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  • 1
    Electronic Resource
    Electronic Resource
    Sequential changes in plasma renin activity and plasma catecholamines in mildly hypertensive patients during acute, furosemide-induced body-fluid loss (1983)
    Springer
    European journal of clinical pharmacology 25 (1983), S. 299-302 
    Details
    ISSN: 1432-1041
    Keywords: furosemide ; hypertension ; plasma renin activity ; plasma adrenaline ; plasma noradrenaline ; body fluid loss ; diuretic response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To evaluate the role of adrenergic mechanisms in the acute response of renin to furosemide, plasma renin activity (PRA) and plasma catecholamine concentrations were measured for 3 h after i.v. administration of furosemide 1 mg/kg to 8 patients with mild essential hypertension. Furosemide induced a prompt and long-lasting increase in renin, with PRA more than doubled at all times. The increase in PRA within the first 30 min paralleled the peak increases in urinary water and sodium flow rates, and significant decreases in plasma volume and central venous pressure. There was no change in plasma catecholamine concentrations. Plasma noradrenaline was increased significantly at 60 min and adrenaline at 90 min, once furosemide had induced a marked loss of body-fluid and ∼65% decrease in central venous pressure. Both catecholamines remained elevated until the end of the study, whereas urinary water and sodium flow rates had returned to their pre-treatment values by 150 min. Mean blood pressure was essentially unchanged throughout the study, whereas heart rate increased significantly after 90 min. The findings suggest that in mildly hypertensive patients adrenergic mechanisms are not involved in the initial renin response to furosemide, but they come into play later, probably as a result of reflex sympathetic activation triggered by marked volume depletion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01037937
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  • 2
    Electronic Resource
    Electronic Resource
    [3H]Ro 16–6491, a Selective Probe for Affinity Labelling of Monoamine Oxidase Type B in Human Brain and Platelet Membranes (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 50 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: [3H]Ro 16–6491 [N-(2-aminoethyl)-p-chloroben-zamide HCl], a reversible “mechanism-based” inhibitor of monoamine oxidase (MAO) type B, binds selectively and with high affinity to the active site of MAO-B in brain and platelet membranes. Under normal conditions, the binding of [3H]Ro 16–6491 is fully reversible. However, [3H]Ro 16–6491 could be irreversibly bound (covalently) to membranes by the addition of the reducing agent NaBH3CN to the sample and adjusting to pH 4.5 with acetic acid. No irreversible labelling occurred in the absence of NaBH3CN and at neutral pH. The presence of the irreversible MAO-B inhibitor /-deprenyl completely abolished the irreversible labelling of the membranes by [3H]Ro 16–6491. The selective inactivation of MAO-B, e.g., by /-deprenyl prevented the covalent incorporation of [3H]Ro 16–6491 whereas selective inhibition of the MAO-A by clorgyline was without effect. The covalent linkage to membranes of unlabelled Ro 16–6491 and Ro 19–6327 (a selective and reversible MAO-B inhibitor closely related to Ro 16–6491) after the addition of NaBH3CN at pH 4.5 irreversibly inactivated MAO-B activity whereas MAO-A activity was unaffected. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of labelled membranes showed that [3H]Ro 16–6491 was incorporated into a single polypeptide with a molecular mass identical to the one labelled by [3H]pargyline (58 kilodaltons). Our results indicate that the polypeptide that is covalently labelled by [3H]Ro 16–6491 corresponds to one of the two MAO-B subunits. Therefore, [3H]Ro 16–6491 represents a selective probe for affinity labelling of MAO-B and for the investigation of the structural composition of the active site of the enzyme. Whether the reduction with NaBH3CN at pH 4.5 of the [3H]Ro 16–6491-MAO-B complex results in the formation of a stable adduct with the amino acid chain of the MAO-B or with its prosthetic group, FAD, remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb10570.x
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  • 3
    Electronic Resource
    Electronic Resource
    Uptake, Release, and Subcellular Localization of l-Methyl-4-Phenylpyridinium in Blood Platelets (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 49 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: : The neurotoxic compound 1-[methyl-3H]-4-phenylpyridinium ([3H]MPP+) was actively taken up by human, rabbit, and guinea pig platelets incubated in plasma. In human platelets, the apparent Km of this uptake (22.6 μM) was 50 times higher than that for serotonin [5-hydroxytryptamine (5-HT)]. The uptake of [3H]MPP+ by human platelets was inhibited by selective 5-HT uptake blockers [cianopramine, (−)-paroxetine, and clomipramine], by metabolic inhibitors (KCN and ouabain), and by drugs that interfere with amine storage in the 5-HT organelles (reserpine, mepacrine, and Ro 4–1284). Impairment of the trans-membrane proton gradient by ionophores (monensin and nigericin) induced a marked release of radioactivity from platelets preincubated with [3H]MPP+. Fractionation of homogenates of rabbit platelets preincubated with [3H]MPP+ showed that the drug was concentrated to a great extent in the 5-HT organelle fraction. MPP+ competitively inhibited [14CJ5-HT uptake by human platelets and reduced the endogenous 5-HT content of human, rabbit, and guinea pig platelets. These investigations show that MPP+ is transported into the platelets via the 5-HT carrier and is accumulated predominantly in the subcellular organelles that store 5-HT and other monoamines. It is suggested that an accumulation of MPP+ in amine storage vesicles of neurons may be involved in the effects of the drug in the CNS, e.g., by protecting other subcellular compartments from exposure to high concentrations of MPP+, by sustaining a gradual release of the toxin, or both.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb03405.x
