-1) and heat-resistant (3012) chinese hamster fibroblasts as well as parental (rif-1) and temperature-resistant (tr-4, tr-5, and tr-10) mouse radiation-induced fibrosarcoma cells were evaluated for thermal and pdt sensitivity. quantitative survival curves were generated, and porphyrin uptake properties were obtained for all cell lines. significant resistanc ...19902143688
genetic toxicology of tricyclic carboxamides, a new class of dna binding antitumour agent.(n-[2-(dimethylamino)ethyl]acridine-4-carboxamide (acridine carboxamide; nsc 601316) is an acridine-derived experimental antitumour agent with curative properties against lewis lung carcinoma in mice. although it intercalates into dna and also appears to interact with topoisomerase ii, its dna binding properties appear distinct from other acridine derivatives such as the clinical antitumour drug, amsacrine. the mutagenic properties of acridine carboxamide, together with three related compounds c ...19902144158
cells secreting tumour necrosis factor show enhanced metastasis in nude mice.a tumour cell may acquire the ability to invade and metastasise via heritable changes in its genome and/or changes in the local environment. chinese hamster ovary (cho) cells transfected with the gene for human tnf (cho/tnf cells) showed a greatly enhanced ability to invade peritoneal surfaces and metastasise in nude mice compared with cells transfected by the vector alone. in situ hybridisation with a riboprobe for human tnf showed that the cho/tnf cells were actively transcribing this cytokine ...19902148875
purification and partial characterization of recombinant human differentiation-stimulating factor.recombinant human differentiation-stimulating factor (rhd-factor) has been isolated to greater than 95% purity from chinese hamster ovary cells. rhd-factor is a glycoprotein with an apparent molecular weight of 45.6 kda as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. on gel filtration in 6 m guanidine-hydrochloride, rhd-factor elutes with an apparent molecular weight of 21.5 kda; it elutes with an apparent molecular weight of 44.8 kda under neutral ph (native) conditi ...19902152185
[further steps in regional localization of the gene coding for human arylsulfatase b (arsb): gene assignment to the section q11-qter of chromosome 5].the structural gene coding for human arylsulfatase b (arsb) has been assigned to chromosome 5 and then to 5p11-5qter by means of somatic cell hybridization. the somatic cell hybrids used in the present studies were derived from fusion experiments between chinese hamster, a3 line (tk-) and human leukocytes from a patient carrying the reciprocal balanced translocation t (5;21) (q11;q22) according to the method described previously. about 90 independent hybrid clones were selected for further analy ...19902152404
carcinogen-induced dna amplification in vitro: overreplication of the simian virus 40 origin region in extracts from carcinogen-treated co60 cells.an in vitro system to study carcinogen-induced amplification in simian virus 40 (sv40)-transformed chinese hamster (co60) cells is described. sv40 amplification in this system resembled in many aspects the viral overreplication observed in drug-treated co60 cells. cytosolic extracts from n-methyl-n'-nitro-n-nitrosoguanidine-treated cells supported de novo dna synthesis in the presence of excess exogenous t antigen and the sv40-containing plasmid psvk1. the pattern of viral replication in these e ...19902152968
various proteins modulate the kinase activity of the insulin receptor.previous studies of the substrate specificity of the purified insulin receptor tyrosine kinase using synthetic random polymers have demonstrated that the receptor kinase phosphorylates poly (glu, tyr) 4:1 but not poly (glu, tyr) 1:1. in the present study, insulin treatment of chinese hamster ovary cells overexpressing the human insulin receptor was found to stimulate the ability of their membrane extracts to phosphorylate poly (glu, tyr) 1:1. it was concluded that this activity was due to the re ...19902153593
