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Biomedical subjects

J F Giudicelli

Publications and source records attributed to J F Giudicelli.

At least 19 recordsLinked to original sources
PubMed1992

Differential effects of nitrovasodilators, K(+)-channel openers, and nicorandil on large and small coronary arteries in conscious dogs.

When administered intravenously to conscious dogs, nicorandil, nitrovasodilators (nitroglycerin and SIN-1), and the K(+)-channel opener cromakalim exhibited marked differential effects on large epicardial and small resistance coronary arteries. Nitrovasodilators markedly increased the left circumflex coronary artery diameter at doses at which coronary resistance was not significantly decreased. In contrast, both cromakalim and nicorandil dilated large and small coronary arteries in the same conditions. When coronary blood flow was held to its control value by partial inflation of a hydraulic occluder implanted around the artery, the nitroglycerin- and nicorandil-induced increases in large coronary diameter remained unchanged whereas the response to cromakalim was reduced significantly. This coronary dynamic profile indicates that both nitrovasodilators and nicorandil directly dilate large coronary vessels, whereas the effect of cromakalim on these vessels is mediated partially through a flow-dependent mechanism. This suggests that nicorandil mainly dilates large coronary arteries through its nitroglycerin-like properties, whereas its ability to dilate coronary resistance vessels depends mainly on its K(+)-channel opener-like properties.

Animals↗
PubMed1992

Effects of an angiotensin converting enzyme inhibitor, ramipril, on intracranial circulation in healthy volunteers. off.

1. The effects of a single oral dose (10 mg) of ramipril on (a) systemic haemodynamics (arterial pressure, cardiac output), (b) carotid artery haemodynamics (blood flow and diameter, pulsed Doppler technique), (c) intracranial haemodynamics (middle cerebral artery mean blood velocity, transcranial Doppler technique), and (d) renin-angiotensin system (plasma converting enzyme and renin activities) have been investigated and compared with those of a placebo during the 24 h period following administration in a randomized, double-blind and cross-over study performed in six healthy volunteers. 2. Ramipril induced a strong and sustained inhibition of plasma converting enzyme activity (-96% at 4 h, -63% at 24 h) and an increase in plasma renin activity (+993% at 8 h). 3. As compared with placebo, ramipril did not significantly affect arterial blood pressure, heart rate, cardiac output and total peripheral resistance. 4. Ramipril significantly increased carotid blood flow (by 27% at 8 h) without significantly changing carotid artery diameter, indicating, given the unchanged arterial pressure, an arteriolar vasodilation in the carotid territory. 5. The middle cerebral artery mean blood flow velocity underwent spontaneous modifications during the placebo period but these changes were not affected by ramipril. This lack of influence of ramipril on intracranial haemodynamics suggests that the drug-induced arteriolar vasodilation and increase in carotid blood flow only concern the extracranial, musculo-cutaneous part of the carotid territory.

Blood Flow Velocity↗
PubMed1979

The role of beta-adrenoceptors in coronary blood flow distribution in normal and ischemic canine myocardium.

beta-Adrenoceptor agonists increase myocardial ischemic injury, mainly by elevating myocardial oxygen consumption. Moreover, it has been shown that isoprenaline may "steal" regional myocardial blood flow (RMBF) from ischemic to non ischemic areas and from epicardium to endocardium. The mechanisms of these two isoprenaline-induced redistributions of RMBF have been investigated by the use of radioactive microspheres in an experimental model of canine myocardial ischemia with simultaneous measurement of ST-segment elevation. Isoprenaline increased RMBF in both epi- and endocardial non ischemic areas and in epicardial ischemic areas, leading to a significant decrease in the endo/epi ratio. After atenolol, isoprenaline still increased RMBF but to a lesser extent and the endo/epi ratio was still decreased. Salbutamol, in doses inducing no significant changes in cardiac parameters or myocardial oxygen consumption, produced effects similar to those of isoprenaline. These results indicate a non-homogeneous beta2-stimulation-induced vasodilation in endo- and epicardium, which might be due either to the higher epicardial coronary vasocilatory reserve or to a heterogeneous distribution of transmural beta2-adrenoceptors. Isoprenaline also decreased the ischemic/non ischemic total blood flow ratio (I/NI) and caused further increases in ST-segment elevation. These effects were abolished by atenolol pretreatment, indicating the deleterious effects of isoprenaline-induced tachycardia in this I/NI decrease and in the ischemic injury.

Albuterol↗
PubMed1979

[Biological determination of the beta blocking activity of human serum].

A method of biological assessment of the Beta blocking activity of human serum is reported. It is based on the catecholamine response of rat myocardial cells in culture, incubated in the serum to be tested. Its advantage is that it takes into account all block-blocking substances present in the serum, not only the drug itself but also its possible active metabolites. The results obtained by this method in 10 healthy subjects after 60 mg penbutolol were compared with those given by chemical dosage and ergometry. The ergometric and biological changes were parallel from the 2nd and the 8th hour while the serum levels of the drug rapidly. This discordance could be due to the presence of an active metabolite, 4-hydroxy-penbutolol.

Adrenergic beta-Antagonists↗
PubMed1978

Chronic atenolol treatment and hypertension development in spontaneously hypertensive rats.

Changes in systolic blood pressure (SBP), heart rate (HR), heart rate and plasma renin concentration (PRC) have been compared in three different groups of rats between the ages of 5 and 20 weeks. The groups were: spontaneously hypertensive rats (SHRs), atenolol-treated SHRs (200 mg/kg/day orally throughout the 15 weeks) and normotensive rats of the same strain (WKYs). Treatment with atenolol markedly inhibited the onset of genetic hypertension, reduced HR and PRC from the outset and diminished the heart weight/body weight ratio. Comparison of changes in these parameters in atenolol-treated SHRs, control SHRs and WKYs strongly suggests that the mechanism of atenolol's preventive action against hypertension development in SHRs primarily involves its effects on heart and on the renin--angiotensin system.

