• Transactions on Electrical and Electronic Materials
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• v.9 no.4
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• pp.143-146
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• 2008

In this study the thermal impact characteristics by forest fire are extensively investigated using temperature controlled ovens. The test conditions for thermal impact damage are simulated according to the characteristics of natural forest fire. The test pieces are suspension porcelain insulators made by KRI in 2005 for transmission lines. In the thermal impact cycle tests with $300\;^{\circ}C$ thermal impact gradient (-70 to $230\;^{\circ}C$), cycling in 10 minute periods, no critical failures occurred in the test samples even with long cycle times. But in tests with thermal impact gradient from room temperature to $200-600\;^{\circ}C$, cycling in 10 to 30 minute periods, there were critical failures of the porcelain insulators according to the thermal impact gradient and quenching method. In the case of thermal impact by forest fire, it was found of that duration time is more important than the cycling time, and the initiation temperature of porcelain insulator failures is about $300\;^{\circ}C$, in the case of water quenching, many cracks and fracture of the porcelain occurred. It was found that the thermal impact failure is closely related to the displacement in the cement by thermal stress as confirmed by simulation. It was estimated that the initiation displacement by the thermal impact of $300\;^{\circ}C$ is about 0.1 %. Above 1% displacement, it is expected that the most porcelain insulators would fail.

• Biomolecules & Therapeutics
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• v.23 no.6
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• pp.571-581
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• 2015

${\beta}$-asarone (BAS) is an active component of Acori graminei rhizoma, a traditional medicine used clinically in treating dementia and chronic stress in Korea. However, the cognitive effects of BAS and its mechanism of action have remained elusive. The purpose of this study was to examine whether BAS improved spatial cognitive impairment induced in rats following chronic corticosterone (CORT) administration. CORT administration (40 mg/kg, i.p., 21 days) resulted in cognitive impairment in the avoidance conditioning test (AAT) and the Morris water maze (MWM) test that was reversed by BAS (200 mg/kg, i.p). Additionally, as assessed by immunohistochemistry and RT-PCR analysis, the administration of BAS significantly alleviated memory-associated decreases in the expression levels of brain-derived neurotrophic factor (BDNF) and cAMP-response element-binding protein (CREB) proteins and mRNAs in the hippocampus. Also, BAS administration significantly restored the expression of Bax and Bcl-2 mRNAs in the hippocampus. Thus, BAS may be an effective therapeutic for learning and memory disturbances, and its neuroprotective effect was mediated, in part, by normalizing the CORT response, resulting in regulation of BDNF and CREB functions and anti-apoptosis in rats.

• The Journal of Internal Korean Medicine
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• v.31 no.3
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• pp.586-599
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• 2010

Objective : The water extract of Yukgunja-tang(YGJT) has been traditionally used in treatment of qi deficiency and phlegm in Oriental medicine. However, little is known about the mechanism by which YGJT protects neuronal cells from injury damages. Therefore, this study was designed to evaluate the protective effects of YGJT on C6 glial cells by glutamate-induced cell death. Methods : The present study describes glutamate, which is known as an excitatory neurotransmitter, related with oxidative damages, and YGJT, which shows protective effects against glutamate-induced C6 glial cell death. One of the main mediators of glutamate-induced cytotoxicity was known on the generation of reactive oxygen species(ROS) via activation of NADPH oxidase (NOX). The protective effects of antioxidant(NAC) and NOX inhibitor(apocynin) on the glutamate-induced C6 glial cells were determined by a MTT reduction assay. Result : YGJT inhibited glutamate-induced ROS generation via inhibition of NOX expression on glutamate-stimulated C6 glial cells. Furthermore, YGJT attenuated glutamate-induced caspase activation. These results suggest that YGJT could be a new potential candidate against glutamate-induced oxidative stress and cell death. Conclusion : These findings indicate that in C6 glial cells, ROS plays an important role of glutamate-induced cell death and that YGJT may prevent cell death from glutamate-induced cell death by inhibiting the ROS generation.

