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Park CB, Kang YN, Jang H, Kim YS, Choi BO, Son SH, Song JH, Choi KH, Lee YK, Sung W, Kim JL. Evaluation of Usefulness of Yeast-Based Biological Phantom and Preliminary Study for Verification of Hypoxic Effect of Flash Radiotherapy. Int J Radiat Oncol Biol Phys 2023; 117:e704. [PMID: 37786063 DOI: 10.1016/j.ijrobp.2023.06.2193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
PURPOSE/OBJECTIVE(S) As a basic hypothesis for the effectiveness of flash radiation therapy, the effect of preserving normal tissue during flash radiation is due to the instantaneous chemical depletion of oxygen. A yeast-based biological phantom was created to verify the hypoxic effect of flash radiation therapy. A study to upgrade the previously developed X-Band LINAC to a flash irradiation mode is in progress, and a preceding study is conducted to evaluate the usefulness of a yeast-based biological phantom manufactured by analyzing the change in oxygen by irradiating a high dose in a general radiation therapy device. MATERIALS/METHODS Freeze-dried yeast sample (Saccharomyces cerevisiae, S288C) is activated and sub-cultured. For mass production of yeast samples, yeast culture medium is prepared by adding yeast colonies to the ypd medium. This study was conducted to verify the hypoxic effect among the biological mechanisms that occur during flash radiation therapy at the basic stage, and the oxygen concentration change during general radiation irradiation was measured in real time using a DO (Dissolved oxygen) meter and fiber optic sensor designed to do that. To prevent scatter, which is a concern during flash irradiation, the fiber form was used, and precise experiments are possible as a non-invasive oxygen concentration measurement method. Based on 10MV of general radiation therapy device, high-dose radiation of 500-10,000 cGy is irradiated to measure real-time oxygen concentration change. RESULTS As a result of irradiation with high-dose (500-10,000 cGy) radiation of general LINAC, it was confirmed that the oxygen concentration of the yeast culture medium decreased by 5.7-63.2%, and the usefulness of the biological phantom fabricated based on the yeast culture medium was evaluated. CONCLUSION Prior to the analysis of oxygen concentration change in yeast cells during X-Band LINAC flash irradiation, a preliminary study was conducted at a high dose in a general LINAC to obtain a significant result of oxygen concentration change and confirm the usefulness of the yeast-based biological phantom. Prior research was conducted and verified as a general irradiation experiment using a yeast-based biological phantom manufactured based on a DO meter and a fiber optic oxygen sensor. After irradiation with high-dose radiation, the oxygen concentration of the yeast culture medium was measured 5 times, and it was confirmed that there was a change in oxygen concentration of 5.7-63.2%, verifying the usefulness and stability of the biological phantom. The usefulness of the yeast-based biological phantom for high doses was confirmed, and it is expected that the usefulness of the biological phantom for flash radiation can be verified by additionally measuring the change in oxygen concentration of the biological phantom according to the high dose rate in the future.
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Affiliation(s)
- C B Park
- Department of Biomedicine & Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - Y N Kang
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - H Jang
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - Y S Kim
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - B O Choi
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - S H Son
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - J H Song
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - K H Choi
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - Y K Lee
- Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - W Sung
- Department of Biomedical Engineering and Department of Biomedicine and Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South) Korea
| | - J L Kim
- Electro-Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan, Korea, Republic of (South) Korea
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Md. Shahin AN, Shaayegan V, Lee PC, Park CB. In Situ Visualization for Control of Nano-Fibrillation Based on Spunbond Processing Using a Polypropylene/Polyethylene Terephthalate System. INT POLYM PROC 2021. [DOI: 10.1515/ipp-2020-4072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
In situ generation of polyethylene terephthalate (PET) nanofibrils in polypropylene (PP) microfibers via fiber spinning in a spunbond process was studied in this work. The effects of polymer flow rate and air speed in the drafter on the formation of PET fibrils were investigated using a pilot scale machine. An in-situ visualization technique was applied to examine the fiber evolution events and stretch profile at die exit. A scanning electron microscope was used to analyze and investigate the morphology of the dispersed domain. The PET dispersed phase was fibrillated within the PP matrix such that a nonofibrillated composite containing fibrils with an average size around 100 nm was obtained. It was found that the final fibril size directly depends on the degree of die swell, the air speed and the polymer flow rate. It was also found that the in situ observed size of the micro-scale PP/PET fibers was well correlated to the size of the nano-scale PET fibers formed in the PP matrix. The visualization results revealed that a smaller fibril diameter was obtainable by increasing the stretching on the spin line and/or decreasing the die swell.
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Affiliation(s)
- A. N. Md. Shahin
- Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto , Toronto , Canada
| | - V. Shaayegan
- Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto , Toronto , Canada
| | - P. C. Lee
- Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto , Toronto , Canada
- Multifunctional Composites Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto , Toronto , Canada
| | - C. B. Park
- Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto , Toronto , Canada
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Abstract
Abstract
Understanding of polypropylene (PP) foaming is critically important to reduce the weight of automotive parts. In this study, we used a batch foaming simulation system with visualization cell, to observe the foaming behaviors of PP that is blown with CO2 and N2 under various experimental conditions. We found that the nucleating agent content, initial temperature, pressure (i. e., gas content), and pressure drop rate during foaming have a significant effect on cell nucleation and cell growth. The cell density and the void fraction of PP foamed with CO2 and N2, respectively, were separately observed and compared. It was found that under the same experimental conditions, the maximum cell density of PP foamed with CO2 was higher than that of PP foamed with N2. However, the maximum cell density of PP foamed with CO2 was determined to be lower than that of PP foamed with N2, when the same gas mole numbers were employed. Based on the experimental results, optimum foaming conditions and effective processing strategies for PP-CO2 system are suggested.
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Affiliation(s)
- Q.-P. Guo
- EHC Canada, Inc., Oshawa , ON, Canada
- Microcellular Plastics Manufacturing Laboratory Department of Mechanical & Industrial Engineering, University of Toronto, Toronto , ON, Canada
| | - J. Wang
- Microcellular Plastics Manufacturing Laboratory Department of Mechanical & Industrial Engineering, University of Toronto, Toronto , ON, Canada
- The Dow Chemical Company, Midland , MI, USA
| | - C. B. Park
- Microcellular Plastics Manufacturing Laboratory Department of Mechanical & Industrial Engineering, University of Toronto, Toronto , ON, Canada
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4
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Affiliation(s)
- Q.-P. Guo
- EHC Canada, Inc., Oshawa, ON, Canada
- Microcellular Plastics Manufacturing Laboratory Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, ON, Canada
| | - J. Wang
- Microcellular Plastics Manufacturing Laboratory Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, ON, Canada
- The Dow Chemical Company, Midland, MI, USA
| | - C. B. Park
- Microcellular Plastics Manufacturing Laboratory Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, ON, Canada
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Abstract
Abstract
Recently, several companies have started to use the foaming technology in blow molding processes, primarily in extrusion blow molding. Despite the design complexity involved in the preform blow molding method, substantial advantages result when microcellular foaming and blow molding are combined. In preform and extrusion blow molding, the preform (i. e., the parison) undergoes significant biaxial stress during the inflation stage. Since either extensional or shear stress can dramatically improve cell nucleation, an externally applied stress can cause small-scale, local pressure variations throughout the sample, thus reducing the energy barrier for cell nucleation. So, unlike the current low-pressure foam blow molding technology, where cell nucleation occurs before inflating the preform/parison, we used a high-pressure system to prevent premature foaming in the shaping stage. Consequently, cell nucleation was induced after biaxial stresses were created to induce a higher cell density.
