| expression of recombinant tgf-beta 2(442) precursor and detection in bsc-40 cells. | analysis of cdna clones encoding transforming growth factor (tgf)-beta 2 predicts two different precursor proteins derived by alternative mrna splicing; a 414 amino acid precursor [tgf-beta 2(414)] and a 442 amino acid precursor [tgf-beta 2(442)]. the two proteins differ by a 28 amino acid insertion within the pro-region of tgf-beta 2(442). in order to characterize the tgf-beta 2-related proteins encoded by the tgf-beta 2(442) cdna and determine whether it could, in fact, direct the synthesis of ... | 1991 | 1777240 |
| monoclonal antibodies against the enzymatic subunit of both pertussis and cholera toxins. | a synthetic peptide corresponding to amino acids 6-17 of the a subunit of pertussis toxin was synthesised and used for the immunization of balb/c mice and the subsequent production of monoclonal antibodies (mabs). this peptide contains a region of eight amino acids which is homologous to a region in the cholera toxin a subunit. the properties of two of the resultant mabs are described. both of the antibodies (cp7-3003f7, an igg3 and cp7-3004g6x1, an igg1) react in an elisa with the peptide and w ... | 1991 | 1778307 |
| an improved elisa system for the measurement of igg antibodies against pertussis toxin (pt) and filamentous hemagglutinin (fha) in human sera. | we have developed a modified assay method for the measurement of antibodies against pt and fha. polystyrene balls coated with purified pt and fha were incubated with standard or test sera, washed, incubated with goat anti-human igg f(ab')2 conjugated with horseradish peroxidase and then washed again. peroxidase activity was then measured by color development using o-phenylenediamine. the anti-pt and anti-fha igg titers were determined using calibration curves. the assay standard curves for anti- ... | 1991 | 1778310 |
| production of a safe, potent and immunogenic partially purified acellular pertussis vaccine using simple indigenous techniques. | partially purified acellular pertussis vaccine was prepared from bordetella pertussis strains 10536, 134, tohama and 509 using simple indigenously available techniques. the stainer-scholte (ss) medium with methylated-beta-cyclodextrin was the most suitable for production of acellular pertussis vaccine. for preparation of the vaccine, 5 day cultures of b. pertussis grown under stationary conditions at 35 degrees c were treated twice with ammonium sulphate and prospective protective antigens were ... | 1991 | 1778314 |
| expression of the s1 sub-unit of pertussis toxin using a recombinant baculovirus. | the full-length genome of the s1 sub-unit containing the native signal sequence was inserted downstream of the polyhedrin promoter of autographa californica nuclear polyhedrosis virus. a large amount of 28 kd protein, which was larger than the authentic s1 sub-unit (26 kd), was detected in insect cells infected with the recombinant virus by coomassie blue staining after resolving by sds-page. although the level of expression of the recombinant s1 sub-unit was high, immunoblotting and n-terminal ... | 1991 | 1778337 |
| a new structural model for the thyrotropin (tsh) receptor, as determined by covalent cross-linking of tsh to the recombinant receptor in intact cells: evidence for a single polypeptide chain. | the most widely held model for the human tsh receptor is of holoreceptor of 80 kda with two subunits of approximately 50 and 30 kda linked by disulfide bridges, with the former subunit containing the major hormone-binding site. we reexamined this model by covalently cross-linking radiolabeled tsh to the recombinant human tsh receptor stably expressed in chinese hamster ovary (cho) cells. when cross-linking was performed after the preparation of cho membranes, analysis of hormone-receptor complex ... | 1991 | 1779967 |
| carbohydrate structures of human interleukin 5 expressed in chinese hamster ovary cells. | the asparagine-linked sugar chains of recombinant human interleukin 5 produced by chinese hamster ovary cells were released quantitatively as oligosaccharides by hydrazinolysis. after n-acetylation followed by nab3h4 reduction, each oligosaccharide was isolated by paper electrophoresis and serial lectin column chromatography. study of their structures by sequential exoglycosidase digestion in combination with methylation analysis, revealed that they are bi-, tri-, and tetraantennary complex-type ... | 1991 | 1783599 |
| the npey sequence is not necessary for endocytosis and processing of insulin-receptor complexes. | the tetrameric amino acid sequence asnproxtyr (npxy), where x represents any amino acid, is conserved in the intracytoplasmic domains of several membrane proteins and has been postulated to play a role in receptor-mediated endocytosis. the human insulin receptor (hir) contains a single copy of the sequence asnproglutyr (npey) in its intracytoplasmic domain. to determine if this putative consensus sequence is necessary for endocytic functions of hir, we constructed a mutant receptor, hir delta np ... | 1991 | 1791832 |
| expression of human o6-methylguanine-dna methyltransferase in chinese hamster ovary cells and restoration of cellular resistance to certain n-nitroso compounds. | we have constructed a plasmid in which the expression of human o6-methylguanine-dna methyltransferase (mgmt) cdna is driven by the rous sarcoma virus promoter sequence. transfection of this plasmid into chinese hamster ovary (cho) cells results in expression of mgmt and in cellular resistance to n-methyl-n'-nitro-n-nitrosoguanidine (mnng) and 1-(2-chloroethyl)-1-nitrosourea (cnu), but not to n-nitroso-n-ethylurea. the specific activity of mgmt in transfected cho cells correlated well with their ... | 1991 | 1793486 |
| stable expression of rat cytochrome p450ia2 cdna and hydroxylation of 17 beta-estradiol and 2-aminofluorene in v79 chinese hamster cells. | in continuation of our work toward the establishment of a working cell bank for metabolic and toxicological studies, v79 chinese hamster cells were genetically engineered for stable expression of rat cytochrome p450ia2. full-length cdna encoding rat p450ia2 was obtained by searching a cdna library made from aroclor 1254-induced rat liver mrna and by joining a small 5'-end fragment to a fragment containing the rest of the cdna. the sequence of the cdna was confirmed by dna sequencing and comparis ... | 1991 | 1793487 |
| expression of mouse cytochrome p450ia1 cdna in repair-deficient and repair-proficient cho cells. | recombinant dna techniques have been used to develop chinese hamster ovary cell lines for studying chemically induced genotoxicity. these cell lines express a specific cytochrome p450 isozyme responsible for the metabolism of polycyclic aromatic hydrocarbons and exhibit defined differences in dna repair capacity. a bacterial gene (neo) conferring resistance to gentamicin was inserted into the pcd expression vector containing the mouse cytochrome p1450 (p450ia1) cdna to facilitate the selection o ... | 1991 | 1793488 |
| correlation between levels of ferritin and the iron-containing component of ribonucleotide reductase in hydroxyurea-sensitive, -resistant, and -revertant cell lines. | the reduction of ribonucleotides to deoxyribonucleotides, a rate-limiting step in dna synthesis, is catalyzed by ribonucleotide reductase. this enzyme is composed of two components, m1 and m2. recent work has shown that inhibition of ribonucleotide reductase by the antitumor drug hydroxyurea leads to a destabilized iron centre in protein m2. we have examined the relationship between the levels of ferritin, the iron storage protein, and the iron-containing m2 component of ribonucleotide reductase ... | 1991 | 1793565 |
