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Biomedical subjects

R Nadeau

Publications and source records attributed to R Nadeau.

At least 163 records · Page 9Linked to original sources
PubMed1982

Plasma catecholamines and response to exercise in 6-hydroxydopamine-treated dogs.

Plasma catecholamine (CA; picograms per millilitre) concentrations were measured simultaneously with heart rate (HR, beats per minute) during short-duration exercise, and with plasma glucose, lactate, and free fatty acid (FFA) concentrations (millimoles per litre) during long-duration exercise, in control dogs (N-dogs) and in sympathectomized dogs (S-dogs) with 6-hydroxydopamine (50 mg X kg-1). At rest, higher plasma CA in S-dogs (690 +/- 90 vs. 320 +/- 60) was associated with higher HR (126 +/- 3 vs. 90 +/- 5), plasma glucose (6.4 +/- 0.2 vs. 5.1 +/- 0.2), lactate (2.9 +/- 0.2 vs. 1.6 +/- 0.2), and FFA concentrations (1.08 +/- 0.11 vs. 0.81 +/- 0.11). During short-duration exercise a normal HR response in S-dogs (226 +/- 9 vs. 228 +/- 8) was dependent upon larger than normal plasma CA values (4280 +/- 680 vs. 1990 +/- 360). Metabolic adjustments to long-duration exercise were impaired in S-dogs as evidenced by the higher plasma glucose and lactate concentrations (8.2 +/- 0.5 and 5.5 +/- 0.3 vs. 6.4 +/- 0.4 and 4.6 +/- 0.3) and the lower plasma FFA concentration (0.66 +/- 0.16 vs. 1.20 +/- 0.09). These occurred despite a normal plasma CA response in S-dogs (6850 +/- 1450 vs. 8740 +/- 1680). Following chemical sympathectomy the adrenal medulla can compensate to ensure an adequate heart rate response to short-duration exercise, but not to ensure adequate metabolic adjustments to prolonged exercise.

Adrenal Medulla↗
PubMed1982

Plasma catecholamines, heart rate, and cardiac sympathetic activity in exercising dogs.

Plasma catecholamines, heart rate, and cardiac sympathetic activity in exercising dogs. Med. Sci. Sports Exercise, Vol. 14, No. 4, pp. 291-285, 1982. The purposes of the study were, 1) to assess the respective roles of locally released norepinephrine in the sinus node and of plasma catecholamines in the control of heart rate during exercise and 2) to verify whether the heart is a source of plasma catecholamines during exercise. Plasma catecholamines (radioenzymatic assay) and heart rate were measured in the last minute of a 5-min exercise period (3.2 km . h-1, 39% slope) in six normal dogs, in six dogs treated with 5 mg . kg-1 sotalol, and in six dogs sympathectomized with 50 mg . kg-1 6-hydroxydopamine. Compared to the exercise heart rate values of the normal dogs (228 +/- 8 beats . min-1) and the sympathectomized dogs (226 +/- 9 beats . min-1), the sotalol-treated dogs had significantly lower rates (148 +/- 6 beats . min-1). However, plasma catecholamine response was higher in the sotalol-treated dogs (7380 +/- 1350 pg . ml-1) and in the sympathectomized dogs (4280 +/- 680 pg . ml-1) than in the normal dogs (1890 +/- 360 pg . ml-1). Since the action of plasma catecholamines on the sinus node is potentiated by denervation hypersensitivity, it is suggested that in exercising normal dogs, heart rate control could be ensured by locally released norepinephrine rather than by plasma catecholamines. Plasma catecholamines were assessed in six normal dogs at rest and at various exercise levels (HR = 90-200 beats . min-1) and in blood sampled simultaneously in the aorta and the coronary sinus. Plasma catecholamines in the coronary sinus and aorta were similar at rest (490 +/- 90 vs 580 +/- 80 pg . ml-1, respectively) and at the low-intensity exercise (710 +/- 140 vs 880 +/- 120 pg . ml-1, respectively). For moderate and severe work loads, plasma catecholamine concentrations in the coronary sinus (960 +/- 160 and 1570 +/- 340 pg . ml-1, respectively) were lower than in the aorta (1380 +/- 260 and 2950 +/- 100 pg . ml-1, respectively). These results suggest that in exercising dogs the heart is not a source of plasma catecholamines.

Animals↗
PubMed1981

Plasma norepinephrine response to exercise before and after training in humans.

