Catálogo de publicaciones - revistas

<jats:title>Natural Resistance</jats:title> <jats:p> Avermectins are the most widely used class of anthelmintic drugs, both as pesticides and as treatments for nematode-borne diseases, with the evolution of resistance presenting a major global health and agricultural problem. <jats:bold> Ghosh <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="574" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214318">574</jats:related-article> ; see the Perspective by <jats:bold>Wolstenholme</jats:bold> ) observed resistance to avermectin in the model nematode <jats:italic>Caenorhabditis elegans</jats:italic> that varies among isolates. This resistance is caused by a naturally occurring four–amino acid deletion in the ligand-binding domain of a glutamate-gated chloride channel. This variant also conferred resistance to the avermectin-producing ubiquitous soil bacterium, <jats:italic>Streptomyces zitilis</jats:italic> . Many nematodes spend at least part of their life cycle in soil, which may explain avermectin resistance among nematode species. </jats:p>

<jats:title>Girl Power</jats:title> <jats:p> The potential of affirmative action policies to reduce overall outcomes because of lower individual performance has been discussed widely and at length. But do quotas or preferential treatment of applicants alter the pool of candidates? <jats:bold>Balafoutas and Sutter</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="579" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1211180">579</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6068" page="544" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1218000">Villeval</jats:related-article> </jats:bold> ) used an existing laboratory-based task to assess the change in composition of winning candidates and the overall outcome as a function of three affirmative action policies. Policies designed to encourage more women to enter a competitive environment served to recruit enough high-performing individuals to ensure that the efficiency in performing the task was preserved. <jats:bold> Beaman <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="335" xlink:href="10.1126/science.1212382">582</jats:related-article> , published online 12 January) examined the effects of a constitutionally mandated reservation of village-council and council-leader positions for women in West Bengal after two election cycles (1998 and 2003). The program appeared to narrow the gender gap in aspirations of parents for their children and of children for themselves; in addition, teenage girls spent more time in school and less on household chores. Beliefs and attitudes changed only after the second set of elections—that is, after a longer exposure to female role models—complementing the more rapid policy changes instituted by women council leaders after the first round of elections. </jats:p>

<jats:title>Girl Power</jats:title> <jats:p> The potential of affirmative action policies to reduce overall outcomes because of lower individual performance has been discussed widely and at length. But do quotas or preferential treatment of applicants alter the pool of candidates? <jats:bold>Balafoutas and Sutter</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="579" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1211180">579</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6068" page="544" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1218000">Villeval</jats:related-article> </jats:bold> ) used an existing laboratory-based task to assess the change in composition of winning candidates and the overall outcome as a function of three affirmative action policies. Policies designed to encourage more women to enter a competitive environment served to recruit enough high-performing individuals to ensure that the efficiency in performing the task was preserved. <jats:bold> Beaman <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="335" xlink:href="10.1126/science.1212382">582</jats:related-article> , published online 12 January) examined the effects of a constitutionally mandated reservation of village-council and council-leader positions for women in West Bengal after two election cycles (1998 and 2003). The program appeared to narrow the gender gap in aspirations of parents for their children and of children for themselves; in addition, teenage girls spent more time in school and less on household chores. Beliefs and attitudes changed only after the second set of elections—that is, after a longer exposure to female role models—complementing the more rapid policy changes instituted by women council leaders after the first round of elections. </jats:p>

<jats:title>Mystery of an Unextreme Microbe</jats:title> <jats:p> Metagenomics has given us glimpses into the huge diversity of microorganisms that are the engines of Earth's elemental cycling. These kinds of surveys can supply a good idea of the dominant organisms in ecosystems, but, because the majority of environmental microbes are difficult to culture and the most abundant organisms swamp metagenomes, it is difficult to discern the functional significance of other contributors. <jats:bold> Iverson <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="587" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1212665">587</jats:related-article> ) sampled the Puget Sound and developed methods to reconstruct individual genomes from metagenomes, which allowed closure of a genome from the enigmatic marine group II <jats:italic>Euryarchaeota</jats:italic> . This Archaean is evidently motile, shows signs of extensive gene-swapping with bacteria, and offers some hints to the origin of proteorhodopsin—a molecule that some marine bacteria use to harvest energy from sunlight. </jats:p>

