Decrease In Labeling Index Research Articles

Changes in rate of cellular proliferation during the differentiation of cartilage and muscle in the mesenchyme of the embryonic chick wing

Summary Changes in the rate of cell division in the embryonic chick wing bud during the first 48 hours of wing development have been described using autoradiographic techniques. The tritiated thymidine labeling index decreased in all regions of the wing between stage 21 and stage 23. Continuous tritiated thymidine labeling experiments showed that the decrease in labeling index was almost entirely due to a cessation of cell division by some fraction of each of the cellular populations studied. At stage 19, the proliferative index in all regions of the wing is 100%. At stage 24, the proliferative index in the dorsal proximal, ventral proximal, and subridge regions was 75%, and the proliferative index in the cartilage-forming region was 25%. Graphical analysis of the continuous labeling data showed that there is very little change in the length of the cell cycle or its component phases during this period of embryonic development.