Korr H, Schultze B
Institut für Anatomie, Universität Aachen, Federal Republic of Germany.
Exp Brain Res. 1989;74(3):573-8. doi: 10.1007/BF00247359.
Very low incorporation of 3H-thymidine (TdR) into neurons and non-proliferating glial and endothelial cells in various brain areas of the adult mouse after 3H-TdR injection and subsequent X-irradiation of the head with 45 Gy has been demonstrated autoradiographically after exposure times of 250 days. In accordance with biochemical studies this incorporation of 3H-TdR represents DNA repair synthesis or UDS (unscheduled DNA synthesis). However, 3H-TdR incorporation into nuclear DNA of non-proliferating cells in the brain was not only found in X-irradiated but also in sham-irradiated mice. This suggests that spontaneous UDS also occurs. Up to now spontaneous UDS has been shown only in HeLa cells in vitro. Nearly all the various types of brain cells tested exhibited UDS after X-irradiation as well as spontaneous UDS. After correcting the mean grain numbers per nucleus not only for background but also for beta-self-absorption, substantial differences became apparent in the extent of UDS between the individual types of cells. After X-irradiation, UDS was highest in Purkinje cells and hippocampal granular cells but comparable UDS was also found in endothelial cells, regardless of the different brain areas studied. The extent of spontaneous UDS is also quite different in the various cell types, being highest in neurons of different sites and considerably lower in endothelial and glial cells.
给成年小鼠注射³H-胸腺嘧啶核苷（TdR）并随后对头部进行45 Gy的X射线照射后，在250天的暴露时间后进行放射自显影显示，³H-TdR在成年小鼠不同脑区的神经元、非增殖性神经胶质细胞和内皮细胞中的掺入量非常低。与生化研究一致，³H-TdR的这种掺入代表DNA修复合成或非定标DNA合成（UDS）。然而，不仅在接受X射线照射的小鼠中，而且在假照射的小鼠中也发现³H-TdR掺入脑内非增殖细胞的核DNA中。这表明自发的UDS也会发生。到目前为止，自发的UDS仅在体外的HeLa细胞中被发现。几乎所有测试的各种类型的脑细胞在X射线照射后以及自发UDS时均表现出UDS。在对每个细胞核的平均颗粒数不仅校正背景而且校正β-自吸收之后，不同类型细胞之间UDS的程度出现了明显差异。X射线照射后，浦肯野细胞和海马颗粒细胞中的UDS最高，但在内皮细胞中也发现了相当的UDS，无论研究的脑区如何。自发UDS的程度在各种细胞类型中也有很大差异，在不同部位的神经元中最高，在内皮细胞和神经胶质细胞中则低得多。
