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Showing papers on "Sterol published in 1994"


Journal ArticleDOI
TL;DR: It is suggested that conversion of cholesterol into 27-hydroxycholesterol and 3 beta-hydroxylate the same methyl group three times to give a carboxylic acid represents a general defence mechanism for macrophages and possibly also other peripheral cells exposed to cholesterol.
Abstract: 27-Hydroxycholesterol was found in surprisingly high amounts in atherosclerotic human femoral arteries. When human macrophages were cultured in a medium containing serum, there was a significant transfer of 27-hydroxy-cholesterol and 3 beta-hydroxy-5-cholestenoic acid from the cells into the medium. Sterol 27-hydroxylase (EC 1.14.13.15) is likely to be responsible for formation of the two products as shown by use of immunoblotting, a specific inhibitor, and the 18O-labeling technique. Sterol 27-hydroxylase has the unusual ability to hydroxylate the same methyl group three times to give a carboxylic acid; thus, 3 beta-hydroxy-5-cholestenoic acid is likely to be a direct product of the enzyme. The production of these steroids increased after addition of cholesterol to the culture medium. By using deuterium-labeled cholesterol, it was ascertained that most of the oxidized products were formed from exogenous cholesterol taken up by the cells. 27-Hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid are present in the circulation and are efficiently converted into bile acids in human liver. It is suggested that conversion of cholesterol into 27-hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid represents a general defence mechanism for macrophages and possibly also other peripheral cells exposed to cholesterol. Absence of this defence mechanism may contribute to the premature atherosclerosis known to occur in patients with sterol 27-hydroxylase deficiency (cerebrotendinous xanthomatosis).

301 citations


Journal ArticleDOI
01 Nov 1994-Yeast
TL;DR: In lipid particles of the yeast mutant strain S. cerevisiae erg6, this protein is missing thereby identifying the protein and confirming the previous finding (Zinser et al., 1993) that sterol Δ24‐methylation is associated with lipid particles.
Abstract: Lipid particles of the yeast, Saccharomyces cerevisiae, were isolated to high purity and their components were analysed. The hydrophobic core of this organelle consists of triacylglycerols and steryl esters, which are almost exclusively located to that compartment. Lipid particles are stabilized by a surface membrane consisting of phospholipids and proteins. Electron microscopy confirmed the purity of the preparations and the proposed structure deduced from biochemical experiments. Major proteins of lipid particles have molecular weights of 72, 52, 43 and 34 kDa, respectively. The 43 kDa protein reacts with an antiserum against human apolipoprotein AII. In lipid particles of the yeast mutant strain S. cerevisiae erg6, which is deficient in sterol delta 24-methyltransferase, this protein is missing thereby identifying the protein and confirming our previous finding (Zinser et al., 1993) that sterol delta 24-methylation is associated with lipid particles. A possible involvement of surface proteins of lipid particles in the interaction with other organelles is discussed with respect to sterol translocation in yeast.

253 citations


Journal ArticleDOI
TL;DR: It is proposed that an increase in plasma membrane fluidity may be correlated with a decrease in the sterol:phospholipid and sterol-protein ratios and a increase in unsaturation index.
Abstract: The lipid composition of a strain of each of two yeasts, Saccharomyces csrevisiae and Kloeckera apiculata, with different ethanol tolerances, was determined for cells grown with or without added ethanol. An increase in the proportion of ergosterol, unsaturated fatty acid levels and the maintenance of phospholipid biosynthesis seemed to be responsible for ethanol tolerance. The association of ethanol tolerance of yeast cells with plasma membrane fluidity, measured by fluorescence anisotropy, is discussed. We propose that an increase in plasma membrane fluidity may be correlated with a decrease in the sterol: phospholipid and sterol: protein ratios and an increase in unsaturation index.

