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Biomedical subjects

D W Seldin

Publications and source records attributed to D W Seldin.

At least 91 records · Page 5Linked to original sources
PubMed1972

Effect of variation in dietary NaCl intake on the intrarenal distribution of plasma flow in the rat.

The effect of dietary variation in sodium chloride intake on the intrarenal distribution of plasma flow was investigated in rats using the antiglomerular basement membrane antibody technique. Rats were placed on a liquid diet containing either 9.86 (n = 9) or 0 (n = 9) mEq NaCl/daily portion for 2 wk. Labeled antibody was injected and the diets were reversed. After an additional 2 wk period, antibody labeled with a different radionuclide was injected and the animals were sacrificed. Fractional plasma flow distribution was then calculated for each dietary period. No change in flow to any cortical region could be detected. In six additional awake rats on identical dietary regimen, total plasma flow was estimated by the clearance of hippuran-(131)I. No change in this parameter occurred with changes in NaCl intake. We conclude, therefore, that no change in either total renal plasma flow or intracortical distribution of plasma flow occurs with wide variations in dietary sodium chloride intake in the rat. The implications of this constancy of regional plasma flow are discussed with reference to presumed concomitant alterations in the intrarenal distribution of nephron filtration rate.

Animals↗
PubMed1971

Angiotensin II in arterial and renal venous plasma and renal lymph in the dog.

Angiotensin II was determined by radioimmunoassay in systemic arterial, pulmonary arterial, and renal venous plasma and in renal hilar lymph in dogs. Levels of the peptide were determined prior to and during progressive graded hemorrhage or reduction in renal perfusion pressure. Levels of angiotensin II in plasma consistently rose during transit through the lung indicating pulmonary conversion of angiotensin I to angiotensin II. On the other hand, angiotensin II in the renal vein plasma was less than that in arterial plasma indicating renal extraction of the peptide from plasma. When renal hilar lymph was sampled under similar conditions, angiotensin II in lymph was consistently higher than that in arterial or renal venous plasma. Furthermore, in some experiments angiotensin II in lymph increased at a time when the concentration in plasma was undetectable. No evidence was found to indicate that angiotensin II in plasma entered renal lymph. It was concluded that angiotensin II levels in lymph reflected the concentration of angiotensin II in renal tissue. The data further suggested that angiotensin II is partially removed from arterial plasma by hydrolysis during transit through the kidney.

Angiotensin II↗
PubMed1971

Resting transmembrane potential difference of skeletal muscle in normal subjects and severely ill patients.

The resting membrane potential difference (Em) of skeletal muscle was measured in 26 normal human subjects, 7 patients with mild illness, and 21 patients with severe, debilitating medical disorders. A closed transcutaneous approach to the muscle was made by needle puncture and the Em was measured utilizing standard Ling electrodes. Measurements revealed an Em of -88 +/-3.8 mv in healthy subjects and -89 +/-2.1 mv in patients hospitalized for minor medical problems. The mean Em in 21 in-hospital patients, judged to be severely ill clinically from a variety of causes, was -66.3 +/-9.0 mv. Open deltoid muscle biopsies were performed in 7 of the healthy subjects and in 13 of the severely ill group. Estimation of the intra-extracellular water partition was made by calculating the chloride space from the previously measured Em. Analysis of the muscle samples revealed no significant difference in the intra-extracellular potassium ratios of the two groups biopsied. Intracellular Na(+) concentrations were uniformly increased in the muscle samples of the severely ill subjects and averaged 42.3% higher than those of the normal subjects. The mechanisms which might account for the elevation of intracellular Na(+) and a depression of Em independent of changes in intra-extracellular K(+) ratios are discussed and it is suggested that this defect may be a generalized cellular abnormality which is a common quality of serious illnesses.

Adult↗
PubMed1971

Effect of saline infusions on intrarenal distribution of glomerular filtrate and proximal reabsorption in the dog.

