| Popis: |
Some examples of motor end-plates and intramuscular nerves found in hindlimb muscles of aged rats were studied by electron microscopy and illustrated in figures. Nine out of ten motor end-plates examined showed variable degrees of abnormality in their terminal axons. It was characterized by simple condensation, shrinkage and eventual dissolution of terminal axons, by absence of any specific degenerative products internally and by lack of active participation on the side of teloglial Schwann cells. It appears to proceed in a rather irregular and uneven manner, both normal and frankly diseased axon terminals often coexisting within any one motor end-plate. The denervated sole plate regions were covered either with or without Schwann cell elements. The denervating process was observed in red as well as white muscle fibres. Definite morphological evidence of denervation of motor end-plates and therefore the role played by the neurogenic factor were thus confirmed in relation to the pathogenesis of muscle fibre changes in ageing rats. The preterminal and more proximal intramuscular nerve fibres only rarely revealed mild varieties of abnormality. The whole picture of intramuscular nervous system appears to represent a slowly progressive ‘involutional’ process affecting primarily and selectively the most distal part of axons. The underlying pathomechanism of this involutional process still awaits future elucidation. |
