Fig. 6. TH upregulates Msi-1 expression in adult progenitor cells of isolated intestines in vitro in the presence of the connective tissue (A-F) but not in its absence (G,H). Cross-sections were immunostained with Msi-1 (C,D,F,H), PCNA (B) and IFABP (E) antibodies and stained with methyl green-pyronin Y (A,G). (A-C) Day 5 in the presence of TH. Adult progenitor cells, which are identified as islets between the larval epithelium (LE) and the connective tissue (CT), are actively proliferating and positive for Msi-1 (arrowhead). (D) Day 5 in the absence of TH. The larval epithelium remains negative. (E,F) Day 7 in the presence of TH. The adult epithelium is differentiated into the absorptive epithelium expressing IFABP and negative for Msi-1. (G,H) Day 5 in the epithelium (E) alone in the presence of TH. Some cells of the simple epithelium are negative for pyronin-Y staining (arrow), whereas the others are positive at various intensities. The epithelium remains negative for Msi-1. Bars, 20 µm.