Showing papers on "Sterol published in 1976"
TL;DR: There is a well-documented negative correlation between plasma concentrations of high-density lipoproteins (H.D.L.L.) and risk of clinically evident atherosclerosis and there could be a second mechanism contributing to the apparent protective effect of high plasma-H. D.L .L.
266 citations
TL;DR: The present findings indicate that peripheral cells, in spite of their capacity to synthesize cholesterol, depend on exogenous cholesterol for the maintenance of normal levels and it is suggested that the native cholesterol "acceptor" in the lipoprotein-depleted serum is an apolipoprotein which under the experimental conditions can form a complex with phospholipids and might also represent the physiological cholesterol " acceptor", in peripheral lymph.
193 citations
TL;DR: Simultaneous measurments of the kinetics of uptake of radioactive unesterified cholesterol of whole serum and cholesteryl succinate, their conversion to lipid products, and the decay in enzyme activity suggest that the cholesterol-induced suppression is mediated by the sterol itself rather than by inhibitory lipid products derived from its metabolism.
138 citations
TL;DR: Cholesterol-enriched cells contained about 2% more lipid than cells enriched in any of the other sterols, which was largely accounted for by increased contents of triacylglycerols and, to a lesser extent, esterified sterols.
Abstract: Saccharomyces cerevisiae NCYC 366, grown under strictly anaerobic conditions to induce requirements for an unsaturated fatty acid (supplied by Tween 80) and a sterol, contained free sterol fractions enriched to the extent of 67 to 93% with the exogenously supplied sterol (campesterol, cholesterol, 7-dehydrocholesterol, 22, 23-dihydrobrassicasterol, beta-sitosterol, or stigmasterol). Cells enriched in any one of the sterols did not differ in volume, growth rate, contents of free sterol, esters and phospholipids, or phospholipid composition. Cholesterol-enriched cells contained about 2% more lipid than cells enriched in any of the other sterols, which was largely accounted for by increased contents of triacylglycerols and, to a lesser extent, esterified sterols. Phospholipids were enriched to the extent of about 52 to 63% with C18:1 residues. Cells enriched in ergosterol or stigmasterol were slightly less susceptible to the action of a wall-digesting basidiomycete glucanase than cells enriched with any one of the other sterols. The capacity of the plasma membrane to resist stretching, as indicated by the stability and volume of spheroplasts suspended in hypotonic solutions of buffered sorbitol (particularly in the range 0.9 to 0.7 M), was greater with spheroplasts enriched in sterols with an unsaturated side chain at C17 (ergosterol or stigmasterol) than with any of the other sterols. Plasma membranes were obtained from spheroplasts enriched in cholesterol or stigmasterol and had free sterol fractions containing 70 and 71%, respectively, of the sterol supplied exogenously to the cells. The sterol-phospholipid molar ratios in these membranes were, respectively, 1:7 and 1:8.
122 citations
TL;DR: Fatty acid distribution patterns in yeast cells consistently coincided with other reports concerning fatty acid composition of yeast cells, and correlation of lipid composition and classification of yeasts is suggested and discussed.
Abstract: The detailed composition of cellular lipid of more than 23 species of yeast has been determined quantitatively by thinchrography on quartz rods, a method previously used for estimating cellular lipids of seven species of yeast. That data was fortified by neutral and phospholipid quantitations on 30 species of yeast cells. Most of the test organisms contained 7-15% total lipid and 3-6% total phospholipid per dry cell weight, except for the extremely high accumulation of triglycerides in two species of Lipomyces. Qualitatively, 30 species of yeast cells contained similar neutral lipid constituents (triglyceride, sterol ester, free fatty acid, and free sterol) and polar lipid components (phosphatidyl choline, phosphatidyl ehtanolamine, phosphatidyl serine, phosphatidyl inositol, cardiolipin, and ceramide monohexoside) without minor constituents. Based on the quantitative composition of neutral lipids, the 30 species of yeast were divided into two groups , the triglyceride predominant group and the sterol derivative group. These groupings were fairly well overlapped from the standpoint of the distribution characteristics of fatty acid. The relative polar lipid compositions also grossly resembled each other. Only one exception of polar lipid composition in yeast cells was found in Rhodotorula rubra species which contained phosphatidyl ethanolamine as the most abundant phospholipid. Fatty acid distribution patterns in yeast cells consistently coincided with other reports concerning fatty acid composition of yeast cells. Correlation of lipid composition and classification of yeasts are suggested and discussed.
