Effects of in Utero Ultrasound Exposure on the Development of the Fetal Mouse Testis1

The dfcct on the dcvdoping fetal testis of in utero c:xposurc to 1-MHz, continuous-wave ultrasound in the spatial peak, temporal average intensity range 0.5-10 W /em• for durations of 400-30 sec on Day 9, 12, or 15 of gestation was determined Results show that two subde, yet potentially ddctcrious, dfccts occurred: a reduction in the ScrtoU cell population and an apparent delay in the cessation of gonocyte mitosJs. An increase was also seen in the number of fetal resorptions and stillborn pups per number of implantation sites in the exposed specimens as compared to the sham and cage controls. Because the reduction in testis weight was proportional to dccrcascd body weight and because there was no dJlfcrcncc in ScrtoU cell numbers due to day of treatment, the testicular dfccts may reflect a gcncralizcd delay in growth. Whether this dfcct of ultrasound on fetal testis will be translated into an equal reduction in germ cell numbers in the adult testis remains to be determined