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101.
Variation in superovulatory responses in cattle may be related to the stage of follicular growth at the time of gonadotropin treatment. Waves of follicle growth are regulated by both follicle-stimulating hormone (FSH) and oestradiol. The objective of experiment 1 was to determine the dynamics of follicle wave emergence and the relationship with FSH and oestradiol concentrations, after treatment of heifers with oestradiol benzoate (ODB) in the presence of an intravaginal progesterone-releasing device (CIDR-B). Experiment 2 examined the superovulatory response, embryo yield and quality following treatment with porcine follicle-stimulating hormone (pFSH) at different times relative to ODB injection. In experiment 1, 28 beef heifers were treated with a CIDR for 9 days and allocated at random to one of four groups to receive either: (I) CIDR only, or 5 mg ODB given as a single intramuscular injection at (II) day 0 (d0); (III) day 1.5 (d1.5); or (IV) day 3 (d3) post CIDR insertion. Ovaries were examined using daily ultrasound and blood samples were collected twice daily for 11 days. In experiment 2, 96 heifers were treated with a CIDR and 5 mg ODB as in experiment 1, and were allocated using a 4 x 3 factorial design plan to a superovulation programme using three doses (400 IU; 600 IU; 800 IU) of pFSH. FSH was given for 4 days at 12-h intervals beginning 6.5 days after CIDR insertion. Heifers received prostaglandin analogue 12 h before CIDR removal and were inseminated (AI) at 48 and 60 h post CIDR withdrawal and embryos were recovered 7 days after AI. In experiment 1, the interval from CIDR insertion to follicle wave emergence (FWE) was longer (P < 0.05) in heifers treated with ODB at d1.5 (5.4 +/- 0.4 days) and d3 (5.1 +/- 0.6 days) compared to heifers treated with CIDR only (2.4 +/- 0.4 days). On the basis of time to proposed injection of pFSH heifers would have had follicle emergence 4.4, 2.3, 1.5 and 1.4 days prior to pFSH for groups I, II, III and IV, respectively. In experiment 2, heifers treated with ODB at d1.5 had a higher (P < 0.05) superovulatory response (18.2 +/- 1.7) than heifers treated at d3 (12.8 +/- 1.7), but superovulatory response in both groups did not differ (P > 0.05) from heifers treated at d0 (14.4 +/- 2.0) or with CIDR only (15.0 +/- 1.8). There were fewer (P < 0.05) freezable-grade embryos recovered from heifers treated with ODB at d0 (1.5 +/- 0.7) and d3 (2.1 +/- 0.5) compared to heifers treated at d1.5 (3.0 +/- 0.6) or in heifers treated with CIDR only (3.4 +/- 0.7). Increasing the dose of pFSH caused a linear increase in the superovulatory response (11.7 +/- 1.0, 15.8 +/- 1.4 and 18.0 +/- 1.9) and in the number of embryos recovered (5.8 +/- 0.9, 7.0 +/- 0.8 and 9.1 +/- 1.0) for 400 IU, 600 IU and 800 IU, respectively. In conclusion, heifers treated with ODB had wide variation in time to follicle wave emergence and there was not a consistent beneficial effect of pretreatment with ODB on embryo yield and quality following superovulation. 相似文献
102.
D Zhang I Botos FX Gomis-Rüth R Doll C Blood FG Njoroge JW Fox W Bode EF Meyer 《Canadian Metallurgical Quarterly》1994,91(18):8447-8451
The structure of the metalloproteinase and hemorrhagic toxin atrolysin C form d (EC 3.4.24.42), from the venom of the western diamondback rattlesnake Crotalus atrox, has been determined to atomic resolution by x-ray crystallographic methods. This study illuminates the nature of inhibitor binding with natural (< Glu-Asn-Trp, where < Glu is pyroglutamic acid) and synthetic (SCH 47890) ligands. The primary specificity pocket is exceptionally deep; the nature of inhibitor and productive substrate binding is discussed. Insights gained from the study of these complexes facilitate the design of potential drugs to treat diseases where matrix metalloproteinases have been implicated, e.g., arthritis and tumor metastasis. 相似文献
103.
多波长泵浦宽带拉曼放大器功率增益研究 总被引:4,自引:0,他引:4
受激拉曼散射(SRS)的Stokes波谱线型比较复杂,本文分别用Gauss线型和Lorentz线型,研究多波长泵浦宽带Raman放大器的增益特性,提出宽带增益平坦的多波长泵浦方案,研究表明增益平坦程序与泵清波频率间隔密切相关。对G.652、G.653、G.655光纤和新型大有效面积非零色散平坦光纤的Raman放大增益分别进行了研究,结果表明Raman增益与光纤种类和光纤传输性有关,特别是随光纤有效纤芯面积的增大而明显减小。 相似文献
104.
