Search

Metal–organic frameworks (MOFs), self-assembled porous materials synthesized from metal ions and organic ligands, are promising candidates for the direct capture of CO2 from the atmosphere. In this work, we developed a regression model to predict the optimal component of the MOF that governs the amount of CO2 adsorption per volume based on experimentally observed adsorption and structure data combined with MOF adsorption sites. The structural descriptors were generated by topological data analysis with persistence diagrams, an advanced mathematical method for quantifying the rings and cavities within the MOF. This enables us to analyze direct effects and significance of the geometric structure of the MOF on the efficiency of CO2 adsorption in a novel way. The proposed approach is proved to be highly correlated with experimental data and thus offers an effective screening tool for MOFs with optimized structures. [ABSTRACT FROM AUTHOR]

Physical activity and sleep are important factors of mental and physical health in children, with some reports indicating that their effects can persist into adulthood. However, there is limited research on the qualitative aspects of physical activity and sleep in preschool children, particularly in those aged < 3 years. Therefore, to elucidate the association between psychosocial health and physical activity/sleep in early childhood in terms of qualitative aspects, we conducted a retrospective cohort study in 2985 3-year-old children (37.2 ± 0.75 months) in Shanghai, China. An analysis using structural equation modeling indicated that current physical activity had a direct and moderate impact on current psychosocial health evaluated using the Strength and Difficulties Questionnaire. In particular, past physical activity had an indirect and mild effect on current psychosocial health via current physical activity in girls. However, regardless of sex, past sleep quality had slight impact on current psychosocial health, not only indirectly via current sleep quality, but also directly. These findings highlight the importance of considering the qualitative aspects of physical activity and sleep quality as significant factors influencing the current and future psychosocial health of children, even at a very early age (< 3 years). [ABSTRACT FROM AUTHOR]

In the first few years of toddlers' locomotion, various gait parameters improve gradually and dynamically with gait development. Therefore, in this study, we hypothesized that the age of gait development, or the level of gait development with age as its indicator, can be estimated from several gait parameters related to gait development, and investigated its estimability. In total, 97 healthy toddlers aged about 1–3 years participated in the study. All five selected gait parameters showed a moderate or higher correlation with age, but the duration with a large change and the strength of the association with gait development varied for each gait parameter. Multiple regression analysis was performed using age as the objective variable and five selected gait parameters as explanatory variables, and an estimation model (R2 = 0.683, adjusted R2 = 0.665) was created. The estimation model was verified using a test dataset separate from the training dataset (R2 = 0.82, p < 0.001). It was suggested that the age of gait development could be estimated from gait alone. Gait analysis based on empirical observations may reduce the need for skilled observers and their potential variability. [ABSTRACT FROM AUTHOR]

We investigated the protective effect of losartan, an angiotensin II type 1 receptor blocker, on soleus muscle atrophy. Age-matched male and female Wistar rats were subjected to hindlimb unloading, and the soleus muscle was removed on days 1 and 7 for analysis. Females showed greater reductions in relative weight and myofiber cross-sectional area of the soleus muscle than males on day 7 post-hindlimb unloading. Losartan partially protected females against muscle atrophy. Activation of the canonical TGF-β signaling pathway, assessed via Smad2/3 phosphorylation, was lower in females following losartan treatment and associated with lower levels of protein ubiquitination after 1 (myofibril) and 7 (cytosol) days of unloading. However, no effect was observed in non-canonical TGF-β signaling (p44/p42 and p38 MAPK phosphorylation) in males or females during unloading. Our results suggest that losartan provides partial protection against hindlimb unloading-induced soleus muscle atrophy in female rats, possibly associated with decreased canonical TGF-β signaling. [ABSTRACT FROM AUTHOR]

Gait maturation in infants develops gradually through several phases. However, external factors such as childrearing practices, especially the wearing of diapers, may affect an infant's motor development. This study investigated the influence of different bulk stresses on the gait of toddlers wearing a disposable diaper. Twenty-six healthy toddlers (age: 19.2 ± 0.9 months) participated in this study. We measured the joint kinematics (pelvis angle and hip-joint angle) and spatiotemporal parameters (step length and step width) of the toddlers' gait under four dress conditions (wearing Type A_WET, Type A_DRY, and Type B_WET diapers and naked). Type B_WET had a higher bulk stress than Type A_WET, and Type A_DRY had lower stress than Type A _ WET. Our results indicate that the walk of toddlers when wearing a diaper differs from that when naked. This difference is due to the effect of the bulk of the diaper on the lower limb. A high bulk stress has a greater influence than that of a low bulk stress on joint dynamics and step width. Therefore, our findings suggest that wearing diapers with high bulk stress may inhibit the natural gait patterns of toddlers. [ABSTRACT FROM AUTHOR]

