A new class of RNA regulatory genes known as microRNAs(miRNAs)has been found to introduce a whole new layer of gene regulation in eukaryotes.The intensive studies of the past several years have demonstrated that miRNA...A new class of RNA regulatory genes known as microRNAs(miRNAs)has been found to introduce a whole new layer of gene regulation in eukaryotes.The intensive studies of the past several years have demonstrated that miRNAs are not only found intracellularly,but are also detectable outside cells,including in various body fluids(e.g.serum,plasma,saliva,urine and milk).This phenomenon raises questions about the biological function of such extracellular miRNAs.Substantial amounts of extracellular miRNAs are enclosed in small membranous vesicles(e.g.exosomes,shedding vesicles and apoptotic bodies)or packaged with RNA-binding proteins(e.g.high-density lipoprotein,Argonaute 2 and nucleophosmin 1).These miRNAs may function as secreted signaling molecules to influence the recipient cell phenotypes.Furthermore,secreted extracellular miRNAs may reflect molecular changes in the cells from which they are derived and can therefore potentially serve as diagnostic indicators of disease.Several studies also point to the potential application of siRNA/miRNA delivery as a new therapeutic strategy for treating diseases.In this review,we summarize what is known about the mechanism of miRNA secretion.In addition,we describe the pathophysiological roles of secreted miRNAs and their clinical potential as diagnostic biomarkers and therapeutic drugs.We believe that miRNA transfer between cells will have a significant impact on biological research in the coming years.展开更多
抗生素抗性基因(antibiotic resistance genes,ARGs)作为一种新型的环境污染物,成为多个学科关注的焦点.其在不同环境介质中的扩散和传播具有极大的环境危害性,对人类健康造成严重威胁.插入序列共同区(insertion sequence common region...抗生素抗性基因(antibiotic resistance genes,ARGs)作为一种新型的环境污染物,成为多个学科关注的焦点.其在不同环境介质中的扩散和传播具有极大的环境危害性,对人类健康造成严重威胁.插入序列共同区(insertion sequence common region,ISCR),是一种新发现的抗性基因传播元件,因其特殊的遗传结构,能够通过滚环复制及同源重组等机制移动邻近的任何DNA序列,是ARGs在不同DNA分子或不同种属细菌间水平传播的高效媒介.目前世界上发现了27种ISCR元件.大量间接证据表明,ISCR可能与许多耐药基因的移动和扩散有关,特别是多重耐药性(multiple drug resistance,MDR)形成与传播.因此,ISCR很可能是抗生素抗性基因在环境中扩散传播的关键因子.本文就ARGs水平传播、ISCR结构特征、ISCR种类及其相关ARGs及其研究方法等进行综述,并揭示ISCR元件可能的生态风险,提出了今后的研究重点,以期为今后深入开展相关研究打下基础.展开更多
In this study, the laminar heat transfer and nanofluid flow between two porous horizontal concentric cylinders was investigated. The problem is investigated in two different geometries and the Re=10, 25, 50, 75, 100 a...In this study, the laminar heat transfer and nanofluid flow between two porous horizontal concentric cylinders was investigated. The problem is investigated in two different geometries and the Re=10, 25, 50, 75, 100 and volume fraction 0, 0.2%, 0.5%, 2% and 5% that related to copper nanoparticles, and porous medium porosity of 0.5 and 0.9. Compared to the first geometry, the convective coefficient in the second geometry increases by 8.3%, 7% and 5.5% at Reynolds numbers of 100, 75 and 50, respectively. Comparison of the outlet temperatures for two heat fluxes of 300 and 1200 W/m^2 indicates a 2.5% temperature growth by a fourfold increase in the heat fluxes. Also, the higher Nusselt number is associated with the second geometry occurring at porosities of 0.9 and 0.5, respectively. In both geometries, the Nusselt number values at the porosity of 0.9 are higher, which is due to the increased nanofluid convection at higher porosities. The velocity of the nanofluid experiences a two-fold increase at the outlet compared to its inlet velocity in the first geometry and for both porosities. Similarly, a three-fold increase was achieved in the second geometry and for both porosities.展开更多
基金by grants from the National Natural Science Foundation of China(Nos.90813035,81101330,81171661,30890044,30772484,30725008,30890032,31071232,31000323,90608010,and J1103512)the Natural Science Foundation of Jiangsu Province(No.BK2011013)the Fundamental Research Funds for the Central Universities(No.1107020839).
