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Transient Nature (transient + nature)
Selected AbstractsMultiple P2 Receptors Contribute to a Transient Increase in Intracellular Ca2+ Concentration in Atp-Stimulated Rat Brown AdipocytesEXPERIMENTAL PHYSIOLOGY, Issue 6 2002Mariko Omatsu-Kanbe Extracellular ATP in micromolar concentrations evokes a transient elevation in intracellular free Ca2+ concentration ([Ca2+]i), which arises primarily from a release of Ca2+ from intracellular stores in rat brown adipocytes. We investigated the mechanisms underlying this transient nature of [Ca2+]i elevation during exposure to ATP by using fura-2 fluorescence measurements together with the P2 receptor antagonists pyridoxal-phosphate-6-azophenyl-2,,4,-disulfonic acid (PPADS) and suramin. Extracellular ATP (10 ,M) almost completely depressed the thapsigargin (100 nM)-evoked [Ca2+]i elevation mediated through store-operated Ca2+ entry. The inhibitory effect of ATP was antagonized by PPADS with IC50 of 0.7 ,M. In the presence of PPADS at concentrations of more than 5 ,M, the ATP-induced [Ca2+]i elevation became sustained during the entire duration of the agonist application, although the magnitude of the sustained [Ca2+]i elevation was reduced in a concentration-dependent manner by PPADS with an IC50 of 200 ,M. In contrast, the ATP-induced [Ca2+]i elevation was blocked by suramin in a concentration range similar to that required to antagonize the inhibitory effect of ATP on the store-operated pathway. These results suggest that the [Ca2+]i responses to extracellular ATP in rat brown adipocytes are mediated through the activation of at least two distinct P2 receptors exhibiting different sensitivities to PPADS but similar sensitivities to suramin. Extracellular ATP stimulates the PPADS-resistant P2 receptor to mobilize intracellular Ca2+ stores, which is probably followed by the activation of store-operated Ca2+ entry. Extracellular ATP, however, would inhibit this Ca2+ entry process through the stimulation of the PPADS-sensitive P2-receptor, which may underlie the transient nature of [Ca2+]i elevation in response to extracellular ATP. [source] A method to solve the multilayer non-continuity problem for heat and moisture transfer in building structuresINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2003X. Su Abstract In this paper a finite-difference method is proposed for the first time for the solution of coupled heat and moisture transfer problems of transient nature in 1-D multilayer building elements. Transient boundary conditions are specified for both heat and moisture transfer at external surfaces, while constant values are assumed for material properties of each layer of the structure. The calculations for a typical three layers wall are conducted to obtain the dynamic distributions of the relative humidity at the interfaces of every layer during 24 h by use of the mentioned method, and the results agree with the transfer function method in (ASHRAE Trans. 1999; 105(2) : 954,961). The method can be extended to 2-D and 3-D coupled heat and moisture transfer problems. Copyright © 2003 John Wiley Sons, Ltd. [source] Three-dimensional transient free-surface flow of viscous fluids inside cavities of arbitrary shapeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2003Kyu-Tae Kim Abstract The three-dimensional transient free-surface flow inside cavities of arbitrary shape is examined in this study. An adaptive (Lagrangian) boundary-element approach is proposed for the general three-dimensional simulation of confined free-surface flow of viscous incompressible fluids. The method is stable as it includes remeshing capabilities of the deforming free-surface, and thus can handle large deformations. A simple algorithm is developed for mesh refinement of the deforming free-surface mesh. Smooth transition between large and small elements is achieved without significant degradation of the aspect ratio of the elements in the mesh. The method is used to determine the flow field and free-surface evolution inside cubic, rectangular and cylindrical containers. These problems illustrate the transient nature of the flow during the mixing process. Surface tension effects are also explored. Copyright © 2003 John Wiley & Sons, Ltd. [source] Binge-like eating in miceINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 5 2009Daniele Consoli MD Abstract Objective Given the lack of reliable murine model of binge-like eating, we tried to induce this pathological behavior in mice. Method We used an experimental protocol mimicking the etiological factors involved in the development of binge eating in humans, that is, food restriction, refeeding (R-R) in presence of high