The role of divalent cations in epidermolysis.

In experiments designed to elucidate the role of divalent cations in maintaining the integrity of the epidermis, newborn mouse skin was incubated in ethylenediamine tetraacetic acid (EDTA) or ethylene glycol tetraacetic acid (EGTA). In EDTA, epidermolysis occurred and was confirmed by rubbing the specimen to demonstrate that a sheet of epidermis could be split off. After 30 min incubation in 0-01 mol/EDTA the split occurred in the lower granular-upper spinous layer; after 45 min, it was in a spinous-suprabasilar location and at 60 min and later at the dermal-epidermal junction.

The effect of MSH on thymidine incorporation by keratinocytes in the epidermal melanin unit.

Epidermal melanocytes were observed in the black but not in the white skin of black-and-white spotted guinea pigs. In experiments designed to determine whether melanocyte-stimulating hormone (MSH) affects the incorporation of thymidine by kerationcyte nuclei of the epidermal melanin unit, the labeling index was the same in all skin before MSH administration. After MSH injections, the level of (3H)thymidine incorporation in keratinocytes increased significantly in black skin but not in white.

The use of ultraviolet light to induce melanogenesis in the epidermis of the rhesus monkey: an ultrastructural and biochemical study.

The general body epidermis of the rhesus monkey (Macaca mulatta) contains no discernible melanocytes, but after repeated ultraviolet irradiation DOPA-positive melanocytes appear and increase numerically up to 30 exposures. With continued irradiation, however, the number again declines. Experiments to determine how melanogenic activity, assayed by the incorporation of labeled DOPA or tyrosine, is related to DOPA positivity indicated that biochemical activity corresponded to the histochemical pattern.

The induction of melanogenesis by ultraviolet light in the pigmentary system of Rhesus monkeys.

Except for the face, eyelids, friction surfaces, and lips, the epidermis of the rhesus monkey contains no discernible melanocytes. After ultraviolet irradiation, however, dopa-positive dendritic cells appeared. With daily sequential irradiation, the number of histochemically demonstrable dopa-positive dendritic cells peaked after 30 exposures, then declined to a basal level which was maintained for the duration of the experiment (216 exposures or 43 weeks).