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  • 1995-1999  (1)
  • 1980-1984  (1)
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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Changes in the activity of pyruvate dehydrogenase [pyruvate: lipoamide oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1, PDH], elicited by inhibition of the phosphorylation of its 40,000 Mrα-subunit, were compared with changes in pyruvate-supported calcium accumulation by rat brain mitochondria. Dichloroacetate (DCA) produces concentration-dependent inhibition of the phosphorylation of intramitochondrial PDH a-subunit, which is accompanied by stimulation of PDH activity and calcium accumulation. DCA did not affect succinate- or ATP-supported mitochondrial calcium accumulation. The concentration of DCA giving half-maximal inhibition of the phosphorylation was almost identical to that giving half-maximal stimulation of PDH activity and calcium accumulation. PDH activity and pyruvate-supported calcium accumulation showed similar dependence on pyruvate concentration with respective apparent affinities for pyruvate of 40 μm and 30 μm, and both activities exhibited positive cooperativity. DCA modified only the maximal activity of PDH or the maximal calcium accumulation without changing either the apparent affinities for pyruvate or calcium or the Hill coefficients. These data provide evidence that calcium accumulation by mitochondria is tightly linked to PDH activity and that changes in the phosphorylation of the PDH α-subunit can be reflected in changes in the calcium-buffering ability of mitochondria. This suggests a possible mechanism by which a variety of manipulations, such as repetitive synaptic stimulation, can alter the regulation of internal calcium levels.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Anions ; System peaks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This study deals with the simultaneous analysis of UV-transparent anions by capillary electrophoresis with indirect UV-detection. With a background electrolyte (BGE) based on UV-absorbing chromate and UV-transparent borate, the interference of system peaks with those of sample anions (chloride, sulfate, citrate, phosphate) is shown. The existence of such system peaks, and their position in relation to the peaks of the sample anions, are explained on the basis of the eigenpeak theory proposed by Poppe [1]. With this BGE the system peaks were manifested as a negative peak followed by a positive peak. Their shapes depended on the relative mobilities of the analyte and BGE anions and their areas depended on the amount of sample. The mobility of the system peak depends on the borate/boric acid mobility, which was adjusted by slight variation of the pH close to its pK a-pH is the key factor governing system-peak mobility. When the locations of the system peaks are optimized, the quantification of citrate can be achieved; this was successfully used for determination of anions in milk.
    Type of Medium: Electronic Resource
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