• Animal cells and systems
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• 제11권1호
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• pp.17-22
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• 2007

The effects of antimetabolite 6-AN (6-amino-nicotinamide) on viability and morphology of L6 myoblast cells have been investigated. 6-AN ($100{\mu}M$) induced a time-dependent decrease in cell viability with respect to the untreated control cells. Following 6-AN administration the viability rate started to decline sharply, reaching about 23% of the untreated control cells at 48 h. Inverted phase-contrast microscopy revealed that 6-AN caused characteristic morphological changes such as irregularly elongated and stellate shape of cells, round-shaped nucleus, cytoplasmic vacuolization, irregular cell arrangements and formation of large spaces among cell clusters. The concentrations of ATP and $NAD^{+}$ in the 6-AN treated cells were significantly lower (p < 0.01) than those of the untreated control cells. In contrast, the concentration of AMP was significantly increased by the 6-AN treatment. Activities of catalase, superoxide dismutase and glutathione peroxidase in 6-AN treated cells were significantly higher (p < 0.01) than those of the untreated control cells. The activities of glyceraldehyde-3-phosphate dehydrogenase in 6-AN treated cells were significantly lower (p < 0.01) than those of the untreated control cells. The results suggest that 6-AN caused marked reduction of cell viability and alterations of some important metabolites and enzymes.

• Coupled systems mechanics
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• 제11권1호
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• pp.15-32
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• 2022

The comprehensive understanding of the fiber reinforced polymer behavior requires the use of advanced non-destructive testing methods due to its heterogeneous microstructure and anisotropic mechanical proprieties. In addition, the material response under load is strongly associated with manufacturing defects (e.g., voids, inclusions, fiber misalignment, debonds, improper cure and delamination). Such imperfections and microstructures induce various damage mechanisms arising at different scales before macrocracks are formed. The origin of damage phenomena can only be fully understood with the access to underlying microstructural features. This makes X-ray Computed Tomography an appropriate imaging tool to capture changes in the bulk of fibrous materials. Moreover, Digital Volume Correlation (DVC) can be used to measure kinematic fields induced by various loading histories. The correlation technique relies on image contrast induced by microstructures. Fibrous composites can be reinforced by different fiber architectures that may lead to poor natural contrast. Hence, a priori analyses need to be performed to assess the corresponding DVC measurement uncertainties. This study aimed to evaluate measurement resolutions of global and regularized DVC for glass fiber reinforced polymers with different fiber architectures. The measurement uncertainties were evaluated with respect to element size and regularization lengths. Even though FE-based DVC could not reach the recommended displacement uncertainty with low spatial resolution, regularized DVC enabled for the use of fine meshes when applying appropriate regularization.

• 대한전자공학회논문지SP
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• 제46권3호
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• pp.52-59
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• 2009

어두운 장면에 대해 획득된 영상의 대비 향상을 위해 일반적으로 사용하는 히스토그램 평활화나 감마 커브 보정 기법들은 영상의 전반적인 대비 향상에는 효과적이나 부분적인 영역에 대한 영상 화질 저하를 유발한다. 이러한 점을 해결하기 위해 최근 주변의 평균 밝기 값을 이용하여 대비를 향상시키는 다중 Retinex 알고리즘이 제안되었다. 그러나 칼라 영상에서 채널별 지역적 평균 밝기 값을 추정할 때, 영상 내에 단색의 채도가 높은 물체가 존재 할 경우 물체의 색도가 영향을 미쳐 색이 왜곡되는 경우가 발생한다. 이를 해결하기 위해 본 논문에서는 다중 Refiner 알고리즘에서 사용되는 채널별 주변의 평균 밝기 값을 보정하기 위해 영상의 주색도 값을 추정한다. 영상의 평균 색도는 광원의 색도 정보를 포함하고 있기 때문에 이를 제거하기 위하여 영상의 밝은 영역에서 광원의 색도 값을 추정하고 이를 평균 색도 값에 나누어주어 영상의 주색도 값을 추정한다. 또한 다중 Retinex 알고리즘의 결점인 낮은 채도를 CIELAB 표준 색 공간에서 색상을 유지하면서 보정하였다.

