الفهرس 
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Abstract
Aging of the brain leads to impairments in cognitive and motor skills. There are multiple factors contributing in the aging process include oxidative stress and its damaging effects starting from the level of molecules.
Imbalance between the production and the detoxification of free radicals leads to oxidative stress. Antioxidant is one of the defense mechanisms against free radical-induced oxidative stress.
Vitamin E is one of the most important natural antioxidants and it has a perfect role in improving the function of the nervous system. The concentration of vitamin E in the cerebellum is the lowest among the whole brain parts.
So the aim of the present study was to detect the possible effect of vitamin E (α-tocopherol) as an antioxidant drug on the structure of cerebellum of senile male albino rats
In the current study, sixty male albino rats were divided into four groups, group I, consisted of 10 adult rats that received no treatment, group II, consisted of ten senile rats that received no treatment, group III, consisted of 20 senile rats which were further subdivided into subgroup IIIa included 10 senile rats that received corn oil (0.4mg/ kg B.W./day) by oral gavage for 2 weeks and subgroup IIIb included 10 senile rats received same dose of corn oil by oral gavage for 4 weeks. GroupIV, consisted of 20 senile rats which were further subdivided into subgroup IVa included 10 senile rats that received vitamin E (200 mg/kg. B.W/day) by oral gavage for 2 weeks and subgroup IVb included 10 senile rats that received the same dose of vitamin E by oral gavage for 4 weeks.
At the end of the experiment, all rats were sacrificed and the cerebella were dissected. Half of the specimens were fixed in 10% formalin and processed for paraffin blocks. Sections 5 microns in thickness were obtained and stained with hematoxylin & eosin and immunohistochemichal stain (GFAP). The other half were fixed in 2.5% glutaraldehyde and processed for Epon blocks, semithin sections were prepared and stained with toluidine blue.
Morphometric studies were also done. The thickness of cerebellar cortex was measured in all groups in the H&E stained sections using digital photomicrographs taken at magnification of 100. The number of Purkinje cells and molecular layer cells were counted in H&E stained sections using digital photomicrographs taken at magnification of 400, while the number of granule cells was counted in toluidine blue stained sections using digital photomicrographs taken at magnification of 1000. The GFAP area percent was measured in all groups in the GFAP immunohistochemistry stained sections using digital photomicrographs taken at magnification of 1000.
The mean of the measurement of each parameter was recorded for each animal and the data were statistically analyzed.
Light microscopic examination of H&E and toluidine blue stained sections of the cerebellar cortex of the adult group (group I) revealed that the cortex consisted of external molecular layer, middle Purkinje cell layer and internal granular layer. Purkinje cells were flask-shaped and closely related to each other in single row. A mild positive reaction of GFAP for astrocytes was detected.
Histological examination of cerebellar sections stained with H&E or with toluidine blue in senile rats treated with corn oil (group III), showed similar findings to those of the senile rats (group II). Purkinje cells were small darkly stained with pyknotic nuclei and distorted with loss of its normal flask-shape. Few widely spaced cells were noted due to loss of some ones. Also, some cells were displaced from their linear arrangement. There were statistically highly significant decrease in the thickness of the cerebellar cortex and in the number of the molecular layer cells, purkinje cells and granule cells compared with the adult group (group I) also GFAP stained sections showed statistically highly significant increase in GFAP area percent. Administration of vitamin E for 2 weeks (group IVa) showed slight improvement. Although some Purkinje cells appeared closely positioned with regular outline, however other cells were distorted in shape with deeply stained nuclei. Moreover, the mean of the cortical thickness and number of different cortical cells showed statistically non-significant increase compared to group II and a non-significant decrease in the GFAP area percent. Administration of vitamin E for 4 weeks (group IVb) showed an improvement especially in the purkinje cells shape as it restore their flask shape and gained their linear arrangement also there was an increase in the thickness of the cerebellar cortex and the cell count when compared with the senile group (group II) decrease of GFAP area percent. Comparing both treated groups (group IVa and IVb) to the adult group (group I) they showed statistically highly significant decrease in the thickness of the cerebellar cortex and in the cell count and statistically highly significant increase in the GFAP area percent.
In conclusion, the results of this study suggest that exogenous vitamin E administration may delay the aging process of tissues by means of its free radical scavenging effects.