排序方式: 共有32条查询结果,搜索用时 31 毫秒
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Based on the chemiluminescence (CL) intensity generated from the potassium ferricyanide [K(3)Fe(CN)(6)]-rhodamine 6G system in sodium hydroxide (NaOH) medium, a new sensitive flow-injection chemiluminescence (FI-CL) method has been developed, validated and applied for the determination of three kinds of H(2)-receptor antagonists: cimetidine (CIMT), ranitidine (RANT) hydrochloride and famotidine (FAMT). Under the optimum conditions, the linear range for the determination was 1.0 x 10(-9)-7.0 x 10(-5) g/ml for CIMT, 1.0 x 10(-9)-5.0 x 10(-5) g/mL for RANT hydrochloride and 5.0 x 10(-9)-7.0 x 10(-5) g/mL for FAMT. During 11 repeated measurements of 1.0 x 10(-6) g/mL sample solutions, the relative standard deviations (RSDs) were all <5%. The detection limit was 8.56 x 10(-10) g/mL for CIMT, 8.69 x 10(-10) g/mL for RANT hydrochloride and 2.35 x 10(-9) g/mL for FAMT (S:N = 3). This method has been successfully implemented for the analysis of H(2)-receptor antagonists in pharmaceuticals. 相似文献
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记述了云南曲靖潇湘区关底组(志留系罗德洛统)真盔甲鱼类一新属、新种——长孔盾鱼(Dunyu longiforus gen.et sp.nov.),丰富了以梦幻鬼鱼为代表的潇湘脊椎动物群的组成.该新属具真盔甲鱼科的鉴别特征:后眶上管和中背管二者连续过渡,后端两侧辏合呈“U”字形,侧背管仅发出3条侧横管.新属内角缺如,这一特征过去在真盔甲鱼科中仅见于真盔甲鱼属.新属区别于真盔甲鱼属的主要特征有:角向后方延伸,呈棘状或叶状;头甲最宽处位于角末端之前,宽长比小于1.1;中背孔末端超越眶孔后缘连线.基于对秀山真盔甲鱼头甲标本的重新观察,将秀山真盔甲鱼归入盾鱼属.新种区别于秀山盾鱼(Dunyu xiushanensis)的特征有:个体较大,头甲长大于宽;角呈棘状;眶孔位置相对靠前,头甲眶前区与眶后区的长度之比小于0.75;多边形崮状瘤点,较大,长可超过2 mm. 相似文献
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Quantitative associations between osteocyte density and biomechanics, microcrack and microstructure in OVX rats vertebral trabeculae 总被引:1,自引:0,他引:1
Ma YL Dai RC Sheng ZF Jin Y Zhang YH Fang LN Fan HJ Liao EY 《Journal of biomechanics》2008,41(6):1324-1332
Osteocytes actively regulate bone modeling and remodeling, direct skeletal mineralization, and regulate calcium/phosphate homeostasis and extracellular matrix metabolism; yet the specific role of osteocytes in maintaining bone structural integrity and strength is unknown. Studies have shown that the density of osteocytes decreases with age and estrogen deficiency, as seen in postmenopausal women. Here, we examined the relationships between osteocyte density and the related variables, including biomechanics, bone mineral density, microcrack and microstructure of vertebral trabeculae, in ovariectomized rats. We found that osteocyte density correlated with some of the parameters that determine the biomechanical quality of bone. Our findings suggest that osteocytes could play a crucial role in maintaining the mechanical quality of bone, and osteocyte density could be considered as an alternative index in assessing bone quality. 相似文献
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Chong-Jun Yang Zhi-Xi Zhai Yu-Hai Guo Peng Gao 《植物学报(英文版)》2007,49(4):550-555
