This month in Science Roundup:
This month's Science Roundup is sponsored by Biocompare.
Life scientists can now find suppliers without using the antiquated system of searching through multiple catalogs to source the right product. Biocompare's Product Discovery System™ allows the comparison of detailed specifications of similar products from different suppliers side-by-side, quickly finding the right product for your research. Visit http://www.biocompare.com/ for the most recent research news, product reviews, and videos, and to learn about the latest research products and technologies.
Systems-Level Brain Development
http://www.sciencemag.org/sciext/braindev/
Researchers are making their way past the surface complexities of the brain to begin to understand the influences and pathways that establish thought, action, and personality. In a collection of articles published with the 4 Nov 2005 issue, Science magazine and its online companions examined how systems-level analysis of brain development is linking cell biology to psychiatry. In a special section of Science, Review and Viewpoint articles explored language acquisition, the molecular signaling events that underlie cortical plasticity and patterning, and sex differences in the brain. A News story described progress in establishing gene-brain-behavior connections in the neurodevelopmental disorder Williams-Beuren syndrome. Articles and a teaching resource in the Signal Transduction Knowledge Environment ( STKE; http://stke.sciencemag.org/ ) focused on the molecular changes that underlie synaptic plasticity in response to physiological or pathological stimuli, while a Perspective in the Science of Aging Knowledge Environment ( SAGE KE; http://sageke.sciencemag.org/ ) looked at working memory and selective attention in cognitive aging. Rounding out the special collection, Science Careers ( http://sciencecareers.sciencemag.org/career_development/issue/articles/2005_11_04/careers_in_neuroscience_research/) offered a special feature on careers in neuroscience research.
Signaling and Schizophrenia
Schizophrenia and related mood disorders are thought to arise from a combination of genetic and environmental factors, but the identification of specific causative genes has been challenging. The most direct evidence for a genetic link involves the gene DISC1 (disrupted in schizophrenia 1), mutations in which have been associated with specific neurodevelopmental defects. However, the function of the DISC1 protein has been unclear. Now, a Report in the 18 Nov 2005 Science by Millar et al. ( http://www.sciencemag.org/cgi/content/short/310/5751/1187 ) shows that DISC1 interacts with an enzyme called phosphodiesterase 4B (PDE4B), which has been extensively implicated in affective and cognitive function. This interaction in turn influences the activity of cAMP -- a key signaling molecule involved in learning, memory, and mood. An accompanying Perspective by A. Sawa and S. H. Snyder ( http://www.sciencemag.org/cgi/content/short/310/5751/1128 ) highlighted the report and discussed the prospect of therapeutic agents developed on the basis of the DISC1-PDE4B interaction.
Ribosome Close-Up
High-resolution crystal structures of the ribosome and its subunits -- the protein production machinery of the cell -- have revealed significant insights into both RNA structure and the mechanisms of protein synthesis. In a Research Article in the 4 Nov 2005 Science, Schuwirth et al. ( http://www.sciencemag.org/cgi/content/short/310/5749/827 ) expanded upon that knowledge by providing the highest-resolution structure yet of a particularly sought after ribosome: that of the infamous bacterium Escherichia coli. The team presented structures of two forms of the intact E. coli ribosome at 3.5 angstrom resolution -- a marked refinement of the best bacterial ribosome structure published previously (5.5 angstroms). The structures show new atomic details of the interaction interface between the small and large ribosomal subunits and reveal how various parts of the ribosome molecule move during protein synthesis. Previous observations made with the E. coli ribosome have been extensively used to interpret ribosome structures published from other organisms. In addition to advancing our understanding of protein synthesis, the new structures should therefore enable more informative cross-species comparisons. An accompanying Perspective by P. B. Moore highlighted the study ( http://www.sciencemag.org/cgi/content/short/310/5749/793 ) .
