bluuebunny/crossref_metadata_2025 huggingface dataset:
Galileo Doppler Measurements of the Deep Zonal Winds at Jupiter
Authors: Atkinson David H. , Pollack James B. , Seiff Alvin
Published: October 2006

Changes in the speed of the Galileo probe caused by zonal winds created a small but measurable Doppler effect in the probe relay carrier frequency. Analysis of the probe relay link frequency allows direct measurements of the speed of Jupiter's zonal winds beneath the cloud tops. The deep winds were prograde and strong, reaching a sustained 190 to 200 meters per second at an altitude marked by a pressure of 24 bars. The depth and strength of the zonal winds severely constrain dynamic modeling of the deeper layers and begin to rule out many shallow weather theories.
Structure of the Atmosphere of Jupiter: Galileo Probe Measurements
Authors: Seiff Alvin , Kirk Donn B. , Knight Tony C. D. , Mihalov John D. , Blanchard Robert C. , Young Richard E. , Schubert Gerald , von Zahn Ulf , Lehmacher Gerald , Milos Frank S. , Wang Jerry
Published: October 2006

Temperatures and pressures measured by the Galileo probe during parachute descent into Jupiter's atmosphere essentially followed the dry adiabat between 0.41 and 24 bars, consistent with the absence of a deep water cloud and with the low water content found by the mass spectrometer. From 5 to 15 bars, lapse rates were slightly stable relative to the adiabat calculated for the observed H
2
/He ratio, which suggests that upward heat transport in that range is not attributable to simple radial convection. In the upper atmosphere, temperatures of >1000 kelvin at the 0.01-microbar level confirmed the hot exosphere that had been inferred from Voyager occultations. The thermal gradient increased sharply to 5 kelvin per kilometer at a reconstructed altitude of 350 kilometers, as was recently predicted. Densities at 1000 kilometers were 100 times those in the pre-encounter engineering model.
Amino Acid Racemization and the Preservation of Ancient DNA
Authors: Poinar Hendrik N. , Höss Matthias , Bada Jeffrey L. , Pääbo Svante
Published: October 2006

The extent of racemization of aspartic acid, alanine, and leucine provides criteria for assessing whether ancient tissue samples contain endogenous DNA. In samples in which the D/L ratio of aspartic acid exceeds 0.08, ancient DNA sequences could not be retrieved. Paleontological finds from which DNA sequences purportedly millions of years old have been reported show extensive racemization, and the amino acids present are mainly contaminates. An exception is the amino acids in some insects preserved in amber.
Polymers with Very Low Polydispersities from Atom Transfer Radical Polymerization
Authors: Patten Timothy E. , Xia Jianhui , Abernathy Teresa , Matyjaszewski Krzysztof
Published: October 2006

A radical polymerization process that yields well-defined polymers normally obtained only through anionic polymerizations is reported. Atom transfer radical polymerizations of styrene were conducted with several solubilizing ligands for the copper(I) halides: 4,4′-di-
tert
-butyl, 4,4′-di-
n
-heptyl, and 4,4′-di-(5-nonyl)-2,2′-dipyridyl. The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities (ratio of the weight-average to number-average molecular weights of 1.04 to 1.05). Similar results were obtained for the polymerization of acrylates.
HIV-1 Entry Cofactor: Functional cDNA Cloning of a Seven-Transmembrane, G Protein-Coupled Receptor
Authors: Feng Yu , Broder Christopher C. , Kennedy Paul E. , Berger Edward A.
Published: October 2006

A cofactor for HIV-1 (human immunodeficiency virus-type 1) fusion and entry was identified with the use of a novel functional complementary DNA (cDNA) cloning strategy. This protein, designated “fusin,” is a putative G protein-coupled receptor with seven transmembrane segments. Recombinant fusin enabled CD4-expressing nonhuman cell types to support HIV-1 Env-mediated cell fusion and HIV-1 infection. Antibodies to fusin blocked cell fusion and infection with normal CD4-positive human target cells. Fusin messenger RNA levels correlated with HIV-1 permissiveness in diverse human cell types. Fusin acted preferentially for T cell line-tropic isolates, in comparison to its activity with macrophage-tropic HIV-1 isolates.
Specification of Pituitary Cell Lineages by the LIM Homeobox Gene

Lhx3
Authors: Sheng Hui Z. , Zhadanov Alexander B. , Mosinger Bedrich , Fujii Tetsuya , Bertuzzi Stefano , Grinberg Alexander , Lee Eric J. , Huang Sing-Ping , Mahon Kathleen A. , Westphal Heiner
Published: October 2006

During pituitary organogenesis, the progressive differentiation of distinct pituitary-specific cell lineages from a common primordium involves a series of developmental decisions and inductive interactions. Targeted gene disruption in mice showed that
Lhx3
, a LIM homeobox gene expressed in the pituitary throughout development, is essential for differentiation and proliferation of pituitary cell lineages. In mice homozygous for the
Lhx3
mutation, Rathke's pouch formed but failed to grow and differentiate; such mice lacked both the anterior and intermediate lobes of the pituitary. The determination of all pituitary cell lineages, except the corticotrophs, was affected, suggesting that a distinct,
Lhx3
-independent ontogenetic pathway exists for the initial specification of this lineage.
Out of Africa: Meat-Eating Dinosaurs That Challenge
Tyrannosaurus rex
Authors: Currie Philip J.
Published: October 2006

