bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutagenesis in Mammalian Cells Induced by Triple Helix Formation and Transcription-Coupled Repair
Authors: Wang Gan , Seidman Michael M. , Glazer Peter M.
Published: October 2006

When mammalian cells were treated with triplex-forming oligonucleotides of sufficient binding affinity, mutations were specifically induced in a simian virus 40 vector contained within the cells. Triplex-induced mutagenesis was not detected in xeroderma pigmentosum group A cells nor in Cockayne's syndrome group B cells, indicating a requirement for excision repair and for transcription-coupled repair, respectively, in the process. Triplex formation was also found to stimulate DNA repair synthesis in human cell extracts, in a pattern correlating with the inhibition of transcription in such extracts. These findings may have implications for therapeutic applications of triplex DNA and raise the possibility that naturally occurring triple helices are a source of genetic instability.
Cell Killing by the
Drosophila
Gene
reaper
Authors: White Kristin , Tahaoglu Elvan , Steller Hermann
Published: October 2006

The
reaper
gene (
rpr
) is important for the activation of apoptosis in
Drosophila
. To investigate whether
rpr
expression is sufficient to induce apoptosis, transgenic flies were generated that express
rpr
complementary DNA or the
rpr
open reading frame in cells that normally live. Transcription of
rpr
from a heat-inducible promoter rapidly caused widespread ectopic apoptosis and organismal death. Ectopic overexpression of
rpr
in the developing retina resulted in eye ablation. The occurrence of cell death was highly sensitive to the dosage of the transgene. Because cell death induced by the protein encoded by
rpr
(RPR) could be blocked by the baculovirus p35 protein, RPR appears to activate a death program mediated by a
ced-3
/ICE (interleukin-1 converting enzyme)-like protease.
Cold-Induced Expression of Δ
9
-Desaturase in Carp by Transcriptional and Posttranslational Mechanisms
Authors: Tiku P. E. , Gracey A. Y. , Macartney A. I. , Beynon R. J. , Cossins A. R.
Published: October 2006

Poikilothermic animals respond to chronic cold by increasing phosphoglyceride unsaturation to restore the fluidity of cold-rigidified membranes. Despite the importance of this compensatory response, the enzymes involved have not been clearly identified, and the mechanisms that control their activity are unknown. In carp liver, cold induces an 8- to 10-fold increase in specific activity of the microsomal stearoyl coenzyme A desaturase. Cold-induced up-regulation of gene transcription resulted in a 10-fold increase in desaturase transcript amounts after 48 to 60 hours. However, this increase was preceded by the activation of latent desaturase, probably by a posttranslational mechanism. These two mechanisms may act sequentially to match desaturase expression to the demands imposed by a progressive decrease in temperature.
Setting a Biological Stopwatch
Authors: Morell Virginia
Published: October 2006

The body's interval timer—a short-term timepiece separate from the better known circadian clock—used to be viewed as something close to a myth, but the neurobiological evidence is getting hard to ignore. This week, at the
annual meeting
of the American Association for the Advancement of Science, researchers detailed some of the clock's neural circuits, showed how disrupting them disrupts a sense of time in people and in animals, and how Parkinson's disease fouls the clock's gears.
Adding Depth to X-ray Maps
Authors: Glanz James
Published: October 2006

X-ray maps of the heavens, constructed from satellite data, indicate that the solar system is surrounded by a bubble of hot plasma emitting soft x-rays. But they don't reveal how extensive the bubble is because they contain no distance information. Now, Q. Daniel Wang of Northwestern University is beginning to add depth to x-ray images. At last month's American Astronomical Society meeting, he described a technique he calls “x-ray shadowing” that uses warm, dense clouds of neutral gas that happen to waft through our galactic neighborhood as a kind of cosmic range finder. His first results have rekindled a debate about the distribution of hot plasmas throughout the Milky Way.
Leishmania
Susceptibility Puzzle Gets Another Twist
Authors: Marx Jean
Published: October 2006

A strain of mice called BALB/c can't fight off infection by a parasitic protozoan called
Leishmania major
. Understanding why the animals fail to mount a cell-mediated immune attack on the parasite might help immunologists understand why human beings also vary in their susceptibility to
Leishmania
, which is believed to afflict 12 million people worldwide. Researchers have been following a promising lead: The animals appear to make an inappropriate antibody response, mediated by the cytokine interleukin-4 (IL-4). Now two papers in this issue (
pp. 984
and
987
) put that idea in doubt. They indicate that IL-4 is not involved at all, but rather that the animals' T cells are unable to respond to another cytokine, interleukin-12, that helps trigger cell-mediated immunity. Still, other immunologists, noting the large amount of contradictory data, are not yet ready to dismiss IL-4 as a cause of the animals'
Leishmania
susceptibility.
Do Big and Little Earthquakes Start Differently?
Authors: Vidale John E.
Published: October 2006

Can the occurrence of earthquakes be predicted? This question has profound social and scientific implications, but little is known about what triggers earthquakes or what precursor events might indicate one is about to happen. In his Perspective, Vidale reviews recent findings that attempt to resolve the question of whether large earthquakes are initiated by different mechanisms than smaller ones.
Catalytic Cleavage of the C-H and C-C Bonds of Alkanes by Surface Organometallic Chemistry: An EXAFS and IR Characterization of a Zr-H Catalyst
Authors: Corker Judith , Lefebvre Frédéric , Lécuyer Christine , Dufaud Véronique , Quignard Françoise , Choplin Agnès , Evans John , Basset Jean-Marie
Published: October 2006