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  • 4
    Electronic Resource
    Electronic Resource
    Binding of [3H]Ro 16-6491, a Reversible Inhibitor of Monoamine Oxidase Type B, to Human Brain Mitochondria and Platelet Membranes (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The reversible inhibitor of monoamine oxidase type B (MAO-B) [3H]Ro 16-6491 binds specifically and with high affinity to a single population of binding sites in human frontal cortex crude mitochondria and platelet membranes. In both tissues binding equilibrium was reached after l h incubation at 20°C. Dissociation of bound radioactivity was relatively fast at 20°C (t1/2= 90–120 min) whereas at 0°C [3H]Ro 16–6491 showed the characteristics of a slowly dissociating ligand. Inhibitors and substrates of MAO-B inhibited binding of [3H]Ro 16-6491, whereas MAO-A blockers were much less potent. Ro 16-6491 was also a substrate for MAO-B and a stable unidentified intermediate of the oxidation of Ro 16-6491 possessing high affinity for the enzyme may account for the marked MAO-B inhibitory effect of the drug. According to this hypothesis Ro 16-6491 would behave as a mechanism-based reversible inhibitor. In conclusion, [3H]Ro 16-6491 binds selectively to MAO-B and represents an excellent new radioligand probe for studying the regional tissue distribution of this enzyme in normal and pathological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb13143.x
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  • 5
    Electronic Resource
    Electronic Resource
    Expression of the kynurenine enzymes in macrophages and microglial cells: regulation by immune modulators (1998)
    Springer
    Amino acids 14 (1998), S. 251-255 
    Details
    ISSN: 1438-2199
    Keywords: Macrophages/monocytes ; Microglia ; Cytokines ; Indoleamine 2,3-dioxygenase ; Nitric oxide synthase ; Nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The regulation of the expression of indoleamine 2,3-dioxygenase (IDO) was studied in cloned murine macrophages (MT2) and microglial (N11) cells. Both cell lines express IDO and inducible nitric oxide synthase activity after interferon-γ (IFN-γ) stimulation. The regulation of IDO expression appears to differ in the two cell lines. Nitric oxide (NO) production negatively modulates the expression of IDO activity in IFN-γ-primed macrophages, thereby indicating a cross-talk between the kynurenine and nitridergic pathways in these cells. Conversely, this down-regulation of IDO activity by NO does not occour in microglial cells. A differential regulation of IDO expression in the two cell lines was also observed with LPS and picolinic acid. Together with previous findings, these results indicate the existence of marked differences in the regulation of the expression of the kynurenine pathway enzymes between macrophages and microglial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01345271
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  • 6
    Electronic Resource
    Electronic Resource
    Brain microdialysis in rats: a technique to reveal competition in vivo between endogenous dopamine and moclobemide, a RIMA antidepressant (1992)
    Springer
    Psychopharmacology 106 (1992), S. S17 
    Details
    ISSN: 1432-2072
    Keywords: Reversibility in vivo ; Microdialysis ; MAO-A inhibition ; Ro 41-1049
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this study, the effect of the interaction between the short-acting reserpine-like dopamine (DA) releaser Ro 4-1284 (1 mg/kg IP) and the reversible inhibitors of monoamine oxidase type A (MAO-A), moclobemide (Aurorix®) and Ro 41-1049 (20 mg/kg IP, each), on the outflow of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) was investigated by rat transstriatal microdialysis. The injection of Ro 4-1284 after MAO-A inhibitors produced a marked increase of DA concentrations corresponding to a bell-shaped change in DOPAC outflow. This effect was more pronounced in rats treated with moclobemide than with Ro 41-1049. These data support the view that the increment of the endogenous substrate DA might displace moclobemide more rapidly than Ro 41-1049 from MAO-A active sites. The microdialysis method is proposed as a more reliable in vivo technique to investigate the degree of reversibility of the reversible MAO-A inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246227
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  • 7
    Electronic Resource
    Electronic Resource
    Biochemistry and pharmacology of moclobemide, a prototype RIMA (1992)
    Springer
    Psychopharmacology 106 (1992), S. S6 
    Details
    ISSN: 1432-2072
