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.

Exogenous ochronosis and pigmented colloid milium from hydroquinone bleaching creams.

An outbreak of ochronosis and colloid milium is described after the use of strong hydroquinone bleaching creams. These phenomena developed only after a few years, and took place when the melanocytes had overcome the bleaching influence. Sun-exposure and thorough inunction of the cream were required for the more advanced changes.