Formation of distal structures from stumps of chick wing buds at stages 24–25 following the grafting of quail tissue from X‐irradiated distal limb buds

Abstract

To examine the regulatory activity of the proximal region of chick limb buds, distal halves of chick wing buds at stages 24-25 were removed, and the distal tips of X-irradiated stage 21 quail limb buds with an apical ectodermal ridge (AER) were grafted onto the chick stumps. The host stumps formed only humerus after removal of the donor distal tips or with tip mesoderm alone. However, when distal tips with an AER were grafted onto the stumps, one or two cartilage elements of host origin were formed at the distal end of the humerus. To examine whether the stump cells have changed to cells of a more distal, progress zone (PZ) cells, the chick stumps with quail tips were immunostained with antibody against AV-1, which reacts with the anterior PZ region of chick limb buds and is specific for an antigen that is expressed under the control of the AER. Within two days of grafting, cells positive for the antigen reappeared in the stump tissues. These results suggest that the some of the stump cells may be converted to PZ cells and their positional values may change to those of more distal structures under the influence of the AER.