Tạp chí khoa học số 2006-10-06

6 October 2006 | $10 www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 5 CONTENTS CONTENTS continued >> DEPARTMENTS 11 Science Online 13 This Week in Science 19 Editors’ Choice 24 Contact Science 27 NetWatch 29 Random Samples 49 Newsmakers 149 New Products 156 Science Careers EDITORIAL 17 Prying Open the Black Box by Floyd Bloom >> Modeling the Mind section p. 75 40 INTRODUCTION Of Bytes and Brains 75 NEWS An Enterprising Approach to Brain Science 76 Vision’s Grand Theorist 78 REVIEWS Modeling Single-Neuron Dynamics and Computations: 80 A Balance of Detail and Abstraction A. V. M. Herz, T. Gollisch, C. K. Machens, D. Jaeger Neuronal Computations with Stochastic Network States 85 A. Destexhe and D. Contreras Biologically Based Computational Models of High-Level 91 Cognition R. C. O’Reilly SPECIAL SECTION Modeling the Mind Volume 314, Issue 5796 COVER Neuroscientists increasingly rely on the use of computers and simulations, because the systems they are studying are usually too complex for all of the data to be collected. It is thus a challenge to focus on the conceptually relevant parameters rather than simply trying to model reality by adding more and more details. See the special section on computational neuroscience beginning on page 75. Image: Kelly Buckheit Krause (Photos: Rob Melnychu/Getty; Matthias Kulka/Corbis) NEWS OF THE WEEK Seeing a ‘Plot,’ deCODE Sues to Block a DNA 30 Research Center Hopes for Innovation Bill Rest on Lame-Duck Congress 31 U.S. Needs New Icebreakers, Report Tells Congress 33 SCIENCESCOPE 33 Method to Silence Genes Earns Loud Praise 34 Astrophysicists Lauded for First Baby Picture of the 35 Universe Speedy Planets Near Galactic Center Show Sun’s 36 Region Is No Fluke Has Lazy Mixing Spoiled the Primordial Stew? 36 >> Science Express Reports by R. Andreasen and M. Sharma and by M. C. Ranen and S. B. Jacobsen Bizarrely, Adding Delay to Delay Produces 37 Synchronization French Presidential Hopefuls Discover a 39 New Issue: Science House Passes Plan for Drug, Vaccine R&D 39 NEWS FOCUS A Physician-Scientist Takes the Helm of NCI 40 Budgets, Patients, Managing Conflicts Picking Apart the Causes of Mysterious Dementias 42 >> Report p. 130 Priorities Needed for Nano-Risk Research and 45 Development American Chemical Society Meeting 46 Power to the (Poor) People Cut-and-Copy Approach Clones Nanotubes Snapshots From the Meeting 75 >> Editorial p. 17; Book Reviews pp. 57, 58, 59, and 60 For related online material, see p. 11 or go to www.sciencemag.org/sciext/compneuro/ www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 7 CONTENTS continued >> SCIENCE EXPRESS www.sciencexpress.org GEOCHEMISTRY Solar Nebula Heterogeneity in p-Process Samarium and Neodymium Isotopes R. Andreasen and M. Sharma Isotope ratios in primitive meteorites vary and differ from Earth’s measured value, implying patchiness in the early solar nebula originating from two stellar sources. >> News story p. 36 10.1126/science.1131708 GEOCHEMISTRY Barium Isotopes in Chondritic Meteorites: Implications for Planetary Reservoir Models M. C. Ranen and S. B. Jacobsen Barium isotope variations in primitive meteorites suggest that they originated in a patch of the protosolar nebula that was enriched in supernova-derived material. >> News story p. 36 10.1126/science.1132595 CONTENTS ESSAY Eppendorf 2006 Winner: A Dedicated System for 72 Processing Faces D. Tsao TECHNICAL COMMENT ABSTRACTS PHYSICS Comment on “Pairing and Phase Separation 54 in a Polarized Fermi Gas” M. W. Zwierlein and W. Ketterle full text at www.sciencemag.org/cgi/content/full/314/5796/54a Response to Comment on “Pairing and Phase Separation in a Polarized Fermi Gas” G. B. Partridge et al. full text at www.sciencemag.org/cgi/content/full/314/5796/54b BREVIA VIROLOGY Generation of Simian-Tropic HIV-1 by Restriction 95 Factor Evasion T. Hatziioannou et al. A modified HIV-1 resistant to certain enzymes can replicate in macaque T cells, potentially allowing the use of nonhuman primates to study AIDS. RESEARCH ARTICLES ASTRONOMY Tests of General Relativity from Timing the Double 97 Pulsar M. Kramer et al. Precision timing measurements of a double radio pulsar for nearly 3 years provide four tests of general relativity under strong gravitational fields and show that it holds to 0.05 percent. PALEONTOLOGY Out of the Tropics: Evolutionary Dynamics of the 102 Latitudinal Diversity Gradient D. Jablonski, K. Roy, J. W. Valentine Analysis of marine bivalve fossils shows that the tendency of taxa to originate in the