• Corrosion Science and Technology
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• v.20 no.6
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• pp.426-434
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• 2021

The effect of two different annealing temperatures on the level of the second phase precipitated in the microstructure and the corrosion behaviors of super austenitic stainless steel were examined. The sample annealed at a higher temperature had a significantly lower fraction of the sigma phase enriched with Cr and Mo elements, showing more stable passivity behavior during the potentiodynamic polarization measurement. However, after the welding process with Inconel-type welding material, severe corrosion damage along the interface between the base metal and the weld metal was observed regardless of the annealing temperature. This was closely associated with the precipitation of the fine sigma phase with a high Mo concentration in the unmixed zone (UMZ) during the welding process, leading to the local depletion of Mo concentrations around the sigma phase. On the other hand, the fraction of the newly precipitated fine sigma phase in the UMZ was greatly reduced by post-weld heat treatment (PWHT), and the corrosion resistance was greatly improved. Based on the results, it is proposed that the alloy composition of welding materials and PWHT conditions should be further optimized to ensure the superior corrosion resistance of welded super austenitic stainless steel.

• Journal of Life Science
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• v.33 no.1
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• pp.15-24
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• 2023

To examine the antitumor effect of proso millet grains, whether proso millet grains exert apoptotic activity against human cancer cells was investigated. When the cytotoxicity of 80% ethanol (EtOH) extract of proso millet grains was tested against various cancer cells using MTT assay, more potent cytotoxicity was observed against human breast cancer MDA-MB-231 cells than against other cancer cells. When the EtOH extract was evaporated to dryness, dissolved in water, and then further fractionated by sequential extraction using four organic solvents (n-hexane, methylene chloride, ethyl acetate, and n-butanol), the BuOH fraction exhibited the highest cytotoxicity against MDA-MB-231 cells. Along with the cytotoxicity, TUNEL-positive apoptotic nucleosomal DNA fragmentation and several apoptotic responses including BAK/BAX activation, mitochondria membrane potential (Δψm) loss, mitochondrial cytochrome c release into the cytosol, activation of caspase-8/-9/-3, and degradation of poly (ADP-ribose) polymerase (PARP) were detected. However, human normal mammary epithelial MCF-10A cells exhibited a significantly lesser extent of sensitivity compared to malignant MDA-MB-231 cells. Irrespective of Fas-associated death domain (FADD)-deficiency or caspase-8-deficiency, human T acute lymphoblastic leukemia Jurkat cells displayed similar sensitivities to the cytotoxicity of BuOH fraction, excluding an involvement of extrinsic apoptotic mechanism in the apoptosis induction. These results demonstrate that the cytotoxicity of BuOH fraction from proso millet grains against human breast cancer MDA-MB-231 cells is attributable to intrinsic apoptotic cell death resulting from BAK/BAX activation, and subsequent mediation of mitochondrial damage-dependent activation of caspase cascade.

• Korean Journal of Medicinal Crop Science
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• v.11 no.2
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• pp.89-96
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• 2003

Korean mistletoes extracts were investigated for in vitro antioxidation activity, with 1,1-diphenyl-2-picrylhydrazine(DPPH), and an inhibitory effect on oxidative DNA damage by using comet assay. The Korean mistletoes were 4 different kinds classified by their host plants (Korean Viscum sp. in Quercus acutissima Carr., Korean Viscum sp. in Castanea crenata, Korean Viscum sp. in Betula platyphylla, and Korean Viscum sp. in Salix koreensis). The samples were extracted with ethanol, and fractonationed with n-butanol, ethyl acetate, chloroform, n-hexane, and second distilled water. Among them, ethyl acetate fraction from Korean Viscum sp. in Betula platyphylla showed the strongest activities to electron donating ability on 1,1-diphenyl-2-picrylhydrazyl(DPPH) and the protective effect on oxidative DNA damage.

