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C W SHEPPARD

Publications and source records attributed to C W SHEPPARD.

29 records · Page 2Linked to original sources
PubMed1951

Cation exchange between cells and plasma of mammalian blood. II. Sodium and potassium exchange in the sheep, dog, cow, and man and the effect of varying the plasma potassium concentration.

Sodium and potassium exchange has been studied in the blood of the sheep, dog, cow, and man. The potassium exchange rate in human cells is practically unaltered by increasing the plasma potassium concentration approximately threefold. Comparing the results in different species the exchange rate for potassium shows a rough correlation with the intracellular amount of the element. Expressed in per cent of the cellular content sodium tends to exchange more rapidly than potassium. In three instances the specific activity curves deviate from the simple exponential behavior of a two compartment system. In the exchange of potassium in canine blood the deviation is caused by the presence of a rapidly exchanging fraction in the buffy coat cells. Such an effect does not account for the inhomogeneity of sodium exchange in human blood.

Animals↗
PubMed1951

Cation exchange in mammalian erythrocytes. III. The prolytic effect of x-rays on human cells.

Freshly drawn heparinized human whole blood is exposed to x-rays in amounts up to 54,000 r in vitro and then equilibrated under a controlled atmosphere at 24 or 38 degrees C. For as long as 26 hours following exposure, potassium is progressively lost from the cells and quantitatively replaced by sodium with little, if any, osmotic disturbance. The mean rate of loss at 20,000 r and 24 degrees C. is about 0.4 per cent of the initial cell potassium per hour and approximately doubles for a 20,000 r increase. It is accentuated if blood is stored at low temperature (5 degrees C.) following radiation exposure. Isotope experiments show that the rate of entrance of potassium into the cells is practically unaltered, the principal effect being an acceleration of the rate from cells to plasma. This suggests that radiation may have interfered with a mechanism of selective potassium accumulation based on preferential retention of the element. The sodium which enters the cells following irradiation contributes to the rapidly exchanging portion of the cellular sodium, suggesting that this fraction is ionic sodium.

Animals↗
PubMed1950

Cation exchange between cells and plasma of mammalian blood; methods and application to potassium exchange in human blood.

The exchange of potassium between cells and plasma of heparinized human blood has been studied in vitro using the radioactive isotope K(42). The changes in cell and plasma specific activity are characteristic of a simple two-compartment system. The mean of seven determinations of the exchange rate at 38 degrees C. is 1.8 per cent of the cellular potassium per hour. The results indicate that at 38 degrees C. the rate is relatively insensitive to oxygenation or reduction of the hemoglobin, and to 1200 r of gamma radiation. With varying temperature the rate follows pseudo first order kinetics with a Q(10) of 2.35. Below 15 degrees C. the rate of loss of potassium exceeds the rate of uptake.

Animals↗