The effect of acute extracellular volume expansion with saline on the intrarenal distribution of glomerular filtrate, was studied in dogs utilizing micropuncture techniques in which samples were obtained by both recollection and from new tubules. Recollection was examined in seven dogs during continuous hydropenia and in five dogs during continuous saline diuresis. Recollection was associated with an increase in nephron flow rate of 8% during hydropenia and 27% during saline diuresis. In addition, during continuous saline diuresis, shortened transit times and lowered intratubular pressures were recorded in previously punctured tubules. Despite increased tubular flow, fractional reabsorption was unchanged. Nephron glomerular filtration rates (gfr) were measured during hydropenia and then after acute volume expansion in 10 dogs. In the repunctured tubules gfr rose 38% more than total glomerular filtration rate (GFR). In contrast, when new tubules were punctured during volume expansion, nephron gfr and total GFR changed proportionately. The disproportionate rise in nephron gfr after volume expansion noted with the recollection technique appears to be artifactual when contrasted to micropuncture of new tubules. With acute volume expansion, fractional reabsorption decreased 15% in recollected samples and 16% in newly sampled tubules. Increased nephron gfr cannot account for the fall in fractional reabsorption. It is concluded that in dogs, saline diuresis is not associated with redistribution of filtrate from deep to superficial nephrons, and that the fall in proximal fractional reabsorption is caused by diminished absolute reabsorption.

Animals↗
PubMed1971

Effective glomerular filtration pressure and single nephron filtration rate during hydropenia, elevated ureteral pressure, and acute volume expansion with isotonic saline.

Free-flow and stop-flow intratubular pressures were measured in rats with an improved Gertz technique using Landis micropipets or a Kulite microtransducer. In hydropenia, average single nephron glomerular filtration rate was 29.3 nl/min, glomerular hydrostatic pressure (stop-flow pressure + plasma colloid osmotic pressure) was 70 cm H(2)O and mean glomerular effective filtration pressure was 12.7-14.3 cm H(2)O, approaching zero at the efferent end of the glomerulus. Thus, the glomerulus is extremely permeable, having a filtration coefficient four to five times greater than previously estimated. Mean effective filtration pressure and single nephron glomerular filtartion rate fell with elevated ureteral pressure and rose with volume expansion, more or less proportionately. Changes in effective filtration pressure were due primarily to increased intratubular pressure in ureteral obstruction and to reduced plasma colloid osmotic pressure in volume expansion; glomerular hydrostatic pressure remained constant in both conditions and thus played no role in regulation of filtration rate.

Animals↗
PubMed1968

Demonstration of a hormonal inhibitor of proximal tubular reabsorption during expansion of extracellular volume with isotonic saline.

Evidence for the elaboration of a hormonal inhibitor of renal tubular reabsorption in response to expansion of extracellular fluid volume was obtained by examining the effects of plasma from rats and dogs undergoing saline diuresis on the rate of proximal tubular reabsorption measured both directly by micropuncture techniques and indirectly by clearance techniques. Intravenous infusion of plasma from salineloaded rats and dogs, but not plasma from control animals, inhibited the intrinsic reabsorptive capacity of the proximal tubule (as estimated from the shrinking-drop technique) by 35%, and reduced fractional reabsorption (as estimated from the tubular fluid-to-plasma ratio) by 20%. In addition the natriuretic plasma increased urine flow, solute-free water clearance, and potassium excretion in rats with hereditary diabetes insipidus, indicating an increase in the delivery of filtrate out of the proximal tubule to the more distal diluting segments of the nephron. The hormonal inhibition of proximal tubular reabsorption had an extremely rapid onset of action (within seconds after instillation into the tubular lumen) and a short duration of action (less than 30 min after cessation of an intravenous infusion). Inhibitory activity was lost from natriuretic plasma upon dialysis and could be recovered in the dialysate. Dialysates of natriuretic plasma, when injected directly into the tubular lumen, also inhibited proximal reabsorption, indicating an action on the luminal side of the cell.

Absorption↗