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A Review of the Technologies and Methodologies Used to Quantify Muscle-Tendon Structure and Function
Published in Cornelius Leondes, Musculoskeletal Models and Techniques, 2001
Sarcomeres are the basic units of shortening and force generation and thus have numerous structures of functional importance. The Z-line is a highly organized structure that interconnects the thin filaments in a very precise array. The M-line is presumed to be responsible for binding the thick filaments and maintaining them in a hexagonal pattern when viewed in a transverse plane. The thick filaments contain myosin molecules which perform several tasks. The HMM portion of myosin is often referred to as the cross-bridge because it is the structure that reaches out and binds to actin during contraction. The HMM-LMM interface is flexible, allowing the S1 portion of HMM to project out about 55 nm8 to reach a thin filament. S1 contains binding sites for two light chains: ATP and actin. Thin filaments play an equally important role in force production. Actin monomers have binding sites compatible with regions of the S1 portion of myosin. These binding sites are normally covered by tropomyosin during rest conditions. However, in the presence of calcium, troponin C, which is sensitive to calcium ion binding, causes troponin I to produce a conformational change in tropomyosin which then exposes the myosin binding sites. Troponin T functions to regulate troponin-tropomyosin binding. Two final structures that may have functional importance are nebulin and titin. Nebulin runs parallel to the actin filaments and may function in length determination during assembly. Titin is a relatively large elastic filament that stretches from M-line to Z-line. It provides passive elasticity and helps to keep the A-band centralized.8
Conditioned medium from the three-dimensional culture of human umbilical cord perivascular cells accelerate the migration and proliferation of human keratinocyte and fibroblast
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Min Ho Kim, Wen Hao Wu, Jee Hyun Choi, Ji Hyun Kim, Seok-Ho Hong, Jin Hyun Jun, Yong Ko, Jong Hun Lee
Although a significant difference was not detected in the proliferation of HDFs, the PVC-conditioned medium obtained from a more physiological environment was more effective in the proliferation and migration tests of cell lines than PVC-CM-2D (Figures 3, 4), suggesting that the two systems have different protein profiles. This finding led to further analyses of PVC-CM using 2D electrophoresis and MALDI-TOF (Figure 5, Table 1). PVC-CM-3D contained higher amounts of type I collagen and myosin heavy chain than PVC-CM-2D. The collagen provides cells with environments that mimic the extracellular matrix (ECM) of human skin; ECM has been regarded as very important for cellular adhesion, proliferation, and migration. It is therefore believed that this protein affects the proliferation and migration of keratinocytes and fibroblasts. KIAA0465, N-RAP, and thioredoxin are exclusively expressed in PVC-CM-3D. KIAA0465, which is also called ‘MACF1’, is a member of a family of proteins that form bridges between different cytoskeletal elements. This protein facilitates actin-microtubule interactions at the cell periphery and couples the microtubule network to cellular junctions. Moreover, KIAA0465 is involved in the organization of the cytoskeleton [30], tissue repair [31], and vertebrate development [32]. N-RAP is a nebulin family member that acts as an organizing center for the initial recruitment and assembly of sarcomeric actin filaments and Z-discs [33]. Thioredoxins are proteins that act as antioxidants by facilitating the reduction of other proteins by cysteine thiol-disulfide exchange. Thioredoxins are found in nearly all known organisms and are essential for life in mammals [34]. Recently, Telorack et al. (2016) reported that a glutathione-Nrf2-thioredoxin cross-talk ensures keratinocyte survival and efficient wound repair [35]. These reports indicate that type I collagen, KIAA0465, N-RAP, and thioredoxin are involved not only in the proliferation, migration, and adhesion of human keratinocytes and fibroblasts, but also in the wound-healing process.