Science.gov

Sample records for cut muscle fibers

  1. Intracellular localization of markers within injected or cut frog muscle fibers.

    PubMed

    Eisenberg, B R; Mathias, R T; Gilai, A

    1979-07-01

    Many experimental procedures require drastic alterations of muscle fibers, such as cutting the fiber or injecting molecular probes through microelectrodes. We report the ultrastructure of similarly altered muscle fibers and the intracellular distribution of injected horseradish peroxidase (HRP). Cut fibers appear structurally normal at distances greater than 500 microM from the cut end, however, the structure deteriorates nearer to the cut. HRP diffuses longitudinally about 2,000 micrometer from the cut end and the concentration is uniform over the fiber's cross section. If HRP is introduced intracellularly either by pressure injection or through a nick in the sarcolemma, it distributes in a C-shaped annulus extending approximately 2,000 micrometer longitudinally and 1-20 micrometer radially. The ultrastructure of injected or nicked fibers appears normal. The HRP freely entered the junctional gap between T-system and sarcoplasmic reticulum (SR) but was excluded from either structure. Occasionally, a light pillar could be seen between T-system and SR; the space of these pillars suggest they are the central area of the "feet" appearing light against the dark marker.

  2. Nile blue fluorescence signals from cut single muscle fibers under voltage or current clamp conditions

    PubMed Central

    1978-01-01

    A method is presented for recording extrinsic optical signals from segments of single skeletal muscle fibers under current or voltage clamp conditions. Such segments, which are cut from intact fibers, are maintained in a relaxed state, while exhbiting otherwise normal physiological properties, including healthy delayed rectifier currents. Extrinsic fluorescence changes are demonstrated, using the permeant potentiometric probe, Nile Blue A. These changes vary nonlinearly with the controlled surface membrane potential, in a manner which suggests that they arise from potential changes in the sarcoplasmic reticulum. According to this interpretation, a simple model based on the gating charge movement implicated in excitation-contraction coupling, provides a self-consistent description of the voltage dependence of the signal that requires no additional parameters. PMID:310445

  3. Simulation of calcium sparks in cut skeletal muscle fibers of the frog.

    PubMed

    Chandler, W K; Hollingworth, S; Baylor, S M

    2003-04-01

    Spark mass, the volume integral of Delta F/F, was investigated theoretically and with simulations. These studies show that the amount of Ca2+ bound to fluo-3 is proportional to mass times the total concentration of fluo-3 ([fluo-3T]); the proportionality constant depends on resting Ca2+ concentration ([Ca2+]R). In the simulation of a Ca2+ spark in an intact frog fiber with [fluo-3T] = 100 microM, fluo-3 captures approximately one-fourth of the Ca2+ released from the sarcoplasmic reticulum (SR). Since mass in cut fibers is several times that in intact fibers, both with similar values of [fluo-3T] and [Ca2+]R, it seems likely that SR Ca2+ release is larger in cut fiber sparks or that fluo-3 is able to capture a larger fraction of the released Ca2+ in cut fibers, perhaps because of reduced intrinsic Ca2+ buffering. Computer simulations were used to identify these and other factors that may underlie the differences in mass and other properties of sparks in intact and cut fibers. Our spark model, which successfully simulates calcium sparks in intact fibers, was modified to reflect the conditions of cut fiber measurements. The results show that, if the protein Ca2+-buffering power of myoplasm is the same as that in intact fibers, the Ca2+ source flux underlying a spark in cut fibers is 5-10 times that in intact fibers. Smaller source fluxes are required for less buffer. In the extreme case in which Ca2+ binding to troponin is zero, the source flux needs to be 3-5 times that in intact fibers. An increased Ca2+ source flux could arise from an increase in Ca2+ flux through one ryanodine receptor (RYR) or an increase in the number of active RYRs per spark, or both. These results indicate that the gating of RYRs, or their apparent single channel Ca2+ flux, is different in frog cut fibers--and, perhaps, in other disrupted preparations--than in intact fibers.

  4. Effect of sarcoplasmic reticulum calcium depletion on intramembranous charge movement in frog cut muscle fibers

    PubMed Central

    1995-01-01

    Cut muscle fibers from Rana temporaria (sarcomere length, 3.3-3.5 microns; temperature, 13-16 degrees C) were mounted in a double Vaseline-gap chamber and equilibrated for at least an hour with an internal solution that contained 20 mM EGTA and phenol red and an external solution that contained predominantly TEA-gluconate; both solutions were nominally Ca-free. The increase in total myoplasmic concentration of Ca (delta[CaT]) produced by sarcoplasmic reticulum (SR) Ca release was estimated from the change in pH produced when the released Ca was complexed by EGTA (Pape, P.C., D.-S. Jong, and W.K. Chandler. 1995. Journal of General Physiology. 106:259-336). The resting value of SR Ca content, [CaSR]R (expressed as myoplasmic concentration), was taken to be equal to the value of delta[CaT] obtained during a step depolarization (usually to -50 to -40 mV) that was sufficiently long (200-750 ms) to release all of the readily releasable Ca from the SR. In ten fibers, the first depolarization gave [CaSR]R = 839-1,698 microM. Progressively smaller values were obtained with subsequent depolarizations until, after 30-40 depolarizations, the value of [CaSR]R had usually been reduced to < 10 microM. Measurements of intramembranous charge movement, Icm, showed that, as the value of [CaSR]R decreased, ON-OFF charge equality held and the amount of charge moved remained constant. ON Icm showed brief initial I beta components and prominent I gamma "humps", even after the value of [CaSR]R was < 10 microM. Although the amplitude of the hump component decreased during depletion, its duration increased in a manner that preserved the constancy of ON charge. In the depleted state, charge movement was steeply voltage dependent, with a mean value of 7.2 mV for the Boltzmann factor k. These and other results are not consistent with the idea that there is one type of charge, Q beta, and that I gamma is a movement of Q beta caused by SR Ca release, as proposed by Pizarro, Csernoch, Uribe

  5. Calcium inactivation of calcium release in frog cut muscle fibers that contain millimolar EGTA or Fura-2

    PubMed Central

    1995-01-01

    Cut muscle fibers from Rana temporaria (sarcomere length, 3.4-4.2 microns) were mounted in a double Vaseline-gap chamber (14-15 degrees C) and equilibrated with end-pool solutions that contained 20 mM EGTA and 1.76 mM Ca. Sarcoplasmic reticulum (SR) Ca release was estimated from changes in pH (Pape, P. C., D.-S. Jong, and W.K. Chandler. 1995. Journal of General Physiology. 106:000-000). Although the amplitude and duration of the [Ca] transient, as well as its spatial spread from the release sites, are reduced by EGTA, SR Ca release elicited by either depolarizing voltage-clamp pulses or action potentials behaved in a manner consistent with Ca inactivation of Ca release. After a step depolarization to -20 or 10 mV, the rate of SR Ca release, corrected for SR Ca depletion, reached a peak value within 5-15 ms and then rapidly decreased to a quasi-steady level that was about half the peak value; the time constant of the last half of the decrease was usually 2- 4 ms. Immediately after an action potential or a 10-15 ms prepulse to - 20 mV, the peak rate of SR Ca release elicited by a second stimulation, as well as the fractional amount of release, were substantially decreased. The rising phase of the rate of release was also reduced, suggesting that at least 0.9 of the ability of the SR to release Ca had been inactivated by the first stimulation. There was little change in intramembranous charge movement, suggesting that the changes in SR Ca release were not caused by changes in its voltage activation. These effects of a first stimulation on the rate of SR Ca release elicited by a second stimulation recovered during repolarization to -90 mV; the time constant of recovery was approximately 25 ms in the action- potential experiments and approximately 50 ms in the voltage-clamp experiments. Fura-2, which is able to bind Ca more rapidly than EGTA and hence reduce the amplitude of the [Ca] transient and its spatial spread from release sites by a greater amount, did not

  6. Optical Fiber Cutting Machine for Rectangular and Circular Fibers

    DTIC Science & Technology

    1977-06-30

    OPTICAL FIBER CUTTING MACHINE FOR RECTANGULAR AND CIRCULAR FIBERS Gordon L. Mitchell -June 30,’1977 Principal Investigators Gordon L. Mitchell and...bet) An optical fiber cutting machine for use with rectangular or round cros- section fibers has been developed. It combines a sliding-weight tension...OP* THIS PAGE (When 13.fe Afn(-’-d) ii Abstract An optical fiber cutting machine for use with rectangular or round cross section fibers has been

  7. Muscle Fiber Types and Training.

    ERIC Educational Resources Information Center

    Karp, Jason R.

    2001-01-01

    The specific types of fibers that make up individual muscles greatly influence how people will adapt to their training programs. This paper explains the complexities of skeletal muscles, focusing on types of muscle fibers (slow-twitch and fast-twitch), recruitment of muscle fibers to perform a motor task, and determining fiber type. Implications…

  8. Muscle Fiber Types and Training.

    ERIC Educational Resources Information Center

    Karp, Jason R.

    2001-01-01

    The specific types of fibers that make up individual muscles greatly influence how people will adapt to their training programs. This paper explains the complexities of skeletal muscles, focusing on types of muscle fibers (slow-twitch and fast-twitch), recruitment of muscle fibers to perform a motor task, and determining fiber type. Implications…

  9. Effect of fura-2 on action potential-stimulated calcium release in cut twitch fibers from frog muscle

    PubMed Central

    1993-01-01

    Cut fibers (striation spacing, 3.6-4.2 microns) were mounted in a double Vaseline-gap chamber and studied at 14-15 degrees C. One or both of the Ca indicators fura-2 and purpurate-3,3' diacetic acid (PDAA) were introduced into the optical recording site by diffusion from the end pools. Sarcoplasmic reticulum (SR) Ca release was elicited by action potential stimulation. With resting [fura-2] = 0 mM at the optical site, the [Ca] transient measured with PDAA was used to estimate SR Ca release (Baylor, S.M., W.K. Chandler, and M.W. Marshall. 1983. Journal of Physiology. 344:625-666). With resting [fura-2] > 0 mM, the contribution from Ca complexation by fura-2 was added to the estimate. When resting [fura-2] was increased from 0 to 0.5-2 mM, both the amount of SR Ca release and the maximal rate of release were increased by approximately 20%. These results are qualitatively similar to those obtained in intact fibers (Baylor, S.M., and S. Hollingworth. 1988. Journal of Physiology. 403:151-192; Hollingworth, S., A. B. Harkins, N. Kurebayashi, M. Konishi, and S. M. Baylor. 1992. Biophysical Journal. 63:224-234) and are consistent with a reduction of Ca inactivation of SR Ca release produced by 0.5-2 mM fura-2. With resting [fura-2] > or = 2 mM, the PDAA [Ca] transient was reduced to nearly zero and SR Ca release could be estimated from delta [Cafura-2] alone. When resting [fura-2] was increased from 2-4 to 5-6 mM, both the amount of SR Ca release and the maximal rate of release were decreased by approximately half, consistent with a possible reduction of Ca- induced Ca release (Jacquemond, V., L. Csernoch, M. G. Klein, and M. F. Schneider. 1991. Biophysical Journal. 60:867-873) or a possible pharmacological effect of fura-2. PMID:8228913

  10. Calcium release and its voltage dependence in frog cut muscle fibers equilibrated with 20 mM EGTA

    PubMed Central

    1995-01-01

    Sarcoplasmic reticulum (SR) Ca release was studied at 13-16 degrees C in cut fibers (sarcomere length, 3.4-3.9 microns) mounted in a double Vaseline-gap chamber. The amplitude and duration of the action- potential stimulated free [Ca] transient were reduced by equilibration with end-pool solutions that contained 20 mM EGTA with 1.76 mM Ca and 0.63 mM phenol red, a maneuver that appeared to markedly reduce the amount of Ca complexed by troponin. A theoretical analysis shows that, under these conditions, the increase in myoplasmic free [Ca] is expected to be restricted to within a few hundred nanometers of the SR Ca release sites and to have a time course that essentially matches that of release. Furthermore, almost all of the Ca that is released from the SR is expected to be rapidly bound by EGTA and exchanged for protons with a 1:2 stoichiometry. Consequently, the time course of SR Ca release can be estimated by scaling the delta pH signal measured with phenol red by -beta/2. The value of beta, the buffering power of myoplasm, was determined in fibers equilibrated with a combination of EGTA, phenol red, and fura-2; its mean value was 22 mM/pH unit. The Ca content of the SR (expressed as myoplasmic concentration) was estimated from the total amount of Ca released by either a train of action potentials or a depleting voltage step; its mean value was 2,685 microM in the action-potential experiments and 2,544 microM in the voltage- clamp experiments. An action potential released, on average, 0.14 of the SR Ca content with a peak rate of release of approximately 5%/ms. A second action potential, elicited 20 ms later, released only 0.6 times as much Ca (expressed as a fraction of the SR content), probably because Ca inactivation of Ca release was produced by the first action potential. During a depolarizing voltage step to 60 mV, the rate of Ca release rapidly increased to a peak value of approximately 3%/ms and then decreased to a quasi-steady level that was only 0

  11. Human Muscle Fiber

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The stimulus of gravity affects RNA production, which helps maintain the strength of human muscles on Earth (top), as seen in this section of muscle fiber taken from an astronaut before spaceflight. Astronauts in orbit and patients on Earth fighting muscle-wasting diseases need countermeasures to prevent muscle atrophy, indicated here with white lipid droplets (bottom) in the muscle sample taken from the same astronaut after spaceflight. Kerneth Baldwin of the University of California, Irvine, is conducting research on how reducing the stimulus of gravity affects production of the RNA that the body uses as a blueprint for making muscle proteins. Muscle proteins are what give muscles their strength, so when the RNA blueprints aren't available for producing new proteins to replace old ones -- a situation that occurs in microgravity -- the muscles atrophy. When the skeletal muscle system is exposed to microgravity during spaceflight, the muscles undergo a reduced mass that translates to a reduction in strength. When this happens, muscle endurance decreases and the muscles are more prone to injury, so individuals could have problems in performing extravehicular activity [space walks] or emergency egress because their bodies are functionally compromised.

  12. Human Muscle Fiber

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The stimulus of gravity affects RNA production, which helps maintain the strength of human muscles on Earth (top), as seen in this section of muscle fiber taken from an astronaut before spaceflight. Astronauts in orbit and patients on Earth fighting muscle-wasting diseases need countermeasures to prevent muscle atrophy, indicated here with white lipid droplets (bottom) in the muscle sample taken from the same astronaut after spaceflight. Kerneth Baldwin of the University of California, Irvine, is conducting research on how reducing the stimulus of gravity affects production of the RNA that the body uses as a blueprint for making muscle proteins. Muscle proteins are what give muscles their strength, so when the RNA blueprints aren't available for producing new proteins to replace old ones -- a situation that occurs in microgravity -- the muscles atrophy. When the skeletal muscle system is exposed to microgravity during spaceflight, the muscles undergo a reduced mass that translates to a reduction in strength. When this happens, muscle endurance decreases and the muscles are more prone to injury, so individuals could have problems in performing extravehicular activity [space walks] or emergency egress because their bodies are functionally compromised.

  13. CO2-Laser Cutting Fiber Reinforced Polymers

    NASA Astrophysics Data System (ADS)

    Mueller, R.; Nuss, Rudolf; Geiger, Manfred

    1989-10-01

    Guided by experimental investigations laser cutting of glass fiber reinforced reactive injection moulded (RRIM)-polyurethanes which are used e.g. in car industry for bumpers, spoilers, and further components is described. A Comparison with other cutting techniques as there are water jet cutting, milling, punching, sawing, cutting with conventional knife and with ultrasonic excited knife is given. Parameters which mainly influence cutting results e.g. laser power, cutting speed, gas nature and pressure will be discussed. The problematic nature in characterising micro and macro geometry of laser cut edges of fiber reinforced plastic (FRP) is explained. The topography of cut edges is described and several characteristic values are introduced to specify the obtained working quality. The surface roughness of laser cut edges is measured by both, an optical and a mechanical sensor and their reliabilities are compared.

  14. Muscle Fiber Orientation Angle Dependence of the Tensile Fracture Behavior of Frozen Fish Muscle

    NASA Astrophysics Data System (ADS)

    Hagura, Yoshio; Okamoto, Kiyoshi; Suzuki, Kanichi; Kubota, Kiyoshi

    We have proposed a new cutting method for frozen fish named "cryo-cutting". This method applied tensile fracture force or bending fracture force to the frozen fish at appropriate low temperatures. In this paper, to clarify cryo-cutting mechanism, we analyzed tensile fracture behavior of the frozen fish muscle. In the analysis, the frozen fish muscle was considered unidirectionally fiber-reinforced composite material which consisted of fiber (muscle fiber) and matrix (connective tissue). Fracture criteria (maximum stress criterion, Tsai-Hill criterion) for the unidirectionally fiber-reinforced composite material were used. The following results were obtained: (1) By using Tsai-Hill criterion, muscle fiber orientation angle dependence of the tensile fracture stress could be calculated. (2) By using the maximum stress theory jointly with Tsai-Hill criterion, muscle fiber orientation angle dependence of the fracture mode of the frozen fish muscle could be estimated.

  15. Muscle Fiber Conduction Velocity, Muscle Fiber Composition, and Power Performance.

    PubMed

    Methenitis, Spyridon; Karandreas, Nikolaos; Spengos, Konstantinos; Zaras, Nikolaos; Stasinaki, Angeliki-Nikoletta; Terzis, Gerasimos

    2016-09-01

    The aim of this study was to explore the relationship between muscle fiber conduction velocity (MFCV), fiber type composition, and power performance in participants with different training background. Thirty-eight young males with different training background participated: sedentary (n = 10), endurance runners (n = 9), power trained (n = 10), and strength trained (n = 9). They performed maximal countermovement jumps (CMJ) and maximal isometric leg press for the measurement of the rate of force development (RFD). Resting vastus lateralis MFCV was measured with intramuscular microelectrodes on a different occasion, whereas muscle fiber type and cross-sectional area (CSA) of vastus lateralis were evaluated through muscle biopsies 1wk later. MFCV, CMJ power, RFD, and % CSA of type II and type IIx fibers were higher for the power-trained group (P < 0.001). No difference was found between sedentary participants and endurance runners in these variables, but both of these groups performed worse than strength/power participants. Close correlations were found between MFCV and fiber CSA as well as the % CSA of all fiber types as well as with RFD and CMJ power (r = 0.712-0.943, P < 0.005). Partial correlations revealed that the % CSA of IIx fibers dictates a large part of the correlation between MFCV and RFD, power performance. Significant models for the prediction of the % CSA of type IIa and type II as well as the CSA of all muscle fibers based upon MFCV, RFD, and CMJ were revealed (P = 0.000). MFCV is closely associated with muscle fiber % CSA. RFD and jumping power are associated with the propagation of the action potentials along the muscle fibers. This link is regulated by the size and the distribution of type II, and especially type IIx muscle fibers.

  16. Reduction of calcium inactivation of sarcoplasmic reticulum calcium release by fura-2 in voltage-clamped cut twitch fibers from frog muscle

    PubMed Central

    1993-01-01

    Cut fibers from Rana temporaria and Rana pipiens (striation spacing, 3.9-4.2 microns) were mounted in a double Vaseline-gap chamber and studied at 14 degrees C. The Ca indicator purpurate-3,3' diacetic acid (PDAA) was introduced into the end pools and allowed to diffuse into the optical recording site. When the concentration at the site exceeded 2 mM, step depolarizations to 10 mV were applied and the [Ca] transient measured with PDAA was used to estimate Ca release from the sarcoplasmic reticulum (SR) (Baylor, S. M., W. K. Chandler, and M. W. Marshall. 1983. Journal of Physiology. 344:625-666). With depolarization, the rate of SR Ca release increased to an early peak and then rapidly decreased several-fold to a quasi-steady level. The total amount of Ca released from the SR at the time of peak rate of release appeared to be independent of SR Ca content, consistent with the idea that a single activated channel might pass, on average, a fixed number of ions, independent of the magnitude of the single channel flux. A possible explanation of this property is given in terms of locally induced Ca inactivation of Ca release. The solution in the end pools was then changed to one with PDAA plus fura-2. SR Ca release was estimated from the [Ca] transient, as before, and from the delta [Cafura-2] signal. On average, 2-3 mM fura-2 increased the quasi-steady level of the rate of SR Ca release by factors of 6.6 and 3.8, respectively, in three fibers from Rana temporaria and three fibers from Rana pipiens. The peak rate of release was increased in five of the six fibers but to a lesser extent than the quasi-steady level. In all fibers, the amplitude of the free [Ca] transient was markedly reduced. These increases in the rate of SR Ca release are consistent with the idea that Ca inactivation of Ca release develops during a step depolarization to 10 mV and that 2-3 mM fura-2 is able to reduce this inactivation by complexing Ca and thereby reducing free [Ca]. Once the concentration

  17. Effects of Partial Sarcoplasmic Reticulum Calcium Depletion on Calcium Release in Frog Cut Muscle Fibers Equilibrated with 20 mM EGTA

    PubMed Central

    Pape, Paul C.; Jong, De-Shien; Knox Chandler, W.

    1998-01-01

    Resting sarcoplasmic reticulum (SR) Ca content ([CaSR]R) was varied in cut fibers equilibrated with an internal solution that contained 20 mM EGTA and 0–1.76 mM Ca. SR Ca release and [CaSR]R were measured with the EGTA–phenol red method (Pape et al. 1995. J. Gen. Physiol. 106:259–336). After an action potential, the fractional amount of Ca released from the SR increased from 0.17 to 0.50 when [CaSR]R was reduced from 1,200 to 140 μM. This increase was associated with a prolongation of release (final time constant, from 1–2 to 10–15 ms) and of the action potential (by 1–2 ms). Similar changes in release were observed with brief stimulations to −20 mV in voltage-clamped fibers, in which charge movement (Qcm) could be measured. The peak values of Qcm and the fractional rate of SR Ca release, as well as their ON time courses, were little affected by reducing [CaSR]R from 1,200 to 140 μM. After repolarization, however, the OFF time courses of Qcm and the rate of SR Ca release were slowed by factors of 1.5–1.7 and 6.5, respectively. These and other results suggest that, after action potential stimulation of fibers in normal physiological condition, the increase in myoplasmic free [Ca] that accompanies SR Ca release exerts three negative feedback effects that tend to reduce additional release: (a) the action potential is shortened by current through Ca-activated potassium channels in the surface and/or tubular membranes; (b) the OFF kinetics of Qcm is accelerated; and (c) Ca inactivation of Ca release is increased. Some of these effects of Ca on an SR Ca channel or its voltage sensor appear to be regulated by the value of [Ca] within 22 nm of the mouth of the channel. PMID:9725889

  18. Aging of skeletal muscle fibers.

    PubMed

    Miljkovic, Natasa; Lim, Jae-Young; Miljkovic, Iva; Frontera, Walter R

    2015-04-01

    Aging has become an important topic for scientific research because life expectancy and the number of men and women in older age groups have increased dramatically in the last century. This is true in most countries of the world including the Republic of Korea and the United States. From a rehabilitation perspective, the most important associated issue is a progressive decline in functional capacity and independence. Sarcopenia is partly responsible for this decline. Many changes underlying the loss of muscle mass and force-generating capacity of skeletal muscle can be understood at the cellular and molecular levels. Muscle size and architecture are both altered with advanced adult age. Further, changes in myofibers include impairments in several physiological domains including muscle fiber activation, excitation-contraction coupling, actin-myosin cross-bridge interaction, energy production, and repair and regeneration. A thorough understanding of these alterations can lead to the design of improved preventative and rehabilitative interventions, such as personalized exercise training programs.

  19. Composition of Muscle Fiber Types in Rat Rotator Cuff Muscles.

    PubMed

    Rui, Yongjun; Pan, Feng; Mi, Jingyi

    2016-10-01

    The rat is a suitable model to study human rotator cuff pathology owing to the similarities in morphological anatomy structure. However, few studies have reported the composition muscle fiber types of rotator cuff muscles in the rat. In this study, the myosin heavy chain (MyHC) isoforms were stained by immunofluorescence to show the muscle fiber types composition and distribution in rotator cuff muscles of the rat. It was found that rotator cuff muscles in the rat were of mixed fiber type composition. The majority of rotator cuff fibers labeled positively for MyHCII. Moreover, the rat rotator cuff muscles contained hybrid fibers. So, compared with human rotator cuff muscles composed partly of slow-twitch fibers, the majority of fast-twitch fibers in rat rotator cuff muscles should be considered when the rat model study focus on the pathological process of rotator cuff muscles after injury. Gaining greater insight into muscle fiber types in rotator cuff muscles of the rat may contribute to elucidate the mechanism of pathological change in rotator cuff muscles-related diseases. Anat Rec, 299:1397-1401, 2016. © 2016 Wiley Periodicals, Inc.

  20. The effects of cutting or of stretching skeletal muscle in vitro on the rates of protein synthesis and degradation

    NASA Technical Reports Server (NTRS)

    Seider, M. J.; Kapp, R.; Chen, C.-P.; Booth, F. W.

    1980-01-01

    Skeletal muscle preparations using cut muscle fibers have often been used in studies of protein metabolism. The present paper reports an investigation of the effect of muscle cutting or stretching in vitro on the rates of protein synthesis and/or degradation. Protein synthesis and content, and ATP and phosphocreatine levels were monitored in soleus and extensor digitorum longus muscles from the rat with various extents of muscle fiber cuts and following stretching to about 120% the resting length. Rates of protein synthesis are found to be significantly lower and protein degradation higher in the cut muscles than in uncut controls, while ATP and phosphocreatine concentrations decreased. Stretched intact muscles, on the other hand, are observed to have higher concentrations of high-energy phosphates than unstretched muscles, while rates of protein degradation were not affected. Results thus demonstrate that the cutting of skeletal muscle fibers alters many aspects of muscle metabolism, and that moderate decreases in ATP concentration do not alter rates of protein concentration in intact muscles in vitro.

  1. The effects of cutting or of stretching skeletal muscle in vitro on the rates of protein synthesis and degradation

    NASA Technical Reports Server (NTRS)

    Seider, M. J.; Kapp, R.; Chen, C.-P.; Booth, F. W.

    1980-01-01

    Skeletal muscle preparations using cut muscle fibers have often been used in studies of protein metabolism. The present paper reports an investigation of the effect of muscle cutting or stretching in vitro on the rates of protein synthesis and/or degradation. Protein synthesis and content, and ATP and phosphocreatine levels were monitored in soleus and extensor digitorum longus muscles from the rat with various extents of muscle fiber cuts and following stretching to about 120% the resting length. Rates of protein synthesis are found to be significantly lower and protein degradation higher in the cut muscles than in uncut controls, while ATP and phosphocreatine concentrations decreased. Stretched intact muscles, on the other hand, are observed to have higher concentrations of high-energy phosphates than unstretched muscles, while rates of protein degradation were not affected. Results thus demonstrate that the cutting of skeletal muscle fibers alters many aspects of muscle metabolism, and that moderate decreases in ATP concentration do not alter rates of protein concentration in intact muscles in vitro.

  2. Longitudinal impedance of single frog muscle fibers

    PubMed Central

    1975-01-01

    The longitudinal impedance of single skeletal muscle fibers has been measured from1 to 10,000 Hz in an oil gap apparatus which forces current to flow longitudinally down the fiber. The impedance observed is purely resistive in some fibers from the semitendinosus muscle and in two fibers from the sartorius muscle. In other fibers from the semitendinosus muscle a small phase shift is observed. The mean value of the maximum phase shift observed from all fibers is 1.07 degrees. The artifacts associated with the apparatus and method are examined theoretically and it is shown that one of the likely artifacts could account for the small phase observed. It is concluded that the longitudinal impedance of skeletal muscle fibers is essentially resistive and that little, if any, longitudinal current crosses the membranes of the sarcoplasmic reticulum. PMID:1078575

  3. Cutting cured carbon fiber composites using electrical discharge machining

    SciTech Connect

    Strong, A.B.; Crockett, T.; Merrell, R.S.; Dredge, J.D. Jr. )

    1991-04-01

    Traditionally, composite materials are cut using mechanical (solid tool) methods (drilling, milling, grinding, etc) or one of the newer cutting methods such as water jet or laser. All of these methods have serious disadvantages, especially when cutting sharp radii and/or working within close tolerances. The electrical discharge machining (EDM) method offers new opportunities to cut conductive composite materials (such as those containing carbon fibers) with excellent accuracy and minimum damage to the composite part.

