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At least 19 recordsLinked to original sources
PubMed1975

The optical activity of D-erythro-sphingomyelin and its contribution to the circular dichroism of sphingomyelin-containing systems.

Circular dichroism studies on bovine brain sphingomyelin show the presence of a strong negative cotton effect below 200 nm, the position and magnitude of which depend on the physical state of the lipid. This cotton effect is thought to arise from the pi-pi transition of the amide group in the sphingomyelin backbone. The sphingomyelin contribution to the observed ellipticity of membranes and lipoprotein complexes depends on the mol fraction of amide groups present as sphingomyelin: this contribution is calculated to be less than 2% in the case of serum high density lipoprotein and the order of 20% below 200 nm in the case of the erythrocyte ghost membrane. Due to the similarity of the CD spectrum of sphingomyelin to that of a random coil polypeptide, use of uncorrected ellipticity data is expected to lead to an overestimate of the random coil content of proteins in systems containing a high sphingomyelin content.

Animals↗
PubMed1978

Correlation between the thermotropic behavior of sphingomyelin liposomes and sphingomyelin hydrolysis by sphingomyelinase of Staphylococcus aureus.

The hydrolysis of D-erythro beef brain sphingomyelin and D,L-erythro-N-palmitoylsphingomyelin dispersed as multilamellar liposomes by sphingomyelinase of Staphylococcus aureus is correlated with the thermotropic behavior of the sphingomyelins. In both cases maximal enzymatic hydrolysis was achieved at the beginning of the gel to liquid crystalline phase transition (30 degrees C for beef brain sphingomyelin and 41 degrees C for N-palmitoylsphingosine-phosphorylcholine) with much lower activity both below and above these temperatures. The enzymatic activity was depressed in the presence of cholesterol in the bilayer which also depressed the phase-transition. The profile of the enzymatic activity is explained by the uniqueness of the lipid molecules arrangement at the phase transition.

Liposomes↗
PubMed1977

Lipid-protein interactions between human apolipoprotein A-I and defined sphingomyelin species. A 13C-NMR spectroscopic study.

Chromatographyically and immunologically homogeneous apolipoprotein A-I (apoLp A-I) from human serum has been recombined in separate experiments with three species of sphingomyelin. The differed in the degree of saturation of their fatty acyl residues, stearoyl (18:0), oleoyl (18:1) and linoleoyl (18:2). The lipoprotein complexes formed were purified by CsCl density gradient centrifugation between 1.07 - 1.09 g/cm3 and by gel filtration. Stearoylsphingomyelin does not recombine with the apoprotein A-I below its phase transition temperature (tc = 41.5 degrees C). The lipoproteins eluted with the following apparent molecular weights: 18:0-sphingomyelin apoLp A-I, 8.0 X 10(5); 18:1-sphingomyelin apoLp A-I, 4.0 X 10(5); and 18:2-sphingomyelin apoLp A-I, 4.0 X 10(5). In electron microscopy the particles appear as discs of 160 - 170 A diameter and 50 - 60 A thickness. Their tendency to form stacked aggregates of discs decreases with the degree of their unsaturation. CD measurements underline the considerable increase in alpha-helicity of the secondary structure of apo A-I after recombination with the phospholipids. This increase in order is equal for the three sphingomyelin species (alpha-helicity of apoLP A-I = 0.46, after recombination 0.89). If the three sphingomyelin species are used in equal molar amounts in the recombination experiment, no preference for any one sphingomyelin species is observed. Recombination of apoLp A-I with sphingomyelin, labelled with the isotope 13C in the choline group, C-14 of stearic or linoleic, or C-11 of oleic acid, were performed for spin lattice relaxation time (T1) experiments. Compared with sphingomyelin liposomes, the polar head groups of these lipids in the lipoprotein particles possess a considerably higher mobility, whereas the changes in T-1-times of the C-atoms in the centre of the fatty acid chains of the lipids refer to their interactions with the polypeptide side chains. A model of the lipoprotein complexes formed is proposed on the basis of the experimental data.

Apolipoproteins↗
PubMed1979

Sphingomyelin storage in a patient with myoclonus epilepsy as a main clinical symptom -- a varient in Niemann-Pick disease type C.

