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  • 1
    Electronic Resource
    Electronic Resource
    Evidence implicating protein kinase C in exocytosis from electropermeabilized bovine chromaffin cells (1988)
    Springer
    The journal of membrane biology 104 (1988), S. 21-34 
    Details
    ISSN: 1432-1424
    Keywords: exocytosis ; secretion ; calcium ; protein kinase C ; adrenal medulla ; catecholamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The calcium sensitivity of exocytosis from electroper-meabilized chromaffin cells is increased by activators of protein kinase C, such as TPA and certain phorbol esters, diacylglycerols, and mezerein. A range of putative inhibitors of protein kinase C block both the phorbol ester-sensitive component of secretion and also the underlying insensitive component. These inhibitors are also shown to inhibit medulla protein kinase C activity in vitro. The extent of secretion is reduced when electropermeabilized cells are exposed to Ca2+ levels much in excess of 50 μm. The onset of inhibition is faster than the relatively slow rate of Ca-dependent exocytosis and is insensitive to inhibitors of proteolysis. Adrenal medulla protein kinase C activity is also irreversibly inhibited by high Ca2+ concentrations. Both the secretory response and the protein kinase C activity in vitro have similar nucleotide and cation specificities. Although these data do not definitely establish an involvement of protein kinase C in exocytosis, none argue against it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871899
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Melatonin biosynthesis in the mammalian pineal gland (1989)
    Springer
    Cellular and molecular life sciences 45 (1989), S. 922-932 
    Details
    ISSN: 1420-9071
    Keywords: Melatonin ; adrenergic receptors ; second messengers ; serotonin N-acetyltransferase ; hydroxyndole-O-methyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rhythmic production of melatonin by the mammalian pineal occurs in response to noradrenergic stimulation which produces a cascade of biochemical events within the pinealocyte. In the rat, massive changes in NAT activity result from an increase in intracellular c-AMP levels produced by a synergistic interaction whereby an α1 activation amplifies β-adrenergic stimulation. The intracellular events mediating this effect are described. A major aspect of the temporal control of melatonin production is the programmed down-regulation of responses to noradrenergic stimulation once the initial surge of c-AMP is produced. Noradrenergic activation of the gland also influences other enzymic functions, including tryptophan hydroxylase and HIOMT activities, and produces a dramatic increase in intracellular c-GMP levels. Other neurotransmitters and neuropeptides, e.g. VIP, may also influence pineal function and comparisons are, made between the rat, the subject of the bulk of experimental studies, and other species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01953049
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Sedative potency and 2-[125I]iodomelatonin binding affinity of melatonin analogues (1995)
    Springer
    Psychopharmacology 117 (1995), S. 364-370 
    Details
    ISSN: 1432-2072
    Keywords: Melatonin ; Sedation ; Pentobarbitone sleeping time ; 2-[125I]iodomelatonin binding sites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Melatonin (5-methoxyN-acetyltryptamine), the hormone synthesized and released from the pineal gland each night, has sedative and sleep-promoting effects in experimental animals and man. In the present study, the sedative effect of melatonin and a number of analogues was determined by examining their ability to extend the duration of the loss of righting reflex (“sleeping time”) in mice injected with pentobarbitone (50 mg/kg IV). All of the analogues tested produced a dose-related (5–20 mg/kg) potentiation of pentobarbitone sleeping time. In radioligand binding assays using 2-[125I]iodomelatonin in chicken brain membranes, all of the analogues were competitive inhibitors. There was no correlation between their ability to inhibit 2-[125I]iodomelatonin binding in chick and sedative potency in the mouse. Potentiation of pentobarbitone sleeping time by diazepam (1 mg/kg IP), but not melatonin (10 mg/kg IP), was blocked by pretreatment with the benzodiazepine antagonist, flumazenil (10 mg/kg IP). Similarly, an increase in pentobarbitone sleeping time produced by the aminoalkylindole cannabinoid receptor agonist, WIN 55212-2 (0.5 mg/kg IP), but not that produced by melatonin (10 mg/kg IP) was reduced by the cannabinoid receptor antagonist WIN 56098 (5 mg/kg IP). These studies confirm that melatonin has sedative activity and show that this action is shared by several structurally-related analogues but does not appear to be mediated by an interaction with benzodiazepine or cannabinoid receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246111
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    Paper (German National Licenses)
    Fulltext
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