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Robert S. Staron - One of the best experts on this subject based on the ideXlab platform.
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effects of sprint cycle training on human skeletal muscle
Journal of Applied Physiology, 1994Co-Authors: C A Allemeier, Fredrick C Hagerman, Andrew C Fry, P Johnson, Robert S Hikida, Robert S. StaronAbstract:Eleven men sprint trained two to three times per week for 6 wk to investigate possible exercise-induced slow-to-Fast Fiber type conversions. Six individuals served as controls. Both groups were tested at the beginning and end of the study to determine anaerobic performance and maximal oxygen consumption. In addition, pre- and postbiopsies were extracted from the vastus lateralis muscle and were analyzed for Fiber type composition, cross-sectional area, and myosin heavy chain (MHC) content. No significant changes were found in anaerobic or aerobic performance variables for either group. Although a trend was found for a decrease in the percentage of type IIb Fibers, high-intensity sprint cycle training caused no significant changes in the Fiber type distribution or cross-sectional area. However, the training protocol did result in a significant decrease in MHC IIb with a concomitant increase in MHC IIa for the training men. These data appear to support previous investigations that have suggested exercise-induced adaptations within the Fast Fiber population (IIb-->IIa) after various types of training (endurance and strength).
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skeletal muscle adaptations during early phase of heavy resistance training in men and women
Journal of Applied Physiology, 1994Co-Authors: Robert S. Staron, Jeffrey E Falkel, Fredrick C Hagerman, Andrew C Fry, D L Karapondo, William J Kraemer, Scott E Gordon, Robert S HikidaAbstract:An 8-wk progressive resistance training program for the lower extremity was performed twice a week to investigate the time course for skeletal muscle adaptations in men and women. Maximal dynamic strength was tested biweekly. Muscle biopsies were extracted at the beginning and every 2 wk of the study from resistance-trained and from nontrained (control) subjects. The muscle samples were analyzed for Fiber type composition, cross-sectional area, and myosin heavy chain content. In addition, Fasting blood samples were measured for resting serum levels of testosterone, cortisol, and growth hormone. With the exception of the leg press for women (after 2 wk of training) and leg extension for men (after 6 wk of training), absolute and relative maximal dynamic strength was significantly increased after 4 wk of training for all three exercises (squat, leg press, and leg extension) in both sexes. Resistance training also caused a significant decrease in the percentage of type IIb Fibers after 2 wk in women and 4 wk in men, an increase in the resting levels of serum testosterone after 4 wk in men, and a decrease in cortisol after 6 wk in men. No significant changes occurred over time for any of the other measured parameters for either sex. These data suggest that skeletal muscle adaptations that may contribute to strength gains of the lower extremity are similar for men and women during the early phase of resistance training and, with the exception of changes in the Fast Fiber type composition, that they occur gradually.
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correlation between myofibrillar atpase activity and myosin heavy chain composition in single human muscle Fibers
Histochemistry and Cell Biology, 1991Co-Authors: Robert S. StaronAbstract:Single human muscle Fibers were analysed using a combination of histochemical and biochemical techniques. Routine myofibrillar adenosine triphosphatase (mATPase) histochemistry revealed a continuum of staining intensities between the Fast Fiber types IIA and IIB (type IIAB Fibers) after preincubation at pH 4.6. Electrophoretic analysis of single, histochemically-identified Fibers demonstrated a correlation between the staining intensity and the myosin heavy chain (MHC) composition. All Fibers classified as type I contained exclusively MHCI and all type IIA Fibers contained only MHCIIa. Type IIAB Fibers displayed variable amounts of both MHCIIa and MHCIIb; the greater the staining intensity of these Fibers after preincubation at pH 4.6, the greater the percentage of MHCIIb. Those Fibers histochemically classified as type IIB contained either entirely MHCIIb or, in addition to MHCIIb, a small amount of MHCIIa. These data establish a correlation between the mATPase activity and MHC content in single human muscle Fibers.
