Gyung-Suk Kil

Profiles of antioxidant gene expression and physiological changes by thermal and hypoosmotic stresses in black porgy (Acanthopagrus schlegeli).

We determined oxidative stress by measuring the expression and activity of 3 antioxidant enzymes [Cu/Zn-superoxide dismutase (Cu/Zn-SOD), catalase (CAT) and glutathione peroxidase (GPX)] in black porgy exposed to thermal (20 degrees C-->30 degrees C) and hypoosmotic (35 psu-->10 psu and 0 psu) stresses. The expression and activity of antioxidant enzymes were significantly higher after exposure to 30 degrees C, 10 psu, and 0psu. Furthermore, we measured H(2)O(2) and lipid peroxidation (LPO) levels. As a result, H(2)O(2) and LPO levels were significantly increased after exposure to thermal (20 degrees C-->30 degrees C) and hypoosmotic stress (35 psu-->10 psu and 0 psu) stress. These results indicate that thermal and hypoosmotic stress induces oxidative stress in black porgy. Additionally, we investigated the changes due to thermal and hypoosmotic stress by measuring plasma cortisol and ion (Na(+) and Cl(-)) levels. Plasma cortisol levels increased at 30 degrees C and at 10 psu and then decreased at 0 psu. However, plasma Na(+) and Cl(-) levels did not change after exposure to thermal stress (30 degrees C), and decreased at 10 psu and 0 psu. In conclusion, thermal and hypoosmotic environments increase oxidative stress, thereby these results may be indicators of oxidative stress in black porgy.

Effect of LED light spectra on starvation-induced oxidative stress in the cinnamon clownfish Amphiprion melanopus

The present study aimed to test starvation-induced oxidative stress in the cinnamon clownfish Amphiprion melanopus illuminated by light-emitting diodes (LEDs): red (peak at 630 nm), green (peak at 530 nm), and blue (peak at 450 nm) within a visible light. We investigated the oxidative stress induced by starvation for 12 days during illumination with 3 LED light spectra through measuring antioxidant enzyme (superoxide dismutase [SOD] and catalase [CAT]) mRNA expression and activity; CAT western blotting; and measuring lipid peroxidation [LPO]), plasma H(2)O(2), lysozyme, glucose, alanine aminotransferase (AlaAT), aspartate aminotransferase (AspAT), and melatonin levels. In green and blue lights, expression and activity of antioxidant enzyme mRNA were significantly lower than those of other light spectra, results that are in agreement with CAT protein expression level by western blot analysis. Also, in green and blue lights, plasma H(2)O(2), lysozyme, glucose, AlaAT, AspAT, and melatonin levels were significantly lower than those in other light spectra. These results indicate that green and blue LEDs inhibit oxidative stress and enhance immune function in starved cinnamon clownfish.

The effect of LED light spectra on antioxidant system by thermal stress in goldfish, Carassius auratus

We investigated the effects of the different light emitting diodes (LEDs; red, green, blue, and mixed purple) on oxidative stress by measuring the expression and activities of antioxidant enzymes, plasma H2O2, lipid peroxidation (LPO), aspartate aminotransferase (AspAT), alanine aminotransferase (AlaAT) levels, and melatonin during thermal stress (low-water temperature, 22 → 14°C; high-water temperature, 22 → 30°C) on goldfish, Carassius auratus. The expression and activity of the antioxidant enzymes and levels of H2O2, LPO, AspAT/AlaAT, and melatonin were significantly higher after the fish were exposed to low-/high-water temperature environments. Furthermore, in green and blue lights, the expression of antioxidant enzymes and mRNA of heat shock protein 70, and the activity of the antioxidant enzymes and plasma H2O2, LPO, and melatonin levels were significantly lower than those under other light spectra. The results indicated that low-/high-water temperature conditions induced oxidative stress in goldfish and green and blue LEDs inhibit oxidative stress.

