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Societies and Academies

Nature volume 110, pages 685687 (18 November 1922) | Download Citation

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LONDON. Royal Society, November 9.—Sir Charles Sherrington, president, in the chair.—H. E. Armstrong: Studies on enzyme action. XXIII. Homo- and hetero-lytic enzymes.—A. V. Hill and W. E. L. Brown: The oxygen-dissociation curve of blood and its thermodynamical basis. An attempt has been made to test the validity of the hypotheses (i) that the reaction of haemoglobin with oxygen is represented by the equation (Hb)n, + nO2 ±(HbO2)n, where Hb represents the simplest possible molecule of hæmoglobin (containing one atom of iron), and n the average degree of polymerisation of the molecule in the presence of the salts in blood: and (ii) that the dissociation curves of oxyhæoglobin under various conditions can be deduced by simple application of the Laws of Mass Action. The heat of reaction q of one gm. mol. of hæmoglobin (Hb), with oxygen has been determined by the application of the van't Hoff isochore to the effect of temperature on the dissociation curve of blood, while the heat of reaction Q of one gm. mol. of oxygen with hæmoglobin has been measured directly in a calorimeter. The value of q/Q is practically equal to n determined in other ways, affording strong confirmation of hypothesis (I). The apparent heat of reaction of oxygen with blood may be very considerably reduced by the driving off of carbon dioxide by the more acid oxyhaemoglobin formed. A direct measurement of the heat of combination of carbon dioxide with blood confirms the theory that carbon dioxide combines with blood by taking base from the ionised hæmoglobin salt to form bicarbonate, leaving the non-ionised hæmoglobin acid. The heat of combination of carbon monoxide with hæmoglobin in blood is about 50 per cent. greater than that of oxygen: this proves that temperature affects the equilibrium of oxygen and carbon monoxide with blood.—H. Hartridge and F. J. W. Roughton: The velocity with which carbon monoxide displaces oxygen from its combination with hæmoglobin. Pt. I. When light falls on a solution containing oxyæmoglobin and carbon monoxide hæoglobin, the incoming light energy changes the position of equilibrium, tending to cause a reduction in the amount of the latter with a corresponding increase of the former. the dark the original position of equilibrium is gradually recovered, the rate of return depending on the velocity constants of the reactions. By determining the percentage saturation of the hemoglobin with carbon monoxide gas at intervals after the light has been turned off, the velocity constants can be calculated. This is done by causing the fluid to flow through two glass tubes in series in the first it is exposed to a powerful light, while in the second it is kept in the dark, so that the original position of equilibrium is gradually regained. The percentage saturation with carbon monoxide gas of the solution at different parts of the "dark "tube was determined with the reversion spectroscope. At I5' C. the two velocity constants had mean values of o-oo67 and ° 55 respectively. At 34-50 C. the value of K2 was 2*66, which gives a temperature coefficient for this velocity constant of 2-3 for a ioo C. rise of temperature,-approximately that given by many ordinary chemical reactions. Pt. II. The method of measuring the velocity of the reaction CO + O2Hb˜=COHb +°2 consists in ascertaining, by means of an electrically controlled stop-watch, the time taken for the equilibrium to shift from an unstable position to a stable one, the change being ascertained by measurements on the absorption bands by means of the reversion spectroscope. The system was changed to an unstable position by (I) subjecting the solution to the action of a powerful beam of light, and by (2) suddenly obstructing the light rays. Thus chance fluctuations in the catalysing light source, and in the flow of the liquid under observation were avoided, but it was difficult to make accurate estimations on absorption bands moving from one position in the spectrum to another. Observations of the equilibrium constant were made by method (I) at I° C. and laboratory temperature, and by method (2) at laboratory temperature and 340 C. At laboratory temperature, method (I) gave 0-5i and 0-59, and method (2) 0-44 and 0o40. The temperature coefficient per io' C. calculated from values obtained by method (I) was 2 3, while method (2) gave 2-5 and 2-7.-L. T. Hogben: Studies on internal secretion. I. The effect of pituitary (anterior lobe) injection upon normal and thyroid-ectomised axolotls. While pituitary feeding has no influence on the metamorphosis of medium-sized or sexually mature axolotl larvie of Arnblystomca tigrinum, injection of anterior lobe extracts into axolotls of the same ages and dimensions was followed by the assumption of the adult characteristics, with rapidity comparable to metamorphosis induced by thyroid administration, and beginning about two to three weeks after the initial injection. Anterior lobe extracts also induce metamorphosis in thyroidless larvae. Spontaneous metamorphosis does not generally occur, as Marie de Chauvin stated, in larvae of six to nine months when placed in shallow water with opportunities for emerging.-L. T. Hogben and F. R. Winton: The pigmentary effector system. II. Apart from caffeine, the only reagents found to induce melanophore contraction were those known to excite peripheral sympathetic nerve-endings, namely, adrenalin, tyramine, ergotoxine, and cocaine. Apart from pituitary extract, the only reagents found to bring about melanophore expansion were apocodeine and nicotine, in quantities sufficient to paralyse all sympathetic nerve-endings. No unequivocal direct evidence is advanced that nervous control of pigment responses in Amphibia has been found. Synchronous colour changes of Amphibia in response to normal environmental stimuli are possibly determined mainly by endocrine influences.-A. Fleming and V. D. Allison: Further observations on a bacteriolytic element found in tissues and secretions. Strains of M. lysodeikticus resistant to lysozyme action can readily be developed. The resistance is not specific, i.e. strains made resistant to one tissue or secretion are equally resistant to all tissues, whether derived from man, the lower animals, or from vegetables, showing that the lysozyme affecting M. lysodeikticus is the same whatever tissue it is derived from. After solution of a large number of M. lysodeikticus there is an increase in the lytic power of the fluid, which affects wholly or mainly the homologous microbe. Different tissues and secretions vary in their capacity to dissolve different bacteria, and some tissue extracts have a marked lytic action on many of the wellknown pathogenic bacteria.

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https://doi.org/10.1038/110685b0

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