Multiple phenotypic changes in mice after knockout of the B3gnt5 gene, encoding Lc3 synthase--a key enzyme in lacto-neolacto ganglioside synthesis.

BACKGROUND: Ganglioside biosynthesis occurs through a multi-enzymatic pathway which at the lactosylceramide step is branched into several biosynthetic series. Lc3 synthase utilizes a variety of galactose-terminated glycolipids as acceptors by establishing a glycosidic bond in the beta-1,3-linkage to GlcNaAc to extend the lacto- and neolacto-series gangliosides. In order to examine the lacto-series ganglioside functions in mice, we used gene knockout technology to generate Lc3 synthase gene B3gnt5-deficient mice by two different strategies and compared the phenotypes of the two null mouse groups with each other and with their wild-type counterparts. RESULTS: B3gnt5 gene knockout mutant mice appeared normal in the embryonic stage and, if they survived delivery, remained normal during early life. However, about 9% developed early-stage growth retardation, 11% died postnatally in less than 2 months, and adults tended to die in 5-15 months, demonstrating splenomegaly and notably enlarged lymph nodes. Without lacto-neolacto series gangliosides, both homozygous and heterozygous mice gradually displayed fur loss or obesity, and breeding mice demonstrated reproductive defects. Furthermore, B3gnt5 gene knockout disrupted the functional integrity of B cells, as manifested by a decrease in B-cell numbers in the spleen, germinal center disappearance, and less efficiency to proliferate in hybridoma fusion. CONCLUSIONS: These novel results demonstrate unequivocally that lacto-neolacto series gangliosides are essential to multiple physiological functions, especially the control of reproductive output, and spleen B-cell abnormality. We also report the generation of anti-IgG response against the lacto-series gangliosides 3'-isoLM1 and 3',6'-isoLD1.

GMab-1, a high-affinity anti-3'-isoLM1/3',6'-isoLD1 IgG monoclonal antibody, raised in lacto-series ganglioside-defective knockout mice.

The lacto-series gangliosides 3'-isoLM1 and 3',6'-isoLD1 have been identified as tumor-associated antigens whose formation is initiated by the Lc3-synthase. Until now, high-affinity IgG monoclonal antibodies (mAbs) against 3'-isoLM1 and 3',6'-isoLD1, which are highly expressed in gliomas, have not been developed, although mAbs against lacto-series gangliosides are powerful tools for functional studies. We previously produced the Lc3-synthase gene beta3Gn-T5 knockout mice. In this study, we immunized beta3Gn-T5 knockout mice with 3'-isoLM1/3',6'-isoLD1 and produced the anti-3'-isoLM1/3',6'-isoLD1 mAb GMab-1, of the IgG(3) subclass, which should be useful for functional analysis of lacto-series gangliosides and for antibody-based therapy of gliomas.

Cerebrospinal fluid markers before and after shunting in patients with secondary and idiopathic normal pressure hydrocephalus.

BACKGROUND: The aim of this study was to explore biochemical changes in the cerebrospinal fluid (CSF) induced by shunt surgery and the relationship between these changes and clinical improvement. METHODS: We measured clinical symptoms and analysed lumbar CSF for protein content, neurodegeneration and neurotransmission markers in patients with secondary (SNPH, n = 17) and idiopathic NPH (INPH, n = 18) before and 3 months after shunt surgery. Patients were divided into groups according to whether or not there was improvement in clinical symptoms after surgery. RESULTS: Preoperatively, the only pathological findings were elevated neurofilament protein (NFL), significantly more so in the SNPH patients than in the INPH patients, and elevated albumin content. Higher levels of NFL correlated with worse gait, balance, wakefulness and neuropsychological performance. Preoperatively, no differences were seen in any of the CSF biomarkers between patients that improved after surgery and those that did not improve. Postoperatively, a greater improvement in gait and balance performance correlated with a more pronounced reduction in NFL. Levels of albumin, albumin ratio, neuropeptide Y, vasoactive intestinal peptide and ganglioside GD3 increased significantly after shunting in both groups. In addition, Gamma amino butyric acid increased significantly in SNPH and tau in INPH. CONCLUSION: We conclude that a number of biochemical changes occur after shunt surgery, but there are no marked differences between the SNPH and INPH patients. The results indicate that NFL may be a marker that can predict a surgically reversible state in NPH.

