4 December 2010 | NewScientist | 19

DNA trick throws ageing into reverse

A TECHNIQUE to keep the tips of your chromosomes healthy could reverse tissue ageing. The work, which was done in mice, is yet more evidence of a causal link between chromosome length and age-related disease.

Telomeres, the caps of DNA which protect the ends of chromosomes, shorten every time cells divide. The enzyme telomerase slows this degradation by adding new DNA to the ends of telomeres, but eventually cells stop dividing and die when telomeres drop below a certain length – a normal part of ageing.

Mariela Jaskelioff and her colleagues at the Dana Farber Cancer Institute in Boston engineered mice with short telomeres and inactive telomerase to see what would happen when they turned the enzyme back on. These mice had shorter lifespans, atrophied organs and smaller brains than mice that hadn’t been engineered.

Four weeks after the team switched on the enzyme, they found that tissue had regenerated in several organs, new brain cells were developing and the mice were living longer (Nature, DOI: 10.1038/nature09603).

LHC recreates early universe as a superhot liquidAN extremely hot, dense liquid. That’s what the universe may have looked like moments after its birth, according to the surprise first findings of the ALICE experiment at the Large Hadron Collider at CERN, near Geneva, Switzerland.

The LHC started smashing together the nuclei of lead atoms on 7 November, producing dense fireballs of subatomic particles at over 10 trillion degrees. The idea is that this will recreate the primordial soup of particles called the quark-gluon plasma that appeared just after the big bang.

Gluons and quarks went on to become the “building blocks” of neutrons and protons.

Many models have suggested that the flow of particles from these high-energy collisions should behave like a gas – but in ALICE they acted like a liquid. A further surprise was the density of particles created by the smash. It is widely assumed that there is an upper limit on how many interacting gluons can be packed into a given volume. If this assumption right, no more new debris particles should be

CANNABIS is a double-edged sword: by dampening the immune system, it provides relief from inflammatory diseases, but this also increase the risk of infections. Now we know how it does this: its active ingredient targets a newly discovered type of cell that lowers the immune response.

Prakash Nagarkatti at the University of South Carolina School of Medicine and colleagues injected the main active ingredient of cannabis, delta-9-tetrahydrocannabinol (THC), into mice. THC activated two types of cannabinoid receptor on immune cells, called CB1 and CB2. Activation

of these receptors led to a “massive mobilisation” of myeloid-derived suppressor cells (MDSCs), which play a crucial role in lowering the immune system response back down to normal levels (European Journal of Immunology, DOI: 10.1002/eji.201040667).

The discovery offers a possible explanation of why cannabis smokers have a higher risk of getting infections, says Nagarkatti. It may also mean THC could be used when there is a need to suppress the immune system – after an organ transplant, for example.

How cannabis calms immune system

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produced during a collision once this point is reached.

But in ALICE, the collisions produced more subatomic particles than expected (arxiv.org/abs/1011.3914 and arxiv.org/abs/1011.3916). “This means that if an upper limit exists, it has not yet been reached at the energies used at LHC,” says David Evans of the University of Birmingham, UK, a member of the ALICE team.

This is especially significant, because ALICE has used the highest energies of any particle accelerator so far.

Moon water experiment fails

OUR best theory of how the moon got its water has just been thrown into doubt.

NASA’s Deep Impact and Cassini missions and the Indian probe Chandrayaan-1 last year reported detecting a water film only a few molecules thick over large parts of the lunar surface. It was thought to have been created by protons that stream in from the sun combining with oxygen atoms pried away from minerals in the lunar soil.

Now Raúl Baragiola and colleagues at the University of Virginia, Charlottesville, have tried to reproduce this reaction in the lab by firing protons at crystals of ilmenite and anorthite, two of the most common lunar minerals. But they found no sign that this produced either water or the hydroxyl (OH) radicals that the reaction should have generated. In fact, they found the opposite: the protons destroyed any residual traces of water in the minerals (Icarus, DOI: 10.1016/j.icarus.2010.11.007).

According to Jeffrey Gillis-Davis, a planetary geologist at the University of Hawaii, the lunar soil may behave differently because its porous, powdery texture may allow it to retain water and hydroxyl better than solid crystals. Thus, he says, failure of the experiment “does not put the final nail in the coffin” of the idea that the water is produced by protons from the sun.

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