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170 results on '"Humphreys, M. H"'

4. Role of distal reabsorption and peritubular environment in glomerulotubular balance.

Author

Schrier, R. W and Humphreys, M. H

Subjects
Biosciences
Abstract

Total kidney glomerulotubular balance was examined during aortic constriction and release in saline-loaded dogs and in dogs undergoing water diuresis. Aortic constriction lowered the glomerular filtration rate by 45% in both groups, and glomerulotubular balance, as judged by changes in absolute sodium reabsorption, was also comparable. During water diuresis, a linear relationship was observed between free water clearance and urine flow during all maneuvers, suggesting that distal sodium reabsorption is related primarily to distal delivery. The results suggest that if alterations in the peritubular environment are responsible for the changes in tubular sodium reabsorption during aortic constriction in the saline- or water-loaded dog, then a change in renal plasma flow, and presumably delivery rate of oncotic force, may be the most likely mediator.

Published
1972

5. Role of cardiac output and the autonomic nervous system in the antinatriuretic response to acute constriction of the thoracic superior vena cava.

Author

Schrier, R. W, Humphreys, M. H, and Ufferman, R. C

Subjects
Biosciences
Abstract

Study of the differential characteristics of hepatic congestion and decreased cardiac output in terms of potential afferent stimuli in the antinatriuretic effect of acute thoracic inferior vena cava (TIVC) constriction. An attempt is made to see if the autonomic nervous system is involved in the antinatriuretic effect of acute TIVC or thoracic superior vena cava constriction.

Published
1971

6. Factors involved in the antinatriuretic effects of acute constriction of the thoracic and abdominal inferior vena cava.

Author

Schrier, R. W and Humphreys, M. H

Subjects
Biosciences
Abstract

Study of the antinatriuretic effect of acute thoracic inferior vena cava (TIVC) constriction in the absence of alterations in renal perfusion pressure. A comparison is made of the effects of equivalent degrees of TIVC and abdominal inferior vena cava constriction on arterial pressure, renal hemodynamics, and electrolyte excretion.

Published
1971

36. Acquired hyperoxaluria with regional enteritis after ileal resection. Role of dietary oxalate.

Author

Stauffer, John Q., Humphreys, Michael H., Weir, G. John, Stauffer, J Q, Humphreys, M H, and Weir, G J

Subjects
OXALATES, ILEUM diseases, INFLAMMATORY bowel diseases, DIARRHEA, DIET, CROHN'S disease, ILEOSTOMY, OXALIC acid, CHOLESTYRAMINE
Abstract

Focuses on a study that measured urinary oxalate excretion in several patients with inflammatory bowel disease involving the terminal ileum. Patients and methods; Results; Discussion.

Published
1973
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37. The Relationship between Sodium Excretion and Renin Secretion by the Perfused Kidney1

Author

Humphreys, M. H., Reid, I. A., Ufferman, R. C., Lieberman, R. A., and Earley, L. E.

Abstract

The effect of altered tubular sodium reabsorption on renin secretion (RSR) was examined under conditions in which other factors influencing renin release could be controlled or excluded. To do this, isolated canine kidneys were perfused at constant pressure with blood circulating from donor animals. Volume expansion or hemorrhage of the donor dogs produced large changes in the animal's blood pressure, renal function, sodium excretion (UNaV), and RSR, but were without effect on renal hemodynamics, UNaV, or RSR in the perfused kidney. Hemodilution without volume expansion, resulted in hypotension, decreased UNaV and increased RSR in the donor dogs, and increased UNaV and suppressed RSR in the perfused kidney. These effects of hemodilution in the perfused kidney were partially reversed when plasma protein concentration was restored to control levels with hyperoncotic albumin, and, overall, there was a significant inverse relationship between electrolyte excretion and RSR. These results provide new evidence for the hypothesis that the rate at which sodium is delivered to the macula densa is an important determinant of the rate of renin secretion.

Published
1975
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39. Modulation of ANP-dependent effects of endothelin by inhibitors of neutral endopeptidase and cGMP phosphodiesterase.

Author

Valentin, J P, Qiu, C, Wiedemann, E, Gardner, D G, and Humphreys, M H

Abstract

Endothelin 3 (ET3) infusion increases the concentration of atrial natriuretic peptide (ANP) in plasma, which in turn raises hematocrit (Hct) through a transcapillary shift of plasma fluid and proteins into the interstitium, thereby reducing plasma volume (PV). The level of ANP bioactivity in peripheral target tissues is a function of ANP secretory rate and the turnover rate of ANP and its intracellular effector mechanisms. Neutral endopeptidase (NEP) is a widely distributed enzyme that participates in ANP catabolism, whereas cGMP-phosphodiesterase (PDE) degrades the intracellular second messenger of ANP. Therefore, we examined the consequences of inhibition of NEP and PDE on the ANP-dependent activity described above using the NEP inhibitor SQ 28,603 and the cGMP-PDE inhibitor zaprinast (M&B 22,948). In anesthetized, bilaterally nephrectomized rats, infusion of SQ 28,603 alone reduced mean arterial pressure (MAP) by 2.5 +/- 0.5% and increased Hct by 4.6 +/- 0.3% (P < .01 for both), leading to a calculated decrease in PV of 7.5 +/- 0.6%. These changes were prevented by pretreatment with rabbit anti-rat ANP antiserum. Simultaneous infusion of ET3 (25 ng/kg/min) and SQ 28,603 caused MAP to increase by 12.8 +/- 2.2%, an effect identical with that observed after ET3 alone (12.7 +/- 2.3%), whereas the increase in Hct of 9.4 +/- 0.4% was greater (P < .05) than the 7.5 +/- 0.4% increase seen with ET3 alone. ET3 increased plasma ANP concentration (599 +/- 135 vs. 108 +/- 13 pg/ml in vehicle-infused rats; P < .0001); ET3 and SQ 28,603 infused simultaneously increased plasma ANP even further (810 +/- 166 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Published
1995

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