Cytochemical and scanning electron-microscopic analysis of apoptotic cells and their phagocytosis in mucoid epithelium of the mouse stomach.

The formation of apoptotic cells and their phagocytosis by viable neighbouring cells in the gastric epithelium of 2- to 6-day-old mice was analysed. In order to observe the topographic relationship between apoptotic and normal epithelial cells using scanning electron microscope, the critical-point dried tissues was cracked before coating with gold. Cytochemical methods for the identification of surface carbohydrates and different tracers for apical and lateral cell membranes were applied for the analysis using the transmission electron microscope. Apoptotic cells were found on apical and lateral surfaces; this indicates the presence of tight connections with viable cells at some points. Ruthenium red strongly stained all accessible surfaces of normal cells and of apoptotic bodies. The quantity of neutral mucosubstances, as revealed by staining with tannic acid-uranyl acetate, seemed to decrease in the glycocalyx of apoptotic cells. The scanning and transmission electron-microscopic results suggest that the phagocytotic vacuoles arise at the lateral side of the cells. The phagocytotic activity is not dependent upon a definite differentiation step of the mucoid cell.