3 April 2010 | NewScientist | 13

Lonely stars born between galaxies

Fight cancer by killing off cells before they turn rogue

JUNK food may seem like an addictive

drug because it is. In rats, at least, too

much fatty food raises the threshold

for feelings of satisfaction, sparking

a cycle of compulsive overeating.

In people, addictive drugs

desensitise the brain by raising the

threshold of “reward” activity that is

needed to feel satisfied: more drug

is needed to achieve the same effect.

Paul Kenny and colleagues at the

Scripps Research Institute in Jupiter,

Florida, wondered if fatty foods

might also cause desensitisation.

They used electrodes to measure

the sensitivity of rats’ brains to reward

activity. Some ate normal rat food

while others had limited or unlimited

access to junk foods, tasty to both rats

and humans. After 40 days, the brains

of those that ate junk freely were

less sensitive than those in the other

groups. They were also obese.

All the rats learned that a flash of

light led to a painful electric shock.

Rather than try to avoid the shock

when the light came on, “addicted”

rats just carried on eating. Like drug-

addicted humans, they also had fewer

receptors for the reward chemical

dopamine (Nature Neuroscience,

DOI: 10.1038/nn.2519).

Fast food ‘addicts’ may be exactly that

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Night skies suited dino-bird’s eyes

LIKE a modern owl, Archaeopteryx

may have come alive at night. The

shapes of eye sockets differ

predictably in birds that feed during

the day, night or twilight, according

to a study that promises to spill the

beans on the dino-bird’s lifestyle.

When Lars Schmitz at the

University of California, Davis,

studied 77 bird species, he found he

could predict the foraging lifestyle

of any species simply by measuring

the bones that their eyes are set in.

Each bird pupil is surrounded by a

ring of bony segments called the

scleral ring. Schmitz found that the

outer and inner diameter of this ring,

combined with the depth of eye

sockets, could closely predict when

a bird forages (Vision Research, DOI:

10.1016/j.visres.2010.03.009). This

opens up the tantalising possibility

of discovering whether extinct birds

were nocturnal.

Schmitz is currently making

detailed measurements, but a quick

look at Archaeopteryx fossils reveals

that it had wide scleral rings and

deep eye sockets, says Derek Yalden

at the University of Manchester.

According to Schmitz’s findings, this

would make the dino-bird nocturnal.

“I don’t think it had occurred

to anyone to suggest this,” says

Yalden. If he is right, all drawings of

Archaeopteryx flying through the

daytime skies of early Earth will

need to be revisited.

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