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Does it matter if genes can jump from GM food to bugs in human gut?
LAST week opponents of genetic engineering seized on a report suggesting that DNA from GM food can enter bacteria in the human gut. Here at last was proof, they claimed, that antibiotic-resistant superbugs could emerge by picking up the marker genes found in some GM crops. So should we be worried? "We've said time and time again there's a risk of this happening. Now they've looked just once and they've found it," says Adrian Bebb of Friends of the Earth. But most microbiologists, including the researchers at the University of Newcastle upon Tyne who did the study, dismiss such concerns. in one of a series of studies for Britain's Food Standards Agency, Harry Gilbert's team at Newcastle fed burgers and milkshake containing GM soya tO 12 healthy volunteers and to seven volunteers who'd had their colons surgically removed. By examining stools from the healthy subjects and material from the others'ileostomy bags, the researchers could see how different parts of the digestive system affected DNA in the GM soya, which has a gene that makes it resistant to the herbicide glyphosate. The team found no trace of DNA from the soya in the stools of the volunteers with intact digestive systems. But they found that up to 3.7 per cent of the soya DNA remained in the contents of the bags. When they grew bacteria from these samples, they were able to detect trace amounts of the GM DNA using a technique called PCR. That suggests a very few bacteria had taken up a foreign gene or transgene from the soya food.
Previous studies have suggested this is possible (New Scientist, 30 January iggg, P 4) but it has never been directly demonstrated before. However, the Newcastle team wasn't able actually to isolate any bacteria containing the soya transgene. Nor was there any evidence that the gene had actually started to function in the bacteria, they say. The researchers conclude that while some DNA might survive as far as the small intestine, in people with normal digestive tracts it's all broken down on the way through the colon. Even if some bacteria take up some of the DNA, they don't make it out the other end. "We have no evidence this has any adverse effects on humans," says team member John Mathers. But Bebb points out that while the soya didn't contain antibiotic resistance genes, other GM crops do. These marker genes are used during the creation of GM plants to reveal which cells have taken up the new bits of DNA. However, Karen Scott of the Rowett Research Institute in Aberdeen has tried and failed to get human gut bacteria to take up ampicillin resistance genes, which are present in some GM crops. What's more, she has found that such resistance genes are already widespread in the gut bacteria of many animals. This is probably because of the misuse of antibiotics in agriculture and medicine. So even if gut bacteria did acquire and turn on antibiotic resistance genes from GM food, they would be a drop in the ocean of existing resistant bacteria. "My opinion is that it's not an issue," Scott says. Despite the fact that the risks are so low, groups such as Britain's Advisory Committee on Releases to the Environment recommend that no antibiotic resistance genes should be incorporated in new GM crops. Andy Coghlan
Insurers count cost of global warming FRED PEARCE
INSURANCE premiums against floods and other disasters are set to rocket because the world's biggest insurance companies are getting nervous about climate change. Swiss Re, a company that provides insurance for other insurers, warned in a report this week that premium hikes are inevitable. The big fish of the insurance industry are already alarmed about the rising tide of large claims for climatic disasters such as floods, hurricanes and heatwaves, which between them have caused damage estimated at half a trillion dollars over the past decade. "The number of really big weather disasters has increased fourfold compared to the 19 6os," says Thomas Loster from Munich Re, another big firm that insures insurers - a business known as reinsurance. Now Swiss Re's risk analysts are pointing to the hidden costs of smaller changes in the weather. "A few rainy days less per year, a somewhat lower incidence of frost, a few more particularly warm days. This may sound relatively harmless, but its not," warns the report (see www.swissre.com). Extreme weather appears much more catastrophic because it wins extensive media coverage. However, persistent but less obvious changes to climate can also cause problems. For instance, in July i995, a heatwave in Britain raised average temperatures bY 3 degrees. This small rise caused the death rate to increase by 5 per cent. Crops failed, cattle breeding faltered and trout tanks emptied. The bill to farmers alone was E18o million. Add in factors such as emergency water supplies that had to be brought in as reservoirs dried up and the total bill goes uP tO EI-5 billion - much of it paid for by insurance companies. "Losses that were previously an exception may become the rule," says Swiss Re's chief risk officer Bruno Porro. He says insurance companies need to reassess the risks for these events now and bump up premiums to offset massive payouts. If other insurance companies are too slow to adapt to the changed climate, Porro says companies such as Swiss Re "will not be prepared to share the burden", and the other companies will have to take the losses on their own. Some high-risk activities, such as insuring property on low-lying islands and providing cover against forest fires or a lack of snow at ski resorts, may prove so risky in the future that no insurance companies wfll cover them at all. Environmentalists will be happy that insurance companies are adding their voice to the cry that climate change is happening and needs to be addressed. But they may not like some of the solutions that insurers suggest to keep down premiums. "A likely answer to a series of failed harvests caused by climate change might be the increased use of genetically modified crops," claims Porro.
