This Week in Science

Science  22 Dec 2006:
Vol. 314, Issue 5807, pp. 1837
  1. Be Prepared

    CREDIT: PHILIPPE HENRY, WWW.PHILIPPE-HENRY.COM

    Reproduction and population growth are driven by the availability of resources. Boutin et al. (p. 1928) provide evidence that two species of squirrel adjust their reproductive investment to match future increases in seed production, rather than simply tracking current or past seed production. Thus, reproductive investment of seed eaters can respond to future food availability, which creates an intriguing parallel in reproductive strategies between trees and the animals that consume their seed.

  2. Looking Closely at Oligocene Climate

    Changes in solar forcing caused by Earth's orbital motion not only have direct effects on climate but can also exert indirect effects on greenhouse gases such as CO2. Pälike et al. (p. 1894) assembled a detailed, 13-million-year—long record of oxygen and carbon isotopes that span the entire Oligocene, a key period of Earth's transformation from a warm world essentially free of high-latitude ice sheets to one with persistent glaciation in Antarctica. Using a box model of the carbon cycle, they show how the global carbon cycle can amplify long-term solar forcing and attenuate shorter-term ones in a manner controlled mainly by the residence time of carbon in the oceans.

  3. Death of a Solar System

    At the end of its life, a star like the Sun blows away all of its outer layers and compresses into a white dwarf. Gänsicke et al. (p. 1908) have spotted the remnant debris from a planetary or asteroidal system orbiting a white dwarf. The disk of material is rich in heavy elements (metals) and shows a double-peaked emission line profile characteristic of material in orbit around a star.

  4. Gently Probing Spins

    Photoluminescent and charge-injection methods can determine single electron spin states but do not leave the spin state intact. For quantum information processing based on the spin storage and manipulation, the states need to be left intact after measurement. Berezovsky et al. (p. 1916, published online 9 November) describe the use of optical Kerr rotation that can probe the spin state of a single electron on a quantum dot nondestructively.

  5. A Gulf Between Two Gaps

    In the high-temperature superconductors, the onset of superconductivity is preceded by a region known as the pseudogap, particularly in underdoped samples. The relation of the pseudogap to superconductivity has been controversial, in part because different experiments have generated conflicting results. With improvements in sample quality and using an optimized, angle-resolved photoemission spectroscopy technique, Tanaka et al. (p. 1910, published online 16 November) reveal the presence of two gaps with different doping dependence, one gap with the pseudogap and the other with the superconducting gap. Valla et al. (p. 1914, published online 16 November) present results of a photoemission and scanning tunneling microscopy study on a nonsuperconducting cuprate that still exhibits the d-wave signature of its superconducting cousins. The results suggest that the pseudogap regime is formed as electrons pair up, but without the global coherence associated with the superconducting state. These results, which suggest that the pseudogap and superconducting gap coexist but are not related, should have implications for understanding superconductivity mechanisms (see the Perspective by Millis and the 17 November news story by Service).

    CREDIT: VALLA ET AL.
  6. Seismic Seafloor Seep

    Most of Earth's crust is created at mid-ocean ridges in eruptions of lava. Tolstoy et al. (p. 1920, published online 23 November; see the Perspective by Chadwick) have captured the seismic signature of a diking event as veins of lava broke through to the surface along the East Pacific Rise for 6 hours in January 2006. Their array of seismic detectors on the site monitored a gradual rise in seismic activity during the years leading up to the event and its waning thereafter.

  7. The Origin of New Species

    Homoploid hybrid speciation, the origin of a new species as a result of hybridization between two distinct species, is relatively rare in animals. Gompert et al. (p. 1923, published online 30 November), demonstrate that an adaptation to an extreme alpine environment has facilitated homoploid hybrid speciation in the Lycaeides butterflies of western North America. The hybrid species possesses a mosaic genome that is a mixture of the parental genomes and is reproductively isolated from both of the parental species.

  8. European Giants

    Enormous dinosaurs are the hallmark of many visions of prehistory, but fossil evidence for these giants has been limited to the New World and Africa. Royo-Torres et al. (p. 1925) now describe a specimen of a huge dinosaur (40 to 48 metric tons) recovered from Upper Jurassic to Lower Cretaceous rocks in Spain. The specimen represents a new clade of sauropods that seems to have distinctly more primitive limb and bone structure than other giant sauropods found on other continents in Jurassic and Cretaceous rocks. Thus, enormous size arose in other groups of dinosaurs aside from the neosauropods.

