An ultrastructural study of the subependymal plate in the hamster.
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The subependymal plate of the hypothalamus of the hamster has been studied in this work. Our observations with the electron microscope show that the basal surface of the ependymal cells in this area are situated directly over the astrocytic elements. Ultrastructural studies which indicate two types of glial cells in the subependymal plate contradicted by the results of the present investigation demonstrating one type of glial cells in the hypothalamic subependymal plate. This fact is interpreted as the final result of a glial differentiation in adult hamsters.Keywords:
Subependymal zone
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This investigation was undertaken to clarify the three dimensional ultrastructure of the subependymal layer in relation with the ependymal cell layer in rat brain using the scanning electron microscope (SEM). The subependymal layer existing below the ependyma of the third ventricle in the brain of mature albino rats was examined with S E M. The hypothalamus freshly excised after median sagittal section was treated by collagenase with or without trypsin for a short while to remove the ependymal cells at the ventricular wall. After the enzymatic pretreatment of the specimen, many ependymal cells were removed and the subependymal layer was partially exposed. Most of the ciliated ependymal cells remaining at the ventricular wall extended long, single basal processes which then penetrated into the subependymal layer. The subependymal layer was composed of a delicate framework of thin processes of glial cells, ependymal cells and, in addition nerve cells. Scattered among the neuropil just beneath the ependymal cell layer, there were relatively small, globular subependymal cells. Occasionally, there were large bundles of unmyelinated nerve fibres in the subependymal layer. The individual nerve fibres distinctly showed many axonal varicosities within the fibres. Intermingled with the nerve fibres, glial processes of various forms were present. The structure of the ependymal cells and the subependymal layer was compared with the findings already reported in the studies using light and transmission electron microscope.
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Golden hamster
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The subependymal plate of the hypothalamus of the hamster has been studied in this work. Our observations with the electron microscope show that the basal surface of the ependymal cells in this area are situated directly over the astrocytic elements. Ultrastructural studies which indicate two types of glial cells in the subependymal plate contradicted by the results of the present investigation demonstrating one type of glial cells in the hypothalamic subependymal plate. This fact is interpreted as the final result of a glial differentiation in adult hamsters.
Subependymal zone
Ependymal Cell
Ependyma
Basal (medicine)
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The ependyma may befall a variety of pathogenic noxae during fetal life, resulting in histological changes which may persist after birth but are without clinical manifestations. Eight of a series of 19 children who died suddenly and unexpectedly, where no explanation as to the cause of death was found at autopsy, were shown to have diverse histological features involving the ependyma. Five μm paraffin-embedded brain tissue sections including frontal, temporal, occipital, and ventricular horns as well as the fourth ventricle were stained with hematoxylin-eosin (H&E) and luxol fast blue (LFB). Immunohistochemical stains using antibodies to glial fibrillary acidic protein (GFAP), vimentin and S-100 were also performed. Findings included areas of denuded and/or desquamated ependyma, rosettes in different stages of formation, vacuoles and/or pseudocysts, inflammatory changes consisting in macro- and microglial nodules in the subependymal layer, and gliosis. Chronic brain edema was seen in 4 cases. Our findings indicate that ependymal changes in sudden infant death syndrome (SIDS) cases belong to the prenatal or early postnatal period, thus providing, indirectly, a morphological substrate for the previous existence of a noxa that may also affect other CNS areas, and thus being in the position to produce cardiorespiratory control dysfunction.
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Electron microscopic features of a brain tumor induced in hamster by BK virus, a human papova virus.
In order to locate the target cells for malignant transformation by BK virus (a human papova virus) in hamster brain, electron microscopic observation of tumor originally induced in hamster brain by BK virus was performed. With light microscopy, the BK virus-induced tumor (Vn 17) bore a close resemblance to human malignant ependymoma. Under the electron microscope, numerous microvilli and few cilia were visible on the surface of the tumor cells. These tumor cells were joined to each other by desmosomes. Gap junctions were not observed. Multilayered cuboidal cells were observed around the lumen and blood vessels in the tumor. With regard to fine structure, three types of Vn 17 cells were recognized; ependymal like cells, tanycytes with prominent cell processes, and undifferentiated cells with few cytoplasmic organelles. There was no basal lamina between the ependymal cells and the connective tissue stroma. The Vn 17 cells showed some similarity to the ultrastructural features of the epemdymal cells of newborn rabbits, suggesting that the target cells for Vn 17 may be cells related to ependyma. Malignant transformation of the cells would be initiated in the early stages after BK virus inoculation into the brain of newborn hamsters.
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Dissociated cerebella of newborn rats were cultured in vitro as a monolayer for a long period, and ependymal cell differentiation was investigated by scanning and transmission electron microscopy. Cells with actively beating cilia were recognized on the 3rd day, and gradually increased in number thereafter. At nine months of culturing, a number of areas appeared, some of which consisted of several hundreds of ciliated cells. Cultured ependymal cells showed a striking resemblance in their fine structure to the intact ependyma. They were always found to grow upon the feltwork of astrocytic processes which served as a subependymal structure, as observed in the intact ependyma. It is possible that astrocytes may play some role in ependymal differentiation. Cultured ependymal cells are helpful in understanding the control mechanism for the metachronal cilial movement.
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