cultures, while boosting prions

did not appear to increase their

infectiousness or particle

numbers. Agents that disrupt

viruses stopped the cells infecting

other cultures.

However, leading prion

researcher Adriano Aguzzi of the

University Hospital of Zurich in

Switzerland says Manuelidis won’t

prove her case without isolating

the proposed virus and showing

it causes TSE. She should also test

other strains for these particles

and see if her infected cultures

cause TSE in animals, he says.

in TSE-infected brains may be the

culprits, but since such brains are

degenerating, the particles have

been dismissed as general debris.

However, when Manuelidis

studied the particles in cultures

of neural cells infected with two

particular strains of scrapie and

CJD, she found they contained

particles that had clustered

in regular arrays, as viruses do

in cells – and no apparent prions

(Proceedings of the National

Academy of Sciences, vol 104,

p 1965). Cells with more particles

were better at infecting other cell

THE mysterious origin of

undersea hills may have been

explained. It’s all down to

trapped wind.

The low hills under the

Arctic Ocean, which can grow up

to 40 metres tall and several

hundred metres across, have

been a puzzle ever since their

discovery in the 1940s. To

investigate, William Ussler from

the Monterey Bay Aquarium

Research Institute in California

and his colleagues mapped the

sea floor of the Beaufort Sea shelf,

off the north coast of Canada.

They found that methane was

being released from the hilltops.

The team believe that when

melting ice sheets flooded the

shelves at the end of the last ice

age 10,000 years ago, it warmed

a frozen mixture of methane and

seawater in the sediment. This

decomposed, releasing methane

gas that bubbled under the sea

floor, pushing the sediment up

and creating the hills

(Geophysical Research Letters,

DOI: 10.1029/2006GL027977).

This is worrying, as methane

is a greenhouse gas. “If warming

continues there may be a

substantial addition of methane

to the atmosphere,” warns Ussler.

The hills are alive

with methane

BREASTFEEDING is well known to boost

an infant’s health, and now it seems

it may be good for the mother as well.

In a study of 96,648 nurses who

gave birth between 1986 and 2002,

those who had spend at least two

years of their lives breastfeeding were

19 per cent less likely to suffer a heart

attack than those who hadn’t

breastfed at all. The difference was

independent of any of the usual risk

factors for heart disease, such as

family history, diet or exercise levels.

One possible explanation, says

study leader Alison Steube of Harvard

Medical School, is that nursing a

newborn may help a mother’s

metabolism switch from pregnancy

mode back to normal. “Pregnancy is

associated with a number of things

that you normally wouldn’t want to

happen to your body,” Steube says,

including storing more fat and having

higher than normal levels of fatty

acids circulating in the blood. By

breastfeeding, mothers can convert

those energy reserves into nutrition

for their infants.

“Breastfeeding isn’t just good for

babies, it’s good for mothers, too,”

says Steube, who presented her

findings at a meeting of the Society

for Maternal-Fetal Medicine in San

Francisco last week. She recommends

that mothers breastfeed for three

months to a year after giving birth.

SANDBLASTING is the key to a

sparkling complexion – at least for

Saturn’s moons.

Astronomers first observed

Saturn’s moons in detail in 2005

using the Hubble Space Telescope,

during a rare perfect alignment

of the sun, Earth and Saturn.

They found that some of the moons,

such as Tethys, shown below,

are dazzlingly white, but no one

could explain why they have such

reflective surfaces.

Now Anne Verbiscer at the

University of Virginia, Charlottesville,

and her colleagues have an answer.

They believe that one of the moons,

the icy Enceladus, has been giving

its neighbours a makeover by

spewing ice crystals into space.

The micrometre-sized particles,

thought to be ejected by geysers

at Enceladus’s poles, bombard the

other moons at speeds of several

kilometres per second, coating

them with ice (Science, vol 315,

p 815). “They churn up the surface

and create this fluffy layer,” says

Verbiscer. “Any light hitting them

then gets reflected right back.”

The geysers are believed to

originate from subsurface reservoirs

of liquid water, which has led

other astronomers to speculate that

Enceladus might harbour life. If so,

microbes may have hitched a ride

on the flying ice to other hospitable

moons, such as Titan, says Joe Burns,

an astronomer at Cornell University

in Ithaca, New York, who was not

involved in Verbiscer’s study.

VIRUSES, not prions, may be

at the root of diseases such as

scrapie, BSE and vCJD.

The widely accepted theory

of what causes these so-called

“transmissible spongiform

encephalopathies” (TSEs), such as

mad cow disease, is that deformed

proteins called prions corrupt

other brain proteins, eventually

clogging and destroying brain

cells. But this theory has never

been proved completely.

Laura Manuelidis of Yale

University has insisted for years

that virus-like particles observed

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What if rogue proteins aren’t to blame for vCJD…Moons reveal their makeover secret

Mothers get heart risk off their chest

www.newscientist.com 17 February 2007 | NewScientist | 17