Showing papers on "Sterol published in 1973"
TL;DR: The unsaponifiables from 19 vegetable oils were divided into a sterol and three other fractions by thin-layer chromatography, and campesterol, stigmasterol and β-sitosterol were present in all oils, and a minor amount of cholesterol in majority of the oils.
Abstract: The unsaponifiables from 19 vegetable oils were divided into a sterol and three other fractions by thin-layer chromatography. All except olive and palm kernel oils gave the sterol fraction in a large quantity. Compositions of the sterol fractions were determined by gas liquid chromatography. Identification of each sterol was carried out by gas liquid chromatography and combined gas chromatograph-mass spectrometry. Campesterol, stigmasterol and β-sitosterol were present in all oils, and a minor amount of cholesterol in majority of the oils. Brassicasterol occurrence was widespread but its content was extremely small in oils other than rapeseed oil. Other sterols, presumably δ7-stigmastenol and δ5- and δ7-avenasterol were detected in most of the oils.
297 citations
TL;DR: The results indicate that when cholesterol is present in membrane with lipids in both the crystalline and liquid-crystalline state, cholesterol preferentially interacts with these lipids which are in the liquid- crystals state.
222 citations
TL;DR: It is concluded that at these temperatures the ATPase is associated with molecular lipid species with the lowest transition temperature.
212 citations
TL;DR: Findings indicate that the excessive tissue deposits of cholesterol and cholestanol that characterize CTX were associated with hyperactive neutral sterol synthesis, and suggests that defective bile acid synthesis may predispose to theneutral sterol abnormalities.
Abstract: The metabolism of cholesterol and its 5-dihydro derivative, cholestanol, was investigated by means of sterol balance and isotope kinetic techniques in 3 subjects with cerebrotendinous xanthomatosis (CTX) and 11 other individuals. All subjects were hospitalized on a metabolic ward and were fed diets practically free of cholesterol and cholestanol. After the intravenous administration of [1,2-(3)H]cholestanol, the radioactive sterol was transported and esterified in plasma lipoproteins in an identical manner to cholesterol. In these short-term experiments, the specific activity-time curves of plasma cholestanol conformed to two-pool models in both the CTX and control groups. However, cholestanol plasma concentrations, total body miscible pools, and daily synthesis rates were two to five times greater in the CTX than control individuals. The short-term specific activity decay curves of plasma [4-(14)C]cholesterol also conformed to two-pool models in both groups. However, in the CTX subjects the decay was more rapid, and daily cholesterol synthesis was nearly double that of the control subjects. Plasma concentrations and the sizes of the rapidly turning over pool of exchangeable cholesterol were apparently small in the CTX subjects, and these measurements did not correlate with the large cholesterol deposits found in tendon and tuberous xanthomas. Despite active cholesterol synthesis, bile acid formation was subnormal in the CTX subjects. However, bile acid sequestration was accompanied by a rise in plasma cholestanol levels and greatly augmented fecal cholestanol outputs. In contrast, the administration of clofibrate lowered plasma cholesterol levels 50% and presumably reduced synthesis in the CTX subjects. Plasma cholesterol concentrations and fecal steroid excretion did not change significantly during this therapy. These findings indicate that the excessive tissue deposits of cholesterol and cholestanol that characterize CTX were associated with hyperactive neutral sterol synthesis. The demonstration of subnormal bile acid formation suggests that defective bile acid synthesis may predispose to the neutral sterol abnormalities.
164 citations
TL;DR: In the entire group of eight patients cholesterol turnover was greater than twice that found previously in nonobese patients studied under similar conditions, and this increment was directly related to excess body fat and to adipose cellularity, with correlation co-efficients of 0.66 and 0.72.
Abstract: An experiment was undertaken to test whether in severe obesity cholesterol production rates obtained by isotope kinetic analysis (two-pool compartmental analysis) are comparable to those measured by chemical sterol balance techniques. Eight severely obese but normocholesterolemic patients were studied by the balance method, and five of these eight were studied by compartmental analysis. Cholesterol turnover was 10% higher by compartmental analysis. In the entire group of eight patients cholesterol turnover was greater than twice that found previously in nonobese patients studied under similar conditions with bile acids and neutral sterols both participating in the increase. This increment was directly related to excess body fat and to adipose cellularity, with correlation co-efficients of 0.66 and 0.72, respectively. The amount of cholesterol in the slowly turning over pool B was related to degree of adiposity, but that in plasma and in pool A did not differ from values in nonobese patients.
