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Biomedical subjects

P Weidmann

Publications and source records attributed to P Weidmann.

At least 253 records · Page 14Linked to original sources
PubMed1980

Effects of chronic alpha and beta adrenoceptor blockade with labetalol on plasma catecholamines and renal function in hypertension.

Plasma catecholamines and renal function were evaluated in 18 patients with essential hypertension treated with the alpha and beta adrenoceptor blocking agent, labetalol. Following 6 weeks of labetalol therapy, blood levels of epinephrine and norepinephrine remained unaltered. Glomerular filtration rate and renal plasma flow were decreased similarly by about 20% (P less than 0.025). Tubular rejection fraction of sodium was increased by 36% (P less than 0.001) while sodium excretion was comparable to control conditions. Labetalol's potential to cause a mild reduction in kidney function should be considered, but may have no clinical consequences in most hypertensive patients receiving such treatment. The lack of increased plasma catecholamine levels during therapy supports the concept that labetalol's alpha-blocking potential is limited to post-junctional receptors, leaving the prejunctional feedback control of catecholamine release intact. Moreover, labetalol's blood pressure-lowering mechanism may be largely independent of changes in sympathetic nervous activity.

Adult↗
PubMed1980

Increased serum low-density lipoprotein cholesterol in men treated short-term with the diuretic chlorthalidone.

The effect of the diuretic chlorthalidone (100 mg/day for 6 weeks) on serum lipoproteins was evaluated in 37 subjects. In 19 men with essential hypertension (aged 41 +/- 3 yr), 8 normal men (26 +/- 3 yr), or all of these men considered together, chlorthalidone significantly increased serum low density lipoprotein--cholesterol (LDL-C) by 20% (p less than 0.05 to less than 0.01). There was also a tendency for increased LDL-C in seven postmenopausal women (+/- 15%) but not in three premenopausal women with essential hypertension. High density lipoprotein--cholesterol was not significantly changed in hypertensive women or normal men and decreased slightly (p less than 0.05) in hypertensive men. Apolipoproteins A-I, A-II, and B were not changed significantly in women or men. Diuretic-induced lipoprotein alterations were not associated with altered plasma volume and unrelated to variations in serum potassium, glucose, insulin levels, blood pressure, and body weight. Short-term diuretic therapy with chlorthalidone may increase serum LDL-C in young or middle-aged men with normal or high blood pressure.

Adolescent↗
PubMed1980

Role of sympathetic nerve inhibition and body sodium-volume state in the antihypertensive action of clonidine in essential hypertension.

A simultaneous analysis of the interrelationships between mean blood pressure (MBP), plasma catecholamines, plasma renin activity (PRA) and aldosterone, exchangeable body sodium, and blood volume was carried out before and after acute and chronic administration of clonidine in 15 patients with essential hypertension, in order to further elucidate the mechanism(s) of action of this drug. After a single oral dose of 200 microgram, clonidine produced a significant fall in MBP, heart rate, plasma norepinephrine (NE), PRA, and aldosterone. There were significant correlations (P < 0.01) between NE and MBP, but not between PRA or aldosterone and MBP both before and after the ingestion of clonidine. Furthermore, there was a significant correlation (P < 0.05) between the magnitude of fall of plasma NE and change in MBP. After 6 weeks of treatment, conidine at a dose of 960 +/- 80 microgram/day produced a significant decrement in MBP and NE, but not in PRA and aldosterone; with upright posture, the magnitude of the fall in MBP was significantly greater (P < 0.01), and the rise in plasma NE was significantly smaller (P < 0.01) after chronic clonidine treatment. There was also a significant fall (P < 0.01) in exchangeable sodium and plasma volume. The data provide evidence that inhibition of the sympathetic nervous system by clonidine plays a major role and that the decrease in exchangeable body sodium and blood volume after chronic treatment may contribute to the antihypertensive action of the drug.

Adult↗
PubMed1980

Role of haemodynamics, catecholamines and renin in acute hypercalcaemic hypertension in man.

1. The effect of acute hypercalcaemia on blood pressure, blood volume, haemodynamic indices, plasma catecholamines, renin and aldosterone levels was investigated in 10 patients. 2. Calcium infusion (15 mg/kg over 3 h) increased (P < 0.05) plasma calcium and adrenaline levels, blood pressure, total peripheral resistance and packed cell volume. Plasma volume was decreased, and heart rate, cardiac output and plasma renin, aldosterone or dopamine levels were not significantly changed. Plasma noradrenaline was increased only minimally after 3 h of calcium infusion. 3. Mean blood pressure before and during calcium infusion correlated with concomitant serum calcium (r = 0.39; P < 0.02) or adrenaline levels (r = 0.57; P < 0.01); changes in blood pressure correlated with variations in plasma adrenaline (r = 0.68; P < 0.001). 4. Acute hypercalcaemic hypertension is mediated by an increase in peripheral vascular resistance and may be induced by a direct effect of calcium on blood vessels. The calcium-mediated increase in adrenaline release may play a contributory, and plasma volume contraction an inhibitory, role.