Plasma norepinephrine (NE) concentration was measured by means of a sensitive radioenzymatic assay in blood collected from an antecubital vein in 10 healthy male subjects (37 +/- 2 yr, mean +/- SE). The subjects were evaluated at rest and during exercise before and after a 20-wk training program on bicycle ergometer (three 30-min sessions per week at 80% of maximal heart rate). Following the training program, maximal oxygen uptake increased significantly from 33 +/- 2 to 42 +/- 1 ml . kg-1 . min-1. Resting plasma NE remained unchanged after training (167 +/- 38 before and 185 +/- 29 pg . ml-1 after training). For a given absolute work load (735 +/- 51 kg . m. min-1) the sympathetic nervous response was lower after training as reflected by the decrease in NE concentration (1,371 +/- 286 vs. 687 +/- 64 pg . ml-1). At the same relative work load (heart rate: 158 +/- 5 before and 157 +/- 5 beats . min-1 after training) plasma NE concentration was unchanged after training (1,371 +/- 286 vs. 1,729 +/0 371 pg . ml-1). Results from the present study show that the sympathetic nervous activity is closely linked to the exercise demands and confirm earlier suggestions that it remains constant in relation to the relative work load.

Adult↗
PubMed1980

Electro- and echocardiographic study of the left ventricle in man after training.

Fourteen sedentary middle-aged men underwent a chest X-ray, a 12 lead ECG, a VCG, and an echocardiographic examination prior to and following 5 months of training a moderately severe intensity, on a cycle ergometer. No modification in the X-ray cardiac profile was observed following training. Some electrocardiographic (R wave amplitude in V5 and V6 and Sokolow index: SV1 + RV5 or V6) and vectorcardiographic (maximal QRS vector amplitude, maximal spatial QRS vector, and R wave amplitude) indices of left ventricular hypertrophy were slightly but significantly increased following training. The echocardiographic measurements in diastole (septal and posterior wall thickness, left ventricular internal diameter, and left ventricular mass) were unchanged after training. Results suggest that electrical changes may not provide adequate indications of left ventricular morphological modifications. The lack of echocardiographic evidences of left ventricular hypertrophy suggest that: (1) training does not necessarily induce left ventricular hypertrophy; (2) the large heart sometimes observed in athletes may be the result of a genetic factor or of a prolonged and very intensive training pursued since a very young age, over a number of years; and (3) left ventricular enlargement probably plays a minor role in the increase in aerobic capacity following training.

Echocardiography↗
PubMed1977

[Use and mechanism of action of digitalis glycosides as anti-arrhythmic drugs].

Digitalis glycosides are used in the supraventricular arrhythmias either to slow the ventricular response or to restore or maintain sinus rhythm. The direct cellular effects of digitalis are probably not involved in its antiarrhythmic action. The indirect effects of digitalis through parasympathetic stimulation and adrenergic inhibition explain the results obtained when treating arrhythmias. At toxic doses, adrenergic stimulation may contribute to the arrhythmias of digitalis toxicity.

Anti-Arrhythmia Agents↗
PubMed1976

Correlation between changes in endogenous catecholamine release from the heart and various physiological responses in anesthetized dogs.

Correlations between the concentration of endogenous catecholamines in coronary sinus blood and various physiological responses to adrenergic stimulation were studied in anesthetized dogs. Plasma catecholamine levels both in coronary sinus and aortic blood were measured by means of a modification of the radiometric-enzymatic assay for tissue catecholamines, and found to be 0.769 +/- 0.110(S.E.) and 0.972 +/-0.127(S.E.) ng/ml, respectively, under basal conditions. Circulating catecholamine levels increased after the intracoronary injection of 6-hydroxydopamine, which has an indirect sympathomimetic action. Both the increment in catecholamine release from the heart and the intensity of physiological response were dose-related. A frequency-dependent increase in coronary sinus blood catecholamine levels occurred during right cardioaccelerator nerve stimulation. Maximum values were observed with a stimulation frequency of 10 Hz, at which maximum physiological responses were obtained. A highly significant correlation was found between endogenous catecholamine levels in coronary sinus blood and the dp/dt of left ventricular pressure (r = 0.750, p less than 0.001), as well as mean coronary blood flow (r =0.706, p less than 0.001). The present preparation may prove to be a reliable means of studying the role of the sympathetic system in regulating cardiac function.

Animals↗
PubMed1975

Properties of acebutolol in twenty patients with cardiac arrhythmias.

Acebutolol (M & B 17,803 A), a new cardioselective beta-adrenergic blocking agent, was given intravenously to 20 selected patients with various cardiac arrhythmias. Cumulative doses ranging from 12.5 to 50 mg were moderately or highly effective in 4 out of 4 patients with sinus tachycardia, 2 out of 3 patients with premature atrial beats, 3 out of 4 patients with premature ventricular beats, 3 out of 5 patients with atrial fibrillation (one was converted to sinus rhythm) and in 2 out of 3 patients with atrial flutter. The drug was ineffective in one patient with atrial tachycardia. Mild systolic hypotension occured in two patients with recent myocardial infarction and there was some aggravation of a preexisting bronchospasm in a patient with congestive heart failure secondary to hyper-thyroidism. It was concluded that acebutolol is a cardioselective beta-blocker which by intravenous route may be useful in the treatment of selected cardiac arrhythmias.