• Korean Journal of Agricultural Science
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• v.43 no.4
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• pp.522-536
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• 2016

Fluorine is unique chemical element which occurs naturally, but is not an essential nutrient for plants. Fluoride toxicity can arise due to excessive fluoride intake from a variety of natural or manmade sources. Fluoride is phytotoxic to most plants. Plants which are sensitive for fluorine exposure even low concentrations of fluorine can cause leave damage and a decline in growth. All vegetation contains some fluoride absorbed from soil and water. The highest levels of F in field-grown vegetables are found up to $40mg\;kg^{-1}$ fresh weight although fluoride is relatively immobile and is not easily leached in soil because most of the fluoride was not readily soluble or exchangeable. Also, high concentrations of fluoride primarily associated with the soil colloid or clay fraction can increase fluoride levels in soil solution, increasing uptake via the plant root. In soils more than 90 percent of the natural fluoride ranging from 20 to $1,000{\mu}g\;g^{-1}$ is insoluble, or tightly bound to soil particles. The excess accumulation of fluorides in vegetation leads to visible leaf injury, damage to fruits, changes in the yield. The amount of fluoride taken up by plants depending on the type of plant, the nature of the soil, and the amount and form of fluoride in the soil should be controlled. Conclusively, fluoride is possible and long-term pollution effects on plant growth through accumulation of the fluoride retained in the soil.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.71-71
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• 2003

Human umbilical cord blood cells(HUCBC) are rich in mesenchymal progenitor cells, endothelial cell precursors and hematopoietic cells. HUCBC have been used as a source of transplantable stem and progenitor cells. However, little is known about survival and development of HUCBC transplantation in the CNS. Estrogen has a neuroprotective potential against oxidative stress-induced cell death so has an effect on reducing infarct size of ischemic brain. We investigated the potential use of HUCBC as donor cells and tested whether estrogen mediates intravenously infused HUCBC enter and survive in ischemic brain. PKH26 labeled mononuclear fraction of HUCBC were injected into the tail vein of ischemic OVX rat brain with or without $17\beta$-estradiol valerate(EV). Under fluorescence microscopy, labeled cells were observed in the brain section. Significantly more cells were found in the ischemic brain than in the non-ischemic brain. HUCBC transplanted into ischemic brain could migrate and survive. Some of cells have shown neuronal like cells in hippocampus, striatum and cortex tissues. These result suggest that estrogen reduces ischemic damage and increases the migration of human umbilical cord blood cells. This Study was supported by the Korea Science and Engineering Foundation(KOSEF) though the Biohealth Products Research Center(BPRC), Inje University, Korea.

• Journal of Microbiology and Biotechnology
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• v.11 no.3
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• pp.524-528
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• 2001

The measurement of radiation response using simple and informative techniques would be of great value in studying the genetic risk following occupational, therapeutic, or accidental exposure to radiation. When patients receive radiation therapy, many suffer from side effects. Since each patient receives a different dose due to different physical conditions, it is important to measure the exact dose of radiation received by each patient to lessen the side effects. Even though several biological dosimetric systems have already been developed, there is no ideal system that can satisfy all the criteria for an idean dosimetric system, especially for low-dose radiation as used in radiation therapy. In this study, an SOS Chromotest of E. coli PQ37 was evaluated as a novel dosimeter for low-dose gamma-rays. E. coli PQ37 was originally developed to screen chemical mutagens using the SOS Chromotest-a colorimtric assay, based on the induction of ${\beta}$-galactosidase ue to DNA damage. The survival fraction of E. coli PQ37 decreased dose-dependently with an increasing dose of cobalt-60 gamma-rays. Also, a good linear correlation was found between the biological damage revealed by the ${\beta}$-galactosidase expression and the doses of gamma-rays. The expression of ${\beta}$-galactosidase activity that responded to low-dose radiation under 1 Gy was $Y=0.404+(0.089{\pm}0.3)D+(-0.018{\pm}0.16)D^2$ (Y, absorbance at 420 nm; D, Dose of irradiation) as calculated using Graph Pad In Plot and Excel. When a rabbit was fed with capsules containing an agar block embdded with E. coli PQ37 showed a linear response to the radiation doses. Accordingly, the results confirm that E. coli PQ37 can be used as a sensitive biological dosimeter fro cobalt-60 gamma-rays. To the best of our knowledge, this is the first time that a bacterium has been used as a biological dosimeter, especially for low-dose radiation.

• Journal of Nutrition and Health
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• v.25 no.1
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• pp.3-11
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• 1992