| in-vitro testing and the carcinogenic potential of several nitrosated indole compounds. | 4-chloro-methoxyindole is a naturally occurring compound in vicia faba which can easily react with nitrite to form a n-nitroso compound. in this in vitro study, the potential genotoxic effects of nitrosated 4-chloro-6-methoxyindole and its structural analogue 4-chloroindole were evaluated for the first time by using both salmonella and chinese hamster v79 cells. additionally, the inhibition of gap junctional intercellular communication in v79 cells by these compounds was determined; this is a va ... | 1991 | 1794111 |
| evaluation of biocompatibility, based on quantitative determination of the vascular response induced by material implantation. | the biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using v79 chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using laser doppler flowmetry (ldf) over 14 days following implantation. in addition, for s ... | 1991 | 1794998 |
| development of assays for the detection of photomutagenicity of chemicals during exposure to uv light--i. assay development. | two complementary assay systems have been adapted for the detection of compounds which may form mutagenic photoproducts during exposure to uv light from an osram ultra-vitalux sunlamp as used in the evaluation of the effectiveness of sun filters. the effects of uva and of uvb were evaluated. a bacterial plate test using escherichia coli strain wp2 allowed the bacteria, co-plated with test chemical in soft agar, to be irradiated with various doses of uv light. mutagenesis was assessed by scoring ... | 1991 | 1795636 |
| chromosomal assignment of human o6-methylguanine-dna-methyltransferase gene by hamster-human somatic cell hybrids. | using an in vitro assay to measure o6-methylguanine-dna-methyltransferase (mt) activity in cell extracts from a panel of human-hamster cell hybrids, we were able to locate the human mt gene on chromosome 10. chinese hamster cells have little or no mt activity and the presence of human chromosome 10 was a necessary condition for mt activity in cell hybrids. in some cell hybrids carrying chromosome 10, however, mt activity was not higher than that of hamster cells. as an explanation for this resul ... | 1991 | 1795645 |
| effects of organotin compounds on mitosis, spindle structure, toxicity and in vitro microtubule assembly. | di- and tri-methyl, -butyl and phenyl tin, all as chlorides were tested for toxicity and spindle disturbances in v79 chinese hamster cells and for effects on in vitro assembly of bovine brain tubulin. the v79 cells were treated for 30 min and in general, loss of a stainable spindle could be demonstrated at slightly higher concentrations than c-mitosis. both these effects were observed at low, non-toxic concentrations. the c-mitotic activity of the compounds was found to increase with increasing ... | 1991 | 1795647 |
| [effects of tumor promoting herb wikstroemia chamaedaphne extract on v79 cells and wb liver cells: i. correlation between cellular growth and gap junctional intercellular communication]. | a chinese herb, wikstroemia chamaedaphen (wc) extract, recently has been shown to be a potential tumor promoting agent on uterine cervical carcinoma induced by hsv-2 or mca in mice. to determine whether the tumor promoting effects of wc extract were mediated through inhibition of gap junctional intercellular communication (gjic) with relation to cellular growth, experiments were conducted on chinese hamster v79 cells and rat wb liver cells by utilization of sldt method for gjic detection and cel ... | 1991 | 1796715 |
| enhancement of the mutagenicity of anticancer drugs by the calcium antagonists verapamil and fendiline. | the enhancement of the mutagenicity of anticancer drugs by the calcium antagonists verapamil (cas 52-53-9) and fendiline (cas 13042-18-7) is reviewed. both calcium antagonists enhance synergistically the induction of chromosome aberrations (dicentric and ring chromosomes) in cultured human lymphocytes by the antitumor agent bleomycin. since two other calcium antagonists, nifedipine and diltiazem, when tested with the same system, did not show this effect, the comutagenicity of verapamil and fend ... | 1991 | 1796917 |
| dna-damaging, mutagenic, clastogenic and cell-cell communication inhibitory properties of gamma-oryzanol. | as a part of short-term safety assessment of gamma-oryzanol, the genotoxic or the carcinogenic initiation activity was studied in three genetic toxicity tests and the promotion activity was studied in a cell-cell communication inhibitory test. gamma-oryzanol showed the negative response in the bacterial dna repair test (rec-assay), the bacterial reverse mutation tests (ames test) and the rat bone marrow chromosome aberration test. also, gamma-oryzanol showed the negative response in the metaboli ... | 1991 | 1798065 |
| mutagenicity studies on catena-(s)-[mu-[n alpha-(3-aminopropionyl)histidinato(2-)-n1,n2,o:n tau]-zinc]. | z-103 (catena-(s)-[mu-[n alpha-(3-aminopropionyl)histidinato (2-)-n1,n2,o:n tau]-zinc], cas 107667-60-7) was examined in the bacterial mutation test, a chromosomal aberration test with mammalian cells in culture and the micronucleus test using male mice. 1. z-103 did not increase the number of revertants in escherichia coli wp2 uvra when tested at up to 5000 micrograms/plate in the presence or absence of metabolic activation. and z-103 did not increase mutants in salmonella typhimurium sd 100 (s ... | 1991 | 1799383 |
| 5' ltr complete nucleotide sequence of chinese hamster intracisternal a-particle. | retrovirus like sequences homologous to mouse iap are present in chinese hamster genome (lueders k.k. and kuff, e.l., 1981, 1983, servenay et al., 1990). murine iap long terminal repeats (ltrs) can function as effective promoters in different cell types (horowitz m. et al., 1984, howe, c.c. et al., 1986). thus cho iap sequences could act as retrotransposons in the cellular genome, and in this way affect the expression of other genes at the target sites. we had sequenced previously a chinese hams ... | 1991 | 1799684 |
| the use of genetically engineered v79 chinese hamster cultures expressing rat liver cyp1a1, 1a2 and 2b1 cdnas in micronucleus assays. | we have undertaken a comparative study of the bioactivation of a panel of promutagens by v79 chinese hamster cells genetically engineered to metabolic competence. in vitro micronucleus assays of the test agents in v79 cultures in the presence of an aroclor induced rat s9 yielded positive results. in the genetically engineered cell lines, benzo[a]pyrene was metabolized specifically by the 3-methylcholanthrene inducible rat liver cyp1a1 (cell line xem2) whereas cyclophosphamide increased the micro ... | 1991 | 1800893 |
| density-dependent inhibition of cell growth is correlated with the activity of a cell surface phosphatidylinositol-specific phospholipase c. | we previously identified a novel phospatidylinositol-specific phospholipase c (pi-plc) present at the surface of swiss 3t3 cells using a fluorescent analog of pi and showed that this cell surface pi-plc (cspi-plc) activity increases with increasing cell density (j. biol. chem. 265, 5337-5340 (1990)). here, we find that cspi-plc activity also increased in cultures in which growth was inhibited due to serum deprivation. cspi-plc was inhibited by agents that inhibit other mammalian pi-plcs, but not ... | 1991 | 1802721 |
| expression of pro-urokinase cdna in chinese hamster ovary cell line. | expression vectors containing the pro-urokinase (pro-uk) cdna (psv2-prouk) and a dihydrofolate reductase cdna (psv2-dhfr or mmtv-dhfr) were cotransfected into cho-dhfr- cells by the calcium phosphate precipitation technique. the dhfr+ transformants were selected by fibrinolytic agarose plate assay. two colonies, named clf-14 and clf-8, exhibited significantly high expression levels of the biological activity of urokinase-type plasminogen activator (mu-pa). they reached more than 24 iu/10(6) cell ... | 1991 | 1806021 |
