• The Korean Journal of Physiology and Pharmacology
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• v.2 no.6
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• pp.661-670
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• 1998

Dopamine has been generally known to exert antinociceptive action in behavioral pain test, such as tail flick and hot plate test, but there appears to be a great variance in the reports on the antinociceptive effect of dopamine depending on the dosage and route of drug administration and type of animal preparation. In the present study, the effects of dopamine on the responses of wide dynamic range (WDR) cells to mechanical, thermal and graded electrical stimuli were investigated, and the dopamine-induced changes in WDR cell responses were compared between animals with an intact spinal cord and the spinal animals. Spinal application of dopamine (1.3 & 2.6 mM) produced a dose-dependent inhibiton of WDR cell responses to afferent inputs, the pinch-induced or the C-fiber evoked responses being more strongly depressed than the brush-induced or the A-fiber evoked responses. The dopamine-induced inhibition was more pronounced in the spinal cat than in the cat with intact spinal cord. The responses of WDR cell to thermal stimulation were also strongly inhibited. Dopamine $D_2$ receptor antagonist, sulpiride, but not $D_1$ receptor antagonist, significantly blocked the inhibitory action of dopamine on the C-fiber and thermal responses of dorsal horn cells. These findings suggest that dopamine strongly suppresses the responses of WDR cells to afferent signals mainly through spinal dopamine $D_2$ receptors and that spinal dopaminergic processes are under the tonic inhibitory action of the descending supraspinal pathways.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2549-2552
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• 2011

In this study, the kinetic properties of wild-type and C117D mutant H. influenzae MurA (Hi MurA), which catalyzes the first reaction in the biosynthetic pathway of the cell wall, were characterized. Purified recombinant Hi MurA was active at pH values ranging from pH 5.5 to pH 10, and its $K_m$ (UNAG), $K_m$ (PEP), and $k_{cat}$ values were measured to be 31 ${\mu}M$, 24 ${\mu}M$, and 210 $min^{-1}$, respectively. Hi MurA activity was effectively inhibited by fosfomycin with an $IC_{50}$ value of 60 ${\mu}M$. Hi MurA contains a cysteine residue (C117) at the loop region near the PEP binding, whereas MurA from fosfomycin resistant Mycobaterium tuberculosis or Chlamydia trachomatis contain an aspartate residue instead of the cysteine at the corresponding site. Aspartate substitution of Cys117 in Hi MurA shifted its optimum pH from 7.8 to 6.0. In addition, the $K_m$ values for UNAG and PEP were increased to 160 ${\mu}M$ and 150 ${\mu}M$, respectively, and the $k_{cat}$ value was significantly reduced to 41 $min^{-1}$. Furthermore, the C117D mutant form of Hi MurA was not inhibited by 1 mM fosfomycin. These results indicate that the Cys117 of Hi MurA is the binding site of fosfomycin and plays an important role in the fast turnover of the catalytic reaction.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.149-152
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• 2002

The effect of pressure on the catalytic properties of glutamate racemase from Aquifex pyrophilus, an extremophilic bacterium, was investigated. The activation volume for the overall reaction $({\Delta}V^{\neq})$ and catalysis $({{Delta}V_{cat}}^{\neq})$ was -96.97 ml/mol and 4.97 ml/mol, respectively, while the reaction volume for the substrate binding (${\Delta}V_{K_m^-1}$) was -101.94 ml/mol. The large negative ${\Delta}V^{\neq}$ for the overall reaction indicated that the pressurization of glutamate racemase resulted in enhanced catalytic efficiencies. In addition, this value was also due to the large negative ${Delta}V_{K_m^-1}$ for the substrate binding. The negative value of ${Delta}V_{K_m^-1}$ implied that the conformational changes in the enzyme molecule occurred during the substrate binding process, thereby increasing the degree of hydration. The small value of ${{Delta}V_{cat}}^{\neq}$suggested that the pressure did not affect the glutamate racemase catalysis after the substrate binding.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.5
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• pp.393-400
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• 2009

