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Biomedical subjects

M H Maxwell

Publications and source records attributed to M H Maxwell.

At least 145 records · Page 8Linked to original sources
PubMed1975

Effect on aging on plasma renin and aldosterone in normal man.

The influence of aging on the renin-angiotensin-aldosterone system was evaluated by comparing young (20 to 30 yr) with elderly (62 to 70 yr) healthy subjects. Despite comparable body sodium-fluid balance in the two age groups, serum renin concentration, plasma renin activity and aldosterone concentrations were lower in the elderly. The age-related decreases in circulating renin and aldosterone concentrations were slight while subjects were supine and receiving normal sodium intake; when upright and during sodium depletion, they were more pronounced. Inverse renin-blood pressure interrelations were noted during two of four study conditions involving normal sodium intake or mild sodium depletion (r = --0.44 and --0.47, respectively), but not during progressive sodium depletion. Plasma renin levels were decreased in the elderly regardless of the presence or absence of an inverse relationship with blood pressure. Aldosterone and cortisol responses to corticotropin infusion were unaltered in the elderly. It is concluded that aging may cause a decrease in circulating renin, with parallel lowering of plasma aldosterone concentrations.

Adrenocorticotropic Hormone↗
PubMed1975

Control of aldosterone responsiveness in terminal renal failure.

Control of aldosterone responsiveness in terminal renal failure. Plasma aldosterone concentration in 30 hemodialysis patients correlated closely with renin concentration, renin activity or renin and potassium concentrations combined (r is greater than or equal to 0.62; P is less than 0.01), and increased consistently in response to upright posture or corticotropin administration. Aldosterone response to hemodialysis was variable. Significant correlations (r is greater than or equal to 0.65; P is less than 0.01) were demonstrated between postural plasma aldosterone and renin responses, between aldosterone responses to corticotropin and basal plasma aldosterone or renin and potassium values, between hemodialysis-induced changes in plasma aldosterone and those in potassium or renin; but not between various indexes of heparin treatment and aldosterone activity. Bilateral nephrectomy reduced basal plasma renin and aldosterone concentrations and aldosterone responsiveness in five preoperatively normoreninemic or hyperreninemic patients, but not in a hyporeninemic patient. These results demonstrate the complementary roles of circulating renin and potassium in the control of aldosterone release under basal and stimulatory conditions in patients with terminal renal failure. Administration of heparin in dosages used during long-term hemodialysis does not appear to significantly interfere with aldosterone control.

Adrenocorticotropic Hormone↗
PubMed1975

Dietary management of patients in chronic renal failure.

A new oral amino acid preparation was given to two groups of patients: group 1, five patients on hemodialysis; and group 2, five patients with chronic renal failure (CRF). In group 1 significant pre- and postdiet changes were: BUN 93-37 mg% (p smaller than 0.01); creatinine 13.0-9.7 mg% (p smaller than 0.001); phosphorus 6.6-4.2 mg% (p smaller than 0.05); uric acid 8.7-6.0 mg% (p smaller than 0.01); CO2 16.3-21.3 mEq/I (p smaller than 0.01); hematocrit 18.0-20.8% (p smaller than 0.05). In group 2: BUN 93-66 mg% (p smaller than 0.05); phosphorus 5.6-3.8 mg% (p smaller than 0.05); hematocrit 27.3-30.7% (p smaller than 0.05). Nitrogen balance was positive in all patients. It is concluded that this oral amino acid mixture is well-tolerated and can be utilized in CRF to attain protein anabolism.

Acid-Base Equilibrium↗
PubMed1975

Role of the renin-angiotensin-aldosterone system in the regulation of plasma potassium in chronic renal disease.

The relationship between plasma potassium concentration and the renin-angiotensin-aldosterone system was evaluated in ten patients with chronic renal failure (creatinine clearance 10-56 ml/min). Under basal conditions and following various stimulation maneuvers, normokalemic patients demonstrated normal plasma renin and aldosterone levels. Five of six patients with hyperkalemia had diminished function of the renin-angiotensin-aldosterone system; their ability to conserve sodium during salt depletion was less than that of normokalemic patients. The data suggest that the maintenance of plasma potassium levels in these patients is dependent of the presence of a normally functioning renin-angiotensin-aldosterone system; aldosterone activity may be an important determinant of sodium conservation in patients with renal failure.

Adrenocorticotropic Hormone↗
PubMed1975

Renal vein renin: value and limitations in the prediction of operative results.

Renal vein renin determinations, in contrast to isolated peripheral venous renin determinations, provide great help in the selection of patients who can benefit from an operation for renal hypertension. Patients with essential hypertension usually have renal vein renin ratios, larger/smaller, close to unity, but the available cumulative data show that, statistically, ratios as large as 2.0 may occur in this group (95 per cent confidence limits). In patients with unilateral stenosis of a main renal artery, large renal vein renin ratios (stenotic/normal) have been followed by operative success in more than 90 per cent of patients. However, many operative successes have also been achieved in patients without a large renal vein renin ratio. This may be explained by inaccurate renal vein catheterization, inactive renin secretion, nonsimultaneous sampling, assay variability, and problems related to bilateral or segmental lesions. Recent refinements in the interpretation of renal vein renin data (contralateral suppression, ipsilateral hypersecretion in absolute terms, and a combination analysis scoring system) appear to increase the accuracy of the test. Detailed anatomic information, provided by arteriography, is essential for proper interpretation of renal vein renin data.

Angiography↗
PubMed1975

Renal vein renin in essential hypertension.

A frequency distribution curve and interval percentages of variations in right versus left renal vein renin (RVR) were calculated from 227 sets of renin data from patients with mild and moderate essential hypertension (EH). A renal vein renin ratio (RVRR), large/small, of approximately 2.0 or more falls beyond the 95 per cent confidence interval, and may therefore by considered to be abnormal. Although assay variability and sampling errors may contribute to artifactually large RVRR's in EH, they usually indicate true disparity, probably secondary to asymmetrical nephrosclerosis. Recent hypotheses regarding diagnostic value of RVR in hypertension are evaluated in light of data yielded by this investigation. Simultaneous and/or replicate sampling should reduced within-patient variability and improve clinical interpretation of test results.

Adult↗
PubMed1975

Effects of prazosin on renal function and fluid-electrolyte metabolism.

This study was designed to determine the effects on renal function and fluid-electrolyte metabolism of prazosin administered intravenously in a single dose and administered orally in a single dose and in multiple doses to patients with essential hypertension. The results indicate that clinically effective doses of prazosin do not observably alter parameters of kidney function. No side effects were reported by patients, all of whom followed the medication schedule as prescribed (adherence was confirmed by measurement of blood levels of the agent).

Administration, Oral↗