High-sensitivity qualitative and quantitative analysis of human, bovine and goat milk glycosphingolipids using HILIC-MS/MS with internal standards.

Glycosphingolipids (GSLs) in human milk regulate the immune system, support intestinal maturation, and prevent gut pathogens. The structural complexity and low abundance of GSLs limits their systematic analysis. Here, we coupled the use of monosialoganglioside 1-2-amino-N-(2-aminoethyl) benzamide (GM1-AEAB) derivatives as internal standards with HILIC-MS/MS to qualitatively and quantitatively compare GSLs in human, bovine, and goat milk. One neutral glycosphingolipid (GB) and 33 gangliosides were found in human milk, of which 22 were newly detected and three were fucosylated. Five GB and 26 gangliosides were identified in bovine milk, of which 21 were newly discovered. Four GB and 33 gangliosides were detected in goat milk, 23 of them newly reported. GM1 was the main GSL in human milk; whereas disialoganglioside 3 (GD3) and monosialogangloside 3 (GM3) were dominant in bovine and goat milk, respectively; N-acetylneuraminic acid (Neu5Ac) was detected in >88 % of GSLs in bovine and goat milk. N-hydroxyacetylneuraminic acid (Neu5Gc)-modified GSLs were 3.5 times more abundant in goat than in bovine milk; whereas GSLs modified with both Neu5Ac and Neu5Gc were 3 times more abundant in bovine than in goat milk. Given the health benefits of different GSLs, these results will facilitate the development of custom-designed human milk-based infant formula.

Plasma Membrane Calcium ATPase-Neuroplastin Complexes Are Selectively Stabilized in GM1-Containing Lipid Rafts.

The recent identification of plasma membrane (Ca2+)-ATPase (PMCA)-Neuroplastin (Np) complexes has renewed attention on cell regulation of cytosolic calcium extrusion, which is of particular relevance in neurons. Here, we tested the hypothesis that PMCA-Neuroplastin complexes exist in specific ganglioside-containing rafts, which could affect calcium homeostasis. We analyzed the abundance of all four PMCA paralogs (PMCA1-4) and Neuroplastin isoforms (Np65 and Np55) in lipid rafts and bulk membrane fractions from GM2/GD2 synthase-deficient mouse brains. In these fractions, we found altered distribution of Np65/Np55 and selected PMCA isoforms, namely PMCA1 and 2. Cell surface staining and confocal microscopy identified GM1 as the main complex ganglioside co-localizing with Neuroplastin in cultured hippocampal neurons. Furthermore, blocking GM1 with a specific antibody resulted in delayed calcium restoration of electrically evoked calcium transients in the soma of hippocampal neurons. The content and composition of all ganglioside species were unchanged in Neuroplastin-deficient mouse brains. Therefore, we conclude that altered composition or disorganization of ganglioside-containing rafts results in changed regulation of calcium signals in neurons. We propose that GM1 could be a key sphingolipid for ensuring proper location of the PMCA-Neuroplastin complexes into rafts in order to participate in the regulation of neuronal calcium homeostasis.

Visualisation of cholesterol and ganglioside GM1 in zebrafish models of Niemann-Pick type C disease and Smith-Lemli-Opitz syndrome using light sheet microscopy.

Lysosomal storage diseases are the most common cause of neurodegeneration in children. They are characterised at the cellular level by the accumulation of storage material within lysosomes. There are very limited therapeutic options, and the search for novel therapies has been hampered as few good small animal models are available. Here, we describe the use of light sheet microscopy to assess lipid storage in drug and morpholino induced zebrafish models of two diseases of cholesterol homeostasis with lysosomal dysfunction: First, Niemann-Pick type C disease (NPC), caused by mutations in the lysosomal transmembrane protein NPC1, characterised by intralysosomal accumulation of cholesterol and several other lipids. Second, Smith-Lemli-Opitz syndrome (SLOS), caused by mutations in 7-dehydrocholesterol reductase, which catalyses the last step of cholesterol biosynthesis and is characterised by intralysosomal accumulation of dietary cholesterol. This is the first description of a zebrafish SLOS model. We find that zebrafish accurately model lysosomal storage and disease-specific phenotypes in both diseases. Increased cholesterol and ganglioside GM1 were observed in sections taken from NPC model fish, and decreased cholesterol in SLOS model fish, but these are of limited value as resolution is poor, and accurate anatomical comparisons difficult. Using light sheet microscopy, we were able to observe lipid changes in much greater detail and identified an unexpected accumulation of ganglioside GM1 in SLOS model fish. Our data demonstrate, for the first time in zebrafish, the immense potential that light sheet microscopy has in aiding the resolution of studies involving lysosomal and lipid disorders.

