Neptune hooks one and throws one back; Lowly wasps work hardest; Human 'overkill' did not cause widespread die-off; Gamma-ray bursts from the most massive stars; Immune molecule fuels tumours; Sugar helps flowers branch out;

Summaries of newsworthy papers from Nature. VOL.441 NO.7090 DATED 11 MAY 2006 including Space ball survived massive impact; Noble gases enter the Earth's mantle from sea water; Turning superconductors on; Silicon feels the strain; Buoyancy vests for six-legged scuba divers


This press release is copyright Nature. VOL.441 NO.7090 DATED 11 MAY 2006

This press release contains:

· Summaries of newsworthy papers:

- Planetary science: Neptune hooks one and throws one back
- Social biology: Lowly wasps work hardest
- Extinction: Human 'overkill' did not cause widespread die-off
- Astronomy: Gamma-ray bursts from the most massive stars
- Cancer: Immune molecule fuels tumours
- Plant biology: Sugar helps flowers branch out
- Planetary science: Space ball survived massive impact
- Earth science: Noble gases enter the Earth's mantle from sea water
- Applied physics: Turning superconductors on
- Photonics: Silicon feels the strain
And finally… Buoyancy vests for six-legged scuba divers

· Mention of papers to be published at the same time with the same embargo
· Geographical listing of authors

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[1] Planetary science: Neptune hooks one and throws one back (pp 192-194; N&V)

As moons go, Neptune's major moon Triton is a whopper. About 40 per cent more massive than the planet Pluto, it has an unusual orbit around Neptune that has led to the belief that Triton was once virtually a planet in its own right, orbiting the Sun until captured in Neptune's gravitational field. But working out how this capture might have happened has been difficult — no one has been able to come up with an explanation that really works.

Craig Agnor and Douglas Hamilton now think that they may have one, and present their findings in this week's Nature. They say that all the pieces fit into place if one assumes that, before its capture by Neptune, Triton was actually one of a pair of planet-like bodies, called planetesimals, orbiting as a twosome in the early Solar System. When this pair came too close to Neptune, the researchers say, one of the bodies was cast away, while the other — Triton — became permanently bound by gravity to the giant planet. In contrast to scenarios that invoke capture of a lone Triton, this mechanism doesn't require any fine-tuned assumptions, but works for a wide range of characteristics of the initial planetesimal pair.

Craig Agnor (University of California, Santa Cruz, CA, USA)
Tel: +1 831 459 2426; E-mail: [email protected]

Alessandro Morbidelli (Observatoire de la Cote d'Azur, Nice, France)
Tel: +33 4 92 00 31 26; E-mail: [email protected]

[2] Social biology: Lowly wasps work hardest (pp 214-217)

A new framework has been suggested for eusociality, an evolutionary feature in which certain members of some animal societies forgo reproduction in order to rear the offspring of others. Researchers in this week's Nature reveal that helpers help out more when their own chances of reproduction are low.

Until now the phenomenon has been mostly explained through kin selection, in which helpers aid their genetic relatives because their own genes will be indirectly distributed. However, this theory does not account for the huge variation observed between individuals in helping effort. Not all help out in the same way, and according to this research, the individuals’ behaviour changes as their status does.

Jeremy Field and colleagues studied the tropical hairy-faced hover wasp Liostenogaster flavolineata and its age-based social system, whereby the oldest female lays the eggs and is replaced by the next oldest when she dies. When the second-in-line females were removed, the third-in-line females, now newly promoted, started to work less than control third-in-line females as they were closer in line to reproduce. In another experiment, all the ranks except for the top two tiers were removed and the researchers found that the second-in-line females worked harder because they would have no helpers if they were to ascend the ranks.

Jeremy P Field (University College London, UK)
Tel: +44 208 567 5517; E-mail: [email protected]

[3] Extinction: Human 'overkill' did not cause widespread die-off (pp 207-209)

New evidence has come to light in one of prehistory's greatest ‘whodunnit’ stories — a curious case involving a spate of animal extinctions more than 10,000 years ago. Overkill by newly arrived humans in North America was proposed as one possible reason for the die-off, which saw species such as the mammoth and wild horse Equus ferus wiped out. But new dating of more than 600 animal bones now suggests that other factors, such as natural climate shifts, were to blame.

