This Week in Science

Science  13 Jun 2014:
Vol. 344, Issue 6189, pp. 1238
  1. Paleoceanography

    The when of Mediterranean water outflow

    1. H. Jesse Smith

    Integrated Ocean Drilling Program expedition in the Gibraltar gateway.

    PHOTO: JOHN BECK/IODP/TAMU

    The trickle of water that began to flow from the Mediterranean Sea into the Atlantic Ocean after the opening of the Strait of Gibraltar turned into a veritable flood by the end of the Pliocene 2 to 3 million years ago. It then began to influence large-scale ocean circulation in earnest. Hernández-Molina et al. describe marine sediment cores collected by an ocean drilling expedition (see the Perspective by Filippelli). The results reveal a detailed history of the timing of Mediterranean outflow water activity and show how the addition of that warm saline water to the cooler less-salty waters of the Atlantic was related to climate changes, deep ocean circulation, and plate tectonics.

    Science, this issue p. 1244; see also p. 1228

  2. Neuronal Repair

    Improving stroke recovery by timing treatment

    1. Pamela J. Hines

    Patients recovering from strokes often fight a long uphill battle, with mixed results. Studying the effect of physical training on regeneration from damaged nerves in a model of stroke in rats, Wahl et al. show that timing matters. First, the researchers gave the rats a stroke, which damaged their ability to reach for food pellets with their forelimbs. The researchers then gave them physical training and treated them with an antibody to encourage neural regeneration. The rats improved more when the researchers waited until after the antibody treatment to start the training. Damaged circuits, it seems, need a little time to regrow before being called into action.

    Science, this issue p. 1250

  3. Dinosaur Physiology

    Not too fast, not too slow, somewhere in between

    1. Sacha Vignieri

    In early depictions, dinosaurs lumbered slowly, dragging their tails. More recently, we have imagined them lifting their tails and running. The question boils down to whether dinosaurs had energetic systems closer to those of rapidly metabolizing mammals and birds, or to those of slower reptiles that do not internally regulate their body temperature. However, determining the metabolic rate of extinct organisms is no easy task. Grady et al. analyzed a huge data set on growth rate in both extinct and living species, using a method that considers body temperature and body size. Dinosaur metabolism seems to have been neither fast nor slow, but somewhere in the middle—so, dinosaurs did not fully regulate their internal temperature but they were also not entirely at the whim of the environment; neither slow goliaths nor supercharged reptiles.

    Science, this issue p. 1268

  4. Nonhuman Genetics

    Male chimps evolve faster with age

    1. Laura M. Zahn

    A family of western chimpanzees.

    PHOTO: © PHILIP MCALLISTER / ALAMY

    Chimpanzees are evolving faster than humans. Venn et al. examined the genetics of three generations of western chimpanzees and found that overall the mutation rate is similar between humans and chimpanzees. However, while male humans had three to four times the mutation rate of females, in chimpanzees the sex difference was even higher, with a male mutation rate five to six times that of females. Blame aging dads. For every extra year of the father's age, baby chimpanzees exhibited approximately one extra mutation. This finding will inform future studies of primate evolution.

    Science, this issue p. 1272

  5. Quantum Gases

    Tilting just right makes atoms tunnel

    1. Jelena Stajic

    One of the most fascinating phenomena in the quantum world is the ability of particles to go through an energy barrier — a process called quantum tunneling. Meinert et al. studied the dynamics of quantum tunneling in an optical lattice of strongly interacting atoms. When the lattice was suddenly tilted, the atoms, originally each in their own lattice site, tunneled to non-neighboring sites.

    Science, this issue p. 1259

  6. Cancer Imaging

    Taking a broader view of cancer imaging

    1. Megan L. Frisk

    Many people think the best way to visualize tumors is to target imaging agents to specific cancers at the molecular level. Kuo et al. feel differently: They developed a new class of small molecules, called alkylphosphocholine (APC) analogs, which are broadly taken up by nearly all cancers, without such molecular specificity. Compared to normal cells, cancer cells have a strong taste for APC analogs. By attaching fluorescent labels or radiolabels to the APC analogs, the researchers could image more than 50 different human cancers in animal models, as well as brain, lung, and liver tumors in human patients. These broadly applicable APC-based agents for imaging—and possibly for treatment—are now poised for further translation to clinical trials.

    Sci. Transl. Med. 6, 240ra75 (2014).

  7. Earth's Interior

    Cycling water through the transition zone

    1. Nicholas S. Wigginton

    The water cycle involves more than just the water that circulates between the atmosphere, oceans, and surface waters. It extends deep into Earth's interior as the oceanic crust subducts, or slides, under adjoining plates of crust and sinks into the mantle, carrying water with it. Schmandt et al. combined seismological observations beneath North America with geodynamical modeling and high-pressure and -temperature melting experiments. They conclude that the mantle transition zone—410 to 660 km below Earth's surface—acts as a large reservoir of water.

    Science, this issue p. 1265

  8. Cancer Metastasis

    Copper for breast cancer metastasis

    1. Wei Wong

    Many patients with breast cancer die from metastases, when cancer cells spread from the primary tumor to other sites. Some of the intracellular proteins that help cells move from one location to another can be activated by a chemical modification called oxidation. MacDonald et al. found that the enzyme Memo bound copper, enhancing the oxidation of proteins involved in cell movement. Mice with tumors formed from breast cancer cells that lacked Memo had fewer lung metastases, and human patients with breast cancers that had high levels of Memo were more likely to develop metastases.

