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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Peripheral nerve glycolipids, with which anti-myelin-associated glycoprotein (MAG) antibodies from patients with demyelinating neuropathy and plasma cell dyscrasia cross-react, proved to be novel glycosphingolipids containing a sulfated glucuronyl residue. Consequently, there has been much interest in the immunological role that these sulfated glucuronyl-glycosphingolipids (SGGLs) may play in the pathogenesis of this disorder. For the determination of the distribution of these glycolipids in various nervous tissues and, thereby, the elucidation of their pathoge-nicity, a quantitative immunostaining-TLC method for their detection has been devised. Using this method, we demonstrated that these glycolipids were distributed in greatly different amounts in the peripheral nerves from human, bovine, chicken, rat, and rabbit. Subcellular localization studies of bovine peripheral nerve also demonstrated that they were enriched in the axolemma-enriched fraction and present in glial-related membranes in lower concentrations. In addition, these glycolipids were present in bovine dura mater and transformed rat Schwann cells. These biochemical results suggest that not only myelin but also axons could be involved as targets of the anti-MAG antibody in macroglobulinemia neuropathy, and it may also be necessary to examine anti-SGGL activity in patients with axonal neuropathy associated with plasma cell dyscrasia.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cultured Schwann cells stimulated with an axolemma- or myelin-enriched fraction incorporated 2.5 to three times as much [3H]thymidine when 10 mM lithium was added to the extracellular medium. The ability of lithium to enhance the mitogenic activity of either fraction was dose dependent. This result was not due to an increase in osmolarity, because addition of 10 mM NaCl had no effect on the amount of labeled thymidine accumulated by Schwann cells treated with either membrane fraction. In an earlier study, the effect of either membrane fraction could be potentiated with active phorbol esters. Lithium significantly enhanced the incorporation of [3H]thymidine into Schwann cells treated with a myelin-enriched fraction and phorbol esters. In contrast, lithium slightly increased the amount of labeled thymidine incorporated into Schwann cells stimulated with an axolemma-enriched fraction and phorbol esters. The mitogenic activity of either membrane fraction was impaired when the calcium channel blockers Mn2+ and nifedipine were added. Addition of lithium stimulated an increase in the amount of [3H]thymidine accumulated by Schwann cells treated with either the axolemma- or myelin-enriched fraction in the presence of either Mn2+ or nifedipine.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A method has been devised for the fractiona-tion of whole peripheral nerve. The procedure utilizes differential centrifugation and separation on a linear sucrose gradient (10–40%, wt/wt). A membrane fraction localized between 26% and 29% sucrose was not only enriched for the plasma membrane markers, 5′-nucleotidase and acetylcholinesterase (AChE), but also possessed the highest binding of [3H]saxitoxin, a specific marker for sodium channels. Neurons in the lumbar dorsal roots and ventral horns of rats were injected with [3H]fucose to label glycoproteins associated with the axolemma from sciatic nerve. Fractionation of the labeled nerves demonstrated a coincidence in the distribution of [3H]fucose-labeled material and AChE activity in the sucrose density gradient. The increase in the specific activity of marker enzymes for plasma membrane, sodium channels, and labeled membrane, previously demonstrated to be of axolemmal origin, identified the 26–29% region of the sucrose gradient as enriched for axolemma derived from peripheral nerve.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 34 (1980), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Leptinotarsin is a neurotoxic protein found in the hemolymph of potato beetles of the genus Leptinotarsa. In order to study the action of leptinotarsin from two species, L. haldemani and L. decemlineata, synaptosomes were prelabeled with [3H]choline in order to synthesize [3H] acetylcholine (ACh). These synaptosomes were then immobilized on Millipore filters and used for assay. Toxins from both species induce the release of radioactivity in this system. Fractionation of the released radioactivity indicated that ACh was released in preference to choline. The toxin that caused release was heat-labile and was partially dependent on Ca2+ in the perfusing medium. Release followed apparent first order kinetics when stimulation was effected with leptinotarsin from L. haldemani (leptinotarsin-h), but was more complex when using leptinotarsin from L. decemlineata (leptinotarsin-d). Increasing the concentration of toxin increased the rate of release, but the shapes of the dose-release curves elicited by the leptinotarsins from the two species were different. While leptinotarsin-h exhibited a simple, saturating dose-release curve, leptinotarsin-d was characterized by a sigmoid function, which was well described, with a Hill coefficient of 1.8. Antibodies directed toward black widow spider venom glands had no effect upon the releasing activity of leptinotarsin-h but could partially neutralize that of leptinotarsin-d. Toxins from both species have been partially purified and do not appear to be identical. The purified toxins should be useful tools with which to study the release of acetylcholine.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 679 (1993), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 6
    ISSN: 1423-0127
    Keywords: Sulfated glucuronyl glycolipids ; Motor and sensory nerve ; Myelin ; Axolemma ; HNK-1 ; Polyneuropathy ; IgM paraprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Sulfated glucuronyl glycolipids (SGGL) have been implicated as important target antigens in patients with demyelinating polyneuropathy and IgM paraproteinemia. Sulfated glucuronyl paragloboside (SGPG), a major species of SGGL, was identified in the subcellular fractions of human peripheral motor and sensory nerves using a simple and quantitative method. SGPG was found to be concentrated in the myelin-enriched fractions of both motor and sensory nerves (1.3±0.3 and 1.5±0.4 µg/mg protein, respectively), whereas its concentration was 0.9±0.2 and 1.8±0.6 µg/mg protein in the axolemma-enriched fractions of motor and sensory nerves, respectively. Our finding that SGPG is more abundant in the human sensory nerve axolemma-enriched fraction may account for the clinical and pathological observations that the lesions are more heavily concentrated in the sensory nerve than in other parts of the nerve tissues in this disorder.