Radiocarbon dates provided by R. Dale Guthrie in this week's Nature give a more precise account of the sequence of events surrounding the mass extinction, which occurred at the Pleistocene–Holocene transition from 13,000 to 10,000 years ago. The samples include bones from bison, wapiti, moose and humans, all of which survived the period, together with horse and mammoth, which did not.

The evidence suggests that climate shifts or more subtle mechanisms were responsible for the extinction of animal species at this time, and not, as had been suggested, a 'Blitzkrieg' of hunting by humans, which were newly arrived in the New World. The detailed analysis also allows the rejection of the 'keystone removal' hypothesis, which had suggested that the extinction of grazing mammoths by humans led to changes in vegetation that caused a knock-on extinction of other beasts.

R. Dale Guthrie (University of Alaska, Fairbanks, AK, USA)
Tel: +1 907 479 6034; E-mail: [email protected]

[4] Astronomy: Gamma-ray bursts from the most massive stars (AOP)
DOI: 10.1038/nature04787

***This paper will be published electronically on Nature's website on 10 May 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 11 May, but at a later date.***

Long gamma-ray bursts (GRBs) are associated with the deaths of only the most massive stars, according to research published online in Nature this week.

Andrew Fruchter and colleagues have found that long GRBs and supernovae are statistically not found in the same galactic environments. The bursts are far more concentrated in the very brightest regions of their host galaxies than are supernovae.

The galaxies with GRBs are also fainter and more irregular than those where supernovae are seen. This evidence suggests that only the very most massive stars produce long GRBs, and that they are restricted to locations where the abundances of elements heavier than helium are much lower than in the Milky Way.

Andrew A S Fruchter (Space Telescope Science Institute, Baltimore, MD, USA)
Tel: +1 410 338 5018; E-mail: [email protected]

[5] Cancer: Immune molecule fuels tumours (AOP)
DOI: 10.1038/nature04808

***This paper will be published electronically on Nature's website on 10 May 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 11 May, but at a later date.***

A molecule central to chronic autoimmune diseases also promotes the incidence and growth of tumours, show Martin Oft and his colleagues in a study to be published online this week by Nature.

Doctors have suspected for more than a century that the inflammation associated with tumours also regulates their growth. Oft’s team find one such link: they show that interleukin-23 (IL-23), a cytokine already implicated in inflammatory bowel disease and other autoimmune disorders, is also central to cancer development.

The researchers show that many human tumours make excess IL-23. Blocking IL-23 in mice — using genetic engineering or an antibody — protects against carcinogens because protective T cells are better able to infiltrate transformed tissue and kill pre-cancerous cells. The results suggest that antibodies that block IL-23 might help these cytotoxic T cells invade and treat human tumours.

Martin Oft (Schering-Plough Biopharma, Palo Alto, CA, USA)
Tel: +1 650 496 1131; E-mail: [email protected]

[6] Plant biology: Sugar helps flowers branch out (pp 227-230)

A common sugar may control the branching of flowering stalks in maize, propose David Jackson and his colleagues in this week’s Nature, demonstrating that a simple metabolite can also guide organism growth and development.

The team studied a classical mutant of maize with oddly branched flowers and found that the gene responsible, RAMOSA3, makes an enzyme located in the budding tissue, or meristem, of flowering branches. The RAMOSA3 protein modifies the sugar trehalose, which is found in every biological kingdom and functions in carbohydrate utilization and metabolic control.

The authors speculate that in maize and other plants, the sugar may also act as a short-range signal to control the identity of the meristem; alternatively, RAMOSA3 itself may regulate the activity of other genes.

David Jackson (Cold Spring Harbor Laboratory, NY, USA)
Tel: +1 516 367 8467; E-mail: [email protected]

[7] Planetary science: Space ball survived massive impact (pp 203-206)

An unaltered meteorite the size of a beach ball has been found in the Morokweng impact crater in South Africa, according to research published in this week's Nature.

