• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.623-629
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• 2017

Flow structure and mixing characteristics in a micro combustor with a multi-hole baffle were numerically studied using the Reynolds stress model. The multi-hole baffle has geometrical features to produce multiple three-dimensional vortices inside combustion chamber. When the thickness of the baffle's geometrical factors changes, variations of vortical structures occur variously. Among these vortices, the vortex generated from the fuel stream exerts a critical influence on the mixing enhancement. The three-dimensional vortical structure, in its development state, was strongly dependent on the baffle thickness. In particular, as the baffle thickness decreases to values less than the diameter of the fuel hole, the jet stream in baffle holes changes from the parabolic to saddleback profile type. The sizes of recirculation zones inside combustion chamber and the mixing state were closely affected by the structure of the jet streams.

• Molecules and Cells
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• v.40 no.10
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• pp.773-786
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• 2017

The loss of green coloration via chlorophyll (Chl) degradation typically occurs during leaf senescence. To date, many Chl catabolic enzymes have been identified and shown to interact with light harvesting complex II to form a Chl degradation complex in senescing chloroplasts; this complex might metabolically channel phototoxic Chl catabolic intermediates to prevent oxidative damage to cells. The Chl catabolic enzyme 7-hydroxymethyl Chl a reductase (HCAR) converts 7-hydroxymethyl Chl a (7-HMC a) to Chl a. The rice (Oryza sativa) genome contains a single HCAR homolog (OsHCAR), but its exact role remains unknown. Here, we show that an oshcar knockout mutant exhibits persistent green leaves during both dark-induced and natural senescence, and accumulates 7-HMC a and pheophorbide a (Pheo a) in green leaf blades. Interestingly, both rice and Arabidopsis hcar mutants exhibit severe cell death at the vegetative stage; this cell death largely occurs in a light intensity-dependent manner. In addition, 7-HMC a treatment led to the generation of singlet oxygen ($^1O_2$) in Arabidopsis and rice protoplasts in the light. Under herbicide-induced oxidative stress conditions, leaf necrosis was more severe in hcar plants than in wild type, and HCAR-overexpressing plants were more tolerant to reactive oxygen species than wild type. Therefore, in addition to functioning in the conversion of 7-HMC a to Chl a in senescent leaves, HCAR may play a critical role in protecting plants from high light-induced damage by preventing the accumulation of 7-HMC a and Pheo a in developing and mature leaves at the vegetative stage.

• Korean Journal of Food Science and Technology
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• v.18 no.4
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• pp.278-282
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• 1986

Rheological properties of naked barley (Songhak and Youngsan) starches were compared. The gelatinized starches at $3{\sim}9%$ concentration showed a Bingham pseudoplastic behavior. Songhak starch had higher values of consistency index and yield stress than those of Youngsan starch. The dependence of consistency index on concentration was mere pronounced in Songhak starch. Consistency index of both starches was exponentially dependent on concentration, but the slopes at $3{\sim}5%\;and\;5{\sim}9%$ starch concentration were different. The activation energies of 7% for Songhak and Youngsan starches were 4.10 and 3.71 Kcal/mole, respectively.

• Korean Journal of Food Science and Technology
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• v.36 no.6
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• pp.974-978
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• 2004

Brown-alga-derived natural agent NX42, mainly composed of algal polysaccharides and phlorotannins, showed mild but dose-dependent inhibition of acetylcholinesterase with $IC_{50}=600-700\;{\mu}g/mL$. Phlorotannin-rich fraction of NX42 showed substantial increase of the activity by more than one order of magnitude ($IC_{50}=54\;{\mu}g/mL$) and significant protection of SK-N-SH cells from oxidative stress by $H_2O_2$. Learning trials of mice for 5 consecutive days revealed electric-shock treatment during learning period significantly retarded learning process, whereas NX42-treated mice showed significant resistance against leaning deficiency possibly mainly due to anticholinesterase and neuroprotective activities of phlorotannin.

