Tomalka André, Borsdorf Mischa, Böl Markus, Siebert Tobias
Department of Sport and Motion Science, University of Stuttgart, Stuttgart, Germany.
Department of Mechanical Engineering, Institute of Solid Mechanics, Braunschweig University of Technology, Braunschweig, Germany.
Front Physiol. 2017 Oct 18;8:802. doi: 10.3389/fphys.2017.00802. eCollection 2017.
The stomach serves as food reservoir, mixing organ and absorption area for certain substances, while continually varying its position and size. Large dimensional changes during ingestion and gastric emptying of the stomach are associated with large changes in smooth muscle length. These length changes might induce history-effects, namely force depression (FD) following active muscle shortening and force enhancement (FE) following active muscle stretch. Both effects have impact on the force generating capacity of the stomach, and thus functional relevance. However, less is known about history-effects and active smooth muscle properties of stomach smooth muscle. Thus, the aim of this study was to investigate biomechanical muscle properties as force-length and force-velocity relations (FVR) of porcine stomach smooth muscle strips, extended by the analysis of history-effects on smooth muscle force. Therefore, in total = 54 tissue strips were dissected in longitudinal direction from the ventral fundus of porcine stomachs. Different isometric, isotonic, and isokinetic contraction protocols were performed during electrical muscle stimulation. Cross-sectional areas (CSA) of smooth muscles were determined from cryo-histological sections stained with Picrosirius Red. Results revealed that maximum smooth muscle tension was 10.4 ± 2.6 N/cm. Maximum shortening velocity ( ) and curvature factor () of the FVR were 0.04 ± 0.01 [optimum muscle length/s] and 0.36 ± 0.15, respectively. The findings of the present study demonstrated significant ( < 0.05) FD [up to 32% maximum muscle force ( )] and FE (up to 16% ) of gastric muscle tissue, respectively. The FE- and FD-values increased with increasing ramp amplitude. This outstanding muscle behavior is not accounted for in existing models so far and strongly supports the idea of a holistic reflection of distinct stomach structure and function. For the first time this study provides a comprehensive set of stomach smooth muscle parameters including classic biomechanical muscle properties and history-dependent effects, offering the possibility for the development and validation of computational stomach models. Furthermore, this data set facilitates novel insights in gastric motility and contraction behavior based on the re-evaluation of existing contractile mechanisms. That will likely help to understand physiological functions or dysfunctions in terms of gastric accommodation and emptying.
胃作为食物储存库、混合器官以及某些物质的吸收区域，其位置和大小不断变化。在摄入和胃排空过程中，胃的尺寸发生较大变化，这与平滑肌长度的大幅改变有关。这些长度变化可能会引发历史效应，即主动肌肉缩短后出现力降低（FD），主动肌肉拉伸后出现力增强（FE）。这两种效应都会影响胃的力产生能力，进而影响其功能相关性。然而，关于胃平滑肌的历史效应和主动平滑肌特性，我们了解得较少。因此，本研究的目的是通过分析历史效应如何影响平滑肌力，来研究猪胃平滑肌条的生物力学肌肉特性，即力-长度关系和力-速度关系（FVR）。为此，总共从猪胃的腹侧胃底纵向解剖出54条组织条。在肌肉电刺激过程中，执行了不同的等长、等张和等动收缩方案。通过用天狼星红染色的冷冻组织学切片确定平滑肌的横截面积（CSA）。结果显示，平滑肌的最大张力为10.4±2.6N/cm。FVR的最大缩短速度（）和曲率因子（）分别为0.04±0.01[最佳肌肉长度/秒]和0.36±0.15。本研究结果分别证明了胃肌肉组织存在显著的（<0.05）FD[高达最大肌肉力（）的32%]和FE（高达的16%）。FE和FD值随斜坡幅度的增加而增加。这种出色的肌肉行为在目前的现有模型中尚未得到解释，有力地支持了对胃独特结构和功能进行整体反映的观点。本研究首次提供了一套全面的胃平滑肌参数，包括经典的生物力学肌肉特性和历史依赖性效应，为计算胃模型的开发和验证提供了可能性。此外，该数据集通过对现有收缩机制的重新评估，有助于对胃运动和收缩行为有新的见解。这可能有助于从胃容纳和排空的角度理解生理功能或功能障碍。
