Underwood L W, Nelson P, Noelke E, Ide C F
Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118.
J Exp Zool. 1992 Jan 1;261(1):18-26. doi: 10.1002/jez.1402610104.
We examined relationships between healing observed during embryonic Xenopus retinal and optic nerve regeneration and resultant visuotectal pattern formation. Dorsal (D) and nasoventral (NV) 1/3 sized eye fragments were surgically created in stage 32 Xenopus laevis embryos. Gross anatomical healing modes of these fragments were examined 2 days post-surgery (stage 43). Healing was categorized according to the degree of cell movements observed. Animals were reared through metamorphosis and electrophysiologic mapping techniques were employed on those animals whose eyes regenerated. All D 1/3 fragments showed normal (non-duplicated) projections to the tectum; most (80%) of the healing observed showed little cell movements (the remaining 20% showed substantial cell movements, yet failed to show duplicated projections). Most NV 1/3 fragments (73%) formed two mirror image projections to the contralateral midbrain optic tectum (pattern duplication). Most (88%) of the healing observed among these animals showed massive cell movements in the ventral retinal region (the remaining 12% showed moderate cell movements). The remaining NV 1/3 fragments (27%) showed moderate cell displacement and failed to show duplicated projections). These data are compatible with a cell-movement:intercalary cell division hypothesis in which duplication is dependent upon specific positional confrontation and subsequent cell division. In additional studies, in adult animals, the optic nerves of eyes with duplicated projections were crushed and allowed to regenerate for 1 year. Duplicated projections were restored, indicating that developmental and maturational factors are probably not responsible for duplicative pattern formation; rather, information intrinsic to the eye, possibly created during healing interactions and/or fiber ingrowth to the tectum, underlies duplicate innervation of the tectum.
我们研究了非洲爪蟾胚胎视网膜和视神经再生过程中观察到的愈合情况与由此产生的视顶盖模式形成之间的关系。在第32期非洲爪蟾胚胎中通过手术创建背侧（D）和鼻腹侧（NV）1/3大小的眼片段。在手术后2天（第43期）检查这些片段的大体解剖愈合模式。根据观察到的细胞运动程度对愈合进行分类。将动物饲养至变态期，并对眼睛再生的动物采用电生理绘图技术。所有D 1/3片段均显示对视顶盖的正常（非重复）投射；观察到的愈合情况中，大多数（80%）显示细胞运动很少（其余20%显示大量细胞运动，但未显示重复投射）。大多数NV 1/3片段（73%）向对侧中脑视顶盖形成两个镜像投射（模式重复）。在这些动物中观察到的愈合情况中，大多数（88%）在视网膜腹侧区域显示大量细胞运动（其余12%显示适度细胞运动）。其余NV 1/3片段（27%）显示适度细胞移位，未显示重复投射。这些数据与细胞运动：插入性细胞分裂假说是一致的，其中重复依赖于特定的位置对抗和随后的细胞分裂。在进一步的研究中，在成年动物中，对具有重复投射的眼睛的视神经进行挤压，并让其再生1年。重复投射得以恢复，这表明发育和成熟因素可能与重复模式形成无关；相反，眼睛固有的信息，可能是在愈合相互作用和/或纤维向视顶盖生长过程中产生的，是视顶盖重复神经支配的基础。
