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  • 1
    ISSN: 0898-6568
    Keywords: GM-CSF ; Neutrophils ; calcium ; haemopoiesis ; inositol phosphates ; phosphatidic acid ; phospholipase D
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract GM-CSF has previously been shown to increase human neutrophil phospholipase D (PLD) activity in response to fMLP. To further define the mechanism by which GM-CSF up-regulates PLD activity, we investigated the effect of GM-CSF pretreatment of neutrophils on phosphatidylcholine breakdown in response to a receptor-coupled stimulus N-formyl-methionyl-leucyl-phenylalanine (fMLP) and to a receptor-independent stimulus phorbol-myristate-acetate (PMA). Treatment of 1-0-[3H]alkyl-2-acetyl-sn-glycero-3-phosphocholine-prelabeled human neutrophils with 200 pM GM-CSF for 1 hour at 37°C led to a more rapid and increased accumulation (2–3 fold) of [3H]-alkyl-phosphatidic acid (or [3H]-alkyl-phosphatidylethanol when cells are stimulated in presence of 0.5% ethanol) in response to both fMLP or PMA. The data indicate GM-CSF up-regulates phosphatidylcholine hydrolysis by a PLD by interfering with the excitation-response coupling sequence at a site distal to the fMLP receptor.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The incubation of brain stem slices from adult rats in a K+-enriched medium containing a 5-HT uptake inhibitor (fluoxetine) significantly increased their capacity to synthesize 5-HT from tryptophan. The K+-induced stimulation of 5-HT synthesis was at least partly dependent on the depletion of the indoleamine in tissues since: (1) a good correlation was found between the respective changes in 5-HT release and synthesis evoked by high K+ concentrations in the presence of various 5-HT uptake inhibitors; (2) the modifications in endogenous 5-HT levels produced by in vim treatments with drugs (reserpine, pargyline) or by incubating slices with 5-HT altered the stimulating effect of high K+ concentrations and fluoxetine on 5-HT synthesis; (3) the replacement of Ca2+ by Co2+ (4 mM) or EGTA (0.1 mM) in the incubating medium completely prevented the increased 5-HT release and synthesis evoked by high K+ concentrations and fluoxetine.The extraction of tryptophan hydroxylase from incubated tissues revealed that the increased 5-HT synthesis occurring in K+-enriched medium was associated with an activation of this enzyme. Kinetic analyses indicated that this activation resulted from an increase in the Vmax of tryptophan hydroxylase, its apparent affinities for both tryptophan and 6-MPH4 being not significantly affected. In contrast to the tryptophan hydroxylase from tissues incubated in normal physiological medium, the activated enzyme from tissues depolarized by K+ was hardly stimulated by Ca2+-mediated phosphorylating conditions. This led to the proposition of a hypothetical model by which the Ca2+ influx produced by the neuronal depolarization would trigger the activity of a Ca2+-dependent protein kinase capable of activating tryptophan hydroxylase. Although this sequence is still largely speculative it must be emphasized that, as expected from such a model, the regional differences in the K+-evoked activation of tryptophan hydroxylase in slices (cerebral cortex 〉 brain stem 〉 spinal cord) were parallel to those of the Ca2+-dependent protein phosphorylation (r= 0.92) and those of the activating effect of phosphorylating conditions on soluble tryptophan hydroxylase (r= 0.96).
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The relationships between plasma tryptophan and 5-HT metabolism in the CNS were studied in newborn rats and compared with adults. Both the concentration of free tryptophan in plasma and that of the amino-acid in brain were much higher immediately after birth than later on. Drugs such as salicylate and chlordiazepoxide, which increased brain tryptophan concentrations in adults by displacing the plasma amino acid bound to serum albumin, were ineffective in newborn rats: most of the amino acid being already free in their plasma. The study of 5-HT metabolism in brain stem slices revealed that the affinity of the uptake process for tryptophan was higher in newborn than in adult animals, whereas the reverse situation was observed for the enzyme complex involved in 5-HT synthesis (lower apparent Km in adults). In addition, the catabolism of newly synthesized 5-HT was more rapid in newborn than in adult tissues. Finally, the free state of tryptophan in plasma of newborn animals induced in brain both a high amino acid concentration and, in contrast to the situation observed in adults, a synthesis rate of 5-HT very near its maximal value.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 20 (1973), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of changes in intraneuronal levels of 5-HT induced by monoamine oxidase inhibitors (MAOI) given in vivo or exogenous 5-HT added in vitro on 5-HT synthesis in striatal slices of the rat have been examined. The synthesis of 5-HT was estimated by the measurement of the total formation of [3H]5-HT and [3H]5-hydroxyindole acetic acid from [3H]tryptophan and by calculation of the conversion index (CI) of tryptophan into 5-HT. The small formation of [3H]tryptamine and [3H]indole acetic acid from [3H]tryptophan was taken into account in the estimation of 5-HT synthesis. Both MAOI pretreament (180 min) and 5-HT (2·8 μM) inhibited synthesis. The latter effect persisted in catecholamine depleted tissues and was related to intraneuronal changes in 5-HT levels, since it could be prevented by chlorimipramine. The inhibition of 5-HT synthesis was related to the decreased conversion of tryptophan into 5-hydroxytryptophan and could not be prevented by p-chloro-phenylalanine pretreatment which depleted 5-HT levels or by dibutyryl cyclic AMP which normally stimulated 5-HT synthesis. Tryptophan uptake in slices was not affected by exogenous 5-HT. The various mechanisms possibly involved in the end product regulation process of 5-HT synthesis are discussed.
