Multivesicular bodies in the transitional epithelium of the neonatal mouse urinary border

The origin of late endosomes - multivesicular bodies (MVBs) in the superficial cells of 16 and 17 embryonic old transitional epithelium of mouse urinary bladder was studied by electron microscopy, lectin labelling and HRP tracing. Analysis of hexagonally structured membrane particles, WGA, and RCA I binding sites revealed structural similarity between plasmalemma, fusiform vesicles and multivesicular bodies. Early endosomes are lined by symmetric unit membrane as well as by asymmetric thickened membrane regions. Multivesicular bodies and fusiform vesicles have asymmetric unit membranes. MVBs may be derived from primary endosomes as well as from fusiform vesicles in the cytoplasm.