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site-directed mutagenesis of an apolipoprotein e mutant, apo e5(glu3----lys) and its binding to low density lipoprotein receptors.apo e5(glu3----lys) is a naturally occurring apolipoprotein e (apo e) mutant found in patients with hyperlipoproteinemia and atherosclerosis. it has been shown to have a high affinity for low density lipoprotein (ldl) receptors. in this study, mutant apo e5 was produced by chinese hamster ovary cells by means of an in vitro site-directed mutagenesis technique, and its ldl receptor binding activity was assessed. the apo e5 obtained from gene expression bound more readily to the ldl receptor than ...19921530612
4-fluorobenzylamine and phenylalanine methyl ester conjugates of 2-nitroimidazole: evaluation as hypoxic cell radiosensitizers.we have synthesized two 2-nitroimidazole derivatives and evaluated their hypoxic radiosensitization properties. the first, a 4-fluorobenzylamine conjugate of 2-nitroimidazole (pk-110), was designed so that it could also be labeled with the f-18 and used for positron emission tomographic imaging of hypoxia. the second, the l-phenylalanine methyl ester conjugate of 2-nitroimidazole (pk-130), was designed in an attempt to exploit amino acid transport channels to enhance drug transport into the tumo ...19921531220
identification of a high molecular weight macrophage colony-stimulating factor as a glycosaminoglycan-containing species.chinese hamster ovary cells transfected with a 4.0-kilobase macrophage colony-stimulating factor (m-csf) cdna express two different m-csf species; one has an apparent molecular weight of 85,000 and is identified as a homodimer of a 43-kda subunit, and the other has an indeterminate structure greater than 200 kda. in this study, we investigated the structure of the high molecular weight m-csf by immunochemical procedures. the high molecular weight m-csf was easily purified, since it bound tightly ...19921531650
sensitization of chinese hamster ovary cells to melphalan by etanidazole under intermittent hypoxia.incubation of chinese hamster ovary cells with etanidazole under hypoxic conditions increases cell killing by subsequent treatment with melphalan under aerobic conditions. we report here that this sensitization can be achieved even if periods of hypoxia are interrupted by reoxygenation. preincubation under hypoxia in the absence of etanidazole also results in sensitization to melphalan. intermittent hypoxia is less effective than continuous hypoxia as a single sensitizing factor. glutathione dep ...19921531977
a single mutation affects both n-acetylglucosaminyltransferase and glucuronosyltransferase activities in a chinese hamster ovary cell mutant defective in heparan sulfate biosynthesis.mutants of chinese hamster ovary cells have been found that no longer produce heparan sulfate. characterization of one of the mutants, pgsd-677, showed that it lacks both n-acetylglucosaminyl- and glucuronosyltransferase, enzymes required for the polymerization of heparan sulfate chains. pgsd-677 also accumulates 3- to 4-fold more chondroitin sulfate than the wild type. cell hybrids derived from pgsd-677 and wild type regained both transferase activities and the capacity to synthesize heparan su ...19921532254
biochemical properties of recombinant single-chain urokinase-type plasminogen activator mutants with deletion of asn2 through phe157 and/or substitution of cys279 with ala.the contribution of the nh2-terminal polypeptide chain and of the cys148-cys279 interchain disulphide bond to the enzyme activity of urokinase-type plasminogen activator (u-pa) was studied using site-specific mutagenesis. recombinant single-chain u-pa (rscu-pa) variants were produced by transfecting chinese hamster ovary cells with cdna encoding des(asn2-phe157)rscu-pa (rscu-pa with deletion of asn2-phe157), [ala279]rscu-pa (rscu-pa with cys279----ala mutation) or des(asn2-phe157)[ala279]rscu-pa ...19921533368
3-hydroxy-3-methylglutaryl-coenzyme a reductase and t cell receptor alpha subunit are differentially degraded in the endoplasmic reticulum.3-hydroxy-3-methylglutaryl-coenzyme a reductase (hmg-coa reductase) is located in the endoplasmic reticulum (er) and responds to rapid degradation which is regulated by mevalonate or sterols. t cell antigen receptor alpha chain (tcr alpha) is also known to be rapidly degraded within the er. in both cases, the membrane domains of the proteins have a crucial role in their rapid degradation. in order to investigate protein degradation in the er, we compared the degradation of hmg-coa reductase and ...19921533625
recombinant dna hepatitis b vaccine containing pre-s components of the hbv coat protein--a preliminary study on immunogenicity.a novel recombinant hepatitis b vaccine, trademarked sci-b-vac, was evaluated for safety, tolerability and immunogenicity in an open label trial performed in singapore. the experimental vaccine, derived from chinese hamster ovary (cho) cells, consists of hepatitis b surface antigen (hbsag) particles harbouring all three viral envelope polypeptides, the major s protein and the minor pre-s2 and pre-s1, in their glycosylated and non-glycosylated forms. the vaccine was administered intramuscularly a ...19921535170
two glucose transporter isoforms are sorted differentially and are expressed in distinct cellular compartments.rat glut4 (adipocyte/muscle-type glucose transporter) was expressed in two fibroblastic cell lines, chinese hamster ovary (cho) cells and 3t3-l1 fibroblasts, under the control of the methallothionein i promoter. although immunoblotting with a glut4-specific anti-peptide antibody demonstrated that the amount of glut4 expressed was comparable with that in 3t3-l1 adipocytes and rat adipose tissues, no increase in 2-deoxy-d-glucose uptake was observed in the basal state in fibroblasts. immunocytoche ...19921536658
inhibition of glutathione reductase activity by a carbamoylating nitrosourea: effect on cellular radiosensitivity.nitrosoureas inactivate cellular glutathione reductase. n,'n'1,3-bis(trans-4-hydroxycyclohexyl)-n'-nitrosoureas (bcynu), a nitrosourea reported to selectively inhibit glutathione reductase (gr) activity, was examined to determine if it could be used as a means to inhibit cellular levels of this enzyme in radiobiology studies. confirmation of drug-induced inhibition of gr activity was demonstrated using a cell-free model system employing purified gr. cellular studies with chinese hamster v79a03 s ...19921537571
isolation and characterization of chinese hamster ovary cells defective in the intracellular metabolism of low density lipoprotein-derived cholesterol.we have isolated clones of an established cell line which express defects in intracellular cholesterol metabolism. chinese hamster ovary cells were mutagenized, and clones unable to mobilize low density lipoprotein (ldl)-derived cholesterol to the plasma membrane were selected. biochemical analysis of two mutant clones revealed a phenotype characteristic of the lysosomal storage disease, niemann-pick type c. the mutant cell lines were found to be defective in the regulatory responses elicited by ...19921537866
loss of one asparagine-linked oligosaccharide from human transferrin receptors results in specific cleavage and association with the endoplasmic reticulum.the coding sequence for the human transferrin receptor gene has been mutated in order to abolish the attachment of the oligosaccharide closest to the transmembrane sequence. expression of the mutant receptor in chinese hamster ovary cells resulted, after analysis under nonreducing conditions, in an 85- and a 73-kda receptor species. after reduction, the 85-kda receptors were mostly converted to 73 kda, although with short labeling periods some 85-kda receptor remained suggesting that the mutated ...19921537870