145 citations
TL;DR: It is demonstrated that the liquefying effect of cholesterol on the membrane lipids of A. laidlawii can be very important in maintaining proper membrane functioning in growing cells.
119 citations
TL;DR: A substantial increase in the linoleic acid content of the milk and meat fat of cattle can be achieved if the ruminal hydrogenation of seed-oil linoleics acid is prevented, thereby increasing the content of these fats by more than 50%.
Abstract: A substantial increase in the linoleic acid content of the milk and meat fat of cattle can be achieved if the ruminal hydrogenation of seed-oil linoleic acid is prevented, thereby increasing the ratio of polyunsaturated to saturated fatty acids in cattle meat and milk 10 times. In a comparison of these and of conventional ruminant fats a significant reduction (10 per cent) in plasma cholesterol was observed in five of six subjects on such diets over periods of three to four weeks. In five subjects, the total excretion of sterols increased by an average of 18 per cent when polyunsaturated ruminant fats were eaten. The significant increase in both mean neutral sterol and bile acid excretion coincided with the fall in plasma cholesterol. Thus, increasing unsaturated fats in the diet of cattle lowered plasma cholesterol of subjects on diets containing food products from such cattle.
119 citations
TL;DR: Triarimol (2 μg/ml) strongly inhibited multiplication of Ustilago maydis sporidia after one doubling, but growth continued and sporidia became abnormally large, branched and multicellular.
83 citations
TL;DR: The results indicate that dietary sterols and bile acids both play a role in the regulation of intestinal HMG CoA reductase, and are associated with an increase in sterol concentration within the intestinal crypt cells.
74 citations
TL;DR: The results support the concepts that membrane lipid composition influences the activity of membrane-bound enzymes, and that sterols promote the gel to liquid phase transition in biological membranes.
74 citations
TL;DR: The sulfate and glucoside conjugates of sterols and ecdysteroids function, primarily, in the inactivation and excretion of steroids in insects, but can have other equally important roles related to the biosynthesis, metabolism, and transport of steroids, or the regulation of hormone titer.
Abstract: Publisher Summary This chapter discusses metabolism of steroids in insects. Insects require a dietary or exogenous source of sterol for normal growth, metamorphosis, and reproduction, and the only known exceptions to this are those species in which a sterol source can be attributed to associated symbiotes. The hornworm utilizes the major sterols of its primary host plant, tobacco—campesterol, sitosterol, and stigmasterol—through their dealkylation and conversion to cholesterol. These conversions proceed through a series of oxidation-reductive steps, and a number of the metabolites and intermediates involved can be characterized. Cholesterol serves both as a structural component of cells and tissues and as a precursor for the ecdysones or molting hormones. While the sulfate and glucoside conjugates of sterols and ecdysteroids function, primarily, in the inactivation and excretion of steroids in insects, these conjugates can have other equally important roles related to the biosynthesis, metabolism, and transport of steroids, or the regulation of hormone titer.
TL;DR: Electron micrographs of thin sections through developing asci show that the principal changes in fine structure occur between 18 and 24 hr and include the appearance of numerous electron-transparent vesicles which become aligned around the meiotic nucleus, and the laying down of extensive endoplasmic reticulum membranes.
Abstract: Eighty to ninety percent of vegetative cells of Saccharomyces cerevisiae DCL 740 incubated in KCl-acetate medium form asci, the majority of which are four-spored. Ascospores are visible in asci after about 24 hr, and spore formation is complete after about 48 hr. The dry weight of the cells increases by about 75% during 48 hr of incubation, while the lipid content of the cells increases by a factor of four. The increase in lipid content is attributed mainly to an increased synthesis of sterol esters and triacylglycerols and to a lesser extent of phospholipids. The phospholipid and sterol compositions do not change appreciably, but there is a marked increase in the proportion of unsaturated fatty acid residues in ascan lipids. Uniformly labeled (14)C-acetate is incorporated mainly into sterol esters and triacylglycerols and phospholipids. Pulse-labeling by adding acetate-U-(14)C to sporulating cultures and harvesting after a further 6 hr of incubation reveal two main periods of acetate incorporation, namely between 0 and 18 hr, and between 24 and 30 hr. Electron micrographs of thin sections through developing asci show that the principal changes in fine structure occur between 18 and 24 hr and include the appearance of numerous electron-transparent vesicles which become aligned around the meiotic nucleus, and the laying down of extensive endoplasmic reticulum membranes. Changes in fine structure are discussed in relation to the alterations in lipid content and composition of asci.
