Cardiac Tissue Organization and Contractility

Abstract

Given standard pulses of free Ca 2þ , we fit the tension data of single and paired pulses with a model that permits cooperativity owing to cycling crossbridges but not Ca 2þ -bound Tn. The model produces time courses of Ca 2þ -bound Tn and the position of the Tm-Tn complex that follow single and paired transients of the meridional 1/38.5 nm À1 reflection intensity changes for both overlap and nonoverlap preparations. The model predicts that a fraction of Ca 2þ -bound Tn correlates in time and amplitude with the tension transient. This fraction represents Tn positioned away from possible interaction with actin by cycling crossbridges acting cooperatively on the position of Tm in the thin filament. Thus, this most parsimonious model of cooperativity is also the one most capable of explaining experimental observations.

Guiding Lights: Tissue Bioprinting Using Photoactivated Materials

“…The heart, composed primarily of cardiac muscle, is a highly cellular contractile tissue, again with hierarchical organization. 51 The cardiac muscle or myocardium is embedded between the epi-and endocardium layers. The myocardium is composed of single cells, the myocardiocytes, which are around approximately 100 μm in length and are joined together at their long ends by intercalated discs, structures that ensure tight connectivity and synchronized contractility of the tissue.…”

“…The heart, composed primarily of cardiac muscle, is a highly cellular contractile tissue, again with hierarchical organization . The cardiac muscle or myocardium is embedded between the epi- and endocardium layers.…”