cell-dependent posttranslational processing and secretion of recombinant mouse renin-2.in the dba/2 mouse submandibular gland (smg), renin is predominantly the expression product of the renin gene ren-2d. prorenin is synthesized and rapidly converted to a constitutively secreted single-chain intermediate, which is then processed to and stored as the mature two-chain (2c) form, which is released by regulated secretion. to evaluate whether the mode of renin processing is cell dependent, renin (ren-2d) complementary dna was stably integrated in the genome of chinese hamster ovary (ch ...19921539649
chemical protection and cell-cycle effects on radiation-induced mutagenesis.chinese hamster ovary cells in the exponential phase of growth were harvested and separated by the method of centrifugal elutriation into subpopulations enriched with up to 95% g1 phase, 70% s phase and 65% g2 + m phase cells. cell cycle distributions were routinely monitored by flow cytometry. following elutriation, aliquots of cells from each of the enriched cell fractions were incubated in the presence or absence of 4 mm of 2-[(aminopropyl)amino] ethanethiol (wr-1065) for 30 min at 37 degrees ...19921540681
analysis of solvent control and 1-nitrosopyrene-induced chinese hamster ovary cell mutants by southern and northern blots and the polymerase chain reaction.1-nitrosopyrene, a metabolite of the tumorigenic environmental pollutant 1-nitropyrene, is a potent mutagen at the hprt locus in chinese hamster ovary (cho) cells. a single dna adduct, n-(deoxyguanosin-8-yl)-1-aminopyrene, is produced in cho cells treated with 1-nitrosopyrene, and this adduct is found in rats and mice exposed to 1-nitropyrene. in this study, the structure of the hprt gene and the structure and amount of hprt mrna were analyzed in 43 cho cell mutants (16 isolated from solvent con ...19921541256
spectrum of spontaneously occurring mutations in the hprt gene of v79 chinese hamster cells.a total of 76 independent spontaneous mutants in the hprt gene of v79 chinese hamster cells have been analyzed. these mutants were obtained in two different laboratories, 17 and 59 mutants in sets 1 and 2, respectively, under different cell culture conditions. mutation analysis was performed by amplification of hprt cdna with the polymerase chain reaction and direct sequencing of the products. the data obtained showed similar spectra of spontaneous mutations in both sets of mutants, suggesting t ...19921542110
isolation and partial characterization of a surface glycoconjugate of entamoeba histolytica.to study surface molecules of entamoeba histolytica we produced monoclonal antibodies from mice immunized with lysates from the pathogenic amebic strain hm1:imss, and screened them for the ability to inhibit e. histolytica adhesion. one monoclonal antibody, cc 8.6, was a potent inhibitor of amebic adhesion to a chinese hamster ovary cell line, and was capable of inhibiting hm1:imss mediated cytotoxicity by 50%. we found that monoclonal antibody cc 8.6 bound to an amebic glycoconjugate. the glyco ...19921542307
biological properties of some benzopsoralen derivatives.the biological activity of some benzopsoralen derivatives, prepared with the aim of obtaining new drugs for photochemotherapy, has been studied. the more interesting compounds are 4-hydroxymethyl-4',5'-benzopsoralen and 4-hydroxymethyl-4',5'-tetrahydro-benzopsoralen, which were found to be active in the dark also: dna and rna synthesis were both inhibited in ehrlich cells, even if in a partially reversible fashion, while protein synthesis remained unaffected. in chinese hamster ovary cells cultu ...19921542703
protection by the fluoride ion against phthalocyanine-induced photodynamic killing of chinese hamster cells.when a dilute f- solution was added to a culture of chinese hamster cells that had been preincubated with an aluminium phthalocyanine sensitizer derived from alpccl, the photosensitivity of the cells was markedly reduced compared to control cells not treated with f-. under the same treatment conditions, the reduction in [3h]thymidine incorporation into cellular dna caused by light and this sensitizer and the production of dna-protein crosslinks caused by light and this sensitizer were also inhib ...19921542704
correlation of insulin receptor level with both insulin action and breakdown of a potential insulin mediator precursor; studies in cho cell-lines transfected with insulin receptor cdna.a phosphatidylinositol-glycan (pi-glycan) has been described previously that may serve as the precursor for a mediator of some of insulins actions. the present study further addresses the potential relevance of this compound by correlating its breakdown with other insulin actions in chinese hamster ovary (cho) cells which express different levels of insulin receptor. comparisons were drawn between parent cho cells expressing 3 x 10(3) receptors/cells and two cell-lines transfected with human ins ...19921543757
characterization of the central region containing the x-inactivation center and terminal region of the mouse x chromosome using irradiation and fusion gene transfer hybrids.the irradiation and fusion gene transfer (ifgt) procedure provides a means of isolating subchromosomal fragments for use in the mapping of loci and for cloning probes from a particular area of a chromosome. using this procedure, two large panels of somatic cell hybrids that contain mouse x chromosome (chr) fragments have been generated. these hybrid panels were generated by irradiating the monochromosomal mouse-hamster hybrid hybx, which retains the mouse x chr, with either 10 k or 50 k rads of ...19921543901
the mink gene for the lambda light immunoglobulin chain: characterization of cdna and chromosomal localization.a cdna library from mink spleen was constructed by use of the phage lambda gt11. the library was screened using polyvalent serum raised against the mink immunoglobulin lambda chain. as a result, several clones expressing mink immunoglobulin lambda light chains were identified. sequencing of one of the clones with an 803 bp insert was performed. the insert comprised nearly the entire coding region for the mature lambda light immunoglobulin gene with the exception of the leader polypeptide and sev ...19921543908
expression of human pituitary adenylate cyclase activating polypeptide (pacap) cdna in cho cells and characterization of the products.cdna encoding human pacap precursor was expressed in non-neuroendocrine chinese hamster ovary cells, cho-k1, the cells were transfected with expression vector (pts705) containing the human pacap cdna by electroporation. a cell line which produced more than 80 ng/ml of immunoreactive pacap (ir-pacap) into the conditioned medium was established. rp-hplc analysis of culture medium of this established cell line exhibited the presence of two types of pacap, i.e. pacap38 and pacap27. at the same time, ...19921544422
characterization of a cho cell line resistant to killing by the hypoxic cell cytotoxin sr 4233.one approach to understanding the mechanism of selective hypoxic cell killing by the benzotriazine-di-n-oxide, sr 4233, is to characterize cell lines that exhibit increased resistance to killing by this drug. the chinese hamster ovary cell line bl-10 was originally isolated on the basis of its hypersensitivity to killing by bleomycin. it is 2.7-fold more resistant to hypoxic cell killing by sr 4233 than wild-type cho on comparison of d0's. however, both bl-10 and cho possess the same sensitivity ...19921544836
