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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: —Forssman hapten (N-acetyl-α-galactosaminosyl-N-acetyl-β-galactosaminosyl-α-galactosyl-β-galactosyl-glucosylceramide), prepared from sheep erythrocytes was specifically labelled with tritium at the terminal N-acetyl-α-galactosamine moiety by the galactose oxidase-sodium [3H]borohydride method. Activities to cleave the terminal N-acetyl-α-galactosamine from Forssman hapten were detected in the high-speed supernatant of the frozen-thawed and sonicated crude mitochondrial fraction from adult rat brain and kidney. The optimal pH of the reaction was approximately 4·4. The reaction was linear for at least 1 h for the kidney enzyme and up to 3 h for the brain enzyme. Taurocholate was required for the activity. The optimal concentration was 1·5-2 mg/ml. Several other detergents and bile salts tested could not replace taurocholate. The apparent Km of the brain and kidney enzymes were 1·0×10−4M and 3·5×10−4m, respectively. During development, Forssman hapten-cleaving activities of both brain and kidney gradually declined in specific activity as the animal matured. These changes were similar to those of nonspecific p-nitrophenyl N-acetyl-α-galactosaminidase. Several rat organs examined all showed detectable activities to cleave Forssman hapten.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 18 (1971), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 18 (1971), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 24 (1975), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: 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’.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 19 (1972), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract— The contents and the fatty acid composition of cholesterol esters were analysed in developing rat brain. The total content did not exceed 20 μg/brain throughout development. Elimination of serum by adequate perfusion was essential for accurate results. Two separate events appeared to affect the levels of cholesterol esters in developing rat brain, one probably reflecting general developmental changes and the other apparently related to myelination. On either a unit weight or a whole brain basis, the curves appeared to be a superimposition of the two events. There was an underlying developmental change, which was characterized on a unit weight basis by the highest level of cholesterol esters immediately after birth and a steady decline to the adult level by 30 days of age or which on the basis of whole brain was characterized by a steady increase throughout the development. A period of transient increase was superimposed on this underlying developmental change between the ages of 7 and 27 days and corresponded to the period of active myelination. The major fatty acids of rat brain cholesterol esters were palmitic, palmitoleic, oleic and arachidonic acids. Palmitic and palmitoleic acids decreased in proportion while oleic acid increased, as the animal matured. The fatty acid composition of serum cholesterol esters was distinctly different from that of brain cholesterol esters; those from serum contained much higher proportions of linoleic and arachidonic acids and much less palmitoleic and oleic acids.
    Materialart: Digitale Medien
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