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expression and characterization of the cloned salmonella typhimurium enterotoxin.earlier, our laboratory reported the cloning of a chromosomally encoded cholera toxin (ct)-like enterotoxin gene from salmonella typhimurium q1 into pbr322. cell lysates from the plasmid clone pc1, containing a 4.8 kb ecor1 dna fragment from salmonella, caused elongation of chinese hamster ovary (cho) cells and this biologic activity was neutralized by anti-ct. however, this cloned gene product did not elicit fluid secretion in the rabbit intestinal loop (ril) model, because of poor expression. ...19921453924
assessment of mitochondrial function in cells grown in tissue culture.to assess mitochondrial function (pyruvate dehydrogenase [pdh] activity), cells were grown in the appropriate media to confluence, rinsed and incubated in glucose free media containing 25 microm l-lactate and [1-14c]-d,l-lactate. lactate oxidation was measured as the amount of lactate oxidized in nmol of 14co2 generated per mg of protein per minute. basal activity varied with cell number and the cell type studied: fibroblast 2.26 +/- 0.01; chinese hamster ovary (cho) 42 +/- 0.4; bc3h-1 52 +/- 2. ...20131456730
isolation of the plasma membrane and organelles from chinese hamster ovary cells.two methods are described enabling the plasma membrane from chinese hamster ovary (cho) cells to be obtained rapidly, relatively pure and with a good yield. in both cases, cells were disrupted by nitrogen cavitation in an isoosmotic buffer either at ph 5.4 or at ph 7.4. in the first approach, cells were lysed at ph 7.4 and the plasma membrane and cell organelles were isolated on a self-generated gradient of percoll, at neutral ph. mitochondria and endoplasmic reticulum were recovered in the dens ...19921457453
ferritin-iron increases killing of chinese hamster ovary cells by x-irradiation.stationary-phase chinese hamster ovary cells were cultured in medium containing ferritin (approximately 19% iron by weight) added at concentrations ranging from 0 to 128 micrograms/ml. one set of cultures was unirradiated, and another set was exposed to 4.0 gy of x-ray. clonogenic cell survival was assessed in each set of cultures. in the absence of added ferritin, 4.0 gy killed approximately 50% of the cells. in the absence of radiation, ferritin was not toxic at less than 48 micrograms/ml; abo ...19921457606
effects of growth media on cell cycle progression in cho cells exposed to the radioprotector wr-1065.wr-1065 (2-[(aminopropyl)amino]ethanethiol) reduces cytotoxic and mutagenic effects caused by exposure of cells to radiation and chemotherapeutic drugs, but the mechanisms involved are not fully known. we have observed an accumulation of cells in g2 in wr-1065 treated chinese hamster ovary cells grown in alpha-minimal essential medium, while others have found no cell cycle effects in wr-1065 treated chinese hamster ovary cells grown in mccoy's 5a medium. to determine if the two types of media ha ...19921457610
characterization of recombinant murine interleukin 5 expressed in chinese hamster ovary cells.we have purified recombinant murine interleukin 5 (rmil-5) from the supernatant of chinese hamster ovary cells. each peptide fragment of the purified rmil-5 generated by achromobacter protease i digestion was characterized and glycosylation sites were determined. although rmil-5 contains three potential sites of n-linked glycosylation (asn-26, asn-55 and asn-69), asn-69 is not glycosylated. the oligosaccharides released from the protein by hydrazinolysis were fractionated by paper electrophoresi ...19921457971
dna sequence analysis of mutations induced by melphalan in the cho aprt locus.in previous work, we established that treatment with melphalan (l-phenylalanine mustard) produced a predominance of a.t-->t.a transversions in the simian virus 40 (sv40)-based shuttle vector pz189 during replication in human 293 cells. mutations were induced with varying doses (4-12 microm) melphalan in the aprt gene of the hemizygous chinese hamster ovary (cho) cell line d422 to determine whether a similar mutation spectrum would be observed in an endogenous gene. dna sequence alterations were ...19921458453
overexpression of metallothionein in chinese hamster ovary cells and its effect on nitrogen mustard-induced cytotoxicity: role of gene-specific damage and repair.overexpression of metallothionein in mammalian cells has been associated with protection from cytotoxic chemicals and acquired resistance of tumors to cytotoxic drugs. the mechanism of this effect, however, remains unclear. we have explored whether cytotoxicity of the bifunctional alkylating agent nitrogen mustard was correlated with the extent of dna damage formation and repair in the metallothionein gene regions in chinese hamster ovary cells. the dna damage and repair were examined in metallo ...19921458473
analysis of soluble human and mouse interferon-gamma receptors expressed in eukaryotic cells.the extracellular domains of the human and mouse interferon-gamma receptors were produced in insect spodoptera frugiperda cells infected with recombinant baculoviruses and in mammalian chinese-hamster-ovary cells. the receptors expressed in both systems are secreted into the culture medium. their signal peptides are cleaved off and the proteins show heterogeneity in glycosylation which, however, does not affect the capacity to bind interferon gamma or specific antibodies. the soluble mouse recep ...19921459135
stimulation of neutrophil leukocyte chemotaxis by a cloned cytolytic enterotoxin of aeromonas hydrophila.a cytolytic enterotoxin produced by aeromonas hydrophila, isolate ssu, has been cloned in our laboratory. this enterotoxin lysed rabbit red blood cells, destroyed chinese hamster ovary cells, caused fluid secretion in rat ligated ileal loops, inhibited the phagocytic function of mouse phagocytes, and was lethal to mice when injected intravenously. in this study, the effect of this cytolytic enterotoxin on the chemotaxis of human leukocytes (cell line rpmi 1788) was examined. this toxin, at conce ...19921459417
nitroxide-mediated protection against x-ray- and neocarzinostatin-induced dna damage.the stable free radical tempol (4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy) has been shown to protect against x-ray-induced cytotoxicity and hydrogen peroxide- or xanthine oxidase-induced cytotoxicity and mutagenicity. the ability of tempol to protect against x-ray- or neocarzinostatin (ncs)-induced mutagenicity or dna double-strand breaks (dsb) was studied in chinese hamster cells. tempol (50 mm) provided a protection factor of 2.7 against x-ray-induced mutagenicity in chinese hamster ovary ( ...19921459474
palmitylation of neuromodulin (gap-43) is not required for phosphorylation by protein kinase c.neuromodulin (also designated gap-43, b-50, and f-1) is a prominent protein kinase c substrate attached to the membranes of neuronal growth cones during development and to presynaptic membranes in discrete subsets of adult synapses. in this study, we have examined the relationship between the attachment of neuromodulin to membranes and its phosphorylation by protein kinase c. to address this issue, we have compared wild-type and mutant neuromodulins expressed in cells that normally lack the prot ...19921460023
analysis of the autonomous replication behavior in human cells of the dihydrofolate reductase putative chromosomal origin of replication.chinese hamster genomic dna sequences from the region downstream of the dihydrofolate reductase (dhfr) gene reported to contain a chromosomal origin of bidirectional dna replication (obr-1) were tested for their ability to support autonomous dna replication in human cells. a 13.3 kilobase fragment containing obr-1 and surrounding sequences supported replication in short-term and long-term replication assays, while a 4.5 kb fragment containing obr-1 did not support substantial replication in eith ...19921461730
