The ultrastructure of the human epidermis following ultracentrifugation

Ultracentrifugation of the human epidermis was undertaken to uncover the forces responsible for the establishment and maintenance of the supranuclear melanin cap in basal cells. The wide spacing and elasticity of the tonofibrils caused a selective trapping of melanosomes in this region. At the same time the experiments produced pictures resembling dedifferentiation of the plasma membrane as in the fetal state, and differentiation of the tonofibrillar mass resembling the granular and horny layers. Once the tonofibrils had retracted and massed together, the order of intracellular sedimentation was: melanosome, chromatin, mitochondrion, tonofibril and ribosome.