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Cardiac Function

Lead Graduate Student: James Kezos

Background: Stress affects both vertebrate and invertebrate organisms throughout their lifetime, and both groups experience and defend against similar stressors, sometimes using the same physiological processes. Adapting to stress can create advantages and disadvantages that may be utilized in experimental evolution studies, such as those focusing on circulatory systems. Vertebrates and invertebrates both have a circulatory system required for numerous physiological processes, although the system can vary in complexity. Invertebrate hearts differ in shape from vertebrate hearts, however, the function and early formation of the hearts are similar. A decline in cardiac function with increasing age has been observed in both vertebrates and invertebrates, implying the potential for parallel genetic and physiological functions between these two groups.  Similar to vertebrates, the invertebrate heart and its open circulatory system function together with multiple physiological systems.

Research Objectives:  The proposed experiments on short-lived lines and long-lived lines in Drosophila will aim to (1) examine the relationships of cardiac function, life-history characters, stress resistance, and athletic performance, (2) conduct multiple manipulative assays to observe the effects of different stresses on cardiac and athletic fitness, (3) develop two new assays: a mass electrocution assay, and a cardiac cage assay to electrically pace and measure athletic performance on hundreds of flies at a single time, respectively, and (4) develop a manipulative assay as a selection protocol for improved fitness and cardiac function.  Determining such physiological interactions should provide useful insights for understanding cardiac function, and its age-related decline in both invertebrates and vertebrates.

Methods and Analysis: We currently utilized two assays: (1) the electrical pacing assay, and (2) the flight exhaustion assay. The electrical pacing assay allow us to measure cardiac performance by applying a cardiac stress on the flies, and monitoring whether the flies’ hearts exhibit cardiac arrest, uncoordinated fibrillation, or return to a state of repeated, productive contractions. In tethered-flight exhaustion assays, a monofilament string is pinned to the dorsal side of a Drosophila’s thorax, the flight reaction is then stimulated through a vibration, and the flight duration time is then recorded. By conducting the electric pacing and flight exhaustion assays, as well as manipulative experiments, we can begin to understand the physiological relationship between cardiac function, athletic fitness and other life-history characteristics such as fecundity, longevity and stress resistance.

Intellectual Merit: My research may be beneficial for further understanding how the circulatory system and cardiac function in Drosophila interact and function with other physiological processes. This project examines the physiological interactions of cardiac function, athletic performance, and stress resistance in Drosophila. By applying a stress on one of these systems, and observing how that stress affects other physiological systems, we can further understand how these systems interact with each other.

Broader Impacts:  The results from these physiological experiments can possibly be applied to cardiac function studies in vertebrates, including humans.  Information can be obtained as to how the heart changes in the short run and the long run in response to a novel or stressful environment.  Establishing a selection regime with improved cardiac function can be beneficial, especially with the emergence of more readily available genomic analysis. The results can be applied in a broader context, such as diminishing the effect of cardiovascular disease and related defects in both invertebrates and vertebrates.

 

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