Kalda M, Vendelin M Sci Rep 2020 Mar;10(1):5530 PMID: 32218497 Full text: https://doi.org/10.1038/s41598-020-62452-7 Abstract Model simulations (top) and the scheme showing cooperativity modes Strong interactions between cross-bridges (XB) and regulatory units (RU) lead to a steep response of cardiac muscle to an increase in intracellular calcium. We developed a model to quantitatively assess the influence of different types of interactions within the sarcomere on the prope...

Karro N, Laasmaa M, Vendelin M, Birkedal R Sci Rep 2019 Aug;9(1):12592 PMID: 31467353 Abstract Sex differences in cardiac physiology are getting increased attention. This study assessed whether isolated, permeabilized cardiomyocytes from male and female C57BL/6 mice differ in terms of their respiration with multiple substrates and overall intracellular diffusion restriction estimated by the apparent ADP-affinity of respiration. Using respirometry, we recorded 1) the activities of respiratory...

Laasmaa M, Karro N, Birkedal R, Vendelin M. PeerJ. 2019 Mar 29;7:e6652 PMID: 30956900 Full text: https://doi.org/10.7717/peerj.6652 Abstract Analysis of calcium sparks in cardiomyocytes can provide valuable information about functional changes of calcium handling in health and disease. As a part of the calcium sparks analysis, sparks detection and characterization is necessary. Here, we describe a new open-source platform for automatic calcium sparks detection from line ...

Laasmaa M, Birkedal R, Vendelin M J. Mol. Cell. Cardiol. Volume 100, November 2016, Pages 93–108 PMID: 27702573 Full text: http://doi.org/10.1016/j.yjmcc.2016.08.015 Abstract In cardiac excitation-contraction coupling (ECC), calcium enters the cytosol via L-type Ca2+ channels (LTCC) and reverse Na+/Ca2+-exchange (NCXrev), or is released from the sarcoplasmic reticulum (SR) by Ca2+-induced Ca2+-release (CICR). The magnitude of Ca2+ influx via the different pathways varies with the ...

Simson P, Jepihhina N, Laasmaa M, Peterson P, Birkedal R, Vendelin M J. Mol. Cell. Cardiol. Volume 97, August 2016, Pages 197–203; PMID: 27261153 Full text: http://doi.org/10.1016/j.yjmcc.2016.04.012 Abstract Adequate intracellular energy transfer is crucial for proper cardiac function. In energy starved failing hearts, partial restoration of energy transfer can rescue mechanical performance. There are two types of diffusion obstacles that interfere with energy transfer from mit...

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...