Browsing by Author "DANIELS, AJ"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    CHARACTER OF STORED MOLECULES IN CHROMAFFIN GRANULES OF ADRENAL-MEDULLA - NUCLEAR MAGNETIC-RESONANCE STUDY
    (1978) DANIELS, AJ; WILLIAMS, RJP; WRIGHT, PE
    The organization of the internal contents of bovine adrenal chromaffin granules were studied using NMR spectroscopy. The method permits an examination of the interactions between ATP metal ions, adrenaline [epinephrine] and the chromogranin proteins. Particular advantage accrues when the naturally occurring cations Mg and Ca are replaced by Mn cations, since Mn2+ is an effective perturbing probe. Protein spectrum in the vesicles was compared with that of the isolated proteins. There was a loose network of interactions between the various components. The major part of the network was the interaction of the chromogranin protein, shown to have approximately a random coil conformation, with the ATP and the adrenaline. The organized loose structure appeared to lower osmotic pressure without hindering rapid release of the vesicle contents breaking the membrane.
  • No Thumbnail Available
    Item
    EFFECT OF INTRANIGRAL MN-2+ ON STRIATAL AND NIGRAL SYNTHESIS AND LEVELS OF DOPAMINE AND COFACTOR
    (1991) DANIELS, AJ; ABARCA, J
    A single injection of manganese chloride into the rat substantia nigra caused a significant and reversible drop in nigral and striatal dopamine and cofactor content ipsilateral to the lesion. Maximal decrease, in both tissues, was observed 60 days after the lesion, and showed complete recovery at 90 days. In vivo striatal tyrosine hydroxylation and GTP cyclohydrolase activities were also decreased maximally at 60 days and were recovered by 90 days after the lesion. No effects were observed on the side contralateral to the injection.
  • No Thumbnail Available
    Item
    RAT STRIATAL DOPAMINE AND TETRAHYDROBIOPTERIN CONTENT FOLLOWING AN INTRASTRIATAL INJECTION OF MANGANESE CHLORIDE
    (1986) LISTA, A; ABARCA, J; RAMOS, C; DANIELS, AJ
    Injection of manganese into the rat corpus striatum causes a rapid fall in the biopterin and dopamine (DA) content ipsilateral to the lesion. Two weeks after the lesion both biopterin and DA are partially recovered. Controls, injected with saline or magnesium, do not show alterations in their DA or cofactor levels. It is proposed that the fall in DA levels results from a rapid displacement of the amine from its storage sites by manganese followed by a decrease in the rate of DA synthesis causes by the drop in cofactor levels.
  • No Thumbnail Available
    Item
    UPTAKE AND RELEASE OF MANGANESE BY RAT STRIATAL SLICES
    (1981) DANIELS, AJ; GYSLING, K; ABARCA, J
    Accumulation of Mn in rat corpus striatum slices was non-saturable, although relatively strongly temperature dependent and inhibited by 2,4-dinitrophenol (2,4-DNP). Once incorporated, the metal ion was released by K+ (55 mM) depolarization in the presence of Ca ions, following a time course of efflux parallel to that of [3H]dopamine ([3H]DA). The release of the metal ion was not induced by tyramine. [3H]DA release was also induced by low concentrations of MnCl2. The possibility exists that these findings may be related in some way to the functional deficiency of the nigro-striatal dopaminergic system found after Mn poisoning.
  • No Thumbnail Available
    Item
    UPTAKE OF MAGNESIUM BY CHROMAFFIN GRANULES INVITRO - ROLE OF THE PROTON ELECTROCHEMICAL GRADIENT
    (1984) FIEDLER, J; DANIELS, AJ
    The [bovine] chromaffin granule membrane in vitro is impermeable to protons as well as to Mg2+. When granules are incubated in the presence of the proton ionophore carbonyl cyanide p-trifluoromethoxy-phenylhydrazone or an inhibitor of the granule membrane Mg2+-dependent ATPase, the metal ion is accumulated inside the granules. This accumulation is dependent upon the granule transmembrane potential. The simultaneous presence of the ATPase inhibitor and the proton ionophore markedly increases metal ion incorporation. Mg2+ incorporation is also promoted by nigericin in the presence of K+ or Na+, indicating that Mg2+ accumulation is also dependent upon the transmembrane pH gradient. Concomitant with the Mg2+ accumulation, there is a significant loss of endogenous catecholamines. Mg2+ accumulation is determined by the electrochemical gradient maintained across the membrane. Once the metal ion has accumulated into the granules it displaces catecholamines from their storage sites.