A research report in this issue by Sereno
et al.
(
p. 986
) describes a new fossil find: bones from a carnivorous dinosaur as big or bigger than
Tyrannosaurus rex
. In his Perspective, Currie discusses the finding in relation to other recent big dinosaur discoveries.
A Far-Field Hydrothermal Plume from Loihi Seamount
Authors: Lupton John E.
Published: October 2006

An extensive helium plume in the north central Pacific emanates from Loihi Seamount on the flanks of Hawaii. The maximum helium signal is found at a depth of about 1100 meters, the same depth as the near-field plume directly above Loihi Seamount. Although this helium plume is strongest near Hawaii, where the
3
He/
4
He ratio at a depth of about 1100 meters reaches values 28 percent above the atmospheric ratio, it can be detected quite clearly at latitude 24°N, over 400 kilometers to the north. Excess
3
He is also present on the same isopycnal between 15°N and 20°N at 135°W, some 2000 kilometers east of the Hawaiian Islands.
Predatory Dinosaurs from the Sahara and Late Cretaceous Faunal Differentiation
Authors: Sereno Paul C. , Dutheil Didier B. , Iarochene M. , Larsson Hans C. E. , Lyon Gabrielle H. , Magwene Paul M. , Sidor Christian A. , Varricchio David J. , Wilson Jeffrey A.
Published: October 2006

Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus
Carcharodontosaurus
. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus
Bahariasaurus
. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous.
Uncertainty in Climate Change Caused by Aerosols
Authors: Schwartz Stephen E. , Andreae Meinrat O.
Published: October 2006

In a recent report, the U. S. National Research Council discussed how aerosols created by human activity influence climate change. In their Perspective, Schwartz and Andreae review the impact of aerosols and argue that the NRC panel did not go far enough in its recommendations.
Arrhenius and Global Warming
Authors: Uppenbrink Julia
Published: October 2006

The Swedish scientist Svante Arrhenius was the first to link changes in atmospheric carbon dioxide with changes in climate. In her Perspective, Uppenbrink marks the 100th anniversary of the publication of Arrhenius's paper on climate change.
Nanotribology and Nanofabrication of MoO
3
Structures by Atomic Force Microscopy
Authors: Sheehan Paul E. , Lieber Charles M.
Published: October 2006

Atomic force microscopy was used to characterize the sliding of molybdenum oxide (MoO
3
) nanocrystals on single-crystal molybdenum disulfide (MoS
2
) surfaces. Highly anisotropic friction was observed whereby MoO
3
nanocrystals moved only along specific directions of the MoS
2
surface lattice. The energy per unit area to move the MoO
3
nanocrystals along their preferred sliding direction was an order of magnitude less than required to slide macroscopic MoS
2
-bearing contacts. This extreme friction anisotropy was exploited to fabricate multicomponent MoO
3
nanostructures. These reversibly interlocking structures could serve as the basis for devices such as mechanical logic gates.
Regulation of T Cell Receptor Signaling by Tyrosine Phosphatase SYP Association with CTLA-4
Authors: Marengère Luc E. M. , Waterhouse Paul , Duncan Gordon S. , Mittrücker Hans-Willi , Feng Gen-Sheng , Mak Tak W.
Published: October 2006

The absence of CTLA-4 results in uncontrolled T cell proliferation. The T cell receptor-specific kinases FYN, LCK, and ZAP-70 as well as the RAS pathway were found to be activated in T cells of
Ctla-4
−/−
mutant mice. In addition, CTLA-4 specifically associated with the tyrosine phosphatase SYP, an interaction mediated by the SRC homology 2 (SH2) domains of SYP and the phosphotyrosine sequence Tyr-Val-Lys-Met within the CTLA-4 cytoplasmic tail. The CTLA-4-associated SYP had phosphatase activity toward the RAS regulator p52
SHC
. Thus, the RAS pathway and T cell activation through the T cell receptor are regulated by CTLA-4-associated SYP.
Entorhinal-Hippocampal Interactions Revealed by Real-Time Imaging
Authors: Iijima Toshio , Witter Menno P. , Ichikawa Michinori , Tominaga Takashi , Kajiwara Riichi , Matsumoto Gen
Published: October 2006

The entorhinal cortex provides the major cortical input to the hippocampus, and both structures have been implicated in memory processes. The dynamics of neuronal circuits in the entorhinal-hippocampal system were studied in slices by optical imaging with high spatial and temporal resolution. Reverberation of neural activity was detected in the entorhinal cortex and was more prominent when the inhibition due to γ-aminobutyric acid was slightly suppressed. Neural activity was transferred in a frequency-dependent way from the entorhinal cortex to the hippocampus. The entorhinal neuronal circuit could contribute to memory processes by holding information and selectively gating the entry of information into the hippocampus.
The Origin of Programmed Cell Death
Authors: Ameisen Jean Claude
Published: October 2006

Cells from multicellular organisms self-destruct when they are no longer needed. Ameisen describes how such programmed cell death has now been found in lower organisms and what this tells us about evolution of the process of cell death.
The Current State of Solar Modeling
Authors: Christensen-Dalsgaard J. , Däppen W. , Ajukov S. V. , Anderson E. R. , Antia H. M. , Basu S. , Baturin V. A. , Berthomieu G. , Chaboyer B. , Chitre S. M. , Cox A. N. , Demarque P. , Donatowicz J. , Dziembowski W. A. , Gabriel M. , Gough D. O. , Guenther D. B. , Guzik J. A. , Harvey J. W. , Hill F. , Houdek G. , Iglesias C. A. , Kosovichev A. G. , Leibacher J. W. , Morel P. , Proffitt C. R. , Provost J. , Reiter J. , Rhodes E. J. , Rogers F. J. , Roxburgh I. W. , Thompson M. J. , Ulrich R. K.
Published: October 2006

Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations.
The Solar Acoustic Spectrum and Eigenmode Parameters
Authors: Hill F. , Stark P. B. , Stebbins R. T. , Anderson E. R. , Antia H. M. , Brown T. M. , Duvall T. L. , Haber D. A. , Harvey J. W. , Hathaway D. H. , Howe R. , Hubbard R. P. , Jones H. P. , Kennedy J. R. , Korzennik S. G. , Kosovichev A. G. , Leibacher J. W. , Libbrecht K. G. , Pintar J. A. , Rhodes E. J. , Schou J. , Thompson M. J. , Tomczyk S. , Toner C. G. , Toussaint R. , Williams W. E.
Published: October 2006

The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances of the sun from data sets lasting 36 days. The frequency resolution of a single data set is 0.321 microhertz. For frequencies averaged over the azimuthal order
m
, the median formal error is 0.044 microhertz, and the associated median fractional error is 1.6 × 10
−5
. For a 3-year data set, the fractional error is expected to be 3 × 10
−6
. The GONG
m
-averaged frequency measurements differ from other helioseismic data sets by 0.03 to 0.08 microhertz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure.
Differential Rotation and Dynamics of the Solar Interior
Authors: Thompson M. J. , Toomre J. , Anderson E. R. , Antia H. M. , Berthomieu G. , Burtonclay D. , Chitre S. M. , Christensen-Dalsgaard J. , Corbard T. , DeRosa M. , Genovese C. R. , Gough D. O. , Haber D. A. , Harvey J. W. , Hill F. , Howe R. , Korzennik S. G. , Kosovichev A. G. , Leibacher J. W. , Pijpers F. P. , Provost J. , Rhodes E. J. , Schou J. , Sekii T. , Stark P. B. , Wilson P. R.
Published: October 2006

Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within the solar interior. The nearly uninterrupted observations by the Global Oscillation Network Group (GONG) yield oscillation power spectra with high duty cycles and high signal-to-noise ratios. Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths. A distinctive shear layer just below the surface is discernible at low to mid-latitudes.
Corundum, Rutile, Periclase, and CaO in Ca,Al-Rich Inclusions from Carbonaceous Chondrites
Authors: Greshake A. , Bischoff A. , Putnis A. , Palme H.
Published: October 2006

Four calcium, aluminum-rich inclusions from four carbonaceous chondrites—Allende, Acfer 082, Acfer 086, and Acfer 094—were studied by transmission electron microscopy. All inclusions contained at least two of the oxides periclase (MgO), rutile (TiO
2
), calcium oxide (CaO), and corundum (Al
2
O
3
). The oxides (50 to 200 nanometers in size) were found inside and at grain boundaries of the constituent minerals of the inclusions. Determining how these oxides formed may provide insight about condensation processes in the early solar nebula and the origin of refractory inclusions in chondrites. Formation of these oxides by exsolution is considered unlikely. An origin by kinetically controlled condensation appears more probable.
The

rf2

Nuclear Restorer Gene of Male-Sterile T-Cytoplasm Maize
Authors: Cui Xiangqin , Wise Roger P. , Schnable Patrick S.
Published: October 2006

The T cytoplasm of maize serves as a model for the nuclear restoration of cytoplasmic male sterility. The
rf2
gene, one of two nuclear genes required for fertility restoration in male-sterile T-cytoplasm (cmsT) maize, was cloned. The protein predicted by the
rf2
sequence is a putative aldehyde dehydrogenase, which suggests several mechanisms that might explain
Rf2
-mediated fertility restoration in cmsT maize. Aldehyde dehydrogenase may be involved in the detoxification of acetaldehyde produced by ethanolic fermentation during pollen development, may play a role in energy metabolism, or may interact with URF13, the mitochondrial protein associated with male sterility in cmsT maize.
An Orphan Nuclear Hormone Receptor That Lacks a DNA Binding Domain and Heterodimerizes with Other Receptors
Authors: Seol Wongi , Choi Hueng-Sik , Moore David D.
Published: October 2006

SHP is an orphan member of the nuclear hormone receptor superfamily that contains the dimerization and ligand-binding domain found in other family members but lacks the conserved DNA binding domain. In the yeast two-hybrid system, SHP interacted with several conventional and orphan members of the receptor superfamily, including retinoid receptors, the thyroid hormone receptor, and the orphan receptor MB67. SHP also interacted directly with these receptors in vitro. In mammalian cells, SHP specifically inhibited transactivation by the superfamily members with which it interacted. These results suggest that SHP functions as a negative regulator of receptor-dependent signaling pathways.
Stress-Induced Phosphorylation and Activation of the Transcription Factor CHOP (GADD153) by p38 MAP Kinase
Authors: Wang XiaoZhong , Ron David
Published: October 2006

