Abstract
LONDON Royal Society, December 12. F. C. COURTICE and C. G. DOUGLAS: The effects of prolonged exercise on metabolism. In the normal postabsorptive subject, there is a striking fall of the respiratory quotient during rest subsequent to work which may last for hours. This is accompanied by ketosis and a progressive slow fall in the carbon dioxide combining power of the blood. Ketosis can readily be prevented by taking a carbohydrate rich diet on the previous day, but still occurred with great frequency when either an ordinary breakfast or a quantity of sugar was ingested shortly before beginning the experiment, the main effect in the latter case being apparently increased utilisation of carbohydrate during the work. The fall of respiratory quotient is attributed mainly to a reduction of the ratio of carbohydrate to fat oxidised owing to depletion of stores of available carbohydrate during the work, but in addition there may be some conversion of fat into stored glycogen, though only to a small extent. During post-exercise rest there is reduced sugar tolerance, and the possible influence of endocrine secretions on carbohydrate metabolism during muscular work is discussed. W. L. FRANCIS: The surface membranes of muscle fibres. Using Osterhout's methods as a guide, the following results have been obtained. The pH of fresh muscle brei is found with a quinhydrone electrode to be 7.1, in agreement with estimates by other workers of the pH. of resting living muscle. The pH after 24 hours is 6.7. The composition of an aqueous solution resembling brei in its inorganic content is discussed. The stumbling block is the phosphate, which can only be made 1/5 as concentrated in aqueous solution as in the muscle fibre. The diffusion potentials between brei and various electrolyte solutions were measured. They point to the mobility of anions being very low in brei compared with their mobilities in aqueous solution. The vapour pressure of brei is found by Barger's method to be equivalent to 1.06 per cent sodium chloride. The effects of cut muscle, brei and various experimental solutions on the resting potential are investigated with the view of finding what the ‘asymmetry’ potential of the surface membrane would be if the media on both sides were the same. The value would be 10–20 mv. reckoned inwards. The diffusing substance need only saturate the inter-fibrillary spaces in order to produce its full effect on the potential at the fibre surface.
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Societies and Academies. Nature 136, 1001–1002 (1935). https://doi.org/10.1038/1361001a0
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DOI: https://doi.org/10.1038/1361001a0