<jats:title>Lineage Identity</jats:title> <jats:p> Segregation of endoderm and mesoderm lineages is a fundamental event in early embryogenesis. Using sea urchin embryos, <jats:bold> Sethi <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="590" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1212867">590</jats:related-article> ) found that Notch and canonical Wnt pathways crosstalk progressively partitions the endomesoderm to discrete endoderm and mesoderm fates. This three-step signaling exchange demonstrates how the timing of signaling crosstalk is regulated in vivo through temporally and spatially staggered genetic circuits that intersect only at specific developmental stages. </jats:p>

<jats:title>Heat or Acid?</jats:title> <jats:p> The question of how tropical coral reefs will respond to increasing atmospheric greenhouse gas concentrations and concomitant climate change is widely debated. Model predictions and laboratory experiments suggest that decreasing carbonate saturation and decreasing pH may reduce calcification in carbonate-depositing organisms, including corals, yet field data are sparse, and recent declines in coral growth rates have been variously attributed to thermal stress or ocean acidification. <jats:bold> Cooper <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="593" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214570">593</jats:related-article> ) demonstrate that there has been no large-scale decline in calcification rates of massive <jats:italic>Porites</jats:italic> on coral reefs along the Indian Ocean coast of Western Australia. Instead, coral growth has increased significantly in the past 110 years, particularly at high latitudes. Thus, coral calcification appears to increase as ocean waters warm, but—at excessive temperatures—coral bleaching and reduced ocean carbonate saturation may lead to growth declines as observed on the Great Barrier Reef. </jats:p>

<jats:title>Immune Sentinels</jats:title> <jats:p> A classic paradigm in immunology holds that the immune response occurs in two waves: Rapidly responding cells of the innate immune system help to contain the invading pathogen and alert lymphocytes. These cells of the adaptive immune system then help to clear the infection and go on to form long-lasting memory. However, some specialized populations of lymphocytes can also respond quickly to an infection and carry out functions that overlap with the innate immune system. Now, <jats:bold> Rauch <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="597" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215173">597</jats:related-article> , published online 12 January) describe one such cell type—innate response activator (IRA) B cells. IRA B cells recognize bacterial liposaccharide through Toll-like receptor 4 and, in response, produce the cytokine GM-CSF, which activates other innate immune cells. Deletion of IRA B cells in mice impaired their ability to clear a bacterial infection and promoted septic shock. </jats:p>

<jats:title>Nature or Drug Abuse?</jats:title> <jats:p> There are significant structural changes in striatal and prefrontal brain regions of stimulant drugdependent individuals. However, it is not clear if these brain abnormalities predate drug-taking, rendering individuals vulnerable for the development of dependence, or if these changes are the effect of many years of drug use. <jats:bold> Ersche <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="601" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214463">601</jats:related-article> ; see the Perpective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6068" page="546" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1218170"> <jats:bold>Volkow and Baler</jats:bold> </jats:related-article> ) investigated brain abnormalities in both drug-dependent individuals and in their biological siblings who have never taken drugs of abuse and compared them with matched healthy volunteers. The brain abnormalities in the sibling pairs were associated with significant impairments in the regulation of behavior; an ability known to be compromised in drug dependence. Because these neural changes were observed in family members who do not take drugs, the changes are likely to represent neurological markers of vulnerability to addiction rather than consequences of chronic drug abuse. </jats:p>

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

<jats:p>The show includes how corals respond to climate change, inherited factors for drug addiction, 2011 Visualization Challenge winners, and more.</jats:p>