[Morpho-functional changes in the frog sartorius muscle fibers during the winter]. / Morfo-funktsional'nye izmeneniia volokon portniazhnoi myshtsy liagushki v zimnii period.

The electrical characteristics, sensitivity to acetylcholine, structure of nerve terminals and SDH activity were studied in the fibers of frog's m. sartorius in winter and summer. The resting MP of muscle fibers remains unchanged through the year but passive electrical characteristics of muscle electrogenic membrane were changed. Sensitivity to acetylcholine increased two-fold in winter. Silver method revealed some degenerative signs in the neuro-muscular junctions during winter.

[Changes in the properties of fast and slow rat muscles following cross-reinnervation]. / Izmenenie svoistv bystroi i medlennoi myshts krysy pri perekrestnoi reinnervatsii.

Qualitative and quantitative histochemical and morphometrical studies in intact white and red muscles of Wistar rats revealed different types of cross-section areas, LDH isozymes spectra of muscle fibers, number of nuclei in neuro-muscle junction. Conformation of red muscle to white and partial conversion of white muscle to red occurred after cross-innervation, and alien white fibers appeared in the m. soleus. Activity of LDH3 and LDH4+5 isozymes of heart type spectrum increased after cross-innervation of the m. soleus. An increase in activity of LDH1 and LDH2 isozymes of muscle type spectrum accurred after cross-innervation of white muscle.

[Morphometric and cytochemical parameters of skeletal muscle during long-term physical exertion]. / Morfometricheskie i tsitokhimicheskie pokazateli skeltnoi myshtsy pri dlitel'noi fizicheskoi nagruzke.

Daily swimming for 40 days increased weight of the fast (gastrocnemius) and slow (soleus) muscles in white rats and altered the size of plane section and the relative amount of different fibers in the muscles. The slow muscle developed an anaerobic spectrum of lactatdehydrogenase isoenzymes characteristic of an intact fast muscle, whereas the fast muscle intensified its specific "muscular" spectrum of isoenzymes. By the 40th day the parameters under study tended to normalize.

[Morphometric and histochemical characteristics of the frog sartorius muscle in ontogeny]. / Morfometricheskaia i gistokhimicheskaia kharakteristika portniazhnoi myshtsy liagushki v ontogeneze.

Morphometric and histochemical investigation of musculus sartorius was performed in ontogenesis in Rana ridibunda and Rana temporaria. Muscular composition was characterized according to the type of muscular fibres. Spectrum of lactatdehydrogenase isoenzymes was studied at different developmental stages. As the studies demonstrated, musculus sartorius underwent some essential changes in ontogenesis which manifested themselves in increasing number of muscular fibres and their areas, in changing LDG isoenzymic spectrum. Differentiation of the muscular fibres three types takes place at the 30th stage after P. V. Terentiev and depends on the nerve system maturation.

[Lactate dehydrogenase isoenzyme activity of a fragment of the soleus muscle transplanted into the anterior chamber of the eye]. / Aktivnost' izofermentov laktatdegidrogenazy transplantirovannogo v peredniuiu kameru glaza fragmenta kambalovidnoi myshtsy.

The equal relative content of LDH H and M subunits has been detected in the soleus muscle of the rat anterior eye chamber. M subunit prevalence over H subunit was revealed after transplantation of the muscle with a spinal cord segment. It is suggested that nervous system controls differential expression of LDH subunits.

[Effect of thyroxine on the phenotype of intact and denervated skeletal muscles in the guinea pig]. / Vliianie tiroksina na fenotip intaktnykh i denervirovannykh skeletnykh myshts morskoi svinki.

Denervation of the guinea-pig fast (m. plantaris) and slow (m. soleus) muscles, administration of alpha-thyroxine (T4) to animals followed by denervation and T4 injection entail changes in the relative content of different types of muscle fibers. The slow muscle shows fast muscle fibers after T4 injection, denervation and T4 injection. Moreover, myosin isolated from the m. soleus shows the precipitation band with antibodies to fast muscle myosin. These data attest to partial reprogramming of myosin synthesis by the m. soleus, pointing to the role played by thyroxine in myosin synthesis regulation.