| expression of a human monoclonal anti-hiv-1 antibody in cho cells. | the cdna coding for the light and heavy chains, respectively, of the human monoclonal antibody 3d6 (igg1, kappa), which binds specifically to human immunodeficiency virus-1 (hiv-1) gp41, was inserted into three different mammalian expression vectors and transfected into chinese hamster ovary (cho) cells. transcription was under the control of rous sarcoma virus long terminal repeat (rsv ltr), human cytomegalovirus major immediate early (cmv ie) promoter, and mouse mammary tumor virus long termin ... | 1991 | 1809191 |
| isolation of a fibroblast mutant resistant to clostridium difficile toxins a and b. | a mutant of chinese hamster lung fibroblasts (don cells), resistant against clostridium difficile toxins a and b, was isolated after mutagenization with ethylmethanesulphonate and a two-step selection with toxin b. the mutant, termed cdtr-q, was 10(4) times more resistant to toxin b than wild-type cells and cross-resistant to toxin a (10(3) times more resistant). the resistance was overcome by increasing the dose of toxin. the resistance has been stable after cultivation for 40 generations in th ... | 1991 | 1816487 |
| the genetic toxicity database of the national toxicology program: evaluation of the relationships between genetic toxicity and carcinogenicity. | the database of the u.s. national toxicology program has been developed over approximately two decades, principally focused on substances evaluated for carcinogenicity in rodent bioassays. these assays generally provide data on the relative toxicity and carcinogenicity of chemicals based upon discrete subchronic (13 week) and chronic (104 week) exposures. a major value of these data are that the assay protocols, rodent strains, and technical methodologies have been generally consistent, thus per ... | 1991 | 1820276 |
| expression of recombinant human apolipoprotein a-i in chinese hamster ovary cells and escherichia coli. | human recombinant apolipoprotein (apo) a-i was produced by chinese hamster ovary (cho) cells and escherichia coli with expression vectors containing cdnas encoding preproapoa-i or apoa-i, respectively. the apoa-i from cho cells was purified from the culture medium by ammonium sulfate precipitation, phenyl-sepharose chromatography, and affinity purification on anti-apoa-i immunoabsorber. human apoa-i was produced in e. coli as a fusion protein with glutathione s-transferase. a four amino acid lin ... | 1991 | 1821801 |
| evaluation of the genotoxic activity and acute toxicity of euphorbia splendens latex, a molluscicide for the control of schistosomiasis. | 1. the latex of euphorbia splendens var. hislopii has a molluscicidal action at low concentration (ld90 less than 1.5 ppm or 1.5 micrograms/ml) against the vector snails of schistosomiasis. 2. in the present study, the latex in natura or after lyophilization was submitted to the ames test and the chromotest to evaluate genotoxicity, to the microtox system to determine acute toxicity, and to the chinese hamster ovary cell assay (cho) to measure cytotoxicity. 3. the latex had no mutagenic activity ... | 1991 | 1823273 |
| semi-intact cho and endothelial cells: a tool to probe the control of integrin activity? | an in vitro assay has been developed using semi-intact cells, made with the bacterial toxin streptolysin o, in order to measure integrin activity in relation to the cytosol environment. in this assay, the cytosolic content can easily be modified while the receptor binding activity is measured by monitoring the interaction of specific radiolabeled substrates with the cell surface. using two different cell types, i.e., wild-type chinese hamster ovary cells and human endothelial cells in culture, i ... | 1991 | 1824586 |
| recombinant soluble human complement receptor type 1 inhibits inflammation in the reversed passive arthus reaction in rats. | the human cr1 was genetically engineered by site directed mutagenesis into a truncated form which was secreted from transfected chinese hamster ovary cells. this soluble recombinant cr1 (scr1) was purified from the supernatants of the chinese hamster ovary cells cultured in a hollow fiber bioreactor. scr1 inhibits the c3 and c5 convertases of the classical and the alternative pathways in vitro. the ability of scr1 to inhibit the immune complex-mediated inflammation in vivo was tested in a rat re ... | 1991 | 1824590 |
| characterization of truncated alpha chain products from human, rat, and mouse high affinity receptor for immunoglobulin e. | the high affinity receptor for immunoglobulin e (ige) is a tetrameric structure (alpha beta gamma 2) consisting of non-covalently associated subunits: one ige-binding alpha chain, one 4-fold membrane spanning beta chain, and two disulfide-linked gamma chains. here, we have engineered alpha cdna constructs (alpha trunc) encoding exclusively the leader peptide and the extracellular domain of the alpha subunit. transfection of human alpha trunc into cos-7 cells resulted in the secretion of soluble ... | 1991 | 1824944 |
| inhibition of interleukin 1 (il-1) binding and bioactivity in vitro and modulation of acute inflammation in vivo by il-1 receptor antagonist and anti-il-1 receptor monoclonal antibody. | recombinant human interleukin 1 receptor antagonist (il-1ra) and 35f5, a neutralizing monoclonal antibody (mab) to the type i mouse il-1 receptor, were examined for their ability to bind to il-1 receptors (il-1rs) on various types of mouse cells and to block immune and inflammatory responses to il-1 in vitro and in mice. il-1ra competed for binding of 125i-il-1 alpha to type i il-1r present on el-4 thymoma cells, 3t3 fibroblasts, hepatocytes, and chinese hamster ovary cells expressing recombinan ... | 1991 | 1826128 |
| expression and reconstitution of a biologically active mouse interferon gamma receptor in hamster cells. chromosomal location of an accessory factor. | in order to localize the chromosome encoding the accessory factor required for function of the murine interferon gamma (ifn-gamma) receptor, we transfected a cdna expression vector encoding the receptor into several chinese hamster x mouse somatic cell hybrids. as mouse chromosome 10 carries the gene which encodes the interferon gamma-receptor (ifgr), we used somatic cell hybrids that lack this chromosome. the presence of mouse chromosome 16 was required to generate a response to murine ifn-gamm ... | 1991 | 1826681 |
| organization and localization to chromosome 5 of the human udp-n-acetylglucosamine:alpha-3-d-mannoside beta-1,2-n-acetylglucosaminyltransferase i gene. | udp-n-acetylglucosamine:alpha-3-d-mannoside beta-1,2-n-acetylglucosaminyltransferase i (glcnac-t i; ec 2.4.1.101) is a medial-golgi enzyme essential for the synthesis of hybrid and complex n-glycans. we have isolated two overlapping genomic dna clones which span 18 kilobases (kb) containing a single 2.5 kb exon for glcnac-t i. the exon includes most of the 5'-untranslated region, the complete coding sequence (1335 bases) for glcnac-t i (445 amino acids) and the complete 3'-untranslated region. t ... | 1991 | 1827260 |
| post-translational processing and secretory pathway of human atriopeptin in rat pheochromocytoma cells. | atriopeptin (ap) is expressed in several tissues with each tissue capable of specific differences in processing of the prohormone (pro-ap) to mature low molecular forms of the peptide. since pro-ap has low biological activity, processing into mature ap is a critical activation event. this observation prompted us to study whether granule storage or regulated secretion of ap is essential for cleavage of mature peptide. we examined the processing of ap in adrenal medulla derived cells, using the ra ... | 1991 | 1828150 |
| phorbol ester induces phosphorylation of the 80 kilodalton murine interleukin 1 receptor at a single threonine residue. | the cytoplasmic domains of some cell surface receptors become phosphorylated in cells treated with phorbol esters. the present study was undertaken in order to determine whether this is also true of the 80 kda interleukin 1 receptor (il1r). recombinant murine il1r, transfected into chinese hamster ovary (cho) cells or murine fibroblasts, was immunoprecipitated from [32p]orthophosphate-labelled cells. il1r phosphorylation was only detected in cells pretreated with phorbol 12-myristate 13-acetate ... | 1991 | 1828344 |
