Growth spurt in rat cranial bases transplanted into adult hosts.

The growth of young rat cranial bases, consisting of the basioccipital, basisphenoid and a fragment of presphenoid bones, transplanted to older sex-matched isohistogenic hosts has been studied longitudinally. Detailed figures are given for absolute growth and velocity of growth both in transplants and in situ. Similarities between the pattern of growth of basisphenoid and in particular the timing of the so-called adolescent growth spurt in the transplanted bones and in situ were found. There was less similarity in the pattern of velocity changes in basiocciput. This was attributed to resorption of basion in the transplants. Significant negative correlations were found between host age and basioccipital length in the females and the velocity of growth of the basisphenoid in the males between 47 and 54 days. There was also a trend for host age to be negatively correlated with basisphenoid length in the males. These findings support the view that intrinsic, presumably genetic, factors regulate the pattern of timing of growth velocity changes in the cranial base.