Figure 2.

The critical window of vulnerability to PTU is from st. 8 to 12.5. Embryos were exposed to PTU (1 mM) or vehicle over different stages of development and scored at st. 45 for gut defects (A), heart defects (B), and L-looping (C); see Table 3. Tadpoles (st. 45) treated with PTU (1 mM) during st. 8–12.5 showed 3 types of abnormal phenotypes: gut miscoiling (E), L-looped heart and gut miscoiling (F), and complete situs inversus (G). Note that the vehicle picture was taken from a different angle to visualize the OFT and note that one embryo can have different malformations. All malformations were scored and counted individually. G, gut; OFT, outflow tract; V, ventricle. *P < 0.0001; 2-way ANOVA with Bonferroni posttest.