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PubMed1973

Sphingolipid composition of human platelets.

Total lipid extracts from washed trypsinized human platelets were fractionated into neutral lipids, glycosphingolipids, and phospholipids by silicic acid chromatography. The concentrations and chemical structures of the neutral and acidic glycosphingolipids were then studied in detail. On the basis of sugar molar ratios, studies of permethylation products, and the action of stereospecific glycosidases on the lipids, identifications were made of four neutral glycosphingolipids. Lactosylceramide was the most abundant type and accounted for 64% of the total neutral glycolipid mixture. The major fatty acids of the lactosylceramide were 20:0, 22:0, 24:0, and 24:1; the major long-chain base was 4-sphingenine. The platelets were surprisingly rich in a ceramide fraction, which represented 1.3% of the total platelet lipids. It had a different fatty acid composition than the neutral glycosphingolipid and ganglioside fractions. Hematoside was also isolated from the total lipid fraction of platelets; the neuraminic acid component was N-acetylneuraminic acid. Treatment of platelets with trypsin, chymotrypsin, or thrombin increased the yield of hematoside as compared with a control, while the level of ceramides was not changed. It was concluded that the platelets are similar to leukocytes, liver, and spleen in that lactosylceramide and hematoside are the principal neutral and acidic glycosphingolipids. The presence of a relatively high proportion of ceramide in platelets may be a unique characteristic of this cellular fraction of blood.

Blood Platelets↗
PubMed1972

Effect of vitamin K depletion and restoration on sphingolipid metabolism in Bacteroides melaninogenicus.

Bacteroides melaninogenicus requires vitamin K for normal growth. Cells incubated in a vitamin K-free medium form defective cell envelopes. Studies with vitamin K-grown "K(+)" and vitamin K-depleted "K(-)" cells showed that [(14)C]choline and [(14)C]glycerol were not taken up, but several amino acids and acetate were incorporated to the same degree by both types of cultures. However, K(-) cells incorporated succinate to a greater degree than did K(+) cultures. The relative incorporation of succinate into ceramide phosphorylethanolamine and ceramide phosphorylglycerol was depressed compared with incorporation into phosphatidylethanolamine in K(-) cultures. B. melaninogenicus can be grown in serial subculture in the absence of vitamin K in the presence of 2.5 mg/ml of succinate. Under these conditions the relative incorporation of [2,3-(14)C]succinate and (32)P into ceramide phosphorylethanolamine and ceramide phosphorylglycerol is markedly depressed. Stimulation of phosphosphingolipid synthesis by vitamin K was shown by comparing the uptake of (32)P and lipid phosphorus levels of a succinate-grown, vitamin K-depleted culture supplemented with (32)P plus 0.1 micro g/ml vitamin K(1) with a similar culture supplemented with (32)P only. The phosphosphingolipids from the vitamin K-supplemented cells incorporated greater amounts of (32)P and had higher levels of phosphorus than did the ceramide phosphorylethanolamine and ceramide phosphorylglycerol of the culture without added vitamin K. It was further shown that vitamin K added to a vitamin K-depleted culture stimulated synthesis of ceramide phosphorylethanolamine and ceramide phosphorylglycerol 38 min and 60 min, respectively, following the addition of the vitamin; incorporation of (32)P into other phospholipids was unaffected.

Acetates↗
PubMed1995

[Sphingolipid changes in rat cerebral cortex during focal ischemia--how does ceramide accumulate in an ischemic condition?].

Levels of ceramide, sphingomyelin, cerebroside and gangliosides were determined in rat cerebral cortex during focal ischemia produced by middle cerebral artery occlusion. Ceramide began to increase at 6 hours of ischemia and increased to 4.5 folds at 96 hours. Amino-linked fatty acids in increased ceramide were composed solely of non-hydroxy fatty acids, and stearic acid was the most prominent. Sphingomyelin, whose amino-linked fatty acids were mostly stearic acid, decreased in a time-dependent manner and became about a half of controls at 96 hours. Hydroxy fatty acid linked cerebroside decreased at and after 6 hours of ischemia, whereas significant decrease of non-hydroxy fatty acid linked cerebroside occurred only at 96 hours of ischemia. There were no measurable changes in the levels of gangliosides. The results suggested that ceramide was produced in the cerebral cortex by the breakdown of sphingomyelin during ischemia.

Animals↗
PubMed1993

[Lysosomal storage diseases, genetic or drug-induced? effect of glycosaminoglycan and sphingolipid disorders on dental tissues].

In vivo studies were carried out on dental tissues of rat incisor after a single injection of suramin, a drug which induces mucopolysaccharidosis-like disease. Accumulation of lysosome-like structures was seen in secretory ameloblasts and odontoblasts. In vitro studies on embryonic tooth germ buds showed similar changes when they were cultured in presence of suramin. Anti-phospholipid immunolabelling revealed a developmentally regulated temporo-spatial pattern. Radiolabeling with 3H-suramin indicated cytosolic and nuclear incorporation. The drug acting as polyanion interacted directly with predentine. 35S sulphate incorporation was impaired by the drug. Another lysosomal storage disease, the sphingolipidosis, Krabbe's disease was also investigated in human. Changes were observed in pulp cells and as a consequence in dentin. Enamel also displayed many changes. Pharmacological or genetically acquired diseases constitute models providing insights on the role played by glycosaminoglycans and phospholipids in biomineralization.

Ameloblasts↗