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최의환,윤서빈,한윤수,김근필 한국분자세포생물학회 2017 Molecules and cells Vol.40 No.2
Homologous recombination (HR) is necessary for maintenance of genomic integrity and prevention of various mutations in tumor suppressor genes and proto-oncogenes. Rad51 and Rad54 are key HR factors that cope with replication stress and DNA breaks in eukaryotes. Rad51 binds to single-stranded DNA (ssDNA) to form the presynaptic filament that promotes a homology search and DNA strand exchange, and Rad54 stimulates the strand-pairing function of Rad51. Here, we studied the molecular dynamics of Rad51 and Rad54 during the cell cycle of HeLa cells. These cells constitutively express Rad51 and Rad54 throughout the entire cell cycle, and the formation of foci immediately increased in response to various types of DNA damage and replication stress, except for caffeine, which suppressed the Rad51-dependent HR pathway. Depletion of Rad51 caused severe defects in re-sponse to postreplicative stress. Accordingly, HeLa cells were arrested at the G2–M transition although a small amount of Rad51 was steadily maintained in HeLa cells. Our results suggest that cell cycle progression and proliferation of HeLa cells can be tightly controlled by the abundance of HR proteins, which are essential for the rapid response to postreplicative stress and DNA damage stress.
HALE 무인기의 게인 스케줄링을 위한 설계점 선정에 관한 연구
최의환,윤남경,문건희,박현주,김기덕,전병주,안재명,방효충,탁민제 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11
본 논문은 고도 10km~20km의 성층권에서 순항하는 고고도 장기체공 무인기(HALE 무인기)의 제어법칙 설계 과정 중 하나인 게인 스케줄링 단계에서의 설계점 선정에 대해 다룬다. HALE 무인기는 성층권이상의 고도에서 장시간 체공하며 감시 및 정찰 등의 고유 임무를 수행하는 무인기이다. 설계점 선정을 위해 HALE 무인기의 고고도에서의 비행 가능 영역과 전체 설계점을 도출하고 순항 고도와 순항 속도로 이루어진 기준 설계점을 정의한다. 기준 설계점에 대해 설계된 제어기를 전체 설계점에 적용하여 비행성 수준과 안정성 여유의 추이를 살펴본다. 이후 게인 스케줄링을 위한 적절한 설계점 선정을 위한 방안을 제시한다. This paper addresses process on selection of operating points for gain scheduling, one of the stages of control law design of the High Altitude Long Endurance Unmanned Aerial Vehicle(HALE UAV) cruising at 10km~20km stratosphere altitude. HALE UAV is UAV which conducts surveillance, reconnaissance and its own missions at the stratosphere altitude with long flight time. In order to select the operating points, flight envelope at high altitude and whole operating points are obtained. Then, a reference operating point of cruise altitude and cruise velocity is defined. The controller designed for the reference operating point is applied to whole operating points to show trends of flying qualities and stability margins. Finally, a method of selecting appropriate operating points for gain scheduling is suggested.
최의환 朝鮮大學校 口腔生物學硏究所 1998 Oral Biology Research (Oral Biol Res) Vol.22 No.2
The purpose of this study was to aid in the prediction of tumor cell tolerance to radiotherapy. For this study, cell surviving curves were obtained for mouse lymphoma YAC-1 cell line using semiautomated MTT assay. 2, 4, 6, 8, 10Gy were irradiated at a dose rate of 210cGy/min using 60^Co Irradiator ALDORADO 8. The viable cells were determined for each radiation dose and compared to control values. The obtained results were as follows : 1. There was significant difference of surviving fractions at 2, 4, 6, 8, 10Gy on YAC-1 cell line(P<.05). 2. The surviving curves with gentle slopes were obtained after irradiation of 2, 4, 6, 8, 10Gy alone on YAC-1 cell line.
최의환,하정완,김수관,정태영,김수흥 대한악안면성형재건외과학회 2001 Maxillofacial Plastic Reconstructive Surgery Vol.23 No.3
Modified surgical technique for transposition of the inferior alveolar nerve followed by immediate placement of endosseous implants in mandibles with moderate to severe atrophy are presented. Five transpositions of the inferior alveolar nerve together with the installation of 10 implants were performed in four patients. The mean postoperative follow-up time was 17 months, with a range of 8 to 20 months. All implants with functioning pontics remained stable, with no mobility or symptoms of pain and infection during the follow-up period. Neurosensory evaluation was performed using the two-point discrimination test. Two patients had objective neurosensory dysfunction at postoperative, but all the nerve function were reported as normal by the patients 4 months postoperatively.
Maintenance of genome integrity and active homologous recombination in embryonic stem cells
최의환,윤서빈,Koh Young Eun,서영진,김근필 생화학분자생물학회 2020 Experimental and molecular medicine Vol.52 No.-
Embryonic stem cells (ESCs) possess specific gene expression patterns that confer the ability to proliferate indefinitely and enable pluripotency, which allows ESCs to differentiate into diverse cell types in response to developmental signals. Compared to differentiated cells, ESCs harbor an elevated level of homologous recombination (HR)-related proteins and exhibit exceptional cell cycle control, characterized by a high proliferation rate and a prolonged S phase. HR is involved in several aspects of chromosome maintenance. For instance, HR repairs impaired chromosomes and prevents the collapse of DNA replication forks during cell proliferation. Thus, HR is essential for the maintenance of genomic integrity and prevents cellular dysregulation and lethal events. In addition, abundant HR proteins in the prolonged S phase can efficiently protect ESCs from external damages and protect against genomic instability caused by DNA breaks, facilitating rapid and accurate DNA break repair following chromosome duplication. The maintenance of genome integrity is key to preserving the functions of ESCs and reducing the risks of cancer development, cell cycle arrest, and abnormal replication. Here, we review the fundamental links between the stem cell-specific HR process and DNA damage response as well as the different strategies employed by ESCs to maintain genomic integrity.
최의환 大韓口腔顎顔面 放射線學會 1992 Imaging Science in Dentistry Vol.22 No.2
The author observed a case of dentinogenesis imperfecta in a 8-year-old a 9-year-old brother with complaints of abnormal morphologic changes of the teeth. 1. Clinically, yellowish brown colored teeth, fractured crown and numerous retained root tips of deciduous teeth with severe attrition were observed in the both deciduous and permanent dentitions. 2. Radiographically, small-sized teeth, partial or complete obliteration of the pulp chambers and pulp canals in the anterior teeth, partial obliteration of the pulp chambers and thin enamel in the permanent tooth germs were observed. 3. The familial history was their father has been lose his teeth early.