27 August 2011 | NewScientist | 15

Hibernation is cool for saving hearts

CHILLED-OUT mice could point the way to reduced heart-attack damage in humans.

Therapeutic hypothermia is already used to protect patients suffering injuries that restrict the flow of blood and oxygen to tissues, but cooling is slow and difficult, not least because the body resists it.

In tests on mice in which heart attacks were induced, Cheng Chi Lee at the University of Texas at Austin showed that a biomolecule called 5’-AMP, which helps suppress metabolism in hibernating mammals, could be used to help induce hypothermia and reduce heart tissue damage.

Untreated mice and those given 5’-AMP but artificially kept at normal temperatures suffered greater heart damage. Injected mice experienced a dramatic drop in metabolic rate, meaning they could be cooled faster and more safely than untreated mice (American Journal of Translational Research, vol 3, p 351).

“This advances the idea that 5’-AMP could be useful as an adjunct therapy to the body cooling already used to protect hearts from injury after heart attack or cardiac surgery,” says Jeremy Pearson of the British Heart Foundation.

Backwards-spinning exoplanets born out of stolen gasSTEALING gas from their siblings could leave stars with a motley crew of planets – including ones with backward orbits.

Our solar system is thought to have formed from a collapsing cloud of gas and dust that flattened out as it spun. This explains why the planets all orbit the sun in the same direction as the sun itself spins, and share the same plane.

Exoplanets tell a different story, with some tilted at jaunty angles and others orbiting their stars backwards. Planet-on-planet violence is one explanation,

but Ingo Thies of the University of Bonn in Germany and colleagues suggest the culprit is the star itself, before its planets are born.

The team made a computer model of stars forming in a cluster. The stars started out forming proto-planetary discs in the usual way. But if a star veered too close to another clump of matter, like another star’s disc or a cloud of gas that hadn’t formed a star yet, it sucked huge streams of gas – up to 30 times the mass of Jupiter – from its neighbours and into its own nascent disc.

FANCY discovering a new species? It shouldn’t be too difficult, as the best estimate yet of how many species the planet supports comes up at 8.74 million. Although about a quarter of those are in the sea, some 7.5 million species remain to be discovered.

Previous estimates varied wildly between 3 and 100 million. Camilo Mora of the University of Hawaii in Honolulu and colleagues say their figure is more accurate because it relies on a validated method consistent across well-catalogued forms of life such as mammals, birds and molluscs. For 18 of these groups,

Mora’s team worked out the numerical patterns by which they fan out hierarchically from phyla into classes, orders, families, genera and species.

Once they had established how these known groups radiate numerically, they extrapolated to less well-known groups such as fungi, enabling them for the first time to estimate with confidence the number of species in each hierarchy (PLoS Biology, DOI: 10.1371/journal.pbio.1001127).

Some 86 per cent of land species and 91 per cent of marine species are yet to be found.

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In the model, this stolen material tilted the disc. And when the angle and the mass of material were just right, the final disc ended up spinning in the opposite direction to the star. Any planets that formed in that disc did the same. The work will appear in Monthly Notices of the Royal Astronomical Society.

The influx of gas could also compress the inner part of the disc, making planets form there more quickly. These may be more susceptible to violent crashes, leading to further eccentric orbits.

Evidence for Mars floods all dried up?

LAVA, not water, may have carved the biggest channels on Mars.

Ever since NASA’s Mariner 9 spacecraft beamed back the first images of the channels in the 1970s, most people have assumed they were created by massive floods. But David Leverington of Texas Tech University in Lubbock says flowing water would have left behind much more sediment than is seen. There are also few minerals that form in liquid water present.

Lava, however, is known to have carved big channels on the moon. And Leverington points out that some of the channels on Mars start on the flanks of volcanoes and end in large deposits of solidified lava (Geomorphology, DOI: 10.1016/ j.geomorph.2011.05.022).

Kelin Whipple of Arizona State University (ASU) in Tempe agrees that lava probably carved the huge channels, such as Kasei Valles (shown). He says the study calls into question the case for huge volumes of water – and possibly an ocean – on ancient Mars.

But Phil Christensen, also at ASU, says clays and fans of sediment still point to the existence of smaller Martian lakes and rivers. These would be better places to search for life, he says, because they would have held water for longer periods than the giant channels, where any floods would have been fleeting.

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