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J M Parry

Publications and source records attributed to J M Parry.

At least 91 records · Page 5Linked to original sources
PubMed1995

Use of multicolour chromosome painting to identify chromosomal rearrangements in human lymphocytes exposed to bleomycin: a comparison with conventional cytogenetic analysis of Giemsa-stained chromosomes.

Exchange aberrations induced by bleomycin were identified by multicolour fluorescence in situ hybridisation (FISH) with probes for chromosomes 1, 2, and 3. The frequency and distribution of aberration types were compared to conventional metaphase analysis of Giemsa-stained chromosomes from the same human lymphocyte cultures. The total percentage of exchanges detectable by painting three pairs of chromosomes with separate colours was calculated as 40%. Giemsa staining revealed predominantly asymmetric chromosome exchanges, which are expected to comprise 50% of the total induced exchanges. Genomic exchange frequencies were, therefore, determined by multiplying the observed frequencies from FISH analysis by 2.5 and the number of asymmetric exchanges identified in Giemsa-stained slides by 2.0. By these calculations, the genomic exchange frequency calculated from chromosome painting exceeded that estimated by Giemsa-staining. This difference was due to the identification by chromosome painting of a unique class of cells in which chromosomes had undergone complex exchanges (nonreciprocal exchanges involving multiple mutual sites). The percentage of cells exhibiting exchanges was similar for both methods.

Azure Stains↗
PubMed1995

A genetically engineered V79 cell line SD1 expressing rat CYP2B1 exhibits chromosomal instability at the integration site of the transfected DNA.

The genetically engineered cell line SD1 was constructed by co-transfection of V79 Chinese hamster cells with two plasmids: one containing a full-length cDNA encoding rat CYP2B1 and the second incorporating a selective marker gene. This cell line has been used in gene mutation tests and in cytokinesis-block micronucleus assays to identify procarcinogens which are metabolized by CYP2B1 to reactive metabolites. An elevated frequency of spontaneous micronuclei was recorded in SD1 cells compared to parental V79 cultures. Karyotypic analysis revealed a chromosomal instability which was manifested by amplification of the p-arms of a chromosome designated 'n' (derived from chromosome 8). This chromosome was variable in length and sometimes exhibited a telomeric fusion which led to the formation of a dicentric chromosome. Fluorescence in situ hybridization with digoxigenin-labelled plasmid DNA showed the presence of pSV450 plasmid DNA coamplified with genomic DNA sequences located in the terminal region of chromosome 'n'.

Animals↗
PubMed1994

Analysis of benzo[a]pyrene induced mutations by the use of Restriction-Site Mutation assays in aquatic species.

Larval and toadlet stages of the clawed toad Xenopus laevis were exposed to benzo[a]pyrene in aquatic media. Mutations were analysed in a variety of restriction enzyme recognition sequences of the adult alpha 1-globin gene. Mutations were detected in the BsiLi recognition site (CCTGG) at early sampling times (6 h) in larval stages and at 8-days sampling time in post-metamorphosis toadlets. The predominant mutation detected was a G-->T base transversion at the 5th base of the CCTGG sequence. The data presented indicates that the Restriction-Site Mutation methodology has considerable potential for development as a technique for monitoring the genotoxic potential of water-borne toxins.

Animals↗
PubMed1994

Mutagenicity of o-anisidine to the bladder of lacI- transgenic B6C3F1 mice: absence of 14C or 32P bladder DNA adduction.

Earlier studies have established that the rodent bladder carcinogen o-anisidine (OA) gives negative results in all of the standard rodent genetic toxicity assays. In the present study, a single oral administration of the maximum tolerated dose level (750 mg/kg) of OA to B6C3F1 mice yielded negative results in 32P-post-labelling assays of bladder and liver DNA (24 h after dosing). Likewise, 14C-ring-labelled OA administered orally to B6C3F1 mice gave no evidence of DNA binding 6, 12 or 24 h later. Administration of OA (750 mg/kg) to transgenic lacI- mice (Big Blue) led to a small increase in mutation frequency (MF) in the bladder, but not in the liver. Increased MFs were observed in the bladder following 1, 3 or 10 daily doses with sampling times of 1 or 2 weeks after the final dose. However, statistical significance (P < 0.01) was only reached 2 weeks after either 3 or 10 daily administrations of OA. The positive control chemical (dimethylnitrosamine) gave a positive result (P < 0.01) in the liver, but not the bladder, 7 days after a single administration of 10 mg/kg. The possibility that OA is mutagenic and carcinogenic to the rodent bladder via formation of radical species is suggested.

