• Molecules and Cells
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• 제25권4호
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• pp.487-493
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• 2008

HoxB4 has been shown to enhance hematopoietic engraftment by hematopoietic stem cells (HSC) from differentiating mouse embryonic stem cell (mESC) cultures. Here we examined the effect of ectopic expression of HoxB4 in differentiated human embryonic stem cells (hESCs). Stable HoxB4-expressing hESCs were established by lentiviral transduction, and the forced expression of HoxB4 did not affect stem cell features. HoxB4-expressing hESC-derived CD34+ cells generated higher numbers of erythroid and blast-like colonies than controls. The number of CD34+ cells increased but CD45+ and KDR+ cell numbers were not significantly affected. When the hESC derived CD34+ cells were transplanted into $NOD/SCID{\beta}2m-/-$ mice, the ectopic expression of HoxB4 did not alter their repopulating capacity. Our findings show that overexpression of HoxB4 in differentiating hESCs increases hematopoietic colony formation and hematopoietic cell formation in vitro, but does not affect in vivo repopulation in adult mice hosts.

• 한국축산식품학회지
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• 제23권4호
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• pp.342-349
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• 2003

Escherichia coli O157:H7, Staphylococcus aureus와 Salmonella enteritidis는 식품에 의해 전염되는 식품질환성 병원균으로서 세계적으로 알려진 식중독 미생물이다. 오미자 물 추출액 첨가 drink yoghurt에 오염된 식중독 유발균인 Esc. coli O157：H7, Sta. aureus와 Sal. enteritidis의 생존에 미치는 영향을 연구하였다. 오미자 물 추출액이 식중독 유발균에 대한생육 저해 활성을 검토하였고, 시험 균주의 최종 균체 농도가 $10^{5}$ CFU/mL 수준이 되도록 오미자 물 추출액 첨가 drink yoghurt에 Esc. coli O157：H7, Sta. aureus와 Sal. enteritidis를 각각 접종하여 37$^{\circ}C$에 배양하면서 시간별로 시험 균주들의 생존 균수를 측정하였다. 시험 결과 시험에 사용된 오미자 물 추출액의 첨가 농도가 증가할수록 모든 시험 균주에서 강한 증식 억제력이 나타났다. 대조구에 비해 오미자 물 추출액 0.4 ,0.6, 0.8과 1.0% 첨가구에서 Esc. coli O157：H7은 각각 0.13, 0.89, 1.99와 2.55의 log cycle 감소 현상을 보였고, Sta. aureus는 각각 0.45, 3.74, 4.13과 5.24의 log cycle이 감소되었으며, Sal. enteritidis는 각각 0.22, 3.44, 4.02와 4.07의 log cycle 감소가 나타나 모든 시험 균주에서 뚜렷한 성장 억제 효과가 관찰되었다. 오미자 물 추출액의 식중독 유발균에 대한 성장 저해 효과는 Sta. aureus, Sal. enteritidis, 그리고 Esc. coli O157：H7의 순으로 강하게 나타났다. 오미자 물 추출액을 0.4, 0.6, 0.8과 1.0% 첨가한 drink yoghurt 내에서 3.55${\times}$$10^{5}$ CFU/mL 수준으로 접종한 Esc. coli O157:H7은 24시간 배양시 1.00${\times}$$10^1$∼3.00${\times}$$10^1$ CFU/mL로 감소되었으며, 48시간 배양하였을 때에는 생육이 완전히 억제되었다. 그리고 1.24${\times}$$10^{5}$ CFU/mL 수준의 Sta. aureus를 접종한 경우 24시간 배양 후 아주 미약한 생존 균수의 감소를 보였으나 48시간 배양시 4.00${\times}$$10^2$∼8.50${\times}$$10^2$ CFU/mL 수준으로 감소하였고, Sal. enteritidis를 1.81${\times}$$10^{5}$ CFU/mL 수준으로 접종한 경우 24시간 배양 후부터 전연 증식을 나타내지 않았다. 이와 같이 오미자 물 추출액 첨가에 의해 drink yoghurt 내에서 식중독 유발균들의 증균 억제 효과를 확인할 수 있었다.할 수 있었다.