| degradation of t-cell receptor chains in the endoplasmic reticulum is inhibited by inhibitors of cysteine proteases. | the endoplasmic reticulum, or an organelle closely associated with it, contains proteases that can be used to remove partially assembled or improperly folded proteins. very little is known at present about the types of protease that degrade these proteins. the beta chain and cluster of differentiation (cd)3 delta subunit of the human t-cell antigen receptor (tcr) are degraded shortly after synthesis. in this study chinese hamster ovary (cho) cells transfected with either beta or delta were incub ... | 1991 | 1835888 |
| dna sequence changes in mutations induced by ultraviolet light in the gpt gene on the chromosome of escherichia coli uvr+ and urva cells. | sequence changes in mutations induced by ultraviolet light are reported for the chromosomal escherichia coli gpt gene in almost isogenic e. coli uvr+ and excision-deficient uvra cells. differences between the mutagenic spectra are ascribed to preferential removal of photoproducts in the transcribed strand by excision repair in uvr+ cells. this conclusion is confirmed by analysis of published results for genes in both uvr+ and uvr- cells, showing a similar selective removal of mutagenic products ... | 1991 | 1836051 |
| fine structure physical mapping of the region of mouse chromosome 10 homologous to human chromosome 21. | comparative mapping of human and mouse dna for regions of genetic homology between human chromosome 21 and the mouse genome is of interest because of the possibility of developing mouse models of human trisomy 21 (down syndrome), understanding chromosome evolution, and isolating novel sequences conserved between the two species. at least two mouse chromosomes are known to carry sequences homologous to those on human chromosome 21: mouse chromosome 16 (d21s16h, d21s13h, d21s52h, app, sod-1, mx-1, ... | 1991 | 1837533 |
| a subclass of cell surface carbohydrates revealed by a cho mutant with two glycosylation mutations. | a novel lectin-resistance phenotype was displayed by a lec10 chinese hamster ovary (cho) cell mutant that was selected for resistance to the erythroagglutinin, e-pha. biochemical and genetic analyses revealed that the phenotype results from the expression of two glycosylation mutations, lec10 and lec8. the lec10 mutation causes the appearance of n-acetylglucosaminyltransferase iii (glcnac-tiii) activity and the production of n-linked carbohydrates with a bisecting glcnac residue. the lec8 mutati ... | 1991 | 1838951 |
| direct comparison of in-vitro and in-vivo photofrin-ii mediated photosensitization using a pulsed ktp pumped dye laser and a continuous wave argon ion pumped dye laser. | a pulsed ktp pumped dye laser (25 khz repetition rate and 470 nsec pulse width) has been compared to a continuous wave argon ion pumped dye laser as the source of 630 nm light during in-vitro and in-vivo photofrin-ii mediated photosensitization studies. individual experiments documented the effectiveness of each laser system on a) photosensitizer induced cytotoxicity and induction of stress protein synthesis using chinese hamster fibroblasts; b) photobleaching of photofrin-ii in aqueous solution ... | 1991 | 1840075 |
| cloning of a tumor-associated antigen: mov18 and mov19 antibodies recognize a folate-binding protein. | monoclonal antibodies mov18 and mov19, raised against a membrane preparation of an ovarian carcinoma surgical specimen, react with a surface antigen present on the majority of nonmucinous ovarian malignant tumors tested but not with normal adult tissue (s. miotti, s. canevari, s. ménard, d. mezzanzanica, g. porro, s. m. pupa, m. regazzoni, e. tagliabue, and m. i. colnaghi, int. j. cancer, 39: 297-303, 1987). this surface antigen was purified as a soluble glycoprotein (molecular mass, 36-38 kda) ... | 1991 | 1840502 |
| embryonic chick heart expresses multiple muscarinic acetylcholine receptor subtypes. isolation and characterization of a gene encoding a novel m2 muscarinic acetylcholine receptor with high affinity for pirenzepine. | muscarinic acetylcholine receptors (machr) are g protein-coupled receptors which are highly conserved across mammalian species. chick cardiac machr, however, have been shown to be pharmacologically, immunologically, and biochemically distinct from m2 machr expressed in mammalian heart. we previously reported the isolation and characterization of a novel chicken machr, cm4, which is expressed in chick heart and brain. we report here the isolation of an additional chicken machr gene whose deduced ... | 1991 | 1840593 |
| cell- and ligand-specific dephosphorylation of acid hydrolases: evidence that the mannose 6-phosphatase is controlled by compartmentalization. | mouse l cells that possess the cation-independent mannose 6-phosphate (man 6-p)/insulin-like growth factor (igf) ii receptor change the extent to which they dephosphorylate endocytosed acid hydrolases in response to serum (einstein, r., and c. a. gabel. 1989. j. cell biol. 109:1037-1046). to investigate the mechanism by which dephosphorylation competence is regulated, the dephosphorylation of individual acid hydrolases was studied in man 6-p/igf ii receptor-positive and -deficient cell lines. 12 ... | 1991 | 1846001 |
| biological activity and metabolic clearance of a recombinant human thyrotropin produced in chinese hamster ovary cells. | the presence and specific structures of the oligosaccharides on tsh have been shown to be important for its production and bioactivity. since the carbohydrate structure of a protein reflects the glycosylation apparatus of the host cells in which the protein is expressed, we examined the biological activity and metabolic clearance of a preparation of purified recombinant human (rh) tsh derived from a stable transfectant of chinese hamster ovary cells. carbohydrate compositional analysis of this r ... | 1991 | 1846103 |
| spontaneous solubilization of membrane-bound human testis angiotensin-converting enzyme expressed in chinese hamster ovary cells. | the testis isozyme of angiotensin-converting enzyme (ace; ec 3.4.15.1) is a membrane-bound protein that, apart from the first 35 n-terminal residues, is identical to the c-terminal half of somatic ace and contains the same putative c-terminal membrane anchor. stable transfection of chinese hamster ovary (cho) cells with an expression vector containing the full-length human testis ace cdna results in the expression of two forms of recombinant human testis ace (htace): membrane-bound ace and, surp ... | 1991 | 1846959 |
| absence of na+,k(+)-atpase regulation of endosomal acidification in k562 erythroleukemia cells. analysis via inhibition of transferrin recycling by low temperatures. | transferrin (tf) acidification has been shown to be limited to ph 6 in murine balb/c 3t3 fibroblasts, human a549 epidermoid carcinoma cells, and chinese hamster ovary cells and is followed by alkalinization during recycling. in contrast, tf acidification in the human erythroleukemic cell line k562 proceeds to below ph 5.5, and alkalinization of internal tf during recycling is not observed. to explore the regulation of endosomal ph in k562 cells, we determined whether the existence of an early en ... | 1991 | 1847374 |
| inhibition of autoproteolytic activation of interstitial procollagenase by recombinant metalloproteinase inhibitor mi/timp-2. | the purification and cloning of a novel metalloproteinase inhibitor (mi or timp-2) related to tissue inhibitor of metalloproteinases (timp) has been recently described by our laboratory (declerck, y.a., yean, t. d., ratzkin, b.j., lu, h.s., and langley, k.e. (1989) j. biol. chem. 264, 17445-17453; boone, t.c., johnson, m.j., declerck, y.a., and langley, k.e. (1990) proc. natl. acad. sci. u. s. a. 87, 2800-2804). we have transfected chinese hamster ovary cells with a vector containing human mi/ti ... | 1991 | 1847392 |
