The Effects of Obstacles on the Dynamics of Ventricular Fibrillation

Background and Objectives：The effects of artificial obstacles on the dynamics of ventricular fibrillation have been extensively investigated with an electrical mapping system. This study was performed to assess the influence of transmural obstacles on the dynamics of wavefronts, and determine whether these can convert ventricular fibrillation to ventricular tachycardia by stabilizing the wavefronts in the fibrillating right ventricular tissues of pigs, using an optical mapping system. Materials and Methods：The right ventricles of pigs (n=15) were excised and placed in a tissue perfusion system, with the epicardium facing up. Holes, with increasing sizes, from 2 to 8 mm in diameter, were created using a skin biopsy punch. Another 8 mm sized hole was then made adjacent to the first, and the changes in the wavefront dynamics and cycle length of the optical action potential waves investigated. Results：In 14 of the 20 obstacles, in ten tissues, transient attachment of electrical activities along the rim of obstacles and transient rotation of the wavefronts were observed. During baseline ventricular fibrillation, the fibrillation cycle length was 118.5±24.7 msec, which was increased to 135.4±30.2 msec after creation of the first hole, and to 159.4±47.7 msec after the second (p=0.01). There was a positive correlation between the obstacle size and cycle length (r=0.43, p=0.007). In three tissues, conversion to ventricular tachycardia from ventricular fibrillation was observed after creation of the two holes. Conclusion：Obstacles of an appropriate size had anti-fibrillatory effects in tissues with ventricular fibrillation, which was partly explained by the temporary attachment of wavefronts to the obstacles.ope

Small-diameter blood vessels engineered with bone marrow-derived cells

OBJECTIVE: The objective of this study is to investigate if bone marrow-derived cells (BMCs) regenerate vascular tissues and improve patency in tissue-engineered small-diameter (internal diameter = 3 mm) vascular grafts. SUMMARY BACKGROUND DATA: BMCs have demonstrated the ability to differentiate into endothelial-like cells and vascular smooth muscle-like cells and may offer an alternative cell source for vascular tissue engineering. Thus, we tissue-engineered small-diameter vascular grafts with BMCs and decellularized arteries. METHODS: Canine BMCs were differentiated in vitro into smooth muscle alpha-actin/smooth muscle myosin heavy-chain-positive cells and von Willebrand factor/CD31-positive cells and seeded onto decellularized canine carotid arteries (internal diameter = 3 mm). The seeded grafts were implanted in cell donor dogs. The vascular-tissue regeneration and graft patency were investigated with immunohistochemistry and angiography, respectively. RESULTS: The vascular grafts seeded with BMCs remained patent for up to 8 weeks in the canine carotid artery interposition model, whereas nonseeded grafts occluded within 2 weeks. Within 8 weeks after implantation, the vascular grafts showed regeneration of the 3 elements of artery (endothelium, media, and adventitia). BMCs labeled with a fluorescent dye prior to implantation were detected in the retrieved vascular grafts, indicating that the BMCs participated in the vascular tissue regeneration. CONCLUSIONS: Here we show that BMCs have the potential to regenerate vascular tissues and improve patency in tissue-engineered small-diameter vascular grafts. This is the first report of a small-diameter neovessel engineered with BMCs as a cell source.ope

Reactive oxygen species inhibit adhesion of mesenchymal stem cells implanted into ischemic myocardium via interference of focal adhesion complex.

The integrity of transplanted mesenchymal stem cells (MSCs) for cardiac regeneration is dependent on cell-cell or cell-matrix adhesion, which is inhibited by reactive oxygen species (ROS) generated in ischemic surroundings after myocardial infarction. Intracellular ROS play a key role in the regulation of cell adhesion, migration, and proliferation. This study was designed to investigate the role of ROS on MSC adhesion. In H(2)O(2) treated MSCs, adhesion and spreading were inhibited and detachment was increased in a dose-dependent manner, and these effects were significantly rescued by co-treatment with the free radical scavenger, N-acetyl-L-cysteine (NAC, 1 mM). A similar pattern was observed on plates coated with different matrices such as fibronectin and cardiogel. Hydrogen peroxide treatment resulted in a marked decrease in the level of focal adhesion-related molecules, such as phospho-FAK and p-Src in MSCs. We also observed a significant decrease in the integrin-related adhesion molecules, alpha V and beta1, in H(2)O(2) treated MSCs. When injected into infarcted hearts, the adhesion of MSCs co-injected with NAC to the border region was significantly improved. Consequently, we observed that fibrosis and infarct size were reduced in MSC and NAC-injected rat hearts compared to in MSC-only injected hearts. These results indicate that ROS inhibit cellular adhesion of engrafted MSCs and provide evidence that the elimination of ROS might be a novel strategy for improving the survival of engrafted MSCsope