• Journal of Physiology & Pathology in Korean Medicine
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• v.27 no.4
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• pp.391-399
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• 2013

The aim of the present study was to investigate the antioxidant efficacies between extracts of Prunus yedoensis(PY) and Betulae platyphyllae var. japonica(BP). HPLC pattern was different between barks and extract solvents. Content of total phenolic compound was the highest in ethanol extract of BP(382.201 mg/g ext.) and its content was 1.9 times higher than that from the water extract of PY. Total antioxidant efficacy also was the highest in ethanol extract of BP (292 copper reducing equivalents). Nitric oxide scavenging activity was almost 70% in ethanol extract of BP treated 200 ug/ml and it was higher than positive control(ascorbic acid). DPPH radical scavenging ability was up by 80% in all samples. ABTS cation decolorization from each barks was activated over 85% in all samples at 100 ug/ml concentration, especially, the activity was the highest (94.4%) in ethanol extract of BP. Hydrogen peroxide scavenging activities were also highest (45%) in ethanol extract of BP at 200 ug/ml concentration and were as high as positive control. Stimulation of the macrophages RAW 264.7 cells with lipopolysaccharide (LPS) increased intracellular ROS levels and ethanol extract of BP at 200 ug/ml concentration reduced ROS levels up to 41 %. The results indicated that the barks of PY and BP has potent antioxidant activities and ethanol extract of BP of them has the highest antioxidant activities.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.1
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• pp.31-35
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• 2004

This experiment was performed to observe morphological changes in rice leaf tissue caused by a successive UV-B radiation. Effect of UV-B radiation on the structural alteration of tissue was not visually found, however, Photosynthate containing phosphate was sharply reduced in proportion with an increase of UV-B radiation. Fundamental components of cuticle layer were being degraded after 6 h of UV-B radiation compared to the control. UV-B-induced mesophyll cell appeared altered because of water stress, the shape of chloroplast appeared to be considerably shrunk and chloroplast thylakoid membranes were severely destructed. Primary cell wall of UV-B-stressed tissue was entirely scattered or disappeared, and the secondary cell wall due to lignin synthesis and deposition resulted in being thickened, almost 2-times, compared with the control.

• Toxicological Research
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• v.22 no.3
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• pp.275-282
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• 2006

In previous our studies, we have reported that eugenol derived from Eugenia caryophyllata(Myrtaceace) exhibits acute N-methyl-D-aspartate(NMDA)- and oxygen/glucose deprivation-induced neurotoxicity in primary cortical cultures and protects hippocampal neurons from global ischemia. In this study, we investigated whether the extracts and fractions of E. caryophyllata or eugenol shows the neuroprotective effects against delayed neuronal injury evoked by NMDA or ${\alpha}$-amino-3-hydroxy-5-methylisoxazole propionate(AMPA), and oxidative damage induced by arachidonic acid-, hydrogen peroxide-, $FeCl_2$/ascorbic acid-, and buthionine sulfoximine(BSO) in primary cortical cultures. We examined the neurotoxicity of eugenol itself in cultures and inhibitory effect of eugenol on NMDA- or kainate(KA)-induced convulsion in BALB/c mice. Each water, methanol extract and methanol fraction of E. caryophyllata was significantly attenuated NMDA-induced delayed neurotoxicity, respectively. Eugenol exhibited a significant inhibitory action against the convulsion evoked by NMDA and KA, and reduced delayed or brief neurotoxicity induced by NMDA, AMPA, and various oxidative injuries. These results suggest that eugenol derived from E. caryophyllata may contribute the neuroprotection against delayed-type excitotoxicity and excitotoxins-mediated convulsion through the amelioration of oxidative stress.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.97-108
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• 2005

This paper presents the effect of tunneling and groundwater interaction on tunnel behavior. As part of this study, design issuses for tunneling situations similar to that considered in this study are first identified. A parametric study is then conducted on tunneling situations frequently encountered in Seoul area using a 3D stress-pore presure coupled finite-element model with emphasis on the effects of ground and lining permeabilities. The results indicate that tunneling in water bearing ground results in a deeper and wider settlement trough, increased axial thrusts in shotcrete lining than those without the groundwater. Also revealed is that the axial thrusts in shotcrete lining are governed by the relative permeability between the ground and the lining. Design implications of the findings from this study are discussed.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.10
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• pp.1433-1439
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• 2000