| mutations of the human beta 2-adrenergic receptor that impair coupling to gs interfere with receptor down-regulation but not sequestration. | the integrity of coupling of the beta 2-adrenergic receptor (beta 2ar) to its guanine nucleotide-binding protein, gs, and phosphorylation events on the receptor molecule have been proposed to be important determinants in the processes of receptor sequestration and down-regulation. however, little is known about the molecular mechanisms underlying these processes, and the regions of the receptor molecule that specifically subserve sequestration and down-regulation have yet to be delineated. to ad ... | 1991 | 1847493 |
| alpha 2-adrenergic receptor stimulation of phospholipase a2 and of adenylate cyclase in transfected chinese hamster ovary cells is mediated by different mechanisms. | the effect of alpha 2-adrenergic receptor activation on adenylate cyclase activity in chinese hamster ovary cells stably transfected with the alpha 2a-adrenergic receptor gene is biphasic. at lower concentrations of epinephrine forskolin-stimulated cyclic amp production is inhibited, but at higher concentrations the inhibition is reversed. both of these effects are blocked by the alpha 2 antagonist yohimbine but not by the alpha 1 antagonist prazosin. pretreatment with pertussis toxin attenuates ... | 1991 | 1847497 |
| molecular cloning and chromosomal localization of a human peripheral-type benzodiazepine receptor. | the sequencing of endopeptidase-generated peptides from the peripheral binding site (pbs) for benzodiazepines, purified from a chinese hamster ovary (cho) cell line, produced internal sequence information, and confirmed and extended the nh2-terminal pbs sequence that we previously reported. since the sequences were highly similar to the corresponding rat pbs sequences, we investigated whether they were also conserved in human pbs. scatchard analysis of [3h]pk11195 (a derivative of isoquinoline c ... | 1991 | 1847678 |
| effects of site-directed mutagenesis at residues cysteine-31 and cysteine-184 on lecithin-cholesterol acyltransferase activity. | native lecithin-cholesterol acyltransferase (lcat; phosphatidylcholine-sterol acyltransferase; phosphatidylcholine:sterol o-acyltransferase, ec 2.3.1.43) protein, and lcat in which either or both of the enzyme free cysteines had been replaced with glycine residues by site-directed mutagenesis, has been expressed in cultured chinese hamster ovary cells stably transfected with the human lcat gene. the mass of lcat secreted, determined by immunoassay, did not differ in the native and mutant species ... | 1991 | 1848009 |
| changes in insulin-receptor tyrosine, serine and threonine phosphorylation as a result of substitution of tyrosine-1162 with phenylalanine. | previous studies, by ourselves and others, have shown that tyrosine residues 1158, 1162 and 1163 are very rapidly autophosphorylated on the human insulin receptor after insulin binding and that this is followed by the autophosphorylation of tyrosine residues 1328 and 1334. the autophosphorylation of these tyrosine residues, and their role in transmembrane signalling, were examined by using chinese-hamster ovary cells transfected with either normal intact insulin receptors or receptors in which t ... | 1991 | 1848075 |
| coupling of a mutated form of the human beta 2-adrenergic receptor to gi and gs. requirement for multiple cytoplasmic domains in the coupling process. | we constructed five genes encoding mutant human beta 2-adrenergic receptor sequence (beta 2ar) which contained 12-22 amino acid substitutions with corresponding sequence from the human alpha 2aar in order to assess the receptor domains involved in gs versus gi recognition and coupling. mutant beta 2ar with substitutions in the n (s1)- and c-terminal (s2) portions of the third intracellular loop, the proximal cytoplasmic tail (s3), and two combinations thereof (s2,3 and s1,2,3), were stably expre ... | 1991 | 1848226 |
| expression and characterization of recombinant human angiotensin i-converting enzyme. evidence for a c-terminal transmembrane anchor and for a proteolytic processing of the secreted recombinant and plasma enzymes. | chinese hamster ovary (cho) cells have been transfected with either a full-length cdna encoding human angiotensin i-converting enzyme (kininase ii; ec 3.4.15.1) (ace) or a mutated cdna, in which the last c-terminal 47 amino acids, including the putative transmembrane domain, are not translated. cell lines expressing high levels of the wild-type ace or the mutant were established. the cells transfected with the wild-type cdna (cho-ace) express a membrane-bound ectoenzyme with an intracellular c t ... | 1991 | 1848554 |
| transfected d2 dopamine receptors mediate the potentiation of arachidonic acid release in chinese hamster ovary cells. | a rat d2l dopamine receptor, a splice variant of the d2 receptor, has recently been cloned. when transfected into and stably expressed in chinese hamster ovary cells, these receptors mediate the inhibition of both basal and forskolin-stimulated camp production, as previously described. we examined what role this receptor might play in the production of the second messenger arachidonic acid. the calcium ionophore a23187 stimulated the release of arachidonic acid, and this release of arachidonic a ... | 1991 | 1848657 |
| expression of three human beta-adrenergic-receptor subtypes in transfected chinese hamster ovary cells. | the genes coding for three pharmacologically distinct subtypes of human beta-adrenergic receptors (beta 1 ar, beta 2 ar and beta 3 ar) were transfected for expression in chinese hamster ovary (cho) cells. stable cell lines expressing each receptor were analyzed by ligand binding, adenylate cyclase activation and photoaffinity labeling, and compared to beta ar subtypes observed in previously described tissues, primary cultures and transfected cell lines. each of the three receptor subtypes displa ... | 1991 | 1848818 |
| characterization of tissue-specific transcription by the human synapsin i gene promoter. | synapsin ia and synapsin ib are abundant synaptic vesicle proteins that are derived by differential splicing from a single gene. to identify control elements directing the neuronal expression of synapsins ia/b, we functionally analyzed the promoter region of the human synapsin i gene. a hybrid gene was constructed containing 2 kilobases of 5' flanking sequence from the synapsin i gene fused to the bacterial gene chloramphenicol acetyltransferase and transfected into 12 different neuronal and non ... | 1991 | 1849657 |
| role of threonine-286 as autophosphorylation site for appearance of ca2(+)-independent activity of calmodulin-dependent protein kinase ii alpha subunit. | to confirm directly the role of thr-286 as the autophosphorylation site responsible for the appearance of ca2(+)-independent activity of ca2+/calmodulin-dependent protein kinase ii alpha subunit, we constructed two mutated cdnas of thr-286 to pro or ala using site-directed mutagenesis and introduced into chinese hamster ovary cells. the mutant enzymes expressed in stable cell lines were partially purified and their catalytic properties were confirmed to be similar to those of wild-type kinase, e ... | 1991 | 1849884 |
| recombinant human interleukin 3 induces proliferation of inflammatory cells and keratinocytes in vivo. | in this preclinical study we investigated the effect(s) of recombinant human (rh) interleukin 3 (il-3) on hemopoietic differentiation and attempted to evaluate possible clinical side effects of this hemopoietic growth factor. rh il-3, derived from either escherichia coli or chinese hamster ovary, was administered subcutaneously to 16 rhesus monkeys (by pairs) at different doses (11, 33, and 100 micrograms/kg/day) for 14 days. during the 2nd week of administration white blood cell counts increase ... | 1991 | 1850054 |
