Showing papers on "Sterol published in 1984"
TL;DR: Long chain (C37–C39) n-alkenones, esters of polyunsaturated n-C36 acids and C27–C29 sterols have been examined in thirteen species from nine genera of algae from the class Prymnesiophyceae and appear to have chemotaxonomic value.
Abstract: Long chain (C37–C39) n-alkenones, esters of polyunsaturated n-C36 acids and C27–C29 sterols have been examined in thirteen species from nine genera of algae from the class Prymnesiophyceae and appear to have chemotaxonomic value. The alkenones and esters have been shown to occur in Chrysotila lamellosa and three species of Isochrysis and their presence in Emiliania huxleyi has been confirmed. They were absent from five other members of the order Isochrysidales, and from those representatives of the orders Coccosphaerales, Prymnesiales and Pavlovales examined. This discrimination was reflected in the distribution of the sterols; all five of the above-named species having high concentrations of 24-methylcholesta-5,22E-dien-3β-ol relative to cholest-5-en-3β-ol (cholesterol). In contrast, the former sterol is a minor component in, or is absent from, members of the Prymnesiales and Pavlovales. The sterol distributions suggest that some species at present included in the Isochrysidales (e.g. Ochrosphaera) have ...
401 citations
TL;DR: Support for the role of a cytosolic oxysterol-binding protein in the regulation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG- CoA) reductase was obtained by correlating the relative binding affinities of a wide range of oxysterols to their potency in suppressing HMG-CoA reduct enzyme activity in mouse fibroblast cell cultures.
302 citations
TL;DR: Current data suggest, therefore, that use of [3H]water yields the most accurate rates of cholesterol synthesis both in vitro and in vivo.
200 citations
TL;DR: The low pH-triggered membrane fusion activity of Semliki Forest virus is dependent on the presence of cholesterol in the target membrane, but fusion activity was not observed when analogs which lacked the 3 beta-OH group were used.
Abstract: The low pH-triggered membrane fusion activity of Semliki Forest virus is dependent on the presence of cholesterol in the target membrane. When liposomes containing phospholipids and cholesterol analogs were used, fusion activity was observed with steroids which did not have a planar nucleus or an isooctyl side chain at C-17, but fusion activity was not observed when analogs which lacked the 3 beta-OH group were used. Binding of virus to liposomes at low pH was similarly, but not totally, dependent on the presence of a 3 beta-OH sterol.
185 citations
TL;DR: The blockage of esterification of exogenous cholesterol in the presence of normal transferase activity is suggestive of a defect in a component involved in the intracellular disposition of this sterol.
178 citations
TL;DR: The question of whether the diet of human populations at low risk for colon cancer is mirrored in their sterol composition is addressed in this study and it is shown that the absolute amounts of cholesterol consumed as a factor by itself might not be as significant as its relationship to total plant sterols in the diet.
128 citations
TL;DR: Although the three fungicides are able to inhibit both enzymes, tridemorph inhibits the Δ 8 -Δ 7 -isomerase better than the Δ 14 -reductase whilst the reverse is true for fenpropidin and to a lesser extent for fenspropimorph.
120 citations
TL;DR: Lanosterol and 4,4-dimethylcholesta-8,24-dien-3 beta-ol were detected in all species studied, and squalene was identified in a stock of L. tropica.
112 citations
TL;DR: The fatty acid, sterol and chlorophyll pigment compositions of the marine dinoflagellates Gymnodinium wilczeki and Prorocentrum cordatum are reported and the role of this sterol in the biosynthesis of 5α-stanols in din oflageLLates is discussed.
105 citations
TL;DR: The data suggest that the primary action of sterol biosynthesis-inhibiting (SBI) fungicides is competitive inhibition of sterl/steroid-type cytochrome P -450 enzymes rather than interference with the function of sterols carrier proteins or enzyme-modulating phospholipids.
90 citations
TL;DR: The primary action of naftifine appears to be the blocking of fungal squalene epoxidation, with inhibition of sterol biosynthesis both in whole cells and in cell extracts of C. albicans.