233 citations


Journal ArticleDOI
TL;DR: It is concluded that the sitostanol ester-induced decrease in cholesterol absorption compensatorily stimulated cholesterol synthesis, had no effect on fractional catabolic rate, but decreased transport rate for LDL apoprotein B so that serum total, VLDL and LDL cholesterol levels were decreased.
Abstract: Cholesterol absorption and metabolism and LDL and HDL kinetics were investigated in 11 hypercholesterolaemic non-insulin-dependent diabetic men off and on a hypolipidaemic treatment with sitostanol ester, (3 g sitostanol daily) dissolved in rapeseed oil margarine, by a double-blind crossover study design. Serum total, VLDL and LDL cholesterol and apoprotein B fell significantly by 6 +/- 2, 12 +/- 6, 9 +/- 3 and 6 +/- 2%, mean +/- SEM, and HDL cholesterol was increased by 11 +/- 4% (p < 0.05) by sitostanol ester. LDL cholesterol and apoprotein B were significantly decreased in the dense (1.037-1.055 g/ml), but not light, LDL subfraction due to a significantly diminished transport rate for LDL apoprotein B, while the fractional catabolic rate was unchanged. HDL kinetics, measured with autologous apoprotein A I, was unaffected by sitostanol ester. Cholesterol absorption efficiency was markedly reduced from 25 +/- 2 to 9 +/- 2% (p < 0.001) during sitostanol ester followed by proportionately decreased serum plant sterol proportions. Cholesterol precursor sterol proportions in serum, fecal neutral sterol excretion, and cholesterol synthesis, cholesterol transport, and biliary secretion were all significantly increased by sitostanol ester. We conclude that the sitostanol ester-induced decrease in cholesterol absorption compensatorily stimulated cholesterol synthesis, had no effect on fractional catabolic rate, but decreased transport rate for LDL apoprotein B so that serum total, VLDL and LDL cholesterol levels were decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

217 citations


Journal ArticleDOI
TL;DR: In this paper, raw and treated sewage from physical-chemical and biological wastewater treatment plants were analyzed for fatty acids and sterols by HPLC and GC, and the results showed that sterols were more efficient with the biological treatment than with the chemical one, especially for the dissolved compounds.

176 citations


Journal ArticleDOI
Udo Seedorf1, P. Brysch1, Thomas Engel1, K Schrage1, Gerd Assmann1 
TL;DR: These findings suggest that SCPx is a previously undescribed peroxisomal 3-ketoacyl-CoA thiolase (EC 2.3.1.16) with intrinsic sterol carrier and lipid transfer activity (suggested name: SCP2/3-oxoACYl- CoA thiolaase).

166 citations


Journal ArticleDOI
TL;DR: It is proposed that this metabolic pathway that leads to bile acid synthesis from cholesterol serves a regulatory function, and becomes most prominent with the interruption of the enterohepatic circulation of bile acids.
Abstract: Bile acid synthesis from cholesterol can occur via two pathways, one initiated by sterol 27-hydroxylase activity or one initiated by that of cholesterol 7 alpha-hydroxylase. In contrast to cholesterol 7 alpha-hydroxylase, which is found in the liver, sterol 27-hydroxylase is a widely distributed mitochondrial enzyme with high activity in vascular endothelial cells. Although both pathways lead to the production of chenodeoxycholic and cholic acids, the key step, 7 alpha-hydroxylation, is governed by two different enzymes. Both 27-hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid, the metabolites of cholesterol occurring via sterol 27-hydroxylase activity, normally circulate in plasma. After their uptake by the liver they are metabolized mostly to chenodeoxycholic acid, which down-regulates the activity of cholesterol 7 alpha-hydroxylase, the rate-limiting step for the production of bile acids in the liver. Because of this relationship and also in view of the accelerated atherosclerosis and cholesterol deposition in tissues that occur as a consequence of genetically determined sterol 27-hydroxylase deficiency and of the potent biologic effect of 27-hydroxycholesterol in cell culture, it is proposed that this metabolic pathway serves a regulatory function. The pathway beginning with cholesterol 7 alpha-hydroxylation is modulated by genetic, hormonal, and probably dietary factors, and becomes most prominent with the interruption of the enterohepatic circulation of bile acids.

