Editors' Choice

Science  02 Sep 2016:
Vol. 353, Issue 6303, pp. 1001
  1. Gut Evolution

    Just passing through

    1. Sacha Vignieri

    Comb jellies have through-guts.

    PHOTO: ANDREY NEKRASOV/ALAMY STOCK PHOTO

    Our understanding of how guts evolved has included a long-held misconception. Despite reports dating back to the 1800s of a gut with more than one opening in metazoans (jellies and comb jellies), textbooks often present this group as having a sac-like gut with only one opening. Presnell et al. housed two species of comb jellies under laboratory conditions and captured high-resolution images of their feeding and excretion. Their detailed imaging revealed that comb jellies do not excrete through the mouth but rather through multiple anal pores, confirming that they do indeed possess a through-gut. These results suggest that our understanding of gut evolution may require a rethink.

    Curr. Biol. 10.1016/j.cub.2016.08.019 (2016).

  2. Celestial Mechanics

    The closest quasi-satellite to Earth

    1. Keith T. Smith

    A quasi-satellite orbits close to a planet, circling the Sun with the same orbital period, but it is not gravitationally bound to the planet. The fifth known quasi-satellite of Earth was discovered earlier this year: an asteroid with the snappy name (469219) 2016 HO3. In a recent study, de la Fuente Marcos and de la Fuente Marcos investigated its orbit with numerical simulations, showing that it will remain an Earth quasi-satellite for a few centuries. The asteroid, which is a few dozen meters across, stays between 38 and 100 times as far away from Earth as the Moon. This proximity and its low relative velocity make the object a tempting target for a visit by a sample-return mission—or even by astronauts.

    Mon. Not. R. Astron. Soc. 10.1093/mnras/stw1972 (2016).

  3. Water Quality

    Drinking water—and what else?

    1. Nicholas S. Wigginton

    Hydrological units with detectable PFASs

    CREDIT: SHU ET AL., ENVIRON. SCI. TECHNOL. LETT.

    Poly- and perfluoroalkyl substances (PFASs) are everywhere, and they are persistent. Exposure to these compounds has been linked to several adverse health effects, so identification of especially vulnerable populations is urgently needed. Hu et al. performed a spatial analysis of PFASs in U.S. drinking water. Higher reported PFAS levels were associated with manufacturing sites and military fire training facilities. In total, water supplies serving 16 million residents contained PFASs at or near minimum reporting levels. Because many U.S. residents rely on undersampled private wells or small public water supplies, exposure from drinking water remains unknown for nearly one-third of the U.S. population.

    Environ. Sci. Technol. Lett. 10.1021/acs.estlett.6b00260 (2016).

  4. Biophysics

    Mechanical coupling of heart cells

    1. L. Bryan Ray

    Myocytes in adult hearts control the heartbeat through electrical signaling, which propagates contractions to neighboring cells. However, Chiou et al. now report that the developing heart may use mechanical coupling between myocytes instead. The authors were able to explain the behavior of embryonic hearts with a model that considers myocytes as mechanically excitable cells that contract when exposed to a sufficient strain. Moreover, blocking ion exchange in hearts from chicken embryos did not prevent coordinated beating. Thus, the authors propose that the heart's first beats reveal a second mechanism for coordination that could be relevant to the development of stem cell–based therapies for damaged heart tissue.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1600362113 (2016).

  5. Metabolic Disease

    Pacemaker cells for insulin release

    1. Paula A. Kiberstis

    Pancreatic islets keep blood glucose levels in check. When glucose is too high, β cells within the islets release insulin, which promotes glucose removal from the blood. But Johnson et al. now find that not all β cells play an equal role in this process. Optogenetic and photo-pharmacological methods revealed that mouse islets contain a handful of specialized β cells or “hubs” with pacemaker properties. Representing 1 to 10% of total β cells, hubs functionally wire the islets to coordinate responsiveness to glucose. Exposure to a proinflammatory milieu, a condition associated with type 2 diabetes, caused hub failure and collapse of islet function. Hub failure may thus underlie defective insulin release in this disorder.

    A light micrograph of pancreatic islets, which house insulin-producing β cells

    CREDIT: ROBERT MARKUS/SCIENCE SOURCE

    Cell Metab. 10.1016/j.cmet.2016.06.020 (2016).

  6. Innovation Economics

    Measuring impacts of technology on growth

    1. Brad Wible

    Schumpter's concept of “creative destruction” reflects how technological innovation plays a key role in a dynamic economy. Questions remain, though, about how to measure the scientific versus the economic impact of a technology. Kogan et al. created a new measure based on identifying U.S. stock market responses to the announcement of new U.S. patents from 1926 to 2010. Compared with basic citation metrics, their measure is a better predictor of firms' innovation-driven growth. Firms that experience a one-standard-deviation increase in innovation output show 2 to 5% growth over the next 5 years. Firms that do not innovate in an industry that experiences a one-standard-deviation increase in innovation see their growth decrease by 2 to 5% over the same period.

    Quart. J. Econ., in press; http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2193068.

  7. Neuroscience

    Brain mapping by barcode

    1. Barbara R. Jasny

    Mapping how neurons functionally connect over long distances promises to offer important insights into brain function. Although optical and fluorescent labeling techniques have provided key information, Kebschull et al. report a new approach called MAPseq that capitalizes on the high throughput of nucleic acid sequencing. A viral vector is used to deliver multiple barcoded RNA fragments into individual neurons. The neurons then transport individual RNA barcodes into the axons that they extend, where they can be recovered, allowing for the mapping of thousands of single neuron projections. To test the system, the authors mapped the projections from individual neurons of the locus coeruleus, a region of the brain that provides noradrenaline to the neocortex.

    Neuron 10.1016/j.neuron.2016.07.036 (2016).