Ritter S, Nasonova E, Gudowska-Novak E
Biophysik, Geselleschaft für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt, Germany.
Int J Radiat Biol. 2002 Mar;78(3):191-202. doi: 10.1080/09553000110097217.
To investigate further the effect of linear energy transfer (LET) on the yield and quality of aberrations at different post-irradiation sampling times.
V79 G(1)-cells were exposed to either 10.6 MeV u-1 Ne ions (360 keV microm-1) or 11.1 MeV u-1 Kr ions (3980 keV microm-1) and chromosomal damage was measured in metaphase cells at several 2-h sampling intervals up to 30 h post-irradiation. To differentiate between cells in the first and second post-irradiation cycle, the fluorescence-plus-Giemsa technique was applied.
In both experiments, an increase in the yield of aberrant cells as well as the number of aberrations per cell was observed in first- and second-cycle metaphases. Yet, the increase in the number of aberrations per cells was more pronounced for Kr ions and at comparable fluences Kr ions produced more aberrations than Ne ions. Because no sampling time was representative for the whole cell population, the total amount of Ne and Kr ion-induced chromosomal damage was determined by means of a mathematical approach and used for the comparison of data. Furthermore, in accordance with previous studies, LET-dependent changes in the spectrum of aberration types were detected, i.e. with increasing LET a higher fraction of chromatid-type aberrations was observed, although cells had been exposed in G1. In addition, more chromosomal breaks and less exchange-type aberrations were found.
The observation that cell-cycle progression is related to the amount of aberrations harboured by a cell demonstrates that the routinely applied method to measure aberration frequencies in metaphase cells at only one post-irradiation sampling time will unavoidably result in an under- or overestimation of the cytogenetic effects of particles. Consequently, for a meaningful quantification of chromosomal damage, multiple fixation regimes should be used so that the complete time-course of aberrations can be taken into account. Moreover, to avoid bias, all aberration types should be recorded and included in the analysis since the aberration spectrum changes with LET.
进一步研究线性能量传递（LET）对不同辐照后采样时间畸变产额和质量的影响。
将V79 G(1)细胞暴露于10.6 MeV u-1的氖离子（360 keV/μm）或11.1 MeV u-1的氪离子（3980 keV/μm），并在辐照后长达30小时的几个2小时采样间隔时，对中期细胞中的染色体损伤进行测量。为区分处于辐照后第一个和第二个周期的细胞，应用了荧光加吉姆萨技术。
在两个实验中，均在第一周期和第二周期中期观察到异常细胞产额以及每个细胞的畸变数量增加。然而，每个细胞畸变数量的增加在氪离子中更为明显，并且在相当的注量下，氪离子产生的畸变比氖离子更多。由于没有一个采样时间能代表整个细胞群体，因此通过数学方法确定了氖离子和氪离子诱导的染色体损伤总量，并用于数据比较。此外，与先前的研究一致，检测到畸变类型谱随LET的变化，即随着LET增加，观察到染色单体型畸变的比例更高，尽管细胞是在G1期暴露的。另外，还发现了更多的染色体断裂和更少的交换型畸变。
细胞周期进程与细胞所携带的畸变数量相关这一观察结果表明，仅在一个辐照后采样时间测量中期细胞畸变频率的常规方法将不可避免地导致对粒子细胞遗传学效应的低估或高估。因此，为了有意义地量化染色体损伤，应使用多种固定方案，以便能够考虑畸变的完整时间进程。此外，为避免偏差，应记录所有畸变类型并将其纳入分析，因为畸变谱会随LET变化。
