| With the changes of military science and transition of strategies and tactics theory, the incidence of blast injuries in the modern battlefield has increased rapidly due to the abusage of modern explosive weapons. In the recent local wars, the injuries, which were caused by the new missiles and new explosive, were more and more widely. In the terrorist activities and incidents, the incidence of such injuries was also high. So the blast injury has become the focus of various medical areas. In battle injuries of spine, the incidence of the blast injury of spinal cord became more and more highly. It was studying the mechanisms and treatment of the blast injury of spinal cord that provide an important theoretical basis and practical guidance for the diagnosis and treatment of such injury.Therefore, the main purpose of the present research was to study the pathos-mechanism of the blast injury of spinal cord, and found the preferred early treatment in order to enhance our fighting strength of military and reduce the disability rate.Objective: (1) To investigate the macro-pathological changes of animals, which were injured at different distance between the explosives and animals, and analyze the early traumatic condition and risk factor of the blast injury to spinal cord; (2) To study morphological changes of the neural cells and the characteristics of temporal and spatial distribution of apoptotic neural cells after the blast injury of spinal cord; (3) Compared with the current conventional treatment for SCI, to investigate the effects of therapy with high-dose Vitamin C combined with sodiumβ-aescinate in spinal cord blast injury.Method: (1) Fifteen rabbits were shaved in the dorsal surface of T9-T10 level and were fixed respectively on the special plate with prone position. Then animals were injured in 1cm, 2cm, 3cm, 3.5cm or 4cm distance under the explosives (n=3). By postmortem examination, to observe the macro-pathological changes of animals and the gross pathology of the spinal cord; (2) The formal experiments were performed on 96 adult male rabbits. And these animals were randomly divided into two groups: sham group (n=16) and experimental group (n=80). After detonation, four rabbits were dead and excluded from the experimental group. So other thirty-six rabbits were anesthetized and perfused with 4% paraformaldehyde for HE and TUNEL staining at 8 hours, 1, 3, 7, 14 or 30 days after explosive detonation (n=6 at each time point). In addition, twenty animals were perfused for TEM at 8 hours, 1, 3 or 7 days after explosive detonation (n=5 at each time point). For DNA analysis, another twenty animals were killed at 8 hours, 1, 3 or 7 days after explosive detonation (n=5 at each time point). All animal's neurological deficit caused by the SCI was assessed by using a modified Tarlov's scale at 8 hours, 1, 3, 7, 14 or 30 days after SCI; (3) Thirty-six rabbits were randomly divided into sham group (Group A,n=6), control group(Group B,n=6), dexamethasone group (Group C), VitC group (Group D,n=6), SA group(Group E,n=6) and VitC+SA group(Group F,n=6). All experimental groups were made explosive wound by 0.7g cyclotrimethylene trinitramine, and the change of neural function was observed by Tarlov's scale. The injured spinal cords were taken for morphological studies at 14d, including HE staining and the TUNEL method. Result: (1) With the extension of distance between the explosives and animals, the grade of the blast injury of spinal cord was significantly reduced. And the individual differences of animals were an obvious factor to the traumatic condition of blast injury to the spinal cord in the model. The blast wave was the main factor to the blast injury of spinal cord injury and the severe lung or other hollow organs injury. However the hollow organs injury was the main reason of animal death. Therefore, the treatment of hollow organs such as lung was very important in the blast injury of spinal cord; (2) In the present study, neuronal apoptosis was confirmed in the blast injury of spinal cord by HE staining and TUNEL methods. However the characteristics of temporal and spatial distribution of apoptotic neural cells after the blast injury of spinal cord were very special.①: The apoptotic cells were found in both the gray matter and white matter. But the apoptotic cells in the gray matter were extremely rare, and most TUNEL positive cells were glial cells. The majority of neurons were probably dead in the form of necrosis.②: The apoptosis of glial cells existed in a very long period after injury. However the death of neurons was mainly necrosis at earlier time.③: The value of apoptotic cells in gray matter was maximal at the 1st day after injury. But most TUNEL positive cells were glial cells in white matter at the same time. The value of apoptotic cells in white matter was maximal at the 7th day after injury and decreased subsequently. But the apoptotic cells still exist at 14th day after detonation.④: Lengthways, the value of positive cells in adjacent spinal cord was more than the value of the centric spinal cord at 7th day after detonation. And the affected area of spinal cord was up to about 4cm. (3) In the present research, motor function was significantly improved in SA group. In SA-treated rabbits, both necrosis and apoptosis decreased and more motoneurons survived. So the SA had neuroprotective effects on the blast injury of the spinal cord in rabbits. However there was no significant difference between hormone therapy and SA therapy. A large dose of Vit C therapy had effective protection to the motor neurons in anterior horn, but could not improve the recovery of motor function and reduce the number of apoptotic cells. Early high-dose Vit C combined with SA was superior to high-dose VitC, SA or hormone therapy.Conclusions: (1) The establishment of an animal model of explosive blast injury to the spinal cord, which the spinal cord was injured with controlled impact in liquid environment after laminectomy, may be useful in the study of the mechanism of the blast injury to spinal cord. (2) Neuronal apoptosis absolutely existed in the blast injury of spinal cord. But apoptotic cells mainly were glial cells and the apoptotic characteristics was particularly. (3) Early high-dose Vit C combined with SA was capable of treating the spinal cord blast injury, and was superior to high-dose Vit C, SA or hormone therapy.
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