[Neuronal NO-synthase as the molecular guard of myofiber stability. NO-dependent signaling pathways in the active and unloaded muscle].

The review is dedicated to the signaling pathways triggered by the nitric oxide II in skeletal muscle. Analysis of the current literature shows that during physical exercise of various intensity and regimen the nitric oxide is an essential trigger of the signaling pathways, leading to the alteration of the structural and metabolic myofiber profile and enhancement of its functional capacity. At the same time during the elevated muscle contractile activity (for instance, eccentric activity), NO serves as a protective and stabilizing agent, preventing from the intensification of the proteolytic processes.

[Effect of 30-day space flight and subsequent readaptation on the signaling processes in m. longissimus dorsi of mice].

Some steps of anabolic and catabolic signaling pathways were investigated in postural/tonic m. longissimus dorsi of mice following the 30-day orbital flight of biosatellite "Bion-M1" and 8-day recovery. Western blotting was used for determining insulin receptor substrate 1 (IRS-1) and AMR-activated protein kinase (AMPK) involved in reciprocal regulation of anabolic and catabolic pathways, as well as E3-ligase MURF-1, and elongation factor eEF2.

[Role of calcium-dependent mechanisms in the development of atrophy in postural muscle deprived of gravitational loading].

Downsizing of muscle fibers, decline of their contractility and alteration of the myosin phenotype towards fast isoforms prevalence are ranked among the main consequences of gravitational unloading of postural muscles. Role of Ca2+ ions in these processes is the subject of the article. Authors revealed increase in the Ca2+ content in myofibers of resting m.

[Expression of splice-variants of the insulin-like growth factor I and the condition of the cell-myosatellite pool in the rat m. soleus under conditions of gravitation relief and passive stretching].

We suggested that satellite proliferation with subsequent incorporation of their nuclei in the fibres was essential for enhancement of the protein synthesis in the rat relieved m. soleus. In passive stretch of the muscle, the number of labelled cells exceeded 2.

[Protective effect of nitric oxide on cytoskeletal proteins in skeletal muscles under eccentric exercise].

The protective effect of nitric oxide (NO) on the cytoskeletal muscle proteins desmin and dystrophin has been studied under eccentric exercise. Experiments were performed on 28 male Wistar rats, which were divided into four groups: cage control (C, n = 7); group of eccentric exercise (running down a motor-driven treadmill, inclination 16 degrees) (20 m/min, 40 min running) (R, n = 7); eccentric exercise + L-arginine group (RA, n = 7) (with a daily supplementation of 500 mg/kg wt L-arginine for 3 days before the running); and eccentric exercise + L-NAME group (RN, n = 7) (with a daily supplementation of 90 mg/kg wt L-NAME (Nomega-nitro-L-arginine methyl ester, nNOS blocker) for 3 days before the running). It was found that increasing the NO concentration (in RA group) prevents the disruption of the dystrophin layer and decreases the loss of desmin in m.

[Effects of creatine phosphokinase competitive inhibitor on system and tissue energy metabolism in rats in the norm and during unloading].

In an experiment with rats system and intracellular energy metabolism was assessed by cell reactions to chronic injection of beta-guanidine propionic acid (beta-GPA) stimulating AMP-dependent protein kinase (AMPK). Suspension was shown to inhibit the succinate dehydrogenase (SDH) activity, reduce glycogen in both types of muscle fibers, and stimulate the activity of alpha-glycerophosphate dehydrogenase (alpha-GPDH) in fast fibers. Supplementing the rat chow with beta-GPA did not modify these parameters during suspension; however, the blood urea level increased considerably in the suspended and control rats.

[The contribution of muscle progenitor cells to maintaining morphological characteristics of unweighted rat soleus muscle during passive stretch].

Skeletal muscle work hypertrophy is usually connected with muscle progenitor SC (satellite cells) activation with subsequent incorporation their nuclei into myofibers. Passive stretch of unloaded muscle was earlier established to prevent atrophic processes and be accompanied by enhanced protein synthesis. We hypothesized that elimination of SC proliferation capacity by gamma-irradiation would partly preavent stretched muscle fiber capability to maintain their size under condition of gravitational unloading.

[The cellular effects of functional unloading and passive stretch on m. soleus of dystrophin-deficient mdx mice].

Dystrophin, subsarcolemmal protein communicating muscle fiber cytoskeleton to extracellular matrix, is believed to participate in mechanical signal transduction. Recent works testify possible signaling role of this protein to prevent development ofproteolytic processes accompanying muscle fiber atrophy and to stimulate the passive stretch anabolic effects. The experiment was carried out to assess the role of dystrophin in these processes.

[Cytoskeletal proteins and heat shock proteins 27 under eccentric exercise of rats: effects of calcium L-type channel blockade].

It is known that during eccentric exercise the calcium accumulation and degradation of cytoskeletal proteins take place. This study was aimed to investigation into the role of baseline calcium accumulation in cytoskeletal degradation and the way of calcium inflow into skeletal muscle un- der conditions of eccentric exercise. Wister rats were divided into control (C), eccentric exercise (EE) (one set of downhill treadmill running (-16 degrees) at a speed of 20 m.

[Role of L-type Ca channels in Ca2+ accumulation and changes in distribution of myosin heavy chain and SERCA isoforms in rat M. soleus under gravitational unloading].

It is known that hindlimb unloading brings about the intracellular Ca2+ accumulation and MyHC slow-to-fast shift in m.soleus. SERCA (sarcoendoplasmatic reticulum Ca ATPase) function as a Ca pump to uptake to sarcoendoplasmatic reticulum after skeletal muscle contraction, and can modulate intracellular resting Ca level.

