EXPERIMENTAL STUDY OF RADIATION-INDUCED DEMENTIA -CHANGES IN GROWTH INHIBITORY FACTOR AFTER HEMICRANIAL IRRADIATION ON NEONATAL RAT BRAINS-

为了探讨脑肿瘤放疗对正常脑的辐射损伤，本文研究了x射线照射对正常大鼠脑的影响。7日龄新生大鼠接受单剂量（5、7.5、10、15Gy） x射线照射右半脑膜。在照射后1、2、3、4和5周，用Northern blotting技术分析髓鞘相关糖蛋白（MAG）、神经元特异性烯醇化酶（NSE）和S-100蛋白mRNA的变化。照射后1周，与未照射半球相比，照射半球中MAG mRNA的表达水平明显降低。照射后1 ~ 5周，照射半球的NSE mRNA和S-100 mRNA水平与未照射半球相同。结果表明，少突胶质细胞比神经元和星形胶质细胞对辐照更敏感。采用Western blotting技术分析15Gy半颅辐照后大鼠生长抑制因子（GIF）和胶质原纤维酸性蛋白（GFAP）的变化。在放射后4周内，对同一7日龄大鼠的辐照右半球（IR）、未辐照左半球（NIL）和年龄匹配大鼠的假辐照右半球（SIR）进行检查。辐照后IR中相对于假手术对照组的GIF水平升高，在放疗后3周最大达到SIR中GIF水平的164%，并保持在升高水平至少4周，而辐照后IR中相对于假手术对照组的GFAP水平升高，在放疗后3周最大达到SIR中GFAP水平的152%，然后迅速下降。这些结果表明，GIF可能在脑损伤后中枢神经系统修复中发挥重要作用，并可能为以GFAP为主的神经胶质瘤和主要由神经营养因子控制的组织重建的机制提供新的见解。在15gy半颅照射后2、3、6小时、1、3和5天，用原位细胞凋亡检测试剂盒（Oncor公司）检测细胞凋亡。照射后3、6小时，脑半球皮层下白质、海马齿状回和侧脑室室管膜下层均可见凋亡细胞。结果提示辐照损伤急性期脑白质紊乱与细胞凋亡密切相关。少

To investigate radiation injury on normal brain in radiotherapy of brain tumors, the effects of X-irradiation on normal rat brain have been studied.1.Neonatal rats, aged 7 days, received single doses (5,7.5,10,15Gy) of X-irradiation to the right hemicranium. At 1,2,3,4, and 5 weeks after irradiation, the changes of mRNA of myelin-associated glycoprotein (MAG), neuron specific enolase (NSE) and S-100 protein were analyzed with Northern blotting technique. The level of expression of MAG mRNA in the irradiated hemisphere was significantly low compared with that in the unirradiated hemisphere at 1 week after radiation. The levels of NSE mRNA and S-100 mRNA in the irradiated hemisphere were as same as that in the unirradiated hemisphere after 1-5 weeks after radiation. The results suggest that oligodendroglias are more sensitive to irradiation than neurons and astrocytes.2.The changes of growth inhibitory factor (GIF) and glial fibrillary acidic protein (GFAP) after 15Gy hemicranial irradia … More tion were analyzed using Western blotting technique. The irradiated right hemispheres (IR), the non-irradiated left hemispheres (NIL) of the same 7-day-old rats, and the sham-irradiated right hemispheres (SIR) of the age-matched rats were examined for a period of 4 weeks postirradiation. The GIF relative level to sham control in IR was increased after irradiation, reached a maximum of 164% of the GIF level in SIR at 3 weeks postirradiation and remained at an increased level until at least 4 weeks, while the GFAP relative level to sham control in IR was increased after irradiation, reached a maximum of 152% of the GFAP level in SIR at 3 weeks postirradiation and then declined rapidly. These results indicate that GIF could play an important role in central nervous system repair following brain damage and may provide new insights into the mechanism of gliosis investigated mainly focusing on GFAP and of tissue reconstruction which is thought to be mainly controlled by neurotrophic factors.3.Apoptosis was examined with in situ apoptosis detection kit (Oncor corporation) at 2,3,6 hours, 1,3 and 5 days post-15Gy hemicranial irradiation. In the irradiated hemisphere apoptotic cells were found in the subcortical white matter, hippocampal dentate gyrus and subependymal layr of the lateral ventricle at 3 and 6 hours after irradiation. The results suggest that apoptosis is closely related with disturbance of cerebral white matter at the acute stage for the irradiation insult. Less