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In vivo and in vitro proton NMR spectroscopic studies of thiamine-deficient rat brains.

Thiamine deficiency (TD) in rats produces lesions similar to those found in humans with Wernicke's encephalopathy, an organic mental disorder associated with alcoholism. Male Sprague-Dawley rats (n = 24) were deprived of thiamine in a regimen of thiamine-deficient chow and daily intraperitoneal injections of the thiamine antagonist pyrithiamine hydrobromide for 12 days (0.5 mg/kg). In rats with TD, significant changes were observed in the choline peak (reduction and dose-dependent recovery after thiamine replenishment), which was confirmed by the extraction study. Changes were mainly due to the reduction in glycerophosphorylcholine (GPC), suggesting that a reduction in GPC may be relevant to the primary biochemical lesion in TD. These data are compatible with the hypothesis that a decrease in choline compounds is the cause of the biochemical abnormalities that precede neuroanatomic damage characteristic of Wernicke's encephalopathy.

Animals↗

Mechanisms of hemolysis in liver disease.

Liver disease, particularly alcoholic cirrhosis, is associated with a number of interesting chemical changes which result in structural and metabolic abnormalities of the erythrocyte membrane leading to microscopically observable cell shape changes and hemolytic anemia varying from very mild to potentially lethal. Increase in unesterified serum cholesterol owing to lecithin cholesterol acyl transferase (LCAT) deficiency in cirrhosis leads to expansion of the lipid bilayer and macrocytosis without megaloblastic changes in precursors. Substitutions of phosphatidyl choline (PC) moieties in the erythrocyte lipid bilayer lead to echinocytes (disaturated PC) or to stomatocytes (diunsaturated PC). In some patients, high density lipoprotein (HDL) abnormalities lead to erythrocyte surface changes causing rapid formation of echinocytes. The rapidity and reversibility of these changes suggest blockade of metabolic transport channels critical to the maintenance of erythrocyte membrane shape. Metabolic changes involving vitamin E deficiency leading to lipid peroxidation and pyruvate kinase instability leading to adenosine triphosphate (ATP) reduction have also been invoked to explain hemolysis associated with acute liver damage. The most severe hemolysis in liver disease is associated with acanthocytes (spur cells) and a marked imbalance in cholesterol-phospholipid ratio. These patients usually have hypersplenism, as well as rigid erythrocyte membrane transformations which are irreversible. Any of the other erythrocyte membrane shape changes described appear to be reversible if the liver disease abates, but they too may become irreversible if bits of projecting membrane are repeatedly removed by the macrophages of an enlarged spleen.

Erythrocyte Deformability↗

The relative effects of protein, choline, and methionine in the treatment of experimental dietary cirrhosis in the rat.

Cirrhosis of the liver was produced in rats by feeding a diet low in protein (4 per cent casein) and deficient in lipotropic factors. The degree of liver cirrhosis was determined from specimens obtained at biopsy. Comparable groups of animals then were treated with diets containing 4 per cent casein and 30 per cent casein. The 4 per cent casein diets were supplemented with choline and methionine; the 30 per cent casein diets were fed with and without added choline. On supplementing the low protein diet with choline and methionine the animals remained feeble, their growth remained stunted, and their livers showed signs of progressive cirrhosis. In contrast, animals fed the higher protein diet (with or without added choline) grew normally, and their livers showed signs indicating arrest and regression of the disease process. These studies suggest that the feeding of high protein (30 per cent casein) diets to rats with nutritional cirrhosis produces reparative effects greater than those attributable to the supplements choline and methionine.

Animals↗

Hemolytic anemia in hereditary pyrimidine 5'-nucleotidase deficiency. II. Effect of pyrimidine nucleotides and their derivatives on glycolytic and pentose phosphate shunt enzyme activity.