Opposing Hunger Hormones
The regulation of appetite, energy balance, and body weight involves a complex network of hormonal and neuronal signaling pathways. One key player is the hunger-inducing hormone ghrelin, which circulates through the blood and is believed to convey information about nutrient availability from the stomach to the brain. In a Research Article in the 11 Nov 2005 Science, Zhang et al. ( http://www.sciencemag.org/cgi/content/short/310/5750/996 ) reported the identification a new hormone regulator of energy balance called obestatin that is processed from the same protein precursor as ghrelin. Paradoxically, the new hormone seems to have the opposite effect of its sister hormone: when administered to adult mice and rats, obestatin suppressed food intake and decreased body-weight gain. Subsequent analysis showed that the new hormone mediates its action through a receptor protein that shares sequences with, but is distinct from the ghrelin receptor. This suggests that both receptors may have evolved from a common ancestor but diverged in their functions, thus maintaining the delicate balance of body weight regulation. An accompanying Perspective by R. Nogueiras and M. Tschöp ( http://www.sciencemag.org/cgi/content/short/310/5750/985 ) discussed the study.
The conceptual framework of evolution by natural selection that Charles Darwin laid out cannot help but clash with fundamentalist creation stories that invoke divine intervention working on time scales that are inconsistent with scientific evidence. Many science educators in the
Barley Success Story
Barley is staple food for humans and domestic animals that thrives in a wide variety of conditions from the Artic Circle to subequatorial near desert regions and the tropics. Plants commonly use day length (photoperiod) to control the timing of flowering during the year and part of barley's success derives from its diverse strains that have various responses to changes in photoperiod. In a Report in the 11 Nov. 2005 Science, Turner et al. ( http://www.sciencemag.org/cgi/content/short/310/5750/1031 ) identified a genetic component of this adaptability. The researchers found that the Ppd-H1 gene participates in the coordinate regulation of flowering by the plant's biological or circadian clock and seasonal changes in photoperiod. In a spring variety of barley, a mutation in this gene causes reduced photoperiod responsiveness accompanied by reduced expression of a FT, a key regulator of flowering. As a result, the plant is able to delay its flowering as long as possible, while accumulating the vegetative mass required to produce more grain. The new finding improves our understanding of how cereal development is regulated by environmental cues and may help plant breeders to tailor crops to specific environments.
Grasses provide a source of food and habitat for countless animals, and can be found on all continents except for Antarctica. But despite their ecological importance, the evolution of grasses is not well understood -- largely due to the absence of an early fossil record for these plants. In a Report in the 18 Nov 2005 Science, Prasad et al. ( http://www.sciencemag.org/cgi/content/short/310/5751/1177 ) presented new fossil data on grasses from the Late Cretaceous (about 65 million years ago) that shed light on the early evolution of grasses and the animals that dined on them. The grass fossils are in the form of phytoliths -- microscopic silica structures found in plant cell walls -- and were isolated from samples of fossilized dinosaur dung (known as coprolites) from central
http://www.sciencemag.org/sciext/materials/
Research at the interface between materials science and biology is inspiring the design of synthetic materials while creating new tools to probe and manipulate living systems. A special section of the 18 Nov 2005 Science examined some of the way in which advances in materials and biology are converging. Four Review articles highlighted mechanical lessons learned from strong natural materials like shell and bone, the design of complex, polymer-based optical systems inspired by living eyes, and current approaches to control cell behavior through the nanoscale engineering of material surfaces. A News story by R. F. Service explored how advances in nanoscale materials science are breaking new ground in cancer detection and treatment. Finally, one of Science's online companions sites, the Science of Aging Knowledge Environment ( SAGE KE; http://sageke.sciencemag.org/ ) reported on how engineers and biologists are making progress toward creating custom-made artificial tissues to rejuvenate aging bodies.
