Application of nanosecond pulsed electric fields (nsPEFs) has attracted rising attention in various scientific fields including medical, pharmacological, and biological sciences, although its effects and molecular mechanisms leading to the effects remain poorly understood. Here, we show that a single, high-intensity (10–30 kV/cm), 60-ns PEF exposure affects gene expression and impairs development of eyes and germ cells in medaka (Oryzias latipes). Exposure of early blastula stage embryos to nsPEF down-regulated the expression of several transcription factors which are essential for eye development, causing abnormal eye formation. Moreover, the majority of the exposed genetic female embryos showed a fewer number of germ cells similar to that of the control (unexposed) genetic male at 9 days post-fertilization (dpf). However, all-trans retinoic acid (atRA) treatment following the exposure rescued proliferation of germ cells and resumption of normal eye development, suggesting that the phenotypes induced by nsPEF are caused by a decrease of retinoic acid levels. These results confirm that nsPEFs induce novel effects during embryogenesis in medaka.

Paper reports on production and focusing of microunderwater shock waves for medical applications. Shock wave focusing has various scientific, industrial and medical applications. For precise shock wave therapies near sensitive organs, such as cranioplasty in the close vicinity of the brain, a micro-shock wave source is required. A half-ellipsoidal cavity with 20.0 mm minor diameter and the ratio of major to minor diameters of 1.41 was designed and constructed as an extracorporeal shock wave (ESW) source. Underwater shock waves were generated by electric discharge produced by a magnetic pulse compression circuit (MPC) and an electrode. Input voltage and input current were measured by using an oscilloscope and a current monitor. Pressure histories were measured at different stand-off distances by using a PVDF needle and a fiber optic probe hydrophones. A wide range of peak overpressures from 10 to 150 MPa at the focus was obtained, and small focal zone and focal energy flux density were measured. It is concluded that the present compact extracorporeal shock wave generator has appropriate characteristics for application in precise and sensitive medical procedures.

This paper reports a preliminary study of underwater shock wave application for modification and possible control of embryonic cell differentiation and proliferation. Underwater shock waves have been of interest for various scientific, industrial, and medical applications. Shock waves have been successfully applied for disintegration of kidney stones in Urology and for bone formation in Orthopedics surgery. In the present study shock waves were generated by electric discharge using a magnetic pulse compression circuit (MPC) and tungsten point to point electrodes. Uniformly formed shock waves were used. Pressure profiles of shock waves were measured by a fiber optic probe hydrophone (FOP H). Underwater shock waves were applied to medaka egg embryos through an experimental setup. A variety range of number of shock waves from 1 to 50 shots and with different overpressures from 15 to 45 MPa was applied. The effects of shock waves on the embryo growth were observed by a fluorescent microscope for three weeks. Propidium iodide (PI) was used to investigate the effects of shock wave on the cell membrane. After shock wave application, a very clear modification was observed; the extents of damage were increased by increasing the shock wave numbers.

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