Catálogo de publicaciones - revistas

<jats:title> Revealing <jats:italic>Volvox</jats:italic> </jats:title> <jats:p> Female and male gametes of the green alga, <jats:italic>Volvox</jats:italic> , significantly differ in size. Those of <jats:italic>Chlamydomonas</jats:italic> , another green algae from a lineage that separated from <jats:italic>Volvox</jats:italic> some 200 million years ago, are the same size. We know sex in <jats:italic>Chlamydomonas</jats:italic> is governed by a sex-determining locus called <jats:italic>MT</jats:italic> . In a detailed comparison of the <jats:italic>MT</jats:italic> loci of <jats:italic>Volvox</jats:italic> and <jats:italic>Chlamydomonas</jats:italic> , <jats:bold> Ferris <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="328" xlink:href="10.1126/science.1186222">351</jats:related-article> ) found that although <jats:italic>MT</jats:italic> has retained some similarity in gene order, its composition has greatly changed between the two species. In <jats:italic>Volvox</jats:italic> , new genes have been coopted into this locus and show sex-specific expression. </jats:p>

<jats:title>Battle of the Sperm</jats:title> <jats:p> In insects, sperm from multiple matings are stored and retained, and are thought to compete for ova within a female's reproductive tract. <jats:bold> Manier <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="354" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1187096">354</jats:related-article> , published online 18 March) visualized sperm from fruit flies transgenically tagged with green or red fluorescent protein within the reproductive tracts of female flies. Sperm showed more mobility within the female storage organs than expected, with those from the most recent copulation displacing sperm from previous males; however, sperm viability remained consistent over long-term storage and each male's sperm was equally competitive in fertilizing the female's eggs. </jats:p>

<jats:title>Swine Flu Neutralized</jats:title> <jats:p> The 2009 H1N1 flu virus had an unusually low infection rate in elderly people. An antibody isolated from survivors of the 1918 flu pandemic was recently shown to cross-neutralize 2009 H1N1 viruses. <jats:bold> Xu <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="357" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1186430">357</jats:related-article> , published online 25 March) report crystal structures of the virus envelope protein, hemagglutinin (HA) from 2009 H1N1 and of 1918 H1 HA in complex with a neutralizing antibody that cross-reacts with both pandemic viruses. These studies reveal an epitope that is conserved in the pandemic viruses, but divergent in other known H1 HAs, from the 1930s to the present. This antigenic similarity explains the age-related immunity to the 2009 H1N1 influenza. </jats:p>

<jats:title>Simultaneously Serving Two Goals</jats:title> <jats:p> What are the neuronal mechanisms underlying dual-task performance? <jats:bold>Charron and Koechlin</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="360" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183614">360</jats:related-article> ) used functional magnetic resonance imaging to study this question under conditions of varying incentive for two tasks. Subjects performed letter-matching tasks either sequentially or concurrently. Reward value for performance of each of the two tasks was manipulated orthogonally. Under conditions of single-task (sequential) performance, they observed bilateral brain activity in the dorsal anterior cingulate and the premotor cortex that correlated with the reward value of the current task. However, under dual-task conditions, activity in these regions on the left corresponded to primary-task reward performance, while on the right, activity corresponded to secondary-task performance. Under dual-task conditions, both reward and stimulus-response representations are thus segregated according to hemisphere. </jats:p>

<jats:title>Orphan No More</jats:title> <jats:p> The glutamate receptor δ2 (GluD2), another member of the ionotropic glutamate receptor family, has long been considered to be an orphan receptor because there are no known endogenous ligands. Nevertheless, GluD2 is essential for the normal development of cerebellar circuits. Using immunocytochemistry, binding assays, electrophysiology, and freeze-fracture electron microscopy, <jats:bold> Matsuda <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="363" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1185152">363</jats:related-article> ) found that Cbln1, a soluble protein secreted from cerebellar granule cells, binds to the extracellular N terminus of GluD2 on Purkinje cells. Binding has two independent consequences: First, it leads to presynaptic differentiation and second, it causes postsynaptic clustering of several important synapse-specific molecules. Both events are needed for synapse formation between granule cells and Purkinje cells. </jats:p>

<jats:title>Domain Swaps to Phenotype Shifts</jats:title> <jats:p> For natural selection there must be mechanisms that create phenotypic diversity, presumably from relatively simple molecular changes in an organism. <jats:bold> Peisajovich <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="368" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1182376">368</jats:related-article> ) tested the extent to which changes in phenotype can occur by systematic swapping of protein domains in the components of the biochemical signaling pathway that controls mating in yeast. Such changes decreased or increased responsiveness to yeast mating pheromone, and some translated into changes in mating efficiency. The authors propose that shuffling of modular protein domains may be an important source of phenotypic diversity in evolution and may also be a useful strategy for the engineering of biological systems. </jats:p>

<jats:title>Yin-Yang T Cell Signaling</jats:title> <jats:p> Immune responses are kept in check by CD4 <jats:sup>+</jats:sup> regulatory T cells (T <jats:sub>reg</jats:sub> ) that suppress other immune cells, including CD4 <jats:sup>+</jats:sup> effector T cells (T <jats:sub>eff</jats:sub> ). T <jats:sub>reg</jats:sub> and T <jats:sub>eff</jats:sub> cells have many signaling components in common, yet triggering through their T cell receptors (TCRs) leads to very different outcomes. <jats:bold> Zanin-Zhorov <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="372" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1186068">372</jats:related-article> , published online 25 March) compared the recruitment of signaling molecules to the immunological synapse after TCR triggering in T <jats:sub>reg</jats:sub> and T <jats:sub>eff</jats:sub> cells. Although T <jats:sub>reg</jats:sub> cells do form synapses, signaling molecules that promote T <jats:sub>eff</jats:sub> activation, such as protein kinase C-θ (PKC-θ), were not recruited. Inhibition or depletion of PKC-θ in T <jats:sub>reg</jats:sub> cells led to suppressive activity against T <jats:sub>eff</jats:sub> cells, whereas costimulation enhanced PKC-θ recruitment and less suppression. Together, this suggests that PKC-θ is inflammatory in both T <jats:sub>reg</jats:sub> and T <jats:sub>eff</jats:sub> cells; however, by excluding it from the synapse, T <jats:sub>reg</jats:sub> cells are able to maintain suppression in the face of TCR signaling. </jats:p>

<jats:p>New, less toxic fluorescent proteins and tags, and strategies for delivering them, are allowing researchers to watch processes within cells never before observed. Industry and academia are now working to not only detect these processes, but also localize and quantify them.</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 the brain pursues concurrent goals, testing and treatment for rare genetic diseases, telescopes in rural Senegal, and more.</jats:p>