163 citations


Journal ArticleDOI
TL;DR: An analogue of SPM is synthesized, 3-deoxy-2-O-stearoyl-SPM, in which an ester-linked acyl chain replaces the amide-linkedAcyl chain at C-2 and a hydrogen replaces the hydroxy group atC-3, which appears to be equally miscible in both SPM monolayers.
Abstract: To understand the structural basis for the apparent strong interaction between cholesterol and sphingomyelin (SPM), we have synthesized an analogue of SPM, 3-deoxy-2-O-stearoyl-SPM, in which an ester-linked acyl chain replaces the amide-linked acyl chain at C-2 and a hydrogen replaces the hydroxy group at C-3. We have compared the behavior of this analogue with that of 3-deoxy-N-stearoyl-SPM in monolayers and vesicles, both as pure phospholipids and in mixtures with cholesterol. The force-area isotherm of 3-deoxy-2-O-stearoyl-SPM was similar to that of 3-deoxy-N-stearoyl-SPM. The surface potential across the pure SPM monolayer at the air-water interface was larger for 3-deoxy-2-O-stearoyl-SPM than for 3-deoxy-N-stearoyl-SPM (about 430 mV and 330 mV, respectively, at 50 A2). The overall dipole moment of 3-deoxy-2-O-stearoyl-SPM was almost constant at 570 mD (between a mean molecular area range of 45-85 A2), whereas that of 3-deoxy-N-stearoyl-SPM was about 420 mD. Cholesterol appeared to be equally miscible in both SPM monolayers, as determined from the condensing effect cholesterol had on the lateral packing of the two SPMs. The oxidation of monolayer cholesterol by cholesterol oxidase was also determined using both SPMs. The stoichiometry at which free cholesterol clusters disappeared in monolayers, when going from high to low cholesterol content, was 2:1 (mol sterol/mol SPM) for both SPMs.(ABSTRACT TRUNCATED AT 250 WORDS)

158 citations


Journal ArticleDOI
TL;DR: Results indicate that myeloperoxidase can convert cholesterol to chlorohydrins and epoxides by a reaction involving HOCl, and chlorinated sterols may prove useful as markers for lipoproteins oxidatively damaged by activated phagocytes.
Abstract: Myeloperoxidase, a heme protein secreted by activated phagocytes, uses hydrogen peroxide to produce potent cytotoxins. One important substrate is chloride, which is converted to hypochlorous acid (HOCl). This diffusible oxidant plays a critical role in the destruction of invading pathogens. Under pathological conditions, HOCl may also injure normal tissue. Recent studies have shown that myeloperoxidase is a component of human atherosclerotic lesions. Because oxidized lipoproteins may play a central role in atherogenesis, we have explored the possibility that cholesterol is a target for damage by myeloperoxidase. Three major classes of sterol oxidation products were apparent when cholesterol-phosphatidylcholine multilamellar vesicles which had been exposed to a myeloperoxidase-hydrogen peroxide-chloride system were subsequently analyzed by normal-phase thin layer chromatography. The products were identified by gas chromatography-mass spectrometry as cholesterol alpha- and beta-chlorohydrins (6 beta-chlorocholestane-3 beta,5 alpha-diol and 5 alpha-chlorocholestane-3 beta,6 beta-diol), cholesterol alpha- and beta-epoxides (cholesterol 5 alpha,6 alpha-epoxide and cholesterol 5 beta,6 beta-epoxide), and a novel cholesterol chlorohydrin. Conversion of cholesterol to the oxidation products required active myeloperoxidase, hydrogen peroxide, and halide and could be blocked by catalase or by scavengers of HOCl. Moreover, in the absence of the enzymatic system, reagent HOCl generated the same distribution of products. These results indicate that myeloperoxidase can convert cholesterol to chlorohydrins and epoxides by a reaction involving HOCl. Other oxygenated sterols are cytotoxic and mutagenic and are potent regulators of cholesterol homeostasis in cultured mammalian cells. Cholesterol chlorohydrins might similarly mediate powerful biological effects in the artery wall. Because chlorohydrins are stable under our experimental conditions, chlorinated sterols may prove useful as markers for lipoproteins oxidatively damaged by activated phagocytes.

141 citations


Journal ArticleDOI
TL;DR: The ergosterol and ergosta-7,22-dien-3-ol content proved to be especially valuable for grouping of these fungi and enabled even the differentiation of two sibling species of Heterobasidion annosum (type S and P).

