bluuebunny/crossref_metadata_2025 huggingface dataset:
New Gene Forges Link Between Fragile Site and Many Cancers
Authors: Pennisi Elizabeth
Published: October 2006

For years, researchers have wondered whether the easily broken "fragile sites" that riddle the chromosomes are somehow involved in the genetic abnormalities that are a hallmark of aggressively growing cancer cells. The discovery of what appears to be an important new tumor-suppressor gene, called
FHIT
, in a fragile site on chromosome 3 now suggests that they are.
FHIT
's location there, for example, may render it susceptible to inactivation by chemical or viral carcinogens. Further studies are needed to confirm this, however, as the gene hasn't been definitively shown to be a tumor suppressor.
Sunfish Shows the Way Through the Fog
Authors: Bains Sunny
Published: October 2006

Anyone who has driven in heavy fog knows how difficult it is to see things clearly in a medium that scatters light. Yet fish appear to move with ease through a dense aquatic fog of swirling algae, plankton, sand, dirt, and all sorts of plant and animal debris. Now, after studying the retina of the green sunfish (
Lepomis cyanellus
), researchers at the University of Pennsylvania, Philadelphia, think they know how this creature, at least, accomplishes the feat. And they are trying to copy the sunfish's presumed strategy, known as polarization difference imaging, to improve the vision of cameras in murky conditions.
Speciation in Action
Authors: Coyne Jerry
Published: October 2006

In a paper in this week's issue, Rieseberg
et al.
(
p. 741
) examine the formation of a new species of sunflower in real time. In his Perspective, Coyne discusses the importance of this scientist-generated evolution and what it tells us about the process of speciation.
NMR Studies of Single-File Diffusion in Unidimensional Channel Zeolites
Authors: Kukla Volker , Kornatowski Jan , Demuth Dirk , Girnus Irina , Pfeifer Harry , Rees Lovat V. C. , Schunk Stefan , Unger Klaus K. , Kärger Jörg
Published: October 2006

Single-file diffusion is the restricted propagation of particles that cannot pass each other. The occurrence of this phenomenon should be reflected by a change in the time dependence of the mean particle displacement in comparison with ordinary diffusion. Although this process is considered to be the rate-controlling mechanism in a large variety of processes, so far no direct evidence of this phenomenon has been provided. Diffusion measurements made with pulsed field gradient nuclear magnetic resonance (NMR) in unidimensional pore systems (zeolites AlPO4-5 and Theta-1) reflect the expected time dependence of single-file diffusion.
Requirement for BMP Signaling in Interdigital Apoptosis and Scale Formation
Authors: Zou Hongyan , Niswander Lee
Published: October 2006

Interdigital cell death leads to regression of soft tissue between embryonic digits in many vertebrates. Although the signals that regulate interdigital apoptosis are not known, BMPs—signaling molecules of the transforming growth factor-β superfamily—are expressed interdigitally. A dominant negative type I BMP receptor (dnBMPR-IB) was used here to block BMP signaling. Expression of dnBMPR in chicken embryonic hind limbs greatly reduced interdigital apoptosis and resulted in webbed feet. In addition, scales were transformed into feathers. The similarity of the webbing to webbed duck feet led to studies that indicate that
BMP
s are not expressed in the duck interdigit. These results indicate BMP signaling actively mediates cell death in the embryonic limb.
NSF to Take Closer Look at How Support Shapes Careers
Authors: Mervis Jeffrey
Published: October 2006

The U.S. government spends more than a billion dollars a year on a variety of programs to support graduate students in science and engineering. But there is scant information on which mechanisms—individual fellowships, institutional traineeships, or grant-funded research assistantships—work best in getting young scientists launched on a successful career. Now the country's two leading research agencies—the National Science Foundation and the National Institutes of Health—are hoping to come up with some answers.
SOHO Turns an Unblinking Eye on a Turbulent Sun
Authors: Hellemans Alexander
Published: October 2006

The European Space Agency's Solar and Heliospheric Observatory (SOHO) spacecraft has already logged 3 months of continuous observations of the sun from its vantage point 1.5 million kilometers from Earth. Last week, SOHO researchers announced the first results from SOHO's diverse instruments. They include spectacular pictures of the sun's violent atmosphere, suggesting that even in its current lull of activity, the sun is unexpectedly turbulent; analyses of the solar wind showing that the sun's surface preserves an unaltered sample of the primordial solar system; and hints from oscillations of the entire sun that its internal engine may have a different structure than theorists had thought.
Volcano-Ice Age Link Discounted
Authors: Kerr Richard A.
Published: October 2006

Modern volcanic eruptions are dwarfed by the massive eruption of Toba, on the island of Indonesia, about 70,000 years ago. According to some theories, fallout from that giant blast cooled the Earth, decimating early human populations and driving the climate system into an ice age. Those hypotheses are put to the test by a year-by-year climate record buried in Greenland ice—and the results show that Toba wasn't such a climatic catalyst afterall.
Recycling Osmium
Authors: Snow Jonathan E.
Published: October 2006

In the vicinity of so-called subduction zones, one crustal plate is pushed under another, leading to recycling of elements in the crust. Noble metals such as platinum and osmium were not thought to participate in this recycling, but as Snow discusses in his Perspective, this picture needs rethinking. He comments on results reported by Brandon
et al.
(
p. 861
) in this same issue that show that osmium is in fact recycled out of subducted oceanic crust into the overlying mantle. Snow also discusses the new tools for measuring rhenium-osmium isotope ratios that made the research possible.
Comparison of Galileo-Probe and Earth-Based Translation Rates of Jupiter's Equatorial Clouds
Authors: Beebe Reta F. , Simon Amy A. , Huber Lyle F.
Published: October 2006

