From the Boston Globe: "The dream of regenerative medicine is that it will one day be possible to replace flawed tissues - to create a new spinal cord, repair a defective heart, or regrow a limb. But as scientists make steady progress toward that tantalizing goal, some are studying a range of simple organisms, from tadpoles to salamanders to flatworms, that can already rebuild complete limbs or tails. In his laboratory at Tufts University, biology professor Michael Levin is investigating an often-overlooked mechanism that may play a key role in triggering this regenerative capacity in such critters: electrical signals. When people think of electricity in the body, they usually think of brain and nerve cells, or muscles. But Levin and other scientists study the bioelectrical signals that exist in all cells, and the role those play in allowing organisms to generate precise, functional replacements for body parts. ... Levin has altered the electrical signaling in cells and observed dramatic effects: A tadpole can regenerate a completely normal tail after it has lost that ability. ... Levin and colleagues triggered that regeneration using drugs that affected the bioelectrical signaling in tadpoles. The drug increased the transport of sodium into cells, triggering the tadpoles to regrow perfectly formed tails, which include a complex mixture of tissues including spinal cord, muscle, and skin. Levin's hope is that electrical signals might be a master switch that allows the organism to boot up its regenerative program, rather than requiring scientists to build a new organ or appendage cell by cell."