This Week in Science

Science  03 Sep 2010:
Vol. 329, Issue 5996, pp. 1125
  1. Vaginal Gel Versus HIV

    HIV prevention technologies for women are urgently needed, especially in sub-Saharan Africa where young women bear the greatest burden of the HIV epidemic. Abdool Karim et al. (p. 1168; published online 19 July) present the results of the CAPRISA 004 randomized control trial. The nearly 3-year-long trial, conducted in urban and rural South African women, tested the efficacy of a vaginal gel containing the antiretroviral drug tenofovir in preventing HIV infection. The dosing strategy required application of the gel both before and after coitus, and with this regime HIV infection was reduced by approximately 39% overall, by 54% in women with high adherence to the protocol, and with no increase in overall adverse event rates.

  2. Antimalarial Drug Candidate

    Spiroindolones were discovered as promising antimalarial drug candidates through a high-throughput screening approach that should be applicable to a range of neglected infectious diseases. Rottmann et al. (p. 1175; see the Perspective by Wells) present the preclinical profile for an optimized spiroindolone drug candidate, NITD609. They obtained evidence for a decrease in drug sensitivity in strains of the malaria parasite Plasmodium falciparum bearing amino acid mutations in the P-type ATPase, indicating possible mechanisms of action and/or resistance.

  3. Icy Adsorption

    CREDIT: XU ET AL.

    The highly mobile nature of adsorbed liquid water on surfaces has made structural studies using atomic force microscopy challenging, especially for the first adsorbed layer. Moreover, scanning probe methods are hindered by the strong interaction between the probe tip and the water molecules. When graphene flakes were deposited on mica, Xu et al. (p. 1188; see the Perspective by Katsnelson) found that they could use atomic force microscopy to image the first and second layers of introduced water. They consistently observed an islandike structure—0.34 nanometers in height, at low humidity—that corresponded to a single layer of ice. At higher humidity, thicker layers with a more liquid nature were observed.

  4. Free Falling Vortices

    When a vessel containing a superfluid is set in rotational motion, the superfluid does not rotate uniformly with it; instead, quantized vortices develop. Vortices have been observed in a range of superfluids, including helium, atomic Bose-Einstein condensates, and type II superconductors in a magnetic field. Freilich et al. (p. 1182) visualized real-time vortex dynamics in the most tunable of superfluid systems, an atomic Bose-Einstein condensate. A small section of condensate was displaced from the trap and imaged as it fell in the gravitational field. The technique is applicable to exploring other complex dynamic systems, such as vortex reconnections and the role of vortices in quantum turbulence.

  5. Join the Club

    An important question for policy-makers is how to communicate information (for example, about public health interventions) and promote behavior change most effectively across a population. The structure of a social network can dramatically affect the diffusion of behavior through a population. Centola (p. 1194) examined whether the number of individuals choosing to register for a health forum could be influenced by an artificially constructed network of neighbors that were signed up for the forum. The behavior spread more readily on clustered networks than on random, poorly clustered ones. Certain types of behavior within human systems are thus more likely to spread if people are exposed to many other people who have already adopted the behavior (for example, in the circumstances where your friends know each other, as well as yourself).

  6. From Simplicity to Complexity

    The relatively simple properties of isolated electrons become rich and complex when the particle-particle interactions are strong enough to form a correlated system. Emergence of complex behavior from relatively simple subunits is an intensely studied topic in condensed-matter physics and applies to many systems in superconductivity and magnetism. Si and Steglich (p. 1161) review the physics of heavy fermion intermetallic compounds. These make ideal materials for study because they can exhibit metallic, magnetic, and superconducting behavior showing novel quantum phases and unconventional quantum criticality.

  7. Sea of Plastic

    Plastics are highly resistant to degradation and persist in the environment after being discarded. Notoriously, plastics accumulate within ocean gyres, where patterns of surface circulation concentrate them into specific regions. One area of plastic buildup lies in the middle of the North Atlantic Gyre. Law et al. (p. 1185; published online 19 August) report results from 22 years of plankton tows in the North Atlantic that showed the pattern of plastics accumulation was indeed as predicted by theories of ocean circulation, but, despite the steady increase in plastic production and disposal, the concentration of plastic debris had not increased.

