• Toxicological Research
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• v.11 no.2
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• pp.329-335
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• 1995

Incubation of aflatoxin $B_1$ $(AFB_1)$ with microsomes isolated from human liver number 110 yielded two metabolite peaks which were aflatoxin $Q_1$ $(AFQ_1)$ and $(AFB_1)$-exo-8, 9-epoxide (exo-epoxide) in high performance liquid chromatography. Production ratio of $AFQ_1$ to exo-epoxide was 2.43$\pm $0.04. Metabolism of $(AFB_1)$ to $(AFQ_1)$ and exo-epoxide was inhibited by troleandomycin in a same degree although troleandomycin was not activated as a mechanism-based inhibitor. The inhibitory effect was dependent upon either the incubation time with $(AFB_1)$ or the preincubation time before the addition of $(AFB_1)$. Incubation of troleandomycin and NADPH by the microsomes resulted in the formation of a cytochrome P 450 (P450)-metabollc intermediate (MI) complex and the level was approximately 80% of total P450 3A4 in the microsomes. This figure was similar to that of the inhibitory effect of troleandomycin on $AFB_1$ metabolism. Glutathione which was reported that it prevented the formation of MI complex in rat liver microsomes did not inhibit the formation of MI complex in human liver microsomes. These results suggested that the inhibitory effect of troleandomycin on $AFB_1$ metabolism is due to the formation of MI complex with P450 3A4. And the reaction mechanism of troleandomycin by human liver microsomes might be dlfferent from that one by rat liver microsomes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.72-82
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• 2004

The deformation mechanism of hexagonal close-packed materials is quite complicate including slips and twins. A deformation mechanism, which accounts for both slip and twinning, was investigated for polycrystalline hop materials. The model was developed in a finite element polycrystal model formulated with initial strain method where the stiffness matrix in FEM is based on the elastic modulus. We predicted numerically the texture of Mg alloy(AZ31B) sheet by using FEM based on crystal plasticity theory. Also, we introduced the recrystallized texture employed the maximum energy release theory after rolling. From the numerical study, it was clarified that the shrink twin could not be the main mechanism for shortening of c-axis, because the lattice rotation due to twin rejects fur c-axis to become parallel to ND(normal direction of plate). It was showed that the deformation texture with the pyramidal slip gives the ring type pole figure having hole in the center.

• Food Science of Animal Resources
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• v.30 no.4
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• pp.568-574
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• 2010

This study introduced a chick embryos’ infection model to elucidate the pathogenesis mechanism of Pseudomonas aeruginosa, which causes serious diseases in human after ingestion of P. aeruginosa-contaminated animal originated foods. The embryonic chick model is able to give a rapid and relatively inexpensive method to assess bacterial pathogenicity compared to embryos of other vertebrates. Embryos were infected with P. aeruginosa and elastase-deficient P. aeruginosa. After infection with P. aeruginosa cells, total bacterial cell numbers and gelatinase activities in the embryos were compared. Thereafter, precartilage condensation and chondrogenesis were assessed by peanut agglutinin (PNA) binding on day 3 and by Alcian blue staining for sulfated proteoglycans on day 5, respectively. P. aeruginosa significantly increased in embryos, resulting in abnormal limb development, whereas P. aeruginosa defective in elastase activity partly impaired proliferation. In addition, P. aeruginosa-infected chick embryos significantly stimulated the production of matrix metalloproteinases. Several analyses showed that elevated proteases suppressed the proliferation and survival of chondrogenic cells. The results show that this infection model was a useful assay to determine the virulence mechanism of P. aeruginosa in human after intake of microbiologically contaminated foods.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.329-339
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• 2006

