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Showing papers on "Sterol published in 1975"


Journal ArticleDOI
TL;DR: Changes in the metabolism of cholesterol, bile acids, and triglycerides in the patients of this study suggests that polyunsaturated fats may cause a lowering of cholesterol through multiple mechanisms, and it seems unlikely that a single action can explain all the effects of these fats on the plasma lipids.
Abstract: Studies were carried out on the effects of polyunsaturated fats on lipid metabolism in 11 patients with hypertriglyceridemia. During cholesterol balance studies performed in eight patients, the feeding of polyunsaturated fats, as compared with saturated fats, caused an increased excretion of endogenous neutral steroids, acidic steroids, or both in most patients. Increases in steroid excretions were marked in some patients and generally exceeded the decrement of cholesterol in the plasma compartment. The finding of a greater excretion of fecal steroids on polyunsaturated fats in hypertriglyceridemic patients contrasts to the lack of change in sterol balance previously reported for patients with familial hypercholesterolemia; however, other workers have found that polyunsaturated fats also enhance steroid excretion in normal subjects. In most of the patients, simultaneous studies were carried out on biliary lipid composition, hourly outputs of biliary lipids, and pool sizes of bile acids. In several but not all patients, fasting gallbladder bile became more lithogenic after institution of polyunsaturated fats. This increased lithogenicity was not due to a decrease in bile acid pools; in no case was the pool decreased by polyunsaturated fats. On the other hand, two patients showed an increased output of biliary cholesterol, and frequently there was an increase in fecal neutral steroids that were derived from cholesterol; thus, polyunsaturated fats may increase bile lithogenicity in some patients through mobilization of cholesterol into bile. Reductions in plasma cholesterol during the feeding of polyunsaturated fats was seen in most patients, and these changes were usually associated with a decrease in concentration of plasma triglycerides. In fact, the degree of cholesterol lowering was closely correlated with the extent of triglyceride reduction. Therefore, in hypertriglyceridimec patients polyunsaturated fats may contribute to cholesterol reduction by changing the metabolism of triglycerides or very low density lipoproteins. The findings of changes in the metabolism of cholesterol, bile acids, and triglycerides in the patients of this study suggests that polyunsaturated fats may cause a lowering of cholesterol through multiple mechanisms, and it seems unlikely that a single action can explain all the effects of these fats on the plasma lipids.

245 citations


Journal ArticleDOI
TL;DR: Palmitoleic, palmitic, eicosapentaenoic and myristic acids were the most prevalent fatty acids and 18-carbon fatty acids were rare.
Abstract: 1. 1. Diatoms in the genera Nitzschia, Phaeodactylum, Amphora, Navicula, Thallasiosira, Biddulphia and Fragilaria were compared for sterol, fatty acid and elemental composition. 2. 2. 24-Methyl-22-dehydrocholesterol (probably the 24S isomer) was the major sterol in five species, 24-ethyl-22-dehydrocholesterol (probably stigma-sterol) was the major sterol in two species and cholesterol the major sterol in one species. Complex mixtures of sterols occurred in three species. 3. 3. Palmitoleic, palmitic, eicosapentaenoic and myristic acids were the most prevalent fatty acids. Eighteen-carbon fatty acids were rare. 4. 4. High sodium concentrations were observed for most species while the concentrations of calcium, magnesium, potassium and nitrogen were typical for algae.

165 citations


Journal ArticleDOI
TL;DR: Human leukocytes isolated from fresh defibinated blood were shown to utilize acetate and mevalonate for sterol synthesis, and it was suggested that the genetic abnormality in heterozygous familial hypercholesterolemia could be accounted for by a mutation resulting in a weaker binding of a sterol repressor by heterozygOUS cells than by normal cells.

135 citations


Journal ArticleDOI
TL;DR: This study indicates that in U. maydis triarimol inhibits three reactions in ergosterol biosynthesis, all of which involve the D ring and the side chain of the sterol molecule: demethylation at C-14; introduction of the C-22(23) double bond; and reduction of theC-24(28) double Bond.

