Insulin Resistance Disrupts the Interaction Between AKT and the NMDA Receptor and the Inactivation of the CaMKIV/CREB Pathway in Minimal Hepatic Encephalopathy.

Hepatic cirrhosis-induced Minimal hepatic encephalopathy (MHE) has been characterized for cognitive dysfunction and central nervous system (CNS) insulin resistance (IR) has been acknowledged to be closely correlated with cognitive impairment while hepatic cirrhosis has been recognized to induce IR. Thus, this study aimed to investigate whether CNS IR occurred in MHE and induced MHE, as well as the underlying mechanism. We found IR in the MHE rats, an especially decreased level of the insulin receptor (InsR), and an increased serine phosphorylation of IRS1 in CNS. PI3K/AKT pathway signaling to the phosphorylation of N-Methyl-d-Aspartate receptors (NMDA receptors, NRs, NR1/NR2B) and downstream activation of the CaMKIV/CREB pathway and final production of neurotrophic factors were triggered by insulin, but impaired in the MHE rats. Additionally, CNS IR, memory impairment, the desensitization of the PI3K/AKT/NMDA receptor (NR)/CaMKIV/CREB pathway and decreased production of BDNF/NT3 in MHE rats were improved by rosiglitazone (RSG). These results suggested that IR, which induces the deficits in the insulin-mediated PI3K/AKT/NR/CaMKIV/CREB/neurotrophin pathway and subsequent memory decline, contributes to the pathogenesis of MHE.

[Differences between cerebellum and hippocampus in antioxidant system].

The effect of portacaval shunting on the antioxidant status of the cerebellum and hippocampus was studied in rats using standard methods of enzymatic analysis. Endogenous ammonia levels and activities of eight antioxidant enzymes were shown to be unequal in two brain regions and to respond differently upon portal-systemic shunt surgery.

A Src family kinase inhibitor improves survival in experimental acute liver failure associated with elevated cerebral and circulating vascular endothelial growth factor levels.

BACKGROUND AND AIMS: Acute liver failure (ALF) is frequently complicated by cerebral oedema, systemic inflammation and multiorgan dysfunction. Vascular endothelial growth factor (VEGF) may stimulate liver regeneration but it can also be pro-inflammatory, activating endothelial cells and increasing permeability, actions mediated through Src kinase signalling. We therefore examined whether a Src inhibitor could have therapeutic potential in ALF. METHODS: Murine ALF was induced with azoxymethane. Liver pathology was graded by a blinded examiner and apoptosis quantified by immunohistochemistry. Cerebral VEGF expression was imaged using VEGF-green fluorescent protein transgenic mice. Circulating and macrophage-secreted VEGF levels were measured. Experimental animals received a Src inhibitor or vehicle controls. RESULTS: VEGF was undetectable in normal plasma but reached a mean of 835 pg/ml at grade III encephalopathy (P<0.001). Ammonia, lipopolysaccharide and interferon-gamma acted synergistically to enhance VEGF secretion by macrophages. Production of VEGF by cerebral cortical astrocytes increased with disease progression. Late treatment with inhibitors of Src or VEGF did not improve liver histology, encephalopathy or survival. However, early use of a Src kinase inhibitor significantly reduced hepatic injury, delayed encephalopathy and allowed 25% of mice to survive an otherwise lethal insult. CONCLUSION: Systemic and cerebral VEGF levels are significantly elevated during experimental ALF and may be exacerbated by hyperammonemia and macrophage activation. Early use of a Src inhibitor reduced hepatocellular injury and enabled survival, indicating such agents may have some promise in the treatment of ALF.

Lack of detrimental or therapeutic effects of cyclooxygenase inhibition in bile duct-ligated rats with hepatic encephalopathy.

