This Week in Science

Science  08 Feb 2019:
Vol. 363, Issue 6427, pp. 594
  1. Textiles

    A cloth that adapts to the heat

    1. Brent Grocholski

    Infrared gating fabric knitted from biomorph fibers

    CREDIT: FAYE LEVINE, UNIVERSITY OF MARYLAND

    Textiles trap infrared radiation, which helps keep us warm in cold weather. Of course, in hot weather, this is less desirable. Zhang et al. constructed an infrared-adaptive textile composed of polymer fibers coated with carbon nanotubes. The yarn itself expanded and collapsed based on heat and humidity, which changed the spacing of the fibers. Wider fiber spacing allowed the textile to breathe but also altered the infrared emissivity of the textile. This allowed for better heat exchange under hot and wet conditions. The self-adjusting emissivity of the textile could help toward wearable thermal-management attire.

    Science, this issue p. 619

  2. Biomedicine

    Delivering fragile drugs to the gut

    1. Marc S. Lavine

    Oral delivery is the simplest and least invasive way to deliver many pharmaceuticals, but many drugs and medications, including insulin, cannot survive passage through the stomach or the gastrointestinal tract. Abramson et al. developed an ingestible delivery vehicle that could self-reorient from any starting position so as to attach to the gastric wall. Encapsulation of a spring in a sugar casing allowed for triggered actuation for the delivery of biomolecules. The approach successfully provided active insulin delivery in pigs.

    Science, this issue p. 611

  3. Chemistry

    Shaking up reaction-site selectivity

    1. Jake Yeston

    It seems intuitive that putting vibrational energy into a chemical bond ought to promote selective cleavage of that bond. In fact, the relation of vibrational excitation to reactivity has generally proven subtler and more complex. Thomas et al. studied how strong coupling of specific vibrational modes to an optical cavity might influence a molecule with two competing reactive sites. The molecule had two silicon centers that could react with fluoride by respective cleavage of a Si–C or Si–O bond. Exciting the vibrations at either center slowed down the overall reaction while favoring otherwise disfavored Si–O cleavage.

    Science, this issue p. 615

  4. Type 1 Diabetes

    Prediabetic microbiome

    1. Anand Balasubramani

    Studies in humans and mice have identified associations between intestinal microbiome composition and development of autoimmune diseases, including type 1 diabetes (T1D). How these microbes influence immune responses in distant tissues is unknown. Paun et al. examined whether serum antibody responses to intestinal commensal bacteria were associated with T1D status in pediatric cohorts. Antibody responses against specific commensals before T1D diagnosis allowed individuals with islet autoantibodies to be distinguished from healthy controls in a human leukocyte antigen haplotype–dependent manner. The results link immune responses to gut microbes with later T1D development.

    Sci. Immunol. 4, eaau8125 (2019).

  5. Cognitive Neuroscience

    The dynamics of human consciousness

    1. Philippa J. Benson

    Inferring the presence or absence of human consciousness is a problem when treating patients with severe brain injury. Demertzi et al. recorded functional magnetic resonance imaging data in 159 patients to assess the alterations in brain connectivity caused by severe brain injury. Dynamic patterns of brain activity in patients in a vegetative state could be distinguished from patients in conscious or minimally conscious states. Furthermore, patterns associated with conscious states sporadically appeared in unresponsive patients, suggesting a potential path toward noninvasive restoration of consciousness.

    Sci. Adv. 10.1126/sciadv.aat7603 (2019).

  6. Epidemiology

    Zika dynamics in South America

    1. Caroline Ash

    The infection dynamics of Zika virus (ZIKV) are difficult to characterize. Many ZIKV infections are asymptomatic, and the clinical presentation of ZIKV is nonspecific. Rodriguez-Barraquer et al. took advantage of a long-term health study under way in Salvador, Brazil, the epicenter of the recent outbreak in the Americas. They used multiple serological assays, from before and after the emergence of ZIKV in October 2015, to distinguish ZIKV immune responses from those against Dengue virus (DENV). About 73% of the population was attacked by ZIKV. The presence of preexisting antibodies to DENV was associated with less risk of ZIKV infection and fewer symptoms.

    Science, this issue p. 607

  7. Solar Cells

    Advantages of adding just enough alkalis

    1. Phil Szuromi

    For organic-inorganic hybrid solar cells, addition of cesium or rubidium cations can improve power conversion efficiency. Correa-Baena et al. used nanoscale x-ray fluorescence imaging to show that the addition of metal cations at low concentrations homogenized the distribution of bromide and iodide anions and also increased charge-carrier lifetimes. However, at high concentrations, aggregation and cluster formation led to increased charge recombination.

    Science, this issue p. 627

  8. Cancer

    Fueling lymph node metastases

    1. Paula A. Kiberstis

    Metastatic cells can migrate from a primary tumor to distant organs through two routes: They can enter the bloodstream directly, or they can enter a lymph node adjacent to the primary tumor. Little is known about the biological mechanisms that allow tumor cells to survive and grow within lymph nodes. Studying mouse models, Lee et al. found that tumor cells adapt to the lymph node microenvironment by shifting their metabolism toward fatty acid oxidation. This occurs through activation of a signaling pathway driven by the yes-associated protein (YAP) transcription factor. Importantly, inhibition of fatty acid oxidation or YAP signaling suppressed lymph node metastasis in the mice.

