Changes in the structure and chemical composition of the mandibular condylar cartilage of the neonatal mouse.

The cartilage of the mandibular condyle of growing mice was used to monitor changes in the content of protein, DNA, hydroxyproline, hydroxylysine, uronic acid, calcium and phosphate. Protein and DNA increased in a stepwise fashion with one spurt seen during the first 2 weeks of post-natal life a second immediately after weaning. Hydroxyproline increased during the entire growth period, i.e. until the 8th post-natal week. Hydroxylysine increased only until week 4. The content of the uronic acid fluctuated and showed highs and lows throughout the growth period. Both calcium and phosphate increased in an almost parallel fashion from birth until the stage of tissue maturation. Morphological studies indicated that the hyaline type of cartilage in the newborn is gradually replaced by a fibrous tissue, which reveals a markedly different structure and composition.