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effect of dapi on chinese hamster chromosomes. 19807389420
the metabolism of benzo(a)pyrene by chinese hamster ovary cells in culture.1. the metabolism off the carcinogenic polycyclic hydrocarbon, benzo(a)pyrene, in chinese hamster ovary cells in culture has been investigated. 2. products with the properties on h.p.l.c. of 3-hydroxybenzo(a)pyrene and the trans-4,5-, 7,8- and 9,10-dihydrodiols of benzo(a)pyrene were detected in the cell medium when cells were incubated with benzo(a)pyrene for 24 h. 3. examination of the nucleoside adducts present in hydrolysates of the dna of chinese hamster ovary cells that had been incubated ...19807385913
reduced n-methyl-n'-nitro-n-nitrosoguanidine sister chromatid exchange induction in chinese hamster v79 cells pre-exposed to 5-bromodeoxyuridine.the sequence in which n-methyl-n'-nitro-n-nitrosoguanidine (mnng) and 5-bromodeoxyuridine (brdu) are added to cell cultures affects the number of sister chromatid exchanges (sce) induced by mnng. when v79 chinese hamster cell monolayer cultures were treated with mnng for 2 h prior to addition of brdurd, approximately a 4-5-fold increase in sce was observed at the second division metaphases compared to controls exposed to brdu alone. this effect was independent of whether one or three dna strands ...19807379643
genetic analysis of tumorigenesis: v. chromosomal analysis of tumorigenic and nontumorigenic diploid chinese hamster cell lines.the chromosomal constitution of four established diploid chinese hamster embryo fibroblast (chef) cell lines is described. chef/18 exhibits anchorage-dependent growth and is not tumorigenic in nude mice. chef/16 has a high plating efficiency in methylcellulose and is highly tumorigenic in nude mice. both chef/8 and chef/16 have a normal giemsa banding pattern and constitutive heterochromatin distribution characteristic of normal diploid chinese hamster cells and exhibit relatively little chromos ...19807368047
on the mechanics of chromosomal aberrations: a study with single and multiple spatially-associated protons.a unique radiation configuration, triads of protons, where mean separation between protons was controlled to be about 0.2 microns, has been used to irradiate chinese hamster v79 cells. these triads of accelerated particles were more effective at producing chromosomal aberrations than randomly incident particles. cells were irradiated with either single or three associated protons, with each proton depositing energy intracellularly at an let of about 30 kev per micron. the associated protons were ...19807360146
neurogenesis in the basal forebrain in the chinese hamster (cricetulus griseus). ii. site of neuron origin: morphogenesis of the ventricular ridges.in the present study the morphogenesis of the ventricular ridges, i.e. the site of origin for neurons in the basal ganglia and various related basal forebrain structures, has been studied in the chinese hamster with the aid of three-dimensional and graphical reconstructions. the first ridge appears at developmental stage 14 (e 12 1/2). it originates at the level of the torus hemisphaericus, thereby obscuring the basal part of the telodiencephalic boundary. later on this ridge passes into the med ...19807356177
polarity of microtubules nucleated by centrosomes and chromosomes of chinese hamster ovary cells in vitro.the structural and growth polarities of centrosomal and chromosomal microtubules were studied by analyzing the kinetics of growth of these microtubules and those initiated by flagellar seeds. by comparing rates of elongation of centrosomal and flagellar-seeded microtubules, we determined whether the centrosomal microtubules were free to grow at their plus ends only, minus ends ony, or at both ends. our results show that centrosomal microtubules elongate at a rate corresponding to the addition of ...19807350167
effect of dihydroxyanthraquinone and radiation on g2 progression.the effect of dihydroxyanthraquinone (dhaq), a potential anticancer chemotherapeutic agent, on the progression of chinese hamster ovary cells into mitosis and on the division delay induced by ionizing radiation was studied using the mitotic selection procedure for cell cycle analysis. following the addition of dhaq, the number of mitotic cells selected from an asynchronous population remained unaltered for a refractory period and then decreased. this effect was concentration dependent with trans ...19807349902
clastogenicity and aberration kinetics of some alkylarylnitrosoureas in chinese hamster v79-e cells.six alkylarylnitrosoureas were checked for induction of chromosome aberrations and sces in chinese hamster v79-e cells and compared with mnu, enu and nitrosocarbaryl. all agents show a dna-damaging activity. studies of the dependence of aberration frequency on recovery time revealed drastic differences within this group of closely related substances.19807228300
repairable and unrepairable dna strand breaks induced by decay of 3h and 125i incorporated into dna of mammalian cells.chinese hamster cells (cl: 1) were labelled with 3h-thymidine or 125iododeoxyuridine for 18 h and after 3 h in non-radioactive medium they were stored at 0 degrees c up to 6 h. the number of dna strand breaks observed after the labelling period (37 degrees c) or after treatment at 0 degrees c was determined using the dna-unwinding technique. 125i-decays in dna were significantly more efficient than 3h-decays in introducing unrepairable dna strand breaks during the labelling period. 32% of 125i-i ...19807220789
platinum compounds with anti-tumour activity.ten platinum (pt) coordination complexes with different ligands, comprising both pt(ii) and pt(iv) complexes of which the cis-compounds all possessed at least some anti-tumour activity and the trans-compounds were inactive, were tested as to their effect on cell survival and the induction and repair of dna damage in cultured chinese hamster cells (cho). the tests used were the determination of cytotoxicity, inhibition of the semi-conservative dna replication, induction of damage in dna and mutag ...19807209999
has diagnostic ultrasound mutagenic effects?chinese hamster ovary cells were treated with ultrasound from a fetal pulse detector (eucotone, siemens) operated at 10 mw/cm2 and 2.2 mhz. the frequencies of structural chromosomal aberrations and of sister chromatid exchanges were not increased by the treatment. there was no indication of single-strand breaks induced by ultrasound in the g2 phase of the cell cycle.19807193644
antagonistic effect of cocultivation on mitomycin c-induced aberration rate in cells of a patient with fanconi's anemia and in chinese hamster ovary cells.the rate of spontaneous chromosomal aberrations in fibroblasts of a patient with fanconi's anemia was slightly reduced after cocultivation with chinese hamster ovary (cho) cells. however, after mitomycin c treatment, a significant reduction of induced chromosomal damage was found in the fa cells while a significant increase was observed in the cho cells. this antagonistic effect could be attributed to some diffusible agent(s). the results are discussed with respect to the underlying mechanism of ...19807193643
