Amphibian Limb Regeneration and its Relation to Nerves

Much circumstantial evidence points to a neurotrophic influencein amphibian limb regeneration. Although fine-structural observationsof nerves in regenerating limbs have indicated the possibilitythat neurosecretory vesicles accumulate distally in these axons,there is no clear-cut demonstration available that these organellesare neurotropic. Evidence is accumulating that the neural influencein newt limb regeneration is transneuronal. There is also evidencethat trophic substances other than those found in the nerveitself may be involved in the supporting limb regeneration.The characterization of the neurotrophic substance is considereda central task for students of regeneration in the future.