To Keep Warm, You Can't Regenerate Your Heart, But Salamanders And Zebrafish Can

I spent today mostly reading Waiting For Snow In Havana."  My book club meets tomorrow and I had a lot of pages left.  I finished it and there is much that is good in the book, but I think a good editor could have helped Carlos Eire cut lots of pages.

So I don't have the creative energy to do much here.  I did jot this done recently and so I'll leet you off easy.  A brief contemplation about your heart.

From Science:

"The price of staying warm
Among vertebrates, zebrafish and salamanders can regenerate their hearts, whereas adult mice and humans cannot. Hirose et al. analyzed diploid cardiomyocyte frequency as a proxy for cardiac regenerative potential across 41 vertebrate species (see the Perspective by Marchianò and Murry). They observed an inverse correlation of these cells with thyroid hormone concentrations during the ectotherm-to-endotherm transition. Mice with defects in thyroid hormone signaling retained significant heart regenerative capacity, whereas zebrafish exposed to excessive thyroid hormones exhibit impaired cardiac repair. Loss of heart regenerative ability in mammals may represent a trade-off for increases in metabolism necessary for the development of endothermy."