Gangliosides in the differentiation process of primary neurons: the specific role of GM1-oligosaccharide.

It has been recently reported by our group that GM1-oligosaccharide added to neuroblastoma cells or administered to mouse experimental model mimics the neurotrophic and neuroprotective properties of GM1 ganglioside. In addition to this, differently from GM1, GM1-oligosaccharide is not taken up by the cells, remaining solubilized into the extracellular environment interacting with cell surface proteins. Those characteristics make GM1-oligosaccharide a good tool to study the properties of the endogenous GM1, avoiding to interfere with the ganglioside natural metabolic pathway. In this study, we show that GM1-oligosaccharide administered to mice cerebellar granule neurons by interacting with cell surface induces TrkA-MAP kinase pathway activation enhancing neuron clustering, arborization and networking. Accordingly, in the presence of GM1-oligosaccharide, neurons show a higher phosphorylation rate of FAK and Src proteins, the intracellular key regulators of neuronal motility. Moreover, treated cells express increased level of specific neuronal markers, suggesting an advanced stage of maturation compared to controls. In parallel, we found that in the presence of GM1-oligosaccharide, neurons accelerate the expression of complex gangliosides and reduce the level of the simplest ones, displaying the typical ganglioside pattern of mature neurons. Our data confirms the specific role of GM1 in neuronal differentiation and maturation, determined by its oligosaccharide portion. GM1-oligosacchairide interaction with cell surface receptors triggers the activation of intracellular biochemical pathways responsible for neuronal migration, dendrites emission and axon growth.

Pre-diagnosing and managing patients with GM1 gangliosidosis and related disorders by the evaluation of GM1 ganglioside content.

GM1 ganglioside, a monosialic glycosphingolipid and a crucial component of plasma membranes, accumulates in lysosomal storage disorders, primarily in GM1 gangliosidosis. The development of biomarkers for simplifying diagnosis, monitoring disease progression and evaluating drug therapies is an important objective in research into neurodegenerative lysosomal disorders. With this in mind, we established fluorescent imaging and flow-cytometric methods to track changes in GM1 ganglioside levels in patients with GM1 gangliosidosis and in control cells. We also evaluated GM1 ganglioside content in patients' cells treated with the commercially available Miglustat, a substrate inhibitor potentially suitable for the treatment of late-onset GM1 gangliosidosis. The flow-cytometric method proved to be sensitive, unbiased, and rapid in determining variations in GM1 ganglioside content in human lymphocytes derived from small amounts of fresh blood. We detected a strong correlation between GM1 ganglioside content and the clinical severity of GM1 gangliosidosis. We confirm the ability of Miglustat to act as a substrate reduction agent in the patients' treated cells. As well as being suitable for diagnosing and managing patients with GM1 gangliosidosis this method could be useful in the diagnosis and management of other lysosomal diseases, such as galactosialidosis, Type C Niemann-Pick, and any other disease with pathologic variations of GM1 ganglioside.

Spatial Relationship and Functional Relevance of Three Lipid Domain Populations at the Erythrocyte Surface.