a panel of irradiation-reduced hybrids selectively retaining human chromosome 11p13: their structure and use to purify the wagr gene complex.the irradiation-fusion technique offers a means to isolate intact subchromosomal fragments of one mammalian species in the genetic background of another. irradiation-reduced somatic cell hybrids can be used to construct detailed genetic and physical maps of individual chromosome bands and to systematically clone genes responsible for hereditary diseases on the basis of their chromosomal position. to assess this strategy, we constructed a panel of hybrids that selectively retain the portion of hu ...19902154397
cloning and functional analysis of a gene encoding a novel muscarinic acetylcholine receptor expressed in chick heart and brain.previous studies have demonstrated that muscarinic acetylcholine receptors (machr) expressed in chick heart are pharmacologically, immunologically, and biochemically distinct from machr expressed in mammalian heart. a chicken genomic clone encoding a machr whose deduced amino acid sequence is most homologous to the mammalian m4 receptor has been isolated. northern blot analysis demonstrated that this gene is expressed in both chick heart and brain. the receptor encoded by this gene was expressed ...19902154460
phenotypic mixing between human immunodeficiency virus and vesicular stomatitis virus or herpes simplex virus.superinfection of h9 cells persistently infected with human immunodeficiency virus (hiv) with thermolabile vesicular stomatitis virus (vsv) or herpes simplex virus (hsv) led to the synthesis of hybrid progeny. these phenotypic mixtures were able to infect hela or chinese hamster ovary cell lines, leading to the production of hiv p24 antigen and infectious hiv. this production was abrogated by prior incubation of the phenotypic mixtures with antiserum against vsv or hsv, as well as by incubation ...19902154577
functional properties of rat brain sodium channels expressed in a somatic cell line.transfection of chinese hamster ovary cells with complementary dna encoding the riia sodium channel alpha subunit from rat brain led to expression of functional sodium channels with the rapid, voltage-dependent activation and inactivation characteristic of sodium channels in brain neurons. the sodium currents mediated by these transfected channels were inhibited by tetrodotoxin, persistently activated by veratridine, and prolonged by leiurus alpha-scorpion toxin, indicating that neurotoxin recep ...19902154850
definition of the limits of the wilms tumor locus on human chromosome 11p13.in a previous report, we described a contiguous restriction map of chromosome band 11p13 that localized the wilms tumor locus to a small group of noti fragments. in an effort to identify and isolate the 11p13-associated sporadic wilms tumor locus, we developed a panel of noti fragment-specific dna probes. these probes were selected from genomic libraries constructed using the chinese hamster ovary-human somatic cell hybrid carrying only human 11p. the libraries were prepared from noti-digested d ...19902155176
autocrine factor-independent growth of mammalian fibroblasts established in fully synthetic medium: no v-onc requirement in establishment.in a previous study chinese hamster fibroblasts carrying a partially deleted v-src were established in a synthetic medium lacking macromolecular supplements and shown to possess a particular serum-free phenotype hereafter designated sf. in cloning efficiency assays, sf, unlike wild-type, fibroblasts required a threshold cell density to grow from single cells, suggesting autocrine stimulation. in the present study a conditioned medium harvested from sf cells was added to the same sf cells, and th ...19902155193
elevated levels of the alpha 5 beta 1 fibronectin receptor suppress the transformed phenotype of chinese hamster ovary cells.we report here on gene transfer studies designed to investigate the function of the alpha 5 beta 1 integrin and its role in transformation. transfection of the human alpha 5 and beta 1 cdnas into transformed chinese hamster ovary (cho) cells followed by methotrexate-induced amplification yielded clonal cell lines overexpression this fibronectin receptor. the overexpressors deposited more fibronectin in their extracellular matrix and migrated less than control cells. in addition, they showed redu ...19902155708
neuropeptide stimulation of calcium flux in human lung cancer cells: delineation of alternative pathways.calcium ion flux following the administration of a series of neuropeptides, n6,o2'-dibutyryladenosine 3',5'-cyclic monophosphate, and serum was monitored by flow cytometry in selected lung and breast cancer cell lines and chinese hamster ovary cell line cho-k1. calcium ion flux was monitored in individual cells by flow cytometry using the indicator indo-1 am. five groups of neuropeptides produced calcium flux changes in lung cancer cell lines and cho-k1 cells but not in breast cancer cells. the ...19902156263
