Green Tea Extract Increases the Expression of Genes Responsible for Regulation of Calcium Balance in Rat Slow-Twitch Muscles under Conditions of Exhausting Exercise.

We studied the role of calcium-regulating structures of slow- (m. soleus, SOL) and fast-twitch (m. extensor digitorum longus, EDL) skeletal muscles of rats during adaptation to exhausting physical activity and the possibility of modulating this adaptation with decaffeinated green tea extract. It was established that EDL adaptation is mainly aimed at Са2+ elimination from the sarcoplasm by Са-ATPase and its retention in the reticulum by calsequestrin. Administration of green tea extract increased endurance due to involvement of slow-twitch muscles whose adaptation is associated with enhanced expression of all the studied genes responsible for the regulation of Ca2+ balance.

[TRANSFORMATION OF INDIVIDUAL CONTRACTILE RESPONSES DURING TETANUS IN FAST AND SLOW RAT SKELETAL MUSCLES].

The last contractile responses (LCRN), where N is the number of individual contractile responses within tetanus, were separated from the integral tetanic responses of fast, m. Extensor digitorum longus (m. EDL), and slow, m. Soleus, rat muscles using a computer-graphic technique. The average amplitude of LCR5 in m. Soleus at a 20 Hz stimulation rate decreased to 64 ± 9 % re the amplitude of a single contraction. As N was increasing, a restoration of LCRN was observed with their subsequent rise to values almost twofold exceeding the initial single contractile responses of that muscle (up to 211 ± 10 % for LCR50). Simultaneously, against the background of rise of individual contractile responses of these muscles, a considerable shortening of their half-life time (to ≈ 50%) and formation of a stationary plateau within LCRN were observed. In m. EDL at a 50 Hz stimulation rate only single-phase rise of LCRN was observed (up to 165 ± 18% for LCR50) without change of their half-life time and plateau formation. After the end of tetanic responses in muscles of both types a prolonged (up to 30 s) "hyper-relaxation effect was shown to develop manifested as a decrease of muscle tension with its subsequent restoration to the initial values. Possible mechanisms of these effects are discussed. It is supposed that transformation of individual contractile responses in skeletal muscles may be executed at the expense of specialized microdomains in muscle fibers regulating accumulation and extrusion levels of Ca2+ ions during tetanic activity. The possible involvement of an additional, Ca(2+)-induced Ca2+ release (CICR), in the basic, depolarization-induced Ca2+ release (DICR), is analyzed.

[PROPERTIES OF INDIVIDUAL CONTRACTILE RESPONSES WITHIN TETANUS OF RAT SLOW MUSCLE UNDER CONDITIONS OF MODULATION OF SARCOPLASMIC RETICULUM Ca²âº RELEASE].

During direct stimulation of m. Soleus by trains of 5, 10 and 50 stimuli with a frequency of 20 Hz in control experiments (n = 16) a biphasic change was observed in the amplitude of the last contractile responses (LCRN) depending on N, where N is the number of individual contractile responses within the te- tanus. Thus, an initial decrease of LCRN amplitude (up to 54 ± 8 % for LCR5) was replaced by their subsequent growth (up 218 ± 14 % for LCR5o) associated with a significant shortening of their half-relaxation time relative to the initial response (to 44 ± 8 % for LCR50). Caffeine at concentrations of 5 mM (n = 6) and 10 mM (n = 4), at the background of developing characteristic stationary contracture respon- ses, increased LCR5 depression during the initial inhibitory phase (31 ± 8 % and 15 ± 4 %, respectively). The subsequent growth of LCRN amplitude was significantly lower than in the control (114 ± 18 % and 46 ± 9 % for LCR50 at 5 and 10 mM caffeine, respectively). LCR50 half-relaxation time during the action of both caffeine concentrations remained still considerably shorter than the individual responses recorded both in the presence of caffeine and in control. In contrast to the control and caffeine effects, LCR5 and 10 (to 143 ± 14 %) than was observed in the control muscle. Additionally, dantrolene enhanced muscle relaxation at rest. Caffeine (10 mM), at the background of dantrolene, restored the dynamics of changes of amplitude time characteristics of the last contractile responses to values close to the control. The time-amplitude characteristics of the extracellular AP recorded in individual muscle fibers in m. Soleus did not change significantly during tetanic stimulation under protocol similar to that used for mechanografical experiments. These data can be interpreted to support the previously suggested theory about the participation of <> as an additional mechanism of excitation-contraction coupling in skeletal muscle under conditions of tetanic stimulation [1, 2].

