Trinitrophenol lesions of the ventricular wall: a SEM-TEM study.

These experiments were performed in order to study the ventricular walls of the brain following more or less extensive lesioning of the ependyma and during the process of repair. Trinitrophenol (TNP, 1% in saline) was injected into the ventricular system of adult rats of both sexes. The animals were fixed for SEM/TEM 26th or 5, 7, 11, 21, 30 and 40d post injection. TNP caused areas of irreversible lesions in ependymal cells but the surrounding unlesioned cells showed no signs of a regenerative reaction. The number of supraependymal cells increased considerably at the sites of lesion, their shapes being markedly different from those of comparable cells in control animals. The subependymal tissue presented spongiosis. After a phase in which the lesioned ventricular surface was covered with abundant cell debris, the subependymal astroglia cell debris, the subependymal astroglia proliferated, producing an extensive layer of cell processes which substituted for the missing ependymal cells. This investigation has given us the opportunity to study the formation and morphological characteristics, particularly as visualized with the SEM, of an experimentally induced gliosis in the ventricular wall of adult rats.