PLEASE CITE NATURE AND OUR WEBSITE www.nature.com/nature AS THE SOURCE OF THE FOLLOWING ITEMS. IF PUBLISHING ONLINE, PLEASE CARRY A HYPERLINK TO http://www.nature.com/nature
[1] Mars: Water, water everywhere at planet's south pole (DOI: 10.1038/nature02461) (http://dx.doi.org/10.1038/nature02461)
***This paper will be published electronically on Nature's website on 17 March 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 18 March, but at a later date.***
There's plenty of water ice at the martian south pole, according to images taken from the European Space Agency's Mars Express Orbiter. The discovery confirms that both poles have permanent watery ice caps.
The planet's south pole has three distinct areas, all containing water ice, report Jean-Pierre Bibring and colleagues in a paper published online this week by Nature. In the centre is a 'bright cap' of frozen carbon dioxide mixed with some water ice, which is surrounded by a region of almost pure water ice. Extending for tens of kilometres around this is a vast area of dirty water ice, containing varying amounts of dust.
The researchers deduced the pole's chemical make-up by studying the amounts of light and heat reflected from the area. The images were taken at the end of the martian summer, when the polar cap is at its smallest, showing that the ice is present all year round. This work is discussed further by Timothy Titus in an accompanying News & Views article.
[2] Oncology: Double anti-cancer whammy (pp332-337; N&V)
The drug rapamycin may prove to be a useful adjunct to chemotherapy, research in this week's Nature suggests. The combined approach prevents some tumours from building up resistance to standard anti-cancer medicines.
Mice with a type of B-cell lymphoma — a cancer of antibody-producing B cells that is caused by the genes Myc and Akt — are resistant to standard chemotherapy, report Scott W. Lowe and colleagues. But when the animals are given rapamycin in combination with chemotherapy, their tumours become sensitive to the anti-cancer drugs.
Rapamycin targets one of the signalling pathways regulated by Akt, a protein that has been implicated in cell survival. But not all tumours express Akt or activate this pathway, so the combination therapy may only work in those that do, the authors caution.
The results point to a possible strategy for reversing drug resistance in human cancers, and underline the importance of tailoring cancer therapy to a tumour's genetic make-up. "The clinical importance of these results is obvious," says Frank McCormick in an accompanying News and Views article. "Indeed, clinical trials of rapamycin and its analogues in combination with other chemotherapeutic agents are already underway."
[3] Astronomy: Galactic gamma glimmer explained (pp293-296; N&V)
The Milky Way's 'soft' gamma-ray glow is largely caused by black holes and neutron stars that are buried inside clouds of gas and dust, according to data from the European Space Agency's INTEGRAL satellite observatory, presented in this week's Nature.
Previously, scientists could not work out exactly where these soft gamma-rays — a very energetic form of radiation — were coming from. But F. Lebrun and colleagues found dozens of faint gamma-ray sources that together make up the Galactic glimmer.
INTEGRAL was launched in October 2002 on a Russian Proton rocket. It will now make a complete census of buried black holes in the Milky Way. "The Universe will appear to be a very different place when viewed clearly with gamma-ray eyes," says Nicholas White in an accompanying News and Views article.
[4] and [5] Infection: Protein-only prions show diverse repertoire (pp319-323 and 323-328; N&V)
Prions, the infectious agents responsible for conditions such as Creutzfeldt"Jakob disease, are made entirely of protein. What's more, different prion strains are generated by particles of the same protein folded into different conformations, two studies in this week's Nature now show.
Chih-Yen King and Ruben Diaz-Avalos took a fragment of a protein called Sup35 that is responsible for prion propagation in yeast (Saccharomyces cerevisiae). They labelled it with fluorescent protein and introduced it into different groups of yeast cells, each containing a specific prion strain. The authors then re-isolated these fragments and used them as 'seeds' to grow fibres from bacterially derived Sup35 outside cells. When they introduced these fibres into uninfected yeast cells, they faithfully propagated the strain they had previously encountered, showing that different strains can be generated by the original Sup35 fragment.
