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comparative study of sexual dimorphism of the innominate bone in rodents and amphibians.sexual dimorphism in the shape of the innominate bone was demonstrated in the rat, mouse, chinese hamster (cricetulus griseus), frog (ranna nigromaculata), and newt (cynops pyrrhogaster) with a computer-assisted morphometric technique. in the rat, mouse, and hamster, ratios of ischium and pubis widths to the innominate bone length (inl) were larger in the males than in the females; however, the ratio of pubis length to inl was larger in the females than in the males. in the frog, the ratio of di ...19921443668
lec15 cells transfer glucosylated oligosaccharides to protein.b4-2-1 cells (lec15 cells) are chinese hamster ovary cells deficient in mannosylphosphoryldolichol synthase activity. they synthesize the truncated lipid intermediate man5glcnac2-p-p-dolichol rather than the glc3man9glcnac2-p-p-dolichol synthesized by wild-type cells. in this report we present evidence that these cells did synthesize glucosylated man5glcnac2-p-p-dolichol, but this species represented only a minor fraction of the labeled oligosaccharide-lipid. on the other hand, glucosylated olig ...19921444460
pi-specific phospholipase c "alpha" from sheep seminal vesicles is a proteolytic fragment of pi-plc delta.phosphatidylinositide-specific phospholipase c enzymes (plcs) catalyze the conversion of the phosphoinositides to biologically important signal transducing molecules. these enzymes may be grouped into "families" which share similar structures and modes of regulation. the existence of a structurally distinct family of plc termed "alpha" has been recently called into question. in the current paper we show by immunoblotting experiments that plc "alpha" from sheep seminal vesicles is recognized by m ...19921445352
cholera toxin diminishes tyrosine kinase activity of the insulin receptor.we have examined the effect of cholera toxin (ct) on the insulin receptor tyrosine kinase. incubation of intact rat hepatoma cells fao with ct (1 microgram/ml/2h) inhibited insulin-induced receptor autophosphorylation by 30% in vivo. this effect persisted after receptor purification in vitro. ct did not alter hormone binding of the insulin receptor, indicating that the toxin affects signal transduction of insulin at the level of the receptor kinase. experiments using chinese hamster ovary (cho) ...19921445389
enhanced stimulation of follicle maturation and ovulatory potential by long acting follicle-stimulating hormone agonists with extended carboxyl-terminal peptides.the induction of granulosa cell differentiation and follicle maturation is dependent upon the stimulatory actions of fsh. our recent studies used recombinant dna technology to fuse the carboxyl-terminal peptide (ctp) of hcg beta-subunit to the carboxyl-terminus of the fsh beta-subunit. the resulting fsh analog has identical in vitro receptor-binding and biological activities as wild-type fsh (wt-fsh), but an increased circulating half-life. the present studies examined further the ability of fsh ...19921446593
improvement in the heterogeneous n-termini and the defective n-glycosylation of human interleukin-6 by genetic engineering.recombinant human interleukin-6 (il-6), expressed in chinese hamster ovary cells, has heterogeneous n-termini of ala1 and val3, as does naturally occurring il-6. this heterogeneity is thought to be caused by difficulty in cleavage of the signal sequence. to obtain homogeneous il-6, pro at -1 was exchanged for ala by site-directed mutagenesis. alternatively, the signal sequence was replaced with that of human granulocyte-colony-stimulating factor. in both cases, the il-6 designed to start with al ...19921446688
genetically engineered v79 chinese hamster cells for stable expression of human cytochrome p450ia2.v79 chinese hamster cells were genetically engineered for stable expression of human p450ia2. full length cdna, encoding human p450ia2, was inserted into an sv40 early promoter containing eukaryotic expression vector and cointroduced with the selection marker neomycin phosphotransferase (conferring resistance to the neomycin derivative g418) into v79 chinese hamster cells. the recombinant expression vector was introduced into two different v79 sublines, one expressing an endogenous acetyltransfe ...19921446722
[a line of chinese hamster cells containing human chromosome 18]. 19921446812
[role of activated cellular c-ha-ras-1 oncogene in the mutagenic effect of the plasmid pej6.6].the role of the activated oncogene c-ha-ras-1 from human bladder carcinoma integrated into the pej6.6 plasmid in the mutagenic effect of the plasmid was studied in chinese hamster cells. the frequency of hypoxanthine-phosphoribosyltransferase defective (hprt-) mutants after treatment with pej6.6 containing an active c-ha-ras-1 exceeded that in control dishes treated with a derivative of pej6.6 plasmid with an inactivated oncogene. the inactivation was achieved by introducing a deletion into the ...19921446813
cell surface expression of the c3b/c4b receptor (cr1) protects chinese hamster ovary cells from lysis by human complement.the c3b/c4b receptor, also known as complement receptor type 1 (cr1, cd35), is a single chain glycoprotein consisting of 30 repeating homologous protein domains known as short consensus repeats (scr) followed by transmembrane and cytoplasmic domains. a series of recombinant proteins derived from cr1 has been prepared and assessed for the capacity to inhibit complement lysis of the host chinese hamster ovary (cho) cells. the full-length recombinant cr1 inhibited human complement-mediated cho cell ...19921447213
structural and functional analysis of the insulin-like growth factor i receptor gene promoter.the insulin-like growth factor i receptor (igf-i-r) gene is expressed in most body tissues. the levels of igf-i-r mrna, however, are regulated by a number of physiological conditions (development, differentiation, and hormonal milieu) as well as in certain pathological states (diabetes and tumors). to understand the molecular mechanisms which control the transcription of the igf-i-r gene, we have cloned the promoter of the rat receptor gene and have characterized its activity by transient expres ...19921448110
application of plasma desorption mass spectrometry to molecular weight determination of human interleukin-4 secreted by a chinese hamster ovary line. 19921449214
quantification by laser scan microscopy of intracellular doxorubicin distribution.changes in intracellular drug localization accompany doxorubicin resistance in multidrug resistant tumor cells. the purpose of this study was to develop a method to quantify these changes and so detect different levels of resistance. tumor cells were incubated with the fluorescent anthracycline doxorubicin (excitation at 480 nm; emission maximum at 560-590 nm) and were quantified using laser scanning microscopy. the fluorescent mode was used to record the intracellular drug distribution, whereas ...19921451589
molecular determinants of human prorenin processing.in humans, active renin is generated by the removal of a 43-amino acid prosegment from the zymogen prorenin. this cleavage event is highly specific, occurring at only one of the seven pairs of basic amino acids in the body of preprorenin. this cleavage site selectivity is also displayed by a number of other proteases in vitro and in mouse pituitary att-20 cells transfected with a human preprorenin expression vector, suggesting that specificity of cleavage is directed in part by the primary seque ...19921452293
