bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal predictions of ice extent in the Arctic Ocean
Authors: Lindsay R. W. , Zhang J. , Schweiger A. J. , Steele M. A.
Published: February 2008

How well can the extent of arctic sea ice be predicted for lead periods of up to one year? The forecast ability of a linear empirical model is explored. It uses as predictors historical information about the ocean and ice obtained from an ice–ocean model retrospective analysis. The monthly model fields are represented by a correlation‐weighted average based on the predicted ice extent. The forecast skill of the procedure is found by fitting the model over subsets of the available data and then making subsequent projections using independent predictor data. The forecast skill, relative to climatology, for predictions of the observed September ice extent for the pan‐arctic region is 0.77 for six months lead (from March) and 0.75 for 11 months lead (from October). The ice concentration is the most important variable for the first two months and the ocean temperature of the model layer with a depth of 200 to 270 m is most important for longer lead times. The trend accounts for 76% of the variance of the pan‐arctic ice extent, so most of the forecast skill is realized by determining model variables that best represent this trend. For detrended data there is no skill for lead times of 3 months or more. The forecast skill relative to the estimate from the previous year is lower than the climate‐relative skill but it is still greater than 0.45 for most lead times. Six‐month predictions are also made for each month of the year and regional three‐month predictions are made for 45‐degree sectors. The ice‐ocean model output significantly improves the predictive skill of the forecast model.
Measuring the potential predictability of ensemble climate predictions
Authors: Tang Youmin , Lin Hai , Moore Andrew M.
Published: February 2008

In this study, ensemble predictions of the El Niño Southern Oscillation (ENSO) and the Arctic Oscillation (AO) were conducted using two coupled models and two atmospheric circulation models, respectively, as well as various ensemble schemes. Several measures of potential predictability including ensemble mean square (EM2), ensemble spread and the ratio of signal‐to‐noise were explored in terms of their ability of estimating a priori the predictive skill of the ENSO and AO ensemble predictions. The emphasis was put on examining the relationship between the measures of predictability that do not use observations and the model prediction skill of correlation and mean square error (MSE) that make use of observations. The relationship identified here offers a practical means of estimating the potential predictability and the confidence level of an individual prediction. It was found that the EM2 is a better indicator of the actual skill of ensemble ENSO and AO prediction than the ratio of signal‐to‐noise. When correlation‐based metrics are used, the prediction skill is likely to be a linear function of EM2, i.e., the larger the EM2 the higher skill the prediction; whereas when MSE‐based metrics are used, a “triangular relationship” is suggested between them, namely, that when EM2 is large, the prediction is likely to be reliable whereas when EM2 is small the prediction skill is highly variable. In contrast with ensemble weather prediction (NWP), the ensemble spread is not a good predictor in quantifying climate prediction skill in the models used in this study because the forced response may be much larger than the noise in the climate timescales compared to the NWP. A statistical framework was proposed to explain why EM2 is a good indicator of actual prediction skill in the ensemble climate predictions.
Assessing objective techniques for gauge‐based analyses of global daily precipitation
Authors: Chen Mingyue , Shi Wei , Xie Pingping , Silva Viviane B. S. , Kousky Vernon E. , Wayne Higgins R. , Janowiak John E.
Published: February 2008

Three objective techniques used to obtain gauge‐based daily precipitation analyses over global land areas are assessed. The objective techniques include the inverse‐distance weighting algorithms of Cressman (1959) and Shepard (1968), and the optimal interpolation (OI) method of Gandin (1965). Intercomparisons and cross‐validation tests are conducted to examine their performance over various parts of the globe where station network densities are different. The gauge data used in the examinations are quality controlled daily precipitation reports from roughly 16,000 stations over the global land areas that have been collected by the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC). Data sources include daily summary files from the Global Telecommunication System (GTS), and the CPC unified daily gauge data sets over the contiguous United States (CONUS), Mexico, and South America. All three objective techniques are capable of generating useful daily precipitation analyses with biases of generally less than 1% over most parts of the global land areas. The OI method consistently performs the best among the three techniques for almost all situations (regions, seasons, and network densities). The Shepard scheme compares reasonably well with the OI, while the Cressman method tends to generate smooth precipitation fields with wider raining areas relative to the station observations. The quality of the gauge‐based analyses degrades as the network of station observations becomes sparser, although the OI technique exhibits relatively stable performance statistics over regions covered by fewer gauges.
A theory for ice‐till interactions and sediment entrainment beneath glaciers
Authors: Rempel A. W.
Published: February 2008