Sulfatide increases adiponectin and decreases TNF-alpha, IL-6, and IL-8 in human adipose tissue in vitro.

Type 2 diabetes is associated with decreased levels of the glycosphingolipid sulfatide, as well as a state of low-grade inflammation. Sulfatide is reported to have anti-inflammatory properties in other cell-types. In the present study, the effects of sulfatide on adipokine (adiponectin, TNF-alpha, IL-6, and IL-8) production in human adipose tissue (AT) was investigated in vitro. Isolated human adipocytes and AT cultures were incubated with sulfatide isolated from pig brain [sulfatide containing a variety of fatty acids or isoforms of sulfatide with defined, saturated fatty acids with 16 (C16:0) or 24 (C24:0) carbon atoms]. Adiponectin production was increased 50-80%, by all sulfatide preparations. Only the C16:0 isoform decreased TNF-alpha, IL-6, and IL-8 production 20-30%. The C16:0 sulfatide has been shown to activate potassium channels in beta-cells, and glibenclamide, an ATP-sensitive K+-(KATP) channel blocker, reversed the C16:0-induced decrement in stimulated TNF-alpha, IL-6, and IL-8 release in adipocytes. Glibenclamide on its own was without effect on the production of adiponectin, TNF-alpha, IL-6, and IL-8. In conclusion, this study shows that, sulfatide exerts anti-inflammatory effects in human adipocytes and AT in vitro. Accordingly, the reported low serum levels of sulfatide in patients with type 2 diabetes might be of importance in relation to the chronic low-grade inflammatory state found in this disease.

Uptake of the glycosphingolipid sulfatide in the gastrointestinal tract and pancreas in vivo and in isolated islets of Langerhans.

BACKGROUND: The glycosphingolipid sulfatide has previously been found in several mammalian tissues, but information on the uptake of exogenously administered sulfatide in different organs in vivo is limited. In pancreatic beta cells, sulfatide has been shown to be involved in insulin processing and secretion in vitro. In this study, we examined the uptake of exogenously administered sulfatide and its distribution to the pancreatic beta cells. This might encourage future studies of the function(s) of sulfatide in beta cell physiology in vivo. Radioactive sulfatide was given orally to mice whereafter the uptake of sulfatide in the gastrointestinal tract and subsequent delivery to the pancreas was examined. Sulfatide uptake in pancreas was also studied in vivo by i.p. administration of radioactive sulfatide in mice, and in vitro in isolated rat islets. Isolated tissue/islets were analysed by scintillation counting, autoradiography and thin-layer chromatography-ELISA. RESULTS: Sulfatide was taken up in the gastrointestinal tract for degradation or further transport to other organs. A selective uptake of short chain and/or hydroxylated sulfatide fatty acid isoforms was observed in the small intestine. Exogenously administered sulfatide was found in pancreas after i.p, but not after oral administration. The in vitro studies in isolated rat islets support that sulfatide, independently of its fatty acid length, is endocytosed and metabolised by pancreatic islets. CONCLUSION: Our study supports a selective uptake and/or preservation of sulfatide in the gastrointestinal tract after oral administration and with emphasises on pancreatic sulfatide uptake, i.p. administration results in sulfatide at relevant location.

C16:0 sulfatide inhibits insulin secretion in rat beta-cells by reducing the sensitivity of KATP channels to ATP inhibition.

Sulfatide (3'-sulfo-beta-galactosyl ceramide) is a glycosphingolipid present in mammalians in various fatty acid isoforms of which the saturated 16 carbon-atom length (C16:0) is more abundant in pancreatic islets than in neural tissue, where long-chain sulfatide isoforms dominate. We previously reported that sulfatide isolated from pig brain inhibits glucose-induced insulin secretion by activation of ATP-sensitive K+ channels (K(ATP) channels). Here, we show that C16:0 sulfatide is the active isoform. It inhibits glucose-stimulated insulin secretion by reducing the sensitivity of the K(ATP) channels to ATP. (The half-maximal inhibitory concentration is 10.3 and 36.7 micromol/l in the absence and presence of C16:0 sulfatide, respectively.) C16:0 sulfatide increased whole-cell K(ATP) currents at intermediate glucose levels and reduced the ability of glucose to induce membrane depolarization, reduced electrical activity, and increased the cytoplasmic free Ca2+ concentration. Recordings of cell capacitance revealed that C16:0 sulfatide increased Ca2+-induced exocytosis by 215%. This correlated with a stimulation of insulin secretion by C16:0 sulfatide in intact rat islets exposed to diazoxide and high K+. C24:0 sulfatide or the sulfatide precursor, beta-galactosyl ceramide, did not affect any of the measured parameters. C16:0 sulfatide did not modulate glucagon secretion from intact rat islets. In betaTC3 cells, sulfatide was expressed (mean [+/-SD] 0.30 +/- 0.04 pmol/microg protein), and C16:0 sulfatide was found to be the dominant isoform. No expression of sulfatide was detected in alphaTC1-9 cells. We conclude that a major mechanism by which the predominant sulfatide isoform in beta-cells, C16:0 sulfatide, inhibits glucose-induced insulin secretion is by reducing the K(ATP) channel sensitivity to the ATP block.