The Doppler wind speeds derived from Galileo probe data are comparable with the maximum translation speeds observed in the equatorial zone by Voyager 1 and the Hubble Space Telescope. Slower published values of east-west winds are based on measurements of larger features and should be interpreted as translation rates of large weather systems interacting with the wind. The nature of the hot-spot region that the Galileo probe entered is compatible with a high-speed jet at 6 degrees north. The hot spot is associated with an equatorial weather system that spans 5 degrees of latitude and translates at 103 meters per second.
A U1/U4/U5 snRNP Complex Induced by a 2′-

O

-Methyl-Oligoribonucleotide Complementary to U5 snRNA
Authors: Ast Gil , Weiner Alan M.
Published: October 2006

Nuclear messenger RNA splicing involves multiple interactions between the five spliceosomal small nuclear ribonucleoprotein particles (snRNPs) U1, U2, U4, U5, and U6 and numerous spliceosomal proteins. Here it is shown that binding of a 2′-
O
-methyl-oligoribonucleotide complementary to U5 small nuclear RNA (snRNA) nucleotides 68 to 88 (BU5Ae) disrupts the initial U4/U5/U6 tri-snRNP complex, enhances the U2/U6 interaction, and induces a U1/U4/U5 snRNP complex. The U1/U4/U5 snRNP complex interacts specifically with an RNA oligonucleotide containing the 5′ splice site sequence and may therefore represent a transitional stage in the displacement of U1 from the 5′ splice site by U5 snRNP.
Chemical Usurpation of a Nest by Paper Wasp Parasites
Authors: Bagnères Anne-Geneviève , Lorenzi Maria Cristina , Dusticier Georges , Turillazzi Stefano , Clément Jean-Luc
Published: October 2006

The paper wasp
Polistes atrimandibularis
is an obligatory social parasite of another
Polistes
species,
P. biglumis bimaculatus
. To control the host nest, the parasite sequentially changes the composition of its chemical signature, the cuticular hydrocarbons, during the colonial cycle. Gas chromatography-mass spectrometry of the cuticular hydrocarbons at every stage of the cycle showed that the parasite can switch on and off an entire chemical family, namely, the unsaturated hydrocarbons. In this way the parasite can match the host signature at a critical moment of the colonial cycle.
An Enhanced Immune Response in Mice Lacking the Transcription Factor NFAT1
Authors: Xanthoudakis Steven , Viola Joao P. B. , Shaw Karen T. Y. , Luo Chun , Wallace James D. , Bozza Patricia T. , Luk Daniel C. , Curran Tom , Rao Anjana
Published: October 2006

Transcription factors of the NFAT family are thought to play a major role in regulating the expression of cytokine genes and other inducible genes during the immune response. The role of NFAT1 was investigated by targeted disruption of the NFAT1 gene. Unexpectedly, cells from NFAT1
−/−
mice showed increased primary responses to
Leishmania major
and mounted increased secondary responses to ovalbumin in vitro. In an in vivo model of allergic inflammation, the accumulation of eosinophils and levels of serum immunoglobulin E were increased in NFAT1
−/−
mice. These results suggest that NFAT1 exerts a negative regulatory influence on the immune response.
Enhanced Degradation of EGF Receptors by a Sorting Nexin, SNX1
Authors: Kurten Richard C. , Cadena Deborah L. , Gill Gordon N.
Published: October 2006

The vectorial movement of proteins requires specific recognition by components of the vesicular trafficking machinery. A protein, sorting nexin-1 (SNX1), was identified in a human cell line that bound to a region of the epidermal growth factor receptor (EGFR) containing the lysosomal targeting code. SNX1 contains a region of homology to a yeast vacuolar sorting protein, and overexpression of SNX1 decreased the amount of EGFR on the cell surface as a result of enhanced rates of constitutive and ligand-induced degradation. Thus, SNX1 is likely to play a role in sorting EGFR to lysosomes.
DNA Replication Fork Pause Sites Dependent on Transcription
Authors: Deshpande Atul M. , Newlon Carol S.
Published: October 2006

Replication fork pause (RFP) sites transiently arresting replication fork movement were mapped to transfer RNA (tRNA) genes of
Saccharomyces cerevisiae
in vivo. RFP sites are polar, stalling replication forks only when they oppose the direction of tRNA transcription. Mutant tRNA genes defective in assembly of transcription initiation complexes and a temperature-sensitive RNA polymerase III mutant (
rpc160-41
) defective in initiation of transcription do not stall replication forks, suggesting that transcription is required for RFP activity.
After 9 Years, a Tangled Case Lurches Toward a Close
Authors: Friedly Jock
Published: October 2006

Last month, the Office of Research Integrity (ORI) overturned four previous not-guilty findings by announcing that James Abbs of the University of Wisconsin, Madison, “intentionally falsified and fabricated” data in a paper he published in 1987. Abbs, who denies the charges, has agreed not to appeal—the financial and personal strain would be too great, he says—in return for avoiding the risk of debarment from government grants and a chance to rebut the charges in writing. But Abbs has submitted a stinging rebuttal that challenges ORI's findings and its use of statistical analyses as evidence of guilt.
Flies Unmask Evolutionary Warfare Between the Sexes
Authors: Morell Virginia
Published: October 2006

