9407348 Callard In all egg laying vertebrates and many viviparous non- mammals, development of eggs depends upon yolk, made in the liver under estrogenic control and deposited in the ovary. In contrast, in some placental non-mammals (viviparous or live bearing species) and all eutherian mammals, yolk protein is either variably or totally suppressed. Dr. Callard has shown that suppression of yolk protein synthesis associated with viviparity is due to progesterone, the major ovarian steroid of gestation. In this proposal, he will investigate the cellular and molecular basis of the progesterone counter-regulatory function using a fish model. ***
