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  • 1
    ISSN: 1420-9071
    Keywords: Juvenile hormone esterase ; juvenile hormone epoxide hydrolase ; juvenile hormone binding protein ; reversed-phase liquid chromatography assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We studied time-dependent metabolism of (10R)-[3H] juvenile hormone (JH) III and (10R, 11S)-[3H]JH I injected intoManduca sexta larvae; the hormones are metabolized to polar metabolites, expecially the JH acid-diol, and an unknown. Products were analyzed using a reversed-phase liquid chromatography assay. (10R)-JH III is metabolized much more rapidly than (10R, 11S)-[3H]JH I, whether injected seperately or as a mixture of hormones. The unknown metabolites of JH I and JH III were identified as phosphate conjugates of JH I and JH III diol by tandem mass spectral analysis of isolated samples. The phosphate conjugate of JH I diol is the principle end product of JH I metabolism.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2576
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lipoxygenase metabolites of arachidonic acid (AA), the leukotrienes (LTs), and hydroxyeicosatetraenoic acids (HETEs) are potent proinflammatory mediators. Release of LTs and HETEs by bovine alveolar macrophages (BAMs) was measured by reverse-phase high performance liquid chromatography. LTB4 (1.1±0.2 ng/106 cells) and 5-HETE (2.2±0.2 ng/106 cells) were the major metabolites calcium ionophore A23187-stimulated BAMs produced from endogenous AA. The tritiated forms of these compounds and their precursor fatty acids were produced following incorporation of [3H]AA into the cells and stimulation by calcium ionophore A23187. Incorporation of an alternative substrate, [3H]eicosapentaenoic acid ([3H]EPA) into BAMs incubated in parallel resulted in production of [3H]LTB5 and [3H]5-hydroxyeicosapentaenoic acid (5-HEPE). Equivalent amounts of [3H]AA and [3H]EPA and of [3H]LTB4 and homologous [3H]LTB5 were released. BAM produced significantly greater amounts of [3H]5-HEPE than [3H]5-HETE, however. These findings indicate that the BAM 5-lipoxygenase is capable of metabolizing EPA to LTB5 and 5-HEPE, with the production of 5-HEPE preferred over 5-HETE.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-2576
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Alveolar macrophages (AMs) are capable of producing a variety of inflammatory mediators including those derived from arachidonic acid, the prostaglandins (PGs), leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs). Inflammation associated with release of arachidonate-derived mediators is a result of the combined actions of all of these mediators. Thus, it is critical to determine the entire spectrum of arachidonate-derived metabolites that AMs are capable of producing. In this study bovine AMs were prelabeled with [3H]arachidonic acid prior to stimulation with serum-treated zymosan, phorbol myristate acetate (PMA), or the calcium ionophore A23187. The total release of arachidonate metabolites into the culture media was measured by reverse-phase HPLC with on-line radiometric detection. All stimuli used induced production of metabolites of the cyclooxygenase pathway with thromboxane B2 and HHT being the major metabolites. Lesser amounts of PGF2α, PGE2, and PGD2 were produced. Only stimulation with A23187 resulted in production of LTB4 and 5-HETE, products of the 5-lipoxygenase pathway. This latter result indicates that the two major pathways of arachidonate metabolism in AMs may be selectively stimulated. Such an effect could have important consequences in the development of pulmonary inflammation. Furthermore, the spectrum of arachidonic acid metabolites produced by bovine AMs closely resembles that of human AMs, in contrast to rodent AMs.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 338-343 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An assay for the N-oxide metabolite of a benzazepine drug by fast atom bombardment ionization with tandem mass spectrometric analysis on a triple quadrupole mass spectrometer has been developed and validated for urine and plasma samples. This methodology allows analysis of this metabolite directly in crude sample extracts, without the need for extensive chromatography or sample derivatization. Quantification was accomplished with the use of a stable isotope analog of the analyte as an internal standard, using the selected reaction monitoring mode of operation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 8 (1981), S. 431-435 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A key initiating event in the induction of neoplasia by a chemical carcinogen is believed to be the covalent reaction of the carcinogen with the DNA of the target cell. Most carcinogens are not biologically active as such, but require metabolic conversion to a chemically reactive form (ultimate carcinogen). Chemical carcinogens undergo an extremely complex set of metabolic reactions, leading for the most part to inactive detoxification products as well as reactive electrophilic species. Direct structural identification of the carcinogen-DNA adduct will (1) immediately confirm that the chemical is acting as a potential carcinogen under a given set of circumstances; and (2) directly identify those critical metabolic pathways which are involved in the metabolism of the chemical to a carcinogenic form rather than an inactive detoxification product. The direct structural identification of carcinogen-DNA adducts represents a formidable analytical challenge, since only picomolar quantities can be isolated. The advent of newer ionization techniques, such as field desorption and mass spectrometric-based separation techniques capable of handling mixtures, are proving to be essential for the characterization of such structures. Examples of nucleic acid-carcinogen adduct structure characterizations that have led to fundamental insights into the mechanisms of chemical carcinogenesis will be discussed, and future trends in mass spectrometry that have a direct bearing on these difficult problems will be pointed out.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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