Origin of Regeneration Cells of Blastema
The origin of the cells making the blastema in vertebrates has been investigated by various workers in the case of regenerating legs of salamanders and newts. Their studies have depicted that cells which form the blastema are of local rather than of systemic origin. To come to this conclusion they have performed various irradiation experiments on urodeles. It has been observed that appropriate dose of x-rays supress the capability of urodeles to regenerate.
Figure: Histological sections of regenerating newt limbs
By using this knowledge scientist found that those urodeles whose bodies were irradiated failed to regenerate their limbs after amputation. Similarly, irradiated limbs also failed to regenerate upon consequent amputation. Though if the limb was shielded from the x-rays while the rest of the body was irradiated then regeneration proceeded normally in the limb while the limb was amputated. If only a portion of limb for example the knee joint was irradiated, after that regeneration of the limb took place only if the amputation was done above or below the irradiated segment and not through it. Figure displays some of the irradiation experiments performed on the urodeles. These experiments clearly depicted the local origin of the cells of the blastema.