bluuebunny/crossref_metadata_2025 huggingface dataset:
Infiltration of a Hawaiian Community by Introduced Biological Control Agents
Authors: Henneman M. L. , Memmott J.
Published: July 2002

To examine the community-wide effects of introduced biocontrol agents on Kauai Island, Hawaii, we constructed quantitative food webs showing interactions among plants, moths, and moth parasitoids in a native forest. Eighty-three percent of parasitoids reared from native moths were biological control agents, 14% were accidental immigrants, and 3% were native species. Although parasitism by biological control agents reached 28% in some species of moth, all biocontrol agents reared had been released before 1945. This study highlights the importance of considering the potential damage caused by an introduced control agent, in addition to that caused by the target alien species.
Chiral Sign Induction by Vortices During the Formation of Mesophases in Stirred Solutions
Authors: Ribó Josep M. , Crusats Joaquim , Sagués Francesc , Claret Josep , Rubires Raimon
Published: July 2002

Achiral diprotonated porphyrins, forming homoassociates in aqueous solution, lead to spontaneous chiral symmetry breaking. The unexpected result is that the chirality sign of these homoassociates can be selected by vortex motion during the aggregation process. This result is confirmed by means of circular dichroism spectra. These experimental findings are rationalized in terms of the asymmetric influence of macroscopic forces on bifurcation scenarios and by considering the specific binding characteristics of the porphyrin units to form the homoassociates.
Seasonal Modulation of Interseismic Strain Buildup in Northeastern Japan Driven by Snow Loads
Authors: Heki Kosuke
Published: July 2002

Distinct periodic variations with annual frequencies are often found in the time series of continuous Global Positioning System (GPS) site coordinates in northeastern Japan. They show maximum arc-normal contraction of a few millimeters as well as maximum subsidence of 1 to 2 centimeters, both in March. In northeastern Japan, it snows heavily on the western flank of the backbone range, attaining a maximum depth of several meters in March. When observed snow depths were compared with the load distribution estimated from the GPS data, the surface loads caused by the snow were found to be largely responsible for the annual displacement of GPS sites. The snow load modulates secular strain buildup in northeastern Japan due to the Pacific Plate subduction, but its relevance to the seasonal change of earthquake occurrences remains uncertain.
Spatiotemporal Self-Organization in a Surface Reaction: From the Atomic to the Mesoscopic Scale
Authors: Sachs C. , Hildebrand M. , Völkening S. , Wintterlin J. , Ertl G.
Published: July 2002

Scanning tunneling microscopy data revealed the atomic processes in propagating reaction fronts that occur in the catalytic oxidation of hydrogen on Pt(111). The fronts were also characterized on mesoscopic length scales with respect to their velocity and width. Simulations on the basis of a reaction-diffusion model reproduce the experimental findings qualitatively well. The quantitative comparison reveals the limitations of this traditional approach to modeling spatiotemporal pattern formation in nonlinear dynamics.
Signal Transduction and the Control of Gene Expression
Authors: Brivanlou Ali H. , Darnell James E.
Published: July 2002

More than 2000 transcription factors are encoded in the human genome. Such proteins have often been classified according to common structural elements. But because transcription factors evolved in the service of biologic function, we propose an alternative grouping of eukaryotic transcription factors on the basis of characteristics that describe their roles within cellular regulatory circuits.
Isolation and Structural Characterization of 1-Zirconacyclopent-3-yne, Five-Membered Cyclic Alkynes
Authors: Suzuki Noriyuki , Nishiura Masayoshi , Wakatsuki Yasuo
Published: July 2002

Stable five-membered cyclic alkynes were synthesized, isolated, and fully characterized. Divalent zirconium species, bis(cyclopentadienyl)zirconium(II) equivalent, reacted with (
Z
)-1,4-disubstituted 1,2,3-butatrienes [(
Z
)-R-CH=C=C=CH-R,
1a
: R = (CH
3
)
3
Si-,
1b
: R =
tert
-C
4
H
9
-] to give 1-zirconacyclopent-3-yne compounds (
2a-b
) in good yields. X-ray diffraction analysis revealed their five-membered cyclic structure with a sufficiently short triple bond to regard this compound as a metallacyclopentyne.
Complete Development of Mosquito Phases of the Malaria Parasite in Vitro
Authors: Al-Olayan Ebtesam M. , Beetsma Annette L. , Butcher Geoff A. , Sinden Robert E. , Hurd Hilary
Published: July 2002

Methods for reproducible in vitro development of the mosquito stages of malaria parasites to produce infective sporozoites have been elusive for over 40 years. We have cultured gametocytes of
Plasmodium berghei
through to infectious sporozoites with efficiencies similar to those recorded in vivo and without the need for salivary gland invasion. Oocysts developed extracellularly in a system whose essential elements include co-cultured
Drosophila
S2 cells, basement membrane matrix, and insect tissue culture medium. Sporozoite production required the presence of para-aminobenzoic acid. The entire life cycle of
P. berghei
, a useful model malaria parasite, can now be achieved in vitro
.
Extraction of Black Hole Rotational Energy by a Magnetic Field and the Formation of Relativistic Jets
Authors: Koide Shinji , Shibata Kazunari , Kudoh Takahiro , Meier David L.
Published: July 2002

Using numerical simulations, we modeled the general relativistic magnetohydrodynamic behavior of a plasma flowing into a rapidly rotating black hole in a large-scale magnetic field. The results show that a torsional Alfvén wave is generated by the rotational dragging of space near the black hole. The wave transports energy along the magnetic field lines outward, causing the total energy of the plasma near the hole to decrease to negative values. When this negative energy plasma enters the horizon, the rotational energy of the black hole decreases. Through this process, the energy of the spinning black hole is extracted magnetically
Molecular Determinants for the Tissue Specificity of SERMs
Authors: Shang Yongfeng , Brown Myles
Published: July 2002