construction of a diphtheria toxin a fragment-c180 peptide fusion protein which elicits a neutralizing antibody response against diphtheria toxin and pertussis toxin.a genetically engineered gene fusion was constructed which encoded a nontoxic derivative of the a fragment of diphtheria toxin joined to the c180 peptide of the s1 subunit of pertussis toxin. the product of this gene fusion, termed the dta-c180 protein, was purified from the periplasm of escherichia coli to approximately 80% purity. the dta-c180 protein possessed an apparent molecular weight of 43,000 by reduced sodium dodecyl sulfate-polyacrylamide gel electrophoresis. the dta-c180 protein was ...19921452339
expression and characterization of the cloned salmonella typhimurium enterotoxin.earlier, our laboratory reported the cloning of a chromosomally encoded cholera toxin (ct)-like enterotoxin gene from salmonella typhimurium q1 into pbr322. cell lysates from the plasmid clone pc1, containing a 4.8 kb ecor1 dna fragment from salmonella, caused elongation of chinese hamster ovary (cho) cells and this biologic activity was neutralized by anti-ct. however, this cloned gene product did not elicit fluid secretion in the rabbit intestinal loop (ril) model, because of poor expression. ...19921453924
characterization of recombinant murine interleukin 5 expressed in chinese hamster ovary cells.we have purified recombinant murine interleukin 5 (rmil-5) from the supernatant of chinese hamster ovary cells. each peptide fragment of the purified rmil-5 generated by achromobacter protease i digestion was characterized and glycosylation sites were determined. although rmil-5 contains three potential sites of n-linked glycosylation (asn-26, asn-55 and asn-69), asn-69 is not glycosylated. the oligosaccharides released from the protein by hydrazinolysis were fractionated by paper electrophoresi ...19921457971
dna sequence analysis of mutations induced by melphalan in the cho aprt locus.in previous work, we established that treatment with melphalan (l-phenylalanine mustard) produced a predominance of a.t-->t.a transversions in the simian virus 40 (sv40)-based shuttle vector pz189 during replication in human 293 cells. mutations were induced with varying doses (4-12 microm) melphalan in the aprt gene of the hemizygous chinese hamster ovary (cho) cell line d422 to determine whether a similar mutation spectrum would be observed in an endogenous gene. dna sequence alterations were ...19921458453
analysis of soluble human and mouse interferon-gamma receptors expressed in eukaryotic cells.the extracellular domains of the human and mouse interferon-gamma receptors were produced in insect spodoptera frugiperda cells infected with recombinant baculoviruses and in mammalian chinese-hamster-ovary cells. the receptors expressed in both systems are secreted into the culture medium. their signal peptides are cleaved off and the proteins show heterogeneity in glycosylation which, however, does not affect the capacity to bind interferon gamma or specific antibodies. the soluble mouse recep ...19921459135
stimulation of neutrophil leukocyte chemotaxis by a cloned cytolytic enterotoxin of aeromonas hydrophila.a cytolytic enterotoxin produced by aeromonas hydrophila, isolate ssu, has been cloned in our laboratory. this enterotoxin lysed rabbit red blood cells, destroyed chinese hamster ovary cells, caused fluid secretion in rat ligated ileal loops, inhibited the phagocytic function of mouse phagocytes, and was lethal to mice when injected intravenously. in this study, the effect of this cytolytic enterotoxin on the chemotaxis of human leukocytes (cell line rpmi 1788) was examined. this toxin, at conce ...19921459417
analysis of the autonomous replication behavior in human cells of the dihydrofolate reductase putative chromosomal origin of replication.chinese hamster genomic dna sequences from the region downstream of the dihydrofolate reductase (dhfr) gene reported to contain a chromosomal origin of bidirectional dna replication (obr-1) were tested for their ability to support autonomous dna replication in human cells. a 13.3 kilobase fragment containing obr-1 and surrounding sequences supported replication in short-term and long-term replication assays, while a 4.5 kb fragment containing obr-1 did not support substantial replication in eith ...19921461730
a non-glycosylated extracellular superoxide dismutase variant.the secretory tetrameric extracellular superoxide dismutase (ec-sod) is the only glycosylated sod isoenzyme. the importance of the carbohydrate moiety for the properties of the enzyme is unknown. an expression vector defining nonglycosylated ec-sod (ngec-sod) was constructed by mutagenesis of the codon for asn-89 into a codon for gln. the vector was transfected into chinese hamster ovary dxb-11 cells and ngec-sod was isolated to 70% purity from the culture media of selected clones. the absence o ...19921463450
basic fibroblast growth factor (bfgf) dissociates rapidly from heparan sulfates but slowly from receptors. implications for mechanisms of bfgf release from pericellular matrix.the effect of heparin on the rate of binding of basic fibroblast growth factor (bfgf) to high affinity (receptor) and low affinity (heparan sulfate) binding sites on endothelial cells and cho cells transfected with fgf receptor-1 or fgf receptor-2 was investigated. radiolabeled bfgf bound rapidly to both high and low affinity sites on all three types of cells. addition of 10 micrograms/ml heparin eliminated binding to low affinity sites and decreased the rate of binding to high affinity sites to ...19921464594
dna strand-specific repair of (+-)-3 alpha,4 beta-dihydroxy-1 alpha,2 alpha-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene adducts in the hamster dihydrofolate reductase gene.we evaluated the formation and removal of (+-)-3 alpha,4 beta-dihydroxy-1 alpha,2 alpha-epoxy-1,2,3,4- tetrahydrobenzo[c]phenanthrene (bcphde)-dna adducts in two chinese hamster ovary (cho) cell lines. one line of repair-proficient cells (mk42) carries a stable 150-fold amplification of the dihydrofolate reductase (dhfr) locus. the other line of repair-deficient cells (uv-5) is diploid for this gene and is defective in excision of bulky dna lesions. two methods were used to quantitate adduct lev ...19921465420
o-linked carbohydrate of recombinant von willebrand factor influences ristocetin-induced binding to platelet glycoprotein 1b.by transfecting the full-length cdna for human von willebrand factor (vwf) into a line of chinese hamster ovary cells with a defect in carbohydrate metabolism, we have prepared recombinant vwf specifically lacking o-linked carbohydrates. we have compared this under-glycosylated protein to fully glycosylated recombinant vwf with respect to several structural and binding properties. vwf deficient in o-linked glycans was synthesized, assembled into multimers, and secreted in an apparently normal ma ...19921469086
relationships between in vitro mutagenicity assays.this paper analyzes the mutagenicity results reported by the us national toxicology program (ntp), relative to 41 chemicals assayed with four in vitro short-term tests [salmonella typhimurium (sty), chromosomal aberrations in chinese hamster ovary (cho) cells (cha), sister chromatid exchange in cho cells (sce), mutation in l5178y mouse lymphoma cells (mly)] and puts this database in perspective with respect to other databases. it is shown that the test relationships pointed out by the experiment ...19921470028
