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  • 1
    ISSN: 1573-4919
    Keywords: myocardial stunning ; ischemic preconditioning ; myocardial relaxation ; diastolic stiffness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of myocardial stunning and ischemic preconditioning on left-ventricular developed pressure and end-diastolic pressure (diastolic stiffness) as well as on coronary-perfusion pressure were examined in isolated isovolumic rabbit hearts. The isovolumic relaxation was evaluated, and the time constant of pressure decay during the isovolumic period was calculated. Our experimental protocol comprised: 1) myocardial stunning-global ischemia (15 min) followed by reperfusion (30 min); 2) myocardial stunning-global ischemia (20 min) followed by reperfusion (30 min); and 3) ischemic preconditioning — a single cycle of brief global ischemia and reperfusion (5 min each), before a second ischemic period, of 20-min duration. There was no effect upon systolic and diastolic parameters when 15 and 20 minutes of ischemia were evaluated. In both stunned groups the left ventricular developed pressure first recovered to near control values, but then stabilized at only 60% of the control values. Whereas the isovolumic relaxation time constant was increased after 5 min of reperfusion, and return to control values at late reperfusion, the end diastolic pressure remained elevated during the entire period. Values of dP/dV calculated at common pressure levels, were used as a second index of diastolic stiffness. They were increased after stunning, as also was the coronary perfusion pressure. When the heart was preconditioned with a single episode of ischemia, the systolic and diastolic alterations were completely abolished. We thus concluded that diastolic abnormalities incurred by myocardial stunning consist in both an increase in diastolic stiffness and an early impairment of isovolumic relaxation. The increase in stiffness cannot result from incomplete relaxation since these two parameters become temporally dissociated during the reperfusion period.
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  • 2
    ISSN: 1573-4919
    Keywords: myocardial relaxation ; phospholamban ; Ca2+-calmodulin dependent phosphorylation ; W7
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The role of the Ca2+-calmodulin dependent pathway of phospholamban phosphorylation on the relaxant effect of β-adrenergic agonists was studied in isolated perfused rat heart. Administration of the calmodulin antagonist W7 or lowering [Ca]0 from 1.35 mM (control) to 0.25 mM, were used as experimental tools to inhibit the Ca2+-calmodulin dependent protein kinase activity. 3×10−8 M isoproterenol increased cAMP levels from 0.613±0.109 pmol/mg wet weight to 1.581±0.123, phospholamban phosphorylation from 36±6 pmol32P/mg protein to 277±26 and decreased time to half relaxation (t1/2) from 61±2 msec to 39±2. Simultaneous perfusion of isoproterenol with 10−6 M W7, decreased phospholamban phosphorylation to 170±23 and prolongated t1/2 to 47±3 but did not affect the increase either in cAMP levels or myocardial contractility produced by isoproterenol. Similar effects on phospholamban phosphorylation and myocardial relaxation were obtained when isoproterenol was perfused in low [Ca]0. Low [Ca]0 did not affect the increase in cAMP elicited by isoproterenol but offset the positive inotropic effect of the β-agonist. The results suggest a physiological role of the Ca2+-calmodulin dependent phospholamban phosphorylation pathway as a mechanism that supports, in part, the β-adrenergic cardiac relaxant effect.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 160-161 (1996), S. 123-128 
    ISSN: 1573-4919
    Keywords: myocardial stunning ; diastolic stiffness ; myocardial relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The present study provides evidences of left ventricular diastolic alterations following reperfusion in a model of global ischemia. Isolated perfused rabbit and rat hearts, were subjected to ischemia for 15 and 20 min respectively, followed by 30 min of reperfusion. In rabbit heart at the end of the reperfusion period, isovolumic left ventricular developed pressure (LVDP) and +dP/dtmax stabilized at 55 ± 3% and 60 ± 2% of preischemic values respectively and, in rat heart LVDP = 61 ± 8% and +dP/dtmax = 57 ± 9% of preischemic values. Stunned heart was then obtained from both species. Left ventricular end diastolic pressure (LVEDP) values stabilized at the end of reperfusion period at values higher than preischemic conditions in both species (38.9 ± 4.4 mmHg and 30.3 ± 3.1 mmHg in rabbit and rat respectively). The time constant of relaxation (T) increased early in reperfusion in both species, but then decreased and stabilized at the end of reperfusion period at values lower than preischemic values. The ratio between both maximal velocities (+P/-P), also showed a transitory impairment in relaxation, followed by normalization and stabilization at values lower than preischemic values. This biphasic pattern in relaxation was detected in both species. The changes in relaxation were dissociated from the diastolic compliance and could be the result of a transitory calcium overload and/or sarcoplasmic reticulum dysfunction. The faster myocardial relaxation at the end of reperfusion period is consistent with the decreased myofilament sensitivity, which characterizes the stunned myocardium.
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  • 4
    ISSN: 0044-2313
    Keywords: Zinc ; Cadmium ; 2,2′-bis(pyrazol-1-yl)propane ; adduct complexes ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zink- und Cadmium-Addukte des 2,2′-Bis(pyrazol-1-yl)propan, (L—L), einem sterisch anspruchsvollen Liganden. Kristallstruktur des (L—L)Zn[OC(=O)CF3]2(H2O)1:1 Addukte zwischen dem Titelliganden und MX2 (M = Zn oder Cd; X = Cl, Br, I oder C2F3O2) bzw. den ionischen Verbindungen [(L—L)5Zn2(H2O)2](ClO4) 4 und [(L—L)2 Cd(H2O)2](ClO4)2 wurden dargestellt. Diese sind stabil im festen Zustand und in Aceton-Lösung, nicht jedoch in Dimethylsulfoxid-Lösung. In der Struktur des (L—L)Zn(H2O)[O—C(=O)CF3]2 liegt, auf Grund einer durch die Methylgruppen verursachten sterischen Behinderung, eine verzerrte trigonale Bipyramide vor, in der zwei Sauerstoffatome (vom Wasser und Trifluoroacetat) und ein Stickstoffatom in der äquatorialen Ebene liegen. Die axialen Zn—X-Bindungen (X = N = 2,125(3) Å; X = O = 2,085(4) Å) sind länger als die äquatorialen.
    Notes: 1:1 adducts between the title ligand and MX2 (M = Zn or Cd; X = Cl, Br, I or trifluoroacetate) as well as ionic compounds [(L—L)5Zn2(H2O)2](ClO4) 4 and [(L—L)2Cd(H2O)2](ClO4) 2 are stable in the solid state and in acetone solution, but not in dimethylsulphoxide. In (L—L)Zn(H2O)[O—C(=O)CF3]2 two oxygen atoms (belonging to water and to one O—C(=O)CF3) at 2.039(4) and 2.008(4) Å from Zn, and one nitrogen atom (Zn—N 2.067(3) Å) from the chelating L—L define the basal plane of a trigonal bipyramid, which is distorted owing to the steric requirements of the bridgehead methyls of L—L; the axial Zn—X bonds (X = N 2.125(3) Å; X = O 2.085(4) Å), are longer than the equatorial Zn—X bonds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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