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Biomedical subjects

G Faucon

Publications and source records attributed to G Faucon.

At least 73 records · Page 4Linked to original sources
PubMed1985

Cellular pharmacokinetics of daunorubicin: uptake by leukaemic cells in vivo and fate.

In 6 patients with acute myeloblastic leukaemia, daunorubicin was assayed in leukaemic cells from peripheral blood or bone marrow. The cells were separated from red blood cells and granulocytes by centrifugation on a Ficoll-Isopac gradient. The assay was performed by high performance liquid chromatography. Daunorubicin concentrations in peripheral leukaemic cells, 2 hours after the end of the infusion, were much higher than in plasma, the cell/plasma concentration ratio reaching about 350 and rising to almost 700 at 24 h. At that time, drug concentrations were even higher in the bone marrow leukaemic cells. The value of the assay of daunorubicin in cells as method for monitoring therapy is discussed.

Adult↗
PubMed1985

A comparison of energy metabolism and the effects of beta-adrenergic stimulation in the tongue and attached gingiva of the dog.

Glucose-6-phosphate (G6P), ATP, phosphorylcreatine (CP) and lactate were assayed in the tongue attached gingiva of dogs. The G6P content was found to be significantly higher, and both the ATP and CP contents even more significantly higher in the tongue than in the attached gingiva. Lactate content was not significantly different in the gingiva and in the tongue. The changes in the concentrations of G6P, ATP, CP and lactate due to the intravenous infusion of isoproterenol hydrochloride (1 micrograms/kg/min) were as follows. In the tongue, G6P exhibited a significant increase, but the decrease in ATP and CP contents as well as the increase in lactate content were not significant. It is possible that these effects were the result of the activation of beta-adrenergic receptors by isoproterenol. In the attached gingiva, there was no significant change in the G6P, ATP, or CP content. Lactate increased to a greater degree than the other three components, but similarly did not reach the significant level.

Adenosine Triphosphate↗
PubMed1985

Efficacy of disopyramide in comparison with verapamil and propranolol in the prevention of acetylcholine-induced atrial fibrillation in the dog.

The efficacy of verapamil and propranolol was studied in comparison with disopyramide on the atrial fibrillation experimentally induced in the dog heart in situ by electrical stimulation combined with intra-aortic injection of acetylcholine (ACh). After reducing the amplitude and duration of the monophasic action potential (MAP) and the duration of the effective refractory period (ERP) of the atrial contractile fibres, ACh lowered the fibrillation threshold (FT), and, when fibrillation had been elicited, it accelerated the fibrillation rate (FR). Verapamil and propranolol failed to prevent atrial fibrillation: they did not counteract any of the alterations in the electrophysiological properties of the atrial contractile fibres due to ACh. In contrast, disopyramide, at doses within the therapeutic range, prevented fibrillation. The fibrillation threshold, which fell from 50 mA to 1 mA in the presence of ACh, was restored to control values by disopyramide. Disopyramide also antagonized the reduction in amplitude of MAP caused by ACh before the triggering of fibrillation and the reductions by ACh of the durations of MAP and ERP. Disopyramide first slowed FR, in association with an increase in amplitude of fibrillation waves and a tendency to synchronous activity, and ultimately terminated the fibrillation.

Acetylcholine↗
PubMed1984

Potentiation by hypokalemia of the effects of acetylcholine on the canine heart in situ.

In the heart in situ of vagotomized dogs, atrioventricular conduction was studied by the His bundle potential recording, sinus rate continuously registered and the effective refractory period (ERP) of the atrial muscle measured by the extrastimulus method. The modifications induced by the acute lowering of plasma potassium concentration from 3.5 to 2.0 mmol/l obtained by hemodialysis appeared to be similar to those due to parasympathetic stimulation and the effects of hypokalemia and acetylcholine (ACh) on the atrioventricular (A-V) and sinoatrial nodes as well as on the atrial contractile tissue gave rise to potentiation. Intraaortically injected near coronary ostia in a dose lower than liminal dose, ACh enhanced to a large extent all the phenomena elicited by hypokalemia, since the variations respectively observed under the influence of hypokalemia alone and the combination of hypokalemia and ACh were as follows: lengthening of conduction time in the A-V node by 100 and 180%, reduction of sinus rate by 10 and 20%, shortening of the atrial ERP by 20 and 40%.

