Developing a Comprehensive Physical Model of Lymph Flow in Amphibians

这项工作的目的是发展一个全面的物理了解淋巴如何移动无尾两栖动物（青蛙和蟾蜍），并调查解剖和生理控制系统，导致淋巴的运动变化。淋巴液是由于心脏产生的流体静压而从循环系统的毛细血管过滤到组织间隙中的流体。淋巴系统的主要作用是将这些液体返回循环。如果淋巴系统的这种功能作用被阻止，液体从循环中流失，就像出血一样，心血管功能下降，最终导致循环休克。无尾两栖动物形成淋巴液的速度大约是哺乳动物的十倍。因此，淋巴液返回循环系统是维持血容量的一个更关键的变量。两栖动物，相对于所有的脊椎动物类，具有最快速的代偿能力，以补充失去的血容量与淋巴和这种淋巴动员能力的变化与物种的陆生程度。了解淋巴如何移动不仅对我们了解两栖动物在器官系统水平上的功能至关重要，而且有助于我们了解陆地环境殖民化中涉及的适应性。因此，两栖动物代表了一个很好的进化模型系统，用于研究淋巴动员如何调节血容量的比较机制。目前的淋巴运动模型从物理角度来看是站不住脚的。工作假设是淋巴响应于由两种机制产生的压力差而移动，淋巴囊的区室化产生不同顺应性的囊，骨骼肌收缩改变淋巴囊顺应性。顺应性是淋巴囊中淋巴体积和压力之间的关系。这些骨骼肌中的许多的主要功能可能仅与淋巴运动有关，并且可能代表骨骼肌流体泵的第一个脊椎动物示例。将使用染料标记的血浆描绘淋巴运动的路径，将通过植入的插管监测这些路径中的压力，并通过植入电极记录的EMG监测骨骼肌收缩。还将研究血容量状态如何影响淋巴囊压力和骨骼肌活动。然后将收集比较解剖数据，以测试哪些物种的解剖差异与淋巴流量的差异相关。

The objective of this work is to develop a comprehensive physical understanding of how lymph moves in anuran amphibians (frogs and toads) and investigate the anatomical and physiological control systems which lead to variations in the movement of lymph. Lymph is the fluid that filters from the capillaries of the circulatory system into the interstitial space as a consequence of the hydrostatic pressure generated by the heart. The principal role of the lymphatic system is to return this fluid back into the circulation. If this functional role of the lymphatic system is prevented, fluid is lost from the circulation much like a hemorrhage, and cardiovascular function declines eventually leading to circulatory shock. Anuran amphibians form lymph, at about ten times the rate of mammals. Hence the return of lymph to the circulatory system is an even more critical variable to their maintenance of blood volume. Amphibians, in relation to all vertebrate classes, have the most rapid compensatory ability to replace lost blood volume with lymph and this lymph mobilization capacity varies with a species' degree of terrestriality. Understanding how lymph moves is fundamental not only to our understanding of how amphibians function at an organ system level, but also aids our understanding of what adaptations are involved in the colonization of terrestrial environments. Consequently, amphibians represent an excellent evolutionary model system for studying comparative mechanisms involved in how lymph mobilization regulates blood volume. Current models of lymph movement are untenable from a physical perspective. The working hypothesis is that lymph moves in response to pressure differences created by two mechanisms, compartmentalization of lymph sacs creating sacs of different compliance and skeletal muscle contractions varying lymph sac compliance. Compliance is the relationship between lymph volume and pressure in a lymph sac. The primary function of many of these skeletal muscles may be solely tied to lymph movement and may represent the first vertebrate example of skeletal muscle fluid pumps. The pathways for lymph movement will be delineated using dye-labeled plasma, the pressures in these pathways will be monitored via implanted cannulae and skeletal muscle contraction monitored via EMGs recorded from implanted electrodes . How blood volume status influences the lymph sac pressures and skeletal muscle activities will also be investigated. Comparative anatomical data will then be collected to test what species' anatomical differences correlate with differences in lymph flow.