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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