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fjord- and bay-region diol-epoxides investigated for stability, sos induction in escherichia coli, and mutagenicity in salmonella typhimurium and mammalian cells.the fjord-region diol-epoxides of benzo(c)phenanthrene combine high mutagenic and carcinogenic activity with low chemical reactivity. to study whether this is a unique property of these compounds or a more general characteristic of fjord-region diol-epoxides, we have synthesized the anti- and syn-diastereomers of r-9,t-10-dihydroxy-11,12-oxy-9,10,11,12-tetrahydrobenzo(c)chrysene and r-11-t-12-dihydroxy-13,14-oxy-11,12,13,14-tetrahydrobenzo(g)chrysene. these compounds as well as the anti- and syn ...19911900215
thrombin cleavage analysis of a novel antihaemophilic factor variant, factor viii delta ii.factor viii delta ii is a genetically engineered deletion variant of factor viii expressed by recombinant chinese hamster ovary cells, in which a major portion of the central (b) domain and a part of the light chain (pro771-asp1666) are missing. after immunoaffinity purification, the kinetics of thrombin cleavage of the novel molecule was analysed by sds/page, western blotting and n-terminal amino acid sequencing. thrombin first cleaves factor viii delta ii at arg740-ser741 to generate the 90-kd ...19911900236
a uv-sensitive chinese hamster lung fibroblast cell line (v79/uc) with a possible defect in dna polymerase activity is deficient in dna repair.studies of repair enzyme activities in a uv-sensitive cell line (v79/uc) derived from chinese hamster v79 cells have revealed levels of total dna polymerase that are about 50% of the levels in the parental cell line. there are a number of dna polymerase inhibitors available which allow us to distinguish between the major forms of dna polymerase (alpha, beta, gamma, and delta) identified in mammalian cells. enzyme assays with these inhibitors indicate that the aphidicolin-sensitive dna polymerase ...19911900371
tissue plasminogen activator has an o-linked fucose attached to threonine-61 in the epidermal growth factor domain.an unusual type of glycosylation has been observed for tissue plasminogen activator (t-pa). the monosaccharide fucose is glycosidically linked to threonine-61 in the epidermal growth factor region of t-pa. the presence of o-linked fucose was demonstrated by carbohydrate analysis and mass spectrometry of tryptic and chymotryptic peptides that contain this site. the susceptibility of the fucose residue to alpha-fucosidase indicated that it was in the alpha-anomeric configuration. fucosylation of t ...19911900431
cytogenetic characterization of the ionizing radiation-sensitive chinese hamster mutant irs1.the x-ray-sensitive mutant v79 cell line irs1 was characterized with respect to chromosomal aberrations induced by 137cs, mitomycin c (mmc), and decarbamoyl mitomycin c (dcmmc). to measure chromosome damage induced at different cell cycle stages, irs1 and the parental v79-4 cell lines were pulse-labeled with bromodeoxyuridine (brdurd) at the time of exposure and harvested at various intervals corresponding to exposure in g1, s, and g2 phases of the cell cycle. metaphase spreads were stained with ...19911900570
isolation and characterization of nitrogen mustard-sensitive mutants of chinese hamster ovary cells.three nitrogen mustard-sensitive lines of chinese hamster ovary cells were isolated from mutagenized cultures using the procedure of thompson et al. (1980). the lines, designated nm1, nm2 and nm3, were 2.1-, 17- and 6.8-fold more sensitive to nitrogen mustard, respectively, than their parent, wild-type, line as determined by the dose required to kill 90% of the cells, ic90. patterns of cross-sensitivity to other dna-damaging agents including ultraviolet light, cis-diamminedichloroplatinum, and o ...19911900571
effect of ph on the activity and stability of clastogens in the in vitro chromosomal aberration test with chinese hamster ovary k1 cells.the effect of the ph of the medium on the clastogenic activity of several direct-acting and indirect clastogens was evaluated in the in vitro chromosomal aberration test with chinese hamster ovary k1 cells. furthermore, the stability of the chemicals in the cell culture medium was measured by hplc over the ph range of 5.0-11.0. the activity of the direct-acting clastogens mitomycin c (mmc), n-ethyl-n'-nitro-n-nitrosoguanidine (enng) and 4-nitroquinoline-1-oxide (4nqo) at various ph values depend ...19911900572
chinese hamster ovary cell lines resistant to mitomycin c under aerobic but not hypoxic conditions are deficient in dt-diaphorase.we have previously reported the isolation of cho cell lines resistant to mitomycin c under aerobic conditions of drug exposure. here it is reported that these cell lines have the same response to mitomycin c under hypoxic conditions as do controls. the cells are shown to have lower levels of dt-diaphorase activity than controls, but similar levels of activity of nadph:cytochrome c reductase, another enzyme involved in the metabolism of mitomycin c. evidence for molecular defects in the dt-diapho ...19911900739
the chinese hamster cell mutant v-h4 is homologous to fanconi anemia (complementation group a).v-h4, a mitomycin c (mmc)-sensitive chinese hamster cell mutant, is phenotypically very similar to fanconi anemia (fa) cells. genetic complementation analysis shows that v-h4 belongs to the same complementation group as fa group a cells. proliferating hybrid cell lines obtained after fusion of v-h4 with normal or fa group b cells show an increased resistance to mmc. absence of complementation was noted in v-h4 x fa group a hybrid cell lines. this was shown not to be due to the absence of a speci ...19911900747
the effect of partial hepatectomy on the genotoxicity of aflatoxin b1.the influence of partial hepatectomy on the genotoxic effect of aflatoxin b1 (afb1) mycotoxin in male chinese hamsters (cricetulus griseus) was studied after application of a single i.p. dose of 1.0 mg afb1/kg. changes in the fractions of proliferating bone marrow cells, values of the mitotic index of liver cells and morphologic changes in liver tissue were also monitored. partial hepatectomy reduced significantly the mutagenic activity of afb1 measured by the frequency of chromosome aberrations ...19911901385
gene for murine alpha 1----3-galactosyltransferase is located in the centromeric region of chromosome 2.the gene for alpha 1----3-galactosyltransferase, termed ggta-1, was mapped to mouse chromosome 2 by southern blot analysis of chinese hamster x mouse somatic cell hybrids. using an intersubspecies back-cross, this locus was positioned to the centromeric region on this chromosome, near the hc locus.19911901427
analysis of protein transport through the golgi in a reconstituted cell-free system.the processes which transport membrane proteins between compartments of the golgi apparatus have been reconstituted in vitro using isolated golgi fractions. this cell-free system allows a detailed analysis of protein transport not possible in intact cells. transport of the membrane glycoprotein (g protein) of vesicular stomatitis virus (vsv) is measured from a "donor" to an "acceptor" golgi fraction. the donor golgi fraction is prepared from vsv-infected chinese hamster ovary (cho) mutant cells ...19911901603
analysis of the genes involved in the insulin transmembrane mitogenic signal in chinese hamster ovary cells, cho-k1, utilizing insulin-independent mutants.cho-k1 cells, wild type (wt), grow in a defined medium with insulin as the only essential hormone. when starved for insulin, these cells accumulate in g0/g1 stage. insulin binding to its receptor stimulates dna synthesis and cell division and induces an increase in abundance of mrna for c-fos, c-jun, krox-20, krox-24 (zif/268), fra-1, jun-b, c-myc, and je. the kinetics of induction of these genes are similar to that shown with serum induction of 3t3. these genes show maximum stimulation at insul ...19911902566
