bluuebunny/crossref_metadata_2025 huggingface dataset:
Bone Marrow Stromal Cells Enhance Inter- and Intracortical Axonal Connections after Ischemic Stroke in Adult Rats
Authors: Liu Zhongwu , Li Yi , Zhang Zheng Gang , Cui Xu , Cui Yisheng , Lu Mei , Savant-Bhonsale Smita , Chopp Michael
Published: February 2010

We investigated axonal plasticity in the bilateral motor cortices in rats after unilateral stroke and bone marrow stromal cell (BMSC) treatment. Rats were subjected to permanent right middle cerebral artery occlusion followed by intravenous administration of phosphate-buffered saline or BMSCs 1 day later. Adhesive-removal test and modified neurologic severity score were performed weekly to monitor limb functional deficit and recovery. Anterograde tracing with biotinylated dextran amine injected into the right motor cortex was used to assess axonal sprouting in the contralateral motor cortex and ipsilateral rostral forelimb area. Animals were killed 28 days after stroke. Progressive functional recovery was significantly enhanced by BMSCs. Compared with normal animals, axonal density in both contralateral motor cortex and ipsilateral rostral forelimb area significantly increased after stroke. Bone marrow stromal cells markedly enhanced such interhemispheric and intracortical connections. However, labeled transcallosal axons in the corpus callosum were not altered with either stroke or treatment. Both interhemispheric and intracortical axonal sprouting were significantly and highly correlated with behavioral outcome after stroke. This study suggests that, after stroke, cortical neurons surviving in the peri-infarct motor cortex undergo axonal sprouting to restore connections between different cerebral areas. Bone marrow stromal cells enhance axonal plasticity, which may underlie neurologic functional improvement.
Differential Changes of Glutathione Levels in Astrocytes and Neurons in Ischemic Brains by Two-Photon Imaging
Authors: Bragin Denis E , Zhou Bo , Ramamoorthy Prabhu , Müller Wolfgang S , Connor John A , Shi Honglian
Published: February 2010

Using two-photon imaging techniques with monochlorobimane as a glutathione (GSH) probe, we investigated GSH levels in both core and penumbra regions of an ischemic brain after middle cerebral artery occlusion. We found that the GSH level significantly decreased in the ischemic core, but increased significantly in the penumbra. Furthermore, we observed a differential change of the GSH levels in neurons and astrocytes in the penumbra. The GSH level in neurons increased significantly whereas it decreased slightly in astrocytes in the penumbra. These findings reveal critical region and cell type-dependent changes of the GSH level in an ischemic brain.
Improved near-field scanning microwave microscope combined with electrical transport measurement for characterizing nonuniformity of electrical dissipation in YBa2Cu3O7−δ films of variable thickness
Authors: Dizon Jonathan R. , Wang Xiang , Wu Judy Z.
Published: February 2010

An improved near-field scanning microwave microscope (NSMM) combined with electrical transport measurement was applied for characterizing nonuniformity of electrical dissipation in YBa2Cu3O7−δ (YBCO) films. We demonstrate identification of the current-obstructing defects in thin (thickness below 300nm) YBCO films by mapping microwave-induced electrical voltage (ΔV) and reflected microwave power on the sample. In addition, the technique was also found to be suitable for characterizing electrical dissipation in thick YBCO films of a few micrometer thick. In order to improve the spatial resolution to submicron regime, we have employed a hybrid probe tip with a submicron tip diameter and operate the NSMM to its second harmonic frequency to increase hot spot microwave absorption. A much improved spatial resolution in the submicrometer range for the microwave maps was achieved while maintaining the sensitivity in the ΔV measurement.
Highly efficient blue organic light emitting device using indium-free transparent anode Ga:ZnO with scalability for large area coating
Authors: Wang Liang , Matson Dean W. , Polikarpov Evgueni , Swensen James S. , Bonham Charles C. , Cosimbescu Lelia , Berry Joseph J. , Ginley David S. , Gaspar Daniel J. , Padmaperuma Asanga B.
Published: February 2010

Organic light emitting devices have been achieved with an indium-free transparent anode, Ga doped ZnO (GZO). A large area coating technique was used (RF magnetron sputtering) to deposit the GZO films onto glass. The respective organic light emitting devices exhibited an operational voltage of 3.7 V, an external quantum efficiency of 17%, and a power efficiency of 39 lm/W at a current density of 1 mA/cm2. These parameters are well within acceptable standards for blue OLEDs to generate a white light with high enough brightness for general lighting applications. It is expected that high-efficiency, long-lifetime, large area, and cost-effective white OLEDs can be made with these indium-free anode materials.
Extraction of poly (3-hexylthiophene) (P3HT) properties from dark current voltage characteristics in a P3HT/n-crystalline-silicon solar cell
Authors: Nolasco J. C. , Cabré R. , Ferré-Borrull J. , Marsal L. F. , Estrada M. , Pallarès J.
Published: February 2010