cloning and functional expression of the canine anaphylatoxin c5a receptor. evidence for high interspecies variability.a cdna clone, dtjp03, encoding an orphan receptor, was isolated from a canine thyroid library, and found to exhibit 68.6% amino-acid identity with the recently described human c5a receptor. this relatively low similarity first suggested that dtjp03 encoded either a c5a receptor subtype, or the presumably related c3a receptor. binding studies performed on membranes from cos-7 cells expressing the recombinant receptor demonstrated that dtjp03 encoded a high-affinity c5a receptor, with a kd of 1.2 ...19921472004
glutathione s-transferase pi in an arsenic-resistant chinese hamster ovary cell line.a glutathione s-transferase (gst) was purified from an arsenic-resistant chinese hamster ovary cell line, sa7. the sa7 gst was shown to catalyse the conjugation of glutathione and ethacrynic acid, a specific substrate for pi class gst. its n-terminal amino-acid sequence has 80% identical residues to that of rat gst p and human gst pi. thus, the gst purified from sa7 cells belongs to the pi family. treatment with cibacron blue or ethacrynic acid, which are gst inhibitors, significantly decreased ...19921472011
clotrimazole-induced modulation of hepatic cytochrome p450 enzymes in syrian and chinese hamsters.clotrimazole, an imidazole antifungal drug, is known to induce cytochrome p450 isozymes of the p450iiia and p450iib subfamilies in rats. this agent modulated hepatic cytochrome p450 enzymes differently in golden syrian and chinese hamsters and also in hamsters and rats. clotrimazole at a daily intraperitoneal dose of 100 mg/kg for three days increased the amount of cytochrome p450 in the livers of the two hamster strains. in syrian hamsters, clotrimazole significantly induced the activities of 7 ...19921472091
the use of human repetitive dna to target selectable markers into only the human chromosome of a human-hamster hybrid cell line (al)we used the plasmid blur-8 that contains an 800-base pair (bp) sequence of human repetitive alu dna in a cotransfection protocol to target the plasmids psv2neo or ebo-pcd-leu-2 (hygro) into a single site of the sole human chromosome, number 11, of a chinese hamster-human hybrid cell line (al). the neo and hygro plasmids confer resistance to the antibiotics g418 and hygromycin, respectively. of the 33 cotransfected clones with single-site insertions, 1/13 without blur-8 and 6/20 with blur-8 were ...19921475708
characterization of the extracellular region of the human thyrotrophin receptor expressed as a recombinant protein.dna encoding the n-terminal 415 residues of the human thyrotrophin receptor (predicted to code for the large extracellular region) was introduced into chinese hamster ovary (cho) cells using the glutamine synthetase/cytomegalovirus amplifiable expression system, and into e. coli using the pgex-3x expression vector. substantial quantities of insoluble fusion protein product resulted from bacterial expression; by western blot analysis, this was shown to be reactive with anti-receptor antibodies ra ...19921476610
effects of fermentation on product consistency.a variety of different fermentation processes has been successfully employed to produce consistent protein-based biopharmaceuticals from genetically engineered animal cells. chinese hamster ovary (cho) cells were genetically modified to produce recombinant human soluble cd4, tissue plasminogen activator (tpa) or erythropoietin (epo). soluble cd4 was collected from extended perfused fermentations of several months' duration, during which some quantitative loss of dna copy level, mrna expression l ...19921478331
rapid desensitization of muscarinic m3 receptor-stimulated polyphosphoinositide responses.chinese hamster ovary (cho) cells transfected with human m3 muscarinic receptor cdna (bmax, 1343 +/- 46.8 fmol/mg of protein) were used to investigate agonist-mediated muscarinic receptor desensitization. stimulation of cho-m3 cells with a maximal dose of carbachol resulted in a biphasic production of mass inositol-1,4,5-trisphosphate [ins(1,4,5)p3], measured by radioreceptor binding assay. the first phase comprises a rapid 8-10-fold increase in ins(1,4,5)p3 that peaks after 10 sec and falls to ...19921480131
embryonic alkaline phosphatase is expressed at m-phase in the spermatogenic lineage of the mouse.we have recently cloned and characterized a novel embryonic alkaline phosphatase (eap) expressed at the two-cell to blastocyst stage of preimplantation development in the mouse. the isozyme is re-expressed in trace amounts in the thymus, intestine and testis during adult life. in the present report, we find that eap transcripts can be detected, by rt-pcr analysis, in very low amounts in the testes of newborn mice, but at 24 days of age eap mrna levels reach the highest concentrations, remaining ...19921483384
expression, purification, and characterization of inactive human coagulation factor xa (asn322ala419).we have expressed in chinese hamster ovary cells a catalytically inactive form of human factor xa (factor rxai). a recombinant precursor of human factor xa was inactivated by two point mutations in the serine protease catalytic triad, asp322asn and ser419ala. a two-step purification to homogeneity of the secreted material involved immunoaffinity followed by heparin-agarose chromatography. two forms were identified; a fully processed dimer (70%) and a partially processed monomer (30%). limited n- ...19921486277
intragenomic repair heterogeneity of dna damage.the mutagenic and carcinogenic consequences of unrepaired dna damage depend upon its precise location with respect to the relevant genomic sites. therefore, it is important to learn the fine structure of dna damage, in particular, proto-oncogenes, tumor-suppressor genes, and other dna sequences implicated in tumorigenesis. both the introduction and the repair of many types of dna lesions are heterogeneous with respect to chromatin structure and/or gene activity. for example, cyclobutane pyrimidi ...19921486861
the gene for bone morphogenetic protein 2a (bmp2a) is localized to human chromosome 20p12 by radioactive and nonradioactive in situ hybridization.bone morphogenetic protein 2a (bmp2a), a member of the decapentaplegic-vg-related family, belongs to the transforming growth factor beta superfamily and has a striking sequence similarity to the decapentaplegic locus in drosophila melanogaster, a major determinant of pattern specification during embryogenesis. bmp2a is thought to be involved in cartilage and bone formation during embryogenesis, but may have additional functions in morphogenesis as implied by its expression in various organs and ...19921487246
conservation of the mammalian rna polymerase ii largest-subunit c-terminal domain.we have isolated and sequenced a portion of the gene encoding the carboxy-terminal domain (ctd) of the largest subunit of rna polymerase ii from three mammals. these mammalian sequences include one rodent and two primate ctds. comparisons of the new sequences to mouse and chinese hamster show a high degree of conservation among the mammalian ctds. due to synonymous codon usage, the nucleotide differences between hamster, rat, ape, and human result in no amino acid changes. the amino acid sequenc ...19921487824
microtubule-mediated golgi capture by semiintact chinese hamster ovary cells. 19921487989