palatable food, and stress (S). Results Mice subjected to at least three cycles of R-R plus S (forced swimming stress), showed a binge-like behavior evident as early as 4 h, persisting 24 h after stress application and not associated to depressive-like behavior. However, after the third R-R/S cycle, food intakes of mice returned to normal levels. Discussion (i) at least three cycles of R-R plus S are required to promote abnormal eating in mice, (ii) this is not associated to depressive-like behaviors, and (iii) the enhanced pathological behavior showed a transient nature not persisting after the third R-R/S cycle. © 2009 by Wiley Periodicals, Inc. Int J Eat Disord, 2009 [source] Determining degree of saturation after application of transiently supersaturated metered dose aerosols for topical delivery of corticosteroidsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2009Stuart A. Jones Abstract A transiently supersaturated drug delivery system has the potential to enhance topical drug delivery via heightened thermodynamic activity. The aim of this work was to quantify the degree of saturation (DS) for transiently supersaturated formulations using three traditional and one novel in vitro assessment methods. Metered dose aerosols (MDA) were formulated containing saturated levels of beclomethasone dipropionate monohydrate (BDP) or betamethasone 17-valerate (BMV) within a pressurised canister, and included ethanol (EtOH), hydrofluoroalkane 134a propellant and poly(vinyl pyrrolidone). Attempts to determine the DS via the measurement of drug flux through synthetic membranes did not correlate and was shown to be dependent on the EtOH concentration. The inability of these methods to accurately assess the drug DS may be due to the transient nature of the formulation and the volatile solvents dehydrating the membrane. A mathematical equation that used the evaporation rate of the formulation was derived to determine the theoretical DS at various time points after MDA actuation. It was shown that the MDAs became supersaturated with a high DS, this enhanced drug release from the formulation and therefore these preparations have the potential to increase the amount of drug delivered into the skin. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:543,554, 2009 [source] Application of subsecond spiral chemical shift imaging to real-time multislice metabolic imaging of the rat in vivo after injection of hyperpolarized 13C1 -pyruvateMAGNETIC RESONANCE IN MEDICINE, Issue 3 2009Dirk Mayer Abstract Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast imaging techniques are a critical requirement for real-time metabolic imaging. We report on the development of an ultrafast, multislice, spiral chemical shift imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized 13C1 -pyruvate and metabolic products 13C1 -lactate and 13C1 -alanine, with a temporal resolution of as fast as 1 s. Metabolic imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic imaging and highlight its potential in assessing organ-specific kinetic parameters. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Discovery of a short orbital period in the Supergiant Fast X-ray Transient IGR J16479,4514MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2009Chetana Jain ABSTRACT We report here the discovery of a 3.32 d orbital period in the Supergiant Fast X-ray Transient (SFXT) source IGR J16479,4514. Using the long-term light curve of this source obtained with Swift Burst Alert Telescope (BAT) in the energy range of 15,50 keV, we have clearly detected an orbital modulation including a full eclipse of duration ,0.6 d. In the hard X-ray band of the BAT instrument, the eclipse ingress and egress are rapid. We have also used the long-term light curve obtained with the Rossi X-ray Timing Explorer (RXTE) All Sky Monitor (ASM) in the energy range of 1.5,12 keV. Taken independently, the detection of orbital modulation in the RXTE,ASM light curve is not significant. However, considering a clear detection of orbital modulation in the BAT light curve, we have used the ASM light curve for a more precise determination of the orbital period. IGR J16479,4514 has the shortest orbital period among the three SFXTs with measured/known orbital period. We discuss the implication of a short orbital period with the various mechanisms proposed to explain the transient nature of this class of sources. [source] Experimental and computational tools useful for (re)construction of dynamic kinase,substrate networksPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 23 2009Chris Soon Heng Tan Abstract The explosion of site- and context-specific in vivo phosphorylation events presents a potentially rich source of biological