Schmued L C, Kyriakidis K, Fallon J H, Ribak C E
Department of Anatomy and Neurobiology, University of California, Irvine 92717.
J Neurocytol. 1989 Jun;18(3):333-43. doi: 10.1007/BF01190836.
The advantages of axonally transported Fluoro-Gold as a retrograde fluorescent marker are numerous. The objective of the present study was to determine whether transported Fluoro-Gold is visible in either semi-thin sections for light microscopy or thin sections for electron microscopy. Rats received injections of Fluoro-Gold into either the striatum or thoracic spinal cord. After appropriate survival times, labelled neurons were observed with the fluorescence microscope in brain regions that are known to project to the injected areas. Sections that contained labelled cells were embedded in plastic and examined with a fluorescence microscope. Semi-thin sections of unosmicated tissue displayed high-resolution fluorescent labelling of somata and dendrites. In contrast, osmicated tissue did not fluoresce, but numerous dark granules were observed in the dendritic and perikaryal cytoplasm of labelled neurons in toluidine blue stained sections that were examined with brightfield optics. The unosmicated tissue did not display these granules, and this finding suggested that the granules are composed of membranes. Neurons in other brain regions that are known not to project to the injection sites did not contain these dark granules. Adjacent thin sections examined with the electron microscope displayed numerous electron-dense, lysosome-like organelles in the cytoplasm of labelled neurons. The electron density of these organelles was greater than that of lysosomes in unlabelled neurons. Three types of distinctive organelles were observed in these preparations: (1) relatively dense concentric lamellar bodies of various sizes; (2) heterogeneous or lipofuscin-like lysosomes; and (3) coarse grained lysosomes. Control sections and unlabelled neurons did not display these organelles. Therefore, these organelles appear to correlate with Fluoro-Gold localized within the somata and dendrites of retrogradely labelled neurons. It is not known if they are the Fluoro-Gold itself, or represent a physiological effect on membranes. The results of this study indicate that Fluoro-Gold may be useful for tract tracing at the electron microscopic level.
轴突运输的荧光金作为逆行荧光标记物有诸多优点。本研究的目的是确定运输后的荧光金在用于光学显微镜观察的半薄切片或用于电子显微镜观察的超薄切片中是否可见。给大鼠的纹状体或胸段脊髓注射荧光金。在适当的存活时间后，用荧光显微镜在已知投射到注射区域的脑区观察标记的神经元。将含有标记细胞的切片包埋在塑料中，并用荧光显微镜检查。未染色组织的半薄切片显示出细胞体和树突的高分辨率荧光标记。相比之下，染色后的组织不发荧光，但在用明场光学显微镜检查的甲苯胺蓝染色切片中，在标记神经元的树突和核周细胞质中观察到许多深色颗粒。未染色的组织没有显示出这些颗粒，这一发现表明这些颗粒由膜组成。已知不投射到注射部位的其他脑区的神经元不含这些深色颗粒。用电子显微镜检查相邻的超薄切片，在标记神经元的细胞质中显示出许多电子致密的、类似溶酶体的细胞器。这些细胞器的电子密度高于未标记神经元中的溶酶体。在这些制剂中观察到三种不同类型的细胞器：(1) 各种大小的相对致密的同心层状体；(2) 异质性或脂褐素样溶酶体；(3) 粗颗粒溶酶体。对照切片和未标记的神经元没有显示出这些细胞器。因此，这些细胞器似乎与逆行标记神经元的细胞体和树突内的荧光金相关。尚不清楚它们是荧光金本身，还是代表对膜的生理效应。本研究结果表明，荧光金可能有助于在电子显微镜水平上进行神经束追踪。