evaluation of bioreductive drugs in multicell spheroids.the therapeutic potential of a variety of bioreductive agents, including misonidazole, rsu-1069, nfvo, mitomycin c, porfiromycin, and sr-4233 was evaluated using chinese hamster v79 multicell spheroids in vitro. fluorescence-activated cell sorting techniques were used to selectively recover cells from various depths within the spheroids to measure the differential cytotoxicity in the cells near the hypoxic core of the spheroid relative to the well oxygenated peripheral cells. at the high cell de ...19921544838
extracellular: intracellular and subcellular concentration gradients of thiols.chinese hamster v79 cells in eagle's minimum essential medium in vitro at room temperature were incubated with the aminothiol, wr-1065, or glutathione (gsh) at extracellular concentrations of approximately 1 mmol dm-3. average intracellular concentrations of gsh, cysteine, and wr-1065 were measured by high performance liquid chromatography, and the effective reducing environment near dna probed by staining the cells with acridine orange (ao) and measuring the delayed fluorescence. exposure to ei ...19921544848
what role do glutathione s-transferases play in the cellular response to ionizing radiation?the glutathione s-transferases (gst's) are cytosolic dimeric proteins that are composed of three family members, alpha, pi, and mu, and a fourth microsomal member. these four family members are primarily involved in cellular detoxification of xenobiotics and hydroperoxides. recently, a strong correlation has been found between the overexpression of gst's and resistance to chemotherapeutic drugs. in comparison to chemotherapy, little is known about the role of gst's in the cellular response to io ...19921544849
topical application of nitroxide protects radiation-induced alopecia in guinea pigs.we have recently found that treatment of chinese hamster v79 cells with the stable nitroxide radical tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) afforded significant protection against superoxide, hydrogen peroxide, and x-ray mediated cytotoxicity. radiation-induced alopecia is a common radiotherapeutic problem. topical application of tempol was evaluated for possible protective effects against radiation-induced alopecia using guinea pig skin as a model. for single acute x-ray doses ...19921544853
protection against azt-induced mutagenesis at the hgprt locus in a human cell line by wr-151326.the anti-aids agent, azt (3'-azido-3'-deoxythymidine), is mutagenic in a cultured human hepatoma cell line designated hepg2 at the hgprt (hypoxanthine-guanine phosphoribosyl transferase) locus. using an exposure time of 3 hr, the number of mutants per 10(6) surviving cells increased as a function of azt dose from 125 to 520. chinese hamster ovary cells, in contrast, are not affected with respect to this endpoint when similar concentrations of azt are used (i.e., 0.1 to 10 mg/ml). the aminothiol ...19921544855
depletion of intracellular glutathione by 1-methyl-2-nitrosoimidazole.in addition to their ability to radiosensitize, nitroimidazoles are selectively toxic toward hypoxic cells. reduction of the nitro group is required to observe cytotoxicity. one of the reduction products believed to play a role in this cytotoxicity is the nitroso-derivative. one-methyl-2-nitrosoimidazole (ino), chemically synthesized from one-methyl-2-nitroimidazole (ino2), has been used as a model to study the reactivity of 2-nitrosoimidazoles. the ability of ino to react rapidly with glutathio ...19921544856
brefeldin a-induced increase of sphingomyelin synthesis. assay for the action of the antibiotic in mammalian cells.brefeldin a leads to an increase of sphingomyelin in chinese hamster ovary cells. the antibiotic is known to cause a dramatic morphological change of the endomembrane system in various mammalian cells resulting in a redistribution of golgi resident proteins to the endoplasmic reticulum (lippincott-schwartz, j., donaldson, j. g., schweizer, a., berger, e. g., hauri, h. p., yuan, l. c., and klausner, r. d. (1990) cell 60, 821-836). a strict correlation was found between the brefeldin a-induced inc ...19781544889
characteristic synthesis and redistribution of 70 kd heat shock protein in thermotolerant chinese hamster v79 cells.upon exposure to heat shock the increased rate of hsp70 synthesis decreased more rapidly in thermotolerant v79 cells than in the non-thermotolerant cells. however, the levels of hsp70 in the thermotolerant cells at 12 h after a heat shock were almost the same as those in the non-thermotolerant cells. on the other hand, the migration of hsp70 from cytoplasm to nucleoli after a heat shock was very rapid in both thermotolerant and non-thermotolerant cells, but hsp70 in the nucleoli disappeared fast ...20131545158
different specificities of platelet-associated and plasma autoantibodies to platelet gpiib-iiia in patients with chronic immune thrombocytopenic purpura.chronic immune thrombocytopenic purpura (itp) is an autoimmune disorder due to antiplatelet autoantibodies, many of which are directed against platelet membrane glycoprotein (gp) iib-iiia or gpib-ix. in a recent study, we described plasma autoantibodies from 13 selected itp patients, which required the presence of the putative gpiiia cytoplasmic region for antibody binding. since this region may not be available for antibody binding under physiologic conditions, we evaluated the frequency of bin ...19921547343
mutagenic activity of arylnitrenium ions from arylazides--induction of sister chromatid exchange in mammalian (v79 chinese hamster) cells.photolysis of arylazides produces short-lived reactive species, very likely arylnitrenium ions which bind to nucleotides and dna and produce mutations in salmonella. the present report shows that arylazides can be photo-activated in mammalian (v79 chinese hamster) cells and that sister chromatid exchange can thus be induced. arylazides studied are (in order of decreasing sce-inducing potency) azido-isoiq, azido-meiq, azido-iq, azido-meiqx, azido-phip, 6-azido-chrysene, 2-azidofluorene, 4-azidofl ...19921547513
glutathione is the antioxidant responsible for resistance to oxidative stress in v79 chinese hamster fibroblasts rendered resistant to cadmium.by manipulation of cd and zn concentrations in the medium, several phenotypes, differing in the contents of glutathione (gsh) and metallothionein (mt), were derived from a parental clone of v79 chinese hamster fibroblast. in some of these phenotypes, resistance to cd and cross-resistance to oxidative stress was developed. the highest levels of gsh and mt were found in cells which were rendered resistant to cd by stepwise increases of cd and zn in the cell medium for over 50 passages. upon remova ...19921547517
role of amino acids 261-418 in proteolytic cleavage of the extracellular region of the human thyrotropin receptor.previous in vivo cross-linking studies of tsh to the recombinant tsh receptor revealed that the receptor exists at least in part as a single chain glycoprotein of approximately about 100 kilodaltons (kda), with intramolecular disulfide bonds. tsh also binds to a 54-kda amino-terminal fragment of the tsh receptor (cleaved up-stream of amino acid residue 317). in the present study in order to better understand the structure of the tsh receptor, we covalently cross-linked radiolabeled tsh to six ts ...19921547731
methotrexate-induced overexpression of functional glucocorticoid receptors in chinese hamster ovary cells.we have used a modified cotransfection and selection strategy to create a series of mammalian cell lines that stably express high levels of intact glucocorticoid receptors. these cell lines were produced by subjecting chinese hamster ovary (cho) cells, which had been previously cotransfected with a glucocorticoid-responsive dihydrofolate reductase (dhfr) gene and the human glucocorticoid receptor gene, to growth in increasing concentrations of methotrexate (mtx). by linking the mtx selection pro ...19921547909
