The influence of host age on the growth of transplanted rat cranial bases and humeri
Harkness, E.M.; Trotter, W.D.
Journal of Anatomy 135(Pt 2): 353-369
1982
ISSN/ISBN: 0021-8782 PMID: 7174508 Document Number: 183894
Cranial bases and humeri from day old rats were transplanted to sex-matched isohistogenic weanling and adult hosts and recovered 14 and 28 days later. Both the cranial bases and the humeri increased in length substantially and in the same proportion during the period of transplantation. Growth in length of cartilage bones evidently is largely determined by factors intrinsic to the transplants; the host environment appears to play only a minor part. After both 14 and 28 days of transplantation there was no difference between weanling and adult hosts in the overall lengths of the basi-occiput, the basisphenoid and the humerus in the transplants. However in cranial bases recovered from the adult hosts after 28 days of transplantation the ossified portion of the basi-occiput was significantly longer and the ossified portion of the basi-sphenoid significantly shorter than in cranial bases recovered from the weanling hosts. These differences in lengths of ossified basi-occiput and basisphenoid are attributed to a postulated slower resorption rate in the transplants than in the adult hosts. The thickness (i.e., rostrocaudal length) of the spheno-occipital synchondrosis was significantly greater in 28-day transplants from adult hosts than in those from weanling hosts; this difference was due to a greater amount of matrix in the central zone of the synchondrosis. A full explanation of these latter findings must await further clarification of the mechanisms controlling growth and metabolism in the basicranial synchondroses, but some of the possibilities are discussed. The basi-occiput and the shaft of the humerus were significantly wider in the 14-day transplants recovered from the weanling hosts. These differences were attributed to the greater weight of the skin in the adult hosts flattening the transplants.