BACKGROUND: The pathogenetic mechanisms of hepatic encephalopathy (HE) are not fully understood. Cerebral blood flow regulated by cyclooxygenase (COX) may be involved in the development of HE. There are no comprehensive data concerning the effects of COX inhibition on HE in chronic liver disease. METHODS: Male Sprague-Dawley rats weighing 240-270 g at the time of surgery were selected for experiments. Secondary biliary cirrhosis was induced by bile duct ligation (BDL). Those rats were then divided into two groups to receive i.p. injection of indomethacin (5 mg/kg per day) or distilled water for 7 days from day 36 to day 42 after BDL. The control group consisted of rats receiving a sham operation. Severity of encephalopathy was assessed by counts of motor activity. Plasma levels of tumor necrosis factor (TNF)-alpha and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), and liver biochemistry tests were determined after treatment. RESULTS: The motor activity in both groups of BDL rats were significantly lower than that of the control group (P < 0.001). As compared with the BDL rats treated with distilled water, BDL rats treated with indomethacin had significant lower levels of 6-keto-PGF(1alpha), but the motor activity, TNF-alpha levels and serum biochemistry tests were not significantly different between both BDL groups. CONCLUSIONS: Chronic indomethacin administration did not have significantly detrimental or therapeutic effects on the severity of encephalopathy in BDL rats.

Hepatocerebral mitochondrial DNA depletion syndrome caused by deoxyguanosine kinase (DGUOK) mutations.

BACKGROUND: Autosomal recessive mutations in deoxyguanosine kinase (DGUOK) have been identified in the hepatocerebral form of mitochondrial DNA (mtDNA) depletion syndrome. OBJECTIVES: To describe the clinical spectrum of DGUOK-related mtDNA depletion syndrome in 6 children and to summarize the literature. RESULTS: We identified pathogenic mutations in DGUOK in 6 children with the hepatocerebral form of mtDNA depletion syndrome. We describe the clinical, neuroradiologic, histologic, and genetic features in these children. All children showed severe hepatopathy, while involvement of other organs (skeletal muscle and brain) was variable. We identified 5 novel mutations (1 of them in 2 children) and 2 previously described mutations. Three different mutations affected the initial methionine, suggesting a mutational hot spot. One of our patients underwent liver transplantation; pathologic findings revealed (in addition to diffuse hepatopathy) a hepatocellular carcinoma, implying a possible link between mtDNA depletion syndrome and tumorigenesis. CONCLUSION: We studied 12 children with infantile hepatoencephalopathies and mtDNA depletion syndrome and found pathogenic DGUOK mutations in 6, suggesting that this gene defect is a frequent but not an exclusive cause of the hepatic form of mtDNA depletion syndrome.

Detrimental effects of nitric oxide inhibition on hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure: role of nitric oxide synthase isoforms.

BACKGROUND: Hepatic encephalopathy is a complex neuropsychiatric syndrome. A previous study showed that chronic nitric oxide (NO) inhibition aggravated the severity of encephalopathy in thioacetamide (TAA)-treated rats. The present study investigated the relative contribution of NO synthase (NOS) isoforms on the severity of hepatic encephalopathy in TAA-treated rats. METHOD: Fulminant hepatic failure was induced in male Sprague-Dawley rats by intraperitoneal injection of TAA (350 mg/kg/day) for 3 days. Rats were divided into three groups to receive N(omega)-nitro-L-arginine methyl ester (L-NAME, a non-selective NOS inhibitor, 25 mg/kg/day in tap water), L-canavanine (an inducible NOS inhibitor, 100 mg/kg/day via intraperitoneal injection) or normal saline (N/S) from 2 days prior to TAA administration and lasting for 5 days. Severity of encephalopathy was assessed by the counts of motor activity. Plasma levels of tumor necrosis factor-alpha (TNF- alpha) were determined by enzyme-linked immunosorbent assay (ELISA), and total bilirubin, alanine aminotransferase (ALT) and creatinine were determined by colorimetric assay. RESULTS: Compared with L-canavanine or N/S-treated rats (0% and 4%, respectively), the mortality rate was significantly higher in rats receiving L-NAME administration (29%, P < 0.005). Inhibition of NO created detrimental effects on the counts of motor activities (P < 0.05). Rats treated with L-NAME had significantly higher plasma levels of total bilirubin, ALT, creatinine and TNF- alpha as compared with rats treated with L-canavanine or N/S (P < 0.01). CONCLUSION: Chronic L-NAME administration, but not L-canavanine, had detrimental effects on the severity of hepatic damage and motor activities in TAA-treated rats. These results suggest that constitutive NOS activities play a major protective role in rats with fulminant hepatic failure.

Role of phosphate-activated glutaminase in the pathogenesis of hepatic encephalopathy.

