Functional MRI.CT Investigation Of Focal Cerebral Ischemia And Reperfusion In Rats

Part â…  MRI Investigation of Focal Cerebral Ischemia and Reperfusion in RatsPurpose: Combined with pathological observation, to study the changes of DWI, PWI in the occlusion and reperfusion of the right middle cerebral artery in rats. To investigate the changes of neuron apoptosis induced after ischemia and reperfusion. Materials and methods: 65 SD rats were divided into six groups, group A (n=10) was sham-operated for control study, group B, C, D (n=10 for each) experience the occlusion and reperfusion of the right middle cerebral artery with thread. DWI, PWI, T1WI and T2WI were performed at B (I2h/R2h, I2h/R24h), C (I2h/R2h, I2h/R24h, I2h/R7d), D (I6h/R2h, I6h/R24h), respectively. The results of serial MRI were compared with TTC stain and pathological observation. The neuron apoptosis was assayed using flow cytometry in group E (n=15) at I2h/R2h, I2h/R24h, I2h/R7d and group F (n=10) at I6h/R2h, I6h/R24h, respectively. Results: After reperfusion, there was no significant change in the abnormal signal area of DWI and the value of ADC in group B (P>0.05) . Seven days after blood reperfusion in group C, DWI showed abnormal signal in six rats but ADC map showed no abnormal in all 10 cases. In group D, twenty-four hours after reperfusion abnormal signal area of DWI was larger than before (P>0.05) . The value of ADC in the region of view was obvious lower in group D than in group B (P<0. 05). Twenty-four hours after reperfusion, there was no obvious difference between the area of hyper-intensity on DWI and the pallid area of TTC in group B, D respectively (P>0. 05) . In group B and C, after reperfusion, CBF, CBV map showed recovery of perfusion, and MTT map showed delay in some cases. The recovery of perfusion in group D showed more inadequacy and more uneven, and perfusion deficit still can be seen in the lesion. The percentage ofapoptosis cell was 3.08%, 41. 11%, 14.82% in group E at I2h/R2h, I2h/R24h, I2h/R7d, respectively. The percentage of apoptosis cell was 28.71% at I6h/R2h, 21.99% at I6h/R24h in group F, respectively. Conclusions: With prolonging of the ischemia duration, more damage of brain can be produced. Early reperfusion at 2 hour after ischemia can rescue penumbra in the rat, while late at 6 hour following ischemia reperfusion would exacerbate brain injury. DWI can reflect the changes of the ischemic lesion, while PWI can monitor the changes of blood dynamics following ischemia and reperfusion.Part â…¡ An investigation of STAT1/STAT3 activation and MRI after focalcerebral ischemia and reperfusion in the ratPurpose: Using MRI guiding to investigate the activation of STAT1/STAT3 in the rat following focal cerebral ischemia reperfusion and to observe time-dependent alteration of STAT1/STAT3 expression level. Materials and methods: 42 SD rats were subjected to middle cerebral artery occlusion (MCAO) with the intraluminal suture occlusion model. Two groups were investigated: group 1 (n=24) for 2 h ischemia and group 2 for 6 h ischemia. Animals of group 1 underwent for sham, I2h/R0h, I2h/R0. 5h, I2h/Rlh, I2h/R2h, I2h/R4h, I2h/R6h, I2h/R24h (each for three rats, respectively). Animals of group 2 treated for sham, I6h/R0h, I6h/R0.5h, I6h/Rlh, I6h/R2h, I6h/R24h (each for three rats, respectively). MRI, including DWI and T2WI was performed at different time. The relative ADC (rADC) was measured in cortex and striatum. Samples taken from the cerebral cortex and striatum according to MRI were analyzed by Western blots using STAT1/STAT3 and p-STATl/p-STAT3 antibodies. Results: rADC ranged from 0.53 to 0.77 at different timing. The rADC in group 2 was lower than in group 1, while lower in striatum than in cortex. The levels of STAT1/STAT3 phosphorylation increased remarkably following ischemia and reperfusion although the level of STAT1/STAT3 expression without change. The level of STAT1/STAT3 phosphorylation increased both in cortex and striatum after ischemia and reperfusion, increased markedly at 0. 