Publications by authors named "Min-Seok Kim"

264 Publications

Revisiting silk: a lens-free optical physical unclonable function.

Nat Commun 2022 Jan 11;13(1):247. Epub 2022 Jan 11.

School of Electrical Engineering and Computer Science (EECS), Gwangju Institute of Science and Technology, 123, Cheomdangwagi-ro, Buk-gu, Gwangju, 61005, Republic of Korea.

For modern security, devices, individuals, and communications require unprecedentedly unique identifiers and cryptographic keys. One emerging method for guaranteeing digital security is to take advantage of a physical unclonable function. Surprisingly, native silk, which has been commonly utilized in everyday life as textiles, can be applied as a unique tag material, thereby removing the necessary apparatus for optical physical unclonable functions, such as an objective lens or a coherent light source. Randomly distributed fibers in silk generate spatially chaotic diffractions, forming self-focused spots on the millimeter scale. The silk-based physical unclonable function has a self-focusing, low-cost, and eco-friendly feature without relying on pre-/post-process for security tag creation. Using these properties, we implement a lens-free, optical, and portable physical unclonable function with silk identification cards and study its characteristics and reliability in a systemic manner. We further demonstrate the feasibility of the physical unclonable functions in two modes: authentication and data encryption.
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http://dx.doi.org/10.1038/s41467-021-27278-5DOI Listing
January 2022

Visual Field Characteristics in East Asian Patients With Occult Macular Dystrophy (Miyake Disease): EAOMD Report No. 3.

Invest Ophthalmol Vis Sci 2022 01;63(1):12

Department of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, South Korea.

Purpose: The purpose of this study was to investigate the perimetric features and their associations with structural and functional features in patients with RP1L1-associated occult macular dystrophy (OMD; i.e. Miyake disease).

Methods: In this international, multicenter, retrospective cohort study, 76 eyes of 38 patients from an East Asian cohort of patients with RP1L1-associated OMD were recruited. Visual field tests were performed using standard automated perimetry, and the patients were classified into three perimetric groups based on the visual field findings: central scotoma, other scotoma (e.g. paracentral scotoma), and no scotoma. The association of the structural and functional findings with the perimetric findings was evaluated.

Results: Fifty-four eyes (71.1%) showed central scotoma, 14 (18.4%) had other scotomata, and 8 (10.5%) had no scotoma. Central scotoma was mostly noted in both eyes (96.3%) and within the central 10 degrees (90.7%). Among the three perimetric groups, there were significant differences in visual symptoms, best-corrected visual acuity (BCVA), and structural phenotypes (i.e. severity of photoreceptor changes). The central scotoma group showed worse BCVA often with severe structural abnormalities (96.3%) and a pathogenic variant of p.R45W (72.2%). The multifocal electroretinogram (mfERG) groups largely corresponded with the perimetric groups; however, 8 (10.5%) of 76 eyes showed mfERG abnormalities preceding typical central scotoma.

Conclusions: The patterns of scotoma with different clinical severity were first identified in occult macular dystrophy, and central scotoma, a severe pattern, was most frequently observed. These perimetric patterns were associated with the severity of BCVA, structural phenotypes, genotype, and objective functional characteristics which may precede in some cases.
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http://dx.doi.org/10.1167/iovs.63.1.12DOI Listing
January 2022

Comprehensive Review on Thermoelectric Electrodeposits: Enhancing Thermoelectric Performance Through Nanoengineering.

Front Chem 2021 21;9:762896. Epub 2021 Dec 21.

Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN, United States.

Thermoelectric devices based power generation and cooling systemsystem have lot of advantages over conventional refrigerator and power generators, becausebecause of solid-state devicesdevices, compact size, good scalability, nono-emissions and low maintenance requirement with long operating lifetime. However, the applications of thermoelectric devices have been limited owingowing to their low energy conversion efficiency. It has drawn tremendous attention in the field of thermoelectric materials and devices in the 21st century because of the need of sustainable energy harvesting technology and the ability to develop higher performance thermoelectric materials through nanoscale science and defect engineering. Among various fabrication methods, electrodeposition is one of the most promising synthesis methods to fabricate devices because of its ability to control morphology, composition, crystallinity, and crystal structure of materials through controlling electrodeposition parameters. Additionally, it is an additive manufacturing technique with minimum waste materials that operates at near room temperature. Furthermore, its growth rate is significantly higher ( a few hundred microns per hour) than the vacuum processes, which allows device fabrication in cost effective matter. In this paper, the latest development of various electrodeposited thermoelectric materials ( Te, PbTe, BiTe and their derivatives, BiSe, BiS, SbTe) in different forms including thin films, nanowires, and nanocomposites were comprehensively reviewed. Additionally, their thermoelectric properties are correlated to the composition, morphology, and crystal structure.
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http://dx.doi.org/10.3389/fchem.2021.762896DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8725800PMC
December 2021

Determinants of left ventricular function improvement for cardiac resynchronization therapy candidates.

ESC Heart Fail 2021 Dec 29. Epub 2021 Dec 29.

Department of Cardiology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea.

Aims: A waiting period of more than 3 months is recommended for patients before undergoing cardiac resynchronization therapy (CRT). However, due to an anticipated high mortality rate, early implementation of CRT might be beneficial for some patients. We aimed to evaluate the rate and the probability of left ventricular (LV) function improvement and their predictors in patients with heart failure (HF) with indications for CRT.

Methods And Results: From March 2011 to February 2014, a total of 5625 hospitalized patients for acute HF were consecutively enrolled in 10 tertiary hospitals. Among them, we analysed 1792 patients (mean age 63.96 ± 15.42 years, female 63.1%) with left ventricular ejection fraction (LVEF) ≤ 35% at the baseline echocardiography and divided them into three groups: 144 with left bundle branch block (LBBB), 136 with wide QRS complexes without LBBB, and 1512 not having these findings (control). We compared and analysed these three groups for improvement of LV function at follow-up echocardiography. In patients who met CRT indications (patients with LBBB or wide QRS complexes without LBBB), logistic regression was performed to identify risk factors for no improvement of LV. No improvement of LV was defined as LVEF ≤ 35% at follow-up echocardiography or the composite adverse outcomes: death, heart transplantation, extracorporeal membrane oxygenation, or use of a ventricular assist device before follow-up echocardiography. A classification tree was established using the binary recursive partitioning method to predict the outcome of patients who met CRT indications. In a median follow-up of 11 months, LVEF improvement was observed in 24.3%, 15.4%, and 40.5% of patients with LBBB, wide QRS complexes without LBBB, and control, respectively. Patients meeting CRT indications had higher 3 month mortality rates than the control (24.6% vs. 17.7%, P = 0.002). Multivariable logistic regression analysis revealed that large LV end-systolic dimension [odds ratio (OR) 1.10, 95% confidence interval (CI) 1.05-1.15, P < 0.001], low LVEF (OR 0.92, 95% CI 0.87-0.98, P = 0.006), diabetes requiring insulin (OR 6.49, 95% CI 2.53-19.33, P < 0.001), and suboptimal medical therapy (OR 6.85, 95% CI 3.21-15.87, P < 0.001) were significant factors predictive of no improvement. A decision tree analysis was consistent with these results.

