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Biomedical subjects

M Legrand

Publications and source records attributed to M Legrand.

At least 109 records · Page 6Linked to original sources
PubMed1987

Opposite central cardiovascular effects of nifedipine and BAY k 8644 in anesthetized rats.

The central cardiovascular effects of the calcium channel blocker nifedipine and the calcium channel activator BAY k 8644 were studied in anesthetized and ventilated normotensive Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHR). Both drugs were administered in a 1.5-microliter volume into the lateral ventricle of the brain (i.c.v.) or into the cisterna magna (i.c.). The injection of vehicle alone (i.c. or i.c.v.) did not significantly change mean arterial pressure (MAP) or heart rate. Nifedipine (5 and 50 micrograms/kg) and BAY k 8644 (5 and 50 micrograms/kg) induced opposite effects on MAP when centrally injected. Nifedipine decreased MAP and induced a bradycardia (i.c.v.) or no change in heart rate (i.c.), and BAY k 8644 increased MAP without any significant change in heart rate (i.c. or i.c.v.). These effects were more marked with the highest dose of either drug. These effects seemed to be of central origin, since they were suppressed by ganglionic blockade by hexamethonium (100 mg/kg i.v.), whereas after hexamethonium the hypotensive and the hypertensive responses to intravenously injected nifedipine and BAY k 8644, respectively, were preserved. Bilateral vagotomy suppressed the bradycardia induced by i.c.v. administered nifedipine. Previously i.c.v. administered nifedipine (5 micrograms/kg) antagonized the pressor response to BAY k 8644 (5 micrograms/kg i.c.v.). Changes in MAP and heart rate were significantly more marked in SHR than in WKY. These results indicate that a calcium channel inhibitor and a calcium channel activator can modulate in opposite fashion central mechanisms involved in blood pressure control.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1987

Opposite central cardiovascular effects of nifedipine and BAY k 8644 in anesthetized rats.

The central cardiovascular effects of the calcium channel inhibitor (CCI) nifedipine and the calcium channel activator BAY k 8644 (BAY) were studied in pentobarbital-anesthetized and ventilated normotensive Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHR). Both drugs were administered under a 1.5 microliter volume into the lateral ventricle of the brain (intracerebroventricular, i.c.v.). The injection of vehicle (ethanol) alone did not significantly change mean arterial pressure (MAP) or heart rate (HR). Nifedipine (5 and 50 micrograms/kg) and BAY (5 and 50 micrograms/kg) induced opposite effects on MAP when centrally injected. Nifedipine decreased MAP and HR while BAY increased MAP without significant change in HR. These effects are likely to be of central origin, because they were suppressed by ganglionic blockade with hexamethonium and by reserpine. Previously i.c.v. administered nifedipine (5 micrograms/kg) antagonized pressor response to BAY (5 micrograms/kg i.c.v.). Changes in MAP and HR were significantly more marked in SHR than in WKY. These results indicate that a calcium channel inhibitor and a calcium channel activator can modulate in opposite fashion central mechanisms involved in blood pressure control.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1986

Interaction between central alpha 1- and alpha 2-adrenoceptors on sympathetic tone in rats.