Abstract: Naftifine, a new antimycotic drug of the allylamine class, is a potent inhibitor of ergosterol biosynthesis in Candida albicans. Treated cells showed a dose-dependent drop in ergosterol content; the level was reduced by 60% at concentrations of greater than 50 mg/liter, causing total inhibition of growth. This inhibition coincided with a heavy accumulation of the sterol precursor squalene. Radiolabeling experiments showed that the inhibition of sterol synthesis was complete within 10 min of exposure of cells to the compound. Control cells incorporated [14C]acetate into nonsaponifiable lipids composed primarily of ergosterol, whereas naftifine-treated cells accumulated only labeled squalene. When the drug was removed by washing cells thoroughly in 1% Tween 80, the accumulated squalene was further metabolized to ergosterol. A similar pattern of inhibition was observed in sterol biosynthesis from [14C]mevalonate in a cell-free system. At 50 mg/liter, naftifine gave greater than 99% inhibition of sterol biosynthesis both in whole cells and in cell extracts of C. albicans. The primary action of naftifine appears to be the blocking of fungal squalene epoxidation.
TL;DR: Ketoconazole was found to inhibit growth and impair sterol biosynthesis of the cultured promastigote stage of Leishmania mexicana Walter Reed 227 in human monocyte-derived macrophages and the mechanism of action may be that postulated for Candida albicans: interference with membrane permeability secondary to loss of desmethyl sterols and accumulation of 14 alpha- methyl sterols.
TL;DR: Direct evidence is provided for a role of SCP2 or a similar peptide in modulating transfer of cholesterol to the inner membrane site of cholesterol side chain cleavage in rats treated with cycloheximide.
TL;DR: The lipid classes, fatty acids of total and individual lipids and sterols of Antarctic krill (Euphausia superba Dana) from two areas of the Antarctic Ocean were analyzed by thin layer chromatography (TLC) and gas liquid chromatography/mass spectrometry (GLC/MS) as discussed by the authors.
Abstract: The lipid classes, fatty acids of total and individual lipids and sterols of Antarctic krill (Euphausia superba Dana) from two areas of the Antarctic Ocean were analyzed by thin layer chromatography (TLC), gas liquid chromatography (GLC) and gas liquid chromatography/mass spectrometry (GLC/MS). Basic differences in the lipid composition of krill from the Scotia Sea (caught in Dec. 1977) and krill from the Gerlache Strait (caught in Mar. 1981) were not observed. The main lipid classes found were: phosphatidylcholine (PC) (33–36%), phosphatidylethanolamine (PE) (5–6%), triacylglycerol (TG) (33–40%), free fatty acids (FFA) (8–16%) and sterols (1.4–1.7%). Wax esters and sterol esters were present only in traces. More than 50 fatty acids could be identified using GLC/MS, the major ones being 14∶0, 16∶0, 16∶1(n−7), 18∶1(n−9), 18∶1(n−7), 20∶5(n−3) and 22∶6(n−3). Phytanic acid was found in a concentration of 3% of total fatty acids. Short, medium-chain and hydroxy fatty acids (C≤10) were not detectable. The sterol fraction consisted of cholesterol, desmosterol and 22-dehydrocholesterol.
TL;DR: In this paper, synthetic mixtures of C40 to C47 sterol esters in groups of 7 esters were effectively separated and analyzed by capillary gas chromatography-mass spectrometry.
Abstract: Synthetic mixtures of C40 to C47 sterol esters in groups of 7 esters were effectively separated and analyzed by capillary gas chromatography-mass spectrometry. Ammonia chemical ionization of all 20 sterol esters analyzed at a source block temperature of 120 C yielded (M+NH4)+ and (M+H-RCO2H)+ ions of high abundance or as base peak, thereby indirectly indicating the molecular weights of the ester and the sterol and acid moieties. Ammonia CI spectra of all esters containing a Δ5-sterol moiety exhibited in addition to the above 2 ions an M+NH4-RCO2 H fragment. At a source block temperature of 150 C, M+H-RCO2 H fragment was the base peak for all esters, and there was little or no indication of an (M+NH4)+ adduct ion. Protonated molecules were not observed for any esters analyzed by methane or isobutane CI. Molecular ions of 3–14% intensity were obtained for only 3 of the esters analyzed by electron impact; they contained a Δ7-bond in the sterol nucleus, and the acid moiety was either saturated normal or branched chain or contained a single double bond. The base peak was a function of both the acid and sterol moieties of the sterol ester. The esters containing both saturated straight chain acid and saturated sterol moieties exhibited a base peak at m/z 215. The Δ5-sterol esters with saturated branched or straight chain acid moieties exhibited base peaks at M-RCO2 H. Other ions also were of diagnostic value.
