| Neurogenesis persists in the subventricular zone (SVZ) of the lateral wall of the lateral ventricle in the adult mammalian brain. The identification of the adult neural stem cell in the SVZ is important for understanding the mechanism of neural plasticity and neural repairing. The cellular composition and organization of the SVZ has been described and more than four cell types have been identified to exist in the SVZ-ependymal region, although which of them being the adult neural stem cell remains unknown. It has been proposed that different types of molecules, like secreted factors, membrane proteins and extracellular matrix components, as well as different cell types act and interact for establishing a microenvironment which is helpful for survival and activity of adult neural stem cell in vivo. The study on the histological features of the subventricular zone in adult rats It has been known well that the neurogenesis persists at the subventricular zone (SVZ ) of the lateral wall of the lateral ventricles in the adult mammals, but little is known about the structural features of this area. In order to explore the morphological characteristics of the SVZ which has been proved to contain the neural stem cells, the semithin sections with Nissl staining and the with scanning electronic microscopy observation combined with morphometry analysis were used in the present study. Those areas including different parts of the lateral (SVZ) and medial walls of the lateral ventricle, the bottom of the 4th ventricle and the wall of the central canal of the spinal cord were observed. The results showed that only in the lateral wall of the lateral ventricles in adult rats existed the SVZ which composed of many dark stained cells with immature structural characteristics. It was also showed that there were abundant vessels in the SVZ compared with that in the striatum. The thickness of the SVZ in the rostral segment of the lateral ventricle was larger than that in theintermediate or the caudal segment, and the number of the cilia outgrowing from the ventricular surface of ependymal layer located in the rostral segment of the SVZ was also larger than that of the intermediate or the caudal segment. The results indicate that the SVZ of the lateral wall of the lateral ventricle has its own histological specialties because of its relations with the neurogenesis. The light and electronic microscopic study on the morphology of the cells in the subventricular zone In order to investigate the cellular composition and organization in the subventricular zone (SVZ) of the lateral wall of the lateral ventricle in the adult brain, the techniques of specific immuno-staining, silver staining and uranyl acetate and lead citrate staining were used in present study. The results showed that there were different types of cells in the SVZ, including the bromodeoxyuridine immuno-positive divided cells morphologically similar to the neuroblasts in the SVZ, glial fibrillary acidic protein positive cells and oligodendrocyte-like cells. In addition, some cells in the ependymal layer, oligodendrocyte-like cells and the network made from different cellular extensions or processes were located closely around theneuroblast-like cells in same area. The present results suggested that the astrocytic sheath around the neuroblast-like cells might not exist in the SVZ, and the neurogenesis in this area might be regulated by different types of cells in the lateral wall of the lateral ventricle. The 3D reconstruction of nuclei in the subventricular zone of adult rats In order to investigate the morphological features of different types of cells in the subventricular zone (SVZ) and the ependymal layer (EL) in the lateral wall of the lateral ventricle in the adult rat, the techniques of semithin sections with Nissl staining and three dimensional (3D) reconstruction of the nuclei were used in present study. The models of 3D reconstructed nuclear surfaces and the corresponding database of these models were established. The 3D images of these nuclei could be displayed in computer when their data were imported to the 3D Slicer applied software, and some morphological indexes such as the distance between two points on the surface of a model were measured with the 3D Slicer. The results showed that there were densities of cells with their nuclei having different shapes and sizes in this area. In the EL, it could be seenthat there were many nuclei with big size and global shape representing the matured ependymal cells, a few of bigger nuclei located under the ependymal cells, and some small nuclei with irregular shape wedged between the ependymal cellular ones. In the SVZ, there were the distinct clusters of monotypic big nuclei with elliptical shape, and they had the nuclear characteristics of the migrating neuroblasts, so we called them the neuroblast-like nuclei here. Some of them were located near the EL while the others near the striatum, but there were different types of nuclei around them. In addition, there were interspersing a few of bigger nuclei with global shape and some small or middle ones with irregular shapes in this area. The results indicated that there were different types of nuclei in the SVZ-EL area. The nuroblast-like nuclei were clustered and it was not seen that the phenomenon that these nuclei were enwrapped by a certain kind of distinct structure. In addition, our results provide a model of the 3D reconstructed nuclei in the SVZ where the neurogenesis persists in adulthood and it could serve as a useful tool for the investigations of the neurogenesis in adult mammalian brains. The effects of the alfactory bulb on the cellular composition and organization of the subventricular zoneIn order to explore the effects of the olfactory bulb (OB) on the neurogenesis in the subventricular zone (SVZ) in adult mammals, the techniques of surgical removal of the OB, serial semithin sections with Nissl staining and three dimensional (3D) reconstruction of the nuclei in the SVZ in adult rats were used in present study. The models of 3D reconstructed nuclei were observed and the morphological indexes of the nuclei were measured in computer. The results showed that after three months of the OB removal, the volume of the SVZ ipsilaterally became smaller, the proportion of the nuclei with a middle or small irregular shape representing the glia-like cells was increased while the number of these nuclei with a bigger and regular shape representing neuroblasts was decreased significantly, and the clusters of these homotypic nuclei were disappeared. The results indicated that the neurogenesis in the SVZ was weakened but the gliogenesis was boosted up after the OB was removed. These results suggested that the OB could improve the neurogenesis in the SVZ of the adult mammalian brain. The expressions of the Group I metabotropic glutamate receptors in the subventricular zone of adult ratsNeurogenesis is proved to persist in the subventricular zone (SVZ) of the lateral wall of the lateral ventricle in adult mammalian brain. Little is known however about endogenous signals for proliferation of precursor cells in this area. In present study, in situ hybridization and immunohistochemistry were used for showing that the Group I metabotropic glutamate receptors (mGluR1 and mGluR5) were expressed in the cells located in the SVZ and adjacent ependymal layer. In addition, the mGluR5 but not mGluR1 was expressed in the cells in the ependymal layer of the medial wall of the ventricle. The results suggested that glutamate might play some roles on SVZ cells through those receptors. Key words: subventricular zone, metabotropic glutamate receptors, neural stem cells, adult rats...
|
PDF Full Text Request