The dark current-voltage characteristics of poly (3-hexylthiophene) (P3HT)/n-type crystalline silicon solar cells were analyzed using an electrical equivalent circuit. We found that without illumination transport occurs due to hopping between localized states at the P3HT/silicon interface not only at low voltages, through multitunneling capture emission, but also at medium voltages, through tunneling-enhanced recombination. At high voltages the current is limited by series resistance and space-charge limited mechanisms. At low reverse voltages the current is limited by shunt resistance. From the temperature dependence of the equivalent circuit’s fitting parameters, we were able to estimate some physical parameters of the P3HT layer, namely the electron affinity, the charge carrier concentration and the characteristic temperature of the exponential trap distribution. The extracted P3HT values are in good agreement with previously reported values obtained using different methods but our approach takes into account that the P3HT layer is in a solar cell.
Barycentric decomposition of quantum measurements in finite dimensions
Authors: Chiribella Giulio , D’Ariano Giacomo Mauro , Schlingemann Dirk
Published: February 2010

We analyze the convex structure of the set of positive operator valued measures (POVMs) representing quantum measurements on a given finite dimensional quantum system, with outcomes in a given locally compact Hausdorff space. The extreme points of the convex set are operator valued measures concentrated on a finite set of k≤d2 points of the outcome space, d<∞ being the dimension of the Hilbert space. We prove that for second-countable outcome spaces any POVM admits a Choquet representation as the barycenter of the set of extreme points with respect to a suitable probability measure. In the general case, Krein–Milman theorem is invoked to represent POVMs as barycenters of a certain set of POVMs concentrated on k≤d2 points of the outcome space.
The radial wave operator in similarity coordinates
Authors: Donninger Roland
Published: February 2010

We present a rigorous functional analytic setting to study the radial wave equation in similarity coordinates. As an application we analyze linear stability of the fundamental self-similar solution of the wave equation with a focusing power nonlinearity. This is Part 1 in a series of papers [Donninger, R., “Asymptotics and analytic modes for the wave equation in similarity coordinates,” J. Evol. Equ. 9, 511 (2009); Donninger, R., “Nonlinear stability of self-similar solutions for semilinear wave equations,” Commun. Partial Differ. Equ.].
Comparing geometric and kinetic cluster algorithms for molecular simulation data
Authors: Keller Bettina , Daura Xavier , van Gunsteren Wilfred F.
Published: February 2010

The identification of metastable states of a molecule plays an important role in the interpretation of molecular simulation data because the free-energy surface, the relative populations in this landscape, and ultimately also the dynamics of the molecule under study can be described in terms of these states. We compare the results of three different geometric cluster algorithms (neighbor algorithm, K-medoids algorithm, and common-nearest-neighbor algorithm) among each other and to the results of a kinetic cluster algorithm. First, we demonstrate the characteristics of each of the geometric cluster algorithms using five two-dimensional data sets. Second, we analyze the molecular dynamics data of a β-heptapeptide in methanol—a molecule that exhibits a distinct folded state, a structurally diverse unfolded state, and a fast folding/unfolding equilibrium—using both geometric and kinetic cluster algorithms. We find that geometric clustering strongly depends on the algorithm used and that the density based common-nearest-neighbor algorithm is the most robust of the three geometric cluster algorithms with respect to variations in the input parameters and the distance metric. When comparing the geometric cluster results to the metastable states of the β-heptapeptide as identified by kinetic clustering, we find that in most cases the folded state is identified correctly but the overlap of geometric clusters with further metastable states is often at best approximate.
Investigations of lower hybrid wave-plasma coupling by gas puffing in HT-7
Authors: Ding B. J. , Li M. H. , Qin Y. L. , Li W. K. , Zhang L. Z. , Shan J. F. , Liu F. K. , Wang M. , Meng L. G. , Xu H. D. , Wang D. X. , Jie Y. X. , Sun Y. W. , Shen B. , Zhang W. , Wang X. M. , Wu J. H. , Gao X. , Zhang X. D. , Zhao Y. P. ,   HT-7 Team
Published: February 2010

Lower hybrid wave (LHW)-plasma coupling experiments in HT-7 [J. K. Xie and HT-7 Group, Proceedings of the 16th International Conference on Fusion Energy, Montreal, 1996 (IAEA, Trieste, 1997), Vol. 1, p. 685] were carried out by means of puffing gas (CD4 and D2) just around the antenna. Both experiments show that wave-plasma coupling is improved by the gas puffing. The maximum distance between the plasma and the antenna is limited to about 8 cm due to the plasma disruption. The variation in the lined averaged density in the different channels gives a possible evidence of the mechanism of the ionization of neutral gas. The effect of the gas flow rate on the wave-plasma coupling shows that an optimized gas flow rate is necessary for good coupling, being consistent with simulation through Brambilla theory qualitatively. Experiments with puffing D2 show that the improved coupling results from the global density increase and the local gas puffing. Langmuir probe measurements indicate that the gas puffing effectively increases the density and decreases the temperature in scrape of layer. Studies show that the ionization of the puffed gas is affected by both LHW electric field and plasma temperature. Comparison of D2 and CD4 puffing shows that D2 improves coupling better with less effect on core density.
A universal support vector machines based method for automatic event location in waveforms and video-movies: Applications to massive nuclear fusion databases
Authors: Vega J. , Murari A. , González S. ,   JET-EFDA Contributors
Published: February 2010