NO released by myenteric neurons controls the off contraction induced by electrical field stimulation (EFS) in distal esophageal smooth muscle, but in the presence of nitric oxide synthase (NOS) inhibitor, L-NAME, contraction by EFS occurs at the same time. The authors investigated the intracellular signaling pathways related with G protein and ionic channel EFS-induced contraction using cat esophageal muscles. EFS-induced contractions were significantly suppressed by tetrodotoxin ($1\;{\mu}M$) and atropine ($1\;{\mu}M$). Furthermore, nimodipine inhibited both on and off contractions by EFS in a concentration dependent meaner. The characteristics of 'on' and 'off contraction and the effects of G-proteins, phospholipase, and $K^+$ channel on EFS-induced contraction in smooth muscle were also investigated. Pertussis toxin (PTX, a $G_i$ inactivator) attenuated both EFS-induced contractions. Cholera toxin (CTX, $G_s$ inactivator) also decreased the amplitudes of EFS-induced off and on contractions. However, phospholipase inhibitors did not affect these contractions. Pinacidil (a $K^+$ channel opener) decreased these contractions, and tetraethylammonium (TEA, ${K^+}_{Ca}$ channel blocker) increased them. These results suggest that EFS-induced on and off contractions can be mediated by the activations Gi or Gs proteins, and that L-type $Ca^{2+}$ channel may be activated by G-protein ${\alpha}$ subunits. Furthermore, ${K^+}_{Ca^-}$ channel involve in the depolarization of esophageal smooth muscle. Further studies are required to characterize the physiological regulation of $Ca^{2+}$ channel and to investigate the effects of other $K^+$ channels on EFS-induced on and off contractions.

• Elastomers and Composites
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• v.49 no.2
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• pp.110-116
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• 2014

We investigated the effect of the concentration of stannous 2-ethylhexanoate catalyst on the esterification rate between adipic acid (AA) and each of two PEG oligomers, diethylene glycol (DEG) and polyethylene glycol (PEG600). The concentration of the catalyst was varied from 0.15 to 2.0 wt.%. To attach hydroxy group to each end of the poly(oxyethylene-co-adipate) synthesized from AA and the PEGs, the esterification was performed with excessive PEG oligomers ([PEG]/[AA]=2) at $170^{\circ}C$. The degree of polymerization of the poly(oxyethylene-co-adipate)diol products were three. The apparent rate constant ($k_{app}$) of the esterification between AA and DEG shows the first order dependency on the catalyst concentration ($k_{app}=0.88[C_{cat}]$), whereas the $k_{app}$ of the esterification between AA and PEG600 has a relation of $k_{app}=0.123[C_{cat}]^{0.55}$ with the catalyst concentration. It is expected that the rate of esterification between AA and DEG has a non-linear dependency on the catalyst concentration as the catalyst concentration approaches to 0.22M.

• BMB Reports
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• v.44 no.7
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• pp.458-461
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• 2011

Enteropeptidase is a serine protease secreted by the pancreas and converts inactive trypsinogen to active trypsin. Enteropeptidase cleaves the C-terminal end of the substrate recognition sequence Asp-Asp-Asp-Asp-Lys ($D_4K$). The assay for enteropeptidase has utilized $GD_4K$-conjugated 2-naphthylamine ($GD_4K$-NA) as a fluorogenic probe over the last 30 years. However, no other $D_4K$-conjugated fluorogenic substrates of enteropeptidase have been reported. Furthermore, naphthalene is known as carcinogenic to humans. In this study, we used shift in the emission spectrum of $GD_4K$-conjugated 7-amino-4-methylcoumarin ($GD_4K$-AMC) as a fluorogenic method to measure enteropeptidase activity. The kinetic analysis revealed that enteropeptidase has a $K_M$ of 0.025 mM and a $k_{cat}$ of 65 $sec^{-1}$ for $GD_4K$-AMC, whereas it has a $K_M$ of 0.5 to 0.6 mM and a $k_{cat}$ of 25 $sec^{-1}$ for $GD_4K$-NA. The optimum pH of $GD_4K$-AMC hydrolysis was pH 8.0. Our data indicate that $GD_4K$-AMC is more suitable as a substrate for enteropeptidase than $GD_4K$-NA.

