My research focuses on the neuromuscular biology of feeding and locomotion from the perspectives of both evolutionary morphology and function. In my laboratory, we are currently studying the structural and functional changes that occur in skeletal muscles during masticatory maturation from infant suckling to chewing of solid food. This behavioral transition during early ontogeny occurs in most mammals, including humans. Newborn infant miniature pigs are the animals of choice for this kind of study because of their unique behavioral similarity to, and morphological convergences with, humans. Data collection includes electromyographic (EMG) recordings from masticatory muscles during feeding, histo- and immunocytochemistry assays of frozen serial sections, and SDS-PAGE electrophoresis of single muscle fibers.
Age-related differences in relative proportions of slow and fast twitch muscle fibers in pigs raised on normal diets are compared to age-related differences in EMG patterns that occur when subjects eat foods of varying consistencies. The results are compared with those from a control group raised on a liquefied, but nutritionally equivalent, diet to assess any facultative effects of food resistance on the otherwise genetic control of fiber type development.
Conclusions drawn from this kind of study are clinically applicable toward modulating the design of prosthetic devices and rehabilitative regimens, particularly with regard to infants and children. Further exploration of specific questions generated by the current study will address (1) the physiologic mechanisms that regulate intramuscular motor unit recruitment, using a combination of electrophysiology, glycogen depletion, and retrograde labeling of motoneurons and (2) the genetic control of fiber type transformation during ontogeny, using in situ hybridization of messenger RNA.