The catalytic cleavage under hydrogen of the C-H and C-C bonds of alkanes with conventional catalysts requires high temperatures. Room-temperature hydrogenolysis of simple alkanes is possible on a well-defined and well-characterized zirconium hydride supported on silica obtained by surface organometallic chemistry. The surface structure resulting from hydrogenolysis of (≡SiO)Zr(Np)
3
(Np, neopentyl) was determined from the extended x-ray absorption fine structure (EXAFS) and
1
H and
29
Si solid-state nuclear magnetic resonance and infrared (IR) spectra. A mechanism for the formation of (≡SiO)
3
Zr-H and (≡SiO)
2
SiH
2
and the resulting low-temperature hydrogenolysis of alkanes is proposed. The mechanism may have implications for the catalytic formation of methane, ethane, and lower alkanes in natural gas.
Genetic Susceptibility to
Leishmania
: IL-12 Responsiveness in T
H
1 Cell Development
Authors: Güler Mehmet L. , Gorham James D. , Hsieh Chyi-Song , Mackey Aaron J. , Steen Robert G. , Dietrich William F. , Murphy Kenneth M.
Published: October 2006

The genetic background of T lymphocytes influences development of the T helper (T
H
) phenotype, resulting in either resistance or susceptibility of certain mouse strains to pathogens such as
Leishmania major
. With an in vitro model system, a difference in maintenance of responsiveness of T cells to interleukin-12 (IL-12) was detected between BALB/c and B10.D2 mice. Although naïve T cells from both strains initially responded to IL-12, BALB/c T cells lost IL-12 responsiveness after stimulation with antigen in vitro, even when cocultured with B10.D2 T cells. Thus, susceptibility of BALB/c mice to infection with
L. major
may derive from the loss of the ability to generate IL-12-induced T
H
1 responses rather than from an IL-4-induced T
H
2 response.
Susceptibility to
Leishmania major
Infection in Interleukin-4-Deficient Mice
Authors: Noben-Trauth Nancy , Kropf Pascale , Müller Ingrid
Published: October 2006

Interleukin-4 (IL-4), a pleiotropic cytokine, is a major regulator of the immune system and is considered crucial for the development of T helper cell type 2 (T
H
2) responses. The susceptibility of BALB/c mice to infection with
Leishmania major
has been associated with a polarized T
H
2 response and an inability to down-modulate IL-4 production. The role of IL-4 in vivo was examined directly by disrupting the IL-4 gene in BALB/c embryonic stem cells. Despite the absence of IL-4, the genetically pure BALB/c mutant mice remained susceptible to
L. major
infection, showed no signs of lesion healing or parasite clearance, and did not switch to a T
H
1 phenotype.
Big Science Is Booming in Japan
Authors: Normile Dennis
Published: October 2006

Tokyo—While many countries are struggling to make room for big science projects in constrained budgets, steady funding and scientific consensus have allowed Japan to build up an impressive array of large, cutting-edge research facilities. And that commitment is increasingly vital to the health of big science around the world.
AAAS Gathering Explores Animals, Aliens, and Atoms
Authors: Service Robert F. , Kerr Richard A. , Seachrist Lisa
Published: October 2006

Baltimore—A cross section of the scientific community, 4200 strong, came out for the 162nd Annual Meeting and Science Innovation Exposition of the American Association for the Advancement of Science (AAAS, the publisher of
Science
), held in Baltimore from 8 to 13 February. We covered early sessions last week (

Science
, 16 February, p. 903s

); this week we cover talks on “giant” molecules, precocious lemurs, and on how the search for extraterrestrial intelligence has fared under private funding.
A Split-Personality X-ray Beacon Tantalizes Theorists
Authors: Glanz James
Published: October 2006

Theorists are losing sleep over a brilliant x-ray source that appeared in the sky last December. The object, thousands of light-years away from Earth in the direction of the galactic center, is an unprecedented hybrid: the only known x-ray source that combines regular, oscillating emissions like those recorded from some sources with the erratic flashes seen from others. Theorists believed that those behaviors could not coexist, so the new object promises to shake up their understanding of the thousands of x-ray sources that dot the galaxy.
Initial Results of Radio Occultation Observations of Earth's Atmosphere Using the Global Positioning System
Authors: Kursinski E. R. , Hajj G. A. , Bertiger W. I. , Leroy S. S. , Meehan T. K. , Romans L. J. , Schofield J. T. , McCleese D. J. , Melbourne W. G. , Thornton C. L. , Yunck T. P. , Eyre J. R. , Nagatani R. N.
Published: October 2006

Recent radio occultation measurements using Global Positioning System satellite transmitters and an orbiting receiver have provided a globally distributed set of high-resolution atmospheric profiles, suggesting that the technique may make a significant contribution to global change and weather prediction programs. Biases in occultation temperatures relative to radiosonde and model data are about 1 kelvin or less in the tropics and are generally less than 0.5 kelvin at higher latitudes. Data quality is sufficient to quantify significant model errors in remote regions. Temperature profiles also reveal either an equatorial Rossby-gravity or an inertio-gravity wave. Such waves provide a fundamental source of momentum for the stratospheric circulation.
Heparin Structure and Interactions with Basic Fibroblast Growth Factor
Authors: Faham S. , Hileman R. E. , Fromm J. R. , Linhardt R. J. , Rees D. C.
Published: October 2006

