Dryer L, Graziadei P P
Department of Biological Science B-221, Florida State University, Tallahassee 32306-3050.
Anat Embryol (Berl). 1993 Jul;188(1):41-51. doi: 10.1007/BF00191450.
The olfactory bulb of many elasmobranch fishes is morphologically subdivided into distinct units or sub-bulbs immediately adjacent to the olfactory epithelium. We investigated this morphological feature in two species of shark and one species of ray in order to understand its impact on the arrangement of the primary olfactory projections onto the bulb. Using anterograde tracing methods in vitro (biocytin) as well as in fixed tissue (DiI), we observed a direct segregated projection of the olfactory afferents onto the bulb. Application of tracers to the lateral part of the olfactory epithelium resulted in staining restricted to this region of the bulb, whereas the same tracers applied to the medial part of the epithelium resulted in staining of the medial olfactory bulb. The sub-bulbs appear to be individual anatomical units that each receive input from the olfactory lamellae. Nissl and myelin staining as well as the Golgi method show that the cytoarchitecture of the sub-bulbs is not substantially different from that of other anamniotes. However, we did note the existence of two types of mitral cell, based on the morphology of their dendritic arborization. Type L cells exhibit a loose dendritic arborization, whereas type T cells are characterized by a dense, bush-like dendritic arborization. Both types of mitral cells lack basal dendrites.
许多板鳃鱼类的嗅球在形态上被细分为紧邻嗅上皮的不同单元或亚球。我们研究了两种鲨鱼和一种鳐鱼的这种形态特征，以了解其对初级嗅觉投射到嗅球上的排列方式的影响。我们使用体外顺行示踪方法（生物素）以及固定组织中的示踪方法（碘化丙啶），观察到嗅觉传入纤维直接分离投射到嗅球上。将示踪剂应用于嗅上皮的外侧部分会导致染色局限于嗅球的该区域，而将相同的示踪剂应用于上皮的内侧部分会导致内侧嗅球染色。这些亚球似乎是各自从嗅板接收输入的独立解剖单元。尼氏染色、髓鞘染色以及高尔基方法表明，亚球的细胞结构与其他无羊膜动物的细胞结构没有实质性差异。然而，基于其树突分支的形态，我们确实注意到存在两种类型的二尖瓣细胞。L型细胞表现出松散的树突分支，而T型细胞的特征是密集的、灌木状的树突分支。两种类型的二尖瓣细胞都缺乏基底树突。
