An improved assay of gangliosides separated by thin-layer chromatography

Characterization and biological activity of gangliosides in buffalo milk

Gangliosides (GS) were evaluated in Swiss cow's milk (SCM), Italian buffalo milk (IBM) and its serum, Pakistan buffalo colostrum (PBC), Pakistan buffalo mature milk (PBM), and Pakistan buffalo milk from rice-growing areas (PBR). Dairy GS were obtained from the Folch's upper (hydrophilic) and lower (lipophilic) extraction phases, respectively, and determined as lipid-bound sialic acid (LBSA) by colorimetry. Molar ratios of LBSA in the hydro- and lipophilic GS fractions were 52:48 to 79:21. Mature buffalo milk types had 40-100% more LBSA in the lipophilic GS fraction compared to SCM. Liquid PBC was higher in LBSA (24 nmol/g) compared to mature milk types (8-11 nmol/g). Thin-layer chromatography (TLC) and scanning densitometry showed distinct profiles of hydrophilic and lipophilic GS fractions. Lipophilic GS (but importantly not hydrophilic GS) from IBM and its serum decreased prostaglandin series 2 production by 75-80% in cultured human colonic epithelial cells exposed to tumor necrosis factor alpha (TNFalpha). Hydrophilic GD(3) and lipophilic GM(3) selectively bound rotavirus particles prepared from a rhesus strain and its mutant. A GS fraction in IBM showed a GM(1)-specific binding to cholera toxin subunit B (CTB). IBM serum (IBMS) was a rich source of LBSA (420 nmol/g proteins). In summary, improved methodology led to increased LBSA recovery and isolation of additional and bioactive milk GS. Human and Italian buffalo milk had similar CTB binding, and both had increased polysialo-GS compared to cows milk. The toxin binding properties of buffalo milk GS, and the anti-inflammatory activity of the lipophilized GS fraction could be important for developing innovative food applications, as well as the subject of future research.

Glycosphingolipids during skeletal muscle cell differentiation: comparison of normal and fusion-defective myoblasts

The regulation of glycosphingolipid (GSL) synthesis in culture by fusion-competent (E63) myoblasts and fusion-defective (fu-1) cells was examined. Upon reaching confluency E63 cells fused to form multinucleated myotubes and demonstrated many characteristics of developing skeletal muscle including induction of creatine kinase activity and a shift in creatine kinase isozymes to the MM isoform. The fu-1 cells displayed none of these characteristics, despite the fact that both cells were cloned from the same parental myoblast line (rat L8). There was a transient increase in the synthesis of total neutral GSLs by E63 cells at the time of membrane fusion. In contrast, neutral GSL synthesis by fu-1 cells gradually decreased with time in culture. The major GSLs synthesized by both cell types were lactosylceramide and ganglioside GM3, with more complex structures being observed with prolonged time in culture. Several glycosyltransferase activities were assayed at varying times in culture. Generally, the changes in activities fell into three groups. One group was maximally activated at the end of the culture period (GalT-3, GalNAcT-1 and GalT-6). Another group was maximally activated during the time of active membrane fusion (GlcT and SAT-1). A third group was maximally activated at the time of cell contact and the beginning of membrane fusion (GlcNAcT-1 and GalT-2). In terms of the times of maximal activation there were few differences between E63 and fu-1 cells, with one notable exception. The activity of GalT-2 (lactosylceramide synthase) in E63 cells increased dramatically upon contact and the beginning of membrane fusion, whereas there were no changes in GalT-2 activity in fu-1 cells during time in culture. These results support our hypothesis that membrane glycosphingolipids play an important role in the differentiation of skeletal muscle cells.

Cocaine exposure during pregnancy affects rat neonate and maternal brain glycosphingolipids

Behavioral dysfunctions in offspring exposed in utero to cocaine have been observed, along with alterations in dopamine systems, but few studies of the underlying biochemistry have been conducted. Because of their documented roles in neuronal maturation, glycosphingolipids were analyzed in whole brains of offspring exposed gestationally to cocaine. Rat offspring exposed to cocaine in utero exhibited markedly elevated levels of both total gangliosides (p < 0.001) and neutral glycosphingolipids (p < 0.01) at postnatal day 1. However, by postnatal day 11 levels of gangliosides and neutral glycosphingolipids returned to control values. These effects were not restricted to chronic cocaine exposure early in life, in that ganglioside content of whole maternal brains was also elevated (p < 0.001), though less than that observed with the neonate brains. Qualitatively, no differences in ganglioside nor neutral glycolipid structure distribution were observed between cocaine-exposed and normal animals following separation by HPTLC and HPLC. These elevations are in contrast to those following alcohol exposure, where decreases in brain gangliosides have been observed. Neurochemical consequences of prenatal exposure to cocaine may be far-reaching and may not be restricted to the dopamine system.