Big physics experiments can collect terabytes (even petabytes) of data under continuous or long pulse basis. The measurement systems that follow the temporal evolution of physical quantities translate their observations into very large time-series data and video-movies. This article describes a universal and automatic technique to recognize and locate inside waveforms and video-films both signal segments with data of potential interest for specific investigations and singular events. The method is based on regression estimations of the signals using support vector machines. A reduced number of the samples is shown as outliers in the regression process and these samples allow the identification of both special signatures and singular points. Results are given with the database of the JET fusion device: location of sawteeth in soft x-ray signals to automate the plasma incremental diffusivity computation, identification of plasma disruptive behaviors with its automatic time instant determination, and, finally, recognition of potential interesting plasma events from infrared video-movies.
Viscous linear stability of axisymmetric low-density jets: Parameters influencing absolute instability
Authors: Srinivasan V. , Hallberg M. P. , Strykowski P. J.
Published: February 2010

Viscous linear stability calculations are presented for model low-density axisymmetric jet flows. Absolute growth transitions for the jet column mode are mapped out in a parametric space including velocity ratio, density ratio, Reynolds number, momentum thickness, and subtle differences between velocity and density profiles. Strictly speaking, the profiles used in most jet stability studies to date are only applicable to unity Prandtl numbers and zero pressure gradient flows—the present work relaxes this requirement. Results reveal how subtle differences between the velocity and density profiles generally used in jet stability theory can dramatically alter the absolute growth rate of the jet column mode in these low-density flows. The results suggest heating/cooling or mass diffusion at the outer nozzle surface can suppress absolute instability and potentially global instability in low-density jets.
Simple filtered repetitively pulsed vacuum arc plasma source
Authors: Chekh Yu. , Zhirkov I. S. , Delplancke-Ogletree M. P.
Published: February 2010

A very simple design of cathodic filtered vacuum arc plasma source is proposed. The source without filter has only four components and none of them require precise machining. The source operates in a repetitively pulsed regime, and for laboratory experiments it can be used without water cooling. Despite the simple construction, the source provides high ion current at the filter outlet reaching 2.5% of 400 A arc current, revealing stable operation in a wide pressure range from high vacuum to oxygen pressure up to more than 10−2 mbar. There is no need in complicated power supply system for this plasma source, only one power supply can be used to ignite the arc, to provide the current for the arc itself, to generate the magnetic field in the filter, and provide its positive electric biasing without any additional high power resistance.
Effect of Ge passivation on interfacial properties of crystalline Gd2O3 thin films grown on Si substrates
Authors: Laha Apurba , Fissel A. , Osten H. J.
Published: February 2010

The incorporation of few monolayers of Ge chemisorbed on Si surface has been found to have significant impact on the electrical properties of crystalline Gd2O3 grown epitaxially on Si substrates. Although the Ge coverage on Si surface does not show any influence on the epitaxial quality of Gd2O3 layers, however, it exhibits a strong impact on their electrical properties. We show that by incorporating few monolayers of Ge at the interface between Gd2O3 and Si, the capacitance-voltage characteristics, fixed charge and density of interface traps of Pt/Gd2O3/Si capacitor are much superior to those layers grown on clean Si surfaces.
Morphological stability and specific resistivity of sub-10 nm silicide films of Ni1−xPtx on Si substrate
Authors: Zhang Zhen , Zhang Shi-Li , Yang Bin , Zhu Yu , Rossnagel Stephen M. , Gaudet Simon , Kellock Andrew J. , Jordan-Sweet Jean , Lavoie Christian
Published: February 2010

This letter studies the morphological stability and specific resistivity of sub-10 nm silicide films of Ni, Ni0.95Pt0.05, and Ni0.9Pt0.1 formed on Si(100) substrate. When the deposited metal films are below 1 to 4 nm in thickness depending on the Pt content, the resultant silicide films tend to become epitaxially aligned to the Si substrate and hence exhibit an extraordinary morphological stability up to 800 °C. The presence of Pt in the silicides increases the film resistivity through alloy scattering, but alleviates, owing to a reduced electron mean free path, the frequently encountered sharp increase in resistivity in the sub-10 nm regime.
Resistive interlayer for improved performance of thin film silicon solar cells on highly textured substrate
Authors: Despeisse M. , Bugnon G. , Feltrin A. , Stueckelberger M. , Cuony P. , Meillaud F. , Billet A. , Ballif C.
Published: February 2010

The deposition of thin-film silicon solar cells on highly textured substrates results in improved light trapping in the cell. However, the growth of silicon layers on rough substrates can often lead to undesired current drains, degrading performance and reliability of the cells. We show that the use of a silicon oxide interlayer between the active area and the back contact of the cell permits in such cases to improve the electrical properties. Relative increases of up to 7.5% of fill factor and of 6.8% of conversion efficiency are shown for amorphous silicon cells deposited on highly textured substrates, together with improved yield and low-illumination performance.
Ethnic Spatial Segregation and Tobacco Consumption: A Multilevel Repeated Cross-Sectional Analysis of Smoking Prevalence in Urban New Zealand, 1981–1996
Authors: Moon Graham , Barnett Ross , Pearce Jamie
Published: February 2010

