High life prompts genetic shift
Extreme altitudes have created different coping strategies.
17 February 2004
HELEN PEARSON

Inhabitants of the harsh, high-altitude plateaus of the world have evolved
to survive lofty conditions in different ways, a new genetic study reveals.

Cynthia Beall of Case Western Reserve University in Cleveland, Ohio, studies
the inhabitants of the Tibetan plateau, the Ethiopian plateau and the Andean
Altiplano in Peru and Bolivia - locations where hardy residents routinely
dwell at altitudes of more than 4,000 metres.

At these altitudes, the thin air leaves most tourists gasping for breath.
"You're getting one third less oxygen every time you take a lungful of
air,"
says Beall. Yet the regular inhabitants appear almost superhuman in their
ability to function normally in such extreme conditions.

Previous studies have shown that the Tibetan, Ethiopian and Andean
populations have developed slightly different ways of boosting their oxygen
levels to cope with the thin air. Those in the Andes pump out more
haemoglobin - a molecule that carries oxygen around in the blood. The
Tibetans, by contrast, have relatively low haemoglobin levels but breathe
faster to take in more oxygen. "The slightest bit of exercise makes them
really pant," Beall says.

To understand what underlies these physiological changes, Beall has begun to
explore each population's genetic code: specifically, a short region of DNA
in the cells' power-generating mitochondria. This DNA is expected to contain
distinctive sequences that might explain how cells churn out energy with
little oxygen to fuel them.

Beall has examined this DNA from several hundred people in populations from
the Andes, Tibet and Ethiopia. Their genetic sequences are largely
dissimilar, she revealed at a meeting of the American Association for the
Advancement of Science in Seattle this week. This supports the idea that the
three groups have separately evolved different tactics to survive in the
thin air.

Read the rest at Nature
http://www.nature.com/nsu/040216/040216-7.html

Pigeons take the highway
Some birds follow roads instead of flying direct.
10 February 2004
HELEN R. PILCHER

 Researchers may have discovered how pigeons find their way along familiar
routes. Instead of heading straight for their destination, they follow main
roads, railways and rivers.

Tim Guilford and colleagues from Oxford University fitted more than 50
homing pigeons with tiny tracking devices. They then monitored them, second
by second, as they made the familiar journey back to their loft.

Some of the birds that used landmarks did so again and again on separate
occasions, says Guilford, following a set path to theirloft. "One pigeon
flies along the road to the first roundabout, takes the third exit, goes
along the dual carriageway to the next roundabout, then leaves the road and
goes cross-country," he says.

The birds can add an extra 20% or more to their journey by following these
features, says Guilford. It may be more demanding physically, he says, but
easier mentally.

Other birds probably use a similar strategy. Even crows may not fly 'as the
crow flies', says Guilford.

http://www.nature.com/nsu/040209/040209-1.html

Comment:
Could pigeons be used as a navigation aid to blind motorists in much the
same way as dogs guide them on foot?


Talking to bacteria
Researchers teach cells a new language.
12 February 2004
PHILIP BALL

Scientists have genetically engineered bacteria to 'talk' to each other in a
new language1. The achievement brings us one step closer to turning cells
into tiny robots that we can control by flooding them with chemicals.

Bacteria already communicate with each other by sending out chemical
signals. A cell might release a certain chemical in response to stress, for
example, letting other cells nearby know they should prepare for some
unpleasant environmental conditions. When the chemicals reach a high enough
concentration, they switch on genes in neighbouring cells that change their
behaviour.

But cells typically have a limited number of stimuli that provoke these
chemical warnings, and a limited number of chemicals that they can use to
communicate. James Liao and co-workers at the University of California, Los
Angeles, wondered if they could get bacteria to talk using a different
chemical.

They started by stitching a 'module' of control genes into the genome of
Escherichia coli bacteria - these genes can switch on or off other genes
naturally present in the bacteria. This technique has been used before. For
example, four years ago researchers at Princeton University in New Jersey
added a gene module to E. coli cells that made them blink on and off like
light bulbs. The genes did this by prompting the cells to make a
light-emitting protein called GFP in regular spurts.2

Liao and colleagues went a step further, modifying E. coli cells to produce
GFP only when triggered by a chemical called acetate. Acetate is a normal
by-product of the metabolism of E. coli - the cells exude it constantly,
rather like sweating. So the bacteria in Liao's lab constantly told each
other to light up.

The team managed to control the conversation by adjusting the acidity of the
cell medium. In non-acidic conditions, it takes more acetate to trigger a
cell, so there needs to be a lot of cells secreting acetate to start the
conversation. In acidic conditions, just a few cells are enough to start a
chat.

http://www.nature.com/nsu/040209/040209-7.html

Comment:
Next we'll hear claims of 'bacteria consciousness'.

Boubous belt out victory duet
Tropical crooners sing when they're winning.
14 February 2004
HELEN R. PILCHER

Football fans aren't the only ones to celebrate a win with a rousing song.
Tropical birds called boubous do the same, a study has found.

The monogamous birds sing a special 'victory duet' after they have seen
potential intruders off their patch, report Ulmar Grafe of the University of
Würzburg and Johannes Bitz of the German Primate Centre in Göttingen,
Germany, who studied the birds.

The researchers played recordings of four bird-song duets, which are often
sung by boubous during contests over territory, to 18 different bird couples
in Africa's Comoé National Park on the Ivory Coast.

Sixteen of the pairs stood their ground. Eleven of these 'winners' broke
into their victory song shortly after the recording was turned off. Losers
never sang at all1.

"The duet is clearly a post-conflict display," says Grafe. Boubous are
extremely territorial - they probably sing to deter others from invading
their patch, he says.

http://www.nature.com/nsu/040209/040209-15.html

Posted by
Robert Karl Stonjek.
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