Regulation of glycolipid synthesis during differentiation of clonal murine muscle cells

The two clonal murine muscle cell lines G7 and G8, originally derived from the M114 line, represent unique models for comparative studies of myogenesis. Glycolipid synthesis was examined during differentiation using [3H]-galactose and [3H]-glucosamine as precursors. Upon G7 contact glucosylceramide labeling increased and nLcOse5Cer labeling stopped. During membrane fusion, glucosylceramide labeling stopped and lactosylceramide became the major synthetic product. G8 cells presented a different pattern, with increased labeling of GbOse3Cer during myogenesis. The major ganglioside synthesized by both myoblasts was GM3, and more complex structures were observed following completion of myotube formation. Total glycopeptide labeling increased when G8 myoblasts fused and remained elevated in myotubes, whereas no differences during fusion of G7 cells were noted. Upon comparison of the two clonal lines, the only consistent observation was a significant increase in the synthesis of total gangliosides and neutral glycolipid during cell contact and membrane fusion (p less than 0.02). The results suggest that changes in the synthesis of specific glycolipid structures during myogenesis are unique to each muscle cell line examined. However, transient increases in synthesis of total myoblast gangliosides and neutral glycolipids may be a more general phenomenon, possibly by curbing proliferation or by altering myoblast membrane fluidity characteristics during differentiation.

A sensitive method to quantitate gangliosides of the gangliotetraose series directly on chromatograms using peroxidase conjugated cholera toxin

A method is described whereby ganglioside GM1 can be quantitated directly on thin-layer chromatograms using cholera toxin subunit B conjugated to horseradish peroxidase and visualized with chloronaphthol. Overlay and color development were performed after separating gangliosides on nano-TLC plates, and fixing with polyisobutylmethacrylate. Absolute quantitation was realized using a Shimadzu CS-9000 integrating spectrodensitometer, scanning at 580 nm. A correlation coefficient of 0.98 was obtained in a linear range of detection from 10(-11) to 10(-16) moles. Statistical analysis revealed good reproducibility and over 99% of the added gangliosides remained with the chromatogram during all overlay and washing procedures. By comparison, standard chemical visualization by resorcinol-HCl was linear in the nanomole range with a detection limit of only 10(-10) moles. Since the carbohydrate portion of gangliosides immobilized in this manner is susceptible to the action of enzymes including neuraminidase, this technique can be applied to all structures of the gangliotetraose series.

In situ visualization of glycosphingolipids on thin-layer chromatograms using lectin-peroxidase conjugates

A technique is described for direct detection by lectins conjugated to horseradish peroxidase of the oligosaccharides of glycosphingolipids on thin-layer chromatograms. Final visualization is accomplished using a substrate medium consisting of hydrogen peroxide and 3,3'-diaminobenzidine. The procedure is rapid, specific, sensitive and highly reproducible, and staining patterns are stable for years. In addition to providing preliminary structural information, this technique can be employed in combination with other methods, such as autoradiographic detection of tritium-labeled glycosphingolipids in the same chromatogram.

A comparative-evolutionary study of lipids in the aging brain of mice

The lipids of aging brain were studied using a comparative-evolutionary model involving two species of mice, Mus Musculus (Mus) and Peromyscus leucopus (Peromyscus). Mus ages 2.5 times faster than does Peromyscus. Brain weight, water content, cholesterol, and ethanolamine plasmalogen decreased and phosphatidyl ethanolamine increased in both species with age. Differences between species included 12% more cholesterol/g total lipid extract in Peromyscus than in Mus throughout life, a linear increase with age in lipid phosphorus/g fresh weight at a faster rate in Peromyscus over Mus, and a linear increase in the total lipid extract weight throughout life in Mus but a decrease in Peromyscus. Cerebroside, sulfatide and GM1 ganglioside all increased during maturation and then decreased in old age in both mice. Lipid-bound sialic acid (ganglioside) increased linearly throughout life in Peromyscus but decreased slightly in Mus. These changes are interpreted to mean that the cellular membranes of Peromyscus may be inherently more stable than those of Mus, Peromyscus is better able to preserve its neuronal cell population with age than is Mus, proliferation of non-myelin membranes may occur in both species in advanced age, and both species of mice may experience some loss of myelin with age.