Selective estrogen receptor modulators (SERMs) mimic estrogen action in certain tissues while opposing it in others. The therapeutic effectiveness of SERMs such as tamoxifen and raloxifene in breast cancer depends on their antiestrogenic activity. In the uterus, however, tamoxifen is estrogenic. Here, we show that both tamoxifen and raloxifene induce the recruitment of corepressors to target gene promoters in mammary cells. In endometrial cells, tamoxifen, but not raloxifene, acts like estrogen by stimulating the recruitment of coactivators to a subset of genes. The estrogen-like activity of tamoxifen in the uterus requires a high level of steroid receptor coactivator 1 (SRC-1) expression. Thus cell type– and promoter-specific differences in coregulator recruitment determine the cellular response to SERMs.
DNA Repair Pathway Stimulated by the Forkhead Transcription Factor FOXO3a Through the Gadd45 Protein
Authors: Tran Hien , Brunet Anne , Grenier Jill M. , Datta Sandeep R. , Fornace Albert J. , DiStefano Peter S. , Chiang Lillian W. , Greenberg Michael E.
Published: July 2002

The signaling pathway from phosphoinositide 3-kinase to the protein kinase Akt controls organismal life-span in invertebrates and cell survival and proliferation in mammals by inhibiting the activity of members of the FOXO family of transcription factors. We show that mammalian FOXO3a also functions at the G
2
to M checkpoint in the cell cycle and triggers the repair of damaged DNA. By gene array analysis, FOXO3a was found to modulate the expression of several genes that regulate the cellular response to stress at the G
2
-M checkpoint. The growth arrest and DNA damage response gene
Gadd45a
appeared to be a direct target of FOXO3a that mediates part of FOXO3a's effects on DNA repair. These findings indicate that in mammals FOXO3a regulates the resistance of cells to stress by inducing DNA repair and thereby may also affect organismal life-span.
Interpretation of Recent Southern Hemisphere Climate Change
Authors: Thompson David W. J. , Solomon Susan
Published: July 2002

Climate variability in the high-latitude Southern Hemisphere (SH) is dominated by the SH annular mode, a large-scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex. We present evidence that recent trends in the SH tropospheric circulation can be interpreted as a bias toward the high-index polarity of this pattern, with stronger westerly flow encircling the polar cap. It is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex, which are due largely to photochemical ozone losses. During the summer-fall season, the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the Antarctic Peninsula and Patagonia and to the cooling over eastern Antarctica and the Antarctic plateau.
Global Azimuthal Anisotropy in the Transition Zone
Authors: Trampert Jeannot , van Heijst Hendrik Jan
Published: July 2002

Surface wave dispersion measurements for Love wave overtones carry evidence of azimuthal anisotropy in the transition zone of Earth's mantle (400 to 660 kilometers deep). A Backus-Gilbert inversion of anisotropic phase velocity maps, with resolution kernels mainly sensitive to the transition zone, shows a robust long-wavelength azimuthally anisotropic velocity structure. This observation puts new constraints on the mineralogy and dynamics of the transition zone because this anisotropy may result from aligned minerals, tilted laminated structures, or even organized pockets of fluid inclusions.
RopGAP4-Dependent Rop GTPase Rheostat Control of
Arabidopsis
Oxygen Deprivation Tolerance
Authors: Baxter-Burrell Airica , Yang Zhenbiao , Springer Patricia S. , Bailey-Serres Julia
Published: July 2002

Transient soil flooding limits cellular oxygen to roots and reduces crop yield. Plant response to oxygen deprivation involves increased expression of the alcohol dehydrogenase gene (
ADH
) and ethanolic fermentation. Disruption of the
Arabidopsis
gene that encodes Rop (RHO-like small G protein of plants) guanosine triphosphatase (GTPase) activating protein 4 (
ROPGAP4
), a Rop deactivator, elevates
ADH
expression in response to oxygen deprivation but decreases tolerance to stress. Rop-dependent production of hydrogen peroxide via a diphenylene iodonium chloride–sensitive calcium-dependent reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is necessary for induction of both
ADH
and
RopGAP4
expression. Tolerance to oxygen deprivation requires Rop activation and
RopGAP4
-dependent negative feedback regulation. This Rop signal transduction rheostat balances the ability to increase ethanolic fermentation with survival.
Mapping of a Gene for Parkinson's Disease to Chromosome 4q21-q23
Authors: Polymeropoulos Mihael H. , Higgins Joseph J. , Golbe Lawrence I. , Johnson William G. , Ide Susan E. , Di Iorio Giuseppe , Sanges Giuseppe , Stenroos Edward S. , Pho Lana T. , Schaffer Alejandro A. , Lazzarini Alice M. , Nussbaum Robert L. , Duvoisin Roger C.
Published: July 2002

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, affecting approximately 1 percent of the population over age 50. Recent studies have confirmed significant familial aggregation of PD and a large number of large multicase families have been documented. Genetic markers on chromosome 4q21-q23 were found to be linked to the PD phenotype in a large kindred with autosomal dominant PD, with a
Z
max
= 6.00 for marker
D4S2380
. This finding will facilitate identification of the gene and research on the pathogenesis of PD.
Draft Research Code Raises Hackles
Authors: Holden Constance
Published: July 2002