    Science, this issue p. 644

  9. Climate Responses

    Timing matters

    1. Sacha Vignieri

    Kalahari meerkat populations respond to rains differently depending on the season.

    PHOTO: PETE OXFORD/MINDEN PICTURES

    How a species responds to rapid climate change is complicated. Paniw et al. used long-term data on the Kalahari meerkat, an arid specialist, to explore how predicted changes might affect population persistence over time. Warming and rainfall changes in one part of the year had a negative impact on survival and persistence, whereas similar changes during another part of the year had the opposite effect. Understanding such variability will be essential as we attempt to understand the broader influence of climate change.

    Science, this issue p. 631

  10. Greenhouse Gases

    The case for endangerment

    1. H. Jesse Smith

    In 2009, the U.S. Environmental Protection Agency (EPA) established the so-called “Endangerment Finding.” This defined a suite of six long-lived greenhouse gases as “air pollution.” Such air pollution was anticipated to represent a danger to the health and welfare of current and future generations. Thus, the EPA has the authority to regulate these gases under the rules of the U.S. Clean Air Act. Duffy et al. provide a comprehensive review of the scientific evidence gathered in the years since then. These findings further support and strengthen the basis of the Endangerment Finding. Thus, a compelling case has been made even more compelling with an enormous body of additional data.

    Science, this issue p. eaat5982

  11. Photosynthesis

    All the hues, even the blues

    1. Michael A. Funk

    Photosynthetic organisms must balance maximizing productive light absorption and protecting themselves from too much light, which causes damage. Both tasks require pigments—chlorophylls and carotenoids—which absorb light energy and either transfer it to photosystems or disperse it as heat. Wang et al. determined the structure of a fucoxanthin chlorophyll a/c–binding protein (FCP) from a diatom. The structure reveals the arrangement of the specialized photosynthetic pigments in this light-harvesting protein. Fucoxanthin and chlorophyll c absorb the blue-green light that penetrates to deeper water and is not absorbed well by chlorophylls a or b. FCPs are related to the light-harvesting complexes of plants but have more binding sites for carotenoids and fewer for chlorophylls, which may help transfer and disperse light energy.

    Science, this issue p. eaav0365

  12. Climate

    Reflections on cloud effects

    1. H. Jesse Smith

    How much impact does the abundance of cloud condensation nuclei (CCN) aerosols above the oceans have on global temperatures? Rosenfeld et al. analyzed how CCN affect the properties of marine stratocumulus clouds, which reflect much of the solar radiation received by Earth back to space (see the Perspective by Sato and Suzuki). The CCN abundance explained most of the variability in the radiative cooling. Thus, the magnitude of radiative forcing provided by these clouds is much more sensitive to the presence of CCN than current models indicate, which suggests the existence of other compensating warming effects.

    Science, this issue p. eaav0566; see also p. 580

  13. Drug Metabolism

    Off-target drug metabolism

    1. Caroline Ash

    Anything humans swallow is exposed to the foraging and transforming activities of the gut microbiota. This applies to therapeutic drugs as well as food components and can be a major source of interpersonal variation in drug efficacy and toxicity. Zimmermann et al. found that individual drug responses depend on the genetics of an individual's microbiota. They explored the metabolism of nucleoside drugs (which are used as antivirals and antidepressants) in mice inoculated with a variety of mutant microbiota. They then modeled the pharmacokinetics in different body compartments and identified the host and microbe contributions. In some individuals, up to 70% of drug transformation can be ascribed to microbial metabolism.

    Science, this issue p. eaat9931

  14. Inorganic Chemistry

    Helping copper glow

    1. Jake Yeston

    Copper's abundance makes the metal an appealing candidate for luminescence applications. However, many copper complexes tend to decay nonradiatively after photoexcitation. A recently described exception involves a two-coordinate complex that sandwiches the metal between an amide ligand and a carbene ligand. Hamze et al. thoroughly explored this motif and measured a nearly perfect luminescence efficiency. They used this property to produce a prototype blue organic light-emitting diode. The photodynamics appeared largely ligand-centered, with the excited state attributed to copper-facilitated charge transfer from amide to carbene.

    Science, this issue p. 601

  15. Neuroscience

    Abstract concepts in the primate brain

    1. Peter Stern

    Do primates have neurons that encode the conceptual similarity between spaces that differ by their appearance but correspond to the same mental schema? Baraduc et al. recorded from monkey hippocampal neurons while the animals explored both a familiar environment and a novel virtual environment that shared the same general structure as the familiar environment but displayed never-before-seen landmarks. About one-third of hippocampal cells showed significantly correlated firing for both familiar and novel landscapes. These correlations hinged on space or task elements, rather than on immediate visual information. The functional features of these cells are analogous to human concept cells, which represent the meaning of a specific stimulus rather than its apparent visual properties.

