| Both apolipoprotein E (apo E) and beta-amyloid precursor protein (β-APP) play significant roles in the nerve system growth, stabilization of function and nervous renovation after brain injury. Reports correlated with these two proteins are few in China and overseas at present, further more no research works about apo E andβ-APP expression in the experimental traumatic brain injury (TBI) in rats by weight-drop has been made up till now. In order to elucidate the effects and the expression levels of apo E andβ-APP in the brain injury, and investigate the application value in the forensic inference of early brain injury time, we carried on thorough studies, using moderate rat brain damage models.We used healthy mature SD rats as our study objects, and adopted the improved experiment model of moderate brain injury impacted by weight-drop. Tissue samples were fixed; paraffin embedded, sectioned and then stained by H.E. (hematoxylin and eosin) or Streptavidin Peroxidase Conjunction immunohistochemical (IHC) techniques (performed to identify the pathologic change of apo E andβ-APP within coronal brain sections in situ at different internals within 14 days after brain injury). All of the (IHC) stained slides were quantitatively analyzed by use of the computer image analysis technology and SAS8.0 to investigate the expression change of apo E andβ-APP in damaged rat cerebra.The experimental groups featured by cerebral contusion in right parietal lobe after weight drop, according to different prearrangement when compartment (0.5h, 2h, 6h, 12h, 24h, 3d, 7d and 14d, 5 rats in each time compartment) executed the animal in turn and took out and fixed the total brain in 4% Para formaldehyde solution immediately (at 4℃). The pseudo damage group after 0.4% pentobarbital sodium (amount: 1ml/kg) anaesthetized only the line to hold the skull surgery but not to weight drop, and executed after day 3 of died, took the brain. Postmortem-injuryed control group was only subjected to the impacted injury of the weight-drop at 1 hour after death. The groups of injury, died after 1 h suffered by weight drop, were executed. Each group of specimens dampen nearby the stove center in the brain to operate in front of the 2mm coronal excision the rear of the bruise stove, making apo E and beta-APP (IHC) group dying observation after the specimen were selected, also H.E. dyeing had been done to make comparison. The result of (IHC) group dying observed through the computer image analysis technology of cell average luminosity value quantitative determination, then with social sciences statistics software package 10.0.7 edition carried on the analysis.Results:(1) In cortex, apo E-positive staining neurons were definitely detected 0.5h after brain injury. PS reached the peak on day 3, then it decrease from 3d to 14d. In hippocampus apo E-positive staining neurons definitely detected 0.5h after brain injury, reaching the peak on day 3 too, in CA1 section and 24h in CA2～CA4. Then it showed gradual decrease. We found the expression of apo E protein in CA3 section is stronger than other groups. (2) The number ofβ-APP-positive staining neurons definitely increased 0.5h after brain injury, and declined trough the following 12h, then reaching the peak on day 3. In CA1 the number ofβ-APP-positive staining neurons definitely increased after 24h of brain injury, declined with in 3 days,but only declined with in 3 days in CA2～CA4. In dentate gyrus (DG) the number ofβ-APP-positive staining neurons at 12h was lower than that of the control after brain injury.Conclusion: In cortex apo E-positive neurons definitely detected in 0.5h after brain injury, which could be contributed to providing a sensitive index for the diagnosis of early traumatic brain injury. There was no apo E-positive neuron in cortex and hippocampus before brain injury, which also could be used for distinguishing ante-mortem and post-mortem brain injury in forensic medicine identification. The apo E andβ-APP expression in cortical substance present certain regularity, which conducted one of the objective indexes of inference brain injury time. However, the changes ofβ-APP expression in hippocampus were not distinct comparing with cortex, which had little value in determination of brain injury time. The concrete contribution to its mechanism needs to spending further investigations. |
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