Crystal structures of heparin-derived tetra- and hexasaccharides complexed with basic fibroblast growth factor (bFGF) were determined at resolutions of 1.9 and 2.2 angstroms, respectively. The heparin structure may be approximated as a helical polymer with a disaccharide rotation of 174° and a translation of 8.6 angstroms along the helix axis. Both molecules bound similarly to a region of the bFGF surface containing residues asparagine-28, arginine-121, lysine-126, and glutamine-135; the hexasaccharide also interacted with an additional binding site formed by lysine-27, asparagine-102, and lysine-136. No significant conformational change in bFGF occurred upon heparin oligosaccharide binding, which suggests that heparin primarily serves to juxtapose components of the FGF signal transduction pathway.
Locus Control Region Function and Heterochromatin-Induced Position Effect Variegation
Authors: Festenstein Richard , Tolaini Mauro , Corbella Paola , Mamalaki Clio , Parrington Jenny , Fox Margaret , Miliou Antigoni , Jones Margaret , Kioussis Dimitris
Published: October 2006

Human CD2 locus control region (LCR) sequences are shown here to be essential for establishing an open chromatin configuration. Transgenic mice carrying an hCD2 minigene attached only to the 3′ CD2 transcriptional enhancer exhibited variegated expression when the transgene integrated in the centromere. In contrast, mice carrying a transgene with additional 3′ sequences showed no variegation even when the latter integrated in centromeric positions. This result suggests that LCRs operate by ensuring an open chromatin configuration and that a short region, with no enhancer activity, functions in the establishment, maintenance, or both of an open chromatin domain.
Cool Gas in the Virgo Cluster?
Authors: Fabian Andrew C.
Published: October 2006

Galaxy clusters often contain hot intergalactic gas that emits x-rays. In his Perspective, Fabian discusses recent results by Lieu
et al.
[
Astrophys. J.
458
, L5 (1996)] showing an unusually high amount of x-radiation at lower energies. This could be the signature of a cooler component to the intergalactic gas, which may require reexamination of current cluster models.
Doping-Induced Change of Superconducting Gap Anisotropy in Bi
2
Sr
2
Ca
1
Cu
2
O
8+
δ
Authors: Kelley R. J. , Quitmann C. , Onellion M. , Berger H. , Almeras P. , Margaritondo G.
Published: October 2006

High-resolution angle-resolved photoemission measurements were performed on single crystals of Bi
2
Sr
2
Ca
1
Cu
2
O
8+
δ
with different oxygen stoichiometries. The data establish that the gap anisotropy (ratio of the gap along Γ-M to the gap along Γ-X) can be reversibly changed from ∼20:1 (optimal or underdoped) to ∼2:1 (overdoped). Differences in sample doping explain the conflicting reports on gap anisotropy in the literature. Possible effects of this change in gap anisotropy on the symmetry of the order parameter are discussed. There remains some ambiguity as to the relation between the order parameter and doping.
Isolated Neutron Stars
Authors: Bignami Giovanni F.
Published: October 2006

Neutron stars are formed in the stellar collapse following a supernova. Some of these, called isolated neutron stars, undergo a short but violent phase of x-ray emission before settling down as radio pulsars. In his Perspective, Bignami discusses recent observations of isolated neutron stars that were detected at short wavelengths and not at radio frequencies by the latest generation of astronomy satellites. Future analysis of such objects may lead to better understanding of their puzzling emission mechanisms.
The Expanding World of Trinucleotide Repeats
Authors: Warren Stephen T.
Published: October 2006

A paper in this week's issue of
Science
(Campuzano
et al.
,
p. 1423
) reports that Friedreich's ataxia has now joined the list of diseases caused by expanding trinucleotide repeats. In his Perspective, S. Warren discusses how some unusual features of the repeats in this disease challenge some generalizations that have been made about the mechanisms by which these unusual mutations cause disease.
Basins of Attraction
Authors: Nusse Helena E. , Yorke James A.
Published: October 2006

Many remarkable properties related to chaos have been found in the dynamics of nonlinear physical systems. These properties are often seen in detailed computer studies, but it is almost always impossible to establish these properties rigorously for specific physical systems. This article presents some strange properties about basins of attraction. In particular, a basin of attraction is a “Wada basin” if every point on the common boundary of that basin and another basin is also on the boundary of a third basin. The occurrence of this strange property can be established precisely because of the concept of a basin cell.
Understanding the Catalytic Behavior of Zeolites: A First-Principles Study of the Adsorption of Methanol
Authors: Shah Rajiv , Payne M. C. , Lee M.-H. , Gale Julian D.
Published: October 2006

Zeolites are microporous aluminosilicate materials used as industrial catalysts, and there is much interest in understanding their catalytic behavior. The adsorption of methanol in the catalytically active zeolite chabazite and in sodalite was examined by performing ab initio calculations within periodic boundary conditions. A direct correlation between zeolite structure and chemical activation of the adsorbate was found. Methanol was protonated without an activation energy by a Brønsted acid site, provided the molecule was situated in the eight-ring window of chabazite, whereas the same molecule was only physisorbed in more open cage regions, such as those found in sodalite.
Comparison of Radiative and Physiological Effects of Doubled Atmospheric CO
2
on Climate
Authors: Sellers P. J. , Bounoua L. , Collatz G. J. , Randall D. A. , Dazlich D. A. , Los S. O. , Berry J. A. , Fung I. , Tucker C. J. , Field C. B. , Jensen T. G.
Published: October 2006

