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Working eyes grafted on to the tails of tadpole

By Catholic Online (NEWS CONSORTIUM)
March 1st, 2013
Catholic Online (www.catholic.org)

The eyes have it - Researchers have made startling discoveries in transplanting working eyes on to the body of another living organism. Scientists have shown that eyes transplanted onto the tails of living tadpoles can still see. These findings may lead to stunning advances in regenerative growth and the restoration of sight in humans.

LOS ANGELES, ca (Catholic Online) - Biologists surgically removed the eyes of donor tadpoles and grafted them onto the posterior of recipient tadpoles, which induced the growth of ectopic - i.e., abnormally placed eyes.

Tadpoles had their natural eyes removed, so only the ectopic, spinal cord-connected eyes remained. The test subjects were then able to complete specially developed sight tests.

Biologists at Tufts University School of Arts and Sciences are excited with the advances.

"The [tadpole's] ability to see when ectopic eyes are connected to spinal cord and not directly to the brain was stunning," Dr. Michael Levin, who led the research, said.

"A primary goal in medicine is to one day be able to restore the function of damaged or missing sensory structures through the use of biological or artificial replacement components.

"There are many implications of this study, but the primary one from a medical standpoint is that we may not need to make specific connections to the brain when treating sensory disorders such as blindness."

Scientists experimented with 134 tadpoles of the African clawed frog Xenopus laevis, a common lab animal. Placing their amphibious subjects in a well where half of the dish was illuminated with red light and the other half with blue light, they inverted at regular intervals.

Whenever the tadpoles ventured into areas bathed in red light they received a little warning zap of electricity.

Just over 19 percent of the animals with optic nerves that connected to the spine demonstrated learned responses to the lights, swimming away from the red light while the blue light stimulated natural movement.

Their response to the lights elicited during the experiments was no different from that of a control group of tadpoles with natural eyes intact. The response was not demonstrated by either the eyeless tadpoles or tadpoles that did not receive any electrical shock.

"This has never been shown before," Levin says.

"No one would have guessed that eyes on the flank of a tadpole could see, especially when wired only to the spinal cord and not the brain."

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