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Estudo da degeneração Walleriana em camundongos isogenicos das linhagens C57BL/6J e A/J

by Rodrigues de, Cristiane Lucia

Abstract (Summary)
Axotomy of a peripheral nerve leads to a degenerative process in the distal stump known as Wallerian degeneratíon (DW), in which macrophages and Schwann cells participate ín phagocytosis ofaxon and myelin debris. Such cells are also responsible for preparing a favorable microenvironment to axonal regeneration through production of neurotrophic and neurotopic substances. Among these substances are cytokines produced mostly by macrophages and neurotrophic factors and components of extracellular matrix produced by Schwann ceUS. Recently, evidence emerged showing that nitric oxide (NO) would also be involved in DWand, consequently in lhe axonal regeneration processo However, partícipation of macrophages and Schwann cells in NO production during DW remains to be investigated .It has been reported in the literature that adult C57BU6J mire have a lower axonal regeneration potential afier sciatic nerve lesion when compared to olher ísogenic strains. The aim of this work was to investigate possíble differences in time course of some events in DW process between C57BU6J and AIJ strains, by using complete sciatic nerve transection model with prevented axonal regeneration. First, we studied the time course of neurofilament breakdown, fragmentation and clearance of myelin sheath and NADPH-diaphorase activity in the distal stump, 1, 3, 5, and 7 days afier axotomy. The stereologicaJ analysis of immunoreactive neurofilaments showed lhat the dephosphorylation and degradation process of these elements in C57BU6J strain is faster than in AIJ strain. On the olher hand, Sudan Black histochemistry did noí show differences between strains as regards the time course of myelin sheath fragmentation. However, jt was evident that a higher number of cells were involved in myelin degradation in C57BU6J mice at 3 and 5 days post-surgery. NADPH-diaphorase histochemistry, a marker for NO production, showed positivecells in the distal stump of both strains from the first to the seventh day afier lesion. Positive-cells in C57BU6J strain showed predominantty an intense and well defined labeling 5 days afier transection, while in AlJ strain granular and dispersed labeling were more abundant. With the goal of better understanding NO involvement in DW, immunofluorescence techniques and confocal microscopy were used to identify ceUs related to NO production and to examine the spacial and temporal expression of inducible nitric oxide synthase (iNOS) afier sciatic nerve transection. Immunoreactivity for iNOS was intense in macrophages and less evident in Schwann cells, but it was present in both cells trom the first to the seventh day afier transection in both strains. Macrophages were the main source of iNOS. We noted a delay in macrophage recruitment and activatíon of iNOS expression in the dista! stump of C57BU6J mire when compared to AJJ mies. These differences in DW between C578U6J and AIJ mice may reflect intrinsic properties ofaxons and/or behavioral dífferences in some cells, probably due influence of cytokines. These dífferences between strains should be taken into account in studies of degeneration and regeneration of the peripheral nervous system
This document abstract is also available in Portuguese.
Bibliographical Information:

Advisor:Francesco Langone; Biologia Celular; Langone, Francesco; Elenice Aparecida de Moraes Ferrari; Leonilda Maria Barbosa dos Santos

School:Universidade Estadual de Campinas

School Location:Brazil

Source Type:Master's Thesis

Keywords:degeneração oxido nitrico microscopio e microscopia

ISBN:

Date of Publication:01/11/2002

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