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Biomedical subjects

W R Keatinge

Publications and source records attributed to W R Keatinge.

At least 55 records · Page 3Linked to original sources
PubMed1982

Adrenergic innervation and sensitivity to vasoconstrictor hormones of inner muscle of sheep pulmonary artery.

Adrenergic nerves penetrated further from the adventitia into the media of medium-sized pulmonary arteries (first branch of main artery), than into carotid arteries, of sheep. They innervated more than 80% of the media in the pulmonary compared to 50-75% in the carotid artery, so that no smooth muscle cells in even the innermost part of the pulmonary arteries were far from a nerve fibre. Inner muscle of pulmonary arteries, unlike that of carotids and other systemic arteries, was little more sensitive than outer muscle to the constrictor action of norepinephrine, with or without desipramine present to block uptake of the norepinephrine by nerves. Nor was it significantly more sensitive than outer muscle to constrictor actions of histamine or 5-hydroxytryptamine; both inner and outer muscle gave only small responses to 5-hydroxytryptamine and to other agents released from blood clot; this is likely to be important in an artery highly prone to embolisation. The results suggest that the lower pressure in pulmonary arteries allows a higher degree of penetration of the vessel wall by nerves, which in turn induces low sensitivity to constrictor hormones in inner as well as outer muscle.

Adrenergic Fibers↗
PubMed1981

Roles of subcutaneous fat and thermoregulatory reflexes in determining ability to stabilize body temperature in water.

1. The lowest water temperature in which different young adults could stabilize body temperature was found to vary from 32 degrees C to less than 12 degrees C, because of large differences in both total body insulation and metabolic heat production. 2. Total body insulation per unit surface area, in the coldest water allowing stability, was quite closely determined by mean subcutaneous fat thickness measured ultrasonically (r = 0.92), regardless of differences in distribution of this fat between men and women. 3. Reactive individuals developed high metabolic rates, and often rather high insulations in relation to fat thickness, which enabled them to stabilize their body temperatures in water more than 10 degrees C colder than was possible for less reactive individuals of similar fat thickness. 4. Measurements of heat flux, after stabilization in the coldest water possible, showed that the trunk was the main site of heat loss and that over half of the internal insulation there could be accounted for by subcutaneous fat; by contrast, fat could account for less than a third of higher insulations found in muscular parts of the limbs, and for less than 3% of very high insulations in the hands and feet. 5. After stabilization of body temperature at rest in the coldest possible water, exercise reduced internal insulation only in muscular parts of the limbs. Exercise also increased heat loss elsewhere by exposing skin of protected regions such as flexural surfaces of joints. During exercise total heat production increased rather more than heat loss in unreactive subjects, but less than loss in subjects whose heat production had already risen to a high level when they were at rest in cold water. 6. In warm (37 degrees C) water, tissue insulations were lower and much more uniform between subjects and between different body regions than in the cold. Even in the warm, however, insulations remained rather higher in fat than thin subjects, higher at rest than during exercise, and usually higher in the limbs than the upper trunk.

Adipose Tissue↗
PubMed1980

Method for measuring regional heat losses in man.

Flexible heat flow devices were constructed from 0.4-mm-thick nylon-reinforced rubber sheet, with multiple copper-constantan thermocouples on each side to measure mean temperature difference across the sheet. A method of calibration is described that corrects for the alteration of local heat loss produced by the device itself. It was shown that such errors would otherwise be large when cutaneous blood flow was high, and tissue insulation low, even with devices as thin as these.

Body Temperature Regulation↗
PubMed1979

Blood-vessels.

Explore the source record for details and available documents.

Action Potentials↗
PubMed1978

Mechanism of slow discharges of sheep carotid artery.

1. Single and double sucrose-gap methods were used to follow changes in membrane potential and conductance of smooth muscle of sheep carotid arteries. 2. K depolarization induced discharges lasting several seconds in various solutions containing Mn, or Mg, or Ca and procaine, sometimes with no other added cations and with only sulphate or ethanesulphonate as anions. 3. Membrane conductance usually rose substantially above resting level in the early part of these discharges, but fell towards resting level during the later part. 4. Large depolarizing currents caused porportionately less voltage displacement than small currents, and reduced voltage displacements induced by superimposed current pulses, even in Cl and HCO3 free solutions, indicating activation of K conductance by depolarization. 5. When procaine was added, or Ca replaced by Mn or Mg, conductance was lower both at rest and on depolarization, and the increase on depolarization often underwent slow inactivation which it never did in simple Ca containing solutions. 6. The results indicate that a slowly inactivated inward current dependent on Ca, Mn or Mg was largely responsible for the slow discharges, and that procaine, Mn or Mg assisted the discharges by reducing the normal rapid outward-rectifying K conductance and allowing it to inactivate on prolonged depolarization.

Animals↗
PubMed1978

How vascular smooth muscle works.

Electrical recordings made from vascular smooth muscle during the last 15 years make it clear that the role of electrical activity in controlling contraction is often important but varies greatly both between different vessels and for different responses of a given vessel. Only a few mammalian vessels have widely conducted electrical activity, but others can develop this activity, with consequent rhythmical contraction, when made anoxic and stimulated. Action potentials play a part in smooth non-rhythmical responses of arteries to nerves and hormones, while passive conduction of depolarization round the vessel wall is responsible for ring contractions of arteries after local injury. Ca and K cause vasodilatation largely by hyperpolarizing the smooth muscle cells. Electrical activity plays no part in some responses. In particular noradrenaline can contract arteries by directly promoting entry of extracellular Ca, and also by releasing Ca stores by non-electrical means. These processes are particularly important in the inner muscle of arteries, which is not directly innervated.

Action Potentials↗
PubMed1976

Action of sympathetic nerves of inner and outer muscle of sheep carotid artery, and effect of pressure on nerve distribution.

1. The direction of torsion produced during active shortening of helical strips of sheep carotid arteries was measured to assess whether inner or outer muscle was contracting. 2. Noradrenaline contracted inner (non-innervated) muscle in lower concentrations than were needed to contract outer (innervated) muscle, even with desipramine present to prevent uptake of noradrenaline by the nerves and with enough cyanide present to rise the normally low O2 tension of inner muscle to that of outer muscle. 3. Activation of sympathetic nerves in the outer part of the artery by nicotine caused almost evenly balanced contraction of both parts of the wall, with slight bias to outer contraction. 4. Moderate external constriction of the artery in vivo for 10-17 days, in order to raise pressure throughout the wall to intraluminal pressure, made the entire wall nerve-free. 5. The results provide evidence that the nerves can induce substantial activation of inner muscle, which is highly sensitive to noradrenaline, and that the absence of nerves from inner muscle can be explained by the high pressure there.

Action Potentials↗