• The Korean Journal of Physiology and Pharmacology
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• v.10 no.6
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• pp.309-315
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• 2006

The protective effects of baicalein, one of the flavonoids in Scutellaria baicalensis Georgi, were evaluated against 6-hydroxydopamine (6-OHDA)-induced neuronal damage in mice and cultured human neuroblastoma cells. Nigrostriatal damage was induced by stereotaxically injecting 6-OHDA into the right striatum. Baicalein was administered intraperitoneally 30 min before and 90 min after lesion induction. Animals received a further daily injection of baicalein for 3 consecutive days. Two weeks after 6-OHDA injection, contralateral rotational asymmetry was observed by apomorphine challenge in lesioned mice. Tyrosine hydroxylase (TH) immunohistochemistry revealed a significant loss of terminals in lesioned striatum and the reduction of the numbers of TH-positive cell in the ipsilateral substantia nigra (SN). In addition, the levels of dopamine (DA) and DA metabolites were reduced and lipid peroxidation was increased in lesioned striatum. However, baicalein treatment reduced apomorphine-induced rotational behavior in 6-OHDA-lesioned mice, and increased TH immunoreactivity in the striatum and SN, and DA levels in lesioned striatum. Lipid peroxidation induced by 6-OHDA was also inhibited by baicalein treatment. Furthermore, when SH-SY5Y human neuroblastoma cells were treated with baicalein, 6-OHDA-induced cytotoxicity and reactive oxygen species (ROS) production were significantly reduced. These results indicate that baicalein effectively protects 6-OHDA-induced neuronal damage through antioxidant action.

• Development and Reproduction
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• v.15 no.3
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• pp.205-213
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• 2011

Ethanol treatment during the brain growth spurt period has been known to induce the death of Purkinje cells. The underlying molecular mechanisms and the role of reactive oxygen species (ROS) in triggering ethanol-induced Purkinje cell death are, however, largely unresolved. We undertook TUNEL staining, western blotting assay and immunohistochemistry for the cleaved forms of caspase-3 and -9, with calbindin D28K double immunostaining to identify apoptotic Purkinje cells. The possibility of ROS-induced Purkinje cell death was immunohistochemically determined by using anti-8-hydroxy-2'deoxyguanosine (8-OHdG), a specific cellular marker for oxidative damage. The results show that Purkinje cell death of PD 5 rat cerebellum following ethanol administration is mediated by the activation of caspase-3 and -9. However, unexpectedly, TUNEL staining did not reveal any positive Purkinje cells while there were some TUNEL-positive cells in the internal and external granular layer. 8-OHdG was detected in the Purkinje cell layers at 8 h, peaked at 12-24 h, but not at 30 h post-ethanol treatment. No 8-0HdG immunoreactive cells were detected in the internal and external granular layer. The lobule specific 8-OHdG staining patterns following ethanol exposure are consistent with that of ethanol-induced Purkinje cell loss. Thus, we suggest that ethanol-induced Purkinje cell death may not occur by the classical apoptotic pathway and oxidative damage is involved in ethanol-induced Purkinje cell death in the developing cerebellum.

• Composites Research
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• v.35 no.6
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• pp.469-476
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• 2022

In this paper, the microwave absorbing characteristics after the impact of the radar-absorbing structure (RAS) consisting of periodic pattern sheet (PPS) and glass fiber-reinforced plastic (GFRP) were experimentally investigated. The fabricated RAS effectively absorbed the microwave in the X-band (8.2-12.4 GHz). In order to induce the damage to the RAS, a low-velocity impact test with various impact energy of 15, 40, and 60 J was conducted. Afterward, the impact damage was observed by using visual inspection, non-destructive test, and image processing method. Moreover, the absorbing performance of intact and damaged RAS was measured by the free-space measurement system. The experiment results revealed that the delamination damage from the impact energy of 15 J did not considerably affect the microwave absorbing performance of the RAS. However, fiber breakage and penetration damage with a relatively large damaged area were occuured when the impact energy was increased up to 40 J and 60 J, and these failures significantly degraded the microwave absorbing characteristics of the RAS.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.2
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• pp.190-197
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• 2002

