Meeting Abstract
To combat neonatal respiratory problems, glucocorticoids are frequently given to pregnant mothers at risk of premature delivery. Previous studies have examined the effect of multi-course exposure to these steroids on the fiber diameters, fiber-type profiles, oxidative capacity, and myosin heavy chain isoform expression in the rectus thoracis (RT), an inspiratory muscle, of fetal guinea pigs (Cavia porcellus). However, little is known about how the morphology of these muscles compares to that of the RT of a full term neonate (one-day old). This comparison will allow us to determine if the administration of prenatal steroids accelerates fetal muscle development. Antibody staining was used to identify and quantify the percentages of type IIX and IIA fast-twitch fibers. The diameter of these fibers was then measured using ImageJ. To determine oxidative capacity of the neonatal RT, citrate synthase activity was measured with enzyme kinetic assays. Finally, we assessed the neonatal RT myosin heavy chain profile with 7% acrylamide, 30% glycerol gels. Bands representing fetal, neonatal /IIA/IIX, and slow myosin were identified, and the proportions of each myosin present relative to the total myosin expressed were measured using ImageJ. The neonatal RT features will be compared to those of fetal muscles exposed to prenatal steroids using ANOVAs. If the characteristics of the muscles are not found to be significantly different, these results would support the hypothesis that multi-course prenatal steroids accelerate fetal breathing muscle development. Therefore, it would be suggested that steroid-treated preterm infants would be just as equipped to handle times of respiratory distress as full term infants.