Disturbed body nitrogen homeostasis due to impaired hepatic urea synthesis leads to an alteration in inter-organ ammonia trafficking, resulting in hyperammonemia. Glutamine (Gln) synthase is the alternative pathway for ammonia detoxification. Gln taken up by several organs is split by the intramitochondrial phosphate-activated enzyme glutaminase (PAG) into glutamate (Glu) and ammonia. In cirrhotic patients with portosystemic intrahepatic shunt, the main source of systemic hyperammonemia is the small intestine, and ammonia derives mainly from Gln deamidation. Recently, PAG has been found increased in cirrhotics showing minimal hepatic encephalopathy and, therefore, could be implicated in the production of systemic hyperammonemia in these patients. Intestinal PAG activity correlates with psychometric test and magnetic resonance spectroscopy findings. Moreover, nitric oxide and tumor necrosis factor seem to be the major factors regulating intestinal ammonia production in cirrhotics. In the brain, PAG localized into the astrocytes is responsible for ammonia and free-radical production. The blockade of PAG, using 6-oxo-5-norleucine, avoids the toxic effects of Gln accumulation in the brain. These data support an important role for intestinal and brain glutaminase in the pathogenesis of hepatic encephalopathy and could be a new target for future therapies.

Altered modulation of soluble guanylate cyclase in lymphocytes from patients with liver disease.

Studies of animal models suggest that the activation of soluble guanylate cyclase by nitric oxide is altered in liver disease. We studied 77 patients with liver disease and 17 controls, to investigate whether the activation of soluble guanylate cyclase is altered in lymphocytes from patients with liver disease. The basal content of guanosine 3',5'-cyclic monophosphate (cGMP) in lymphocytes was decreased both in patients with liver cirrhosis (by 52%) and in patients with chronic hepatitis (by 62%). Activation of soluble guanylate cyclase by nitric oxide was higher in lymphocytes from patients with cirrhosis (3100+/-1000% of basal) or with hepatitis (5200+/-2500% of basal) than in lymphocytes from controls (1200+/-500% of basal). cGMP in plasma was increased in patients with liver disease. Successful (but not unsuccessful) treatment with interferon of patients with hepatitis due to virus C reversed all the above alterations. Altered modulation of soluble guanylate cyclase by nitric oxide in liver disease may play a role in the hemodynamic alterations found in these patients.

Cytochrome oxidase activity of the suprachiasmatic nucleus and pineal gland in rats with portacaval shunt.

Rhythmic behavioral and biochemical changes have been observed in both human and animal models with hepatic insufficiency. The basis of all these alterations is the principal endogenous pacemaker, the suprachiasmatic nucleus. The aim of this work, therefore, is to determine cytochrome c oxidase activity, a marker of neuronal activity and oxidative metabolism, in this nucleus in rats with portacaval shunt. In order to do this, this enzyme was histochemically marked and quantified by computer-assisted optical densitometry. Results show a reduced cytochrome oxidase activity in the suprachiasmatic nucleus in animals with portacaval shunts and, inversely, an increase in oxidative metabolism in the pineal gland, another circadian structure. However, the activity measured in a noncircadian brain structure, the hippocampus, which served as a control, showed no changes with surgery. Additionally, locomotor activity was assessed by actimeters and revealed a clearly reduced activity in animals with portacaval shunt. We conclude that the suprachiasmatic nucleus is possibly involved in the rhythmic changes associated with hepatic insufficiency.

Striatal manganese accumulation induces changes in dopamine metabolism in the cirrhotic rat.

Manganese (Mn) is an essential metal that, in excess, causes an extrapyramidal syndrome consisting in tremor, rigidity and akinesia. Recently, Mn was found to accumulate in brains of cirrhotic patients who also present motor abnormalities. Manganese alters dopaminergic transmission promoting an increase in the turnover of dopamine (DA). In this study, we studied the changes in dopamine and its main metabolite homovanillic acid (HVA) to evaluate DA turnover following administration of manganese to bile-duct obstructed rats. Some groups of rats were treated with manganese chloride in two concentrations: 0.5 and 1 mg/ml of Mn2+ in their drinking water. Four weeks after surgery and treatment with manganese, striatal Mn, DA and HVA were assessed. Marked increases (P<0.05) of striatal manganese content were observed in cirrhotic rats treated and untreated with manganese, these augments were dependent on the Mn concentration in water. Striatal contents of DA in cirrhotic rats diminished by 30% (P<0.05), administration of 0.5 mg/ml of manganese in drinking water to these rats returned dopamine to the basal level and 1 mg/ml of manganese increased dopamine content by 27%. The relationship of Mn content and DA turnover (HVA:DA) in the same animal showed a positive and statically significant correlation (P<0.05), with differences in slope for sham (b1=0.1528) and cirrhotic rats (b1=0.0174). These results suggest that manganese brain accumulation observed in liver failure could be a key element to understand dopamine metabolism in cirrhotic condition of humans.

