Straume T, Dobson R L, Kwan T C
Radiat Res. 1987 Jul;111(1):47-57.
The highly radiosensitive immature oocytes of mice were irradiated in vivo with graded doses of 252Cf fission radiation, 0.43- or 15-MeV neutrons, or 60Co gamma rays. Comparisons of oocyte survival for neutrons and for gamma rays demonstrate that neutron RBEs for the killing of these important cells do not reach the high values (30-50 or more) at low doses observed for several other biological end points. Rather, neutrons differ little in effectiveness from gamma rays in killing these extremely sensitive murine oocytes. For 0.43-MeV neutrons, RBEs obtained from fitted survival curves reach only 1.7 at 0.1 rad. For 15-MeV neutrons, they are not significantly different from 1 at any dose tested (lowest, 4.5 rad). For 252Cf fission neutrons (E = 2.15 MeV), RBEs are intermediate between those for 0.43- and 15-MeV neutrons. For all neutron energies tested, the RBEs are particularly low in the juvenile period, a time when murine immature oocytes are especially radiosensitive. With exposure just prior to birth, however, when these cells are much less easily killed, higher, more usual RBEs are found. The minimum size of the lethality target in mouse immature oocytes, estimated from the inactivation constant for 0.43-MeV neutrons and microdosimetric values, is larger than the nucleus but not larger than the cell. This and related analytical considerations suggest that the hypersensitive target in these particular oocytes is the plasma membrane, a finding which is in excellent accord with results from other experiments using different, contrasting radiations and dose deliveries (accelerated Si14+ ions, gamma rays, and beta rays from 3HOH compared with those from [3H]thymidine).
用不同剂量的252Cf裂变辐射、0.43 MeV或15 MeV中子或60Coγ射线对体内高度放射敏感的小鼠未成熟卵母细胞进行辐照。中子和γ射线的卵母细胞存活率比较表明，对于这些重要细胞的杀伤，中子的相对生物效应（RBE）在低剂量时并未达到其他几个生物学终点所观察到的高值（30 - 50或更高）。相反，在杀死这些极其敏感的小鼠卵母细胞方面，中子与γ射线的有效性差异不大。对于0.43 MeV中子，从拟合存活曲线获得的RBE在0.1 rad时仅达到1.7。对于15 MeV中子，在任何测试剂量（最低4.5 rad）下，它们与1没有显著差异。对于252Cf裂变中子（E = 2.15 MeV），RBE介于0.43 MeV和15 MeV中子之间。对于所有测试的中子能量，RBE在幼年时期特别低，而此时小鼠未成熟卵母细胞对辐射特别敏感。然而，在出生前暴露时，当这些细胞更不容易被杀死时，会发现更高、更常见的RBE。根据0.43 MeV中子的失活常数和微剂量学值估计，小鼠未成熟卵母细胞中致死靶点的最小尺寸大于细胞核，但不大于细胞。这一点以及相关的分析考虑表明，这些特定卵母细胞中的超敏靶点是质膜，这一发现与使用不同、对比辐射和剂量传递方式（加速的Si14 +离子、γ射线以及与[3H]胸腺嘧啶相比的3HOH的β射线）的其他实验结果非常一致。