The ice‐till interface beneath soft‐bedded glaciers can be marked by an abrupt transition from an ice layer above to unfrozen sediments below. Alternatively, the transition can be more gradual, with ice infiltrating the underlying sediments to form a fringe layer that contains a mixture of ice, liquid water, and sediment particles. The fringe thickness h is predicted to commonly be several decimeters to meters in scale, implying that significant sediment transport can occur when sliding occurs beneath. I adapt theories for the thermodynamic and mechanical balances that control freezing and melting in porous media to determine h as a function of effective stress N, the rate of basal heat flow, and key sediment properties. A fringe is expected only when N > pf ≈ 1.1 (Tm − Tf) MPa/°C, where Tm − Tf is the temperature drop below the pressure‐melting point that is needed for ice to infiltrate the pore space; pf increases with decreased grain size. For sediment properties that are within the typical range expected of the tills beneath glaciers, pf = O (104) Pa. The rate that water can be transported through the fringe and frozen onto or melted from the glacier base can achieve a steady state that is in balance with the rate that latent heat is transported to or from the basal interface. At constant N, when a gradual increase in heat flow from the glacier base causes the rate of melting to decrease, h increases and continues to do so when the heat flow is great enough to produce freezing. As freezing becomes more rapid and h increases further, the rate of fluid supply to the glacier base reaches a maximum when the effective permeability is sufficiently reduced by the partial ice saturation in the fringe. Larger h can be achieved with slower freezing at the glacier base, but steady states with larger h are unstable. The maximum rate of fluid supply to the glacier base is greater at lower N, higher temperature gradients, and for sediments with higher permeabilities. Unsteady behavior can lead to large changes in h when there is a mismatch between the rate that latent heat can be extracted and the rate that fluid is supplied to the glacier base. Transient behavior driven by abrupt changes in N is characterized by rapid variations in freezing rate, followed by slower adjustments to h that are limited by the timescale for the conduction of latent heat. The resulting patterns of sediment deformation are expected to commonly be distributed over finite depth ranges even when shear is perfectly localized at any single instant in time.
Lipoic acid significantly restores, in rats, the age‐related decline in vasomotion
Authors: Smith A R , Visioli F , Frei B , Hagen T M
Published: February 2008

Background and purpose: The age‐related decline in vasorelaxation is largely due to ceramide‐induced induction of phosphatase 2A (PP2A), which limits nitric oxide synthase (eNOS) phosphorylation at stimulatory sites. We hypothesized that ceramide accumulation was from an age‐related loss of endothelial glutathione (GSH) and subsequent activation of neutral sphingomyelinase (nSMase), an enzyme whose activity increases when GSH is limited.

Experimental approach: Old (30‐32 mo) F344xBN rats were given (R)‐α‐lipoic acid (LA), an agent known to induce GSH synthesis. Vasorelaxation was measured in aortic rings; GSH and ceramide levels, activity of nSMase and eNOS phosphorylation (by Western blot) was measured in aortic endothelial cells, isolated from the same aortas.

Key results: In old animals, endothelium‐dependent relaxation in aortic rings was decreased, GSH levels and its redox state in aortic endothelia were over 30% lower and nSMase activity and endothelial ceramide levels were three‐fold increased, relative to young (2‐4 mo) rats. LA treatment of old animals improved relaxation in aortic rings, reversed the changes in endothelial GSH, in nSMase activities and in ceramide levels. Similar effects on GSH levels and nSMase activity in old rats were also induced by treatment with GSH monoethylester. Activation (by phosphorylation) of eNOS was decreased by about 50% in old rats and this age‐related decrease was partially reversed by LA treatment.

Conclusions and implications: Decreased endothelial GSH was partly responsible for the age‐related loss of vascular endothelial function and LA might be therapeutically evaluated to treat endothelial dysfunction.

British Journal of Pharmacology (2008) 153, 1615–1622; doi:10.1038/bjp.2008.28; published online 25 February 2008
Prostaglandin E2 glycerol ester, an endogenous COX‐2 metabolite of 2‐arachidonoylglycerol, induces hyperalgesia and modulates NFκB activity
Authors: Hu S Shu‐Jung , Bradshaw H B , Chen J S‐C , Tan B , Walker J Michael
Published: February 2008

Background and purpose:

Recombinant cyclooxygenase‐2 (COX‐2) oxygenates 2‐arachidonoylglycerol (2‐AG) in vitro. We examined whether prostaglandin E2 glycerol ester (PGE2‐G), a COX‐2 metabolite of 2‐AG, occurs endogenously and affects nociception and immune responses.

Experimental approach:

Using mass spectrometric techniques, we examined whether PGE2‐G occurs in vivo and if its levels are altered by inhibition of COX‐2, monoacylglycerol (MAG) lipase or inflammation induced by carrageenan. We also examined the effects of PGE2‐G on nociception in rats and NFκB activity in RAW264.7 cells.

Key results:

PGE2‐G occurs endogenously in rat. Its levels were decreased by inhibition of COX‐2 and MAG lipase but were unaffected by carrageenan. Intraplantar administration of PGE2‐G induced mechanical allodynia and thermal hyperalgesia. In RAW264.7 cells, PGE2‐G and PGE2 produced similar, dose‐related changes in NFκB activity. PGE2‐G was quickly metabolized into PGE2. While the effects of PGE2 on thermal hyperalgesia and NFκB activity were completely blocked by a cocktail of antagonists for prostanoid receptors, the same cocktail of antagonists only partially antagonized the actions of PGE2‐G.

Conclusions and implications:

Thermal hyperalgesia and immunomodulation induced by PGE2‐G were only partially mediated by PGE2, which is formed by metabolism of PGE2‐G. PGE2‐G may function through a unique receptor previously postulated to mediate its effects. Taken together, these findings demonstrate that 2‐AG is oxygenated in vivo by COX‐2 producing PGE2‐G, which plays a role in pain and immunomodulation. COX‐2 could act as an enzymatic switch by converting 2‐AG from an antinociceptive mediator to a pro‐nociceptive prostanoid.

