A model of injury potential for myelinated nerve fiber.

Excellent models have been described in literatures which related membrane potential to extracellular electric or magnetic stimulation and which described the formation and propagation of action potentials along the axon, for both myelinated and nonmyelinated fibers. There is not, however, an adequate model for nerve injury which allows to compute the distribution of injury potential, a direct current potential difference between intact and injured nerve, because its importance has been ignored in the shadow of the well-known action potential. This paper focus on the injury potential and presents a model of the electrical properties of myelinated nerve which describes the time course of events following injury. The time-varying current and potential at all nodes can be computed from the model, and the factors relate to the amplitude of injury potential can be determined. It is shown that the amplitude of injury potential decreased gradually with injury time, and the recession curve was exponential. Results also showed that the initial amplitude of injury potential is positively related to the grade of injury and fiber diameter. This model explained the mechanism of formation of injury potential and can provide instruction for applied electric field to prevent the formation injury potential.

Injury potentials of spinal cord in ex vivo compression injury model.

The effect of applied electric field on neuroprotection and axonal regeneration has been studied in previous studies of acute spinal cord injury (SCI). However, due to the complexity of the microenvironment of the lesion site, the underlying mechanism of applied electric field is not yet fully understood. Thus, the injury potential, a significant index of the microenvironment change, was investigated in ex vivo spinal cords compression injury. Spinal cords isolated from rat were cultured in a double sucrose gap recording chamber. Both compound action potential (CAP) and injury potential were measured. Compression induced the decreasement of compound action potential, but the amplitude of CAP increased gradually after decompression. Compression also lead to the appearance of injury potential, represented by the voltage difference between the gap potential before and after compression, and the injury potential decreased with time logarithmicly after decompression. Intracellular Na(+) and Ca(2+) concentrations were measured and results showed that after injury these ions flowed into intracellular space. Therefore, the current approach can provide a basis for investigating the formation mechanism of the injury potential and help understand the pathophysiology of the SCI.

The effects of chronic repetitive transcranial magnetic stimulation on glutamate and gamma-aminobutyric acid in rat brain.

Recent studies have shown that repetitive transcranial magnetic stimulation (rTMS) has therapeutic potential for some neurological and psychiatric disorders. However, the neurobiological effects of this tool are not sufficiently explained so far, previous research reported that rTMS can change dopamine release, there have been few studies to examine a possible effect of rTMS on amino acid neurotransmitter. This study aimed to determine the effects of chronic rTMS on glutamate and gamma-aminobutyric acid concentration in the rat brain. Sprague­Dawley rat was subject to 500 pulses of 0.5 Hz rTMS for 15 days, or sham stimulation. After last stimulation, glutamate and gamma-aminobutyric acid content were measured by high performance liquid chromatography (HPLC). Results showed that the content of glutamate and gamma-aminobutyric acid increased significantly in hippocampus and striatum after chronic rTMS, but reduced significantly in the hypothalamus. These results indicate that chronic rTMS has a modulatory effect on the glutamate and gamma-aminobutyric acid systems. This change in amino acid neurotransmitter may contribute to its beneficial effects.

Effects of extremely low frequency pulsed electromagnetic field on different-derived osteoblast-like cells / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the effect of the extremely low frequency pulsed electromagnetic field (PEMF) on the proliferation and differentiation of osteoblast-like cells.</p><p><b>METHODS</b>The MC3T3-E1 cell and the primary osteoblast cell derived from 2-day-old Sprague Dawley (SD) rat calvaria were exposed to PEMF with a magnetic flux density of 1.55 mT at 48 Hz for 24 or 48 h. MTS was applied to analyze cell proliferation and flow cytometry to detect cell cycle. The intracellular alkaline phosphatase (ALP) activity was measured by colorimetry.</p><p><b>RESULTS</b>PEMF of 1.55 mT at 48 Hz decreased significantly the cell percentage of S or G(2)M phase (P < 0.05), but did not affect cell number of MC3T3-E1 cells. Although the number of the primary osteoblast cells did not alter by MTS assay after exposure to PEMF for 24 h continuously, the cell percentage of G(2)M phase increased significantly (P < 0.01). When the culture time extended to 48 h, the cell number increased greatly (P < 0.01) and the cell percentage of G(2)M phase decreased significantly despite of the exposure type (P < 0.01). After the primary osteoblast cells were exposed to PEMF for 24 h continuously, the ALP activity decreased significantly (P < 0.05), whereas it increased significantly after exposure to PEMF for 48 h continuously (P < 0.05).</p><p><b>CONCLUSION</b>PEMF of 1.55 mT at 48 Hz does not affect proliferation and differentiation of MC3T3-E1 cell, but it promotes proliferation of primary osteoblast cell, inhibits differentiation at proliferation stage and promotes differentiation at differentiation stage of primary osteoblast cell.</p>

The effect of low frequency transcranial magnetic stimulation on neuropeptide-Y expression and apoptosis of hippocampus neurons in epilepsy rats induced by pilocarpine / 中华外科杂志

