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Biomedical subjects

J Metcalfe

Publications and source records attributed to J Metcalfe.

At least 73 records · Page 4Linked to original sources
PubMed1981

Improvement in the relationship between flow to ischemic myocardium and the extent of necrosis with glycolytic intermediates that decrease blood oxygen affinity in dogs.

Reducing blood oxygen affinity may enhance myocardial oxygen delivery during ischemia. We evaluated this hypothesis in awake, previously instrumented dogs that received a 20 ml/kg infusion of a solution of dihydroxyacetone, phosphate, and pyruvate after acute occlusion of either the left anterior descending or circumflex coronary artery. This infusion reduced blood oxygen affinity (BOA) after 2 hours; the P50 increased from 29.9 +/- 0.7 torr (mean +/- SD) to 32.1 +/- 0.6 torr; P less than 0.01 (BOA group). Four dogs received 20 ml/kg of phosphate and pyruvate solution to assess volume effects (V group), and five dogs were controls (C group). The 2-hour P50 values in V and C were unchanged. Regional flow (15-mum spheres) reduction 2 hours postocclusion was compared to the percent tissue infarcted determined by histology 7-9 days after occlusion for multiple samples from the endocardial layer of the left ventricle. When flow was less than 40% of normal, V and C had 55% infarction while BOA had 37% (P less than 0.05); at flow less than 20% of normal, V and C had 79% infarction while BOA had 38% (P less than 0.001); and at less than 10% of normal, V and C 87% and 94% infarction, respectively, while BOA had 56% (P less than 0.001). Reducing blood oxygen affinity after coronary artery occlusion significantly decreased the extent of myocardial necrosis for the same degree of ischemia. Reducing BOA may increase oxygen delivery to ischemic myocardium when flow is restricted.

Animals↗
PubMed1981

Oestrogen concentrations in systemic plasma of pregnant pygmy goats.

Concentrations of oestradiol-17 beta, oestradiol-17 alpha, and oestrone in systemic plasma of pregnant pygmy goats (Capra hircus) remained low until about Day 60 and then rose to maximum values at Days 120-140 (parturition Day 140-145). Oestradiol-17 alpha was the predominant oestrogen. All 3 oestrogens at Days 100-130 were higher in females carrying 3 fetuses than in those carrying only one, but at Days 70-90 only oestrone values were higher. It is suggested that the feto-placental unit is the source of oestrogens during gestation in goats.

Animals↗
PubMed1980

Uterine oxygen uptake in the pregnant Pygmy goat.

The diffusion equilibrium method was used to measure uterine blood flow (Qut) and oxygen consumption (VutO2) of 7 Pygmy goats in the last third of pregnancy. VutO2 was 9.3 +/- 1.3 (mean +/- SEM) ml.min-1.kg-1 weight of the uterus and its contents: the placenta, fetus and fetal membranes. This O2 requirement was provided by a high blood flow (349 +/- 48 ml.min-1.kg-1) and a narrow arteriovenous difference (2.4 +/- 0.1 vol%) across the uterus. Maternal arterial O2 content (CaO2) was varied by incurring chronic anemia in 3 animals. CaO2 over the range 6.5 - 12.8 vol% did not affect uterine blood flow or the arteriovenous oxygen content difference across the uterus. Weight specific (ml.min-1.kg-1) VutO2 did not differ in animals whose total uterine weights varied over a wide range and uterine vein oxygen tension and content did not fall prior to delivery. We conclude that the absolute uterine blood flow varies over a wide range to meet the requirements of the uterine contents.

Animals↗
PubMed1980

Respiratory and hemodynamic effects of methadone in pregnant women.

Minute ventilation, end-tidal PCO2, O2 and CO2 concentrations in expired air, pulse rate and arterial blood pressure were measured in the last half of pregnancy in eight women taking methadone daily. Measurements were made with the subjects seated at rest, during the steady state of 50-watt bicycle exercise, and during recovery. Calculations of O2 consumption. CO2 production, alveolar ventilation and oxygen debt were made. Studies were repeated in five subjects postpartum. Methadone diminishes the normal hyperventilation of pregnancy and its effect persists for more than 24 h. When comparisons are made of pregnant and postpartum values, some respiratory stimulation during pregnancy is apparent. Maternal oxygen debt following standard exercise during pregnancy is diminished after the daily dose of methadone and the maternal heart rate response to exercise is diminished concurrently. The maternal hypoventilation induced by methadone and maintained during exercise may be relevant to the low birth weights and high incidence of sudden infant death syndrome observed by others in the offspring of methadone-dependent women.