[NFATc1 and slow-to-fast shift of myosin heavy chain isoforms under functional unloading of the rat m. soleus].

It was determined whether the content of NFATc1 (nuclear factor of activation of T cells) in the nuclear and cytoplasmic extracts is related to an increase in the content of fibers containing type IIa myosin heavy chains under gravitational unloading of m. soleus. It was found that three isoforms of NFATc1 with molecular masses of 140, 110, and 86 kDa are present in m.

[Creatine as a metabolic controller of skeletal muscles structure and function in strength exercises in humans. The cellular mechanisms].

The effects of creatine oral supplementation combined with a 10-week resistive training of morphometric, contractile and molecular characteristics of human vast lateral muscle fibers were studied. 2 groups consisting of 9 young healthy men each were involved in resistive training of knee extensors for 10 weeks. Volunteers of the first group received per os 20 g of creatine for the 1st week of training and 5 g for the rest of the experimental training period.

Comparison of hypo- and hypergravity effects on skeletal muscle.

Numerous observations suggest importance of gravitational loading in regulating muscle mass. Thus, centrifugation is believed to be useful for preventing muscle functional and structural losses under microgravity conditions. The aim of the present work was to evaluate plasticity of skeletal muscle exposed to chronic hypergravity.

[Effect of long-term hypergravitation on the skeletal-muscular tissue in rats].

The space flight or simulated gravitational unloading lead to the muscle atrophy, slow-to-fast transformation of muscle fibers and myofibrillar damages both in humans and animals (1, 7, 13, 17). This process could be prevented by the exercise training during space flight (1), (partly) by periodic weight support during unloading (13). It has been demonstrated in these studies that there is some level of force production necessary for the maintenance of skeletal muscle properties.

[Human soleus fibers contractile characteristics and sarcomeric cytoskeletal proteins after gravitational unloading. Contribution of support stimulus].

The effects of support withdrawal and support stimulation on the contractile characteristics of human soleus fibers and cellular factors which influence them were studied. The experimental model of the "dry" head-out water immersion was used in the study. In this model, the hydrostatic pressure on different sites of the body surface are equal so that the experimental conditions are close to the complete supportlessness.

[Sarcomeric cytoskeletal proteins and myosin phenotype in stretched soleus of hindlimb-suspended rats].

Changes in sarcomeric cytoskeletal proteins of rat m. soleus fibers upon the chronic stretching against the background of gravitational unloading were analyzed and compared with changes in fiber size and myosin phenotype. For rats exposed to gravitational unloading in the usual microgravity-simulating experimental model (hindlimb suspension (HS) according to Morey-Holten), a considerable reduction in the mass of m.

Effects of long duration +2G hypergravity on MHC distribution and maximal tension of rat m.soleus fibers.

Effects of long duration hypergravity on skeletal muscles are much less studied than effects of microgravity. For instance, it was revealed that hypergravity of 2 week duration induces decrease in cross sectional area (CSA) of slow fibers (SF), while their size remains constant, or increases. Exposure to +2G of 14 day duration results in decreased number of type I fibers, and in changed myosin heavy chain (MHC) profiles of rat hindlimb extensor muscle.

[Contractile characteristics of single skinned rat soleus muscle fibers under gravitational load: effects of a calcium-binding agent].

Excessive intracellular calcium accumulation is believed to trigger the development of functional and structural changes in muscle fibers under microgravity conditions. The hypothesis was testified in the 14-day hindlimb suspension study with the application of a Ca(2+)-binding agent (10% EGTA). Twenty one rats were divided into 3 groups: cage controls (7), hindlimb-suspended rats that received intraperitoneal injections of saline (7), and hindlimb-suspended rats with EGTA treatment.

[Effect of deafferentation on the size and myosin phenotype of muscle fibers during stretching of rat m. soleus and gravitational unloading].

The study was purposed to evaluate the contribution of the reflectory and local components during the chronic stretch of the postural muscle to the attenuation of the unloading-induced fiber size reduction and changes in the myosin heavy chain (MHC) profile. The surgical unilateral deafferentation (dorsal rhizotomy) was used. It was shown that unilateral deafferentation didn't influence on the amelioration of unloading-induced fiber size reduction in chronically stretched soleus muscle.

Morphology changes in rat skeletal muscles after 19 day exposure to +2 G.

Effects of long duration hypergravity on m. soleus morphology characteristics are still unknown. Particularly, only one paper describes the size and myosin heavy chain profiles of rat hindlimb extensor muscle fibers after 2 weeks of +2 G exposure.

[Changes in structure and metabolism in the m. vastus lateralis in monkeys after a space flight].

Monkeys developed a significant reduction in size of the m. vastus lateralis' fast and slow fibres, the amount of protein in them remaining the same.

[Effect of weightlessness and movement restraint on structure and metabolism of M. soleus in monkeys after space flight].

After staying in real and simulated weightlessness, the most obvious changes were recorded in the "slow" tonic muscles like m. soleus, the protein loss in the fibres being greater than the loss of other components, water included.

[Structural and metabolic characteristics of m. vastus lateralis of monkeys during 30-day hypokinesia: effects of prophylactic Gz-accelerations].

Studies of m. vastus lateralis in Rhesus monkeys exposed to weightlessness on board of the Russian biosatellites showed the profound changes of the muscle structural and metabolic profile. It is known that exposure to head-down tilt berets (BR) induces the similar changes though not so pronounced.