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Affiliation(s)
- L. H. Mark
- Microcellular Plastics Manufacturing Laboratory , Department of Mechanical and Industrial Engineering, University of Toronto, Toronto , Canada
| | - R. K. M. Chu
- Microcellular Plastics Manufacturing Laboratory , Department of Mechanical and Industrial Engineering, University of Toronto, Toronto , Canada
- Sabic Limburg B.V. , Geleen , The Netherlands
| | - G.-L. Wang
- Microcellular Plastics Manufacturing Laboratory , Department of Mechanical and Industrial Engineering, University of Toronto, Toronto , Canada
- School of Material Science and Engineering , Shandong University, Jinan, Shandong , PRC
| | - C. B. Park
- Microcellular Plastics Manufacturing Laboratory , Department of Mechanical and Industrial Engineering, University of Toronto, Toronto , Canada
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Choi SY, Park CB, Moon MH, Jeon HW, Song SW, Won YD, Kim YH, Kim YD, Cho DG, Jeong SC. P-225DOES OXYGEN THERAPY INCREASE THE RESOLUTION RATE OF SMALL PNEUMOTHORAX? Interact Cardiovasc Thorac Surg 2017. [DOI: 10.1093/icvts/ivx280.225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Abstract
A microcellular plastic is a foamed polymer of a cell size in the range of 0.1 to 10 μm and a cell density in the range of 109 to 1015 cells/cm3. Typically, microcellular plastics have been shown to possess superior impact strength, toughness, and fatigue life to solid polymers. Polymer/cellulosic-fibre composites make use of cellulosic-fibres as a reinforcing filler in the polymer matrix and are known to be advantageous over the neat polymers in terms of the material cost and some mechanical properties such as stiffness and specific strength. These polymer/cellulosic-fibre composites are microcellular processed to create a new class of materials with unique properties. In this paper, the feasibility of the production of microcellular PVC/cellulosic-fibre composites and the effect of the fibre content on the cell morphology are studied. Particular emphasis is given to the fibre surface treatment to investigate its effect on the microcellular morphology. Each step of microcellular PVC/cellulosic-fibre composite processing is addressed including the treatment of the cellulosic-fibre surface, the manufacture of the composite by the mixing of PVC and cellulosic-fibre, the saturation of the composite with gas, and the bubble nucleation and growth. The preliminary experimental results indicate that the surface modification of cellulosic-fibre plays a strong role in determining the interface between the polymer and fibre as well as the cellular morphology of the foamed composites.
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Affiliation(s)
- L. Matuana-Malanda
- Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario, Canada M5S 3B3
| | - C. B. Park
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8
| | - J. J. Balatinecz
- Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario, Canada M5S 3B3
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Abstract
In this study, cell coarsening in plastic foaming is investigated through numerical simulation. Cell coarsening occurring in two adjacent bubbles of different sizes in a finite volume of polymer melt is considered to be representative of the whole foaming system. A quadratic triangle-based finite element analysis with an implicit scheme for time evolution is utilized to solve the governing diffusion equation in the axisymmetric coordinate system. The effects of the bulk gas concentration, the intercellular distance, and the initial bubble sizes on cell coarsening are estimated. Efforts are made to improve a fundamental understanding of cell coarsening in plastic foaming.
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Affiliation(s)
- Z. Zhu
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
| | - D. Xu
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
| | - C. B. Park
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8,
| | - R. G. Fenton
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
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Shaayegan V, Mark LH, Tabatabaei A, Park CB. A new insight into foaming mechanisms in injection molding via a novel visualization mold. EXPRESS POLYM LETT 2016. [DOI: 10.3144/expresspolymlett.2016.44] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Mahmood SH, Xin CL, Lee JH, Park CB. Study of volume swelling and interfacial tension of the polystyrene-carbon dioxide-dimethyl ether system. J Colloid Interface Sci 2015; 456:174-81. [PMID: 26122798 DOI: 10.1016/j.jcis.2015.06.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 06/02/2015] [Accepted: 06/03/2015] [Indexed: 10/23/2022]
Abstract
We investigated the interaction of blended carbon dioxide (CO2) and dimethyl ether (DME) with polystyrene (PS) through volume swelling and interfacial tension. The experiments were carried out over a temperature range of 423-483 K, and the pressure was varied from 6.89 MPa to 20.68 MPa. With an incremental concentration of DME in the blend, the volume swelling increased while the interfacial tension between the PS/blend gas mixture and the blend gas decreased. The validity of the Simha-Somcynsky (SS) equation of state (EOS) for the ternary system was established by comparing experimentally measured volume swelling to that obtained via SS-EOS.
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Affiliation(s)
- S H Mahmood
- Microcellular Plastic Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Canada
| | - C L Xin
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing, China
| | - J H Lee
- Microcellular Plastic Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Canada
| | - C B Park
- Microcellular Plastic Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Canada.
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Lee E, Yang J, Ku M, Kim NH, Park Y, Park CB, Suh JS, Park ES, Yook JI, Mills GB, Huh YM, Cheong JH. Metabolic stress induces a Wnt-dependent cancer stem cell-like state transition. Cell Death Dis 2015; 6:e1805. [PMID: 26136078 PMCID: PMC4650724 DOI: 10.1038/cddis.2015.171] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 04/17/2015] [Accepted: 04/21/2015] [Indexed: 12/21/2022]
Abstract
Reciprocal interactions between cancer cells and the tumor microenvironment drive multiple clinically significant behaviors including dormancy, invasion, and metastasis as well as therapy resistance. These microenvironment-dependent phenotypes share typical characteristics with cancer stem cells (CSC). However, it is poorly understood how metabolic stress in the confined tumor microenvironment contributes to the emergence and maintenance of CSC-like phenotypes. Here, we demonstrate that chronic metabolic stress (CMS) in a long-term nutrient deprivation induces a Wnt-dependent phenoconversion of non-stem cancer cells toward stem-like state and this is reflected in the transcriptome analysis. Addition of Wnt3a as well as transfection of dominant-negative Tcf4 establishes an obligatory role for the Wnt pathway in the acquisition of CSC-like characteristics in response to metabolic stress. Furthermore, systematic characterization for multiple single cell-derived clones and negative enrichment of CD44+/ESA+ stem-like cancer cells, all of which recapitulate stem-like cancer characteristics, suggest stochastic adaptation rather than selection of pre-existing subclones. Finally, CMS in the tumor microenvironment can drive a CSC-like phenoconversion of non-stem cancer cells through stochastic state transition dependent on the Wnt pathway. These findings contribute to an understanding of the metabolic stress-driven dynamic transition of non-stem cancer cells to a stem-like state in the tumor metabolic microenvironment.