Lipid content of swine influenza and other vaccines

An analysis of the lipids in swine influenza vaccines was performed, comparing six different lots of swine influenza, other influenza and noninfluenza vaccines. Cholesterol content and phospholipid content varied greatly, but there were no major differences between the types of vaccines. Appreciable amounts of phosphatidylethanolamine were found in only one swine influenza vaccine. The major phospholipids of influenza vaccines were phosphatidylcholine, sphingomyelin and phosphatidic acid. A detectable amount of phosphatidylserine was not found in any swine influenza vaccine, but was present in two of three nonswine influenza vaccines. Only two of six swine influenza vaccines showed trace amounts (less than 0.5 microgram/ml) of ganglioside (GM3). However, larger quantities of galactocerebroside were found (2.24-6.43 micrograms/ml) in all influenza vaccines examined, including swine influenza vaccines.

A simplified procedure for the preparation of tritiated GM1 ganglioside and other glycosphingolipids

The ganglioside II3NeuAc-GgOse4Cer and other glycosphingolipids can be radiolabeled to high specific activity by the galactose oxidase-NaB3H4 procedure, by purifying the oxidized compounds prior to reductive labeling. The oxidized products are separated from nonoxidized compounds and detergents (Triton X-100 and sodium taurocholate) present during the enzymatic oxidation. Since the oxidized derivatives are separated, the final specific activity depends solely upon the specific activity of the NaB3H4 and the reduction conditions.

Changes of glycolipids dependent on cell density of Ehrlich ascites carcinoma cells

The glycolipid composition of Ehrlich ascites carcinoma cells was found to depend strongly on the cell density of the suspension. The general trend observed upon dilution of the cell suspension was a reduction of the less complex gangliosides GM3 and GM2 with concomitant increase of the more complex gangliosides, especially GM1. The increase of the content of ganglioside GM1 upon dilution was accompanied by a comparable decrease of the content of its immediate precursor, asialo-GM1, whereas the content of other neutral glycosphingolipids did not change very much. When the cell suspension was diluted with medium conditioned by dense cells the ganglioside profile of the diluted suspension remained similar to that of the dense cell suspension. It is postulated that the medium conditioned with dense cells contains a transferable factor inhibiting sialylation of asialo-GM1.

Glycosphingolipids of an alveolar rhabdomyosarcoma and normal human muscle. A case study

The distribution of neutral, or asialosyl-, glycosphingolipids and gangliosides in a rhabdomyosarcoma of alveolar type have been studied. Histologically, this muscle tumor is composed primarily of two cell types: one with oval or round hyperchromatic nuclei and very little cytoplasm, and one a giant cell, with multiple, peripherally placed nuclei and weakly staining eosinophillic cytoplasm. In comparing glycolipids of the rhabdomyosarcoma with normal muscle from the same leg, the striking alteration in the tumor was a virtual disappearance of ganglioside GM2. There was also a slight increase in GM3 and a decrease in GD1a. The asialosyl derivative of GM2 (GalNac-Gal-Glc-Cer) was markedly increased in the tumor. A loss of glucosylceramide was also observed. The results are discussed in terms of glycolipid metabolic changes in muscle oncogenesis and their implications.

Properties of endogenous, membrane-associated sialidase activity (N-acetylneuraminidase) of the goldfish visual system

The endogenous sialidase (N-acetylneuraminidase) activity of membranes prepared from goldfish retina and optic tectum displays characteristics similar to those reported for neural plasma membrane sialidases of other organisms. Endogenous membrane sialidase activity was found to be optimal at ph 4.0, and maximal release was obtained at 37-50 degrees C, above which temperature thermal instability of the preparations was observed. Optic nerve crush, which results in regeneration of retinal ganglion cell axons, did not result in significant changes in measured endogenous membrane sialidase activity in either the retina or the optic tectum. Enzymatic hydrolysis of membrane sialoglycolipid (ganglioside) accounted for about 70% of the total sialic acid released. Ganglioside GM1 accumulated as the major lipid product in both retina and tectum, indicating that the inner sialosylgalactosyl linkage in the ganglio oligosaccharide series was resistant to hydrolysis by the endogenous enzyme.