Clusterin in cerebrospinal fluid: analysis of carbohydrates and quantification of native and glycosylated forms.

Clusterin is suggested to be involved in the pathogenesis of Alzheimer's disease. Clusterin expression is increased in brain tissue in affected regions of Alzheimer patients, and intense clusterin staining is found in both senile plaques and in neuronal and glia cells. In contrast, the cerebrospinal fluid level of clusterin in Alzheimer patients has, thus far, been found unchanged. Clusterin is a glycosylated protein, and an alteration of its glycosylation in Alzheimer's disease might influence accurate quantification in cerebrospinal fluid through interference of antibody binding to the protein. Using enzymatic deglycosylation of clusterin isolated from cerebrospinal fluid, we found that the carbohydrates attached to clusterin were of the N-linked type and sialic acids. Based on this finding, cerebrospinal fluid samples from Alzheimer patients (n=99) and controls (n=39) were analysed. The samples were treated with peptide: N-glycanase F, cleaving off N-linked carbohydrates, and clusterin was quantified before and after deglycosylation using a new sandwich enzyme-linked immunosorbent assay. Clusterin was significantly increased in Alzheimer patients, in both native (7.17+/-2.43 AU versus 5.73+/-2.09 AU; p=0.002), and deglycosylated samples (12.19+/-5.00 AU versus 9.68+/-4.38 AU; p=0.004). Deglycosylation led to increased measured levels of clusterin by 70% (p<0.001) in Alzheimer patients and 67% (p<0.001) in controls. These findings indicate that glycosylation of proteins may interfere with their quantification. The results show that clusterin is significantly increased in cerebrospinal fluid from Alzheimer patients as a group, supporting that clusterin might be involved in the pathogenesis of Alzheimer's disease. However, the individual clusterin levels overlap between the two groups, and thus cerebrospinal fluid clusterin measurement is not suitable as a biochemical marker in the diagnosis of Alzheimer's disease.

Temporarily controlled HIV-1 replication after intravenous immunoglobulin treatment of Guillain-Barré syndrome.

HIV establishes a latent infection in resting CD4(+) T-lymphocytes. A possible strategy to eliminate cellular reservoirs in long-lived, HIV-1-infected quiescent CD4(+) T-lymphocytes might be to add T-cell-activating agents to potent antiretroviral therapy. In this report we describe a patient with Guillain-Barré syndrome treated with high dose intravenous immunoglobulin (IVIG) in addition to antiretroviral therapy. A transiently increased viral load and immunoactivation during the IVIG treatment suggest activation of latently infected cells and increased turnover rate of the latent viral reservoir. HIV replication was controlled with plasma viral load <20 copies/ml, for at least 3 months after antiretroviral treatment interruption. CSF neural markers reflecting degenerative processes in the brain during the symptomatic period and follow-up were also analysed. Very high CSF sulfatide concentrations were found indicating that the pathology involves severe demyelination.We hypothesize that IVIG in this case contributed to an activation of latently infected cells, which led to a transient increase in plasma HIV-1 RNA during the IVIG treatment and a long period of undetectable viral load after antiretroviral treatment interruption. Further, this is the first time, to our knowledge, that detailed CSF findings are described in HIV-1 associated GBS.

Structural characterization of the GM1 ganglioside by infrared multiphoton dissociation, electron capture dissociation, and electron detachment dissociation electrospray ionization FT-ICR MS/MS.

