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Electric Pulses (electric + pulse)
Selected Abstracts900 MHz modulated electromagnetic fields accelerate the clathrin-mediated endocytosis pathwayBIOELECTROMAGNETICS, Issue 3 2009Mihaela G. Moisescu Abstract We report new data regarding the molecular mechanisms of GSM-induced increase of cell endocytosis rate. Even though endocytosis represents an important physical and biological event for cell physiology, studies on modulated electromagnetic fields (EMF) effects on this process are scarce. In a previous article, we showed that fluid phase endocytosis rate increases when cultured cells are exposed to 900 MHz EMF similar to mobile phones' modulated GSM signals (217 Hz repetition frequency, 576 µs pulse width) and to electric pulses similar to the GSM electrical component. Trying to distinguish the mechanisms sustaining this endocytosis stimulation, we exposed murine melanoma cells to Lucifer Yellow (LY) or to GSM,EMF/electric pulses in the presence of drugs inhibiting the clathrin- or the caveolin-dependent endocytosis. Experiments were performed at a specific absorption rate (SAR) of 3.2 W/kg in a wire patch cell under homogeneously distributed EMF field and controlled temperature (in the range of 28.5,29.5 °C). Thus, the observed increase in LY uptake was not a thermal effect. Chlorpromazine and ethanol, but not Filipin, inhibited this increase. Therefore, the clathrin-dependent endocytosis is stimulated by the GSM,EMF, suggesting that the cellular mechanism affected by the modulated EMF involves vesicles that detach from the cell membrane, mainly clathrin-coated vesicles. Bioelectromagnetics 30:222,230, 2009. © 2008 Wiley-Liss, Inc. [source] Tumour cell,dendritic cell fusion for cancer immunotherapy: comparison of therapeutic efficiency of polyethylen-glycol versus electro-fusion protocolsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 3 2002M. Lindner Abstract Background ,Fusion of tumour cells with dendritic cells (DC) is a powerful new technology to increase tumour vaccine immunogenicity. The aim of this study was to compare fusion protocols with syngenic DCs with respect to the efficiency of polyethylen-glycol-(PEG) and electric pulse-mediated fusions for induction of protective anti-tumour immune responses. As a model we chose a low immunogenic and metastatic murine mammary carcinoma cell line, which mimics clinically relevant tumour features. Methods FACS-staining, chromium release assay, therapeutic immunization, adoptive transfer. Results ,We show that the parental line with low cell surface expression of MHC molecules as well as a lacZ transfectant becomes highly immunogenic upon fusion with DCs. This was true for PEG- as well as for electro-fused cells. Immunization with products of DCs and tumour cells cocultivated for 16 h without the fusing agent PEG also caused induction of profound anti-tumour immunity, while this was not the case when using parental tumour cells or their lacZ transfectants as vaccines. Immune protection against the parental tumour cells after vaccination with fused cells was long-lasting and could be transferred via immune spleen cells into immuno-incompetent nude (nu/nu) mice. Conclusion ,Fusion products of DA3hi mammary carcinoma cells and DCs produced by an electric pulse were similar to those produced by PEG fusion with regard to vaccine potency in prophylactic antitumour immunization assays in vivo. Therefore, both techniques seem to be promising for clinical application. [source] Electric-Field-Assisted Nanostructuring of a Mott InsulatorADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Vincent Dubost Abstract Here, the first experimental evidence for a strong electromechanical coupling in the Mott insulator GaTa4Se8 that allows highly reproducible nanoscaled writing by means of scanning tunneling microscopy (STM) is reported. The local electric field across the STM junction is observed to have a threshold value above which the clean (100) surface of GaTa4Se8 becomes mechanically instable: at voltage biases >1.1,V, the surface suddenly inflates and comes in contact with the STM tip, resulting in nanometer-sized craters. The formed pattern can be indestructibly "read" by STM at a lower voltage bias, thus allowing 5,Tdots inch,2 dense writing/reading at room temperature. The discovery of the electromechanical coupling in GaTa4Se8 might give new clues in the understanding of the electric pulse induced resistive switching recently observed in this stoichiometric Mott insulator. [source] Sustained expression of Epstein,Barr virus episomal vector mediated factor VIII in vivo following muscle electroporationHAEMOPHILIA, Issue 3 2006W.