The growing literature on the role of ethnic segregation in understanding spatial inequalities in mortality and morbidity has not yet been extended to the study of health-related behaviours. We address this gap in knowledge through an examination of the geography of smoking prevalence in New Zealand, using a multilevel repeated cross-sectional analysis of smoking prevalences in 1981 and 1996 as revealed in the New Zealand census. Smoking prevalences are explored for fourteen age and sex groups, nested in 1110 census area units. These in turn are nested in forty primary and secondary urban areas. We consider different measures of segregation and focus in detail on the relationship between smoking and Māori ethnic isolation. We examine the interplay between deprivation and segregation, addressing questions concerning the impact of changing segregation on changes in smoking behaviour. We hypothesise that more highly segregated populations suffer more psychosocial stress and so may smoke more. Results reveal the changing dynamics of smoking prevalence over time, and challenge initial assumptions that spatial ethnic segregation should relate to smoking prevalence.
Homeownership and Labour-Market Behaviour: Interpreting the Evidence
Authors: Rouwendal Jan , Nijkamp Peter
Published: February 2010

This paper attempts to explain the repeated empirical finding that homeowners have shorter unemployment durations than tenants, even though Oswald's hypothesis predicts longer unemployment durations for homeowners. The search models that have been proposed to motivate Oswald's thesis have difficulties in providing an explanation for the reverse of the Oswald effect. The model proposed in this paper is close to the ones proposed earlier, in that it also studies search behaviour, but contains a richer set of effects of homeownership on search behaviour. In our model, homeowners may have a higher intensity of job search (and hence shorter unemployment durations) when their housing expenses are—all other things being equal—higher than those of tenants. Some studies have indeed found that the shorter unemployment durations occur especially among highly leveraged homeowners. We show that, in the Netherlands, many homeowners have higher housing costs than otherwise comparable tenants. The model developed in this paper is therefore able to explain the existing evidence of shorter unemployment durations for Dutch homeowners.
Discrimination of Facial Features by Adults, 10-Year-Olds, and Cataract-Reversal Patients
Authors: Mondloch Catherine J , Robbins Rachel , Maurer Daphne
Published: February 2010

In previous studies we created 8 new versions of a single face: 4 differed only in the spacing among features and 4 differed in the shape of the eyes and mouth. Compared to the spacing set, results for this feature set indicated little impairment by inversion, earlier adult-like accuracy (Mondloch et al, 2002 Perception31 553–566), and normal performance after a history of early visual deprivation from bilateral congenital cataract (Le Grand et al, 2001 Nature410 890, 412 786). Here we addressed the possibility that this pattern might have resulted from our having inadvertently selected easily discriminated features or including some faces with make-up. We created 20 featural versions of a single female face and asked adults, 10-year-old children, and patients treated for bilateral congenital cataract to make same/different judgments for 120 pairings (half different). The results confirm that adults easily discriminate facial features, even after early visual deprivation from cataract, and that inversion has only a small effect. By the age of 10 years, children are close to, but not quite at, adult levels of accuracy. The previous findings cannot be attributed to our having inadvertently created a feature set that was unusually easy to discriminate.
In-situ sampling of soil pore water: evaluation of linear-type microdialysis probes and suction cups at varied moisture contents
Authors: Miró Manuel , Fitz Walter J. , Swoboda Siegfried , Wenzel Walter W.
Published: February 2010

Environmental context. There is a need for slightly invasive techniques capable of in-situ probing of target analytes in environmental compartments. Owing to its passive sampling mode and small probe dimensions, microdialysis-based dosimetry is an appealing tool for monitoring of solute concentrations in both water bodies and pore soil waters with minimum disturbance of natural equilibrium. The development of field applications is challenging but will provide novel insights as to the speciation and bioaccessibility of environmental pollutants, e.g. trace metals, at high spatial resolution.
Abstract. In-situ sampling of soil pore water is still a challenge for environmental scientists. Here, microdialysis is explored for probing metal concentrations in soil pore water at soil moisture contents ranging from 50 to 115% of the maximal water holding capacity and is compared with traditional sampling by suction cups. Metal concentrations obtained by the suction cup technique were consistently larger than those measured in the dialysate. Good agreement was obtained for Pb and Cu at soil moistures close to saturation after accounting for diffusion resistances whereas corrected Ni and Cd concentrations in the dialysates exceeded those measured by the suction cup technique. These deviations reflect inherent differences in the sampling mode and effects of soil heterogeneity at the microscale. Microdialysis offers new opportunities to probe solute concentrations at high spatial resolution and minimal disturbance of soil conditions at environmental interfaces such as the plant rhizosphere or at the transition between forest floors and the mineral soil.
Assessing the colloidal properties of engineered nanoparticles in water: case studies from fullerene C60 nanoparticles and carbon nanotubes
Authors: Chen Kai Loon , Smith Billy A. , Ball William P. , Fairbrother D. Howard
Published: February 2010

Environmental context. The fate and bioavailability of engineered nanoparticles in natural aquatic systems are strongly influenced by their ability to remain dispersed in water. Consequently, understanding the colloidal properties of engineered nanoparticles through rigorous characterisation of physicochemical properties and measurements of particle stability will allow for a more accurate prediction of their environmental, health, and safety effects in aquatic systems. This review highlights some important techniques suitable for the assessment of the colloidal properties of engineered nanoparticles and discusses some recent findings obtained by using these techniques on two popular carbon-based nanoparticles, fullerene C60 and multi-walled carbon nanotubes.
Abstract. The colloidal properties of engineered nanoparticles directly affect their use in a wide variety of applications and also control their environmental fate and mobility. The colloidal stability of engineered nanoparticles depends on their physicochemical properties within the given aqueous medium and is ultimately reflected in the particles’ aggregation and deposition behaviour. This review presents some of the key experimental methods that are currently used to probe colloidal properties and quantify engineered nanoparticle stability in water. Case studies from fullerene C60 nanoparticles and multi-walled carbon nanotubes illustrate how the characterisation and measurement methods are used to understand and predict nanoparticle fate in aquatic systems. Consideration of the comparisons between these two classes of carbon-based nanoparticles provides useful insights into some major current knowledge gaps while also revealing clues about needed future developments. Key issues to be resolved relate to the nature of near-range surface forces and the origins of surface charge, particularly for the reportedly unmodified or ‘pure’ carbon-based nanoparticles.
Manufactured nanoparticles in the environment
Authors: Lead Jamie R.
Published: February 2010

