Mechanical loads play a pivotal role in the growth and maintenance of bone and joints. Although loading can activate anabolic genes and induce bone remodeling, damping is essential for preventing traumatic bone injury and fracture. In this study we investigated the damping capacity of bone, joint tissue, muscle, and skin using a mouse hindlimb model of enhanced loading in conjunction with finite element modeling to model bone curvature. Our hypothesis was that loads were primarily absorbed by the joints and muscle tissue, but that bone also contributed to damping through its compression and natural bending. To test this hypothesis, fresh mouse distal lower limb segments were cyclically loaded in axial compression in sequential bouts, with each subsequent bout having less surrounding tissue. A finite element model was generated to model effects of bone curvature in silico. Two damping-related parameters (phase shift angle and energy loss) were determined from the output of the loading experiments. Interestingly, the experimental results revealed that the knee joint contributed to the largest portion of the damping capacity of the limb, and bone itself accounted for approximately 38% of the total phase shift angle. Computational results showed that normal bone curvature enhanced the damping capacity of the bone by approximately 40%, and the damping effect grew at an accelerated pace as curvature was increased. Although structural curvature reduces critical loads for buckling in beam theory, evolution apparently favors maintaining curvature in the tibia. Histomorphometric analysis of the tibia revealed that in response to axial loading, bone formation was significantly enhanced in the regions that were predicted to receive a curvature-induced bending moment. These results suggest that in addition to bone’s compressive damping capacity, surrounding tissues, as well as naturally-occurring bone curvature, also contribute to mechanical damping, which may ultimately affect bone remodeling and bone quality.
Western blotting is a popular technique for examining expression levels of proteins using gel-based electrophoretic fractionation followed by blotting and antibody reactions. Although this is a mature technique, one of the major limitations is the need to prepare an individual electrophoretic gel for each of the protein species to be analyzed. Since most analyses require the detection of multiple protein species, a procedure that allows utilization of a single gel for detecting multiple protein species should significantly save time and resources. In this paper, we developed a novel multiprotein detection device, which enabled simultaneous detection of several proteins species from a single electrophoretic gel. In this device, a protein transfer unit utilized a multi-anode plate that generated a non-uniform voltage profile. This voltage profile enabled uniform transfer regardless of molecular mass of proteins. <i>In vitro </i> experiments using samples, isolated from boneforming osteoblast cells, showed that the expression levels of 5 - 7 different proteins were detectable in the presence and absence of mechanical stimulation that activated genes necessary for bone formation. The result supports the notion that through simultaneous detection of multiple protein species, the described device contributes to reduction in procedural time and sample amounts, as well as a removal of variations among multiple gels
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