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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The cholesterol ester hydrolase of rat brain, localized almost exclusively in the myelin sheath, has been solubilized from the acidic high-molecular-weight protein fraction of purified myelin. Solubilization required both high ionic strength and an amphoteric detergent, Miranol H2M. Solubilized preparations with apparent purification factors of 300–500 fold over the starting homogenate still contained approx 25% lipid but were retarded on the Sephadex G-200 column. The enzyme was reversibly precipitated when the concentration of either Miranol H2M or KCI was lowered below certain critical levels. The soluble enzyme was characterized for the pH optimum, linearity against incubation time and enzyme protein, and apparent Km. Activity was dependent on the presence of exogenously added lipid. Phosphatidylserine at optimum concentrations stimulated the hydrolytic activity 25-Fold. Effects of other lipids, bile salts, cations, heating and potential inhibitors were examined. β-Naphthyl oleate was a competitive inhibitor but both β-naphthyl acetate and cholesteryl butyrate were non-competitive inhibitors. These results suggested a heterogenous nature of the rat myelin cholesterol ester hydrolase, possibly with different specificities with respect to the chain length of the acyl group of substrates.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 18 (1971), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Lactosylceramide-cleaving activities were examined in the canine form of globoid cell leuko-dystrophy. Lactosylceramidase I activities were deficient in the brains and livers of affected dogs, while they were intermediate in heterozygous carriers. In contrast, lactosylceramidase II activities were normal in affected dogs. Examination of the total tissue activities, solubilization characteristics, and the behavior in Sephadex G-200 gel filtration, of the activities of lactosylceramidase I and II, galactosylceramidase, and 4-methylumbelliferyl β-galactosidase, indicated that, as in human tissues, lactosylceramidase 1 is probably identical with galactosylceramidase, and that lactosylceramidase II is closely associated with 4-methylumbelliferyl β-galactosidase. The canine form of globoid cell leukodystrophy is analogous with the human disease with respect to lactosylceramidases, and the lactosylceramidase I assay system of Wengeret al. (1974) is directly applicable also for canine tissues.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Activity of cholesterol ester hydrolase localized almost exclusively in the myelin sheath (Eto & Suzuki, 1973a) was greatly affected by exogenous lipids added to the assay mixture. With isolated myelin as the enzyme source, phosphatidylserine was most effective in stimulating the activity. Other phospholipids were less effective. Efhanolamine phospholipid was slightly inhibitory and lysolecithin was strongly inhibitory. Differences in the fatty acid composition did not appear to account for such different effects. Glucosylceramide, galactosylceramide and digalactosylceramide were stimulatory while sulfatide, ganglioside and its asialo-derivative were inhibitory. Saturated fatty acids were generally stimulatory while corresponding unsaturated acids were strongly inhibitory. In order for exogenous lipids to be effective they had to be added to the assay mixture as free dispersion. When heat-inactivated myelin was used as the lipid source, no effect was observed, while equivalent amounts of a whole white matter lipid mixture was effective. Although phosphatidylserine was the most effective activator among the lipids tested, it could not completely replace sodium taurocholate present in the standard assay system. When isolated myelin was stored frozen, the activity of the enzyme declined gradually in the standard system without additional lipids. The stimulating effect of phosphatidylserine was greater for such partially inactivated enzyme sources, although it did not completely restore the activity to that of fresh preparations. When myelin was fractionated into basic protein, proteolipid protein and the high molecular weight acidic protein (Wolfgram) fractions, the last fraction contained most of the recovered activity. However, Wolfgram protein was less active than the intact myelin when assayed without additional lipid. The addition of phosphatidylserine completely restored the activity of this partially delipidated preparation.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 24 (1975), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A simple spectrofluorometric procedure has been devised to determine serum antibodies, directed to constituents of the myelin sheath. It is an adaptation of the indirect immunofluorescent technique. A suspension of highly purified bovine myelin is incubated successively with a test rabbit serum and fluoresceinisothiocyanate-conjugated anti-rabbit gamma-globulin. Intensity of fluorescence in the final myelin suspension is determined spectrofluorometrically. Sera from rabbits with experimental allergic encephalomyelitis, induced by whole bovine spinal cord, generally gave fluorescence at least 10 times that of normal rabbit serum. Fluorescence of sera with high demyelinating activity was more intense than that of sera with equivocal demyelinating activity. The assay is specific for immunoglobulins directed to myelin constituents, organ-specific and species-independent. Rabbit anti-galactosylceramide serum with known demyelinating activity gave high fluorescence similar to that in sera of rabbits inoculated with whole spinal cord. Galactosylceramide could absorb a substantial portion of‘anti-myelin antibodies’of the anti-galactosylceramide serum but it did not absorb‘anti-myelin antibodies’of serum of rabbits with whole tissue-induced experimental allergic encephalomyelitis. This assay system may be useful for further studies of ‘anti-myelin antibodies’.