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Nature press release for 31 May issue

May 31, 2001

GENETICS: CROHN’S DISEASE GENETICS
Scientists in America and Europe have independently found a gene for Crohn’s disease, a debilitating inflammatory bowel disease affecting about one in every thousand people in Western countries.
Crohn’s disease often affects young adults, and its incidence has increased greatly over the last 50 years, probably reflecting changes in the environment and lifestyles. Possibly as a result of faulty responses to microbes living in the gut, the immune system of a patient is triggered to attack the gut lining, causing it to ulcerate and break up. Crohn’s disease has complex genetic causes, but no major gene contributing to disease susceptibility or pathology has previously been identified. One susceptibility gene was mapped in 1996 to human chromosome 16.
Now, advances in molecular genetics and the availability of the human genome sequence have led to the identification of a gene that occurs on the previously implicated region on chromosome 16. This gene is mutated in a subset of patients with Crohn’s disease.
The gene encodes a protein called Nod2. Intriguingly, Nod2 is involved in the recognition of microbes and signalling events leading to an appropriate immune response. The mutations found in patients disrupt proper signalling, which suggests a close link between the immune response to gut microbes and the development of disease.
There is no single gene for Crohn’s disease, and not every person with mutations in the gene for Nod2 will be affected. Nevertheless, Nod2 does seem normally to protect against the disease, and mutations in the gene increase disease susceptibility. Restoration of proper Nod2 function in such individuals could represent a promising preventative therapy.
CONTACT:
Dr Gilles Thomas - Fondation Jean Dausset CEPH, Paris, France
Tel +33 6 08 98 22 00, E-mail Thomas@cephb.fr

Dr Gabriel Nunez - University of Michigan Medical School, Ann Arbor, Michigan, USA
Tel +1 734 764 8514, E-mail Bclx@umich.edu

[411581] COVER: BEES GO WITH THE FLOW (pp581-583)
As a bee flies, it measures how far it has travelled by how much scenery it has passed. By jamming this navigation system, researchers have shown that bees incorporate this measurement into the dances that alert their nestmates to the location of food.
By training bees to fly down a pipe, Harald Esch, of the University of Notre Dame, Indiana, and colleagues, deceived bees into thinking they had flown a greater distance to reach a food source than they actually had. These bees then communicated their false impressions to their hivemates, who took off in search of nectar, only to overshoot the mark.
Bees measure distance using optic flow. This is the amount that an image appears to move as the position of the observer moves. Nearby things produce more optic flow than those further away - this is why the scenery near to a moving train seems to zip by more quickly than the distant landscape, and why driving a ground-hugging vehicle such as a go-kart gives such an impression of speed.
CONTACT:
Harald Esch tel +1 219 631 6552, e-mail harald.e.esch.1@nd.edu

[411558] TECHNOLOGY: MGB2 TAKES PRACTICAL STEPS (pp558-560, 561-563, 563-565; N&V)
Commercial prospects for magnesium diboride, the exciting new superconductor discovered in January this year, get a boost from three papers in this week’s Nature. These results help to allay earlier fears that the new material might not be well suited to practical applications.
Chang-Beom Eom, of the University of Wisconsin at Madison, and co-workers inadvertently contaminated one of their samples of magnesium diboride with oxygen, and found that this allowed it to carry a higher current in the presence of a magnetic field.
David Caplin of Imperial College in London, UK, and collaborators describe another way to increase the critical current: they blast the magnesium diboride with an ion beam, a stream of positively charged hydrogen atoms. The resulting defects act similarly to the contaminating oxygen atoms, by ‘snagging’ the vortices of magnetic field inside the sample and reducing their influence on the material’s superconductivity.
Sungho Jin and co-workers at Agere Systems/Lucent Technologies in New Jersey have made magnesium diboride into superconducting wires. Iron-clad tubes do the trick: they have critical currents similar to those of a lump of the bulk material, even if a little of the iron gets mixed into the superconductor.
These papers make “substantial progress towards improving the properties vital to high electric current and magnetic field applications,” comments Paul Grant of the Electric Power Research Institute, Palo Alto, California, in an accompanying News and Views article.
CONTACT:
Chang-Beom Eom tel +1 608 263 6305, e-mail eom@engr.wisc.edu
David Caplin tel +44 20 7594 7608/7603, e-mail a.caplin@ic.ac.uk
Sungho Jin tel +1 908 582 4076, e-mail jin@agere.com
Paul Grant tel +1 650 855 2234/4182, e-mail pgrant@epri.com