When large meteorites fall to Earth they are normally completely melted or vaporized, so the 25-centimetre-wide space rock is a unique find that overturns conventional wisdom about what can and cannot survive an impact.

W. D. Maier and colleagues say that at 145 million years old, this is the oldest known unaltered meteorite of significant size found in a melt sheet. It also has an unusual chemical composition, being rich in sulphur and metal-poor, which suggests that the nature of impacting bodies has changed over time.

Wolfgang WD Maier Maier (Universite du Quebec a Chicoutimi, Canada)
Tel: +1 418 545 5011 5230; E-mail: [email protected]

[8] Earth science: Noble gases enter the Earth's mantle from sea water (pp 186-191; N&V)

Heavy, unreactive noble gases such as xenon that are found in the Earth's mantle are largely delivered there by sea water, according to research published in this week's Nature. The mantle is the solid layer that lies between the Earth's outer crust and liquid core.

This overturns previous theories suggesting that as oceanic plates plunge into the Earth at subduction zones, gases are not incorporated back into the surrounding rocks but instead rise to the surface in volcanic activity.

Greg Holland and Chris Ballentine studied the composition of mantle gases at the Bravo Dome natural gas field in New Mexico, and found that a substantial proportion of the xenon had the same isotopic make-up as xenon in the atmosphere.

Understanding how chemical elements are exchanged between the Earth's surface and mantle will help to trace the planet's evolution, comments Takuya Matsumoto in a related News and Views article.

Greg Holland (University of Manchester, UK)
Tel: +44 161 2755668 or +44 7707 025766; E-mail: [email protected]

Chris Ballentine (University of Manchester, UK)
Tel: +44 161 2753832; E-mail: [email protected]

Takuya Matsumoto (Osaka University, Japan)
Tel +81 6 6850 5541; E-mail: [email protected]

[9] Applied physics: Turning superconductors on – and off (pp 195-198)

A neat and simple way to turn superconductivity 'on' and 'off', reported by Jean-Marc Triscone and colleagues in Nature this week, now points the way to the creation of new electronic devices based on superconductors.

The system devised by the team makes use of the fact that superconductivity in some metal oxide materials depends on their having the right concentration of current-carrying particles — electrons. The researchers have found a way to pump these electrons in and out of a superconductor called niobium-doped strontium titanate (Nb-STO), using a related metal oxide material called lead zirconate-titanate (PZT). Their 'switchable superconductor' consists of a thin film of Nb-STO with a layer of PZT grown on top.

PZT is a so-called ferroelectric material: it has an internal electric field that points in a certain direction, just as a ferromagnet like iron has a magnetic field with a particular orientation. The researchers could use a very fine metal needle to alter the direction of the electric field in PZT just in the region brushed by the tip. This in turn changes the concentration of electrons in the underlying Nb-STO film, which, at a given (very low) temperature, can turn it from a superconductor to a non-superconductor or vice versa. This makes the electrical resistance of the material change drastically. By using the needle tip as a kind of ultrafine pen, one can 'draw' regions of superconductivity in a flat layer of Nb-STO, and thus mark out superconducting circuits or device structures.

Jean-Marc Triscone (University of Geneva, Switzerland)
Tel: +41 22 379 6827; E-mail: [email protected]

[10] Photonics: Silicon feels the strain (pp 199-202)

Information processing using light rather than electronic signals offers a number of advantages, but has been hindered on silicon chips owing to the difficulty of creating and manipulating light signals in silicon. Rune Jacobsen and colleagues show in this week’s Nature how one of these obstacles might be overcome.

They have created a kind of electronically operated light switch, in which the passage of a light beam along a microscopic silicon channel called a waveguide can be electrically controlled. Such a device makes use of an electro-optic effect, in which the transmission of light is altered by an electric field.

Crystalline silicon doesn't generally show a strong electro-optic effect. But it can be induced, the researchers say, by breaking the symmetry of the crystal lattice, so that it does not look the same in all directions. Jacobsen and colleagues achieve this by depositing a thin layer of silicon nitride glass on top of their silicon waveguide. (In fact, a layer of silica is sandwiched between the nitride and silicon.) The upper nitride layer has the effect of pushing the silicon atoms apart, thereby physically straining the underlying silicon.

