Partial denervation effects on limb cartilage regeneration.

Partially innervated axolotl arms gave regenerates of reduced size with deficient skeletal element replacement. This deficiency was most pronounced when nerve 4 (the largest of the brachial nerves) estimated to make up 50-60% of forelimb axons was removed by repeated resection. Nerve 3 or 5 removal gave less pronounced reduction deformities in the newly formed regenerate. The dependency of skeletal element formation upon nerves is emphasized but does not follow a strict segmental subtraction in axolotl forelimbs--perhaps because of overlapping innervation of nerves 3, 4, and 5 to all four digits. These effects of partial innervation add tentative support for an hypothesis of neurotome subtraction that was proposed to account for the syndrome of thalidomide abnormalities.