The purpose of this experimental work is to examine the joint formation in limb bud grafts lacking the anterior or posterior necrotic zones where programmed cell death (apoptosis) occurs.
Methods: The embyonic chick limbs were transplanted onto the chorioallantoic membrane. The limbs of experimental group were transplanted without the prospective anterior or posterior necrotic zones. Transplants containing all limb bud material served as the control group.
Results: Most experimental grafts showed wide or complete fussions of the bones forming the elbow joint in the early developmental stages. The regression of the elbow joint in the control grafts was gradually progressive: from the narrow cartilaginous bridges between articular surfaces in early stages to extensive fusion of bone primodia in late developmental stages.
Conclusions: The elimination of the anterior or posterior necrotic zones suppressed apoptosis in the "opaque patch" and caused the fussion of the bones in elbow joint.