fine-structure map of the human ribosomal protein gene rps14.we have used polymerase chain reaction-mediated chemical mutagenesis (j.-j. diaz, d. d. rhoads, and d. j. roufa, biotechniques 11:204-211, 1991) to analyze the genetic fine structure of a human ribosomal protein gene, rps14. eighty-three dna clones containing 158 random single-base substitution mutations were isolated. mutant rps14 alleles were tested for biological activity by transfection into cultured chinese hamster cells. the resulting data permitted us to construct a map of the s14-coding ...19921549121
common double- and single-stranded dna binding factor for a sterol regulatory element.a cis-acting element necessary for sterol regulation, sre-1, has previously been identified in the promoters of the low density lipoprotein receptor, hydroxymethylglutaryl (hmg)-coa reductase, and hmg-coa synthase genes. in this report we describe a nuclear factor, sre-bf, isolated from chinese hamster ovary nuclear extracts, that binds to the sre-1 octanucleotide sequence. in addition to sequence-specific binding to sre-1, as indicated by competition analysis with double-stranded dna fragments, ...19921549579
angiogenin supports endothelial and fibroblast cell adhesion.when coated on bacteriological plastic at doses greater than or equal to 0.1 microgram/cm2, human and bovine angiogenin support calf pulmonary artery endothelial and chinese hamster fibroblast cell adhesion and spreading, but do not affect cell adhesion when in solution. the kinetics of endothelial cell attachment to angiogenin are indistinguishable from those in the presence of gelatin. calcium and/or magnesium ions are critical for cell adhesion or spreading onto angiogenin but protein synthes ...19921549588
inhibition of p34cdc2 kinase activation, p34cdc2 tyrosine dephosphorylation, and mitotic progression in chinese hamster ovary cells exposed to etoposide.p34cdc2 kinase, an enzyme essential for mitosis in mammalian cells, may play a role in etoposide-induced g2 phase arrest of chinese hamster ovary cells. in this study, etoposide is shown to cause inhibition of a specific p34cdc2 kinase activation pathway, that of tyrosine dephosphorylation. exposure of asynchronously dividing cells to etoposide caused a simultaneous rapid decline of both mitotic index and p34cdc2 kinase activity, suggesting that the kinase was not activated and that the arrest p ...19921551112
cell-specific carbohydrate metabolism regulates s14 gene transcription.carbohydrate administration rapidly regulates hepatic mrna-s14 content. both sucrose and fructose but not glucose increase the transcription of hepatic mrna-s14 in vivo. in primary hepatocyte cultures, mrna-s14 transcription responds to either fructose or glucose. to test the hypothesis that the difference in hexose response is due to differences in cellular metabolism, we studied the regulation of this gene with a transient transfection assay system in chinese hamster ovary (cho) cells, hamster ...19921551493
biochemical and immunological properties of rat recombinant interleukin-2 and interleukin-4.we have previously described the isolation and sequencing of cdna clones encoding rat interleukin-2 (il-2) and interleukin-4 (il-4). in the present study, we report the generation of stably transfected chinese hamster ovary (cho) cell lines which constitutively synthesize and secrete high levels of rat recombinant il-2 (ril-2) and il-4 (ril-4). the expression of the cytokine cdna sequences is driven by the human cytomegalovirus promoter/enhancer within the respective pee6. hcmv-gs vector constru ...19921551691
requirement for ercc-1 and ercc-3 gene products in dna excision repair in vitro. complementation using rodent and human cell extracts.numerous rodent cell lines exist that have defects in nucleotide excision repair of dna caused by alterations in genes that fall into 10 different complementation groups. the precise roles in the repair of these genes are unknown. we report here that extracts from chinese hamster ovary cells of excision repair-defective complementation groups 1 and 3 are defective in dna excision repair in a cell-free system. in vitro complementation can be achieved by mixing extracts from the two groups with on ...19921551896
cysteine 647 in the insulin receptor is required for normal covalent interaction between alpha- and beta-subunits and signal transduction.we have investigated the structural and functional properties of two mutant insulin receptors in which cys647 and cys682,683,685 have been replaced with ser (irs647 and irs682,683,685, respectively). compared with the wild-type receptor (irwt), both mutant receptors displayed altered sensitivities to dithiothreitol with respect to insulin binding and reduction of oligomeric forms. subunit composition of the oligomeric forms of the receptors as determined by two-dimensional sodium dodecyl sulfate ...20061551916
potentiation of cytotoxicity of mitoxantrone toward cho-k1 cells in vitro by dipyridamole.dipyridamole (dp), a clinically used vasodilator and an antiplatelet compound, augmented the activity of the anticancer drug mitoxantrone (mxn) toward chinese hamster ovary (cho-k1) cells in culture. clonogenic assays indicated that dp (1.0, 2.5, and 5.0 microm) decreased the survival of cells treated with mxn (5 to 25 nm) in a dose-dependent manner. further, dp (1 and 5 microm) decreased the mxn concentration required for 50% inhibition of cell growth from 3.2 to 1.8 and from 3.0 to 0.5 nm, res ...19921553337
identification and functional importance of tyrosine sulfate residues within recombinant factor viii.sulfated tyrosine residues within recombinant human factor viii were identified by [35s]sulfate biosynthetic labeling of chinese hamster ovary cells which express human recombinant factor viii. alkaline hydrolysis of purified [35s]sulfate-labeled factor viii showed that greater than 95% of the [35s]sulfate was incorporated into tyrosine. [3h]tyrosine and [35s]sulfate double labeling was used to quantify the presence of 6 mol of tyrosine sulfate per mole of factor viii. amino acid sequence analys ...19921554716
construction of a dominant selectable marker using a novel dihydrofolate reductase.simian virus 40 promoter-enhancer-based mammalian expression plasmids using dihydrofolate reductase (dhfr)-encoding cdna sequences originally isolated from two methotrexate (mtx)-resistant, dhfr-overproducing chinese hamster lung cell lines were constructed. one, designated psva75, contains a dhfr cdna that encodes leucine (leu22) and corresponds to the wild type (wt), mtx-sensitive form of the enzyme [melera et al., j. biol. chem. 263 (1988) 1978-1990]. the other plasmid, psva3, contains a cdna ...19921555767
recovery of sublethal radiation damage and its inhibition by hyperthermia in normal and transformed mouse cells.radiation resistance may be related in part to the capacity of cells to repair radiation damage which can usually be characterized by the survival curve shoulder and split dose recovery. c3h-10t1/2 normal and transformed cells and v79 cells were evaluated for their ability to recover from sublethal radiation damage and for hyperthermia to affect this recovery. the transformed cell line of the 10t1/2 cell system displayed a much larger capacity to recover from radiation damage than did the parent ...19921555949
