Mitotic neuroblasts in the 9-day-old and 11-month-old rodent hippocampus

Abstract

Ultrastructural identification of mitotic neuronal precursors beneath the basal hippocampal granule cell layer was made using electron micrographs of [3H]thymidine-labeled cells. Ultrathin sections were obtained by a method that allows serial thin sectioning of reembedded sections previously prepared for light microscopic radioautography.The electron microscopic observations reported in this study reveal: (I) that a steady rate of granule cell neurogenesis occurs during the first year of a rodent's life; (2) that newly formed granule neurons in the dentate gyrus of the newborn mouse and adult rat are a result of neuroblast division; and (3) two distinct classes of mitotic cells can be identified during the peak period of postnatal neurogenesis-those with synapses on their cell bodies and processes and those with no synapses or processes.

The microenvironment of the embryonic neural stem cell: Lessons from adult niches?

“…These separate the A, B, and C cells from the ventricle although type B (stem) cells may extend fine processes through the ependymal cell layer to contact the ce- A number of other potential locations for neural stem cell niches in the adult CNS have been described. First, the generation of new neurons and glia in the hippocampus has been reported in rodents, primates, and humans (Altman and Das, 1965;Kaplan and Bell 1984;Cameron et al, 1993;Eriksson et al, 1998;Gould et al, 1999). The source of these new cells originating from the subgranular zone (SGZ) could potentially to be astrocyte stem cells (Seri et al, 2001), as has also been reported in the SEZ.…”

HIV-1, chemokines and neurogenesis

“…The close juxtaposition of the sites of expression of SDF-1 and its receptors suggest an interaction, whereby it would be possible for SDF-1 released from granule cells to influence progenitor cells (or neurons) in the immediate vicinity. Indeed, it has been suggested that granule neurons actually form mossy-like terminations (Kaplan and Bell, 1984) as well as other types of close contacts with progenitors in the SGZ (Seri et al, 2004). It is clear that there is a connection between these two types of cells so that changes of activity in the granule cell layer can regulate the rate of neurogenesis (Kronenberg et al, 2003), what has been described as "excitationneurogenesis" coupling (Deisseroth et al, 2004).…”

Mechanism of stem cells in the central nervous system

“…However, markers to distinguish among cell types were still not available at that time (Altman and Das, 1962, 1965, 1967Altman, 1966). The next landmark was achieved by Kaplan and colleagues when they presented evidence that labeled cells in the olfactory bulb and the dentate gyrus of adult rats had the ultrastructural characteristics of neurons, namely, synapses and dendrites (Kaplan and Hinds, 1977;Kaplan, 1984). This was followed by a set of elegant experiments in the 80s showing that songbirds generate new neurons that not only integrate into the brain and form synapses but were also functionally active able to respond to stimuli (Goldman and Nottebohm, 1983;Burd and Nottebohm, 1985).…”