[Effect of insulin on characteristics of contractile responses of fast and slow skeletal muscles of rats with streptozotocin-induced overt diabetes].

Comparison of amplitude-time characteristics of fast (m. EDL) muscles in rats with acute model of streptozotocin diabetes (SD) (12 and 30 days after treatment with streptozotocin) did not reveal significant changes in strength of single normalized contractile responses as compared with control. In slow (m. Soleus) muscles of rats with the 30-day SD there were observed essential changes in amplitude-time characteristics of such contractile responses: a decrease of their amplitude and an increase of duration. In diabetic rats treated with a course of insulin, resistance of skeletal muscles to both types of exogenous insulin is developing. Both in control and in diabetic animals the fatiguing stimulation of m. EDL by firing from 5 impulses did not reveal significant differences at early (up to 3 min) terms of development of fatigue. Under similar conditions, fatigue of m. Soleus in rats of both diabetic groups developed significantly faster as compared with control (as early as 30 s after the beginning of stimulation). Insulin at a concentration of 5-1 nM produced a dose-dependent decrease of amplitude of single contractile responses in fast and slow muscles of rats with the acute SD model (the negative inotropic action). The same effect of insulin, but at the higher concentrations, we demonstrated earlier in health rats. Insulin at a concentration of 10 nM did not produce essential effect on the time course of depression of responses in the course of development of fatigue at tetanic stimulation of m. EDL and m. Soleus both in control and in diabetic rats, but affected essentially the time course of change in duration of the half-decline (T(hd)) of their tetanic responses. The presence of insulin in the bath solution led to stabilization of the muscle relaxation period in the course of development fatigue in all studied animal groups.

[Action of insulin on contraction and electrical responses of rat skeletal muscle].

The effect of insulin on contractility of directly stimulated skeletal muscles was studied in experiments in isolated preparations of rat fast, extensor digitorum longus (m. EDL), slow, soleus (m. SOL) and mixed, diaphragm muscles. In addition (diaphragm only) characteristics of extracellularly recorded muscle fiber action potentials (APs) were evaluated before and after addition of insulin to a bath solution. Insulin (0.5-10 nM) decreased muscle twitch force. This negative inotropic effect of insulin was dose-dependent, with m. SOL appearing to be more sensitive to insulin than either m. EDL or diaphragm. Insulin did not affect strength of isotonic KCL- or caffeine-induced muscle contractures, but decreased second and increased first and third phases of extracellularly recorded muscle fiber APs. The analysis of the data obtained in this study and the data from the literature suggests changes in electrogenesis of the muscle fiber's t-tubular plasma membrane as a key element of the negative inotropic effect of the hormone on contractility of mammalian skeletal musculature. Possible mechanisms of such putative changes are discussed.

[Morphogenesis and ultrastructure of basidiomycetes Agaricus and Pleurotus mitochondria].

Mitochondrial morphogenesis in 31 strains of 9 species of Agaricus--A. arvensis Schaeff., A. bisporus (Lange) Imbach, A. bitorquis (Quel.) Sacc., A. campestris L., A. excellens (F. H. Moller) F. H. Moller, A. macrocarpus (F. H. Möller) F. H. Möller, A. silvaticus Schaeff., A. silvicola (Vittad.) Peck, A. xanthodermus Genev--and 2 strains of Pleurotus--P. ostreatus (Jacg.) P. Kumm., P. pulmonarius (Fr.) Quel.--has many common features in mitochondria distribution under favorable growth conditions (type 1) and in reconstruction of chondriom (fission or fragmentation) under unfavorable growth conditions and aging (type 2). The first type of mitochondria distribution was observed in heterokaryotic mycelium of some Agaricus strains and Pleurotus grown in agar medium during 7-14 days, and also in submerged mycelium of some Agaricus strains and Pleurotus. The second type of mitochondria distribution was observed in homokaryotic Agaricus strains under condition of starvation, in aging mycelium (28 days of growth), and in submerged mycelium of most of Agaricus strains. The first type of chondriom consists of small granular mitochondria in the apical cells and long snake-like network in subapical cells, and restores almost completely the mitochondrial network in the aging mycelium cells. The second type of chondriom consists of small granular mitochondria in all cells of mycelium. The surface of chondriom type 2 mitochondrial membrane was usually closely associated with ribosomes and changed crists. Such mycelium cells in A. bisporus strain Bs94 were TUNEL positive. So, the types of mitochondria morphogenesis in the Agaricus and Pleurotus mycelium cells are similar at different time and growth conditions and depend on complex of physiological and biochemical process in the mycelium cells.