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This press release is copyright Nature.
VOL.441 NO.7097 DATED 29 JUNE 2006
This press release contains:
* Summaries of newsworthy papers:
Hydrogeology: How earthquakes squeeze the Earth
Prions: Brittleness key to prion behaviour
Plant biology: Who needs bacteria?
Stem cells: Hopes and realities
Materials chemistry: Semiconductor sponge
Quantum physics: Flat gas comes to order
And finally… The recipe for a healthy ecosystem
* Mention of papers to be published at the same time with the same embargo
* Geographical listing of authors
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[1] Hydrogeology: How earthquakes squeeze the Earth (pp 1135-1138)
Earthquakes many miles away can dramatically increase the ability of rocks to transmit fluid, according to a paper in Nature this week. The results suggest that creating artificial seismic waves, for example with underground explosions, might enhance the extraction of oil and gas from natural reservoirs. Studying such waves may lead to insights into how seismically induced changes in fluid flow within geological faults might trigger further earthquakes.
Jean Elkhoury and colleagues study the effect of earthquakes on the rate at which water seeps in and out of two wells in southern California over a period of 20 years. The water levels in the wells rises and falls gradually owing to changes in local weather and rainfall - but superimposed on these long-term trends are regular, daily variations of a few centimetres owing to the ‘solid Earth tides’. As the motion of the Moon around the Earth makes local sea levels rise and fall tidally each day, so this and the Earth’s rotation cause tidal ‘squeezing’ of the solid Earth. The effect is tiny, but it squeezes the porous rock of the aquifer that feeds the wells, pressurizing the water held in the pores and forcing regular changes of up to 3 centimetres in the level of well water.
As the squeezing subsides, well water flows back into the aquifer. How quickly this happens depends on the permeability of the rock. The team find that seven earthquakes in the California region during the study triggered changes in the synchronization of the solid Earth tides and the daily rise and fall of the well levels, which they interpret as a result of a change in rock permeability caused by the passage of the seismic waves. The earthquakes can increase permeability by a factor of two or three. The rock then relaxes back to its original state over several weeks. Such changes should occur in porous rocks that hold oil or natural gas, influencing the ease with which the oil could be extracted.
CONTACT
Jean Elkhoury (University of California Los Angeles, CA, USA)
Tel: +1 310 206 8698; E-mail: [email protected] <mailto:[email protected]>
Emily E. Brodsky (University of California Santa Cruz, CA, USA) Co-author
Tel: +1 831 459 1854; E-mail: [email protected] <mailto:[email protected]>
[2] Prions: Brittleness key to prion behaviour (AOP)
DOI: 10.1038/nature04922
***This paper will be published electronically on Nature's website on 28 June 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 28 June, but at a later date.***
Working in yeast, Jonathan Weissman and his colleagues report online this week in Nature why some prion strains act differently to others.
It's thought that prion proteins in their misfolded form are able to convert normal proteins into the misfolded conformation - and even small changes in the conformation of the prion can alter its effects. The team examined how three strains of prions that differ in conformation cause different phenotypes in yeast (assayed as various colony shades from white to red). They show that these prions grow by forming fibres at different rates and fragment into new prion seeds with differing ease. Surprisingly, they show that one prion type with a particularly strong phenotype (white) is actually slow-growing, but forms brittle fibres that fragment easily and so readily generates more seeds to establish new fibres.
The researchers suggest that the brittleness of prion fibres may be important in determining prion propagation, and say that therapies for prion diseases, could potentially work by slowing the rate of protein aggregate fragmentation.
CONTACT
Jonathan Weissman (Howard Hughes Medical Institute, University of California San Francisco, CA, USA)
Tel: +1 415 502 7642; E-mail: [email protected] <mailto:[email protected]>
[3] & [4] Plant biology: Who needs bacteria? (pp 1149-1152; 1153-1156)
Leguminous plants (for example, peas and lentils) can be coaxed to form nodules without the help from symbiotic bacteria that is normally required, a study in this week’s Nature suggests.