BACKGROUND/AIMS: Red blood cells (RBC) have been shown to exhibit stable submicrometric lipid domains enriched in cholesterol (chol), sphingomyelin (SM), phosphatidylcholine (PC) or ganglioside GM1, which represent the four main lipid classes of their outer plasma membrane leaflet. However, whether those lipid domains co-exist at the RBC surface or are spatially related and whether and how they are subjected to reorganization upon RBC deformation are not known. METHODS: Using fluorescence and/or confocal microscopy and well-validated probes, we compared these four lipid-enriched domains for their abundance, curvature association, lipid order, temperature dependence, spatial dissociation and sensitivity to RBC mechanical stimulation. RESULTS: Our data suggest that three populations of lipid domains with decreasing abundance coexist at the RBC surface: (i) chol-enriched ones, associated with RBC high curvature areas; (ii) GM1/PC/chol-enriched ones, present in low curvature areas; and (iii) SM/PC/chol-enriched ones, also found in low curvature areas. Whereas chol-enriched domains gather in increased curvature areas upon RBC deformation, low curvature-associated lipid domains increase in abundance either upon calcium influx during RBC deformation (GM1/PC/chol-enriched domains) or upon secondary calcium efflux during RBC shape restoration (SM/PC/chol-enriched domains). Hence, abrogation of these two domain populations is accompanied by a strong impairment of the intracellular calcium balance. CONCLUSION: Lipid domains could contribute to calcium influx and efflux by controlling the membrane distribution and/or the activity of the mechano-activated ion channel Piezo1 and the calcium pump PMCA. Whether this results from lipid domain biophysical properties, the strength of their anchorage to the underlying cytoskeleton and/or their correspondence with inner plasma membrane leaflet lipids remains to be demonstrated.

Detection and Characterization of Different Brain-Derived Subpopulations of Plasma Exosomes by Surface Plasmon Resonance Imaging.

The use of exosomes for diagnostic and disease monitoring purposes is becoming particularly appealing in biomedical research because of the possibility to study directly in biological fluids some of the features related to the organs from which exosomes originate. A paradigmatic example are brain-derived exosomes that can be found in plasma and used as a direct read-out of the status of the central nervous system (CNS). Inspired by recent remarkable development of plasmonic biosensors, we have designed a surface plasmon resonance imaging (SPRi) assay that, taking advantage of the fact that exosome size perfectly fits within the surface plasmon wave depth, allows the detection of multiple exosome subpopulations of neural origin directly in blood. By use of an array of antibodies, exosomes derived from neurons and oligodendrocytes were isolated and detected with good sensitivity. Subsequently, by injecting a second antibody on the immobilized vesicles, we were able to quantify the amount of CD81 and GM1, membrane components of exosomes, on each subpopulation. In this way, we have been able to demonstrate that they are not homogeneously expressed but exhibit a variable abundance according to the exosome cellular origin. These results confirm the extreme variability of exosome composition and demonstrate how SPRi can provide an effective tool for their characterization. Besides, our work paves the road toward more precise clinical studies on the use of exosomes as potential biomarkers of neurodegenerative diseases.

A new purified Lawsoniaside remodels amyloid-ß42 fibrillation into a less toxic and non-amyloidogenic pathway.

Mounting evidence indicates soluble Aß42 oligomers as the most toxic species causing neuronal death which leads to the onset and progression of Alzheimer disease (AD). Recently, it has been found that neurotoxic Aß42 oligomers grow from monomeric species or arise following secondary nucleation by preformed mature fibrils. Thus, the use of natural compounds such as polyphenols to hinder the growth or to remodel Aß42 fibrils is one of the most promising strategies for AD treatment. In our previous study, we showed that 1, 2, 4-trihydroxynaphthalene-2-O-ß-d-glucopyranoside (THNG) inhibits Aß42 aggregation during the early steps of the aggregation process, inhibits its conformational change to a ß-sheet-rich structure, decreases its polymerization, inhibits its fibrillogenisis and reduces oxidative stress and aggregate cytotoxicity. Here, we used different spectroscopic and cell culture methods to check the effect of THNG on fibrils disaggregation. We showed that THNG binds to mature Aß42 fibrils, rearrange their secondary structure, and remodels them into non-amyloid, less toxic, species by inhibiting their interaction with the plasma membrane. Our findings reveal that THNG is a good agent to remodel amyloid fibrils and could be used as a starting molecular scaffold to design new anti-AD drugs.