British Journal of Pharmacology (2008) 153, 1538–1549; doi:10.1038/bjp.2008.33; published online 25 February 2008
Microarray-based whole-genome hybridization as a tool for determining procaryotic species relatedness
Authors: Wu Liyou , Liu Xueduan , Fields Matthew W , Thompson Dorothea K , Bagwell Christopher E , Tiedje James M , Hazen Terry C , Zhou Jizhong
Published: February 2008

The definition and delineation of microbial species are of great importance and challenge due to the extent of evolution and diversity. Whole-genome DNA–DNA hybridization is the cornerstone for defining procaryotic species relatedness, but obtaining pairwise DNA–DNA reassociation values for a comprehensive phylogenetic analysis of procaryotes is tedious and time consuming. A previously described microarray format containing whole-genomic DNA (the community genome array or CGA) was rigorously evaluated as a high-throughput alternative to the traditional DNA–DNA reassociation approach for delineating procaryotic species relationships. DNA similarities for multiple bacterial strains obtained with the CGA-based hybridization were comparable to those obtained with various traditional whole-genome hybridization methods (r=0.87, P<0.01). Significant linear relationships were also observed between the CGA-based genome similarities and those derived from small subunit (SSU) rRNA gene sequences (r=0.79, P<0.0001), gyrB sequences (r=0.95, P<0.0001) or REP- and BOX-PCR fingerprinting profiles (r=0.82, P<0.0001). The CGA hybridization-revealed species relationships in several representative genera, including Pseudomonas, Azoarcus and Shewanella, were largely congruent with previous classifications based on various conventional whole-genome DNA–DNA reassociation, SSU rRNA and/or gyrB analyses. These results suggest that CGA-based DNA–DNA hybridization could serve as a powerful, high-throughput format for determining species relatedness among microorganisms.
Away‐from‐home Food Intake and Risk for Obesity: Examining the Influence of Context
Authors: Ayala Guadalupe X. , Rogers Morgan , Arredondo Elva M. , Campbell Nadia R. , Baquero Barbara , Duerksen Susan C. , Elder John P.
Published: February 2008

Objective: This study examined sociodemographic and cultural determinants of away‐from‐home food consumption in two contexts and the influence of frequency of away‐from‐home food consumption on children's dietary intake and parent and child weight status.

Methods and Procedures: Parents of children (N = 708) in grades K‐2 were recruited from 13 elementary schools in Southern California. Parents were asked through a questionnaire the frequency with which they eat meals away from home and the restaurant they frequented most often. The height and weight of the parents and their children were measured to calculate BMI.

Results: Consuming foods at least once a week from relatives/neighbors/friends (RNF) homes was associated with children's dietary intake and children's risk for obesity. For example, children of parents with weekly or greater RNF food consumption drank more sugar‐sweetened beverages. Parents of families who ate at restaurants at least weekly reported that their children consumed more sugar‐sweetened beverages, more sweet/savory snacks, and less water compared with families who did not frequent restaurants this often. The type of restaurant visited did not affect diet intake or obesity. More acculturated families exhibited less healthy dietary behaviors than less acculturated families.

Discussion: Restaurants remain an important setting for preventing child and adult obesity, but other settings outside the home need to be considered in future intervention research. This may especially involve eating in the homes of RNF.
The influence of ambipolarity on plasma confinement and on the performance of electron cyclotron resonance ion sources
Authors: Schachter L. , Dobrescu S. , Stiebing K. E. , Thuillier T. , Lamy T.
Published: February 2008

Charge diffusion in an electron cyclotron resonance ion source (ECRIS) discharge is usually characterized by nonambipolar behavior. While the ions are transported to the radial walls, electrons are lost axially from the magnetic trap. Global neutrality is maintained via compensating currents in the conducting walls of the vacuum chamber. It is assumed that this behavior reduces the ion breeding times compared to a truly ambipolar plasma. We have carried out a series of dedicated experiments in which the ambipolarity of the ECRIS plasma was influenced by inserting special metal-dielectric structures (MD layers) into the plasma chamber of the Frankfurt 14GHz ECRIS. The measurements demonstrate the positive influence on the source performance when the ECR plasma is changed toward more ambipolar behavior.
Electron cyclotron resonance ion source experience at the Heidelberg Ion Beam Therapy Center
Authors: Winkelmann T. , Cee R. , Haberer T. , Naas B. , Peters A. , Scheloske S. , Spädtke P. , Tinschert K.
Published: February 2008

Radiotherapy with heavy ions is an upcoming cancer treatment method with to date unparalleled precision. It associates higher control rates particularly for radiation resistant tumor species with reduced adverse effects compared to conventional photon therapy. The accelerator beam lines and structures of the Heidelberg Ion Beam Therapy Center (HIT) have been designed under the leadership of GSI, Darmstadt with contributions of the IAP Frankfurt. Currently, the accelerator is under commissioning, while the injector linac has been completed. When the patient treatment begins in 2008, HIT will be the first medical heavy ion accelerator in Europe. This presentation will provide an overview about the project, with special attention given to the 14.5GHz electron cyclotron resonance (ECR) ion sources in operation with carbon, hydrogen, helium, and oxygen, and the experience of one year of continuous operation. It also displays examples for beam emittances, measured in the low energy beam transport. In addition to the outlook of further developments at the ECR ion sources for a continuously stable operation, this paper focuses on some of the technical processings of the past year.
Thermodynamics of peptide aggregation processes: An analysis from perspectives of three statistical ensembles
Authors: Junghans Christoph , Bachmann Michael , Janke Wolfhard
Published: February 2008

