• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.267-267
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• 2006

Human umbilical cord blood was stored at $4^{\circ}C$ in the Pluronic-immobilized flask as well as commercially available bio-inert flasks, and flow cytometric analysis of surface markers was performed on hematopoietic stem cells after cultivation. The number of cells expressing $CD34^{+}$ in umbilical cord blood on the Pluronic-immobilized flask was extremely higher than those obtained using other flasks. It is concluded that the flexible and hydrophilic segments of Pluronic conjugated on the flask surface are the reason for the effective preservation of hematopoietic stem cells in the Pluronic-immobilized flask.

• 생명과학회지
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• 제10권1호
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• pp.37-44
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• 2000

The mammary gland contains a subpopulation of epithelial cells with large proliferative potentials which are the likely targets for carcinogens. These clonogenic cells can proliferate and differentiate into functional glandular structures. Rat mammary epithelial cells (RMEC) were isolated and characterized in vitro. By flow cytometry of RMEC stained with fluorescein isothiocyanate-peanut agglutinin(PNA) and phycoerythrin anti-Thy-1.1 monoclonal antibody, it was possible to four cell subpopulations from 7-8 week old F344 female rat mammary glands: cells negative to both reagents (B-), PNA-positive cells (PNA+), Thy-1.1-positive cells (Thy-1.1+), and cells positive to both reagents (B+). When single PNA+ cells were isolated and cultured in Matrigel with irradiated (∼50 Gray) 3T3 fibroblast feeder layer, they gave rise to multicellular clonal structures of three types: alveolar, foamy alveolar, and squamous colonies. The developed structures were similar to the mammary glands in vivo. These results suggest that some of PNA+ cells possesses many of the characteristics of multipotent clonogenic stem-like cells.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.180-180
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• 2015

Weather radar has been widely used in measuring precipitation and discharge and predicting flood risks. The radar rainfall estimate has one of the essential problems in terms of uncertainty and accuracy. Previous study analyzed radar errors to reduce its uncertainty or to improve its accuracy. Furthermore, a recent analyzed the effect of radar error on rainfall-runoff using spatial error model (SEM). SEM appropriately reproduced radar error including spatial correlation. Since the SEM does not take the time dependence into account, its time variability was not properly investigated. Therefore, in the current study, we extend the SEM including time dependence as well as spatial dependence, named after Spatial-Temporal Error Model (STEM). Radar rainfall events generated with STEM were tested so that the peak runoff from the response of a basin could be investigated according to dependent error. The Nam River basin, South Korea, was employed to illustrate the effects of STEM on runoff peak flow.

• Tribology and Lubricants
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• 제31권5호
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• pp.205-212
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• 2015

In this research, effects of profile changes of stem section of the plunger on the lubrication characteristics of a fuel injection pump (FIP) were evaluated by hydrodynamic lubrication analysis. The clearance between plunger and barrel was divided into two regions, head and stem. The head was not involved in preventing a decrease of fuel oil pressure. So, research efforts were focused on both edges of the plunger’s stem. The two -dimensional Reynolds equation was used to evaluate lubrication characteristics with variations in viscosity, clearance and profile for a laminar, incompressible, unsteady-state flow. Moreover, the equilibrium equation of moment and forces in the vertical and horizontal directions were used to determine the motion of the plunger. The equations were discretized using the finite difference method. Lubrication characteristics of the FIP were investigated by comparing the dimensionless minimum film thickness, or film parameter, which is the ratio of minimum film thickness to surface roughness. Through numerical analyses, we showed that the profile of the lower edge of the stem had no effect on lubrication characteristics, but the profile of the upper edge had a significant influence on lubrication characteristics. In addition, changes in the profile were more effective in improving lubrication characteristics under low viscosity conditions.

• International Journal of Oral Biology
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• 제43권2호
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• pp.77-82
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• 2018

The mesenchymal stem cells (MSCs) that reside in dental tissues hold a great potential for future applications in regenerative dentistry. In this study, we used human dental pulp cells, isolated from the molars (DPCs), in order to establish the organoid culture. DPCs were established after growing pulp cells in an MSC expansion media (MSC-EM). DPCs were subjected to organoid growth media (OGM) in comparison with human dental pulp stem cells (DPSCs). Inside the extracellular matrix in the OGM, the DPCs and DPSCs readily formed vessel-like structures, which were not observed in the MSC-EM. Immunocytochemistry analysis and flow cytometry analysis showed the elevated expression of CD31 in the DPCs and DPSCs cultured in the OGM. These results suggest endothelial cell-prone differentiation of the DPCs and DPSCs in organoid culture condition.

• 대한기계학회논문집
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• 제19권11호
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• pp.3022-3030
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• 1995

The irreversibility of condensation process in the supersonic flow of steam turbine cascade causes the entropy to increase and the total pressure loss to be generated. In the present study, in order to investigate the moist air flow in two dimensional steam turbine cascade made as the configuration of the last stage tip section of the actual steam turbine moving blade, the static and total pressures along suction side of the blade are measured by pressure taps and Pitot tube. The flow field is visualized by a Schlieren system. The effects of stagnation temperature and the degree of supersaturation on energy loss and entropy change in the flow are clearly identified.

