Lean mass dynamics during flight and refueling in migratory birds: causes, consequences, and mechanisms

候鸟在繁殖地和越冬地之间完成长途旅行。 这段旅程包括一系列的长途直飞航班，大多数鸣禽的飞行时间为6-8小时，但有些水鸟可能会持续数天。在飞行过程中，代谢率非常高，候鸟主要用储存的脂肪为这些长途飞行提供燃料。然而，在飞行过程中也会发生蛋白质分解，导致器官和肌肉质量急剧减少。 肌肉和器官质量的这种急剧减少可能导致器官系统的显著功能丧失，但这尚未得到彻底的研究。该项目旨在研究候鸟飞行过程中蛋白质分解的原因、后果和机制。这项研究将进一步深入了解候鸟在飞行中的独特代谢，加深我们对候鸟如何在关键器官系统急剧减少的情况下保持体内平衡的理解，并将为肌肉和器官退化和再生所涉及的分子和生化机制提供新的见解。此外，该项目将提供一个平台，让来自不同背景的许多本科生和研究生参与综合研究，提供广泛的尖端技术的曝光和培训，这些技术将适用于许多STEM领域。这些学生还将为当地低收入学区的中学生制定和实施科学传播和推广计划。在飞行期间，新陈代谢率比休息时高10倍，水分流失率非常高，对鸟类管理水和能量预算的能力提出了极端要求。候鸟主要通过脂肪的氧化为长时间飞行提供燃料，但大量的蛋白质也被分解代谢，导致肌肉和器官质量比飞行前减少20% - 40%。然而，在飞行过程中瘦体重catastrophin的功能限制和潜在的机制仍然不清楚。候鸟将在一个气候控制的风洞中飞行很长一段时间，以评估蛋白质catenories的原因的假设，而蛋白质catenories的后果和机制将通过测量整个动物和组织水平的变化，在关键的生理过程中进行评估，并通过调查在飞行过程中发生的转录差异。这将提供深入了解的生理机制，允许维持体内平衡，尽管戏剧性的器官和肌肉重塑，并将进一步我们的理解的基本机制控制的表型灵活性的脊椎动物。 作为该项目的一部分，研究生和本科生将接受许多尖端技术的综合培训，这将广泛适用于许多STEM职业。这项研究将为许多本科生提供真正的研究经验，重点是提供指导和培训，以鼓励来自代表性不足群体的妇女和学生进一步追求STEM学科的职业生涯。

Migratory birds complete long journeys between the breeding and wintering grounds. This journey is comprised of a series of long-distance non-stop flights that can be 6-8 hours in duration for most songbirds, but could last for days in some shorebirds. During flight, metabolic rate is very high and migratory birds primarily fuel these long flights with stored fat. However, protein breakdown also occurs during flight resulting in dramatic organ and muscle mass reductions. Such dramatic reductions in muscle and organ mass could result in significant functional losses of organ systems but this has not been thoroughly investigated. This project proposes to investigate the causes, consequences, and mechanisms of protein breakdown during flight in migratory birds. This research will further our insight into the unique metabolism of migratory birds in flight, deepen our understanding of how migratory birds maintain homeostasis despite dramatic reductions in critical organ systems, and will provide novel insight into the molecular and biochemical mechanisms involved in muscle and organ degeneration and regeneration. Additionally, this project will provide a platform to engage many undergraduate and graduate students from diverse backgrounds in integrative research, providing exposure and training in a broad range of cutting edge techniques that will be applicable to many STEM fields. These students will also develop and implement science communication and outreach programming for middle school students in a local low-income school district.During flight, metabolic rate is 10-fold higher than at rest and rates of water loss are very high, placing extreme demands on the ability of birds to manage water and energy budgets. Migratory birds fuel long-duration flight primarily by the oxidation of fat, but a large amount of protein is also catabolized, resulting in reductions in muscle and organ mass of 20% - 40% from pre-flight levels. However, the functional limits and underlying mechanisms of lean mass catabolism during flight remain unclear. Migratory birds will be flown in a climatically controlled wind tunnel for extended periods to evaluate hypotheses for the causes of protein catabolism, while the consequences and mechanisms of protein catabolism will be assessed by measuring whole animal and tissue level changes in key physiological processes, and by investigating transcriptional differences that occur during flight. This will provide insight into physiological mechanisms that allow the maintenance of homeostasis despite dramatic organ and muscle remodeling, and will further our understanding of the basic mechanisms controlling phenotypic flexibility in vertebrates. Graduate and undergraduate students will receive integrative training in many cutting-edge techniques as part of this project, which will be broadly applicable to many STEM careers. This research will provide genuine research experiences for many undergraduates with emphasis on providing mentorship and training to encourage women and students from underrepresented groups to further pursue careers in STEM disciplines.