tropics and then expand poleward accounts for decreasing diversity toward the poles. >> Perspective p. 66 LETTERS Post-Fire Logging Debate Ignores Many Issues 51 D. A. Dellasala et al. Preventing HIV/AIDS in Adolescents J. Roberts On Purpose in Conservation G. M. Woodwell Response T. M. Brooks et al. BOOKS ET AL. Moral Minds How Nature Designed Our Universal 57 Sense of Right and Wrong M. D. Hauser, reviewed by M. R. Waldmann Rhythms of the Brain 58 G. Buzsáki, reviewed by P. Fries Neurobiology of Addiction 59 G. F. Koob and M. Le Moal, reviewed by B. J. Everitt Social Neuroscience People Thinking About 60 Thinking People J. T. Cacioppo, P. S. Visser, C. L. Pickett, Eds., reviewed by S. J. Blakemore >> Modeling the Mind section p. 75 POLICY FORUM Genomics and Medicine at a Crossroads in Chernobyl 62 G. S. Ginsburg, M. Angrist, R. Cook-Deegan PERSPECTIVES The Double Life of a Transcription Factor Takes It 64 Outside the Nucleus C. Y. Park and R. Dolmetsch >> Report p. 122 Mass Spectrometry: Bottom-Up or Top-Down? 65 B. T. Chait >> Report p. 109 Fossil Record Reveals Tropics as Cradle and Museum 66 C. R. Marshall >> Research Article p. 102 Cancer Immunotherapy Is More Than a Numbers Game 68 R. Offringa >> Report p. 126 Boron Goes On the Attack 69 T. B. Marder >> Report p. 113 Galactic Prominences on the Rise 70 M. Morris >> Report p. 106 ECOLOGY From Plant Traits to Plant Communities: a Statistical Mechanistic Approach to Biodiversity B. Shipley, D. Vile, É. Garnier A quantitative model based on plant traits can predict with more than 90 percent success the changes in species abundance that follow abandonment of agricultural sites in southern France. 10.1126/science.1131344 NEUROSCIENCE Diminishing Reciprocal Fairness by Disrupting the Right Prefrontal Cortex D. Knoch, A. Pascual-Leone, K. Meyer, V. Treyer, E. Fehr Inhibition of a high-level brain region reduces an individual’s ability to suppress selfish desires and produce generous acts. 10.1126/science.1129156 www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 9 CONTENTS continued >> REPORTS ASTRONOMY Molecular Loops in the Galactic Center: 106 Evidence for Magnetic Flotation Y. Fukui et al. Maps of emissions from carbon monoxide in the inner Milky Way reveal giant loops of fast-moving molecular gas that may be created by magnetic instabilities. >> Perspective p. 70 CHEMISTRY Extending Top-Down Mass Spectrometry to Proteins 109 with Masses Greater Than 200 Kilodaltons X. Han, M. Jin, K. Breuker, F. W. McLafferty Sheets of cadmium telluride particles can be assembled in a solvent without the usual constraint provided by a template or patterned surface. >> Perspective p. 65 CHEMISTRY Boryllithium: Isolation, Characterization, and 113 Reactivity as a Boryl Anion Y. Segawa, M. Yamashita, K. Nozaki A long-sought compound inverts the typically electropositive character of boron and acts as a base and nucleophile. >> Perspective p. 69 ATMOSPHERIC SCIENCE Unraveling the Mystery of Indian Monsoon Failure 115 During El Niño K. Krishna Kumar et al. Droughts in India are associated with only those El Niño events characterized by particularly warm sea surface temperatures in the central equatorial Pacific. EVOLUTION Large Punctuational Contribution of Speciation to 119 Evolutionary Divergence at the Molecular Level M. Pagel, C. Venditti, A. Meade About one-fifth of the amino acid changes producing genetic differences among species groups occur during rapid bursts of evolution; the rest accumulate during gradual divergence. CELL SIGNALING Action of TFII-I Outside the Nucleus as an Inhibitor 122 of Agonist-Induced Calcium Entry G. Caraveo et al. Although multiple genes are generally thought to control an individual’s resistance to infection, only one gene determines susceptibility to a herpesvirus. >> Perspective p. 64 CANCER Cancer Regression in Patients After Transfer of 126 Genetically Engineered Lymphocytes R. A. Morgan et al. Immune cells of cancer patients can be altered to carry genes that, in several cases, can successfully cause regression of some metastatic melanomas. >> Perspective p. 68 SCIENCE (ISSN 0036-8075) is published weekly on Friday, except the last week in December, by the American Association for the Advancement of Science, 1200 New York Avenue, NW, Washington, DC 20005. Periodicals Mail postage (publication No. 484460) paid at Washington, DC, and additional mailing offices. Copyright © 2006 by the American Association for the Advancement of Science. The title SCIENCE is a registered trademark of the AAAS. Domestic individual membership and subscription (51 issues): $139 ($74 allocated to subscription). 