125 citations


Journal ArticleDOI
TL;DR: In vitro data taken together with the in vivo mammillary compartmental analysis data are compatible with the possiblity that the excess cholesterol synthesis of obesity occurs in pool 1, most likely from hepatic or intestinal sites.
Abstract: By analysis of 124 specimens in 16 different patients, isolated human adipocyte cholesterol concentration is highly correlated with fat cell size but not with plasma cholesterol concentration. Less than 6 percent of total cholesterol is esterified; after subcellular fractionation, 88 percent of the cholesterol is recovered in the triglyceride-rich supernatant oil. This latter finding supports the observation that fat cell cholesterol is determined by triglyceride content, and hence by fat cell size. After intravenous administrtion of radioactive cholesterol, the sum of a three-exponential equation was fit simultaneously to both the plasma and adipocyte specific activity time curves in six patients. In five of the six, a slowly turning over pool (pool 3) closely fit the adipocyte data. Two model structures, mammillary and catenary, were fitted to the data. There was no synthesis in pool 3 using a mammillary model but a mean 5.3 percent of the total body production rate was found in compartment 3 if a catenary model was assumed. Although a catenary model is biologically unlikely, it could not be excluded. Obesity is associated with an increased cholesterol synthetic rate equal to 20 mg/day for each kilogram of body fat. To test (by an independent method) if this synthesis might be occurring in adipose tissue, human fat cells were obtained under a wide variety of dietary conditions and incubated in vitro with radioactive glucose or acetate. Incorportation of these precursors into sterol could account for no more than 1 mg cholesterol synthesis/kg fat per day. These in vitro data taken together with the in vivo mammillary compartmental analysis data are compatible with the possiblity that the excess cholesterol synthesis of obesity occurs in pool 1, most likely from hepatic or intestinal sites.

112 citations


Journal ArticleDOI
TL;DR: Sterol synthesis in cultured mouse liver cells and in L cell fibroblasts is not inhibited by purified exogenous cholesterol, however, derivatives of cholesterol produced by the introduction of a ketone or hydroxyl function in the 7, 20, 22 or 25 positions effectively inhibit sterol synthesis by specifically depressing the level of HMG CoA reductase activity.
Abstract: Sterol synthesis in liver in vivo is regulated at the site of the reaction catalyzed by 3-hydroxy-3-methylglutaryl-CoA reductase through a feedback system thought to involve either cholesterol or one or more of the products of its metabolism. Cholesterol feeding results in repression of the synthesis of the enzyme, but inactivation of the enzyme seems to precede repressroblasts is not inhibited by purified exogenous cholesterol. However, derivatives of cholesterol produced by the introduction of a ketone or hydroxyl function in the 7, 20, 22 or 25 positions effectively inhibit sterol synthesis by specifically depressing the level of HMG CoA reductase activity. As a result of this specific effect prolonged incubation of an inhibitory sterol with growing L cells results in depletion of cellular sterol. Growth of the culture then ceases and the cells die unless an appropriate sterol or a sterol precursor is supplied in the medium. The inhibitory sterols, 25-hydroxycholesterol and 7-ketocholesterol appear to be taken up by L cells through processes that involve their specific interactions with saturable cellular receptors. The uptake of cholesterol by L cells appears to be by a different process--possibly through physical diffusion.

104 citations


Journal Article
TL;DR: In this article, the authors demonstrate the existence of a cell surface receptor that binds plasma low density lipoproteins and regulates the sterol content of cells by modulating the rates of uptake, esterification, and synthesis of cholesterol.
Abstract: Deposition of cholesterol esters in the arterial intima is a characteristic feature of human atherosclerosis. Very little is known about the mechanisms by which cells normally regulate their cholesterol ester content. Recent studies in cultured human cells demonstrate the existence of a cell surface receptor that binds plasma low density lipoproteins and regulates the sterol content of cells by modulating the rates of uptake, esterification, and synthesis of cholesterol. A possible role for this lipoprotein receptor in the pathogenesis of atherosclerosis is discussed.