Blood Pressure↗
PubMed1980

Postnatal regulation of canine oxygen delivery: erythrocyte components affecting Hb function.

A rightward shift in the blood oxygen dissociation curve occurs during the 1st mo of canine life. A detailed peptide analysis indicated that dogs do not have a separate fetal hemoglobin. Other erythrocyte components such as ATP, K+, Na+, and H+ were excluded as significant mediators of the postnatal oxygen affinity change. Erythrocyte 2,3-DPG levels essentially zero in fetal dogs, increased rapidly during the 1st mo of canine life. There was a significant correlation between this postnatal 2,3-DPG increase and the postnatal decrease in blood oxygen affinity. Dialyzed hemolysates of fetal or adult canine blood have the same intrinsic oxygen affinity and the same response to normal adult levels of 2,3-DPG. Furthermore, the magnitude and direction of this 2,3-DPG-induced decrease in oxygen affinity in vitro are comparable to the in vivo postnatal change in oxygen affinity.

Aging↗
PubMed1979

Metabolic consequences of atenolol and propranolol in treatment of essential hypertension.

A six-month study of triglyceride, cholesterol, free fatty acid (FFA), glucose, insulin, growth hormone, and glucagon concentrations was carried out in asymptomatic hypertensive normal-weight men randomly allocated to treatment with atenolol or propranolol. A highly significant increase in the basal plasma triglyceride concentration was observed in propranolol-treated patients after three and six months' treatment, with a smaller but significant increase in atenolol-treated subjects after six months' treatment. The changes in triglyceride concentration could not be ascribed to variations in plasma insulin, growth hormone, or glucagon concentrations. Basal FFA concentrations were reduced during the first three months of treatment in both groups but returned to pretreatment levels after six months. Plasma cholesterol concentrations were unchanged by either agent.

Adult↗
PubMed1979

Hen's eggs with retarded gas exchange. I. Chorioallantoic capillary growth.

The diffusing capacity of the hen's egg for carbon monoxide (D tau co) increases during incubation, reflecting the development of the chorioallantoic circulation. Previous work showed that the increase in D tau co could be diminished by incubating eggs in a 60% oxygen environment. The present work explored the effects of impeding gas exchange on the development of D tau co. Half the shell area was covered during incubation by a removable neoprene membrane which limited D tau co by approximately 20%. No difference could be detected between the D tau co values (measured with the membrane removed) of these eggs and control eggs incubated in the same 21% oxygen environment without a neoprene membrane. We conclude that the development of the chorioallantoic circulation is at its maximum under normal conditions of incubation and cannot be accelerated by restricting gas exchange.

Allantois↗
PubMed1979

Resting hemodynamics and oxygen transport in unanesthetized adult cats.

Characteristics of blood, oxygen transport were determined in seven adult female cats with inlying catheters in the pulmonary artery and a carotid artery. Measurements were made without anesthesia. Cardiac output averaged 167 ml.kg-1.min-1. Blood oxygen capacity averaged 11.6 ml.dl-1. Mean arterial oxygen saturation was 94% and mixed venous oxygen saturation was 49%. Mean oxygen tensions were 97.3% and 36.9 mm Hg in arterial and mixed venous blood, respectively. Mean arteriovenous oxygen concentration difference was 5.1 ml.dl-1, yielding a calculated oxygen consumption of 8.4 ml.kg-1 min-1, 5% higher than the value obtained by spirometric measurements on four of the animals. These data, when compared with previously reported values from species ranging widely in body size, show that the increased oxygen consumption per kg associated with decreasing body size is provided by progressive increases in cardiac output per kg and in arteriovenous oxygen concentration difference. Mixed venous oxygen tension is held within narrow limits in resting, unanesthetized animals.

Animals↗