• 과학기술학연구
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• 제12권1호
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• pp.185-207
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• 2012

황우석 사태 이후 한국의 국가는 줄기세포 연구를 장려하고 시험관 아기 산업을 장려하겠다는 입장과 "글로벌 스탠다드"에 부합하는 윤리적 규제를 도입하겠다는, 많은 경우 서로 모순될 수밖에 없는 입장을 표명하여 왔다. 줄기세포 연구에 대한 윤리적 규제가 점점 강화되면서 인간배아세포 연구가 위축되면서, 연구 공동체와 바이오산업, 임상의사와 환자, 그리고 국가 자체를 위기로부터 구원해줄 대안으로 떠오른 것은 체세포 줄기세포였다. 그러나 한국 생명공학기술에 대한 연구들은 주로 배아줄기세포에 초점을 맞추고 있으며, 조혈줄기세포나 지방유래줄기세포와 같은 체세포 줄기세포에 대한 연구에는 상대적으로 관심이 적은 것으로 보인다. 배아줄기세포가 흔히 실험적이고 윤리적으로 논란거리로 여겨지는 반면에, 조혈모 혹은 간엽줄기세포와 체세포 줄기세포는 별다른 공적인 논의 없이 대중들의 일상 속으로 들어와 있다. 한국의 많은 일반인들은 조혈모 줄기세포 치료를 통해 백혈병으로부터 생명을 구한 환자들의 사례에 이미 익숙한가 하면, 다른 한편에서 지방유래줄기세포 치료를 선전하는 의사들의 수가 늘고 있고, 지방유래줄기세포의 개념을 활용하여 만든 화장품이 소비자들의 주목을 받고 있기도 한 현실이 이미 진행되고 있다. 이러한 맥락에서, 본 논문은 배아줄기세포나 국가 정책이나 연구 규제에만 집중되어 시장을 놓치고 있는 윤리적 논의는 한국에서 줄기세포 기술의 정치의 전모를 다루기에 한계가 크다는 사실을 주장하고자 한다.

• 소성∙가공
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• 제20권2호
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• pp.173-178
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• 2011

Environmental Stress Cracking(ESC) is one of the most common causes of unexpected brittle failure of thermoplastic polymers. The exposure of polymers to liquid chemicals tends to accelerate the crazing process, initiating crazes at stresses that are much lower than the stress causing crazing in air. In this study, ESC of acrylonitirile butadiene styrene(ABS) was investigated as a function of the molding conditions such as injection velocity, packing pressure, and melt temperature. A constant strain was applied to the injection molded specimens through a 1.26% strain jig and a mixture of toluene and isopropyl alcohol was used as the liquid chemical. In order to examine the effects of the molding conditions on ESC, an experimental design method was adopted and it was found that the injection velocity was the dominant factor. In addition, predictions from numerical analyses were compared with the experimental results. It was found that the residual stress in the injection molded part was associated with the environmental stress cracking resistance (ESCR).

• Reproductive and Developmental Biology
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• 제35권1호
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• pp.1-8
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• 2011

Techniques to evaluate gene expression profiling, such as sufficiently sensitive cDNA microarrays or real-time quantitative PCR, are efficient methods for monitoring human pluripotent stem cell (hESC/iPSC) cultures. However, most of these high-throughput tests have a limited use due to high cost, extended turn-around time, and the involvement of highly specialized technical expertise. Hence, there is an urgency of rapid, cost-effective, robust, yet sensitive method development for routine screening of hESCs/hiPSCs. A critical requirement in hESC/hiPSC cultures is to maintain a uniform undifferentiated state and to determine their differentiation capacity by showing the expression of gene markers representing all three germ layers, including ectoderm, mesoderm, and endoderm. To quantify the modulation of gene expression in hESCs/hiPSC during their propagation, expansion, and differentiation via embryoid body (EB) formation, we developed a simple, rapid, inexpensive, and definitive multimarker, semiquantitative multiplex RT-PCR platform technology. Among the 9 gene primers tested, 5 were pluripotent markers comprising set 1, and 3 lineage-specific markers were combined as set 2, respectively. We found that these 2 sets were not only effective in determining the relative differentiation in hESCs/hiPSCs, but were easily reproducible. In this study, we used the hES/hiPS cell lines to standardize the technique. This multiplex RT-PCR assay is flexible and, by selecting appropriate reporter genes, can be designed for characterization of different hESC/hiPSC lines during routine maintenance and directed differentiation.