CHOP, a member of the C/EBP family of transcription factors, mediates effects of cellular stress on growth and differentiation. It accumulates under conditions of stress and undergoes inducible phosphorylation on two adjacent serine residues (78 and 81). In vitro, CHOP is phosphorylated on these residues by p38 mitogen-activated protein kinase (MAP kinase). A specific inhibitor of p38 MAP kinase, SB203580, abolished the stress-inducible in vivo phosphorylation of CHOP. Phosphorylation of CHOP on these residues enhanced its ability to function as a transcriptional activator and was also required for the full inhibitory effect of CHOP on adipose cell differentiation. CHOP thus serves as a link between a specific stress-activated protein kinase, p38, and cellular growth and differentiation.
G Protein-Mediated Neuronal DNA Fragmentation Induced by Familial Alzheimer's Disease-Associated Mutants of APP
Authors: Yamatsuji Tomoki , Matsui Takashi , Okamoto Takashi , Komatsuzaki Katsumi , Takeda Shizu , Fukumoto Hiroaki , Iwatsubo Takeshi , Suzuki Nobuhiro , Asami-Odaka Asano , Ireland Scott , Kinane T. Bernard , Giambarella Ugo , Nishimoto Ikuo
Published: October 2006

Missense mutations in the 695-amino acid form of the amyloid precursor protein (APP
695
) cosegregate with disease phenotype in families with dominantly inherited Alzheimer's disease. These mutations convert valine at position 642 to isoleucine, phenylalanine, or glycine. Expression of these mutant proteins, but not of normal APP
695
, was shown to induce nucleosomal DNA fragmentation in neuronal cells. Induction of DNA fragmentation required the cytoplasmic domain of the mutants and appeared to be mediated by heterotrimeric guanosine triphosphate-binding proteins (G proteins).
SIV Data Raise Concern on Oral-Sex Risk
Authors: Cohen Jon
Published: October 2006

The results of a monkey study, reported in this issue on
page 1486
, may lead to a reexamination of the risk of HIV infection from a practice that has seemed relatively safe: oral sex. The new study, headed by oncologist Ruth Ruprecht of the Dana-Farber Cancer Institute, found that six of seven monkeys became infected by SIV when the virus was placed gently on the backs of their tongues. Even more surprising: The minimum dose needed to infect monkeys with this strain of SIV was 6000 times lower than the minimum dose needed to infect them via the rectum. The amount of SIV needed to establish an infection was still relatively high and, as the paper underscores, it is highly unlikely that anyone could become infected by HIV from casual contact, such as kissing or sharing a fork. But Ruprecht says: “Given enough inoculum, the oral route can lead to infection.”
Lithospheric Contributions to Arc Magmatism: Isotope Variations Along Strike in Volcanoes of Honshu, Japan
Authors: Kersting Annie B. , Arculus Richard J. , Gust David A.
Published: October 2006

Major chemical exchange between the crust and mantle occurs in subduction zone environments, profoundly affecting the chemical evolution of Earth. The relative contributions of the subducting slab, mantle wedge, and arc lithosphere to the generation of island arc magmas, and ultimately new continental crust, are controversial. Isotopic data for lavas from a transect of volcanoes in a single arc segment of northern Honshu, Japan, have distinct variations coincident with changes in crustal lithology. These data imply that the relatively thin crustal lithosphere is an active geochemical filter for all traversing magmas and is responsible for significant modification of primary mantle melts.
Structural Evidence for Functional Domains in the Rat Hippocampus
Authors: Risold P. Y. , Swanson L. W.
Published: October 2006

The hippocampus has two major outputs: multisynaptic pathways to the cerebral cortex and a massive descending projection directly to the lateral septal part of the basal ganglia. Here it is shown that the descending output is organized in such a way that different hippocampal regions map in an orderly way onto hypothalamic systems mediating the expression of different classes of goal-oriented behavior. This mapping is characterized by a unidirectional hippocampo-lateral septal projection and then by bidirectional lateral septo-hypothalamic projections, all topographically organized. The connectional evidence predicts that information processing in different regions of the hippocampus selectively influences the expression of different classes of behavior.
A Subfamily of P-Type ATPases with Aminophospholipid Transporting Activity
Authors: Tang Xiaojing , Halleck Margaret S. , Schlegel Robert A. , Williamson Patrick
Published: October 2006

The appearance of phosphatidylserine on the surface of animal cells triggers phagocytosis and blood coagulation. Normally, phosphatidylserine is confined to the inner leaflet of the plasma membrane by an aminophospholipid translocase, which has now been cloned and sequenced. The bovine enzyme is a member of a previously unrecognized subfamily of P-type adenosine triphosphatases (ATPases) that may have diverged from the primordial enzyme before the separation of the known families of ion-translocating ATPases. Studies in
Saccharomyces cerevisiae
suggest that aminophospholipid translocation is a general function of members of this family.
Adherence of
Plasmodium falciparum
to Chondroitin Sulfate A in the Human Placenta
Authors: Fried Michal , Duffy Patrick E.
Published: October 2006

Women are particularly susceptible to malaria during first and second pregnancies, even though they may have developed immunity over years of residence in endemic areas.
Plasmodium falciparum-
infected red blood cells (IRBCs) were obtained from human placentas. These IRBCs bound to purified chondroitin sulfate A (CSA) but not to other extracellular matrix proteins or to other known IRBC receptors. IRBCs from nonpregnant donors did not bind to CSA. Placental IRBCs adhered to sections of fresh-frozen human placenta with an anatomic distribution similar to that of naturally infected placentas, and this adhesion was competitively inhibited by purified CSA. Thus, adhesion to CSA appears to select for a subpopulation of parasites that causes maternal malaria.
Structural Analysis of Substrate Binding by the Molecular Chaperone DnaK
Authors: Zhu Xiaotian , Zhao Xun , Burkholder William F. , Gragerov Alexander , Ogata Craig M. , Gottesman Max E. , Hendrickson Wayne A.
Published: October 2006

