• Journal of Life Science
• /
• v.16 no.1
• /
• pp.37-43
• /
• 2006

Gap junction is an ion channel forming between adjacent cells. It also acts as a membrane channel like sodium or potassium channels in a single cell. The amino acid residues up to the $10^{th}$ position in the amino (N)-terminus of gap junction hemichannel affect gating polarity as well as current-voltage (I-V) relation. While wild-type Cx32 channel shows negative gating polarity and inwardly rectifying I-V relation, T8D channel in which threonine residue at $8^{th}$ position is replaced with negatively charged aspartate residue shows reverse gating polarity and linear I-V relation. It is still unclear whether these changes are resulted from the charge effect or the conformational change of the N-terminus. To clarify this issue, we made a mutant channel harboring cysteine residue at the $8^{th}$ position (T8C) and characterized its biophysical properties using substituted-cysteine accessibility method (SCAM). T8C channel shows negative gating polarity and inwardly rectifying I-V relation as wild-type channel does. This result indicates that the substitution of cysteine residue dose not perturb the original conformation of wild-type channel. To elucidate the charge effect two types of methaenthiosulfonate (MTS) reagents (negatively charged $MTSES^-$ and positively charged $MTSET^+$) were used. When $MTSES^-$ was applied, T8C channel behaved as T8D channel, showing positive gating polarity and linear I-V relation. This result indicates that the addition of a negative charge changes the biophysical properties of T8C channel. However, positively charged $MTSET^+$ maintained the main features of T8C channel as expected. It is likely that the addition of a charge by small MTS reagents does not distort the conformation of the N-terminus. Therefore, the opposite effects of $MTSES^-$ and $MTSETT^+$ on T8C channel suggest that the addition of a charge itself rather than the conformational change of the N-terminus changes gating polarity and I-V relation. Furthermore, the accessibility of MTS reagents to amino acid residues at the $8^{th}$ position supports the idea that the N-terminus of gap junction channel forms or lies in the aqueous pore.

• Toxicological Research
• /
• v.14 no.2
• /
• pp.171-176
• /
• 1998

The biological effects of the water extracts of Rhus Verniciflua Stokes (RVS) were evaluated by protection against hydroxyl radicals. Antioxidative activities were measured using both 1,1-diphenyl-2-picrylhydrazyl (DPPH) and thiocyanate method. Also we used the Glucose oxidase (GO) 20 mU/$\textrm{m}{\ell}$ hydroxyl radical generating system in mouse forebrain cell culture. Water was used for ex-traction from RVS as a solvent which has high polarity especially. In DPPH method, the antioxidative activities of the crude water extract were stronger than any other extracts of low polar-solvents. In the antioxidative effects of mouse forebrain culture using 20 mU/$\textrm{m}{\ell}$ GO, cell viabilities were evaluated 65.6%, 68.8% at 1 $\mu\textrm{g}$. 5 $\mu\textrm{g}$ addition of crude water extracts (30 mg/$\textrm{m}{\ell}$) respectively. 10 $\mu\textrm{g}$ addition of crude water extracts had more than 86.1% cell viabilities, P<0.0l significantly, compared with the group treated with GO alone. In comparison with the antioxidative activities of several commercial antioxidants (ascorbic acid, $\alpha$-tocopherol, catalase, serum), 273 $\mu\textrm{g}$/$\textrm{m}{\ell}$ addition of crude water extracts (300 $\mu\textrm{g}$/$\textrm{m}{\ell}$) showed equivalent antioxidative effect to 25 uM ascorbic acid.

• Molecules and Cells
• /
• v.38 no.3
• /
• pp.243-250
• /
• 2015

Patterning of the polar axis during the early leaf developmental stage is established by cell-to-cell communication between the shoot apical meristem (SAM) and the leaf primordia. In a previous study, we showed that the DRL1 gene, which encodes a homolog of the Elongator-associated protein KTI12 of yeast, acts as a positive regulator of adaxial leaf patterning and shoot meristem activity. To determine the evolutionally conserved functions of DRL1, we performed a comparison of the deduced amino acid sequence of DRL1 and its yeast homolog, KTI12, and found that while overall homology was low, well-conserved domains were presented. DRL1 contained two conserved plant-specific domains. Expression of the DRL1 gene in a yeast KTI12-deficient yeast mutant suppressed the growth retardation phenotype, but did not rescue the caffeine sensitivity, indicating that the role of Arabidopsis Elongator-associated protein is partially conserved with yeast KTI12, but may have changed between yeast and plants in response to caffeine during the course of evolution. In addition, elevated expression of DRL1 gene triggered zymocin sensitivity, while overexpression of KTI12 maintained zymocin resistance, indicating that the function of Arabidopsis DRL1 may not overlap with yeast KTI12 with regards to toxin sensitivity. In this study, expression analysis showed that class-I KNOX genes were downregulated in the shoot apex, and that YAB and KAN were upregulated in leaves of the Arabidopsis drl1- 101 mutant. Our results provide insight into the communication network between the SAM and leaf primordia required for the establishment of leaf polarity by mediating histone acetylation or through other mechanisms.

