Developmental changes in excitation-contraction mechanisms of the mouse ventricular myocardium as revealed by functional and confocal imaging analyses.

Developmental changes in excitation-contraction mechanisms were examined in the ventricular myocardium from fetal, neonatal, and 1-, 2-, and 4-week-old mice. In isolated tissue, the negative inotropic effect of nifedipine decreased, while that of ryanodine increased with age. Action potential duration decreased with age, especially during the late fetal period. In ventricular cardiomyocytes, fluorescence imaging revealed that the sarcoplasmic reticulum increases progressively during pre- and postnatal development. t-Tubules were absent in the fetus and neonate, were observed only in the subsarcolemmal region at 1 week after birth, and were present throughout the cytoplasm at 2 and 4 weeks after birth. The amplitude of Ca(2+) transients, as well as its ryanodine-sensitive component, increased with age. In the neonate and 1-week-old mice, Ca(2+) at the cell center showed slower rise than the subsarcolemmal region, but in 2- and 4-week-old mice, Ca(2+) increased simultaneously across the entire width of the cell. These results suggest that in the mouse ventricular myocardium, the shortening of the action potential during the late fetal period and the development of t-tubule-sarcoplasmic reticulum coupling during the second postnatal week largely contribute to the developmental increase in the dependence of contraction on sarcoplasmic reticulum function.

Experimental Observations of Dual-Polarization Oscillations in Laser-Diode-Pumped Wide-Aperture Thin-Slice Nd:GdVO(4) Lasers.

Dual-polarization oscillations (DPO) on different transitions have been observed for the first time in a mirror-coated thin-slice Nd:GdVO(4) laser possessing a large fluorescence anisotropy with laser-diode (LD) pumping. Oscillation spectra, input-output characteristics, pump-dependent pattern formations and noise power spectra are studied experimentally. Simultaneous oscillations of orthogonally-polarized different (higher-order) transverse modes and the resultant violation of inherent antiphase dynamics in multimode lasers have been demonstrated. The experimental results have been explained in terms of the reduced three-dimensional cross-saturation of population inversions among orthogonally-polarized modes peculiar to LD-pumped wide-aperture anisotropic lasers, in which a pumped area is larger than a lasing beam diameter.

Chaos synchronization among orthogonally polarized emissions in a dual-polarization laser.

We report on the experimental observations of chaos synchronizations among orthogonally polarized emissions in a dual-polarization laser. With a three-mode scheme with a single mode in one polarization and two modes in orthogonal polarizations, synchronization was achieved by the cross-saturation dynamics of population inversions when one of the dual-polarized emissions was subjected to external perturbations, i.e., self-mixing modulation or optical fiber feedback. In-phase synchronization or lag synchronization among orthogonally polarized emissions was achieved depending on the degree of cross saturation in the self-mixing modulation. Synchronization of random bursting was observed in the fiber feedback, in which two chaotic-spiking modes in one polarization with anticorrelated intensity variations synchronize the remaining mode in the orthogonal polarization cooperatively with their total intensity variation. Information sender-mediator-receiver relationships among modes, which represent the dynamical roles of individual modes for establishing the observed three types of collective synchronizations, were identified in terms of an information circulation analysis.