Editors' Choice

Science  03 Sep 2004:
Vol. 305, Issue 5689, pp. 1371

    Tear-Away Spots

    Predation is thought to be one of the primary selective factors that influence the frequently conspicuous color patterns on the wings of butterflies. Wing markings, particularly those at the outer margins, may have the effect of deflecting predatory attention away from the insect's vital parts—head and body—to the more expendable wing edges. The century-old deflection hypothesis also suggests that wings would be selected to tear, enabling the butterfly to escape its predator; if correct, then wings would be expected to tear more easily at deflection markings. Hill and Vaca tested whether wing tear weight varied with hindwing pattern in neotropical butterfly species in the genus Pierella. They found that wing tear weight in species with conspicuous white wing patches (P. astyoche) was significantly lower than in species lacking the patch (P. lamia and P. lena), providing evidence in favor of the second part of the deflection hypothesis: that deflection markings coincide with mechanically weak areas of wing. — AMS

    Biotropica 36, 362 (2004).


    On the Hot Seat

    Iceland straddles a plate boundary, the mid-oceanic ridge that separates the North American and Eurasian plates, and a hotspot plume. This placement results in the many volcanoes, geothermal systems, and earthquakes that are all carefully monitored in an attempt to understand subsurface complexity.

    Claesson et al. have been sampling fluid from a 1.5-km-deep borehole that taps into four aquifers at one end of the Húsavík-Flatey fault. They measured sharp increases in Cu, Zn, Mn, and Cr at 1, 2, 5, and about 10 weeks, respectively, prior to a moment magnitude 5.8 earthquake (16 September 2002) whose epicenter was 90 km north of the borehole. They theorize that the elemental transients were caused by the accumulation of stress that then squeezed the hydrothermal system and allowed fluids that had recently been in contact with hotter basaltic rock to enter the borehole; therefore, these chemical signals may be useful for earthquake prediction. About 2 to 9 days after the earthquake, the chemistry shifted again, even more rapidly, with increases in B, Ca, Na, and S, and with changes in oxygen and hydrogen isotopes. These postseismic shifts imply that the borehole is now tapping a 10,000-year-old aquifer from the last ice age. — LR

    Geology 32, 641 (2004).


    One Carbene Helps Another

    Homogeneous copper catalysts are widely used to add electrophilic carbenes to organic substrates. In a typical variant of the reaction, the Cu center stabilizes a carbene formed by N2 loss from an ethyl diazoacetate (EDA) precursor; next, the carbene can transfer from Cu to an olefin to form the desired cyclopropane derivative. Unfortunately, the Cu- carbene complex also tends to react with another EDA molecule, giving undesired carbene dimers.

    Fructos et al. have prepared a Cu(I) chloride catalyst that effectively eliminates the EDA dimerization pathway, while transferring a carbene to olefins, alcohols, and amines at high rates and efficiencies. It turns out that the key to this catalyst is another carbene, bound to Cu as a ligand. Unlike the electrophilic reagent derived from EDA, the ligand is an electron-rich substituted N-heterocyclic carbene, a class of molecule increasingly used as an alternative to phosphines and amines in coordination compounds. How EDA dimerization is avoided is not yet clear, but the authors speculate that the order of steps may be reversed, with olefin (or alcohol or amine) coordination to the Cu complex preceding reaction with EDA. — JSY

    J. Am. Chem. Soc. 10.1021/ja047284y (2004).


    Refreshing Water

    The Everglades is maintained by the slow sheet-like flow of fresh water from a series of control gates in central Florida southward into Florida Bay, and is representative of many other coastal wetlands. The crux of a recent restoration effort is the reengineering of a more natural flow after decades of diversions, levees, and canals, and is complicated by the variable habitats and permeability of the Everglades. Part of the difficulty in monitoring this effort is that the flow is driven by subtle variations in water level that are difficult to capture by scattered gauges (elevation changes of less than 1 m in 10 km). Wdowinski et al. show that the large-scale variations in flow, as reflected in water elevation, as well as other details, can be captured by satellite interferometry. Their observations, gathered in 1994, show that flow was sheetlike in the eastern Everglades, but more radial in the western region, and provide an estimate of the diffusivity, an important hydrologic parameter for inferring flow dynamics. — BH

    Geophys. Res. Lett. 31, 10.1029/2004GL20383 (2004).


    Moving Supplies to the Front

    The decentralized approach to decision-making in neurons, in which synaptic plasticity is locally determined, implies that transcription (which occurs back in the cell body) cannot be relied upon as a means of regulation. Instead, messenger RNAs (mRNAs), quite possibly in an inactive state, are transported along dendrites to postsynaptic regions where they may be translated when protein is needed.

    Kanai et al. have used a battery of techniques to identify components, including the RNA-binding protein staufen and the mRNA encoding calcium/calmodulin protein kinase II (CaMKII), that are carried by the molecular motor kinesin in the form of large 1000S granules. Staufen is already known to participate in the transport and localization of mRNAs in the Drosophila embryo, and CaMKII is a central player in activity-dependent phosophorylation at the synapse. The authors propose that core components would assemble on mRNAs to form granules and that cell- or dendrite-specific factors would be added as requisitioned by synaptic events. — GJC

    Neuron 43, 513 (2004).


    Inflammation Revisited

    There has been a resurgence of interest in the concept that inflammatory mechanisms can profoundly affect the pathogenesis of many common human diseases. In the case of cancer, much research has focused on the role of NF-κB, a transcription factor that is normally activated in response to pro-inflammatory cytokines and that regulates the expression of more than 200 genes. Many tumor cell lines show constitutive activation of NF-κB signaling, but there has been conflicting evidence as to whether this promotes or inhibits tumorigenesis.

    Three groups have studied mouse models of intestinal (Greten et al.), liver (Pikarsky et al.), and mammary (Huber et al.) tumors; they conclude that activation of the NF-κB pathway enhances tumor development and may act primarily in late stages of tumorigenesis. Inhibition of NF-κB signaling uniformly suppressed tumor development but, depending on the model studied, this salutary effect was attributed to an increase in tumor cell apoptosis, reduced expression of tumor cell growth factors supplied by surrounding stromal cells, or abrogation of a tumor cell dedifferentiation program that is critical for tumor invasion/metastasis. Although collectively these results support the development of NF-κB inhibitors as potential anticancer agents, they illustrate that such inhibitors could have complex physiological effects. — PAK

    Cell 118, 285 (2004); Nature 10.1038/nature02924 (2004); J. Clin. Invest. 114, 569 (2004).

  7. STKE

    Arousal Without Anxiety

    Xu et al. have investigated the physiological function and anatomical localization of a recently deorphanized G protein-coupled receptor (GPCR) and its peptide ligand, named neuropeptide S (NPS). Nanomolar concentrations of human, rat, or mouse NPS increased intracellular calcium concentrations in cultured cell lines stably transfected with the NPS receptor, suggesting that it couples to Gq proteins. The peptide and its receptor were highly expressed in brain, as well as in thyroid, salivary glands, and mammary glands. In situ hybridization for the NPS precursor, tyrosine hydroxylase, and corticotropin-releasing factor (CRF) revealed the existence of a pontine cluster of NPS-producing neurons between the locus coeruleus (norepinephrine-producing neurons) and Barrington's nucleus (CRF-producing neurons). NPS both enhanced locomotor activity in mice and promoted several behaviors that are associated with anxiolytic activity. The authors note that this receptor may also be linked to asthma susceptibility (see Laitinen et al., Reports, 9 April 2004, p. 300). — EMA

    Neuron 43, 487 (2004).