antithrombotic effect of recombinant human thrombomodulin on thrombin-induced thromboembolism in mice.antithrombotic effect of recombinant human thrombomodulin in mice, both in vitro and in vivo, was studied. the soluble recombinant human thrombomodulin was expressed in chinese hamster ovary cells and purified from the conditioned medium by a modification of the conventional method. recombinant thrombomodulin prolonged thrombin clotting time for mouse plasma in a dose-dependent manner. thrombin was injected into the lateral tail vein of mice and caused acute thromboembolism. all mice injected wi ...19902156578
biochemical and functional characterization of human tissue-type plasminogen activator variants obtained by deletion and/or duplication of structural/functional domains.five cdna encoding human tissue-type plasminogen activator (t-pa) variants with deletion and/or duplication of structural/functional domains were cloned and expressed in chinese hamster ovary cells. the mutants included: rt-pa-delta fe (where r represents recombinant), with deletion of the finger (f) and growth factor (e) domains; rt-pa-delta k1 delta k2, with replacement of kringle 1 (k1) by a second copy of kringle 2 (k2); and rt-pa-delta fk1 delta k2, rt-pa-delta ek1 delta k2, and rt-pa-delta ...19902156824
insulin action on activity and cell surface disposition of human hepg2 glucose transporters expressed in chinese hamster ovary cells.complementary dna encoding a facilitative glucose transporter was isolated from a human hepatoma cell line (hepg2) cdna library and subcloned into a metal-inducible mammalian expression vector, plen (california biotechnology) containing human metallothionein gene ii promoter sequences. chinese hamster ovary (cho) cells transfected with this transporter expression vector, plengt, exhibited a 2-17-fold increase in immunoreactive hepg2-type glucose transporter protein, as measured by protein immuno ...19902156829
characterization of the yeast low km camp-phosphodiesterase with camp analogues. applications in mammalian cells that express the yeast pde2 gene.the essential interactions between camp and the yeast low km camp-phosphodiesterase have been analyzed using camp analogues and phosphodiesterase inhibitors. camp specificity is conferred by hydrogen bonding at the n-6 and n-7 positions. in contrast to the other yeast phosphodiesterase, (rp)-adenosine 3',5'-monophosphorothioate is not hydrolyzed. eleven standard phosphodiesterase inhibitors were not highly effective. in chinese hamster ovary (cho) cells that express the yeast camp-phosphodiester ...19902156832
novel use of a chimpanzee pseudogene for chromosomal mapping of human cytochrome c oxidase subunit iv.we have isolated a chimpanzee processed pseudogene for subunit iv of cytochrome c oxidase (cox; ec 1.9.3.1) by screening a chimpanzee genomic library in lambda charon 32 with a bovine liver cdna encoding cox subunit iv (cox iv), and localized it to a 1.9-kb hindiii fragment. southern-blot analysis of genomic dna from five primates showed that dnas from human, gorilla, and chimpanzee each contained the 1.9-kb pseudogene fragment, whereas orangutan and pigtail macaque monkey dna did not. this resu ...19902157630
the murine homologue of the t lymphocyte antigen cd28. molecular cloning and cell surface expression.the human t lymphocyte ag cd28 (tp44) is a homodimeric glycoprotein expressed on the surface of a majority of human peripheral t cells and thymocytes. although exposure of t cells to anti-cd28 mab does not activate t cells, stimulation of cd28 can synergize with signals transmitted through the tcr or other stimuli to augment proliferation and lymphokine production. we have used a portion of the human cd28 cdna to isolate a homologous murine cdna from an el4 t lymphoma library. the murine clone h ...19902157764