112 citations
TL;DR: The effect of altered sterol concentration on the ability of cultured cells to carry out endocytosis is investigated, to clarify further the role of cholesterol in membrane-dependent cytological functions.
Abstract: THE engulfment of droplets of fluid, from the surrounding medium (endocytosis or pinocytosis), represents a phenomenon of the plasma membrane of many mammalian cells1–3. The physiological significance of the process is not well understood although circumstantial evidence seems to suggest that it is necessary for normal functions of certain cell types. Steinman et al.4 have established the qualitative and quantitative aspects of endocytosis and have demonstrated that a variety of cells directly interiorise soluble proteins (for example, horseradish peroxidase) by invagination of the plasma membrane without previous binding of the proteins to cell-surface receptors. Cholesterol is a prominent constituent of the plasma membrane of mammalian cells, and its role in many complex functions of the cell membrane is just beginning to be understood. It buffers the ‘fluidity’ of the plasma membrane, increasing the viscosity at high temperatures and inpeding the transition into the gel state at reduced temperatures5–7. Through its action on membrane fluidity, or possibly more directly, it affects specific functions of the membrane such as ion transport and enzyme activities8. With these manifold effects of cholesterol on membrane structure and function in mind, we investigated the effect of altered sterol concentration on the ability of cultured cells to carry out endocytosis, to clarify further the role of cholesterol in membrane-dependent cytological functions.
105 citations
TL;DR: Fractional digitonin precipitation and alumina column chromatography were found to possess greater sterol separation abilities than previously recognized and many of the minor sterols were find to possess novel structures including a series of short side chain sterols, 19-nor sterols and 4-monomethyl sterols for which structure elucidation work is continuing.
103 citations
TL;DR: This work has shown that the addition of cholesterol or Δ5-cholesten-3 β-ol to liposomes decreases their permeability, whereas epicholesterol, a 3 α-isomer of cholesterol, exerts no apparent effect.
Abstract: FROM many recent studies on the phospholipid–sterol interaction, it has become increasingly clear that the 3 α-and 3 β-hydroxy isomers of a range of sterols have quite different effects on the molecular mobility and functional property of lipid bilayer membranes1,2. For example, the addition of cholesterol or Δ5-cholesten-3 β-ol to liposomes decreases their permeability, whereas epicholesterol, a 3 α-isomer of cholesterol, exerts no apparent effect. It has been proposed that the 3 β-hydroxyl group engages in hydrogen bonding with the carbonyl oxygen of the fatty acyl groups in phospholipids in the bilayer3. Evidence supporting such hydrogen bond formation is strong4. The problem is, then, why does the 3 β-OH group of cholesterol, but not the 3 α-OH group of epicholesterol form such bonds?
98 citations
TL;DR: Substantial evidence supports the hypothesis that SCP1 operates as a noncatalytic carrier protein for the water-insoluble substrate squalene in the enzymatic conversion ofSqualene to lanosterol by liver microsomal membranes.
83 citations
TL;DR: It is proposed that cholesteryl sulfate, an amphipathic molecule ideally suited for interaction with membrane components and implicated in erythrocyte membrane stabilization, may be involved in membrane modifications of the spermatozoa during the process of fertilization.
73 citations
TL;DR: The results obtained emphasize that the close biochemical similarities noted between rER and nuclear membranes of animal cells extend to these fractions from plant cells.
