A simplified Probabilistic Safety Assesment of a Steam-Methane Reforming Hydrogen Production Plant coupled to a High-Temperature Gas Cooled Nuclear Reactor

A Probabilistic Safety Assessment (PSA) is being developed for a steam-methane reforming hydrogen production plant linked to a High-Temperature Gas Cooled Nuclear Reactor (HTGR). This work is based on the Japan Atomic Energy Research Institute’s (JAERI) High Temperature Test Reactor (HTTR) prototype in Japan. This study has two major objectives: calculate the risk to onsite and offsite individuals, and calculate the frequency of different types of damage to the complex. A simplified HAZOP study was performed to identify initiating events, based on existing studies. The initiating events presented here are methane pipe break, helium pipe break, and PPWC heat exchanger pipe break. Generic data was used for the fault tree analysis and the initiating event frequency. Saphire was used for the PSA analysis. The results show that the average frequency of an accident at this complex is 2.5E-06, which is divided into the various end states. The dominant sequences result in graphite oxidation which does not pose a health risk to the population. The dominant sequences that could affect the population are those that result in a methane explosion and occur 6.6E-8/year, while the other sequences are much less frequent. The health risk presents itself if there are people in the vicinity who could be affected by the explosion. This analysis also demonstrates that an accident in one of the plants has little effect on the other. This is true given the design base distance between the plants, the fact that the reactor is underground, as well as other safety characteristics of the HTGR. Sensitivity studies are being performed in order to determine where additional and improved data is needed.

Gestión del boil off gas en la planta de regasificación de Cartagena

Este proyecto trata sobre la gestión del boil-off gas, o BOG (vapor de gas natural que se produce en las instalaciones de gas natural licuado de las plantas de regasificación), generado en la planta de regasificación de Gas Natural Licuado de Cartagena, tanto en las situaciones en las que se opera por debajo del mínimo técnico, como en las cargas y descargas de buques, en las cuales se ha de gestionar una cantidad del boil-off adicional. Para recuperar el boil-off, las plantas cuentan con un relicuador (intercambiador de calor) en el que el BOG es relicuado por el GNL que se envía a los vaporizadores para ser regasificado y emitido a la red. De forma complementaria cuentan también con una antorcha/venteo donde se quema el exceso de boil-off que no puede ser tratado por el relicuador. Se procede a un análisis de la situación actual, y de cómo la baja demanda de regasificación dificulta la gestión del boil-off. Se simula el proceso de relicuación actual en distintas situaciones de operación. Ante la situación de baja demanda, ha aumentado considerablemente el número de días en los que las plantas españolas en general, y la planta de Cartagena en particular, operan por debajo del mínimo técnico, que es el nivel de producción mínimo para recuperar todo el boil-off generado en cualquier situación de operación al tiempo que mantiene en frío todas las instalaciones, y garantiza el 100% de disponibilidad inmediata del resto de los equipos en condiciones de seguridad de funcionamiento estable. Esta situación supone inconvenientes tanto operativos como medioambientales y acarrea mayores costes económicos, a los cuales da solución el presente proyecto, decidiendo qué alternativa técnica es la más adecuada y definiéndola. Abstract This project is about the management of the boil-off gas (BOG), natural vapour gas that is produced in liquefied natural gas (LNG) regasification plants. Specifically, the study is focused on the LNG regasification plant located in Cartagena, when it operates both below the technical minimum level of regasification and in the loading/unloading of LNG carriers, situations when it is needed to handle additional BOG. In order to make the most of BOG, the plants have a re-condenser (heat exchanger). Here, the BOG is re-liquefied by the LNG that is submitted to the vaporizers and delivered to the grid. The plants also have a flare/vent where the excess of BOG that cannot be treated by the re-condenser is burned. An analysis of the current situation of the demand is performed, evaluating how low markets demand for regasification difficult the BOG management. Besides, it is simulated the current re-liquefaction operating in different environments. Due to the reduction of the demand for natural gas, the periods when Spanish LNG regasification plants (and particularly the factory of Cartagena) are operating below the technical minimum level of regasification are more usual. This level is the minimum production to recover all the BOG generated in any operating situation while maintaining cold all facilities, fully guaranteeing the immediate availability from other equipment in a safely and stable operation. This situation carries both operational and environmental drawbacks, and leads to higher economic costs. This project aims to solve this problem, presenting several technical solutions and deciding which is the most appropriate.

