• International Journal of Oral Biology
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• v.30 no.1
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• pp.23-30
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• 2005

Bone remodeling is a process controlled by the action of two major bone cells; the bone forming osteoblast and the bone resorbing osteoclast. In the process of osteoclastogenesis, stromal cells and osteoblast produce RANKL, OPG, and M-CSF, which in turn regulate the osteoclastogenesis. During the bone resorption by activated osteoclasts, extracellular $Ca^{2+}/{PO_4}^{2-}$ concentration and degraded organic materials goes up, providing the hypertonic microenvironment. In this study, we tested the effects of hypertonicity due to the degraded organic materials on osteoclastogenesis in co-culture system. It was examined the cellular response of osteoblastic cell in terms of osteoclastogenesis by applying the sucrose, and mannitol, as a substitute of degraded organic materials to co-culture system. Apart from the sucrose, mannitol, and NaCl was tested to be compared to the effect of organic osmotic particles. The addition of sucrose and mannitol (25, 50, 100, 150, or 200 mM) to co-culture medium inhibited the number of tartrate-resistant acid phosphatase (TRAP) positive multinucleated cells induced by 10 nM $1{\alpha},25(OH)_2vitaminD_3$ ($1{\alpha},25(OH)_2D_3$). However, NaCl did exert harmful effect upon the cells in this co-culture system, which is attributed to DNA damage in high concentration of NaCl. To further investigate the mechanism by which hypertonicity inhibits $1{\alpha},25(OH)_2D_3$-induced osteoclastogenesis, the mRNA expressions of receptor activator of nuclear factor (NF)-kB ligand (RANKL) and osteoprotegerin (OPG) were monitored by RT-PCR. In the presence of sucrose (50 mM), RANKL mRNA expression was decreased in a dose-dependent manner, while the change in OPG and M-CSF mRNA were not occurred in significantly. The RANKL mRNA expression was inhibited for 48 hours in the presence of sucrose (50 mM), but such a decrement recovered after 72 hours. However, there were no considerable changes in the expression of OPG and M-CSF mRNA. Conclusively, these findings strongly suggest that hypertonic stress down-regulates $1{\alpha},25(OH)_2D_3$-induced osteoclastogenesis via RANKL signal pathway in osteoblastic cell, and may playa pivotal role as a regulator that modulates osteoclastogenesis.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.24
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• pp.10659-10663
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• 2015

Background: Rapamycin is an effective anti-angiogenic drug. However, the mode of its action remains unclear. Therefore, in this study, we aimed to elucidate the antitumor mechanism of rapamycin, hypothetically via apoptotic promotion, using MCF-7 breast cancer cells. Materials and Methods: MCF-7 cells were plated at a density of $1{\times}10^5$ cells/well in 6-well plates. After 24h, cells were treated with a series of concentrations of rapamycin while only adding DMEM medium with PEG for the control regiment and grown at $37^{\circ}C$, 5% $CO_2$ and 95% air for 72h. Trypan blue was used to determine the cell viability and proliferation. Untreated and rapamycin-treated MCF-7 cells were also examined for morphological changes with an inverted-phase contrast microscope. Alteration in cell morphology was ascertained, along with a stage in the cell cycle and proliferation. In addition, cytotoxicity testing was performed using normal mouse breast mammary pads. Results: Our results clearly showed that rapamycin exhibited inhibitory activity on MCF-7 cell lines. The $IC_{50}$ value of rapamycin on the MCF-7 cells was determined as $0.4{\mu}g/ml$ (p<0.05). Direct observation by inverted microscopy demonstrated that the MCF-7 cells treated with rapamycin showed characteristic features of apoptosis including cell shrinkage, vascularization and autophagy. Cells underwent early apoptosis up to 24% after 72h. Analysis of the cell cycle showed an increase in the G0G1 phase cell population and a corresponding decrease in the S and G2M phase populations, from 81.5% to 91.3% and 17.3% to 7.9%, respectively. Conclusions: This study demonstrated that rapamycin may potentially act as an anti-cancer agent via the inhibition of growth with some morphological changes of the MCF-7 cancer cells, arrest cell cycle progression at G0/G1 phase and induction of apoptosis in late stage of apoptosis. Further studies are needed to further characterize the mode of action of rapamycin as an anti-cancer agent.

• Solar Energy
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• v.11 no.2
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• pp.51-62
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• 1991

Heat transfer characteristics for heat retrieving processes in a paraffin-filled horizontal circular cylinder was studied. Theoretical and experimental analyses were carried out. In the theoretical analysis, solid and liquid phases were treated separately. Namely, convection for liquid and conduction for solid phase were investigated respectively. The retrieved heat was calculated from the experimentally determined solidified mass. Furthermore, the effects of initial temperature of the liquid and cooling temperature on the heat discharge rate were also studied. In the heat retrieving process, the governing factor for the solidifying rate is the cooling temperature, because most of the liquid sensible heat is rapidly discharged in the initial stage of solidification. Hence heat transfer mechanism during heat retrieving process can be safely considered as conduction. In the cut of frozen paraffin, there showed an empty space in the upper region. It is caused by the temperature drop in the liquid paraffin. While volume shrinkage caused by phase transition was indiscernible. Irrespective of cooling temperature and initial liquid temperature, solidified mass was well-correlated with the product of Fourier number and Stefan number in the solid phase.