The interaction between piperoxan and alpha 2-agonists on sympathetic tone was studied in rats. The sympatho-inhibitory effect of alpha 2-agonists (clonidine, guanfacine, B-HT 933) was assessed by recording heart rate in normotensive bilaterally-vagotomized rats. Clonidine (3 micrograms/kg, i.c.v.) and B-HT 933 (100 micrograms/kg, i.c.v.) induced a bradycardia which was fully reversed by piperoxan (30 micrograms/kg, i.c.v.). However, in rats treated with guanfacine, piperoxan induced a partial recovery of the bradycardic effect. The injection of a small dose of the specific alpha 1-adrenoceptor blocking drug, AR-C 239 (10 micrograms/kg, i.c.v.) which, by itself did not modify heart rate, completely inhibited the reversal effect of piperoxan in rats treated with clonidine, B-HT 933 or guanfacine. In rat brainstem membranes, B-HT 933 was found to bind to both alpha 1- and alpha 2-adrenoceptors and was as potent as clonidine in competing for alpha 1-sites bound by [3H]prazosin. On the other hand, in bilaterally vagotomized rats, piperoxan (30 micrograms/kg, i.c.v.) induced an increase in blood pressure and heart rate which was inhibited by previous administration of AR-C 239 (10 micrograms/kg, i.c.v.). These data suggest that, by inhibiting central alpha 2-adrenoceptors, piperoxan unmasks central alpha 1-adrenoceptor stimulation by endogenous catecholamines leading to an increase in the sympathetic tone, but a full recovery in heart rate could be observed only with the mixed alpha 1- and alpha 2-adrenoceptor agonists, clonidine and B-HT 933. In addition, these data further indicate that alpha 1-adrenoceptors are implicated in a tonic control of the sympathetic nerve activity in normotensive rats.

Animals↗
PubMed1983

Central cardiovascular action of penicillin in anaesthetized dogs and rats.

Penicillin (2-3 mg X kg-1) administered into the cisterna magna (i.c.) of dogs anaesthetized with alpha-chloralose induced a significant increase in mean blood pressure (MBP) and bradycardia, whereas intravenous injections of the same doses had negligible effects. Moreover, dogs receiving central injections of penicillin showed seizures abolished by administration of decamethonium bromide (100 micrograms X kg-1, i.v.). In urethane anaesthetized rats, intracerebroventricular (i.c.v.) injections of penicillin (0.3-3 mg X kg-1) caused dose-dependent increases in mean blood pressure while the intravenous route led to opposite effects. gamma-aminobutyric acid (GABA) (1 mg X kg-1), its agonist muscimol (2 micrograms X kg-1) and the alpha 2-adrenoceptor agonist clonidine (1 micrograms X kg-1) injected intracisternally induced hypotension and bradycardia in dogs. These effects were abolished in animals pretreated with penicillin. In rats, the same agents injected intraventricularly respectively at 0.5 mg X kg-1, 0.5 micrograms X kg-1 induced also hypotension. The effect of clonidine only, was antagonized by pretreatment with penicillin, while penicillin administered at the peak of the hypotensive effect caused by GABA or muscimol reversed it. It is suggested that penicillin acts centrally as a GABA-antagonist, and that the cardiovascular effects of clonidine seem to be mediated, at least in part, by the stimulation of a GABAergic pathway controlling the autonomic nervous system.

Adrenalectomy↗
PubMed1983

Plant Disease and the Regulation of Enzymes Involved in Lignification: Increased Rate of De Novo Synthesis of the Three Tobacco O-Methyltransferases during the Hypersensitive Response to Infection by Tobacco Mosaic Virus.

The mechanism underlying the increase of activity of the three O-methyltransferases of tobacco (Nicotiana tabacum) after infection by tobacco mosaic virus (TMV) has been investigated with a density-labeling method. The three O-methyltransferases from healthy or TMV-infected leaves fed with H(2)O or (2)H(2)O were purified by ion-exchange chromatography and their mean buoyant densities were calculated from their respective distribution profiles after centrifugation to equilibrium on RbCl gradients. Densities were corrected with respect to the mean buoyant density of a radioactive density marker prepared from tobacco leaves floated on a solution containing l-[(3)H]leucine and selected on a preparative gradient for its density close to those of the O-methyltransferases. The introduction of (2)H into the pool of amino acids from which the enzymic proteins were synthesized was monitored. By measurement of the labeling of beta-galactosidase synthesized by bacteria from the plant amino acids, it was shown that infection did not alter the rate of labeling of the pool of amino acids. The buoyant-density values of the three O-methyltransferases were determined, and density-labeled enzymes from healthy and infected materials were compared. The largest density shifts from the native enzyme were measured for O-methyltransferases from infected leaves. These results show that the increase in activity of the three enzymes after infection is due to the stimulation of the rate of de novo synthesis of enzyme proteins.

