PubMed Health⌕ Search

Biomedical subjects

J M Parry

Publications and source records attributed to J M Parry.

At least 19 recordsLinked to original sources
PubMed1992

Application of the standard mutagenesis assay results in underestimation of ethyl methanesulphonate-induced mutations to ouabain-resistance in Chinese hamster cells.

Chinese hamster V79 cells were exposed to ethyl methanesulphonate (EMS) and the incidence of mutant cells resistant to 8-azaguanine (8AZG), 6-thioguanine (6TG) or ouabain (OUA) was determined both by the respreading and the in situ techniques. In the former assay, the mutagen-treated cultures were grown for several days to permit the expression of mutations after which the cells were trypsinized, replated (10(5) cells/100-mm dish), and grown in medium supplemented with a selective agent. In the in situ assay, cultures were left undisturbed between EMS treatment and incubation in the presence of the selective agents. The yield of 8AZG-resistant mutants observed at optimal expression times after EMS treatment was comparable for both techniques; the induced mutation frequency (corrected for spontaneous mutation frequency) was estimated to be 82 x 10(-6) mutations per viable cell per unit dose (mM) of EMS. The frequency of 6TG-resistant mutants equalled 45 and 4 x 10(-6)/mM EMS as determined by the respreading and the in situ assays, respectively. In sharp contrast to that observed with 6TG, the frequency of OUA-resistant mutants scored by the in situ assay (30 x 10(-6)/mM EMS) proved to be an order of magnitude greater than that determined by the respreading assay (3 x 10(-6)/mM EMS). Our data therefore indicate that, when OUA is used for mutant selection, the application of the respreading technique, which has been widely adopted as the standard mammalian mutational assay over the past decade, may result in a marked underestimation of the actual mutation frequency (approximately 10-fold in V79 cells).

Animals↗
PubMed1992

Morphological transformation of an established Syrian hamster dermal cell with the anti-tussive agent noscapine.

Following exposure to the alkaloid noscapine hydrochloride over a concentration range of 10-120 micrograms/ml immortal cultures of Syrian hamster dermal fibroblasts were shown to undergo morphological transformation. The resultant transformed foci produced cultures which were anchorage independent as confirmed by soft agar tests. Karyotype analysis of a noscapine transformed colony demonstrated an increase in chromosome number compared to the immortal culture and the non-random duplication of a translocated chromosome 9 previously identified in the immortal culture. These data indicate that noscapine, which has previously been shown to be a spindle inhibitor and inducer of polyploidy in cultured cells, is capable of inducing in vitro cell transformation. Such data indicate a carcinogenic potential for this widely used cough suppressant.

Animals↗
PubMed1991

The effects of ventilation and the dilution of smoke upon the clastogenic and aneugenic activity of tobacco particulate matter in cultured mammalian cells.

We demonstrate here that tobacco particulate matter (TPM) produced from both non-ventilated and ventilated cigarettes of varying tar contents induced structural and numerical aberrations in cultured Chinese hamster cells. Our data indicate that TPM from ventilated cigarettes is of lower potency in inducing both clastogenic and aneugenic effects compared with TPM from non-ventilated cigarettes. These observations provide support for the concept that the genotoxic activity (to cultured Chinese hamster cells) of cigarette smoke is reduced by increased ventilation to a greater extent than a 1:1 ratio between yield reduction and smoke dilution.

Aneuploidy↗
PubMed1991

32P-postlabelling analysis and micronuclei induction in primary Chinese hamster lung cells exposed to tobacco particulate matter.

The genotoxicity of tobacco particulate matter (TPM) derived from a low-tar, low-nicotine cigarette has been examined by measuring micronucleus induction in a primary pulmonary cell line, both in the absence and presence of an exogenous source of metabolic activation. In an attempt to correlate the cytogenetic damage observed with DNA adduct formation, DNA extracted from TPM-treated cells has been analysed with two different modifications of the 32P-postlabelling assay. The results from the 32P-postlabelling analysis taken together with the pattern of micronucleus induction provide strong evidence that bioreactivated aromatic carcinogens, such as benzo[a]pyrene, are unlikely to be responsible for the TPM-induced cytogenetic damage observed in cultured mammalian cells.

Animals↗
PubMed1991

The use of genetically engineered V79 Chinese hamster cultures expressing rat liver CYP1A1, 1A2 and 2B1 cDNAs in micronucleus assays.

We have undertaken a comparative study of the bioactivation of a panel of promutagens by V79 Chinese hamster cells genetically engineered to metabolic competence. In vitro micronucleus assays of the test agents in V79 cultures in the presence of an Aroclor induced rat S9 yielded positive results. In the genetically engineered cell lines, benzo[a]pyrene was metabolized specifically by the 3-methylcholanthrene inducible rat liver CYP1A1 (cell line XEM2) whereas cyclophosphamide increased the micronucleus frequency only in cultures expressing the phenobarbital inducible CYP2B1 (SD1). Following exposure to the mycotoxin sterigmatocystin, elevated frequencies of micronucleated cells were recorded in XEM2, SD1 and XEMd-MZ (expresses the isosafrole inducible CYP1A2) cells. The aromatic amine 2-amino-anthracene elicited a weak response in the cell line XEMd-MZ which expressed CYP1A2. This response was enhanced when this cDNA was expressed in a V79 variant cell strain which also possessed endogenous acetyltransferase activity. Upon exposure to tobacco particulate matter, a greater induction of micronuclei was observed in the XEM2 cell line compared to V79 cultures, implicating polycyclic aromatic hydrocarbons in addition to direct-acting compounds as causal agents in the genotoxicity of tobacco particulate matter. The cytokinesis blocked in vitro micronucleus assay provides a faster, simpler alternative to metaphase analysis, and kinetochore labelling techniques enable the discernment of both structural and numerical chromosome changes. The inclusion of metabolically competent test strains in the in vitro micronucleus assay therefore creates a powerful system for detecting genotoxins and may be extended to elucidate both mechanisms of bioactivation and modes of genotoxic insult.

