Rapid measurement of isolated cardiac muscle cell length using a line-scan camera.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
L M Delbridge
Publications and source records attributed to L M Delbridge.
Heterogeneity of the action potential in isolated rat ventricular myocytes and tissue.
The objectives of this study were to measure action potential parameters in enzyme-dissociated, adult rat ventricular myocytes stimulated at 1 Hz, to compare these measurements with those obtained from intact ventricular tissue, and to determine myocyte and tissue responses at stimulus frequencies between 0.1 and 5 Hz. Action potentials were characterized in terms of amplitude, overshoot, resting potential, duration at 25% and 75% repolarization (APD25, APD75), and Vmax. Based on statistical differences in APD25 and APD75, myocyte action potentials were classified as type I (3.1 +/- 1.0 and 21.5 +/- 3.6 msec), type II (7.4 +/- 1.1 and 38.2 +/- 6.7 msec), or type III (14.5 +/- 1.9 and 46.0 +/- 4.1 msec). Action potentials corresponding to type I were found in right ventricular endocardium and right papillary muscles, and those corresponding to types II and III in the left ventricular endocardium [apex, middle (II); base (III)] and left papillary muscles (II). Myocytes and papillary muscles responded to increases in driving rate with nearly identical lengthening of APD25 and shortening of APD75. The one exception was at 5 Hz where a lengthening of the APD75 occurred in some myocytes. We conclude that action potential configuration in rat ventricle is heterogeneous, and that this is reflected by the different types of action potentials in isolated myocytes. It is likely that the magnitude of a transient outward current is a determinant of action potential configuration, and that slow reactivation of this current is a significant factor underlying the stimulus frequency response.
Action Potentials↗
An ultrastructural investigation into the size dependency of contractility of isolated cardiac muscle.
The maximal stress (force per cross-sectional area), maximal rate of stress development, and cross-sectional area of 30 rabbit right ventricular papillary muscles were measured. Both mechanical parameters declined with increasing muscle size (the stress-area relation). Three large and three small muscles were fixed for electronmicroscopy. Stereological analyses of these six muscles were undertaken to test the hypothesis that the stress-area relation is caused by differences in the relative proportions of mitochondria and contractile matrix between muscles of large and small cross-sectional area. No difference in the proportion of these two cytoplasmic components was found. Other possible explanations underlying the stress-area relation are discussed.
Animals↗