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Search Results: 1 - 10 of 34824 matches for " Young-Jin Son "
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Extrinsic and intrinsic determinants of nerve regeneration
Toby A. Ferguson,Young-Jin Son
Journal of Tissue Engineering , 2011, DOI: 10.1177/2041731411418392
Abstract: After central nervous system (CNS) injury axons fail to regenerate often leading to persistent neurologic deficit although injured peripheral nervous system (PNS) axons mount a robust regenerative response that may lead to functional recovery. Some of the failures of CNS regeneration arise from the many glial-based inhibitory molecules found in the injured CNS, whereas the intrinsic regenerative potential of some CNS neurons is actively curtailed during CNS maturation and limited after injury. In this review, the molecular basis for extrinsic and intrinsic modulation of axon regeneration within the nervous system is evaluated. A more complete understanding of the factors limiting axonal regeneration will provide a rational basis, which is used to develop improved treatments for nervous system injury.
Fisetin Inhibits Osteoclast Differentiation via Downregulation of p38 and c-Fos-NFATc1 Signaling Pathways
Sik-Won Choi,Young-Jin Son,Jung-Mi Yun,Seong Hwan Kim
Evidence-Based Complementary and Alternative Medicine , 2012, DOI: 10.1155/2012/810563
Abstract: The prevention or therapeutic treatment of loss of bone mass is an important means of improving the quality of life for patients with disorders related to osteoclast-mediated bone loss. Fisetin, a flavonoid dietary ingredient found in the smoke tree (Continus coggygria), exhibits various biological activities, but its effect on osteoclast differentiation is unknown. In this study, fisetin dose-dependently inhibited the RANKL-induced osteoclast differentiation with downregulation of the activity or expression of p38, c-Fos, and NFATc1 signaling molecules. The p38/c-Fos/NFATc1-regulated expression of genes required for cell fusion and bone resorption, such as DC-STAMP and cathepsin K, was also inhibited by fisetin. Considering the rescue of fisetin's inhibitory action by NFATc1 over-expression, the cascade of p38-c-Fos-NFATc1 could be strongly involved in the inhibitory effect of fisetin on osteoclast differentiation. Furthermore, fisetin inhibited the bone-resorbing activity of mature osteoclasts. In conclusion, fisetin may be of use in the treatment of osteoclast-related disorders, including osteoporosis.
The role of Cra in regulating acetate excretion and osmotic tolerance in E. coli K-12 and E. coli B at high density growth
Young-Jin Son, Je-Nie Phue, Loc B Trinh, Sang Jun Lee, Joseph Shiloach
Microbial Cell Factories , 2011, DOI: 10.1186/1475-2859-10-52
Abstract: The deletion of the cra gene in E. coli B (BL21) minimally affected the growth and maximal acetate accumulation, while the deletion of the same gene in E.coli K-12 (JM109) caused the cells to stop growing as soon as acetate concentration reached 6.6 g/L and the media conductivity reached 21 mS/cm. ppsA (gluconeogenesis gene), aceBA (the glyoxylate shunt genes) and poxB (the acetate producing gene) were down-regulated in both strains, while acs (acetate uptake gene) was down-regulated only in E.coli B (BL21). These transcriptional differences had little effect on acetate and pyruvate production. Additionally, it was found that the lower growth of E. coli K-12 (JM109) strain was the result of transcription inhibition of the osmoprotectant producing bet operon (betABT).The transcriptional changes caused by the deletion of cra gene did not affect the activity of the central carbon metabolism, suggesting that Cra does not act alone; rather it interacts with other pleiotropic regulators to create a network of metabolic effects. An unexpected outcome of this work is the finding that cra deletion caused transcription inhibition of the bet operon in E. coli K-12 (JM109) but did not affect this operon transcription in E. coli B (BL21). This property, together with the insensitivity to high glucose concentrations, makes this the E. coli B (BL21) strain more resistant to environmental changes.Acetate accumulation is one of the main concerns during high cell density growth of E. coli [1,2]. It was established that acetate concentrations above 40 mM (2.4 g/L) negatively affect cellular growth and recombinant protein production [3-5]. Acetate accumulation is dependent on the bacterial strain [6] and is affected by high growth rate and low oxygen concentration [4,7]. Methods have been developed to reduce acetate accumulation, including different glucose feeding strategies, usage of lower acetate producing carbon sources, and the development of mutant strains with altered acetic aci
