The maximum speed of shortening in living and skinned frog muscle fibres.
The maximum speed of shortening in living and skinned frog muscle fibres.
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活体和剥皮青蛙肌肉纤维的最大缩短速度。
DOI：
10.1113/jphysiol.1986.sp015929
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Striz,S
中科院分区：
文献类型：
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作者：
Julian,FJ;Rome,LC;Stephenson,DG;Striz,S
这项研究是为了确定从力-速度曲线推断的最大缩短速度Viso是否等于Vu(由松弛试验确定的卸载缩短速度)。在活体纤维(R.Temporaria)中，我们通过在非常低的载荷(0.005等长张力，P0)下执行力钳(等张)和长度斜坡(等速)获得了改进的Viso估计。由力夹和长度斜率确定的力-速度特性是相同的。在高载荷和低载荷下，双曲线Hill曲线都与力-速度数据有不同程度的偏离，并不同程度地低估了Viso。通过线性外推0.005-0.02P0的负荷数据得到了更好的VISO估计，7.5C时的平均VISO为4.08肌长/S+/-0.11(平均+/-S.E.，n=14)。通过照相校准SLACK测试，获得了活纤维中Vu的改进估计。平均肌长/S+/-0.13(平均+/-SE，n=14)，截距0.0156纤维长度(L0)+/-0.0013(平均+/-SE，n=14)。马达速度与Vu匹配的阶梯斜坡照相法是一种独立的测量活纤维中Vu的方法。用这种方法测得的VU与松弛测试测得的VU吻合得很好。在所有活纤维中，Vu的改进估计值与Viso的改进估计值吻合良好。VU/Viso=0.99+/-0.01(平均值+/-S.E.，n=14)。在机械剥皮的淡管罗非鱼纤维中，力钳被执行到0.01mN的载荷。剥皮纤维的力-速度曲线与活纤维的力-速度曲线形状不同。虽然在低负荷时与Hill方程有较大的偏差，但在高负荷时，Hill曲线能很好地拟合数据。在7.5℃时，将Hill方程外推至零负荷所测得的Viso为5.87肌长/S+/-0.38(平均值+/-S.E.，n=9)。在五种纤维中，低负荷(0.01-0.05 P0)的线性外推显示Hill方程低估了真实Viso的6%。机械剥皮纤维的松弛测试是通过在每个长度步骤之后的不同时间对纤维进行一系列摄影曝光来校准的。VU=6.12肌长/S+/-0.44(平均+/-SE，n=10)，截距0.0585 L0+/-0.0069(平均+/-SE，n=10)。
This study was performed to determine whether Viso (the maximum speed of shortening extrapolated from force‐velocity curves) equalled Vu (the unloaded speed of shortening determined by the slack test) in both living fibres from Rana temporaria and mechanically skinned fibres from Rana pipiens. In living fibres (R. temporaria) we obtained improved estimates of Viso by performing force clamps (isotonic) and length ramps (isovelocity) down to very low loads (0.005 isometric tension, P0). Force‐velocity characteristics determined by force clamps and length ramps were the same. The hyperbolic Hill curves deviated from the force‐velocity data at both high and low loads and underestimated Viso by varying degrees. A better estimate of Viso was obtained by linear extrapolation of data at loads from 0.005‐0.02 P0 and the mean Viso at 7.5 degrees C was 4.08 muscle lengths/s +/‐ 0.11 (mean +/‐ S.E., n = 14). Improved estimates of Vu in living fibres were obtained by photographically calibrating the slack test. The mean Vu was 4.05 muscle lengths/s +/‐ 0.13 (mean +/‐ S.E., n = 14) and the intercept was 0.0156 fibre lengths (L0) +/‐ 0.0013 (mean +/‐ S.E., n = 14). The step‐ramp photographic method, in which the motor speed is matched to Vu, was developed as an independent way to measure Vu in living fibres. Vu measured in this way agreed well with Vu measured by the slack test. In all living fibres, the improved estimates of Vu agreed well with the improved estimates of Viso. Vu/Viso = 0.99 +/‐ 0.01 (mean +/‐ S.E., n = 14). In mechanically skinned R. pipiens fibres, force clamps were performed down to loads of 0.01 mN. The force‐velocity curve of the skinned fibres differed in shape from that of the living fibres. Although there was significant deviation from the Hill equation at low loads, the data at high loads were well fitted by the Hill curve. Viso determined by extrapolating the Hill equation to zero load was 5.87 muscle lengths/s +/‐ 0.38 (mean +/‐ S.E., n = 9) at 7.5 degrees C. In five fibres, the linear extrapolation of low loads (0.01‐0.05 P0) showed that the Hill equation underestimated the true Viso by 6%. The slack test with mechanically skinned fibres was calibrated by taking a series of photographic exposures of the fibre at various times following each length step. Vu = 6.12 muscle lengths/s +/‐ 0.44 (mean +/‐ S.E., n = 10) and the intercept was 0.0585 L0 +/‐ 0.0069 (mean +/‐ S.E., n = 10).(ABSTRACT TRUNCATED AT 400 WORDS)