  4. Single muscle fiber adaptations with marathon training.

    PubMed

    Trappe, Scott; Harber, Matthew; Creer, Andrew; Gallagher, Philip; Slivka, Dustin; Minchev, Kiril; Whitsett, David

    2006-09-01

    The purpose of this investigation was to characterize the effects of marathon training on single muscle fiber contractile function in a group of recreational runners. Muscle biopsies were obtained from the gastrocnemius muscle of seven individuals (22 +/- 1 yr, 177 +/- 3 cm, and 68 +/- 2 kg) before, after 13 wk of run training, and after 3 wk of taper. Slow-twitch myosin heavy chain [(MHC) I] and fast-twitch (MHC IIa) muscle fibers were analyzed for size, strength (P(o)), speed (V(o)), and power. The run training program led to the successful completion of a marathon (range 3 h 56 min to 5 h 35 min). Oxygen uptake during submaximal running and citrate synthase activity were improved (P < 0.05) with the training program. Muscle fiber size declined (P < 0.05) by approximately 20% in both fiber types after training. P(o) was maintained in both fiber types with training and increased (P < 0.05) by 18% in the MHC IIa fibers after taper. This resulted in >60% increase (P < 0.05) in force per cross-sectional area in both fiber types. Fiber V(o) increased (P < 0.05) by 28% in MHC I fibers with training and was unchanged in MHC IIa fibers. Peak power increased (P < 0.05) in MHC I and IIa fibers after training with a further increase (P < 0.05) in MHC IIa fiber power after taper. These data show that marathon training decreased slow-twitch and fast-twitch muscle fiber size but that it maintained or improved the functional profile of these fibers. A taper period before the marathon further improved the functional profile of the muscle, which was targeted to the fast-twitch muscle fibers.

  5. Muscle profiling to improve the value of retail meat cuts.

    PubMed

    Jung, E Y; Hwang, Y H; Joo, S T

    2016-10-01

    Nutrition and meat quality are always important to consumers, but vary by individual muscle or muscle groups in retail meat cuts. Muscle profiling of nutrient content and palatability for all retail beef cuts is necessary to suggest healthy and tasty beef cuts and to inform consumers of the benefits of beef consumption. The current paper reviews numerous studies that provide muscle profiles for nutrients and palatability attributes of muscles or muscle groups in retail beef cuts. The composition of nutrients including protein, fat, moisture, vitamins, and minerals in beef cuts is documented as well as the nutritive role as a part of a healthy diet. In addition, this review presents knowledge in relation to innovative carcass fabrication and value-added cuts to improve the value of beef carcass. Finally, the current work emphasize the palatability assessment of individual beef muscles, and concludes that all retail beef cuts should be merchandised for proper cooking according to the palatability profiles of beef muscles. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Effect of Sarcoplasmic Reticulum (SR) Calcium Content on SR Calcium Release Elicited by Small Voltage-Clamp Depolarizations in Frog Cut Skeletal Muscle Fibers Equilibrated with 20 mM EGTA

    PubMed Central

    Pape, Paul C.; Carrier, Nicole

    1998-01-01

    Cut muscle fibers from Rana temporaria (sarcomere length, 3.5–3.9 μm; 14–16°C) were mounted in a double Vaseline-gap chamber and equilibrated with an external solution that contained tetraethyl ammonium– gluconate and an internal solution that contained Cs as the principal cation, 20 mM EGTA, and 0 Ca. Fibers were stimulated with a voltage-clamp pulse protocol that consisted of pulses to −70, −65, −60, −45, and −20 mV, each separated by 400-ms periods at −90 mV. The change in total Ca that entered into the myoplasm (Δ[CaT]) and the Ca content of the SR ([CaSR]) were estimated with the EGTA/phenol red method (Pape, P.C., D.-S. Jong, and W.K. Chandler. 1995. J. Gen. Physiol. 106:259–336). Fibers were stimulated with the pulse protocol, usually every 5 min, so that the resting value of [CaSR] decreased from its initial value of 1,700–2,300 μM to values near or below 100 μM after 18–30 stimulations. Three main findings for the voltage pulses to −70, −65, and −60 mV are: (a) the depletion-corrected rate of Ca release (release permeability) showed little change when [CaSR] decreased from its highest level (>1,700 μM) to ∼1,000 μM; (b) as [CaSR] decreased below 1,000 μM, the release permeability increased to a maximum level when [CaSR] was near 300 μM that was on average about sevenfold larger than the values observed for [CaSR] > 1,000 μM; and (c) as [CaSR] decreased from ∼300 μM to <100 μM, the release permeability decreased, reaching half its maximum value when [CaSR] was ∼110 μM on average. It was concluded that finding b was likely due to a decrease in Ca inactivation, while finding c was likely due to a decrease in Ca-induced Ca release. PMID:9689025

  7. Efficiency of Laser Cutting of Carbon Fiber Textiles

    NASA Astrophysics Data System (ADS)

    Fuchs, Alexander N.; Zaeh, Michael F.

    Laser cutting of carbon fiber textiles has various advantages over conventional processes like ultrasonic knife cutting: It is wear free, no fibers are left uncut in the kerf, it is able to cut complex contours, and the cut edge is clearly defined. To ensure a complete cut under variable conditions, e.g. the thickness of the material, line energy has to be applied at a higher level than theoretically necessary to account for those variations. This energy is transilluminated through the kerf. In addition, not all laser energy is absorbed by the fibers but reflected and transmitted within the space between the fibers. Experiments were carried out to measure the percentage of laser power transilluminated through multi-layered carbon fiber textiles during laser cutting with maximum speed. To do so, blocks of poly(methyl methacrylate) (PMMA) were placed underneath the samples and the mass of the sublimed material was measured. Depending on the angle of the fiber, between 9% and 40% of the laser power was transilluminated.

  8. Hydrostatic compression in glycerinated rabbit muscle fibers.

    PubMed

    Ranatunga, K W; Fortune, N S; Geeves, M A

    1990-12-01

    Glycerinated muscle fibers isolated from rabbit psoas muscle, and a number of other nonmuscle elastic fibers including glass, rubber, and collagen, were exposed to hydrostatic pressures of up to 10 MPa (100 Atm) to determine the pressure sensitivity of their isometric tension. The isometric tension of muscle fibers in the relaxed state (passive tension) was insensitive to increased pressure, whereas the muscle fiber tension in rigor state increased linearly with pressure. The tension of all other fiber types (except rubber) also increased with pressure; the rubber tension was pressure insensitive. The pressure sensitivity of rigor tension was 2.3 kN/m2/MPa and, in comparison with force/extension relation determined at atmospheric pressure, the hydrostatic compression in rigor muscle fibers was estimated to be 0.03% Lo/MPa. As reported previously, the active muscle fiber tension is depressed by increased pressure. The possible underlying basis of the different pressure-dependent tension behavior in relaxed, rigor, and active muscle is discussed.

  9. Experimental investigation on fiber laser cutting of aluminium thin sheets

    NASA Astrophysics Data System (ADS)

    Scintilla, Leonardo Daniele

    2014-02-01

    The most extensively used lasers for aluminum and its alloys cutting, are CO2 and Nd:YAG operating in continuous wave and pulsed mode. High power solid state fiber lasers operating in continuous wave mode offer a great potential in improving the cut quality and productivity of highly reflective materials cutting process due to the better absorptivity of 1 μm laser radiation. The high processing speeds of CW mode and a good cut quality could be achieved at the same time. In this work, cutting experiments were performed on Al1050 1mm thick sheets using a fiber laser and Nitrogen as assist gas. A DOE approach that consists of fitting the regression models by means of response surface method (RSM) was adopted. The effects of cutting speed, focal position and assist gas pressure on dross height, kerf width and roughness parameters were investigated. Results showed that processing in CW with fiber laser increases the cutting speed and gives a cut quality comparable with results obtained with CO2 and Nd:YAG lasers and reported in literature.

  10. CO2 Laser Cutting of Glass Fiber Reinforce Polymer Composite

    NASA Astrophysics Data System (ADS)

    Fatimah, S.; Ishak, M.; Aqida, S. N.

    2012-09-01

    The lamination, matrix properties, fiber orientation, and relative volume fraction of matrix of polymer structure make this polymer hard to process. The cutting of polymer composite using CO2 laser could involve in producing penetration energy in the process. Identification of the dominant factors that significantly affect the cut quality is important. The objective of this experiment is to evaluate the CO2 spot size of beam cutting for Glass Fiber Reinforce Polymer Composite (GFRP). The focal length selected 9.5mm which gave smallest focus spot size according to the cutting requirements. The effect of the focal length on the cut quality was investigated by monitoring the surface profile and focus spot size. The beam parameter has great effect on both the focused spot size and surface quality.

  11. Fiber architecture of canine abdominal muscles.

    PubMed

    Boriek, Aladin M; Ortize, Jaime; Zhu, Deshen

    2002-02-01

    During respiration, abdominal muscles experience loads, not only in the muscle-fiber direction but also transverse to the fibers. We wondered whether the abdominal muscles exhibit a fiber architecture that is similar to the diaphragm muscle, and, therefore, we chose two adjacent muscles: the internal oblique (IO), with about the same muscle length as the diaphragm, and the transverse abdominis (TA), which is twice as long as the diaphragm. First, we used acetylcholinesterase staining to examine the distribution of neuromuscular junctions on both surfaces of the TA and IO muscles in six dogs. A maximum of four irregular bands of neuromuscular junctions crossed the IO, and as many as six bands crossed the TA, which is consistent with a discontinuous fiber architecture. In six additional dogs, we examined fiber architecture of these muscles by microdissecting 103 fascicles from the IO and 139 from the TA. Each fascicle contained between 20 and 30 muscle fibers. The mean length of nonspanning fibers (NSF) ranged from 2.8 +/- 0.3 cm in the IO to 4.3 +/- 0.5 cm in the TA, and the mean length of spanning fibers ranged from 4.3 +/- 0.5 cm in the IO to 7.6 +/- 1.4 cm in the TA. NSF accounted for 89.6 +/- 1.5% of all fibers dissected from the IO and 99.1 +/- 0.2% of all fibers dissected from the TA. The percentage of NSF with both ends tapered was 6.2 +/- 1.0 and 41.0 +/- 2.3% for IO and TA, respectively. These data show that fiber architecture in either IO or TA is discontinuous, with much more short-tapered fibers in the TA than in the IO. When abdominal muscles are submaximally activated, as during both normal expiration and maximal expiratory efforts, muscle force could be transmitted to the cell membrane and to the extracellular intramuscular connective tissue by shear linkage, presumably via structural transmembrane proteins.

  12. An evaluation of the reliability of muscle fiber cross-sectional area and fiber number measurements in rat skeletal muscle

    USDA-ARS?s Scientific Manuscript database

    Background: The reliability of estimating muscle fiber cross-sectional area (measure of muscle fiber size) and fiber number from only a subset of fibers in rat hindlimb muscle cross-sections has not been systematically evaluated. This study examined the variability in mean estimates of fiber cross-s...

  13. Remote Fiber Laser Cutting System for Dismantling Glass Melter - 13071

    SciTech Connect

    Mitsui, Takashi; Miura, Noriaki; Oowaki, Katsura; Kawaguchi, Isao; Miura, Yasuhiko; Ino, Tooru

    2013-07-01

    Since 2008, the equipment for dismantling the used glass melter has been developed in High-level Liquid Waste (HLW) Vitrification Facility in the Japanese Rokkasho Reprocessing Plant (RRP). Due to the high radioactivity of the glass melter, the equipment requires a fully-remote operation in the vitrification cell. The remote fiber laser cutting system was adopted as one of the major pieces of equipment. An output power of fiber laser is typically higher than other types of laser and so can provide high-cutting performance. The fiber laser can cut thick stainless steel and Inconel, which are parts of the glass melter such as casings, electrodes and nozzles. As a result, it can make the whole of the dismantling work efficiently done for a shorter period. Various conditions of the cutting test have been evaluated in the process of developing the remote fiber cutting system. In addition, the expected remote operations of the power manipulator with the laser torch have been fully verified and optimized using 3D simulations. (authors)

  14. Single Muscle Fiber Proteomics Reveals Fiber-Type-Specific Features of Human Muscle Aging.

    PubMed

    Murgia, Marta; Toniolo, Luana; Nagaraj, Nagarjuna; Ciciliot, Stefano; Vindigni, Vincenzo; Schiaffino, Stefano; Reggiani, Carlo; Mann, Matthias

    2017-06-13

    Skeletal muscle is a key tissue in human aging, which affects different muscle fiber types unequally. We developed a highly sensitive single muscle fiber proteomics workflow to study human aging and show that the senescence of slow and fast muscle fibers is characterized by diverging metabolic and protein quality control adaptations. Whereas mitochondrial content declines with aging in both fiber types, glycolysis and glycogen metabolism are upregulated in slow but downregulated in fast muscle fibers. Aging mitochondria decrease expression of the redox enzyme monoamine oxidase A. Slow fibers upregulate a subset of actin and myosin chaperones, whereas an opposite change happens in fast fibers. These changes in metabolism and sarcomere quality control may be related to the ability of slow, but not fast, muscle fibers to maintain their mass during aging. We conclude that single muscle fiber analysis by proteomics can elucidate pathophysiology in a sub-type-specific manner. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  15. Age-related changes in rat intrinsic laryngeal muscles: analysis of muscle fibers, muscle fiber proteins, and subneural apparatuses.

    PubMed

    Nishida, Naoya; Taguchi, Aki; Motoyoshi, Kazumi; Hyodo, Masamitsu; Gyo, Kiyofumi; Desaki, Junzo

    2013-03-01

    We compared age-related changes in the intrinsic laryngeal muscles of aged and young adult rats by determining the number and diameter of muscle fibers, contractile muscle protein (myosin heavy chain isoforms, MHC) composition, and the morphology of the subneural apparatuses. In aged rats, both the numbers and the diameters of muscle fibers decreased in the cricothyroid (CT) muscle. The number of fibers, but not diameter, decreased in the thyroarytenoid (TA) muscle. In the posterior cricoarytenoid (PCA) muscle, neither the number nor the diameter of fibers changed significantly. Aging was associated with a decrease in type IIB and an increase in type IIA MHC isoform levels in CT muscle, but no such changes were observed in the TA or PCA muscles. Morphological examination of primary synaptic clefts of the subneural apparatus revealed that aging resulted in decreased labyrinthine and increased depression types in only the CT muscle. In the aged group, morphologically immature subneural apparatuses were found infrequently in the CT muscle, indicating continued tissue remodeling. We suggest, therefore, that age-related changes in the intrinsic laryngeal muscles primarily involve the CT muscle, whereas the structures of the TA and PCA muscles may better resist aging processes and therefore are less vulnerable to functional impairment. This may reflect differences in their roles; the CT muscle controls the tone of the vocal folds, while the TA and PCA muscles play an essential role in vital activities such as respiration and swallowing.

  16. Intermuscular relationship of human muscle fiber type proportions: slow leg muscles predict slow neck muscles.

    PubMed

    Vikne, Harald; Gundersen, Kristian; Liestøl, Knut; Maelen, Jan; Vøllestad, Nina

    2012-04-01

    Our aim in this study was to examine whether the muscle fiber type proportions in different muscles from the same individual are interrelated. Samples were excised from five skeletal muscles in each of 12 human autopsy cases, and the fiber type proportions were determined by immunohistochemistry. We further examined the intermuscular relationship in fiber type proportion by reanalyzing three previously published data sets involving other muscles. Subjects demonstrated a predominantly high or low proportion of type 1 fibers in all examined muscles, and the overall difference between individuals was statistically significant (P < 0.001). Accordingly, the type 1 fiber proportions in most muscles were positively correlated (median r = 0.42, range -0.03-0.80). Similar results were also obtained from the three reanalyzed data sets. We suggest the existence of an across-muscle phenotype with respect to fiber type proportions; some individuals display generally faster muscles and some individuals slower muscles when compared with others. Copyright © 2011 Wiley Periodicals, Inc.

  17. Radial forces within muscle fibers in rigor.

    PubMed

    Maughan, D W; Godt, R E

    1981-01-01

    Considering the widely accepted cross-bridge model of muscle contraction (Huxley. 1969. Science [Wash. D. C.]. 164:1356-1366), one would expect that attachment of angled cross-bridges would give rise to radial as well as longitudinal forces in the muscle fiber. These forces would tend, in most instances, to draw the myofilaments together and to cause the fiber to decrease in width. Using optical techniques, we have observed significant changes in the width of mechanically skinned frog muscle fibers when the fibers are put into rigor by deleting ATP from the bathing medium. Using a high molecular weight polymer polyvinylpyrrolidone (PVP-40; number average mol. wt. (Mn) = 40,000) in the bathing solution, we were able to estimate the magnitude of the radial forces by shrinking the relaxed fiber to the width observed with rigor induction. With rigor, fiber widths decreased up to approximately 10%, with shrinking being greater at shorter sarcomere spacing and at lower PVP concentrations. At higher PVP concentrations, some fibers actually swelled slightly. Radial pressures seen with rigor in 2 and 4% PVP ranged up to 8.9 x 10(3) N/m2. Upon rigor induction, fibers exerted a longitudinal force of approximately 1 x 10(5) N/m2 that was inhibited by high PVP concentrations (greater than or equal to 13%). In very high PVP concentrations (greater than or equal to 20%), fibers exerted an anomalous force, independent of ATP, which ranged up to 6 x 10(4) N/m2 at 60% PVP. Assuming that all the radial force is the result of cross-bridge attachment, we calculated that rigor cross-bridges exert a radial force of 0.2 x 1.2 x 10(-9) N per thick filament in sarcomeres near rest length. This force is of roughly the same order of magnitude as the longitudinal force per thick filament in rigor contraction or in maximal (calcium-activated) contraction of skinned fibers in ATP-containing solutions. Inasmuch as widths of fibers stretched well beyond overlap of thick and thin filaments

  18. Distribution of slow muscle fiber of muscle spindle in postnatal rat masseter muscle.

    PubMed

    Sato, Iwao; Imura, Kosuke; Miwa, Yoko; Ide, Yoshiaki; Murata, Megumi; Sunohara, Masataka

    2007-11-01

    We investigated the properties of the muscle spindle in the masseter muscle at an immunohistochemical level in rats fed for 6 weeks. Slow myosin heavy chain (MyHC) isoforms were measured and intrafusal fibers in the muscle spindle were studied to determine the relationship between the superficial and deep regions of rat masseter muscle after alternated feeding pattern. However, muscle spindles were found in both regions, mainly in the deep region of the posterior superficial region of masseter muscle. The total number of the slow fiber in the intrafusal fiber and number of muscle spindle in the deep region were high from 5 to 8 weeks old in spite of various dimensions of data such as diameter and the compositions of the intrafusal fiber. The relationship of the protein expression of slow MyHC in the two regions at 5 weeks old reversed five weeks later (10 weeks old). This period is an important stage because the mastication system in masseter muscle with muscle spindle may be changed during the alternated feeding pattern of suckling to mastication. The changes may be a marker of the feeding system and of the control by the tension receptor of muscle spindle in this stage of masseter muscle after postnatal development.

  19. Micro-hole drilling and cutting using femtosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Huang, Huan; Yang, Lih-Mei; Liu, Jian

    2014-05-01

    Micro-hole drilling and cutting in ambient air are presented by using a femtosecond fiber laser. At first, the micro-hole drilling was investigated in both transparent (glasses) and nontransparent (metals and tissues) materials. The shape and morphology of the holes were characterized and evaluated with optical and scanning electron microscopy. Debris-free micro-holes with good roundness and no thermal damage were demonstrated with the aspect ratio of 8∶1. Micro-hole drilling in hard and soft tissues with no crack or collateral thermal damage is also demonstrated. Then, trench micromachining and cutting were studied for different materials and the effect of the laser parameters on the trench properties was investigated. Straight and clean trench edges were obtained with no thermal damage.

  20. Production and characterization of cut resistant acrylic/copolyaramid fibers via bicomponent wet spinning

    NASA Astrophysics Data System (ADS)

    Hipp, Stephen James

    A composite fiber system consisting of a sheath core bicomponent polymer fiber loaded with hard ceramic particles was developed and characterized for use in cut protective clothing. The core component was comprised of a copolyaramid in order to provide high base cut resistance. An acrylic-copolyaramid polymer blend was used for the sheath component to improve processability and provide potential benefits such as dyeability. Lastly, aluminum oxide particles were incorporated into the fiber core to deflect and deform the cutting edge, further improving cut resistance. A series of designed experiments was used to explore the effects of the wet spinning and heat treatment processes on the structure and properties of the bicomponent fiber. Cut strength of the as-spun fibers was highest when the coagulation rate was slow, promoting the formation of a dense, macrovoid free fiber structure. Upon drawing, fibrillar domains developed within the fiber, further improving cut performance. Cut strength was greatly improved by the heat treatment process despite the fibers becoming highly anisotropic. Addition of the hard particle fillers to the bicomponent fibers showed a decrease in cut strength at the fiber level but nearly doubled the cut strength of resulting fabrics. Finally, the processability of the particle loaded bicomponent fibers was evaluated.

  1. Graded Activation in Frog Muscle Fibers

    PubMed Central

    Costantin, L. L.; Taylor, S. R.

    1973-01-01

    The membrane potential of frog single muscle fibers in solutions containing tetrodotoxin was controlled with a two-electrode voltage clamp. Local contractions elicited by 100-ms square steps of depolarization were observed microscopically and recorded on cinefilm. The absence of myofibrillar folding with shortening to striation spacings below 1.95 µm served as a criterion for activation of the entire fiber cross section. With depolarizing steps of increasing magnitude, shortening occurred first in the most superficial myofibrils and spread inward to involve axial myofibrils as the depolarization was increased. In contractions in which the entire fiber cross section shortened actively, both the extent of shortening and the velocity of shortening at a given striation spacing could be graded by varying the magnitude of the depolarization step. The results provide evidence that the degree of activation of individual myofibrils can be graded with membrane depolarization. PMID:4540418

  2. Adherent Primary Cultures of Mouse Intercostal Muscle Fibers for Isolated Fiber Studies

    PubMed Central

    Robison, Patrick; Hernández-Ochoa, Erick O.; Schneider, Martin F.

    2011-01-01

    Primary culture models of single adult skeletal muscle fibers dissociated from locomotor muscles adhered to glass coverslips are routine and allow monitoring of functional processes in living cultured fibers. To date, such isolated fiber cultures have not been established for respiratory muscles, despite the fact that dysfunction of core respiratory muscles leading to respiratory arrest is the most common cause of death in many muscular diseases. Here we present the first description of an adherent culture system for single adult intercostal muscle fibers from the adult mouse. This system allows for monitoring functional properties of these living muscle fibers in culture with or without electrical field stimulation to drive muscle fiber contraction at physiological or pathological respiratory firing patterns. We also provide initial characterization of these fibers, demonstrating several common techniques in this new model system in the context of the established Flexor Digitorum Brevis muscle primary culture model. PMID:21869860

  3. Regional heterogeneity in muscle fiber strain: the role of fiber architecture

    PubMed Central

    Azizi, E.; Deslauriers, Amber R.

    2014-01-01

    The force, mechanical work and power produced by muscle fibers are profoundly affected by the length changes they undergo during a contraction. These length changes are in turn affected by the spatial orientation of muscle fibers within a muscle (fiber architecture). Therefore any heterogeneity in fiber architecture within a single muscle has the potential to cause spatial variation in fiber strain. Here we examine how the architectural variation within a pennate muscle and within a fusiform muscle can result in regional fiber strain heterogeneity. We combine simple geometric models with empirical measures of fiber strain to better understand the effect of architecture on fiber strain heterogeneity. We show that variation in pennation angle throughout a muscle can result in differences in fiber strain with higher strains being observed at lower angles of pennation. We also show that in fusiform muscles, the outer/superficial fibers of the muscle experience lower strains than central fibers. These results show that regional variation in mechanical output of muscle fibers can arise solely from architectural features of the muscle without the presence of any spatial variation in motor recruitment. PMID:25161626

  4. Influence of Fiber Orientation on Single-Point Cutting Fracture Behavior of Carbon-Fiber/Epoxy Prepreg Sheets

    PubMed Central

    Wei, Yingying; An, Qinglong; Cai, Xiaojiang; Chen, Ming; Ming, Weiwei

    2015-01-01

    The purpose of this article is to investigate the influences of carbon fibers on the fracture mechanism of carbon fibers both in macroscopic view and microscopic view by using single-point flying cutting method. Cutting tools with three different materials were used in this research, namely, PCD (polycrystalline diamond) tool, CVD (chemical vapor deposition) diamond thin film coated carbide tool and uncoated carbide tool. The influence of fiber orientation on the cutting force and fracture topography were analyzed and conclusions were drawn that cutting forces are not affected by cutting speeds but significantly influenced by the fiber orientation. Cutting forces presented smaller values in the fiber orientation of 0/180° and 15/165° but the highest one in 30/150°. The fracture mechanism of carbon fibers was studied in different cutting conditions such as 0° orientation angle, 90° orientation angle, orientation angles along fiber direction, and orientation angles inverse to the fiber direction. In addition, a prediction model on the cutting defects of carbon fiber reinforced plastic was established based on acoustic emission (AE) signals. PMID:28793597

  5. Mapping of intramuscular tenderness and muscle fiber orientation of muscles in the beef round.

    PubMed

    Senaratne, L S; Calkins, C R; de Mello, A S; Pokharel, S; Hinkle, J B

    2010-09-01

    Intramuscular tenderness variation and muscle fiber orientation of beef M. adductor femoris (AF), M. biceps femoris (BF), M. gracilis (GL), M. pectineus (PT), M. sartorius (SR), M. semimembranosus (SM), M. semitendinosus (SO), M. vastus intermedius (VI), M. vastus medialis (VM), and M. vastus lateralis (VL) were investigated. The USDA Choice boxed beef subprimals were purchased and aged for 14 d from boxed date. The AF, BF, GL, PT, SR, SM, SO, VI, VM, and VL (n = 10 each) were fabricated from subprimals. Crust-frozen AF, BF, SO, SM, and VL were cut into 2.54-cm steaks perpendicular to the long axis and grilled (71 degrees C). The PT, SR, VI, and VM were grilled (71 degrees C) as whole muscles, whereas the GL was grilled after cutting into anterior and posterior regions. Grilled muscles were cut into equal size sections perpendicular to long axis of muscles. Location-specific cores were prepared from each steak/section, and Warner-Bratzler shear force (WBSF) was measured. The muscle fiber orientations of BF, PT, and VI were bipennate, SR and SO were fusiform, and AD, SM, VL, GL, and VM were unipennate. The overall mean WBSF values for BF, SO, AF, SM, PT, SR, GL, VI, VM, and VL were 5.62, 4.86, 4.18, 4.90, 3.76, 4.44, 4.75, 4.78, 4.24, and 6.53 kg, respectively. Based on WBSF values, PT was tender, BF and VL were tough, and VM, VI, SM, GL SR, AF, and SO were intermediate. The first 2 proximal steaks of long head BF were more tender than the rest (P < 0.05). In the SO, the tenderness decreased from the middle of the muscle to both ends (P < 0.05). The anterior sides of the long head BF and SO were tougher than their posterior sides (P < 0.05).The first 4 steaks of the SM were more tender than the rest of the muscle (P < 0.05). There was a significant tenderness increment from the middle of the AF and SR to both ends of each muscle (P < 0.05). The medial side of the VI was more tender than its lateral side (P < 0.05). The VM had its smallest shear force value at the

  6. Slow fiber cluster pattern in pig longissimus thoracis muscle: implications for myogenesis.

    PubMed

    Fonseca, S; Wilsons, I J; Horgan, G W; Maltin, C A

    2003-04-01

    Recent evidence implicates fiber type proportions as playing a role in meat eating quality, and in pigs it has been suggested that the slow oxidative fibers contribute to both juiciness and tenderness. The fiber distribution in pigs is different from that found in most other species, in which the various types of skeletal muscle fiber are distributed in a "checkerboard" pattern, because in pigs the slow oxidative fibers have a clustered distribution. The initial processes leading to fiber clustering are likely to occur during myogenesis, but the precise mechanistic aetiology of this patterning and whether the slow oxidative fiber clusters occur in a random or ordered fashion is unknown. In the present study longissimus thoracis muscle from Large White crossbred pigs was sampled at the 10th rib, 48 h postmortem. Transverse cryo-sections were cut and histochemically stained to allow the identification of the main muscle fiber types: slow oxidative, fast glycolytic, and fast oxidative glycolytic. Images of the sections were captured and analyzed using point processes and Voronoi Tesselations to examine the randomness and spatial distribution of the clusters of slow oxidative fibers found in pig longissimus thoracis muscle. The results showed that an assumption of complete spatial randomness can be rejected and that a mathematical model incorporating a minimum distance of 1.7 to 2.0 microm between cluster centers produced fiber patterns similar to those observed in the original transverse sections of the muscle. In addition, if it assumed that the central fiber in each cluster is derived from primary myoblast progenitors, these results suggest that there may be some degree of repulsion between the primary fibers during the initial stages of cluster formation. The mechanistic basis of such repulsion is not clear, but it is speculated that secreted factors, such as sonic hedgehog or myostatin may play a role.