Environmental context. Nanotechnology is a very important industry which may be socially transformative, but produces nanomaterials (NMs) which have a potential but poorly characterised risk to the environment. This Research Front describes new research investigating NM environmental chemistry, particularly in relation to ecotoxicology. This Research Front shows some of the most exciting research undertaken currently and fits within a dynamic research program, which is global in scope and which attempts to unravel these complex areas.
Glycosphingolipids keep signaling in top-Notch condition
Authors: Short Ben
Published: February 2010

Membrane lipids promote the endocytosis and signaling capacity of Notch receptor ligands.
Graham Warren: Gaining ground on the Golgi
Authors: Sedwick Caitlin
Published: February 2010

Warren's studies of the Golgi have yielded a rich trove of insights.
Directly probing the mechanical properties of the spindle and its matrix
Authors: Gatlin Jesse C. , Matov Alexandre , Danuser Gaudenz , Mitchison Timothy J. , Salmon Edward D.
Published: February 2010

Several recent models for spindle length regulation propose an elastic pole to pole spindle matrix that is sufficiently strong to bear or antagonize forces generated by microtubules and microtubule motors. We tested this hypothesis using microneedles to skewer metaphase spindles in Xenopus laevis egg extracts. Microneedle tips inserted into a spindle just outside the metaphase plate resulted in spindle movement along the interpolar axis at a velocity slightly slower than microtubule poleward flux, bringing the nearest pole toward the needle. Spindle velocity decreased near the pole, which often split apart slowly, eventually letting the spindle move completely off the needle. When two needles were inserted on either side of the metaphase plate and rapidly moved apart, there was minimal spindle deformation until they reached the poles. In contrast, needle separation in the equatorial direction rapidly increased spindle width as constant length spindle fibers pulled the poles together. These observations indicate that an isotropic spindle matrix does not make a significant mechanical contribution to metaphase spindle length determination.
A Syd-1 homologue regulates pre- and postsynaptic maturation in Drosophila
Authors: Owald David , Fouquet Wernher , Schmidt Manuela , Wichmann Carolin , Mertel Sara , Depner Harald , Christiansen Frauke , Zube Christina , Quentin Christine , Körner Jorg , Urlaub Henning , Mechtler Karl , Sigrist Stephan J.
Published: February 2010

Active zones (AZs) are presynaptic membrane domains mediating synaptic vesicle fusion opposite postsynaptic densities (PSDs). At the Drosophila neuromuscular junction, the ELKS family member Bruchpilot (BRP) is essential for dense body formation and functional maturation of AZs. Using a proteomics approach, we identified Drosophila Syd-1 (DSyd-1) as a BRP binding partner. In vivo imaging shows that DSyd-1 arrives early at nascent AZs together with DLiprin-α, and both proteins localize to the AZ edge as the AZ matures. Mutants in dsyd-1 form smaller terminals with fewer release sites, and release less neurotransmitter. The remaining AZs are often large and misshapen, and ectopic, electron-dense accumulations of BRP form in boutons and axons. Furthermore, glutamate receptor content at PSDs increases because of excessive DGluRIIA accumulation. The AZ protein DSyd-1 is needed to properly localize DLiprin-α at AZs, and seems to control effective nucleation of newly forming AZs together with DLiprin-α. DSyd-1 also organizes trans-synaptic signaling to control maturation of PSD composition independently of DLiprin-α.
A homology model of the pore domain of a voltage-gated calcium channel is consistent with available SCAM data
Authors: Bruhova Iva , Zhorov Boris S.
Published: February 2010

In the absence of x-ray structures of calcium channels, their homology models are used to rationalize experimental data and design new experiments. The modeling relies on sequence alignments between calcium and potassium channels. Zhen et al. (2005. J. Gen. Physiol. doi:10.1085/jgp.200509292) used the substituted cysteine accessibility method (SCAM) to identify pore-lining residues in the Cav2.1 channel and concluded that their data are inconsistent with the symmetric architecture of the pore domain and published sequence alignments between calcium and potassium channels. Here, we have built Kv1.2-based models of the Cav2.1 channel with 2-(trimethylammonium)ethyl methanethiosulfonate (MTSET)-modified engineered cysteines and used Monte Carlo energy minimizations to predict their energetically optimal orientations. We found that depending on the position of an engineered cysteine in S6 and S5 helices, the ammonium group in the long flexible MTSET-modified side chain can orient into the inner pore, an interface between domains (repeats), or an interface between S5 and S6 helices. Different local environments of equivalent positions in the four repeats can lead to different SCAM results. The reported current inhibition by MTSET generally decreases with the predicted distances between the ammonium nitrogen and the pore axis. A possible explanation for outliers of this correlation is suggested. Our calculations rationalize the SCAM data, validate one of several published sequence alignments between calcium and potassium channels, and suggest similar spatial dispositions of S5 and S6 helices in voltage-gated potassium and calcium channels.
Activation of Slo2.1 channels by niflumic acid
Authors: Dai Li , Garg Vivek , Sanguinetti Michael C.
Published: February 2010

