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Biomedical subjects

A Amery

Publications and source records attributed to A Amery.

At least 145 records · Page 8Linked to original sources
PubMed1989

Effect of endurance training on blood pressure at rest, during exercise and during 24 hours in sedentary men.

The effect of 4 months of physical training on resting, exercise and 24-hour blood pressure (BP) was studied using a randomized crossover design in 26 healthy, sedentary men, with an average age of 39 +/- 10 (standard deviation) years. Peak oxygen uptake increased by 14% (p less than 0.001) and the physical working capacity at a heart rate of 130 beats/min by 25% (p less than 0.001). The heart rate was reduced by 7 beats/min at night (p less than 0.01) and by 6 beats/min during the day (p less than 0.001). Training-induced changes of BP varied according to measuring conditions. A decrease in BP at rest while sitting in the morning in the laboratory was significant for diastolic (-5 mm Hg, p less than 0.01) but not for systolic BP. During exercise, systolic BP was significantly lower after training, when measured at the same submaximal workloads. However, when workload was expressed as a percentage of peak oxygen uptake, systolic BP was not different before and after training. When measured during 24 hours, the training-induced change in BP was not significant at night either for systolic or diastolic BP. During the day the decrease in diastolic BP was significant (-5 mm Hg, p less than 0.001), but the change in systolic BP was not.

Adult↗
PubMed1989

Humoral and cellular effects of the K(+)-channel activator cromakalim in man.

The effect of cromakalim, a K(+)-channel activator, on the plasma renin-angiotensin-aldosterone system, catecholamines and alpha-atrial natriuretic peptide, and on the intraerythrocyte concentration and transmembrane fluxes of Na+ and K+ has been investigated in 18 normal male subjects, in a double-blind parallel study. After a run-in period on placebo for 1 week, the subjects were treated either with placebo (n = 6) or cromakalim (n = 12) for 1 week. Plasma renin activity was significantly increased during cromakalim. No effect of cromakalim on plasma angiotensin II, aldosterone, adrenaline, noradrenaline and alpha-atrial natriuretic peptide was demonstrated. The intra-erythrocyte K+ concentration was decreased during cromakalim administration and Ca2(+)-dependent K(+)-channels in red blood cells were increased.

Adult↗
PubMed1989

Plasma atrial natriuretic peptide and the renin-aldosterone system during long-term administration of the diuretic xipamide in man.

We have studied the effect of xipamide on plasma alpha-atrial natriuretic peptide and the renin-aldosterone-kallikrein system in twelve healthy men, using a double-blind cross-over design. After a run-in period on placebo for 1 week the subjects were treated with either placebo (n = 6) or xipamide 20 mg once daily (n = 6) for 16 weeks and were then switched to the alternative medication for another 16 weeks. The plasma concentration of alpha-atrial natriuretic peptide fell after 1 week of xipamide administration and increased during prolonged xipamide administration but remained suppressed. The changes in plasma alpha-ANP observed after 1 week of xipamide were negatively correlated with the changes in haematocrit and haemoglobin. Plasma renin activity (PRA), aldosterone concentration (PAC), and urinary excretion of aldosterone and kallikrein increased after 1 week of xipamide administration, levelled off during the second and fourth weeks, but remained elevated during further prolonged xipamide administration for 16 weeks. The xipamide-induced changes in PRA and PAC were positively correlated with the changes in the haematocrit and haemoglobin. Our data suggest that the changes in plasma renin, aldosterone, and alpha-atrial natriuretic peptide during xipamide administration may be related to diuretic-induced volume contraction.

Aldosterone↗
PubMed1989

Acute calcium entry blockade inhibits the blood pressure but not the hormonal responses to angiotensin II.

The effects of acute calcium entry blockade by isradipine (IS) and placebo (P) on the haemodynamic and humoral responses to angiotensin II (A II) have been compared in two groups of 9 patients with essential hypertension. During 4 sequential periods each of 20 min, an i.v. infusion of A II 0, 2, 4 and 8 ng.kg-1.min-1 was given before (control) and 30 min after the oral administration either of IS or P. After IS, both the blood pressure and the angiotensin II-induced pressor effect were significantly reduced. Isradipine increased the heart rate and this cardio-acceleration was potentiated by A II. In contrast, when A II was infused in the absence of IS, heart rate tended to decrease. IS stimulated plasma renin activity and reduced plasma aldosterone. However, it did not affect either the inhibition of plasma renin activity or the rise in plasma aldosterone in response to A II. In conclusion, acute calcium entry blockade in patients with essential hypertension reduces the pressor response to A II, but not the A II-induced inhibition of renin and increase in plasma aldosterone.