Evidence of increased guanylate cyclase activation by acetylcysteine in fulminant hepatic failure.

Patients with fulminant hepatic failure (FHF) have a severe microcirculatory disturbance causing tissue hypoxia. Infusion of acetylcysteine improves survival and reduces the incidence of multiorgan failure by enhancing tissue oxygenation. Because the observed circulatory effects of acetylcysteine in FHF are similar to and synergistic with those produced by the microcirculatory vasodilator prostacyclin, we postulated that acetylcysteine might potentiate an endogenous vasodilator. Nitric oxide, a vasodilator that activates soluble guanylate cyclase, is a possible candidate as plasma cyclic 3',5'-guanosine monophosphate (cGMP) is raised in FHF, and in vitro acetylcysteine has been found to enhance soluble guanylate cyclase activity. To investigate this possible mechanism further, plasma cGMP was measured before and after acetylcysteine infusion in 24 patients with FHF and again in 6 patients after recovery from acute illness. cGMP levels were high in FHF during acute illness (median, 7.0 nmol/L [interquartile range, 2.6-10.0]) in comparison with levels taken after recovery (1.5 nmol/L [1.0-1.9]; P < .05). Levels rose further after acetylcysteine infusion in the FHF cases (mean increase, 204% [95% CI; 49 to +360]; P < .01) but not in the cases after recovery (38% [-7 to +84]). There were no significant changes in levels of plasma atrial natriuretic peptide (ANP) or cyclic adenosine monophosphate (cAMP) (mean increases, 8% [-6 to +22] and 17% [-9 to +43], respectively). The findings further support the hypothesis that the beneficial hemodynamic effects of acetylcysteine in FHF are mediated by enhancing the activity of the nitric oxide/soluble guanylate cyclase enzyme system.

Identification of the enzyme responsible for oxidative halothane metabolism: implications for prevention of halothane hepatitis.

BACKGROUND: Fulminant hepatic necrosis ("halothane hepatitis") is an unusual and often fatal complication of halothane anaesthesia. It is mediated by immune sensitisation in susceptible individuals to trifluoroacetylated liver protein neoantigens, formed by oxidative halothane metabolism. The seminal event in halothane hepatitis is hepatic metabolism, yet the enzyme responsible for oxidative halothane metabolism and trifluoroacetylated neoantigen formation remains unidentified. This investigation tested the hypothesis that cytochrome P450 2E1 (CYP2E1) is responsible for human halothane metabolism in vivo. METHODS: 20 elective surgical patients received either disulfiram (500 mg orally, n = 10) or nothing (controls, n = 10) the night before surgery. Disulfiram, converted in vivo to an effective inhibitor of P450 2E1, was used as a metabolic probe for P450 2E1. All patients received standard halothane anaesthesia (1.0% end-tidal, 3 h). Blood halothane and plasma and urine trifluoroacetic acid, bromide, and fluoride concentrations were measured for up to 96 h postoperatively. FINDINGS: Total halothane dose, measured by cumulative end-tidal (3.8 SE 0.1 minimum alveolar concentration hours) and blood halothane concentrations, was similar in the two groups. Plasma concentrations and urinary excretion of trifluoroacetic acid and bromide, indicative of oxidative and total (oxidative and reductive) halothane metabolism, respectively, were significantly diminished in disulfiram-treated patients. In control and disulfiram-treated patients cumulative 96 h postoperative trifluoroacetic acid excretion was 12,900 (SE 1700) and 2010 (440) mumol, respectively (p < 0.001) while that of bromide was 1720 (290) and 160 (70) mumol (p < 0.001). INTERPRETATION: The substantial attenuation of trifluoroacetic acid production by disulfiram after halothane anaesthesia suggests that P450 2E1 is a predominant enzyme responsible for human oxidative halothane metabolism. Inhibition of P450 2E1 by a single preoperative oral disulfiram dose greatly diminished production of the halothane metabolite responsible for the neoantigen formation that initiates halothane hepatitis. Single-dose disulfiram may provide effective prophylaxis against halothane hepatitis.