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Authorization to photocopy material for internal or personal use under circumstances not falling within the fair use provisions of the Copyright Act is granted by AAAS to libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that $18.00 per article is paid directly to CCC, 222 Rosewood Drive, Danvers, MA 01923. The identification code for Science is 0036-8075. Scienceis indexed in the Reader’s Guide to Periodical Literature and in several specialized indexes. MEDICINE Ubiquitinated TDP-43 in Frontotemporal Lobar 130 Degeneration and Amyotrophic Lateral Sclerosis M. Neumann et al. The protein involved in the pathology of certain neurodegenerative diseases is identified. >> News story p. 42 MICROBIOLOGY Infectious Prions in the Saliva and Blood of Deer 133 with Chronic Wasting Disease C. K. Mathiason et al. Body fluids from infected deer contain infectious prions, possibly explaining the ease with which chronic wasting disease passes among deer and elk. IMMUNOLOGY Modulation of Cell Adhesion and Motility in the 136 Immune System by Myo1f S. V. Kim et al. An unconventional form of long-tailed myosin regulates the adhesion proteins of immune cells, explaining the immunological defects in mice lacking this protein. NEUROSCIENCE Genetic Variant BDNF (Val66Met) Polymorphism 140 Alters Anxiety-Related Behavior Z Y. Chen Mice carrying a neurotransmitter with one defective amino acid display memory and mood problems similar to those of humans with the same variant. NEUROSCIENCE Activity- and mTOR-Dependent Suppression of 144 Kv1.1 Channel mRNA Translation in Dendrites K. F. Raab-Graham, P. C. G. Haddick, Y. N. Jan, L. Y. Jan The synthesis of a potassium channel is decreased by neuronal activity near synapses of hippocampal cells, providing a local feedback circuit. CONTENTS 115 CREDIT: DISTRIBUTED BY NATIONAL GEOPHYSICAL DATA CENTER Protein Standards Visit us on the Web at discover.bio-rad.com Call toll free at 1-800-4BIORAD (1-800-424-6723); outside the US, contact yourlocal sales office. Precision Plus Protein ™ Standards Family Setting New Heights Elevate your research with Bio-Rad’s wide range of high-quality protein standards for electrophoresis and blotting applications. ■ Recombinant protein standards offer 10 sharp, nonshifting bands for MW determination on gels and blots ■ Natural protein standards are available in high, low, and broad ranges to monitor transfer efficiency and for MW estimation on gels and blots ■ IEF standards allow reproducible, dependable pI calibration in native polyacrylamide and agarose IEF gels ■ 2-D SDS-PAGE standards provide calibrated references for the pI and MW of proteins in 2-D SDS-PAGE applications For more information on our wide selection of standards, visit us on the Web at www.bio-rad.com/ad/proteinstandards/ www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 11 ONLINE SCIENCENOW www.sciencenow.org DAILY NEWS COVERAGE The Prophet of Gases Geologists are debating what kinds of fumes might have inspired an ancient Greek story about a trance-inducing temple. Why Did the Lion Lose His Mane? New report may solve mystery of ‘maneless’ lions in Kenya. Is Radiation Contagious? X-rayed fish may pass ill effects onto their unexposed companions. SCIENCE CAREERS www.sciencecareers.org CAREER RESOURCES FOR SCIENTISTS US: Who We Are As Scientists B. Benderly Spurred by the stem-cell scandal, a group of young Korean scientists organized an international conference on ethical issues. Scandal sparks ethics conference. Separate individual or institutional subscriptions to these products may be required for full-text access. www.sciencemag.org SPECIAL SECTION Modeling the Mind SCIENCE CAREERS www.sciencecareers.org CAREER RESOURCES FOR SCIENTISTS GLOBAL: Special Feature—Careers in Computational Neuroscience A. Kotok Career and funding opportunities are growing for researchers who combine neuroscience with informatics and engineering. EUROPE: Leading the Blue Brain Project E. Pain Postdoc Felix Schürmann leads the Blue Brain Project, a joint effort of IBM and the Brain Mind Institute to model the mammalian brain. GLOBAL: Financing Your Research in Computational Neuroscience A. Kotok Read about the leading American sources of funding for research and training in computational neuroscience. SCIENCE’S STKE www.stke.org SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT EDITORIAL GUIDE: Focus Issue—Exciting Times for Signaling in the Brain