high level expression of wild type and variant mouse glucocorticoid receptors in chinese hamster ovary cells.we have isolated chinese hamster ovary (cho) cell lines expressing elevated levels of wild-type (w) and mutant forms of the glucocorticoid receptor (gr) using the technique of coamplification with a selectable dihydrofolate reductase (dhfr) cdna. a prominent doublet at 90/92 kilodaltons was observed by western blotting or labeling with [3h]-dexamethasone mesylate in extracts from cells transfected with w, the hormone binding mutant (na), and the dna binding mutant (nb). quantification of recepto ...19902157974
biochemical and genetic analysis of the chinese hamster mutants irs1 and irs2 and their comparison to cultured ataxia telangiectasia cells.two mutants of the chinese hamster cell line v79-4 (irs1 and irs2) were previously isolated on the basis of their hypersensitivity (2- to 3-fold) to cell inactivation by ionizing radiation. one of these mutants, irs1, displays an unusual phenotype of cross-sensitivity to other varied genotoxic agents including uv light (2- to 3-fold), ethyl methanesulphonate (approximately 10-fold) and mitomycin c (approximately 60-fold). the possibility that these sensitivities might be due to more than one gen ...19902158612
kringle 1 domain of human tissue-type plasminogen activator is a functional module mediating fibrinogen-stimulated plasminogenolytic activity.the functions of the finger and kringle-2 (k2) domains of human tissue-type plasminogen activator (t-pa) in mediating fibrin-stimulated plasminogenolytic activity are well documented. contradictory results have been reported for the kringle-1 (k1) domain with respect to this property. to clarify this issue we have deleted the finger and the k2 domains of t-pa according to the exon-intron organization of the gene by site-directed mutagenesis. the resulting derivative (gk1l) was constitutively exp ...19902158930
functional expression of ca2(+)-mobilizing alpha-thrombin receptors in mrna-injected xenopus oocytes.alpha-thrombin (th) initiates a program of intracellular events that lead to dna replication in quiescent ccl39 chinese hamster lung fibroblasts via membrane receptors that have yet to be characterized at a molecular level. functional th receptors were expressed in xenopus laevis oocytes following injection of poly(a)+ rna from th-responsive ccl39 cells; their presence was demonstrated by th-stimulated 45ca2+ efflux or ca2(+)-dependent cl- channel activation. in voltage clamp experiments on micr ...19902159419
functional expression of the human receptor for colony-stimulating factor 1 (csf-1) in hamster fibroblasts: csf-1 stimulates na+/h+ exchange and dna-synthesis in the absence of phosphoinositide breakdown.the human csf-1 receptor (c-fms protooncogene product) was introduced into csf-1-unresponsive chinese hamster lung fibroblasts (ccl39 cell line) in order to study its coupling to biochemical signal-transducing systems and to compare the growth-regulating properties of csf-1 to those of other growth factors. independent clones expressing different levels of csf-1 receptors were isolated and characterized. csf-1 increased [3h]thymidine incorporation in serum-starved cells and potentiated the mitog ...19902159762
complementary dnas for choline acetyltransferase from spinal cords of rat and mouse: nucleotide sequences, expression in mammalian cells, and in situ hybridization.complementary dna clones containing the entire coding region of choline acetyltransferase (chat) were isolated from the spinal cords of rat and mouse. the cdnas of rat and mouse coded for 640 and 641 amino acids, respectively, and showed 95% mutual homology and 80% homology with the cdna of porcine chat. northern blot analysis revealed a single band of 4.4 kb in the spinal cord and brain in each species. introduction of the cdnas into chinese hamster ovary cells and neuron-derived cell lines, n1 ...19902160042
continuous monitoring of receptor-mediated changes in the metabolic rates of living cells.activation of beta-adrenergic or muscarinic acetylcholine receptors expressed in transfected cells or epidermal growth factor receptors in human keratinocytes produces 15% to 200% changes in cellular metabolic rates. changes in cell metabolism were monitored continuously with a previously described silicon-based microphysiometer that detects small changes in extracellular ph. the amplitude and kinetics of the metabolic changes depend upon several factors including pretreatment of the cells prior ...19902160082