In this thesis, ZnO varistors with various formulation, such as A∼E, were fabricated according to ceramic fabrication method. The microstructure, electrical properties, and surge characteristics of ZnO varistors were investigated according to ZnO varistors with various formulation. In the microstructure, A∼E\`s ZnO varistor ceramics sintered at 1130$\^{C}$ was consisted of ZnO grain(ZnO), spinel phase (Zn$\_$2.33/Sb$\_$0.67/O$\_$4/), Bi-rich phase(Bi$_2$O$_3$) and intergranuler phase, wholly. Lightning impulse residual voltage of A, B, C and E\`s ZnO varistors suited standard characteristics, below 12kV at current of 5kA. On the contrary, D\`s ZnO varistor exhibited high residual voltage as high reference voltage. In the accelerated aging test, leakage current and watt loss of B, C and D\`s ZnO varistors increases abruptly with stress time under the first a.c. stress(115$\^{C}$/3.213kV/300h). Consequently, C varistor exhibited a thermal run away. On the contrary, leakage current and watt loss of A and C\`s ZnO varistors which show low initial leakage current exhibited constant characteristics. After high current impulse test, A\`s ZnO varistor has broken the side of varistor but impulse current flowed. On the contrary, E\`s ZnO Varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After long duration impulse current test, E\`s ZnO varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After high current impulse test and long duration impulse current test, E\`s ZnO varistor exhibited very good characteristics which variation rate of residual voltage is 1.4% before and after test.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.59-66
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• 2011

Lifeline Damages induced by earthquake loading brings not only a structure damage but the communication problems by the interruption of various energy utilities such as electric power, gas, and water resources. Earthquake loss estimation systems in USA and Japan, called as HAZUS (Hazard in US) and HERAS (Hazards Estimation and Restoration Aid System), respectively, have been established for the purpose of efficient responding to the earthquake hazard. Sufficient damage records are required to establish these systems. However, there are insufficient data set of damage records obtained from previous earthquakes in Korea. In this study, according to the construction specifications of the pipelines in both Korea and USA, the behavior of both ductile and brittle pipelines embedded in dense sand overlying various soils, such as clay, sand, and gravel were examined with respect to the pipeline characteristics under various earthquake loadings. The applicability of pipeline damage prediction used in HAZUS program to Korea has been investigated.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.8-17
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• 2008

Wrenching climatic changes due to ecocide and global wanning are producing a natural disaster. Coastal zones have been damaged by typhoons and accompanying storm surges. Severe waves, and destruction of the environment are adding to the severity of coastal disasters. There has been an increased interest in these coastal zone problems, and associated social confusion, after the loss of life and terrible property damage caused by typhoon Maemi. Especially if storm surges coincide with high ticks, the loss of life and property damage due to high waters are even worse. Therefore, it is desirable to accurately forecast not only the timing of storm surges but also the amount water level increase. Such forecasts are very important from the view point of coastal defense. In this study, using a numerical model, storm surge was simulated to examine its fluctuation characteristics for the coastal area behind Masan Bay, Korea. In the numerical model, a moving boundary condition was incorporated to explain wave run-up. Numerically predicted inundation regimes and depths were compared with measurements from a field survey. Comparisons of the numerical results and measured data show a very good correlation. The numerical model adapted in this study is expected to be a useful tool for analysis of storm surges, and for predicting inundation regimes due to coastal flooding by severe water waves.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.6
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• pp.493-502
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• 2020

Apigenin, a naturally occurring flavonoid, is known to exhibit significant anticancer activity. This study was designed to determine the effects of apigenin on two malignant mesothelioma cell lines, MSTO-211H and H2452, and to explore the underlying mechanism(s). Apigenin significantly inhibited cell viability with a concomitant increase in intracellular reactive oxygen species (ROS) and caused the loss of mitochondrial membrane potential (ΔΨm), and ATP depletion, resulting in apoptosis and necroptosis in monolayer cell culture. Apigenin upregulated DNA damage response proteins, including the DNA double strand break marker phospho (p)-histone H2A.X. and caused a transition delay at the G₂/M phase of cell cycle. Western blot analysis showed that apigenin treatment upregulated protein levels of cleaved caspase-3, cleaved PARP, p-MLKL, and p-RIP3 along with an increased Bax/Bcl-2 ratio. ATP supplementation restored cell viability and levels of DNA damage-, apoptosisand necroptosis-related proteins that apigenin caused. In addition, N-acetylcysteine reduced ROS production and improved ΔΨm loss and cell death that were caused by apigenin. In a 3D spheroid culture model, ROS-dependent necroptosis was found to be a mechanism involved in the anti-cancer activity of apigenin against malignant mesothelioma cells. Taken together, our findings suggest that apigenin can induce ROS-dependent necroptotic cell death due to ATP depletion through mitochondrial dysfunction. This study provides us a possible mechanism underlying why apigenin could be used as a therapeutic candidate for treating malignant mesothelioma.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.6
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• pp.1053-1061
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• 2017

