Science  01 Apr 2011:
Vol. 332, Issue 6025, pp. 21

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  1. How a Dinosaur Is Like a Vacuum Cleaner

    The plant-eating sauropod dinosaurs, such as Brachiosaurus and Apatosaurus (formerly called Brontosaurus), were the largest animals ever, weighing up to 80 metric tons and stretching up to 30 meters in length. Many also sported very long necks—though researchers have debated their purpose. Now, two scientists in the United Kingdom may finally have the answer.

    Evolutionary ecologists Graeme Ruxton of the University of Glasgow and David Wilkinson of Liverpool John Moores University created a simplified mathematical model of Brachiosaurus. By varying the dinosaur's dimensions, the duo found that its 9-meter neck gave Brachiosaurus an 80% energy savings in foraging compared with a 6-meter-long-neck. Like a clunky, old-fashioned vacuum cleaner with a long tube, Brachiosaurus could graze widely without having to move its huge body. The energy savings might even have allowed the dinosaur to browse the treetops, the pair suggest in a paper published online 23 March in Biology Letters.

    Not so fast, says physiologist Roger Seymour of the University of Adelaide in Australia: Pumping blood to a raised head would require 50% of the animal's entire energy stores. The paper shows a long neck's advantage on the ground, he contends. “Let's just leave it there and not ask the sauropods to raise their necks.”

  2. Test Tells If the Heart Fits

    Every year, about 4000 people worldwide get a heart transplant; roughly 40% of them experience at least one episode of acute organ rejection within a year. Usually patients must undergo regular biopsies of their new organ to monitor its health. The procedure is both painful and expensive, but now a new blood test could help.

    Biophysicist Stephen Quake and his colleagues at Stanford University developed a test that monitors fragments of DNA that are released into the bloodstream when cells from the transplant tissue are broken down. When a transplant goes well, donor organ DNA typically makes up 1% of free DNA in the recipient's blood. During a rejection event, that fraction increases to an average of 3%, the team reports online this week in the Proceedings of National Academy of Sciences. Researchers hope that this test can eliminate the need for regular biopsies as a means of rejection monitoring. The new test is likely to be available to doctors in a year's time.