A somewhat meandering article from the Boston Globe looks at the state of regenerative medicine: "Cut an arm off a starfish, and an exact duplicate emerges. The salamander, upon losing a tail, sprouts another. The conventional thinking has been that we, along with all other mammals, lost the ability to regrow entire organs and limbs. Yet there are exceptions. Deer show off new antlers every year. Even children retain vestiges of regenerative capacity: Up to an age of between 7 and 11, if a child loses the top third of a finger, that tip will reemerge. How can we, [like] starfish and salamanders, harness the power of regeneration? ... Each and every cell has an electric flow across its membrane ... researchers have known for some time that the site of a wound produces an electrical field. But only recently have research instruments allowed this flow to be investigated at the molecular level. ... electrical signals tell cells what to repair and how to re-create what was lost. Levin deciphered one of those cues, a protein in a tadpole that creates a flow of protons, which produces an electric field at the site of a lost tail, starting a voltage flow. ... If you block that flow, the tail won't grow back. ... Levin took a tadpole that matured past the ability to regenerate a lost tail. He removed the tail, then manipulated proteins to turn on the switch. [This] triggers tail regeneration and stops the tail growth when it's complete. The tadpoles end up with perfectly sized tails like their siblings. Levin is now working with tissue engineer David Kaplan to develop [a] bioreactor, which could encourage the same regeneration in mammals, starting with rats."