X-RAY EVIDENCE FOR THE ELONGATION OF THIN AND THICK FILAMENTS DURING ISOMETRIC CONTRACTION OF A MOLLUSCAN SMOOTH-MUSCLE
X-RAY EVIDENCE FOR THE ELONGATION OF THIN AND THICK FILAMENTS DURING ISOMETRIC CONTRACTION OF A MOLLUSCAN SMOOTH-MUSCLE
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DOI：
10.1007/bf00121073
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发表时间：
1994-12-01
影响因子：
2.7
通讯作者：
AMEMIYA, Y
中科院分区：
文献类型：
--
作者：
TAJIMA, Y;MAKINO, K;AMEMIYA, Y
本文通过测量中角X射线衍射图中衍射峰间距的变化，研究了软体动物平滑肌等长收缩过程中细丝和粗丝的伸长。从贻贝的前足丝牵开肌在休息，活动，和捕捉状态的X射线模式，从同一部分的肌肉束在一个固定的探头到探测器的距离，使用成像板和10 s曝光同步辐射。肌动蛋白轴向周期的第三级反射（9.2埃）和粗丝轴向亚单位重复的第十四级反射（10.4埃）在活动状态和捕获状态下的间距增加。根据精确测量的9.2埃层线与原点的轴向距离的变化，在活动状态下保持12.2 kg cm（-2）张力的肌肉和在捕获状态下保持9.8 kg cm（-2）张力的肌肉中，活动状态和捕获状态下的细丝伸长分别估计为0.48%和0.32%。基于10.4埃反射的轴向位移，在活动状态和捕获状态下的粗丝伸长类似地分别估计为0.33和0.28%。活性状态下细丝的0.48%伸长率与白色和Thorson（1973）为估计细丝刚度下限而假定的伸长率一致。似乎在捕获状态下，激活的和静止的细丝结构是混合在一起的。细丝的活化部分可能比表观值0.32%更长。
The elongation of thin and thick filaments during isometric contraction of a molluscan smooth muscle was studied by measuring spacing changes of meridional reflections in the medium-angle X-ray diffraction pattern. X-ray patterns from the anterior byssus retractor muscle of Mytilus edulis in the resting, active, and catch states were taken from the same part of a muscle bundle at a fixed specimen-to-detector distance, using imaging plates and 10 s exposure to synchrotron radiation. The third-order reflection (9.2 Angstrom) of the axial period of actin, and the fourteenth-order reflection (10.4 Angstrom) of the axial subunit-repeat of the thick filament are increased in spacing in the active and catch states. From accurately measured changes in the axial distance of the 9.2 Angstrom layer line from the origin, thin filament elongations in the active and catch states are estimated to be 0.48 and 0.32%, respectively, in a muscle that maintains a tension of 12.2 kg cm(-2) in the active state and 9.8 kg cm(-2) in the catch state. Thick filament elongations in the active and catch states are similarly estimated to be 0.33, and 0.28%, respectively, based on the axial shift of the 10.4 Angstrom reflection. The 0.48% elongation of the thin filament in the active state agrees with an elongation that is presumed by White and Thorson (1973) to estimate the lower limit of the thin-filament stiffness. It seems that in the catch state the activated and resting thin filament structures are intermixed. The activated parts of the thin filament are probably more elongated than the apparent value, 0.32%.