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Pulsed Electromagnetic Fields
Published in Marko S. Markov, James T. Ryaby, Erik I. Waldorff, Pulsed Electromagnetic Fields for Clinical Applications, 2020
An example of the use of Equation 2.6 to compare the expected efficacy of PRF signals with different pulse modulations, assuming Ca/CaM binding as the transduction pathway, is shown in Figure 2.1a. As may be seen, the rate of Ca2+ binding to CaM is expected to be increased identically using either a 2 ms burst of 27.12 MHz repeating at 1 burst/s with 5 μT peak amplitude (signal A) or a 0.065 ms burst of 27.12 MHz repeating at 1 burst/s with 200 μT peak amplitude (signal B). However, the 0.065 ms burst signal at 5 μT peak amplitude (signal C) is not expected to be effective. This was tested on CaM-dependent myosin light chain kinase (MLCK) in a cell-free enzyme assay for myosin light chain (MLC) phosphorylation (Markov et al., 1994; Pilla, 2006). MLC is a contractile protein of physiological importance in muscle and blood and lymph vessel tone. As may be seen in Figure 2.1b, MLC phosphorylation was increased twofold versus control after a 5 min exposure for signals A and B, whereas there was no significant difference versus shams for signal C, just as predicted by the ECM model.
Functional Properties of Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Ca2+ bind to the protein calmodulin (Section 6.3.1), which activates the enzyme myosin light chain kinase (MLCK). This enzyme phosphorylates the myosin light chain in the myosin head, in the presence of ATP. Only when the myosin head is phosphorylated can it combine with actin to form cross bridges and initiate cross-bridge recycling through ATP splitting. To relax the muscle, the myosin is dephosphorylated by the enzyme myosin light chain phosphatase, which is continuously active in smooth muscle. However, when the concentration of Ca2+ rises, the rate of phosphorylation exceeds that of dephosphorylation and cross-bridge recycling occurs. The converse applies when the concentration of Ca2+ falls.
Proteomic analysis of whole-body responses in medaka (Oryzias latipes) exposed to benzalkonium chloride
Published in Journal of Environmental Science and Health, Part A, 2020
Young Sang Kwon, Jae-Woong Jung, Yeong Jin Kim, Chang-Beom Park, Jong Cheol Shon, Jong-Hwan Kim, June-Woo Park, Sang Gon Kim, Jong-Su Seo
Myosin light chain is a component of myosin, a structural protein important for the formation of thick filaments, and increased myosin light chain protein causes structural changes, such as increased muscle fiber diameter, that promotes myosin ATPase activity.[31] Tropomyosins are a family of actin-binding proteins present in virtually all eukaryotic cells that play a role in muscle relaxation and contraction.[32,33] Our current proteomic study detected increased expression of myosin light chain protein (spot 2) and tropomyosin 1 (spot 7) in medaka exposed to BAC. These results indicated that upregulation of myosin light chain and tropomyosin 1 in BAC-exposed medaka may be a protective response to strengthen the cytoskeleton, which may be compromised by BAC-induced toxicity and oxidative stress.