TL;DR: Interestingly, platelets can convert [14C]desmosterol to cholesterol, although not nearly as efficiently as liver, which suggests that a major block exists in vitro in demethylation of lanosterol by human platelets.
TL;DR: The occurrence of accelerated cholesterol uptake and turnover in Y-organs of summer intermolt, followed by accumulation in premolt of newly synthesized ecdysone-like metabolites, supports physiological evidence that these organs are involved in the molting process.
TL;DR: Mutant strains of Saccharomyces cerevisiae which require ergosterol for growth have been isolated and are of value not only in studies of sterol biosynthesis, but also in assessing the biological role of sterols in the cytoplasmic yeast membrane.
TL;DR: Polyene-induced permeability alteration in model membrane systems is effected by the composition of membrane phospholipid fatty acyl chains; the distribution of double bonds in the sterol nucleus is related to the selective toxicity of the polyenes toward natural sterol-containing membranes; and polyenes differ in membrane selectivity.
Abstract: In the absence of sterol, amphotericin B at 5 × 10−6 M caused maximum marker release from the saturated dipalmitoyl lecithin liposomes, minimum release from the unsaturated dioleoyl lecithin liposomes, and an in-between response from egg lecithin liposomes. Nystatin at 2.5 to 4.0 × 10−5 M induced appreciable marker release from all three types of sterol-free liposomes. The amphotericin B- and nystatin-induced permeability changes in dipalmitoyl lecithin liposomes were drastically suppressed by the incorporation of cholesterol or stigmasterol (with identical Δ5 sterol nuclei), but were unaffected by the incorporation of ergosterol or 5,7-cholestadien-3β-ol (with identical Δ5,7 sterol nuclei). The nystatin sensitivity of dioleoyl lecithin liposomes remained low after the incorporation of cholesterol or stigmasterol, but was greatly enhanced by the incorporation of ergosterol or 5,7-cholestadien-3β-ol. Digitonin, a compound known to interact specifically with membrane sterol, induced marker release from liposomes in proportion to the amount of either cholesterol or ergosterol incorporated; epicholesterol did not sensitize to digitonin. These results lead to the following conclusions: (i) polyene-induced permeability alteration in model membrane systems is effected by the composition of membrane phospholipid fatty acyl chains; (ii) the distribution of double bonds in the sterol nucleus is related to the selective toxicity of the polyenes toward natural sterol-containing membranes; and (iii) polyenes differ in membrane selectivity.
TL;DR: It is established that a sterol 24‐hydroxylase system is present in bovine cerebral cortex.
Abstract: The presence of cholest-5-ene-3β, 24-diol (cerebrosterol) in samples of human, bovine, and rabbit brains has been established by isolation of the sterol therefrom and identification by comparison of physical properties. Cholest-5-ene-3β, 24-diol was present at the level of 66.5 sg/g of dried tissue in human brain, 42.9 μg/g in cattle brain, and 89.5 pg/g in rabbit brain. Cholest-5-ene-3β, 24-diol was the only readily detectable hydroxycholesterol derivative in these brain tissues and was concentrated in the 105,000 g pellet (microsomal fraction) of both human and bovine cerebral cortex, with no demonstrable amounts of the sterol present in nuclear or mitochondrial fractions. Incubation of [1,2-3H]- or of [4-14C]-cholesterol with the 105,000 g microsomal pellet from bovine cerebral cortical homogenates demonstrated 0.1-0.38 per cent conversions to radioactive cholest-5-ene-3β, 24-diol, isolated and purified as the 3β, 24-dibenzoate. The bioconversion required oxygen, and a stimulation of hydroxylation by added NADPH2 was demonstrated. Our observations establish that a sterol 24-hydroxylase system is present in bovine cerebral cortex.
TL;DR: The effect of polyene antibiotics on Candida albicans, human erythrocytes, and Acholeplasma laidlawii was studied and the distribution of double bonds in the membrane sterol nucleus appears to be of major importance in conferring polyene susceptibility.
Abstract: The effect of polyene antibiotics on Candida albicans, human erythrocytes, and Acholeplasma laidlawii was studied. The results sustain the observations made with lecithin-sterol liposomes. The distribution of double bonds in the membrane sterol nucleus appears to be of major importance in conferring polyene susceptibility; those sterols with the ergosterol nucleus are far more effective than those with a nucleus similar to cholesterol. Different polyenes vary in their membrane selectivity. The clinical implications of these observations are discussed.
