Biological cells reveal brain chemistry secrets

Scientists have developed biological cells that can give insight into the chemistry of the brain.

The cells, which change colour when exposed to specific chemicals, have been used to show how a class of schizophrenia drug works.

The researchers hope they will also help shed light on how many other drugs work on the brain.

The study, by the University of California - San Diego, is published in Nature Neuroscience.

Schizophrenia is most commonly associated with symptoms such as delusions and hallucinations.

But people with the illness also struggle to sustain attention or recall information.

A class of drugs called atypical neuroleptics has become commonly prescribed, in part because they seem to improve these problems.                                                           

However, the way they altered brain chemistry was uncertain.

It was known that the drugs trigger the release of a large amount of a chemical called acetylcholine, which enables brain cells to communicate with each other.

However, the drugs have also been shown to hobble a receptor on the surface of the receiving cell, which would effectively block the message.

The San Diego team designed biological cells - called CNiFERs - which changed colour when acetylcholine latched onto this particular class of receptors - an event scientists have not previously been able to detect in a living brain.

They implanted the cells into rat brains, then stimulated a deeper part of the brain in a way known to release acetylcholine nearby.

In response, CNiFERs changed colour - proving that they were working.

They then gave the rats one of two atypical neuroleptics. In both cases the drug severely depressed the response from the CNiFERs.

This suggested that the drugs' receptor-blocking action over-rides the increase they trigger in acetylcholine.

Researcher Professor David Kleinfeld said the new cells had great potential to reveal the mysteries of chemical action in the brain.

He said: "It's a world of signalling between cells that we were blind to before."

The researchers say they are already working to redesign CNiFERS so they can detect the activity of other types of receptors as well.

Paul Corry, of the mental health charity Rethink, said: "This study shows the value of mental health research.

"It is eliciting new information that could lead to the development of more effective drug treatments for schizophrenia, which have fewer of the debilitating side-effects associated with even the most modern atypical medicines.

"That in itself would benefit millions of people around the world.

"But the research also offers a new technique for understanding the workings of the brain that could also be developed for use across broad areas of medicine.

"We really do need to recognise that mental health research is starved of funds compared to other areas of medicine and recognise also that much of it takes place at the frontiers of our understanding which means that results from it could have far-reaching applications."

Mars' ancient lake beds spied by Nasa probe

New images of Mars suggest the Red Planet had large lakes on its surface as recently as three billion years ago.

The evidence comes from Nasa's Mars Reconnaissance Orbiter (MRO) which spied a series of depressions linked by what look like drainage channels.

Scientists tell the journal Geology that the features bear the hallmarks of being produced by liquid water.

But they appear to have formed much later in Mars' history than many thought possible, the researchers add.

The team, from Imperial and University Colleges London, studied pictures of several flat-floored depressions located above Ares Vallis, a giant gorge running some 2,000km across Mars' equator.

The hollows are about 20km in diameter.

Scientists had previously ascribed their formation to the slumping of the ground as ice in the soil was lost to Mars' thin atmosphere almost four billion years ago in the process of sublimation (in which the ice turns directly from a solid into a vapour).

But the detail in the MRO pictures has allowed the Imperial-UCL team to trace a series of channels that connect the depressions.

The group says these channels could only be formed by running water, and not by ice turning directly into gas.

The scientists' ageing of the region, which on bodies like Mars is done by counting craters, suggests the features formed during the so-called Hesperian Epoch on the Red Planet.

This was a time when Mars is supposed to have been too cold and its atmosphere too thin to sustain liquid water on its surface.

The researchers propose instead that Mars may have experienced bouts of short-lived warming during this epoch that were caused perhaps by volcanic activity, meteorite impacts, or even shifts in the planet's orbit.

This could have provided both the warmth to melt ice in the soil and the pressure needed in the atmosphere to maintain liquid water on the surface.

It would be possible then for lakes to fill with meltwater and even overflow, cutting channels as the liquid ran from a higher depression to a lower one.

The giant Amazon arapaima fish is 'under threat'

The arapaima, a giant species of fish that lurks in the Amazon river, may be threatened by overfishing.

Studies reveal that errors in the classification of the species could mean that it is being pushed closer to the edge of extinction than thought.

The arapaima is the largest freshwater fish with scales in the world.

But there may actually be four species rather than one, say scientists, and a lack of research and management may allow some to be fished to extinction.

The threat to the future of these fish has been revealed in research conducted by Dr Leandro Castello of the Woods Hole Research Center in Falmouth, Massachusetts, US, and Professor Donald Stewart of the State University of New York in Syracuse, US.

They have reviewed what is known about populations of the arapaima, and conducted detailed investigations into the status of the fish in the wild.

Previously, it was thought there was one species of arapaima (Arapaima gigas), which also goes by the common names pirarucu or paiche.

This perspective is based on a taxonomic review done over 160 years ago.

Adults grow to almost 3m in length and can weigh more than 200kg, making the fish the largest with scales living in freshwater anywhere in the world.

They are also air-breathers, coming to the surface every 5 to 15 minutes to gulp air, a behaviour which allows them to colonise muddy oxygen-poor rivers and lakes within the Amazonian basin and prey on other fish that find it difficult to move in such conditions.

However, in an ongoing study, Prof Stewart has analysed nearly all preserved specimens of supposed arapaima available in museums in the world.

So far he has only found one specimen of Arapaima gigas.

The others are suspected to be closely related species, including some as yet unreported.

"Our new analyses indicate that there are at least four species of arapaima," says Dr Castello.

"So, until further field surveys of appropriate areas are completed, we will not know if Arapaima gigas is extinct or still swimming about."

Concern about the fish's numbers comes from other work done by Dr Castello and Prof Stewart.

For a split second, an arapaima surfaces to gulp air

That suggests that arapaima sexually mature relatively late, and need very specific habitats to both live and reproduce.

Their research also shows that populations of the fish are being put under severe pressure by fishermen.

Because of the fish's huge size and habit of coming to the surface, it has long been a favoured fish to catch, with fisherman using harpoons and gill nets to land their prey.

"They have the curse of being tasty and of having to breathe air," says Dr Castello.

Fishermen have been catching large numbers of arapaima in this way since the 1800s.

But now, while a few populations are increasing, others are being overfished, say the researchers, who have published a paper warning of the fish's fate in the Journal of Applied Ichthyology.

And while Brazil implemented regulations to manage arapaima fisheries some 20 years ago, most fishermen do not follow the regulations, say the authors.

Fishermen capture a young arapaima for ecological studies

"Arapaima can be viewed as badly overexploited and under some level of threat of extinction," says Dr Castello.

One solution, they say, is to encourage community-based schemes for fisheries, and there is much need for additional action on the part of the government.

For example, their research shows that fishermen who specialise in hunting arapaima with harpoons can accurately count the fish, due to the fish's habit of breaching the surface for air.

The fishermen can then select a sustainable proportion of the population to hunt.

"Populations of arapaima managed with this system increased about 50% annually, while yielding increasing catches and hence economic profits to the fishermen," says Dr Castello.

Around 100 such community schemes are in place, and some previously overexploited populations have recovered.

"Such results are extremely rare in wildlife conservation, especially in tropical countries where wildlife conservation challenges are greater than elsewhere," says Dr Castello.

But much more needs to be done to research these fish in more detail and prevent overfishing, the scientists warn.

In particular, "the present situation may be one in which one species of arapaima is recovering in certain areas, while unrecognised species are going extinct," they say.