AGE-DEPENDENT CHANGES IN THE GLIAL-CELL NESTS OF THE CANINE RHINENCEPHALIC ALLOCORTEX - A MORPHOMETRIC STUDY

In the present study, the morphological features as well as the age-de pendent changes of the glial cell nests (GCN) within the rhinencephali c allocortex of the dog are described. A combination of two stereologi cal methods, i.e., Cavalieri's principle and the optical disector, was used to obtain unbiased estimates of the volumes of the whole brain, the allocortex, and the GCN. Furthermore, the numerical densities and total number of the two prevailing populations of undifferentiated cel ls within these nests were determined. Cells with medium-sized dark nu clei (CMD) and cells with large pale nuclei (CLP) were distinguished. The volume of the GCN in relation to the volume of the allocortex decr eased with increasing age. The numerical density and the total number of all cells of the GCN and of the CMD were reduced with age, whereas the numerical density and number of the CLP increased with advancing a ge. Similar morphological features as well as age-dependent changes ha ve already been described of the cell populations in the subependymal layer. Therefore, in analogy, we presume that the glial cells of the G CN have emigrated from the subependymal layer. The significance of the se age-dependent changes remains as obscure as does the function of th e GCN. (C) 1994 Wiley-Liss, Inc.