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  • 1
    Electronic Resource
    Electronic Resource
    Fabrication Conditions, Microstructures and Mechanical Properties of P/M Processed 2XXX Al-SiCW Composites (1998)
    Springer
    Advanced performance materials 5 (1998), S. 307-318 
    Details
    ISSN: 1572-8765
    Keywords: powder metallurgy ; Al-SiCW composite ; vacuum hot pressing ; extrusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The powder metallurgy fabrication of 2XXX Al composites reinforced with SiC whiskers was studied by investigating the evolution of microstructure and its relation to the mechanical properties. In this study, SiC whiskers and gas-atomized aluminum powders were mixed by fluid zone mixer, consolidated by vacuum hot press, and then extruded. The optimum condition for consolidation was 620°C and 50 MPa, at which fully densified pore-free billets were obtained. The composites with relatively homogeneous microstructures were produced by extrusion at 450–500°C under the extrusion pressure of 700–1000 MPa. The mechanical properties of the extruded bars were found to be comparable with those of the composites processed by Advanced Composite Materials Corp. The optimum fabrication conditions have been proposed for producing composites of improved mechanical properties through elimination of coarse intermetallic particles, uniform distribution of reinforcements, and minimization of whisker breakage. The possibility of using particulates rather than whiskers, and the modification of the alloy matrices for high temperature applications are also discussed in relation to the distribution of reinforcements and the optimization of the consolidation temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008609216359
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  • 2
    Electronic Resource
    Electronic Resource
    Role of actin microfilament in osmotic stretch-induced increase of voltage-operated calcium channel current in guinea-pig gastric myocytes (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 502-504 
    Details
    ISSN: 1432-2013
    Keywords: Key words Gastric smooth muscle ; Calcium current ; Actin microfilament ; Osmotic stretch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Using the whole-cell patch clamp technique, the role of actin microfilament in hyposmotic increase of voltage-operated calcium channel current (I Ba) was studied in guinea-pig gastric myocytes. Hyposmotic superfusate (212 mOsm) increased peak I Ba amplitude by 32.7 ± 6.5%; when cytochalasin-D (Cyt-D, 20 μM), an actin cytoskeleton disruptor, was used, an increase of only 9.7 ± 3.1% was seen. I Baresponse to osmotic stress was potentiated (45.1 ± 4.1% increase) by 20 μM phalloidin, an actin microfilament stabilizer. However, colchicine (100 μM), an microtubule cytoskeleton disruptor, had no effect on either I Ba or its response to hyposmotic solution. Phalloidin also induced a rightward shift of the I/V relationship of I Ba, while Cyt-D itself had no effect. These results suggest that actin cytoskeleton may mediate hyposmotic stretch-induced I Ba increase in gastric smooth muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050428
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of stretch on calcium channel currents recorded from the antral circular myocytes of guinea-pig stomach (1996)
    Springer
    Pflügers Archiv 432 (1996), S. 159-164 
    Details
    ISSN: 1432-2013
    Keywords: Key words Ca channel current ; Gastric myocytes ; Stretch ; Membrane capacitance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of membrane stretch on voltage-activated Ba2+ current (I Ba) was studied in antral circular myocytes of guinea-pig using the whole- cell patch-clamp technique. The changes in cell volume were elicited by superfusing the myocytes with anisosmotic solutions. Hyposmotic superfusate (202 mosmol/l) induced cell swelling and increased peak values of I Ba at 0 mV (from −406.6 ± 45.5 pA to −547.5 ± 65.6 pA, mean ± SEM, n = 8) and hyperosmotic superfusate (350 mosmol/l) induced cell shrinkage and decreased peak values of I Ba at 0 mV (to −269.5 ± 39.1 pA, n = 8). Such changes were reversible and the extent of change was dependent on the osmolarity of superfusate. The values of normalized I Ba at 0 mV were 1.43 ± 0.04, 