Influence of clinicopathological variables on CYP protein expression in human liver.

Drug metabolism is usually impaired in malnourished patients with decompensated cirrhosis, but the separate influence of clinicopathological variables, including nutritional status, on the expression of hepatic cytochrome P450 proteins has not been well characterized. We determined the hepatic content of CYP1A2, CYP2C8/10, CYP2E1 and CYP3A proteins in 71 subjects, 21 with histologically normal livers and 50 with chronic liver disease, and then tested for potential relationships between patient variables and individual CYP proteins by multivariate linear regression analysis. Variables analysed included nutritional status (determined by experienced clinicians), serum albumin and bilirubin concentrations, prothrombin time, the grade of ascites and hepatic encephalopathy, and the Child-Pugh score. Impaired nutrition and cachexia were associated with reductions of CYP2C8/10 levels of approximately 19 and 39%, respectively, relative to cases in which nutrition was replete. Similarly, CYP2E1 protein was reduced by approximately 13 and 26%, according to the apparent severity of nutritional impairment. In contrast, nutritional status did not contribute to variability in expression of CYP1A2 or CYP3A proteins. Of the clinicopathological variables analysed, only serum bilirubin was shown to have an independent influence on CYP protein content. Thus, elevated serum bilirubin concentrations were associated with significant declines in the contents of CYP1A2 and CYP2C8/10 but not CYP3A or CYP2E1. The mechanisms for the effects of nutritional status and serum bilirubin concentration on the levels of CYP proteins are unclear, but could be mediated by factors such as cytokines, dietary composition and alterations in the level of serum bile acids. Knowledge of the influence of clinicopathological factors and nutritional status on CYP expression should lead to more rational drug prescribing in patients with hepatic disease.

Cerebral phosphorus-31 magnetic resonance spectroscopy in patients with chronic hepatic encephalopathy.

Cerebral phosphorus-31 magnetic resonance spectroscopy was undertaken in 33 patients with biopsy-proven cirrhosis: 6 had no evidence of neuropsychiatric impairment on standard clinical, psychometric and electrophysiological testing; 8 had evidence of subclinical hepatic encephalopathy; and 19 were classified as having overt hepatic encephalopathy. The reference population comprised 15 healthy volunteers. Unlocalized spectra were acquired from the entire head with a 45-degree pulse angle and repetition times of 1 and 5 sec. Spectra localized to the basal ganglia were acquired with a 45-degree pulse angle and a repetition time of 1 sec. Peak area ratios of phosphomonoesters, inorganic phosphate, phosphodiesters and phosphocreatine relative to beta-ATP were measured in the spectra acquired. We noted no consistent change in the ratios of inorganic phosphate to ATP and phosphocreatine to ATP. Mean values of the ratios of phosphomonoesters to ATP and phosphodiesters to ATP were significantly lower in the total patient population than in the reference population, and they correlated with the patients' neuropsychiatric status. Thus we found no significant reductions in the mean ratios of phosphomonoesters to ATP and phosphodiesters to ATP in patients who were neuropsychiatrically unimpaired, but significant reductions were observed in the mean ratios of phosphomonoesters to ATP and phosphodiesters to ATP in patients with both subclinical and overt hepatic encephalopathy. The most marked reductions in these metabolite ratios were observed in patients with overt encephalopathy.

Clinical evaluation of serum ornithine carbamoyltransferase by enzyme-linked immunosorbent assay in patients with liver diseases.

