No description available.

No description available.

No description available.

"The class IX myosin is a member of the myosin superfamily and found in variety of tissues. Myosin IX is quite unique among the myosin superfamily in that the tail region contains a GTPase activating protein (GAP) domain for the small GTP-binding protein, Rho. Recently it was reported that myosin IX shows processive movement that travels on an actin filament for a long distance. This was an intriguing discovery, because myosin IX is a “single-headed” myosin unlike other processive myosins which have “double-headed” structure. It has been thought that “processive” motors walk on their track with their two heads, thus traveling for a long distance. Therefore, it is reasonable to expect that the processive movement of single headed myosin IX is based on the unique feature of myosin IX motor function. In this study, I investigated the mechanism of processive movement of single-headed myosins by analyzing the mechanism of ATPase cycle of myosin IX that is closely correlated with the cross-bridge cycle (the mechanical cycle of actomyosin). In the first part, I performed the transient enzyme kinetic analysis of myosin IX using the motor domain construct to avoid the complexity raised by the presence of the tail domain. It was revealed that the kinetical characteristics of myosin IX ATPase is quite different from other processive myosins. It was particularly notable that the affinity of the weak actin binding state of Myosin IX was extremely high comparing with known myosins. It is thought that the high affinity for actin throughout the ATPase cycle is a major component to explain the processive movement of myosin IX. In the second part of this study, I cloned full length human myosin IX construct to further investigate the regulation of motor activity of myosin IX. It was revealed that the basal ATPase activity but not the actin dependent ATPase activity of myosin IX is inhibited by its tail region. Furthermore full-length myosin IX is regulated by calcium, presumably due to the calcium binding to the CaM light chain. These result suggest that the tail domain serves as a regulatory component of myosin IX."

Satellite cells (SCs) are mononuclear myogenic stem cells located between the basal lamina and plasmalemma of the skeletal muscle fiber. They are responsible for postnatal skeletal muscle growth, repair and regeneration. Once activated, SCs divide and fuse to the muscle fibers where their nuclei become new myonuclei. Earlier studies suggested that SCs were either randomly or evenly distributed along muscle fibers. However, myonuclei were found to be more concentrated at tapered ends of muscle fibers. Myogenic regulatory factors, mainly MyoD and Myogenin, are expressed by active SCs. Previous in vitro and prenatal studies suggested that MyoD expression demarcates the end of proliferation while Myogenin can demarcate the differentiation stage within myoblasts. Few in vivo studies have reported the expression of MyoD and Myogenin within SCs, and none have attempted to discern their expression patterns during growth. Meat producing chickens represent a unique model for natural hypertrophy within muscle fibers. However, very little is known about the distribution of SCs within these naturally hypertrophied fibers, and whether this distribution is comparable to that of experimental models of hypertrophy. Nandrolone Decanoate is the anabolic steroid most commonly used to increase skeletal muscle mass and strength, although little is known of its effects on SCs. This thesis expands our understanding of SCs by examining the following hypotheses: 1) there is a greater frequency (number of SC nuclei over all nuclei within the basal laminae) and a higher concentration (less surface area of sarcolemma per SC) of SCs at the ends of developing skeletal muscle fibers, 2) MyoD and Myogenin transcription myogenic factors have distinctive patterns of expression within SC nuclei during maturation, 3) there are greater frequency and concentration of SCs and greater number of myonuclei in naturally hypertrophied muscle fibers compared to their control, and 4) there is a greater frequency and a greater concentration of SCs in Nandrolone treated birds than in controls. Chicken pectoralis muscle was the main experimental model used in this thesis because of its overlapping fibers arranged in series, the presence of neonatal myosin at the fiber ends and relative homogeneity of fiber type. Immunocytochemical techniques that include an antibody against Pax7 to identify SC nuclei were applied, and computer image analyses were then used to quantify the numbers of SC nuclei and myonuclei within muscle fibers. This thesis demonstrates that throughout development there is a greater frequency and concentration of SCs at the ends of developing skeletal muscle fibers, which indicates a major contribution of these cells in the longitudinal growth of muscle fibers. It also reveals that MyoD and Myogenin each has a distinctive pattern of expression within SCs during in vivo postnatal development. The expression of MyoD increases significantly during maturation, while Myogenin expression remains steady. This finding suggests that each of these myogenic factors play a different role in the postnatal activation of SCs. Lastly, it is the first study to show a greater frequency and a higher concentration of SCs within both naturally and Nandrolone induced hypertrophied muscle fibers. This indicates SCs may be critically involved during postnatal skeletal muscle growth and hypertrophy.

