Catálogo de publicaciones - revistas

<jats:title>Hexing Complement</jats:title> <jats:p> Complement activation is an immediate and potent immune defense mechanism, but how immunoglobulin G (IgG) antibodies activate complement at the molecular level is poorly understood. Using high-resolution crystallography, <jats:bold> Diebolder <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6176" page="1260" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1248943">1260</jats:related-article> ) show that human IgGs form hexameric structures by interacting with neighboring IgG molecules, and the complex then activates complement. Thus, IgG molecules and the complement system can coexist in the blood because complement activation will only be triggered after IgG senses a surface antigen and starts to aggregate. </jats:p>

<jats:title>Quick, Quick, Slow</jats:title> <jats:p> The slow muscles of postural stability and the fast muscles of running and jumping are driven by motor neurons that are differentiated by fast and slow biophysical properties. By retrograde labeling of mouse and chick muscle fibers, <jats:bold> Müller <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6176" page="1264" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1246448">1264</jats:related-article> ) characterized the developmental distinctions between fast and slow motor neurons. A transmembrane protein, when over- or underexpressed, was discovered to drive specification of the motor neurons and a downstream effector specified some, but not all, of the biophysical attributes. </jats:p>

<jats:p>Toxicity assays based on embryonic and adult stem cells could soon replace unreliable cellular and animal testing, helping toxicologists detect which drugs might be dangerous long before they reach the market.</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>On this week's show: avoiding big-data traps and a roundup of shorts from our daily news site.</jats:p>

<jats:title>Oscillate to Synchronize</jats:title> <jats:p> In the social amoeba <jats:italic>Dictyostelium discoideum</jats:italic> , periodic waves of the small-molecule cyclic adenosine monophosphate (cAMP) guide chemotactic migration and cell differentiation. <jats:bold> Cai <jats:italic>et al.</jats:italic> </jats:bold> ( <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.1249531">10.1126/science.1249531</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="6177" page="1326" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1252247">Wollman</jats:related-article> </jats:bold> ) found that a GATA family transcription factor shuttles between the nucleus and the cytoplasm of the amoeba in response to oscillatory cAMP signals acting through G protein–coupled receptors. Each oscillation generates a transient burst of gene activation, such that gene expression is linked to the number rather than the level of stimulus, which then brings about transcriptional synchrony in populations of cells. </jats:p>

<jats:title>HIV Virulence</jats:title> <jats:p> A major focus of research on HIV is on host responses to infection—understandably, because the virus targets the immune system and because of the interest in vaccine development. In reviewing what little research has been done on viral virulence determinants, <jats:bold> Fraser <jats:italic>et al.</jats:italic> </jats:bold> ( <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.1243727">10.1126/science.1243727</jats:related-article> ) present evolutionary explanations for some of the poorly understood phenomena that mark HIV infection, including long-term survivorship, latency, rapid within-host evolution, and inheritability of between-host virulence. </jats:p>