• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.389-403
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• 2023

In order to explore the influence of tooth root cracks on the dynamic characteristics of multi-stage planetary gear transmission systems, a concentrated parameter method was used to construct a nonlinear dynamic model of the system with 30-DOF in bending and torsion, taking into account factors such as crack depth, length, angle, error, time-varying meshing stiffness (TVMS), and damping. In the model, the energy method was used to establish a TVMS model with cracks, and the influence of cracks on the TVMS of the system was studied. By using the Runge- Kutta method to calculate the differential equations of system dynamics, a series of system vibration diagrams containing cracks were obtained, and the influence of different crack parameters on the vibration of the system was analyzed. And vibration testing experiments were conducted on the system with planetary gear cracks. The results show that when the gear contains cracks, the TVMS of the system will decrease, and as the cracks intensify, the TVMS will decrease. When cracks appear on the II-stage planetary gear, the system will experience impact effects with intervals of rotation cycles of the II-stage planetary gear. There will be obvious sidebands near the meshing frequency doubling, and the vibration trajectory of the gear will also become disordered. These situations will become more and more obvious as the degree of cracks intensifies. Through experiments, the theoretical results are in good agreement with experimental results, verifying the correctness of the theoretical model. This provides a theoretical basis for fault diagnosis and reliability research of the system.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.699-709
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• 2023

As the global air traffic volume has shown a rapid increase, doubling every 15 years since 1977, domestic and international air traffic control services and air navigation safety facility operation management system and status review It is necessary to present the feasibility of establishing an air traffic control agency with integrated functions and establish an operating system for an independent dedicated agency to provide advanced air traffic control services in preparation for the future air transport environment. In particular, in 2021, the national ATM reformation and enhancement (NARAE) a customized comprehensive plan for operations, facilities, and systems to handle air traffic safely and efficiently by actively reflecting changes in the navigation environment such as international policies and standards as this is established, the role of the air traffic control agency becomes more important, and an improved action plan for the control and navigation operating system must be promoted.

• Journal of Veterinary Science
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• v.25 no.2
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• pp.31.1-31.8
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• 2024

Background: Recently, there has been a growing interest in stem cells for human medicine. Limited feline endometrial mesenchymal stem cell (fEM-MSC) research in veterinary medicine necessitates reporting for future feline disease research and therapy. Objectives: This study aimed to isolate fEM-MSCs from feline endometrial tissues and evaluate their morphology, proliferative ability, differentiation ability, and immunophenotype. Methods: Feline endometrial tissues were obtained from the ovariohysterectomies of healthy cats and isolated using an enzymatic method. The morphology and proliferative ability of the isolated cells were assessed using a doubling time (DT) assay from passages 3 to 6 (P3 - P6). We measured pluripotency gene expressions of cells in P2 using quantitative real-time polymerase chain reaction (qRT-PCR). To investigate MSC characteristics, a trilineage differentiation assay was conducted in P4, and cells in P4 were immunophenotyped using flow cytometry. Results: fEM-MSCs showed a typical spindle-shaped morphology under a microscope, and the DT was maintained from P3 to P6. fEM-MSCs could differentiate into adipocytes, osteoblasts, and chondrocytes, and expressed three pluripotency markers (OCT4, SOX2, and NANOG) by qRT-PCR. Immunophenotypic analysis showed that the fEM-MSCs were CD14 ^-, CD34 ^-, CD45 ^-, CD9⁺, and CD44⁺. Conclusions: In this study, the feline endometrium was a novel source of MSCs, and to the best of our knowledge, this is the first report on the isolation method and characteristics of fEM-MSCs.

• Korean Circulation Journal
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• v.53 no.10
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• pp.710-719
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• 2023

Background and Objectives: In previous studies, high homocysteine levels were associated with high cardiovascular mortality. However, these results were inconsistent with those of randomized controlled trials. We aimed to evaluate the causal role of homocysteine on allcause and cardiovascular mortality using Mendelian randomization (MR) analysis. Methods: This study included the 10,005 participants in the Namwon Study. In conventional observational analysis, age, sex, survey years, lifestyles, body mass index, comorbidities, and serum folate level were adjusted using multivariate Cox proportional regression. MR using 2-stage least squares regression was used to evaluate the association between genetically predicted plasma homocysteine levels and mortality. Age, sex, and survey years were adjusted for each stage. The methylenetetrahydrofolate reductase (MTHFR) polymorphism was used as an instrumental variable for predicting plasma homocysteine levels. Results: Observed homocysteine levels were positively associated with all-cause (hazard ratio [HR], 1.40; 95% confidence interval [CI], 1.26-1.54) and cardiovascular (HR, 1.62; 95% CI, 1.28-2.06) mortality when plasma homocysteine levels doubled. However, these associations were not significant in MR analysis. The HRs of doubling genetically predicted plasma homocysteine levels for all-cause and cardiovascular mortality were 0.99 (95% CI, 0.62-1.57) and 1.76 (95% CI, 0.54-5.77), respectively. Conclusions: This MR analysis did not support a causal role for elevated plasma homocysteine concentrations in premature deaths.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.37.1-37.15
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• 2022

