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임종은,Jeffrey A. Hubbell,이승태,한동근,임정묵 한국고분자학회 2015 Macromolecular Research Vol.23 No.4
The development of an in vitro culture system, comparable to the in vivo environment in terms of effectson oocyte growth and development, could provide a valuable experimental tool for studying the mechanisms governingoocyte development as well as practical clinical, agricultural, zoological, and biotechnological applications. This studyreports on the importance of the microenvironment for the ovarian folliculogenesis process. The complexity of sucha microenvironment was approached with a strategy based on functionalized PEG-hydrogels. The PEG matrix notonly serves as a scaffold, but it is also used a reservoir of immobilized cues. Using tethered integrin-binding peptidesin combination with other signaling factors, we aimed at better understanding the interactions of the oocyte and itssurrounding granulosa that may determine the efficiency of the actual and the future in vitro mature oocyte production. Ina first step, the mechanical properties of PEG-hydrogel were optimized for producing secondary follicles, in whichthe oocyte is surrounded by two layers of granulosa cells. Follicle growth was highly dependent on the mechanicalproperties of the surrounding environment, with the optimal elastic modulus being approx. 1 kPa. The effects of keysoluble factors were also investigated to confirm their compatibility with the established 3-D culture system and tofurther qualitatively and quantitatively improve the produced mature oocytes. Accordingly, various combinations ofthe gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were tested. Interestingly, theeffects of the gonadotropins in the 3-D PEG system were close to their known in vivo effects. In conclusion, this studydemonstrates the efficiency and the flexibility of a novel 3-D culture system, PEG-hydrogel. Circumventing problemsinherent to the “on-plastic” standard culture, such as the loss of the granulosa-oocyte interactions, allowed the emergenceof a culture system tailored for investigating fundamental folliculogenesis-related questions. Furthermore, the reportedculture system may serve as a platform for developing clinical and biotechnology applications.
S.C.Wirasinghe,L. Kattan,M.M. Rahman,J. Hubbell,R. Thilakaratne,S. Anowar 서울시립대학교 도시과학연구원 2013 도시과학국제저널 Vol.17 No.1
Bus Rapid Transit (BRT) has been demonstrated to provide efficient and effective public transport that can even increase transit ridership and attractiveness within defined urban corridors in both developing and developed countries. The merit of the BRT system lies in its ability to provide a high quality public transit service with limited infrastructure and at a relatively low capital and operating cost. In this paper an attempt is made to review BRT characteristics in some detail. An overview of the elements of BRT systems: the running ways, vehicles, stations, as well as operational control, fare collection and passenger information systems is presented. This paper also discusses how these elements allows BRT services to achieve the speed, capacity, reliability, accessibility and operational safety characteristics that distinguishes such systems from regular express bus services. Each built BRT system is unique and depends on how these basic elements are designed and integrated. Environmental, social and economic impacts, users’ perception and modal shift towards BRT have also been critically reviewed. With the presence of local land use and transport policies that support high-density and mixed developments, BRT has been found to attract potential developments around stations and along its corridor, increasing land values and promoting sustainable development. As reported in the literature, the infrastructure costs vary greatly depending on the costs of land acquisition, station design, degree of separation from traffic, technological features and material, labor costs. Thus, BRT capital costs cannot be generalised and must be transferred carefully based on the changes of the input costs that vary from one place to another. The barriers to BRT that block the achievement of significant success in customer satisfaction and ridership gains are mentioned with specific case studies. The review of BRT indicates that in some cases it has similar performance to higher order public transit; however, it still has its unique characteristics that set it apart.
