Prions 'may keep nerves healthy'

Experiments on mice may help scientists understand the workings of the prion protein linked to brain disease vCJD.

Swiss researchers say there is evidence that prions play a vital role in the maintenance of the sheath surrounding our nerves.

They say it is possible that an absence of prions causes diseases of the peripheral nervous system.

One expert said there was growing evidence that the prion had a number of important roles in the body.

As well as the latest research in the journal Nature Neuroscience, other studies have indicated prions may protect us from Alzheimer's disease or even play a role in our sense of smell.

The prion protein only came to the attention of scientists in recent years as they searched for the cause of vCJD - the human variant of BSE, or Mad Cow Disease.

This degenerative and incurable brain condition is now thought to be caused by a "mis-folded" version of the prion.

However, there is still little understanding of what the protein is supposed to do in its normal, healthy, form.

Healthy prions

The study, by scientists at the University Hospital in Zurich, looked at mice bred with fewer prion proteins.

While these mice are known to be resistant to prion diseases equivalent to vCJD in humans, they showed a number of abnormalities, including a degeneration, later in life, of the peripheral nerve cells, and the protective myelin sheath which surrounds them.

Peripheral nerves are those which link the limbs and organs to the central nervous system - the spinal cord and brain.

Looking more closely, researchers examined the effects of removing the prion protein in both the nerve cells themselves, and the Schwann cells surrounding them, which are responsible for making the myelin sheath.

While removing protein from the Schwann cells had no effect, taking it from the neurons led to a breakdown of the myelin and degeneration of the nerve cells.

They said that the knowledge that prion protein played some role in the healthy upkeep of nerve cells could offer a new avenue of research into diseases affecting humans.

However, scientists caution that it is too early to pick out a particular peripheral nerve condition which might correspond to the mouse experiments.

Recent work

Professor Nigel Hooper, from the University of Leeds, agreed that the role of the protein was not well understood.

His own work, published in 2007, suggested that it might offer some protection from the development of Alzheimer's disease.

But he said this was unlikely to be the complete answer.

He said: "Most people started by focusing on prions in relation to a human disease, and have only recently started to examine what it normally does.

"There is some evidence that it could have a number of different roles, depending on its whereabouts in the body - a recent paper linked it to olfaction or the sense of smell."

Ambidextrous children 'more likely to be hyperactive'

Children who write with both hands are more likely to struggle in school and have hyperactivity disorder symptoms, research suggests.

A study by scientists from Imperial College London found ambidextrous children were twice as likely to struggle as their classmates.

They were also more likely to have difficulties with language.

Experts told Paediatrics journal the differences might be down to the brain's wiring.

But they said much more work was needed to explore this.

Lead researcher Dr Alina Rodriguez said: "Mixed-handedness is intriguing - we don't know why some people prefer to make use of both hands when most people use only one."

Ambidextrous

Around one in every 100 people is ambidextrous, or mixed-handed.

The study looked at nearly 8,000 children from Northern Finland, of whom 87 were mixed-handed.

Mixed-handed children aged seven and eight were twice as likely as their right-handed peers to have difficulties with language and to perform poorly in school.

When they reached 15 or 16, mixed-handed adolescents were also at twice the risk of having symptoms of Attention Deficit Hyperactivity Disorder (ADHD).

And they tended to have more severe symptoms of ADHD than their right-handed schoolmates.

They also reported having greater difficulties with language than those who were left or right-handed.

This is in line with earlier studies that have linked mixed-handedness with dyslexia.

Hard-wired

Experts know that handedness is linked to the brain's left and right halves or hemispheres.

Research has shown that where a person's natural preference is for using their right hand, the left hemisphere of their brain is more dominant, which is where the centre for language lies.

Scientists have suggested that ADHD could be linked to having a weaker function in the right hemisphere of the brain.

Dr Rodriguez said it was possible that brain differences might explain the findings.

But she cautioned: "Our results should not be taken to mean that all children who are mixed-handed will have problems at school or develop ADHD.

"We found that mixed-handed children and adolescents were at a higher risk of having certain problems, but we'd like to stress that most of the mixed-handed children we followed didn't have any of these difficulties."

Marjorie Wallace, chief executive of the mental health charity SANE, said they had been carrying out similar work.

"In particular, Professor Tim Crow and his team are exploring the idea that brain asymmetry and handedness may play a role in the development of language and the origins of psychosis.

"All research which investigates possible links between brain difference and behaviour is vital to increase our understanding of many conditions, including mental health problems."