genotoxic effects of the drinking water mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5h]-furanone (mx) in mammalian cells in vitro and in rats in vivo.the potent bacterial mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5h]- furanone) (mx), which is formed during chlorination of drinking water and accounts for about one third of the ames mutagenicity of tap water, has been studied with respect to its genotoxicity in vitro and in vivo. treatment with 30-300 microm mx (1 h) induced dna damage in a concentration-dependent manner in suspensions of rat hepatocytes, as measured by an automated alkaline elution system. the effect was similar in hepat ...19911902909
evaluation of the probability of spontaneous transfer of drug resistance between cells in culture.coculture of two different cell lines in monolayer or spheroids was used to investigate the spontaneous transfer of dominant genes determining drug resistance. mgh-u1 human bladder cancer cells (ouabain-sensitive, mitomycin c-resistant) were cocultured with uv-20 cells (a subline of chinese hamster ovary cells which is ouabain-resistant and mitomycin c-sensitive). we investigated the possible transfer of mitomycin-c resistance from human to rodent cells by selection in both ouabain and mitomycin ...19911903383
expression, isolation, and characterization of an active site (serine 528----alanine) mutant of recombinant bovine prothrombin.an active site mutant bovine prothrombin cdna (ser528----ala) has been constructed, subcloned, and expressed in chinese hamster ovary cells. the recombinant mutant prothrombin, expressed at the level of 1.5-2.0 micrograms/ml of cell medium, was fully carboxylated (9.9 +/- 0.4 mol of gamma-carboxyglutamic acid/mol of prothrombin). the mutant prothrombin could be activated to thrombin by taipan snake venom and activated to meizothrombin by ecarin in a manner comparable to native bovine prothrombin ...19911903392
effect of pd 128763, a new potent inhibitor of poly(adp-ribose) polymerase, on x-ray-induced cellular recovery processes in chinese hamster v79 cells.the modifying effects of pd 128763 (3,4-dihydro-5-methyl-1(2h)-isoquinolinone), a potent inhibitor of poly(adenosine-diphosphate (adp)-ribose) polymerase, on radiation-induced cell killing were examined in chinese hamster v79 cells. this compound has an ic50 value against the purified enzyme approximately 50x lower than 3-aminobenzamide (3-ab), a widely used specific inhibitor of the enzyme. exposure of exponentially growing cells to a noncytotoxic concentration (0.5 mm) of pd 128763 for 2 h imm ...19911903547
electrotransfer of [32p]nad allows labeling of adp-ribosylated proteins in intact chinese hamster ovary cells.cho-k1d cells electroporated in buffers containing [32p]nad incorporated the label in a voltage-dependent manner. electroporation with 650 v/cm at 1460 microf in ham's f12 medium supplemented with 10 mm hepes, ph 7.1, resulted in a greater than 20-fold increase in [32p]nad uptake, while decreasing relative cellular survival by only 6%. exposure of cells to gamma irradiation (20 gy) prior to electroporation increased the steady-state level of poly(adp-ribosylated) nuclear proteins two- to four-fo ...19911903609
metabolic formation, synthesis and genotoxicity of the n-hydroxy derivative of the food mutagen 2-amino-1-methyl-6-phenylimidazo (4,5-b) pyridine (phip).hepatic microsomes from rats pretreated with pcb were found to metabolize the food mutagen 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (phip) to two major metabolites, one of which was identified as the n-hydroxy derivative, 2-hydroxy-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (n-oh-phip). this identification was based on mass spectral (ms), uv and hplc data by comparison with n-oh-phip prepared by chemical synthesis, as well as the specific activity of the compound in the ames salmonella ...19911903830
cultured human fibroblasts contain a large pool of precursor beta 1-integrin but lack an intracellular pool of mature subunit.previous work has shown the presence of an important intracellular pool of beta 1-integrin subunit in human skin fibroblasts as detected with monoclonal antibody dh12 [de strooper, b., van der schueren, b., jaspers, m., saison, m., spaepen, m., van leuven, f., van den berghe, h. & cassiman, j. j. (1989) j. histochem. cytochem. 37,299-307]. to analyze this more quantitatively, a radioimmunoassay with radioiodinated monoclonal antibody was developed. the total amount of specific binding sites for ...19911906002
carbachol-activated muscarinic (m1 and m3) receptors transfected into chinese hamster ovary cells inhibit trafficking of endosomes.we examined the effects of isoproterenol and carbachol on fluid-phase endocytosis by chinese hamster ovary (cho) cells transfected with beta-adrenergic, m1, or m3 cholinergic receptors. isoproterenol increased camp production and carbachol increased intracellular ca, indicating successful expression of the receptor genes and coupling to typical signal transduction pathways. carbachol inhibited the uptake of horseradish peroxidase (hrp) or lucifer yellow (markers of fluid-phase endocytosis) in bo ...19911906173
inhibition of degradation of 3-hydroxy-3-methylglutaryl-coenzyme a reductase in vivo by cysteine protease inhibitors.3-hydroxy-3-methylglutaryl-coenzyme a (hmg-coa) reductase is a key regulatory enzyme of cholesterol biosynthesis and is located in the endoplasmic reticulum (er). a fusion protein, hmgal, consisting of the membrane domain of hmg-coa reductase fused to escherichia coli beta-galactosidase and expressed in chinese hamster ovary (cho) cells from the sv40 promoter, was previously constructed and was found to respond to regulatory signals for degradation in a similar fashion to the intact hmg-coa redu ...19911906466
recombinant expression of human follistatin with 315 and 288 amino acids: chemical and biological comparison with native porcine follistatin.follistatin is a glycosylated monomeric protein originally isolated from ovarian follicular fluid based on its ability to specifically inhibit pituitary fsh release. to further explore the physiological role of follistatin, we have expressed recombinant human follistatins with 315 (rhfs-315) and 288 (rhfs-288) amino acids in chinese hamster ovary cells under the control of the simian virus-40 promoter. the two types of fs originated from alternatively spliced mrnas and rhfs-315 differed from rhf ...19911906804
gtpase-deficient g alpha i2 oncogene gip2 inhibits adenylylcyclase and attenuates receptor-stimulated phospholipase a2 activity.the gtpase activity of a g protein alpha subunit functions as a timer to control the lifetime of the activated conformation of the protein. expression of the gtpase-deficient gi2 alpha subunit oncogene, gip2 (alpha i2q205l), in chinese hamster ovary cells inhibited the stimulation of adenylylcyclase and altered the calcium regulation of the gi2-phospholipase a2 (pla2) effector complex. the phenotypic consequence of the activated alpha i2 mutant on hormonal stimulation of pla2 varied depending on ...19911907271
changes in cell cycle distribution of v79 chinese hamster fibroblasts after irradiation at different wavelengths.changes in cell cycle distribution of v79 chinese hamster fibroblasts were investigated at different wavelengths between 254 and 313 nm. the fluences applied led to surviving fractions of 0.61. in all cases, the s fraction was temporarily increased within 8-12 h after irradiation, whereas the g1 fraction was decreased. the maximum deviations from the initial values did not significantly depend on the wavelength.19911907649