• Natural Product Sciences
• /
• v.15 no.3
• /
• pp.162-166
• /
• 2009

Oxczaasssaidative stress plays an important role in neuronal cell death, which is associated with neurodegenerative conditions such as Alzheimer's and Parkinson's disease. This study evaluated the neuroprotective effect of Euryale ferox (EF) extracts against glutamate-induced cytotoxicity in hybridoma N18-RE-105 cells. Specifically, neuroprotective effects of methanol and ethanol extracts were evaluated by the MTT reduction assay. The ethanol extracts of EF displayed dose dependent protection against neuronal cell death induced by 20 mM of glutamate. Furthermore, the ethanol extracts of EF was sequentially fractionated with hexane, diethyl ether, ethyl acetate, and water layer according to degree of polarity. The hexane fractions exhibited neuroprotective effect against glutamate-stressed N18-RE-105 cells. Overall, results suggest that EF extracts can potentially be used as chemotherapeutic agents against neuronal diseases.

• Korean Journal of Pharmacognosy
• /
• v.27 no.3
• /
• pp.173-177
• /
• 1996

For the search of anticancer compounds from natural products, 43 plants were extracted with benzene and methanol, separately, and the extracts were screened for the cytotoxicity against L1210 and HL60 cancer cell lines. From the results, 22 samples in benzene extracts showed cytotoxicity against L1210 cells and 23 samples against HL60 cells, respectively. However, any methanol extracts did not exhibit cytotoxicity against two cancer cell lines, it suggested that cytotoxic compounds seemed to have low polarity. $ED_{50}$ values less than $5\;{\mu}g/ml$ were observed in 14 and 9 samples in benzene extracts against L1210 and HL60 cancer cells, respectively.

• YAKHAK HOEJI
• /
• v.36 no.5
• /
• pp.491-495
• /
• 1992

For the research of cytotoxic natural products, 50 medicinal plants were extracted with benzene and methanol, separately, and screened against L1210 cells. From the results(Table I), 6 samples showed cytotoxicity both in benzene and methanol extracts of 17 samples in benzene extracts and 3 samples in methanol extracts, respectively. Generally, the cytotoxicity exhibited high frequency (34%) in benzene extract but low frequency in methanol extract (6%), it meant that active cytotoxic components had less polarity. $ED_{50}$ values less than $10\;{\mu}g/ml$ were observed in 17 medicinal plants.

• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.677-681
• /
• 2005

This Paper presents a 6 pulse shift operation control mode of current-source-inverter to make improvement of efficiency and to reduce the frequency of inverter switching for photovoltaic generation system using PWM current-source-inverter. This system is connected solar cell energy directly without using a storage cell. The proposed circuit can maintain maximum voltage of photovoltaic generation of take advantage of six Buck-Boost converter and a full-bridge inverter determines the polarity of AC output. That is controlled by using digital signal processor TMS320F2812 for operation about a 6 pulse shift operation control of current-source-inverter, and it is verified through the experimental results.

• BMB Reports
• /
• v.51 no.3
• /
• pp.106-118
• /
• 2018

How the organ size is adjusted to the proper size during development and how organs know that they reach the original size during regeneration remain long-standing questions. Based on studies using multiple model organisms and approaches for over 20 years, a consensus has been established that the Hippo pathway plays crucial roles in controlling organ size and maintaining tissue homeostasis. Given the significance of these processes, the dysregulation of the Hippo pathway has also implicated various diseases, such as tissue degeneration and cancer. By regulating the downstream transcriptional coactivators YAP and TAZ, the Hippo pathway coordinates cell proliferation and apoptosis in response to a variety of signals including cell contact inhibition, polarity, mechanical sensation and soluble factors. Since the core components and their functions of the Hippo pathway are evolutionarily conserved, this pathway serves as a global regulator of organ size control. Therefore, further investigation of the regulatory mechanisms will provide physiological insights to better understand tissue homeostasis. In this review, the historical developments and current understandings of the regulatory mechanism of Hippo signaling pathway are discussed.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.6
• /
• pp.446-453
• /
• 2021

This paper proposes enhanced single-phase pulse width modulation buck, boost, and buck-boost type ac-ac converters. The proposed converters, where input and output voltages share a common ground, require no isolated voltage sensor and have no leakage current problem. The commutation problem is solved with series-connected switching cell structures without using an additional RC snubber. In addition, with the use of the polarity of input voltage, switching patterns are determined so that the inductor currents can flow through switching devices during all operational modes. Two switches are always turned on during a half-period of the input voltage; thus, the switching loss is significantly reduced. Detailed analysis and experimental results are provided to verify the performance of the proposed converter.

• Journal of Microbiology and Biotechnology
• /
• v.29 no.1
• /
• pp.141-150
• /
• 2019

The spatial landmark protein Bud8 plays a crucial role in bipolar budding in the budding yeast Saccharomyces cerevisiae. The unconventional yeast Yarrowia lipolytica can also bud in a bipolar pattern, but is evolutionarily distant from S. cerevisiae. It encodes the protein YALI0F12738p, which shares the highest amino acid sequence homology with S. cerevisiae Bud8, sharing a conserved transmembrane domain at the C-terminus. Therefore, we named it YlBud8. Deletion of YlBud8 in Y. lipolytica causes cellular separation defects, resulting in budded cells remaining linked with one another as cell chains or multiple buds from a single cell, which suggests that YlBud8 may play an important role in cell separation, which is distinct from the function of Bud8 in S. cerevisiae. We also show that the YlBud8-GFP fusion protein is located at the cell membrane and enriched in the bud cortex, which would be consistent with a role in the regulation of cell separation. The coiled-coil domain at the N-terminus of YlBud8 is important to the correct localization and function of YlBud8, as truncated proteins that do not contain the coiled-coil domain cannot rescue the defects observed in $Ylbud8{\Delta}$. This finding suggests that a new signaling pathway controlled by YlBud8 via regulation of cell separation may exist in Y. lipolytica.