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目的 :应用神经轴突示踪方法 ,研究人类视觉神经通路在胚胎期 12w时的发育情况。方法 :取 12w胎龄的胚胎 ,浸泡在 4 %的甲醛缓冲液中固定后 ,分别在视束、上丘臂和视皮质下植入DiI染料 (DiI,1,1’ dioctadecyl 3,3,3’ ,3’ tetramethylin docarbocyanineperchlorate)。于室温下放置 4w ,待DiI晶体充分扩散后 ,根据神经轴突方向切片 ,通过共焦激光扫描显微镜观察并记录结果。结果 :大体标本观察可见到 ,视网膜神经纤维投射已到达外侧膝状体、上丘。切片观察发现 :外侧膝状体处尚未出现分层现象 ;上丘处 ,来自视网膜的神经纤维位于上丘臂的背侧 ;视皮质下已存在板层结构 ,板层内神经元呈多种形态。结论 :通过神经轴突示踪技术发现 ,12w时视网膜的神经纤维投射已经到达外侧膝状体和上丘 ,视皮质下存在板层结构。这说明人类视觉神经通路发育存在“等待期”。
OBJECTIVE: To study the development of human visual nerve pathways at embryonic day 12w by using axon tracing method. Methods: The embryos of 12w gestational age were soaked in 4% formalin for fixation. DiI dye (DiI, 1,1 ’dioctadecyl 3,3,3 ’, 3’ tetramethylin docarbocyanineperchlorate). After 4w at room temperature, until the DiI crystal fully diffused, sliced according to the direction of axon, and the result was observed by confocal laser scanning microscope. Results: The gross specimen observation can be seen, retinal nerve fiber projection has reached the lateral geniculate body, the superior colliculus. Slice observation showed that there was no stratification in the lateral geniculate body. In the superior colliculus, the nerve fibers from the retina were located on the dorsal side of the superior superior arm. There existed the lamellar structure under the visual cortex, . CONCLUSION: The axon tracing technique found that the projection of the retina nerve fiber at 12w had reached the lateral geniculate body and the superior colliculus, and there was a lamellar structure under the visual cortex. This shows that there is “waiting period” for the development of human visual neural pathways.