[State of the contractile apparatus during the development of a pathological process in the muscles. V. The effect of Zenker's necrosis and of denervation atrophy on F-actin structure].

By means of polarized UV fluorescent microscopy, the state of F-actin was studied in single glycerinized muscle fibers from intact, locally damaged and denervated m. semi-tendinosus of the frog. It was shown that F-actin of denervated muscle fiber lost the ability to reply by increasing tryptophan fluorescence anisotropy during the fiber relaxation and its stretching in the rigor solution by 1--4 per cent compared to the original length.

[Effect of stretching muscle fibers on the conformation of F-actin].

By means of polarized UV fluorescent microscopy the conformational changes of F-actin of "ghost" glycerinated muscle fibers during the stretching 30 per cent of the resting length was found. It was observed that F-actin of the stretched fibre responds by more marked changes in their structure to ATP, glutaraldehyde and glycerin as compared to F-actin of the unstretched fibre. It was assumed that the fibre stretching changes the spatial characteristics of actin helix and increases the rigidity of thin filaments.

[State of the contractile apparatus during the development of a pathological process in the muscles. III. The nature and sequence of the structural changes in the contractile apparatus in Zenker's necrosis].

Using polarized ultraviolet (UV) fluorescence microscopy, it was shown that the local damage of muscle fibres causes in their morphologically unchanged parts the alternation of regions, being in different functional states referred to as "pseudocontraction" and "superrelaxation". The pattern of UV fluorescence anisotropy suggests that conformation of contractile proteins by "pseudocontraction" is similar to that at contraction, though changes in sarcomere length do not occur. The "superrelaxation" is characterized by a desorganization of myofilaments.

[Electrophoretic study of the protein makepup of the muscles in Zenker's necrosis].

Changes of protein composition within necrotic areas of muscle at the late stages of Zenker's necrosis (3--5 hours after damage) have been studied using the disc-DSN-electrophoresis method. These changes are presumably associated with a disarrangement of the structure of thick and thin fillaments. The disturbance of the contractile system is accompanied by the loss of water soluble protein specific fractions.

Studies on conformational changes in F-actin of glycerinated muscle fibers during relaxation by means of polarized ultraviolet fluorescence microscopy.

By means of polarized ultraviolet fluorescence microscopy the conformational changes of F-actin occuring in glycerinated muscle fibers of rabbit and barnacle (Balanus rostratus Hock.) under the influence of adenosine triphosphate in the presence of ethylene glycol bis(beta-amino-ethyl ether)-N,N'-tetraacetic acid were discovered. These changes seem to be located near the surface of the globules thus hampering the penetration of univalent iones and neutral molecules into the F-actin macromolecule.