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W V Welshons G E Rottinghaus D J Nonneman M Dolan-Timpe P F Ross 《Journal of veterinary diagnostic investigation》1990,2(4):268-273
Estrogen-responsive proliferation in the MCF-7 cell line was used as a bioassay for detection of dietary estrogens. The bioassay procedure was adapted to screen for estrogenic activity in feedstuffs that have been associated with hyperestrogenism in livestock. Methanolic feed extracts were added to the cell culture medium at microliter/ml concentrations for 4 days, after which the cell proliferation response was measured as DNA content. The half-maximal response for estradiol occurred at 2 pM, or 0.54 pg/ml. For zearalenone, a weaker estrogen, the half-maximal response occurred at approximately 200 pM, or 64 pg/ml. The bioassay was calibrated against a number of known estrogens (estradiol, diethylstilbestrol, zearalenone, zearalanol [cattle implant], beta-zearalenol, zearalane), including the naturally occurring phytoestrogens (formononetin, genistein, daidzein, biochanin A, and coumestrol). The estrogenic activity of feed samples was expressed as equivalents of zearalenone (ppm zearalenone) that would have to be present to equally stimulate proliferation of the MCF-7 cells. The sensitivity of the bioassay was 0.05-0.1 ppm equivalents of zearalenone in feed, well below the threshold level associated with reproductive problems. The feed additive melengestrol acetate (MGA) showed no estrogenic activity in this assay. Estrogenic activity of feed extracts was confirmed by competitive inhibition with the antiestrogens tamoxifen or LY156758 (keoxifene) to show that stimulation of growth by feed extracts was through an estrogenic mechanism. Confirmation of known estrogens was by tandem mass spectroscopy. The assay is a sensitive and reliable screening procedure for detecting estrogenic activity in feedstuffs. 相似文献
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To provide insight into potential mechanisms contributing to the various biological responses of cattle to treatment with progesterone, norgestomet, and melengestrol acetate (MGA), MCF-7 cells were utilized to determine the relative binding affinity of the progesterone receptor for MGA, norgestomet, progesterone, and a progesterone agonist (R5020), and to determine if progesterone, MGA, or norgestomet have estrogenic and/or anti-estrogenic activities. The progesterone receptor had greater affinity (P<0.05) for MGA, R5020, and norgestomet than for progesterone; and the affinity for norgestomet exceeded (P<0.05) that of MGA and R5020. Estrogen stimulates proliferation of MCF-7 cells; therefore these cells have been utilized as a bioassay to detect estrogenic and anti-estrogenic activity. Progesterone (10(-11) to 10(-5)M) did not promote cellular proliferation. However, MGA (10(-8), 10(-7), and 10(-6)M) increased (P<0.05) cell proliferation compared to the control group (10(-11) to 10(-9) and 10(-5)M MGA did not stimulate cell proliferation), and MGA-induced cell proliferation (10(-8)M) was reduced (P=0.095) by an estradiol antagonist (ICI 182,780; ICI). Cellular proliferation increased (P<0.05) with norgestomet (10(-5)M) compared to the control group (10(-11) to 10(-6)M norgestomet did not stimulate cell proliferation) and the increased proliferation was decreased (P<0.05) by ICI. Neither progesterone nor MGA demonstrated anti-estrogenic activity. Norgestomet (10(-10) to 10(-6)M) did reduce (P<0.05) maximal estrogen-stimulated cell proliferation, but not to basal levels. In summary, the affinities of the progesterone receptor for norgestomet, MGA, and progesterone are consistent with their effective dose to inhibit ovulation in vivo, but their progestin and their estrogenic/anti-estrogenic activities cannot fully explain why progesterone and norgestomet are more capable of reprogramming the reproductive axis in anestrous postpartum cows compared to MGA. 相似文献
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WV Holt 《Reproduction in domestic animals》2009,44(S3):31-38
Any mammalian spermatozoon that achieves successful in vivo fertilization has to perform almost perfectly in many disparate functions and overcome a series of obstacles imposed by the female reproductive tract. This implies that during formation in the testis and epididymis, the spermatozoa did not incur any morphological, metabolic, immunological or genetic abnormalities. Given that the spermatozoa are such highly differentiated cells, this means that every cellular compartment must not only be intact but must also respond appropriately to intracellular and extracellular signals. Assuming that a spermatozoon possesses this level of perfection, and is able to reach and penetrate an oocyte, it can only be regarded as 'fertile' if the DNA it carries is intact and able to sustain embryonic development. Although the proportion of inseminated spermatozoa that meet these criteria is vanishingly small, the female reproductive tract applies stringent selection criteria during sperm transport and, as a result, the probability of conception around the time of ovulation is very high. If laboratory tests of semen quality could approach the efficacy of the female reproductive tract, it would be possible to predict the odds of spermatozoa meeting the egg; however, this is not possible at present. In this article, I suggest a simple model to illustrate how a battery of laboratory tests could eventually be used to make these predictions. 相似文献
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Analysis of a gene in drosophila 总被引:17,自引:0,他引:17
W J Welshons 《Science (New York, N.Y.)》1965,150(700):1122-1129
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