Increased slow transport in axons of regenerating newt limbs after a nerve conditioning lesion

Dev Biol. 1990 Jul;140(1):172-81. doi: 10.1016/0012-1606(90)90064-p.


We have previously shown that a nerve conditioning lesion (CL) made 2 weeks prior to amputation results in an earlier onset of limb regeneration in newts. Studies in fish and mammals demonstrate that when a CL precedes a nerve testing lesion, slow component b (SCb) of axonal transport is increased compared to axons that had not received a CL. We wanted to know whether the earlier initiation of limb regeneration after a CL was associated with an increase in SCb transport. The transport of [35S]methionine labeled SCb proteins was measured by using SDS-PAGE, fluorography, and scintillation counting. The rate of transport and quantity of SCb proteins was determined at 7, 14, 21, and 28 days after injection of [35S]methionine into the motor columns of normal; single lesioned (i.e., transection axotomy, amputation axotomy, or sham CL followed by amputation); and double-lesioned limb axons (i.e., nerve transection CL followed 2 weeks later by amputation axotomy). The rate of SCb transport in axons of unamputated newt limbs was 0.19 mm/day. There was an increase in the amount of labeled SCb proteins transported in axons regenerating as the result of a single lesion but no acceleration in the rate of SCb transport, which was 0.21 mm/day in axons that received a sham CL followed by limb amputation. The rate of SCb transport doubled (0.40 mm/day) and the amount of labeled SCb proteins being transported was increased when amputation was preceded by a CL. This study demonstrates that the earlier onset of limb regrowth, seen when amputation follows a CL, is associated with an increased transport of SCb proteins. This suggests that limb regeneration is, in part, regulated by axonal regrowth. We propose that the blastema requires a minimum quantity of innervation before progressing to the next stage of limb regeneration, and that the transport of SCb proteins determines when that quantity will be available.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / pharmacokinetics
  • Animals
  • Axons / physiology*
  • Calmodulin / pharmacokinetics
  • Carrier Proteins / pharmacokinetics
  • Electrophoresis, Polyacrylamide Gel
  • Extremities / physiology*
  • Microfilament Proteins / pharmacokinetics
  • Microtubule-Associated Proteins / pharmacokinetics
  • Regeneration*
  • Salamandridae
  • Tubulin / pharmacokinetics


  • Actins
  • Calmodulin
  • Carrier Proteins
  • Microfilament Proteins
  • Microtubule-Associated Proteins
  • Tubulin
  • fodrin