A patient with myoclonus epilepsy as a main clinical symptom was histopathologically diagnosed as a generalized sphingolipidosis. It was found that both sphingomyelin and globoside I fairly increased in kidney, heart, lung and liver. While, only sphingomyelin was found to increase in cerebral gray and white matters and cerebellum, but other lipids were within the normal range. Sphingomyelin accounted for 22% of the total phospholipids especially in cerebellum. No cholesterol ester and ganglioside GM2 or asialo GM2 were in particular found in the brain. Fatty acid compositions of phospholipids, glycosphingolipids and gangliosides were found to be normal. Judging from the sphingomyelin storage not only in visceral organs but also in brain tissues, it was proposed that this disease might be a variant in Niemann-Pick disease Type C, although an enzymatic assay of sphingomyelinase still remains.

Adult↗
PubMed1976

Effect of Triton X-100 on the hydrolysis of sphingomyelin by sphingomyelinase of rat brain.

Mixed dispersions of the nonionic detergent Triton X-100 and sphingomyelin were used as substrate for sphingomyelinase of rat brain. The dependence of the rate of hydrolysis on the concentration of sphingomyelin was measured in two ways: at a fixed concentration of Triton X-100 or at varying concentrations of this detergent, while maintaining a fixed molar ratio of Triton X-100 to sphingomyelin. In either case, the upsilon vs. S curves deviated from the hyperbolic shape predicted by the Michaelis-Menten kinetic theory. These deviations are discussed and interpreted on the basis of the physicochemical properties of the mixed dispersions of detergent and lipid studied in previous papers.

Animals↗
PubMed1976

Properties of a toxin from the sea anemone Stoichacis helianthus, including specific binding to sphingomyelin.

Stoichactis helianthus toxin, a protein derived presumably from the nematocysts, was purified to homogeneity. It has a molecular weight of about 16,000, an isoelectric pH of 9.8, and it contains approximately 3.7% carbohydrate. It is powerfully hemolytic for erythrocytes derived from a variety of animal species, those of the cat being the most sensitive and those of the guinea pig the most resistant. The toxin is lytic also for rabbit blood platelets, and it destroys cultured fibroblasts but is inactive for several kinds of bacterial protoplasts and spheroplasts. The hemolytic activity is specifically inhibited by sphingomyelin, and it is proposed that this phospholipid is the constituent of the membrane which functions as receptor for the toxin. Supporting evidence includes the findings that enzymes known to destroy sphingomyelin (a) prevent erythrocyte membranes from inhibiting hemolysis, and (b) render erythrocytes resistant to lysis by the toxin. The mechanism underlying hemolysis may involve translocation of membrane sphingomyelin by virtue of a specific affinity of the coelenterate protein for this phospholipid.

Animals↗
PubMed2026

Targeting CD44 reverses sphingomyelin-induced oligodendrocyte maturation arrest in acid sphingomyelinase deficiency.

Loss-of-function mutations in the smpd1 gene cause acid sphingomyelinase deficiency (ASMD). Early neurodegeneration and lethality characterize its infantile neurovisceral form (type A). While neuronal dysfunction was traditionally considered the primary driver of the pathology, recent evidence suggests that dysmyelination and microgliosis are not merely secondary features. Specifically, myelin debris undermines the protective role of microglia, contributing to neuroinflammation and neuronal death. Herein, we examined central myelin and oligodendrocyte lineage progression in ASM knockout mice. We show that early-onset dysmyelination results from compromised oligodendrocyte maturation driven by aberrant sphingomyelin-mediated signaling. Transcriptomic profiling revealed that mature oligodendrocytes in these mice retain a gene expression signature similar to oligodendrocyte precursor cells, indicating a differentiation arrest. The cell adhesion molecule CD44 remained significantly upregulated in mature ASMko oligodendrocytes. Pharmacological inhibition of CD44 with verbascoside rescued oligodendroglial maturation in primary culture. Verbascoside administration in vivo restored myelin integrity and improved motor behavior. These findings establish that sphingomyelin homeostasis is critical for oligodendrocyte maturation and identify myelin defects as both primary pathological triggers and therapeutic targets for ASMD with neurologic symptoms.

Animals↗
PubMed1977

The fatty acid composition of sphingomyelin from adult human cerebral white matter and changes in childhood, senium and unspecific brain damage.

A micromethod for the investigation of the fatty acid composition of sphingomyelin in presented. In the cerebral white matter of 17 normal adult brains, analyzed for reference, the predominant fatty acids are C 18:0 and C 24:1. Our results are in agreement with those of other authors. Short chained fatty acids are relatively increased in young children; this shift is typical of "immature" myelin. Similar changes are described here in old persons and cases of non-specific brain damage associated with demyelination (autolysis, chronic uremia, juvenile chorea). Sphingomyelin fatty acid composition can be considered a sensitive measure of both disturbed myelination and demyelination.