Aniline Compounds↗
PubMed1994

The application of the restriction site mutation assay to the study of the induction of mutations in the tissues of rodents.

The restriction site mutation (RSM) assay has been developed as a methodology for the study of base changes induced in restriction enzyme recognition sequences. In principle, the RSM methodology may be used to the study mutation induction in any organ, of any species, for which DNA sequence information is available. This paper describes the analysis of the induction of base sequence changes in restriction enzyme recognition sites present in the p53 and alpha-haemoglobin genes of male mice exposed to 1-ethyl-1-nitrosourea. Our results demonstrate the induction of G-->A transitions and G-->T transversions in a number of restriction enzyme recognition sites (BamH1, Pst1, Ban1, Msp1, Alu1) in DNA extracted from a number of different tissues from animals harvested 2-7 days after exposure. The data presented indicates that the RSM methodology has considerable potential for development for the study of induced base changes in the endogenous genes of a variety of species.

Animals↗
PubMed1993

A comparative study of the use of primary Chinese hamster liver cultures and genetically engineered immortal V79 Chinese hamster cell lines expressing rat liver CYP1A1, 1A2 and 2B1 cDNAs in micronucleus assays.

Liver microsome preparations (S9 mix) have been extensively used for in vitro genotoxicity studies to provide the capacity for the activation of indirect genotoxins. However, the use of S9 preparations with mammalian cell cultures has raised considerable toxicity problems which limit their use to exposure times which are only a small fraction of the cell cycle. In addition, false negative results may be obtained if reactive metabolites are unable to penetrate the cell membrane or have short half-lives. The generation and detection of a promutagen within a single cell would therefore be advantageous. To this end, we have studied the bioactivation of a panel of promutagens (benzo[a]pyrene, cyclophosphamide, 2-aminoanthracene and sterigmatocystin) in low passage Chinese hamster fibroblasts of hepatic origin (LiC2 cells) and in a series of V79 Chinese hamster cell lines genetically engineered to express rat liver cytochrome P450 cDNAs. These include strains XEM2 (expresses CYP1A1), SD1 (CYP2B1) and strains XEMd-MZ and XEMd-NH which express CYP1A2. The end point selected for study was the induction of micronuclei. The protocol incorporated a cytochalasin B-induced cytokinesis block and the enumeration of micronuclei in the resulting binucleate cells which have undergone one nuclear division following the induction of chromosome damage. Micronuclei containing whole chromosomes and chromosome fragments were distinguished by the use of CREST antibody specific for kinetochore protein as a measure for the presence of centromeres. Micronuclei were induced by the test agents in low passage liver fibroblasts and in immortal V79 cultures only in the presence of Aroclor-induced S9 preparations. The data obtained from micronucleus assays of the genetically engineered V79 cell lines demonstrated the utility of each strain for the optimal detection and quantification of the activity of the individual test compounds. Kinetochore antibody demonstrated differences in the kinetics of induction of micronuclei containing chromosome fragments and whole chromosomes with chemicals such as benzo[a]pyrene. As part of this cytogenetic study, we also conducted karyotypic analyses and spindle fidelity assays of the V79 cell lines to investigate the presence of chromosomal instabilities which may arise as a consequence of the genetic engineering procedure. Such studies represent an important quality control step in the validation of the suitability of each cell line prior to their use in genotoxicity studies.

Animals↗
PubMed1993

The detection and assessment of the aneugenic potential of environmental chemicals: the European Community Aneuploidy Project.

