Scientists eye secrets of retinal re...( NEW YORK (Sept. 10 2007) -- Peering ...)

NEW YORK (Sept. 10, 2007) -- Peering at microscopic changes within the retina, scientists in the Department of Ophthalmology at Weill Cornell Medical College in New York City, have discovered a key mechanism driving eye health and eye disease.

Reporting in the cover article of a recent edition of Cell, the team says they have discovered just how light-sensing discs in the retina's rod cells regenerate themselves.

The retina uses two cell types -- rods and cones -- to sense incoming light.

"Rod cells make up the majority of photoreceptors in the human eye, and disruptions in these discs' ability to grow and capture light may be at the root of a host of disabling or blinding eye diseases such as retinitis pigmentosa," explains senior author Dr. Ching-Hwa Sung, professor of cell biology in ophthalmology and professor of cell and developmental biology at Weill Cornell Medical College.

"Rod cells contain tiny organelles called the 'outer segment,' which contain about 1,000 flattened discs containing rhodopsin -- a visual pigment that absorbs light," Dr. Sung explains. "Each day, our eyes shed the top 10 percent of these discs, but until now, no one really knew how the retina generated new discs. We believe we have solved that riddle."

According to the researchers, the rod cell's outer segment is constantly pushing up and forming new discs in a bottom-up process as older discs get shed at the segment's tip.

"There were theories as to how this might occur, but no hard evidence to back any of them up," explains lead researcher Dr. Jen-Zen Chuang, assistant professor of cell biology in ophthalmology at Weill Cornell.

In the study, the researchers used a variety of state-of-the-art techniques, including a gene-based method called "retinal transfection," to gain a more accurate picture of outer segment growth in rat retinas.

"Basically, retinal transfection means introducing different genes int
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