The effects of vitamin A on blastemal epidermis were studied during the early postamputational period of forelimb regeneration in Triturus alpestris. Vitamin A was administered through oral intubation at a dose of 250 IU per gram of body weight per day. The results were evaluated by morphometry, histology, and autoradiography. After 7, 11 and 14 days of treatment, several alterations were observed in the wound epidermis: a) reversal of keratinization; fewer keratinized cells were counted in

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... ions from vitamin A-treated limbs; b) decrease in the incorporation of tritiated thymidine, as judged by estimation of labeling indices; c) increased mitotic activity in the cells of the stratum germinativum, and in the middle layer of the epithelial cells, as well. The significance of these cellular effects is discussed against the relevant literature.