135 citations


Journal ArticleDOI
TL;DR: The fluorescence dips provide compelling evidence that a naturally occurring sterol is regularly distributed at fixed compositional fractions, consistent with the presence of hexagonal super-lattices in the fluid membranes.
Abstract: To investigate the lateral organization of sterols in membranes, the fluorescence intensity of dehydroergosterol at different mole fractions in liquid crystalline dimyristoyl phosphatidylcholine bilayers was examined. A number of intensity drops were observed at specific mole fractions, as predicted from a hexagonal super-lattice model. The fluorescence dips provide compelling evidence that a naturally occurring sterol is regularly distributed at fixed compositional fractions, consistent with the presence of hexagonal super-lattices in the fluid membranes. Regularly distributed regions, however, coexist with irregularly distributed regions. The extent of regular distribution varies periodically with sterol mole fraction and, consequently, similar variations take place in the membrane volume and lipid packing. This level of modulation in local membrane structure by minute changes in sterol concentration should have profound implications for the functional role of cholesterol content in cell membranes.

Journal ArticleDOI
TL;DR: A negative correlation between the changes in LDL apolipoprotein B removal and LDL cholesterol suggests that LDL receptor activity was down-regulated, allowing more of the LDL precursor lipoproteins to be converted to LDL.

Journal ArticleDOI
TL;DR: Two Cryptococcus neoformans strains isolated from an AIDS patient were investigated and the sterol composition of CN3 indicated a defect in sterol delta 8-->7 isomerase in this strain and depletion of ergosterol, the major sterol of the CN1.
Abstract: Two Cryptococcus neoformans strains isolated from an AIDS patient were investigated, a pretreatment isolate (CN1) and a second isolate (CN3) following failure of fluconazole and amphotericin B treatment. No difference in fluconazole sensitivity, but relative resistance to amphotericin B was observed for CN3. The sterol composition of CN3 indicated a defect in sterol delta 8-->7 isomerase in this strain and depletion of ergosterol, the major sterol of the CN1.

Journal ArticleDOI
TL;DR: The oils from wild seeds were characterized by higher percentages of unsaponifiables compared to cultivated seeds, mainly due to their high contents of lignan, and the four species varied widely in the identity and levels of the different lignans.
Abstract: Seeds from different collections of cultivatedSesamum indicum Linn and three related wild species [specifically,S. alatum Thonn.,S. radiatum Schum & Thonn. andS. angustifolium (Oliv.) Engl.] were studied for their oil contents and fatty acid composition of the total lipids. The oils from wild seeds were characterized by higher percentages of unsaponifiables (4.9, 2.6 and 3.7%, respectively) compared toS. indicum (1.4–1.8%), mainly due to their high contents of lignans. Total sterols accounted forca. 40, 22, 20 and 16% of the unsaponifiables of the four species, respectively. The four species were different in the relative percentages of the three sterol fractions (the desmethyl, monomethyl and dimethyl sterols) and in the percentage composition of each fraction. Campesterol, stigmasterol, sitosterol and Δ5-avenasterol were the major desmethyl sterols, whereas obtusifoliol, gramisterol, cycloeucalenol and citrostandienol were the major monomethyl sterols, and α-amyrin, β-amyrin, cycloartenol and 24-methylene cycloartanol were the main dimethyl sterols in all species. Differences were also observed among the four species in sterol patterns of the free sterols compared to the sterol esters.Sesamum alatum contained less tocopherols (210–320 mg/kg oil), andS. radiatum andS. angustifolium contained more tocopherols (ca. 750 and 800 mg/kg oil, respectively) than didS. indicum (490–680 mg/kg oil). The four species were comparable in tocopherol composition, with γ-tocopherol representing 96–99% of the total tocopherols. The four species varied widely in the identity and levels of the different lignans. The percentages of these lignans in the oils ofS. indicum were sesamin (0.55%) and sesamolin (0.50%).Sesamum alatum showed 1.37% of 2-episesalatin and minor amounts of sesamin and sesamolin (0.01% each).Sesamum radiatum was rich in sesamin (2.40%) and contained minor amounts of sesamolin (0.02%), whereS. angustifolium was rich in sesangolin (3.15%) and also contained considerable amounts of sesamin (0.32%) and sesamolin (0.16%).