Legumes are induced to form nodules on their roots by symbiotic bacteria. While the plant provides shelter and sugars, the bacteria fix atmospheric nitrogen into forms that can be used by the plant.
Using two different approaches, teams led by Giles Oldroyd and Jens Stougaard identify Ca2+ /calmodulin-dependent protein kinase (CCaMK) as a key regulatory molecule in plant nodule formation. When auto-inhibition of CCaMK is disrupted, plants form nodules in the absence of bacteria.
If the procedure was applied to non-legumes, it could help increase the growth and crop yield of other plant species.
CONTACT
Giles Oldroyd (John Innes Centre, Norwich, UK) Author paper [3]
Tel: +44 1603 450 206; E-mail: [email protected] <mailto:[email protected]>
Jens Stougaard (University of Aarhus, Denmark) Author paper [4]
Tel: +45 89 42 50 11; E-mail: [email protected] <mailto:[email protected]>
Stem cells: Hopes and realities
The potential of stem cell biology in the battle against human disease has captured the public imagination. Scientists are engaged in a hunt to identify molecules that aid their unique ability to self-renew and to differentiate, and to understand these mechanisms in order to exploit them therapeutically.
An Insight in this week’s Nature provides an overview of the field and its promise. The proposed use of stem cells to generate replacement cells for damaged heart muscle and neural and glial cells in the brain to combat neurodegeneration has been much heralded, but what will it take to translate the advances from the laboratory to the clinic?
Transplantation of haematopoietic stem cells to treat blood and immune disorders has proved successful for decades but are difficult to sustain. It is important to improve not only accessibility to treatments, particularly in developing countries, but also protocols and understanding of such uses of these cells.
Finally, as tissue regeneration potential declines with age, scientists are trying to understand whether this is due to the ageing of stem cells or to the impairment of their function in the ageing tissue environment. Greater knowledge of the role of stem cells in these processes is vital if the emerging field of regenerative medicine and tissue injury is to come close to meeting expectations.
The full details of this Insight and the contact details of authors are listed below:
Nuclear reprogramming and pluripotency
Rudolf Jaenisch (Whitehead Institute for Biomedical Research, MIT, Cambridge, MA, USA)
Tel: +1 617 258 5186; E-mail: [email protected] <mailto:[email protected]>
Asymmetric and symmetric stem-cell divisions in development and cancer
Sean J Morrison (University of Michigan, Ann Arbor, MI, USA)
Tel: + 1 734 647 6261; E-mail: [email protected] <mailto:[email protected]>
The stem-cell niche as an entity of action
David T Scadden (Massachusetts General Hospital & Harvard Medical School, Boston, MA, USA)
Tel: +1 617 726 5615; E-mail: [email protected] <mailto:[email protected]>
Stem cells, ageing and the quest for immortality
Thomas A Rando (Stanford University, CA, USA)
Tel: +1 650 849 0444; E-mail: [email protected] <mailto:[email protected]>
Generation of neuronal variability and complexity
Fred H Gage (The Salk Institute, La Jolla, CA, USA)
Tel: +1 858 453 4100; E-mail: [email protected] <mailto:[email protected]>
Stem cells for the treatment of neurological disorders
Olle Lindvall (Wallenberg Neuroscience Center, Lund, Sweden)
Tel: +1 46 46 222 0543; E-mail: [email protected] <mailto:[email protected]>
Potential of stem-cell-based therapies for heart disease
Deepak Srivastava (University of California, San Francisco, CA, USA)
Tel: +1 415 734 2716; E-mail: [email protected] <mailto:[email protected]>
Stem-cell therapies for blood diseases
Claudio Bordignon (Istituto Scientifico HS Raffaele, Milan, Italy)
Tel: +1 39 02 2643 2351; E-mail: [email protected] <mailto:[email protected]>
Nature Podcast Special: stem cells
To accompany the Nature Insight on stem cells, we have produced a special podcast featuring interviews with authors, reports from the European Society of Human Reproduction and Embryology in Prague, and a live panel discussion on the scientific and ethical issues that are emerging with the latest stem cell research.
