“…Embryos exposed to low levels of TCDD, hydrocortisone, or retinoic acid do not develop cleft palate; however, exposure to either compound and TCDD simultaneously produces an incidence of 100% cleft palate (Birnbaum et al, 1986(Birnbaum et al, , 1989. These agents interact to disrupt cellular proliferation and differentiation and these effects are accompanied by altered expression of TGFa, EGF, the TGFPs, and the EGF receptor Birnbaum, 1989, 1990;Abbott et al, 1992). The interaction of A and 8).…”