<p><b>OBJECTIVE</b>To analyze the effect of low frequency transcranial magnetic stimulation (LF-TMS) on changing neuropeptide-Y (NPY) expression and apoptosis of hippocampus neurons in epilepsy rats induced by pilocarpine (PLO).</p><p><b>METHODS</b>Thirty male Sprague Dawley rats (240 g +/- 20 g) were randomly divided into 2 groups. I group simply celiac injected pilocarpine. II group celiac injected PLO after LF-TMS. Pathological item included HE staining, NPY immunohistochemical staining and apoptosis staining.</p><p><b>RESULTS</b>HE staining revealed neurons of hippocampus were obviously death and cell's structure was destroyed in PLO group. The PLO + LF-TMS group was less injured and destroyed. Using One-Way ANOVA, NPY immunohistochemical staining shown the positive cell number was increased at all areas of hippocampus in PLO group contrasting with the low positive cell number in the PLO + LF-TMS group. In PLO group the number of apoptosis cell at hippocampus areas was significant higher than the PLO + LF-TMS group.</p><p><b>CONCLUSIONS</b>Using the PLO evoked epilepsy model, LF-TMS alleviated neurons injury at hippocampus area, so LF-TMS might playing an important role in resisting the progressing of epilepsy. The positive cell number of NPY increased at all areas of hippocampus, which indicated the close relation between NPY and epilepsy. NPY might have some function on resisting epilepsy.</p>

The design of a transcranial magnetic stimulation (TMS) system and its implementation / 中国医疗器械杂志

Transcranial magnetic stimulation (TMS) is a non-invasive diagnostic and therapeutic technigue. This paper expounds the design and manufacture of the TMS system, which meets all the requirements of the TMS study and clinical diagnosis and treatments.

Low frequency transcranial magnetic stimulation changes seizure and neuropeptide Y expression of hippocampal neurons in rats epilepsy induced by pilocarpine / 中华物理医学与康复杂志

Objective To observe the effects of low frequency transcranial magnetic stimulation (LF-TMS) on the electroencephalogram (EEG),expression of NPY in hippocampus in pilocarpine (PLO)-induced epileptic rats. Methods Forty male Sprague-Dawley rats (240-260 g) were used to establish a model of epilepsy by in- tradominal injection of pilocarpine,and then randomized into 2 groups:a control group and an intervention group. The control group was treated by sham LF-TMS,while the intervention group was treated by LF-TMS once daily for 7 days.Ⅰgroup simply celiac inject pilocarpine.Ⅱgroup celiac inject PLO after LF-TMS.The EEG was recorded in both groups and the checked pathology.Pathological item include HE staining,NPY immunohisto chemical staining. Results The latency for seizure attack was significantly lengthened,while the frequency of seizure attack and times of major seizure attack were significantly decreased in the intervention group.The HE staining revealed significant de- generation and necrosis of neurons in the hippocampus,especially in the CA3 region,in rats in the control group. The pathologic changes were significantly less severe in the intervention,Immunohistochemical staining showed a sig- nificantly higher expression of NPY in the hippocampus as compared with the intervention group. Conclusion U- sing the PLO-induced epilepsy model,LF-TMS could not only postpone the generation of kindling but also inhibit the progress of epilepsy.The increased NPY expression in the hippocampusin the intervention group implied a close rela- tionship between NPY and epilepsy attack.

Effects of low frequency pulsed magnetic field on the proliferation and differentiation of HepG2 cells / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effects of low frequency pulsed magnetic field on the proliferation and differentiation of HepG2 cells.</p><p><b>METHODS</b>3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) colorimetry method and ELISA assay of alpha-fetoprotein (AFP) were used to determine the cell proliferation and differentiation after the cells were exposed to pulsed magnetic fields with different frequency but the same field intensity.</p><p><b>RESULTS</b>There were no significant differences in cell proliferation between sham and treated groups exposed to the field of 80 Hz, 1.55 mT for 1, 4, 8, 12, 24 h (P > 0.05). There were also no significant differences in cell proliferation and AFP secretion between sham and treated groups exposed to 16 Hz, 1.55 mT pulsed magnetic fields for 1, 4, 8, 24 h (P > 0.05).</p><p><b>CONCLUSION</b>There were no "window effects" found in HepG2 cells proliferation or AFP secretion at 16 Hz and 80 Hz pulsed magnetic fields.</p>

Effect of extremely low frequency magnetic fields on intracellular free calcium in HepG2 cells / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effect of extremely low frequency magnetic fields on intracellular calcium concentration ([Ca(2+)]i).</p><p><b>METHODS</b>Fura-2 loaded HepG2 cells were exposed to 1.55 mT (average value), 16 Hz pulsed magnetic fields for 60 min and to 300 mT, 2 Hz rotating magnetic fields for 5 min, and then [Ca(2+)]i was measured by fluorescence spectrophotometer. [Ca(2+)]i of HepG2 cells was also measured when they were exposed to 0.9 mT [root mean square (rms)], 16 Hz sinusoidal magnetic fields in real time.</p><p><b>RESULTS</b>The R values (F(340) nm/F(380) nm) of the control and the exposed group were 2.4519 +/- 0.2378 and 2.5266 +/- 0.2915 respectively after HepG2 cells were exposed to 1.55 mT, 16 Hz magnetic fields, 1.365 0 +/- 0.0626 and 1.3602 +/- 0.0771 respectively to 300 mT, 2 Hz rotating magnetic fields. The ratios of the trendline slope [r((501 - 1,000)) / r((0 - 500))] from the data of R values were 1.1213 +/- 0.4559 and 1.0727 +/- 0.1971 respectively (P > 0.05), and the ratios of the intercept [b((501 - 1,000)) / b((0 - 500))] from the trendline were 0.9912 +/- 0.0098 and 0.9979 +/- 0.0060 (P > 0.05) when HepG2 cells were exposed to the 0.9 mT, 16 Hz sinusoidal magnetic fields.</p><p><b>CONCLUSION</b>The effect of extremely low frequency magnetic fields on [Ca(2+)]i of HepG2 cells under the experimental condition has not been found.</p>