Journal ArticleDOI
TL;DR: The presence of the enzyme in endothelium provides a mechanism for preventing accumulation of intracellular cholesterol by initiating a pathway of bile acid synthesis different from that initiated by 7 alpha-hydroxylation of cholesterol in the liver.

Journal ArticleDOI
TL;DR: Two new different point mutations are described in the heme-ligand binding domain of the sterol 27-hydroxylase gene in three Japanese CTX patients and one CTX heterozygote, which result in two restriction fragment length polymorphisms (RFLPs) for the enzymes StuI or HpaII.

Journal ArticleDOI
TL;DR: Overall, sulfated sterols active against HIV-1 were also active againstAIDS, and those compounds which were sulfated on the sterol D ring were completely inactive against both HIV- 1 and HIV-2.
Abstract: A total of 22 sulfated sterols isolated from marine sponges, ophiuroids (brittle stars), and asteroids (sea stars) were comparatively evaluated for their antiviral activity against HIV-1 and HIV-2. In general, sterols with sulfate groups at position 2, 3, or 6 were the most active, with EC50 values of 3-13 microM against HIV-1 (RF) and 2-8 microM against HIV-2 (CBL20). Those compounds which were sulfated on the sterol D ring were completely inactive against both HIV-1 and HIV-2. Overall, sulfated sterols active against HIV-1 were also active against HIV-2.

Journal ArticleDOI
TL;DR: In this article, the effect of progesterone on the movement of sterols from the cell surface to the rough endoplasmic reticulum (ER) was examined in rat hepatoma cells.

Journal ArticleDOI
01 Jan 1994-Gene
TL;DR: The Saccharomyces cerevisiae ERG24 gene, encoding sterol delta 14 reductase (Erg24p), was cloned by selecting strains carrying sequences on a 2 mu-based vector for resistance to the morpholine fungicide, fenpropimorph (Fp).

Journal ArticleDOI
TL;DR: The results of the present study on niger seed oil are discussed in comparison with known data for common oils from Compositae,viz, safflower and sunflower.
Abstract: Niger seed samples were collected from different regions in Ethiopia for determination of oil content, and of fatty acid, tocopherol and sterol composition in the seed oil by gas-liquid chromatography and high-performance liquid chromatography methods. There was a large variation in oil content, ranging from 29 to 39%. More than 70% of the fatty acids was linoleic acid (18∶2) in all samples analyzed. The other predominant fatty acids were palmitic (16∶0), stearic (18∶0) and oleic (19∶1) at a range of 6 to 11% each. Total polar lipids recovered after preparative thin-layer chromatography comprised a small fraction of the total lipids. They had higher 16∶0 and lower 18∶2 contents than the triacylglycerols.α-Tocopherol was the predominant tocopherol in all samples, 94–96% of the total amounting to 630–800 μg/g oil. More than 40% of the total sterols wasβ-sitosterol,ca. 2000μg/g oil. The other major sterols were campesterol and stigmasterol, ranging from 11 to 14%. The Δ5- and Δ7-avenasterols were in the range of 4 to 7%. From the samples studied, no conclusion could be drawn regarding the influence of altitude or location on oil content, tocopherol and/or sterol contents. The results of the present study on niger seed oil are discussed in comparison with known data for common oils from Compositae,viz, safflower and sunflower.

Journal ArticleDOI
TL;DR: It is concluded that the MVA-derived component that is required for the accelerated degradation of HMG-CoA reductase is derived from farnesyl disphosphate and/or squalene in the isoprenoid biosynthetic pathway.

Journal ArticleDOI
TL;DR: The sterol hydroxylase was shown to be present on the mitochondrial inner membrane-matrix, to be inactivated by carbon monoxide, and to be activated by 450 nm radiation, establishing its membership in the P450 class.

Journal ArticleDOI
TL;DR: Three species contained small amounts of a dihydroxylated C29 sterol identified at 24-ethylcholesta-5,28(29)-dien-3β,24-diol (saringosterol), with the highest abundance in the tropical Australian isolate Micromonas aff.

Journal ArticleDOI
TL;DR: Regulation of cholesterol 7 alpha-hydroxylase mRNA level in Hep-G2 cells was studied and compared with that of two other sterol-responsive genes, those for the low density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase.