    Sci. Signal. 7, ra56 (2014).

  9. Stem Cell Plasticity

    The versatility of epithelial stem cells

    1. Beverly A. Purnell

    Stem cells are very important in the maintenance of our bodies' tissues and organs. Blanpain and Fuchs review how different populations of naturally lineage-restricted epithelial stem cells and committed progenitors can also display remarkable plasticity. These cells can reacquire long-term self-renewing capacities and multilineage differentiation potential during physiological and regenerative conditions. These abilities depend on whether the stem cell remains within its resident niche or has been mobilized to repair a wound. Such cellular plasticity has implications for regenerative medicine and for cancer.

    Science, this issue p. 10.1126/science.1242281

  10. Quantum Nonlocality

    Testing nonlocality for many particles

    1. Jelena Stajic

    Distant parts of a quantum-mechanical system can be correlated in ways that cannot be described classically—a concept known as nonlocality. Tura et al. propose a simple test for nonlocality in systems with multiple particles. The test involves quantities that should readily be measurable in, for example, cold atom experiments. This is an improvement over currently available tests, which are difficult to implement experimentally.

    Science, this issue p. 1256

  11. Quantum Mechanics

    Avoiding back-action in quantum measurements

    1. Ian S. Osborne

    The very process of measuring a quantum system has an influence on the system through the process of back-action. Suh et al. used a back-action evasion scheme to monitor the motion of a miniature oscillator without influencing its motion (see the Perspective by Bouwmeester). The scheme should help in the understanding of the fundamental limits associated with measurement and will have practical implications in providing a low-temperature thermometer and a probe of extremely weak forces.

    Science, this issue p. 1262

  12. Neural Migration

    Dissecting how signaling directs axon growth

    1. Valda Vinson

    During development of the nervous system, nerve cells send out projections called axons that must be guided to their proper targets. Netrins are secreted proteins that bind to receptors to either attract or repel the growing axons. Xu et al. present x-ray structures that show that complexes of netrin with two different receptors, neogenin and DCC, have different architectures. How netrin signals remains to be understood in detail, but netrin's ability to create different assemblies probably plays a role in the diverse signaling outcomes it mediates.

    Science, this issue p. 1275

  13. Human Genetics

    The population structure of Native Mexicans

    1. Laura M. Zahn

    The genetics of indigenous Mexicans exhibit substantial geographical structure, some as divergent from each other as are existing populations of Europeans and Asians. By performing genome-wide analyses on Native Mexicans from differing populations, Moreno-Estrada et al. successfully recapitulated the pre-Columbian substructure of Mexico. This ancestral structure is evident among cosmopolitan Mexicans and is correlated with subcontinental origins and medically relevant aspects of lung function. These findings exemplify the importance of understanding the genetic contributions of admixed individuals.

    Science, this issue p. 1280

  14. Transcription

    Pausing for control of gene expression

    1. Guy Riddihough

    Pausing during gene transcription can play a critical role in gene regulation. Vvedenskaya et al. mapped pause sites across the whole genome in actively growing Escherichia coli (see the Perspective by Roberts). Thousands of undocumented pause sites were identified across well-transcribed genes, allowing the definition of a consensus pause sequence that is dependent on specific interactions of RNA polymerase with the DNA template and nascent RNA transcript.

    Science, this issue p. 1285; see also p. 1226

  15. Disease Ecology

    Many connections are not always bad for health

    1. Caroline Ash

    Contrary to expectations, highly connected populations can experience less impact from infectious disease than isolated groups. What happens to pathogens in natural populations has been poorly studied, because they rarely cause devastating disease outbreaks. Thanks to a long-term study of an inconspicuous fungal-plant disease system, we have now gained some surprising insights. During a 12-year study, Jousimo et al. discovered that clustered and linked host-plant patches showed lower levels of fungal damage and higher fungal extinction rates than more distant patches (see the Perspective by Duffy). This phenomenon is explained by high gene flow and rapid evolution of host resistance within the connected patches. Populations of the modest weed Plantago, growing on the Åland Islands in the Baltic, were less than 10% infected by the Podosphaera mildew fungus in any given year, but infection turnover was high. These findings have broad implications for ecology, disease biology, conservation, and agriculture.

    Science, this issue p. 1289; see also p. 1229

  16. Comparative Behavior

    The crayfish that was afraid of the light

    1. Sacha Vignieri

    We tend to assume that complex emotions, such as anxiety, only occur in mammals or other cognitively complex vertebrates. But a heightened sense of awareness and the avoidance of novel or dangerous environments could be helpful for any animal species. Fossat et al. show that crayfish exposed to a stressful electric field refuse to enter light arms in a light/dark maze, even after the electric field has been removed. The animals calmed down when they were injected with an anxiolytic drug used to treat anxiety in humans, and they entered the light as normal. The stressed animals had increased levels of the neurotransmitter serotonin in the brain, and injections of serotonin induced anxiety-like behavior in control animals. Thus, these invertebrates display a primitive form of anxiety that shares a mechanism with the more complex emotions displayed by vertebrates.

    Science, this issue p. 1293

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