[Effect of hormonal and neurotrophic factors on the expression of fast myosin in slow muscle]. / Vliianie gormonal'nogo i neirotrofichestkogo faktorov na ékspressiiu miozina bystrogo tipa v medlennoi myshtse.

Myosin ATPase and succinic dehydrogenase activity and fast myosin (indirect immunochemical test) were assayed in m. soleus of guinea-pigs after the administration of T4 (200 micrograms/kg) to animals every day for 3 weeks. This was followed by the application of 10 mM colchicine solution to sciatic nerve for 6 min. Fast muscle fibers and the line of precipitation with antiserum to fast myosin were revealed in soleus muscle of experimental animals after the application of colchicine and T4 injection.

[Differentiation of the sartorius muscle during frog ontogeny]. / Differentsirovka portniazhnoi myshtsy liagushki v ontogeneze.

Stages of morphological differentiation of muscular fibres in the musculus sartorius were studied at light optic and electron microscopic levels on tadpoles and mature frogs (Rana ridibunda). Three stages were detected in the development of the muscle--stage of mature myotubes, stage of young and mature fibres. At the 29th stage of development, the sarcomere length is statistically greater, at subsequent stages it is smaller and does not practically differ from that of mature animals. The T-tubes thickness and the A-discs width in the tadpole muscular fibres at different stages of development and those of mature animals do not differ statistically. Muscular differentiation and acquirement of features peculiar for mature animals continue after metamorphosis is completed.

[Histo- and biochemical characteristics of rat skeletal muscle after prolonged static loading]. / Gisto- i biokhimicheskaia kharakteristika skeletnykh myshts krys posle dlitel'noi staticheskoi nagruzki.

For 100 days the rats were kept in vertical position, and after histo- and biochemical characteristics of the musc. gastrocnemius (fast) and musc. soleus (slow) were studied. A prolonged static loading was stated to produce increasing number of white and intermediate fibres in the m. gastrocnemius and intermediate fibres in the m. soleus. The fast and slow muscles reacted differently to the static loading; this was evident from a decreased content of glycogen in muscle fibers. A statistically important decrease in lactate dehydrogenase (LDH) activity in blood serum and the m. gastrocnemius was found, while in the m. soleus its level remained unchanged. It was found for certain that lactic acid content increased in the muscles studied, and its content did not change in blood serum. As to pyruvic acid content, it increased in blood serum, decreased in the m, gastrocnemius and did not differ from the control in the m. soleus. In the m. gastrocnemius an increased activity of slowly migrating LDH isoenzymes was noted, while in the m. soleus--that of fast migrating ones. At a prolonged static loading there was normalization in histo- and biochemical characteristics as it is at the dynamic loading.

[Lactate dehydrogenase isoenzyme spectrum of fast and slow muscles with innervation disorders]. / Izuchenie spektra izofermentov laktatdegidrogenazy bystroi i medlennoi myshts pri narushenii innervatsii.

A relative content of muscle fibers of various types and the spectrum of lactate dehydrogenase (LDH) isozymes were studied in fast-twitch (extensor digitorum longus) and slow-twitch (soleus) muscles of newborn rats, of those aged 2, 3 weeks and one month and of adult rats after neonatal sciatic denervation and application of 0.5 mM colchicine solution to the sciatic nerve. No muscle fibers of various types were found (from the level of succinate dehydrogenase activity) in one-month-old rats, whereas the control and fast-twitch muscles showed A, B and C types and the slow-twitch one B and C types. The denervation brought about an increase in the content of LDH4 and LDH5 in both the muscles, while colchicine application gave rise to an increase in LDH2 activity, diminution of LDH1 in the fast-twitch muscle and elevation of LDH4 in the slow-twitch one. The data obtained attest to the retardation of muscle differentiation under application of the colchicine-induced blockade of axoplasmic transport.

[Morphologic and morphometric characteristics of rat skeletal muscles following prolonged static loading]. / Morfologicheskaia i morfometricheskaia kharakteristika skeletnykh myshts krys posle dlitel'noistaticheskoi nagruzki.

