12 October 2019 | New Scientist | 35remarkable feat of brain preservation. Brains
guzzle energy to keep the electrical charges
on the inside and outside of their cells
properly balanced. Stifle the oxygen supply in
humans – for example, in a stroke – and there
is a catastrophic power cut: the pumps that bail
electrical charge across cell membranes fail,
upsetting the electrical balance inside neurons.
This makes them dump toxic quantities of
chemical signals known as neurotransmitters
onto their neighbours, triggering further
electrical mayhem and cell death.
Paradoxically, restoring oxygen makes
things worse. As energy-depleted cells
resume power generation, they create harmful
by-products, known as reactive oxygen species,
which damage and kill yet more cells.
To survive this last step, red-eared sliders
have several tricks. One is to modify their
metabolism so that they produce fewer
reactive oxygen species. Another is to make
specialised proteins that defend cells against
damage. Humans have similar defences, but
we deploy them differently. For example, we
ramp up production of some of these proteins
after damage has occurred, whereas turtles
are constantly making them. The similarities
are good news because they suggest we could
tweak our biology to make it more like that
of the turtles, says Milton. Potential medical
applications extend to any condition where
oxygen starvation is a problem, including
stroke and heart attack.Frozen frogs
Other animals have superpowers that allow
them to endure freezing and thawing. The
poster beast for this is the wood frog, which
survives harsh Canadian winters by letting
up to two-thirds of its body freeze – so solidly
that it makes a clinking noise if gently tapped.
“Biochemistry still goes on at -5°C, but at one
10,000th the normal rate,” says Ken Storey at
Carleton University in Canada. The animal’s
secret is producing a chemical that stops
moisture being sucked from its cells as ice
forms in the spaces around them. This ability
suggests a possible solution to a pressing
medical problem.
At the moment, preserving human organs
for transplant operations is difficult because
conventional freezing would destroy them.
Two-thirds of all donated hearts go to waste
every year. A team at Harvard University is
now trying to harness the wood frog’s “partial
freezing” strategy to better preserve organs.developing new tactics to tackle cancer and
ageing – seem feasible. In fact, the US has
launched a research project to exploit animal
powers that could help injured soldiers on
the battlefield (see “Stop the clock”, page 36).
“This is going to be mind-blowing,” says
Rochelle Buffenstein at Calico, a biotechnology
company in California backed by Google that
aims to combat ageing.
The astonishing skills of animals have long
fascinated scientists, but until recently it was
tricky to work out the genetic underpinnings
of their adaptations. This changed with the
advent of^ “omics”, technologies revealing the
instructions contained in all of an animal’s
genes – its genome – and the shifting activity
of these genes and other bodily molecules
in response to changes in the environment.
The genomes of an ever-expanding range
of astounding animals are being sequenced.
This allows scientists to open new doors on
the biology behind their superpowers, to
spot relevant stretches of DNA and cellular
processes and to zero in on them for further
investigation. “We can actually see what has
not been seen before,” says Sarah Milton at
Florida Atlantic University.
Milton’s interest is in turtles, in particular
their brains. Although not quite in the
painted turtle’s league, the red-eared slider, a
freshwater terrapin, can survive an impressive
six weeks without oxygen under the ice and
two days at room temperature. This is a >