DnaK and other members of the 70-kilodalton heat-shock protein (hsp70) family promote protein folding, interaction, and translocation, both constitutively and in response to stress, by binding to unfolded polypeptide segments. These proteins have two functional units: a substrate-binding portion binds the polypeptide, and an adenosine triphosphatase portion facilitates substrate exchange. The crystal structure of a peptide complex with the substrate-binding unit of DnaK has now been determined at 2.0 Å resolution. The structure consists of a β-sandwich subdomain followed by α-helical segments. The peptide is bound to DnaK in an extended conformation through a channel defined by loops from the β sandwich. An α-helical domain stabilizes the complex, but does not contact the peptide directly. This domain is rotated in the molecules of a second crystal lattice, which suggests a model of conformation-dependent substrate binding that features a latch mechanism for maintaining long lifetime complexes.
Identification of MAP Kinase Domains by Redirecting Stress Signals into Growth Factor Responses
Authors: Brunet Anne , Pouysségur Jacques
Published: October 2006

Mitogen-activated protein kinase (MAPK) cascades, termed MAPK modules, channel extracellular signals into specific cellular responses. Chimeric molecules were constructed between p38 and p44 MAPKs, which transduce stress and growth factor signals, respectively. A discrete region of 40 residues located in the amino-terminal p38MAPK lobe directed the specificity of response to extracellular signals, whereas the carboxyl-terminal half of the molecule specified substrate recognition. One p38-p44MAPK chimera, expressed in vivo, redirected stress signals into early mitogenic responses, demonstrating the functional independence of these domains.
Evidence for Glacial Control of Rapid Sea Level Changes in the Early Cretaceous
Authors: Stoll Heather M. , Schrag Daniel P.
Published: October 2006

Lower Cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves. Strontium data from an interval spanning 7 million years in the Berriasian-Valanginian imply that global sea level fluctuated about 50 meters over time scales of 200,000 to 500,000 years, which is in agreement with the Exxon sea level curve. Oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes. If glaciation caused all the rapid sea level changes in the Cretaceous that are indicated by the Exxon curve, then an Antarctic ice sheet may have existed despite overall climatic warmth.
Fine-Scale Doppler Radar Observations of Tornadoes
Authors: Wurman Joshua , Straka Jerry M. , Rasmussen Erik N.
Published: October 2006

Observations obtained with a mobile pencil-beam Doppler radar revealed many previously unresolved structures within tornadic storms and tornadoes and helped verify various aspects of conceptual models. Radar data from the parent circulations indicate the existence of spiral reflectivity bands, intense radial wind shear zones, and multiple larger-scale velocity maxima. Tornado structures observed include debris shields, clear axial (eye) regions, multiple reflectivity bands surrounding the center of the eye, and occasional reflectivity protrusions into the eye. Velocity and reflectivity data from tornado-scale circulations show evidence of axial downdrafts.
Patch-Clamp Detection of Neurotransmitters in Capillary Electrophoresis
Authors: Orwar Owe , Jardemark Kent , Jacobson Ingemar , Moscho Alexander , Fishman Harvey A. , Scheller Richard H. , Zare Richard N.
Published: October 2006

Gamma-aminobutyrate acid, L-glutamate, and
N
-methyl-D-aspartate were separated by capillary electrophoresis and detected by the use of whole-cell and outside-out patch-clamp techniques on freshly dissociated rat olfactory interneurons. These neuroactive compounds could be identified from their electrophoretic migration times, unitary channel conductances, and power spectra that yielded corner frequencies and mean single-channel conductances characteristic for each of the different agonist-receptor interactions. This technique has the sensitivity to observe the opening of a single ion channel for agonists separated by capillary electrophoresis.
Adenosine Diphosphate as an Intracellular Regulator of Insulin Secretion
Authors: Nichols C. G. , Shyng S.-L. , Nestorowicz A. , Glaser B. , Clement J. P. , Gonzalez G. , Aguilar-Bryan L. , Permutt M. A. , Bryan J.
Published: October 2006

Adenosine triphosphate (ATP)-sensitive potassium (K
ATP
) channels couple the cellular metabolic state to electrical activity and are a critical link between blood glucose concentration and pancreatic insulin secretion. A mutation in the second nucleotide-binding fold (NBF2) of the sulfonylurea receptor (SUR) of an individual diagnosed with persistent hyperinsulinemic hypoglycemia of infancy generated K
ATP
channels that could be opened by diazoxide but not in response to metabolic inhibition. The hamster SUR, containing the analogous mutation, had normal ATP sensitivity, but unlike wild-type channels, inhibition by ATP was not antagonized by adenosine diphosphate (ADP). Additional mutations in NBF2 resulted in the same phenotype, whereas an equivalent mutation in NBF1 showed normal sensitivity to MgADP. Thus, by binding to SUR NBF2 and antagonizing ATP inhibition of K
ATP
channels, intracellular MgADP may regulate insulin secretion.
Stable Expression of Mosaic Coats of Variant Surface Glycoproteins in

Trypanosoma brucei
Authors: Muñoz-Jordán Jorge L. , Davies Kelvin P. , Cross George A. M.
Published: October 2006