The production of lower olefins from methanol becomes an attractive process because of the rapid increase in crude oil price. This paper reivews the conversion mechanisms of methanol to hydrocarbons over zeolite and SAPO molecular sieve catalysts to understand the formation steps of lower olefins from methanol. The feasibility of the conversion mechanisms such as the direct mechanism based on well-defined intermediates and the hydrocarbon pool mechanism involving hydrocarbon moieties as an active centers is discussed with reepect to the induction period, the selectivity for products and the deactivation phenomena of the methanol conversion. The literature appeered since 1999 for the structure of the hydrocarbon pool and its catalytic role in the methanol conversion are summariged, and the prospect for the methanol-to-olefins process is described.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.11
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• pp.1130-1137
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• 2006

Relaxed Static Stability(RSS) concept has been applied to improve aerodynamic performance of modern version supersonic jet fighter aircraft. Therefore, the flight control systems are necessary to stabilizes the unstable aircraft and provides adequate handling qualities. The initial production flight control system are verified by flight test and it's always an elements of danger because of flight-critical nature of control law function and design error due to model base design method. These critical issues impact to flight safety, and it could be lead to a loss of aircraft and pilot's life. Therefore, development of an easily modifiable RFCS(Research Flight Control System) capable of reverting to a PFCS(Primary Flight Control System) of reliable control law must be developed to guarantee the flight safety. This paper addresses the concept of SSWM(Software Switching Mechanism) using the fader logic such as TFS(Transient Free Switch) based on T-50 flight control law. The result of the analysis based on non-real time simulation in-house software using SSWM reveals that the flight control system are switching between two computers without any problem.

• Journal of Drive and Control
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• v.16 no.3
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• pp.8-15
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• 2019

Wheelchair users experience difficulty when using transportation. This is because wheelchair users must use transportation means together with wheelchairs. Therefore, in this paper, we developed a wheelchair storage system for passenger's car trunk. The mechanism is designed to allow a wheelchair and the device to be housed simultaneously in the narrow space of the trunk of the sedan passenger car. Additionally, this wheelchair storage system has implemented an initial load reduction mechanism that can mechanically reduce the initial load. This wheelchair storage system verified the system's operability through the production of the prototype. This system was actually installed in the trunk of the sedan passenger's car to verify the storage process. The operation and storage process of the wheelchair storage system was been perfectly verified. This wheelchair storage system will help a lot of self-driver or an assistant (female or elderly) who use wheelchairs.

• Journal of Applied Biological Chemistry
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• v.65 no.3
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• pp.167-172
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• 2022

Pathophysiological reaction of platelets in the blood vessel is an indispensable part of thrombosis and cardiovascular disease, which is the most common cause of death in the world. In this study, we performed in vitro assays to evaluate antiplatelet activity of artemether in human platelets and attempted to identify the mechanism responsible for protein phosphorylation. Artemether is a derivative of artemisinin, known as an active ingredient of Artemisia annua, which has been reported to be effective in treating malaria, and is known to function through antioxidant and metabolic enzyme inhibition. However, the role of artemether in platelet activation and aggregation and the mechanism of action of artemether in collagen-induced human platelets are not known until now. In this study, the effect of artesunate on collagen-induced human platelet aggregation was confirmed and the mechanism of action of artemether was clarified. Artemether inhibited the phosphorylation of PI3K/Akt and Mitogen-activated protein kinases, which are phosphoproteins that are known to act in the signal transduction process when platelets are activated. In addition, artemether decreased TXA₂ production and decreased granule secretion in platelets such as ATP and serotonin release. As a result, artemether strongly inhibited platelet aggregation induced by collagen, a strong aggregation inducer secreted from vascular endothelial cells, with an IC₅₀ of 157.92 μM. These results suggest that artemether has value as an effective antithrombotic agent for inhibiting the activation and aggregation of human platelets through vascular injury.

