Hauser M, Van Eys H
J Cell Sci. 1976 May;20(3):589-617. doi: 10.1242/jcs.20.3.589.
At the ultrastructural level length changes accompanying linear movements of resting (non-feeding) tentacles of the suctorian Heliophrya involve not only altered microtubule numbers, but also marked changes in the specific microtubule pattern of cross-sectioned tentacles. These changes in number and pattern indicate a sliding between axonemal microtubules. The visualization of microfilaments in the cytoplasm at the tentacle base and in the knob region could shed new light on the problem of whether microtubular sliding is an active or passive process. At the tentacle base, microfilaments are either arranged in a ring-shaped configuration around the axoneme, or they run parallel to the axonemal microtubules, whereas at the tentacle tip during the resting state, microfilaments are closely associated with the plasma membrane of the knob. They form a filamentous reticular layer, which is continuous at the anchorage site of axonemal microtubules with the dense epiplasmic layer of the tentacle shaft. Obiously, this filamentous layer is engaged in positioning the haptocysts at the plasma membrane and in holding the membrane itself under tension. The putative contractile nature of microfilaments and the epiplasmic layer is argued from ATP-sensitive glycerol models of tentacles and from the results of halothane treatment of native tentacles. Halothane treatment of resting tentacles also gave indications of the presence of differentially stable intermicrotubule-bridges. The role of micro-filaments and halothane-resistant dynein-like inter-row bridges in tentacle movement is discussed. As soon as the plasma membrane of the knob is 'sealed' with the prey pellicle during feeding, the microtubules of the sleeve region slide into the knob where they bend back and outwards. The microtubules now appear decorated and sometimes cross-connected by microfilaments which adhere closely to the plasma membrane- now acting as a peritrophic membrane-lining the prey cytoplasm against the microtubules of the inner tube. These microfilaments which show a close association with the microtubules of the active knob area, are thought to be engaged in microtubular bending and stretching during feeding. They may also be involved in the transport of the peritrophic membrane in distal tentacle regions. Microinematographically recorded oscillations in tentacle diameter in these regions are in agreement with the electron-microscopic findings of various states of collapsed tentacle axonemes. These observations, as well as the occurrence of helically twisted tentacles during feeding, suggest microfilament mediated sequential back and forth movements of sleeve microtubules in the knob region which generate a proximally migrating helical wave.
在超微结构水平上，吸管虫类太阳虫属静止（非摄食）触手的线性运动所伴随的长度变化，不仅涉及微管数量的改变，还包括横切触手特定微管模式的显著变化。数量和模式的这些变化表明轴丝微管之间存在滑动。对触手基部和瘤状区域细胞质中微丝的观察，可能会为微管滑动是主动还是被动过程这一问题提供新的线索。在触手基部，微丝要么围绕轴丝呈环形排列，要么与轴丝微管平行，而在静止状态下的触手尖端，微丝与瘤状结构的质膜紧密相连。它们形成一个丝状网状层，在轴丝微管与触手轴致密表质层的附着部位连续。显然，这个丝状层参与将吸胞定位在质膜上，并使膜本身处于张力之下。从触手的ATP敏感甘油模型以及对天然触手进行氟烷处理的结果来看，微丝和表质层具有推测的收缩性质。对静止触手进行氟烷处理也表明存在稳定性不同的微管间桥。讨论了微丝和耐氟烷动力蛋白样排间桥在触手运动中的作用。在摄食过程中，一旦瘤状结构的质膜与猎物表皮“密封”，套筒区域的微管就会滑入瘤状结构，在那里它们向后弯曲并向外伸展。此时微管表面似乎有装饰，有时还会被微丝交叉连接，这些微丝紧密附着在质膜上——此时质膜充当围食膜，将猎物细胞质与内管的微管隔开。这些与活跃瘤状区域微管密切相关的微丝，被认为在摄食过程中参与微管的弯曲和伸展。它们也可能参与围食膜在触手远端区域的运输。这些区域通过显微电影记录的触手直径振荡，与塌陷触手轴丝不同状态的电子显微镜观察结果一致。这些观察结果，以及摄食过程中出现的螺旋扭曲触手，表明微丝介导了套筒微管在瘤状区域的顺序来回运动，从而产生向近端迁移的螺旋波。