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  • 6
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Normal human blood neutrophils were studied for their capacity to synthesize leukotriene B4 (LTB4) and its Ω-oxidized metabolites after phagocytosis of zymosan. Phagocytosis of serum-opsonized particles led to a higher release of LTs than did unopsonized zymosan. The most stricking effect of phagocytosis was observed when neutrophils were primed with granulocyte-macrophage colony-stimulating factor (GM-CSF): opsonization and GM-CSF synergistically increased LTB4 synthesis by neutrophils.
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Double reciprocal plots of tryptophan hydroxylase activity against tryptophan concentration. Effects of in vivo methiothepin (O) or methiothepin-LSD treatment (x); ?, control. Methiothepin and LSD were injected as described in Table 2. Soluble enzyme was prepared from the brainstem of rats. ...
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Possible interactions between Met-enkephalin and cholecystokinin (CCK)-containing neurons in the rat sub-stantia nigra were investigated by looking for the effects of various opioid receptor ligands and inhibitors of enkephalin-degrading enzymes on the K+-evoked overflow of CCK-like material (CCKLM) from substantia nigra slices. The δ-opioid agonists d-Pen2,dPen5-enkephalin (50 μM) and Tyr-D-Thr-Gly-Phe-Leu-Thr (DTLET; 3 μM) enhanced, whereas the n-opioid agonists Tyr-D-Ala-Gly-MePhe-Gly-ol (DAGO; 10 μM) and MePhe3, D-Pro4-morphiceptin (PL 017; 10 μM) decreased, the K+-evoked release of CCKLM. By contrast, the δ-opioid agonist U-50488 H (5 μM) was inactive. The stimulatory effect of DTLET could be prevented by the 5 antagonist ICI-154129 (50 μM but not by the μ antagonist naloxone (1 μM). Conversely, the latter drug, but not ICI-154129, prevented the inhibitory effect of DAGO and PL 017. A significant increase in CCKLM overflow was observed upon tissue supervision with the peptidase inhibitors kelatorphan or bestatin plus thiorphan. This effect probably resulted from the stimulation of δ-opioid receptors by endogenous enkephalins protected from degradation, because it could be prevented by ICI-154129 (50 μM Furthermore, the peptidase inhibitors did not enhance CCKLM release further when S-opioid receptors were stimulated directly by DTLET (3 μM). These data indicate that opioids acting on d and n receptors may exert an opposite influence, i.e., excitatory and inhibitory, respectively, on CCK-containing neurons in the rat substantia nigra. Because CCK has anti-opioid properties, the δ-opioid control of CCKLM release might participate in the central mechanisms of opiate tolerance.
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Under control conditions, superfused slices of the dorsal half of the lumbar enlargement from adult rats released Met-enkephalin-like material (MELM) that behaved as authentic Met-enkephalin under two different chromatographic procedures (Bio-gel filtration, HPLC). MELM release increased markedly on exposure of slices to batrachotoxin (0.5 μM) or to an excess of K+ (28 and 56 mM instead of 5.6 mM). The K + -evoked release was totally dependent on the presence of Ca2+ in the super-fusing fluid whereas the spontaneous efflux of MELM was only partially Ca2+-dependent. Further experiments performed with tissues of polyarthritic rats indicated that the increase in their MELM levels was associated with a lower fractional rate constant of MELM release, therefore suggesting that spinal Met-enkephalin turnover might be reduced in chronically suffering animals. Examination of the possible modulation of MELM release by various neuroactive compounds present within the dorsal horn revealed that cholecystokinin (10 μM), but not its desulphated derivative, substance P-sulphoxide (10 μM), and to a lesser extent substance P, enhanced the K+-evoked MELM release. In contrast, γ-aminobutyric acid (10 μM) and (–)-baclofen (1 μM) partially prevented the stimulatory effect of K+ on MELM release. Other compounds such as serotonin, somatostatin, and neurotensin altered neither the spontaneous nor the K+-evoked release of MELM.
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  • 10
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Biochemical mapping of five different peptide-like materials—calcitonin gene-related peptide (CGRP), substance P (SP), Met5-enkephalin (ME), cholecystokinin (CCK), and dynorphin A (1–8) (DYN)—was conducted in the dorsal and ventral zones of the spinal cord at the cervical, thoracic, and lumbar levels in 3-month-old rats 10 days after unilateral dorsal rhizotomy at the cervical level (C4-T2) or after neonatal administration of capsaicin (50 mg/kg s.c). In control rats, all peptide-like materials were more abundant in the dorsal than in the ventral zone all along the spinal cord. However, in both zones, absolute concentrations of CGRP, SP, ME, and CCK were significantly higher at the lumbar than at the cervical level. Rhizotomy-induced CGRP depletion (-85%) within the ipsilateral dorsal zone of the cervical cord was more pronounced than that due to neonatal capsaicin (-60%), a finding suggesting that this peptide is contained in both capsaicin-sensitive (mostly unmyelinated) and -insensitive (myelinated) primary afferent fibers. In contrast, similar depletions of SP (-50%) were observed after dorsal rhizotomy and neonatal capsaicin treatment, as expected from the presence of SP only in the capsaicin-sensitive small-diameter primary afferent fibers. Although the other three peptides remained unaffected all along the cord by either intervention, evidence for the existence of capsaicin-insensitive CCKergic primary afferent fibers could be inferred from the increased accumulation of CCK (together with SP and CGRP) in dorsal root ganglia ipsilateral to dorsal root sections.
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