The cell cycle during amphibian limb regeneration

Abstract

The duration of the cell cycle in the blastema of regnerating limbs of axolotls has been measured by means of [3H]thymidine pulse labelling and autoradiography. A chase was required to define the pulse period. An average cell cycle at 20°C takes 53 h, S phase takes 38 h; including parts of mitosis, G1 is 10 h and G2 is 5 h long. The protracted cycle and S phase are consonant with the large genome in axolotls and other urodeles. The rapidly growing blastema probably contains a steady population of about 5000 proliferating cells, as there is a regular withdrawal of differentiating cells from the population. The kinds of determination which exist in this population of cells, or are exerted on it, are briefly considered.