Numerical Model of a Variable-Combined-Cycle Engine for Dual Subsonic and Supersonic Cruise

Efficient high speed propulsion requires exploiting the cooling capability of the cryogenic fuel in the propulsion cycle. This paper presents the numerical model of a combined cycle engine while in air turbo-rocket configuration. Specific models of the various heat exchanger modules and the turbomachinery elements were developed to represent the physical behavior at off-design operation. The dynamic nature of the model allows the introduction of the engine control logic that limits the operation of certain subcomponents and extends the overall engine operational envelope. The specific impulse and uninstalled thrust are detailed while flying a determined trajectory between Mach 2.5 and 5 for varying throttling levels throughout the operational envelope.

Diseño y test VHDL de un cambiador de formato para ver TV3D en un televisor convencional

La difusión de TV3D actual utiliza formatos como el Side-by-Side o Top-and-Bottom, en los que cada par de imágenes, correspondiente a las vistas de los ojos derecho e izquierdo, se encapsula con la mitad de la resolución espacial en una sola imagen. Estas imágenes se muestran de manera casi simultánea de forma que el ojo humano compone una imagen con profundidad que se asemeja a la visión binocular natural. Desde hace un par de años las principales plataformas de televisión han empezado a crear canales con contenido 3D. La televisión 3D (TV3D) se ha introducido en los hogares gracias a los televisores estereoscópicos. Estos televisores, que son compatibles con los formatos antes mencionados, extraen de cada imagen sus dos vistas, recuperan la resolución original y presentan cada vista alternativamente en la pantalla, generando al mismo tiempo una señal de sincronismo para las gafas activas, creando de esta forma la sensación tridimensional de las imágenes. En este PFC se pretende realizar el diseño VHDL de un cambiador de formato que genere en tiempo real la secuencia de imágenes correspondiente a los ojos derecho e izquierdo, con resolución completa, a partir de una secuencia codificada en formato tipo Top-and-Bottom y el banco de test para su prueba. Este circuito se implementará como un periférico del procesador NIOS II de Altera. El diseño podría utilizarse como parte de un sistema que permita la visualización de las actuales emisiones de televisión 3D en un televisor convencional. La tecnología de referencia que se utilizará serán las FPGAs, más concretamente la tarjeta Cyclone III FPGA Starter Kit (EP3C25 FPGA) de Altera, junto a una tarjeta de ampliación de Microtronix con entrada y salida HDMI para video y audio. Además se pretende crear la documentación necesaria para el desarrollo de futuros trabajos relacionados con la televisión 3D. ABSTRACT Current TV3D broadcasting uses formats as Side-by-Side or Top-and-Bottom, where every single pair of images, corresponding to left and right eyes views, are encapsulated with half spatial resolution in one single image. These images are almost simultaneously displayed so that the human eye forms an image with depth resembling naturally binocular vision. From a couple of years the major TV platforms have begun to create 3D content channels. 3D Television (3DTV) has been introduced in homes through stereoscopic televisions. These televisions, which are compatible with the above formats, each image is extracted from the two views, and recover the original resolution and displays alternately each view in screen, while generating a synchronization signal for active glasses, thereby creating the three-dimensional sensation of the images. The main objective in this PFC is to make the design of an exchanger VHDL format in real time to generate the image sequence corresponding to the right and left eyes, with full resolution from an encoded sequence type format Top-and-Bottom and test bench for testing. This circuit is implemented as a Altera NIOS II processor peripheral.The design could be used as part of a system enabling the display of current television broadcasts 3D on a conventional television. The reference technology that will be use are FPGAs, more specifically Cyclone III FPGA Starter Card Kit (EP3C25 FPGA) Altera, along with an expansion card Microtronix with HDMI input and output video and audio. It also aims to create documentation for the development of future works related to 3D TV.