TL;DR: Various nystatin-resistant mutants defective in S-adenosylmethionine: delta 24-sterol-C-methyltransferase were shown to possess alleles of the same gene, erg6, and the genetic map location of erg6 was shown to be close to trp1 on chromosome 4.1.
Abstract: Various nystatin-resistant mutants defective in S-adenosylmethionine: delta 24-sterol-C-methyltransferase (EC 2.1.1.41) were shown to possess alleles of the same gene, erg6. The genetic map location of erg6 was shown to be close to trp1 on chromosome 4. Despite the single locus for erg6, S-adenosylmethionine: delta 24-sterol-C-methyltransferase enzyme activity was found in three separate fractions: mitochondria, microsomes, and the "floating lipid layer." The amount of activity in each fraction could be manipulated by assay conditions. The lipids and lipid synthesis of mutants of Saccharomyces cerevisiae defective in the delta 24-sterol-C-methyltransferase were compared with a C5(6) desaturase mutant and parental wild types. No ergosterol (C28 sterol) could be detected in whole-cell sterol extracts of the erg6 mutants, the limits of detection being less than 10(-11) mol of ergosterol per 10(8) cells. The distribution of accumulated sterols by these mutants varied with growth phase and between free and esterified fractions. The steryl ester concentrations of the mutants were eight times higher than those of the wild type from exponential growth samples. However, the concentration of the ester accumulated by the mutants was not as great in stationary-phase cells. Whereas the head group phospholipid composition was the same between parental and mutant strains, strain-dependent changes in fatty acids were observed, most notably a 40% increase in the oleic acid content of phosphatidylethanolamine of one erg6 mutant, JR5.
TL;DR: The seagrass species were clearly separated into five chemical groups using the combined fatty acid and sterol composition data and the need for a reappraisal of the taxonomic position of Halophila was indicated.
TL;DR: The interactions of sonicated vesicles with the polyene antibiotics amphotericin B, candicidin, mediocidin , and a water-soluble, guanidine derivative of amphoteric in B were examined by UV-visible spectroscopy at concentrations below which the polyenes become self-associated, suggestive of penetration of the polyeners toward the interior of the bilayer when sterol is present.
Abstract: The interactions of sonicated vesicles with the polyene antibiotics amphotericin B, candicidin, mediocidin , and a water-soluble, guanidine derivative of amphotericin B were examined by UV-visible spectroscopy at concentrations below which the polyenes become self-associated. The association constants, Kapp, and the numbers of binding sites per sterol or phospholipid molecule (n) were determined at 30 degrees C and pH 7.4. A single class of binding sites was found, with no evidence of cooperativity. For the binding of mediocidin , amphotericin B, and the guanidine derivative with phosphatidylcholine (PC), PC/cholesterol, and PC/ergosterol vesicles, Kapp was in the range of (1.0-3.0) X 10(6) M-1; Kapp was higher for candicidin-vesicle interaction, reaching 9.0 X 10(6) M-1 with PC/ergosterol vesicles. Binding of the guanidine derivative of amphotericin B to PC vesicles lacking sterol was extensive (n = 0.46); since the other polyenes, which have low aqueous solubilities, had n less than 0.05, positive charges in the mycosamine moiety appear to enhance the extent of polyene antibiotic interaction with the glycerophospholipid head group. Higher values of n (and, therefore, of nKapp ) were found with sterol-containing than with sterol-free vesicles, suggestive of penetration of the polyenes toward the interior of the bilayer when sterol is present. For binding to PC/sterol vesicles, nKapp followed the order of candicidin greater than guanidine derivative of amphotericin B greater than amphotericin B much greater than mediocidin . The values of n and nKapp were appreciably higher for amphotericin B-ergosterol than for amphotericin B-cholesterol interaction in vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: A method for separating and quantifying seed oil steryl esters and free sterols was developed using a combination of preparative column, thin layer (TLC), and gas liquid chromatography (GLC) as discussed by the authors.
