May 19, 2004.
Paris: US scientists are exploring whether pigments from spinach can help to cure forms of blindness, New Scientist reports.
Their "truly extraordinary" experiments entail taking a cluster of proteins called photosystem I (PSI) reaction centres from spinach plants and delivering them to retinal cells that have been affected by cancer.
The commonest form of blindness among developed countries include degenerative diseases of the retina, such as macular degeneration and retinitis pigmentosa. These ailments see a tragic deterioration in the photoreceptor cells at the back of the eye, but the nerve cells in front of them usually remain intact.
Scientists have already learnt that some rudimentary vision can be restored by implanting electrodes in the retina to stimulate these nerve cells.
PSI centres, though, offer a new path, and one uncramped by the limitations of electrodes, whose numbers are constrained by the tiny space available for implanting them.
Straddling the chloroplast membrane in plant cells, PSI centres play a vital role in photosynthesis. They generate electric potential when struck by light, providing an energy source for the plant.
Three years ago, a team led by Eli Greenbaum of Oak Ridge National Laboratories successfully inserted PSI centres from spinach into the membranes of fatty molecules called liposomes, which can be used to deliver drugs or genes to cells.
Greenbaum found the implanted PSI centres generated electricity across the liposome membrane when they were exposed to light and the voltage was more than enough needed to activate a retinal nerve cell.
He has now gone a step further by using the liposomes to deliver PSI centres to the membranes of eye cancer cells.
When the cells were exposed to light, calcium ion channels opened up in the membrane - an invaluable confirmation that the cells can at least respond to light when treated this way.
Experts say the lab-dish experiments have a long way to go before they are convinced that the full array of retinal cells can be fired by the implants.
Meanwhile, other scientists are exploring ways of restoring vision using stem-cell implants or retinal transplants, the report notes. - Sapa-AFP
©2004 The Mercury. All rights reserved.
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