• Toxicological Research
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• 제21권4호
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• pp.339-345
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• 2005

Aflatoxins are produced by Aspergillus flavus, parasiticus that grows in improperly stored cereals. Aflatoxin $B_1\;(AFB_1)$ is a potent hepatocarcinogen in a variety of experimental animals including human beings. In spite of a high attention to the hepatocarcinogenecity of aflatoxins, the relative toxicity of other types $(AFB_2,\;AFG_1\;and\;AFG_2)$ of the toxins is not fully clarified. Sprague-Dawley male rats were orally administered with $AFB_1,\;AFB_2,\;AFG_1\;and\;AFG_2$ at the dose of 250, 1250, and $2500\;{\mu}g/kg$ body weight. Animals were then killed at 12, 24 or 48 hrs following aflatoxin adminstration. Subsequently the relative weight of liver was measured and histopathological examination on the liver was performed. Level of 8-OxodG and expression of ras gene in the liver was determined. The relative liver weights at high doses of $AFB_1\;and\;AFG_1$ was significantly low. The treatment of $AFB_1$ at the high dose of $2500\;{\mu}g/kg$ showed vacuolar degeneration and centrilobular hepatic necrosis with inflammatory cells. The pathological changes by $AFB_2\;AFG_1,\;and\;AFG_2$ were not clearly found. The formation of 8-OxodG by $AFB_1$ increased in a dose-dependent manner up to 24 hrs after a single treatment of $AFB_1$ thereafter decreased to the level of the control. The treatments of $AFB_2\;AFG_1,\;and\;AFG_2$ showed an inconsistent pattern in the formation of 8-OxodG in the liver of rats with increasing time. The expression of ras oncogene in the liver by $AFB_1$ at the dose of $1250\;{\mu}g/kg$ was increased twice compared to the control. The treatments of $AFB_2\;AFG_1,\;and\;AFG_2$ at all doses decreased the expression of ras in the liver. These results in the present study indicate that $AFB_1$ among aflatoxins with low comparable levels is the most toxic as determined by early biomarkers such as 8-OxodG formation and ras expression. However, the levels of 8-OxodG and ras as biomarkers were not useful to predict the relative hepatocarcinogenicity of aflatoxins to $AFB_1$ in the present model. Further studies are required to look for other biomarkers to predict carcinogenic potency of aflatoxins.

• BMB Reports
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• 제41권6호
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• pp.479-484
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• 2008

In the present study, we demonstrate that ephrin-A5 is able to induce a transient increase of MAP kinase activity in PC12 cells. However, the effects of ephrin-A5 on the MAP kinase signaling pathway are about three-fold less than that of EGF. In addition, we demonstrate that EphA4 is the only Eph member expressed in PC12 cells, and that tyrosine phosphorylation induced by ephrin-A5 treatment is consistent with the magnitude and longevity of MAP kinase activation. Experiments using the Ras dominant negative mutant N17Ras reveal that Ras plays a pivotal role in ephrin-A5-induced MAP kinase activation in PC12 cells. Importantly, we found that the EphA4 receptor is rapidly internalized by endocytosis upon engagement of ephrin-A5, leading to a subsequent reduction in the MAP kinase activation. Together, these data suggest a novel regulatory mechanism of differential Ras-MAP kinase signaling kineticsexhibited by the forward signaling of EphA4 in PC12 cells.

• The Korean Journal of Physiology and Pharmacology
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• 제1권2호
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• pp.151-159
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• 1997