A draft code for research with human subjects in Canada has the research community in an uproar. Advocates say it will foster a “subject-centered perspective” in research, while critics contend it will make funding decisions vulnerable to political pressures.
Attenuation of the Obesity Syndrome of
ob/ob
Mice by the Loss of Neuropeptide Y
Authors: Erickson Jay C. , Hollopeter Gunther , Palmiter Richard D.
Published: July 2002

The obesity syndrome of
ob
/
ob
mice results from lack of leptin, a hormone released by fat cells that acts in the brain to suppress feeding and stimulate metabolism. Neuropeptide Y (NPY) is a neuromodulator implicated in the control of energy balance and is overproduced in the hypothalamus of
ob
/
ob
mice. To determine the role of NPY in the response to leptin deficiency,
ob
/
ob
mice deficient for NPY were generated. In the absence of NPY,
ob
/
ob
mice are less obese because of reduced food intake and increased energy expenditure, and are less severely affected by diabetes, sterility, and somatotropic defects. These results suggest that NPY is a central effector of leptin deficiency.
Multiple Extracellular Elements of CCR5 and HIV-1 Entry: Dissociation from Response to Chemokines
Authors: Atchison Robert E. , Gosling Jennifa , Monteclaro Felipe S. , Franci Christian , Digilio Laura , Charo Israel F. , Goldsmith Mark A.
Published: July 2002

The human β-chemokine receptor CCR5 is an important cofactor for entry of human immunodeficiency virus-type 1 (HIV-1). The murine form of CCR5, despite its 82 percent identity to the human form, was not functional as an HIV-1 coreceptor. HIV-1 entry function could be reconstituted by fusion of various individual elements derived from the extracellular region of human CCR5 onto murine CCR5. Analysis of chimeras containing elements from human CCR5 and human CCR2B suggested that a complex structure rather than single contact sites is responsible for facilitation of viral entry. Further, certain chimeras lacking the domains necessary to signal in response to their natural chemokine ligands retained vigorous HIV-1 coreceptor activity.
Mining the Deep Field
Authors: Vogel Gretchen
Published: July 2002

A year ago, the Hubble Space Telescope took the most penetrating look ever out into space and back in time, capturing galaxies and their precursors when the universe was less than 10% of its current age. Now astronomers are extracting cosmic history from the image. Among other things, they've chronicled how the universe turned primordial gas into stars and galaxies and picked out individual objects that may be the most distant ever seen.
Loss of Heterozygosity in Normal Tissue Adjacent to Breast Carcinomas
Authors: Deng Guoren , Lu You , Zlotnikov Galina , Thor Ann D. , Smith Helene S.
Published: July 2002

Loss of heterozygosity (LOH) was detected in morphologically normal lobules adjacent to breast cancers. The most frequent aberration was at chromosome 3p22-25; of ten cases with this LOH in the carcinoma, six displayed the same LOH in adjacent normal lobules. This suggests that in a subset of sporadic breast cancers, a tumor suppresser gene at 3p22-25 may be important in initiation or early progression of tumorigenesis. Among sixteen breast cancers with LOH at 17p13.1 and five breast cancers with LOH at 11p15.5, one case each displayed the same LOH in adjacent normal lobules. Thus the molecular heterogeneity that characterizes invasive breast cancers may occur at the earliest detectable stages of progression.
Ex-Rep. Walker Joins Lobbying Firm
Authors: Lawler Andrew
Published: July 2002

WASHINGTON, D.C.
—Robert Walker, the former chair of the House Science Committee, stepped through a well-worn revolving door on 6 January: He was named president of the Wexler Group, a prominent Washington lobbying firm.
Synaptic Depression and Cortical Gain Control
Authors: Abbott L. F. , Varela J. A. , Sen Kamal , Nelson S. B.
Published: July 2002

Cortical neurons receive synaptic inputs from thousands of afferents that fire action potentials at rates ranging from less than 1 hertz to more than 200 hertz. Both the number of afferents and their large dynamic range can mask changes in the spatial and temporal pattern of synaptic activity, limiting the ability of a cortical neuron to respond to its inputs. Modeling work based on experimental measurements indicates that short-term depression of intracortical synapses provides a dynamic gain-control mechanism that allows equal percentage rate changes on rapidly and slowly firing afferents to produce equal postsynaptic responses. Unlike inhibitory and adaptive mechanisms that reduce responsiveness to all inputs, synaptic depression is input-specific, leading to a dramatic increase in the sensitivity of a neuron to subtle changes in the firing patterns of its afferents.
Stereoselective Bimolecular Phenoxy Radical Coupling by an Auxiliary (Dirigent) Protein Without an Active Center
Authors: Davin Laurence B. , Wang Huai-Bin , Crowell Anastasia L. , Bedgar Diana L. , Martin Diane M. , Sarkanen Simo , Lewis Norman G.
Published: July 2002

The regio- and stereospecificity of bimolecular phenoxy radical coupling reactions, of especial importance in lignin and lignan biosynthesis, are clearly controlled in some manner in vivo; yet in vitro coupling by oxidases, such as laccases, only produce racemic products. In other words, laccases, peroxidases, and comparable oxidases are unable to control regio- or stereospecificity by themselves and thus some other agent must exist. A 78-kilodalton protein has been isolated that, in the presence of an oxidase or one electron oxidant, effects stereoselective bimolecular phenoxy radical coupling in vitro. Itself lacking a catalytically active (oxidative) center, its mechanism of action is presumed to involve capture of
E
-coniferyl alcohol-derived free-radical intermediates, with consequent stereoselective coupling to give (+)-pinoresinol.
Niobium/Uranium Evidence for Early Formation of the Continental Crust
Authors: Sylvester Paul J. , Campbell Ian H. , Bowyer Deborah A.
Published: July 2002