detection of x-ray damage repair by the immediate versus delayed plating technique is dependent on cell shape and cell concentration.a method commonly used to measure the ability of cells to repair potentially lethal damage (pld) is to compare immediate plating (ip) and delayed plating (dp) survival. lower cell survival under ip conditions relative to that after dp conditions has been interpreted to indicate a higher ability of cells to repair potentially lethal damage (pld) under dp conditions. however, this ip radiosensitization has not been observed in several cell lines and tumor models. ip conditions involve treatment of ...19921462139
a non-glycosylated extracellular superoxide dismutase variant.the secretory tetrameric extracellular superoxide dismutase (ec-sod) is the only glycosylated sod isoenzyme. the importance of the carbohydrate moiety for the properties of the enzyme is unknown. an expression vector defining nonglycosylated ec-sod (ngec-sod) was constructed by mutagenesis of the codon for asn-89 into a codon for gln. the vector was transfected into chinese hamster ovary dxb-11 cells and ngec-sod was isolated to 70% purity from the culture media of selected clones. the absence o ...19921463450
a practical method for uniform isotopic labeling of recombinant proteins in mammalian cells.a method to obtain uniformly isotopically labeled (15n and 15n/13c) protein from mammalian cells is described. the method involves preparation of isotopically labeled media consisting of amino acids isolated from bacterial and algal extracts supplemented with cysteine and enzymatically synthesized glutamine. the approach is demonstrated by producing 15n-labeled and 15n/13c-labeled urokinase from sp2/0 cells and successfully growing chinese hamster ovary (cho) cells on the labeled media. thus, us ...19921463742
basic fibroblast growth factor (bfgf) dissociates rapidly from heparan sulfates but slowly from receptors. implications for mechanisms of bfgf release from pericellular matrix.the effect of heparin on the rate of binding of basic fibroblast growth factor (bfgf) to high affinity (receptor) and low affinity (heparan sulfate) binding sites on endothelial cells and cho cells transfected with fgf receptor-1 or fgf receptor-2 was investigated. radiolabeled bfgf bound rapidly to both high and low affinity sites on all three types of cells. addition of 10 micrograms/ml heparin eliminated binding to low affinity sites and decreased the rate of binding to high affinity sites to ...19921464594
dna strand-specific repair of (+-)-3 alpha,4 beta-dihydroxy-1 alpha,2 alpha-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene adducts in the hamster dihydrofolate reductase gene.we evaluated the formation and removal of (+-)-3 alpha,4 beta-dihydroxy-1 alpha,2 alpha-epoxy-1,2,3,4- tetrahydrobenzo[c]phenanthrene (bcphde)-dna adducts in two chinese hamster ovary (cho) cell lines. one line of repair-proficient cells (mk42) carries a stable 150-fold amplification of the dihydrofolate reductase (dhfr) locus. the other line of repair-deficient cells (uv-5) is diploid for this gene and is defective in excision of bulky dna lesions. two methods were used to quantitate adduct lev ...19921465420
o-linked carbohydrate of recombinant von willebrand factor influences ristocetin-induced binding to platelet glycoprotein 1b.by transfecting the full-length cdna for human von willebrand factor (vwf) into a line of chinese hamster ovary cells with a defect in carbohydrate metabolism, we have prepared recombinant vwf specifically lacking o-linked carbohydrates. we have compared this under-glycosylated protein to fully glycosylated recombinant vwf with respect to several structural and binding properties. vwf deficient in o-linked glycans was synthesized, assembled into multimers, and secreted in an apparently normal ma ...19921469086
relationships between in vitro mutagenicity assays.this paper analyzes the mutagenicity results reported by the us national toxicology program (ntp), relative to 41 chemicals assayed with four in vitro short-term tests [salmonella typhimurium (sty), chromosomal aberrations in chinese hamster ovary (cho) cells (cha), sister chromatid exchange in cho cells (sce), mutation in l5178y mouse lymphoma cells (mly)] and puts this database in perspective with respect to other databases. it is shown that the test relationships pointed out by the experiment ...19921470028
molecular biology approaches to biological monitoring of genotoxic substances.genetic testing is subdivided into genetic monitoring (evaluation over time of induced genetic changes) and genetic screening (detection of inherited traits). genetic factors in relation to susceptibility to environmental agents are briefly examined, as well as mutation assays suitable for use in genetic monitoring, techniques for identifying specific dna lesions, and oncogene products as biomarkers. in vitro studies with as52 chinese hamster ovary cells indicate that the distribution of lesions ...19921471181
cloning and functional expression of the canine anaphylatoxin c5a receptor. evidence for high interspecies variability.a cdna clone, dtjp03, encoding an orphan receptor, was isolated from a canine thyroid library, and found to exhibit 68.6% amino-acid identity with the recently described human c5a receptor. this relatively low similarity first suggested that dtjp03 encoded either a c5a receptor subtype, or the presumably related c3a receptor. binding studies performed on membranes from cos-7 cells expressing the recombinant receptor demonstrated that dtjp03 encoded a high-affinity c5a receptor, with a kd of 1.2 ...19921472004
glutathione s-transferase pi in an arsenic-resistant chinese hamster ovary cell line.a glutathione s-transferase (gst) was purified from an arsenic-resistant chinese hamster ovary cell line, sa7. the sa7 gst was shown to catalyse the conjugation of glutathione and ethacrynic acid, a specific substrate for pi class gst. its n-terminal amino-acid sequence has 80% identical residues to that of rat gst p and human gst pi. thus, the gst purified from sa7 cells belongs to the pi family. treatment with cibacron blue or ethacrynic acid, which are gst inhibitors, significantly decreased ...19921472011
clotrimazole-induced modulation of hepatic cytochrome p450 enzymes in syrian and chinese hamsters.clotrimazole, an imidazole antifungal drug, is known to induce cytochrome p450 isozymes of the p450iiia and p450iib subfamilies in rats. this agent modulated hepatic cytochrome p450 enzymes differently in golden syrian and chinese hamsters and also in hamsters and rats. clotrimazole at a daily intraperitoneal dose of 100 mg/kg for three days increased the amount of cytochrome p450 in the livers of the two hamster strains. in syrian hamsters, clotrimazole significantly induced the activities of 7 ...19921472091
kinetic properties of aromatase mutants pro308phe, asp309asn, and asp309ala and their interactions with aromatase inhibitors.mutant forms of aromatase cytochrome p-450 bearing modifications of amino acid residues pro308 and asp309 and expressed in transfected chinese hamster ovary cells were subjected to kinetic analysis and inhibition studies. the km for androstenedione for expressed wild type (11.0 +/- 0.3 nm sem, n = 3) increased 4-, 25- and 31-fold for mutants pro308phe, asp309asn and asp309ala, respectively. there were significant differences in sensitivity among wild type and mutants to highly selective inhibito ...19921472461