Role of gangliosides in reception of influenza virus

The ganglioside composition of Ehrlich ascites carcinoma (EAC) cells and the role of the individual gangliosides in binding and penetration into the cell of influenza virus were determined. EAC gangliosides identical with or close to GM3, GM2, GM1, GT1a and GT1b were characterized by thin-layer chromarography, compositional analyses, methylation analysis and mass-spectrometry. The ganglioside uptake capacity of native and neuraminidase-treated EAC cells was studied with tritium-labeled gangliosides of definite structure and the binding of influenza virus to cells was determinated by using [3H]uridine-labeled virus and by hemagglutination studies. Treatment of the cells with Vibrio cholerae neuraminidase largely decreased binding of the virus. Exogenous gangliosides with a terminal galactose unit or a penultimate galactose masked by neuraminic acid were able to restore the virus-binding capacity of neuraminidase-treated cells, however, the main ganglioside of EAC cells, GM2, which carbohydrate chain is terminated by N-acetylgalactosamine, was completely ineffective. The common carbohydrate sequence of the gangliosides showing binding activity (formula; see text) is proposed to be the main recognition structure of the influenza virus receptor on the surface of EAC cells. Penetration of labeled influenza virus into the nuclei of EAC cells was evaluated by measuring the radioactivity of the nuclei of neuraminidase-treated ganglioside-loaded cells after exposition to the labeled virus. Of all gangliosides tested only trisialogangliosides of the GT1b type were able to induce increased entry of the virus into the cells and accumulation of its radioactive component into the nuclei. It is suggested that GT1b gangliosides react specifically with the virus protein responsible for membrane fusion (apparently the hemagglutinin HA2 subunit) and thus are involved in virus penetration and delivery of the virus genome to the nuclei.

Effects of postmortem autolysis on the lipids of rat spinal cord

The lipid composition of rat spinal cord undergoing postmortem autolysis for 3 min and for 4 h at 38 degrees C was investigated as a model for lipid changes in total spinal cord ischemia. The only change in cords incubated for 3 min was an 11.7% decrease in cholesterol/g fresh weight. The cords incubated for 4 h showed a similar 11.6% decrease in cholesterol/g fresh weight as well as a 5.6% increase in water content and a 22% decrease in phosphatidyl serine. Changes of marginal statistical significance included a 15% increase in lipid phosphorus/g dry wt. and a 15% decrease in G4 (GM1)1 in the 4 h incubated cords. Therefore, autolytic processes are of little consequence in total spinal cord ischemia and attention should now be focused on exogenous pathogenetic factors to explain such ischemic changes in spinal cord. We also report discovery of an alkali-labile ganglioside, G1a in rat spinal cord.

Chemical and morphological studies on garfish peripheral nerves

Gangliosides were extracted, separated by thin layer chromatography, and quantitated in three cranial nerves of the garfish (Lepisosteus osseus): the completely unmyelinated olfactory nerve (OLF), and two nerves composed of both myelinated and unmyelinated fibers, viz., the main trunk of the maxillary nerve (MAX) and a branch of the maxillary nerve (BR-MAX). Morphological studies on each of these nerves were done to verify that the OLF had been excised free of any contamination from the accompanying myelinated BR-MAX, to aid in the interpretation of the biochemical findings, and to clarify the nature of the OLF supporting cell. The chief chemical findings were (1) documentation of the presence of gangliosides in nerves previously thought not to contain them, (2) demonstration that gangliosides can be associated with unmyelinated nerves, (3) demonstration of a greater proportion of one simple ganglioside (G-6) in the OLF but greater proportions of two complex gangliosides (G-2 and G-0) in the MAX and BR-MAX, and (4) that either GM4 or a variant of the GM3 is present in OLF. The morphological findings with respect to the difficulty of ascribing only peripheral nervous system characteristics to the OLF supporting cell are discussed in relation to the ganglioside band chromatographing slightly ahead of GM4 in the OLF.

Large-scale preparation of synaptosomes from bovine brain using a zonal rotor technique

A zonal rotor technique for the preparation of synaptosomes in bulk from bovine brain frontal cortex based on an impirical transformation of a small-volume discontinuous sucrose density gradient arrangement is presented in detail. The procedure yields new information concerning synaptosomes prepared in sucrose gradients. Cerebroside analysis and electron microscopy show myelin contamination to be restricted to the leading, less dense edge of the synaptosomal profile, free mitochondria to the trailing, more dense edge. Exclusion of fringe areas yields a highly purified synaptosome preparation which entirely enters the next dense layer beyond the 0.8 : 1.2 M sucrose interface. This interface collects most of the oubain-sensitive (Na+, K+) adenosine triphosphatase activity. The purified synaptosomes display very high intrinsic sialidase activity and are rich in di-, tri-, and tetrasialogangliosides, the preferred substrates for the enzyme. Up to 90% of the cholinesterase activity in the zonal rotor synaptosome preparation is specific acetylcholinesterase.