According to an ingenious new experiment, behind the act of making love lies evolutionary war—at least in fruit flies. By blocking female flies' evolution while allowing males to evolve, researchers revealed a coevolutionary struggle waged through compounds in seminal fluid and in the female's reproductive tract. In the experiment, highly evolved “supermale” flies fathered more offspring, but their evolutionarily “stuck” female partners died young, apparently because of toxins in the males' seminal fluid. The work provides experimental evidence for sociobiological theory and also has implications for how new species are formed.
Synapse-Making Molecules Revealed
Authors: Wickelgren Ingrid
Published: October 2006

Every bend of the knee or blink of the eye depends on biochemical conversations between motor neurons and muscle cells. The lingua franca of these chats is the neurotransmitter, and during an embryo's development, the two cells must devise an intricate molecular junction, or synapse, to transfer these chemical signals. Now, with the help of two “conversationally impaired” mice, researchers have identified molecules that lay the groundwork for these vital talks. They've made “knockout” mice that are missing the gene for agrin, a nerve-derived protein, and are virtually devoid of neuromuscular junctions; another knockout that can't make these connections lacks the gene for MuSK, a newly identified muscle protein. MuSK, it appears, is the agrin receptor: The two proteins bind and could spark a cascade of events that lead to the making of a synapse.
High-Resolution Imaging of the Self-Assembly of Organic Monolayers
Authors: Chiang Shirley
Published: October 2006

Thin films of organic molecules are useful for lubrication, as chemical sensors, and for optical applications. Controlled fabrication of these films requires an understanding of how they form on a surface. In her Perspective, Chiang discusses results by Poirier and Pylant (
p. 1145
) that show scanning tunneling microscope images of alkanethiol molecules on silver. The images show the details of nucleation, growth, and phase transitions of these films.
The Whole Structure of the 13-Subunit Oxidized Cytochrome c Oxidase at 2.8 Å
Authors: Tsukihara Tomitake , Aoyama Hiroshi , Yamashita Eiki , Tomizaki Takashi , Yamaguchi Hiroshi , Shinzawa-Itoh Kyoko , Nakashima Ryosuke , Yaono Rieko , Yoshikawa Shinya
Published: October 2006

The crystal structure of bovine heart cytochrome c oxidase at 2.8 Å resolution with an
R
value of 19.9 percent reveals 13 subunits, each different from the other, five phosphatidyl ethanolamines, three phosphatidyl glycerols and two cholates, two hemes A, and three copper, one magnesium, and one zinc. Of 3606 amino acid residues in the dimer, 3560 have been converged to a reasonable structure by refinement. A hydrogen-bonded system, including a propionate of a heme A (heme a), part of peptide backbone, and an imidazole ligand of Cu
A
, could provide an electron transfer pathway between Cu
A
and heme a. Two possible proton pathways for pumping, each spanning from the matrix to the cytosolic surfaces, were identified, including hydrogen bonds, internal cavities likely to contain water molecules, and structures that could form hydrogen bonds with small possible conformational change of amino acid side chains. Possible channels for chemical protons to produce H
2
O, for removing the produced water, and for O
2
, respectively, were identified.
The Self-Assembly Mechanism of Alkanethiols on Au(111)
Authors: Poirier G. E. , Pylant E. D.
Published: October 2006

The self-assembly mechanism of alkanethiol monolayers on the (111) surface of gold was discovered with the use of an ultrahigh-vacuum scanning tunneling microscope. Monolayer formation follows a two-step process that begins with condensation of low-density crystalline islands, characterized by surface-aligned molecular axes, from a lower density lattice-gas phase. At saturation coverage of this phase, the monolayer undergoes a phase transition to a denser phase by realignment of the molecular axes with the surface normal. These studies reveal the important role of molecule-substrate and molecule-molecule interactions in the self-assembly of these technologically important material systems.
Dynamic Ocean-Atmosphere Coupling: A Thermostat for the Tropics
Authors: Sun De-Zheng , Liu Zhengyu
Published: October 2006

The ocean currents connecting the western tropical Pacific Ocean with the eastern tropical Pacific Ocean are driven by surface winds. The surface winds are in turn driven by the sea-surface temperature (SST) differences between these two regions. This dynamic coupling between the atmosphere and ocean may limit the SST in the tropical Pacific Ocean to below 305 kelvin even in the absence of cloud feedbacks.
A Shared Strategy for Virulence
Authors: Barinaga Marcia
Published: October 2006

A versatile bacterial weapon that can deliver harmful proteins directly into host cells has recently turned up in a wide range of pathogens. Called the type III secretion system, this biochemical launch pad can sidestep host defenses, and it helps cause diseases ranging from bubonic plague to tree blight.
Hyakutake Produces Another Surprise
Authors: Peterson Kim
Published: October 2006

When comet Hyakutake sped past Earth last March, it offered a revelation about comet makeup that is hard to reconcile with standard explanations of how these objects originated. A paper in this issue (
p. 1310
) reports that sensitive infrared spectroscopy reveals that Hyakutake is rich in methane—a compound expected in comets but never before seen clearly—and in ethane, which was entirely unexpected. Its presence, say researchers, implies that Hyakutake could not have formed from unaltered interstellar material in the primordial cloud that gave birth to the solar system. Instead, Hyakutake and other comets probably formed later, after ultraviolet radiation from the newborn sun had "processed" the ice grains, driving chemical reactions that yielded ethane.
SOHO Probes Sun's Interior by Tuning In to Its Vibrations
Authors: Hellemans Alexander
Published: October 2006