cell mutants as a tool to study malignant transformation of fibroblasts.from 3t3 balb/c cells, mutants with low adhesiveness to plastic substratum were selected. one of these clones, ad6, was found to be deficient in glucosamine-6-phosphate n-acetylase. a result of this block is a decrease by 60-70% of cell surface carbohydrates, and as a consequence there is a general reduction in the exposure of glycoproteins at the cell surface. this biochemical defect is fully reverted to normal, simply by growing the mutant cells in presence of 10 mm n-acetylglucosamine. this s ...19807192865
an air-drying method for preparing metaphase from spermatogonial cells of chinese hamster (cricetulus griseus). 19807004102
detection of laser--uv microirradiation-induced dna photolesions by immunofluorescent staining.a low-power laser-uv microbeam of wavelength 257 nm was used for microirradiation of a small part of the nucleus of chinese hamster cells. following fixation in interphase or in the subsequent metaphase indirect immunofluorescent staining was performed with antiserum to photoproducts of dna treated with far uv light. the results show that antibodies specific for uv-irradiated dna can be used for a direct detection of laser-uv microirradiation-induced dna photolesions. the potential usefulness of ...19806993338
ultrasound lethality to synchronous and asynchronous chinese hamster v-79 cells. 19806989076
ethylnitrosourea-induced mutagenesis in asynchronous and synchronous chinese hamster ovary cells.the toxic and mutagenic activity of the alkylating carcinogen n-ethyl-n-nitrosourea (enu) was studied in chinese hamster ovary (cho) cells. cell killing and induction of 6-thioguanine-resistant (tgr) and ouabain-resistant (ouar) mutants were determined as a function of enu dose and treatment time in asynchronous cell populations. a dose-dependent induction of mutants was observed. the mutation frequency did not increase with longer than 30-min treatment times, implying that enu breaks down rapid ...19806987492
genetic markers for quantitative mutagenesis studies in chinese hamster ovary cells: characteristics of some recently developed selective systems.selection conditions have been optimized in the chinese hamster ovary (cho) cell system for a number of genetic markers. the genetic systems studied include resistance to the protein-synthesis inhibitors emetine (emtr) and diphtheria toxin (dipr), resistance to methylglyoxalbisguanylhydrazone (mbgr) which affects polyamine transport, resistance to the nucleoside analogs toyocamycin and tubercidin (toyr), and resistance to thioguanine (thgr) and ouabain (ouar). the optimal expression time followi ...19806987491
induction of chromosome shattering and micronuclei by ultraviolet light and caffeine. i. temporal relationship and antagonistic effects of the four deoxyribonucleosides.it is known that nucleosides may have antimutagenic and anticlastogenic effects. here, we have investigated the influence of nucleosides on the induction of shattered chromosomes (fragmentation and/or pulverization of chromosomes of a mitotic cell) and of micronuclei by ultraviolet (uv) light and caffeine. asynchronous cell cultures of a v79 subline of the chinese hamster were irradiated at wavelength 254 nm using fluences up to 5.2 joules/m2. following irradiation, the cells were postincubated ...19806976265
sister chromatid exchanges in chinese hamster embryonic liver cells exposed transplacentally to bromodeoxyuridine (brdu) and chemical mutagens.5 mg cyclophosphamide, injected intraperitoneally to pregnant hamsters, increased the rate of sister chromatid exchanges (sces) in embryonic liver cells from 4.1 to 8.8 sces per cell. 20 mg methyl metanesulfonate induced 11.8 sces per embryonic cell.19806933907
random segretation of multiple genetic markers from cho-cho hybrids: evidence for random distribution of functional hemizygosity in the genome.the linkage relationship between various recessive markers isolated in chinese hamster ovary (cho) cells has been investigated. for such studies, multiple recessive markers conferring resistance to various drugs, e.g., resistance to emetine (emtr), thioguanine (thgr), azaadenine (azar), phytohemagglutinin (phar), diphtheria toxin (dipr), toyocamycin (toyr), aminopterin (amnr), and methylglyoxalbisguanyl hydrazone (mbgr), were introduced into cho lines by selecting successively for one drug at a ...19806929113
[effect of long-term exposure to thiophosphamide on the frequency of chromosome aberrations in chinese hamster cell cultures].the paper contains the results of the study on the frequency of chromosome aberrations in the cell culture of chinese hamster under a prolonged action of low concentrations of thiophosphamide (thph). the frequency of chromosome aberrations in the initial period somewhat increases and then keeps to a certain constant level independently on the duration of action of thiophosphamide. with the heightening of the concentration of the chemical, a sharp increase in the number of chromosome aberrations ...19806778773
flow cytogenetics of uncloned and cloned chinese hamster cells.flow cytometry has greatly facilitated the routine use of dna content as a cellular indicator of the stages of the cell cycle and ploidy. dna content can also be used to distinguish individual chromosomes. fluorescent staining of chromosome dna was done with a combination of ethidium bromide and mithramycin in hypotonic solution. subsequent detergent treatment of the cells with triton x-100 facilitated chromosome isolation. dna flow cytometry of chromosomes of four established uncloned chinese m ...19806446447
specific protein phosphorylation during cyclic amp-mediated morphological reversion of transformed cells.treatment of transformed chinese hamster ovary cells with dibutyryl camp or other agents that elevate camp results in the acquisition of growth and morphology characteristic of normal fibroblasts. the role of specific protein phosphorylation in this process of morphological reversion has been examine using metabolic labeling of chinese hamster ovary (cho) cells with 32p-orthophosphate in the presence or absence of n6o2'-dibutyryladenosine 3':5'-cyclic monophosphoric acid (bt2camp). analysis of l ...19806262578
isolation of multiple classes of mutants of cho cells resistant to cyclic amp.from mutagenized chinese hamster ovary (cho) cells we have isolated, in a single step, 11 independent mutants resistant to the growth-inhibitory effects of 8-br-cyclic amp, cholera toxin, and methylisobutylxanthine. two major classes and several subclasses of mutants were obtained. mutants from all classes have a normal doubling time. none of the mutants respond to cyclic amp treatment with increased flattening and elongation as do the parental cells. members of the first class have an altered p ...19806245473
silver stained core-like structures in chinese hamster metaphase chromosomes.chinese hamster metaphase chromosomes, subjected to prolonged hypotonic pretreatment and subsequently stained with ammoniacal silver, contained a darkly-stained core-like structure in each chromatid, surrounded by a halo of dispersed chromatin which was pale yellow to brown in color. the core was variable in its appearance, ranging from a continuous linear configuration to a spiral structure or a discontinuous, particulate structure. within the centromeric regions, the cores frequently appeared ...19806165446
