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Fig. 1. Clustering of β-cells during spontaneous and T3-induced metamorphosis of X. laevis. (A) premetamorphic tadpoles (NF54); (B) froglet (NF66). A and B panels are stained with an insulin antibody (red) and DAPI (blue). (C) Average number of insulin cells per islet increases as the animal proceeds to metamorphosis. The pie-diagram above each bar represents the distribution of the different sized clusters marked with different colors as described in the insert. For example the blue color represents the fraction of total islets that consist of 1–5 β-cells. (a) The average cluster sizes at prometamorphosis and in the methimazole arrested animals is significantly higher (p < 0.05) than that of premetamorphic stages. Rearing tadpoles in methimazole (MMI) inhibits TH-induced changes including enlargement of islets. (b) The cluster size in froglets is larger than any of the tadpole islet sizes. (D) Exogenous triiodothyronine (T3) induces an increase in β-cell cluster size in premetamorphic tadpoles. Premetamorphic tadpoles were exposed to 10 nM T3 in rearing water and the insulin cluster sizes were calculated at 3 and 6-day of exposure and compared with the cluster size of control animals. There was a significant increase in cluster size on the 6th day of T3 treatment (p < 0.05). Scale bar (A and B) 20 μm. |
