The effects of x‐radiation on limb development and regeneration in Amblystoma

Abstract

Abstract The regeneration of the early fore limb bud of Amblystoma larvae has been prevented by exposure to x‐radiation. Histological studies show that the failure to regenerate is due to a destruction of the undifferentiated mesenchyme cells which normally furnish the materials for regeneration. Data have also been gathered as to the minimal dosage of x‐rays necessary to prevent the regeneration of the early limb bud. By properly governed radiations the development of unamputated limb buds can also be controlled; larvae with permanent two‐, three‐ or four‐digit limbs can be produced. The effect here is primarily on the differentiation processes of the limb. These limbs in which digit formation has been controlled by x‐radiation also fail to regenerate if subsequently amputated. After amputation there is a complete dedifferentiation of all the formed structures of the limb stump. The dedifferentiated cells of the limb stump. The dedifferentiated cells of the limb stump regain their power of mitotic cell division 30 to 35 days after amputation, but are never able to differentiate into the components of a new limb. The primary effects of radiation in this case appears to be on cellular differentiation rather than on cellular proliferation.