| [Objective] To modify the method of global cerebralischemia-reperfusion model in rat and this model was confirmed by symptomatology , the expression of heat-shock protein 70(HSP70) in the hippocampus CA1 region , the pathological changes in the hippocampus and the stained Willis' circle after perfusion of hematoxylin solution into the ascending aorta. On the basis of this modified model to investigate the expression of Heat-shock protein 70 (HSP70) after different duration of global cerebral ischemia pretreatment in rats and the relation to cerebral ischemia tolerance. [Materials and methods] In part one, the 42 male adult healthy Sprague-Dawley rats were randomly distributed into five groups: the group of four vessels occlusion (group A), the group of bilateral common carotid arteries occlusion (group B), the group of four vessels occlusion and stained in vivo (group C), the group of bilateral common carotid arteries occlusion and stained in vivo (group D), the sham group (group E). In group A, the rat's vertebral arteries weredestroyed by 4.5 size injector pinhead and the common carotid arteries were clapped by atraumatic miniature aneurysm clip. The group A was further divided into 10-min ischemia group(A I ) and 30-min ischemia group(A II). The rats of group B were subjected the occlusion of the bilateral common carotid arteries and also divided into 10-min ischemiagroup(B I ) and 30-min ischemia group(B II). Following 10 minutes ischemia , the rats of group A I and group B I were reperfused for 2 days and the expression of Heat-shock protein 70 (HSP 70) in the hippocampus CA1 region was assessed by immunohistochemistry (SP method) . After 30 minutes ischemia, the group AII and group B II were reperfused for 5 days and then were killed . Using HE staining method to investigate the pathological changes in the hippocampus. All rats were anesthetized by inhalation of ether in operation. In part two, 60 male adult healthy SD rats were employed to establish the global ischemia-reperfusion model using modified four-vessel occlusion method. They were divided into four groups: the only pre-ischemia group (group A), preischemia-reischemia group (group B), single ischemia group (group C) and the sham-operated group (group D). The group A was further divided into A I - IV groups and respectively exposed to different global ischemia duration : 1 minute, 2 minutes, 5 minutes and 10 minutes. After 2 days of global reperfusion they were sacrificed and the expression of HSP70 in the hippocampus CA1 region was determined with immunohistochemistry. The group B was also further divided into four groups (B I - IV) and they were pretreated with short time global ischemia of 1 min , 2 min , 5 min and 10 min respectively . After 2 days of reperfusion they were subjected to 20 min of global ischemia again. The pathological changes in the hippocampus CA1 region was observed after another 5 days. [Results] In part one: 1. After 1 min of four-vessel occlusion, the rats of group A appeared loss of consciousness, disappearance of righting reflex and corneal reflex, cyanosis of lips, pale in bilateral eyes, pupil dilatation, no gnawing after lips were stimulated by tweezers. In 1-2 min after the clip was moved away, all thesesymptoms disappeared. Group B and sham group kept consciousness, the righting reflex and corneal reflex existed all the time during the operation, the pupil just became pale lightly, the gnawing activity weakened not markedly. 2. Lots of grown stained granules appeared in the neuron cells' nucleus and cytoplast of bilateral hippocampus CA1 region. Group B I and sham group stained negative . HE stained in the hippocampus CA1 subfield of group AII showed mass of neuron cells necrosis . These death cells represented cell shrinkage, nucleus crimple and stained heavily, nucleolus disappearance, the gap between cells broaden. Group B II and sham-operated group showed no pathological alteration. The forebrain and Willis' circle of group C showed no...
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