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THEY may seem to just eat, cry,

sleep and poo, but 3-month-old

babies may already be aware of how

many animals are dangling from

their mobiles. Véronique Izard at

the University of Paris-South in

France and her colleagues have

discovered that babies have brain

circuits dedicated to noticing

quantity, adding weight to the

argument that humans possess

an innate sense of numbers .

Izard had already shown

in adults and 4-year-olds that

numbers seem to be processed in

a particular part of the brain, and

separately from other information.

To find out if 3-month-old babies

did the same, the team fitted

36 infants with caps designed

to record their brain waves.

The babies were then shown a

series of images on a screen. Most

of the time consistent objects and

quantities appeared, for instance,

four ducks. Occasionally, though,

either the number or the object

would be changed, and researchers

recorded changes in their brain

activity in response. Like adults,

the babies processed changes

in the identity of the object in

a different part of the brain to

changes in number (PLoS Biology,

DOI: 10.1371/journal.pbio.0060011).

Babies get to grips

with quantities

DEPOSITS of plaque that clog

up the brains of people with

Alzheimer’s disease may form

much faster than expected. Brains

imaging experiments involving

live mice have shown that plaques

can form within a single day, and

seem to be the cause of brain

damage, rather than the result of

earlier brain injury.

Bradley Hyman of

Massachusetts General Hospital

in Boston and his colleagues

imaged the brains of mice

genetically engineered to develop

the equivalent of Alzheimer’s

disease. Whenever a plaque

began to form, repair cells called

microglia congregated nearby

and stopped the plaque from

growing any larger. But after two

or three days, damage always

appeared in nearby brain tissue,

with connections between brain

cells disappearing altogether or

becoming abnormal (Nature,

DOI: 10.1038/nature06616).

The results provide the best

evidence yet that plaque formation

initiates brain degeneration. “Our

results are consistent with the

model that’s widely thought to be

plausible – that the plaques cause

widespread damage throughout

the brain cortex,” says Hyman.

But the speed of plaque formation

was the big surprise. “The

assumption has been that they

take years to form in humans, and

months in mice, but they formed

in less than 24 hours.”

Hyman thinks the same

thing probably happens in

humans, with the slow

progression of the disease being

marked by a multitude of small

but sudden eruptions of plaque

over many years.

Alzheimer’s-like plaques can form in mice ‘within a day’

IF YOU want to lose weight but can’t

stand running, lift weights instead.

New research in mice shows that

strength training is just as good as

endurance training at burning off fat.

Running and other endurance

activities build up what’s known

as “slow” or type I muscle. It is

rich in mitochondria, the energy

powerhouses of cells, and research

has shown that this type of muscle

combats weight gain and reduces

the incidence of metabolic problems .

“Fast” or type II muscle – the kind

you build when pumping iron – is

mitochondria-poor and was thought

to be less effective in reversing

weight gain.

Kenneth Walsh at Boston

University School of Medicine and

his colleagues were curious to know

how weight training affects

metabolism. So they designed a

mouse in which Akt1, a gene involved

in building type II muscle , could be

switched on and off by giving the

mice a drug.

The mice ate a high-fat, high-

sugar diet and got fat. But when

the gene was activated, not only did

the rodents’ muscles bulk up, they

also lost body fat. This was despite

them not exercising and continuing

to overindulge (Cell Metabolism,

DOI: 10.1016/j.cmet.2007.11.003).

There were other metabolic

improvements too, such as a decrease

in fat around the liver. “It was

stunning,” says Walsh. “Type II

muscle has been under-appreciated.”

To dump fat, pump iron

SOME microbes are happy to hide

away from the big, bad world.

Joachim Reitner at the University of

Göttingen in Germany and colleagues

have found the first evidence that

microbes could survive inside gas

bubbles within volcanic rock.

The team examined lava that

had been extruded under water

around 390 million years ago, and

found curved filaments of minerals

lining the inside of bubble

chambers. The filaments’ shape

and chemical composition suggest

they are the remnants of micro-

organisms (Geobiology, DOI: 10.1111/

j.1472-4669.2007.00131.x).

A layer of cement deposited

before the filaments suggests that

the microbes probably colonised the

lava more than 1000 years after it

had solidified. Reitner believes they

managed to get deep into the rock

via tiny fractures, which would have

opened up as the lava cooled quickly

under water, and speculates that they

fed on reduced iron in the rock.

Such colonies could have been

living inside bubbles for billions of

years, says Reitner. He points out that

organic carbon and marks etched by

microbes have previously been found

in 3.5 billion-year-old volcanic glass.

Today, similar microbes may well

be found beneath much of the ocean

floor, Reitner adds.

Fossil bugs found in volcanic bubble

20 | NewScientist | 9 February 2008 www.newscientist.com

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