Spermatogonial stem-cell survival after irradiation injury has been studied in rodents by histological counts of surviving cells. Many studies, including previous work from our laboratory, show that the spermatogonial population demonstrates a heterogeneous response to irradiation. The spermatogonia increase in radio-sensitivity as differentiation proceeds through the sequence As - Apr - A1 - A2 - A3 - A4 - In - B. The stem (As) cell is the most resistant and the B cell is the most sensitive. The purpose of this work is to investigate the response of spermatogonial cell to low doses (less than 10 0 rads) of helium particle irradiation.
