The influence of local environment on the organization of mesenchyme cells.

Limb, somite, and neural crest mesenchyme from quail embryos were implanted orthotopically and heterotopically into chick hosts to ascertain the relative importance of the local environment on mesenchyme migration. It was found that mesenchyme behavior is strongly influenced by the environment. Normally non-migratory, limb mesenchyme is capable of spreading like sclerotome when placed in the somite region. A somite placed in the limb acquires an appearance typical of limb mesenchyme. Neural crest placed in the limb migrates only along the co-implanted neural tube or axons growing out from it. The orthotopic transplantations showed that quail mesenchyme behaves normally in chick embryos. Furthermore, it was observed in the orthotopic transplants that there was no intermingling of quail and chick cells even at the edge of the graft. This result indicates that cells within mesenchyme are normally not locomotory; rather, the mesenchyme "migrates" by spreading and expansion of the tissue as a unit in response to local influences.