文摘A new class of RNA regulatory genes known as microRNAs(miRNAs)has been found to introduce a whole new layer of gene regulation in eukaryotes.The intensive studies of the past several years have demonstrated that miRNAs are not only found intracellularly,but are also detectable outside cells,including in various body fluids(e.g.serum,plasma,saliva,urine and milk).This phenomenon raises questions about the biological function of such extracellular miRNAs.Substantial amounts of extracellular miRNAs are enclosed in small membranous vesicles(e.g.exosomes,shedding vesicles and apoptotic bodies)or packaged with RNA-binding proteins(e.g.high-density lipoprotein,Argonaute 2 and nucleophosmin 1).These miRNAs may function as secreted signaling molecules to influence the recipient cell phenotypes.Furthermore,secreted extracellular miRNAs may reflect molecular changes in the cells from which they are derived and can therefore potentially serve as diagnostic indicators of disease.Several studies also point to the potential application of siRNA/miRNA delivery as a new therapeutic strategy for treating diseases.In this review,we summarize what is known about the mechanism of miRNA secretion.In addition,we describe the pathophysiological roles of secreted miRNAs and their clinical potential as diagnostic biomarkers and therapeutic drugs.We believe that miRNA transfer between cells will have a significant impact on biological research in the coming years.
文摘抗生素抗性基因(antibiotic resistance genes,ARGs)作为一种新型的环境污染物,成为多个学科关注的焦点.其在不同环境介质中的扩散和传播具有极大的环境危害性,对人类健康造成严重威胁.插入序列共同区(insertion sequence common region,ISCR),是一种新发现的抗性基因传播元件,因其特殊的遗传结构,能够通过滚环复制及同源重组等机制移动邻近的任何DNA序列,是ARGs在不同DNA分子或不同种属细菌间水平传播的高效媒介.目前世界上发现了27种ISCR元件.大量间接证据表明,ISCR可能与许多耐药基因的移动和扩散有关,特别是多重耐药性(multiple drug resistance,MDR)形成与传播.因此,ISCR很可能是抗生素抗性基因在环境中扩散传播的关键因子.本文就ARGs水平传播、ISCR结构特征、ISCR种类及其相关ARGs及其研究方法等进行综述,并揭示ISCR元件可能的生态风险,提出了今后的研究重点,以期为今后深入开展相关研究打下基础.
文摘In this study, the laminar heat transfer and nanofluid flow between two porous horizontal concentric cylinders was investigated. The problem is investigated in two different geometries and the Re=10, 25, 50, 75, 100 and volume fraction 0, 0.2%, 0.5%, 2% and 5% that related to copper nanoparticles, and porous medium porosity of 0.5 and 0.9. Compared to the first geometry, the convective coefficient in the second geometry increases by 8.3%, 7% and 5.5% at Reynolds numbers of 100, 75 and 50, respectively. Comparison of the outlet temperatures for two heat fluxes of 300 and 1200 W/m^2 indicates a 2.5% temperature growth by a fourfold increase in the heat fluxes. Also, the higher Nusselt number is associated with the second geometry occurring at porosities of 0.9 and 0.5, respectively. In both geometries, the Nusselt number values at the porosity of 0.9 are higher, which is due to the increased nanofluid convection at higher porosities. The velocity of the nanofluid experiences a two-fold increase at the outlet compared to its inlet velocity in the first geometry and for both porosities. Similarly, a three-fold increase was achieved in the second geometry and for both porosities.
