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排序方式: 共有1460条查询结果,搜索用时 15 毫秒
1.
N Delanty MP Reilly D Pratico JA Lawson JF McCarthy AE Wood ST Ohnishi DJ Fitzgerald GA FitzGerald 《Canadian Metallurgical Quarterly》1997,95(11):2492-2499
BACKGROUND: Myocardial reperfusion is believed to be associated with free radical injury. However, indexes of oxidative stress in vivo have been limited by their poor specificity and sensitivity. Isoprostanes are stable products of arachidonic acid formed in a nonenzymatic, free radical-catalyzed manner. We have developed a sensitive and specific assay for one of these compounds, 8-epi prostaglandin (PG) F2 alpha. METHODS AND RESULTS: To address its utility as an index of oxidative stress during coronary reperfusion, we measured urinary levels by gas chromatography/mass spectrometry in a canine model of coronary thrombolysis, in patients with acute myocardial infarction treated with thrombolytic therapy, and in patients after elective coronary artery bypass surgery. Urinary 8-epi PGF2 alpha was unchanged after circumflex artery occlusion in a canine model of coronary thrombolysis (n = 13; 437.2 +/- 56.4 versus 432.7 +/- 55.2 pmol/mmol creatinine) but increased significantly (P < .05) immediately after reperfusion (553.8 +/- 64.7 pmol/mmol). Urinary levels were increased (P < .001) in patients (n = 12) with acute myocardial infarction given lytic therapy (265.8 +/- 40.8 pmol/mmol) compared with age-matched control subjects (n = 20; 91.5 +/- 11.8 pmol/mmol) and patients with stable coronary disease (n = 20; 95.7 +/- 6.3 pmol/mmol). Preoperative levels rose from 113.2 +/- 11.8 to 248.2 +/- 86.3 pmol/mmol at 30 minutes into revascularization to 332.2 +/- 82.6 pmol/mmol by 15 minutes after global myocardial reperfusion (P < .05) and dropped to 181.2 +/- 50.4 pmol/mmol at 30 minutes and 120.2 +/- 9.9 pmol/mmol at 24 hours after bypass surgery (n = 5). Corresponding changes in spin adduct formation, found with electron paramagnetic resonance, were noted in 2 patients. CONCLUSIONS: These data support the hypothesis that free radical generation occurs during myocardial reperfusion. Measurement of isoprostane production may serve as a noninvasive index of oxidative stress. 相似文献
2.
The potential of a gonadotropin-releasing hormone (GnRH) agonist (goserelin acetate), delivered constantly for 28 days via a subcutaneous depot, to induce ovulation in seasonally anestrous mares, was investigated. Two experiments were conducted, in which a range of doses (30 to 240 micrograms/mare/d) was examined. Mares were selected on the basis of lack of substantial follicular development (follicle diameter < 20 mm determined ultrasonically) and low serum concentrations of luteinizing hormone (LH) and progesterone. Constant administration of the GnRH agonist-induced ovulation in anestrous mares, but a dose-response relation was not observed. Furthermore, with identical doses tested in consecutive or alternate years, considerable variation was observed in the ovulatory response. In general, ovulation in all treated mares was accompanied by increased circulating concentrations of LH and a decrease in follicle-stimulating hormone values. Ovulation was preceded by an increase in estradiol and LH concentrations. In mares in which ovulation did not occur, concentration of LH increased during agonist treatment, whereas that of follicle-stimulating hormone either increased or did not change. It was concluded that constant administration of GnRH agonists may induce ovulation in mares during seasonal anestrus; however, percentage of mares ovulating and the lack of reproducibility of effect indicate that this approach is inappropriate for use as a reliable method to manipulate breeding activity in commercial broodmares. 相似文献
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JR Stout TJ Housh GO Johnson TK Evetovich DB Smith 《Canadian Metallurgical Quarterly》1997,76(4):363-367
Brucella abortus strain RB51 was recently approved as an official brucellosis calfhood vaccine for cattle by the Animal and Plant Health Inspection Service branch of the United States Department of Agriculture. Currently available serologic surveillance tests for B. abortus do not detect seroconversion following SRB51 vaccination. The purpose of this study was to evaluate a dot-blot assay using gamma-irradiated strain RB51 bacteria for its specificity and sensitivity to detect antibody responses of cattle vaccinated with strain RB51. Dot-blot titers of sera at a recommended dosage (10(10) colony-forming units) were similar to those of sera from cattle vaccinated with similar numbers of B. abortus strain 19 and greater (P < 0.05) than titers of nonvaccinated cattle. In the first 12 weeks after vaccination with 10(10) colony-forming units of strain RB51, the RB51 dot-blot assay had 100% specificity for titers of 80 or less and a 53% sensitivity for titers of 160 or greater. Sensitivity of the RB51 dot-blot assay peaked at 4 weeks after vaccination with 10(10) colony-forming units of strain RB51. Dot-blot responses of sera from cattle vaccinated with a reduced dosage of strain RB51 (10(9) colony-forming units) did not differ (P > 0.05) from titers of sera from nonvaccinated cattle. Following intraconjunctival challenge with B. abortus strain 2308, titers on the RB51 dot-blot assay did not differ (P > 0.05) between nonvaccinated cattle and cattle vaccinated at calfhood with strain 19 or strain RB51. 相似文献
