The most common outcome of a stroke is paralysis of the left or right side
of the body (although a brain tumour or an injury to the brain can have a
similar effect). While people often recover some movement, in a large number
of people who have had a stroke this movement is partial and the hand and
arm may remain useless. Immediately after a stroke, the paralysed hand is
flaccid. But it will become clenched permanently if efforts are not made to
keep the fingers open and straight.

Patrick Crago and his colleagues at the Rehabilitation Center of Case
Western Reserve Hospital in Ohio have successfully opened the hands of
seven stroke victims. The electrical nerve stimulator they have developed
stimulated the nerves in the forearm via electrodes which were fixed to the
skin with adhesive patches. To achieve functional opening of the hand, the
device simultaneously stimulated two nerves that control the muscles to the
hand – the extensor digitorum communis and the ulnar nerve.

Similar techniques used for helping people with injuries to the spinal cord
regain some use of their arms and legs have been successful in the past, so
there is optimism for the new technique.

Carl Billian, a specialist in rehabilitating stroke patients who has been
involved in the study, comments that opening the hand in this way remains
‘somewhat artificial’. But it enables the hand to hold or support objects
and assist the ‘normal’ hand, he says.

In their experiments, Rein Anton at the University of California in
Los Angeles and his colleagues used brain cells of a type called nigral
cells which produce the neurotransmitter dopamine; most people with Parkinson’s
disease are deficient in this substance. The researchers inserted into the
cells a gene which allowed the cells to proliferate indefinitely at a temperature
below body temperature. In this state, the cells are said to be ‘conditionally
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Anton and his colleagues next inserted into the cells a gene for the
enzyme tyrosine hydroxylase, which is necessary for the production of dopamine.
This markedly boosted their dopamine production. Rats in which symptoms
of Parkinson’s disease had been experimentally induced were given transplants
of these brain cells.

The researchers found that the transplanted cells produced a 70 per
cent reduction in the rats’ symptoms. ‘The results we found are encouraging,’
said Anton, speaking at the annual meeting of the American Academy of Neurology
in San Diego.

When the genetically modified cells are implanted, they reach body temperature,
stop growing, and send out sprouts. But they still produce dopamine, says
Anton. The technique does not require the use of human fetal tissue, and
all the cells used are descended from a single brain cell. According to
Anton, the conditionally immortalised cells can be made available in unlimited
quantities, and can be genetically manipulated at below body temperature.
Yet they remain capable of performing their specialised role at body temperature.

Anton believes there is considerable potential to improve his cells
through further genetic engineering. ‘Further studies are necessary so we
can measure the animals’ reaction, record data, and study their brains,’
he says. ‘Perhaps this will lead to therapy in humans with Parkinson’s disease.’