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  • 1990-1994  (5)
  • 1960-1964
  • glycolysis  (2)
  • ion channels  (2)
  • Analytical Chemistry and Spectroscopy  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Phosphorylation modulates the voltage dependence of channels reconstituted from the major intrinsic protein of lens fiber membranes (1992)
    Springer
    The journal of membrane biology 126 (1992), S. 75-88 
    Details
    ISSN: 1432-1424
    Keywords: ion channels ; phosphorylation ; modulation of ion channels ; lens fibers ; reconstitution ; intercellular junctions ; major intrinsic protein ; gap junctions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Major intrinsic polypeptide (MIP), a 28-kDa protein isolated from lens fiber cell membranes, forms large, nonselective channels when reconstituted into lipid bilayers. MIP channels are regulated by voltage, such that these channels close when the potential across the membrane is greater than 30 mV. We have investigated the modulation of the voltage-dependent closure of MIP channels by phosphorylation. In this report, we describe the isolation of two isomers of MIP from lens fiber cell membranes. These isomers differ by a single phosphate at a protein kinase A phosphorylation site. The phosphorylated isomer produces channels that close in response to applied voltages when reconstituted into bilayers. The nonphosphorylated isomer produces voltage-independent hannels. Direct phosphorylation with protein kinase A converts voltage-independent channels to voltage-dependent channels in situ. Analyses of macroscopic and single channel currents suggest that phosphorylation increases the voltage-dependent closure of MIP channels by increasing closed channel lifetimes and the rate of channel closure following the application of voltage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233462
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  • 2
    Electronic Resource
    Electronic Resource
    Single-membrane and cell-to-cell permeability properties of dissociated embryonic chick lens cells (1992)
    Springer
    The journal of membrane biology 128 (1992), S. 91-102 
    Details
    ISSN: 1432-1424
    Keywords: lens ; embryonic ; gap junctions ; ion channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Ion channels are believed to play an important role in the maintenance of lens transparency. In order to ascribe junctional and nonjunctional permeability properties to specific lens cell types, embryonic chick lenses were enzymatically dissociated into cell clusters, cell pairs and single cells, and both cell-to-cell and single-membrane permeability properties were characterized with the patch-clamp technique. Double patch-clamp experiments and single patch-clamp experiments with Lucifer yellow in the pipette demonstrated that the cells in the dissociated preparation were well coupled, the average conductance between pairs being 42 ± 27 nS. Double patch-clamp experiments also revealed single cell-to-cell channel events with a predominant unitary conductance of 286 ± 38 pS. Whole-cell measurements of surface membrane conductance indicate heterogeneity within the population of dissociated embryonic chick lens cells: 63% of the cells have a voltage-independent leak current, 14% of the cells have a potassium-selective inward rectifier current, and 23% of the cells have a current which turns off with positive voltage on a time scale on the order of seconds. The time constant for this turnoff is voltage dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231882
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Alanine, glutamate, and ammonia exchanges in acutely ischemic swine myocardium (1992)
    Springer
    Basic research in cardiology 87 (1992), S. 184-192 
    Details
    ISSN: 1435-1803
    Keywords: Anoxia ; glycolysis ; heart ; ischemia ; myocardialmetabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Coronary artery disease causes an increase in glutamate uptake and alanine output by the heart. We assessed the effects of acute myocardial ischemia on alanine and glutamate exchange and ammonia production in 10 anesthetized open-chest domestic swine (46.9±0.7 kg). Coronary blood flow was controlled through an extracorporal perfusion circuit. After a nonischemic control period (aerobic) the blood flow in the left anterior descending coronary artery was reduced by 60%. Arterial and anterior interventricular venous samples where drawn before and during 35 min of ischemia. Subendocardial blood flow, measured using radiolabeled microspheres, decreased from 1.27±0.16 to 0.25±0.09 (ml/g)/min, and left-ventricular wall-thickening fell to 47% of aerobic values. Ischemia resulted in a significant increase in the rate of glucose uptake (p〈0.05) and a switch to net lactate production (p〈0.01). Ischemia did not affect the rates of alanine output (−0.9±1.0 vs. −0.3±0.3 μmol/min) or glutamate uptake (−0.4±1.1 vs. 0.3±0.6 μmol/min), but did increase the venous-arterial difference for ammonia (−4.1±4.1 to 52.7±5.5 μM, p〈0.0001) and the ammonia output (−0.33±0.24 to 1.34±0.14 μmol/min, p〈0.0001). In conclusion, acute ischemia did not stimulate greater alanine output or glutamate uptake. However, acute ischemia did cause an increase in anaerobic glycolysis rate and ammonia output, which reflects a profound disruption in myocardial energy metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00801965
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  • 4
    Electronic Resource
    Electronic Resource
    Decreased interstitial glucose and transmural gradient in lactate during ischemia (1994)
    Springer
    Basic research in cardiology 89 (1994), S. 468-486 
    Details
    ISSN: 1435-1803
    Keywords: Cardiac ; glycolysis ; heart ; myocardial ; metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this investigation was to assess the effects of ischemia and reperfusion on the transmural levels of glucose and lactate in the interstitium in 11 open-chest swine. Microdialysis probes were used to estimate changes in interstitial metabolities across the ventricular wall. Probes were placed in the subepicardium and the subendocardium of the left anterior descending (LAD) coronary artery perfusion bed and in the midmyocardium of the circumflex (CFX) perfusion bed. The LAD coronary artery was cannulated and perfused with blood from the femoral artery through an extracorporal perfusion circuit. Ischemia was induced in the LAD perfusion bed by reducing the flow of the LAD perfusion pump by 60% for 50 min, and was followed by 30 min of reperfusion. Regional myocardial blood flow was assessed with fluorescent microspheres. Ischemia resulted in a transmural gradient in blood flow, with the most severe reduction in flow occurring in the subendocardium (p〈0.05). We found a significant reduction in interstitial glucose in both the LAD subepicardium (1.26±0.24 mM) (p=0.0009) and subendocardium (0.89±0.21 mM) (p=0.0001) during ischemia compared to the aerobic (non-ischemic) period (1.97±0.25 mM, 2.03±0.29 mM for the subepicardium and subendocardium, respectively). This coincided with a significant reduction in glucose delivery (LAD pump flow* arterial glucose) to the LAD perfusion bed during ischemia (54.5±8.5 μmol/min) compared to aerobic values (182.1±25.3 μmol/min) (p〈0.05). Interstitial lactate levels were significantly increased during ischemia in the LAD subendocardium (3.39±0.46 mM) compared to the aerobic values (1.73±0.46 mM) (p〈0.0029). A transmural gradient in interstitial lactate levels was observed during ischemia: this gradient was not seen during the aerobic period and was negated upon reperfusion. In conclusion, ischemia resulted in a decrease in interstitial glucose in both the LAD subepicardium and subendocardium, and an increase in interstitial lactate in the LAD subendocardium. Further, a transmural gradient in interstitial lactate levels was observed during ischemia, with the highest lactate values appearing in the subendocardium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00788283
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Dual capillary column supercritical fluid chromatography (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 22-26 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Dual capillary columns ; Polycyclic aromatic hydrocarbons ; Hop and beer bitter acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chromatograph equipped with one injection valve, two capillary columns with different selectivities, two flame ionization detectors and two electrometers is used to perform simultaneous dual capillary supercritical fluid chromatography. Two sets of retention times and indices are obtained for a mixture of polycyclic aromatic hydrocarbons, from one injection, enabling positive identification. The system is also used to rapidly select a stationary phase for separating hop and beer bittering acids.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240130106
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    Paper (German National Licenses)
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