SolarPaces 2013: Innovations on direct steam generation in linear fresnel collectors

Direct Steam Generation (DSG) in Linear Fresnel (LF) solar collectors is being consolidated as a feasible technology for Concentrating Solar Power (CSP) plants. The competitiveness of this technology relies on the following main features: water as heat transfer fluid (HTF) in Solar Field (SF), obtaining high superheated steam temperatures and pressures at turbine inlet (500ºC and 90 bar), no heat tracing required to avoid HTF freezing, no HTF degradation, no environmental impacts, any heat exchanger between SF and Balance Of Plant (BOP), and low cost installation and maintenance. Regarding to LF solar collectors, were recently developed as an alternative to Parabolic Trough Collector (PTC) technology. The main advantages of LF are: the reduced collector manufacturing cost and maintenance, linear mirrors shapes versus parabolic mirror, fixed receiver pipes (no ball joints reducing leaking for high pressures), lower susceptibility to wind damages, and light supporting structures allowing reduced driving devices. Companies as Novatec, Areva, Solar Euromed, etc., are investing in LF DSG technology and constructing different pilot plants to demonstrate the benefits and feasibility of this solution for defined locations and conditions (Puerto Errado 1 and 2 in Murcia Spain, Lidellin Newcastle Australia, Kogran Creek in South West Queensland Australia, Kimberlina in Bakersfield California USA, Llo Solar in Pyrénées France,Dhursar in India,etc). There are several critical decisions that must be taken in order to obtain a compromise and optimization between plant performance, cost, and durability. Some of these decisions go through the SF design: proper thermodynamic operational parameters, receiver material selection for high pressures, phase separators and recirculation pumps number and location, pipes distribution to reduce the amount of tubes (reducing possible leaks points and transient time, etc.), etc. Attending to these aspects, the correct design parameters selection and its correct assessment are the main target for designing DSG LF power plants. For this purpose in the recent few years some commercial software tools were developed to simulatesolar thermal power plants, the most focused on LF DSG design are Thermoflex and System Advisor Model (SAM). Once the simulation tool is selected,it is made the study of the proposed SFconfiguration that constitutes the main innovation of this work, and also a comparison with one of the most typical state-of-the-art configuration. The transient analysis must be simulated with high detail level, mainly in the BOP during start up, shut down, stand by, and partial loads are crucial, to obtain the annual plant performance. An innovative SF configurationwas proposed and analyzed to improve plant performance. Finally it was demonstrated thermal inertia and BOP regulation mode are critical points in low sun irradiation day plant behavior, impacting in annual performance depending on power plant location.

Exact solution for the conjugate fluid-fluid problem in the thermal entrance region of laminar counterflow heat exchangers

A generalized Lévêque solution is presented for the conjugate fluid–fluid problem that arises in the thermal entrance region of laminar counterflow heat exchangers. The analysis, carried out for constant property fluids, assumes that the Prandtl and Peclet numbers are both large compared to unity, and neglects axial conduction both in the fluids and in the plate, assumed to be thermally thin. Under these conditions, the thermal entrance region admits an asymptotic self-similar description where the temperature varies as a power ϳ of the axial distance, with the particularity that the self-similarity exponent must be determined as an eigenvalue by solving a transcendental equation arising from the requirement of continuity of heat fluxes at the heat conducting wall. Specifically, the analysis reveals that j depends only on the lumped parameter ƙ = (A2/A1)1/3 (α1/α2)1/3(k2/k1), defined in terms of the ratios of the wall velocity gradients, A, thermal diffusivities, α i, and thermal conductivities,k i, of the fluids entering, 1, and exiting, 2, the heat exchanger. Moreover, it is shown that for large (small) values of K solution reduces to the classical first (second) Lévêque solution. Closed-form analytical expressions for the asymptotic temperature distributions and local heat-transfer rate in the thermal entrance region are given and compared with numerical results in the counterflow parallel-plate configuration, showing very good agreement in all cases.

