The effects of nerve growth factor on bullfrog tadpoles (<i>Rana catesbiana</i>) after limb amputation

Abstract Tadpoles of the bullfrog, Rana catesbiana , lose the ability to regenerate limbs at a very early stage of development. Non‐regenerating limbs either show rapid healing of connective tissue over the cut surface with no breakdown of skeletal structures, or else show dedifferentiative processes in the cartilage but the rudimentary blastema formed does not proliferate, and becomes separated from the epidermis by the regrowth of the connective tissue layer. This condition is termed the “critical stage.” When tadpoles were treated with NGF, enlargement of spinal ganglia resulted due to an increase in cell number. The density of nerve fibers in the limbs was likewise increased. This increase in nerve supply to the limbs resulted in a greater incidence of critical stage limbs over non‐regenerating ones, and in several cases, produced limbs which appeared histologically to be, in fact, regenerating.

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