The Nature Podcast Special: stem cells is hosted by BBC World Service presenter Gareth Mitchell, and Allan Coukell, science reporter at WBUR, Boston's NPR news station, with conference reporting from Nature’s News Editor Jo Marchant. The show features interviews and debate with leading stem cell scientists including Amy Wagers, Tom Rando, Fred Gage, Robert Lanza and many others.
This show is a special edition of the Nature Podcast series, will be available free at www.nature.com/podcast/stemcells <http://www.nature.com/podcast/stemcells>
[5] & [6] Materials chemistry: Semiconductor sponge (pp 1122-1125; 1126-1130; N&V)
Two groups in the USA have developed methods for honeycombing the semiconductor germanium with microscopic channels. These tiny holes alter the electronic properties of the material, and suggest new ways to ‘tune’ its behaviour for applications such as solar cells, photodetectors, sensors and light-emitting devices. Both groups publish their results in Nature this week.
Germanium, like silicon, is a semiconductor used in microelectronics. Carving out miniature pores in such materials can alter their properties spectacularly - for example, silicon has previously been turned into a light-emitting material by using an acid to etch it into a holey, sponge-like form.
Gerasimos Armatas and Mercouri Kanatzidis use a mixture of magnesium germanide - in which the germanium atoms carry a negative charge - and germanium tetrachloride - in which the germanium atoms are positively charged - to make a nanoporous form of germanium templated by a surfactant. The material is threaded by an ordered but labyrinthine network of pores, and absorbs light at shorter wavelengths than ordinary crystalline germanium.
Sarah Tolbert and colleagues have used a similar approach, involving a compound of germanium and potassium containing small clusters of nine atoms of germanium that become linked into chains. Again, these are combined with a surfactant that imprints the solidifying germanium with a porous network, in this case having a honeycomb-like arrangement. The researchers find that again the porous material absorbs light at shorter wavelengths than bulk germanium, and they can tune this wavelength by altering the thickness of the walls between pores, converting some of the germanium to its oxide. The method also works with a mixture of germanium and silicon: such semiconductor ‘alloys’ are commonly used in microelectronics and optoelectronics, because their electronic and optical behaviour can then be tuned by varying its composition.
CONTACT
Mercouri Kanatzidis (Michigan State University, East Lansing, MI, USA) Author paper [5]
Tel: +1 517 355 9715; E-mail: [email protected] <mailto:[email protected]>
Sarah Tolbert (University of California Los Angeles, CA, USA) Author paper [6]
Tel: +1 310 206 4767; E-mail: [email protected] <mailto:[email protected]>
Andreas Stein (University of Minnesota, MN, USA)
Tel: +1 612 624 1802; E-mail: [email protected] <mailto:[email protected]>
[7] Quantum physics: Flat gas comes to order (pp 1118-1121; N&V)
A theory dating back to the 1970s proves that perfectly ordered crystals aren't possible in two dimensions. But it is possible to make a poor approximation to such a thing - a 'rough crystal' that forms at low temperatures but 'melts' as the temperature is increased. In this week’s Nature, Jean Dalibard and colleagues report the occurrence of this 'melting' process in a very strange flatland containing an ultracold gas in which a 'rough crystal' can form from whirlpool-like quantum vortices.
The 'crystal' studied by the team looks nothing like a slice of diamond or table salt. Certain kinds of atomic gas can, in three dimensions, undergo a process called Bose-Einstein condensation when they are very cold. Here the laws of quantum physics dictate that all the atoms seem to move in step, as though they are all just one big super-atom. The formation of a Bose-Einstein condensate (BEC) is formally ruled out in two dimensions. But, just as two-dimensional pseudocrystals are possible, a two-dimensional 'quasi-BEC' could also be formed at low temperatures. This quasi-BEC can in principle be spotted by the behaviour of quantum-mechanical vortices in the gas - at high temperatures they move about more or less freely, but in the quasi-BEC they are bound into pairs, like two tornadoes that have attracted one another.
