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  • 1
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  Desloratadine is a selective H1-antihistamine used in the treatment of allergic rhinitis and chronic idiopathic urticaria. Desloratadine inhibits the release of allergic inflammatory mediators in vitro. We studied the impact of desloratadine on mast cell degranulation due to activation and re-activation by the secretagogue, compound 48/80.Methods:  Rat peritoneal eluate containing 5–6% mast cells were activated by a low concentration of compound 48/80 in a medium containing the vital fluorescent dye, Sulforhodamine-B (SFRM-B, 200 μg/ml), which is engulfed by activated mast cells. The fluorescent image of activated mast cells was captured digitally and the total fluorescent area was analyzed when desloratadine was applied before or after compound 48/80.Results:  Mast cells were not activated by desloratadine (10−4 M), SFRM-B (200 μg/ml), or diluent alone. A low concentration of compound 48/80 (0.125 μg/ml) induced fluorescence, while mast cells lost fluorescent images due to further degranulation on re-exposure to compound 48/80. Desloratadine (10−8–10−4 M), inhibited compound 48/80-induced mast cell degranulation in a concentration-dependent manner. Desloratadine also reduced the loss of fluorescent images due to re-exposure to compound 48/80.Conclusions:  Desloratadine may have a mast cell stabilizing effect at low concentrations in response to repeated mast cell activation in vitro.
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  • 2
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Sedation limits the clinical utility of classical H, antihistamines. while newer antihistamincs such as loratadine and terfenadine arc non-sedating. However, clinical use of terfenadine has been associated with rare but severe cardiac arrhythmias, in particular lorsades de pointes.Objective To establish a quantitative experimental model for assessing the sedating and cardiotoxicity potential of non-sedating and sedating antihistamines.Methods Drugs were administered intravenously and the integrated amplitude of the conical electroencephalogram (EEC) signal was recorded. The threshold dose that depressed EEG activity was compared with the dose required lo inhibit by 50% the peripheral bronchospasm elicited by 10 μg/ kg i.v., of histamine. In separate studies, the electrocardiogram (ECG) and cardiovascular effects of loratadine (30 and 100mg/kg, i.v.). terfeuadine (10mg/kg. i.v.). promethazine (5mg/kg. i.v.) and diphenhydramine (20 mg kg, i.v.) were evaluated.Results The sedating antihistamines. diphenhydramine and promethazine. depressed the integrated EEG at doses between 0.6 and 2.0 limes their peripheral antihisiamine doses. Loratadine had no EEG depressant activity at 100 mg kg. i.v., a dose more than I 70 times its LD50 (0.58 mg kg, i.v.) against histamine bronchospasm. We were unable lo evaluate the EEG effects of terfenadine. because it produced cardiovascular collapse at 10 mg/kg. i.v. Loratadine and promethazinc did not produce adverse cardiovascular effects. nor did they alter normal ECG activity. Diphenhydramine produced brady-cardia followed by a transient hypertensive phase without affecting the QTc interval. In contrast, terfenadine elicited hypotension, bradycardia and significant arrhythmogenic activiy, causing a prolongation of the QTc interval and a torsades de pointes like ventricular arrhythmia. Pharmacokinetic studies after i.v. administration of loraladine (30 and 100 mg/kg) demonstrated plasma levels of loratadine and its major metabolite descarboethoxyloratadine to be several orders of magnitude greater than levels found in humans at the clinical dose of 10mg.Conclusion The CNS depressant effects of H1 antihislamines arc promcthazine≅ diphenhdramine ≫ loratadine = placebo. Of the non-sedating antihistamines. loratadine was devoid of adverse cardiovascular effects whereas terfenadine caused a pronounced disruption of the normal ECG. characterized by a torsades de pointes-like effect.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    Clinical & experimental allergy 29 (1999), S. 0 
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The extremely low reporting rate of cardiovascular adverse events for loratadine, the possible preferential use of loratadine in patients with pre-existing cardiovascular disorders, and the impressive lack of cardiovascular effects at extremely high concentrations in clinical and preclinical studies demonstrate the very safe cardiovascular profile of loratadine.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 31 (2001), S. 0 
