VICTIMS of Parkinson's, Huntington's and Alzheimer's diseases have reason to cheer: scientists may soon be able to treat -- if not cure -- their illnesses. Cyto Therapeutics, a US firm that develops cell implants, has signed an agreement with biologists Sam Weiss and Brent Reynolds of the University of Calgary in Canada to investigate cures for damaged brain cells (Science, Vol 257 No 5075).

Neurons, specialised nerve cells, are not normally replaced once they are damaged. Weiss and Reynolds, however, discovered certain mouse brain cells, called stem cells, could produce new generations of neurons when cultured in the lab. The discovery meant certain brain cells could be induced to produce neurons to replace dead neurons or at least provide the substances they would have supplied.

The two researchers say if similar cells exist in the adult human brain, they could be made to produce certain neurons or they could be removed, treated and put back into the brain. If cells from other species have to be used to produce the neurons, they would have to be enveloped in a porous membrane developed by Cyto Therapeutics that protects them from immune system reactions, but allows secretion.

However, it is still not clear how many types of neurons brain cells can be made to produce and whether the ones they do spawn can treat specific diseases.