ELECTRICAL AND CONTRACTILE PROPERTIES OF MUSCLE

在脊椎动物的痉挛肌肉纤维中，收缩通常是由 横管系统膜的去极化。这 导致钙从肌浆网(SR)内部移动 进入肌浆，在那里它可以与肌钙蛋白上的钙调节位点结合 这样就可以发生收缩。这项研究的长期目标 在本应用中是为了了解控制SR CA的因素 放手。其中一个因素是管子两端的电压 膜，由电压传感器(二氢吡啶)监测 受体)HAT位于肾小管膜上。结构性 这种感受器运动的重新排列导致膜内 电荷运动电流，可用电压钳位检测 方法。控制肌浆网钙释放的另一个因素是游离钙的值 [CA]，在肌浆溶液中或在肌浆附近 SR释放点的表面。钙诱导的钙释放可能起到一定的作用 在一些SR钙通道的激活和钙失活中 一旦钙释放充足，可能在关闭肌浆网钙通道中起作用 钙离子已被释放，与肌钙蛋白上的大多数钙调节位点结合。 了解这些过程是了解如何 骨骼肌被激活。 拟议的实验将在青蛙短切抽搐纤维上进行。 安装在一个双凡士林缝隙的腔室中。将引发SR钙释放 通过动作电位或电压钳刺激。在大多数 实验中，释放的量和时间进程将用 EGTA-酚红法。膜内电流变化 运动将用电压钳位法测量。CA发布自 单个SR CA通道将用Fluo-3荧光在 激光扫描共聚焦显微镜，被誉为“钙火花”。其中一些 这些实验应该回答的问题包括： A.钙灭活钙释放是否显著降低脑电活动峰值 正电压阶跃过程中的钙释放？ B.钙失活对钙释放的影响是否减少或消除 SR的含量降低了吗？ C.膜内改变运动是如何调节开机和 关闭钙释放(在没有钙失活影响的情况下 钙的释放)？ D.钙对钙释放的失活是否有助于关闭 动作电位或电压后复极化过程中的钙释放 在具有正常SR钙含量的光纤中的脉冲？ 即重新激活的SR钙通道能够使钙失活 释放？如果是，则是由EGTA屏蔽的单个重新启动的通道 邻近开放渠道的游离[Ca]增加，能够发展 钙失活钙释放？ F.骨骼中单个SR钙通道能记录到钙火花吗 肌肉？如果是这样，它们的空间分布是什么，电压是如何 会影响它们的频率，它们会持续多久？

In vertebrate twitch muscle fibers, contraction is normally activated by a depolarization of the membranes of the transverse tubular system. This leads to a movement of Ca from inside the sarcoplasmic reticulum (SR) into myoplasm where it can bind to the Ca-regulatory sites on troponin so that contraction can occur. The long-term objectives of the research in this application are to understand the factors that control SR CA release. One of these factors is the voltage across the tubular membranes, which is monitored by a voltage sensor (the dihydropyrydine receptor) hat is located in the tubular membranes. Structural rearrangements of movements of this sensor give rise to intramembranous charge movement currents, which can be detected with the voltage-clamp method. Another factor that controls SR Ca release is the value of free [Ca], either in the bulk myoplasmic solution or near the myoplasmic surface of the SR release sites. Ca-induced Ca release may play a role in the activation of some of the SR Ca channels and Ca inactivation of Ca release may play a role in shutting off SR Ca channels once sufficient Ca has been released to bind most of the Ca-regulatory sites on troponin. Understanding these processes is fundamental to understanding how skeletal muscle is activated. The proposed experiments will be carried out on frog cut twitch fibers mounted in a double Vaseline-gap chamber. SR Ca release will be elicited by either action-potential or voltage-clamp stimulation. In most experiments, the amount and time course of release will be measured with the EGTA-phenol red method. Currents from intramembranous change movement will be measured with the voltage-clamp method. Ca release from single SR CA channels will be measured with fluo-3 fluorescence in a laser scan confocal microscope, as "calcium sparks." Some of the questions that the experiments should answer are: A. Does Ca inactivation of Ca release markedly reduce the peak rate of SR Ca release during a positive voltage step? B. Is Ca inactivation of Ca release reduced or eliminated when the Ca content of the SR is reduced? C. How does intramembranous change movement regulate the turning on and turning off of Ca release (in the absence of effects of Ca inactivation of Ca release)? D. Does Ca inactivation of Ca release contribute to the turning off of Ca release during repolarization after an action potential or voltage pulse in a fiber with normal SR Ca content? E. Are reprimed SR Ca channels able to develop Ca inactivation of Ca release? If so, is a single reprimed channel, shielded by EGTA from increases in free [Ca] from neighboring open channels, able to develop Ca inactivation of Ca release? F. Can calcium sparks be recorded from single SR Ca channels in skeletal muscle? If so, what is their spatial distribution, how does voltage affect their frequency, and how long do they last?