斯氏并殖吸虫抗原致大鼠脑组织病变的光镜、电镜观察

摘 要 目的 研究斯氏并殖吸虫大鼠脑病的病理改变。方法 自并殖吸虫流行区采集溪蟹,分离斯氏并殖吸虫囊蚴,经腹腔注射感染犬,3个月后剖杀,检获斯氏狸殖吸虫成虫制备抗原,用于制作SD大鼠肺吸虫脑病模型。将6只SD雄性大鼠随机等分为并殖吸虫注射抗原的实验组、注射生理盐水的对照组。24h后解剖大鼠,取脑组织、固定、切片。光镜观察大鼠脑组织病理变化,电镜观察超微结构病理变化。结果 HE显示抗原注射大鼠脑血肿周围组织水肿明显,且局灶状坏死,神经元皱缩,尼氏小体溶解,周围出现间隙,神经突呈浅淡或消失,可见单核细胞及胶质细胞反应。电镜显示抗原注射组大鼠大脑皮质神经元胞体肿胀,核移位且形状不规则,核膜凸凹不平,核质溢出;染色质为絮状;线粒体肿胀,粗面内质网扩张呈囊泡化;脂褐素较多。结论 肺吸虫抗原注射大鼠脑可引起脑组织光镜和超微结构改变：细胞肿胀,线粒体肿胀,内质网扩张。 关键词：斯氏并殖吸虫;抗原;大鼠;脑组织;超微结构病理     

嗅成鞘细胞移植对AD大鼠脑内COX活性和线粒体超微结构的影响

目的 探讨嗅成鞘细胞(OECs)移植对阿尔茨海默病(AD)大鼠脑内COX活性和线粒体超微结构的影响.方法 SD大鼠双侧海马注射Aβ1～40,建立AD大鼠模型.实验动物分为四组:正常对照组、AD模型组、OECs移植组、人工脑脊液(MCSF)注射组,每组12只.体外原代培养OECs并将其移植至AD大鼠双侧海马.运用行为学测试、组织化学、原位杂交结合图像分析以及电镜等技术和工具,观察、比较各组大鼠学习记忆能力、海马CA1区线粒体细胞色素氧化酶(COX)活性、细胞色素氧化酶Ⅱ型亚基(COⅡ)mRNA表达,以及CA1区神经元线粒体超微结构等指标的变化.结果 与正常对照组比较,AD模型组大鼠空间学习记忆能力、海马CA1区线粒体COX活性及COⅡmRNA表达明显降低(P<0.05),线粒体数量减少,结构不清、肿胀、空泡样变、嵴断裂;OECs移植明显上调上述指标(P<0.05),并对线粒体超微结构有明显的保护作用.结论 OECs移植通过改善AD大鼠学习记忆能力、提高海马COX活性和COⅡmRNA表达以及保护线粒体等作用,对大鼠AD具有明显的治疗效果.     

蒿甲醚引起线粒体跨膜电位下降在神经毒性中的作用

目的　用嗜铬细胞瘤细胞(PC12细胞)、原代培养的大鼠神经元细胞和大鼠脑线粒体作为体外模型观察线粒体跨膜电位(mitochondrialmembranepotential,MMP)和细胞膜通透性改变在蒿甲醚引起的神经毒性中的作用。　方法　用流式细胞仪测定蒿甲醚对线粒体跨膜电位和细胞膜通透性的影响,用分光光度法分析蒿甲醚对线粒体肿胀度的影响。　结果　蒿甲醚能够降低两种细胞的MMP,使其峰值左移,摄入的Rh123荧光强度降低,量效关系明显;能增加两种细胞的细胞膜通透性,使细胞内的PI摄入增加;能引起大鼠脑线粒体肿胀,有一定的时间效应和剂量效应关系。结论　MMP下降是蒿甲醚引起神经毒性的重要环节,可通过影响线粒体膜通透性转运孔,改变线粒体跨膜电位和线粒体肿胀度,并能增加细胞膜通透性,引起细胞能量代谢障碍,最终导致神经毒性     