signaling function of reconstituted cd16: zeta: gamma receptor complex isoforms.natural killer cells express an fc receptor for igg (cd16) in association with disulfide-linked dimers composed of two homologous subunits: the zeta chain of the t cell antigen receptor complex and the gamma chain of the mast cell/basophil fc receptor for ige. the ability of zeta and gamma to transduce cd16-mediated activation signals was compared by reconstituting distinct cd16 receptor isoforms composed of various combinations of zeta- and gamma-containing dimers. stably transformed non-hemato ...19921472481
clastogenic and aneuploidogenic effects of cigarette smoke condensate, mitomycin c and vincristine sulfate.immunofluorescent staining of kinetochores in micronuclei (mn) of cytochalasin-b-blocked cells was used to distinguish between clastogenic and aneuploidogenic effects of cigarette smoke condensate (csc), mitomycin c (mmc) and vincristine sulfate (vs) in chinese hamster lung v79 cells by using an anti-kinetochore antibody. within the base-line micronucleated cells (2%), 50 to 58% contained kinetochore-positive (kc+) mn. mmc induced a significantly higher number of mn compared to the controls (p < ...19921474921
the use of human repetitive dna to target selectable markers into only the human chromosome of a human-hamster hybrid cell line (al)we used the plasmid blur-8 that contains an 800-base pair (bp) sequence of human repetitive alu dna in a cotransfection protocol to target the plasmids psv2neo or ebo-pcd-leu-2 (hygro) into a single site of the sole human chromosome, number 11, of a chinese hamster-human hybrid cell line (al). the neo and hygro plasmids confer resistance to the antibiotics g418 and hygromycin, respectively. of the 33 cotransfected clones with single-site insertions, 1/13 without blur-8 and 6/20 with blur-8 were ...19921475708
characterization of the extracellular region of the human thyrotrophin receptor expressed as a recombinant protein.dna encoding the n-terminal 415 residues of the human thyrotrophin receptor (predicted to code for the large extracellular region) was introduced into chinese hamster ovary (cho) cells using the glutamine synthetase/cytomegalovirus amplifiable expression system, and into e. coli using the pgex-3x expression vector. substantial quantities of insoluble fusion protein product resulted from bacterial expression; by western blot analysis, this was shown to be reactive with anti-receptor antibodies ra ...19921476610
effects of fermentation on product consistency.a variety of different fermentation processes has been successfully employed to produce consistent protein-based biopharmaceuticals from genetically engineered animal cells. chinese hamster ovary (cho) cells were genetically modified to produce recombinant human soluble cd4, tissue plasminogen activator (tpa) or erythropoietin (epo). soluble cd4 was collected from extended perfused fermentations of several months' duration, during which some quantitative loss of dna copy level, mrna expression l ...19921478331
rapid desensitization of muscarinic m3 receptor-stimulated polyphosphoinositide responses.chinese hamster ovary (cho) cells transfected with human m3 muscarinic receptor cdna (bmax, 1343 +/- 46.8 fmol/mg of protein) were used to investigate agonist-mediated muscarinic receptor desensitization. stimulation of cho-m3 cells with a maximal dose of carbachol resulted in a biphasic production of mass inositol-1,4,5-trisphosphate [ins(1,4,5)p3], measured by radioreceptor binding assay. the first phase comprises a rapid 8-10-fold increase in ins(1,4,5)p3 that peaks after 10 sec and falls to ...19921480131
differential utilization of poly (a) signals between dhfr alleles in chl cells.the chinese hamster cell line, dc-3f, is heterozygous at the dhfr locus, and each allele can be distinguished on the basis of a unique dna restriction pattern, protein isoelectric profile and in the abundancy of the dhfr mrnas it expresses. although each allele produces four transcripts, 1000, 1650 and 2150 nucleotides [corrected] in length, the relative distribution of these rnas differs for each; the 2150 nt mrna represents the major (60%) species generated from one allele, while the 1000 nt m ...19921480480
fibronectin receptors are functional on mitotic chinese hamster ovary cells.in this paper, evidence is provided indicating that the blockade of presynchronized cho 15b cells in prometaphase by nocodazole is fully reversible and efficient enough to allow us to analyze the function of the integrin receptors. flow cytometry analysis using a specific antibody raised against the fibronectin receptor, and binding studies of the radiolabeled fibronectin on the cell membrane, indicated a stable number of receptors at the cell surface during mitosis. furthermore, in the mean tim ...19921482358
n-linked glycosylation of beta-amyloid precursor protein.the beta-amyloid peptide that accumulates in the brain of patients with alzheimer's disease is derived by proteolytic processing of a family of membrane bound beta-amyloid precursor proteins (beta apps). the three major isoforms of beta app, derived by alternative splicing, contain 695, 751, and 770 amino acids. they are heavily o-glycosylated and contain two n-linked glycosylation sites. the pathways leading to beta-amyloid deposition in brain are not clear. it is possible that defects in metab ...19921482372
embryonic alkaline phosphatase is expressed at m-phase in the spermatogenic lineage of the mouse.we have recently cloned and characterized a novel embryonic alkaline phosphatase (eap) expressed at the two-cell to blastocyst stage of preimplantation development in the mouse. the isozyme is re-expressed in trace amounts in the thymus, intestine and testis during adult life. in the present report, we find that eap transcripts can be detected, by rt-pcr analysis, in very low amounts in the testes of newborn mice, but at 24 days of age eap mrna levels reach the highest concentrations, remaining ...19921483384
expression, purification, and characterization of inactive human coagulation factor xa (asn322ala419).we have expressed in chinese hamster ovary cells a catalytically inactive form of human factor xa (factor rxai). a recombinant precursor of human factor xa was inactivated by two point mutations in the serine protease catalytic triad, asp322asn and ser419ala. a two-step purification to homogeneity of the secreted material involved immunoaffinity followed by heparin-agarose chromatography. two forms were identified; a fully processed dimer (70%) and a partially processed monomer (30%). limited n- ...19921486277
intragenomic repair heterogeneity of dna damage.the mutagenic and carcinogenic consequences of unrepaired dna damage depend upon its precise location with respect to the relevant genomic sites. therefore, it is important to learn the fine structure of dna damage, in particular, proto-oncogenes, tumor-suppressor genes, and other dna sequences implicated in tumorigenesis. both the introduction and the repair of many types of dna lesions are heterogeneous with respect to chromatin structure and/or gene activity. for example, cyclobutane pyrimidi ...19921486861
the gene for bone morphogenetic protein 2a (bmp2a) is localized to human chromosome 20p12 by radioactive and nonradioactive in situ hybridization.bone morphogenetic protein 2a (bmp2a), a member of the decapentaplegic-vg-related family, belongs to the transforming growth factor beta superfamily and has a striking sequence similarity to the decapentaplegic locus in drosophila melanogaster, a major determinant of pattern specification during embryogenesis. bmp2a is thought to be involved in cartilage and bone formation during embryogenesis, but may have additional functions in morphogenesis as implied by its expression in various organs and ...19921487246
