N. Nomura

Kumamoto University, Kumamoto-shi, Kumamoto Prefecture, Japan

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Publications (6)2.72 Total impact

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    ABSTRACT: Intracellular DNA damages caused by intense burst sinusoidal electric fields (IBSEFs) were investigated by means of an alkaline comet assay method. Non-thermal, 200 mus-long IBSEF with various frequency values (300 kHz-100 MHz) and strengths (up to 200 kV/m) was applied to Chinese hamster ovary (CHO) cells in a suspending medium between 1 mm gap parallel electrodes. The comet assay suggests that 100 kV/m IBSEF with frequencies exceeding 1 MHz or 100 MHz IBSEFs with field strengths exceeding 3 kV/m induces significant DNA damage. According to the numerical calculation of the electric field over a simplified cell model under an alternating electric field, the intracellular field strength increases with increasing alternating frequency. The minimum level of the field strength that induces the DNA damage is in the range of 10-30 kV/m. This intracellular strong field might trigger biological processes leading to the DNA damage.
    IEEE Transactions on Dielectrics and Electrical Insulation 11/2009; · 1.36 Impact Factor
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    ABSTRACT: Intracellular DNA breakage induced by exposing to non-thermal, intense burst sinusoidal electric fields (IBSEF) was studied by means of alkaline comet assay, single cell electrophoresis. The IBSEFs with frequency in the range of 300 kHz-100 MHz and with field strength up to 200 kV/m were applied to cultured Chinese hamster ovary (CHO) cells. The DNA breakage indicated by the comet pattern was evaluated by using Olive Moment Method. The experiment shows that the DNA breakage depends both on the field strength and on the frequency of the IBSEF. For the frequency of 100 MHz, the critical field strength is 10 kV/m. For the strength of 100 kV/m, the DNA is damaged only with the frequency exceeding 1 MHz. Two dimensional calculation of the electric field distribution under an alternating field implies that the DNA breakage occurs only when the intracellular electric field exceeds 30 kV/m, which might trigger biological processes leading to the DNA breakage.
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    ABSTRACT: It is a well known fact that intense electric fields with frequencies exceeding MHz ranges cause intracellular effect to mammalian cells. We have used the Intense Burst Sinusoidal Electric Field (IBSEF) which is narrow band spectra, to put the electrical energy into biological cells efficiently. We have experimentally demonstrated here the presence of intense electric fields inside the cell membrane, which is achieved by frequency of 100 MHz, amplitude up to 200 kV/m and duration of 200 μs, induces DNA fragmentation to Chinese Hamster Ovary (CHO) cells. The DNA damage was investigated by means of comet assay method. Additionally, we have performed the agarose gel electrophoresis method for human genomic DNAs exposed to IBSEF with various frequencies, electric field strength up to 400 kV/m, and duration of 5 ms. The electrophoresis did not show significant changes between the IBSEF treated and untreated samples. The results imply that IBSEF does not break the DNA physically, and the possibility of IBSEF being a trigger to biological reaction connected to the DNA fragmentation, such as apoptosis.
    Pulsed Power Conference, 2007 16th IEEE International; 07/2007
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    ABSTRACT: This paper describes the process of narrow band pulsed electric fields (NPEFs) and its effect on mammalian cells. The NPEF consists of a pulse modulated sinusoidal wave (PMSW), which allows delivery of well-defined electric fields in terms of frequency, field strength and deposition energy to the biological systems. 100 mus long sinusoidal electric fields with a frequency of 0.02, 2 or 50 MHz and field strengths of up to 2 kV/cm are applied to CHO cells with variation in the DNA density in the cells investigated by means of Acridine Orange assay. The experiments indicate that 50 MHz fields cause DNA degradation without cell membrane defects, while 0.02 MHz fields lead to an increase in membrane permeability which is similar to the effect known as electroporation. The intermediate frequency of 2 MHz influences both the membrane and DNA. It is demonstrated that the MHz range narrowband electric fields with the amplitude level of 1 kV/cm cause intracellular effects in mammalian cells.
    IEEE Transactions on Dielectrics and Electrical Insulation 07/2007; · 1.36 Impact Factor
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    ABSTRACT: This paper describes the effect of intense burst RF electric fields (IBRFFs) on DNA in living mammalian cells. Chinese hamster ovary (CHO) cells were placed between two parallel plane electrodes and exposed to the IBRFF with a MHz range frequency and an electric field strength of a couple of kV/cm. The IBRFF duration was fixed to 100 ps, which was sufficiently short so as to not raise the temperature of suspension media of the cell due to Joule heating. A single cell electrophoresis analysis, comet assay method, was employed to investigate the reaction of the intracellular DNA to the lBRFF. The experiment shows the MHz range and 2kV/cm IBRFF physically introduces the fragmentation to intracellular DNA
    Power Modulator Symposium, 2006. Conference Record of the 2006 Twenty-Seventh International; 06/2006
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    ABSTRACT: Burst RF fields (BRFFs) were applied to Chinese Hamster Ovary (CHO) cells, and the cell response to the BRFF of two different frequencies, 20 kHz and 50 MHz, was investigated by means of the fluorescent microscopy. The field strength and duration of the BRFF were fixed at 1 kV/cm, and 100 mus, respectively. Cells were placed in a 100 mum-gap electrode plated on the slide glass for a microscopy. Acridine orange (AO), which mainly reacts to DNA, was used as the fluorescent dye. From the experiment, the BRFF of 20 kHz initiates the increase in the permeability of cell membrane. In contrast, the BRFF of 50 MHz does not act on cell membrane but causes degeneration of DNA or RNA. We have experimentally demonstrated that the burst RF fields with only a small electric field of 1 kV/cm cause not only membrane reaction but also intracellular effects.
    Pulsed Power Conference, 2005 IEEE; 07/2005

Publication Stats

29 Citations
2.72 Total Impact Points


  • 2005–2009
    • Kumamoto University
      • • Graduate School of Science and Technology
      • • Department of Computer Science and Elecrical Engineering
      Kumamoto-shi, Kumamoto Prefecture, Japan