Fat-burning bacteria An excess of one of the major intestinal bacteria may encourage obesity, according to two studies, using mice and humans. Most of the 100,000 million bacteria in the gut are firmicutes or bacteroidetes, which help break down food. Obese people tend to have relatively fewer of the latter and more of the former, which seem to help extract more calories from food, AFP reports. In Washington University studies, lean mice given a boost of firmicutes got twice as fat. In another study, dieting boosted the relative levels of bacteroidetes in people from 3 per cent to 15 per cent. Memorable chemical tracker A chemical that shows how Alzheimer's affects the brain may be useful in diagnosis and treatments, a University of California, Los Angeles, study shows. The compound FDDNP binds with the plaques and tangles in the brain that are characteristic of the disease and is used with brain imaging, WebMD reports. 'We showed that this is an accurate diagnostic tool,' says researcher Gary Small. 'This could be to Alzheimer's what a cholesterol test is to heart disease and stroke.' And tests on male mice at the University of Southern California suggest that testosterone, levels of which decrease with age, may help guard against Alzheimer's. Long lives for positives Optimists may live longer than pessimists, according to a 40-year study of almost 7,000 people in the US. On average, the Duke University, North Carolina, study found the most pessimistic people were 42 per cent more likely to die of any cause than the most positive, Reuters reports. Among the possible reasons are that optimists are less likely to suffer from depression, and may be more likely to have healthier lifestyles. Healing hands Holding hands can provide instant stress relief - even among strangers, says a small University of Virginia study in which 16 married women were given mild electric shocks. 'We found when you're holding a hand - any hand - the parts of your brain responsible for mobilising your body into action calm down,' says team leader James Coan. But a husband's hand is best, healthday.com reports. 'Only a husband's hand calmed the region of the brain that keeps your emotions in check,' Coan says. And the happier the marriage, the greater the benefits. Shake that scent A controversial theory that smell is based on the vibration of molecules rather than their shape has received support from a British study. It helps explain how a biological system such as the sense of smell can measure vibrations that normally require sophisticated equipment such as a spectroscope, Science Daily reports. 'This mechanism is more like swipe-card identification than a key fitting a lock,' says research team leader Andrew Horsfield of the London Centre for Nanotechnology. Botox moves you in many ways Botulinum toxin, or Botox, best known for getting rid of wrinkles, can relieve constipation and may help ease the pain of writer's cramp, two studies show. Italian trials successfully used ultrasound-guided local injections of Botox to relieve constipation in 24 people who were unable to relax their pelvic floor muscles, Reuters reports. In a Dutch study, Botox injections - which block signals from nerves to muscles - improved symptoms of writer's cramp in 70 per cent of those treated, WebMD reports. Jason Sankey is a tennis professional
