Cellular mechanisms of protection and repair induced by radiation exposure and their consequences for cell system responses.
Cellular mechanisms of protection and repair induced by radiation exposure and their consequences for cell system responses.
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辐射暴露诱导的细胞保护和修复机制及其对细胞系统反应的影响。
作者：
L. Feinendegen;Loken Mk;J. Booz;H. Mühlensiepen;C. Sondhaus;Victor P. Bond
构成活的有机体的复杂生物系统在不同层次的组织中运作，从原子-分子到细胞，再到器官-有机体。生物体对有损结构和功能的干扰的反应通常始于发生原发损伤的组织水平。在相对较低的组织级别上同时或顺序、或单一或多个相互作用所产生的损害往往会转移到较高级别。然而，在每一级组织中，根据该级别特有的对伤害的耐受性，存在消除这种损害的给定概率。因此，在较低级别的组织中发生损害事件的频率与在最终表现这种损害的较高级别的系统的结构复杂程度之间存在直接关系。任何给定级别的结构中断程度决定了该级别的功能故障程度。在组织暴露于电离辐射中，最初的损伤始于能量沉积事件(轨迹或命中)，其中包括在细胞内原子-分子水平的亚微观维度的局部簇中的许多电离和激发，并且细胞作为一个整体受到影响。细胞是生命的基本单位，单个细胞反应的总和决定了组织和有机体的反应。然而，根据吸收剂量的不同，单个细胞的反应在类型和程度上也有所不同。随着组织吸收剂量的降低，细胞被能量沉积事件击中的概率呈线性下降。在对组织的吸收剂量值非常低的情况下，只有一小部分细胞群体经历一次击打，而且这些细胞的大小不同。这些命中的大小分布或光谱是不变的，在低剂量水平下与它们在相当大的范围内的总数无关，并且只由给定辐射的类型和质量决定。一个被击中的细胞遭受特定损害的概率，如染色体异常、基因突变或死亡，已经被证明是随着击中的大小的增加而以S形方式增加的。
The complex biological systems that constitute living organisms operate at various levels of organization, from the atomic-molecular to the cellular to the organ-organism level. The response of an organism to disturbances that are detrimental to structure and function generally begin at the level of organization where the primary injury has occurred. Detriment that occurs from simultaneous or sequential, or single or multiple interactions at a relatively low level of organization tends to be transferred to higher levels. However, at each level of organization there is a given probability of such detriment being removed according to the tolerance to injury that is peculiar to that level. There is thus a direct relationship between the frequency of injurious events at a lower level of organization, and the degree of structural complexity of the system at the high level at which such detriment is eventually manifested. The extent of structural disruption at any given level determines the degree of functional failure at that level. In the exposure of tissue to ionization radiation, the primary injury begins with energy deposition events (tracks or hits) consisting of many ionizations and excitations in localized clusters of submicroscopic dimensions at the atomic-molecular level of organization within the cell, and the cell is affected as a whole. The cell is the elementary unit of life and the sum of the individual cell responses determines the response of the tissue and the organism. Individual cell responses are nevertheless found to differ in type and degree depending on the absorbed dose. With decreasing values of absorbed dose to the tissue, the probability of a cell being hit by an energy deposition event decreases linearly. At very low values of absorbed dose to tissue, only a fraction of the total cell population experiences single hits and these are of different sizes. The size distribution or spectrum of these hits is invariant, independent of their total number over a considerable range at low-dose levels and is determined only by the type and quality of the given radiation. The probability that a hit cell will suffer a given detriment such as a chromosomal aberration, gene mutation or death has been shown to increase in a sigmoid fashion with increasing hit size.(ABSTRACT TRUNCATED AT 400 WORDS)