• Korean Journal of Pharmacognosy
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• v.49 no.2
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• pp.182-187
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• 2018

Many plant derived phytochemicals have been considered as the main therapeutic strategy against Alzheimer's disease (AD). AD is a progressive neurodegenerative disorder, and the most predominant cause of dementia in the elderly. Cholinergic deficit, senile plaque/${\beta}$-amyloid ($A{\beta}$) peptide deposition and oxidative stress have been identified as three main pathogenic pathways which contribute to the progression of AD. We screened many different plant species for their effective use in both modern and traditional system of medicines. In this study, we tested that MeOH extract of the stem bark of Hopea chinensis (Merr.) Hand.-Mazz. (HCM) affects on the processing of Amyloid precursor portein (APP) from the APPswe over-expressing Neuro2a cell line. We showed that HCM reduced the secretion level of $A{\beta}42$ and $A{\beta}40$ in a dose dependent manner. We found that HCM increased over 1.5 folds of the secretion level of $sAPP{\alpha}$, a metabolite of ${\alpha}$-secretase. Furthermore, we found that HCM inhibited acetylcholinesterase activity in vitro. We suggest that the stem bark of Hopea chinensis may be a useful source to develop a therapeutics for AD.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.2
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• pp.350-356
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• 2008

Etiological studies of diabetes and its complications showed that oxidative stress might play a major role. Therefore, many efforts have been tried to regulate free oxygen radicals for treating diabetes and its complications. Cheonghyul-san has been known to be effective for the antidiabetic, antihyperlipidemic and antiobesitic prescription, and composed of four crude herbs. In male ob/ob mouse with severe obesity, hyperinsulinemia, hypergiycemia, hyperlipidemia, the acting mechanisms of Cheonghyul-san were examined. Mice were grouped and treated for 5 weeks as follows. Both the lean (C57/BL6J black mice) and diabetic (ob/ob mice) control groups received standard chow. The experimental groups were fed with a diet of chow supplemented with 7.5, 15 and 30 mg Cheonghyul-san per 1 kg of body weight for 14 days. The effects of Cheonghyul-san extract on the ob/ob mice were observed by measuring the serum levels of glucose, insulin, lipid components, and the kidney levels of reactive oxygen species (ROS), MDA+HAE, GSH and also the enzyme activities involved in polyol pathway. Cheonghyul-san lowered the levels of serum glucose and insulin in a dose dependent manner. Total cholesterol, triglyceride and free fatty acid levels were decreased, while the HDL-cholesterol level was increased, in Cheonghyul-san treated groups. Renal aldose reductase and sorbitol dehydrogenase activities were increased in the ob/ob mice, whereas those were inhibited in the Cheonghyul-san-administered groups. Cheonghyul-san inhibited the generation of ROS in the kidney. Finally, MDA+HAE level was increased and the GSH level was decreased in the ob/ob mice, whereas those were improved in the Cheonghyul-san-administered groups. The results suggested that Cheonghyul-san exerted the antidiabetic and antihyperlipidemic activities by regulating the activities of polyol pathway enzymes, scavenging ROS, regulating the MDA+HAE and GSH levels in the ob/ob mice.

• Toxicological Research
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• v.31 no.2
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• pp.173-180
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• 2015

Extract from Gryllus bimaculatus crickets inhibits oxidation at the DNA level, with reduced production of 8-hydroxy-2'-deoxyguanosine (8-OHdG). Microarray analyses were performed with a rat 28K cDNA clone set array to identify the gene expression profiles of aged (10 months old) Wistar Kyoto rats treated for one month with 100 mg/kg G. bimaculatus ethanol extract to assess the effects. The extract produced a meaningful anti-edema effect, evident by the inhibition of creatinine phosphokinase activity. The weights of abdominal and ovarian adipose tissues were reduced and the proportion of unsaturated fatty acids in adipose tissues was increased in an extract dose-dependent manner. Compared with untreated control rats, rats treated with the extract displayed the upregulation of 1053 genes including Fas (tumor necrosis factor receptor superfamily, member 6), Amigo3 (adhesion molecule with an immunoglobulin-like domain), Reticulon 4, 3-hydroxy-3-methylglutaryl-coenzyme (Hmgcr; a reductase), related anti-fatigue (enzyme metabolism), and Rtn antioxidant, and the downregulation of 73 genes including Ugt2b (UDP glycosyltransferase 2 family), Early growth response 1, and Glycoprotein m6a. Data suggest that G. bimaculatus extract may have value in lessening the effects of aging, resulting in a differential gene expression pattern indicative of a marked stress response and lower expression of metabolic and biosynthetic genes.

