The role of the lizard thyroid gland in tail regeneration

Abstract

Hypothyroidism in Anolis carolinensis caused almost a two week delay in blastema formation and tail elongation was completely inhibited. Hormonal replacement therapy (L-thyroxine) in hypothyroid lizards allowed for normal blastema formation as well as subsequent tail elongation.Hyperthyroidism in Anolis initiated the early development and subsequently the early completion of blastema formation but had no significant effect on tail elongation.Histological observations in the hypothyroid regenerates when compared with those receiving thyroxine replacement revealed that: (a) the inhibition of tail elongation was due to an inhibition of the outgrowth of the ependyma into the developing blastema; (b) although tail elongation was inhibited in hypothyroid lizards, many tissues within the blastema did differentiate along the same time course as those found in hormonal replacement regenerates and controls; thus, thyroxine apparently had little to do with tissue differentiation in these animals.Hypophysectomy was found to delay blastema formation by one and one-half weeks and to inhibit tail elongation in the same manner as was found in hypothyroid lizards. A dose response relationship was found to exist between certain levels of thyroxine (0.04 to 0.2 pg) and tail regeneration in hypophysectomized lizards. The intermediate dose of thyroxine (0.2 pg) produced a maximum response with respect to lizard tail elongation. A greater dose of thyroxine (1.0 pg) did not further augment the regeneration process and any greater dose would likely produce an inhibitory effect.

The Purification and Properties of an NADPH‐Linked Aldehyde Reductase from Pig Brain

“…The properties of this enzyme are discussed with reference to biogenic amine metabolism and are related to the properties of NADPH-linked aldehyde reductases studied from other sources [14-171. A preliminary account of this work has already been presented [18].…”

In vitro assays for characterization of distinct multiple catalytic activities of thyroid peroxidase using LC-MS/MS

“…Assays that detect the generation of THs and their intermediates in thyroglobulin are limited by longer time reactions, cumbersome isolation, and analysis of thyroglobulin as well as their low sensitivities. Some of the published methods, also involve the use of radioactive iodine for the TPO assay ( Turner and Tipton, 1971 , Vannucchi et al, 2009 ). HPLC or LC-MS based assays that study L-Tyr conversion into MIT and DIT fill this gap and have been described before ( Divi and Doerge, 1996 , Freyberger and Ahr, 2006 , Kasai et al, 1989 , Price et al, 2020 ).…”

Appendage regeneration in anamniotes utilizes genes active during larval‐metamorphic stages that have been lost or altered in amniotes: The case for studying lizard tail regeneration

“…There is also a size limit to regeneration as no organs or appendage wider than 1–2 cm can regenerate, keeping the outgrowth size to an embryonic dimension (Alibardi, 2018a). The regulation of metamorphosis through TH hormones also occur during regeneration since the disruption of the thyroid gland determines regeneration failure in fish, amphibians and lizards (Furlow & Neff, 2006; McMenamin & Parichy, 2013; Rhamachandran & Kurup, 2006; Schmidt, 1968; Turner & Tipton, 1971). Like in fish and amphibians, some thyroid related genes in lizards such as thy1 , cga , and dio2 are up‐regulated during tail regeneration (Hutchins et al, 2014).…”