Supercritical Steam power cycle for Line-Focus Solar Power Plants

The supercritical Rankine power cycle offers a net improvement in plant efficiency compared with a subcritical Rankine cycle. For fossil power plants the minimum supercritical steam turbine size is about 450MW. A recent study between Sandia National Laboratories and Siemens Energy, Inc., published on March 2013, confirmed the feasibility of adapting the Siemens turbine SST-900 for supercritical steam in concentrated solar power plants, with a live steam conditions 230-260 bar and output range between 140-200 MWe. In this context, this analysis is focused on integrating a line-focus solar field with a supercritical Rankine power cycle. For this purpose two heat transfer fluids were assessed: direct steam generation and molten salt Hitec XL. To isolate solar field from high pressure supercritical water power cycle, an intermediate heat exchanger was installed between linear solar collectors and balance of plant. Due to receiver selective coating temperature limitations, turbine inlet temperature was fixed 550ºC. The design-point conditions were 550ºC and 260 bar at turbine inlet, and 165 MWe Gross power output. Plant performance was assessed at design-point in the supercritical power plant (between 43-45% net plant efficiency depending on balance of plantconfiguration), and in the subcritical plant configuration (~40% net plant efficiency). Regarding the balance of plant configuration, direct reheating was adopted as the optimum solution to avoid any intermediate heat exchanger. One direct reheating stage between high pressure turbine and intermediate pressure turbine is the common practice; however, General Electric ultrasupercritical(350 bar) fossil power plants also considered doubled-reheat applications. In this study were analyzed heat balances with single-reheat, double-reheat and even three reheating stages. In all cases were adopted the proper reheating solar field configurations to limit solar collectors pressure drops. As main conclusion, it was confirmed net plant efficiency improvements in supercritical Rankine line-focus (parabolic or linear Fresnel) solar plant configurations are mainly due to the following two reasons: higher number of feed-water preheaters (up to seven)delivering hotter water at solar field inlet, and two or even three direct reheating stages (550ºC reheating temperature) in high or intermediate pressure turbines. However, the turbine manufacturer should confirm the equipment constrains regarding reheating stages and number of steam extractions to feed-water heaters.

Investigación sobre la aplicación de energía solar a una depuradora convencional de fangos activos