polyol pathway in tissues of spontaneously diabetic chinese hamsters (cricetulus griseus) and the effect of an aldose reductase inhibitor, ono-2235.1. sorbitol and fructose levels were significantly elevated in the lens, the sciatic nerve, the retina and the kidney of diabetic chinese hamsters and inositol level was significantly decreased in the lens and sciatic nerve of diabetics. 2. the activity of an aldose reductase in the kidney was not different between normal and diabetic chinese hamsters. 3. an aldose reductase inhibitor (ono-2235) had no effect in sorbitol, fructose and inositol contents of all these tissues from diabetic chinese ...19911907900
molecular cloning and characterization of a complete chinese hamster provirus related to intracisternal a particle genomes.we report here the nucleotide sequence of a full-length chinese hamster genomic proviral element, chiap34. chiap34 is 6,403 bp long with long terminal repeats of 311 bp at each end. the genetic organization of chiap34 was determined by comparison with intracisternal a particle (iap) genetic elements from the mouse and syrian hamster. extensive homology at the nucleotide and deduced amino acid sequence levels was observed between chiap34 and the mouse and syrian hamster iap elements. chiap34 may ...19911908027
severe cachexia in mice inoculated with interferon-gamma-producing tumor cells.nude mice were inoculated with cho/ifn-gamma cells, a line of chinese hamster ovary tumor cells, that had been genetically engineered to produce murine ifn-gamma. severe cachexia, as evident from body weight loss and reduced food intake, occurred in these mice, but not in those injected with cho/control cells, i.e. the original, non-ifn-gamma-producing line. the essential role of ifn-gamma in the pathogenesis of cachexia was confirmed by the demonstration that monoclonal antibodies (mabs) agains ...19911908442
decreased clastogenicity of dinitropyrenes in chinese hamster lung (chl) subclone cells with low nadph-cytochrome p-450 reductase activity.clastogenic potentials of 1,3-, 1,6- and 1,8-dinitropyrenes (dnps) were compared between chinese hamster lung (chl) cells and its subclone mm1 cells, which were recently isolated as menadione-resistant cells after treatment with mnng. nadph-cytochrome p-450 reductase activity of the mm1 cells decreased to 50% of that in the parental chl cells. all 3 dnps induced chromosomal aberrations without exogenous metabolic activation systems in the chl cells. 1,6- and 1,8-dnp showed equivalent clastogenic ...19911908946
secretion of the beta/a4 amyloid precursor protein. identification of a cleavage site in cultured mammalian cells.alzheimer's disease, a progressive neurodegenerative disorder, affects greater than 10% of the population of individuals greater than 65 years of age. a principal neuropathological feature of this disease is the senile plaque, a fibrillar extracellular deposit primarily composed of a approximately 4-kda peptide, beta/a4, derived from the amyloid precursor protein (app). studies in cultured cells have documented that app matures through a constitutive secretory pathway and is cleaved at or near t ...19911909332
dopamine activation of the arachidonic acid cascade as a basis for d1/d2 receptor synergism.understanding the actions of the neurotransmitter dopamine in the brain is important in view of its roles in neuropsychiatric illnesses. dopamine d1 receptors, which stimulate both adenylyl cyclase and phospholipase c, and d2 receptors, which inhibit them, can nevertheless act synergistically to produce many electrophysiological and behavioral responses. because this functional synergism can occur at the level of single neurons, another, as yet unidentified, signalling pathway activated by dopam ...19911909771
quantitative immunocytochemical staining for recombinant tissue-type plasminogen activator in transfected chinese hamster ovary cells.tissue-type plasminogen activator (tpa) is a serine protease which cleaves plasminogen to its active form, plasmin. tpa plays a physiologic role in hemostasis, wound healing, and embryogenesis. therapeutically, recombinant human tpa is used as a thrombolytic in myocardial infarction. although production of therapeutic quantities of tpa in chinese hamster ovary (cho) cells transfected with the human gene for tpa is practical, production costs remain high. one important factor which determines the ...19911909792
inhibition by 2,6-dithiopurine and thiopurinol of binding of a benzo(a)pyrene diol epoxide to dna in mouse epidermis and of the initiation phase of two-stage tumorigenesis.the chemotherapeutic agent 6-mercaptopurine was previously shown to inhibit the binding of 7r,8t-dihydroxy-9,10t-oxy-7,8,9,10-tetrahydro-benzo(a) pyrene (bpde-i) to dna in chinese hamster ovary cells. two compounds related to 6-mercaptopurine, 2,6-dithiopurine (dtp) and thiopurinol (tp), have been tested for inhibition of the binding of bpde-i to epidermal dna in mouse skin. doses of test compound (0.2-20 mumol) or solvent control were applied to the shaved backs of female sencar mice. fifteen m ...19911909930
differential locus sensitivity to mutation induction by ionizing radiations of different lets in chinese hamster ovary k1 cells.mutation induction after exposures to 250 kvp x-rays, alpha-particles from the radon daughter 212bi, and fission-spectrum neutrons from the janus reactor was studied in chinese hamster ovary (cho) k1 cells and in cho-10t5, a k1 derivative containing the bacterial gene xanthine-guanine phosphoribosyl transferase (gpt). mutation induction was analyzed at three genetic loci: the gpt locus, the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus, and the thymidine kinase (tk) locus. after x ...19911909939
anthrax protective antigen interacts with a specific receptor on the surface of cho-k1 cells.the interaction of protective antigen (pa), a component of the anthrax toxin, with receptors on the chinese hamster ovary cell line cho-k1 was characterized. protective antigen binding at 4 degrees c is highly specific, concentration dependent, saturable (kd = 0.9 nm), and reversible. scatchard analysis indicates the presence of a single class of pa binding sites at a concentration of 10,000 +/- 2,000 per cell. pretreatment of cells with a number of different proteases strongly inhibits pa bindi ...19911909998
slit scan flow cytometry of isolated chromosomes following fluorescence hybridization: an approach of online screening for specific chromosomes and chromosome translocations.the recently developed methods of non radioactive in situ hybridization of chromosomes offer new aspects for chromosome analysis. fluorescent labelling of hybridized chromosomes or chromosomal subregions allows to facilitate considerably the detection of specific chromosomal abnormalities. for many biomedical applications (e.g. biological dosimetry in the low dose range), a fast scoring for aberrations (e.g. dicentrics or translocations) in required. here, we present an approach depending on flu ...19911910388
overexpression of low density lipoprotein receptor on chinese hamster ovary cells generates foam cells.the atherosclerotic lesion is characterized by the presence of cholesterol-loaded foam cells. chinese hamster ovary (cho) cells do not normally store cholesteryl esters because low density lipoprotein (ldl) receptors are suppressed by exposure of these cells to ldl cholesterol. we transfected ldl receptor cdna linked to the simian virus 40 early promoter into cho cells (cho 29) and found that ldl receptor binding in these cells was not suppressed by an excess amount of ldl cholesterol, indicatin ...19911911717
