HETEROGENEITY OF EMBRYONIC CHICK MYOCARDIUM

胚胎心血管系统在结构和功能上同时调节着剧烈的转变。这一过程对于实现成熟心脏的复杂三维几何和功能至关重要，这一过程中的错误/失败是先天性心血管畸形的一种被提出的发病机制。这个修订后的建议代表了一种新的方法来定义机械负荷条件的特定变化如何改变区域CV收缩性，肌上皮Ca2+电流和肌细胞被动和主动特性。1 .定义18至34期鸡胚胎在正常发育、重新分配的预负荷（LA结痂）或增加的后负荷（CT带）期间的机械壁应变、心肌收缩力和Cab电流之间的关系，以确定响应改变的机械负荷而发生的功能适应的时间过程、位置和程度。假设1 - 1。通过2D和/或3D心外膜应变测量的局部心室机械负荷增加增加了体内收缩壁应力-应变关系和收缩力（Eav-max）以及体外力-长度、力-频率和力-速度关系测量的局部胚胎收缩力。假设1 - 2。增加的机械负荷增加胚胎t型和l型Ca2+电流，通过同时测量体外力-长度关系和细胞内Ca2+（条）来定义；全细胞膜片钳和Ca2+成像和Ni2+，米贝弗拉地尔，硝苯地平和瑞诺定阻断（条和细胞）。具体目标2。定义18 - 34期鸡胚胎在正常发育、重新分配的预负荷（LA结扎）或增加的后负荷（CT带）期间的机械壁应变、肌纤维和胶原排列以及粘弹性特性之间的关系，补充体内和体外研究。假设2 - 1。增加的心室机械负荷加速并重新分配肌纤维排列。假设2 - 2。增加的心室机械负荷降低了被动壁应力-应变关系计算的顺应性（体外有限元伪应变能密度函数），增加了胶原蛋白含量和排列。意义：这项修订的提案测试了机械负荷、心肌功能、肌纤维和基质结构之间的特定关系，并为未来的实验提供了重要的基础，以确定在发育中的心肌中传导机械力的细胞内机制（基因、蛋白质、反式激活因子）。

Embryonic cardiovascular systems regulate dramatic transitions in structure and function simultaneously. This process is critically important to achieve the complex 3D geometry and function of the mature heart and errors/failures in this process are one proposed pathogenetic mechanism for congenital cardiovascular malformations. This revised proposal represents an novel approach to define how specific changes in mechanical loading conditions alter regional CV contractility, sarcolemmal Ca2+ currents and myocyte passive and active properties. Specific Aim I. Define the relationship between mechanical wall strain, myocardial contractility, and Cab currents in stage 18 to 34 chick embryos during normal development, redistributed preload (LA ligation) or increased afterload (CT band) to define the time-course, location, and extent of functional adaptation that occurs in response to altered mechanical load. Hypothesis 1-1. Increased regional ventricular mechanical load measured as 2D and/or 3D epicardial strain increases local embryonic contractility measured as in vivo systolic wall stress- strain relations and contractility (Eav-max) and in vitro force-length, force-frequency, and force-velocity relations. Hypothesis 1-2. Increased mechanical load increases embryonic T-type and L-type Ca2+ currents as defined by simultaneous measurement of in vitro force-length relations and intracellular Ca2+ (strips); whole-cell patch clamp and Ca2+- imaging and Ni2+, mibefradil, nifedipine, and ryanodine blockade (strips and cells). Specific Aim 2. Define the relationship between mechanical wall strain, myofiber and collagen alignment, and viscoelastic properties in stage 18 to 34 chick embryos during normal development, redistributed preload (LA ligation) or increased afterload (CT band), complementing both in vivo and in vitro studies. Hypothesis 2-1. Increased ventricular mechanical load accelerates and redistributes myofiber alignment. Hypothesis 2-2. Increased ventricular mechanical load decreases compliance calculated from passive wall stress-strain relations (in vitro, finite element pseudo-strain energy density function) and increases collagen content and alignment. Significance: This revised proposal TESTS specific relationships between mechanical load, myocardial function, and myofiber and matrix architecture in the developing heart and provides a critical foundation for future experiments to identify the intracellular mechanisms (genes, proteins, trans-activating factors) that transduce mechanical forces in the developing myocardium.