McNally N J, de Ronde J
Int J Radiat Biol Relat Stud Phys Chem Med. 1976 Mar;29(3):221-34. doi: 10.1080/09553007614550251.
Unfed plateau-phase cells have been irradiated with either single doses or up to ten fractions of X-rays 6 hours apart. The single-dose survival curve had an extrapolation number of 11-4, and the oxygen-enhancement ratio (o.e.r.) was 3-1. Cells were exposed to multiple fractions of 200 rad or 150 rad in air and 600 rad or 450 rad in hypoxia. The resulting survival curves did not fit a multi-target, single-hit model of cell survival, being much steeper than that would predict. The curves were exponential up to five fractions of X-rays, but tended to bend downwards with increasing number of fractions. Cells that had survived five fractions of 200 rad (or 600 rad in hypoxia) 6 hours apart, were less able to absorb damage as sub-lethal than those which had not previously been exposed to radiation. The ratio of the initial slopes of the fractionated survival curves for irradiation in air and hypoxia was 2-1, implying that the o.e.r. "on the shoulder" may be less than that in the exponential region of survival.
未进食的平台期细胞接受了单次剂量或间隔6小时分十次给予的X射线照射。单次剂量存活曲线的外推数为11 - 4，氧增强比（OER）为3 - 1。细胞在空气中接受200拉德或150拉德的多次照射，在缺氧条件下接受600拉德或450拉德的多次照射。所得的存活曲线不符合细胞存活的多靶单击模型，比该模型预测的要陡得多。曲线在接受五次X射线照射之前呈指数形式，但随着照射次数增加倾向于向下弯曲。间隔6小时接受五次200拉德（或缺氧条件下600拉德）照射后存活的细胞，与之前未接受过辐射的细胞相比，吸收亚致死损伤的能力较弱。空气中和缺氧条件下分次照射存活曲线初始斜率的比值为2 - 1，这意味着“肩部”的氧增强比可能低于存活曲线指数区域的氧增强比。
