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[1] Neuroanatomy: Lop-sided brains boost fruitflies' memory (pp605-606)
Fruitflies need asymmetrical brains to form long-term memories, a Brief Communication in this week's Nature shows. Those with structurally similar brain hemispheres cannot retain information for more than a few hours.
Most fruitflies (Drosophila melanogaster) have a round structure called the 'asymmetrical body' in the right half of the brain, say Thomas Préat and colleagues. But the 7.6 per cent of flies who have one such structure on each side of the brain fail in tests that require memories to be stored for several days, the team reports.
The researchers trained the flies to associate a smell with an electric shock. All flies took avoiding action when tested after three hours, showing that both asymmetrical and symmetrical brains can form short-term memories. But even with more rigorous training, only those flies with the asymmetrical body on one side could recall the association after four days.
[2] Nanoscience: DNA shapes up (pp618-621)
A strand of DNA that spontaneously folds up into an octahedron is reported in this week's Nature. The structure may prove useful as a building block for nanotechnology — the science of engineering on the atomic scale.
Although many other artificial DNA structures have been produced before, Gerald F. Joyce and colleagues say that the benefit of their synthetic DNA strand is that it can be copied very easily, opening up the possibility of large-scale production. This 'clonability' may also allow scientists to evolve new DNA strands that are optimized for folding in new and useful ways.
The structure is the shape of two Egyptian pyramids stuck together at the base, and has eight triangular faces. At only 22 nanometres across, it is roughly the size of a small virus, and 2,000 times smaller than the width of a human hair. The authors claim that their technique could also be used to make DNA cubes and other useful bits of nano-scaffolding.
[3] Health and Medicine: Gene for rare vascular disorder identified (pp640-645; N&V)
Researchers have identified a gene that helps to regulate blood vessel growth. Mutations in the gene may contribute to the rare vascular disorder Klippel"Trenaunay syndrome (KTS).
Patients with KTS have malformed blood vessels in the skin. The problems often occur in just one enlarged limb, and the condition's cause is unknown. In this week's Nature, Qing Wang and colleagues show that patients with the condition carry a mutated version of a gene called VG5Q. The gene is thought to control blood vessel growth.
The unusual means by which these scientists identified and evaluated VG5Q, using a combination of human genetics and functional assays, underscores the importance of using similar approaches to help identify other factors involved in angiogenesis, the formation of new blood vessels, say Diether Lambrechts and Peter Carmeliet in an accompanying News and Views article. "Such factors could include molecules that are clinically relevant, or potential drug targets," they add.
Peter Carmeliet and Diether Lambrechts (University of Leuven, Belgium)Tel: +32 16 34 57 74 (PC), E-mail: [email protected]
[4] Earth Science: Large earthquakes have unpredictable aftermath (pp621-624)
Small earthquakes triggered remotely by a single large shock may be more ubiquitous than experts had thought, according to an analysis of a severe quake that struck Alaska in 2002.
The magnitude 7.9 Denali earthquake of 3 November 2002 — one of the largest earthquakes to hit the United States in the past century — triggered increases in seismic activity in British Columbia, Canada, and as far south as Nevada and Utah, report Joan Gomberg and colleagues in this week's Nature. Even areas not thought to be tectonically active were affected, implying that such triggered earthquake activity may be less predictable than was thought.
[5] Health and Medicine: The imperfection of human design (pp633-636)
Human lungs are not perfect in their design. A modelling study in this week's Nature suggests that if they were, they wouldn't work at all.
The human lung is a complex tree-like structure. The main airway or 'trunk' divides into more than one million billion smaller branches. In turn, these split many times, and gas exchange occurs at the tiny terminals. The shape and dimensions of these branched structures help to determine lung efficiency, say B. Mauroy and colleagues. Small variations in geometry can lead to large variations in net air flux. The researchers claim that if the airways were designed for maximum flow efficiency, they would fail catastrophically.
[6] Infection: Black Death theory plagued by mouse result (p606)
Research published in this week's Nature deals a blow to a popular theory of how a mutation that protects against HIV infection became widespread in Europe. It was thought that the mutation developed as a guard against plague, but a study of the effects of the same mutation in mice shows that this may not have been the case.
