Crawford B J, Campbell S S
Department of Anatomy, University of British Columbia, Vancouver, Canada.
Anat Rec. 1993 Aug;236(4):697-709. doi: 10.1002/ar.1092360414.
Early stage embryos of the starfish Pisaster ochraceus exhibit one cilium per cell which is primarily involved in locomotion. SEM observations have demonstrated two types of microvilli "stage horn"-like and "finger-like" microvilli (CMs), both of which probably serve to anchor and support the hyaline layer (HL). The CMs arise from the cellular membrane a short distance from the base of the ciliary shaft and form a circle around the base of each cilium. This arrangement is found in embryos and larvae as well as in adult tissues of many other marine organisms. TEM observations of material prepared by freeze substitution has demonstrated that the HL unites the circle of CMs and forms two collars. The outer ECM collar is single and attached directly to the CMs, while the inner collar consists of multiple rings of ECM located between the cilium and the CMs. The inner collar elements are not attached to the cilium but are attached to the inner aspects of the CMs by a complex arrangement consisting of a loop of ECM and two short ECM fibers. The arrangement of the ECM of the collars could provide an excellent way to transmit the movements of the cilium to the surrounding microvilli. Although the bases of the CMs always encircle the ciliary shaft, the shafts of the CMs are seen in different positions. This suggests that the CM/ECM collar may be able to change position relative to the cilium. Confocal laser scanning microscopy demonstrates that the CMs contain phalloidin positive material which extends into a phalloidin positive region located in the apex of the cells. The CMs and apical web contain microfilaments which are probably actin and could be involved in movement of the CMs. A movable circle of CMs with their associated ECM could represent a mechanism to sense the position of the cilium and/or to define the direction and extent of the stroke.
赭色海星的早期胚胎每个细胞有一根纤毛，主要用于运动。扫描电子显微镜观察显示有两种类型的微绒毛——“阶段角状”和“手指状”微绒毛（CMs），两者可能都用于固定和支撑透明层（HL）。CMs从距纤毛轴基部一段短距离的细胞膜处产生，并在每个纤毛基部周围形成一个环。这种排列在胚胎和幼虫以及许多其他海洋生物的成体组织中都能找到。对通过冷冻置换制备的材料进行的透射电子显微镜观察表明，HL将CMs环连接起来并形成两个环。外部的细胞外基质环是单一的，直接附着在CMs上，而内部环由位于纤毛和CMs之间的多层细胞外基质环组成。内部环元件不附着在纤毛上，而是通过由一个细胞外基质环和两根短细胞外基质纤维组成的复杂排列附着在CMs的内侧。环的细胞外基质排列可能提供了一种将纤毛运动传递到周围微绒毛的绝佳方式。尽管CMs的基部总是环绕着纤毛轴，但CMs的轴在不同位置可见。这表明CM/细胞外基质环可能能够相对于纤毛改变位置。共聚焦激光扫描显微镜显示，CMs含有鬼笔环肽阳性物质，该物质延伸到位于细胞顶端的鬼笔环肽阳性区域。CMs和顶端网含有微丝，这些微丝可能是肌动蛋白，可能参与CMs的运动。带有相关细胞外基质的可移动CMs环可能代表一种感知纤毛位置和/或确定摆动方向和幅度的机制。