Background: Among former Olympic-level athletes, engagement in different sport disciplines has been associated with mortality risk in subsequent years. However, limited evidence is available on whether engagement in different sport disciplines at a young age is associated with locomotive syndrome (LS) risk later in life. This study examined the relationship between engagement in different sport disciplines during university years and LS risk in older age among former university athletes. Methods: Participants were 274 middle-aged and 294 older men alumni who graduated from a school of physical education in Japan. LS risk was defined as answering "yes" to any of the Loco-check questions. Data on university sports club membership were collected using questionnaires. University clubs were classified into three groups of cardiovascular intensity (low, moderate, high), following the classification system of sport disciplines by the American College of Cardiology. This classification considers the static and dynamic components of an activity, which correspond to the estimated percent of maximal voluntary contraction reached and maximal oxygen uptake achieved, respectively. University clubs were grouped based on the risk of bodily collision (no, yes) and extent of physical contact (low, moderate, high). Relationships between engagement in different sport disciplines and LS risk were analyzed using Cox proportional hazards models, and adjusted for age, height, weight, joint disease, habitual exercise, and smoking and drinking status. Results: Adjusted hazard ratios and 95% confidence intervals associated with the low, moderate, and high cardiovascular intensity sports were 1.00 (reference), 0.48 (0.22–1.06, P = 0.070), and 0.44 (0.20–0.97, P = 0.042) in older men, respectively; however, there was no significant association between these parameters among middle-aged men. Engagement in sports associated with physical contact and collision did not affect LS risk in either group. Conclusions: Engagement in sports associated with high cardiovascular intensity during university years may reduce the risk of LS in later life. Encouraging young people to participate in such activities might help reduce LS prevalence among older populations. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes have attracted attention in various fields, but lack of congeners with discrete molecular structures has hampered developments based on in-depth, chemical understandings. In this study, a nanotube molecule doped periodically with multiple nitrogen atoms has been synthesized by combining eight 2,4,6-trisubstituted pyridine units with thirty-two 1,3,5-trisubstituted benzene units. A synthetic strategy involving geodesic phenine frameworks is sufficiently versatile to tolerate pyridine units without requiring synthetic detours. Crystallographic analyses adopting aspherical multipole atom models reveal the presence of axially rotated structures as a minor disordered structure, which also provides detailed molecular and electronic structures. The nitrogen atoms on the nanotube serve as chemically distinct sites covered with negatively charged surfaces, and they increase the chance of electron injections by lowering the energy levels of the unoccupied orbitals that should serve as electron acceptors. Replacing carbon atoms in nanocarbons with heteroatoms alters their intrinsic properties, and nitrogen-doped nanocarbons attract much attention in various fields. Here, the authors synthesize a discrete nitrogen-doped nanotube molecule and clarify its structure to reveal unique features of nitrogen dopants. [ABSTRACT FROM AUTHOR]

Purpose: Iron is an important component of the oxygen-binding proteins and may be critical to optimal athletic performance. Previous studies have suggested that the G allele of C/G rare variant (rs1799945), which causes H63D amino acid replacement, in the HFE is associated with elevated iron indexes and may give some advantage in endurance-oriented sports. The aim of the present study was to investigate the association between the HFE H63D polymorphism and elite endurance athlete status in Japanese and Russian populations, aerobic capacity and to perform a meta-analysis using current findings and three previous studies.Methods: The study involved 315 international-level endurance athletes (255 Russian and 60 Japanese) and 809 healthy controls (405 Russian and 404 Japanese). Genotyping was performed using micro-array analysis or by PCR. VO2max in 46 male Russian endurance athletes was determined using gas analysis system.Results: The frequency of the iron-increasing CG/GG genotypes was significantly higher in Russian (38.0 vs 24.9%; OR 1.85, P = 0.0003) and Japanese (13.3 vs 5.0%; OR 2.95, P = 0.011) endurance athletes compared to ethnically matched controls. The meta-analysis using five cohorts (two French, Japanese, Spanish, and Russian; 586 athletes and 1416 controls) showed significant prevalence of the CG/GG genotypes in endurance athletes compared to controls (OR 1.96, 95% CI 1.58-2.45; P = 1.7 × 10-9). Furthermore, the HFE G allele was associated with high V̇O2max in male athletes [CC: 61.8 (6.1), CG/GG: 66.3 (7.8) ml/min/kg; P = 0.036].Conclusions: We have shown that the HFE H63D polymorphism is strongly associated with elite endurance athlete status, regardless ethnicities and aerobic capacity in Russian athletes. [ABSTRACT FROM AUTHOR]

Aging is associated with a progressive loss of skeletal muscle mass and strength, resulting in frailty and lower quality of life in older individuals. At present, a standard of clinical or pharmacological care to prevent the adverse effects of aging does not exist. Determining the mechanism(s) responsible for muscular atrophy in disused aged muscle is a required key step for the development of effective countermeasures. Studies suggest an age-related differential response of genes and signalings to muscle disuse in both rodents and humans, implying the possibility that effective countermeasures to prevent disuse muscle atrophy may be age-specific. Notably, exercise preconditioning can attenuate disuse-induced muscular atrophy in rodent and human skeletal muscles; however, information on age-specific mechanisms of this exercise-induced protection remains limited. This mini-review aimed to summarize the protective effects of acute exercise preconditioning on muscular atrophy in aged muscle and provide potential mechanisms for its preventive effect on skeletal muscle wasting. [ABSTRACT FROM AUTHOR]

