• Title/Summary/Keyword: Nuclear Material

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Radioimmunoassay Reagent Survey and Evaluation (검사별 radioimmunoassay시약 조사 및 비교실험)

  • Kim, Ji-Na;An, Jae-seok;Jeon, Young-woo;Yoon, Sang-hyuk;Kim, Yoon-cheol
    • The Korean Journal of Nuclear Medicine Technology
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    • v.25 no.1
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    • pp.34-40
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    • 2021
  • Purpose If a new test is introduced or reagents are changed in the laboratory of a medical institution, the characteristics of the test should be analyzed according to the procedure and the assessment of reagents should be made. However, several necessary conditions must be met to perform all required comparative evaluations, first enough samples should be prepared for each test, and secondly, various reagents applicable to the comparative evaluations must be supplied. Even if enough comparative evaluations have been done, there is a limit to the fact that the data variation for the new reagent represents the overall patient data variation, The fact puts a burden on the laboratory to the change the reagent. Due to these various difficulties, reagent changes in the laboratory are limited. In order to introduce a competitive bid, the institute conducted a full investigation of Radioimmunoassay(RIA) reagents for each test and established the range of reagents available in the laboratory through comparative evaluations. We wanted to share this process. Materials and Methods There are 20 items of tests conducted in our laboratory except for consignment tests. For each test, RIA reagents that can be used were fully investigated with the reference to external quality control report. and the manuals for each reagent were obtained. Each reagent was checked for the manual to check the test method, Incubation time, sample volume needed for the test. After that, the primary selection was made according to whether it was available in this laboratory. The primary selected reagents were supplied with 2kits based on 100tests, and the data correlation test, sensitivity measurement, recovery rate measurement, and dilution test were conducted. The secondary selection was performed according to the results of the comparative evaluation. The reagents that passed the primary and secondary selections were submitted to the competitive bidding list. In the case of reagent is designated as a singular, we submitted a explanatory statement with the data obtained during the primary and secondary selection processes. Results Excluded from the primary selection was the case where TAT was expected to be delayed at the moment, and it was impossible to apply to our equipment due to the large volume of reagents used during the test. In the primary selection, there were five items which only one reagent was available.(squamous cell carcinoma Ag(SCC Ag), β-human chorionic gonadotropin(β-HCG), vitamin B12, folate, free testosterone), two reagents were available(CA19-9, CA125, CA72-4, ferritin, thyroglobulin antibody(TG Ab), microsomal antibody(Mic Ab), thyroid stimulating hormone-receptor-antibody(TSH-R-Ab), calcitonin), three reagents were available (triiodothyronine(T3), Tree T3, Free T4, TSH, intact parathyroid hormone(intact PTH)) and four reagents were available are carcinoembryonic antigen(CEA), TG. In the secondary selection, there were eight items which only one reagent was available.(ferritin, TG, CA19-9, SCC, β-HCG, vitaminB12, folate, free testosterone), two reagents were available(TG Ab, Mic Ab, TSH-R-Ab, CA125, CA72-4, intact PTH, calcitonin), three reagents were available(T3, Tree T3, Free T4, TSH, CEA). Reasons excluded from the secondary selection were the lack of reagent supply for comparative evaluations, the problems with data reproducibility, and the inability to accept data variations. The most problematic part of comparative evaluations was sample collection. It didn't matter if the number of samples requested was large and the capacity needed for the test was small. It was difficult to collect various concentration samples in the case of a small number of tests(100 cases per month or less), and it was difficult to conduct a recovery rate test in the case of a relatively large volume of samples required for a single test(more than 100 uL). In addition, the lack of dilution solution or standard zero material for sensitivity measurement or dilution tests was one of the problems. Conclusion Comparative evaluation for changing test reagents require appropriate preparation time to collect diverse and sufficient samples. In addition, setting the total sample volume and reagent volume range required for comparative evaluations, depending on the sample volume and reagent volume required for one test, will reduce the burden of sample collection and planning for each comparative evaluation.