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Affiliation(s)
- E Lee
- Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
- Nanomedical National Core Research Center, Yonsei University, Seoul 120-749, Republic of Korea
| | - J Yang
- Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
- Yonsei-KRIBB Medical Convergence Research Institute, Yonsei University Health System, Seoul, Korea
| | - M Ku
- Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
- Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-752, Republic of Korea
| | - N H Kim
- Department of Oral pathology, Oral Cancer Research Institute, Yonsei University College of Dentistry, Seoul 120-752, Republic of Korea
| | - Y Park
- Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
| | - C B Park
- Department of Oral pathology, Oral Cancer Research Institute, Yonsei University College of Dentistry, Seoul 120-752, Republic of Korea
| | - J-S Suh
- Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
- Yonsei-KRIBB Medical Convergence Research Institute, Yonsei University Health System, Seoul, Korea
- Severance Biomedical Science Institute (SBSI), Seoul 120-752, Republic of Korea
| | - E S Park
- Yonsei-KRIBB Medical Convergence Research Institute, Yonsei University Health System, Seoul, Korea
| | - J I Yook
- Department of Oral pathology, Oral Cancer Research Institute, Yonsei University College of Dentistry, Seoul 120-752, Republic of Korea
| | - G B Mills
- Department of Systems Biology, MD Anderson Cancer Center, Houston, TX, USA
| | - Y-M Huh
- Department of Radiology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
- Yonsei-KRIBB Medical Convergence Research Institute, Yonsei University Health System, Seoul, Korea
- Severance Biomedical Science Institute (SBSI), Seoul 120-752, Republic of Korea
| | - J-H Cheong
- Severance Biomedical Science Institute (SBSI), Seoul 120-752, Republic of Korea
- Department of Surgery, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
- Department of Biochemistry & Molecular Biology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
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Sarikhani K, Jeddi K, Thompson RB, Park CB, Chen P. Adsorption of Surface-Modified Silica Nanoparticles to the Interface of Melt Poly(lactic acid) and Supercritical Carbon Dioxide. Langmuir 2015; 31:5571-5579. [PMID: 25919815 DOI: 10.1021/acs.langmuir.5b00306] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
With the purpose of fabricating polymer nanocomposite foams and preventing coalescence in foaming processes, the interfacial tension of poly(lactic acid) (PLA)-silica composites is investigated in this work. Synthesized silica nanoparticles (SNs) with a CO2-philic surface modification are used as the dispersed nanoparticles. Interfacial tension is a key parameter in processing of polymer foams since it directly affects the final foam properties, such as cell size and cell density. Interfacial tension of silica-containing PLA and supercritical carbon dioxide (CO2) is measured using axisymmetric drop shape analysis profile (ADSA-P) pendant drop method at high pressures and high temperatures. The interfacial tension between PLA and supercritical CO2 is observed to decrease as a result of the nanoparticles' adsorption to the interface. These results indicate that the reduction in interfacial tension with increasing silica content significantly deviates from a linear trend; there is a minimum at 2 wt % loading of the SNs and then the interfacial tension curve reaches a plateau. Contact angle measurements show an affinity of the SNs for the polymer-supercritical CO2 interface, and these obtained results are used to calculate the binding energy of the nanoparticles to the PLA/CO2 interface. In addition to interfacial properties, the adsorption of silica nanoparticles at the interface is also studied in detail with scanning electron microscopy.
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Affiliation(s)
| | | | | | - C B Park
- ∥Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto,5 King's College Road, Toronto, Ontario, Canada M5S 3G8
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Hasan MM, Park CB. Simha-Somcynsky Equation of State Modeling of the PVT Behavior of PP/Clay-Nanocomposite/CO2 Mixtures. INT POLYM PROC 2014. [DOI: 10.3139/217.2815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
The Pressure-Volume-Temperature (PVT) property of polymer nanocomposite (PNC)/gas solutions is an important fundamental property in the foaming of PNC. However, accurate data have not yet been reported. We examined the PVT behaviors of polypropylene (PP) and PP/organoclay polymer nanocomposite (PP-PNC) by monitoring the swelling changes of the polymer melt in supercritical carbon dioxide (scCO2). A model was adopted that describes the PVT behaviors of PP-PNC with and without dissolved gas. Based on the model, a PNC consists of two sections: a hard section (a nanoparticle surrounded by solidified polymer) and a soft section (neat polymer). It was observed that an infusion of nanoparticles decreased the swelling. It seems that the hard section had a minimal free volume in which to dissolve the blowing agents, and that the number of hard sections increased with the infusion of nanoparticles. As a result, the total gas absorption capacity of the system decreased, and consequently, the swelling also decreased.
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Affiliation(s)
- M. M. Hasan
- Microcellular Plastics Manufacturing Laboratory , Department of Mechanical and Industrial Engineering University of Toronto, Toronto, Ontario , Canada
| | - C. B. Park
- Microcellular Plastics Manufacturing Laboratory , Department of Mechanical and Industrial Engineering University of Toronto, Toronto, Ontario , Canada
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Petit G, Kornreich C, Noel X, Verbanck P, Campanella S, Choi J, Park SM, Park CB, Gwak AR, Hwang JY, Lee JY, Jung HY, Maurage P, Noel X, Joassin F, Philippot P, Hanak C, Verbank P, Luminet O, de Timary P, Campanella S, Grynberg D, Maurage P, Noel X, Joassin F, Hanak C, Verbank P, Luminet O, de Timary P, Campanella S, Philippot P, Grynberg D, Nyssen L, Quertemont E, Noel X, Doallo S, Gomez-Suarez A, Malkowska A, Topolewska-Wochowska A, Bamburowicz-Klimkowska M, Matsumoto H, Szutowski M, Wojnar M, Corral M, Mateos P, Porras C, Garcia-Moreno LM, Cadaveira F, Rubio G, Libman-Sokolowska M, Matsumoto H, Sygitowicz G, Filipek A, Piwowarska J, Dziklinska A, Radziwon-Zaleska M, Ryszewska-Pokrasniewicz B, Skalski M, Naruszewicz M, Biecek P, Tyce M, Zwierzchowska K, Nasierowski T, Sitkiewicz D, Wojnar M, Kalk N, Cherian R, Naveed M, Newson M, Cavanagh J, Rabiner E, Dar K, McInnes I, Lingford-Hughes A, Neumann A, Vande Weghe N, Philippot P, Luminet O, de Timary P, Vilenne A, Kreusch F, Quertemont E, Brkic S, Soderpalm B, Soderpalm-Gordh A, Oswald L, Wand G, Kuwabara H, Wong D, Brown C, Hutchison KE, Karoly H, Bryan AD, Thayer R, Weiland B, Harlaar N, Bryan AD, Thayer R, Weiland B, Montanaro E, Hutchison K, Lason W, Walecki P, Gorzelanczyk EJ, Walecki P, Gorzelanczyk EJ, Feit J, Pasgreta K, Lason W, Ziolkowski M. PSYCHOLOGY AND MARKERS. Alcohol Alcohol 2013. [DOI: 10.1093/alcalc/agt117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Lee SH, Zhang Y, Kontopoulou M, Park CB, Wong A, Zhai W. Optimization of Dispersion of Nanosilica Particles in a PP Matrix and Their Effect on Foaming. INT POLYM PROC 2013. [DOI: 10.3139/217.2403] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Nanocomposites based on isotactic polypropylene (PP) and nanosilica (SiO2) were prepared using a co-rotating twin-screw extruder (TSE). The effect of operating variables, such as screw speed and screw configuration on the dispersion of nanosilica in the polymer matrix has been studied, using TEM imaging. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good nanosilica dispersion. Furthermore, the effects of filler loading and amount of a maleated polypropylene (PP-g-MA) compatibilizer on the degree of SiO2 dispersion were investigated. The foaming performance of the composites was evaluated using a batch foaming simulation system, and an extrusion foaming setup that employed respectively N2 and CO2 blowing agents. Well-dispersed surface-modified hydrophobic SiO2 particles acted as effective nucleating agents for foaming, when used at loadings below 1 phr.
