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  • 1
    Electronic Resource
    Electronic Resource
    Low resting potentials in single isolated heart cells due to membrane damage by the recording microelectrode (1984)
    Springer
    Pflügers Archiv 400 (1984), S. 197-199 
    Details
    ISSN: 1432-2013
    Keywords: rat heart ; enzymatically isolated ventricular myocytes ; membrane potential ; microelectrodes ; suction pipettes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Single myocytes from adult rat hearts were prepared following the method of Powell and co-workers (9, 10, 11). Low resting potentials (Em) could be improved by three techniques. (i) Elevation of Cao to 7.2 mM which, however, mostly resulted in spontaneity and irreversible contracture. (ii) Pre-incubation in a “KB medium” (6). (iii) Use of suction pipettes instead of tapered microelectrodes for intracellular recordings (2). It is concluded that low Em measured previously (11) were due to membrane damage upon microelectrode impalement accopanied by insfufficient healing of the membrane around the electrode insertion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585040
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  • 2
    Electronic Resource
    Electronic Resource
    The use of the creatine kinase reaction to determine free energy change of ATP hydrolysis in anoxic cardiomyocytes (1989)
    Springer
    Pflügers Archiv 413 (1989), S. 435-437 
    Details
    ISSN: 1432-2013
    Keywords: Anoxia ; adult cardiomyocytes ; creatine kinase ; free energy change ; ATP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In isolated cardiomyocytes from adult rat heart the free energy change of ATP hydrolysis (dG) was determined under conditions of substrate-free anoxia. Changes of free cytosolic ADP concentrations, needed for the calculation of dG, were determined by two indirect methods since a direct measurement is not feasible: (i) via the mass action ratio of the creatine kinase reaction (CK) assuming near equilibrium conditions, and (ii) via quantification of the net hydrolysis of ATP to ADP by a detailed balancing of possible contribution to Pi production. Both approaches gave virtually identical results, showing that in anoxia only 6% of the ATP hydrolysed are hydrolysed to ADP and 94% completely to adenosine and further degradation products. The convergence of both methods also indicates that in this model the CK reaction is indeed catalysed near its equilibrium. Therefore estimations of free ADP and dG using its mass action ratio are valid. In anoxic cardiomyocytes dG values fell from 57 kJ/mol in normoxia to 42 kJ/mol after 120 min anoxia, corresponding to a decrease of ATP contents from 24 to 4 nmol/mg protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584495
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  • 3
    Electronic Resource
    Electronic Resource
    Energy deficiency, calcium overload or oxidative stress: Possible causes of irreversible ischemic myocardial injury (1989)
    Springer
    Journal of molecular medicine 67 (1989), S. 465-476 
    Details
    ISSN: 1432-1440
    Keywords: Myocardial ischemia ; Reperfusion injury ; Oxygen paradox ; Contracture ; Calcium ; Oxygen radicals ; ATP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary After prolonged ischemia or hypoxia myocardial injury is not reversed but exacerbated by a resupply of the tissue with oxygen and substrates. The mechanism by which reversible ischemic or hypoxic myocardial injury becomes irreversible is not yet understood. It has been debated whether “reperfusion injury” merely uncovers pre-existing irreversible injury, or is indeed caused by the reperfusion/reoxygenation process. In recent years, three theories have been discussed that relate the onset of irreversibility either to: a critical energy loss; a critical accumulation of cellular calcium; or to the deleterious effects of free radical formation. In certain experimental models for each of these theories favourable results have been obtained. Current research suggests that absolute reversibility thresholds in energy depletion or calcium accumulation in the ischemic or hypoxic cell do not exist. A key role of free radical injury for reperfusion injury must also be questioned. There is, however, evidence that in tissue reversibility of ischemic cardiomyocyte injury is limited by conditions that make calcium-induced hypercontracture upon reoxygenation unavoidable. This occurs when, by hypercontracture, mutual mechanical disruption of the cells destroys the tissue. From isolated cardiomyocytes that are able to metabolically survive hypercontracture it has been observed that these metabolic conditions do not represent the last biological possibility to reverse injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01721672
