Interesting article about the energetics of healing:
http://www.ucdmc.ucdavis.edu/publish/ne ... ticle_7652
"Think of a cell as a blob of fluid and protein gel wrapped in a membrane. Cells crawl along surfaces by sliding and ratcheting protein fibers inside the cell past each other, advancing the leading edge of the cell while withdrawing the trailing edge.
Assistant project scientist Yaohui Sun found that when whole cells were exposed to an electric field, actin protein fibers collected and grew on the side of the cell facing the negative electrode (cathode), while a mix of contracting actin and myosin fibers formed toward the positive electrode (anode). Both actin alone, and actin with myosin, can create motors that drive the cell forward.
The polarizing effect set up a tug-of-war between the two mechanisms. In whole cells, the actin mechanism won, and the cell crawled toward the cathode. But in cell fragments, the actin/myosin motor came out on top, got the rear of the cell oriented toward the cathode, and the cell fragment crawled in the opposite direction.
The results show that there are at least two distinct pathways through which cells respond to electric fields, Mogilner said. At least one of the pathways — leading to organized actin/myosin fibers — can work without a cell nucleus or any of the other organelles found in cells, beyond the cell membrane and proteins that make up the cytoskeleton.
Upstream of those two pathways is some kind of sensor that detects the electric field. In a separate paper to be published in the same journal issue, Mogilner and StanfordUniversity researchers Greg Allen and Julie Theriot narrow down the possible mechanisms. The most likely explanation, they conclude, is that the electric field causes certain electrically charged proteins in the cell membrane to concentrate at the membrane edge, triggering a response.
The team also included Hao Do, Jing Gao and Ren Zhao, all at the Institute for Regenerative Cures and the UC Davis departments of Ophthalmology and Dermatology. Sun is co-advised by Mogilner and Zhao; Gao is now working at Yunnan Normal University, Kunming, China; and Ren Zhao is at the Third Military Medical University, Chongqing, China.
The work was funded by the National Institutes of Health (grant GM068952), the California Institute for Regenerative Medicine (grant RB1-01417) and the National Science Foundation (grant MCB-0951199)."