An experiment was carried out with 48 IVRI 2CQ rats 6-8 week old, weighing 50-100 g, to study the effect of lead exposure on antioxidant defense, lipid peroxide level, status of thiol groups and concentration of lead in the liver and kidneys at the end of the exposure and also after withdrawal of lead administration. Twenty four rats were given lead at a daily dose rate of 1 mg lead/2 ml of distilled water/kg body weight as lead acetate solution intraperitoneally for a period of 30 days. Another 24 control rats received 2 ml of sterile normal saline solution (0.85% NaCl)/kg body weight in an identical manner. A many-fold increase in concentration of lead was associated with a non-significant (p>0.05) decrease in the activities of superoxide dismutase (SOD) in the liver (27%) and kidneys (12%) and catalase in kidneys (22%). A significant (p<0.05) increase in lipid peroxide level was recorded in the liver (40%) compared with control values. There were significant (p<0.05) decreases in the total thiol and protein bound thiol contents in liver and an increase in non-protein bound thiol groups in the kidneys of lead exposed rats. During the 10 day observation period after withdrawal of lead administration, no significant change was observed with respect to any of the above parameters indicating that a 10 day withdrawal period was not enough for restoration of normality. It is concluded that the magnitude of response and the resultant changes in the lipid peroxide concentration, and the activities of SOD and catalase were not identical in the liver and kidneys of lead-exposed rats.

• The Korean Journal of Pharmacology
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• v.19 no.1
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• pp.61-69
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• 1983

Hypothermia is an essential preparatory procedure for cardiac surgery, which lows the metabolic rate and myocardial oxygen demand. However, hypothermia itself is a stress enough to change the tonus of sympathoadrenal system, especially the cardiovascular responses to the catecholamines. It is reported that the positive chronotropic and inotropic response of catecholamines is exaggerated during hypothermia because of decreased norepinephrine uptake at the junctional cleft or decreased catecholamine metabolism. On the other hand, there are evidences of diminished catecholamines responses in low temperature ana further, interconversion of adrenergic receptors is also suggested. Present investigation was planned to observe the cardiovascular changes and its responses to catecholamines during surface hypothermia in cat. Healthy mongrel cats, weighing $2{\sim}3\;kg$, anesthetized with secobarbital(30 mg/kg), were permitted to hypothermia by external cooling technic. Esophageal temperature, ECG (lead II), heart rate, left ventricular pressure with dP/dt, carotid artery pressure and left ventricular contractile force were monitored with Polygragh (Model 7, Grass), and the respiration was maintained with artificial respirator (V 5 KG, Narco). Followings are summarized results. 1) Surface cooling caused progressive decrease of body temperature and reached $l8.8{\pm}0.8^{\circ}C$ and $16.9{\pm}0.6^{\circ}C$ in 120 and 150 min respectively, after immersion into ice water, and ventricular fibrillation was developed at $20.4{\pm}0.65^{\circ}C$. 2) Heart rate, blood pressure and myocardial contractility were decreased after initial increase as the body temperature falls. 3) Systolic and diastolicdd P/dt of left ventricular pressure were decreased and that the decrement of diastolic dP/dt was more marked. 4) On ECG, ST depression, Twave inversion and prolongation of PR interval were prominent in hypothermia, and moreover, the prolongation of PR interval was marked just prior to the development of ventricular fibrillation. 5) The cardiovascular responses to catecholamines, especially to isoproterenol, were suppressed under hypothermia.

• Nutrition Research and Practice
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• v.2 no.3
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• pp.158-164
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• 2008

This study investigated that the antioxidative effect of freeze-dried cranberry powder against protein and lipid oxidation and ameliorative effect of serum lipid profile in rat fed atherogenic diet. Six weeks old male Sprague-Dawley rats were divided into the following four groups: normal diet group with 5% com oil(control), atherogenic diet group with 5% com oil, 10% lard, 1% cholesterol, and 0.5% sodium cholate(HFC), atherogenic plus 2% cranberry powder diet group(HFC+C2), and atherogenic plus 5% cranberry powder diet group(HFC+C5), and respective diet and water were fed daily for 6 weeks. After the experimental period, the serum lipid profile, such as total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglyceride, ferric reducing ability of plasma(FRAP), plasma phenolics content, superoxide dismutase(SOD) activity, serum protein carbonyl and thiobarbituric acid reactive substances(TBARS) levels were examined. Total phenolic compound and total flavonoid levels in freeze-dried cranberry powder were 9.94 mg/g and 8.12 mg/g, respectively. Serum total cholesterol and LDL-cholesterol levels were not significantly different for cranberry powder treatment, but serum HDL-cholesterol level was significantly increased in HFC+C5 group compared with HFC group. Plasma FRAP value tended to be increased by cranberry powder treatment though there was no significant difference. Plasma total phenol concentrations and SOD activities were not significantly different among all groups. Serum protein carbonyl and TBARS levels were significantly decreased in HFC+C5 group compared with HFC group. Overall results suggested that freeze-dried cranberry powder might have the serum lipid improving effect, as well as anti oxidative effect demonstrated by its protective effect against protein and lipid oxidation.