Editors' Choice

Science  12 Oct 2018:
Vol. 362, Issue 6411, pp. 195
  1. Microbiology

    Plague, one lymph node at a time

    1. Stella M. Hurtley

    The bacterium that causes plague, Yersinia pestis, in false color

    CREDIT: EYE OF SCIENCE/SCIENCE SOURCE

    Swollen lymph nodes, or buboes, are the hallmark of plague, which is caused by the pathogen Yersinia pestis. Buboes result from a massive influx of immune cells into draining lymph nodes (DLNs). Recently, Y. pestis was shown to disseminate by carriage within immune cells migrating from one DLN to the next. Arifuzzaman et al. investigated how Y. pestis exploits the features of buboes to promote pathogenesis. Infiltration of infected monocytic cells into tightly packed buboes coincided with cytolysis triggered by Yersinia outer protein J, resulting in the release of intracellular bacteria and extensive infection of neighboring cells. The dying monocytic cells released sphingosine 1-phosphate (S1P), which attracted yet more cells, and up-regulated expression of the S1P receptor promoted the exit of newly infected monocytic cells from buboes. Preventing necrotic cell death protected mice from otherwise lethal infection. Thus, Y. pestis commandeers cell-death and immune-cell trafficking programs to convert the host's DLNs into specialized hubs for dissemination.

    JCI Insight 3, e122188 (2018).

  2. Heart Disease

    Rethinking aspirin use

    1. Priscilla N. Kelly

    A daily aspirin may not be so benign.

    CREDIT: TAYLOR JORJORIAN/ALAMY STOCK PHOTO

    Low-dose aspirin is a popular daily prevention strategy for individuals with a history of heart attack or stroke, owing to aspirin's ability to reduce the clotting action of blood, which is often compromised in cardiovascular patients. Many healthy people with no known cardiovascular problems have since adopted a daily aspirin regimen to safeguard against future heart attack or stroke. Yet a new study by McNeil et al. suggests that an aspirin per day might not be beneficial for healthy individuals 65 years of age or older. The researchers recruited more than 19,000 healthy participants and found that daily low-dose aspirin did not stave off heart attack, stroke, or major hemorrhage. In fact, daily aspirin use correlated with an increased risk of major bleeding to the gut and brain of otherwise healthy older individuals.

    N. Engl. J. Med. 10.1056/NEJMoa1805819 (2018).

  3. Spintronics

    Making graphene useful for spintronics

    1. Jelena Stajic

    Thanks to graphene's weak spin-orbit coupling, spin currents flow through it unimpeded. However, this also means that the spin currents are hard to manipulate—a drawback for using graphene in spintronics. Two groups now show that this needn't be the case. Leutenantsmeyer et al. and Xu et al. studied spin transport in heterostructures of bilayer graphene with hexagonal boron nitride. In the presence of an electric field, the spin lifetimes in the directions parallel to the heterostructural layers and perpendicular to them were markedly different. The long and anisotropic lifetimes may lead to useful spintronics applications.

    Phys. Rev. Lett. 121, 127702, 127703 (2018).

  4. Carbon Cycle

    Deciphering atmospheric CO2 change

    1. H. Jesse Smith

    Many different processes and carbon sources can affect the concentration of atmospheric carbon dioxide (CO2), so to understand past, present, and likely future variability of CO2, those mechanisms and reservoirs must be identified. Bauska et al. present a record of the stable carbon isotopic composition of CO2 over the interval between 50,000 and 35,000 years ago, which reveals that the primary source of atmospheric carbon during millennial-duration events probably was organic carbon residing in the deep ocean, whereas more abrupt events occurring over centennial time scales were associated both with hydrological change in the tropics and rapid increases in Northern Hemisphere temperature.

    Geophys. Res. Lett. 45, 7731 (2018).

  5. Protein Design

    Learning from diminutive ligand design

    1. Michael A. Funk

    One strategy for understanding the origin of life is proposing simple replacements for the complex biomolecules that have developed through billions of years of evolution. Ferredoxins are small proteins that contain simple, cubic clusters of iron and sulfur atoms and act as mobile electron carriers in cells. Kim et al. designed a 12-residue peptide with alternating D and L amino acids that can replicate the placement of cysteine ligands found in many natural ferredoxins. After reconstitution with iron and sulfur, the peptides bound a single iron-sulfur cluster. The resulting minimal, artificial ferredoxin exhibited a redox potential compatible with some biological processes.

    J. Am. Chem. Soc. 140, 11210 (2018).

  6. Microbiota

    The long reach of the gut

    1. Seth Thomas Scanlon

    How does the gut microbiota shape the composition and function of distal host organs, despite being segregated in the gut? Uchimura et al. used stable isotope tracing to show that microbial metabolites penetrate host tissues and fluids to influence host immunological and metabolic signaling networks. However, metabolite impact is modulated by a high rate of urinary excretion of microbial products. Furthermore, secretory immunoglobulin A antibodies limit bacterial dwell times in the small intestine, which also ameliorates host exposure to microbial metabolites. The joint effect contributes to resolving gut function as both nutrient gateway and barrier.

    Immunity 49, 545 (2018).

  7. Neuroscience

    Memory recirculation and integration

    1. Peter Stern

    Hippocampal pattern separation minimizes interference between experiences and is critical to episodic memory (a person's collection of memories of an event). However, the hippocampus is also critical for the integration of information across episodes. These two roles are apparently in conflict. Using high-resolution brain scanning, Koster et al. investigated information flow through the layers of the entorhinal cortex that are the inputs and outputs of the hippocampus. Rather than the output of the system being the end product of hippocampal processing, it is recirculated as a new input. This result indicates big-loop recurrence, predicted by computational theories, which states that episodic memory and the integration of information across experiences need not conflict.

    Neuron 99, 1342 (2018).

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