[411583] BRAIN: ONE DOSE CHANGES BRAIN (pp583-587)
A single dose of cocaine can change the way that nerve connections transmit signals in a part of the brain thought to be crucially involved in drug addiction, Antonello Bonci of the University of California, San Francisco, and colleagues now report.
Apparently, from the very first contact with an addictive drug, the long-term potentiation — where interlinked neurons acting simultaneously become more strongly connected — that forms the basis for some kinds of memory can be hijacked as a first step towards addiction or relapse.
CONTACT:
Antonello Bonci tel +1 510 985 3890, e-mail bonci@itsa.ucsf.edu

[411565] CHEMISTRY: NEW SPIN ON ETHANE (pp565-568;N&V)
Attractive interactions and stabilization determine how ethane rotates about its central bond, switching between unstable and stable conformations. So say Voljislava Pophristic and Lionel Goodman, of Rutgers University, New Brunswick, this week, overthrowing the text-book explanation that destabilizing repulsive forces make this simple organic compound prefer a staggered structure.
Ethane’s structural state is determined principally by hyperconjugation, the duo report. This quantum mechanical effect involves charge delocalization owing to transfer of electrons from occupied to unoccupied orbitals.
This new perspective may have important implications in analysing such diverse molecular phenomena as polymer rheology (where rotations about single bonds may allow one polymer chain to wriggle past another) and protein folding, Pophristic and Goodman conclude.
In an accompanying News and Views article Frank Weinhold of the University of Wisconsin, Madison, looks into how considerations of quantum mechanics are informing structural chemistry.
CONTACT:
Lionel Goodman tel +1 732 445 2603, e-mail goodman@rutchem.rutgers.edu
Frank Weinhold tel +1 608 262 0263, e-mail weinhold@chem.wisc.edu

[411546] CLIMATE: ARCTIC SHRUBS UP (pp546-547)
Researchers have found that warming in the Alaskan Arctic has led to a significant
increase in deciduous shrub cover over vast swathes of the landscape. The vegetation changes will alter how this community grows in summer and the effects of snow in winter. They will also lead to more carbon being stored in the region.
Matthew Sturm, of the US Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, Alaska, and colleagues compared aerial photos taken in 1948–50 with those of the same areas in 1999–2000. In a Brief Communication, they report that over this period, dwarf birch (Betula nana), willow (Salix spp.) and green alder (Alnus crispa) have all thrived, colonizing previously shrub-free zones.
CONTACT:
Matthew Sturm tel +1 907 353 5183, e-mail msturm@crrel.usace.army.mil

[411545] LIFELINES: TIME COULD DELAY AIDS (pp545-546)
At current rates of infection and mortality, a teenage boy in Botswana has about a 90% chance of dying of AIDS. Researchers have calculated that in some African countries over the next century, there will be natural selection for genotypes that decrease a person’s susceptibility to HIV infection and increase the time to onset of AIDS. The payoff for extending this interval will be to prolong the victim’s survival at his or her time of peak fertility.
One factor in susceptibility to HIV infection and the time taken for infection to progress to full-blown AIDS is the form of a receptor molecule found on the surface of cells, called CCR5 in some people. In a Brief Communication, Paul Schliekelman and colleagues, of the University of California, Berkeley, model how the more resistant forms of CCR5, which now extend the lifespan of an HIV-positive person by 2 to 4 years, will spread through sub-Saharan Africa. Over the 100-year timespan of the simulation, the AIDS-delaying form of CCR5 will rise in frequency so that more than 50% of the population will carry it.
CONTACT:
Paul Schliekelman tel +1 510 643 6299, e-mail pdschlie@socrates.berkeley.edu