Slo2.1 channels conduct an outwardly rectifying K+ current when activated by high [Na+]i. Here, we show that gating of these channels can also be activated by fenamates such as niflumic acid (NFA), even in the absence of intracellular Na+. In Xenopus oocytes injected with <10 ng cRNA, heterologously expressed human Slo2.1 current was negligible, but rapidly activated by extracellular application of NFA (EC50 = 2.1 mM) or flufenamic acid (EC50 = 1.4 mM). Slo2.1 channels activated by 1 mM NFA exhibited weak voltage dependence. In high [K+]e, the conductance–voltage (G-V) relationship had a V1/2 of +95 mV and an effective valence, z, of 0.48 e. Higher concentrations of NFA shifted V1/2 to more negative potentials (EC50 = 2.1 mM) and increased the minimum value of G/Gmax (EC50 = 2.4 mM); at 6 mM NFA, Slo2.1 channel activation was voltage independent. In contrast, V1/2 of the G-V relationship was shifted to more positive potentials when [K+]e was elevated from 1 to 300 mM (EC50 = 21.2 mM). The slope conductance measured at the reversal potential exhibited the same [K+]e dependency (EC50 = 23.5 mM). Conductance was also [Na+]e dependent. Outward currents were reduced when Na+ was replaced with choline or mannitol, but unaffected by substitution with Rb+ or Li+. Neutralization of charged residues in the S1–S4 domains did not appreciably alter the voltage dependence of Slo2.1 activation. Thus, the weak voltage dependence of Slo2.1 channel activation is independent of charged residues in the S1–S4 segments. In contrast, mutation of R190 located in the adjacent S4–S5 linker to a neutral (Ala or Gln) or acidic (Glu) residue induced constitutive channel activity that was reduced by high [K+]e. Collectively, these findings indicate that Slo2.1 channel gating is modulated by [K+]e and [Na+]e, and that NFA uncouples channel activation from its modulation by transmembrane voltage and intracellular Na+.
Diffusion of a soluble protein, photoactivatable GFP, through a sensory cilium
Authors: Calvert Peter D. , Schiesser William E. , Pugh Edward N.
Published: February 2010

Transport of proteins to and from cilia is crucial for normal cell function and survival, and interruption of transport has been implicated in degenerative and neoplastic diseases. It has been hypothesized that the ciliary axoneme and structures adjacent to and including the basal bodies of cilia impose selective barriers to the movement of proteins into and out of the cilium. To examine this hypothesis, using confocal and multiphoton microscopy we determined the mobility of the highly soluble photoactivatable green fluorescent protein (PAGFP) in the connecting cilium (CC) of live Xenopus retinal rod photoreceptors, and in the contiguous subcellular compartments bridged by the CC, the inner segment (IS) and the outer segment (OS). The estimated axial diffusion coefficients are DCC = 2.8 ± 0.3, DIS = 5.2 ± 0.6, and DOS = 0.079 ± 0.009 µm2 s−1. The results establish that the CC does not pose a major barrier to protein diffusion within the rod cell. However, the results also reveal that axial diffusion in each of the rod’s compartments is substantially retarded relative to aqueous solution: the axial diffusion of PAGFP was retarded ∼18-, 32- and 1,000-fold in the IS, CC, and OS, respectively, with ∼20-fold of the reduction in the OS attributable to tortuosity imposed by the lamellar disc membranes. Previous investigation of PAGFP diffusion in passed, spherical Chinese hamster ovary cells yielded DCHO = 20 µm2 s−1, and estimating cytoplasmic viscosity as Daq/DCHO = 4.5, the residual 3- to 10-fold reduction in PAGFP diffusion is ascribed to sub-optical resolution structures in the IS, CC, and OS compartments.
Nitric oxide induces airway smooth muscle cell relaxation by decreasing the frequency of agonist-induced Ca2+ oscillations
Authors: Perez-Zoghbi Jose F. , Bai Yan , Sanderson Michael J.
Published: February 2010