Silicon does not perform quite as well as lithium niobate, the material commonly used to make electro-optic light switches. But Jacobsen and colleagues point out how much cheaper and more convenient it would be to make such devices from silicon, taking advantage of standard chip-making fabrication methods, rather than from this pricier alternative.

Rune Jacobsen (Technical University of Denmark, Lyngby, Denmark)
Tel: +45 4525 6371; E-mail: [email protected]

[11] And finally… Buoyancy vests for six-legged scuba divers (pp)

Scuba divers would be lost without their buoyancy vests, which allow them to control the depth at which they hover in the water. But like many of the best inventions, the animal kingdom got there first — insects called backswimmers use a similar strategy to stabilize themselves in the water column while they breathe the bubble of oxygen they take with them on their dive. Unlike humans though, they can top up this oxygen while still underwater.

The trick allows backswimmers to spend their lives diving for food in the mid-water zone, rather than scavenging at the surface or clinging to submerged objects, say Philip Matthews and Roger Seymour, who describe the discovery in a Brief Communication in this week’s Nature. As the insects breathe the contents of the bubble, they maintain buoyancy by releasing oxygen from the haemoglobin in their bodies. Backswimmers, found the world over, are the only insects to inhabit the mid-water zone as adults, and the only ones to possess haemoglobin throughout their entire life — a link that may be explained by the new findings.

Matthews and Seymour made the discovery by placing a submerged backswimmer on a sensitive weight balance and measuring the gas pressure inside its bubble. They found that foraging insects sport an overinflated bubble when embarking on a dive — but the effort of dragging this buoyant cargo downwards through the water quickly uses up enough oxygen, while saturating the insect’s haemoglobin, to restore the balance once it reaches the right depth.

Philip Matthews (Adelaide University, Australia)
Tel: +61 8 8303 3997; E-mail: [email protected]


[12] Systems biology approaches identify ATF3 as a negative regulator of Toll-like receptor 4 (pp 173-178)

[13] Specification of the neural crest occurs during gastrulation and requires Pax7 (pp 218-222)

[14] A mechanical explanation of RNA pseudoknot function in programmed ribosomal frameshifting (pp 244-247)


***This paper will be published electronically on Nature's website on 10 May 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 11 May, but at a later date.***

[15] A putative flip–flop switch for control of REM sleep
DOI: 10.1038/nature04767


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.

Adelaide: 11

Chicoutimi: 7

Santiago: 4

Arhus: 10
Copenhagen: 4
Lyngby: 10

Orsay: 9
Paris: 14

Jerusalem: 15

Trieste: 4

Chiba: 9

Amsterdam: 4

Oslo: 4

Pretoria: 7
Witwatersrand: 7

Granada: 4

Stockholm: 4

Geneva: 9

Birkenhead: 4
Cambridge: 14
Cardiff: 7
East Kilbride: 7
Hatfield: 4
Leicester: 4
London: 2
Manchester: 8
Nottingham: 4
Oxford: 14

Huntsville: 4
Fairbanks: 3
Berkeley: 4
La Jolla: 9
Long Beach: 6
Los Angeles: 13
Pasadena: 4, 13
Palo Alto: 5
Santa Cruz: 1, 4
New Haven: 13
Wilmington: 6
Bloomington: 9
Notre Dame: 4
Bowling Green: 4
Baltimore: 4
College Park: 1
Greenbelt: 4
Boston: 15
St Louis: 6
New York
Cold Spring Harbour: 6
East Setauket: 4
Columbus: 12
Nashville: 4
Seattle: 12

For North America and Canada
Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail: [email protected]

For Japan, Korea, China, Singapore and Taiwan
Rinoko Asami, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected]

For the UK/Europe/other countries not listed above
Ruth Francis, Nature London
Tel: +44 20 7843 4562; E-mail [email protected]

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Published: 10 May 2006

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