| With the modernization of weapons and transition of strategies and tactics, the incidence of blast injuries in the battlefield has increased rapidly. Spine and spinal cord, owing to their central nervous system property, once injured, would at least affect the battle force, and in many severe cases cause paralysis. Especially for those paralyzed proning to develop various kinds of complications, the nursing is very difficult and expensive. Therefore, battle injuries of spine and spinal cord have been the focus of the research of relevant departments in every country.In the past, research of weapon injuries of the spine and spinal cord mainly focused on bullet shot injuries. However, with the refurnishment of single soldier protective facilities, and the increasing terrorist activities, the number of simple bullet shot injuries decreased, but the number of blast injuries increased markedly. Our department has established a spinal cord blast injury animal model. We utilized an automatic impact impulsing machine to establish the mechanic impacted cell model, which to the largest extent simulated the shock wave in battlefield. It made the research of pinal cord blast injury to the cell level. We also observed the histopathological progression of spinal cord during injury. We hope this can provide some suggestion for the clinical treatment of spinal cord blast injuries.Partâ… . Establishment of the animal model of spinal cord blast injury and the protection of HSP70The first part of the research was the improvement of the spinal cord blast injury animal model and research based on it. First of all, we chose the C4 admix military explosive to take the place of the RDX military explosive as the explosive material. It can ensure the repeatability by ruling out the bias of shrapnel. The animal was sheltered, leaving only the thoracic spine at the level of inferior scapula angulus right inferior to the explosive source. Electricity detonates the explosion. The optimal distance to the explosive source was decided by pre-measurement of explosive parameters and severity of injuries of the animal at different distances. The distance of 1, 2, 3 and 4 cm were assessed, and finally 4 cm was chosen to be the standard distance to establish the spinal cord blast injury model. Then, we utilized some methods to analyse the spinal cord injury, for example,HE dyeing, silver dyeing and TEM. The results indicated:1. The cause of death of the blast injuryed animal is the contused wound of organ, for example, bellows contusion. The advantages of our spinal cord blast injury model are nice controllability and repetitiveness, high survival rate, no spine fracture and purely impact injury. These studies settled good foundation to the further study of spinal cord blast injury.2. Although the impact wave injury can not cause the spine fracture, it can injury the vessel wall and result in spinal cord's ischemia. The inchoate damage of spinal cord is neuronal nucleus condensing,dyssymmetry rupture and Nissl's body disappearance, the structure disorder of substantia alba, for example,swelling, myelinolysis, congestion or thrombosis in the blood vessel of spinal cord.3. The pictures of TEM showed that medullary sheath become loosing and vacuolization. The chondriosome is swelling, microfilament breakage, and nucleus dense. The endocytoplasmic reticulums distend to be a bu.In the second part, we compared the pathological change of spinal cord blast injury and mechanic injury. We chose the Allen's method to establish the mechanic injury model of the spinal cord (20g, 10cm). Firstly, the pathological change of two kind's injury models was observed by HE dyeing. Then, Tunel's dyeing was used to shown the histiocyte's apoptosis at 6h, 12h and 24h. Secondly, we analyzed the process of apoptosis with DNA ladder, and observed the ultra structure of the spinal cord through TEM. Thirdly, we compared the functional recovery of the nerves between these two models by BBB. The results indicated: The mechanic spinal cord injury has a severe bleeding and congestion in traumatic region. Most spinal neuron became inreversible degeneration. On the contrary, the spinal cord blast injury has a wide damage range. The apoptosis cell in undamaged spinal cord segment can be detected. The injured neuron was soon to be necrosis. Compare with mechanic injury group, the cell membrane structure of spinal cord of blast injury shows a severe damage by TEM.In the third part, we focused on the protection of heat shock protein 70 (HSP70) to spinal cord blast injury. We firstly investigated the HSP70 expression in spinal cord after blast with immunohistochemistry. Secondly, compared with the control group, the apoptosis of neurocyte in heat shock primed animal's spinal cord was observed. Lastly, we compared the nerves functional recovery of the two groups by BBB. The results indicated: The HSP70 is seldom detected in blast injuried spinal cord. It might be the immediate occuration of the explosive and the severity of the damage that the tissue has no time to produce HSP70 for stress. However, the HSP70 can be detected in heat shock primed animal's spinal cord, and inhibiting the myeloid tissue apoptosis. Compared with the control group, the functional restoration of heat shock primed animal was better. Partâ…¡. Establishment of cell model of impact injury and the menchism of impact injury to PC12cellsThe purpose of this part is to establish impact injury cell models and research the relationship between early apoptosis and cytoskeleton disorder of PC12 cells under progressive pressure in vitro. Firstly, the pc12 cells were compressed by 0.1MPa to 0.3, 0.5 or 0.7 MPa for 10, 20, 30 min. According to the result of MTT, we took the 0.5 MPa for 10min group as impact injury cell's models. Then early apoptosis were detected through flow cytometry and TEM. HE dyeing and immunohistochemistry stain were used to detect the construction changes of microtubules. The results indicated:1. The apoptosis of PC12 cell increased in a time- and force-dependent manner corresponding to the pressure within 8h, and the disruption of microtubules of cell occurred after pressure exposure.2. That mechanic impact pressure influences morphology and induces early apoptosis in PC12 cells. And the phase of apoptosis is parallel to the damage of the microtubules. It suggests that the injury of the cell undergoing mechanic pressure begin with the damage of the cystoskeleton.The overall results suggested that spinal cord blast injury is different from mechanic injury. The blast injury may cause more complicated traumatic change and even more extensive damage range expanding to entire spinal cord. The impact wave damage myelocytic cytoskeleton, and lead cells to apoptosis quickly. These opinions prompt us to study the impact injury cytoskeleton in future research. And, it might give some experimental hint to the early intervention for spinal cord blast injury.
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