The role of interstitial cells in the maintenance of hydra. IV. Migration of interstitial cells in homografts and heterografts

Abstract

Abstract Normal and mustard‐treated halves of Hydra pseudoligactis and Hydra pirardi were grafted in distal‐proximal combinations. In all cases H. pseudoligactis grafted more readily than H. pirardi. Mustard‐treated H. pseudoligactis were grafted to normal H. pseudoligactis after various intervals from the time of treatment. Interstitial cells migrated from the normal portions into treated portions lacking them and within 5 to 10 days the animals appeared normal. Normal portions of H. pseudoligactis and H. pirardi were grafted together and in some cases they remained attached for 60 days. Large numbers of interstitial cells accumulated in each portion, near the graft junction. After 15 days, some of these interstitial cells differentiated into cnidoblasts. Interstitial cells migrated from a normal portion of H. pirardi into a mustard‐treated portion of H. pseudoligactis. Differentiation of interstitial cells into cnidoblasts was observed in the host tissue. In heterografts between normal H. pseudoligactis and mustard‐treated H. pirardi there was no exchange of interstitial cells. There was, however, an accumulation of interstitial cells near the graft junction. In both species successful homografts were made between mustard‐treated portions, indicating that interstitial cells are not required for acceptance of grafts. Grafts between mustard‐treated H. pirardi and mustard‐treated H. pseudoligactis showed less initial acceptance than any of the other groups. The rate of detachment was very high in this group. It was suggested that mustard treatment may inhibit production of substances required for adherence of cells. The results are discussed in terms of possible mechanisms controlling interstitial cell migration, division and differentiation.