DIFFERENTIAL EFFECTS OF OSMOTIC COMPRESSION ON MYOFLIAMENT LATTICE STRUCTURES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Skinned muscle fibers have been used extensively for structure-function of muscle contraction. Methods of osmotic compression have been used to return the otherwise swollen skinned fibers to in vivo size (Kawai et al., 1993; Chinn et al., 2000). Complicating the issue, osmotic agents can affect internal structures differentially, thereby confounding the interpretation of structural and kinetic data. Dextran T500 (the agent used in most skinned fiber studies), for example, does not permeate the myofilament lattice, while Dextran T10 or PEG 4000 does. The former compresses the lattice and, presumably, the filaments within, whereas the latter do permeate the lattice and therefore compress the filaments but not the filament lattice. The objectives of the proposed experiments are to understand the range of structural effects at the lattice and filament levels resulting from osmotic compression of muscle fibers. We will also determine the differential changes in spacing, diameter, and mass ratio between thick and thin filaments as a function of compressive pressure. The results of the experiments will provide a structural basis for interpreting past and future functional studies investigating effects of osmotic compression on kinetic properties of muscle. (Experiments will be done March 2006)