Electric Switch Could Turn on Limb Regeneration
Tadpoles can achieve something that humans may only dream of: pull off a tadpole’s thick tail or a tiny developing leg, and it’ll grow right back-spinal cord, muscles, blood vessels and all. Now researchers have discovered the key regulator of the electrical signal that convinces Xenopus pollywogs to regenerate amputated tails. The results, reported last November in Gene and Development, give some researchers hope for new approaches to stimulating tissue regeneration in humans.
Researchers have known for decades that an electrical current is created at the site of regenerating limbs. Furthermore, applying an external current speeds up the regeneration process, and drugs that block the current prevent regeneration. The electrical signals help to tell cells what type to grow into, how fast to grow, and where to position themselves in the new limb.
Michael Levin, who, with his colleagues, conducted the study at the Forsyth Center for Regenerative and Developmental Biology in Boston, speculates that the current generated by this proton pump produces a long-range electric field that helps to direct what happens to nerve cells pouring into the site. “We can use this hydrogen pumping as a top-level master control to initiate the regeneration response,” says Levin. “We didn’t have to specifically say, ‘put a little muscle over here, a little muscle over there’.”
The proton pump could also be used to turn on limb regeneration in older tadpoles that would normally have lost this ability. When Levin and his colleagues activated the proton pump during this older phase, tadpoles were more than four times more likely to regrow a perfectly formed tail than their normal counterparts.
Source: news.nature.com//news/2007/070226/070226-8.html.
Biomedical Engineers Advance on ‘Smart Bladder Pacemaker’
Duke University biomedical engineering researchers have moved a step closer to a “smart bladder pacemaker” that might one day restore bladder control in patients with spinal cord injury or neurological disease.
The team’s latest findings show that a device that taps into the urinary “circuit” in the spinal cord could selectively coordinate the contraction and release of muscles required for maintaining continence. Warren Grill of Duke’s Pratt School of Engineering and his colleagues have shown in cats that electrical stimulation can engage the spinal circuitry to effectively empty the bladder, while delivery of lower frequency pulses to the same nerve can significantly increase bladder capacity and improve continence. In fact, manipulating the nervous system provides a more flexible way of influencing urinary function than would direct bladder stimulation, Grill said.
“Stimulating the bladder directly can cause it only to contract, not to keep it from contracting,” Grill said. “We stimulate the sensory inputs in the spinal cord to orchestrate either the inhibition or activation of urination. “This illustrates an important principle: we can use the ’smarts’ of the nervous system to orchestrate control of complex functions,” he said. Please visit www.dukenews.duke.edu/2007/02/bladder.html to read the full press release on the findings of this study.