The physiological response of terrestrial vegetation when directly exposed to an increase in atmospheric carbon dioxide (CO
2
) concentration could result in warming over the continents in addition to that due to the conventional CO
2
“greenhouse effect.” Results from a coupled biosphere-atmosphere model (SiB2-GCM) indicate that, for doubled CO
2
conditions, evapotranspiration will drop and air temperature will increase over the tropical continents, amplifying the changes resulting from atmospheric radiative effects. The range of responses in surface air temperature and terrestrial carbon uptake due to increased CO
2
are projected to be inversely related in the tropics year-round and inversely related during the growing season elsewhere.
The Amyloid Precursor Protein of Alzheimer's Disease in the Reduction of Copper(II) to Copper(I)
Authors: Multhaup Gerd , Schlicksupp Andrea , Hesse Lars , Beher Dirk , Ruppert Thomas , Masters Colin L. , Beyreuther Konrad
Published: October 2006

The transition metal ion copper(II) has a critical role in chronic neurologic diseases. The amyloid precursor protein (APP) of Alzheimer's disease or a synthetic peptide representing its copper-binding site reduced bound copper(II) to copper(I). This copper ion-mediated redox reaction led to disulfide bond formation in APP, which indicated that free sulfhydryl groups of APP were involved. Neither superoxide nor hydrogen peroxide had an effect on the kinetics of copper(II) reduction. The reduction of copper(II) to copper(I) by APP involves an electron-transfer reaction and could enhance the production of hydroxyl radicals, which could then attack nearby sites. Thus, copper-mediated toxicity may contribute to neurodegeneration in Alzheimer's disease.
Uncoupling of GTP Binding from Target Stimulation by a Single Mutation in the Transducin α Subunit
Authors: Mittal Rohit , Erickson Jon W. , Cerione Richard A.
Published: October 2006

Glutamic acid-203 of the alpha subunit of transducin (α
T
) resides within a domain that undergoes a guanosine triphosphate (GTP)-induced conformational change that is essential for effector recognition. Changing the glutamic acid to an alanine in bovine α
T
yielded an alpha subunit (α
T
E203A) that was fully dependent on rhodopsin for GTP-guanosine diphosphate (GDP) exchange and showed GTP hydrolytic activity similar to that measured for wild-type α
T
. However, unlike the wild-type protein, the GDP-bound form of α
T
E203A was constitutively active toward the effector of transducin, the cyclic guanosine monophosphate phosphodiesterase. Thus, the α
T
E203A mutant represents a short-circuited protein switch that no longer requires GTP for the activation of the effector target phosphodiesterase.
Rearrangement-Enhancing Element Upstream of the Mouse Immunoglobulin Kappa Chain J Cluster
Authors: Ferradini Laurent , Gu Hua , De Smet Annie , Rajewsky Klaus , Reynaud Claude-Agnès , Weill Jean-Claude
Published: October 2006

Transcriptional regulatory elements have been shown to be necessary but not sufficient for the developmental regulation of immunoglobulin gene rearrangement in mouse precursor B cells. In the chicken λ light chain locus, additional elements in the V-J intervening sequence are involved in negative and positive regulation of rearrangement. Here, mutation of the mouse homolog of a chicken element, located in the V
κ
-J
κ
intervening sequence upstream of the J
κ
cluster, was shown to significantly decrease rearrangement. This cis-acting recombination-enhancing element affects the rearrangement process without being involved in regulating transcription.
Study Inflames Ward Valley Controversy
Authors: Weisman Jonathan
Published: October 2006

Lawrence Livermore National Laboratory has been dragged reluctantly into the dispute over a planned low-level radioactive waste dump at Ward Valley, California. If the Department of Energy gives the nod, Livermore scientists would examine how fast radionuclides deposited decades ago by nuclear tests are permeating the soil at the dump site. The results could indicate whether contaminants from the dump—designed to hold waste from utilities, hospitals, and laboratories—could seep into California's water supply. But supporters of the dump view the study as a delaying tactic, and opponents question Livermore's impartiality.
Support Builds for Curbs on Lifetime Faculty Posts
Authors: Normile Dennis
Published: October 2006

Tokyo—Lifetime appointments to Japanese national universities are a tradition that has restricted the flow of scientists among institutions and between academia and industry. But an influential committee to the Ministry of Education appears ready to propose significant changes in the practice, a move that supporters say will improve the quality of research.
Biodiversity Is a Boon to Ecosystems, Not Species
Authors: Moffat Anne Simon
Published: October 2006

Ecologists have long been at odds over the value of biodiversity. Does it make an ecosystem more resilient and productive, or does it make it less stable, prone to drastic population swings? Both, according to a pair of years-long studies in the Minnesota prairie. Diversity stabilizes an ecosystem as a whole. But for individual species the complex interactions within a diverse ecosystem can lead to drastic fluctuations in abundance.
HIV-1 Dynamics in Vivo: Virion Clearance Rate, Infected Cell Life-Span, and Viral Generation Time
Authors: Perelson Alan S. , Neumann Avidan U. , Markowitz Martin , Leonard John M. , Ho David D.
Published: October 2006

A new mathematical model was used to analyze a detailed set of human immunodeficiency virus-type 1 (HIV-1) viral load data collected from five infected individuals after the administration of a potent inhibitor of HIV-1 protease. Productively infected cells were estimated to have, on average, a life-span of 2.2 days (half-life
t
1/2
= 1.6 days), and plasma virions were estimated to have a mean life-span of 0.3 days (
t
1/2
= 0.24 days). The estimated average total HIV-1 production was 10.3 × 10
9
virions per day, which is substantially greater than previous minimum estimates. The results also suggest that the minimum duration of the HIV-1 life cycle in vivo is 1.2 days on average, and that the average HIV-1 generation time—defined as the time from release of a virion until it infects another cell and causes the release of a new generation of viral particles—is 2.6 days. These findings on viral dynamics provide not only a kinetic picture of HIV-1 pathogenesis, but also theoretical principles to guide the development of treatment strategies.
Communists Dominate Science Panels
Authors: Pokrovsky Vladimir
Published: October 2006

