ELECTRON MICROSCOPICAL STUDIES ON THE LINING EPITHELIUM OF THE GLANDULAR STOMACH OF ADULT FOWL WITH SPECIAL REFERENCE TO PROGRAMMED CELL DEATH, APOPTOSIS

Light, transmission and scanning electron microscopical investigations were conducted on the lining epithelial cells of the glandular stomach of ten healthy adult fowl of both sexes (Dandarawi strain). The lining epithelial cells appeared tall columnar, that became cuboidal type in the basal region of the mucosal folds. These cells revealed strong and moderate reactivity with PAS and alcian blue respectively and consequently, they were considered as mucin producing cells with predominance of the neutral type. Scanning electron microscope revealed that the mucous membrane showed both concentrically and finger-like longitudinally arranged mucosal folds. The lining cells of these folds possessed hexagonal-shaped luminal surface with numerous microvilli. These cells revealed the characteristic features of highly active secretory cells. They contained well-developed infranuclearly located rough endoplasmic reticulum, conspicuous Golgi-apparatus and numerous secretory granules in the cell apex. The later possessed electron-lucent fine filamentous matrix. The rough endoplasmic reticulum was characterized by very long and dilated tubular shaped cisternae, that were easily demonstrable in scanning electron microscope. Mitochondria, cytoplasmic filaments, ribosomes, lysosomes and phagocytic vacuoles were also observed. The apoptotic cells appeared as shrinkaged cells, characterized by small darkly stained nuclei, increased cytoplasmic density and protruded cell apices. By scanning electron microscope, these cells were frequently observed at the tip of the mucosal folds. They were characterized by bulged irregular luminal surfaces and reduction in the number of microvilli. Later on, these apoptotic cells disintegrated into spherical apoptotic bodies seen upon the mucosal surfaces. At the transmission electron microscopical level, the apoptotic cells were characterized by condensation of the nuclear chromatin, preserved membranous integrity. Later on, fragmentation of the nucleus occur. Four types of endocrine cell were distinguishable on the basis of the size and shape of their secretory granules. Lymphocytes were also demonstrated in the basal region of the mucosal folds.