| hyperthermia enhances the cytotoxic effects of reactive oxygen species to chinese hamster cells and bovine endothelial cells in vitro. | hyperthermia is under intensive investigation as a treatment for tumors both alone and in combination with other therapeutic agents. hyperthermia has a profound effect on the function and structural integrity of tumor microvasculature; this has often been cited as a reason for its effectiveness in treatment of tumors. to test the role of hyperthermia in cytotoxic effects of active oxygen species, chinese hamster, v79, and bovine endothelial cells were treated by the active oxygens, o not equal t ... | 1991 | 1850533 |
| comparison of the activities of variant forms of eif-4d. the requirement for hypusine or deoxyhypusine. | eukaryotic protein synthesis initiation factor 4d (eif-4d) (current nomenclature, eif-5a) contains the unique amino acid hypusine (n epsilon-(4-amino-2-hydroxybutyl)lysine). the first step in hypusine biosynthesis, i.e. the formation of the intermediate, deoxyhypusine (n epsilon-(4-aminobutyl)lysine), was carried out in vitro using spermidine, deoxyhypusine synthase, and ec-eif-4d(lys), an eif-4d precursor prepared by over-expression of human eif-4d cdna in escherichia coli. in a parallel reacti ... | 1991 | 1850732 |
| protease treatment of pertussis toxin identifies the preferential cleavage of the s1 subunit. | trypsin digestion of pertussis toxin (pt) preferentially cleaved the s1 subunit at arg-218 without detectable degradation of the b oligomer. the fragment produced, termed the tryptic s1 fragment, appears to remain associated with the b oligomer. chymotrypsin digestion of pt also preferentially cleaved the s1 subunit without detectable degradation of the b oligomer. the chymotryptic s1 fragment possessed a slightly lower apparent molecular weight than the tryptic s1 fragment and was more accessib ... | 1991 | 1850738 |
| rabbit haemorrhagic disease: an investigation of some properties of the virus and evaluation of an inactivated vaccine. | an inactivated vaccine against rabbit haemorrhagic disease (rhd), developed and tested in our laboratory, is produced commercially by bioveta, ivanovice, czechoslovakia. rabbits developed full protection against infection 3 weeks after the administration of a single dose. antibodies were detectable from day 5 after vaccination. naturally acquired antibodies were demonstrated in some rabbits kept on commercial farms. the virus survived at least 225 days in an organ suspension kept at 4 degrees c, ... | 1991 | 1850893 |
| the two homologous domains of human angiotensin i-converting enzyme are both catalytically active. | molecular cloning of human endothelial angiotensin i-converting enzyme (kininase ii; ec 3.4.15.1) (ace) has recently shown that the enzyme contains two large homologous domains (called here the n and c domains), each bearing a putative active site, identified by sequence comparisons with the active sites of other zinc metallopeptidases. however, the previous experiments with zinc or competitive ace inhibitors suggested a single active site in ace. to establish whether both domains of ace are enz ... | 1991 | 1851160 |
| structural and biological properties of human recombinant myeloperoxidase produced by chinese hamster ovary cell lines. | the cdna encoding human myeloperoxidase carries three atg codons in frame; 144, 111 and 66 bp upstream from the proprotein dna sequence. in order to determine the most efficient signal sequence, three cdna modules starting at each of the atg were cloned into an eucaryotic expression vector and stably expressed in chinese hamster ovary cell lines. in all three cases, recombinant human myeloperoxidase (recmpo) was secreted into the culture medium of transfected cells, indicating that each of the s ... | 1991 | 1851479 |
| recognition and plasma clearance of endotoxin by scavenger receptors. | lipid a is the active moiety of lipopolysaccharide (lps, also referred to as endotoxin), a surface component of gram-negative bacteria that stimulates macrophage activation and causes endotoxic shock. macrophages can bind, internalize and partially degrade lps, lipid a and its bioactive precursor, lipid iva. we report here that lipid iva binding and subsequent metabolism to a less active form by macrophage-like raw 264.7 cells is mediated by the macrophage scavenger receptor. scavenger-receptor ... | 1991 | 1852209 |
| mutagenesis and dna adduct formation by 1-nitropyrene in chinese hamster ovary cells without exogenous metabolic activation. | the direct-acting mutagenicity of 1-nitropyrene (1-np), a tumorigenic environmental pollutant and model nitropolycyclic aromatic hydrocarbon, was studied in chinese hamster ovary (cho) cells. previous reports indicated that 1-np, a potent direct-acting mutagen in salmonella typhimurium, was mutagenic in cho cells only in the presence of an exogenous activation system. in this study, a dna-repair-deficient cho cell line, cho-uv5, and the repair-proficient cho-k1-bh4 cell line were used to measure ... | 1991 | 1853350 |
| modulation of genotoxic activity of tobacco smoke. | tobacco smoke (ts) caused a three- to nine-fold increase in the frequency of his+ revertants in salmonella typhimurium ta98 but not in ta97a, ta100 or ta102. activation by a post-mitochondrial fraction obtained from the liver of rats pretreated with aroclor-1254 or methylcholanthrene was required; fractions from phenobarbital-pretreated or untreated rats had no effect. vitamins a and e, but not ascorbic acid, inhibited the ts-induced mutagenesis by up to 63%, whereas glutathione and cysteine inc ... | 1991 | 1855912 |
| inhibition by fatty acids of direct mutagenicity of n-nitroso compounds. | fatty acids inhibited the direct mutagenicity of n-nitroso compounds in salmonella typhimurium ta1535, escherichia coli wp2 and wphcr-, and e. coli h/r30r (wild) and hs30r (uvra). this inhibitory activity was dependent on the concentration of fatty acids, and fatty acids with longer alkyl chain were more potent. of the n-nitroso compounds tested, alpha-hydroxy nitrosamines underwent the strongest inhibitory effect. the rate of decomposition was not changed by addition of fatty acids. the partiti ... | 1991 | 1855917 |
| design of constructs for the expression of biologically active recombinant human factors x and xa. kinetic analysis of the expressed proteins. | activation of vitamin k-dependent plasma proteases occurs by specific interaction with components of the blood coagulation cascade. in this report, we describe the direct expression and enzymatic characterization of the human coagulation zymogen factor x and its activated form, factor xa, from transformed chinese hamster ovary fibroblast cell lines. expression was achieved using either a full-length factor x cdna or a unique mutant factor xa cdna. the functional factor xa precursor contained a n ... | 1991 | 1856206 |
| biosynthesis of glycosylated human lysozyme mutants. | complementary dna encoding human lysozyme was subjected to oligonucleotide-directed mutagenesis. at one of three selected positions, amino acid residues 22, 68, or 118, the signal for n-linked glycosylation was created. the mutant dnas were inserted into a eucaryotic vector and transfected into cultured hamster cells. the three mutant cdnas directed synthesis of lysozyme mutants, which were named li, lii, and liii. the mutant lysozymes li and lii comprised mixtures of glycosylated and nonglycosy ... | 1991 | 1856221 |
| cloning and expression of an a1 adenosine receptor from rat brain. | we have used the polymerase chain reaction technique to selectively amplify guanine nucleotide-binding regulatory protein (g protein)-coupled receptor cdna sequences from rat striatal mrna, using sets of highly degenerate primers derived from transmembrane sequences of previously cloned g protein-coupled receptors. a novel cdna fragment was identified, which exhibits considerable homology to various members of the g protein-coupled receptor family. this fragment was used to isolate a full-length ... | 1991 | 1857334 |