Adolescent↗
PubMed1977

The effect of phosphatidylcholine to sphingomyelin mole ratio on the dynamic properties of sheep erythrocyte membrane.

Sheep red blood cells are shown to incorporate phosphatidylchline when incubated in human plasma in the presence of EGTA. This treatment results in up to a 5-fold increase in mol ratio of phosphatidylcholine to sphingomyelin. By replacing EGTA with Ca+ the increase of phsphatidylcholine content is completely inhibited, due to the activation of the membrane bound lecithinase which rapidly degrades the incorporated phosphatidylcholine. Analogous treatments of the isolate membranes resulted in similar phosphatidylcholine incorporation but in the presence of Ca+ a residual phosphatidylcholine uptake was still oberved. These results suggest that in the isolated membranes small amounts of phosphatidylcholine can be incorporated into an additional region which is unavailable for the membrane lecithinase. The increase in the phosphatidylcholine to sphingomyelin mol ratio in sheep red blood cells is concomitant with an increase in lipid fluidity, as well as increase in osmotic fragility9

Animals↗
PubMedDate not supplied

Fatty acid composition of myelin lipids (cerebrosides, sulphatides and sphingomyelin) from normal human sural nerve, and changes in peripheral neuropathy.

Fatty acids of cerebrosides, sulphatides and sphingomyelin from normal human sural nerve, by comparison with brain, show a diminution of long-chained fatty acids as well as unsaturated fatty acids. The findings in brachial plexus are intermediate. In cases of peripheral neuropathy from various causes sphingomyelin fatty acid composition reveals pronounced loss of long-chained fatty acids, a phenomenon that is probably unspecific and may be associated with all forms of demyelination. Problems associated with the limited amount of nervous tissue available from biopsy specimens are discussed.

Adult↗
PubMed1978

Sphingomyelinase activity levels in human peripheral blood leukocytes, using [3H]sphingomyelin as substrate: study of heterozygotes and homozygotes for Niemann-Pick disease variants.

Patients and heterozygous carriers of Niemann-Pick disease types A and B as well as the primary (genetic) sea-blue histiocyte syndrome were investigated for their leukocyte sphingomyelinase activity. In parallel, glucocerebrosidase activity was determined in all cases studied. [3H]Sphingomyelin and [14C]glucocerebroside served as substrates for sphingomyelinase and glucocerebrosidase activity measurements, respectively. Conditions for these enzymes' assays are discussed. Sphingomyelinase activity was completely absent in three cases of Niemann-Pick disease type A and significantly diminished in one patient with Niemann-Pick disease type B and two with the sea-blue histiocyte syndrome. Sphingomyelinase activity in obligatory heterozygotes of all variants investigated represented about 40 to 70% of normal activity. Nevertheless, some overlapping with normal values occasionally occurred. Interestingly, glucocerbrosidase activity was elevated in patients with Niemann-Pick disease variants.

Glucosylceramidase↗
PubMed1976

[Adult Niemann-Pick disease: a 26 years follow-up. Report of a case with isolated visceral involvement, excess of tissue sphingomyelin, and deficient sphingomyelinase activity (author's transl)].

The case report of Niemann-Pick disease, in a 26 years old woman whose first symptoms appeared when she was 17 months old, is described. The disease, involving considerable hepatosplenomegaly and pulmonary infiltration, was diagnosed by the presence of lipid laden macrophages (resembling foam cells, sea blue histiocytes and kidney intermediate forms) in the bone marrow, liver and kidney, and an excess of tissue sphingomyelin and cholesterol, and a decrease in sphingomyelinase in circulating leucocytes. The results of ultrastructural, histochemical and biochemical studies on hepatic and renal lipids are reported. The relationship of the case to the sea blue histiocyte syndrome is discussed.

Adult↗
PubMed1976

Study of the long chain bases of sphingomyelin of Entomophthora coronata.

Sphingomyelin was isolated from a strain of Entomophthora coronata, a fungus pathogenic for humans. After hydrolysis, the long chain bases were converted to their dinitrophenyl (N2pH) derivatives and the aldehydes prepared by oxidizing these compounds with periodic acid. The aldehydes were studied by gas chromatography. Twelve different aldehydes were identified, the chain distributiion ranging from C14 to C17. The prominent chains were unsaturated. Straight and branched chains were found. The most abundant parent base which formed 52% of the total aldehyde was a 1,3-dihydroxy-2-aminohexadecene.