In the second study, Jonathan S. Weissman and colleagues showed that recombinant Sup35 aggregates formed at different temperatures adopt different conformations. Infection of yeast with these disparate particles results in different strains. "The two studies provide the coup de grâce for the protein-only hypothesis," says Mick F. Tuite in an accompanying News and Views article.
[6] Anthropology: The culture club (pp275-278)
No other species in history has come close to the wealth of culture that humans can boast. The world is full of different religions, marriage systems, diets and housing styles. What spawned this profusion, and what advantages does our culture offer us? Mark Pagel and Ruth Mace tackle these questions in a News and Views Feature in this week's Nature.
Genetically, humans the world over are very similar. But Pagel and Mace show that cultures distribute themselves around the world in patterns that are similar to the distribution of animal species. Different languages — a useful standard by which to differentiate cultures — can occur every few square kilometres in equatorial areas, whereas less hospitable regions have few languages. The authors argue that this pattern arises because humans living in harsh conditions band together into wider-ranging, more inclusive groups, whereas tropical dwellers form close-knit communities to protect their slice of paradise.
But why bother with culture anyway? The answer, suggest Pagel and Mace, may be down to making cooperative groups work for individuals. Historically, complex tasks such as hunting and competing for territory have required cooperation. Human cultures, perhaps uniquely, act to enforce norms of cooperation, making it more difficult for cheats to prosper. This strong sense of the group in modern humans may underpin some of our tendencies to be mistrustful of strangers.
[7] Ecology: Rainforest insects united by common enemy (pp310-313)
Researchers working in Belize have shown how populations of one species of leaf-eating insect can indirectly affect the population of a second, related herbivorous insect through a shared parasitic enemy, even when the two species do not compete directly for resources such as food or shelter. As numbers of one of the species drop, the overall level of parasitism is reduced, which in turn allows other related species to increase in abundance.
This is the first demonstration of such 'apparent competition' in a rainforest setting, report H. Charles J. Godfray and colleagues in this week's Nature. They artificially reduced numbers of a leaf-eating fly called Calycomyza, which is attacked by parasitic wasps, by removing leaves from the trees on which they specifically feed. A year later, parasitism on related flies had fallen by a factor of 0.6, and these flies were more abundant.
A similar increase in abundance was seen in a group of wasp-parasitized beetles after one species was removed, the authors report. The discovery shows that practices such as selective logging — which is widely perceived as more ecologically friendly than blanket clearance — could have unforeseen effects on rainforest food webs, they add.
[8] Molecular Biology: New ribozyme is in a class of its own (pp281-286; N&V)
Researchers have discovered a new class of RNA-based enzyme or ribozyme. The molecule, called GlmS, is part of a biological feedback loop that helps to regulate gene expression in bacteria. It is described in this week's Nature.
The ribozyme, described by Ronald R. Breaker and colleagues, acts as a metabolite-responsive switch in Gram-positive bacteria. When levels of a simple sugar, called glucosamine-6-phosphate, build up, the sugar binds to a ribozyme sequence at one end of the messenger RNA of the glmS gene. Binding of the sugar activates the ribozyme, which then cleaves the messenger RNA. This prevents the expression of the GlmS protein, and in turn, sugar production goes down.
Switches like this may have functioned as metabolite sensors in primitive organisms, the authors say. The finding may be putative evidence for an ancient pre-DNA, pre-protein 'RNA world', they add.
"The findings might have prompted some to wonder why nature failed to use, or perhaps to retain, such an elegant mechanism. But it's clear now that this perhaps ancient talent of RNA is alive and well, and is currently used by at least some bacteria to control their glmS genes," says Thomas R. Cech in an accompanying News and Views article.
[9] Animal vision: Salmon colour their view to suit hunting strategy (p279)
Salmon use a previously undiscovered process to alter the colour-sensitivity of their eyes as they grow older, a Brief Communication in this week's Nature shows. The strategy may help them to make the transition from feeding on plant material near the surface to predatory hunting in deeper waters.
Newly hatched Pacific pink salmon (Oncorhynchus gorbuscha) have visual pigments — contained in retinal structures called cones — that are most sensitive to ultraviolet light, report Christiana L. Cheng and Inˇigo Novales Flamarique. But as the fish grow, these are replaced in their individual cones by pigments that detect blue light. This is accomplished by switching off the production of one type of visual protein, or opsin, and making another instead.