We investigated the role of the "sieve tube-companion cell complex" lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement (acetylcholine, (ACh) a neurotransmitter in animals and insects; cytochalasin B, (CB) a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos-methyl, (APM) a specific inhibitor of many cellular responses that are mediated by microtubule systems). Their effects on phloem transport were estimated by two experimental devices: (i) a comparison of changes in the amount of assimilates in terms of carbohydrates and ^14C-labeled photosynthetic production that is left in the leaf blade of treated plants; and (ii) distribution patterns of ^14C-labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations (5.0×10^-4 mol/L) but inhibited it in higher concentrations (2.0×10^-3 mol/L) from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi-permeable membrane, but is also directly involved in phloem transport. 相似文献
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我国禽流感研究进展及成就 总被引:3,自引:0,他引:3
禽流感不仅严重危害养禽业,而且给公共卫生造成巨大威胁。为了科学认识和积极防控禽流感,我国科学家进行了大量且富有成效的研究,取得了举世瞩目的成果。通过长期的监测,基本掌握了禽流感在我国的流行情况和进化规律;利用反向遗传操作技术和蛋白质组学技术,发现了影响流感病毒致病力、传播力和受体结合能力的部分关键位点,阐释了其作用机制;通过对传统技术的改进和先进方法的应用,不断成功建立禽流感诊断、检测技术;新型禽流感疫苗不断涌现并逐步被推广和应用,取得了良好的免疫效果。上述成果为我国禽流感的防控奠定了良好的基础,也为后续研究提供了依据。但是禽流感的防控形势依然严峻,2013年新型H7N9病毒的出现,使禽流感的防控面临新的挑战。 相似文献
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记述了云南曲靖潇湘区关底组(志留系罗德洛统)真盔甲鱼类一新属、新种——长孔盾鱼(Dunyu longiforus gen.et sp.nov.),丰富了以梦幻鬼鱼为代表的潇湘脊椎动物群的组成。该新属具真盔甲鱼科的鉴别特征:后眶上管和中背管二者连续过渡,后端两侧辏合呈"U"字形,侧背管仅发出3条侧横管。新属内角缺如,这一特征过去在真盔甲鱼科中仅见于真盔甲鱼属。新属区别于真盔甲鱼属的主要特征有:角向后方延伸,呈棘状或叶状;头甲最宽处位于角末端之前,宽长比小于1.1;中背孔末端超越眶孔后缘连线。基于对秀山真盔甲鱼头甲标本的重新观察,将秀山真盔甲鱼归入盾鱼属。新种区别于秀山盾鱼(Dunyu xiushanensis)的特征有:个体较大,头甲长大于宽;角呈棘状;眶孔位置相对靠前,头甲眶前区与眶后区的长度之比小于0.75;多边形崮状瘤点,较大,长可超过2mm。 相似文献
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Jing Liu Fei-Fan Leng Yu-Hai Gao Wen-Fang He Ju-Fang Wang Cory J. Xian Hui-Ping Ma Ke-Ming Chen 《Journal of cellular and molecular medicine》2023,27(1):36-51
The molecular mechanism for the microgravity-induced decrease in bone formation remains unclear and there is a lack of effective specific preventative therapies. We recently reported that primary cilia of osteoblasts became shorter and even disappeared when the cells were exposed to random positioning machine (RPM)-simulated microgravity and that the microgravity-induced loss of osteogenic potential of osteoblasts could be attenuated when the resorption of primary cilia was prevented by treatment with 0.1 μM cytochalasin D. In the current study, it was further found that the loss of the osteogenic capacity of rat calvarial osteoblasts (ROBs) was associated with the inhibition of the BMP-2/Smad1/5/8 signalling pathway, of which most of the signalling proteins including BMP-2, BMPRII, Smad1/5/8 and p-Smad1/5/8 were found localized to primary cilia. Accompanying the resorption of primary cilia following the cells being exposed to simulated microgravity, the expression levels of these signalling proteins were reduced significantly. Furthermore, the expression of miRNA-129-3p, a microRNA previously reported to control cilium biogenesis, was found to be reduced quickly and changed in a similar tendency with the length of primary cilia. Moreover, overexpression of miRNA-129-3p in ROBs significantly attenuated microgravity-induced inhibition of BMP-2 signalling and loss of osteogenic differentiation and mineralization. These results indicated the important role of miRNA-129-3p in microgravity-induced resorption of primary cilia of osteoblasts and the potential of replenishing the miRNA-129-3p as an effective countermeasure against microgravity-induced loss of primary cilia and impairment of osteoblast function. 相似文献