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Immunohistochemical analyses of nervous system structure, development and regeneration Toma, Jeremy Steven


Specific aspects of nervous system structure, development, and regeneration were investigated in two separate studies. The first study was concerned with development of sensory root entry zones. Sensory information enters the central nervous system (CNS) via root entry zones where sensory axons span a glial environment consisting of Schwann cells in the peripheral nervous system (PNS) and astrocytes and oligodendrocytes in the CNS. Little is known about the postnatal development of the glial elements of many root entry zones. I sought to establish a comparative developmental timecourse of the glial elements in the postnatal (PO, P3, P7, P14) and adult rat of three root entry zones: the spinal nerve dorsal root entry zone, the trigeminal root entry zone, and the vagal dorsal root entry zone. I compared entry zone development based on the expression of antigens in peripheral glia, central glia, and the PNS extracellular matrix. While all three root entry zones had reached maturity by PI4, the glial elements comprising the PNS-CNS interface of the trigeminal root entry zone and the vagal dorsal root entry zone matured earlier than those of the spinal nerve dorsal root entry zone. This study revealed unexpected expression patterns of certain glial antigens. For example, the antibody used to label mature oligodendrocytes (RIP) labelled Schwann cell cytoplasm. I sought to follow up on this observation and characterized RTP immunoreactivity in peripheral glia in the second study. In uninjured rats, RIP demarcated paranodal regions of myelinated axons and clearly defined Schmidt- Lantermann incisures. Robust RIP immunoreactivity was present in Remak bundles. Low levels of RIP immunoreactivity were detectable in satellite cells surrounding dorsal root ganglion (DRG) neurons and in terminal Schwann cells at neuromuscular junctions. These results suggested a correlation between RIP immunoreactivity and amount of axoglial contact. Injury induced sympathetic sprouting and pericellular basket formation in the DRG was conducted to further examine this correlation. All perineuronal sympathetic sprouts infiltrated heavily RlP-immunoreactive satellite cell sheaths. RIP immunoreactivity was absent from placodal-derived olfactory ensheathing cells, suggesting that correlation between axoglial contact and RIP immunoreactivity is confined to peripheral glia of neural crest origin.

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