Conclusions: Patients with CRT indications had higher mortality during their follow-up compared with control. LV function improvement was rare in this population, especially when they had some risk factors. These results suggest that the uniform waiting period before CRT implantation could be reconsidered and individualized.
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http://dx.doi.org/10.1002/ehf2.13765DOI Listing
December 2021

Vari-Focal Light Field Camera for Extended Depth of Field.

Micromachines (Basel) 2021 Nov 26;12(12). Epub 2021 Nov 26.

Gwangju Institute of Science and Technology, School of Electrical Engineering and Computer Science, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Korea.

The light field camera provides a robust way to capture both spatial and angular information within a single shot. One of its important applications is in 3D depth sensing, which can extract depth information from the acquired scene. However, conventional light field cameras suffer from shallow depth of field (DoF). Here, a vari-focal light field camera (VF-LFC) with an extended DoF is newly proposed for mid-range 3D depth sensing applications. As a main lens of the system, a vari-focal lens with four different focal lengths is adopted to extend the DoF up to ~15 m. The focal length of the micro-lens array (MLA) is optimized by considering the DoF both in the image plane and in the object plane for each focal length. By dividing measurement regions with each focal length, depth estimation with high reliability is available within the entire DoF. The proposed VF-LFC is evaluated by the disparity data extracted from images with different distances. Moreover, the depth measurement in an outdoor environment demonstrates that our VF-LFC could be applied in various fields such as delivery robots, autonomous vehicles, and remote sensing drones.
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http://dx.doi.org/10.3390/mi12121453DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8706624PMC
November 2021

Infrared Clinical Enamel Crack Detector Based on Silicon CCD and Its Application: A High-Quality and Low-Cost Option.

J Imaging 2021 Dec 2;7(12). Epub 2021 Dec 2.

Department of Orthodontics, School of Dentistry, Dental 4D Research Institute, Dental Science Research Institute, Chonnam National University, Gwangju 61186, Korea.

Enamel cracks generated in the anterior teeth not only affect the function but also the aesthetics of the teeth. Chair-side tooth enamel crack detection is essential for clinicians to formulate treatment plans and prevent related dental disease. This study aimed to develop a dental imaging system using a near-IR light source to detect enamel cracks and to investigate the relationship between anterior enamel cracks and age in vivo. A total of 68 subjects were divided into three groups according to their age: young, middle, and elderly. Near-infrared radiation of 850 nm was used to identify enamel cracks in anterior teeth. The results of the quantitative examination showed that the number of enamel cracks on the teeth increased considerably with age. For the qualitative examination, the results indicated that there was no significant relationship between the severity of the enamel cracks and age. So, it can be concluded that the prevalence of anterior cracked tooth increased significantly with age in the young and middle age. The length of the anterior enamel cracks tended to increase with age too; however, this result was not significant. The silicon charge-coupled device (CCD) with a wavelength of 850 nm has a good performance in the detection of enamel cracks and has very good clinical practicability.
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http://dx.doi.org/10.3390/jimaging7120259DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8703581PMC
December 2021

Epigallocatechin-3-Gallate as a Novel Vaccine Adjuvant.

Front Immunol 2021 12;12:769088. Epub 2021 Nov 12.

Department of Microbiology, College of Medicine, Yonsei University, Seoul, South Korea.

Vaccine adjuvants from natural resources have been utilized for enhancing vaccine efficacy against infectious diseases. This study examined the potential use of catechins, polyphenolic materials derived from green tea, as adjuvants for subunit and inactivated vaccines. Previously, catechins have been documented to have irreversible virucidal function, with the possible applicability in the inactivated viral vaccine platform. In a mouse model, the coadministration of epigallocatechin-3-gallate (EGCG) with influenza hemagglutinin (HA) antigens induced high levels of neutralizing antibodies, comparable to that induced by alum, providing complete protection against the lethal challenge. Adjuvant effects were observed for all types of HA antigens, including recombinant full-length HA and HA1 globular domain, and egg-derived inactivated split influenza vaccines. The combination of alum and EGCG further increased neutralizing (NT) antibody titers with the corresponding hemagglutination inhibition (HI) titers, demonstrating a dose-sparing effect. Remarkably, EGCG induced immunoglobulin isotype switching from IgG1 to IgG2a (approximately >64-700 fold increase), exerting a more balanced T1/T2 response compared to alum. The upregulation of IgG2a correlated with significant enhancement of antibody-dependent cellular cytotoxicity (ADCC) function (approximately 14 fold increase), providing a potent effector-mediated protection in addition to NT and HI. As the first report on a novel class of vaccine adjuvants with built-in virucidal activities, the results of this study will help improve the efficacy and safety of vaccines for pandemic preparedness.
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http://dx.doi.org/10.3389/fimmu.2021.769088DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8632720PMC
November 2021

Vasoactive-Inotropic Score as a Determinant of Timely Initiation of Venoarterial Extracorporeal Membrane Oxygenation in Patients With Cardiogenic Shock.

Circ J 2021 Nov 9. Epub 2021 Nov 9.

Division of Cardiology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine.

Background: The predictive role of the vasoactive-inotropic score (VIS) for clinical outcomes after venoarterial extracorporeal membrane oxygenation (VA-ECMO) in patients with cardiogenic shock is not well known. This study investigated the predictive value of VIS on in-hospital outcomes and the determination of optimal timing for the initiation of VA-ECMO.Methods and Results:Overall, 160 patients with cardiogenic shock requiring VA-ECMO who were treated between December 2012 and August 2018 were analyzed. The in-hospital outcomes according to VIS were compared. Pre-ECMO VIS had an area under the receiver-operating characteristic curve (AUC) of 0.60 (P=0.03) for the prediction of in-hospital death. When the patients were divided into the high (≥32) and low (<32) VIS groups, the high VIS group had a higher rate of in-hospital death (P=0.002) and a lower rate of ECMO weaning (P=0.004). The difference in in-hospital death according to VIS was significant only in patients with a cardiogenic shock of non-ischemic etiology (P=0.01). Extracorporeal cardiopulmonary resuscitation (hazard ratio [HR], 1.99), age (HR, 1.02), pre-ECMO lactate (HR, 1.06), and VIS ≥32 (HR, 2.46) were independently predictive of in-hospital death.