Brussels—From a listening post well away from the turbulence of Earth's atmosphere, 1.5 million kilometers toward the sun, the European Space Agency's SOHO spacecraft is tuning in to the sun's vibrations 24 hours a day. These vibrations—waves of pressure or buoyancy that penetrate deep into the sun—carry clues to its internal structure, from the churning layers just beneath its surface to the nuclear furnace at its core. While ground-based observers are successfully pursuing this strategy, known as helioseismology (see Articles, this issue), the first results from SOHO, reported last week, far surpass the clarity of ground-based measurements.
The Seismic Structure of the Sun
Authors: Gough D. O. , Kosovichev A. G. , Toomre J. , Anderson E. , Antia H. M. , Basu S. , Chaboyer B. , Chitre S. M. , Christensen-Dalsgaard J. , Dziembowski W. A. , Eff-Darwich A. , Elliott J. R. , Giles P. M. , Goode P. R. , Guzik J. A. , Harvey J. W. , Hill F. , Leibacher J. W. , Monteiro M. J. P. F. G. , Richard O. , Sekii T. , Shibahashi H. , Takata M. , Thompson M. J. , Vauclair S. , Vorontsov S. V.
Published: October 2006

Global Oscillation Network Group data reveal that the internal structure of the sun can be well represented by a calibrated standard model. However, immediately beneath the convection zone and at the edge of the energy-generating core, the sound-speed variation is somewhat smoother in the sun than it is in the model. This could be a consequence of chemical inhomogeneity that is too severe in the model, perhaps owing to inaccurate modeling of gravitational settling or to neglected macroscopic motion that may be present in the sun. Accurate knowledge of the sun's structure enables inferences to be made about the physics that controls the sun; for example, through the opacity, the equation of state, or wave motion. Those inferences can then be used elsewhere in astrophysics.
Coulomb Staircase at Room Temperature in a Self-Assembled Molecular Nanostructure
Authors: Andres Ronald P. , Bein Thomas , Dorogi Matt , Feng Sue , Henderson Jason I. , Kubiak Clifford P. , Mahoney William , Osifchin Richard G. , Reifenberger R.
Published: October 2006

Double-ended aryl dithiols [α,α′-xylyldithiol (XYL) and 4,4′-biphenyldithiol] formed self-assembled monolayers (SAMs) on gold(111) substrates and were used to tether nanometer-sized gold clusters deposited from a cluster beam. An ultrahigh-vacuum scanning tunneling microscope was used to image these nanostructures and to measure their current-voltage characteristics as a function of the separation between the probe tip and the metal cluster. At room temperature, when the tip was positioned over a cluster bonded to the XYL SAM, the current-voltage data showed "Coulomb staircase" behavior. These data are in good agreement with semiclassical predictions for correlated single-electron tunneling and permit estimation of the electrical resistance of a single XYL molecule (∼18 ± 12 megohms).
Crystal Structure of the Dual Specificity Protein Phosphatase VHR
Authors: Yuvaniyama Jirundon , Denu John M. , Dixon Jack E. , Saper Mark A.
Published: October 2006

Dual specificity protein phosphatases (DSPs) regulate mitogenic signal transduction and control the cell cycle. Here, the crystal structure of a human DSP, vaccinia H1-related phosphatase (or VHR), was determined at 2.1 angstrom resolution. A shallow active site pocket in VHR allows for the hydrolysis of phosphorylated serine, threonine, or tyrosine protein residues, whereas the deeper active site of protein tyrosine phosphatases (PTPs) restricts substrate specificity to only phosphotyrosine. Positively charged crevices near the active site may explain the enzyme's preference for substrates with two phosphorylated residues. The VHR structure defines a conserved structural scaffold for both DSPs and PTPs. A "recognition region," connecting helix α1 to strand β1, may determine differences in substrate specificity between VHR, the PTPs, and other DSPs.
PKD2

, a Gene for Polycystic Kidney Disease That Encodes an Integral Membrane Protein
Authors: Mochizuki Toshio , Wu Guanqing , Hayashi Tomohito , Xenophontos Stavroulla L. , Veldhuisen Barbera , Saris Jasper J. , Reynolds David M. , Cai Yiqiang , Gabow Patricia A. , Pierides Alkis , Kimberling William J. , Breuning Martijn H. , Deltas C. Constantinou , Peters Dorien J. M. , Somlo Stefan
Published: October 2006

A second gene for autosomal dominant polycystic kidney disease was identified by positional cloning. Nonsense mutations in this gene (
PKD2
) segregated with the disease in three PKD2 families. The predicted 968-amino acid sequence of the
PKD2
gene product has six transmembrane spans with intracellular amino- and carboxyl-termini. The PKD2 protein has amino acid similarity with PKD1, the
Caenorhabditis elegans
homolog of PKD1, and the family of voltage-activated calcium (and sodium) channels, and it contains a potential calcium-binding domain.
Biogeographers Take a New View of the Ancient Andes
Authors: Moffat Anne Simon
Published: October 2006

Chicago—For years scientists have had only a sketchy view of the Andes, as the lofty peaks defied easy exploration. But recent expeditions have yielded a new view of these mountains, as discussed at a recent interdisciplinary meeting at The Field Museum in Chicago. New data shows surprising geological complexity, and suggest that many of the Andes' unique animals are members of ancient lineages
Transition State Spectroscopy
Authors: Neumark Daniel M.
Published: October 2006