98 citations


Journal ArticleDOI
TL;DR: The data indicate that CDCA suppressed elevated cholesterol and cholestanol synthesis in CTX, and suggest that this primary bile acid may be useful in preventing the clinical progression of this disease.

94 citations


Journal ArticleDOI
TL;DR: Evidence is presented that sterol esters of ergosterol precursors are unable to be metabolized to ergosterols, and once esterified, the fatty acids do not appear to be scavenged during starvation conditions.
Abstract: Variation in the percentage of sterols esterified to long-chain fatty acids during cellular growth has been examined. Under all conditions, a constant percentage of sterol esters was maintained during exponential growth. This maintenance level was found to vary with different growth conditions. A sharp increase in the rate of esterification was observed upon entry of the culture into the stationary growth phase. The minor cellular sterol components were found to accumulate after this period of rapid sterol ester synthesis, with a relative decrease in the size of the ergosterol pool. Evidence is presented that sterol esters of ergosterol precursors are unable to be metabolized to ergosterol. Once esterified, the fatty acids do not appear to be scavenged during starvation conditions.

94 citations


Journal Article
TL;DR: A possible role for a cell surface receptor that binds plasma low density lipoproteins and regulates the sterol content of cells by modulating the rates of uptake, esterification, and synthesis of cholesterol is discussed.
Abstract: Deposition of cholesterol esters in the arterial intima is a characteristic feature of human atherosclerosis. Very little is known about the mechanisms by which cells normally regulate their cholesterol ester content. Recent studies in cultured human cells demonstrate the existence of a cell surface receptor that binds plasma low density lipoproteins and regulates the sterol content of cells by modulating the rates of uptake, esterification, and synthesis of cholesterol. A possible role for this lipoprotein receptor in the pathogenesis of atherosclerosis is discussed.

94 citations


Journal ArticleDOI
TL;DR: Enhanced sterol excretion with polyunsaturated fat was potentiated with higher cholesterol intake, and enhanced excretion was generally greater during the first than during the second 3-week period of polyuns saturated fat.
Abstract: Previous studies have shown that polyunsaturated ruminant fats in the diets of human subjects cause an increase in cholesterol and bile acid excretion during the first 3 weeks of such diets. The present studies were designed to compare the effects of polyunsaturated (P) and conventional (S) ruminant fats at two levels of dietary cholesterol intake: a higher (HC) and lower (LC). Four study periods, each of about 3 weeks' duration, were conducted in 5 healthy subjects providing these dietary combinations: HCS, HCP, LCS, LCP. Neutral sterols and bile acids were measured in the feces, and sterol balances were calculated. Plasma cholesterol levels were significantly lower with P than with S diets at both HC and LC intakes. Changes attributable to differences in fatty acids and to differences in cholesterol intake appeared to exert independent effects. The major changes occurred in lipoproteins with density 1.019–1.045. Cholesterol absorption expressed as a percentage of the dietary intake was not significantly different with the four diets. Neutral sterol excretion of probable endogenous origin and bile acid excretion were significantly higher during the HCP than during the HCS periods, but the difference between LCP and LCS periods was less marked. Net sterol excretion was therefore significantly greater with HCP and LCP than with HCS and LCS diets, the differences being greater at HC than at LC intakes. Comparisons of diets with similar fatty acid but differing cholesterol intakes showed lower net sterol excretion with HCS than with LCS diets (presumably due to suppression by HC of cholesterol synthesis), but this difference was not seen between HCP and LCP diets. This finding, together with greater sterol excretion with HCP than with HCS diets, showed that enhanced sterol excretion with polyunsaturated fat was potentiated with higher cholesterol intake. This enhanced excretion was generally greater during the first than during the second 3-week period of polyunsaturated fat.

