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  • thiamine deficiency  (5)
  • Hepatic encephalopathy  (4)
  • Thiamine deficiency  (3)
  • manganese  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Metabolic brain disease 10 (1995), S. 1-8 
    ISSN: 1573-7365
    Keywords: Alcoholic brain damage ; Ethanol neurotoxicity ; Thiamine deficiency ; Alcoholic liver disease ; Hepatic Encephalopathy ; Cerebral energy deficit ; NMDA receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Chronic alcoholism results in brain damage and dysfunction leading to a constellation of neuropsychiatric symptoms including cognitive dysfunction, the Wernicke-Korsakoff Syndrome, alcoholic cerebellar degeneration and alcoholic dementia. That these clinically-defined entities result from independent pathophysiologic mechanisms is unlikely. Alcohol and its metabolite acetaldehyde are directly neurotoxic. Alcoholics are thiamine deficient as a result of poor diet, gatrointestinal disorders and liver disease. In addition, both alcohol and acetaldehyde have direct toxic effects on thiamine-related enzymes in liver and brain. Alcoholics frequently develope severe liver disease and liver diseaseper se results in altered thiamine homeostasis, in cognitive dysfunction and in neuropathologic damage to astrocytes. The latter may result in the loss of neuron-astrocytic trafficking of neuroactive amino acids and thiamine esters, essential to CNS function. The present review article proposes mechanisms whereby the effects of alcohol, thiamine deficiency and liver disease combine synergistically to contribute to the phenomena of cognitive dysfunction and “alcoholic brain damage”.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Metabolic brain disease 11 (1996), S. 165-173 
    ISSN: 1573-7365
    Keywords: Hepatic encephalopathy ; Amino acids ; Glutamate ; GABA ; Taurine ; Endogenous benzodiazepines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is abundant evidence to suggest that alterations of excitatory and inhibitory amino acids play a significant role in the pathogenesis of hepatic encephalopathy (HE) in both acute and chronic liver diseases. Brain glutamate concentrations are reduced in patients who died in hepatic coma as well as in experimental HE, astrocytic reuptake of glutamate is compromised in liver failure and postsynaptic glutamate receptors (both NMDA and non-NMDA subclasses) are concomitantly reduced in density. Recent studies in experimental acute liver failure suggest reduced capacity of the astrocytic glutamate transporter in this condition. Together, this data suggests that neuron-astrocytic trafficking of glutamate is impaired in HE. Other significant alterations of neuroactive amino acids in HE include a loss of taurine from brain cells to extracellular space, a phenomenon which could relate both to HE and to brain edema in acute liver failure. Increased concentrations of benzodiazepine-like compounds have been reported in human and experimental HE. Clinical trials with the benzodiazepine antagonist flumazenil reveal a beneficial effect in some patients with HE; the mechanism responsible for this effect, however, remains to be determined.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7365
    Keywords: thiamine ; thiamine deficiency ; thiamine-dependent enzymes ; maternal thiamine requirements ; pyruvate dehydrogenase complex ; α-ketoglutarate dehydrogenase ; transketolase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thiamine needs in pregnancy and lactation are known to be increased. Previous studies suggest that developing rat brain is more susceptible to a lack of thiamine intake than is adult brain. In order to study the basis of this susceptibility, activities of the three thiamine-dependent enzymes [pyruvate dehydrogenase complex (PDHC), α-ketoglutarate dehydrogenase (aKGDH), and transketolase (TK)] were measured in homogenates of brain tissue from thiamine-deficient female rats and their offspring. The study revealed a more rapid progression of thiamine deficiency in pregnant thiamine-deficient rats compared to nonpregnant rats as seen by significantly increased “TPP effect” values. No differences in activities of the three thiamine-dependent enzymes in brain were observed between pregnant and nonpregnant animals. However, activities of all three thiamine-dependent enzymes were significantly reduced in cerebral cortex of the offspring of thiamine-deficient mothers 13 days postnatally. TK activities were also reduced in cerebellum and brain stem of these animals. Since thiaminedependent enzymes are important for the establishment of adult patterns of cerebral energy metabolism and also in myelin synthesis, maternal thiamine deficiency resulting in reductions of activities of these enzymes at a vulnerable period in brain development could have serious metabolic consequences leading to permanent neurological sequellae in the offspring.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-7365
