Fine structure of sensory ganglion cells during limb regeneration of the newt Triturus

The regeneration of the limb of the newt depends upon the nervous system. The fine structure of sensory ganglion cells of the newt Triturus viridescens was studied during limb regeneration to determine whether any changes could be associated with trophic function. Several changes were noted in the cell bodies following amputation of the limb. Lipofuscin pigment bodies are greatly increased in number. Some cells contain giant mitochondria with a diameter of 2 μ and others contain clusters of many small mitochondria. Small Golgi complexes occur in close proximity to the giant mitochondria. Dense membrane‐bounded granules, not observed normally, with a diameter of ∼ 1000A occur in the region of these Golgi complexes. The endoplasmic reticulum becomes more dispersed during regeneration while the ratio of free to attached ribosomes increases. Some cells show extensive chromatolytic changes consisting of dissolution of the endoplasmic reticulum. The structural changes are discussed in relation to the trophic action of nerves and regeneration of the nerve fiber. Changes in lipofuscin granules and mitochondria may be indicative of increased oxidative metabolic activity. The changes in the endoplasmic reticulum and ribosomes are suggestive of a reorganization of the protein synthetic machinery of the cell. The appearance of dense granules in the perikaryon coincides with the accumulation of granules in the peripheral regenerating nerves. These structures may be associated with the formation, transport, and release of a possible trophic substance or hormone.