  7. Diffusion-Tensor MRI Based Skeletal Muscle Fiber Tracking.

    PubMed

    Damon, Bruce M; Buck, Amanda K W; Ding, Zhaohua

    2011-11-01

    A skeletal muscle's function is strongly influenced by the internal organization and geometric properties of its fibers, a property known as muscle architecture. Diffusion-tensor magnetic resonance imaging-based fiber tracking provides a powerful tool for non-invasive muscle architecture studies, has three-dimensional sensitivity, and uses a fixed frame of reference. Significant advances have been made in muscle fiber tracking technology, including defining seed points for fiber tracking, quantitatively characterizing muscle architecture, implementing denoising procedures, and testing validity and repeatability. Some examples exist of how these data can be integrated with those from other advanced MRI and computational methods to provide novel insights into muscle function. Perspectives are offered regarding future directions in muscle diffusion-tensor imaging, including needs to develop an improved understanding for the microstructural basis for reduced and anisotropic diffusion, establish the best practices for data acquisition and analysis, and integrate fiber tracking with other physiological data.

  8. Disodium cromoglycate protects dystrophin-deficient muscle fibers from leakiness.

    PubMed

    Marques, Maria Julia; Ventura Machado, Rafael; Minatel, Elaine; Santo Neto, Humberto

    2008-01-01

    In dystrophin-deficient fibers of mdx mice and in Duchenne dystrophy, the lack of dystrophin leads to sarcolemma breakdown and muscle degeneration. We verified that cromolyn, a mast-cell stabilizer agent, stabilized dystrophic muscle fibers using Evans blue dye as a marker of sarcolemma leakiness. Mdx mice (n=8; 14 days of age) received daily intraperitoneal injections of cromolyn (50 mg/kg body weight) for 15 days. Untreated mdx mice (n=8) were injected with saline. Cryostat cross-sections of the sternomastoid, tibialis anterior, and diaphragm muscles were stained with hematoxylin and eosin. Cromolyn dramatically reduced Evans blue dye-positive fibers in all muscles (P<0.05; Student's t-test) and led to a significant increase in the percentage of fibers with peripheral nuclei. This study supports the protective effects of cromolyn in dystrophic muscles and further indicates its action against muscle fiber leakiness in muscles that are differently affected by the lack of dystrophin.

  9. Muscle fiber type diversification during exercise and regeneration.

    PubMed

    Qaisar, Rizwan; Bhaskaran, Shylesh; Van Remmen, Holly

    2016-09-01

    The plasticity of skeletal muscle can be traced down to extensive metabolic, structural and molecular remodeling at the single fiber level. Skeletal muscle is comprised of different fiber types that are the basis of muscle plasticity in response to various functional demands. Resistance and endurance exercises are two external stimuli that differ in their duration and intensity of contraction and elicit markedly different responses in muscles adaptation. Further, eccentric contractions that are associated with exercise-induced injuries, elicit varied muscle adaptation and regenerative responses. Most adaptive changes are fiber type-specific and are highly influenced by diverse structural, metabolic and functional characteristics of individual fiber types. Regulation of signaling pathways by reactive oxygen species (ROS) and oxidative stress also plays an important role in muscle fiber adaptation during exercise. This review focuses on cellular and molecular responses that regulate the adaptation of skeletal muscle to exercise and exercise-related injuries.

  10. Diffusion-Tensor MRI Based Skeletal Muscle Fiber Tracking

    PubMed Central

    Damon, Bruce M.; Buck, Amanda K. W.; Ding, Zhaohua

    2014-01-01

    A skeletal muscle's function is strongly influenced by the internal organization and geometric properties of its fibers, a property known as muscle architecture. Diffusion-tensor magnetic resonance imaging-based fiber tracking provides a powerful tool for non-invasive muscle architecture studies, has three-dimensional sensitivity, and uses a fixed frame of reference. Significant advances have been made in muscle fiber tracking technology, including defining seed points for fiber tracking, quantitatively characterizing muscle architecture, implementing denoising procedures, and testing validity and repeatability. Some examples exist of how these data can be integrated with those from other advanced MRI and computational methods to provide novel insights into muscle function. Perspectives are offered regarding future directions in muscle diffusion-tensor imaging, including needs to develop an improved understanding for the microstructural basis for reduced and anisotropic diffusion, establish the best practices for data acquisition and analysis, and integrate fiber tracking with other physiological data. PMID:25429308

  11. An improved vaseline gap voltage clamp for skeletal muscle fibers

    PubMed Central

    1976-01-01

    A Vaseline gap potentiometric recording and voltage clamp method is developed for frog skeletal muscle fibers. The method is based on the Frankenhaeuser-Dodge voltage clamp for myelinated nerve with modifications to improve the frequency response, to compensate for external series resistance, and to compensate for the complex impedance of the current-passing pathway. Fragments of single muscle fibers are plucked from the semitendinosus muscle and mounted while depolarized by a solution like CsF. After Vaseline seals are formed between fluid pools, the fiber ends are cut once again, the central region is rinsed with Ringer solution, and the feedback amplifiers are turned on. Errors in the potential and current records are assessed by direct measurements with microelectrodes. The passive properties of the preparation are simulated by the "disk" equivalent circuit for the transverse tubular system and the derived parameters are similar to previous measurements with microelectrodes. Action potentials at 5 degrees C are long because of the absence of delayed rectification. Their shape is approximately simulated by solving the disk model with sodium permeability in the surface and tubular membranes. Voltage clamp currents consist primarily of capacity currents and sodium currents. The peak inward sodium current density at 5 degrees C is 3.7 mA/cm2. At 5 degrees C the sodium currents are smoothly graded with increasing depolarization and free of notches suggesting good control of the surface membrane. At higher temperatures a small, late extra inward current appears for small depolarizations that has the properties expected for excitation in the transverse tubular system. Comparison of recorded currents with simulations shows that while the transverse tubular system has regenerative sodium currents, they are too small to make important errors in the total current recorded at the surface under voltage clamp at low temperature. The tubules are definitely not under voltage

  12. A Computational Approach to Detect and Segment Cytoplasm in Muscle Fiber Images

    PubMed Central

    Guo, Yanen; Xu, Xiaoyin; Wang, Yuanyuan; Yang, Zhong; Wang, Yaming; Xia, Shunren

    2015-01-01

    We developed a computational approach to detect and segment cytoplasm in microscopic images of muscle fibers. The computational approach provides computer-aided analysis of cytoplasm objects in muscle fiber images to facilitate biomedical research. Cytoplasm in muscle fibers plays an important role in maintaining the functioning and health of muscular tissues. Therefore, cytoplasm is often used as a marker in broad applications of musculoskeletal research, including our search on treatment of muscular disorders such as Duchenne muscular dystrophy, a disease that has no available treatment. However it is often challenging to analyze cytoplasm and quantify it given the large number of images typically generated in experiments and the large number of muscle fibers contained in each image. Manual analysis is not only time consuming but also prone to human errors. In this work we developed a computational approach to detect and segment the longitudinal sections of cytoplasm based on a modified graph cuts technique and iterative splitting method to extract cytoplasm objects from the background. First, cytoplasm objects are extracted from the background using the modified graph cuts technique which is designed to optimize an energy function. Second, an iterative splitting method is designed to separate the touching or adjacent cytoplasm objects from the results of graph cuts. We tested the computational approach on real data from in vitro experiments and found that it can achieve satisfactory performance in terms of precision and recall rates. PMID:25900156

  13. A computational approach to detect and segment cytoplasm in muscle fiber images.

    PubMed

    Guo, Yanen; Xu, Xiaoyin; Wang, Yuanyuan; Yang, Zhong; Wang, Yaming; Xia, Shunren

    2015-06-01

    We developed a computational approach to detect and segment cytoplasm in microscopic images of skeletal muscle fibers. The computational approach provides computer-aided analysis of cytoplasm objects in muscle fiber images to facilitate biomedical research. Cytoplasm in muscle fibers plays an important role in maintaining the functioning and health of muscular tissues. Therefore, cytoplasm is often used as a marker in broad applications of musculoskeletal research, including our search on treatment of muscular disorders such as Duchenne muscular dystrophy, a disease that has no available treatment. However, it is often challenging to analyze cytoplasm and quantify it given the large number of images typically generated in experiments and the large number of muscle fibers contained in each image. Manual analysis is not only time consuming but also prone to human errors. In this work we developed a computational approach to detect and segment the longitudinal sections of cytoplasm based on a modified graph cuts technique and iterative splitting method to extract cytoplasm objects from the background. First, cytoplasm objects are extracted from the background using the modified graph cuts technique which is designed to optimize an energy function. Second, an iterative splitting method is designed to separate the touching or adjacent cytoplasm objects from the results of graph cuts. We tested the computational approach on real data from in vitro experiments and found that it can achieve satisfactory performance in terms of precision and recall rates. © 2015 Wiley Periodicals, Inc.

  14. Quantitative force comparison of polyacrylonitrile fibers with skeletal muscle

    NASA Astrophysics Data System (ADS)

    Gonzalez, Roger V.; Lee, Christopher Y.

    1998-07-01

    The possibility of using certain polymer gels as artificial skeletal muscle was investigated due to its ability to shorten or contract when saturated in acidic or basic solutions, respectively. Polyacrylonitrile (PAN) fiber is such an example of a polymer gel. Mechanical performance characteristics of PAN fibers were studied and compared to voluntary muscle mechanical properties. The experimental methods used to determine the mechanical properties of the PAN fibers were modeled after A. V. Hill's classic experiments of the force-length and force-velocity properties of voluntary muscle. In addition, the force-molarity, length-molarity, and force-time characteristics were measured for the PAN fibers. These characteristics were quantitatively and qualitatively compared to voluntary muscle properties when relevant and used to determine the feasibility of implementing PAN fibers as artificial skeletal muscle in modeling movement across the human elbow joint. The results indicated qualitative similarities with the mechanical characteristics of voluntary muscle, especially force-velocity property. The force capabilities of the PAN fibers were at the lower end of voluntary muscle force generation. (i.e. 20 - 200 N/cm2) Activation- contraction time was also substantially larger than skeletal muscle. Based on these data, it was concluded that using PAN fibers as artificial muscles in modeling the human elbow joint is feasible only under certain conditions. Additional characterization studies are needed to determine if individual PAN fibers can generate higher forces using a different experimental protocol or a different architectural arrangement of the fibers.

  15. Ultrastructural organization of muscle fiber types and their distribution in the rat superior rectus extraocular muscle.

    PubMed

    Rashed, Rashed M; El-Alfy, Sherif H

    2012-05-01

    Extraocular muscles (EOMs) are unique as they show greater variation in anatomical and physiological properties than any other skeletal muscles. To investigate the muscle fiber types and to understand better the structure-function correlation of the extraocular muscles, the present study examined the ultrastructural characteristics of the superior rectus muscle of rat. The superior rectus muscle is organized into two layers: a central global layer of mainly large-diameter fibers and an outer C-shaped orbital layer of principally small-diameter fibers. Six morphologically distinct fiber types were identified within the superior rectus muscle. Four muscle fiber types, three single innervated fibers (SIFs) and one multiple innervated fiber (MIF), were recognized in the global layer. The single innervated fibers included red, white and intermediate fibers. They differed from one another with respect to diameter, mitochondrial size and distribution, sarcoplasmic reticulum and myofibrillar size. The orbital layer contained two distinct MIFs in addition to the red and intermediate SIFs. The orbital MIFs were categorized into low oxidative and high oxidative types according to their mitochondrial content and distribution. The highly specialized function of the superior rectus extraocular muscle is reflected in the multiplicity of its fiber types, which exhibit unique structural features. The unique ultrastructural features of the extraocular muscles and their possible relation to muscle function are discussed. Copyright © 2011 Elsevier GmbH. All rights reserved.

  16. ULTRASTRUCTURE OF BARNACLE GIANT MUSCLE FIBERS

    PubMed Central

    Hoyle, Graham; McNeill, Patricia A.; Selverston, Allen I.

    1973-01-01

    Increasing use of barnacle giant muscle fibers for physiological research has prompted this investigation of their fine structure. The fibers are invaginated by a multibranched system of clefts connecting to the exterior and filled with material similar to that of the basement material of the sarcolemmal complex. Tubules originate from the surface plasma membrane at irregular sites, and also from the clefts They run transversely, spirally, and longitudinally, making many diadic and some triadic contacts with cisternal sacs of the longitudinal sarcoplasmic reticulum. The contacts are not confined to any particular region of the sarcomere. The tubules are wider and their walls are thicker at points of contact with Z material. Some linking of the Z regions occurs across spaces within the fiber which contain large numbers of glycogen particles. A-band lengths are extremely variable, in the range 2.2 µm–20.3 µm (average 5.2 µm) Individual thick filaments have thin (110 Å) hollow regions alternating with thick (340 Å) solid ones. Bridges between thick filaments occur at random points and are not concentrated into an M band The thin:thick filament ratio is variable in different parts of a fiber, from 3:1 to 6:1. Z bands are basically perforated, but the number of perforations may increase during contraction. PMID:4264604

  17. Laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) by single-mode fiber laser irradiation

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Kawaguchi, Yoshizo; Sato, Tadatake; Narazaki, Aiko; Kurosaki, Ryozo; Muramatsu, Mayu; Harada, Yoshihisa; Anzai, Kenji; Aoyama, Mitsuaki; Matsushita, Masafumi; Furukawa, Koichi; Nishino, Michiteru; Fujisaki, Akira; Miyato, Taizo; Kayahara, Takashi

    2014-03-01

    We report on the laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) with a cw IR fiber laser (single-mode fiber laser, average power: 350 W). CFRTP is a high strength composite material with a lightweight, and is increasingly being used various applications. A well-defined cutting of CFRTP which were free of debris and thermal-damages around the grooves, were performed by the laser irradiation with a fast beam galvanometer scanning on a multiple-scanpass method.

  18. Effect of altering starting length and activation timing of muscle on fiber strain and muscle damage.

    PubMed

    Butterfield, Timothy A; Herzog, Walter

    2006-05-01

    Muscle strain injuries are some of the most frequent injuries in sports and command a great deal of attention in an effort to understand their etiology. These injuries may be the culmination of a series of subcellular events accumulated through repetitive lengthening (eccentric) contractions during exercise, and they may be influenced by a variety of variables including fiber strain magnitude, peak joint torque, and starting muscle length. To assess the influence of these variables on muscle injury magnitude in vivo, we measured fiber dynamics and joint torque production during repeated stretch-shortening cycles in the rabbit tibialis anterior muscle, at short and long muscle lengths, while varying the timing of activation before muscle stretch. We found that a muscle subjected to repeated stretch-shortening cycles of constant muscle-tendon unit excursion exhibits significantly different joint torque and fiber strains when the timing of activation or starting muscle length is changed. In particular, measures of fiber strain and muscle injury were significantly increased by altering activation timing and increasing the starting length of the muscle. However, we observed differential effects on peak joint torque during the cyclic stretch-shortening exercise, as increasing the starting length of the muscle did not increase torque production. We conclude that altering activation timing and muscle length before stretch may influence muscle injury by significantly increasing fiber strain magnitude and that fiber dynamics is a more important variable than muscle-tendon unit dynamics and torque production in influencing the magnitude of muscle injury.

  19. Muscle Histology Characterization Using H&E Staining and Muscle Fiber Type Classification Using Immunofluorescence Staining

    PubMed Central

    Wang, Chao; Yue, Feng; Kuang, Shihuan

    2017-01-01

    Muscle function is determined by its structure and fiber type composition. Here we describe a protocol to examine muscle histology and myofiber types using hematoxylin and eosin (H&E) and immunofluorescence staining, respectively. H&E stain nucleus in blue and cytoplasm in red, therefore allowing for morphological analyses, such as myofiber diameter, the presence of degenerated and regenerated myofibers, and adipocytes and fibrotic cells. Muscle fibers in adult skeletal muscles of rodents are classified into 4 subtypes based on the expression of myosin heavy chain proteins: Myh7 (type I fiber), Myh2 (type IIA fiber), Myh1 (type IIX fiber), Myh4 (type IIB fiber). A panel of monoclonal antibodies can be used to specifically label these muscle fiber subtypes. These protocols are commonly used in the study of muscle development, growth and regeneration (for example: Wang et al., 2015; Nie et al., 2016; Yue et al., 2016; Wang et al., 2017). PMID:28752107

  20. Hybrid fibers transform into distinct fiber types in maturing mouse muscles.

    PubMed

    Brummer, Hannah; Zhang, Min Yi; Piddoubny, Maria; Medler, Scott

    2013-01-01

    The role of hybrid fibers as intermediates in fiber type transformations is not completely understood. In some cases hybrids are clearly transitional fibers changing from one type to another, but in others they represent phenotypically stable fibers in normal muscles. In the current study, our goal was to understand the fate of hybrid fibers in fiber type transitions that take place during muscle maturation. Previous studies have reported high proportions of hybrid fibers during postnatal development, but few have followed the fate of these fibers past the time of weaning. We quantified proportions of hybrid fibers in three different mouse skeletal muscles from newly weaned to 6-month-old mice. Hybrid fibers were very prevalent in the brachioradialis (BR) and tibialis anterior (TA) muscles from newly weaned mice, where they constituted 50 and 40% of the fibers, respectively. These hybrids declined steadily to about 15-30% over the next several months. In the soleus muscle the proportion of hybrids did not change, but constituted approximately 20% of fibers. The reduction in IIX/IIB hybrids resulted from different processes in the BR and the TA. In the BR, the reduction was coincident with an increase in type IIX fibers. In the TA, the number of IIX/IIB hybrids was inversely correlated with the proportion of IIB fibers. These patterns reveal that the role of hybrid fibers as intermediates in muscle development is complex. Some hybrid fibers in maturing muscles represent transitional fiber types, while others are phenotypically stable. Moreover, the fate of transitional fibers may be distinct among similar fiber types within different muscles.

  1. Electrical activation of artificial muscles containing polyacrylonitrile gel fibers.

    PubMed

    Schreyer, H B; Gebhart, N; Kim, K J; Shahinpoor, M

    2000-01-01

    Gel fibers made from polyacrylonitrile (PAN) are known to elongate and contract when immersed in caustic and acidic solutions, respectively. The amount of contraction for these pH-activated fibers is 50% or greater, and the strength of these fibers is shown to be comparable to that of human muscle. Despite these attributes, the need of strong acids and bases for actuation has limited the use of PAN gel fibers as linear actuators or artificial muscles. Increasing the conductivity by depositing platinum on the fibers or combining the fibers with graphite fibers has allowed for electrical activation of artificial muscles containing gel fibers when placed in an electrochemical cell. The electrolysis of water in such a cell produces hydrogen ions at an artificial muscle anode, thus locally decreasing the pH and causing the muscle to contract. Reversing the electric field allows the PAN muscle to elongate. A greater than 40% contraction in artificial muscle length in less than 10 min is observed when it is placed as an electrode in a 10 mM NaCl electrolyte solution and connected to a 10 V power supply. These results indicate potential in developing electrically activated PAN muscles and linear actuators, which would be much more applicable than chemically activated muscles.

  2. Calcium Efflux from Barnacle Muscle Fibers

    PubMed Central

    Russell, J. M.; Blaustein, M. P.

    1974-01-01

    Calcium-45 was injected into single giant barnacle muscle fibers, and the rate of efflux was measured under a variety of conditions. The rate constant (k) for 45Ca efflux into standard seawater averaged 17 x 10–4 min–1 which corresponds to an efflux of about 1–2 pmol/cm2·s. Removal of external Ca (Cao) reduced the efflux by 50%. In most fibers about 40% of the 45Ca efflux into Ca-free seawater was dependent on external Na (Nao); treatment with 3.5 mM caffeine increased the magnitude of the Nao-dependent efflux. In a few fibers removal of Nao, in the absence of Cao, either had no effect or increased k; caffeine (2–3.5 mM) unmasked an Nao-dependent efflux in these fibers. The Nao-dependent Ca efflux had a Q10 of about 3.7. The data are consistent with the idea that a large fraction of the Ca efflux may be carrier-mediated, and may involve both Ca-Ca and Na-Ca counterflow. The relation between the Nao-dependent Ca efflux and the external Na concentration is sigmoid, and suggests that two, or more likely three, external Na+ ions may activate the efflux of one Ca+2. With a three-for-one Na-Ca exchange, the Na electrochemical gradient may be able to supply sufficient energy to maintain the Ca gradient in these fibers. Other, more complex models are not excluded, however, and may be required to explain some puzzling features of the Ca efflux such as the variable Nao-dependence. PMID:4812633

  3. Automated recognition of the iliac muscle and modeling of muscle fiber direction in torso CT images

    NASA Astrophysics Data System (ADS)

    Kamiya, N.; Zhou, X.; Azuma, K.; Muramatsu, C.; Hara, T.; Fujita, H.

    2016-03-01

    The iliac muscle is an important skeletal muscle related to ambulatory function. The muscles related to ambulatory function are the psoas major and iliac muscles, collectively defined as the iliopsoas muscle. We have proposed an automated recognition method of the iliac muscle. Muscle fibers of the iliac muscle have a characteristic running pattern. Therefore, we used 20 cases from a training database to model the movement of the muscle fibers of the iliac muscle. In the recognition process, the existing position of the iliac muscle was estimated by applying the muscle fiber model. To generate an approximation mask by using a muscle fiber model, a candidate region of the iliac muscle was obtained. Finally, the muscle region was identified by using values from the gray value and boundary information. The experiments were performed by using the 20 cases without abnormalities in the skeletal muscle for modeling. The recognition result in five cases obtained a 76.9% average concordance rate. In the visual evaluation, overextraction of other organs was not observed in 85% of the cases. Therefore, the proposed method is considered to be effective in the recognition of the initial region of the iliac muscle. In the future, we will integrate the recognition method of the psoas major muscle in developing an analytical technique for the iliopsoas area. Furthermore, development of a sophisticated muscle function analysis method is necessary.

  4. Ca fluxes in single twitch muscle fibers.

    PubMed

    Curtis, B A

    1966-11-01

    Ca influx and efflux in single twitch muscle fibers were determined by the movement of 45Ca. The isotope was assayed by counting the center 1 cm of a fiber while it was in nonradioactive Rnger's solution. The average resting influx in 1.0 mM Ca Ringer's was 0.26 pM Ca/cm2. sec for 5 to 20 min influx periods. The average additional influx upon stimulation in 1.0 mM Ca was 0.73 pM Ca/cm2. twitch. The efflux after both resting and stimulated 45Ca influx can be described by a single exponential curve with an average time constant of 125 min. This relationship is an indication of Ca exchange with a single intracellular compartment. This compartment contains an estimated 47% of the total muscle Ca at 1.0 mM Ca. When the Ca in the Ringer was reduced to 0.5 mM Ca, both the resting and stimulated Ca fluxes decreased. When Ca was raised to 1.8 mM, the stimulated influxes increased but the resting influx did not.

  5. A retracting wire knife for cutting fiber bundles and making sheet lesions of brain tissue.

    PubMed

    Shibata, M; Russell, I S

    1979-07-01

    A retracting knife which has two cutting wires for the transection of fiber bundles is described. The knife holds the fiber bundles of the stria terminalis between the two cutting wires and transects them by a shearing movement as the wires close. In addition, the feasability of such a knife producing a sheet lesion around the n. caudatus is also described.

  6. Mechanisms of nascent fiber formation during avian skeletal muscle hypertrophy

    NASA Technical Reports Server (NTRS)

    McCormick, K. M.; Schultz, E.

    1992-01-01

    This study examined two putative mechanisms of new fiber formation in postnatal skeletal muscle, namely longitudinal fragmentation of existing fibers and de novo formation. The relative contributions of these two mechanisms to fiber formation in hypertrophying anterior latissimus dorsi (ALD) muscle were assessed by quantitative analysis of their nuclear populations. Muscle hypertrophy was induced by wing-weighting for 1 week. All nuclei formed during the weighting period were labeled by continuous infusion of 5-bromo-2'-deoxyuridine (BrdU), a thymidine analog, and embryonic-like fibers were identified using an antibody to ventricular-like embryonic (V-EMB) myosin. The number of BrdU-labeled and unlabeled nuclei in V-EMB-positive fibers were counted. Wing-weighting resulted in significant muscle enlargement and the appearance of many V-EMB+ fibers. The majority of V-EMB+ fibers were completely independent of mature fibers and had a nuclear density characteristics of developing fibers. Furthermore, nearly 100% of the nuclei in independent V-EMB+ fibers were labeled. These findings strongly suggest that most V-EMB+ fibers were nascent fibers formed de novo during the weighting period by satellite cell activation and fusion. Nascent fibers were found primarily in the space between fascicles where they formed a complex anastomosing network of fibers running at angles to one another. Although wing-weighting induced an increase in the number of branched fibers, there was no evidence that V-EMB+ fibers were formed by longitudinal fragmentation. The location of newly formed fibers in wing-weighted and regenerating ALD muscle was compared to determine whether satellite cells in the ALD muscle were unusual in that, if stimulated to divide, they would form fibers in the inter- and intrafascicular space. In contrast to wing-weighted muscle, nascent fibers were always found closely associated with necrotic fibers. These results suggest that wing-weighting is not simply another

  7. Mechanisms of nascent fiber formation during avian skeletal muscle hypertrophy

    NASA Technical Reports Server (NTRS)

    McCormick, K. M.; Schultz, E.

    1992-01-01

    This study examined two putative mechanisms of new fiber formation in postnatal skeletal muscle, namely longitudinal fragmentation of existing fibers and de novo formation. The relative contributions of these two mechanisms to fiber formation in hypertrophying anterior latissimus dorsi (ALD) muscle were assessed by quantitative analysis of their nuclear populations. Muscle hypertrophy was induced by wing-weighting for 1 week. All nuclei formed during the weighting period were labeled by continuous infusion of 5-bromo-2'-deoxyuridine (BrdU), a thymidine analog, and embryonic-like fibers were identified using an antibody to ventricular-like embryonic (V-EMB) myosin. The number of BrdU-labeled and unlabeled nuclei in V-EMB-positive fibers were counted. Wing-weighting resulted in significant muscle enlargement and the appearance of many V-EMB+ fibers. The majority of V-EMB+ fibers were completely independent of mature fibers and had a nuclear density characteristics of developing fibers. Furthermore, nearly 100% of the nuclei in independent V-EMB+ fibers were labeled. These findings strongly suggest that most V-EMB+ fibers were nascent fibers formed de novo during the weighting period by satellite cell activation and fusion. Nascent fibers were found primarily in the space between fascicles where they formed a complex anastomosing network of fibers running at angles to one another. Although wing-weighting induced an increase in the number of branched fibers, there was no evidence that V-EMB+ fibers were formed by longitudinal fragmentation. The location of newly formed fibers in wing-weighted and regenerating ALD muscle was compared to determine whether satellite cells in the ALD muscle were unusual in that, if stimulated to divide, they would form fibers in the inter- and intrafascicular space. In contrast to wing-weighted muscle, nascent fibers were always found closely associated with necrotic fibers. These results suggest that wing-weighting is not simply another

  8. High-speed fiber laser cutting of thick stainless steel for dismantling tasks

    NASA Astrophysics Data System (ADS)

    Shin, Jae Sung; Oh, Seong Yong; Park, Hyunmin; Chung, Chin-Man; Seon, Sangwoo; Kim, Taek-Soo; Lee, Lim; Choi, Byung-Seon; Moon, Jei-Kwon

    2017-09-01

    A high-speed fiber laser cutting technology of thick steels for dismantling tasks was achieved using a 6-kW fiber laser system. At first, a new cutting head for efficient cutting of thick steels was developed, which was composed by a collimator with a focal length of 160 mm and mirror-type focusing objects with a long focal length of 600 mm. The long focal length of the focusing object made it possible for the beam size to be small through the thick cutting material and the cutting efficiency was expected to increase compared with the short focal length. In addition, folding the beam facilitated the compact cutting head with a size of 160 mm (width) × 80 mm (height) × 640 mm (length) and a weight of 6.9 kg. In the cutting experiment, the laser beam was delivered to the cutting head by a 25-m long process fiber with a core diameter of 100 μm. The cutting performances were studied against the thicknesses of stainless steel plates. A maximum cutting speed of 72 mm/min was obtained for the 60-mm thick stainless steel plate cutting and the cut specimen showed an excellent kerf shape and a narrow kerf width. To the best of our knowledge, this cutting speed was higher than other previously reported results when cutting with a 6-kW laser power.