• 대한의생명과학회지
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• 제15권4호
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• pp.349-353
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• 2009

Lysophosphatidic Acid (LPA) is a bioactive lysophospholipid that is a potent signaling molecule able to provoke a variety of cellular responses in many cell types such as differentiation, inflammation and apoptosis. In this study, we have investigated the effect of LPA on Nitric oxide (NO)-induced apoptosis in rabbit articular chondrocytes. LPA dramatically reduced NO induced apoptosis of chondrocytes determined by phase contrast microscope and MTT assay. When chondrocytes alone treated with LPA, LPA induced phosphorylation of p70S6kinase, a serine/threonine kinase that acts downstream of phosphatidylinositol 3,4,5-trisphosphate (PIP3) and phosphoinositide-dependent kinase-1 (PDK-1) in the PI3 kinase pathway, dose-dependently detected by Western blot analysis. Phosphorylation of p70S6k with LPA was reduced expression of p53 in NO-induced apoptosis of chondrocytes. Also, inhibition of p70S6kinase with rapamycin was enhanced expression of p53 in chondrocytes. Our findings collectively suggest that LPA regulates NO induced apoptosis through p70S6kinase pathway in rabbit articular chondrocytes.

• Biomolecules & Therapeutics
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• 제10권3호
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• pp.152-158
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• 2002

The present study elucidated the effect of $\beta$-carbolines (harmaline and harmalol) on brain mitochondlial dysfunction caused by the tyrosinase-induced oxidation of dopamine. Harmaline, harmalol and antioxidant enzymes (SOD and catalase) attenuated the dopamine-induced alteration of membrane potential, cytochrome c release and thiol oxidation in mitochondria. In contrast, antioxidant enzymes failed to reverse mitochondrial dysfunction induced by dopmnine plus tyrosinase. $\beta$-Carbolines decreased the damaging effect of dopamine plus tyrosinase against mitochondria, except no effect of harmalol on thiol oxidation. Antioxidant enzymes decreased the melanin formation from dopamine in the reaction mixture containing mitochondria but did not reduce the formation of dopamine quinone caused by tyrosinase. Both harmalol and harmaline inhibited the formation of reactive quinone and melanin. Harmalol being more effective for quinone formation and vise versa. The results indicate that compared to MAO-induced dopamine oxidation, the toxic effect of dopamine in the presence of tyrosinase against mitochondria may be accomplished by the dopamine quinone and toxic substances other than reactive oxygen species. $\beta$-Carbolines may decrease the dopamine plus tyrosinase-induced brain mitochondrial dysfunction by inhibition of the formation of reactive quinone and the change in membrane permeability.

• 한국전기전자재료학회논문지
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• 제14권11호
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• pp.892-897
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• 2001

Variations of dielectric and piezoelectric properties and associated phase transformation of <001> -oriented rhombohedral 0.92Pb (Zn$\sub$1/3/Nb$\sub$2/3/)O$_3$-0.08PbTiO$_3$ single crystals were investigated. The longitudinal strain level was found to abruptly increase at 15 kV/cm, corresponding to that where an induced phase appears within a multidomain matrix. Drastic decreases in the dielectric constant, transverse coupling, and transverse piezoelectric coefficient associated with the E-field induced phase were the result of increased crystal anisotropy in PZN-PT crystals. By contrast, the thickness coupling increased from 53 % at 0 kV/cm to 64 % at 45 kV/cm, also associated with this phase transition under the E-field. The measured dielectric and piezflelectric properties found for the induced phase state were nearly identical to those of <001> poled tetragonal (1-x)PZN-xPT (x>0.1) crystals. Based on these results, it is evident that the symmetry of induced phase is tetragonal.