Glycolipid GD3 and GD3 synthase are key drivers for glioblastoma stem cells and tumorigenicity.

The cancer stem cells (CSCs) of glioblastoma multiforme (GBM), a grade IV astrocytoma, have been enriched by the expressed marker CD133. However, recent studies have shown that CD133(-) cells also possess tumor-initiating potential. By analysis of gangliosides on various cells, we show that ganglioside D3 (GD3) is overexpressed on eight neurospheres and tumor cells; in combination with CD133, the sorted cells exhibit a higher expression of stemness genes and self-renewal potential; and as few as six cells will form neurospheres and 20-30 cells will grow tumor in mice. Furthermore, GD3 synthase (GD3S) is increased in neurospheres and human GBM tissues, but not in normal brain tissues, and suppression of GD3S results in decreased GBM stem cell (GSC)-associated properties. In addition, a GD3 antibody is shown to induce complement-dependent cytotoxicity against cells expressing GD3 and inhibition of GBM tumor growth in vivo. Our results demonstrate that GD3 and GD3S are highly expressed in GSCs, play a key role in glioblastoma tumorigenicity, and are potential therapeutic targets against GBM.

Improved characterization of EV preparations based on protein to lipid ratio and lipid properties.

In recent years the study of extracellular vesicles has gathered much scientific and clinical interest. As the field is expanding, it is becoming clear that better methods for characterization and quantification of extracellular vesicles as well as better standards to compare studies are warranted. The goal of the present work was to find improved parameters to characterize extracellular vesicle preparations. Here we introduce a simple 96 well plate-based total lipid assay for determination of lipid content and protein to lipid ratios of extracellular vesicle preparations from various myeloid and lymphoid cell lines as well as blood plasma. These preparations included apoptotic bodies, microvesicles/microparticles, and exosomes isolated by size-based fractionation. We also investigated lipid bilayer order of extracellular vesicle subpopulations using Di-4-ANEPPDHQ lipid probe, and lipid composition using affinity reagents to clustered cholesterol (monoclonal anti-cholesterol antibody) and ganglioside GM1 (cholera toxin subunit B). We have consistently found different protein to lipid ratios characteristic for the investigated extracellular vesicle subpopulations which were substantially altered in the case of vesicular damage or protein contamination. Spectral ratiometric imaging and flow cytometric analysis also revealed marked differences between the various vesicle populations in their lipid order and their clustered membrane cholesterol and GM1 content. Our study introduces for the first time a simple and readily available lipid assay to complement the widely used protein assays in order to better characterize extracellular vesicle preparations. Besides differentiating extracellular vesicle subpopulations, the novel parameters introduced in this work (protein to lipid ratio, lipid bilayer order, and lipid composition), may prove useful for quality control of extracellular vesicle related basic and clinical studies.

Simultaneous multi-species tracking in live cells with quantum dot conjugates.

Quantum dots are available in a range of spectrally separated emission colors and with a range of water-stabilizing surface coatings that offers great flexibility for enabling bio-specificity. In this study, we have taken advantage of this flexibility to demonstrate that it is possible to perform a simultaneous investigation of the lateral dynamics in the plasma membrane of i) the transmembrane epidermal growth factor receptor, ii) the glucosylphospatidylinositol-anchored protein CD59, and iii) ganglioside GM1-cholera toxin subunit B clusters in a single cell. We show that a large number of the trajectories are longer than 50 steps, which we by simulations show to be sufficient for robust single trajectory analysis. This analysis shows that the populations of the diffusion coefficients are heterogeneously distributed for all three species, but differ between the different species. We further show that the heterogeneity is decreased upon treating the cells with methyl-ß-cyclodextrin.