坐骨神经卡压对脊髓运动神经元及胶质细胞的影响

目的探讨周围神经卡压对大鼠脊髓神经元、神经胶质细胞及超微结构的影响。方法以坐骨神经卡压法建立大鼠周围神经卡压模型50只,设左侧为实验侧,右侧为正常对照,按试验设计分别于12、18、24、30、36 w后入路取材(L4^L6),进行两侧神经元计数、两侧神经元数目之比(L/R)等指标检测,观察神经胶质细胞和神经细胞超微结构变化。结果①HE染色:术后12 w,脊髓前角神经元数目无明显变化,术后18、24、30、36 w神经元数目分别减少7.46%、12.24%、16.83%、20.98%,术后18 w发现"卫星现象",30 w时位于laminaⅨ区的前角细胞明显减少,局部可见大量神经胶质细胞。②电镜观察:脊髓前角细胞于12 w时可见核仁清晰,染色质分布均匀,呈正常染色质状态,但线粒体肿胀,内质网扩张;18 w时染色质边集,异染色质增多,线粒体肿胀加剧,内质网进一步扩张,溶酶体消失;24、30、36 w核变小且深染浓缩,细胞空化,核周膜模糊不清,神经细胞趋向坏死。结论坐骨神经卡压后相应节段脊髓前角α运动神经元数目减少,并随卡压时间延长、程度加重而加重且超微结构发生改变;神经胶质细胞在神经损伤早期修复起重要作用。     

脑室内移植嗅成鞘细胞改善大鼠阿尔茨海默病的症状

目的探讨嗅成鞘细胞（olfactory ensheathing cells,OECs）脑室内注射对大鼠阿尔茨海默病的影响。方法sD大鼠双侧海马注射ABl．40,建立AD大鼠模型。实验动物分为四组：正常对照组、AD模型组、OECs移植组、MCSF注射组,每组10只。体外原代培养嗅成鞘细胞并将其移植至AD大鼠侧脑室。运用行为学测试、组织化学、原位杂交结合图像分析以及电镜等技术,观察、比较各组大鼠学习记忆能力、海马CA1区线粒体细胞色素氧化酶（cytochrome oxidase,COX）活性、细胞色素氧化酶Ⅱ型亚基（COⅡ）mRNA表达、一氧化氮合酶（nitric oxide synthase,NOS）阳性神经元数,以及CA1区神经元线粒体超微结构等指标的变化。结果与正常对照组比较,AD模型组大鼠空间学习记忆能力、海马CA1区线粒体COX活性及CO II mRNA表达、NOS阳性神经元数明显降低或减少俨〈0．05）,线粒体数肇减少,结构不清、肿胀、空泡样变、嵴断裂;嗅成鞘细胞移植明显上调上述指标俨〈0．05）,并对神经元线粒体超微结构有明显的保护作用。结论嗅成鞘细胞移植通过改善AD大鼠学习记忆能力、提高海马COX活性和CO1ImRNA、NOS阳性神经元表达以及保护神经元线粒体等作用,对大鼠阿尔茨海默病具有明显的治疗作用。     

低剂量T-2毒素对大鼠体外培养软骨细胞影响的超微结构观察

目的观察低剂量T-2毒素对大鼠体外培养软骨细胞的影响。方法单层原代培养的软骨细胞加入不同浓度T-2毒素(0．5、1．0μg／L)培养24h，用透射电子显微镜观察软骨细胞超微结构。结果0．5μg/L T-2毒素组软骨细胞细胞质内细胞器数量明显减少，核固缩，染色质形成斑块状散布核内，核膜增厚，双层膜结构不清；粗面内质网数量减少且不扩张；部分线粒体空泡变性和髓样变。1．0μg/L T-2毒素组软骨细胞表面微绒毛脱失，细胞核改变非常明显，可见许多畸形核；胞质内可见大量空泡变性的线粒体，并可见线粒体的髓样变；粗面内质网扩张成囊状，脱颗粒，偶见凋亡的软骨细胞，细胞核固缩，形成高密度斑块。结论0．5μg/L T-2毒素即可对体外培养软骨细胞造成损害，剂量越大．损害越严重。     

实验性肝硬化大鼠纹状体中神经元的形态定量学研究

目的 观察肝硬化大鼠纹状体中神经元的形态及数目的变化，探讨肝性脑病的发病机制。方法 用四氯化碳（CCL4）建立肝硬化模型，尼氏染色法观察纹状体神经元的变化。图像分析仪对神经元的形态及数量变化做定量分析。结果 肝硬化模型制备成功。肝硬化大鼠纹状体中神经元数量减少，染色变浅，尼氏小体减少或消失。结论 提示纹状体神经元的变化有可能与肝性脑病时出现的运动异常有关。     

