Search

Purpose: This study was to investigate the effect of high-intensity intermittent training (HITT) under normobaric hypoxic conditions on mitochondrial biogenesis and fission/fusion-related protein expressions in rat gastrocnemius muscle. Methods: Five-week-old Wistar male rats (n = 24) were randonily assigned to sedentary or training groups under normobaric normoxic (20.9% O2) and hypoxic (14,5% O2) conditions. The training groups in both conditions were engaged in HHT on the treadmill for 9 weeks. From the 4111 week of the training period. the groups assigned to hypoxic conditions were exposed to normobaric hypoxia. Results: Hypoxic training enhanced citrate synthase activity as well as the protein levels of PGC- 1 a and the mitochondrial respiratory chain complex in the gastrocnemius muscle, when compared to the other 3 groups. Moreover, hypoxic training also elevated the level of expression of mitochondrial fusion-related protein (OPA 1 ) compared to the other groups. Discussion: 1-HIT under not-mobaric hypoxia improved the oxidative capacity of rat gastrocnemius muscles, possibly by increasing the expression of mitochondrial biogenesis and dynamics-related proteins. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effects of combined circuit training on muscle size and peak oxygen uptake for elderly women. Methods: Twelve elderly women were divided into either a low-intensity aerobic exercise group (LOW-Ex) or a high-intensity aerobic exercise group (HIGH-Ex) in random order. Participants performed a combined circuit training consisting of resistance exercise and walking, 3 days per week for 8 weeks. Lower body resistance exercises were based on body mass and upper body resistance exercises performed using an elastic tube. Both groups carried out the same resistance exercise program. Between these resistance exercises, LOW-Ex group performed 40 seconds walking at the previously-determined speed equivalent to 55% VO2peak, whereas HIGH-Ex group performed 30 seconds walking at 75% VO2peak. Results: Body-mass based resistance exercises significantly increased muscle thickness in the anterior aspect of thigh and the relative change was negatively correlated to the absolute value at pre-intervention. Isokinetic knee extension strength also improved by body-mass based resistance exercises and the relative change was negatively correlated to the relative value of isokinetic knee strength to body mass at pre-intervention. Furthermore, two-way repeated measures ANOVA showed that a significant group x time interaction existed in V02peak. V02peak increased only for HIGH-Ex group. [ABSTRACT FROM AUTHOR]

Purpose: This study was performed to investigate the effects of icing or heat stress on the regeneration of injured rat skeletal muscles. Methods: To induce muscle injury, bupivacaine (BPVC) was injected into soleus muscles of both legs of male Wistar strain rats (9-week-old). Icing (with ice pack, 20 min) was performed immediately after injury. Heat stress (42°C, 30min) was applied 2 days after injury and every other day up to a maximum of 2 weeks during the following recovery periods. Soleus muscle were removed 3 days and 1, 2 and 4 weeks after injury and analyzed by histochemical and biochemical procedures. Results and Discussion: Four weeks after injury, the relative wet weight and protein content of soleus muscle in the heat stress group recovered to control level, but not in BPVC and icing groups. Icing delayed the timing of the reduction in TGF-ß expression and promoted the increase in fibrotic area. However, heat stress induced the early recovery of heat shock protein 72 expression, delayed the timing of the reduction in satellite cell number, and inhibited the increase in fibrotic area. Our data suggest that muscle regeneration after BPVC injection could be promoted by heat stress, but inhibited by icing. [ABSTRACT FROM AUTHOR]

