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Biomedical subjects

J W Davis

Publications and source records attributed to J W Davis.

At least 271 records · Page 15Linked to original sources
PubMed1978

The roll-bar hand.

This report describes a new hand injury seen in passengers in dune buggies having rollover accidents. Since these vehicles are usually driven off the road and far from treatment centers the treatment of these injuries is often delayed. As the rollover takes place, the reflex action--usually of the passenger--is to grasp the roll bar. A crush-avulsion injury occurs at the level of the metacarpals, with the thumb frequently spared. Wound contamination, delay in treatment, and the frequency of other serious injuries add to the seriousness of this injury. Redesign of the roll bar, provision of better passenger protection, and an internal grasp support are suggested to reduce its incidence.

Accidents↗
PubMed1978

Failure of diphenhydramine hydrochloride to prevent thrombosis at sites of endarterectomy in dogs.

Our previous work has shown that the addition of diphenhydramine hydrochloride to platelet-rich plasma is capable of causing disaggregation of platelet aggregates already induced by adenosine diphosphate as well as of inhibiting platelet aggregation when added prior to the aggregating agent. This led us to attempt to prevent arterial thrombosis in a canine experimental model. Ten dogs received an injection of diphenhydramine (approximately 3 mg/kg of body-weight) into the right common femoral artery 1 cm proximal to the proximal end of a 2 cm endarterectomy immediately after closure of the endarterectomy site and prior to performing an endarterectomy of the other common femoral and both common carotid arteries. The dogs which received diphenhydramine were compared with ten control dogs and found to have no protection against thrombosis at the sites of endarterectomy after 4 and 24 hours.

Animals↗
PubMed1978

The effect of epinephrine on phenylethanolamine N-methyltransferase in cultured explants of adrenal medulla.

The investigation reported here was designed to gain further insight into the mechanisms by which phenylethanolamine N-methyltransferase (PNMT) is regulated. Explants of adrenal medullae were cultured in defined media for up to 48 h, during which time the tissue remained histologically intact. Addition of epinephrine to the medium led to a diminution in the activity of PNMT, measurable in the dialyzed homogenates of the cultured tissue. The enzyme activity was inversely proportional to the concentration of epinephrine present in the culture medium. A diminution in the amount of PNMT protein also resulted from incubation of the explants in the presence of epinephrine. The extent of loss of PNMT, measured by immunochemical titration, corresponded to the degree of loss in PNMT activity under the same conditions. None of the metabolites of epinephrine, including 3,4-dihydroxy- or 3-methoxy-4-hydroxymandelate, or metanephrine, had an effect on PNMT. Tyrosine hydroxylase and catechol O-methyltransferase activities were also diminished, whereas tyrosine transaminase, acid phosphatase, and monoamine oxidase activities were not affected by addition of epinephrine to the medium. Ascorbic acid added to the medium prolonged the lifetime of epinephrine but did not alter the degree of diminution of PNMT. The results obtained are consistent with the view that epinephrine is rapidly assimilated into the cytoplasm of medullary cells and plays an important role in regulating the concentration of PNMT in the adrenal gland.

Adrenal Medulla↗
PubMed1978

Hematologic comparisons of shot and live trapped cottontail rabbits.

Comparisons were made between hematologic measurements of shot and box-trapped cottontail rabbits (Sylvilagus floridanus). Trapped rabbits had significantly (P less than 0.001) higher serum corticoid levels and segmented neutrophil percentages and significantly (P less than 0.001) lower lymphocyte percentages than did shot rabbits. Trapped rabbits also had significantly (P less than 0.05) higher packed cell volumes and blood urea nitrogen values than did shot rabbits.

Adrenal Cortex Hormones↗
PubMed1977

Heparin neutralizing activity and coronary artery disease.

It has been previously shown and confirmed in the present investigation that the disaggregation of adenosine diphosphate (ADP)-induced platelet aggregates occurs at a slow rate more frequently in the platelet-rich plasma (PRP) of men with coronary artery disease. ADP-induced platelet aggregation was studied in the citrated PRP of 32 men (21 with and 11 without coronary artery disease) to determine the relation between release of heparin neutralizing activity (HNA) from platelets and the rate of platelet diaggregation. Each of the five PRP with slow (less than 10 per cent) disaggregation were from men with coronary artery disease. Platelets from these five PRP released from 34 to 51 per cent of their content of HNA during ADP-induced aggregation in contrast to the 27 PRP with more rapid disaggregation, only three of which had a detectable release of HNA. Of the latter 27 PRP, 21 had a second phase of aggregation which usually reached a peak of light transmission less than that of the first phase. These data are consistent with (but do not prove) the hypothesis that HNA released during aggreation may be one of the factors tending to prevent disaggregation of ADP-induced platelet aggregates.

