EDITORS’CHOICE EDITED BY GILBERT CHIN AND JAKE YESTON

B I O M E C H A N I C S No Skimming Allowed Pterosaurs were flying reptiles and the first air-borne vertebrates; they dominated the skies from the late Triassic to the end of the Cretaceous, during the epoch of their relatives, the dinosaurs. On the basis of similarities in jaw structure, it has been suggested that several pterosaurs, including Thalassodromeus and the giant Quetzalcoatlus (with a wingspan of up to 15 m), could have fed by skimming in a manner akin to that of extant ternlike shorebirds (Rynchops spp.) Skimmers fly low over calm

shallow water with the tip of their lower beak dipping beneath the water surface. Humphries et al. have used full-sized mod- on August 31, 2007 els of mandibles from Thalassodromeus and the modern skimmer R. niger to demonstrate that the pterosaur bill would have generated an order of magnitude more drag in traveling through the water. Modeling indicated that the energetic cost to a shorebird of flying with its beak in the water is almost prohibitive (~20% of the total cost of flight), and the authors sug- gest this levy might explain the rarity of the skimming life-style. The substantially greater cost for a pterosaur larger than 2 kg appears to exclude outright skimming as a possible means for procuring food. Furthermore, many of the morpho- logical specializations to the head and neck seen in Rynchops are not found in pterosaurs of any size, including the ability to regenerate broken or abraded bill tips and the presence of a reinforced lower jaw. — GR PLoS Biol. 5, e204 (2007). www.sciencemag.org

B I O M E D I C I N E study involving about 2000 HPV-positive women syndrome similar to the human autoimmune dis- Timing is Everything in Costa Rica who were monitored for 12 ease systemic lupus erythematosus. Green et al. months, the authors found that HPV clearance provide evidence that αM-II deficiency in mice Cervical cancer is the second leading cause of rates—measured as cell-mediated immunity to involves activation of the innate immune system. cancer deaths in women, with more than 80% the virus—were comparable in subjects receiv- The first piece of evidence emerged from the

of these occurring in developing countries that ing the HPV vaccine (specifically, the bivalent observation that initiation of disease did not Downloaded from have limited access to screening programs. HPV-16/18 cervical cancer candidate vaccine) require cells of hematopoietic origin; rather, the Some strains of a sexually transmitted virus, and those who had received a control vaccine mesangial cells of the kidney were stimulated to human papillomavirus (HPV), play an essential directed against an unrelated virus. Although the produce inflammatory proteins. Subsequently, role in the pathogenesis of this cancer. Newly long-term effects of the current HPV vaccines are other cells of the innate immune system partici- developed vaccines directed against these onco- not yet known, the apparent absence of thera- pated in the development of glomerulonephritis, genic strains have shown promising results in peutic efficacy noted in this study reinforces the which unexpectedly could be attenuated by boost- clinical trials aimed at assessing their prophy- view that the optimal time to vaccinate is before ing the adaptive immune system via injection of lactic activity—that is, their ability to prevent the onset of sexual activity. — PAK immunoglobulin G. The absence of αM-II resulted high-grade precancerous lesions or cervical can- J. Am. Med. Assoc. 298, 743 (2007). in a surfeit of hybrid-type N-glycans that were rec- cer in women who had not been exposed to HPV ognized by innate immune lectins otherwise dedi- before vaccination. I M M U N O L O G Y cated to sensing the structurally similar mannose Hildesheim et al. have examined whether Wearing One’s Own Coat linkages of foreign glycoproteins. Future work HPV vaccination can promote an immune might determine if the maturation of branched response to HPV in women who are already Autoimmunity conventionally falls within the glycans on self-proteins broadly helps avert harm- infected with the virus. Such therapeutic activity realm of the adaptive immune system because it ful innate immune responses, and whether had not been observed in animal studies of the pertains to responses to self-constituents in pathogens might cloak themselves in complex- WITTON HPV vaccines, but data addressing this question humans and in a variety of animal models. Previ- type garb as a means of evading detection. — SJS MARK

: in humans are important for ongoing discussions ous studies have shown that mice lacking the Immunity 27, 10.1016/j.immuni.2007.06.008 of when and to whom the vaccines should be enzyme alpha-mannosidase-II (αM-II) exhibit a (2007).

