The establishment of the cartilage pattern in the embryonic chick wing, and evidence for a role of the dorsal and ventral ectoderm in normal wing development.

Abstract

Abstract Previous investigations have indicated that the limb bud behaves as a mosaic after some experimental manipulations and regulates after others. In light of new maps of the prospective cartilage-forming regions of the chick wing, we have reinvestigated the stability of the limb pattern by two experimental procedures. First, the prospective long bone regions were excised to examine the ability of the cells outside of the prospective long bone regions to form normal long bones. Second, the mesoderm, mesoderm + dorsal and ventral ectoderm, or dorsal ectoderm (with a small amount of subjacent mesoderm) of the prospective elbow region were rotated 180° to examine the ability of the limb to control and regulate the differentiation of the cells in the limb. We can conclude from these experiments that the cartilage-forming regions of the limb mesoderm gradually become stabilized between stage 22 and stage 24, and that the stabilization is due to the advanced state of differentiation and to the decreased rate of cell division after stage 22. In addition, the dorsal and ventral ectoderm have been shown to aid in stabilization of the cartilage pattern and to influence the development of the humerus. We conclude that the dorsal and ventral ectoderm play a significant role in limb development.