The major events leading to the activation of a skeletal muscle have been worked out, but there are further details that are important to know if one is to understand this system fully.
The aims of the present proposal are to study some of the excitation-contraction (e-c) coupling steps not well-defined yet, and some mechanisms by which they are controlled. These are: I. The mechanisms that produce mechanical fatigue. We would like to determine in fatigue fibers: the depth and rate of propagation of the T-tubule action potential, the differences in the ability of action potentials and steady-state depolarizations to release Ca ions, the duration of the active state and the twitch-tetanus tension ratio, and changes in fiber capacitance. II. The influence of extracellular and intracellular pH (pHe and pHi) on the contractility.
Our aim i s to determine the effect of low pHe with non-penetrating buffers on: the twitch and tetanic forces, the Ca ions release from the SR and the actomyozin interaction, the contractility at 3 degrees C, pHi in the above conditions, and the action potential characteristics at low pHe. III. Intracellular ionic movement analysis during mechanical activation with electron probe techniques.
Our aim i s first to obtain better resolution Ca X-ray maps in muscles in which K has been replaced with Rb, then to measure: the changes in the composition of terminal cisternae during the early phase of activation when the SR calcium pump has been reduced, the subcellular distribution of Ca ions in muscle following the contraction and the maximal amount of Ca released at 3 degrees C through either tetanus or K-contractures.
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| Rasgado-Flores, H; Gonzalez-Serratos, H; DeSantiago, J (1994) Extracellular Mg(2+)-dependent Na+, K+, and Cl- efflux in squid giant axons. Am J Physiol 266:C1112-7 |
| Rozycka, M; Gonzalez-Serratos, H; Goldman, W (1993) Non-homogeneous Ca release in isolated frog skeletal muscle fibres. J Muscle Res Cell Motil 14:527-32 |
| Perreault, C L; Gonzalez-Serratos, H; Litwin, S E et al. (1992) A chemical method for intracellular loading of the calcium indicator aequorin in mammalian skeletal muscle. Proc Soc Exp Biol Med 199:178-82 |
| Garcia, M C; Gonzalez-Serratos, H; Morgan, J P et al. (1991) Differential activation of myofibrils during fatigue in phasic skeletal muscle cells. J Muscle Res Cell Motil 12:412-24 |
| Castillo, E; Gonzalez-Serratos, H; Rasgado-Flores, H et al. (1991) Na-Ca exchange studies in frog phasic muscle cells. Ann N Y Acad Sci 639:554-7 |
| Gonzalez-Serratos, H; Rasgado-Flores, H (1990) Extracellular magnesium-dependent sodium efflux in squid giant axons. Am J Physiol 259:C541-8 |
| Lundblad, A; Gonzalez-Serratos, H; Inesi, G et al. (1986) Patterns of sarcomere activation, temperature dependence, and effect of ryanodine in chemically skinned cardiac fibers. J Gen Physiol 87:885-905 |
| Alvarez-Leefmans, F J; Gamino, S M; Giraldez, F et al. (1986) Intracellular free magnesium in frog skeletal muscle fibres measured with ion-selective micro-electrodes. J Physiol 378:461-83 |
| Somlyo, A V; McClellan, G; Gonzalez-Serratos, H et al. (1985) Electron probe X-ray microanalysis of post-tetanic Ca2+ and Mg2+ movements across the sarcoplasmic reticulum in situ. J Biol Chem 260:6801-7 |