Upregulation of estrogen receptor subtypes and vitellogenin mRNA in cinnamon clownfish Amphiprion melanopus during the sex change process: profiles on effects of 17β-estradiol.

In the present study, we investigated the expression pattern of estrogen receptors (esr) and vitellogenin (vtg) mRNA in the gonads and liver during sex change in cinnamon clownfish by using quantitative polymerase chain reaction. We divided gonadal development during the sex change from male to female into 3 stages (mature male, male at 90days after removing female, and mature female) and investigated esr and vtg mRNA expressions during the sex change. With female, the esr and vtg mRNA expressions increased. In western blot analysis, Esr1 protein was detected only in the ovaries of female cinnamon clownfish. Also, to understand the effect of 17beta-estradiol (E(2)), we investigated the esr and vtg mRNA expression patterns in the gonads and liver, and the changes in plasma E(2) level after E(2) injection. E(2) treatment increased both mRNA expression levels of esr and vtg and plasma E(2) levels. The present study describes the molecular characterization of esr subtypes and the interactions between esr and vtg after E(2) treatment in cinnamon clownfish.

Effects of LED spectral sensitivity on circadian rhythm-related genes in the yellowtail clownfish, Amphiprion clarkii

Abstract Using clock genes in the yellowtail clownfish Amphiprion clarkii, we investigated the effects of light spectra and melatonin on circadian rhythms using light-emitting diodes (LEDs): red, green, and blue. To assess differences in circadian rhythms under different LED light spectra, we measured changes in the expressions of Melatonin receptor 1 (MT1) and Period 2 (Per2) and Cryptochrome 1 (Cry1) genes and changes in the plasma melatonin levels. Under red light, MT1 expression was significantly higher than that under other light spectra, but Per2 and Cry1 expressions were significantly lower than were those under other light spectra. Plasma glucose was significantly higher under red light than under other light spectra. These results indicate that, because red light is rapidly absorbed by water molecules, it cannot be detected by fish and acts as a stressor. In addition, melatonin regulates circadian rhythms via clock genes, and green and blue lights may be the most suitable for altering circadian rhythms in yellowtail clownfish, as these wavelengths generally penetrate seawater more efficiently than that by red light.

Effects of waterborne selenium exposure on the antioxidant and immunological activity in the goldfish, Carassius auratus

Selenium (Se) is an essential element that has relevant roles in growth, immunity, and the protection of cell membranes in organisms under normal conditions. The aim of this study was to test the antioxidant and immune functions of goldfish Carassius auratus after Se treatment. At the end of the experiment, levels of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and immune functions (immunoglobulin M protein and plasma lysozyme, thyroxine, and triiodothyronine) were significantly higher in goldfish exposed to 1 and 2 mg/L of Se than those exposed to 0.5 and 3 mg/L doses. In addition, plasma glutathione, H2O2, and lipid peroxidation levels were significantly lower in the 1 and 2 mg/L treatment group than 0.5 and 3 mg/L treatment group. These results indicated that 1 and 2 mg/L of Se enhance antioxidant defense and immune system function under aquarium conditions.

Effect of hypoosmotic and thermal stress on gene expression and the activity of antioxidant enzymes in the cinnamon clownfish, Amphiprion melanopus

We studied oxidative stress in cinnamon clownfish exposed to hypoosmotic (35 psu → 17.5 psu and 17.5 psu with prolactin (PRL)) and low temperature (28°C → 24°C and 20°C) conditions by measuring the expression and activity of Cu/Zn-superoxide dismutase (Cu/Zn-SOD), catalase (CAT), and glutathione peroxidase (GPX). The expression and activity of the antioxidant enzymes were significantly higher after the fish were exposed to 24°C, 20°C, and 17.5 psu, and expression was repressed by PRL treatment. Furthermore, we measured H2O2 and lipid peroxidation levels and found that they were significantly higher after exposure to the hypoosmotic and low-temperature environments. Additionally, we investigated changes in plasma AST and ALT levels after exposure to low temperature and hypoosmotic stress. These levels increased upon exposure of the clownfish to 24°C, 20°C, and 17.5 psu, but the levels of these parameters decreased in the 17.5 psu with PRL treatment during a salinity change. The results indicate that hypoosmotic and low-temperature conditions induce oxidative stress in cinnamon clownfish and that the parameters tested in this study may be indices of oxidative stress in the cinnamon clownfish.