conservation of the mammalian rna polymerase ii largest-subunit c-terminal domain.we have isolated and sequenced a portion of the gene encoding the carboxy-terminal domain (ctd) of the largest subunit of rna polymerase ii from three mammals. these mammalian sequences include one rodent and two primate ctds. comparisons of the new sequences to mouse and chinese hamster show a high degree of conservation among the mammalian ctds. due to synonymous codon usage, the nucleotide differences between hamster, rat, ape, and human result in no amino acid changes. the amino acid sequenc ...19921487824
microtubule-mediated golgi capture by semiintact chinese hamster ovary cells. 19921487989
assay for expression of methotrexate-resistant dihydrofolate reductase activity in the presence of drug-sensitive enzyme.a simple, continuous spectrophotometric assay for dihydrofolate reductase (dhfr) activity was adapted for determination of drug-resistant enzyme activity expressed from transfected genes in cells containing drug-sensitive enzyme. methotrexate inhibition characteristics in this assay system were assessed for the murine wild-type (wt) enzyme as well as variant genes encoding amino acid substitutions at codon positions 22 (arg22) or 31 (trp31) expressed in dhfr-deficient chinese hamster ovary (cho) ...19921489988
characterization and pathogenic potential of a soil isolate and an ocular isolate of acanthamoeba castellanii in relation to acanthamoeba keratitis.acanthamoeba castellanii, one isolate from the eye and one from the soil, were compared on the basis of: (a) pathogenic potential; (b) plasminogen activator activity; (c) chemotactic activity; (d) cytopathic effects; (e) collagenolytic activity; (f) binding ability to contact lenses; and (g) and binding ability to corneal buttons. the ocular isolate of a. castellanii was found to be pathogenic based on its ability to produce corneal infections in chinese hamsters. by contrast, the soil isolate p ...19921490339
ligand-dependent down-regulation of stably transfected human glucocorticoid receptors is associated with the loss of functional glucocorticoid responsiveness.the effect of glucocorticoids on the regulation of stably transfected human glucocorticoid receptors has been examined. exposure of a chinese hamster ovary-derived cell line containing stably transfected human glucocorticoid receptor genes and glucocorticoid-responsive dihydrofolate reductase genes to 5 nm dexamethasone resulted in a rapid, time-dependent reduction in the level of glucocorticoid receptor protein to 50% of control levels within 5 h of steroid treatment. this decrease in receptor ...19921491690
identification of two cysteines closely positioned in the ligand-binding pocket of the human estrogen receptor: roles in ligand binding and transcriptional activation.we have previously identified cysteine 530 in the human estrogen receptor (er) as the major site of attachment for covalently binding affinity ligands and have shown that when this cysteine is mutated to alanine (c530a mutant), the affinity ligand [tamoxifen aziridine (taz)] can still bind covalently to the er, presumably by interaction with a different cysteine(s) in the hormone-binding domain (hbd). using site-directed mutagenesis, we have determined the alternative ligand attachment site and ...19921491695
the effects of cryopreservation on early development and chromosome constitution in chinese hamster embryos.the effects of cryopreservation on early embryonic development were investigated in chinese hamster embryos. embryos were randomly divided into 3 groups, as follows: the control group, embryos which were simply cultured; the dmso group, embryos which were exposed to dimethyl sulfoxide (dmso) and then cultured; the cryopreservation group, embryos which were cryopreserved and then cultured. the percentages of embryos which developed into blastocysts after 40 hours of cultivation were high in all g ...19921492813
application of alkaline unwinding assay for detection of mutagen-induced dna strand breaks.the frequency of single-strand breaks in parental dna and gaps in nascent dna in various cells exposed to methyl methanesulfonate (mms) or methylnitrosourea (mnu) was investigated by alkaline unwinding assay using two types of alkaline lysis conditions, 22 degrees c lysis versus 0 degrees c lysis. the dna damage induced by mms and mnu is considered to be characteristic of lesions produced in dna by alkylating agents. the aim of our research project was to adjust this method to be able to detect ...19921493582
[effects of a medium ph on the ability of chinese hamster cells to repair radiation injuries].in experiments with chinese hamster cells at exponential and stationary growth phases, it has been shown that the postirradiation incubation of irradiated cells in a medium with low ph (up to 6.0) promotes the recovery of cells from potentially lethal damages; it has also been found that the recovery from sublethal radiation damages does not depend on the medium ph. the long-term incubation of nonirradiated cells with low phc causes death of part of cells.20141494659
salmonella cytotonic and cytolytic factors: their detection in chinese hamster ovary cells and antigenic relatedness.thirty nine strains of salmonella belonging to 14 different serotypes were screened for the production of cytotonic and cytolytic factors by assayed chinese hamster ovary (cho) cells. the cell-free culture supernatants (cfcs) of 32 isolates caused elongation and increase in size of cho cells while the cfcss completely lysed the cells. the cytotonic effect in cho cells correlated precisely with fluid the cfcss completely lysed the cells. the cytotonic effect in cho cells correlated precisely with ...19921496811
analysis of kidney mrnas expressed from the rat beta-galactoside alpha 2,6-sialyltransferase gene.beta-galactoside alpha 2,6-sialyltransferase (siat-1), like other glycosyltransferases, is differentially expressed in rat tissues. two distinct size classes of siat-1 mrnas expressed in rat kidney are comprised of at least three siat-1 transcripts. one mrna, rke, represents the larger transcript class (4.7 kb) and predicts a polypeptide identical to the hepatic siat-1. in transfected chinese hamster ovary (cho) cells, rke polypeptides exhibit hemi-perinuclear staining with a siat-1 antibody (ab ...19921498423
bioactivation of aflatoxin b1 in the bovine olfactory mucosa: dna binding, mutagenicity and induction of sister chromatid exchanges.nasal olfactory tumours occur in cattle in relatively high frequencies in several developing countries. since affected animals sometimes show signs of severe aflatoxicosis, a role of aflatoxin b1 (afb1) in tumorigenesis can be proposed. the results of the present study show that microsomal preparations of the bovine olfactory mucosa have a much higher ability than liver microsomes to induce covalent binding of afb1 to calf thymus dna and to microsomal proteins. the major dna adduct formed was 8, ...19921499086
characterisation of a human bilirubin udp-glucuronosyltransferase stably expressed in hamster lung fibroblast cell cultures.a cdna encoding a human bilirubin udp-glucuronosyltransferase has been isolated and stably expressed in chinese hamster v79 lung fibroblast cell line. western blotting of cell homogenates with anti-ugt antibody revealed a highly expressed protein of approx. 55.5 kda in size. the expressed enzyme specifically catalysed the formation of bilirubin mono- and diglucuronides, and also catalysed the glucuronidation of two phenolic compounds, which are good substrates for other human ugt isoenzymes, at ...19921499725
