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  • Demyelination  (3)
  • Reinnervation  (3)
  • 1
    ISSN: 1432-2307
    Keywords: Muscle spindle ; Elastic fibres ; Elaunin fibres ; Oxytalan fibres ; Denervation ; Reinnervation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Muscle spindles in the lower lumbrical muscles of rats were studied by transmission electron microscopy following denervation with or without reinnervation. The number and total area of elastic fibres per muscle spindle increased at 3–12 months following various experimental procedures: (1) denervation and reinnervation after a single crush lesion to the sciatic nerve; (2) reinnervation after four-fold repeated crush injuries; and (3) transection and suture of the nerve. The increased number of oxytalan and elaunin fibres, the precursors of mature elastic fibres, within these muscle spindles provided further evidence for their numerical and dimensional increase. An attachment site of elastic fibres at the spindle pole was identified at the inner cells of the outer spindle capsule. The processes of these cells embraced terminating elastic fibres tightly. Attachment of elastic fibres to intrafusal muscle fibres was less conspicuous since they were not similarly embraced but were rather indistinctly, though closely, associated with the basal lamina along longitudinal surface indentations of intrafusal muscle fibres. It is concluded from this series of experiments that muscle spindles, as dynamic mechanoreceptors, maintain their elastic properties even under pathological conditions. The increase of elastic fibres following denervation and reinnervation represents an obviously meaningful reaction that may compensate for loss of tonic properties of muscle spindles without causing stiffness.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 80 (1990), S. 163-171 
    ISSN: 1432-0533
    Keywords: Neuromuscular spindle ; Reinnervation ; Nerve endings ; Autonomic innervation ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Muscle spindles from the lower lumbrical muscles of rats were studied by transmission and scanning electron microscopy following reinnervation (i) after a single sciatic nerve crush lesion and (ii) after transection and immediate epineurial suture of the sciatic nerve. In all muscle spindles, regenerated sensory or motor nerve endings were encountered 3 months after making the lesions although in the nerve-transection group, regenerated nerve endings were seen less frequently before 6 months of recovery. Abnormalities in reinnervated spindles following neurotomy comprised: (1) multiplicity of axonal sprouts (hyperinnervation), sometimes irregularly related to, although never in direct contact with, regenerated sensory nerve endings; (2) altered contact relationships between sensory nerve endings and intrafusal muscle fibers; (3) abnormal structure of nerve endings; and (4) irregular association of Schwann cell processes to regenerated sensory nerve endings. These findings indicate that reinnervation of muscle spindles following transection and suture of a peripheral nerve, i.e., after complete interruption of its continuity, in fact, occurs although the fine structural abnormalities observed are supposed to interfere with adequate functional restoration.
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  • 3
    ISSN: 1432-0533
    Keywords: Key words Schwann cell inclusions ; Demyelination ; Myelinated nerve fibers ; Morphometry ; Peripheral ; neuropathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the cytoplasm of Schwann cells of a sural nerve biopsy from a 21-year-old female patient with chronic neuropathy we noted numerous unique, usually double membrane-bound, osmiophilic, granular or globular inclusions, approximately 30–600 μm in diameter. Some of these membrane-bound vesicular or tubular structures contained less dense or no osmiophilic inclusions. Morphometry revealed a reduction of the myelin area per endoneural area to approximately 13% (normal value: 20– 30%) and of the density of myelinated nerve fibers to 5,412/mm2 (normal value at this age: 6,000–9,000/mm2). Large myelinated nerve fibers were predominantly reduced in number, and no myelinated nerve fibers with diameters larger than 4.5 μm were seen. Numerous, usually small onion bulb formations indicated a predominantly demyelinating type of neuropathy. This is to the best of our knowledge the first case of a chronic demyelinating neuropathy in which this kind of presumably pathognostic deposits in the cytoplasm of Schwann cells was detected.