人参皂苷Rg2对阿尔茨海默病模型大鼠海马神经元结构及突触素表达的影响

目的探讨人参皂苷Rg2对Aβ25～35诱导的阿尔茨海默病(AD)模型大鼠海马神经元结构及突触素(SY)表达的影响。方法大鼠腹腔注射人参皂苷Rg2预防给药,海马内注射Aβ25～35建立AD模型,5 w后采用HE染色法光镜观察大鼠海马神经元的一般结构;免疫组化染色显示大鼠海马神经元SY的表达,并进行定量分析;透射电子显微镜观察大鼠海马神经元的超微结构。结果与正常对照组相比,AD模型组大鼠海马神经元数量明显减少,暗细胞神经元数量增多;SY免疫组化染色浅,吸光度值显著下降;神经元核内异染色质增多,胞质内线粒体肿胀、嵴断裂,可见脂褐素颗粒,神经毡内突起空化,神经丝和线粒体减少。人参皂苷Rg2各剂量组大鼠海马神经元的一般形态结构和超微结构较AD模型组均有不同程度的改善;SY免疫组化染色加深,吸光度值上升。结论人参皂苷Rg2对AD模型大鼠海马神经元的结构和SY的表达均有一定的保护作用。     

雷公藤内酯醇对Tca 8113细胞增殖周期进程的影响

目的 观察雷公藤内酯醇(TL)对体外培养的人舌癌细胞系Tca8113细胞诱导分化机制,为人舌癌治疗提供理论依据.方法 应用噻唑蓝(MTT)比色法检测不同浓度的TL对Tca8113细胞的增殖抑制率,相差显微镜观察细胞形态学改变,流式细胞仪检测Tca8113细胞周期进程改变及凋亡率,电子显微镜观察经TL作用后的Tca8113细胞超微结构改变.结果 TL对Tca8113细胞的增殖抑制率呈明显的剂量依赖性,相差显微镜下实验组细胞贴壁不佳,并且数目减少,细胞圆缩.流式细胞仪结果显示G1期细胞增多,S期细胞减少,G2/M期细胞增多,细胞凋亡率升高.电子显微镜下可见细胞高度空化,线粒体肿胀,细胞核染色质趋边,可见凋亡小体.结论 TL对Tca8113细胞有显著的增殖抑制作用,阻止Tca8113细胞G1期向S期转化进程,诱导Tca8113细胞凋亡及亚细胞结构改变.     

亚低温对SAH大鼠ROS表达水平及神经元细胞的影响

目的 探究亚低温对自发性蛛网膜下腔出血(SAH)大鼠线粒体活性氧(ROS)表达水平及神经元细胞的影响。方法 将所选取的大鼠(18只健康雄性SD大鼠，体重150～186 g,鼠龄3～4 w)随机分组：常温组(NT组)、对照组(CO组)和亚低温组(MH组),每组6只。通过二氯荧光素法检测线粒体ROS产生速率、TUNEL法检测神经元细胞凋亡、RT-PCR法检测降钙素基因相关肽(CGRP) mRNA的表达量、Western印迹检测大鼠脑组织中CGRP蛋白表达。结果 CO组CA1区脑组织结构正常，核周边内质网、线粒体等细胞器丰富；NT组大鼠CA1区部分脑组织损伤明显，细胞器溶解；MH组CA1区脑组织结构基本正常，细胞膜、核结构存在轻微损伤。NT组线粒体ROS产生速率明显高于MH组，MH组产生速率明显高于CO组(均P<0.05)。NT组神经元细胞凋亡数量显著高于MH组(P<0.05),MH组神经元细胞凋亡数量明显高于CO组(P<0.05)。NT组大鼠脑组织的CGRP蛋白含量、CGRP mRNA表达量显著低于MH组，MH组大鼠脑组织的CGRP蛋白含量、CGRP mRNA表达量明显低...     

