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961.
Ultra High Molecular Weight Polyethylene(UHMWPE)has been widely used as a bearing material for artificial joint replacementover forty years.It is usually crosslinked by gamma rays irradiation before its implantation into human body.In thisstudy,UHMWPE and UHMWPE/nano-hydroxyapatite(n-HA)composite were prepared by vacuum hot-pressing method.Theprepared materials were irradiated by gamma rays in vacuum and molten heat treated in vacuum just after irradiation.The effectof filling n-HA with gamma irradiation on tribological properties of UHMWPE was investigated by using friction and wearexperimental machine(model MM-200)under deionized water lubrication.Micro-morphology of worn surface was observedby metallographic microscope.Contact angle and hardness of the materials were also measured.The results show that contactangle and hardness are changed by filling n-HA and gamma irradiation.Friction coefficient and wear rate under deionized waterlubrication are reduced by filling n-HA.While friction coefficient is increased and wear rate is reduced significantly by gammairradiation.The worn surface of unfilled material is mainly characterized as adhesive wear and abrasive wear,and that of n-HAfilled material is mainly characterized as abrasive wear.After gamma irradiation,the degrees of adhesive and abrasive wear forunfilled material and abrasive wear of n-HA filled material are significantly reduced.Unfilled and filled materials after irradiationare mainly shown as slight fatigue wear.The results indicate that UHMWPE and UHMWPE/n-HA irradiated at the doseof 150 kGy can be used as bearing materials in artificial joints for its excellent wear resistance compared to original UHMWPE. 相似文献
962.
Xiao-Fang Li Yu-Ju Li Ying-Hui An Li-Jun Xiong Xing-Hua Shao Yang Wang Yue Sun 《植物学报(英文版)》2009,51(5):513-520
Sucrose non-fermenting-1-related protein kinase 1 (SnRK1) has been located at the heart of the control of metabolism and development in plants. The active SnRK1 form is usually a heterotrimeric complex. Subcellular localization and specific target of the SnRK1 kinase are regulated by specific beta subunits. In Arabidopsis , there are at least seven genes encoding beta subunits, of which the regulatory functions are not yet clear. Here, we tried to study the function of one beta subunit, AKINβ1. It showed that AKINβ1 expression was dramatically induced by ammonia nitrate but not potassium nitrate, and the investigation of AKINβ1 transgenic Arabidopsis and T-DNA insertion lines showed that AKINβ1 negatively regulated the activity of nitrate ruductase and was positively involved in sugar repression in early seedling development. Meanwhile AKINβ1 expression was reduced upon sugar treatment (including mannitol) and did not affect the activity of sucrose phosphate synthase. The results indicate that AKINβ1 is involved in the regulation of nitrogen metabolism and sugar signaling. 相似文献
963.
Wenling Zhang ;Zhaoyang Zeng ;Yanhong Zhou ;Wei Xiong ;Songqing Fan ;Lan Xiao ;Donghai Huang ;Zheng Li ;Dan Li ;Minghua Wu ;Xiaoling Li ;Shourong Shen ;Rong Wang ;Li Cao ;Ke Tang ;Guiyuan Li 《Acta biochimica et biophysica Sinica》2009,(5):414-428
Previous studies have revealed that Epstein-Barr virus (EBV) was closely associated with nasopharyngeal carcinoma (NPC). This study aimed to characterize the global pathways affected in the EBV-associated NPC. Combined with microdissection, gene expression profries in 22 NPCs and 10 non-tumor nasopharyngeal epithelial (NPE) tissue samples were analyzed. All NPC specimens served in the microarray analysis were positive for EBV, as judged by identification of the expression of EBV nuclear antigen 1 (EBNA1). Through gene set enrichment analysis (GSEA), we found that cell cycle pathway was the most disregulated pathway in NPC (P = 0.000, false discovery rate q-value = 0.007), which included some aberrant expressed components. We first found that overexpression of CDK4, cyclin D1, and Rb proteins, and loss of expression of proteins p16, p27, and p19 were statistically significant in NPC tissues compared with non-cancerous NPE (P〈 0.05) by real-time RT- PCR and tissue microarray. EBV-encoded small RNA-1 (EBER-1) hybridization signals in the NPC showed significant associations with the overexpression of Rb (P = 0.000), cyclin D1 (P = 0.000), CDK4 (P = 0.000), and the loss of expression of p16 proteins (P = 0.039). In the final logistic regression analysis model, EBER-1 and abnormal expression of p16, Rb, cyclin D1, and E2F6 were inde- pendent contributions to nasopharyngeal carcinogenesis. Through survival analysis, only cyclin D1 could predict the prognosis of NPC patients. These results suggested that cell cycle pathway was the most disregulated pathway in the EBV-associated NPC, and EBER-1 was closely associated with p16, CDK4, cyclin D1, and Rb. cyclin D1 could be the prognosis biomarker for NPC. 相似文献
964.