• BMB Reports
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• 제39권4호
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• pp.426-431
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• 2006

Embryonic stem cells (ESCs), representing a population of undifferentiated pluripotent cells with both self-renewal and multilineage differentiation characteristics, are capable of spontaneous differentiation into cardiomyocytes. The present study sought to define the kinetic characterization of lactate dehydrogenase (LDH) and creatine kinase (CK) of ESC- and neonatal-derived cardiomyocytes. Spontaneously differentiated cardiomyocytes from embryoid bodies (EBs) derived from mouse ESC line (Royan B1) and neonatal cardiomyocytes were dispersed in a buffer solution. Enzymes were extracted by sonication and centrifugation for kinetic evaluation of LDH and CK with spectrophotometric methods. While a comparison between the kinetic properties of the LDH and CK of both groups revealed not only different Michaelis constants and optimum temperatures for LDH but also different Michaelis constants and optimum pH for CK, the pH profile of LDH and optimum temperature of CK were similar. In defining some kinetic properties of cardiac metabolic enzymes of ESC-derived cardiomyocytes, our results are expected to further facilitate the use of ESCs as an experimental model.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.257-269
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• 2016

Early-strength-concrete (ESC) made of Type I cement with a high Blaine value of $500m^2/kg$ reaches approximately 60 % of its compressive strength in 1 day at ambient temperature. Based on the 210 compressive test results, a generalized rateconstant material model was presented to predict the development of compressive strengths of ESC at different equivalent ages (9, 12, 18, 24, 36, 100 and 168 h) and maximum temperatures (20, 30, 40, 50 and $60^{\circ}C$) for design compressive strengths of 30, 40 and 50 MPa. The developed material model was used to find optimum curing regimes for precast prestressed members with ESC. The results indicated that depending on design compressive strength, conservatively 25-40 % savings could be realized for a total curing duration of 18 h with the maximum temperature of $60^{\circ}C$, compared with those observed in a typical curing regime for concrete with Type I cement.

• Clinical and Experimental Reproductive Medicine
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• 제38권4호
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• pp.216-221
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• 2011

Objective: To differentiate the human embryonic stem cells (hESCs) into the retinal pigment epithelium (RPE) in the defined culture condition and determine its therapeutic potential for the treatment of retinal degenerative diseases. Methods: The embryoid bodies were formed from hESCs and attached on the matrigel coated culture dishes. The neural structures consisting neural precursors were selected and expanded to form rosette structures. The mechanically isolated neural rosettes were differentiated into pigmented cells in the media comprised of N2 and B27. Expression profiles of markers related to RPE development were analyzed by reverse transcription-polymerase chain reaction and immunostaining. Dissociated putative RPE cells ($10^5$ cells/5 ${\mu}L$) were transplanted into the subretinal space of rat retinal degeneration model induced by intravenous sodium iodate injection. Animals were sacrificed at 1, 2, and 4 weeks after transplantation, and immnohistochemistry study was performed to verify the survival of the transplanted cells. Results: The putative RPE cells derived from hESC showed characteristics of the human RPE cells morphologically and expressed molecular markers and associated with RPE fate. Grafted RPE cells were found to survive in the subretinal space up to 4 weeks after transplantation, and the expression of RPE markers was confirmed with immunohistochemistry. Conclusion: Transplanted RPE cells derived from hESC in the defined culture condition successfully survived and migrated within subretinal space of rat retinal degeneration model. These results support the feasibility of the hESC derived RPE cells for cell-based therapies for retinal degenerative disease.