evidence for the involvement of endogenous thymidine in the density-inhibition of tumorigenic chinese hamster v79 cells.two distinct low-molecular-weight growth inhibitory activities were isolated from supernatants of a density-inhibited, tumorigenic v79 chinese hamster cell line. by chromatographic analyses, one of these was purified to homogeneity and eventually proved to be thymidine (dthd). in order to investigate the biological role of dthd in a density-inhibited culture of these cells, a dthd-kinase deficient (tk-) clone resistant to the excess of dthd was isolated from v79 cells and the effect of the super ...19911911877
increased survival after treatments with anticancer agents of chinese hamster cells expressing the human mr 27,000 heat shock protein.a family of 10 thermoresistant cell lines cloned from chinese hamster cells transfected with a plasmid containing the structural gene for the small human mr 27,000 heat shock protein (hsp27) was used to assess the putative role of this heat shock protein in chemoresistance. these cells express varying amounts of human hsp27 in addition to the normal level of endogenous hamster hsp27. as previously observed in the case of thermoresistance, a significant positive linear correlation (p less than 0. ...19911913647
cell-cycle specific cytotoxicity mediated by stizophyllin (2 alpha,3 beta,12 beta-trihydroxypregna-4,7,16-trien-20-one), a novel electrophilic pregnane isolated from stizophyllum riparium.a structurally-novel pregnane derivative, 2 alpha,3 beta,12 beta-trihydroxypregna-4,7,16-trien-20-one (stizophyllin), was isolated from an extract of stizophyllum riparium (h.b.k.) sandw. on the basis of bioactivity-guided fractionation and confirmed to mediate a potent cytotoxic response with cultured p-388 cells. we presently report a detailed isolation procedure and the results of studies designed to examine its mechanism of action. by means of a michael-type addition, stizophyllin formed add ...19911913978
antimutagenic activities of naturally occurring polyamines in chinese hamster ovary cells in vitro.spermine and spermidine, ubiquitous polyamines present in bacteria and animal cells, are also involved in cell growth. since they interact with the double helix, they can stabilize the dna molecule. recent evidence of the antimutagenic and anticarcinogenic capacity of spermine has focused attention on the mechanism(s) by which such agents can protect cells from induced damages. in the present paper we show the ability of spermine and spermidine to decrease the level of sister chromatid exchanges ...19911915315
identification of the cdna clone which encodes the 58-kda protein containing the amino acid sequence of rat liver non-specific lipid-transfer protein (sterol-carrier protein 2). homology with rat peroxisomal and mitochondrial 3-oxoacyl-coa thiolases.the relationship between the rat liver non-specific lipid-transfer protein (nsltp) and the 58-kda protein cross-reactive with anti-nsltp antibodies, was investigated by cdna analysis. a 1945-bp cdna clone was isolated which encodes a 58.7-kda protein. this protein is identical to the 58-kda immunoreactive protein determined by n-terminal sequence analysis of the purified 58-kda protein. it consists of 546 amino acid residues, of which the 123 c-terminal residues are identical to the sequence of ...19911915369
cloning and expression of human ciliary neurotrophic factor.ciliary neurotrophic factor (cntf) is a survival factor for avian ciliary ganglion neurons and a variety of other neuronal cell types in vitro. we report here the cloning of the entire genomic sequence encoding human cntf and its primary structure. biologically active cntf has been expressed in chinese hamster ovary cells from a human genomic dna clone. human cntf has no significant sequence similarity to any previously reported protein, although approximately 84% similarity exists compared with ...19911915374
interferon-gamma inhibits serotonin release from mouse peritoneal mast cells.conditioned medium (cm) from concanavalin a-activated mouse spleen cells inhibits antigen-induced 5-hydroxytryptamine (5-ht) release from mouse peritoneal mast cells when added for 24 or 48 h to cell cultures containing monoclonal ige sensitizing antibody. we present the following evidence that the spleen cell-derived inhibitory factor is interferon-gamma (ifn-gamma): (a) cm from con a-activated spleen cells and from chinese hamster ovary (cho) cells transfected with the murine (mu)ifn-gamma gen ...19911915558
effects of cholesterol- or 7-ketocholesterol-containing liposomes on colony-forming ability of cultured cells.experiments with cultured chinese hamster cells showed that incubation of the cells with (phosphatidylcholine + cholesterol + 7-ketocholesterol)-containing liposomes (4:3:1 by weight) during two hours led to a decrease in the colony-forming ability of cells down to zero, while (phosphatidylcholine + cholesterol)-containing liposomes (1:1 by weight) reduce this parameter by 90%. furthermore, the cholesterol-containing liposomes (without 7-ketocholesterol) induce a decrease in the number of the ma ...19911915871
localization of the xeroderma pigmentosum group b-correcting gene ercc3 to human chromosome 2q21.the human excision-repair gene ercc3 was cloned after dna-mediated gene transfer to the uv-sensitive chinese hamster ovary mutant cell line 27-1, a member of complementation group 3 of the excision-defective rodent cell lines. the ercc3 gene specifically corrects the dna repair defect of xeroderma pigmentosum (xp) complementation group b, which displays the clinical symptoms of xp as well as of another rare excision-repair disorder, cockayne syndrome. the gene encodes a presumed dna and chromati ...19911916809
an amino acid substitution in biobreeding rat corticosteroid binding globulin results in reduced steroid binding affinity.biobreeding (bb) rats are derived from an outbred colony of wistar rats and are used as a model of autoimmune diabetes mellitus. a corticosteroid binding globulin (cbg) variant with reduced affinity for glucocorticoids has now been found in the blood of these animals. the dissociation rate constants of bb cbg for cortisol (4.42 nm) and corticosterone (1.43 nm) are both about 50% higher than those associated with wistar cbg, but no obvious difference in the steroid binding specificity of bb and w ...19911917978
mouse submandibular gland prorenin-converting enzyme is a member of glandular kallikrein family.mouse submandibular gland prorenin-converting enzyme (prece) consists of the two polypeptide chains of 17 and 10 kda and cleaves mouse ren-2 prorenin at a dibasic site to yield mature renin. western blot analysis using an antiserum against this enzyme gave rise to multiple bands in mouse submandibular glands, suggesting that prece is a member of a protease family. partial amino acid sequence analysis of purified prece and cloning and sequence analyses of its cdna indicated that it is identical t ...19911918045
role of the invariant aspartic acid 99 of human choriogonadotropin beta in receptor binding and biological activity.the four human glycoprotein hormones are heterodimers that contain a common alpha subunit and a hormone-specific beta subunit. within this hormone family, 23 amino acid sequences from 11 mammalian species are available. there are 19 invariant amino acid residues in the beta subunits, 12 of which are cys that form six disulfide bonds. of the remaining seven conserved amino acid residues, we have investigated the role of an asp which occurs at position 99 in human choriogonadotropin beta (hcg beta ...19911918051