Abstract: Nuclei, nuclear membranes and rough endoplasmic reticulum (rER) were isolated from onion root tips and stems. Structural preservation and purity of the fractions was determined by electron microscopic and biochemical methods. Gross compositional data (protein, phospholipid, nonpolar lipids, sterols, RNA, DNA), phospholipid and fatty acid patterns, enzyme activities (ATPases, ADPase, IDPase, glucose-6-phosphatase, 5'-nucleotidase, acid phosphatase, and NADH- and NADPH-cytochrome C reductases), and cytochrome contents were determined. A stable, high salt-resistant attachment of some DNA with the nuclear membrane was observed as well as the association of some RNA with high salt-treated nuclear and rER membranes. The phospholipid pattern was identical for both nuclear and rER membranes and showed a predominance of lecithin (about 60%) and phosphatidyl ethanolamine (20-24%). Special care was necessary to minimize lipid degradation by phospholipases during isolations. Nonpolar lipids, mostly sterols and triglycerides, accounted for 35-45% of the membrane lipids. Sterol contents were relatively high in both membrane fractions (molar ratios of sterols to phospholipids ranged from 0.12 to 0.43). Sitosterol accounted for about 80% of the total sterols. Palmitic, oleic, and linoleic acids were the most prevalent acids in membrane-bound lipids as well as in storage lipids and occurred in similar proportions in phospholipids, triglycerides and free fatty acids of the membrane. About 80% of the fatty acids in membrane phospholipids and triglycerides were unsaturated. A cytochrome of the b5 type was characterized in these membranes, but P-450-like cytochromes could not be detected. Both NADH and NADPH-cytochrome c reductases were found in nuclear and rER membranes and appeared to be enriched in rER membranes. Among the phosphatases, Mg2+-ATPase and, to lesser extents, ADPase, IDPase and acid phosphatase activities occurred in the fractions, but significant amounts of monovalent ion-stimulated ATPase, 5'-nucleotidase and glucose-6-phosphatase activities did not. The results obtained emphasize that the close biochemical similarities noted between rER and nuclear membranes of animal cells extend to these fractions from plant cells.
TL;DR: The absorption of cholesterol from diets containing various proportions of triglycerides and an unabsorbable fat, sucrose polyester (SPE), was determined in rats and cholesterol was found to be equally soluble in triolein or SPE.
Abstract: The absorption of cholesterol from diets containing various proportions of triglycerides and an unabsorbable fat, sucrose polyester (SPE), was determined in rats. Each replacement of 1% dietary triglyceride with SPE resulted in a 1.2% decrease in cholesterol absorption. The SPE was a mixture of the hexa-, hepta- and octa-esters of long chain fatty acids. The physical properties of this material are similar to those of the usual dietary triglycerides. Relative to these studies, cholesterol was found to be equally soluble in triolein or SPE. If water was present as well, the solubility of the sterol was decreased by the same amount in both fats. The distribution coefficients of cholesterol between an oil phase of either triolein or SPE and a micellar phase simulating that found in the lumen of the intestinal tract were identical. These two types of fats differ in that SPE is neither digested nor absorbed. The decrease in cholesterol absorption is attributed to the continued presence of an oil phase of SPE in the lumen of the intestine. Dietary cholesterol distributes itself between this oil phase and the micellar phase. That portion in the oil phase is not absorbed but is egested in the feces.
TL;DR: Suspensions of dimyristoyl and dipalmitoyl phosphatidylcholine vesicles bearing 10 to 40 (w/w)% cholesterol inhibited the fertilizing ability of uterine-capacitated rabbit spermatozoa at concentrations of 1 to 10 mg of lipid/ml.
Abstract: SummarySuspensions of dimyristoyl and dipalmitoyl phosphatidylcholine vesicles bearing 10 to 40 (w/w)% cholesterol inhibited the fertilizing ability of uterine-capacitated rabbit spermatozoa at concentrations of 1 to 10 mg of lipid/ml. Recovery of fertilizing ability by treated sperm cells was observed following insemination into the uterus 5 to 6 hr before ovulation. Vesicles lacking the sterol were not inhibitory under the conditions employed. Suspensions of cholesterol (0.4 to 4 mg of sterol/ml) without phospholipid, in contrast, inhibited fertilization. Implication of cholesterol in sperm decapacitation by seminal plasma membrane vesicles is discussed in terms of these results.I am indebted to Mr. R. Byrne and Mrs. N. Davis for their helpful assistance. The electron micrographs were prepared by Mr. K. Bedigian. Financial support was received from NIH Contract No. 1-HD-3-2781.
TL;DR: The hyperlipemic serum stimulated a greater incorporation of free cholesterol into the monkey medial cells, accompanied by a 2-fold increase in the cellular esterification of this free cholesterol.
TL;DR: In this article, the composition of the terpenic alcohol and sterol fractions of ten algal species, fiveMyxophyceae and fiveChlorophycea, is discussed.
