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Query: UMLS:C0085584 (encephalopathy)
 18,178 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A large portosystemic shunt between the inferior mesenteric vein and the right internal iliac vein in a 28-yr-old non-cirrhotic man is presented. This collateral was discovered by ultrasound done as a screening examination for gastrointestinal bleeding. The direct communication of the inferior mesenteric vein with the internal iliac vein was demonstrated by computed tomography and percutaneous transhepatic portography. Surgical ligation of the collateral, performed to prevent future portosystemic encephalopathy, resulted in reduction of serum ammonia level and cessation of long-standing hemorrhoidal bleeding.
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PMID:A large inferior mesenteric-caval shunt via the internal iliac vein. 306 36

Valproic acid is known to cause an increase in blood ammonia levels in humans at the usual clinical dose. In most patients, this increase is small and asymptomatic, but in some patients the increase is larger and is associated with encephalopathy. In this study, valproate also caused a small increase in blood ammonia level (from 50 to 83 mumol/l) in Wistar rats. Salicylate potentiated this increase in blood ammonia (greater than 210 mumol/l) when coadministered with valproate at a dose of salicylate which did not cause a significant increase when given alone. Other nonsteroidal anti-inflammatory drugs tested (ibuprofen and naproxen) did not potentiate valproate-induced hyperammonemia, and paracetamol actually appeared to decrease ammonia levels. The degree of hyperammonemia was dependent upon diet, and fasting decreased the level of hyperammonemia. In order to determine what component of the diet was responsible for this effect, protein, fat and carbohydrate were given by gavage, individually and also a mixture of the three. Only the mixture was able to increase the degree of hyperammonemia, even though the number of calories in the mixture and in each nutrient given individually was approximately the same. 2,4-Dinitrophenol, which like salicylate uncouples oxidative phosphorylation, potentiated valproate-induced hyperammonemia at a much lower dose than salicylate. Whether salicylate can potentiate hyperammonemia and lead to encephalopathy in some patients and therefore represents one of the risk factors for observed cases of valproate toxicity remains to be determined. Potentiation of hyperammonemia by salicylates is also consistent with the apparent association between salicylates and Reye's syndrome which is also characterized by hyperammonemia.
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PMID:Salicylate potentiates valproate-induced hyperammonemia in the rat. 311 9

In five patients with cirrhosis given an oral methionine load, blood mercaptan concentrations were not significantly affected by neomycin and metronidazole therapy. Methanethiol and dimethyl sulphide rose after methionine to levels encountered in hepatic encephalopathy but in stable cirrhotics no neurological abnormalities were evident. In one patient with chronic hepatic encephalopathy there was no significant change in methanethiol, dimethyl sulphide or ammonia concentration 4 h after methionine when conscious state had deteriorated by two stages of encephalopathy. Elevations in blood methanethiol and dimethyl sulphide concentration in children with congenital hypermethioninaemia were not associated with any neurological or electroencephalographic features of hepatic coma. These studies do not support an important role for mercaptans in hepatic encephalopathy although a synergistic effect cannot be excluded. Furthermore, mercaptans appear to arise from endogenous metabolism rather than bacterial action in the gut.
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PMID:Effect of methionine loading and endogenous hypermethioninaemia on blood mercaptans in man. 316 96

The case records of 21 dogs with congenital portosystemic encephalopathy are reviewed. The disorder was most common in Australian cattledogs (blue heelers; 8 cases), Old English sheepdogs (3 cases) and Maltese terriers (3 cases). Extra-hepatic shunts occurred in small breeds, with the exception of 1 cattledog, while intra-hepatic shunts occurred in the medium to large breeds. The most common clinical pathology abnormalities were abnormal ammonia tolerance, mild to moderate increases in plasma alanine aminotransferase or alkaline phosphatase concentrations, decreased total serum protein concentrations, increased fasting ammonia concentrations and ammonium biurate crystalluria. Radiological examination revealed that all the dogs had a small liver. The kidneys were enlarged in 5 of 10 dogs in which kidney size could be estimated. Surgical ligation of an extra-hepatic shunt was successful in 2 of 4 dogs in which it was attempted. Medical management resulted in alleviation of clinical signs in 5 of 8 dogs. The period of successful treatment ranged from a few months to over a year.
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PMID:Canine congenital portosystemic encephalopathy. 319 May 91