Moscow—Last December's elections gave the Communist Party the largest bloc of seats in the Duma, the lower house of Russia's parliament. Communists now hold the majority of seats on the new Science and Education Committee, including the chair. Some members of the committee predict that it will become mired in infighting. But the chair, Ivan Melnikov, is widely respected, and he told Science he has high hopes that the committee will transcend petty factionalism. One of its first acts, at least, shows promise: It sponsored a debate in the Duma that offered strong support for the Russian Academy of Sciences in its efforts to secure long-overdue budget payments.
Are Single Molecular Wires Conducting?
Authors: Bumm L. A. , Arnold J. J. , Cygan M. T. , Dunbar T. D. , Burgin T. P. , Jones L. , Allara D. L. , Tour J. M. , Weiss P. S.
Published: October 2006

Molecular wire candidates inserted into “nonconducting”
n
-dodecanethiol self-assembled monolayers on Au{111} were probed by scanning tunneling microscopy (STM) and microwave frequency alternating current STM at high tunnel junction impedance (100 gigohms) to assess their electrical properties. The inserted conjugated molecules, which were 4,4′-di(phenylene-ethynylene)benzenethiolate derivatives, formed single molecular wires that extended from the Au{111} substrate to about 7 angstroms above and had very high conductivity as compared with that of the alkanethiolate.
Gravitational Enrichment of
84
Kr/
36
Ar Ratios in Polar Ice Caps: A Measure of Firn Thickness and Accumulation Temperature
Authors: Craig H. , Wiens R. C.
Published: October 2006

Measurements of
84
Kr/
36
Ar ratios in Greenland ice show that gravitational separation in the firn layer is responsible for the enrichments relative to atmospheric ratios. The
84
Kr/
36
Ar ratio is enriched by 12.8 per mil and is 24 times the
18
O/
16
O enrichment in trapped O
2
, as predicted for gravitational fractionation. Because gravitational enrichment depends on firn thickness, which in turn depends on annual mean temperature, noble gas ratios provide a method for determining paleotemperatures and ancient firn thicknesses in polar ice caps. The gravitational effects are modulated by about 10 to 15 percent by atmospheric concentration changes caused by temperature effects on oceanic gas solubilities. The availability of five noble gases should make it possible to deconvolute the solubility and gravitational enrichments for calibration of
18
O paleotemperatures throughout the polar ice sheets.
Induction of Protective CTL Responses in Newborn Mice by a Murine Retrovirus
Authors: Sarzotti Marcella , Robbins Deanna S. , Hoffman Paul M.
Published: October 2006

The susceptibility of neonates to virus-induced disease is thought to reflect, in part, the immaturity of their immune systems. However, inoculation of newborn mice with low doses of Cas-Br-M murine leukemia virus induced a protective cytotoxic T lymphocyte (CTL) response. The inability of neonates to develop a CTL response to high doses of virus was not the result of immunological immaturity but correlated with the induction of a nonprotective type 2 cytokine response. Thus, the initial viral dose is critical in the development of protective immunity in newborns.
Diversity Takes a Student Body Blow
Authors: Holden Constance
Published: October 2006

5257 1801 1801 271 Holden, Constance Alarms rang on campuses across the United States last week after a court ruled that the University of Texas (UT) law school's admissions policies violated the U.S. Constitution's guarantee of equal protection under the law by giving preference to blacks and Hispanics over whites. The ruling could dismantle programs to improve minority admissions rates at U.S. professional schools. And while its effects on science graduate programs are likely to be indirect, primarily shrinking the undergraduate pool of minority applicants, observers say they could still be profound.
"Amplifying" the Fine Details of Molecular Structure Is a Gas
Authors: Service Robert F.
Published: October 2006

Certain atoms on proteins and other molecules resonate at unique frequencies in a magnetic field, giving off signals that can indicate what these molecules are made of. But these signatures are weak, so researchers “listening” for them with nuclear magnetic resonance (NMR) spectroscopy struggle to make out the fine details. In this issue (
p. 1848
), scientists report a way to get hydrogen atoms to sound off at a higher level, using xenon gas as a “preamplifier.” The xenon atoms are pretreated to give off a powerful magnetic signal, and they in turn raise the volume of the hydrogens when the two types of atoms come in contact. The result may be a boon not only for those interested in molecular structure, but for medical imaging as well, which uses similar methods.
Minerals in Rock Mass Hold Clues to 400-Kilometer Ascent
Authors: Kerr Richard A.
Published: October 2006

As a rule, rocks don't have much vertical mobility in the planet. But a report in this issue (
p. 1841
) breaks that rule by presenting evidence that a chunk of rock in the Swiss Alps once rested 400 kilometers or more down in the mantle. The shape and composition of tiny mineral grains in the half-kilometer rock mass imply that they were sweated out of the surrounding material as the rock rose from deep in the Earth. The researchers speculate that the ascent took place when the deep rock was caught in a region of light crustal rock that had been forced deep into the planet during a continental collision, then bobbed back to the surface.
Science and Diversity: A Compelling National Interest
Authors: Malcom Shirley M.
Published: October 2006

Affirmative action has emerged as a center-stage issue in higher education. This policy forum reviews the history of affirmative action, its impact on science and engineering, and the status of the groups affected by affirmative action policies. Structural changes are suggested that may lead to widespread adoption of practices that support diversity and inclusion in science and engineering.
Chemical Communication in Honeybees
Authors: Robinson Gene E.
Published: October 2006

In a paper in this issue, Plettner
et al.
(
p. 1851
) describe the biosynthesis of honeybee queen mandibular pheromone. In his Perspective, Robinson discusses the social behaviors of bees that are controlled by this pheromone and highlights why elucidation of this pathway is a particularly significant achievement in the field of chemical ecology.