maturation of lipoprotein lipase. expression of full catalytic activity requires glucose trimming but not translocation to the cis-golgi compartment.the relationship between maturation of lipoprotein lipase (lpl) and its translocation from the endoplasmic reticulum (er) to the golgi complex was determined by measuring lipolytic activity under conditions preventing transport of the enzyme from the er to the golgi compartment. in the presence of brefeldin a, a reagent that inhibits movement of proteins from the er and causes the disassembly of the golgi complex, pro-5 chinese hamster ovary cells accumulated catalytically active lpl, while secr ...19921556130
elemental composition in the pancreatic b cell is normal in the prediabetic chinese hamster.to clarify whether elemental changes are present before the onset of diabetes, freeze-dried pancreas sections from young (18-19 days old), genetically prediabetic chinese hamsters were subjected to proton bombardment and the concentrations of 15 elements (na, mg, al, p, s, cl, k, ca, mn, fe, cu, zn, rb, cd, and pb) in b cells and exocrine pancreas were calculated from the x-rays emitted. we have previously shown that islet b cells and exocrine pancreas from adult, overtly diabetic chinese hamste ...19921557338
the human cytokine i-309 is a monocyte chemoattractant.the human cytokine i-309 is a small glycoprotein secreted by activated t lymphocytes and structurally related to a number of inflammatory cytokines. to investigate the biological activities of i-309 protein, we produced a stable chinese hamster ovary cell transfectant, cdi.10, which constitutively secretes i-309 protein into culture supernatant. affinity chromatography on a heparin-sepharose matrix followed by reverse-phase hplc was used to purify to homogeneity a glycoprotein doublet of 15-16 k ...19921557400
isolation and initial characterization of a large repeat sequence element specific to mouse chromosome 8.a clone containing 15.6 kb of mouse genomic dna was specifically localized to murine chromosome 8 by fluorescence in situ hybridization. the major signal, mapping just below the centromeric heterochromatin, was much too intense for a single-copy probe. two additional weak hybridization signals were detected in or near distal bands 8b3 and 8d. six subclones spanning the entire 15.6-kb insert gave strong centromere proximal signals; however, none of these clones cross-hybridized with each other, s ...19921559702
activation of phospholipase d by protein kinase c. evidence for a phosphorylation-independent mechanism.the role of protein kinase c (pkc) in the regulation of phosphatidylcholine-hydrolyzing phospholipase d (pld) was investigated. in membranes from chinese hamster lung fibroblasts that had been incubated with [14c]choline to label endogenous phosphatidylcholine, phorbol 12-myristate 13-acetate (pma) failed to stimulate production of [14c]choline. however, stimulation was observed if fibroblast cytosolic fraction or pkc partially purified from this fraction was added. when incubated with membranes ...19921559964
brefeldin a binds to glutathione s-transferase and is secreted as glutathione and cysteine conjugates by chinese hamster ovary cells.radioactively labeled brefeldin a was used to probe for proteins that interact with this metabolite. the most prominent protein labeled after in vivo incubation of chinese hamster ovary cells with [3h]brefeldin a turned out to have an apparent molecular mass of 26 kda. radioactive peptides derived from the [3h]brefeldin a-labeled protein showed sequence identity with glutathione s-transferases, and immunoblotting after two-dimensional gel electrophoresis confirmed this result. in addition, chine ...19921560007
the signal anchor and stem regions of the beta-galactoside alpha 2,6-sialyltransferase may each act to localize the enzyme to the golgi apparatus.the beta-galactoside alpha 2,6-sialyltransferase has been localized to the trans cisternae of the golgi apparatus and the trans golgi network where it transfers sialic acid residues to terminal positions on n-linked oligosaccharides. it is a type ii transmembrane protein possessing a 9-amino acid amino-terminal cytoplasmic tail, a 17-amino acid signal anchor domain, and a 35-amino acid stem region which tethers the large luminal catalytic domain to the membrane anchor. previous work has demonstr ...19921560012
heat-resistant variants of the chinese hamster ovary cell: alteration of cellular structure and expression of vimentin.three heat-resistant mutant cell lines (78-1, 78-2, 78-3) were previously selected from chinese hamster ovary cells. in this study, we investigated whether the differences in intrinsic thermal sensitivity result from alteration of stress protein levels or cellular structural changes. although there was no significant difference in the levels of stress proteins, i.e., constitutive hsp70 in wild type and three heat-resistant mutant strains, there were marked differences in the amounts of vimentin ...19921560039
localization and dna sequence of a replication origin in the rhodopsin gene locus of chinese hamster cells.a chromosomal origin of dna replication has been localized within the single-copy rhodopsin gene locus in chinese hamster (line cho) cells using two methods. in the first method, single-copy segments were identified at 3 to 15 kb intervals within approximately 75 kb (kb = 10(3) bases) of cloned genomic dna containing the early-replicating rhodopsin gene near its middle. the cloned single-copy segments were then used as hybridization probes to quantify the replication of their corresponding genom ...19921560457
the paradoxical nature of dna damage and cell death induced by 125i decay.chinese hamster ovary cells were synchronized at the g1/s-phase boundary of the cell cycle and pulse-labeled for 10 min with 125i-iododeoxyuridine 30 min after entering the s phase. cell samples were harvested for freezing and 125i-decay accumulation at intervals ranging from 15 to 480 min after termination of labeling. the survival data showed a marked shift from cell killing characteristic of low-let radiation to that more characteristic of killing by high-let radiation with increasing interva ...19921561311
heat-induced changes in the membrane fluidity of chinese hamster ovary cells measured by flow cytometry.flow cytometry was used to measure the fluorescence polarization of the lipid probe trimethylammonium-diphenylhexatriene as an indicator of plasma membrane fluidity of chinese hamster ovary (cho) cells heated under various conditions. fluorescence polarization was measured at room temperature about 25 min after heating. when cells were heated for 45 min at temperatures above 42 degrees c, fluorescence polarization decreased progressively, signifying an increase in plasma membrane fluidity. the f ...19921561317
the effect of 45 degrees c hyperthermia on the membrane fluidity of cells of several lines.the membrane fluidity of cells of human (ag1522 human foreskin fibroblasts), rodent [chinese hamster ovary (cho) and radiation-induced mouse fibrosarcoma], and feline (crandall feline kidney) cell lines after heating at 45 degrees c was measured by flow cytometry. in addition, a heat-resistant variant of radiation-induced mouse fibrosarcoma cells and two heat-sensitive cho strains were studied. fluorescence polarization of the plasma membrane probe trimethylammonium-diphenylhexatriene was used a ...19921561318
the relationship of doxorubicin binding to membrane lipids with drug resistance.doxorubicin (dox, adriamycin) binds with high affinity to cellular membranes inflicting multiple lesions which are believed to be important in dox-mediated neoplastic cell death. using fluorescence and radioactive [14-14c-14]dox assays for dox, we have measured the partitioning of dox between the cytosolic and membrane fractions of erythrocytes and of dox-sensitive (v-79) and -resistant (lz) chinese hamster lung fibroblast cells. in both erythrocytes and fibroblasts, a significant fraction of do ...19921562987