The paradigm of antigenic variation in parasites is the variant surface glycoprotein (VSG) of African trypanosomes. Only one VSG is expressed at any time, except for short periods during switching. The reasons for this pattern of expression and the consequences of expressing more than one VSG are unknown.
Trypanosoma brucei
was genetically manipulated to generate cell lines that expressed two VSGs simultaneously. These VSGs were produced in equal amounts and were homogeneously distributed on the trypanosome surface. The double-expressor cells had similar population doubling times and were as infective as wild-type cells. Thus, the simultaneous expression of two VSGs is not intrinsically harmful.
Punctuated Evolution Caused by Selection of Rare Beneficial Mutations
Authors: Elena Santiago F. , Cooper Vaughn S. , Lenski Richard E.
Published: October 2006

For more than two decades there has been intense debate over the hypothesis that most morphological evolution occurs during relatively brief episodes of rapid change that punctuate much longer periods of stasis. A clear and unambiguous case of punctuated evolution is presented for cell size in a population of
Escherichia coli
evolving for 3000 generations in a constant environment. The punctuation is caused by natural selection as rare, beneficial mutations sweep successively through the population. This experiment shows that the most elementary processes in population genetics can give rise to punctuated evolutionary dynamics.
Aberrant B Cell Development and Immune Response in Mice with a Compromised BCR Complex
Authors: Torres Raul M. , Flaswinkel Heinrich , Reth Michael , Rajewsky Klaus
Published: October 2006

The immunoglobulin α (Ig-α)-Ig-β heterodimer is the signaling component of the antigen receptor complex on B cells (BCR) and B cell progenitors (pre-BCR). A mouse mutant that lacks most of the Ig-α cytoplasmic tail exhibits only a small impairment in early B cell development but a severe block in the generation of the peripheral B cell pool, revealing a checkpoint in B cell maturation that ensures the expression of a functional BCR on mature B cells. B cells that do develop demonstrate a differential dependence on Ig-α signaling in antibody responses such that a signaling-competent Ig-α appears to be critical for the response to T-independent, but not T-dependent, antigens.
Substitution of
l
-Fucose by
l
-Galactose in Cell Walls of

Arabidopsis mur1
Authors: Zablackis Earl , York William S. , Pauly Markus , Hantus Stephen , Reiter Wolf-Dieter , Chapple Clint C. S. , Albersheim Peter , Darvill Alan
Published: October 2006

An
Arabidopsis thaliana
mutant (
mur1
) has less than 2 percent of the normal amounts of L-fucose in the primary cell walls of aerial portions of the plant. The survival of
mur1
plants challenged the hypothesis that fucose is a required component of biologically active oligosaccharides derived from cell wall xyloglucan. However, the replacement of L-fucose (that is, 6-deoxy-L-galactose) by L-galactose does not detectably alter the biological activity of the oligosaccharides derived from xyloglucan. Thus, essential structural and conformational features of xyloglucan and xyloglucan-derived oligosaccharides are retained when L-galactose replaces L-fucose.
Lysogenic Conversion by a Filamentous Phage Encoding Cholera Toxin
Authors: Waldor Matthew K. , Mekalanos John J.
Published: October 2006

Vibrio cholerae
, the causative agent of cholera, requires two coordinately regulated factors for full virulence: cholera toxin (CT), a potent enterotoxin, and toxin-coregulated pili (TCP), surface organelles required for intestinal colonization. The structural genes for CT are shown here to be encoded by a filamentous bacteriophage (designated CTXφ), which is related to coliphage M13. The CTXφ genome chromosomally integrated or replicated as a plasmid. CTXφ used TCP as its receptor and infected
V. cholerae
cells within the gastrointestinal tracts of mice more efficiently than under laboratory conditions. Thus, the emergence of toxigenic
V. cholerae
involves horizontal gene transfer that may depend on in vivo gene expression.
Off-Resonance Conduction Through Atomic Wires
Authors: Yazdani Ali , Eigler D. M. , Lang N. D.
Published: October 2006

The electrical resistance of wires consisting of either a single xenon atom or two xenon atoms in series was measured and calculated on the basis of an atom-jellium model. Both the measurement and the calculation yielded a resistance of 10
5
ohms for the single-xenon atom system and 10
7
ohms for the two-xenon atom system. These resistances greatly exceeded the 12,900-ohm resistance of an ideal one-dimensional conduction channel because conduction through the xenon atoms occurs through the tail of the xenon 6
s
resonance, which lies far above the Fermi level. This conduction process in an atom-sized system can now be understood in terms of the electronic states of individual atoms.
Shape-Controlled Synthesis of Colloidal Platinum Nanoparticles
Authors: Ahmadi Temer S. , Wang Zhong L. , Green Travis C. , Henglein Arnim , El-Sayed Mostafa A.
Published: October 2006

The shapes and sizes of platinum nanoparticles were controlled by changes in the ratio of the concentration of the capping polymer material to the concentration of the platinum cations used in the reductive synthesis of colloidal particles in solution at room temperature. Tetrahedral, cubic, irregular-prismatic, icosahedral, and cubo-octahedral particle shapes were observed, whose distribution was dependent on the concentration ratio of the capping polymer material to the platinum cation. Controlling the shape of platinum nanoparticles is potentially important in the field of catalysis.
Nuclear Encoding of a Chloroplast RNA Polymerase Sigma Subunit in a Red Alga
Authors: Tanaka Kan , Oikawa Kosuke , Ohta Niji , Kuroiwa Haruko , Kuroiwa Tsuneyoshi , Takahashi Hideo
Published: October 2006