连续性血液滤过治疗重型肝炎合并肝性脑病16例临床疗效观察

目的观察连续性血液滤过（CVVH）治疗重型肝炎合并肝性脑病的临床疗效。方法将32例重型肝炎合并肝性脑病患者随机分为两组。治疗组：内科综合疗法＋CVVH。对照组：内科综合疗法。治疗前后分别检测肝肾功能、血氨、TNF和IL-6等。结果治疗组、对照组患者的清醒率分别为75．0％和31．3％。CVVH治疗后血清尿素氮、肌酐、氨、TNF及IL-6比对照组明显下降（P〈0．05）。血清胆红素、TBA下降与对照组比较无显著性差异（P〉0．05）。治疗组肝性脑病Ⅰ-Ⅱ期患者的存活率明显高于Ⅲ-Ⅳ期（P〈0．05）。结论CVVH是辅助治疗重型肝炎合并肝性脑病的有效方法,早期治疗能进一步提高疗效。     

Ammonia and related amino acids in the pathogenesis of brain edema in acute ischemic liver failure in rats.

The pathogenesis of brain edema in acute liver failure is poorly understood. We have previously shown that rats with ischemic acute liver failure (portacaval anastomosis followed by hepatic artery ligation) exhibit brain edema and intracranial hypertension, with swelling of cortical astrocytes as the most prominent neuropathological abnormality. Because ammonia has been shown to induce swelling of astrocytes in vivo and in vitro, we examined the relationship between brain ammonia, amino acids generated from ammonia metabolism and brain water content in this model. Four groups of animals were studied: rats subjected to two sham operations, rats subjected to portacaval anastomosis and a sham operation, rats subjected to a sham operation and hepatic artery ligation and rats subjected to portacaval anastomosis and hepatic artery ligation. The last group of animals was studied at three progressive stages of encephalopathy. Cortical gray matter water increased from 80.26% +/- 0.22% (sham + sham) to 82.46% +/- 0.06% (last stage of devascularization). In cerebral cortex, brain ammonia increased to a maximum of 5.4 mmol/L. Glutamine, generated in glial cells from ammonia and glutamate, increased sixfold to 24 mmol/L and remained at this level throughout all stages of encephalopathy. Alanine, which may be generated from the transamination of glutamine, increased in parallel to the increase in water (r = 0.80, n = 15). In this model of fulminant liver failure and associated brain edema, brain ammonia increases to levels associated with in vitro swelling of brain slices and glial cells. The accumulation of osmogenic aminoacids such as glutamine and alanine may contribute to the selective astrocyte swelling seen in this condition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in brain metabolism during hyperammonemia and acute liver failure: results of a comparative 1H-NMR spectroscopy and biochemical investigation

The effects of hyperammonemia on brain function have been studied in three different experimental models in the rat: acute liver ischemia, urease-treated animals and methionine sulfoximine-treated animals. To quantify the development of encephalopathy, clinical grading and electroencephalographic spectral analysis were used as indicators. In all three experimental models brain ammonia concentrations increased remarkably associated with comparable increases in severity of encephalopathy. Furthermore, in vivo 1H-nuclear magnetic resonance spectroscopy of a localized cerebral cortex region showed a decrease in glutamate concentration in each of the aforementioned experimental models. This decreased cerebral cortex glutamate concentration was confirmed by biochemical analysis of cerebral cortex tissue post mortem. Furthermore, an increase in cerebral cortex glutamine and lactate concentration was observed in urease-treated rats and acute liver ischemia rats. As expected, no increase in cerebral cortex glutamine was observed in methionine sulfoximine-treated rats. These data support the hypothesis that ammonia is of key importance in the pathogenesis of acute hepatic encephalopathy. Decreased availability of cerebral cortex glutamate for neurotransmission might be a contributing factor to the pathogenesis of hyperammonemic encephalopathy. A surprising new finding revealed by 1H-nuclear magnetic resonance spectroscopy was a decrease of cerebral cortex phosphocholine compounds in all three experimental models. The significance of this finding, however, remains speculative.     

