Branchial innervation and ciliary control in the ascidian Corella
Branchial innervation and ciliary control in the ascidian Corella
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海鞘 Corella 的鳃神经支配和纤毛控制
DOI：
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发表时间：
1974
期刊：
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通讯作者：
D. Williams
中科院分区：
文献类型：
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作者：
G. Mackie;D. H. Paul;C. Singla;M. Sleigh;D. Williams
海鞘鳃囊的柱头上的纤毛使水循环通过动物。这些气门纤毛受神经控制;当任一虹吸管受到刺激时，两个虹吸管通过肌肉收缩关闭，同时在鳃囊的所有部分中的气门纤毛同时停止跳动。也可能发生自发性纤毛停止，伴随或不伴随虹吸管的关闭。在鳃杆上运行的鳃神经系统的元素被认为是在纤毛逮捕的协调有关。大多数鳃神经纤维从形成后脑根的内脏神经背侧出现，尽管神经也被认为沿着其前缘沿着进入鳃囊。在鳃神经和内脏神经中均未发现细胞体，因此推测鳃神经纤维的细胞体位于中枢神经系统中。鳃神经纤维形成一个外周传导网，延伸到整个鳃囊。这些神经纤维的分支终止于与一些纤毛细胞的接触;细胞间传导（通过紧密连接？）可能会将兴奋传播到其他纤毛细胞。神经-神经连接处似乎比神经和纤毛细胞之间的连接处对箭毒更敏感。从鳃囊的电记录，获得与吸力电极，表明逮捕的纤毛是伴随着电活动，并延长逮捕是由列车的定期脉冲。纤毛细胞的细胞内微电极表明，这些细胞具有30 - 40 mV的负静息电位，纤毛停滞与45 - 50 mV的正向尖峰有关。外部记录的“纤毛阻滞电位”可能代表了许多纤毛细胞的协调去极化。脉冲串的节律性可能取决于起搏器活动;这不是局部的，因为完整的生物体或鳃囊的孤立的小部分能够产生类似的脉冲串。在阻滞反应期间，气门纤毛首先进行反向搏动，然后在缓慢放松之前保持反向位置数秒，并且在数秒之后重新开始以逐渐增加的幅度搏动。逮捕反应的持续时间不同的媒体与不同浓度的常见阳离子，也不同的重复刺激，在某种程度上，这表明纤毛细胞的去极化与Ca2+的流入，使纤毛控制在这里可能有一些密切的平行草履虫描述。
The cilia lining the stigmata of the branchial sac of an ascidian circulate water through the animal. These stigmatal cilia are under nervous control; when either siphon is stimulated, both siphons close by muscular contractions and at the same time the stigmatal cilia stop beating simultaneously in all parts of the branchial sac. Spontaneous ciliary arrests may also occur, with or without associated closure of the siphons. Elements of the branchial nervous system that run in the gill bars are assumed to be concerned in coordination of the ciliary arrests. The majority of the branchial nerve fibres emerge dorsally from the visceral nerves that form the posterior brain roots, although nerves are also believed to enter the branchial sac along its anterior margin. No cell bodies could be found in the branchial nerves or in the visceral nerves, so that the cell bodies of the branchial nerve fibres are assumed to lie in the central nervous system. The branchial nerve fibres form a peripheral conducting net extending throughout the branchial sac. Branches of these nerve fibres terminate in contact with some of the ciliated cells; cell-to-cell conduction (through close junctions?) probably spreads excitation to the other ciliated cells. Nerve-nerve junctions appear to be more sensitive to curare than those between nerves and ciliated cells. Electrical recordings from the branchial sac, obtained with suction electrodes, show that arrest of the cilia is accompanied by electrical activity, and that prolonged arrest is maintained by trains of regular pulses. Intracellular microelectrodes in the ciliated cells indicate that these cells have a negative resting potential of 30-40 mV, and that a ciliary arrest is associated with a positive-going spike of 45-50 mV. The externally recorded ‘ciliary arrest potentials’ probably represent the coordinated depolarization of many ciliated cells. The rhythmical character of the trains of pulses presumably depends on pacemaker activity; this is not localized, since intact organisms or isolated small portions of the branchial sac are capable of generating similar trains of pulses. During the arrest response the stigmatal cilia first perform a reverse beat, then maintain the reverse position for several seconds before slowly relaxing and after several more seconds recommencing to beat with progressively increasing amplitude. The duration of the arrest response varies in media with different concentrations of the common cations, and also varies in response to repetitive stimulation, in a manner which suggests that the depolarization of the ciliated cells is associated with an influx of Ca2+, so that the ciliary control here may have some close parallels with that described for Paramecium.