We evaluated the glycolytic intermediate concentrations from the erythrocytes of a patient with hereditary pyrimidine 5'-nucleotidase (P5'N) deficiency. Conclusive evidence for a metabolic block was not found. We evaluated the effects of the pyrimidine (cytidine and uridine) tri- and diphosphate nucleotides (CTP, CDP, UTP, UDP) and the choline and ethanolamine derivatives of CDP (CDP-choline, CDP-ethanolamine) on the activities of key enzymes of the Embden-Meyerhof pathway. CTP and UTP inhibited fructose-6-phosphate competitively for phosphofructokinase and phosphoenolpyruvate competitively for pyruvate kinase. In both cases, the Ki of the pyrimidine nucleotide and Km of the glycolytic substrate were above their intraerythrocytic concentrations. CTP was a competitive inhibitor of ADP for pyruvate kinase with a Ki near its intraerythrocytic concentration. CDP-choline and CDP-ethanolamine had no effect on the activities of Embden-Meyerhof or pentose phosphate shunt enzymes. Thus, the nature of the hemolytic anemia in hereditary P5'N deficiency remains enigmatic.

5'-Nucleotidase↗

Yeast mutants auxotrophic for choline or ethanolamine.

Three mutants of the yeast Saccharomyces cerevisiae which require exogenous ethanolamine or choline were isolated. The mutants map to a single locus (cho1) on chromosome V. The lipid composition suggests that cho1 mutants do not synthesize phosphatidylserine under any growth conditions. If phosphatidylethanolamine or phosphatidylcholine, which are usually derived from phosphatidylserine, were synthesized from exogenous ethanolamine or choline, the mutants grew and divided relatively normally. However, mitochondrial abnormalities were evident even when ethanolamine and choline were supplied. Diploids homozygous for the cho1 mutation were defective in sporulation. Growth on nonfermentable carbon sources was slow, and a high proportion of respiratory-deficient (petite) cells were generated in cho1 cultures.

Choline↗

Fracture of the femur, fish odour, and copper deficiency in a preterm infant.

A preterm baby boy with blood and bone changes of copper deficiency is described. Copper deficiency was suspected after fracture of the left femur during examination of the hip joint. A low serum copper concentration (2.7 mumol/l; 17.2 micrograms/100 ml) and caeruloplasmin (0.04 g/l; 0.004 g/100 ml) confirmed the diagnosis. Despite the introduction of solids at 18 weeks the copper concentration remained low, and treatment with copper sulphate (2.5 mg daily) was started at 6 months. Treatment was stopped at 9 months, when he was both physically and developmentally normal. When given a choline-containing vitamin preparation (Ketovite) he developed a fish odour because of the accumulation of trimethylamine. Withdrawal of this preparation at 6 weeks and substitution with a choline-free preparation (Abidec) was soon followed by disappearance of the odour. It is speculated that prematurity rather than copper deficiency was responsible for the poor activity of liver enzyme, trimethylamine oxidase.

Copper↗

Cloning and characterization of the phosphatidylserine synthase gene of Agrobacterium sp. strain ATCC 31749 and effect of its inactivation on production of high-molecular-mass (1-->3)-beta-D-glucan (curdlan).

Genes involved in the production of the extracellular (1-->3)-beta-glucan, curdlan, by Agrobacterium sp. strain ATCC 31749 were described previously (Stasinopoulos et al., Glycobiology 9:31-41, 1999). To identify additional curdlan-related genes whose protein products occur in the cell envelope, the transposon TnphoA was used as a specific genetic probe. One mutant was unable to produce high-molecular-mass curdlan when a previously uncharacterized gene, pss(AG), encoding a 30-kDa, membrane-associated phosphatidylserine synthase was disrupted. The membranes of the mutant lacked phosphatidylethanolamine (PE), whereas the phosphatidylcholine (PC) content was unchanged and that of both phosphatidylglycerol and cardiolipin was increased. In the mutant, the continued appearance of PC revealed that its production by this Agrobacterium strain is not solely dependent on PE in a pathway controlled by the Pss(AG) protein at its first step. Moreover, PC can be produced in a medium lacking choline. When the pss(AG)::TnphoA mutation was complemented by the intact pss(AG) gene, both the curdlan deficiency and the phospholipid profile were restored to wild-type, demonstrating a functional relationship between these two characteristics. The effect of the changed phospholipid profile could occur through an alteration in the overall charge distribution on the membrane or a specific requirement for PE for the folding into or maintenance of an active conformation of any or all of the structural proteins involved in curdlan production or transport.

