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Park, Sang-In,Oh, Jaeseong,Jang, Kyungho,Yoon, Jangsoo,Moon, Seol Ju,Park, Jong Sun,Lee, Jae Ho,Song, Junghan,Jang, In-Jin,Yu, Kyung-Sang,Chung, Jae-Yong American Society for Microbiology 2015 Antimicrobial Agents and Chemotherapy Vol.59 No.8
<P>Therapeutic drug monitoring (TDM) of second-line antituberculosis drugs would allow for optimal individualized dosage adjustments and improve drug safety and therapeutic outcomes. To evaluate the pharmacokinetic (PK) characteristics of clinically relevant, multidrug treatment regimens and to improve the feasibility of TDM, we conducted an open-label, multiple-dosing study with 16 healthy subjects who were divided into two groups. Cycloserine (250 mg), <I>p</I>-aminosalicylic acid (PAS) (5.28 g), and prothionamide (250 mg) twice daily and pyrazinamide (1,500 mg) once daily were administered to both groups. Additionally, levofloxacin (750 mg) and streptomycin (1 g) once daily were administered to group 1 and moxifloxacin (400 mg) and kanamycin (1 g) once daily were administered to group 2. Blood samples for PK analysis were collected up to 24 h following the 5 days of drug administration. The PK parameters, including the maximum plasma concentration (<I>C</I><SUB>max</SUB>) and the area under the plasma concentration-time curve during a dosing interval at steady state (AUC<SUB>τ</SUB>), were evaluated. The correlations between the PK parameters and the concentrations at each time point were analyzed. The mean <I>C</I><SUB>max</SUB> and AUC<SUB>τ</SUB>, respectively, for each drug were as follows: cycloserine, 24.9 mg/liter and 242.3 mg · h/liter; PAS, 65.9 mg/liter and 326.5 mg · h/liter; prothionamide, 5.3 mg/liter and 22.1 mg · h/liter; levofloxacin, 6.6 mg/liter and 64.4 mg · h/liter; moxifloxacin, 4.7 mg/liter and 54.2 mg · h/liter; streptomycin, 42.0 mg/liter and 196.7 mg · h/liter; kanamycin, 34.5 mg/liter and 153.5 mg · h/liter. The results indicated that sampling at 1, 2.5, and 6 h postdosing is needed for TDM when all seven drugs are administered concomitantly. This study indicates that PK characteristics must be considered when prescribing optimal treatments for patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT02128308.)</P>
MYC quantitation in cell-free plasma DNA by real-time PCR for gastric cancer diagnosis
Park, Kyoung Un,Lee, Hee Eun,Park, Do Joong,Jung, Eun Ji,Song, Junghan,Kim, Hyung-Ho,Choe, Gheeyoung,Kim, Woo Ho,Lee, Hye Seung Walter de Gruyter GmbH 2009 Clinical chemistry and laboratory medicine Vol.47 No.5
<P>BACKGROUND: Detection of tumor-associated genetic alterations in plasma of cancer patients has recently been suggested to be an accurate method for detecting early or recurrent cancer. METHODS: We performed quantitative real-time PCR for MYC and GAPDH in tissue and plasma samples of 57 patients with gastric cancer and in plasma of 79 cancer-free individuals. We also performed two-color MYC fluorescence in situ hybridization (FISH) in tissue from the 57 patients with gastric cancer. RESULTS: The tissue MYC/GAPDH ratio by real-time PCR was significantly correlated with MYC status by FISH (p<0.001). The mean ratio of plasma MYC/GAPDH was 5.226+/-3.578 (range: 1.25-18.35) in gastric cancer patients, and 2.436+/-0.881 (range: 1.00-5.00) in the healthy volunteers (p<0.001). We used receiver-operating characteristics (ROC) curve analysis to select two optimal plasma MYC/GAPDH cut-offs of 2.725 and 5.225. The sensitivity and specificity were 75.4% and 76.9% at 2.725, 38.6% and 100% at 5.225, respectively. The plasma MYC/GAPDH ratio from cancer patients was significantly correlated with the tissue MYC/GAPDH ratio (p=0.009), and tissue MYC status by FISH (p=0.024). CONCLUSIONS: These findings suggest that the plasma MYC/GAPDH ratio, as determined by real-time PCR, may be an alternative non-invasive approach for detecting gastric cancer.</P>
Serum Levels of Antituberculosis Drugs and Their Effect on Tuberculosis Treatment Outcome
Park, Jong Sun,Lee, Jae-Yeon,Lee, Yeon Joo,Kim, Se Joong,Cho, Young-Jae,Yoon, Ho Il,Lee, Choon-Taek,Song, Junghan,Lee, Jae Ho American Society for Microbiology 2016 Antimicrobial agents and chemotherapy Vol.60 No.1
<P>Therapeutic drug monitoring in tuberculosis remains controversial. We evaluated the relationship between antituberculosis drug levels in blood and clinical outcome. Serum concentrations of first-line antituberculosis drugs were measured in tuberculosis patients between March 2006 and April 2013. Venous blood was drawn 2 h after drug ingestion and was analyzed using high-performance liquid chromatography-tandem mass spectrometry. We retrospectively reviewed the data and determined the association of serum drug levels with clinical outcome. Among 413 patients, the prevalences of low serum concentrations of isoniazid (INH), rifampin (RMP), ethambutol (EMB), and pyrazinamide (PZA) were 59.9%, 27.8%, 12.8%, and 8.7%, respectively. The low INH group had a greater percentage of patients with a history of tuberculosis treatment (19.2% versus 11.0%; P = 0.026) and was more likely to present with drug-resistant strains (17.6% versus 8.8%; P = 0.049) than the normal INH group; however, low levels of INH, RMP, EMB, and PZA were not related to treatment outcome. Low INH level had a tendency to be associated with 2-month culture positivity, but it was not statistically significant (P = 0.072) in multivariate analysis. Seventeen (4.1%) patients experienced a recurrence. However, the recurrence rate was not statistically different between the low and normal INH groups. Low serum INH may play a role in recurrence and in acquired drug resistance. However, the serum level of INH was not directly related to either treatment response or recurrence rate. The role and usefulness of therapeutic drug monitoring should be evaluated in further prospective studies.</P>
