Time-Resolved X-Ray Diffraction from Frog Skeletal Muscle during an Isotonic Twitch under a Small Load
Time-Resolved X-Ray Diffraction from Frog Skeletal Muscle during an Isotonic Twitch under a Small Load
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小负荷下等张抽搐过程中青蛙骨骼肌的时间分辨 X 射线衍射
DOI：
10.2183/pjab.54.559
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
H. Hashizume
中科院分区：
文献类型：
--
作者：
H. Sugi;Y. Amemiya;H. Hashizume
当脊椎动物骨骼肌等长收缩时，1，0赤道反射（I1，o）的强度降低，而1，1反射（I1，1）的强度增加。F. Podolsky等人报道了在等长收缩和等张收缩中强度比11，0/11，1几乎相同，声称在等长收缩和等张收缩条件下连接的横桥的数量可能没有显著差异。由于重复许多强直性收缩的困难，他们的工作似乎不是结论性的，上述问题仍然有待澄清。本实验进行了研究的时间过程中的变化的强度比11，0/11，1在等张缩短在小负荷下，通过时间分辨的X射线衍射技术，给出有关的动力学特性的横桥负责肌肉收缩。从牛蛙蛙解剖缝匠肌安装在一个实验室中，两个聚酯薄膜窗口和多电极组件;骨盆端被夹紧，而胫骨端连接到等渗杠杆，其运动是用差分Transformer感测。通过He-Ne激光的衍射图案将初始肌节长度调节至2.2-2.4 μ m。用充氧林格溶液（2-4°C）连续地对肌肉进行穿孔，并且用单个超大电流脉冲刺激，以在最大等长张力P0的2-3%的小负荷下产生后负荷抽搐。用线性位置敏感的X射线衍射仪记录等张收缩过程中的低角赤道X射线衍射图（样品到焦点的距离，36 cm）。
When vertebrate skeletal muscle contracts isometrically, the intensity of 1,0 equatorial reflection (Il,o) decreases while that of the 1,1 reflection (I1,1) increases.l>'2) This has been interpreted as being due to the movement of the cross-bridges from the vicinity of the thick filaments towards the thin filaments.2>-4) Though, in the sliding filament model of A. F. Huxley,5~ the number of the cross-bridges attached to the thin filaments at any one moment is less the greater the shortening velocity, Podolsky et al.° have reported that the intensity ratio 11,0/11,1 is almost the same in both isometric and isotonic contractions, claiming that the number of attached cross-bridges may not differ significantly between isometric and isotonic conditions. Since their work seems not conclusive because of the difficulty in repeating many tetanic contractions, the above problem still remains to be clarified. The present experiments were undertaken to study the time course of change in the intensity ratio 11,0/11,1 during isotonic shortening under a small load by means of a time-resolved X-ray diffraction technique, to give information about the kinetic properties of the cross-bridges responsible for muscle contraction. The sartorius muscle dissected from the bullfrog Rana catesbiana was mounted in an experimental chamber with two Mylar windows and a multi-electrode assembly ; the pelvic end was clamped while the tibial end was connected to an isotonic lever, the movement of which was sensed with a differential transformer. The initial sarcomere length was adjusted to 2.2-2.4 pm by the diffraction pattern of He-Ne laser light. The muscle was continuously perf used with oxygenated Ringer solution (2-4°C), and stimulated with a single supramaximal current pulse to produce an after-loaded twitch under a small load of 2-3% of the maximum isometric tension P0. The low angle equatorial X-ray diffraction patterns (specimen to focus distance, 36 cm) during the isotonic twitch were recorded with a linear position-sensitive