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Affiliation(s)
- S. H. Lee
- Department of Chemical Engineering, Queen's University, Kingston, Canada
| | - Y. Zhang
- Department of Chemical Engineering, Queen's University, Kingston, Canada
| | - M. Kontopoulou
- Department of Chemical Engineering, Queen's University, Kingston, Canada
| | - C. B. Park
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | - A. Wong
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
| | - W. Zhai
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada
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Abstract
Abstract
This paper uses a finite element analysis to investigate the morphological changes of nano-cells in a polystyrene (PS) – CO2 foaming system. The system was composed of a finite polymer melt with a central cell and eight surrounding cells. The computational domain was discretized using linear triangular elements. The growth and shrinkage of nano-sized cells were tracked using the moving mesh method. The effects of the initial bulk gas concentration, cell size, intercellular distance, and system temperature on cell ripening were examined. The results show that smaller nano-sized cell(s) are doomed to collapse very quickly once they have interacted with larger cell(s), making it difficult to survive. Efforts were made to improve the general understanding of the challenges posed to the formation of nano-cells in foaming processes.
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Affiliation(s)
- Z. Zhu
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
| | - C. B. Park
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
| | - J. H. Zong
- Department of Materials, Mechanical & Automation Engineering, Yanbian University of Science and Technology, Yanji, Jilin, PRC
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Oh YC, Kang OH, Kim SB, Mun SH, Park CB, Kim YG, Kim YI, Lee YS, Han SH, Keum JH, Shin DW, Ma JY, Kwon DY. Anti-inflammatory effect of sinomenine by inhibition of pro-inflammatory mediators in PMA plus A23187-stimulated HMC-1 Cells. Eur Rev Med Pharmacol Sci 2012; 16:1184-1191. [PMID: 23047501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
BACKGROUND AND OBJECTIVES Sinomenine is an alkaloid compound and a prominent anti-inflammatory agent found in the root of the climbing plant Sinomenium acutum. However, its effects on the mechanism of human mast cell line (HMC)-1-mediated inflammation remained unknown. MATERIALS AND METHODS To provide insight into the biological effects of sinomenine, we examined its influence on the pro-inflammatory cytokine production in HMC-1 cells stimulated by phorbol 12-myristate-13-acetate (PMA) plus A23187 by evaluating the stimulated cells in the presence or absence of sinomenine. In the present study, the pro-inflammatory cytokine production was measured using ELISA, Reverse Transcription-polymerase chain reaction (RT-PCR) and nuclear factor (NF)-kappaB, mitogen-activated protein kinases (MAPKs) pathway activation, as determined by Western blot analysis. Also, cyclooxygenase (COX)-2 expression was measured through Western blot and RT-PCR analysis. RESULTS Sinomenine inhibited the pro-inflammatory cytokine production induced by PMA plus A23187 in a dose-dependent manner. Furthermore, sinomenine inhibited the phosphorylations of extracellular signal-regulated kinase (ERK) and p38 MAPKs as well as the translocation of NF-kappaB p65 through reduced IkappaBalpha degradation. In addition, sinomenine suppressed COX-2 protein and mRNA expression dose-dependently. CONCLUSIONS Taken together, the results of this study indicate that the anti-inflammatory effects of sinomenine may occur via the inhibition of pro-inflammatory cytokine and COX-2 production through the inhibition of MAPKs and NF-kappaB pathway activation by PMA plus A23187 stimulation in HMC-1 cells.
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Affiliation(s)
- Y C Oh
- College of Pharmacy and Wonkwang-Oriental Medicines Research Institute, Wonkwang University, Iksan, Jeonbuk, Korea
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Park CB, Dufort D. Elsevier Trophoblast Research Award lecture: The multifaceted role of Nodal signaling during mammalian reproduction. Placenta 2010; 32 Suppl 2:S125-9. [PMID: 21195476 DOI: 10.1016/j.placenta.2010.12.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 12/02/2010] [Accepted: 12/07/2010] [Indexed: 01/12/2023]
Abstract
Nodal, a secreted signaling protein in the transforming growth factor-beta (TGF-β) superfamily, has established roles in vertebrate development. However, components of the Nodal signaling pathway are also expressed at the maternal-fetal interface and have been implicated in many processes of mammalian reproduction. Emerging evidence indicates that Nodal and its extracellular inhibitor Lefty are expressed in the uterus and complex interactions between the two proteins mediate menstruation, decidualization and embryo implantation. Furthermore, several studies have shown that Nodal from both fetal and maternal sources may regulate trophoblast cell fate and facilitate placentation as both embryonic and uterine-specific Nodal knockout mouse strains exhibit disrupted placenta morphology. Here we review the established and prospective roles of Nodal signaling in facilitating successful pregnancy, including recent evidence supporting a potential link to parturition and preterm birth.
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Affiliation(s)
- C B Park
- Division of Experimental Medicine, Royal Victoria Hospital, McGill University Health Centre, Montreal, QC, Canada.