Cardiomyocytes from phorbol myristate acetate-activated mesenchymal stem cells restore electromechanical function in infarcted rat hearts

Despite the safety and feasibility of mesenchymal stem cell (MSC) therapy, an optimal cell type has not yet emerged in terms of electromechanical integration in infarcted myocardium. We found that poor to moderate survival benefits of MSC-implanted rats were caused by incomplete electromechanical integration induced by tissue heterogeneity between myocytes and engrafted MSCs in the infarcted myocardium. Here, we report the development of cardiogenic cells from rat MSCs activated by phorbol myristate acetate, a PKC activator, that exhibited high expressions of cardiac-specific markers and Ca(2+) homeostasis-related proteins and showed adrenergic receptor signaling by norepinephrine. Histological analysis showed high connexin 43 coupling, few inflammatory cells, and low fibrotic markers in myocardium implanted with these phorbol myristate acetate-activated MSCs. Infarct hearts implanted with these cells exhibited restoration of conduction velocity through decreased tissue heterogeneity and improved myocardial contractility. These findings have major implications for the development of better cell types for electromechanical integration of cell-based treatment for infarcted myocardium.ope

A Study of astronomical ideas in ancient China and Korea : the sacrificial rituals to heaven from the Han to the T`ang dynasty period and the astronomical charts in Koguryo murals

학위논문(박사)--서울대학교 대학원 :종교학과,1999.Docto

"단군론"의 역사적 변천 연구 : 조선 중기∼일제 시대를 중심으로

학위논문(석사)--서울大學校 大學院 :宗敎學科,1995.Maste

19세기초 유희 물명고 의 분류명 내원과 분류체계 연구

이 글은 19세기초 한글물명이 부기된 유희의 물명고 (1824)를 대상으로 여기에 적용된 대중소의 3단계 물명 분류 체계와 분류명 구성의 특성을 고찰한 연구이다. 유희가 매우 특이한 분류명으로 사용한 4종의 대범주명이 지닌 사상적 배경을 고찰하여, 불교의 유정무정 지각론, 북 송대 신유학의 태극도설 에서 기반한 태극동정론과 오행질료론 및 한의학의 본초서가 전개시켜 온 오행적 광물분류론이 복합된 것으로 파악하였고, 그 결과 동식물류는 지각의 관점인 정식(情 識)의 유무에 따라 제1 유정류는 지각운동이 있는 동물류, 제2 무정류는 지각운동이 없는 식물류 를 지칭하는 분류명으로 수립되었고, 광물류는 능동의 유무에 따라 제3 부동류는 불능동하는 고 정성의 토석금 광물류, 제4 부정류는 정적이지 않는 유동성의 수화류를 분류하는 이름으로 수립 한 것이라 추론하였다. 이들 전체는 동식광물의 ‘생활자연물’에 대한 물명 분류로 조망되고, 그래 서 물명고 는 ‘물명 자연물 세계’에 대한 탐구서 성격으로 규정되었다. 다음 소분류명에서 동물류를 분류한 우충, 모충, 나충, 인충, 개충은 고대 진한시대에 성립된 오행사상적 동물분류설인 오충설(五蟲說)을 그대로 전승한 체제이고, 이때 털이 가는 세모(細毛) 의 모충(毛蟲)은 초식동물류를, 털이 얕은 천모(淺毛)의 나충(臝蟲)은 육식과 야생동물류를 지칭 하는 분류틀로 사용한 것이라 파악되었다. 나머지 우충(羽蟲)은 조류, 인충(鱗蟲)은 어류, 개충 (介蟲)은 패류ㆍ갑각류를 분류하여, 전체적으로 물명고 의 오충 소분류가 각각 조류, 초식동물, 육식동물, 어류, 패갑류의 분류틀이라 고찰되었다. 여기에 빠진 곤충은 동물류 전체를 포괄하는 광의의 용법과 작은 벌레의 소충류(小蟲類)를 지 칭하는 협의의 용법이 있고, 이중 물명고 는 소충의 충치류를 포괄하는 분류명으로 사용되었다. 그런데 이를 고찰하는 과정에서 남송초 정초의 통지 (1116) ｢곤충초목략｣이 공자가 강조한 시 명다식(詩名多識)의 물명(物名) 중요성에 의거하여 자연의 조수초목에 대한 분류와 물명 고찰을 적용한 것이어서 유희가 물명고 를 편찬한 것과 동궤의 문제의식으로 크게 주목되었다. 또한 중 간분류명으로 수중동물(鱗蟲, 介蟲)을 묶은 수족(水族)과 동물(毛蟲, 臝蟲)을 묶은 수족(獸族)을 사용한 문제도 아울러 고찰하였다. 최종적으로 물명 자연물을 궁극 대상으로 삼은 물명고 는 4류-7족-13부의 대중소 3단계 분류 체계 아래 총 685항의 물명 표제항을 수록한 것으로 집계되었고, 그중 광물류가 1할 정도(81항, 12%)인 반면에, 나머지 9할(604항, 88%)이 동식물류에 집중된 분포여서, 물명고 의 물명 연구 에 본초서 계통과의 심화 비교가 크게 요청되었다. 또한 물명고 가 선행된 재물보 (1798)의 항 목을 취사선택한 방식이어서 향후 양자의 비교연구를 통해 한글물명의 문제도 심화할 필요성이 크다 보았다