Satellite cells (SCs) are mononuclear myogenic stem cells located between the basal lamina and plasmalemma of the skeletal muscle fiber. They are responsible for postnatal skeletal muscle growth, repair and regeneration. Once activated, SCs divide and fuse to the muscle fibers where their nuclei become new myonuclei. Earlier studies suggested that SCs were either randomly or evenly distributed along muscle fibers. However, myonuclei were found to be more concentrated at tapered ends of muscle fibers. Myogenic regulatory factors, mainly MyoD and Myogenin, are expressed by active SCs. Previous in vitro and prenatal studies suggested that MyoD expression demarcates the end of proliferation while Myogenin can demarcate the differentiation stage within myoblasts. Few in vivo studies have reported the expression of MyoD and Myogenin within SCs, and none have attempted to discern their expression patterns during growth. Meat producing chickens represent a unique model for natural hypertrophy within muscle fibers. However, very little is known about the distribution of SCs within these naturally hypertrophied fibers, and whether this distribution is comparable to that of experimental models of hypertrophy. Nandrolone Decanoate is the anabolic steroid most commonly used to increase skeletal muscle mass and strength, although little is known of its effects on SCs. This thesis expands our understanding of SCs by examining the following hypotheses: 1) there is a greater frequency (number of SC nuclei over all nuclei within the basal laminae) and a higher concentration (less surface area of sarcolemma per SC) of SCs at the ends of developing skeletal muscle fibers, 2) MyoD and Myogenin transcription myogenic factors have distinctive patterns of expression within SC nuclei during maturation, 3) there are greater frequency and concentration of SCs and greater number of myonuclei in naturally hypertrophied muscle fibers compared to their control, and 4) there is a greater frequency and a greater concentration of SCs in Nandrolone treated birds than in controls. Chicken pectoralis muscle was the main experimental model used in this thesis because of its overlapping fibers arranged in series, the presence of neonatal myosin at the fiber ends and relative homogeneity of fiber type. Immunocytochemical techniques that include an antibody against Pax7 to identify SC nuclei were applied, and computer image analyses were then used to quantify the numbers of SC nuclei and myonuclei within muscle fibers. This thesis demonstrates that throughout development there is a greater frequency and concentration of SCs at the ends of developing skeletal muscle fibers, which indicates a major contribution of these cells in the longitudinal growth of muscle fibers. It also reveals that MyoD and Myogenin each has a distinctive pattern of expression within SCs during in vivo postnatal development. The expression of MyoD increases significantly during maturation, while Myogenin expression remains steady. This finding suggests that each of these myogenic factors play a different role in the postnatal activation of SCs. Lastly, it is the first study to show a greater frequency and a higher concentration of SCs within both naturally and Nandrolone induced hypertrophied muscle fibers. This indicates SCs may be critically involved during postnatal skeletal muscle growth and hypertrophy.

Nanoscale biological systems operate in the presence of overwhelming viscous drag and thermal diffusion, thus invalidating the use of macroscopically oriented thinking to explain such systems. Rectified Brownian motion (RBM), in contrast, is a distinctly nanoscale approach that thrives in thermal environments. The thesis discusses both the foundations and applications of RBM, with an emphasis on nano-biology. Results from stochastic non-equilibrium steady state theory are used to motivate a compelling definition for RBM. It follows that RBM is distinct from both the so-called power stroke and Brownian ratchet approaches to nanoscale mechanisms. Several physical examples provide a concrete foundation for these theoretical arguments. Notably, the molecular motors kinesin and myosin V are proposed to function by means of a novel RBM mechanism: strain-induced bias amplification. The conclusion is reached that RBM is a versatile and robust approach to nanoscale biology.

Thesis (M.S.) --Marshall University, 2008. / Title from document title page. Includes abstract. Document formatted into pages: contains 51 pages. Includes bibliographical references (p. 37-38).

Thesis (M.S.) --Marshall University, 2008. / Title from document title page. Includes abstract. Document formatted into pages: contains 51 pages. Includes bibliographical references (p. 37-38).

Thesis (M.S.)--Marshall University, 2009. / Title from document title page. Includes abstract. Document formatted into pages: contains viii, 74 p. Includes bibliographical references p. 39-42.