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Biomedical subjects

E J HARRIS

Publications and source records attributed to E J HARRIS.

At least 37 records · Page 2Linked to original sources
PubMed1959

Surgical management of dissecting aneurysm; the use of a simplified bypass.

The alarming mortality in cases of dissecting aneurysm of the aorta has stimulated the development of a surgical technique which results in re-entry of the dissecting channel. During the operative procedure prolonged cross-clamping of the aorta is necessary. While hypothermia will provide protection to the spinal cord and kidneys during reasonable periods of aortic occlusion it will not relieve back pressure on the left ventricle. By the use of a simple bypass blood is drained from the left atrium into a reservoir and then pumped into the lower aorta via the femoral artery. Thus an adequate supply of oxygenated blood is delivered to the spinal cord and kidneys distal to the occlusion while the left ventricular pressure is decompressed to normal levels. The volume of the shunted blood is simply controlled by monitoring the brachial artery pressure with a cuff sphygmomanometer. This simplified bypass has permitted successful repair of a dissecting aneurysm with complete occlusion of the thoracic aorta for a period of two hours.

Aortic Dissection↗
PubMed1957

Permeation and diffusion of K ions in frog muscle.

The movements of tracer K and net changes of K have been measured in frog muscle. The quantities moving can be linearly related to the square root of the time after a delay of 4 to 30 minutes depending on the external K concentration. The slope of the uptake-t((1/2)) line is increased when the external K concentration is raised. The Q(10) of the uptake is about 1.9 per unit t((1/2)). K uptake from 1 to 2 mM concentration is diminished by a factor of about 2 if strophanthin is applied. The output per unit t((1/2)) is increased by a factor of about 1.4 by strophanthin. Tetrabutylammonium substituted for 10 per cent of the Na in the medium causes a reversible slowing of K uptake and Na output. The rates of movement found in the tracer experiments can be used to calculate the net losses of K taking place in K-free or strophanthin-containing media. The results are interpreted on the basis of K movement being limited both by a resistive outer layer and by diffusion within a K-rich region. The internal diffusion constant is 10(-11) to 10(-10) cm.(2) sec.(-1) depending on the K concentration. The rate of movement of the K can be related to the electrochemical activity of the ion, the lability of the sites on which it is absorbed, and cation + anion pair diffusion within the cell. The surface resistance to K ions can be accounted for as the sum of a membrane resistance equal to that found by electrical methods and the resistance offered to the movement of K by an annulus sufficiently thick (ca. 3 micro) to accommodate the cell Na at a density equal to the mean density of cation within the cell through which K diffuses with the same diffusion constant as holds in the K-rich region. Na movement, if assumed to take place by diffusion from the annulus with diffusion constant equal to that for K ions, has a rate which agrees well with observed values. The influence of strophanthin and tetrabutylammonium on the ion movements is interpreted as being the result of these agents causing an expansion of the outer non-selective region, normally occupied mainly by Na, at the expense of the inner K-rich region.

Animals↗
PubMed1957

Diffusion and permeation of cations in human and dog erythrocytes.

The kinetics of movement of tracer Na into human and dog red cells have been studied. The time courses of these processes and of K transfer were compared with the theoretical time course for saturation of a flat sheet having a resistive surface. The theoretical and the experimental curves when plotted against t((1/2)) have a considerable portion which is linear; on the basis of this resemblance the results are interpreted in terms of a permeability constant and an internal diffusion constant. It is supposed that selective adsorption acts to bring about concentration of K in the human cell and that the bulk of the Na of that cell is present in a thin outer region, while the K is in the interior. The action of strophanthin is to remove the usual limit to the Na capacity of the cell and it is proposed that the Na region increases in thickness at the expense of the K region. Omission of K from the medium has a similar result. Na uptake into poisoned cells measured either with tracer or as a net gain has a linear dependence upon t((1/2)) after a delay. The permeability of the dog cell to Na is reduced when K is added to the medium; this may be due to the formation of an outer K-rich region which imposes a resistance to Na movement.

Animals↗