Nationalistic Tendency in the Understanding of Tan-gun in 17th Century

본 연구는 현대 단군이해의 역사적 형성과정을 밝히려는데 그 목적이 있다. 김교헌, 신채호, 이능화 등의 논의와 거기서 파생된 여러 논의가 현대 단군론의 주요한 부분을 구성하는데, 17세기 眉叟 許穆 (1595-1682)과 玄默子 洪萬宗(1643-1725)의 한국 영성적 논의에 그 뿌리가 있음을 밝히고자 한다. 이런 역사적 연구를 하게 된 배경은 다양한 현대 단군론의 접근방법 속에서 초래되는 여러 혼란스러움을 극복하기 위한 토대의 하나를 마련하기 위함에서이다. 이에 본 연구에서는 이상의 문제를 보편주의와 특수주의가 대립 갈등하는 변증법적 맥락에서 파악하고, 이 두 전통들의 변천 과정을 탐색하려는 데 일차적인 목표를 둔다. 하지만 두 전통 중에서 특수주의 전통의 생성과 변천 과정을 중점적으로 천착하게 될 것이다. 이것은 특수주의 전통이 현대 단군론을 이해하는 데 가장 중요한 실마리를 제공하고 있기 때문이며, 또한 송시열계의 보편주의적 입장은 기왕에 많은 연구가 되어 있기 때문이다

Smooth muscle-like tissues engineered with bone marrow stromal cells

Bone marrow-derived cells have demonstrated the ability to differentiate into multiple mesenchymal cell lineages. Here we tested whether smooth muscle (SM)-like tissues can be created in vivo with bone marrow stromal cells (BMSCs). Cultured canine BMSCs, which expressed SM cell-specific markers including SM α-actin and SM myosin heavy chain, were seeded on three-dimensional, biodegradable polymer scaffolds and implanted into peritoneal cavity of athymic mice. The cell–scaffold constructs retrieved 4 weeks after implantation formed three-dimensional tissues. Immunohistochemical analyses showed that the tissue reconstructs expressed SM α-actin and SM myosin heavy chain. Masson’s trichrome staining showed the presence of significant amounts of collagen in the tissue reconstructs. Cells labeled with a fluorescent tracer prior to implantation were still present in the tissue reconstructs 4 weeks after implantation. Non-seeded scaffolds (control groups) retrieved 4 weeks after implantation did not exhibit extensive tissue formation. This study demonstrates the potential of BMSCs as an alternative cell source for tissue engineering of SM.ope