• Transactions of Materials Processing
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• v.32 no.3
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• pp.114-121
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• 2023

During rolling, rolling mill rolls endure wear when shaping metal billets into a desired form, such as bars, plates, and shapes. Such wear affects the lifespan of the rolls and product quality. Therefore, in addition to rigidity, wear performance is a key factor influencing the performance of rolling mill rolls. Conventional methods such as casting and forging have been used to manufacture rolling mill rolls. However, powder alloying methods are increasingly being adopted to enhance wear resistance. These powder manufacturing methods include atomization, canning to shape the powder, hot isostatic pressing to combine the powder alloy with conventional metals, and various wear performance tests on rolls prepared with powder alloys. In this study, numerical simulations and experimental tests were used to develop and elucidate the wear analysis mechanism of rolling mill rolls. The wear characteristics of the rolls under various rolling conditions were analyzed. In addition, experimental tests (wear and surface analysis tests) and wear theory (Archard wear model) were used to evaluate wear. These tests were performed on two different materials in various powder states to evaluate the different aspects of wear resistance. In particular, this study identifies the factors influencing the wear behavior of rolling mill rolls and proposes an analytical approach based on the actual production of products. The developed wear analysis mechanism can serve the future development of rolls with high wear resistance using new materials. Moreover, it can be applied in the mechanical and wear performance testing of new products.

• Clinical and Experimental Reproductive Medicine
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• v.50 no.1
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• pp.1-11
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• 2023

In reproduction, mitochondria produce bioenergy, help to synthesize biomolecules, and support the ovaries, oogenesis, and preimplantation embryos, thereby facilitating healthy live births. However, the regulatory mechanism of mitochondria in oocytes and embryos during oogenesis and embryo development has not been clearly elucidated. The functional activity of mitochondria is crucial for determining the quality of oocytes and embryos; therefore, the underlying mechanism must be better understood. In this review, we summarize the specific role of mitochondria in reproduction in oocytes and embryos. We also briefly discuss the recovery of mitochondrial function in gametes and zygotes. First, we introduce the general characteristics of mitochondria in cells, including their roles in adenosine triphosphate and reactive oxygen species production, calcium homeostasis, and programmed cell death. Second, we present the unique characteristics of mitochondria in female reproduction, covering the bottleneck theory, mitochondrial shape, and mitochondrial metabolic pathways during oogenesis and preimplantation embryo development. Mitochondrial dysfunction is associated with ovarian aging, a diminished ovarian reserve, a poor ovarian response, and several reproduction problems in gametes and zygotes, such as aneuploidy and genetic disorders. Finally, we briefly describe which factors are involved in mitochondrial dysfunction and how mitochondrial function can be recovered in reproduction. We hope to provide a new viewpoint regarding factors that can overcome mitochondrial dysfunction in the field of reproductive medicine.

• IMMUNE NETWORK
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• v.21 no.5
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• pp.36.1-36.16
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• 2021

Peroxiredoxins (Prxs) are ubiquitously expressed peroxidases that reduce hydrogen peroxide or alkyl peroxide production in cells. Prxs are released from cells in response to various stress conditions, and they function as damage-associated molecular pattern molecules. However, the secretory mechanism of Prxs and their roles have not been elucidated. Thus, we aimed to determine whether inflammasome activation is a secretory mechanism of Prxs and subsequently identify the effect of the secreted Prxs on activation of the classical complement pathway. Using J774A.1, a murine macrophage cell line, we demonstrated that NLRP3 inflammasome activation induces Prx1, Prx2, Prx5, and Prx6 secretion in a caspase-1 dependent manner. Using HEK293T cells with a transfection system, we revealed that the release of Prx1 and Prx2 relies on gasdermin-D (GSDMD)-mediated secretion. Next, we confirmed the binding of both Prx1 and Prx2 to C1q; however, only Prx2 could induce the C1q-mediated classical complement pathway activation. Collectively, our results suggest that inflammasome activation is a secretory mechanism of Prxs and that GSDMD is a mediator of their secretion. Moreover, secreted Prx1 and Prx2 bind with C1q, but only Prx2 mediates the classical complement pathway activation.