Engraftment as a function of radiation dose, age, genotype, and donor cell number. For the newborn transplants, 18, 25, 16, and 13 female transplant recipients were analyzed for the 0, 200, 400, and 800 cGy groups, respectively. For the adult transplants, 10, 11, 12, and 9 female recipients were analyzed for each group, respectively (▪, normal; ○, ASMKO). Engraftment = the number of male cells detected among 300 nuclei analyzed in the female recipients. A t-test analysis showed that engraftment was signficantly less in the ASMKO mice as compared with normal mice (see Table 1).