  9. Impact of diaphragm muscle fiber atrophy on neuromotor control.

    PubMed

    Mantilla, Carlos B; Sieck, Gary C

    2013-11-01

    In skeletal muscles, motor units comprise a motoneuron and the group of muscle fibers innervated by it, which are usually classified based on myosin heavy chain isoform expression. Motor units displaying diverse contractile and fatigue properties are important in determining the range of motor behaviors that can be accomplished by a muscle. Muscle fiber atrophy and weakness may disproportionately affect specific fiber types across a variety of diseases or clinical conditions, thus impacting neuromotor control. In this regard, fiber atrophy that affects a specific fiber type will alter the relative contribution of different motor units to overall muscle structure and function. For example, in various diseases there is fairly selective atrophy of type IIx and/or IIb fibers comprising the strongest yet most fatigable motor units. As a result, there is muscle weakness (i.e., reductions in force per cross-sectional area) associated with an apparent improvement in resistance to fatiguing contractions. This review will examine neuromotor control of respiratory muscles such as the diaphragm muscle and the impact of muscle fiber atrophy on motor performance. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Self-reinnervated cat medial gastrocnemius muscles. II. analysis of the mechanisms and significance of fiber type grouping in reinnervated muscles.

    PubMed

    Rafuse, V F; Gordon, T

    1996-01-01

    1. The technique of glycogen depletion was used to determine whether regenerating motor axons reestablish the normal regionalization of motor units (MUs) in the cat medial gastrocnemius (MG) muscle, 2) whether the extent of clumping between MU fibers and/or type grouping of muscle fibers progressively increases with a decrease in reinnervated MU numbers, and 3) whether the pattern of innervation can explain why MUs fail to increase significantly in size when the cut nerve is sutured directly to the muscle, even when few axons make functional connections. 2. Distributions of MU fibers were analyzed in 5 normal and 14 reinnervated cat MG muscles 4.5-16 mo after sectioning of its nerve and suturing of the proximal end to the distal nerve sheaths (N-N suture) or directly to the muscle fascia (N-M suture). Muscle unit distributions were quantified according to location, territory size, density, and extent of clumping between fibers from the same MU. 3. Normal MU fibers were regionalized within five regions along the muscle's longitudinal and transverse axes. Reinnervated MUs were located within similar regions, indicating that regenerating axons follow the major proximal nerve branches to restore normal compartmentalization. 4. Muscle unit fibers were diffusely scattered within discrete MU territories in normal muscles. Territory size tended to increase with MU size, whereas density of muscle unit fibers within the territory decreased. 5. Territories increased with MU size after N-N suture but were smaller and showed little size variation after N-M suture. The extent of muscle unit fiber clumping was inversely related to the number of reinnervated MUs. On average, the extent of clumping was substantially higher in muscles reinnervated after N-M suture. These results indicate that distal nerve sheaths facilitate proximal axon branching, which establishes MU territory size. Once the territory is established, motor axons branch distally to increase MU size, which in turn

  11. Anisotropic Smoothing Improves DT-MRI-Based Muscle Fiber Tractography

    PubMed Central

    Buck, Amanda K. W.; Ding, Zhaohua; Elder, Christopher P.; Towse, Theodore F.; Damon, Bruce M.

    2015-01-01

    Purpose To assess the effect of anisotropic smoothing on fiber tracking measures, including pennation angle, fiber tract length, and fiber tract number in the medial gastrocnemius (MG) muscle in healthy subjects using diffusion-weighted magnetic resonance imaging (DW-MRI). Materials and Methods 3T DW-MRI data were used for muscle fiber tractography in the MG of healthy subjects. Anisotropic smoothing was applied at three levels (5%, 10%, 15%), and pennation angle, tract length, fiber tract number, fractional anisotropy, and principal eigenvector orientation were quantified for each smoothing level. Results Fiber tract length increased with pre-fiber tracking smoothing, and local heterogeneities in fiber direction were reduced. However, pennation angle was not affected by smoothing. Conclusion Modest anisotropic smoothing (10%) improved fiber-tracking results, while preserving structural features. PMID:26010830

  12. Muscle organizers in Drosophila: the role of persistent larval fibers in adult flight muscle development

    NASA Technical Reports Server (NTRS)

    Farrell, E. R.; Fernandes, J.; Keshishian, H.

    1996-01-01

    In many organisms muscle formation depends on specialized cells that prefigure the pattern of the musculature and serve as templates for myoblast organization and fusion. These include muscle pioneers in insects and muscle organizing cells in leech. In Drosophila, muscle founder cells have been proposed to play a similar role in organizing larval muscle development during embryogenesis. During metamorphosis in Drosophila, following histolysis of most of the larval musculature, there is a second round of myogenesis that gives rise to the adult muscles. It is not known whether muscle founder cells organize the development of these muscles. However, in the thorax specific larval muscle fibers do not histolyze at the onset of metamorphosis, but instead serve as templates for the formation of a subset of adult muscles, the dorsal longitudinal flight muscles (DLMs). Because these persistent larval muscle fibers appear to be functioning in many respects like muscle founder cells, we investigated whether they were necessary for DLM development by using a microbeam laser to ablate them singly and in combination. We found that, in the absence of the larval muscle fibers, DLMs nonetheless develop. Our results show that the persistent larval muscle fibers are not required to initiate myoblast fusion, to determine DLM identity, to locate the DLMs in the thorax, or to specify the total DLM fiber volume. However, they are required to regulate the number of DLM fibers generated. Thus, while the persistent larval muscle fibers are not obligatory for DLM fiber formation and differentiation, they are necessary to ensure the development of the correct number of fibers.

  13. Muscle fiber types composition and type identified endplate morphology of forepaw intrinsic muscles in the rat.

    PubMed

    Pan, Feng; Mi, Jing-Yi; Zhang, Yan; Pan, Xiao-Yun; Rui, Yong-Jun

    2016-06-01

    The failure to accept reinnervation is considered to be one of the reasons for the poor motor functional recovery of intrinsic hand muscles (IHMs) after nerve injury. Rat could be a suitable model to be used in simulating motor function recovery of the IHMs after nerve injury as to the similarities in function and anatomy of the muscles between human and rat. However, few studies have reported the muscle fiber types composition and endplate morphologic characteristics of intrinsic forepaw muscles (IFMs) in the rat. In this study, the myosin heavy chain isoforms and acetylcholine receptors were stained by immunofluorescence to show the muscle fiber types composition and endplates on type-identified fibers of the lumbrical muscles (LMs), interosseus muscles (IMs), abductor digiti minimi (AM) and flexor pollicis brevis (FM) in rat forepaw. The majority of IFMs fibers were labeled positively for fast-switch fiber. However, the IMs were composed of only slow-switch fiber. With the exception of the IMs, the other IFMs had a part of hybrid fibers. Two-dimensional morphological characteristics of endplates on I and IIa muscle fiber had no significant differences among the IFMs. The LMs is the most suitable IFMs of rat to stimulate reinnervation of the IHMs after nerve injury. Gaining greater insight into the muscle fiber types composition and endplate morphology in the IFMs of rat may help understand the pathological and functional changes of IFMs in rat model stimulating reinnervation of IHMs after peripheral nerve injury.

  14. Twitch tension, muscle weight, and fiber area of exercised reinnervating rat skeletal muscle.

    PubMed

    Hie, H B; van Nie, C J; Vermeulen-van der Zee, E

    1982-12-01

    The purpose of this study was to evaluate the effect of dynamic exercise on weight and isometric twitch tension of the reinnervating rat gastrocnemius-plantaris muscle complex as well as on histology of the reinnervating plantaris muscle. Two groups of 6-week-old female Wistar rats, 1 control (n = 17) and 1 experimental (n = 17), were denervated unilaterally by cutting and resecting the sciatic nerve. To effect reinnervation a skin grafting operation was carried out on the nerve so that the gap caused by resection was bridged. The experimental group began exercising on a motor-driven treadmill 18 days following the graft. A progressive training program of 18 weeks of treadmill running, 5 days/week, was carried out by the animals. Training intensity was gradually increased until during the final 3 weeks they were running up a 25% grade at a speed of 720m/hour for 2 hours a day. Exercise did not damage the reinnervating muscle. Absolute wet weight and maximum isometric twitch tension of the reinnervating gastrocnemius-plantaris muscle complex were increased significantly, by 15 1/2% and 30% respectively, after exercise. Training resulted in a significant increase in fiber and muscle cross-sectional areas of the reinnervating plantaris, by 28% and 23% respectively. Exercise brought about no change in total relative amount of connective tissue in the reinnervating plantaris. This study indicates that dynamic exercise has a significant positive effect on the weight, twitch tension and histologic appearance of the reinnervating gastrocnemius-plantaris muscle and thus may enhance their functional recovery. It is likely that this type of training is also effective in the treatment of patients recovering from peripheral nerve injuries.

  15. Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles

    NASA Technical Reports Server (NTRS)

    Vijayan, K.; Thompson, J. L.; Norenberg, K. M.; Fitts, R. H.; Riley, D. A.

    2001-01-01

    Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms caused fatigue. Lesions occurred only in eccentrically contracted control and HU muscles. Fatigue did not cause lesions. HU increased damage because lesioned- fiber percentages within fiber types and lesion sizes were greater than control. Fast oxidative glycolytic (FOG) fibers were predominantly damaged. In no case did damaged SO fibers predominate. Thus, when FOG, SO, and hybrid fibers are actively lengthened in chronically unloaded muscle, FOG fibers are intrinsically more susceptible to damage than SO fibers. Damaged hybrid-fiber proportions ranged between these extremes.

  16. Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles

    NASA Technical Reports Server (NTRS)

    Vijayan, K.; Thompson, J. L.; Norenberg, K. M.; Fitts, R. H.; Riley, D. A.

    2001-01-01

    Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms caused fatigue. Lesions occurred only in eccentrically contracted control and HU muscles. Fatigue did not cause lesions. HU increased damage because lesioned- fiber percentages within fiber types and lesion sizes were greater than control. Fast oxidative glycolytic (FOG) fibers were predominantly damaged. In no case did damaged SO fibers predominate. Thus, when FOG, SO, and hybrid fibers are actively lengthened in chronically unloaded muscle, FOG fibers are intrinsically more susceptible to damage than SO fibers. Damaged hybrid-fiber proportions ranged between these extremes.

  17. Preferential Type II Muscle Fiber Damage From Plyometric Exercise

    PubMed Central

    Macaluso, Filippo; Isaacs, Ashwin W.; Myburgh, Kathryn H.

    2012-01-01

    Context Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. Objective To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Design Descriptive laboratory study. Setting Research laboratory. Patients or Other Participants Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Intervention(s) Participants completed an acute bout of plyometric exercise (10 sets of 10 squat-jumps with a 1-minute rest between sets). Main Outcome Measure(s) Blood samples were collected 9 days and immediately before and 6 hours and 1, 2, and 3 days after the acute intervention. Muscle samples were collected 9 days before and 3 days after the exercise intervention. Blood samples were analyzed for creatine kinase activity. Muscle biopsies were analyzed for damage using fluorescent and electron transmission microscopy. Results Creatine kinase activity peaked 1 day after the exercise bout (529.0 ± 317.8 U/L). Immunofluorescence revealed sarcolemmal damage in 155 of 1616 fibers analyzed. Mainly fast-twitch fibers were damaged. Within subgroups, 7.6% of type I fibers, 10.3% of type IIa fibers, and 14.3% of type IIx fibers were damaged as assessed by losses in dystrophin staining. Similar damage was prevalent in IIx and IIa fibers. Electron microscopy revealed clearly distinguishable moderate and severe sarcomere damage, with damage quantifiably predominant in type II muscle fibers of both the glycolytic and oxidative subtypes (86% and 84%, respectively, versus only 27% of slow-twitch fibers). Conclusions We provide direct evidence that a single bout of plyometric exercise affected mainly type II muscle

  18. Preferential type II muscle fiber damage from plyometric exercise.

    PubMed

    Macaluso, Filippo; Isaacs, Ashwin W; Myburgh, Kathryn H

    2012-01-01

    Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Descriptive laboratory study. Research laboratory. Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Participants completed an acute bout of plyometric exercise (10 sets of 10 squat-jumps with a 1-minute rest between sets). Blood samples were collected 9 days and immediately before and 6 hours and 1, 2, and 3 days after the acute intervention. Muscle samples were collected 9 days before and 3 days after the exercise intervention. Blood samples were analyzed for creatine kinase activity. Muscle biopsies were analyzed for damage using fluorescent and electron transmission microscopy. Creatine kinase activity peaked 1 day after the exercise bout (529.0 ± 317.8 U/L). Immunofluorescence revealed sarcolemmal damage in 155 of 1616 fibers analyzed. Mainly fast-twitch fibers were damaged. Within subgroups, 7.6% of type I fibers, 10.3% of type IIa fibers, and 14.3% of type IIx fibers were damaged as assessed by losses in dystrophin staining. Similar damage was prevalent in IIx and IIa fibers. Electron microscopy revealed clearly distinguishable moderate and severe sarcomere damage, with damage quantifiably predominant in type II muscle fibers of both the glycolytic and oxidative subtypes (86% and 84%, respectively, versus only 27% of slow-twitch fibers). We provide direct evidence that a single bout of plyometric exercise affected mainly type II muscle fibers.

  19. Effective fiber hypertrophy in satellite cell-depleted skeletal muscle

    PubMed Central

    McCarthy, John J.; Mula, Jyothi; Miyazaki, Mitsunori; Erfani, Rod; Garrison, Kelcye; Farooqui, Amreen B.; Srikuea, Ratchakrit; Lawson, Benjamin A.; Grimes, Barry; Keller, Charles; Van Zant, Gary; Campbell, Kenneth S.; Esser, Karyn A.; Dupont-Versteegden, Esther E.; Peterson, Charlotte A.

    2011-01-01

    An important unresolved question in skeletal muscle plasticity is whether satellite cells are necessary for muscle fiber hypertrophy. To address this issue, a novel mouse strain (Pax7-DTA) was created which enabled the conditional ablation of >90% of satellite cells in mature skeletal muscle following tamoxifen administration. To test the hypothesis that satellite cells are necessary for skeletal muscle hypertrophy, the plantaris muscle of adult Pax7-DTA mice was subjected to mechanical overload by surgical removal of the synergist muscle. Following two weeks of overload, satellite cell-depleted muscle showed the same increases in muscle mass (approximately twofold) and fiber cross-sectional area with hypertrophy as observed in the vehicle-treated group. The typical increase in myonuclei with hypertrophy was absent in satellite cell-depleted fibers, resulting in expansion of the myonuclear domain. Consistent with lack of nuclear addition to enlarged fibers, long-term BrdU labeling showed a significant reduction in the number of BrdU-positive myonuclei in satellite cell-depleted muscle compared with vehicle-treated muscle. Single fiber functional analyses showed no difference in specific force, Ca2+ sensitivity, rate of cross-bridge cycling and cooperativity between hypertrophied fibers from vehicle and tamoxifen-treated groups. Although a small component of the hypertrophic response, both fiber hyperplasia and regeneration were significantly blunted following satellite cell depletion, indicating a distinct requirement for satellite cells during these processes. These results provide convincing evidence that skeletal muscle fibers are capable of mounting a robust hypertrophic response to mechanical overload that is not dependent on satellite cells. PMID:21828094

  20. Effective fiber hypertrophy in satellite cell-depleted skeletal muscle.

    PubMed

    McCarthy, John J; Mula, Jyothi; Miyazaki, Mitsunori; Erfani, Rod; Garrison, Kelcye; Farooqui, Amreen B; Srikuea, Ratchakrit; Lawson, Benjamin A; Grimes, Barry; Keller, Charles; Van Zant, Gary; Campbell, Kenneth S; Esser, Karyn A; Dupont-Versteegden, Esther E; Peterson, Charlotte A

    2011-09-01

    An important unresolved question in skeletal muscle plasticity is whether satellite cells are necessary for muscle fiber hypertrophy. To address this issue, a novel mouse strain (Pax7-DTA) was created which enabled the conditional ablation of >90% of satellite cells in mature skeletal muscle following tamoxifen administration. To test the hypothesis that satellite cells are necessary for skeletal muscle hypertrophy, the plantaris muscle of adult Pax7-DTA mice was subjected to mechanical overload by surgical removal of the synergist muscle. Following two weeks of overload, satellite cell-depleted muscle showed the same increases in muscle mass (approximately twofold) and fiber cross-sectional area with hypertrophy as observed in the vehicle-treated group. The typical increase in myonuclei with hypertrophy was absent in satellite cell-depleted fibers, resulting in expansion of the myonuclear domain. Consistent with lack of nuclear addition to enlarged fibers, long-term BrdU labeling showed a significant reduction in the number of BrdU-positive myonuclei in satellite cell-depleted muscle compared with vehicle-treated muscle. Single fiber functional analyses showed no difference in specific force, Ca(2+) sensitivity, rate of cross-bridge cycling and cooperativity between hypertrophied fibers from vehicle and tamoxifen-treated groups. Although a small component of the hypertrophic response, both fiber hyperplasia and regeneration were significantly blunted following satellite cell depletion, indicating a distinct requirement for satellite cells during these processes. These results provide convincing evidence that skeletal muscle fibers are capable of mounting a robust hypertrophic response to mechanical overload that is not dependent on satellite cells.

  1. Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition

    PubMed Central

    Kawai, Nobuhiko; Sano, Ryota; Korfage, Joannes A M; Nakamura, Saika; Tanaka, Eiji; van Wessel, Tim; Langenbach, Geerling E J; Tanne, Kazuo

    2009-01-01

    Skeletal muscles have a heterogeneous fiber type composition, which reflects their functional demand. The daily muscle use and the percentage of slow-type fibers have been shown to be positively correlated in skeletal muscles of larger animals but for smaller animals there is no information. The examination of this relationship in adult rats was the purpose of this study. We hypothesized a positive relationship between the percentage of fatigue-resistant fibers in each muscle and its total duration of use per day. Fourteen Wistar strain male rats (410–450 g) were used. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, deep masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time) exceeding specified levels of the peak activity (2, 5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of the fibers by means of immunohistochemical staining. At lower activity levels (exceeding 2 and 5% of the peak activity), the duty time of the anterior belly of digastric muscle was significantly (P < 0.01) longer than those of the other muscles. The anterior belly of digastric muscle also contained the highest percentage of slow-type fibers (type I fiber and hybrid fiber co-expressing myosin heavy chain I + IIA) (ca. 11%; P < 0.05). By regression analysis for all four muscles, an inter-muscular comparison showed a positive relationship between the duty time (exceeding 50% of the peak activity) and the percentage of type IIX fibers (P < 0.05), which demonstrate intermediate physiological properties relative to type IIA and IIB fibers. For the jaw muscles of adult male rats, the variations of fiber type composition and muscle use suggest that the muscle containing the largest amounts of slow-type fibers (the anterior belly of digastric muscle) is mainly

  2. Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition.

    PubMed

    Kawai, Nobuhiko; Sano, Ryota; Korfage, Joannes A M; Nakamura, Saika; Tanaka, Eiji; van Wessel, Tim; Langenbach, Geerling E J; Tanne, Kazuo

    2009-12-01

    Skeletal muscles have a heterogeneous fiber type composition, which reflects their functional demand. The daily muscle use and the percentage of slow-type fibers have been shown to be positively correlated in skeletal muscles of larger animals but for smaller animals there is no information. The examination of this relationship in adult rats was the purpose of this study. We hypothesized a positive relationship between the percentage of fatigue-resistant fibers in each muscle and its total duration of use per day. Fourteen Wistar strain male rats (410-450 g) were used. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, deep masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time) exceeding specified levels of the peak activity (2, 5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of the fibers by means of immunohistochemical staining. At lower activity levels (exceeding 2 and 5% of the peak activity), the duty time of the anterior belly of digastric muscle was significantly (P < 0.01) longer than those of the other muscles. The anterior belly of digastric muscle also contained the highest percentage of slow-type fibers (type I fiber and hybrid fiber co-expressing myosin heavy chain I + IIA) (ca. 11%; P < 0.05). By regression analysis for all four muscles, an inter-muscular comparison showed a positive relationship between the duty time (exceeding 50% of the peak activity) and the percentage of type IIX fibers (P < 0.05), which demonstrate intermediate physiological properties relative to type IIA and IIB fibers. For the jaw muscles of adult male rats, the variations of fiber type composition and muscle use suggest that the muscle containing the largest amounts of slow-type fibers (the anterior belly of digastric muscle) is mainly

  3. Experimental Investigations on Fusion Cutting Stainless Steel with Fiber and CO2 Laser Beams

    NASA Astrophysics Data System (ADS)

    Stelzer, S.; Mahrle, A.; Wetzig, A.; Beyer, E.

    First results of an experimental study on inert-gas fusion cutting stainless steel with different types of laser are presented. In particular, the cutting capabilities of a fiber and a CO2 laser beam with similar Rayleigh length have been compared as a function of material thickness with respect to achievable maximum cutting speed, cut edge surface roughness and cut kerf geometry. The most interesting finding achieved so far concerns the observation that the cut kerfs are nearly identical in size but differ qualitatively in shape for both laser teypes.

  4. Muscle growth and fiber type composition in hind limb muscles during postnatal development in pigs.

    PubMed

    Wank, Veit; Fischer, Martin S; Walter, Bernd; Bauer, Reinhard

    2006-01-01

    Rapid postnatal development in pigs is reflected by differentiation in skeletal muscle. This process depends on muscle function and demands, but a comprehensive overview of individual developmental characteristics of quickly growing leg muscles in pigs is still missing. This study focused on the development of 10 hind limb muscles in pigs. To determine these changes in mass, fiber type patterns and fiber diameters were analyzed 0, 2, 4, 7, 14, 28, 42, 56 and 400 days after birth. Generally, the proportion of slow fibers increased from birth to 8 weeks. Thereafter, only minor changes in muscle fiber type composition were observed. The majority of the muscles contained less then 10% slow-twitch fibers at birth, increasing to between 12 (Musculus vastus lateralis) and 38% (M. gastrocnemius medialis) in adult pigs. By contrast, postural muscles already had 20-30% slow fibers at birth, and this contribution increased up to 65% in adults (i.e. M. vastus intermedius). From birth to the 2nd week, only in slow fibers could activity of oxidative enzymes be detected. A differentiation of fast-twitch fibers into subtypes with high (comparable to type IIA) and low oxidative metabolism (equivalent to type IIB) occurred between the 2nd and 4th week of life. The ratio between type II fibers with high and low oxidative enzyme activity did not change markedly through development in any muscle, although there was a trend towards an increasing proportion of type IIA fibers in the soleus. In the majority of the muscles investigated, the fast-twitch fibers with low oxidative metabolism (IIB) obtained the largest cross-sectional area. In contrast, at birth no remarkable differences in the diameter of fast and slow fibers were found. The rapid increase in muscle mass compared to body mass reflects the high performance in meat production of the cross pig investigated.

  5. Individual sarcomere lengths in whole muscle fibers and optimal fiber length computation.

    PubMed

    Infantolino, Benjamin W; Ellis, Michael J; Challis, John H

    2010-11-01

    Estimation of muscle fiber optimum length is typically accomplished using either laser diffraction or by counting the number of sarcomeres in a portion of the muscle fiber, measuring the distance that encompasses those sarcomeres and dividing by the number of sarcomeres to obtain an average sarcomere length. If the sarcomeres are not uniformly distributed, either of these techniques could produce errors when estimating optimum lengths. The purposes of this study were: to describe new software that automatically analyzes digital images of skeletal muscle fibers to measure individual sarcomere lengths; and to use this software to measure individual sarcomere lengths along complete muscle fibers to examine the influence of computing whole muscle fiber properties from portions of the fiber. Six complete muscle fibers were imaged using a digital camera attached to a microscope. The images were then processed to achieve the best resolution possible, individual sarcomeres along the image were detected, and each individual sarcomere length was measured. The software accuracy was compared with that of manual measurement and was found to be as accurate. In addition, the time to measure individual sarcomere lengths was greatly reduced using the software compared with manual measurement. The arrangement of individual sarcomere lengths demonstrated long-range correlations, which indicates problems in assuming only a portion of a fiber can be used to determine whole fiber properties. This study has provided evidence on the number of sarcomeres which must be analyzed to infer the properties of whole muscles.

  6. Changes in muscle fiber contractility and extracellular matrix production during skeletal muscle hypertrophy.

    PubMed

    Mendias, Christopher L; Schwartz, Andrew J; Grekin, Jeremy A; Gumucio, Jonathan P; Sugg, Kristoffer B

    2017-03-01

    Skeletal muscle can adapt to increased mechanical loads by undergoing hypertrophy. Transient reductions in whole muscle force production have been reported during the onset of hypertrophy, but contractile changes in individual muscle fibers have not been previously studied. Additionally, the extracellular matrix (ECM) stores and transmits forces from muscle fibers to tendons and bones, and determining how the ECM changes during hypertrophy is important in understanding the adaptation of muscle tissue to mechanical loading. Using the synergist ablation model, we sought to measure changes in muscle fiber contractility, collagen content, and cross-linking, and in the expression of several genes and activation of signaling proteins that regulate critical components of myogenesis and ECM synthesis and remodeling during muscle hypertrophy. Tissues were harvested 3, 7, and 28 days after induction of hypertrophy, and nonoverloaded rats served as controls. Muscle fiber specific force (sFo), which is the maximum isometric force normalized to cross-sectional area, was reduced 3 and 7 days after the onset of mechanical overload, but returned to control levels by 28 days. Collagen abundance displayed a similar pattern of change. Nearly a quarter of the transcriptome changed over the course of overload, as well as the activation of signaling pathways related to hypertrophy and atrophy. Overall, this study provides insight into fundamental mechanisms of muscle and ECM growth, and indicates that although muscle fibers appear to have completed remodeling and regeneration 1 mo after synergist ablation, the ECM continues to be actively remodeling at this time point.NEW & NOTEWORTHY This study utilized a rat synergist ablation model to integrate changes in single muscle fiber contractility, extracellular matrix composition, activation of important signaling pathways in muscle adaption, and corresponding changes in the muscle transcriptome to provide novel insight into the basic

  7. Molecular Mechanisms Regulating Muscle Fiber Composition Under Microgravity

    NASA Technical Reports Server (NTRS)

    Rosenthal, Nadia A.

    1999-01-01

    The overall goal of this project is to reveal the molecular mechanisms underlying the selective and debilitating atrophy of specific skeletal muscle fiber types that accompanies sustained conditions of microgravity. Since little is currently known about the regulation of fiber-specific gene expression programs in mammalian muscle, elucidation of the basic mechanisms of fiber diversification is a necessary prerequisite to the generation of therapeutic strategies for attenuation of muscle atrophy on earth or in space. Vertebrate skeletal muscle development involves the fusion of undifferentiated mononucleated myoblasts to form multinucleated myofibers, with a concomitant activation of muscle-specific genes encoding proteins that form the force-generating contractile apparatus. The regulatory circuitry controlling skeletal muscle gene expression has been well studied in a number of vertebrate animal systems. The goal of this project has been to achieve a similar level of understanding of the mechanisms underlying the further specification of muscles into different fiber types, and the role played by innervation and physical activity in the maintenance and adaptation of different fiber phenotypes into adulthood. Our recent research on the genetic basis of fiber specificity has focused on the emergence of mature fiber types and have implicated a group of transcriptional regulatory proteins, known as E proteins, in the control of fiber specificity. The restriction of E proteins to selected muscle fiber types is an attractive hypothetical mechanism for the generation of muscle fiber-specific patterns of gene expression. To date our results support a model wherein different E proteins are selectively expressed in muscle cells to determine fiber-restricted gene expression. These studies are a first step to define the molecular mechanisms responsible for the shifts in fiber type under conditions of microgravity, and to determine the potential importance of E proteins as

  8. Overexpression of SMPX in adult skeletal muscle does not change skeletal muscle fiber type or size.

    PubMed

    Eftestøl, Einar; Alver, Tine Norman; Gundersen, Kristian; Bruusgaard, Jo C

    2014-01-01

    Mechanical factors such as stretch are thought to be important in the regulation of muscle phenotype. Small muscle protein X-linked (SMPX) is upregulated by stretch in skeletal muscle and has been suggested to serve both as a transcription factor and a mechanosensor, possibly giving rise to changes in both fiber size and fiber type. We have used in vivo confocal imaging to study the subcellular localization of SMPX in skeletal muscle fibers of adult rats using a SMPX-EGFP fusion protein. The fusion protein was localized predominantly in repetitive double stripes flanking the Z-disc, and was excluded from all nuclei. This localization would be consistent with SMPX being a mechanoreceptor, but not with SMPX playing a role as a transcription factor. In vivo overexpression of ectopic SMPX in skeletal muscle of adult mice gave no significant changes in fiber type distribution or cross sectional area, thus a role of SMPX in regulating muscle phenotype remains unclear.

  9. Statistical characteristics of surface integrity by fiber laser cutting of Nitinol vascular stents

    NASA Astrophysics Data System (ADS)

    Fu, C. H.; Liu, J. F.; Guo, Andrew

    2015-10-01

    Nitinol alloys have been widely used in manufacturing of vascular stents due to the outstanding properties such as superelasticity, shape memory, and superior biocompatibility. Laser cutting is the dominant process for manufacturing Nitinol stents. Conventional laser cutting usually produces unsatisfactory surface integrity which has a significant detrimental impact on stent performance. Emerging as a competitive process, fiber laser with high beam quality is expected to produce much less thermal damage such as striation, dross, heat affected zone (HAZ), and recast layer. To understand the process capability of fiber laser cutting of Nitinol alloy, a design-of-experiment based laser cutting experiment was performed. The kerf geometry, roughness, topography, microstructure, and hardness were studied to better understand the nature of the HAZ and recast layer in fiber laser cutting. Moreover, effect size analysis was conducted to investigate the relationship between surface integrity and process parameters.