The study is concerned with providing the improvement method on making a reasonable and scientific decision on the damages accrued from the bid rigging in the construction work. According to the review on the precedent studies and decision cases on the damages caused by bid rigging, the representative problems include the insufficiency of the classification system on the damage calculation method and the omission of the necessary stage in the damage determination process. First, the improved classification system on calculating the damages caused by bid rigging is presented with the application to the bid rigging in the construction work by adding the ratio factor in addition to the damage calculation parameters such as price and cost. Second, the standard procedures organized with six stages is presented as the process required for determining the damages if the indemnification for bid rigging is claimed. The study becomes the foundation for resolving the problem with the undue burden on a party and for preventing the opportunity loss by resolving a dispute early through the improvement classification system and standard procedures presented in the study.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1633-1638
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• 2014

[6]-Gingerol is known as the major bioactive constituent of ginger. In the study, it was observed to effectively protect against ${\bullet}OH$-induced DNA damage ($IC_{50}$ $328.60{\pm}24.41{\mu}M$). Antioxidant assays indicated that [6]-gingerol could efficiently scavenge various free radicals, including ${\bullet}OH$ radical ($IC_{50}$ $70.39{\pm}1.23{\mu}M$), ${\bullet}O_2{^-}$ radical ($IC_{50}$ $228.40{\pm}9.20{\mu}M$), $DPPH{\bullet}$radical ($IC_{50}$ $27.35{\pm}1.44{\mu}M$), and $ABTS{^+}{\bullet}$radical ($IC_{50}$ $2.53{\pm}0.070{\mu}M$), and reduce $Cu^{2+}$ ion ($IC_{50}$ $11.97{\pm}0.68{\mu}M$). In order to investigate the possible mechanism, the reaction product of [6]-gingerol and $DPPH{\bullet}$ radical was further measured using HPLC combined mass spectrometry. The product showed a molecular ion peak at m/z 316 $[M+Na]^+$, and diagnostic fragment loss (m/z 28) for quinone. On this basis, it can be concluded that: (i) [6]-gingerol can effectively protect against ${\bullet}OH$-induced DNA damage; (ii) a possible mechanism for [6]-gingerol to protect against oxidative damage is ${\bullet}OH$ radical scavenging; (iii) [6]-gingerol scavenges ${\bullet}OH$ radical through hydrogen atom ($H{\bullet}$) transfer (HAT) and sequential electron (e) proton transfer (SEPT) mechanisms; and (iv) both mechanisms make [6]-gingerol be oxidized to semi-quinone or quinone forms.

• The Journal of Internal Korean Medicine
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• v.42 no.6
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• pp.1269-1284
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• 2021

Objectives: Phragmitis Rhizoma is the fresh or dried rhizome of Phragmites communis Trin., which has been prescribed in traditional Korean medicine to relieve fever and vomiting and to nourish the body fluids. Recently, the protective effect of Phragmitis Rhizoma extract or its components on myelotoxicity and inflammatory responses have been reported, but no study has yet been conducted on oxidative stress. Methods: The present study investigated whether an ethanol extract of Phragmitis Rhizoma (PR) could protect against cellular damage induced by oxidative stress in Chang liver cells. Results: Pretreatment with PR significantly suppressed the hydrogen peroxide (H₂O₂)-induced reduction of Chang cell viability and generation of reactive oxygen species (ROS), thereby deferring apoptosis. PR also markedly inhibited H₂O₂-induced comet tail formation and phospho-γH2AX expression, suggesting that PR protected against oxidative stress-mediated DNA damage. PR also effectively prevented the inhibition of ATP synthesis in H₂O₂-treated Chang cells by inhibiting the loss of mitochondrial membrane potential, indicating that PR maintains energy metabolism through preservation of mitochondrial function while eliminating ROS generated by H₂O₂. Immunoblotting results indicated that PR attenuated the H₂O₂-induced downregulation of Bcl-2 and upregulation of Bax expression. Conclusions: PR protects against oxidative injury in Chang liver cells by regulating energy homeostasis via ROS generation blockade, which is at least partly mediated through inactivation of the mitochondria-mediated apoptosis pathway.