Adrenocorticotropic Hormone↗
PubMed1989

Effect of prolonged physical exercise on intra-erythrocyte and plasma potassium.

The intracellular concentrations of sodium [Na+] and potassium [K+] and the water content in human erythrocytes were investigated in 21 male runners before and after a marathon. From 2 to 5 min after the race, the intra-erythrocyte [K+] was significantly decreased (p less than 0.001) by 7% whereas the plasma [K+], intra-erythrocyte [Na+] and the erythrocyte water content were unchanged. The change in the intra-erythrocyte [K+] observed immediately after the marathon, was negatively correlated with the race time (r = -0.44; p less than 0.05). Furthermore, the change in the plasma [K+] (r = -0.64; p less than 0.001) and the amount of K+ excreted in the urine during the race (r = 0.54; p less than 0.05) were also, respectively, negatively and positively correlated with the race time. It is concluded that during prolonged physical exercise the erythrocytes could serve as a kind of K+ reservoir that is drained with increasing magnitude of body K+ loss. This might explain why in the faster marathon runners, in whom the urinary K+ loss is smaller and the K+ intake is greater than in the slower runners during race, the intra-erythrocyte [K+] is unchanged after a marathon whereas in the slower runners it is decreased.

Adult↗
PubMed1989

Carotid baroreflex sensitivity at rest and during exercise is not influenced by opioid receptor antagonism.

Physical effort involves, along with an increase in the plasma concentration of beta-endorphin, profound cardiovascular adaptations. The aim of the present study was to investigate with the use of the variable neck chamber technique, the influence of the endogenous opioids on the carotid baroreflex control of blood pressure and heart rate at rest as well as during exercise. Ten normal volunteers exercised in the supine position up to 33% and 66% of their maximal exercise capacity and received, in a randomized double-blind cross-over protocol, either saline or naloxone (10 mg intravenously, followed by a continuous infusion of 10 mg.h-1). During exercise a progressive attenuation of the carotid baroreceptor reflex control of blood pressure and heart rate was noted. However, neither at rest nor during exercise, did opioid antagonism influence the carotid baroreceptor control of blood pressure and heart rate. Intra-arterial pressure and heart rate also remained unaffected. In contrast, both at rest and during exercise, naloxone administration produced a significant increase in the plasma concentration of cortisol. The latter suggests that in vivo the opioid receptors were effectively antagonized. In conclusion the present study confirms that opioids play only a minor role in cardiovascular homeostasis at rest. In addition, this study demonstrates that they are not involved in the cardiovascular adaptation to exercise, nor in the exercise-related attenuation of the carotid baroreceptor control of pressure and heart rate.

Adult↗
PubMed1989

Left ventricular dynamics during exercise in elite marathon runners.

To assess left ventricular structure and function at rest and during exercise in endurance athletes, 10 elite marathon runners, aged 28 to 37 years, and 10 matched nonathletes were studied by echocardiography and supine bicycle ergometry. Each athlete's best marathon time was less than 2 h 16 min. Echocardiography was performed at rest, at a 60 W work load and at an individually adjusted work load, at which heart rate was 110 beats/min (physical working capacity 110 [PWC110]). Oxygen uptake at PWC110 averaged (+/- SD) 1.14 +/- 0.2 liters/min in the nonathletes and 2.0 +/- 0.2 liters/min in the runners (p less than 0.001). The left ventricular internal diameter at end-diastole was similar at the three activity levels in the control subjects but increased significantly from rest to exercise in the runners (p less than 0.001). Left ventricular systolic meridional wall stress remained unchanged during exercise in the nonathletes but was significantly higher at PWC110 in the athletes (p less than 0.05). Both the systolic peak velocity of posterior wall endocardial displacement and fractional shortening of the left ventricular internal diameter increased with exercise; at PWC110 the endocardial peak velocity was higher in the runners than in the control subjects (p less than 0.01). The endocardial peak velocity during relaxation was comparable in athletes and control subjects at rest, increased similarly at a 60 W work load, but was higher in the runners at PWC110 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Body weight, sodium intake and blood pressure.

The aim of the present review is to examine the evidence that blood pressure may be reduced and hypertension prevented by decreasing body weight and sodium consumption. Cross-sectional and longitudinal population studies, and intervention studies in individual subjects, suggest that hypertension can be prevented by avoiding excessive weight. Children and adolescents should particularly avoid becoming overweight as this is strongly associated with hypertension in adult life. In contrast, the hypothesis that hypertension might be reduced by restricting sodium intake is less convincing. Moreover, the amount of sodium restriction needed to significantly reduce blood pressure might make it a less practical preventative measure in the struggle against hypertension than weight loss.

Blood Pressure↗
PubMed1989

Changes in potassium content and membrane potassium channels in circulating cells from normal volunteers treated with cromakalim.

