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22 | NewScientist | 3 December 2011 Poisoning cancer cells with sugar IT’S a heavy price to pay for a sweet tooth. Researchers have tricked glucose-eating cancer cells into consuming a sugar that essentially poisons them – it leaves a “suicide” switch within the cells open to attack. “Most cancer cells rely almost exclusively on glucose to fuel their growth,” says Guy Perkins of the University of California at San Diego. With Rudy Yamaguchi of Kyushu University in Fukuoka, Japan, Perkins found the cells would take up a similar sugar called 2-deoxyglucose. But this sugar physically dislodges a protein within the cell that guards a suicide switch. Once exposed, the switch can be activated by a drug called ABT-263. This kills the cell by liberating proteins that order it to commit suicide (Cancer Research, DOI: 10.1158/0008-5472. can-11-3091). The approach could ultimately spell doom for several types of cancer, including liver, lung, breast and blood. In mice, the treatment made aggressive human prostate cancer tumours virtually disappear within days. Yamaguchi and Perkins are now hoping to mount a clinical trial at UC San Diego. It’s just one model, but warming might not be so severe TEMPERATURE rises due to climate change could be smaller than expected. That’s the surprise result of a new analysis of the last ice age, but it comes with a cautionary note: the result is from a single climate model and must be replicated using other models. As more greenhouse gases enter the atmosphere, more heat is trapped and temperatures go up – but by how much? In 2007, the Intergovernmental Panel on Climate Change (IPCC) said that if carbon dioxide in the atmosphere doubles, temperatures will rise by between 2 and 4.5 °C, with a best estimate of 3 °C. This is the much disputed “climate sensitivity”. Andreas Schmittner of Oregon State University, Corvallis, took a closer look at the Last Glacial Maximum some 20,000 years ago, when ice sheets reached their greatest extent. His team compiled a world map of surface temperatures, which showed that the planet was 3 °C cooler than in pre-industrial years. We know from ice cores what greenhouse gas levels were at the time, and these allowed Schmittner to calculate a TREES may get their beautiful shapes from battling the elements. A mathematical model shows that the pattern some branches make, first noted by Leonardo da Vinci, is the best at withstanding gusts of wind. Da Vinci observed that at any height above the ground, the total cross section of some trees’ branches has roughly the same area as that of the trunk. This pattern was thought to accommodate the tree’s plumbing, as water flows fastest when the branched pipes can hold as much water as the original pipe. But Christophe Eloy at the University of California in San Diego thought trees contained too little plumbing to be the reason behind the pattern. Instead he thought wind might play a role. So he built a model to simulate the bending forces exerted by the wind, and found that trees with branch thicknesses fitting da Vinci’s rule resisted breakage. The work will appear in Physical Review Letters. The model could help architects design wind-resistant buildings that mimic tree branches, says plant biophysicist Karl Niklas at Cornell University in Ithaca, New York. Da Vinci pattern helps trees resist wind MARTIN BORG/PLAINPICTURE climate sensitivity of 2.4 °C (Science, DOI: 10.1126/science.1203513). That could be good news. If climate sensitivity really is that low, global warming this century will be at the lower end of the IPCC’s estimates: around 2.4 °C above the average for 1980 to 1999, assuming we keep burning fossil fuels heavily, instead of 4 °C. But climate scientists contacted by New Scientist, including Schmittner himself, cautioned that the finding would have to be repeated with other models before making its mark on the consensus. Superbubble fires cosmic rays at us HIGH-ENERGY protons and other atomic nuclei bombard our planet from all directions. The origin of some of these cosmic rays has now been traced to the same nebular nurseries where stars are born. In 2006, astronomers saw a slight excess of cosmic rays from the direction of Cygnus X, a star-forming nebula in the constellation Cygnus (the swan). But because magnetic fields force cosmic rays to take a meandering path through the galaxy, that does not prove Cygnus X is a source. So Isabelle Grenier of the Paris Diderot University in France and colleagues looked instead at gamma rays – high-energy photons produced when cosmic rays interact with the matter or light around them. Gamma rays are not deflected by magnetic fields. Images of Cygnus X taken by the Fermi Gamma-ray Space Telescope show a superbubble – a huge cavity in the nebula carved out by stellar winds – glowing in gamma rays and forming a vaguely duck-like bright region (Science, DOI: 10.1126/ science.1210311). “An ugly duckling inside the swan,” says Grenier. Cosmic rays are thought to be accelerated to high energies by shock waves. Inside Cygnus X, those waves could be generated by supernova explosions and by the colliding winds from massive stars. JAYANNE ENGLISH (CGPS/U. MANITOBA), A. R. TAYLOR (CGPS/U. CALGARY) IN BRIEF For new stories every day, visit newscientist.com/news