assay for expression of methotrexate-resistant dihydrofolate reductase activity in the presence of drug-sensitive enzyme.a simple, continuous spectrophotometric assay for dihydrofolate reductase (dhfr) activity was adapted for determination of drug-resistant enzyme activity expressed from transfected genes in cells containing drug-sensitive enzyme. methotrexate inhibition characteristics in this assay system were assessed for the murine wild-type (wt) enzyme as well as variant genes encoding amino acid substitutions at codon positions 22 (arg22) or 31 (trp31) expressed in dhfr-deficient chinese hamster ovary (cho) ...19921489988
characterization and pathogenic potential of a soil isolate and an ocular isolate of acanthamoeba castellanii in relation to acanthamoeba keratitis.acanthamoeba castellanii, one isolate from the eye and one from the soil, were compared on the basis of: (a) pathogenic potential; (b) plasminogen activator activity; (c) chemotactic activity; (d) cytopathic effects; (e) collagenolytic activity; (f) binding ability to contact lenses; and (g) and binding ability to corneal buttons. the ocular isolate of a. castellanii was found to be pathogenic based on its ability to produce corneal infections in chinese hamsters. by contrast, the soil isolate p ...19921490339
ligand-dependent down-regulation of stably transfected human glucocorticoid receptors is associated with the loss of functional glucocorticoid responsiveness.the effect of glucocorticoids on the regulation of stably transfected human glucocorticoid receptors has been examined. exposure of a chinese hamster ovary-derived cell line containing stably transfected human glucocorticoid receptor genes and glucocorticoid-responsive dihydrofolate reductase genes to 5 nm dexamethasone resulted in a rapid, time-dependent reduction in the level of glucocorticoid receptor protein to 50% of control levels within 5 h of steroid treatment. this decrease in receptor ...19921491690
identification of two cysteines closely positioned in the ligand-binding pocket of the human estrogen receptor: roles in ligand binding and transcriptional activation.we have previously identified cysteine 530 in the human estrogen receptor (er) as the major site of attachment for covalently binding affinity ligands and have shown that when this cysteine is mutated to alanine (c530a mutant), the affinity ligand [tamoxifen aziridine (taz)] can still bind covalently to the er, presumably by interaction with a different cysteine(s) in the hormone-binding domain (hbd). using site-directed mutagenesis, we have determined the alternative ligand attachment site and ...19921491695
application of alkaline unwinding assay for detection of mutagen-induced dna strand breaks.the frequency of single-strand breaks in parental dna and gaps in nascent dna in various cells exposed to methyl methanesulfonate (mms) or methylnitrosourea (mnu) was investigated by alkaline unwinding assay using two types of alkaline lysis conditions, 22 degrees c lysis versus 0 degrees c lysis. the dna damage induced by mms and mnu is considered to be characteristic of lesions produced in dna by alkylating agents. the aim of our research project was to adjust this method to be able to detect ...19921493582
salmonella cytotonic and cytolytic factors: their detection in chinese hamster ovary cells and antigenic relatedness.thirty nine strains of salmonella belonging to 14 different serotypes were screened for the production of cytotonic and cytolytic factors by assayed chinese hamster ovary (cho) cells. the cell-free culture supernatants (cfcs) of 32 isolates caused elongation and increase in size of cho cells while the cfcss completely lysed the cells. the cytotonic effect in cho cells correlated precisely with fluid the cfcss completely lysed the cells. the cytotonic effect in cho cells correlated precisely with ...19921496811
analysis of kidney mrnas expressed from the rat beta-galactoside alpha 2,6-sialyltransferase gene.beta-galactoside alpha 2,6-sialyltransferase (siat-1), like other glycosyltransferases, is differentially expressed in rat tissues. two distinct size classes of siat-1 mrnas expressed in rat kidney are comprised of at least three siat-1 transcripts. one mrna, rke, represents the larger transcript class (4.7 kb) and predicts a polypeptide identical to the hepatic siat-1. in transfected chinese hamster ovary (cho) cells, rke polypeptides exhibit hemi-perinuclear staining with a siat-1 antibody (ab ...19921498423
bioactivation of aflatoxin b1 in the bovine olfactory mucosa: dna binding, mutagenicity and induction of sister chromatid exchanges.nasal olfactory tumours occur in cattle in relatively high frequencies in several developing countries. since affected animals sometimes show signs of severe aflatoxicosis, a role of aflatoxin b1 (afb1) in tumorigenesis can be proposed. the results of the present study show that microsomal preparations of the bovine olfactory mucosa have a much higher ability than liver microsomes to induce covalent binding of afb1 to calf thymus dna and to microsomal proteins. the major dna adduct formed was 8, ...19921499086
characterisation of a human bilirubin udp-glucuronosyltransferase stably expressed in hamster lung fibroblast cell cultures.a cdna encoding a human bilirubin udp-glucuronosyltransferase has been isolated and stably expressed in chinese hamster v79 lung fibroblast cell line. western blotting of cell homogenates with anti-ugt antibody revealed a highly expressed protein of approx. 55.5 kda in size. the expressed enzyme specifically catalysed the formation of bilirubin mono- and diglucuronides, and also catalysed the glucuronidation of two phenolic compounds, which are good substrates for other human ugt isoenzymes, at ...19921499725
recombinant salmonella typhimurium strains that invade nonphagocytic cells are resistant to recognition by antigen-specific cytotoxic t lymphocytes.to address the question of whether salmonella-infected nonphagocytic cells could serve as target cells for recognition by antigen-specific, major histocompatibility complex class i-restricted cytotoxic t lymphocytes (ctl), four recombinant salmonella typhimurium constructs that expressed full-length, or fragments of, influenza a virus nucleoprotein (np) were made. the bacteria were shown to infect chinese hamster ovary (cho) cells. appropriate major histocompatibility complex restriction molecul ...19921500187
action spectra of phthalocyanines with respect to photosensitization of cells.human carcinoma cells (nhik 3025 cells) and chinese hamster cells (v79 cells) were incubated with alpcs1, alpcs2 and alpcs4, phthalocyanines with different lipophilicity but with similar photochemical properties when in monomeric solutions. the absorption- and fluorescence spectra of the dyes in the cells were recorded as well as their action spectra with respect to sensitizing cells to photoinactivation. these spectra show that under the present conditions alpcs1 is strongly aggregated in both ...19921502260
a leu----his substitution at residue 93 in human corticosteroid binding globulin results in reduced affinity for cortisol.a steroid binding capacity assay and a radioimmunoassay were both used to measure corticosteroid binding globulin (cbg) in serum samples from 22 patients with sepsis. an approximately 50% discordancy between the two values in one patient suggested the presence of a cbg variant with reduced affinity for cortisol, and this was confirmed by scatchard analysis. we therefore used the polymerase chain reaction to amplify exons that encode for human cbg from the genomic dna of this patient. this reveal ...19921504007
