SHORT-RANGE RADIATIONS--LESIONS AND CHROMOSOMAL CHANGES

电离辐射能量的空间分布 细胞是放射生物学反应的一个强有力的决定因素。 是 这项研究的目的是了解这一点， 使用短程辐射源的依赖性。 在 特别地，我们打算探索染色体 染色体的变化是基于 与细胞死亡，突变，anj癌症密切相关。 我们已经成功地将Al软X射线用于放射生物学 研究并打算构造气体靶（B、C、N、O、Ne、Ar） 对于作为宽范围软X射线源的入射质子， 能量沉积低至约200 eV，具有电子轨道 只有几纳米 我们还将使用软中子， 反冲质子轨道的亚微米范围。 这种辐射 来源将提供与辐射直接相关信息 保护，其中人员暴露于软中子携带 尚未确定的风险。 第三，局部能量 I-125衰变的沉积物将用于询问 畸变形成的基础。 哺乳动物细胞（人和 仓鼠）将在细胞周期的不同阶段接受辐照 以及染色体变化的频率和类型， 监测存活和细胞动力学变化。 低剂量研究 在第一部分强调反应及其基础， 将强调剂量-反应曲线。 答复分析将 注重生物物理作用模式之间的区别， 例如，在一个实施例中，“严重病变”与“双重病变”。“详细的轨道 辐射的结构将被计算，并分析 生物反应将导致对其他生物的预测， 辐射 生物物理作用模型的严格检验 这种方式将导致模型接受或拒绝。 在帮助理解导致形成的机制， 染色体变化和电离辐射的生物效应 辐射，该提案将对地区产生重大影响， 关注放射治疗的优化， 确定人体辐射防护标准。

The spatial distribution of energy from ionizing radiations in cells is a strong determinant of radiobiological response. It is the objective of this research to derive an understanding of this dependence by the use of short-ranged radiation sources. In particular we intend to probe the mechanism(s) whereby chromosomal changes come about, on the understanding that chromosomal changes are intimately associated with cell death, mutation, anj cancer. We have successfully used Al soft X rays for radiobiological investigations and intend to construct a gas target (B,C,N,O,Ne,Ar) for incident protons as a source of a wide range of soft X rays with energy depositions down to about 200 eV with electron tracks of a few nanometers. We will also use soft neutrons which produce recoil Proton tracks of sub-micrometer ranges. This radiation source will provide information of direct relevance to radiation protection, where personnel exposure to soft neutrons carries an as yet undetermined risk. Thirdly, the localized energy depositions from I-125 disintegrations will be used to ask about the basis of aberration formation. Mammalian cells (human and hamster) will be irradiated at different stages of the cell cycle and the frequencies and types of chromosomal changes, cell survival and cytokinetic changes monitored. Low-dose studies emphasizing response and the basis thereof in the initial part of dose-response curves will be stressed. Analyses of responses will be oriented to distinction between models of biophysical action, e.g., "critical lesion" versus "dual lesion." The detailed track structures of the radiations will be calculated, and analyses of the biological responses will lead to predictions for other radiations. Stringent testing of models of biophysical action in this way will lead to model acceptance or rejection. In aiding understanding of mechanisms leading to the formation of chromosomal changes and to the biological effects of ionizing radiations, this proposal will impact significantly in areas concerned with optimization of radiation therapy and the determination of standards for human radiation protection.