Vol 450|1 November 2007 RESEARCH HIGHLIGHTS
MOLECULAR NEUROBIOLOGY Active resilience Extraordinary sound Cell 131, 391–404 (2007) A molecule known as BDNF may provide Nature Phys. doi:10.1038/nphys774 a pivotal distinction between people who (2007) succumb to conditions such as depression Light squeezed through a hole or post-traumatic stress disorder and the of smaller diameter than its majority who do not. wavelength can emerge in a Eric Nestler of the University of Texas collimated beam when the Southwestern Medical Center in Dallas and hole is set in a periodic array his colleagues had previously identified mice of indentations. This counter- that avoided social contact with cage-mates intuitive phenomenon is known after repeated ‘social defeat’ — brought as “extraordinary optical transmission”. Now researchers about by forced encounters with more in Spain have shown that an aggressive mice. analogous effect can be achieved The researchers found that resilience with sound waves. to stress in this social-defeat model is an Using their understanding of active process in which stress-induced firing the role of surface plasmons in the in part of the brain’s neuronal circuitry optical case, Francisco Garcia-Vidal associated with reward and drug addiction at the Autonomous University is suppressed. This lowers levels of brain- of Madrid and his colleagues derived neurotrophic factor (BDNF), and designed systems of holes and mice with a natural variation in their BDNF grooves in which acoustic surface gene were resilient to stress. The researchers waves have a similar effect, also found high levels of BDNF in a region producing a beam of sound through associated with reward in post-mortem cunningly contrived interference brains of people with a history of depression. and reinforcement. The authors think this effect might be applied in ECOLOGY non-destructive materials testing Smelly fish and medical ultrasound. Proc. R. Soc. B doi:10.1098/rspb.2007.1283 (2007) Fish that have been exposed to even very MICROBIOLOGY Institue of Technology in Pasadena, Ron low levels of a common pollutant are Weiss at Princeton University, New Jersey, shunned by their conspecifics, according to A time to die and their colleagues report engineering research by Ashley Ward at the University Science 318, 652–655 (2007); Proc. Natl Acad. Sci. a system into populations of E. coli that of Sydney and his co-workers. The effect USA doi:10.1073/pnas.0704256104 (2007) allows a specific pattern of gene expression may put the tainted fish at increased risk of Bacteria communicate with each other to a only when both populations are present in predation. greater extent, and in more ways, than was sufficient numbers. They suggest that such The research looks at the effect of low levels once thought. Hanna Engelberg-Kulka of systems could be used to engineer specific of 4-nonylphenol, a surfactant sometimes the Hebrew University in Jerusalem and her responses in artificial biofilms. found in shampoos and soaps, on schooling colleagues report that Escherichia coli can send Intriguingly, three years ago these labs in juvenile banded killifish (Fundulus out messages that encourage their neighbours engineered a ‘neighbour killing’ system diaphanous, pictured below). Unexposed fish to kill themselves. The ‘extracellular death into bacteria quite similar to that now being were unwilling to school with fish that had factor’ involved turns out to be a chain of five reported (L. You et al. Nature 428, 868–871; been exposed for as little as an hour to levels amino acids that seems to be produced by the 2004). This may be the first example of
G. MESZAROS/VISUALS UNLIMITED G. MESZAROS/VISUALS commonly found in sewage outflows. degradation of a metabolic enzyme, glucose-6- synthetic biology anticipating a function only phosphate dehydrogenase. later revealed in nature. The authors suggest that the ability to RELATIVISTIC PHYSICS coordinate cell death may allow bacteria to Hot at any speed release nutrients from a Phys. Rev. Lett. 99, 170601 (2007) proportion of individuals According to the theory of special relativity, when the population is measurements of length and time differ under stress, or to defeat depending on the relative velocity of the phage attacks by means observer and the thing being measured. similar to a ‘scorched- Einstein and other prominent physicists earth’ policy. believed that the measured temperature of Meanwhile, Frances a gas would also depend on the speed of the Arnold at the California observer.
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