Growth of transplanted tails of infant rats in adolescent allogeneic recipients.

The tails of newborn rats, consisting of slender continuous cones of avascular cartilage, were transplanted in subcutaneous spaces of allogeneic adolescents; colloidal carbon was injected in a vein before the transplants were harvested on days 7-28. Between 97 and 100% of the transplants were accepted, underwent differentiation into bone with bone marrow, and grew at a brisk rate. Acceptance was recognized by (i) a zebra-stripe effect, visible in the gross, resulting from accumulation of carbon in reticuloendothelial cells; (ii) increase of alkaline phosphatase [or-thophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] and of incorporated 45Ca in the transplant; and (iii) the presence of dense cortical bone with lacunae populated with osteocytes demonstrable by histology. Differentiation of the cartilaginous transplant into bone with subsequent growth of the transplant occurred in recipients fed sucrose as their sole ration.