Niobium/uranium ratios in greenstone-belt basalts and gabbros indicate that parts of the Late Archean mantle beneath Western Australia underwent a level of melt extraction, resulting in formation of the continental crust, comparable to that seen in the present mantle. The implication is either that (i) the amount of continental crust that formed before 2.7 × 10
9
years ago was much greater than generally thought or (ii) crustal growth occurred by severe depletion of small volumes of the mantle rather than by moderate depletion of a large volume of mantle.
Europe Ponders Space Constraints
Authors: Hellemans Alexander
Published: July 2002

PARIS
—European space scientists gathering in Geneva last week had the unenviable task of trying to fit too many top-rated projects into the European Space Agency's shrinking budget. They made one painful decision: to recommend that a mission to the planet Mercury, slated for launch in the first decade of next century, be delayed indefinitely. But even that loss will not free up enough money to fly all the other missions space scientists had planned by 2010, nor will it guarantee Europe's participation in future collaborations such as the Next Generation Space Telescope.
Senate Bills Back Huge Increases
Authors: Mervis Jeffrey
Published: July 2002

Last week, Senate Republicans were falling all over themselves with promises to do more for basic research than advocates had dreamed possible. Although the proposals are so far just kind words, supporters see them as a very good way to begin another tough budget year.
Gas Clouds May Be Relics of Creation
Authors: Glanz James
Published: July 2002

TORONTO
—Astronomers had thought that the high-speed clouds of hydrogen atoms that roam through space are accelerated by supernova explosions within our galaxy. But a new proposal argues that they may be something much grander: huge, distant remnants of the galaxy's formation that extend well beyond the Milky Way and could fuel the formation of new stars for billions of years into the future.
Fluorous Synthesis: A Fluorous-Phase Strategy for Improving Separation Efficiency in Organic Synthesis
Authors: Studer Armido , Hadida Sabine , Ferritto Rafael , Kim Sun-Young , Jeger Patrick , Wipf Peter , Curran Dennis P.
Published: July 2002

Recovery and purification difficulties can limit the yield and utility of otherwise successful organic synthesis strategies. A “fluorous synthesis” approach is outlined in which organic molecules are rendered soluble in fluorocarbon solvents by attachment of a suitable fluorocarbon group. Fluorocarbon solvents are usually immiscible in organic solutions, and fluorous molecules partition out of an organic phase and into a fluorous phase in a standard liquid-liquid extraction. Simple yet substantive separations of organic reaction mixtures are achieved without resorting to chromatography. Because fluorous synthesis combines in many respects the favorable purification features of solid-phase synthesis with the favorable reaction, identification, and analysis features of traditional organic synthesis, it should prove valuable in the automated synthesis of libraries of individual pure organic compounds.
Chemical Selection for Catalysis in Combinatorial Antibody Libraries
Authors: Janda Kim D. , Lo Lee-Chiang , Lo Chih-Hung L. , Sim Mui-Mui , Wang Ruo , Wong Chi-Huey , Lerner Richard A.
Published: July 2002

For the past decade the immune system has been exploited as a rich source of de novo catalysts. Catalytic antibodies have been shown to have chemoselectivity, enantioselectivity, large rate accelerations, and even an ability to reroute chemical reactions. In many instances catalysts have been made for reactions for which there are no known natural or man-made enzymes. Yet, the full power of this combinatorial system can only be exploited if there was a system that allows for the direct selection of a particular function. A method that allows for the direct chemical selection for catalysis from antibody libraries was so devised, whereby the positive aspects of hybridoma technology were preserved and re-formatted in the filamentous phage system to allow direct selection of catalysis. This methodology is based on a purely chemical selection process, making it more general than biologically based selection systems because it is not limited to reaction products that perturb cellular machinery.
Enantiomeric Excesses in Meteoritic Amino Acids
Authors: Cronin John R. , Pizzarello Sandra
Published: July 2002

Gas chromatographic-mass spectral analyses of the four stereoisomers of 2-amino-2,3-dimethylpentanoic acid (DL-α-methylisoleucine and DL-α-methylalloisoleucine) obtained from the Murchison meteorite show that the L enantiomer occurs in excess (7.0 and 9.1%, respectively) in both of the enantiomeric pairs. Similar results were obtained for two other α-methyl amino acids, isovaline and α-methylnorvaline, although the α hydrogen analogs of these amino acids, α-amino-
n
-butyric acid and norvaline, were found to be racemates. With the exception of α-amino-
n
-butyric acid, these amino acids are either unknown or of limited occurrence in the biosphere. Because carbonaceous chondrites formed 4.5 billion years ago, the results are indicative of an asymmetric influence on organic chemical evolution before the origin of life.
Hipparcos Charts the Heavens
Authors: Watson Andrew
Published: July 2002

On 1 June, a set of six CDs, containing the most comprehensive star catalog ever created, will go on sale. They have been put together from data collected between 1989 and 1993 by a European satellite called Hipparcos. The leap in accuracy that the Hipparcos catalog represents will send ripples throughout astrophysics, affecting everything from the age of the universe to the evolution of stars.
Electron Mirror Gives a Clearer View
Authors: Stokstad Erik
Published: July 2002

Electron microscopes suffer from optical aberrations much like the ones that add a fringe of color to the images seen with a magnifying glass. Now a fix is in sight: a corrective “electron mirror” that precisely counteracts the aberrations introduced by the electron lens. The mirror could increase the resolution of some high-powered electron microscopes by a factor of 5 or more.
Macromolecular Trafficking Indicated by Localization and Turnover of Sucrose Transporters in Enucleate Sieve Elements
Authors: Kühn Christina , Franceschi Vincent R. , Schulz Alexander , Lemoine Rémi , Frommer Wolf B.
Published: July 2002