Automated measurement of peak widths for the determination of peak capacity in complex chromatograms
In a large number of cases, the etiology of community-acquired pneumonia (CAP) is not established. Some cases are probably caused by Streptococcus pneumoniae. Transthoracic needle aspiration (TNA) culture has a limited sensitivity which might be improved by antigen detection or gene amplification techniques. We evaluated the capacity of a PCR assay and a latex agglutination test to detect S. pneumoniae in samples obtained by TNA from 95 patients with moderate-to-severe CAP. Latex agglutination and PCR had sensitivities of 52.2 and 91.3%, specificities of 88.7 and 83.3%, positive predictive values of 62.3 and 65.6%, and negative predictive values of 83.3 and 96.5%, respectively, when culture techniques were used as the "gold standard." When we considered expanded criteria for the diagnosis of pneumococcal pneumonia as a standard for our calculations, latex agglutination and PCR had sensitivities of 53.6 and 89.7%, specificities of 93.0 and 90.0%, positive predictive values of 78.9 and 81.3%, and negative predictive values of 80.3 and 94.7%, respectively. The additional diagnosis provided by the PCR assay compared to latex agglutination was 12.2% (95% confidence interval of the difference from 0.4 to 20. 1%). PCR was more sensitive than TNA culture, particularly in patients who had received prior antibiotic therapy (83.3 versus 33. 3%). Although PCR is a very sensitive and specific technique, it has not proved to be cost-effective in clinical practice. Conversely, latex agglutination is a fast and simple method whose results might have significant implications for initial antibiotic therapy. 相似文献
105.
106.
PURPOSE: Ischemic neurodegeneration contributes to many retinal diseases. An isolated retina model has been used to examine the neuronal cell death induced by deprivation of oxygen and glucose (simulated ischemia) as a model for ischemic disease. METHODS: Neurodegeneration in the isolated chick embryo retina was induced by simulated ischemia and assessed using biochemical (lactate dehydrogenase release) and morphologic (light microscopy) techniques. RESULTS: Simulated ischemia led to lactate dehydrogenase release gradually in a period of 6 to 24 hours. Light microscopic observations demonstrated morphologic cell degeneration well before lactate dehydrogenase release occurred. N-Methyl-D-aspartate (NMDA) and non-NMDA receptor blockers individually provided partial protection, and the combination was fully protective. No protection was provided if the antagonists were added after simulated ischemia. When NMDA receptors were blocked by MK-801, cyclothiazide, an inhibitor of desensitization at non-NMDA receptors, enhanced lactate dehydrogenase released after 1 or 2 hours of simulated ischemia. Low concentrations of glucose effectively prevented lactate dehydrogenase release, despite anoxic conditions. CONCLUSIONS: The isolated retina provided a convenient system to characterize quantitatively ischemic cell death. Retinal ischemic neurodegeneration is an excitotoxic process that involves overactivation of NMDA and non-NMDA glutamate receptors. Blockade of both of these receptor subtypes was necessary for complete neuroprotection. Receptor desensitization played a protective role. If even low concentrations of glucose were delivered to an ischemic retina in vitro, substantial neuroprotection could be achieved. This may have implications for the management of acute retinal ischemic episodes. 相似文献
107.
JW Coebergh 《Canadian Metallurgical Quarterly》1998,142(27):1542-1545
Many a doctor from time to time encounters people concerned about environmental causes of disease, whom he or she cannot answer properly because of lack of knowledge concerning the effects of chemical or physical exposure of the human body (nuclear plants, environmental pollution, electromagnetic radiation). Usually post hoc cluster investigation is very unrewarding especially when there is no clearcut hypothesis or evidence of a causal relation, and when the relative risk is well below 8. From an epidemiological point of view it is surprising that an unexpectedly low frequency of a certain disease in a particular region does not attract this kind of attention. Concerned people will most probably benefit more from risk communication by environmental epidemiologists than from cluster investigation or extensive case-control studies ('fishing expeditions') in case little is known of the etiology. 相似文献
108.
109.
110.
BD Milliken JV Turian RJ Hamilton SJ Rubin FT Kuchnir CX Yu JW Wong 《Canadian Metallurgical Quarterly》1998,25(8):1419-1423
The optimal field shape achieved using a multileaf collimator (MLC) often requires collimator rotation to minimize the adverse effects of the scalloped dose distribution the leaf steps produce. However, treatment machines are designed to deliver wedged fields parallel or perpendicular to the direction of the leaves. An analysis of cases from our clinic showed that for 25% of the wedged fields used to treat brain and lung tumors, the wedge direction and optimal MLC orientation differed by 20 degrees or more. The recently published omni wedge technique provides the capability of producing a wedged field with orientation independent of the orientation of the collimator. This paper presents a comparison of the three-dimensional (3D) dose distributions of the omni wedged field with distributions of wedged fields produced using both the universal and dynamic wedge techniques. All measurements were performed using film dosimetry techniques. The omni wedge generated fields closely matched the conventional wedged fields. Throughout 95% of the irradiated volume (excluding the penubra), the dose distribution of the omni wedged field ranged from +5.5 to -3.5 +/- 1.5% of that of the conventionally wedged fields. Calculation of the omni wedged field is as accurate as conventional wedged field calculation when using a 3D treatment planning systems. For two-dimensional treatment planning systems, where one must assume that the omni wedged field is identical to a conventional field, the calculated field and the delivered field differs by a small amount. 相似文献