Ishii S
Cell Tissue Res. 1980;206(3):451-8. doi: 10.1007/BF00237974.
A systematic electron microscopic investigation was undertaken to elucidate the regional differentiation of the protonephridial tubules of the freshwater planarian Bdellocephala brunnea. The excretory system consists of many independent protonephridia, each made up of the repeatedly branching "proximal tubules," and highly tortuous "distal tubule." The proximal tubules are composed of a simple ciliated epithelium except in the trunk which lacks ciliation. The cytoplasmic features of the ciliated cell closely resemble those of the flame cell, indicating highly active protein reabsorption by pinocytosis. Pinocytosis seems also active in the trunk of the proximal tubules and in the distal tubule, resulting in cytoplasmic vesicles of typical appearance. Salient features of the distal tubule cell are the increased density of the cytoplasmic matrix and the presence of many basal compartments of cytoplasm with mitochondria, a pattern common to many epithelia with osmoregulatory function. The morphology and possible functions of the planarian protonephridium are discussed in comparison with the vertebrate nephron.
进行了一项系统的电子显微镜研究，以阐明淡水涡虫布朗氏蛭头涡虫原肾管的区域分化。排泄系统由许多独立的原肾组成，每个原肾由反复分支的“近端小管”和高度曲折的“远端小管”组成。近端小管由单层纤毛上皮组成，但在无纤毛的躯干部分除外。纤毛细胞的细胞质特征与焰细胞的非常相似，表明通过胞饮作用进行高度活跃的蛋白质重吸收。胞饮作用在近端小管的躯干部分和远端小管中似乎也很活跃，导致出现典型外观的细胞质小泡。远端小管细胞的显著特征是细胞质基质密度增加，并且存在许多带有线粒体的细胞质基部小室，这是许多具有渗透调节功能的上皮细胞共有的模式。将涡虫原肾的形态和可能的功能与脊椎动物肾单位进行了比较讨论。