  10. Fiber optic submarine cables cuts cost modeling and cable protection aspects

    NASA Astrophysics Data System (ADS)

    Al-Lawati, Ali

    2015-03-01

    This work presents a model to calculate costs associated with submarine fiber optic cable cuts. It accounts for both fixed and variable factors determining cost of fixing cables and restoring data transmission. It considers duration of a cut, capacity of fibers, number of fiber pairs and expected number of cuts during cable life time. Moreover, it provides templates for initial feasibility assessments by comparing cut costs to cost of different cable protection schemes. It offers a needed tool to assist in guiding decision makers in selecting type of cable, length and depth of cable burial in terms of increase in initial investment due to adapting such protection methods, and compare it to cost of cuts repair and alternative restoration paths for data.

  11. Regulation of muscle fiber type and running endurance by PPARdelta.

    PubMed

    Wang, Yong-Xu; Zhang, Chun-Li; Yu, Ruth T; Cho, Helen K; Nelson, Michael C; Bayuga-Ocampo, Corinne R; Ham, Jungyeob; Kang, Heonjoong; Evans, Ronald M

    2004-10-01

    Endurance exercise training can promote an adaptive muscle fiber transformation and an increase of mitochondrial biogenesis by triggering scripted changes in gene expression. However, no transcription factor has yet been identified that can direct this process. We describe the engineering of a mouse capable of continuous running of up to twice the distance of a wild-type littermate. This was achieved by targeted expression of an activated form of peroxisome proliferator-activated receptor delta (PPARdelta) in skeletal muscle, which induces a switch to form increased numbers of type I muscle fibers. Treatment of wild-type mice with PPARdelta agonist elicits a similar type I fiber gene expression profile in muscle. Moreover, these genetically generated fibers confer resistance to obesity with improved metabolic profiles, even in the absence of exercise. These results demonstrate that complex physiologic properties such as fatigue, endurance, and running capacity can be molecularly analyzed and manipulated.

  12. Diagnostic value of the muscle fiber conduction velocity for evaluation of muscle hypotrophy.

    PubMed

    Gechev, Antonin G; Ilieva, Elena M; Marinkev, Marin D; Hadjigeorgiev, Georgi H

    2004-01-01

    To find an objective method of evaluation of the thigh muscle hypothrophy in gonarthrosis. The subjects of the study were 24 patients with gonarthrosis (mean age 58.4 +/- 2.6 years). Of these 8 (33%) were males and 16 (67%) females. The following methods of examination were used: computed tomography (CT) of the thigh musculature--linear measurement and area of the cross-section of the vastus medialis muscle; electromyography--muscle fiber conduction velocity; and measurement of thigh girth. Significant reduction of the cross-section area and linear measurement of the vastus medialis muscle and significant delay of the muscle fiber conduction velocity was found in the symptomatic side compared with the asymptomatic side. No correlation was found between the tape measure of the thigh and cross-section area of the muscle. A significant correlation was found between the cross-section area of the muscle and the fast fiber conduction velocity as well as between the linear measurement of the vastus medialis muscle cross-section and fast fiber conduction velocity. The correlation between the macromorphological changes of the vastus medialis muscle assessed by computed tomography and the functional changes detected by electromyography allows the conclusion that the muscle fiber conduction velocity can be used as an objective method of evaluation of muscle atrophy in degenerative joint diseases.

  13. An investigation on co-axial water-jet assisted fiber laser cutting of metal sheets

    NASA Astrophysics Data System (ADS)

    Madhukar, Yuvraj K.; Mullick, Suvradip; Nath, Ashish K.

    2016-02-01

    Water assisted laser cutting has received significant attention in recent times with assurance of many advantages than conventional gas assisted laser cutting. A comparative study between co-axial water-jet and gas-jet assisted laser cutting of thin sheets of mild steel (MS) and titanium (Ti) by fiber laser is presented. Fiber laser (1.07 μm wavelength) was utilised because of its low absorption in water. The cut quality was evaluated in terms of average kerf, projected dross height, heat affected zone (HAZ) and cut surface roughness. It was observed that a broad range process parameter could produce consistent cut quality in MS. However, oxygen assisted cutting could produce better quality only with optimised parameters at high laser power and high cutting speed. In Ti cutting the water-jet assisted laser cutting performed better over the entire range of process parameters compared with gas assisted cutting. The specific energy, defined as the amount of laser energy required to remove unit volume of material was found more in case of water-jet assisted laser cutting process. It is mainly due to various losses associated with water assisted laser processing such as absorption of laser energy in water and scattering at the interaction zone.

  14. From single muscle fiber to whole muscle mechanics: a finite element model of a muscle bundle with fast and slow fibers.

    PubMed

    Marcucci, Lorenzo; Reggiani, Carlo; Natali, Arturo N; Pavan, Piero G

    2017-06-05

    Muscles exhibit highly complex, multi-scale architecture with thousands of muscle fibers, each with different properties, interacting with each other and surrounding connective structures. Consequently, the results of single-fiber experiments are scarcely linked to the macroscopic or whole muscle behavior. This is especially true for human muscles where it would be important to understand of how skeletal muscles disorders affect patients' life. In this work, we developed a mathematical model to study how fast and slow muscle fibers, well characterized in single-fiber experiments, work and generate together force and displacement in muscle bundles. We characterized the parameters of a Hill-type model, using experimental data on fast and slow single human muscle fibers, and comparing experimental data with numerical simulations obtained from finite element (FE) models of single fibers. Then, we developed a FE model of a bundle of 19 fibers, based on an immunohistochemically stained cross section of human diaphragm and including the corresponding properties of each slow or fast fiber. Simulations of isotonic contractions of the bundle model allowed the generation of its apparent force-velocity relationship. Although close to the average of the force-velocity curves of fast and slow fibers, the bundle curve deviates substantially toward the fast fibers at low loads. We believe that the present model and the characterization of the force-velocity curve of a fiber bundle represents the starting point to link the single-fiber properties to those of whole muscle with FE application in phenomenological models of human muscles.

  15. Ultrastructural alterations in skeletal muscle fibers of rats after exercise

    NASA Technical Reports Server (NTRS)

    Akuzawa, M.; Hataya, M.

    1982-01-01

    Ultrastructural alterations in skeletal muscle fibers were electron microscopically studied in rats forced to run on the treadmill until all-out. When they were mild and limited to relatively small areas, the reconstruction of filaments ensued within 10 days without infiltration of cells. When they were severe and extensive, phagocytes infiltrated in the lesions and removed degenerative sacroplasmic debris from muscle fibers. A little later, myoblasts appeared and regeneration was accomplished in 30 days in much the same manner as in myogenesis.

  16. Single muscle fiber properties in aging and disuse.

    PubMed

    Canepari, M; Pellegrino, M A; D'Antona, G; Bottinelli, R

    2010-02-01

    Since the middle of the 1980s, it was understood that myosin, the motor of contraction, can be expressed in several isoforms. The isoforms of the myosin heavy-chain (MHC) portion of the molecule were found to be mostly responsible for the diversity in the contractile and energetic properties of muscle fibers. In humans, three MHC isoforms are expressed in limb muscles (MHC-1, MHC-2A and MHC-2X) and they generate three pure fiber types (types 1, 2A and 2X) and two hybrid types (types 1-2A and -2AX). Type 1, 2A and 2X fibers widely differ with respect to most of their contractile and energetic properties, and a change in their relative distribution within muscles is known to modulate their functional properties in vivo through a "qualitative" mechanism. On the basis of the MHC regulation of muscle fibers properties, it is expected that a given fiber type develops the same force and shortens at the same speed regardless of the physiologic and pathologic conditions under which the muscle works. Surprisingly, several evidences have been accumulating to show that in aging and disuse, the properties of a muscle fiber type can change with no change in its myosin isoform content. This short review considers the latter phenomenon and the possible underlying mechanisms.

  17. Differential Responses of Soleus and Plantaris Muscle Fibers to Overloading

    NASA Astrophysics Data System (ADS)

    Kawano, Fuminori; Shibaguchi, Tsubasa; Ohira, Takashi; Nakai, Naoya; Ohira, Yoshinobu

    2013-02-01

    Responses of slow and fast fibers in soleus and plantaris muscles of adult rats to overloading by the tendon transection of synergists were studied. Overloading-related hypertrophy was noted in the slow fibers of plantaris and soleus, although the magnitude was greater in plantaris. Five genes with minor expression in slow soleus muscle were identified by microarray analysis. Base-line expressions of these genes in slow fibers of plantaris were also low. Further, repressive effects of overloading on these genes were seen in some fast fibers of plantaris, not in whole plantaris and soleus. The data suggested that the repression of particular genes might be related to the pronounced morphological response of fibers expressing type II, including I+II, myosin heavy chain (MyHC), although these genes with lower base-line expression in slow fibers did not respond to overloading.

  18. Effect of swim taper on whole muscle and single muscle fiber contractile properties.

    PubMed

    Trappe, S; Costill, D; Thomas, R

    2001-01-01

    To examine the changes in whole muscle function and single cell contractile properties of Type I and II muscle fibers from the deltoid muscle of highly trained swimmers before and after a 21-d reduction in training volume (taper). Six college male swimmers (age, 20+/-1 yr; height, 187+/-2 cm, weight, 79+/-3 kg, fat, 7+/-1%) who had been, on average, swimming 6200 m x d(-1) for 5 months before the taper participated in this investigation. Whole muscle power increased (P < 0.05) 17% and 13% on the swim bench and swim power tests, respectively. Swim times improved by 4% (range: 3.0-4.7%; P < 0.05). There was no change in Type I fiber diameter, whereas Type IIa fibers were 11% larger (P < 0.05) after taper. Peak force (Po) of the Type I fibers was unaffected by the taper but increased (P < 0.05) from 0.63+/-0.02 to 0.82+/-0.05 mN in the IIa fibers. However, the specific force (Po/CSA) of the IIa fibers was unchanged. Shortening velocity (Vo) was 32% and 67% faster (P < 0.05) in the Type I and IIa fibers, respectively. Although Type I fiber power was unaltered, the IIa fibers increased 2.5-fold from 24.6+/-2.8 to 56.2+/-3.9 microN x FL x s(-1). When power was normalized for cell size, the power was still elevated twofold. These data suggest that tapering induces alterations in the contractile properties of single muscle fibers. Further, it appears that the Type IIa fibers are more affected than the Type I fibers by the taper. The increased size, strength, velocity, and power of the IIa fibers may be responsible for the improvements in whole muscle strength and power after the taper.

  19. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  20. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  1. Adaptations of human skeletal muscle fibers to spaceflight

    NASA Technical Reports Server (NTRS)

    Day, M. Kathleen; Allen, David L.; Mohajerani, Laleh; Greenisen, Michael C.; Roy, Roland R.; Edgerton, V. Reggie

    1995-01-01

    Human skeletal muscle fibers seem to share most of the same interrelationships among myosin ATPase activity, myosin heavy chain (MHC) phenotype, mitochondrial enzyme activities, glycolytic enzyme activities, and cross-sectional area (CSA) as found in rat, cat, and other species. One difference seems to be that fast fibers with high mitochrondrial content occur less frequently in humans than in the rat or cat. Recently, we have reported that the type of MHC expressed and the size of the muscle fibers in humans that have spent 11 days in space change significantly. Specifically, about 8% more fibers express fast MHCs and all phenotypes atrophy in the vastus lateralis (VL) post compared to preflight. In the present paper we examine the relationships among the population of myonuclei, MHC type, and CSA of single human muscle fibers before and after spaceflight. These are the first data that define the relationship among the types of MHC expressed, myonuclei number, and myonuclei domain of single fibers in human muscle. We then compare these data to similar measures in the cat. In addition, the maximal torque that can be generated by the knee extensors and their fatigability before and after spaceflight are examined. These data provide some indication of the potential physiologica consequences of the muscle adaptations that occur in humans in response to spaceflight.

  2. Adaptations of human skeletal muscle fibers to spaceflight

    NASA Technical Reports Server (NTRS)

    Day, M. Kathleen; Allen, David L.; Mohajerani, Laleh; Greenisen, Michael C.; Roy, Roland R.; Edgerton, V. Reggie

    1995-01-01

    Human skeletal muscle fibers seem to share most of the same interrelationships among myosin ATPase activity, myosin heavy chain (MHC) phenotype, mitochondrial enzyme activities, glycolytic enzyme activities, and cross-sectional area (CSA) as found in rat, cat, and other species. One difference seems to be that fast fibers with high mitochrondrial content occur less frequently in humans than in the rat or cat. Recently, we have reported that the type of MHC expressed and the size of the muscle fibers in humans that have spent 11 days in space change significantly. Specifically, about 8% more fibers express fast MHCs and all phenotypes atrophy in the vastus lateralis (VL) post compared to preflight. In the present paper we examine the relationships among the population of myonuclei, MHC type, and CSA of single human muscle fibers before and after spaceflight. These are the first data that define the relationship among the types of MHC expressed, myonuclei number, and myonuclei domain of single fibers in human muscle. We then compare these data to similar measures in the cat. In addition, the maximal torque that can be generated by the knee extensors and their fatigability before and after spaceflight are examined. These data provide some indication of the potential physiologica consequences of the muscle adaptations that occur in humans in response to spaceflight.

  3. Functional sparing of intrafusal muscle fibers in muscular dystrophies.

    PubMed

    Aimonetti, Jean-Marc; Ribot-Ciscar, Edith; Rossi-Durand, Christiane; Attarian, Shahram; Pouget, Jean; Roll, Jean-Pierre

    2005-07-01

    In a previous study, we showed that patients with muscular dystrophies (MDs) perceive passive movements, experience sensations of illusory movement induced by muscle tendon vibration, and have proprioceptive-regulated sways in response to vibratory stimulation applied to the neck and ankle muscle tendons. These findings argue for preserved proprioceptive functions of muscle spindles. However, it is unclear whether the function of intrafusal muscle fibers is spared, i.e., whether they retain their ability to contract when submitted to a fusimotor drive. To answer this question, we analyzed the effects of reinforcement maneuvers (mental computation and the Jendrassik maneuver) that are known to increase muscle spindle sensitivity via fusimotor drive in healthy subjects. Nine patients with different MDs participated in the study. Reinforcement maneuvers increased both the mean amplitude of the Achilles tendon reflex (187 +/- 52.9% of the mean control amplitude) and the sensitivity of muscle spindle afferents to imposed movements of the ankle. The same reinforcement maneuvers failed to alter the amplitude of the Hoffmann reflex in the triceps surae muscle. These results suggest that the intrafusal muscle fibers preserve their contractile abilities in slowly progressive MDs. The reasons for a differential impairment of intrafusal and extrafusal muscle fibers and the clinical implications of the present results are discussed.

  4. Polarization of Tryptophan Fluorescence from Single Striated Muscle Fibers

    PubMed Central

    dos Remedios, C. G.; Millikan, R. G. C.; Morales, M. F.

    1972-01-01

    Instrumentation has been developed to detect rapidly the polarization of tryptophan fluorescence from single muscle fibers in rigor, relaxation, and contraction. The polarization parameter (P⊥) obtained by exiciting the muscle tryptophans with light polarized perpendicular to the long axis of the muscle fiber had a magnitude P⊥ (relaxation) > P⊥ (contraction) > P⊥ (rigor) for the three types of muscle fibers examined (glycerinated rabbit psoas, glycerinated dorsal longitudinal flight muscle of Lethocerus americanus, and live semitendinosus of Rana pipiens). P⊥ from single psoas fibers in rigor was found to increase as the sarcomere length increased but in relaxed fibers P⊥ was independent of sarcomere length. After rigor, pyrophosphate produced little or no change in P⊥, but following an adenosine triphosphate (ATP)-containing solution, pyrophosphate produced a value of P⊥ that fell between the contraction and relaxation values. Sinusoidal or square wave oscillations of the muscle of amplitude 0.5–2.0% of the sarcomere length and frequency 1, 2, or 5 Hz were applied in rigor when the myosin cross-bridges are considered to be firmly attached to the thin filaments. No significant changes in P⊥ were observed in either rigor or relaxation. The preceding results together with our present knowledge of tryptophan distribution in the contractile proteins has led us to the conclusion that the parameter P⊥ is a probe of the contractile state of myosin which is probably sensitive to the orientation of the myosin S1 subfragment. PMID:4332133

  5. Human Masseter Muscle Fiber Type Properties, Skeletal Malocclusions, and Muscle Growth Factor Expression

    PubMed Central

    Sciote, James Joseph; Horton, Michael J.; Rowlerson, Anthea M.; Ferri, Joel; Close, John M.; Raoul, Gwenael

    2013-01-01

    Purpose We identified masseter muscle fiber type property differences in subjects with dentofacial deformities. Patients and Methods Samples of masseter muscle were collected from 139 young adults during mandibular osteotomy procedures to assess mean fiber areas and percent tissue occupancies for the 4 fiber types that comprise the muscle. Subjects were classified into 1 of 6 malocclusion groups based on the presence of a skeletal Class II or III sagittal dimension malocclusion and either a skeletal open, deep, or normal bite vertical dimension malocclusion. In a subpopulation, relative quantities of the muscle growth factors IGF-I and GDF-8 gene expression were quantified by real-time polymerase chain reaction. Results Fiber properties were not different in the sagittal malocclusion groups, but were very different in the vertical malocclusion groups (P ≤ .0004). There were significant mean fiber area differences for type II (P ≤ .0004) and type neonatal—atrial (P = .001) fiber types and for fiber percent occupancy differences for both type I–II hybrid fibers and type II fibers (P ≤ .0004). Growth factor expression differed by gender for IGF-I (P = .02) and GDF-8 (P < .01). The ratio of IGF-I:GDF-8 expression associates with type I and II mean fiber areas. Conclusion Fiber type properties are very closely associated with variations in vertical growth of the face, with statistical significance for overall comparisons at P ≤ .0004. An increase in masseter muscle type II fiber mean fiber areas and percent tissue occupancies is inversely related to increases in vertical facial dimension. PMID:21821327

  6. Change in the contractile behavior of muscle fibers in subjects with primary muscle dysfunction.

    PubMed

    Back, Claudio Gregório Nuernberg; Benedini-Elias, Priscila C O; Mattiello, Stela M; Sobreira, Claudia; Martinez, Edson Z; Mattiello-Sverzut, Ana Claudia

    2013-01-01

    The mechanical and metabolic characteristics of skeletal muscle fibers can interfere with muscle contractile performance in healthy subjects. Few studies have investigated the degree of association between muscle function and muscle fiber morphology in patients with myopathy. A biopsy was obtained from the left biceps brachii muscle of 12 subjects with myopathic disorders. The relative cross-sectional area of type 2 fibers and their subtypes was determined by the ATPase technique. Relative torque (RT) was calculated by dividing isokinetic elbow flexion peak torque (PT) values (90 and 180° s-1) by isometric PT values. Correlations were analyzed using Spearman's coefficient (r). The relative cross-sectional area of type 2b fibers was positively correlated with RT90 (r = 0.71, P = 0.009) and RT180 (r = 0.73, P = 0.007). The relative cross-sectional area of type 2a fibers showed a moderate and negative correlation with RT180 (r = -0.62, P = 0.03) and a low correlation with RT90 (r = -0.57, P = 0.05). In contrast to healthy subjects, patients with myopathy presented changes in the contractile behavior of type 2a fibers and compensatory adaptations in type 2b fibers. The results suggest that RT in combination with morphometric parameters provides data regarding muscle function in patients with myopathic disorders and can contribute to the establishment of therapeutic exercises.

  7. Injury and recovery of fast and slow skeletal muscle fibers affected by ACL myotoxin isolated from Agkistrodon contortrix laticinctus (Broad-Banded copperhead) venom.

    PubMed

    Morini, C C; Pereira, E C; Selistre de Araújo, H S; Ownby, C L; Salvini, T F

    1998-07-01

    The response of different types of skeletal muscle fibers to a snake venom PLA2 myotoxin was tested in vivo by injecting ACL myotoxin (ACLMT) into mice. Both the soleus (slow-twitch) and gastrocnemius (fast-twitch) were examined at different time periods (3 h, 3 and 21 d) after the injection. All animals received 5 mg/kg myotoxin into the subcutaneous lateral region of the right hind limb, near the Achilles tendon; contralateral muscles were used as controls. Cross-sections (10 microm) of frozen muscle tissue were cut from the medial region of the muscle. Alternate serial sections were stained either with toluidine blue or for acid phosphatase, myofibrillar ATPase activity after alkali (pH 10.3) or acid preincubation (pH 4.3), succinate dehydrogenase or acetylcholinesterase. Several stages of necrosis were observed 3 h after ACLMT injection, in both superficial and deep regions of both muscles. In these same regions 3 d after injection, clusters of regenerated muscle fibers were present, and some of them presented AChE activity. Twenty-one days after ACLMT injection the muscle fibers of soleus and gastrocnemius presented only chronic signs of damage such as split fibers and centralized nuclei. Using m-ATPase reactions it was possible to determine that both muscle fiber types I and II were injured in both muscles. The number of type IIC fibers was significantly increased, and the number of type II fibers significantly decreased in the gastrocnemius 21 d after ACLMT injection, suggesting a change in muscle fiber type from type II to type I, through type IIC. The increased number of type IIC fibers and the presence of AChE activity in clusters of regenerating fibers and split fibers indicate that injury by ACLMT produces axonal remodeling and muscle fiber type change.

  8. The importance of material structure in the laser cutting of glass fiber reinforced plastic composites

    SciTech Connect

    Caprino, G. . Dipt. di Ingegneria dei Materiali e della Produzione); Tagliaferri, V. . Istituto di Ingegneria Meccanica); Covelli, L. )

    1995-01-01

    A previously proposed micromechanical formula, aiming to predict the vaporization energy Q[sub v] of composite materials as a function of fiber and matrix properties and fiber volume ratio, was assessed. The experimental data, obtained on glass fiber reinforced plastic panels with different fiber contents cut by a medium power CO[sub 2] cw laser, were treated according to a procedure previously suggested, in order to evaluate Q[sub v]. An excellent agreement was found between experimental and theoretical Q[sub v] values. Theory was then used to predict the response to laser cutting of a composite material with a fiber content varying along the thickness. The theoretical predictions indicated that, in this case, the interpretation of the experimental results may be misleading, bringing to errors in the evaluation of the material thermal properties, or in the prediction of the kerf depth. Some experimental data were obtained, confirming the theoretical findings.

  9. Measuring mitochondrial respiration in intact single muscle fibers

    PubMed Central

    Schuh, Rosemary A.; Jackson, Kathryn C.; Khairallah, Ramzi J.; Ward, Christopher W.

    2012-01-01

    Measurement of mitochondrial function in skeletal muscle is a vital tool for understanding regulation of cellular bioenergetics. Currently, a number of different experimental approaches are employed to quantify mitochondrial function, with each involving either mechanically or chemically induced disruption of cellular membranes. Here, we describe a novel approach that allows for the quantification of substrate-induced mitochondria-driven oxygen consumption in intact single skeletal muscle fibers isolated from adult mice. Specifically, we isolated intact muscle fibers from the flexor digitorum brevis muscle and placed the fibers in culture conditions overnight. We then quantified oxygen consumption rates using a highly sensitive microplate format. Peak oxygen consumption rates were significantly increased by 3.4-fold and 2.9-fold by simultaneous stimulation with the uncoupling agent, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), and/or pyruvate or palmitate exposure, respectively. However, when calculating the total oxygen consumed over the entire treatment, palmitate exposure resulted in significantly more oxygen consumption compared with pyruvate. Further, as proof of principle for the procedure, we isolated fibers from the mdx mouse model, which has known mitochondrial deficits. We found significant reductions in initial and peak oxygen consumption of 51% and 61% compared with fibers isolated from the wild-type (WT) animals, respectively. In addition, we determined that fibers isolated from mdx mice exhibited less total oxygen consumption in response to the FCCP + pyruvate stimulation compared with the WT mice. This novel approach allows the user to make mitochondria-specific measures in a nondisrupted muscle fiber that has been isolated from a whole muscle. PMID:22160545

  10. Measuring mitochondrial respiration in intact single muscle fibers.

    PubMed

    Schuh, Rosemary A; Jackson, Kathryn C; Khairallah, Ramzi J; Ward, Christopher W; Spangenburg, Espen E

    2012-03-15

    Measurement of mitochondrial function in skeletal muscle is a vital tool for understanding regulation of cellular bioenergetics. Currently, a number of different experimental approaches are employed to quantify mitochondrial function, with each involving either mechanically or chemically induced disruption of cellular membranes. Here, we describe a novel approach that allows for the quantification of substrate-induced mitochondria-driven oxygen consumption in intact single skeletal muscle fibers isolated from adult mice. Specifically, we isolated intact muscle fibers from the flexor digitorum brevis muscle and placed the fibers in culture conditions overnight. We then quantified oxygen consumption rates using a highly sensitive microplate format. Peak oxygen consumption rates were significantly increased by 3.4-fold and 2.9-fold by simultaneous stimulation with the uncoupling agent, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), and/or pyruvate or palmitate exposure, respectively. However, when calculating the total oxygen consumed over the entire treatment, palmitate exposure resulted in significantly more oxygen consumption compared with pyruvate. Further, as proof of principle for the procedure, we isolated fibers from the mdx mouse model, which has known mitochondrial deficits. We found significant reductions in initial and peak oxygen consumption of 51% and 61% compared with fibers isolated from the wild-type (WT) animals, respectively. In addition, we determined that fibers isolated from mdx mice exhibited less total oxygen consumption in response to the FCCP + pyruvate stimulation compared with the WT mice. This novel approach allows the user to make mitochondria-specific measures in a nondisrupted muscle fiber that has been isolated from a whole muscle.

  11. Elevated nuclear Foxo1 suppresses excitability of skeletal muscle fibers

    PubMed Central

    Hernández-Ochoa, Erick O.; Schachter, Tova Neustadt

    2013-01-01

    Forkhead box O 1 (Foxo1) controls the expression of proteins that carry out processes leading to skeletal muscle atrophy, making Foxo1 of therapeutic interest in conditions of muscle wasting. The transcription of Foxo1-regulated proteins is dependent on the translocation of Foxo1 to the nucleus, which can be repressed by insulin-like growth factor-1 (IGF-1) treatment. The role of Foxo1 in muscle atrophy has been explored at length, but whether Foxo1 nuclear activity affects skeletal muscle excitation-contraction (EC) coupling has not yet been examined. Here, we use cultured adult mouse skeletal muscle fibers to investigate the effects of Foxo1 overexpression on EC coupling. Fibers expressing Foxo1-green fluorescent protein (GFP) exhibit an inability to contract, impaired propagation of action potentials, and ablation of calcium transients in response to electrical stimulation compared with fibers expressing GFP alone. Evaluation of the transverse (T)-tubule system morphology, the membranous system involved in the radial propagation of the action potential, revealed an intact T-tubule network in fibers overexpressing Foxo1-GFP. Interestingly, long-term IGF-1 treatment of Foxo1-GFP fibers, which maintains Foxo1-GFP outside the nucleus, prevented the loss of normal calcium transients, indicating that Foxo1 translocation and the atrogenes it regulates affect the expression of proteins involved in the generation and/or propagation of action potentials. A reduction in the sodium channel Nav1.4 expression in fibers overexpressing Foxo1-GFP was also observed in the absence of IGF-1. We conclude that increased nuclear activity of Foxo1 prevents the normal muscle responses to electrical stimulation and that this indicates a novel capability of Foxo1 to disable the functional activity of skeletal muscle. PMID:23804205

  12. Staining of Human Thyroarytenoid Muscle with Myosin Antibodies Reveals Some Unique Extrafusal Fibers, but no Muscle Spindles

    PubMed Central

    Brandon, Carla A.; Rosen, Clark; Georgelis, George; Horton, Michael J.; Mooney, Mark P.; Sciote, James J.

