Mixture Of Ceramides Research Articles

Evidence That the Corneocyte Has a Chemically Bound Lipid Envelope

The stratum corneum of mammalian epidermis contains a mixture of ceramides, free fatty acids, cholesterol, and cholesteryl sulfate, amounting to 14% of the dry weight of the tissue, that can be removed by exhaustive extraction with chloroform/methanol. Subsequent mild alkaline hydrolysis liberates additional lipid, consisting almost exclusively of C30-C34 omega-hydroxyacids in amide linkage with sphingosine, equal to 2% of the tissue mass. In the present study, transmission electron microscopy was used to demonstrate that the initial extraction removes the intercellular lamellae that constitute the epidermal water barrier but leaves the lucent band that has been termed the corneocyte plasma membrane. The subsequent alkaline hydrolysis and lipid extraction remove the lucent band, which must therefore contain the omega-hydroxyacylsphingosines. From the results of in situ derivatization of these lipids and the construction of molecular models, it is inferred that the bound lipids exist in ester linkage with protein on the surface of the corneocyte envelope. The tightly packed hydroxyacylsphingosine molecules thus form a lipid envelope for each corneocyte.

Preparation of Liposomes from Stratum Corneum Lipids

Mammalian stratum corneum contains multiple intercellular lipid bilayers that constitute the epidermal water barrier. Unlike all other biologic membranes, the epidermal lamellae do not contain phospholipids, as a result of which the ability of the stratum corneum lipid mixture to form bilayers has been questioned. In the present study, a lipid mixture containing only epidermal ceramides (40%), cholesterol (25%), palmitic acid (25%), and cholesteryl sulfate (10%), approximating the composition of stratum corneum lipids, formed stable, unilamellar liposomes when sonicated at 80 degrees C in buffer containing 100 mM NaCl, 5 mM Tris, and 1 mM EDTA at pH 7.5. The size and form of the liposomes were studied by both freeze fracture and negative staining electron microscopy. Lipid mixtures from which either the palmitic acid or the cholesteryl sulfate were omitted were still capable of forming similar liposomes, but a mixture of ceramides and cholesterol, or ceramides alone, were incapable of forming liposomes. The results indicate that lipid mixtures similar to those found in stratum corneum are capable of forming bilayers at physiologic pH.

Final structure of caulerpicin, a toxin mixture from the green alga Caulerpa racemosa

Caulerpicin from the green alga Caulerpa racemosa is shown to consist of a mixture of ceramides derived from 2S, 3R-sphinganine with C18 (32%), C20(2%), C22(6%), C24(35%) and C26(25%) saturated fatty acid

Final structure of caulerpicin, a toxin mixture from the green alga Caulerpa racemosa

Caulerpicin from the green alga Caulerpa racemosa is shown to consist of a mixture of ceramides derived from 2 S, 3 R-sphinganine with C 18 (32%), C 20(2%), C 22(6%), C 24(35%) and C 26(25%) saturated fatty acid

Galactosyl ceramides of the myelin sheath: Thermal studies

The thermal properties of several hydrated glycosyl ceramides have been investigated by differential scanning calorimetry in relation to the role of galactosyl ceramides in the myelin sheath of central nerve tissue. Myelin galactosyl ceramides are characterised by the presence of a large proportion of α-hydroxy fatty acids which lower the phase transition of this lipid class in comparison to galactosyl ceramides with normal fatty acids of similar chain length. Alteration of the sugar headgroup from galactose to glucose produced no significant change in the transition temperature of the lipid. The presence of a disaccharide headgroup lowered the transition temperature and altered the structure of the endotherm. Increasing concentrations of cholesterol in aqueous dispersions of galactosyl ceramide progressively decreased the enthalpy of the phase transition until, in the presence of 34 mole % cholesterol, it was no longer detectable. Examination of the effects of a range of phospholipids on the phase transition of galactosyl ceramides suggest that the phase behaviour of phospholipid-galactosyl ceramide mixtures is complex. However, only a single endotherm was observed in all the phospholipid-galactosyl ceramide systems examined. This tends to indicate that segregated phases enriched in galactosyl ceramides do not occur in the intact myelin membrane.

Sphingolipids in fruit bodies of the basidiomycete Lactarius deliciosus

A rather complex mixture of ceramides from Lactarius deliciosus (L. ex Fr.) S. F. Gray, was separated into nine groups by column chromatography and preparative thin-layer chromatography (tlc). Saturated and unsaturated, 2-hydroxy and nonhydroxylated fatty acids of chain lengths C 12 to C 20 were obtained by hydrolysis of the ceramides and were analyzed by quantitative gas-liquid chromatography. A group of cerebrosides (ceramide monohexosides), seemingly homogeneous on tlc, was separated. The dominant fatty acids were h16:0 and 18:0. The sugar was identified as glucose. The long-chain bases in ceramides and cerebrosides were mainly phytosphingosines (trihydroxy series) and, to a lesser extent, sphingosines (dihydroxy series).

On the biosynthesis of cerebrosides containing non-hydroxy acids: 2. Mass spectrometric evidence for the ceramide pathway

The transformation of a mixture of [4,5,5′,6′,8′,9′,11′,12′,14′,15′- 2H 10] N (eicosanoyl) DL- barerythro -1,3-dihydroxy-2-amino-4- trans -octadecene and N (eicosanoyl) D- erythro -1,3-dihydroxy-2-amino-4- trans -octadecene to cerebroside has been studied. The incubation mixture contained mouse brain microsomes, UDPGal and lecithin in addition to the ceramide mixture. Both galactosyl ceramide and glucosyl ceramide were formed. The products were analyzed by gas-liquid chromatography - mass spectrometry as the trimethylsilyl ether derivatives. The analyses demonstrated that both products had been synthesized via the ceramide pathway.