Hufnagel L A
Department of Microbiology, University of Rhode Island, Kingston 02881.
Microsc Res Tech. 1992 Aug 1;22(3):225-64. doi: 10.1002/jemt.1070220304.
The ciliated protists (ciliates) offer a unique opportunity to explore the relationship between chemoreception and cell structure. Ciliates resemble chemosensory neurons in their responses to stimuli and presence of cilia. Ciliates have highly patterned surfaces that should permit precise localization of chemoreceptors in relation to effector organelles. Furthermore, ciliates are easy to grow and to manipulate genetically; they can also be readily studied biochemically and by electrophysiological techniques. This review contains a comparative description of the ultrastructural features of the ciliate cell surface relevant to chemoreception, examines the structural features of putative chemoreceptive cilia, and provides a summary of the electron microscopic information available so far bearing on chemoreceptive aspects of swimming, feeding, excretion, endocytosis, and sexual responses of ciliates. The electron microscopic identification and localization of specific chemoreceptive macromolecules and organelles at the molecular level have not yet been achieved in ciliates. These await the development of specific probes for chemoreceptor and transduction macromolecules. Nevertheless, the electron microscope has provided a wealth of information about the surface features of ciliates where chemoreception is believed to take place. Such morphological information will prove essential to a complete understanding of reception and transduction at the molecular level. In the ciliates, major questions to be answered relate to the apportionment of chemoreceptive functions between the cilia and cell soma, the global distribution of receptors in relation to the anterior-posterior, dorsal-ventral, and left-right axes of the cell, and the relationship of receptors to ultrastructural components of the cell coat, cell membrane, and cytoskeleton.
纤毛原生动物（纤毛虫）为探索化学感受与细胞结构之间的关系提供了独特的机会。纤毛虫在对刺激的反应和纤毛的存在方面类似于化学感觉神经元。纤毛虫具有高度规则的表面，这应该允许化学感受器相对于效应细胞器进行精确的定位。此外，纤毛虫易于培养且易于进行基因操作；它们还可以很容易地通过生物化学和电生理技术进行研究。这篇综述包含了与化学感受相关的纤毛虫细胞表面超微结构特征的比较描述，研究了假定的化学感受纤毛的结构特征，并总结了迄今为止有关纤毛虫游泳、进食、排泄、内吞作用和性行为的化学感受方面的电子显微镜信息。在纤毛虫中，尚未在分子水平上实现对特定化学感受大分子和细胞器的电子显微镜鉴定和定位。这些有待开发针对化学感受器和转导大分子的特异性探针。尽管如此，电子显微镜已经提供了大量关于纤毛虫表面特征的信息，而化学感受被认为发生在这些表面。这样的形态学信息对于在分子水平上全面理解感受和转导至关重要。在纤毛虫中，有待回答的主要问题涉及纤毛和细胞体之间化学感受功能的分配、受体相对于细胞前后轴、背腹轴和左右轴的整体分布，以及受体与细胞被膜、细胞膜和细胞骨架的超微结构成分之间的关系。