a role for the transient increase of cytoplasmic free calcium in cell rescue after photodynamic treatment.chinese hamster ovary (cho) cells and t24 human bladder transitional carcinoma cells were treated with the photosensitizers aluminum phthalocyanine (alpc) and hematoporphyrin derivative (hpd), respectively. exposure of both sensitized cell lines to red light caused an immediate increase of cytoplasmic free calcium, [ca2+]i, reaching a peak within 5-15 min after exposure and then returning to basal level (approximately 200 nm). the level of the peak [ca2+]i depended on the light fluence, reaching ...19921504070
comparison of rat liver parenchymal and nonparenchymal cells in the activation of promutagens.while the liver consists of both parenchymal cells (pc) and nonparenchymal cells (npc), virtually all studies on promutagen activation have been performed using pc. to evaluate the comparative roles of pc and npc in promutagen activation, we cocultivated a cell line generally considered to have an insignificant level of xenobiotic metabolism, chinese hamster ovary (cho) cells, with either pc, npc, or a combination of both. the mixed culture was treated with two promutagens: dimethylnitrosamine ( ...19921505529
assignment of a human dna double-strand break repair gene (xrcc5) to chromosome 2.the chinese hamster ovary (cho-k1) cell mutant xrs-6 is defective in rejoining of dna double-strand breaks and is hypersensitive to x-rays, gamma-rays, and bleomycin. radiation resistance or sensitivity of somatic cell hybrids constructed from the fusion of xrs-6 cells with primary human fibroblasts strongly correlated with the retention of human chromosome 2 isozyme and molecular markers. discordancies between some chromosome 2 markers and the radiation resistance phenotype in some of the hybri ...19921505945
hypoxia-selective antitumor agents. 5. synthesis of water-soluble nitroaniline mustards with selective cytotoxicity for hypoxic mammalian cells.nitroaniline mustards have potential as hypoxia-selective cytotoxic agents, with reductive metabolism activating the nitrogen mustard by converting the electron-withdrawing nitro group to an electron-donating hydroxylamine or amine. however, the parent compounds have poor aqueous solubility, and their potencies are limited by low reduction potentials (e1/2 ca. -600 mv versus the normal hydrogen electrode) and corresponding slow rates of nitro reduction. to address these limitations, a series of ...19921507207
functional expression of an ovine growth hormone receptor in transfected chinese hamster ovary cells.structural heterogeneity has been demonstrated for growth hormone (gh) receptors from a number of species, and both high and low affinity art receptors have been characterised by ligand binding studies. in the present study, we have transfected chinese hamster ovary (cho-k1) cells with a cdna clone encoding a full-length transmembrane ovine (o) gh receptor, under the regulatory control of the human metallothionein iia promoter. a stably transfected cell line was established (ghr9.5) which expres ...19921511779
characterization of the murine thymidine kinase-encoding gene and analysis of transcription start point heterogeneity.we have determined the molecular organization and transcription start points (tsp) for the murine gene (tk) encoding thymidine kinase. the exon/intron structure and sequences present at the splice junctions of the mammalian tk genes have been highly conserved; however, the promoter sequences of these genes have diverged widely. both the human and chinese hamster tk promoter regions contain ccaat and tata consensus motifs, whereas the mouse promoter has neither element. this difference between sp ...19921511894
complex allosteric modulation of cardiac muscarinic receptors by protamine: potential model for putative endogenous ligands.a large number of diverse pharmacological agents bind to a secondary domain on the muscarinic receptor, to influence allosterically the interaction of ligands at the primary binding site. based on common structural features of these antagonists, we examined the interaction of protamine, an endogenous polycationic peptide, and of polyamines with muscarinic receptors in rat heart. our results provide several lines of qualitative evidence that protamine allosterically modulates the conformation of ...19921513329
clastogenic and mutagenic actions of active species generated in the 6-hydroxydopamine/oxygen reaction: effects of scavengers of active oxygen, iron, and metal chelating agents.a pro-oxidant triphenol, 6-hydroxydopamine (6-ohda), induced mutations in the salmonella typhimurium ta 104 tester strain (over the concentration range to 800 microm), and induced chromosomal aberrations in cultured chinese hamster ovary (cho) cells at lower concentrations (up to 90 microm). it was however only marginally mutagenic (up to cytotoxic levels of 200 microm) in the ta102 tester strain. clastogenicity in the more sensitive cho cell assay was mediated by activated oxygen. superoxide di ...19921516844
the role of extracellular medium components and specific amino acids in the cytotoxic response of escherichia coli and chinese hamster ovary cells to hydrogen peroxide.a concentration of h2o2 resulting in mode one killing of escherichia coli is more toxic when exposure to the oxidant is performed in complete medium (k medium), as compared to a saline (m9 salts). inorganic salts (mgso4 and cacl2), thiamine or glucose, when added separately, or combined, to m9 salts had no effect on the cytotoxic response to h2o2. in contrast, the lethality of the oxidant was highly dependent on the presence of the amino acids in the incubation medium. the addition of glucose fu ...19921516848
the inhibitory effects of müllerian-inhibiting substance on epidermal growth factor induced proliferation and progesterone production of human granulosa-luteal cells.this study was undertaken to determine if müllerian-inhibiting substance (mis) could block basal and/or epidermal growth factor (egf)-induced proliferation and progesterone production by cultured human granulosa-luteal cells. cells from follicles of individual patients were pooled, counted, and aliquoted into ham's f-10 medium containing 10% mis-free female fetal calf serum at 37 c in 95% air and 5% co2. after assessing viability, cells were counted on days 4, 8, 12, and 16 of culture. egf was a ...19921517385
[structure and function of oligosaccharide chains of the envelope glycoprotein gp120 of human immunodeficiency virus type 1].the surface of the human immunodeficiency virus (hiv-1), a causative agent for acquired immunodeficiency syndrome (aids), is covered with the major envelope glycoprotein gp120, of which the carbohydrate moiety accounted for 50% of the molecular mass. there is evidence that glycosylation of gp120 is prerequisite to the various stages of hiv infection. the oligosaccharide structures of gp120 have been determined using recombinant gp120 of hiv-1 (iiib) produced in chinese hamster ovary cells and vi ...19921518160
effects of adenine arabinoside and coformycin on the kinetics of g2 chromatid aberrations in x-irradiated human lymphocytes.the kinetics of chromatid aberrations have been studied in human lymphocytes exposed to x-rays in the g2 phase of the cell cycle and incubated with or without the nucleoside analogue 9-beta-d-arabinofuranosyladenine (ara a), known to inhibit the repair of dna double-strand breaks. in the absence of ara a an exponential decrease in frequencies of chromatid breaks occurred which we interpret as repair. few breaks were observed if samples were harvested immediately following irradiation. the freque ...19921518412