• Reproductive and Developmental Biology
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• 제35권1호
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• pp.9-15
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• 2011

The functional cardiovascular system is comprised of distinct mesoderm-derived lineages including endothelial cells, vascular smooth muscle cells and other mesenchymal cells. Recent studies in the human embryonic stem cell differentiation model have provided evidence indicating that these cell lineages are developed from the common progenitors such as hemangioblasts and cardiovascular progenitor cells. Also, the studies have suggested that these progenitors have a common primordial progenitor, which expresses KDR (human Flk-1, also known as VEGFR2, CD309). We demonstrate here that sustained activation of BMP4 (bone morphogenetic protein 4) in hESC line, CHA15 hESC results in $KDR^+$ mesoderm specific differentiation. To determine whether the $KDR^+$ population derived from hESCs enhances potential to differentiate along multipotential mesodermal lineages than undifferentiated hESCs, we analyzed the development of the mesodermal cell types in human embryonic stem cell differentiation cultures. In embryoid body (EB) differentiation culture conditions, we identified an increased expression of $KDR^+$ population from BMP4-stimulated hESC-derived EBs. After induction with additional growth factors, the $KDR^+$ population sorted from hESCs-derived EBs displays mesenchymal, endothelial and vascular smooth muscle potential in matrix-coated monolayer culture systems. The populations plated in monolayer cultures expressed increased levels of related markers and exhibit a stable/homologous phenotype in culture terms. In conclusion, we demonstrate that the $KDR^+$ population is stably isolated from CHA15 hESC-derived EBs using BMP4 and growth factors, and sorted $KDR^+$ population can be utilized to generate multipotential mesodermal progenitors in vitro, which can be further differentiated into cardiovascular specific cells.

• Clinical and Experimental Reproductive Medicine
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• 제29권1호
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• pp.1-12
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• 2002

Objective: In order to acquire the technique for the establishment of human embryonic stem cells (ESe) derived from the human frozen-thawed embryos produced in IVF-ET program, this study was performed to establish mouse ESC derived from the in vitro fertilized embryos. Materials and Methods: After Fl hybrid (C57BL female $\times$ CBA mael) female mice were superovulated with PMSG and hCG treatment, their oocytes were retrieved and inseminated, and the fertilized embryos were cultured for 96-120 hours until the expected stages of blastocysts were obtained. To isolate the inner cell mass (ICM), either the blastocysts were treated with immunosurgery, or the whole embryos were cultured for 4 days. Isolated ICMs were then cultured onto STO feeder cell layer, and the resultant ICM colonies were subcultured with trypsin-EDTA treatment. During the subculture process, ESC-like cell colonies were observed with phase contrast microscopy. To identify ESC in the subcultured ESC-like cell colonies, alkaline phosphatase activity and Oct-4 (octamer-binding transcription factor-4) expression were examined by immunohistochemistry and RT-PCR, respectively. To examine the spontaneous differentiation, ESC-like cell colonies were cultured without STO feeder cell layer and leukemia inhibitory factor (LIF). Results: Seven ESC-like cell lines were established from ICMs isolated from the in vitro fertilized embryos. According to the developmental stage, the growth of ICMs isolated from the expanded blastocysts was significantly better than that of ICMs isolated from the hatched blastocysts (80.3% vs. 58.7%, p<0.05). ESC-like cell colonies were only obtained from ICMs of expanded blastocysts. However, the ICMs isolated from the embryos treated with immunosurgery were poorly grown and frequently differentiated during the culture process. The established ESC-like cell colonies were positively stained with alkaline phosphatase and expressed Oct-4, and their morphology resembled that observed in the previously reported mouse ESC. In addition, following the extended in vitro culture process, they maintained their expression of cell surface markers characteristic of the pluripotent stem cells such as alkaline phosphatase and Oct-4. When cultured without STO feeder cell layer and LIF, they were spontaneously differentiated into the various types of cells. Conclusion: The findings of this study suggest that the establishment of mouse ESC can be successfully derived from the in vitro fertilized embryos. The established ESC-like cells expressed the cell surface markers characteristic of the pluripotent stem cells and spontaneously differentiated into the various types of cells.