Alkaline Phosphatase↗

Rett Syndrome -- an update.

Rett syndrome is a progressive, usually sporadic and rarely familial, disabling neurodevelopmental disorder with onset in early childhood presenting clinically with mental retardation, behavioral changes, late movement disturbances, loss of speech and hand skills, ataxia, apraxia, irregular breathing with hyperventilation while awake, and frequent seizures. It occurs almost exclusively in females with an estimated prevalence of 1 in 10-22000 births and is considered a manifestation of defective brain maturation caused by dominant mutation of the MeCP2 gene encoding the transcriptional repressor methyl-CpG-binding protein 2 related to the Xq28 locus. Although many different mutations of this protein are being studied in humans and in mice, the molecular pathogenesis of this disorder remains unclear. Electroencephalography is abnormal in the final stages of the syndrome. Neuroimaging showing brain atrophy may be required for differential diagnosis that includes neurodegenerative and metabolic disorders. Neuropathology shows decreased brain growth and reduced size of individual neurons, with thinned dendrites in some cortical layers and abnormalities in substantia nigra (decreased neuromelanin content), suggestive of deficient synaptogenic development, probably starting before birth. Neurometabolic changes include reduced levels of dopamine, serotonin, noradrenalin, choline acetyltransferase (ChAT), nerve growth factors, endorphines, glutamate, and other amino acids and their receptor levels in brain. Current treatment includes symptomatic, anticonvulsive and physiotherapy.

Brain↗

Sphingomyelinase and nonspecific phosphodiesterase activities in Epstein-Barr virus-transformed lymphoid cell lines from Niemann-Pick disease A, B and C.

Acid sphingomyelinase activity determined using the natural substrate, [choline-methyl-14C]sphingomyelin, or the chromogenic synthetic analogue, 2-N-(hexadecanoyl)amino-4-nitrophenylphosphorylcholine, was deficient in Epstein-Barr virus-transformed lymphoid cell lines from Niemann-Pick disease types A and B. In contrast, lines from Niemann-Pick disease type C and "sea-blue histiocyte syndrome" showed a sphingomyelinase activity within the normal range. Bis(4-methylumbelliferyl)phosphate and bis(4-methylumbelliferyl)pyrophosphate phosphodiesterase activities were not deficient in any Niemann-Pick disease cell line. These results demonstrate the validity of such cell lines as an experimental model system for enzymatic studies of Niemann-Pick disease.

Adult↗

[Pharmacological studies on supersensitization (IV). Site and mode of action of cocaine to potentiate acetylcholine in isolated tracheal preparation of rat (author's transl)].

Effects of cocaine on acetylcholine-induced contracture of isolated rat tracheal preparation were determined. The sensitivity of the preparation to acetylcholine but not methacholine and carbachol was increased by cocaine. The maximum responses induced by choline esters were not augmented by cocaine. The potentiation of acetylcholine was remarkable in calcium-deficient medium and cocaine augmented acetylcholine-contracture of the preparation suspended in calcium-free Tyrode solution. Calcium-contracture of the preparation susspended in isotonic 60 mM- or 100 mM-K+ Locke-Ringer solution was not augmented by cocaine. Extrapolating the time course of decrease in acetylcholine-contracture in calcium-free Tyrode solution, rates of calcium movement from and into calcium-stores were determined and it was found that cocaine did not change the calcium-content and rate of calcium-efflux but the rate of calcium-uptake was apparently increased with cocaine. The contribution of anticholinesterase activity of cocaine to potentiation of acetylcholine appeared negligible and the affinity of acetylcholine-receptor to acetylcholine and atropine was not changed with cocaine. Thus, cocaine increases acetylcholine-induced calcium-release and potentiates acetylcholine-contracture of isolated rat tracheal preparation.