The relationship between long-term intensive training and brain plasticity in gymnasts has recently been reported. However, the relationship between abilities in different gymnastic events and brain structural changes has not been explored. This study aimed to evaluate the correlation between world-class gymnasts (WCGs)’ specific abilities in different gymnastics events and their gray matter (GM) volume. Ten right-handed Japanese male WCGs and 10 right-handed gender- and age-matched controls with no history of gymnastic training participated in this study. Whole brain three-dimensional T1-weighted images (magnetization-prepared rapid gradient-echo sequence) with 0.90 mm3 voxels were obtained using a 3 T-MRI scanner from each subject. Volume-based morphometry (VolBM) was used to compare GM volume differences between WCGs and controls. We then explored the correlation between specific gymnastic abilities using different gymnastic apparatuses, and GM volume. Significantly higher GM volumes (false discovery rate-corrected p < 0.05) in the inferior parietal lobule, middle temporal gyrus, precentral gyrus, rostral middle frontal gyrus, and superior frontal gyrus were demonstrated in WCGs, compared with controls using VolBM. Moreover, significant positive correlations were observed between brain regions and the difficulty scores for each gymnastic event, for example, rings and inferior parietal lobule and parallel bars and rostral middle frontal gyrus. These results may reflect the neural basis of an outstanding gymnastic ability resulting from brain plasticity in areas associated with spatial perception, vision, working memory, and motor control. [ABSTRACT FROM AUTHOR]

Presently, there is no convenient method to measure 24-h urinary Na excretion, which is an important index of daily Na intake, and 24-h urine collection involves a complex process. However, the Na-to-creatinine ratio (NCR) in spot urine has the potential to evaluate 24-h Na excretion and is useful for point-of-care testing. Thus, this study aimed to realize a near-infrared spectroscopic system to assess NCR in spot urine: (1) We attempted to estimate Na concentration using fewer than 10 wavelengths; (2) we calculated NCR using creatinine concentrations from our previous report and verified the NCR predictability. A calibration model was created using multi-linear regression analysis using 10 selected wavelengths in the range of Fourier-transform infrared spectrometer. Spot urine samples were obtained from healthy adults, and glucose powder was added to them to simulate diabetic samples. NCR was calculated using only six wavelengths, and the results confirmed the high accuracy of the estimated Na concentration even though inorganic components do not absorb near-infrared light. Our method enables to optically estimate NCR in spot urine, and it will be useful for point-of-care testing. Graphical abstract. [ABSTRACT FROM AUTHOR]

Males and females of many species, including humans, exhibit different muscle responses and adaptations to exercise stress; however, the molecular mechanisms that underlie these changes are poorly understood. Therefore, the present study assessed sex-related differences in intracellular signaling pathway responses to bouts of horizontal or downhill running in rat soleus muscles. Age-matched male and female Wistar rats (10 weeks old, n = 18/group) were either rested (control group) or subjected to an either a bout of horizontal (22 m/min, 20 min, 0° incline) or downhill (16 m/min, 10 min, − 16% incline) treadmill running. Soleus muscle samples were collected both prior to and immediately after exercise (n = 6/group). Intramuscular signaling responses to each type of exercise were determined via real-time (RT) PCR and western blot analyses. Although mTOR signaling (mTOR/S6K1/S6) responses to both horizontal and downhill exercise were found to be similar in both sexes, ERK phosphorylation levels were found to be significantly higher in male than in female rats after downhill exercise. Similarly, heat shock protein (Hsp) 72 and myostatin protein expression levels were both found to be significantly altered after downhill exercise: Hsp levels increased in male and decreased in female rats, whereas myostatin increased in female but decreased in male rats. Thus, the results of the present study suggest that downhill exercise may elicit sex-specific differential changes to Hsp72 expression, ERK phosphorylation, and myostatin-signaling activation in female compared with those in male rat soleus muscles. Further study is required to confirm these findings and to determine the way in which they impact sex-specific differences in exercise-induced muscle adaptations. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that there are sex differences in hindlimb unloading-induced activation of the forkhead box subfamily O3a (FoxO3a) signaling pathway in rat soleus muscle. Age-matched male and female Wistar rats were subjected to hindlimb unloading, and the soleus muscle was removed before or 1 or 7 days after unloading. Female rats showed greater percent changes in relative soleus muscle weight than males. FoxO3a phosphorylation was lower in females than in males and was associated with higher levels of protein ubiquitination 7 days after unloading. Heat shock protein 72 (Hsp72) levels were lower in female rats and increased in males during unloading. Female rats showed slightly higher myostatin levels, which showed a non-significant decline in male rats following unloading. Thus, males and females show different responses to the FoxO3a/ubiquitin-proteasome pathway following hindlimb unloading in rat soleus muscle, which may be associated with differences in Hsp72 expression and myostatin signaling. [ABSTRACT FROM AUTHOR]

We examined the effect of a combination of astaxanthin (AX) supplementation, repeated heat stress, and intermittent reloading (IR) on satellite cells in unloaded rat soleus muscles. Forty-nine male Wistar rats (8-week-old) were divided into control, hind-limb unweighting (HU), IR during HU, IR with AX supplementation, IR with repeated heat stress (41.0-41.5 °C for 30 min), and IR with AX supplementation and repeated heat stress groups. After the experimental period, the antigravitational soleus muscle was analyzed using an immunohistochemical technique. Our results revealed that the combination of dietary AX supplementation and heat stress resulted in protection against disuse muscle atrophy in the soleus muscle. This protective effect may be partially due to a higher satellite cell number in the atrophied soleus muscle in the IR/AX/heat stress group compared with the numbers found in the other groups. We concluded that the combination treatment with dietary AX supplementation and repeated heat stress attenuates soleus muscle atrophy, in part by increasing the number of satellite cells. [ABSTRACT FROM AUTHOR]

