Caixin Sun

Study of Transmembrane Potentials of Inner and Outer Membranes Induced by Pulsed-Electric-Field Model and Simulation

A more proper and realistic multilayer dielectric model of spherical biological cell, in which nuclear was taken into consideration, was proposed based on the classic dielectric model in this paper. The general analytical method was also deduced and analyzed in detail in calculating the time courses of transmembrane potentials of both inner and outer membranes induced by constant and time-varying electric field. The time course of transmembrane potential of the outer membrane for multilayer dielectric model was compared to that of the classical model. It is shown that the latter is larger than the former, particularly for a cell with larger nuclear. The time courses of transmembrane potentials of both inner and outer membranes induced by pulsed electric fields (PEFs) with different durations were also studied based on the multilayer dielectric model. Long PEF targets outer membrane mainly, and there is little influence to cell nucleus, mitochondrion, and other organelles; thus, it causes electroporation to the outer membrane. As the pulse duration decreases, the electroporation effect changes gradually from the outer membrane to intracellular organelle membrane. Ultrashort PEF (tens of nanoseconds) induces larger voltage across the inner membrane and acts mostly on intracellular substructures. However, submicrosecond PEF (several hundreds of nanoseconds) can induce significant voltages across both the inner and outer membranes, therefore, causing damage to both the inner and outer membranes. This property of submicrosecond PEF has much practical value for tumor treatment.

Study of Transmembrane Potentials on Cellular Inner and Outer Membrane—Frequency Response Model and Its Filter Characteristic Simulation

Based on the multilayer dielectric model for a spherical cell, a frequency response model of transmembrane potentials on cellular inner and outer membranes is established with a simulating method. The simulating results indicate that transmembrane potential on the inner membrane shows first-order bandpass filter characteristic, while transmembrane potential on the outer membrane shows first-order low-pass filter characteristic approximately. It could be found that the transmembrane potential on the inner membrane is greater than that on the outer membrane, and can keep a higher value in the range from a center frequency to an upper cutoff frequency, which is desirable to induce intracellular electromanipulation. Both a discussion about an equivalent RC model of the cell and the experimental result are in agreement with the aforementioned conclusion. Therefore, the frequency response model could help to choose reasonable window parameters for the application of a nanosecond pulsed electric field to tumor treatment.

The effect of high frequency steep pulsed electric fields on in vitro and in vivo antitumor efficiency of ovarian cancer cell line skov3 and potential use in electrochemotherapy

BackgroundPatients received electrochemotherapy often associated with unpleasant sensations mainly result from low-frequency electric pulse induced muscle contractions. Increasing the repetition frequency of electric pulse can reduce unpleasant sensations. However, due to the specificity of SPEF, frequency related antitumor efficiency need to be further clarified. The aim of this study was to compare in vitro cytotoxic and in vivo antitumor effect on ovarian cancer cell line SKOV3 by SPEF with different repetition frequencies. Explore potential benefits of using high frequency SPEF in order to be exploitable in electrochemotherapy.MethodsFor in vitro experiment, SKOV3 cell suspensions were exposed to SPEF with gradient increased frequencies (1, 60, 1 000, 5 000 Hz) and electric field intensity (50, 100, 150, 200, 250, 300, 350, 400 V/cm) respectively. For in vivo test, SKOV3 subcutaneous implanted tumor in BALB/c nude mice (nu/nu) were exposure to SPEF with gradient increased frequencies (1, 60, 1 000, 5 000 Hz) and fixed electric field intensity (250 V/cm) (7 mice for each frequency and 7 for control). Antitumor efficiency was performed by in vitro cytotoxic assay and in vivo tumor growth inhibition rate, supplemented by histological and TEM observations. Data were analyzed using one-way ANOVA followed by the comparisons of multiple groups.ResultsSPEF with a given frequency and appropriate electric field intensity could achieve similar cytotoxicity until reached a plateau of maximum cytotoxicity (approx. 100%). SPEF with different frequencies had significant antitumor efficiency in comparison to the control group (P < 0.05). However, there was no difference in tumor responses among test groups (P > 0.05). Histological and TEM observations demonstrated obvious cell damages in response to SPEF exposure. Furthermore, SPEF with 5 kHz could induce apoptosis under TEM observations both in vitro and in vivo.ConclusionSPEF with high frequency could also achieve similar antitumor efficiency which can be used to reduce unpleasant sensations in tumor electrical treatment. Our research proposed potential applications of using high frequency SPEF in clinical cancer treatment.