evidence that erythroid-type glucose transporter intrinsic activity is modulated by cadmium treatment of mouse 3t3-l1 cells.previous studies suggest that regulation of hexose uptake in chinese hamster ovary fibroblasts can occur by alterations in glucose transporter intrinsic activity without changes in cell surface transporter number (harrison, s. a., buxton, j. m., helgerson, a. l., macdonald, r. g., chlapowski, f. j., carruthers, a., and czech, m. p. (1990) j. biol. chem. 265, 5793-5801). we tested this hypothesis using 3t3-l1 fibroblasts and adipocytes which exhibit 5-6-fold increases in 2-deoxyglucose or 3-o-met ...19911918056
dna-mediated transfer of a human gene that confers resistance to mitomycin c.attempts to complement the defect in the mitomycin c (mmc)-sensitive chinese hamster ovary (cho) mutant mmc3 led to the isolation of hybrids with high resistance to the cytotoxic action of the drug. hybrid cells selected with mmc after fusion of mmc3 cells to human diploid fibroblasts were approximately five times more resistant to mmc than wild-type cho cells but retained the original mmc3 sensitivity to another dna cross-linking agent, diepoxybutane. to confirm that the mmc resistance was gene ...19911918174
chinese hamster ovary cell assays for mutation and chromosome damage: data from non-carcinogens.in vitro genotoxicity tests are employed to screen chemicals for their capability to cause various dna and chromosomal alterations, and the results are often used to predict their potential for carcinogenicity. however, there is controversy regarding the apparent low specificity of some in vitro genotoxicity assays, which result in a high false positive rate. since we use and rely upon in vitro assays for risk assessment and prediction of carcinogenicity, this specificity issue is of serious con ...19911918790
the hiv-1 gp120 envelope protein has the intrinsic capacity to stimulate monokine secretion.results and conclusions concerning the ability of hiv glycoprotein (gp) 120 to stimulate monokine secretion have been equivocal, based on observations using natural gp120 derived from infected human cells and a chinese hamster ovary (cho) cell-derived recombinant fusion protein. current studies were designed to determine whether differences in recombinant gp120 proteins could result in failure to trigger monokine production. we found that natural gp120 could stimulate monocytes to release tnf-al ...19911918997
effect of chronically induced thermotolerance on thermosensitization in cho cells.chronic thermotolerance was induced in chinese hamster ovary (cho) cells by pretreatment at 40 degrees c for various times ranging from 15 min to 16 h. the thermotolerant cells were either exposed to single heat treatments at 43 degrees c or subjected to step-down heating consisting of a priming treatment at 43 degrees c for 90 min immediately followed by a graded test treatment at 40 degrees c. the results showed that chronic thermotolerance affected the thermal sensitivity of step-down-heated ...20081919157
molecular evolution of the mammalian ribosomal protein gene, rps14.ribosomal protein s14 genes (rps14) in eukaryotic species from protozoa to primates exhibit dramatically different intron-exon structures yet share homologous polypeptide-coding sequences. to recognize common features of rps14 gene architectures in closely related mammalian species and to evaluate similarities in their noncoding dna sequences, we isolated the intron-containing s14 locus from chinese hamster ovary (cho) cell dna by using a pcr strategy and compared it with human rps14. we found t ...19911921707
latent forms of transforming growth factor-beta (tgf beta) derived from bone cultures: identification of a naturally occurring 100-kda complex with similarity to recombinant latent tgf beta.transforming growth factor-beta (tgf beta) is produced by most tissues, including bone, as a complex that is biologically inert. release of tgf beta homodimer from this latent complex is necessary for tgf beta to exert effects on target cells. thus, the nature of the latent complex and the mechanisms responsible for tgf beta release are the key to understanding tgf beta actions. we have found that murine calvarial bone cultures secrete multiple latent forms of tgf beta. using analytical chromato ...19911922093
the origin of o6-methylguanine-dna methyltransferase in chinese hamster ovary cells transfected with human dna.transfection of chinese hamster ovary (cho) cells with human dna has been shown in several laboratories to produce clones which stably express the dna-repair protein, o6-methylguanine-dna methyltransferase (mgmt), that is lacking in the parent cell lines (mex- phenotype). we have investigated the genetic origin of the mgmt in a number of such mgmt-positive (mex+) clones by using human mgmt cdna and anti-human mgmt antibodies as probes. none of the five independently isolated mex+ lines has human ...19911922149
the genetic defect in the chinese hamster ovary cell mutant uv61 permits moderate selective repair of cyclobutane pyrimidine dimers in an expressed gene.we examined removal of cyclobutane pyrimidine dimers (cpds) from the dihydrofolate reductase (dhfr) gene in ultraviolet-irradiated chinese hamster ovary (cho) uv61 and uv5 cells. the sensitivity of uv61 cells to uv-irradiation is intermediate between that of the parental cho cells and that of mutants such as uv5 that are highly defective in excision repair. uv61 cells have been characterized as having normal repair of pyrimidine(6-4)pyrimidone photoproducts (6-4 pps) but no detectable removal of ...19911922150
genotoxicity testing of extracts of a swedish moist oral snuff.the present study was designed to investigate the potential genotoxicity of aqueous and methylene chloride extracts of swedish moist oral snuff. the test systems were selected to provide optimal data for the prediction of carcinogenicity in rodents and included assays for the induction of mutation in bacteria, sister-chromatid exchanges (sce) in human lymphocytes, of chromosome aberrations and gene mutations in v79 chinese hamster cells and of micronuclei in mouse bone marrow cells. in addition, ...19911922153
the effects of ventilation and the dilution of smoke upon the clastogenic and aneugenic activity of tobacco particulate matter in cultured mammalian cells.we demonstrate here that tobacco particulate matter (tpm) produced from both non-ventilated and ventilated cigarettes of varying tar contents induced structural and numerical aberrations in cultured chinese hamster cells. our data indicate that tpm from ventilated cigarettes is of lower potency in inducing both clastogenic and aneugenic effects compared with tpm from non-ventilated cigarettes. these observations provide support for the concept that the genotoxic activity (to cultured chinese ham ...19911922161
functional analysis of the tobacco mosaic virus trna-like structure in cytoplasmic gene regulation.the 3'-untranslated region (utr) of tobacco mosaic virus (tmv), which terminates in a trna-like structure, functionally substitutes for a poly(a) tail in both plant and animal cells. the addition of the tmv 3'-utr to chimeric mrna constructs increases their expression up to 100-fold, increasing both translational efficiency and mrna stability. the domain largely responsible for the regulation maps to a 72 base region immediately upstream of the trna-like structure, however, the 3'-terminal, trna ...19911923770
characterization of chinese hamster ovary cells stably transformed by a plasmid with an inducible aprt gene.a plasmid was constructed by fusion of a selectable mammalian gene, hamster adenine phosphoribosyltransferase (aprt), to the zn(2+)-inducible sheep metallothionein i (mt i) promoter. this plasmid was used to produce stable chinese hamster ovary (cho) cell transformants by electroporation to study the effects of induced gene expression on dna-mediated transformation. the sheep mt ia promoter was chosen for these experiments because it regulates gene expression differently than murine mt promoters ...19911924558