The leaf sucrose transporter SUT1 is essential for phloem loading and long-distance transport of assimilates. Both SUT1 messenger RNA (mRNA) and protein were shown to be diurnally regulated and to have high turnover rates. SUT1 protein was detected by immunolocalization in plasma membranes of enucleate sieve elements (SEs) in tobacco, potato, and tomato. Analysis by in situ hybridization showed that SUT1 mRNA localizes mainly to the SE and is preferentially associated with plasmodesmata. Antisense inhibition of
SUT1
expression under control of a companion cell (CC)-specific promoter indicated synthesis of
SUT1
mRNA in the CC. These results provide evidence for targeting of plant endogenous mRNA and potentially SUT1 protein through phloem plasmodesmata and for sucrose loading at the plasma membrane of SE.
The Product of the Proto-Oncogene c-
cbl
: A Negative Regulator of the Syk Tyrosine Kinase
Authors: Ota Yasuo , Samelson Lawrence E.
Published: July 2002

Engagement of antigen and immunoglobulin receptors on hematopoietic cells is directly coupled to activation of nonreceptor protein tyrosine kinases (PTKs) that then phosphorylate critical intracellular substrates. In mast cells stimulated through the FcɛRI receptor, activation of several PTKs including Syk leads to degranulation and release of such mediators of the allergic response as histamine and serotonin. Regulation of Syk function occurred through interaction with the Cbl protein, itself a PTK substrate in this system. Overexpression of Cbl led to inhibition of Syk and suppression of serotonin release from mast cells, demonstrating its ability to inhibit a nonreceptor tyrosine kinase. Complex adaptor proteins such as Cbl can directly regulate the functions of the proteins they bind.
Current Problems and the Future of Antiretroviral Drug Trials
Authors: Lange Joep M. A.
Published: July 2002

Now that a growing arsenal of new and potential anti-HIV drugs exists, debate and discussion about the optimal way to test and use these drugs has begun. In his Policy Forum, Joep Lange, director of the National AIDS Therapy Evaluation Centre in Amsterdam, takes the controversial stand that suboptimal therapies and drug trial designs are still being used. He discusses the underlying reasons for this situation and the challenges for the future.
Control of Mouse Cardiac Morphogenesis and Myogenesis by Transcription Factor MEF2C
Authors: Lin Qing , Schwarz John , Bucana Corazon , N. Olson Eric
Published: July 2002

Members of the myocyte enhancer factor–2 (MEF2) family of MADS (MCM1, agamous, deficiens, serum response factor)–box transcription factors bind an A-T–rich DNA sequence associated with muscle-specific genes. The murine
MEF2C
gene is expressed in heart precursor cells before formation of the linear heart tube. In mice homozygous for a null mutation of
MEF2C
, the heart tube did not undergo looping morphogenesis, the future right ventricle did not form, and a subset of cardiac muscle genes was not expressed. The absence of the right ventricular region of the mutant heart correlated with down-regulation of the
dHAND
gene, which encodes a basic helix-loop-helix transcription factor required for cardiac morphogenesis. Thus, MEF2C is an essential regulator of cardiac myogenesis and right ventricular development.
Substantial Genetic Influence on Cognitive Abilities in Twins 80 or More Years Old
Authors: McClearn Gerald E. , Johansson Boo , Berg Stig , Pedersen Nancy L. , Ahern Frank , Petrill Stephen A. , Plomin Robert
Published: July 2002

General and specific cognitive abilities were studied in intact Swedish same-sex twin pairs 80 or more years old for whom neither twin had major cognitive, sensory, or motor impairment. Resemblance for 110 identical twin pairs significantly exceeded resemblance for 130 fraternal same-sex twin pairs for all abilities. Maximum-likelihood model-fitting estimates of heritability were 62 percent for general cognitive ability, 55 percent for verbal ability, 32 percent for spatial ability, 62 percent for speed of processing, and 52 percent for memory. There was also evidence for the significant influence of idiosyncratic experience as the environmental component that most determines individual differences in cognitive abilities late in life.
Synthesis and Characterization of a Stable Dibismuthene: Evidence for a Bi-Bi Double Bond
Authors: Tokitoh Norihiro , Arai Yoshimitsu , Okazaki Renji , Nagase Shigeru
Published: July 2002

Treatment of an overcrowded triselenatribismane, 2,4,6-tris(bis(trimethylsilyl)methyl)phenyl-1,3,5-triselena-2,4,6-tribismane, with hexamethylphosphorous triamide in toluene at 100°C resulted in the quantitative formation of a stable dibismuthene [TbtBi=BiTbt, where Tbt is 2,4,6-tris(bis(trimethylsilyl)methyl)phenyl], a compound containing a double bond formed between two bismuth atoms. The compound formed as deep purple crystals upon cooling. Ultraviolet-visible and Raman spectra, x-ray crystallographic structural analysis, and theoretical calculations provided evidence for the double bond character of the Bi–Bi bond.
Ethical and Policy Issues of Human Cloning
Authors: Shapiro Harold T.
Published: July 2002

Tremendous debate was stirred by the announcement of the successful cloning of a sheep from a differentiated somatic cell. One result was that the National Bioethics Advisory Commission was asked by the president of the United States to report on the ethical and legal issues arising from the possibility that the cloning of humans could become a reality. In this Policy Forum, the chairman of that commission, Harold Shapiro of Princeton University, summarizes the recommendations of the panel and the challenges and concerns that led them to advocate a moratorium on the cloning of humans at the present time.
Inhibition of Bax Channel-Forming Activity by Bcl-2
Authors: Antonsson Bruno , Conti Franco , Ciavatta AnnaMaria , Montessuit Sylvie , Lewis Shareta , Martinou Isabelle , Bernasconi Lilia , Bernard Alain , Mermod Jean-Jacques , Mazzei Gonzalo , Maundrell Kinsey , Gambale Franco , Sadoul Rémy , Martinou Jean-Claude
Published: July 2002

