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Nature press release for 28 September issue

September 28, 2000

[407487] PHYSICS: PANIC OVER? (pp487–490; N&V)
Engineers and architects try to design buildings in anticipation of the worst; but the worst is hard to predict. When panic strikes, people do not behave rationally. This week, Dirk Helbing of the Dresden University of Technology and colleagues present a model that should help predict how people do behave under such circumstances.
The researchers use a computer model developed to study crowd motion, in which individuals move with a preferred velocity and try to avoid collisions. They ran simulations in which people tried to leave a room through a single door. Under normal conditions, there is a steady flow of people through the door. But when the average desired velocity increases above a certain value, the desire for speed overwhelms the desire to avoid collision, and the people jam up and clog the exit.
In this panic state, the room empties more slowly even though everyone is trying to move faster. It is a classic case of ‘more haste, less speed’. David Low of Heriot-Watt University, UK, discusses the work in an accompanying News & Views article.
CONTACT:
Dirk Helbing tel +49 351 463 6805 (between 9am and 11am only), mobile +49 172 712 5045 (between 10pm and 12pm only), fax +49 351 463 6809, no e-mailing please
David Low tel +44 131 449 5111 ext. 4428, fax +44 131 451 5078, e-mail d.j.low@hw.ac.uk

[407469] LIFELINES: BOUNCING BABIES? (pp469–470)
Mice give birth to bouncing babies if they have their first litter as young adults, a Brief Communication reports this week. Male pups born to early adolescent and middle-aged mothers tend to be smaller, and have delayed puberty and smaller reproductive organs, Frederick vom Saal and Ming-Hseng Wang at the University of Missouri, Columbia, report.
        Different hormone levels during pregnancy are the culprit. The youngest and oldest mice have less serum oestradiol and a different pattern of serum testosterone when pregnant than do young adult animals.
        In turn, female offspring also produce pups whose birthweight depends on their maternal grandmother’s age when first pregnant. Because very early and very late pregnancies are becoming increasingly common in people, the researchers say that the influence of age-related changes on offspring merits further investigation.
CONTACT
Frederick vom Saal tel +1 573 882 4367, fax +1 573 884 5020, e-mail vomsaal@missouri.edu

[407496] TECHNOLOGY: BRINGING BETTER BATTERIES (pp496–499)
Rechargeable lithium-ion batteries are emerging as the chosen power source of portable electronics. This week, Jean-Marie Tarascon and colleagues at Université de Picardie Jules Verne, Amiens, France, describe electrodes made of nano-sized transition-metal oxides that should bring more durable lithium batteries.
        Over time, fewer and fewer vital lithium ions can be pushed back into the negative electrodes of existing rechargeable batteries. The new electrodes use a different recharging mechanism, based on the formation and decomposition of lithium oxide; they retain 100% capacity for up to 100 discharge–recharge cycles, and have high recharging rates.
        The new systems are based on oxides of cobalt, nickel, copper or iron. Per unit mass, these oxides have about twice the capacity of the carbon used in existing electrodes and three times its density: a similar-sized metal oxide electrode has six times the capacity of carbon.
CONTACT
Jean-Marie Tarascon tel +33 322 827 571, fax +33 322 827 590, e-mail Jean-Marie.Tarascon@u-picardie.fr

[407483] EVOLUTION: PRION PRYING OFFERS EVOLUTION CLUES (pp477–483; N&V)
It is something of a mystery how survival skills requiring multiple genetic changes arise when the individual mutations involved are unsuccessful or even harmful. This week, Susan Lindquist and Heather True from the University of Chicago describe a novel mechanism that seems to offer an explanation, at least in yeast.
        The duo investigated the effect of a naturally occurring ‘prion’ protein on yeast trying to live under different conditions. In nearly half of 150 comparisons, yeast containing the prion had altered growth rates.
        The prion affects gene expression, effectively making it run through ‘stop-signs’ and switching on many — previously silent — genes. Because these regions are not usually expressed, they never face the selective pressures that prevent harmful mutations accumulating. This allows yeast to stockpile an arsenal of genetic variation, which is then released en masse to bring a whole range of novel characteristics, including — in this case — the ability to grow in altered conditions.
Linda Partridge of University College London, UK, and Nicholas Barton of the University of Edinburgh, UK, discuss this research in an accompanying News and Views article.
CONTACT
Susan Lindquist tel +1 773 702 8049, fax +1 773 702 7254, e-mail
s-lindquist@uchicago.edu
Linda Partridge tel +44 207 380 7418, fax +1 207 383 2048, e-mail l.partridge@ucl.ac.uk

