The zebrafish is a potentially important and cost-effective model for studies of development, motility, regeneration, and inherited human diseases. The object of our work was to show whether myofibrils isolated from zebrafish striated muscle represent a valid subcellular contractile model. These organelles, which determine contractile function in muscle, were used in a fast kinetic mechanical technique based on an atomic force probe and video microscopy.

The sarcomere is the core structure responsible for active mechanical heart function. It is formed primarily by myosin, actin, and titin filaments. Cyclic interactions occur between the cross-bridges of the myosin filaments and the actin filaments. The forces generated by these cyclic interactions provide the molecular basis for cardiac pressure, while the motion produced by these interactions provides the basis for ejection. The cross-bridge cycle

Muscle contraction results from force-generating interactions between myosin cross-bridges on the thick filament and actin on the thin filament. The force-generating interactions are regulated by Ca2+ via specialized proteins of the thin filament. It is controversial how the contractile and regulatory systems dynamically interact to determine the time course of muscle contraction and relaxation. Whereas kinetics of Ca2+-induced thin filament regulation

AIMS: To understand the functional consequences of the Lys184 deletion in murine cardiac troponin I (mcTnI(DeltaK184)), we have studied the primary effects of this mutation linked to familial hypertrophic cardiomyopathy (FHC) at the sarcomeric level. METHODS AND RESULTS: Ca(2+) sensitivity and kinetics of force development and relaxation were investigated in cardiac myofibrils from transgenic mice expressing mcTnI(DeltaK184), as a model which co-segregates

The kinetics of Ca(2+)-dependent conformational changes of human cardiac troponin (cTn) were studied on isolated cTn and within the sarcomeric environment of myofibrils. Human cTnC was selectively labeled on cysteine 84 with N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1,3-diazole and reconstituted with cTnI and cTnT to the cTn complex, which was incorporated into guinea pig cardiac myofibrils. These exchanged myofibrils, or the isolated

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Sudden Ca2+ removal from isometrically contracting cardiac myofibrils induces a biphasic relaxation: first a slow, linear force decline during which sarcomeres remain isometric and then a rapid, exponential decay originating from sequential lengthening, i.e., successive mechanical relaxation, of individual sarcomeres (Stehle et al. 2002; Biophys J 83:2152-2162). Step-stretches were applied to the myofibrils, in order to study the mechanical properties

Fast and slow mammalian muscle myosins differ in the heavy chain sequences (MHC-2, MHC-1) and muscles expressing the two isoforms contract at markedly different velocities. One role of slow skeletal muscles is to maintain posture with low ATP turnover, and MHC-1 expressed in these muscles is identical to heavy chain of the beta-myosin of cardiac muscle. Few studies have addressed the biochemical kinetic properties of the slow MHC-1 isoform. We report

This study aimed to determine the changes in soleus myofibrillar ATPase (m-ATPase) activity and MHC isoform expression after endurance training and/or chronic hypoxic exposure. Dark Agouti rats were randomly divided into four groups: control, normoxic sedentary (N, n = 14); normoxic endurance trained (NT, n = 14); hypoxic sedentary (H, n = 10) and hypoxic endurance trained (HT, n = 14). Rats lived and trained in normoxia at 760 mmHg (N and NT), or

The ATPases (+/-Ca2+) of myofibrils from rabbit soleus (a slow muscle) and psoas (a fast muscle) have different Ea: -Ca2+, 78 and 60 kJ/mol and +Ca2+, 155 and 71 kJ/mol, respectively. At physiological temperatures, the two types of myofibrillar ATPase are very similar and yet the mechanical properties of the muscles are different (Candau et al. (2003) Biophys J 85: 3132-3141). Muscle contraction relies on specific interactions of the different chemical