This Week in Science

Science  23 Jan 2015:
Vol. 347, Issue 6220, pp. 384
  1. Chronic Infection

    Chronic malaria shortens telomeres

    1. Caroline Ash

    Great reed warbler

    CREDITS: (TOP TO BOTTOM) PITCHER ET AL.; © BLICKWINKE /ALAMY

    Chronic infections are assumed to cause little damage to the host, but is this true? Migrant birds can pick up various species of malaria parasite while overwintering in the tropics. After initial acute malaria, migrant great reed warblers, which nest in Sweden and overwinter in Africa, are asymptomatically infected for life. Asghar et al. discovered that these cryptically infected birds laid fewer eggs and were less successful at rearing healthy offspring than uninfected birds. Furthermore, infected birds had significantly shorter telomeres (the protective caps on the ends of chromosomes) and produced chicks with shortened telomeres.

    Science, this issue p. 436

  2. Human Evolution

    Getting a grip

    1. Andrew M. Sugden

    The evolution of the hand—particularly the opposable thumb—was key to the success of early humans. Without a precise grip, involving forceful opposition of thumb with fingers, tool technology could not have emerged. Skinner et al. analyzed the internal bone structure of Pliocene Australopithecus hands, dated at 3.2 million years old. Internal bone structure reveals the patterns and directions of forces operating on the hand, providing clues to the kinds of activities performed. Modern human-like hand postures consistent with the habitual use of tools appeared about half a million years earlier than the first archaeological evidence of stone tools.

    Science, this issue p. 395

  3. T Cell Immunity

    For T cells, variety is the spice of life

    1. Kristen L. Mueller

    CD4+ helper T cells come in a variety of flavors. This allows them to respond in a manner that is tailored to the pathogen they encounter. Becattini et al. wondered whether multiple “flavors” of human CD4+ T cells respond to specific stimuli or if just one flavor dominates. To find out, they stimulated human memory CD4+ T cells with a fungus, a bacteria, or a vaccine antigen. Multiple helper cell subsets participated in each response. T cell receptor sequencing revealed that in some cases, T cells with the same specificity acquired different helper cell fates. Thus, there is more heterogeneity in human T cell responses than previously appreciated.

    Science, this issue p. 400

  4. Astrophysics

    A light on the origin of cosmic rays

    1. Margaret M. Moerchen

    There's a new lab for studying the origins of cosmic rays: our neighbor galaxy, the Large Magellanic Cloud. Astronomers are now making progress on this topic by examining the gamma rays that are produced when cosmic rays interact with gas or lower-energy photons. The H.E.S.S. Collaboration has detected three sources of gamma rays in a variety of forms in the galactic satellite to the Milky Way. The sources include the pulsar wind nebula of N 157B, the supernova remnant N 132D, and the superbubble 30 Dor C. Oddly, supernova 1987A was not detected.

    Science, this issue p. 406

  5. Planetary Science

    Melting silica in massive planets

    1. Brent Grocholski

    To simulate the extreme conditions inside large planets requires extreme experiments. Millot et al. used high-pressure shock waves almost twice that of the center of Earth to melt silica, one of the primary components of planetary interiors. This was possible only by shocking a very dense form of silica called stishovite. Determining the melting point of silica is vital for developing better computational models of the interior of planets several times the mass of Earth. The high-pressure liquid was electrically conductive, a property that may contribute to magnetic dynamos in very large terrestrial exoplanets.

    Science, this issue p. 418

  6. Materials Chemistry

    Soldering semiconductor nanoparticles

    1. Phil Szuromi

    The optical and electronic properties of semiconductor nanoparticles can be tuned through changes in their size and composition. However, poor contact between interfaces can degrade nanoparticle performance in devices. Dolzhnikov et al. report the synthesis of a gel-like “solder” for metal chalcogenide nanoparticles, such as cadmium selenide and lead telluride, by cross-linking molecular wires of these materials.

    Science, this issue p. 425

  7. Cancer Imaging

    Seeing nanostars

    1. Megan Frisk

    Nanostars can reveal microscopic tumors

    CREDIT: V. ALTOUNIAN/SCIENCE

    Microscopic tumors may be invisible to the naked eye, but they are no match for nanosized imaging agents that penetrate cancer tissue and signal the presence of disease. Harmsen et al. created a new generation of cancer-imaging agents called “nanostars”—star-shaped gold cores and Raman reporter molecules wrapped in silica—that can be visualized by Raman scattering. A new feature that puts the nanostars in resonance with the near-infrared window lets them outshine any previous nanoparticles. With these surface-enhanced resonance Raman scattering nanostars, the authors visualized microscopic lesions in animal models of pancreatic, breast, and prostate cancer, as well as sarcomas.

    Sci. Transl. Med. 7, 271ra7 (2015).