• The Korean Journal of Physiology and Pharmacology
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• 제25권4호
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• pp.297-305
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• 2021

Luteolin, a sort of flavonoid, has been reported to be involved in neuroprotective function via suppression of neuroinflammation. In this study, we investigated the protective effect of luteolin against oxidative stress-induced cellular senescence and its molecular mechanism using hydrogen peroxide (H₂O₂)-induced cellular senescence model in House Ear Institute-Organ of Corti 1 cells (HEI-OC1). Our results showed that luteolin attenuated senescent phenotypes including alterations of morphology, cell proliferation, senescence-associated 𝛽-galactosidase expression, DNA damage, as well as related molecules expression such as p53 and p21 in the oxidant challenged model. Interestingly, we found that luteolin induces expression of sirtuin 1 in dose- and time-dependent manners and it has protective role against H₂O₂-induced cellular senescence by upregulation of sirtuin 1 (SIRT1). In contrast, the inhibitory effect of luteolin on cellular senescence under oxidative stress was abolished by silencing of SIRT1. This study indicates that luteolin effectively protects against oxidative stress-induced cellular senescence through p53 and SIRT1. These results suggest that luteolin possesses therapeutic potentials against age-related hearing loss that are induced by oxidative stress.

• 한국안광학회지
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• 제19권1호
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• pp.93-98
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• 2014

목적: 광학적으로 유발된 망막흐림의 정도에 따른 시력감소의 개인차와 대비도의 변화에 따른 개인차를 알아보았다. 방법: 전체 69안을 대상으로 소수시력 각 단계별로 10단계의 다른 대비도로 구성된 시표를 사용하였다. 대상자들의 굴절이상을 완전교정한 후 눈 앞에 +0.25 D씩 순차적으로 증가시켜 망막흐림을 유발한 다음 각 시표에 대한 단안시력과 인식대비도를 측정하였다. 결과: 유발된 망막상의 흐림이 증가됨에 따라 시력은 점차적으로 감소되었다. +0.25 D 부가하여 유발된 망막흐림에서 시력저하의 개인차는 1.2~0.6의 범위로 나타났다. +0.50 D와 +0.75 D 부가되었을 경우 각각 1.0~0.3과 0.9~0.1 범위의 개인차를 보였다. +1.00 D가 부가되었을 때 일부 0.1 시표를 인식하지 못하는 대상안이 나타났고, +1.75 D 부가된 경우 모든 대상안들이 0.1 시표를 인식하지 못하였다. 그리고 망막흐림의 정도가 증가할수록 인식 대비도는 점진적으로 감소하였다. 결론: 최종적인 굴절이상 교정값을 결정할 때 잔여굴절이상의 정도에 따른 시력감소의 개인차를 고려해야 할 것이다.

• 약학회지
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• 제43권2호
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• pp.251-262
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• 1999

In order to investigate pharmacological properties of New Wonbang Woohwangchungsimwon Pill (NSCH) and Wonbang Woohwangchungsimwon Pill (SCH), the effects of NSCH and SCH on cerebral ischemia and central nervous system were compared. Cerebral ischemia insult was performed using unilateral carotid artery occlusion in mongolian gerbils. The histological observations showed preventive effects of NSCH and SCH treatments with ischemia-induced brain damage. The ATP in brain tissue was decreased in vehicle-treated ischemic gerbils. This decrease was prevented by SCH treatment. In contrast to what was inhibited by NSCH and SCH treatments. While NSCH and SCH had no effects on the hexobarbital-induced sleeping time, they prevented the seizures induced by electric shock and strychnine. NSCH and SCH showed sedative effect in rotarod and spontaneous activity test. Furthermore, NSCH and SCH showed anti-stress effect. Our findings suggest that the pharmacological profiles of NSCH on cerebral ischemia and central nervous system are similar to those of SCH.

• Animal cells and systems
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• 제8권1호
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• pp.57-63
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• 2004

This study provides evidence that expression of EphA8 receptor in NG108-15 cells results in a substantial increase in the number of neurite-bearing cells. However, the EphA8-induced neurite outgrowth does not require either ephrin-A5 stimulation or ectopic expression of $p110{\gamma}$ PI-3 kinase. In contrast, co-expression of a lipid kinase-inactive $p110{\gamma}$ mutant together with EphA8 causes neurite retraction in the presence of ephrin-A5 stimulation. This effect was not observed in the absence of ephrin-A5 stimulation. Significantly, the tyrosine kinase activity of EphA8 is not important for either of these processes. Taken together, our results strongly suggest that $p110{\gamma}$ PI-3 kinase is critically involved in the regulatory process by which ephrin-A5 exerts effects on the EphA8-induced neurite outgrowth.