Proliferation of differentiated glial cells in the brain stem

Abstract

Classical studies of macroglial proliferation in muride rodents have provided conflicting evidence concerning the proliferating capabilities of oligodendrocytes and microglia. Furthermore, little information has been obtained in other mammalian orders and very little is known about glial cell proliferation and differentiation in the subclass Metatheria although valuable knowledge may be obtained from the protracted period of central nervous system maturation in these forms. Thus, we have studied the proliferative capacity of phenotypically identified brain stem oligodendrocytes by tritiated thymidine radioautography and have compared it with known features of oligodendroglial differentiation as well as with proliferation of microglia in the opossum Didelphis marsupialis. We have detected a previously undescribed ephemeral, regionally heterogeneous proliferation of oligodendrocytes expressing the actin-binding, ensheathment-related protein 2'3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), that is not necessarily related to the known regional and temporal heterogeneity of expression of CNPase in cell bodies. On the other hand, proliferation of microglia tagged by the binding of Griffonia simplicifolia B4 isolectin, which recognizes an alpha-D-galactosyl-bearing glycoprotein of the plasma membrane of macrophages/microglia, is known to be long lasting, showing no regional heterogeneity and being found amongst both ameboid and differentiated ramified cells, although at different rates. The functional significance of the proliferative behavior of these differentiated cells is unknown but may provide a lowgrade cell renewal in the normal brain and may be augmented under pathological conditions.

Expression of 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (CNPase) in the developing olfactory bulb and subventricular zone rostral extension

“…The precocity of expression of CNPase, the third most abundant myelin protein (Tsukada and Kurihara, 1992), was not surprising in view of previous evidence of the early appearance of CNPase activity (Bansal and Pfeiffer, 1985) or CNPase mRNA or protein in cultured oligodendrocytes (Amur‐Umarjee et al, 1990; Pfeiffer et al, 1993; and early references therein) and in the brain parenchyma (Kanfer et al, 1989; Hardy and Reynolds, 1991; Peyron et al, 1997). Furthermore, it was known that a low percentage of CNPase + cells with few or very delicate processes occurred in the SVZ adjoining the lateral ventricles in the rat (Braun et al, 1988) and that similar cells in the fourth ventricle SVZ or cortical white matter of the developing opossum have proliferating capacities in vivo (Barradas and Cavalcante, 1998; Barradas et al, 1998). In addition, there is in vitro evidence for a significant fraction (about 20%) of cultured A2B5 + oligodendrocyte precursors expressing CNPase (Scherer et al, 1994).…”

Lumbosacral plexus in Brazilian Common Opossum

“…The use of opossums in experimental studies on nervous system has been conducted since the 1970s [3,9,39,40,43]. Despite the abundance of morphological data of the opossum nervous system [16,17,19,23,24,26,27,35,42], the anatomy of the lumbosacral plexus is not widely reported.…”

Distribution of microglial cells in the cerebral hemispheres of embryonic and neonatal chicks

“…Specific labels, such as the lectins, are able to recognize the microglial phenotypes with greater precision (16)(17)(18)(19)(20). The localization of reactive microglial cells during the normal development of the nervous system could be used as an accessory procedure for delineating areas of neurotoxicant-induced brain injury (8,21).…”