Adenosine Diphosphate↗
PubMed1976

Estimation of assortative mating preferences in the Arctic skua.

Methods are described for the maximum likelihood estimation of mating preferences in models of assortative mating for monogamous and polygamous organisms. These methods are applied to data of matings of the three phenotypes, pale, intermediated and dark of the Arctic Skua. The data were obtained by exhaustive surveys of the Arctic Skua populations on the islands of Fair Isle and Foula. The data give evidence of significant assortative mating of pale birds on Foula and intermediate birds on Fair Isle. The combined data show that there is very highly significant assortative mating, but only of intermediates. In previous surveys, data, in which intermediates and darks were not distinguished, were obtained from a number of islands in the Shetlands. These data, combined with the present data, show that the overall assortative mating of pale is very highly significant with no evidience of heterogeneity. The assortative mating of intermediate birds on Fair Isle agrees with other evidence showing that inermediate males have an advantage as a result of sexual selection.

Animals↗
PubMed1976

A demographic analysis of the components of selection in a population of Arctic Skuas.

From previously published demographic data of the age distributions and reproductive rates of the pale, intermediate and dark phenotypes of the Arctic Skua, revised estimates are obtained of the intrinsic rates of increase and selective coefficients of the phenotypes in each sex. Two significant components of selection are variation in age of maturity and variation in reproductive success. Sexual selection is a component of the variation in reproductive success. Dark and intermediate birds have a greater reproductive success than pales, partly as a result of their advantage in sexual selection. Pale birds have an overall advantage, however, because they are younger when they first breed. Given the estimated selective coefficients, a computer model predicts that pale birds will gradually replace the others. So far there are not enough data collected over a sufficiently long time to test the model rigorously.

Animals↗
PubMed1976

Experimentally induced lead poisoning in goats: clinical observations and pathologic changes.

The effects of orally administered lead acetate were investigated in 9 adult and 3 kid goats by clinical and necropsy studies. One kid and 6 adults died after having received from 100 to 1392.5 Gm each, given over periods of from 10 to 52 days. Anorexia, diarrhea and body weight loss occurred in all lead treated goats in the study. Basophilic strippling of red blood cells was found in 6 of 8 animals on which weekly hemograms were performed. The pathologic changes were essentially the same as those that have been recorded for other ruminant species with lead poisoning. Intranuclar acid-fast inclusions in the cells of the proximal convulted tubules of the kidney were demonstrated in 9 of 12 lead treated goats and in the liver parenchymal cells of 2 of these animals.

Animals↗
PubMed1975

Amino acids and collagen-induced platelet aggregation. Lack of effect of three amino acids that are elevated in homocystinuria.

Arterial thrombosis frequently occurs in homocystinuric children whose plasma levels of homocystine, homocysteine, and methionine are elevated. Since platelet aggregation is important in the pathogenesis of arterial thrombosis, we wondered whether the elevated concentrations of these amino acids might predispose to arterial thrombosis by enhancing platelet aggregation. Addition of the above amino acids to normal platelet-rich plasma to achieve concentrations within or above the range found in homocystinuric children had no effect on collagen-induced platelet aggregation. These data give no support to the hypothesis that the arterial thromboses of homocystinuric children are a result of enhancement of platelet aggregation by homocystine, homocysteine, or methionine.

Collagen↗
PubMed1975

Failure of methylhistidines to inhibit platelet aggregation at concentrations found in uremic plasma.

Methylhistidines are among the amino acids which are present in increased concentrations in the plasma of severely uremic patients who may have a hemorrhagic diathesis. Histidine contains an imidazole ring, and our previous work has shown inhibition of collagen-induced platelet aggregation by imidazole in concentrations as low as 0.5 mM. Collagen-induced, adenosine diphosphate-induced, and norepinephrine-induced platelet aggregation were tested in platelet-rich plasma by a turbidimetric technique after incubation of the plasma with varying concentrations of the methylhistidines for 1 hour. Platelet aggregation was unaffected by methylhistidine concentrations up to 0.6 mM. Only norepinephrine-induced platelet aggregation was slightly inhibited at a concentration of 4.7 (mM far higher than found in uremic patients). The imidazole ring as a portion of the methylhistidine molecule appears to have lost much of its effect on platelet aggregation.

Adenosine Diphosphate↗