We employ a mesoscopic model for studying aggregation processes of proteinlike hydrophobic-polar heteropolymers. By means of multicanonical Monte Carlo computer simulations, we find strong indications that peptide aggregation is a phase separation process, in which the microcanonical entropy exhibits a convex intruder due to non-negligible surface effects of the small systems. We analyze thermodynamic properties of the conformational transitions accompanying the aggregation process from the multicanonical, canonical, and microcanonical perspective. It turns out that the microcanonical description is particularly advantageous as it allows for unraveling details of the phase-separation transition in the thermodynamic region, where the temperature is not a suitable external control parameter anymore.
Electronic structure of Co doped ZnO: Theory and experiment
Authors: Sanyal B. , Grånäs O. , Knut R. , Coleman V. A. , Thunström P. , Iuşan D. M. , Karis O. , Eriksson O. , Westin G.
Published: February 2008

We have studied the electronic structure of Co doped ZnO by theory and experiment. Photoelectron and x-ray absorption spectroscopy experiments were performed on 5% Co doped ZnO thin films. The results show that Co-3d states lie in the valence band and hybridize considerably with O-2p states. These results compare qualitatively with our density functional calculations combined with a Hubbard approach to include strong electron correlations within the Co-3d state.
Theory of gelation, vitrification, and activated barrier hopping in mixtures of hard and sticky spheres
Authors: Viehman Douglas C. , Schweizer Kenneth S.
Published: February 2008

Naive mode coupling theory (NMCT) and the nonlinear stochastic Langevin equation theory of activated dynamics have been generalized to mixtures of spherical particles. Two types of ideal nonergodicity transitions are predicted corresponding to localization of both, or only one, species. The NMCT transition signals a dynamical crossover to activated barrier hopping dynamics. For binary mixtures of equal diameter hard and attractive spheres, a mixture composition sensitive “glass-melting” type of phenomenon is predicted at high total packing fractions and weak attractions. As the total packing fraction decreases, a transition to partial localization occurs corresponding to the coexistence of a tightly localized sticky species in a gel-like state with a fluid of hard spheres. Complex behavior of the localization lengths and shear moduli exist because of the competition between excluded volume caging forces and attraction-induced physical bond formation between sticky particles. Beyond the NMCT transition, a two-dimensional nonequilibrium free energy surface emerges, which quantifies cooperative activated motions. The barrier locations and heights are sensitive to the relative amplitude of the cooperative displacements of the different species.
The homogeneous turbulent dynamo
Authors: Shebalin John V.
Published: February 2008

Ideal, homogeneous, magnetohydrodynamic turbulence is represented by finite Fourier series whose coefficients form a canonical ensemble. Here, the relevant statistical theory is substantially extended. This includes finding eigenvalues and eigenvectors of the covariance matrix for each modal probability density. The eigenvectors allow for a special unitary transformation of phase space coordinates into a set of eigenvariables. The smallest eigenvalues occur at the lowest wavenumber and are associated with three dominant eigenvectors. The lowest wavenumber eigenvariables, in statistical equilibrium, are seen to have large mean values containing significant energy and thus define a homogeneous turbulent dynamo. These large mean values arise because the symmetry of phase space is dynamically broken. Nonzero viscosity and magnetic diffusivity are expected to have minimal effect, since this coherent structure exists at the lowest wavenumber, where dissipation is least.
Influence of antiferromagnetic exchange interaction on magnetic properties of ZnMnO thin films grown pseudomorphically on ZnO (0001¯) single-crystal substrates
Authors: Masuko K. , Ashida A. , Yoshimura T. , Fujimura N.
Published: February 2008

This study investigated the influence of antiferromagnetic exchange interaction on magnetic properties of ZnMnO thin films grown on ZnO (0001¯) single-crystal substrates. Using pulsed laser deposition, ZnMnO films with Mn concentrations as high as 14.1at.% were prepared. Investigations revealed that the lattice constant along the c axis of the ZnMnO films increases linearly with increasing Mn concentration. The lattice constant along the a axis is independent of the Mn concentration and is equal to that of the ZnO substrate, suggesting pseudomorphic growth of ZnMnO films. An atomic force microscopy image of the ZnMnO film grown at 640°C shows a step-and-terrace structure. An interference fringe around the ZnMnO 0004 symmetric diffraction image is clearly visible in the 2θ-ω x-ray diffraction profile, suggesting that the samples have a smooth surface and an abrupt interface. The intrinsic magnetic properties of these pseudomorphically grown ZnMnO films with smooth surfaces were evaluated. At temperatures greater than 1.85K, ZnMnO films with Mn concentration up to 14.1at.% exhibit typical paramagnetic characteristics. As calculated using the probabilities for a random Mn distribution, the theoretically magnetic moment agreed with the experimentally determined saturated magnetic moment, indicating an antiferromagnetic exchange interaction between the nearest-neighbor Mn ions.
A new technique for time-resolved daughter ion mass spectrometry on the microsecond to millisecond time scale using an electrostatic ion storage ring
Authors: Støchkel Kristian , Kadhane Umesh , Andersen Jens Ulrik , Holm Anne I. S. , Hvelplund Preben , Kirketerp Maj-Britt Suhr , Larsen Mikkel Koefoed , Lykkegaard Morten Køcks , Nielsen Steen Brøndsted , Panja Subhasis , Zettergren Henning
Published: February 2008