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  • 4
    Electronic Resource
    Electronic Resource
    Single voltage-dependent and outward rectifying K+-channels in isolated rat heart cells (1985)
    Springer
    European biophysics journal 11 (1985), S. 259-263 
    Details
    ISSN: 1432-1017
    Keywords: K+-channels ; patch-clamp ; heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Studies on single K+-channel currents recorded from isolated rat heart muscle cells, in which early repolarization is known to be exceptionally fast, are reported here. A K+-channel which is blocked by TEA (tetraethylammonium) from the inside only has been found. The total open time of the channel, measured in steady-state after activation, indicated outward rectifying properties. The single channel conductance increases with depolarization from 25 pS at-70 mV to 75 pS at+70 mV. Selectivity of the channel has also been measured and it was found that only Rb+ and K+ can permeate the channel, whereas the permeability (P) for Li+, Na+, Cl-, Mg2+, and Ca2+ is less than 0.05 times $${\text{P}}_{{\text{K}}^{\text{ + }} } $$ . Ba2+ and Cs+ block the channel activity. These results clearly demonstrate the existence of K+-selective outward rectifying conductance pathways in rat ventricular myocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262003
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  • 5
    Electronic Resource
    Electronic Resource
    Absence of reoxygenation damage in isolated heart cells after anoxic injury (1984)
    Springer
    Pflügers Archiv 401 (1984), S. 71-76 
    Details
    ISSN: 1432-2013
    Keywords: Cardiac anoxia ; Enzyme release ; Reoxygenation damage ; Mitochondrial swelling ; Contracture development ; Cell lysis ; Adult heart cells ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cultured adult cardiac myocytes were exposed to anoxia under substrate-free conditions and then reoxygenated. When comparing the oxygen deficient organ to the anoxic cell culture, we see that metabolic changes in the latter system proceed in a similar, yet prolonged manner, as in arrested hearts. Release of cytosolic enzymes starts with minor energetic disturbances and proceeds closely correlated to the actual ATP level. Below 2 μmol ATP/gww, an increasing number of cells becomes irreversibly damaged, above this level, 30 min reoxygenation leads to extensive recovery of the whole preparation. The results indicate that leakage of cytosolic enzymes during the early stage of anoxia is due to a gradual protein release from the individual cells and is related to reversible membrane alterations. Reoxygenation does not induce changes considered typical of the ‘oxygen paradox’. Since mechanical cell-cell interactions are absent in this model, it is suggested that aggravation of tissue damage in heart tissue reoxygenated late is mainly caused by mechanical forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581535
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  • 6
    Electronic Resource
    Electronic Resource
    A new method for continuous measuring of respiratory quotient in a computer-assisted working heart preparation (1983)
    Springer
    Basic research in cardiology 78 (1983), S. 1-7 
    Details
    ISSN: 1435-1803
    Keywords: respiratory quotient ; working rat heart ; substrate utilization ; oxygen demand ; oxygen consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wurde eine Methode entwickelt, um an einem isolierten, arbeitenden Rattenherzen kontinuierlich den RQ sowie das Verhältnis aus O2-Verbrauch und O2-Bedarf (EQ) zu registrieren. Aus dem aktuellen RQ können Aussagen über die aktuell oxidierten Substrate gemacht werden; der EQ ist im Steady-state ein Maß für den ATP/O-Quotienten der oxidierten Substrate, außerdem kann damit eine vorübergehende O2-Schuld erfaßt werden. Für die RQ-Messung wird die O2-AVD und die CO2-Freisetzung gemessen. Da bei Verwendung eines bikarbonathaltigen Perfusionsmediums die CO2-AVD nur sehr gering gegenüber der arteriellen CO2-und Bikarbonatkonzentration ist, wird ein bikarbonatfreies Perfusat verwendet. Im Koronareffluat wird nach Absenken des pH-Wertes auf ca. 4, um das CO2/HCO 3 t- -Gleichgewicht auf die Seite des gelösten CO2 zu verlagern, der CO2-Partialdruck gemessen. Weiterhin wird fortlaufend der Ventrikeldruck, das HZV sowie der Koronarfluß registriert. Alle Meßdaten werden über einen AD-Converter in einen LSI11-Computer eingelesen. Daraus werden Herzfrequenz, max. Ventrikeldruck, dP/dtmax, O2-Verbrauch, O2-Bedarf nach Bretschneider, der RQ und der EQ errechnet. An zwei Beispielen wird dargestellt, daß dieses Modell für physiologische, metabolische und pharmakologische Untersuchungen gut geeignet ist.
