The role of irradiated tissue during pattern formation in the regenerating limb.

The amphibian limb regeneration blastema is used here to examine whether irradiated, non-dividing tissue can participate in the development of new pattern of morphogenesis. Irradiated blastemas were rotated 180 degrees on normal stumps and normal blastemas rotated on irradiated stumps. In both cases supernumerary elements developed from the unirradiated tissue. The supernumeraries were defective but this did not seem to be due to a lack of tissue. Rather it suggested that this could be a realization of compartments in vertebrate development or simply reflect the limited regulative ability of the blastema. The results are also discussed in relation to a recent model of pattern formation.