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Biomedical subjects

P Hamet

Publications and source records attributed to P Hamet.

At least 289 records · Page 16Linked to original sources
PubMed1975

Studies of the elevated extracellular concentration of cyclic AMP in uremic man.

This study was designed to elucidate the mechanism of elevation of plasma cyclic AMP in uremic man. Plasma cyclic AMP was measured in 15 normal subjects and in 18 patients with severe renal failure. In some members from both groups the kinetic parameters of the metabolism of extracellular cyclic AMP were measured. Plasma cyclic AMP was elevated from 23 nM in control subjects to 59 nM in uremic patients, regardless of the presence or absence of the kidneys or parathyroid glands. A single pass of uremic blood through a Kiil hemodialyzer decreased plasma cyclic AMP from 58 to 30 nM. The clearance of cyclic AMP by the dialyzer correlated directly with the blood flow passing through the machine. Hemodialysis for 6 h decreased plasma cyclic AMP levels in the systemic circulation by only 12%. Studies with tritiated cyclic AMP revealed a plasma clearance rate of 624 ml/min in normal subjects and of 344 ml/min in patients with uremia. Such a large decrease in plasma clearance rate cannot be explained by a failure of urinary excretion of cyclic AMP and suggests impairment of "metabolic clearance." In addition, the "plasms production rate" of cyclic AMP was 65% higher in patients with renal failure than in normal subjects. It is concluded that the elevation of plasma cyclic AMP in uremic man is due to a combination of: (a) lack of urinary excretion, (b) decreases metabolic clearance, and (c) increased production of plasma cyclic AMP.

Adult↗
PubMed1975

Labile (borderline) hypertension--new aspects of a common disorder.

Labile hypertension in patients under 50 years of age (the non-atherosclerotic form) was found to be characterized by higher urinary excretion of catecholamines and particularly of homovanillic acid; when further analyzed it was shown to be a heterogeneous entity with two types of patients clinically and biochemically distinguishable from each other, from control subjects and from patients with stable hypertension. Reactivity to assuming an upright posture distinguishes one type of labile hypertension having a normal postural pulse rate response from another having an excessive postural increase in pulse rate. The first group also showed normal responses of plasma norepinephrine concentration and of urinary cyclic AMP to posture. The group with excessive pulse rate response, in contrast, showed a decrease in plasma norepinephrine and an excessive increase of urinary cyclic AMP excretion in response to upright posture. The results suggest that not only circulating catecholamines but also the reactivity of their target tissues (as probably reflected by cyclic AMP measurements) are important in bringing about signs of adrenergic excess. The hypothesis that cyclic AMP changes reflect beta-adrenergic receptor reactivity is strongly favoured by data indicating qualitative differences in cyclic AMP responses to beta-adrenergic stimulation or inhibition between control subjects and those labile hypertensive patients with clinical signs of excessive sympathetic reactivity. The study stresses the need for more precise definition of labile hypertension, for dynamic clinical and biochemical correlative studies, and for consideration not only of the circulating hormones but also of the "second messengers" (such as cyclic AMP and cyclic GMP) which reflect the cellular action of hormones. Blood pressure is a very labile parameter in health and disease. In one sense, therefore, hypertension can be considered "labile" in every hypertensive patient. Usually, however, labile (or borderline) hypertension is regarded as characterized by a blood pressure over 140/90 mmHg, falling below these values with physical and emotional rest. This clinical entity, which affects some 20% (variously estimated between 16 and 30%) of the adult population, gives rise to uncertainties in both definition and prognosis. In some patients labile hypertension represents the precursor of a fixed hypertensive state, whereas in many others it remains labile throughout life, never progressing to the stable phase nor becoming associated with hypertensive cardiovascular disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Catecholamines↗
PubMed1975

Urinary and plasma cyclic adenosine 3',5'-monophosphate in patients with idiopathic edema.

Urinary excretion and plasma concentrations of adenosine 3',5'-monophosphate were determined in idiopathic edema patients both at rest and after assumption of the upright position. Patients and normal subjects responded similarly to upright posture with decreases in urinary volume and creatine excretion and their urinary excretion of cyclic AMP was not significantly different. The plasma concentration of cyclic AMP was high in patients, both in the recumbent and upright positions, and its renal clearance (unlike that of creatinine) was low. Plasma cyclic AMP increased in response to upright posture both in patients and normal subjects. Even if the significance of elevated plasma cyclic AMP is unknown, its presence without an increase in urinary cyclic AMP suggests that the renal handling of cyclic AMP is abnormal is idiopathic edema; this may be related to an excessive beta-adrenergic tone.

Adult↗
PubMed1974

Plasma adenosine 3',5'-cyclic monophosphate in human hypertension.

