The Subventricular Zone

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The SVZ was first recognized by Schaper and Cohen (1905) by the presence of mitotic figures in a location distant from the lateral ventricles. It was first shown definitively to have proliferating cells using 3H-thymidine label in vitro using slabs of human brain (Rakic and Sidman, 1968). The proliferating cells of the SVZ differ in two major ways from those of the VZ (Fig. 4). First, the nuclei of proliferating cells of the SVZ do not move during the cell cycle, but reflecting the fact that cells of the SVZ, in contrast to those of the VZ, are not attached to each other as a pseudostratified epithelium, this population does not undergo interkinetic nuclear migration in the course of the cell cycle (Boulder Committee, 1970; Smart, 1972; Altman and Bayer, 1990). Second, the cell bodies of the SVZ cells do not have long

FIGURE 13. Schematic diagrams of the proportions of the changes in the proportions of symmetric non-terminal (S/NT), symmetric-terminal (S/T) and asymmetric cell divisions as a function of changes in P (abscissa) during the neuronogenetic interval. At any given time the sum of the proportions of the 3 types of cell divisions adds up to 1.0 (ordinate). The changes shown are the changes in the 3 types of cell divisions for the 3 different models developed for this study. For a detailed explanation of the assumptions of each model, see the text.

FIGURE 13. Schematic diagrams of the proportions of the changes in the proportions of symmetric non-terminal (S/NT), symmetric-terminal (S/T) and asymmetric cell divisions as a function of changes in P (abscissa) during the neuronogenetic interval. At any given time the sum of the proportions of the 3 types of cell divisions adds up to 1.0 (ordinate). The changes shown are the changes in the 3 types of cell divisions for the 3 different models developed for this study. For a detailed explanation of the assumptions of each model, see the text.

Medial Ganglionic Eminence Sagittal

FIGURE 14. Contributions of the SVZ of the medial ganglionic eminence (MGE), lateral ganglionic eminence (LGE), and caudal ganglionic eminence (CGE) to early brain development. (A) A coronal view of the rodent forebrain germinal zones at E12.5. (B) The LGE and MGE are prominent structures in the E15.5 brain. By contrast, at this age the neocortical SVZ is unremarkable. (C) Directional movements of MGE and LGE cells as they migrate to the striatum, neo-cortex, and nucleus accumbens (na). Cells from the MGE also may migrate through the LGE en route to the neocortex. (D) Sagittal view of the rodent brain at E15.5 shows directional movements from the MGE, LGE, and CGE. Cells of the CGE migrate to the hippocampus, thalamus, pallidum, olfactory tract (ot), and olfactory bulb (ob). Panels (A), (B), (C) were adapted from Lavdas et al. (1999) and panel (D) was adapted from Wichterle et al. (2001). Figure modified from Brazel et al., 2003.

FIGURE 14. Contributions of the SVZ of the medial ganglionic eminence (MGE), lateral ganglionic eminence (LGE), and caudal ganglionic eminence (CGE) to early brain development. (A) A coronal view of the rodent forebrain germinal zones at E12.5. (B) The LGE and MGE are prominent structures in the E15.5 brain. By contrast, at this age the neocortical SVZ is unremarkable. (C) Directional movements of MGE and LGE cells as they migrate to the striatum, neo-cortex, and nucleus accumbens (na). Cells from the MGE also may migrate through the LGE en route to the neocortex. (D) Sagittal view of the rodent brain at E15.5 shows directional movements from the MGE, LGE, and CGE. Cells of the CGE migrate to the hippocampus, thalamus, pallidum, olfactory tract (ot), and olfactory bulb (ob). Panels (A), (B), (C) were adapted from Lavdas et al. (1999) and panel (D) was adapted from Wichterle et al. (2001). Figure modified from Brazel et al., 2003.

radially oriented processes, but rather they have shorter processes that remain confined to the SVZ (Rakic et al., 1974).

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