• 생명과학회지
• /
• 제16권1호
• /
• pp.37-43
• /
• 2006

간극결합은 이웃하는 두 세포 사이에 형성된 이온채널이며 또한 단일세포막에서도 작용한다. 간극결합채널을 형성하는 아미노 말단의 10번째 아미노산 잔기 부위까지가 개폐극성(gating polarity)과 전류-전압관계에 영향을 미친다. 정상적인 Cx32 채널은 음성의 개폐극성과 내향적인 정류현상을 보이는 반면, 음성전하를 띠는 aspartate로 치환된 T8D 채널은 반대의 개폐극성과 직선의 정류현상을 보인다. 이러한 개폐극성과 정류현상의 변화가 전하 자체에 의한 것인지 아니면 아미노 말단의 구조적인 변화에 의한 것인지는 아직 불명확하다. 이러한 문제점을 규명하기 위하여 아미노 말단의 8번째 아미노산 잔기를 cysteine기로 치환시킨 T8C 채널을 만들어 substituted-cysteine accessibility method (SCAM) 방법으로 이 채널의 생물리학적 특성을 조사하고자 하였다. T8C 채널은 정상적인 Cx32 채널처럼 음성의 개폐극성과 내향적인 정류현상을 보였으며, cysteine기로 치환이 정상적인 Cx32 채널의 원래 구조를 변화시키지 않았다는 것을 의미한다. 본 연구에서는 이런 전하효과를 규명하기 위하여 음성 전하를 갖는 MTSES-와 양성전하를 갖는 MTSET+를 사용하였다. MTSES-를 처리하면 T8C 채널은 T8D 채널의 특성처럼 양성의 개폐극성과 직선의 정류현상을 보였다. 그러나 양성전하를 갖는 MTSET+를 처리한 경우에는 T8C 채널은 본래의 특성을 그대로 유지하였다. 작은 분자의 MTS에 의해서 부여된 전하가 아미노 말단의 구조적인 변화를 초래하지는 않을 것으로 생각된다. 따라서 반대의 전하를 띠는 MTSES-와 MTSET+가 서로 상반대는 영향을 미치는 것으로 보아 본 연구에서 관찰된 개폐극성과 전류-전압의 변화는 아미노말단의 구조적인 변화라기보다는 MTS에 의해서 부여된 전하 자체에 기인한다고 할 수 있다. 또한 MTS가 아미노말단의 8번째 부위에 접근하여 반응을 일으킬 수 있다는 결과는 간극결합채널의 아미노말단이 채널의 통로(pore)를 형성한다는 가설을 뒷받침한다.

• Toxicological Research
• /
• 제14권2호
• /
• 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
• /
• 제38권3호
• /
• 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
• /
• 제15권3호
• /
• 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.

• 생약학회지
• /
• 제27권3호
• /
• 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.

• 약학회지
• /
• 제36권5호
• /
• 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.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2005년도 전력전자학술대회 논문집
• /
• 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
• /
• 제51권3호
• /
• 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.

• 전력전자학회논문지
• /
• 제26권6호
• /
• 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
• /
• 제29권1호
• /
• 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.