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Biomedical subjects

J M Parry

Publications and source records attributed to J M Parry.

At least 145 records · Page 8Linked to original sources
PubMed1983

Cyclic variations in sensitivity to X-irradiation during meiosis in Saccharomyces cerevisiae.

Cyclic variation in mutation induction and lethality was found following X-irradiation during meiosis in Saccharomyces cerevisiae. An enhanced mutagenic response was found in meiotic G1 phase cells in comparison to cells later in meiosis, similar to the response shown during mitosis, but meiotic G1 phase cells appeared more resistant to the lethal effects of X-irradiation than mitotic G1 phase cells. Resistance to the lethal effects of X-rays was found during meiotic DNA synthesis in the strain SK1, which may indicate the operation of a sister-chromatid exchange repair mechanism. A difference was found between gene conversion which appeared to be at a maximum by the end of meiotic DNA synthesis and reciprocal recombination, which could be induced up to prophase I.

DNA Repair↗
PubMed1983

The induction of mutation and recombination following UV irradiation during meiosis in Saccharomyces cerevisiae.

Irradiation of yeast cultures with ultraviolet light at discrete stages during meiosis produces cyclic variations in sensitivity, i.e. cells are more sensitive to the lethal effects of UV light prior to entry into the meiotic DNA synthesis, and this corresponds to a peak of induction of point mutation. Cells become more resistant to both induced point mutation and lethality as they enter meiotic DNA synthesis, but become more sensitive again during spore formation. The induced level of intragenic recombination rises during the period of commitment to recombination to a level indistinguishable from the full meiotic level of spontaneous intragenic recombination. Induced reciprocal recombination remains above the spontaneous level up to the point of commitment to sporulation.

Meiosis↗
PubMed1983

Metabolic activation of cytochrome P-450/P-448 in the yeast Saccharomyces cerevisiae.

The strains D6 and JD1 of the yeast Saccharomyces cerevisiae were used to assay the genetic activity of several compounds, benzo[a]pyrene, 15,16-dihydro-11-methyl-cyclopenta[a]phenanthren-17-one, 2-naphthylamine and cyclophosphamide, which require metabolic activation by cytochromes P-450 and P-448 to produce genetically active chemical species. Cells from both strains were harvested from cultures grown in low concentrations of glucose and switched to growth in high glucose containing media. Treatments under these conditions resulted in increased sensitivity of the test systems without the presence of an exogenous S9 mix and the presence of S9 was found not to enhance this sensitivity. The yeasts used under these treatment conditions showed a P-450/P-448 type metabolism.

2-Naphthylamine↗
PubMed1983

Synthesis of 1,6-diaminopyrene from 1,6-dinitropyrene and its S9 dependent mutagenicity to S. typhimurium.

1,6-Dinitropyrene elicits a potent mutagenic response in a range of microorganisms in the absence of auxiliary metabolism (S9 mix). This activity is considered to be dependent upon nitroreductase enzymes endogenous to the marker organism producing electrophilic species from one or both of the nitro groups. In order to evaluate this suggestion 1,6-diaminopyrene has been synthesised, characterized and found to elicit a mutagenic response in strain TA98 of Salmonella typhimurium, but only when evaluated in the presence of S9 mix. The active dose-range of the diamino compound was 10(4) times higher than that of the parent dinitro compound.

Dose-Response Relationship, Drug↗
PubMed1983

N-methyl-N'-nitro-N-nitrosoguanidine induced genetic change during the meiotic cell cycle in Saccharomyces cerevisiae: an absence of S-phase specificity.

In the yeast Saccharomyces cerevisiae enhanced nuclear mutagenesis was found during meiotic DNA synthesis after treatment with N-methyl-N'-nitrosoguanidine (MNNG), but not during meiotic DNA synthesis. Further experiments found no significant variation in the mol. wt. of DNA from control or MNNG-treated samples during meiosis after alkaline sucrose gradient analysis. Using tritiated MNNG no variation in uptake of MNNG by meiotic cells was found, but enhanced binding of label from [3H]MNNG to mitochondrial DNA was detected during meiotic DNA synthesis when mitochondrial DNA synthesis occurred. In contrast, no enhanced binding of label from [3H]MNNG to the nuclear DNA during meiotic DNA synthesis was found.

DNA Replication↗
PubMed1982

Differential staining of chromosomes and spindle and its use as an assay for determining the effect of diethylstilboestrol on cultured mammalian cells.

A differential staining technique that allows for the simultaneous visualization of chromosome and spindle fibres has been used to investigate the action of diethylstilboestrol (DES) on cultured human fibroblasts. It was found that the mitotic index increased while spindle-fibre formation was inhibited with increasing DES concentration. Normal cellular division was severely affected by DES exposure in a dose-related manner. It has been demonstrated that this new staining technique may help to show up some mitotic poisons which are an important group currently missed by bacterial and clastogenic tests.