In an attempt to investigate whether hemorrhage affects the gene expression of the renin-angioteusin system (RAS) components in the brain and peripheral angiotensin-generating tissues, changes in mRNA levels of the RAS components in response to hemorrhage were measured in conscious unrestrained rats. Wistar rats were bled at a rate of 3 ml/kg/min for 5 min, and then decapitated 7 h after hemorrhage. Levels of mRNA for renin, angiotensinogen and angiotensin $II-AT_1$ receptor subtypes ($AT_{1A}$ and $AT_{1B}$) were determined with the methods of northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR). Hemorrhage produced a profound hypotension with tachycardia, but blood pressure and heart rate recovered close to the basal level at 7 h. Plasma and renal renin levels were significantly increased at 7 h. Hemorrhage induced rapid upregulation of gene expression of both $AT_{1A}$ and $AT_{1B}$ receptor subtypes in the brainstem and hypothalamus, downregulation of them in the adrenal gland and liver. However, renin mRNA level increased in the brainstem, decreased in the liver, but was not changed in the hypothalamus, kidney and adrenals after hemorrhage. Angiotensinogen mRNA level was not significantly changed in any of the tissue except a slight increase in the liver. The kidney and liver did not show any significant change in gene expression of the RAS components. These results suggest that gene expression of the RAS in central and peripheral tissues are, at least in part, under independent control and the local RAS in each organ plays specific physiologic role.

• 한국지역지리학회지
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• 제16권2호
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• pp.100-109
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• 2010

미국 메사추세츠주 보스턴시의 네폰셋 강의 서로 다른 토지이용지역을 사례지역으로 선정하여, 강의 밑짐으로 토지이용의 차이를 분석할 수 있는지 실험하였다. 네폰셋 강은 거주지역, 산업지역, 농업과 삼림지역 등으로 토지이용이 구분되는데, 토질의 화학적 특성이 가장 차이가 나는 거주지역과 삼림지역 두 곳을 찾아 매닝의 'n'값과 HEC-RAS 모델의 결과치를 비교하여 두 지역의 차이를 분석하였다. HEC-RAS는 US Army Corp에서 개발한 모델로 강의 윤곽 및 흐름, 진행 및 경사 등을 면밀하게 분석할 수 있다. 거주지역 분석 결과는 매닝의 계수와 HEC-RAS 결과치가 매우 다르게 나타나는데, 이는 인공적으로 설치된 강 하류의 댐과 일반적이지 않은 경사에 기인한다고 판단되었다. 일반적인 경사를 지닌 댐상류에는 임계수위가 나타나는데, 매닝의 'n' 계수가 서로 다른 깊이를 반영해주고 있다. 댐은 강의 분리와 유속에 많은 영향을 미치고 있고, 상류 수위는 증가하는 대신 유속은 감소하게 된다. HEC-RAS 모델은 강의 구조와 형태 및 행태 등을 분석하는데 좋은 기법으로, 현재 많은 연구의 대상이 되고 있는 도시 내 강의 관리와 지역개발에 지리학적으로도 크게 활용할 수 있을 것이라 예상된다.

• 한국분말재료학회지
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• 제10권3호
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• pp.168-171
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• 2003

Interpenetrating phase composites of $TiB_2$-Cu system were produced via Spark-Plasma Sintering (SPS) oi nanocomposite powders. Under simultaneous action of pressure, temperature and electric current titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a fine-grained skeleton. Increasing SPS-temperature and he]ding time promote densification due to local melting of copper matrix When copper melting is avoided the compacts contain 17-20% porosity but titanium diboride skeleton is still formed representing the feature of SPS . High degree of densification and formation of titanium diboride network result in increased hardness of high-temperature SPS-compacts.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4265-4271
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• 2022

Determination of ¹³⁷Cs, ⁴⁰K and ²¹⁰Po in water, bottom sediments and suspended matter of river systems of the Can Gio Biosphere Reserve, Vietnam was carried out. The average activity concentration of ¹³⁷Cs in waters of Ca Gau and Long Tau was 0.89 ± 0.14 and 1.08 ± 0.15 Bq m^-3 and was comparable to the levels of this radioisotope in waters of the East Sea. The activity concentration of ¹³⁷Cs in bottom sediments was 2.23 ± 0.81 and 3.63 ± 1.24 Bq kg^-1. The activity concentration of ¹³⁷Cs in water and bottom sediments could be characterized as low. So, the water areas of the Ca Gau and Long Tau rivers could be attributed to areas with insignificant pollution by technogenic radionuclides. The ²¹⁰Po activity concentration in bottom sediments of the Ca Gau and Long Tau rivers ranged from 9.2 ± 1.2 to 25.5 ± 2.1 Bq kg^-1, which is typical for river bottom sediments. Such values indicate the absence of anthropogenic enhancement of the entry of this radionuclide into the Can Gio river systems. The ⁴⁰K activity concentration varied within 467 ± 42-651 ± 39 Bq kg^-1 and represented typical values of potassium content in the bottom sediments of coastal water bodies, subject to a significant influence of the lithogenic component of suspended matter.