Study on Radioactive Material Management Plan and Environmental Analysis of Water (II) Study of Management System in Water Environment of Japan (물 환경의 방사성 물질 관리 방안과 분석법에 관한 연구 (II) 일본의 물 환경 방사성물질 관리 체계에 대한 고찰)

  • Han, Seong-Gyu;Kim, Jung-Min
    • Journal of radiological science and technology
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    • v.38 no.3
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    • pp.305-313
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    • 2015
  • After Fukushima Daiichi nuclear disaster in 2011, study and maintenance of monitoring systems have been made at home and abroad. As concerns about radioactive contamination of water have increased in Korea, update of maintenance of managing radioactive materials in water is being made mainly by Ministry of Environment. In this study, we analysed current state of monitoring system modification in Japan, the country directly involved and neighboring country. According to the result, Japan modified the legislations first. Then Ministry of Education, Culture, Sports, Science and Technology (MEXT) provides theoretical background of radiological monitoring. And Ministry of the Environment actually watches state of water pollution in public waters and underground water. Finally related agencies like local government are monitoring current state of radioactive contamination in water environment. By region, local monitoring stations share the investigation of the whole country. Also, additional monitoring is running around nuclear facilities. After Fukushima disaster, monitoring for area near Fukushima is added. Among the reference levels, management target value of drinking water and tap water is 10 Bq/kg, and those of public water and underground water are 1 Bq/L. Measuring intervals varied from every hour to once a year, regularly or irregularly depending on the investigation. The main measuring items are air dose rate, gross ${\alpha}$, gross ${\beta}$, ${\gamma}$ radionuclide, Cs-134, Cs-137, Sr-89, Sr-90, I-131, and so on. In comparison, regulations about general public water in Korea need to be modified, while those about area near nuclear facility and drinking water are organized well. In future, therefore, domestic system would be expected to be modified with making reference to the guidelines like WHO's one. As good case of applying international guideline to domestic environment, Japanese system could be a reference when general standard of radioactivity in public water is made in Korea.

Approach to improve construction management using Information Technology (IT) (정보기술(IT) 기반을 통한 시공관리 선진화 방안)

  • Lee Woo-Bang;Moon Jin-Yeong;Moon Byeong-Suk
    • Proceedings of the Korean Institute Of Construction Engineering and Management
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    • autumn
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    • pp.115-122
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    • 2002
  • There is various points that should be improved in Fairness such as our contract practice to propose construction projects, project managing and the stakeholders' way of thinking and culture. We consider that the revision of construction related provisions and systems is required but even more, an overall change in business management through the implementation of Integrated Construction Information Management System that will enable the owner, which drives the project, and contractor sharing construction information is required. To mange construction related information in an integrated manner, designing information should be smoothly transferred to purchasing information, and changes are required in order to move ahead to process-oriented work system. Finally information created from various construction organizations should be delivered in an aligned and standardized manner as well. The domestic Nuclear Power Plant Construction has been accepting various technology transfers from U.S, France, Canada and UK, which enabled us to self-support technology and recently even proceeded to the phase exporting our technology to others. However, continuous effort is required to improve internal business efficiency and to respond to external environmental change such aselectricity market deregulation. Recently, in accordance with the result in number of CEO's intention to make progress in IT and improve business efficiency, the number of enterprises introducing Enterprise Resource Planning is increasing. ERP is an innovative tool which changes the way of performing work from organization and department orientation to process-orientation in order to optimize the resources, such as human and material resources, through out the Enterprise by performing BPR which will maximize overall business efficiency of the enterprise, such includes not only construction management, but also business management. KHNP continued to performing large scaled construction projects such as nuclear power plant construction for past 30 years and took the initiatives of large scale project management and Quality management ability in domestic industry by having independent capability of over all construction planning, purchasing and, construction and start up management etc. To maintain our leading position of improving construction management technology based on our accumulated project management experience and technology, KHNP included construction into our ERP project in purpose of innovating construction business. We would like to discuss the characteristics of nuclear construction business, project management system, information system infrastructure and information sharing system among construction related entities, and implementation practices for information system, and consider how to resolve our practice that should be improved in this thesis.

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Anti-Oxidative and Anti-Inflammatory Activities of Euptelea Pleiosperma Ethanol Extract (Euptelea pleiosperma 에탄올 추출물의 항산화 및 항염증 활성)