The effect of cromakalim, a K+-channel activator, on the intracellular concentration and transmembrane fluxes of Na+ and K+, was studied in 18 normal male subjects, using a double-blind parallel study design. After a run-in period on placebo for 1 week the subjects were treated with either placebo (n = 6) or cromakalim (n = 12) for 1 week. Blood pressure was not changed during cromakalim administration in these normal male subjects but heart rate was increased. The intraerythrocyte and intraleucocyte K+ concentration was decreased during cromakalim administration while the Ca2+-dependent K+ channels in the red blood cells were increased. No significant effect of cromakalim could be demonstrated on the intracellular Na+ and Mg2+ concentration, on the ouabain-sensitive or bumetanide-sensitive 86Rb uptake and on the maximal 3H-ouabain binding in erythrocytes and leucocytes. The red cell Na+Li+ countertransport, anion carrier and ground membrane leak of Na+ and K+ were also not changed in the cromakalim-treated subjects.

Adult↗
PubMed1989

Effects of the new calcium entry blocker isradipine (PN 200-110) in essential hypertension.

In this double-blind cross-over study 16 patients with mild-to-moderate hypertension were treated with placebo and the dihydropyridine derivative, isradipine 5-10 mg twice daily. In the supine position isradipine reduced systolic (-18 mm Hg; p less than 0.002) and diastolic (-15 mm Hg; p less than 0.001) pressures, while heart rate was not changed; in the standing position, systolic (-15 mm Hg; p less than 0.002) and diastolic (-14 mm Hg; p less than 0.001) pressures decreased, whereas heart rate increased (+6 bpm; p less than 0.05). Body weight and lower leg volumes remained unaltered, suggesting that isradipine did not cause fluid retention. On IS plasma angiotensin I (+40 pg/ml), angiotensin II (+ 14 pg/ml), and aldosterone (+4.1 ng/dl) rose. The intracellular Na+ and K+ concentrations and the transmembrane cation transport activities (Na+-K+ pump, Na+-K+ cotransport, Na+-Li+ countertransport), measured ex vivo in the erythrocytes of eight male patients, were not significantly influenced by isradipine. Hot flushes and facial erythema occurred more frequently (p less than 0.05) on isradipine than on placebo. In conclusion, the new calcium entry blocker isradipine at a dose of 5-10 mg twice daily lowers blood pressure and is well tolerated in most patients with essential hypertension.

Blood Pressure↗
PubMed1989

Long-term double-blind comparison of doxazosin and atenolol in patients with mild to moderate hypertension.

The antihypertensive effect and safety of doxazosin once daily as well as the effect on serum lipids was compared with that of atenolol once daily in 40 patients with mild to moderate hypertension. During the first 4 weeks, all patients received placebo therapy. During the subsequent 46 weeks, patients were randomized to doxazosin or atenolol treatment. Treatment was initiated with 1 mg doxazosin or 50 mg atenolol once daily. The dose could be doubled biweekly for 10 weeks until a final dose of 16 mg doxazosin or 100 mg atenolol was reached. The patients then entered the maintenance phase for 36 weeks. The average final dose of doxazosin was 9.2 +/- 1.3 (SEM) mg and that of atenolol was 76.5 +/- 6.2 mg. During the 46 weeks of active treatment, the recumbent diastolic blood pressure (DBP) tended to be lower (p less than 0.05) in patients receiving atenolol at 10, 12, and 22 weeks of treatment. Recumbent systolic BP (SBP) and standing SBP and DBP were not different, however, between patients receiving doxazosin and those receiving atenolol. Recumbent and standing heart rate (HR) were lower (p less than 0.01) during atenolol. The decrease in serum total triglycerides, total cholesterol, and low-density lipoprotein (LDL)-cholesterol after 46 weeks of doxazosin was different (p less than 0.05) from the changes observed during atenolol therapy. Our data indicate that the antihypertensive action of doxazosin is accompanied by favorable effects on serum lipids.

Adult↗
PubMed1989

Effect of verapamil on systemic and brachial artery hemodynamics in normal humans: comparison with effect of atenolol.

To clarify the hemodynamic effects of verapamil, we investigated in normal volunteers the effects of 4-day treatment with verapamil (240 mg/day) on left ventricular function and on systemic and brachial artery haemodynamics, in comparison with the effects of placebo and atenolol (100 mg/day). Left ventricular structure and function was evaluated by echocardiography, systemic hemodynamics were assessed by pulsed Doppler velocimetry of the ascending aorta, and brachial artery hemodynamics were assessed pulsed Doppler velocimetry of the brachial artery. Verapamil decreased systemic and brachial artery vascular resistance (p less than 0.05), increased cardiac output (CO, p less than 0.01) and brachial flow (p = 0.054), and did not affect blood pressure (BP) and heart rate (HR). In contrast, atenolol decreased BP, HR, and CO (p less than 0.001) but did not significantly affect brachial flow and systemic and brachial artery vascular resistance. We conclude that short-term administration of verapamil in normal humans produces systemic and brachial artery vasodilatation, with a reflex increase of stroke volume but not of HR.