Before reactants become products in a chemical reaction, they pass through an intermediate condition called the transition state. Because it lasts for a short time, the transition state is hard to observe. In his Perspective, Neumark describes results reported by Wenthold
et al
., on
page 1456
, in which lasers were used to create the transition state and probe its energy level.
The "Bio" in Biochemistry: Protein Folding Inside and Outside the Cell
Authors: Ellis John R.
Published: October 2006

After proteins are made, they must be folded into their final structure. In a report in this week's issue of
Science
, Frydman and Hartl, on
page 1497
, compare how molecular chaperones (proteins that assist folding) affect folding of proteins as they are synthesized from ribosomes and proteins that have been artificially denatured. In his Perspective, Ellis discusses why the differences that are found tell us something about how chaperones really work in the cell.
Far-Infrared Hydrogen Lasers in the Peculiar Star MWC 349A
Authors: Strelnitski Vladimir , Haas Michael R. , Smith Howard A. , Erickson Edwin F. , Colgan Sean W. J. , Hollenbach David J.
Published: October 2006

Far-infrared hydrogen recombination lines H15α (169.4 micrometers), H12α (88.8 micrometers), and H10α (52.5 micrometers) were detected in the peculiar luminous star MWC 349A from the Kuiper Airborne Observatory. Here it is shown that at least H15α is strongly amplified, with the probable amplification factor being greater than or about equal to 10
3
and a brightness temperature that is greater than or about equal to 10
7
kelvin. The other two lines also show signs of amplification, although to a lesser degree. Beyond H10α the amplification apparently vanishes. The newly detected amplified lines fall into the laser wavelength domain. These lasers, as well as the previously detected hydrogen masers, may originate in the photoionized circumstellar disk of MWC 349A and constrain the disk's physics and structure.
Intrinsic Transport Properties and Performance Limits of Organic Field-Effect Transistors
Authors: Torsi L. , Dodabalapur A. , Rothberg L. J. , Fung A. W. P. , Katz H. E.
Published: October 2006

The field-effect mobility in thin-film transistors based on α-sexithiophene (α-6T) and related materials displays a temperature dependence that is remarkably nonmonotonic. Above a transition temperature
T
T
(specific to a given material) the transport is thermally activated, whereas below
T
T
there is a very steep enhancement of the mobility. In the activated regime, the results are well described by the theoretical predictions for small polaron motion made by Holstein in 1959. An analysis of the transistor characteristics shows that the hopping transport in these devices is intrinsic. Performance limits for devices based on α-6T and related materials were established; these limits point to the strong possibility that better molecular materials for transistor applications may be designed from first principles.
Inhibition of Myogenic bHLH and MEF2 Transcription Factors by the bHLH Protein Twist
Authors: Spicer Douglas B. , Rhee James , Cheung Wang L. , Lassar Andrew B.
Published: October 2006

The myogenic basic helix-loop-helix (bHLH) and MEF2 transcription factors are expressed in the myotome of developing somites and cooperatively activate skeletal muscle gene expression. The bHLH protein Twist is expressed throughout the epithelial somite and is subsequently excluded from the myotome. Ectopically expressed mouse Twist (Mtwist) was shown to inhibit myogenesis by blocking DNA binding by MyoD, by titrating E proteins, and by inhibiting trans-activation by MEF2. For inhibition of MEF2, Mtwist required heterodimerization with E proteins and an intact basic domain and carboxyl-terminus. Thus, Mtwist inhibits both families of myogenic regulators and may regulate myotome formation temporally or spatially.
twist

: A Myogenic Switch in

Drosophila
Authors: Baylies Mary K. , Bate Michael
Published: October 2006

Somatic muscle is derived from a subset of embryonic mesoderm. In
Drosophila
, Twist (Twi), a basic helix-loop-helix transcription factor, is a candidate regulator of mesodermal differentiation and myogenesis. Altering amounts of Twist after gastrulation revealed that high levels of Twist are required for somatic myogenesis and block the formation of other mesodermal derivatives. Expression of
twist
in the ectoderm drives these cells into myogenesis. Thus, after an initial role in gastrulation,
twist
regulates mesodermal differentiation and propels a specific subset of mesodermal cells into somatic myogenesis. Vertebrate homologs of
twist
may also participate in the subdivision of mesoderm.
Synergistic Activation of Estrogen Receptor with Combinations of Environmental Chemicals
Authors: Arnold Steven F. , Klotz Diane M. , Collins Bridgette M. , Vonier Peter M. , Guillette Louis J. , McLachlan John A.
Published: October 2006

Certain chemicals in the environment are estrogenic. The low potencies of these compounds, when studied singly, suggest that they may have little effect on biological systems. The estrogenic potencies of combinations of such chemicals were screened in a simple yeast estrogen system (YES) containing human estrogen receptor (hER). Combinations of two weak environmental estrogens, such as dieldrin, endosulfan, or toxaphene, were 1000 times as potent in hER-mediated transactivation as any chemical alone. Hydroxylated polychlorinated biphenyls shown previously to synergistically alter sexual development in turtles also synergized in the YES. The synergistic interaction of chemical mixtures with the estrogen receptor may have profound environmental implications. These results may represent a previously uncharacterized level of regulation of estrogen-associated responses.
Simple Mice Test Antibody Complexity
Authors: Williams Nigel
Published: October 2006

The world, from an immune system's view, is filled with enemies: a mind-boggling multitude of bacteria, viruses, and parasites just waiting to pounce. And the system has to maintain a staggering range of antibodies tailored to take on these threats. Just how it does so is something of a puzzle. And the intricacy of the immune system makes the answers hard to come by. Now researchers have simplified things. On
page 1649
, scientists report that they've genetically altered mice so the animals are born with the ability to make only a few antibody types that recognize just one invader, or antigen. Yet these so-called “quasi-monoclonal” mice developed a near-normal repertoire of antibodies as they grew, clearing the way for scientists to explore possible mechanisms that create such diversity.
Nonequilibrium Structures in Condensed Systems
Authors: Mikhailov A. S. , Ertl G.
Published: October 2006