The majority of dorsal spinal cord gastrin releasing peptide is synthesized locally whereas neuromedin B is highly expressed in pain- and itch-sensing somatosensory neurons
Michael S Fleming, Daniel Ramos, Seung Baek Han, Jianyuan Zhao, Young-Jin Son, Wenqin Luo
Molecular Pain , 2012, DOI: 10.1186/1744-8069-8-52
Abstract: Grp mRNA is highly expressed in dSC but is barely detectable in DRGs of juvenile and adult mice. Anti-bombesin serum specifically recognizes Grp but not Nmb. Grp is present in a small number of small-diameter DRG neurons and in abundance in layers I and II of the spinal cord. The reduction of dSC Grp after dorsal root rhizotomy is significantly different from those of DRG derived markers but similar to that of a spinal cord neuronal marker. Double fluorescent in situ of Nmb and other molecular markers indicate that Nmb is highly and selectively expressed in nociceptive and itch-sensitive DRG neurons.The majority of dSC Grp is synthesized locally in dorsal spinal cord neurons. On the other hand, Nmb is highly expressed in pain- and itch-sensing DRG neurons. Our findings provide direct anatomic evidence that Grp could function locally in the dorsal spinal cord in addition to its roles in DRG neurons and that Nmb has potential roles in nociceptive and itch-sensitive neurons. These results will improve our understanding about roles of Grp and Nmb in mediating itch sensation.
A Class E Power Amplifier with Coupling Coils for a Wireless Power Transfer System
Jong-Ryul Yang;Hyeon-Chang Son;Young-Jin Park
PIER C , 2013, DOI: 10.2528/PIERC12100914
Abstract: A class E power amplifier including coupling coils is proposed for application in a wireless power transfer system using magnetic coupling. The proposed amplifier is directly connected to the coils with no discrete components for harmonic filtering and dc feeding, which could cause efficiency degradation of the amplifier. The system with the differential amplifier shows 6.95 W of transmitted power and 44.6% transmission efficiency at 6.8 MHz with 14-cm distant coils. The power-added efficiency of the amplifier is 92.1% with a 14 V supply voltage, excluding the coupling efficiency of the wireless power transfer network.
Anti-Osteoclastogenic Activity of Praeruptorin A via Inhibition of p38/Akt-c-Fos-NFATc1 Signaling and PLCγ-Independent Ca2+ Oscillation
Jeong-Tae Yeon, Kwang-Jin Kim, Sik-Won Choi, Seong-Hee Moon, Young Sik Park, Byung Jun Ryu, Jaemin Oh, Min Seuk Kim, Munkhsoyol Erkhembaatar, Young-Jin Son, Seong Hwan Kim
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0088974
Abstract: Background A decrease of bone mass is a major risk factor for fracture. Several natural products have traditionally been used as herbal medicines to prevent and/or treat bone disorders including osteoporosis. Praeruptorin A is isolated from the dry root extract of Peucedanum praeruptorum Dunn and has several biological activities, but its anti-osteoporotic activity has not been studied yet. Materials and Methods The effect of praeruptorin A on the differentiation of bone marrow–derived macrophages into osteoclasts was examined by phenotype assay and confirmed by real-time PCR and immunoblotting. The involvement of NFATc1 in the anti-osteoclastogenic action of praeruptorin A was evaluated by its lentiviral ectopic expression. Intracellular Ca2+ levels were also measured. Results Praeruptorin A inhibited the RANKL-stimulated osteoclast differentiation accompanied by inhibition of p38 and Akt signaling, which could be the reason for praeruptorin A-downregulated expression levels of c-Fos and NFATc1, transcription factors that regulate osteoclast-specific genes, as well as osteoclast fusion-related molecules. The anti-osteoclastogenic effect of praeruptorin A was rescued by overexpression of NFATc1. Praeruptorin A strongly prevented the RANKL-induced Ca2+ oscillation without any changes in the phosphorylation of PLCγ. Conclusion Praeruptorin A could exhibit its anti-osteoclastogenic activity by inhibiting p38/Akt-c-Fos-NFATc1 signaling and PLCγ-independent Ca2+ oscillation.
