Effect of hypervitaminosis-A-on the development of the medulla oblongata of the chick embryo

ABSTRACT

Morphological and histological studied were made on the medulla oblongata of 11 and 15 days chick embryos injected on the 6th and 7th days of incubation with one and two successive doses of vitamin [A] each containing [6000 I.U.], Retardation of growth of the medulla oblongata was indicated by reduction in the size of the medulla, thickening of the ependymal layer and norrowing of the floor of the fourth ventricle, there was thickening in the mantle layer of the middle and caudal levels of the medulla oblongata with poor development of some nuclei. Many neuroblastic cells showed ill- defined cell menbranes and pyknotic nuclei with increased glial tissues and oedema in between. The marginal layer was disrupted, these effects were found to be more marked in chick embryos injected by a second dose of vitamin [A]