    Keywords: AIDS ; AIDS-related complex ; thiamine deficiency ; Wernicke's Encephalopathy ; α-ketoglutarate dehydrogenase ; transketolase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Several neuropathological reports in the last 5 years have described brain lesions characteristic of Wernicke's Encephalopathy in patients with AIDS. Using the erythrocyte transketolase activation assay, we now report biochemical evidence of thiamine deficiency in 9/39 (23%) of patients with AIDS or AIDS-related complex. In no cases was there history of alcohol abuse nor were there clinical signs of Wernicke's Encephalopathy. Thiamine deficiency in these patients most likely results from the cachexia and catabolic state characteristic of AIDS. In view of (i) the confirmed neuropathological evidence of Wernicke's Encephalopathy in AIDS patients, (ii) the significant thiamine deficiency in these patients and (iii) the difficulties of clinical diagnosis of Wernicke's Encephalopathy, it is recommended that dietary thiamine supplementation be initiated in all newly diagnosed cases of AIDS or AIDS-related complex.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-7365
    Keywords: Portacaval anastomosis ; Hepatic encephalopathy ; 3H-PK11195 binding ; “Peripheral-type” benzodiazepine receptor ; Astrocyte ; Portal-systemic encephalopathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Quantitative receptor autoradiography was used to measure the densities of binding sites for the “peripheral-type” benzodiazepine receptor ligand3H-PK11195 in regions of the rat brain 1, 3, 7 and 28 days following portacaval anastomosis (PCA) and in sham-operated control animals. The results demonstrate that densities of3H-PK11195 binding sites were significantly increased in the cerebral cortex (by 40%, p〈0.05) as early as 24 hours following PCA. In the thalamus significant increases in densities of3H-PK11195 binding sites were seen 3 days after PCA, whereas in brain regions such as the striatum and cerebellum, significant increases in3H-PK11195 binding sites were not evident until 7 days following PCA. By 28 days following PCA increased densities of3H-PK11195 binding sites were well established and widespread throughout the brain. Previous studies demonstrate early increases of brain ammonia following. PCA. PTBRs or their endogenous ligands could play an important role in the early astrocytic response (mitochondrial proliferation, swelling) to ammonia following PCA.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-7365
    Keywords: manganese ; hepatic encephalopathy ; MR signal hyperintensity ; globus pallidus ; dopamine D2 receptors ; MAO ; extrapyramidal symptoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patients with chronic liver disease manifest a high incidence (〉75%) of pallidal signal hyperintensity on T1-weighted Magnetic Resonance Imaging (MRI), the intensity of which correlates with blood manganese levels and the presence of extrapyramidal symptoms. A major cause of pallidal hyperintensity on T1-weighted MRI is manganese deposition; chronic manganese intoxication in the absence of liver disease results in pallidal MR signal hyperintensity, in extrapyramidal symptoms and in selective effects on the dopaminergic neurotransmitter system in basal ganglia. Direct measurements in globus pallidus obtained at autopsy from patients with chronic liver disease who died in hepatic coma reveal 2 to 7-fold increases of pallidal manganese and a concomitant loss of dopamine D2 binding sites. Liver transplantation results in normalization of pallidal MR signals and of blood manganese levels. These findings suggest that (1) pallidal MR signal hyperintensity in patients with chronic liver disease is the result of manganese deposition and (2) alterations of dopaminergic function due to the toxic effects of manganese may contribute to the extrapyramidal symptoms in these patients.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-7365
    Keywords: Wernicke's encephalopathy ; thiamine deficiency ; peripheral-type benzodiazepine receptors ; GABA-benzodiazepine receptor complex ; positron emission tomography ; 3H-PK11195 ; 3H-Ro 15-1788
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thiamine deficiency in humans is associated with Wernicke's encephalopathy (WE) which is characterized neuropathologically by neuronal loss in selective brain regions. Pyrithiamine-induced thiamine-deficiency in the rat results in lesions which are similar in nature and distribution to those seen in human WE. Several mechanisms have been implicated in the pathogenesis of neuronal loss in thiamine deficiency including, (i) impaired cerebral energy metabolism, (ii) focal lactic acidosis, (iii) NMDA-receptor mediated excitotoxicity and (iv) blood-brain barrier breakdown. WE is difficult to diagnose during life and a large number of cases are missed by routine clinical neurological evaluation. Recently, non-invasive diagnostic procedures such as CT and MRI have been used for the evaluation of acute and chronic WE. Autoradiographic studies reveal that increased densities of binding sites for the astrocytic ligand3H-PK11195 closely parallel the topographic distribution of reactive gliosis and neuronal loss in selective brain regions of pyrithiamine-induced thiamine-deficient rats. In contrast, binding sites for the neuronal ligand3H-Ro15-1788 show poor regional correlation with neuronal loss in thiamine deficiency. Both of these ligands are available, and have been used in PET assessment of various disorders in humans. The results of autoradiographic studies suggest that11C-PK11195 may offer a useful PET ligand for the assessment of brain damage in WE in humans.