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Affiliation(s)
- C. Wang
- Department of Mechanical & Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
| | - S. N. Leung
- Department of Mechanical & Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
| | - M. Bussmann
- Department of Mechanical & Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
| | - W. T. Zhai
- Department of Mechanical & Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
| | - C. B. Park
- Department of Mechanical & Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8
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Wang C, Bussmann M, Park CB. Numerical investigation of the effect of screw geometry on the mixing of a viscous polymer melt. J Appl Polym Sci 2010. [DOI: 10.1002/app.31039] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Affiliation(s)
- Y. G. Li
- Department of Mechanical and Industrial Engineering, Microcellular Plastics Manufacturing Laboratory, University of Toronto, Canada M5S 3G8
| | - C. B. Park
- Department of Mechanical and Industrial Engineering, Microcellular Plastics Manufacturing Laboratory, University of Toronto, Canada M5S 3G8
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Park H, Park CB, Tzoganakis C, Tan KH, Chen P. Simultaneous Determination of the Surface Tension and Density of Polystyrene in Supercritical Nitrogen. Ind Eng Chem Res 2008. [DOI: 10.1021/ie071472q] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- H. Park
- Departments of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1; Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8; and Epson Research & Development, San Jose, CA
| | - C. B. Park
- Departments of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1; Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8; and Epson Research & Development, San Jose, CA
| | - C. Tzoganakis
- Departments of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1; Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8; and Epson Research & Development, San Jose, CA
| | - K.-H. Tan
- Departments of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1; Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8; and Epson Research & Development, San Jose, CA
| | - P. Chen
- Departments of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1; Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8; and Epson Research & Development, San Jose, CA
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Park H, Park CB, Tzoganakis C, Chen P. Effect of Molecular Weight on the Surface Tension of Polystyrene Melt in Supercritical Nitrogen. Ind Eng Chem Res 2007. [DOI: 10.1021/ie070311j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- H. Park
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, and Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8
| | - C. B. Park
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, and Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8
| | - C. Tzoganakis
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, and Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8
| | - P. Chen
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, and Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8
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Park H, Thompson RB, Lanson N, Tzoganakis C, Park CB, Chen P. Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide. J Phys Chem B 2007; 111:3859-68. [PMID: 17388548 DOI: 10.1021/jp065851t] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The surface tension of polymers in a supercritical fluid is one of the most important physicochemical parameters in many engineering processes, such as microcellular foaming where the surface tension between a polymer melt and a fluid is a principal factor in determining cell nucleation and growth. This paper presents experimental results of the surface tension of polystyrene in supercritical carbon dioxide, together with theoretical calculations for a corresponding system. The surface tension is determined by Axisymmetric Drop Shape Analysis-Profile (ADSA-P), where a high pressure and temperature cell is designed and constructed to facilitate the formation of a pendent drop of polystyrene melt. Self-consistent field theory (SCFT) calculations are applied to simulate the surface tension of a corresponding system, and good qualitative agreement with experiment is obtained. The physical mechanisms for three main experimental trends are explained by using SCFT, and none of the explanations quantitatively depend on the configurational entropy of the polymer constituents. These calculations therefore rationalize the use of simple liquid models for the quantitative prediction of surface tensions of polymers. As pressure and temperature increase, the surface tension of polystyrene decreases. A linear relationship is found between surface tension and temperature, and between surface tension and pressure; the slope of surface tension change with temperature is dependent on pressure.
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Affiliation(s)
- H Park
- Department of Chemical Engineering, Physics and Astronomy, and Applied Mathematics, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada
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Guo G, Wang KH, Park CB, Kim YS, Li G. Effects of nanoparticles on the density reduction and cell morphology of extruded metallocene polyethylene/wood fiber nanocomposites. J Appl Polym Sci 2007. [DOI: 10.1002/app.25778] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
This paper discusses the control of the foaming process for production of variable microcellular structures and morphologies for novel acoustical foams under investigation. For that purpose, the foaming process was controlled for production of foam samples with various microcellular structures. Crosslinked LDPE was used as a base material for the produced foams. Very high open-cell content (ranging between 43 – 95%), high microcellular cell densities (9×108 – 1.6×109 cells/cm3) and desired expansion ratios (3 – 9 folds) were successfully obtained. While the material is overly porous, it is noted that the unfoamed skins on the outer surfaces of the samples have prevented sound waves from penetrating the samples. Manual skin removal resulted in slight improvement in sound absorption testing. However, in order to get more reliable data, skinless samples need to be produced.
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Affiliation(s)
- M.Y. Serry Ahmed
- Microcellular Plastics Manufacturing Laboratory (MPML), University of Toronto
| | - C. B. Park
- Microcellular Plastics Manufacturing Laboratory (MPML), University of Toronto
| | - N. Atalla
- Groupe d'Acoustique De l'Universitέ de Sherbrooke (GAUS), Universitέ de Sherbrooke
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Affiliation(s)
- H. Park
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8, Epson R&D, 3145 Porter Drive, Suite 104, Palo Alto, California 94304-1224
| | - C. B. Park
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8, Epson R&D, 3145 Porter Drive, Suite 104, Palo Alto, California 94304-1224
| | - C. Tzoganakis
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8, Epson R&D, 3145 Porter Drive, Suite 104, Palo Alto, California 94304-1224
| | - K. H. Tan
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8, Epson R&D, 3145 Porter Drive, Suite 104, Palo Alto, California 94304-1224
| | - P. Chen
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue, Waterloo, Ontario, Canada N2L 3G1, Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8, Epson R&D, 3145 Porter Drive, Suite 104, Palo Alto, California 94304-1224
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Li G, Gunkel F, Wang J, Park CB, Altstädt V. Solubility measurements of N2 and CO2 in polypropylene and ethene/octene copolymer. J Appl Polym Sci 2006. [DOI: 10.1002/app.25163] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Park CB, Lee SB. Inhibitory effect of mineral ion accumulation on high density growth of the hyperthermophilic archaeon Sulfolobus solfataricus. J Biosci Bioeng 2005; 87:315-9. [PMID: 16232474 DOI: 10.1016/s1389-1723(99)80038-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/1998] [Accepted: 11/11/1998] [Indexed: 10/18/2022]
Abstract
A fed-batch operation for high density cultivation of Sulfolobus solfataricus (DSM 1617) in a bench-top fermentor using a feed medium composed of glucose and yeast extract was investigated. The highest maximal cell density obtained in controlled fed-batch cultures was 21.7 g/l. Although higher yeast extract concentrations in the medium favored greater cell biomass yield, cell growth ceased with low cell densities. It was observed that large amounts of inorganic ions, such as sulfate, ammonium, potassium and phosphate ions, were accumulated in the culture broth at higher yeast extract concentrations. This was due to either the addition of the titrant or feeding of yeast extract during cultivation. Fed-batch cultures with additional mineral salts in the feed medium showed much lower cell biomass, indicating that accumulation of inorganic ions has a significant inhibitory effect on the growth of S. solfataricus. Inhibition of cell growth by the presence of mineral ions was further confirmed by the batch culture experiments. Some plausible mechanisms which can account for the growth inhibition at higher mineral ion concentrations have been suggested.
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Affiliation(s)
- C B Park
- Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyoja Dong, Pohang 790-784, Korea
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Rizvi GM, Park CB, Lin WS, Guo G, Pop-Iliev R. Expansion mechanisms of plastic/wood-flour composite foams with moisture, dissolved gaseous volatiles, and undissolved gas bubbles. POLYM ENG SCI 2004. [DOI: 10.1002/pen.10115] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Zhang H, Rizvi GM, Park CB. Development of an extrusion system for producing fine-celled HDPE/wood-fiber composite foams using CO2 as a blowing agent. Adv Polym Technol 2004. [DOI: 10.1002/adv.20016] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Kwok DY, Cheung LK, Park CB, Neumann AW. Study on the surface tensions of polymer melts using axisymmetric drop shape analysis. POLYM ENG SCI 2004. [DOI: 10.1002/pen.10241] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Guo G, Rizvi GM, Park CB, Lin WS. Critical processing temperature in the manufacture of fine-celled plastic/wood-fiber composite foams. J Appl Polym Sci 2003. [DOI: 10.1002/app.13193] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Erickson D, Li D, Park CB. Numerical Simulations of Capillary-Driven Flows in Nonuniform Cross-Sectional Capillaries. J Colloid Interface Sci 2002; 250:422-30. [PMID: 16290680 DOI: 10.1006/jcis.2002.8361] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2001] [Accepted: 03/15/2002] [Indexed: 11/22/2022]
Abstract
In this study the wetting behavior of converging-diverging and diverging-converging capillaries is investigated numerically using an in-house written, finite-element code. An interface tracking procedure based on the predicted change in the total liquid volume, to update the interface location, and Cox's formulation, to determine the dynamic contact angle and the interface shape, is proposed and used. Flow simulations revealed that both converging-diverging and diverging-converging capillaries exhibit significantly slower wetting behavior than straight capillaries and that any deviation in the capillary diameter necessarily tends to slow the overall wetting speed. This behavior was attributed to local regions of very low capillary pressure and high viscous retardation force when the capillary diameter at the interface was significantly larger than the capillary diameter over the upstream fluid. Though the local wetting velocities were different, when equivalent capillaries were compared it was found that both converging-diverging and diverging-converging capillaries had the same total fill time independent of the number of irregular regions, suggesting that the simple model is sufficient for predicting the overall effect. The influence of surface tension and contact angle on the total wetting time was found to be similar for both straight and irregularly shaped capillaries.