-H. MEI Summary., Haemophilia A treatment is an attractive candidate for gene therapy. The aim of haemophilia gene therapy is to obtain long-term therapeutic level of factor VIII (FVIII). We investigated Epstein,Barr virus (EBV)-based episomal vector combined with in vivo electroporation of naked DNA as a safe, efficient and simple method for correcting FVIII deficiency. A combinant FVIII expression EBV-based episomal vector pcDNA3-FVIII-EBVR was constructed and expressed in COS-7 cells. Then the naked plasmid DNA was injected into the quadriceps of mice following the electric pulse stimulation. Our data showed that pcDNA3-FVIII-EBVR expression in transfected COS-7 can maintain stably for at least 60 days and the hFVIII:Ag in plasma in two pcDNA3-FVIII-EBVR groups mice was higher than that in pcDNA-FVIII groups no matter with or without electric pulse stimulation. With the stimulating of electric pulse, the FVIII expression in plasma of recipient mice was increased two- to fourfolds and can be lasted for at least 90 days. No severe muscle damage was detected. So this novel strategy that FVIII expression mediated by EBV episomal vector following muscle electroporation is efficient, safe, simple and economic and may be applicable to clinical usage. [source] Enhanced Q-switched distributed feedback fiber laser based on acoustic pulsesLASER PHYSICS LETTERS, Issue 2 2009M. Delgado-Pinar Abstract An acoustically Q-switched distributed feedback fiber laser with enhanced performance is presented. It is based on an FBG written in an erbium doped fiber, in which a dynamic defect is introduced by means of a short acoustic pulse. The performance of the laser depends on the reflectivity of the grating. In this work, we present two different Q-switched distributed feedback fiber lasers realized with active gratings of different reflectivities. Both lasers are characterized at different pump powers and repetition rates. It is shown that the performance of the laser based on the weaker grating was significantly improved with respect to the laser based on the stronger grating. In terms of peak power, the improvement was a factor of two. The average power was also improved. For example, at 50 kHz, it was increased from 280 , W up to 500 , W. In addition, we studied the performance of the laser when an electric square signal was used to drive the transducer, obtaining similar results to the case when a harmonic electric pulse was used. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laserLASER PHYSICS LETTERS, Issue 8 2007H. Lei Abstract A stable repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laser is presented. A 0.8 mm-thickness 7 mm-diameter Nd:YAG crystal at 1.6 at.% is adapted as active medium and the saturable absorber for passively Q-switched pulse generating, a 0.2 mm-thickness 6.8-mm diameter Cr4+:YAG piece was thermal bonded into the Nd:YAG after primary optical contact. By using pulse pump and controlling the duty cycle of electric pulse and temperature of laser diode, a 1 W C-mount packaged fast-collimated laser diode, we can continuously achieve repetition rate from 1 kHz to 10 kHz as active Q-switched laser. The delay time at 10 kHz is 90 ,s, while the single pulse energy is 2.8 ,J with pulse width of 2 ns. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Use of the Rotation Vector in Brownian Dynamics Simulation of Transient Electro-Optical PropertiesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 1 2009Tom Richard Evensen Abstract We have recently developed a new singularity-free algorithm for Brownian dynamics simulation of free rotational diffusion. The algorithm is rigorously derived from kinetic theory and makes use of the Cartesian components of the rotation vector as the generalized coordinates describing angular orientation. Here, we report on the application of this new algorithm in Brownian dynamics simulations of transient electro-optical properties. This work serves two main purposes. Firstly, it demonstrates the integrity of the new algorithm for BD-simulations of the most common transient electro-optic experiments. Secondly, it provides new insight into the performance of the new algorithm compared to algorithms that make use of the Euler angles. We study the transient electrically induced birefringence in