THE CATCH MECHANISM IN MOLLUSCAN MUSCLE - AN ELECTRON-MICROSCOPY STUDY OF FREEZE-SUBSTITUTED ANTERIOR BYSSUS RETRACTOR MUSCLE OF MYTILUS-EDULIS
THE CATCH MECHANISM IN MOLLUSCAN MUSCLE - AN ELECTRON-MICROSCOPY STUDY OF FREEZE-SUBSTITUTED ANTERIOR BYSSUS RETRACTOR MUSCLE OF MYTILUS-EDULIS
复制标题
DOI：
10.1007/bf01758426
复制
发表时间：
1989-08-01
影响因子：
2.7
通讯作者：
ELLIOTT, A
中科院分区：
文献类型：
--
作者：
BENNETT, PM;ELLIOTT, A
描述了一种快速解冻肌肉的方法，同时观察肌肉的力学性能直到冻结时刻。用该方法冷冻紫贻贝的前股骨缩窄肌。在蔗糖作为冷冻保护剂的情况下，将完整的肌肉冷冻在丙酮中，固定并包埋在电子显微镜下。ABRM在多种机械状态下被冻结，包括“Catch”，这是一种特别与一些软体动物肌肉相关的高被动张力状态。横切面检查以确定肌细胞内细丝的分布。在松弛的肌肉中，粗丝和细丝相当随机地分布。细丝和粗丝的组合很常见，两者之间没有明显的联系。相比之下，在僵直的肌肉中，无论是甘油提取的还是完整的，大多数细丝被发现存在于粗丝周围的环状或玫瑰花环中。在某些地方，可以区分粗丝和细丝之间的桥梁。在主动收缩肌肉(阶段性收缩)中，肌肉的外观介于放松肌肉和僵硬肌肉之间。许多粗丝被细丝的花环包围，但许多细丝是成组的，与粗丝没有联系。在紧张性收缩一段时间后留下的“捕捉”状态，其粗细细丝的分布类似于活动状态，许多细细丝位于粗细之间。通常情况下，粗丝和细丝似乎比肌肉的其他状态更紧密，在其他状态下，粗丝周围存在明显的隔离区。没有证据表明这些粗丝之间存在关联。如果假定对12 nm赤道反射的大部分贡献来自于细丝群，则不同状态下细丝的不同分布与前述X射线衍射数据是一致的。我们的数据支持一种渔获量模型，在该模型中，粗丝和细丝之间的关联发生了变化，而不是粗丝成团。
A method for quick-freeezing muscles while observing their mechanical properties until the moment of freezing is described. This method was used to freeze the anterior byssus retractor muscle (ABRM) of Mytilus edulis. Intact muscle in the presence of sucrose as a cryoprotectant was freeze-substituted in acetone, fixed and embedded for electron microscopy. ABRM was frozen in a number of mechanical states including ''catch'', the state of high passive tension particularly associated with some molluscan muscles. Transverse sections were examined to determine the distribution of filaments in the muscle cells. In the relaxed muscle thick and thin filaments are fairly randomly distributed. Groups of thin filaments and of thick filaments are often seen, and there is no obvious association between the two types of filaments. In contrast, in rigor muscles, both glycerol-extracted and intact, most of the thin filaments were found to lie in rings or rosettes around the thick filaments. In some places bridges between thick and thin filaments could be distinguished. In actively contracting muscle (phasic contraction) the appearance is intermediate between that of the relaxed and rigor muscles. Many thick filaments are surrounded by rosettes of thin filaments but many of the thin filaments are grouped and have no connections with thick filaments. The ''catch'' state, left after a period of tonic contraction, is similar in its distribution of thick and thin filaments to the active state, many of the thin filaments lying between the thick. Frequently thick and thin filamens seem to be closer together than in other states of the muscle where a pronounced exclusion zone is present around the thick filaments. There is no evidence for association between the thick filaments. The different distribution of the thin filaments in the different states is consistent with the previously described X-ray diffraction data if it is assumed that most of the contribution to the equatorial reflection at 12 nm comes from the groups of thin filaments. Our data support a model for catch in which there is a change in the association between thick and thin filaments, rather than one in which thick filaments are clumped.