Wagner H J
J Neurocytol. 1980 Oct;9(5):573-90. doi: 10.1007/BF01205026.
Horizontal cell terminals lateral to the synaptic ribbons in goldfish cone pedicles give rise to 0.3 micron long, finger-like extensions in the light-adapted state. These structures, called spinules, disappear almost completely after dark adaptation. The ultrastructure of the horizontal cell terminals is characterized by the presence of occasional microtubules, microfilaments and sparse irregular vesicles; in the dark, large multivesicular bodies can also be found. Two types of membrane densities are described in the horizontal cell terminals, one of which is typically located at the tip of the spinules. Their positive reaction to E-PTA makes it probable that the spinules are synaptic structures. Reconstruction of serial sections shows about 12 spinules per terminal in the light but only two in the dark. Formation and disappearance of the spinules takes about 60 min and involves a transitional stage in the form of a spherical structure. Spinules can be found in five other teleost species, with a darkness-induced reduction in number, but not in the horizontal cell terminals of the mudpuppy, turtle and mammals.
在金鱼视锥细胞突触小体中，位于突触带外侧的水平细胞终末在明适应状态下会产生0.3微米长的指状突起。这些结构被称为棘状小体，在暗适应后几乎完全消失。水平细胞终末的超微结构特征是偶尔存在微管、微丝和稀疏不规则的囊泡；在暗处，还能发现大型多囊泡体。在水平细胞终末描述了两种膜密度类型，其中一种通常位于棘状小体的顶端。它们对E-PTA的阳性反应表明棘状小体可能是突触结构。连续切片重建显示，明处每个终末约有12个棘状小体，而暗处只有两个。棘状小体的形成和消失约需60分钟，且涉及一个球形结构形式的过渡阶段。在其他五种硬骨鱼中也能发现棘状小体，其数量在暗处会减少，但在泥螈、龟和哺乳动物的水平细胞终末中则未发现。
