On the nature of the neurotrophic phenomenon in urodele limb regeneration

Abstract

The nervous control of regeneration of body parts in the urodele amphibian and other animals has been one of the best model systems for the study of the neurotrophic phenomenon. In the past most of these studies were experimental morphological, but recently the salient problems on the nature of the cellular response to the neurotrophic agent and the nature of the nervous agent itself are also analyzed molecularly. The ensemble of studies reviewed in the present work, which also show that the agent of the nerve is a peptide and defines aspects of its effect on molecular synthesis in regenerate cells, leads me to advance the following theories. I propose that the neurotrophic agent affects only the rate of ongoing events in the cell and not the quality and kind of the events; that the events are already indigenous to the responding cells; that alteration in therate of events, for example increasing the rate of molecular syntheses, yields an increased cell population which by its size and increased cellular interactions has formative and differentiated capabilities which do not exist in a smaller cell population; and finally that the neurotrophic factor (NTF) is one of many "conversational" peptides including nervegrowth factor (NGF) and epidermal growth factor (EGF) which function to alter the absolute rate of ongoing cellular events. © 1978 American Society of Zoologists.