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FIG. 6. ln situ hybridization histochemistry using a 35S-labeled cRNA localized STS gene expression to connective tissue cells (C) of tadpole
small intestine after thyroid hormone t reatment., whereas STS mRNA was not detectable in untreated tadpoles (not shown). Bl·ight-field and
dark-field photomicrographs of cross sections from the small intestines hybridized with an antisense S1'3 probe (A) but not with a sense probe
(B) showed loosely clustered ST3-e~pressing cells (arrows) in the stroma of the typhlosole, but not in the intestinal epithelium (E). muscle (M),
or lumen (L). (C) At higher magnification, "Mtivated" STS-e:<r>ressing cells appear to be polarized and fibroblast-like (large arrows) and intermixed
with "unactivated"' fibroblast-like ce lls (smaller arrows) that do not ex(>ress detectable levels of ST3 mRNA. Note similar cell types
appear to express STS in mammalian tissue~ and carcinomas (see Discussion). Cali bration bars arc 200 ,.,m (A. B) and 100 ,.m (C). |