6 August 2011 | NewScientist | 19

Slipped a disc? Grow a new one

A LIVE implant could kill the pain associated with slipped discs, a study in rats suggests.

Between 1.5 and 4 million Americans are waiting for surgery to fix a herniated spinal disc, but the relief provided from a synthetic implant is the best it’s ever going to be “the minute you put it into the patient”, says Lawrence Bonassar of Cornell University in Ithaca, New York. Living tissue can grow and adapt, so may provide a better long-term solution, he says.

Bonassar’s team used cells taken from sheep spines to build replicas of rat discs, and implanted them into the spines of rats.

The implanted discs stood up to pulling and compression like the original discs. Crucially, they also improved with age, growing new cells and binding to nearby vertebrae in the six months after surgery (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1107094108).

Although the study was in rats, “it shows us what is possible”, says Abhay Pandit at the National University of Ireland in Galway. He adds that future studies will need to address the load borne by upright human spines.

Bite me and taste my poison, says killer African ratTHE deadly secret of a rat that kills lions and jackals has at last been revealed. Unlike some mammals that produce their own toxins, the African crested rat is the first known to protect itself by daubing its fur with poisons from plants.

The same lethal toxins are used by African tribal hunters to coat their arrow-tips.

Suspecting that Lophiomys imhausi may obtain toxins from chewing on the bark of the poison-arrow plant, acokanthera, Fritz Vollrath of the University of Oxford and his team offered some

to a captive animal. Over the course of a week, it periodically chewed the bark then smeared its saliva over a section of short hairs that lies along its flank, hidden inside its fur.

Placing the hairs under a microscope revealed that their surface is perforated. Each also contains fibres at its core, allowing it to soak up the toxins and store them (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2011.1169).

Vollrath says the findings tally with reports that when attacked,

A MORSEL of good news: having a gastric bypass gives people a taste for a healthier diet.

To understand why people often say they eat less fat after a bypass, a team led by Carel le Roux of Imperial College London carried out either a gastric bypass or a sham operation on rats (American Journal of Physiology, DOI: 10.1152/ajpregu.00139.2011). They found that the bypass rats ate less and regained less weight after the surgery than the others.

The researchers then gave the rats sugar water while infusing corn oil directly into their stomachs, so that

the rats had to digest the fat without tasting it. The bypass rats learned to avoid the water but the others did not. This suggests that the bypass rats avoided high-fat foods, not because they disliked the taste, but because they found it harder to digest after the operation.

Le Roux’s team also found that levels of some hormones that make people feel full were higher in rats with a gastric bypass than in the sham-operated rats after eating. They are now doing studies to see if these hormones could be used to tackle obesity.

Gastric bypass puts people off fat

Pete

r D

aze

ley/

get

ty

the rat stands its ground, parts its fur to reveal the stripe of poisonous hair, and invites the aggressor to bite its flank. Aggressors who do go in for the kill have been seen to shrink back, froth at the mouth and often collapse and die, apparently from heart failure.

The rats are also known to have abnormally thick skins and skulls, which probably evolved so that they could survive attacks until the poison kicks in. They have also – clearly – evolved immunity to the toxins.

Geyser moon is Saturn’s rain cloud

LIKE a hapless cartoon character, Saturn has its own personal “rain cloud” that follows it around. Water vapour spewing from its moon Enceladus appears to drizzle onto the giant planet from space.

When water was discovered in Saturn’s cloud tops in 1997, the source was a mystery. It is too cold there for water to linger – it should condense and rain down to lower altitudes.

But now Europe’s Herschel space observatory has an answer: space rain. It spotted the infrared signature of water vapour in a vast ring around the planet (Astronomy and Astrophysics, DOI: 10.1051/0004-6361/201117377). The most likely source is Enceladus’s geysers, which shoot 900 tonnes of water into space per second from the moon’s south pole.

Models suggest that up to 5 per cent of that water may rain down onto Saturn, making Enceladus the only moon known to affect the chemical make-up of its planet.

“There is no analogy to this behaviour on Earth,” says Paul Hartogh of the Max-Planck Institute for Solar System Research in Katlenburg-Lindau, Germany.

Leigh Fletcher of the University of Oxford says the space rain offers “a rare chance to glimpse the processes through which a planet’s stratosphere is determined”.

Na

Sa/J

Pl/S

Pace

Sci

eNce

iNSt

itu

te

For new stories every day, visit newscientist.com/news

110806_N_InBrief.indd 19 1/8/11 16:48:45