CELL-CYCLE CHANGES AFTER DENERVATION OF THE NEWT LIMB REGENERATE, STUDIED INVITRO

The proliferation of the mesenchyme of medium bud stage blastemas of Pleurodeles, measured by 3H-thymidine incorporation and mitotic index, decreases about 40-50% under denervated conditions when cultivated in vitro for 4 days; epidermis is not affected in this case. Autoradiography of blastemas after 3H-thymidine long-term labeling shows that 3/4 of the mesenchymal cells and 1/4 of the epidermal cells are cycling when the blastema is innervated; there is no significant change of these percentages when the blastema is denervated. The results show, contrary to in vivo experiments, that denervation does not provoke an exiting from the cell-cycle but only lengthening of the cycle of the mesenchymal cells (probably of the G1 phase).