Effects of 50 Hz sinusoidal magnetic field on Ca2+ release channel ryanodine receptor of sarcoplasmic reticulum vesicles / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the effects of sinusoidal magnetic field on isolated sarcoplasmic reticulum (SR) calcium release channel (RyR1) function.</p><p><b>METHODS</b>With the Ca2+ dynamic spectrum and isotope labeled methods, the Ca2+ release and [(3)H]-Ryanodine binding, the initial rates of NADH oxidation and the production of superoxide of SR exposed to 50 Hz sinusoidal magnetic field (MF) were investigated respectively.</p><p><b>RESULTS</b>0.4 mT, 50 Hz sinusoidal MF exposure for 30 min increased SR Ca2+ release initial rate about 35% from (10.82 +/- 0.89) pmol.mg(-1) pro.s(-1) to (14.69 +/- 1.21) pmol.mg(-1) pro.s(-1); and the [(3)H]-Ryanodine binding by about 15% from (2.13 +/- 0.05) pmol/mg pro to (2.45 +/- 0.07) pmol/mg pro, which regulated by 1 mmol/L NADH with 1 mmol/L NAD+. Meanwhile MF upregulated the rate of NADH oxidation by about 22% from (0.88 +/- 0.11) x 10(-4) FI/s to (1.07 +/- 0.13) x 10(-4) FI/s and upregulated the production of superoxide by about 32% from (0.99 +/- 0.09) x 10(-5) FI/s to (1.31 +/- 0.06) x 10(-5) FI/s.</p><p><b>CONCLUSION</b>0.4 mT sinusoidal MF increases the activity of RyR1 within the low redox potential environment, and promotes NADH oxidase activity and superoxide production.</p>

Effect of 50 Hz power frequency magnetic field on microfilament cytoskeleton assembly of human amnion FL cells / 中华预防医学杂志

<p><b>OBJECTIVE</b>Investigations were carried out to understand the effect of 50 Hz power frequency magnetic field on microfilament assembly of human amniotic cells and on expression of actin and epidermal growth factor receptor.</p><p><b>METHODS</b>Human amnion FL cells were exposed to 0.1, 0.2, 0.3, 0.4, 0.5 mT power frequency magnetic field for 30 minutes. Microfilaments were marked using Phalloidin-TRITC, and then were observed under a fluorescence microscope. An optical method was used to detect the relative content of microfilament in cells. A scanning electron microscope was used to detect the cell shape. The content of actin and epidermal growth factor receptor in the preparation of the detergent-insoluble cytoskeleton were measured by western-blotting to analyse the potential mechanism of the change induced by magnetic field.</p><p><b>RESULTS</b>Intracellular stress fibers were found to decrease after exposing cells to a 0.2 mT power frequency magnetic field for 30 minutes. New microfilament and filopodia bundles appeared at the cell periphery after exposure, but the detected total F-actin content per cell was not significantly changed, detected by a F-actin-specific dye. The change in the amount of microfilaments caused by the field could be recovered 2 hours later when the field was withdrawn. The mean height of microfilament cytoskeleton decreased from (12.37 +/- 1.28) microm to (9.97 +/- 0.38) microm (t = 6.96, P > 0.05) after exposure using a confocal microscope. The cell shapes became more flat and lamellipodia appeared after exposure observed by a scanning electron microscope. By using Western blotting method, the intracellular contents of epidermal growth factor receptor and of actin in the preparation of the detergent-insoluble cytoskeleton which are associated with high-affinity epidermal growth factor receptors, increased about (31.2 +/- 4.1)% (t = 17.10, P < 0.05) and (16.8 +/- 2.3)% (t = 16.68, P < 0.05) respectively, compared with that of the control.</p><p><b>CONCLUSION</b>These results suggest that a short time exposure to a 0.2 mT power frequency magnetic field induces re-organization of microfilament in human amnion FL cells. These changes could be recovered by field withdraw and may have something with the clustering of epidermal growth factor receptors induced by magnetic field.</p>

Effects of power frequency magnetic field on Ca2+ transport of skeletal muscle sarcoplasmic reticulum vesicles / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of power frequency magnetic field on the Ca2+ transport dynamics of isolated sarcoplasmic reticulum vesicles.</p><p><b>METHODS</b>The assays of Ca2+ uptake time course and the Ca2+-ATPase activity of sarcoplasmic reticulum vesicles were investigated by using dynamic mode of spectrometry with a Ca2+ dye; Ca2+ release channel activation was examined by 3H-ryanodine binding and Ca2+ release assays; membrane fluidity of sarcoplasmic reticulum vesicles was examined by fluorescence polarization, without or with exposure to the vesicles at a 0.4 mT, 50 Hz sinusoidal magnetic field.</p><p><b>RESULTS</b>0.4 mT, 50 Hz sinusoidal magnetic field exposure caused about a 16% decline of the initial Ca2+ uptake rate from a (29.18 +/- 3.90) pmol.mg(-1).s(-1) to a (24.60 +/- 3.81) pmol.mg(-1).s(-1) and a 26% decline of the Ca2+-ATPase activity from (0.93 +/- 0.05) micromol.mg(-1).min(-1) to (0.69 +/- 0.07) micromol.mg(-1).min(-1) of sarcoplasmic reticulum vesicles, whereas caused a 15% increase of the initial Ca2+ release rate from (4.83 +/- 0.82) pmol.mg(-1).s(-1) to (5.65 +/- 0.43) pmol.mg(-1).s(-1) and a 5% increase in 3H-ryanodine binding to the receptor from (1.10 +/- 0.12) pmol/mg to (1.16 +/- 0.13) pmol/mg, respectively.</p><p><b>CONCLUSION</b>The decline of Ca2+-ATPase activity and the increase of Ca2+ release channel activity should result in a down-regulation of Ca2+ dynamic uptake and an up-regulation of Ca2+ release induced by exposing the sarcoplasmic reticulum to a 0.4 mT, 50 Hz power frequency magnetic field.</p>