a sequestered pool of aminoacyl-trna in mammalian cells.we have recently proposed that aminoacyl-trna is channeled during protein synthesis in vivo--i.e., it is directly transferred among the components of the protein-synthesizing machinery and does not mix with aminoacyl-trna molecules introduced from outside the cell. to understand the structural basis for these functional properties, we have examined the disposition of aminoacyl-trna within the cell. to do this we have developed a chinese hamster ovary (cho) permeabilized-cell system using the pla ...19921565655
[the combined action of gamma irradiation and hyperthermia on the structure of the cell population in the chinese hamster].a change in the structure of faf-28 chinese hamster cell population occurred during 24 h following gamma-irradiation or hyperthermia heating, or the effect of both factors was studied by flow cytofluorometry. with radiation delivered immediately after heating the distribution of cells among cycle phases was nearly the same as with hyperthermia alone: the share of cells at the s-phase was invariable during the first 4-6 h, then it slowly diminished; at g1 it slowly decreased and at g2 increased. ...19921565762
[biogenesis of peroxisome--targeting signal and peroxisome assembly factor].peroxisome, an ubiquitous subcellular organelle in eukaryotes, functions in many crucial pathways in metabolisms such as catabolism by beta-oxidation of very long chain fatty acids, biosynthesis of etherglycerolipids, and metabolism of cholesterol. to address the question how peroxisomes are assembled in eukaryotic cells, we discuss here two topics undertaken in our laboratory. peroxisomes are formed by posttranslational assembly mechanism; peroxisomal proteins are synthesized on free polysomes ...19921567655
surfactant protein c precursor is palmitoylated and associates with subcellular membranes.surfactant protein c (sp-c) is a 3.7 kda, hydrophobic protein that enhances the adsorption of phospholipids in pulmonary surfactant. sp-c is generated by proteolytic processing of a 21 kda precursor. murine fetal lung explant cultures and a chinese hamster ovary cell line expressing recombinant human sp-c gene (cho/spc) were used to determine the subcellular location and post-translational modification(s) of prosp-c. after in vitro translation, prosp-c of mr = 21,000 was generated. prosp-c was a ...19921567893
effects of synthetic and naturally occurring flavonoids on metabolic activation of benzo[a]pyrene in hamster embryo cell cultures.biochanin a, an isoflavone, has previously been shown to inhibit the metabolic activation of the carcinogen benzo[a]pyrene (b[a]p) to metabolites that bind to dna in hamster embryo cells and are mutagenic in chinese hamster v79 cells. to determine the structural features required for this activity and to attempt to find more effective inhibitors, a series of synthetic and naturally occurring flavonids were tested for their ability to modulate b[a]p metabolism in hamster embryo cell cultures. the ...19921568269
sequence requirements for precursor cleavage within the constitutive secretory pathway.we have recently demonstrated that the arg-x-lys/arg-arg sequence is a signal for precursor cleavage catalyzed by furin, a mammalian homologue of the yeast precursor-processing endoprotease kex2, within the constitutive secretory pathway. in this study, we further examined sequence requirements for the constitutive precursor cleavage by expression of various prorenin mutants with amino acid substitutions around the native lys-arg cleavage site in chinese hamster ovary cells. the results delineat ...19921569080
mutants in a macrophage-like cell line are defective in plasmalogen biosynthesis, but contain functional peroxisomes.we have used a fluorescence-activated cytotoxicity protocol, 9-(1'-pyrene)nonanol (p9oh)/uv selection (morand, o. h., allen, l.-a. h., zoeller, r. a., and raetz, c. r. h. (1990) biochim. biophys. acta 1034, 132-141), to isolate a series of plasmalogen-deficient mutants in a murine, macrophage-like cell line, raw 264.7. three of these mutants, raw.7, raw.12, and raw.108, displayed varying degrees of plasmalogen deficiency (48, 17, and 14% of wild-type levels, respectively), and all three mutants ...19921569085
recombinant human thyrotropin stimulates thyroid function and radioactive iodine uptake in the rhesus monkey.the administration of bovine tsh to stimulate thyroid radioactive iodine uptake to detect functioning thyroid tissue in man after surgery for thyroid cancer is rarely, if ever, used, due to allergic reactions and/or the development of tsh antibodies. human (h) tsh would be far less likely to induce allergic reactions or tsh antibodies. recombinant htsh (rec-htsh) was produced by a line of chinese hamster ovary cells that had been transfected with cdna for the two subunit proteins that comprise h ...19921569160
cloning and expression of the defective genes from a patient with delta-aminolevulinate dehydratase porphyria.cloning and expression of the defective genes for delta-aminolevulinate dehydratase (alad) from a patient with inherited alad deficiency porphyria (adp) were carried out. cloning of cdnas for the defective alad were performed from ebv-transformed lymphoblastoid cells of the proband, and nucleotide sequences were determined. two separate point mutations resulting in a single amino acid change in each alad allele were identified. one, c718----t, termed 'g1', occurred in the allele within the subst ...20061569184
development and characterization of a whole-cell radioligand binding assay for [125i]gp120 of hiv-1.the binding of hiv-1 envelope glycoprotein, gp120, to the cd4 receptor is an important step in productive infection. the development of agents which interrupt this binding phenomenon should be of therapeutic interest. the present study characterizes a whole cell gp120/cd4 radioligand binding assay (radioligand binding assay) modified for use in a high volume screening format. modifications include the use of human cd4 receptor stably expressed in a chinese hamster ovary cell line and the gentle ...19921569213
site-directed mutagenesis defines a domain in the gonadotropin alpha-subunit required for assembly with the chorionic gonadotropin beta-subunit.hcg, lh, fsh, and tsh are a family of heterodimeric glycoprotein hormones that share a common alpha-subunit, but differ in their hormone-specific beta-subunits. using site-directed mutagenesis and gene transfer, we studied the region in the common alpha-subunit that has been implicated in the assembly with the beta-subunits. the wild-type or mutated alpha-gene was cotransfected into chinese hamster ovary cells with the wild-type hcg beta gene. deletion of the sequence pro38-thr39-pro40 or a chan ...19921569970
esterified cholesterol and triglyceride are present in plasma membranes of chinese hamster ovary cells.the chemical composition of highly purified plasma membrane preparations from a series of malignant chinese hamster ovary (cho) cell lines were undertaken to ascertain if neutral lipid, including cholesteryl ester and triacylglycerol, were present. triacylglycerols (33-41 nmol/mg total lipid) and cholesteryl ester (226-271 nmol/mg) were measured in the plasma membranes and differences in the chemical composition of these membranes recorded. the most significant difference was a gradual decrease ...19921572374