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 18 (1971), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Seven sphingoglycolipids were isolated from the white matter of a patient with globoid cell leucodystrophy (Krabbe's disease). After purification by saponification and column and preparative thin-layer chromatography, these compounds were analysed for the carbohydrate composition and sequence and for fatty acid composition by paper and gas-liquid chromatography. The compounds were identified as gluco- and galactocerebrosides, lactosyl-ceramide, digalactosy I-glucosyl-ceramide, two types of tetrahexosyl-ceramides (asialo-ganglioside and globoside), and sulphatide. Glucocerebrosideconstituted 13 percent of total cerebroside in white matter, but sulphatide contained only galactose. Galactocere-broside and sulphatide exhibited compositions of fatty acids similar to those in normal white matter, with only minor abnormalities. Other sphingoglycolipids showed fatty acid patterns with relatively high proportions of longer-chain fatty acids, rather than the predominant C18:0 acid usually found in ceramide hexosides of the brain. Hematoside, also found in the white matter in a significant amount, similarly contained a large proportion of longer-chain fatty acids, whereas other gangliosides contained predominantly C18:0 acid. The abnormal ceramide hexoside pattern was restricted mostly to white matter except for glucocerebroside, which constituted 32 per cent of grey matter cerebroside. We postulate that the visceral type of sphingoglycolipids may be constituents of globoid cells, abundantly present in white matter and considered to be cells of mesenchymal origin.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Activities of rat brain galactosylsphingosine (psychosine) and galactosylceramide (galactocerebroside) galactosyl hydrolases were compared using several criteria. Aqueous homogenates of rat brain were extracted at -30°C with a mixture of ether-methanol (3:1, v/v). This procedure eliminated most of endogenous galactosylceramide and improved the linearity of the enzymatic reaction without inactivating the enzyme. The thermostability of both enzymes was identical while the reference 4-methylumbelliferyl β-galactosidase was less thermostable. The enzymes, solubilized from the ether-methanol powder, were quantitatively precipitated in the combined ammonium sulphate fractions of 20–30% and 30–40% saturation. DEAE-cellulose column chromatography gave identical elution patterns for the two enzymes, with a single major and two minor peaks. Electrofocusing of the major activity peak, obtained from the DEAE-cellulose column, produced a sharp single peak of galactosylsphingosine- and galactosylceramidehydrolysing activities at an isoelectric point of pH 4.45. Developmental changes of these enzymes were identical, showing the most rapid rise concomitant with the period of active myelination. During development, at different purification steps, and in different organs, the ratio of the activities of galactosylsphingosine and galactosylceramide galactosyl hydrolases was relatively constant. While none of these criteria provides definitive proof of identity, they collectively suggest strongly that a single enzyme might catalyse hydrolysis of both galactosylsphingosine and galactosylceramide.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 19 (1972), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Three enzymes of cholesterol ester metabolism, a cholesterol-esterifying enzyme which incorporates free fatty acids into cholesterol esters without participation of CoA, and two cholesterol ester hydrolases with differing pH optima, all showed distinct changes in developing rat brains. The specific activity of the esterifying enzyme was approx. 20 percent of the adult level at birth, increased gradually to the adult level by 20 days of age and remained constant thereafter. The pH 4.2 hydrolase at birth also had a specific activity of about 20 per cent of the adult level but it increased rapidly to reach a peak at 13 days, by which time the activity had increased eight-fold. The activity declined somewhat thereafter to reach the adult level by 23–30 days. In contrast, there already was 60 per cent of the adult specific activity of the pH 6.6 cholesterol ester hydrolase at birth. The activity remained constant until 12 days and then doubled during the next two weeks, reaching a broad peak, then declining slightly to reach the adult activity by 50 days. Therefore, the developmental changes of both of the hydrolases appeared to be related to the process of myelination. The period of active myelination (10–30 days) was characterized by the sharp rise in the activity of pH 6.6 cholesterol ester hydrolase and by the rapid decrease of pH 4.2 cholesterol ester hydrolase.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Cholesterol esters were isolated from cerebral cortex and white matter of patients with Schilder's disease, GM1-gangliosidosis and Tay-Sachs disease, and the fatty acid composition was determined by gas-liquid chromatography. The fatty acid composition was similar among the three pathological conditions, but it was entirely different from that reported for cholesterol esters of normal brain. Lecithin and ethanolamine phospholipids were isolated from the same brain specimens, treated with snake venom phospholipase A, and the fatty acids at the a’and β-positions of the glycerol moiety were determined separately. The fatty acid composition of cholesterol esters was similar to that of the β-position fatty acids of lecithin of white matter in all samples, and was quite different from those of the a'-position of lecithin, or of the a’or β-position of ethanolamine phospholipids. The results indicate that the source of fatty acids for cholesterol esterification in nonspecific sudanophilic demyelination is different from that in normal brain, and that the most likely source is the β-linked fatty acids of lecithin. There are two possible enzymic mechanisms; activation of phospholipase A and subsequent esterification of the liberated β-position fatty acids to cholesterol, or direct transacylation by lecithin-cholesterol acyl transferase.
    Type of Medium: Electronic Resource
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