CREDITS administered to maximize their benefits. In a dearth of complex-type N-glycans and develop a Continued on page 1149

www.sciencemag.org SCIENCE VOL 317 31 AUGUST 2007 1147 Published by AAAS EDITORS’CHOICE Continued from page 1147

C H E M I S T R Y tinct, interspersed populations of visual and Networked Polyhedra motor neurons within these regions. — GJC J. Neurophysiol. 98, 10.1152/jn.00238.2007 One approach to engineering porous solids has (2007). focused on combining metallic and organic building blocks. Linking multiple organic ligands C L I M AT E S C I E N C E to metal-ion nodes can produce microporous Change in the Water three-dimensional networks. In an extension of this method, small bidentate ligands such as The rapid, millennial-scale cooling episodes 1,3-benzenedicarboxylate (bdc) (called Dansgaard-Oeschger events) that occurred can bind to Cu2+ ions to form repeatedly throughout the last glacial period are discrete polyhedra (rhombi- normally associated with climate change in the hexahedra) that in turn act North Atlantic region. However, research over the as larger nodes for past decade has also implicated their expression assembling expanded in the Pacific and Indian Oceans, leading to two networks. Perry et al. competing explanations for the connection: atmo- now show that when spheric or oceanic transmission of the signal. two bdc units are Schmittner et al. used an ocean-atmosphere bridged with a flexible climate model to show that changes in buoyancy- aryloxy spacer group, self- forced ocean circulation can cause large variations assembly with Cu2+ ions leads to in subsurface oxygen levels by changing oxygen a covalently linked set of the poly- demand. This result suggests that the climate sig- hedral units, arranged together in an interpene- nal of Dansgaard-Oeschger events originating in

trating tetragonal net. Crystallography reveals the North Atlantic was transmitted by oceanic, on August 31, 2007 that the ligands adopt two independent confor- rather than atmospheric, teleconnections; further, mations, one syn and one anti, in different direc- it is consistent with the association of Dansgaard- tions within the lattice. — PDS Oeschger events with changes in the Meridional J. Am. Chem. Soc. 129, 10076 (2007). Overturning Circulation of the Atlantic Ocean. The influence of changes in wind stress and North N E U R O S C I E N C E Pacific Intermediate Water formation was also Playing with Mirrors notable, though somewhat weaker than that of thermohaline circulation. Thus, ocean ecosystems Since the initial characterization of mirror neu- and biogeochemical cycles appear to respond www.sciencemag.org rons in the monkey—visuomotor neurons that sensitively to ocean circulation changes. — HJS fire during both execution and observation of Paleoceanography 22, 10.1029/2006PA001384 movements—more than a decade ago, there has (2007). been much speculation about whether similar neurons in the human brain are involved in a P H Y S I C S wide range of social cognitive processes, such as Harmonizing High Harmonics understanding the emotions and intentions of Downloaded from others. Dinstein et al. point out that many of the Intense infrared laser pulses can ionize the human brain areas thus implicated were charac- atoms of an inert gas and give rise to x-ray terized as being active during imitation and have emission at high multiples (or harmonics) of not always been shown to encode movements in the driving field frequency when the liberated a selective manner. Using brain imaging of sub- electrons recombine with their parent ions. jects playing the rock-paper-scissors game, they Selecting the output wavelength and boosting describe a set of six cortical areas that were its intensity, however, have been experimentally active during the observation and the execution challenging and have in large part been (2007) of the three types of hand configurations, where approached by trial-and-error. One severe prob- 10076

, selectivity was defined as a suppressed response lem is that the phase of emitted x-rays is out of

129 to a repeated configuration (for instance, play- kilter with the driving infrared laser field. Cohen

SOC. ing rock followed by rock). The same regions, in et al. propose to address this issue by using a addition to a host of others, were active during weak counter-propagating, quasi-continuous

CHEM. imitation trials (simultaneous observation and laser field to modulate the phase of the emitted AM.

J. execution) and also were active, albeit only harmonics. They show by simulation that tuning

AL., weakly, during instructed movement trials— the wavelength of the counter-propagating laser ET

Y these two kinds of tasks having been used in field, and thus modulating the refractive index most prior studies of human mirror neuron–like experienced by the driving field, could effi- PERR : responses. One intriguing question raised by ciently correct the phase mismatch. — ISO

CREDIT these findings is whether there might exist dis- Phys. Rev. Lett. 99, 53902 (2007).

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