This Week in Science

Science  02 Dec 2011:
Vol. 334, Issue 6060, pp. 1180
  1. I Know You


    The paper wasp, Polistes fuscatus, which lives in multiple queen social groups, is able to differentiate among individuals based on varying facial markings. This suggests that this species has evolved the ability to learn and recognize facial features as a response to their highly social environment. However, this ability could also be due to a well-developed form of pattern recognition. To differentiate among these hypotheses, Sheehan and Tibbets (p. 1272) compared the facial learning ability in P. fuscatus to that in a related species, P. metricus, which nests singly. P. fuscatus wasps were able to learn faces much more accurately than they were non-face (or manipulated face) images. Furthermore, P. metricus wasps were unable to learn faces, despite the fact that both species were able to differentiate equally among images of prey or patterns.

  2. Exploiting X-rays

    X-rays have been used to study materials for a long time, from examining broken bones, to identifying the crystal structure of proteins. The development of high-intensity centralized facilities now allows the study of more scientific questions, including those involving dynamic behavior. Advances in optics have also made it possible to focus x-rays, making it possible to look at localized behavior. Ice et al. (p. 1234) review the developments in beam sources and focusing methods and highlight a wide range of studies now using x-ray techniques.

  3. Diamond Quantum Mechanics


    The separation between the classical and quantum mechanical worlds is becoming less distinct. Experiments are beginning to reveal quantum mechanical behavior in a variety of macroscopic systems. Lee et al. (p. 1253; see the Perspective by Duan) generated and verified entanglement between the vibrational modes of two macroscopic diamonds at room temperature. The results confirm that quantum phenomena may persist in ambient conditions in a laboratory-scale system and point toward a possible platform for ultrafast quantum information processing at room temperature, based on optical phonons.

  4. Make Hydrogen

    Mature technologies exist to generate hydrogen from water, using electric power, but vigorous efforts are now under way to enhance the efficiency of the process on account of its potential importance in renewable energy. Subbaraman et al. (p. 1256) combined nickel oxide and platinum to produce a more effective catalyst than either component alone. The findings suggest that the nickel helps to cleave the O-H bond, and the platinum then directs the separated H intermediates to form H2.

  5. Missing Metals?

    Before the first stars formed, the only elements present in the universe were hydrogen, helium, and lithium. All the other elements, which astronomers refer to as metals, were produced in stars. Fumagalli et al. (p. 1245, published online 10 November; see the Perspective by Kacprzak) report the detection of two gas clouds without discernible metals. These clouds date to about two billion years after the Big Bang, an epoch by which plenty of stars and galaxies had formed and thus by which most of the gas in the universe was expected to have been enriched with metals. Thus, the transport of metals from stars and galaxies to their surroundings was not as efficient or as homogeneous as previously assumed.

  6. Cooperating to Ice Histories

    Antarctica has been covered with ice for the past 34 million years. Falling concentrations of atmospheric CO2 have been the prime suspects in causing the cooling that produced the accumulation of ice, but reconstructions of atmospheric CO2 content have contradicted this notion. Pagani et al. (p. 1261) present alkenone-based CO2 reconstructions, from both high- and low-latitude sites in the Atlantic and Southern oceans, which show that CO2 levels did in fact decline precipitously just prior to and during the onset of glaciations, confirming that CO2 played a dominant role in the inception of Antarctic glaciation. The temperature histories of Antarctica and the Arctic during the last deglaciation are quite different. What about changes in the masses of the ice sheets? Weber et al. (p. 1265) present marine sedimentary records from the Weddell Sea coast of the East Antarctic ice sheet which show that the ice sheet reached its maximum extent contemporaneously with that of Northern Hemispheric ice sheets.

  7. Yeast Model of Alzheimer's Disease

    Yeast cell biology has yielded fundamental insight into a variety of processes involved in human disease. Treusch et al. (p. 1241, published online 27 October; see the Perspective by McGurk and Bonini) have now created a yeast model of the cellular toxicity caused by the beta-Amyloid peptide Aβ 1-42, which is thought to be causal in Alzheimer's disease (AD). An unbiased genome-wide screen for modifiers of toxicity revealed the yeast homolog of PICALM, a confirmed AD risk factor involved in endocytosis. Three additional genes were also identified that appear to impact AD risk, based on their associations with AD onset and pathologic burden. A model of Aβ toxicity in the glutamatergic neurons of nematodes was created and used to confirm the role of the toxicity modifiers. PICALM was also shown to protect rat cortical neurons from toxic Aβ oligomers.

  8. Diffusing Healthy Behavior

    How can we influence people to adopt healthy behaviors? While support groups are helpful in this regard, studies have suggested that having similar people together (a condition known as homophily) may not help to spread information about health innovations. Centola (p. 1269; see the Perspective by van der Leij) devised an online experiment which controlled the extent of homophily and the structure of an online community network. Participants were randomly assigned to a group in which the network structure was the same, but, in one case, the participants were connected to similar partners. While in the other group, the partners had random characteristics. In the homophilic group, the subjects were more likely to adopt the healthy behavior (for example, sign up for a health diary).