Abstract: A method for separating and quantitating seed oil steryl esters and free sterols was developed using a combination of preparative column, thin layer (TLC), and gas liquid chromatography (GLC). Cholesteryl heneicosanoate and cholesterol served as internal standards. The method was applied to corn-oil samples (Mazola, Kroger) obtained from the local market and peanut-oil samples prepared in the laboratory from commercial varieties of peanuts (Florunner, Starr). Concentration (mg/100 g oil; mean ± SD) of steryl esters and free sterols in the 4 oils were: Mazola, 1420±40 and 370±8; Kroger, 950±40 and 320±4; Florunner, 74±0.5 and 150±3; and Starr, 51±0.5 and 130±2. Sitosterol was the major sterol in both the free sterol and steryl ester fractions of all oils and together with campesterol, stigmasterol and Δ5-avenasterol made up 90–95% of all sterols. Steryl esters of peanut oil contained higher proportions of linoleic acid and long-chain acids (C20–C24) than did whole oil. Corn-oil steryl esters also contained a higher proportion of linoleic acid than did whole oil. Squalene was the major hydrocarbon of all oils with the remaining hydrocarbon fraction consisting of a mixture of compounds.
TL;DR: All of the properties exhibited by partially purified 14-reductase are consistent with the suggestion that the solubilized and enriched enzyme catalyzes the microsomal reduction of the 14-double bond of the sterol-conjugated dienes.
TL;DR: The observations that phospholipid exchange was one order of magnitude slower than cholesterol exchange and that dimethyl sulfoxide, potassium thiocyanate, and potassium salicylate enhanced the cholesterol exchange rate are consistent with a mechanism involving lipid exchange by diffusion through the aqueous phase.
TL;DR: The complexity of the sterol distributions, together with the predominance of dinostanol, distinguishes the sterols composition of this alga from those of other members of theGonyaulacaceae.
Abstract: Free and esterified sterols of the common marine dinoflagellateGonyaulax polygramma were identified using capillary gas chromatography—mass spectrometry (GC-MS). Fractions containing free 4α-methyl and 4-desmethyl sterols were isolated by column chromatography and shown to consist of at least 20 components. Major sterols included 4α,23,24-trimethyl-5α-cholestan-3β-ol (dinostanol), 4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol), cholest-5-en-3β-ol (cholesterol), 23,24-dimethyl-5α-cholest-22E-en-3β-ol and 23,24-dimethylcholesta-5,22E-dien-3β-ol. Although the same group of sterols was found in the free and esterified sterol fractions, the proportions of individual sterols were quite different. The complexity of the sterol distributions, together with the predominance of dinostanol, distinguishes the sterol composition of this alga from those of other members of theGonyaulacaceae.
TL;DR: It is concluded that changes in membrane fluidity are not important in determining ATPase activity in these systems.
Abstract: Cholesterol hemisuccinate has been shown to equilibrate readily with liposomes and with the (Ca2+-Mg2+)-ATPase from sarcoplasmic reticulum and has been used to modify the sterol content of these membranes. Cholesterol hemisuccinate incorporates into dioleoylphosphatidylcholine (DOPC) up to a molar ratio of 3:1 sterol to DOPC. Effects on lipid order as detected by electron spin resonance and fluorescence polarization are comparable to those of cholesterol. Binding constants have been determined, and the uncharged form of the sterol binds more strongly than the anionic form. Binding to DOPC and to the lipid component of the ATPase system is comparable. From use of the fluorescence quenching properties of 1,2-bis(9,10- dibromooleoyl )phosphatidylcholine and dibromocholesterol hemisuccinate, two classes of binding sites on the ATPase have been deduced. At the lipid/protein interface, the binding constant for cholesterol hemisuccinate is considerably less than that for DOPC. At the second set of sites ( nonannular sites), binding occurs with Kd = 0.55 in molar ratio units. The effect of cholesterol hemisuccinate on the activity of the ATPase depends on the phospholipid present in the system: ATPase reconstituted with DOPC is inhibited whereas ATPase reconstituted with dimyristoleoylphosphatidylcholine is activated. We conclude that changes in membrane fluidity are not important in determining ATPase activity in these systems.
TL;DR: With growth and aging in the rat there is a dramatic decrease in the rate of tissue cholesterol synthesis while the uptake of LDL-cholesterol remains essentially unchanged, and total cholesterol acquisition decreased several-fold primarily as a consequence of the diminished rate of sterol synthesis.