We developed a sensitive enzyme-linked immunosorbent assay (ELISA) for serum ornithine carbamoyltransferase (OCT) protein, and examined serum OCT concentrations in patients with various liver diseases. OCT concentrations were markedly elevated in cases of hepatic encephalopathy, 'acute on chronic', and those with the acute phase of acute hepatitis, moderately in chronic hepatitis, liver cirrhosis, hepatocellular carcinoma, primary biliary cirrhosis, and slightly in those with a fatty liver. High percentages (92-98%) of patients with chronic hepatitis, liver cirrhosis and hepatocellular carcinoma had higher than normal concentrations of serum OCT protein. There was a close correlation with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and moderate correlations with those of mitochondrial AST, glutamate dehydrogenase and gamma-glutamyltranspeptidase. The OCT/ALT ratio was higher in patients with liver cirrhosis than in those with chronic hepatitis (p < 0.001), and was still higher in cases of hepatocellular carcinoma (p < 0.05). In 2 patients with 'acute on chronic' disease, OCT concentrations decreased similarly with or more rapidly than AST or ALT activities after admission. In 2 patients with hepatic encephalopathy, the OCT concentrations changed similarly with AST and ALT activities. This OCT ELISA system will aid in diagnosing various liver diseases and in the follow-up of the patients, and the OCT/ALT ratio may serve for a differential diagnosis of liver diseases.

In vivo evidence of enhanced guanylyl cyclase activation during the hyperdynamic circulation of acute liver failure.

Nitric oxide and atrial natriuretic peptides are the main activators of guanylyl cyclases, which transform GTP into cyclic GMP and thereby contribute to the decrease of vascular tone. To investigate the increase, if any, of plasma cyclic GMP concentrations in human patients with hyperdynamic circulation resulting from acute liver failure and to ascertain whether guanylyl cyclase activation is involved in the decline of systemic vascular resistance that occurs in this pathophysiological condition, we simultaneously recorded hemodynamic data and cyclic GMP levels in patients with fulminant liver failure before and after liver transplantation and in normokinetic patients undergoing abdominal nonseptic surgery. We also compared these data with those recorded in patients with hyperkinetic shock resulting from gram-negative sepsis or nitric oxide-independent vasomotor agent (carbamate) over-dose. In all these patients we simultaneously studied kidney function, platelet counts and atrial natriuretic peptides. Patients with fulminant liver failure had higher cyclic GMP concentrations than did control patients undergoing abdominal surgery (11.02 +/- 1.55 pmol.ml-1 vs. 1.77 +/- 0.18 pmol.ml-1, p < 0.001). At similar heart-loading conditions these concentrations were lower than those in gram-negative septic shock (18.2 +/- 1.35 pmol.ml-1, p < 0.05) but higher than those in carbamate-induced shock (3.6 +/- 0.7 pmol.ml-1, p < 0.01). In addition, cyclic GMP concentrations significantly decreased from the fulminant liver failure period to the posttransplantation period, although atrial natriuretic peptide levels did not change significantly and kidney function worsened.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional changes of brain mitochondria during experimental hepatic encephalopathy.

Several functional parameters were studied in a non-synaptic population of brain mitochondria from rats made cirrhotic by chronic treatment with carbon tetrachloride, with and without coma produced by a single injection of ammonium acetate. The following changes were observed in mitochondria from cirrhotic rats, independently of the presence of coma: (a) a large decrease in oxygen consumption with pyruvate-malate as substrate, but not with succinate, in both states 3 and 4; (b) a modified volume oscillation pattern, characterized by a notable diminution in the amplitude of the oscillation; (c) an altered pattern of acyl groups, with a decrease in the proportion of unsaturated with respect to saturated fatty acids. The following parameters were also measured in brain mitochondria from the cirrhotic rats and were found unchanged: (a) malate dehydrogenase and ATPase activities; (b) content of cytochromes; (c) phospholipid composition; (d) total fatty acid content. The possible significance of the changes observed is discussed in terms of the membranal and biochemical alterations that may be involved in the mechanism of hepatic encephalopathy.

[Experimental studies of the pathomechanism of portal encephalopathy. I. Changes in monoamine oxidase (MAO) activity in the cerebral cortex and cerebellum of rats after portacaval shunt]. / Badania doswiadczalne nad patomechanizmem encefalopatii wrotnej. I. Zmiany aktywnosci monoaminooksydazy (MAO) w korze mózgowej i w mózdzku szczurow po chirurgicznym wytworzeniu przetoki wrotno-czczej.

Rats with portacaval shunt (PCS) were used as a model of hepatic encephalopathy and compared to sham operated controls. Neurochemical studies in rats have demonstrated increased activity of MAO in brain cortex and cerebellum at 20, 40, and 60 days after surgery. The greatest increase of MAO activity was seen 60 days after PCS.