HIV can infect only cells bearing a surface protein called CCR5; cells carrying a mutation called CCR5?32, which cripples this protein, therefore resist infection. As CCR5?32 appeared about 800 years ago and is widespread in Europe, experts surmised that its prevalence may have been boosted by offering protection from the plague bacterium Yersinia pestis, which killed some 25 million Europeans during the Black Death plague of 1346"52.
But mice carrying CCR5?32 are just as vulnerable to Y. pestis as their normal counterparts, report Donald E. Mosier and colleagues in a Brief Communication. Recent work published elsewhere suggests that smallpox, rather than plague, may be responsible for the mutation's prevalence among Europeans, the authors add.
[7] Electronics: Silicon shines on (pp615-618; N&V)
Scientists have made the first silicon-based high-frequency optical modulator, a device that can quickly change the intensity of the light it transmits. The research, published in this week's Nature, provides an important component for photonics, the technology of moving information around in packets of light rather than electricity.
The modulator, invented by Ansheng Liu and colleagues, can turn on and off more than a billion times a second. Photonic devices made from silicon are unusual because the properties of this material, although excellent for manipulating electrons, are far from ideal when it comes to handling light. Nevertheless, using silicon for photonics would help to link the new technology with conventional electronics, and exploit an established manufacturing base.
In an accompanying News and Views article, Graham T. Reed says, "Breakthrough developments such as this suggest that a low cost silicon optical superchip could soon be a reality" .
[8] And Finally"¦: Early insects were among first to set foot on land (pp627-630)
Insects arrived on the evolutionary scene earlier than experts imagined — more than 400 million years ago, according to a study in this week's Nature. This puts them among the earliest animals to have ventured onto land, and may help to explain their staggering abundance and diversity today.
The finding comes from a fresh analysis of a fossilized creature from Scotland called Rhyniognatha hirsti, carried out by Michael S. Engel and David A. Grimaldi. The structure of the animal's mandible shows that it is definitely an insect — the earliest known.
The insects almost certainly appeared during the Silurian period, 438"408 million years ago, the authors say. The previous title-holders were a pair of 379-million-year-old insects found in New York. Although it was itself flightless, Rhyniognatha shares several characteristics with winged insects, indicating that wings may also have evolved earlier than palaeontologists thought.
ALSO IN THIS ISSUE"¦
[9] Reversible redox energy coupling in electron transfer chains (pp607-612)[10] The central image of a gravitationally lensed quasar (pp613-615)[11] Ramp initiation in a thrust wedge (pp624-627)[12] A conserved siRNA-degrading RNase negatively regulates RNA interference in C. elegans (pp645-649)[13] Cytoplasmic dynein functions as a gear in response to load (pp649-652)[14] Structural basis for removal of adenine mispaired with 8-oxoguanine by MutY adenine DNA glycosylase (pp652-656; N&V)
ADVANCE ONLINE PUBLICATION"¦
***This paper will be published electronically on Nature's website on 11 February at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 12 February, but at a later date.***
[15] Tension between two kinetochores suffices for their bi-orientation on the mitotic spindle (DOI: 10.1038/nature02328) (http://dx.doi.org/10.1038/nature02328)
GEOGRAPHICAL LISTING OF AUTHORS"¦
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
AUSTRIAVienna: 15
CANADASidney: 4
CHINAShanghai: 3
FRANCECachan: 5Gif-sur-Yvette: 1Palaiseau: 5
ISRAELJerusalem: 7
POLANDKrakow: 9
SPAINSeville: 1
SWITZERLANDBern: 5
UNITED KINGDOMDundee: 15Manchester: 3
UNITED STATES OF AMERICA
California Fremont: 6 La Jolla: 2, 6 Irvine: 13 Santa Clara: 7 Stanford: 6Colorado Boulder: 4Kansas Lawrence: 8Massachusetts Boston: 12 Cambridge: 3, 10, 14Michigan East Lansing: 6Minnesota Rochester: 3Missouri Kansas City: 13New York New York: 8Ohio Cleveland: 3 Columbus: 10Pennsylvania Philadelphia: 9, 10Tennessee Memphis: 4Texas Austin: 6 College Station: 11 Houston: 3
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