Research on Regeneration of the Optic Nerve and Functional Recovery of Retinal Ganglion Cells with Regenerated Axons

成年哺乳动物视网膜神经节细胞的轴突沿自体移植物的坐骨神经延伸很长一段距离。研究了成年猫视网膜神经节细胞（RGCs）的形态和生理特性，并与文献报道的结果进行了比较。横断成年猫视神经，移植自体外周神经于残肢。两个月后，将轴突再生的rgc逆行标记，并将荧光染料注射到移植物中。标记细胞4000余个，占完整视网膜神经节细胞总数的3.0% ~ 4.3%，呈水平细长的高密度区分布，与完整视网膜相似。在体外细胞内注射HRP或路西法黄，观察具有再生轴突的RGCs的树突形态。a和g细胞的形态与正常细胞相似，而一些β细胞的树突似乎退化了。一些“未分类”细胞不能被识别为α、β或γ细胞。通过检查局部斑块中所有路西法黄注射细胞，评估再生细胞群中α、β和其他细胞（包括γ和未分类细胞）的比例。α细胞的平均比例为23.9%，约为完整视网膜的6倍。β细胞的平均比例为50.3%，略高于完整视网膜。其余细胞（25.7%）不能归类为α或β；这一比例约为完整视网膜的一半。这些发现表明，α细胞在轴突再生成神经移植物方面的能力最高，而不是所有类型的细胞都能同样再生轴突。在坐骨神经移植到视神经残端2个月后，用生物细胞素顺行标记再生的轴突，电镜下观察雪旺细胞形成髓鞘的情况。在3个横切面移植的511个标记轴突中，96个纤维有髓鞘。髓鞘纤维的比例从2.8%到76%不等。平均直径。有髓纤维为1.28 μ m（范围0.71 ~ 2.47），无髓纤维为0.76 μ m（范围0.18 ~ 2.46）。髓鞘内径与外径之比（g值）的平均值为0.72，略小于成年猫视轴突的平均值（0.8）。从一只猫的神经移植物的梳理纤维中记录到的102个单位对受限视野的刺激有反应。28个单位具有较大的感受野和轻快的Y细胞特征；51个单位具有X细胞的小感受野和轻快的相-张力反应特征；10个单位有W细胞特有的迟滞性或强直性反应。每个类别的一些例子都有抑制性或对抗性的环境。8个单元不能划分为Y、X或W单元。Y（28%）、X（50%）和其他（22%）的比例与形态学研究中得到的alpha、beta和其他的比例相似。少

Transected axons of retinal ganglion cells elongate a long distance along the autografted sciatic nerve in adult mammals. Morphological and physiological properties of retinal ganglion cells (RGCs) were examined in adult cats in order to compare the results with knowledge reported.The optic nerve of adult cats was transected and an autologous peripheral nerve was transplanted to the stump. Two months later RGCs that had regenerated their axons were retrogradely labeled with fluorescent dye injected into the graft. The more than 4,000 labeled cells, which were 3.0% to 4.3% of total ganglion cell number in the intact retina, were distributed in a high density area elongating horizontally, in a pattern similar to that observed in the intact retina.The dendritic morphology of RGCs with regenerated axons was examined after intracellular injections of HRP or Lucifer yellow in vitro. The morphology of a and g cells appeared comparable to normal, whereas the dendrites of some beta cells seemed … More to degenerate. Some "unclassified" cells could not be identified as alpha, beta, or gamma cells. The proportion of alpha,beta and other cells including gamma and unclassified in the regenerating cell population was evaluated by examining all the Lucifer yellow injected cells in local patches. The average proportion of alpha cells was 23.9%, about 6 times higher than in intact retinas. The average proportion of beta cells was 50.3%, slightly higher than in intact retinas. The remaining cells (25.7%) could not be categorized as alpha or beta ; this proportion is about half that found in intact retinas. These findings suggest that alpha cells have the highest capacity to regenerate their axon into nerve grafts, rather than all the types equally regenerate their axons.Regenerated axons were labeled anterogradely with biocytin two months after transplanting the sciatic nerve to the axotomized optic stump, and myelin formation by Schwann cells was examined electron microscopically. Among 511 labeled axons in three cross-sectioned grafts, 96 fibers were myelinated. Proportions of myelinated fibers varied from 2.8% to 76%. Mean diameter. of myelinated fibers was 1.28 mum (range 0.71-2.47) and that of unmyelinated fibers was 0.76 mum (range 0.18-2.46). Mean ratio of inner versus outer diameters of myelin sheath (g-value) was 0.72 which was a little smaller than the value (0.8) in the optic axons of intact adult cats.A total of 102 units recorded from teased fibers of a nerve graft in one cat responded to stimulation of a restricted visual field. 28 units had large receptive fields and brisk phasic responses characteristic of Y cells ; 51 units had small receptive fields and brisk phasic-tonic responses characteristic of X cells ; 10 units had sluggish phasic or tonic responses characteristic of W cells.Some examples of each category had suppressive or antagonistic surrounds. 8 units could not be classified as Y,X or W cells. The proportions of Y (28%), X(50%) and others (22%) were similar to the proportions of alpha, beta and other obtained in the morphological study. Less