Journal ArticleDOI
TL;DR: The results show that the overproduced sterols of mutant tissues accumulate as steryl-esters in hyaloplasmic bodies, and suggest that the expression of the LAB 1–4 phenotype is dependent on the differentiation state of cells.
Abstract: The study of sterol overproduction in tissues of LAB 1–4 mutant tobacco (Nicotiana tabacum L. cv Xanthi) (P. Maillot-Vernier, H. Schaller, P. Benveniste, G. Belliard [1989] Biochem Biophys Res Commun 165: 125–130) over several generations showed that the overproduction phenotype is stable in calli, with a 10-fold stimulation of sterol content when compared with wild-type calli. However, leaves of LAB 1–4 plants obtained after two steps of self-fertilization were characterized by a mere 3-fold stimulation, whereas calli obtained from these plants retained a typical sterol-overproducing mutant phenotype (i.e. a 10-fold increase of sterol content). These results suggest that the expression of the LAB 1–4 phenotype is dependent on the differentiation state of cells. Most of the sterols accumulating in the mutant tissues were present as steryl-esters, which were minor species in wild-type tissues. Subcellular fractionation showed that in both mutant and wild-type tissues, free sterols were associated mainly with microsomal membranes. In contrast, the bulk of steryl-esters present in mutant tissues was found in the soluble fraction of cells. Numerous lipid droplets were detected in the hyaloplasm of LAB 1–4 cells by cytochemical and cytological techniques. After isolation, these lipid granules were shown to contain steryl-esters. These results show that the overproduced sterols of mutant tissues accumulate as steryl-esters in hyaloplasmic bodies. The esterification process thus allows regulation of the amount of free sterols in membranes by subcellular compartmentation.

Journal Article
TL;DR: Administration of fresh leaves of Ocimum sanctum (Tulsi) mixed as 1 g and 2 g in 100 gms of diet given for four weeks, brought about significant changes in the lipid profile of normal albino rabbits.
Abstract: Administration of fresh leaves of Ocimum sanctum (Tulsi) mixed as 1 g and 2 g in 100 gms of diet given for four weeks, brought about significant changes in the lipid profile of normal albino rabbits. This resulted in significant lowering in serum total cholesterol, triglyceride, phospholipid and LDL-cholesterol levels and significant increase in the HDL-cholesterol and total faecal sterol contents.


Journal ArticleDOI
TL;DR: Results suggest that the 56-kD protein represents the UDPG-SGTase, which was specific for UDP-glucose (Km = 34 [mu]M), for which UDP was a competitive inhibitor (inhibitor constant = 47 [mu)M).
Abstract: Membrane-bound UDP-glucose:sterol [beta]-D-glucosyltransferase (UDPG-SGTase) catalyzes the formation of steryl glucosides from UDP-glucose and free sterols. This enzyme was purified from etiolated oat shoots (Avena sativa L. cv Alfred) in five steps. UDPG-SGTase was solubilized from a microsomal fraction with the detergent n-octyl-[beta]-D-thioglucopyranoside and then extracted into diethyl ether. Subsequent removal of the organic solvent, resolubilization with an aqueous buffer, and two column chromatographic steps on Q-Sepharose and Blue Sepharose resulted in a 12,500-fold overall purification. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the final preparation revealed a 56-kD protein band, the intensity of which correlated with enzyme activity in the respective fractions. Polyclonal antibodies raised against this 56-kD protein did not inhibit enzyme activity but specifically bound to the native UDPG-SGTase. These results suggest that the 56-kD protein represents the UDPG-SGTase. The purified enzyme was specific for UDP-glucose (Km = 34 [mu]M), for which UDP was a competitive inhibitor (inhibitor constant = 47 [mu]M). In contrast to the specificity with regard to the glycosyl donor, UDPG-SGTase utilized all tested sterol acceptors, such as [beta]-sitosterol, cholesterol, stigmasterol, and ergosterol.