El consumo de energía es responsable de una parte importante de las emisiones a la atmósfera de CO2, que es uno de los principales causantes del efecto invernadero en nuestro planeta. El aprovechamiento de la energía solar para la producción de agua caliente, permite economizar energía y disminuir el impacto del consumo energético sobre el medio ambiente y por tanto un menor impacto medioambiental. El objetivo de la presente investigación consiste en estudiar el aprovechamiento solar para el calentamiento de los fangos en los digestores anaerobios mediante agua caliente circulando en el interior de un serpentín que rodea la superficie de dicho digestor, como apoyo a los métodos convencionales del calentamiento de fangos como la resistencia eléctrica o el intercambiador de calor mediante la energía obtenida por el gas metano producido en la digestión anaerobia. Para el estudio se utilizaron 3 digestores, dos delos cuales se calentaron con agua caliente en el interior de un serpentín (uno aislado mediante una capa de fibra de vidrio y poliuretano y otro sin aislar).El tercer digestor no tenía calentamiento exterior con el objetivo de observar su comportamiento y comparar su evolución con el resto de los digestores .La comparación de los digestores 1 y 2 nos permitió estudiar la conveniencia de proveer de aislamiento al digestor. La transferencia de calor mediante serpentín de cobre dio valores comprendidos entre 83 y 92%. La aplicación de la instalación a una depuradora a escala real para mantenimiento en el interior del digestor a T=32ºC en diferentes climas: climas templados, cálidos y fríos, consistió en el cálculo de la superficie de colectores solares y superficie de serpentín necesario para cubrir las necesidades energéticas anuales de dicho digestor, así como el estudio de rentabilidad de la instalación, dando los mejores resultados para climas cálidos con períodos de retorno de 12 años y una tasa interna de rentabilidad (TIR) del 16% obteniendo una cobertura anual del 79% de las necesidades energéticas con energía solar térmica. Energy consumption accounts for a significant part of the emissions of CO2, which is one of the main causes of the greenhouse effect on our planet. The use of solar energy for hot water production. can save energy and reduce the impact of energy consumption on the environment and therefore a reduced environmental impact. The objective of this research is to study the solar utilization for heating the sludge in anaerobic digesters by hot water circulating inside a coil surrounding the surface of digester, to support conventional heating methods sludge as the electrical resistance or heat exchanger by energy generated by the methane gas produced in the anaerobic digestion. To study 3 digesters used two models which are heated with hot water within a coil (one insulated by a layer of fiberglass and polyurethane and other uninsulated) .The third digester had no external heating in order to observe their behavior and compare their evolution with the rest of the .The comparison digesters digesters 1 and 2 allowed us to study the advisability of providing insulation to the digester. Heat transfer through copper coil gave values between 83 and 92%. The installation application to a treatment for maintaining full scale within the digester at T = 32ºC in different climates: temperate, warm and cold climates, consisted of calculating the surface area of solar collectors and coil required to cover the annual energy needs of the digester, and the study of profitability of the installation, giving the best results for hot climates with return periods of 12 years and an internal rate of return (IRR) of 16% achieving an annual coverage of 79 % of energy needs with solar energy.

Molecular cloning and functional analysis of SUT-1, a sulfate transporter from human high endothelial venules

High endothelial venules (HEV) are specialized postcapillary venules found in lymphoid organs and chronically inflamed tissues that support high levels of lymphocyte extravasation from the blood. One of the major characteristics of HEV endothelial cells (HEVEC) is their capacity to incorporate large amounts of sulfate into sialomucin-type counter-receptors for the lymphocyte homing receptor L-selectin. Here, we show that HEVEC express two functional classes of sulfate transporters defined by their differential sensitivity to the anion-exchanger inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS), and we report the molecular characterization of a DIDS-resistant sulfate transporter from human HEVEC, designated SUT-1. SUT-1 belongs to the family of Na+-coupled anion transporters and exhibits 40–50% amino acid identity with the rat renal Na+/sulfate cotransporter, NaSi-1, as well as with the human and rat Na+/dicarboxylate cotransporters, NaDC-1/SDCT1 and NaDC-3/SDCT2. Functional expression studies in cRNA-injected Xenopus laevis oocytes showed that SUT-1 mediates high levels of Na+-dependent sulfate transport, which is resistant to DIDS inhibition. The SUT-1 gene mapped to human chromosome 7q33. Northern blotting analysis revealed that SUT-1 exhibits a highly restricted tissue distribution, with abundant expression in placenta. Reverse transcription–PCR analysis indicated that SUT-1 and the diastrophic dysplasia sulfate transporter (DTD), one of the two known human DIDS-sensitive sulfate transporters, are coexpressed in HEVEC. SUT-1 and DTD could correspond, respectively, to the DIDS-resistant and DIDS-sensitive components of sulfate uptake in HEVEC. Together, these results demonstrate that SUT-1 is a distinct human Na+-coupled sulfate transporter, likely to play a major role in sulfate incorporation in HEV.