Conclusions: Among patients with cardiogenic shock requiring VA-ECMO, the initiation of VA-ECMO before reaching high VIS (≥32) showed better in-hospital outcomes, suggesting that VIS may be a potential marker for determining the initiation of hemodynamic support with VA-ECMO.
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http://dx.doi.org/10.1253/circj.CJ-21-0614DOI Listing
November 2021

The association between effort-reward imbalance, work-life balance and depressive mood in Korean wage workers: The 4th Korean Working Conditions Survey.

Ann Occup Environ Med 2021 25;33:e2. Epub 2021 Jan 25.

Department of Preventive Medicine, Seoul National University, College of Medicine, Seoul, Korea.

Background: This study was conducted to determine the association between work-life (WL) balance, effort-reward (ER) imbalance, and depressive mood in Korean wage workers when 2 models were considered simultaneously.

Methods: We analyzed 26,014 Korean workers including 13,471 men and 12,543 women from the 4th Korean Working Conditions Survey data. Multiple logistic regression was used to analyze the association between WL, ER status, and the depressive mood of Korean workers. We classified the subjects into a total of 4 groups as follows. Group 1: WL and ER status are both "balanced", group 2: WL status is "imbalanced" and ER status is "balanced", group 3: WL status is "balanced" and the ER status is "imbalanced", group 4: WL and ER status are both "imbalanced."

Results: We found significantly increased odds ratios (ORs) for depressive mood in groups 2, 3, and 4 compared with group 1 after adjusting for the general and occupational characteristics of the subjects in both men and women. We also found that the trend of ORs increased gradually from groups 2 to 4 compared with group 1 in both men and women; group 2: OR: 1.23 (95% confidence interval [CI]: 1.12-1.35), group 3: OR: 1.40 (95% CI: 1.27-1.55), group 4: OR: 1.99 (95% CI: 1.74-2.28) compared with group 1 in men; group 2: OR: 1.28 (95% CI: 1.15-1.42), group 3: OR: 1.45 (95% CI: 1.31-1.59), group 4: OR: 2.04 (95% CI: 1.76-2.36) compared with group 1 in women.

Conclusions: As a result, we found the association between imbalanced WL, ER status, and depressive mood in Korean workers using 2 models simultaneously. It is important to provide a balanced WL and ER condition to improve the mental health of workers.
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http://dx.doi.org/10.35371/aoem.2021.33.e2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7952773PMC
January 2021

Anti-fibrotic effect of pycnogenol® in a polyhexamethylene guanidine-treated mouse model.

Respir Physiol Neurobiol 2022 Feb 12;296:103802. Epub 2021 Oct 12.

Inhalation Toxicity Research Group, Korea Institute of Toxicology, Jeongeup-si, Jeollabuk-do, 56212, Republic of Korea. Electronic address:

Pulmonary fibrosis (PF) is a respiratory disease that causes serious respiratory problems. The effects of French marine pine bark extract (Pycnogenol®), with antioxidant and anti-inflammatory properties, were investigated on lung fibrosis in polyhexamethylene guanidine (PHMG)-treated mice. Mice were separated into four groups (n = 6): vehicle control (VC, saline 50 μl); PHMG (1.1 mg/kg); PHMG + Pycnogenol® (0.3 mg/kg/day); and PHMG + Pycnogenol® (1 mg/kg/day). PF was induced via intratracheal instillation of PHMG. Treatment with PHMG decreased body weight and increased lung weight, both of which were improved by treatment with PHMG + Pycnogenol® (1 mg/kg). Enzyme-linked immunosorbent assay, western blotting, and PCR revealed that Pycnogenol® attenuated PHMG-induced increase in inflammatory cytokines and fibrosis-related factors in a dose-dependent manner. Finally, histopathological analysis revealed reduced inflammation/fibrosis in the PHMG + Pycnogenol® (1 mg/kg) group. Collectively, the results indicate that Pycnogenol® can be used to treat PF as it hinders fibrosis progression by inhibiting inflammatory responses in the lungs of PHMG-treated mice.
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http://dx.doi.org/10.1016/j.resp.2021.103802DOI Listing
February 2022

Increased expression of TCF3, transcription factor 3, is a defense response against methylmercury toxicity in mouse neuronal C17.2 cells.

Toxicol Res 2021 Oct 22;37(4):451-458. Epub 2021 Jan 22.

Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 Japan.

Methylmercury is an environmental pollutant that induces potent neurotoxicity. We previously identified transcription factor 3 (TCF3) as a transcription factor that is activated in the brains of mice treated with methylmercury, and reported that methylmercury sensitivity was increased in cells in which TCF3 expression was suppressed. However, the mechanisms involved in the activation of TCF3 by methylmercury and in the reduction of methylmercury toxicity by TCF3 remained unclear. We found that treatment of mouse neuronal C17.2 cells with methylmercury increased TCF3 protein levels and promoted the binding of TCF3 to DNA consensus sequences. In cells treated with actinomycin D, a transcription inhibitor, an increase in TCF3 protein levels was also observed under methylmercury exposure. However, in the presence of cycloheximide, a translation inhibitor, methylmercury delayed the degradation of TCF3 protein. In addition, treatment with MG132, a proteasome inhibitor, increased TCF3 protein levels, and there was not significant increase in TCF3 protein levels by methylmercury under these conditions. These results suggest that methylmercury may activate TCF3 by increasing its levels through inhibition of TCF3 degradation by the proteasome. It has been previously reported that the induction of apoptosis in neurons is involved in methylmercury-induced neuronal damage in the brain. Although apoptosis was induced in C17.2 cells treated with methylmercury, this induction was largely suppressed by overexpression of TCF3. These results indicate that TCF3, which is increased in the brain upon exposure to methylmercury, may be a novel defense factor against methylmercury-induced neurotoxicity.
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http://dx.doi.org/10.1007/s43188-021-00087-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8476663PMC
October 2021

Long-Term Development and Progression of Peripapillary Hyper-reflective Ovoid Mass-like Structures: Two Case Reports.