studies of mammalian chromosome replication. i. brdu-induced differential staining patterns in interphase and metaphase chromosomes.the patterns of differential staining based on the effects of brdu-substitution in chromosomal dna have been examined in both metaphase chromosomes and prematurely condensed chromosomes (pcc) of interphase chinese hamster cells. results indicate that differential staining may be obtained in chromosomes from all stages of the cell cycle and correspond to the semi-conservation mode of dna replication. such fidelity of differential staining in both interphase and metaphase chromosomes suggests that ...19806156800
chromosome bands and the subunit structure of chinese hamster metaphase chromosomes.isolated chinese hamster chromosomes dissociate into a series of specific chromatin subunits approximately the size of stainable chromosome bands upon reduction of the divalent ion concentration during or after isolation. at high ph the chromatin in some bands is differentially removable during chromosome isolation, leaving a banded chromosome with a pattern typical of most g-band procedures. this provides an alternate molecular mechanism to explain the production of banded chromosomes by a vari ...19806156054
synaptonemal complex karyotyping in spermatocytes of the chinese hamster (cricetulus griseus). iv. light and electron microscopy of synapsis and nucleolar development by silver staining.synaptonemal complexes (scs), x and y axes, and various nucleolar structures stain preferentially with silver in surface microspread preparations and are analyzable by both light and electron microscopy. central elements, kinetochore region material and nuclear annuli which stain with ethanolic phosphotungstic acid are seldom visible after silver staining. scs can be characterized by length measurements equally well in light and electron micrographs, from which stages of pachytene can also be de ...19806153596
the effect of maternally inhaled styrene on embryonal and foetal development in mice and chinese hamsters.pregnant mice and chinese hamsters were exposed to styrene 6 hrs daily during the period of major organogenesis via inhalation in concentrations 250 p.p.m., and 300, 500, 750 and 1000 p.p.m., respectively. both in mice and in chinese hamsters embryotoxicity was raised. some minor skeletal malformations (rib fusions, extra ribs) were noted in mice but not in chinese hamsters.19807435197
the sce-inducing capacity of vitamin c: investigations in vitro and in vivo.in contrast with results in vitro, vitamin c did not lead to an induction of sister-chromatid exchanges (sces) in the bone marrow of chinese hamsters in the sce test in vivo. the test dose ranged from 200 to 10 000 mg/kg body weight and was administered orally as well as by intraperitoneal injection. sulfhydryl compounds such as cysteine and glutathione inhibited the sce induction by vitamin c in vitro owing to their reducing capacity. these results are discussed with regard to the primary damag ...19807432363
vinyl chloride: an example for evaluating mutagenic effects in mammals in vivo after exposure to inhalation.as part of a programme of investigations on the mutagenic effects in mammals in vivo after inhalation of environmental chemicals, the effects of the industrial compound vinyl chloride (vc) was analysed. chinese hamsters were exposed to 1.25%, 2.5% or 5% (v/v) vc in air for 6, 12 or 24 hr. bone marrow chromosomes were analysed for induced chromosome aberrations and sister-chromatid exchanges (sces) 26 h after beginning of exposure. the frequency of vc-induced chromosome aberrations and sces both ...19807396717
spontaneous endomyometrial neoplasms in aging chinese hamsters.twenty-one endomyometrial neoplasms among 93 nulliparous noninbred chinese hamsters were evaluated. the median survival time of the 93 females was 1,040 days. the median age of hamsters with endomyometrial neoplasms was 1,200 days. neoplasms were classified as carcinoma or malignant mixed müllerian tumors of the endometrium and benign or malignant myometrial neoplasms. there were 13 endometrial adenocarcinomas. three tumors were mixed adenosquamous carcinomas, which occurred in significantly old ...19806929019
induction of aryl hydrocarbon hydroxylase in chinese hamsters and mice following intratracheal instillation of benzo(a)pyrene. 19807394318
chromosomal aberrations in bone marrow of chinese hamsters exposed to styrene and ethanol.no significant increase was detected in the number of chromosomally damaged cells in bone marrow of chinese hamsters after either inhalation exposure to 300 ppm styrene or oral intake of 15% ethanol in drinking water (exposure time 4 days or 3 weeks). in combined exposure, a slight increase of chromosomal aberrations was observed in the group exposed for 4 days (2.0% aberrant cells vs. 0.0% in controls). the group exposed for 3 weeks to combined treatment showed no response (0.3% aberrant cells ...19807466852
autoantibody to centromere (kinetochore) in scleroderma sera.sera from patients with scleroderma contained several autoantibodies to nuclear antigens which were distinguished by different patterns of nuclear immunofluorescence staining. one of these autoantibodies reacted with centromeric regions of chromosomes. in chromosome spreads, the staining appeared as two small spheres at the centromere, resembling kinetochores. the antigenic determinant appeared to be a protein or polypeptide tightly bound to dna. the autoantibody was reactive with centromeres of ...19806966403
separation of human and chinese hamster arylsulfatases a and b by two-directional polyacrylamide gel electrophoresis.two-directional or 'mirrow' polyacrylamide gel electrophoresis permits one simultaneously to separate and detect human and chinese hamster arylsulfatases a and b. such a separation was not possible in conventional one-dimensional polyacrylamide gel systems. the amount of each enzyme present could be quantitated by scanning at 515 nm after incubation of the gel in nitrocatechol sulfate. direct comparisons showed that this system is at least as sensitive as a cellogel-methylumbelliferone sulfate m ...19806103805
an ultrastructural study of the cytotoxic effect of the venoms from the sea nettle (chrysaora quinquecirrha) and portugese man-of-war (physalia physalis) on cultured chinese hamster ovary k-1 cells. 19806111138
binding to cellular macromolecules as a possible mechanism for the cytotoxicity of misonidazole.reduction of the nitro group occurred when [14c]misonidazole was treated with zinc dust in aqueous solution in the presence of ammonium chloride. when the reduction mixture was allowed to react with calf thymus dna or bovine albumin, radioactivity was bound to both dna and protein. under the same conditions, misonidazole did not bind to these macromolecules. analysis of the reduction mixture indicated that the hydroxylamine, amine, and hydrazo derivatives of mizonidazole were the major products. ...19806155991
