Regulation of Intracardiac Shunting in Chelonians

海龟（龟类）表现出非凡的生存能力， 没有呼吸的时间 例如在水中潜水时， 海龟，呼吸暂停1至2小时已被观察到。 器官 在海龟的呼吸过程中起着关键作用 潜水时的能力是心脏。 乌龟的心脏是 由仅3个腔室组成（与哺乳动物的4个腔室相比 人）。 独特的解剖结构使得血液 从体内返回，通过肺部循环， 绕过肺部 当血液绕过肺部时， 从右到左的心内分流 之前的科学 调查报告称，绕过 肺常伴以右向左的呼吸模式， 呼吸时分流增加。 相反，在呼吸过程中， 循环到肺部的血液量增加， 向左分流减少。 而一个大的右向左分流 对哺乳动物和人类产生有害的影响， 绕过肺部可能会发挥几个重要作用， 呼吸困难 这些措施包括减少能源消耗的 心脏，“计量”来自肺部的氧气（类似于水肺 罐）和维持肺和血液之间的液体平衡。 然而，海龟的心脏能够 实现不同水平的血液分流一直是有争议的， 没有很好地理解。 希克斯博士提出的研究将利用 结合先进的放射技术，血流 测量和注射示踪气体以成像心脏， 确定在各种不同的时间段内通过心脏的血流模式， 生理条件。 这些技术和实验 希克斯博士的建议中概述的将决定血液的过程 分流由心脏外部的因素（即， 肺的调节）或心脏固有的因素， 了解心血管疾病的进化发展 脊椎动物的系统。 他对这一机制的阐述 爬行动物的血液分流将有助于回答 血液分流在这个古老但重要的 一群动物。

Turtles (chelonians) exhibit the remarkable ability to survive long periods without breathing. For example during diving in aquatic turtles, breatholds for 1 to 2 hours have been observed. The organ that plays a critical role in the turtles remarkable breatholding ability during diving is the heart. The heart of the turtle is comprised of only 3 chambers (as compared to the 4 chambers of mammals and humans). The unique anatomy results in the potential for the blood returning from the body to either circulate through the lungs or to bypass the lungs. When the blood bypasses the lungs it is referred to as a right-to-left intracardiac shunt. Previous scientific investigations have reported that the amount of blood bypassing the lung is often coupled with ventilatory patterns, with the right-to-left shunt increasing during breatholding. In contrast, during breathing the amount of blood circulating to the lungs increases and the right- to-left shunt is reduced. While a large right-to-left shunt would produce harmful results in mammals and humans, the ability of reptiles to bypass the lungs may play several important roles during breatholding. These include reducing the energy expenditure of the heart, the "metering" of oxygen from the lung (analogous to a scuba tank) and maintaining the balance of fluids between the lung and blood. However, the precise process by which the heart of turtles can accomplish varying levels of blood shunting have been controversial and not well understood. The study proposed by Dr. Hicks will utilize a combination of sophisticated radiological techniques, blood flow measurements and injections of tracer gases to image the heart and determine blood flow patterns through the heart during a variety of physiological conditions. These techniques and the experiments outlined in Dr. Hicks' proposal will determine if the process of blood shunting results either from factors external to the heart (i.e. regulation by the lung) or factors intrinsic to the heart to understanding the evolutionary development of the cardiovascular system in vertebrate animals. His elucidation of the mechanism of blood shunting in reptiles will help to answer the question of what functional role blood shunting plays in this ancient but important group of animals.