J Neuroophthalmol 2021 Sep 30. Epub 2021 Sep 30.

Department of Ophthalmology (MSK, J-MH, SJW), Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea; and Retina Center (MSK), Moon's Eye Clinic, Suwon, Korea.

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http://dx.doi.org/10.1097/WNO.0000000000001366DOI Listing
September 2021

Exposure to cigarette smoke exacerbates polyhexamethylene guanidine-induced lung fibrosis in mice.

J Toxicol Sci 2021 ;46(10):487-497

Inhalation Toxicity Research Group, Korea Institute of Toxicology, Korea.

Cigarette smoke (CS) is the leading cause of chronic pulmonary diseases, including lung cancer, chronic obstructive pulmonary disease, and pulmonary fibrosis. In this study, we aimed to investigate the effects of repeated CS exposure on polyhexamethylene guanidine (PHMG)-induced pulmonary fibrosis in mice. A single intratracheal instillation of 0.6 mg/kg PHMG enhanced the immune response of mice by increasing the number of total and specific inflammatory cell types in the bronchoalveolar lavage fluid. It induced histopathological changes such as granulomatous inflammation/fibrosis and macrophage infiltration in the lungs. These responses were upregulated upon exposure to a combination of PHMG and CS. In contrast, a 4-hr/day exposure to 300 mg/m CS alone for 2 weeks by nose-only inhalation resulted in minimal inflammation in the mouse lung. Furthermore, PHMG administration increased the expression of fibrogenic mediators, especially in the pulmonary tissues of the PHMG + CS group compared with that in the PHMG alone group. However, there was no upregulation in the expression of inflammatory cytokines following exposure to a combination of PHMG and CS. Our results demonstrate that repeated exposure to CS may promote the development of PHMG-induced pulmonary fibrosis.
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http://dx.doi.org/10.2131/jts.46.487DOI Listing
January 2022

MACULAR HOLE ASSOCIATED WITH AGE-RELATED MACULAR DEGENERATION: Pathogenesis and Surgical Outcomes.

Retina 2021 Oct;41(10):2079-2087

Department of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Gyeonggi-do, Republic of Korea.

Purpose: To ascertain the pathogenesis of macular hole (MH) associated with age-related macular degeneration (AMD) and its surgical outcomes.

Methods: Patients with full-thickness MH associated with AMD (higher grades than intermediate) were enrolled. The mechanism of MH formation and closure rate after vitrectomy (surgical outcome) were determined using optical coherence tomography imaging.

Results: The mechanism of MH formation (35 eyes) associated with AMD was classified into four types: vitreomacular traction (42.9%), gradual retinal thinning caused by subretinal drusen or pigment epithelial detachment (22.9%), massive subretinal hemorrhage (20.0%), and combined (14.3%). In the 41 eyes that underwent vitrectomy, the logarithm of the minimum angle of resolution best-corrected visual acuity improved from 0.82 (0.10-2.30) preoperative to 0.69 (0.10-2.30) postoperative (P = 0.001). Successful closure of the MH was achieved in 33 eyes (80.5%) after vitrectomy. No significant association was observed between the closure rate of MH after vitrectomy and mechanism of MH formation (P = 0.083).

Conclusion: The mechanism of MH formation associated with AMD was classified into four types and was not related to its surgical outcome. Considering visual improvement and surgical outcome after vitrectomy in our study, active surgical treatment can be considered for MH associated with AMD.
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http://dx.doi.org/10.1097/IAE.0000000000003148DOI Listing
October 2021

Saphenous Vein Versus Right Internal Thoracic Artery as a Y-Composite Graft: Ten-Year Angiographic and Long-Term Clinical Results of the SAVE RITA Trial.

Circulation 2021 10 8;144(14):1186-1188. Epub 2021 Sep 8.

Cardiovascular Center, Myongji Hospital, Gyeonggi-do, Korea (K.-B.K.).

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http://dx.doi.org/10.1161/CIRCULATIONAHA.121.056438DOI Listing
October 2021

Dexamethasone Intravitreal Implant for the Treatment of Macular Edema Following Retinal Vein Occlusion: Post Hoc Analysis of Post-Marketing Surveillance Data in the Real-World Setting in Korea.

Clin Ophthalmol 2021 27;15:3623-3636. Epub 2021 Aug 27.

Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.

Purpose: To supplement established efficacy and safety data, this analysis evaluated the real-world use of dexamethasone (DEX) intravitreal implant 700 µg for retinal vein occlusion (RVO)-related macular edema in an Asian population and baseline factors potentially associated with DEX implant efficacy.

Patients And Methods: A prospective, observational, post-marketing surveillance study was conducted at 38 sites in South Korea in patients consecutively presenting with macular edema following branch or central RVO (BRVO, CRVO), and administered a first DEX implant. Follow-up visits and subsequent DEX or other therapies conformed with local practice. Outcome measures included best-corrected visual acuity (BCVA), change in BCVA from baseline, responder rates, and adverse events. Associations between baseline characteristics and BCVA gains were evaluated. Month-1, -2, -4, and -6 visit analysis windows were established.

Results: In all, 700 patients (79.1% BRVO, 20.9% CRVO) received 1.12 DEX implants (mean) and were followed for 101.5 days (standard deviation, 51.7); 90% received a single implant. Among patients with analyzable data, mean BCVA improved from baseline with peak changes in Month 2 of -0.193 and -0.212 LogMAR, ( < 0.0001) and remained significant in the BRVO subgroup at the Month 4 and 6 windows ( < 0.0001 and = 0.0039, respectively). Treatment-naïve patients experienced greater BCVA increases. The proportion of patients with stable/improved BCVA tended to decrease after Month 2 through Month 6 and the decline was greater in the CRVO subgroup. At the Month-2 window, ≥1-, 2- and 3-line increases were positively associated with younger age, worse baseline BCVA, and treatment naivety. The most common adverse event was increased intraocular pressure.

Conclusion: In the real-world clinical setting in South Korea, DEX implant improved visual acuity and had a favorable safety profile similar to that reported in randomized controlled trials and observational European and North American studies. These data further support the value of DEX implant as a treatment option for RVO.

Clinicaltrialsgov Identifier: NCT01976650. Date of registration: November 6, 2013.
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http://dx.doi.org/10.2147/OPTH.S302014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8407780PMC
August 2021

Reopening of the occluded saphenous vein composite grafts after coronary artery bypass grafting.

