A Series Study On Quantitative Pathology And Prevention For Hearing-loss Induced By Blast Exposure

This study is granted by key laboratory fund of PLA. The main content concludes three parts: (1) A computer assistant quantitative study on the cochlear hair cells , spiral ganglion cells and the efferent florae across the cortf s tunnel after blast exposure in guinea pigs. (2) Using the technique of immunohistochemistry and hybridization to evaluate the expression of ciliary neaurotrophic factor(CNTF) and its mRNA in spiral ganglion cells of guinea pigs. (3) To study the intervenient effects of ciliary neurotrophic factor on hearing-loss induced by blast exposure. The main results are as follows:Part 1Objective: To study the pathologic quantitative changes of the cochlear hair cells , spiral ganglion cells and the damaged extent of efferent fibrae across the corti's tunnel in guinea pigs after blast exposure in guinea pigs. Methods: The hair cells were calculatedusing the surface specimen technique and computer image analysis technique after blast exposure. The spiral ganglion cells were calculated using pathologic technique and computer image analysis technique after blast exposure. A computer assistant quantitative observation of the eflFerent fibrae across the corti's tunnel was also carried out in guinea pigs after the cochlear AchE (acetylcholinesterase) decoration . Results: The quantitative observation was carried out 21 days after blast exposure. The number of total hair cells in normal control group and blast group was 9045 102.6 and 7351 196.5. The number of spiral ganglion cells in the 2-low part of cochlear in normal control group and blast group was 51 4.72 and 27 6.94. There were significantly statistic differences in both of them. The quantitative of the efferent fibrae across the cortfs tunnel in every 0.24mm length in the first turn and the second turn of the cochlear are 11.4 3.2 , 10.6 2.5respectively in 21 days group; and in the normal control group they were 23.2 3.2, 20.7 2.9 respectively. There were significantly statistic difference(p<0.01) between 21days group and the normal control group. The ultrastructural observation of cochlear spiral ganlion cell was carried out in two groups of animals after blast exposure 3 days and 21 days. Mitochondria swollen was observed apparently 3 days afterblast exposure and abnormal mitochondrion was also observed 21 days after blast exposure in blast group. But there is no any abnormal in normal group. Conclusion:Not only the hair cells reduced, but also the spiral ganglion cells and efferent fibre across the corti's tunnel damaged severely after blast exposure.Part 2Objective : To evaluate the expression of ciliary neaurotrophic factor (CNTF) and its mRNA in spiral ganglion cells of guinea pigs. Methods: The expression of CNTF in spiral ganglion cells was detected using immunohistochemistry method and the expression of CNTF mRNA in spiral ganglion cells was detected using hybridization method. Results: Both hybridization and immunohistochemistry methods demonstrated that the expression of CNTF and its mRNA in spiral ganglion cells was positive. The positive expression spiral ganglion cells reduced 21 days after blast. Conclusion: There were CNTF and its mRNA in spiral ganglion cells and the blast injuries may reduce the positive expression of CNTF and its mRNA in spiral ganglion cells.Part 3Objective: To explore the possibility of using ciliary neurotrophic factor (CNTF) to treat blast exposure induced hearing-loss. Methods: ABR threshold determination , the cochlear AchE(acetylcholinesterase) decoration and a quantitative observation on the cochlear hair cells and spiral ganlion cells were carried out in three groups guinea pigs. The guinea pigs of CNTF group were given CNTF 21 days after exposure of intensive impulse noise, the NS controls were given 0.9% sodium chloride 21 days after blast exposure, and the normal controls received neither medicine nor noise. Result: The number of noise damaged cochlear hair cells and spiral ganlion cells in CNTF group was smaller than that in NS control group; The activity damaged extent of cochle...