effects of ellipticine on cell survival and cell cycle progression in cultured mammalian cells.the effects of ellipticine [5,11-dimethyl-6h-pyrido(4,3-b)carbazole; nsc 71795] on cell viability, growth, and colony formation were investigated in suspension (friend leukemia and l1210) and adherent [chinese hamster ovary (cho)]tumor cell systems as well as in mitogen-stimulated human peripheral blood lymphocyte cultures. cell cycle progression and the terminal point of action of the drug were monitored by flow cytometry. ellipticine was cytostatic for all cell lines tested, blocking cells in ...19806155993
differential expression of type i and type ii cyclic amp-dependent protein kinases during cell cycle and cyclic amp-induced growth arrest.the activation state of cyclic amp-dependent protein kinase(s)(atp:protein phosphotransferase, ec 2.7.1.37) is transiently increased 2-fold as a function of g1 progression in mitotically synchronized chinese hamster ovary cells. the cellular content of type i kinase increases concomitantly with the increase in general protein, whereas the activity of type ii kinase increases as a function of time in g1 to a maximum at the g1/s border. in contrast, in the presence of dibutyryl-cyclic amp, there i ...19806158048
classification of polyene antibiotics according to their synergistic effect in combination with bleomycin a2 or fusidic acid.five polyene antibiotics were compared for their effects on colony formation of either chinese hamster v79 or saccharomyces cerevisiae cells. a 10 to 40 times higher concentration of amphotericin b (heptaene) or nystatin (degenerated heptaene) was necessary to inhibit colony formation of hamster cells than that needed to inhibit colony formation of yeast cells. in contrast, colony formation of both hamster and yeast cells was inhibited to the same extent by similar concentrations of filipin (pen ...19806160808
action of dihydroxyanthraquinone on cell cycle progression and survival of a variety of cultured mammalian cells.dihydroxyanthraquinone, 1,4-dihydroxy-5,8-bis(( (2-[(2-hydroxyethyl)amino]ethyl)amino))-9,10-anthracenedione (nsc 279836), was observed to alter the cell cycle kinetics of a variety of mammalian cell lines as monitored by flow cytometry. continuous exposure of friend leukemia, l1210, and chinese hamster cells to the drug in vitro at concentrations of 1.0 to 10 ng/ml resulted in the accumulation of cells in g2 by 24 hr in culture. when cells were exposed to dihydroxyanthraquinone for 30 min, wash ...19806162553
molecular mechanisms involved in the production of chromosomal aberrations. ii. utilization of neurospora endonuclease for the study of aberration production by x-rays in g1 and g2 stages of the cell cycle.chinese hamster ovary cells (cho) were x-irradiated in g1 and g2 stages of the cell cycle and subsequently neurospora endonuclease (ne) (e.c.3.1.4), an enzyme which is specific in cleaving single-stranded dna, was introduced into the cells, after making the cells permeable by treatment with inactivated sendai virus. with this treatment all classes of x-ray-induced chromatid aberrations increased in g2 cells, whereas in g1 cells an increase in chromosome type of aberrations was found, associated ...19806244487
distribution of endogenous murine leukemia virus dna sequences among mouse chromosomes.we used mouse-chinese hamster somatic cell hybrids which lose mouse chromosomes to examine the distribution of murine leukemia virus dna sequences in the genome of a/hej mice. we analyzed total cellular dna from various hybrid clones for the presence of viral sequences by molecular hybridization and used the southern blot hybridization procedure to identify viral dna in cellular restriction endonuclease fragments. our results show that murine leukemia virus dna sequences are distributed among ma ...19806245275
ubiquitous, interspersed repeated sequences in mammalian genomes.dna base sequence comparisons demonstrate that the principal family of 300-nucleotide interspersed human dna sequences, the repetitive double-strand regions of hela cell heterogeneous nuclear rna, and specific rna polymerase iii in vitro transcripts of cloned human dna sequences are all representatives of a closely related family of sequences. a segment of approximately 30 residues of these sequences is highly conserved in mammalian evolution because it is also present in the interspersed repeat ...19806246492
the synergistic effects of sv40 and budr on induction of gene mutations and chromosomal aberrations in chinese hamster cells.the induction of chromosomal aberrations and gene mutations was studied in chinese hamster cells after separate and combined treatment with budr and sv40. separate treatment of cells with budr or virus infection increased the yield of chromosomal aberrations and reversions from glutamine requirement, expressed at 40 degrees c (a ts mutant), to prototrophy. the combined effect of the incorporation of budr into one dna strand, and a subsequent infection by sv40 was additive as regards the percenta ...19806247650
atp enhances cyclic amp accumulation by intact p388 mouse lymphoma cells.one of the characteristics of malignant cells is a poor response to hormones and a low level of cyclic amp. whilst this is true of intact p388 mouse lymphoma cells, high levels of adenylate cyclase (atp pyrophosphate-lyase (cyclizing), ec 4.6.1.1) activity can be measured in particulate preparations of these cells. when atp is added to the incubation medium of intact lymphoma cells, the cyclic amp level is enhanced. this effect of atp is not mediated by adenosine, nor is it enhanced by naf. the ...19806248129
alteration of the membrane lipid composition and infectivity of vesicular stomatitis virus by growth in a chinese hamster ovary cell sterol mutant and in lipid-supplemented baby hamster kidney clone 21 cells.the cholesterol and phospholipid composition of the membrane of vesicular stomatitis (vs) virus was altered by growth in a sterol auxotroph chinese hamster ovary (cho mi) host cell and by infection of cho mi and baby hamster kidney (bhk)-21 cells supplemented with fatty acids and dimethylethanolamine. vs virus released from infected cho mi sterol auxotroph cells grown in delipidated serum had a 50% lower ratio of cholesterol to phospholipid and an 80% drop in infectivity measured by plaque forma ...19806249809
cytopathogenic mechanisms of entamoeba histolytica.cinemicrography of entamoeba histolytica destruction of chinese hamster ovary (cho) cells shows that ameba cytopathogenicity consists of separate components: a contact-dependent cytolethal effect, and phagocytosis. cells not in contact with amebae remain intact. quantitation of ameba destruction of cho cells by applying the one-hit hypothesis confirms that the cytoethal effect of amebae is contact dependent. studies with 111indium oxine-labeled cells provide further evidence of extracellular kil ...19806249882
