Lipids ceramides

The permeability of unionizable compounds is a function of their lipid solubilities, determined by their oil water partition coefficients. Squier et al. [16] demonstrated this dependence of water permeability on the lipid contents of keratinized and nonkeratinized epithelia. The lipids present however contribute to this effect more in the keratinized epithelia (more total lipid content, nonpolar lipids, ceramides) than in the nonkeratinized epithelia where permeability seems to be related to the amount of glycosylceramides present. 

Cholesterol is a major component of the alcoholic fraction of lanolin.15 It is also an essential constituent of the lipids of the stratum corneum, which form the epidermal permeability barrier.29,30 However, the other stratum corneum lipids (ceramides and fatty acids) are different from those of lanolin. Clark and Steel have suggested that the a-, ()-, and m-hydroxy lanolin acids are esterified with diols to form diesters with two long acyl chains, which are similar to those found in ceramides.16,31,32... 

In addition to restoring the clinical appearance of xerotic skin, lanolin can also accelerate the restoration of normal barrier function to normal skin that has been acutely perturbed. Elias and colleagues have demonstrated that lanolin accelerated epidermal barrier recovery following perturbation with acetone.41 Three percent lanolin not only significantly (p < 0.001) decreased the TEWL at 45 min, but also after 4 h compared to vehicle-treated sites (Table 25.1). However, the rate of barrier recovery of lanolin-treated sites between 45 min and 4 h was not significantly different compared to vehicle treatment. This indicates that lanolin has an immediate effect on restoring a permeability barrier and does not interfere with the process of lamellar body extrusion and lipid synthesis, which are required for continued recovery. The effect of 3% lanolin on barrier recovery was very similar to that of the optimized ratio of stratum corneum lipids (ceramides, cholesterol, and fatty acids).42,43... 

These glycolipids form a large fraction of neuronal cell membranes, and defects in their metabolism leads to a series of devastating diseases, the best known of which is Tay-Sachs. The compounds are synthesized from the lipid ceramide by successive addition of monosaccharides (Figure 21.14), where the numbers in boxes correspond to the E.C. number for the enzyme responsible... 

Five lipids (ceramide IV, sphingosine, sphingosine phosphate, and dihydro- and phytosphingosine) were isolated from cell cultures and analyzed on a silica column (ELSD, drift tube T = 70°, N2 nebulizer gas at 1.6 bar) using a 90/01/1/1 chloroform/ethanol (200 proof)/triethylamine/formic acid mobile phase [782]. Good resolution and peak shapes were achieved and elution was complete in 16 min. A linear response from 1.7 to 17 ig injected was generated and a detection limit of 100 ng injected were reported. 

Cauwet-Martin D, Dubief C. Cosmetic compositions containing a lipid ceramide compound and a peptide having a fatty chain, and their uses 1998. Patent US 5830481 A. 

The first chapter of the book deals with the properties and activities of fatty acids. This is followed by detailed discussions of diacylglycerols and phosphoinositides. The lysolipids are represented by sphingosine 1-phosphate and lysophosphatidic acid, followed by an overview of the properties of ether lipids. Ceramides and glycosphingolipids are covered in two chapters. The metabolites of the arachidonic acid cascade are discussed in a further two chapters on prostanoids, leukotrienes and lipoxins, followed by the last two chapters of the book which focus on endocannabinoids and isoprostanes. The authors come from several European countries and North America, each one of them bringing on board their individual research and teaching experience, and insight of their expertise. 

Kooijman EE, Sot J, Montes LR, et al. Membrane organization and ionization behavior of the minor but crucial lipid ceramide-l-phosphate. Biophys ]. 2008 94(ll) 4320-4330. 

SA-Le and SA-diLe type oligosaccharides attached to proteins or lipids (ceramides) may play a major role in cell-cell and cell-molecule recognition events (Bradley et al., 1990). Recently, it has been reported that SA-Le which is expressed on colon carcinoma cell surfaces (Magnani, 1991 Rice and Belivacqua,... 

Lipid phosphate phosphohydrolases (LPPs), formerly called type 2 phosphatidate phosphohydrolases (PAP-2), catalyse the dephosphorylation of bioactive phospholipids (phosphatidic acid, ceramide-1-phosphate) and lysophospholipids (lysophosphatidic acid, sphingosine-1-phosphate). The substrate selectivity of individual LPPs is broad in contrast to the related sphingosine-1-phosphate phosphatase. LPPs are characterized by a lack of requirement for Mg2+ and insensitivity to N-ethylmaleimide. Three subtypes (LPP-1, LPP-2, LPP-3) have been identified in mammals. These enzymes have six putative transmembrane domains and three highly conserved domains that are characteristic of a phosphatase superfamily. Whether LPPs cleave extracellular mediators or rather have an influence on intracellular lipid phosphate concentrations is still a matter of debate. 

The glycosphingolipids (GSLs) are sugar-containing lipids built on a backbone of ceramide they include galactosyl- and glucosylceramide (cerebrosides) and the gangliosides. Their structures are described in Chapter 14. They are mainly located in the plasma membranes of cells. 

Raith and Neubert [57] have developed a method for the profihng of human stratum comeum ceramides. The method enables the investigation of the role of ceramides in maintaining the barrier function of stratum comeum. TLC using automated multiple development was modified for semipreparative purposes. The fractionation of complex lipid extracts using this method ensured specific, sensitive, and... 

Sphingolipids (ceramids, sphingomyelin, cerebrosides, sulfatides, gangliosides) and lipids with secondary amines produce blue spots on a white backgound (CAUTION benzidine is a carcinogen)... 

Kudo, N., Kumagai, K., Tomishige, N. et al. 2008. Structural basis for specific lipid recognition by CERT responsible for nonvesicular trafficking of ceramide. Proc. Natl. Acad. Sci. U.S.A., 105(2) 488 493. 

Because membranes components participate in nearly every cell activity their structures are also dynamic and far from the equilibrium states that are most readily understood in biophysical terms. Newly synthesized bilayer lipids are initially associated with endoplasmic reticulum (Ch.3) whereas phospholipids initially insert into the cytoplasmic leaflet while cholesterol and sphingolipids insert into the luminal endoplasmic reticulum (ER) leaflet. Glycosylation of ceramides occurs as they transit the Golgi compartments, forming cerebrosides and gangliosides in the luminal leaflet. Thus, unlike model systems, the leaflets of ER membranes are asymmetric by virtue of their mode of biosynthesis. 

Mutant or knockout mice defective in specific enzymes involved in lipid synthesis have provided powerful tools for genetic analysis of lipid function in the nervous system. For example, disruption of the genes for ceramide galactosyl transferase or galactosyl ceramide sulfotransferase,... 

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