| Objective: This study researched the effect of the nail length on the degree of brain injury in the Feeney's weight-dropping brain injury model. The aim was to establish an accurate,stable and controllable model of traumatic brain injury. And we measured the AQP-4 mRNA expression of the cerebral tissue which was injuried in order to understand the relationship between AQP-4 and traumatic brain edema.Methods: 55 Sprague-Dawley rats were randomly divided into sham operation group included 20 rats, short nail group included 15 rats and long nail group included 20 rats.Traumatic brain injury in rats was set up by self-modified Feeney's weight-dropping brain injury model with the impact of 600g×cm (Moderate injury) .The rats of short nail group and long nail group were hit by the long nail and the short nail .The rats of sham operation group only had their scalp cut and skull opened ,but were not injured. The rats were sacrificed by decollated and taken cerebral tissue at 24 hours later.5 rats was taken from each group to measured the changes of Histopathology, brain water content and blood-brain barrier (BBB) permeability by the methods of HE staining ,wet-dry weight and Evans Blu(eEB)extravasation. 5 rats was taken from sham operation group and long nail group to measured the changes of expression of AQP-4 mRNA by the methods of real-time PCR.Results:1.The view of naked-eye and histopathology:The view of naked-eye: Sham operation group: The local capillaries of brain surface on which the skull was cut out expand slightly, and the cerebral cortex is not bleeding.The cerebral tissue is normal.Short nail group: There is a little of bleeding and mild contusion on cerebral cortex.It may has acute subdural hematoma or local subarachnoid hemorrhage. The cerebral tissue only swells slightly. Losng nail group :it can be seen that there is significant brain contusion,and hemorrhage on the cerebral cortex and subcortical region.The cerebral tissue swelles Seriously. The general view of histopathology :From the coronal section of the cerebral tissue ,it can be seen: The cerebral tissue of sham operation group is normal . The cerebral cortex of short nail group is damaged partly,and it has only mild brain edema.The midline of brain does not shift.Long nail group: the cerebral cortex is destroyed completely, and the subcortical hippocampus does not keep well. The brain edema is obvious, and its midline shifts Seriously.2.Brain water content: The brain water content of the cerebral tissue which was injuried of sham operation group, short nail group and long nail group is 78.850±0.391 (%),79.917±0.664 (%) and 81.210±0.493(%). Long nail group is significantly higher compared with short nail group (P=0.002).3.The blood - brain barrier (BBB) permeability : EB staining: EB staining of sham operation group is negative, while the cerebral tissue of traumatic brain injury group with different degree of blue staining. It is can be seen from the coronal section of the brain tissue : The blue staining range of long nail group is wider than short nail group ,and the color is more darker. EB content:The EB content of the cerebral tissue which was injuried of sham operation group, short nail group and long nail group is 4.179±1.419 (μg/g brain tissue),15.143±4.998 (μg/g brain tissue), 23.193±4.575 (μg/g brain tissue). Long nail group is significantly higher than short nail group.(P=0.027)4.The expression of AQP-4 mRNA :The expression of AQP-4 mRNA of sham operation group and long nail group is 0.855±0.112 and 2.747±0.470. The long group is higher compared with sham operation group (P = 0.001).Conclusions:1.In the self-modified Feeney's weight-dropping mode, the length of nail significantly effected the degree of brain injury. The long nail (the actual length is 8mm,and the effective length is 4.5mm)was the suitable selection accorded with the requirements of this model.2.Traumatic brain edema formation was related to the up-regulate of AQP-4. |
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