identification, characterization, and localization of the dopamine d3 receptor in rat brain using 7-[3h]hydroxy-n,n-di-n-propyl-2-aminotetralin.we have identified 7-[3h]hydroxy-n,n-di-n-propyl-2-aminotetralin ([3h]7-oh-dpat) as a selective probe for the recently cloned dopamine d3 receptor and used it to assess the presence of this receptor and establish its distribution and properties in brain. in transfected chinese hamster ovary (cho) cells, it binds to d3 receptors with subnanomolar affinity, whereas its affinity is approximately 100-, 1000-, and 10,000-fold lower at d2, d4, and d1 receptors, respectively. specific [3h]7-oh-dpat bin ...19921518841
the binding of human alloantibodies to recombinant glycophorin a.chinese hamster ovary (cho) cells were transfected with the wild-type, m allele of glycophorin a cdna. the binding of human alloantibodies to recombinant glycophorin a was assessed with a modified hemagglutination-inhibition assay. patient sera were incubated with acetone powders derived from cho cells, and the adsorbed supernatants were tested in standard hemagglutination assays. five m antibodies and one sample containing anti-en(a) bound to transfected cho cells expressing glycophorin a but d ...19921519325
expression of a gene encoding a specific human sperm protein in chinese hamster ovarian cells.the cdna (rsd-2) encoding a human sperm protein (ywk-ii) was isolated from a rat testis lambda gt11 expression library. its nucleotide sequence was determined. the deduced polypeptide showed high identity with the transmembrane-cytoplasmic domains of a4 amyloid precursor protein of alzheimer's disease. the rsd-2 was inserted into the ecori site of the psv2-ep vector to construct the psvrs-2 vector. chinese hamster ovarian (cho-dhfr) cells were cotransformed with psv2-neo and psvrs-2. mrna and ch ...19921520040
expression, purification and biochemical comparison of natural and recombinant human non-pancreatic phospholipase a2.the gene coding for human non-pancreatic phospholipase a2 (nppla2) was cloned in a eukaryotic expression vector and transfected into chinese hamster ovary (cho) cells. a number of cell lines stably expressing nppla2 were obtained. northern analysis of these cell lines showed an abundant transcript of expected size 1200 nt. the recombinant enzyme was efficiently secreted in quantities up to 400 micrograms nppla2 per liter culture medium in the most productive cell lines. nppla2 was purified to ho ...19921520345
elevation of glutathione levels in bovine pulmonary artery endothelial cells by n-acetylcysteine.n-acetylcysteine (nac), a cysteine derivative with chemoprotective and radioprotective effects, was found to elevate bovine pulmonary artery endothelial cell (ec) glutathione after in vitro incubation. the elevation in glutathione was associated with enhanced uptake of radioactivity of cystine from the medium. because cystine in medium was converted rapidly to cysteine and cysteinyl-nac in the presence of nac and given that cysteine has a higher affinity for uptake by ec than cystine, we conclud ...19921520492
a human osteoblastic cell line, mg-63, produces two molecular types of macrophage-colony-stimulating factor.a human osteoblastic cell line, mg-63, mouse primary osteoblasts, and a mouse osteoblastic cell line, mc3t3-e1, were shown to produce macrophage-colony-stimulating factor (m-csf) by bone-marrow-cell colony assay, using a specific neutralizing antibody for m-csf. immunoblot analysis of m-csf, produced by mg-63 cells, revealed the presence of a higher-molecular-weight species of m-csf, in addition to the 85-kda m-csf. the higher-molecular-weight species had a high affinity to the deae-sephacel col ...19921520704
the activated human c-ha-ras-1 oncogene as a mutagen.the induction of gene mutations and chromosome aberrations by plasmid pej6.6 carrying the activated c-ha-ras-1 oncogene from human bladder carcinoma was studied in cultured chinese hamster cells. both an increase in the frequency of hypoxanthine-phosphoribosyltransferase-deficient (hprt-) mutants and chromosome aberrations was observed after pej6.6 transfection as compared to control series (pbr322). in order to define whether it is the oncogene which is responsible for the mutagenic effect of p ...19921521228
[the plasmid pej6.6 carrying the activated c-ha-ras-1 oncogene increases the mutation frequency in chinese hamster cells].the induction of gene mutations and chromosome aberrations by the plasmid pej6.6 carrying the activated c-ha-ras-1 oncogene from human bladder carcinoma was studied in cultured chinese hamster cells. both an increase in the frequency of gene mutations to 6-mercaptopurine resistance and of chromosome aberrations was observed after pej6.6 treatment as compared to control series (pbr322). thus the results of experiments carried out show that the pej6.6 plasmid possesses a mutagenic activity.19921521799
enteropathogenicity of non-toxigenic vibrio cholerae o1 for adult mice.the enteropathogenic potential of 32 vibrio cholerae o1 isolates that do not produce cholera toxin was examined in the orally inoculated, sealed adult mouse model. live cultures (2 x 10(10) cfu/ml) of 7/16 clinical and 6/16 environmental isolates produced a positive intestinal fluid accumulation (fa) ratio that reached near maximum at approximately 5 h post-inoculation. colony hybridization did not detect genes for cholera toxin, escherichia coli heat-labile and heat-stable toxins, or shiga-like ...19921522800
heat-labile toxin from bordetella parapertussis induces contraction of smooth muscle cells in culture.the ability of bordetella heat-labile toxin (hlt) to contract various types of cells in culture was examined. hlt from b. parapertussis induced contraction of cultured smooth muscle cells from trachea, intestine, uterus and vas deferens as well as from aorta. the time required for contraction decreased as the dose of b. parapertussis hlt increased from 3 to 100 mid/ml. upon exposure of cells to concentrations of toxin greater than 100 mid/ml, at least 2 hr was required for contraction. hlt from ...19921522812
generation of recombinant cho(dhfr-) cell lines by single selection for dhfr+ transformants.in order to establish a mammalian cell expression system with a minimum of selection steps and a stable expression of microgram amounts of recombinant protein (human tissue-type plasminogen activator mutants and chimeric proteins) per 10(6) cells per day, we investigated chinese hamster ovary cells and the dihydrofolate reductase-deficient chinese hamster ovary cell line cho(dhfr-). the 1tpa expression vector pcmvtpa was cotransfected either with the sv40 enhancer sequence containing dhfr expres ...19921524211
amplification and expression of heterologous oncostatin m in chinese hamster ovary cells.a stable chinese hamster ovary (cho) cell line producing high levels of human oncostatin m (om) was generated by transfecting a heterologous gene coding for the protein. this novel construct was comprised of the gene for the transforming growth factor-beta 1 (tgf-beta 1) signal peptide fused to the gene for mature human om. amplification with methotrexate produced milligram quantities of this recombinant om, which was processed correctly, glycosylated, and found to have biological functions simi ...19921524679
genotoxic properties of (e)-5-(2-bromovinyl)-2'-deoxyuridine (bvdu).(e)-5-(2-bromovinyl)-2'-deoxyuridine (bvdu)is a 5-substituted 2'-deoxyuridine antiviral compound that inhibits thymidylate synthetase. the selectivity of bvdu for virus-infected cells has been attributed to phosphorylation of bvdu by a virus-induced thymidine kinase. since the closely related compounds 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine are in vitro and in vivo mutagens, bvdu was tested for genotoxic activity in bacterial and mammalian cell mutation assays as well as in assays me ...19921526360