Purpose: Maximum force exertion against various resistance levels (heavy-light) is commonly implemented to improve both strength- and speed-oriented components of power. Medium-light resistances allow rapid accelerations, yet incur significant decelerations in the later concentric phase to bring the bar to a halt, which may limit the concentric effort and, therefore, the effectiveness of training. Accordingly, ballistic actions have been recommended. This study evaluated the effectiveness of power bench press training, with the bar thrown on a Smith machine (BPthrow) or without throwing (BPnon-throw), for developing strength and shot put distance.Methods: Nine university shot-putters performed BPthrow and BPnon-throw at 50, 40 and 30% 1RM, as well as seated and standing shot put trials. Peak angular velocities at the elbow were measured in these tasks using a wireless electro-goniometer. Participants underwent 24 sessions of training (12 weeks) with either BPthrow (n = 5) or BPnon-throw (n = 4) at the three intensities (20 s × 2 sets at 50, 40 and 30% 1RM).Results: The peak elbow velocity during BPthrow was 1.7 times greater than BPnon-throw for all intensities. The velocity of BPthrow at 30% 1RM (854.7°/s), however, was still slower than seated (1121.3°/s) and standing (1539.1°/s) shot puts. BPthrow training significantly improved 1RM (+ 10.0%) and the distances of seated (+ 11.7%) and standing (+ 3.8%) shot puts, while no performance changes occurred after BPnon-throw training.Conclusion: When undergoing power bench press against medium-light resistances, maximum ballistic actions are important strategies for improving 1RM and shot put performance of university shot-putters. [ABSTRACT FROM AUTHOR]

Purpose: High-intensity neuromuscular electrical stimulation (NMES) training can induce muscle hypertrophy at the whole muscle and muscle fiber levels. However, whether low-intensity NMES training has a similar result is unknown. This study aimed to investigate whether low-intensity NMES training could elicit muscle hypertrophy at the whole muscle and muscle fiber levels in the human skeletal muscle.Methods: Eight untrained young males were subjected to 18 min of unilateral NMES training for 8 weeks. One leg received NMES at maximal tolerable intensity (HIGH); the other leg received NMES at an intensity half of that in the HIGH condition (LOW). Quadriceps muscle thickness (MT), muscle fiber cross-sectional area (CSA), and knee extension strength were measured before and after the training period.Results: The average training intensity throughout the intervention period in the HIGH and LOW conditions were 62.5 ± 4.6% maximal voluntary contraction (MVC) and 32.6 ± 2.6% MVC, respectively. MT, CSA, and muscle strength increased in both exercise conditions (p < 0.05); however, training effects in the LOW condition were lower than those in the HIGH condition (p < 0.05). The average training intensity showed a positive correlation with percent changes in muscle strength (r = 0.797, p = 0.001), MT (r = 0.876, p = 0.001), type I fiber CSA (r = 0.730, p = 0.01), and type II fiber CSA (r = 0.899, p = 0.001).Conclusions: Low-intensity NMES could increase MT, muscle fiber CSA, and muscle strength in healthy human skeletal muscles. However, the magnitude of increase is lower in low-intensity than in high-intensity NMES training. [ABSTRACT FROM AUTHOR]

Heat shock proteins (Hsps) have a critical role in maintaining cellular homeostasis and in protecting cells from a range of acute and chronic stressful conditions. Treadmill running exercise results in increased Hsp72 and Hsp25 levels in various tissues and heat production during exercise has been shown to be the main factor for the increased levels of Hsp72 in myocardium. Since the adrenal gland plays a vital role in general response to stress, regulation of Hsps in adrenal glands following stressful events seems to be critical for controlling the whole-body stress response appropriately. This study tested the hypothesis of whether elevation of temperature is solely responsible for exercise-induced adrenal Hsp72 and Hsp25 expression. Female Sprague-Dawley rats (3 months old) were randomly assigned to either a sedentary control group or one of two treadmill-running groups: a cold exercise group run in a cold room at 4 °C (CE), and a warm exercise group run at 25 °C temperature (WE). Animals were run 60 min a day at 30 m min speed for 4 consecutive days following adaptation to treadmill exercise. Exercise resulted in a significant elevation of body temperature only in the WE group ( p < 0.05). Adrenal Hsp72 and Hsp25 levels were significantly higher in the WE group compare to the other groups ( p < 0.05). These data demonstrated that exercise-related elevations of body temperature could be the only factor for the inductions of adrenal Hsp72 and Hsp25 expression. [ABSTRACT FROM AUTHOR]

Heat shock proteins (HSPs) play an important role in insulin resistance and improve the cellular stress response via HSP induction by exercise to treat type 2 diabetes. In this study, the effects of exercise-induced HSP72 expression levels on whole-body insulin resistance in type 2 diabetic rats were investigated. Male 25-week-old Otsuka Long-Evans Tokushima Fatty rats were divided into three groups: sedentary (Sed), trained in a thermal-neutral environment (NTr: 25 °C), and trained in a cold environment (CTr: 4 °C). Exercise training was conducted 5 days/week for 10 weeks. Rectal temperature was measured following each bout of exercise. An intraperitoneal glucose tolerance test (IPGTT) was performed after the training sessions. The serum, gastrocnemius muscle, and liver were sampled 48 h after the final exercise session. HSP72 and heat shock cognate protein 73 expression levels were analyzed by Western blot, and serum total cholesterol, triglyceride (TG), and free fatty acid (FFA) levels were measured. NTr animals exhibited significantly higher body temperatures following exercise, whereas, CTr animals did not. Exercise training increased HSP72 levels in the gastrocnemius muscle and liver, whereas, HSP72 expression was significantly lower in the CTr group than that in the NTr group ( p < 0.05). Glucose tolerance improved equally in both trained animals; however, insulin levels during the IPGTT were higher in CTr animals than those in NTr animals ( p < 0.05). In addition, the TG and FFA levels decreased significantly only in NTr animals compared with those in Sed animals. These results suggest that attenuation of exercise-induced HSP72 expression partially blunts improvement in whole-body insulin resistance and lipid metabolism in type 2 diabetic rats. [ABSTRACT FROM AUTHOR]