Experiment and mechanism research of SKOV3 cancer cell apoptosis induced by nanosecond pulsed electric field

This paper studies the apoptosis of human ovarian carcinoma cell Line (SKOV3) induced by the nanosecond pulsed electric field (10kV/cm, 100ns, 1 Hz) and its effect on intracellular calcium concentration ([Ca2+]i). These cells were doubly marked by Annexin V-FITC/PI, and the apoptosis rate was analyzed with flow cytometry. After AO/EB staining the morphological changes were observed under fluorescent microscope, and their ultrastructural changes were observed under scanning electron microscope (SEM). With Fluo-3/AM as calcium fluorescent marker, laser scanning confocal microscope (LSCM) was used to detect the effect of nsPEF on [Ca2+]i and the source of Ca2+. The results showed that the early apoptosis rate of the treatment group was (22.21±2.71)%, significantly higher than that of the control group (3.04±0.44)% (P<0.01). The typical features of apoptotic cell have been observed by fluorescent microscope and SEM. It is proved that nsPEF can induce apoptosis of SKOV3 cells and result in distinct increase in [Ca2+]i (P<0.01), which was independent of extracellular calcium concentration (P>0.05). Since nsPEF can penetrate cell membrane due to its high frequency components, one of the mechanisms of nsPEF-induced apoptosis may be that activating intracellular calcium stores can increase the [Ca2+]i, and consequently, the apoptotic signal pathway can be induced.This paper studies the apoptosis of human ovarian carcinoma cell Line (SKOV3) induced by the nanosecond pulsed electric field (10kV/cm, 100ns, 1 Hz) and its effect on intracellular calcium concentration ([Ca2+] i ). These cells were doubly marked by Annexin V-FITC/PI, and the apoptosis rate was analyzed with flow cytometry. After AO/EB staining the morphological changes were observed under fluorescent microscope, and their ultrastructural changes were observed under scanning electron microscope (SEM). With Fluo-3/AM as calcium fluorescent marker, laser scanning confocal microscope (LSCM) was used to detect the effect of nsPEF on [Ca2+] i and the source of Ca2+. The results showed that the early apoptosis rate of the treatment group was (22.21±2.71)%, significantly higher than that of the control group (3.04±0.44)% (P i (P 0.05). Since nsPEF can penetrate cell membrane due to its high frequency components, one of the mechanisms of nsPEF-induced apoptosis may be that activating intracellular calcium stores can increase the [Ca2+] i , and consequently, the apoptotic signal pathway can be induced.

Electromagnetic environment of the EHV transmission line and its effect

Based on the characteristic of electromagnetic field around the EHV transmission line, this paper discusses the effect of electromagnetic environment of the EHV transmission line by analyzing power frequency electric field, magnetic field, radio interference and audio noises. Then this paper studies the lasting effect and transient electric breakdown effect by power frequency electric field to zoology, corona discharge to radio interference, power frequency magnetic field and audio noises to nearby environment. At last, example some limits rule and propose the steps to minish its effect to the environment by analyzing the transmission line electric field distribution rule and its affected factors.

Effects of Steep Pulsed Electric Fields (SPEF) on Mitochondrial Transmembrane Potential of Human Liver Cancer Cell

Mitochondrial plays an important role in apoptosis, and measuring the change of mitochondrial transmembrane potential (DeltaPsim) is a useful method for apoptosis. Exposing human liver cancer cell SMMC-7721 dyed with Rhodamine 123 to steep pulsed electric fields (SPEF), this paper observed the real-time change of DeltaPsim using laser scanning confocal microscope (LSCM) to study the apoptosis effect of SPEF. The experiment results showed that DeltaPsim decreased gradually in process of exposing to SPEF, SPEF with higher voltage (600 V) and shorter width (100 ns) could cause a quicker decrease than SPEF with lower voltage (200 V) and longer width (1.3 mus). Such phenomenon kept up even after canceling SPEF, this may lead to collapse of DeltaPsim and induce apoptosis with tremendous possibilities. The experiment results of flow cytometry (SMMC-7721 dyed with Annexin V-FITC) approved that SPEF could induce apoptosis markedly (P<0.01); SPEF with lower voltage (200 V) and longer width (1.3 mus) could induce apoptosis more effectively (P<0.01) than SPEF with higher voltage (600 V) and shorter width (100 ns). These experiment results supply possible mechanism and parameter selection basis for tumor treatment using SPEF.