Ultrastructural findings in the brains and livers of four calves affected with citrullinaemia due to a hereditary deficiency of the urea cycle enzyme arginosuccinate synthetase are described. The calves were affected in the 1st week of life with severe neurological disease characterised by depression, head pressing, stupor, convulsions and coma, accompanied by marked elevation of plasma citrulline and increasing plasma ammonia levels. Lesions included mild to moderate diffuse astroglial oedema in the cerebrocortical grey matter, and mild to severe hepatocellular hydropic change. The onset of the severe neurological signs was correlated with increasing levels of plasma ammonia, and the cerebral lesions were considered consistent with a bovine hyperammonaemic encephalopathy.
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PMID:Ultrastructural findings in citrullinaemia in Holstein-Friesian calves. 321 35

A 40-year-old woman with a history of alcohol abuse, drug-related suicide attempts, and depression presented with a flu-like illness, vomiting, and changes in mentation. On admission, therapeutic blood levels of salicylates, trazadone, and acetaminophen were found. A tentative diagnosis of a psychotic crisis with possible superimposed drug overdose was made. The etiology of the patient's acute encephalopathy remained unclear until a plasma ammonia and liver biopsy established the diagnosis of Reye's syndrome. The patient was given supportive therapy and recovered completely.
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PMID:Adult Reye's syndrome. 327 49

There is substantial clinical and experimental evidence to suggest that ammonia toxicity is a major factor in the pathogenesis of hepatic encephalopathy associated with subacute and chronic liver disease. Ammonia levels in patients with severe liver disease are frequently found to be elevated both in blood and cerebrospinal fluid (csf). Hepatic encephalopathy results in neuropathological damage of a similar nature (Alzheimer type II astrocytosis) to that found in patients with congenital hyperammonemia resulting from inherited defects of urea cycle enzymes. Following portocaval anastomosis in the rat, blood ammonia concentration is increased 2-fold, and brain ammonia is found to be increased 2-3-fold. Administration of ammonia salts or resins to rats with a portocaval anastomosis results in coma and in Alzheimer type II astrocytosis. Since the CNS is devoid of effective urea cycle activity, ammonia removal by brain relies on glutamine formation. Cerebrospinal fluid and brain glutamine are found to be significantly elevated in cirrhotic patients with encephalopathy and in rats following portocaval anastomosis. In both cases, glutamine is found to be elevated in a region-dependent manner. Several mechanisms have been proposed to explain the neurotoxic action of ammonia. Such mechanisms include: Modification of blood-brain barrier transport; alterations of cerebral energy metabolism; direct actions on the neuronal membrane; and decreased synthesis of releasable glutamate, resulting in impaired glutamatergic neurotransmission.
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PMID:Ammonia: key factor in the pathogenesis of hepatic encephalopathy. 330 79