Nitric oxide (NO) induces airway smooth muscle cell (SMC) relaxation, but the underlying mechanism is not well understood. Consequently, we investigated the effects of NO on airway SMC contraction, Ca2+ signaling, and Ca2+ sensitivity in mouse lung slices with phase-contrast and confocal microscopy. Airways that were contracted in response to the agonist 5-hydroxytryptamine (5-HT) transiently relaxed in response to the NO donor, NOC-5. This NO-induced relaxation was enhanced by zaprinast or vardenafil, two selective inhibitors of cGMP-specific phosphodiesterase-5, but blocked by ODQ, an inhibitor of soluble guanylyl cyclase, and by Rp-8-pCPT-cGMPS, an inhibitor of protein kinase G (PKG). Simultaneous measurements of airway caliber and SMC [Ca2+]i revealed that airway contraction induced by 5-HT correlated with the occurrence of Ca2+ oscillations in the airway SMCs. Airway relaxation induced by NOC-5 was accompanied by a decrease in the frequency of these Ca2+ oscillations. The cGMP analogues and selective PKG activators 8Br-cGMP and 8pCPT-cGMP also induced airway relaxation and decreased the frequency of the Ca2+ oscillations. NOC-5 inhibited the increase of [Ca2+]i and contraction induced by the photolytic release of inositol 1,4,5-trisphosphate (IP3) in airway SMCs. The effect of NO on the Ca2+ sensitivity of the airway SMCs was examined in lung slices permeabilized to Ca2+ by treatment with caffeine and ryanodine. Neither NOC-5 nor 8pCPT-cGMP induced relaxation in agonist-contracted Ca2+-permeabilized airways. Consequently, we conclude that NO, acting via the cGMP–PKG pathway, induced airway SMC relaxation by predominately inhibiting the release of Ca2+ via the IP3 receptor to decrease the frequency of agonist-induced Ca2+ oscillations.
Successful Control of an Outbreak ofKlebsiella pneumoniaeCarbapenemase—ProducingK. pneumoniaeat a Long-Term Acute Care Hospital
Authors: Munoz-Price L. Silvia , Hayden Mary K. , Lolans Karen , Won Sarah , Calvert Karen , Lin Michael , Sterner Alexander , Weinstein Robert A.
Published: February 2010

Objective.

To determine the effect of a bundle of infection control interventions on the horizontal transmission ofKlebsiella pneumoniaecarbapenemase (KPC)-producingK. pneumoniaeduring an outbreak.

Design.

Quasi-experimental study.

Setting.

Long-term acute care hospital.

Intervention.

On July 23,2008, a bundled intervention was implemented: daily 2% Chlorhexidine gluconate baths for patients, enhanced environmental cleaning, surveillance cultures at admission, serial point prevalence surveillance (PPS), isolation precautions, and training of personnel. Baseline PPS was performed before the intervention was implemented. Any gram-negative rod isolate suspected of KPC production underwent a modified Hodge test and, if results were positive, confirmatory polymerase chain reaction testing. Clinical cases were defined to occur for patients whose samples yielded KPC-positive gram-negative rods in clinical cultures.

Results.

Baseline PPS performed on June 17, 2008, showed a prevalence of colonization with KPC-producing isolates of 21% (8 of 39 patients screened). After implementation of the intervention, monthly PPS was performed 5 times, which showed prevalences of colonization with KPC-producing isolates of 12%, 5%, 3%, 0%, and 0% (P< .001). From January 1, 2008, until the intervention, 8 KPC-positive clinical cases—suspected to be due to horizontal transmission—were detected. From implementation of the intervention through December 31, 2008, only 2 KPC-positive clinical cases, both in August 2008, were detected. From January 1 through December 31, 2008, 8 patients were detected as carriers of KPC-producing isolates at admission to the institution, 4 patients before and 4 patients after the intervention.

Conclusion.

A bundled intervention was successful in preventing horizontal spread of KPC-producing gram-negative rods in a long-term acute care hospital, despite ongoing admission of patients colonized with KPC producers.
Child Care Center Exclusion Policies and Directors' Opinions on the Use of Antibiotics
Authors: M'ikanatha Nkuchia M. , Gasink Leanne B. , Kunselman Allen , Warren Kimberly , Lautenbach Ebbing
Published: February 2010

We studied exclusion policies and child care center directors' opinions regarding antibiotic use for childhood illnesses. Among 135 respondents, 96.9% reported that they had written policies on exclusion of children for acute illnesses. Although 52.4% of respondents agreed that children are prescribed antibiotics unnecessarily, 89.1% believed that parents pressure physicians to prescribe unnecessary antibiotics.
Control of an Outbreak of Carbapenem-ResistantAcinetobacter baumanniiin Australia after Introduction of Environmental Cleaning with a Commercial Oxidizing Disinfectant
Authors: Doidge Michelle , Allworth Anthony M. , Woods Marion , Marshall Penelope , Terry Michael , O'Brien Kathryn , Goh Hwee Mian , George Narelle , Nimmo Graeme R. , Schembri Mark A. , Lipman Jeffrey , Paterson David L.
Published: February 2010

In the midst of an outbreak, carbapenem-resistantAcinetobacter baumanniiwas grown from samples of multiple environmental sites in an intensive care unit. A commercial oxidizing disinfectant (potassium peroxomonosulphate 50%, sodium alkyl benzene sulphonate 15%, and sulphamic acid 5%) was introduced throughout the intensive care unit, and its use coincided with cessation of the outbreak.
Comparative genomics as a tool to reveal functional equivalences between human and mouse dendritic cell subsets
Authors: Crozat Karine , Guiton Rachel , Guilliams Martin , Henri Sandrine , Baranek Thomas , Schwartz‐Cornil Isabelle , Malissen Bernard , Dalod Marc
Published: February 2010