Introduction: This study compared the distribution of the α-actinin-3 (ACTN3) gene R577X polymorphism between Japanese recreational cyclists and untrained adults. Methods: Forty-nine recreational cyclists (age, 41 ± 11 y) and thirty-eight untrained adults (age, 43 ± 13 y) participated in this study and metabolic syndrome risk factors were measured by blood samples. Genomic DNA was prepared from blood samples. The ACTN3 R577X polymorphism was genotyped using real-time polymerase chain reaction assays with TaqMan probes and a sequence detector. Twelve relational cyclists in them performed a maximal incremental cycling exercise test to determine their maximal oxygen uptake (V02) and the lactate threshold (LT) test Results: There was no statistical difference in genotypes (RR, RX, XX) frequencies between recreational cyclists (14, 57, 29%) and untrained adults (20, 35, 22%). In the V02, LT and blood makers, there were no differences among the genotypes in recreational cyclist. Conclusion: The results of this study suggest that the ACTN3 genotype does not affect their aerobic capacity and metabolic syndrome risk factors in Japaneserecreational cyclists. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effect of intermittent reloading with heat stress on autolysis of calpain 1 and 2 in atrophied rat soleus muscle Methods: Forty male Wistar rats (10wks of age, 261. 7± 1.17 g) were randomly divided into four groups: control (CON, n=1O), hindlimb unloading (HU, n=1O), hindlimb unloading with intermittent reloading (IR, n=1O), hindlimb unloading with intermittent reloading and heat stress (IR+H, n=1O). The HU, IR and IR+H group were unloaded for 7 days. IR and IR+H group were released from unweighting for 1 h every second day. During this time, IR+H group was placed in a heat chamber for 30 min (41.5-42°C). After 7days unloading, soleus muscle were removed and analyzed. Results and Discussions: Seven-days unloading resulted in a 31% reduction in the soleus muscle mass, but only IR+H significantly prevented the reduction (CON; 168.2±6.7, HU; 116.3±3.7, IR; 121.0±3.7, IR+H; 131.1±2.4 mg). Autolyzed form of calpain 2 (HU; 267, IR; 236 and IR+H; 105% of CON) and ubiquitinated protein (HU; 164, IR; 140 and IR+H; 112% of CON) in particulate fraction was significantly increased in HU, but also IR+H significantly prevented the increase. Calpain plays a role in a release of myofibrillar protein from the sarcomere, and the released proteins are degradated by ubiquitin-proteasome system. Therefore, these data indicate that inhibition of calpain autolysis by the intermittent reloading with heat stress could be effective to prevent the muscle atrophy. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effects of 12-h of mechanical ventilation (MV) on fibertype-specific expression of alpha-actinin3 protein in rat diaphragm. Methods: Adult Wistar rats were randomly divided into either a control (n=8) or a 12-h of MV (n=8) group. Mechanically ventilated animals were anesthetized, tracheostomized, and ventilated with 21% 0 2 for 12 hours. The carotid artery was cannulated for measurement of arterial blood pressure, pH, and blood gases. The jugular vein was also cannulated for the infusion of saline and pentobarbital. Animals in the control group were acutely anesthetized but were not exposed to MV. After the treatment, diaphragms were removed and immunohistochemical detection of muscle fiber type (Type I, Type Ila and Type Ilx+b) and alpha-actinin3 expression were performed. Results and Discussion: MV resulted in a decrease of the cross-sectional area (CSA) by 16.5% (P < 0.05) and area percentage in Type Ilx+b fiber (P < 0.05). Fiber composition was not changed after MV. There was no alpha-actinin3 positive Type I fiber in all animals. In contrast, alpha-actinin3 expressed in all Type Ilx+b fibers. Interestingly, alpha-actinin3 expression was observed in 14% of Type Ila fibers, and this percentage did not change regardless of MV. Our results demonstrated that 1) selective atrophy of the Type Ilx+b fiber was caused by 12-h of MV in rat diaphragm, and 2) expression pattern of alpha-actinin3 protein was not affected by 12-h ofMV [ABSTRACT FROM AUTHOR]

