• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.1 s.49
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• pp.25-33
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• 2005

Melanocytes synthesize melanin within discrete organelle termed melanosomes which are transferred to the surrounding keratinocytes and can be produced in varying sizes, numbers and densities. Skin whitening products have become increasingly popular in the past few years. The most successful natural skin whitening agents are: arbutin, vitamin C, kojic acid, and mulberry, which are all tyrosinase inhibitors. In this work, melanoston, a melanogenesis inhibitor isolated from yeast was studied to understand its mechanism of melanogenesis inhibition. It was found that melanoston was not a tyrosinase inhibitor, while when melanoston was applied to the B16 melanoma cell culture media, the intracellular tyrosinase activity was decreased by more than $30\%$. When B16 melanoma was stimulated with $\alpha$-MSH, cell morphololgy was dramatically changed to have lots of dendrites on the cell membrane surface. On the other hand, B16 was treated with $\alpha$-MSH and melanoston, simultaneously, the change of cell morphologv was not so great. This inhibitory effect of melanoston was found to be related to the inhibition of intracellar activation and transportation of tyrosinase, which was observed by irmmunostaining of B16 melanoma using anti-tyrosinase antibody. From these results, melanoston was regarded as an inhibitor to the differentiation of melanoma cells.

• Journal of the Korean institute of surface engineering
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• v.54 no.1
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• pp.1-11
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• 2021

Porous dendrite structure AuCu alloy was formed using a hydrogen bubble template (HBT) technique by electroplating to improve the catalytic performance of gold, known as an excellent oxygen reduction reaction (ORR) catalyst in alkaline medium. The rich Au surface was maximized by selectively electrochemical etching Cu on the AuCu dendrite surface well formed in a leaf shape. The catalytic activity is mainly due to the synergistic effect of Au and Cu existing on the surface and inside of the particle. Au helps desorption of OH- and Cu contributes to the activation of O2 molecule. Therefore, the porous AuCu dendrite alloy catalyst showed markedly improved catalytic activity compared to the monometallic system. The porous structure AuCu formed by the hydrogen bubble template was able to control the size of the pores according to the formation time and applied current. In addition, the Au-rich surface area increased by selectively removing Cu through electrochemical etching was measured using an electrochemical calculation method (ECSA). The results of this study suggest that the alloying of porous AuCu dendrites and selective Cu dissolution treatment induces an internal alloying effect and a large specific surface area to improve catalyst performance.

• Journal of Korea Foundry Society
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• v.41 no.6
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• pp.505-515
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• 2021

Creep properties of directionally solidified Ni-based superalloy CM247LC under various temperature and stress conditions have been investigated. In the heat-treated specimen, some portion of eutectic γ-γ' remained, and uniform cubic γ' was observed in the dendrites. At low temperature (750℃) and high stress condition, a large amount of deformation occurred during the primary creep, while the tertiary creep region accounted for most of the creep deformation under high temperature and low stress condition. γ' particles are sheared by dislocation dissociated into super lattice partial dislocations separated by stacking faults at 750℃. No stacking faults in γ' were found at and above 850℃ due to the temperature dependence of the stacking fault energy. Raft structure of γ' was found after creep test at high temperature of 950℃ and 1000℃. At 850℃, the deformation mechanism was shown to be dependent on the stress condition, and so rafting was observed only under low stress condition.

