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The East African : Aug 25th 2014
32 The EastAfrican OUTLOOK AUGUST 23-29,2014 S CI E N C E How bacteria control our behaviour Pa≥asites ≥elease molecules that can di≥ectly o≥ indi≥ectly influence thei≥ host’s b≥ain By CARL ZIMMER Special Correspondent Y our body is home to about 100 trillion bacteria and other mi- crobes, collectively known as your microbiome. Naturalists first became aware of our invisible lodgers in the 1600s, but it was not until the past few years that we have become really familiar with them. This recent research has given the microbiome a cuddly kind of fame. We have come to appreciate how beneficial our microbes are, breaking down our food, fighting off infections and nurturing our immune system. It is a lovely, invisible garden we should be tending for our own well-being. But in the journal BioEssays, a team of scientists has raised a creepier possibility. Perhaps our menagerie of germs is also influencing our behaviour in order to advance its own evolutionary success — giving us cravings for certain foods, for example. Maybe the microbiome is our puppet master. “One of the ways we started thinking about this was in a crimenovel perspective,” said Carlo C. Maley, an evolutionary biologist at the University of California, and a co-author of the new paper. “What are the means, motives and opportunity for the microbes to manipulate us? They have all three.” The idea that a simple organism could control a complex animal may sound like science fiction. In fact, there are many well-documented examples of parasites controlling their hosts. Some species of fungi, for ex- ample, infiltrate the brains of ants and coax them to climb plants and clamp onto the underside of leaves. The fungi then sprout out of the ants and send spores showering ria to a normal mouse’s microbiome reveals other ways in which they can influence behaviour. Some bacteria lower stress levels in the mouse. When scientists sever the nerve relaying signals from the gut to the brain, this stress-reducing effect disappears. Some experiments suggest that bacteria also can influence the way their hosts eat. Germ-free mice develop more receptors for sweet flavours in their intestines, for example. They also prefer to drink sweeter fluids than normal mice do. Govern appetite Scientists have also found that bacteria can alter levels of hormones that govern appetite in mice. Maley and his colleagues argue that our eating habits create a strong motive for microbes to manipulate us. “From the microbe’s perspective, Different species of microbes thrive on different kinds of food. They can prompt us to eat more of the food they depend on, like chocolate. Picture: File SOCIAL BONDING John F. Cryan, a neuroscientist at University College Cork in Ireland, who was not involved in the new study, suggested that microbes may also manipulate us in ways that benefit both them and us. “It’s probably not a simple parasitic scenario,” he said. onto uninfected ants below. How parasites control their hosts remains mysterious. But it looks as if they release molecules that can directly or indirectly influence their host’s brain. Our microbiome has the biochem- ical potential to do the same thing. In our guts, bacteria make some of the same chemicals that our neurons use to communicate with one another, such as dopamine and serotonin. And the microbes can de- Research by Cryan and others suggests that a healthy microbiome helps mammals develop socially. Germ-free mice, for example, tend to avoid contact with other mice. That social bonding, good for the mammals, may also be good for the bacteria. liver these neurological molecules to the dense web of nerve endings that line the gastrointestinal tract. A number of recent studies have shown that gut bacteria can use these signals to alter the biochemistry of the brain. Compared with ordinary mice, those raised free of germs behave differently in a number of ways. They are more anxious, for example, and have impaired memory. Adding certain species of bacte- what we eat is a matter of life and death,” Maley said. Different species of microbes thrive on different kinds of food. If they can prompt us to eat more of the food they depend on, they can multiply. Microbial manipulations might fill in some of the puzzling holes in our understanding of food cravings, Maley said. Scientists have tried to explain food cravings as the body’s way to build up a supply of nutrients after deprivation, or as addictions, much like those for drugs like tobacco and cocaine. But both explanations fall short. Take chocolate: Many people crave it fiercely, but it is not an essential nutrient. And chocolate does not drive people to increase the dose to get the same high. “You don’t need more chocolate at every sitting to enjoy it,” Maley said. Perhaps, he suggests, the cer- tain kinds of bacteria that thrive on chocolate are coaxing us to feed them. NYT Service New vaccine to combat dust-mite alle≥gies By CHRISTABEL LIGAMI Special Correspondent RESEARCHERS AT the University of Iowa in the US have developed a vaccine that can combat dust-mite allergies by naturally switching the body’s immune response. The vaccine package, whose key ingredient is normally used in cancer vaccines, works because it contains a booster that alters the body’s inflammatory response to dust-mite allergens. The package contains a booster that ignites an anti-inflammatory response to the microscopic mites — which, when amassed by the millions, could resemble dust and cause breathing difficulties even for those who are not allergic. “We have developed a vaccine against dust- mite allergens that hasn’t been used before,” said Aliasger Salem, professor of pharmaceuti- cal sciences at the UI and a corresponding author of the study. Dust mites are universal, microscopic bugs that burrow in mattresses, sofas and other such spots. They are found in 84 per cent of households globally. Preying on skin cells on the body, the mites trigger allergies and breathing difficulties among 45 per cent of those who suffer from asthma, according to some studies, and prolonged exposure can cause lung damage. Treatment is limited to temporary relief from inhalers or regular exposure to build up tolerance, which is long-term and has no guarantee “This work suggests a way forward to alleviate mite-induced asthma.” Peter Thorne, researcher of success. “Our research explores a novel approach to treating mite allergy, in which specially encapsulated minuscule particles are administered with sequences of bacterial DNA that direct the immune system to suppress allergic immune responses,” said Peter Thorne, public health professor at the UI and a contributing author of the paper. “This work suggests a way forward to allevi- ate mite-induced asthma.” The UI vaccine takes advantage of the body’s natural inclination to defend itself against foreign bodies. A key to the formula lies in the use of an adjuvant — which boosts the potency of the vaccine — called CpG. The booster has been used successfully in cancer vaccines but never had been tested as a vaccine for dust-mite allergies. HIV could be brought under control by 2030 There is a chance that HIV/Aids will be brought under control by 2030, a report by the United Nations Aids agency says. UNAIDS said the number of new HIV infections and deaths are falling. The report showed that 35 million people around the world are living with HIV. There were 2.1 million new cases in 2013, 38 per cent fewer than the 3.4 million reported in 2001. But the agency called for more international efforts, as the “current pace cannot end the epidemic.” Male infants’ brains grow faster — report Human brains grow most rapidly just after birth and reach half their adult size within three months, according to a study published in JAMA Neurology. Using advanced scanning techniques, researchers found that brains of male infants grew more quickly than those of females. Areas involved in movement developed at the fastest pace. Those associated with memory grew more slowly. Scientists say collating this data may help them identify early signs of developmental disorders such as autism. BRIEFS Scientists release GM fruit fly to save crops A genetically engineered fruit fly could provide an effective method of pest control, new research has shown. The mutant males of the Mediterranean fruit fly developed by researchers have a lethal gene that interrupts female development. If released into the wild, they could prevent damage to crops in a way that is cheap, and environmentally friendly, say the researchers. “The flies are not sterile, but they are only capable of producing male offspring after mating with local pest females — which rapidly reduces the number of crop-damaging females in the population,” said Philip Leftwich, lead researcher from the University of East Anglia’s School of Biological Sciences in England. New app to help track mother, child health Samsung has partnered with the World Health Organisation to distribute smartphones and cloud-based collectors to store data for use by health workers. The smartphones will be loaded with software to track the health of a pregnant mother until the child is born. This will provide a database for health workers and help reduce maternal deaths.
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Aug 18th 2014