Proteins of the Bcl-2 family are intracellular membrane-associated proteins that regulate programmed cell death (apoptosis) either positively or negatively by as yet unknown mechanisms. Bax, a pro-apoptotic member of the Bcl-2 family, was shown to form channels in lipid membranes. Bax triggered the release of liposome-encapsulated carboxyfluorescein at both neutral and acidic pH. At physiological pH, release could be blocked by Bcl-2. Bcl-2, in contrast, triggered carboxyfluorescein release at acidic pH only. In planar lipid bilayers, Bax formed pH- and voltage-dependent ion-conducting channels. Thus, the pro-apoptotic effects of Bax may be elicited through an intrinsic pore-forming activity that can be antagonized by Bcl-2.
Development and Diversity
Authors: Mahowald Anthony P.
Published: July 2002

Cells, Embryos, and Evolution.
Toward a Cellular and Developmental Understanding of Phenotypic Variation and Evolutionary Adaptability. JOHN GERHART and MARC KIRSCHNER. Blackwell Science, Cambridge, MA, 1997. xiv, 642 pp., illus., + plates. Paper, $69.95 or £29.50. ISBN 0-86542-574-4.
Particles and Peregrinations
Authors: Gross David
Published: July 2002

A Tale of Two Continents.
A Physicist's Life in a Turbulent World. ABRAHAM PAIS. Princeton University Press, Princeton, NJ, 1997. xvi, 511 pp. + plates. $35 or £25. ISBN 0-691-01243-1.
IRAK (Pelle) Family Member IRAK-2 and MyD88 as Proximal Mediators of IL-1 Signaling
Authors: Muzio Marta , Ni Jian , Feng Ping , Dixit Vishva M.
Published: July 2002

The interleukin-1 receptor (IL-1R) signaling pathway leads to nuclear factor kappa B (NF-κB) activation in mammals and is similar to the Toll pathway in
Drosophila
: the IL-1R–associated kinase (IRAK) is homologous to Pelle. Two additional proximal mediators were identified that are required for IL-1R–induced NF-κB activation: IRAK-2, a Pelle family member, and MyD88, a death domain–containing adapter molecule. Both associate with the IL-1R signaling complex. Dominant negative forms of either attenuate IL-1R–mediated NF-κB activation. Therefore, IRAK-2 and MyD88 may provide additional therapeutic targets for inhibiting IL-1–induced inflammation.
Hydrogen Partitioning into Molten Iron at High Pressure: Implications for Earth's Core
Authors: Okuchi Takuo
Published: July 2002

Because of dissolution of lighter elements such as sulfur, carbon, hydrogen, and oxygen, Earth's outer core is about 10 percent less dense than molten iron at the relevant pressure and temperature conditions. To determine whether hydrogen can account for a major part of the density deficit and is therefore an important constituent in the molten iron outer core, the hydrogen concentration in molten iron was measured at 7.5 gigapascals. From these measurements, the metal-silicate melt partitioning coefficient of hydrogen was determined as a function of temperature. If the magma ocean of primordial Earth was hydrous, more than 95 mole percent of H
2
O in this ocean should have reacted with iron to form FeH
x
, and about 60 percent of the density deficit is reconciled by adding hydrogen to the core.
Accelerating Invasion Rate in a Highly Invaded Estuary
Authors: Cohen Andrew N. , Carlton James T.
Published: July 2002

Biological invasions are a major global environmental and economic problem. Analysis of the San Francisco Bay and Delta ecosystem revealed a large number of exotic species that dominate many habitats in terms of number of species, number of individuals and biomass, and a high and accelerating rate of invasion. These factors suggest that this may be the most invaded estuary in the world. Possible causes include a large number and variety of transport vectors, a depauperate native biota, and extensive natural and anthropogenic disturbance.
A Determination of the HDO/H
2
O Ratio in Comet C/1995 O1 (Hale-Bopp)
Authors: Meier Roland , Owen Tobias C. , Matthews Henry E. , Jewitt David C. , Bockelée-Morvan Dominique , Biver Nicolas , Crovisier Jacques , Gautier Daniel
Published: July 2002

Deuterated water (HDO) was detected in comet C/1995 O1 (Hale-Bopp) with the use of the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The inferred D/H ratio in Hale-Bopp's water is (3.3 ± 0.8) × 10
−4
. This result is consistent with in situ measurements of comet P/Halley and the value found in C/1996 B2 (Hyakutake). This D/H ratio, higher than that in terrestrial water and more than 10 times the value for protosolar H
2
, implies that comets cannot be the only source for the oceans on Earth.
Communication with Chaotic Lasers
Authors: VanWiggeren Gregory D. , Roy Rajarshi
Published: July 2002

Recent experiments with chaotic electronic circuits have shown the possibility of communication with chaos. The experimental demonstration of chaotic communication with an optical system is described. An erbium-doped fiber ring laser (EDFRL) was used to produce chaotic light with a wavelength of 1.53 micrometers. A small 10-megahertz message was embedded in the larger chaotic carrier and transmitted to a receiver system where the message was recovered from the chaos. Chaotic optical waveforms can thus be used to communicate masked information at high bandwidths.
A Distinctive Class of Integron in the
Vibrio cholerae
Genome
Authors: Mazel Didier , Dychinco Broderick , Webb Vera A. , Davies Julian
Published: July 2002