Dalibard and colleagues have now seen this switch between unbound and bound vortices in a two-dimensional gas of rubidium atoms. They use light to split and shape a gas cloud into two flat pancakes, and can monitor the behaviour of vortices in these slabs of gas by watching how the two slabs interact with each other when the light, which keeps the gas layers separate, is turned off. This interaction creates a pattern of stripes, like those formed when two waves intersect, and unbound vortices cause glitches in this pattern. This enables the researchers to see that, as predicted by the BKT theory, free vortices proliferate above the temperature at which the quasi-BEC 'melts'.
CONTACT
Jean Dalibard (Ecole Normale Superieure, Paris, France)
Tel: +33 1 44 32 25 34; E-mail: [email protected] <mailto:[email protected]>
Tilman Esslinger (ETH-Zurich, Switzerland) N&V author
Tel: +41 1 633 2340; E-mail: [email protected] <mailto:[email protected]>
Gianni Blatter (ETH-Zurich, Switzerland) N&V author
Tel: +41 1 633 2568; E-mail: [email protected] <mailto:[email protected]>
[8] And finally… The recipe for a healthy ecosystem (pp 1139-1143)
Healthy ecosystems require a complex interaction of species diversity and habitat structure, a letter in Nature suggests.
Kristin E. France and J. Emmett Duffy constructed an ecosystem made of seagrass and crustaceans. Different numbers of crustacean species were allowed to feed on isolated and interconnected patches of seagrass. Ecosystems were most stable when the biodiversity of grazers was increased and when crustaceans were given the opportunity to move between seagrass patches.
The results suggest that preserving a variety of habitats and species can help to stabilize ecosystems over time - an important finding, as human influence continues to exert an increasing and uncertain effect on species diversity and habitat structure.
CONTACT
Kristin France (Virginia Institute of Marine Science, Gloucester Point, VA, USA)
Tel: +1 804 815 7751; E-mail: [email protected] <mailto:[email protected]>
ALSO IN THIS ISSUE…
[9] Soft equations of state for neutron-star matter ruled out by EXO 07482676 (pp1115-1117)
[10] Subcontinental-scale crustal velocity changes along the Pacific-North America plate boundary (pp 1131-1134)
[11] Activity-dependent dynamics and sequestration of proteasomes in dendritic spines (pp 1144-1148)
[12] Structure of the S-adenosylmethionine riboswitch regulatory mRNA element (pp 1172-1175)
ADVANCE ONLINE PUBLICATION
***These papers will be published electronically on Nature's website on 28 June 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 them on this release to avoid multiple mailings they will not appear in print on 28 June, but at a later date.***
[13] Degradation of Id2 by the anaphase-promoting complex couples cell cycle exit and axonal growth
DOI: 10.1038/nature04895
[14] Hierarchy and adaptivity in segmenting visual scenes
DOI: 10.1038/nature04977
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.
DENMARK
Aarhus: 4
FRANCE
Paris: 7
GERMANY
Munich: 4
ISRAEL
Rehovot: 14
JAPAN
Chiba: 4
Ibaraki: 4
Saitama: 2
Tokyo: 4
SPAIN
Barcelona: 10
UNITED KINGDOM
Norwich: 3, 4
UNITED STATES OF AMERICA
Arizona
Tucson: 9
California
Los Angeles: 1, 6
Pasadena: 10, 11
San Diego: 1
San Francisco: 2
Santa Cruz: 1
Colorado
Boulder: 12
Massachusetts
Boston: 13
Cambridge: 10
Charlestown: 14
Michigan
Ann Arbor: 10
East Lansing: 5
New York
New York: 13
Virginia
Gloucester Point: 8
Washington
Pullman: 3
PRESS CONTACTS…
For North America and Canada
Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail: [email protected] <mailto:[email protected]>
For Japan, Korea, China, Singapore and Taiwan
Rinoko Asami, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected] <mailto:[email protected]>
For the UK/Europe/other countries not listed above
Helen Jamison, Nature London
Tel: +44 20 7843 4658; E-mail [email protected] <mailto:[email protected]>
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