Hepatic encephalopathy. Experimental studies in a rat model of fulminant hepatic failure

A new approach to pathogenetic study of hepatic encephalopathy was recently undertaken in order to identify the neurological alterations of the brain which characterize the coma. In this study attention was firstly addressed to a correct and objective evaluation of the comatose state in rats with fulminant hepatic failure induced by galactosamine. For this purpose visual evoked potentials were utilized since this electrophysiological test proved reliable and sensitive on the basis of an extensive pharmacological study. Two different stages of coma were identified in the rat and they were named mild and severe. Receptor binding studies performed on brain membranes of these rats show in the mild stage an increased number of low and high affinity GABA receptors and a decreased affinity of dopamine receptors. The severe stage is characterized by the persistence of only high affinity GABA receptors and a reduced number of dopamine receptors. This imbalance between inhibitory and excitatory receptor systems may explain the generalized central nervous system depression which characterizes the hepatic encephalopathy while the increased number of benzodiazepine receptors found in both stages of coma may account for the brain supersensitivity to sedative administration of patients with liver disease and for the sedative-induced episodes of coma. These receptor alterations may be attributed to a disuse and/or a partial degeneration of nerve terminals due to peripheral neurotoxins (i.e., ammonia, mercaptans, short chain fatty acids) and the decrease of glutamate decarboxylase activity and of zinc levels in brain tissues seems to be respectively a direct and an indirect demonstration of this phenomenon. Bearing in mind the supersensitivity of the GABA-benzodiazepine receptor system and their reciprocal interaction, a benzodiazepine antagonist was administered to rats in mild stage of encephalopathy. Electrophysiological and benzodiazepine binding studies demonstrated that this treatment can temporarily counteract some of the neurological disturbances of the earlier stage of coma and act as antidote of the sedative-induced episodes of coma.     

Hepatic encephalopathy in thioacetamide-induced acute liver failure in rats: characterization of an improved model and study of amino acid-ergic neurotransmission

An imbalance of excitatory and inhibitory amino acid-ergic neurotransmission has been suggested to play a role in the pathogenesis of hepatic encephalopathy. For further evaluation of this hypothesis, several parameters of amino acid-ergic neurotransmission were studied in rats with acute liver failure induced by the administration of 300 mg per kg thioacetamide by gavage on two consecutive days. By appropriate supportive care, hypoglycemia, renal failure and hypothermia were avoided. Rats were monitored clinically and neurologically. Hepatic encephalopathy evolved in four distinct, easily recognizable stages. Light and electron microscopic examination of brains of rats with hepatic encephalopathy revealed only a slight swelling of nuclei of neurons and astrocytes without signs of neuronal degeneration or brain edema. In rats with hepatic encephalopathy, the concentrations of GABA, glutamate and taurine were decreased in the cerebral cortex, the hippocampus and the striatum, whereas those of aspartate and glycine were unchanged or increased. GABAA and benzodiazepine receptors were studied as parameters for the postsynaptic GABAA-benzodiazepine receptor complex, glutamic acid decarboxylase as parameter for presynaptic GABA-ergic neurons and stimulation of benzodiazepine binding by GABA as a parameter for a GABA-mediated postsynaptic event. None of these parameters was different in hepatic encephalopathy as compared to controls. Similarly, Ca++/Cl(-)-dependent and -independent glutamate receptors as parameters for glutamatergic neurons were unchanged in rats with hepatic encephalopathy. Thus, in rats with thioacetamide-induced liver failure and hepatic encephalopathy, changes of the concentrations of neurotransmitter amino acids occur in the brain. Other neurochemical parameters, however, failed to identify alterations of GABA-ergic or glutamatergic neurotransmission in hepatic encephalopathy.     

Changes in glutamate-cycle enzyme mRNA levels in a rat model of hepatic encephalopathy

To detect possible changes in the regulation of glutamate/-aminobutyric acid (GABA) enzymes at the level of gene expression in a thioacetamide-induced rat model of acute hepatic encephalopathy, we have examined changes in the mRNAs of four glutamate/GABA enzymes by quantitative RNA blot hybridization analysis. Such changes could reflect cell adaptation to excess ammonia or some other associated metabolic stress. The mRNA levels of glutamate dehydrogenase (GDH) decreased similarly in three different brain regions, whereas those of glutamine synthetase (GS) and glutaminase (GA) increased. The mRNA levels of glutamate decarboxylase (GAD) were unchanged. The results indicate that some effect of liver damage, presumably hyperammonemia, affected the expression of some, but not all, genes associated with ammonia and glutamate metabolism in the brain. This adaptation of gene expression to secondary effects of ammonia on brain amino acid neurotransmitter metabolism or brain energy metabolism could play a role in the physiological changes observed in hepatic encephalopathy.     

