Independent Active Contraction of Extraocular Muscle Compartments
Independent Active Contraction of Extraocular Muscle Compartments
复制标题
DOI：
10.1167/iovs.14-15968
复制
发表时间：
2015-01-01
影响因子：
4.4
通讯作者：
Demer, Joseph L.
中科院分区：
文献类型：
--
作者：
Shin, Andrew;Yoo, Lawrence;Demer, Joseph L.
目的。水平直肌外肌 (EOM) 的肌内神经支配分为上、下（横向）室，而所有 EOM 也分为全局 (GL) 和眼眶 (OL) 层，分别具有巩膜和滑轮插入。在被动拉伸加载过程中，两种类型的隔室之间的机械独立性已得到证明。我们检查了主动离体收缩过程中 EOM 室之间的耦合。方法。取出新鲜的牛 EOM，并在每个隔室中涂上疏水性凡士林。通过在 38°C 下浸入用荧光素钠染料标记的 50 mM CaCl2 溶液中来诱导未涂层隔室的收缩，而两个隔室中的张力均通过应变计进行监测。对照实验省略了凡士林，使得整个 EOM 收缩。生理实验后，将 EOM 横向切片，以证明蓝光激发的黄色荧光染料对 CaCl2 渗透的特异性。结果。在没有凡士林的对照实验中，横向隔室以及 GL 和 OL 隔室收缩相似。无论是在 GL 或 OL 插入处测量还是在巩膜插入处的横向隔室中测量，选择性地省略凡士林引起明显独立的隔室收缩。尽管发生了一些 CaCl2 扩散，但相对于未涂覆的隔室，涂覆隔室中的平均 (+/- SD) 张力在 GL/OL 和横向隔室中平均分别仅为 10.5 +/- 3.3% 和 6.0 +/- 1.5%。荧光素渗透证实了选择性 CaCl2 渗透。结论。这些数据证实了 EOM 隔室机械独立性的被动拉伸发现，并将结果扩展到主动收缩。 EOM 的行为活跃，就好像由具有不同插入目标的机械独立的平行纤维束组成，与主动滑轮和横向隔室假设一致。
PURPOSE. Intramuscular innervation of horizontal rectus extraocular muscle (EOMs) is segregated into superior and inferior (transverse) compartments, whereas all EOMs are also divided into global (GL) and orbital (OL) layers with scleral and pulley insertions, respectively. Mechanical independence between both types of compartments has been demonstrated during passive tensile loading. We examined coupling between EOM compartments during active, ex vivo contraction.METHODS. Fresh bovine EOMs were removed, and one compartment of each was coated with hydrophobic petrolatum. Contraction of the uncoated compartment was induced by immersion in a solution of 50 mM CaCl2 at 38 degrees C labeled with sodium fluorescein dye, whereas tensions in both compartments were monitored by strain gauges. Control experiments omitted petrolatum so that the entire EOM contracted. After physiological experiments, EOMs were sectioned transversely to demonstrate specificity of CaCl2 permeation by yellow fluorescence dye excited by blue light.RESULTS. In control experiments without petrolatum, both transverse and GL and OL compartments contracted similarly. Selective compartmental omission of petrolatum caused markedly independent compartmental contraction whether measured at the GL or the OL insertions or for transverse compartments at the scleral insertion. Although some CaCl2 spread occurred, mean (+/- SD) tension in the coated compartments averaged only 10.5 +/- 3.3% and 6.0 +/- 1.5% in GL/OL and transverse compartments, respectively relative to uncoated compartments. Fluorescein penetration confirmed selective CaCl2 permeation.CONCLUSIONS. These data confirm passive tensile findings of mechanical independence of EOM compartments and extend results to active contraction. EOMs behave actively as if composed of mechanically independent parallel fiber bundles having different insertional targets, consistent with the active pulley and transverse compartmental hypotheses.