acidification-dependent dissociation of endocytosed insulin precedes that of endocytosed proteins bearing the mannose 6-phosphate recognition marker.a key step in the sorting of endocytosed ligands from their receptors is dissociation, which is triggered by the acidic ph of endosomes. to determine whether dissociation occurs synchronously for all ligands, we compared in chinese hamster ovary cells the intracellular dissociation of insulin, which dissociates between ph 6.3 and 7.0, with that of lysosomal hydrolases bearing the mannose 6-phosphate recognition marker (man-6-p proteins), which dissociate around ph 5.8. chinese hamster ovary cell ...19902160460
inhibition of n-methyl-n'-nitro-n-nitrosoguanidine-induced methotrexate and adriamycin resistance in cho cells by adeno-associated virus type 2.we studied the effects of helper-dependent parvovirus aav [adeno-associated virus] type 2 on carcinogen-inducible resistance to methotrexate (mtx) and adriamycin (adr) in chinese hamster ovary cells. both types of drug resistance were monitored by determination of the number of drug-resistant colonies normalized for the respective value of plating efficiency under non-selective conditions. treatment of cells with n-methyl-n'-nitro-n-nitrosoguanidine (mnng) drastically enhanced the frequency of r ...19902161803
cytocidal activity of a synthetic isoprenoid, n-solanesyl-n,n'-bis(3,4-dimethoxybenzyl)ethylenediamine, and its potentiation of antitumor drugs against multidrug-resistant and sensitive cells in vitro.a synthetic isoprenoid, n-solanesyl-n,n'-bis(3,4-dimethoxybenzyl)ethylenediamine (sdb-ethylenediamine), inhibited the colony formation of multidrug-resistant mutant cell lines derived from chinese hamster v79 (v79/adm) and human hepatoma plc/prf/5 (plc/col) cells to a greater extent than that of the parental cells. when combined with other clinically useful antitumor agents, it potentiated the cytotoxic activity of almost all kinds of drugs tested including adriamycin (adm), actinomycin d, vincr ...19902161816
fibroblast growth factor receptor is a portal of cellular entry for herpes simplex virus type 1.herpes simplex virus type 1 (hsv-1) is a ubiquitous pathogen responsible for considerable morbidity in the general population. the results presented herein establish the basic fibroblast growth factor (fgf) receptor as a means of entry of hsv-1 into vertebrate cells. inhibitors of basic fgf binding to its receptor and competitive polypeptide antagonists of basic fgf prevented hsv-1 uptake. chinese hamster ovary (cho) cells that do not express fgf receptors are resistant to hsv-1 entry; however, ...19902162560
guanosine 5'-o-(3-thiotriphosphate) and guanosine 5'-o-(2-thiodiphosphate) activate g proteins and potentiate fibroblast growth factor-induced dna synthesis in hamster fibroblasts.addition of guanosine 5'-o-(3-thiotriphosphate) (gtp gamma s) to intact chinese hamster lung fibroblasts (ccl39) depolarized by high k+ concentrations results in activation of phosphoinositide-specific phospholipase c (plc) (at gtp gamma s concentrations greater than 0.1 mm), inhibition of adenylate cyclase (between 10 microm and 0.5 mm), and activation of adenylate cyclase (above 0.5 mm). since gtp gamma s-induced activation of plc is dramatically enhanced upon receptor-mediated stimulation of ...19902164008
increased sensitivity to killing by restriction enzymes in the xr-1 dna double-strand break repair-deficient mutant.repair or misrepair of dna double-strand breaks (dsbs) is critical in determining cellular survival after gamma-irradiation. in this report, we focus on the cellular and biochemical consequences of restriction enzyme induced dsbs in wild-type chinese hamster ovary (cho) cells and the dna dsb repair-defective mutant xr-1. we find that xr-1 possesses reduced cellular survival after the introduction of restriction enzymes that produce either cohesive or blunt ends. xr-1's sensitivity to killing by ...19902164147
t-cell antigen cd28 mediates adhesion with b cells by interacting with activation antigen b7/bb-1.studies using monoclonal antibodies (mabs) have implicated the homodimeric glycoprotein cd28 as an important regulator of human t-cell activation, in part by posttranscriptional control of cytokine mrna levels. although the cd28 antigen has functional and structural characteristics of a receptor, a natural ligand for this molecule has not been identified. here we show that the cd28 antigen, expressed in chinese hamster ovary (cho) cells, mediated specific intercellular adhesion with human lympho ...19902164219