    Science, this issue p. 635

  16. Lasers

    Stability through symmetry

    1. Ian S. Osborne

    A common route to get more light out of a laser system is to couple multiple lasers to form an array. However, instabilities owing to cross-talk and interference between different modes of individual cavities is generally detrimental to performance and could ultimately be damaging to the laser cavities. Hokmabadi et al. applied notions derived from supersymmetry, a theory developed in high-energy physics to describe the make-up and properties of particles, to design a stable array of semiconductor lasers (see the Perspective by Kottos). Based on symmetry arguments, the method is scalable and could provide a practical platform to design and develop complex photonic systems.

    Science, this issue p. 623; see also p. 586

  17. Neuroimmunology

    ChAT-ty T cells fight viral infection

    1. Seth Thomas Scanlon

    The neurotransmitter acetylcholine (ACh) is involved in processes such as muscle contraction, neuron communication, and vasodilation. Along with neurons, a population of immunological T cells and B cells express the enzyme choline acetyltransferase (ChAT), which catalyzes the rate-limiting step of ACh production. However, the role of immune cell–derived ACh is unclear. Cox et al. report that the cytokine interleukin-21 (IL-21) induces ChAT expression in CD4+ and CD8+ T cells during lymphocytic choriomeningitis virus infection (see the Perspective by Hickman). T cell–specific deletion of ChAT strongly impaired vasodilation and trafficking of antiviral T cells into infected tissues, which undermined the effective control of a chronic viral infection. Thus, IL-21 plays a critical role during chronic infection. Furthermore, the findings reveal a cholinergic mechanism that can regulate immune cell migration into tissues.

    Science, this issue p. 639; see also p. 585

  18. HIV Vaccines

    HIV glycans and nanoparticle vaccines

    1. Priscilla N. Kelly

    Synthetic nanoparticles have attracted widespread interest for vaccine design, but how the immune system generates a response to multimeric nanoparticles remains unclear. Tokatlian et al. studied immunity generated by HIV envelope antigens arranged in either multivalent nanoparticle forms or as single monomers (see the Perspective by Wilson). The nanoparticle HIV immunogens triggered greater antibody responses compared with the monomeric forms. Glycosylation appeared key for enhanced humoral immunity because it spurred binding to mannose-binding lectin, complement fixation, and antigen trafficking to follicular dendritic cells. The findings highlight how the innate immune system recognizes HIV nanoparticles and the importance of antigen glycosylation in the design of next-generation nano-based vaccines.

    Science, this issue p. 649; see also p. 584

  19. Environment

    Too much for some, too little for others

    1. Julia Fahrenkamp-Uppenbrink

    In developed nations and emerging economies, excess nitrogen from agriculture and fossil fuel combustion is having negative effects on biological diversity, climate, and human health. But in other parts of the world, nitrogen-poor soils threaten food security. In a Perspective, Stevens discusses the effects of these major perturbations to the nitrogen cycle on plants and ecosystems and stresses the urgent need to address the problems of both excess and lack of nitrogen through locally appropriate nitrogen management approaches.

    Science, this issue p. 578

  20. Metabolism

    Changing views in cardiometabolic disease

    1. Gemma Alderton

    Branched-chain amino acids (BCAAs) are a subset of essential amino acids that are acquired from the diet. In a Perspective, White and Newgard discuss the evidence linking increased circulating BCAAs with obesity-associated conditions, including type 2 diabetes and cardiovascular diseases. The authors discuss how BCAAs can provide biomarkers of cardiometabolic health and also the mechanisms by which BCAAs promote phenotypes of cardiometabolic disease.

    Science, this issue p. 582

  21. Cancer

    The secret(ing) life of the tumor stroma

    1. Wei Wong

    Hypoxic solid tumors develop a dysfunctional vasculature that prevents efficient chemotherapeutic penetration. Kugeratski et al. analyzed the proteome and secretome of cancer-associated fibroblasts, a prominent cell type in the tumor stroma. Hypoxia increased the levels of a protein called hypoxia-induced angiogenesis regulator (HIAR) in cancer-associated fibroblasts. HIAR promoted the release of the pro-angiogenic factor VEGF from these cells and induced VEGF-dependent signaling in endothelial cells. Thus, HIAR could be targeted by antiangiogenic therapy, which has been unsuccessful when directly targeting VEGF signaling.

    Sci. Signal. 12, eaan8247 (2019).

  22. Pediatrics

    Teasing apart tonsillitis

    1. Lindsey Pujanandez

    Although exposure to group A Streptococcus is prevalent, only some children develop recurrent tonsillitis, which can lead to tonsillectomy. To discern why some children are susceptible and others resistant, Dan et al. examined tonsil samples from two cohorts. Children with a history of recurrent tonsillitis had tonsils with smaller germinal centers and had reduced antibacterial antibodies compared with children with nonrecurrent tonsillitis. Moreover, the T follicular helper cells from those subjects could be cytotoxic toward B cells. Class II human leukocyte antigen analysis also identified protective and risk alleles. Thus, altered adaptive immune responses to group A Streptococcus may differentiate those at risk of recurrent infection.

    Sci. Transl. Med. 11, eaau3776 (2019).