Acetylcholine↗

MR imaging and MR spectroscopy in rhizomelic chondrodysplasia punctata.

A case of rhizomelic chondrodysplasia punctata was investigated with MR imaging of the brain and hydrogen-1 MR spectroscopy of the brain and blood. Areas with abnormal signal hyperintensity on T2-weighted images or hypointensity on T1-weighted images were detected in the subcortical white matter. MR spectroscopy of the brain showed that normal-appearing white matter was characterized by increased levels of mobile lipids and myo-inositol, reduced levels of choline, and the presence of acetate. The importance of these metabolic anomalies is correlated to the deficiency in plasmalogen biosynthesis.

Acyltransferases↗

Alcohol and cancer: genetic and nutritional aspects.

Chronic alcohol consumption is a major risk factor for cancer of upper aero-digestive tract (oro-pharynx, hypopharynx, larynx and oesophagus), the liver, the colo-rectum and the breast. Evidence has accumulated that acetaldehyde is predominantly responsible for alcohol-associated carcinogenesis. Acetaldehyde is carcinogenic and mutagenic, binds to DNA and protein, destroys the folate molecule and results in secondary cellular hyper-regeneration. Acetaldehyde is produced by mucosal and cellular alcohol dehydrogenase, cytochrome P450 2E1 and through bacterial oxidation. Its generation and/or its metabolism is modulated as a result of polymorphisms or mutations of the genes responsible for these enzymes. Acetaldehyde can also be produced by oral bacteria. Smoking, which changes the oral bacterial flora, also increases salivary acetaldehyde. Cigarette smoke and some alcoholic beverages, such as Calvados, contain acetaldehyde. In addition, chronic alcohol consumption induces cytochrome P450 2E1 enxyme activity in mucosal cells, resulting in an increased generation of reactive oxygen species and in an increased activation of various dietary and environmental carcinogens. Deficiencies of riboflavin, Zn, folate and possibly retinoic acid may further enhance alcohol-associated carcinogenesis. Finally, methyl deficiency as a result of multiple alcohol-induced changes leads to DNA hypomethylation. A depletion of lipotropes, including methionine, choline, betaine and S-adenosylmethionine, as well as folate, results in the hypomethylation of oncogenes and may lead to DNA strand breaks, all of which are associated with increased carcinogenesis.

Acetaldehyde↗

Effect of ethanol on axonal transport of cholinergic enzymes in rat sciatic nerve.

The aim of this study was to investigate whether the fast axonal transport of acetylcholinesterase (AChE) and the slow transport of choline acetyltransferase (ChAT) in the sciatic nerve of the rat are affected by chronic ethanol consumption or by associated nutritional deficiency. Adult rats drank ethanol (20% [vol./vol.]) instead of water for 20 weeks. Animals that consumed an isocaloric diet, representing a nutritional deficiency, received the same amount of food as ethanol-treated rats and water with sucrose replacing ethanol isocalorically. The control group received food and water ad libitum. Axonal transport was investigated by the stop-flow ligation technique as follows. After 20 weeks, the sciatic nerve was ligated for 24 h, and accumulation of AChE and ChAT was measured above and below the ligature. No significant differences in the accumulation of both enzymes were found above the ligature. However, the accumulation of AChE transported retrogradely below the nerve ligature was reduced by 60%, but only in ethanol-treated animals. Our study results seem to indicate that, under experimental conditions, (1) neither ethanol nor associated nutritional deficiency has any effect on anterograde axonal transport of AChE and ChAT and (2) the deficit in retrograde transport of AChE is due to the direct toxic effect of ethanol and probably precedes the axonal degeneration from the most distal portions of axons toward the cell body.

Acetylcholinesterase↗