  8. Proteasomes

    A detailed look at proteasomes in situ

    1. Stella M. Hurtley

    The 26S proteasome is a protein machine that degrades intracellular proteins in the cytosol. The proteasome is critical for protein quality control and for the regulation of numerous cellular processes in eukaryotic cells. The structure of isolated proteasomes is well established, but how intact proteasomes look within the cell is less clear. Asano et al. used an improved approach to electron cryotomography to look at proteasomes in intact hippocampal neurons. Their analysis suggests that these cells only use about 20% of their proteasomes in an unstressed state, which leaves significant spare capacity to deal with proteotoxic stress.

    Science, this issue p. 439

  9. Cell Biology

    A binding partner for an orphan receptor

    1. Jason D. Berndt

    Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that is important during the development of the nervous system. ALK can also be aberrantly activated in certain types of cancers, including neuroblastoma and lung adenocarcinoma. Until now, ALK was an “orphan” receptor because its ligand was not known. Now, Murray et al. show that heparin binds directly to ALK and stimulates its activity (see the Focus by Lemke). An antibody that blocked the binding prevented heparin from activating this receptor tyrosine kinase, providing a potential avenue for therapeutic intervention.

    Sci. Signal. 8, ra6; see also fs2 (2015).

  10. Proteomics

    Protein expression across human tissues

    1. Valda Vinson

    Sequencing the human genome gave new insights into human biology and disease. However, the ultimate goal is to understand the dynamic expression of each of the approximately 20,000 protein-coding genes and the function of each protein. Uhlén et al. now present a map of protein expression across 32 human tissues. They not only measured expression at an RNA level, but also used antibody profiling to precisely localize the corresponding proteins. An interactive website allows exploration of expression patterns across the human body.

    Science, this issue 10.1126/science.1260419

  11. Sea Level Change

    Volume and shape combine to find a level

    1. H. Jesse Smith

    How can we understand the geological record of sea level change? Sea level varies on time scales from decades to millions of years. These changes have local, regional, and global components and are caused by a wide variety of earth processes. Cloetingh and Haq review how the views of stratigraphers (who interpret the record of marine sediments) and geodynamicists (who consider changes in the shape of Earth caused by lithospheric and mantle processes) have begun to complement each other and are moving toward a more coherent interpretation of the history of sea level. They focus on cyclic sea-level changes 0.5 to 3.0 million years in duration that occurred in the Cretaceous period, approximately 145 to 65 million years ago.

    Science, this issue 10.1126/science.1258375

  12. Drug Resistance

    Mechanisms propelling drug resistance

    1. Caroline Ash

    If it were to spread, resistance to the drug artemisinin would seriously derail the recent gains of global malaria control programs (see the Perspective by Sibley). Mutations in a region called the K13-propeller are predictive for artemisinin resistance in Southeast Asia. Mok et al. looked at the patterns of gene expression in parasites isolated from more than 1000 patients sampled in Africa, Bangladesh, and the Mekong region. A range of mutations that alter protein repair pathways and the timing of the parasite's developmental cycle were only found in parasites from the Mekong region. Straimer et al. genetically engineered the K13 region of parasites obtained from recent clinical isolates. Mutations in this region were indeed responsible for the resistance phenotypes.

    Science, this issue p. 431, p. 428; see also p. 373

  13. Mars Atmosphere

    Of water and methane on Mars

    1. Margaret M. Moerchen

    The Curiosity rover has been collecting data for the past 2 years, since its delivery to Mars (see the Perspective by Zahnle). Many studies now suggest that many millions of years ago, Mars was warmer and wetter than it is today. But those conditions required an atmosphere that seems to have vanished. Using the Curiosity rover, Mahaffy et al. measured the ratio of deuterium to hydrogen in clays that were formed 3.0 to 3.7 billion years ago. Hydrogen escapes more readily than deuterium, so this ratio offers a snapshot measure of the ancient atmosphere that can help constrain when and how it disappeared. Most methane on Earth has a biological origin, so planetary scientists have keenly pursued its detection in the martian atmosphere as well. Now, Webster et al. have precisely confirmed the presence of methane in the martian atmosphere with the instruments aboard the Curiosity rover at Gale crater.

    Science, this issue p. 412, p. 415; see also p. 370

  14. Magnetic Materials

    Tilting toward two properties

    1. Phil Szuromi

    Opposing electronic and symmetry constraints can make it difficult to combine some pairs of material properties in a single crystalline material. Magnetization and electrical polarization are such a pair, but their combination could be useful for applications such as magnetoelectric information storage. Pitcher et al. now show that careful design of chemical substitutions in a layered perovskite are both electrically polar and weakly ferromagnetic at temperatures up to 330 K.

    Science, this issue p. 420