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Biomedical subjects

F M Johnson

Publications and source records attributed to F M Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1979

Action of N-isopropyl-alpha-(2-methylhydrazino)-p-toluamide hydrochloride (procarbazine hydrochloride) in the germ tissue of mice: dominant lethal effects.

A study was carried out on the effects of N-isopropyl-alpha-(2-methylhydrazino)-p-toluamide (procarbazine, Natulan) in the dominant lethal test in the mouse. Male mice were dosed once and mated with fresh virgin females each week. The utilization of sperm, treated as spermatids or testicular sperm with 100-800 mg/kg, resulted in significant post- and pre-implantation death of embryos. Fertility was markedly reduced after the injection of 200 mg/kg of procarbazine and over. This is probably due to a cell killing effect, the most sensitive stages being differentiating spermatogonia, type A sermatogonia and resting primary spermatocytes. Total sterility was induced for several weeks with doses of 600 and 800 mg/kg. Up to 12 weeks after treatment the number of females with implants was still significantly lower than controls indicating a severe depletion of spermatogonial cells. The spectrum of effects correlates well with the drug's effect on nucleic acid and protein synthesis.

Animals↗
PubMed1978

Variance component analysis of allozyme frequency data from eastern populations of Drosophila melanogaster.

Gene frequency variation at eight polymorphic allozyme loci in Drosophila melanogaster populations in North Carollina and the east coast of the United States were analyzed utilizing the variance component estimation procedures suggested by Cockerham (1969, 1973). These variance components were used to estimate correlations of genes within small geographic regions. The average (over loci) correlation between genes in the same individual within subpopulations was estimated to be 0.033. That between genes in the same subpopulation in different individuals was estimated to be very small, although significantly different from zero. The macrogeographic variation measured by the correlation of genes sampled from the same local region was large for some loci and smaller for others. this variation was also analyzed by correlation with latitude and longitude. Several previously recognized clines were identified as were several new clines.--These results were interpreted as indicating either some degree of nonrandom mating and local breeding unit isolation or a low frequency of null alleles. The geographic and temporal variation has no simple interpretation.

Aldehyde Oxidoreductases↗
PubMed1978

The importance of adrenocortical steroids in the pathogenesis of ketosis in diabetic guinea pigs (Caviae porcellus)

The roles of adrenocortical steroids in the pathogenesis of diabetic ketosis were investigated in guinea pigs. Groups of normal and Streptozotocin-induced diabetic animals were either given saline as a control, methylprednisilone as an exogenous steroid, or adrenocorticotrophin to stimulate endogenous steroid production. Plasma and urine ketone determinations were made daily for six days at which time animals were necropsied. The qualitative procedure used failed to detect ketonemia, and ketonuria was only found in diabetic guinea pigs treated with steroids. The results support the hypothesis that the absence of ketosis in spontaneously diabetic guinea pigs may be the result of a relative glucocorticoid insufficiency secondary to fatty degeneration of the adrenal glands, a common lesion in spontaneously diabetic guinea pigs.

Adrenal Cortex Hormones↗
PubMed1977

Genetic control and racial variation of beta-glucosidase isozymes in maize (Zea mays L.)

beta-Glucosidase (beta-D-glucoside glucohydrolase, E.C. 3.2.1.21, beta-Glu) isozyme variants were studied in a large number of inbred lines, crosses, and races of maize (Zea mays L.). The pattern of Mendelian inheritance demonstrated for beta-GLU variants indicated that they are under nuclear gene control. Twenty-two allelic forms at a single locus were identified in the materials studied by starch gel electrophoresis. Genetic data indicate that beta-GLU in maize is functionally a dimer. Variation of beta-GLU isozymes in 51 racial collections of maize from Mexico showed little correlation with morphological or geographical data. In 39 collections from Central America, variation patterns appeared to have some association with altitude.

Alleles↗
PubMed1976

Isozyme variability in species of the genus Drosophila. VIII. The alcohol dehydrogenase polymorphism in North Carolina populations of D. melanogaster.

Adult Drosophila melanogaster flies collected from populations broadly dispersed over ecological and geographic strata of North Carolina, and over a period of 4 years, were analyzed for alcohol dehydrogenase phenotypes by gel electrophoresis. Gene frequencies in spring-summer-fall field collections were remarkably stable over all strata. Two winter collections exhibited contrasting gene frequency changes. In one case the results are interpreted in terms of long-distance migration from Florida, while the other is explicable by assignment of a causal role to environmental factors which accompany the winter season.

Alcohol Oxidoreductases↗
PubMed1974

The alcohol dehydrogenases of Drosophila melanogaster: frequency changes associated with heat and cold shock.

Laboratory populations of Drosophila melanogaster were subjected to heat and cold shock of sufficient duration and intensity to cause about 90 percent mortality. Alcohol dehydrogenase phenotypes were determined in survivors and controls. Significant changes in phenotypic frequencies occurred as a result of both treatments such that relative fitness appeared to be dependent on temperature. The alcohol dehydrogenase phenotype most frequently surviving heat under laboratory conditions is the same phenotype as that previously found to be higher in frequency in natural populations in areas with higher average temperature.

Alcohol Oxidoreductases↗
PubMed1974

Isozyme allelic frequencies related to selection and gene-flow hypotheses.

Significant correlations between allelic frequencies and environmental variables in a number of insect species have been demonstrated by multivariate techniques. Since many environmental variables show a strong relationship to geographic location and since gene flow between populations can also produce patterns of gene frequencies which are related to the geographic location, both selection and gene-flow hypotheses are consistent with the observed correlations. The genetic variables can be corrected for geographic location and so for linear gene-flow patterns. If, after correction, the genetic variables still show significant correlations with similarly corrected environmental variables, then these correlations are consistent with hypotheses of selection but not of gene flow. The data of Johnson and Schaffer (1973) have been reanalyzed using the method of canonical correlation after correction for geographical location by means of multiple regression. Five of the nine loci studied exhibit significant canonical correlations. These results, under the assumption of linear gene flow, support hypotheses of selective action of environmental variables in the genotype-environment relationships observed.

Alleles↗
PubMed1973

Isozyme genotype-environment associations in natural populations of the harvester ant, Pogonomyrmex badius.

Harvester ants (P. badius) were collected from 49 localities in the southeastern U.S. Amylase and naphthylamidase activities were assayed by gel electrophoresis, and the frequencies of alleles controlling electrophoretic variation were calculated. Soil samples were analyzed and plotted against allelic frequencies. Climatographic and genetic data were analyzed by the method of principal components. Statistically significant correlations were found to occur between the patterns of genetic variation, and between the genetic and environmental patterns. These correlations are consistent with a selective basis for the maintenance of isozyme polymorphisms.

Amylases↗