[407523] LIFELINES: HELPING HAND AGAINST HIV (pp523–526)
Virus-specific T-helper cells are thought to be crucial for controlling HIV levels. This week, Bruce Walker and colleagues at Harvard Medical School in Boston, Massachusetts, show that early treatment of HIV infection can boost this immune response.
        Eight HIV patients stopped taking drug therapy and were carefully monitored. In all cases, their bodies could keep the viral numbers below a stable, manageable level — at least temporarily. Drug therapy was restarted in some patients whose viral load rose significantly, but over half are still keeping HIV in check some six months later.
        Increased levels of both virus-specific T lymphocytes and T-helper cell responses were seen in all patients. This suggests that functional immune responses can be augmented during chronic HIV infection, the researchers say, showing the importance of drug treatment during early or acute HIV infection.
CONTACT
Bruce Walker tel +1 617 724 8332, fax +1 617 726 4691, e-mail bwalker@helix.mgh.harvard.edu   

[407485] SPACE: THERE IS A LIGHT THAT NEVER GOES OUT (pp485–487; N&V)
        This week, Shri Kulkarni and colleagues at the Palomar Observatory of the California Institute of Technology, Pasadena, announce the first detection of the changes in diameter of a pulsating ‘Cepheid variable star’. Astronomers use these pulsating stars as a means to anchor the Hubble constant, which is a measure of the expansion rate of the Universe.
         The team use an instrument called an ‘optical interferometer’ to measure directly the puffing up and deflating of the Cepheid. By correlating the star’s brightness with changes in its size, they can directly estimate its distance. This first determination agrees with existing estimates, but the researchers say that improvements to the instrument will bring greater accuracy.
        The observations “bring together a continuing revolution in telescope resolution and one of the hottest questions in extragalactic astronomy,” says Tyler Nordgren of the US Naval Observatory Flagstaff Station, Arizona, in an accompanying News and Views article.
CONTACT:
S. Kulkarni tel +1 626 395 4010, fax +1 626 568 9352, e-mail srk@astro.caltech.edu   
Tyler Nordgren tel +1 520 779 5132, fax +1 520 774 3626, e-mail nordgren@nofs.navy.mil

[407513] LIFELINES: SNP SHOT OF HUMAN DISEASES (pp513–516, 516–520)
Past explorers heading into unknown territory had little idea of where they were going or how to know when they had arrived. Biologists investigating the uncharted human genome will be better prepared — maps to guide them through the sequence are being developed. A new method of preparing these ‘SNP’ maps is reported this week, alongside one such chart for human chromosome 22.
           David Bentley and colleagues at the Sanger Centre, Cambridge, UK, have charted 2,730 ‘single nucleotide polymorphisms’ (SNPs) on chromosome 22. These events — the substitution of a ‘T’ nucleotide for ‘A’ for instance — cause most genomic variation, and finding them can help track disease. For diabetes sufferers, for example, SNPs in similar locations within the genome that are inherited with the disease could lead researchers to the gene responsible.
        In a second paper, Eric Lander of Massachusetts Institute of Technology, Cambridge, USA, and colleagues describe a new technique used to generate SNP maps. ‘Reduced representation shotgun’ (RRS) sequencing analyses specific genome regions from several people and compares them for SNPs.
        Both research groups are members of the SNP Consortium — an international collaboration aiming to discover and release 300,000 human SNPs.
CONTACT
David Bentley tel +44 1223 494 886, fax +44 1223 494 969, e-mail drb@sanger.ac.uk   
Eric Lander tel +1 617 258 5192, fax +1 617 252 1933, e-mail lander@wi.mit.edu   

