Editors' Choice

Science  27 Jul 2018:
Vol. 361, Issue 6400, pp. 376
  1. Marine Pollution

    Use the beach

    1. Sacha Vignieri

    Beach-filtered intake systems could decrease the impact of power plant draws on aquatic ecosystems.

    PHOTO: MICHELLE MCMAHON/GETTY IMAGES

    Coastal power stations regularly draw water from the ocean as a cooling source, and this water is later returned to the marine environment. The water and any marine organisms that happen to be drawn in with it are exposed to high temperatures and other mechanical processes that generally reduce survival and affect populations near outflows. Jebakumar et al. looked at the impacts of this process on an Indian creek system influenced by power station cooling draws. They found reductions in abundance, decreases in survival, and changes in community structure across marine taxa influenced by the draws. Further, regulations to reduce the temperature of the water before it is returned, though necessary, increased the impact owing to the need to draw larger amounts of water into the plant for cooler outflows. The authors suggest that a relatively simple solution would be to widely institute subsurface intake systems, or “beach wells,” which naturally filter out marine organisms before intake and improve water quality, across tropical regions.

    Mar. Pol. Bull. 10.1016/j.marpolbul.2018.05.053 (2018).

  2. Education

    Taking anxiety out of active learning

    1. Melissa McCartney

    As STEM (science, technology, engineering, and mathematics) education becomes more centered on active learning practices, what happens to students' anxiety levels? Specifically, what aspects of evaluative active learning practices cause student anxiety to increase or decrease? After measuring students' baseline anxiety levels, Cooper et al. conducted semi-structured interviews to explore how students' anxiety levels were altered in an active learning classroom. Results show that the way that the active learning activity is implemented and the extent to which students perceive the activity to be beneficial influence its effect on their anxiety. The authors encourage instructors to consider student anxiety when implementing active learning.

    Int. J. STEM Educ. 10.1186/s40594-018-0123-6 (2018).

  3. Molecular Biology

    tRNA lost in translation

    1. Steve Mao

    Transfer RNAs (tRNAs), the adaptor molecules between messenger RNAs (mRNAs) and ribosomes during translation, are subjected to various types of chemical modifications, one of which is N7--methylguanosine (m7G). Mutations in the human m7G methyltransferase complex lead to developmental disorders such as microcephalic primordial dwarfism and Down syndrome. Lin et al. mapped the m7G tRNA methylome at single-nucleotide resolution and demonstrated its essential role in mouse embryonic stem cells. Depletion of members of the m7G methyltransferase complex resulted in increased ribosome pausing on, and inefficient translation of, mRNAs involved in the cell cycle and brain development, thereby disrupting differentiation to neural lineages. This study is an important step toward a fuller understanding of how defects in tRNA methylation cause neurodevelopmental disorders.

    Mol. Cell 10.1016/j.molcel.2018.06.001 (2018).

  4. Biomaterials

    Using biology to remove cells

    1. Marc S. Lavine

    Decellularization is used to obtain extracellular matrix (ECM) scaffolds for use in tissue engineering and regenerative medicine, but the methods for stripping out the cells can be chemically harsh and cause damage to the ECM components or their overall architecture. Cornelison et al. treated peripheral nerve tissue with camptothecin, which triggers apoptosis, causing cell death and degradation. The fragments and any remaining cytotoxic compounds were removed with only a mild wash using saline solution or deoxyribonuclease, leaving the nerve scaffold intact without substantive loss of collagen or glycosaminoglycan content. In vivo testing in rats found no immunogenic response and a lower histological score than in isograft negative controls after 4 weeks.

    Acta Biomat. 10.1016/j.actbio.2018.07.009 (2018).

  5. Neurodegeneration

    Alzheimer's disease in a dish?

    1. Stella M. Hurtley

    Alzheimer's disease is characterized by extracellular deposits of β-amyloid (Aβ) and intracellular aggregation of hyperphosphorylated tau in the brain. These lead to the hyperactivation of glial cells in the brain and neuronal loss. However, it has been difficult to serially link this series of pathological events. Park et al. developed a three-dimensional triculture system composed of human-derived neurons, astrocytes, and microglia. The model demonstrated hallmark features of Alzheimer's disease and Aβ aggregation, phospho-tau accumulation, and neuroinflammation. The ability to see ongoing microglia recruitment in the microfluidic platform and consequent neurotoxicity bodes well for the utility of this type of approach as a platform for dissecting pathomechanisms and preliminary testing of potential therapeutics.

    Nat. Neurosci. 21, 941 (2018).

  6. Cancer Immunology

    Neutrophils take a different tack

    1. Seth Thomas Scanlon

    Antibody-dependent cellular cytotoxicity is an important process by which cancer cells can be targeted and killed. Immune cells, such as T and NK (natural killer) cells, express Fc receptors that recognize cancer cells coated with antibodies. They then release cytotoxic granules that result in apoptosis. Matlung et al. show that neutrophils induce antibody-dependent cellular cytotoxicity via a completely different mechanism. This process entails trogocytosis-induced lysis of tumor cells, which the authors term “trogoptosis.” They find that neutrophils endocytose cytoplasmic fragments of target cells, which induces cancer cell necroptosis. In addition to direct killing, this mechanism may be important for the release of cancer neoantigens and damage-associated molecular patterns, which further activate and direct the immune response to tumors.

    Cell Rep. 23, 3946 (2018).

  7. Martian Geology

    Ghost dunes spotted on Mars

    1. Keith T. Smith

    Voids in martian surface strata show where sand dunes once existed.

    CREDIT: M. D. DAY AND D. C. CATLING, J. GEOPHYS. RES. PLANETS 10.1029/2018JE005613 (2018)

    Sand dunes are imposing physical structures, but few signs of them are preserved in the geological record because their grains do not stick together and are moved by wind. Preservation can occur if a dune field is partially buried by lava or mud, which then forms a layer of hard rock. Subsequent erosion of the sand leaves holes where the dunes once were. These features, termed ghost dunes, were only recently identified on Earth. Day and Catling used images from the Mars Reconnaissance Orbiter spacecraft to identify two locations on Mars where there are hundreds of ghost dunes. Revealing long-vanished dunes will enable studies of Mars' ancient winds.

    J. Geophys. Res. Planets 10.1029/2018JE005613 (2018).