OBSERVATIONS ON MORPHOLOGY AT TRANSITION BETWEEN PERIPHERAL AND CENTRAL NERVOUS-SYSTEM IN CAT .5. LIGHT MICROSCOPICAL AND HISTOCHEMICAL STUDY OF S1 DORSAL ROOTLETS IN DEVELOPING KITTENS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 446  (1) , 73-+
Abstract
The postnatal development of the transitional region (TR), i.e., the proximal free part of a spinal rootlet that contained both P[peripheral]NS and CNS tissue, was studied by light microscopy in semi-thin sections and after histochemical staining according to the Marchi and OTAN methods for the demonstration of degenerating myelin and according to the Gomori method for the demonstration of acid phosphatase activity. In the newborn kitten the PNS tissue extended well up to the spinal cord surface and the rootlets lacked a transitional region. The CNS tissue entered the root during the 2nd postnatal week, and a transitional region was fully established at the beginning of the 2nd mo. The degree of myelination in the group of large fibers differed on the 2 sides of the PNS-CNS borderline: well myelinated PNS fibers were transformed into poorly myelinated or apparently unmyelinated CNS fibers. PNS and CNS myelin sheaths of large fibers appeared to be of equal thickness in the 4 wk old kitten. During the 1st postnatal month large amounts of Marchi positive material and a high acid phosphatase activity occurred in complex paranodes and very short internodes in the PNS compartment just distally to the PNS-CNS borderline. In the adult cat Marchi positive bodies were numerous in the CNS compartment just proximally to the PNS-CNS borderline. The results were discussed against previous studies on focal demyelination as found during the normal development of the feline PNS.