  9. Immunity and Influenza

    Seasonal influenza exhibits high morbidity and mortality worldwide, so understanding its phylogenetics and dynamics is important. Despite its high mutation rate, there is limited observed diversity of influenza, perhaps because of generalized strain-transcendent immunity, but there is no evidence for generalized immunity in humans. However, there is evidence of antigenic clusters that sweep through the global human community between successive seasons. Koelle et al. (p. 1898; see the Perspective by van Nimwegen) introduce a phylodynamic model that allows for differences between influenza's genetic and antigenic properties and show that influenza's characteristic phylogeny can arise from cluster-specific immunity alone.

  10. Details Define Double Duty

    CREDIT: WALDEN ET AL.

    Iron regulatory protein 1 (IRP1) is a dual-function protein. With an iron-sulfur cluster bound, it is a cytosolic aconitase enzyme, but without it, IRP1 binds iron-responsive elements (IREs) in messenger RNA and regulates the expression of genes involved in iron transport, storage, and utilization. Walden et al. (p. 1903; see the Perspective by Rouault) now describe the structure of IRP1 bound to ferritin H IRE at 2.8 angstrom resolution and compare it with the known structure of cytosolic aconitase. The switch between the two functions is coupled to large-scale domain rearrangements, from a compact structure in the aconitase to an extended structure that interacts with the IRE at two sites. The RNA binding and enzyme active sites overlap with many amino acids that serve different roles in each state.

  11. Small, But Not Overlooked

    From a fragment of DNA obtained during a metagenomic study of a microbial community living in acid mine drainage, Baker et al. (p. 1933) have obtained evidence for a low-abundance lineage of archaea they call ARMAN (Archaeal Richmond Mine Acidophilic Nanoorganism). The DNA fragment carries a ribosomal RNA gene that indicates the organism's deep divergence from other archaeal groups. Members of the ARMAN group carry a gene encoding a pyrophosphatase that can be used in extracting energy from pyrite. Visualization with fluorescent in situ hybridization has revealed very small, ribosome-packed, irregularly shaped cells.

  12. What's in a Vaccine?

    After vaccination, the efficiency with which protective antibodies are produced often depends on the presence of an adjuvant, a substance that promotes activation of antibody-producing B cells. It has been anticipated that Toll-like receptors (TLRs) might be major players in mediating the effects of adjuvants. However, Gavin et al. (p. 1936; see the news story by Wickelgren) now find that the known TLR pathways do not modulate B cell responses and so adjuvants containing TLR ligands must depend on other properties. Such a revision to thinking about the effects of TLR on B cell responses will likely refocus current thinking about vaccine development.

  13. The Pacemaker in the Pituitary

    Endogenous annual rhythms drive many long-term cycles in physiology and behavior in long-lived vertebrates, but the anatomical and cellular basis of such rhythm generation remains a mystery. Lincoln et al. (p. 1941) analyzed prolactin secretion and its associated biological changes in sheep whose pituitary gland had been surgically disconnected from the central nervous system. Melatonin secretion by the pineal gland regulated the hormonal effect. Timer cells in the pituitary possess melatonin receptors that permit their regulation by the duration of the melatonin signal. These timer cells, in turn, drive the prolactin synthesizing and secreting cells, which themselves lack melatonin receptors.

  14. Shoot the Messenger

    Catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines, is implicated in the modulation of persistent pain, as well as cognition and mood. Common genetic variants of COMT, coding for reduced enzymatic activity, are associated with increased pain sensitivity and the likelihood of developing a persistent musculoskeletal pain condition. Three common single-nucleotide polymorphisms (SNPs) in the coding region of the gene, two of which lead to synonymous changes and one of which leads to a nonsynonymous change, form three major haplotypes, and a haplotype rather than a single SNP better accounts for variability in pain sensitivity. Nackley et al. (p. 1930) explain these findings by showing that the changes in the coding region of the gene affect the secondary structure of the corresponding messenger RNA, which dramatically altered efficiency of protein synthesis.

  15. News on Networking

    Analysis of large data sets describing protein interactions is helping to define how networks of protein interactions control cell function. Kim et al. (p. 1938; see the Perspective by Yeates and Beeby) analyze an improved data set that includes information on three-dimensional protein structure and protein domains, which allows distinctions to be made between particular interaction domains and clarifies, for example, whether interactions between two proteins containing the same domain with another protein are expected to be mutually exclusive. This analysis restricts the estimated maximal numbers of protein partners (14) compared with previous estimates. The number of interaction interfaces on a protein is a key defining factor in whether a protein is essential for cell function and for its evolutionary rate.

Log in to view full text

Via your Institution

Log in through your institution

Log in through your institution