Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line

The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 G ohms, and 50 pF, respectively. Under the voltage-clamp condition, no voltage-dependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time- and voltage-independent K+ current. The ACh-induced hyperpolarization and K+ current persisted, while the His response desensitized quickly (< 1 min). These effects of ACh and His were mediated predominantly by m3-muscarinic and H1-His receptors, respectively. The K+ current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca(2+)-activated K+ channel current (IK.Ca). The measurement of intracellular Ca2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca. When EGTA in the pipette solution was increased from 0.15 to 10 mM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate IK.Ca by increasing [Ca2+]i in JR-1 cells. In the Ca(2+)-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca2+ (1.8 mM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca2+ release-related initial transient activation and the Ca2+ influx-related sustained activation of IK.Ca. Probably because of desensitization, the Ca2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without inositol 1,3,4,5-tetrakisphosphate (IP4), mimicked the ACh response. IP4 alone did not affect the membrane current. Under the steady effect of IP3 or IP3 plus IP4, neither ACh nor His further evoked IK.Ca. Intracellular application of heparin or of the monoclonal antibody against the IP3 receptor, mAb18A10, inhibited the ACh and His responses in a concentration-dependent fashion. Neomycin, a phospholipase C (PLC) inhibitor, also inhibited the agonist-induced response in a concentration-dependent fashion. Although neither pertussis toxin (PTX) nor N-ethylmaleimide affected the ACh or His activation of IK,Ca, GDP beta S attenuated and GTP gamma S enhanced the agonist response.(ABSTRACT TRUNCATED AT 400 WORDS)     

The effects of nucleotides and potassium channel openers on the SUR2A/Kir6.2 complex K+ channel expressed in a mammalian cell line, HEK293T cells

The aim of this study was to evaluate whether long-term administration of L-arginine, a physiological substrate for the production of nitric oxide, improved blood pressure, heart rate, cardiac hypertrophy and particularly structural changes in the coronary and carotid artery of spontaneously hypertensive rats (SHR). The experiments started with three groups of 10-week-old animals: control Wistar rats, untreated SHR and SHR treated with L-arginine (SHR + L-arginine). L-Arginine was administered to SHR in a daily dose of 300 mg kg-1 intraperitoneally for 6 weeks. Blood pressure and heart rate were recorded each week. At the end of the experiment in one-half of each group heart weight and body weight were determined and the heart weight/body weight index was calculated. In the other animals, the cardiovascular system was perfused via the left ventricle with a glutaraldehyde fixative at 120 mmHg and the coronary and carotid arteries were processed for transmission electron microscopy. The inner diameter and wall thickness (tunica intima and tunica media) were measured on semithin sections. The reliability of the genetic feature in the SHR group was proved by the increased heart weight, heart weight/body weight index, wall thickness and wall thickness/inner diameter ratio of coronary and carotid arteries in comparison to the group of control Wistar rats. Long-term administration of L-arginine did not significantly influence blood pressure and heart rate in comparison with untreated SHR. Neither were any differences found in cardiac hypertrophy or the geometry of the coronary and carotid arteries (thickness of arterial wall, inner diameter, wall/diameter ratio). In conclusion, the changes in the cardiovascular system in SHR were not reversed, or even alleviated, by chronic treatment with L-arginine.     

Micro-fabrication techniques applied to aluminosilicate glass surfaces: Micro-indentation and wet etching process

Micro-indentation and HF etching were explored as micro-fabrication techniques applied to glass surfaces. The effects of the aluminosilicate glass composition and of the etching conditions on the etching rate were investigated. It was found that the etching rate increased with increasing the ratio of Al₂O₃ to SiO₂ in the aluminosilicate glass. Etching parameters, such as pH, concentration and temperature of HF acid, had effects on etching rate. However, the effects of these parameters were much smaller at indented area than at non-indented area. The results indicated that the etching rate difference between the two areas, which is one of the key factors in the micro-fabrication technique, could be controlled with these parameters. And the phenomena can be well explained in terms of etching and leaching mechanism of aluminosilicate glass.     

Combination gene delivery of the cell cycle inhibitor p27 with thymidine kinase enhances prodrug cytotoxicity

Cytoxicity induced by the herpesvirus thymidine kinase (TK) gene in combination with prodrugs is dependent on cell growth and leads to the elimination of genetically modified cells, thus limiting the duration of expression and efficacy of this treatment in vivo. Here, an effort was made to enhance TK/prodrug efficacy by coexpression of a cyclin-dependent kinase inhibitor (CKI), p27, to render cells resistant to TK/prodrug by inhibiting DNA synthesis. Expression of p27 by transfection substantially reduced cell cycle progression, and its activity was enhanced by mutations designed to stabilize the protein. Coexpression of p27 and TK or a p27/TK fusion protein led to greater prodrug cytotoxicity than that produced by TK alone in the Renca cell line, which is sensitive to bystander killing. Combination gene transfer of this CKI with TK therefore sustained the synthesis of TK by genetically modified cells to enhance the susceptibility of bystander cells to prodrug cytotoxicity and increased the efficacy of this gene transfer approach.     

