Catálogo de publicaciones - revistas

<jats:title>Lunar Water</jats:title> <jats:p> The Moon has been thought to be primarily anhydrous, although there has been some evidence for accumulated ice in permanently shadowed craters near its poles (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="531" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181471">Lucey</jats:related-article> </jats:bold> , published online 24 September). By analyzing recent infrared mapping by Chandrayaan-1 and Deep Impact, and reexamining Cassini data obtained during its early flyby of the Moon, <jats:bold> Pieters <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="568" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178658">568</jats:related-article> , published online 24 September), <jats:bold> Sunshine <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="565" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1179788">565</jats:related-article> , published online 24 September), and <jats:bold> Clark <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="562" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178105">562</jats:related-article> , published online 24 September) reveal a noticeable absorption signal for H <jats:sub>2</jats:sub> O and OH across much of the surface. Some variability in water abundance is seen over the course of the lunar day. The data imply that solar wind is depositing and/or somehow forming water and OH in minerals near the lunar surface, and that this trapped water is dynamic. </jats:p>

<jats:title>A Smooth(ened) Path to Drug Resistance</jats:title> <jats:p> The Hedgehog (Hh) signaling pathway has emerged as a key contributor to the growth of medulloblastoma, an aggressive brain tumor. GDC-0449, a drug that ramps down this signaling pathway by binding to the Hh pathway component Smoothened, was recently shown to induce rapid and dramatic tumor regression in a patient with metastatic medulloblastoma, but the tumor eventually developed resistance to the drug. <jats:bold> Yauch <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="572" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1179386">572</jats:related-article> , published online 3 September) show that resistance arose because the tumor acquired a mutation in Smoothened that disrupts binding of the drug. Identification of this resistance mechanism may facilitate the design of next-generation drugs for this type of cancer. </jats:p>

<jats:title>Cdc20-APC in Synapse Formation</jats:title> <jats:p> The E3 ubiquitin ligase Cdc20-anaphase promoting complex (Cdc20-APC) has important roles in the control of the cell division cycle. <jats:bold> Yang <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="575" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1177087">575</jats:related-article> ) now show that Cdc20-APC also appears to be required for proper formation of synapses by developing neurons in the rat brain. When Cdc20-APC was depleted from cultured neurons or in the brains of developing rat pups, synapse formation was inhibited. The brain-enriched transcription factor NeuroD2 was shown to be a possible target of Cdc20-APC–stimulated degradation. NeuroD2 may act by promoting synthesis of Complexin II, a protein that regulates synaptic vesicle fusion. </jats:p>

<jats:title>Life in Dead Zones</jats:title> <jats:p> Oxygen minimum zones, or oceanic “dead zones,” are expanding. Marine dead zone expansion and intensification results in amplification of biological nitrogen and greenhouse gas production, with implications for marine fisheries' productivity and for climate balance. Little is known about the microbial communities mediating the underlying biogeochemistry of dead zones. <jats:bold> Walsh <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="578" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1175309">578</jats:related-article> ) present metagenomic analyses of a ubiquitous, abundant, and uncultivated bacterium in oceanic dead zones. Similar bacteria, related to chemoautotrophic gill symbionts of deep-sea clams and mussels, play a role in sulfide detoxification in African shelf waters. Reconstruction of the carbon and energy metabolism of this enigmatic lineage revealed a metabolic repertoire mediating carbon sequestration, sulfur-detoxification, and biological nitrogen loss in oxygen-deficient oceanic waters. </jats:p>

<jats:title>Croaking Frogs</jats:title> <jats:p> The global amphibian decline has been attributed, among other causes, to an amphibian skin disease chytridiomycosis caused by the fungus <jats:italic>Batrachochytrium dendrobatidis</jats:italic> . However, how this pathogen causes mortality has been unclear. <jats:bold> Voyles <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="582" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1176765">582</jats:related-article> ) show that this superficial skin infection may lead to cardiac failure owing to changes caused by lowered ion transport through the skin and consequent electrolyte reduction in the blood. </jats:p>

<jats:title>Viral Link to Chronic Fatigue</jats:title> <jats:p> Chronic fatigue syndrome (CFS) is a complex and debilitating disorder that is often linked to immune system dysfunction but whose cause(s) remain mysterious. <jats:bold> Lombardi <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="585" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1179052">585</jats:related-article> , published online 8 October; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="530" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181349">Coffin and Stoye</jats:related-article> </jats:bold> ) now present a tantalizing new lead. In blood samples from 101 patients with well-documented CFS, over two-thirds (68) contained DNA from a recently described human gammaretrovirus, xenotropic murine leukemia virus–related virus (XMRV), which possesses sequence similarity to a murine leukemia virus. Cell culture assays confirmed that XMRV derived from CFS patient plasma and from T and B lymphocytes was infectious. Although the correlation with CFS is striking, whether the virus plays a causal role in the disorder remains to be determined. Interestingly, nearly 4% of the 218 healthy donors tested were positive for XMRV, which suggests that this virus—whose pathogenic potential is unknown—may be present in a significant proportion of the general population. </jats:p>

<jats:title>Dissecting Megaenzyme Mechanisms</jats:title> <jats:p> Filamentous fungi contain a class of multidomain enzymes, the highly-reducing iterative polyketide synthases (HR-IPKSs), which produce important natural products such as the cholesterol-lowering drug lovastatin. To produce their complex products, these megasynthases use multiple catalytic domains repeatedly in different combinations, but mechanistic details remain unclear. <jats:bold> Ma <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="589" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1175602">589</jats:related-article> ) now report in vitro reconstitution of the complete catalytic function of lovastatin nonaketide synthase (LovB), the megasynthase that works together with a partner enzyme LovC to complete nearly 40 chemical steps required to construct the core of lovastatin. Analyses of the dependency of enzyme function on cofactors and on the partner enzyme elucidate the programming rules for this system. </jats:p>

<jats:title>Toward Neuronal Regeneration</jats:title> <jats:p> Neurons in the central nervous system that are severed or crushed do not regenerate well. Part of the problem derives from the glial scars left behind after such damage. The scar tissue contains sulfated proteoglycans that seem to inhibit axon regeneration. <jats:bold> Shen <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="592" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178310">592</jats:related-article> , published online 15 October) have now identified a protein tyrosine phosphatase (PTP) in mouse neuronal membranes that functions as a receptor for the proteoglycans. Neurons that lacked this particular PTP showed improved regeneration. Regeneration remained incomplete, presumably due to other inhibitory factors in the way of complete axon regeneration. </jats:p>

<jats:title>Observing Unrevealed Preferences</jats:title> <jats:p> Ideally, it would be possible to design a system of incentives for the production and allocation of public goods with the following properties: (i) it would be budget-balanced; (ii) people would participate willingly because they would not be made worse off by doing so; (iii) it would be easy for each participant to find his or her optimal strategy; and (iv) the equilibrium solution would yield the optimal production of the public good. Sadly, this set of conditions cannot be satisfied simultaneously because it requires that self-interested individuals reveal voluntarily and truthfully how much they value the public good. <jats:bold> Krajbich <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="596" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1177302">596</jats:related-article> , published online 10 September) ask whether a neuroimaging measurement can be used to circumvent this reliance on observed behavior by decoding individual valuations. A decoding accuracy of 55% would be sufficient, and, in a laboratory experiment, an optimal provision of public goods was indeed achieved. </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>