Atorvastatin Rejuvenates Neural Stem Cells Injured by Oxygen-Glucose Deprivation and Induces Neuronal Differentiation Through Activating the PI3K/Akt and ERK Pathways

Choi, Na-Young,Kim, Ji Young,Hwang, Mina,Lee, Eun-Hye,Choi, Hojin,Lee, Kyu-Yong,Lee, Young Joo,Koh, Seong-Ho Springer-Verlag 2019 Molecular neurobiology Vol.56 No.4

Candesartan Restores the Amyloid Beta-Inhibited Proliferation of Neural Stem Cells by Activating the Phosphatidylinositol 3-Kinase Pathway

Choi, Hojin,Choi, Na-Young,Lee, Kyu-Yong,Lee, Young Joo,Koh, Seong-Ho Korean Dementia Association 2017 Dementia and Neurocognitive Disorders Vol.16 No.3

<P><B>Background and Purpose</B></P><P>Neurogenesis in the adult brain is important for memory and learning, and the alterations in neural stem cells (NSCs) may be an important aspect of Alzheimer's disease (AD) pathogenesis. The phosphatidylinositol 3-kinase (PI3K) pathway has been suggested to have an important role in neuronal cell survival and is highly involved in adult neurogenesis. Candesartan is an angiotensin II receptor antagonist used for the treatment of hypertension and several studies have reported that it also has some neuroprotective effects. We investigated whether candesartan could restore the amyloid-β(25–35) (Aβ<SUB>25-35</SUB>) oligomer-inhibited proliferation of NSCs by focusing on the PI3K pathway.</P><P><B>Methods</B></P><P>To evaluate the effects of candesartan on the Aβ<SUB>25-35</SUB> oligomer-inhibited proliferation of NSCs, the NSCs were treated with several concentrations of candesartan and/or Aβ<SUB>25-35</SUB> oligomers, and MTT assay and trypan blue staining were performed. To evaluate the effect of candesartan on the Aβ-inhibited proliferation of NSCs, we performed a bromodeoxyuridine (BrdU) labeling assay. The levels of p85α PI3K, phosphorylated Akt (pAkt) (Ser473), phosphorylated glycogen sinthase kinase-3β (pGSK-3β) (Ser9), and heat shock transcription factor-1 (HSTF-1) were analyzed by Western blotting.</P><P><B>Results</B></P><P>The BrdU assays demonstrated that NSC proliferation decreased with Aβ<SUB>25-35</SUB> oligomer treatment; however, a combined treatment with candesartan restored it. Western blotting displayed that candesartan treatment increased the expression levels of p85α PI3K, pAkt (Ser473), pGSK-3β (Ser9), and HSTF. The NSCs were pretreated with a PI3K inhibitor, LY294002; the effects of candesartan on the proliferation of NSCs inhibited by Aβ<SUB>25-35</SUB> oligomers were almost completely blocked.</P><P><B>Conclusions</B></P><P>Together, these results suggest that candesartan restores the Aβ<SUB>25-35</SUB> oligomer-inhibited proliferation of NSCs by activating the PI3K pathway.</P>

Understanding the role of glycogen synthase kinase-3 in L-DOPA-induced dyskinesia in Parkinson’s disease

Choi, Hojin,Koh, Seong-Ho Informa UK (Taylor Francis) 2018 Expert opinion on drug metabolism & toxicology Vol.14 No.1

<P>Expert opinion: GSK-3 plays critical roles in L-DOPA-induced neurotoxicity, and the development of specific methods to inhibit GSK-3 function may help prevent L-DOPA neurotoxicity and LID in PD. However, balanced GSK-3 inhibition and less beta-catenin degradation is essential for preventing LID, because too much GSK-3 inhibition increases beta-catenin levels, which is related to cancers.</P>

Air Pollution and Dementia

Hojin Choi,김승현 대한치매학회 2019 Dementia and Neurocognitive Disorders Vol.18 No.4

.

Coronavirus Disease 2019 and Dementia: The Survey for Dementia Patients in COVID-19 Crisis

Choi Hojin,Lim Jae-Sung,Lee Chan-Nyoung,장재원,이상학,Na Seunghee,Ryoo Nayoung,Park Kun Woo,Shim Yong S. 대한치매학회 2021 Dementia and Neurocognitive Disorders Vol.20 No.2

Au-doped PtCo/C catalyst preventing Co leaching for proton exchange membrane fuel cells

Choi, Juhyuk,Cho, Jinwon,Roh, Chi-Woo,Kim, Beom-Sik,Choi, Min Suk,Jeong, Hojin,Ham, Hyung Chul,Lee, Hyunjoo Elsevier 2019 Applied catalysis. B, Environmental Vol.247 No.-