Kinetic studies on β-SiC formation from homogeneous precursors

The kinetics of the carbothermic reduction of SiO₂ by carbon to produce -SiC from a homogeneous organic precursor has been investigated over the temperature range 1500 to 1800 °C in nitrogen by the use of a high-temperature thermobalance. The kinetic behaviour differed significantly from that of the heterogeneous reaction of SiO₂ and carbon particles. The weight-loss curves could be fitted well by the Avrami-Erofe'ev equation with an exponent of 1.5. The result was interpreted as showing instantaneous nucleation in a homogeneous matrix followed by the diffusion-controlled growth of -SiC. The obtained activation energy of 391 kJ mol^–1 was consistent with the assumption that the reaction is controlled by the diffusion of carbon through the amorphous matrix to the growing surface of -SiC.     

Preparation and applications of novel fluoroalkyl end‐capped sulfonic acid oligomers–silica gel polymer hybrids

Fluoroalkyl end‐capped 2‐methacryloxyethanesulfonic acid homo‐oligomer [R_F–(MES)_n–R_F] and 2‐methacryloxyethanesulfonic acid–N,N‐dimethylacrylamide co‐oligomers [R_F–(MES)_x–(DMAA)_y–R_F] reacted with tetraethoxysilane (TEOS) under acidic conditions to afford R_F–(MES)_n–R_F homo‐oligomer–SiO₂ polymer hybrid and R_F–(MES)_x–(DMAA)_y–R_F co‐oligomer–SiO₂ polymer hybrid, respectively. Thermogravimetric–mass spectra showed that the thermal stability of R_F–(MES)_n–R_F homo‐oligomer–SiO₂ polymer hybrid was superior to that of traditionally well‐known perfluorinated ion exchange polymers such as Nafion 112 (TR). The sol solutions of the fluorinated co‐oligomer–SiO₂ polymer hybrid were applied to the surface modification of glass to exhibit not only a strong oleophobicity imparted by fluorine but also a good hydrophilicity on the glass surface. On the other hand, R_F–(MES)_x–(DMAA)_y–R_F co‐oligomer reacted with TEOS in the presence of a variety of silica nanoparticles (mean diameters: 11–95 nm) under alkaline conditions to afford fluoroalkyl end‐capped oligomers–silica nanoparticles (mean diameters: 32–173 nm) with a good dispersibility and stability in methanol. Similarly, a variety of fluorinated oligomers containing sulfo groups–silica nanoparticles were prepared by the homo‐ and co‐oligomerizations of fluoroalkanoyl peroxides with 2‐methacryloxyethane sulfonic acid (MES) and comonomers such as N,N‐dimethylacrylamide (DMAA) and acryloylmorpholine (ACMO) in the presence of silica nanoparticles. Interestingly, these isolated fluorinated particle powders were found to afford nanometer size‐controlled colloidal particles with a good redispersibility and stability in aqueous and organic media such as methanol. These fluorinated nanoparticles containing sulfo groups were also applied to an excellent heterogeneous catalyst for Bronsted acid‐catalyzed transformations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 110–117, 2007     

电沉积Co-Ni-Al2O3复合镀层微观结构及高温性能

在氨基磺酸盐电解液中,利用复合电沉积技术制备得到了Co-Ni合金基中弥散分布Al₂O₃颗粒的金属基复合镀层。通过SEM,AFM以及XRD等分析测试方法,研究了Co-Ni-Al₂O₃复合镀层的表面形貌和微观晶体结构。结果发现:Co-Ni-Al₂O₃的表面形貌和微观晶体结构主要受镀层中钴含量的影响。高钴含量复合镀层具有Hcp结构,其表面形貌比具有Fcc结构的低钴含量镀层的表面更加均匀细致。Al₂O₃颗粒在Co-Ni合金中的共沉积,没有改变合金固溶体的相组成,但却改变了各晶面的优势生长。通过研究复合镀层的硬度、高温耐磨性、高温抗氧化性、热膨胀系数和热导率表明:Co-Ni-Al₂O₃具有较好的高温耐磨性和高温抗氧化能力,并且高钴含量的复合镀层相对于低钴镀层具有较低的热膨胀系数和较高的热导率。      

High‐luminance 1.8‐mm‐pixel‐pitch CNT‐FED for ubiquitous color character displays

Abstract— A high‐luminance 1.8‐mm‐pixel‐pitch CNT‐FED for color character displays has been developed. The display panel has 32 × 256 color pixels, and the subpixel size is 0.6 × 1.8 mm. The display panel can provide good visibility when installed even in outdoor locations. The power consumption is low enough for the display to be battery driven. The practical application is the display of important messages regarding the evacuation from disaster areas, even under emergent no‐power conditions similar to the messages on vending machines.     

Synthesis and properties of poly(organophosphazenes) electrolyte [NP(NHC6H5)2−x(NHC6H4SO3H-p)x]n

Poly(anilino sulphanic)phosphazene [NP(NHC₆H₅)_2–x (NHC₆H₄SO₃H) _x ] _n was prepared by the reaction between poly(anilino)phosphazene [NP(NHC₆H₅)₂] _n and sulphonic chloride (HSO₃Cl) in tetrachloroethane solvent. It was found that the glass transition temperature and conductivity of poly(anilino sulphanic)phosphazene increased with increasing value ofx. In addition, the storage power of the polymer withx=0.74 was determined and they were possible to charge by repitation of the use.