TL;DR: The carrier protein binds fatty acids as well as cholesterol precursors, suggesting that it may more generally be a lipid carrier protein with "squalene and sterol carrier protein" describing the functional aspects of the lipid carrier in cholesterol biosynthesis.
Abstract: Squalene and sterol carrier protein of liver plays a general role as a vehicle for cholesterol and its water-insoluble precursors; the carrier protein is essential for enzymic cholesterol synthesis. Liver microsomal enzymes contain a small amount of endogenous carrier protein, which is readily removed by washing or purification of the enzyme. Enzymic conversion to products of a cholesterol precursor·carrier protein complex is markedly faster than that for initially unbound sterol. The protomer form of the carrier protein has a molecular weight of 16,000; during sodium dodecyl sulfate gel electrophoresis one band is observed. Phospholipid facilitates the aggregation of the protomer to the oligomer form (>150,000 daltons; purified 720-fold) accompanied by the binding of cholesterol precursors to the oligomer. The carrier protein binds fatty acids as well as cholesterol precursors, suggesting that it may more generally be a lipid carrier protein with “squalene and sterol carrier protein” describing the functional aspects of the lipid carrier in cholesterol biosynthesis. Studies with several steroids and related compounds revealed that the binding sites of lipid carrier protein must contain highly specific hydrophobic and polar regions.
TL;DR: There were differences in the fatty acid composition of the steryl esters, in the extent of ester formation, as well as in the proportion and nature of bile acids derived from the two sterols.
TL;DR: A method is described for isolating sterol mutants of the filamentous fungus, Neurospora crassa, which carries gene mutations affecting the later stages of ergosterol biosynthesis and they accumulate other, as yet unidentified, sterol components.
Abstract: A method is described for isolating sterol mutants of the filamentous fungus, Neurospora crassa. Most of the mutants carry gene mutations affecting the later stages of ergosterol biosynthesis and they accumulate other, as yet unidentified, sterol components but two mutants are blocked earlier in the pathway and respond to exogenous mevalonic acid. Altered sterol metabolism is associated with a reduced rate of growth, abnormal morphology, poor fertility and resistance to a variety of polyene antibiotics.
TL;DR: Incubations carried out under CO + O2 in which the flasks were illuminated with high intensity light of around 450 nm wavelength completely reversed the inhibitory effect of CO on cholesterol biosynthesis from lanosterol.
Abstract: The rates of cholesterol biosynthesis were studied in rat liver microsomal preparations incubated with [14C]lanosterol in the presence of gas mixtures of either carbon monoxide + oxygen (90:10, v/v) or nitrogen + oxygen (90:10, v/v). The presence of CO in the gas mixture resulted in a considerable decrease in the amount of cholesterol synthesized, and there was also a reduction in the radioactivity of the 4α-methyl sterol fraction. The maximum rate of cholesterol biosynthesis in the presence of either N2+ O2 or CO + O2 occurred when the concentration of the substrate [14C]lanosterol was greater than 25 μM. The rate of cholesterol biosynthesis was constant for at least 40 min irrespective of the nature of the gas phase. During each time period studied, however, the amount of cholesterol formed was greater in the presence of N2+ O2. Removal of either ATP or NADPH from the incubation medium resulted in a significant decrease in the rate of microsomal cholesterol biosynthesis. Pre-treatment of rats with phenobarbital resulted in a 35–40% increase in the rate of microsomal cholesterol biosynthesis from lanosterol. Incubations carried out under CO + O2 in which the flasks were illuminated with high intensity light of around 450 nm wavelength completely reversed the inhibitory effect of CO on cholesterol biosynthesis from lanosterol.
TL;DR: Ascofuranone significantly reduced serum lipid levels of rats fed with normal diet 6 hours after a single oral administration of 108 mg/kg and the antibiotic did not induce hepatomegaly which is the main side effect of a positive control agent, ethyl-p-chlorophenoxyisobutyrate.
