Eat a little less, remember more

EATING less doesn’t just boost physical health. In elderly people, it seems to improve memory, too.

As well as extending lifespan in mice , restricting calorie intake has been shown to boost cognitive ability in elderly animals.

To see if the cognitive benefit held for people, Agnes Flöel and colleagues at the University of Münster in Germany tested the short-term memory of 50 people, with an average age of 60. The people were overweight, but not obese, and one-third of them were instructed to eat 30 per cent fewer calories than normal each day.

After three months, the dieters scored 20 per cent higher on the word-based memory test than they had before dieting, recalling on average 12.5 out of 15 words, compared to 10.5. “Two words may not seem like much, but it’s more than the difference between people under 30 and above 50,” says Flöel. Those who did not go on the diet showed no change (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0808587106).

The dieters had lower levels of glucose and insulin in their blood, which previous studies have linked to improved brain function.

Leaky membranes may be key to Parkinson’s disease

THE origin of the mysterious filaments that clog the brains of people with Parkinson’s and other neurodegenerative diseases may have been identified.

It seems that the barrier enclosing the nucleus inside cells grows leakier with age, admitting proteins from outside. One, called tubulin, forms long filaments that clog up the nucleus and may damage chromosomes.

Lead researcher Martin Hetzer of the Salk Institute for Biological Sciences in La Jolla, California, says that in people with Parkinson’s,

tubulin filaments abound in the substantia nigra, the part of the brain affected by the disease.

Finding a way to reverse nuclear “leakiness” could lead to new treatments as well as slowing ageing more generally , he says .

The barrier between nucleus and cytoplasm is usually policed by nuclear pore complexes, molecular sentinels regulating passage of molecules in and out. Hetzer and his colleagues investigated the fate of these complexes as cells age. They showed that Caenorhabditis

BRAIN activity in babies listening to

a drum beat suggests they are born

with a keen sense of rhythm. The

finding might help to spot abnormal

brain development at an early age.

Babies under a year old often clap

or bounce to a rhythm, but whether

they are born with the ability to

recognise a beat, or learn it later, was

unclear. To find out, a team led by

István Winkler from the Institute for

Psychology in Budapest, Hungary,

and Henkjan Honing from the

University of Amsterdam in the

Netherlands placed electrodes on

the scalps of sleeping babies just

two or three days old, while playing

them a rock drum rhythm.

When the rhythm stopped briefly

and then restarted out of sync with

the original beat, the babies’ brains

produced electrical activity known to

be associated with the violation of

sensory expectations (Proceedings

of the National Academy of Sciences,

DOI: 10.1073/pnas.0809035106).

This didn’t happen after the rhythm

merely missed a single beat.

“Beat perception is there right

from birth,” Winkler concludes. He

now plans to investigate whether

poor beat perception in newborns is

a sign of speech and communication

problems to come.

Born to follow the beat

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elegans, a roundworm whose cells do not divide in adulthood, retains the same complexes for life. This was also true in non-dividing rat neurons (Cell, DOI: 10.1016/j.cell.2008.11.037).

But these pore scaffolds gradually break down with age, admitting proteins. “We think the age-dependent deterioration of pores might lead to defects in nuclear function,” Hetzer says. “We are now investigating the possibility of plugging the leaky pores and preventing breakdown of cell compartmentalisation.”

A shape-shifting fishy trinity

IT IS the very opposite of family

resemblance: three groups of

strikingly different-looking fish that

turn out to be males, females and

young of the same family.

Tapetails (top picture) live in

shallow waters and are named for

the long streamers that trail behind

them. Whalefish and bignoses are

both deep-sea fish , but while

whalefish (middle) lack scales and

have huge jaws, bignoses (bottom)

have long nasal organs and

immobile jaws, and live off energy

stored in their gigantic livers.

Nobody thought these groups

were related. “The differences were

so extreme,” says marine biologist

David Johnson of the Smithsonian

Institution in Washington DC.

Then a study found that

whalefish and tapetail

mitochondrial DNA is virtually

identical, prompting Johnson to

re-examine museum specimens.

This revealed one in the process of

changing from a tapetail into a

whalefish. Specimens intermediate

between tapetails and bignoses

were collected in 2007, and

together with more DNA analysis

this proved that the three families

are really one (Biology Letters,

DOI: 10.1098/rsbl.2008.0722).

A “tapetail” larva grows up to be

a “whalefish” female or “bignose”

male. Johnson claims this is the

most extreme metamorphosis

ever seen in a vertebrate.

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31 January 2009 | NewScientist | 15