E. M. Adler Glutamate receptors are central to brain function and pathology. PERSPECTIVE: D-Serine Regulation of NMDA Receptor Activity H. Wolosker Does D-serine released from neurons and glia play distinct roles in regulating NMDA receptor activity? REVIEW: A Unified Model of the Presynaptic and Postsynaptic Changes During LTP at CA1 Synapses J. Lisman and S. Raghavachari A structural model for long-term potentiation accounts for seemingly contradictory results. REVIEW: Molecular Signaling Mechanisms Underlying Epileptogenesis J. O. McNamara, Y. Z. Huang, A. S. Leonard Calcium in dendritic spines may play a key role in epileptogenesis. Geologists debate which gases caused trances. CREDIT (SCIENCENOW IMAGE): BETSY MASON Roche Diagnostics GmbH Roche Applied Science 68298 Mannheim Germany Bring Power and Sensitivity to Two-Step qRT-PCR www.roche-applied-science.com Transcriptor First Strand cDNA Synthesis Kit Choose the new Transcriptor First Strand cDNA Synthesis Kit for sensitive results from standard and difficult templates in two-step RT-PCR on blockcyclers andreal-time PCRinstruments (e.g., the LightCycler®Instruments or ABI PRISM Instruments). ■ Increase sensitivity in quantitative RT-PCR Improve gene-expression studies by i ncreasing sensitivity(see figure) and simultaneously reverse transcribing rare and abundant RNA (over a 10 8 -fold range ofRNA)–without distortinggene-expression levels. ■ Power through challenging RNA secondary structures Reverse transcribe at 55°C to obtain RT-PCRproducts from templates that M-MuLV reverse transcriptases can’t handle. ■ Produce large quantities of full-length cDNA in qualitative two-step RT-PCR Achieve high yields ofcDNAs up to 12 kb using the kit’s anchored- oligo(dT) 18 primer, which prevents mispriming within the poly(A) tail. To maximize powerand sensitivityin two-stepRT-PCR, insist on the new Tr anscriptor First StrandcDNA Synthesis Kit. For more information, visit www.roche-applied-science.com/pcr or contact your local Roche representative. † Purchase of this product is accompanied by a limited license to use it in the PCR process, including homoge- neous PCR methods described in U.S. Patents Nos. 5,994,056, 6,171,785, 6,569,627 and corresponding patents outside the United States, for life science research in conjunction with a thermal cycler whose use in the auto- mated performance of the PCR process is covered by the up-front license fee, i.e., an authorized thermal cycler. No real-time apparatus or system patent rights or any other patent rights owned by Applera Corporation are conveyed expressly, by implication or by estoppel. No rights for any other application, including any in vitro diag- nostic application, are conveyed expressly, by implication or by estoppel under U.S. Patents Nos. 6,174,670 and 6,245,514 and corresponding patent claims outside the United States, or any other patents owned by Roche Molecular Systems, Inc. and F. Hoffmann-La Roche Ltd, claiming real-time amplification and detection methods. The product is covered in-part by US 5,871,908, co-exclusively licensed from Evotec OAI AG. The technology used for the LightCycler ® System is licensed from Idaho Technology Inc., Salt Lake City, UT, USA. LIGHTCYCLER and FASTSTART are trademarks of Roche. Other brands or product names are trademarks of their respective holders. © 2006 Roche Diagnostics GmbH. All rights reserved. Transcriptor First Strand cDNA Synthesis Kit Cat. No. 04 379 012 001 1 kit for 50 reactions Transcriptor Reverse Transcriptase Cat. No. 03 531 317 001 25 reactions 03 531 295 001 50 reactions 03 531 287 001 200 reactions Sensitivity of two-step RT-PCR for the quantification of gene- expression levels on the LightCycler ® 2.0 Instrument. Either the Transcriptor First Strand cDNA Synthesis Kit (blue curves) or another supplier’s RNase H — M-MuLV Reverse Transcriptase (red curves) was used to perform reverse transcription on 100 ng to 10 pg of total RNA from K-562 cells. LightCycler ® FastStart DNA MasterPLUS SYBR Green I † was then used with primers for G6PDH to quantify gene-expression levels on the LightCycler ® 2.0 Instrument. for larger proteins, and top-down approaches are usually limited to proteins with masses below 50 kilodaltons (kD). Han et al. (p. 109; see the Perspective by Chait) extend this approach to proteins with masses in excess of 200 kD by adding small molecules to the electrospray solu- tion that inhibits folding and by activating the ions through heating and collisions induced by voltage acceleration. This process creates hun- dreds