[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]. / Izuchenie sostoianiia sokratitel'noigo apparata pri razvitii patologicheskogo protsessa v myshtsakh. V. Vliianie tsenkerovskogo nekroza i denervatsionnoi atrofii na strukturu F-aktina.

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. Zenker's necrosis retains this ability only slightly. It is supposed that both the denervation atrophy and Zenker's necrosis change the structure of F-actin.

[Effect of stretching muscle fibers on the conformation of F-actin]. / Vliianie rastiazheniia myshechnogo volokna na konformatsiiu F-aktina.

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. The changes of F-actin conformation seems to play an important role in the regulation of tension level which is developed by each cross-bridge.

[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]. / Izuchenie sostoianiia sokratitel'nogo apparata pri razvitii patologicheskogo protsessa v myshtsakh. III. Kharakter i posledovatel'nost' strukturnykh izmenenii sokratitel'nogo apparata pri tsenkerovskom nekroze.

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. During the spreading of Zenker's necrosis, the "pseudocontraction" is seen transferred first into "superrelaxation", and then into irreversible contracture and rigor. "The boundary of Zenker's necrosis" overlaps with the boundary of the self-propagating irreversible contracture. There is no proper boundary of Zenker's necrosis, because the destructive changes are observed over all the muscle fibre. Contraction nodules arise in the regions of "superrelaxation" and follow the changes of the contractile system, peculiar of contracture. The study of the influence of medium ionic composition on the development of Zenker's necrosis suggests that the arising and spreading of destruction are inseparably associated with the irreverrsible changes of intracellular membrane structures, and with the possibility of propogation of the damage signal by these structures along muscle fibres.

[Electrophoretic study of the protein makepup of the muscles in Zenker's necrosis]. / Elektroforeticheskoe issledovanie belkovogo sostava myshts pri tsenkerovskom nekroze.

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. It is suggested that similar changes of F-actin take place in thin myofilaments of living muscle fiber during the contraction-relaxation process.

[Polarized ultraviolet fluorescence microscopic study of the structural changes in muscle fiber contractile proteins. V. The possible nature of the conformational rearrangements in heavy meromyosin in fiber relaxation]. / Izuchenie strukturnykh izmenenii sokratitel'nykh belkov myshechnogo volokna s pomoshch'iu poliarizatsionnoi ul'trafioletovoi fluorestsentnoi mikroskopii. V. O vozmozhnom kharaktere konformatsionnykh perestroek tiazhelogo meromiozina pri rasslablenii volokna.

The mode and degree of tryptophanyl orientation relative to muscle fiber axes within hydrophobic and hydrophylic sites of myosin macromolecule in the presence of a fluorescence quencher (acrylamide, NO-3) during rigor and relaxation of glycerinated muscle fibers were studied using the polarized ultraviolet fluorescent microscopy. It was shown that myosin tryptophanyls both in LMM and HMM are oriented with their short axes along the longer axis of muscle fiber. Tryptophanyls in LMM have a more pronounced anisotropy of orientation in comparison with the fluorophore orientation anisotropy in hydrophobic sites of HMM. During the muscle fiber relaxation, conformational changes in HMM take place owing to which a section of polypeptide chain with a hydrophilic fluorophore is probably submerged deep into the macromolecule and becomes unapprochable to the quencher.

[Study of structural changes in muscle fiber contractile proteins using polarization ultraviolet fluorescent microscopy. IV. Several features of the conformational changes in F-actin during muscle fiber relaxation]. / Izuchenie strukturnykh izmenenii sokratitel'nykh belkov myshechnogo volokna s pomoshch'iu poliarizatsionnoi ul'trafioletovoi mikroskopii. IV. Nekotorye osobennosti konformatsionnykh perestroek F-aktina pri rasslablenii myshechnogo volokna.

Using the polarized ultraviolet fluorescent microscopy in the presence of a fluorescence quencher (acrylamide, NO3-) it has been shown that actin tryptophanyls are oriented with their short axes perpendicular to the long axis of the thin filament. Fluorophores in hardly accessible sites of the macromolecule have a more pronounced anisotrophy of orientation in comparison with those in the protein sites easily available by a fluorescence quencher. During the muscle fiber relaxation, conformational changes of F-actin take place which embrace seemingly the sites of subunits, close to the surface of macromolecule, and make difficult the penetration of univalent ions and neutral molecules deep into the protein macromolecule. Some connection between conformational changes of the surface areas of F-actin subunits and the actin incapability of combining with HMM in the presence of ATP is assumed.

[Study of structural changes of contractile muscle proteins with the aid of polarization ultraviolet fluorescence microscopy. 1. Conformational changes of F-actin in the muscle fiber caused by ATP and its analogs]. / Izuchenie strukturnykh izmenenii sokratitel'nykh belkov myshechnogo volvokna s pomoshch'iu poliarizatsionnoi ul'trafioletovoi fluorestsentn*56i mikroskopii. 1. Konformatsionnye izmeneniia F-aktina v myshechnom volokne, vyzvannye ATF i ego analogami.

Increase of anisotropy of F-actin fluorescence of balanus and rabbit muscle fibers under the influence of ATP, AMP and pyrophosphate in EGTA presence was detected by means of the polarized ultraviolet (UV) fluorescent microscopy methods. The fluorescence anisotropy changes are assumed to be associated with the conformational changes in the actin. ATP cause more noticeable changes of actin structure, than pyrophosphate and AMP. The conformational changes in the actin of balanus and rabbit muscle fibres were similar. ATP and its analogs induced also decrease of UV fluorescence anisotropy of A-band which appears to be associated with conformational changes in myosin. It was siggested that the changes in fluorescence of anisotropy of A-bands are due to structural changes in both HMM and LMM parts of myosin molecule.