Bishayee A, Rao D V, Howell R W
Division of Radiation Research, Department of Radiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark 07103, USA.
Radiat Res. 1999 Jul;152(1):88-97.
A new multicellular cluster model has been developed to assess the impact of nonuniform distributions of radioactivity on the biological response of mammalian cells, and the relative importance of bystander effects compared to conventional radiation effects. Chinese hamster V79 cells are labeled with tritiated thymidine ([H]dThd), mixed with unlabeled V79 cells, and centrifuged gently to form multicellular clusters about 1.6 mm in diameter. The short range of the H β particles effectively allows only self-irradiation of labeled cells and no cross-irradiation of unlabeled cells. The percentage of labeled cells is controlled precisely by varying the number of labeled cells mixed with unlabeled cells prior to assembling the cluster. The clusters are assembled in the absence or presence of 100 μ lindane, a chemical that is known to inhibit formation of gap junctions. After the clusters are maintained at 10.5°C for 72 h, the cells are dispersed and plated for colony formation. In the case of 100% labeling, the survival of cells in the cluster depends exponentially (SF = e) on the cluster activity (in kBq), and lindane has no effect on the response. A two-component exponential response is obtained for 50% labeling in the absence of lindane (SF = 0.33 e + 0.67 e), and lindane has a marked effect on the response (SF = 0.33 e + 0.67 e). These data suggest that bystander effects play an important role in the biological response of V79 cells when the H is localized in the cell nucleus and distributed nonuniformly among the cells. In contrast, bystander effects cannot be detected above traditional radiation effects (i.e. direct + indirect) when the H is localized in the cell nucleus and distributed uniformly among the cells. These results indicate that this multicellular cluster model is well suited for studying the effects of nonuniform distributions of radioactivity, including bystander and “hot-particle” effects. Furthermore, these results suggest that by-stander effects may play an important role in the prediction of the biological effects of radiopharmaceuticals used in medical diagnosis and treatment.
一种新的多细胞团簇模型已被开发出来，用于评估放射性不均匀分布对哺乳动物细胞生物学反应的影响，以及旁观者效应与传统辐射效应相比的相对重要性。中国仓鼠V79细胞用氚标记的胸腺嘧啶核苷（[H]dThd）进行标记，与未标记的V79细胞混合，并轻轻离心以形成直径约1.6毫米的多细胞团簇。Hβ粒子的短程有效地仅允许标记细胞的自我辐射，而不会对未标记细胞进行交叉辐射。通过在组装团簇之前改变与未标记细胞混合的标记细胞数量，可以精确控制标记细胞的百分比。团簇在不存在或存在100μl林丹（一种已知可抑制间隙连接形成的化学物质）的情况下组装。在将团簇在10.5°C下维持72小时后，将细胞分散并接种以形成集落。在100%标记的情况下，团簇中细胞的存活率与团簇活性（以kBq为单位）呈指数关系（SF = e），林丹对反应没有影响。在不存在林丹的情况下，对于50%标记获得了双组分指数反应（SF = 0.33 e + 0.67 e），而林丹对反应有显著影响（SF = 0.33 e + 0.67 e）。这些数据表明，当H定位于细胞核并在细胞之间不均匀分布时，旁观者效应在V79细胞的生物学反应中起重要作用。相反，当H定位于细胞核并在细胞之间均匀分布时，无法检测到高于传统辐射效应（即直接+间接）的旁观者效应。这些结果表明，这种多细胞团簇模型非常适合研究放射性不均匀分布的影响，包括旁观者效应和“热粒子”效应。此外，这些结果表明，旁观者效应可能在预测用于医学诊断和治疗的放射性药物的生物学效应中起重要作用。
