Meeting Abstract
Moles have modified forelimbs that allow them to apply remarkably high levels of force per gram body mass. To further understand the high force capabilities of moles, myosin heavy chain (MHC) fiber types were quantified in the star-nosed mole (Condylura cristata). Its hypertrophied pectoral girdle muscles have the advantage of mass for high force and power output, thus we hypothesize that slow MHC-1 and fast, oxidative MHC-2A fibers would best meet the metabolic requirements for locomotion under the surface. Fiber types were determined by protein gel electrophoresis (SDS-PAGE) and histo/immunohistochemical staining techniques, enabling identification of the MHC isoforms expressed. An abundance of fast MHC-2A, 2X, and 2B fibers are distributed in the major limb musculature of C. cristata (N=3), including mm. teres major, pectoralis profundus, triceps brachii, quadriceps femoris, and gastrocnemius. Small amounts of the slow isoform were resolved in the gels of each muscle studied; however, no clear evidence of MHC-1 fibers was determined by either acid-mATPase incubations or reactions with anti-slow antibodies. The findings do not agree with our hypothesis and indicate that contractile properties of fast MHC isoforms contribute to the high out-forces of mole forelimbs. Fast fiber types of moles are additionally found to be moderately oxidative, suggesting that prolonged contractile activity in fast-contracting muscles may be important to thermoregulation in small, burrowing mammals. This finding would also seem to suggest that expression of slow MHC-1 fibers may be derived in larger mammals.