    Notes: Summary A method was developed for continuous monitoring of the respiratory quotient (RQ) and the ratio of O2-consumption to O2-demand (EQ) in an isolated working rat heart preparation. The RQ allows to get informations about substrates actually oxidized in the myocardium. The EQ is a parameter which behaves reciprocally to the ATP/O of the oxidized substrates during steady state and additionally it allows monitoring of a transitory oxygen debt. For registration of RQ the arterio-venous O2-difference and the CO2-release are measured. As the CO2-production is very small compared with arterial CO2- and HCO 3 − -concentrations when using a bicarbonate buffer for perfusion, a bicarbonate-free perfusion-fluid is used. In a portion of coronary effluent the pH is lowered to shift the CO2/HCO 3 − -equilibrium to the side of dissolved CO2. Then the pCO2 is measured with a CO2-Nelectrode. Additionally, ventricular pressure, cardiac input and coronary flow are continuously registrated. All data are fed via an AD-converter into an LSI 11-computer. Heart rate, maximum ventricular pressure, dP/dtmax, oxygen demand after Bretschneider's formula, RQ and EQ are calculated. The advantages of the system described are demonstrated with two examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01923188
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  • 7
    Electronic Resource
    Electronic Resource
    A new method for studying the incorporation of nonesterified fatty acids into cardiac lipids by using deuterium-labelled palmitate (1988)
    Springer
    Basic research in cardiology 83 (1988), S. 87-93 
    Details
    ISSN: 1435-1803
    Keywords: nonesterifiedfatty acids ; myocardiallipids ; stable-isotope-labelledfatty acids ; cholesterol esters ; mass fragmentography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A new method for measuring the incorporation of exogenous fatty acids into myocardial lipids of working rat hearts using deuterium-labelled palmitate has been developed. After perfusing isolated hearts, the fatty acid composition of triglycerides, diglyccrides, monoglycerides, cholesterol esters, and nonesterified fatty acids (NEFA) was measured by a mass fragmentographic method. Hearts perfused only with 5 mM glucose and 1 mM lactate perfusion as basic substrates showed a significant decrease of triglyceride content, while the other lipids were not found to be significantly reduced. The fatty acid composition of all lipids were not affccted. An addition of D31-palmitate complexed to albumin at a molar ratio of 5∶1, caused a dose-dependent incorporation into triglycerides and diglycerides which suggested saturation kinetics. The tissue content of nonesterified D31-palmitate was found to be linearly related to its concentration in the perfusate. It may be of note that the concentration of the other NEFA was significantly affected neither by a fatty-acid-free perfusion nor by a perfusion with D31-palmitate. A significant incorporation of the supplied fatty acid into cholesterol esters and monoglycerides could not be detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01907108
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  • 8
    Electronic Resource
    Electronic Resource
    Fatty acids are not an important fuel for coronary microvascular endothelial cells (1989)
    Springer
    Molecular and cellular biochemistry 88 (1989), S. 59-64 
    Details
    ISSN: 1573-4919
    Keywords: substrate oxidation ; fatty acids ; glycolysis ; Crabtree effect ; microvascular endothelial cells ; coronary system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The metabolism by coronary microvascular endothelial cells (CMEC) of the heart typical substrates palmitate and lactate was compared to that of glucose and glutamine. Confluent cultures of CMEC were used. Palmitate oxidation was saturable and independent of the exogenous albumin concentration. Palmitate, 300 μM, lactate, 1 mM, and glutamine, 0.5 mM, were oxidized to 35, 46, and 56 nmol CO2/h × mg protein. These oxidation rates were decreased by 80, 66, and 48% in presence of 5 mM glucose. The largest energy yield was obtained by glycolytic breakdown of glucose. Glucose, 5 mM, was degraded to lactate by 99%, and oxidized in the Krebs cycle by only 0.04%. 