Abstract: The composition of the terpenic alcohol and sterol fractions of the unsaponifiables of ten algal species, fiveMyxophyceae and fiveChlorophyceae, is discussed. The major component of the terpenic fraction is phytol, a diterpenic alcohol. Minor amounts of straight chain and triterpenic alcohols are also present. Practically all the species examined contain ten components in the sterol fraction: cholesterol, brassicasterol, Δ5-ergostenol, poriferasterol, Δ7-ergostenol, clionasterol, chondrillasterol, Δ5-avenasterol, Δ7-chondrillastenol, and an unidentified component. Identification of the sterols was made by gas chromatography-mass spectrometry, and a 24 S configuration was assumed. The prokaryotic blue-green algae are characterized by a higher content in cholesterol (3.5–14%) than the eucaryotic green algae (0–2.5). Also, brassicasterol, poriferasterol, clionasterol, and Δ5-avenasterol are more abundant in blue-green algae. Δ7-Ergostenol, chondrillasterol, and Δ7-chondrillastenol predominate, on the contrary, in green algae.
TL;DR: Kidney proved to be by far the most active tissue site of mevalonate metabolism by the shunt mechanism in that, on an average, renal tissue metabolized (R)-[14C]mevalonates over the non-sterol pathway at a rate that was 21 times that of any other tissue examined.
TL;DR: Sterol composition and biosynthesis in Candida utilis and C. albicans have been investigated and it was revealed that the major sterols of these successively more resistant cultures were successfully more primitive biogenetic precursors of ergosterol in the parent strain.
TL;DR: Three different plant sterol fractions were added to refined cottonseed oil and the rate of oxidation followed by changes in the composition and in physical constants reduced the extent of oxidation and β-sitosterol was initially ineffective and became slightly prooxidant after prolonged heating.
Abstract: Three different plant sterol fractions were added to refined cottonseed oil. The first fraction was isolated from olive oil, the second fraction Δ5-avenasterol was extracted from the green algae (Ulva lactuca) and the third fraction was a sterol mixture, made up chiefly of β-sitosterol. Cottonseed oil with the different sterols added was heated at 180±5°C and the rate of oxidation followed by changes in the composition and in physical constants. Olive oil sterol mixtures containing Δ5-avenasterol and Δ5-avenasterol alone reduced the extent of oxidation. β-sitosterol was initially ineffective and became slightly prooxidant after prolonged heating.
TL;DR: A great deal more evidence from well constructed human diet studies will be needed before low cholesterol diets can be recommended to the general population as an aid to control of cholesterol balance and heart disease.
TL;DR: Like most other mycoplasmas, S. citri was shown to be unable to synthesize fatty acids or esterify cholesterol and to grow best on cholesterol and beta-sitosterol and was able to grow on stigmasterol and ergosterol to a lesser degree.
Abstract: In a horse serum-based medium containing a full complement of fatty acids, cells of Spiroplasma citri were seen to preferentially incorporate palmitic acid. In the same medium, which had a steryl ester-to-sterol ratio of 3.64, a steryl ester-to-sterol ratio of 0.23 was seen in the cells, cholesterol being preferentially incorporated over cholesteryl ester. Like most other mycoplasmas, S. citri was shown to be unable to synthesize fatty acids or esterify cholesterol. The neutral lipids of S. citri grown in a medium containing horse serum consisted of free cholesterol, cholesteryl ester, free fatty acids, triglycerides and diglycerides. All polar lipids were phospholipids, with no glycolipids detected. These phospholipids, which are characteristic of many mycoplasmas, are phosphatidyl glycerol, diphosphatidyl glycerol, and their lyso derivatives. Sphingomyelin was also incorporated when cells were grown on horse serum. A sterol requirement for the growth of S. citri was confirmed using a serum-free medium supplemented with bovine serum albumin, palmitic acid, and various concentrations of sterols dissolved in Tween 80. The addition of palmitic acid stimulated growth but was not essential for growth. S citri was shown to grow best on cholesterol and beta-sitosterol and was able to grow on stigmasterol and ergosterol to a lesser degree. No growth was obtained using mevalonate, deoxycholate, or taurodeoxycholate as an alternative to sterol. S. citri was also able to grow when palmitic acid was replaced with oleic acid, linoleic acid, or linolenic acid. Alterations in the lipid composition of the growth medium and hence in the lipid composition of S. citri induced changes in the characteristic helical morphology of the cells, concurrent with loss of cell viability. Culture, age, and pH were also factors in determining cell morphology and viability.