Purpose: High-intensity resistance training generally reduces central arterial compliance in young subjects. However, the effect of low-intensity resistance training with blood flow restriction (BFR) on carotid arterial compliance has not yet been explored. We investigated the effect of differences in exercise intensity of resistance training on carotid arterial compliance. Methods: Nineteen healthy young men, aged 22-32 years, were randomly divided into either low-intensity resistance training with BFR group (LT-BFR; 30%1RM, 4 sets, 75 reps [30-15-15-15]) or high-intensity resistance training group (HT; 75%1RM, 3 sets, 30 reps [10-10-10]). They performed free weight bench press exercise, 3 days per week, for 6 weeks. The LT-BFR group wore pressure cuff belts on both arms during training (external compression: 160mrnHg). Results&Discussion: MRI-measured pectoralis major muscle cross-sectional area and 1RM bench press strength significantly increased in both training groups after the training (p<0.05). Carotid arterial compliance was reduced (p<0.05) in only the HT group. Systolic blood pressure in thigh during exercise significantly were higher for HT group than LT-BFR group (p<0.05). The present study suggested that low-intensity resistance training with blood flow restriction does not influence carotid arterial compliance. [ABSTRACT FROM AUTHOR]

The alpha-actinin is actin-binding protein. In skeletal muscle, alpha-actinins-2 (ACTN2) and alpha-actinins-3 (ACTN3) isoforms are playing an important role as structural component of the Z-lines that anchor the actin-containing thin filaments and maintain the spatial relationship between myofilaments. ACTN3 is expressed only in type II muscle fibers while the ACTN2 is found in all muscle fibers. A common nonsense mutation in ACTN3 (R577X) results in ACTN3 deficiency that appears to be non-pathogenic and it is postulated that ACTN2 compensates for the deficiency. Therefore, it is hypothesized that ACTN3 genotype (RR, RX, XX) may influence variation in muscle function in humans and many studies have confirmed that the presence of the ACTN3 protein, or RR genotype is associated with greater success in activities requiring sprint or power performance. In contrast to the findings in power athletes, it is controversial that a lack of ACTN3 protein, or XX genotype is beneficial to endurance athletes. And associations of ACTN3 genotype with trainability, exercise-induced muscle damage and age-related changes of muscular function have been studied. However, these results are different among the studies because of differences of human race, age, sex, and physical activity level and so on. To clarify roles of ACTN3 genotype on skeletal muscle functions and their mechanisms, further studies with genetically modified animal models would be useful. [ABSTRACT FROM AUTHOR]

An abstract of the study "Hormonal responses following eccentric exercise with and without heat preconditioning and damage experience," by Norio Saga, Hisashi Naito, and Shizuo Katamoto, is presented.

An abstract of the study "Effects of the combination of heat stress and dietary antioxidant intake on the recovery of atrophied muscle," by Tsubasa Shibaguchi and colleagues, is presented.

An abstract of the study "The expressions of alpha-actinin isoforms in rat damaged muscle," by Ryo Kakigi and colleagues is presented.

An abstract of the article "Prevention of sarcopenia by antioxidants intake," by Takao Sugiura and colleagues is presented.

An abstract of the study "Whey Peptide HW-3 enhances the recovery from muscle atrophy in rat," by Hisashi Naito and colleagues is presented.

An abstract of the study "Prevention of skeletal muscle atrophy by the combination of intermittent reloading and heat stress," by Tsubasa Shibaguchi and colleagues is presented.

An abstract of the study "The effects of heat stress on skeletal muscle atrophy as seen from the expression of cytoskeletal protein," by Takao Sugiura and colleagues is presented.

An abstract of the study "Effects of heat stress on mTOR signaling pathway in rat skeletal muscle," by Ryo Kakigi and colleagues is presented.

An abstract of the article "Effect of Heat Treatment at 1-day Before Eccentric Contraction on Eccentric Isokinetic Torque," by Norio Saga and colleagues is presented.

An abstract of the article "Body Temperature Influences Exercise-Increased Heat Shock Protein 72 Level in Rat Plasma," by Yuji Ogura, Hisashi Naito, Noriko I.-Sekine, Mitsutoshi Kurosaka and Shizuo Katamoto is presented.