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Fig. 7. (A) Thyroid hormone receptor alpha (TRα) mRNA colocalizes with BrdU-ir in tadpole brain. Premetamorphic (NF stage 52) tadpoles were treated as described for Experiment 3 (see Fig. 1). Dual labeling histochemistry was conducted for TRα mRNA (red; by ISHH) and BrdU (green; by IHC) on sagittal sections of T3-treated tadpole brain (regions shown are the diencephalon and cerebellum). Sections were analyzed by confocal microscopy. Note the colocalization of TRα mRNA and BrdU-ir in cords of cells adjacent to the ventricles. Hypo, hypothalamus; Pit, pituitary. Scale bar = 50 μm. (B) Treatment with T3 increases TRβ immunoreactivity (ir) in tadpole brain, and TRβ is excluded from the majority of BrdU-positive cells. Premetamorphic tadpoles (NF stage 52) were treated as described for Experiment 3 (see Fig. 1). Dual fluorescent immunohistochemistry was conducted for BrdU (green) and TRβ (red) without (1–3) or with (4–6) T3 treatment. Sections were analyzed by confocal microscopy. Shown is the region of the thalamus and optic tectum in the sagittal plane. In untreated tadpoles few BrdU-ir or TR-ir cells are detected (1 — TRβ, 2 — BrdU, 3 — merge), but T3 treatment significantly increased TRβ-ir (4 — TRβ) and cell proliferation (5 — BrdU). Only a small proportion of BrdU-ir cells express TRβ, as indicated by the yellow cells (6 — merge). Scale bar = 50 μm. |