Musculus gastrocnemius and m. soleus in Wistar rats have been studied at a prolonged static loading. The static loading does not produce any changes in the animals' body mass and in m. gastrocnemius, while the mass of m. soleus statistically differs after the experiment. There are some changes in relative amount of muscle fibres: in m. gastrocnemius the number of white muscle fibres increases, and the number of red muscle fibres decreases, in m. soleus the number of intermediate muscle fibres increases. In m. gastrocnemius of the test animals the transversal section areas of white and intermediate muscle fibres statistically decrease, and in m. soleus the transversal section areas of both muscle fibre types increase. Examination of semi-thin and celloidin sections demonstrate fibre-targets, fibres with centrally situated nuclei, partly splitting fibres and fibres of small diameter, their number reaching 4.3% of the whole number of fibres. Possible mechanisms for muscle fibre formation are discussed.

[Effect of trivalent iron on denervated skeletal muscles]. / Vliianie trekhvalentnogo zheleza na denervirovannye skeletnye myshtsy.

The activity of succinic dehydrogenase, myosin ATPase, as well as lactic dehydrogenase (LDG) spectrum and cross-section area of different type of muscle fibers have been studied for 3 weeks after denervation (control) and after denervation and intraperitoneal injection of 10(-6) M FeCl3. Intraperitoneal injection of FeCl3 prevented the development of denervation phenomena (increase in cross-section area of muscle fibers, changes in LDG spectrum).

[Effect of thyroidectomy on the histochemical and electrophysiological properties of the soleus muscle in rats]. / Vliianie tireoidéktomii na gistokhimicheskie i élektrofiziologiches-kie svoistva kambalovidnoi myshtsy krysy.

In the musculus soleus of mature male rats, 6 weeks after thyroidectomy, muscle fibers with a low adenosin triphosphatase activity of myosin decrease in number, as well as the cross section area of the muscle fibers with a moderate and high activity of the enzyme. Optic density of the muscle fibers staining also decreases when succinatedehydrogenase activity is determined histochemically. There is no change in the rest membrane potential and in the character of the muscle fiber membrane sensitivity to acetylcholine. The change in the muscle fiber histochemical properties is combined with chromatolysis in the motor neurons of the spinal cord ventral horns.

[Ultrastructure of rat skeletal muscle fibers during prolonged static loading]. / Ul'trastruktura skeletnykh myshechnykh volokon krys pri dlitel'noi staticheskoi nagruzke.

Ultrastructural characteristics of the rat skeletal muscle fibers was studied under a prolonged static loading. Disruption of the mitochondrial membranes, desintegration and lysis of myofibrils, desorganization of the T-system and Z-bands were revealed. Destructive processes were accompanied with the physiological reparative regeneration evidenced by a large number of polysomes and accumulation of myofibrils at the peripheral zone of the muscle fibre. The satellite cells with poorly developed organells were revealed in cytoplasm. Mitotic figures were present in the satellite cells. Clusters of the satellite cells were revealed in the interstitial connective tissue with their successive differentiation into mature muscle fibres. Possible mechanisms of the skeletal muscle fibre formation were discussed.

[Electrophysiologic, morphometric and histocytochemical characteristics of frog sartorius muscle fibers]. / Elektrofiziologicheskaia, morfometricheskaia i gistokhimicheskaia kharakteristika myshechnykh volokon portniazhnoi myshtsy liagushki.

Three groups of muscle fibers (dark, light, and intermediate) were revealed in the fibers of the frog sartorius muscle in examination of the succinate dehydrogenase (SDH) activity. There was revealed a reverse relationship between the diameter of the muscle fibers an the SDH activity in them. The external surface of sartorius muscle is chiefly represented by dark muscle fibers, whereas the internal one--by light ones. Microelectrode study demonstrated that the fibers of the external surface were characterized, in comparison with those of the internal one, by lesser action potentials, prolonged trace negative potential, low quant composition of the end plate potentials, high amplitude and low frequency of the end plate miniature potentials. Analysis of the data obtained demonstrated definite interrelationship between the histochemical profile of the muscle fibers of the frog sartorius muscle and their electrophysiological characteristics.