When the temperature of a substance in thermal equilibrium is lowered, it often becomes more ordered. When externally excited, such systems can exhibit new structures that are not in equilibrium. Mikhailov and Ertl describe in their Perspective such structures that have recently been observed in films of ordered molecules (called Langmuir-Blodgett films) by a group at the Electrotechnical Laboratory in Tsukuba, Japan. The results show important connections with similar behavior in reacting chemical systems.
Spatial Response of Mammals to Late Quaternary Environmental Fluctuations
Authors: Graham Russell W. , Lundelius Ernest L. , Graham Mary Ann , Schroeder Erich K. , Toomey Rickard S. , Anderson Elaine , Barnosky Anthony D. , Burns James A. , Churcher Charles S. , Grayson Donald K. , Guthrie R. Dale , Harington C. R. , Jefferson George T. , Martin Larry D. , McDonald H. Gregory , Morlan Richard E. , Semken Holmes A. , Webb S. David , Werdelin Lars , Wilson Michael C.
Published: October 2006

Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene.
Thymine-Thymine Dimer Bypass by Yeast DNA Polymerase ζ
Authors: Nelson John R. , Lawrence Christopher W. , Hinkle David C.
Published: October 2006

The
REV3
and
REV7
genes of the yeast
Saccharomyces cerevisiae
are required for DNA damage-induced mutagenesis. The Rev3 and Rev7 proteins were shown to form a complex with DNA polymerase activity. This polymerase replicated past a thymine-thymine
cis-syn
cyclobutane dimer, a lesion that normally severely inhibits replication, with an efficiency of ∼10 percent. In contrast, bypass replication efficiency with yeast DNA polymerase α was no more than 1 percent. The Rev3-Rev7 complex is the sixth eukaryotic DNA polymerase to be described, and is therefore called DNA polymerase ζ.
Appropriators Bullish on Biomedicine
Authors: Marshall Eliot
Published: October 2006

A key House subcommittee last week approved a 1997 Department of Health and Human Services appropriation bill that would give the National Institutes of Health (NIH) a budget increase of 6.9%—more than Congress allowed in 1996 (5.7%) and much more than the 4% the Administration is requesting. The bill—the first step in the appropriations process—would also give the NIH director more administrative flexibility, while curbing the authority of NIH's Office of AIDS Research. And it would partly lift a ban on human embryo research imposed earlier this year by Congress.
Microbes Hint at a Mechanism Behind Punctuated Evolution
Authors: Mlot Christine
Published: October 2006

A soldier's life is said to be filled with long periods of boredom punctuated by short periods of terror, and some researchers have long suspected that evolution proceeds the same way, with long periods of stasis and brief episodes of dramatic change. Results on
page 1802
. support that idea, showing that for thousands of generations, bacteria evolved in spurts toward larger sizes. Researchers suggest a simple explanation: that the lack of beneficial mutations kept the cells in stasis until such a rare mutation appeared. But paleontologists caution that these results from a single, asexual population may not apply to the sweeping forces that cause new species to arise.
High-Pressure Framework Silicates
Authors: Hazen Robert M. , Downs Robert T. , Finger Larry W.
Published: October 2006

Recent syntheses of high-pressure alkali and alkaline earth silicates reveal a class of framework structures with corner-linked 4- and 6-coordinated silicon. These compounds possess the structural formula (A
1+

4−2
x

B
2+

x

)Si
VI

m

(Si
IV

n

O

2(
m+n
)+2

), where
x
,
m
, and
n
specify the amounts of alkaline earth, 6-coordinated silicon, and 4-coordinated silicon, respectively. Appropriate values of
m
and
n
yield a range of high-pressure structures, from fully 4-coordinated to fully 6-coordinated silicate frameworks. Recognition of this class of framework silicates leads to predictions of high-pressure structures as well as room-pressure isomorphs of high-pressure silicates.
HIV Therapeutics
Authors: Richman Douglas D.
Published: October 2006

Douglas Richman (University of California at San Diego, USA) captures the current excitement in the field of HIV therapeutics. New drugs, new treatment regimens, and new insights into the relation of disease progression to the quantity of viral RNA in patients' plasma have led to an unprecedented sense of optimism among researchers.
A Perspective on AIDS Vaccines
Authors: Bloom Barry R.
Published: October 2006

To many people it is unfathomable that after more than 10 years of research, there is no human immunodeficiency virus (HIV) vaccine ready for large-scale efficacy trials. A complex web of scientific, political, and social issues remains to be untangled. Barry Bloom (Howard Hughes Medical Institute, Albert Einstein College of Medicine, USA) takes a hard look at the fundamental questions that must be answered before a vaccine against acquired immunodeficiency syndrome (AIDS) becomes a reality.
Glacial Climate in the Tropics
Authors: Broecker Wallace
Published: October 2006

During glacial cycles, different parts of the Earth cool by different amounts. A growing collection of evidence has begun to show that cooling in the tropical oceans was greater than previously thought. In his Perspective, Broecker discusses the oxygen isotope evidence reported by Schrag
et al
. (
p. 1930
) that indicates that the cooling in deep tropical water was close to the freezing point.
Tickling Memory T Cells
Authors: Ahmed Rafi
Published: October 2006