Extended periods of skeletal muscle disuse results in muscle atrophy and weakness. Currently, no therapeutic treatment is available for the prevention of this problem. Nonetheless, growing evidence suggests that prevention of disuse-induced oxidative stress in inactive muscle fibers can delay inactivity-induced muscle wasting. Therefore, this study tested the hypothesis that dietary supplementation with the antioxidant astaxanthin would protect against disuse muscle atrophy, in part, by prevention of myonuclear apoptosis. Wistar rats (8 weeks old) were divided into control (CT, n = 9), hindlimb unloading (HU, n = 9), and hindlimb unloading with astaxanthin (HU + AX, n = 9) groups. Following 2 weeks of dietary supplementation, rats in the HU and HU + AX groups were exposed to unloading for 7 days. Seven-day unloading resulted in reduced soleus muscle weight and myofiber cross-sectional area (CSA) by ~30 and ~47 %, respectively. Nonetheless, relative muscle weights and CSA of the soleus muscle in the HU + AX group were significantly greater than those of the HU group. Moreover, astaxanthin prevented disuse-induced increase in the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive nuclei. We conclude that astaxanthin supplementation prior to and during hindlimb unloading attenuates soleus muscle atrophy, in part, by suppressing myonuclear apoptosis. [ABSTRACT FROM AUTHOR]

The study described herein aimed to examine changes in HDAC4 and its downstream targets in immobilization-induced rat skeletal muscle atrophy. Eleven male Wistar rats were used, and one hindlimb was immobilized in the plantar flexion position using a plaster cast. The contralateral, non-immobilized leg served as an internal control. After 10 days, the gastrocnemius muscles were removed from both hindlimbs. Ten days of immobilization resulted in a significant reduction (−27.3 %) in gastrocnemius muscle weight. A significant decrease in AMPK phosphorylation was also observed in nuclear fractions from immobilized legs relative to the controls. HDAC4 expression was significantly increased in immobilized legs in both the cytoplasmic and nuclear fractions. Moreover, Myogenin and MyoD mRNA levels were upregulated in immobilized legs, resulting in increased Atrogin-1 mRNA expression. Our data suggest that nuclear HDAC4 accumulation is partly related to immobilization-induced muscle atrophy. [ABSTRACT FROM AUTHOR]

The effects of icing or heat stress on the regeneration of injured soleus muscle were investigated in male Wistar rats. Bupivacaine was injected into soleus muscles bilaterally to induce muscle injury. Icing (0 °C, 20 min) was carried out immediately after the injury. Heat stress (42 °C, 30 min) was applied every other day during 2-14 days after the bupivacaine injection. Injury-related increase in collagen deposition was promoted by icing. However, the level of collagen deposition in heat-stressed animals was maintained at control levels throughout the experimental period and was significantly lower than that in icing-treated animals at 15 and 28 days after bupivacaine injection. Furthermore, the recovery of muscle mass, protein content, and muscle fiber size of injured soleus toward control levels was partially facilitated by heat stress. These results suggest that, compared with icing, heat stress may be a beneficial treatment for successful muscle regeneration at least by reducing fibrosis. [ABSTRACT FROM AUTHOR]

Skeletal muscles are composed of two major muscle fiber types: slow-twitch oxidative fibers and fast-twitch glycolytic fibers. The proteins in these muscle fibers are known to differ in their expression, relative abundance, and post-translational modifications. In this study, we report a previously unreported post-translational modification of α-skeletal muscle actin in the skeletal muscles of adult male F344 rats in vivo. Using two-dimensional electrophoresis (2D-PAGE), we first examined the differences in the protein expression profiles between the soleus and plantaris muscles. We found higher intensity protein spots at approximately 60 kDa and pH 9 on 2D-PAGE for the soleus muscle compared with the plantaris muscle. These spots were identified as α-skeletal muscle actin by liquid chromatography-nanoelectrospray ionization-tandem mass spectrometry and western blot analyses. In addition, we found that the 60 kDa α-skeletal muscle actin is modified by small ubiquitin-like modifier (SUMO) 1, using 2D-PAGE and western blot analyses. Furthermore, we found that α-skeletal muscle actin with larger molecular weight was localized in the nuclear and cytosol of the skeletal muscle, but not in the myofibrillar fraction by the combination of subcellular fractionation and western blot analyses. These results suggest that α-skeletal muscle actin is modified by SUMO-1 in the skeletal muscles, localized in nuclear and cytosolic fractions, and the extent of this modification is much higher in the slow muscles than in the fast muscles. This is the first study to show the presence of SUMOylated actin in animal tissues. [ABSTRACT FROM AUTHOR]