integration of the simian virus 40 genome into cellular dna in temperature-sensitive (n) and temperature-insensitive (a) transformants of 3t3 rat and chinese hamster lung cells.we studied the pattern of integration of the simian virus 40 (sv40) genome into the cellular dna of n-transformants (temperature sensitive) and a-transformants (temperature insensitive) derived from 3t3-fisher rat and chinese hamster lung cells. the sv40 dna was covalently linked to the cellular dna in both types of transformants. in the rat cells, most n-transformants contained sv40 sequences integrated at a single site; most a-transformants contained sv40 sequences integrated at two to five si ...19806251267
replication of chinese hamster embryo cells transformed by temperature-sensitive t-antigen mutants of simian virus 40.chinese hamster embryo cells transformed by simian virus 40 temperature-sensitive t-antigen mutants replicated when confluent at 40.5 degrees c, regardless of the selection method, selection temperature, or virus strain used.19806251272
comparative analysis of proteins selectively released from cell nuclei of different eukaryotic species under conditions of mild hydrolysis by nucleases.nuclei of cultured chinese hamster fibroblasts, dechoryonized eggs of drosophila melanogaster, calf thymocytes and mouse spleen were digested with micrococcal nuclease or dnase i under conditions when about 15-20% of nuclear dna is hydrolyzed. proteins released from the nuclei with this dna were analyzed by electrophoresis in polyacrylamide gels in the presence of sds and the most prominent components were purified in each case. it is shown that these components derived from different species ha ...19806251362
transformation of mammalian cells with an amplifiable dominant-acting gene.we have transferred a mutant hamster gene coding for an altered dihydrofolate reductase to wild-type cultured mouse cells by using total genomic dna from methotrexate-resistant chinese hamster ovary a29 cells as donor. by demonstrating the presence of hamster gene sequences in transformants we have provided direct evidence for gene transfer. transformants selected for increased resistance to methotrexate contain increased amounts of the newly transferred gene. we have used this mutant dhfr gene ...19806251468
identification of 5-methylcytosine in dna fragments immobilized on nitrocellulose paper.a method to identify 5-methylcytosine (m5cyt) in dna immobilized on nitrocellulose paper by using antibody against m5cyt raised in rabbits is described. immobilized restriction fragments of dna are incubated first with purified antibody against m5cyt and then with goat anti-rabbit igg labeled with 125i. restriction fragments containing m5cyt are visualized by autoradiography. by using this method, a heavily methylated fragment of about 1700 base pairs was identified in nuclear dna fom chinese ha ...19806251470
comparative gene mapping: order of loci on the x chromosome is different in mice and humans.for comparative studies we have used the somatic cell hybridization approach to regionally map genes on the mouse x chromosome. fibroblasts from a mouse with the balanced reciprocal translocation t(xd;16b5)16h were fused with a chinese hamster cell line (v79/380-6) deficient in activity of the enzyme hypoxanthine phosphoribosyltransferase (hprt). interpecific cell hybrids were initially selected for retention of the mouse translocation chromosome carrying the hprt gene. subsequently, hybrid clon ...19806251472
dna of simian virus 40 mutates chinese hamster cells.infection of chinese hamster cells with sv 40 dna gives rise to mutants resistant both to s-axaguanine (ag) and aminopterin (ap). this mutagenic effect can be raised when facilitating dna uptake of cells by a helper agent. the extent of muyagenic action depends further on the concentration of dna applied to the cells, with 2 micrograms/ml being more effective than 10 micrograms/ml, as well as on the period of incubation of infected cells before onset of mutant selection (mutation expression time ...19806251786
the specific organisation of satellite dna sequences on the x-chromosome of mus musculus: partial independence of chromosome evolution.dna was isolated from a chinese hamster/mouse hybrid cell line containing a single mouse chromosome, the x-chromosome, and digested with a variety of restriction endonucleases known to cut mouse satellite dna. after agarose gel electrophoresis and transfer to nitrocellulose, hybridisation was carried out to a radioactive mouse satellite dna probe. in this manner the organisation of satellite sequences at an individual chromosome was determined. we have found that the organisation of centromeric ...19806253924
altered synthesis and processing of oligosaccharides of vesicular stomatitis virus glycoprotein in different lectin-resistant chinese hamster ovary cell lines.to determine the particular intracellular steps in the glycosylation of the vesicular stomatitis virus (vsv) glycoprotein that were altered in several lectin-resistant cho cell lines, vsv-infected parental and mutant cells were pulse-labeled for 30 and 120 min with [3h]mannose and [3h]glucosamine. cell-associated viral glycopeptides were analyzed by gel filtration combined with specific glycosidase digestions and compared with the corresponding mature virion oligosaccharides. the intracellular g ...19806255177
simian virus 40-chinese hamster kidney cell interaction. v. cooperative effect of 5-iodo-2'-deoxyuridine and mitomycin c in the enhancement of virus replication in infected cells.a cooperative effect of 5-iodo-2'-deoxyuridine and mitomycin c which amplified (10- to 50-fold) their stimulating effect on simian virus 40 replication was obtained in infected chinese hamster kidney cells. the results indicate that these drugs act at different levels to modify the permissiveness of cells to simian virus 40.19806255213
structure and organization of the highly repeated and interspersed 1.3 kb ecori-bg1ii sequence family in mice.ecori digestion of total mouse dna yields a prominant 1.3 kb fragment amounting to between 1 and 2% of the mouse genome. the majority of the 1.3 kb ecori fragments have a single bg1ii site 800 bp from one end. this ecori-bg1ii sequence family shows hindiii and haeiii sequence heterogeneity. we have cloned representatives of the ecori-bg1ii gene family in charon 16a and studied their structure and organization within the genome. the cloned 1.3 kb fragments show the expected restriction enzyme pat ...19806255440
control of sv40 replication by a simple chromosome in monkey-hamster cell hybrids.somatic cell hybrids produced between cercopithecoid monkey and chinese hamster cells were used to assay susceptibility to sv40 viral infection in an attempt to define the primate factors that determine permissiveness to viral replication. these cell hybrids, which differed in their primate chromosome complement, were found to differ also in their ability to sustain viral replication. a correlation was found between an elevated sv40 viral replication and the presence of the chromosomes 11 in the ...19806255616