Viruses cause immediate induction of type I interferons (which include IFN-alpha and IFN-beta). These IFN I cytokines limit spread of the virus until antigen-specific responses can fully control the infection. A report by Tough
et al
. (
p. 1947
) show that these IFN I have another function: They also augment the proliferation of T cells, including a subset of T cells that may mediate long-term immunological memory. In his Perspective, Ahmed discusses the possible contribution of this bystander effect of IFN I to immunological memory.
A Benzene-Thermal Synthetic Route to Nanocrystalline GaN
Authors: Xie Yi , Qian Yitai , Wang Wenzhong , Zhang Shuyuan , Zhang Yuheng
Published: October 2006

A thermal reaction of Li
3
N and GaCl
3
in which benzene was used as the solvent under pressure has been carried out for the preparation of 30-nanometer particles of gallium nitride (GaN) at 280°C. This temperature is much lower than that of traditional methods, and the yield of GaN reached 80%. The x-ray powder diffraction pattern indicated that sample was mainly hexagonal-phase GaN with a small fraction of rocksalt-phase GaN, which has a lattice constant a = 4.100 angstroms. This rocksalt structure, which had been observed previously only under high pressure (at least 37 gigapascals) was observed directly with high-resolution electron microscopy.
Prevention of Islet Allograft Rejection with Engineered Myoblasts Expressing FasL in Mice
Authors: Lau Henry T. , Yu Ming , Fontana Adriano , Stoeckert Christian J.
Published: October 2006

Allogeneic transplantation of islets of Langerhans was facilitated by the cotransplantation of syngeneic myoblasts genetically engineered to express the Fas ligand (FasL). Composite grafting of allogeneic islets with syngeneic myoblasts expressing FasL protected the islet graft from immune rejection and maintained normoglycemia for more than 80 days in mice with streptozotocin-induced diabetes. Graft survival was not prolonged with composite grafts of unmodified myoblasts or Fas-expressing myoblasts. Islet allografts transplanted separately from FasL-expressing myoblasts into the contralateral kidney were rejected, as were similarly transplanted third-party thyroid allografts. Thus, the FasL signal provided site- and immune-specific protection of islet allografts.
NAE Strives to Re-Engineer Itself
Authors: Lawler Andrew
Published: October 2006

The new leaders of the National Academy of Engineering are struggling with problems that predate the stormy 1-year reign of its former president, Harold Liebowitz, who was ousted last month. One set of issues involves how NAE runs itself; the other relates to its strained relationship to its older spouse, the National Academy of Sciences. No easy solutions are in sight.
Patterns of Aging
Authors: Kelner Katrina L. , Marx Jean
Published: October 2006

One of the most profound changes of recent years has been the dramatic aging of populations everywhere. This graying of the world is a tribute to the success of such modern public health measures as vaccines and improved sanitation. At the same time, as the first three reports in the News section that begins this special issue on Patterns of Aging show, it is posing serious problems for societies and governments worldwide as the costs of caring for their elderly populations soar.

But the news on the aging front is not all grim. Indeed, aging research is flourishing as the combined power of genetics and molecular biology provides new clues about the causes of aging. In his Article on the genetics of aging, for example, S. M. Jazwinski describes the isolation of mutants that lengthen or shorten life-spans in species that are extremely amenable to genetic studies, such as yeast, the fruit fly
Drosophila melanogaster,
and the worm
Caenorhabditis elegans
, as well as in rodents and man. The Article by J. R. Smith and O. M. Pereira-Smith describes additional molecules, including tumor suppressors, found to be important in cellular senescence. Such information may one day lead to longer, perhaps healthier, lives.

So far the one environmental manipulation that reliably extends life-span, at least in rodents, is caloric restriction. As R. S. Sohal and R. Weindruch outline in their Article, several lines of evidence now suggest that caloric restriction may lengthen life because it slows down the oxidative damage that may underlie aging. Lithgow and Kirkwood echo this theme in their Perspective, where they argue that the ability to withstand stressors (such as oxidizing molecules) may be the key requirement for a longer life-span.

Two more Articles look at critical physiological systems that decay with age. P. Wise
et al
.'s review on menopause concludes that both the neuroendocrine control system of the brain and the aging ovary contribute to the loss of female reproductive capacity with age, while R. A. Miller describes changes in the immune system that increase the risk of certain diseases with age. And the last two reports in the News section describe some hopeful new results about the aging brain. One story deals with evidence suggesting that the normal brain may not suffer as much damaging neuronal loss with age as once thought, and the other describes a host of efforts aimed at finding ways to treat or prevent the neuronal loss that does occur in Alzheimer's disease. Finally, for links to World Wide Web sites with more information on the topics covered in this Special Issue, see the individual News summaries below.
The Aging Immune System: Primer and Prospectus
Authors: Miller Richard A.
Published: October 2006

Changes in T lymphocyte populations underlie much of the age-related decline in the protective immune response. Aging leads to the replacement of virgin T cells by memory T cells and to the accumulation of cells with signal transduction defects. Studies of antibody gene assembly, accessory cell function, post-thymic T cell development, skewed selection of T cell receptor repertoire, and the clinical concomitants of immune senescence will shed new light on the causes and consequences of age-dependent immune failure.
Mechanism of Suppression of Cell-Mediated Immunity by Measles Virus
Authors: Karp Christopher L. , Wysocka Maria , Wahl Larry M. , Ahearn Joseph M. , Cuomo Peter J. , Sherry Barbara , Trinchieri Giorgio , Griffin Diane E.
Published: October 2006