[407499] EARTH: SALT, SOIL AND SNOW (pp499–502)
Researchers have long puzzled over the very high salt concentrations in Antarctic dry-valley soil, particularly sulphate levels. This week, Huiming Bao of the University of California San Diego and colleagues offer an explanation: the atmospheric oxidation of gaseous sulphur compounds.
        The researchers analysed oxygen isotopes in soil sulphates. All samples, especially those far inland, have a significant excess of the 17O isotope. This rules out sea salt as the only sulphate source: atmospheric oxidation of volatile sulphur species and subsequent deposition is the only known process that can generate so much 17O in surface minerals. And these volatile compounds can be transported much further inland than the larger sea-salt particles.
         Martian meteorites — also with high 17O levels — have been found on these Antarctic dry valleys, which are some of the oldest land surfaces on the Earth. These results raise the possibility that some 17O found in these meteorites may be terrestrial contamination, the researchers say.
CONTACT
Huiming Bao tel +1 858 534 6053, fax +1 858 534 7042, e-mail hbao@chem.ucsd.edu

[407508] LIFELINES: SOME GENOMES LIKE IT HOT (pp508–513; N&V)
The complete genome sequence of the acid- and heat-loving bacterium Thermoplasma acidophilum is published this week. This hardy bug grows best at a blistering pH 2 and 59 C without the structural protection of a conventional cell wall.
        There are some surprises among the 1.5 million base pairs sequenced by Andreas Ruepp of the Max-Planck-Institute, Martinsried, Germany, and colleagues. High proportions of genes appear to have been acquired from other species; the researchers speculate these ‘life-style’ genes are shared around to help organisms survive harsh environments.
        Some researchers think that T. acidophilum is an ancestor of more advanced ‘eukaryotic’ cells, but its genome suggests otherwise — key eukaryotic marker genes are missing. This is the ninth bug from the Archaea group to be sequenced entirely, and the eighth to love heat: this indicates the biotechnological potential of thermophile genes and gene products.
        Don Cowan of University College London, UK, discusses this research and its implications in an accompanying News and Views article.
CONTACT
Andreas Ruepp tel +49 89 8578 2646, fax +49 89 8578 2641, e-mail ruepp@biochem.mpg.de
Don Cowan tel +44 207 679 2246, fax +44 207 679 7193, e-mail d.cowan@biochemistry.ucl.ac.uk

[407493] TECHNOLOGY: COMPUTER, BUILD THYSELF (pp493–496)
All computers contain thousands of simple calculating circuits called logic gates. But logic gates need not be an exclusively electronic device. This week, Nadrian Seeman and colleagues at New York University build logic gates from DNA molecules that organise themselves to perform sequential logical operations.
        Simple logic gates are devices whose single output is determined by two inputs. Flat tiles could be used as logic gates if laid out so that the ‘output’ of one tile fitted the ‘input’ of the next, as in a jigsaw. But such a computational jigsaw would require somebody to fit the tiles together. By using DNA, Seeman and colleagues have produced ‘tiles’ that self-assemble.
        The DNA tiles are formed from four strands of DNA, so single-stranded sticky ends are left exposed to form the ‘inputs’ and ‘outputs’. These bind to complementary strands on other ‘tiles’. To run the calculation, the DNA tiles are mixed and the final ‘output’ read by DNA sequencing.
Here the DNA tiles are used to form four consecutive logical steps, but they could also be used in cryptography and in the construction of self-assembling, ‘smart’ materials.
CONTACT
Nadrian Seeman tel +1 212 998 8395, fax +1 212 260 7905, e-mail ned.seeman@nyu.edu

[407470] AND FINALLY… AMAZING AMOEBAE (p470)
The reputation of amoebae as less than intelligent members of the animal kingdom may be undeserved. In a Brief Communication this week, Toshiyuki Nakagaki of the Bio-Mimetic Control Research Centre, Nagoya, Japan, and colleagues show that a single-celled organism can negotiate the shortest way out of a maze.
        Pieces of the slime mould Physarum polycephalum placed in a 30-centimetre- square maze join up and expand to fill all available space. But when two pieces of food are placed at separate exit points in the labyrinth, the organism withdraws itself from dead ends until its entire ‘body’ runs between the two nutrients along the shortest possible route. Effectively, it solves the puzzle.
        “This remarkable process of cellular computation implies that cellular materials can show a primitive intelligence,” the researchers say.
CONTACT
Toshiyuki Nakagaki tel: +81 52 736 5870, fax +81 52 736 5871, e-mail nakagaki@bmc.riken.go.jp

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