recombinant salmonella typhimurium strains that invade nonphagocytic cells are resistant to recognition by antigen-specific cytotoxic t lymphocytes.to address the question of whether salmonella-infected nonphagocytic cells could serve as target cells for recognition by antigen-specific, major histocompatibility complex class i-restricted cytotoxic t lymphocytes (ctl), four recombinant salmonella typhimurium constructs that expressed full-length, or fragments of, influenza a virus nucleoprotein (np) were made. the bacteria were shown to infect chinese hamster ovary (cho) cells. appropriate major histocompatibility complex restriction molecul ...19921500187
action spectra of phthalocyanines with respect to photosensitization of cells.human carcinoma cells (nhik 3025 cells) and chinese hamster cells (v79 cells) were incubated with alpcs1, alpcs2 and alpcs4, phthalocyanines with different lipophilicity but with similar photochemical properties when in monomeric solutions. the absorption- and fluorescence spectra of the dyes in the cells were recorded as well as their action spectra with respect to sensitizing cells to photoinactivation. these spectra show that under the present conditions alpcs1 is strongly aggregated in both ...19921502260
a leu----his substitution at residue 93 in human corticosteroid binding globulin results in reduced affinity for cortisol.a steroid binding capacity assay and a radioimmunoassay were both used to measure corticosteroid binding globulin (cbg) in serum samples from 22 patients with sepsis. an approximately 50% discordancy between the two values in one patient suggested the presence of a cbg variant with reduced affinity for cortisol, and this was confirmed by scatchard analysis. we therefore used the polymerase chain reaction to amplify exons that encode for human cbg from the genomic dna of this patient. this reveal ...19921504007
a role for the transient increase of cytoplasmic free calcium in cell rescue after photodynamic treatment.chinese hamster ovary (cho) cells and t24 human bladder transitional carcinoma cells were treated with the photosensitizers aluminum phthalocyanine (alpc) and hematoporphyrin derivative (hpd), respectively. exposure of both sensitized cell lines to red light caused an immediate increase of cytoplasmic free calcium, [ca2+]i, reaching a peak within 5-15 min after exposure and then returning to basal level (approximately 200 nm). the level of the peak [ca2+]i depended on the light fluence, reaching ...19921504070
comparison of rat liver parenchymal and nonparenchymal cells in the activation of promutagens.while the liver consists of both parenchymal cells (pc) and nonparenchymal cells (npc), virtually all studies on promutagen activation have been performed using pc. to evaluate the comparative roles of pc and npc in promutagen activation, we cocultivated a cell line generally considered to have an insignificant level of xenobiotic metabolism, chinese hamster ovary (cho) cells, with either pc, npc, or a combination of both. the mixed culture was treated with two promutagens: dimethylnitrosamine ( ...19921505529
assignment of a human dna double-strand break repair gene (xrcc5) to chromosome 2.the chinese hamster ovary (cho-k1) cell mutant xrs-6 is defective in rejoining of dna double-strand breaks and is hypersensitive to x-rays, gamma-rays, and bleomycin. radiation resistance or sensitivity of somatic cell hybrids constructed from the fusion of xrs-6 cells with primary human fibroblasts strongly correlated with the retention of human chromosome 2 isozyme and molecular markers. discordancies between some chromosome 2 markers and the radiation resistance phenotype in some of the hybri ...19921505945
hypoxia-selective antitumor agents. 5. synthesis of water-soluble nitroaniline mustards with selective cytotoxicity for hypoxic mammalian cells.nitroaniline mustards have potential as hypoxia-selective cytotoxic agents, with reductive metabolism activating the nitrogen mustard by converting the electron-withdrawing nitro group to an electron-donating hydroxylamine or amine. however, the parent compounds have poor aqueous solubility, and their potencies are limited by low reduction potentials (e1/2 ca. -600 mv versus the normal hydrogen electrode) and corresponding slow rates of nitro reduction. to address these limitations, a series of ...19921507207
[single-stranded dna from viruses, prokaryotes and eukaryotes].the review presents the results of investigations of single-stranded dnas of viruses, bacteria and cells of higher organisms. methods of revealing, isolating and analysis of these dnas are presented. a large variety of single-stranded dna containing genomes of plant and animal viruses was revealed. attention is drawn to the integration and replication of viral genomes. results of sv40 integration during the first two days after infection of chinese hamster cells are shown. results of studying mu ...20061508172
effect of vitamin e on cytotoxicity, dna single strand breaks, chromosomal aberrations, and mutation in chinese hamster v-79 cells exposed to ultraviolet-b light.the effect of pretreatment with vitamin e on cytotoxicity, dna single strand breaks, and chromosomal aberrations as well as on mutation induced by ultraviolet-b light (uv-b) was investigated in chinese hamster v-79 cells. cellular pretreatment with non-toxic levels of 25 microm alpha-tocopherol succinate (vitamin e) for 24 h prior to exposure resulted in a 10-fold increase in cellular levels of alpha-tocopherol. using a colony-forming assay, this pretreatment decreased the cytotoxicity of uv-b l ...19921508980
mutational specificity of 1,3-bis-(2-chloroethyl)-1-nitrosourea in a chinese hamster ovary cell line.the mutational specificity of the alkylating agent 1-3-bis-(2-chloroethyl)-1-nitrosourea (bcnu) was analyzed at the endogenous hemizygous adenine phosphoribosyl transferase gene of the chinese hamster ovary cell line d422. a 1-h treatment of the chinese hamster ovary cells with 50 microm bcnu resulted in a toxicity level of 62% and induced mutation at this target with a frequency of 32.1 mutants/10(6) survivors (6-fold above background). analysis of 49 bcnu-induced mutants at the dna sequence le ...19921511435
chlorpromazine enhancement of epirubicin cytotoxicity in vitro: effects on plasma membrane and dna damage.the frequently used antiemetic drug chlorpromazine has previously been shown to augment anthracycline-induced toxicity to cultured chinese hamster fibroblasts measured by cloning /1/. we therefore tested the ability of chlorpromazine to affect the induction of plasma membrane and dna damage by the anthracycline epirubicin. plasma membrane damage was determined by the cells' ability to accumulate 86rb after incubation with 10 mg/l epirubicin, and dna damage was determined by measuring the amount ...19921511613
functional expression of an ovine growth hormone receptor in transfected chinese hamster ovary cells.structural heterogeneity has been demonstrated for growth hormone (gh) receptors from a number of species, and both high and low affinity art receptors have been characterised by ligand binding studies. in the present study, we have transfected chinese hamster ovary (cho-k1) cells with a cdna clone encoding a full-length transmembrane ovine (o) gh receptor, under the regulatory control of the human metallothionein iia promoter. a stably transfected cell line was established (ghr9.5) which expres ...19921511779