A new method for time-resolved daughter ion mass spectrometry is presented, based on the electrostatic ion storage ring in Aarhus, ELISA. Ions with high internal energy, e.g., as a result of photoexcitation, dissociate and the yield of neutrals is monitored as a function of time. This gives information on lifetimes in the microsecond to millisecond time range but no information on the fragment masses. To determine the dissociation channels, we have introduced pulsed supplies with switching times of a few microseconds. This allows rapid switching from storage of parent ions to storage of daughter ions, which are dumped into a detector after a number of revolutions in the ring. A fragment mass spectrum is obtained by monitoring the daughter ion signal as a function of the ring voltages. This technique allows identification of the dissociation channels and determination of the time dependent competition between these channels.
Surface plasmon polariton modes in a single-crystal Au nanoresonator fabricated using focused-ion-beam milling
Authors: Vesseur E. J. R. , de Waele R. , Lezec H. J. , Atwater H. A. , García de Abajo F. J. , Polman A.
Published: February 2008

We use focused-ion-beam milling of a single-crystal Au surface to fabricate a 590-nm-long linear ridge that acts as a surface plasmon nanoresonator. Cathodoluminescence imaging spectroscopy is then used to excite and image surface plasmons on the ridge. Principal component analysis reveals distinct plasmonic modes, which proves confinement of surface plasmon oscillations to the ridge. Boundary-element-method calculations confirm that a linear ridge is able to support highly localized surface plasmon modes (mode diameter <100nm). The results demonstrate that focused-ion-beam milling can be used in rapid prototyping of nanoscale single-crystal plasmonic components.
Regulation of synaptic inhibition by phospho-dependent binding of the AP2 complex to a YECL motif in the GABA
A
receptor γ2 subunit
Authors: Kittler Josef T. , Chen Guojun , Kukhtina Viktoria , Vahedi-Faridi Ardeschir , Gu Zhenglin , Tretter Verena , Smith Katharine R. , McAinsh Kristina , Arancibia-Carcamo I. Lorena , Saenger Wolfram , Haucke Volker , Yan Zhen , Moss Stephen J.
Published: February 2008

The regulation of the number of γ2-subunit-containing GABA
A
receptors (GABA
A
Rs) present at synapses is critical for correct synaptic inhibition and animal behavior. This regulation occurs, in part, by the controlled removal of receptors from the membrane in clathrin-coated vesicles, but it remains unclear how clathrin recruitment to surface γ2-subunit-containing GABA
A
Rs is regulated. Here, we identify a γ2-subunit-specific Yxxφ-type-binding motif for the clathrin adaptor protein, AP2, which is located within a site for γ2-subunit tyrosine phosphorylation. Blocking GABA
A
R-AP2 interactions via this motif increases synaptic responses within minutes. Crystallographic and biochemical studies reveal that phosphorylation of the Yxxφ motif inhibits AP2 binding, leading to increased surface receptor number. In addition, the crystal structure provides an explanation for the high affinity of this motif for AP2 and suggests that γ2-subunit-containing heteromeric GABA
A
Rs may be internalized as dimers or multimers. These data define a mechanism for tyrosine kinase regulation of GABA
A
R surface levels and synaptic inhibition.
MHC class II stabilization at the surface of human dendritic cells is the result of maturation-dependent MARCH I down-regulation
Authors: De Gassart Aude , Camosseto Voahirana , Thibodeau Jacques , Ceppi Maurizio , Catalan Nadia , Pierre Philippe , Gatti Evelina
Published: February 2008

In response to Toll-like receptor ligands, dendritic cells (DCs) dramatically enhance their antigen presentation capacity by stabilizing at the cell-surface MHC II molecules. We demonstrate here that, in human monocyte-derived DCs, the RING-CH ubiquitin E3 ligase, membrane-associated RING-CH I (MARCH I), promotes the ubiquitination of the HLA-DR β-chain. Thus, in nonactivated DCs, MARCH I induces the surface internalization of mature HLA-DR complexes, therefore reducing their stability and levels. We further demonstrate that the maturation-dependent down-regulation of MARCH I is a key event in MHC class II up-regulation at the surface of LPS-activated DCs. MARCH I is, therefore, a major regulator of HLA-DR traffic, and its loss contributes to the acquisition of the potent immunostimulatory properties of mature human DCs.
Internal body state influences topographical plasticity of sensory representations in the rat gustatory cortex
Authors: Accolla Riccardo , Carleton Alan
Published: February 2008

Primary sensory cortices are remarkably organized in spatial maps according to specific sensory features of the stimuli. These cortical maps can undergo plastic rearrangements after changes in afferent (“bottom-up”) sensory inputs such as peripheral lesions or passive sensory experience. However, much less is known about the influence of “top-down” factors on cortical plasticity. Here, we studied the effect of a visceral malaise on taste representations in the gustatory cortex (GC). Using
in vivo
optical imaging, we showed that inducing conditioned taste aversion (CTA) to a sweet and pleasant stimulus induced plastic rearrangement of its cortical representation, becoming more similar to a bitter and unpleasant taste representation. Using a behavior task, we showed that changes in hedonic perception are directly related to the maps plasticity in the GC. Indeed imaging the animals after CTA extinction indicated that sweet and bitter representations were dissimilar. In conclusion, we showed that an internal state of malaise induces plastic reshaping in the GC associated to behavioral shift of the stimulus hedonic value. We propose that the GC not only encodes taste modality, intensity, and memory but extends its integrative properties to process also the stimulus hedonic value.
Distinct regulatory role for
RFL
, the rice
LFY
homolog, in determining flowering time and plant architecture
Authors: Rao Nagashree N. , Prasad Kalika , Kumar Puja Ravi , Vijayraghavan Usha
Published: February 2008

