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排序方式: 共有3743条查询结果,搜索用时 15 毫秒
31.
DL Lacey JM Erdmann SL Teitelbaum HL Tan J Ohara A Shioi 《Canadian Metallurgical Quarterly》1995,136(6):2367-2376
Interleukin 4 (IL-4) is an immune cytokine that inhibits bone resorption in mice and suppresses osteoclastic cell formation in vitro through an undefined mechanism. In this report, we have established the cellular identity of the IL-4 target cell using a variety of bone marrow/stromal cell coculture methods. Initially, we found that the majority of IL-4's inhibition of osteoclastic cell formation was due to its effect on bone marrow cells, not stromal cells. Consequently, bone marrow macrophages were used as osteoclastic cell progenitors after they had been transiently exposed to IL-4 (48 h), before the addition of stromal cells, 1,25-dihydroxyvitamin D3, and dexamethasone. In this circumstance, IL-4 impaired subsequent osteoclastic cell formation, suggesting that the macrophage may be potentially targeted by many factors known to influence osteoclast formation. Consequently, we discovered that interferon-gamma (IFN gamma), prostaglandin E (PGE), and cell-permeant cAMP analogs also impacted osteoclastic cell formation when used to selectively treat bone marrow macrophages. IFN gamma suppressed osteoclastic cell formation, whereas PGE and cAMP analog treatment led to the formation of significantly enlarged osteoclastic cells. Importantly, PGE antagonized the inhibitory effects of both IL-4 and IFN gamma on the osteoclastic cell-forming potential of bone marrow macrophages. Collectively, these findings establish bone marrow macrophages as osteoclastic cell precursors with the degree of their commitment to the osteoclast pathway sensitive to the effects of soluble mediators, including IL-4, IFN gamma, and PGE. 相似文献
32.
This paper introduces genetic algorithms (GA) as a complete entity, in which knowledge of this emerging technology can be integrated together to form the framework of a design tool for industrial engineers. An attempt has also been made to explain “why” and “when” GA should be used as an optimization tool 相似文献
33.
RG Wilde JT Billheimer SJ Germain EA Hausner PC Meunier DA Munzer JK Stoltenborg PJ Gillies DL Burcham SM Huang JD Klaczkiewicz SS Ko RR Wexler 《Canadian Metallurgical Quarterly》1996,4(9):1493-1513
Acyl-CoA:cholesterol acyltransferase (ACAT) is the enzyme largely responsible for intracellular cholesterol esterification. A systemic inhibitor of ACAT is believed to be able to slow or even reverse the atherosclerotic process. Towards that goal, a series of cyclic sulfides, derived from the hetero-Diels-Alder reaction of thioaldehydes with 1,3-dienes, and bearing carboxamide substituents, were prepared and evaluated for in vitro (in several tissues and species) and ex vivo ACAT inhibition. Minor changes in subsequent structure were found to have a significant effect in optimization of the biological activity of this series of compounds. 相似文献
34.
Performance analysis of the bidirectional associative memory and animproved model from the matched-filtering viewpoint 总被引:1,自引:0,他引:1
Bai-Ling Zhang Bing-Zheng Xu Chung-Ping Kwong 《Neural Networks, IEEE Transactions on》1993,4(5):864-872
This paper discusses the bidirectional associative memory (BAM) model from the matched-filtering viewpoint and offers it a new interpretation. Our attention is focused on the problem of stability and attractivity of equilibrium states. Several sufficient and/or necessary conditions are presented. To improve the BAM performance, an exponential function is used to enhance the correlations between the binary vectors of the retrieval key and that of the stored pattern similar to the key. The modified model is shown to be asymptotically stable. Theoretical analysis and simulation results demonstrate that the modified model performs much better than the original BAM in terms of memory capacity and error correction capability. 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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To determine the most effective treatment for acrodermatitis chronica atrophicans, several clinical trials were undertaken in recent years to evaluate whether a 2-week course of ceftriaxone would be superior to oral antibiotics. Of the 46 patients suffering from acrodermatitis chronica atrophicans, 14 were treated with ceftriaxone 2g for 15 days. The remaining patients received either oral penicillin V 1.5 million IU t.i.d. or doxycycline 100 mg b.i.d. for 20 to 30 days. Patients were followed up for at least 1 year. Of the 14 ceftriaxone-treated patients four showed incomplete regression of the inflammatory skin changes after 6 to 12 months. Two out of five patients who were monitored for Borrelia burgdorferi DNA excretion were still positive after 12 months as compared to none of six patients who were treated orally for 20-30 days. Six out of 11 patients treated orally for only 20 days needed retreatment after 6 months because of continuing skin manifestations, neuropathy or arthralgia. A 30-day duration of treatment with oral antibiotics and not the chosen antibiotic is crucial for curing acrodermatitis chronica atrophicans. The duration of treatment with ceftriaxone needed for eradication of Borrelia in acrodermatitis chronica atrophicans has yet to be determined in future studies. 相似文献