assessment of cytotoxicity assays as predictors of ocular irritation of pharmaceuticals.we have evaluated the use of cytotoxicity assays in vitro as an alternative to predicting ocular irritation potential in animals. three different measures of cytotoxicity--leucine incorporation into protein, mtt dye reduction, and neutral red uptake--were measured in a presumed target cell, corneal epithelial cells from rabbit, as well as in a nontarget cell, v79 (chinese hamster lung fibroblasts). an ic50 value was determined for each endpoint in one or both target cells for a series of 27 comm ...19921526363
assessment of the potential genotoxicity of perfluorodecanoic acid and chlorotrifluoroethylene trimer and tetramer acids.perfluoro-n-decanoic acid (pfda) is a perfluorinated fatty acid that produces hepatomegaly and increased peroxisomal beta-oxidation when administered to rodents. chlorotrifluoroethylene (ctfe) trimer acid and ctfe tetramer acid are metabolites of the six- and eight-carbon oligomers of ctfe, respectively. they are structurally related to pfda, and ctfe tetramer acid has caused toxic effects in rodents that are similar to those observed following pfda administration. because of the correlation bet ...19921526368
domains responsible for the differential targeting of glucose transporter isoforms.facilitative glucose transporter isoforms, glut1 and glut4, have different intracellular distributions despite their very similar structure. in insulin-responsive tissues such as adipose tissues and muscle, glut4 protein resides mainly in the intracellular region in a basal condition and is translocated to the plasma membrane upon stimulation of insulin. in contrast, glut1 protein was distributed about equally between plasma membranes and low density microsomal membranes in 3t3-l1 adipocytes. fu ...19921527083
expression and phosphorylation of a three-repeat isoform of tau in transfected non-neuronal cells.the neuronal microtubule-associated protein, tau, is expressed as a set of isoforms containing either three or four tandemly repeated 31-amino-acid motifs in the c-terminal half of the molecule that can bind to microtubules. three-repeat forms are the only ones expressed early in development. a single three-repeat isoform of tau has been stably expressed in non-neuronal cells which do not express endogenous tau. chinese hamster ovary (cho) cells were transfected with a full-length cdna coding fo ...19921530572
biochemical properties of recombinant single-chain urokinase-type plasminogen activator mutants with deletion of asn2 through phe157 and/or substitution of cys279 with ala.the contribution of the nh2-terminal polypeptide chain and of the cys148-cys279 interchain disulphide bond to the enzyme activity of urokinase-type plasminogen activator (u-pa) was studied using site-specific mutagenesis. recombinant single-chain u-pa (rscu-pa) variants were produced by transfecting chinese hamster ovary cells with cdna encoding des(asn2-phe157)rscu-pa (rscu-pa with deletion of asn2-phe157), [ala279]rscu-pa (rscu-pa with cys279----ala mutation) or des(asn2-phe157)[ala279]rscu-pa ...19921533368
two glucose transporter isoforms are sorted differentially and are expressed in distinct cellular compartments.rat glut4 (adipocyte/muscle-type glucose transporter) was expressed in two fibroblastic cell lines, chinese hamster ovary (cho) cells and 3t3-l1 fibroblasts, under the control of the methallothionein i promoter. although immunoblotting with a glut4-specific anti-peptide antibody demonstrated that the amount of glut4 expressed was comparable with that in 3t3-l1 adipocytes and rat adipose tissues, no increase in 2-deoxy-d-glucose uptake was observed in the basal state in fibroblasts. immunocytoche ...19921536658
loss of one asparagine-linked oligosaccharide from human transferrin receptors results in specific cleavage and association with the endoplasmic reticulum.the coding sequence for the human transferrin receptor gene has been mutated in order to abolish the attachment of the oligosaccharide closest to the transmembrane sequence. expression of the mutant receptor in chinese hamster ovary cells resulted, after analysis under nonreducing conditions, in an 85- and a 73-kda receptor species. after reduction, the 85-kda receptors were mostly converted to 73 kda, although with short labeling periods some 85-kda receptor remained suggesting that the mutated ...19921537870
cell-dependent posttranslational processing and secretion of recombinant mouse renin-2.in the dba/2 mouse submandibular gland (smg), renin is predominantly the expression product of the renin gene ren-2d. prorenin is synthesized and rapidly converted to a constitutively secreted single-chain intermediate, which is then processed to and stored as the mature two-chain (2c) form, which is released by regulated secretion. to evaluate whether the mode of renin processing is cell dependent, renin (ren-2d) complementary dna was stably integrated in the genome of chinese hamster ovary (ch ...19921539649
analysis of solvent control and 1-nitrosopyrene-induced chinese hamster ovary cell mutants by southern and northern blots and the polymerase chain reaction.1-nitrosopyrene, a metabolite of the tumorigenic environmental pollutant 1-nitropyrene, is a potent mutagen at the hprt locus in chinese hamster ovary (cho) cells. a single dna adduct, n-(deoxyguanosin-8-yl)-1-aminopyrene, is produced in cho cells treated with 1-nitrosopyrene, and this adduct is found in rats and mice exposed to 1-nitropyrene. in this study, the structure of the hprt gene and the structure and amount of hprt mrna were analyzed in 43 cho cell mutants (16 isolated from solvent con ...19921541256
isolation and partial characterization of a surface glycoconjugate of entamoeba histolytica.to study surface molecules of entamoeba histolytica we produced monoclonal antibodies from mice immunized with lysates from the pathogenic amebic strain hm1:imss, and screened them for the ability to inhibit e. histolytica adhesion. one monoclonal antibody, cc 8.6, was a potent inhibitor of amebic adhesion to a chinese hamster ovary cell line, and was capable of inhibiting hm1:imss mediated cytotoxicity by 50%. we found that monoclonal antibody cc 8.6 bound to an amebic glycoconjugate. the glyco ...19921542307
biological properties of some benzopsoralen derivatives.the biological activity of some benzopsoralen derivatives, prepared with the aim of obtaining new drugs for photochemotherapy, has been studied. the more interesting compounds are 4-hydroxymethyl-4',5'-benzopsoralen and 4-hydroxymethyl-4',5'-tetrahydro-benzopsoralen, which were found to be active in the dark also: dna and rna synthesis were both inhibited in ehrlich cells, even if in a partially reversible fashion, while protein synthesis remained unaffected. in chinese hamster ovary cells cultu ...19921542703
correlation of insulin receptor level with both insulin action and breakdown of a potential insulin mediator precursor; studies in cho cell-lines transfected with insulin receptor cdna.a phosphatidylinositol-glycan (pi-glycan) has been described previously that may serve as the precursor for a mediator of some of insulins actions. the present study further addresses the potential relevance of this compound by correlating its breakdown with other insulin actions in chinese hamster ovary (cho) cells which express different levels of insulin receptor. comparisons were drawn between parent cho cells expressing 3 x 10(3) receptors/cells and two cell-lines transfected with human ins ...19921543757