effects of procaine on the intracellular ph of chinese hamster ovary cells heated at 42.0 or 45.0 degrees c.the local anesthetic procaine greatly sensitizes cells to hyperthermia. though it is generally accepted that procaine is a membrane-active agent that increases membrane fluidity in cells, the mechanism by which it potentiates heat killing is unknown. in this paper we report changes in intracellular ph (phi) of chinese hamster ovary (cho) cells heated at 42.0 or 45.0 degrees c in the presence of procaine. the phi was measured with flow cytometry using the dye 1,4-diacetoxy-2,3-dicyanobenzene (adb ...19911924724
basic radiobiological investigations of fast neutrons.the radiobiological properties of a cyclotron-produced 43-mev (p----be) fast-neutron beam relative to gamma rays have been investigated using chinese hamster v79 cells in culture. as expected, the relative biological effectiveness (rbe) of this neutron beam for cell killing was shown to increase as dose decreased, and the effectiveness per unit dose was slightly less compared to a 25-mev (d----be) neutron beam. by tracing single cells that formed microcolonies after irradiation, we found cell pr ...19911924757
effect of backscatter on cell survival for a clinical electron beam.relative to homogeneous scattering conditions in tissue-like materials, a large increase in dose for clinical electron beams can occur upstream from high atomic number heterogeneities due to backscattered electrons. the degree of this dose increase is uncertain due to the unknown energy distribution of the backscattered electron fluence. cell survival after irradiation was studied for chinese hamster cells at the depth of maximum dose in a clinical 6 mev electron beam under normal scattering con ...19911924865
a linear-quadratic model of cell survival considering both sublethal and potentially lethal radiation damage.we assessed the dose-dependence of repair of potentially lethal damage in chinese hamster ovary cells x-irradiated in vitro. the recovery ratio (rr) by which survival (sf) of the irradiated cells was enhanced increased exponentially with a linear and a quadratic component, namely xi and psi: rr = e xi d + psi d2. survival of irradiated cells can thus be expressed by a combined linear-quadratic model considering four variable, namely alpha and beta for the capacity of the cells to accumulate subl ...20071924866
synthesis and characterization of a pertussis toxin-biotin conjugate.we prepared a pertussis toxin-biotin conjugate and found its biological properties to be similar to those of native pertussis toxin with respect to the hemagglutination, chinese hamster ovary cell, and lymphocyte proliferation assays. direct binding to chinese hamster ovary and jurkat cells was observed using fluorescence microscopy. pertussis toxin-biotin was also found to possess similar glycoconjugate binding specificities as those of 125i-labeled pertussis toxin.19911930187
molecular cloning of chinese hamster metallothionein ii gene and its 5' flanking region.a genomic dna clone containing chinese hamster metallothionein ii (mtii) gene and its 5' flanking region was isolated from cd resistant chinese hamster ovary (cho) cells. dna sequence analysis showed that there are three exons and two introns in the structure of the mtii gene. further characterization of the 5' flanking region reveals the possible transcription initiation site, metal responsive element and basal-level enhancer sequence. putatively, this is the promoter region of cho mtii gene.19911932120
purification and characterization of natural human interleukin-3.the human interleukin-3 gene was cloned in 1986 and the biochemical and biological properties of recombinant human interleukin-3 (rhuil-3) protein were described. in this report we compare rhuil-3 with nonrecombinant, natural huil-3, purified from the supernatant of the human t cell leukemia line jurkat. the main purification step, affinity chromatography, using a selected monoclonal anti-huil-3 antibody, resulted in an approximately 40,000-fold enrichment of huil-3. combination of this step wit ...19911932378
hyperthermic sensitivity and cholesterol levels of mammalian cell lines in culture.in this study, we asked whether cholesterol contents were specifically correlated with cellular sensitivity to hyperthermia. to examine this possibility, we employed two isogenic mammalian cell lines, chinese hamster v79 cell line and its amphotericin b-resistant (ambr) cell line. ambr cells had a decreased content of membrane sterols in comparison with v79 cells. clonogenic assays showed that ambr cells were more sensitive to hyperthermic treatment at 45 degrees c than v79 cells. cholesterol co ...19911933839
correspondence re: michiel m. van lookeren campagne et al., 8-chloroadenosine 3',5'-monophosphate inhibits the growth of chinese hamster ovary and molt-4 cells through its adenosine metabolite. cancer res., 51: 1600-1605, 1991. 19911933880
relationship between mutagenicity and dna adduct formation in mammalian cells for fjord- and bay-region diol-epoxides of polycyclic aromatic hydrocarbons.chinese hamster v79 cells were treated with the anti- and syn-diastereomers of the bay- or fjord-region diol-epoxides of four polycyclic aromatic hydrocarbons, namely benzo[a]pyrene (bp), benzo[c]chrysene (bcc), benzo[g]chrysene (bgc) and benzo[c]phenanthrene (bcph). the frequency of induction of 6-thioguanine-resistant mutations was determined, and the extent of formation of dna adducts was measured by 32p-postlabelling. when expressed as mutation frequency per nanomoles compound per millilitre ...19911934148
site specificity of n-methyl-n-nitrosourea-induced transition mutations in the hprt gene.the reaction product of n-methyl-n-nitrosourea (mnu) with dna, o6-methylguanine (o6-meg), is responsible for the mutagenic and carcinogenic effects of this carcinogen. these involve activation of the h-ras proto-oncogene in rat mammary tumors by mnu, with a high frequency of gc to at transitions in codon 12 of this gene. the present study aimed to investigate the types and position specificities of mutations induced by mnu in another gene, the hprt gene of v79 chinese hamster cells. furthermore, ...19911934271
comparative in vitro and in vivo studies on the biological characteristics of recombinant human follicle-stimulating hormone.the in vitro and in vivo activities of recombinant human fsh (recfsh) produced by a chinese hamster ovary cell line were studied and compared with those of natural fsh preparations. the specific fsh activities of recfsh established by immunoassay and in vivo bioassay were greater than 10,000 iu/mg protein and considerably higher than the activities of tested urinary fsh references, while the in vivo bio/immuno ratios of these preparations were not significantly different. compared to a highly pu ...19911935792
dna-protein complexes induced by chromate and other carcinogens.dna-protein complexes induced in intact chinese hamster ovary cells by chromate have been isolated, analyzed, and compared with those induced by cis-platinum, ultraviolet light, and formaldehyde. actin has been identified as one of the major proteins complexed to dna by chromate based upon its molecular weight, isoelectric point, positive reaction with an actin polyclonal antibody, and proteolytic mapping. chromate and cis-platinum both complex proteins of similar molecular weight and isoelectri ...19911935851