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Desloratadine is a non-sedating, clinically effective, anti-allergic therapy that has been shown to exhibit anti-inflammatory properties that extend beyond its ability to antagonize histamine at H1-receptor sites. This latter effect has been shown in vitro to be both IgE-dependent and -independent.Objective In this study, we addressed the ability of desloratadine to inhibit the in vitro generation of interleukin (IL)-4 and IL-13 from human basophils while concurrently comparing its efficacy in preventing mediator release by these cells.Methods Basophil-enriched suspensions were treated with various concentrations of desloratadine for 15 min before stimulating with either anti-IgE antibody, calcium ionophore, IL-3 or phorbol ester. Histamine (fluorimetry), LTC4 (RIA) and IL-4 (ELISA) were all assayed using the same 4-h culture supernatants. IL-13 (ELISA) was measured in supernatants harvested after 20 h incubation. IL-4 mRNA expression (dilutional RT-PCR) was also examined.Results Desloratadine was found to be nearly six–seven times more potent in preventing the secretion of IL-4 and IL-13 induced by anti-IgE than it was at inhibiting the release of histamine and LTC4. These cytokines were equally inhibited by desloratadine following activation with ionomycin despite the lack of an effect on the histamine induced with ionomycin. Desloratadine had a lesser effect regarding inhibition of the IL-13 secreted in response to IL-3 and PMA. There was no evidence that desloratadine mediated its inhibitory effects by causing decreased cell viability. Finally, IL-4 mRNA accumulation was remarkably inhibited, by as much as 80%, following pretreatment with desloratadine.Conclusion While capable of inhibiting histamine and LTC4 release by human basophils, desloratadine is more effective at targeting the signals regulating IL-4 and IL-13 generation in these cells. This inhibitory effect on cytokine generation provides additional evidence that this antihistamine exerts anti-inflammatory properties.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Allergy 42 (1987), S. 0 
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Loratadine is a new non-sedating antihistamine. The present studies compared loratadine and terfenadine, another non-sedating antihistamine, for their ability to inhibit the bronchial response to histamine and other autacoids which have been implicated as contributing to the symptoms of an allergic reaction. In addition, the two antihistamines were evaluated in models of immunologically mediated allergic reactions. Loratadine is a more potent inhibitor of histamine-induced bronchospasm in guinea pigs than is terfenadine. Both antihistamines exhibit marked antiserotonin activity at doses 10 times their antihistamine ED50 values. In contrast, loratadine and terfenadine produce little or no inhibition of the bronchial responses to methacholine, leukotriene C4 or platelet-activating factor. An allergic bronchospasm in guinea pigs is inhibited by loratadine (ED50= 0.40 mg/kg, p.o.) and terfenadine (ED50= 1.7 mg/kg, p.o.). The bronchospasm associated with allergic anaphylaxis in rats is significantly inhibited by 10 mg/kg, p.o. loratadine and 30 mg/kg, p.o. terfenadine. Loratadine exhibits antiallergy activity in vitro. At micromolar concentrations, loratadine inhibits the release of histamine from Con A and A23187-stimulated rat peritoneal mast cells and the release of histamine and leukotrine C4 from a Con A-stimulated cloned murine mast cell line
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Bioorganic & Medicinal Chemistry Letters 4 (1994), S. 1327-1332 
    ISSN: 0960-894X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Medicine
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  • 7
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Leukotrienes (LT) C4, D4, and E4 are major contributors to the pathobiology of human bronchial asthma. Therefore, it is likely that compounds that antagonize the action or inhibit the formation of LTs will be useful therapeutic agents. We have studied the effects of LT antagonists, 5-lipoxygenase inhibitors and selected standards in a model of LT-mediated allergic bronchospasm in guinea pigs. Sensitized animals were pretreated with mepyramine, indomethacin and propranolol to eliminate the influence of histamine, prostaglandins, thromboxanes and circulating catecholamines. In these animals, inhalation of antigen resulted in a bronchospasm consistent with a LT-mediated response that was slow in onset, of long duration and was inhibited by the selective LTD4, antagonists FPL-55712, LY-171,883 and ICI-198,615 ICI-198, 615 was approximately 50-times more potent than FPL-55712 by the intravenous and intratracheal routes. However, of thirteen compounds known to inhibit 5-lipoxygenase and LT biosynthesisin vitro only phenidone, piriprost and AA-861 were active in thisin vivo model. The allergic bronchospams was inhibited by bronchodilators (e.g. PGE2, aminophylline and forskolin) and by some mast cell stabilizers, but was otherwise insensitive to other pharmacological classes of compounds including calcium channel blockers and antagonists of serotonin, acetylcholine and platelet-activating factor. This model seems useful and reasonably selective for the evaluation of new antianaphylactic compounds that are LT antagonists. The inactivity of many 5-lipoxygenase inhibitors in this model suggests they do not inhibit LT formationin vivo.