Within the framework of its' Environment Research and Development Programme, the European Communities (EC) Directorate General (DG) XII has supported a research project aimed at developing and validating assay systems for the detection and evaluation of chemicals capable of inducing numerical chromosome changes such as aneuploidy and polyploidy. A range of test chemicals were selected, which include a core set comprising; colchicine, econazole nitrate, chloral hydrate, hydroquinone, diazepam, thiabendazole, cadmium chloride, thimerosol, pyrimethamine and vinblastine sulphate. These test chemicals were used to evaluate the ability of test systems ranging from tubulin polymerisation, fungal cultures, cultured mammalian cells and intact rodents to detect chemical aneugens and to assess the significance of such activity to exposed human populations.

Aneuploidy↗
PubMed1993

An evaluation of the use of in vitro tubulin polymerisation, fungal and wheat assays to detect the activity of potential chemical aneugens.

The test chemicals included in the EC Aneuploidy Project were evaluated for their ability to induce aneuploidy or aneuploidy related endpoints in assays using in vitro tubulin polymerisation, fungi and wheat. The results obtained demonstrated considerable qualitative and quantitative differences between the responses of the assays to the 10 test chemicals. Fungal assays failed to respond to the potent mammalian spindle poisons colchicine and vinblastine and only three chemicals were positive in all three fungal test systems i.e. chloral hydrate, thimerosol and thiabendazole. The in vitro tubulin polymerisation assays produced unambiguous positive results with three chemicals i.e. colchicine, thimerosol and vinblastine sulphate. The hexaploid wheat assay produced a positive response with 8 of the test chemicals i.e. colchicine, econazole, thimerosol, pyrimethamine, thiabendazole, cadmium chloride, vinblastine and diazepam. However, the wheat assay was relatively insensitive to the potent spindle poison colchicine.

Aneuploidy↗
PubMed1993

A comparison of two in vitro mammalian cell cytogenetic assays for the detection of mitotic aneuploidy using 10 known or suspected aneugens.

Two in vitro cytogenetic assays were evaluated for their ability to detect aneugenic and polyploidy-inducing agents using a battery of 10 known or suspected aneugens supplied as part of the EEC 4th Environmental Research and Development Programme. The compounds tested were colchicine, vinblastine, chloral hydrate, thiabendazole, hydroquinone, thimerosal, cadmium chloride, econazole nitrate, pyrimethamine and diazepam. The cell division aberration assay employed a differential chromosome/spindle staining procedure to detect perturbations of the mitotic division apparatus. This assay was carried out in two pulmonary-derived Chinese hamster cell lines; the immortal DON:Wg3h culture and a low passage LUC2 culture. The second assay involved quantification of metaphase chromosomes, for which only the LUC2 cell line was used, due to the stability of its diploid karyotype. All the chemicals induced spindle disturbances in the immortal line. In addition, all the compounds except cadmium chloride yielded positive results in the LUC2 culture, although many were not as potent. In the low passage line, 8 of the compounds (colchicine, vinblastine, chloral hydrate, thiabendazole, thimerosal, econazole nitrate, pyrimethamine and diazepam) induced aneuploidy and/or tetraploidy. Cadmium chloride was negative in the chromosome enumeration assay and hydroquinone yielded inconclusive results. The study of cell division aberrations was much less time-consuming and technically complex than the counting of metaphase chromosomes. In addition, it provided a degree of mechanistic understanding of the mode of action of some aneugenic and polyploidy-producing agents. However, the enumeration of chromosomes provides a more definitive data set for the evaluation of a chemical's aneugenic potential.

Aneuploidy↗
PubMed1993

The cytochalasin-B micronucleus/kinetochore assay in vitro: studies with 10 suspected aneugens.