Cholera toxin B subunit-binding and ganglioside GM1 immuno-expression are not necessarily correlated in human salivary glands.

OBJECTIVE: To determine and compare the presence and in situ localization of the glycosphingolipid ganglioside GM1 in human salivary glands using the biomarkers for GM1: cholera toxin and antibodies against GM1. MATERIALS AND METHODS: Immunohistochemical analyses were performed on sections of adult human submandibular, parotid and palatinal glands using cholera toxin sub-unit B and two polyclonal antibodies against ganglioside GM1 as biomarkers. RESULTS: Immunofluorescence microscopy showed that the toxin and antibodies were co-localized in some acini but not in others. The cholera toxin mainly reacted with the cell membranes of the mucous acini in the submandibular gland, while incubation with the antibody against GM1 gave rise to a staining of the cytoplasm. The cytoplasm in some secretory acinar cells in the parotid gland was stained by the cholera toxin, whereas only small spots on the plasma membranes reacted with anti-GM1. The plasma membranes in the parotid excretory ducts appeared to react to anti-GM1, but not to cholera toxin. CONCLUSIONS: Cholera toxin induces the expression of ion channels and carriers in the small intestine and increases the production of secretory mucins. Although their mutual immunohistochemical localization may differ, both cholera toxin and ganglioside GM1 are present in the mucin-producing acini from salivary glands. This could point to a relationship between ganglioside expression and production of salivary mucins.

Effect of various commercial buffers on sperm viability and capacitation.

A wide variety of sperm preparation protocols are currently available for assisted conception. They include density gradient separation and washing methods. Both aim at isolating and capacitating as much motile sperm as possible for subsequent oocyte fertilization. The aim of this study was to examine the effects of four commercial sperm washing buffers on sperm viability and capacitation. Semen samples from 48 healthy donors (normal values of sperm count, motility, morphology, and volume) were analyzed. After separation (density gradient 40/80%), sperm were incubated in various buffers then analysed for reactive oxygen species (ROS) production, viability, tyrosine phosphorylation (Tyr-P), cholera toxin B subunit (CTB) labeling, and the acrosome reaction (AR). The buffers affected ROS generation in various ways resulting either in rapid cell degeneration (when the amount of ROS was too high for cell survival) or the inability of the cells to maintain correct functioning (when ROS were too few). Only when the correct ROS generation curve was maintained, suitable membrane reorganization, evidenced by CTB labeling was achieved, leading to the highest percentages of both Tyr-P- and acrosome-reacted-cells. Distinguishing each particular pathological state of the sperm sample would be helpful to select the preferred buffer treatment since both ROS production and membrane reorganization can be significantly altered by commercial buffers.

The adaptive remodeling of endothelial glycocalyx in response to fluid shear stress.

The endothelial glycocalyx is vital for mechanotransduction and endothelial barrier integrity. We previously demonstrated the early changes in glycocalyx organization during the initial 30 min of shear exposure. In the present study, we tested the hypothesis that long-term shear stress induces further remodeling of the glycocalyx resulting in a robust layer, and explored the responses of membrane rafts and the actin cytoskeleton. After exposure to shear stress for 24 h, the glycocalyx components heparan sulfate, chondroitin sulfate, glypican-1 and syndecan-1, were enhanced on the apical surface, with nearly uniform spatial distributions close to baseline levels that differed greatly from the 30 min distributions. Heparan sulfate and glypican-1 still clustered near the cell boundaries after 24 h of shear, but caveolin-1/caveolae and actin were enhanced and concentrated across the apical aspects of the cell. Our findings also suggest the GM1-labelled membrane rafts were associated with caveolae and glypican-1/heparan sulfate and varied in concert with these components. We conclude that remodeling of the glycocalyx to long-term shear stress is associated with the changes in membrane rafts and the actin cytoskeleton. This study reveals a space- and time- dependent reorganization of the glycocalyx that may underlie alterations in mechanotransduction mechanisms over the time course of shear exposure.

Visualization of lipid raft membrane compartmentalization in living RN46A neuronal cells using single quantum dot tracking.