• Biomolecules & Therapeutics
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• v.22 no.3
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• pp.200-206
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• 2014

N-(p-Coumaryol) tryptamine (CT), a phenolic amide, has been reported to exhibit anti-oxidant and anti-inflammatory activities. However, the underlying mechanism by which CT exerts its pharmacological properties has not been clearly demonstrated. The objective of this study is to elucidate the anti-inflammatory mechanism of CT in lipopolysaccharide (LPS)-challenged RAW264.7 macrophage cells. CT significantly inhibited LPS-induced extracellular secretion of pro-inflammatory mediators such as nitric oxide (NO) and $PGE_2$, and protein expressions of iNOS and COX-2. In addition, CT significantly suppressed LPS-induced secretion of pro-inflammatory cytokines such as TNF-${\alpha}$ and IL-$1{\beta}$. To elucidate the underlying anti-inflammatory mechanism of CT, involvement of MAPK and Akt signaling pathways was examined. CT significantly attenuated LPS-induced activation of JNK/c-Jun, but not ERK and p38, in a concentration-dependent manner. Interestingly, CT appeared to suppress LPS-induced Akt phosphorylation. However, JNK inhibition, but not Akt inhibition, resulted in the suppression of LPS-induced responses, suggesting that JNK/c-Jun signaling pathway significantly contributes to LPS-induced inflammatory responses and that LPS-induced Akt phosphorylation might be a compensatory response to a stress condition. Taken together, the present study clearly demonstrates CT exerts anti-inflammatory activity through the suppression of JNK/c-Jun signaling pathway in LPS-challenged RAW264.7 macrophage cells.

• Molecular & Cellular Toxicology
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• v.1 no.4
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• pp.268-274
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• 2005

Bromobenzene (BB) is well known hepatotoxicant. Also, BB is an industrial solvent that arouses toxicity predominantly in the liver where it causes centrilobular necrosis. BB is subjected to Cytochrome P450 mediated epoxidation followed by either conjugation with glutathione, enzymatic hydrolysis or further oxidation. In this study, we focused on BB-induced gene expression at non-hepatotoxic dose. Mice were exposed to two levels of BB, sampled at 24 h, and hepatic gene expression levels were determined to evaluate dose dependent changes. When examining the toxic dose of BB treated group in other previous studies, genes related to heat shock protein, oxidative stress, and drug metabolism are expressed. Compared to these results, our study, in which non-toxic dose of BB was administrated, showed similar patterns as the toxic conditions above. The purpose of the study was to select genes that showed changes in relation to the differing dose through confirmation of the difference within transcriptomic boundaries, but those that are not detected by the existing classic toxicology tools in non-hepatotoxic dose.

• Journal of Applied Biological Chemistry
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• v.62 no.4
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• pp.347-353
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• 2019

Stings of jellyfish, which frequently occur in a warm season, cause severe pain, inflammation and sometimes irreversible results such as the death. Harmful venoms from jellyfish, therefore, have been studied for finding the therapeutic agents to relieve pain or to neutralize toxic components. However, it is still unclear if and how jellyfish venom reveal neuronal toxicity even though pain induction seems to result from the activation of nociceptors such as nerve endings. In this study, using HT-22 cell line, we investigated neurotoxic effects of the venom of Chrysaora pacifica (CpV) which appears in South-East ocean of Korea. In 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, CpV significantly reduced the viability of HT-22 cells in a dose-dependent manner. Additionally, in 2',7'-Dichlorofluorescin diacetate fluorescence test under the culture condition lacking dominant inflammatory factors, CpV remarkably increased the production of intracellular reactive oxygen species (ROS). Reduced responsive fluorescence to Rhodamine123 and increased expression of intracellular cytochrome c were also observed in HT-22 cells treated with CpV. These indicate that CpV-reduced viability of HT-22 cells may be due to the activation of apoptotic signalings mediated with oxidative stress and mitochondrial dysfunction. Furthermore, removing Ca²⁺ ion or adding N-acetyl-Lcystein remarkably blocked the CpV effect to reduce the viability of HT-22 cells. The findings in this study clearly demonstrate that CpV may activate Ca²⁺-mediated ROS signalings and mitochondrial dysfunction resulting in neuronal damage or death, and suggest that blocking Ca²⁺ pathway is a therapeutic approach to possibly block toxic effects of jellyfish venoms.