1.30 ± 0.06, 1.23 ± 0.04, 1.19 ± 0.04, 1 and 0.68 ± 0.06 at 202, 220, 245, 267, 290 and 350 mosmol/l, respectively (n = 8). I Ba was almost completely blocked by nicardipine (5 μM) under hyposmotic conditions. The values of steady-state half-inactivation voltage (−37.7 ± 3.3 and −36.5 ± 2.6 mV, under control and hyposmotic conditions, respectively) or the half-activation voltage (−13.6 ± 2.3 and −13.9 ± 1.9 mV) of I Ba were not significantly changed (P 〉 0.05, n = 6). Cell membrane capacitance was slightly increased from 50.00 ± 2.86 pF to 50.22 ± 2.82 pF by a hyposmotic superfusate (P 〈 0.05, n = 6). It is suggested that cell swelling increases voltage-operated L-type calcium channel current and that such a property is related to the response of gastric smooth muscle to mechanical stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050119
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  • 4
    Electronic Resource
    Electronic Resource
    Inhibitory effect of phorbol 12, 13 dibutyrate on carbachol-activated nonselective cationic current in guinea-pig gastric myocytes (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 505-507 
    Details
    ISSN: 1432-2013
    Keywords: Key words Carbachol ; Nonselective cationic current ; Protein kinase C ; smooth muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effect of protein kinase C (PKC) on carbachol (CCh)-activated nonselective cationic current (I CCh) was investigated in guinea-pig gastric myocytes using a PKC activator, phorbol 12, 13 dibutyrate (PDBu). Pretreatment with 1 μ M PDBu suppressed I CCh by 96.5 ± 2.9% (n = 14) in a reversible manner in nystatin-perforated mode. In the presence of 1 μM chelerythrine , a PKC inhibitor, inhibition of I CChby PDBu was not seen. In whole-cell mode, the inhibition of I CCh by PDBu was dependent on intracellular MgATP. In the presence of MgATP in the pipette, PDBu decreased I CCh by 98.8 ± 1.2% (n = 5) as was observed in nystatin-perforated mode. However, PDBu had little effect on I CCh in the absence of MgATP in the pipette; the extent of inhibition was 12.7 ± 4.3% (n = 8). PDBu also suppressed the generation of cationic current induced by intracellularly perfused GTP[γS]. In the PDBu-pretreated group (n = 9) and PDBu-untreated control group (n = 6), GTP[γS]-induced currents were 6.7 ± 2.4 pA and 236 ± 23 pA, respectively. These results suggest that PKC modulates I CCh at postreceptor sites via protein phosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050429
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  • 5
    Electronic Resource
    Electronic Resource
    Volume-sensitive chloride current activated by hyposmotic swelling in antral gastric myocytes of the guinea-pig (1997)
    Springer
    Pflügers Archiv 435 (1997), S. 9-19 
    Details
    ISSN: 1432-2013
    Keywords: Key words Smooth muscle ; Cell volume ; Chloride current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The characteristics of volume-sensitive chloride current (I Cl) induced by osmotic cell swelling were studied using the whole-cell patch-clamp technique and cell diameters of antral circular guinea-pig myocytes were simultaneously measured under isosmotic and hyposmotic conditions by using a video image analysis system. At –60 mV, osmotic cell swelling (200 mosmol/l) activated a sustained inward current. Instantaneous current/voltage (I-V) relations obtained by step voltage pulses showed an outward rectification. At potentials above +40 mV, the current exhibited time-dependent decay. The outward current amplitude was decreased and the reversal potential was shifted to more positive potentials by replacement of external Cl– with gluconate–, while the current amplitude and the I/V relation were not affected by replacing extracellular Na+ with N-methyl-D-glucamine. The anion permeability sequence of the swelling-induced current was I– (1.80) 〉 Br– (1.31) 〉 Cl– (1) 〉 F– (0.85) 〉 gluconate– (0.18). The I Cl was effectively inhibited by the Cl– channel blockers, 4,4′-diisothiocyanatostilbene-2,2’-disulphonic acid (DIDS, 100 μM), and niflumic acid (10 μM). DIDS suppressed outward current more effectively than inward current. Also, the I Cl was dose-dependently inhibited by arachidonic acid, an unsaturated fatty acid and also inhibited by other unsaturated fatty acids (linoleic