| distribution of m2 muscarinic receptors in rat brain using antisera selective for m2 receptors. | the dna fragment encoding the third intracellular loop of rat m2 muscarinic receptor was fused to the gene for staphylococcal protein a. the resultant fusion protein, expressed in bacteria, was purified via igg affinity chromatography and used as an antigen to raise a polyclonal antiserum. chinese hamster ovary cells transfected with cdna coding for a single muscarinic receptor subtype were used as tissue sources to screen antisera. the antiserum was shown to immunoprecipitate quantitatively (gr ... | 1991 | 1857338 |
| 32p-postlabelling analysis and micronuclei induction in primary chinese hamster lung cells exposed to tobacco particulate matter. | the genotoxicity of tobacco particulate matter (tpm) derived from a low-tar, low-nicotine cigarette has been examined by measuring micronucleus induction in a primary pulmonary cell line, both in the absence and presence of an exogenous source of metabolic activation. in an attempt to correlate the cytogenetic damage observed with dna adduct formation, dna extracted from tpm-treated cells has been analysed with two different modifications of the 32p-postlabelling assay. the results from the 32p- ... | 1991 | 1860172 |
| chemical induction of somatic gene mutations and chromosomal aberrations in lung fibroblasts of rats. | rats can be used to detect both somatic gene mutations and chromosomal aberrations induced in vivo. the technique adapted from chinese hamsters for the isolation and analysis of lung fibroblasts confirm the surprising results obtained in hamsters; namely, methyl methanesulphonate induces many micronuclei but no significant increase in gene mutations. in contrast ethylnitrosourea induces both micronuclei and gene mutations. | 1991 | 1861691 |
| preferential integration of marker dna into the chromosomal fragile site at 3p14: an approach to cloning fragile sites. | fragile sites are specific regions of chromosomes that are prone to breakage. in cells cultured under conditions that induce fragile site expression, high levels of inter- and intrachromosomal recombination have been observed involving chromosomal bands containing fragile sites. to determine whether expression of specific fragile sites would facilitate preferential integration of exogenous dna at these recombination hot spots, the vector psv2neo was transfected into a chinese hamster-human somat ... | 1991 | 1862089 |
| mast cell tryptase is a mitogen for cultured fibroblasts. | mast cells appear to promote fibroblast proliferation, presumably through secretion of growth factors, although the molecular mechanisms underlying this mitogenic potential have not been explained fully by known mast cell-derived mediators. we report here that tryptase, a trypsin-like serine proteinase of mast cell secretory granules, is a potent mitogen for fibroblasts in vitro. nanomolar concentrations of dog tryptase strongly stimulate thymidine incorporation in chinese hamster lung and rat-1 ... | 1991 | 1864960 |
| [the relationship of the saturation density of multilayer cell cultures to their mass exchange with the medium]. | chinese hamster fibroblasts (chf) and nih 3t3 cells were cultured on a glass substrate at different distances from the porous membrane separating the cells from the perfusing medium. it is shown that with perfusion of medium above the membrane there is no movement of the medium near the cells. in both the types of culture, the cells grow in multilayers, however the multilayer character of growth in chf is more pronounced than in nih 3t3 cells. the saturation density of the cultures depends on th ... | 1991 | 1866795 |
| [the proliferative characteristics of cells in culture during perfusion of the medium]. | the proliferation of chinese hamster fibroblasts (chf) and nih 3t3 cells was studied at different flow rates immediately above the cells. it is shown that there is a limiting density of saturation of the perfused culture that accounts for 1.7 x 10(6) - 2.0 x 10(6) cells/cm2 for nih 3t3 cells, and for 6 x 10(6) - 7 x 10(6) cells/cm2 for chf. the growth curves and the distribution of cells with respect to the phases of the cell cycle during cultivation with and without perfusion are presented. bas ... | 1991 | 1866796 |
| mutagenic properties of 2-amino-n6-hydroxyadenine in salmonella and in chinese hamster lung cells in culture. | the mutagenicity of the base analogue, 2-amino-n6-hydroxyadenine (aha), was tested in salmonella typhimurium ta100 and ta98 and in chinese hamster lung (chl) cells. aha showed very potent mutagenicity in ta100 without s9 mix, inducing 25,000 revertants/micrograms. the mutagenicity increased about 2-fold upon addition of s9 mix containing 10 microliters s9. aha was found to be one of the strongest mutagens for ta100. addition of s9 mix containing 100 microliters s9 induced no significant increase ... | 1991 | 1870613 |
| high level expression of recombinant human tissue factor in chinese hamster ovary cells as a human thromboplastin. | tissue factor (tf) is the high affinity transmembrane receptor and cofactor for cellular initiation of the plasma coagulation protease cascades by factor viia. we describe the synthesis of recombinant hutf by stably transfected cho cell lines carrying integrated hutf dna, and the isolation of hutf glycoprotein with specific functional activity equivalent to natural hutf. the expression vector (pcdm8), carrying the cytomegalovirus promoter to drive transcription of a partial cdna construct encodi ... | 1991 | 1871713 |
| dna double-strand breaks measured in individual cells subjected to gel electrophoresis. | microscopic examination of individual mammalian cells embedded in agarose, subjected to electrophoresis, and stained with a fluorescent dna-binding dye provides a novel way of measuring dna damage and more importantly, of assessing heterogeneity in dna damage within a mixed population of cells. with this method, dna double-strand breaks can be detected in populations of cells exposed to x-ray doses as low as 5 gy. the radiation dose-response relationship for initial formation of double-strand br ... | 1991 | 1873812 |
| sequence requirements for the stimulation of gene amplification by a mammalian genomic element. | hsag-1 is a 3.4-kb genomic element from a human chronic lymphocytic leukemia--chinese hamster ovary (cho) hybrid cell line shown to stimulate the amplification of expression vectors in cis when transfected into a variety of cell lines [mcarthur and stanners, j. biol. chem. 266 (1991) 6000-6005]. subfragments of hsag-1 were tested for amplification activity by insertion into the vector, psv2dhfr. the results suggest that multiple positive- and negative-acting elements were present that influenced ... | 1991 | 1874442 |
| an experimental approach to identifying the genotoxic risk from cooked meat mutagens. | in order to define the toxicological risk to the human population from the chemical compounds formed during the process of cooking animal meat, which have been described as possessing mutagenic, genotoxic and carcinogenic activities, an extensive study was undertaken of cooked meat extract and two cooked meat mutagens, 2-amino-3-methylimidazo(4,5-f)quinoline (iq) and 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline (meiqx). the study involved toxicokinetics and mouse-tissue distribution studies of ... | 1991 | 1874465 |