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-7365
    Keywords: Hepatic encephalopathy ; manganese ; copper ; zinc ; globus pallidus ; liver disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Concentrations of zinc, copper and manganese were measured by atomic absorption spectrometry in samples of globus pallidus obtained at autopsy from 9 patients with chronic liver disease and an equal number of age-matched controls. Manganese concentrations were significantly increased several fold (p〈0.01) in globus pallidus of liver disease patients accompanied by smaller but significant 2-fold increases of copper. Zinc concentrations, on the other hand, were within normal limits. Increased pallidal manganese offers a cogent explanation for the observed T1-weighted MRI signal hyperintensity in pallidum of cirrhotic patients. Increased copper content in brain suggests the existence of common pathophysiologic mechanisms in inherited (Wilson Disease) and acquired hepatocerebral disorders.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Metabolic brain disease 13 (1998), S. 337-349 
    ISSN: 1573-7365
    Keywords: Portal-systemic encephalopathy ; hepatic encephalopathy ; ammonia ; manganese ; gene expression ; peripheral-type benzodiazepine receptors ; monoamine oxidase ; serotonin ; neurosteroids ; nitric oxide synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Portal-systemic encephalopathy (PSE) is a serious neuropsychiatric condition that results from chronic liver failure and portal-systemic shunting of venous blood. PSE is particularly prevalent following treatment of portal hypertension or ascites by the TIPS procedure. Recent studies both in autopsied brain tissue from PSE patients as well as in experimental animal models of PSE reveal that chronic liver failure results in altered expression of several genes coding for proteins having key roles in the control of neuronal excitability. Such alterations include increased expression of monoamine oxidase (MAO-A isoform), the “peripheral-type” benzodiazepine receptor (PTBR) as well as constitutive, neuronal nitric oxide synthase (nNOS). Such changes result in altered protein expression and in increased degradation of monoamine neurotransmitters, increased synthesis of neurosteroids with inhibitory properties and increased production of nitric oxide (respectively) in brain in chronic liver failure. In the case of PTBR and nNOS, increases in expression result from exposure to ammonia and/or manganese, two neurotoxic agents shown previously to be increased in brain in chronic liver failure. Further elucidation of the consequences of neurotransmitter-related gene expression could identify new pathophysiologic mechanisms and result in new approaches to the prevention of PSE in chronic liver disease in humans.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-7365
    Keywords: thiamine deficiency ; pyrithiamine ; glutamate release ; glutamate ; hippocampal slice ; Wemicke's encephalopathy ; Wemicke-Korsakoff syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Alterations of excitatory amino acids in brain may be of pathophysiological significance in thiamine-deficiency encephalopathy. The present study was undertaken to evaluate the effects of thiamine deficiency induced by the central thiamine antagonist, pyrithiamine, on the glutamate content of glutamatergic nerve terminals. Electrically-stimulated, Ca2+-dependent release of glutamate from hippocampal slices obtained from symptomatic pyrithiamine-treated rats was significantly decreased compared to pair-fed controls. Possible explanations for the decreased “neurotransmitter pool” of glutamate in thiamine-deficient rat brain include decreased synthesis of glutamate as a result of decreased activities of the thiamine-dependent enzyme α-ketoglutarate dehydrogenase or increased release of glutamateper se. There is evidence to suggest that the latter mechanism with ensuing excitotoxic neuronal damage could be involved in the pathogenesis of selective neuronal death in thiamine deficiency. Similar mechanisms could be implicated in Wemicke's encephalopathy in humans.
    Type of Medium: Electronic Resource
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