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<jats:title>Shelling Turtles</jats:title> <jats:p> In almost all vertebrates, the shoulder girdle (scapula) lies outside the ribs. The turtle is unique in that the carapace, the dorsal part of the shell, which is formed from the ribs, encapsulates the scapula. To understand the origin of the turtle-specific body plan, <jats:bold> Nagashima <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="193" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173826">193</jats:related-article> ; see the cover; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="154" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1177446">Rieppel</jats:related-article> </jats:bold> ) compared chicken, mouse, and the Chinese soft shelled-turtle, <jats:italic>Pelodiscus sinensis</jats:italic> . Modern embryos were studied via whole-mount immunostaining, three-dimensional reconstructions, and with markers for early skeletal precursors and compared with previously reported fossils. Initially, embryos of the three animals share a common developmental pattern, one that is likely to have been shared with their last common ancestor. This pattern, however, is modified in the turtle by a specific folding of its body wall during embryogenesis. This folding preserves some of the connectivity between skeletal and muscle elements but also produces new connections. </jats:p>

<jats:title>Generation of Swine Flu</jats:title> <jats:p> As the newly emerged influenza virus starts its journey to infect the world's human population, the genetic secrets of the 2009 outbreak of swine influenza A(H1N1) are being revealed. In extensive phylogenetic analyses, <jats:bold> Garten <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="197" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176225">197</jats:related-article> , published online 22 May) confirm that of the eight elements of the virus, the basic components encoded by the hemagglutinin, nucleoprotein, and nonstructural genes originated in birds and transferred to pigs in 1918. Subsequently, these formed a triple reassortant with the RNA polymerase PB1 that transferred from birds in 1968 to humans and then to pigs in 1998, coupled with RNA polymerases PA and PB2 that transferred from birds to pigs in 1998. The neuraminidase and matrix protein genes that complete the virus came from birds and entered pigs in 1979. The analysis offers insights into drug susceptibility and virulence, as well as raising the possibility of hitherto unknown factors determining host specificity. A significant question is, what is the potential for the H1 component of the current seasonal flu vaccine to act as a booster? Apart from the need for ongoing sequencing to monitor for the emergence of new reassortants, future pig populations need to be closely monitored for emerging influenza viruses. </jats:p>

<jats:title>Starved to Life?</jats:title> <jats:p> Caloric restriction—reducing the calories ingested by around 30% of that of a normal, fit individual—leads to substantial increases in life span in experimental animals. In an extensive study of caloric restriction in primates, <jats:bold> Colman <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="201" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173635">201</jats:related-article> ) report that rhesus monkeys, which were subjected to caloric restriction as adults and followed for the last 20 years, show decreased mortality and delayed onset of age-related diseases when compared to normally fed control animals. If compliance with such a diet were not so difficult, many humans would be strongly tempted to enjoy the decreased incidence of brain degeneration, cardiovascular disease, diabetes, and cancer apparent in this population of monkeys. </jats:p>

<jats:title>Not Reston at All</jats:title> <jats:p> <jats:italic>Reston ebolavirus</jats:italic> is named, mistakenly perhaps, for Reston, Virginia, where it was discovered in the 1970s in imported macaques. After some alarm it was found not to be virulent in humans, uniquely among the ebola viruses, which are characteristically fatal causing a horrific spectrum of symptoms. Using a panviral detection assay, <jats:italic>Reston ebolavirus</jats:italic> has been rediscovered by <jats:bold> Barrette <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="204" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1172705">204</jats:related-article> ) in domesticated pigs in the Philippines in association with other viruses that cause respiratory illness. The strains involved are closely related to the original macaque strain and, given how little variance there is among the viruses, it appears that it is freely circulating between these species possibly, like several other zoonotic viruses, having a reservoir in bats. Serological assays indicated that farm workers have become infected, although no obvious symptoms of human disease have been reported. </jats:p>

<jats:title>Paradoxical Pain After Opioid Withdrawal</jats:title> <jats:p> Opioids are widely used both by pain patients and substance abusers. Withdrawal from opioids can be complicated by opioid-induced hyperalgesia, a paradoxical amplification of pain by opioids. <jats:bold> Drdla <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="207" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1171759">207</jats:related-article> ) detected a novel cellular opioid action that may help to explain this paradoxical pain: the induction of synaptic long-term potentiation (LTP) in pain pathways by opioids. In vitro and in vivo µ-opioid receptor agonist withdrawal induced robust LTP at synapses of nociceptive C fibers. This is in contrast to the presynaptic inhibition by opioids at these synapses. Because opioidergic LTP and acute synaptic depression are spatially and mechanistically distinct, it may be possible to treat opioid-induced hyperalgesia selectively without compromising opioid analgesia. </jats:p>

<jats:title>Neurogenesis and Spatial Memory</jats:title> <jats:p> The dentate gyrus of the hippocampus is one of two sites in the brain where new neurons are produced throughout life. Adult-born neurons integrate into the dentate gyrus circuitry and are thought to play a role in learning and memory. However, their contribution to hippocampal function remains unclear. <jats:bold> Clelland <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="210" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173215">210</jats:related-article> ) disrupted neurogenesis in mice and used two behavioral tasks to test for impairment in the formation of uncorrelated episodic memory representations. In one task, two arms were presented and the mice were rewarded for choosing the most recently visited arm in an earlier sequence; in the second task, animals were rewarded for choosing a certain location on a touch screen. Ablation of neurogenesis affected discrimination performance in both tasks but only when the arms or screen locations were close to one another. Neurogenesis is thus necessary for spatial pattern separation in the dentate gyrus. </jats:p>

<jats:title>Let Me Present to You</jats:title> <jats:p> The presentation of exogenous antigens by major histocompatibility (MHC) class I molecules is referred to as cross-presentation. Cross-presentation by dendritic cells plays a central role in the priming of cytolytic T lymphocyte responses to natural and vaccine antigens and also in the initiation of autoimmune diseases such as type 1 diabetes. A satisfactory cell biological model of cross-presentation is not available, which would be required to decipher the link, inherent in cross-presentation, between the secretory and the endocytic pathways. <jats:bold> Saveanu <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="213" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1172845">213</jats:related-article> , published online 4 June) identify an aminopeptidase, insulin-regulated aminopeptidase (IRAP), which interacts directly with MHC class I molecules. IRAP plays an exclusive and important role in MHC class I cross-presentation of receptor-targeted and phagocytosed antigens. In particular, a specific endosomal compartment, which carries IRAP as a unique marker, is implicated in cross-presentation of phagocytosed antigens. </jats:p>

<jats:title>Making the Choice</jats:title> <jats:p> The importance of cytokine signals for the generation of specific blood lineages is well known. However, whether cytokines only influence survival and proliferation of cells that have already committed to one lineage, or if they also influence the lineage choice is unclear. For decades, researchers disputed whether lineage choice of hematopoietic progenitor cells be influenced by cell extrinsic cytokines. Using bioimaging approaches that allow long-term observation of all cells in progenitor cell cultures, <jats:bold> Rieger <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="217" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1171461">217</jats:related-article> ) now demonstrate that certain cytokines can indeed instruct blood lineage choice. </jats:p>

<jats:p> The show includes swine as a host for <jats:italic>Reston ebolavirus</jats:italic> , the art and science of hominin reconstruction, nuclear-waste management in the U.S., and more. </jats:p>

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