Han Zhang - One of the best experts on this subject based on the ideXlab platform.
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microFiber based few layer black phosphorus saturable absorber for ultra Fast Fiber laser
Optics Express, 2015Co-Authors: Xiaofang Jiang, Chujun Zhao, Xuefeng Yu, Wencheng Xu, Han ZhangAbstract:Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics. However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage. Herein, we demonstrate that, few-layer BPs, which was fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microFiber. The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band. The microFiber-based BP device had been found to show a saturable average power of ~4.5 mW and a modulation depth of 10.9%, which is further confirmed through a balanced twin detection measurement. By integrating this optical SA device into an erbium-doped Fiber laser, it was found that it can deliver the mode-locked pulse with duration down to 940 fs with central wavelength tunable from 1532 nm to 1570 nm. The prevention of BP from oxidation through the “lateral interaction scheme” owing to this microFiber-based few-layer BP SA device might partially mitigate the optical damage problem of BP. Our results not only demonstrate that black phosphorus might be another promising SA material for ultraFast photonics, but also provide a practical solution to solve the optical damage problem of black phosphorus by assembling with waveguide structures such as microFiber.
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microFiber based few layer black phosphorus saturable absorber for ultra Fast Fiber laser
arXiv: Optics, 2015Co-Authors: Zhichao Luo, Chujun Zhao, Xiaofang Jiang, Meng Liu, Zhinan Guo, Aiping Luo, Han ZhangAbstract:Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics. However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage. Herein, we demonstrate that, few-layer BPs, fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microFiber. The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band and the microFiber-based BP device had been found to show a saturable average power of ~4.5 mW and a modulation depth of 10.9%, which is further confirmed through a balanced twin detection measurement. By further integrating this optical SA device into an erbium-doped Fiber laser, it was found that it can deliver the mode-locked pulse with duration down to 940 fs with central wavelength tunable from 1532 nm to 1570 nm. The prevention of BP from oxidation through the 'lateral interaction scheme' owing to this microFiber-based few-layer BP SA device might partially mitigate the optical damage problem of BP. Our results not only demonstrate that black phosphorus might be another promising SA material for ultraFast photonics, but also provide a practical solution to solve the optical damage problem of black phosphorus by assembling with waveguide structures such as microFiber.
Fleur Garton - One of the best experts on this subject based on the ideXlab platform.
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deficiency of α actinin 3 is associated with increased susceptibility to contraction induced damage and skeletal muscle remodeling
Human Molecular Genetics, 2011Co-Authors: Peter J Houweling, Monkol Lek, Xi F Zheng, Fleur GartonAbstract:Sarcomeric α-actinins (α-actinin-2 and -3) are a major component of the Z-disk in skeletal muscle, where they crosslink actin and other structural proteins to maintain an ordered myofibrillar array. Homozygosity for the common null polymorphism (R577X) in ACTN3 results in the absence of Fast Fiber-specific α-actinin-3 in ∼20% of the general population. α-Actinin-3 deficiency is associated with decreased force generation and is detrimental to sprint and power performance in elite athletes, suggesting that α-actinin-3 is necessary for optimal forceful repetitive muscle contractions. Since Z-disks are the structures most vulnerable to eccentric damage, we sought to examine the effects of α-actinin-3 deficiency on sarcomeric integrity. Actn3 knockout mouse muscle showed significantly increased force deficits following eccentric contraction at 30% stretch, suggesting that α-actinin-3 deficiency results in an increased susceptibility to muscle damage at the extremes of muscle performance. Microarray analyses demonstrated an increase in muscle remodeling genes, which we confirmed at the protein level. The loss of α-actinin-3 and up-regulation of α-actinin-2 resulted in no significant changes to the total pool of sarcomeric α-actinins, suggesting that alterations in Fast Fiber Z-disk properties may be related to differences in functional protein interactions between α-actinin-2 and α-actinin-3. In support of this, we demonstrated that the Z-disk proteins, ZASP, titin and vinculin preferentially bind to α-actinin-2. Thus, the loss of α-actinin-3 changes the overall protein composition of Fast Fiber Z-disks and alters their elastic properties, providing a mechanistic explanation for the loss of force generation and increased susceptibility to eccentric damage in α-actinin-3-deficient individuals.