chinese hamster ovary cells produce an enzyme that nicks heat-labile enterotoxin from enterotoxigenic escherichia coli.chinese hamster ovary (cho) cells were examined for production of an enzyme that nicked the polypeptide chain of the heat-labile enterotoxin from enterotoxigenic escherichia coli between the a1 and a2 fragments of its a subunit. serum-free culture medium prepared each day after cho cell inoculation was concentrated 100 times and its proteolytic activity for formation of the a1 fragment was examined by western blotting with anti-lt a antibody. the a subunit was detected in culture medium on day 6 ...19921572434
cloning and characterization of a rat gene encoding ornithine decarboxylase antizyme.we cloned an ornithine decarboxylase antizyme-encoding gene (oaz) from a rat liver genomic library. the entire gene was located on a 4367-bp ecori fragment, which corresponded to one of two fragments hybridizable with the antizyme-encoding cdna, z1, on southern blot analysis. sequence analysis of the cloned gene showed that it consisted of five exons which were identical with the cdna. the transcription start points of the oaz mrna were located 75 and 76 nucleotides upstream from the first atg c ...19921572540
thiol uptake by chinese hamster v79 cells and aerobic radioprotection as a function of the net charge on the thiol.a series of thiols having net charge (z) varying from -2 to +3 were studied using aerobic suspensions of chinese hamster v79-171 cells in ph 7.4 medium at 297 k to evaluate the rate of uptake by cells and the extent of radioprotection as a function of thiol concentration in cells. for measurement of cellular levels, cells were separated from medium by centrifugation through silicone oil and tritiated water was employed to determine cell water volume. estimated half-lives for uptake were: 2-merca ...19921574575
radiation-induced dna unwinding is influenced by cell shape and trypsin.incubation of cells in high salt/alkali typically leads to denaturation and unwinding of dna, yet dna from chinese hamster v79 cells grown for 1 day as spheroids stops unwinding after only 5-10 min. we previously postulated that this was a result of "constraints" to dna unwinding present in cells in spheroids but not in monolayers, and that these constraints could be responsible for the increased resistance of spheroids of v79 cells to killing by ionizing radiation (i.e., the contact effect). ho ...19921574581
transcription initiation and temporal expression of thymidine kinase mrna in chinese hamster cells.the induction of thymidine kinase mrna has proved to be a valuable model for understanding regulatory events at the g1/s boundary of the cell cycle (1, 2, 3). as an initial step toward characterizing the regulation of this gene in chinese hamster cells, i have mapped the transcription start sites for tk mrna in chef/18 cells. two closely spaced sites of transcription initiation were detected downstream of a nonconsensus tataa element in the promoter region. using primer extension analyses, i dem ...19921575759
effect of estradiol and ethynylestradiol on microtubule distribution in chinese hamster v79 cells.the effects of estradiol (e2) and ethynylestradiol (ee2) on the chromosome number and cellular microtubule architecture of chinese hamster v79 cells were studied using fluorescent anti-tubulin antibody. treatment with 20 microm e2 for 48 h induced only a small amount of tetraploid cells, but the normal microtubule network was disrupted completely by only 3 h of treatment. this data reveals that e2 has higher microtubule-disruptive activity than diethylstilbestrol in v79 cells.19921576671
a conserved region in human and chinese hamster x chromosomes can induce cellular senescence of nickel-transformed chinese hamster cell lines.cellular senescence is the genetically programmed cessation of cellular proliferation. we have recently mapped a putative senescence gene(s) on the x chromosome of chinese hamster embryo (che) cells. in the present study, we have utilized microcell-mediated chromosome transfer (microcell fusion) to test whether: (i) the human x chromosome exhibits similar genetic potential to induce senescence and (ii) the deletion or inactivation of the x-linked senescence gene(s) in che cells is associated wit ...19921576706
reversion of the hprt mutant clone sp5 by intrachromosomal recombination.the spontaneous hprt mutant clone sp5, derived from v79 chinese hamster cells, was shown to exhibit a duplication of approximately 2 kb, including exon 2 and its flanking intron sequences, inserted into the intron 1 sequence of the hprt gene. the most striking feature of sp5 is that this clone is quite unstable, demonstrating an extremely high spontaneous reversion frequency. molecular analysis of 25 independent revertant clones of sp5 indicated that they arose after precise deletion of the dupl ...19921576714
demonstration of replication patterns in the last premeiotic s-phase of male chinese hamsters after brdu pulse labeling.chromosome replication in the last premeiotic s-phase of male mammals has been previously studied by [3h]thymidine autoradiography and by a 5-bromodeoxyuridine (brdu)/giemsa technique. we used a recently developed brdu-antibody technique (bat) in this study. the following conclusions were drawn: (1) the replication patterns observed are similar to that of somatic cells. (2) the heterochromatin starts replication in early s-phase. (3) the euchromatic part of the x chromosome of the male chinese h ...19921576880
kinetics of folding and assembly of the human chorionic gonadotropin beta subunit in transfected chinese hamster ovary cells.we have employed chinese hamster ovary (cho) cell lines transfected with either the wild type human chorionic gonadotropin beta (hcg-beta) gene alone (cho beta cells) or in conjunction with the gene expressing the alpha subunit (cho alpha,beta cells) to study the folding pathway of the hcg-beta subunit. in both cho beta and cho alpha,beta cells, the earliest detectable hcg-beta precursor, p beta 1, which had two of six potential disulfide bonds (34-88 and 38-57) formed, was converted to p beta 2 ...19921577726
hyaluronate binding properties of versican.we have previously cloned a large chondroitin sulfate proteoglycan (versican) from human fibroblasts. the primary sequence shows that the n terminus contains sequence homology with known hyaluronate-binding molecule, suggesting that versican can bind hyaluronate. to test this hypothesis we have reconstructed a full-length versican cdna and a versican cdna fragment encoding the n terminus and have transfected chinese hamster ovary cells and mouse 3t3 fibroblasts, respectively, with these construc ...19921577773
in vitro genotoxic effects of areca nut extract and arecoline.the genotoxic potential of the aqueous extract of areca nut as well as arecoline, the major alkaloid of the areca nut, was tested with the help of cytogenetic markers such as sister-chromatid exchanges and chromosome aberrations, utilizing chinese hamster ovary (cho) cells. the continuous-treatment and pulse-treatment schedules yielded dose-dependent elevations in the frequencies of sister-chromatid exchange and chromosomal aberration in cho cells, indicating a genotoxic effect of both the extra ...19921577847
retention of secretory proteins in an intermediate compartment and disappearance of the golgi complex in an end4 mutant of chinese hamster ovary cells.mutant v.24.1, a member of the end4 complementation group of temperature-sensitive cho cells, is defective in secretion at the restrictive temperature (wang, r.-h., p. a. colbaugh, c.-y. kao, e. a. rutledge, and r. k. draper. 1990. j. biol. chem. 265:20179-20187; presley, j. f., r. k. draper, and d. t. brown. 1991. j. virol. 65:1332-1339). we have further investigated the secretory lesion and report three main findings. first, the block in secretion is not due to aberrant folding or oligomerizat ...19921577851