TL;DR: Since cholesterol turnover did not appear to be necessarily influenced by ethanol, as judged either by total endogenous sterol excretion or from the slope of the plasma cholesterol specific radioactivity-time curve, the ethanol-induced increase in bile acids excretion amy not be analogous to other clinical disorders in which increased bile acid excretion and hypertriglyceridemia are associated with raised sterol production.
TL;DR: The effects of filipin and amphotericin methyl ester upon the K+ efflux from Mycoplasma mycoides subsp.
TL;DR: Gas chromatography/mass spectrometry analyses of the plasma lipids from a much more limited number of subjects and animals showed that the GLC peaks corresponding to the free C28 and C29 sterols were largely due to the plant sterols campesterol, stigmasterol, and β-sitosterol.
Abstract: Direct gas liquid chromatography (GLC) of total plasma lipids showed small peaks (0.5-1.5% of total free sterol area) corresponding to free C28 and C29 sterols in ca. 50% of some 3,000 normal subjects and patients with hyperlipemia. Comparable proportions of similar peaks were present in the sterol fraction isolated from the red blood cells of many of these subjects. The maximum levels of these components in the plasma and red blood cells of domestic and laboratory animals were up to 10 times higher than those seen in man. Detailed gas chromatography/mass spectrometry analyses of the plasma lipids from a much more limited number of subjects and animals showed that the GLC peaks corresponding to the free C28 and C29 sterols were largely due to the plant sterols campesterol, stigmasterol, and beta-sitosterol. In all instances, variable amounts (0.05-0.2% of the total free sterol area) of 7-dehydrocholesterol, desmosterol, lanosterol, and cholesterol alpha-oxide were also detected. While the total content and composition of the plasma plant sterols appeared to vary greatly among the subjects, it never exceeded 2% of total sterol in the normal subjects and patients examined. There was no evidence for a significant increase in the plant sterol content of the plasma of patients with hypercholesterolemia or hypertriglyceridemia.
TL;DR: There was a positive correlation between overall lipogenic rate and the percentage of isotope appearing in free sterol, while the relative proportions of the other lipid classes were unchanged, and in control epidermis sterol percentage was negatively correlated withlipogenic rate.
Abstract: SUMMARY
The rate and pattern of epidermal lipogenesis from [14C] glucose were measured in fifteen patients with psoriasis and three with lichen simplex, compared with twenty controls. In ‘uninvolved’ epidermis from psoriatic subjects the mean lipogenic rate was slightly raised, although the increase was not statistically significant. There was a positive correlation between overall lipogenic rate and the percentage of isotope appearing in free sterol, while the relative proportions of the other lipid classes were unchanged. By contrast, in control epidermis sterol percentage was negatively correlated with lipogenic rate.
In psoriatic lesions total epidermal lipogenesis (per unit surface area) was raised compared with matched control ‘uninvolved’ epidermis. Also raised were percentage labelling of free sterol and of combined (free sterol and monoesters), and the free sterol: monocstcr ratio was increased. Similar findings were obtained with lesions of lichen simplex, suggesting that disturbed sterol metabolism may be a common feature in conditions of abnormal keratinization.
TL;DR: Since end product inhibition of methyl sterol oxidase may be produced by accumulation of cholesterol or cholesterol metabolites, the soluble protein may participate in regulation of the activity of some microsomal enzymes of cholesterol biosynthesis.
TL;DR: Analysis of the nonpolar lipids of the flagellar membrane showed that free fatty acids constitute about 12 molar per cent of the total lipids, which could be true components of the membrane or artifacts of the extraction procedure although every precaution was taken to prevent artifactual production offree fatty acids.
TL;DR: Results indicate blockage of the side chain methylation that normally occurs during the biosynthesis of ergosterol in yeast by compound 10 is efficient and the inhibited yeast thus provides a source of a potentially new provitamin D3 substitute.
Abstract: The effect of low concentrations of a specifically designed sterol-24-transmethylase inhibitor, 25-aza-24,25-dihydrozymosterol (10) on sterol production in Saccharomyces cerevisiae was examined. Th...
TL;DR: The results suggest that the sterol side-chain exerts a great influence on membrane rigidity within its immediate environment.
TL;DR: The data support the view that one mode of regulation of hepatic HMG-CoA reductase is dependent on the relative rates of movement of cholesterol into and out of cells.