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  • 8
    ISSN: 1432-0649
    Keywords: PACS: 06.60.Jn; 33.50.j; 34.50.Ez; 82.40.Py
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Laser-induced fluorescence of OH (A 2Σ+, v’=1) was measured in hydrogen/oxygen and hydrogen/air/nitrogen flames using laser pulses of 80 psec duration. A 2D signal acquisition scheme simultaneously employed wavelength, temporal, and polarization resolution. The signals emitted in different rotational branches exhibit polarization-dependent intensities, depending on the rotational branch of the absorption line used. It is possible to select experimental conditions such that rotational and vibrational relaxation as well as electronic quenching can be monitored simultaneously. Advantages and limitations of the experimental approach are discussed. Numerical simulations are presented of the LIF spectra affected by energy transfer.
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  • 9
    ISSN: 1432-0649
    Keywords: PACS: 33.50.-j; 34.50.Ez; 82.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 2 Σ+) was measured in a low-pressure H2/O2 flame for three rotational levels of OH (v′=1). Rate coefficients for collisions with H2O and N2 were determined. At 1600 K, kVET (N2) is (in 10-11 cm3s-1) 10.1±2, 6.1±1.8, and 3.8±1.3 for N′=0, 5, and 13, respectively. The kVET (H2O) is 〈1.1±1.8. The kQ (N2) is 〈2.4±8 for both vibrational levels. The kQ (H2O) in v′=1 is 59.1±6.5, 54.7±6.4, and 54.9±6.6 for N′=0, 5, and 13, respectively, and, determined indirectly, 74.6±10.4, 70.6±10.3, and 63.4±7.3 for N′=0, 5, and 13 in v′=0. A multi-level model of OH population dynamics, which is being developed for the quantitative simulation of experimental LIF spectra, was extended to include VET. It was attempted to simulate state-to-state-specific VET coefficients for N2 collisions. From these simulations it appears that angular momentum conservation does not determine the N dependence of the vibrational relaxation step.
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  • 10
    ISSN: 1432-0649
    Keywords: PACS: 34.50.Ez; 82.40.Py
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A computer code based on a kinetic rate-equation model for describing the collisional dynamics of OH (A 2Σ+) in laser-induced fluorescence experiments was developed. In this work, the capabilities of the simulation code are extended to include the vibrational states up to the OH (A 2Σ+, v′=3) level. The calculation of quenching, rotational and vibrational relaxation rate coefficients for different collider species is discussed. Problems that arise for the description of vibrational relaxation include the branching ratio between single- and multiple-quantum steps and the form of the nascent rotational distribution after a vibrational relaxation step. Experimental spectra recorded under a variety of conditions are simulated using a consistent set of model assumptions. The calculations must include vibrational relaxation steps up to Δv=3 to account for the experimental intensity distributions. Effects due to polarized laser excitation become more important for vibrational states with v′〉1. Areas for future work are identified, including determination of experimental rate coefficients for state-changing and depolarizing collisions in the upper vibrational levels.
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