This Week in Science

Science  10 Jun 2005:
Vol. 308, Issue 5728, pp. 1513
  1. Titin and Muscle Transcriptional Regulation

    CREDIT: LANGE ET AL.

    During muscle differentiation, gene expression leads to the translation of myofibrillar proteins and their assembly into contractile units, the sarcomeres, which are constantly remodeled to adapt to changes in mechanical load. The giant protein titin acts as a molecular blueprint for sarco- mere assembly by providing specific attachment sites for sarcomeric proteins, as well as acting as a molecular spring. Lange et al. (p. 1599, published online 31 March 2005) identify the components of a novel sarcomere-associated pathway that links the sarcomere to the control of muscle gene transcription. The kinase domain of titin initiates a signal transduction cascade that controls sarcomere assembly, protein turnover, and transcriptional control in response to mechanical changes. A mutation in the titin kinase domain affects this signal transduction pathway and leads to a lethal hereditary human myopathy.

  2. Say NO to Asthma

    Physiological nitric oxide (NO) is strongly associated with asthma, although there has been considerable debate about whether it is present in a protective capacity, or contributes to pathogenesis of the disease. Endogenous nitrosothiols (SNO) are NO- carrying molecules present in airway tissue and one, S-nitroso- glutathione (GSNO), is depleted in asthmatics. Que et al. (p. 1618, published online 26 May 2005; see the Perspective by Gerard) show that modulation of GSNO levels has direct consequences for susceptibility to an asthma-like condition in mice. Animals lacking an enzyme that breaks down GSNO, GSNO-reductase, showed reduced airway hyperreactivity in response to an experimental allergen. Drugs that reduced GSNO levels re- instated asthma susceptibility in these mice, which suggests that accumulated GSNO was directly responsible for protecting the mice. Thus, NO can help protect against asthma, provided that it is “channeled” through SNOs.

  3. First Impressions

    It is sometimes said that first impressions are everything. Todorov et al. (p. 1623; see the Perspective by Zebrowitz and Montepare) provide a remarkable demonstration of how quickly those impressions are formed and what the consequences might be. Several distinct groups of undergraduates were asked to make judgments of relative competence based on 1-second views of black-and-white photographs of unrecognized candidates for the United States Senate and House of Representative contests from 2000, 2002, and 2004. The judgment of competence—unlike those for attractiveness, likeability, or trustworthiness—could be used to predict the outcomes of each of the elections with an accuracy of about 70%.

  4. Super-Sized Food Drops

    CREDIT: ROBISON ET AL.

    The amount of food transported to the deep sea floor by sinking particles, as measured with sediment traps, does not seem to be great enough to fulfill the metabolic requirements of benthic organisms that live there. Robison et al. (p. 1609) conducted a 10-year study in Monterey Bay, off the coast of California, in which a video camera mounted on a remotely operated undersea vehicle was used to measure the vertical distribution and abundance of large organic structures. Discarded mucus feeding structures of giant larvaceans transport approximately half as much carbon to the sea floor as do the small sinking particles that sediment traps capture, and on which past estimate of organic carbon rain rates were based. This finding closes the gap that hitherto has existed between the demand and the supply of food to the benthos for at least this location.

  5. Tuning In to Nanooptics

    The interconversion of optical excitations between propagating modes and localized light fields first requires the ability to harness the propagating photons. However, designing and fabricating structures on the size scale of the propagating light is challenging. Mühlschlegel et al. (p. 1607; see the Perspective by Greffet) show that antennas can be fabricated from split gold strips and can be designed to be resonant at optical wavelengths. These antennas can focus energy into a small gap region strongly enough to generate a supercontinuum of white light. Optical antennas should find a number of applications in creating spectroscopy and interfaces between propagating and localized optical modes.

  6. From Locust Control to Malaria Control?

    There is a pressing need for alternatives to chemical insecticides for targeting adult mosquitoes, the vectors of malaria, owing to the development of resistance and worries about human toxicity (see the news story by Enserink). Blanford et al. (p. 1638) found that treating surfaces with a fungal pathogen of insects reduced the number of mosquitoes able to transmit malaria after an infectious blood meal by more than 100-fold. Fungal infection via contact with netting or solid surfaces was sufficient to cause more than 90% mortality. Scholte et al. (p. 1641) performed field-based research in rural African village houses, using a fungus in real-life conditions, to target wild mosquito vector populations. Large numbers of mosquitoes could be infected with the fungus, which could inhibit malaria parasite development. Even at moderate coverage rates, a dramatic fall in malaria transmission intensity should be achievable. This biopesticide technology has been adapted from registered technology developed for locust control and could be available for immediate use.

  7. Apparently Very Fast

    Cassiopeia A is the well-studied remnant of a supernova explosion that occurred in 1680. Krause et al. (p. 1604) used the Spitzer Space Telescope to reveal areas of infrared (IR) emission outside the shell of the remnant that appear to be moving at the speed of light. These apparent relativistic motions may be the result of IR echoes produced by energetic flashes from within the remnant that are heating up the interstellar dust. Such flashes are consistent with emission from objects called soft gamma repeaters or strongly magnetized neutron stars (magnetars).