Before 1 July 1996, the author will be in the Department of Biological Chemistry and the Charles E. Smith Family Laboratory for Collaborative Research in Psychobiology, Hebrew University, Jerusalem, Israel 91904.
mailto:generobi@pop.life.uiuc.edu
After 1 July, he will be in the Department of Entomology, University of Illinois, 505 South Goodwin Avenue, Urbana, IL 61801, USA.
Interaction Between Wingless and Notch Signaling Pathways Mediated by Dishevelled
Authors: Axelrod Jeffrey D. , Matsuno Kenji , Artavanis-Tsakonas Spyros , Perrimon Norbert
Published: October 2006

In
Drosophila
, the Wingless and Notch signaling pathways function in many of the same developmental patterning events. Genetic analysis demonstrates that the
dishevelled
gene, which encodes a molecule previously implicated in implementation of the Wingless signal, interacts antagonistically with Notch and one of its known ligands, Delta. A direct physical interaction between Dishevelled and the Notch carboxyl terminus, distal to the cdc10/ankyrin repeats, suggests a mechanism for this interaction. It is proposed that Dishevelled, in addition to transducing the Wingless signal, blocks Notch signaling directly, thus providing a molecular mechanism for the inhibitory cross talk observed between these pathways.
Altered Sensory Processing in the Somatosensory Cortex of the Mouse Mutant Barrelless
Authors: Welker E. , Armstrong-James M. , Bronchti G. , Ourednik W. , Gheorghita-Baechler F. , Dubois R. , Guernsey D. L. , Van der Loos H. , Neumann P. E.
Published: October 2006

Mice homozygous for the
barrelless
(
brl
) mutation, mapped here to chromosome 11, lack barrel-shaped arrays of cell clusters termed “barrels” in the primary somatosensory cortex. Deoxyglucose uptake demonstrated that the topology of the cortical whisker representation is nevertheless preserved. Anterograde tracers revealed a lack of spatial segregation of thalamic afferents into individual barrel territories, and single-cell recordings demonstrated a lack of temporal discrimination of center from surround information. Thus, structural segregation of thalamic inputs is not essential to generate topological order in the somatosensory cortex, but it is required for discrete spatiotemporal relay of sensory information to the cortex.
Replay of Neuronal Firing Sequences in Rat Hippocampus During Sleep Following Spatial Experience
Authors: Skaggs William E. , McNaughton Bruce L.
Published: October 2006

The correlated activity of rat hippocampal pyramidal cells during sleep reflects the activity of those cells during earlier spatial exploration. Now the patterns of activity during sleep have also been found to reflect the order in which the cells fired during spatial exploration. This relation was reliably stronger for sleep after the behavioral session than before it; thus, the activity during sleep reflects changes produced by experience. This memory for temporal order of neuronal firing could be produced by an interaction between the temporal integration properties of long-term potentiation and the phase shifting of spike activity with respect to the hippocampal theta rhythm.
Age-Dependent Diarrhea Induced by a Rotaviral Nonstructural Glycoprotein
Authors: Ball Judith M. , Tian Peng , Zeng Carl Q.-Y. , Morris Andrew P. , Estes Mary K.
Published: October 2006

The rotavirus nonstructural glycoprotein NSP4 is an intracellular receptor that mediates the acquisition of a transient membrane envelope as subviral particles bud into the endoplasmic reticulum. NSP4 also causes an increase in intracellular calcium in insect cells. Purified NSP4 or a peptide corresponding to NSP4 residues 114 to 135 induced diarrhea in young (6 to 10 days old) CD1 mice. This disease response was age-dependent, dose-dependent, and specific. Electrophysiologic data from intestinal mucosa showed that the NSP4 114–135 peptide potentiates chloride secretion by a calcium-dependent signaling pathway. Diarrhea is induced when NSP4, acting as a viral enterotoxin, triggers a signal transduction pathway.
Protective Effect of Rotavirus VP6-Specific IgA Monoclonal Antibodies That Lack Neutralizing Activity
Authors: Burns John W. , Siadat-Pajouh Majid , Krishnaney Ajit A. , Greenberg Harry B.
Published: October 2006

Rotaviruses are the leading cause of severe gastroenteritis and dehydrating diarrhea in young children and animals worldwide. A murine model and “backpack tumor” transplantation were used to determine the protective effect of antibodies against VP4 (an outer capsid viral protein) and VP6 (a major inner capsid viral protein). Only two non-neutralizing immunoglobulin A (IgA) antibodies to VP6 were capable of preventing primary and resolving chronic murine rotavirus infections. These antibodies were not active, however, when presented directly to the luminal side of the intestinal tract. These findings support the hypothesis that in vivo intracellular viral inactivation by secretory IgA during transcytosis is a mechanism of host defense against rotavirus infection.
Manic-Depression Findings Spark Polarized Debate
Authors: Morell Virginia
Published: October 2006