acid and oleic acid) but not by stearic acid, a saturated fatty acid. The inhibitory effect of arachidonic acid on I Cl was not prevented by indomethacin, a cyclo-oxygenase inhibitor and chelerythrine, a protein kinase C inhibitor. Under whole-cell patch-clamp conditions, the cell diameter was continuously measured using video image analysis, which reflects the change in cell volume. A hyposmotic-stimulation-induced increase of cell diameter was followed by I Cl activation. In intact single gastric myocytes, relatively severe hyposmotic (176 mosmol/l) superfusing solution increased the cell diameter and the pretreatment with DIDS or with niflumic acid significantly potentiated the above effect of hyposmotic superfusion. These results suggest that volume-sensitive outwardly rectifying chloride current (I Cl) is present in guinea-pig gastric myocyte and the I Cl may play a role in smooth muscle cell volume regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050478
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  • 6
    Electronic Resource
    Electronic Resource
    Role of calmodulin in the activation of carbachol-activated cationic current in guinea-pig gastric antral myocytes (1995)
    Springer
    Pflügers Archiv 430 (1995), S. 757-762 
    Details
    ISSN: 1432-2013
    Keywords: Gastrointestinal myocytes ; Nonselective cation channels ; Carbachol ; Calmodulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In mammalian gastrointestinal myocytes, it is known that muscarinic stimulation activates nonselective cation channels through a G-protein and a Ca2+dependent pathway. We recorded inward cationic currents following application of carbachol (I CCh) to guinea-pig gastric myocytes, which were held at −20 mV using the whole-cell patch-clamp method. I CCh was suppressed by nicardipine or removal of Ca2+ from the bath solution. The peak value of inward current induced by repetitive applications of carbachol (CCh) decreased progressively (run-down phenomenon). This run-down was significantly alleviated by the addition of calmodulin to the pipette solution (0.15 mg/ml) or by using the perforated-patch whole-cell voltage-clamp technique. Moreover, W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide], a calmodulin antagonist, was a reversible inhibitor of I CCh. However, W-7 had only a weak inhibitory effect on the same cationic current which was induced by guanosine 5′-O-(3-thiotriphosphate) (GTP[γS] 0.2 mM) in the pipette solution. This GTP[γS]-induced cationic current was still markedly suppressed by the Ca2+-free bath solution. W-7 itself had a weak inhibitory effect on voltage-operated Ca2+ channels as well as the effects on I CCh. These data suggest that multiple Ca2+-dependent pathways are involved in the activation of CCh-gated cation channels in guinea-pig antral myocytes and a Ca2+/calmodulin-dependent pathway would be one of them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386173
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of myosin light chain kinase inhibitors on carbachol-activated nonselective cationic current in guinea-pig gastric myocytes (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 346-353 
    Details
    ISSN: 1432-2013
    Keywords: Key words Smooth muscle ; Nonselective cationic current ; Carbachol ; Myosin light chain kinase ; ML-7
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effects of myosin light chain kinase inhibitors on muscarinic stimulation-activated nonselective cationic current (I CCh) in guinea-pig gastric antral myocytes were studied using the whole-cell patch-clamp technique. I CCh was induced by carbachol (CCh, 50 μM) at a holding potential of –30 mV or –60 mV. ML-7, a chemical inhibitor of myosin light chain kinase (MLCK), inhibited I CCh concentration dependently in a reversible manner (53 ± 8.6% at 1 μM, mean ± SE, n = 11). In addition, amplitudes of I CCh were only 37 ± 2.7% of the daily control values following the addition of a peptide inhibitor of MLCK to the pipette solution. On the other hand, ML-7 had an inhibitory effect on voltage-operated Ca2+ channel current. The peak value of Ba2+ current at 0 mV was reduced to 35 ± 7.4% (n = 9) by 3 μM of ML-7. As I CCh is known to have an intracellular Ca2+ dependence, we tried to exclude the possibility that ML-7 inhibited I