Media playback is unsupported on your device Media caption Professor Giovanna Mallucci says the hope is to arrest the process of brain cell death

The discovery of the first chemical to prevent the death of brain tissue in a neurodegenerative disease has been hailed as the "turning point" in the fight against Alzheimer's disease.

More work is needed to develop a drug that could be taken by patients.

But scientists say a resulting medicine could treat Alzheimer's, Parkinson's, Huntington's and other diseases.

In tests on mice, the Medical Research Council showed all brain cell death from prion disease could be prevented.

Prof Roger Morris, from King's College London, said: "This finding, I suspect, will be judged by history as a turning point in the search for medicines to control and prevent Alzheimer's disease."

He told the BBC a cure for Alzheimer's was not imminent but: "I'm very excited, it's the first proof in any living animal that you can delay neurodegeneration.

"The world won't change tomorrow, but this is a landmark study."

Cells starve

The research team at the Medical Research Council Toxicology Unit, based at the University of Leicester, focused on the natural defence mechanisms built into brain cells.

Neurodegeneration A neurodegenerative disease is one in which the cells of the brain and spinal cord are lost

The functions of these cells include decision making and control of movements

These cells are not easily regenerated, so the effects of diseases can be devastating

Neurodegenerative diseases include Alzheimer's, Parkinson's, multiple sclerosis and Huntington's Source: London Brain Centre

When a virus hijacks a brain cell it leads to a build-up of viral proteins. Cells respond by shutting down nearly all protein production in order to halt the virus's spread.

However, many neurodegenerative diseases involve the production of faulty or "misfolded" proteins. These activate the same defences, but with more severe consequences.

The misfolded proteins linger and the brain cells shut down protein production for so long that they eventually starve themselves to death.

This process, repeated in neurons throughout the brain, can destroy movement or memory or even kill, depending on the disease.

This process is thought to take place in many forms of neurodegeneration, so safely disrupting it could treat a wide range of diseases.

The researchers used a compound which prevented those defence mechanisms kicking in and in turn halted neurodegeneration.

Analysis It is rare to get cautious scientists keen to describe a study in mice as a turning point in treating Alzheimer's. It is early science, a lot can go wrong between a drug for mice and a drug for humans and the only published data is for prion disease, not even Alzheimer's. So why the excitement? It is the first time that any form of neurodegeneration has been completely halted, so it is a significant landmark. It shows that the process being targeted has serious potential. If this can be successfully developed, which is not guaranteed, the prize would be huge. In Parkinson's the alpha-synuclein protein goes wrong, in Alzheimer's it's amyloid and tau, in Huntington's it's the Huntingtin protein. But the errant protein is irrelevant here as the researchers are targeting the way a cell deals with any misfolded protein. It means one drug could cure many diseases and that really would be something to get excited about. Alzheimer's Research UK: Is it a cure?

The study, published in Science Translational Medicine, showed mice with prion disease developed severe memory and movement problems. They died within 12 weeks.

However, those given the compound showed no sign of brain tissue wasting away.

Lead researcher Prof Giovanna Mallucci told the BBC news website: "They were absolutely fine, it was extraordinary.

"What's really exciting is a compound has completely prevented neurodegeneration and that's a first.

"This isn't the compound you would use in people, but it means we can do it and it's a start."

She said the compound offered a "new pathway that may well give protective drugs" and the next step was for drug companies to develop a medicine for use in humans.

'Very dramatic'

Prof Mallucci's lab is also testing the compound on other forms of neurodegeneration in mice but the results have not yet been published.

Side effects are an issue. The compound also acted on the pancreas, meaning the mice developed a mild form of diabetes and lost weight.

Any human drug would need to act only on the brain. However, this gives scientists and drug companies a starting point.

David Allsop, professor of neuroscience at Lancaster University described the results as "very dramatic and highly encouraging" but cautioned that more research was needed to see how the findings would apply to diseases such as Alzheimer's and Parkinson's.

Dr Eric Karran, the director of research at the charity Alzheimer's Research UK, said: "Targeting a mechanism relevant to a number of neurodegenerative diseases could yield a single drug with wide-reaching benefits, but this compound is still at an early stage.

"It will be important for these findings to be repeated and tested in models of other neurodegenerative diseases, including Alzheimer's disease."