TL;DR: Some of the steatotic cholesterol oxides, such as the alpha and beta epimers of cholestan-5,6-epoxy-3 beta-ol were highly active with respect to steatosis, increasing the grade 3 value to 209 and 390% of control, respectively, but were not cytotoxic.
TL;DR: A portion and possibly all of the sterol requirement of juvenile lobsters is specific for cholesterol, and total replacement of cholesterol with a mixture of phytosterols composed primarily of β-sitosterol did not yield good growth and survival.
TL;DR: Changes in sterol composition during the development of tomato indicated a low proportion of glycosylated sterols in the ungerminated seeds with these compounds becoming progressively predominant compared with other sterols during the course of germination.
TL;DR: Fenpropimorph was found to be highly active against Penicillium italicum (EC50 0.01/μg ml−1) as discussed by the authors, which showed distorted germ tubes.
Abstract: Fenpropimorph was found to be highly active against Penicillium italicum (EC50 0.01/μg ml−1). Conidia of P. italicum, treated with low concentrations of fenpropimorph, swelled in size and showed distorted germ tubes. During the initial stages of mycelial growth, fenpropimorph had little or no effect on the dry weight increase, which became strongly inhibited within 24 h after addition of the toxicant (0.05, 0.1 and 0.2 μg ml−1). Irregular deposition of β–1,3 and β–1, 4 polysaccharides, probably chitin, was observed after treatment with fenpropimorph or imazalil. Fenpropimorph (0.05 and 0.2 μ ml−1) caused the accumulation of a major demethyl-sterol that was different from ergosterol. It was identified as ergosta-8, 14, 24(28)-trien-3β-ol by mass, infrared, ultraviolet and proton nuclear magnetic resonance, spectrometric procedures. At both concentrations, the accumulation was already detected after incubation for 2 h. In contrast, imazalil (0.1 μg ml−1) caused the accumulation of several methyl- and dimethyl-sterols which were tentatively identified as eburicol (24-methylene-24, 25-dihydrolanosterol), 4, 14α-dimethylergosta-8, 24(28)-dien-3-one, 14α-methylergosta-8, 24(28)-dien-3-one and obtusifoliol (4, 14α-dimethylergosta-8, 24(28)-dien-3α-ol). The accumulation of ergosta-8, 14,24(28)-trien-3β-ol indicates inhibition of the Δ14-reductase in P. italicum in a similar manner to that found previously in Ustilago maydis.
TL;DR: The composition of lipids extracted from a sample of millet seeds by each of 8 solvent systems is reported, and contrary to previously published observations, lysophosphatidylcholine was the major phospholipid in Millet seeds.
Abstract: The composition of lipids extracted from a sample of millet seeds by each of 8 solvent systems is reported. Lipid components were separated by silicic acid column and thin layer chromatography (TLC) and quantitated by analysis of fatty acid methyl esters by gas liquid chromatography (GLC), with heptadecanoic acid as internal standard. Best results were obtained by extraction with hot water-saturated butanol. Lipids extracted amounted to 7.2% of the seed dry weight and consisted of 85% neutral lipids, 12% phospholipids and 3% glycolipids. Neutral lipids contained mostly (85%) triacylglycerols and small amounts of mono- and diacylglycerols, sterols and free fatty acids. Sterols consisted of campesterol, stigmasterol and 2 unidentified sterols, occurring in the same proportions in free and esterified forms. Ten glycolipid and 10 phospholipid components were separated and characterized. Contrary to previously published observations, lysophosphatidylcholine was the major phospholipid (42%) in millet seeds; smaller amounts of phosphatidylcholine (24%), lysophosphatidylethanolamine (21%) and trace amounts of phosphatidylglycerol, phosphatidic acid, phosphatidylserine and phosphatidylinositol also were present. The major glycolipids were esterified sterol glycoside, sterol glycoside, monogalactosyldiacylglycerol, digalactosyldiacylglycerol and cerebrosides (ceramide monohexosides).
TL;DR: This is the first time codisterol has been found in a higher plant and also the firsttime the structures and configurations of the Δ 5 -sterols from a Cucurbitaceae species have been clearly characterized.