Adult↗
PubMed1980

Relationships between sodium clearance, plasma renin activity, plasma aldosterone, renal hemodynamics and blood pressure in essential hypertension.

Renal hemodynamics, plasma renin activity (PRA), plasma aldosterone (PA) and sodium excretion were studied in essential hypertension. PAH clearance (CPAH) and glomerular filtration rate (GFR) were normal or increased in early hypertension and depressed at later stages, especially in malignant cases. The PAH extraction ratio was depressed only in patients with low CPAH values. CPAH did not correlate inversely with blood pressure in benign hypertension. Later reexamination of untreated patients revealed a decrease in CPAH, but no further increase in blood pressure. Antihypertensive treatment prevented the decrease in CPAH. Patients with essential hypertension showed no abnormality in basal sodium excretion, plasma aldosterone, plasma renin activity and the sodium:aldosterone relationship. Basal sodium clearance did not correlate with GFR and the fractional sodium excretion was not pressure-dependent. When clearance determinations and measurements of PA and PRA were performed simultaneously under standardized conditions, PA and PRA were correlated inversely with CPAH and GFR. There was no relationship between PA or PRA and the blood pressure. Unless a defective release of renal prostaglandins and/or kinins could be shown to be responsible for the increase in systemic blood pressure, there is no evidence for a primary renal disturbance in essential hypertension.

Aldosterone↗
PubMed1980

Influence of 1,25 dihydroxycholecalciferol on sexual dysfunction and related endocrine parameters in patiens on maintenance hemodialysis.

It has been postulated that hyperparahyroidism is in part responsible for sexual dysfunction in dialyzed patients and that this could improved by 1,25(Oh)2D3. In a single blind study patients on maintenance hemodialysis were treated after a control period with 1,25 (OH)2D3 and with placebo in random order. Sexual performance was assessed with a detailed semistructured psychiatric interview protocol in 14 and several endocrine parameters were analyzed in 15 patients. Under control conditions sexual function was disturbed in 11/14 patients. Plasma testosterone was moderately decreased in men, PRL and PTH levels were distinctly elevated in both sexes. 1,25(OH)2D3 raised serum calcium levels significantly from 9.6 to10.6 mg/100 ml ( P < 0.01) and lowered PTh from 1.39 to 0.82 ng/ml ( P < 0.01). However, no improvement in sexual function (such as libido, frequency of intercourse or masturbation) was found, and apart from a slight rise of testosterone in men and moderate fall of PRl in men and women endocrine parameters remained unchanged. It is concluded that in spite of an improvement of secondary hyperparathyroidism, treatment with 1,25(OH)2D3 for 2 to 4 months was of no value in improving sexual dysfunction in these hemodialysis patients.

Adult↗
PubMed1979

Interrelationships between sodium clearance, plasma aldosterone, plasma renin activity, renal hemodynamics and blood pressure in renal disease.

This study was designed to evaluate the role of aldosterone, glomerular filtration and blood pressure on sodium excretion in renal disease. Sodium clearance (CNa), plasma aldosterone (PA), plasma renin activity (PRA), glomerular filtration rate (GF), paraaminohippurate clearance (CPAH) and blood pressure were measured simultaneously in 19 normal subjects, 38 patients with benign essential hypertension, 3 with renal artery stenosis, 48 with chronic glomerulonephritis, 20 with the nephrotic syndrome, 24 with tubulo-interstitial disease and 21 with a renal homograft. CNa was significantly depressed in patients with the nephrotic syndrome. Mean PA and PRA were increased in renal artery stenosis but within the normal range in other groups. CNa correlated inversely with PA in all groups but one (tubulo-interstitial disease). CNa correlated directly with GF in the nephrotic syndrome and with the mean blood pressure (mBP) in chronic glomerulonephritis and tubulo-interstitial disease. PA correlated directly with PRA and inversely with GF or CPAH in most groups. It is concluded that PA is an important determinant of the basal natriuresis in renal disease with the exception of tubulo-interstitial nephropathies. In the nephrotic syndrome sodium retention is largely determined by the interaction of PA and GF. In chronic nephropathies, but not in benign essential hypertension, the fractional sodium excretion is partly blood pressure-dependent. Impairment of renal function is often accompanied by a rise in PA.