effects of vitamins on chromium(vi)-induced damage.the effects of vitamin e and vitamin b2 on dna damage and cellular reduction of chromium(vi) were investigated using chinese hamster v-79 cells. pretreatment with alpha-tocopherol succinate (vitamin e) resulted in a decrease of dna single-strand breaks produced by na2cro4, while similar treatment with riboflavin (vitamin b2) enhanced levels of dna breaks. in contrast, levels of dna-protein crosslinks induced by na2cro4 were unaffected by these vitamins. electron spin resonance (esr) studies show ...19911935852
overexpression of an immunologically-intact, secreted form of human thyroid peroxidase in eukaryotic cells.recombinant human thyroid peroxidase (htpo) has been expressed in eukaryotic cells as both the membrane-associated enzyme and as a secreted protein. we now report overexpression of the secreted form of recombinant htpo in eukaryotic cells. for htpo gene amplification we used a vector containing the mouse dihydrofolate reductase (dhfr) gene. stably transfected chinese hamster ovary (cho) cells were grown in the presence of increasing concentrations of methotrexate (mtx) and htpo expression was me ...19911936519
effects of hypoxia and reoxygenation on the conversion of xanthine dehydrogenase to oxidase in chinese hamster v79 cells.the effects of hypoxia and reoxygenation on the conversion of xanthine dehydrogenase to the free radical-producing xanthine oxidase in chinese hamster v79 cells have been investigated using a newly developed fluorimetric enzyme assay. hypoxia caused an increase in xanthine oxidase activity from 25% to 80% of the total activity of xanthine oxidase and dehydrogenase. the ratio returned to normal levels within 24 h of aerobic incubation. hypoxia caused the release of xanthine oxidase in the medium ...19911937136
evidence that functional erythrocyte-type glucose transporters are oligomers.in this study we tested the hypothesis that functional erythrocyte-type glucose transporters (glut1) exist as oligomeric complexes by expressing chimeric transporter proteins in chinese hamster ovary cells harboring endogenous glut1 transporters. the chimeric transporters were glut1-4c, in which the 29 c-terminal residues of human glut1 were replaced by the 30 c-terminal residues of rat skeletal muscle glucose transporter (glut4), and glut1n-4, containing the n-terminal 199 residues of glut1 and ...19911939082
protease specificity and heparin binding and activation of recombinant protease nexin i.structural and functional properties of alpha-protease nexin i (alpha-pni) expressed in chinese hamster ovary cells were studied. all three cysteines were in the reduced form, showing that the potential disulfide bridge between residues cys117 and cys131 was not formed. heparin association rate enhancements were from ka = 8.3 x 10(5) to 0.7-1.6 x 10(9) m-1 s-1 for the interaction of pni with thrombin, from ka = 5.1 x 10(3) to 3.5 x 10(5) m-1 s-1 for interaction with factor xa, and from ka = 2.2 ...19911939253
isolation of variants of chinese hamster ovary cells with abnormally low levels of gsh: decreased ability to cleave endocytosed disulfide bonds.mutants of chinese hamster ovary cells were selected for resistance to a 3 hour exposure to 4 microgram/ml n-methyl-n'-nitro-n-nitrosoguanidine and tested for glutathione (gsh) levels. six of eight clones that survived the initial treatment had reduced gsh levels ranging from 26 to 61% of wild-type values. these eight cell lines were tested for their susceptibility to a drug conjugate in which methotrexate (mtx) is disulfide-linked to poly(d-lysine) (mtx-ss-pdl) to test their capacity to cleave ...19911939347
differences in preferential synthesis and redistribution of hsp70 and hsp28 families by heat or sodium arsenite in chinese hamster ovary cells.since both heat and sodium arsenite induce thermotolerance, we investigated the differences in synthesis and redistribution of stress proteins induced by these agents in chinese hamster ovary cells. five major heat shock proteins (hsps; mr 110, 87, 70, 28, and 8.5 kda) were preferentially synthesized after heat for 10 min at 45.5 degrees c, whereas four major hsps (mr 110, 87, 70, and 28 kda) and one stress protein (33.3 kda) were preferentially synthesized after treatment with 100 microm sodium ...19911939348
effect of chronic thermotolerance on thermosensitization in chinese hamster ovary cells studied at various temperatures.the effect of chronic thermotolerance on the thermal responses of chinese hamster ovary (cho) cells to single and step-down heating was studied. thermotolerance was induced by pre-heating exponentially growing cells at 39 degrees c for 9 h, followed by test treatments for variable times at temperatures ranging from 39 to 43 degrees c. in the temperature range studied, the heat sensitivity of thermotolerant cho cells was characterized by an arrhenius activation energy of ea = 1175 +/- 40 kj/mol. ...20081940509
lipoproteins in pinnipeds: analysis of a high molecular weight form of apolipoprotein e.we have examined the apolipoprotein content of the lipoproteins of several marine mammals by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. their apolipoprotein (apo) b-100, apob-48, and apoa-i migrated to virtually the same position as the comparable human apolipoproteins. in cetaceans (bottlenose dolphins and killer whales), the molecular mass of the apoe was identical to that of human apoe (35 kda). in contrast, in the lipoproteins of pinnipeds (harbor seals, sea lions, and walrus ...19911940617
binding of [3h]af-dx 384 to cloned and native muscarinic receptors.the binding selectivity of [3h]af-dx 384 [(+-)-5,11-dihydro-11- ([(2-(2-[(dipropylamino)methyl]-1- piperidinyl)ethyl)amino]carbonyl)-h-pyrido(2,3-b)(1,4)benzodiazepine-6-o ne] was evaluated with cloned human muscarinic receptors (m1-m4) in chinese hamster ovary (cho-k1) cell lines as well as in rat heart and brain. there were uniform classes of sites for the radioligand in the m2-rich tissues, heart (kd = 2.3 nm) and brainstem (kd = 2.4 nm). however, [3h]af-dx 384 bound to all four cloned recept ...19911941609
metabolic activation and cytogenetic effects of 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (phip) in chinese hamster ovary cells expressing murine cytochrome p450 ia2.we have utilized chinese hamster ovary cell lines which stably express a murine cytochrome p450ia2 (p(3)450) cdna to characterize more fully the mechanisms of genotoxicity of heterocyclic amines derived from cooked meats. to verify that these cell lines were capable of converting promutagens into active metabolites, we studied the microsomal metabolism and cytogenetic effects of 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pridine (phip). microsomal preparations derived from excision repair-deficient ...19911943715
investigations into the induction of aneuploidy and polyploidy in mammalian cells by the anti-tussive agent noscapine hydrochloride.noscapine, a non-narcotic, centrally-acting anti-tussive drug induces polyploidy in chinese hamster chl cells; further studies were carried out to investigate whether similar effects could be induced in other rodent cells (chinese hamster v79) and in human lymphocytes. in both cases, large increases in the frequency of polyploid cells were induced at test concentrations ranging from 15 to 120 micrograms/ml after 24 and 48 h continuous treatment in the absence of s9 mix. in addition, spindle dama ...19911943718
