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排序方式: 共有363条查询结果,搜索用时 31 毫秒
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S Caceres G Silvan L Martinez‐Fernandez MJ Illera P Millan B Monsalve L Peña JC Illera 《Reproduction in domestic animals》2014,49(4):611-617
Isoflavones are the most common phytoestrogens found in human diets. However, it is still not clear whether isoflavones have effects on the reproductive and the endocrine systems under normal dietary intake and overdose. The aim of this study was to determine how the most important isoflavones, genistein and daidzein, affect androgen and glucorticoid levels on male prepuberal rats. A hundred and seventy‐five 30‐day‐old male Wistar rats were dosed orally by stomach tube every day for 35 days, with saline solution, low and high doses of genistein, daidzein and a mixture of both. Serum samples were analysed by an enzyme immunoassay for hormone determinations. In control group, there was a peak of testosterone (T) and dihydrotestosterone levels associated to the onset of puberty, at the third week. However, in low‐dose groups, the same peak was found at the fourth week (p < 0.05), indicating a delay in the onset of puberty in these groups. Moreover, high doses groups serum androgen levels were significantly lower (p < 0.05) than the control group from the first week until fifth week. This fact was supported by a epididymal histological analysis that indicate in low doses there were several content of spermatozoa at fourth week and in high doses there were few content of spermatozoa. Besides, corticosterone levels followed the same pattern of androgens in all groups. We can conclude that oral administration of isoflavones in male rats decreased the secretion of androgens and glucocorticoids causing a delay in the onset of puberty and may cause physiological and developmental problems. 相似文献
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Ding Z Quinn BM Haram SK Pell LE Korgel BA Bard AJ 《Science (New York, N.Y.)》2002,296(5571):1293-1297
Reversible electrochemical injection of discrete numbers of electrons into sterically stabilized silicon nanocrystals (NCs) (approximately 2 to 4 nanometers in diameter) was observed by differential pulse voltammetry (DPV) in N,N'-dimethylformamide and acetonitrile. The electrochemical gap between the onset of electron injection and hole injection-related to the highest occupied and lowest unoccupied molecular orbitals-grew with decreasing nanocrystal size, and the DPV peak potentials above the onset for electron injection roughly correspond to expected Coulomb blockade or quantized double-layer charging energies. Electron transfer reactions between positively and negatively charged nanocrystals (or between charged nanocrystals and molecular redox-active coreactants) occurred that led to electron and hole annihilation, producing visible light. The electrogenerated chemiluminescence spectra exhibited a peak maximum at 640 nanometers, a significant red shift from the photoluminescence maximum (420 nanometers) of the same silicon NC solution. These results demonstrate that the chemical stability of silicon NCs could enable their use as redox-active macromolecular species with the combined optical and charging properties of semiconductor quantum dots. 相似文献
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James S. Latimer Eva J. Hoffman Gerald Hoffman James L. Fasching James G. Quinn 《Water, air, and soil pollution》1990,52(1-2):1-21
In an effort to provide a better understanding of the sources of petroleum hydrocarbons in urban runoff, petroleum products as well as probable source materials were analyzed for hydrocarbons and trace metals and then compared to urban runoff samples from four different land use areas. The petroleum products considered were No. 2 and No. 6 fuel oils, used and virgin crankcase oils, and gasoline. Source materials included street dust, roadside soil, roadside vegetation, and atmospheric fallout; and the land use categories were commercial, residential, interstate highway, and industrial areas. The samples were compared on the basis of hydrocarbon (saturated and aromatic) and trace metal (Cd, Pb, Mn, Cu, Fe, Zn) loadings and distributions. Results indicated that the hydrocarbon content in runoff at all four land use sites originated primarily from used crankcase oil, with a small amount of No. 2 fuel oil detected at the industrial site. Only a small portion of the crankcase oil component came from the sources surveyed, and the majority of this oil probably came from: (1) oil drops within the driving lanes on the road surfaces or deposits in parking areas, and/or (2) direct dumping of waste crankcase oil down storm drains. 相似文献
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Konrad Dabrowski Stephen Hassard John Quinn Tony J. Pitcher A.M. Flinn 《Aquaculture (Amsterdam, Netherlands)》1980,21(3):213-232
Three experiments were conducted with rainbow trout to determine if Geotrichum candidum GC single cell protein could replace 100, 75 or 50% of fish meal in a pelleted diet. When the fish meal was completely replaced by GC the fish growth was retarded after 3 weeks of the experiment. With the larger fish (individual weight 47–54 g) in the short trial there were significant differences between fish fed the control diet (fish meal) and those fed the 75% substitution of GC diet. The most remarkable differences in fish growth appeared in a 42-day trial with small fish (5 g individual weight) when fish groups fed diets with 0.50 and 75% replacement gave significantly different results (P < 0.05), being 93,9, 46.6 and 34.2% gain, with feed coefficients of 1.49, 2.77 and 3.67, respectively. With large fish fed diets with 0,50 and 75% GC replacement, apparent digestibility of protein was 64.7, 68.2 and 37.5%, but fat digestibility was 79.5, 91.1 and 81.0%, respectively. No significant differences in amounts of free plasma amino acid (PAA) were found between rainbow trout fed diets with 0 or 50% substitution, but there was a marked decrease in PAA in the group fed the diet with 75% GC substitution. Analysis of chosen heavy metals was made on diets, fish and faeces, and Cu in particular was found not to be accumulated in the fish body. 相似文献
110.
Han Kyu Lim Ned William Pankhurst Quinn Patrick Fitzgibbon 《Aquaculture (Amsterdam, Netherlands)》2004,240(1-4):505-516
Spermiated male greenback flounder (Rhombosolea tapirina) were implanted with gonadotropin releasing hormone analog (GnRHa) pellets at different dosages to examine their effects on milt characteristics and plasma levels of testosterone (T), 11-ketotestosterone (11KT) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Milt and blood samples were collected for up to 28 or 42 days post-implantation (p.i.) in two separate experiments using fish that were slightly or moderately spermiated, respectively. In both experiments, fish treated with GnRHa pellets showed a consistent and significant increase in milt volume relative to controls, and the increase of milt volume was more rapid than the increase in numbers of spermatozoa. Spermatocrit (Sct) was significantly lower in GnRHa-treated fish than in controls. Plasma levels of T and 11KT were elevated at 7 and 14 days p.i. in slightly spermiated fish treated with GnRHa and elevated plasma T and 11KT levels were accompanied by increased milt volume early in the spermiation period. In contrast, there was no significant difference in plasma T levels between GnRHa-treated and control fish in fish that were moderately spermiated at the time of implant. Treatment with GnRHa tended to result in lower plasma levels of 11KT and higher levels of 17,20βP relative to controls, and there was a positive relationship between the elevation of plasma 17,20βP and the increase in milt volume in response to implantation of GnRHa pellet. Slow release GnRHa administration had no effect on sperm activity or pH and osmolality of seminal plasma in either experiment. 相似文献