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At least 1,063 records · Page 59Linked to original sources
PubMed1992

Models of stratum corneum intercellular membranes: the sphingolipid headgroup is a determinant of phase behavior in mixed lipid dispersions.

During formation of the intercellular membranes of mammalian stratum corneum, sphingomyelin and glucosylceramide are converted enzymatically to ceramide. To model in isolation the possible effect of such a lipid modification on the phase behavior of the ensemble, we used proton and deuterium nuclear magnetic resonance to compare an equimolar dispersion of bovine brain sphingomyelin, cholesterol, and perdeuterated palmitic acid (at pH 6.2), with an equivalent dispersion in which bovine brain ceramide was substituted for sphingomyelin. While the sphingomyelin dispersions remain in a homogeneous fluid lamellar phase from 20-75 degrees C under these conditions, those containing ceramide display complex polymorphism.

Ceramides↗
PubMed1977

Phosphonosphingoglycolipid, a novel sphingolipid from the viscera of Turbo cornutus.

A novel lipid which contained long-chain base, fatty acid, galactose and N-methylamino-ethylphosphonic acid in an equimolar was isolated from the viscera of Turbo cornutus. The method used for the structural elucidation of this lipid were partial acid hydrolysis, alkaline hydrolysis, periodate oxidation and Smith degradation. The structure of break-down products were mainly identified by combined gas chromatography and mass spectrometry. The structure of the novel lipid was determined to be 1-O-[6'-O-(N-methylaminoethyl-phosphonyl) galactopyranosyl] ceramide. Mass spectra of galactose-N-methylaminoethylphospnate and glycerol-N-methylamino-ethylphosphonate are given.

Animals↗
PubMed1977

Molecular arrangements of sphingolipids. The monolayer behaviour of ceramides.

A series of synthetic ceramides have been studied at the air-water interface by recording the surface pressue-area isotherms at continuous compression. Ceramides that contain a 4,5-trans-double bond in the long chain base were found to condense into a close-packed arrangement with vertical chains already at a very low surface pressure. The corresponding saturated compounds adopt a similar close packed arrangement only at high surface pressue. At 30 dynes/cm, a lateral pressure representative of biological membranes, the area per molecule and compressibility was further found to depend on the number and configuration of the hydroxyl groups. The presence of a 2-D-hydroxyl group in the fatty acid generally promotes the condensation. A similar effect is observed if the long chain base contains a 4-D-hydroxyl group. Cis-double bonds or methyl branches in the fatty acid chain, which increase the space requirement, limit the lateral interaction of the polar group. However the 15-cis-double bond of nervonic acid can be accomodated without any distortion of the close-packing arrangement.

Air↗
PubMed1986

Animal and cellular models of sphingolipid storage disorders of humans.

The synthesis of L-galactosylceramide is described. Data are presented indicating that this enantiomorph of D-galactocerebroside is not cleaved by galactocerebroside-beta-galactosidase obtained from mammalian tissues. The synthesis of L-glucosylceramide and beta-D-glucothiocerebroside are outlined. These compounds are also refractory to catabolism by glycosidases in mammalian tissues that catalyze the hydrolysis of naturally occurring cerebrosides. L-Hexosyl- and thioanalogs of cerebrosides and perhaps psychosines as well may be helpful for investigating the pathogenesis of Krabbe's disease and Gaucher's disease.

Animals↗
PubMed1980

The bile salt activation of leucocyte sphingolipid hydrolase activity and the modifying effects of triton X-100.

The activation of sphingomyelinase, galactosyl- and lactosylceramide beta-galactosidases, GM1, beta-galactosidase, cerebroside sulphate sulphatase, trihexosylceramide alpha-galactosidase and globoside beta-hexosaminidase by a number of bile salts was studied. Most of the salts examined, except glycolithocholate and deoxycholate, were effective activators of enzyme activity. Pure, but not crude, taurocholate elicited poor trihexosylceramide alpha-galactosidase and cerebroside sulphate sulphatase activities. The bile salt activation was often dependent on a number of parameters including the bile salt concentraion, pH, protein to bile salt ratio, and the nature of the enzyme preparation. In the absence of bile salts, Triton X-100 induced little activity of any of the hydrolases except sphingomyelinase; in their presence however, Triton either promoted or inhibited the activation depending on the enzyme. Our data suggest that bile salt structure is an important factor in determining the degree of activation of individual hydrolases and that this may be due to intramicellar lipid substrate/bile salt interactions, which either facilitate or inhibit the corresponding enzyme reaction.

Adult↗