Editors' Choice

Science  02 Jan 2015:
Vol. 347, Issue 6217, pp. 39
  1. Metabolism

    You are not just what, but when you eat

    1. L. Bryan Ray

    Avoiding nighttime eating may reduce the effects of an unhealthy diet

    PHOTO: © D. HURST/ALAMY

    Limiting food intake to an 8-hour window that corresponds to a time of high activity protects mice from obesity and metabolic disease caused by a diet high in fat. Chaix et al. extended such studies to examine what would happen in a regimen more adaptable to peoples' lifestyles. Promisingly, they found protective effects from fasting periods as short as 12 hours. Even better, mice showed improved metabolic fitness even when they took the weekends off. This was most likely because the changes in gene expression caused by restricting food during the week continued even when mice had full access to food on the weekends.

    Cell Metab. 20, 991 (2014).

  2. Biodeography

    Origins of the Southern Hemisphere flora

    1. Andrew M. Sugden

    Which plants of the Southern Hemisphere represent descendants of the ancient flora of Gondwana, the southerly part of the supercontinent Pangaea? Evidence from molecular clocks suggests that many plant lineages descended from a more recent common ancestor. Wilf and Escapa challenge this view by comparing molecular origin dates with fossil dates for groups of plants in Patagonia, such as cycads, that are incontrovertibly Gondwanan. They find that the molecular dates are artificially recent even for these ancient groups, and are a poor match for the reliable fossil dates. These findings suggest that biogeographers may have to temper reliance on molecular evidence for determining how flora dispersed.

    New Phytol. 10.1111/nph.13114 (2014).

  3. Antibiotic Resistance

    How bacteria develop resistance

    1. Guy Riddihough

    E. coli form filaments in microhabitats after antibiotic exposure

    PHOTO: BOS ET AL. PNAS (9 DECEMBER 2014) © 2014 NATIONAL ACADEMY OF SCIENCES

    Bacteria can develop resistance to antibiotics very rapidly, and understanding how might help to combat emerging antibiotic-resistant, disease-causing strains. Bos et al. studied the process in Escherichia coli exposed to low levels of the antibiotic ciprofloxacin and found that this caused the rod-shaped bacteria to transiently form filaments. Resistant cells then budded off from the tips of the antibiotic-sensitive filaments. Each filament contained multiple E. coli chromosomes, which because of the antibiotic stress, mutated at a greatly increased rate. Local relief of the antibiotic stress allowed cell division to recommence, generating the newly resistant cells.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1420702111 (2014).

  4. Surface Chemistry

    Assessing slow surface heating

    1. Phil Szuromi

    Calorimetry can provide essential information about surface reactions, but the small amount of heat released from a surface makes experiments challenging. Pyroelectric detection can measure the heat produced when molecules are adsorbed by a thin metal surface, but calibration is simple only for rapid reactions (ones over in ~30 ms). For slower reactions, it is more difficult to assess how the experimental setup distorts the signal. Wolcott and Campbell report a fast Fourier transform method that can deconvolute the measured signal for slower reactions. They use it to reproduce successfully how heat is generated when methyl iodide is adsorbed by a platinum surface, as determined with a more complex modeling method.

    Surf. Sci. 10.1016/j.susc.2014.11.005 (2014).

  5. Heart Disease

    Triglycerides, bedside to bench

    1. Paul A. Kiberstis

    Blood tests for heart disease risk measure cholesterol and fat molecules called triglycerides. Interest in triglycerides recently intensified with the discovery that people who carry mutations that disrupt the function of a glycoprotein called APOC3 (apolipoprotein C-III) have lower plasma triglyceride levels and a reduced risk of heart disease. Scientists thought APOC3 inhibited lipoprotein lipase, an enzyme catalyzing triglyceride breakdown. Gaudet et al. now reveal a more complicated mechanism. They found that three patients who had extremely high triglyceride levels because of a genetic deficiency in lipoprotein lipase nonetheless benefited from a drug that inhibits APOC3 synthesis. Clearly, APOC3 still has secrets to reveal.

    N. Engl. J. Med. 371, 2200 (2014).

  6. Ultrafast Optics

    Constraining the speed of tunneling

    1. Ian S. Osborne

    In contrast to expectation and experience in the classical world, a particle in the quantum world hitting a barrier can appear on the other side, having tunneled through the otherwise impassible obstruction. Debate about how quickly tunneling occurs has existed almost since the discovery of quantum mechanics. Now, Landsman et al. use ultrafast optical techniques to measure the amount of time it takes to ionize a helium atom. By following an electron on attosecond time scales as it passes through the energy barrier and leaves the bonds of its parent atom, the authors rule out certain theoretical possibilities, thereby providing a clearer picture of the tunneling process.

    Optica 1, 343 (2014); 10.1364/optica.1.000343 (2014).

  7. Planetary Accretion

    Tacking the mantle for planet formation

    1. Brent Grocholski

    Earth's distance from the Sun and its mass help constrain planetary accretion models. Rubie et al. use the initial composition of the mantle as another constraint for accretion simulations, by considering the chemical effects of metallic core formation. The simulations that produce a realistic Earth require that impacting planetessimals span a range of compositions, metalsilicate element equilibration occurs at progressively greater depths as the planet grows, and only a small amount of interaction takes place between the metal impactor core and the proto-mantle. Adding terrestrial mantle composition to accretion simulations provides insights into the most important factors for planetary formation.

    Icarus 10.1016/j.icarus.2014.10.015 (2014).

  8. Paleonthropology

    Human skeleton became lighter over time

    1. Lizzie Wade

    CT scans of hand bones from (clockwise from top left): chimp, Australopithecus, Neandertal, modern human.

    PHOTO: © AMNH/J. STEFFEY AND BRIAN RICHMOND

    Chimp bones are packed with microscopic structures known as spongy bone; modern human bones aren't, increasing risk of fractures and osteoporosis. Two studies propose an explanation for this change: Chirchir et al. found that skeletons from modern chimpanzees, Australopithecus africanus, Neandertals, and early Homo sapiens all had higher densities of spongy bone than modern humans, suggesting that our sedentary lifestyle is to blame. Ryan and Shaw also found lower spongy bone density in the hip joints of ancient farmers compared with hips from nonhuman primates and ancient hunter-gatherers, supporting the idea that a lack of rigorous exercise, not evolutionary pressure, is responsi ble for our weak bones.

    Proc. Natl. Acad. Sci., 10.1073/pnas.1411696112(2014), 10.1073/pnas.1418646112(2014).

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