Biomedical subjects
J R Powell
Publications and source records attributed to J R Powell.
Microgeographic differentiation of chromosomal and enzyme polymorphisms in Drosophila persimilis.
We studied microgeographic and temporal genetic differentiation in natural populations of Drosophila persimilis with respect to chromosome inversion and enzyme polymorphisms. Both inversion frequencies and allozyme frequencies varied significantly over short distances. Neither differed significantly between morning and evening collections. Because several studies of the dispersal behavior of this species have been performed, we attempt to fit the observed data to mathematical models which relate dispersion to random genetic drift and to spatially varying selection coefficients. We conclude that the observations are due at least partly to behavioral differences among genotypes. i.e., habitat preferences. These results have implications for genetic load theory and models of selection in heterogeneous environments.
The influence of cigarette smoking and sex on theophylline disposition.
The effects of cigarette smoking and sex on theophylline clearance, elimination rate constant, and apparent volume of distribution were examined in 28 healthy, young adults given single oral doses of theophylline or aminophylline. Two-way analysis of variance showed no sex effect but a significant effect of smoking habit on theophylline clearance and elimination rate constant. Neither sex nor smoking had an effect on the apparent volume of distribution. The respective mean clearance, elimination rate constant, and volume of distribution were, in nonsmokers, 0.040 +/- 0.008 (SD) liter per hour per kg, 0.084 +/- 0.015 hr-1, 0.47 +/- 0.08 liter per kg; heavy smokers, 0.063 +/- 0.019 liter per hour per kg, 0.129 +/- 0.045 hr-1, 0.50 +/- 0.06 liter per kg; and ex-smokers, 0.051 +/- 0.10 liter per hour per kg, 0.108 +/- 0.025 hr-1, 0.49 +/- 0.08 liter per kg. Cigarette smoking appeared to induce theophylline metabolism as reflected by the mean theophylline half-life in smokers (5.4 hours) versus nonsmokers (8.3 hours). The effect of cigarette smoking on theophylline clearance may be an important consideration in the clinical use of the drug.
Genetics of natural populations, XLIII. Further studies on rates of dispersal of Drosophila pseudoobscura and its relatives.
The amount of gene flow among local populations of a species is determined by the dispersal capacity of that species. Population samples of Drosophila pseudoobscura, D. persimilis, D. azteca, and D. miranda were collected, marked with ultraviolet fluorescent dusts, and released as soon as possible after capture. One and two days after release, recaptures were made on baits placed at 40-meter intervals in straight lines intersecting the release point. On alternative days, the baits were placed in North-South or in East-West directions. The distribution of the recaptured flies about the release point is very nearly normal. No significant differences between the dispersal rates of the four species are observed; however, males disperse slightly further than females. The variances averaged 50,822 m2 on the first day and 80,048 m2 on the second day and the estimated mean distances from the release point averaged 263 m and 361 m respectively. The genetic implications of the results are discussed.
A new sutureless technique for skin closure.
A sutureless wound-closure device was used in 150 patients. The average time spent to effect skin closure was reduced; removal was easy; skin apposition was satisfactory; and patient response was favorable. Sutureless tape closures eliminate the disadvantages of invasive skin closures. The device described provides secure tape adhesion to the skin and does not cover the wound. It can be easily applied, adjusted, and removed, in addition to serving as a protective splint to the healing wound. This method can reduce operative time of skin closure with highly satisfactory cosmetic results.
Participation of H1 and H2 histamine receptors in physiological vasodilator responses.
Histamine causes vasodilation in the dog by activation of H1 and H2 receptors blocked by mepyramine and metiamide, respectively. Experiments were conducted in anesthetized dogs to determine the participation of H1 and H2 receptors in several forms of physiological dilatation. Mepyramine attenuated both histamine-induced and active-reflex dilatation in the hindlimb. Metiamide caused a further reduction in both sets of dilatation. Neither single nor combined antihistamines reduced dilatation due to exercise or after temporary occlusion of the circulation in the hindlimb. Poststimulation dilatation in the gracilis muscle was partially attenuated by metiamide or mepyramine. Neither dilatation caused by sympathetic nerve stimulation in the hindpaw nor dilatation in the gracilis muscle caused by compound 48/80 was reduced by mepyramine. Following combined H1- and H2-receptor blockade, portions of both types of dilatation were reduced. These data provide evidence for the participation of both types of histamine receptor in active reflex dilatation, low-frequency neurogenic dilatation, dilatation caused by compound 48/80, and poststimulation dilatation. Neither type of histamine receptor appears to be involved in reactive hyperemia or dilatation caused by exercise.
Identification and specific blockade of two receptors for histamine in the cardiovascular system.
Histamine caused a fall in blood pressure in anesthetized dogs and cats which was only partially attenuated by mepyramine (pyrilamine), a histamine type H1-receptor antagonist. Further treatment with burimide or metiamide, type H2-receptor antagonists, caused nearly complete attenuation of the response to histamine. Burimamide alone had no effect on vasodilatation produced by histamine in the dog gracilis muscle whereas mepyramine alone caused a partial attenuation. An H2-receptor agonist, 4-methylhistamine and an H1-receptor agonist, 2-(2-pyridyl)ethylamine, both produced vasodilatation which was blocked by metiamide and mepyramine, respectively. Constriction of the saphenous vein produced by histamine was found to involve interaction with H1-receptors only. In the intact dog, histamine increased heart rate and decreased left ventricular dp/dt through direct effects. Mepyramine prevented the increase in heart rate but did not affect the chronotropic actions of isoproterenol and glyceryl trinitrate. H1-receptor blockade did not alter inotropic effects whereas subsequent H2-receptor blockade prevented the negative inotropic effect of histamine. It is concluded that both peripheral vascular and cardiac responses to histamine are mediated through activation of H1- and H2-histamine receptors.