• Applied Microscopy
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• v.30 no.4
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• pp.347-355
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• 2000

Zinc is one of the most abundant oligoelements in the living cell. It appears tightly bound to some metalloproteins and nucleic acids, loosely bound to some metallothioneins or even as free ion. Small amounts of zinc ions (in the nanomolar range) regulate a plentitude of enzymatic proteins, receptors and transcription factors, thus rolls need accurate homeostasis of zinc ions. Zinc is an essential catalytic or structural element of many proteins, and a signaling messenger that is released by neural activity at many central excitatory synapses. Growing evidences suggest that zinc may also be a key mediator and modulator of the neuronal death associated with transient global ischemia and sustained seizures, as well as perhaps other neurological disease stoles. Some neurons have developed mechanisms to accumulate zinc in specific membrane compartment ('vesicular zinc') which can be evidenced using histochemical techniques. Substances giving a bright colour or emitting fluorescence when in contact with divalent metal ions are currently used to detect them inside cells; their use leads to the so called 'direct' methods. The fixation and precipitation of metal ions as insoluble salt precipitates, their maintenance along the histological process and, finally, their demonstration after autometallographic development are essential steps for other methods, the so called 'indirect methods'. This study is a short report on the autometallograhical approaches for zinc detection in the central nervous system (CNS) by means of a modified selenium method.

• Journal of Radiation Protection and Research
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• v.36 no.2
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• pp.93-98
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• 2011

We induced the activation of melanocytes in the epidermis of C57BL/6 mice by ultraviolet-B (UV-B) irradiation, and observed the effect of an herbal preparation (HemoHIM, HH) on the formation, and decrease of UV-B-induced epidermal melanocytes. C57BL/6 mice were irradiated by UV-B $80\;mJ{\cdot}cm^{-2}$ ($0.5\;mW{\cdot}sec^{-1}$) daily for 7 days, and HH was intraperitoneally, orally or topically applied pre- or post-irradiation. For the estimation of change of epidermal melanocytes, light microscopic observation with dihydroxyphenylalanine (DOPA) stain was performed. Split epidermal sheets prepared from the ear of untreated mice exhibited 13~15 melanocytes${\cdot}mm^{-2}$, and one week after UV irradiation, the applied areas showed an increased number of strongly DOPA-positive melanocytes with stout dendrites. But intraperitoneal, oral or topical treatment with HH before each irradiation interrupted UV-B-induced pigmentation and resulted in a marked reduction in the number of epidermal melanocytes as compared to the number found in UV-B-irradiated, untreated control skin. The number and size of DOPA-positive epidermal melanocytes were also significantly decreased in intraperitoneally injected or topically applicated group after irradiation with HH at 3rd and 6th weeks after irradiation. The present study suggests the HH as inhibitor of UV-B-induced pigmentation, and depigmenting agent.

• Applied Microscopy
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• v.35 no.3
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• pp.165-176
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• 2005

Studies on molecular plasticity of Bermann glia (BG) after harmaline-induced Purkinje cell (PC) degeneration in the rat cerebellum. The intimate structural relationship between BG and PC, evidenced by the sheathing of the PC dendrites by veil-like process from the BG has been suggestive of the close functional relationship between these two cell types. However, little is known about metabolic couplings between these cells. This study designed to investigate molecular plasticity of BG in the rat cerebellum in which PCs were chemically ablated by harmaline treatment. Immunohistochemical examination reveals that harmaline induced PC degeneration causes a marked glial reaction in the cerebellum with activated BG and microglia aligned in parasagittal stripes within the vermis. In these strips, activated BG were associated with upregulaion of metallotheionein, while GLAST and was down regulated, as compared with nearby intact area where both BG are in contact with PCs. The data from this study demonstrate that BG can change their phenotypic expression when BG loose their contact with PCs. It is conceivable that activated BG may upregulate structural proteins, metallothionein expression to use for their proliferation and hypertrophy; metallothionein expression to cope with oxidative stress induced by PC degeneration and microglial activation. On the contrary, BG may down regulated expression of GLAST because sustained loss of contact with PCs would eliminate the necessity for the cellular machinery involved glutamate metabolism. In conclusion, BG might respond man to death of PCs by undergoing a change in metabolic state. It seems possible that signaling molecules released from PCs regulates the phenotype expression of BG. Also ultrastructures in the organelles of normal PC and BG are distinguished by mitochondrial appearance, and distributed vesicles at the synaptic area in the cytoplasm.