This transformation occurs at about the time when the salmon make the shift from surface grazing to deeper hunting, the authors add. This makes sense, as surface waters have plenty of ultraviolet light, whereas deeper waters are lit predominantly in blue"green.
[10] Neuroscience: Development gene is double-edged sword (pp337-341)
The Bmi1 gene is a double-edged sword, research in this week's Nature suggests. It promotes cell growth in the developing brain, but may also prompt tumour development.
Bmi1 is found in proliferating cerebellar precursor cells in the developing mouse and human brain, report Silvia Marino and colleagues. When the gene is absent, cerebellar neurons proliferate less.
But Bmi1 overexpression may cause excessive proliferation and tumour formation. The protein is found in primary human medulloblastomas, a type of brain tumour, the team report.
[11] Health and Medicine: Glioma gene identified (pp328-332)
Researchers have identified a gene that may be involved in the development of certain aggressive brain tumours.
Gliomas are the most common type of brain tumour. Around 1,500 new cases are diagnosed every year in the United States. Most will die within the following year. The growth of the tumour and its blood supply may be regulated by the potential tumour-suppressor gene ING4, report Igor Garkavtsev and colleagues in this week's Nature. Human glioma tissue contains less ING4 than does normal control tissue, and the extent of the reduction correlates with the progression from lower to higher grades of tumours.
The suggestion is backed up by animal studies. In mice, grafted brain tumours with low levels of ING4 grow faster than control tumours. Importantly, they also have more vasculature owing to the overproduction of a molecule called interleukin-1, which is normally kept in check by ING4. Intervention with this or other pathways controlled by ING4 may have therapeutic potential.
[12] Materials: Semiconductors get a boost (pp299-303; N&V)
Scientists report a new and easy way to make semiconductors into extremely thin films in this week's Nature. The secret ingredient is hydrazine, a liquid that was once commonly used as rocket fuel.
Semiconductors are used in every area of electronics — each of the 42 million or so transistors in your computer relies on them. Certain applications, such as flat-panel displays, need transistors in the form of thin films. But making these materials with the right electronic properties is a tricky business.
David B. Mitzi and colleagues have now made inorganic thin film semiconductors by pouring a hydrazine solution containing carefully controlled amounts of tin disulphide and tin diselenide onto a silicon wafer rotating at 3,500 r.p.m. This spinning pushes the liquid outwards, forming a film only a few molecules thick. The hydrazine allows a clean chemical reaction that gives nice, even films with useful electronic properties.
In an accompanying News and Views article, Mercouri G. Kanatzidis says, "It is this simple chemistry that not only makes the work attractive, but probably technologically significant as well."
[13] Earth science: Cracking continents caused 'snowball Earth' (pp303-306)
The break-up of ancient continents could have been responsible for the Earth turning into a gigantic snowball 750 million years ago. In this week's Nature, Yannick Donnadieu and colleagues use a computer model to show how this movement of land masses could have removed large amounts of the greenhouse gas carbon dioxide from the atmosphere.
Geologists believe that during at least two periods between 550 and 800 million years ago, ice sheets may have reached all the way from the poles to the Equator, a situation nicknamed 'snowball Earth'. But this could only happen if there was very little carbon dioxide in the atmosphere. Atmospheric carbon dioxide acts as a blanket, stopping heat from the Earth's surface escaping into space. Exactly how this carbon dioxide could have been removed from the atmosphere, causing global cooling, is unknown.
The researchers claim that when one large continent broke into smaller fragments, this led to an increase in rain over the land. More rain caused more weathering of the rocks in these land masses, which absorbed large amounts of carbon dioxide from the atmosphere.
[14] Health and medicine: Regulating body weight (DOI: 10.1038/nature02440) (http://dx.doi.org/10.1038/nature02440)
***This paper will be published electronically on Nature's website on 17 March 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 18 March, but at a later date.***
A brain enzyme, called AMP-activated protein kinase (AMPK), may help to regulate food intake and body weight, according to research published online by Nature this week. The discovery could lead to new approaches for the treatment of obesity.