cloning and expression of the canine interferon-gamma gene.the canine interferon-gamma (cifn-gamma) chromosomal gene was isolated from a recombinant library, containing the entire dog genome, by screening with a rat ifn-gamma genomic probe. the structural organization of the cifn-gamma gene closely resembles that of the human, murine, and rat ifn-gamma genes. it contains three intervening sequences and encodes a signal sequence of 23 amino acids followed by a mature protein of 143 amino acids. two potential n-glycosylation sites are located at positions ...19921578190
characterization of the galactose-specific binding activity of a purified soluble entamoeba histolytica adherence lectin.we studied galactose (gal)-specific binding of the soluble purified 260-kda entamoeba histolytica adherence protein to glycosylation deficient chinese hamster ovary (cho) cell mutants. our goal was to further define the lectin's functional activity and carbohydrate receptor specificity. the adherence protein was purified by acid elution from an immunoaffinity column; however, exposure of the surface membrane lectin on viable trophozoites to identical acid ph conditions had no effect on carbohydr ...19921578406
the analysis of 10 potential spindle poisons for their ability to induce crest-positive micronuclei in human diploid fibroblasts.ten compounds selected for use within a coordinated commission of the european communities programme on aneuploidy induction (cadmium chloride, chloral hydrate, colchicine, diazepam, econazole, hydroquinone, pyrimethamine, thiabendazole, thimerosal and vinblastine) were tested for their ability to induce crest-positive micronuclei in cultured human diploid fibroblasts. significant increases in crest-positive micronuclei were produced by cadmium chloride, chloral hydrate, colchicine, diazepam and ...19921579065
different effectiveness of 4-nitroquinoline-1-oxide, mitomycin c and ethyl methanesulfonate to induce lesions in dna leading to sister chromatid exchange throughout successive cell cycles in chinese hamster ovary cells.the present study was carried out in chinese hamster ovary cells in order to determine whether lesions induced by three different mutagens, namely 4-nitroquinoline-1-oxide (4-nqo), mitomycin c (mmc) and ethyl methanesulfonate (ems), can persist for more than one cell generation leading to sister chromatid exchanges (sce) or, alternatively, they are efficiently repaired during the next replicative period after treatment. in order to accurately score the number of sces arising during the first (s1 ...19921579069
chromosomal aberration tests in vitro: problems with protocol design and interpretation of results.in vitro chromosomal aberration (ca) tests have come to play a central role in testing for mutagenic/carcinogenic potential of chemicals in most countries. guidelines on the conduct of such assays have therefore been published by a variety of sources, and, if anything, recommended protocols have become even more extensive as time has progressed and revisions have been made. yet there is very little comparative data from within or between laboratories to form a basis for these recommendations. so ...19921579073
acellular pertussis vaccination of 2-month-old infants in the united states.this is the first study in children from the united states that evaluates the immunogenicity of and adverse reactions to the connaught/biken two-component acellular pertussis vaccine compared with whole-cell pertussis vaccine when given as a primary immunization series at 2, 4, and 6 months of age. three hundred eighty infants were studied; 285 received acellular diphtheria-tetanus toxoids-pertussis (dtp (adtp)) and 95 received whole-cell dtp (wdtp). following the third dose, adtp vaccination pr ...19921579399
isolation and partial characterisation of a chinese hamster o6-alkylguanine-dna alkyltransferase cdna.the cdna encoding chinese hamster o6-alkylguanine-dna-alkyltransferase (atase) has been isolated from a library prepared from rna isolated from v79 lung fibroblasts which had an upregulated level of this repair activity following stepwise selection with a chloroethylating agent (1, 2). expression of the cdna in e. coli produced functionally active atase at levels of 2.5% of total cellular protein as determined by in vitro assay. the recombinant hamster protein has a molecular weight of 28 kda as ...19921579490
[intraocular barrier permeability in spontaneously diabetic chinese hamster].fluorophotometry was performed with normal and spontaneously diabetic chinese hamsters (chad) in order to investigate differences in blood-ocular barrier permeability and lens autofluorescence. blood-aqueous barrier permeability was evaluated by the fluorescence value in the anterior chamber which was corrected using both autofluorescence value and the concentration of fluorescein in the plasma. the results showed that the diabetic group had significantly higher values than the normal group (p l ...19921580215
dimethylarsenic acid induces tetraploids in chinese hamster cells. 19921581670
heterogeneity of microtubule organizing center components as revealed by monoclonal antibodies to mammalian centrosomes and to nucleus-associated bodies from dictyostelium.the molecular composition of two morphologically distinct microtubule-organizing centers (mtocs) was compared by probing with monoclonal antibodies raised against (i) nucleus-associated bodies (nabs) isolated in a complex with nuclei from the cellular slime mold dictyostelium discoideum and (ii) mammalian mitotic spindles isolated from chinese hamster ovary (cho) cells. the staining patterns observed by immunofluorescence microscopy in whole cho cells and dictyostelium amoebae showed that the di ...19921581981
conversion of human interferon-beta from a secreted to a phosphatidylinositol anchored protein by fusion of a 17 amino acid sequence to its carboxyl terminus.a number of cell-surface proteins are anchored in plasma membranes by a glycosylated phosphatidylinositol (pi) moiety that is covalently attached to the carboxyl-terminal amino acid of the mature protein. we have previously reported the construction of a cdna clone of a truncated platelet-derived growth factor (pdgf) receptor that consists of the extracellular domain without the transmembrane and cytoplasmic domains. in the construction of the vector, a sequence of 51 base pairs (bp) from the 3' ...19921584209
studies on the role of amino acids 38-45 in the expression of a functional thyrotropin receptor.we previously reported that deletion or substitution of a unique eight-amino acid tract (residues 38-45) in the extracellular domain of the human tsh receptor led to the loss of specific ligand binding to the surface of transfected cells. in the present study we analyzed this region in more detail. using site-directed mutagenesis of the tsh receptor cdna, we substituted amino acid residues 38-45, either in three overlapping groups of four amino acids each or individually. the resultant tsh recep ...19921584215
confirmation of assignment of the bovine k-casein locus by pcr.the provision of a bovine gene map will allow the ready identification of genetic disease in cattle and will lead to the identification of the genetic loci responsible for quantitative traits of economic importance. an extension of the polymerase chain reaction to the identification of linkage in bovine-chinese hamster cell hybrids has improved the speed and facility of the assignment of genes to linkage groups and thus makes it easier to achieve a bovine linkage map.19921585084
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