Microdissection by ultrasonication: porosity of the intestinal epithelial basal lamina.

The porosity of the epithelial basal lamina of normal rat intestine was studied by SEM. Epithelial removal was accomplished by prolonged fixation of tissue samples in OsO4 or immersion in aqueous H3BO3, followed by dehydration in acetone and microdissection by ultrasonic vibration. The underlying basal lamina of intestinal epithelium reveals numerous pores of variable size. These pores are more numerous in small than in large intestine and penetrate the entire thickness of the basal lamina. Within the basal lamina overlying lymph nodules, they are numerically increased. Their occurrence is evident in fixed and unfixed, sonicated and unsonicated tissue samples. Microprojections of epithelial cytoplasm are often observed within these pores. The results of this study suggest that migrating cells or epithelial-cell processes induce pore formation in epithelial basal laminae and that these pores may be eventually repaired.