Chicken Erythroid AE1 Anion Exchangers Associate with the Cytoskeleton During Recycling to the Golgi

Chicken erythroid AE1 anion exchangers receive endoglycosidase F (endo F)-sensitive sugar modifications in their initial transit through the secretory pathway. After delivery to the plasma membrane, anion exchangers are internalized and recycled to the Golgi where they acquire additional N-linked modifications that are resistant to endo F. During recycling, some of the anion exchangers become detergent insoluble. The acquisition of detergent insolubility correlates with the association of the anion exchanger with cytoskeletal ankyrin. Reagents that inhibit different steps in the endocytic pathway, including 0.4 M sucrose, ammonium chloride, and brefeldin A, block the acquisition of endo F-resistant sugars and the acquisition of detergent insolubility by newly synthesized anion exchangers. The inhibitory effects of ammonium chloride on anion exchanger processing are rapidly reversible. Furthermore, AE1 anion exchangers become detergent insoluble more rapidly than they acquire endo F-resistant modifications in cells recovering from an ammonium chloride block. This suggests that the cytoskeletal association of the recycling anion exchangers occurs after release from the compartment where they accumulate due to ammonium chloride treatment, and prior to their transit through the Golgi. The recycling pool of newly synthesized anion exchangers is reflected in the steady-state distribution of the polypeptide. In addition to plasma membrane staining, anion exchanger antibodies stain a perinuclear compartment in erythroid cells. This perinuclear AE1-containing compartment is also stained by ankyrin antibodies and partially overlaps the membrane compartment stained by NBD C6-ceramide, a Golgi marker. Detergent extraction of erythroid cells in situ has suggested that a substantial fraction of the perinuclear pool of AE1 is cytoskeletal associated. The demonstration that erythroid anion exchangers interact with elements of the cytoskeleton during recycling to the Golgi suggests the cytoskeleton may be involved in the post-Golgi trafficking of this membrane transporter.

Na–H Exchange Acts Downstream of RhoA to Regulate Integrin-induced Cell Adhesion and Spreading

The ubiquitously expressed Na–H exchanger NHE1 functions in regulating intracellular pH and cell volume. NHE1 activity is stimulated by hormones, growth factors, and activation of integrin receptors. We recently determined that NHE1 activity is also stimulated by activation of the low molecular weight GTPase RhoA and that increases in NHE1 activity are necessary for RhoA-induced formation of actin stress fibers. We now show that NHE1 acts downstream of RhoA to modulate initial steps in integrin signaling for the assembly of focal adhesions. Adhesion of CCL39 fibroblasts on fibronectin was markedly delayed in the presence of the NHE inhibitor ethylisopropylamiloride. In mutant PS120 cells, derived from CCL39 fibroblasts but lacking NHE1, adhesion was also delayed but was rescued in PS120 cells stably expressing NHE1. In the absence of NHE1 activity, cell spreading was inhibited, and the accumulation of integrins, paxillin, and vinculin at focal contacts was impaired. Additionally, tyrosine phosphorylation of p125FAK induced by integrin clustering was also impaired. Inactivation of RhoA with C3 transferase and inhibition of the Rho-kinase p160ROCK with the pyridine derivative Y-27632 completely abolished activation of NHE1 by integrins but not by platelet-derived growth factor. These findings indicate that NHE1 acts downstream of RhoA to contribute a previously unrecognized critical signal to proximal events in integrin-induced cytoskeletal reorganization.

Transport of uncharged organic solutes in Xenopus oocytes expressing red cell anion exchangers (AE1s)

When expressed in Xenopus oocytes, the trout red cell anion exchanger tAE1, but not the mouse exchanger mAE1, elicited a transport of electroneutral solutes (sorbitol, urea) in addition to the expected anion exchange activity. Chimeras constructed from mAE1 and tAE1 allowed us to identify the tAE1 domains involved in the induction of these transports. Expression of tAE1 (but not mAE1) is known to generate an anion conductance associated with a taurine transport. The present data provide evidence that (i) the capacity of tAE1 and tAE1 chimeras to generate urea and sorbitol permeability also was associated with an anion conductance; (ii) the same inhibitors affected both the permeability of solutes and anion conductance; and (iii) no measurable water transport was associated with the tAE1-dependent conductance. These results support the view that fish red blood cells, to achieve cell volume regulation in response to hypotonic swelling, activate a tAE1-associated anion channel that can mediate the passive transport of taurine and electroneutral solutes.

