ROLES OF MYOFILAMENT BOUND CALCIUM IN MUSCLE CONTRACTION

本研究的总体长期目标是了解 肌浆游离钙升高调节 收缩脊椎动物横纹肌，特别是，探索 与肌丝结合的钙离子可能调节 由收缩事件调节。待检验的假设提出 钙离子与细丝的结合通过附着 在心肌和骨骼肌中循环连接肌动蛋白。这 提出的现象已被引用为弗兰克的分子基础， Starling关系，并且可能是收缩性的其他特征的基础。 横纹肌事件。这一假设将通过绘制 用定量电子显微镜观察肌节内钙沿着分布 探针X射线显微分析（EPXMA）和元素成像 甘油化兔腰肌冷冻切片，青蛙半腱化， 以及兔子和青蛙的心室小梁。纤维会被冻住 含有或不含MgATP和不同水平的游离钙的溶液。 部分提取TnC和肌球蛋白调节蛋白后纤维的EPXMA 轻链将用于鉴定任何观察到的 在重叠区域的钙结合增强。原钒酸盐或N- 苯基马来酰亚胺将被用来确定的特性， 所以，执着导致了这种现象。任何空间的范围 钙增强将被检查，以确定是否薄 细丝在钙结合方面表现为单个单元，或 其他预测较短合作范围的模型是否 青睐还需要检查的是， 沿着细丝的钙亲和力沿着，与相互作用无关 肌动蛋白和肌球蛋白之间的联系这些研究将提供深入了解 调节骨骼和肌肉中力的激活的基本机制 心肌

The overall long term goal of this research is to understand the mechanisms by which elevation in myoplasmic free calcium regulates contraction of vertebrate striated muscle and in particular, to explore the ways in which calcium binding to myofilaments may modulate and be modulated by the contractile event. The hypothesis to be examined proposes that calcium binding to the thin filament is enhanced by the attachment of cycling crossbridges to actin in both cardiac and skeletal muscle. This proposed phenomenon has been cited as a molecular basis for the Frank- Starling relation, and may underlie other features of the contractile event in striated muscle. This hypothesis will be tested by mapping the distribution of calcium along the sarcomere using quantitative electron probe X-ray microanalysis (EPXMA) and elemental imaging of freeze dried cryosections of glycerinated rabbit psoas muscles, frog semitendinosis, and rabbit and frog ventricular trabeculae. Fibers will be frozen in solutions with or without MgATP and with varying levels of free calcium. EPXMA of fibers following partial extractions of TnC and myosin regulatory light chains would be used to identify the source of any observed enhancement in calcium binding in the overlap region. Orthovanidate or N- phenylmaleimide will be used to determine characteristics of the attachments with lead to this phenomenon. The spatial extent of any calcium enhancement will be examined to determine whether the thin filament behaves as a single unit with respect to calcium binding, or whether other models predicting a shorter range of cooperativity are favored. Also to be examined is whether there are intrinsic variations in calcium affinity along the thin filament, independent of interactions between actin and myosin. These studies will provide insight into the fundamental mechanisms which modulate activation of force in skeletal and cardiac muscle.