Sterol

About: Sterol is a research topic. Over the lifetime, 8117 publications have been published within this topic receiving 309926 citations. The topic is also known as: sterols & sterol lipids.

Lipids of Plasma Membranes Prepared from Oat Root Cells: Effects of Induced Water-Deficit Tolerance

Abstract: Plasma membranes were isolated from oat (Avena sativa) roots by the phase-partitioning method. The membranes were exposed to repeated periods of moderate water-deficit stress, and a water-deficit tolerance was induced (acclimated plants). The plasma membranes of the controls (nonacclimated plants) were characterized by a high phospholipid content, 79% of total lipids, cerebrosides (9%) containing hydroxy fatty acids (>90% 24:1-OH) and free sterols, acylated sterylglucosides, sterylglucosides, and steryl esters, together amounting to 12%. Major phospholipids were phosphatidylcholine and phosphatidylethanolamine with lesser amounts of phosphatidylglycerol, phosphatidylinositol, and phosphatidic acid. After the membranes were acclimated to dehydration, the lipid to protein ratio decreased from 1.3 to 0.7 micromoles per milligram. Furthermore, the cerebrosides decreased to 5% and free sterols increased from 9% (nonacclimated plants) to 14%. Because the total phospholipids did not change significantly, the free sterol to phospholipid ratio increased from 0.12 to 0.19. There was no change in the relative distribution of sterols after acclimation. The ratio of phosphatidylcholine to phosphatidylethanolamine changed from 1.1 in the nonacclimated plants to 0.69 in the acclimated plants. The results show that acclimation to dehydration implies substantial alterations in the lipid composition of the plasma membrane.

Effect of alkyl-substituted precursors of cholesterol on artificial and natural membranes and on the viability of Mycoplasma capricolum

Abstract: Various alkyl-substituted sterols and stanols representative of the intermediates in cholesterol biosynthesis from lanosterol have been compared with respect to (a) their effect on the physical state of lecithin vesicles, (b) their efficacy as growth factors for the sterol auxotroph Mycoplasma capricolum, and (c) their effect on the physical state of the respective mycoplasma membranes. By all three criteria, sterol effectiveness progresses in the order lanosterol less than 4,4-dimethylcholestanol less than or equal to 4 beta-methylcholestanol less than 4 alpha-methylcholestanol less than cholestanol less than cholesterol. Since the corresponding steps in cholesterol biosynthesis occur in the same order, we conclude that the nuclear modifications of the lanosterol structure by oxidative demethylation serve to improve the membrane function of the sterol molecule.

Studies on the sterols and sterol esters of the intracellular organelles of maize shoots

Abstract: 1. The composition of the esterified and unesterified sterols of the nuclear, chloroplastidic, mitochondrial and microsomal fractions of 21-day-old maize shoots was examined. 2. The microsomal and mitochondrial fractions contain the bulk of the sterols of the tissue. 3. Only 1% of the sterol isolated from all the organelles is esterified. 4. The nuclear fraction has the greatest proportion of esterified sterol and the microsomal fraction the least. 5. 4-Demethyl sterols constitute the bulk of both esterified and unesterified sterols in all organelle fractions. 6. Cholesterol is the major esterified 4-demethyl sterol of the nuclear and chloroplastidic fractions, but only the nuclear fraction has an appreciable proportion of unesterified cholesterol. 7. Sterol esters of linolenic acid are more abundant in the mitochondrial and microsomal fractions than in the other two fractions.