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Fundamental study on degeneration mechanisms of the masseter muscle

咬肌退变机制的基础研究

基本信息

批准号：
60570880
负责人：
HORIGUCHI Tsuyoshi
金额：
$ 1.02万
依托单位：
Nihon University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

项目摘要

The actin-degrading enzyme was extracted from the metamorphosing bullfrog tadpole tail. This enzyme was partially purified and characterized. The molecular weight was determined as 26,000 by the gel chromatography. The enzyme was active in degrading actin molecules in the broad range of pH (5.5 to 7.5) with the maximum activity at pH 6.0, and hydrolyzed native actin, myosin H chain, troponin C and I. To get information on the physiological role of this enzyme, the following investigation was carried out. The tail muscle fibers of prometamorphic tadpole were incubated in vitro with the enzyme after they were treated with saponin to obtain uniform penetration of the enzyme, and ultrastructural changes of the myofibrils in course of time were investigated. The initial changes were seen after 5 min in actin filaments within I-band to be irregular arrangement as like waste threads. Most of the I-bands and Z-discs disappeared by 15 min so that the myofibrils fragmentized at the level of the I-bands, or the myofilaments fanned out from the terminals of the intact myofibrils. The A-band then overlapped with the neighboring A-bands, but the H-bands including M-lines remained intact.These ultrastructural changes have many points of resemblance to those of the myofibrils during spontaneous metamorphosis. Therefore, this enzyme was supposed to play an important role in degeneration of the myofibrils of the anuran tadpole tail during spontaneous metamorphosis.

肌动蛋白降解酶是从变态牛蛙蝌蚪尾部提取的。该酶经过部分纯化和表征。通过凝胶色谱测定分子量为26,000。该酶在较宽的 pH 范围（5.5 至 7.5）内具有降解肌动蛋白分子的活性，在 pH 6.0 时活性最大，并水解天然肌动蛋白、肌球蛋白 H 链、肌钙蛋白 C 和 I。为了获得有关该酶的生理作用的信息，进行了以下研究。将原变态蝌蚪的尾部肌纤维用皂苷处理，使酶均匀渗透后，在体外与酶一起孵育，并研究肌原纤维随时间的超微结构变化。 5 分钟后，I 带内的肌动蛋白丝出现了最初的变化，呈不规则排列，就像废丝一样。大多数 I 带和 Z 盘在 15 分钟后消失，因此肌原纤维在 I 带水平破碎，或者肌丝从完整肌原纤维的末端呈扇形散开。然后，A 带与邻近的 A 带重叠，但包括 M 线在内的 H 带保持完整。这些超微结构变化与自发变态过程中的肌原纤维的变化有很多相似之处。因此，这种酶被认为在无尾蝌蚪自发变态过程中尾部肌原纤维的退化中发挥了重要作用。