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15 September 2012 | NewScientist | 13 Viruses trigger asthma in mice WHAT doesn’t kill you doesn’t always make you stronger. Many studies have linked asthma and viral infections in humans, but it is not clear whether the virus causes asthma, or whether children who are susceptible to viruses are also vulnerable to asthma. Research in mice now brings us closer to an answer. Anuradha Ray and Prabir Ray at the University of Pittsburgh in Pennsylvania and colleagues exposed mother mice to ovalbumin, a protein in egg white that can trigger allergic reactions. Offspring of these mice gained tolerance against ovalbumin through their mother’s milk. Then the researchers repeatedly infected some of the baby mice with respiratory syncytial virus. Three weeks later, these mice had lost tolerance to ovalbumin. Their regulatory T-cells, which normally protect against infection, were instead secreting proteins and signalling factors that cause allergic responses (Nature Medicine, doi.org/jbb). The result is important, but its relevance to human asthma remains to be seen, says Tina Hartert of Vanderbilt University in Nashville, Tennessee. How to boil water with no bubbles or explosions IMAGINE water boiling without bubbling. Although the effect has been achieved before, a new version allows water to maintain its bubble-free state even as the hot materials around it cool. The phenomenon is based on the Leidenfrost effect. If a frying pan is hot enough, droplets of water will skitter around rather than spreading into a puddle. That is because high heat evaporates enough of the water to create a vapour layer. The liquid floats on this cushion and boils without bubbling, says Neelesh Patankar of Northwestern University in Evanston, Illinois. As the surface cools, the vapour layer can collapse and the water will bubble, triggering a violent outburst. The Leidenfrost effect is a concern in chemical plants and nuclear reactors, where liquid water touching hot metal may cause explosions. But if hot water can be kept away from the material long enough, the team hypothesised, the vapour might stay in place past when the material cools to the boiling point of water, and FLUFFY, snow-white and dedicated trekkers. Arctic foxes (Vulpes lagopus) are known for their mammoth wanderings across the ice. Those journeys may have taken some to Iceland during the Little Ice Age. Recent research into the foxes’ genetics has revealed that there are at least five distinct groups – or haplotypes – found in Iceland. But when Greger Larson at Durham University, UK, and his team looked at fox DNA in 1000-year-old bones from archaeological sites in Iceland, they found that all of the ancient Arctic foxes belonged to just one of the five haplotypes. “It’s too short a time for the [other four] to have evolved,” says Larson. Instead, his team think the Little Ice Age might provide an explanation. This period of cooling, about 800 years ago, froze huge areas of the Arctic seas. It provided nomadic Arctic foxes elsewhere in the frozen north with a bridge to Iceland (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2012.1796). “Some foxes are known to roam for hundreds of miles on sea ice,” says Larson. “All you need is a little ice, and bang – the foxes are there.” Foxes took the ice bridge to Iceland JENNY E. ROSS/CORBIS there is no more explosion risk. To test this, the team covered steel balls in a nanoparticle-based coating that gave them a rough texture (Nature, DOI: 10.1038/ nature11418). They heated the balls to 400 °C and submerged them in hot water. Rather than bubbling against the scorching metal, water droplets stretched across the grooves in the rough coating and cavities beneath them filled with vapour. This kept the surrounding water undisturbed as the temperature of the balls fell all the way to 100 °C. Hurt a crow and it’ll never forget YOU can run from a crow that you’ve wronged, but you can’t hide. Wild crows remember human faces in the same way that mammals do. Crows can distinguish human faces and remember how different people treated them, says John Marzluff of the University of Washington in Seattle. To work out how the crows process this information, Marzluff had members of his team wear a latex mask as they captured 12 wild American crows (Corvus brachyrhynchos). The crows learned to associate the captor’s mask with this traumatic experience. While in captivity, the crows were fed and looked after by people wearing a different mask. After four weeks, the researchers imaged the birds’ brains while they were looking at either the captor or feeder mask. The brain patterns looked similar to those seen in mammals: the feeder sparked activity in areas involved in motivation and reward, whereas the captor stimulated regions associated with fear (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1206109109). The result makes sense, says Kevin McGowan of the Cornell Lab of Ornithology in Ithaca, New York. Crows don’t mind if humans are in their habitat – but they need to keep a close eye on what we do. JAMES NELSON/GETTY For new stories every day, visit newscientist.com/news