Purpose: Hyperventilation, implemented during recovery of repeated maximal sprints, has been shown to attenuate performance decrement. This study evaluated the effects of hyperventilation, using strength exercises, on muscle torque output and EMG amplitude. Methods: Fifteen power-trained athletes underwent maximal isokinetic knee extensions consisting of 12 repetitions × 8 sets at 60°/s and 25 repetitions × 8 sets at 300°/s. The inter-set interval was 40 s for both speeds. For the control condition, subjects breathed spontaneously during the interval period. For the hyperventilation condition, subjects hyperventilated for 30 s before each exercise set (50 breaths/min, PCO: 20-25 mmHg). EMG was recorded from the vastus medialis and lateralis muscles to calculate the mean amplitude for each contraction. Results: Hyperventilation increased blood pH by 0.065-0.081 and lowered PCO by 8.3-10.3 mmHg from the control values ( P < 0.001). Peak torque declined with repetition and set numbers for both speeds ( P < 0.001), but the declining patterns were similar between conditions. A significant, but small enhancement in peak torque was observed with hyperventilation at 60°/s during the initial repetition phase of the first ( P = 0.032) and fourth sets ( P = 0.040). EMG amplitude also declined with set number ( P < 0.001) for both speeds and muscles, which was, however, not attenuated by hyperventilation. Conclusion: Despite a minor ergogenic effect in peak torque at 60°/s, hyperventilation was not effective in attenuating the decrement in torque output at 300°/s and decrement in EMG amplitude at both speeds during repeated sets of maximal isokinetic knee extensions. [ABSTRACT FROM AUTHOR]

In this paper, we study optimization of the first eigenvalue of $$-\nabla \cdot (\rho (x) \nabla u) = \lambda u$$ in a bounded domain $$\Omega \subset {\mathbb {R}}^n$$ under several constraints for the function $$\rho $$ . We consider this problem in various boundary conditions and various topologies of domains. As a result, we numerically observe several common criteria for $$\rho $$ for optimizing eigenvalues in terms of corresponding eigenfunctions, which are independent of topology of domains and boundary conditions. Geometric characterizations of optimizers are also numerically observed. [ABSTRACT FROM AUTHOR]

Purpose: Body weight in young growing and young adult animals was reduced by a high dietary density of whey protein concentrate; however, it is unclear whether dietary proteins similarly affect body weight in aging animals. Here, we examined whether whey protein or whey peptide ingestion suppressed body fat accumulation and affected protein expression and phosphorylation in skeletal muscle in aging mice. Methods: Twenty-six male senescence-accelerated mouse prone 6 (SAMP6) mice were assigned randomly to three dietary treatment groups: 18.7 % casein control (CON), 18.7 % whey protein (WPR), and 18.7 % whey peptide (WPE). After 28 weeks of treatment, skeletal tissues were dissected and weighed for analysis. Western blotting was performed to examine the expression of AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), and adipose triglyceride lipase (ATGL) in quadriceps muscles. Results: Body (CON: 47.6 ± 2.2 g, WPR: 48.2 ± 2.7 g, WPE: 38.3 ± 2.0 g) and relative white adipose tissue (CON: 38.5 ± 3.5 mg/g, WPR: 43.8 ± 4.0 mg/g, WPE: 21.1 ± 4.4 mg/g) weights were lower in the WPE group compared with the other two groups ( p < 0.05), and no significant differences were observed between the CON and WPR groups. The relative weights of tibialis anterior muscle (CON: 1.04 ± 0.04 mg/g, WPR: 0.97 ± 0.03 mg/g, 1.23 ± 0.05 mg/g) and gastrocnemius muscle (CON: 3.02 ± 0.12 mg/g, WPR: 2.92 ± 0.15 mg/g, WPE: 3.65 ± 0.18 mg/g) were higher in the WPE group compared with the other groups ( p < 0.05). The phosphorylation of AMPK (WPR: 1.03 ± 0.11, WPE: 1.36 ± 0.12; fold change from control) and ACC (WPR: 1.08 ± 0.07, WPE: 1.18 ± 0.05; fold change from control) in WPE was higher than in CON ( p < 0.05). There were no significant differences in the expression levels of ATGL among the three groups. Conclusions: These data suggest that a normal (or moderate excess) dietary density of whey peptide attenuates body fat accumulation via upregulation of fatty acid oxidation in skeletal muscle in aging mice. [ABSTRACT FROM AUTHOR]

Purpose: Protein ingestion after resistance exercise increases muscle protein synthesis (MPS) in a dose-dependent manner. However, the molecular mechanism(s) for the dose-dependency of MPS remains unclear. This study aimed to determine the dose response of mammalian target of rapamycin (mTOR) signaling in muscle with ingestion of protein after resistance exercise. Methods: Fifteen male subjects performed four sets of six unilateral isokinetic concentric knee extensions. Immediately after exercise, eight subjects consumed water only. The other seven subjects, in a randomized-order crossover design, took either a 10 [3.6 g essential amino acids (EAA)] or 20 g (7.1 g EAA) solution of whey protein. Muscle biopsies from the vastus lateralis muscle were taken 30 min before and 1 h after resistance exercise. Phosphorylation of Akt (Ser473), mTOR (Ser2448), 4E-BP1 (Thr37/46), and S6K1 (Thr389) was measured by western blotting. Results: Concentric knee extension exercise alone did not increase phosphorylation of Akt and mTOR 1 h after exercise, but ingesting protein after exercise significantly increased the phosphorylation of Akt and mTOR in a dose-dependent manner ( P < 0.05). 4E-BP1 phosphorylation significantly decreased after resistance exercise ( P < 0.05), but subjects who took 10 or 20 g of protein after exercise showed increased 4E-BP1 from post-exercise dephosphorylation ( P < 0.05). S6K1 phosphorylation significantly increased after resistance exercise ( P < 0.05), and 20 g of protein further increased S6K1 phosphorylation compared with ingestion of 10 g ( P < 0.05). Conclusions: These findings suggest that whey protein intake after resistance exercise activates mTOR signaling in a dose-dependent manner in untrained men. [ABSTRACT FROM AUTHOR]

