الفهرس 
ContentsOnly 14 pages are availabe for public view
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Abstract
The cerebellum is an important part of the circuitry that links sensory to motor areas of the brain. It functions to coordinate movement and provides corrections during movement, which are the basis for precision and accuracy. Valproic acid is a well-known anticonvulsant that used for the treatment of epilepsy. It is also used for treatment of anxiety, bipolar disorder and migraine. Valproic acid causes widespread and dose-dependent neurodegeneration in the developing brain. Folic acid (vitamin B9) is essential for the DNA synthesis and certain biological reactions as consider an essential co-factor in the regulation of gene expression and new protein production which is vital for foetal cell differentiation, development and growth In the current study 60 adult females albino rats and 12 adult males were used. The animals were left to mate with each other. The pregnant rats were equally divided into three groups (16 rats in each group): The first group (control group) The second group (valproic acid treated group) The third group (valproic acid and folic acid treated group) The offsprings were sacrificed at the following ages: Prenatal ages: These include 15, 17 and 19 days. Postnatal ages: These include new born, 14 days, 21 days and Adult (3 months). In each prenatal age group 6 rats were used and each postnatal age group 18 rats were used. The cerebellum from 6 animals at each pre and postnatal ages were processed for Haematoxylin and Eosin staining. 6 animals at each postnatal age of the three studied age groups were processed for transmission electron microscopic examination. Furthermore, Immunohistochemical study using anti glial fibrillary acidic protein (GFAP) was performed at each postnatal age in the three experimental groups. The thickness of the cerebellar cortex and its layers and volume proportion of Purkinje and granular cells, in addition, cell number and nuclear diameter of Purkinje and granular cells were measured in the morphometric study. The parameters were statistically analyzed. In the present study, the primitive cerebellum was well identified on day 15 of embryonic period of control group formed of a plate of neuroepithelial cells covered with a fibrous layer. At embryonic day 17, the cerebellar cortex in control animals showed the first appearance of the external granular layer that expanded over the surface of the cerebellum. The primitive molecular layer started to appear as thin rim deep to external granular layer and the Purkinje cell layer appeared under the molecular layer and contained differentiating cells arranged in several layers. At embryonic day 19 of control group, the external granular layer and the molecular layer appeared more developed and the Purkinje cell layer appeared as muli-cellular layer of larger sized cells. After treatment with valproic acid, the superficial fibrous layer of the primitive cerebellum showed low differentiation and the neuroepithelial cell layer appeared with degenerated cells and areas of necrosis. The external granular layer appeared less in thickness compared to the control group with darkly stained cells. The Purkinje cell layer appeared with small darkly stained degenerated cells. After treatment with valproic and folic acids, the different layers of cerebellar cortex showed improvement and appeared similar to that in control group. Our study revealed that, by light microscopic examination, the cerebellar cortex of newborn rat in the control group is composed of the external granular layer, the molecular layer, the Purkinje cell layer and the internal granular layer from outside inwards. The external granular layer was differentiated into; outer multiplying zone that present parallel to the pial surface and inner premigratory zone that were arranged in rows perpendicular to the surface. The Purkinje cell layer was formed of several rows of Purkinje cells that appear oval or rounded with vesicular nuclei. The internal granular layer appeared ill-defined and had small rounded cells. At the postnatal age 14 days old in the control group, the developing cerebellar cortex showed apparent decrease in thickness of the external granular layer and increase in the thickness of molecular layer than that in the newborn age. The Purkinje cells were regularly arranged in monolayer. This age also revealed an apparent increase in the area occupied by the internal granular layer.
The cerebellar cortex at postnatal age 21 days old in control group revealed an adult like structure and consisted of the molecular layer, the Purkinje cell layer and the internal granular layer from outside inwards. The molecular layer has vesicular basket and stellate cells. The Purkinje cells were arranged in one row. The internal granular layer was well developed and is stuffed with small rounded cells.
Semi thin sections in adult revealed flask shaped or oval Purkinje cells with large rounded vesicular nuclei and prominent nucleoli surrounded by pale basophilic cytoplasm. The granule cells appeared small rounded with vesicular nuclei arranged in clusters with cerebellar islands in between, Electron microscopic examination in the control group at all postnatal ages showed that the Purkinje cell has large nucleus with uniformly distributed chromatin and prominent nucleolus. The cytoplasm contains normal organelles. The ultrastructural study of the granule cells revealed large nuclei containing normal dispersed chromatin and regular nuclear envelope. The granule cells have also a thin rim of cytoplasm containing normal organelles. Examination of the presynaptic nerve terminal showed the presence of many synaptic vesicles and normal mitochondria.
Immunohistochemical examination using anti GFAP of control group at all postnatal ages, showed weak immune expression in all layers of cerebellar cortex.
In valproic acid received group at the age of newborn, the light microscopic examination revealed that the external granular layer appeared decreased in thickness compared to the control group. The Purkinje cells appeared shrunken and disfigured and the granule cells of internal granular layer appeared small and darkly stained.
The age of 14 days of valproic acid treated group, the external granular layer appeared reduced in thickness. The Purkinje cells showed depletion in some areas and appeared disfigured, shrunken with pyknotic nuclei. The internal granular layer showed darkly stained small cells packed together.
In valproic acid received group at the age of 21 days and adult age, there was apparent decrease in the thickness of all cerebellar cortical layers and degenerative changes of the cells. The Purkinje cells appeared shrunken, irregular darkly stained with irregular shrunken nuclei and vacuolated cytoplasm. The granule cells appeared darkly stained, shrunken and grouped in clusters with wide intervening spaces.
Ultrastructurally in valproic acid treated group at all postnatal ages, The Purkinje cell has small shrunken nucleus with discontinuity of the nuclear envelope and
unequal distribution of chromatin. Their cytoplasm appears rarefied vacuolated and shows damaged organelles. Examination by electron microscope revealed that the internal granular cells have shrunken small nuclei with uneven distribution of chromatin. Ultrastructural study of the presynaptic terminal making synaptic contact with Purkinje cell revealed apparent decrease in the amount of synaptic vesicles and the presence of damaged mitochondria.
Immunohistochemical examination of the cerebellar cortex of valproic acid treated group revealed strong positive immune-expression of anti GFAP with extensive extensive network of fibers and astrocytes with its processes in all layers of the cerebellar cortex in comparison to control.
In valproic acid and folic acid treated group at all postnatal ages, the light microscopic examination revealed improvement of the cerebellar cortical layers architecture to be near the control. Most neurons of the Purkinje cells appeared large and flask shaped or oval and contain large rounded vesicular nuclei, but some cells appeared small shrunken and disfigured. The internal granular layer showed rounded cells with vesicular nuclei but others appeared with darkly stained nuclei.
By electron microscopic examination in all postnatal ages, the Purkinje cell exhibited large euchromatic nucleus and the cytoplasm appeared with normal mitochondria, rough endoplasmic reticulum, free ribosomes and some small vacuoles. In the ultrastructure of the granule cells of the internal granular layer it appeared nearly equal in size containing normal oval or rounded nuclei as compared to control with normal organelles in the cytoplasm. The electron microscopic examination the presynaptic terminal showed improvement of its structure as compared to control.