Oscillating field stimulation promotes axon regeneration and locomotor recovery after spinal cord injury.

Oscillating field stimulation (OFS) is a potential method for treating spinal cord injury. Although it has been used in spinal cord injury (SCI) therapy in basic and clinical studies, its underlying mechanism and the correlation between its duration and nerve injury repair remain poorly understood. In this study, we established rat models of spinal cord contusion at T10 and then administered 12 weeks of OFS. The results revealed that effectively promotes the recovery of motor function required continuous OFS for more than 6 weeks. The underlying mechanism may be related to the effects of OFS on promoting axon regeneration, inhibiting astrocyte proliferation, and improving the linear arrangement of astrocytes. This study was approved by the Animal Experiments and Experimental Animal Welfare Committee of Capital Medical University (supplemental approval No. AEEI-2021-204) on July 26, 2021.

Early electrical field stimulation prevents the loss of spinal cord anterior horn motoneurons and muscle atrophy following spinal cord injury.

Our previous study revealed that early application of electrical field stimulation (EFS) with the anode at the lesion and the cathode distal to the lesion reduced injury potential, inhibited secondary injury and was neuroprotective in the dorsal corticospinal tract after spinal cord injury (SCI). The objective of this study was to further evaluate the effect of EFS on protection of anterior horn motoneurons and their target musculature after SCI and its mechanism. Rats were randomized into three equal groups. The EFS group received EFS for 30 minutes immediately after injury at T10. SCI group rats were only subjected to SCI and sham group rats were only subjected to laminectomy. Luxol fast blue staining demonstrated that spinal cord tissue in the injury center was better protected; cross-sectional area and perimeter of injured tissue were significantly smaller in the EFS group than in the SCI group. Immunofluorescence and transmission electron microscopy showed that the number of spinal cord anterior horn motoneurons was greater and the number of abnormal neurons reduced in the EFS group compared with the SCI group. Wet weight and cross-sectional area of vastus lateralis muscles were smaller in the SCI group to in the sham group. However, EFS improved muscle atrophy and behavioral examination showed that EFS significantly increased the angle in the inclined plane test and Tarlov's motor grading score. The above results confirm that early EFS can effectively impede spinal cord anterior horn motoneuron loss, promote motor function recovery and reduce muscle atrophy in rats after SCI.

Design of site-directed magnetic targeting system in acute spinal cord injury.

Effective repair immediately after spinal cord injury can improve the prognosis of the patient. Injection of membrane resealing nanomaterial is one of the most promising technique to repair the membrane. In order to improve the retention rate of membrane repair material at injury site, membrane resealing nanomaterial can be combined with magnetic nanoparticle and magnetic targeting system. In this paper, a special site directed magnetic targeting system, which contain a C-shaped permanent magnet and a ferromagnetic needle, was constructed. Simulation was conducted to analyze the influence of the shape of needle on the magnetic field to provide magnetic force large enough to make the magnetic particles stay at the target site. Results showed that the appearance of ferromagnetic needle raised both the strength and the gradient of magnetic field at the target site. Moreover, with similar apex angles, longer needles with larger diameters can produced lager magnetic field, but smaller needles has better focal area at the small injury site in spinal cord injury. These results provide a basis for design and fabrication of ferromagnetic needles when the targeting system is applied in future experiments.

[The effect of low frequency transcranial magnetic stimulation on neuropeptide-Y expression and apoptosis of hippocampus neurons in epilepsy rats induced by pilocarpine].

OBJECTIVE: 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). METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Effects of extremely low frequency pulsed electromagnetic field on different-derived osteoblast-like cells].

OBJECTIVE: To investigate the effect of the extremely low frequency pulsed electromagnetic field (PEMF) on the proliferation and differentiation of osteoblast-like cells. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

[The design of a transcranial magnetic stimulation (TMS) system and its implementation].

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.

[Effects of low frequency pulsed magnetic field on the proliferation and differentiation of HepG2 cells].

OBJECTIVE: To study the effects of low frequency pulsed magnetic field on the proliferation and differentiation of HepG2 cells. METHODS: 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. RESULTS: 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). CONCLUSION: There were no "window effects" found in HepG2 cells proliferation or AFP secretion at 16 Hz and 80 Hz pulsed magnetic fields.

[Effect of extremely low frequency magnetic fields on intracellular free calcium in HepG2 cells].

OBJECTIVE: To study the effect of extremely low frequency magnetic fields on intracellular calcium concentration ([Ca(2+)]i). METHODS: 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. RESULTS: 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. CONCLUSION: The effect of extremely low frequency magnetic fields on [Ca(2+)]i of HepG2 cells under the experimental condition has not been found.