Stargazer takes on gravity EUGENIE SAMUEL
ALONEastronomersays observations of the cosmos go further towards ruling out one of physicists'most popular theories than the most expensive particle accelerators have so far. His claims are causing constemation among particle physicists, who say that his work relies on assumptions that may not be true. Most physicists and astronomers agree that for rotating galaxies not to fly apart, they must contain much more matter than we actually see. It's believed that more than go per cent of the Universe is made up this "dark matter". Dark matter particles are called "WIMPS" - weakly interacting massive particles - because it's thought they interact with each other too feebly to produce observable radiation. The most popular WIMP candidate is the hypothetical neutralino. It's predicted by a theory called "supersymmetry", which has been proposed by particle physicists to explain observations that the Standard Model of physics cannot. One of its main attractions is that it can explain dark matter. It says that every particle we know has a host of heavier cousins - particles with the same characteristics but much greater mass. The neutralino is the lightest of these supersymmetric particles. Particle accelerators have so far been unable to create or detect any of these particles. And as for ruling out some of the theoretical masses for the neutralino, they've hardly made a dent. But now astronomer Craig Tyler says he may have excluded at least half of all the possible values in one sweep, by peering into the heart of a galaxy. Although we would never normally see neutralinos, they might give themselve,s away if squashed together tightly enough. Depending on their mass, they would collide and annihilate each other, giving off gamma rays. So for his PhD thesis at the University of Chicago in Illinois, Tyler focused on a tiny galaxy called Draco. It contains far more dark matter than most galaxies - 99.8 per cent of its total - yet the space-based Compton Gamma Ray Observatory looked at Draco last year and saw no gamma rays coming from the galaxy's heart. In Physical Review D (vol 66, p 023509) Tyler says that if Draco's core is as dense as he predicts, then the lack of gamma rays severely restricts the possible mass of the neutralino. What's more, if Draco's magnetic field is similar to those detected in comparable galaxies, it should deflect other decay products of the neutrahnos, producing radio waves. But no radio waves have been detected either, in theory ruling out almost every possible mass for the neutrauno - bad news for supersymmetry. "if you make his assumptions, this would be a problem for neutralinos," says astrophysicist Katherine Freese at the University of Michigan in Ann Arbor. But she says Tyler has extrapolated too far from the available data on Draco: he assumes that its core is very dense, yet we only have data on regions further out, she says. "You're relying on an untested assumption that almost everyone in the dark matter community thinks is wrong." Tyler is undaunted. "This method has the potential to eliminate most popular WIMPS," he says. "There will be fewer and fewer things you can imagine doing with direct detection.' indeed, the Gamma Ray Large Area Space Telescope, due for launch in 2005, should provide enough data to rule out or detect most wimps, even given doubts over where they are. But Thomas Dent, who works on supersymmetry theory at the University of Michigan, insists stargazing could never replace particle accelerators. "Looking at annihilation in galaxies might be more powerful than direct detection, but there is a trade-off since the results are subject to more theoretical uncertainty," he says.
Define life. You can't? Neither can the scientists
DONT even bother asking what life is. Coming up with a definition right now is impossible, according to US researchers. In recent decades, scientists haw been worrying aboutthis question more than ever. Without a definition, how will astronomers looking for life on other planets know if they've found it? If we created life artificially, would we even know? Last week, news that scientists had made a polio virus from scratch sparked renewed discussions about what is alive (NewScientist, 20 July, p 6). But in an upcoming issue of Origins of Life and Evolution of the Biosphere, philosopher Carol Cieland of the University of Colorado at Boulder, and biologist Chris Chyba of the SErl Institute, California, argue that we should admit defeat - for now. lt won't be possible to define life until biologists have a theoretical explanation of it, they say. They use the historic struggle to define water to support their argument. Before the theory of atoms and molecules was developed in the Igth and 19th centuries, water had scientists stumped. Definitions such as "an odourless, colouriess, thirst-quenching liquid" came unstuck when considering things like acid solutions, muddy water, ice or steam.