Summary:  During evolution, vertebrates have developed an adaptive immune system able to cope with a variety of pathogens. Dendritic cells (DCs) are central to this process. DCs integrate information derived from pathogens or endogenous danger signals and convey them to T lymphocytes. Most of the present knowledge on DCs was generated in mice or by using human DCs differentiated in vitro from monocytes. In both species, several DC subsets have been identified in vivo based on differences in their phenotypes, anatomical locations or functions. In mice, protective immunity against intracellular pathogens or tumors can be induced most efficiently by targeting antigens to the CD8α+ DCs, a subset of DCs which resides in lymphoid tissues and is especially efficient at cross‐presenting exogenous antigens to CD8+ T lymphocytes. In contrary, harnessing human DC subsets for medical purposes is currently hampered by insufficient knowledge about these cells. To overcome this cognitive gap, we are using comparative genomics as a tool for designing hypotheses and experiments to further characterize DC subset functions and their molecular control, including the investigation of the functional equivalences that might exist between human and mouse DC subsets.
Defining dendritic cells by conditional and constitutive cell ablation
Authors: Bar‐On Liat , Jung Steffen
Published: February 2010

Summary:  Recent years have seen a major advance in our understanding of the organization of the dendritic cell (DC) compartment. Particularly rewarding in this respect have been studies investigating DC origins, based on the identification of transcription factor and growth factor requirements, as well as direct demonstrations of precursor/progeny relationships by adoptive cell transfers. However, to fully understand the organization of the DC compartment, functional definitions of DC subsets must be provided and potential task divisions revealed that distinguish DC from other immune cells, including the closely related mononuclear phagocytes, such as macrophages. In fact, functional definitions might eventually replace the current distinction between DC and macrophages, which is in part based on arbitrary historic considerations, i.e. mononuclear phagocytes identified before the advent of DC in the mid 1970s generally termed macrophages. In this article, we review recent insight in the functions of classical DC in the mouse, focusing on our own work involving conditional and constitutive cell ablation.
Instructive cytokine signals in dendritic cell lineage commitment
Authors: Schmid Michael A. , Kingston Dior , Boddupalli Sekhar , Manz Markus G.
Published: February 2010

Summary:  Clarifying the signals that lead to dendritic cell (DC) development and identifying cellular intermediates on their way to DC differentiation are essential steps to understand the dynamic regulation of number, localization, and functionality of these cells. In the past decade, much knowledge on cytokines, transcription factors, and successive progenitors involved in steady‐state and demand‐adapted DC development was gained. From the stage of multipotent progenitors, DCs are generated from Flt3+ intermediates, irrespective of lymphoid or myeloid commitment, making fms‐related tyrosine kinase 3 ligand one of the major regulators for DC development. Additional key cytokines involved are granulocyte–macrophage colony‐stimulating factor (GM‐CSF) and M‐CSF, with each being essential for particular DC subsets and leading to specific activation of downstream transcription factors. In this review, we seek to draw an integrative view on how instructive cytokine signals acting on intermediate progenitors might lead to the generation of specific DC subsets in steady‐state and during inflammation. We hypothesize that the lineage potential of a progenitor might be determined by the set of cytokine receptors expressed that make it responsive to further receive lineage instructive signals. Commitment to a certain lineage might consequently occur when lineage‐relevant cytokine receptors are further upregulated and others for alternative lineages are lost. Along this line, we emphasize the role that diverse microenvironments have in influencing the generation of DC subsets with specific functions throughout the body.
Long‐term dynamics of submerged macrophytes and algae in a small and shallow, eutrophic lake: implications for the stability of macrophyte‐dominance
Authors: SAYER CARL D. , BURGESS AMY , KARI KATERINA , DAVIDSON THOMAS A. , PEGLAR SYLVIA , YANG HANDONG , ROSE NEIL
Published: February 2010

1. Submerged macrophyte and phytoplankton components of eutrophic, shallow lakes have frequently undergone dynamic changes in composition and abundance with important consequences for lake functioning and stability. However, because of a paucity of long‐term survey data, we know little regarding the nature, direction and sequencing of such changes over decadal–centennial or longer timescales.

2. To circumvent this problem, we analysed multiple (n = 5) chronologically correlated sediment cores for plant macro‐remains and a single core for pollen and diatoms from one small, shallow, English lake (Felbrigg Hall Lake, Norfolk, U.K.), documenting 250 years of change to macrophyte and algal communities.

3. All five cores showed broadly similar stratigraphic changes in macrophyte remains with three distinct phases of macrophyte development: Myriophyllum–Chara–Potamogeton (c. pre‐1900), to Ceratophyllum–Chara–Potamogeton (c. 1900–1960) and finally to Zannichellia–Potamogeton (c. post‐1960). Macrophyte species richness declined from at least 10 species pre‐1900 to just four species at the present day. Additionally, in the final Zannichellia–Potamogeton phase, a directional shift between epi‐benthic and phytoplankton‐based primary production was indicated by the diatom data.

4. Based on macrophyte–seasonality relationships established for the region, concomitant with the final shift to Zannichellia–Potamogeton, we infer a reduction in the seasonal duration of plant dominance (plant‐covered period). Furthermore, we hypothesise that this change in species composition resulted in a situation whereby macrophyte populations were seasonally ‘sandwiched’ between two phytoplankton peaks in spring and late summer as observed in the contemporary lake.

5. We suggest that eutrophication‐induced reductions in macrophyte species richness, especially if the number of plant‐seasonal strategies is reduced, may constrict the plant growing season. In turn, this may render a shallow lake increasingly vulnerable to seasonal invasions of phytoplankton resulting in further species losses in the plant community. Thus, as part of a slow (over perhaps 10–100s of years) and self‐perpetuating process, macrophytes may be gradually pushed out by phytoplankton without the need for a perturbation as required in the alternative stable states model of plant loss.