AMPK is known to help cells monitor their energy levels. Now Barbara B. Kahn and colleagues show that hormones involved in appetite control can also regulate AMPK activity in the hypothalamus, a brain region known to be involved in the regulation of food intake. For example, leptin, a hormone that suppresses appetite, inhibits AMPK activity.
The team also found that when AMPK was inhibited directly in the brain, mice ate less and lost weight. When enzyme levels were boosted, mice ate more and gained weight. Understanding how AMPK fits in with other feeding-related molecules may help researchers design new therapies to prevent or reverse obesity, the team say.
[15] And finally: Buckyballs fix nitrogen (pp279-280)
Football-shaped carbon molecules can help to turn nitrogen into ammonia, according to research published in a Brief Communication to this week's Nature. Ammonia is the starting point for manufacturing fertilizers, making this an important chemical for food production.
Sakae Uemura and colleagues use the carbon molecule C60 — also known as buckminsterfullerene (or 'buckyball') — wrapped up in two cyclodextrin molecules, to bring nitrogen and water together to make ammonia.
Many plants 'fix' nitrogen from the air to make their own ammonia, which they use to make proteins. The industrial synthesis of ammonia relies on high temperatures and pressures. But both need a metal catalyst to help chivvy the inert nitrogen molecule into action. Interestingly, Uemura and colleagues' strategy relies on a non-metallic carbon molecule under mild conditions to do the same job.
ALSO IN THIS ISSUE"¦
[16] Crystal structure of spinach major lightharvesting complex at 2.72 A° resolution (pp287-292)
[17] Structural relaxation in supercooled water by time-resolved spectroscopy (pp296-299)
[18] Millennial and orbital variations of El Ninõ/Southern Oscillation and high-latitude climate in the last glacial period (pp306-310)
[19] The protein kinase PKR is required for macrophage apoptosis after activation of Toll-like receptor 4 (pp341-345)
ADDITIONAL ADVANCE ONLINE PUBLICATION PAPERS"¦
***This paper will be published electronically on Nature's website on 17 March 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 18 March, but at a later date.***
[20] The decline and fate of an iron-induced subarctic phytoplankton bloom (DOI: 10.1038/nature02437) (http://dx.doi.org/10.1038/nature02437)
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.
AUSTRALIAClayton: 18Canberra: 18Wollongong: 18
CANADABritish Columbia Burnaby: 9 Sidney: 20 Vancouver: 20 Victoria: 20Newfoundland St. Johns: 20Nova Scotia Halifax: 20Quebec Laval: 20 Montreal: 2
PEOPLE'S REPUBLIC OF CHINABeijing: 16Hong Kong: 20
DENMARKCopenhagen: 3
FRANCEGif sur Yvette: 1, 13Orsay: 1Nantes: 1Paris: 1, 3, 14Toulouse: 1, 3, 13
GERMANYMunich: 3Berlin: 1Lindau: 1
ITALYFlorence: 17Rome: 1, 3
JAPANChiba: 20Hokkaido: 20Kyoto: 15Miyagi: 20Osaka: 15Tokyo: 20Tsukuba: 20
THE NETHERLANDSNoordwijk: 3
NEW ZEALANDDunedin: 20Wellington: 20
RUSSIAMoscow: 1
SWITZERLANDVersoix: 3Zurich: 10
UNITED KINGDOMAscot: 7Belfast: 18Egham: 18London: 6Oxford: 7Reading: 6Southampton: 3
UNITED STATES OF AMERICACalifornia La Jolla: 19 Pasadena: 1 San Francisco: 2, 5Connecticut New Haven: 8Delaware Wilmington: 2Florida Gainesville: 13 Tallahassee: 4Massachusetts Boston: 11, 14Michigan Ann Arbor: 19Missouri St. Louis: 1New York Cold Spring Habor: 2 New York: 2 Yorktown Heights: 12Pennsylvania Philadelphia: 14Ohio Bowling Green: 20 Cleveland: 11Rhode Island Providence: 1, 18Wisconsin Madison: 18
Nature Publishing Group is a division of Macmillan Publishers Ltd.
Macmillan is an international publisher serving the information and education community as well as publishing fiction and non-fiction.
RSS