knowledge and calls for novel data analysis and modeling paradigms. Perhaps the most immediate challenge is delineating detected phosphorylation sites to their effector kinases. This is important for (re)constructing transient kinase,substrate interaction networks that are essential for mechanistic understanding of cellular behaviors and therapeutic intervention, but has largely eluded high-throughput protein-interaction studies due to their transient nature and strong dependencies on cellular context. Here, we surveyed some of the computational approaches developed to dissect phosphorylation data detected in systematic proteomic experiments and reviewed some experimental and computational approaches used to map phosphorylation sites to their effector kinases in efforts aimed at reconstructing biological signaling networks. [source] A deterministic approach to evaluate and implement monitored natural attenuation for chlorinated solventsREMEDIATION, Issue 4 2007Michael J. Truex A US EPA directive and related technical protocol outline the information needed to determine if monitored natural attenuation (MNA) for chlorinated solvents is a suitable remedy for a site. For some sites, conditions such as complex hydrology or perturbation of the contaminant plume caused by an existing remediation technology (e.g., pump-and-treat) make evaluation of MNA using only field data difficult. In these cases, a deterministic approach using reactive transport modeling can provide a technical basis to estimate how the plume will change and whether it can be expected to stabilize in the future and meet remediation goals. This type of approach was applied at the Petro-Processors Inc. Brooklawn site near Baton Rouge, Louisiana, to evaluate and implement MNA. This site consists of a multicomponent nonaqueous-phase source area creating a dissolved groundwater contamination plume in alluvial material near the Mississippi River. The hydraulic gradient of the groundwater varies seasonally with changes in the river stage. Due to the transient nature of the hydraulic gradient and the impact of a hydraulic containment system operated at the site for six years, direct field measurements could not be used to estimate natural attenuation processes. Reactive transport of contaminants were modeled using the RT3D code to estimate whether MNA has the potential to meet the site-specific remediation goals and the requirements of the US EPA Office of Solid Waste and Emergency Response Directive 9200.4-17P. Modeling results were incorporated into the long-term monitoring plan as a basis for evaluating the effectiveness of the MNA remedy. As part of the long-term monitoring plan, monitoring data will be compared to predictive simulation results to evaluate whether the plume is changing over time as predicted and can be expected to stabilize and meet remediation goals. This deterministic approach was used to support acceptance of MNA as a remedy. © 2007 Wiley Periodicals, Inc. [source] Supersoft sources in M31: Comparing the XMM-Newton deep survey, ROSAT and Chandra catalogues,ASTRONOMISCHE NACHRICHTEN, Issue 2 2010H. Stiele Abstract To investigate the transient nature of supersoft sources (SSSs) in M 31, we compared SSS candidates ofthe XMM-Newton Deep Survey, ROSAT PSPC surveys and the Chandra catalogues in the same field. We found 40 SSSs in the XMM-Newton observations. While 12 of the XMM-Newton sources were brighter than the limiting flux of the ROSAT PSPC survey, only two were detected with ROSAT ,10 yr earlier. Five correlate with recent optical novae which explains why they were not detected by ROSAT. The remaining 28 XMM-Newton SSSs have fluxes below the ROSAT detection threshold. Nevertheless we found one correlation with a ROSAT source, which had significantly larger fluxes than during the XMM-Newton observations. Ten of the XMM-Newton SSSs were detected by Chandra with <1, ,6yr between the observations. Five were also classified as SSSs by Chandra. Of the 30 ROSAT SSSs three were confirmed with XMM-Newton, while for 11 sources other classifications are suggested. Of the remaining 16 sources one correlates with an optical nova. Of the 42 Chandra very-soft sources five are classified as XMM-Newton SSSs, while for 22 we suggest other classifications. Of the remaining 15 sources, nine are classified as transient by Chandra, one of them correlates with an optical nova. These findings underlined the high variability of the sources of this class and the connection between SSSs and optical novae. Only three sources, were detected by all three missions as SSSs. Thus they are visible for more than a decade, despite their variability (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||