dilute solutions of rigid particles with anisotropic polarization tensor in response to external electric field pulses. The use of both one single electric pulse and two electric pulses with opposite polarity are being analyzed. We document that the new singularity-free algorithm performs flawlessly. We find that, for these types of systems, the new singularity-free algorithm, in general, outperforms similar algorithms based on the Euler angles. In a wider perspective, the most important aspect of this work is that it serves as an important reference for future development of efficient BD-algorithms for studies of more complex systems. These systems include polymers consisting of rigid segments with single-segment translational,rotational coupling, segment,segment fluid-dynamic interactions and holonomic constraints. [source] In vitro and in vivo evaluation and a case report of intense nanosecond pulsed electric field as a local therapy for human malignanciesINTERNATIONAL JOURNAL OF CANCER, Issue 3 2007Edward B. Garon Abstract When delivered to cells, very short duration, high electric field pulses (nanoelectropulses) induce primarily intracellular events. We present evidence that this emerging modality may have a role as a local cancer therapy. Five hematologic and 16 solid tumor cell lines were pulsed in vitro. Hematologic cells proved particularly sensitive to nanoelectropulses, with more than a 60% decrease in viable cells measured by MTT assay 96 hr after pulsing in 4 of 5 cell lines. In solid tumor cell lines, 10 out of 16 cell lines had more than a 10% decrease in viable cells. AsPC-1, a pancreatic cancer cell line, demonstrated the greatest in vitro sensitivity among solid tumor cell lines, with a 64% decrease in viable cells. When nanoelectropulse therapy was applied to AsPC-1 tumors in athymic nude mice, responses were seen in 4 of 6 tumors, including clinical complete responses in 3 of 6 animals. A single human subject applied nanoelectropulse therapy to his own basal cell carcinoma and had a complete pathologic response. In summary, we demonstrate that electric pulses 20 ns or less kill a wide variety of human cancer cells in vitro, induce tumor regression in vivo, and show efficacy in a single human patient. Therefore, nanoelectropulse therapy deserves further study as a potentially effective cancer therapy. © 2007 Wiley-Liss, Inc. [source] Electroporation-mediated muscarinic M3 receptor gene transfer into rat urinary bladderINTERNATIONAL JOURNAL OF UROLOGY, Issue 11 2004MASAYUKI OTANI Abstract Background: Muscarinic M3 (M3) receptor has been recognized as a major muscarinic receptor for smooth muscle contractions of the urinary bladder. Under the hypothesis that overexpression of M3 receptor in the urinary bladder would enhance urinary bladder contractions, we have transferred the M3 receptor gene into rat bladders using electroporation (EP) and evaluated the functional expression of the transferred gene. Methods: Plasmids expressing luciferase, a green fluorescence protein and M3 receptor were injected into the rat bladder and square-wave electric pulses were immediately applied. Two days after gene transfer, we analyzed gene expression. Immunohistochemical staining was performed and the contractile responses from isolated bladder strips, which were induced KCl, carbachol and electrical field stimulation (EFS), were evaluated. Results: The optimal conditions of electroporation were 8 pulses, 45 voltages, 50 milliseconds/pulses and 1 Hz. Under these conditions, luciferase gene expression was enhanced approximately 300-fold, compared to an injection of DNA only. Regarding immunohistochemistry with an anti-M3 receptor, an increase in immunoactivity was observed in the M3 receptor gene transferred rat bladder, compared to the bladder of the control rat. In rats with the transferred M3 receptor gene, carbachol- and EFS-induced maximum contractile responses of bladder smooth muscle strips significantly increased. Conclusions: These findings suggest that an in vivo EP procedure is an useful method for gene transfer into the bladder and that an overexpression of M3 receptor in the rat bladder enhances bladder contractility. This technique may become a new treatment modality for detrusor underactivity. [source] Sintering Diamond/Cemented Carbides by the Pulse Plasma Sintering MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008Andrzej Michalski Under the conditions of thermodynamic instability, we produced dense sintered composites