Acebutolol↗
PubMed1975

Catecholamine-ouabain interaction on the isolated perfused rat heart.

The effect of catecholamine-depleting pretreatments, reserpine, and 6-hydroxydopamine (6-OH-DA) on left ventricular pressure (LVP) and the inotropic response to graded doses of ouabain (up to 300 mug/0.05 ml) was studied in isolated perfused rat and guinea-pig hearts. In rats, reserpine and 6-OH-DA depleted the cardiac content of catecholamine, but did not increase initial LVP and did not reduce the inotropic response to the highest dose of ouabain. It is concluded that in isolated rat hearts, these catecholamine-depleting pretreatments nearly abolish the inotropic response to ouabain, and this effect appears to be mediated mainly through an increase in initial LVP. The reason why catecholamine depletion failed to increase initial LVP in guinea pigs remains unexplained.

Animals↗
PubMed1975

Correlation between the response of the heart to sympathetic stimulation and the release of endogenous catecholamines into the coronary sinus of the dog.

The relationship between the increase in catecholamine levels of the coronary sinus blood and the amplitude of various cardiac responses to adrenergic nerve stimulation was studied in anesthetized dogs. Plasma catecholamine levels in both coronary sinus and aortic blood were measured by a modification of the radiometric enzymatic assay for tissue catecholamines and were found to be 0.622 plus or minus 0.104 (SE) ng/ml and 0.933 plus or minus 0.116 ng/ml, respectively, under basal conditions. The catecholamine levels in coronary sinus blood increased linearly during right cardioaccelerator nerve stimulation up to a frequency of 10 Hz. At this frequency, maximum values were observed in both coronary sinus blood catecholamine levels and cardiac responses. The correlation between the response in heart rate, mean coronary blood flow, and dP/dt of left ventricular pressure and the increase in endogenous catecholamine levels of coronary sinus blood was significant, but the relationship was nonlinear. The present experimental design may prove to be a reliable means of studying the role of the sympathetic nervous system in the regulation of cardiovascular function in vivo.

Animals↗
PubMed1974

Selective binding of (3H)gibberellin A1 by protein fractions from dwarf pea epicotyls.

A homogenate from dwarf pea seedlings that had been treated with [(3)H]gibberellin A(1) was separated by Sephadex G-200 into two protein fractions, of high and intermediate molecular weight, with affinity for [(3)H]gibberellin A(1). Neither fraction bound [(3)H]gibberellin A(8), the only metabolite of [(3)H]gibberellin A(1) detected in significant quantity in extracts of pea seedlings. These proteinhormone complexes were noncovalently bound, as evidenced by their rapid disruption in ethanol. Approximate molecular weights of the fractions were 500,000 and 60,000. In experiments designed to detect competition for the binding proteins between [(3)H]gibberellin A(1) and closely related [(3)H]gibberellin molecules, [(3)H]gibberellin A(8) and pseudo [(3)H]gibberellin A(1) were inactive, but keto [(3)H]gibberellin competed favorably. Equilibrium dialysis experiments revealed that both high-molecular-weight and intermediate-molecular-weight protein-hormone complexes could undergo hormone exchange with nonlabeled gibberellin A(1).

Chromatography, Gel↗
PubMed1974

An amphoteric conjugate of [h]gibberellin a(1) from barley aleurone layers.

The major metabolite produced during incubation of [(3)H]gibberellin A(1) ([(3)H]GA(1)) with barley aleurone layers is an amphoteric, water-soluble compound tentatively called [(3)H]ampho GA(1). Formation of [(3)H]ampho GA(1) in barley aleurones begins after a period of 2.5 hours. As judged by degradation studies as well as Sephadex column chromatography, GA(1) appears to be linked to a peptide; positions C-3 and C-7 were ruled out as conjugation sites.

Journal Article↗
PubMed1973

Comparative bioavailability of two oral preparations of digoxin in healthy volunteers.

The serum levels of digoxin resulting from the oral administration of 0.25 mg. of Lanoxin and Rougoxin preparations were studied in 12 healthy volunteers by means of a double-blind crossover design. No differences between the two brands could be demonstrated with respect to disintegration time, content uniformity, peak serum levels and cumulative areas under the curve for an eight-hour period.

Administration, Oral↗