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  • 7
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Axolemma-enriched and myelin-enriched fractions were prepared from bovine CNS white matter and conjugated to fluorescein isothiocyanate (FITC). Both unlabelled and FITC-labelled axolemma and myelin were mitogenic for cultured rat Schwann cells. Treatment of Schwann cells with the FITC-labelled mitogens for up to 24 h resulted in two distinct morphological appearances. FITC-myelin-treated cells were filled with numerous round, fluorescent-labelled intracellular vesicles, while FITC-axolemma-treated cells appeared to be coated with a patchy, ill-defined fluorescence, primarily concentrated around the cell body but extending onto the cell processes. These observations were corroborated under phase microscopy. Electron microscopy revealed multiple, membrane-bound, membrane-containing phagosomes within myelin-treated cells and to a far lesser extent in axolemma-treated cells. The effect on the expression of the myelin-mediated and axolemma-mediated mitogenic signal when Schwann cells were treated with the lysosomal inhibitors, ammonium chloride and chloroquine, was evaluated. The mitogenicity of myelin was reduced 70–80% by these agents whereas the mitogenicity of axolemma was not significantly altered under these conditions. These results suggest that axolemma and myelin stimulate the proliferation of cultured Schwann cells by different mechanisms. Myelin requires endocytosis and lysosomal processing for expression of its mitogenic signal; in contrast, the mitogenicity of axolemma may be transduced at the Schwann cell surface.
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  • 8
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cultured Schwann cells were found to phagocytose exogenously applied myelin membranes within 1 h. However, the resulting proliferative response required an additional 9 h of incubation. Treatment with ammonium chloride, a lysosomal inhibitor, delayed the appearance of the proliferative response to the myelin membranes by 12 h. Processing of myelin within the Schwann cells was followed by the appearance of immunocytochemically detectable myelin basic protein which was first visible at 4 h. Similar to the proliferative response, the appearance of immunoreactive material was delayed by the addition of ammonium chloride. Schwann cells were observed initially to ingest myelin fragments at their distal-most tips after which time the myelin phagosomes collected in the perinuclear region and fused with lysosomes. Phagocytic Schwann cells had a notable increase in Golgi membranes and microfilaments and contained widely dilated, rough endoplasmic reticulum cisternae. In purified cell cultures, Schwann cells phagocytosed myelin slower than macrophages, but displayed phagocytic abilities much greater than fibroblasts. The ability of cultured Schwann cells to phagocytose myelin rapidly suggests that these cells may aid in the breakdown and removal of myelin during Wallerian degeneration. These data further confirm the mitogenic effect of myelin and its possible role during nerve regeneration.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 15 (1990), S. 279-282 
    ISSN: 1573-6903
    Keywords: Glucocerebroside ; galactocerebroside ; [3H]galactose ; Schwann cells ; peripheral nerve ; nerve explants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Schwann cell biosynthesis of glycolipids was studied by in vitro incorporation of [3H]galactose into neonatal rat sciatic nerves before and after endoneurial explant culture and in culture of purified Schwann cells. In neonatal nerves prior to culture, [3H]galactose was actively incorporated into galactocerebrosides (GalCe), monogalactosyl diacylglycerol (MGDG), and the sulfatides (Su). In contrast, the incorporation of [3H]galactose into MGDG, GalCe, and Su was nearly undetected in endoneurial explants after 4 days in vitro (div). Instead, there was increased3H-labeling of glucocerebrosides (GlcCe) and its homologues, with tetrahexosylceramides (GL-4) being a major product, which continued through 8 div. This shift in glycolipid biosynthesis was further demonstrated in the purified Schwann cell cultures. These observations, together with our early findings in the permanent transection paradigm support a direct role of axons in specifying Schwann cell biosynthesis of the GalCe, MGDG, and Su and that the absence of this Schwann cell-axon interaction results in the phenotypic expression of glucocerebroside homologues by the Schwann cell.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 19 (1994), S. 1277-1281 
    ISSN: 1573-6903
    Keywords: Schwann cells ; myelin ; glycolipids ; basement membrane ; Axons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Schwann cells that are deprived of axonal contact switch their glycolipid metabolic pathway from primarily galactocerebroside (GalCe) synthesis to the formation of glucocerebroside (GlcCe) and its homologs. The removal of axonal influence has a dual effect on Schwann cell phenotype; they lose the ability to assemble both myelin and basement membrane. To determine whether a loss of basement membrane directly affects glycolipid expression, we have examined lipid biosynthesis in Schwann cells which were allowed to interact with axons of dorsal root ganglion neurons but which were deprived of the ability to assemble basal lamina. These Schwann cells resemble those from myelinating nerve in that they synthesize a large amount of galactohydroxycerebroside. This suggests that axon contact, even in the absence of basement membrane, is sufficient to induce the GalCe metabolic pathway.
    Type of Medium: Electronic Resource
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