LaVail J H, Sugino I K, McDonald D M
J Cell Biol. 1983 Feb;96(2):373-81. doi: 10.1083/jcb.96.2.373.
The distribution of 125I-wheat germ agglutinin (WGA) transported by axons of chick retinal ganglion cells to layer d of the optic tectum was studied by electron microscopic autoradiography. We found that 52% of the radioactivity was located in axons and axon terminals in the contralateral optic tectum 22 h after intravitreal injection of affinity-purified 125I-WGA. Axons comprised 43% of the volume of layer d. Dendrites, glial cells, and neuron cell bodies contained 20%, 17%, and 3% of the label, whereas these structures comprised 24%, 21%, and 2% of the tissue volume, respectively. We also measured the distances between the autoradiographic silver grains and the plasma membranes of these profiles, and compared observed distributions of grains to theoretical distributions computed for band-shaped sources at various distances from the plasma membranes. This analysis revealed that the radioactive source within axons was distributed in a band of cytoplasm extending in from the plasma membrane a distance of 63 nm. Because WGA is known to bind to specific membrane glycoconjugates, we infer that at least some glycoconjugates may be concentrated within an annular region of cytoplasm just beneath the axonal plasma membrane after axoplasmic transport from the neuron cell body.
通过电子显微镜放射自显影术研究了鸡视网膜神经节细胞轴突将125I-小麦胚凝集素（WGA）运输到视顶盖d层的分布情况。我们发现，玻璃体内注射亲和纯化的125I-WGA后22小时，52%的放射性位于对侧视顶盖的轴突和轴突终末。轴突占d层体积的43%。树突、胶质细胞和神经元细胞体分别含有20%、17%和3%的标记物，而这些结构分别占组织体积的24%、21%和2%。我们还测量了放射自显影银颗粒与这些结构的质膜之间的距离，并将观察到的颗粒分布与针对距质膜不同距离的带状源计算的理论分布进行了比较。该分析表明，轴突内的放射源分布在从质膜向内延伸63 nm的细胞质带中。由于已知WGA与特定的膜糖缀合物结合，我们推断，从神经元细胞体进行轴浆运输后，至少一些糖缀合物可能集中在轴突质膜下方细胞质的环形区域内。
