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The biochemical characteristics of cyclic 3',5'-nucleotide phosphodiesterase were studied in homogenates of male albino rat skin using preparations which were predominantly epidermal. Enzymatic activity was detected in both the particulate and soluble fractions of these skin homogenates. Two kinetically distinct phosphodiesterase (PDE) activities were detected in the soluble fraction (100,000 times g supernatant). This 100,000 times g supernatant contains at least two distinct protein bands that hydrolyze cyclic AMP as demonstrated by gel electrophoresis. Divalent cations (Mg-++ or Mn-++) and 2-mercaptoethanol were required for maximal enzymatic activity. Epinephrine, dibutyryl cyclic AMP, and methylxanthines inhibited while imidazole and histamine phosphate stimulated the cyclic AMP phosphodiesterase activity at high and low cyclic AMP concentrations. Cyclic GMP competitively inhibited hydrolysis of low, but not high, concentrations of cyclic AMP. Hydrocortisone phosphate in pharmacologic concentrations blocked PDE denaturation by heat. These studies indicate that there are complex interrelationships between cyclic nucleotides and PDE in rat skin.

Light and electron microscopic observations were made on seventeen palmar or plantar pits of the nevoid basal cell epithelioma syndrome. In two specimens, typical basal cell epitheliomas were seen arising from the epithelium at the base of the pits; one of them was a pigmented basal cell epithelioma. The epithelium under the pit was stained only weakly with azure B; this was attributed to a very poor development of tonofibrils. Keratohyaline granules were small and the discharge of the cementsomes was incomplete. Premature desquamation of the horny cells took place along the intercellular spaces and was not due to degeneration of horny cells. It was thought that incomplete discharge of cementsomes, perhaps due to shortened transit time of keratinocytes, failed to provide enough intercellular cement. Surrounding the rete ridges and particularly surrounding the fully grown tumor, collagen stroma showed various degrees of dissolution.