Summary— An unusual form of mycosis fungoides was characterized clinically by the spontaneous resolution of ulcerated nodular lesions into poikiloderma and histologically by a granulomatous malignant lymphoma.

The ultrastructure of the epidermis at different stages of the shedding cycle has been studied in Anolis carolinensis. Cells of the germinal layer are morphologically similar at all stages in the cycle. Immediately after leaving the germinal layer all daughter cells resemble one another closely. However, they later acquire specific ultrastructural features that enable them to be classified into six distinct fully differentiated types corresponding to the grouping previously set forth by light microscopy. A comparison of cytoplasmic filament size with the known X-ray diffraction data suggests that the Oberhautchen and player contain a protein similar to that of avian feather; the protein in the a-layer and lacunar tissue is similar to that in mammalian hair, and the mesos layer cells probably contain a mixture of feather and hair-like proteins, The nature of the amorphous cytoplasmic material i n the mature clear layer is as yet unknown.

Human keratinocytes grown in vitro as epithelial outgrowths or as organ cultures maintain many of their normal functions such as proliferation and keratinization. These in vitro systems have been used to analyze the effect of various agents on proliferation. All adenine nucleotides, including dibutyryl cyclic AMP, blocked mitosis in the G2 part of the cell cycle at concentrations of 1 times 10(-4) M. Some nonadenine nucleotides also showed this effect, but only at higher concentrations, an indication that the effect was specific for adenine nucleotides. Dibutyryl cyclic AMP and theophylline both depressed the incorporation of [3H]thymidine into DNA. Catecholamines such as isoproterenol, epinephrine, and norepinephrine were also potent inhibitors of mitosis (G2 block) at concentrations of 1 times 10(-8) to 1 times 10(-10) M. The fact that the effect could be blocked by the beta-blocking agent, propranolol, suggests the existence of specific membrane receptor sites. However, dichloroisoproterenol, another beta blocker, had distinct inhibitory properties in itself and thus indicated that the mechanism of action of catecholamines in human keratinocytes is complex and may involve more than binding to specific receptor sites. Histamine at a concentration of 2 times 10(-6) M was also a strong mitotic inhibitor. This finding is directly opposed to that in rat skin where mitosis is stimulated. Imidazole acetate, a histamine breakdown product, was found to be a striking mitotic stimulator in organ culture. A water-extractable protein (chalone) from human skin also caused a block in G2. Most of the substances tested occur naturally in the cell or organism and their ability to stimulate or depress proliferation in vitro suggests that they play a regulatory role in vivo.

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