16 | New Scientist | 2 November 2019AntarcticaGalaxies seem to be
caught in cosmic webA CURIOUS link has been spotted
between galaxies separated by
large distances, pointing to the
existence of a vast structure
underlying the universe known
as the cosmic web.
Joon Hyeop Lee at the Korea
Astronomy and Space Science
Institute in South Korea and his
team looked at 445 galaxies and
found the rotation of each was
linked to the motion of thousandsHow a high-salt diet
can gum up the brainEATING too much salt can lead to
cognitive impairment, and now
we may know why. It kicks off an
immune response that causes the
build-up of a protein that may stop
brain cells from working properly.
Scientists have long known that
a high-salt diet increases risk of a
stroke. It was first thought that salt
led to high blood pressure, which
damaged the brain, but recent
research shows that too much salt
can cause problems even among
those with normal blood pressure.
Costantino Iadecola at Cornell
University in New York and his
colleagues wanted to find out
why. To do so, they fed mice a diet
containing between eight and
16 times the normal amount of
salt, then had them perform
cognitive tests. After two months
on this diet, the mice were unable
to recognise new objects they were
presented with and were muchNutrition^ SpaceICE shelves that have disintegrated
in part of the Antarctic may have
been primed to collapse because of
thinning over the past 300 years.
An analysis suggests ice shelves
on the east side of the Antarctic
Peninsula have thinned since 1700,
leaving them at risk as human-
caused climate change took hold.
What scientists know about past
losses from the Antarctic ice sheet
is limited because satellite records
only go back to the 1990s. To go
further, James Smith at the British
Antarctic Survey and his team
looked at fossils of single-celled
algae in mud near the South Orkney
Islands, off the tip of the peninsula.
They used the ratio of oxygen
isotopes in the fossils to estimate
past changes in the climate and
glacier discharge – which is the
melting of the ice into ocean.This revealed the rate of glacier
discharge was stable for most of the
past 6000 years, picking up around
the start of the 16th century, but not
beyond natural variations. A faster
acceleration started around 1700,
followed by an even more rapid one
at the start of the 20th century.
The greater losses from 1700
correlate with a strengthening of
a climate phenomenon that brings
stronger westerly winds, warmer
air and possibly warmer water into
the area, melting ice from above
and below (Scientific Reports,
doi.org/dc9d).
However, Eric Rignot at the
University of California, Irvine, says
the study puts too much emphasis
on the recent collapses being down
to changes around 1700 rather
than the dramatic warming seen in
the past 50 years. Adam VaughanBreak up of huge ice shelves
may have much older roots
of neighbouring galaxies.
Essentially, the rotation of
the galaxies seems to match the
motion of those nearby. If a galaxy
rotates towards us, its neighbours
are also moving towards us. The
same goes for galaxies that are
rotating away: their neighbours
are moving away from us. This
effect doesn’t appear to be due to
direct interaction, as the galaxies
are too far apart (The Astrophysical
Journal, doi.org/dc7d).
The team suggests this is
evidence for the existence of
large-scale structure within the
cosmic web, theorised filaments
of material that pervade the
universe. The galaxies that appear
to have a shared motion may be
on similar strands of the web.
This evidence for the cosmic
web isn’t conclusive, says Michele
Cappellari at the University of
Oxford. He says it is possible the
galaxies may have just formed in
the same environment and retain
signs of those initial movements.
Jonathan O’Callaghanslower at finding their way out of a
maze than those on a normal diet.
Initially the team believed
that excess salt was reaching the
brain and causing damage there.
However, an analysis of brain
tissue suggested something else
was going on. In this tissue, the
team found a build-up of tau,
a protein that has been linked to
Alzheimer’s disease.
The researchers think
they know why the tau began
accumulating. They found that the
high-salt diet also increased the
number of immune system T-cells
in the gut. These cells produce
small chemical messengers that
travel to blood vessels in the brain,
where they reduce the production
of nitric oxide.
Lower levels of nitric oxide in
the brain led to reduced blood
flow and also increased the
activity of an enzyme in brain
cells called CDK5. It is this enzyme
that prompts the build-up of tau
proteins (Nature, doi.org/dc7h).
Ruby Prosser ScullyROSEY GRANT/BRITISH ANTARCTIC SURVEY
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