A chloroplast RNA polymerase sigma factor is encoded by a nuclear gene,
sigA
, in the red alga
Cyanidium caldarium
RK-1. The encoded protein functions as an RNA polymerase sigma factor in vitro and it is localized to the chloroplast in vivo. SigA shows high sequence similarity to the sigma factors of cyanobacteria, which is indicative of the ancestral endosymbiotic event and subsequent transfer of the
sigA
gene to the nuclear genome.
Requirement for the Adapter Protein GRB2 in EGF Receptor Endocytosis
Authors: Wang Zhixiang , Moran Michael F.
Published: October 2006

Activated epidermal growth factor (EGF) receptors induce the formation of various complexes of intracellular signaling proteins that are mediated by SRC homology 2 (SH2) and SH3 domains. The activated receptors are also rapidly internalized into the endocytotic compartment and degraded in lysosomes. EGF stimulation of canine epithelial cells induced a rapid and transient association of the SH3-SH2-SH3 protein GRB2 with dynamin, a guanosine triphosphatase that regulates endocytosis. Disruption of GRB2 interactions by microinjection of a peptide corresponding to the GRB2 SH2 domain or its phosphopeptide ligand blocked EGF receptor endocytosis; other SH2 domains that bind EGF receptors or antibodies that neutralize RAS did not. Both activation and termination of EGF signaling appear to be regulated by the diverse interactions of GRB2.
Antiviral Effect and Ex Vivo CD4
+
T Cell Proliferation in HIV-Positive Patients as a Result of CD28 Costimulation
Authors: Levine Bruce L. , Mosca Joseph D. , Riley James L. , Carroll Richard G. , Vahey Maryanne T. , Jagodzinski Linda L. , Wagner Kenneth F. , Mayers Douglas L. , Burke Donald S. , Weislow Owen S. , St. Louis Daniel C. , June Carl H.
Published: October 2006

Because stimulation of CD4
+
lymphocytes leads to activation of human immunodeficiency virus-type 1 (HIV-1) replication, viral spread, and cell death, adoptive CD4
+
T cell therapy has not been possible. When antigen and CD28 receptors on cultured T cells were stimulated by monoclonal antibodies (mAbs) to CD3 and CD28 that had been immobilized, there was an increase in the number of polyclonal CD4
+
T cells from HIV-infected donors. Activated cells predominantly secreted cytokines associated with T helper cell type 1 function. The HIV-1 viral load declined in the absence of antiretroviral agents. Moreover, CD28 stimulation of CD4
+
T cells from uninfected donors rendered these cells highly resistant to HIV-1 infection. Immobilization of CD28 mAb was crucial to the development of HIV resistance, as cells stimulated with soluble CD28 mAb were highly susceptible to HIV infection. The CD28-mediated antiviral effect occurred early in the viral life cycle, before HIV-1 DNA integration. These data may facilitate immune reconstitution and gene therapy approaches in persons with HIV infection.
CC CKR5: A RANTES, MIP-1α, MIP-1β Receptor as a Fusion Cofactor for Macrophage-Tropic HIV-1
Authors: Alkhatib Ghalib , Combadiere Christophe , Broder Christopher C. , Feng Yu , Kennedy Paul E. , Murphy Philip M. , Berger Edward A.
Published: October 2006

Human immunodeficiency virus-type 1 (HIV-1) entry requires fusion cofactors on the CD4
+
target cell. Fusin, a heterotrimeric GTP-binding protein (G protein)-coupled receptor, serves as a cofactor for T cell line-tropic isolates. The chemokines RANTES, MIP-1α, and MIP-1β, which suppress infection by macrophage-tropic isolates, selectively inhibited cell fusion mediated by the corresponding envelope glycoproteins (Envs). Recombinant CC CKR5, a G protein-coupled receptor for these chemokines, rendered CD4-expressing nonhuman cells fusion-competent preferentially with macrophage-tropic Envs. CC CKR5 messenger RNA was detected selectively in cell types susceptible to macrophage-tropic isolates. CC CKR5 is thus a fusion cofactor for macrophage-tropic HIV-1 strains.
Auguste D. and Alzheimer's Disease
Authors: O'Brien Claire
Published: October 2006

Psychiatrists at the University of Frankfurt, Germany, have unexpectedly unearthed a long-lost treasure: the original case file of Auguste D., a 51-year-old woman who came under the care of Alois Alzheimer in 1901 and who is generally thought to be the first recognized patient with the disease that bears his name. Ironically, however, it now appears that Auguste D.'s dementia may have been at least partly caused, not by the typical neurodegeneration of Alzheimer's, but by arteriosclerosis of the brain.
Replicative Senescence: Implications for in Vivo Aging and Tumor Suppression
Authors: Smith James R. , Pereira-Smith Olivia M.
Published: October 2006

Normal cells have limited proliferative potential in culture, a fact that has been the basis of their use as a model for replicative senescence for many years. Recent molecular analyses have identified numerous changes in gene expression that occur as cells become senescent, and the results indicate that multiple levels of control contribute to the irreversible growth arrest. These include repression of growth stimulatory genes, overexpression of growth inhibitory genes, and interference with downstream pathways. Studies with cell types other than fibroblasts will better define the role of cell senescence in the aging process and in tumorigenesis.
Homogeneous Linewidths in the Optical Spectrum of a Single Gallium Arsenide Quantum Dot
Authors: Gammon D. , Snow E. S. , Shanabrook B. V. , Katzer D. S. , Park D.
Published: October 2006