Adolescent↗
PubMed1979

[Acute combined alpha- and beta-adrenergic blockade in essential hypertension: effects on blood pressure, renal function, renin, and aldosterone].

In seven patients with uncomplicated essential hypertension the effects of an acute alpha-adrenergic blockade, alone and combined with a chronic beta-adrenergic blockade, on blood pressure, renal function as measured by standard clearance methods, plasma renin activity, and plasma aldosterone were evaluated. Acute alpha-adrenergic blockade with phentolamine (20 mg by intravenous infusion) significantly enhanced the antihypertensive effect of chronic beta-adrenergic blockade with slow-oxprenolol (160 mg/ day X 14 days) (- 14.5% verus - 7.4% for pulse pressure, - 12.4% versus - 6.0% for diastolic pressure, 2 alpha less than 0.05). Under combined adrenergic blockade renal plasma flow increased, glomerular filtration rate and filtration fraction decreased (2 alpha less than 0.05 each), whereas the fractional clearances of sodium, potassium, free water, and solute load remained unchanged. The activation of the renin-angiotensin-axis, elicited by alpha-adrenergic blockade alone, was suppressed by the preceding beta-adrenergic blockade. These findings demonstrate a favourable antihypertensive action of a combined blockade of alpha- und beta-adrenergic receptor sites without untoward side effects on renal function or the renin-angiotensin-axis.

Adult↗
PubMed1979

Evaluation of autonomic neuropathy in diabetes mellitus. Comparison of clinical, functional and biochemical parameters.

Quantitative assessment of signs or symptoms of neuropathy, and the beat-to-beat variation, valsalva, orthostasis, handgrip and cold pressor tests, and measurements of plasma renin and catecholamine excretion rate were performed in 23 diabetic patients and 10 age-matched normal subjects. Significant inverse correlations were found between the clinical score and the beat-to-beat variation (a test of efferent vagus function) (r=-0.55, -0.72, P less than 0.0005) or the pressor response to handgrip (possible test of efferent sympathetic integrity (r=p less than 0.005) or the values of both tests combined (r=-0.79, P less than 0.0005); but not with the other measured parameters. Beat-to-beat variation was abnormal in all 9 diabetics with increased and in 9 of 14 with normal clinical score, whereas only seven and one patient from these subgroups, respectively, had an abnormal Valsalva ratio. The pressor response to handgrip was only slightly reduced in the diabetic patients, with greater tendency in those with abnormal clinical score. Additional possible indices of adrenergic dysfunction such as the pressor response to cold stimulus, plasma renin levels and noradrenaline or adrenaline excretion rates did not differ significantly between normal subjects and diabetics. These finding demonstrate a greater prevalence of parasympathetic as compared to sympathetic impairment in diabetic autonomic neuropathy; the beat-to-beat variation was the most sensitive among the tests used. An assessment of clinical evidence combined with non-invasive functional procedures such as the beat-to-beat variation and handgrip tests provide a valuable and easy to perform tool in the evaluation of diabetic neuropathy.

Adult↗
PubMed1979

[The effect of diuretic therapy on serum lipoproteins: an undesirable effect?].

The effect of diuretics on serum lipids and lipoproteins was evaluated in 23 patients with essential hypertension treated with chlorthalidone for six weeks. Compared to placebo conditions, diuretic therapy significantly increased serum beta (+8%, p less than 0.05) or low-density-lipoprotein (LP) cholesterol (+17%, p less than 0.025). Since alpha-LP or high-density-LP cholesterol was unchanged or tended to decrease slightly, there was also an increase in the beta/alpha-LP (+26%, p less than 0.025) or low/high-density-LP cholesterol (21%, p less than 0.025) ratio. Serum cholesterol (+4%), triglycerides (+3%), phospholipids and the Apo-LP A-I, A-II and B were not changed significantly. Blood pressure and plasma potassium were decreased (p less than 0.01), blood volume and serum insulin were not changed significantly, and serum glucose was increased mildly. Plasma renin, aldosterone and norepinephrine levels rose significantly (p less than 0.05), while circulating epinephrine was unaltered. Alterations in LP were not related to variations in blood pressure, blood volume, plasma electrolytes or serum glucose or insulin; and they did not correlate with chlorthalidone-induced increases in plasma renin, aldosterone or norepinephrine. Treatment with certain diuretics may have an adverse influence on lipoprotein metabolism.

Adolescent↗