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Volume 36 (2011)
- Issue 6 Pages 271-
- Issue 5 Pages 203-
- Issue 4 Pages 128-
- Issue 3 Pages 83-
- Issue 2 Pages 49-
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Volume 36, Issue 6
Displaying 1-9 of 9 articles from this issue
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Foreword
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Yoshinori Marunaka2011 Volume 36 Issue 6 Pages 271
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSDownload PDF (523K)
Special Topic : Features and Functions of the Epithelial Cell Membrane
Review Article
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Naomi Niisato, Yoshinori Marunaka2011 Volume 36 Issue 6 Pages 272-277
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSTo sense an environmental change such as osmotic stress is crucial for cells to survive and adjust to a new environment. In the epithelium of distal nephron, basolateral hypotonic stress is known to stimulate epithelial Na+ channel (ENaC)-mediated Na+ reabsorption for recovery of normal plasma osmolality without hormonal regulation. On the other hand, hypotonic stress causes drastic cell volume changes; initial cell swelling followed by regulatory volume decrease (RVD). Recently an increase in membrane tension by the initial cell swelling is considered to play an important role in conversion of extracellular physical stress to intracellular chemical signals. In this review, we focus our study on possible roles of plasma membrane itself and membrane proteins such as mechano-sensitive (MS) ion channels and growth factor receptors in sensing extracellular osmolality (hypotonic stress) and leading to regulation of Na+ reabsorption.View full abstractDownload PDF (744K) -
Shinji Asano2011 Volume 36 Issue 6 Pages 278-285
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSGastric acid secretion in parietal cells is performed by proton pump, H+, K+- ATPase, in combination with several related ion transporters located on the apical and basolateral membranes. In this review I will introduce several recent topics about molecular basis of gastric acid secretion in parietal cells. First, I wish to introduce 3D structures of H+, K+-ATPase resolved recently. The structures demonstrated the interaction between the α- and β- subunits fixes and favors the E2P conformation (the “rachet effect”). The binding site of a K+-competitive inhibitor SCH 28080 on the α- subunit of H+, K+-ATPase was also identified in the 3D structure. Secondly, I wish to introduce ion transporters on the apical membrane necessary for gastric acid secretion. Among others KCNQ1/KCNE2 was identified as a K+ channel involved in K+ recycling and replenishment of K+ in the lumen. Thirdly, I wish to introduce actin-binding proteins, ezrin and Huntingtin interacting protein 1 related (Hip1r), which are necessary for gastric acid secretion. Ezrin is involved in membrane fusion between tubulovesicles and apical membrane whereas Hip1r is involved in endocytosis and regeneration of tubulovesicles from apical membrane. Finally, the roles of parietal cells in differentiation of gastric epithelial cells as well as gastric acid secretion will be introduced.View full abstractDownload PDF (763K) -
Takashi Nakahari, Yukinori Sawabe, Chikao Shimamoto2011 Volume 36 Issue 6 Pages 286-292
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSThe mucosal surface of the gastric antrum was covered with mucous layers, which protect the mucosa from acidpeptic injuries. The mucous layers are maintained by the Ca2+- regulated exocytosis from antral mucous cells. The Ca2+- regulated exocytosis in antral mucous cells, which is stimulated by an increase in intracellular Ca2+ concentration ([Ca2+]i), has a characteristic feature in the secretion pattern, that is, an initial transient phase (high frequency) followed by a sustained phase (low frequency). The final process of Ca2+- regulated exocytosis consists of three steps, docking, ATP-dependent priming and Ca2+- dependent fusion. Cyclic AMP (cAMP) increases the sensitivity to Ca2+ in the fusion step. Moreover, cAMP, cyclic GMP (cGMP) and a decrease in intracellular Cl- concentration accelerate the priming step and increase the number of primed granules. This enhances the frequency of initial phase. In antral mucous cells, ACh released from vagal nerve endings induces an increase in [Ca2+]i which stimulates arachidonic acid (AA) accumulation leading to prostaglandin E2 (PGE2) production. AA directly stimulates the peroxisome proliferation activation receptor α(PPAR α), which enhances the Ca2+. regulated exocytosis. PGE2, which is immediately released from cells, stimulates EP4 receptors resulting in the enhancement of Ca2+- regulated exocytosis via cAMP accumulation in antral mucous cells. Thus, two autocrine mechanisms via PPAR α and EP4 activated by AA modulate Ca2+- regulated exocytosis in ACh-stimulated antral mucous cells and maintain massive mucous secretion in the gastric antrum.View full abstractDownload PDF (882K) -
Hisayoshi Hayashi, Yuichi Suzuki2011 Volume 36 Issue 6 Pages 293-299