Acetylcholine↗
PubMed1983

Pharmacokinetics of diltiazem in severe renal failure.

The acute effects of a single dose of diltiazem (Tildiem), a calcium antagonist, were studied in 9 patients with severely impaired renal function (GFR between 0.03 and 0.87 ml/s/1.73 m2). Control measurements were made of inulin and PAH clearance, creatinine, blood pressure, heart rate and ECG. Following administration of diltiazem 120 mg, 7 blood samples were collected in the first 12 h and after 24 h, 32 h, 48 h; urine was collected for the first 12 h, 12-24 h and 24-48 h, and blood pressure, heart rate and ECG were recorded after 6 h. Diltiazem and its main metabolite, desacetyldiltiazem, had a pharmacokinetic profile similar to that in patients with normal renal function (peak plasma concentration, half-life and urinary excretion). Diltiazem is normally eliminated in the urine to a small extent, because it is metabolized, and this also applies to desacetyldiltiazem, which is probably further metabolized.

Adult↗
PubMed1983

Enhancement by Ca2+ ions of cholinergic effects on the canine heart in situ.

The effects of Ca2+ ions were studied on the canine heart in situ, submitted to vagal influence or not. In addition to heart rate, conduction time was determined separately in atrial muscle, atrioventricular node and His-Purkinje system by means of His bundle potential recording and the effective refractory period (ERP) measured in atrioventricular node, atrial and ventricular muscle according to the extrastimulus method. In the presence of acetylcholine (ACh) released by vagal endings, an increase in plasma calcium concentration from 2.40 to 4.12 mmol/l, acutely induced by the infusion of calcium chloride, elicits the following alterations: slowing down of sinus rate, lengthening of conduction time in atrioventricular node without change of this time in atrial muscle and His-Purkinje system, prolongation of atrioventricular node ERP, but notable decrease of atrial muscle ERP and slight decrease of ventricular muscle ERP. These effects are similar to those of ACh:Ca2+ ions probably enhance the responsiveness to ACh.

Acetylcholine↗
PubMed1983

Blockade by verapamil of cholinergic effects on atrial specialised tissue in the anaesthetised dog.

The effects of verapamil were studied in anaesthetised dogs administered dextromoramide intrathecally to provide background vagal tone. Measurements were made of spontaneous heart rate, and, in paced hearts, of conduction times in atrial muscle, the atrioventricular node (A-V node) and His-Purkinje system by means of His bundle potential recording. The effective refractory period (ERP) of A-V node was measured by the extrastimulus method. In atropinised and vagotomised animals, verapamil reduced sinus rate and increased A-V nodal conduction time. In dogs high vagal tone after dextromoramide, however, verapamil increased sinus rate and reduced A-V nodal ERP. After dextromoramide alone, A-V block was observed at an atrial pacing rate of 150 beats X min-1, but after verapamil 1:1 A-V conduction was restored. The decrease in conduction velocity in the A-V node due to ACh was neither attenuated nor enhanced by verapamil.

Acetylcholine↗
PubMed1983

Pharmacokinetics of caffeine during and after pregnancy.

The pharmacokinetic parameters of caffeine were measured in 9 pregnant women and 4 women 4 days post partum. The results show a significant prolongation of caffeine elimination in pregnant women. Normal pharmacokinetic parameters seem to be restored as soon as 4 days post partum. Steroids hormones (estriol, estradiol, and progesterone) were measured in both cases.

Adult↗
PubMed1983

Study of the ventricular antifibrillatory effects of calcium channel blocking agents in comparison with lidocaine on canine normal heart in situ.