• 한국분말재료학회지
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• 제15권6호
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• pp.466-470
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• 2008

Experiments with a URT-0.5 accelerator (0.5 MeV, 50 ns, 1 kW) generating a nanosecond electron beam for irradiation of silver nitrate in various liquid solutions (water and toluene) were performed with the aim of producing silver nanopowders. A radiochemical reaction allows making weakly agglomerated pure Ag powders with particles of 10-15 nm and 30-50 nm in size by irradiation in toluene and water respectively. The injection of the nanosecond electron beam energy to the solution is optimal. As the absorbed dose increases, the output of the radiochemical reaction does not grow, but more agglomerated powders are synthesized.

• Journal of Magnetics
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• 제12권1호
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• pp.17-20
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• 2007

We performed magnetic force microscopy (MFM) observation on array of Co dots in order to understand magnetic state and magnetization behavior of submicron sized Co dots patterned on GaMnAs bridge. MFM observations showed the magnetization reversal and processes of local magnetization of individual ferromagnetic Co nanodots. Magnetic state of Co dots either single domain or vortex is dependent on geometrical size and thickness. Transition from single domain to vortex state can be realized with MFM tip assisted local field. Magnetization reversal process takes place through sequential reversal of individual dots. Localized inhomogeneous magnetic field can be manipulated by controlling magnetic state of individual Co dot in the array structure.

• 셀메드
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• 제9권4호
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• pp.9.1-9.4
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• 2019

Ayurveda is one of the ancient systems of traditional medicine in India, however, there is a lack of proper scientific research and controlled studies on efficacy and toxicity of several Ayurvedic formulations using the methods of modern science, which hinders the proper development of Ayurveda, both in India and abroad. The present study was undertaken to further corroborate the efficacy of some popular anthelmintic Ayurvedic medicines, as evident by the pharmacological effects of Ayurvedic formulations on body surface of a cestode parasite. This study employed a common intestinal cestode of domestic fowl, Raillietina sp., as a model parasite, that was exposed in vitro to different concentrations of three common Indian Ayurvedic anthelmintic drugs, namely Krimimudgar Ras, Kriminol and Vidangasava, and also to a modern anthelmintic drug, praziquantel (PZQ). After the paralysis of parasites, the specimens from the highest drug-treated concentration (50 mg/ml), praziquantel (1 mg/ml), and control groups, were collected and processed for scanning electron microscopic studies to document the effects of drugs on the body surface of parasite. In this study, maximum degree of alterations on parasite body surface was observed in the worms exposed to Krimimudgar Ras, indicating this drug to be highly efficacious against intestinal worms and brings out a transtegumental mode of action on parasite. In conclusion, the findings of present study suggest that of the three Ayurvedic formulations tested, Krimimudgar Ras possesses significant anthelmintic effects, which are mediated through parasite's body surface. Therefore, Krimimudgar Ras may be considered as a reliable anthelmintic Ayurvedic formulation, as validated through this study.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1084-1085
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• 2006

We studied formation of nanostructured $TiB_2$-Cu composites under shock wave conditions. We investigated the influence of preliminary mechanical activation (MA) of Ti-B-Cu powder mixtures on the peculiarities of the reaction between Ti and B under shock wave. In the MA-ed mixture the reaction proceeded completely while in the non-activated mixture the reagents remained along with the product . titanium diboride. The size of titanium diboride particles in the central part of the compact was 100-300 nm.