  • Jin, Kyong-Suk;Park, Jung Ae;Lee, Ji Young;Kang, Ji Sook;Kwon, Hyun Ju;Kim, Byung Woo
    • Microbiology and Biotechnology Letters
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    • v.42 no.2
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    • pp.170-176
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    • 2014
  • In this study, the anti-oxidative and anti-inflammatory activities of Euptelea pleiosperma ethanol extract (EPEE) were evaluated using in vitro assays and cell culture model systems. EPEE possessed a more potent scavenging activity against 1,1-diphenyl-2-picryl hydrazyl than the ascorbic acid used as a positive control. EPEE effectively suppressed lipopolysaccharide (LPS), in addition to hydrogen peroxide induced reactive oxygen species on RAW 264.7 cells. Furthermore, EPEE induced the expression of the anti-oxidative enzyme heme oxygenase 1 (HO-1) and its upstream transcription factor, nuclear factor-E2-related factor 2 (Nrf2), dose and time dependently. The modulation of HO-1 and Nrf2 expression might be regulated by mitogen-activated protein kinases and phosphatidyl inositol 3 kinase/Akt as their upstream signaling pathways. On the other hand, EPEE inhibited LPS induced nitric oxide (NO) formation without cytotoxicity. Suppression of NO formation was the result of the down regulation of inducible NO synthase (iNOS) by EPEE. Suppression of NO and iNOS by EPEE may be modulated by their upstream transcription factor, nuclear factor ${\kappa}B$, and AP-1 pathways. Taken together, these results provide important new insights into E. pleiosperma, namely that it possesses anti-oxidative and anti-inflammatory activities, indicating that it could be utilized as a promising material in the field of nutraceuticals.

A Review of the Influence of Sulfate and Sulfide on the Deep Geological Disposal of High-level Radioactive Waste (고준위방사성폐기물 심층처분에 미치는 황산염과 황화물의 영향에 대한 고찰)

  • Jin-Seok Kim;Seung Yeop Lee;Sang-Ho Lee;Jang-Soon Kwon
    • Economic and Environmental Geology
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    • v.56 no.4
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    • pp.421-433
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    • 2023
  • The final disposal of spent nuclear fuel(SNF) from nuclear power plants takes place in a deep geological repository. The metal canister encasing the SNF is made of cast iron and copper, and is engineered to effectively isolate radioactive isotopes for a long period of time. The SNF is further shielded by a multi-barrier disposal system comprising both engineering and natural barriers. The deep disposal environment gradually changes to an anaerobic reducing environment. In this environment, sulfide is one of the most probable substances to induce corrosion of copper canister. Stress-corrosion cracking(SCC) triggered by sulfide can carry substantial implications for the integrity of the copper canister, potentially posing a significant threat to the long-term safety of the deep disposal repository. Sulfate can exist in various forms within the deep disposal environment or be introduced from the geosphere. Sulfate has the potential to be transformed into sulfide by sulfate-reducing bacteria(SRB), and this converted sulfide can contribute to the corrosion of the copper canister. Bentonite, which is considered as a potential material for buffering and backfilling, contains oxidized sulfate minerals such as gypsum(CaSO4). If there is sufficient space for microorganisms to thrive in the deep disposal environment and if electron donors such as organic carbon are adequately supplied, sulfate can be converted to sulfide through microbial activity. However, the majority of the sulfides generated in the deep disposal system or introduced from the geosphere will be intercepted by the buffer, with only a small amount reaching the metal canister. Pyrite, one of the potential sulfide minerals present in the deep disposal environment, can generate sulfates during the dissolution process, thereby contributing to the corrosion of the copper canister. However, the quantity of oxidation byproducts from pyrite is anticipated to be minimal due to its extremely low solubility. Moreover, the migration of these oxidized byproducts to the metal canister will be restricted by the low hydraulic conductivity of saturated bentonite. We have comprehensively analyzed and summarized key research cases related to the presence of sulfates, reduction processes, and the formation and behavior characteristics of sulfides and pyrite in the deep disposal environment. Our objective was to gain an understanding of the impact of sulfates and sulfides on the long-term safety of high-level radioactive waste disposal repository.

Relationship between Compressive Strength and Dynamic Modulus of Elasticity in the Cement Based Solid Product for Consolidating Disposal of Medium-Low Level Radioactive Waste (중·저준위 방사성 폐기물 처리용 시멘트 고화체의 압축강도와 동탄성계수의 관계)

