Nerve-independent DNA synthesis and mitosis in regenerating hindlimbs of larval Xenopus laevis.

Xenopus laevis larvae at stage 52-53 (according to Nieuwkoop and Faber 1956) were subjected to amputation of both limbs at the thigh level as well as to repeated denervations of the right limb. Results obtained in larvae sacrificed during wound healing (1 after amputation), blastema formation (3 days) and blastema growth (5 and 7 days) showed that denervated right limbs have undergone the same histological modifications observed in innervated left limbs and have formed a regeneration blastema consisting of mesenchymal cells with a pattern of DNA synthesis and mitosis very similar to that in presence of nerves. Also, the patterns of cellular density in regenerating right and left limbs were very similar. On the whole, the data here reported show a highly remarkable degree of nerve-independence for regeneration in hindlimbs of larval Xenopus laevis at stage 52-53 and lend some substance to the hypothesis that, in early limbs, there would exist trophic factors capable of replacing those released by nerves, promoting DNA synthesis and mitosis in blastemal cells.