  9. Cancer Cell Vulnerability

    Many cancer cells express an alternatively spliced form of the metabolic enzyme pyruvate kinase, pyruvate kinase M2 (PKM2). PKM2 is thought to help cancer cells use glucose efficiently to help in the production of molecules required for rapid cellular proliferation. Anastasiou et al. (p. 1278, published online 3 November; see the Perspective by Hamanaka and Chandel) now report another advantage for cancer cells expressing PKM2. PKM2 is sensitive to oxidation by reactive oxygen species (ROS), which decreases its activity. Alterations in cancer cells and properties of their environment tend to increase ROS levels, causing toxicity. Inhibition of PKM2 appears to combat toxicity by promoting metabolic changes that help the cell to cope with the excess ROS. Thus, promoting sustained activation of PKM could offer a way to selectively target cancer cells.

  10. Parasite Paradise?


    The human malaria parasite, Plasmodium falciparum, has exerted an evolutionary pressure on the human population that has led to the selection of various polymorphisms in hemoglobin that protect carriers against severe malaria-related disease and death. Cyrklaff et al. (p. 1283, published online November 10) now show that the malaria parasite “mines” actin from the erythrocyte's membrane skeleton to generate an actin cytoskeleton associated with the Maurer's cleft machinery involved in the transfer of parasite proteins to the erythrocyte surface. In parasitized erythrocytes containing hemoglobin S or C, actin remodeling by the parasite is impaired, resulting in an aberrant actin cytoskeleton and degenerated Maurer's clefts.

  11. Meiosis Matters

    During meiosis, diploid cells make four haploid gametes or spores. In the first meiotic division, homologous chromosomes become physically connected through carefully controlled DNA breaks that initiate crossing over. These connections, or chiasmata, facilitate the correct segregation of the homologs and drive the recombination that occurs during sexual reproduction. Rosu et al. (p. 1286) analyzed the regulation of crossing over in Caenorhabditis elegans and found that even a single DNA break in a homolog was converted with high efficiency into a cross-over event. The ability of the homologs to interact through DNA breaks was temporally regulated, first to ensure that crossing over did indeed occur, and then to ensure that the number of cross-overs was limited.

  12. More than a Scratch

    Immunological T cells that express the γδ T cell receptor respond rapidly to various stressors in the skin by binding to stress-induced ligands. It is thought that this response helps to prevent dissemination of an infection or to restore tissue homeostasis after injury. The effects of this “lymphoid stress surveillance” response are primarily local; however, systemic effects on the immune response are possible. Working in mice, Strid et al. (p. 1293) show that antigen given in the context of mild skin abrasion can induce a systemic T helper 2 (TH2)–type immune response. TH2 responses are most commonly associated with allergy and asthma. In this case, the induction of the TH2 response was dependent on lymphoid stress surveillance: Skin-resident γδ T cells were required for the response, as was the receptor NKG2D, which γδ T cells use to recognize molecules that are induced in response to physicochemical stress. Thus, skin allergies may arise when normally benign antigens are encountered at the same time as a tissue injury or abrasion.

  13. Not So Massive

    Numerical simulations of the formation of the first stars in the universe have suggested that these stars were hundreds of times more massive than the Sun. However, the oldest stars in our Galaxy, which are thought to have descended from the remains of those initial stars, do not bear the traces of such massive ancestors. Based on two-dimensional numerical simulations, Hosokawa et al. (p. 1250, published online 10 November) discuss the effects of the primordial protostars' radiation on their own accretion and growth. The calculations suggest that growth of the first stars to masses above a few tens of times that of the Sun would have been difficult. Thus, the first stars in the universe were probably not so massive after all.

  14. Impossible to Predict?

    As we have begun to recognize that our environment is rapidly changing, we have tasked ourselves with understanding, and predicting, how such changes may influence species, communities, and ecosystems. Coulson et al. (p. 1275; see the Perspective by Schreiber) used an integral projection model to explore the interaction between ecological and evolutionary components of the response to environmental change in wolves, since their reintroduction into Yellowstone National Park over 20 years ago. Ecological and evolutionary components of change were indeed intertwined and both responded to changes in the environment, but often in conflicting ways. Furthermore, changes to the average environment were likely to be more influential than changes in environmental variability. However, predicting the shape and consequences of such changes was extremely difficult, and accurate predictions of how particular environmental changes may affect population sizes and life histories may be beyond our current abilities.

  15. How to Make a Good Antibody Better

    A major goal in HIV vaccine design is to generate a vaccine that is able to elicit highly potent, broadly neutralizing antibodies. Such antibodies are found in some infected individuals, and when these antibodies are injected into nonhuman primates, they can protect against the acquisition of SIV. By focusing on a pair of clonal antibody variants, Diskin et al. (p. 1289, published online 27 October) sought to determine the structural requirements for such potency and breadth. They solved the crystal structure of NIH45-46 bound to gp120 and compared it to the structure of gp120 bound to VRC01, which exhibits reduced potency and breadth of neutralization. In contrast to VRC01, which predominantly interacts with the outer domain of gp120, a four–amino acid insertion in NIH45-46 allowed the antibody to interact with the inner domain of gp120 and correlated with enhanced neutralization. Mutation of a single amino acid residue to improve interaction with the gp120 bridging sheet further enhanced the neutralization of NIH45-46. Thus, residues outside the outer domain of gp120 may be important for antibody-mediated neutralization and should be considered when designing vaccine immunogens.

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