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D M Parry

Publications and source records attributed to D M Parry.

98 records · Page 6Linked to original sources
PubMed1973

A new method for analyzing electron microscope autoradiographs using hypothetical grain distributions.

A new method for the analysis of electron microscope autoradiographs is described which has two advantages over other methods. This method provides estimates for the activity in different regions of the section and takes into account the actual geometrical shape and position of different regions within the section. Use is made of the measured distribution of grains about a thin line source to construct a hypothetical distribution of autoradiographic grains which is then compared with the actual distribution of grains. Different activities are then ascribed to various regions until a satisfactory agreement with the autoradiographic grains is obtained using the chi(2) significance. In the next paper, an example of the use of this method is given for the distribution of grains in the nucleus of erythroid bone marrow cells labeled with radioactive iron, (55)Fe.

Autoradiography↗
PubMed1973

A meiotic mutant affecting recombination in female Drosophila melanogaster.

mei-S282 is a female meiotic mutant isolated from a natural population of Drosophila melanogaster. It is a recessive mutation located at approximately map position 5 on the third chromosome which has two major effects. It causes a nonuniform decrease in recombination which is most drastic in distal chromosome regions and nondisjunction of all chromosome pairs is elevated at the first meiotic division. Nondisjunctional events are positively correlated; furthermore, nondisjoining chromosomes, themselves nonrecombinant, are preferentially recovered from cells in which nonhomologs are preferentially recovered from cells in which nonhomologs are also non-recombinant.-It is concluded that mei-S282 is a defect which occurs early in meiosis I prior to the time of exchange. In the mutant, the frequency of no-exchange tetrads for each of the major chromosomes is increased-and in cells which contain two or more no-exchange tetrads, an interaction between these chromosomes leads to correlated nondisjunction. mei-S282(+) then, is an exchange precondition necessary for the normal frequency and distribution of exchanges.

Animals↗
PubMed1972

Segmental aneuploidy and the genetic gross structure of the Drosophila genome.

By combining elements of two Y-autosome translocations with displaced autosomal breakpoints, it is possible to produce zygotes heterozygous for a deficiency for the region between the breakpoints, and also, as a complementary product, zygotes carrying a duplication for precisely the same region. A set of Y-autosome translocations with appropriately positioned breakpoints, therefore, can in principle be used to generate a non-overlapping set of deficiencies and duplications for the entire autosomal complement.-Using this method, we have succeeded in examining segmental aneuploids for 85% of chromosomes 2 and 3 in order to assess the effects of aneuploidy and to determine the number and location of dosage-sensitive loci in the Drosophila genome (Figure 5). Combining our data with previously reported results on the synthesis of Drosophila aneuploids (see Lindsley and Grell 1968), the following generalities emerge.-1. The X chromosome contains no triplo-lethal loci, few or no haplo-lethal loci, at least seven Minute loci, one hyperploid-sensitive locus, and one locus that is both triplo-abnormal and haplo-abnormal. 2. Chromosome 2 contains no triplo-lethal loci, few or no haplo-lethal loci, at least 17 Minute loci, and at least four other haplo-abnormal loci. 3. Chromosome 3 contains one triplo-lethal locus that is also haplo-lethal, few or no other haplo-lethal loci, at least 16 Minute loci, and at least six other haplo-abnormal loci. 4. Chromosome 4 contains no triplo-lethal loci, no haplo-lethal loci, one Minute locus, and no other haplo-abnormal loci.-Thus, the Drosophila genome contains 57 loci, aneuploidy for which leads to a recognizable effect on the organism: one of these is triplo-lethal and haplo-lethal, one is triplo-abnormal and haplo-abnormal, one is hyperploid-sensitive, ten are haplo-abnormal, 41 are Minutes, and three are either haplo-lethals or Minutes. Because of the paucity of aneuploid-lethal loci, it may be concluded that the deleterious effects of aneuploidy are mostly the consequence of the additive effects of genes that are slightly sensitive to abnormal dosage. Moreover, except for the single triplo-lethal locus, the effects of hyperploidy are much less pronounced than those of the corresponding hypoploidy.

Aneuploidy↗
PubMedDate not supplied

Renal metabolite concentrations and the activities of glutaminase and glutamate dehydrogenase during recovery from metabolic acidosis in the rat.

Metabolite content was determined in freeze-clamped kidneys to elucidate the rate-controlling steps which are responsible for the inhibition of renal ammoniagenesis that occurs when rats are allowed to recover from metabolic acidosis. After 1 day of recovery from acidosis there were increased renal contents of glutamate, glutamine, alpha-ketoglutarate, citrate, lactate, and malate. The calculated cytoplasmic concentration of oxaloacetate was also increased. The renal content of phosphoenolpyruvate, 3-phosphoglycerate, and ammonia decreased during recovery. No changes were observed in the renal content of the adenine nucleotides or of inorganic phosphate. The activities of phosphate-dependent glutaminase and glutamate dehydrogenase were elevated even after 7 days of recovery although the renal contents of glutamate and alpha-ketoglutarate had returned to control levels by this time. The changes in oxaloacetate and phosphoenolpyruvate are consistent with the fall in the activity of phosphoenolpyruvate carboxykinase observed by Parry and Brosnan. The increased levels of alpha-ketoglutarate and of glutamate are considered to be a consequence of a primary change in the activity of alpha-ketoglutarate dehydrogenase. These results are discussed in the light of the known effects of these metabolites on glutaminase activity and on glutamine entry into renal mitochondria.

Acidosis↗
PubMedDate not supplied

In vitro radiosensitivity of fibroblasts from thyroid and skin cancer patients treated with X-rays for tinea capitis.

To investigate the hypothesis that persons who developed thyroid or skin cancer subsequent to scalp irradiation for tinea capitis are particularly sensitive to radiation, possibly because of a high frequency of ataxia-telangiectasia, we used an in vitro cell survival assay to evaluate radiosensitivity of their fibroblast cell strains. Study subjects were selected from a cohort of 10,834 Israelis irradiated during childhood for tinea capitis. Skin fibroblasts were obtained from thyroid and skin cancer patients (cases) as well as a sample of subjects who did not have cancer (controls). Fibroblasts were cultured and then loss of colony-forming ability as a result of acute X-irradiation was evaluated. Comparison of survival curve parameters (mean inverse of the slope and the dose needed to reduce colony survival to 10%) between 12 thyroid cancer and 12 control strains showed no differences (P > 0.5). A slightly increased radiation sensitivity of the skin cancer cases compared with their controls was observed. Although based on few subjects (14 cases and 11 controls), the findings were similar whether the mean inverse of the slope (P = 0.06) or the dose needed to reduce colony survival to 10% (P = 0.05) was evaluated. However, because of the small size of the study and potential errors inherent in survival assays, our finding that cell strains derived from patients who developed skin cancer exhibit enhanced radiosensitivity should be viewed as preliminary and interpreted cautiously.

Ataxia Telangiectasia↗