For researchers trying to decipher the genetics of manic depression, the past decade has been a long “down” period with few “up” interludes. Candidate genetic loci on different chromosomes have been announced, disproved, and cast aside with dispiriting frequency. Scientists now think the illness likely involves interactions among many genes, and two research groups have just published some of the first studies designed to search for multiple genes. But in a debate mirroring the polarized nature of the disease, some researchers see their results—which identify possible loci on chromosomes 6, 13, 15, and 18—as signs of an upswing, while others take a darker view and doubt the new work is much of an improvement over the past.
Fullerene Formation and Annealing
Authors: Mintmire J. W.
Published: October 2006

The symmetric carbon molecule C
60
, also known as buckminsterfullerene, can be synthesized in macroscopic quantities, yet no satisfactory theoretical model of its creation exists. In his Perspective, Mintmire discusses calculations by Eggen
et al.
in the same issue (
p. 87
) suggesting that atomic carbon may act as a catalyst during fullerene formation in a carbon arc, thus enabling open graphitic sheets to anneal into closed structures.
New Lessons for Rotavirus Vaccines
Authors: Glass Roger I. , Gentsch Jon R. , Ivanoff Bernard
Published: October 2006

Rotavirus infects nearly all humans early in their lives and can sometimes prove dangerous or fatal. In his Perspective, Glass recounts the successes of first and second generation vaccines against rotaviruses. Nevertheless he believes that two papers in this week's issue [Ball
et al.
(
p. 101
) and Burns
et al.
(
p. 104
)] illuminate aspects of the virulence of rotavirus and its susceptibility to immune attack that may guide the development of an even more effective third generation vaccine.
The Instructive Role of Innate Immunity in the Acquired Immune Response
Authors: Fearon Douglas T. , Locksley Richard M.
Published: October 2006

Innate immunity has been considered only to provide rapid, incomplete antimicrobial host defense until the slower, more definitive acquired immune response develops. However, innate immunity may have an additional role in determining which antigens the acquired immune system responds to and the nature of that response. Knowledge of the molecules and pathways involved may create new therapeutic options for infectious and autoimmune diseases.
Homogeneous NMR Spectra in Inhomogeneous Fields
Authors: Vathyam Sujatha , Lee Sanghyuk , Warren Warren S.
Published: October 2006

Researchers interested in high-resolution nuclear magnetic resonance (NMR) spectroscopy have long sought higher magnetic fields to enhance resolution and simplify spectra. Magnets with substantially larger fields than those available in the best commercial spectrometers are available, but the inhomogeneity is unacceptable for high-resolution spectra. A detection method (termed HOMOGENIZED) is presented that removes inhomogeneity while retaining chemical shift differences and
J
couplings. With existing inhomogeneous magnets, this method could nearly double the largest resonance frequency available for high-resolution NMR. The HOMOGENIZED sequence is based on observations of intermolecular zero-quantum coherences between a solute molecule and solvent molecules that are micrometers away; as long as the field is homogeneous over this short distance, sharp resonances are recovered without echoes. Experimental demonstrations and a detailed density matrix theory to explain the effect are presented.
The Energetics of Hydrogen Bonds in Model Systems: Implications for Enzymatic Catalysis
Authors: Shan Shu-ou , Loh Stewart , Herschlag Daniel
Published: October 2006

Low-barrier or short, strong hydrogen bonds have been proposed to contribute 10 to 20 kilocalories per mole to transition-state stabilization in enzymatic catalysis. The proposal invokes a large increase in hydrogen bond energy when the p
K
a
values of the donor and acceptor (where
K
a
is the acid constant) become matched in the transition state (Δp
K
a
= 0). This hypothesis was tested by investigating the energetics of hydrogen bonds as a function of Δp
K
a
for homologous series of compounds under nonaqueous conditions that are conducive to the formation of low-barrier hydrogen bonds. In all cases, there was a linear correlation between the increase in hydrogen-bond energy and the decrease in Δp
K
a
, as expected from simple electrostatic effects. However, no additional energetic contribution to the hydrogen bond was observed at Δp
K
a
= 0. These results and those of other model studies suggest alternative mechanisms by which hydrogen bonds can contribute to enzymatic catalysis, in accord with conventional electrostatic considerations.
A Disconnect for NTT Labs?
Authors: Normile Dennis
Published: October 2006

Tokyo—One of Japan's leading industrial labs could be broken up as part of a proposed restructuring of Nippon Telegraph & Telephone Corp. (NTT). The idea, a political hot potato, has also sparked intense debate in the research community. Scientists and industrial leaders warn it would weaken basic science in Japan, while government officials argue that increased competition would bolster research
Australia Fends Off Critic of Plan to Eradicate Rabbits
Authors: Drollette Dan
Published: October 2006

Geelong, Australia—A plan to study the natural course of the Rabbit Hemorrhagic Disease (RHD) virus, also known as Rabbit Calicivirus Disease, among a quarantined population of feral rabbits went awry last fall when the virus escaped and spread to the mainland. Now the Australian government is awaiting approval for a large-scale release of the deadly virus in an effort to free the country of a $115-million-a-year scourge. A U.S. virologist, however, is waging a vocal campaign to delay the release until more is known about the virus's ability to infect other animals, including humans.
Chemists Clean Ceramics and Coat Enzymes in Plastic
Authors: Service Robert F.
Published: October 2006

New Orleans—Southern hospitality welcomed nearly 13,000 scientists here from 24 to 28 March for the 210th national meeting of the American Chemical Society (ACS). In return, researchers shared their ideas on topics including ways to take toxic chemicals out of the ceramics production line, push up the catalytic activity of enzyme-plastic hybrids in organic solvents, and drive up student interest in chemistry.
Error-Correcting Code Keeps Quantum Computers on Track
Authors: Cipra Barry
Published: October 2006