A new device for 100 per cent humidification of inspired air

A new humidifier for use during mechanical ventilation in endotracheally intubated patients is described and tested. The humidifier is based on a heat-moisture exchanger, which absorbs the expired heat and moisture and releases it into the inspired air. External heat and water are then added at the patient side of the heat-moisture exchanger, so that the inspired gas should reach 100% humidity (44 mg/l) at 37°C. In bench tests using constant and decelerating inspiratory flow and minute volumes of 3–25 l the device gave an absolute humidity of 41–44 mg/l, and it reduced the amount of water consumed in eight mechanically ventilated patients compared with a conventional active humidifier. During a 24-h test period there was no water condensation in the ventilator tubing with the new device.

Coupling of histamine H3 receptors to neuronal Na+/H+ exchange: A novel protective mechanism in myocardial ischemia

In myocardial ischemia, adrenergic nerves release excessive amounts of norepinephrine (NE), causing dysfunction and arrhythmias. With anoxia and the concomitant ATP depletion, vesicular storage of NE is impaired, resulting in accumulation of free NE in the axoplasm of sympathetic nerves. Intraneuronal acidosis activates the Na+/H+ exchanger (NHE), leading to increased Na+ entry in the nerve terminals. These conditions favor availability of the NE transporter to the axoplasmic side of the membrane, causing massive carrier-mediated efflux of free NE. Neuronal NHE activation is pivotal in this process; NHE inhibitors attenuate carrier-mediated NE release. We previously reported that activation of histamine H3 receptors (H3R) on cardiac sympathetic nerves also reduces carrier-mediated NE release and alleviates arrhythmias. Thus, H3R activation may be negatively coupled to NHE. We tested this hypothesis in individual human SKNMC neuroblastoma cells stably transfected with H3R cDNA, loaded with the intracellular pH (pHi) indicator BCECF. These cells possess amiloride-sensitive NHE. NHE activity was measured as the rate of Na+-dependent pHi recovery in response to an acute acid pulse (NH4Cl). We found that the selective H3R-agonist imetit markedly diminished NHE activity, and so did the amiloride derivative EIPA. The selective H3R antagonist thioperamide abolished the imetit-induced NHE attenuation. Thus, our results provide a link between H3R and NHE, which may limit the excessive release of NE during protracted myocardial ischemia. Our previous and present findings uncover a novel mechanism of cardioprotection: NHE inhibition in cardiac adrenergic neurons as a means to prevent ischemic arrhythmias associated with carrier-mediated NE release.

A role for intracellular pH in membrane IgM-mediated cell death of human B lymphomas

We show that anti-IgM-induced cell death in a human B lymphoma cell line, B104, is associated with early intracellular acidification and cell shrinkage. In contrast, another human B cell lymphoma line, Daudi, less susceptible to B cell antigen receptor-mediated cell death, responded to anti-IgM with an early increase in intracellular pH (pHi). The anti-IgM-induced changes of pHi were associated with different levels of activation of the Na+/H+ exchanger isoform 1 (NHE1) as judged by its phosphorylation status. Prevention of anti-IgM-induced cell death in B104 cells by the calcineurin phosphatase inhibitor, cyclosporin A, abrogated both intracellular acidification and cell shrinkage and was associated with an increase in the phosphorylation level of NHE1 within the first 60 min of stimulation. This indicates a key role for calcineurin in regulating pHi and cell viability. The potential role of pHi in cell viability was confirmed in Daudi cells treated with an Na+/H+ exchanger inhibitor 5-(N,N-hexamethylene)amiloride. These observations indicate that the outcome of the anti-IgM treatment depends on NHE1-controlled pHi. We suggest that inactivation of the NHE1 in anti-IgM-stimulated cells results in intracellular acidification and subsequently triggers or amplifies cell death.