PHYSIOLOGICAL SOCIETY, October 17, 1925.

Transcription

1 PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY, October 17, The excretion of phosphate during water diuresis. By R. E. HAVARD and G. A. REAY. Large diureses (500 to 1500 c.c. per hour) were produced in the normal human subject by drinking water. Samples of urine and blood were obtained at intervals of about 30 minutes. As the diuresis sets in the kidney turns from concentrating to diluting the plasma phosphate, which remains constant during the whole experiment. Sulphates and urea, however, continue to be concentrated in heavy diuresis. The urinary phosphate may represent as much as a 50 p.c. dilution of the plasma phosphate. This behaviour excludes phosphate from the category of " no-threshold" bodies, as defined in terms of Cushny' s theory of kidney excretion. Mayrs admits the possibility of a very slight reabsorption of no-threshold bodies by the tubules, but regards this as mere "renal inefficiency." This can hardly be urged in the case of a 50 p.c. reabsorption. If phosphate is a "threshold" body, the actual mechanism which allows the kidney to change over from concentrating to diluting, while the plasma phosphate remains steady, is difficult to picture. On the other hand, we find that during diuresis the diluted phosphate maintains a constant rate of output, and this lends some support to the view of Eicholtz and Starling, that all phosphate is secreted by the tubules. A constant rate of.secretion may thus be maintained, which is independent of the amount of filtrate passing the glomerulus. Capillary permeability. By HOWARD FLOREY. The following experiments were performed with the object of ascertaining the precise path traversed by crystalloids and colloids in their passage from the interior of the blood capillaries. A solution of 0 5 p.c. pot. ferrocyanide and 0 5 p.c. iron ammonium a

2 ii PROCEEDINGS OF THE PHYSIOLOGICAL citrate was perfused through a loop of intestine (dog), the experiment being arranged so that the perfusion was begun as soon as the blood flow was arrested. Perfusion lasted 4 minutes. 10 p.c. formalin acidified with 0 5 p.c. HCl was then perfused. This rapidly fixed the capillary wall and precipitated prussian blue wherever the perfusion fluid had penetrated. Sections demonstrated that the prussian blue was precipitated within the cytoplasm of the endothelial cell. The nuclei of these cells remained free from deposit. This was taken to indicate that the perfusate passed directly through the cell protoplasm in its exit from the capillary. Similar perfusions were performed on the rabbit, using 8 p.c. soluble starch solution. To allow of the escape of the starch two procedures were adopted. (a) After washing out the blood from the selected portion of gut (1-2 min. perfusion) the portal vein was tied and the pressure within the vessels thus raised to the perfusion pressure (75 mm. Hg). The vessels were fixed in formalln-iodine, the starch being precipitated as the insoluble blue compound. Sections were cut by embedding in gelatine (at 370 C. so as to prevent dissociation of starch-iodine compound) and with a freezing microtome. (b) The gut was inflamed by a preliminary injection of abrin (in dog). The capillaries were thus made more permeable than in their normal condition. Starch solution was perfused and sections obtained in the way just described. The sections prepared in this way showed a precipitate of starch in the cytoplasm of the endothelial cells-this being evenly spread throughout the cell longitudinally but being more copious towards the inner surface of the cell (i.e. the one towards the blood stream). It would seem that colloids such as starch also find exit directly through the endothelial protoplasm. Under conditions producing deformation, structures such as gelatine and soap gels become doubly refractive. The effect of stretching gelatine on the rate of diffusion of Hb solution into it was tried. 2-5 p.c. gelatine was layered 4-5 mm. thick over a rubber- membrane capable of being stretched. The membrane was tied over the mouth of a large thistle funnel and stretching was accomplished by inflation of the thistle funnel. Each set of experiments was carried out under identical conditions. It was found that diffusion occurred up to 27 p.c. more rapidly into the stretched than the unstretched gelatine. The increase of surface suffered by the gelatine was about 11 p.c., so that there was a real difference in the diffusion rate. It is suggested that the increase of permeability on dilatation of a blood capillary may be partly explained thus. At least