J Card Surg 2021 Nov 26;36(11):4061-4067. Epub 2021 Aug 26.

Cardiovascular Center, Myongji Hospital, Goyang-si, Gyeonggi-do, Korea.

Background: We have observed reopening of the occluded "no-touch" saphenous vein (NT SV) composite grafts on follow-up angiograms in patients who underwent coronary artery bypass graftings (CABGs).

Methods: Between 2008 and 2018, 1283 patients received NT SV conduits without or with surrounding pedicle tissue as composite grafts based on the in situ left internal thoracic artery (ITA) for CABG and underwent early postoperative angiographies. Among the 1283 patients, 53 patients showed 55 occluded SV conduit anastomoses, and 46 patients who had 48 occluded SV anastomoses were re-evaluated by 1-year postoperative angiographies.

Results: Early postoperative angiographies in 1283 patients demonstrated overall occlusion rates of 1.2% (56/4518); occlusion rates of the ITA and SV were 0.08% (1/1259) and 1.7% (55/3260), respectively. One-year angiograms demonstrated that 14 occluded SV anastomoses (29.2% [14/48 occluded SV]) of 14 patients became patent. Reopening of occluded SV conduits occurred more frequently in NT SV with pedicle tissue than in NT SV without pedicle tissue (45.0% [9/20] vs. 17.9% [5/28]; p = .057). When we examined the preoperative and 1-year postoperative angiograms, reopening of the occluded SV conduits was not related with progression (p = .258) or preoperative reversibility score (p = .115) of native target coronary artery disease.

Conclusions: More than a quarter of the occluded SV composite grafts on early postoperative angiograms were patent in the 1-year angiograms. The reopening rates were higher in patients who had received NT SV conduits with pedicle tissue than those who had received NT SV conduits without pedicle tissue.
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http://dx.doi.org/10.1111/jocs.15936DOI Listing
November 2021

Identification of novel candidate genes implicated in odontogenic potential in the developing mouse tooth germ using transcriptome analysis.

Genes Genomics 2021 09 24;43(9):1087-1094. Epub 2021 Jul 24.

Dental Science Research Institute, School of Dentistry, Chonnam National University, 300 Yongbong-Dong, Buk-Ku, Gwangju, 61186, South Korea.

Background: In tooth bioengineering for replacement therapy of missing teeth, the utilized cells must possess an inductive signal-forming ability to initiate odontogenesis. This ability is called odontogenic potential. In mice, the odontogenic potential signal is known to be translocated from the epithelium to the mesenchyme at the early bud stage in the developing molar tooth germ. However, the identity of the molecular constituents of this process remains unclear.

Objective: The purpose of this study is to determine the molecular identity of odontogenic potential and to provide a new perspective in the field of tooth development research.

Methods: In this study, whole transcriptome profiles of the mouse molar tooth germ epithelium and mesenchyme were investigated using the RNA sequencing (RNA-seq) technique. The analyzed transcriptomes corresponded to two developmental stages, embryonic day 11.5 (E11.5) and 14.5 (E14.5), which represent the odontogenic potential shifts.

Results: We identified differentially expressed genes (DEGs), which were specifically overexpressed in both the E11.5 epithelium and E14.5 mesenchyme, but not expressed in their respective counterparts. Of the 55 DEGs identified, the top three most expressed transcription factor genes (transcription factor AP-2 beta isoform 3 [TFAP2B], developing brain homeobox protein 2 [DBX2], and insulin gene enhancer protein ISL-1 [ISL1]) and three tooth development-related genes (transcription factor HES-5 [HES5], platelet-derived growth factor D precursor [PDGFD], semaphrin-3 A precursor [SEMA3A]) were selected and validated by quantitative RT-PCR. Using immunofluorescence staining, the TFAP2B protein expression was found to be localized only at the E11.5 epithelium and E14.5 mesenchyme.

Conclusions: Thus, our empirical findings in the present study may provide a new perspective into the characterization of the molecules responsible for the odontogenic potential and may have an implication in the cell-based whole tooth regeneration strategy.
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http://dx.doi.org/10.1007/s13258-021-01130-yDOI Listing
September 2021

Comprehensive analysis of blood-based biomarkers for predicting immunotherapy benefits in patients with advanced non-small cell lung cancer.

Transl Lung Cancer Res 2021 May;10(5):2103-2117

Department of Internal Medicine, Chonnam National University Medical School and Hwasun Hospital, Jeonnam, Republic of Korea.

Background: This study aimed to investigate the feasibility of using circulating tumor cells (CTCs), peripheral blood cells (PBCs), and circulating cell-free DNA (cfDNA) as biomarkers of immune checkpoint inhibitor treatment response in patients with advanced non-small cell lung cancer (NSCLC).

Methods: We recruited patients diagnosed with advanced NSCLC who received pembrolizumab or atezolizumab between July 2019 and June 2020. Blood was collected before each treatment cycle (C1-C4) to calculate absolute neutrophil count (ANC), neutrophil-to-lymphocyte ratio (NLR), derived NLR (dNLR), and platelet-to-lymphocyte ratio (PLR). CTCs, isolated using the CD-PRIME system, exhibited EpCAM/CK+/CD45- phenotype in BioViewCCBS. The cfDNA was extracted from plasma at the beginning of C1 and C4.

Results: The durable clinical benefit (DCB) rate among 83 response-evaluable patients was 34%. CTC, PBC, and cfDNA levels at baseline (C1) were not significantly correlated with treatment response, although patients with DCB had lower CTC counts from C2 to C4. However, patients with low NLR, dNLR, PLR, and cfDNA levels at C1 had improved progression-free survival (PFS) and overall survival (OS). Patients with decreased CTC counts from C1 to C2 had higher median PFS (6.2 2.3 months; P=0.078) and OS (not reached 6.8 months, P=0.021) than those with increased CTC counts. Low dNLR (≤2.0) at C1 and decreased CTC counts were independent factors for predicting survival.

Conclusions: Comprehensive analysis of CTC, PBC, and cfDNA levels at baseline and during treatment demonstrated they might be biomarkers for predicting survival benefit. This finding could aid in risk stratification of patients with advanced NSCLC who are undergoing immune checkpoint inhibitor treatment.
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http://dx.doi.org/10.21037/tlcr-21-100DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8182702PMC
May 2021

Outdoor-Useable, Wireless/Battery-Free Patch-Type Tissue Oximeter with Radiative Cooling.