• Journal of Life Science
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• v.17 no.7 s.87
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• pp.896-904
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• 2007

Regulation mechanism of apoptosis has been known to be important for understanding the pathogenesis of a number of human diseases including cancers. The effects of $RRR-{\alpha}-tocopheryl$ succinate(vitamin E succinate, VES) on the cell viability, generation of ROS, expression of proteins involved in apoptosis, and growth of human chronic myelogenous leukemia K562 cells were analyzed in this study. VES treatment not only induced the generation of the ROS but also increased the levels of $NF-{\kappa}B$, COX-2, and $p21^{WAF1/CIP1}$ in K562 cells. It modulates the levels of pro-apoptotic proteins such as Bax provoking the apoptosis in K562 cells. The cleavage of PARP into 89 kDa was also increased upon VES treatment in a dosage-dependent manner. Induction of an apoptosis was evident by the increase of sub-Gl peak and cell shrinkage condensed chromatin in K562 cells treated with VES. It also resulted in an inhibition of tumor growth by 50% and prolonged survival of the Iymphoma-induced mice. This potentiation of VES obtained in vitro and in vivo may indicate the feasibility of more effective chemotherapy in chronic myelogenous leukemia.

• International Journal of Oral Biology
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• v.34 no.1
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• pp.7-14
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• 2009

Nitric oxide (NO) acts as an intracellular messenger at the physiological level but can be cytotoxic at high concentrations. The cells within periodontal tissues, such as gingival and periodontal fibroblasts, contain nitric oxide syntheses and produce high concentrations of NO when exposed to bacterial lipopolysaccharides and cytokines. However, the cellular mechanisms underlying NO-induced cytotoxicity in periodontal tissues are unclear at present. In our current study, we examined the NO-induced cytotoxic mechanisms in human gingival fibroblasts (HGF). Cell viability and the levels of reactive oxygen species (ROS) were determined using a MTT assay and a fluorescent spectrometer, respectively. The morphological changes in the cells were examined by Diff-Quick staining. Expression of the Bcl-2 family and Fas was determined by RT-PCR or western blotting. The activity of caspase-3, -8 and -9 was assessed using a spectrophotometer. Sodium nitroprusside (SNP), a NO donor, decreased the cell viability of the HGF cells in a dose- and time-dependent manner. SNP enhanced the production of ROS, which was ameliorated by NAC, a free radical scavenger. ODQ, a soluble guanylate cyclase inhibitor, did not block the SNP-induced decrease in cell viability. SNP also caused apoptotic morphological changes, including cell shrinkage, chromatin condensation, and DNA fragmentation. The expression of Bax, a member of the proapoptotic Bcl-2 family, was upregulated in the SNP-treated HGF cells, whereas the expression of Bcl-2, a member of the anti-apoptotic Bcl-2 family, was downregulated. SNP augmented the release of cytochrome c from the mitochondria into the cytosol and enhanced the activity of caspase-8, -9, and -3. SNP also upregulated Fas, a component of the death receptor assembly. These results suggest that NO induces apoptosis in human gingival fibroblast via ROS and the Bcl-2 family through both mitochondrial- and death receptor-mediated pathways. Our data also indicate that the cyclic GMP pathway is not involved in NO-induced apoptosis.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.164-171
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• 2019

Radiation therapy has many side effects, such as digestive mucosal ulcers, without regard to its efficacy. The purpose of this study is to address an alternative method to replace the limitation of radiation therapy using radiomimetic microbial ribotoxins. In the evaluation of cancer therapy, we analyzed the formation of colorectal cancer (CRC) cell spheroids, which can take into account the heterogeneous cellular constitution, tumor stem cells, and the surrounding microenvironment. Ribotoxic stress interfered with the spheroid structure composed of relatively small clusters. Spheroids under ribotoxic stress were structurally sparse and their shrinkage was very slow. In the control group, the clusters of strongly aggregated cells were resistant to physical stress, but the ribotoxic stress-exposed spheroids were easily broken up by the physical stress. Moreover, the ribosome-insulted CRC cells slowly migrated to form clusters and the cell-cell junctional points in the ribosome-insulted spheroids were rarer than those in the control CRC spheroid. Moreover, levels of the cell-to-cell junctional protein E-cadherin were suppressed by ribotoxic stress in both allograft and xenograft spheroids. In conclusion, the radiomimetic microbial ribotoxins induced structural defects in CRC cell spheroids via retardation of migration and cell-cell junction in the formation of three-dimensional structures, and provides a basis for the mechanism of pharmacological radiomimetic anticancer actions as an alternate to radiotherapy against cancer.