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  • 1
    ISSN: 0306-4603
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine , Psychology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 39 (1983), S. 953-963 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 28 (1972), S. 1210-1212 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Elektronenmikroskopische Untersuchungen der Neuriten in der Peripherie des dorsalen Nervenstranges im Schwanz der Aszidien-LarveAmaroucium constellatum zeigen, dass die in der Nähe liegenden Schwanzmuskelzellen Verbindungen mit den Neuriten eingehen, die den neuromuskulären Kontaktstellen im Skelettmuskel der Wirbeltiere ähnlich sind. Diese neuromuskulären Verbindungen verteilen sich über die Gesamtlänge des Schwanzes und sind offenbar die Innervation der Schwanzmuskulatur.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Ultrasructure Research 42 (1973), S. 434-450 
    ISSN: 0022-5320
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous attempts to generate myelin in the myelin-deficient rat spinal cord by transplanting mouse glia were not successful. In order to determine whether this result was due to graft rejection or to interspecies mismatch of cellular or molecular components at the axoglial junction, we have repeated the experiment in cyclosporine-treated rats. Our results show that in the immunosuppressed hosts, foetal glial xenografts form an abundance of myelin within the dorsal columns at or near the injection site about two weeks after the operation. In some cases, myelination extends virtually across the entire width of the dorsal columns. Ultrastructurally, the myelin sheaths are normal in all respects, including the presence of the ‘radial component’. The lateral edges of the myelin lamellae form typical paranodal axoglial junctions, some displaying periodic ‘transverse bands’. We infer that previous mouse to rat xenograft failures reflect host immune response rather than mismatch of heterologous junctional components. We also compared foetal, early post-natal and adult xenografts. Foetal donor cells, containing an abundance of precursors but virtually no mature oligodendrocytes, are more effective than neonatal donor cells in forming myelin, and after adult grafts, we found no myelin formation. Thus, in xenografts, as in allografts, foetal precursor cells are far more suitable than glia from mature donors in generating significant amounts of myelin.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nodal and paranodal regions of myelinated sciatic nerve fibres from diabetic (db/db) mice were examined in freeze fracture replicas. In some fibres, the axolemma was found to display abnormalities in the paranodal region. These include shallow, undifferentiated junctional indentations, thinning of the indentations with widening of the non-junctional grooves between them, particle clusters within the non-junctional grooves, and patches in which axolemmal E-face particles are distributed randomly rather than in the form of linear strings within grooves. Nodal structure, in contrast, is hardly affected. Nodal E-face and P-face particle densities indb/db axons are not significantly different from those in age-matched controls, although we found a few examples in which the E-face density fell slightly below the normal range. Occasional fibres showing evidence of paranodal or segmental demyelination were also seen. The results support paranodal pathology as a potential basis for reduced nerve conduction velocity in diabetic nerves but provide no evidence for significant changes in nodal structure or in nodal Na channel density in sciatic nerve fibres of thedb/db mouse.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary O1 hybridoma cells, which produce a monocolonal IgM antigalactocerebroside, were implanted into the spinal cords of immature and mature rats and the cords examined 5–24 days later. Study of the younger group, in which myelin was developing at the time of implantation, revealed examples of abnormal myelin sheaths in which the repeat period was markedly increased. The paranodal regions of these abnormal sheaths were superficially normal in configuration; i.e. myelin lamellae terminated one by one as ‘terminal loops’ that indented the axolemma and formed normal axoglial junctions displaying periodic ‘transverse bands’. Neighbouring terminal loops are normally joined by tight junctions that block passage of tracers from the paranodal periaxonal space into the compact myelin, as seen after implantation of a control hybridoma. In the abnormal sheaths that developed after O1 implantation, in contrast, terminal loops were usually widely separated from each other. As a result, multiple pathways from the paranodal periaxonal space into the myelin sheath remained patent, forming potential routes for shunting nodal action currents. This subtle abnormality could thus compromise conduction, even though the sheaths might appear to be normally myelinated at the histological level. Equivalent abnormalities in human neurological diseases, including multiple sclerosis and paraproteinemic neuropathies, could underlie functional loss in the absence of frank demyelination.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurocytology 8 (1979), S. 655-672 
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary ‘Amyelinated’ axons in the spinal roots of dystrophic mouse nerves lack typical nodal and paranodal membrane specializations. However, at the periphery of the amyelinated bundles some of the naked axons form aberrant junctions with Schwann cells belonging to neighbouring myelinated axons. These junctions are characterized by a narrow intercellular cleft containing regularly-spaced densities that closely resemble the ‘transverse bands’ found at paranodal axoglial junctions with respect to both configuration and spacing. In addition, the Schwann cells sometimes extend fingerlike projections towards amyelinated axons in regions where the axolemma has a dense cytoplasmic undercoating. Such regions resemble nodes of Ranvier, where Schwann cell processes interlace over the axolemma. Freeze-fracture replicas show no typical nodal or paranodal membrane specializations in the amyelinated fibres where they are apposed to each other. However, isolated paracrystalline patches of membrane occur corresponding to the aberrant junctions between amyelinated axons and Schwann cells at the periphery of the bundles. The observations show that structural differentiation of the axolemma occurs only where axons are in intimate contact with myelinating cells and does not develop independently in the amyelinated regions. Sodium channels, which are normally concentrated in the specialized nodal membrane, are, therefore, probably distributed uniformly along the amyelinated axon segments that show no sign of such regional differentiation. In addition, it is shown that Schwann cells are capable of forming specialized junctions with more than one axon at the same time.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Structurally normal myelin sheaths develop in the spinal cord of juvenile myelin-deficient rats (mdr) 11 days after transplantation of normal fetal spinal cord fragments or cultured cells that do not yet express galactocerebroside. Cultures result in more extensive myelin formation, and in both cases the myelin that forms is located primarily at or near the site of transplantation. Myelin formation also occurs after transplantation of postnatal donor tissue, but the extent diminishes with donor age, and none was seen after transplantation of adult donor tissue over the two-week period studied. Injection of killed tissue, tissue derived from mouse donors or an extract of myelin also did not lead to myelin formation. The results imply that myelin formed in the host following transplantation was generated by oligodendrocytes newly differentiated from donor precursor cells rather than by donor oligodendrocytes that were already mature at the time of transplantation or by host oligodendrocytes that took up components of the injected material. We conclude that exogenous fetal glial cell precursors are able to survive, differentiate and form myelin in the environment of the juvenile mdr spinal cord.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Implantation of hybridoma cells that secrete a monoclonal antigalactocerebroside into the dorsal columns of ⩽ 9-day-old rat spinal cord results in failure of development of dorsal column myelin in the vicinity of the implant. Clusters of apparently undamaged amyelinated axons remain among the hybridoma cells. Ventral myelin is unaffected. These in vivo results support antibody-mediated inhibition of myelin formation as a potential mechanism underlying failure of remyelination in multiple sclerosis.
    Type of Medium: Electronic Resource
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