Antihypertensive Effect of Heimia Salicifolia
In order to evaluate the effects produced by the alkaloids of leaves from H. salicifolia on the blood pressure of rats, four alkaloids from H. salicifolia were isolated by column and thin layer chromatography. The alkaloids’ antihypertensive effects on angiotensin II-caused acute hypertension as well as their hypotensive effects on normotensive rats were studied. The alkaloid 3, the most abundant isolated alkaloid, turned out to be the most effective, while the other alkaloids showed a slight, non-significant vascular activity. Their mixture showed an additive effect, though slightly different from the alkaloid 3.
[Role of nitric oxide and other endothelium-derived factors].
The endothelial cell layer displays the features of a distributed organ and has a variety of biological functions such as keeping the balance between coagulation and fibrinolysis, expression of adhesion molecules for cells in the immune system, metabolism of noradrenaline and 5-hydroxytryptamine, and conversion of angiotensin I and bradykinin. The endothelium also regulates the underlying smooth muscle layer and vascular tone by release of endothelium-derived relaxing factors such as nitric oxide (NO), prostaglandins, and endothelium-derived hyperpolarizing factor (EDHF) as well as vasoconstricting factors such as endothelin, superoxide (O(2)(-)), and thromboxane. We have reviewed the nature, mechanisms of action, and role of these factors in regulation of vascular tone, with special emphasis on NO. By a process catalyzed by NO synthase, NO and citrulline is formed from the substrates molecular O(2) and L-arginine. The main receptor for NO is guanylyl cyclase leading to formation of smooth muscle cyclic guanosinmonophosphate and relaxation. EDHF is an endothelium-derived factor causing vasorelaxation of the underlying smooth muscle layer by hyperpolarization. The nature of EDHF is still unknown, but several candidates for EDHF have been proposed such as potassium ions, hydrogen peroxide, and epoxyeicosatrienoic acids. Prostaglandins such as prostacyclin and prostaglandin E2 binds to specific receptors followed by increases in cyclic adenosinmonophosphate and vasorelaxation, while contractile prostaglandins constrict vessels by activation of thromboxane and endoperoxidase receptors. Superoxide anions induce contraction of vascular smooth muscles cells by scavenging NO. Endothelin is a potent endothelium-derived contractile factor. The synthesis of endothelin-1 is induced by hypoxia, thrombin, interleukin-1, transforming growth factor-beta1, vasopressin, and catecholamines. Cardiovascular risk factors like age, hypertension, and hyperlipidemia are associated with impaired endothelium-dependent vasodilation either as a consequence of increased inactivation of endothelium-derived vasodilators or increased formation of endothelium-derived contracting factors. This imbalance of endothelium-derived factors plays a role for development of atheroslerosis and ischemic vascular diseases.
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more