• Journal of the speleological society of Korea
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• v.41 no.1
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• pp.16-26
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• 1994

Karst in Korean peninsula is not widely known. Since karst studies had been initiated a few hundred years ago based on the historic records “Dong Guck Ye Jee Seoung Lam” and “Sae Jong Sill Rok Gee Ri Jee” (1993, Oh), modern caverns during the 60s have inactively started to search on the karst phenomena to the eastern mountaineious areas.(omitted)

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.20-20
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• 2017

Plant genomes include heterochromatic loci that consist of repetitive sequences and transposable elements. LTR retrotransposon is the major class of transposons in advanced plants in terms of proportion in plant genome. The elements contribute not only to genome size but also to genome stability and gene expression. A number of cases have been reported transposon insertions near genic regions affect crop traits such as fruit pigments, stress tolerance, and yields. Functional LTR retrotransposons produce extrachromosomal DNA from genomic RNA by reverse transcription that takes place within virus-like-particles (VLPs). DECREASED DNA METHYLATION 1 (DDM1) plays important roles in maintaining DNA methylation of heterochromatin affecting all sequence contexts, CG, CHG, and CHH. Previous studies showed that ddm1 mutant exhibits massive transcription of retrotransposons in Arabidopsis, but only few of them were able to create new insertions into the genome. RNA-dependent RNA POLYMERASE 6 (RDR6) is known to function in restricting accumulation of transposon RNA by processing the transcripts into 21-22 nt epigenetically activated small interfering RNA (easiRNA). We purified VLPs and sequence cDNA to identify functional LTR retrotransposons in Arabidopsis ddm1 and ddm1rdr6 plants. Over 20 LTR copia and gypsy families were detected in ddm1 and ddm1rdr6 sequencing libraries and most of them were not reported for mobility. In ddm1rdr6, short fragments of ATHILA gypsy elements were detected. It suggests easiRNAs might regulate reverse transcription steps. The highest enriched element among transposon loci was previously characterized EVADE element. It has been reported that active EVADE element is more efficiently silenced through female germline than male germline. By genetic analyses, we found ddm1 and rdr6 mutation affect maternal silencing of active EVADE elements. DDM1-GFP protein accumulated in megaspore mother cell but was not found in mature egg cell. The fusion protein was also found in early embryo and maternal DDM1-GFP allele was more dominantly expressed in the embryo. We observed localization of DDM1-GFP in Arabidopsis and DDM1-YFP in maize and found the proteins accumulated in dividing zone of root tips. Currently we are looking at cell cycle dependency of DDM1 expression using maize system. Among 10 AGO proteins in Arabidopsis, AGO9 is specifically expressed in egg cell and shoot meristematic cells. In addition, mutation of AGO9 and RDR6 caused failure in maternal silencing, implying 21-22 nt easiRNA pathway is important for retrotransposon silencing in female gametophyte or/and early embryo. On the other hand, canonical 24 nt sRNA-directed DNA methylation (RdDM) pathways did not contribute to maternal silencing as confirmed by this study. Heat-activated LTR retrotransposon, ONSEN, was not silenced by DDM1 but the silencing mechanisms require RdDM pathways in somatic cells. We will propose distinct mechanisms of LTR retrotransposons in germline and somatic stages.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.97-97
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• 2017

Plant genomes include heterochromatic loci that consist of repetitive sequences and transposable elements. LTR retrotransposon is the major class of transposons in advanced plants in terms of proportion in plant genome. The elements contribute not only to genome size but also to genome stability and gene expression. A number of cases have been reported transposon insertions near genic regions affect crop traits such as fruit pigments, stress tolerance, and yields. Functional LTR retrotransposons produce extrachromosomal DNA from genomic RNA by reverse transcription that takes place within virus-like-particles (VLPs). DECREASED DNA METHYLATION 1 (DDM1) plays important roles in maintaining DNA methylation of heterochromatin affecting all sequence contexts, CG, CHG, and CHH. Previous studies showed that ddm1 mutant exhibits massive transcription of retrotransposons in Arabidopsis, but only few of them were able to create new insertions into the genome. RNA-dependent RNA POLYMERASE 6 (RDR6) is known to function in restricting accumulation of transposon RNA by processing the transcripts into 21-22 nt epigenetically activated small interfering RNA (easiRNA). We purified VLPs and sequence cDNA to identify functional LTR retrotransposons in Arabidopsis ddm1 and ddm1rdr6 plants. Over 20 LTR copia and gypsy families were detected in ddm1 and ddm1rdr6 sequencing libraries and most of them were not reported for mobility. In ddm1rdr6, short fragments of ATHILA gypsy elements were detected. It suggests easiRNAs might regulate reverse transcription steps. The highest enriched element among transposon loci was previously characterized EVADE element. It has been reported that active EVADE element is more efficiently silenced through female germline than male germline. By genetic analyses, we found ddm1 and rdr6 mutation affect maternal silencing of active EVADE elements. DDM1-GFP protein accumulated in megaspore mother cell but was not found in mature egg cell. The fusion protein was also found in early embryo and maternal DDM1-GFP allele was more dominantly expressed in the embryo. We observed localization of DDM1-GFP in Arabidopsis and DDM1-YFP in maize and found the proteins accumulated in dividing zone of root tips. Currently we are looking at cell cycle dependency of DDM1 expression using maize system. Among 10 AGO proteins in Arabidopsis, AGO9 is specifically expressed in egg cell and shoot meristematic cells. In addition, mutation of AGO9 and RDR6 caused failure in maternal silencing, implying 21-22 nt easiRNA pathway is important for retrotransposon silencing in female gametophyte or/and early embryo. On the other hand, canonical 24 nt sRNA-directed DNA methylation (RdDM) pathways did not contribute to maternal silencing as confirmed by this study. Heat-activated LTR retrotransposon, ONSEN, was not silenced by DDM1 but the silencing mechanisms require RdDM pathways in somatic cells. We will propose distinct mechanisms of LTR retrotransposons in germline and somatic stages.