of interresidue cleavages at the C- and N- terminal ends of the chain that allow for identifi- cation of larger proteins and pro- vides sufficient mass resolution to assign features such as disul- fide linkages. Monsoon Forecasting The agricultural output of India depends heavily on the strength of the summer monsoon. Most seasonal fore- casts scale the strength of the monsoon to the intensity of the El Niño−Southern Oscillation, a strategy that works well enough predicting heavy rains when equatorial Pacific sea surface temperatures are cold but not nearly as well in predicting drought when temperatures are warm. Krishna Kumar et al. (p. 115, pub- lished online 7 September) used Indian rainfall records extending back more than 130 years and an atmospheric general-circulation model to show that drought occurrence in central India depends on whether the warmest sea sur- face temperatures occur in the central or the eastern parts of the equatorial Pacific Ocean. Incorporating this result into forecasts of the Relativity Tests The double-pulsar system PSR J0737-3039A/B, which comprises two radio pulsars that orbit one another quickly and with high acceleration, is the best system that has been identified for tests of general relativity. Kramer et al. (p. 97, pub- lished online 14 September; see the 15 Septem- ber news story by Cho) report precision timing observations for a 3-year period. With mass measurements possible, four independent tests confirm the validity of general relativity at the 0.05% level in the strong-field regime. From Cradle to Museum For most major groups of organisms, diversity decreases from the tropics to the poles, which may either reflect greater rates of speciation or of species persistence in the tropics. A large- scale analysis of the fossil record of marine bivalves by Jablonski et al. (p. 102; see the Perspective by Marshall) shows that the present- day latitudinal gradient in biodiversity reflects both higher originations in the tropics and pole- ward expansions of distributional limits of taxa over time. Thus, the tropics are both a cradle and a museum of biodiversity. Unraveling Protein Analysis Mass spectrometry is a rapid method for pro- teomic analysis and for identifying posttransla- tional modifications. Identification is less ambiguous for “top-down” approaches, where the entire protein is introduced into the gas phase (as opposed to bottom-up approaches that analyze proteolytic fragments). However, frag- mentation of the protein becomes more difficult monsoon could have a significant effect on economic planning and risk mitigation. Magnetic Loops The center of the Milky Way Galaxy not only har- bors a black hole, but within the inner hundreds of parsecs lie many unusual features, including oddly shaped gas filaments and regions of hot molecular gas with very violent motions. Fukui et al. (p. 106; see the Perspective by Morris) obtained a sequence of CO spectral-line images of the region taken at millimeter wave- lengths that reveal vast loops of fast- moving molecular gas. They suggest the loops are expelled by magnetic buoyancy effects similar to those on the Sun’s surface. Modeling shows that this magnetic picture can explain the high velocity dispersions of the hot-gas regions. Gradual Versus Punctuational Evolution Punctuational evolution has been a contentious idea, but recently, it has become possible to detect signals of punctuational and gradual evolution on molecular phylogenetic trees. Pagel et al. (p. 119) show that bursts of evolution associated with spe- ciation across a wide range of organisms account for approximately 20% of the nucleotide substitu- EDITED BY STELLA HURTLEY AND PHIL SZUROMI www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 13 CREDITS (TOP TO BOTTOM): SEGAWA ET AL.; FUKAI ET AL. Boron Goes Negative The chemistry of boron is generally characterized by elec- tron deficiency. Neutral boron compounds tend to be strong Lewis acids, and in borate anions, the B center is typically electropositive, which is reflected in the utility of borohydride salts as hydride (H − ) donors. Segawa et al. (p. 113; see the Perspective by Marder) have prepared a molecule that inverts this reactivity pattern. By reductive cleavage of a B−Br bond in a cyclic precursor, they isolate a boryl lithium com- pound in which the negatively charged B center acts as a base and nucleophile. The compound is stabilized by elec- tron-donating nitrogens that flank the B atom, in analogy with the isoelectronic N-heterocyclic carbenes that have recently been