ABSTRACT
The hippocampal formation plays a demonstrated role in learning and memory, and it is selectively impaired in many developmental brain diseases. Developmental studies on this brain area are important for understanding the neurodevelopmental disorders. To study the postnatal development of the hippocampal formation. Five male albino rats from the following postnatal ages PO, P7, P14, and P90 were studied by histological, immunohistochemical, and morphometric methods. The general architecture of the hippocampus proper with its polymorphic, pyramidal, and molecular layers was present at PO, whereas the details of the adult structure appeared at P14. In the dentate gyrus, distinct lamination appeared at P7 and its maturation continued with the production of neurons at the interhilar zone that peaked at P14. Astrocytes increased in size and staining affinity for glial filaments, and acquired a stellate shape with age. Microtubule-associated protein 2 immunoreactivity was observed in the perikarya at PO and in the sprouting dendrites at P7 and P14. At P90, the dendrites occupied the whole thickness of the molecular layer. Number of light pyramidal neurons decreased, whereas that of dark neurons increased from PO to P90. Furthermore, the number of granule cell layers increased concomitantly with the increase in thickness of the molecular and polymorphic layers of both the hippocampus proper and the dentate gyrus. The important sequences of events in the growth and maturation of the hippocampal formation in male albino rat occurred in the first 2 postnatal weeks
Subject(s)
Male , Animals, Laboratory , Hippocampus/anatomy & histology , Immunohistochemistry , Rats , MaleABSTRACT
In the present study, age-related histological, histochemical, and ultrastructural changes in both the olfactory epithelium [OE] and the vomeronasal organ [VNO] have been investigated. A total number of 30 albino rats were used in this study Animals were divided equally into two groups; [adult group] and [aged group]. The OE of the aged animals was reduced in thickness, with a relative disturbance in the zonal arrangement of its layers and invaded by acini of Bowman's glands. A basal nuclear-free zone and apical pale cells were also observed within the aged OE. Both mitotic figures and apoptotic bodies were seen in the aged OE. Periodic acid schief-Alcian blue [PAS-AB,] reaction revealed an increase in the PAS-reaction both in the apical and basal parts of the aged OE. Alkaline phosphatase reaction showed a marked reduction in the enzyme activity within the basal cell layer with the appearance of scattered positive cells with the aged OE. On the other hand an increase in the enzyme activity of Bowman 'S glands was observed. The most frequent ultrastructural finding within the aged OE was the accumulation of dense inclusion bodies within the mature ORNs. Less frequently filamentous inclusions were also detected. SEM investigation revealed reduction in the olfactory area and shortening in the olfactory cilia. In aged animals the vomerosensory cells showed vacuolated cytoplasm. Intraepithelial blood capillaries appeared irregular. Histochemically, the PAS-reaction was increased in the apical processes of the supporting cells and reduced in the VS cells whereas alkaline phosphatase along the apical surface was not affected. Ultrastructurally, vomerosensory cells exhibited dilatation of most organelles mainly sER and Golgi bodies, numerous clear vesicles of variable sizes, multiple electron-dense inclusions and lipofuscin granules. VNO are more vulnerable to the aging process than the OE. Sensory cells in particular are more affected than other cell types