Adv Sci (Weinh) 2021 05 9;8(10):2004885. Epub 2021 Mar 9.

School of Electrical Engineering and Computer Science (EECS) Gwangju Institute of Science and Technology (GIST) 123, Cheomdangwagi-ro, Bukgu Gwangju 61005 Republic of Korea.

For wearable electronics/optoelectronics, thermal management should be provided for accurate signal acquisition as well as thermal comfort. However, outdoor solar energy gain has restricted the efficiency of some wearable devices like oximeters. Herein, wireless/battery-free and thermally regulated patch-type tissue oximeter (PTO) with radiative cooling structures are presented, which can measure tissue oxygenation under sunlight in reliable manner and will benefit athlete training. To maximize the radiative cooling performance, a nano/microvoids polymer (NMVP) is introduced by combining two perforated polymers to both reduce sunlight absorption and maximize thermal radiation. The optimized NMVP exhibits sub-ambient cooling of 6 °C in daytime under various conditions such as scattered/overcast clouds, high humidity, and clear weather. The NMVP-integrated PTO enables maintaining temperature within ≈1 °C on the skin under sunlight relative to indoor measurement, whereas the normally used, black encapsulated PTO shows over 40 °C owing to solar absorption. The heated PTO exhibits an inaccurate tissue oxygen saturation (StO) value of ≈67% compared with StO in a normal state (i.e., ≈80%). However, the thermally protected PTO presents reliable StO of ≈80%. This successful demonstration provides a feasible strategy of thermal management in wearable devices for outdoor applications.
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http://dx.doi.org/10.1002/advs.202004885DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8132059PMC
May 2021

Primary Graft Dysfunction After Isolated Heart Transplantation - Incidence, Risk Factors, and Clinical Implications Based on a Single-Center Experience.

Circ J 2021 Aug 16;85(9):1451-1459. Epub 2021 Apr 16.

Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine.

Background: Since the international consensus on primary graft dysfunction (PGD) following heart transplantation (HT) was reported in 2014, few clinical studies have been reported. We aimed to analyze the incidence, predictive factors, and clinical implications of PGD following the International Society of Heart and Lung Transplant criteria in a single center.Methods and Results:This study enrolled 570 consecutive adult patients undergoing isolated HT between November 1992 and December 2017. Under a new set of criteria, PGD-left ventricle (PGD-LV) occurred in 35 patients (6.1%; mild, n=1 [0.2%]; moderate, n=14 [2.5%]; severe, n=20 [3.5%]), whereas PGD-right ventricle (PGD-RV) occurred in 3 (0.5%). Multivariable analysis demonstrated that preoperative admission (odds ratio [OR] 4.20; 95% confidence interval [CI] 1.24-14.26; P=0.021), preoperative extracorporeal membrane oxygenation (OR 4.03; 95% CI 1.75-9.26; P=0.001), and prolonged total ischemic time (OR 1.09; 95% CI 1.02-1.15; P=0.006) were significant predictors of moderate to severe PGD-LV. Moderate to severe PGD-LV was an independent and significant risk factor for early death (OR 55.64; 95% CI 11.65-265.73; P<0.001), with its effects extending up to 3 months after HT.

Conclusions: Moderate to severe PGD-LV, as defined by the new guidelines, is an important predictor of early mortality, with effects extending up to 3 months after HT. Efforts to reduce the occurrence of moderate to severe PGD-LV may lead to better outcomes.
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http://dx.doi.org/10.1253/circj.CJ-20-0960DOI Listing
August 2021

Electrochemical Nitrogen Reduction Kinetics on a Copper Sulfide Catalyst for NH Synthesis at Low Temperature and Atmospheric Pressure.

ACS Appl Mater Interfaces 2021 Jun 7;13(21):24593-24603. Epub 2021 Apr 7.

Division of Energy & Environment Technology, KIST School, University of Science and Technology (UST), Seoul 02792, Republic of Korea.

We studied the electrochemical synthesis of NH on Fe-CuS/C catalysts in an alkaline aqueous solution under ambient conditions. The metal chalcogenide catalyst is active in the nitrogen reduction reaction (NRR) for approximately 45 min with an NH production yield of 16 μg h cm at -0.4 , while it decomposes to CuO. The rapid degradation of the catalyst hinders the precise investigation of the NH production activity in longer time measurements. Herein, the electrochemical NH production rate is enhanced with increased overpotentials when the degradation effect is mitigated in the measurement, which was difficult to observe in the NRR reports. In the Tafel analysis, the exchange current density, heterogeneous rate constant, and transfer coefficient of the Fe-CuS/C catalyst on the NRR were estimated. When the electrode degradation is mitigated, one of the best NH production activities among the reported metal sulfide electrochemical NRR catalysts is obtained, which is 42 μg h cm at -0.6 V.
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http://dx.doi.org/10.1021/acsami.1c00850DOI Listing
June 2021

Efficacy and dose of afatinib in patients with non-small cell lung cancer after failure of prior gefitinib or erlotinib treatment.

Thorac Cancer 2021 05 3;12(10):1598-1604. Epub 2021 Apr 3.

Lung and Esophageal Cancer Clinic, Department of Internal Medicine, Chonnam National University Medical School, Chonnam National University Hwasun Hospital, Hwasun, South Korea.

Background: We report a subgroup analysis of afatinib with respect to its efficacy, safety, and the long-term survival of patients in a Named Patient Use program at a single institution.

Methods: We analyzed 60 patients with stage IV non-small cell lung cancer (NSCLC) who had been treated with ≥1 line of platinum-based chemotherapy and had activating epidermal growth factor receptor (EGFR) mutations or disease control for ≥6 months with prior EGFR inhibitors. Afatinib was started on a daily dose of 50 mg, which was decreased according to the adverse events and tolerability.

Results: A total of 13 patients achieved partial remission, whereas 33, 12, and two showed stable disease, had progression, and were not evaluable, respectively, resulting in an objective response rate and disease control rate of 21.7% and 76.7%, respectively. The median progression-free survival (PFS) was 5.4 (95% confidence interval [CI]: 4.0-7.7) months and median overall survival (OS) was 10.1 (8.5-13.6) months. Toxicities leading to drug discontinuation were experienced by four patients (6.7%). Grade 3 diarrhea occurred in 10 patients (16.7%), and afatinib dose reductions were required in 35 patients. The PFS and OS were significantly longer for patients whose dose was reduced to 40 or 30 mg than for those without dose reduction (7.0 vs 3.1 months and 13.5 vs 8.1 months, respectively, p < 0.05).

