Thought this is smwhat related to urs...

Reduced cross-bridge dependent stiffness of skinned myocardium from mice lacking cardiac myosin binding protein-C:

The role of cardiac myosin binding protein-C (MyBP-C) on myocardial stiffness was examined in skinned papillary muscles of wild-type (WT+/+) and homozygous truncated cardiac MyBP-C (MyBP-Ct/t) male mice. No MyBP-C was detected by gel electrophoresis or by Western blots in the MyBP-Ct/t myocardium. Rigor-bridge dependent myofilament stiffness, i.e., rigor minus relaxed stiffness, in the MyBP-Ct/t myocardium (281 ± 44 kN/m2) was 44% that in WT+/+ (633 ± 141 kN/m2). The center-to-center spacing between thick filaments as determined by X-ray diffraction in MyBP-Ct/t (45.0 ± 1.2 nm) was not significantly different from that in WT+/+ (43.2 ± 0.9 nm). The fraction of cross-sectional area comprised of myofibrils, as determined by electron microscopy, was reduced in the MyBP-Ct/t (39.9%) by 10% compared to WT+/+ (44.5%). These data suggest that the 56% reduction in rigor-bridge dependent stiffness of the skinned MyBP-Ct/t myocardium could not be due solely to a 10% reduction in the number of thick filaments per cross-sectional area and must also be due to approximately 50% reduction in the stiffness of the rigor-bridge attached thick filaments lacking MyBP-C.

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Source: SpringerLink

Magnetic resonance microscopy is device used for investigating heart of a mouse....more about it below...

Four-dimensional MR microscopy of the mouse heart using radial acquisition and liposomal gadolinium contrast agent

Magnetic resonance microscopy (MRM) has become a standard tool for investigating cardiac structure and function in the mouse. The majority of MR work on mice has been done with 2D acquisition methods with limited resolution along the third axis (1-4). 3D studies have shown promise in the clinical arena as they increase signal-to-noise-ratio (SNR) per unit time and allow for higher in-plane resolution, ultimately allowing more sensitive calculation of cardiac function. But 3D applications in small animal imaging thus far have been limited. While 3D studies have been performed in the rat (5), those studies had limited temporal resolution (systole and diastole). Feintuch et al. have shown 4D (3D spatial+time) data in the mouse at limited spatial resolution (8 nL), limited temporal resolution (12 ms), and with long scan times of 1–2 hours (6).

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Source: http://www.ncbi.nlm.nih.gov