characterization of the murine thymidine kinase-encoding gene and analysis of transcription start point heterogeneity.we have determined the molecular organization and transcription start points (tsp) for the murine gene (tk) encoding thymidine kinase. the exon/intron structure and sequences present at the splice junctions of the mammalian tk genes have been highly conserved; however, the promoter sequences of these genes have diverged widely. both the human and chinese hamster tk promoter regions contain ccaat and tata consensus motifs, whereas the mouse promoter has neither element. this difference between sp ...19921511894
complex allosteric modulation of cardiac muscarinic receptors by protamine: potential model for putative endogenous ligands.a large number of diverse pharmacological agents bind to a secondary domain on the muscarinic receptor, to influence allosterically the interaction of ligands at the primary binding site. based on common structural features of these antagonists, we examined the interaction of protamine, an endogenous polycationic peptide, and of polyamines with muscarinic receptors in rat heart. our results provide several lines of qualitative evidence that protamine allosterically modulates the conformation of ...19921513329
influence of gonadotropin (fsh + lh) and thyrotropin (tsh) on the multiplication of chinese hamster ovary (cho) cells. impact of the age of the culture.cho cells repeatedly treated with gonadotropin showed peak division rates after their third exposure and a decrease in the mitotic rate after their fourth exposure. thyrotropin induced a considerable decrease in the mitotic rate following the first exposure, a significant increase after the second and a further decrease following the third and fourth exposures. the pattern did not differ between the two hormones when the cells were exposed further. the age (density of the cell cultures) had an a ...19921516141
clastogenic and mutagenic actions of active species generated in the 6-hydroxydopamine/oxygen reaction: effects of scavengers of active oxygen, iron, and metal chelating agents.a pro-oxidant triphenol, 6-hydroxydopamine (6-ohda), induced mutations in the salmonella typhimurium ta 104 tester strain (over the concentration range to 800 microm), and induced chromosomal aberrations in cultured chinese hamster ovary (cho) cells at lower concentrations (up to 90 microm). it was however only marginally mutagenic (up to cytotoxic levels of 200 microm) in the ta102 tester strain. clastogenicity in the more sensitive cho cell assay was mediated by activated oxygen. superoxide di ...19921516844
the role of extracellular medium components and specific amino acids in the cytotoxic response of escherichia coli and chinese hamster ovary cells to hydrogen peroxide.a concentration of h2o2 resulting in mode one killing of escherichia coli is more toxic when exposure to the oxidant is performed in complete medium (k medium), as compared to a saline (m9 salts). inorganic salts (mgso4 and cacl2), thiamine or glucose, when added separately, or combined, to m9 salts had no effect on the cytotoxic response to h2o2. in contrast, the lethality of the oxidant was highly dependent on the presence of the amino acids in the incubation medium. the addition of glucose fu ...19921516848
site-directed mutagenesis of glut1 in helix 7 residue 282 results in perturbation of exofacial ligand binding.the structure-function relationship of the hepg2/erythrocyte-type glucose transporter (glut1) has been studied by in vitro site-directed mutagenesis. chinese hamster ovary clones in which glucose transporters were transfected were shown by western blotting with a glut1 anti-cooh-terminal peptide antibody to have expression levels of gln282----leu, asn288----ile, and asn317----ile mutations that were comparable with the wild type. all three mutant glut1 clones had high 2-deoxy-d-glucose transport ...19921517202
the heparin-binding domain of extracellular superoxide dismutase c and formation of variants with reduced heparin affinity.a fundamental property of the secretory tetrameric extracellular superoxide dismutase (ec-sod) is its affinity for heparin and analogues, in vivo, mediating attachment to heparan sulfate proteoglycans located on cell surfaces and in the connective tissue matrix. ec-sod is in vivo heterogeneous with regard to heparin affinity and can be divided into subclasses; a which lacks heparin affinity, b with intermediate affinity, and c with strong heparin affinity. the ec-sod c subunits contain 222 amino ...19921517248
induction/repair of strand breakage in mature and nascent dna of cultured chinese hamster ovary cells exposed to hydrogen peroxide.treatment of cultured mammalian cells with hydrogen peroxide results in the production of extensive dna damage. strand breakage was produced at the level of either nascent or mature dna and the former target appeared slightly more resistant than the latter. although inhibitors of the enzyme poly(adp-ribose) polymerase similarly retarded the repair of such lesions, removal of dna strand breaks was much slower for the newly synthesized dna as compared to mature dna.19921517280
purification of sufficiently gamma-carboxylated recombinant protein c and its derivatives. calcium-dependent affinity shift in immunoaffinity and ion-exchange chromatography.protein c, which is an important anti-thrombotic factor in the blood coagulation cascade, undergoes several post-translational modifications. gamma-carboxylation on nine glutamic acid residues at the n-terminal region of the light chain [gamma-carboxylated glutamic acid (gla) domain] is considered to be critical for full anti-clotting activity. it is also known that when recombinant protein c is expressed in animal cells this particular modification is often lost. we were successful in preparing ...19921517329
the inhibitory effects of müllerian-inhibiting substance on epidermal growth factor induced proliferation and progesterone production of human granulosa-luteal cells.this study was undertaken to determine if müllerian-inhibiting substance (mis) could block basal and/or epidermal growth factor (egf)-induced proliferation and progesterone production by cultured human granulosa-luteal cells. cells from follicles of individual patients were pooled, counted, and aliquoted into ham's f-10 medium containing 10% mis-free female fetal calf serum at 37 c in 95% air and 5% co2. after assessing viability, cells were counted on days 4, 8, 12, and 16 of culture. egf was a ...19921517385
[structure and function of oligosaccharide chains of the envelope glycoprotein gp120 of human immunodeficiency virus type 1].the surface of the human immunodeficiency virus (hiv-1), a causative agent for acquired immunodeficiency syndrome (aids), is covered with the major envelope glycoprotein gp120, of which the carbohydrate moiety accounted for 50% of the molecular mass. there is evidence that glycosylation of gp120 is prerequisite to the various stages of hiv infection. the oligosaccharide structures of gp120 have been determined using recombinant gp120 of hiv-1 (iiib) produced in chinese hamster ovary cells and vi ...19921518160
a chinese hamster ovary cell mutant (em-c11) with sensitivity to simple alkylating agents and a very high level of sister chromatid exchanges.we have isolated a chinese hamster ovary cell mutant hypersensitive to monofunctional alkylating agents. the mutant, designed as em-c11, showed hypersensitivity to ethyl methanesulfonate (ems), methyl methanesulfonate and ethylnitrosourea (8-, 7- and 2-fold, respectively, based on d10 values). about 2-fold increased sensitivity towards 4-nitroquinoline-1-oxide and only slightly increased sensitivity to x-rays (1.4-fold) and mitomycin c treatment (1.6-fold) were found in this mutant. em-c11 was n ...19921518409