Lipid rafts are cholesterol-enriched subdomains in the plasma membrane that have been reported to act as a platform to facilitate neuronal signaling; however, they are suspected to have a very short lifetime, up to only a few seconds, which calls into question their roles in biological signaling. To better understand their diffusion dynamics and membrane compartmentalization, we labeled lipid raft constituent ganglioside GM1 with single quantum dots through the connection of cholera toxin B subunit, a protein that binds specifically to GM1. Diffusion measurements revealed that single quantum dot-labeled GM1 ganglioside complexes undergo slow, confined lateral diffusion with a diffusion coefficient of ∼7.87 × 10(-2) µm(2)/s and a confinement domain about 200 nm in size. Further analysis of their trajectories showed lateral confinement persisting on the order of tens of seconds, comparable to the time scales of the majority of cellular signaling and biological reactions. Hence, our results provide further evidence in support of the putative function of lipid rafts as signaling platforms.

Expression of tyrosine kinase receptors in cultured dorsal root ganglion neurons in the presence of monosialoganglioside and skeletal muscle cells.

The neurotrophic factor-like activity of monosialoganglioside (GM1) has been shown to activate tyrosine kinase receptors (Trk). Targets of neuronal innervation play a vital role in regulating the survival and differentiation of innervating neurotrophin-responsive neurons. Both GM1 and target skeletal muscle (SKM) cells are essential for the maintenance of the function of neurons. However, much less is known about the effects of GM1 or/and target SKM cells on the expression of Trk receptors in dorsal root ganglion (DRG) neurons. Here we have tested what extent to the expression of TrkA, TrkB, and TrkC receptors in primary cultured of DRG neurons in absence or presence of GM1 or/and SKM cells. In this experiment, we found that: (1) GM1 promoted expression of TrkA and TrkB but not TrkC in primary cultured DRG neurons; (2) target SKM cells promoted expression of TrkC but not TrkA and TrkB in neuromuscular cocultures without GM1 treatment; and (3) GM1 and target SKM cells had additional effects on expression of these three Trk receptors. The results of the present study offered new clues for a better understanding of the association of GM1 and target SKM on the expression of Trk receptors.

Glycosphingolipid composition of epithelial cells isolated along the villus axis of small intestine of a single human individual.

A 6-cm fresh proximal ileum surgical specimen from a blood group A(1)Le(a-b+) secretor individual was used for stepwise isolation of epithelial cells from villus tip to crypt bottom by gentle washing with ethylenediaminetetraacetic acid-containing buffer. Acid and non-acid sphingolipids were prepared from the epithelial cell fractions and the non-epithelial intestinal residue. Molecular information on the sphingolipid composition was obtained without further isolation of individual species by applying thin-layer chromatography using chemical and biological (monoclonal antibodies, cholera toxin, Escherichia coli) detection reagents, mass spectrometry and proton NMR spectroscopy of derivatized glycolipids. In this way, the structure of major and minor saccharides, ceramide components and their relative amounts were obtained. Epithelial cells and non-epithelial residue were distinctly different in their sphingolipid composition. Sphingomyelin was the major single component in both compartments. Characteristic for epithelial cells was the dominance of monoglycosylceramides, sulphatides and blood group fucolipids (mainly Le(b) hexaglycosylceramides and ALe(b) heptaglycosylceramides). The non-epithelial residue had about five times less glycolipids mainly mono-, di-, tri- and tetra-glycosylceramides and gangliosides, including the GM1 ganglioside. The ceramides were more hydroxylated (1-2 additional hydroxyls) in epithelial cell glycolipids compared with the non-epithelial residue. Combined with a separate detailed study on the glycoproteins of the same epithelial cell preparation, this human intestinal sample is the only epithelial cell preparation where both protein- and lipid-linked saccharides are characterized in detail.

Evidence for the presence of functional lipid rafts in immune cells of ectothermic organisms.