The homogeneous linewidths in the photoluminescence excitation spectrum of a single, naturally formed gallium arsenide (GaAs) quantum dot have been measured with high spatial and spectral resolution. The energies and linewidths of the homogeneous spectrum provide a new perspective on the dephasing dynamics of the exciton in a quantum-confined, solid-state system. The origins of the linewidths are discussed in terms of the dynamics of the exciton in zero dimensions, in particular, in terms of lifetime broadening through the emission or absorption of phonons and photons.
Helium Isotopic Evidence for a Lower Mantle Component in Depleted Archean Komatiite
Authors: Richard Denis , Marty Bernard , Chaussidon Marc , Arndt Nicholas
Published: October 2006

Archean magnesium-rich komatiites require hot and presumably deep mantle sources, but their trace-element composition and radiogenic isotope composition are similar to those of modern mid-ocean ridge basalts, which originate in the upper mantle. The isotopic composition of helium extracted by sequential crushing of fresh olivines separated from two Archean and one mid-Proterozoic komatiites varies over three orders of magnitude, between a radiogenic end-member rich in helium-4 and a component rich in helium-3. Such helium-3 enrichment suggests the presence of a lower mantle component in Archean komatiites.
Transition Element-Like Chemistry for Potassium Under Pressure
Authors: Parker L. J. , Atou T. , Badding J. V.
Published: October 2006

At high pressure the alkali metals potassium, rubidium, and cesium transform to metals that have a
d
1
electron configuration, becoming transition metal-like. As a result, compounds were shown to form between potassium and the transition metal nickel. These results demonstrate that the chemical behavior of the alkali metals under pressure is very different from that under ambient conditions, where alkali metals and transition metals do not react because of large differences in size and electronic structure. They also have significant implications for the hypothesis that potassium is incorporated into Earth's core.
Transcription Processivity: Protein-DNA Interactions Holding Together the Elongation Complex
Authors: Nudler Evgeny , Avetissova Ekaterina , Markovtsov Vadim , Goldfarb Alex
Published: October 2006

The elongation of RNA chains during transcription occurs in a ternary complex containing RNA polymerase (RNAP), DNA template, and nascent RNA. It is shown here that elongating RNAP from
Escherichia coli
can switch DNA templates by means of end-to-end transposition without loss of the transcript. After the switch, transcription continues on the new template. With the use of defined short DNA fragments as switching templates, RNAP-DNA interactions were dissected into two spatially distinct components, each contributing to the stability of the elongating complex. The front (F) interaction occurs ahead of the growing end of RNA. This interaction is non-ionic and requires 7 to 9 base pairs of intact DNA duplex. The rear (R) interaction is ionic and requires approximately six nucleotides of the template DNA strand behind the active site and one nucleotide ahead of it. The nontemplate strand is not involved. With the use of protein-DNA crosslinking, the F interaction was mapped to the conserved zinc finger motif in the NH
2
-terminus of the β′ subunit and the R interaction, to the COOH-terminal catalytic domain of the β subunit. Mutational disruption of the zinc finger selectively destroyed the F interaction and produced a salt-sensitive ternary complex with diminished processivity. A model of the ternary complex is proposed here that suggests that trilateral contacts in the active center maintain the nonprocessive complex, whereas a front-end domain including the zinc finger ensures processivity.
Formation of Atomically Flat Silver Films on GaAs with a "Silver Mean" Quasi Periodicity
Authors: Smith Arthur R. , Chao Kuo-Jen , Niu Qian , Shih Chih-Kang
Published: October 2006

A flat epitaxial silver film on a gallium arsenide [GaAs(110)] surface was synthesized in a two-step process. Deposition of a critical thickness of silver at low temperature led to the formation of a dense nanocluster film. Upon annealing, all atoms rearranged themselves into an atomically flat film. This silver film has a close-packed (111) structure modulated by a “silver mean” quasi-periodic sequence. The ability to grow such epitaxial overlayers of metals on semiconductors enables the testing of theoretical models and provides a connection between metal and semiconductor technologies.
Platelet-Mediated Lymphocyte Delivery to High Endothelial Venules
Authors: Diacovo Thomas G. , Puri Kamal D. , Warnock R. Aaron , Springer Timothy A. , von Andrian Ulrich H.
Published: October 2006

Circulating lymphocytes gain access to lymph nodes owing to their ability to initiate rolling along specialized high endothelial venules (HEVs). One mechanism of rolling involves L-selectin binding to peripheral node addressin (PNAd) on HEVs. Activated platelets are shown to bind to circulating lymphocytes and to mediate rolling in HEVs, in vivo, through another molecule, P-selectin, which also interacts with PNAd. In vitro, activated platelets enhanced tethering of lymphocytes to PNAd and sustained lymphocyte rolling, even in the absence of functional L-selectin. Thus, a platelet pathway operating through P-selectin provides a second mechanism for lymphocyte delivery to HEVs.
APS Starts Electronic Preprint Service
Authors: Taubes Gary
Published: October 2006

The American Physical Society (APS), the pre-eminent publisher of physics journals in print, has gone on line with an
electronic preprint server
. The APS server could eventually compete with the electronic preprint archives located at the Los Alamos National Laboratory, which provide fast, virtually free, electronic distribution of unreviewed papers. But the initial goal of the APS server, which is still a prototype, is to serve as a testing ground for electronic publication and to provide a point of submission to APS journals.