Geneticists, archeologists, and anthropologists alike have debated the ancestry of modern Europeans for decades. Are living Europeans descendants of farmers of the Neolithic Age 7500 years ago, or of Paleolithic hunter-gatherers who arrived in Europe some 40,000 years ago? A Report in the 11 Nov 2005 Science provided new clues to this ancestral puzzle. Haak et al. ( http://www.sciencemag.org/cgi/content/short/310/5750/1016 ) presented mitochondrial DNA sequence data from 7500-year-old Neolithic human remains excavated from sites in Central Europe to explore the extent to which early farmers generated the present-day genetic profile of Europe. The team extracted DNA from 24 skeletons buried at early farming locations in
Analyzing air trapped in glacial ice is the only way to directly determine the atmospheric composition for times before routine scientific sampling began. Since 1997, the oldest ice available for analysis was that from the Vostok, Antarctica, ice core, which extends back to 420,000 years ago and covers four complete glacial cycles. Two Reports in the 25 Nov 2005 Science presented data from new samples obtained by the European Project for Ice Coring in Antarctica (EPICA) that extend our window into the past more than 200,000 years. Siegenthaler et al. ( http://www.sciencemag.org/cgi/content/short/310/5752/1313 ) reconstructed a record of atmospheric carbon dioxide concentration going back 650,000 years and showed that concentration varied during a much more narrow range than it did during the past 400,000 years. However, their measurements also indicate that the coupling of Antarctic temperature and carbon dioxide concentration has not changed significantly over the last 650,000 years, indicating a stable relationship between climate and the carbon cycle during the late Pleistocene. Spahni et al. ( http://www.sciencemag.org/cgi/content/short/310/5752/1317 ) presented parallel measurements for methane and nitrous oxide, two other important greenhouse gases. As with carbon dioxide, methane varied between much more narrow bounds between 400,000 and 650,000 years ago, although nitrous oxide varied just as much as it did in the half-million years since then. The covariation of carbon dioxide and methane evident in the Vostok record also follows essentially the same pattern in the earlier time period.
The new results, discussed in an accompanying Perspective by E. J. Brook ( http://www.sciencemag.org/cgi/content/short/310/5752/1285 ), confirm that the modern atmosphere is highly anomalous and reinforce the view that greenhouse gases and climate are intimately related.
As a star forms out of a collapsed cloud of interstellar dust and gas, a swirling disk of dust grains forms around its dense, central core. The particles in this disk grow, collide, and eventually combine to form planets and asteroids. In a Report in the 4 Nov 2005 Science (published online 20 Oct 2005), Apai et al. ( http://www.sciencemag.org/cgi/content/short/310/5749/834 ) provided evidence that the same early planet-building steps are occurring around brown dwarfs, sometimes referred to as "failed stars." Brown dwarfs lack sufficient mass and heat to ignite internally and shine brightly, and are therefore smaller, colder, and dimmer than normal stars. Using NASA's Spitzer Space Telescope, the researchers recorded the detailed infrared light spectrum of the dust disks around several brown dwarfs, which allowed them to derive information about the size of the radiated particles and their mineral composition. Interestingly, the spectra show three key markers of planet formation: dust grain growth, crystallization, and grain settling in the disk plane. The findings suggest that this kind of planet-forming process may be more widespread than previously thought and that brown dwarfs might be good targets for future planet-hunting missions. A ScienceNOW story by M. Schirber ( http://sciencenow.sciencemag.org/cgi/content/full/2005/1020/3 ) highlighted the Report.
Saturn's rings have fascinated astronomers for decades. Ever since Voyager sent back detailed images of the rings in 1980, scientists have been particularly intrigued by the planet's narrow, outermost F ring, which appeared to exhibit "clumps", "kinks" and "braids". In a Research Article in the 25 Nov 2005 Science, Charnoz et al. ( http://www.sciencemag.org/cgi/content/short/310/5752/1300 ) offered a new and perhaps more puzzling description of this enigmatic ring. Detailed images taken by the Cassini spacecraft reveal that the wispy interweaving strands of the F ring take the form of a loose single-arm spiral that wraps around Saturn at least three times and rotates around the planet with the orbital motion of its constituent particles. How did this curious structure form? The researchers used simulations to explore the spiral's origin and propose that an object called S/2004 S6, an orbiting moonlet or clump of dust, may have interacted with particles in the main F-ring band, causing them to disperse in a cloud, and after many orbits, settle into a spiral pattern. Another possible scenario is that the spiral is the outcome of a random large impact event. As noted in an accompanying Perspective by M. R. Showalter ( http://www.sciencemag.org/cgi/content/short/310/5752/1287 ), continued monitoring of Saturn by Cassini should help decide among the possible mechanisms.
This month's Science Roundup is sponsored by Biocompare.
Life scientists can now find suppliers without using the antiquated system of searching through multiple catalogs to source the right product. Biocompare's Product Discovery System™ allows the comparison of detailed specifications of similar products from different suppliers side-by-side, quickly finding the right product for your research. Visit http://www.biocompare.com/ for the most recent research news, product reviews, and videos, and to learn about the latest research products and technologies.