Gangliosides play important biological roles and structural characterization of both the carbohydrate and the lipid moieties is important. The FT-ICR MS/MS techniques of electron capture dissociation (ECD), electron detachment dissociation (EDD), and infrared multiphoton dissociation (IRMPD) provide extensive fragmentation of the protonated and deprotonated GM1 ganglioside. ECD provides extensive structural information, including identification of both halves of the ceramide and cleavage of the acetyl moiety of the N-acetylated sugars. IRMPD provides similar glycan fragmentation but no cleavage of the acetyl moiety. Cleavage between the fatty acid and the long-chain base of the ceramide moiety is seen in negative-ion IRMPD but not in positive-ion IRMPD of GM1. Furthermore, this extent of fragmentation requires a range of laser powers, whereas all information is available from a single ECD experiment. However, stepwise fragmentation by IRMPD may be used to map the relative labilities for a series of cleavages. EDD provides the alternative of electron-induced fragmentation for negative ions with extensive fragmentation, but suffers from low efficiency as well as complication of data analysis by frequent loss of hydrogen atoms. We also show that analysis of MS/MS data for glycolipids is greatly simplified by classification of product ion masses to specific regions of the ganglioside based solely on mass defect graphical analysis.

Structural membrane alterations in Alzheimer brains found to be associated with regional disease development; increased density of gangliosides GM1 and GM2 and loss of cholesterol in detergent-resistant membrane domains.

The formation of neurotoxic beta-amyloid fibrils in Alzheimer's disease (AD) is suggested to involve membrane rafts and to be promoted, in vitro, by enriched concentrations of gangliosides, particularly GM1, and the cholesterol therein. In our study, the presence of rafts and their content of the major membrane lipids and gangliosides in the temporal cortex, reflecting late stages of AD pathology, and the frontal cortex, presenting earlier stages, has been investigated. Whole tissue and isolated detergent-resistant membrane fractions (DRMs) were analysed from 10 AD and 10 age-matched control autopsy brains. DRMs from the frontal cortex of AD brains contained a significantly higher concentration (micromol/micromol glycerophospholipids), of ganglioside GM1 (22.3 +/- 4.6 compared to 10.3 +/- 6.4, p <0.001) and GM2 (2.5 +/- 1.0 compared to 0.55 +/- 0.3, p <0.001). Similar increases of these gangliosides were also seen in DRMs from the temporal cortex of AD brains, which, in addition, comprised significantly lower proportions of DRMs. Moreover, these remaining rafts were depleted in cholesterol (from 1.5 +/- 0.2 to 0.6 +/- 0.3 micromol/micromol glycerophospholipids, p <0.001). In summary, we found an increased proportion of GM1 and GM2 in DRMs, and accelerating plaque formation at an early stage, which may gradually lead to membrane raft disruptions and thereby affect cellular functions associated with the presence of such membrane domains.

In vivo administration of the C16:0 fatty acid isoform of sulfatide increases pancreatic sulfatide and enhances glucose-stimulated insulin secretion in Zucker fatty (fa/fa) rats.

BACKGROUND: Sulfatide is present in the secretory granules of beta cells and has been shown, in vitro, to be involved in insulin processing and secretion. Of particular interest is one of the major sulfatide isoforms in the beta cells, the C16:0 fatty acid isoform, which has been shown to be involved in insulin crystal preservation in vitro. The aim of this study was to investigate the ability of C16:0 fatty acid isoform of sulfatide to affect insulin secretion and/or action and glycaemic control in the adipogenic 'prediabetic' Zucker rat. METHODS: The C16:0 sulfatide was administered to Zucker rats for 10 weeks, and fasting levels of plasma insulin and glucose were measured as well as levels after an intravenous (i.v.) glucose load. In addition, the sulfatide expression, examined by thin-layer chromatography-enzyme-linked immunosorbent assay and mass spectrometry, in the pancreas of C16:0 sulfatide-treated Zucker rats was compared to controls. RESULTS: The in vivo treatment of Zucker rats with C16:0 sulfatide resulted in significantly elevated glucose-stimulated insulin secretion (60-80% increase, p < 0.05), without significant changes in glucose tolerance. The treatment was associated with an ameliorated first-phase insulin response (3-4-fold, p = 0.009, 0.016) and a 60% increase of pancreatic sulfatide content (p = 0.001), possible by an uptake of C16:0 sulfatide. The fasting hyperinsulinaemia and blood glucose levels were unchanged. CONCLUSIONS: The treatment with C16:0 sulfatide elevates glucose-stimulated insulin secretion and enhances sulfatide content in the pancreas of Zucker rats.