involvement of tyrosine residues located in the carboxyl tail of the human beta 2-adrenergic receptor in agonist-induced down-regulation of the receptor.chronic exposure of various cell types to adrenergic agonists leads to a decrease in cell surface beta 2-adrenergic receptor (beta 2ar) number. sequestration of the receptor away from the cell surface as well as a down-regulation of the total number of cellular receptors are believed to contribute to this agonist-mediated regulation of receptor number. however, the molecular mechanisms underlying these phenomena are not well characterized. recently, tyrosine residues located in the cytoplasmic t ...19902164220
position effects on the timing of replication of chromosomally integrated simian virus 40 molecules in chinese hamster cells.simian virus 40 (sv40) dna molecules chromosomally integrated at different sites in three chinese hamster lung fibroblast lines replicated during the middle portion of s phase but not precisely at the same time in all three cell lines. the time of replication was unrelated to the presence of t antigen or to its relative activity in promoting sv40 replication. sv40 sequences and chromosomal dna sequences adjacent to the sv40 insert in one cell line expressing a temperature-sensitive t antigen sho ...19902164638
trans-acting factors in chromosomal instability.the hypothesis that trans-acting factors affect chromosome stability was explored using human x chinese hamster somatic cell hybrids. two types of hybrids were examined. in either case, the human parent consisted of human diploid fibroblasts, the chromosomes of which tended to be lost from the hybrid cell. comparisons were made between hybrid clones in which the hamster parent had a very stable karyotype (line cho) and clones from a hamster parent with an unusual ongoing unstable karyotype (line ...19902164880
photoaffinity labeling and binding studies reveal the existence of two types of phencyclidine receptors in the ncb-20 cell line.the mouse neuroblastoma-chinese hamster brain hybrid cell line ncb-20 is the only clonal cell line in which binding studies indicate the presence of phencyclidine (pcp) receptor-like sites. we report here that polypeptide components of ncb-20 cell pcp sites were identified with the photolabile pcp derivative [3h]n-[1-(3-azidophenyl)cyclohexyl]piperidine ([3h]az-pcp). the pharmacological selectivity of [3h]az-pcp binding (under reversible conditions) was similar to that observed for [3h]n-[1-(2-t ...19902166931
the functional expression of recombinant human thyrotropin receptors in nonthyroidal eukaryotic cells provides evidence that homologous desensitization to thyrotropin stimulation requires a cell-specific factor.tsh desensitization involves decreased coupling of the tsh receptor to the adenylate cyclase regulatory protein, gs. there is evidence that a desensitization protein in thyroid cells plays a role in this process. the molecular cloning of the human tsh receptor and its stable expression in chinese hamster ovary (cho-tshr) cells allowed us to test whether or not tsh desensitization can occur in a nonthyroidal cell. similar to human thyroid cells, maximal stimulation of camp levels in cho-tshr cell ...19902167212
regulation of glycosylation. three enzymes compete for a common pool of dolichyl phosphate in vivo.we examined changes in the levels of the dolichol forms in chinese hamster ovary cells containing alterations in the levels of activity of two enzymes in the oligosaccharyl-p-p-dolichol biosynthetic pathway, namely udp-glcnac:dolichyl phosphate:glcnac-phosphotransferase (glcnac-1-phosphotransferase) and mannosylphosphoryldolichol (man-p-dol) synthase. under normal conditions in wild type cells, glc3man9glcnac2-pyrophosphoryldolichol was the most abundant form. of the other anionic forms of dolic ...19902167320
transcription stimulates homologous recombination in mammalian cells.transcription stimulates homologous recombination in saccharomyces cerevisiae and has been implicated in the control of recombinational events during the development of mammalian immune systems. here, we describe a plasmid-based system in which an inducible promoter from the mouse mammary tumor virus is located upstream of heteroallelic neomycin genes carried on two plasmids. pairs of plasmids are introduced into chinese hamster ovary cells by electroporation, and recombination is monitored by s ...19902167441