We examined the effects of high-intensity resistance training (HIT) and low-intensity blood flow-restricted (LI-BFR) resistance training on carotid arterial compliance. Nineteen young men were randomly divided into HIT ( n = 9) or LI-BFR ( n = 10) groups. The HIT and LI-BFR groups performed 75 and 30 %, respectively, of one-repetition maximum (1-RM) bench press exercise, 3 days per week for 6 weeks. During the training sessions, the LI-BFR group wore elastic cuffs around the most proximal region of both arms. Muscle cross-sectional area (CSA), 1-RM strength, and carotid arterial compliance were measured before and 3 days after the final training session. Acute changes in systolic arterial pressure (SAP), plasma endothelin-1 (ET-1), nitrite/nitrate (NOx), and noradrenalin concentrations were also measured during and after a bout of training session. The training led to significant increases ( P < 0.01) in bench press 1-RM and arm and chest muscle CSA in the two training groups. Carotid arterial compliance decreased significantly ( P < 0.05) in the HIT group, but not in the LI-BFR group. There was a significant correlation ( r = −0.533, P < 0.05) between the change in carotid arterial compliance and the acute change in SAP during training sessions; however, ET-1 and NOx did not correlate with carotid arterial compliance. Our results suggest that muscle CSA and strength increased following 6 weeks of both HIT and LI-BFR training. However, carotid arterial compliance decreased in only the HIT group, and the changes were correlated with SAP elevations during exercise sessions. [ABSTRACT FROM AUTHOR]

This study investigated the effect of heat stress (HS) on mammalian target of rapamycin (mTOR) signaling involved in translation initiation after resistance exercise in human skeletal muscle. Eight young male subjects performed four sets of six maximal repetitions of knee extension exercises, with or without HS, in a randomized crossover design. HS was applied to the belly of the vastus lateralis by using a microwave therapy unit prior to and during exercise. Muscle biopsies were taken from the vastus lateralis before, immediately after, and 1 h after exercise. HS significantly increased the phosphorylation of Akt/PKB, mTOR, and ribosomal protein S6 at 1 h after exercise ( P < 0.05), and the 4E-BP1 phosphorylation level, which had initially decreased with exercise, had recovered by 1 h after exercise with HS. In addition, the phosphorylation of ribosomal S6 kinase 1 was significantly increased immediately after exercise with HS ( P < 0.05). These results indicate that HS enhances mTOR signaling after resistance exercise in human skeletal muscle. [ABSTRACT FROM AUTHOR]

The present study was performed to investigate the effects of long-term heat stress on mass, strength and gene expression profile of human skeletal muscles without exercise training. Eight healthy men were subjected to 10-week application of heat stress, which was performed for the quadriceps muscles for 8 h/day and 4 days/week by using a heat- and steam-generating sheet. Maximum isometric force during knee extension of the heated leg significantly increased after heat stress (~5.8%, P < 0.05). Mean cross-sectional areas (CSAs) of vastus lateralis (VL, ~2.7%) and rectus femoris (~6.1%) muscles, as well as fiber CSA (8.3%) in VL, in the heated leg were also significantly increased (P < 0.05). Statistical analysis of microarrays (SAM) revealed that 10 weeks of heat stress increased the transcript level of 925 genes and decreased that of 1,300 genes, and gene function clustering analysis (Database for Annotation, Visualization and Integrated Discovery: DAVID) showed that these regulated transcripts stemmed from diverse functional categories. Transcript level of ubiquinol-cytochrome c reductase binding protein (UQCRB) was significantly increased by 10 weeks of heat stress (~3.0 folds). UQCRB is classified as one of the oxidative phosphorylation-associated genes, suggesting that heat stress can stimulate ATP synthesis. These results suggested that long-term application of heat stress could be effective in increasing the muscle strength associated with hypertrophy without exercise training. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate whether hypoxia can alter anaerobic energy release during supramaximal exercise. Seven male subjects performed 12 submaximal cycling tests to establish the relationship between workload and O2 demand. The subjects also performed 40 s Wingate tests (WT) under normoxia (room air), two levels of moderate hypoxia of 16.4% O2 and 12.7% O2. We measured the power output and oxygen uptake (VO2) during each test and estimated the O2 demand, O2 deficit and percentage of anaerobic energy release (%AnAER). These data were analyzed for each 20 s interval. At all intervals, there were no differences in Pmean per body mass (BM)(-1), O2 demand per BM(-1) or O2 deficit per BM(-1) among the three O2 conditions. However, under hypoxia of 12.7%, VO2 per BM(-1) was significantly decreased and %AnAER was significantly increased in the late phase (20-40 s) of the WT, compared to normoxia (P<0.05). There were no such significant differences between normoxia and hypoxia of 16.4%. Thus, the present results show that the degree of hypoxia affects the magnitude of the hypoxia-induced increase in anaerobic energy release in the late phase of the WT and suggest that certain degrees of hypoxia induce significant increases in the amount of anaerobic energy released, compared to normoxia. [ABSTRACT FROM AUTHOR]