Journal ArticleDOI
TL;DR: The results fail to support the suggestion that neomycin acts as a bile acid precipitant, and the finding of increased fecal neutral steroid excretion is consistent with decreased cholesterol absorption, but also with increased cholesterol absorption and increased cholesterol synthesis.
Abstract: The mode of action of the hypocholesteremic drug neomycin (2 g/day) was studied in four patients. All showed a significant reduction in plasma cholesterol concentrations (mean 25 percent, range 18-31 percent), and in one of three patients with hyperglyceridemia there was a decrease of plasma triglycerides of 26 percent. Cholesterol absorption was measured in three of four patients: there was a marked decrease. Sterol balance studies in four patients showed an unabating increase in fecal neutral steroid excretion (mean increase 345 mg/day, range 323-361) for 3-5 wk after plasma cholesterol levels had reached a new and lower plateau. Fecal acidic steroid excretion increased temporarily in two patients, with a sustained increase of 93 mg/day in only one. Daily stool weights increased significantly in three of four patients, though none had steatorrhea; there was a significant reduction in excretion of secondary bile acids; neutral sterol degradation rates were not affected by the drug. Slopes of plasma cholesterol-specific activity time curves did not change. These results fail to support the suggestion that neomycin acts as a bile acid precipitant. The finding of increased fecal neutral steroid excretion is consistent with decreased cholesterol absorption, but also with increased cholesterol absorption, but also with increased cholesterol synthesis (secondary to release of negative feedback control), with increased flux of cholesterol from tissues, or with a combination of all three actions.

Journal ArticleDOI
TL;DR: Measurements of the activities of the rate-limiting enzymes showed fair correlation with cholesterol-bile acid balance, and in beta-sitosterol-fed animals, the reductase was increased 2-fold and cholesterol 7 alpha-hydroxylase was not significantly different from controls.

Journal ArticleDOI
TL;DR: The cholesterol content of the lymphocyte was raised by incubation with liposomes of high cholesterol content and the extra cholesterol was present, at least in part, in the plasma membrane.

Journal ArticleDOI
TL;DR: Sphingolipid fatty acid composition was influenced by ergosterol supplementation, and among the glycerophospholipids, cardiolipin and phosphatidylcholine were least affected, while the mixture of 1-alkyl-2-acyl-sn-glycero-3-(2-aminoethyl)-phosphonate and 1,2-diacyl

Journal ArticleDOI
TL;DR: Investigation of 4,4-dimethyl-Δ 8, 24 (28) -ergostadienol in untreated mycelia indicates that the C-14 methyl group is the first methyl group removed in the biosynthesis of ergosterol by A. fumigatus, which implies that both fungicides inhibit sterol C- 14 demethylation.

Journal ArticleDOI
TL;DR: The sterol concentrations in fourteen surface and nine deep water samples collected from the continental shelf and slope waters of the western North Atlantic and Sargasso Sea ranged from 1 to 13μ/l seawater as discussed by the authors.

Journal ArticleDOI
TL;DR: The plasma membrane contained more sterols than other membrane fractions, and the relative proportions of the different sterols were similar in all fractions.

Journal ArticleDOI
TL;DR: In this paper, an extract of Calyx nicaensis calysterol (C 29 cyclopropene-containing sterol) has been isolated and its structure elucidated.

Journal ArticleDOI
26 Sep 1975-Science
TL;DR: A detergent, N-(N-dodecanoylsarcosyl)taurine, representative of a set of detergents synthesized by the crustacean hepatopancreas and secreted into the intestine, is capable of efficient cholesterol solubilization, and thus of promoting sterol absorption.
Abstract: Although crustacean tissue cholesterol content is high, Crustacea, like other arthropods; are incapable of cholesterol synthesis, and presumably are dependent for maintaining tissue cholesterol stores on the intestinal absorption of ingested sterol. A detergent, N-(N-dodecanoylsarcosyl)taurine, representative of a set of detergents synthesized by the crustacean hepatopancreas and secreted into the intestine, is capable of efficient cholesterol solubilization, and thus of promoting sterol absorption.

Journal ArticleDOI
TL;DR: Triterpene acids of lanostane group were detected exclusively from the fungi causingbrown-rot of woods, while sterols were found to occur commonly in both brown-rot and white-rot fungi.