Background: This study investigated the effect of dispatch frequency on blood cadmium levels and the effect of blood cadmium levels on hypertension in male firefighters in a metropolitan city. Methods: We conducted a retrospective longitudinal study of male firefighters who completed the regular health checkups, including a health examination survey and blood cadmium measurements. We followed them for 3 years. To investigate the effect of dispatch frequency on blood cadmium levels and the effect of blood cadmium levels on hypertension, we estimated the short-term (model 1) and long-term (model 2) effects of exposure and hypothesized a reversed causal pathway model (model 3) for sensitivity analysis. Sequential conditional mean models were fitted using generalized estimating equations, and the odds ratios (ORs) and the respective 95% confidence intervals (CIs) were calculated for hypertension for log-transformed (base 2) blood cadmium levels and quartiles. Results: Using the lowest category of dispatch frequency as a reference, we observed that the highest category showed an increase in blood cadmium levels of 1.879 (95% CI: 0.673, 3.086) ㎍/dL and 0.708 (95% CI: 0.023, 1.394) ㎍/dL in models 2 and 3, respectively. In addition, we observed that doubling the blood cadmium level significantly increased the odds of hypertension in model 1 (OR: 1.772; 95% CI: 1.046, 3.003) and model 3 (OR: 4.288; 95% CI: 1.110, 16.554). Using the lowest quartile of blood cadmium levels as a reference, the highest quartile showed increased odds of hypertension in model 1 (OR: 2.968; 95% CI: 1.121, 7.861) and model 3 (OR: 33.468; 95% CI: 1.881, 595.500). Conclusions: We found that dispatch frequency may affect blood cadmium levels in male firefighters, and high blood cadmium levels may influence hypertension in a dose-response manner.

• Journal of Animal Reproduction and Biotechnology
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• v.39 no.3
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• pp.153-163
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• 2024

Background: The clinical application of canine mesenchymal stem cells (MSCs) necessitates efficient and safe culture methods to produce large quantities of cells. Traditionally, fetal bovine serum (FBS) has been used for MSC expansion, but it carries risks such as contamination and adverse immune responses. Methods: In this study, we investigate the efficacy and efficiency of canine allogeneic serum as an effective alternative to FBS for the in vitro culture of canine MSCs. We measured the population doubling time of canine MSCs in allogeneic serum conditions and utilized qRT-PCR, flowcytometric analysis, and cellular staining/color-metric assay for investigating its effects on cellular senescence during long-term culture and the expression of key pluripotency-related transcriptomes. Results: Our findings demonstrate that canine MSCs cultured with allogeneic serum exhibited enhanced proliferation rates, reduced cellular senescence, and lower apoptosis levels compared to those cultured with FBS. Additionally, the expression of key pluripotency-related transcription factors, including Oct4, Sox2, and Nanog, was increased in canine MSCs cultured with allogeneic serum. Conclusions: These results highlight the potential of canine allogeneic serum to provide a safer and more effective culture environment, supporting the large-scale expansion and maintenance of canine MSCs for clinical applications.

• Journal of Life Science
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• v.28 no.6
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• pp.718-725
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• 2018

Toll-like receptor 4 (TLR4) has been implicated in cell proliferation and apoptosis in several types of cancer. In this study, the impact of TLR4 activation on apoptotic cell death in gynecologic cancers induced by lipopolysaccharide (LPS) was investigated. Cervical cancer cell lines were produced from isolated surgical specimens supplied by Paik Hospital. The primary cultures of normal myometrium and gynecologic cancers, including cervical, endometrial, and ovarian cancers, were used to examine the differences in morphological characteristics between normal and cancerous cells. A reverse transcription polymerase chain reaction analysis was used to determine the relative expression levels of TLR4 gene involved in apoptosis-associated signaling in cervical cancer cells. The cancer cell colonies showed a tendency to reach high levels of confluency compared with normal cells. In addition, an enhanced growth rate and loss of contact inhibition were observed in gynecologic cancer cells compared with normal cells (doubling times of 16.6 hr vs. 26 hr, respectively). The expression level of ITGA5, an alpha-5 integrin marker, was upregulated in normal myometrial cells, but this tendency was not exhibited in cervical cancer cells. Furthermore, p53 tumor suppressor gene expression was upregulated, whereas TLR4 and caspase-3 gene expressions were downregulated in cervical cancer cells. Notably, the expression levels of TLR4 and caspase-3 were increased significantly in LPS-treated cancer cells compared with those in non-LPS-treated cells. These results suggest that the TLR4-mediated caspase-dependent apoptotic signaling pathway could be suggested as a therapeutic target for the treatment of gynecologic cancers, including cervical cancers.