The Alzheimer type II astrocyte change is the distinctive morphologic alteration in brain of humans and experimental animals succumbing to hepatic encephalopathy (HE). Whether this change is a primary event in the pathogenesis of HE or whether it is secondary to injury of some other component(s) of the CNS has not been clarified. Studies in a rat model of HE have revealed early reactive changes in astrocytes characterized by cytoplasmic hypertrophy. During the later phases, degenerative changes ensue corresponding to the Alzheimer type II change observed by light microscopy. In view of the role of astrocytes in ammonia detoxification and the importance of ammonia in the pathogenesis of HE, we have suggested that the initial astrocytic changes are the morphological correlates of ammonia detoxification. We have speculated that the later degenerative alterations could lead to failure by astrocytes to carry out key functions (e.g., neurotransmitter uptake, ion regulation, and the like) and contribute the development of the encephalopathy. Recently, the potential involvement of astrocytes in HE has been further investigated, using primary astrocyte cultures. Exposure of cultures to ammonia at clinically relevant concentrations has shown morphologic changes closely resembling those observed in experimental HE in vivo. These deleterious effects can partly be prevented by raising cyclic AMP levels in cells. Other potential toxins (octanoic acid, phenol) have shown pathologic changes as well. Although some alterations were common to all three, they each possessed distinctive pathological effects. A synergistic interaction has also been demonstrated with these toxins. Functional studies of ammonia-treated astrocytes have shown the following: With low doses or short-term exposure, the uptakes of K+, glutamate, and GABA remained unchanged or slightly increased, whereas with higher doses or longer treatment, those activities diminished. A fall in ATP values occurred with prolonged ammonia treatment. Preliminary findings have shown no significant derangements in the beta-adrenergic receptor, except for a slight decrease in receptor affinity. However, cyclic AMP production was diminished following stimulation with isoproterenol. A slight rise in the number of benzodiazepine receptors was found. These studies indicate that profound changes occur in astrocytes following exposure to ammonia and other putative toxins. It is proposed that toxins and factors involved in the precipitation of HE do so by affecting astroglial properties. Derangements in such properties may lead to glial dysfunction (primary gliopathy), resulting in an encephalopathic state.
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PMID:The role of astrocytes in hepatic encephalopathy. 330 80

To assess side effects of propranolol in the treatment of portal hypertension, we measured blood ammonia in 14 cirrhotics before and after administration of propranolol, and in six cirrhotics before and after placebo. We evaluated ammonia blood levels obtained from three sites: venous, arterial, and arterialized-venous, obtained by warming the forearm. Ammonia concentration of arterial and arterialized-venous blood were abnormal for all cirrhotics studied and significantly greater than the ammonia concentration of venous blood (p less than 0.01). When propranolol was administered to patients with alcoholic cirrhosis and marginal liver function, as reflected by ammonia levels above 60 microM, it caused a significant increase in ammonia levels in arterialized-venous and arterial, but not in venous, blood (p less than 0.05). Propranolol caused a significant increase in the time required to perform sensitive psychometric tests (p less than 0.05). Encephalopathy usually became clinically apparent when the mean of the arterial and arterialized-venous blood ammonia levels rose above 122 microM.
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PMID:Venous, arterial, and arterialized-venous blood ammonia levels and their relationship to hepatic encephalopathy after propranolol. 334 27

Portocaval anastomosis (PCA) in the rat leads, within 4 weeks, to severe liver atrophy, sustained hyperammonemia, and increased brain ammonia. Because brain is not equipped with an effective urea cycle, removal of ammonia involves glutamine synthesis and PCA results in significantly increased brain glutamine. Glutamine synthetase activities, however, are decreased by 15% in cerebral cortex and are unchanged in brainstem of shunted rats. Administration of ammonium acetate to rats following PCA results in severe encephalopathy (loss of righting reflex and, ultimately, coma). Glutamine concentrations in brainstem of comatose rats are increased a further two-fold, whereas those of cerebral cortex are unchanged. Consequently, ammonia levels in cerebral cortex reach disproportionately high levels (of the order of 5 mM). These findings suggest a limitation in the capacity of cerebral cortex to remove additional blood-borne ammonia by glutamine formation following PCA. Such mechanisms may explain the hypersensitivity of rats with PCA and of patients with portal-systemic shunting to small increases of blood ammonia. Disproportionately high levels of brain ammonia in certain regions, such as cerebral cortex, may then result in alterations of inhibitory neurotransmission and, ultimately, loss of cellular (astrocytic) integrity.
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PMID:Regional differences in the capacity for ammonia removal by brain following portocaval anastomosis. 339 40


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