Apparently cells from the inner, or pigment, layer of the eye's retina make levodopa, which Parkinson's patients commonly take in pill form to replace lost production of the neurotransmitter dopamine.

Dopamine allows the brain to control and smooth the body's movements.

However for most patients, the levodopa pills lose their effectiveness over five years or less, and larger and larger doses are needed to keep at bay the involuntary movements and shaking symptomatic of the disease, and many people on the drug develop involuntary writhing or dance-like movements.

Natividad Stover, a researcher at the University of Alabama, says the retina cells were cultivated and implanted in the brains of six patients with advanced Parkinson's disease.

Stover says that one year later, the patients scored 48 percent higher on tests of movement and coordination, and the improvement was sustained after two years.

The research showed that the implants were well tolerated,and improvement was observed in activities of daily living and in the quality of life.

Parkinson's is a degenerative disease in which key brain cells that produce dopamine die off.

Symptoms start with tremors and rigidity and patients can end up paralyzed.

The cause of the disease that attacks 2 percent of men and 1.3 percent of women is unknown, and there is no cure.

Some scientists have considered implanting fetal stem cells into the brains of Parkinson's patients to be a promising avenue to restoring dopamine production, but preliminary human trials proved to be disappointing, and animal experiments have yielded mixed results.

Other promising treatments include deep brain stimulation with implanted electrodes, drugs that promote brain cell growth, and gene therapy.

The researchers say a larger study has been started to test the efficacy and safety of retina cell implants.

The research is published in the journal Archives of Neurology.

But how to find such an enzyme? John D. Sutherland and his team at the University of Manchester have used a sample reaction, the conversion of an alcohol into an aldehyde, to demonstrate how this might work. The secret of their success is the coupling of the desired reaction to a second reaction that can be easily detected. This is how it goes: The researchers fragment the complete DNA of a microorganism and incorporate the individual fragments into bacteria. These form colonies that produce many copies of the corresponding proteins. All of the colonies together represent all of the proteins of the microorganism, its proteome. The alcohol to be converted is then added to the medium. If one of the colonies contains a useful enzyme, the alcohol is converted into an aldehyde. The trick is this: An additional gene that codes for the enzyme luciferase was implanted into all of the bacteria. Luciferase converts aldehydes into their corresponding acids. This process releases energy in the form of light. Colonies in which the alcohol is converted into the desired aldehyde can easily be recognized by their glow. The detection is so sensitive that even very low enzymatic activities are obvious. Glowing colonies are then selected and the sought-after, alcohol-converting enzyme is identified by means of the foreign gene fragment.

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