Jiri A Mejsnar

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Using liquid ion-exchanger semimicroelectrodes with a side pore, we measured changes of extracellular potassium concentration (Ke +) in adult rabbit and cat gastrocnemius muscles and in venous effluent blood flowing from the cat gastrocnemius muscle during various bouts of activity induced by sciatic nerve stimulation. 1. Isometric tetanic contractions (at(More)
In order to advance our understanding of the phenomenon of flow-induced increases in the metabolism of the relaxed muscle, the metabolic rate of the isolated rat gracilis muscle was investigated at 28 degrees C in vitro. The muscle was perfused with cell-free Krebs-Henseleit bicarbonate buffer containing 5% bovine serum albumin and 5 mM glucose, saturated(More)
Adenosine 5'-triphosphate (ATP), phosphocreatine (PCr), creatine (Cr), inorganic phosphate (Pi), lactate (LAC), pyruvate (PYR) and glycogen as glucose (GLU) were determined and free adenosine 5'-diphosphate (ADP) was calculated from ATP:creatine phosphokinase (CPK) reaction in the gracilis muscle of cold-acclimated rats in vivo, and in completely isolated(More)
The authors studied the effect of the blood perfusion rate and of noradrenaline (NA) on the oxygen consumption of the isolated hind limb and on the partly - and vascularly completely - isolated cranial gracilis muscle of cold-acclimated rats. Oxygen consumption of the limb was stimulated by a raised perfusion rate together with growth of the oxygen(More)
Creatine kinase (CK) (E.C. buffers cellular ATP concentration during fluctuating ATP turnover. Muscle cytosolic CK isoform interacts with various subcellular structures where it is functionally coupled with relevant ATPases. However, how this interaction affects its activity is not known. We have therefore studied the interaction of CK with(More)
To estimate oxidative capacity of noncontracting rat skeletal muscle, the isolated gracilis muscle was perfused at various high flow rates with high-PO2 (88 kPa) saline-albumin solution and simultaneously perifused at either low (6.3 kPa) or high PO2 in a calorimeter at 28 degrees C. Under low-PO2 perifusion, specific O2 consumption and heat production(More)
Myofibrillar creatine kinase (CK) that buffers ATP during fluctuating muscle energy metabolism has been selected for studies of conformational changes underlying the cellular control of enzyme activity. The force field was computed for three energetic states, namely for the substrate-free CK molecule, for the molecule conjugated with the MgATP complex, and(More)
The aim of this study was to evaluate myofibrillar creatine kinase (CK) activity and to quantify the substrate channelling of ATP between CK and myosin ATPase under different pH conditions within the integrity of myofibrils. A pure myofibrillar fraction was prepared using differential centrifugation. The homogeneity of the preparation and the purity of the(More)
The oxygen consumption-heat relationship is analyzed using a scheme of reactions underlying muscle aerobic metabolism. The enzymatic chemical reactions of the scheme are considered near equilibrium during a contraction, and far from equilibrium during energy dissipation in a non-contracting state. Implications show that for two different metabolic rates,(More)
Myofibril-bound creatine kinase EC (CK), a key enzyme of muscle energy metabolism, has been selected for studies of conformational changes that underlie the cellular control of enzyme activity. For fluorescence spectroscopy measurements, the CK molecule was double-labeled with IAF (5-iodoacetamidofluorescein) and ErITC (erythrosin(More)