enhanced sensitivity of tumorigenic cells to rapid rounding induced by phenylalaninol.this study describes a rounding reaction induced in mammalian cells by the addition of phenylalaninol. in the chinese hamster ovary tsh1 line the rounding occurred rapidly with a half time of 1 min at 25 mm phenylalaninol. after the removal of phenylalaninol, the rounding was reversed, leading to the reflattening of the cells with a half-time of 3.5 min. rounding was inhibited by dibutyryl-camp and testosterone, and reflattening by cytochalasin b. either in the case of the tsh1 line and its grow ...19806257353
structure of the abelson murine leukemia virus genome and the homologous cellular gene: studies with cloned viral dna.circular double-stranded dna produced after infection of mouse cells with abelson murine leukemia virus (a-mulv) was isolated and cloned in the phage vector charon 21a. the resulting clones of the a-mulv genome show homology to the ends of moloney mulv and to a 3.5 kb central region containing sequences unique to abelson virus. a 2.3 kb restriction fragment containing only a-mulv-specific sequences was subcloned in the plasmid vector pbr322 and used as a probe for the cellular gene that had been ...19806257398
isolation and characterization of a pseudomonas aeruginosa mutant producing a nontoxic, immunologically crossreactive toxin a protein.nitrosoguanidine mutagenesis of pseudomonas aeruginosa strain pao-1 yielded a mutant strain, pao-pr1, which produced a protein that was immunologically indistinguishable from native toxin a and was nontoxic for cultured chinese hamster ovary cells. in contrast to native toxin, the cell-associated and extracellular crossreactive material (crm), designated "crm protein," possessed no adenosine diphosphate-ribosylating activity. this crm protein comigrated with native toxin a on sodium dodecyl sulf ...19806261247
studies on the cytopathogenicity of entamoeba histolytica.we have explored the interaction of virulent and avirulent e. histolytica (hm1 and 303 respectively) with human polymorphonuclear leukocytes (pmns) and chinese hamster ovary (cho) cells. pmns exhibit chemotaxis to both hml and 303. on contact with hml, pmns degranulate and die (trypan blue uptake); incubation at a ratio of 100 pmns per ameba for 40 minutes revealed 70 per cent pmn death with 84 per cent hml viability. 303s are often ingested by pmns on contact; after incubation as above, only 1 ...19806258505
absence of arsenite mutagenicity in e coli and chinese hamster cells.because exposure to compounds of arsenic has been implicated as a cause of cancer, an investigation of the mutagenicity of sodium aresenite in e coli and in chinese hamster cells was performed. in the e coli system, trp + revertants were not induced by arsenite in a variety of experimental protocols including spot tests, treat and plate protocols, and fluctuation tests. the mutator effect of a tif-1 strain was partially blocked by arsenite. arsenite did not cause the induction of lambda prophage ...19806459229
the use of liver cell cultures in mutagenesis studies.a sensitive cell-mediated assay has been developed for testing the mutagensis of liver carcinogens. mutagenesis was detected in chinese hamster v79 cells that were cocultivated with hepatocytes isolated after collagenase/hyaluronidase digestion of rat liver slices. mutations were characterized by resistance to ouabain and 6-thioguanine. seven of the nitrosamines, which are potent liver carcinogens, exhibited a mutagenic response. mutagensis with the carcinogens could be detected at micromolar do ...19806784635
mutagenicity testing in mammalian cells. ii. validation of multiple drug-resistance markers having practical application for screening potential mutagens.chinese hamster ovary (cho) cell lines heterozygous at both the adenine phosphoribosyltransferase (aprt) and thymidine kinase (tk) loci were used for single-step selection of spontaneous and induced mutants resistant to 8-azaadenine (aar), 6-thioguanine (tgr), ouabain (ouar), or 5-fluorodeoxyuridine (fudrr). mutation data are reported for direct mutagens (ems, ethyl methanesulfonate; mnng, n-methyl-n'-nitro-n-nitrosoguanidine; nqo, 4-nitroquinoline 1-oxide) and promutagens (dmn, dimethylnitrosam ...19806449664
assignment of pgm3 to the long arm of human chromosome 6. studies using chinese hamster x human cell hybrids containing a human 6/15 translocation.hybrids derived from the fusion of thymidine kinase deficient chinese hamster cells and human cells carrying a 6/15 translocation, 46,xx,t(6;15)(cen;p13), were analyzed for the expression of human pgm3, glo and me1. the results show that pgm3 and me1 are on the long arm and glo is on the short arm of human chromosomes 6.19806450030
posttranslational modification of elongation factor 2 in diphtheria-toxin-resistant mutants of cho-k1 cells.we have identified two types of mutants of chinese hamster ovary cells in which the unique adp-ribose attachment site in elongation factor 2 (ef-2) is altered, thereby rendering them resistant to diphtheria and pseudomonas toxins (toxr). the first is mutant in the gene for ef-2 and possesses a permanently altered, toxr gene product. the second lacks a component of a posttranslational modification system that converts toxr ef-2 to the toxin-sensitive (toxs) state. we postulate that this modificat ...19806928655
cotransfer of linked eukaryotic genes and efficient transfer of hypoxanthine phosphoribosyltransferase by dna-mediated gene transfer.the efficiency of dna-mediated transfer of the gene (hprt) for hypoxanthine phosphoribosyltransferase (hprt; imp: pyrophosphate phosphoribosyltransferase, ec 2.4.2.8) is dependent upon the recipient cell used. hprt has been transferred into mouse tg8 or chinese hamster chtg49 cells at a high frequency, similar to the frequency of the gene (tk) for thymidine kinase (tk; atp:thymidine 5'-phosphotransferase, ec 2.7.1.21) transfer into mouse lmtk- cells (i.e., 10(-6)). in contrast, the frequency of ...19806929511
isolation and localization of dna segments from specific human chromosomes.recombinant dna techniques have been combined with somatic cell genetic methods to identify, isolate, and amplify fragments of human dna localized at specific regions of human chromosome 11 selected as a model system. a library of genomic dna segments has been constructed, in lambda charon 4a bacteriophage, from the dna of a somatic cell hybrid carrying a portion of human chromosome 11 on a chinese hamster ovary cell background. using a nucleic acid hybridization technique that distinguishes hum ...19806930670
drb resistance in chinese hamster and human cells: genetic and biochemical characteristics of the selection system.stable mutants resistant to the nucleoside analog 5,6-dichloro-1-beta-d-ribofuranosyl benzimidazole (drb), which interferes with rna synthesis, have been selected in chinese hamster ovary (cho) and human diploid fibroblasts. in cho cells, upon treatment with the mutagen ethyl-methane sulfonate (ems), a linear dose--response between the concentration of mutagen and the frequency of drbr mutants was observed in the range of 20--300 micrograms/ml. the selection system did not show cell density or c ...19806930702