effects of adenine arabinoside and coformycin on the kinetics of g2 chromatid aberrations in x-irradiated human lymphocytes.the kinetics of chromatid aberrations have been studied in human lymphocytes exposed to x-rays in the g2 phase of the cell cycle and incubated with or without the nucleoside analogue 9-beta-d-arabinofuranosyladenine (ara a), known to inhibit the repair of dna double-strand breaks. in the absence of ara a an exponential decrease in frequencies of chromatid breaks occurred which we interpret as repair. few breaks were observed if samples were harvested immediately following irradiation. the freque ...19921518412
the restriction endonuclease alui induces sister chromatid exchange in chinese hamster ovary cells.chinese hamster ovary (cho) cells were exposed to the restriction endonuclease alui in the presence of 1.1 m glycerol. chromosomal aberrations and sister chromatid exchange (sce) were scored in first post-treatment metaphases following recovery times of 6-18 h. at all recovery times chromosomal aberrations were induced by the enzyme. in alui-treated damaged cells significant elevations of sce frequencies were found after recovery times of 12-18 h. these results indicate that sce, unlike chromoso ...19921518413
identification, characterization, and localization of the dopamine d3 receptor in rat brain using 7-[3h]hydroxy-n,n-di-n-propyl-2-aminotetralin.we have identified 7-[3h]hydroxy-n,n-di-n-propyl-2-aminotetralin ([3h]7-oh-dpat) as a selective probe for the recently cloned dopamine d3 receptor and used it to assess the presence of this receptor and establish its distribution and properties in brain. in transfected chinese hamster ovary (cho) cells, it binds to d3 receptors with subnanomolar affinity, whereas its affinity is approximately 100-, 1000-, and 10,000-fold lower at d2, d4, and d1 receptors, respectively. specific [3h]7-oh-dpat bin ...19921518841
the binding of human alloantibodies to recombinant glycophorin a.chinese hamster ovary (cho) cells were transfected with the wild-type, m allele of glycophorin a cdna. the binding of human alloantibodies to recombinant glycophorin a was assessed with a modified hemagglutination-inhibition assay. patient sera were incubated with acetone powders derived from cho cells, and the adsorbed supernatants were tested in standard hemagglutination assays. five m antibodies and one sample containing anti-en(a) bound to transfected cho cells expressing glycophorin a but d ...19921519325
expression of a gene encoding a specific human sperm protein in chinese hamster ovarian cells.the cdna (rsd-2) encoding a human sperm protein (ywk-ii) was isolated from a rat testis lambda gt11 expression library. its nucleotide sequence was determined. the deduced polypeptide showed high identity with the transmembrane-cytoplasmic domains of a4 amyloid precursor protein of alzheimer's disease. the rsd-2 was inserted into the ecori site of the psv2-ep vector to construct the psvrs-2 vector. chinese hamster ovarian (cho-dhfr) cells were cotransformed with psv2-neo and psvrs-2. mrna and ch ...19921520040
expression, purification and biochemical comparison of natural and recombinant human non-pancreatic phospholipase a2.the gene coding for human non-pancreatic phospholipase a2 (nppla2) was cloned in a eukaryotic expression vector and transfected into chinese hamster ovary (cho) cells. a number of cell lines stably expressing nppla2 were obtained. northern analysis of these cell lines showed an abundant transcript of expected size 1200 nt. the recombinant enzyme was efficiently secreted in quantities up to 400 micrograms nppla2 per liter culture medium in the most productive cell lines. nppla2 was purified to ho ...19921520345
elevation of glutathione levels in bovine pulmonary artery endothelial cells by n-acetylcysteine.n-acetylcysteine (nac), a cysteine derivative with chemoprotective and radioprotective effects, was found to elevate bovine pulmonary artery endothelial cell (ec) glutathione after in vitro incubation. the elevation in glutathione was associated with enhanced uptake of radioactivity of cystine from the medium. because cystine in medium was converted rapidly to cysteine and cysteinyl-nac in the presence of nac and given that cysteine has a higher affinity for uptake by ec than cystine, we conclud ...19921520492
a human osteoblastic cell line, mg-63, produces two molecular types of macrophage-colony-stimulating factor.a human osteoblastic cell line, mg-63, mouse primary osteoblasts, and a mouse osteoblastic cell line, mc3t3-e1, were shown to produce macrophage-colony-stimulating factor (m-csf) by bone-marrow-cell colony assay, using a specific neutralizing antibody for m-csf. immunoblot analysis of m-csf, produced by mg-63 cells, revealed the presence of a higher-molecular-weight species of m-csf, in addition to the 85-kda m-csf. the higher-molecular-weight species had a high affinity to the deae-sephacel col ...19921520704
the activated human c-ha-ras-1 oncogene as a mutagen.the induction of gene mutations and chromosome aberrations by plasmid pej6.6 carrying the activated c-ha-ras-1 oncogene from human bladder carcinoma was studied in cultured chinese hamster cells. both an increase in the frequency of hypoxanthine-phosphoribosyltransferase-deficient (hprt-) mutants and chromosome aberrations was observed after pej6.6 transfection as compared to control series (pbr322). in order to define whether it is the oncogene which is responsible for the mutagenic effect of p ...19921521228
specific chromosomal aberrations correlated to transformation in chinese hamster cells.cytogenetic changes were investigated during the spontaneous progression of chef18 chinese hamster cells towards tumorigenicity. we further report the chromosomal characterization of a series of spontaneous anchorage-independent clones, as well as of a series of tumor-derived cell lines resulting from injection of late passage cells in nude mice. the high karyotypic homogeneity (presence of four marker chromosomes strictly associated in all the metaphases analyzed) in all clones and tumor-derive ...19921521240
[the plasmid pej6.6 carrying the activated c-ha-ras-1 oncogene increases the mutation frequency in chinese hamster cells].the induction of gene mutations and chromosome aberrations by the plasmid pej6.6 carrying the activated c-ha-ras-1 oncogene from human bladder carcinoma was studied in cultured chinese hamster cells. both an increase in the frequency of gene mutations to 6-mercaptopurine resistance and of chromosome aberrations was observed after pej6.6 treatment as compared to control series (pbr322). thus the results of experiments carried out show that the pej6.6 plasmid possesses a mutagenic activity.19921521799
enteropathogenicity of non-toxigenic vibrio cholerae o1 for adult mice.the enteropathogenic potential of 32 vibrio cholerae o1 isolates that do not produce cholera toxin was examined in the orally inoculated, sealed adult mouse model. live cultures (2 x 10(10) cfu/ml) of 7/16 clinical and 6/16 environmental isolates produced a positive intestinal fluid accumulation (fa) ratio that reached near maximum at approximately 5 h post-inoculation. colony hybridization did not detect genes for cholera toxin, escherichia coli heat-labile and heat-stable toxins, or shiga-like ...19921522800
heat-labile toxin from bordetella parapertussis induces contraction of smooth muscle cells in culture.the ability of bordetella heat-labile toxin (hlt) to contract various types of cells in culture was examined. hlt from b. parapertussis induced contraction of cultured smooth muscle cells from trachea, intestine, uterus and vas deferens as well as from aorta. the time required for contraction decreased as the dose of b. parapertussis hlt increased from 3 to 100 mid/ml. upon exposure of cells to concentrations of toxin greater than 100 mid/ml, at least 2 hr was required for contraction. hlt from ...19921522812