    2013-01-01

    Summary This study describes the myosin composition of extrafusal and intrafusal muscle fibers found in the human thyroarytenoid (TA) and sternohyoid (control) muscles. We sought to determine the presence of muscle spindles in the TA muscle, and to identify unusual extrafusal fiber types, using the commonly accepted approach of tissue stainng with myosin isoform specific antibodies. Extrafusal fibers are organized into motor units, which subsequently produce muscle movement, whereas intrafusal fibers compose muscle spindles, the primary stretch receptor that provides afferent (feed back) information to the nervous system for regulation of motor unit length and tonicity. Immunohistochemical identification of muscle spindles was confirmed in sternohyoid, but not in TA samples; however, some extrafusal fibers contained tonic myosin. These results indicate that human TA muscle functions similar to some mammalian extraocular muscle, performing unloaded (non-weight bearing) contractions without afferent information from native muscle spindles. PMID:12825656

  13. Effect of swim taper on whole muscle and single muscle fiber contractile properties.

    PubMed

    Trappe, SCOTT; Costill, DAVID; Thomas, ROBERT

    2000-12-01

    TRAPPE, S., D. COSTILL, and R. THOMAS. Effect of swim taper on whole muscle and single muscle fiber contractile properties. Med. Sci. Sports Exerc., Vol. 32, No. 12, 2000, pp. 48-56. Purpose: To examine the changes in whole muscle function and single cell contractile properties of Type I and II muscle fibers from the deltoid muscle of highly trained swimmers before and after a 21-d reduction in training volume (taper). Methods: Six college male swimmers (age, 20 +/- 1 yr; height, 187 +/- 2 cm, weight, 79 +/- 3 kg, fat, 7 +/- 1%) who had been, on average, swimming 6200 m.d-1 for 5 months before the taper participated in this investigation. Results: Whole muscle power increased (P < 0.05) 17% and 13% on the swim bench and swim power tests, respectively. Swim times improved by 4% (range: 3.0-4.7%; P < 0.05). There was no change in Type I fiber diameter, whereas Type IIa fibers were 11% larger (P < 0.05) after taper. Peak force (Po) of the Type I fibers was unaffected by the taper but increased (P < 0.05) from 0.63 +/- 0.02 to 0.82 +/- 0.05 mN in the IIa fibers. However, the specific force (Po/CSA) of the IIa fibers was unchanged. Shortening velocity (Vo) was 32% and 67% faster (P < 0.05) in the Type I and IIa fibers, respectively. Although Type I fiber power was unaltered, the IIa fibers increased 2.5-fold from 24.6 +/- 2.8 to 56.2 +/- 3.9 µN.FL.s-1. When power was normalized for cell size, the power was still elevated twofold. Conclusions: These data suggest that tapering induces alterations in the contractile properties of single muscle fibers. Further, it appears that the Type IIa fibers are more affected than the Type I fibers by the taper. The increased size, strength, velocity, and power of the IIa fibers may be responsible for the improvements in whole muscle strength and power after the taper.

  14. Muscle Transcriptional Profile Based on Muscle Fiber, Mitochondrial Respiratory Activity, and Metabolic Enzymes

    PubMed Central

    Liu, Xuan; Du, Yang; Trakooljul, Nares; Brand, Bodo; Muráni, Eduard; Krischek, Carsten; Wicke, Michael; Schwerin, Manfred; Wimmers, Klaus; Ponsuksili, Siriluck

    2015-01-01

    Skeletal muscle is a highly metabolically active tissue that both stores and consumes energy. Important biological pathways that affect energy metabolism and metabolic fiber type in muscle cells may be identified through transcriptomic profiling of the muscle, especially ante mortem. Here, gene expression was investigated in malignant hyperthermia syndrome (MHS)-negative Duroc and Pietrian (PiNN) pigs significantly differing for the muscle fiber types slow-twitch-oxidative fiber (STO) and fast-twitch-oxidative fiber (FTO) as well as mitochondrial activity (succinate-dependent state 3 respiration rate). Longissimus muscle samples were obtained 24 h before slaughter and profiled using cDNA microarrays. Differential gene expression between Duroc and PiNN muscle samples were associated with protein ubiquitination, stem cell pluripotency, amyloid processing, and 3-phosphoinositide biosynthesis and degradation pathways. In addition, weighted gene co-expression network analysis within both breeds identified several co-expression modules that were associated with the proportion of different fiber types, mitochondrial respiratory activity, and ATP metabolism. In particular, Duroc results revealed strong correlations between mitochondrion-associated co-expression modules and STO (r = 0.78), fast-twitch glycolytic fiber (r = -0.98), complex I (r=0.72) and COX activity (r = 0.86). Other pathways in the protein-kinase-activity enriched module were positively correlated with STO (r=0.93), while negatively correlated with FTO (r = -0.72). In contrast to PiNN, co-expression modules enriched in macromolecule catabolic process, actin cytoskeleton, and transcription activator activity were associated with fiber types, mitochondrial respiratory activity, and metabolic enzyme activities. Our results highlight the importance of mitochondria for the oxidative capacity of porcine muscle and for breed-dependent molecular pathways in muscle cell fibers. PMID:26681915

  15. CYTOLOGICAL STUDIES OF FIBER TYPES IN SKELETAL MUSCLE

    PubMed Central

    Gauthier, Geraldine F.; Padykula, Helen A.

    1966-01-01

    A comparative investigation of the mammalian diaphragm has revealed a correlation between certain cytological aspects of red and white muscle fibers and functional activity. This skeletal muscle presents the advantage of a similar and constant function among the mammals, but its functional activity varies in a quantitative manner. Both the rate of breathing (and hence the rate of contraction of the diaphragm) and metabolic activity are known to be inversely related to body size; and this study has demonstrated a relationship between cytological characteristics of the diaphragm and body size of the animal. Small fibers rich in mitochondria (red fibers) are characteristic of small mammals, which have high metabolic activity and fast breathing rates; and large fibers with relatively low mitochondrial content predominate in large mammals, which have lower metabolic activity and slower breathing rates. In mammals with body size intermediate between these two groups (including the laboratory rat), the diaphragm consists of varying mixtures of fiber types. In general, the mitochondrial content of diaphragm fibers is inversely related to body size. It appears, then, that the red fiber reflects a high degree of metabolic activity or a relatively high rate of contraction within the range exhibited by this muscle. PMID:5950272

  16. Molecular Mechanisms Regulating Muscle Fiber Composition Under Microgravity

    NASA Technical Reports Server (NTRS)

    Rosenthal, Nadia A.

    1999-01-01

    The overall goal of this project is to reveal the molecular mechanisms underlying the selective and debilitating atrophy of specific skeletal muscle fiber types that accompanies sustained conditions of microgravity. Since little is currently known about the regulation of fiber-specific gene expression programs in mammalian muscle, elucidation of the basic mechanisms of fiber diversification is a necessary prerequisite to the generation of therapeutic strategies for attenuation of muscle atrophy on earth or in space. Vertebrate skeletal muscle development involves the fusion of undifferentiated mononucleated myoblasts to form multinucleated myofibers, with a concomitant activation of muscle-specific genes encoding proteins that form the force-generating contractile apparatus. The regulatory circuitry controlling skeletal muscle gene expression has been well studied in a number of vertebrate animal systems. The goal of this project has been to achieve a similar level of understanding of the mechanisms underlying the further specification of muscles into different fiber types, and the role played by innervation and physical activity in the maintenance and adaptation of different fiber phenotypes into adulthood. Our recent research on the genetic basis of fiber specificity has focused on the emergence of mature fiber types and have implicated a group of transcriptional regulatory proteins, known as E proteins, in the control of fiber specificity. The restriction of E proteins to selected muscle fiber types is an attractive hypothetical mechanism for the generation of muscle fiber-specific patterns of gene expression. To date our results support a model wherein different E proteins are selectively expressed in muscle cells to determine fiber-restricted gene expression. These studies are a first step to define the molecular mechanisms responsible for the shifts in fiber type under conditions of microgravity, and to determine the potential importance of E proteins as

  17. Interactions between muscle fibers and segment boundaries in zebrafish.

    PubMed

    Henry, Clarissa A; McNulty, Ian M; Durst, Wendy A; Munchel, Sarah E; Amacher, Sharon L

    2005-11-15

    The most obvious segmental structures in the vertebrate embryo are somites: transient structures that give rise to vertebrae and much of the musculature. In zebrafish, most somitic cells give rise to long muscle fibers that are anchored to intersegmental boundaries. Therefore, this boundary is analogous to the mammalian tendon in that it transduces muscle-generated force to the skeletal system. We have investigated interactions between somite boundaries and muscle fibers. We define three stages of segment boundary formation. The first stage is the formation of the initial epithelial somite boundary. The second "transition" stage involves both the elongation of initially round muscle precursor cells and somite boundary maturation. The third stage is myotome boundary formation, where the boundary becomes rich in extracellular matrix and all muscle precursor cells have elongated to form long muscle fibers. It is known that formation of the initial epithelial somite boundary requires Notch signaling; vertebrate Notch pathway mutants show severe defects in somitogenesis. However, many zebrafish Notch pathway mutants are homozygous viable suggesting that segmentation of their larval and adult body plans at least partially recovers. We show that epithelial somite boundary formation and slow-twitch muscle morphogenesis are initially disrupted in after eight (aei) mutant embryos (which lack function of the Notch ligand, DeltaD); however, myotome boundaries form later ("recover") in a Hedgehog-dependent fashion. Inhibition of Hedgehog-induced slow muscle induction in aei/deltaD and deadly seven (des)/notch1a mutant embryos suggests that slow muscle is necessary for myotome boundary recovery in the absence of initial epithelial somite boundary formation. Because we have previously demonstrated that slow muscle migration triggers fast muscle cell elongation in zebrafish, we hypothesize that migrating slow muscle facilitates myotome boundary formation in aei/deltaD mutant

  18. Effect of carbon nanotubes upon emissions from cutting and sanding carbon fiber-epoxy composites

    NASA Astrophysics Data System (ADS)

    Heitbrink, William A.; Lo, Li-Ming

    2015-08-01

    Carbon nanotubes (CNTs) are being incorporated into structural composites to enhance material strength. During fabrication or repair activities, machining nanocomposites may release CNTs into the workplace air. An experimental study was conducted to evaluate the emissions generated by cutting and sanding on three types of epoxy-composite panels: Panel A containing graphite fibers, Panel B containing graphite fibers and carbon-based mat, and Panel C containing graphite fibers, carbon-based mat, and multi-walled CNTs. Aerosol sampling was conducted with direct-reading instruments, and filter samples were collected for measuring elemental carbon (EC) and fiber concentrations. Our study results showed that cutting Panel C with a band saw did not generate detectable emissions of fibers inspected by transmission electron microscopy but did increase the particle mass, number, and EC emission concentrations by 20-80 % compared to Panels A and B. Sanding operation performed on two Panel C resulted in fiber emission rates of 1.9 × 108 and 2.8 × 106 fibers per second (f/s), while no free aerosol fibers were detected from sanding Panels A and B containing no CNTs. These free CNT fibers may be a health concern. However, the analysis of particle and EC concentrations from these same samples cannot clearly indicate the presence of CNTs, because extraneous aerosol generation from machining the composite epoxy material increased the mass concentrations of the EC.

  19. Effect of Carbon Nanotubes Upon Emissions From Cutting and Sanding Carbon Fiber-Epoxy Composites

    PubMed Central

    Heitbrink, William A.; Lo, Li-Ming

    2015-01-01

    Carbon nanotubes (CNTs) are being incorporated into structural composites to enhance material strength. During fabrication or repair activities, machining nanocomposites may release CNTs into the workplace air. An experimental study was conducted to evaluate the emissions generated by cutting and sanding on three types of epoxy-composite panels: Panel A containing graphite fibers, Panel B containing graphite fibers and carbon-based mat, and Panel C containing graphite fibers, carbon-based mat, and multi-walled CNTs. Aerosol sampling was conducted with direct-reading instruments, and filter samples were collected for measuring elemental carbon (EC) and fiber concentrations. Our study results showed that cutting Panel C with a band saw did not generate detectable emissions of fibers inspected by transmission electron microscopy but did increase the particle mass, number, and EC emission concentrations by 20% to 80% compared to Panels A and B. Sanding operation performed on two Panel C resulted in fiber emission rates of 1.9×108 and 2.8×106 fibers per second (f/s), while no free aerosol fibers were detected from sanding Panels A and B containing no CNTs. These free CNT fibers may be a health concern. However, the analysis of particle and EC concentrations from these same samples cannot clearly indicate the presence of CNTs, because extraneous aerosol generation from machining the composite epoxy material increased the mass concentrations of the EC. PMID:26478716

  20. Effect of Carbon Nanotubes Upon Emissions From Cutting and Sanding Carbon Fiber-Epoxy Composites.

    PubMed

    Heitbrink, William A; Lo, Li-Ming

    2015-08-01

    Carbon nanotubes (CNTs) are being incorporated into structural composites to enhance material strength. During fabrication or repair activities, machining nanocomposites may release CNTs into the workplace air. An experimental study was conducted to evaluate the emissions generated by cutting and sanding on three types of epoxy-composite panels: Panel A containing graphite fibers, Panel B containing graphite fibers and carbon-based mat, and Panel C containing graphite fibers, carbon-based mat, and multi-walled CNTs. Aerosol sampling was conducted with direct-reading instruments, and filter samples were collected for measuring elemental carbon (EC) and fiber concentrations. Our study results showed that cutting Panel C with a band saw did not generate detectable emissions of fibers inspected by transmission electron microscopy but did increase the particle mass, number, and EC emission concentrations by 20% to 80% compared to Panels A and B. Sanding operation performed on two Panel C resulted in fiber emission rates of 1.9×10(8) and 2.8×10(6) fibers per second (f/s), while no free aerosol fibers were detected from sanding Panels A and B containing no CNTs. These free CNT fibers may be a health concern. However, the analysis of particle and EC concentrations from these same samples cannot clearly indicate the presence of CNTs, because extraneous aerosol generation from machining the composite epoxy material increased the mass concentrations of the EC.

  1. Postnatal development of fiber type composition in rabbit jaw and leg muscles.

    PubMed

    Korfage, J A M; Helmers, R; Matignon, M de Goüyon; van Wessel, T; Langenbach, G E J; van Eijden, T M G J

    2009-01-01

    We examined the difference in fiber type composition and cross-sectional areas during postnatal development in male rabbit jaw muscles and compared these with changes in leg muscles. The myosin heavy chain (MyHC) content of the fibers was determined by immunohistochemistry. No fiber type difference was found between the jaw muscles in 20-week-old rabbits. However, the way this adult fiber type composition was reached differed between the muscles. The deep temporalis, medial pterygoid, and superficial masseter displayed an increase in alpha fibers during early and a decrease during late postnatal development. Other jaw muscles displayed an increase in alpha fibers during early development only. In contrast, alpha fibers were not found in the soleus, in which fiber type changes were completed at week 4. The gastrocnemius muscle did not change its fiber type composition. Initially, fibers in jaw-opening muscles had larger cross-sectional areas than in other muscles, but they increased less during development. Although there were no large differences in the fiber type composition of muscles in young adult rabbits, large differences were found in the jaw muscles, but not in the leg muscles, during development. In part, these developmental changes in fiber percentages within the jaw muscles can be explained by functional modifications in this muscle group. In the present study, the deep temporalis, medial pterygoid, and superficial masseter showed the most dramatic percent changes in fibers during postnatal development. (c) 2008 S. Karger AG, Basel.

  2. Muscle fiber size increases following resistance training in multiple sclerosis.

    PubMed

    Dalgas, U; Stenager, E; Jakobsen, J; Petersen, T; Overgaard, K; Ingemann-Hansen, T

    2010-11-01

    To test the hypothesis that lower body progressive resistance training (PRT) leads to an increase of the muscle fiber cross-sectional area (CSA) and a shift in the proportion of fiber types in patients with multiple sclerosis (MS). The present study was a two-arm, randomized controlled trial (RCT). Thirty-eight MS patients (Expanded Disability Status Scale (EDSS) 3-5.5) were randomized to a PRT group (Exercise, n = 19) or a control group (Control, n = 19). The Exercise group performed a biweekly 12-week lower body PRT program [five exercises progressing from 15RM (Repetition Maximum) towards 8RM], whereas the Control group maintained their usual daily activity level during the trial period. Muscle biopsies from vastus lateralis were taken before (pre) and after the trial (post). Thigh volume (TV) was estimated from anthropometric measurements. Isokinetic muscle strength of the knee extensors (KE) and flexors (KF) were evaluated at slow (90(°)/s) and fast (180(°)/s) angular velocities. In the Exercise group the mean CSA of all muscle fibers (7.9 ± 15.4% vs. -3.5 ± 9.0%, p = 0.03) and of type II muscle fibers (14.0 ± 19.4% vs. -2.6 ± 15.5%, p = 0.02) increased in comparison with the Control group. No changes occurred in the proportion of fiber types in the Exercise group. Neither was there any change in total TV. Isokinetic strength at KE180, KF90 and KF180 improved significantly after PRT when compared with the control group (10.2-21.3%, p ≤ 0.02). We conclude that progressive resistance training induces a compensatory increase of muscle fiber size in patients with the central nervous system disorder, multiple sclerosis.

  3. Inhibition of platelet-derived growth factor signaling prevents muscle fiber growth during skeletal muscle hypertrophy.

    PubMed

    Sugg, Kristoffer B; Korn, Michael A; Sarver, Dylan C; Markworth, James F; Mendias, Christopher L

    2017-03-01

    The platelet-derived growth factor receptors alpha and beta (PDGFRα and PDGFRβ) mark fibroadipogenic progenitor cells/fibroblasts and pericytes in skeletal muscle, respectively. While the role that these cells play in muscle growth and development has been evaluated, it was not known whether the PDGF receptors activate signaling pathways that control transcriptional and functional changes during skeletal muscle hypertrophy. To evaluate this, we inhibited PDGFR signaling in mice subjected to a synergist ablation muscle growth procedure, and performed analyses 3 and 10 days after induction of hypertrophy. The results from this study indicate that PDGF signaling is required for fiber hypertrophy, extracellular matrix production, and angiogenesis that occur during muscle growth.

  4. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    SciTech Connect

    Kononenko, T. V.; Komlenok, M. S.; Konov, V. I.; Freitag, C.; Onuseit, V.; Weber, R.; Graf, T.

    2014-03-14

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres.

  5. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Kononenko, T. V.; Freitag, C.; Komlenok, M. S.; Onuseit, V.; Weber, R.; Graf, T.; Konov, V. I.

    2014-03-01

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres.

  6. Satellite cell depletion prevents fiber hypertrophy in skeletal muscle.

    PubMed

    Egner, Ingrid M; Bruusgaard, Jo C; Gundersen, Kristian

    2016-08-15

    The largest mammalian cells are the muscle fibers, and they have multiple nuclei to support their large cytoplasmic volumes. During hypertrophic growth, new myonuclei are recruited from satellite stem cells into the fiber syncytia, but it was recently suggested that such recruitment is not obligatory: overload hypertrophy after synergist ablation of the plantaris muscle appeared normal in transgenic mice in which most of the satellite cells were abolished. When we essentially repeated these experiments analyzing the muscles by immunohistochemistry and in vivo and ex vivo imaging, we found that overload hypertrophy was prevented in the satellite cell-deficient mice, in both the plantaris and the extensor digitorum longus muscles. We attribute the previous findings to a reliance on muscle mass as a proxy for fiber hypertrophy, and to the inclusion of a significant number of regenerating fibers in the analysis. We discuss that there is currently no model in which functional, sustainable hypertrophy has been unequivocally demonstrated in the absence of satellite cells; an exception is re-growth, which can occur using previously recruited myonuclei without addition of new myonuclei. © 2016. Published by The Company of Biologists Ltd.

  7. Aging affects different human muscles in various ways. An image analysis of the histomorphometric characteristics of fiber types in human masseter and vastus lateralis muscles from young adults and the very old.

    PubMed

    Kirkeby, S; Garbarsch, C

    2000-01-01

    This study is an attempt to objectively evaluate age-related changes in human muscles by use of histomorphometric methods. Aging in humans induces dramatic transformations in the skeletal muscles but little is known as to whether or not the aging processes per se may affect all muscles equally. In this study aging of two human muscles with different functions, origin and nerve supply is compared. Sections were cut from masseter and vastus lateralis muscles obtained from young adults aged 18-24 years and from the very old aged 90-102 years. Muscle fiber types were classified with the traditional myofibrillar ATPase staining. Various histomorphometric parameters of the different fiber types in human masseter and vastus lateralis muscle sections were obtained by image analyses to evaluate the age-related changes in the muscle fibers. The following variables were calculated: the number of each fiber type per photographed area; the area of each fiber and two indicators for the shape of the muscle fibers. In the aging muscles there was no relative preferential loss of a fiber type. High numbers of intermediate ATPase-stained fibers (IM fibers) were found in some old vastus muscles but were only sporadic in young vastus muscles. However, there was no change in the percentage distribution of intermediate ATPase-stained fibers when young and very old human masseter muscles were compared. Incubation of the sections with antimyosin antibodies showed that the IM fibers in old masseter and old vastus contained different myosin heavy chains. Thus ATPase activity and anti-myosin staining displayed a somewhat different pattern of fiber type distribution. The main changes in the shape and area indicated that type I fibers in the masseter became more circular while in the vastus they decreased significantly in size. The type II fibers in the vastus became very small and deviated significantly from circularity whereas the type II fibers in the masseter only exhibited a decrease in

  8. Estimation of cut-off wavelength of rare earth doped single-mode fibers

    NASA Astrophysics Data System (ADS)

    Kaur, Jagneet; Thyagarajan, K.; Pal, B. P.

    1999-11-01

    A new empirical relation is proposed describing spectral variation of mode-field radius (MFR) as inferred from measurements in the far-field of the fiber. It is shown that using this relation, it is possible to estimate the cut-off wavelength ( λc) of the fiber. The proposed technique is successfully tested through measurements made on two standard step index single-mode fibers, as well as on an erbium doped fiber (EDF) having λc falling within its strong absorption band around 980 nm. This empirical formula is more accurate than the widely used Marcuse's formula to describe spectral dependence of MFR determined through measurements made in the fiber's far-field. The proposed technique is especially suited for estimation of λc of doped fibers in which λc falls within an absorption band.

  9. Experimental comparisons between McKibben type artificial muscles and straight fibers type artificial muscles

    NASA Astrophysics Data System (ADS)

    Nakamura, Taro

    2007-01-01

    This paper describes experimental comparison between a conventional McKibben type artificial muscle and a straight fibers type artificial muscle developed by the authors. A wearable device and a rehabilitation robot which assists a human muscle should have characteristics similar to those of human muscle. In addition, because the wearable device and the rehabilitation robot should be light, an actuator with a high power/weight ratio is needed. At present, the McKibben type is widely used as an artificial muscle, but in fact its physical model is highly nonlinear. Further, the heat and mechanical loss of this actuator are large because of the friction caused by the expansion and contraction of the sleeve. Therefore, the authors have developed an artificial muscle tube in which high strength glass fibers have been built into the tube made from natural latex rubber. As results, experimental results demonstrated that the developed artificial muscle is more effective regarding its fundamental characteristics than that of the McKibben type; the straight fibers types of artificial muscle have more contraction ratio and power, longer lifetime than the McKibben types. And it has almost same characteristics of human muscle for isotonic and isometric that evaluate it dynamically.

  10. Equilibrium distribution of ions in a muscle fiber.

    PubMed Central

    Maughan, D W; Godt, R E

    1989-01-01

    We have developed a mathematical description of the equilibrium (Donnan) distribution of mobile ions between two phases containing fixed charges. This differs from the classical Donnan derivation by including mobile polyvalent ions such as those present in intact muscle fibers and in solutions used with skinned muscle fibers. Given the average concentrations of ionic species present in intact frog muscle, we calculate that the myofibrillar fixed charge density (-42 meq/liter cytoplasmic fluid) is in close agreement with estimates from amino acid analysis of myofibrillar proteins. As expected, with negative fixed charges in the myofibril, anions are excluded from the myofibrillar space while cations are concentrated in this space; the ratio between the average intra- and extramyofibrillar concentrations for an ion of valence n is (1.11)n. This model allowed us to design a bathing solution for skinned muscle fibers in which the intramyofibrillar ion concentrations closely approximate those found in intact frog muscle cells. Our model, applied to the A- and I-bands of the sarcomere, suggests that likely differences in fixed charge densities in these regions accounts for only a small fraction of the extreme concentration of phosphocreatine observed in the I-bands of intact frog muscle. PMID:2819235

  11. Severely Atrophic Human Muscle Fibers With Nuclear Misplacement Survive Many Years of Permanent Denervation

    PubMed Central

    Carraro, Ugo; Kern, Helmut

    2016-01-01

    Likewise in rodents, after complete spinal cord injury (SCI) the lower motor neuron (LMN) denervated human muscle fibers lose completely the myofibrillar apparatus and the coil distribution of myonuclei that are relocated in groups (nuclear clumps) in the center of severely atrophic muscle fibers. Up to two years of LMN denervation the muscle fibers with nuclear clumps are very seldom, but in this cohort of patients the severely atrophic muscle fibers are frequent in muscle biopsies harvested three to six years after SCI. Indeed, the percentage increased to 27 ± 9% (p< 0.001), and then abruptly decreased from the 6th year onward, when fibrosis takes over to neurogenic muscle atrophy. Immunohistochemical analyses shown that nuclear misplacements occurred in both fast and slow muscle fibers. In conclusion, human muscle fibers survive permanent denervation much longer than generally accepted and relocation of nuclei is a general behavior in long term denervated muscle fibers. PMID:27478559

  12. The muscle fiber type–fiber size paradox: hypertrophy or oxidative metabolism?

    PubMed Central

    van Wessel, T.; de Haan, A.; van der Laarse, W. J.

    2010-01-01

    An inverse relationship exists between striated muscle fiber size and its oxidative capacity. This relationship implies that muscle fibers, which are triggered to simultaneously increase their mass/strength (hypertrophy) and fatigue resistance (oxidative capacity), increase these properties (strength or fatigue resistance) to a lesser extent compared to fibers increasing either of these alone. Muscle fiber size and oxidative capacity are determined by the balance between myofibrillar protein synthesis, mitochondrial biosynthesis and degradation. New experimental data and an inventory of critical stimuli and state of activation of the signaling pathways involved in regulating contractile and metabolic protein turnover reveal: (1) higher capacity for protein synthesis in high compared to low oxidative fibers; (2) competition between signaling pathways for synthesis of myofibrillar proteins and proteins associated with oxidative metabolism; i.e., increased mitochondrial biogenesis via AMP-activated protein kinase attenuates the rate of protein synthesis; (3) relatively higher expression levels of E3-ligases and proteasome-mediated protein degradation in high oxidative fibers. These observations could explain the fiber type–fiber size paradox that despite the high capacity for protein synthesis in high oxidative fibers, these fibers remain relatively small. However, it remains challenging to understand the mechanisms by which contractile activity, mechanical loading, cellular energy status and cellular oxygen tension affect regulation of fiber size. Therefore, one needs to know the relative contribution of the signaling pathways to protein turnover in high and low oxidative fibers. The outcome and ideas presented are relevant to optimizing treatment and training in the fields of sports, cardiology, oncology, pulmonology and rehabilitation medicine. Electronic supplementary material The online version of this article (doi:10.1007/s00421-010-1545-0) contains

  13. Common errors in textbook descriptions of muscle fiber size in nontrained humans.

    PubMed

    Chalmers, Gordon R; Row, Brandi S

    2011-09-01

    Exercise science and human anatomy and physiology textbooks commonly report that type IIB muscle fibers have the largest cross-sectional area of the three fiber types. These descriptions of muscle fiber sizes do not match with the research literature examining muscle fibers in young adult nontrained humans. For men, most commonly type IIA fibers were significantly larger than other fiber types (six out of 10 cases across six different muscles). For women, either type I, or both I and IIA muscle fibers were usually significantly the largest (five out of six cases across four different muscles). In none of these reports were type IIB fibers significantly larger than both other fiber types. In 27 studies that did not include statistical comparisons of mean fiber sizes across fiber types, in no cases were type IIB or fast glycolytic fibers larger than both type I and IIA, or slow oxidative and fast oxidative glycolytic fibers. The likely reason for mistakes in textbook descriptions of human muscle fiber sizes is that animal data were presented without being labeled as such, and without any warning that there are interspecies differences in muscle fiber properties. Correct knowledge of muscle fiber sizes may facilitate interpreting training and aging adaptations.

  14. Hormone-sensitive stages in the sexual differentiation of laryngeal muscle fiber number in Xenopus laevis

    PubMed Central

    Marin, Melanie L.; Tobias, Martha L.

