| Part 1:Radiation induced cognitive dysfunction:an experimental model in the ratObjective:To develop a model of radiation-induced cognitive dysfunction in the young rat, in order to further explore the mechanism of radiation-induced cognitive dysfunction.Methods:Rats were irradiated in turn by 4 MeV electron beam which generated by a linear accelerator. One-month-old Sprague-Dawley male rats were divided randomly into lmonth,2months,3month,6months after radiation, according to the single radiation doses each of the four groups subdivided again into 6 groups, which were:the control(C), sham control(Sham),2Gy, lOGy,20Gy and 30Gy. Sequential behavioral tests including open field, novel location and novel object recognition and Morris water maze were under taken after radiation. The gross neurological symptoms, body weight, the topical skin response and histopathology changes were observed.Results:During the course of the experiments, the body increases of the 30Gy irradiatied group was less than the other groups, the lose weight and the mortality rate increased since 4 months after radiation. The infield alopecia was observed 10-15 days among the rats those received 20Gy or 30Gy irradiation, which is corresponding to the beam entrance, most of them recovered at one month. The eating habits and daily activity of the rats that experience anesthesia and radiation did not differ from those of the control rats.In open field test, there were no radiation-induced alterations in the distance moved in the center zone, or in the total distance traveled. In novel location and novel object recognition tests,3 months after 20Gy radiation spent less time exploring the novel object and the novel location than the other groups. During the place navigationtest, the spatial working memory of the 20 Gy-irradiatied rats was impaired since 2 months after irradiation, and the 30 Gy-irradiatied rats was impaired since 1 months after irradiation. There are no gross morphologic changes such as demyelination, hemorrhage, or neuronal damage was observed at the control, sham control,2Gy, 10Gy,20Gy irradiation group. For the 30Gy irradiation group, the morphological changes include:the blood vessel dilation, wall thickening, the neuronal atrophy and the relative number of glial cells increased.Conclusion:The radiation induced cognitive dysfunction without detectable anatomic abnormalities were explored in our rat model. working memory of the 20 Gy-irradiatied rats was impaired since 2 months after irradiation, and the 30 Gy-irradiatied rats was impaired since 1 months after irradiation. There are no gross morphologic changes such as demyelination, hemorrhage, or neuronal damage was observed at the control, sham control,2Gy, 10Gy,20Gy irradiation group. For the 30Gy irradiation group, the morphological changes include:the blood vessel dilation, wall thickening, the neuronal atrophy and the relative number of glial cells increased.Conclusion:The radiation induced cognitive dysfunction without detectable anatomic abnormalities were explored in our rat model.Part 2 Radiation compromises the neurite growth of hippocampusObjective:To explore the radiation-induced changes of neurite growth in rat hippocampal in vivo and vitro.Methods:In vivo experiment, one-month-old Sprague-Dawley male rats were irradiated in turn by 4 MeV electron beam which generated by a linear accelerator at the dose of 0Gy,2Gy, 10Gy and 20Gy. 1day after radiation, rats were anesthetized and GFP labed retrovirus was delivered to the dentate gyrus of the rat hippocampus through stereotaxic surgery. Only dividing cells at the time of surgery can be infected, and the expression of GFP in labeled cells is persistent. At 1w,2w,4w and 8w after irradiation the sample for axonal growth analyses were preparied, the number of GFP labeled cells and axonal growth were detected by immunofluorescence staining. In vitro, primary cultured hippocampal neurons one day were employed to evaluate the change of neurite length, total dendritic branch tip number after irradiation of 0 Gy and 2 Gy.Results:There was a substantial reduction in the number of GFP labeled cells after 10Gy or 20Gy irradiation, only occasional GFP labeled cells was found. The decrease of GFP labeled neuron after 2Gy irradiation was not obvious, but the dendrite length was reduced significantly at 1w,2w, and 4w after irradiation.In vitro experiment, we found that irradiation of 2 Gy decreased neurite length in neurons at 1d and 3d after irradiation,and total dendritic branch tip numberwas decreased at 3d after irradiation.Conclusion:2Gy irradiationimpaired neurite growth of hippocampus, and the effect may focus on delay the process of dendritic growth in vivo.Part 3 Radiation induced the decline of the expression of transcription factorNFATc4/3 in rat hippocampalObjective:On the base of radiation induced cognitive dysfunction model we have been established, explore the radiation-induced changes of the expression of transcription factorNFATc4/3 in rat hippocampal.Methods:Rats were irradiated in turn by 4 MeV electron beam which generated by a linear accelerator. One-month-old Sprague-Dawley male rats were divided randomly into 6 hours,12 hours, 1day,3 days, 1week and 2 weeks after radiation, according to the single radiation doses each of the four groups subdivided again into 4 groups, which were:sham control(Sham),2Gy, lOGy and 20Gy.Western blot and RT-PCR was performed to analyze the expression ofNFATc4/3, p-NFATc4/3, GSK-3 β and CaN.Results:At 12 hours after 20Gyirradiation, the expression of total NFATc4/3 start to decline in Western blot analysis, at 3days, lweek and 2 weeks after radiation, the decline of the expression of total NFATc4/3 were still observed. At 3days, lweek after radiation, the 10Gy irradiation,2Gy irradiation induced the expression of total NFATc4/3 since to decline respectively. The gene expression of NFATc4/3analyzed by RT-PCR was in line with the results of Western blot.At 1 day, the p-NFATc4 increases as the radiation increasing, it indicates that the nuclear dephoshorlated NFATc4/3 decreases. At 6hours, 12hours,3day,1 week and 2 weekstheexpression of p-NFATc4/3 was higher at irradiated group, but not obvious as the lday. But the protein and gene levels of CaN and GSK-3β were no differences among these groups at the various time points.Conclusion:Radiation induced the decline of the expression of transcription factorNFATc4/3 in rat hippocampal in a dose dependent manner. |
PDF Full Text Request