characterization of the central region containing the x-inactivation center and terminal region of the mouse x chromosome using irradiation and fusion gene transfer hybrids.the irradiation and fusion gene transfer (ifgt) procedure provides a means of isolating subchromosomal fragments for use in the mapping of loci and for cloning probes from a particular area of a chromosome. using this procedure, two large panels of somatic cell hybrids that contain mouse x chromosome (chr) fragments have been generated. these hybrid panels were generated by irradiating the monochromosomal mouse-hamster hybrid hybx, which retains the mouse x chr, with either 10 k or 50 k rads of ...19921543901
the mink gene for the lambda light immunoglobulin chain: characterization of cdna and chromosomal localization.a cdna library from mink spleen was constructed by use of the phage lambda gt11. the library was screened using polyvalent serum raised against the mink immunoglobulin lambda chain. as a result, several clones expressing mink immunoglobulin lambda light chains were identified. sequencing of one of the clones with an 803 bp insert was performed. the insert comprised nearly the entire coding region for the mature lambda light immunoglobulin gene with the exception of the leader polypeptide and sev ...19921543908
expression of human pituitary adenylate cyclase activating polypeptide (pacap) cdna in cho cells and characterization of the products.cdna encoding human pacap precursor was expressed in non-neuroendocrine chinese hamster ovary cells, cho-k1, the cells were transfected with expression vector (pts705) containing the human pacap cdna by electroporation. a cell line which produced more than 80 ng/ml of immunoreactive pacap (ir-pacap) into the conditioned medium was established. rp-hplc analysis of culture medium of this established cell line exhibited the presence of two types of pacap, i.e. pacap38 and pacap27. at the same time, ...19921544422
topical application of nitroxide protects radiation-induced alopecia in guinea pigs.we have recently found that treatment of chinese hamster v79 cells with the stable nitroxide radical tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) afforded significant protection against superoxide, hydrogen peroxide, and x-ray mediated cytotoxicity. radiation-induced alopecia is a common radiotherapeutic problem. topical application of tempol was evaluated for possible protective effects against radiation-induced alopecia using guinea pig skin as a model. for single acute x-ray doses ...19921544853
protection against azt-induced mutagenesis at the hgprt locus in a human cell line by wr-151326.the anti-aids agent, azt (3'-azido-3'-deoxythymidine), is mutagenic in a cultured human hepatoma cell line designated hepg2 at the hgprt (hypoxanthine-guanine phosphoribosyl transferase) locus. using an exposure time of 3 hr, the number of mutants per 10(6) surviving cells increased as a function of azt dose from 125 to 520. chinese hamster ovary cells, in contrast, are not affected with respect to this endpoint when similar concentrations of azt are used (i.e., 0.1 to 10 mg/ml). the aminothiol ...19921544855
mutagenic activity of arylnitrenium ions from arylazides--induction of sister chromatid exchange in mammalian (v79 chinese hamster) cells.photolysis of arylazides produces short-lived reactive species, very likely arylnitrenium ions which bind to nucleotides and dna and produce mutations in salmonella. the present report shows that arylazides can be photo-activated in mammalian (v79 chinese hamster) cells and that sister chromatid exchange can thus be induced. arylazides studied are (in order of decreasing sce-inducing potency) azido-isoiq, azido-meiq, azido-iq, azido-meiqx, azido-phip, 6-azido-chrysene, 2-azidofluorene, 4-azidofl ...19921547513
role of amino acids 261-418 in proteolytic cleavage of the extracellular region of the human thyrotropin receptor.previous in vivo cross-linking studies of tsh to the recombinant tsh receptor revealed that the receptor exists at least in part as a single chain glycoprotein of approximately about 100 kilodaltons (kda), with intramolecular disulfide bonds. tsh also binds to a 54-kda amino-terminal fragment of the tsh receptor (cleaved up-stream of amino acid residue 317). in the present study in order to better understand the structure of the tsh receptor, we covalently cross-linked radiolabeled tsh to six ts ...19921547731
methotrexate-induced overexpression of functional glucocorticoid receptors in chinese hamster ovary cells.we have used a modified cotransfection and selection strategy to create a series of mammalian cell lines that stably express high levels of intact glucocorticoid receptors. these cell lines were produced by subjecting chinese hamster ovary (cho) cells, which had been previously cotransfected with a glucocorticoid-responsive dihydrofolate reductase (dhfr) gene and the human glucocorticoid receptor gene, to growth in increasing concentrations of methotrexate (mtx). by linking the mtx selection pro ...19921547909
fine-structure map of the human ribosomal protein gene rps14.we have used polymerase chain reaction-mediated chemical mutagenesis (j.-j. diaz, d. d. rhoads, and d. j. roufa, biotechniques 11:204-211, 1991) to analyze the genetic fine structure of a human ribosomal protein gene, rps14. eighty-three dna clones containing 158 random single-base substitution mutations were isolated. mutant rps14 alleles were tested for biological activity by transfection into cultured chinese hamster cells. the resulting data permitted us to construct a map of the s14-coding ...19921549121
angiogenin supports endothelial and fibroblast cell adhesion.when coated on bacteriological plastic at doses greater than or equal to 0.1 microgram/cm2, human and bovine angiogenin support calf pulmonary artery endothelial and chinese hamster fibroblast cell adhesion and spreading, but do not affect cell adhesion when in solution. the kinetics of endothelial cell attachment to angiogenin are indistinguishable from those in the presence of gelatin. calcium and/or magnesium ions are critical for cell adhesion or spreading onto angiogenin but protein synthes ...19921549588
biochemical and immunological properties of rat recombinant interleukin-2 and interleukin-4.we have previously described the isolation and sequencing of cdna clones encoding rat interleukin-2 (il-2) and interleukin-4 (il-4). in the present study, we report the generation of stably transfected chinese hamster ovary (cho) cell lines which constitutively synthesize and secrete high levels of rat recombinant il-2 (ril-2) and il-4 (ril-4). the expression of the cytokine cdna sequences is driven by the human cytomegalovirus promoter/enhancer within the respective pee6. hcmv-gs vector constru ...19921551691
requirement for ercc-1 and ercc-3 gene products in dna excision repair in vitro. complementation using rodent and human cell extracts.numerous rodent cell lines exist that have defects in nucleotide excision repair of dna caused by alterations in genes that fall into 10 different complementation groups. the precise roles in the repair of these genes are unknown. we report here that extracts from chinese hamster ovary cells of excision repair-defective complementation groups 1 and 3 are defective in dna excision repair in a cell-free system. in vitro complementation can be achieved by mixing extracts from the two groups with on ...19921551896
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