Yuji Ogura - One of the best experts on this subject based on the ideXlab platform.
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alpha actinin 3 levels increase concomitantly with Fast Fibers in rat soleus muscle
Biochemical and Biophysical Research Communications, 2008Co-Authors: Yuji Ogura, Hisashi Naito, Ryo Kakigi, Noriko Ichinosekisekine, Mitsutoshi Kurosaka, Shizuo KatamotoAbstract:Alpha (α)-actinin-3 is located in the skeletal muscle Z-line and forms actin–actin crosslinks. An interesting property of α-actinin-3 is its expression pattern, which is restricted to Fast type II skeletal muscle Fibers. However, little is known about the response of α-actinin-3 levels to changes in skeletal muscle such as Fiber type transformation. This study examined α-actinin-3 levels in the soleus muscles of rats subjected to hindlimb unloading, which causes a slow-to-Fast Fiber transformation in the soleus muscle. After unloading, type II myosin heavy chain (MyHC) and Fast myosin levels increased significantly (P < 0.0001 for type II MyHC, P < 0.005 for Fast myosin). Along with these increases in Fast Fibers, α-actinin-3 expression levels increased significantly (P < 0.0007) and dramatically. These results indicate that α-actinin-3 levels increase concomitantly with increases in skeletal muscle Fast Fibers.
Xiaofang Jiang - One of the best experts on this subject based on the ideXlab platform.
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microFiber based few layer black phosphorus saturable absorber for ultra Fast Fiber laser
Optics Express, 2015Co-Authors: Xiaofang Jiang, Chujun Zhao, Xuefeng Yu, Wencheng Xu, Han ZhangAbstract:Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics. However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage. Herein, we demonstrate that, few-layer BPs, which was fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microFiber. The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band. The microFiber-based BP device had been found to show a saturable average power of ~4.5 mW and a modulation depth of 10.9%, which is further confirmed through a balanced twin detection measurement. By integrating this optical SA device into an erbium-doped Fiber laser, it was found that it can deliver the mode-locked pulse with duration down to 940 fs with central wavelength tunable from 1532 nm to 1570 nm. The prevention of BP from oxidation through the “lateral interaction scheme” owing to this microFiber-based few-layer BP SA device might partially mitigate the optical damage problem of BP. Our results not only demonstrate that black phosphorus might be another promising SA material for ultraFast photonics, but also provide a practical solution to solve the optical damage problem of black phosphorus by assembling with waveguide structures such as microFiber.
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microFiber based few layer black phosphorus saturable absorber for ultra Fast Fiber laser
arXiv: Optics, 2015Co-Authors: Zhichao Luo, Chujun Zhao, Xiaofang Jiang, Meng Liu, Zhinan Guo, Aiping Luo, Han ZhangAbstract:Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics. However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage. Herein, we demonstrate that, few-layer BPs, fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microFiber. The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band and the microFiber-based BP device had been found to show a saturable average power of ~4.5 mW and a modulation depth of 10.9%, which is further confirmed through a balanced twin detection measurement. By further integrating this optical SA device into an erbium-doped Fiber laser, it was found that it can deliver the mode-locked pulse with duration down to 940 fs with central wavelength tunable from 1532 nm to 1570 nm. The prevention of BP from oxidation through the 'lateral interaction scheme' owing to this microFiber-based few-layer BP SA device might partially mitigate the optical damage problem of BP. Our results not only demonstrate that black phosphorus might be another promising SA material for ultraFast photonics, but also provide a practical solution to solve the optical damage problem of black phosphorus by assembling with waveguide structures such as microFiber.