Journal ArticleDOI
TL;DR: It is shown that acyl structure is a key parameter controllingGalCer's ability to interact with cholesterol, and cholesterol exerts a marked condensing effect on liquid-disordered (liquid-expanded) GalCer species regardless of whether the acyl chain is saturated or unsaturated.
Abstract: Because cholesterol is a major lipid component of many cellular membranes, a great deal of effort has gone into understanding how this sterol interacts with other membrane lipids [eg, Finegold (1993)] To date, the majority of these efforts have focused on cholesterol’s mixing behavior with glycerol-based phospholipids, but occasionally they have included sphingomyelin, a sphingoid-based phospholipid The results from many, but not all, of the studies suggest that cholesterol has a greater “affinity” for sphingomyelin compared with other phospholipids Less clear is whether other simple sphingolipids (eg, monoglycosylceramides) display a similar high “affinity” for cholesterol and to what extent changes in ceramide and/or headgroup composition affect the interaction with cholesterol Investigating the interfacial interactions of cholesterol and monoglycosylceramides is important physiologically because of the unique structural properties conferred upon membranes (eg, myelin and brush border membranes) by these lipids Maintaining proper function requires not only that these lipids be present but also that their membrane concentration be optimized In certain pathological conditions, membrane concentrations of galactosylceramides are deficient (eg, Pelizaeius-Merzbacher’s disease) or grossly exceed optimum levels (eg, globoid cell leukodystrophy), and membrane function is impaired (Witter et al, 1980; Suzuki & Suzuki, 1989) Because the molecular basis for this impairment is not clear, investigations including high as well as low mole fractions of monoglycosylceramides should help to define the underlying physicochemical properties responsible for the fundamental defect in the diseased membranes A particularly informative approach for assessing lipid lateral interactions is to determine the molecular area of mixed-lipid monolayers as a function of surface pressure Using this approach, previous investigations indicated that cholesterol has a relatively greater condensing effect on sphingomyelin than on phosphatidylcholine (Lund-Katz et al, 1988) The effect could not be adequately explained by differences in acyl chain composition Here we have used the monolayer approach to assess condensation and compressibility in mixed films composed of cholesterol and galactosylceramides containing various homogeneous acyl chain compositions An important advantage of studying lipid-lipid interactions in this way is that the range of molecular areas known to occur in membrane systems can be investigated systematically while avoiding mesophasic changes that often occur in bulk aqueous systems (eg, bilayer vesicles, micelles) as lipid composition is varied Moreover, with lipid monolayers, other complicating issues such as lipid compositional changes due to either transbilayer asymmetry or vesicle-to-vesicle variation are avoided While the monolayer approach has been useful for studying the mixing behavior of many phospholipids and neutral lipids [for a review, see Dorfler (1990)], little has been reported for glycosphingolipid mixing with cholesterol Unlike previous investigations in which cholesterol mixing was studied with galactosylceramides bearing heterogeneous acyl chains (Johnston & Chapman, 1988; Slotte et al, 1993), this report focuses on cholesterol’s ability to condense and lower the compressibility of different molecular species of galactosylcermide containing homogeneous acyl chains that bear either zero, one, or two double bonds in their acyl chains The results clearly show that cholesterol exerts a large condensing effect on liquid-expanded, but not on liquid-condensed, Ga1Cer1 Nonetheless, cholesterol’s condensing effect on sphingomyelin is 25–30% larger than on liquid-expanded GalCer A preliminary report of portions of this work has appeared elsewhere (Ali et al, 1992)

Patent
Tracy K. Hunt1, Joerg Schwarzer1
01 Aug 1994
TL;DR: In this paper, a mixture containing tocopherol, fats and fat derivatives, more particularly fatty acids, and optionally sterol and/or sterol derivatives, is esterified with an alcohol in the presence of a basic catalyst.
Abstract: Starting from a mixture containing tocopherol, fats and/or fat derivatives, more particularly fatty acids, and optionally sterol and/or sterol derivatives, the free fatty acids present in the mixture are esterified with an alcohol. The mixture is then transesterified with an alcohol in the presence of a basic catalyst. After the transesterification, the excess lower alcohol is distilled off from the reaction mixture. The transesterification catalyst and the glycerol present, if any, are removed and the fatty acid alkyl ester is distilled off from the mixture. Distillation of fatty acid alkyl esters can be accomplished with a packed column in sequence with a wiped film evaporator. The simultaneous recovery of tocopherol and sterol is possible. Tocopherols and sterols can be separated by the crystallization of sterols from a blend of organic solvents.