Geology: After the flood
Geology 34, 461–464 (2006)
What caused the mass extinction at the end of the Early Cambrian epoch, about 508 million years ago?
Linda Glass and David Phillips of the Australian National University in Canberra have identified a new suspect: a massive outpouring of volcanic rock in what is now northern Australia. They have used radioisotope dating to fix the age of this formation, christened the Kalkarindji ‘flood basalt’ province, to around the time of the Cambrian mass extinction. Flood basalts elsewhere have been linked to other mass extinctions because of their effect on global climate and atmospheric chemistry — this is the oldest such association.
Cell biology: Neurons and nematodes
Cell 125, 987–1001 (2006)
Scientists have identified a mechanism that plays a role in both a cell's response to stress and an organism's lifespan.
Azad Bonni of Harvard Medical School in Boston, Massachusetts, and his colleagues studied the response of mammalian neurons to oxidative stress. They found that FOXO transcription factors are the long-sought targets of a family of stress-activated enzymes, the MST kinases: the enzyme MST1 alters FOXO3, ultimately triggering the death of the damaged cell.
In nematode worms, the researchers implicated MST–FOXO signalling in ageing. Worms lacking the MST analogue CST-1 died young. Those with more of the enzyme had a longer lifespan, providing that the FOXO3 analogue was present.
Microbiology: Hole punch
J. Cell Biol. doi:10.1083/jcb.200509009 (2006)
Disease-causing Staphylococcus aureus bacteria (pictured below) may escape from the bloodstream by punching holes through the cells lining blood vessels, say researchers.
Emmanuel Lemichez at the National Institute of Health and Medical Research in Nice, France, and his colleagues studied the effects of an S. aureus toxin known as EDIN. EDIN blocks a protein called RhoA, which acts rather like the foreman on a building site, telling cells where to construct their internal scaffolding in response to external signals. The loss of this coordination results in long tunnels, dubbed macroapertures, forming in the cell.
Organic chemistry: Symmetry selective
J. Am. Chem. Soc. doi:10.1021/ja061853f (2006)
Dichroanone is part of a family of natural chemicals with anti-tumour properties. Now chemists have made one of its optical isomers from scratch — the first enantioselective synthesis of any chemical in this family.
Dichroanone includes three carbon rings fused to a central carbon atom in a configuration that is notoriously hard to build.
Ryan McFadden and Brian Stoltz of the California Institute of Technology, Pasadena, managed to produce (+)-dichroanone in 11 chemical steps with a 4% overall yield (pretty impressive for an asymmetric natural product synthesis). They avoid using protecting groups, which are normally needed to shield one part of a molecule while another segment is being transformed — a strategy that cuts the number of steps.
Astronomy: Hydrogen hunt over
Astrophys. J. 643, 675–679 (2006)
Maps of nearby galaxies have resolved an astronomical riddle concerning the whereabouts of the material that fuels star formation — molecular hydrogen.
The light from some quasars contains absorption lines, created when it passed through galaxies en route to Earth, which provide information about the galaxies' content. Atomic hydrogen shows up clearly in these systems, dubbed ‘damped lyman alpha absorbers’, but there has been little evidence for molecular hydrogen.
Martin Zwaan of the European Southern Observatory and Jason Prochaska of the University of California's Lick Observatory, Santa Cruz, report that, in nearby galaxies, molecular hydrogen clusters densely in the galactic centre — occupying an area 150 times smaller than the atomic hydrogen. Hardly surprising, then, that light from quasars rarely passes through it.
Material science: Polished finish
Science 312, 1504–1508 (2006)
Round nanoparticles will give silicon a better polish, say researchers who have developed a recipe for cooking them up.
Abrasive pastes made from cerium oxide nanoparticles are used to flatten silicon wafers, a key step in the manufacture of integrated circuits. But such particles tend to have a faceted shape, with angular edges that can damage the wafer surface.
Xiangdong Feng, then at the Ferro Corporation in Independence, Ohio, and Zhong Lin Wang of the Georgia Institute of Technology in Atlanta synthesized their particles by setting a cerium spray alight. Adding titanium to this burning precursor mix gave nearly round particles, because the titanium forms a liquid shell around the crystallizing cerium oxide (pictured above).
Ecology: The truth about trees
Science doi:10.1126/science.1124712 (2006)
A vast survey of the world's tropical forests is set to fuel the debate over what determines their diversity.