Conclusions: The efficacy of afatinib was similar to that identified in the global data without unexpected adverse events. Survival analyses support the currently approved dose of afatinib as first-line treatment for NSCLC.
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http://dx.doi.org/10.1111/1759-7714.13957DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8107028PMC
May 2021

Structural Insights into a Bifunctional Peptide Methionine Sulfoxide Reductase MsrA/B Fusion Protein from .

Antioxidants (Basel) 2021 Mar 5;10(3). Epub 2021 Mar 5.

Department of Biotechnology, Korea University, Seoul 02841, Korea.

Methionine sulfoxide reductase (Msr) is a family of enzymes that reduces oxidized methionine and plays an important role in the survival of bacteria under oxidative stress conditions. MsrA and MsrB exist in a fusion protein form (MsrAB) in some pathogenic bacteria, such as (), , and . To understand the fused form instead of the separated enzyme at the molecular level, we determined the crystal structure of MsrAB at 2.2 Å, which showed that a linker region (, 193-205) between two domains interacted with each MsrA or MsrB domain via three salt bridges (E193-K107, D197-R103, and K200-D339). Two acetate molecules in the active site pocket showed an planar electron density map in the crystal structure, which interacted with the conserved residues in fusion MsrABs from the pathogen. Biochemical and kinetic analyses revealed that is required to increase the catalytic efficiency of MsrAB. Two salt bridge mutants (D193A and E199A) were located at the entrance or tailgate of . Therefore, the linker region of the MsrAB fusion enzyme plays a key role in the structural stability and catalytic efficiency and provides a better understanding of why MsrAB exists in a fused form.
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http://dx.doi.org/10.3390/antiox10030389DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8000184PMC
March 2021

Insights into the structure of mature streptavidin C1 from reveal the self-binding of the extension C-terminal peptide to biotin-binding sites.

IUCrJ 2021 Mar 11;8(Pt 2):168-177. Epub 2021 Jan 11.

Department of Biotechnology, School of Life Sciences and Biotechnology for BK21 PLUS, Institute of Life Science and Natural Resources, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, South Korea.

The members of the avidin protein family are well known for their high affinity towards d-biotin and their structural stability. These properties make avidins a valuable tool for various biotechnological applications. In the present study, two avidin-like biotin-binding proteins (named streptavidin C1 and C2) from were newly identified while exploring antifungal proteins against f. sp. . Streptavidin C1 reveals a low correlation (a sequence identity of approximately 64%) with all known streptavidins, whereas streptavidin C2 shares a sequence identity of approximately 94% with other streptavidins. Here, the crystal structures of streptavidin C1 in the mature form and in complex with biotin at 2.1 and 2.5 Å resolution, respectively, were assessed. The overall structures present similar tetrameric features with symmetry to other (strept)avidin structures. Interestingly, the long C-terminal region comprises a short α-helix (C-Lid; residues 169-179) and an extension C-terminal peptide (ECP; residues 180-191) which stretches into the biotin-binding sites of the same monomer. This ECP sequence (-VTSANPPAS-) is a newly defined biotin-binding site, which reduces the ability to bind to (strept)avidin family proteins. The novel streptavidin C1 could help in the development of an engineered tetrameric streptavidin with reduced biotin-binding capacity as well as other biomaterial tools.
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http://dx.doi.org/10.1107/S2052252520015675DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7924230PMC
March 2021

Efficacy of an inpatient smoking cessation program at a single regional cancer center: A prospective observational study.

Medicine (Baltimore) 2021 Feb;100(6):e24745

Jeonnam Tobacco Control Center, Chonnam National University Hwasun Hospital, Jeonnam.

Abstract: Smoking is the leading cause of preventable death and a risk factor for cancer, but smoking cessation is difficult even in patients who need hospitalization. This study aimed to investigate the usefulness of an inpatient smoking cessation consultation program and to analyze the clinical factors associated with abstinence. In this observational study, patients received regular counseling for 6 months, and abstinence was objectively assessed via urine and exhaled carbon monoxide testing. Cessation rates were assessed at 4 weeks and 6 months, and clinical characteristics associated with cessation success were investigated. Of the 571 patients referred to participate in the program, 170 (29.8%) were enrolled, and only 2 (1.2%) used smoking cessation drugs in addition to counseling. The smoking cessation rate was 77.6% after 4 weeks and 59.1% after 6 months. The cessation rates were significantly higher in patients with cancer than in those without cancer at both timepoints (63.8% vs 21.9%, P < .001, 53.6% vs 12.5%, P < .001), and they were also higher in the first admission group than in the re-admission group (87.4% vs 74.7%, P = .033, 88.5% vs 76.1%, P = .037). In patients with lung cancer, progression-free survival and overall survival tended to be better in those enrolled in the program (P = .158, P = .183). In conclusion, the inpatient smoking cessation program was associated with a high abstinence rate. Most patients maintained cessation without medication, suggesting that initial admission, along with a cancer diagnosis, can provide enough motivation to abstain from smoking. In addition, the smoking cessation effort showed potential to improve survival during lung cancer treatment.
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http://dx.doi.org/10.1097/MD.0000000000024745DOI Listing
February 2021

Clinical characteristics and prognosis of patients with Pneumocystis jirovecii pneumonia without a compromised illness.

PLoS One 2021 4;16(2):e0246296. Epub 2021 Feb 4.

Department of Internal Medicine, Chonnam National University Hospital, Gwangju, Republic of Korea.

Objective: Pneumocystis jirovecii pneumonia (PCP) is a fatal respiratory infection, mostly associated with immunocompromised conditions. Several reports have described PCP development in patients who were not immunocompromised, but the clinical course and prognosis of PCP are not well understood. We compared the clinical characteristics and prognoses between patients with and without immunocompromised conditions who developed PCP.

Methods: We retrospectively analyzed patients who had been treated for PCP from three hospitals. We defined immunocompromised (IC) status as following: human immunodeficiency virus (HIV) infection; hematological malignancy; solid organ tumor under chemotherapy; rheumatic disease; medication with immunosuppressive agents. Patients without immunocompromised status were defined as being non-immunocompromised (non-IC).

