THE METABOLISM OF PALMITIC ACID IN THE PHOSPHOLIPIDS, NEUTRAL GLYCERIDES AND GALACTOLIPIDS OF MOUSE BRAIN

Abstract— Following intracerebral injection, [¹⁴C]palmitic acid was rapidly incorporated into a variety of brain lipids. After 12 hr, 78 per cent of the lipid radioactivity was in phospholipids, 15 per cent was in triacylglycerols, 1 per cent each was in free fatty acids and galactolipids, and the remainder was in other neutral glycerides. Over 65 per cent of the phospholipid radioactivity was found in the choline phosphoglycerides but this proportion decreased substantially with time. At later times, increasing portions of the radioactivity were present in the monounsaturated acyl groups and the alkenyl groups but no radioactivity was detected in cholesterol or polyunsaturated acyl groups. These results indicate that most of the extensive recycling of radioactivity took place without oxidative degradation of the palmitoyl groups. The relative rates of incorporation of radioactivity were compared at 12 hr after injection. The specific radioactivities of the serine, ethanolamine, and choline phosphoglycerides had ratios of 6:3:2 based on the palmitoyl group content and 1:2:4 based on their phosphorus content. The specific radioactivities of galactolipids with O -acyl groups were higher than the specific radioactivitiesof cerebrosides or cerebroside sulphates. A new solvent mixture for thin-layer chromatography of brain galactolipids was described (chloroform-acetone-methanol-water, 60:20:20:1, by vol.).     

ENZYMES OF PHOSPHOINOSITIDE METABOLISM DURING RAT BRAIN DEVELOPMENT

—The activities of four enzymes concerned with inositol lipid metabolism have been determined in homogenates of rat brains of different ages. The enzymes are CDP-diglyceride inositol phosphatidate transferase, phosphatidylinositol kinase, diphosphoinositide kinase and triphosphoinositide phosphomonoesterase. The activities of all the enzymes increased with age. Phosphatidylinositol kinase activity rose most sharply well before myelination, reaching a maximum at about 6 days of age. Diphosphoinositide kinase and triphosphoinositide phosphomonoesterase activities increased most rapidly during myelination. The increase in CDP-diglyceride inositol phosphatidate transferase showed no definite association with any period of development. It is concluded that triphosphoinositide metabolism is associated with myelin or a closely related structure.     

REVERSIBLE DEACTIVATION OF NEUROSPORA ASCOSPORES BY LOW TEMPERATURE

Sun, Clare Y., and Alfred S. Sussman. (U. Michigan, Ann Arbor.) Reversible deactivation of Neurospora ascospores by low temperature. Amer. Jour. Bot. 47(7): 589-593. Illus. 1960.—Heat-activated ascospores of Neurospora tetrasperma are reversibly deactivated after incubation at 4°C. for 36–48 hr. Two cycles of deactivation and reactivation are possible although the percentage germination decreases in the last cycle. By contrast, spores held at 20°C., or in glycerol at 4°C., will remain activated for much longer periods of time. If an incubation period at 20°C. greater than 30 min. is interposed before the activated spores are placed at 4°C., germination occurs despite the cold-treatment. Furfural-activated ascospores, when held at 4°C., are deactivated but can be reactivated only by heat, pointing up a difference between ascospores activated by these different means. Although a fraction of the stimulus afforded by heat-sensitization to chemical activators is preserved for 2 days at —20°C., it is dissipated completely after a short time at 4°C. These data are discussed on the basis of the suggestion that the reversible production of a substance initiates a series of steps which lead to germination. Thus, the temperature minimum of the forward reaction is greater than 4°C. whereas the back reaction proceeds at this temperature.     

大黄蒽醌衍生物与环核苷酸磷酸二酯酶、钙调素相互作用的研究

大黄蒽醌衍生物是中药大黄的主要成份。该类衍生物与钙调素(calmo-dulin,CaM)依赖的磷酸二酯酶(PDE)的相互作用表明:它们可作用子钙调素。其中,大黄酸结合CaM并抑制CaM依赖的磷酸二酯酶(CaM-PDE);而大黄素、大黄酚和芦荟大黄素既刺激CaM-PDE的活力,又刺激PDE的基础活力,其作用机制尚待阐明;当有Ca~(2+)或无Ca~(2+)条件下测定时,大黄酸对PDE基础活力均无影响。表明:象其它的CaM拮抗剂一样,大黄酸能抑制钙调素依赖的PDE的活力。     

四膜虫中存在角蛋白样成分(简报)

中等纤维是脊椎动物细胞中普遍存在的一种细胞骨架成分,在一些无脊椎动物细胞中也发现有这类成分存在。据报道,枪乌贼的巨     

棉属栽培种与野生种杂交的不亲和性

本文研究了棉属栽培种与野生种杂交的不亲和性,试验材料涉及5个染色体组,包括2个栽培种(陆地棉和中棉)和5个野生种(戴维逊氏棉、瑟伯氏棉、三裂棉、阿拉伯棉和比克氏棉)。以陆地棉作母本,异己花粉管在花柱中生长缓慢,有花粉管胚珠低于10%,陆地棉×戴维逊氏棉杂种胚在子叶期坏死。以中棉作母本,不亲和性主要表现在受精后的胚胎发育过程中。