analysis of the aneuploidy inducing capacity of 2-chlorobenzylidene malonitrile (cs) and metabolites in v79 chinese hamster cells.the aneuploidy inducing capacity of 2-chlorobenzylidene malonitrile (cs), a chemical used as a riot control agent, and its hydrolysis products o-chlorobenzaldehyde and malonitrile was studied at various exposure conditions in v79 chinese hamster cells. chromosomes were counted in metaphase preparations with preserved cytoplasm. a significant increase in the number of aneuploid cells was found after cs and o-chlorobenzaldehyde exposure but not after malonitrile exposure. o-chlorobenzaldehyde, whi ...19911943720
effect of antioxidants on hyperoxia-induced chromosomal breakage in chinese hamster ovary cells: protection by carnosine.we have studied the effect of various compounds, known as antioxidants, on the level of hyperoxia (80-90% o2)-induced chromosomal aberrations in chinese hamster ovary cells: ascorbic acid, alpha-tocopherol, carnosine, imidazole-4-acetic acid, glutathione monoethylester, n-acetylcysteine and ethoxyquin. carnosine (beta-alanyl-histidine) appeared to be the only compound that reduced chromosomal breakage. the effect was also present in cultures post-treated with caffeine (at 2.5 mm, 3 h before harv ...19911943722
müllerian inhibiting substance blocks epidermal growth factor receptor phosphorylation in fetal rat lung membranes.neonatal males develop respiratory distress syndrome more frequently than females for unknown reasons. the fetal testis secretes testosterone and müllerian inhibiting substance (mis); mis has been shown to inhibit fetal lung maturation in vitro and in vivo and to block phosphorylation of epidermal growth factor (egf) receptors in a431 cells. we hypothesized that mis would also inhibit membrane phosphorylation of egf receptors in fetal lung, and that ultrastructural study of mis-exposed lung migh ...19911943746
strand-specific mutation spectra in repair-proficient and repair-deficient hamster cells.the mutation spectrum induced by uv light has been determined at the hprt locus for both cultured normal (aa8) and uv-sensitive (uv-5) chinese hamster ovary cells to investigate the effect of dna repair on the nature of induced mutations. dna base-pair changes of 23 hprt mutants of aa8 and of 28 hprt mutants of uv-5 were determined by sequence analysis of in vitro amplified hprt cdna. almost all mutants in aa8 carried single-base substitutions, transitions and transversions accounting for 38% an ...19911944372
gene targeting in chinese hamster ovary cells is conservative.two fundamentally different pathways for homologous recombination have been identified in mammalian cells. for most chromosomal recombination events, two copies of a homologous sequence recombine to yield two copies in the products; such events are said to be conservative because the number of copies is preserved. by contrast, virtually all extrachromosomal recombination events are nonconservative; two copies recombine to give a product containing a single intact copy (the other copy is destroye ...19911946364
human alpha-l-iduronidase: cdna isolation and expression.alpha-l-iduronidase (idua; ec 3.2.1.76) is a lysosomal hydrolase in the metabolic pathway responsible for the degradation of the glycosaminoglycans heparan sulfate and dermatan sulfate. a deficiency of idua in humans leads to the accumulation of these glycosaminoglycans and results in the lysosomal storage disorder mucopolysaccharidosis type i. we have isolated and sequenced cdna clones containing part of the human idua coding region and used pcr from reverse-transcribed rna to obtain the full i ...19911946389
ds28-6, a temperature-sensitive mutant of chinese hamster ovary cells, expresses key phenotypic changes associated with brefeldin a treatment.the temperature-sensitive chinese hamster ovary (cho) cell mutant ds28-6 has been previously shown to be pleiotropically defective in protein secretion. we have examined the mutant cells to determine the intracellular site of the block in secretion. by transmission electron microscopy a time-dependent disassembly of the golgi apparatus was found under nonpermissive temperature, which resulted in the loss of the cisternal stack. complete reorganization of the golgi apparatus occurred after shift ...19911946407
relative biological effectiveness of high-energy photons (up to 50 mv) and electrons (50 mev).in vitro studies of the relative biological effectiveness (rbe) of 50-mv x rays have shown an rbe of 1.1 relative to 4-mv x rays. this will be important in clinical radiotherapy. the aim of this study was to verify these results and to investigate whether photonuclear processes might cause the difference in rbe. to do so, 50- and 20-mv x rays and 50-mev electrons were investigated with respect to rbe. chinese hamster v79 cells were irradiated in a specially designed system which allows for a hig ...19911947015
use of pulsed-field gel electrophoresis to measure x-ray-induced double-strand breaks in dna substituted with brdu.the substitution of brdu for tdr in the dna of chinese hamster ovary cells caused radiosensitization for both cell killing and an increase in the rate of neutral elution of the dna. however, no radiosensitization was observed for the amount of dna that migrated from the plug of agarose gels subjected to pulsed-field gel electrophoresis. an unexpected observation, however, was that the migration rate of brdu-substituted dna was relatively independent of radiation dose and was much less than that ...19911947018
single strand breaks in cho cell dna induced by ultrasonic cavitation in vitro.ultrasonic cavitation induces a multiplicity of bioeffects in cell suspensions exposed in a 72 rpm rotating-tube exposure system. single strand dna breaks (ssbs) were found in cultured chinese hamster ovary (cho) cells exposed directly to 1.61 mhz ultrasound at a continuous 8 w/cm2 spatial peak temporal average (spta) intensity with cavitation for 10 min at 2 degrees c. viability assessed by the trypan blue test was less than 1%, which indicates that these ssbs were in dead cells. burst mode exp ...20071949351
[the standardization of the in-vitro tetanus toxin neutralization test on chinese hamster ovary cells].a test for the titration of b. pertussis toxin with antisera on chinese hamster ovary (cho) cells has been worked out. b. pertussis protective antigenic cell-free complex containing 48-54% of b. pertussis toxin has been used as antigen. the specificity of the effect of this complex on cho cells has been confirmed in the toxicity neutralization test with antisera. cho cells have been adapted to reagents and culture media made in the ussr. the titration of b. pertussis toxin and antisera on cho ce ...19911950278
[the number and soma size of retinal ganglion cells in chinese hamsters].the number and somatic size of retinal ganglion cells in chinese hamsters were examined by means of the horseradish peroxidase (hrp) staining method. the hrp staining is a method by which only the retinal ganglion cells can be stained. the number of ganglion cells per eye was 67,636-79,545 (mean: 73,575, n = 3). there was a tendency for the density of retinal ganglion cells to be larger in the central than in the peripheral retina. the diameter of retinal ganglion cells was 6-28 microns (mean: 1 ...19911950830
inhibition and enhancement of eukaryotic gene expression by potential non-b dna sequences.in a transient or constitutive expression assay we have examined the effect of non-b dna sequences d(ca)40 and d(caaaaatgcc)n on gene expression in eukaryotic cells. these sequences were cloned adjacent to the weak eukaryotic promoter (cgtatttatttg) and located upstream from the coding sequence of galactokinase enzyme. recombinants were micro-injected in cultured cells (chinese hamster fibroblasts r1610, mutant gal-k-) and expression levels have been determined. the alternating purine-pyrimidine ...19911953778
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