Figure 10. VIP stimulates growth during the early postimplantation period of embryogenesis (62). Embryonic day (E) 9 mouse embryos, 15 to 18 somites in size, with yolk sac and ectoplacental cone intact, were cultured for four hours in serum alone or in the presence of various concentrations of VIP or 10-7 M secretin at 37o C, gas phase 5% CO2 and 95% O2. Membranes have been removed to permit viewing and size comparisons among the embryos. 1. Typical appearance of E9 embryo before whole embryo culture (T0). 2. Typical appearance of E9 embryo after four hour culture in serum alone (C). 3.–5. Typical appearance of E9 embryos after four hour culture in secretin (SEC) or increasing concentrations of VIP.