Activity of axillary meristems dictates the architecture of both vegetative and reproductive parts of a plant. In
Arabidopsis thaliana
, a model eudicot species, the transcription factor LFY confers a floral fate to new meristems arising from the periphery of the reproductive shoot apex. Diverse orthologous
LFY
genes regulate vegetative-to-reproductive phase transition when expressed in
Arabidopsis
, a property not shared by
RFL
, the homolog in the agronomically important grass, rice. We have characterized
RFL
by knockdown of its expression and by its ectopic overexpression in transgenic rice. We find that reduction in
RFL
expression causes a dramatic delay in transition to flowering, with the extreme phenotype being no flowering. Conversely,
RFL
overexpression triggers precocious flowering. In these transgenics, the expression levels of known flowering time genes reveal
RFL
as a regulator of
OsSOC1
(
OsMADS50
), an activator of flowering. Aside from facilitating a transition of the main growth axis to an inflorescence meristem,
RFL
expression status affects vegetative axillary meristems and therefore regulates tillering. The unique spatially and temporally regulated
RFL
expression during the development of vegetative axillary bud (tiller) primordia and inflorescence branch primordia is therefore required to produce tillers and panicle branches, respectively. Our data provide mechanistic insights into a unique role for
RFL
in determining the typical rice plant architecture by regulating distinct downstream pathways. These results offer a means to alter rice flowering time and plant architecture by manipulating RFL-mediated pathways.
Altered morphology and 3D architecture of brain vasculature in a mouse model for Alzheimer's disease
Authors: Meyer Eric P. , Ulmann-Schuler Alexandra , Staufenbiel Matthias , Krucker Thomas
Published: February 2008

Substantial evidence from epidemiological, pathological, and clinical reports suggests that vascular factors are critical in the pathogenesis of Alzheimer's disease (AD), and changes in blood flow are currently the most reliable indicators of the disease. We previously reported that older APP23 transgenic (tg) mice have significant blood flow alterations correlated with structural modifications of blood vessels. For the present study, our objective was to analyze the age-dependent morphological and architectural changes of the cerebral vasculature of APP23 tg mice. To visualize the 3D arrangement of the entire brain vasculature, we used vascular corrosion casts. Already at young ages, when typically parenchymal amyloid plaques are not yet present, APP23 tg mice had significant alterations, particularly of the microvasculature, often accompanied by small deposits attached to the vessels. In older animals, vasculature abruptly ended at amyloid plaques, resulting in holes. Often, small deposits were sitting near or at the end of truncated vessels. Between such holes, the surrounding vascular array appeared more dense and showed features typical for angiogenesis. We propose that small amyloid aggregates associated with the microvasculature lead to morphological and architectural alterations of the vasculature, resulting in altered local blood flow. The characteristic early onset of vascular alterations suggests that imaging blood flow and/or vasculature architecture could be used as a tool for early diagnosis of the disease and to monitor therapies.
Behavioral consequences of innate preferences and olfactory learning in hawkmoth–flower interactions
Authors: Riffell Jeffrey A. , Alarcón Ruben , Abrell Leif , Davidowitz Goggy , Bronstein Judith L. , Hildebrand John G.
Published: February 2008

Spatiotemporal variability in floral resources can have ecological and evolutionary consequences for both plants and the pollinators on which they depend. Seldom, however, can patterns of flower abundance and visitation in the field be linked with the behavioral mechanisms that allow floral visitors to persist when a preferred resource is scarce. To explore these mechanisms better, we examined factors controlling floral preference in the hawkmoth
Manduca sexta
in the semiarid grassland of Arizona. Here, hawkmoths forage primarily on flowers of the bat-adapted agave,
Agave palmeri
, but shift to the moth-adapted flowers of their larval host plant,
Datura wrightii
, when these become abundant. Both plants emit similar concentrations of floral odor, but scent composition, nectar, and flower reflectance are distinct between the two species, and
A. palmeri
flowers provide six times as much chemical energy as flowers of
D. wrightii
. Behavioral experiments with both naïve and experienced moths revealed that hawkmoths learn to feed from agave flowers through olfactory conditioning but readily switch to
D. wrightii
flowers, for which they are the primary pollinator, based on an innate odor preference. Behavioral flexibility and the olfactory contrast between flowers permit the hawkmoths to persist within a dynamic environment, while at the same time to function as the major pollinator of one plant species.
Peptidergic influences on proliferation, migration, and placement of neural progenitors in the adult mouse forebrain
Authors: Stanić Davor , Paratcha Gustavo , Ledda Fernanda , Herzog Herbert , Kopin Alan S. , Hökfelt Tomas
Published: February 2008