The ventricular antifibrillatory effects of two calcium channel blocking agents have been studied by determining fibrillation threshold several times in the course of an experiment on dogs placed under total cardiopulmonary by-pass to avoid the impairment of the myocardium properties subsequent to the interruption of blood circulation. These drugs were used in therapeutic or even higher doses (verapamil 0.40 mg.kg-1, diltiazem 0.60 mg.kg-1). They failed to modify fibrillation threshold significantly, and did not influence fibrillation rate or the effective refractory period of contractile fibres. Lidocaine, on the contrary, under the same experimental conditions, induced a dose-dependent rise in fibrillation threshold of up to nearly 200%, correlated to a fall in fibrillation rate and a prolongation in effective refractory period.

Animals↗
PubMed1982

Interaction of diltiazem with propranolol on atrioventricular conduction and refractoriness in the dog.

Propranolol pretreatment (0.1 mg X kg-1) significantly increased the lengthening induced by diltiazem (0.15 mg X kg-1 + 0.01 mg X kg-1 X min-1, 20 min) of the A-H interval of His bundle potential recordings in the dog. In the presence of propranolol, diltiazem also significantly increased the atrioventricular effective refractory period. The results suggest the possible occurrence of AV blocks as a result of the use of a diltiazem-beta blocker combination in clinical practice.

Animals↗
PubMed1982

Effects of hypokalemia on the various parts of the conduction system of the dog heart in situ.

The effects of hypokalemia were studied on the various parts of the conduction system by means of His bundle potential recording in the heart of vagotomized dogs. Plasma potassium concentration was lowered by extracorporeal dialysis, precautions being taken against the simultaneous impairment of other parameters, especially humoral. In order to make sure that the changes in atrioventricular conduction observed were due to hypokalemia, a control series of experiments was carried out, under strictly identical conditions except that the dialysis fluid was not devoid of potassium. The following alterations were observed during the lowering of potassium concentration from 3.2 to 1.6 mmol/l: atrioventricular node conduction time (AH interval) increased steadily up to 250% of control values; conduction time in atrial contractile tissue (SA interval) and His Purkinje system (HV interval) exhibited variations much later and much smaller; conduction time in ventricular contractile tissue was not significantly affected; effective refractory period (ERP) of atrial muscle, initially the longest in ERPs of conduction system in vagotomized animals, was shortened by about 20%. The mechanism of all these alterations is discussed.

Acetylcholine↗
PubMed1982

Kinetics of a high dose of piretanide in renal failure.

The kinetics of piretanide was studied in patients with renal failure. After oral administration of a high dose of piretanide (96 mg), the pharmacokinetic parameters were: elimination rate constant 0.346 +/- 0.072 h-1, half life 2.00 +/- 0.35 h, and total plasma clearance 119.55 +/- 35.90 ml x min-1. Compared to the values obtained in adults with normal renal function, these results show a decrease in total plasma clearance, but conservation of the metabolic clearance which amounts to 45% of the total clearance in the healthy adult.

Administration, Oral↗
PubMed1982

Relationship between lactate arteriovenous gradient and tissue lactate content in subendocardial and subepicardial layers of the ischaemic in situ heart.

Myocardial lactate content and simultaneous evolution of a lactate arteriovenous gradient associated with incomplete obstruction of the left coronary bed were studied in dog hearts. Samples of blood were taken from a peripheral artery and the coronary sinus; transmural samples of myocardial tissue were obtained from the left ventricular wall by drill biopsy in animals under total cardiopulmonary by-pass. Lactate content was assessed in subendocardial and subepicardial layers separately. A 40 to 70% reduction in coronary flow induced a quick reduction and even an inversion of the positive lactate gradient while the tissue content, which was similar to the arterial content, rose considerably, chiefly in the subendocardial layer. Lactate accumulating in tissue was released into the blood approximately in proportion to the tissue concentration. The value of employing the lactate concentration difference between arterial blood and coronary sinus blood as an index of the severity and duration of myocardial ischaemia is discussed.