  • Kim, Jin-Man;Jeong, Ji-Yong;Choi, Ji-Ho;Shin, Sang-Chul
    • Journal of the Korea Concrete Institute
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    • v.25 no.3
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    • pp.321-329
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    • 2013
  • Recently, the medium-low level radioactive waste from nuclear power plant must be transported from temporary storage to the final repository. Medium-low level radioactive waste, which is composed mainly of the liquid ion exchange resin, has been consolidated with cementitious material in the plastic or iron container. Since cementitious material is brittle, it would generate cracks by impact load during transportation, signifying leakage of radioactive ray. In order to design the safety transporting equipment, there is a need to check the compressive strength of the current waste. However, because it is impossible to measure strength by direct method due to leakage of radioactive ray, we will estimate the strength indirectly by the dynamic modulus of elasticity. Therefore, it must be identified the relationship between of strength and dynamic modulus of elasticity. According to the waste acceptance criteria, the compressive strength of cement based solid is defined as more than 3.44 MPa (500 psi). Compressive strength of the present solid is likely to be significantly higher than this baseline because of continuous hydration of cement during long period. On this background, we have tried to produce the specimens of the 28 day's compressive strength of 3 to 30 MPa having the same material composition as the solid product for the medium-low level radioactive waste, and analyze the relationship between the strength and the dynamic modulus of elasticity. By controling the addition rates of AE agent, we made the mixture containing the ion exchange resin and showing the target compressive strength (3~30 MPa). The dynamic modulus of elasticity of this mixtures is 4.1~10.2 GPa, about 20 GPa lower in the equivalent compressive strength level than that of ordinary concrete, and increasing the discrepancy according to increase strength. The compressive strength and the dynamic modulus of elasticity show the liner relationship.

A Study on the Knowledge and Attitude about Tuberculosis on Elementary School student in Seoul (서울 시내 일부 국민학교 6학년 학생들의 결핵에 대한 지식 및 실태에 관한 연구)

  • Kim, Eun-Hee
    • Research in Community and Public Health Nursing
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    • v.5 no.2
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    • pp.181-202
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    • 1994
  • This study was conducted in order to grasp the condition of the student's knowledge and attitude about tuberculosis. And to offer the basic materials for the prevent tuberculosis in elementary school. The objects were comprised 395 of volunteered 6th grade students who study in two elementary schools. The material of this study was the questionaire(chronbach $\alpha=.9016$) suited to the purposed of this research which has been made through studying references. All the questionaire were collected immediately without explanation. The data was collected from 13rd to 25th of May on 1994. Analysis of the data was done utilizing SPSS for percentage, mean, ANOVA and pearson-Correlation Coefficient. The Result are as follows; 1. General features of the objects of study. Sex distribution was similar. Salary of 1000-1500 thousand won were highest (40.2%), nuclear family was highest (87.1%), fathers of graduated high school were the highest(44.0%), mothers of graduated high school were the highest(56.8%). And there was nobody about tuberculosis patient in one's close relatives were highest(95.4%). 2. The conditions of attitude about tuberculosis. Having experience of tuberculin test were highest(59.0%). Less than 9mm indulation among the tuberculin tested group were 85.1%, more than indulation were 14.9%. Have a B. C. G. injection among the less than 9mm indulation were 83.2%. Leave alone among the more than 10mm indulation were 56.0%. Think it too much trouble to do not tuberculine test were 63.0%. Do not take a chest X-ray in the past were 60.3%. And take a chest X-ray in the past were 39.7%. Health educated group was 74.3%. If tuberculosis sign was developed, notified to parent was 73.8%. 3. The condition of knowledge about tuberculosis. When 5 points was given to 'very affiming' and 1 point was given to 'very deny', the total average was 3.54. And symptom of tuberculosis secion was 3.67, vaccination of tuberculosis section was 3.66, tuberculine test section was 3.56, epidemiology of tuberculosis section was 3.54, infection of tuberculosis section was 3.38. And every section showed affirmative correlation(P<.001). 4. Correlation between the general features and attitude variables. High incomed group may have more attitude on tuberculin test than low incomed group($x^2=16.$ 190, P<.01). High educated group may have more attitude on tuberculin test than low educated group(Father : $x^2=28.530$, P<.001, Mother: $x^2=26.060$, P<.001). High educated group may have more attitude on health education than low educated group(Father: $x^2=20.$ 767, P<.000, Mother: $x^2=10.639$, P<.05). Nuclear family may have more attitude on notify to parent than others($x^2=51.45$, P<.000). Tuberculosis patient in one's close associates have more attitude on notify to parent than others($x^2=51.$ 45, P<.000). 5. Difference between the general features and knowledge of tuberculosis. High incomed group were highest score in knowledge (F=3.99, P<.01). High educated group were highest score in knowledge(Father : F=8.81, P<.000, Mother: F=9.09, P<.000). 6. Difference between the attitude and knowledge of tuberculosis. Tuberculin tested group were highest score in knowledge(t=9.88, P<.000). Taken chest X-ray group were highest score in knowledge (t=2.07, P<.05). Received health education group were highest score in knowledge(t=6.83, P<.000). Notified symptoms to teachers and parent group were highest score in knowledge(F=3.89, P<.01).