    2012-01-01

    Summary The number of muscle fibers in the vocal organ of the adult male African clawed frog, Xenopus laevis, exceeds that of adult females. This sex difference is the result of rapid fiber addition in males between the end of metamorphosis, post-metamorphic stage 0 (PM0) and PM2. At PM0, male and female frogs have similar numbers of laryngeal muscle fibers. Males then add more muscle fibers than females and achieve an adult value that is 1.7 times the female number. Males castrated at PM0 have the same fiber number as females. Ovariectomy at PM0 does not alter muscle fiber addition in females. Gonadectomy at PM2 has no effect on fiber addition in either sex. Females attain masculine muscle fiber number if their ovaries are replaced with a testis at metamorphosis. Exogenous testosterone treatment at PM0 significantly increases fiber number in females but not in males. Exogenous testosterone given at PM2 has no effect on fiber number in females but decreases fiber number in males. We conclude that the testes are necessary for the marked addition of laryngeal muscle fibers seen in male X. laevis between PM0 and PM2. The masculine pattern of muscle fiber addition can be induced in females provided with a testis. Androgen secretion from the testes most probably accounts for masculinization of laryngeal muscle fiber number. After PM2, androgens are no longer necessary for muscle fiber addition and cannot increase fiber number in females. PMID:2088715

  15. Comparisons of different muscle metabolic enzymes and muscle fiber types in Jinhua and Landrace pigs.

    PubMed

    Guo, J; Shan, T; Wu, T; Zhu, L N; Ren, Y; An, S; Wang, Y

    2011-01-01

    Western and indigenous Chinese pig breeds show obvious differences in muscle growth and meat quality, however, the underlying molecular mechanism remains unclear. The main objective of this study was to evaluate the breed-specific mechanisms controlling meat quality and postmortem muscle metabolism. The specific purpose was to investigate the variations in meat quality, muscle fiber type, and enzyme activity between local Jinhua and exotic Landrace pigs at the same age (180 d of age), as well as the same BW of 64 kg, respectively. We compared differentially expressed muscle fiber types such as types I and IIa (oxidative), type IIb (glycolytic), as well as type IIx (intermediate) fibers in LM and soleus muscles of Jinhua and Landrace pigs using real-time reverse-transcription PCR. Furthermore, the metabolic enzyme activities of lactate dehydrogenase, as well as succinic dehydrogenase and malate dehydrogenase, were used as markers of glycolytic and oxidative capacities, respectively. Results showed that Jinhua pigs exhibited greater intramuscular fat content and less drip loss compared with the Landrace (P < 0.01). Meanwhile, the mRNA abundance of oxidative and intermediate fibers was increased in Jinhua pigs, whereas the glycolytic fibers were more highly expressed in the Landrace (P < 0.01). In addition, Jinhua pigs possessed greater oxidative capacity than that of the Landrace (P < 0.05). These results suggested that the increased expression of the oxidative and intermediate fibers and greater activities of oxidative enzymes in Jinhua pigs were related to meat quality as indicated by a greater intramuscular fat and reduced drip loss. Based on these results, we conclude that muscle fiber composition and postmortem muscle metabolism can explain, in part, the variation of meat quality in Jinhua and Landrace pigs. These results may provide valuable information for understanding the molecular mechanism responsible for breed specific differences in growth performance

  16. Single muscle fiber gene expression with run taper.

    PubMed

    Murach, Kevin; Raue, Ulrika; Wilkerson, Brittany; Minchev, Kiril; Jemiolo, Bozena; Bagley, James; Luden, Nicholas; Trappe, Scott

    2014-01-01

    This study evaluated gene expression changes in gastrocnemius slow-twitch myosin heavy chain I (MHC I) and fast-twitch (MHC IIa) muscle fibers of collegiate cross-country runners (n = 6, 20±1 y, VO₂max = 70±1 ml•kg-1•min-1) during two distinct training phases. In a controlled environment, runners performed identical 8 kilometer runs (30:18±0:30 min:s, 89±1% HRmax) while in heavy training (∼72 km/wk) and following a 3 wk taper. Training volume during the taper leading into peak competition was reduced ∼50% which resulted in improved race times and greater cross-section and improved function of MHC IIa fibers. Single muscle fibers were isolated from pre and 4 hour post run biopsies in heavily trained and tapered states to examine the dynamic acute exercise response of the growth-related genes Fibroblast growth factor-inducible 14 (FN14), Myostatin (MSTN), Heat shock protein 72 (HSP72), Muscle ring-finger protein-1 (MURF1), Myogenic factor 6 (MRF4), and Insulin-like growth factor 1 (IGF1) via qPCR. FN14 increased 4.3-fold in MHC IIa fibers with exercise in the tapered state (P<0.05). MSTN was suppressed with exercise in both fiber types and training states (P<0.05) while MURF1 and HSP72 responded to running in MHC IIa and I fibers, respectively, regardless of training state (P<0.05). Robust induction of FN14 (previously shown to strongly correlate with hypertrophy) and greater overall transcriptional flexibility with exercise in the tapered state provides an initial molecular basis for fast-twitch muscle fiber performance gains previously observed after taper in competitive endurance athletes.

  17. Energy characteristics of cutting of thick steel sheets by a CO2 and fiber laser

    NASA Astrophysics Data System (ADS)

    Orishich, A. M.; Shulyatyev, V. B.; Malikov, A. G.; Golishev, A. A.

    2013-02-01

    Oxygen-assisted laser cutting of low-carbon steel with a fiber laser is studied experimentally. The objective of the work is to find the link between the cutting quality (which is low roughness and no dross) and energy characteristics of the cutting. Cutting parameters are expressed though two dimensionless complexes, namely the Peclet number and dimensionless laser power. It is founded that for the cutting with minimal roughness, the Peclet number is of 0.35…0.4, and the contribution of the absorbed laser energy in the unit of removed material volume is 12…14 J/mm3 for sheets of 3, 5, and 10 mm. The results are compared to the data obtained for the СО2 laser.

  18. Evaluation of palatability and muscle composition of novel value-added beef cuts.

    PubMed

    Yeh, Y; Omaye, S T; Ribeiro, F A; Calkins, C R; de Mello, A S

    2017-09-14

    The aim of this study was to evaluate the muscle profile of novel added-value beef cuts including the caudal tip of the M. infraspinatus (Bonanza Cut; TIP) and M. subscapularis (SUB) and two traditional sirloin steak cuts, M. gluteus medius (top sirloin; GLM) and M. rectus femoris (sirloin tip; REC). Samples were subjected to Warner-Braztler Shear Force (WBSF), sensory, cooking loss, and proximate analysis. The muscle TIP had superior values of subjective tenderness, juiciness, and slight off-flavor intensity when compared to all other muscles. The TIP and SUB were similar in WBSF. Cooking loss and moisture values of raw samples were lowest for TIP. Results suggest that TIP can provide enhanced eating experience for consumers and improved marketability for the meat industry. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Effects of aging on Type II muscle fibers: a systematic review of the literature.

    PubMed

    Brunner, Florian; Schmid, Annina; Sheikhzadeh, Ali; Nordin, Margareta; Yoon, Jangwhon; Frankel, Victor

    2007-07-01

    The authors conducted a systematic review of the literature for scientific articles in selected databases to determine the effects of aging on Type II muscle fibers in human skeletal muscles. They found that aging of Type II muscle fibers is primarily associated with a loss of fibers and a decrease in fiber size. Morphological changes with increasing age particularly included Type II fiber grouping. There is conflicting evidence regarding the change of proportion of Type II fibers. Type II muscle fibers seem to play an important role in the aging process of human skeletal muscles. According to this literature review, loss of fibers, decrease in size, and fiber-type grouping represent major quantitative changes. Because the process of aging involves various complex phenomena such as fiber-type coexpression, however, it seems difficult to assign those changes solely to a specific fiber type.

  20. Green nanotechnology: a short cut to beneficiation of natural fibers.

    PubMed

    Fahmy, Tamer Y A; Mobarak, Fardous

    2011-01-01

    For the first time worldwide, it is shown that our novel nanocomposite produced from natural fibers vaccinated with glucose--by fully green nanotechnology--possesses surprising reactivity towards urea. Magic super absorbent carbamated nanocomposite cotton fabrics having remarkable distinguished properties were obtained in few minutes. It is well established that carbamates possess antibacterial effects. The produced magic nanocomposite fabrics, we discovered for the first time worldwide, find their use as woven or nonwoven hygienic pads, bandages or paper nanocomposites.

  1. Energetic aspects of skeletal muscle contraction: implications of fiber types.

    PubMed

    Rall, J A

    1985-01-01

    In this chapter fundamental energetic properties of skeletal muscles as elucidated from isolated muscle preparations are described. Implications of these intrinsic properties for the energetic characterization of different fiber types and for the understanding of locomotion have been considered. Emphasis was placed on the myriad of physical and chemical techniques that can be employed to understand muscle energetics and on the interrelationship of results from different techniques. The anaerobic initial processes which liberate energy during contraction and relaxation are discussed in detail. The high-energy phosphate (approximately P) utilized during contraction and relaxation can be distributed between actomyosin ATPase or cross-bridge cycling (70%) and the Ca2+ ATPase of the sacroplasmic reticulum (30%). Muscle shortening increases the rate of approximately P hydrolysis, and stretching a muscle during contraction suppresses the rate of approximately P hydrolysis. The economy of an isometric contraction is defined as the ratio of isometric mechanical response to energetic cost and is shown to be a fundamental intrinsic parameter describing muscle energetics. Economy of contraction varies across the animal kingdom by over three orders of magnitude and is different in different mammalian fiber types. In mammalian skeletal muscles differences in economy of contraction can be attributed mainly to differences in the specific actomyosin and Ca2+ ATPase of muscles. Furthermore, there is an inverse relationship between economy of contraction and maximum velocity of muscle shortening (Vmax) and maximum power output. This is a fundamental relationship. Muscles cannot be economical at developing and maintaining force and also exhibit rapid shortening. Interestingly, there appears to be a subtle system of unknown nature that modulates the Vmax and economy of contraction. Efficiency of a work-producing contraction is defined and contrasted to the economy of contraction

  2. Contractile properties of thin (actin) filament-reconstituted muscle fibers.

    PubMed

    Ishiwata, S; Funatsu, T; Fujita, H

    1998-01-01

    Selective removal and reconstitution of the components of muscle fibers (fibrils) is a useful means of examining the molecular mechanism underlying the formation of the contractile apparatus. In addition, this approach is powerful for examining the structure-function relationship of a specific component of the contractile system. In previous studies, we have achieved the partial structural and functional reconstitution of thin filaments in the skeletal contractile apparatus and full reconstitution in the cardiac contractile apparatus. First, all thin filaments other than short fragments at the Z line were removed by treatment with plasma gelsolin, an actin filament-severing protein. Under these conditions, no active tension could be generated. By incorporating exogenous actin into these thin filament-free fibers, actin filaments were reconstituted by polymerization on the short actin fragments remaining at the Z line, and active tension, which was insensitive to Ca2+, was restored. The active tension after the reconstitution of thin filaments reached as high as 30% of the original level in skeletal muscle, while it reached 140% in cardiac muscle. The augmentation of tension in cardiac muscle is mainly attributable to the elongation of reconstituted filaments, longer than the average length of thin filaments in an intact muscle. These results indicate that a muscle contractile apparatus with a high order structure and function can be constructed by the self-assembly of constituent proteins. Recently, we applied this reconstitution system to the study of the mechanism of spontaneous oscillatory contraction (SPOC) in thin (actin) filament-reconstituted cardiac muscle fibers. As a result, we found that SPOC occurs even in regulatory protein-free actin filament-reconstituted fibers (Fujita & Ishiwata, manuscript submitted), although the SPOC conditions were slightly different from the standard SPOC conditions. This result strongly suggests that spontaneous oscillation

  3. Prediction of cutting forces in machining of unidirectional glass fiber reinforced plastics composite

    NASA Astrophysics Data System (ADS)

    Gill, Surinder Kumar; Gupta, Meenu; Satsangi, P. S.

    2013-06-01

    Machining of plastic materials has become increasingly important in any engineering industry subsequently the prediction of cutting forces. Forces quality has greater influence on components, which are coming in contact with each other. So it becomes necessary to measure and study machined forces and its behavior. In this research work, experimental investigations are conducted to determine the effects of cutting conditions and tool geometry on the cutting forces in the turning of the unidirectional glass fiber reinforced plastics (UD-GFRP) composites. In this experimental study, carbide tool (K10) having different tool nose radius and tool rake angle is used. Experiments are conducted based on the established Taguchi's technique L18 orthogonal array on a lathe machine. It is found that the depth of cut is the cutting parameter, which has greater influence on cutting forces. The effect of the tool nose radius and tool rake angles on the cutting forces are also considerably significant. Based on statistical analysis, multiple regression model for cutting forces is derived with satisfactory coefficient ( R 2). This model proved to be highly preferment for predicting cutting forces.

  4. Effects of chronic heart disease on skeletal muscle fiber size.

    PubMed

    Mattiello-Sverzut, A C; Chimelli, L; Teixeira, S; Pierre, M; Oliveira, L

    2005-02-01

    Size changes in muscle fibers of subjects with chronic heart disease (CHD) have been reported, although a consensus has not been achieved. The aims of the present study were to investigate a possible association between CHD and fiber size changes in the brachial biceps compared to subjects without heart disease. Forty-six muscle samples were obtained in autopsies of individuals (13 to 84 years) without neuromuscular disorders, 19 (10 males and 9 females) with, and 27 (14 males and 13 females) without CHD. In all cases muscle sections were stained with hematoxylin and eosin and processed for the visualization of myofibrillar ATPase activity. The lesser diameter of type 1 and type 2 fibers was obtained tracing their outlines (at least 150 fibers of each type per sample) onto an image analyzer connected to a computer. The results were analyzed statistically comparing males and females with and without CHD. Type 1 fiber mean lesser diameters were 51.51 and 54.52 microm in males (normal range 34-71 microm) and 45.65 and 55.42 microm in females (normal range 34-65 microm) without and with CHD, respectively; type 2 fibers measured 54.31, 58.23, 41.15, and 49.57 microm, respectively (normal range 36-79 microm for males and 32-59 microm for females). No significant difference in fiber size was detected in 24 males with and without CHD, while in 22 females there was a significant increase in size in those with cardiomyopathy. We concluded that CHD does not determine significant changes in fiber size. However, in females, there is some hypertrophy which, despite within normal range, may reflect morphologic heterogeneity of the sample, or the daily life activities in the upper limbs as a compensatory mechanism to fatigability that affect predominantly the lower limbs in subjects with CHD.

  5. Two rigor states in skinned crayfish single muscle fibers

    PubMed Central

    1976-01-01

    We studied the tension and stiffness of crayfish skinned single muscle fibers during and after the induction of rigor by removal of MgATP (substrate). We found that the rigor state is not unique but depends on the condition of the muscle before rigor. Fibers induced into rigor with a minimum of activation (low rigor) develop a small tension and moderate stiffness, while those entering rigor during maximum activation (high rigor) maintain near peak tension (80%) and develop a high stiffness. These rigor states are insensitive to Ca addition or deletion but they are partially interconvertible by length change. Stiffness changes when the rigor muscle length is varied, a condition in which the number of attached cross-rigor muscle length is varied, a condition in which the number of attached cross-bridges cannot change, and high-rigor muscle becomes less stiff than low-rigor muscle when the former is brought to the same tension by length release. The sensitivity of low, high, or length-released high-rigor muscles to trace substrate concentration (less than muM) differs, and rigor at lower strain is more suscepitible to substrate. PMID:821913

  6. Electrically and Hybrid-Induced Muscle Activations: Effects of Muscle Size and Fiber Type

    PubMed Central

    Stratton, Kelly; Faghri, Pouran D.

    2016-01-01

    The effect of three electrical stimulation (ES) frequencies (10, 35, and 50 Hz) on two muscle groups with different proportions of fast and slow twitch fibers (abductor pollicis brevis (APB) and vastus lateralis (VL)) was explored. We evaluated the acute muscles’ responses individually and during hybrid activations (ES superimposed by voluntary activations). Surface electromyography (sEMG) and force measurements were evaluated as outcomes. Ten healthy adults (mean age: 24.4 ± 2.5 years) participated after signing an informed consent form approved by the university Institutional Review Board. Protocols were developed to: 1) compare EMG activities during each frequency for each muscle when generating 25% Maximum Voluntary Contraction (MVC) force, and 2) compare EMG activities during each frequency when additional voluntary activation was superimposed over ES-induced 25% MVC to reach 50% and 75% MVC. Empirical mode decomposition (EMD) was utilized to separate ES artifacts from voluntary muscle activation. For both muscles, higher stimulation frequency (35 and 50Hz) induced higher electrical output detected at 25% of MVC, suggesting more recruitment with higher frequencies. Hybrid activation generated proportionally less electrical activity than ES alone. ES and voluntary activations appear to generate two different modes of muscle recruitment. ES may provoke muscle strength by activating more fatiguing fast acting fibers, but voluntary activation elicits more muscle coordination. Therefore, during the hybrid activation, less electrical activity may be detected due to recruitment of more fatigue-resistant deeper muscle fibers, not reachable by surface EMG. PMID:27990244

  7. Polarization-sensitive optical projection tomography for muscle fiber imaging

    PubMed Central

    Fang, Mengjie; Dong, Di; Zeng, Chaoting; Liang, Xiao; Yang, Xin; Arranz, Alicia; Ripoll, Jorge; Hui, Hui; Tian, Jie

    2016-01-01

    Optical projection tomography (OPT) is a tool used for three-dimensional imaging of millimeter-scale biological samples, with the advantage of exhibiting isotropic resolution typically in the micron range. OPT can be divided into two types: transmission OPT (tOPT) and emission OPT (eOPT). Compared with eOPT, tOPT discriminates different tissues based on their absorption coefficient, either intrinsic or after specific staining. However, it fails to distinguish muscle fibers whose absorption coefficients are similar to surrounding tissues. To circumvent this problem, in this article we demonstrate a polarization sensitive OPT system which improves the detection and 3D imaging of muscle fibers by using polarized light. We also developed image acquisition and processing protocols that, together with the system, enable the clear visualization of muscles. Experimental results show that the muscle fibers of diaphragm and stomach, difficult to be distinguished in regular tOPT, were clearly displayed in our system, proving its potential use. Moreover, polarization sensitive OPT was fused with tOPT to investigate the stomach tissue comprehensively. Future applications of polarization sensitive OPT could be imaging other fiber-like structures such as myocardium or other tissues presenting high optical anisotropy. PMID:26752330

  8. The passive properties of muscle fibers are velocity dependent.

    PubMed

    Rehorn, Michael R; Schroer, Alison K; Blemker, Silvia S

    2014-02-07

    The passive properties of skeletal muscle play an important role in muscle function. While the passive quasi-static elastic properties of muscle fibers have been well characterized, the dynamic visco-elastic passive behavior of fibers has garnered less attention. In particular, it is unclear how the visco-elastic properties are influenced by lengthening velocity, in particular for the range of physiologically relevant velocities. The goals of this work were to: (i) measure the effects of lengthening velocity on the peak stresses within single muscle fibers to determine how passive behavior changes over a range of physiologically relevant lengthening rates (0.1-10Lo/s), and (ii) develop a mathematical model of fiber viscoelasticity based on these measurements. We found that passive properties depend on strain rate, in particular at the low loading rates (0.1-3Lo/s), and that the measured behavior can be predicted across a range of loading rates and time histories with a quasi-linear viscoelastic model. In the future, these results can be used to determine the impact of viscoelastic behavior on intramuscular stresses and forces during a variety of dynamic movements. © 2013 Published by Elsevier Ltd.

  9. THE PASSIVE PROPERTIES OF MUSCLE FIBERS ARE VELOCITY DEPENDENT

    PubMed Central

    Rehorn, Michael R.; Schroer, Alison K.; Blemker, Silvia S.

    2014-01-01

    The passive properties of skeletal muscle play an important role in muscle function. While the passive quasi-static elastic properties of muscle fibers have been well characterized, the dynamic visco-elastic passive behavior of fibers has garnered less attention. In particular, it is unclear how the visco-elastic properties are influenced by lengthening velocity, in particular for the range of physiologically relevant velocities. The goals of this work were to: (i) measure the effects of lengthening velocity on the peak stresses within single muscle fibers to determine how passive behavior changes over a range of physiologically relevant lengthening rates (0.1–10 Lo/s), and (ii) develop a mathematical model of fiber viscoelasticity based on these measurements. We found that passive properties depend on strain rate, in particular at the low loading rates (0.1–3 Lo/s), and that the measured behavior can be predicted across a range of loading rates and time histories with a quasi-linear viscoelastic model. In the future, these results can be used to determine the impact of viscoelastic behavior on intramuscular stresses and forces during a variety of dynamic movements. PMID:24360198

  10. Biochemical adaptations of antigravity muscle fibers to disuse atrophy

    NASA Technical Reports Server (NTRS)

    Booth, F. W.

    1978-01-01

    Studies are presented in four parts of this report. The four parts include; (1) studies to gain information on the molecular basis of atrophy by antigravity muscle; (2) studies on the work capacity of antigravity muscles during atrophy and during recovery from atrophy; (3) studies on recovery of degenerated antigravity fibers after removal of hind-limb casts; and (4) studies on the atrophy and recovery of bone. The philosophy of these studies was to identify the time sequence of events in the soleus muscle of the rat following immobilization of the hind limbs, so that the length of the soleus muscle within the fixed limb is less than its resting length. In two separate studies, no decline in the weight of the soleus muscle could be detected during the first 72 hours of limb immobilization.

  11. Fiber optic biofluorometer for physiological research on muscle slices

    NASA Astrophysics Data System (ADS)

    Belz, Mathias; Dendorfer, Andreas; Werner, Jan; Lambertz, Daniel; Klein, Karl-Friedrich

    2016-03-01

    A focus of research in cell physiology is the detection of Ca2+, NADH, FAD, ATPase activity or membrane potential, only to name a few, in muscle tissues. In this work, we report on a biofluorometer using ultraviolet light emitting diodes (UV-LEDs), optical fibers and two photomultipliers (PMTs) using synchronized fluorescence detection with integrated background correction to detect free calcium, Ca2+, in cardiac muscle tissue placed in a horizontal tissue bath and a microscope setup. Fiber optic probes with imaging optics have been designed to transport excitation light from the biofluorometer's light output to a horizontal tissue bath and to collect emission light from a tissue sample of interest to two PMTs allowing either single excitation / single emission or ratiometric, dual excitation / single emission or single excitation / dual emission fluorescence detection of indicator dyes or natural fluorophores. The efficient transport of light from the excitation LEDs to the tissue sample, bleaching effects of the excitation light in both, polymer and fused silica-based fibers will be discussed. Furthermore, a new approach to maximize light collection of the emission light using high NA fibers and high NA coupling optics will be shown. Finally, first results on Ca2+ measurements in cardiac muscle slices in a traditional microscope setup and a horizontal tissue bath using fiber optic probes will be introduced and discussed.

  12. Prostaglandin E2/cyclooxygenase pathway in human skeletal muscle: influence of muscle fiber type and age.

    PubMed

    Liu, Sophia Z; Jemiolo, Bozena; Lavin, Kaleen M; Lester, Bridget E; Trappe, Scott W; Trappe, Todd A

    2016-03-01

    Prostaglandin E2 (PGE2) produced by the cyclooxygenase (COX) pathway regulates skeletal muscle protein turnover and exercise training adaptations. The purpose of this study was twofold: 1) define the PGE2/COX pathway enzymes and receptors in human skeletal muscle, with a focus on type I and II muscle fibers; and 2) examine the influence of aging on this pathway. Muscle biopsies were obtained from the soleus (primarily type I fibers) and vastus lateralis (proportionally more type II fibers than soleus) of young men and women (n = 8; 26 ± 2 yr), and from the vastus lateralis of young (n = 8; 25 ± 1 yr) and old (n = 12; 79 ± 2 yr) men and women. PGE2/COX pathway proteins [COX enzymes (COX-1 and COX-2), PGE2 synthases (cPGES, mPGES-1, and mPGES-2), and PGE2 receptors (EP1, EP2, EP3, and EP4)] were quantified via Western blot. COX-1, cPGES, mPGES-2, and all four PGE2 receptors were detected in all skeletal muscle samples examined. COX-1 (P < 0.1) and mPGES-2 were ∼20% higher, while EP3 was 99% higher and EP4 57% lower in soleus compared with vastus lateralis (P < 0.05). Aging did not change the level of skeletal muscle COX-1, while cPGES increased 45% and EP1 (P < 0.1), EP3, and EP4 decreased ∼33% (P < 0.05). In summary, PGE2 production capacity and receptor levels are different in human skeletal muscles with markedly different type I and II muscle fiber composition. In aging skeletal muscle, PGE2 production capacity is elevated and receptor levels are downregulated. These findings have implications for understanding the regulation of skeletal muscle adaptations to exercise and aging by the PGE2/COX pathway and related inhibitors. Copyright © 2016 the American Physiological Society.

  13. Repeated blood flow restriction induces muscle fiber hypertrophy.

    PubMed

    Sudo, Mizuki; Ando, Soichi; Kano, Yutaka

    2017-02-01

    We recently developed an animal model to investigate the effects of eccentric contraction (ECC) and blood flow restriction (BFR) on muscle tissue at the cellular level. This study clarified the effects of repeated BFR, ECC, and BFR combined with ECC (BFR+ECC) on muscle fiber hypertrophy. Male Wistar rats were assigned to 3 groups: BFR, ECC, and BFR+ECC. The contralateral leg in the BFR group served as a control (CONT). Muscle fiber cross-sectional area (CSA) of the tibialis anterior was determined after the respective treatments for 6 weeks. CSA was greater in the BFR+ECC group than in the CONT (P < 0.01) and ECC (P < 0.05) groups. CSA was greater in the BFR group than that in the CONT group (P < 0.05). These results suggest that repeated BFR alone as well as BFR+ECC induces muscle fiber hypertrophy at the cellular level. Muscle Nerve 55: 274-276, 2017. © 2016 Wiley Periodicals, Inc.

  14. Ultrafiltration Membrane Module Virus Reduction at Different Fluxes, and with a Cut Fiber

    EPA Science Inventory

    NSF International evaluated The Dow Chemical Company SFD-2880 UF membrane module for MS2 reduction at four different fluxes, and also with and without a cut fiber, to compare MS2 log reduction under the different scenarios. All tests were conducted in accordance with the U.S. En...

  15. Ultrafiltration Membrane Module Virus Reduction at Different Fluxes, and with a Cut Fiber

    EPA Science Inventory

    NSF International evaluated The Dow Chemical Company SFD-2880 UF membrane module for MS2 reduction at four different fluxes, and also with and without a cut fiber, to compare MS2 log reduction under the different scenarios. All tests were conducted in accordance with the U.S. En...

  16. Studies in fiber guided excimer laser surgery for cutting and drilling bone and meniscus.

    PubMed

    Dressel, M; Jahn, R; Neu, W; Jungbluth, K H

    1991-01-01

    Our experiments on transmitting high-power excimer laser pulses through optical fibers and our investigations on excimer laser ablation of hard tissue show the feasibility of using the excimer laser as an additional instrument in general and accident surgery involving minimal invasive surgery. By combining XeCl-excimer lasers and tapered fused silica fibers we obtained output fluences up to 32 J/cm2 and ablation rates of 3 microns/pulse of hard tissue. This enables us to cut bone and cartilage in a period of time which is suitable for clinical operations. Various experiments were carried out on cadavers in order to optimize the parameters of the excimer laser and fibers: e.g., wavelength, pulse duration, energy, repetition rate, fiber core diameter. The surfaces of the cut tissue are comparable to cuts with conventional instruments. No carbonisation was observed. The temperature increase is below 40 degrees C in the tissue surrounding the laser spot. The healing rate of an excimer laser cut is not slower than mechanical treatments; the quality is comparable.

  17. Effect of swim exercise training on human muscle fiber function

    NASA Technical Reports Server (NTRS)

    Fitts, R. H.; Costill, D. L.; Gardetto, P. R.

    1989-01-01

    The effect of swim exercise training on the human muscle fiber function was investigated in swimmers trained in a typical collegiate swim-training program followed by an intensified 10-day training period. The measured parameters included the peak tension (P0), negative log molar Ca(2+) concentration (pCa)-force, and maximal shortening speed (Vmax) of the slow-twitch type I and fast-twitch type II fibers obtained by biopsy from the deltoid muscle. The P0 values were found to be not altered after either the training or the 10-day intensive program. The type I fibers from the trained swimmers showed pCa-force curves shifted to the right, such that higher free Ca(2+) levels were required to elicit a given percent of P0. The training program significantly increased the Vmax in the type I fibers and decreased that of the type II fibers, and the 10-day intensive training produced a further significant decrease of the type II fibers.

  18. Effect of swim exercise training on human muscle fiber function

    NASA Technical Reports Server (NTRS)

    Fitts, R. H.; Costill, D. L.; Gardetto, P. R.

    1989-01-01

    The effect of swim exercise training on the human muscle fiber function was investigated in swimmers trained in a typical collegiate swim-training program followed by an intensified 10-day training period. The measured parameters included the peak tension (P0), negative log molar Ca(2+) concentration (pCa)-force, and maximal shortening speed (Vmax) of the slow-twitch type I and fast-twitch type II fibers obtained by biopsy from the deltoid muscle. The P0 values were found to be not altered after either the training or the 10-day intensive program. The type I fibers from the trained swimmers showed pCa-force curves shifted to the right, such that higher free Ca(2+) levels were required to elicit a given percent of P0. The training program significantly increased the Vmax in the type I fibers and decreased that of the type II fibers, and the 10-day intensive training produced a further significant decrease of the type II fibers.

