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Biomedical subjects

J Davis

Publications and source records attributed to J Davis.

At least 469 records · Page 26Linked to original sources
PubMed1981

Transport of radioactive oxygen, nitrogen and xenon into the rabbit thoracic aorta in situ.

An in situ preparation of the rabbit thoracic aorta has been used to study the transport of short-lived radioactive isotopes of oxygen (15O16O), nitrogen (13N14N) and an isotope of xenon (133Xe) from 0.9% NaCl into the artery wall. At a luminal hydrostatic pressure of 2 kPa the uptake of all three isotopes by the intima-media increased with time in experiments of up to 15 min duration. Uptake of labelled oxygen was an order of magnitude higher than that of xenon and almost two orders of magnitude higher than nitrogen uptake. Adventitial uptake was similar for all three species. For a perfusion time of 2 1/2 min, the intimal-medial uptake of all three gases increased by almost an order of magnitude as luminal pressure increased from 2 to 13 kPa. Adventitial uptake increased rapidly and at a similar rate for all three gases. The studies were limited in depth and accuracy by the small quantities of isotope available.

Animals↗
PubMed1981

Hemispheric asymmetry in the processing of Stroop stimuli: an examination of age and gender differences.

In responding to Stroop stimuli, individuals consistently respond with shorter latencies when reading the color word than when reporting the hue of the color word stimulus. The responses of second graders and sixth graders and data from an earlier study of university students were included in the analyses. For all groups the expected Stroop effect was present. An analysis of covariance revealed that the covariable, the word score, was significantly related to the color score for all age groups. Whether or not the data were controlled for handedness and language, there was a significant difference between sexes for university students but not for second or sixth graders.

Adult↗
PubMed1981

Comparison of the antihypertensive effects of indapamide and cyclopenthiazide.

The antihypertensive effects of indapamide, 2.5 mg, and cyclopenthiazide, 0.5 mg daily were compared over a two week period. The falls in both diastolic and systolic blood pressure were greater with indapamide than with cyclopenthiazide reaching statistical significance for the supine diastolic values. This difference was still seen when matching patient groups of similar age, sex or severity of blood pressure were compared.

Antihypertensive Agents↗
PubMed1981

Uptake of low molecular weight materials in an in situ preparation of the rabbit thoracic aorta.

1. An in situ preparation of the rabbit thoracic aorta is described in which the integrity of the intimal endothelium is shown to be preserved. An extensive system of vasa vasorum and lymphatic vessels distributed throughout the adventitia, but not penetrating the media, are demonstrated using resin casts and lead chromate precipitation techniques and are shown to be patent in this preparation. 2. The role of the vasa vasorum in the medial uptake of low molecular weight materials is investigated as a function of luminal hydrostatic pressure and perfusion time. Comparison of uptake in vessels with and without patent vasa vasorum indicates that at physiological pressures medial uptake of 125I ions is dominated by entry from the adventitial surface. Analysis of the transmural distribution of 125I demonstrates that iodide is not retarded at the endothelial surface but a barrier exists within the intima which is tentatively identified as the internal elastic lamina. Qualitative studies show that Patent Blue V whose coloured anion has a molecular weight of 500 is able, at longer perfusion times, to penetrate this barrier. There is no circumferential variation in intimal uptake, but in contrast, adventitial uptake is rather patchy and generally more intense on the dorsal surfaces of the aorta. 3. Iodide transport across the intimal surface is argued to be predominantly diffusive in short duration experiments with an effective diffusion coefficient of (1.6 +/- 0.9) X 10(-6) cm2 min-1.

Animals↗
PubMed1980

Covalent affinity labeling of the formyl peptide chemotactic receptor.

The formyl peptide chemotactic receptor present on human neutrophil membranes has been covalently affinity-labeled using three different techniques. N-Formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys was cross-linked to the receptor with dimethyl suberimidate, N-formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys-Nepsilon-4-azido-2-nitrophenyl was cross-linked by photoactivation, and N-formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys-Nepsilon-bromoacetyl reacted spontaneously with the receptor. With each method, a polypeptide which migrated as a broad band on sodium dodecyl sulfate-polyacrylamide electrophoresis, with an apparent molecular weight between 55,000 and 70,000, was specifically labeled. A dose-response curve for inhibition of covalent cross-linking of the formyl peptide derivatives by unlabeled N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys correlated closely with a dose-response curve for inhibition of binding of the same formyl peptide derivatives to the receptor. The nonformylated analog, Nle-Leu-Phe-Nle-Tyr-Lys, did not inhibit binding or covalent cross-linking.