Park, Chul Min,Lee, Kyunghoon,Jun, Sun-Hee,Song, Sang Hoon,Song, Junghan Elsevier 2017 Journal of chromatography. B, Analytical technolog Vol.1060 No.-
<P><B>Abstract</B></P> <P>Deficiencies in erythrocyte metabolic enzymes are associated with hereditary hemolytic anemia. Here, we report the development of a novel multiplex enzyme assay for six major enzymes, namely glucose-6-phosphate dehydrogenase, pyruvate kinase, pyrimidine 5′-nucleotidase, hexokinase, triosephosphate isomerase, and adenosine deaminase, deficiencies in which are implicated in erythrocyte enzymopathies. To overcome the drawbacks of traditional spectrophotometric enzyme assays, the present assay was based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS). The products of the six enzymes were directly measured by using ion pairing UPLC–MS/MS, and the precision, linearity, ion suppression, optimal sample amounts, and incubation times were evaluated. Eighty-three normal individuals and 13 patients with suspected enzymopathy were analyzed. The UPLC running time was within 5min. No ion suppression was observed at the retention time for the products or internal standards. We selected an optimal dilution factor and incubation time for each enzyme system. The intra- and inter-assay imprecision values (CVs) were 2.5–12.1% and 2.9–14.3%, respectively. The linearity of each system was good, with R<SUP>2</SUP> values >0.97. Patient samples showed consistently lower enzyme activities than those from normal individuals. The present ion paring UPLC–MS/MS assay enables facile and reproducible multiplex evaluation of the activity of enzymes implicated in enzymopathy-associated hemolytic anemia.</P>
Method for Predicting Thermal Fatigue Life of Thermal Barrier Coatings Using TGO Interface Stress
Junghan Yun,Sunguk Wee,Soo Park,Jeong-Min Lee,Hyunwoo Song,Chang-Sung Seok 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.9
Thermal barrier coatings (TBCs) applied to high-temperature components of gas turbines consist of a ceramic top coat, a metallic bond coat, and thermally grown oxide (TGO) generated between the top coat and bond coat. Because TBCs are subjected to repeated thermal stress at the coating interface under thermal fatigue conditions and eventually breakage, it is crucial to evaluate the thermal fatigue durability of TBCs according to the stress. In this study, coin-type TBC specimens were prepared by depositing commercial coating powders on Ni-based super alloys via the air plasma spray method, and the thermal fatigue life of the TBCs was experimentally evaluated. According to the test results and references, a finite-element analysis was conducted. The maximum stress of the TGO interface was evaluated according to the thickness and equivalent elastic modulus, and simulating the microstructure including the pores of the top coat. Using these relationships, a thermal fatigue life prediction equation considering the coating thickness (t), equivalent elastic modulus (E), and operating temperature (T) was derived, and subsequently verified.
Park, Jin-Seong,Kim, Junghan,Lee, Kwan-Soo Elsevier 2017 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.108 No.2
<P><B>Abstract</B></P> <P>We carried out experiments of repeated frosting/defrosting cycles while varying the heat exchanger inclination angles (0°, 15°, 30°, and 45°) of a louvered fin heat exchanger and analyzed the variations in thermal performance, residual water, and defrosting efficiency according to the heat exchanger inclination angle. For larger inclination angles, the heat transfer rate and pressure drop varied less during repeated cycling. The use of high inclination angles improved the drainage performance of the louvered fin heat exchanger and reduced the mass of its residual water. The defrosting efficiency varied less during repeated cycling for high inclination angles than for low inclination angles.</P>
Junghan Kim,Yoon-Ah Kook,Mohamed Bayome,Jae Hyun Park,Won Lee,Hojae Choi,Noha H. Abbas 대한치과교정학회 2019 대한치과교정학회지 Vol.49 No.4
Objective: The aim of this study was to evaluate the amount of tooth movement and histologic changes with different corticotomy designs and micro-osteoperforation in rabbits. Methods: The sample consisted of 24 rabbits divided into three experimental groups (triangular corticotomy [TC] and indentation corticotomy [IC] with flap, and flapless micro-osteoperforations [MP]) and a control. A traction force of 100 cN was applied by connecting the first premolars to the incisors. The amount of tooth movement was measured. Kruskal–Wallis test was used to assess differences in tooth movement between the groups. Micro-computed tomography, hematoxylin and eosin staining, and tartrate-resistant acidic phosphatase (TRAP) analysis were performed. Analysis of variance was applied to assess differences in TRAP-positive osteoclast count between the groups. Results: The amount of tooth movement increased by 46.5% and 32.0% in the IC and MP groups, respectively, while the bone fraction analysis showed 69.7% and 8.5% less mineralization compared to the control. There were no significant intergroup differences in the number of TRAPpositive osteoclasts. Conclusions: The micro-osteoperforation group showed no significant differences in the amount of tooth movement compared to the corticotomy groups, nor in the TRAP-positive osteoclast count compared to both corticotomy groups and control.