| [study of antimutagenic properties of bio-ginseng in mammalian cells in vitro and in vivo]. | the impact was studied of bio-ginseng produced from ginseng callus cells on the rate of chromosome rearrangements in chinese hamster cells and in continuous tumor cells of mice (ehrlich strain). bio-ginseng reduced rate of spontaneous sce as well as the level of mitomycin c-induced chromosome aberrations in chinese hamster cells. it protected ascitic tumor cells (ehrlich strain) against the mutagen action of urea nitrosomethyl. | 1991 | 1878567 |
| immunization with soluble murine cd4 induces an anti-self antibody response without causing impairment of immune function. | the t cell surface molecule cd4 (l3t4 in mouse) is important in the t lymphocyte response to ag presented in association with mhc class ii molecules. to examine the role of cd4 in immune function, we expressed a soluble form of murine cd4 by deleting the transmembrane and cytoplasmic regions of the l3t4 gene and transfecting the altered gene into chinese hamster ovary cells. the recombinant soluble mouse cd4 (smcd4) retained the native conformation of the external portion, as indicated by the bi ... | 1991 | 1880414 |
| site-specific mutagenesis of human follistatin. | follistatin is a monomeric protein originally discovered in ovarian follicular fluid as a suppressor of pituitary follicle-stimulating hormone (fsh) secretion, and later identified as a binding protein for activin. to explore the role of the asn-linked carbohydrate chains on the follistatin molecule in regard to the inhibition of fsh secretion and activin binding ability, site-specific mutations were introduced at either or both of the two potential asn-linked glycosylation sites of human follis ... | 1991 | 1883364 |
| expression, purification and characterization of secreted recombinant human insulin-like growth factor-i (igf-i) and the potent variant des(1-3) igf-i in chinese hamster ovary cells. | recombinant human insulin-like growth factor-i (higf-i) and a biologically potent variant lacking the n-terminal tripeptide (des(1-3)igf-i) were produced from transfected chinese hamster ovary cells. the constructs encoding the signal peptide, sequence of the mature peptide and a c-terminal extension peptide were expressed under the control of a rous sarcoma virus promoter. successfully transfected clones secreting correctly processed recombinant higf-i or des(1-3)igf-i were selected by their se ... | 1991 | 1883485 |
| posttranslational modifications of fibromodulin. | tyrosine sulfate residues were identified in fibromodulin produced by tracheal chondrocytes, by tendon and sclera fibroblasts in primary culture, as well as in chinese hamster ovary cells transfected with a construct containing fibromodulin cdna. the tyrosine sulfate residues were located in the n-terminal part of fibromodulin. thus, chinese hamster ovary cells expressing a deleted variant of fibromodulin lacking the n-terminal 52 amino acids following the predicted signal peptide did not contai ... | 1991 | 1885612 |
| effects of substrate texture and curvature on the morphology of cultured cells. | the ultrastructural characteristics of several growth matrices were examined using two cell types chosen for their distinct growth habits. chinese hamster ovary cells and balb-c 3t3 mouse fibroblasts were grown on flat substrates (glass, tissue culture plastic, millipore filters) as well as spherical (glass, tissue culture plastic, cross-linked dextran) substrates. cells were plated maintaining equal densities and growth surface area. once the majority of the cells reached confluency, the cell's ... | 1991 | 1885994 |
| post-transcriptional regulation in higher eukaryotes: the role of the reporter gene in controlling expression. | we have investigated whether reporter genes influence cytoplasmic regulation of gene expression in tobacco and chinese hamster ovary (cho) cells. two genes, uida encoding beta-glucuronidase (gus) from escherichia coli and luc, encoding firefly luciferase (luc), were used to analyze the ability of a cap, polyadenylated tail, and the 5'- and 3'-untranslated regions (utr) from tobacco mosaic virus (tmv) to regulate expression. the regulation associated with the 5' cap structure and the tmv 5'-utr, ... | 1991 | 1886610 |
| transduction of the cho aprt gene into mouse l cells using an adeno-5/aprt recombinant virus. | an adenovirus-5 recombinant virus adapt1 carrying the chinese hamster ovary (cho) adenine phosphoribosyltransferase (aprt) gene was constructed by insertion of a 2.5-kb fragment containing the complete cho aprt structural gene linked to a moloney murine sarcoma virus (msv) promoter into the e3 region of adenovirus-5. the cho aprt gene was in the opposite orientation to the adenovirus e3 promoter. mouse lapt- tk- (lat) cells expressed the cho aprt gene when infected with the virus, even at low mo ... | 1991 | 1887332 |
| expression of a human cdna encoding a protein containing gar synthetase, air synthetase, and gar transformylase corrects the defects in mutant chinese hamster ovary cells lacking these activities. | the isolation of a human cdna encoding the multifunctional protein containing gar synthetase, air synthetase, and gar transformylase by functional complementation of purine auxotrophy in yeast has been reported. chinese hamster ovary (cho) cell mutant purine auxotrophs deficient in gar synthetase (ade-c) or air synthetase plus gar transformylase (ade-g) activities were transfected with this human gart cdna subcloned into a mammalian expression vector. this restored 49-140% of the activities of g ... | 1991 | 1887337 |
| [expression of human lymphotoxin gene in cho-dhfr- cells]. | a recombinant plasmid p91-hult was constructed with a human lymphotoxin (hult) gene 2.4 kb ecori fragment and a mammalian cell expression vector plasmid p91023. the hult ecori dna fragment covers entire coding sequence and some 3(1) non-translated region sequence of the gene, p91-hult dna was used to transfect chinese hamster cell line cho-dhfr- cells by using calcium phosphate-dna coprecipitation method, and dhfr+ transfectants were obtained. rna dot blot hybridization analysis showed that the ... | 1991 | 1888532 |
| structure/activity investigations in eight arylalkyltriazenes comparison of chemical stability, mode of decomposition, and sce induction in chinese hamster v79-e cells. | a series of seven 1-aryl-3.3-dialkyltriazenes, including 1-phenyl-3.3-dimethyltriazene (dmpt), 1-phenyl-3.3-di-(trideuteromethyl)-triazene (dmpt-ds), 1-p-methylphenyl-3.3-dimethyltriazene (dmpmpt), 1-p-nitrophenyl-3.3-dimethyltriazene (dmpnpt), 1-phenyl-3.3-diethyltriazene (dept), 1-phenyl-3.3-di-n-propyltriazene (dnprpt) and 1-phenyl-3.3-diisopropyltriazene (diprpt) and 1.3-diphenyl-3-methyltriazene (dpmt), was synthesized and characterized by uv/vis, ir and 1h-nmr spectroscopy. chemical half-l ... | 1991 | 1889006 |
| adaptation of the interspersed repetitive sequence polymerase chain reaction to the isolation of mouse dna probes from somatic cell hybrids on a hamster background. | a strategy for the rapid isolation of dna probes from radiation-fusion chinese hamster cell hybrids containing overlapping portions of the murine x chromosome based on the interspersed repetitive sequence polymerase chain reaction (irs-pcr) previously used with human somatic cell hybrids has been developed. this specific amplification of mouse dna on a hamster background depends on the use of primers directed to the b2 short interspersed repeat element family and the r repeat, from the long inte ... | 1991 | 1889819 |
| inhibition of mutagenesis and transformation by root extracts of panax ginseng in vitro. | the root extract of panax ginseng was investigated for its inhibitory effects on dna synthesis, mutagenicity, and cellular transformation using v79 and nih 3t3 cells. dna synthesis measured by the [3h]thymidine incorporation into v79 chinese hamster lung cells was significantly decreased by the addition of ginseng extract (0-1 microgram/ml) to the medium. however, ginseng extract was found to increase the rate of dna excision repair synthesis in v79 cells in response to treatment with uv radiati ... | 1991 | 1891494 |