In a previous study we observed an increase in urinary cyclic AMP in labile hypertension in the upright position and during isoproterenol infusion, in contrast to a decrease in control subjects. In the present study we measured the plasma level of cyclic AMP in control subjects and patients with various types of hypertension. We obtained the following results: (1) plasma cyclic AMP increases in response to upright posture in control subjects and hypertensive patients; (2) values of cyclic AMP in the recumbent and upright positions are comparable in control subjects and patients with essential hypertension, but are significantly higher in those with true renovascular hypertension due to bilateral renal artery stenosis; (3) propranolol inhibits the increase of plasma cyclic AMP in response to posture in control subjects, but has an opposite effect in labile hypertension where there is a further increase; (4) the rise in blood pressure in pheochromocytoma is associated with a considerable increase in plasma cyclic AMP.Present and previous data suggest that kidney handling of cyclic AMP is abnormal in hypertension, and that the specific defect may be related to the type of hypertension.

Adolescent↗
PubMed1973

Effect of propranolol on cyclic AMP excretion and plasma renin activity in labile essentrial hypertension.

Labile hypertension is often associated with elevated cardiac output, increased plasma renin activity (PRA) and urinary cyclic AMP excretion in response to upright posture and to isoproterenol. The beta-blocking agent propranolol was demonstrated to be an effective therapeutic agent in this condition. The effect of posture on cyclic AMP, PRA, pulse rate and blood pressure was therefore studied during the administration of propranolol and a placebo in patients with labile hypertension. With the patient on placebo, upright posture induced an increase in pulse rate, cyclic AMP excretion and PRA. Propranolol administration decreased the recumbent and upright blood pressures, pulse rate and PRA. Cyclic AMP excretion remained unchanged in the recumbent position but the postural increase was abolished. No appreciable changes in catecholamine excretion occurred during propranolol administration. Propranolol normalizes some humoral as well as hemodynamic abnormalities of labile hypertension and therefore may be of benefit in long-term treatment and possibly also in the prevention of stable hypertension.

Adolescent↗
PubMedDate not supplied

Gene-environment interactions in hypertension.

Environmental factors such as stress, diet, and physical activity have long been recognized as playing an important role in the pathogenesis of essential hypertension. Individuals may vary in their response to these factors depending on differences in genes determining physiologic systems that mediate the response. In this article we discuss gene-environment interactions that contribute to the development of essential hypertension (environmental susceptibility to hypertension) and those that are involved in control of the disease (pharmacogenetics).

Animals↗
PubMedDate not supplied

Hypertension in hyperthyroidism: is there an epinephrine connection?

Since hypertension seen in euthyroid subjects with depressed conjugated epinephrine and moderately elevated free epinephrine in plasma is strikingly similar to the beta-hyperadrenergic, high-output hypertension seen in some hyperthyroid patients, the possibility is discussed that thyroid action on sulfoconjugation could affect the biodisposability of endogenous free E and so indirectly the manifestation of sympathetic hyperactivity. There is only circumstantial evidence for such a possibility at present. Differences in the conjugation system may be operative in dealing with endogenous as well as exogenous catecholamines. If the latter are used in evaluating the adrenergic receptor reactivity, this may result in incorrect dose-response curves if the concentrations of catecholamines remaining free following infusion are not monitored. The conjugation of catecholamines, E in particular, is a variable which has to be taken account of in the investigation of catecholamine-like manifestation of T3 and T4 excess and in the evaluation of adrenergic influences on thyroid function.

Blood Pressure↗
PubMedDate not supplied

Hormone receptor abnormalities in adrenal Cushing's syndrome.

Cortisol secretion in ACTH-independent primary adrenal Cushing's syndromes was previously believed to be autonomous. In most cases, the pathophysiology of the disease was largely unknown. However, recent work by our group and others have shown that these cortisol-producing adrenocortical tumors may be under the control of inappropriate, illicit or ectopic hormone receptors. This review provides a rapid overview of the physiology of the normal adrenal cortex and outlines recent findings supporting the hypothesis that cortisol production may be regulated by a diversity of abnormal or ectopic hormone receptors in primary adrenal Cushing's syndrome.

Adrenal Gland Diseases↗
PubMedDate not supplied

Labetalol in essential hypertension.

Labetalol is an orally active adrenoreceptor-blocking drug which is a competitive antagonist of both alpha- and beta-adrenoreceptor sites. Thirty patients with essential hypertension were admitted to the study. The mean of initial systolic and diastolic blood pressures of these patients was 160/101 +/- 3/1 supine and 155/104 +/- 3/1 mm Hg standing, and the mean blood pressures at the end of the 16 week trial was 142/90 +/- 4/2 supine and 131/91 +/- 3/2 mm Hg standing. The average dose of labetalol was 546 mg: eight patients received a dose of 300 mg, seven a dose of 600 mg, six a dose f 900 mg, and two a dose of 1,200 mg. The patients who needed the highest doses of labetalol had an initial lowering of their blood pressures followed by a gradual increase despite the higher doses of labetalol. There was no significant change in the mean peripheral renin activity value. Side effects were reported by 18 of the 30 patients, but only 1 patient withdrew for this reason. Two patients were considered to be treatment failures. Overall, labetalol was found to be an effective antihypertensive agent in 15 patients.

Adult↗