• Archives of Pharmacal Research
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• v.27 no.9
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• pp.906-911
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• 2004

In order to evaluate estrogenic compounds in natural products, an in vitro detection system was established. For this system, the human breast cancer cell line MCF7 was stably trans-fected using an estrogen responsive chloramphenicol acetyltransferase (CAT) reporter plas-mid yielding MCF7/pDsCAT-ERE119-Ad2MLP cells. To test the estrogenic responsiveness of this in vitro assay system, MCF7/pDsCAT-ERE119-Ad2MLP cells were treated with various concentrations of 17f3-estradiol. Treatments of 10$^{-8}$ to 10$^{-12}$ M 17$\beta$-estradiol revealed significant concentration dependent estrogenic activities compared with ethanol. We used in vitro assay system to detect estrogenic effects in Puerariae radix and Ginseng radix Rubra extracts. Treat-ment of 500 and 50 $\mu\textrm{g}$/ml of Puerariae radix extracts increased the transcriptional activity approximately 4- and 1.5-fold, respectively, compared with the ethanol treatment. Treatment of 500, 50, and 5 $\mu\textrm{g}$/ml of Ginseng radix Rubra extracts increased the transcriptional activity approximately 3.2-,2.7, and 1.4-fold, respectively, compared with the ethanol treatment. These observations suggest that Puerariae radix and Ginseng radix Rubra extracts have effective estrogenic actions and that they could be developed as estrogenic supplements.

• Korean Journal of Ichthyology
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• v.22 no.1
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• pp.1-8
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• 2010

We determined oxidative stress caused by thermal stress in olive flounder Paralichthys olivaceus based on the altered-mRNA expression and enzymatic activity of two key antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), along with monitoring of several other biomarkers. When the fish were exposed to acute thermal change (from $20^{\circ}C$ to $25^{\circ}C$ and $30^{\circ}C$), the expression and activity of both enzymes were significantly higher at elevated temperatures ($25^{\circ}C$ and $30^{\circ}C$) than at $20^{\circ}C$. Lipid peroxidation (LPO) was also higher at $25^{\circ}C$ and $30^{\circ}C$ than at $20^{\circ}C$. In addition, the plasma $H_2O_2$ concentration was significantly increased by thermal stress. Furthermore, we investigated changes due to thermal stress by measuring levels of plasma alanine aminotransferase (AlaAT) and aspartate aminotrasferase (AspAT). Both were significantly increased by thermal stress. As an immune indicator, the lysozyme concentration was lower at $30^{\circ}C$ than at $20^{\circ}C$, indicating that thermal stress decreases immune function. Therefore, thermal stress could induce oxidative stress and suppress immune function and can cause physiological stress.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.860-868
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• 2014

The study was performed to investigate changes in hematological responses and antioxidative enzyme activities (superoxide dismutase, SOD; catalase, CAT) of Japanese eel Anguilla japonica following exposure to 0 (control), 2.33, 4.60, 6,64 and 8.78 mM nitrite-N in fresh water for 48 h. Hematological parameters such as plasma nitrite, electrolytes, cortisol, glucose, glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), hemoglobin (Hb), methemoglobin (metHb) and NADH-methemoglobin reductase (NMR) were measured. Plasma nitrite, cortisol, metHb and NMR increased directly with increasing ambient nitrite concentration, while Hb content showed a progressive decline. Levels of plasma potassium, GOT and GPT of the eel exposed to 6.64 mM ambient nitrite were significantly higher than the control fish. The activity of SOD and CAT in plasma, gill and liver of the eel following exposure to nitrite were augmented by increasing ambient nitrite. Levels of plasma nitrite, metHb, NMR, cortisol, glucose and antioxidative enzyme activities of the eel exposed to 2.33 mM ambient nitrite were significantly higher than the control fish. This study suggested that the eel acutely exposed to elevated ambient nitrite causes nitrite-induced stress responses, changes in antioxidative enzyme activities and hematological parameters.

• Journal of Microbiology and Biotechnology
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• v.19 no.8
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• pp.818-822
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• 2009

A ${\beta}-1$,3-1,4-glucanase from the fungus Laetiporus sulphureus var. miniatus was purified as a single 26 kDa band by ammonium sulfate precipitation, HiTrap Q HP, and UNO Q ion-exchange chromatography, with a specific activity of 29 U/mg. The molecular mass of the native enzyme was 52 kDa as a dimer by gel filtration. ${\beta}-1$,3-1,4-Glucanase showed optimum activity at pH 4.0 and $75^{\circ}C$. The half-lives of the enzyme at $70^{\circ}C$ and $75^{\circ}C$ were 152 h and 22 h, respectively. The enzyme showed the highest activity for barley ${\beta}$-glucan as ${\beta}-1$,3-1,4-glucan among the tested polysaccharides and p-nitrophenyl-${\beta}$-D-glycosides with a $K_m$, of 0.67 mg/ml, a $k_{cat}$ of 13.5 $S^{-1}$ and a $k_{cat}/K_m$ of 20 mg/ml/s.