Diurnal and circadian regulations by three melatonin receptors in the brain and retina of olive flounder Paralichthys olivaceus: profiles following exogenous melatonin

To establish the molecular basis of circadian rhythm control by melatonin receptors (MTs), we investigated the mitochondrial ribonucleic acid (mRNA) expressions of three types of MTs in different tissues of the olive flounder (Paralichthys olivaceus). All three types of MT mRNAs were expressed in the neural tissues, while MT1 mRNA was expressed in the peripheral tissues and MT2 and MT3 mRNAs were weakly expressed or undetected in these tissues. We observed increased MT mRNA expression in the neural tissues at night under both light–dark (LD) and constant dark (DD) conditions. Although the melatonin-treated cultured pineal gland samples showed similar diurnal variations with high-MT mRNA expression levels at night compared to those of untreated cultured pineal gland samples, the expression levels were considerably higher in the melatonin-treated samples. The plasma melatonin level also significantly increased at night. Under DD conditions, the expression patterns of MT mRNAs were similar to those under the LD photocycle, but the peak was lower and the circadian change patterns were less clear. These findings reinforce the hypothesis that MTs are active in processing light information, and that these genes are regulated by the circadian clock and light, thus suggesting that MTs play an important role in daily and circadian variations in the brain and retina of olive flounders.

Frequency Spectrum Analysis of Electromagnetic Waves Radiated by Electric Discharges

In this study, we analyzed the frequency spectrum of the electromagnetic waves radiated by an electric discharge as a basic method for developing an on-line diagnostic technique for power equipment installed inside closed-switchboards. In order to simulate local and series discharges caused by an electric field concentration and poor connections, three types of electrode systems were fabricated, consisting of needle and plane electrodes and a series arc generator meeting the specifications of UL 1699. The experiment was carried out in an electromagnetically shielded room, and the measurement system consisted of a PD free transformer, a loop antenna with a frequency bandwidth of 150 [kHz]-30 [MHz], an ultra log antenna with a frequency bandwidth of 30 [MHz]-2 [GHz], and an EMI test receiver with a frequency bandwidth of 3 [Hz]-3 [GHz]. According to the experimental results, the frequency spectra of the electrical discharges were widely distributed across a range of 150 [kHz]-160 [MHz], depending on the defects, while commonly found between 150 [kHz] and 10 [MHz]. Therefore, considering the ambient noise and antenna characteristics, the best frequency bandwidth for a measurement system to monitor abnormal conditions by detecting electromagnetic waves in closed-switchboards is 150 [kHz]-10 [MHz].

Optimization of wavelet and thresholding for partial discharge detection under HVDC

With the rapid development of HVDC technology, the detection and analysis of partial discharge (PD) under HVDC are new challenges to ensure reliable operation of the related power apparatus. The wavelet technique has been proposed for analyzing PD pulses under HVAC and ultra-high frequency signal, but its application for PD under HVDC has not been discussed. This paper dealt with the selection of the optimal wavelet and thresholding for PD pulses in order to apply the wavelet technique to PD detection under HVDC. Four electrode systems, namely protrusion on conductor, protrusion on enclosure, free particle, and crack inside spacer were fabricated to simulate typical defects in a gas insulated switchgear. The detected PD pulses were decomposed by multiresolution analysis. The correlation coefficient and dynamic time warping methods were used to select the optimal wavelet. The optimal threshold and thresholding function were chosen from various combinations with the simulated pulses. The results revealed that processing PD pulses with the mother wavelet of bior2.6, automatic threshold, and intermediate thresholding function presented the best performance.