• Korean Journal of Head & Neck Oncology
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• v.23 no.1
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• pp.41-45
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• 2007

A 60 years old female patient presented with $8{\times}6\;cm$ sized painless oval mass in the left parietal region. She had left lobectomy of thyroid gland 10 years ago. Cranial CT, MRI, FGD PET-CT showed a solid mass which invaded left parietal bone. After embolization, craniectomy with tumor excision was performed. Histological examination revealed metastatic follicular cancer originated thyroid gland, with vascular and dura invasion. Postoperatively, neck CT showed right thyroid multiple nodules and right level III multiple lymph node enlargement. Thyroid function test was normal, but level of thyroglobulin was high (72ng/ml). So she had right lobectomy of thyroid gland with lymph node dissection under a diagnosis of follicular carcinoma. But histological examination revealed adenomatous hyperplasia and not lymph node metastasis. After operation, she received radioiodine therapy of 150mCi and then the level of thyroglobulin normalized (8.4ng/ml). The patient is under follow-up since she had operation 4 months ago.

• Journal of Chest Surgery
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• v.29 no.1
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• pp.115-119
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• 1996

Malignant fibrous histiocytoma after radiation therapy is very rare and its prognosis is poor. A 52-year-old male patient was admitted due to painful mass at the sternal area which developed 6 months ago. The patient had a history of radiation therapy for esophageal cancer 5 years ago. The incisional biopy disclosed sternal sarcoma. In spite of 5 cycles of chemotherapy, the m ss progressively enlarged, and an operation was performed. Total sternectomy with overlying skin and postal cartilage was performed and reconstruction was carried out with autologous rib bone graft, bilateral pectoralis klajor muscle flap and skin graft. The microscopic examination was consistent with malignant fibrous histiocytoma. The postoperative course was uneventful and the patient was discharged on postoperative 36 day.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.277-280
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• 2006

Many industrial fields were constructed on the reclaimed land which was used to be a tidal land. Because the industrial fields stand on weak basement, they are likely to be influenced by surface subsidence. Therefore, the surface subsidence monitoring is required for civil protection. In this study, a novel method to monitor land displacement, PSInSAR technique, was applied to monitor the land subsidence of Incheon Port, which happened a decade ago. Although the land was reclaimed more than 20 years ago, quite a bit of deformation was observed during six years. The maximum subsidence rate reached to 30 mm/year. JERS-1 data was exploited in this study.

• Korean Journal of Veterinary Research
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• v.47 no.1
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• pp.135-138
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• 2007

A 3 year-old female Afghan hound came to the Veterinary Referral Hospital of the College of Veterinary Medicine, Seoul National University for artificial insemination (AI) with frozen semen. In order to inseminate, semen was frozen in USA 3 years ago. Frozen semen was sent by air from Santiago to Seoul for AI. The stud died 2 years ago, so we could only use a limited amount of frozen semen in that estrus cycle. The number of total motile spermatozoa was $59.4{\times}10^6$and the total volume was 1.2 ml. The frozen spermatozoa were thawed in $70^{\circ}C$ water for 8 sec, which were then deposited at the bilateral uterine horns by a surgical method. The number of corpus luteum was 6. Sixty days after artificial insemination resulted in the birth of 4 puppies, all of which are alive and healthy.

• The Journal of the Korean bone and joint tumor society
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• v.18 no.1
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• pp.32-36
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• 2012

A 56 year-old female presented with dysphagia 8 weeks ago and newly developed dysphonia 2 weeks ago. The radiology study and swallowing difficulty evaluation study revealed the esophagus and the posterior wall of the laryngopharynx to be severely compressed by the mass of the anterior $4^{th}$ and $5^{th}$ vertebral body of cervical spine. En bloc excisional biopsy of the bony mass was performed, which completely resolved the clinical symptoms. We report a rare case of osteochondroma occurring at the anterior portion of cervical spine leading to dysphasia and dysphonia with a review of relevant literature.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.1
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• pp.69-73
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• 2018

Korean-peacekeeper's transparent armors in Iraq showed delamination, cracking and clouding a decade ago. And there were also similar deterioration recurrences in KLTV during the operational test a few years ago. Also, the differences between operational capability & lab Bullet-proof test condition, and insufficiency of military protection spec resulted in incomplete bullet-proof results. Moreover, although so many ground weapon systems have been developed, there were not secure test & evaluation codes to verify transparent armoured glasses equal to advanced-overseas products. So in this study, first, environmental test codes were established that all tests should be carried out as the application of only one specimen with newly adopted thermal shock test instead of completing each test with different one. Second, protection standards were integrated through the analysis of global developed country's specifications and reinforced as adding to the real mock-up condition if vehicle's glasses are smaller than standard specimen. Hereby, by applying to test-codes which including actual operational & vehicular conditions, the gap between development test and operational environment was minimized.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.1
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• pp.1-2
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• 2023

2-Bromopropane, a causative chemical that caused the outbreak of reproductive toxicity 28 years ago, was classified as Group 2A in the recently held IARC monograph 133 meeting. Korean research data were used as supporting data in the carcinogenicity evaluation of 2-bromopropane and other carcinogens. I would like to share my memories with the researchers at the Occupational Safety and Health Research Institute who worked hard to identify the cause.