| Nitric oxide (NO) plays key roles in brain hypoxia or ischemia. A great deal ofresearch works have been carried to study the physiological and pathological role of NO in brain hypoxia or ischemia, however, its mechanism is not clear till now. The understanding of the mechenism would be of great significance in clinic and drug development.In this study, we applied the cultured hippocampal neurons as research cell model. Methods in biomedical engineering such as image processing and mathematical modeling and simulation were utilized to study the NO intracellular distribution in single neuron, the NO diffusion and reaction dynamics in brain hypoxia or ischemia. Researches have shown that NOS intracellular distribution is not homogenous, but locate in partically site within the cell; usually it is locates near its targets. These studies are based on the methods of immunochemistry. Whether the NO signal intensity is consistent with the NOS's localization (that is some sites high and some low depends on NOS's localization) needs further study.First, by applied the methods of fluorescent label and confocal laser scanning in real time, images of NO distribution intracellular were acquired. And then, by utilizing the methods of image processing, NO intracellular distribution was studied deeply. The results from this study are as follow:1,NO distribution intracellular in single cultured hippocampal neuron is not homogenous. The highest site is located in cell body, then in dendrites, and the lowest is in axon. These results are consistent with the result of NOS distribution from immunochemistry. Therefore, it was verified directly by methods of image process.2, By analyzing the series reconstructed 3D images, it was also found that the change of NO distribution in different sites of cell is different after the cell is stimulated.3, Experiment on DAF-2 intracellular distribution was also done to study whether the dye's intracellular distribution is homogenous or not. Results showed that NO intracellular distribution would not be affect by DAF-2 distribution intracellularNO will diffuse through the cell membrane when it is generated, and will react with other chemicals while it is in diffusing. The phenomenon of NO diffusion and rection is very complex. Because of difficulty to detect the change of NO in real time, it is impossible to apply biological methods only to understand some NO characteristics, such as the threshold, the effective time, the diffusion distance and the reactions with other chemicals. Mathematical modeling and simulation is a very useful method in analyze complex biological phenomenon. Considering the high incidence of brain ischemia such as stroke, and the important role of NO in brain ischemia, we applied the methods of mathematical modeling and simulation to study NO diffusion and reaction of NO in brain ischemia..In vitro model of cultured hippocampal neurons with OGD was applied. The changes of NO and O2 in single neuron under OGD were detected by confocal laser scanning with fluorescence label. Results from mathematical modeling and simulation are as follows:1, Dynamics research of NO synthesis to hippocampal neuron and endothelial cells in OGD state.There are NO increasing for the hippocampal neuron and endothelial cells in OGD state, however, it takes early for the hippocampal neuron than it does of the endothelial cells. Therefore, the time course of NO synthesis is temporal for hippocampal neuron and endothelial cells in OGD state. We dedicated possible mechanism of what cause this difference by compare the time course of Ca2+ increasing.2, The diffusion and reaction of NO generated by neurons in OGD state Simulation results showed that it is possible for the NO generated by neurons in OGD state to diffuse to brain vessels nearby. Therefore, it might have the functionof neuronal protection except the role of neurotoxity that was accepted widely. 3, Net model of NO reactionsNO will reacted with other chemicals during brain hypoxia/ischemia. The rel...
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