Aldehydes↗
PubMed1977

Cholesterol ester accumulation in cultured aortic smooth muscle cells. Induction of cholesterol ester retention by chloroquine and low density lipoprotein and its reversion by mixtures of high density apolipoprotein and sphingomyelin.

Accretion of cholesterol ester was studied in rat aortic smooth muscle cells in culture. Confluent multilayers of smooth muscle cells were exposed to human low density lipoprotein (LDL) and chloroquine and this treatment resulted in a very marked increase in cellular cholesterol ester. The degree of enrichment in cholesterol ester was related inversely to the cell density in the petri dish and was maximal in 48 h. The morphological changes after 48 h incubation with chloroquine and LDL consisted of accumulation of numerous membrane-bound inclusions containing electron-dense and electron-lucent material, some of which resembled secondary lysosomes. These changes resembled some of the changes observed in human and experimental atheromatosis. Similar inclusions were seen also in cultured human skin fibroblasts which accumulated large amounts of cholesterol ester during 48 h incubation with LDL and chloroquine. Removal of the accumulated cellular cholesterol ester was studied in the two cell types and it was markedly enhanced in the presence of lipoprotein-deficient serum and high density apolipoprotein-sphingomyelin mixture. The morphological findings after 24 h of post incubation revealed the presence of empty vacuoles, membrane whorls and cytoplasmic lipid droplets. The present results indicate that aortic smooth muscle cells in culture can serve as a good model to study the role of the lysosomal system in atherogenesis.

Adult↗
PubMed1976

Biosynthesis of sphingomyelin in rat liver endoplasmic reticulum.

Rat liver microsomal sphingomyelin synthetase (CDPcholine: N-acylspingosine choline phosphotransferase (EC 2.7.8.3)) has been shown to be markedly stimulated by ATP and pantothenic acid derivatives such as CoA, pantethine, pantetheine and 4'-phosphopantetheine.

Animals↗
PubMed1977

Chemical proof of lipid-protein interactions by crosslinking photosensitive lipids to apoproteins. Intermolecular cross-linkage between high-density apolipoprotein A-I and lecithins and sphingomyelins.

The molecular interactions and spatial arrangements of phospholipids and apoproteins of human high-density lipoprotein were studied by a chemical approach. Phosphatidylcholines and sphingomyelins substituted with fatty acyl residues of high specific radioactivity and labelled with the photosensitive azido group in specific positions were prepared by chemical synthesis. They were recombined with apolipoprotein A-I of human serum high density lipoprotein. The lipoprotein complexes containing either azido lecithins or azidosphingo-myelins were purified by agarose chromatography from excess lipids. The irradiation was performed under conditions which prohibit the interference with the apoprotein structure as proven by circular dichroism, fluorescence spectroscopy, immunodiffusion test and disc electrophoresis. Non-covalently bound lipid molecules were removed by Sephadex LH 20 chromatography. Mild alkaline treatment liberated radioactive fatty acids which were not directly linked to the polypeptide chain, but rather via neighbouring phospholipid molecules. The lipoprotein appeared as a single radioactive band in dodecylsulfate polyacrylamide gel electrophoresis as seen by radioscanning, which further proved the covalent linkage of the fatty acyl residues to the polypeptide chain. In the immunodiffusion test, there is no difference between covalently crosslinked phospholipid-apoLp A-I complex and the non-photolyticall treated complex. This is the first chemical proof of the spatial relationship of the hydrophobic side chains of the lipid and polypeptide chains in a lipoprotein complex.

Apolipoproteins↗
PubMedDate not supplied

[A comparative study of the fatty acid composition of the sphingomyelins in the whole brain and its parts in vertebrates].

The fatty acid composition of sphingomyelin (Spm) was studied in the total brain, the forebrain and the brain stem in frogs (Rana temporaria and Rana ridibunda), the tortoise (Emys orbicularis), the hen and the cat. A typical fatty acid pattern of Spm was revealed irrespectively of the brain part examined. Regular differences in fatty acid composition of Spm between various brain parts were found irrespectively of the level of development of the nervous system. It may be concluded that corresponding changes in the fatty acid composition of Spm in the forebrain as well as in the brain stem are taking place in the course of evolution of the central nervous system.

Animals↗