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Immunohistochemical Expression of Nuclear Retinoid Receptor and CREB(cAMP Response Element Binding Protein) in Lung Cancers (폐암종에서 Nuclear Retinoid Receptor 및 CREB의 면역조직화학적 발현 양상)

  • Shin, Jong Wook;Gi, Seung-Seok;Paik, Kwang Hyun;Choi, Won;Park, In Won;Kim, Mi Kyung
    • Tuberculosis and Respiratory Diseases
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    • v.59 no.6
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    • pp.631-637
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    • 2005
  • Background : Transcriptional factors of the CREB(cAMP Response Element Binding Protein) are involved in the regulation of gene expression in response to a variety of signaling pathways. Proteins produced by the CREB genes play key roles in many physiological processes, including memory and long-term potentiation. The retinoic acid receptor (RAR) axis mediates epithelial cell differentiation and proliferation in many tissues including the lung. Material and method : The RAR and CREB expression levels were examined in 60 adenocarcinomas and 60 squamous cell carcinomas of the lung using immunohistochemical staining. Results : 1) RAR protein expression was found in 58.3%(35/60) of adenocarcinomas and 36.7%(22/60) of squamous cell carcinomas(P<0.05). 2) RAR protein expression was found in 80%(16/20) of well differentiated adenocarcinomas, 60%(12/20) of moderately differentiated adenocarcinomas, and 35%(7/20) of poorly differentiated adenocarcinomas (P<0.01). 3) RAR protein expression was found in 45%(9/20) of well differentiated squamous cell carcinomas, 35%(7/20) of moderately differentiated squamous cell carcinomas, and 30%(6/20) of poorly differentiated squamous cell carcinomas (P>0.05). 4) CREB expression was found in 61.7%(37/60) of adenocarcinomas and 40%(24/60) of squamous cell carcinomas( P<0.05). 5) CREB expression was found in 85%(17/20) of well differentiated adenocarcinomas, 60%(12/20) of moderately differentiated adenocarcinomas, and 40%(8/20) of poorly differentiated adenocarcinomas (P<0.01). 6) CREB expression was found in 45%(9/20) of well differentiated squamous cell carcinomas, 35%(7/20) of moderately differentiated squamous cell carcinomas, and 35%(8/20) of poorly differentiated squamous cell carcinomas(P>0.05). 7) RAR and CREB expression was found in 68.5% of lung cancers, and there was a significant correlation between them(P<0.05). Conclusion : RAR and CREB expression can be used to indirectly determine the malignant potentiality of a cell.

Effect of Steviol β-Glucopyranosyl Ester on The Production of Nitric Oxide and Inflammatory Cytokines in RAW 264.7 Cells (Steviol β-Glucopyranosyl Ester가 RAW 264.7 세포의 산화질소 및 염증성 사이토카인 생성에 미치는 영향)

  • Jung, Heehoon;Cho, Uk Min;Hwang, Hyung Seo;Cho, Kun;Lee, Sang Rin;Kim, Moo Sung
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.44 no.3
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    • pp.239-247
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    • 2018
  • Chronic inflammation is known to have effects on various diseases such as gout, cancer, dementia, atopic disease, and obesity. In addition, since some signal cascades involved in the development of inflammation are known to affect the damage and aging of the skin tissue, studies are being conducted actively to control the inflammation mechanism. In order to mitigate or prevent inflammatory response, a number of researches have been made to develop anti-inflammatory materials from some plants. In particular, Stevia rebaudiana produces steviol glycosides (SG), a natural sweetener with a distinctive flavor. Studies on some of SG have been shown to have anti-inflammatory activity. Researchers of this study expected that more SG also possess anti-inflammatory activity, besides stevioside, rebaudioside A, and steviol. In order to confirm this possibility, the researchers screened inhibition activity of various steviol glucosides for NO production in RAW 264.7 cell lines. As a result, steviol ${\beta}-glucopyranosyl$ ester (SGE) showed the highest inhibitory activity among steviol derivatives treated at the same molar concentration. In addition, we found that mRNA expression level of $interleukin-1{\alpha}$ ($IL-1{\alpha}$), $interleukin-1{\beta}$ ($IL-1{\beta}$), cyclooxygenase-2 (COX-2), nuclear factor kappa-light chain-enhancer of activated B cells ($NF-{\kappa}B$) and inducible nitric oxide synthase (iNOS) was also decreased in a dose-dependent manner. These results show that SGE inhibits anti-inflammatory activity and NO production in mouse macrophage RAW 264.7 cells. It was confirmed that SGE has potential to be applied as an anti-inflammatory material.

