Dephospho-dynamin 1 coupled to activity-dependent bulk endocytosis participates in epileptic seizure in primary hippocampal neurons.

BACKGROUND AND PURPOSE: Epilepsy is a severe neurological and mental disorder, and not all patients adequately respond to the current treatments. Dynamin 1 plays a key role in synaptic endocytosis and the modulation of neurological function. MATERIAL AND METHODS: Cultured hippocampal neurons were used in the study. First, the viability of neurons was determined by the CCK-8 assay after culturing in magnesium-free medium, DMSO, dynasore (dynamin agonist), and PIP2 (dynamin antagonist). Then, the effect of dynasore on seizure activity was evaluated. Next, we tested the levels of phospho-dynamin 1/total dynamin 1 and dynamin 1 mRNA in the control group and four epilepsy groups. Moreover, the uptake of tetramethylrhodamine-dextran in the different groups was measured. RESULTS: Dephospho-dynamin 1 expression was significantly increased in hyperexcitable neurons, while there was no change in total dynamin 1 level. The level of dephospho-dynamin 1 in hyperexcitable neurons was reduced when cultured with dynasore but increased with PIP2 treatment. Activity-dependent bulk endocytosis (ADBE) was upregulated in hyperexcitable neurons. Along with a decrease in dephospho-dynamin 1 level, ADBE was also downregulated with dynasore treatment, while PIP2 did not affect ABDE. The close link between the dephosphorylation status of dynamin 1 and ADBE suggests that ADBE activation depends on dynamin 1 dephosphorylation. CONCLUSION: Dephospho-dynamin 1 triggers ADBE to meet the requirements of high-frequency discharges during epileptic seizures.

Upregulated dynamin 1 in an acute seizure model and in epileptic patients.

Dynamin 1 is a neuron-specific guanosine triphosphatase (GTPase) that is an essential component of membrane fission during synaptic vesicle recycling and endocytosis. This study evaluated the dynamin 1 expression pattern in the acute lithium-pilocarpine rat model and in patients with temporal lobe epilepsy (TLE) and investigated whether altering the dynamin 1 expression pattern affects epileptic seizures in vivo and in vitro. The immunofluorescence, western blot analysis, and reverse transcription-PCR results show that the dynamin 1 expression level increased significantly in experimental rats from day 1 to day 7 after the onset of seizures and was significantly higher in TLE patients. The behavioral study revealed that inhibiting dynamin 1 increased the latency time of the first seizure and decreased the frequency and severity of the seizures. In addition, electrophysiological recordings from brain slices showed that inhibiting dynamin 1 reduces the frequency of Mg-free induced seizure-like activity. The anticonvulsant effect of dynasore was more effective at 10 µM than at 1 µM or 160 µM. These results indicate that the altered level of dynamin 1 may contribute to the development of epileptic seizures and that the targeted regulation of dynamin 1 activity may control epileptic seizures.

Biomechanical comparison of two types of posterior pedicle instrumentation / 中华创伤骨科杂志

Objective To compare the biomechanical properties between the two-level fixation by im- plantation of pedicle-screws into the adjacent upper and lower vertebrae of the fractured vertebra and the three-level fixation by implantation of pedicle screws into the fractured vertebra and its adjacent upper and lower vertebrae in the treatment of thoracolumbar burst fractures.Methods Eight fresh frozen calf spines were used in this study.Each specimen was tested in four models:intact model as the control,L1 burst fracture model,two-level fixation model, and three-level fixation model.The L1 burst fracture model was created on a biaxial material testing machine (MTS858 Bionix test system,America).During the experiment,the flexion,extension,bilateral bending and axial rotation loadings were applied to the specimens and the range of motion(ROM)was measured with a three-dimensional laser analysis apparatus and the stiffness was calculated subsequently.One-way statistical analysis was used.Results The ROMs under six different loadings in the fracture model became larger obviously(P＜0.05)and the stiffness decreased(P＜0.05).The ROMs in both fixation models were smaller than those in the other models(P＜0.01)and the stiffness increased distinctly(P＜0.05).There were no significant differences in ROMs and stiffness between the two-level fixation and three-level fixation models(P＞0.05).Conclusion Two-level fixation provides similar biomechanical stability as three-level fixation does in the reconstruction of unstable thoracolumbar fractures.