Results: The IC and non-IC groups comprised 173 and 14 patients. The median ages were 62.0 and 74.0 years in the IC and the non-IC group, respectively. The median interval between admission and anti-PCP treatment was significantly longer for patients in the non-IC group than that for patients in the IC group (7 vs. 2 days). The in-hospital mortality rates were significantly higher for patients in the non-IC group than that for patients in the IC group (71.4% vs. 43.9%; P = 0.047). A longer interval between admission and anti-PCP therapy was associated with increased 90-day mortality rate in patients with PCP (hazard ratio, 1.082; 95% confidence interval, 1.015-1.153; P = 0.016).

Conclusions: Patients with PCP with no predisposing illnesses were older and had higher mortality rates than IC patients with PCP. Delayed anti-PCP treatment was associated with increased 90-day mortality.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0246296PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7861382PMC
July 2021

Inhalation exposure by cigarette smoke: Effects on the progression of bleomycin- and lipopolysaccharide-induced lung injuries in rat models.

Toxicology 2021 03 28;451:152695. Epub 2021 Jan 28.

Laboratory of Biochemistry and Immunology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea. Electronic address:

The toxic substances of cigarette smoke (CS) induce inflammatory responses in the lung by recruiting inflammatory cells. In this study, we investigated the effects of CS on the progression of lung disease in bleomycin (BLM) and lipopolysaccharide (LPS)-induced lung injury rat models. Briefly, rats were exposed to CS via inhalation (nose-only) for 28 consecutive days, for 4 h per day. Using an automatic video instillator, rats were administered a single dose of 2.5 mg/kg BLM (day 1) or 0.5 mg/kg LPS (day 26), prepared in 50 μL phosphate-buffered saline (PBS) solution. Examination of the bronchoalveolar lavage fluid (BALF) revealed that the number of neutrophils increased in a concentration-dependent manner of CS. Exposure to CS also enhanced the expression of cytokines, i.e., CCL2 (MCP-1), CCL3 (MIP-1α), CXCL2 (CINC3), CXCL10 (IP-10), TNF-α, IFN-γ, IL-2, IL-4 in the BALF of the vehicle (VC) and BLM groups in a concentration-dependent manner. In particular, the expressions of CCL2, CXCL10 and TNF-α were remarkably upregulated in the BLM + CS 300 treatment as compared to VC, while there were no differences in these cytokine levels in the serum following CS exposure. Exposure to CS resulted in compacted alveolar spaces and macrophage aggregation in the lung tissues following BLM and LPS treatments. Compared to VC, pulmonary fibrosis and chronic inflammation of bronchioloalveoli were observed in the BLM + CS treatment and inflammatory cell infiltration of bronchioloalveoli was observed in the LPS + CS treatment in a concentration-dependent manner by CS. The expression levels of CCL2 and IFN-γ in the lung tissues were increased similar to the levels obtained in BALF, in a concentration-dependent manner by CS. Taken together, these results indicate that repeated exposure to CS may exacerbate the lung injury initially caused by BLM and LPS.
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http://dx.doi.org/10.1016/j.tox.2021.152695DOI Listing
March 2021

An Experimental Study on Condition Diagnosis for Thrust Bearings in Oscillating Water Column Type Wave Power Systems.

Sensors (Basel) 2021 Jan 11;21(2). Epub 2021 Jan 11.

Department of Naval Architecture and Ocean Engineering, INHA University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Korea.

In order to utilize wave energy, various wave power systems are being actively researched and developed and interest in them is increasing. To maximize the operational efficiency, it is very important to monitor and maintain the fault of components of the system. In recent years, interest in the management cost, high reliability and facility utilization of such systems has increased. In this regard, fault diagnosis technology including fault factor analysis and fault reproduction is drawing attention as an important main technology. Therefore, in this study, to reproduce and monitor the faults of a wave power system, firstly, the failure mode of the system was analyzed using FMEA analysis. Secondly, according to the derived failure mode and effect, the thrust bearing was selected as a target for fault reproduction and a test equipment bench was constructed. Finally, with the vibration data obtained by conducting the tests, the vibration spectrum was analyzed to extract the features of the data for each operating status; the data was classified by applying the three machine learning algorithms: naïve Bayes (NB), k-nearest neighbor (k-NN), and multi-layer perceptron (MLP). The criteria for determining the fault were derived. It is estimated that a more efficient fault diagnosis is possible by using the standard and fault monitoring method of this study.
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http://dx.doi.org/10.3390/s21020457DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7827786PMC
January 2021

Comparative Analysis of Stress in the Periodontal Ligament and Center of Rotation in the Tooth after Orthodontic Treatment Depending on Clear Aligner Thickness-Finite Element Analysis Study.

Materials (Basel) 2021 Jan 9;14(2). Epub 2021 Jan 9.

Department of Biomedical Engineering, Inje University, Gimhae 50834, Korea.

Lately, in orthodontic treatments, the use of transparent aligners for the correction of malocclusions has become prominent owing to their intrinsic advantages such as esthetics, comfort, and minimal maintenance. Attempts at improving upon this technology by varying various parameters to investigate the effects on treatments have been carried out by several researchers. Here, we aimed to investigate the biomechanical and clinical effects of aligner thickness on stress distributions in the periodontal ligament and changes in the tooth's center of rotation. Dental finite element models comprising the cortical and cancellous bones, gingiva, teeth, and nonlinear viscoelastic periodontal ligaments were constructed, validated, and used together with aligner finite element models of different aligner thicknesses to achieve the goal of this study. The finite element analyses were conducted to simulate the actual orthodontic aligner treatment process for the correction of malocclusions by generating pre-stresses in the aligner and allowing the aligner stresses to relax to induce tooth movement. The results of the analyses showed that orthodontic treatment in lingual inclination and axial rotation with a 0.75 mm-thick aligner resulted in 6% and 0.03% higher principal stresses in the periodontal ligament than the same treatment using a 0.05 mm-thick aligner, respectively. Again, for both aligner thicknesses, the tooth's center of rotation moved lingually and towards the root direction in lingual inclination, and diagonally from the long axis of the tooth in axial rotation. Taken together, orthodontic treatment for simple malocclusions using transparent aligners of different thicknesses will produce a similar effect on the principal stresses in the periodontal ligament and similar changes in the tooth's center of rotation, as well as sufficient tooth movement. These findings provide orthodontists and researchers clinical and biomechanical evidence about the effect of transparent aligner thickness selection and its effect on orthodontic treatment.
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http://dx.doi.org/10.3390/ma14020324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7826543PMC
January 2021
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