Accumulation of sulfatide in neuronal and glial cells of arylsulfatase A deficient mice.

Arylsulfatase A (ASA) degrades sulfatide, seminolipid and lactosylceramide sulfate, glycolipids recognized by the Sulph I antibody although sulfatide is considered the main antigen. Sulfatide is myelin associated but studies have shown a minor distribution also in non-myelin forming cells. The aim of this work was to further study sulfatide in neurons and astrocytes by immunohistochemistry, facilitated by investigation of tissue from adult ASA deficient (ASA -/-) mice. Cells with a low presence of sulfatide might be detected due to lack of ASA activity and accumulation of Sulph I antigens. Sulfatide positive astrocytes and neurons were more numerous and intensely stained in ASA -/- mice, demonstrating a sulfatide accumulation compared to controls. Sulph I staining was especially increased in the molecular layer of cerebellum, in which Purkinje cell dendrites displayed an altered morphology, and in layer IV-VI of cerebral cortex. In hippocampus, immunostaining was found in neuronal cytoplasm in ASA -/- but in nuclear membranes of control mice. We observed a gray matter astrogliosis, which appeared to be associated to sulfatide accumulation. In addition, the developmental change (<20 months) of Sulph I antigens, galactosylceramide, phospholipids and cholesterol were followed by lipid analyses which verified sulfatide and seminolipid accumulation in adult ASA -/- mice, although no lactosylceramide sulfate could be detected. In addition to demonstrating sulfatide in neurons and astrocytes, this study supports the value of ASA -/- mice as a model for metachromatic leukodystrophy and suggests that accumulation of sulfatide beyond myelin might contribute to the pathology of this disease.

S100 in mild traumatic brain injury.

PRIMARY OBJECTIVES: To examine the diagnostic value of S100 in mild traumatic brain injury (MTBI). RESEARCH DESIGN: Prospective cohort study. METHODS AND PROCEDURES: S100B, S100A1B and S100BB concentrations were examined in sera from patients with MTBI with an arrival Glasgow Coma Scale score of 15 or 14, patients with orthopaedic injuries and non-injured subjects. MAIN OUTCOME AND RESULTS: Mean values and proportions of subjects above cut-off limits for S100B and S100A1B were significantly higher in each trauma group than in non-injured controls, but only for S100A1B when patients with MTBI were compared with controls with orthopaedic injuries. Using a 97.5 percentile cut-off limit, the sensitivity of S100A1B for MTBI vs orthopaedic injury was 61% (95% confidence interval (CI) 49-73%), specificity 77% (95% CI 62-93%). The area under the ROC curve did not approach 0.9 for any cut off limit. CONCLUSIONS: Diagnostic validity of S100 in acute MTBI was not demonstrated. S100A1B has merits for long-term prognostic studies.

Lipids and glycosphingolipids in caveolae and surrounding plasma membrane of primary rat adipocytes.

We have made a comprehensive and quantitative analysis of the lipid composition of caveolae from primary rat fat cells and compared the composition of plasma membrane inside and outside caveolae. We isolated caveolae from purified plasma membranes using ultrasonication in carbonate buffer to disrupt the membrane, or extraction with nonionic detergent, followed by density gradient ultracentrifugation. The carbonate-isolated caveolae fraction was further immunopurified using caveolin antibodies. Carbonate-isolated caveolae were enriched in cholesterol and sphingomyelin, and the concentration was three- and twofold higher, respectively, in caveolae compared to the surrounding plasma membrane. The concentration of glycerophospholipids was similar suggesting that glycerophospholipids constitute a constant core throughout the plasma membrane. The composition of detergent-insoluble fractions of the plasma membrane was very variable between preparations, but strongly enriched in sphingomyelin and depleted of glycerophospholipids compared to carbonate-isolated caveolae; indicating that detergent extraction is not a suitable technique for caveolae preparation. An average adipocyte caveola contained about 22 x 10(3) molecules of cholesterol, 7.5 x 10(3) of sphingomyelin and 23 x 10(3) of glycerophospholipid. The glycosphingolipid GD3 was highly enriched in caveolae, whereas GM3, GM1 and GD1a were present inside as well as outside the caveolae membrane. GD1b, GT1b, GM2, GQ1b, sulfatide and lactosylceramide sulfate were not detected in caveolae.

