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描述心肌纤维中残余力和被动力的增强。

Characterizing residual and passive force enhancements in cardiac myofibrils.

机构信息

Institute of Physiology II, Faculty of Medicine, University of Münster, Münster, Germany; Faculty of Kinesiology, University of Calgary, Calgary, Canada.

Faculty of Kinesiology, University of Calgary, Calgary, Canada; Kinesiology Program, Trent University, Peterborough, ON, Canada; Department of Human Health and Nutritional Science, University of Guelph, Guelph, ON, Canada.

出版信息

Biophys J. 2023 Apr 18;122(8):1538-1547. doi: 10.1016/j.bpj.2023.03.022. Epub 2023 Mar 17.

Abstract

Residual force enhancement (RFE), an increase in isometric force after active stretching of a muscle compared with the purely isometric force at the corresponding length, has been consistently observed throughout the structural hierarchy of skeletal muscle. Similar to RFE, passive force enhancement (PFE) is also observable in skeletal muscle and is defined as an increase in passive force when a muscle is deactivated after it has been actively stretched compared with the passive force following deactivation of a purely isometric contraction. These history-dependent properties have been investigated abundantly in skeletal muscle, but their presence in cardiac muscle remains unresolved and controversial. The purpose of this study was to investigate whether RFE and PFE exist in cardiac myofibrils and whether the magnitudes of RFE and PFE increase with increasing stretch magnitudes. Cardiac myofibrils were prepared from the left ventricles of New Zealand White rabbits, and the history-dependent properties were tested at three different final average sarcomere lengths (n = 8 for each), 1.8, 2, and 2.2 μm, while the stretch magnitude was kept at 0.2 μm/sarcomere. The same experiment was repeated with a final average sarcomere length of 2.2 μm and a stretching magnitude of 0.4 μm/sarcomere (n = 8). All 32 cardiac myofibrils exhibited increased forces after active stretching compared with the corresponding purely isometric reference conditions (p < 0.05). Furthermore, the magnitude of RFE was greater when myofibrils were stretched by 0.4 compared with 0.2 μm/sarcomere (p < 0.05). We conclude that, like in skeletal muscle, RFE and PFE are properties of cardiac myofibrils and are dependent on stretch magnitude.

摘要

残余力增强(RFE),即在肌肉主动拉伸后与相应长度的纯等长力相比,等长力的增加,在骨骼肌肉的结构层次中一直得到一致观察。类似于 RFE,被动力增强(PFE)在骨骼肌肉中也是可观察到的,并且定义为在肌肉在主动拉伸后失活时与在纯等长收缩后失活时的被动力相比,被动力的增加。这些与历史相关的特性在骨骼肌肉中得到了充分的研究,但它们在心肌中的存在仍然没有解决,存在争议。本研究的目的是研究 RFE 和 PFE 是否存在于心肌肌小节中,以及 RFE 和 PFE 的幅度是否随拉伸幅度的增加而增加。从新西兰白兔的左心室中制备心肌肌小节,并在三个不同的最终平均肌小节长度(每个长度 n=8)下测试历史相关特性,分别为 1.8、2 和 2.2μm,同时保持拉伸幅度为 0.2μm/sarcomere。在最终平均肌小节长度为 2.2μm 且拉伸幅度为 0.4μm/sarcomere 的情况下,重复进行相同的实验(n=8)。与相应的纯等长参考条件相比,所有 32 个心肌肌小节在主动拉伸后表现出增加的力(p<0.05)。此外,当肌小节被 0.4μm/sarcomere 而不是 0.2μm/sarcomere 拉伸时,RFE 的幅度更大(p<0.05)。我们得出结论,与骨骼肌肉一样,RFE 和 PFE 是心肌肌小节的特性,并且取决于拉伸幅度。

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