Affinity Labels↗
PubMed1980

Mechanisms of host defense in well nourished patients with chronic alcoholism.

Tests of immune function were performed on five recently abstinent, well nourished,and disease-free patients with chronic alcoholism. No significant defects in adherence, metabolic, or bactericidal activity of polymorphonuclear leukocytes were found when compared to sex-matched controls. Antibody-dependent and natural killer cellular cytotoxicity of monocyte-macrophages and lymphocytes also were normal. These data support the concept that immunity might be intact in the group of patients with chronic alcoholism who are recently sober, well nourished, and free of underlying disease.

Alcoholism↗
PubMed1980

Hemispheric asymmetry in the processing of Stroop stimuli: an examination of gender, hand-preference, and language differences.

The present investigation examined the possibility that the explanation for the Stroop phenomenon lies in the hemispheric asymmetry of the human brain. Forty-eight male and 73 female students from freshman psychology classes served as subjects for this study. There were 37 males and 53 females who were right-handed and monolingual; 16 left-handers (five males, 11 females); and 13 bilingual subjects (four male, nine female) included in the sample. Only one person was both left-handed and bilingual. All subjects responded to color words printed in incongruent colors by reading the word or reporting the color in which the word was printed. Response latencies were recorded in hundredths of a second for each of the 36 trials for each subject. For all individuals, response latency was consistently shorter when reading the word than when reporting the color. Females demonstrated a shorter latency for the color stimuli than did males; however males demonstrated a shorter latency for the word stimuli. Evidence indicated that the Stroop phenomenon may best be explained by different modes of neural processing for symbolic and iconic stimuli for all individuals. It was further indicated that females have greater flexibility between hemispheres unless other intervening factors (i.e., hand preference or language differences) provide a symmetry in hemispheric functioning not ordinarily found in males.

Adolescent↗
PubMed1980

Validity of the Vocational Adaptation Rating Scale: prediction of mentally retarded workers' placement in sheltered workshops.

The validity of the Vocational Adaptation Rating Scale (VARS) for predicting placement of mentally retarded workers in sheltered-workshop settings was investigated. The VARS was administered by workshop supervisors to noninstitutionalized adolescents and adults, ranging from severely to mildly retarded. Frequency and severity of maladaptive behavior in six domains predicted the concurrent placement of retarded workers in workshops and their placement one year later. Results indicated low to moderate significant partial correlations with concurrent placement and one-year follow-up placement (controlling IQ, age, and sex). Multiple-correlation analyses indicated that the VARS provided significant increments in predictable variance in workshop placements (13.8 to 16.1 percent) relative to predictions based on IQ, age, and sex. Results support the instrument's incremental validity as a measure of maladaptive behavior in vocational settings.

Adaptation, Psychological↗
PubMed1980

Determination of pulmonary tissue volume, pulmonary capillary blood flow and diffusing capacity of the lung before and after hemodialysis.

In order to better understand changes in lung function before and after dialysis, we studied eight patients with end-stage renal disease undergoing chronic hemodialysis. Pulmonary tissue volume (Vt), pulmonary capillary blood flow (Qc), the diffusion capacity for carbon monoxide (DLCO), arterial blood gases and body weight were measured before and after dialysis. A single breath, constant expiratory flow technique for determination of of DLCO, Qc and Vt was used. DLCO, Qc, arterial carbon dioxide, and body weight were reduced post dialysis (P less than or equal to .01) while Vt failed to change. The alveolar-arterial oxygen difference rose 123 mmHg (P = .01). These results are consistent with pulmonary microembolization during dialysis with deterioration of gas exchange and Qc. These changes appear to occur independent of significant changes in Vt. Possible physiologic mechanisms are discussed.

Adult↗
PubMed1979

Human hexosaminidase isozymes. IV. Effects of oral contraceptive steroids on serum hexosaminidase activity.

Data from a mass screening program for identification of persons who are heterozygous for Tay-Sachs disease have been analyzed for the effects of oral contraceptive steroids on the activity in serum of hexosaminidase (hex) and the various hex isozymes. Women using oral contraceptives show a significantly higher total serum hex activity, reflecting mainly an increase in the heat-stable hex isozyme (hex I), and a smaller increase in the heat-labile hex A than do women using no medications. The changes in women using oral contraceptives are qualitatively similar to those observed during pregnancy. The distribution of responses to oral contraceptives is unimodal, and some of the variations may be related to differences in amount of steroid ingested. In addition, underlying genetic variation may contribute to the observed differences in enzyme activities.

Adolescent↗