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Query: UMLS:C0023890 (cirrhosis)
 42,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is proposed that hyperammonaemia in liver cirrhosis or after portacaval shunt contributes to plasma neutral aminoacid imbalance and to increased activity of the blood-brain neutral amino-acid transport system. Plasma neutral aminoacid concentrations are deranged, partly, but not completely, because ammonia stimulates glucagon secretion; a high rate of gluconeogenesis and hyperinsulinaemia follow. Brain uptake of neutral aminoacids rises because ammonia stimulates brain-glutamine synthesis, which results in rapid exchange of brain glutamine for plasma neutral aminoacids. Hyperammonaemia therefore contributes to encephalopathy indirectly, by raising the brain concentration of neutral aminoacids which after neurotransmitter metabolism, rather than directly, by toxic effects on neuronal metabolism.
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PMID:Hyperammonaemia, plasma aminoacid imbalance, and blood-brain aminoacid transport: a unified theory of portal-systemic encephalopathy. 9 Aug 64

Cirrhosis of the liver in rats was induced by the administration of carbon tetrachloride (0.1 ml/100 g of body weight, s.c.) biweekly for 13 weeks. In the pylorus ligation preparation, acetylsalicylic acid (ASA) 100 mg/kg p.o. induced much more serious gastric damage in CC14-induced cirrhotic rats as compared with rats with a normal liver. L-glutamine 750 mg/kg p.o. prevented the ASA-induced gastric lesions in both normal and cirrhotic rats, even though the degree of the inhibition was weaker in cirrhotic rats. Gastric analysis indicated that L-glutamine 750 mg/kg p.o. markedly inhibited the gastric ionic changes (acid back diffusion) in response to ASA in both cirrhotic and normal rats.
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PMID:Effects of L-glutamine on acetylsalicylic acid-induced gastric lesions in normal and cirrhotic rats. 108 32

In two groups of patients with liver cirrhosis and normal EEG (Group A) and with pathological EEG (Group B) it was possible to demonstrate a correlation between the severity grade of the EEG changes, the livertypical deviations of serum chemistry and alterations in cerebral oxidative metabolism. The metabolism of the brain showed a reduced oxygen consumption and carbon dioxide output in the patients with pathological EEG changes. All patients showed a raised glucose uptake, an increased lactate release, a raised ammonia uptake and glutamine output. These findings in patients with liver cirrhosis indicate a disturbance of the oxidative energy metabolism of the brain with secondary intensification of glycolysis. Pathological changes in the EEG only appear if the oxygen consumption of the brain is limited (as in the patients of Group B). These EEG changes have a poor prognosis in respect to life expectancy. With consideration of the data from animal experiments and the reported results of cerebral blood flow and oxydative metabolism in patients with liver cirrhosis it might be assumed that liver insufficiency with elevated serum ammonia results in a deranged oxydative cerebral metabolism which might explain hepatic encephalopathy.
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PMID:Comparative studies of the electroencephalogram and the cerebral oxidative metabolism in patients with liver cirrhosis. 120 68

In patients with liver cirrhosis the fasting plasma alpha-amino nitrogen concentration is high as the rule, due to reduced clearance of total alpha-amino nitrogen. The urea cycle is diminished of its capacity in cirrhotic patients than in the control subject, and to compensate for this, the extrahepatic glutamine cycle capacity is enlarged in the patients. The following important topics were taken up in this mini review: some problems concerning Fischer ratio, amino acids metabolism and pH regulation in the liver, and the supplementation therapy with branched chain amino acids under the condition of organ relationship.
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PMID:[Amino acid metabolism in liver cirrhosis]. 140 91

An effect of Aminosteril-Hepa intravenous infusions or plasmapheresis on selected amino acids, ammonia, alpha-aminonitrogen serum levels and serum GGTP activity was analysed in 28 patients with liver cirrhosis with and without hepatic encephalopathy. The patients were given protein controlled dietary treatment. It was found, that plasmapheresis exerted more potent effect on previously elevated ammonia and serum alpha-aminonitrogen levels as well as serum GGTP activity than intravenous infusions of Aminosteril-Hepa. It was clearly seen in patients with liver cirrhosis without hepatic encephalopathy. Aminosteril-Hepa intravenous infusions decreased serum glutamine levels to higher degree than plasmapheresis. Both types of therapy have had no significant effect on serum phenylalanine, tyrosine, and tryptophan levels in all patients.
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PMID:[Plasmapheresis and amino acid mixtures of "Aminosteril-Hepa" type preparations in treating hepatic encephalopathy]. 166 87

At present in vivo NMR spectroscopic studies of brain glutamate and glutamine concentrations relative to encephalopathy have mainly been performed in hepatic encephalopathy (HE). In vivo proton NMR studies were performed in rats with hyperammonemia and acute HE due to acute liver ischemia as well as in rats with hyperammonemia due to either repeated urease i.p. injection or i.p. administration of methionine sulfoximine, a well known inhibitor of glutamine synthetase. In man, in vivo proton NMR is described in patients with chronic liver disease: cirrhosis of different etiology and associated with different degrees of HE. In the experimental models proton NMR spectroscopy of the cerebral cortex revealed an increase in glutamine concentration, a decrease in glutamate concentration and a decrease in phosphocholine compounds. In humans no clear distinction between cerebral cortex glutamate and glutamine concentration could be made by in vivo 1H NMR spectroscopy. However, the combined glutamate/glutamine peak increased in a way compatible with an increased cerebral cortex glutamine concentration during chronic HE. In the cirrhotic patients too a decrease in cerebral cortex phosphocholine compounds was observed, the explanation of which is unclear. Both the experimental work and the clinical observations support the hypothesis that impairment of the glutamate/glutamine cycle between astrocytes and neurons plays a role in the pathogenesis of hepatic encephalopathy.
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PMID:What the clinician can learn from MR glutamine/glutamate assays. 167 85