    Keywords: MAO-A inhibitor ; Moclobemide ; Antidepressant biochemistry ; Pharmacology ; Monoamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract RIMA is a term for reversible inhibitors of monoamine oxidase (MAO) with preference for MAO-A; moclobemide is a prototype of this new class of antidepressants and is a highly selective inhibitor of MAO-A in vitro. This inhibition is reversible by dialysis in vitro, which accounts for the dose-dependent duration of in vivo enzyme inhibition of 12–24 h. Moclobemide increases the content of serotonin, noradrenaline and dopamine in the brain, and decreases that of their deaminated metabolites. Its biochemical, neurological and behavioural effects indicate that it increases the extracellular concentration of the classic monoamine neurotransmitters/neuromodulators — in particular 5-HT. Potentiation of the cardiovascular effects of tyramine is less pronounced after taking moclobemide than after irreversible MAO-A inhibitors. Understanding of the physiological role of MAO and of the events that link inhibition of the enzyme with modulation of neuronal activities in the CNS remains incomplete. A major physiological role of intraneuronal MAO is to keep cytosolic amine concentration very low, to enable the neuronal monoamine carriers to produce a net inward transport of monoamines, and thereby to act as the first step in the termination of action of extracellular monoamines. MAO is likely to have a similar function in non-monoaminergic cells with respect to the monoamine carriers they contain. In addition to the classic monoamines, “trace” amines may become functionally active after MAO inhibition. An alternative role for MAO is that of a scavenger, preventing natural substrates from accumulating in monoaminergic neurons and interacting with storage, release, uptake and receptor function of monoamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246225
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  • 8
    Electronic Resource
    Electronic Resource
    Mode of action and characteristics of monoamine oxidase-A inhibition by moclobemide (1992)
    Springer
    Psychopharmacology 106 (1992), S. S15 
    Details
    ISSN: 1432-2072
    Keywords: Moclobemine ; Monoamine oxidase-A ; Inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The mode of interaction of the reversible monoamine oxidase-A (MAO-A) inhibitor moclobemide with the enzyme was investigated. The inhibition of rat brain or human placenta MAO-A by moclobemide showed an initial competitive phase, with a relatively low affinity (KI=0.2–0.4 mM). However, the potency of the inhibitor was increased with incubation time. The time-dependent component of the association of moclobemide with MAO-A followed pseudo-first order kinetics. In contrast to mechanism-based inhibitors, no indication for adduct or product formation was detected after incubation of moclobemide with the enzyme. Even though some aspects of the moclobemide interaction with MAO-A are still not completely elucidated, this compound seems to have the characteristics of a slow-binding inhibitor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246226
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  • 9
    Electronic Resource
    Electronic Resource
    Platelets as a model for neurones? (1988)
    Springer
    Cellular and molecular life sciences 44 (1988), S. 115-126 
    Details
    ISSN: 1420-9071
    Keywords: 5-HT releases ; monoamine oxidase type B ; 5-hydroxytryptamine ; 5-HT blockers ; platelet receptors ; MPTP ; MPP+ ; 5-HT storage ; Ro 19-6327
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The multiple biochemical and pharmacological similarities existing between blood platelets and 5-hydroxytryptamine (5-HT)-containing neurones of the CNS point to the platelets as a reliable model for the biochemical characterization of 5-HT releasers and uptake blockers which interfere with the storage and the active carrier mechanism of 5-HT in the neurones, respectively. In addition, the affinity displayed by dopamine and by dopaminergic neurotoxin MPP+ for the platelet 5-HT transport and storage indicates also some similarities between platelets and the dopaminergic system of the CNS. Since human platelets contain almost exclusively monoamine oxidase type B (MAO-B), they can be used as a source for the purification and characterization of this human enzyme. Human platelets thus offer an excellent peripheral model to indirectly assess the degree and duration of MAO-B inhibition occurring in the CNS. To date, knowledge of the many biochemical mechanisms underlying platelet physiology is still fragmentary. In fact, the functional role of binding sites located on the platelet cytoplasmic membrane, i.e. their coupling to a specific transmembrane signalling mechanism, is still in need of a precise biochemical and physiological characterization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01952193
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  • 10
    Electronic Resource
    Electronic Resource
    Serotonin and noradrenaline concentrations and serotonin uptake in platelets from hyperphenylalaninaemic patients (1988)
    Springer
    Journal of inherited metabolic disease 11 (1988), S. 285-290 
    Details
    ISSN: 1573-2665
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In three untreated patients with phenylketonuria (PKU), three PKU and six hyperphenylalaninaemic (HPA) patients in good metabolic control, the kinetic constants of plateletin vitro uptake of [14C]serotonin (5HT) did not significantly differ from those in 12 control subjects matched for age. The platelet concentrations of endogenous 5HT and noradrenaline (NA), taken as long-term indices of the amount of these amines circulating in plasma, were lower than normal in PKU and HPA patients, whether or not they were kept on a diet. However, a reduction in plasma NA concentrations at the moment of blood collection was seen only in untreated PKU patients. These data indicate that there may be a chronic inhibition of 5HT and possibly of NA synthesis even in PKU or HPA subjects in good metabolic control, with normal psychomotor development and only slightly raised plasma phenylalanine levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01800371
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