Anker R L
J Comp Neurol. 1977 May 1;173(1):185-204. doi: 10.1002/cne.901730111.
Lesions were made in the visual system in a series of cat fetuses of known gestational age, and fiber and terminal degeneration were stained by the Eager method. The times of development of the retinal projection, of the thalamcortical and corticothalamic projections of area 17 of the visual cortex, and of the intrinsic fibers in the visual cortex were examined. Enucleation of one eye resulted in degeneration being detected bilaterally in the lateral geniculate nuclei (LGN), superior colliculi (SC) and optic tracts. The optic nerves reached the optic chiasm by the thirtieth embryonic day (E30) and the optic tract connections with the LGN and SC were made by E37. The projection always appeared stronger in the contralateral LGN and SC, and the amount of degeneration increased in both sides with increasing age. A parasagittal knife cut was made in the dorsomedial crest of the visual cortex. Where the lesion passed through the cellular layers of the cortex, intrinsic fibers were cut when these were present. The deeper part of the incision through the white matter undercut the medial wall of the visual cortex, interrupting thalamocortical and corticothalamic fibers when these were present. The longer horizontal fibers that were intrinsic to the visual cortex began to develop during the last two weeks of gestation but were not fully developed at birth. In the undercut visual cortex distant from the place of entry of the lesion, and before the intrinsic fibers of the cortex had developed, degeneration was found in layers 1 and 4, demonstrating the presence of a thalamocortical pathway. The youngest fetus to show this degeneration was operated at E48. This degeneration was not present three days earlier at E45. Fiber plexuses that have been described earlier in development (Marin-Padilla, '71; Cragg, '75) do not appear to degenerate after undercutting the cortex. The corticothalamic pathway to the lateral posterior nucleus medial to the LGN was developed at E45. The descending pathways to the ipsilateral LGN and SC were developed by E48, but it is not known whether they are present before this. Thus degeneration has been used to detect the development of axonal pathways in the fetus for the first time; the major afferent and efferent pathways are developed at an earlier stage than has previously been described.
在一系列已知胎龄的猫胎儿的视觉系统中制造损伤，并用伊格尔方法对纤维和终末变性进行染色。研究了视网膜投射、视觉皮层17区的丘脑皮质和皮质丘脑投射以及视觉皮层内纤维的发育时间。摘除一只眼睛导致双侧外侧膝状体（LGN）、上丘（SC）和视束出现变性。视神经在胚胎第30天（E30）到达视交叉，视束与LGN和SC的连接在E37完成。投射在对侧LGN和SC中总是显得更强，并且随着年龄的增长，两侧的变性量都增加。在视觉皮层的背内侧嵴处进行矢状旁切口。当损伤穿过皮层的细胞层时，如果存在内源性纤维，则将其切断。穿过白质的切口较深部分在视觉皮层内侧壁下方切开，当存在丘脑皮质和皮质丘脑纤维时将其中断。视觉皮层特有的较长水平纤维在妊娠的最后两周开始发育，但在出生时并未完全发育。在远离损伤进入部位的被切开的视觉皮层中，并且在皮层的内源性纤维发育之前，在第1层和第4层发现了变性，这表明存在丘脑皮质通路。显示这种变性的最年轻胎儿在E48接受手术。在E45时，三天前还没有这种变性。早期发育过程中描述的纤维丛（Marin-Padilla，'71；Cragg，'75）在切开皮层后似乎不会变性。到LGN内侧的外侧后核的皮质丘脑通路在E45时发育。到同侧LGN和SC的下行通路在E48时发育，但不知道在此之前是否存在。因此，变性首次被用于检测胎儿轴突通路 的发育；主要的传入和传出通路比以前描述的发育阶段更早。