Cell Line↗
PubMed1982

The clastogenic activity of dinitropyrenes in a rat-liver epithelial cell line.

The ability of 1,6-dinitropyrene and 1,8-dinitropyrene to induce chromosome aberrations has been examined in a rat epithelial cell line (RL4). Both compounds were found to be potent clastogenic agents in these cells, inducing predominantly chromatid type abberations. The number of aberrant metaphases was dose-related up to 1.25 micrograms/ml, after which the response showed a plateau at a frequency of around 60%. The number of chromatid gaps per 100 cells also increased linearly with concentration from 3.5 in the control cultures up to 117 with 1,6-DNP (1.25 micrograms/ml) and 98 with 1,8-DNP (2.5 micrograms/ml), indicating that the induction of chromatid gaps was a valid and sensitive measure of chromosome damage in this cell line. The fact that a positive result as obtained in RL4 cells implies that these cells contain enzyme systems which are capable of converting dinitropyrenes to a mutagenic form.

2,4-Dinitrophenol↗
PubMed1982

The use of a yeast strain with a temperature-sensitive DNA ligase to estimate DNA repair after exposure to mutagens.

The yeast strain cdc9 which possesses a temperature-sensitive DNA ligase, was used to estimate DNA repair after mutagen exposure. Following low UV fluences, single-strand breaks in DNA were detected after an incubation at the restrictive temperature but were absent at the permissive temperature. These DNA breaks were shown to be equal to the number of pyrimidine dimers induced in DNA as measured by the presence of UV-endonuclease sensitive sites. Similarly, after exposure to the chemical mutagen 4-chloromethyl-biphenyl (4CMB) single-strand breaks accumulated at the restrictive temperature. Hence the technique described should be applicable for the estimation of the early steps of repair of a wide range of different types of DNA damage induced in yeast by exposure to either physical or chemical mutagens.

DNA Ligases↗
PubMed1981

The genetic activity of dinitropyrenes in yeast: unusual dose response curves for induced mitotic gene conversion.

1,6-Dinitropyrene (1,6DNP) and 1,8-dinitropyrene (1,8DNP) were tested for their ability to induce mitotic gene conversion at the trp 5 and his 4 loci in the yeast Saccharomyces cerevisiae JD1. Both compounds were shown to be potent inducers of gene conversion in yeast, with 1,6DNP being somewhat more active than 1,8DNP. Unusual dose-response curves were obtained in that toxicity and genetic activity decreased at the higher concentrations examined. This reduction in genetic activity may reflect a decrease in the ability of yeast cells to convert the dinitropyrenes to their mutagenic forms when the concentration of the compounds exceeds a certain level.

Cell Survival↗
PubMed1980

Studies on the heat resistance of Bacillus cereus spores and growth of the organism in boiled rice.

A comparison was made of the heat resistance of Bacillus cereus spores at 95 degrees C. Spores of serotype 1 strains were more resistant than those of the other types tested. However, there was little difference in the growth rate of the various serotypes in boiled rice at 22 degrees C. Most samples of uncooked rice contained multiple serotypes of B. cereus. These results indicate that the cooking procedure used for the preparation of cooked rice is likely to be selective for certain serotypes, and this is the most likely reason why type 1 is the most common serotype implicated in outbreaks of food poisoning and can be isolated from many routine samples of cooked rice.

Bacillus cereus↗
PubMed1979

Radiation-induced mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae.

A number of genetic systems are described which in yeast may be used to monitor the induction of chromosome aneuploidy during both mitotic and meiotic cell division. Using these systems we have been able to demonstrate the induction of both monosomic and trisomic cells in mitotically dividing cells and disomic spores in meiotically dividing cells after both UV light and X-ray exposure. The frequency of UV-light-induced monosomic colonies were reduced by post-treatment with photoreactivity light and both UV-light- and X-ray-induced monosomic colonies were reduced by liquid holding post-treatment under non-nutrient conditions. Both responses indicate an involvement of DNA-repair mechanisms in the removal of lesions which may lead to monosomy in yeast. This was further confirmed by the response of an excision-defective yeast strain which showed considerably increased sensitivity to the induction of monosomic colonies by UV-light treatment at low doses. Yeast cultures irradiated at different stages of growth showed variation in their responses to both UV-light and X-rays, cells at the exponential phase of growth show maximum sensitivity to the induction of monosomic colonies at low doses whereas stationary phase cultures showed maximum induction of monosomic colonies at high does. The frequencies of X-ray-induced chromosome aneuploidy during meiosis leading to the production of disomic spores was shown to be dependent upon the stage of meiosis at which the yeast cells were exposed to radiation. Cells which had proceeded beyond the DNA synthetic stage of meiosis were shown to produce disomic spores at considerably lower radiation doses than those cells which had only recently been inoculated into sporulation medium. The results obtained suggest that the yeast sustem may be suitable for the study of sensitivities of the various stages of meiotic cell division to the induction of chromosome aneuploidy after radiation exposure.

Aneuploidy↗