Ceramides: Members of the class of neutral glycosphingolipids. They are the basic units of SPHINGOLIPIDS. They are sphingoids attached via their amino groups to a long chain fatty acyl group. They abnormally accumulate in FABRY DISEASE.Sphingolipids: A class of membrane lipids that have a polar head and two nonpolar tails. They are composed of one molecule of the long-chain amino alcohol sphingosine (4-sphingenine) or one of its derivatives, one molecule of a long-chain acid, a polar head alcohol and sometimes phosphoric acid in diester linkage at the polar head group. (Lehninger et al, Principles of Biochemistry, 2nd ed)Sphingomyelins: A class of sphingolipids found largely in the brain and other nervous tissue. They contain phosphocholine or phosphoethanolamine as their polar head group so therefore are the only sphingolipids classified as PHOSPHOLIPIDS.Glucosylceramides: Cerebrosides which contain as their polar head group a glucose moiety bound in glycosidic linkage to the hydroxyl group of ceramides. Their accumulation in tissue, due to a defect in beta-glucosidase, is the cause of Gaucher's disease.Alkaline Ceramidase: A ceramidase subtype that is active at alkaline pH. It is found at high levels within the SMALL INTESTINE.Sphingosine: An amino alcohol with a long unsaturated hydrocarbon chain. Sphingosine and its derivative sphinganine are the major bases of the sphingolipids in mammals. (Dorland, 28th ed)Sphingomyelin Phosphodiesterase: An enzyme that catalyzes the hydrolysis of sphingomyelin to ceramide (N-acylsphingosine) plus choline phosphate. A defect in this enzyme leads to NIEMANN-PICK DISEASE. EC 3.1.4.12.Cerebrosides: Neutral glycosphingolipids that contain a monosaccharide, normally glucose or galactose, in 1-ortho-beta-glycosidic linkage with the primary alcohol of an N-acyl sphingoid (ceramide). In plants the monosaccharide is normally glucose and the sphingoid usually phytosphingosine. In animals, the monosaccharide is usually galactose, though this may vary with the tissue and the sphingoid is usually sphingosine or dihydrosphingosine. (From Oxford Dictionary of Biochemistry and Molecular Biology, 1st ed)Sphingosine N-Acyltransferase: An enzyme that catalyzes the acyltransferase of SPHINGOSINE to N-acylsphingosine using acyl-COENZYME A as donor and COENZYME A as acceptor. The enzyme is mainly localized in the MITOCHONDRIA.Ceramidases: Amidohydrolases that are specific for the cleavage of the N-acyl linkage of CERAMIDES. Ceramidases are classified as acidic, neutral or basic according to the optimal pH with which they function.Serine C-Palmitoyltransferase: A key enzyme in SPHINGOLIPIDS biosynthesis, this enzyme catalyzes the pyridoxal-5'-phosphate-dependent condensation of L-SERINE and PALMITOYL COENZYME A to 3-dehydro-D-sphinganine. The enzyme consists of two different subunits.Chromatography, Thin Layer: Chromatography on thin layers of adsorbents rather than in columns. The adsorbent can be alumina, silica gel, silicates, charcoals, or cellulose. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Glycosphingolipids: Lipids containing at least one monosaccharide residue and either a sphingoid or a ceramide (CERAMIDES). They are subdivided into NEUTRAL GLYCOSPHINGOLIPIDS comprising monoglycosyl- and oligoglycosylsphingoids and monoglycosyl- and oligoglycosylceramides; and ACIDIC GLYCOSPHINGOLIPIDS which comprises sialosylglycosylsphingolipids (GANGLIOSIDES); SULFOGLYCOSPHINGOLIPIDS (formerly known as sulfatides), glycuronoglycosphingolipids, and phospho- and phosphonoglycosphingolipids. (From IUPAC's webpage)Epidermis: The external, nonvascular layer of the skin. It is made up, from within outward, of five layers of EPITHELIUM: (1) basal layer (stratum basale epidermidis); (2) spinous layer (stratum spinosum epidermidis); (3) granular layer (stratum granulosum epidermidis); (4) clear layer (stratum lucidum epidermidis); and (5) horny layer (stratum corneum epidermidis).I Blood-Group System: A blood group related both to the ABO and P systems that includes several different antigens found in most people on erythrocytes, in milk, and in saliva. The antibodies react only at low temperatures.Chromatography, Gas: Fractionation of a vaporized sample as