polyomavirus-based shuttle vectors for studying mechanisms of mutagenesis in rodent cells.we have constructed a series of polyomavirus-based shuttle vectors for analyzing mechanisms of mutagenesis in rodent cell systems. these vectors contain the supf suppressor trna gene which serves as the mutagenesis target; the pbr327 replication functions and ampr gene for replication and selection in bacteria; and the polyomavirus genome which permits replication in rodent cells. the polyoma genomes used in these vectors vary in their enhancer regions, causing varying efficiencies of replicatio ...19902168017
sensitivity of cultured mammalian cells to oxidative stress: adaptation to repeated exposures of hyperbaric oxygen.four established cell lines (mouse neuroblastoma, n2a; chinese hamster lung, v79; chinese hamster ovary, cho; and rabbit kidney, rk13) were made o2-tolerant by repetitive exposure to hyperbaric oxygen (hbo). the cultures were exposed to 100% o2 at pressures ranging from 6 to 10 ata for time periods up to 3 h, and the surviving cells were regrown to monolayer confluency and reexposed; by the end of three cycles of treatment these cells were tolerant to exposures of 10 ata o2 for greater than 5 h. ...19902168598
vaccinia virus host range genes.a gene encoding an 18-kda polypeptide (orf c7l) located in the vaccinia virus hindiii c fragment was shown to be functionally equivalent to previously described host range gene (orf k1l) spanning the hindiii k/m fragment junction. either c7l or k1l host range gene is necessary and sufficient by itself to allow replication of vaccinia virus on human cells. deletion of both c7l and k1l genes from the wild-type vaccinia genome is required to derive a virus deficient for replication on human cells. ...19902171207
role of hypoxanthine and thymidine in determining methotrexate plus dipyridamole cytotoxicity.the nucleoside transport inhibitor dipyridamole can potentiate the cytotoxicity of methotrexate by a mechanism that was thought to be related to the inhibition of thymidine salvage. in human ovarian carcinoma cells thymidine only partly reversed the in vitro cytotoxicity of methotrexate plus dipyridamole at sub-millimolar concentrations, above which the cytotoxicity of thymidine itself became evident. hypoxathine with thymidine, or hypoxanthine alone at a higher concentration, completely reverse ...19902171601
expression and characterization of rat surfactant protein a synthesized in chinese hamster ovary cells.rat surfactant protein a (sp-a) was expressed in a chinese hamster ovary (cho-k1) cell line and characterized for biologic activity using assays for receptor binding and modulation of phospholipid secretion from isolated type ii cells. the cho-k1 cell line was cotransfected with separate plasmids encoding for the rat sp-a, dihydrofolate reductase and neomycin phosphotransferase, respectively. antibiotic (geneticin-g418)-resistant transformants were screened by elisa for the secretion of recombin ...19902171680
molecular cloning of the human dna excision repair gene ercc-6.the uv-sensitive, nucleotide excision repair-deficient chinese hamster mutant cell line uv61 was used to identify and clone a correcting human gene, ercc-6. uv61, belonging to rodent complementation group 6, is only moderately uv sensitive in comparison with mutant lines in groups 1 to 5. it harbors a deficiency in the repair of uv-induced cyclobutane pyrimidine dimers but permits apparently normal repair of (6-4) photoproducts. genomic (hela) dna transfections of uv61 resulted, with a very low ...19902172786
purification of rip60 and rip100, mammalian proteins with origin-specific dna-binding and atp-dependent dna helicase activities.replication of the chinese hamster dihydrofolate reductase gene (dhfr) initiates near a fragment of stably bent dna that binds multiple cellular factors. investigation of protein interactions with the dhfr bent dna sequences revealed a novel nuclear protein that also binds to domain b of the yeast origin of replication, the autonomously replicating sequence ars1. the origin-specific dna-binding activity was purified 9,000-fold from hela cell nuclear extract in five chromatographic steps. protein ...19902174103
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