Dedifferentiation and mitotic activity in amputated newt tails locally deprived of the spinal cord (Including a note on effects of amputation level on mitosis)

The spinal cord of freshly amputated newt tails was displaced cranially by pushing several paraplast chips into the spinal canal with a glass needle. That part of the canal formerly occupied by the spinal cord was then packed with paraplast. Tails treated in this manner failed to regenerate, forming no more than a millimeter of new tissue with little or no cartilage and muscle. Dedifferentiation and early mitotic activity, however, was normal, indicating that the spinal cord exerts its effect on tail regeneration in the later stages. Amputation through the proximal region of a vertebra led to a significantly lower mitotic rate at four days than did amputation through the distal region, a situation contrary to the principle that during regeneration, elongation rate is gennerally faster from proximal than distal levels.