Richard Condit of the National Center for Ecological Analysis and Synthesis in Santa Barbara, California, and his colleagues analysed data from sites ranging from a dry forest in India, with just 73 species in 50 hectares, to a rainforest in Malaysia with 1,167 species in a similar-sized area.
It was previously thought that having tree species with a broad range of lifespans and growth rates would promote diversity, reasoning that a slow-growing tree, for example, would better compete with fast-growing neighbours if it were longer lived. Instead, the researchers found that the most diverse forests were the least varied demographically.
Biology: Three-way feast
PLoS Biol. doi:10.1371/journal.pbio.0040188 (2006)
The glassy-winged sharpshooter, Homalodisca coagulata, unlike many sap-sucking insects, sups from the water-carrying cells of the xylem, rather than the sugary sap of the phloem. Jonathan Eisen, then at the Institute for Genomic Research in Rockville, Maryland, and his colleagues have now shown how a division of labour between the symbiotic bacteria living in the insect's cells makes this low-nutrient lifestyle possible.
A complete genome of the bacterium Baumannia cicadellinicola and a partial sequence of Sulcia muelleri reveal that Baumannia has the metabolic pathways needed to provide its insect host with vitamins, but has lost those for the essential amino acids. Sulcia devotes most of its very small genome to that neglected task, thus complementing its colleague. Each of the three organisms thus requires both of the others.
Nanotechnology: Trombone scales
Phys. Rev. Lett. 96, 215503 (2006)
Tiny vibrating rods can be used as highly sensitive weighing scales, because an attached mass — down to a single virus particle — will change their oscillation frequency.
Researchers led by Alex Zettl at the University of California, Berkeley, have built such a device using a carbon nanotube that can be extended like a telescope. They say this allows them, “like a trombone player shifting notes”, to tune the rod's vibrational frequency.
This should make the device sensitive to a wider range of masses than a tube of fixed length, as the resonant frequency can be matched to the mass to be measured.
Marine biology: In hot water
Proc. R. Soc. Lond. B doi:10.1098/rspb.2006.3567 (2006)
Warming waters threaten the intimate relationship between stony corals and the nutrient-providing zooxanthella algae that live within their tissues. But research from the Australian Institute of Marine Science, Townsville, offers some hope.
Ray Berkelmans and Madeleine van Oppen transplanted Great Barrier Reef coral colonies from cooler reefs to warmer inshore bays, where the corals expelled their symbiotic algae, a process known as coral bleaching (see white colonies, pictured). Some of the corals that recovered from the first bleaching event could then tolerate temperatures 1–1.5 °C warmer than previously. The researchers show that these corals had changed their algae to a more heat-resistant form.
Bart de Strooper
Flanders Interuniversity Institute for Biotechnology and the Catholic University of Leuven, Belgium
An expert in Alzheimer's disease wonders why striking findings didn't hit the headlines.
Last year, Nature Medicine published a paper that, in my sincere naivety as a basic science researcher, I expected to prompt headlines such as ‘Major crisis in pharmaceutical sector’ and ‘Stock owners dump shares’.
The paper (T. Kukar et al. Nature Med. 11, 545–550; 2005) showed that a bunch of compounds, some registered as therapeutics, could augment in human cell cultures production of the small amyloid-beta peptide Aβ42, believed to cause Alzheimer's disease.
The increases in Aβ42 levels observed were quite dramatic, equaling or even surpassing those caused by the genetic mutations that lead to early and aggressive forms of genetic Alzheimer's.
To my surprise, the publication went largely unnoticed, even though many more modest papers get easily into the news. Recently, for instance, I was asked to comment on an ominous report claiming that intellectuals might be at higher risk of dementia. I felt immediately depressed, considering my secret long-term plans as emeritus professor. This insignificant story slipped easily out of my mind.
By contrast, the Kukar et al. paper leaves me uneasy. The authors, well aware of the potential implications of their observations, are careful in their extrapolations. However, they conclude: “exogenous compounds... may represent an unrecognized risk for the development of Alzheimer's disease”.
I bet in many pharmaceutical companies the press officers were on red alert, while lawyers and managers spent precious time drafting a response to possible litigation because medication X could have caused Alzheimer's in grandad or grandma.
I wonder why this didn't happen.