CROSS-BRIDGE DETACHMENT AND SARCOMERE GIVE DURING STRETCH OF ACTIVE FROGS MUSCLE
CROSS-BRIDGE DETACHMENT AND SARCOMERE GIVE DURING STRETCH OF ACTIVE FROGS MUSCLE
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DOI：
10.1113/jphysiol.1978.sp012246
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发表时间：
1978-01-01
影响因子：
5.5
通讯作者：
HIRST, DG
中科院分区：
文献类型：
--
作者：
FLITNEY, FW;HIRST, DG
1.一项研究已经对施加于等距收缩的青蛙肌肉的伺服控制拉伸产生的张力反应和肌节长度变化进行了研究。通过激光照射小面积肌肉获得的衍射光谱的电影摄影监测肌节长度。2.由约1 mm（约1.5 mm）的斜升和保持拉伸产生的张力增量肌肉长度的4%）包括三个阶段，其极限由两个点S1和S2限定，在这两个点处，响应的斜率突然减小。S1和S2对应于肌肉长度的0.13%和1.2%的延伸。3.运动的一阶光谱相对于零级记录在拉伸过程中显示，S2与突然伸长的肌节。这被称为肌节“屈服”，当肌丝从其稳态（等距）位置移位11 - 12 nm时发生。4.肌节的刚度，Es，直到S2随着肌节长度的增加而减小。在S2，PS2，肌肉持续的最大力，也显示出肌节长度的反向依赖性。Es和PS2都在3.6 - 3.7微米的外推肌节间距处降至零，与肌动蛋白和肌球蛋白丝不再重叠的长度一致。5.比率PS2/P0（其中P0 =最大等轴张力）随温度和拉伸速度而变化。它随着拉伸速度的增加而增加，直到达到某个临界速度Vc，超过该临界速度，它几乎与任何进一步的增加无关。Vc具有正温度系数，在0 - 30 ℃范围内增加5 - 6（Q10 = 1.8）。等张缩短的最大速度（Vmax）与收缩速度之间存在正相关性。和Vc的含量。6.肌节在拉伸过程中“屈服”被认为是由于肌动蛋白和肌球蛋白细丝之间的横桥的强制分离。这导致肌肉中的延伸系列弹性元件以肌角为代价的回缩。诱导肌节“屈服”所需的细丝位移量（11 - 12 nm）被认为代表了在拉伸过程中横桥可以保持附着于肌动蛋白的运动范围。
1. A study has been made of the tension responses and sarcomere length changes produced by servo‐controlled stretches applied to isometrically contracting frog muscle. Sarcomere lengths were monitored by cine‐photography of diffiraction spectra obtained by illuminating a small area of muscle with a laser. 2. The tension increment produced by a ramp‐and‐hold stretch of approximately 1 mm (ca. 4% of the muscle length) comprises three phases whose limits are defined by two points, S1 and S2, where the slope of the response decreases abruptly. S1 and S2 correspond to extensions of 0.13 and 1.2% of the muscle length. 3. Movements of the first order spectra relative to the zero order recorded during stretch reveal that S2 coincides with an abrupt elongation of the sarcomeres. This is termed sarcomere 'give' and it occurs when the filaments are displaced by 11‐12 nm from their steady‐state (isometric) position. 4. The stiffness of the sarcomeres, Es, up to S2 decreases with increasing sarcomere length. The maximum force sustained by the muscle at S2, PS2, also shows an inverse dependence on sarcomere length. Both Es and PS2 fall to zero at an extrapolated sarcomere spacing of 3.6‐3.7 micrometer, coinciding with the length at which the actin and myosin filaments no longer overlap. 5. The ratio PS2/P0 (where P0 = maximum isometric tension) varies with temperature and speed of stretch. It increases with increasing speeds of stretch until a certain critical velocity, Vc, is reached, beyond which it is almost independent of any further increase. Vc has a positive temperature coefficient, increasing 5‐6 in the range 0‐30 degrees C (Q10 = 1.8). There is a positive correlation between the maximum speed of isotonic shortening (Vmax.) and Vc in different muscles. 6. Sarcomere 'give' during stretch is considered to be due to forcible detachment of cross‐bridges between the actin and myosin filaments. This results in recoil of the extended series elastic elements in the muscle at the expense of the sarcomers. The amount of filament displacement required to induce sarcomere 'give' (11‐12 nm) is thought to represent the range of movement over which a cross‐bridge can remain attached to actin during a stretch.