Animals↗
PubMed1978

Clazepam: pharmacokinetics and effects on performance.

1. The effects of clazepam, a new benzodiazepine (30 mg orally) on performance tests and the cardiovascular system have been compared to those of chlordiazepoxide (30 mg orally) and a placebo in a double-blind trial involving six healthy volunteers. Simultaneously, the pharmacokinetics of clazepam were investigated. 2. While clazepam itself could be detected neither in plasma nor in urine, it gave rise to two plasma metabolites, the former, an alcoholic derivative with a short half-life, and the second, desmethyldiazepam, with a long half-life. These two metabolites and oxazepam were excreted in urine and, within the 24 h period following drug intake, accounted for 73% of the ingested dose. 3. Seven hours after its administration, clazepam slightly improved performance and reduced anxiety. The kinetics of these effects and the metabolic data suggest that clazepam acts mainly through the formation of desmethyldiazepam. However, owing to the low blood levels of this metabolite, the activity of clazepam was very moderate.

Adult↗
PubMed1978

Beta adrenergic blockade, regional left ventricular blood flow and ST-segment elevation in canine experimental myocardial ischemia.

The effects of dl-propranolol, d-propranolol, dl-pindolol and dl-practolol on regional myocardial blood flow (assessed by means of tracer microspheres) and on ST-segment elevation in ischemic and nonischemic areas of the canine left ventricle have been investigated. dl-Propranolol and dl-pindolol, but not dl-practolol and d-propranolol, induced blood flow redistribution from the epicardium to the endocardium both in ischemic and nonischemic areas. dl-Propranolol-induced redistribution was abolished by atrial pacing at the control heart rate value. These results indicate that the redistribution phenomenon only occurs if both a bradycardia-inducing beta1 adrenoreceptor blockade and a coronary vessels beta2 adrenoceptor blockade are simultaneously achieved. All four drugs significantly decreased ST-segment elevation in ischemic areas. Under atrial pacing, this effect was abolished with dl-practolol but only reduced with dl- and d-propranol, suggesting that, besides bradycardia, membrane stabilization might be involved in protection against ST-segment elevation in ischemic areas.

Adrenergic beta-Antagonists↗
PubMed1978

Pharmacological findings on cetiedil.

The molecule of cetiedil (Stratène) has strong papaverine-like and weak atropine-like properties. It brings about peripheral vasodilation at doses which do not affect arterial blood pressure, heart beat and cardiac efficacy; this new drug increases the activity of beta-adrenergic stimulants. There may be different hypotheses to explain the therapeutic effect of cetiedil; beside its papaverinic and synergistic beta-stimulant properties, it increases the haemodynamic coefficient, plays a role in the process of membrane Ca++ exchange and inhibits phosphodiesterase and platelet aggregation.

Animals↗
PubMed1977

[Determination of plasma digoxin in newborn infants. Practical applications].

Measurement of plasma digoxin concentrations in infants after three increasing dosage levels shows that the optimal dose of this glycoside in 20 microgram/kg/day, i.e. a loading dose of 20 microgram/kg followed every 8 hours by a maintenance dose of 7 microgram/kg. The plateau concentration achieved is 3.0 +/- 0,5 ng/ml 8 hours after the last administration. When digoxin levels exceed 5 ng/ml (overdosage, renal failure or low body weight), toxic manifestations occur.

Digoxin↗
PubMed1977

Comparative beta-adrenoceptor blocking effects and pharmacokinetics of penbutolol and propranolol in man.

1 The beta-adrenoceptor blocking effects of penbutolol were compared with those of propranolol and a placebo in a double-blind trial involving six healthy volunteers. 2 Heart rate (HR), systolic blood pressure (SBP) and peak expiratory flow rate (PEFR) were measured at rest and during vigorous exercise before and at intervals up to 7 h after oral administration of the drugs. In addition, plasma renin activity (PRA) at rest and plasma levels of penbutolol and propranolol were determined. 3 Penbutolol proved to be a non-cardioselective beta-adrenoceptor blocking drug, antagonizing exercise-induced tachycardia, reducing exercise-induced increase in PEFR and decreasing PRA. The beta-adrenolytic potency of penbutolol was shown to be four-fold that of propranolol but the duration of its effect was similar. 4 The peak plasma level of penbutolol was reached 1 h after administration and its half-life was 4.5 h. 5 Comparison of plasma levels and biological activity of penbutolol revealed that after oral administration this drug is transformed into an active metabolite in man.

Adrenergic beta-Antagonists↗
PubMed1977

Effects of atenolol on regional myocardial blood flow and ST segment elevation in the canine myocardium.

1 The effects of atenolol on regional myocardial blood flow (RMBF) and on ST segment elevation were studied both in normal and ischaemic regions of the myocardium in dogs. Some of the experiments were performed with cardiac pacing or after bilateral stellectomy. 2 In the absence of cardiac pacing, atenolol (1 mg/kg, i.v.) induced a marked reduction in heart rate and contractile force and a decrease in RMBF, which was of the same magnitude in normal and ischaemic areas. There was no modification in the endo/epi flow ratio. ST segment elevation in ischaemic areas was significantly reduced. 3 Bilateral stellectomy induced similar effects to those of atenolol. Atenolol after bilateral stellectomy exhibited no additional effects. 4 In dogs submitted to cardiac pacing, atenolol no longer decreased RMBF and ST segment elevation. 5 These results demonstrate that with atenolol, there is no correlation between bradycardia and the endo/epi flow ratio while there is one between bradycardia and reduction in ST segment elevation.

Animals↗