Gram Of Substrate Research Articles

Cardiovascular epilepsy: Fuad Kandalla, M.D., Bagdad, Iraq

Renin substrate, or hypertensinogen, can be properly assayed only in terms of the angiotonin, or hypertensin, formed from it on incubation with renin. The angiotonin so formed is assayed in terms of the rise in blood pressure in an animal on intravenous injection of the angiotonin. In the course of bioassay, the unit of angiotonin is arbitrary and is defined as the amount with presser activity equal to that of 1 mg. of a crude preparation kept for a standard. Assays are performed on dogs. Dogs pretreated by section of the sine-aortic buffer nerves and injection of tetraethyl ammonium chloride are more responsive to angiotonin. In anesthetized dogs so treated, 4 units of the reference standard, intravenously injected, causes an arterial blood pressure rise of 40 to 60 mm. of Hg. Activity of the renin substrate is reported as units of angiotonin formed per gram of substrate. The purification is also followed by ultraviolet absorption of the angiotonin formed. The method described for purification is designed primarily for the preparation of large amounts of renin substrate to be used for the subsequent preparation of angiotonin. Ammonium sulfate fractionations at different acidities are employed, but the most essential step in the procedure is selective acid denaturation. This step removes most of the inactive protein and, also, the angiotonase which destroys angiotonin. Thus both the yield and the purity are greatly increased by this one step.

THE REACTION OF β,β′-DICHLORODIETHYL SULPHIDE WITH PROTEINS

The reaction of β,β′-dichlorodiethyl sulphide with various proteins and their constituents has been tested under relatively mild conditions. Most reactions have been carried out in aqueous media at 25 °C., usually in the presence of sodium chloride. The rate of disappearance of mustard has been followed iodimetrically as an index of the reaction.No reaction could be demonstrated with the prolamins, zein and gliadin, in ethanol. There was a definite reaction with keratin of human skin in which a 24% increment in total sulphur occurred and a more doubtful one with keratein from human hair.The most notable reaction took place with yeast and thymus nucleoproteins in which increases of 250 and 156% in sulphur occurred, respectively. Combination of mustard with both the protein and nucleic acid portions was demonstrated. The extent of these reactions is indicated in terms of milligrams of mustard per gram of substrate as follows: yeast nucleoprotein, 216; thymus nucleoprotein, 47; salmine, 47; globin, 22; yeast nucleic acid, 126. The purines, adenine and guanine, were found to combine readily with mustard at 25 °C., forming thiazans. No reaction could be demonstrated with uracil or thiamine.These experiments have led us to the conclusion that one of the major effects of mustard in its physiological action is the combination and precipitation of the nucleoproteins of the cell, thus inhibiting natural processes of cellular regeneration.