임종은,Irina Krier,임정묵,심수진,한동근,Jeffrey A. Hubbell 한국고분자학회 2015 Macromolecular Research Vol.23 No.4
Polyethylenimine (PEI) is a promising gene carrier among polymeric vectors because of its high transfectionefficiency, buffering capacity, which is responsible for its escape from endosomes, facility of modification,reasonable price and wide range of molecular weight. However, toxicity of PEI is an important obstacle to overcomefor using it as a gene carrier in gene therapy protocols. In our study, PEI (10 kDa) was modified with urocanic acid,which has an imidazole ring (PEIU). This modification of PEI played an important role by improving transfectionefficiency and reducing toxicity. The PEIU was condensed with DNA in different nitrogen of polycation/phosphateof DNA (N/P) ratios starting from 1.25. The PEIU/DNA complexes formed smaller (60-80 versus 100-400 nm) andless dispersible particles than PEI/DNA complexes. Cell viability test showed that in all the transfection experimentsPEIU was always found less toxic than the PEI on three different cell-lines, Cos-7, HeLa, and 293T. The PEIUdemonstrated improved biocompatibility as compared to the PEI. The in vitro transfection experiments showed thatthe PEIU displayed similar or lower transfection efficiencies than the PEI in the absence of serum. In medium complementedwith serum, the PEIU had higher transfection efficiencies than the PEI. In vivo transfection experimentswere carried out with intravenous and subcutaneous injections into mice. Five different organs were taken and lysedfor quantification of expressed GFP. The quantification of the fluorescence of these organs exhibited that the PEIUhas better transfection efficiency in in vivo experiments compared to the PEI. This study generated a strong evidenceindicating that PEIU can be considered as a promising versatile gene carrier because of its biocompatibility and goodtransfection efficiency.
Nasari, Masoud M.,Szyszkowicz, Mieczysław,Chen, Hong,Crouse, Daniel,Turner, Michelle C.,Jerrett, Michael,Pope III, C. Arden,Hubbell, Bryan,Fann, Neal,Cohen, Aaron,Gapstur, Susan M.,Diver, W. Ryan,Stie Springer Netherlands 2016 AIR QUALITY ATMOSPHERE AND HEALTH Vol.9 No.8
<P>The effectiveness of regulatory actions designed to improve air quality is often assessed by predicting changes in public health resulting from their implementation. Risk of premature mortality from long-term exposure to ambient air pollution is the single most important contributor to such assessments and is estimated from observational studies generally assuming a log-linear, no-threshold association between ambient concentrations and death. There has been only limited assessment of this assumption in part because of a lack of methods to estimate the shape of the exposure-response function in very large study populations. In this paper, we propose a new class of variable coefficient risk functions capable of capturing a variety of potentially non-linear associations which are suitable for health impact assessment. We construct the class by defining transformations of concentration as the product of either a linear or log-linear function of concentration multiplied by a logistic weighting function. These risk functions can be estimated using hazard regression survival models with currently available computer software and can accommodate large population-based cohorts which are increasingly being used for this purpose. We illustrate our modeling approach with two large cohort studies of long-term concentrations of ambient air pollution and mortality: the American Cancer Society Cancer Prevention Study II (CPS II) cohort and the Canadian Census Health and Environment Cohort (CanCHEC). We then estimate the number of deaths attributable to changes in fine particulate matter concentrations over the 2000 to 2010 time period in both Canada and the USA using both linear and non-linear hazard function models.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1007/s11869-016-0398-z) contains supplementary material, which is available to authorized users.</P>
Lih, Eugene,Park, Wooram,Park, Ki Wan,Chun, So Young,Kim, Hyuncheol,Joung, Yoon Ki,Kwon, Tae Gyun,Hubbell, Jeffrey A.,Han, Dong Keun American Chemical Society 2019 ACS central science Vol.5 No.3
<▼1><P/><P>Kidney diseases are a worldwide public health issue. Renal tissue regeneration using functional scaffolds with biomaterials has attracted a great deal of attention due to limited donor organ availability. Here, we developed a bioinspired scaffold that can efficiently induce renal tissue regeneration. The bioinspired scaffold was designed with poly(lactide-<I>co</I>-glycolide) (PLGA), magnesium hydroxide (Mg(OH)<SUB>2</SUB>), and decellularized renal extracellular matrix (ECM). The Mg(OH)<SUB>2</SUB> inhibited materials-induced inflammatory reactions by neutralizing the acidic microenvironment formed by degradation products of PLGA, and the acellular ECM helped restore the biological function of kidney tissues. When the PLGA/ECM/Mg(OH)<SUB>2</SUB> scaffold was implanted in a partially nephrectomized mouse model, it led to the regeneration of renal glomerular tissue with a low inflammatory response. Finally, the PLGA/ECM/Mg(OH)<SUB>2</SUB> scaffold was able to restore renal function more effectively than the control groups. These results suggest that the bioinspired scaffold can be used as an advanced scaffold platform for renal disease treatment.</P></▼1><▼2><P>PLGA scaffold with Mg(OH)<SUB>2</SUB> and renal ECM facilitates kidney reconstruction (histological structure and biological function) by neutralizing the acidic microenvironment and improving biocompatibility.</P></▼2>