dna-mediated cotransfer of unlinked mammalian cell markers into mouse l cells.purified dna from three different types of mammalian cells was precipitated with calcium phosphate and added to mouse l cells deficient in thymidine kinase (tk). donor dna was prepared from three cell lines: (a) mouse cells transfected with uv-inactivated herpes simplex virus (hsv) type 1, or a purified fragment of hsv carrying the tk gene (b) human hela cells, and (c( cho, a cell line derived from chinese hamster ovaries. several hypoxanthine-aminopterin-thymidine resistant colonies were isolat ...19806932400
effects of prospidine on survival and growth of mammalian cells in culture.the effects of prospidine, chemically known as 3, 12-diaza-6,9 diazoniadispiro[5.2.5.2]hexadecane,3,12-bis(3-chloro-2-hydroxypropyl)-dichloride (nsc-166100), on cell viability, growth, and colony formation were investigated in several mammalian cell lines. cell cycle progression and the terminal point of action of the drug were monitored by flow cytometry. prospidine was cytostatic for two suspension cultures (friend leukemia and l1210 cells) at a concentration of 10 mg/ml during the first cell ...19806933266
sister-chromatid exchange induction by metabolically activated retinoids in human diploid fibroblast cultures.13-cis-retinoic acid, retinyl-mthyl-ether, retinyl-phenyl-ether, retinyl-thio-ether and axerophthene each induced dose-dependent sister-chromatid exchanges (sce) in human diploid fibroblasts. the functional relationship between retinoid concentration and sce rate was similar in each of the 5 retinoids tested. the relationship reached a plateau at concentrations exceeding 8 micrograms/ml. alpha-naphthoflavone (anf), an inhibitor of p448-dependent mono-oxygenase, prevented the retinoid-induced inc ...19806933309
prevalent deficiency in tumor cells of cycloheximide-induced cycle arrest.mammalian cell growth is regulated by a process that is completed at a restriction point in the late g1 part of the cycle. this process is highly sensitive to serum concentration and to moderate inhibition of protein synthesis by cycloheximide (chm) or other agents. we have proposed that a cell must accumulate a labile protein in a critical amount before events related to its dna synthesis can start. the accumulation of this protein requires conditions suitable for growth, including sufficient a ...19806933461
expression of the human argininosuccinate synthetase gene in hamster transferents.the structural gene for human argininosuccinate synthetase [l-citrulline:l-aspartate ligase (amp-forming), ec 6.3.4.5] was transferred to argininosuccinate synthetase-deficient chinese hamster cells via metaphase chromosomes isolated from human lymphoblast line mgl8d1, a constitutive overproducer of argininosuccinate synthetase, and from its repressible parent, mgl8b2. argininosuccinate synthetase expression was selected for in citrulline-containing medium, and the human origin of the argininosu ...19806933472
high molecular weight polypeptides (270,000-340,000) from cultured cells are related to hog brain microtubule-associated proteins but copurify with intermediate filaments.high molecular weight polypeptides (hmwps) of 270,000 to 340,000 were found to be major components of intermediate filaments prepared by triton x-100 extraction after spreading of rat glioma c6, hela, chinese hamster ovary, and simian virus 40-transformed chinese hamster lung cells. c6 hmwps were shown to resemble high molecular weight microtubule-associated proteins from hog brain by four criteria: (i) comigration in electrophoresis on high-resolution sodium dodecyl sulfate/polyacrylamide gels, ...19806933530
branched-chain aminotransferase deficiency in chinese hamster cells complemented by two independent genes on human chromosomes 12 and 19.branched-chain aminotransferase (bct) catalyzes the reversible transamination of the branched-chain alpha-keto acids to the branched-chain l-amino acids. since branched-chain l-amino acids (l-isoleucine, l-leucine, and l-valine) are essential for cell growth, cells which lack bct were unable to proliferate in media containing alpha-keto acids in place of the corresponding l-amino acids. chw-1102, a chinese hamster cell line, lacks bct and does not grow in alpha-keto acid media. somatic cell hybr ...19806933702
assignment of a human genetic locus to chromosome 5 which corrects the heat sensitive lesion associated with reduced leucyl-trna synthetase activity in ts025cl chinese hamster cells.a heat-sensitive (hs) leucyl-trna synthetase (leurs) deficient cho mutant, ts025cl, was fused with human leukocytes and hybrids isolated in hat medium at the nonpermissive temperature. nineteen heat-resistant (hr) and 14 hs subclones were isolated from four independent primary hybrids and tested for the expression of 24 human isozymes which have been assigned to 17 human chromosomes. four hr independent subclones and three hs independent subclones were analyzed for the presence of human chromoso ...19806933703
assignment of the sorbitol dehydrogenase locus to human chromosome 15 pter leads to q21.the locus for sorbitol dehydrogenase (sord, e.c. 1.1.1.14) has been shown to segregate with hexosaminidase a and mannose phosphate isomerase in a series of human-chinese hamster somatic cell hybrids. cytogenetic analysis supports the assignment to chromosome 15 and further defines the gene locus to the region 15pter leads to q21.19806933990
chromosomal assignment of the gene for folylpolyglutamate synthetase to human chromosome 9.an auxotrophic mutant, gat-, derived from the chinese hamster cell line cho-k1 and exhibiting multiple growth requirements for glycine, adenine, and thymidine, has been shown to be deficient in one of the folate-dependent enzymes, folylpolyglutamate synthetase (fpgs). this mutant was fused with normal human lymphocytes and human lymphoblasts and 41 gat+ primary hybrid clones were isolated in medium lacking glycine, adenine, and thymidine. in addition, 71 secondary clones were isolated after grow ...19806934068
assignment of a gene for succinate dehydrogenase to human chromosome 1 by somatic cell hybridization.a chinese hamster cell mutant has been described with little or no activity of succinate dehydrogenase (soderberg et al., 1977). we described here the selection and characterization of human-hamster hybrids obtained from the fusion of these mutant cells and human lymphoblasts or ht1080 fibrosarcoma cells. the presence of human chromosome 1, identified by cytogenetic techniques and isozyme analysis, is correlated with the restoration of succinate dehydrogenase activity in the hybrids, and segrega ...19806934864
regional assignment of the gene locus for steroid sulfatase.the gene locus for steroid sulfatase, deficiency of which causes x-linked ichthyosis, is assigned to xp11 leads to xpter by analysis of 24 man-chinese hamster somatic cell hybrids. high steroid sulfatase activity in a hybrid clone having retained only part of xq is explained by demonstration of an additional late-replicating human x chromosome. this observation confirms previous evidence for noninactivation of the sts locus.19806985463