This paper examines the effects of dietary fats on the fatty acid composition and market enzyme activites during liver damage in 2-acetylaminofluorene treated rats. Weaning Sprague-Dawley male rats were fed the diet of beef tallow(BT source of sturated fatty acid) corn oil(CO source of n-6 fatty acid) and perilla oil(PO source of n-3 fatty acid) at the level of 15% fat. Ten days after feeding 2-acetylaminofluorene(2-AAF) was injected intraperitoneally twice every week at the level of 50mg/kg body weight for 7 weeks. Liver microsomal and cytosolic fractions were collected to determine the microsomal fatty acid composition lipid peroxide(malondialdehyde MDA) contents glucose 6-phosphatase(G6 Pase) activity cytochrome(Cyt) P-450 contents and cytosolic glutathione S-transferase(G6 Pase) activity cytochrome(Cyt) P-450 contents and cytosolic glutathione S-transferase(GST) activity. The fatty acid composition in microsomal fraction was reflected by different dietary fats. By 2-AAF treatment linoleic acids were increased regardless of the diet MDA contents were higher in CO group than it was in BT group. However 2-AAF treatment decreased MDA contents in all dietary groups. G6Pase activity of BT group was higher than those of the other gropus. CO group had the highest Cyt P-450 contents and 2-AAF treatment lowered Cyt P-450 contents only in CO gropu GST activites were higher in CO than in BT group whereas the enzyme activites were increased by 20AAF treatment in all dietary groups. These results suggest that dietary fats and 2-AAF treatment in all dietary groups,. These results suggest that dietary fats and 2-AAF treatment affect microsomal fatty acid composition The enzyme activities concerned with liver damage were influenced differently by dietary fats and 2-AFF treatment Although PO diet contains much more polyunsaturated fatty acids than CO diet PO diet doesn't cause more oxidant stress compared with CO diet in these data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.777-785
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• 2000

The low-cycle fatigue behaviors of cast AI-Si alloy and composite with reinforcement of SIC particles were compared with those of extruded unreinforced matrix alloy and composite in order to investigate the influence of cast and extrusion processes on the cyclic deformation and fatigue life. Generally, both cast and extruded composites including the unreinforced alloy exhibited cyclic hardening behaviour, with more pronounced strain-hardening for the composites with a higher volume fraction of the SiC particles. However, cast composite under a low applied cyclic strain showing no observable plastic strain exhibited cyclic softening behavior due to the cast porosities. The elastic modulus and yield strength of the cast composite were found to be quite comparable to those of the extruded composite, however, the extrusion process considerably improved the ductility and fracture strength of the composite by effectively eliminating the cast porosities. Low-cycle fatigue lives of the cast alloy and composite were shorter than those of the extruded counterparts. Large difference in life between cast and extruded composites was attributed to the higher influence of the cast porosities on the fatigue life of the composite than that of the unreinforced alloy material. A fatigue damage parameter using strain energy density effectively represented the inferior life in the low-cycle regime and superior life in the high-cycle regime for the composite, compared to the unreinforced alloy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.437-445
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• 2016

Recently, polyurethane foam has been used in various industry fields to preserve temperature environment of structures, and a wide range of loads from the static to the dynamic are imposed on the material during a life period. The biggest characteristic of polyurethane foam is porosity as being polymeric material, and it is generally known that insulation performance of the material strongly depends on internal void size. In addition, polyurethane foam's mechanical behavior has high dependence on strain rate and temperature as well as being highly non-linear ductile for compression. In the non-linear compressive behavior, volume fraction of voids and elastic modulus decrease as strain increases. Therefore, in this study, temperature-dependent viscoplastic-damage constitutive model was developed to describe the non-linear compressive behavior with the aforementioned features of polyurethane foam.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.2235-2245
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• 2016

Ulcerative colitis (UC) results from colonic epithelial barrier defects and impaired mucosal immune responses. In this study, we aimed to investigate the modifying effects of a Spirogyra neglecta extract (SNE), a polysaccharide extract (PE) and a chloroform fraction (CF) on dextran sodium sulfate (DSS)-induced colitis in mice and to determine the mechanisms. To induce colitis, ICR mice received 3% DSS in their drinking water for 7 days. Seven days preceding the DSS treatment, oral administration of SNE, PE and CF at doses of 50, 25 and 0.25 mg/kg body weight (low dose), 200, 100 and 1 mg/kg body weight (high dose) and vehicle was started and continued for 14 days. Histologic findings showed that DSS-induced damage of colonic epithelial structure and inflammation was attenuated in mice pre-treated with SNE, PE and CF. Furthermore, SNE and PE significantly protected colonic epithelial cells from DSS-induced cell cycle arrest, while SNE, PE and CF significantly diminished apoptosis. Proteome analysis demonstrated that SNE and PE might ameliorate DSS-induced colitis by inducing antioxidant enzymes, restoring impaired mitochondria function, and regulating inflammatory cytokines, proliferation and apoptosis. These results suggest that SNE and PE could prevent DSS-induced colitis in ICR mice by protection against and/or aiding recovery from damage to the colonic epithelium, reducing ROS and maintaining normal mitochondrial function and apoptosis.