Growth of the cartilages of the mid-line cranial base: an autoradiographic study using tritium labelled thymidine.

Proliferative and kinetic activity of chondrocytes in five sites of endochondral growth in the mid-line cranial base of the rat have been studied using a single injection of 3H-thymidine in animals aged 4-80 days. The marked caudorostral gradient and temporal gradient of the labelling index and labelling profiles is indicative of a proliferative activity specific to each endochondral growth site. Measurements of the growth rate indicate that each growth site in the cranial base bones has a specific growth rate.