Journal Article↗
PubMed1980

Central cardiovascular actions of d-tubocurarine and inhibition of the hypotensive effect of clonidine.

Intracisternal (i. cist.) administration of d-tubocurarine (0.025-0. 100 mg. kg-1) in alpha-chloralose-anaesthetized dogs caused a dose-related increase in blood pressure associated with seizures. When injected in dogs pretreated with guanethidine (15 mg. i.v.), d-tubocurarine elicited the same effect while bilateral adrenalectomy abolished the pressor response. The hypotensive effect of clonidine (0.003 mg. kg-1 i. cist.) was reversed when clonidine was given after the alkaloid. These results suggest possbile interactions of the drugs at central GABA-ergic, glycinergic or cholinergic synapses.

Adrenalectomy↗
PubMed1978

[Lung biopsy by thoracotomy. 23 cases (author's transl)].

This series of surgical lung biopsies performed for diffuse lung disease indicates the excellent tolerance of the procedure and the high diagnostic rate. It is indicated above all in the presence of bilateral reticulo-nodular radiological appearances, suggestive of focal lesions not identified by the usual means. The surgical procedure was felt to be justified on the one hand because of the time gained in reaching a precise diagnosis whilst the results of usual laboratory investigations, even the most sophisticated, remain uncertain, and secondly in view of the discovery by the method of malignant lesions which are still curable and which it would have been impossible to identify otherwise, except by awaiting the development of more accessible lesions. Whilst percutaneous needle biopsy found favour amongst many, it would now seem to have been virtually abandoned, particular in France, in view of its risks and it's poor diagnostic rate. By contrast, open surgical biopsy provides in all cases not only lung but also pleural and mediastinal tissue. Its risks are confined to those of any surgical procedure under general anaesthesia, but appear to be sufficiently slight (mortality of 0,5 to 2%) that the technique may be used successfully in intensive care units to obtain a diagnosis in cases of certain types of respiratory distress.

Adult↗
PubMed1977

[Statistical study of the correlations between spirometric data and arterial blood gas tensions. II. During a 40-watt exercise (author's transl)].

PaO2 and PaCO2, after 5 min of a 40-Watt exercise, and spirometric data have been statistically evaluated in 152 patients with chronic obstructive bronchitis. In these patients, the hypoventilation syndrome increases during exercise. The correlation between age and PaO2 is identical during rest and exercise, but the correlation between PaO2 or PaCO2 and FEV1 (% predicted) is closer during exercise than during rest. The value 50 of the FEV1 (% predicted) divides the patients into two groups: the patients who stay normocapnic and those who become hypercapnic or increase their hypercapnemia. These data show the interest of the FEV1 (% predicted) values and allow to explain the evolution of the arterial blood gas tensions during exercise.

Adult↗
PubMed1976

[Spontaneous pneumothorax in women].

Among cases of spontaneous pneumothorax, female cases are extremely rare. They represent only about 10% of observed cases and form a special clinical type. The authors discuss 20 cases out of a total of 261 cases of pneumothorax observed over a period of 7 years. A certain number of facts were noted which distinguished the female forms from the male forms of this disease. Although there is no difference in the symptoms, the disease tends to occur later in women, in the fourth decade of life, and only three of the 20 cases in this series were idiopathic. On the other hand, among the secondary cases, the frequency of E.N.T. or respiratory disease is remarkable for it concerned 75% of cases. None of the cases observed responded to the usual criteria of menstrual pneumothorax although seven occurred during the menstrual period. However the forms which relapse during the periods should lead to a search for pelvic endometriosis. Finally the proportion of rib malformations is not negligible. These facts emphasise that pneumothorax in women, contrary to men, appears much more as a complication of another disease than as an autonomous pleural disease.

Adolescent↗