Mechano growth factor (MGF) promotes proliferation and inhibits differentiation of porcine satellite cells (PSCs) by down-regulation of key myogenic transcriptional factors.

Porcine satellite cells represent an ideal model system for studying the cellular and molecular basis regulating myogenic stem cell proliferation and differentiation and for exploring the experimental conditions for myoblast transplantation. Here, we investigated the effects of mechano growth factor (MGF), a spliced variant of the IGF-1 gene, on porcine satellite cells. We show that MGF potently stimulated proliferation while inhibited differentiation of porcine satellite cells. MGF-treatment acutely down-regulates the expression of myogenic determination factor (MyoD) and the cyclin-dependent kinase inhibitor p21. MGF-treatment also markedly reduced the overall expression of cyclin B1 and key factors of the myogenic regulatory and myocyte enhancer families, including Myogenein and MEF2A. Taken together, the gene expression data from MGF-treated porcine satellite cells are in favor of a molecular model in which MGF inhibits porcine satellite cell differentiation by down-regulating either the activity or expression of MyoD, which, in turn, suppresses the expression of key genes required for cell cycle progression and differentiation, such as p21, Myogenin, and MEF2. Overall, our findings are in support of the previous suggestion that MGF may be used in vivo and in vitro to promote proliferation of myogenic stem cells to prevent and treat age-related muscle degenerative diseases.

Micellization and synergistic interaction of binary surfactant mixtures based on sodium nonylphenol polyoxyethylene ether sulfate.

Mixed micelle formation and synergistic interactions of binary surfactant combinations of sodium nonylphenol polyoxyethylene ether sulfate (NPES) with typical surfactants such as sodium dodecyl sulfate (SDS), Triton X-100 (TX100), cetyl trimethyl ammonium bromide (CTAB), and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) at 25 degrees C in the presence of NaCl have been investigated. The critical micelle concentration of the binary mixtures has been quantitatively estimated by steady-state fluorescence measurements. The micellar characteristics such as composition, activity coefficients, and mutual interaction parameters have been estimated following different theoretical treatments. Investigation on the micellization and synergistic interaction of NPES with four kinds of surfactants showed that the behavior of the binary mixture deviated from the ideal state. The analysis revealed that the interaction parameter values (beta) varied with variation of solvent composition. Besides the strong electrostatic attraction between the oppositely charged surfactant NPES-CTAB mixture, the interaction between NPES and SDS also showed far more deviation from ideal behavior than that of TX100 and AOT. The reason for the synergism is also discussed and the results show that an ionic and a nonionic surfactant character existed concurrently in NPES due to the combination of a sulfate group and polyoxyethylene as a hydrophilic moiety. Zeta potential and diffusion coefficient measurements of micelles confirmed the synergistic interaction between the binary surfactants.

Development of an electrophysiology (EP)-enabled intracardiac ultrasound catheter integrated with NavX 3-dimensional electrofield mapping for guiding cardiac EP interventions: experimental studies.

OBJECTIVE: We have developed an integrated high-resolution intracardiac echocardiography (ICE) catheter for electrophysiology (EP) testing, which can be coregistered in 3-dimensional space with EP testing and ablation catheters using electrofield sensing. METHODS: Twelve open-chest pigs (34-55 kg) and 3 closed-chest pigs were studied. After introduction from the jugular or femoral venous locations, the 9F side-looking, highly steerable (0 degrees -180 degrees), 64-element array catheters could be manipulated easily throughout the right side of the heart. Multisite cardiac pacing was performed for assessing left ventricular (LV) synchrony using tissue Doppler methods. Also, in the open-chest pigs, right atrial (RA) and right ventricular (RV) ablations were performed with a separate radio frequency catheter under fluoroscopic guidance and visualized with ICE to characterize the changes. In the 3 closed-chest pigs, electrofield NavX 3-dimensional coregistration (St Jude Medical Corp, Minneapolis, MN) allowed us to test whether this additional feature could shorten the time necessary to perform 4 targeted ablations in each animal while imaging the ablation catheter and the adjacent region by ICE. RESULTS: Intracardiac anatomy, tricuspid, aortic, pulmonary, and mitral valve function, and pulmonary vein flow were all imaged reproducibly from scanning locations in the RA or RV in all animals, along with assessment of cardiac motion and the effects of multisite pacing. Three-dimensional electrofield displays detailed the spatial relationship between the ICE catheter and ablation catheters such that the time to visualize and ablate 4 sites in each of the 3 closed-chest animals was reduced. CONCLUSIONS: This new technology is a first step in the integration of ICE with EP procedures.

