D. D. Van Slyke

The globulin and albumin content of the plasma in nephritis

Bright and a number of subsequent observers have described a diminution of proteins in the plasma of some persons suffering from albuminuria and edema; and later it has also been found that the decrease occurs chiefly in the plasma albumin (Epstein) the globulin not being diminished. We have determined the albumin and globulin over varying periods of time in the plasmas of a number of nephritics by the recent method of Howe, with the results indicated below. The cases were classified as glomerular nephritis, nephrosis, and nephrosclerosis according to Volhard and Fahr. In glomsrular nephritis a return to a normal total protein content has been observed in some cases, but a return to a normal albumin: globulin ratio has not yet been observed in any of our cases. In one typical nephrosis patient a great loss of edema was observed without any change in plasma proteins, but after the edema had disappeared the total proteins began to rise towards the normal. The case of nephrosis with normal total content at the first examination was already ccrnvalescent.

Nature of Nitrogenous Constituents in Petroleum Ether Extract of Plasma

Neither the amino nor the non-amino nitrogen obtained in the petroleum ether extract of plasma by the technique of Kirk, Page, and Van Slyke 1 derives entirely from phosphatides. The N:P ratio for lecithin and cephalin is 1, while the Amino N:P ratios are 0 and 1 respectively. In a mixture of these phosphatides the N:P ratio would accordingly be 1, and the Amino N:P ratio between 0 and 1, according to the proportion of cephalin present. Petroleum ether extracts from 10 normal plasmas were prepared and analyzed according to the method of Kirk, Page, and Van Slyke. The N:P ratios varied from 1.7 to 5.5, and averaged 3.4. The Amino N:P ratios varied from 0.6 to 1.7, and averaged 1.7. There was accordingly more of both total N and amino N present in the extract than could be combined in these phosphatides. In extracts from plasma of uremic patients the excess of N and NH2 was still greater. The N:P ratio in 8 cases varied from 3 to 18, and averaged 9, while the Amino N:P ratio ranged from 0.9 to 4.7 and averaged 2.5. Part of both the amino and the non-amino nitrogen is removable from the petroleum ether by shaking with acidified water. The nature of the material is being studied further.

The determination of oxygen in blood

This requires 5 minutes for human blood, unless a little sapanin has been added to the ammonia, in which case 15 seconds may suffice for the laking. The apparatus for determining carbon dioxid in blood, described in the Proceedings for the meeting April 21, 1915, can be used with equal facility and accuracy for determination of oxygen. 6 c.c. of ammonia made by diluting the concentrated solution with 200 parts of water, are introduced into the apparatus with 5 drops of caprylic alcohol. The apparatus is evacuated and the air extracted from the ammonia by shaking for a few seconds. The extracted air is expelled and the process completed to make certain that none is left. 2 c.c. of blood are then introduced. The blood and ammonia are mixed and allowed to stand until the blood is laked. Then half a c.c. of saturated potassium ferricyanide solution is introduced (the cyanide solution is made air-free by boiling or by shaking in an evacuated flask, and is kept in a burrette under a layer of paraffin oil two or three centimeters thick to exclude air). The apparatus is now evacuated, shaken and the oxygen set free determined exactly as is carbon dioxid. The solubility of oxygen in water is so slight that no correction is made ¢or what remains in solution. The only correction necessary is for the small amount of nitrogen gas which 2 C.C. of blood contain.

The formation of urea in the liver

In dogs etherized and operated at various intervals after feeding, we have found the urea content of blood from the hepatic vein to be from 3 to 20 per cent. higher than the portal blood. A similar increase in the urea content during passage of the blood through the muscle tissue of etherized dogs did not occur.

Studies of Renal Metabolism.

A kidney is drawn out of the body cavity of a dog and sutured under the skin of the back, with the renal vein located in such a position that it can be punctured through the skin with a needle. The metabolism of the kidney has been studied by simultaneous analyses of arterial and renal bloods and of urine secreted during the observation periods. The rate of blood flow through the kidney has been estimated by comparing the amount of urea removed from a unit volume of blood in passing through the kidney with the amount excreted per minute. In most of our experiments only one kidney at a time has been studied; one is brought out under the skin, and the other is removed, in order to simplify the experiments. In a few controls in which one kidney was brought out and the other left in situ excretion was similar in both. Through a single kidney in clogs of 15 to 20 kilos weight the blood flow is in the neighborhood of 200-250 cc. per minute. Increasing the urea content of the blood as much as 10-fold does not significantly accelerate the blood flow. The urea excretion increases 10-fold, but the increase is due to the fact that the proportion of blood urea removed during perfusion of the kidney remains constant, so that the amount removed per liter of blood passing through the kidneys rises in proportion to the amount present in the blood. This explains the manner in which the blood urea clearance is kept constant during wide fluctuations in blood urea content. The proportion of oxygen removed from the blood by the kidney is rather low, 10 to 20% of the arterial oxygen content as a rule.

Blood reaction and respiration.

