Physiological and morphological studies on the madreporite of echinoderms

棘皮动物的一个独特器官是madreporite。它通过纤毛孔将水维管系统与外部海水连接起来。madreporite的生理功能，甚至水运动的方向，如果有的话，通过madreporite，尚未阐明。为了研究madreporitel的功能，我们用电子显微镜研究了madreporite的外部圆形开口，以及化学刺激对madreporite孔径的影响。当用低真空扫描电子显微镜（Akashi WS- 250，“WET-SEM”）观察新鲜的、未固定的和未涂覆的马粪海胆（Hemicentrotus pulcherrimus）的madreporites时，其圆形开口显示出尺寸的广泛变化，而周围听小骨中的孔的尺寸几乎恒定。这表明每个孔可以改变其直径。为了了解孔径是否会因药物刺激而发生变化，我们研究了化学物质对madreporite的孤立背口片的影响。&gt; 10 μ M的乙酰胆碱<-9>诱导可逆的孔收缩。高浓度的K^+也能诱导类似的反应，但肾上腺素没有影响，这些发现表明每个孔的大小都受到胆碱能神经的控制。在开放和关闭状态下固定的孔的形态计量学分析表明，在孔关闭过程中，孔道的外径和内径都减小。虽然存在一个括约肌样的结构可能已被预期，没有这样的结构尚未被发现之间的表皮细胞覆盖的madreporite的外表面或内衬的孔道通过透射电子显微镜。我们现在正在开发一种新的程序，以分离表皮细胞层从madreporite这是处理与胶原酶。这种新的制剂似乎是有用的madreporite进一步的形态和生理研究。

The madreporite is an organ unique to the echinoderms. It connects the water-vascular system to the external sea water through ciliated pores. The physiological function of the madreporite, even the direction of water movement, if any, through the madreporite, has not yet been elucidated. To investigate the function of the madreporitel, we studied the external circular openings of the madreporite with electron microscopy and also the effect of chemical stimulation on the pore size of the madreporite. When fresh, unfixed and uncoated madreporites of Hemicentrotus pulcherrimus were observed with a low-vacuum scanning electron microscope (Akashi WS- 250, "WET-SEM"), its circular openings showed a wide variation in size while the pores in the surrounding ossicles were almost constant in size. This suggests that each pore can change its diameter. To see if the pore size changes in response to pharmacological stimulation, we studied the effect of chemicals on the isolated aboral piece of madreporite. Acetylcholine at > 10^<-9> M induced a reversible pore constriction. A high concentration of K^+ also induced a similar response, but adrenaline was without effect.These findings suggest that the size of each pore is under a cholinergic nervous control. Morphometrical analyses of the pores fixed in both open and closed states suggested that both the outer and the inner diameters of the pore canal decrease during the pore closure. Although the existence of a sphincter-like structure might have been expected, no such structure has not yet been found among the epidermal cells covering the outer surface of the madreporite or lining the pore canals by transmission electron microscopy. We are now developing a new procedure to isolate the epidermal cell layer from the madreporite which is treated with collagenase. This new preparation appears to be useful for further morphological and physiological studies of the madreporite.