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Affiliation(s)
- D Erickson
- Department of Mechanical & Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8, Canada
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Kang WS, Lim MY, Lee EJ, Kim IB, Oh SJ, Brecha NC, Park CB, Chun MH. Light- and electron-microscopic analysis of neuropeptide Y-immunoreactive amacrine cells in the guinea pig retina. Cell Tissue Res 2001; 306:363-71. [PMID: 11735036 DOI: 10.1007/s004410100460] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2001] [Accepted: 08/01/2001] [Indexed: 11/28/2022]
Abstract
We investigated the morphology and synaptic connections of neuropeptide Y (NPY)-containing neurons in the guinea pig retina by immunocytochemistry, using antisera against NPY. Specific NPY immunoreactivity was localized to a population of wide-field and regularly spaced amacrine cells with processes ramifying mainly in stratum 1 of the inner plexiform layer (IPL). Double-label immunohistochemistry demonstrated that all NPY-immunoreactive cells possessed glutamic acid decarboxylase 65 immunoreactivity. The synaptic connectivity of NPY-immunoreactive amacrine cells was identified in the IPL by electron microscopy. The NPY-labeled amacrine cell processes received synaptic input from other amacrine cell processes and bipolar cell axon terminals in stratum 1 of the IPL. The most frequent postsynaptic targets of NPY-immunoreactive amacrine cells were other amacrine cell processes. Synaptic outputs to bipolar cells were also observed in a small number of cases. This finding suggests that NPY-containing amacrine cells may influence inner retinal circuitry in stratum 1 of the IPL, thus mediating visual processing.
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Affiliation(s)
- W S Kang
- Department of Biology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
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Toriyama-Baba H, Iigo M, Asamoto M, Iwahori Y, Park CB, Han BS, Takasuka N, Kakizoe T, Ishikawa C, Yazawa K, Araki E, Tsuda H. Organotropic chemopreventive effects of n-3 unsaturated fatty acids in a rat multi-organ carcinogenesis model. Jpn J Cancer Res 2001; 92:1175-83. [PMID: 11714441 PMCID: PMC5926667 DOI: 10.1111/j.1349-7006.2001.tb02137.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Organotropic chemopreventive effects of n-3 unsaturated fatty acids were studied using a multi-organ carcinogenesis model in male rats. Rats were treated with diethylnitrosamine (DEN), N-methyl-N-nitrosourea (MNU), N-butyl-N-4-hydroxybutylnitrosamine (BBN), 1,2-dimethylhydrazine (DMH) and dihydroxy-di-n-propylnitrosamine (DHPN) during the first 7 weeks, and then given unsaturated fatty acid (UFAs), docosahexaenoic acid (n-3, C(22:6)) (DHA), eicosapentaenoic acid (n-3, C(20:5)) (EPA), linoleic acid (n-6, C(18:2)) (LA) or oleic acid (n-9, C(18:1)) (OA) at a dose of 1.0 ml/rat, 3 times a week by gavage for the consecutive 30 weeks. All rats were fed a low LA basal diet throughout the experiment and a calorie-restricted basal diet during the period of UFAs feeding administration. DHA significantly reduced tumor size and numbers in the large intestine as compared to OA treatment. Furthermore, DHA showed a tendency to inhibit carcinogenesis in the small intestine and lung. EPA also showed a tendency to inhibit intestinal carcinogenesis. On the other hand, LA showed a tendency to inhibit lung carcinogenesis, but to promote large intestinal carcinogenesis. However these UFAs did not influence preneoplastic and neoplastic lesion development in the liver, kidney, and urinary bladder. Levels of the administered fatty acids were clearly increased in the serum and organs. In contrast, arachidonic acid (AA) levels in the large and small intestines and liver were markedly decreased by treatment with DHA and EPA. Decreased levels of AA in the large intestine correlated well with tumor incidence, although the number of glutathione S-transferase-positive (GST-P(+)) foci showed an inverse correlation with AA levels. The data thus provide evidence that an organotropism exists with regard to the influence of UFAs on carcinogenesis, which correlates with reduction of tissue AA levels in the target organs.
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Affiliation(s)
- H Toriyama-Baba
- Experimental Pathology and Chemotherapy Division, National Cancer Center Research Institute, Tokyo
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Park CB, Lee SB, Ryu DD. L-pyroglutamate spontaneously formed from L-glutamate inhibits growth of the hyperthermophilic archaeon Sulfolobus solfataricus. Appl Environ Microbiol 2001; 67:3650-4. [PMID: 11472943 PMCID: PMC93067 DOI: 10.1128/aem.67.8.3650-3654.2001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Identification of physiological and environmental factors that limit efficient growth of hyperthermophiles is important for practical application of these organisms to the production of useful enzymes or metabolites. During fed-batch cultivation of Sulfolobus solfataricus in medium containing L-glutamate, we observed formation of L-pyroglutamic acid (PGA). PGA formed spontaneously from L-glutamate under culture conditions (78 degrees C and pH 3.0), and the PGA formation rate was much higher at an acidic or alkaline pH than at neutral pH. It was also found that PGA is a potent inhibitor of S. solfataricus growth. The cell growth rate was reduced by one-half by the presence of 5.1 mM PGA, and no growth was observed in the presence of 15.5 mM PGA. On the other hand, the inhibitory effect of PGA on cell growth was alleviated by addition of L-glutamate or L-aspartate to the medium. PGA was also produced from the L-glutamate in yeast extract; the PGA content increased to 8.5% (wt/wt) after 80 h of incubation of a yeast extract solution at 78 degrees C and pH 3.0. In medium supplemented with yeast extract, cell growth was optimal in the presence of 3.0 g of yeast extract per liter, and higher yeast extract concentrations resulted in reduced cell yields. The extents of cell growth inhibition at yeast extract concentrations above the optimal concentration were correlated with the PGA concentration in the culture broth. Although other structural analogues of L-glutamate, such as L-methionine sulfoxide, glutaric acid, succinic acid, and L-glutamic acid gamma-methyl ester, also inhibited the growth of S. solfataricus, the greatest cell growth inhibition was observed with PGA. We also observed that unlike other glutamate analogues, N-acetyl-L-glutamate enhanced the growth of S. solfataricus. This compound was stable under cell culture conditions, and replacement of L-glutamate with N-acetyl-L-glutamate in the medium resulted in increased cell density.