The ability of bacteria to acquire and disseminate heterologous genes has been a major factor in the development of multiple drug resistance. A gene,
intI4
, was identified that encodes a previously unknown integrase that is associated with a “gene-VCR” organization (VCRs are
Vibrio cholerae
repeated sequences), similar to that of the well-characterized antibiotic resistance integrons. The similarity was confirmed by IntI1-mediated recombination of a gene-VCR cassette into a class 1 integron. VCR cassettes are found in a number of
Vibrio
species including a strain of
V. metschnikovii
isolated in 1888, suggesting that this mechanism of heterologous gene acquisition predated the antibiotic era.
Earthquakes on Dipping Faults: The Effects of Broken Symmetry
Authors: Oglesby David D. , Archuleta Ralph J. , Nielsen Stefan B.
Published: July 2002

Dynamic simulations of earthquakes on dipping faults show asymmetric near-source ground motion caused by the asymmetric geometry of such faults. The ground motion from a thrust or reverse fault is larger than that of a normal fault by a factor of 2 or more, given identical initial stress magnitudes. The motion of the hanging wall is larger than that of the footwall in both thrust (reverse) and normal earthquakes. The asymmetry between normal and thrust (reverse) faults results from time-dependent normal stress caused by the interaction of the earthquake-generated stress field with Earth's free surface. The asymmetry between hanging wall and footwall results from the asymmetric mass and geometry on the two sides of the fault.
Viscosity of Oceanic Asthenosphere Inferred from Remote Triggering of Earthquakes
Authors: Pollitz Fred F. , Bürgmann Roland , Romanowicz Barbara
Published: July 2002

A sequence of large interplate earthquakes from 1952 to 1965 along the Aleutian arc and Kurile-Kamchatka trench released accumulated stresses along nearly the entire northern portion of the Pacific Plate boundary. The postseismic stress evolution across the northern Pacific and Arctic basins, calculated from a viscoelastic coupling model with an asthenospheric viscosity of 5 × 10
17
pascal seconds, is consistent with triggering of oceanic intraplate earthquakes, temporal patterns in seismicity at remote plate boundaries, and space-based geodetic measurements of anomalous velocity over an area 7000 by 7000 kilometers square during the 30-year period after the sequence.
Phase-Matched Generation of Coherent Soft X-rays
Authors: Rundquist Andy , Durfee Charles G. , Chang Zenghu , Herne Catherine , Backus Sterling , Murnane Margaret M. , Kapteyn Henry C.
Published: July 2002

Phase-matched harmonic conversion of visible laser light into soft x-rays was demonstrated. The recently developed technique of guided-wave frequency conversion was used to upshift light from 800 nanometers to the range from 17 to 32 nanometers. This process increased the coherent x-ray output by factors of 10
2
to 10
3
compared to the non–phase-matched case. This source uses a small-scale (sub-millijoule) high repetition-rate laser and will enable a wide variety of new experimental investigations in linear and nonlinear x-ray science.
HIV Treatment Failure: Testing for HIV Resistance in Clinical Practice
Authors: Perrin Luc , Telenti Amalio
Published: July 2002

Perrin and Talenti discuss how to evaluate antiretroviral therapy for AIDS. Their examination of data from the Swiss HIV cohort study suggest that failure or success is more complicated than analysis of virus replication. These observations have an impact on discussions of the relevance of HIV resistance testing to clinical practice.
The HIV-1 Envelope Glycoproteins: Fusogens, Antigens, and Immunogens
Authors: Wyatt Richard , Sodroski Joseph
Published: July 2002

The human immunodeficiency virus–type 1 (HIV-1) envelope glycoproteins interact with receptors on the target cell and mediate virus entry by fusing the viral and cell membranes. The structure of the envelope glycoproteins has evolved to fulfill these functions while evading the neutralizing antibody response. An understanding of the viral strategies for immune evasion should guide attempts to improve the immunogenicity of the HIV-1 envelope glycoproteins and, ultimately, aid in HIV-1 vaccine development.
Global Elemental Maps of the Moon: The Lunar Prospector Gamma-Ray Spectrometer
Authors: Lawrence D. J. , Feldman W. C. , Barraclough B. L. , Binder A. B. , Elphic R. C. , Maurice S. , Thomsen D. R.
Published: July 2002

Lunar Prospector gamma-ray spectrometer spectra along with counting rate maps of thorium, potassium, and iron delineate large compositional variations over the lunar surface. Thorium and potassium are highly concentrated in and around the nearside western maria and less so in the South Pole–Aitken basin. Counting rate maps of iron gamma-rays show a surface iron distribution that is in general agreement with other measurements from Clementine and the Lunar Prospector neutron detectors.
Dendritic Integration and Its Role in Computing Image Velocity
Authors: Single Sandra , Borst Alexander
Published: July 2002

The mechanisms underlying visual motion detection can be studied simultaneously in different cell compartments in vivo by using calcium as a reporter of the spatiotemporal activity distribution in single motion-sensitive cells of the fly. As predicted by the Reichardt model, local dendritic calcium signals are found to indicate the direction and velocity of pattern motion but are corrupted by spatial pattern properties. The latter are canceled out by spatial integration, thus leading to a purely directional selective output signal in the axon. These findings attribute a specific computational task to the dendrites of visual interneurons and imply a functional interpretation of dendritic morphology.
Protein Kinase C Isotypes Controlled by Phosphoinositide 3-Kinase Through the Protein Kinase PDK1
Authors: Le Good J. Ann , Ziegler Wolfgang H. , Parekh Davey B. , Alessi Dario R. , Cohen Philip , Parker Peter J.
Published: July 2002