• Clinical and Experimental Reproductive Medicine
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• v.36 no.1
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• pp.23-34
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• 2009

Objectives: Mesenchymal stem cells (MSC) comprise a promising tool for cellular therapy. It is known that long-term in vitro culture of human bone marrow and adipose tissue derived-MSCs lead to a reduction of life span and a change of stem-like characters. The aim of our study was to examine whether stem cell properties of human umbilical cord-derived stem cells (HUC) could be affected by in vitro expansion. Methods: HUC were isolated from human umbilical cord and cultured for 10 passages in vitro. Morphology and population doubling time (PDT) were investigated, and changes of stem cell properties were examined using RT-PCR and immunocytochemistry during serial subcultures. Results: Morphology and PDT of HUC began to change slightly from the 7th passage (p7). Expression level of nestin and vimentin mRNAs increased along with the culture period from p4 until p10. In contrast, expression level of SCF mRNA decreased during the same culture period. Expression level of Oct-4 and HNF-4${\alpha}$ mRNAs was not significantly changed throughout the culture period until p10. Expression level of BMP-4, FGF-5, NCAM and HLA-ABC mRNAs appeared to increase as the culture continued, however, the difference was not significant. Immunocytochemical studies showed that HUC at p3, p6 and p9 positively were stained with antibodies against SSEA-3 and SSEA-4 proteins. Interestingly, staining intensity of HUC for ICAM-1 and HLA-ABC gradually increased throughout the culture period. Intensity against thy-1 and fibronectin antibodies increased at p9 while that against TRA-1-60 and VCAM-1 antibodies began to decrease at p6 until p9. Conclusions: These results suggest that HUC change some of their stem cell characteristics during in vitro culture. Development of culture system might be needed for the maintenance of characteristics.

• Journal of Yeungnam Medical Science
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• v.10 no.2
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• pp.432-444
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• 1993

Multidrug resistance(MDR) phenotype is frequently observed in animal and human cancer cell lines selected for in vitro resistance to a single chemotherapeutic agent. It is characterized by the diminished drug accumulation and is related to the drug efflux mechanism in resistant cells. In the present study, adriamycin resistant cells(L1210-$AdR_6$ : $10^{-6}M$ adriamycin, $-AdR_5$ : $10^{-5}M$) and vincristine resistant cells (L1210-$VcR_7$ : $10^{-7}M$ vincristine, $-VcR_6$ : $10^{-6}M$) were produced from mouse lymphoblastic leukemia cell line L1210. Growth profiles of survived cells were observed for 5 days with MTT(thiazolyl blue) assay and resistance was compared with $IC_{50}$(drug concentration of 50% survival reduction in absorbance). Resistant cells proliferated more slowly than sensitive cell. Doubling times were 29.7hr in L1210, 68.7hr in L1210-$AdR_5$ and 58.2hr in $-VcR_6$. MDRs expressed as resistance factor were as follows, L1210-$AdR_5$ was 76.4 times for vincristine, L1210-$VcR_6$ was 96.4 times for adriamycin. The cell membrane proteins with three different M.W. were recognized to be related resistance, 220, 158, and 88 kd in L1210-$AdR_5$, 158, 140 and 88 kd in L1210-$VcR_6$ by SDS-PAG electrophoresis. Cell surface membrane proteins were identified by radio-iodination and autoradiogram, their molecular weights were 158, 72.8, and 42.4 Kd in L1210-$VcR_6$.

• Journal of Korean Society of Forest Science
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• v.87 no.3
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• pp.358-365
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• 1998

To offer the basic information for sustainable production of forest resources and conservation of the global environment, change in potential natural vegetation (PNV) associated with climate change due to doubling atmospheric carbon dioxide ($2{\times}CO_2$) was estimated with the global natural vegetation mapping system based an K${\ddot{o}}$ppen scheme. The system interpolates climate data spherically to each grid cell, determines the vegetation types onto the grid cell, and produces potential vegetation map and area on the globe and continents. The climate data consist of the current, ($1{\times}CO_2$) climate prior to AD 1958 observed at some 2,000 stations and the doubling ($2{\times}CO_2$) climate estimated from Meteorological Research Institute of Japan. The vegetation zone under the $2{\times}CO_2$ climate scenario expanded mainly toward the poles due to the rise in temperature. The changed PNV area on the globe amounts to 1/3 (4.91 billion (G) ha) of the total land area (15.04 Gha). Kappa statistic for judging agreement between the patterns of vegetation distribution under $1{\times}CO_2$ climate and $2{\times}CO_2$ climates shows good agreement (0.63) for the globe as a whole. The most stable areas are desert and ice. The potential forest area (PFA) was estimated at 6.82 Gha of the land area in $2{\times}CO_2$ climate scenario. In terms of continental changes in PFA, North America and Asis are increased under the $2{\times}CO_2$ climate. However, the potential forest arms of the other continents are decreased by the climate. Europe has no change in the PFA. Especially, the expansion of desert area in Oceania would be accelerated by the $2{\times}CO_2$ climate.