Showing papers on "Subventricular zone published in 1992"

Generation of neurons and astrocytes from isolated cells of the adult mammalian central nervous system

Abstract: Neurogenesis in the mammalian central nervous system is believed to end in the period just after birth; in the mouse striatum no new neurons are produced after the first few days after birth. In this study, cells isolated from the striatum of the adult mouse brain were induced to proliferate in vitro by epidermal growth factor. The proliferating cells initially expressed nestin, an intermediate filament found in neuroepithelial stem cells, and subsequently developed the morphology and antigenic properties of neurons and astrocytes. Newly generated cells with neuronal morphology were immunoreactive for gamma-aminobutyric acid and substance P, two neurotransmitters of the adult striatum in vivo. Thus, cells of the adult mouse striatum have the capacity to divide and differentiate into neurons and astrocytes.

Development of GABA-immunoreactivity in the neocortex of the mouse.

Abstract: The prenatal and postnatal development of GABAergic elements in the neocortex of the mouse was analyzed by GABA-immunocytochemistry. Radial distribution of cells and laminar numerical densities were calculated at each developmental stage to substantiate qualitative observations. The first immunoreactive neurons were observed in the cortical anlage at embryonic day 12-embryonic day 13 (E12-E13) in the primitive plexiform layer. At following prenatal stages (E14-E19), most GABA-positive neurons were present in the marginal zone, subplate, and subventricular zone. GABA-immunoreactivity in the cortical plate appeared early (E14), although the complete maturation of its derivatives was achieved postnatally. At prenatal stages we noted a well-developed system of immunopositive fibers in the subplate. As indicated by the direction of growth cones, most of these fibers had an extracortical origin and invaded the cortex laterally through the internal capsule and striatum. In rostral and middle telencephalic levels, fibers originating in the septal region contributed to the cingulate bundle. Presumably corticofugal fibers and callosal axons were also noticed. At postnatal stages the maturation of GABA-immunoreactivity appeared to be a complex, long-lasting process, in which the adult pattern was produced at the same time as the appearance of certain regressive phenomena. Thus, between postnatal day 0 and postnatal day 8 (P0-P8), GABA-positive populations disappeared from the subventricular zone, marginal zone and to a lesser extent from the subplate. At the same ages we noticed the presence of morphologically abnormal, GABA-immunoreactive neurons in the subventricular zone and subplate which are interpreted as correlates of neuronal degeneration. Most GABA-positive subplate fibers also disappeared whereas GABA-immunoreactive axons were seen in the cingulate bundle until the adult stage. In the derivatives of the cortical plate, the maturation of GABA-immunoreactive elements progressed according to the "inside-out" gradient of cortical development, with the important exception of layer IV, which was the last layer to exhibit an adult-like appearance. Within each layer deriving from the cortical plate (layers VIa to II-III), GABA-immunoreactivity showed a protracted maturation in which the first GABA-positive cells were detected a few days after cell birth but substantial numbers of neurons began to express GABA considerably later. The later phase occurred concurrently with the maturation of GABA-positive axonal plexuses. These results suggest that different GABA-positive populations show different developmental regulation of GABA expression during cortical ontogenesis.

Regional differentiation of the human fetal ependyma: immunocytochemical markers.

Abstract: The development of the ependyma from 6 weeks (wk) gestation to term was studied in 26 human fetuses and infants for immunocytochemical differentiation using antibodies against vimentin, several cytokeratins, glial fibrillary acidic protein (GFAP) and S-100 protein Acridine orange-RNA fluorescence was uniform in all differentiated ependymal cells Marked differences were demonstrated among various anticytokeratin antibodies Vimentin was demonstrated in undifferentiated cells, particularly during mitosis, and persisted as the ependyma matured It was strong in floor plate cells and processes forming the ventral median septum Vimentin and cytokeratin CK-904 coexisted with other immunoreactive proteins but disappeared in a caudorostral gradient with maturation At 8 wk gestation, GFAP was detected in roof plate cells and their processes forming the dorsal median septum S-100 protein appeared as early as 6 wk and had a more restricted regional distribution than GFAP at all ages It was strong in the basal plate ependyma ofthe spinal cord in young fetuses; The temporal and spatial distributions of the immunoreactive proteins studied correlate with evidence that fetal ependymal cells synthesize compounds that attract or repel axonal growth cones to prevent axons from entering the ventricles or deviating from programmed projection pathways An additional role may be to induce the transformation of radial glial cells in the subventricular zone