“…This adaptive response to IR, which occurs after exposures that are so low (0.005-0.01 Gy) that they do not induce discernible aberrations themselves, has been attributed to the induction of a repair mechanism that causes the restitution of X-rayinduced chromosome breaks (Wolff, 1998). Variations and the absence of adaptive responses have also been reported (Jacobson-Kram and Williams, 1988;Bauchinger et al, 1989;Bosi and Olivieri, 1989;Sankaranarayanan et al, 1989;Schmid et al, 1989;Hain et al, 1992;Müller et al, 1992;Wojcik et al, 1992Wojcik et al, , 1993Shadley, 1994;UNSCEAR, 1994;Vijayalaxmi et al, 1995;Boothman et al, 1996;Raaphorst and Boyden, 1999;Sorensen et al, 2002). Azzam et al (1996) exposed quiescent mouse fibroblasts (C3H 10T1/2) cells to doses of 1-100 mGy -rays and observed that the risk of neoplastic transformation was reduced from the spontaneous level to a rate three-to four-fold below that level.…”