a consequence of partition between a mobile gaseous phase and a stationary phase held in a column. Two types are gas-solid chromatography, where the fixed phase is a solid, and gas-liquid, in which the stationary phase is a nonvolatile liquid supported on an inert solid matrix.Water Loss, Insensible: Loss of water by diffusion through the skin and by evaporation from the respiratory tract.Fatty Acids: Organic, monobasic acids derived from hydrocarbons by the equivalent of oxidation of a methyl group to an alcohol, aldehyde, and then acid. Fatty acids are saturated and unsaturated (FATTY ACIDS, UNSATURATED). (Grant & Hackh's Chemical Dictionary, 5th ed)Lipidoses: Conditions characterized by abnormal lipid deposition due to disturbance in lipid metabolism, such as hereditary diseases involving lysosomal enzymes required for lipid breakdown. They are classified either by the enzyme defect or by the type of lipid involved.Fumonisins: A group of MYCOTOXINS found in CORN contaminated with FUSARIUM fungus. They are chains of about 20 carbons with acidic ester, acetylamino and sometimes other substituents. They inhibit ceramide synthetase conversion of SPHINGOLIPIDS to CERAMIDES.Acid Ceramidase: A ceramidase subtype that is active at acid pH. It plays an important role in sphingolipid degradation by catalyzing the lysosomal hydrolysis of ceramide to sphingosine and free fatty acid. Inherited deficiency of acid ceramidase activity results in FARBER LIPOGRANULOMATOSIS.Neutral Glycosphingolipids: A subclass of GLYCOSPHINGOLIPIDS containing one or more sugars within their head group connected directly to a ceramide moiety. They consist of monoglycosyl-, and oligoglycosylsphingoids and monoglycosyl- and oligoglycosylceramides.Lipids: A generic term for fats and lipoids, the alcohol-ether-soluble constituents of protoplasm, which are insoluble in water. They comprise the fats, fatty oils, essential oils, waxes, phospholipids, glycolipids, sulfolipids, aminolipids, chromolipids (lipochromes), and fatty acids. (Grant & Hackh's Chemical Dictionary, 5th ed)Sulfoglycosphingolipids: GLYCOSPHINGOLIPIDS with a sulfate group esterified to one of the sugar groups.Hydroxy Acids: Organic compounds containing both the hydroxyl and carboxyl radicals.Lipid Metabolism: Physiological processes in biosynthesis (anabolism) and degradation (catabolism) of LIPIDS.Amino Alcohols: Compounds possessing both a hydroxyl (-OH) and an amino group (-NH2).Glycolipids: Any compound containing one or more monosaccharide residues bound by a glycosidic linkage to a hydrophobic moiety such as an acylglycerol (see GLYCERIDES), a sphingoid, a ceramide (CERAMIDES) (N-acylsphingoid) or a prenyl phosphate. (From IUPAC's webpage)Lysophospholipids: Derivatives of PHOSPHATIDIC ACIDS that lack one of its fatty acyl chains due to its hydrolytic removal.Mice, Hairless: Mutant strains of mice that produce little or no hair.G(M3) Ganglioside: A ganglioside present in abnormally large amounts in the brain and liver due to a deficient biosynthetic enzyme, G(M3):UDP-N-acetylgalactosaminyltransferase. Deficiency of this enzyme prevents the formation of G(M2) ganglioside from G(M3) ganglioside and is the cause of an anabolic sphingolipidosis.DiglyceridesGlucosylceramidase: A glycosidase that hydrolyzes a glucosylceramide to yield free ceramide plus glucose. Deficiency of this enzyme leads to abnormally high concentrations of glucosylceramide in the brain in GAUCHER DISEASE. EC 3.2.1.45.Molecular Structure: The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.Mass Spectrometry: An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers.Fatty Alcohols: Usually high-molecular-weight, straight-chain primary alcohols, but can also range from as few as 4 carbons, derived from natural fats and oils, including lauryl, stearyl, oleyl, and linoleyl alcohols. They are used in pharmaceuticals, cosmetics, detergents, plastics, and lube oils and in textile manufacture. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Skin: The outer covering of the body that protects it from the environment. It is composed of the DERMIS and the EPIDERMIS.Galactosylceramides: Cerebrosides which contain as their polar head group a galactose moiety bound in glycosidic linkage to the hydroxyl group of ceramide. Their accumulation in tissue, due to a defect in beta-galactosidase, is the cause of galactosylceramide lipidosis or globoid cell leukodystrophy.Galactosylgalactosylglucosylceramidase: An enzyme that catalyzes the hydrolysis of a ceramidetrihexoside to a ceramidedihexoside plus galactose.Apoptosis: One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA; (DNA FRAGMENTATION); at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.Oxidoreductases: The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)Spectrometry, Mass, Electrospray Ionization: A mass spectrometry technique used for analysis of nonvolatile compounds such as proteins and macromolecules. The technique involves preparing electrically charged droplets from analyte molecules dissolved in solvent. The electrically charged droplets enter a vacuum chamber where the solvent is evaporated. Evaporation of solvent reduces the droplet size, thereby increasing the coulombic repulsion within the droplet. As the charged droplets get smaller, the excess charge within them causes them to disintegrate and release analyte molecules. The volatilized analyte molecules are then analyzed by mass spectrometry.Neutral Ceramidase: A ceramidase subtype that is active at neutral pH. It is found at high levels within the SMALL INTESTINE and in the BRAIN.Lipid Bilayers: Layers of lipid molecules which are two molecules thick. Bilayer systems are frequently studied as models of biological membranes.Phospholipase D: An enzyme found mostly in plant tissue. It hydrolyzes glycerophosphatidates with the formation of a phosphatidic acid and a nitrogenous base such as choline. This enzyme also catalyzes transphosphatidylation reactions. EC 3.1.4.4.Lactosylceramides: Glycosphingolipids which contain as their polar head group a lactose moiety bound in glycosidic linkage to the hydroxyl group of ceramide. Their accumulation in tissue, due to a defect in lactosylceramide beta-galactosidase, is the cause of lactosylceramidosis.Optical Rotation: The rotation of linearly polarized light as it passes through various media.Sphingolipidoses: A group of inherited metabolic disorders characterized by the intralysosomal accumulation of SPHINGOLIPIDS primarily in the CENTRAL NERVOUS SYSTEM and to a variable degree in the visceral organs. They are classified by the enzyme defect in the degradation pathway and the substrate accumulation (or storage). Clinical features vary in subtypes but neurodegeneration is a common sign.AmidohydrolasesSpectrophotometry, Infrared: Spectrophotometry in the infrared region, usually for the purpose of chemical analysis through measurement of absorption spectra associated with rotational and vibrational energy levels of molecules. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)X-Ray Diffraction: The scattering of x-rays by matter, especially crystals, with accompanying variation in intensity due to interference effects. Analysis of the crystal structure of materials is performed by passing x-rays through them and registering the diffraction image of the rays (CRYSTALLOGRAPHY, X-RAY). (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Spectrometry, Mass, Fast Atom Bombardment: A mass spectrometric technique that is used for the analysis of a wide range of biomolecules, such as glycoalkaloids, glycoproteins, polysaccharides, and peptides. Positive and negative fast atom bombardment spectra are recorded on a mass spectrometer fitted with an atom gun with xenon as the customary beam. The mass spectra obtained contain molecular weight recognition as well as sequence information.Glucosyltransferases: Enzymes that catalyze the transfer of glucose from a nucleoside diphosphate glucose to an acceptor molecule which is frequently another carbohydrate. EC 2.4.1.-.Hydrolysis: The process of cleaving a chemical compound by the addition of a molecule of water.Glycerophospholipids: Derivatives of phosphatidic acid in which the hydrophobic regions are composed of two fatty acids and a polar alcohol is joined to the C-3 position of glycerol through a phosphodiester bond. They are named according to their polar head groups, such as phosphatidylcholine and phosphatidylethanolamine.