Neural progenitor proliferation, differentiation, and migration are continually ongoing processes in the subventricular zone (SVZ) and rostral migratory stream (RMS) of the adult brain. There is evidence that peptidergic systems may be involved in the molecular cascades regulating these neurogenic processes, and we examined a possible influence of neuropeptide Y (NPY) and cholecystokinin (CCK) systems in cell proliferation and neuroblast formation in the SVZ and RMS and generation of interneurons in the olfactory bulb (OB). We show that NPY and the Y1 and Y2 receptor (R) proteins are expressed in and surrounding the SVZ and RMS and that Y1R is located on neuroblasts in the anterior RMS. Mice deficient in Y1Rs or Y2Rs have fewer Ki-67-immunoreactive (ir) proliferating precursor cells and doublecortin-ir neuroblasts in the SVZ and RMS than WT mice, and less calbindin-, calretinin-, and tyrosine hydroxylase-ir interneurons in the OB. Mice lacking CCK1Rs have fewer proliferating cells and neuroblasts than normal and a shortage of interneurons in the OB. These findings suggest that both NPY and CCK through their receptors help to regulate the proliferation of precursor cells, the amount of neuroblast cells in the SVZ and RMS, and influence the differentiation of OB interneurons.
Distinct genomic signatures of adaptation in pre- and postnatal environments during human evolution
Authors: Uddin Monica , Goodman Morris , Erez Offer , Romero Roberto , Liu Guozhen , Islam Munirul , Opazo Juan C. , Sherwood Chet C. , Grossman Lawrence I. , Wildman Derek E.
Published: February 2008

The human genome evolution project seeks to reveal the genetic underpinnings of key phenotypic features that are distinctive of humans, such as a greatly enlarged cerebral cortex, slow development, and long life spans. This project has focused predominantly on genotypic changes during the 6-million-year descent from the last common ancestor (LCA) of humans and chimpanzees. Here, we argue that adaptive genotypic changes during earlier periods of evolutionary history also helped shape the distinctive human phenotype. Using comparative genome sequence data from 10 vertebrate species, we find a signature of human ancestry-specific adaptive evolution in 1,240 genes during their descent from the LCA with rodents. We also find that the signature of adaptive evolution is significantly different for highly expressed genes in human fetal and adult-stage tissues. Functional annotation clustering shows that on the ape stem lineage, an especially evident adaptively evolved biological pathway contains genes that function in mitochondria, are crucially involved in aerobic energy production, and are highly expressed in two energy-demanding tissues, heart and brain. Also, on this ape stem lineage, there was adaptive evolution among genes associated with human autoimmune and aging-related diseases. During more recent human descent, the adaptively evolving, highly expressed genes in fetal brain are involved in mediating neuronal connectivity. Comparing adaptively evolving genes from pre- and postnatal-stage tissues suggests that different selective pressures act on the development vs. the maintenance of the human phenotype.
Association between a Mediterranean‐type diet and risk of preterm birth among Danish women: a prospective cohort study
Authors: MIKKELSEN TINA B. , LOUISE ØSTERDAL MARIE , KNUDSEN VIBEKE K. , HAUGEN MARGARETHA , MELTZER HELLE M. , BAKKETEIG LEIV , OLSEN SJURDUR F.
Published: February 2008

Background. Thus far, few factors with a causal relation to preterm birth have been identified. Many studies have focused on the woman's diet, but most have been discouraging. The aim of the present study was to examine if maternal intake of a Mediterranean‐type diet (MD) is associated with reduced risk of preterm birth.Methods. The Danish National Birth Cohort assessed diet in mid‐pregnancy by food frequency questionnaires (FFQ). Women consuming MD were those who ate fish twice a week or more, used olive or rape seed oil, consumed 5+ fruits and vegetables a day, ate meat (other than poultry and fish) at most twice a week, and drank at most 2 cups of coffee a day.Results. Of 35,530 non‐smoking women, 1,137 (3.2%) fulfilled all MD criteria, and 540 (1.5%) none. Odds ratios for preterm birth and early preterm birth were 0.61 (95% Confidence Interval (CI): 0.35–1.05) and 0.28 (0.11–0.76), respectively, in MD women compared to women fulfilling none of the MD criteria.Conclusion. Shifting towards a MD during pregnancy may reduce the risk of early delivery in Danish women.
Increased fetal cardiac natriuretic peptide secretion in type‐1 diabetic pregnancies
Authors: GIRSEN ANNA , ALA‐KOPSALA MINNA , MÄKIKALLIO KAARIN , VUOLTEENAHO OLLI , RÄSÄNEN JUHA
Published: February 2008

Background. We hypothesised that human fetal cardiac natriuretic peptide secretion is increased in type‐1 diabetic pregnancies with normal placental hemodynamics, and this increase is related to the first trimester maternal glycemic control. Methods. Thirty‐two neonates of type‐1 diabetic mothers and 60 neonates born after uncomplicated pregnancy and labour (control group) were included in this study. Diabetic pregnancies were divided into two subgroups based on the first trimester HbA1c value. Group 1 pregnancies (n =22) had a good glycemic control (HbA1c <7.5%) and Group 2 pregnancies (n =10) had a poor glycemic control (HbA1c ≥7.5%). At delivery, an umbilical artery (UA) blood sample was obtained for assessment of N‐terminal peptide of proatrial (NT‐proANP) and proB‐type (NT‐proBNP) natriuretic peptide levels. In diabetic pregnancies, each fetus had normal UA Doppler velocimetry for gestational age. Results. The newborn UA NT‐proANP and NT‐proBNP concentrations were significantly higher in type‐1 diabetic pregnancies than in the control group. Group 2 fetuses with poor glycemic control showed significantly higher UA NT‐proANP levels than Group 1 fetuses. UA NT‐proANP levels correlated significantly with maternal HbA1c values in the first, second and third trimesters, while UA NT‐proBNP levels did not correlate with maternal HbA1c values. Conclusions. In type‐1 diabetic pregnancies, fetal cardiac natriuretic peptide secretion is increased, even in the presence of good glycemic control and normal placental hemodynamics. In addition, fetal NT‐proANP levels are already related to maternal glycemic control in the first trimester of pregnancy.
Twin‐to‐twin delivery time interval: influencing factors and effect on short‐term outcome of the second twin
Authors: STEIN WERNER , MISSELWITZ BJÖRN , SCHMIDT STEFAN
Published: February 2008