Identifying the Internal and the External Overvoltage of Distribution Networks Based on Fisher Discriminate Method

It has been testified by running practice to that the internal and the external overvoltage of distribution networks are the main causes of electrical accidents. To capture and analyze the overvoltage in power system, authors have developed a set of overvoltage on-line monitoring system, and it has been running in a 10 kV distribution network for more than 36 months. Thousands of detailed data files have been collected and saved. Based on the brief introduction to the structure and the operational principle of the monitoring system, this paper presents an intelligently identification method of the internal overvoltage and the external overvoltage based on Fisher discriminate method. Firstly, the statistical parameters should be extracted from the original data recorded by the on-line monitoring system. According to the performance of many parameters during the period of the overvoltage occurrence, 8 of them such as time to crest, time to half value of voltage, total duration of overvoltage and etc. are selected as the characteristic parameters of identifying overvoltage types. Secondly, according to the operational data tracked by other monitoring instruments in the field and the daily report, the corresponding reference sample for either overvoltage are brought forward. Then, the identifying function can be constructed by the Fisher discrimination method. Any 8-dimensions data will be projected to 1-dimension. Lastly, the unknown overvoltage data samples are substituted to the identifying function. The distinguished results to 266 samples indicate that the outcomes are accordant, the identifying method along with the identifying function are correct and effective.

Vascular effect and immunity effect of steep pulse electric field on Walker 256-bearing Wistar mice

The vascular effect and immunity effect of SPEF on Wistar mice were studied, and the possible treatment mechanisms and clinical trial methods of SPEF were discussed. We tested lymphocyte proliferation ratio and activity of NK cell, and the contents of IFN-/spl alpha/ and IL-4 in the serum lymphocyte were inspected with ELISA method. Moreover, macrophage were collected, the content of TNF-/spl alpha/ excreted by macrophage were inspected with ELISA method, too. Statistical analysis was performed using the SPSS10.0 software package and t-test. VEGF level in test group was significantly decreased, and VEGF expression was weakened evidently. SPEF strengthened activity of NK cell, enlarged quantities of TNF-/spl alpha/ from test group, accelerated exudation of TH1 cell factor and slowed exudation of TH2 cell factor. SPEF showed effective anti-tumor effect through restraining the formation of fresh vessels and baffling the birth and transfer of tumor cell. It could strengthen organism immunity function, and had visible effect on Walker-256 tumor.

Analysis of Transmembrane Potentials Induced by Pulsed Electric Field with Different Durations Based on Five-shelled Dielectric Model of Cell

In order to account for the influence of subcellular organelles on transmembrane potential, five-shelled dielectric model of spherical cell was developed in this paper. And the calculation method of transmembrane potential induced by any pulsed electric field (PEF) was put forward. Thus the effects of different pulse duration on transmembrane potentials of cell membrane and nuclear membrane were also analyzed. It is shown that there is a strong relationship between the amplitude and waveform of transmembrane potential and pulse duration. PEF with shorter duration can reach into the cell easily, thus with shorter duration pulses, transmembrane potential of nuclear membrane is increasing and close to that of cell membrane. So PEF with shorter duration will bring on some important biological effects, such as electroporation or apoptosis

A GA-based grey prediction model for predicting the gas-in-oil concentrations in oil-filled transformer

Dissolved-gas-analysis (DGA) techniques are widely used to diagnose oil-filled transformer insulation, but the conventional procedure acquiring the gas-in-oil concentrations is not timely. To make up the disadvantage, a new method based on a genetic algorithm and the grey theory to predict the gas-in-oil concentrations is proposed in This work. The grey model (GM(1,1)) has been improved and a new optimized grey model (GM(1,1,/spl beta/)) has been constructed. The genetic algorithm has been applied to search the optimal parameters of the GM(1,1,/spl beta/) model. The validity of the GA-based GM(1,1,/spl beta/) model was verified with two prediction examples.