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  • 4
    ISSN: 1432-0533
    Keywords: Muscle spindle ; Denervation ; Reinnervation ; Muscle fiber atrophy ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The fine structure of normal, denervated, and reinnervated muscle spindles in lower lumbrical muscles of rats was studied morphometrically at time intervals ranging from 3–14 months. In control spindles, the mean transverse area of mitochondria was estimated to be more than twice as large in nuclear chain than in typical nuclear bag fibers. Following denervation, there was a severe decrease of the mean number and transverse area of mitochondria, and a moderate, but statistically significant decrease of the mean transverse area of intrafusal muscle fibers (IMFs) despite an increase of the number of IMFs. At 12–14 months of reinnervation, changes of the transverse areas of IMFs were statistically insignificant, but the mean values for the mitochondria were incompletely restored. At 4×3 months, after fourfold repeated crush injuries to the nerve, most of the values estimated (transverse area of mitochondria; number, shape, and transverse area of IMFs and nuclei) tended to approach those in denervated rather than in reinnervated IMFs. The differences of the reactions of intra- and extrafusal muscle fibers following complete motor and sensory denervation appeared to be in accordance with their normal dimensional dissimilarities.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 14 (1970), S. 261-283 
    ISSN: 1432-0533
    Keywords: Allergic Neuritis ; Electron Microscopy ; Mononuclear Cells ; Demyelination ; Remyelination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Kaninchen mit einer experimentell-allergischen Neuritis (EAN) wurden 8 Tage bis 4 Monate nach der Injektion einer Emulsion aus heterologem Nervengewebe mit Freundschem Adjuvans phasenkontrast- und elektronenmikroskopisch untersucht. Im akuten Stadium der Demyelinisation ist eine Beteiligung von mononucleären Infiltratzellen am Vorgang der Entmarkung peripherer Nervenfasern in der gleichen Weise nachweisbar, wie es Lampert (1969) bei der EAN von Ratten dargestellt hat. Da die Markscheidenschäden jedoch nicht immer in unmittelbarem Kontakt mit den Infiltratzellen auftreten, sind humorale Faktoren, die möglicherweise von den Infiltratzellen ausgeschieden werden, als Ursache der Markscheidenschäden nicht mit Sicherheit auszuschließen. Der weitere Abbau der geschädigten Markscheiden findet dann sowohl in den zu Makrophagen transformierten Infiltratzellen als auch in den proliferierenden Schwann-Zellen statt. Ausnahmsweise dominieren unter den Infiltratzellen auch bei der einfachen experimentell-allergischen Neuritis neutrophile Leukocyteninfiltrate; sie kommen in Zusammenhang mit anderen Zeichen einer schweren Störung der Gefäßnervenschranke wie Erythrodiapedesen und Fibrinexsudaten im fortgeschrittenen Stadium der Gewebsschädigung vor. Auf Axonläsionen und die im Ausheilungsstadium der EAN vorkommenden Zwiebelschalenformationen sowie die wiederholt beobachteten Gruppen regenerierter, von einer gemeinsamen Basalmembran gebündelter Nervenfasern wird kurz hingewiesen.
    Notes: Summary Rabbits with experimental allergic neuritis (EAN), induced by intradermally injected emulsified heterologous antigen together with Freund's adjuvant, were investigated by phase and electron microscopy 8 days to 4 months after the injection. Early lesions of the myelin sheaths in EAN can be demonstrated to occur in close contact with infiltrated mononuclear cells as has been reported by Lampert (1969) in rats. Yet since myelin lesions are not always restricted to areas of immediate contact with infiltrated mononuclear cells, it cannot be excluded that humoral factors, possibly excreted by the infiltrated cells, may initiate the myelin lesions. Further breakdown of myelin sheaths takes place in proliferating Schwann cells as well as in infiltrated mononuclear cells. Occasionally, neutrophilic leucocytes predominate among the cellular infiltrates. They occur together with erythrodiapedesis, and fibrinous exsudates in areas of severance of the blood-nerve barrier. Axonal lesions, and during remyelination, “onion bulb” formation were also seen as a sequence of the demyelinating lesions. Also, bundles of small regenerated nerve fibers enclosed by a single basement membrane were repeatedly observed in areas with remyelinated nerve fibers.
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  • 6
    ISSN: 1432-1459
    Keywords: Ethylene oxide ; Peripheral neuropathy ; Morphometry ; Electron microscopy ; Demyelination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case is reported of ethylene oxide polyneuropathy after 5 months of exposure. There was symmetrical distal weakness of both lower extremities and transitory reduced nerve conduction velocities with increased latencies. Sural nerve biopsy revealed nerve fibre degeneration of the Wallerian type, associated with reduction of axonal cross-sectional areas and some degree of nerve fibre regeneration that could be confirmed morphometrically. In addition, there was conspicuous paranodal vesicular disintegration of individual myelin lamellae. Unusual cisternae with introverted hemidesmosomes were noted in endoneurial fibroblasts.
    Type of Medium: Electronic Resource
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