The mechanisms underlying the profound suppression of cell-mediated immunity (CMI) accompanying measles are unclear. Interleukin-12 (IL-12), derived principally from monocytes and macrophages, is critical for the generation of CMI. Measles virus (MV) infection of primary human monocytes specifically down-regulated IL-12 production. Cross-linking of CD46, a complement regulatory protein that is the cellular receptor for MV, with antibody or with the complement activation product C3b similarly inhibited monocyte IL-12 production, providing a plausible mechanism for MV-induced immunosuppression. CD46 provides a regulatory link between the complement system and cellular immune responses.
Regulation of Myosin Phosphatase by Rho and Rho-Associated Kinase (Rho-Kinase)
Authors: Kimura Kazushi , Ito Masaaki , Amano Mutsuki , Chihara Kazuyasu , Fukata Yuko , Nakafuku Masato , Yamamori Bunpei , Feng Jianhua , Nakano Takeshi , Okawa Katsuya , Iwamatsu Akihiro , Kaibuchi Kozo
Published: October 2006

The small guanosine triphosphatase Rho is implicated in myosin light chain (MLC) phosphorylation, which results in contraction of smooth muscle and interaction of actin and myosin in nonmuscle cells. The guanosine triphosphate (GTP)-bound, active form of RhoA (GTP⋅RhoA) specifically interacted with the myosin-binding subunit (MBS) of myosin phosphatase, which regulates the extent of phosphorylation of MLC. Rho-associated kinase (Rho-kinase), which is activated by GTP⋅RhoA, phosphorylated MBS and consequently inactivated myosin phosphatase. Overexpression of RhoA or activated RhoA in NIH 3T3 cells increased phosphorylation of MBS and MLC. Thus, Rho appears to inhibit myosin phosphatase through the action of Rho-kinase.
Biotech Finds a Growth Industry
Authors: Roush Wade
Published: October 2006

Developmental genetics firms have high hopes for harnessing the regenerative power of the embryo to treat disease. Because species from fruit flies to humans have similar developmental genes, these companies rely on model organisms to find human genes, aiming to eventually treat diseases ranging from Parkinson's disease to skin cancer. Investors are pumping in money, although these young firms face a maze of scientific and commercial obstacles before they mature into commercially successful ventures.
Mutant Alga Blurs Classic Picture of Photosynthesis
Authors: Williams Nigel
Published: October 2006

Biochemists have been fairly confident for nearly 3 decades that they understand photosynthesis, perhaps the most important reaction in biology. But work reported on page
364
is now challenging one of the longest standing tenets of that understanding. A team at Oak Ridge National Laboratory has disabled one of the two key photosystems in photosynthesis in a single-celled alga and found that it still thrives in normal conditions. The results may force researchers to reconsider the ubiquity of the accepted two-stage scheme and may also throw light on the evolution of photosynthesis.
Complex Optical Surfaces Formed by Replica Molding Against Elastomeric Masters
Authors: Xia Younan , Kim Enoch , Zhao Xiao-Mei , Rogers John A. , Prentiss Mara , Whitesides George M.
Published: October 2006

Complex, optically functional surfaces in organic polymers can be fabricated by replicating relief structures present on the surface of an elastomeric master with an ultraviolet or thermally curable organic polymer, while the master is deformed by compression, bending, or stretching. The versatility of this procedure for fabricating surfaces with complex, micrometer- and submicrometer-scale patterns was demonstrated by the production of (i) diffraction gratings with periods smaller than the original grating; (ii) chirped, blazed diffraction gratings (where the period of a chirped grating changes continuously with position) on planar and curved surfaces; (iii) patterned microfeatures on the surfaces of approximately hemispherical objects (for example, an optical surface similar to a fly's eye); and (iv) arrays of rhombic microlenses. These topologically complex, micropatterned surfaces are difficult to fabricate with other techniques.
Modification of Phytohormone Response by a Peptide Encoded by

ENOD40

of Legumes and a Nonlegume
Authors: van de Sande Karin , Pawlowski Katharina , Czaja Inge , Wieneke Ursula , Schell Jeff , Schmidt Jürgen , Walden Richard , Matvienko Martha , Wellink Joan , van Kammen Ab , Franssen Henk , Bisseling Ton
Published: October 2006

The gene
ENOD40
is expressed during early stages of legume nodule development. A homolog was isolated from tobacco, which, as does
ENOD40
from legumes, encodes an oligopeptide of about 10 amino acids. In tobacco protoplasts, these peptides change the response to auxin at concentrations as low as 10
−
12
to 10
−
16
M. The peptides encoded by
ENOD40
appear to act as plant growth regulators.

Sequence alignment of full ENDO40 gene sequences from soybean, pea, alfalfa, and tocacco plants.
New Methods for Expanding the Chromosomal Paint Kit
Authors: Marx Jean
Published: October 2006

Two groups of researchers, one of which reports its results on
page 494
, have found a way to tag chromosomes with fluorescent markers so that each chromosome can be depicted by a computer as having a distinctive color. The techniques are likely to be useful for detecting chromosomal rearrangements and other abnormalities in cancer cells, and in screening for defects that underlie genetic disorders such as Down syndrome.
The Changing Frontiers of Science and Technology
Authors: Abelson Philip H.
Published: October 2006

Leadership in science and technology by the United States is being challenged. Other countries, in particular those of East Asia, are becoming effective competitors in many high-technology products, and these other countries, in contrast to the United States, are increasing their support of scientific research.