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Affiliation(s)
- C B Park
- Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyoja-Dong, Pohang 790-784, Korea
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Abstract
We demonstrate the formation of micropatterned sol-gel structures containing active proteins by patterning with polydimethylsiloxane (PDMS) microchannels. To transport sol solution efficiently into the hydrophobic PDMS microchannels, a hydrophilic-hydrophobic block copolymer was used to impart hydrophilicity to the PDMS microchannels. Poor adhesion of the micropatterned gel structure onto glass slides was improved by treating the glass surface with a polymeric substrate. To minimize cracks in the gel microstructure, hybrid matrices of interpenetrating organic and inorganic networks were prepared containing the reactive organic moieties polyvinylalcohol or polyvinylpyrrolidone. Retention of biochemical activity within the micropatterned gel was demonstrated by performing immunobinding assays with immobilized immunoglobulin G (IgG) antibody. The potential application of microfluidics technology to immobilized-enzyme biocatalysis was demonstrated using PDMS-patterned microchannels filled with trypsin-containing sol-gels. This work provides a foundation for the microfabrication of functional protein chips using sol-gel processes.
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Affiliation(s)
- Y D Kim
- Department of Chemical Engineering, University of California, 110-C Gilman Hall, Berkeley, CA 94720, USA
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Han BS, Park CB, Takasuka N, Naito A, Sekine K, Nomura E, Taniguchi H, Tsuno T, Tsuda H. A ferulic acid derivative, ethyl 3-(4'-geranyloxy-3-methoxyphenyl)-2-propenoate, as a new candidate chemopreventive agent for colon carcinogenesis in the rat. Jpn J Cancer Res 2001; 92:404-9. [PMID: 11346462 PMCID: PMC5926721 DOI: 10.1111/j.1349-7006.2001.tb01109.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The inhibitory influence of ferulic acid (FA), a rice germ component, and its geranylated derivative 3-(4'-geranyloxy-3-methoxyphenyl)-2-propenoate (EGMP) on the post-initiation stage of azoxymethane (AOM)-induced colon carcinogenesis was studied in male F344 rats given two s.c. injections of AOM (15 mg / kg body weight) during week 1. Diets containing EGMP or FA at doses of 0.1 or 0.2% were then fed for 3 weeks from week 2 to 5, when the animals were sacrificed. The numbers of aberrant crypt foci (ACF) and aberrant crypts (AC) per rat in the group given 0.2% FA were significantly decreased (P < 0.001) as compared to the AOM alone group. Furthermore, the numbers of ACF and AC per rat fed the 0.2% and 0.1% EGMP were significantly reduced (P < 0.001 and P < 0.01, respectively). Colonic epithelial cells in S-phase, as measured by bromodeoxyuridine (BrdU) labeling, in rats fed EGMP were significantly decreased in the 0.2 and 0.1% EGMP groups as compared to the AOM alone group (P < 0.05). BrdU labeling indices in rats fed FA and EGMP assessed by a test using a coefficient for linear contrast were also significantly decreased as compared to the AOM alone value (P < 0.05, P < 0.01, respectively). The results indicate that FA and EGMP have inhibitory effects on ACF and AC development, EGMP being more potent, possibly due to stronger suppressive effects on cell proliferation. No toxic effects were observed in rats given either compound in terms of body and organ weights, and liver or kidney histology. The findings thus suggest that EGMP and FA, especially the former, might have potential as chemopreventive agents against colon tumor development.
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Affiliation(s)
- B S Han
- Experimental Pathology and Chemotherapy Division, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
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Yoon YS, Shin JW, Park CB, Oh YS, Lee IS, Lee HS, Lee JS. Morphological structure of accessory spleen in Chinese hamsters. J Vet Sci 2000; 1:73-5. [PMID: 14614300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
To attempt a rigorous definition of the structure of the accessory spleen (AS) in the Chinese hamster, we examined twenty-one animals, and found AS in 5 animals (23.8%), which were over 7-month-old. The AS had no connection with the main spleen and was seen as a dark red oval organ (0.7 mm x 1.5 mm), which was embedded in the adipose tissue near the tail of the pancreas. It was demarcated from the adipose tissue and some pancreatic tissue. The organ was encapsulated by thin collagenous connective tissue and smooth muscle fibers, and contained lymphatic nodules, reticular fibers, nodular central arterioles, macrophages and megakaryocytes. Notably the incidence of AS appeared to increase with age in the Chinese hamsters.
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Affiliation(s)
- Y S Yoon
- College of Veterinary Medicine and School of Agricultural Biotechnology, Seoul National University, Suwon 441-744, Korea.
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46
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Ju WK, Kim KY, Park SJ, Park DK, Park CB, Oh SJ, Chung JW, Chun MH. Nitric oxide is involved in sustained and delayed cell death of rat retina following transient ischemia. Brain Res 2000; 881:231-6. [PMID: 11036166 DOI: 10.1016/s0006-8993(00)02816-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have investigated the role of nitric oxide (NO) in the rat retina following ischemic injury induced by transient increase of intraocular pressure. The thickness of both the inner plexiform layer and inner nuclear layer decreased during early postischemic stages (up to 1 week). In late postischemic stages (2-4 weeks), the thickness of the outer nuclear layer (ONL) decreased markedly. Thus, mechanisms other than excitotoxic ones may contribute to postischemic retinal cell death. Treatment of rats with N(G)-nitro-L-arginine methyl ester, a nitric oxide synthase (NOS) inhibitor, significantly reduced ischemic damage. Our findings suggest that NO is involved in the mechanism of ischemic injury, and plays a key role in the delayed and sustained cell death in the ONL following transient retinal ischemia.
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Affiliation(s)
- W K Ju
- Department of Anatomy, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, 137-701, Seoul, South Korea
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Kim HS, Yoon H, Minn I, Park CB, Lee WT, Zasloff M, Kim SC. Pepsin-mediated processing of the cytoplasmic histone H2A to strong antimicrobial peptide buforin I. J Immunol 2000; 165:3268-74. [PMID: 10975843 DOI: 10.4049/jimmunol.165.6.3268] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The intestinal epithelium forms a first line of innate host defense by secretion of proteins with antimicrobial activity against microbial infection. Despite the extensive studies on the antimicrobial host defense in many gastrointestinal tracts, little is known about the antimicrobial defense system of the stomach. The potent antimicrobial peptide buforin I, consisting of 39 aa, was isolated recently from the stomach tissue of an Asian toad, Bufo bufo gargarizans. In this study we examined the mechanism of buforin I production in toad stomach tissue. Buforin I is produced by the action of pepsin isozymes, named pepsin Ca and Cb, cleaving the Tyr39-Ala40 bond of histone H2A. Immunohistochemical analysis revealed that buforin I is present extracellularly on the mucosal surface, and unacetylated histone H2A, a precursor of buforin I, is localized in the cytoplasm of gastric gland cells. Furthermore, Western blot analysis showed that buforin I is also present in the gastric fluids, and immunoelectron microscopy detected localization of the unacetylated histone H2A in the cytoplasmic granules of gastric gland cells. The distinct subcellular distribution of the unacetylated histone H2A and the detection of the unacetylated buforin I both on the mucosal surface and in the lumen suggest that buforin I is produced from the cytoplasmic unacetylated histone H2A secreted into the gastric lumen and subsequently processed by pepsins. Our results indicate that buforin I along with pepsins in the vertebrate stomach may contribute to the innate host defense of the stomach against invading microorganisms.
