Effect of fluorodeoxyuridine, colcemid, and bromodeoxyuridine on developing neocortex of the mouse.
Effect of fluorodeoxyuridine, colcemid, and bromodeoxyuridine on developing neocortex of the mouse.
复制标题
氟脱氧尿苷、秋水仙胺和溴脱氧尿苷对小鼠新皮质发育的影响。
作者：
William Webster;Morimi Shimada;Jan Langman
本研究的目的是获得信息的因素控制的相互运动的神经上皮细胞和皮质迁移的神经母细胞在发育中的小鼠新皮层。在第一个实验中，给怀孕15天的小鼠注射单剂量的氟脱氧尿苷，这是一种抑制胸苷酸合成酶从而阻断DNA复制的化合物。在给药后不同时间和天数处死动物。处理后2小时，神经上皮细胞的有丝分裂指数严重降低，在神经上皮层的DNA合成区出现具有异常核的细胞。到了5小时，出现了更多的异常细胞，许多细胞显示出退化的细胞核。到12小时，在神经上皮层的外半部分和迁移区中观察到具有异常核的细胞。由于在管腔处未观察到它们，因此这些观察结果表明氟脱氧尿苷影响的核不移动到管腔并且不分裂。到24小时，在迁移区和皮质板中观察到异常细胞核，表明皮质迁移没有预先细胞分裂。在第二个实验中，用秋水仙胺处理15天的怀孕小鼠，秋水仙胺是一种在中期阻止分裂细胞的化合物。注射后2h和4h，大量中期神经上皮细胞聚集在管腔内。到7和12小时，被阻滞的中期分裂相数量迅速减少，但与此同时，在邻近的神经上皮中出现了具有致密、深染核的细胞。到24小时，这些异常核出现在迁移区和皮质板中，表明它们向皮质表面迁移，尽管未能完成有丝分裂。在第三个实验中，给怀孕15天的小鼠注射溴脱氧尿苷，这是一种掺入DNA中的化合物，被认为会干扰分化。在处理后的前12小时内，在管腔处观察到正常有丝分裂像数量的显著增加。然而，到16小时，开始出现异常的有丝分裂像。由于神经上皮细胞在此发育阶段的生成时间约为13小时，因此异常有丝分裂像必须代表自治疗开始以来经历了两个DNA合成期的细胞。异常的有丝分裂像产生具有致密核的细胞，到24小时时，在整个发育中的新皮质的宽度上都可以发现这些细胞。因此，在每个实验中，产生了具有异常的、可能是无功能的细胞核的细胞。尽管分裂失败或进行正常分裂，细胞核从神经上皮层向皮质板迁移的方式类似于正常的有丝分裂后神经母细胞。
The purpose of this study was to obtain information about factors controlling the interkinetic movement of neuroepithelial cells and the cortical migration of neuroblasts in the developing mouse neocortex. In the first experiment 15-day pregnant mice were injected with a single dose of fluorodeoxyuridine, a compound which inhibits the enzyme thymidylate synthetase thus blocking DNA-replication. The animals were sacrificed at various hours and days following treatment. Two hours after treatment the mitotic index of the neuroepithelial cells was severely reduced and cells with abnormal nuclei appeared in the DNA-synthesizing zone of the neuroepithelial layer. By five hours more abnormal cells appeared and many showed degenerating nuclei. By 12 hours cells with abnormal nuclei were seen in the outer half of the neuroepithelial layer and some in the migratory zone. Since they were not seen at the lumen, these observations indicate that fluorodeoxyuridine-affected nuclei do not move to the lumen and do not divide. By 24 hours abnormal nuclei were seen in the migratory zone and cortical plate suggesting cortical migration without preceding cell division. In the second experiment 15-day pregnant mice were treated with col-cemid, a compound which arrests dividing cells in metaphase. Two and four hours after injection a large number of neuroepithelial cells in metaphase accumulated at the lumen. By seven and 12 hours the number of arrested metaphases decreased rapidly, but at the same time cells with dense, darkly stained nuclei appeared in the adjacent neuroepithelium. By 24 hours these abnormal nuclei were present in the migratory zone and cortical plate, suggesting that they were migrating towards the surface of the cortex despite the failure to complete mitosis. In the third experiment 15-day pregnant mice were injected with bromodeoxyuridine, a compound incorporated into DNA and thought to interfere with differentiation. During the first 12 hours after treatment a striking increase in the number of normal mitotic figures was seen at the lumen. By 16 hours, however, abnormal mitotic figures started to appear. Since the generation time of neuroepithelial cells at this stage of development is about 13 hours, the abnormal mitotic figures must represent cells which have gone through two DNA-synthetic periods since the beginning of the treatment. The abnormal mitotic figures give rise to cells with dense pycnotic nuclei which by 24 hours are found throughout the width of the developing neocortex. Thus in each experiment cells with abnormal, presumably non-functional, nuclei were produced. Despite the failure to divide or to carry out a normal division, the nuclei migrate from the neuroepithelial layer towards the cortical plate in a fashion similar to that of normal postmitotic neuroblasts.