3 SOCIETY, OCTOBER 17, iii the surface of an endothelial cell may be considered as presenting a gel structure composed of molecules which have one axis longer than the other. On dilatation this structure is stretched-its molecules become orientated and present larger paths for the passage of molecules from the blood stream than exist in the unorientated condition of the molecules. The experiments with the diffusion of Hb into gelatine suggest that the stretch opens up more paths for diffusion. Further observations on the changes in the adrenal bodies under varying conditionis. By SWALE VINCENT1 (Middlesex Hospital Medical School). I have recently2 recorded that if white rats be exercised at laboratory (winter) temperature their body temperature will fall and the chromaphil reaction o( the adrenal medulla will be very considerably reduced. If they are fatigued at higher temperatures their body temperature will rise and the chromaphil reaction will not be reduced. At about C. t4e temperature of the animal will neither rise nor fall under the influence of fatigue and the chromaphil tissue is unaffected. Reduction of the temperature of the surrounding medium will, independently of fatigue, cause a reduction in the chromaphil reaction if the animal's temperature becomes lowered, which does not always occur. It seems, then, that the effect of exercise to the point of fatigue on the chromaphil reaction is not direct, but secondary to the lowering of the animal's temperature. Further experiments show that if adrenin be injected subcutaneously into the rat half-an-hour before exercise begins, fatigue carried to the point of collapse will not then reduce the intensity of the chromaphil reaction in the adrenal medulla. The body temperature, however, in most cases, falls as usual. There appears to be a definite correlation between the intensity of the chromaphil reaction in the adrenal medulla and the cstrous cycle. Recent investigations by Stockard and Papanicolaou3 have made it possible, by the study of vaginal smears, to determine precisely what stage in the cestrous cycle the animal has reached. Using this method it is not difficult to satisfy oneself that in the late cestrous and early post-cestrous stages there is a very marked reduction, amounting some- 1 Towards the expenses of this investigation a grant has been made by the Govern. ment Grant Committee of the Royal Society. by Mr R. H. Pittman. 2 Quart. Journ. Exp. Phy8iol (In the Press.) 3 Amer. Journ. Anat. 22. p Much valuable assistance has been rendered a2

4 iv PROCEEDINGS OF THE PHYSIOLOGICAL times to practical disappearance, of the chromaphil reaction of the adrenal medulla. The stage referred to is that in which large numbers of " cornified" epithelial cells can be recognised in the preparation. Lactic acid and rigor mortis in fish muscle. By A. D. RITCHIE. The lactic acid content of the muscle of three species of Gadidee before, during, and after rigor mortis are given below. The fish were caught in the St Croix Estuary, New Brunswick, or in that neighbourhood during June to September 1925, except for two of the Cod caught off Halifax, N.S., in May Lactic acid p.c. Before rigor During rigor After rigor Fish Mean Extremes Mean Extremes Mean Extremes Haddock. Melanogrammus ceglhfinu 015 (11) (10) (6) Cod * Gadws callaria (2) (5) (5) Hake O Urophycis chu8s or teruia (2) (7) The figures in brackets are the number of experiments performed. The estimations were made by weighing the lactic acid as zinc lactate. The variations within each species are probably not due to age or size differences, as the haddock are at least as variable as the others but appeared to be all of one school spawned in 1920 and were fairly uniform in size. The figures for lactic acid before rigor do not represent the resting minimum, which is about 0-08 p.c. or less for haddock. The differences between the three species correspond to the usual notion of their muscular activity. The haddock is most active, the hake least. In muscles which had passed out of rigor, very little more lactic acid could be obtained by chopping with chloroform or keeping for some hours at about 30 C. or even by keeping the chopped muscle in alkaline phosphate solution. This suggests that the lactic acid maximum in these fish, unlike the frog, is due to approximate exhaustion of the glycogen. A rough estimation of glycogen in a haddock, confirmed the suggestion. muscle containing 0-17 p.c. lactic acid contained also 0-16 p.c. of glycogen, (C6H0O6)nj, allowing 0 33 p.c. for the lactic acid maximum. In all these fishes rigor passes off within 12 hours after death at

5 SOCIETY, OCTOBER 17, room temperature in the neighbourhood of 200 C. Confirming the suggestion made many years ago by Halliburton, the passing off of rigor was found to be accompanied by hydrolysis of the muscle proteins. The free amino groups in the whole muscle substance were estimated by S6rensen's Formol Titration method. The method is very rough but the changes found were well outside the experimental error.. In four different haddock the mean value for amino nitrogen was equivalent to 7*9 c.c. of normal alkali per 100 gms. at the beginning of rigor. The value increased gradually from the time when rigor was maximal or a little earlier and reached 10x2 c.c. by the time it had passed off. That this effect is due to protein amino groups and not to ammonia or any other soluble base was shown by titrating alcohol extracts (80 p.c. alcohol) in a similar way. With haddock muscle the change is not more than 01 c.c. per 100 gms., the total titre of the alcohol extract being about 0x2 c.c. This result may be contrasted with the figures for alcoholic extracts of skate muscle, in which ammonia is produced post mortem. In a skate (Raja Radiata) the titre of the 80 p.c. alcohol extract rose from 3-3 c.c. to 5-3 c.c. in 21 hours. v