This Week in Science

Science  09 Mar 2012:
Vol. 335, Issue 6073, pp. 1145
  1. Bee Adventurous


    Individuals differ in their behavior, sometimes in consistent ways. For example, some people may seek out new experiences, while others prefer to stick with what they know. This is true in bees as well, where some workers take on the dangerous, novelty-seeking task of scouting more often than others. Liang et al. (p. 1225) found that bees that display such scouting behavior not only tend to scout in multiple contexts (both foraging and searching for nests) but also show differences in gene expression in their brains. Experimental manipulation of gene expression predictably changed scouting behavior. The molecular underpinnings of bee scouting behavior appear to be similar to those associated with novelty-seeking in vertebrate species, including humans.

  2. Mechanics of a Meltdown

    For all the potential hazards presented by nuclear power plants, there have been very few incidents that have caused human or environmental harm. However, those that have happened have often had disastrous consequences, for example, the accidents at Chernobyl in Ukraine and, just last year, at Fukushima Daiichi in Japan. Burns et al. (p. 1184; see the cover) review the state of knowledge on the chemical and physical processes following the nuclear reactor accident and how these results may inform decision-making during future events. Because a large portion of prior research has focused on radionuclide transport following leaks from nuclear waste repositories, and not active reactors, experiments at the more extreme conditions experienced in major nuclear core-melt accidents may have more predictive value.

  3. Lessons from SIV

    HIV infection in humans is a chronic infection and, if left untreated, the majority of infected individuals will succumb to AIDS. Many species of African nonhuman primates are chronically infected with simian immunodeficiency virus (SIV); however, in the majority of these species, the animals remain healthy despite the presence of high viral loads. Chahroudi et al. (p. 1188) review the underlying immune mechanisms that help protect natural hosts from progressing to AIDS and how these responses differ from what is observed in HIV-infected humans and SIV-infected nonhuman primate species that develop AIDS.

  4. Smooth Operator


    When thin sheets are compressed they can buckle and wrinkle, such as when the edges of a sheet of paper, or two areas of skin, are pushed together. Variations in local thickness and stiffness will alter the buckling patterns, but controlling this in a simple and predictable way is difficult. Kim et al. (p. 1201; see the Perspective by Sharon) used halftone lithography with two photomasks to create highly cross-linked dots embedded in a lightly cross-linked matrix of a swellable polymer. This material could generate “smooth” swelling profiles on thin sheets with arbitrary two-dimensional geometries so that complex three-dimensional structures could be produced.

  5. Making Immune Cells Young Again

    Hematopoiesis, the development of the immune system, occurs in distinct waves. The immune system is first populated by cells that arise from fetal hematopoietic stem cells (HSCs) and then later by cells derived from adult HSCs. Furthermore, fetal HSCs give rise to lymphocytes with innate immunelike properties, whereas adult HSCs give rise to classical T and B cells. Yuan et al. (p. 1195, published online 16 February) now uncover the molecular mechanism behind these distinct waves of hematopoiesis. Expression of the RNA binding proteins Lin28 and Lin28b is enriched in fetal hematopoietic stem/progenitor cells (HSPCs) in mice and humans. Ectopic expression of Lin28 in mouse adult HSPCs was sufficient to induce the differentiation of both classical and innate-like lymphocyte lineages.

  6. A Price of Civilization

    Large expanses of rainforests in parts of Central Africa were abruptly replaced by savannas around 3000 years ago, presumably because of climate change. However, that succession occurred at a time of expansion by Bantu tribes, from near the border of present-day Cameroon and Nigeria to the south and east, in a migration that brought with it agriculture and iron-smelting technologies. Bayon et al. (p. 1219, published online 9 February; see the Perspective by Dupont) analyzed the nearby marine sedimentary record and found that chemical weathering in Central Africa also increased markedly at this time. This increase in weathering could have been caused by forest clearing by the Bantu to create arable land and to fuel their smelters, rather than climate change alone.

  7. Nucleosome Maps and Mutation

    Understanding the processes governing the accumulation of mutations impacts many facets of evolutionary biology. Combining data from a mutation accumulation experiment in a DNA repair-deficient yeast strain with genome-wide substitution, Chen et al. (p. 1235) demonstrate that C/G to T/A changes are more likely to affect regions that are nucleosome-free. Furthermore, a similar pattern was seen when comparative analyses were performed among yeast species and in lines of Medaka fish and nematodes. The results are consistent with a model in which DNA bound by nucleosomes is protected against mutations caused by DNA damage.

  8. Flashy Feathers

    Feather colors play key roles in the lives of birds, functioning in everything from camouflage, to thermoregulation, to sexual signaling. Much recent research has revealed that some dinosaurs also had feathers, and examination of feather components in fossil and preserved feathers has begun to reveal how feather color may have played a role in the lives of these dinosaurs. Li et al. (p. 1215) compared the characteristics of the melanosomes of the paravian dinosaur Microraptor to those found in extant birds, which suggest that its feathers were black and iridescent. The existence of this subtle color reflectance, together with morphological aspects of the feathered tail, suggests an important role for signaling in the early evolution of feathers.

  9. A Toxic Barrel

    Many studies have suggested that oligomers are an important toxic species in amyloid diseases such as Alzheimer's disease. In an effort to better define these oligomers, Laganowsky et al. (p. 1228) identified a segment of the fibril-forming protein αB crystalline (ABC) that forms both amyloid fibrils and a relatively stable oligomer. ABC oligomers were toxic in a cell viability assay and were recognized by an amyloid-oligomer–specific antibody. A crystal structure of the oligomers showed that six peptides formed an antiparallel barrel termed a cylindrin. Amyloid oligomers are likely to be structurally polymorphic, but cylindrin-like assemblies offer a model for these elusive structures.

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