Kalda M, Peterson P, Vendelin M PLoS ONE 2015;10(9):e0137438 PMID: 26361396 Full text: http://doi.org/10.1371/journal.pone.0137438 Abstract The aim of this work is to incorporate cooperativity into Huxley-type cross-bridge model in thermodynamically consistent way. While the Huxley-type models assume that cross-bridges act independently from each other, we take into account that each cross-bridge is influenced by its neighbors and cooperativity is induced by tropomyosin movement. For that...

Birkedal R, Laasmaa M, Vendelin M Front Physiol 2014;5:376 PMID: 25324784 Full text: http://dx.doi.org/10.3389/fphys.2014.00376 Abstract The heart relies on accurate regulation of mitochondrial energy supply to match energy demand. The main regulators are Ca(2+) and feedback of ADP and Pi. Regulation via feedback has intrigued for decades. First, the heart exhibits a remarkable metabolic stability. Second, diffusion of ADP and other molecules is restricted specifically in heart an...

Sepp M, Sokolova N, Jugai S, Mandel M, Peterson P, Vendelin M PLoS ONE 2014;9(6):e99413 PMID: 24932585 Abstract The effective integrated organization of processes in cardiac cells is achieved, in part, by the functional compartmentation of energy transfer processes. Earlier, using permeabilized cardiomyocytes, we demonstrated the existence of tight coupling between some of cardiomyocyte ATPases and glycolysis in rat. In this work, we studied contribution of two membrane ATPases and w...

Sokolova N, Pan S, Provazza S, Beutner G, Vendelin M, Birkedal R, Sheu SS PLoS ONE 2013;8(12):e83214 PMID: 24349464 Abstract ADP is not only a key substrate for ATP generation, but also a potent inhibitor of mitochondrial permeability transition pore (mPTP). In this study, we assessed how oxidative stress affects the potency of ADP as an mPTP inhibitor and whether its reduction of reactive oxygen species (ROS) production might be involved. We determined quantitatively the effects of ...

Branovets J, Sepp M, Kotlyarova S, Jepihhina N, Sokolova N, Aksentijevic D, Lygate CA, Neubauer S, Vendelin M, Birkedal R Am. J. Physiol. Heart Circ. Physiol. 2013 Aug;305(4):H506-20 PMID: 23792673   Abstract Disruption of the creatine kinase (CK) system in hearts of CK-deficient mice leads to changes in the ultrastructure and regulation of mitochondrial respiration. We expected to see similar changes in creatine-deficient mice, which lack the enzyme guanidinoacetate methyltr...

Peterson P, Kalda M, Vendelin M Am. J. Physiol., Cell Physiol. 2013 Mar;304(6):C519-31 PMID: 23255581 Abstract Sarcomere length of a cardiomyocyte is an important control parameter for physiology studies on a single cell level; for instance, its accurate determination in real time is essential for performing single cardiomyocyte contraction experiments. The aim of this work is to develop an efficient and accurate method for estimating a mean sarcomere length of a contracting cardiomy...

Schryer DW, Peterson P, Illaste A, Vendelin M PLoS Comput. Biol. 2012;8(12):e1002795 PMID: 23236266 Abstract To characterize intracellular energy transfer in the heart, two organ-level methods have frequently been employed: ³¹P − NMR inversion and saturation transfer, and dynamic ¹⁸O labeling. Creatine kinase (CK) fluxes obtained by following oxygen labeling have been considerably smaller than the fluxes determined by ³¹P − NMR saturation transfer. It has been proposed that dynamic ¹...

Illaste A, Laasmaa M, Peterson P, Vendelin M Biophys. J. 2012 Feb;102(4):739-48 PMID: 22385844 Abstract Intracellular diffusion in muscle cells is known to be restricted. Although characteristics and localization of these restrictions is yet to be elucidated, it has been established that ischemia-reperfusion injury reduces the overall diffusion restriction. Here we apply an extended version of raster image correlation spectroscopy to determine directional anisotropy and coefficients ...