Changes in intercellular junctions during peripheral nerve regeneration in insects.

Peripheral nerves of the adult cockroach have been cut and the changes in glial cells followed during the subsequent process of regeneration. After three to four weeks of regrowth, the severed tips of nerves were examined by freeze-fracture to assess the state of intercellular junctions between the perineurial sheath cells as well as the underlying glial cells. Both pleated septate and gap junctions were found in the immature state; their intramembranous particle (IMP) distribution was characteristic of junctions in the process of assembly, since the IMPs were irregularly and loosely arrayed in contrast with the parallel septate junctional IMP rows and gap junctional plaques found in the fully regenerated or control tissues. These junctional stages resembled those occurring in developing embryonic or metamorphosing insect tissues.