[411571] EARTH: ALL CHANGE (pp571-574, 574-577; N&V)
The properties of the Earth’s mantle change abruptly 660 km below the surface, with sharp rises in both density and the transmission speed of seismic waves created by earthquakes. This discontinuity was thought to result from a phase transition taking place in mantle minerals at the pressure corresponding to 660 km depth. But in 1998 highly-sophisticated laboratory experiments found that the candidate phase transition actually occurs at much lower pressures and therefore could not be responsible for the observed changes in properties at 660 km depth.
Now two new papers suggest that the problem may be calibration, rather than a fundamental misunderstanding of the chemistry of Earth’s interior. Using diamond-anvils, L Chudinovskikh and R Boehler of the Max-Planck Institut für Chemie, Mainz, Germany, subjected samples of Mg2 SiO4 to high pressures and temperatures, swiftly cooled them to room temperature, and examined them using Raman spectroscopy. Sang-Heon Shim of Princeton University, New Jersey and colleagues examined such samples in situ, at high pressures and temperatures, using synchrotron X-rays.
In an accompanying News and Views article Craig R. Bina of Northwestern University, Evanston, Illinois, discusses the background and implications of this work.
CONTACT:
Reini Boehler tel +49 6131 30 52 52, e-mail boe@mpch-mainz.mpg.de
Sang-Heon Shim tel +1 609 258 3261, e-mail sangshim@princeton.edu
Craig Bina tel +1 847 491 5097, e-mail craig@earth.northwestern.edu

[411548] EVOLUTION: LUNGFISH HAVE KEPT THEIR TEETH (p548)
Lungfish — the closest living relatives of four-limbed animals — have maintained the same pattern of tooth development throughout 360 million years of evolution. Moreover, this pattern is unique to lungfish, suggesting that it evolved within this group and became the only possible pattern for its modern descendants.
Moya Smith of Kings College London and Robert Reisz of the University of Toronto examined the tooth development of Neoceratodus, a modern lungfish that occurs in Australia, and compared it to a series of fossils of Andreyevichthys, an extinct species from the Late Devonian period. These fossils, found in central Russia, are the only known example showing all the stages from hatchling to adult.
Modern adult lungfish have ‘tooth plates’ on the palate and lower jaw which, unlike in humans, are formed by addition of new teeth without losing previous ones. This process could also be seen in the fossil series. In addition, hatchlings have a separate set of teeth further forward that are lost by the juvenile stage, starting with the single middle tooth. This was again seen in the fossil series — hatchling fossils possessed these teeth but juvenile and adult fossils did not.
CONTACT:
Moya Smith tel +44 20 7955 4414, e-mail moya.smith@kcl.ac.uk

[411547] …AND FINALLY: TUNABLE COLOUR VISION (pp547-548)
The light in deep water is much bluer than that just beneath the surface. So the mantis shrimp Haptosquilla trispinosa, which inhabits environments ranging from shallow tide pools to a depth of 30 m, has sophisticated colour filters on its photoreceptors that tune its vision to compensate for the changing wavelengths of light underwater.
The type of filter on the shrimps’ eyes depends on the light environment in which they develop, say Thomas Cronin, of the University of Maryland, Baltimore County, and colleagues, in a Brief Communication this week. This means that individuals living at different depths perceive colours differently, and may use different signals to communicate. This is the first such form of tunable colour vision found in any species.
CONTACT:
Thomas Cronin tel +1 410 455 3449, e-mail cronin@umbc.edu
        


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