Mathematical learning models that depend on prior knowledge and instructional strategies
David E. Pritchard,Young-Jin Lee,Lei Bao
Physical Review Special Topics. Physics Education Research , 2008,
Abstract: We present mathematical learning models—predictions of student’s knowledge vs amount of instruction—that are based on assumptions motivated by various theories of learning: tabula rasa, constructivist, and tutoring. These models predict the improvement (on the post-test) as a function of the pretest score due to intervening instruction and also depend on the type of instruction. We introduce a connectedness model whose connectedness parameter measures the degree to which the rate of learning is proportional to prior knowledge. Over a wide range of pretest scores on standard tests of introductory physics concepts, it fits high-quality data nearly within error. We suggest that data from MIT have low connectedness (indicating memory-based learning) because the test used the same context and representation as the instruction and that more connected data from the University of Minnesota resulted from instruction in a different representation from the test.
A Survey of Low-power Techniques for Liquid Crystal Display Systems with Light Emitting Diode Backlight Units
Anggorosesar Aldhino,Kim Young-Jin,Rim Kee-Wook
IETE Technical Review , 2011,
Abstract: As the technology evolves, end-users are stuffed with many kinds of handheld devices along with an enormous number of interactive multimedia applications and communication functionalities. These devices consume much power, especially for displaying their services or functions. In contrast, the battery, which is the main power supplier for such devices, has a much lower capacity growth compared to the power demands. This gap has inspired many researchers to study low-power display techniques. In the mean time, there came the invention of a light emitting diode (LED) as a new backlight source for a display panel. LEDs have been adopted in the most widely used Liquid Crystal Display (LCD) system. This paper focuses on recent noticeable low-power display techniques based on LCD systems, especially associated with an LED backlight unit as its light source. We categorize these techniques into four groups: 1) low-power techniques with backlight dimming, 2) low-power techniques with dynamic voltage scaling, 3) software-based low-power techniques, and 4) hardware-based low-power techniques, and review the core of each technique briefly. Among many techniques, concurrent brightness and contrast scaling technique in a color sequential LED-backlit display system achieved the largest power saving ratio by up to 90% of the total system power with a small distortion level. As future research, it is one of important methods to combine the pros from each beneficial technique into one synergistically in the aspect of the whole system power.
Temperature-responsive electrospun nanofibers for 'on–off' switchable release of dextran
Young-Jin Kim, Mitsuhiro Ebara and Takao Aoyagi
Science and Technology of Advanced Materials , 2012,
Abstract: We propose a new type of 'smart' nanofiber (NF) with dynamically and reversibly tunable properties for the 'on–off' controlled release of the polysaccharide dextran. The fibers are produced by electrospinning copolymers of N-isopropylacrylamide (NIPAAm) and N-hydroxymethylacrylamide (HMAAm). The OH groups of HMAAm are subsequently crosslinked by thermal curing. The copolymers were successfully fabricated into a well-defined nanofibrous structure with a diameter of about 600–00 nm, and the fibers preserved their morphology even after thermal curing. The resulting crosslinked NFs showed rapid and reversible volume changes in aqueous media in response to cycles of temperature alternation. The fibrous morphology was maintained for the crosslinked NFs even after the cycles of temperature alternation, while non-crosslinked NFs collapsed and dispersed quickly in the aqueous solution. Dextran-containing NFs were prepared by electrospinning the copolymers blended with fluorescein isothiocyanate (FITC)-dextran, and the 'on–off' switchable release of FITC-dextran from the crosslinked NFs was observed. Almost all the FITC-dextran was released from the NFs after six heating cycles, whereas only a negligible amount of FITC-dextran was evolved during the cooling process. The reported incorporation of smart properties into NFs takes advantage of their extremely large surface area and porosity and is expected to provide a simple platform for on–off drug delivery.
Revascularization in the Tendon Graft Following Anterior Cruciate Ligament Reconstruction of the Knee: Its Mechanisms and Regulation
Harukazu Tohyama,Toshikazu Yoshikawa,Young-Jin Ju,Kazunori Yasuda
Chang Gung Medical Journal , 2009,
Abstract: In anterior cruciate ligament (ACL) reconstruction, slowgraft maturation may result in graft failure or elongation duringthe postoperative rehabilitation period. Vascular endothelialgrowth factor (VEGF) is a potent mediator of angiogenesis.The findings of recent studies suggest that VEGF applicationis a potential strategy to accelerate angiogenesis in thegraft after ACL reconstruction. However, the biomechanicalresults indicate that exogenous VEGF application decreasesthe stiffness of the grafted tendon at least temporarily.Therefore, we should take into account this adverse effect ofexogenous VEGF application on the mechanical characteristicsof the grafted tendon.
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