ph dependence of the phototoxic and photomutagenic effects of chlorpromazine.the ph dependence of the phototoxic effects of chloropromazine (cpz) in escherichia coli, salmonella typhimurium and chinese hamster cells were studied at ph 6--8. all three biological systems displayed higher photosensitization of the drug at lower ph-values. in s. typhimurium the combined action of drug and light also showed mutagenic activity which correlated with toxicity when exposed at ph 7 or 8. when solutions of protein or dna and cpz were exposed to near ultraviolet (uv) light, the drug ...19806986208
molecular dosimetry of the chemical mutagen ethyl methanesulfonate: quantitative comparison of mutation induction in escherichia coli, v79 chinese hamster cells and l5178y mouse lymphoma cells, and some cytological results in vitro and in vivo.molecular dosimetry studies were carried out to measure the extent of binding of radio-labeled ethyl groups to the dna of escherichia coli, v79 chinese hamster cells and l5178y mouse lymphoma cells treated with ethyl methanesulfonate (ems). the results show that (1) the amount of ethylation of the dna is similar in these cells when treatment conditions are identical, (2) the relationship between dose to dna (ethylations per nucleotide) versus exposure (mm applied concentration) is non-linear in ...19806987499
mutagenicity of sulphonylureas.the 11 derivatives of beta-cytotropic sulphonylureas commonly used in the treatment of diabetes mellitus were tested in vivo in the highly sensitive sister-chromatid exchange test. chlorpropamide and tolbutamide gave a positive reaction with a clear dose-response in chinese hamsters and mice. the two compounds gave a mutagenic response neither in the salmonella/mammalian-microsome mutagenicity test (with and without microsomal activation) nor in the chromosomal aberration test. in the micronucle ...19806990252
cytogenetic effect of ortho-phenylenediamine in the mouse, chinese hamster, and guinea pig and of derivatives, evaluated by the micronucleus test.the mutagenic potential of ortho-phenylenediamine--known by studies on salmonella typhimurium--was studied in mice, chinese hamsters and guinea pigs with the use of the micronucleus test. in bone marrow of all three species, chromosomal damage was detected following intraperitoneal injections of the test chemical, this damage was seen also after peroral administration to mice. four derivatives of ortho-phenylenediamine containing one or two methyl-, nitro- or chlorosubstituents in 4- or 5-positi ...19806992742
validation and comparative studies on 180 chemicals with s. typhimurium strains and v79 chinese hamster cells in the presence of various metabolizing systems. 19806993936
identification of a cytotoxin produced by legionella pneumophila.culture filtrates of legionella pneumophila were cytotoxic for chinese hamster ovary cells. the cytotoxin was found to be methanol soluble, heat stable, and stable from ph 5 through 8.19806995339
a flow cytometric study of chromosomes from rat kangaroo and chinese hamster cells.chromosomes from rat kangaroo (ptk) and chinese hamster (chv 79) cells have been prepared for quantitative flow-cytometric analysis. the preparation time was otimized down to 30 (ptk) and 40 min (chv 79). dapi was used as a at-sensitive fluorescent dye to stain for monoparameter dna measurements. simultaneous two-parameter dna-protein analysis was carried out with dapi and sr 101 (as a general protein fluorochrome) in combination. the karyotype of the ptk cells with 13 (14) chromosomes was separ ...19806995409
[organization of mammalian genome replication: data on the high rate of dna replication in replicons of structural heterochromatin].by the autoradiography, the increase of the mean rate of replication fork movement in dna was shown for human skin fibroblasts during s-period induced by reseeding the stationary culture; the portion of high-rate replicons growing parallel to the increase in numbers of cells, in which the constitutive heterochromatin was replicating. furthermore, the heterogeneity of replicons was investigated in regard to the rate of dna chain growth in asynchronous cell populations of human and three rodent sp ...19806998067
biological studies of a baculovirus in a mammalian cell line.in two of five experiments, replication (tcid50) was observed following inoculation of chinese hamster cells with autographa californica nuclear polyhedrosis virus (npv). radiolabeling experiments employing tritiated thymidine consistently resulted in a labeled entity which banded in sucrose gradients at a density of 1.24-1.25 g/ml, similar to that observed for a. californica npv in the permissive trichoplusia ni cell line. the labeled entity is believed to be a. californica npv, based on infect ...19806998919
golden hamster pancreatic islets: a tissue rich in monoamine oxidase.we compared the steady state monoamine oxidase (mao) activity of collagenase-isolated pancreatic islets of the golden hamster with the steady state mao activity of liver, kidney, median eminence, pituitary, acinar pancreas, and cerebral cortex. the mao activity of the islets (5384 +/- 412 pmol/mg protein . min) was 3-fold greater than the activity of the next highest tissue (liver) and 12.5 times greater than the activity of the acinar pancreas. this high mao activity was not due to collagenase ...19807000496
chinese hamster lung cells synthesize and confine to the cellular domain a collagen composed solely of b chains.the acid-soluble collagen extracted from cultured chinese hamster lung (chl) cell layers has been isolated after limited pepsin digestion and differential salt fractionation. polyacrylamide gel electrophoresis of this material under denaturing conditions showed the presence of collagen chains with an apparent molecular mass of 120,000 daltons both before and after reduction, indicating the absence of interchain disulfide bonds in the native molecule. when chromatographed on cm-cellulose under de ...19807001474
chromosome aberration tests with chinese hamster cells in vitro with and without metabolic activation--a comparative study on mutagens and carcinogens.chromosome aberration tests (ch-test) in vitro were carried out on more than 400 chemicals from our environment, which included carcinogens and other compounds such as food additives, medical drugs, pesticides and those used in laboratories or industries. all results were compared with those obtained by mutation assays with bacteria (ames test). nearly half of these chemicals tested were positive either in the ch-tests or in the ames tests. among the chemicals being positive in the ch-tests, how ...19807002106
chromosomal events in carcinogenic initiation and promotion: implications for carcinogenicity testing and cancer prevention strategies.we have provided experimental evidence in favour of the hypothesis that carcinogenesis is triggered by at least two chromosomal events, which must occur in a single diploid somatic cell in a specific time sequence: (i) specific recessive mutational or epigenetic chromosomal change(s) resulting in a heterozygous (m/+), latently premalignant state (initiation); this must be followed by (ii) a chromosomal rearrangement involving the affected locus, and leading to homozygosity (m/m) or hemizygosity ...19807002784
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