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Biomedical subjects

L G Welt

Publications and source records attributed to L G Welt.

At least 19 recordsLinked to original sources
PubMed1975

Arginase activity of human erythrocyte ghosts in uremia.

Arginase activity of erythrocyte membrane fragments has been determined in normal subjects and in two groups of uremic patients: 1) those having a blood urea concentration of 100 mgm/100 ml or higher and with an elevated erythrocyte sodium concentration and 2) patients with a blood urea concentration of 100 mgm/100 ml and higher and a normal erythrocyte sodium concentration. No statistically significant difference was detected between the normal subjects and the uremic patients. It is concluded, therefore, that the effect of uremia on the magnesium dependant, Na and K activated adenosine triphosphatase of erythrocyte membranes is not applicable to all enzymes of the erythrocyte.

Arginase↗
PubMed1975

Dissociation of Na-K-ATPase specific activity and net reabsorption of sodium.

Prevoius studies have suggested that the increase in specific activity of Na-K-ATPase in renal tissue during treatment with glucocorticoids occurred as a result of aconcurrent rise in net tubular reabsorption of sodium. Since recent data have indicated a specific effect of glucocortiocoids on epithelial cells, experiments were performed to determine whether enzyme activity and net sodium reabsorption could be dissociated. Evidence is provided demonstrating that base-line specific activity of Na-K-ATPase in rat renal cortex and outer medulla does not correlate directly with net sodium reabsorption since enzyme activity did not change after a chronic reduction in glomerularfiltration rate and the rate of sodium reabsorption. Further studies showed a markedrise in Na-K-ATPase after 4 days of treatment with methylprednisolone despite a fall in sodium absorption. These results suggest a direct effect of glucocorticoids onrenal Na-K-ATPase and illistrate the difficulty in assigning a transport role tothis enzyme from the correlation of specific activity with rates of net electrolyte transport.

Adenosine Triphosphatases↗
PubMed1974

Intracellular potassium. A determinant of the sodium-potassium pump rate.

Normal human red cells which have had their intracellular sodium (Na(c)) reduced have a diminished Na-K pump rate, but only if intracellular potassium (K(c)) is high. If most of the K(c) is replaced by tetramethylammonium or choline, both ouabain-sensitive Na efflux and K influx are significantly increased even with Na(c) below normal. Cells with reduced Na(c) and high K(c) have an unchanged Na efflux if external potassium (K(ext)) is removed. In contrast, low-Na, low-K cells have a large ouabain-sensitive Na efflux which shows a normal response to removal of K(ext). Neither low-K nor high-K cells have an altered ouabain-sensitive K efflux. Measurement at constant low Na(c) and varying K(c) shows the pump Na efflux to be an inverse function of K(c). Thus, in low-Na cells, K(c) appears to act as an inhibitor of the pump. Inhibition by high K(c) can be seen even when Na(c) is normal. The effects attributed to K(c) are distinguished experimentally from other variables such as cell volume, adenosine triphosphate concentration, effects of the replacement cations, and the method used to alter intracellular cation concentrations. A role is proposed for K(c), in cooperation with Na(c), in regulating the pump rate of normal human red cells.

Adenosine Triphosphate↗
PubMed1968

Red-cell transport defect in patients with cystic fibrosis and in their parents.

The ouabain-sensitive and the ethacrynic acid-sensitive sodium efflux from erythrocytes of patients with cystic fibrosis are both decreased. Furthermore, the ouabain-sensitive adenosine triphosphatase activity is diminished in the red blood cell ghosts of these patients. Perhaps of greater significance is the fact that ethacrynic acid-sensitive sodium efflux is clearly diminished in the erythrocytes of the asymptomatic parents of these sick children. This defect in sodium transport may be valuable for detecting the heterozygous carrier state.

Adenosine Triphosphatases↗