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Affiliation(s)
- H S Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon, Korea
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48
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Park CJ, Park CB, Hong SS, Lee HS, Lee SY, Kim SC. Characterization and cDNA cloning of two glycine- and histidine-rich antimicrobial peptides from the roots of shepherd's purse, Capsella bursa-pastoris. Plant Mol Biol 2000; 44:187-97. [PMID: 11117262 DOI: 10.1023/a:1006431320677] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Two novel antimicrobial peptides were isolated and characterized from the roots of shepherd's purse, Capsella bursa-pastoris. These antimicrobial peptides, named shepherin I and shepherin II, consist of 28 and 38 amino acids, respectively, and are glycine- and histidine-rich peptides. Shepherin I and shepherin II have 67.9% and 65.8% (mol/mol) glycine, respectively, and 28.6% and 21.1% (mol/mol) histidine, respectively. Both shepherins have a Gly-Gly-His motif. These antimicrobial peptides exhibit antimicrobial activity against Gram-negative bacteria and fungi. Circular dichroism spectra of shepherin I and shepherin II showed that shepherin I and shepherin II in 50% trifluoroethanol have 66.7% and 75% random coils, respectively, without any alpha-helices. cDNA sequence analysis revealed that shepherin I and shepherin II are produced from a single polypeptide, designated shep-GRP, consisting of 120 amino acids; shep-GRP has five distinct domains, an amino-terminal putative signal peptide, a shepherin I, a linker dipeptide, a shepherin II and a carboxy-terminal peptide. Southern blot analysis indicates that the gene encoding shepherins belongs to a low-complexity gene family. Northern blot analysis revealed that transcripts of shep-GRP are present in roots but not in leaves and stems.
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MESH Headings
- Amino Acid Sequence
- Anti-Bacterial Agents/chemistry
- Anti-Bacterial Agents/isolation & purification
- Anti-Bacterial Agents/pharmacology
- Bacteria/drug effects
- Bacteria/growth & development
- Base Sequence
- Blotting, Northern
- Blotting, Southern
- Brassicaceae/genetics
- Cell Division/drug effects
- Circular Dichroism
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Plant/genetics
- Fungi/drug effects
- Fungi/growth & development
- Gene Expression Regulation, Plant
- Glycine/genetics
- Histidine/genetics
- Microbial Sensitivity Tests
- Molecular Sequence Data
- Peptides
- Plant Proteins/genetics
- Plant Proteins/pharmacology
- Plant Roots/genetics
- Protein Isoforms/genetics
- Protein Isoforms/pharmacology
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Analysis, Protein
- Sequence Homology, Amino Acid
- Tissue Distribution
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Affiliation(s)
- C J Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong-gu, Taejon
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Kobayashi S, Takeshima K, Park CB, Kim SC, Matsuzaki K. Interactions of the novel antimicrobial peptide buforin 2 with lipid bilayers: proline as a translocation promoting factor. Biochemistry 2000; 39:8648-54. [PMID: 10913273 DOI: 10.1021/bi0004549] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Buforin 2 is an antimicrobial peptide discovered in the stomach tissue of the Asian toad Bufo bufo gargarizans. The 21-residue peptide with +6 net charge shows antimicrobial activity an order of magnitude higher than that of magainin 2, a membrane-permeabilizing antimicrobial peptide from Xenopus laevis [Park, C. B., Kim, M. S., and Kim, S. C. (1996) Biochem. Biophys. Res. Commun. 218, 408-413]. In this study, we investigated the interactions of buforin 2 with phospholipid bilayers in comparison with magainin 2 to obtain insight into the mechanism of action of buforin 2. Equipotent Trp-substituted peptides were used to fluorometrically monitor peptide-lipid interactions. Circular dichroism measurements showed that buforin 2 selectively bound to liposomes composed of acidic phospholipids, assuming a secondary structure similar to that in trifluoroethanol/water, which is an amphipathic helix distorted around Pro(11) with a flexible N-terminal region [Yi, G. S., Park, C. B., Kim, S. C., and Cheong, C. (1996) FEBS Lett. 398, 87-90]. Magainin 2 induced the leakage of a fluorescent dye entrapped within lipid vesicles coupled to lipid flip-flop. These results have been interpreted as the formation of a peptide-lipid supramolecular complex pore [Matsuzaki, K. (1998) Biochim. Biophys. Acta 1376, 391-400]. Buforin 2 exhibited much weaker membrane permeabilization activity despite its higher antimicrobial activity. In contrast, buforin 2 was more efficiently translocated across lipid bilayers than magainin 2. These results suggested that the ultimate target of buforin 2 is not the membrane but intracellular components. Furthermore, buforin 2 induced no lipid flip-flop, indicating that the mechanism of translocation of buforin 2 is different from that of magainin 2. The role of Pro was investigated by use of a P11A derivative of buforin 2. The derivation caused a change to magainin 2-like secondary structure and membrane behavior. Pro(11) was found to be a very important structural factor for the unique properties of buforin 2.
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Affiliation(s)
- S Kobayashi
- Graduate Schools of Pharmaceutical Sciences and Biostudies, Kyoto University, Japan
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50
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Park CB, Yi KS, Matsuzaki K, Kim MS, Kim SC. Structure-activity analysis of buforin II, a histone H2A-derived antimicrobial peptide: the proline hinge is responsible for the cell-penetrating ability of buforin II. Proc Natl Acad Sci U S A 2000; 97:8245-50. [PMID: 10890923 PMCID: PMC26932 DOI: 10.1073/pnas.150518097] [Citation(s) in RCA: 389] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Buforin II is a 21-aa potent antimicrobial peptide that forms, in a hydrophobic medium, an amphipathic structure consisting of an N-terminal random coil region (residues 1-4), an extended helical region (residues 5-10), a hinge (residue 11), and a C-terminal regular alpha-helical region (residues 12-21). To elucidate the structural features of buforin II that are required for its potent antimicrobial activity, we synthesized a series of N- and C-terminally truncated or amino acid-substituted synthetic buforin II analogs and examined their antimicrobial activity and mechanism of action. Deletion of the N-terminal random coil region increased the antibacterial activity approximately 2-fold, but further N-terminal truncation yielded peptide analogs with progressively decreasing activity. Removal of four amino acids from the C-terminal end of buforin II resulted in a complete loss of antimicrobial activity. The substitution of leucine for the proline hinge decreased significantly the antimicrobial activity. Confocal fluorescence microscopic studies showed that buforin II analogs with a proline hinge penetrated the cell membrane without permeabilization and accumulated in the cytoplasm. However, removal of the proline hinge abrogated the ability of the peptide to enter cells, and buforin II analogs without a proline hinge localized on the cell surface, permeabilizing the cell membrane. In addition, the cell-penetrating efficiency of buforin II and its truncated analogs, which depended on the alpha-helical content of the peptides, correlated linearly with their antimicrobial potency. Our results demonstrate clearly that the proline hinge is responsible for the cell-penetrating ability of buforin II, and the cell-penetrating efficiency determines the antimicrobial potency of the peptide.
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Affiliation(s)
- C B Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Yusong-gu, Kusong-dong, Taejon 305-701, Korea
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