Editors' Choice

Science  11 Nov 2016:
Vol. 354, Issue 6313, pp. 717
  1. Circadian Rhythms

    Airplane air

    1. L. Bryan Ray

    The low oxygen concentration in airplane air may help fight jet lag.

    PHOTO: FLIGHTLEVEL80/ISTOCKPHOTO.COM

    Can flying help alleviate jet lag? Studies of the biochemical mechanisms that synchronize biological clocks throughout the body show that the low-oxygen environment of airplanes may actually help you adjust to your new time zone. Adamovich et al. observed daily cycles in the concentration of oxygen in blood and tissues of mice kept on a normal light-dark cycle. These variations were sufficient to alter the abundance of the transcription factor HIF1α (hypoxia-inducible factor 1α). In cultured cells, changes in oxygen concentration could entrain the circadian clock only if HIF1α was present. When animals were subjected to a 6-hour change in the light cycle (like traveling eastward on a jet), animals kept in a low concentration of oxygen adapted more quickly.

    Cell Metab. 10.1016/j.cmet.2016.09.014 (2016).

  2. Host Defense

    How macrophages build a wall

    1. Kristen L. Mueller

    Granulomas are a defining feature of infection with Mycobacterium tuberculosis, the causative agent of tuberculosis. Macrophages are the primary component of these cell structures, which are thought to protect the host by walling off the pathogen. Cronan et al. studied granulomas in optically transparent zebrafish infected with M. marinum to directly visualize how they form. They observed that macrophages in granulomas undergo epithelial reprogramming, up-regulating many molecules and adhesion structures characteristic of epithelial cells. Disrupting this process by blocking E-cadherin, a protein that drives the epithelialization process, led to granulomas with a disorganized appearance. Unexpectedly, however, this reduced the fishes' bacterial burden, suggesting that granulomas may not always be host-protective.

    Immunity 45, 861 (2016).

  3. Conservation Genomics

    Essential immigrants

    1. Laura M. Zahn

    Connectivity is essential for sustaining endangered Florida scrub jays.

    PHOTO: NATURE PHOTOGRAPHERS LTD./ALAMY STOCK PHOTO

    As more and more species near extinction, conservation efforts will need to understand the genetic structure and consequences of declining population size. Chen et al. document the negative effects of reduced population connectivity over multiple generations in the Florida scrub jay. Their 19-year data set demonstrates that, for the Florida scrub jay, immigration between small satellite populations into larger, more stable groups is an essential component for maintaining genetic diversity. The reduction in the number of individuals, and hence in the size of satellite populations and immigration, has resulted in increased levels of inbreeding and reduced fitness in this species, demonstrating the impact of habitat fragmentation.

    Curr. Biol. 10.1016/j.cub.2016.08.062 (2016).

  4. Nanomaterials

    A nano dagger to the heart

    1. Guy Riddihough

    Nanomaterials consist of nanometer-scale molecules or particles, which can have unusual mechanical, electrical, or optical properties. Industrial-scale fabrication of such material requires an assessment of their potential toxicity. Zhu et al. use molecular modeling and intracellular imaging to show that long (high aspect ratio), stiff carbon nanotubes can damage lysosome vesicle membranes. Persistent contact with the tip of the tube results in loss of membrane lipids and lysosome membrane instability, potentially activating the cell death pathway.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1605030113 (2016).

  5. Aquatic Microbiology

    Lake bacteria make methane from P

    1. Nicholas S. Wigginton

    Freshwater lakes are a major contributor of methane to the atmosphere—more so than the world's oceans combined. Some anaerobic microorganisms produce methane in sediments or deep anoxic water, but methane can also be produced biologically in oxic surface water. In the upper layers of methane-supersaturated Lake Matano, Indonesia, Yao et al. find that bacterial methane production is linked to phosphorus availability. Heterotrophic bacteria break down methylphosphonate as a phosphorus source, releasing methane in the process. Methane production decreases in culture when phosphate is added. Models for methane emissions from lakes should therefore incorporate nutrient availability in oxic water columns as another potential factor to help improve global methane predictions.

    Appl. Environ. Microbiol. 10.1128/AEM.02399-16 (2016).

  6. Adaptive Optics

    Becoming clearer step by step

    1. Ian S. Osborne

    When a camera or sensor is in an environment of strong illumination or high background noise, scattering from the object, or glare, can be so high that the object can be obscured. Daniel et al. used an adaptive optics technique to manipulate the wavefront of a coherent light source illuminating an object, in this case a toy mannequin, and showed that the direction of scattered light from the object can be controlled. As the wavefront of the illuminating light is iteratively manipulated through a spatial light modulator, the glare is reduced and the image becomes clearer. The technique is general and could be applied to different scenarios such as sensing, microscopy, and other demanding imaging tasks.

    Optica 3, 1104 (2016).

  7. Geophysics

    Metallic melt for the mantle

    1. Brent Grocholski

    Ultralow velocity zones (ULVZs) are distinct and dense patches at the very base of Earth's rocky mantle. Liu et al. suggest that iron carbide may be a vital component of ULVZs on the basis of measurements of iron carbide melting temperatures. Iron carbides could form as iron and carbon exsolve from slabs subducting into the mantle. The high temperature near the base of the mantle could then lead to iron carbide melting and ponding in the ULVZ regions. If this hypothesis is correct, ULVZs are an unrecognized and important carbon reservoir within Earth.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1519540113 (2016).

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