Experimental and clinical observations indicate that when the respiratory mechanism is normal, increase in alkaline reserve is only partially compensated by increase in CO2 tension, so that increase in pH also occurs. In the same way decrease in alkaline reserve is accompanied by decrease in pH. There is a decrease in CO2 tension but not sufficient to prevent pH change. The usual percentage change in hydrion concentration is about twice that in CO2 tension. The arterial CO2 tension is kept normally between 35 to 45 mm., which is a much narrower range than would be necessitated for the maintenance of normal pH. The conception of the CO2 tension as a factor physiologically important only from its relationship to blood pH is not consistent with these facts. When conditions force the organism to choose between change in CO2 tension and change in pH it tends to compromise between the two, and acts in a manner to indicate that maintenance of normal CO2 tension is in itself an important factor.

The cause of low plasma protein concentration in nephritis

The reduction in concentration of plasma proteins observed in a considerable proportion of nephritic patients has been attributed by some authors to a decrease in the amount of plasma proteins in the body, by others to a dilution of the blood with water (hydremic plethora). We have made one or more determinations of the blood volume by Keith, Rowntree, and Geraghtys “Vital Red” method on all but three of the patients above reported with reduced plasma protein concentration, and on some others. The cause of the reduced protein concentration was found to be not hydremic plethora, but an actual decrease in the amount of plasma proteins in the body. Normal blood volumes were found, even in cases of extreme edema. The amount of total plasma proteins per kilo body weight (the weight being corrected as nearly as possible for estimated edema fluid present) however, varied from 1.5 to 3.0 grams, compared with 3.5 grams found in normal individuals.

Blood changes in ether anesthesia

During light ether anesthesia the bicarbonate content of the arterial blood falls, the carbon dioxide tension (determined directly by the tonometric method on the blood) rises, as does the hydrogen ion concentration. These phenomena indicate a state of uncompensated acidosis. The oxygen saturation increases, indicating that ventilation is accelerated in response to the stimulus of increased carbon dioxide tension. The acceleration does not, however, as under normal conditions, reach the height necessary to keep CO2 tension and hydrogen ion concentration down to normal limits. It therefore appears that even in light etherization the respiratory center is markedly deadened. In deep etherization the carbon dioxide tension rises still higher (over 80 mm. has been observed) and the PH may fall to below 7.2. Respiration not only fails to be accelerated in response to the increased CO2 tension but may even be so retarded that the oxygen saturation of the arterial blood falls below that normally found in venous. The blood tends to become concentrated. Conductivity and chloride determinations on the serum indicate only minute changes. The only striking electrolyte changes appear to be the increase in hydrogen ions and the replacement of part of the bicarbonate HCO3 anions by the anions of acids as yet unidentified.

The excretion of urea

The excretion rate of urea in normal men increases directly as the blood urea concentration, and as the square root of the volume of urine, so long as the latter remains within ordinary limits, under about 5 liters per day. These relations are expressed in the formula, D representing the rate of urea excretion, calculated as grams per 24 hours, B the blood urea concentration (grams per liter), V the rate of urine excretion, calculated as liters per 24 hours. When the size of the individual (W = weight in kilos) is introduced the equation becomes , or . K = 7.5 ± 3 for normal individuals. When deficiency of the urea-excreting function is present K has a lower value. Increase in volume output beyond the rate of about 200 c.c. per hour, or 5 liters per 24 hours, ceases to accelerate urea excretion, so that for volumes of V in excess of 5, the figure 5 may be inserted in place of the actual V. The above formula gives more consistent results than that of Ambard, which assumes erroneously that the excretion rate increases as the square rather than the first power of the blood urea; and correlates the excretion with the concentration of the urea in the urine rather than with the volume of the urine. In calculating the rate of urine and urea output from short time periods, errors occasionally occur from failure completely to empty the bladder at either the beginning or end of the period. Such errors may be reduced by basing the output calculations on the creatinine content of the sample, rather than the time over which it is collected, since Shaffer has shown the hourly creatinine output to be constant throughout the 24 hours, e.g., if the creatinine content of the sample analyzed is 1/20 of the individuals known daily creatinine output, the urea and volume output are calculated to a 24-hour basis by multi-plying by 20.

Gravimetric determination of beta-oxybutyric acid

If beta-oxybutyric acid is oxidized with dichromate in the presence of sulfuric acid and mercuric sulfate, a precipitate of the acetone compound of mercury sulfate can be obtained in an amount proportional to the beta-oxybutyric present. Thus, if 175 c.c. of a beta-oxybutyric solution containing 9 per cent. of sulfuric acid, 2 per cent. of mercuric sulfate, and 0.25 gram of potassium dichromate are boiled under a reflex for an hour, 7.7 milligrams of mercury-acetone compound are precipitated for each milligram of beta-oxybutyric acid present. The beta-oxybutyric acid may vary from 1 to 9 mg. without affecting the ratio, if the concentrations of the other reagents are kept constant.