prepared as ligands. Continued on page 15 EDITED BY STELLA HURTLEY AND PHIL SZUROMI www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 15 This Week in Science tions in published gene-sequence alignments, the remainder being attributable to more gradual forces of evolution. These “punctuational” effects are more frequent in plants and fungi, compared with animals, presumably because of their higher rates of polyploidy and hybridization. Tale of Two Two-Timing Proteins Cells put many proteins to more than one use, including the transcription factor TFII-I. Caraveo et al. (p. 122; see the Perspective by Park and Dolmetsch) found that TFII-I may inhibit calcium entry into cells by interacting with another protein that itself has dual roles in regulating cellular calcium concentra- tions—phospholipase C–γ (PLC-γ). PLC-γ promotes the generation of inositol-1,4,5-trisphosphate, a second messenger that causes calcium release from intracellular stores, and also interacts with the membrane calcium channel TRPC3 and promotes insertion of the channel into the plasma membrane. The interaction of TFII-I with PLC-γ appears to depend on TFII-I’s phosphorylation, which may keep PLC-γ from interacting with the TRPC3 channel and thereby limit calcium entry through the plasma membrane. Immune Gene Therapy for Cancer Cancer immunotherapy is based on the premise that the sometimes reluctant immune system can be cajoled into efficiently destroying tumors, either through vaccination or the adoptive transfer of cancer-killing cells. Morgan et al. (p. 126, published online 31 August; see the Perspective by Offringa) genetically modified T cells to express a T cell receptor (TCR) with strong specificity for a selected melanoma tumor antigen. Peripheral blood lymphocytes isolated from patients with advanced metastatic melanoma were transduced with a retroviral vector containing genes of the two chains of the TCR. After re-infusion, the transgenic cells were maintained and, encouragingly, 2 of the original 17 patients carrying the highest numbers of cells also responded with a noticeable regression of their established tumors. Channeling Local Translation Local, activity-dependent changes in excitability are thought to play a role in various aspects of neuromodulation. Translation of dendritically localized messenger RNAs is one way for a neuron to modify its excitability and signal processing machinery at or near active synapses. Raab- Graham et al. (p. 144) used photoconvertible fluorophores to show that potassium chan- nels are locally translated in dendrites. This local translation is regulated by N-methyl- D- aspartate receptor activation via the mammalian target of rapamycin/phosphatidylinositol 3- kinase signaling pathway. Chronic Wasting Disease Transmission Chronic wasting disease (CWD) is a fatal prion disease found in deer and elk. Its transmission between animals seems to be much easier than that of so-called mad cow disease between cattle. Mathiason et al. (p. 133) demonstrate the presence of infectious prions capable of transmitting CWD in body fluids, including the saliva and the blood, of CWD-infected cervids. The results emphasize the need for caution regarding contact with body fluids of infected animals. Anxious Mice and Men The genes that contribute to depression and anxiety disorders are still unknown, but the recently dis- covered single-nucleotide polymorphism (Val66Met) in the brain-derived neurotrophic factor (BDNF) gene may be related to mood and anxiety disorders common in human populations. Chen et al. (p. 140) report that, in transgenic mice expressing the variant BDNF Met version, there are alterations in brain anatomy and memory as has been described in humans. This allelic variant also reproduces the phenotypic hallmarks of anxiety in humans, but these mutant mice did not respond to a common, widely used antidepressant. Continued from page 13 CREDITS (TOP TO BOTTOM): RAAB-GRAHAM ET AL. . 2006 | $10 www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 5 CONTENTS CONTENTS continued >> DEPARTMENTS 11 Science Online 13 This Week in Science 19 Editors’ Choice 24 Contact Science 27. material, see p. 11 or go to www.sciencemag.org/sciext/compneuro/ www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 7 CONTENTS continued >> SCIENCE EXPRESS www.sciencexpress.org GEOCHEMISTRY Solar. visit us on the Web at www.bio-rad.com/ad/proteinstandards/ www.sciencemag.org SCIENCE VOL 314 6 OCTOBER 2006 11 ONLINE SCIENCENOW www.sciencenow.org DAILY NEWS COVERAGE The Prophet of Gases Geologists