The role of lipid rafts in non-mammalian leukocytes has been scarcely investigated. We performed biochemical and functional analysis of lipid rafts in fish leukocytes. Fish Flotillin-1 and a fish GM1-like molecule (fGM1-L) were found in low density detergent-resistant membranes (LD-DRM) in goldfish macrophages and catfish B lymphocytes, similarly to mammals. The presence of flotillin-1 and fGM1-L in LD-DRM was sensitive to increased detergent concentrations, and cholesterol extraction. Confocal microscopy analysis of flotillin-1 and fGM1-L in fish leukocytes showed a distinctive punctuated staining pattern, suggestive of pre-existing rafts. Confocal microscopy analysis of macrophages showed that the membrane of phagosomes containing serum-opsonized zymosan was enriched in fGM1-L, and zymosan phagocytosis was reduced after cholesterol extraction. The presence of flotillin-1 and fGM1-L in LD-DRM, the microscopic evidence of flotillin-1 and fGM1-L on fish macrophages and B-cells, and the sensitivity of phagocytosis to cholesterol extraction, indicate that lipid rafts are biochemically and functionally similar in leukocytes from fish and mammals.

Distribution of mono-, di- and trisialo gangliosides in the brain of Actinopterygian fishes.

BACKGROUND: Mono-, di- and trisialo gangliosides are major glycosphingolipids in the brain of higher vertebrates involved in lipid raft assembly. In contrast, the fish brain is abundant in polisialo-gangliosides, whose function is implicated in the modulation of repulsive and attractive intercellular interactions during embryonic development and a temperature adaptation process. The histological distribution of gangliosides is usually studied in rodent and mammalian brains, but to date it has not been described in the case of fish brain. METHODS: Gangliosides were extracted from adult brains of trout, carp and zebrafish and separated by TLC. High-affinity anti-ganglioside (GM1, GD1a, GD1b, GT1b) IgG antibodies were used for immunohistochemistry. RESULTS: In trout and carp brains GM1 and GT1b are expressed in the same neuronal cell bodies from the telencephalon to the spinal cord. In zebrafish brain GM1 was not detected, whereas GT1b is a general neuropil staining. GD1a is specific for unmyelinated parallel fibers in carp and zebrafish brains as well as parallel fibers in the molecular layer of all cerebellar divisions. In trout brain GD1b is found in parallel fibers of the cerebellum, but not in the tectum mesencephali. GD1b is expressed in zebrafish neuronal cell bodies. CONCLUSIONS: Each studied species has a different expression of complex gangliosides. GT1b is widely present, whereas GD1a and GD1b appear in a specific group of unmyelinated fibers and could be used as their specific marker. GENERAL SIGNIFICANCE: This is the first report on mono-, di- and trisialo ganglioside (GM1, GD1a, GD1b and GT1b) distribution in the brain of adult Actinopterygian fishes. This article is part of a Special Issue entitled Glycoproteomics.

The immunohistochemical localization of the glycosphingolipid asialo-GM1 in the intestine of weaned piglets.

The duodenum, jejunum, ileum, cecum and colon of three male hybrid piglets, 4 weeks old just after weaning, were investigated for the immunohistochemical localization of the asialoganglioside, GM1 (asialo-GM1). The study revealed various degrees of labelling for this acid glycosphingolipid in neural, epithelial and blood elements in all the gut segments. The immunolabelled neural structures, represented by ganglionic perikarya and nerve fibers, were distributed throughout the intestinal wall and showed quantitative variations in the various regions. In contrast the numerical evaluation of labelled epithelial cells was encountered only in the terminal jejunum and along the entire ileum, cecum and large intestine. In addition, a heterogeneous population of immunolabelled leukocytes was spread randomly in the lamina propria and submucosa of the entire intestine and did not show any apparent quantitative fluctuations between the different parts. The observations regarding the typical distribution patterns of the asialoganglioside GM1 in ganglionic perikarya and epithelial cells of weaned piglets are discussed in relation to their possible functional significance in the intestine and other mammalian organs.