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSChloride ions play many physiological roles, including regulation of cell volume, fluid secretion and acid.base balance. An efficient absorption of Cl- in the intestine is important to maintain the optimal levels of Cl- in the body. Three chloride absorptive pathways have been proposed : 1) a paracellular pathway, which is dependent on potential difference; 2) an electroneutral pathway involving parallel functioning of Na+/H+ exchange and Cl-/HCO3- exchange; 3) an HCO3- dependent Cl- absorptive pathway, which is not coupled to a parallel Na+/H+ exchange. Among these chloride absorptive mechanisms, the second electroneutral NaCl absorption is thought to be a predominant pathway. At least six Cl-/HCO3- exchangers (SLC4A1, SLC4A2, SLC4A3, SLC26A2, SLC26A3, SLC26A6) have been found in intestinal epithelial cells. However, the role of each exchanger and regulatory mechanisms in the intestine have not been well studied. This review in particular focuses on the role and regulation of SLC26A3 in the gastrointestinal tract.View full abstractDownload PDF (737K) -
Akiyuki Taruno, Naomi Niisato, Yoshinori Marunaka2011 Volume 36 Issue 6 Pages 300-307
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSThe epithelial sodium channel (ENaC) forms a pathway for transpepithelial Na+ transport in a variety of epithelial tissues including the kidney collecting duct, airway epithelium, and distal colon. In the kidney, ENaC plays a crucial role in body Na+ content and blood pressure control; abnormalities in ENaC function lead to several diseases such as Liddle’s syndrome and pseudohypoaldosteronism. Recent studies have revealed that ENaC function in epithelia is mainly regulated through membrane trafficking controlling the number of channels at the surface of the apical membrane. Apical membrane expression of ENaC is regulated through multiple steps, including synthesis, exocytosis, endocytosis, recycling, and degradation. Hormones such as aldosterone and vasopressin increase ENaC delivery to the apical surface by regulating those steps. This review discusses current understanding of molecular mechanisms of ENaC trafficking and introduces a newly-observed phenomenon that suggests the existence of undiscovered regulatory mechanisms of membrane trafficking: dependence of recycling rate constants on total ENaC amounts in recycle.View full abstractDownload PDF (733K)
Special Topic : Membrane Award for Young Scientists (2011)
Review Article
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Takashi Okuno2011 Volume 36 Issue 6 Pages 308-314
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSActivity and interaction of membrane proteins, which regulates bacterial cell division, was analyzed by using various types of the spectrophotometric technique. FtsZ, which is an essential participant in prokaryotic cell division, forms a filamentous ring structure that involves GTP-dependent polymerization at the mid cell before division in Escherichia coli ( E. coli ). In E. coli, the site of cell division is known to be regulated in part by the three types of Min proteins: MinC, MinD, and MinE, which prevent the dividing site from forming at the cell pole. FtsZ and Min proteins system is essential for normal cell growth. Information about regulation mechanism of FtsZ polymerization and Min protein system should be useful for development of a new class of antibacterial drug. We have revealed Min protein system by using fluorescent polarization and FRET analysis.View full abstractDownload PDF (886K)
Special Topic : ICOM 2011
Report
Original Contribution
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Rika Homma, Seigo Sato, Sosaku Ichikawa2011 Volume 36 Issue 6 Pages 326-331
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL RESTRICTED ACCESSMolecular aggregation of aqueous carboxybetaines with bulky hydrophobic alkyl chains was examined. Monoalkyl carboxybetaine with a phytol.like structure in the alkyl chain, namely, 3, 7, 11, 15.Tetramethylhexadecyl carboxybetaine (TetraMeC16BE), formed vesicles, as indicated by freeze.fracture electron microscopy. The vesicles would be formed because of the truncated cone structure of the TetraMeC16BE which has four methyl groups in the alkyl chain and zwitterionic hydrophilic head-group. In contrast, didodecyl carboxybetaine (2C12BE), which has two alkyl chains, adopted a lamellar liquid crystalline structure, as indicated by X.ray diffraction analysis. However, when 2C12BE was mixed with dodecyl carboxybetaine, which has a single alkyl chain, vesicles formed; that is, mixing a carboxybetaine bearing bulky alkyl chains with one bearing a single alkyl chain permitted the formation of a closed.shell vesicular membrane with spherical curvature.View full abstractDownload PDF (610K)
Products Spotlight
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Yuya Sato2011 Volume 36 Issue 6 Pages 332-334
Published: 2011
Released on J-STAGE: May 18, 2012
JOURNAL OPEN ACCESSRecently, the wastewater reclamation system has been popular in the electronic industry field, not only for inorganic wastewater but also for organic wastewater that is difficult to reclaim. We tried the reclamation test for the electronic industry organic wastewater using MBR and RO system.
In this test, the quality of the final treated water (RO permeate) is less than 100 μS/cm for electronic conductivity and about 0.5 mg/L for TOC. We could obtain the enough water quality for the makeup water of a cooling tower. Moreover, MBR and RO have been operated very stably in this test period.View full abstractDownload PDF (734K)
Editor’s note
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