"You can argue over which characteristics of water are fundamental, but without molecular theory, a predse, unambiguous definition is impossible. That's where we are with our definitions of life," says Chyba- We might never work out a theory that explains life. If so, "this argument is going to be interminable". In the meantime, the hunt for alien life continues. Jupiter's moon Eumpa, one of the most likely homes fbr extraterrestrial life in our Solar System, was named earlier this month as a priority for exploration by the US National Research Council. But NASA's working definition of life, "a setf-sustained chemical system capable of undergoing Darwinian evolution", is farftm ideal. ft risks excluding some novel life forms that could exist, such as ones that replicate so haphazardly that natural selection is not an option. And there's a pracflcal problem - just how long are you going to hang amund on Europa to see whether potential life forms are evomne Instead, the search will have to rely on a list of expected characteristics, such as the presence of complex organic molecules, or entities with a morphology that can't be explained by chemistry alone. Rachel Nowak
New trials put heart into gene therapy
GENE therapy could soon be used to treat heart failure. inifial results suggest the treatment is both effective and long-lasting. When the heart can't pump enough blood, fluids collect in the body's Ussues, causing swelling, shortness of breath and fatigue. In the worst cases, the only treatment is a new heart, but many patients die waiting for a donor. While heart failure has many causes, Kenneth Chien at the University of California, San Diego, and his team have shown that a common feature is an overactive protein called phospholamban or PLN. In healthy people it helps regulate the activity of heart muscle cells, but in people with heart failure it seems to be too effective and prevents cells both from contracting fully and relaxing completely. To see if blocking PLN could help, Chien's team created a virus carrying a gene for a mutated PLN pmtein that inhibits the normal protein. When they injected this into a breed of hamster that suffers from pmgressive heart failure it had a dramatic effect. The treatment doubled the capacity of the animals' hearts to contract and relax, and they were able to sustain blood pressure about a third higher than untreated animals (Nature Medicine, DOI:10.10381 nm739). The benefits were sill apparent seven months later. "It's fabulous work for a number of reasons," says Elizabeth Nabel, a cardiologist at the National lnstitute of Heath near Washington DC. For one thing, she says, the treatment doesn't appear to damage the heart as some drug treatments that cause long-term hyperactivation of cardiac musde do. Chien's team already has unpublished data showing the treatment works in mice and rats with heart failure. They now plan to test the technique in pigs. If it works fbr them, Chien says the therapy will be tested on patients whose ap or health makes them poor candidates for transplants. "We aren't cowoycardiolo istseagertogetthis into any patient," he says. "We're going to err on the side of caution." Philip Cohen
Spookiness is in the brain of the beholder
WHETHER or not you believe in the paranormal may depend entirely on your brain chemistry. People with high levels of dopamine are more likely to find significance in coincidences, and pick out meaning and patterns where there are none. Peter Brugger, a neurologist from the University Hospital in Zurich, Switzerland, has suggested before that people who believe in the paranormal often seem to be more willing to see pattems or relationships between events where sceptics perceive nothing. To find out what could be triggering these thoughts, Brugger persuaded 20 self-confessed believers and 20 sceptics to take part in an experiment. Brugger and his colleagues asked the two groups to distinguish real faces from scrambled faces as the images were flashed up briefly on a screen. The volunteers then did a similar task, this time identifying real words from made-up ones. Believers were much more likely than sceptics to see a word or face when there wasn't one, Brugger revealed last week at a meeting of the Federation of European Neuroscience Societies in Paris. However, sceptics were more likely to miss real faces and words when they appeared on the screen.
The researchers then gave the volunteers a drug called L-dopa, which is usually used to relieve the symptoms of Parkinson's disease by increasing levels of dopamine in the brain. Both groups made more mistakes under the influence ofthe drug, but the sceptics became more likely to interpret scrambled words or faces as the real thing. That suggests that paranormal thoughts are associated with high levels of dopamine in the brain, and the L-dopa makes sceptics less sceptical. "Dopamine seems to help people see pattems," says Brugger. However, the single dose ofthe drug didn't seem to increase the tendency ofbelievers to see coincidences or relationships between the words and images. That could mean that there is a plateau effect for them, with more dopamine having relatively little effect above a certain threshold, says Peter Krummenacher, one of Brugger's colleagues. Dopamine is an important chemical involved in the brain's reward and motivation system, and in addiction. Its role in the reward system may be to help us decide whether information is relevant or irrelevant, says Franqoise Schenk from the University of Lausanne in Switzerland. Helen Philips