[Effect of pulsed ultrasound exposure on development of early embryos].

Ultrasonography is indispensable for medical treatment, particularly in the field of reproductive medicine. Therefore, it is important to confirm safety when exposing preimplantation embryos to ultrasound. For this purpose, the study was designed to elucidate the bioeffects of pulsed ultrasound on preimplanted mice embryos. One-cell stage embryo, 2-cell stage embryo, morula and expanded blastocysts of mice in vitro cultured were exposed to experimental pulsed ultrasound for 15 minutes in degassed water at 37 degrees C. The ultrasound used in this study was 2MHz; [spatial-average temporal-average intensity (ISATA): 120mW/cm2, maximum intensity (Im): 39.1W/cm2, the peak rarefactional pressure (Pr): 1.0MPa, pulse width: 10 mus' and pulse repetition frequency: 1.0kHz.]. The development to expanded blastocyst and the nucleic acid synthesis in expanded blastocyst were compared in the embryos exposed (study group) and those not exposed (control) to the ultrasound. There were no significant differences between the two groups in the rates of development to expanded blastocysts and the nucleic acid synthesis. The temperature of the irradiated medium in cell container straw did not rise. These results suggest that pulsed ultrasound at the intensity used in this study does not have a harmful effect on early preimplantation embryos.