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Environmental exposure of heavy metal (lead and cadmium) and hearing loss
Gu Hyeok Kang,Jun Young Uhm,Young Gon Choi,Eun Kye Kang,Soo Young Kim,Won Oh Choo,Seong Sil Chang 대한직업환경의학회 2018 대한직업환경의학회지 Vol.30 No.-
Background: Lead and cadmium have been identified as risk factors for hearing loss in animal studies, but largescale studies targeting the general human population are rare. This study was conducted to investigate the link between heavy metal concentrations in blood and hearing impairment, using a national population-based survey. Methods: The study participants comprised 6409 Koreans aged 20 or older, who were included in the Fifth and Sixth Korea National Health and Nutrition Examination Surveys (KNHANES 2010–2013). Hearing impairment was categorized into two types, low- and high-frequency hearing impairment, using pure tone audiometry. Lowfrequency hearing impairment was defined as having a binaural average of hearing thresholds for 0.5, 1, and 2 kHz exceeding 25 dB, and high-frequency hearing impairment was defined as having a binaural average of hearing thresholds for 3, 4, and 6 kHz exceeding 25 dB. The blood levels of heavy metals (lead and cadmium) were classified into quartiles. Cross-sectional association between hearing impairment and the level of heavy metals (lead and cadmium) was examined in both sexes. Multivariate logistic regression was used to obtain adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Results: Among men, the prevalence of low- and high- frequency hearing impairment was 13.9% and 46.7%, respectively, which was higher than the prevalence among women (11.8% and 27.0%, respectively). Regarding lead, the adjusted OR of high-frequency hearing impairment for the highest blood level group versus the lowest group was significant in both men (OR = 1.629, 95% CI = 1.161-2.287) and women (OR = 1.502, 95% CI = 1.027-2.196), after adjusting for age, body mass index, education, smoking, alcohol consumption, exercise, diagnosis of diabetes mellitus, hypertension, and noise exposure (occupational, loud, firearm noises). No links were found between blood lead levels and low-frequency hearing impairment, or between blood cadmium levels and low- or high-frequency hearing impairment in either sex. Conclusions: The present study findings suggest that even exposure to low-level lead is a risk factor for highfrequency hearing loss. A prospective epidemiologic study should be conducted to identify the causal relationship between human health and exposure to heavy metals, and efforts to reduce heavy metal exposure in the general population should continue.
탄소나노튜브 및 마이크로 글래스 버블 기반 열전 복합재
강구혁 ( Gu-hyeok Kang ),성광원 ( Kwang Won Seong ),김명수 ( Myung Soo Kim ),김인국 ( In Guk Kim ),방인철 ( In Cheol Bang ),박형욱 ( Hyung Wook Park ),박영빈 ( Young-bin Park ) 한국복합재료학회 2015 Composites research Vol.28 No.2
본 논문에서는 탄소나노튜브(CNT)와 마이크로 글래스 버블(GB)을 포함한 폴리아마이드 6(PA6) 복합재의 열전 특성을 다뤘다. 복합재에 포함된 GB은 복합재 내에서 큰 공간을 차지하게 되는데, 이때 CNT는 GB가 없는 공간으로 밀려나면서 고밀도로 격리된(segregated) 네트워크를 형성한다. CNT의 분산을 위해, 소니케이션(Sonicatoin)으로 CNT를 분산시킨 PA6, 포름산 용액을 증류수를 이용하여 응고시킨 후 압축성형하여 복합재 판을 제조하였다. 복합재 판의 열전성능을 평가하기 위해서 열전도도, 전기전도도, 제벡계수(Seebeck coefficient) 등을 측정하였고, 최고 0.016의 성능지수를 얻었다. In this paper, carbon nanotubes (CNTs) and micro glass bubbles (GBs) have been incorporated into a polyamide6 (PA6) matrix to impart thermoelectric properties. The spaces created in the matrix by GBs allows the formation of “segregated” CNT network. The tightly bound CNT network, if controlled properly, can serve as a conductive path for electron transport, while prohibiting phonon transport, which would provide an ideal configuration for thermoelectric applications. The CNTs and GBs were dispersed in a nylon-formic acid solution using horn sonication followed by coagulation in deionized water, and nanocomposite panels were fabricated using a hot press. The performance of nanocomposite panels was evaluated from thermal and electrical conductivities and Seebeck coefficient, and a thermoelectric figure of merit as high as 0.016 was achieved.
Gu Min KANG,Jin Sol KIM,Jun Hyeok LIM 국제과학영재학회 2015 APEC Youth Scientist Journal Vol.7 No.1
Magnesium alloy is a light material but has a strong characteristic. However, its high corrosive and monotonous color interrupts the magnesium alloy from commercialization. In this research we have studied the process of improving magnesium corrosion and its esthetic function. After the process for cleaning and etching, the magnesium alloy was put on a panel and ultrapure water on Teflon airtight container, and then heated in a specific condition. After that, the change of color at the surface was observed. It was found out that the surface color changed after it was heated in a dye. Besides, Lauric acid is widely known in improving the hydrophobic property. We observed it on a specific condition, and the result shows that higher contact angle appeared above the surface when it was heated in high temperatures and for longer times. Subsequently it improved its higher hydrophobicity. The tensile strength was measured by 11.0 Mpa in this result. It was found that this research can be used as a basic data on the development of magnesium components and materialize color.
Post-translational modification of OCT4 in breast cancer tumorigenesis
Cho, Yunhee,Kang, Hyeok Gu,Kim, Seok-Jun,Lee, Seul,Jee, Sujin,Ahn, Sung Gwe,Kang, Min Jueng,Song, Joon Seon,Chung, Joon-Yong,Yi, Eugene C.,Chun, Kyung-Hee Nature Publishing Group 2018 CELL DEATH AND DIFFERENTIATION Vol. No.
<P>Recurrence and drug resistance of breast cancer are still the main reasons for breast cancer-associated deaths. Cancer stem cell (CSC) model has been proposed as a hypothesis for the lethality of breast cancer. Molecular mechanisms underlying CSC maintenance are still unclear. In this study, we generated mammospheres derived from breast cancer MDA-MB231 cells and MCF7 cells to enrich CSCs and performed DNA microarray analysis. We found that the expression of carboxy terminus of HSP70-interacting protein (CHIP) E3 ubiquitin ligase was significantly downregulated in breast CSCs. CHIP depletion increased mammosphere formation, whereas CHIP overexpression reversed this effect. We identified interactomes by mass spectrometry and detected CHIP directly interacted with OCT4, a stemness factor. CHIP overexpression decreased OCT4 stability through proteasomal degradation. CHIP induced OCT4 ubiquitination, whereas H260Q, a catalytic CHIP mutant, did not. Interestingly, we determined that OCT4 was ubiquitinated at lysine 284, and CHIP overexpression did not degrade K284R mutant OCT4. CHIP overexpression decreased the proliferation and side population of breast cancer cells, but these were not occurred in K284R mutant OCT4 overexpressed cells. Only 1000 cells showing CHIP depletion or OCT4 overexpression sufficiently generated breast tumors and lung metastases in xenografted mice. Ubiquitination-defective mutant of OCT4(K284R) overexpressed cells drastically generated tumor burdens in mice. Patients with breast cancer who showed low CHIP expression had poor survival probability. Taken together, we suggest that CHIP-induced OCT4 ubiquitination is important in breast CSCs. Regulation of CHIP expression and OCT4 protein stability is a considerable approach for breast cancer therapy.</P>