Fig. 7

EdU and TUNEL-labeling reveals that apoptotic and proliferating cells are non-overlapping epithelial cells during T3-induced intestinal metamorphosis. Premetamorphic stage 54 tadpoles treated with 10 nM T3 for 0 (A), 3 (B), or 6 days (C) and were sacrificed 1 h after injection with EdU. Cross-sections of the intestine from the resulting tadpoles were double-stained for apoptosis by TUNEL and for EdU. Higher magnifications of boxed areas in (A–C) are shown in (a′–c′). The dotted lines depict the epithelium-mesenchyme boundary (see Fig. 1). Note that apoptosis in the epithelium occurred prior to the appearance of the clusters (islets) of EdU labeled cells and in distinct epithelial cells during T3 treatment (C, c′)