generation of recombinant cho(dhfr-) cell lines by single selection for dhfr+ transformants.in order to establish a mammalian cell expression system with a minimum of selection steps and a stable expression of microgram amounts of recombinant protein (human tissue-type plasminogen activator mutants and chimeric proteins) per 10(6) cells per day, we investigated chinese hamster ovary cells and the dihydrofolate reductase-deficient chinese hamster ovary cell line cho(dhfr-). the 1tpa expression vector pcmvtpa was cotransfected either with the sv40 enhancer sequence containing dhfr expres ...19921524211
amplification and expression of heterologous oncostatin m in chinese hamster ovary cells.a stable chinese hamster ovary (cho) cell line producing high levels of human oncostatin m (om) was generated by transfecting a heterologous gene coding for the protein. this novel construct was comprised of the gene for the transforming growth factor-beta 1 (tgf-beta 1) signal peptide fused to the gene for mature human om. amplification with methotrexate produced milligram quantities of this recombinant om, which was processed correctly, glycosylated, and found to have biological functions simi ...19921524679
new isoxazole derivatives of retinoids: synthesis and activity on growth and differentiation of tumor cells.the effects of several newly synthesized isoxazole analogues of retinoids on differentiation and proliferation of 'in vitro' cultured tumor cell lines are reported. some of the tested compounds exhibit significative differentiating action, inducing adipogenic conversion of the chinese hamster fh06t1-1 cell line in a range of 2-10 times the activity of retinoic acid and retinol. in addition, most of the compound tested display antiproliferative activity comparable to that of natural retinoids. th ...19921525301
comparative studies of galactose-6-mustard and l-phenylalanine mustard on cell growth and cell cycle kinetics in vitro.the effect of galactose-6-mustard (g-6-m) on cell growth and cell cycle kinetics was studied in murine p388 leukemia and chinese hamster ovary (cho) cells in vitro and compared with the effect of l-phenylalanine mustard (l-pam). the ic50 values of g-6-m for the p388 and cho cells were 10 and 100 microm, respectively. no difference of the ic50 value of l-pam (2 microm) between the two cell lines was found. the effect of g-6-m and l-pam on cell kinetics was similar for the two cell lines at ic50 d ...19921525389
inhibitors of sterol synthesis. chemical synthesis and spectral properties of (25r)-5 alpha-cholest-8(14)-ene-3 beta,15 beta,26-triol, a potential metabolite of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one and its effects on 3-hydroxy-3-methylglutaryl-coenzyme a reductase in cho-k1 cells.(25r)-5 alpha-cholest-8(14)-ene-3 beta,15 beta,26-triol (iii) was prepared by reduction of (25r)-3 beta,26-diacetoxy-5 alpha-cholest-8(14)-en-15-one with sodium borohydride followed by treatment of the crude product with lithium aluminium hydride. the trihydroxysterol iii, a potential metabolite of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one, was characterized by the results of mass spectral studies and by nuclear magnetic resonance (nmr) spectroscopy. full 1h and 13c nmr assignments for iii ...19921525963
genotoxic properties of (e)-5-(2-bromovinyl)-2'-deoxyuridine (bvdu).(e)-5-(2-bromovinyl)-2'-deoxyuridine (bvdu)is a 5-substituted 2'-deoxyuridine antiviral compound that inhibits thymidylate synthetase. the selectivity of bvdu for virus-infected cells has been attributed to phosphorylation of bvdu by a virus-induced thymidine kinase. since the closely related compounds 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine are in vitro and in vivo mutagens, bvdu was tested for genotoxic activity in bacterial and mammalian cell mutation assays as well as in assays me ...19921526360
assessment of cytotoxicity assays as predictors of ocular irritation of pharmaceuticals.we have evaluated the use of cytotoxicity assays in vitro as an alternative to predicting ocular irritation potential in animals. three different measures of cytotoxicity--leucine incorporation into protein, mtt dye reduction, and neutral red uptake--were measured in a presumed target cell, corneal epithelial cells from rabbit, as well as in a nontarget cell, v79 (chinese hamster lung fibroblasts). an ic50 value was determined for each endpoint in one or both target cells for a series of 27 comm ...19921526363
assessment of the potential genotoxicity of perfluorodecanoic acid and chlorotrifluoroethylene trimer and tetramer acids.perfluoro-n-decanoic acid (pfda) is a perfluorinated fatty acid that produces hepatomegaly and increased peroxisomal beta-oxidation when administered to rodents. chlorotrifluoroethylene (ctfe) trimer acid and ctfe tetramer acid are metabolites of the six- and eight-carbon oligomers of ctfe, respectively. they are structurally related to pfda, and ctfe tetramer acid has caused toxic effects in rodents that are similar to those observed following pfda administration. because of the correlation bet ...19921526368
squalene synthase-deficient mutant of chinese hamster ovary cells.squalene synthase (farnesyldiphosphate:farnesyldiphosphate farnesyltransferase, ec 2.5.1.21) converts farnesyl pyrophosphate to squalene, the first metabolic step committed solely to the biosynthesis of sterols. using a fluorescence-activated cell sorting technique designed to screen for cells defective in the regulated degradation of 3-hydroxy-3-methylglutaryl coenzyme a (hmg-coa) reductase, we isolated a squalene synthase-deficient mutant of chinese hamster ovary cells. the mutant cell line, d ...19921526971
myristic acid utilization in chinese hamster ovary cells and peroxisome-deficient mutants.chinese hamster ovary (cho) cells convert [9,10-3h]myristic acid ([3h]14:0) to several lipid-soluble, radioactive metabolites that are released into the medium. the main products are lauric (12:0) and decanoic (10:0) acids. some of the 12:0 formed also is retained in cell lipids. similar metabolites are not synthesized from palmitic (16:0), oleic (18:1), or arachidonic (20:4) acids, and the addition of these fatty acids does not reduce the conversion of [3h]14:0 to 12:0. two peroxisome-deficient ...19921527024
domains responsible for the differential targeting of glucose transporter isoforms.facilitative glucose transporter isoforms, glut1 and glut4, have different intracellular distributions despite their very similar structure. in insulin-responsive tissues such as adipose tissues and muscle, glut4 protein resides mainly in the intracellular region in a basal condition and is translocated to the plasma membrane upon stimulation of insulin. in contrast, glut1 protein was distributed about equally between plasma membranes and low density microsomal membranes in 3t3-l1 adipocytes. fu ...19921527083
expression and phosphorylation of a three-repeat isoform of tau in transfected non-neuronal cells.the neuronal microtubule-associated protein, tau, is expressed as a set of isoforms containing either three or four tandemly repeated 31-amino-acid motifs in the c-terminal half of the molecule that can bind to microtubules. three-repeat forms are the only ones expressed early in development. a single three-repeat isoform of tau has been stably expressed in non-neuronal cells which do not express endogenous tau. chinese hamster ovary (cho) cells were transfected with a full-length cdna coding fo ...19921530572
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