Influence de la taille des vitroplants et du type d’explant sur la réponse à la callogenèse chez le cotonnier (Gossypium hirsutum L.) cultivé en Côte d’Ivoire

L’aptitude à la callogenèse chez le cotonnier a été estimée par le taux d’induction et le poids sec des cals en fonction de la source de l’explant et de la taille des plantules. Le taux d’induction des cals augmente avec la taille des plantules alors que le poids sec des cals ; résultat de la croissance des cals, évolue en sens contraire. L’hypocotyle permet d’induire une bonne callogenèse suivi de la racine et du cotylédon quelle que soit la taille des plantules. Les plantules de petite taille ont une bonne aptitude à la  callogenèse pour les explants hypocotyles et racines alors que pour les explants cotylédons, ce sont les plantules de grande taille qui favorisent l’induction des cals.Mots clés: Cal, explant, cotonnier, <i>Gossypium hirsutum</i>, vitroplants

Effets pharmacologiques d’un extrait aqueux de Bidens pilosa L. (Asteraceae) sur le système cardiovasculaire de mammifères

Pharmacological effects of an aqueous extract of Bidens pilosa L.(Asteraceae) on the cardiovascular system of mammalsThe crude aqueous extract of Bidens pilosa L. (Asteraceae), for concentrations ranging from 1x10-3 to 1.4x10-2 g/kg of body weight (b. w.) induced a transient dose dependant hypotension in the rabbit whereas the respiratory wide range and frequency were lessaffected. On the isolated heart of rat, this natural substance caused negative inotropic and chronotropic effects from the concentration of 10-10 mg/mL. These effects reached their maximum values at 10-8 mg/mL and then decreased at 10-6 mg/mL. At 10-4 mg/mL,no major changes were noticed in the recordings. These results suggest that the hypotension induced by Bidens pilosa L. could result, onthe one hand, from the relaxing effects observed by some authors on the vascular smooth muscle and on the other hand, from the cardiodepressant effects of the active principles contained in the plant.Three kinds of active principles were revealed in the presence of atropine, a muscarinic cholinoceptors antagonist. These are : 1) Muscarinic cholinomimetic active principles inhibited by atropine.2) Cardiodepressant principles insensible to atropine.3) Cardioactive principles acting at high doses of Bidens pilosa.At the dose of 1.3x10-1 g/kg of b.w., the crude extract of Bidens pilosa caused a deep hypotension followed by a respiratory arrest lethal for the rabbit. The results obtained justify the use of Bidens pilosa in traditional medicine to treat hypertension

Effet antihypertensif de BpF2, une fraction d\'extrait aqueux de feuilles de Bidens pilosa L. (Asteraceae) chez le lapin

Les feuilles de Bidens pilosa L. sont largement utilisées dans la pharmacopée traditionnelle. Nous avons cherché à mettre en évidence les effets antihypertensifs de ces feuilles. L'analyse phytochimique révèle que la fraction 2, dénommée BpF2, de l\'extrait aqueux des feuilles de Bidens pilosa L. (Asteraceae), contient des flavonoïdes, des polyphénols et des tanins catéchiques. Pour des doses comprises entre 1 et 25 mg/kg de poids corporel, cette fraction chromatographique induit une hypotension dose-dépendante chez le lapin. Cet effet explique le potentiel antihypertenseur de cette fraction. Ces effets ressemblent à ceux bien connus de l\'acétylcholine (ACh). Toutefois, alors que l\'atropine inhibe totalement l\'hypotension induite par l\'ACh, elle ne reverse que partiellement l\'hypotension provoquée par BpF2. Ces résultats suggèrent fortement la présence de deux types de principes actifs dans cette fraction active BpF2: - les principes actifs cholinomimétiques de type muscarinique, - les principes actifs non cholinomimétiques dont la nature reste à déterminer. La présence de ces substances dans la fraction active pourrait justifier, au moins en partie, l\'utilisation traditionnelle de Bidens pilosa L. contre l\'hypertension artérielle.The fraction 2, called BpF2, of the aqueous extract from Bidens pilosa L. (Asteraceae) leaves, contained flavonoids, polyphenols and catechic tannins. For doses ranging from 1 to 25 mg/kg of body weight, this chromatographic fraction induced a dose-dependent hypotension in the rabbit. This effect explained the antihypertensive potential of the fraction. These effects resembled those well-known of acetylcholine (ACh). However, whereas atropine completely inhibited the effect induced by ACh, its action remained partial on that caused by BpF2. These results suggested the presence of two types of active components in BpF2 fraction. - muscarinic and cholinomimetic activity, - non cholinomimetic activity to be clarified. The study showed at least two hypotensive activities in BpF2 fraction, justifying the traditional use of Bidens pilosa L. against hypertension. Keywords: Bidens pilosa L., acetylcholine, muscarinic cholinomimetic activity, non cholinomimetic activity.Sciences & Nature Vol. 5 (1) 2008: pp. 29-3

Myostimulating effect of Sesamum radiatum aqueous leaf extract in isolated guinea-pig Tainia caeci contractile activity

This study was carried to examine the effects of the aqueous leaf extract of Sesamum radiatum,a laxative plant on the contractile activity of Taenia caeci, an intestinal smooth muscle. Strips of Taenia caeci were rapidly removed from guinea-pig and were suspended between two L-shaped stainless steel hooks in a 10 ml organ bath with Mac Ewen solution. The isometric contractile force of the Taenia caeci strips were recorded by using a strain gauge. S. radiatum aqueous leaf extract (ESera) is a spasmogenic substance. This myostimulant effect is characterized by the increase of the rhythm and the amplitude of isolated guinea-pig Taenia caeci smooth muscle in normal solution and by the development of contracture in modified solution and in solution without calcium. A similar effect was observed with ACh which caused a graded increase of the contractile activity of Taenia caeci. The effects induced by ESera and ACh were reversed in the presence of atropine. The spasmogenic effect induced by ESera could justify partially the use of S. radiatum as laxative in traditional medicine.Key words: Sesamum radiatum, acetylcholine, Taenia caeci, contractile activitydoi: 10.4314/ajtcam.v8i4.