Selective lack of the C16:0 fatty acid isoform of sulfatide in pancreas of type II diabetic animal models.

Sulfatide (3'-sulfogalactosyl-ceramide) is a glycosphingolipid mainly located in the nervous system, but has also been found in the islets of Langerhans. Previous studies have suggested that sulfatide is involved in insulin processing and secretion. In this study, sulfatide expression and metabolism in pancreas and isolated islets of the type II diabetes models, ob/ob- and db/db mouse, was investigated using TLC-ELISA, metabolic labelling and electron microscopy. As in non-diabetic Lewis rat and human pancreas, sulfatide was located in secretory granules of the beta cells. However, the type II diabetic animal models and their background strains had an altered sulfatide expression, involving the lack of the C16:0 sulfatide fatty acid isoform, compared to non-diabetic Lewis rat, BALB/c mouse and human pancreatic tissue, in which the two dominating pancreatic sulfatide isoforms C16:0 and C24:0 are expressed. Correspondingly, in isolated ob/ob islets, sulfatide synthesis excluded the production of C16:0 sulfatide. Insulin administration to ob/ob mouse, which lowers beta cell activity, resulted in significantly increased sulfatide expression in pancreas (p=0.0003), but still no expression of the C16:0 sulfatide isoform. In vitro, the C16:0 sulfatide was shown to be the isomer involved in the preservation of insulin crystals. Thus, it is hypothesized that the selection of sulfatide isomers in pancreas might be a genetic factor contributing to disease development in type II diabetic animal models.

Gangliosides as therapeutic targets for cancer.

Gangliosides, sialic acid-containing glycosphingolipids, have engendered great interest for more than 20 years in the search for target molecules of relevance for tumour growth and formation of metastases and as potential targets for immunotherapy. These molecules show large quantitative and structural variability, which is related to cell type and developmental stage. Their potential role in the formation of tumour metastases was suggested from data supporting that they are involved in cell growth regulation and in cell-cell and cell-matrix adhesion. Moreover, gangliosides are expressed on the cell surface and thereby are accessible for antibodies or other ganglioside-binding molecules to induce cell death, inhibit cell growth and/or inhibit formation of tumour metastasis. All tumours exhibit aberrant ganglioside expression. This includes overexpression of normal ganglioside constituents, which appears to be common among various tumours, and expression of gangliosides not found in normal adult tissue but often found during fetal development. The ganglioside composition of melanoma cells has been found to correlate with their metastatic potential and also to be selectively expressed in cells of a tumour mass and invading tumour cells. Passive immunotherapy using murine or murine/human chimeric monoclonal antiganglioside antibodies in their native form or combined with various effector molecules has been investigated. However, the vaccination strategy using native or structurally modified tumour-associated gangliosides in combination with adjuvants is currently the dominant method in clinical trials. The outcomes reported so far vary between type of tumour and treatment strategies. However, we believe that targeting gangliosides is as promising as any other immune therapeutic strategy, and basic research as well as clinical trials utilising new aspects is encouraged.

Developmental expression of the type I diabetes related antigen sulfatide and sulfated lactosylceramide in mammalian pancreas.

Previous studies have shown that sulfatide is present and functionally involved in beta cells, and that anti-sulfatide antibodies (ASA) exist during development of type I diabetes mellitus. To further explore the possible role of sulfatide in type I diabetes, developmental expression was examined in human pancreas and in pancreas of the type I diabetes models BB rat and NOD mouse compared to Lewis rat and BALB/c mouse, respectively. Sulfatide was not only expressed in adult pancreas, but also in human fetal and rodent neonatal pancreas, i.e., during the growing period of the immunological self. Sulfatide had a different expression pattern in human beings and rodents, concerning both the amounts of sulfatide and expression during development. There was no change in the sulfatide fatty acid isoform expression during development. The pancreatic expression of another sulfated glycosphingolipid, sulfated lactosylceramide, indicated that this molecule is a potential fetal/neonatal marker, which was further expressed in the type I diabetic models. In conclusion, these findings give further support to the possibility that sulfatide is a relevant autoantigen in type I diabetes and that sulfated lactosylceramide might function as a potential risk factor for disease development, at least in the animal models.

