Low doses of pulsed ultrasound and chromosomal abnormalities in male mouse germ cells.

Male mice were exposed to pulsed ultrasound (intensity less than 1 mW, frequency 3.5 MHz) for 30 min or to sham treatment. After 30 h, 11, 12 or 13 days, the testes were cytologically and histologically examined (using squash preparations, air-drying and sections). The resulting damage was studied at diakinesis-metaphase I and II, spermatogonial metaphase and anaphase. The investigation by air-drying did not show any significant increase in chromosome damage, 30 h, 11, 12 and 13 days after treatment (spermatogonial and spermatocytic metaphases). There was, however, a significant increase of the frequency of aneuploid cells detected at metaphase II. Investigations by squash techniques or sections did not reveal adverse effects on the spindles at spermatogonial and spermatocytic anaphases. We suggest that the reduction of fertility previously observed in our clinic could be explained by an increase of aneuploidy if germ cells are exposed to ultrasound during diakinesis of the first meiotic division.