Animals↗
PubMed1981

[Electrophysiological study of cardiac effects of succinylcholine: role of vagal tone and hyperkalemia in anesthetized dog (author's transl)].

The effects of intravenously infused succinylcholine (SCh): 1 mg/kg/minute during 30 minutes were assessed in anesthetized dogs on spontaneous heart rate, conduction within the atrio-ventricular node and the His-Purkinje system and on atrial (AERP) and atrio-ventricular (AVERP) effective refractory periods with varying levels of vagal tone and under mild hyperkalemia. 1) The heart rate which was not affected by SCh in the absence of vagal tone was by contrast increased by 50 p. cent when vagal tone was maintained. Under hyperkalemia, the vagolysis-mediated tachycardia did not prove more marked. 2) The conduction velocity, which was never modified by SCh in either the atria or the His-Purkinje system, was always accelerated with vagal tone. This acceleration is directly related to the vagolytic properties of SCh, but also partly to a mild hyperkalemia. The changes of potassium blood levels tend to reverse the potassium outflow due to the parasympathetic neuromediator. 3) The AERP was was lengthened by SCh and hyperkalemia; the latter impaired the outflow of potassium ions responsible for repolarization. The AVERP was always shortened when the vagal tone is maintained, however less largely under mild hyperkalemia which limits SCh anticholinergic effect owing to its own anticholinergic action.

Anesthesia, General↗
PubMed1981

Effects of diltiazem therapeutic plasma levels on cardiac conduction and refractoriness.

The effects of diltiazem, a new slow channel inhibitor, on the cardiac conduction and refractoriness have been studied using His bundle recordings and the extrastimulus method. In order to determine the role played by possible changes in vagal tone, diltiazem (0.15 mg.kg-1, followed immediately by a 30 min infusion of 0.01 mg.kg-1.min-1) has been administered intravenously to six atropinized dogs, anesthetized with chloralose (100 mg.kg-1) ("atropine group") and to six others which were given chloralose (80 mg.kg-1) and dextromoramide (0.1 mg.kg-1) to ensure the persistence of vagal tone ("vagal tone group"). In the "atropine group", atrioventricular (AV) nodal conduction time increased by 137% and AV node effective refractory period by 55%. Heart rate was slowed down by 15% and arterial pressure fell slightly. In the "vagal tone group", the only significant changes were a 26% increase in AV nodal conduction time and a slight fall in arterial pressure. Inhibition of the slow channel accounts for the effects of diltiazem within the "atropine group". A reflex decrease in vagal tone is probably responsible for the somewhat different results observed in the "vagal tone group". Diltiazem resembles verapamil and should share its antiarrhythmic properties.

Animals↗
PubMed1980

Effects of mild hyperkalemia on conduction velocity and effective refractory period in various parts of the dog heart in situ.

Effects of mild hyperkalemia on conduction velocity, effective refractory periods (ERPs) and sinus rate were studied on 16 anesthetized dogs, using endocavitary His bundle recordings, the extrastimulus method and standard electrocardiogram. Six dogs were placed under acetylcholine infusion (300 micrograms/kg/min) (ACh group), 10 received atropine sulfate 0.2 mg/kg intravenously (atropine group). Intraventricular conduction time, ventricular ERP and QRS duration of the EKG were studied on 7 other open-chested dogs (ventricular group). During a 60 min potassium chloride infusion (0.025 mmol/kg/min, 30 min, then 0.05 mmol/kg/min, 30 min), following observations were made: - In the ACh group, AV node conduction time (A-H interval) decreased by 20% and AV node ERP by 17%, whereas, in the atropine group, the former parameter was not affected and atrial ERP increased by 29%. - At the same time, sinus rate increased in the ACh group and was unaffected in the atropine group. - Conduction times in atrial contractile tissue (S-A interval), His-Purkinje system (H-V interval) and ventricular contractile tissue, like ventricular ERP, exhibited no variation or very slight, occasionally biphasic variations under both conditions. These results can be accounted for by an "anticholinergic" effect of mild hyperkalemia which is discussed.

Animals↗