Desmosome Differentiation During Epidermal Cornification: New Observations Obtained from Intermediate Voltage Electron Microscopy

Human epidermis was examined under 400-kV intermediate voltage electron microscopy using epon sections cut 5–8 times thicker than usual ultrathin sections. Asymmetry of desmosomal structures occurred as cells became cornified. Electron-dense proteins deposited at the inner leaflet of the plasma membrane of corneocytes do not extend into the desmosomal area, which connects to granular cells. Stereo micrographs revealed the existence of two different cellular elements at the cell surface confirming that the plasma membrane first thickened in areas without desmosomes. Examination of the three-dimensional nature of desmosomes and keratin-filament aggregation without serial sectioning and/or selecting a strict angle of the tissues will allow us to extend our ultrastructural knowledge