Local immunity in Newcastle disease: some recent experiments.
Following primary exposure by the ocular route to lentogenic Newcastle disease virus (NDV) the lacrymal fluid, saliva and tracheal washes of three-week old specific pathogen free chickens acquired specific virus-neutralizing activity which considerably exceeded transudation of circulating antibody. All three secretions contain IgA which, at least in saliva, accounted for 85% of its activity, the remanider being due to IgG. Antibody in secretions limited, but did not prevent, reinfection of the trachea when birds were challenged two weeks later. In contrast to an elevation of circulating antibody titre, challenge induced only a repeated primary response in secreted antibody. Ocular infection induced marked lymphoid and plasma cell activity in the Harderian gland which is a major source of specific antibody in lachrymal and possibly other fluids. Functional ablation of the gland can be effected by occlusion of its draining duct, providing a means for evaluation of its immunological significance.
Identification and blockade of vascular H2 receptors.
Experiments were conducted in anesthetized dogs to determine the nature of receptors mediating vascular actions of histamine. In the perfused gracilis muscle histamine caused vasodilatation that was attenuated in part by mepyramine, an H1-receptor blocker. Metiamide, an H2 blocker, given alone had no effect on dilatation. However, the combination of mepyramine and metiamide resulted in a large attenuation of dilatation. Histamine caused constriction of the perfused saphenous vein that was totally blocked by mepyramine suggesting that venoconstriction by histamine involves only H1 receptors. Histamine infusion caused a fall in arterial pressure and a large reduction in peripheral resistance. Mepyramine attenuated the fall in pressure but not the reduction in resistance. Combined H1- and H2-receptor blockade largely eliminated the effects of histamine infusion further documenting the existence of H1 and H2 receptors. The effects of H1 and H2 antihistamines on a variety of physiological vasodilator responses were examined. Evidence was obtained to indicate that H1- and H2-histamine receptors are involved in the active component of baroreceptor-mediated reflex vasodilatation, poststimulation vasodilatation, sympathetic vasodilatation in the guanethidine-treated dog, and vasodilator responses following compound 48/80. No evidence for the participation of either H1- or H2-histamine receptors in reactive hyperemia or the dilatation accompanying exercise was found. It is concluded that in the dog both endogenously-released and exogenous histamine exert vascular effects by activation of both H1 and H2 receptors.
Rates of dispersal of Drosophila pseudoobscura and its relatives.
Explore the source record for details and available documents.
Interaction of genetic loci: the effect of linkage disequilibria on Hardy-Weinberg expectations.
Explore the source record for details and available documents.
Heterosis at an enzyme locus of Drosophila: evidence from experimental populations.
Explore the source record for details and available documents.
Flounder effects and linkage disequilibria in experimental populations of Drosophila.
Six laboratory populations of Drosophila paulistorum were examined for changes in gene frequencies at an enzyme locus, tetrazolium oxidase (To). In some of the populations, the alleles were introduced on over 100 independently derived chromosomes. These populations showed considerable stability in gene frequencies although they were at widely different starting frequencies. Other populations were begun with only a few (about 6) independently derived chromosomes. These populations showed significant and somewhat erratic changes in To gene frequencies. The difference in behavior of the two sets of populations was almost certainly caused by linkage effects due to sample size. The implication of these studies in understanding the role of the founder effect in natural populations is briefly discussed.
Effect of renal pressor systems on vascular capacity during hemorrhage.
Explore the source record for details and available documents.
Concordance of arthritis and iritis in identical twins with ulcerative colitis.
Explore the source record for details and available documents.
Inadequately written prescriptions. "As directed" prescriptions analyzed.
Explore the source record for details and available documents.
Apparent selection of enzyme alleles in laboratory populations of Drosophila.
Twelve laboratory populations of recently collected Drosophila willistoni were begun with different frequencies of alleles at three enzyme loci, six populations at 25 degrees and six at 19 degrees . Periodic sampling of the populations allowed monitoring of the frequency changes in allozymes over time.-At Lap-5 (a locus coding for leucine amino peptidase), three alleles converged to the same frequencies in all populations at both temperatures. The apparent equilibrium frequency of the major allele was about.75; this is different from the frequency (.57) found in the natural population from which the experimental populations were begun. Allele frequency changes at the esterase-5 locus (Est-5) were slower but consistent in all cages. It is difficult to determine if an equilibrium has been reached. However, the frequency of the rare allele in all cages is about the same as in wild populations, 5%. Alleles at both Lap-5 and Est-5 are non-randomly associated with inversions in the chromosomes onto which they map. Because of these associations, it is impossible to unambiguously attribute the change in allele frequencies to selection at the loci being observed.-After one year, no significant gene frequency changes were detected at Est-7, the third locus studied.
Peripheral facilitation of reflex vasoconstriction by prostaglandin F2alpha.
Explore the source record for details and available documents.