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Biomedical subjects

J Grayson

Publications and source records attributed to J Grayson.

62 records · Page 4Linked to original sources
PubMed1966

Observations on temperature distribution in the cardiovascular system, thorax and abdomen of monkeys in relation to environment.

1. Thermo-electric observations of temperature distribution in the ;core' area of monkeys and baboons are reported.2. Temperature gradients were shown to exist in the inferior vena cava, temperatures rising by a mean value of 0.2 degrees C at the entry of the renal veins and again by a further 0.2 degrees C at the level of the hepatic veins.3. Temperatures in the right atrium were on average 0.1 degrees C lower than in the inferior vena cava due to the return of relatively cooler blood from the superior vena cava.4. Net heat exchanges in the thorax were small. Right atrial and aortic blood temperatures were not significantly different and it was concluded that heat losses in the thorax were balanced by heat production in lungs and heart.5. The mean liver temperature was 0.1 degrees C higher than that of the aortic blood irrespective of the environment.6. The mean temperature recorded from the lumen of the jejunum was 0.2 degrees C warmer than the aorta in the ;warm' environment and 0.4 degrees C hotter than the aorta in the ;cool' environment. In both environments intrajejunal temperature was higher than the liver but the differential was increased by exposure to a ;cool' environment.7. Evidence is adduced to suggest that the gastro-intestinal tract in the body at rest is a major heat producer contributing about double the amount of heat generated by the liver.8. It is suggested that blood flow redistribution in the splanchnic area on exposure of the body to cold is the main cause of the change in aortic-jejunal and jejunal-liver differentials. Metabolic factors have, however, not been excluded.

Animals↗
PubMed1966

A species comparison of the effects of changing perfusion pressure on blood flow and metabolic heat production in the myocardium.

1. A heated thermocouple technique (internal calorimetry) has been used to investigate blood flow and heat production responses in the myocardium to changing blood pressure in monkeys, dogs, rabbits, guinea-pigs and rats. 2. Perfusion experiments (isolated guinea-pig and dog hearts) showed linear relations between conductivity increment and coronary blood flow up to 1 x 5 ml. g(-1) min(-1) (dog heart perfused with blood) and 5 ml. g(-1) min(-1) (guinea-pig heart perfused with saline). This relation was the same in the beating and non-beating heart. 3. In rabbits, guinea-pigs and rats the relation between flow (conductivity increment) and blood pressure was linear. In contrast, in monkeys and dogs, over the range 100-40 mm Hg, little change in blood flow occurred. After the injection of procaine around the stellate ganglion, the relation between pressure and flow in both species was linear. It is suggested that the constancy of blood flow displayed in the monkey and dog over this blood pressure range was due to the activity of adrenergic rasodilator fibres. 4. Evidence is adduced to show an increased myocardial heat production when systemic arterial pressure fell below about 60 mm Hg. This was not affected by cardiac denervation. The possible significance of this effect is discussed.

Animals↗
PubMedDate not supplied

Dynamics of myocardial infarction--the role of critical closing pressure.

Pressure in the primary distributing network of a vessel on the surface of the heart is normally sufficient to prevent critical closure of its derivative vessels. It is proposed that acute occlusion of a major supply vessel or over activity of the heart in the presence of an impairment of the lumen of a major supply vessel may reduce transmural pressure in parts of the network. In consequence vasospasm, the result directly of critical closure, is postulated as the basis for myocardial infarction, together with maximal dilatation of vessels in which pressure did not fall to critical levels.

Coronary Circulation↗