Animals↗
PubMed1991

Hazards of horse-riding as a popular sport.

The increasing incidence of horse-riding accidents, which are often severe in nature, prompted a pilot study of a questionnaire designed to elucidate the cause of such accidents. It was hoped that, on a larger scale, the information gleaned would highlight possible preventative measures which might improve the safety of an important recreational pursuit enjoyed by young and old from many walks of life. A retrospective study of riders sustaining serious spinal injuries admitted to Stoke Mandeville Hospital was compared with riders sustaining minor but significant injuries as the accidents came to the attention of the authors. The detailed analysis paid particular attention to the setting and to the experience and task of horse and rider. It was found that 70% of the 20 accidents could be thought attributable to the behaviour of the horse at the time, and seven of these were in the spinal injuries group. Rider error was a significant contribution in seven cases, and in two instances the rider was under instruction at the time. There was also inadequate experience of the rider in seven cases, of which five were thought to show inadequate supervision. The limited number of cases studied precludes significant observations, but, as the majority of accidents seemed preventable, a larger study has been initiated in collaboration with the British Horse Society.

Adult↗
PubMed1990

Methyl vinyl sulphone: a new class of Michael-type genotoxin.

Methyl vinyl sulphone (MVS) is a labile, Michael-reactive chemical, similar in structure to acrylamide (AA). Given that acrylamide is a reference mammalian mutagen and a rodent carcinogen, studies were undertaken to evaluate the potential genotoxicity of MVS. In common with AA, MVS was non-mutagenic to Salmonella but active as an aneugen to cultured mammalian cells. It is concluded that vinyl sulphones should be regarded as representative of a new class of genotoxic chemical whose mode of action is probably primarily dependent upon Michael reactivity to proteins.

Acrylamide↗
PubMed1990

A study of mitotic division fidelity and numerical chromosome changes in ageing Syrian hamster dermal cells.

Events associated with culture ageing in Syrian hamster dermal cells have been studied from the time of culture isolation during continuous passage until they senesced and died. Microscopic examination of mitotic cells using differential staining of chromosome and spindle apparatus assessed the faithfulness of cell division. Other indicators of the quality of cell division were obtained from chromosome counts, micronucleus frequencies and incidences of binucleate cells. A loss of spindle fidelity and an increase in aneuploidy corresponded to the period of culture senescence. The data presented indicate that the loss of division fidelity and chromosome number instability is an important indicator of the progression of a mammalian culture to senescence under in vitro conditions. Such information may provide the basis of a model for the study of factors which modify mitotic fidelity and senescence and provide a methodology for monitoring the suitability of mammalian cultures for commercial usage.

Animals↗
PubMed1990

Restriction site mutation analysis, a proposed methodology for the detection and study of DNA base changes following mutagen exposure.

We propose a methodology for the detection of DNA base changes in restriction enzyme recognition sites. The restriction site mutation (RSM) technique is based upon the detection of DNA sequences resistant to the cutting action of specific restriction enzymes and the amplification of these resistant sequences using the polymerase chain reaction. As outlined, the RSM method has the potential for use in the study of induced base changes in any species, tissue and genes of known DNA sequence for which unique DNA primers are available, and which contains a number of unique restriction enzyme recognition sites.

Animals↗
PubMed1989

The effects of 1,6-dinitropyrene on spindle morphology in transformed human cells.

The effects of 1,6-dinitropyrene (1,6-DNP) on the fidelity of cell division were studied in the transformed human fibroblast cell line MRC5VA. Over a dose range of 0.1-10 micrograms/ml of 1.6-DNP, we observed significant increases in the levels of abnormal division stages, associated with damage to the spindle apparatus of the cell. Qualitative changes in spindle morphology and a quantitative decrease in pole-to-pole spindle length were also observed with increasing doses of 1.6-DNP. Such changes in the size and morphology of the spindle corresponded with an accumulation of cells blocked at metaphase. The presence of catalase did not modify the response, suggesting that the effects on the spindle apparatus and cell division were not caused by the generation of radicals but by the direct action of 1.6-DNP.

Catalase↗
PubMed1989

The expression of cytochrome P450IIB1 in Saccharomyces cerevisiae results in an increased mutation frequency when exposed to cyclophosphamide.

A recombinant plasmid containing a full length cDNA encoding the rat cytochrome P450IIB1 under the control of the Saccharomyces cerevisiae ADC1 promoter was constructed and transformed into the yeast strain KY118. The encoded P450IIB1 protein was produced at a level of between 0.1 and 0.2% of total yeast cellular protein (0.068 nmol/mg total cellular protein). This protein was localized in the microsomal fraction and had activity towards the substrate benzyloxyresorufin, the activity being 0.16 nmol resorufin produced/min/mg microsomal protein. When exposed to the anticancer drug cyclophosphamide the mutation frequency, as determined by the development of resistance to the arginine analogue canavanine, increased in a dose-dependent manner over a control strain and was up to 16-fold higher at the highest doses used.

Biotransformation↗