Quantum computers, which could exploit systems such as the energy states of a row of atoms to perform vast numbers of computations at the same time, have remained in the realm of fantasy. A major barrier has been the fragility of quantum states, which makes quantum systems vulnerable to errors. Classical error-correction schemes won't work in a quantum computer, because they rely on duplicate bits, and in quantum systems information vanishes when you read and copy it. A new mathematical scheme, however, makes it possible—at least in theory—to nudge a quantum system back into line without directly looking at it. Computers/Math
A History of Global Metal Pollution
Authors: Nriagu Jerome O.
Published: October 2006

Pollution caused by heavy metals can be traced back to the Roman Empire. In his Perspective, Nriagu considers the historical record of metal pollution and discusses results published in the same issue by Honget al.(p. 246) in which ice core records were used to determine the quantity of copper emitted into the atmosphere by ancient smelters.
Long-Term Effects of Acid Rain: Response and Recovery of a Forest Ecosystem
Authors: Likens G. E. , Driscoll C. T. , Buso D. C.
Published: October 2006

Long-term data from the Hubbard Brook Experimental Forest, New Hampshire, suggest that although changes in stream pH have been relatively small, large quantities of calcium and magnesium have been lost from the soil complex and exported by drainage water because of inputs of acid rain and declines in atmospheric deposition of base cations. As a result, the recovery of soil and streamwater chemistry in response to any decreases in acid deposition will be delayed significantly.
In Vivo Gene Delivery and Stable Transduction of Nondividing Cells by a Lentiviral Vector
Authors: Naldini Luigi , Blömer Ulrike , Gallay Philippe , Ory Daniel , Mulligan Richard , Gage Fred H. , Verma Inder M. , Trono Didier
Published: October 2006

A retroviral vector system based on the human immunodeficiency virus (HIV) was developed that, in contrast to a murine leukemia virus-based counterpart, transduced heterologous sequences into HeLa cells and rat fibroblasts blocked in the cell cycle, as well as into human primary macrophages. Additionally, the HIV vector could mediate stable in vivo gene transfer into terminally differentiated neurons. The ability of HIV-based viral vectors to deliver genes in vivo into nondividing cells could increase the applicability of retroviral vectors in human gene therapy.
Green Light for Steroid Hormones
Authors: Russell David W.
Published: October 2006

Plants do not use steroid hormones for intercellular communication. In his Perspective, D. Russell describes how this truism is now proven incorrect by two papers—one in this week's issue of
Science
(Li
et al
.,
p. 398
) and one in the 19 April issue of
Cell
(M. Szekeres
et al
.)—in which two enzymes that synthesize steroid hormones are cloned from
Arabidopsis
. These enzymes, DET2 and CPD, are in the biosynthetic pathway for brassinolides, steroids that seem to participate in the regulation of gene expression by light.
Paleoindian Cave Dwellers in the Amazon: The Peopling of the Americas
Authors: Roosevelt A. C. , Lima da Costa M. , Machado C. Lopes , Michab M. , Mercier N. , Valladas H. , Feathers J. , Barnett W. , Imazio da Silveira M. , Henderson A. , Sliva J. , Chernoff B. , Reese D. S. , Holman J. A. , Toth N. , Schick K.
Published: October 2006

A Paleoindian campsite has been uncovered in stratified prehistoric deposits in Caverna da Pedra Pintada at Monte Alegre in the Brazilian Amazon. Fifty-six radiocarbon dates on carbonized plant remains and 13 luminescence dates on lithics and sediment indicate a late Pleistocene age contemporary with North American Paleoindians. Paintings, triangular bifacial spear points, and other tools in the cave document a culture distinct from North American cultures. Carbonized tree fruits and wood and faunal remains reveal a broad-spectrum economy of humid tropical forest and riverine foraging. The existence of this and related cultures east of the Andes changes understanding of the migrations and ecological adaptations of early foragers.
Engineered Interfaces for Adherent Diamond Coatings on Large Thermal-Expansion Coefficient Mismatched Substrates
Authors: Singh Rajiv K. , Gilbert D. R. , Fitz-Gerald J. , Harkness S. , Lee D. G.
Published: October 2006

Adhesion of thin or thick films on substrates is a critical issue in systems where the thermal-expansion coefficients of the coating and bulk material are significantly different from each other. The large mismatch of the expansion coefficients results in the generation of very high stresses in the coating that may lead to delamination, cracking, or other deleterious effects. A method to increase the adherence of diamond coatings on tungsten-carbide and stainless steel substrates is reported based on a substrate-modification process that creates a three-dimensional thermally and compositionally graded interface. Scratch and indentation tests on diamond-coated steel and tungsten-carbide samples did not exhibit film fracture at the interface and concomitant catastrophic propagation of interfacial cracks.
A Role for Brassinosteroids in Light-Dependent Development of

Arabidopsis
Authors: Li Jianming , Nagpal Punita , Vitart Veronique , McMorris Trevor C. , Chory Joanne
Published: October 2006

Although steroid hormones are important for animal development, the physiological role of plant steroids is unknown. The
Arabidopsis DET2
gene encodes a protein that shares significant sequence identity with mammalian steroid 5α-reductases. A mutation of glutamate 204, which is absolutely required for the activity of human steroid reductase, abolishes the in vivo activity of DET2 and leads to defects in light-regulated development that can be ameliorated by application of a plant steroid, brassinolide. Thus,
DET2
may encode a reductase in the brassinolide biosynthetic pathway, and brassinosteroids may constitute a distinct class of phytohormones with an important role in light-regulated development of higher plants.