Background. Following vaginal delivery of the first twin, the further management to deliver the second twin is in dispute. Controversial discussions have taken place on the importance of the time interval between the birth of the first and the second twin. Objective. To evaluate factors influencing twin‐to‐twin delivery time interval, and short‐term outcome of the second twin in a complete population‐based cohort in Hesse, Germany. Study design. In a population‐based cohort study, between January 1990 and December 2004, all twin pregnancies of ≥34+0 weeks’ gestation with a vaginally delivered first twin were evaluated. Pregnancies with intrauterine death of either one of the twins before the onset of labour, complicated by twin–twin transfusion or fetal malformations were excluded. Some 4,110 twin pregnancies were analysed. Maternal and fetal characteristics for an increased twin‐to‐twin delivery time interval and its impact on an adverse short‐term neonatal outcome, and the effect of the twin‐to‐twin delivery interval on umbilical arterial pH and base excess of the second twin have been investigated. Results. In univariate analysis, breech, transverse lie, birth weight discordance with the second twin ≥20% larger, fetal distress, vaginal operative delivery, and caesarean section were associated with an increased time interval. Maternal characteristics were not related to an increased time interval. Increasing time interval was related to a decline in the mean umbilical arterial pH and base excess, and fetal acidosis, Apgar score <7 after 1, 5 and 10 min. In multivariate analysis, birth weight discordance, mode of delivery, and twin‐to‐twin delivery time interval were associated with an adverse short‐term outcome of the second twin. Conclusion. As twin‐to‐twin delivery time interval seems to be an independent risk factor for adverse short‐term outcome of the second twin, it should be kept short.
Role for SUR2A ED Domain in Allosteric Coupling within the KATP Channel Complex
Authors: Karger Amy B. , Park Sungjo , Reyes Santiago , Bienengraeber Martin , Dyer Roy B. , Terzic Andre , Alekseev Alexey E.
Published: February 2008

Allosteric regulation of heteromultimeric ATP-sensitive potassium (KATP) channels is unique among protein systems as it implies transmission of ligand-induced structural adaptation at the regulatory SUR subunit, a member of ATP-binding cassette ABCC family, to the distinct pore-forming K+ (Kir6.x) channel module. Cooperative interaction between nucleotide binding domains (NBDs) of SUR is a prerequisite for KATP channel gating, yet pathways of allosteric intersubunit communication remain uncertain. Here, we analyzed the role of the ED domain, a stretch of 15 negatively charged aspartate/glutamate amino acid residues (948–962) of the SUR2A isoform, in the regulation of cardiac KATP channels. Disruption of the ED domain impeded cooperative NBDs interaction and interrupted the regulation of KATP channel complexes by MgADP, potassium channel openers, and sulfonylurea drugs. Thus, the ED domain is a structural component of the allosteric pathway within the KATP channel complex integrating transduction of diverse nucleotide-dependent states in the regulatory SUR subunit to the open/closed states of the K+-conducting channel pore.
Gating Charge Immobilization in Kv4.2 Channels: The Basis of Closed-State Inactivation
Authors: Dougherty Kevin , De Santiago-Castillo Jose A. , Covarrubias Manuel
Published: February 2008

Kv4 channels mediate the somatodendritic A-type K+ current (ISA) in neurons. The availability of functional Kv4 channels is dynamically regulated by the membrane potential such that subthreshold depolarizations render Kv4 channels unavailable. The underlying process involves inactivation from closed states along the main activation pathway. Although classical inactivation mechanisms such as N- and P/C-type inactivation have been excluded, a clear understanding of closed-state inactivation in Kv4 channels has remained elusive. This is in part due to the lack of crucial information about the interactions between gating charge (Q) movement, activation, and inactivation. To overcome this limitation, we engineered a charybdotoxin (CTX)-sensitive Kv4.2 channel, which enabled us to obtain the first measurements of Kv4.2 gating currents after blocking K+ conduction with CTX (Dougherty and Covarrubias. 2006J. Gen. Physiol. 128:745–753). Here, we exploited this approach further to investigate the mechanism that links closed-state inactivation to slow Q-immobilization in Kv4 channels. The main observations revealed profound Q-immobilization at steady-state over a range of hyperpolarized voltages (−110 to −75 mV). Depolarization in this range moves <5% of the observable Q associated with activation and is insufficient to open the channels significantly. The kinetics and voltage dependence of Q-immobilization and ionic current inactivation between −153 and −47 mV are similar and independent of the channel's proximal N-terminal region (residues 2–40). A coupled state diagram of closed-state inactivation with a quasi-absorbing inactivated state explained the results from ionic and gating current experiments globally. We conclude that Q-immobilization and closed-state inactivation at hyperpolarized voltages are two manifestations of the same process in Kv4.2 channels, and propose that inactivation in the absence of N- and P/C-type mechanisms involves desensitization to voltage resulting from a slow conformational change of the voltage sensors, which renders the channel's main activation gate reluctant to open.