<P><B>Abstract</B></P> <P>Proton exchange membrane fuel cells (PEMFCs) are promising mobile power supply systems, and operate without noise or polluting emissions. Because the oxygen reduction reaction (ORR) at the cathode suffers from high overpotential and sluggish kinetics, many catalysts have been developed in efforts to enhance activity and durability for the ORR. However, most of them have complicated synthetic procedures which cannot be scaled-up easily, and have only been tested in a half-cell. High activity in a half-cell does not necessarily guarantee better performance in a single-cell. In this work, we synthesized an Au-doped PtCo/C catalyst using a simple method of gas-phase reduction and subsequent galvanic replacement, and its activity and durability were tested in a single-cell. When current densities were compared at 0.6 V after a durability test of 30,000 cycles in 0.6–1.0 V, the values were 1.40, 0.81, and 0.63 A cm<SUP>−2</SUP> for the Au-doped PtCo/C, acid-treated PtCo/C, and commercial Pt/C catalysts, respectively. Co leaching was much less in the Au-doped PtCo/C. Density functional theory (DFT) calculations confirmed that surface oxygen species bound more weakly at the catalyst surface and migration of a Co atom (Co segregation) to the surface was suppressed in the presence of Au. This facile method can provide a more realistic strategy to design better ORR catalysts for PEMFC application.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Au-doped PtCo/C catalyst was prepared by gas-phase reduction and subsequent galvanic replacement in a gram-scale. </LI> <LI> The Au-doped catalyst showed enhanced activity and durability for ORR in half-cell and single-cell tests. </LI> <LI> The maximum power density after durability tests was 1.12 W cm<SUP>−2</SUP> for Au-doped catalyst and 0.69 W cm<SUP>−2</SUP> for commercial Pt/C. </LI> <LI> DFT calculations confirmed that Co leaching could be suppressed by Au doping at Pt shell. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electromagnetic dipole coupling mechanism in layered terahertz metamaterials.

Choi, Jeongmook,Jung, Hyunseung,Lee, Hojin,Choi, Hyunyong Optical Society of America 2013 Optics express Vol.21 No.14

<P>Interplay between adjacent dipoles is an experimental priori for designing artificially-engineered structure because the dipole coupling is one critical factor for determining the electromagnetic response in metamaterials. Although numerous investigations have been performed to study the coupling effect of the split-ring resonator (SRR), the interlayer dipole coupling of its complementary SRR, called C-SRR, has been largely unexplored. Here, we present experimental and theoretical investigations on the electromagnetic coupling effect in the two stacks of layered C-SRR structures. By adjusting the relative lateral distance between the two-dimensionally stacked meta-structures, we observe that the confined magnetic dipole plays an important role in determining the resonance frequency and the bandwidth broadening of the C-SRR, exhibiting an exactly opposite behavior to the SRR structure. Our investigation provides experimental basis for developing frequency tunable three-dimensional metamaterial devices.</P>

