Dynamic Study On The Early Variation Of CT Value And The Expression Of GFAP After Experimental Cerebral Infarction Of Rat

【Background】Cerebral infarction is not scare in clinical forensic medicine identification and neurology, farther more there are used to be severe sequelaes among patients. The etiological factors include pathologic or injuries, so identification the relationship between"injury and illness"in cerebral infarction is the precondition which can correctly estimate the injury degrees in cerebral infarction patients. How to identificate it is also one of an important task for forensic medicine doctors. Among several identification factors we believe cerebral infarction time is critical to distinguish injury and illness. After cerebral infarction the brain tissues will swell and the low density focus in cerebral infarction area can be observed by CT. So CT is an essential means for checking cerebral infarction in clinical, at the same time it becomes important evidence for diagnose cerebral infarction in clinical forensic medicine. Moreover glial fibrillouy acidic protein (GFAP) is a sign for astrocyte and also one of a significant molecule, which is studied in pathologic morphology variations of cerebral injury and is evaluated injury time. But till then there are not much research in CT values or GFAP expression variations after cerebral infarction, so the critical task of this article is to explore the two indexes change rules after cerebral infarction.【Object】We have discussed the variation rules of cerebral infarction by medical imaging , pathologic morphology and molecule level in order to evaluate cerebral infarction time indirectly. This research will bring a light to judge the relationship between cerebral infarction and injury correctly in clinical forensic medicine cases.【Materials and Method】There are 55 mature Wistar rats(sex is not differentiated) which are divided into 11 groups and are named control(1 group), pseudo-artificial operation groups(3h, 6h, 12h/3 groups) and experiment groups (2h, 3h, 4h, 6h, 8h, 12h, 24h/7 groups) respectively. There are 5 animals in each group. The pseudo-artificial operation groups are divided by the executing time. The experiment groups refer to the thread embolism method of the articles and have been made everlasting animal models in which the middle cerebral arteries are embolized. After injury they are divided into 7 groups under the survival, which are 2h, 3h, 4h, 6h, 8h, 12h and 24h. At the same time the brains of rats have been coronary scanned with CT, then note the CT values and request experienced imaging doctors to diagnose the images by simple blind. After CT scan the animals are affused for fixation, and then the brain specimens are sampled and sliced up. We have applied HE dyeing and immunohistochemistry to observe the morphology changes and GFAP expression levels in brain. Then we have analyzed the relationship among CT values, GFAP expression variations and injury time after infarction and contrasted the pathologic variations during different time phases.【Result】In experiment groups 2 hours after death none of the animals can be observed of exact infarction focuses by CT scan. After 3 hours infarction focuses can be found in 2 animals and the tethers are not clear. All animals can be observed of exact infarction focuses till 6 hours. Different extents of low density focuses have appeared within the blood supply of the middle cerebral arteries after 3 hours. The time is longer, the density is lower. The CT value differences between the normal and cerebral infarction sides have increased, and there is significant positive liner correlation between the CT value difference and the infarction time(correlation coefficientr=0.967, P<0.05, regression equation: Y=0.158+0.58X). It means the average CT value difference between the normal and cerebral infarction side will increase 0.738HU if the infarction time increases 1 hour. During 24 hours after cerebral infarction the brain tissues have undergone a series of changes such as ischemia, degeneration, necrosis with cerebral swelling, neuron or nerve fiber break, dissolution. Edema and karyopyknosis have appeared in the brain white matter after infarction 3 hours, but it has not been serious and appeared to a focus; after infarction 6 hours edema and karyopyknosis in brain white matter have been clear; till infarction 24 hours the nucleuses of some cells have dissolved and the tissues have loosened clearly. At the same time, with the cerebral infarction time becoming longer, GFAP expressions have varied regularly. In normal cerebral tissues GFAP reaction positive has been low, the cell side been small and the dendrite been minute. After infarction 6 hours the astrocytes have mainly limited distributed around the infarction focuses. GFAP reaction positive has increased, dying has become heavier and the dendrite has got more. After infarction 12 hours the astrocytes bodies have got fat and the rate of GFAP reaction positive area has increased distinctly. After infarction 24 hours the astrocytes have spread all over the brain and the rate of GFAP reaction positive area has increased persistently.【Conclusion】The cerebral tissues edema after infarction is the main pathologic base for CT value decreasing contrast to normal side. With the infarction time becoming longer, the edema extent of cerebral tissues in infarction area has got heavier, which is the important reason for CT value progressive decreasing. GFAP is a mark molecule for research on the pathologic morphology of cerebral injury and estimate the injury time. Both the CT differences between the injury and normal sides and the GFAP expression have shown significant correlation with time. At least 6 hours after cerebral infarction clear infarction focus can be observed in the CT images. With time becoming longer, the density of infarction focus has decreased but the area increased, which can definitely guide the forensic medicine doctor to evaluate the cerebral infarction time preliminary and master the identification chance. It has also brought evidence for deeper imaging research on cerebral infarction. At the same time there is significant correlation between the morphology variations, GFAP expression after cerebral infarction and the infarction time. These have not only brought important evidences for understanding the pathologic base of cerebral infarction correctly and for deeper research on pathology, but also brought evidences for evaluating infarction time and mastering identification chance of forensic medicine identification on molecular level.