ABSTRACT
Differentiation of rat embryonic shields in vitro is inferior to that obtained in grafts under the kidney capsule. To see whether the in vitro differentiation is stable or whether it can be improved in a better environment, rat embryonic shields, isolated on gestation days 8 and 9, were transplanted under the kidney capsule after a period of 7 or 14 days in vitro.
After transfer, some tissues appear in the kidney that never appear in vitro. Many but not all tissues appear more frequently in grafts than in vitro. Most tissues differentiate further in grafts than in vitro, though skeletal muscle, when cultivated for 14 days before transplantation, is an exception.
Thus the effect on differentiation of imperfect culture conditions can be counteracted, for some tissues but not all, by grafting to the kidney. The effect depends partly on the time spent in vitro before transfer.
