Effects of postnatal exposure to static magnetic field on the development of the cerebellar granule cells

ABSTRACT

Many studies were performed to evaluate the effects of static magnetic fields [SMFs] on the processes of proliferation and migration of cerebellar cells to their final postnatal destinations. Granule cells are the most abundant interneurons in the cerebellum. Progenitors of these neurons actively proliferate during the first 2 postnatal weeks in external granular layer [EGL]. The granule cells in the EGL migrate inwards to form the internal granular layer [IGL], and the EGL disappears. So the postnatal development of the cerebellum depends on their postnatal proliferation and migration which is vulnerable to any micro-environmental insult. to evaluated the light and electron microscopic changes occurred to the cerebellar granule cells of the pups after postnatal exposure to SMF [20 mT]. Postnatal exposure to SMFs showed that there was a significant thinning in the EGL at the beginning of the study at postnatal thy 4, this significant decrease in thickness progressed in the first week. At two weeks when normally the EGL starts to disappear, it showed persistent increase in its thickness indicating delayed migration. At all ages of exposed group [P], EGL contained many apoptotic cells and some degenerated cells. IGL showed significant decrease in its cellular density till the postnatal day 15 concomitant with the period of delayed migration in the EGL. At the postnatal days 22, the cells in IGL began to regain its near normal cellular density but the IGL showed disarrangement of its crowded granule cells with absence of appearance of regular glomeruli among them with appearance of some degenerated cells among the granule cells. Many cells of the IGL also showed areas of cytoplasmic vacuolation. Postnatal exposure to SMFs produces some delay in the development and appearance of more apoptotic cells. But some of these changes in different stages of the postnatal development of the cerebellar cortex began to be less apparent with advancement of age