16 | NewScientist | 13 December 2014

IS YOUR brain to blame for your high blood pressure? We’ve known for more than 30 years that fat and high blood pressure are linked, and at last we know this is thanks to the action of a hormone in the brain.

Leptin is produced by fat cells and normally makes a person feel full. But in people who are obese, the body stops responding to the message to stop eating, so leptin levels build.

The hormone was suspected of raising blood pressure in obese people via its effect on the sympathetic nervous system, which is involved in flight-or-fight responses. This network’s action in the kidneys seems to raise blood pressure, but conclusive evidence of leptin’s role has been hard to find.

Michael Cowley of Monash University in Melbourne,

Australia, and his colleagues have now shown that leptin is involved via its action in the brain. They have pinpointed an area in the mouse brain that increases blood pressure when exposed to high leptin levels (Cell, doi.org/xkr).

Turning to humans, the team found that obese people who either couldn’t produce leptin or couldn’t respond to leptin did not have high blood pressure – suggesting that leptin is indeed a linking factor.

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Trick of the light makes bird feathers blue, but not red

LIKE the colour blue? You’re not the only one. Blue jays and cardinals get their vivid hues in different ways, but for the same reasons. Efforts to understand why may help create coloured displays for devices like e-readers.

Colours in nature normally come from pigments, which absorb most light wavelengths, except for ones that they reflect to give the colour we see. But blue pigment is rare. Instead, the blue sported by bluebirds comes from tiny air pockets inside the feathers, which scatter light to create blue. Red feathers, however, rely on pigment alone.

Vinothan Manoharan at Harvard University and his

colleagues wondered if red colours were impossible to achieve without pigment. “We thought, maybe the birds know something we don’t,” he says. The team studied nanometer-scale plastic beads, an inverse version of the air pockets that give blue feathers their colour. Changing the size of the beads alters how light scattered from nearby beads interferes, enhancing particular shades.

Manoharan’s team used large beads to try to enhance red light but, instead, purple appeared. The unexpected blue component appears for the same reason the sky is blue, Manoharan says: individual particles preferentially scatter blue light (Physical Review E, doi.org/xk7).

The group is now seeing if hollow beads can form reds, and hopes to use such “structural” colours in reflective displays that aren’t backlit — think a Kindle, but in colour.

Brain links obesity with blood pressure

Young, hot-headed stars could host life

STARS go through a fiery youth, burning up to 180 times as brightly as their mature counterparts. Planets orbiting such stars had therefore been neglected in the hunt for life – but they may be good hosts after all.

A planet is considered habitable when it is the right distance from its star to host liquid water on a rocky surface. Lisa Kaltenegger and Ramses Ramirez at Cornell University in Ithaca, New York, calculated that young, hot stars would have habitable zones further from the star than previously thought. The smallest and coolest stars can stay youthful for 2.5 billion years – which may be enough time for life to develop (arxiv.org/1412.1764).

“We call them ‘infant Earths’ because this will happen really early on in planetary evolution,” Kaltenegger says. “It’s a really simple idea but nobody seems to have ever thought about it.”

Rocky rain brought lunar water

A RAIN of soggy space rocks may have brought water to the moon.

The moon is thought to have formed when a giant object smashed into the early Earth. The heat from this impact should have left the moon drier than a bone, so researchers were surprised to find water in rocks from deep below the lunar surface.

Erik Hauri at the Carnegie Institution of Washington and his colleagues analysed lunar rocks and estimate that meteorites equivalent to just 0.001 to 0.004 lunar masses could have brought water to the molten moon when it was 100 million years old (Earth and Planetary Science Letters, doi.org/xk6). “Anything that crashed into the moon at that point got mixed in wholesale,” says Hauri.

in Brief

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