Catálogo de publicaciones - revistas

<jats:title>Who Influences Who?</jats:title> <jats:p> A goal in social science is how to assess people's influence over one. <jats:bold>Aral and Walker</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="337" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1215842">337</jats:related-article> , published online 21 June) describe a generalized method for identifying influential and susceptible members of social networks based on large-scale in vivo randomized experimentation. The method was used to estimate peer effects in consumer demand for a commercial Facebook application in a representative sample of 12 million Facebook users. Older users were more influential than younger users, women were more influential over men than men over women, and married individuals were the least susceptible to influence in the decision to adopt the product studied. </jats:p>

<jats:title>Sex Chromosome Evolution</jats:title> <jats:p> The fly genus <jats:italic>Drosophilia</jats:italic> has repeatedly generated evolutionarily new sex chromosomes. To understand the changes shaping the X and Y chromosomes, <jats:bold>Zhou and Bachtrog</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="341" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225385">341</jats:related-article> ), sequenced the genome of <jats:italic>D. miranda</jats:italic> , which formed neo-X and neo-Y chromosomes approximately 1 million years ago. The data illuminate the ongoing conflict between selection for male and female function on the sex chromosomes and show that Y chromosome evolution is characterized both by a loss of gene function and selection for male-specific adaptations in genes beneficial to male functions. </jats:p>

<jats:title>Redox Status Incites Gametogenesis</jats:title> <jats:p> Germ cells differ from somatic cells in their chromosomal complement, being haploid rather than diploid. In animals, the germ cells are generally produced by a separate lineage set aside early in development. Plants, however, lack a reserved germ cell lineage. <jats:bold>Kelliher and Walbot</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="345" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220080">345</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="6092" page="301" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1224362">Whipple</jats:related-article> </jats:bold> ) now show that, in maize, the key signal for germ cell production is hypoxia, which triggers differentiation of anther germ cells from a generalized field of progenitors. The specializing germ cells then induce differentiation of supportive somatic cells. </jats:p>

<jats:title>Diversity of Interactions</jats:title> <jats:p> The diversity in interactions that occur between different species—such as predation, competition, and mutualism—is a fundamental feature of natural ecological systems. Using a theoretical model, <jats:bold>Mougi and Kondoh</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="349" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220529">349</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="6092" page="306" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225049">Boyd</jats:related-article> </jats:bold> ) show that the diversity of ecological relationship helps a biological community to be stable and thus may be key to the maintenance of biodiversity itself. </jats:p>

<jats:title>Lysosomal Amino Acid Transporter</jats:title> <jats:p> Cystinosis is characterized by intralysosomal accumulation of free cystine, which results in age-dependent problems in the kidney, muscle, retina, and central nervous system. The disease-causing gene encodes a lysosomal cystine transporter. The most effective therapeutic agent for cystinosis, cysteamine, depletes lysosomal free cystine by converting it to cysteine and the mixed disulfide cysteine-cysteamine, which can then be exported from lysosomes as a lysine analog through a putative lysine/cationic amino acid transporter. Using an unbiased genetic screen for <jats:italic>Caenorhabditis elegans</jats:italic> mutants with increased accumulation of apoptotic cells or autophagosomes, <jats:bold> Liu <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="351" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220281">351</jats:related-article> ) now reveal the molecular identity of a lysosomal lysine/arginine transporter that plays a role in maintaining lysosome function and amino acid homeostasis and that can explain how cysteamine alleviates a lysosomal storage disease. </jats:p>

<jats:title>Never Let Me Go</jats:title> <jats:p> Kinetochores are the structures within chromosomes that interact with the microtubules of the mitotic spindle during mitosis. By measuring the deformation of individual kinetochores in live mammalian cells, <jats:bold> Dumont <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="355" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1221886">355</jats:related-article> , published online 21 June) asked, how do kinetochores harness the free energy of microtubule depolymerization without losing grip of microtubules? Kinetochores contacted microtubules using two distinct mechanical interfaces: an active, force-generating interface near the microtubule tip, and a passive, frictional interface at least 20 nanometers away along the microtubule lattice. The separate active and passive interfaces allowed for intermittent force generation and persistent microtubule attachment—both required for accurate chromosome segregation. </jats:p>

<jats:title>Born to Stay Together</jats:title> <jats:p> For as many neurons as there are in the brain, there are many more astrocytes. These backstage workers perform a variety of functions, such as sustaining the blood-brain barrier and providing a stabilized environment for neurons. Diversity of astrocyte function is reflected in different molecular expression profiles. <jats:bold> Tsai <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="358" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1222381">358</jats:related-article> , published online 28 June) selectively labeled astrocytes that originated from different domains of the mouse spinal cord and found that not all astrocytes are created equal: Neighborhoods of astrocytes were defined by shared birthplaces. </jats:p>

<jats:title>Size Matters Less</jats:title> <jats:p> X-ray crystallography is a central research tool for uncovering the structures of proteins and other macromolecules. However, its applicability typically requires growth of large crystals, in part because a sufficient number of molecules must be present in the lattice for the sample to withstand x-ray—induced damage. <jats:bold> Boutet <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="362" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1217737">362</jats:related-article> , published online 31 May) now demonstrate that the intense x-ray pulses emitted by a free-electron laser source can yield data in few enough exposures to uncover the high-resolution structure of microcrystals. </jats:p>

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

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