CCh indirectly via suppression of Ca2+ current and the similar inhibitory effects of ML-7 on I CChwere confirmed under the following conditions: (1) clamp of membrane potential at –60 mV; (2) clamp of intracellular [Ca2+] to 1 μM by 10 mM BAPTA; (3) pre-inhibition of Ca2+ channel by verapamil. Different from the effects on I CCh, ML-7 barely inhibited the same cationic current induced by guanosine 5’-O-(3-thiotriphosphate) (GTP[γS], 0.2 mM) in the pipette solution. These results suggest that a Ca2+/calmodulin-MLCK-dependent pathway can modulate the activation of I CCh in guinea-pig gastric antral myocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050407
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  • 8
    Electronic Resource
    Electronic Resource
    Suppression of the carbachol-activated nonselective cationic current by antibody against alpha subunit of Go protein in guinea-pig gastric myocytes (1998)
    Springer
    Pflügers Archiv 436 (1998), S. 494-496 
    Details
    ISSN: 1432-2013
    Keywords: Key words Carbachol (CCh) ; G protein ; Nonselective cationic current ; Smooth muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study, we investigated which subtype of GTP-binding protein (G protein) is related to muscarinic activation of nonselective cation (NSC) channels in gastric smooth muscle. Inward cationic current was activated by the application of 50 µM carbachol (I CCh) at a holding potential of –60 mV with the same CsCl-rich solution in both pipette and bath. The same cationic current as I CCh was slowly activated by the dialysis of guanosine 5′-O-(3-thiotriphosphate) (GTP[γ-S]) through the pipette. Since it is known that pertussis toxin pretreatment can block I CCh, antibodies (Abs) against Gα,i (anti-Gα,i) or Gα,o (anti-Gα,o) were tested. Activation of I CCh was blocked by the addition of anti-Gα,o. However, anti-Gα,i Abs had no significant effect on I CCh.The expression of Gα,o in guinea-pig gastric smooth muscle was confirmed by Western immunoblot analysis. These results suggest that Go-type protein may mediate signals from the muscarinic receptor to NSC channel in guinea-pig gastric myocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050663
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  • 9
    Electronic Resource
    Electronic Resource
    Protein kinase C mediates the desensitization of CCh-activated nonselective cationic current in guinea-pig gastric myocytes (1998)
    Springer
    Pflügers Archiv 436 (1998), S. 1-8 
    Details
    ISSN: 1432-2013
    Keywords: Key words Smooth muscle ; Nonselective cationic current ; Carbachol (CCh) ; Protein kinase C (PKC) ; Desensitization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The possibility of the protein kinase C (PKC) pathway being a mechanism underlying the desensitization of carbachol- (CCh-)activated nonselective cationic current (I CCh) was investigated in a study of guinea-pig gastric myocytes. Using the conventional whole-cell patch-clamp technique with symmetrical CsCl-rich solution in pipette and bath, I CCh was induced by bath application of 50 µM CCh. With 0.5 mM EGTA [ethyleneglycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid] in the pipette solution (0.5 mM [EGTA]i), I CCh decayed spontaneously (desensitization of I CCh) to around 20% within 10 min. Desensitization of I CCh was significantly attenuated with 2 mM [EGTA]i. At a concentration of 20 µM OAG (1-oleoyl-2-acetyl-sn-glycerol), a PKC activator, inhibited I CCh at 0.5 mM [EGTA]i but far less at 2 mM [EGTA]i (18% and 81% of control, respectively). The same cationic current induced by intracellular guanosine-5′-O-(3-thiotriphosphate) (GTP[γ-S]) was not inhibited by OAG with 0.5 mM [EGTA]i. The pretreatment of gastric myocytes with PKC inhibitors, either 1 µM chelerythrine or 1 µM peptide inhibitor, attenuated the desensitization of I CCh. [Ca2+]i was also measured by single cell microfluorometry using fura-2. Under CCh stimulation with 2 mM [EGTA]i, [Ca2+]i did not increase above 100 nM while it increased to around 260 nM with 0.5 mM [EGTA]i. These results suggest that the desensitization of I CCh is partly due to the Ca2+-dependent PKC pathway in guinea-pig gastric myocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050597
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