정보통신망법의 악성프로그램에 대한 형법정책

최호진(Choi, Hojin) 한국형사정책학회 2020 刑事政策 Vol.32 No.2

악성 프로그램은 개인의 정보처리장치에 대한 위협인 동시에 금융 거래 네트워크와같은 정보 통신 인프라에 대한 위협이다. 또한, 악성프로그램은 정보통신시스템의해킹이나 정보통신망장애죄를 범하는데 필수적인 행위수단이다. 따라서 정보통신망법에 따라 악성프로그램에 대하여 형사적 규제를 하는 것은 당연한다. 하지만 정보통신망법의 악성 프로그램에 대한 정의나 악성 프로그램에 대한 행위유형은 상당히 포괄적이며 내용이 명확하지 않다. 컴퓨터 바이러스, 웜 및 트로이목마와 같은 일반적인 악성 프로그램을 염두에 두고 법률이 만들어졌기 때문이라고 생각한다. 정보통신기술의 발전에 따라 다양한 유형의 악성 프로그램이 개발되어 정보 통신 시스템의 안정성을 위협하고 있는 상황을 고려한다면 현행 정보통신망법은 이에 대한 적절한 법률로 평가하기는 어렵다. 이를 해결하기 위해서는 정보통신망법에서 악성 프로그램 에 대한 새로운 정의를구성할 필요가 있다. 정보통신망법 제48조가 아니라, 동법 제2조의 정의 규정조항에 악성 프로그램의 정의를 규정하는 것이 바람직하다. 입법을 고려할 때 정보통신시스템의 정상적인 운영을 방해하기위한 목적의 조항도 고려해야 한다. 악성 프로그램의 배포 및 배포뿐만 아니라 “제작행위”도 처벌해야 한다. 프로그램이 악의적인지여부를 판단할 때 프로그램 및 해당 기술 구성을 고려한다면 제작행위를 처벌하는것에 큰 문제는 없을 것으로 예상한다. 악성프로그램의 단순한 배포외에도 ‘영리목적으로’ 악성프로그램을 유포하는 행위도 처벌할 필요가 있다. The malicious program in the Internet user s information processing device is not only a threat to the personal information processing device but also a threat to information communication infrastructure such as a financial transaction network. In addition, malicious programs are essential for committing crimes such as hacking into the telecommunications network, crimes in the telecommunications network, and obstructing computer work. It can be said that without a malicious program, the crime cannot be committed. Therefore, the criminal regulatory policy through the punishment regulation of the Information and Communication Network Act for malicious programs is extremely natural. However, the definition rules for malicious programs in the Information and Communication Network Act and the punishment rules for malicious programs are fairly comprehensive and the content is unclear. I think it was because legislation was created with typical malicious programs in mind, such as computer viruses, worms, and Trojan horses. Although various types of malicious programs have been developed and threatened the stability of the information and communication system with the development of information and communication technology, it is difficult to evaluate it as an appropriate legislation. In order to solve this, it is necessary to construct a new definition of malignant program in the Information and Communication Network Act. It is desirable not to be defined in Article 48 of the Information and Communications Network Act, but to put the definition of malicious programs in the definition of Article 2, and spyware and ransomware, which are the current problems in defining malicious programs through these regulations Rather, it is necessary to consider programs that may emerge as technological advances occur. In considering legislative considerations, it is also necessary to consider the provisions of the purpose of preventing the normal operation of information and communication systems. In addition, it is necessary to punish not only the delivery and distribution of malicious programs, but also the “production” of them. In considering the use of the program and its technical composition in determining whether a program is malicious, it is expected that there will be no major problems in punishing production. Also, in addition to simple delivery and distribution, regulations for aggravating punishment for “selling” malicious programs for “for commercial purposes” are also necessary.

흡열연료를 이용한 연료분사 및 연소 특성 연구동향

최호진(Hojin Choi),이형주(Hyungju Lee),황기영(Kiyoung Hwang) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11

장거리 극초음속 비행체에 적용 가능한 유일한 냉각방안으로 알려져 있는 흡열연료 적용기술을 개발하기 위하여 흡열반응에 의해 분해된 연료의 분사 및 연소특성에 대한 연구사례를 살펴보았다. 흡열반응을 거친 연료가 연소실에 분사될 때 처해지는 초임계 상태의 분사 특성, 초임계 연료가 초음속 유동장에 분사될 때의 공기혼합 특성 등에 관한 연구사례를 살펴보았고, 연소특성으로서 점화 지연시간 및 화염전파 속도에 미치는 영향, 초음속 연소실에서 연소될 때의 연소효율 상승 연구사례 등을 살펴보았다. 국내에서 수행된 흡열연료 관련 연구동향을 살펴보았다. Endothermic fuel utilizing technology is considered as a unique practical method of hypersonic vehicle. Research activities about characteristics of fuel injection and combustion using cracked fuel by endothermic reaction are reviewed. Studies on characterization of supercritical fuel injection and mixing within supersonic flow field are surveyed. In addition, researches on combustion characteristics such as ignition delay time, laminar burning velocity and combustion efficiency at supersonic model combustor are reviewed.

초임계상태 항공유의 인젝터 형상에 따른 분사특성 변화 연구

최호진(Hojin Choi),이형주(Hyung Ju Lee),김일두(Ildoo Kim),진유인(Yuin Jin),황기영(Ki-Young Hwang) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12

실제 항공유가 온도 및 압력이 상승하여 초임계상태에 도달하는 동안 보이는 분사특성 변화를 실험적으로 연구하였다. 특히 오리피스 인젝터의 형상이 분무특성에 미치는 영향을 유량계수의 변화를 통해 살펴보았는데, 오리피스 유로의 길이 대 직경비 (L/D) 와 오리피스 인젝터 직경이 미치는 영향을 살펴보았다. 결과적으로 변화된 오리피스 인젝터의 형상은 액체상태와 초임계상태에서의 분사특성변화에 미치는 영향은 미미하였으나 연료비등에 의해 유량계수가 급격히 감소하는 구간에서는 의미있는 수준의 변화를 동반함을 확인하였다. An experimental study was conducted to investigate fuel injection characteristics with temperature and pressure increase to supercritical phase using aviation fuel. The effect of injector shape like diameter of orifice and ratio of orifice flow path to orifice diameter (L/D) on injection characteristics, especially flow coefficient, are examined. The effects of changed shape of orifice are minimal at liquid and supercritical state injection, although those on trend of flow coefficient decrease during fuel vaporization are notable.