  8. Skin Reaction

    CREDIT: P. VERDINO AND D. A. WITHERDEN, THE SCRIPPS RESEARCH INSTITUTE

    Lymphocytes in the skin known as γδ T cells provide an important barrier against infection and injury. Unlike classical αβ T cells, less is known about the molecular requirements of γδ T cell activation. Two studies demonstrate that the junctional adhesion molecule–like protein (JAML) is a costimulatory molecule for mouse γδ T. Witherden et al. (p. 1205; see the Perspective by Shaw and Huang) showed that JAML, binding to its ligand Coxsackie and adenovirus receptor (CAR), leads to proliferation, as well as cytokine and growth factor production by γδ T cells. In vivo, JAML-CAR interactions contributed to the wound healing response in mice. Verdino et al. (p. 1210; see the Perspective by Shaw and Huang) present a crystal structure of CAR/JAML, which revealed an intracellular signaling motif similar to that known for the αβ T cell costimulatory receptor that signals through phosphoinositide 3-kinase.

  9. Cosmic Fullerenes

    Since the discovery of the buckminsterfullerene C60 in laboratory experiments, it has been speculated that fullerenes could form abundantly in carbon-rich evolved stars and, because of their stability, survive the harsh radiation field in the interstellar medium as a gas-phase species. Cami et al. (p. 1180; published online 22 July; see the Perspective by Ehrenfreund and Foing) have detected large amounts of fullerenes in a peculiar planetary nebula with an extremely hydrogen-poor dust formation zone. Contrary to expectations, the fullerenes are not gaseous; they are cool, are in a neutral charge state, and represent about 1.5% of the available carbon.

  10. No Guide to the Future

    Although fossils can provide glimpses of evolution, the accuracy for predictions made on the basis of commonality among geographically and hierarchically distinct taxa is unknown. Alroy (p. 1191; see the Perspective by Marshall) looked at the global marine fossil record and found that major taxonomic groups of animals have distinctive patterns of diversification and unpredictable responses to mass extinctions. Extrapolating from the current ongoing extinction event predicted a geologically rapid rebound of a number of species, although the future taxonomic composition of the marine biosphere could not be forecast.

  11. Gee-Up, NEDD8

    CREDIT: CUI ET AL.

    Diverse bacterial pathogens, such as Burkholderia pseudomallei and enteropathogenic Escherichia coli (EPEC), inject effector proteins into eukaryotic host cells to subvert host cell biology. Cui et al. (p. 1215; published online 5 August) show that certain bacterial effector proteins promoted the glutamine deamidation of ubiquitin and the ubiquitin-related protein, NEDD8. The modification of ubiquitin inhibited the formation of polyubiquitin chains while, unexpectedly, the same chemical alteration on NEDD8 interfered with the cell cycle, offering insights not only into the cytopathic effects of bacterial infection but also into mechanisms that may operate during viral infection and cancer.

  12. Regulation of Energy Homeostasis

    The mammalian AMP-activated protein kinase (AMPK) is a serine/threonine kinase complex that regulates cellular energy homeostasis. However, the mechanisms by which AMPK mediates transcriptional responses to metabolic perturbations has been unclear. Bungard et al. (p. 1201; published online 17 August; see the Perspective by Hardie) have found that AMPK activated transcription directly on chromatin, combined with phosphorylation of histone H2B at Serine-36. Both signals colocalized at genes regulated in the pathway, and both the enzyme and phosphorylation were required for the direct transcription of stress-responsive genes.

  13. Here to Stay

    For systemic infection, bacterial pathogens must breach the mucosal epithelial barrier. Our bodies have developed a variety of strategies to protect the mucosa, including rapid turnover of epithelial cells. Muenzner et al. (p. 1197; see the cover) show how invasive bacteria overcome this host defense in a humanized mouse model susceptible to Neisseria gonorrhoeae urogenital infection. The bacteria bind to a host-cell surface protein called carcinoembryonic antigen (CEA), which triggers a cascade of changes modulating the cell adhesion properties of the targeted epithelium to prevent the cells from being shed.

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