Adult↗
PubMed1989

Isolated systolic blood pressure elevation in the elderly: mechanisms, risk, and the need for further studies.

Isolated systolic hypertension (ISH) is generally defined as a systolic pressure of 160 mm Hg or more, with a diastolic pressure cutoff point below 95 mm Hg in some studies and 90 mm Hg in others. Its prevalence and incidence vary from 3 to 30% depending on the definition applied, methodology of measurement, as well as the population and the age and sex of the patient. Mechanisms that could lead to the development of isolated systolic hypertension are discussed, especially the role of atherosclerosis. The risks of systolic hypertension on mortality and morbidity in the elderly are considered. The need for further studies to quantify the risk and the effect of treatment is emphasized. The Syst-Eur trial enters patients above the age of 60 years with a diastolic pressure below 95 mm Hg and a systolic of 160 mm Hg or more. The study is a double-blind, placebo-controlled trial and the main purpose is to examine the influence of ISH on morbidity, mortality, and general well-being. Investigation of blood pressure variation over 24 h and its relationship to morbidity and use for planning treatment will be incorporated. Other centers are invited to join in the enlarging project.

Adult↗
PubMed1989

Percutaneous transluminal renal angioplasty and renal function.

Renal function was studied before and after percutaneous transluminal renal angioplasty (PTRA) in 79 patients. In a prospective study of 28 patients with unilateral renal artery stenosis, renal function was similar during angiotensin-converting enzyme (ACE) inhibition and after PTRA. In 37 patients with bilateral renal artery stenoses, 9 patients with solitary kidneys and renal artery stenoses and 5 patients with transplant renal artery stenoses, there was no statistical difference in the renal function before and after PTRA. Of the 79 patients studied, 50 had normal renal function before PTRA. In 5 of these renal function decreased, requiring temporary hemodialysis in 1. Of 29 patients with impairment of renal function due to renal artery stenosis, improvement was noted in 14, stabilization of renal function in 11, and decrease of renal function in 4. It is concluded that PTRA is a safe technique that can make life-long drug treatment unnecessary in antihypertensive patients. It can restore or stabilize renal function in renal insufficiency caused by renal artery stenosis. It has to be kept in mind that contrast medium toxicity and cholesterol embolization can induce severe renal insufficiency after PTRA.

Angioplasty, Balloon↗
PubMed1989

Percutaneous transluminal renal angioplasty versus renovascular surgery: statistical, medical and economical considerations.

Retro- and prospective comparative studies in patients with renal artery stenosis demonstrate that technical results and blood pressure improvement after renovascular surgery or percutaneous transluminal renal angioplasty (PTRA) are strictly comparable. The lesser invasive character of PTRA together with its lower complication rate and the lower cost explain why PTRA is the method of choice in the treatment of renal artery stenosis, with less restrictive selection criteria than used for surgery.

Angioplasty, Balloon↗
PubMed1989

Converting enzyme inhibitors in the treatment of elderly hypertensives.

Angiotensin-converting enzyme inhibitors are gaining acceptance as safe and effective agents for treatment of hypertension. Addressed in this review of the available literature are the questions whether they are effective in lowering blood pressure in the elderly, whether their effects are age-related, and what effects, if any, do they have on morbidity and mortality in geriatric hypertension.

Aged↗
PubMed1989

Erythrocyte sodium and potassium transport systems during longterm administration of the diuretic xipamide in men.

The effects of xipamide on the intracellular concentration and transmembrane fluxes of Na+ and K+ were studied in twenty-four normal sodium-replete or -deplete male subjects, using a double-blind study design. After a run-in period on placebo for 1 week on their regular diet, subjects were treated on their regular diet or on a low-sodium diet with either placebo or xipamide 20 mg once a day for 16 weeks. Intra-erythrocyte Na+ concentration was increased during xipamide administration in sodium-replete and deplete subjects, while intra-erythrocyte K+ and total intraleukocyte Ca2+ concentrations were decreased. Red cell Na+, K+-cotransport activity was lower in xipamide-treated subjects, while Na+, Li-countertransport activity was increased. No significant effect of xipamide could be demonstrated on ouabain-sensitive 86Rb-uptake or on maximal [3H]-ouabain binding in erythrocytes.

Adult↗