Phosphorylation sites in members of the protein kinase A (PKA), PKG, and PKC kinase subfamily are conserved. Thus, the PKB kinase PDK1 may be responsible for the phosphorylation of PKC isotypes. PDK1 phosphorylated the activation loop sites of PKCζ and PKCδ in vitro and in a phosphoinositide 3-kinase (PI 3-kinase)–dependent manner in vivo in human embryonic kidney (293) cells. All members of the PKC family tested formed complexes with PDK1. PDK1-dependent phosphorylation of PKCδ in vitro was stimulated by combined PKC and PDK1 activators. The activation loop phosphorylation of PKCδ in response to serum stimulation of cells was PI 3-kinase–dependent and was enhanced by PDK1 coexpression.
An
Arabidopsis
Mutant Defective in the Plastid General Protein Import Apparatus
Authors: Jarvis Paul , Chen Lih-Jen , Li Hsou-min , Peto Charles A. , Fankhauser Christian , Chory Joanne
Published: July 2002

Elaborate mechanisms have evolved for the translocation of nucleus-encoded proteins across the plastid envelope membrane. Although putative components of the import apparatus have been identified biochemically, their role in import remains to be proven in vivo. An
Arabidopsis
mutant lacking a new component of the import machinery [translocon at the outer envelope membrane of chloroplasts (Toc33), a 33-kilodalton protein] has been isolated. The functional similarity of Toc33 to another translocon component (Toc34) implies that multiple different translocon complexes are present in plastids. Processes that are mediated by Toc33 operate during the early stages of plastid and leaf development. The data demonstrate the in vivo role of a translocon component in plastid protein import.
Cell Surface Trafficking of Fas: A Rapid Mechanism of p53-Mediated Apoptosis
Authors: Bennett Martin , Macdonald Kirsty , Chan Shiu-Wan , Luzio J. Paul , Simari Robert , Weissberg Peter
Published: July 2002

p53 acts as a tumor suppressor by inducing both growth arrest and apoptosis. p53-induced apoptosis can occur without new RNA synthesis through an unknown mechanism. In human vascular smooth muscle cells, p53 activation transiently increased surface Fas (CD95) expression by transport from the Golgi complex. Golgi disruption blocked both p53-induced surface Fas expression and apoptosis. p53 also induced Fas-FADD binding and transiently sensitized cells to Fas-induced apoptosis. In contrast,
lpr
and
gld
fibroblasts were resistant to p53-induced apoptosis. Thus, p53 can mediate apoptosis through Fas transport from cytoplasmic stores.
Three-Dimensional Structure at the Base of the Mantle Beneath the Central Pacific
Authors: Bréger Ludovic , Romanowicz Barbara
Published: July 2002

Forward modeling of differential travel times of phases sensitive to lowermost mantle beneath the central Pacific reveals lateral heterogeneity that is higher in amplitude than predicted by tomographic models. A broad zone of low S velocity (−4 percent with respect to standard models), which may correspond to the base of a thermal “plume,” narrows and is deflected as it extends to about 1000 kilometers above the core-mantle boundary. To the east of this zone, a localized region of fast S velocity (+5 percent) suggests strong heterogeneity or anisotropy related to the presence of high pressure and temperature assemblages, which may or may not involve core material. Its presence could also explain the observation of precursors to core reflected phases in this region.
Thermodynamics of Calcite Growth: Baseline for Understanding Biomineral Formation
Authors: Teng H. Henry , Dove Patricia M. , Orme Christine A. , De Yoreo James J.
Published: July 2002

The complexity of biomineralized structures suggests the potential of organic constituents for controlling energetic factors during crystal synthesis. Atomic force microscopy was used to investigate the thermodynamic controls on carbonate growth and to measure the dependence of step speed on step length and the dependence of critical step length on supersaturation in precisely controlled solutions. These data were used to test the classic Gibbs-Thomson relationship and provided the step edge free energies and free energy barriers to one-dimension nucleation for calcite. Addition of aspartic acid, a common component in biomineralizing systems, dramatically affected growth morphology and altered the magnitude of the surface energy.
Control of Cyclin Ubiquitination by CDK-Regulated Binding of Hct1 to the Anaphase Promoting Complex
Authors: Zachariae Wolfgang , Schwab Michael , Nasmyth Kim , Seufert Wolfgang
Published: July 2002

Proteolysis of mitotic cyclins depends on a multisubunit ubiquitin–protein ligase, the anaphase promoting complex (APC). Proteolysis commences during anaphase, persisting throughout G
1
until it is terminated by cyclin-dependent kinases (CDKs) as cells enter S phase. Proteolysis of mitotic cyclins in yeast was shown to require association of the APC with the substrate-specific activator Hct1 (also called Cdh1). Phosphorylation of Hct1 by CDKs blocked the Hct1-APC interaction. The mutual inhibition between APC and CDKs explains how cells suppress mitotic CDK activity during G
1
and then establish a period with elevated kinase activity from S phase until anaphase.
Expressing Freudian Influences
Authors: Licinio Julio
Published: July 2002

Sigmund Freud: Conflict and Culture
. Michael S. Roth, curator. At the Library of Congress, Washington, DC, until 16 January 1999; future venues include New York; Vienna; Los Angeles; São Paulo and Porto Alegre, Brazil; and Chicago ().

Freud: Conflict and Culture
Essays on His Life, Work, and Legacy. Michael S. Roth, Ed. Knopf, New York, 1998. 288 pp. $26, $C36. ISBN 0-679-45116-1.

The controversial exhibition presents artifacts from collections including the U.S. Library of Congress, the Sigmund Freud Museum in Vienna, and the Freud Museum in London to explore the influences of Freud and his theories on 20th-century culture.