Quality assurance for cerebrospinal fluid protein analysis: international consensus by an Internet-based group discussion.

A group of neurologists and clinical neurochemists representing twelve countries worked towards a consensus on laboratory techniques to improve the quality of analysis and interpretation of cerebrospinal fluid (CSF) proteins. Consensus was approached via a virtual Lotus Notes-based TeamRoom. This new approach respecting multicultural differences, common views, and minority opinions, is available in http://www.teamspace.net/ CSF, presenting the implicit, complementary version of this explicit, printed consensus. Three key recommendations were made: CSF and (appropriately diluted) serum samples should be analyzed together in one analytical run, i.e., with reference to the same calibration curve. Results are evaluated as CSF/serum quotients, taking into account the non-linear, hyperbolic relation between immunoglobulin (Ig)- and albumin-quotients rather than using the linear IgG index or IgG synthesis rate. Controls should include materials with values within the reference ranges (IgM: 0.5-1.5 mg/l; IgA: 1-3 mg/l; IgG: 10-30 mg/l and albumin: 100-300 mg/l). The physiological, methodological and clinical significance of CSF/serum quotients is reviewed. We confirmed the previous consensus on oligoclonal IgG, in particular the usefulness of the five typical interpretation patterns. The group compared current external and internal quality assurance schemes and encouraged all members to maintain national or local traditions. Values for acceptable imprecision in the CSF quality assurance are proposed.

Sulfatide controls insulin secretion by modulation of ATP-sensitive K(+)-channel activity and Ca(2+)-dependent exocytosis in rat pancreatic beta-cells.

The glycosphingolipid sulfatide is present in secretory granules and at the surface of pancreatic beta-cells, and antisulfatide antibodies (ASA; IgG1) are found in serum from the majority of patients with newly diagnosed type 1 diabetes. Here we demonstrate that sulfatide produced a glucose- and concentration-dependent inhibition of insulin release from isolated rat pancreatic islets. This inhibition of insulin secretion was due to activation of ATP-sensitive K(+)-(K(ATP)) channels in single rat beta-cells. No effect of sulfatide was observed on whole-cell Ca(2+)-channel activity or glucose-induced elevation of cytoplasmic Ca(2+) concentration. It is interesting that sulfatide stimulated Ca(2+)-dependent exocytosis determined by capacitance measurements and depolarized-induced insulin secretion from islets exposed to diazoxide and high external KCl. The monoclonal sulfatide antibody Sulph I as well as ASA-positive serum reduced glucose-induced insulin secretion by inhibition of Ca(2+)-dependent exocytosis. Our data suggest that sulfatide is important for the control of glucose-induced insulin secretion and that both an increase and a decrease in the sulfatide content have an impact on the secretory capacity of the individual beta-cells.

Expression of the myelin and oligodendrocyte progenitor marker sulfatide in neurons and astrocytes of adult rat brain.

Sulfatide is a myelin component of the central (CNS) and peripheral nervous system (PNS) and is used extensively to identify oligodendrocyte progenitor cells. We have explored sulfatide expression in CNS gray matter (cerebellum, cerebral cortex, and hippocampus) and the PNS in adult rats using an anti-sulfatide antibody (Sulph I) and confocal microscopy. Biochemical analyses revealed two Sulph I antigens, sulfatide and seminolipid; sulfatide was present at about five times higher concentration, and the affinity of Sulph I for sulfatide was 2.5 times higher than that for seminolipid. Thus sulfatide was considered the dominant antigen. We found Sulph I immunostaining, in addition to that in myelinated areas in subpopulations of astrocytes and neurons. Astrocyte Sulph I staining was localized to the cell bodies and in some cases also to the processes. In the cerebellum, some Sulph I-positive astrocytes corresponded to Golgi epithelial cell bodies. We also found Sulph I staining in neuronal cell bodies, which in some neurons was clearly localized to the cytoplasm and in others to the nuclear membrane. Sulph I immunostaining in the PNS was located in the myelin sheath and paranodal end segments. These results demonstrate the expression of sulfatide in cell types other than oligodendrocytes and Schwann cells, showing that sulfatide is not a selective marker for adult oligodendrocyte progenitor cells. Moreover, these findings show that sulfatide is localized also to intracellular compartments and indicate that other roles of sulfatide in astrocytes and neurons, compared to myelin, might be considered.