  8. Light Therapy Reduces Stress

    The mechanical properties of a polymer depend on both its chemistry, including chain length and distributions, and its processing history. Cross-linking is used to fix a polymer into a particular shape and to stiffen the material by creating chains that are infinitely long. However, this process tends to introduce residual stresses, and there is typically no way to change the shape of a cross-linked network. Scott et al. (p. 1615) show that ultraviolet (UV) irradiation introduces radicals into the polymer by photocleavaging residual initiator molecules. These radicals then cause the chains to fragment at specific locations along the polymer backbone which can then react to relink the network structure and relieve the residual stress.

  9. North Atlantic Trophic Cascade

    Oceanic food webs represent one of the world's most important sources of food for humans. Using data from several different standardized monitoring programs initiated more than 30 years ago, Frank et al. (p. 1621) establish the existence of a trophic cascade—a series of predatory interactions between different levels of the food chain—in a North Atlantic fishery. The removal of cod by overfishing led to effects that extended across five trophic levels. The large scale of the observed ecosystem change gives rise to pessimism for the recovery of cod in this fishery and perhaps other ecosystems where cod populations have collapsed.

  10. Protozoan's Eleven

    CREDIT: YAROVINSKY ET AL.

    Mammalian Toll-like receptors (TLRs) are critical modulators of the immune response to pathogens. TLR recognition of bacteria and some viruses are well known, but there have been few examples of recognition of parasite ligands. Yarovinsky et al. (p. 1626, published online 28 April 2005) describe detection of a profilin-like protein derived from the protozoan parasite Toxoplasma gondii by a recently characterized mouse TLR, TLR11. The li- gand induced the production of the proinflammatory cytokine interleukin-12 (IL-12) by engaging the TLR signaling pathway. In the absence of TLR11, loss of IL-12 production rendered mice susceptible to T. gondii infection. Similar detection of parasite proteins by TLRs may influence the course of immunity against a range of protozoan parasitic diseases.

  11. Ebola Virus: Breaking and Entering

    Infection with Ebola virus causes a severe and often fatal hemorrhagic disease, for which there is currently no effective treatment. The molecular mechanisms by which Ebola virus enters host cells and initiates infection are poorly understood. Chandran et al. (p. 1643, published online 14 April 2005) now show that the endosomal protease cathepsin B is an essential host factor for Ebola virus infection that facilitates viral entry by cleaving a specific protein, glycoprotein GP1, on the surface of the virus. In a cell culture model, inhibitors of cathepsin B activity reduced the production of infectious Ebola virus.

  12. Not Nearly Enough

    A rapid and large global warming event, the Paleocene-Eocene Thermal Maximum (PETM), raised interior ocean temperatures by 4° to 5°C around 55 million years ago, a rise not equaled in any single event since then. This warming, whose origin is still debated, was accompanied by a dramatic negative carbon isotopic excursion. One hypothesis is that the release of 2000 gigatons of carbon from the destabilization of methane clathrates on the sea floor account for both the carbon isotopic signal and the temperature increase. Zachos et al. (p. 1611) now show that the carbonate compensation depth (roughly the depth at which calcium carbonate is no longer found in the sediment, because of dissolution during sinking) of the ocean rose by more than 2 kilometers during the PETM, which could have happened only if the amount of CO2 added to the ocean was much more than that which has been estimated in the clathrate scenario. They find that 4000 gigatons of carbon would have been needed, so the release of clathrates alone could not have been the cause of the warming.

  13. Microsatellite Vole Society

    Repetitive microsatellites mutate at relatively high rates and may contribute to the rapid evolution of species-typical traits. To study the role of repetitive microsatellite DNA in generating behavioral diversity, Hammock and Young (p. 1630; see the news story by Pennisi) used the highly social prairie voles as a model system. A polymorphic regulatory microsatellite was shown to regulate levels of the vasopressin 1a receptor (avpr1a) gene in cell culture. Animals were selectively bred for the length of this functional regulatory locus. Differences in paternal care in the breeder males and in social investigation and social bonding behavior were associated with particular alleles whose length only differed by 19 base pairs. Distribution patterns of avpr1a in behaviorally relevant brain regions also varied with the allele. Thus, microsatellite variations can provide a genetic mechanism for variation and evolution of complex behaviors.

  14. Who Lurks Within

    The human gut contains several hundred species of microbes and roughly half the total number of cells in our bodies. However, we know almost nothing about these cohabitants or their contribution to human health and disease. Eckburg et al. (p. 1635, published online 14 April 2005) describe the microbial diversity at various sites in the colons of three healthy people by 16S ribosomal RNA-based analysis and offer a comprehensive, detailed molecular survey of the microbiota. The study also suggests analytical and ecological approaches for the future study of complex human endogenous communities.

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