The contribution of left ventricular muscle bands to left ventricular rotation: assessment by a 2-dimensional speckle tracking method.

BACKGROUND: Torsion is an essential component of left ventricular (LV) function. Systolic rotation, as a component of torsion, winds the heart muscle up like a spring, setting up recoil for early diastole. We used a new 2-dimensional speckle tracking strain method to study differences in twisting in subendocardial and subepicardial layers of the LV in open-chest pigs. Our aim was to identify the relative contributions of the inner or outer layers of the LV wall to rotation and, hence, systole. METHODS: A total of 23 juvenile pigs were imaged in the short axis, epicardially, to obtain images at a level just below the papillary muscles with high-frequency (14 MHz) ultrasound. Speckle tracking software using scanline files was used to measure the torsional contribution of septum, anterior, posterior, and inferior LV wall segments. Two zones on the septum were evaluated separately: one with apparent circumferential fiber orientation in the inner layer and one with a speckle pattern suggesting longitudinal fiber orientation on the right ventricular aspect of the septum. Pressure rate changes (dP/dt) during the cardiac cycle were measured as an index of LV function and correlated with the regional torsion. RESULTS: Mean peak rotations measured by speckle tracking echocardiography at the apex showed counterclockwise rotation of LV septal wall (10.68 +/- 2.67 degrees for the inner layer and 8.27 +/- 1.73 degrees for the outer layer). The time difference for time to peak rotation was 213.22 +/- 77.95 and 241.17 +/- 54.67 milliseconds for inner and outer layers, respectively. Significant differences were shown between the inner and outer layer of the LV for both rotation (P = .000) and timing of rotation (P = .02). The dP/dt measurements correlated well with the inner rotation magnitude of the LV and with the difference of short-axis rotation between inner and outer layers of the LV wall. CONCLUSIONS: Inner and outer layers of the LV wall, especially at the septum, have different rotational behaviors. When used with very high-resolution imaging, this method could contribute to the understanding of functional contributions of the LV wall and their relative contribution to cardiac segmental twisting.

Delineation of cardiac twist by a sonographically based 2-dimensional strain analysis method: an in vitro validation study.

OBJECTIVE: Normal left ventricular contraction involves a twisting component that helps augment stroke volume, the unwinding of which also very usefully contributes to early diastolic filling. Abnormalities of cardiac twist have been related to abnormal cardiac function. We sought to quantify the twisting action using a new sonographically based angle-independent motion-detecting echo method. METHODS: A twist model was developed with a variable-speed motor to rotate a wheel in water bath. A freshly harvested pig heart was mounted on it as a twist phantom. Short axis views were acquired with a GE/VingMed Vivid 7 system (GE Healthcare, Milwaukee, WI) at 3.5 MHz and more than 100 frames/s. Eight different speeds (30-100 cycles/min of winding and unwinding) were studied at 5 degrees of rotation (10 degrees , 20 degrees , 30 degrees , 40 degrees , and 50 degrees ). Data were analyzed off-line for twist analysis with a new 2-dimensional speckle-tracking-based program (2-dimensional strain rate method [2DSR]) embedded in EchoPac software (GE Healthcare). Ten freshly harvested pig hearts were studied in this model. RESULTS: The 2DSR program tracked the twist well (mean determination at 10 degrees = 16.88 degrees +/- 1.81 degrees [SD]; at 20 degrees = 26.5 degrees +/- 1.05 degrees ; at 30 degrees = 36.47 degrees +/- 1.31 degrees ; at 40 degrees = 44.03 degrees +/- 1.39 degrees ; and at 50 degrees = 54.1 degrees +/- 1.96 degrees ). CONCLUSIONS: The 2DSR program can be used to study twisting action of the heart.