Allison Henry earned an Odyssey Grant to undertake a study of the striped dolphin diaphragm this summer. She is comparing the fiber-type profiles (percent slow-twitch fibers) and myoglobin contents of the costal and caval regions of the diaphragm to determine if a sphincter exists around the vena cava where it passes through the diaphragm. A caval sphincter would prevent high pressure blood from returning to the heart during a dive to depth. Allison is determining if there is a larger proportion of slow-twitch fibers and a higher concentration of myoglobin in the caval region, both characteristics of a sphincter.

 
Rachel Lee joined the lab this summer to study the effects of prenatal steroids on the glycogen storage of the guinea pig diaphragm. A study by Tommy Dornhoffer demonstrated that prenatal steroid exposure increased the oxidative capacity of both the slow- and fast-twitch fibers of the guinea pig scalenus. Thus, if prenatal steroids increase the numbers of mitochondria in treated muscles, one would expect the fuel of these organelles, glycogen, to also be increased in concentration in these muscles. Rachel's work will test this hypothesis.

Sophie Moore is volunteering in the lab this summer. Her project is a study of the effects of prenatal steroids on the oxidative capacity of the guinea pig rectus thoracis, an accessory inspiratory muscle. Based on Tommy Dornhoffer's results, we expect that the slow- and fast-twitch fibers in the treated muscles will also display higher oxidative capacities than those in the control muscles. To test this hypothesis, she is staining the muscle for its NADH-TR (oxidative enzyme) activity and measuring the density of staining in the slow- and fast-twitch fibers.

 
Sara Prince is another new student in the lab this summer. She is working to determine the effects of prenatal steroid exposure on the myosin light chain (MLC) and myoglobin expression of guinea pig intercostal muscles. To look at these effects, Sara is running SDS-polyacrylamide gels to separate the low molecular weight proteins in her muscle samples. Soon, she will use densitometry to compare the expression of MLC1, MLC2, and myoglobin between the treated and control muscles. Sara's project is a new direction for the lab, and we are excited to start analyzing her gels.

Ashley Redo also joined the lab this summer to determine if prenatal steroids affect the glycogen storage of the guinea pig rectus abdominis, an accessory expiratory muscle. Based on the work completed by Tommy Dornhoffer, we expect to see increased glycogen storage in the fibers of treated muscles. To test this hypothesis, Ashley is staining treated and control muscle samples for glycogen using the Periodic Acid Schiff reaction. She is then measuring the staining density of the slow- and fast-twitch fibers using Scion Image. Once her data set is complete, she will compare the staining densities of the fibers in control and treated muscles to determine if the treated muscles contain more glycogen.

 
Lance Riley, another new addition to the lab, is working to determine if prenatal steroids increase the fatigue resistance of the guinea pig diaphragm. To test this hypothesis, Lance is hooking up fetal guinea pig diaphragms to a force transducer and electrically stimulating the muscles. After exercising the muscles for two minutes, he will compare the force produced before exercise to the force produced after the exercise is complete. Fatigue resistant muscles will produce a greater percentage of the initial force after exercise than fatiguable muscles.

Josi Robertson was also awarded an Odyssey Grant to determine the role of the scalenus muscle in striped dolphin ventilation. Previous work has shown that muscles that work together to drive ventilation have similar fiber-type profiles (percent slow-twitch) and oxidative capacitites. Thus, Josi is using the myosin ATPase assay to compare the fiber-type profiles of the striped dolphin scalenus and diaphragm. She is also measuring the density of staining of the fibers in these muscles for NADH. Similar fiber-type profiles and NADH staining densities will suggest that the scalenus and diaphragm work together in the striped dolphin to power inspiration.

 
Rebekah Walker joined the lab in the spring of this year. She is studying the effects of prenatal steroids on the oxidative capacity of the guinea pig scalenus muscle, to follow up on Tommy Dornhoffer's project. In addition, Rebekah is helping complete a project looking at the development of breathing muscles in guinea pigs by running myosin heavy chain (MHC) gels. She is also using the MHC gels to determine if prenatal steroid exposure has any affect on the breathing muscles of the pregnant females. Finally, as the laboratory technician for the guinea pig projects, she assists all of the students in the lab with their work.