Mammalian Cloning by Nuclear transfer, Stem Cell, and Enzyme Telomerase (핵치환에 의한 cloning, stem cell, 그리고 효소 telomerase)

  • 한창열
    • Korean Journal of Plant Tissue Culture
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    • v.27 no.6
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    • pp.423-428
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    • 2000
  • In 1997 when cloned sheep Dolly and soon after Polly were born, it had become head-line news because in the former the nucleus that gave rise to the lamb came from cells of six-year-old adult sheep and in the latter case a foreign gene was inserted into the donor nucleus to make the cloned sheep produce human protein, factor IX, in e milk. In the last few years, once the realm of science fiction, cloned mammals especially in livestock have become almost commonplace. What the press accounts often fail to convey, however, is that behind every success lie hundreds of failures. Many of the nuclear-transferred egg cells fail to undergo normal cell divisions. Even when an embryo does successfully implant in the womb, pregnancy often ends in miscarriage. A significant fraction of the animals that are born die shortly after birth and some of those that survived have serious developmental abnormalities. Efficiency remains at less than one % out of some hundred attempts to clone an animal. These facts show that something is fundamentally wrong and enormous hurdles must be overcome before cloning becomes practical. Cloning researchers now tent to put aside their effort to create live animals in order to probe the fundamental questions on cell biology including stem cells, the questions of whether the hereditary material in the nucleus of each cell remains intact throughout development, and how transferred nucleus is reprogrammed exactly like the zygotic nucleus. Stem cells are defined as those cells which can divide to produce a daughter cell like themselves (self-renewal) as well as a daughter cell that will give rise to specific differentiated cells (cell-differentiation). Multicellular organisms are formed from a single totipotent stem cell commonly called fertilized egg or zygote. As this cell and its progeny undergo cell divisions the potency of the stem cells in each tissue and organ become gradually restricted in the order of totipotent, pluripotent, and multipotent. The differentiation potential of multipotent stem cells in each tissue has been thought to be limited to cell lineages present in the organ from which they were derived. Recent studies, however, revealed that multipotent stem cells derived from adult tissues have much wider differentiation potential than was previously thought. These cells can differentiate into developmentally unrelated cell types, such as nerve stem cell into blood cells or muscle stem cell into brain cells. Neural stem cells isolated from the adult forebrain were recently shown to be capable of repopulating the hematopoietic system and produce blood cells in irradiated condition. In plants although the term$\boxDr$ stem cell$\boxUl$is not used, some cells in the second layer of tunica at the apical meristem of shoot, some nucellar cells surrounding the embryo sac, and initial cells of adventive buds are considered to be equivalent to the totipotent stem cells of mammals. The telomere ends of linear eukaryotic chromosomes cannot be replicated because the RNA primer at the end of a completed lagging strand cannot be replaced with DNA, causing 5' end gap. A chromosome would be shortened by the length of RNA primer with every cycle of DNA replication and cell division. Essential genes located near the ends of chromosomes would inevitably be deleted by end-shortening, thereby killing the descendants of the original cells. Telomeric DNA has an unusual sequence consisting of up to 1,000 or more tandem repeat of a simple sequence. For example, chromosome of mammal including human has the repeating telomeric sequence of TTAGGG and that of higher plant is TTTAGGG. This non-genic tandem repeat prevents the death of cell despite the continued shortening of chromosome length. In contrast with the somatic cells germ line cells have the mechanism to fill-up the 5' end gap of telomere, thus maintaining the original length of chromosome. Cem line cells exhibit active enzyme telomerase which functions to maintain the stable length of telomere. Some of the cloned animals are reported prematurely getting old. It has to be ascertained whether the multipotent stem cells in the tissues of adult mammals have the original telomeres or shortened telomeres.

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