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R Bascom J Kesavanathan TK Fitzgerald KH Cheng DL Swift 《Canadian Metallurgical Quarterly》1995,103(11):1026-1030
Nasal mucociliary clearance (NMC) is a biomarker of nasal mucosal function. Tobacco smokers have been shown to have abnormal NMC, but the acute effect of environmental tobacco smoke (ETS) on nonsmokers is unknown. This study evaluated acute tobacco smoke-induced alterations in NMC in 12 healthy adults. Subjects were studied on 2 days, separated by at least 1 week. Subjects underwent a 60-min controlled exposure at rest to air or sidestream tobacco smoke (SS) (15 ppm CO) in a controlled environmental chamber. One hour after the exposure, 99mTc-sulfur colloid was aerosolized throughout the nasal passage and counts were measured with a scintillation detector. Six out of 12 subjects showed more rapid clearance after smoke exposure than after air exposure, and 3/12 had rapid clearance on both days. However, substantial decreases in clearance occurred in 3/12 subjects, all of whom had a history of ETS rhinitis. In two subjects, more than 90% of the tracer remained 1 hr after tracer administration (2 hr after smoke exposure). Understanding the basis for biologic variability in the acute effect of tobacco smoke on NMC may advance our understanding of pathogenesis of chronic effects of ETS. 相似文献
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Andre C.L. Carlin J.A. Boeckl J.J. Wilt D.M. Smith M.A. Pitera A.J. Lee M.L. Fitzgerald E.A. Ringel S.A. 《Electron Devices, IEEE Transactions on》2005,52(6):1055-1060
High-performance p/sup +//n GaAs solar cells were grown and processed on compositionally graded Ge-Si/sub 1-x/Ge/sub x/-Si (SiGe) substrates. Total area efficiencies of 18.1% under the AM1.5-G spectrum were measured for 0.0444 cm/sup 2/ solar cells. This high efficiency is attributed to the very high open-circuit voltages (980 mV (AM0) and 973 mV (AM1.5-G)) that were achieved by the reduction in threading dislocation density enabled by the SiGe buffers, and thus reduced carrier recombination losses. This is the highest independently confirmed efficiency and open-circuit voltage for a GaAs solar cell grown on a Si-based substrate to date. Larger area solar cells were also studied in order to examine the impact of device area on GaAs-on-SiGe solar cell performance; we found that an increase in device area from 0.36 to 4.0 cm/sup 2/ did not degrade the measured performance characteristics for cells processed on identical substrates. Moreover, the device performance uniformity for large area heteroepitaxial cells is consistent with that of homoepitaxial cells; thus, device growth and processing on SiGe substrates did not introduce added performance variations. These results demonstrate that using SiGe interlayers to produce "virtual" Ge substrates may provide a robust method for scaleable integration of high performance III-V photovoltaics devices with large area Si wafers. 相似文献
10.
This paper reports the findings of a detailed study of Web-based systems design (WBSD) practices in Ireland based on data
collected over a 3-year period (2002–2005), the objectives of which were to (1) contribute towards a richer understanding
of the current “real-world” context of WBSD by characterising the profile of a typical project (team size, timeframe, nature
of requirements, etc.) and identifying the key challenges, constraints, and imperatives (i.e. “mediating factors”) faced by
Web-based system designers, and (2) understand how those contextual parameters and mediating factors influence the activity
of WBSD as regards the selection and enactment of whatever design practices are therefore engaged (i.e. the use of methods,
procedures, etc.). Data was gathered through a survey which yielded 165 usable responses, and later through a series of semi-structured
qualitative interviews. Using grounded theory, an explanatory conceptual framework is derived, based on an extension of the
“method-in-action” model, the application of which to WBSD has not been previously investigated in depth. It is proposed that
this framework of WBSD issues is valuable in a number of ways to educators, researchers, practitioners, and method engineers. 相似文献