Localized 1H NMR spectra of human brain in vivo are affected by signal overlap, strong spin-spin coupling, and complex J modulation, and therefore differ considerably from those obtained at higher magnetic fields. This paper deals with the assignment of 1H NMR resonances of cerebral metabolites under the experimental conditions used for human investigations. Conventional 7.0-T FID spectra and 2.0 T localized, short echo time STEAM spectra (TE = 20 ms) of aqueous metabolite solutions are compared to in vivo brain spectra of human volunteers and patients. In addition to singlet resonances from N-acetyl aspartate (NAA), creatines, and cholines, short echo time STEAM spectra exhibit multiplets due to the NAA aspartyl group, glutamate, taurine, and myo-inositol. Enhanced levels of cerebral glutamine are detected in patients with liver cirrhosis. For the first time elevated levels of brain glucose are observed in patients with diabetes mellitus.
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PMID:On the identification of cerebral metabolites in localized 1H NMR spectra of human brain in vivo. 167 88

To study the effect of ammonia administration on amino acids and indoleamines in cerebrospinal fluid (CSF) and on amino acids, insulin, and glucagon in plasma in humans with liver cirrhosis, we performed seven ammonia tolerance tests on six patients with stable liver cirrhosis. The grade of encephalopathy was determined by psychometric tests. Only one of the patients had pronounced encephalopathy. The other patients had no or only slight encephalopathy. The plasma concentrations of valine, leucine, isoleucine, phenylalanine, tyrosine, and methionine decreased after the ammonia load, whereas no changes were found in the plasma concentrations of glucagon and insulin. In CSF the concentrations of glutamine, aromatic amino acids, and indoleamines increased only in the patient who had pronounced encephalopathy, whereas no changes were found in the other patients. The effect of an ammonia load on the concentrations of neutral amino acids in CSF in patients with pronounced encephalopathy remains to be demonstrated.
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PMID:The effects of ammonia tolerance tests on the cerebrospinal fluid concentrations of amino acids and indoleamines in patients with liver cirrhosis. 169 97

The amino acid composition of proteins from liver mitochondrial membranes has been studied in patients with normal liver, with biliary diseases and fatty liver, with obstructive jaundice or liver cirrhosis. A characteristic pattern of the amino acid composition in patients with normal liver has been found. In the mitochondrial membranes of patients with fatty liver tryptophan and lysine were decreased while [aspartic acid plus asparagine] and [glutamic acid plus glutamine] were increased compared to their counterpart in the normal liver. In patients with obstructive jaundice of short duration (less than two months) only a slight decrease in methionine content was found, while in the case of liver cirrhosis amino acid composition was markedly changed.
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PMID:Amino acid composition of human liver mitochondrial membranes in normal and pathological conditions. 186 76

Ammonia is generated from a large number of metabolically important reactions. Despite its central importance in whole body nitrogen homeostasis excess ammonia is neurotoxic and its concentration must be kept low. Ammonia generated in most extrahepatic tissues is detoxified by incorporation into glutamine (amide). This glutamine may be used in a number of biosynthetic reactions (e.g. in pyrimidine synthesis). Alternatively, as a means of maintaining nitrogen balance, glutamine may be released to the blood. Resting skeletal muscle is particularly important 1) as a "sink" for removal of blood ammonia, and 2) as a major source of circulating glutamine. However, during vigorous exercise skeletal muscle may become a net contributor of ammonia to the blood. A few tissues and cell types (e.g. lymphocytes, macrophages, enterocytes, colonocytes, thymocytes, fibroblasts, bone) and tumors exhibit marked rates of glutamine utilization. In the kidney, glutamine is an important source of urinary ammonia. Ammonia generated from 1) the breakdown of nitrogenous substances in the gut, and 2) from the use of glutamine as a metabolic fuel in the small intestine, is taken up by the liver wherein it is detoxified by conversion to urea and to a lesser extent, glutamine. Some portal vein glutamine acts as a source of urea nitrogen. Ultimately, however, most excess ammonia nitrogen is detoxified indirectly (via glutamine (blood)----glutamine (small intestine)----ammonia (portal vein) or directly in the liver as urea. Portal-systemic shunting of blood, as occurs in chronic cirrhosis of the liver or following the surgical construction of a portacaval shunt results in portal blood bypassing the normal ammonia detoxification machinery of the liver. Under this condition blood ammonia levels rise markedly, increasing the burden on extrahepatic tissues, such as skeletal muscle, brain, and kidney, in maintaining ammonia homeostasis. The most commonly employed animal model of human liver disease is the rat in which an end-to-side portacaval shunt (PCS) has been surgically constructed. Brain glutamine synthetase activity is not increased in PCS rats and in some areas of the brain there may even be a decrease in activity. The brain glutamine synthetase appears to be working at near maximal capacity. Thus, the PCS rats exhibit profound neurological dysfunction when administered ammonium salts in amounts easily tolerated by normal animals. Because of the limited capacity of brain to remove excess ammonia, a rational approach to the treatment of patients with liver disease should include a regimen directed toward lowering the associated hyperammonemia.
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PMID:Ammonia metabolism in normal and portacaval-shunted rats. 210 90


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