Abstract: Ascofuranone significantly reduced serum lipid levels of rats fed with normal diet 6 hours after a single oral administration of 108 mg/kg. When the antibiotic was orally given for consecutive 10 days to normolipidemic rats, the treatment resulted in marked reduction of serum cholesterol, triglycerides, phospholipids and free fatty acids without affecting organ weight gain, serum total protein, albumin/globulin ratio and serum transaminases. Reduction was also noted with cardiac cholesterol content but liver total sterol and fecal sterol excretion were unchanged. Acute toxicity of ascofuranone is weak to mice and rats and the antibiotic did not induce hepatomegaly which is the main side effect of a positive control agent, ethyl-p-chlorophenoxyisobutyrate.
TL;DR: The amounts of linoleic and linolenic acids in esterified sterol glucosides were increased after 5 days of germination in all the embryonic tissues, especially in the coleoptile half, and the desaturation in sterol esters was much less pronounced.
Abstract: Barley seeds,Hordeum vulgare, var. Kenia, were dissected before and after 5 days of germination, to distinguish between the scutellum, the coleoptile half of the embryo and the coleorhiza half of the embryo. Total lipids were extracted from each fraction and analyzed by thin layer chromatography and gas liquid chromatography. In tissues from the coleoptile and coleorhiza halves of the embryo there was a concurrent disappearance of triglycerides with a marked increase of esterified sterols and esterified sterol glucosides. In the scutellum there was also a change in triglycerides, but the variations in contents of esterified sterols and esterified sterol glucosides were much smaller. Mono- and digalactolipids were virtually absent from embryonic tissue. The amounts of linoleic and linolenic acids in esterified sterol glucosides were increased after 5 days of germination in all the embryonic tissues, especially in the coleoptile half. In sterol esters, linoleic acid comprised nearly half of the total fatty acids, and the desaturation after 5 days of germination was much less pronounced.
TL;DR: Sterols extracted from Xanthoria parietina with organic solvents and released by saponification of the residual lichen tissue were analysed by GC-MS and the previously unreported ergosta-5,8,22-trien-3β-ol, IIa, for which the name lichesterol is proposed was proposed.
TL;DR: Examination of the sterols produced by Mucor rouxii showed significant variations in the relative amounts of free and bound sterols contained in the aerobic and anaerobic cells, which were due at least in part to both the differences in the cell growth environment and changes in cell morphology.
TL;DR: The sterol components of the spores were qualitatively identical to those of the mycelial tissues, but several minor components remain to be identified.
TL;DR: Co results in a qualitative as well as a quantitative difference in the 4,4-dimethyl sterol fraction which arises during cholesterol biosynthesis from mevalonic acid, suggesting that enzymic reduction of the sterol side chain occurs predominantly at a stage after that of lanosterol.
Abstract: Cholesterol biosynthesis was studied in rat liver subcellular fractions incubated with dl-[2-14C]mevalonic acid under gas phases consisting of either N2+O2 (90:10) or CO+O2 (90:10). CO inhibits cholesterol biosynthesis from [2-14C]mevalonic acid and results in a large accumulation of radioactive 4,4-dimethyl sterols. Separation of the components of the 4,4-dimethyl sterol fraction showed that lanosterol and dihydrolanosterol are the major components that accumulate during cholesterol biosynthesis in an atmosphere containing CO, whereas 14-demethyl-lanosterol and 14-demethyldihydrolanosterol are the major components of the much less intensely radioactive 4,4-dimethyl sterol fraction isolated from incubations with N2+O2 as the gas phase. The identities of lanosterol, dihydrolanosterol and 14-demethyldihydrolanosterol were confirmed by both radiochemical and physicochemical methods, including g.l.c. and combined g.l.c.–mass spectrometry. CO therefore results in a qualitative as well as a quantitative difference in the 4,4-dimethyl sterol fraction which arises during cholesterol biosynthesis from mevalonic acid. The specific radioactivity of the [14C]lanosterol biosynthesized in the presence of CO was lower than that of its companion, [14C]dihydrolanosterol. The relative amounts of 4,4-dimethyl-Δ24-sterols and 4,4-dimethyl-24,25-dihydrosterols present in each type of incubation suggest that enzymic reduction of the sterol side chain occurs predominantly at a stage after that of lanosterol.
TL;DR: The thermal decomposition of the allylic alcohols was established and six common major pyrolysis products cholest-5-ene-3β,7α-diol, cholesta-3,5-dien-7-one, cholsesta-4,6-diens-3- one, andcholesta2,4, 6-triene was established.
TL;DR: Asterosterol, a new marine C26 sterol, was isolated from the asteroid A. amurensis, and its structure was characterized as 22-trans-24-nor-5α-cholesta-7,22-dien-3β-ol (1).