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  • 1
    ISSN: 0014-5793
    Keywords: (Bradyrhizobium japonicum) ; Gene regulation ; Nitrogen fixation ; Protein, NifA ; Site-directed mutagenesis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European food research and technology 209 (1999), S. 153-179 
    ISSN: 1438-2385
    Keywords: Key words Hormones ; Food ; Steroids ; Phytoestrogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The present review gives an overview of the occurrence of hormones, hormone mimics, and hormone antagonists in food. The first part deals comprehensively with concentrations of the human sex steroid hormones progesterone, 17β-estradiol estrone, and testosterone in animal and vegetable food. The dietary intake of steroid hormones (10 μg/day progesterone, 0.1 μg/day estrogens, and 0.05 μg/day testosterone) is negligible compared to the human endogenous hormone synthesis. The second part addresses the phytoestrogens (isoflavones, coumestans, other bioflavonoids, lignans, phytosterols), which occur in food in much higher amounts than steroid hormones. Therefore, they can cause hormonal effects although their estrogen equivalents (relative to 17β-estradiol) are estimated to be 10–2–10–4. These effects can be beneficial or adverse, depending on the effectiveness and amount of the ingested hormone agonist, synergistic, and antagonistic effects with other dietary or endogenous hormones, interactions with other dietary compounds (e.g. fiber and fat intake), and the hormonal status of the individual. The review also summarizes the occurrence of steroid hormone precursors and of other growth-related hormones in food (corticosteroids, indole-3-carbinol, protein hormones). It ends with the presentation of residues and contaminants of fungal or anthropogenic origin (mycoestrogens, pesticides, plastic or food additives, industrial chemicals) which have also shown hormonal or hormone-blocking properties.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1438-2385
    Keywords: Key words Hormone pattern ; Gas chromatography-mass spectrometry ; Beef ; Bulls ; Steers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A rapid and economical method was developed for the simultaneous determination of androgens, progestogens, and glucocorticoids and their precursors and metabolites in meat. Steroids were isolated with liquid extraction followed by C18-solid-phase extraction (C18-SPE). Corticoids were separated from the less polar steroids by Si-SPE. The non-polar steroids required additional purification by filtration through an NH2 cartridge. The fractions were combined and derivatized with a universally applicable trimethylsilylation of both hydroxyl and keto groups. Determination was performed with gas chromatography-mass selective detection (determination limits: 0.02–0.1 μg/kg). Hormone profiles of 15 muscle tissue samples of both bulls and steers were analysed. Beef from bulls contained higher concentrations of testosterone and epitestosterone (P〈0.001), 11-deoxycorticosterone (P〈0.01), androstenedione (P〈0.05) and cortisone (P〈0.05), and significantly lower proportions of cortisol (P〈0.001) than beef from steers.
    Type of Medium: Electronic Resource
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