built of diamond particles (30 vol%) and a cemented carbide matrix. The composites were consolidated by high-current electric pulses at a temperature of about 1100°C and load of 75 MPa for 5 min. The diamond particles are strongly bound with the cemented carbide matrix, by a transition layer composed of a solid solution of carbon and tungsten in cobalt. No graphite precipitates were found in the sintered composites, as examined by microstructure observations, examinations of the phase composition, and an analysis of the Raman scattering spectra. The hardness of the diamond/cemented carbide was 23 GPa. [source] Use of the Rotation Vector in Brownian Dynamics Simulation of Transient Electro-Optical PropertiesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 1 2009Tom Richard Evensen Abstract We have recently developed a new singularity-free algorithm for Brownian dynamics simulation of free rotational diffusion. The algorithm is rigorously derived from kinetic theory and makes use of the Cartesian components of the rotation vector as the generalized coordinates describing angular orientation. Here, we report on the application of this new algorithm in Brownian dynamics simulations of transient electro-optical properties. This work serves two main purposes. Firstly, it demonstrates the integrity of the new algorithm for BD-simulations of the most common transient electro-optic experiments. Secondly, it provides new insight into the performance of the new algorithm compared to algorithms that make use of the Euler angles. We study the transient electrically induced birefringence in dilute solutions of rigid particles with anisotropic polarization tensor in response to external electric field pulses. The use of both one single electric pulse and two electric pulses with opposite polarity are being analyzed. We document that the new singularity-free algorithm performs flawlessly. We find that, for these types of systems, the new singularity-free algorithm, in general, outperforms similar algorithms based on the Euler angles. In a wider perspective, the most important aspect of this work is that it serves as an important reference for future development of efficient BD-algorithms for studies of more complex systems. These systems include polymers consisting of rigid segments with single-segment translational,rotational coupling, segment,segment fluid-dynamic interactions and holonomic constraints. [source] Optically and electrically induced dissipation in quantum Hall systemsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2008G. Nachtwei Abstract We have studied the onset of dissipation in quantum Hall systems (QHSs), patterned in various geometries (Hall bars, meanders and Corbino rings) from wafers with heterojunctions (GaAs/GaAlAs) and HgTe quantum wells with adjacent HgCdTe barriers. The QH samples were excited by electrical pulses with pulse durations tP of 0.5 ns , tP , 180 ns or by illumination with electromagnetic waves of 1.7 THz , f , 2.5 THz. These waves were either emitted coherently by a pulsed p-Ge laser system or by a thermal source. In the case of excitation by electric pulses, it is necessary to exceed a certain critical pulse length which is a function of various extrinsic parameters and sample properties. For no dissipation occurs inside the QHSs. Also, using THz illumination, the QHSs can be driven to dissipation. We found different mechanisms to be responsible for the photoresponse (PR) of the QHSs: non-resonant (bolometric) and resonant (cyclotron resonance) contributions to the PR of the QHSs. First attempts to develop a quantitative model for the observed data are made. We are able to describe a part of the observations by either a drift model or a two-level model. The quantitative agreement of these calculations with the measured data is, however, limited. This is due to the simplicity of the models applied so far and to the complex behaviour of QHSs when nonlinearly excited. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] On the high-resolution mass analysis of the product ions in tandem time-of-flight (TOF/TOF) mass spectrometers using a time-dependent re-acceleration techniqueRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2010Sergey Kurnosenko The time-dependent reacceleration of product ions produced as a result of dissociation of a single precursor ion in a tandem time-of-flight mass spectrometer is considered for the first time. Analytical expressions for the shapes of electric pulses bringing all the kinetic energies of the product ions to the same value are derived for two cases: forward acceleration mode and deceleration, followed by re-acceleration in the reversed direction (reversed mode). Secondary time-of-flight focusing resulting from the re-acceleration in the reversed mode is shown to be mass-dependent and, when averaged over a wide mass range, the focusing is tight enough to provide mass resolution exceeding 10,000. After time-dependent re-acceleration, additional compression of the ion packet width leading to better mass resolution can be obtained by decelerating the ions in a constant field. Copyright © 2009 John Wiley & Sons, Ltd. [source] Intramuscular SP1017-formulated DNA electrotransfer enhances transgene expression and distributes hHGF to different rat tissuesTHE JOURNAL OF GENE MEDICINE, Issue 1 2004Marta Riera Abstract Background The systemic administration of a therapeutic protein is a common approach for the treatment of multiple disorders. Intramuscular (i.m.) injection of plasmids, followed by electroporation, has been shown to facilitate naked DNA gene transfer in skeletal muscle allowing proteins to be produced and secreted at therapeutically relevant levels. Methods Plasmid DNA, unformulated or formulated with the non-ionic carrier SP1017, was injected at the rat tibialis anterior muscle followed by the application of electric pulses. Follow-up of protein expression was measured. Results In our study we report that the non-ionic carrier SP1017 significantly increases transgene expression in rat muscle after the i.m. injection of a formulated-pCMV, plasmid followed by electroporation. Such increased expression was observed after delivering square-wave unipolar electric pulses at two different field strengths: low (110 V/cm) and high (175 V/cm). Moreover, elevated secreted placental alkaline phosphatase (SEAP) plasma levels were achieved with low-voltage (110 V/cm) electroporation. Our results also show that human hepatocyte growth factor (hHGF) can be produced from rat muscle and delivered to blood circulation at a biologically active level after a single i.m. injection of an SP1017-formulated plasmid (pCMV/hHGF) followed by electroporation. Tissue distribution studies mostly identified hHGF in the liver, but it was also found in the kidneys and lungs suggesting that here too the HGF could be of therapeutic benefit. Conclusions Our results indicate that SP1017 enhances the expression of electrotransferred genes. Such a delivery approach could prove an efficient method for the systemic production of therapeutic proteins. Copyright © 2003 John Wiley & Sons, Ltd. [source] Plasma membrane permeabilization by 60- and 600-ns electric pulses is determined by the absorbed doseBIOELECTROMAGNETICS, Issue 2 2009Bennett L. Ibey Abstract We explored how the effect of plasma membrane permeabilization by nanosecond-duration electric pulses (nsEP) depends on the physical characteristics of exposure. The resting membrane resistance (Rm) and membrane potential (MP) were measured in cultured GH3 and CHO cells by conventional whole-cell patch-clamp technique. Intact cells were exposed to a single nsEP (60 or 600 ns duration, 0,22 kV/cm), followed by patch-clamp measurements after a 2,3 min delay. Consistent with earlier findings, nsEP caused long-lasting Rm decrease, accompanied by the loss of MP. The threshold for these effects was about 6 kV/cm for 60 ns pulses, and about 1 kV/cm for 600 ns pulses. Further analysis established that it was neither pulse duration nor the E-field amplitude per se, but the absorbed dose that determined the magnitude of the biological effect. In other words, exposure to nsEP at either pulse duration caused equal effects if the absorbed doses were equal. The threshold absorbed dose to produce plasma membrane effects in either GH3 or CHO cells at either pulse duration was found to be at or below 10 mJ/g. Despite being determined by the dose, the nsEP effect clearly is not thermal, as the maximum heating at the threshold dose is less than 0.01 °C. The use of the absorbed dose as a universal exposure metric may help to compare and quantify nsEP sensitivity of different cell types and of cells in different physiological conditions. The absorbed dose may also prove to be a more useful metric than the incident E-field in determining safety limits for high peak, low average power EMF emissions. Bioelectromagnetics 30:92,99, 2009. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||||||||