Hyperammonemia,brain edema and blood-brain barrier alterations in prehepatic portal hypertensive rats and paravrtamol intoxication

AIM: To study the blood-brain barrier integrity, brain edema,animal behavior and ammonia plasma levels in prehepatic portal hypertensive rats with and without acute liver intoxication.METHODS: Adults male Wistar rats were divided into four groups. Group Ⅰ: sham operation; Ⅱ: Prehepatic portal hypertension, produced by partial portal vein ligation; Ⅲ:Acetaminophen intoxication and Ⅳ: Prehepatic portal hypertension plus acetaminophen. Acetaminophen was administered to produce acute hepatic injury. Portal pressure, liver serum enzymes and ammonia plasma levels were determined. Brain cortex water content was registered and trypan blue was utilized to study blood brain barrier integrity. Reflexes and behavioral tests were recorded.RESULTS: Portal hypertension was significantly elevated in groups Ⅱ and Ⅳ. Liver enzymes and ammonia plasma levels were increased in groups Ⅱ, Ⅳ and Ⅳ. Prehepatic portal hypertension (group Ⅱ), acetaminophen intoxication (group Ⅲ) and both (group Ⅳ) had changes in the blood brain-barrier integrity (trypan blue) and hyperammonemia. Cortical edema was present in rats with acute hepatic injury in groups Ⅲ and Ⅳ. Behavioral test (rota rod) was altered in group Ⅳ.CONCLUSION: These results suggest the possibility of another pathway for cortical edema production because blood brain barrier was altered (vasogenic) and hyperammonemia was registered (cytotoxic). Group Ⅳ, with behavioral altered test, can be considered as a model for study at an early stage of portal-systemic encephalopathy.     

Hyperammonemia, brain edema and blood-brain barrier alterations in prehepatic portal hypertensive rats and paracetamol intoxication

AIM: To study the blood-brain barrier integrity, brain edema, animal behavior and ammonia plasma levels in prehepatic portal hypertensive rats with and without acute liver intoxication. METHODS: Adults male Wistar rats were divided into four groups. Group I: sham operation; II: Prehepatic portal hypertension, produced by partial portal vein ligation; III: Acetaminophen intoxication and IV: Prehepatic portal hypertension plus acetaminophen. Acetaminophen was administered to produce acute hepatic injury. Portal pressure, liver serum enzymes and ammonia plasma levels were determined. Brain cortex water content was registered and trypan blue was utilized to study blood brain barrier integrity. Reflexes and behavioral tests were recorded. RESULTS: Portal hypertension was significantly elevated in groups II and IV. Liver enzymes and ammonia plasma levels were increased in groups II, III and IV. Prehepatic portal hypertension (group II), acetaminophen intoxication (group III) and both (group IV) had changes in the blood brain-barrier integrity (trypan blue) and hyperammonemia. Cortical edema was present in rats with acute hepatic injury in groups III and IV. Behavioral test (rota rod) was altered in group IV. CONCLUSION: These results suggest the possibility of another pathway for cortical edema production because blood brain barrier was altered (vasogenic) and hyperammonemia was registered (cytotoxic). Group IV, with behavioral altered test, can be considered as a model for study at an early stage of portal-systemic encephalopathy.     

Hepatic encephalopathy,ammonia, glutamate,glutamine and oxidative stress

This review addresses recent and not so recent works that emphasize on the mechanisms by which liver damage can induce encephalopathy. Hepatic encephalopathy constitutes an intriguing complication in severe liver acute and chronic disease, whose pathophysiology is still not completely understood. In this pathology, alterations in normal brain function are associated with morphological and functional impairments of astrocytes and neurons. A wide spectrum of psychoneurological symptoms has been described and the anatomical substratum is usually associated with brain edema and intracranial hypertension, as well as with changes in the function of brain cells. An increase in blood ammonia, toxic to the brain, depends on the activity of the enzyme glutamine synthetase, the glutamine/glutamate cycle and the brain capacity to eliminate toxic substances. When the concentration of the excitotoxic neurotransmitter glutamate is increased, it acts as a toxic agent, especially when its specific transporters are altered and its uptake is decreased. Glutamine has also been recently considered a toxic substance when its concentration is high, and consequently contributes to brain edema. Finally, the formation of reactive oxygen species, basically produced by mitochondria, influence with their toxic action on membrane lipids, proteins and DNA. In conclusion we suggest that at least these four elements are involved directly in the mechanism of hepatic encephalopathy.