• Reproductive and Developmental Biology
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• 제32권1호
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• pp.9-14
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• 2008

조혈 줄기 세포에의 효과적인 유전자 전달은 유전자 치료의 새로운 가능성을 제시할 수 있다. 레트로바이러스를 이용한 유전자 전달 기술은 많은 기초 연구와 임상 시도가 이루어진 대표적인 바이러스이다. 그러나 현재 사용되고 있는 in vitro에서의 조혈 줄기 세포에의 유전자 도입은 조혈 줄기 세포의 분화 유도, 자기 복제 능력과homing 능력의 저하 등 많은 문제점이 있다. 본 연구는 이러한 문제점을 극복하기 위한 방법으로서 마우스의 대퇴골에 직접 레트로바이러스를 이식하는 IBM (Intra-Bone Marrow) 방법을 이용하여 조혈 줄기 세포에의 효과적인 유전자 도입을 시도하였다. IBM 이식 2주 후 마우스의 각 조직을 분석한 결과, 골수뿐 아니라 림파절, 비장, 간장 세포 등에서 유전자가 안정적으로 발현하는 것을 관찰하였다. 또한, $6.4{\pm}2.7%$의 골수조직 존재 조혈줄기/전구세포에서 도입된 유전자가 안정적으로 발현하고 있는 사실을 확인하였다. 본 연구의 결과를 바탕으로 IBM 이식 방법을 이용한 생체 조직 내 레트로바이러스의 유전자 도입은 조혈 줄기 세포를 이용한 유전자 치료에 매우 효과적인 방법이라는 사실을 시사해주고 있다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권8호
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• pp.4891-4896
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• 2013

Objective: To separate/enrich tumor stem-like cells from the human esophageal carcinoma cell line OE-19 by using serum-free suspension culture and to identify their biological characteristics and radiation resistance. Methods: OE-19 cells were cultivated using adherent and suspension culture methods. The tumor stem-like phenotype of CD44 expression was detected using flow cytometry. We examined growth characteristics, cloning capacity in soft agar, and radiation resistance of 2 groups of cells. Results: Suspended cells in serum-free medium formed spheres that were enriched for CD44 expression. CD44 was expressed in 62.5% of suspended cells, but only in 11.7% of adherent cells. The suspended cells had greater capacity for proliferation and colony formation in soft agar than the adherent cells. When the suspended and adherent cells were irradiated at 5 Gy, 10 Gy, or 15 Gy, the proportion of CD44+ suspended cells strongly and weakly positive for CD44 was 77.8%, 66.5%, 57.5%; and 21.7%, 31.6%, 41.4%, respectively. In contrast, the proportion of CD44+ adherent cells strongly positive for CD44 was 18.9%, 14.%, and 9.95%, respectively. When the irradiation dose was increased to 30 Gy, the survival of the suspended and adherent cells was significantly reduced, and viable CD44+ cells were not detected. Conclusion: Suspended cell spheres generated from OE-19 esophageal carcinoma cells in serum-free stem medium are enriched in tumor stem-like cells. CD44 may be a marker for these cells.

• 대한의생명과학회지
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• 제21권1호
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• pp.40-49
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• 2015

Mesenchymal stem cells (MSCs) have the ability to self-renew and differentiate into multi-lineage cells, thus highlighting the feasibility of using umbilical cord blood-derived MSCs (UCB-MSCs) for cell-therapy and tissueengineering. However, the low numbers of UCB-MSC derived from clinical samples requires that an ex vivo expansion step be implemented. As most stem cells reside in low oxygen tension environments (i.e., hypoxia), we cultured the UCBMSCs under 3% $O_2$ or 21% $O_2$ and the following parameters were examined: proliferation, senescence, differentiation and stem cell specific gene expression. UCB-MSCs cultured under hypoxic conditions expanded to significantly higher levels and showed less senescence compared to UCB-MSCs cultured under normoxic conditions. In regards to differentiation potential, UCB-MSCs cultured under hypoxic and normoxic conditions both underwent similar levels of osteogenesis as determined by ALP and von Kossa assay. Furthermore, UCB-MSCs cultured under hypoxic conditions exhibited higher expression of OCT4, NANOG and SOX2 genes. Moreover, cells expanded under hypoxia maintained a stem cell immnunophenotype as determined by flow cytometry. These results demonstrate that the expansion of human UCB-MSCs under a low oxygen tension microenvironment significantly improved cell proliferation and differentiation. These results demonstrate that hypoxic culture can be rapidly and easily implemented into the clinical-scale expansion process in order to maximize UCB-MSCs yield for application in clinical settings and at the same time reduce culture time while maintaining cell product quality.

• Asian Pacific Journal of Cancer Prevention
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• 제16권8호
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• pp.3509-3515
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• 2015

Background: Diallyl disulfide (DADS) may exert potent anticancer action both in vitro and in vivo. Although its effects on cancer are significant, the underlying mechanisms remain unknown. In this study, we sought to elucidate possible links between DADS and pyruvate kinase (PKM2). Materials and Methods: $KG1{\alpha}$, a leukemia cell line highly expressing PKM2 was used with a cell counting kit (CCK)-8 and flow cytometry (FCM) to investigate the effects of DADS. Relationships between PKM2 and DADS associated with phosphorylation of EGFR, ERK1/2 and MEK, were assessed by western blot analysis. Results: In $KG1{\alpha}$ cells highly expressing PKM2, we found that DADS could affect proliferation, apoptosis and EGFR/ERK/PKM2 signaling pathways, abrogating EGF-induced nuclear accumulation of PKM2. Conclusions: These results suggested that DADS suppressed the proliferation of $KG1{\alpha}$ cells, providing evidence that its proapoptotic effects are mediated through the inhibition of EGFR/ERK/PKM2 signaling pathways.