目的:探讨一氧化氮供体药物硝酸甘油对对裸鼠胰腺癌皮下成瘤的抑制作用及对瘤体组织中低氧诱导因子1α(hypoxia induced factor 1α,HIF-1α),P糖蛋白(P-glucoprotein,P-gP)和谷胱甘肽S转移酶-π(Glutathione S-transferase pi,GST-π)的表达影响.方法:40只6-8周的18-22g的BALB/c裸鼠双侧腹股沟皮下注射胰腺癌PANC-1细胞成瘤,瘤体超过150mm3后随机分组,干预组用硝酸甘油帖剂干预,对照组贴安慰剂,并分别绘制生长曲线.采用免疫组织化学方法检测成瘤裸鼠中瘤体组织中HIF-1α、P-gP和GST-π的表达.结果:32例裸鼠成瘤,成瘤率80%,干预28天后,干预组和对照组的瘤体大小分别为1550.4±148.6mm3和750.6±71.2mm3.16只对照组瘤体组织中HIF-1α阳性表达12例(75%),P-gp阳性表达10例(62.5%),GsT-π阳性表达8例(50%).在16例干预组裸鼠瘤体组织中HIF-1α、P-gP、GST-π阳性表达分别是11例(68.8%),8例(50%),7例(43.8%).结论:特定剂量硝酸甘油对裸鼠皮下成瘤有明显抑制作用,且对HIF-1α及P-gp、GsT-π的表达也有一定的抑制作用. 相似文献
965.
1998年,Thomson等成功分离出了人类胚胎干细胞(embryonic stem cell,ES)系为研究再生医学和人类早期发育开辟了一个新领域.通过转染人类ES细胞进行遗传操作(genetic manipulation)可以帮助我们更好地理解人类Es细胞的生物学特性,同时为研究人类ES细胞在细胞及基因治疗中潜在的治疗用途提供了基础.本文综述了人类ES细胞外源基因转染方法及其应用的进展. 相似文献
966.
967.
Lijuan Zhang Zhaoqin Zhu Huaiqi Jing Jingyun Zhang Yanwen Xiong Meiying Yan Shouyi Gao Long-Fei Wu Jianguo Xu Biao Kan 《BMC microbiology》2009,9(1):114-13
Background
The Twin-arginine translocation (Tat) system serves to translocate folded proteins, including periplasmic enzymes that bind redox cofactors in bacteria. The Tat system is also a determinant of virulence in some pathogenic bacteria, related to pleiotropic effects including growth, motility, and the secretion of some virulent factors. The contribution of the Tat pathway to Vibrio cholerae has not been explored. Here we investigated the functionality of the Tat system in V. cholerae, the etiologic agent of cholera. 相似文献968.
Background
The phylogeny of Cetacea (whales) is not fully resolved with substantial support. The ambiguous and conflicting results of multiple phylogenetic studies may be the result of the use of too little data, phylogenetic methods that do not adequately capture the complex nature of DNA evolution, or both. In addition, there is also evidence that the generic taxonomy of Delphinidae (dolphins) underestimates its diversity. To remedy these problems, we sequenced the complete mitochondrial genomes of seven dolphins and analyzed these data with partitioned Bayesian analyses. Moreover, we incorporate a newly-developed "relaxed" molecular clock to model heterogenous rates of evolution among cetacean lineages. 相似文献969.
Xia Xiong Sha Huang Hai Zhang Jianjun Li Jianying Shen Jixian Xiong Yong Lin Liping Jiang Xianchun Wang Sonping Liang 《Proteome science》2009,7(1):41-10
Background
Dorsal root ganglion (DRG) neurons are primary sensory neurons that conduct neuronal impulses related to pain, touch and temperature senses. Plasma membrane (PM) of DRG cells plays important roles in their functions. PM proteins are main performers of the functions. However, mainly due to the very low amount of DRG that leads to the difficulties in PM sample collection, few proteomic analyses on the PM have been reported and it is a subject that demands further investigation. 相似文献970.
Effects of elevated CO2 concentration, supplemental irrigation and nitrogenous fertilizer application on rain-fed spring wheat yield
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It is expected that the CO2 concentration of the Earth’s atmosphere will reach 600–1000 ppm by the end of the 21st century. Therefore, in this study, we evaluated the effects of elevated CO2 concentrations on the development of rain-fed spring wheat in an attempt to identify a practical pathway to increase crop production. To accomplish this, a field experiment was conducted at Guyuan Experimental Station in a semiarid region of China during 2005–2007. During this experiment, the CO2 concentration was increased to 40.0 ppm and supplemental irrigation and nitrogenous fertilizer (N fertilizer) were applied. The experimental results showed that the elevated CO2 concentration significantly improved the thousand-grain weight and the grain number per spike. Furthermore, supplemental irrigation and N fertilizer application during the elongation and booting stage of rain-fed spring wheat in conjunction with an elevated CO2 concentration improved the water use efficiency (WUE), nitrogen use efficiency (NUE), thousand-grain weight, and the yield by 14.6%, 39.6%, 9.3%, and 14.7%, respectively, when compared to groups subjected to the same treatment but not grown under elevated CO2 concentrations. Furthermore, the spring wheat yield was improved by 81.8% in response to an elevated CO2 concentration, 60 mm of supplemental irrigation and applied N fertilizer (37.5 g m?2 NH4NO3). However, the presence of an elevated CO2 concentration without supplemental irrigation and N fertilizer only resulted in an increase in the wheat yield of 7.8%. Consequently, the combination of elevated CO2 concentration, supplemental irrigation and N fertilizer application played an important role in the improvement of WUE, NUE, thousand-grain weight, and grain yield of rain-fed spring wheat in this region. 相似文献