Brown DD and Cai L (2007), Amphibian metamorphosis.

XB-ART-52219

Dev Biol 2007 Jun 01;3061:20-33. doi: 10.1016/j.ydbio.2007.03.021.

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Amphibian metamorphosis.

Brown DD , Cai L .

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Species referenced: Xenopus
Genes referenced: thra thrb tshb

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	Fig. 1. Schematic representation of some key events during X. laevis tadpole development. The time post fertilization is on the x axis. Above the line are “tadpole” blots of animals incubated for 24 h with Na 125I, fixed with formaldehyde, and washed to lower background (see Brown, 1997for the method). The tadpoles were dried on filter paper and filmed. X. laevis has 2 thyroid glands located on either side of the midline (solid arrow). The first incorporation of iodine into the thyroid gland occurs 10 days after fertilization (NF46). The solid line represents the concentrations of both TH and TRβ during development. TRβ is a direct response gene of TH.
	Fig. 2. The negative feedback loop between the thyroid gland and the anterior pituitary regulates the circulating levels of T4. Throughout tadpole growth TSH is secreted by the anterior pituitary and stimulates the thyroid gland to synthesize increasing amounts of T4. However, TSH production is not shut down until D2 is up-regulated at metamorphic climax in the anterior pituitary (Huang et al., 2001) and converts local T4 to the active hormone T3. This figure shows where pharmacological inhibitors interfere with the formation or inactivation of thyroid hormone.
	Fig. 3. Limb phenotypes at climax (NF62). (A) Control. A dominant negative form of the thyroid receptor is expressed in (B) neural tissue; (C) collagen and skeletal structures; (D) muscle. This figure was taken from Brown et al. (2005). Scale bar: 2 mm.
	Fig. 4. Skin remodeling. The tadpole epidermis (upper) has 3 cell layers covering a collagen lamella and contains no glands. The cells in all three layers replicate. At climax (middle) a dermis forms, and two different kinds of skin glands appear for the first time. The skin becomes a germinative epithelium with replication only in the basal cell layer.

References [+] :

Allen, Transgenic Xenopus laevis embryos can be generated using phiC31 integrase. 2005, Pubmed, Xenbase