5 h and peaked at 24 h of reperfusion. Activation of STAT1/STAT3 instriatum was markedly increased compared with in cortex. Activation of STAT3 was later in striatum than in cortex. Conclusions: Focal cerebral ischemia and reperfusion can induce STAT1/STAT3 activation. With prolongation of reperfusion duration, level of activation increase gradually, peak at 24 h following reperfusion. Biochemical analysis of special brain regions following ischemia reperfusion guiding by MRI has a potential prospect.PartHI MRI and the blood-brain barrier changes following focal cerebralischemia and reperfusion in ratsPurpose: To investigate MRI and the changes of blood-brain barrier (BBB) in the rat of focal cerebral ischemia and reperfusion. Materials and methods: 78 SD rats were subjected to middle cerebral artery occlusion (MCAO) with the intraluminal suture occlusion model. Animals were divided into seven groups (n=10 for each group). MRI were performed in group A (sham), B (I2h/R2h), C (I2h/R24h), D (I6h/R2h), E (I6h/R24h) consisting of 10 rats for each group. Relative signal intensity (rSI) and relative ADC (rADC) were measured and calculated on TIWI, T2WI, FLAIR, postcontrast TIWI, postcontrast FLAIR and ADC images in striatum. Brain water content was determined by a dry-wet weight method in 6 rats of each group. Histopathologic examination was performed with light and electron microscopy in 4 rats of each group. Animals of group F and group G (n=14 for each group) were performed with Evans blue (EB) staining and the content of EB in the brain tissue was assayed with spectrophotometry. Two rats were treated as sham, every 6 rats were subjected to ischemia reperfusion in group F (I2h/2h, I2h/R24h) and group G (I6h/R2h, I6h/R24h), respectively. Results: The number of rats with enhancement on postcontrast FLAIR was more than the number on postcontrast TIWI. The value of post enhancement rSI was significantly greater on FLAIR than on TIWI (P<0. 05). With prolongation of reperfusion duration, Signal intensity increased gradually on T2WI, whichwas significantly greater than pre-reperfusion (P<0. 05). The value of rADC at striatum did not differ significantly between the bleeding and no-bleeding rats of group E. Brain water content increased along with prolongation of ischemia and reperfusion duration, which was obviously higher than pre-reperfusion and the ipsilateral hemisphere(P<0.05). In group F, patch blue staining was seen in the right striatum of 8 animals, while was grossly visible in cortex and striatum of all 12 rats of group G. The content of EB in the right hemisphere was different between group F and G (P<0.01). The content in the right hemisphere was significantly higher than the left (P<0. 05). The content of EB in the I2h/R24h group was higher than in the I2h/R2h group (P<0. 05), the tissue injury was seen more severe along with prolongation of ischemia duration. Conclusions: With prolongation of the ischemia duration, injury of the BBB after ischemia and reperfusion is more severe. The application of MRI is useful to non-invasively and repeatable evaluate the condition of BBB following acute cerebral ischemia. Early Gd-DTPA enhancement after cerebral ischemia and reperfusion is predictive of subsequent hemorrhagic transformation. Post enhancement FLAIR is more sensitive than post enhancement TIWI in detecting BBB injury.PartIV An investigation of MSCT perfusion imaging and focal cerebralischemia reperfusion in ratsPurpose: Using multi-slice CT perfusion imaging to investigate the changes of cerebral blood perfusion following focal ischemia and reperfusion. Materials and methods: 58 SD rats were divided into three groups: group A (n=10), group B (n=28) and group C (n=20). Group A was sham-operated for control study. Group B, C experienced the occlusion and reperfusion of the right middle cerebral artery with the intraluminal suture. Rats of group B were divided into eight subgroup (n=4 for each) at I2h/R0, I2h/R0.5tu I2h/Rltu I2h/R2h> I2h/R4h, I2h/R6h, I2h/R24h. In groupCrats were divided...