Regular physical exercise retards a number of age-associated disorders, in spite of the paradox that free radical generation is significantly enhanced with exercise. Eight weeks of treadmill running resulted in nearly a 40% increase in maximal oxygen uptake in both middle-aged (20-month-old) and aged (30-month-old) rats. The age-associated increase in 8-hydroxy-2′-deoxyguanosine (8-OHdG) content was significantly attenuated in gastrocnemius muscle by exercise. The 8-OHdG repair, as measured by the excision of 32P-labeled damaged oligonucleotide, increased in muscle of exercising animals. The reactive carbonyl derivatives (RCD) of proteins did not increase with aging. However, when the muscle homogenate was exposed to a mixture of 1 mM iron sulfate and 50 mM ascorbic acid, the muscle of old control animals accumulated more RCD than that of the trained or adult groups. The chymotrypsin-like activity of proteasome complex increased in muscle of old trained rats. We suggest that regular exercise-induced adaptation attenuates the age-associated increase in 8-OHdG levels, and increases the activity of DNA repair and resistance against oxidative stress in proteins. [ABSTRACT FROM AUTHOR]

Radical-mediated oxidative damage of skeletal muscle membranes has been implicated in the fatigue process. Vitamin E (VE) is a major chain breaking antioxidant that has been shown to reduce contraction-mediated oxidative damage. We hypothesized that VE deficiency would adversely affect muscle contractile function, resulting in a more rapid development of muscular fatigue during exercise. To test this postulate, rats were fed either a VE-deficient (EDEF) diet or a control (CON) diet containing VE. Following a 12-week feeding period, animals were anesthetized and mechanically ventilated. Muscle endurance (fatigue) and contractile properties were evaluated using an in situ preparation of the tibialis anterior (TA) muscle. Contractile properties of the TA muscle were determined before and after a fatigue protocol. The muscle fatigue protocol consisted of 60 min of repetitive contractions (250 ms trains at 15 Hz; duty cycle=11%) of the TA muscle. Prior to the fatigue protocol, no significant differences existed in the force-frequency curves between EDEF and CON animals. At the completion of the fatigue protocol, muscular force production was significantly (P<0.05) lower in the EDEF group (reduced by 69%) compared to CON group (reduced by 38%). Following the fatigue protocol, a right shift existed in the force-frequency curve at low stimulation frequencies (≤40 Hz) in the EDEF animals compared to the CON animals (P<0.05). The stimulated and the contralateral TA muscle from the EDEF animals had significantly higher markers of lipid peroxidation compared to the same muscles in the CON animals (P<0.05). These data support the hypothesis that VE deficiency impairs muscular endurance and alters muscle contractile properties following a prolonged series of contractions. [ABSTRACT FROM AUTHOR]

These experiments tested the hypothesis that short-term endurance exercise training would rapidly improve (within 5 days) the diaphragm oxidative/antioxidant capacity and protect the diaphragm against contraction-induced oxidative stress. To test this postulate, male Sprague-Dawley rats (6 weeks old) ran on a motorized treadmill for 5 consecutive days (40–60 min · day-1) at approximately 65% maximal oxygen uptake. Costal diaphragm strips were excised from both sedentary control (CON, n=14) and trained (TR, n=13) animals 24 h after the last exercise session, for measurement of in vitro contraction properties and selected biochemical parameters of oxidative/antioxidant capacity. Training did not alter diaphragm force-frequency characteristics over a full range of submaximal and maximal stimulation frequencies (P > 0.05). In contrast, training improved diaphragm resistance to fatigue as contraction forces were better-maintained by the diaphragms of the TR animals during a submaximal 60-min fatigue protocol (P < 0.05). Following the fatigue protocol, diaphragm strips from the TR animals contained 30% lower concentrations of lipid hydroperoxides compared to CON (P < 0.05). Biochemical analysis revealed that exercise training increased diaphragm oxidative and antioxidant capacity (citrate synthase activity +18%, catalase activity +24%, total superoxide dismutase activity +20%, glutathione concentration +10%) (P < 0.05). These data indicate that short-term exercise training can rapidly elevate oxidative capacity as well as enzymatic and non-enzymatic antioxidant defenses in the diaphragm. Furthermore, this up-regulation in antioxidant defenses would be accompanied by a reduction in contraction-induced lipid peroxidation and an increased fatigue resistance. [ABSTRACT FROM AUTHOR]

Endurance exercise training promotes a small but significant increase in antioxidant enzyme activity in the costal diaphragm (DIA) of rodents. It is unclear if these training-induced improvements in muscle antioxidant capacity are large enough to reduce oxidative stress during prolonged contractile activity. To test the hypothesis that training-related increases in DIA antioxidant capacity reduces contraction-induced lipid peroxidation, we exercise trained adult female Sprague-Dawley ( n = 7) rats on a motor-driven treadmill for 12 weeks at ≈ 75% maximal O2 consumption (90 min/day). Control animals ( n = 8) remained sedentary during the same 12-week period. After training, DIA strips from animals in both experimental groups were excised and subjected to an in vitro fatigue contractile protocol in which the muscle was stimulated for 60 min at a frequency of 30 Hz, every 2 s, with a train duration of 330 m. Compared to the controls, endurance training resulted in an increase ( P < 0.05) in diaphragmatic non-protein thiols and in the activity of the antioxidant enzyme superoxide dismutase. Following the contractile protocol, lipid peroxidation was significantly lower ( P < 0.05) in the trained DIA compared to the controls. These data support the hypothesis that endurance exercise training-induced increases in DIA antioxidant capacity protect the muscle against contractile-related oxidative stress. [ABSTRACT FROM AUTHOR]