Fig. 7

Knocking out of TRβ tadpoles reduces epithelial cell death after T3 treatment. A Reduced TUNEL labeling for apoptotic cells in TRβ knockout tadpoles. Cross-sections of the intestine isolated from wild type (a–j) and TRβ knockout (k–t) tadpoles at stage 54 treated with or without 5 nM T3 treatment for up to 5 days were subjected to TUNEL labeling for apoptotic cells and Hoechst 33342 staining for DNA. The dotted lines depict the epithelium-mesenchyme boundary, drawn based on morphological differences between epithelial cells and mesenchyme cells in the pictures of the stained tissues, under enhanced contrast and/or brightness by using Photoshop, if needed. Dashed yellow boxes (d, f, n and p) indicate the higher magnification (i, j, s and t), respectively. TUNEL: green, and Hoechst: blue. T: typhlosole. At least 3 tadpoles were analyzed for each genotype. Bars: 100 µm. B Reduced or delayed cell death in TRβ knockout tadpoles. The TUNEL positive area in A was quantified and normalized against the Hoechst 33342 positive area. Different lower case letters denote statistically significant differences (P < 0.05) when compared in a single genotypes and asterisks (***) indicate a significant difference between the two genotypes (P < 0.001). ns no significant difference