Journal ArticleDOI
TL;DR: Evidence is consistent with the proposal that a given sterol carrier protein is a soluble constituent of a single microsomal enzyme or enzyme complex, and that it participates both as a carrier for the water-insoluble substrate and as an essential enzyme constituent facilitating catalysis.

Journal ArticleDOI
TL;DR: Leaves of varying maturity from 84-day-old tobacco plants were harvested and analyzed for total sterol and their individual sterol components, and stimgasterol was principally responsible for this increase.

Journal ArticleDOI
TL;DR: Scanning electron microscopic studies demonstrate that the normal biconcave shape of the human erythrocyte is maintained in hypotonic saline when physiological levels (10 minus 5M) of cholesterol sulfate are added to the solutions.

Journal ArticleDOI
TL;DR: In this article, the composition of sterol and 4-methylsterol fractions isolated from virgin olive oil and from olive oil held at 180 °C for different periods of time, was determined by gas-liquid chromatography.
Abstract: The composition of sterol and 4-methylsterol fractions isolated from virgin olive oil and from olive oil held at 180 °C for different periods of time, was determined by gas-liquid chromatography. Characterisation of each sterol was carried out by gas-liquid chromatography and in some cases by combined gas chromatography-mass spectrometry. The percentage distribution of individual sterols in the fresh and heated samples indicated that citrostadienol deteriorates more rapidly upon heating than the other components of the 4-methylsterol fraction. Among sterols Δ5-avenasterol appeared more susceptible to air oxidation at high temperatures.

Journal ArticleDOI
TL;DR: Because of the rapidity of the rate of squalene synthesis, the results obtained reflect cholesterol synthesis over a period of less than 10 hr and are therefore uniquely applicable to unsteady state situations.
Abstract: A method for measuring the rate of total daily cholesterol synthesis in man has been developed through isotope kinetic studies of squalene biosynthesis after intravenous administration of [14C]mevalonic acid. Plasma squalene becomes rapidly labeled, reaching maximal specific activity approximately 100 min after mevalonate administration and then decays exponentially to reach undetectable levels in 12 hr. The rate of daily squalene synthesis equals the percent dose of mevalonate converted to cholesterol divided by the area under the specific activity curve of squalene; the fraction of the dose of mevalonate converted to cholesterol is calculated by the simultaneous injection of [3H]- and [14C] cholesterol in plasma. The premise that squalene and cholesterol synthetic rates are equivalent was tested. In seven patients it was found that the mean daily cholesterol synthesis rates estimated simultaneously by sterol balance and by sqyalene kinetic methods agreed within 8%. In addition, fractional conversions of mevalonic acid to cholesterol were highly correlated with cholesterol synthesis rates. Maximum estimates of the pool sizes and half-lives of metabolically "active" squalene also were obtained. This measurement of daily cholesterol synthesis by squalene kinetics minimizes patient inconvenience, is suitable for outpatient studies, and yields results in 4 weeks or less. Because of the rapidity of the rate of squalene synthesis, the results obtained reflect cholesterol synthesis over a period of less than 10 hr and are therefore uniquely applicable to unsteady state situations.

Journal ArticleDOI
TL;DR: The neutral lipids from whole cells and cell envelopes of aerobic Saccharomyces cerevisiae and anaerobic Sacch.

Journal ArticleDOI
TL;DR: Results show that in the production of sitosterol a 24-ethylidenesterol intermediate is produced and it is suggested that this is isomerized to give a Δ 24,(25) sterol prior to reduction to the saturated C 29 sterol side chain.

Journal ArticleDOI
TL;DR: The major constituent fatty acids are palmitic, oleic, linoleic and linolenic acids, which occur in the seed lipids of certain plants, are not found in tissue cultures derived from these plants.

Journal ArticleDOI
TL;DR: The sterol composition of 17 red algae has been determined and only C-27 sterols have been found in substantial amounts; details of the structural elucidation of liagosterol (cholesta-5,23-diene-3β,25-diol) are given.