An in vitro micronucleus assay in low passage Chinese hamster Luc2 cells capable of detecting numerical and structural chromosome changes was developed. Chromosome loss was inferred by indirect visualisation of human CREST antikinetochore antibodies bound to centromeres in chemically-induced micronuclei of cytochalasin-B arrested binucleated cells. The assay was used to evaluate 10 chemicals which had been selected for their known or suspected effects upon various components of the cell-division apparatus. These chemicals were colchicine (COL), vinblastine (VBL), thiabendazole (TBZ), chloral hydrate (CH), thimerosal (TM), diazepam (DZ), pyrimethamine (PYR), hydroquinone (HQ), cadmium chloride (CdCl2) and econazole nitrate (EZ). Mitomycin-C (MMC) was used as a positive control for the induction of micronuclei. 8 of the core chemicals induced micronuclei in Chinese hamster Luc2 cells. 4 of the chemicals (COL, VBL, TBZ, CH) increased levels of micronuclei which were positive for kinetochore antibody labelling and hence chromosome loss. 3 of the chemicals (DZ, PYR, HQ) and the positive control (MMC) increased the levels of Mn which were negative for kinetochore antibody labelling. The results with TM were equivocal and EN was negative. The results of these studies suggest that the cytochalasin-B Mn/k assay is a cost-effective, simple and rapid alternative to classical cytogenetic assays for the detection of chemically induced aneuploidy.

Aneuploidy↗
PubMed1993

Correlation of carcinogenic potency with mouse-skin 32P-postlabeling and muta-Rmouse lac Z- mutation data for DMBA and its K-region sulphur isostere: comparison with activities observed in standard genotoxicity assays.

The genotoxicities in vitro and in vivo of the mouse-skin carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) have been compared with those of its weakly carcinogenic 4,5-sulphur analogue, 6,11-dimethylbenzo[b]naphtho-[2,3-d]thiophene (S-DMBA). The only datasets that correlated with the relative carcinogenicity of these agents to the skin were those conducted using topically exposed mouse skin. Thus, both chemicals induced lacZ- mutations in the skin of lacZ+ transgenic mice, and both produced DNA adducts on mouse-skin DNA as assessed using the 32P-postlabeling technique. In each case, DMBA gave a stronger response than did S-DMBA. In contrast to these responses, only DMBA was active in the mouse bone-marrow micronucleus assay and in the C3H10T1/2 in vitro cell transformation assay. Both chemicals were mutagenic to Salmonella and of approximately equal potency. The molecular geometry of DMBA and S-DMBA are compared, and divergent CASE predictions of activity in the Salmonella assay and skin-painting bioassay are discussed. The importance of conducting predictive genotoxicity assays in systems close to those in which carcinogenicity is to be assessed is emphasized by these data.

Aniline Compounds↗
PubMed1993

Development of screening tests for aneuploidy induction by environmental pollutants.

When legally required mutagenicity testing of chemicals is undertaken, the important genetic end point of aneuploidy is not included because validated test methods are lacking. Therefore, the Commission of the European Communities (CEC) has funded a research program to develop and validate tests for aneuploidy induction. Ten chemicals, selected on the basis of their ability to interact with cell organelles relevant for aneuploidy induction, were tested in 11 laboratories. The assays ranged from in vitro tubulin assembly studies to in vivo germ-cell tests. The results allow several conclusions: a) Fungal aneuploidy tests are not capable of detecting inhibitors of mammalian tubulin polymerization such as colchicine and vinblastine. Therefore, they will not play a role in screening for aneuploidy but are of value for studying the relationship between induced aneuploidy and recombination. b) Chemicals that induce aneuploidy in mammalian germ cells are readily detected in the in vitro mammalian cell systems. Some chemicals such as thiabendazole and thimerosal induce aneuploidy in vitro but do not appear to be very effective in vivo. c) Cell division aberrations induced in mammalian cells in vitro seem to be predictive for aneuploidy induction in the same cell type. Likewise, c-mitotic effects and cell cycle delay in vivo in mitotic and meiotic cells correlate with aneuploidy induction in the respective tissue. A second CEC Aneuploidy Program has started recently to refine the most promising test protocols, to provide understanding of variety of mechanisms by which chemicals induce aneuploidy, and to establish a data base for aneugens among environmental pollutants.

Aneuploidy↗