| IntroductionTissue hypoxia is a major factor in immediate and secondary cell damage caused by focal cerebral ischemia. Bioenergetic failure occurs rapidly in the severely hypoperfused ischemic core following cerebral ischemia. As the penumbra is a metabolically unstable zone , it develop repetitive spontaneous periinfarct depolarization which lead to cell death ultimately. Due to the important role of hypoxia in ischemic cell death, improving tissue oxygen supply during focal ischemia has remained a promising therapeutic concept. Hyperbaric oxygen ( HBO ) , the inhalation of 100% O2 at greater than atmospheric ambient pressure, efficiently increases the diffusional driving force for oxygen, thereby increasing tissue oxygen availability. HBO also decreases in-farct size and behavioral deficit, improving prognosis. But the exact mechanisms of HBO in cerebral ischemia remain to be elucidated. Apoptosis is one of the way to cell death in cerebral ischemia , which is the programmed cell death regulated by various agents including genes. Bcl - 2 family is a well studied gene related to apoptosis in which Bcl - 2 gene can prevent cells from apoptosis. Bax is homologous to Bcl - 2 and prompt cell apoptosis. The ratio between level of anti - apoptotic gene - Bcl - 2 and pro - apoptotic gene - Bax is im-portant for determining whether cell death is initiated or not. There were seldom reports about whether the protections of HBO against cerebral ischemia are related to apoptosis and apoptotic gene. Infarct volume,apoptosis, Bcl - 2 and Bax were detected by making rat model of focal cerebral ischemia induced by intraluminal filament occlusion of middle cerebral artery. The purpose is to investigate the effect of HBO on apoptosis and relevant mechanism after permanent focal cerebral ischemia.Meterials and MethodsA total of 70 healthy adult male Sprague - Dawley ( SD) rats aged 4 -5 months, weighting 180 - 200g , randomly divided into 4 groups: (1)normal control group ( n = 5 ) (2)sham operated group ( n = 5) (3)ischemic group (4)HBO ?treated group. (3) - (4)groups consisted of 6 groups including 6h,24h,48h,72h, 120h,10d respectively(n =5). Permanent focal cerebral ischemia was induced using intraluminal filament occlusion of middle cerebral artery introduced by Nagasawa et al. Animals in the HBO - treated groups received 100% O2at 2. 0 ata within 6h after filament introdution in single hyperbaric chamber. Pure oxygen was applied to replace 100% O2at 2.0 ata about 10min during hyperbaric treatment. The compression time in the chamber was 60min. The decompression was performed in 20min. Animals in ische-mic groups received pure oxygen. The treatment was performed each day. At various times after ischemia (6h,24h,48h,72h,120h, 10d) , animals were deeply anesthetized with 10% Chloral Hydrate and perfused by intracadiac puncture using 4% poly formaldehyde -0. 1PB (PH 7.4). Brain were then excised and postfixted for 24h . Brain tissues were embedded in paraffin, coronally sectioned ( 6 um). The sizeof infarct on coronal sections of HE staining were measured using Q570 image analysis system. The infarct volume was calculated as the sum of the sectional infarct areas multiplied by the interval thickness. In situ end labeling TUNEL method was use to study cell apoptosis in brain. Immunohistochemistry(SP) was used to observe the expression of Bel - 2 and Bax protein. Semi - quantitative method was applied to analysis apoptotic and immunohistochemical cells. All values were stated as mean S. D. Comparisons between ischemic group and HBO group at different time - points of cerebral ischemia were made using t - test.Result1. Infarct volum;The infarct lesion was initially found at 6h of ischemia within the territory of the occluded middle cerebral artery including cortex and subcortical areas with light microscope. The boundaries between areas of ischemic damage and the adjacent normal areas of the brain could be sharply delineated. The infarct volum then e-volved until 24h of ischemia and did not significa... |
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