1% was catabolized via the hexose monophosphate pathway. The rate of glucose oxidation in the Krebs cycle could be 30-fold increased by the uncoupler 2,4-dinitrophenol, 30 µM. At concentrations lower than 1 mM the amount of glucose oxidized in the Krebs cycle also grew, indicating existence of the Crabtree effect. The energy demand of CMEC seems to be of the same order as that of the arrested heart.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223424
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  • 9
    Electronic Resource
    Electronic Resource
    Myocardial fatty acid oxidation: Evidence for an albumin-receptor-mediated membrane transfer of fatty acids (1984)
    Springer
    Basic research in cardiology 79 (1984), S. 274-282 
    Details
    ISSN: 1435-1803
    Keywords: myocardial fatty acid oxidation ; oxygen consumption ; respiratory quotient ; myocardial fatty acid uptake ; dichloroacetate ; acetate ; albumin receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Using a computer-assisted working rat heart preparation, which allows continuous registration of the respiratory quotient, it was tested which parameters determine fatty acid oxidation in the myocardium. Supplying albumin and palmitate in different concentrations the rate of fatty acid oxidation was measured. The UFA concentrations were calculated using stepwise equilibrium constants. When keeping constant the NEFA/albumin ratio and raising total NEFA concentration, an increase in fatty acid oxidation was found showing a saturation curve. Increasing NEFA at constant albumin concentration, however, results in a linear increase in fatty acid oxidation. Keeping constant the total NEFA concentration elevation of albumin shows an inhibitory effect. These results suggest the existence of a receptor for albumin on heart cell surface, which mediates uptake of albumin-bound NEFA. An additional supply of glucose and lactate does not show any effect on these relations. Acetate and dichloroacetate, an activator of the pyruvate dehydrogenase, are found to be competitive inhibitors of fatty acid oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01908027
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  • 10
    Electronic Resource
    Electronic Resource
    The role of fatty acids in ischemic tissue injury: difference between oleic and palmitic acid (1986)
    Springer
    Basic research in cardiology 81 (1986), S. 373-383 
    Details
    ISSN: 1435-1803
    Keywords: myocardial ischemia ; long-chain fatty acids ; high-energy phosphates ; anacrobic glycolysis ; enzyme release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Guinea pig hearts were subjected to low-flow perfusion (0.3 ml/g fresh weight/min) with an oxygen depleted perfusate. Fatty acids (palmitic or oleic acid), added to the perfusate, accelerated in a dose-dependent manner the anoxic decay of creatine phosphate and ATP, impaired lactate production and augmented enzyme release (lactate dehydrogenase, malate dehydrogenase). Palmitic and olcic acid, however, differed distinctly in their deleterious effect, this being greater for oleic acid. After 60 min anoxic low-flow perfusion with 11 mM glucose and 0.2 mM of either fatty acid, complexed in 5∶1 molar relationship to albumin, the creatine phosphate content with palmitate is 39% greater than with oleate, the ATP content 23%, lactate production 15% greater, and release of malate dehydrogenase 24% lower, but the elevated contents of long-chain acyl CoA and acyl carnitine are not significantly different for the two fatty acids. These results accord with earlier experiences on subcellular systems showing that the physicochemical effects of the oleyl residue are more harmful than those of the palmityl residue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01907458
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