Scientists Seek New Medicines From the Ocean

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The sea is calm, the sun is radiant, and the clouds are slowly rolling in off the coast of Gay Head on Martha's Vineyard as two fishermen haul in nets loaded with more than 50 skate fish. Though the scene is vintage New England, these fishermen are working for scientists back at the Marine Biological Lab who are fascinated by the skates' unique eyes.

"The way you identify disease is its variation from normal. If you don't know what normal is, you don't know disease. From the skate retina, we've learned what's normal," explained Harris Ripps, an ophthalmologist and neurobiologist based at the University of Illinois in Chicago.

Though Ripps spends his summers at Woods Hole studying fish eyes, his real interest is diseases that damage the human retina, the light-sensitive tissue that lines the back of the eyeball. In particular, Ripps is concerned about retinitis pigmentosa, a disease that can lead to total blindness and affects an estimated 100,000 Americans.

The human retina contains two kinds of light-sensitive cells—rods, which allow people to see peripherally and detect light, and cones, which can distinguish color and distinct objects.

But Ripps and his colleague, John Dowling, a Harvard neurobiologist and president of the Marine Biological Lab, discovered early on that skates made a useful model for studying the human retina because they can detect light in the darkest and lightest condition using only rods.

By focusing on skates, the researchers could focus on what goes wrong in rod cells that can lead to blindness.

As a result, Ripps and other scientists understand that a single defective protein can corrupt the rods, and they are studying how this protein is communicated between cells through the use of genetic engineering.

Though they still haven't discovered a cure, doctors have found effective means of slowing down the disease in some patients. Minimizing exposure to light and doses of vitamin A have produced some positive results.

Ripps said he believes that through basic research, he and other scientists have unraveled part of the puzzle.

Common Biological Functions

Researchers studying cardiomyopathy—where the heart muscle loses the ability to relax normally and cannot properly pump blood—hope that toadfish muscles can help them the way that skates' eyes are aiding the study of blindness.

"In my studies of the toadfish, I've hypothesized that there is a molecule that helps it to relax as quickly as it does," said Larry Rome, who studies toadfish both at the University of Pennsylvania and at the Marine Biological Lab.

That molecule, a protein called parvalbumin, is found in human skeletal muscles but not in the heart. Some researchers, such as Joseph Metzger, a muscle physiologist at the University of Michigan Medical School, are examining how the human heart afflicted with such diseases as cardiomyopathy could benefit from inserting this protein.

But the toadfish's value may extend beyond heart disease. Though it barely has to move much of the time, somewhere in the evolutionary process the toadfish developed an unusual ability to regenerate its central nervous system.

"There is a curiosity about why this stage developed in evolution. It's not necessary for a fish to regenerate, so why does it and why not humans? The cues to guide nerve regeneration in fish could be important to humans," explained neurophysiologist Al Mensinger of the University of Minnesota at Duluth.

Mensinger is working with a technology that will allow the study of toadfish behavior in its natural habitat by monitoring neural activity leading into its brain. Scientists have learned that, unlike the human spinal chord, which, when cut, will fail to regenerate, the toadfish nerves grow back completely.

By implanting electrodes in the toadfish, they have watched the tissue regenerate in less than a month and actually grow through the holes of the device. One day, Mensinger said, the toadfish research may lead to advances in prosthetic devices for people with central nerve damage.

Part 2: A deadly snail from Fiji and the lowly horseshoe crab could hold keys to blood diseases and to protection from microbes from other worlds. Go>>

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