  19. A study examining the effects of water-miscible cutting fluids for end milling process of carbon fiber reinforced plastic

    NASA Astrophysics Data System (ADS)

    Anan, Ruito; Matsuoka, Hironori; Ono, Hajime; Ryu, Takahiro; Nakae, Takashi; Shuto, Schuichi; Watanabe, Suguru; Sato, Yuta

    2017-04-01

    This study examined the improvements to the tool life and finished surface roughness by using water-miscible cutting fluids in carbon fiber reinforced plastics end milling. In cutting tests, it was found that the use of emulsion type, soluble type, and solution type cutting fluids improved tool life compared with the case of dry cutting. Specifically, significant differences in tool life were observed at a high cutting speed of 171 m/min. In addition, the finished surface exhibited a low level of roughness when the solution type cutting fluid was used, regardless of the cutting speed.

  20. Morphology of the lumbar transversospinal muscles examined in a mouse bearing a muscle fiber-specific nuclear marker.

    PubMed

    Cornwall, Jon; Deries, Marianne; Duxson, Marilyn

    2010-12-01

    Although the morphology of human lumbar transversospinal (TSP) muscles has been studied, little is known about the structure of these muscles in the mouse (Mus musculus). Such information is relevant given mice are often used as a "normal" phenotype for studies modeling human development. This study describes the gross morphology, muscle fiber arrangement, and innervation pattern of the mouse lumbar TSP muscles. A unique feature of the study is the use of a transgenic mouse line bearing a muscle-specific nuclear marker that allows clear delineation of muscle fiber and connective tissue boundaries. The lumbar TSP muscles of five mice were examined bilaterally; at each spinal level muscles attached to the caudal edge of the spinous process and passed caudally as a single complex unit. Fibers progressively terminated over the four vertebral segments caudad, with multiple points of muscle fiber attachment on each vertebra. Motor endplates, defined with acetylcholinesterase histochemistry, were consistently located half way along each muscle fiber, regardless of length, with all muscle fibers arranged in-parallel rather than in-series. These results provide information relevant to interpretation of developmental and functional studies involving this muscle group in the mouse and show mouse lumbar TSP muscles are different in form to descriptions of equivalent muscles in humans and horses.

  1. Computational Model of Cellular Metabolic Dynamics in Skeletal Muscle Fibers during Moderate Intensity Exercise

    PubMed Central

    Li, Yanjun; Lai, Nicola; Kirwan, John P.; Saidel, Gerald M.

    2012-01-01

    Human skeletal muscles have different fiber types with distinct metabolic functions and physiological properties. The quantitative metabolic responses of muscle fibers to exercise provide essential information for understanding and modifying the regulatory mechanisms of skeletal muscle. Since in vivo data from skeletal muscle during exercise is limited, a computational, physiologically based model has been developed to quantify the dynamic metabolic responses of many key chemical species. This model distinguishes type I and II muscle fibers, which share the same blood supply. An underlying hypothesis is that the recruitment and metabolic activation of the two main types of muscle fibers differ depending on the pre-exercise state and exercise protocols. Here, activation measured by metabolic response (or enzymatic activation) in single fibers is considered linked but distinct from fiber recruitment characterized by the number (or mass) of each fiber type involved during a specific exercise. The model incorporates species transport processes between blood and muscle fibers and most of the important reactions/pathways in cytosol and mitochondria within each fiber type. Model simulations describe the dynamics of intracellular species concentrations and fluxes in muscle fibers during moderate intensity exercise according to various experimental protocols and conditions. This model is validated by comparing model simulations with experimental data in single muscle fibers and in whole muscle. Model simulations demonstrate that muscle-fiber recruitment and metabolic activation patterns in response to exercise produce significantly distinctive effects depending on the exercise conditions. PMID:22942911

  2. Fiber type composition of pubococcygeus and bulbospongiosus striated muscles is modified by multiparity in the rabbit.

    PubMed

    López-García, Kenia; Mariscal-Tovar, Silvia; Serrano-Meneses, Martín Alejandro; Castelán, Francisco; Martínez-Gómez, Margarita; Jiménez-Estrada, Ismael

    2017-08-01

    We analyzed the effect of multiparity on the fiber type composition of two skeletal muscles involved in the maintenance of the micturition process, the pelvic pubococcygeus (Pc) and perineal bulbospongiosus (Bs) muscles in nulliparous and multiparous rabbits (Oryctolagus cuniculus). We used the basic ATPase and NADH-TR techniques to identify and characterize slow, intermediate, and fast fiber types and glycolitic and oxidative fibers in muscles, respectively. Pc muscles of multiparous rabbits present relatively high percentages of slow and intermediate fibers but a low percentage of fast fibers (P < 0.05) as compared to Pc muscles from nulliparous rabbits, while percentages of glycolytic and oxidative fibers were similar (P > 0.05). Bs muscles of multiparous rabbits had a higher proportion of intermediate and glycolytic fibers (P < 0.05) than muscles of nulliparous. Both, Pc and Bs muscles of nulliparous and multiparous rabbits contain slow fibers with similar large cross sectional area, but fast fibers in multiparous muscles showed small cross sectional area than in nulliparous. Multiparity modified the fiber type composition of Pc and Bs muscles in female rabbits. We propose that the contractile force and the physiological role of both muscles during micturition are affected because of the observed changes in the relative composition of muscle fiber types. © 2016 Wiley Periodicals, Inc.

  3. Myriocin prevents muscle ceramide accumulation but not muscle fiber atrophy during short-term mechanical unloading.

    PubMed

    Salaun, Erwann; Lefeuvre-Orfila, Luz; Cavey, Thibault; Martin, Brice; Turlin, Bruno; Ropert, Martine; Loreal, Olivier; Derbré, Frédéric

    2016-01-15

    Bedridden patients in intensive care unit or after surgery intervention commonly develop skeletal muscle weakness. The latter is promoted by a variety of prolonged hospitalization-associated conditions. Muscle disuse is the most ubiquitous and contributes to rapid skeletal muscle atrophy and progressive functional strength reduction. Disuse causes a reduction in fatty acid oxidation, leading to its accumulation in skeletal muscle. We hypothesized that muscle fatty acid accumulation could stimulate ceramide synthesis and promote skeletal muscle weakness. Therefore, the present study was designed to determine the effects of sphingolipid metabolism on skeletal muscle atrophy induced by 7 days of disuse. For this purpose, male Wistar rats were treated with myriocin, an inhibitor of de novo synthesis of ceramides, and subjected to hindlimb unloading (HU) for 7 days. Soleus muscles were assayed for fiber diameter, ceramide levels, protein degradation, and apoptosis signaling. Serum and liver were removed to evaluate the potential hepatoxicity of myriocin treatment. We found that HU increases content of saturated C16:0 and C18:0 ceramides and decreases soleus muscle weight and fiber diameter. HU increased the level of polyubiquitinated proteins and induced apoptosis in skeletal muscle. Despite a prevention of C16:0 and C18:0 muscle accumulation, myriocin treatment did not prevent skeletal muscle atrophy and concomitant induction of apoptosis and proteolysis. Moreover, myriocin treatment increased serum transaminases and induced hepatocyte necrosis. These data highlight that inhibition of de novo synthesis of ceramides during immobilization is not an efficient strategy to prevent skeletal muscle atrophy and exerts adverse effects like hepatotoxicity. Copyright © 2016 the American Physiological Society.

  4. Potassium-induced contractures in crab (Callinectes danae) muscle fibers.

    PubMed

    Leal-Cardoso, J H; Suarez-Kurtz, G

    1984-01-01

    The contractures induced by 20-200 mM [K+]o in single crab muscle fibers were resolved into two components. The first component, consisting of single twitches or brief tetanic contractions, was associated with electrogenic membrane responses. The second occurred after spiking subsided with an amplitude that increased linearly with the [K+]o between 20 and 90 mM. The amplitude and time course of the contractures elicited by a given [K+]o differed markedly between different fibers. Contracture reproducibility of a single fiber was best when 90 mM [K+]o was used. The K-induced contractures were abolished after brief (3 min) exposure of the fibers to a calcium-free solution and were greatly depressed by 8 mM procaine. The data suggest that the contractures require both Ca2+-influx across the sarcolemma and release of Ca2+ stored in the sarcoplasmic reticulum.

  5. Muscle fiber type specific induction of slow myosin heavy chain 2 gene expression by electrical stimulation

    SciTech Connect

    Crew, Jennifer R.; Falzari, Kanakeshwari; DiMario, Joseph X.

    2010-04-01

    Vertebrate skeletal muscle fiber types are defined by a broad array of differentially expressed contractile and metabolic protein genes. The mechanisms that establish and maintain these different fiber types vary throughout development and with changing functional demand. Chicken skeletal muscle fibers can be generally categorized as fast and fast/slow based on expression of the slow myosin heavy chain 2 (MyHC2) gene in fast/slow muscle fibers. To investigate the cellular and molecular mechanisms that control fiber type formation in secondary or fetal muscle fibers, myoblasts from the fast pectoralis major (PM) and fast/slow medial adductor (MA) muscles were isolated, allowed to differentiate in vitro, and electrically stimulated. MA muscle fibers were induced to express the slow MyHC2 gene by electrical stimulation, whereas PM muscle fibers did not express the slow MyHC2 gene under identical stimulation conditions. However, PM muscle fibers did express the slow MyHC2 gene when electrical stimulation was combined with inhibition of inositol triphosphate receptor (IP3R) activity. Electrical stimulation was sufficient to increase nuclear localization of expressed nuclear-factor-of-activated-T-cells (NFAT), NFAT-mediated transcription, and slow MyHC2 promoter activity in MA muscle fibers. In contrast, both electrical stimulation and inhibitors of IP3R activity were required for these effects in PM muscle fibers. Electrical stimulation also increased levels of peroxisome-proliferator-activated receptor-{gamma} co-activator-1 (PGC-1{alpha}) protein in PM and MA muscle fibers. These results indicate that MA muscle fibers can be induced by electrical stimulation to express the slow MyHC2 gene and that fast PM muscle fibers are refractory to stimulation-induced slow MyHC2 gene expression due to fast PM muscle fiber specific cellular mechanisms involving IP3R activity.

  6. Respiratory muscle fiber remodeling in chronic hyperinflation: dysfunction or adaptation?

    PubMed

    Clanton, Thomas L; Levine, Sanford

    2009-07-01

    The diaphragm and other respiratory muscles undergo extensive remodeling in both animal models of emphysema and in human chronic obstructive pulmonary disease, but the nature of the remodeling is different in many respects. One common feature is a shift toward improved endurance characteristics and increased oxidative capacity. Furthermore, both animals and humans respond to chronic hyperinflation by diaphragm shortening. Although in rodent models this clearly arises by deletion of sarcomeres in series, the mechanism has not been proven conclusively in human chronic obstructive pulmonary disease. Unique characteristics of the adaptation in human diaphragms include shifts to more predominant slow, type I fibers, expressing slower myosin heavy chain isoforms, and type I and type II fiber atrophy. Although some laboratories report reductions in specific force, this may be accounted for by decreases in myosin heavy chain content as the muscles become more oxidative and more efficient. More recent findings have reported reductions in Ca(2+) sensitivity and reduced myofibrillar elastic recoil. In contrast, in rodent models of disease, there is no consistent evidence for loss of specific force, no consistent shift in fiber populations, and atrophy is predominantly seen only in fast, type IIX fibers. This review challenges the hypothesis that the adaptations in human diaphragm represent a form of dysfunction, secondary to systemic disease, and suggest that most findings can as well be attributed to adaptive processes of a complex muscle responding to unique alterations in its working environment.

  7. Laser Cutting of Carbon Fiber Reinforced Polymers using Highly Brilliant Laser Beam Sources

    NASA Astrophysics Data System (ADS)

    Klotzbach, Annett; Hauser, Markus; Beyer, Eckhard

    Carbon fiber reinforced polymers (CFRP) are applied more and more in the aircraft industry as well as in the automobile industry. The principal reason is the highly mechanical load capacity along with the low density. Moreover, the corrosion resistance plus the damping behavior of the material can be utilized fully in highly stressed structures. However, the concept of manufacture CFRP-parts close to the final contour does not substitute the need of cutting them. The different properties of fiberand matrix-material constitute an ambitious challenge while cutting CFRP using a laser beam. This paper deals with elementary analysis of the laser remote cutting process and the gas assisted laser cutting of CFRP.

  8. Isolation of satellite cells from single muscle fibers from young, aged, or dystrophic muscles.

    PubMed

    Di Foggia, Valentina; Robson, Lesley

    2012-01-01

    Skeletal muscle contains an identified resident stem cell population called the satellite cells. This cell is responsible for the majority of the postnatal growth and regenerative potential of skeletal muscle. Other cells do contribute to skeletal muscle regeneration and in cultures of minced whole muscle these cells are cultured along with the satellite cells and it is impossible to dissect out their contribution compared to the satellite cells. Therefore, a method to culture pure satellite cells has been developed to study the signaling pathways that control their proliferation and differentiation. In our studies into the role of the resident myogenic stem cells in regeneration, myopathic conditions, and aging, we have optimized the established techniques that already exist to isolate pure satellite cell cultures from single muscle fibers. We have successfully isolated satellite cells from young adults through to 24-month-old muscles and obtained populations of cells that we are studying for the signaling events that regulate their proliferative potential.

  9. Thin Filament-Reconstituted Skinned Muscle Fibers for the Study of Muscle Physiology

    PubMed Central

    Higuchi, Sayaka; Tsukasaki, Yoshikazu; Fukuda, Norio; Kurihara, Satoshi; Fujita, Hideaki

    2011-01-01

    We review the use of thin filament-reconstituted muscle fibers in the study of muscle physiology. Thin filament extraction and reconstitution protocol is a powerful technique to study the role of each component of the thin filament. It is also useful for studying the properties of genetically modified molecules such as actin and tropomyosin. We also review the combination of this protocol with sinusoidal analysis, which will provide a solid technique for determining the effect of regulatory proteins on actomyosin interaction and concomitant cross-bridge kinetics. We suggest that thin filament-reconstituted muscle fibers are an ideal system for studying muscle physiology especially when gene modifications of actin or tropomyosin are involved. PMID:22131807

  10. Niacin supplementation induces type II to type I muscle fiber transition in skeletal muscle of sheep

    PubMed Central

    2013-01-01

    Background It was recently shown that niacin supplementation counteracts the obesity-induced muscle fiber transition from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PPARδ (encoded by PPARD), PGC-1α (encoded by PPARGC1A) and PGC-1β (encoded by PPARGC1B), leading to type II to type I fiber transition and upregulation of genes involved in oxidative metabolism. The aim of the present study was to investigate whether niacin administration also influences fiber distribution and the metabolic phenotype of different muscles [M. longissimus dorsi (LD), M. semimembranosus (SM), M. semitendinosus (ST)] in sheep as a model for ruminants. For this purpose, 16 male, 11 wk old Rhoen sheep were randomly allocated to two groups of 8 sheep each administered either no (control group) or 1 g niacin per day (niacin group) for 4 wk. Results After 4 wk, the percentage number of type I fibers in LD, SM and ST muscles was greater in the niacin group, whereas the percentage number of type II fibers was less in niacin group than in the control group (P < 0.05). The mRNA levels of PPARGC1A, PPARGC1B, and PPARD and the relative mRNA levels of genes involved in mitochondrial fatty acid uptake (CPT1B, SLC25A20), tricarboxylic acid cycle (SDHA), mitochondrial respiratory chain (COX5A, COX6A1), and angiogenesis (VEGFA) in LD, SM and ST muscles were greater (P < 0.05) or tended to be greater (P < 0.15) in the niacin group than in the control group. Conclusions The study shows that niacin supplementation induces muscle fiber transition from type II to type I, and thereby an oxidative metabolic phenotype of skeletal muscle in sheep as a model for ruminants. The enhanced capacity of skeletal muscle to utilize fatty acids in ruminants might be particularly useful during metabolic states in which fatty acids are

  11. Muscle fatigue, nNOS and muscle fiber atrophy in limb girdle muscular dystrophy.

    PubMed

    Angelini, Corrado; Tasca, Elisabetta; Nascimbeni, Anna Chiara; Fanin, Marina

    2014-12-01

    Muscle fatigability and atrophy are frequent clinical signs in limb girdle muscular dystrophy (LGMD), but their pathogenetic mechanisms are still poorly understood. We review a series of different factors that may be connected in causing fatigue and atrophy, particularly considering the role of neuronal nitric oxide synthase (nNOS) and additional factors such as gender in different forms of LGMD (both recessive and dominant) underlying different pathogenetic mechanisms. In sarcoglycanopathies, the sarcolemmal nNOS reactivity varied from absent to reduced, depending on the residual level of sarcoglycan complex: in cases with complete sarcoglycan complex deficiency (mostly in beta-sarcoglycanopathy), the sarcolemmal nNOS reaction was absent and it was always associated with early severe clinical phenotype and cardiomyopathy. Calpainopathy, dysferlinopathy, and caveolinopathy present gradual onset of fatigability and had normal sarcolemmal nNOS reactivity. Notably, as compared with caveolinopathy and sarcoglycanopathies, calpainopathy and dysferlinopathy showed a higher degree of muscle fiber atrophy. Males with calpainopathy and dysferlinopathy showed significantly higher fiber atrophy than control males, whereas female patients have similar values than female controls, suggesting a gender difference in muscle fiber atrophy with a relative protection in females. In female patients, the smaller initial muscle fiber size associated to endocrine factors and less physical effort might attenuate gender-specific muscle loss and atrophy.

  12. Latent mitochondrial DNA deletion mutations drive muscle fiber loss at old age.

    PubMed

    Herbst, Allen; Wanagat, Jonathan; Cheema, Nashwa; Widjaja, Kevin; McKenzie, Debbie; Aiken, Judd M

    2016-08-25

    With age, somatically derived mitochondrial DNA (mtDNA) deletion mutations arise in many tissues and species. In skeletal muscle, deletion mutations clonally accumulate along the length of individual fibers. At high intrafiber abundances, these mutations disrupt individual cell respiration and are linked to the activation of apoptosis, intrafiber atrophy, breakage, and necrosis, contributing to fiber loss. This sequence of molecular and cellular events suggests a putative mechanism for the permanent loss of muscle fibers with age. To test whether mtDNA deletion mutation accumulation is a significant contributor to the fiber loss observed in aging muscle, we pharmacologically induced deletion mutation accumulation. We observed a 1200% increase in mtDNA deletion mutation-containing electron transport chain-deficient muscle fibers, an 18% decrease in muscle fiber number and 22% worsening of muscle mass loss. These data affirm the hypothesized role for mtDNA deletion mutation in the etiology of muscle fiber loss at old age.

  13. Myoplasmic calcium transients monitored with purpurate indicator dyes injected into intact frog skeletal muscle fibers

    PubMed Central

    1991-01-01

    Intact single twitch fibers from frog muscle were studied on an optical bench apparatus after microinjection with tetramethylmurexide (TMX) or purpurate-3,3' diacetic acid (PDAA), two compounds from the purpurate family of absorbance Ca2+ indicators previously used in cut muscle fibers (Maylie, J., M. Irving, N. L. Sizto, G. Boyarsky, and W. K. Chandler. 1987. J. Gen. Physiol. 89:145-176; Hirota, A., W. K. Chandler, P. L. Southwick, and A. S. Waggoner. 1989. J. Gen. Physiol. 94:597-631.) The apparent longitudinal diffusion constant of PDAA (mol wt 380) in myoplasm was 0.99 (+/- 0.04, SEM) x 10(-6) cm2 s-1 (16-17 degrees C), a value which suggests that 24-43% of the PDAA molecules were bound to myoplasmic constituents of large molecular weight. The corresponding values for TMX (mol wt 322) were 0.98 (+/- 0.05) x 10(-6) cm2 s-1 and 44-50%, respectively. Muscle membranes (surface and/or transverse-tubular) appear to be permeable to TMX and, to a lesser extent, to PDAA, since the total amount of indicator contained within a fiber decreased with time after injection. The average time constants for disappearance of indicator were 46 (+/- 7, SEM) min for TMX and 338 (+/- 82) min for PDAA. The fraction of indicator in the Ca2(+)-bound state in resting fibers was significantly different from zero for TMX (0.070 +/- 0.008) but not for PDAA (0.026 +/- 0.009). In in vitro calibrations PDAA but not TMX appeared to react with Ca2+ with 1:1 stoichiometry. In agreement with Hirota et al. (Hirota, A., W. K. Chandler, P. L. Southwick, and A. S. Waggoner. 1989. J. Gen. Physiol. 94:597-631), we conclude that PDAA is probably a more reliable myoplasmic Ca2+ indicator than TMX. In fibers that contained PDAA and were stimulated by a single action potential, the calibrated peak value of the myoplasmic free [Ca2+] transient (delta[Ca2+]) averaged 9.4 (+/- 0.6) microM, a value about fivefold larger than that calibrated with antipyrylazo III under otherwise identical conditions (Baylor, S. M

  14. Fiber type characterization of striated muscles related to micturition in female rabbits.

    PubMed

    López-García, Kenia; Mariscal-Tovar, Silvia; Martínez-Gómez, Margarita; Jiménez-Estrada, Ismael; Castelán, Francisco

    2014-04-01

    Pelvic and perineal striated muscles are relevant for reproduction and micturition in female mammals. Damage to these muscles is associated with pelvic organ prolapse and stress urinary incontinence. The fiber type composition of skeletal muscle influences the susceptibility for damage and/or regeneration. The aim of the present study was to determine the fiber type composition of a perineal muscle, the bulbospongiosus, and a pelvic muscle, the pubococcygeus. Both muscles were harvested from adult female rabbits (8-10 months old). NADH-TR (nicotinamide adenine dinucleotide tetrazolium reductase) histochemistry was undertaken to identify oxidative and glycolytic muscle fibers. Alkaline (pH 9.4) ATP-ase (actomyosin adenosine triphosphatase) histochemistry was used to classify type I, type IIb or type IIa/IId muscle fibers. Results showed that the content of glycolytic fibers in the bulbospongiosus muscle was higher than that of oxidative fibers. Meanwhile, the opposite was true for the pubococcygeus. In the bulbospongiosus muscle, the content of type IIb muscle fibers was higher than that of type I, but was similar to that of type IIa/IId. In contrast, the content of each fiber type was similar in the pubococcygeus muscle. The relative proportion of fibers in bulbospongiosus and pubococcygeus muscles is consistent with their function during voiding and storage phases of micturition.

  15. Spectrum of temperature pulsations of the melt in gas-assisted cutting with fiber laser

    NASA Astrophysics Data System (ADS)

    Dubrov, Alexander V.; Zavalov, Yury N.; Dubrov, Vladimir D.; Grezev, Anatoly N.; Grezev, Nikolay V.; Makarova, Elena S.; Dubrovin, Nickolay G.

    2012-09-01

    Measurements of the temperature behavior in the zone of action of the laser-radiation on the molten metal have been performed using multichannel pyrometer. Measurements were carried out for test cutting of a 3-mm mild-steel plate with several values of cutting speed and pressure of assist gas (oxygen), using an 1800-watt Ytterbium fiber laser. It is shown that fluctuations of temperature are related to local melt's surface deformations due to unequal radiation absorption; thus the noise spectrum of temperature fluctuations reflects turbulent surface deformation caused by gas jet and capillary waves. The maximum density of turbulent energy dissipation ε depends on cutting conditions: its value rises with increasing cutting velocity and oxygen pressure in a described range of parameters. The maximum of ε is localized near depth of (1.2…1.5) mm along the cutting front. We can distinguish the specific radiation pulsation spectrum of laser cutting from other processes of radiation affection to the sample, including unwanted degrading of the quality of technological operations. The spectrum of capillary waves on the melt's surface is formed under the effect of assisted gas jet and has a function of ω-3, ω is cycle frequency. The results of this investigation can be useful for the development of monitoring and quality-control systems for the laser-cutting process.

  16. Skeletal muscle: energy metabolism, fiber types, fatigue and adaptability.

    PubMed

    Westerblad, Håkan; Bruton, Joseph D; Katz, Abram

    2010-11-01

    Skeletal muscles cope with a large range of activities, from being able to support the body weight during long periods of upright standing to perform explosive movements in response to an unexpected threat. This requires systems for energy metabolism that can provide energy during long periods of moderately increased energy consumption as well as being able to rapidly increasing the rate of energy production more than 100-fold in response to explosive contractions. In this short review we discuss how muscles can deal with these divergent demands. We first outline the major energy metabolism pathways in skeletal muscle. Next we describe metabolic differences between different muscle fiber types. Contractile performance declines during intense activation, i.e. fatigue develops, and we discuss likely underlying mechanisms. Finally, we discuss the ability of muscle fibers to adapt to altered demands, and mechanisms behind these adaptations. The accumulated experimental evidence forces us to conclude that most aspects of energy metabolism involve multiple and overlapping signaling pathways, which indicates that the control of energy metabolism is too important to depend on one single molecule or mechanism. Copyright © 2010 Elsevier Inc. All rights reserved.

  17. Myoglobin plasma level related to muscle mass and fiber composition: a clinical marker of muscle wasting?

    PubMed

    Weber, Marc-André; Kinscherf, Ralf; Krakowski-Roosen, Holger; Aulmann, Michael; Renk, Hanna; Künkele, Annette; Edler, Lutz; Kauczor, Hans-Ulrich; Hildebrandt, Wulf

    2007-08-01

    Progressive muscle wasting is a central feature of cancer-related cachexia and has been recognized as a determinant of poor prognosis and quality of life. However, until now, no easily assessable clinical marker exists that allows to predict or to track muscle wasting. The present study evaluated the potential of myoglobin (MG) plasma levels to indicate wasting of large locomotor muscles and, moreover, to reflect the loss of MG-rich fiber types, which are most relevant for daily performance. In 17 cancer-cachectic patients (weight loss 22%) and 27 age- and gender-matched healthy controls, we determined plasma levels of MG and creatine kinase (CK), maximal quadriceps muscle cross-sectional area (CSA) by magnetic resonance imaging, muscle morphology and fiber composition in biopsies from the vastus lateralis muscle, body cell mass (BCM) by impedance technique as well as maximal oxygen uptake (VO(2)max). In cachectic patients, plasma MG, muscle CSA, BCM, and VO(2)max were 30-35% below control levels. MG showed a significant positive correlation to total muscle CSA (r = 0.65, p < 0.001) and to the CSA fraction formed by type 1 and 2a fibers (r = 0.80, p < 0.001). However, when adjusted for body height and age by multiple regression, MG yielded a largely improved prediction of total CSA (multiple r = 0.83, p < 0.001) and of fiber type 1 and 2a CSA (multiple r = 0.89, p < 0.001). The correlations between CK and these muscle parameters were weaker, and elevated CK values were observed in 20% of control subjects despite a prior abstinence from exercise for 5 days. In conclusion, plasma MG, when adjusted for anthropometric parameters unaffected by weight, may be considered as a novel marker of muscle mass (CSA) indicating best the mass of MG-rich type 1 and 2a fibers as well as VO(2)max as an important functional readout. CK plasma levels appear to be less reliable because prolonged increases are observed in even subclinical myopathies or after exercise. Notably, cancer

  18. Investigation and experimental measurement of scissor blade cutting forces using fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Callaghan, D. J.; Rajan, G.; McGrath, M. M.; Coyle, E.; Semenova, Y.; Farrell, G.

    2011-10-01

    This paper reports on unique and scalable sensorized medical scissor blades for application in minimally invasive robotic surgery. The blades exploit the strain sensing capabilities of a single fiber Bragg grating (FBG) sensor bonded to the blade surface. This smart sensing structure allows detection of friction and material fracture forces during cutting and subsequently enables accurate estimation of the blade kinetic friction coefficient and fracture toughness values of the material being cut. We present theory on the determination of strain variation along the blade length during combined direct and lateral loading of the blade element during operation. Demonstration of the sensorized instrument is realized on an application specific experimental test-bed employing a commercial interrogation system for signal demodulation. Friction and cutting forces measured using the FBG are validated against load cell force data from the test-bed. Characterization tests showed that the sensorized blade has an unfiltered force sensing resolution of 0.5 N over a 30 N load range. This work demonstrates that a single optical fiber placed onto cutting instrument blades can, in an unobtrusive manner, reliably measure friction forces and material fracture properties during surgical cutting.

  19. Modeling the dispersion effects of contractile fibers in smooth muscles

    NASA Astrophysics Data System (ADS)

    Murtada, Sae-Il; Kroon, Martin; Holzapfel, Gerhard A.

    2010-12-01

    Micro-structurally based models for smooth muscle contraction are crucial for a better understanding of pathological conditions such as atherosclerosis, incontinence and asthma. It is meaningful that models consider the underlying mechanical structure and the biochemical activation. Hence, a simple mechanochemical model is proposed that includes the dispersion of the orientation of smooth muscle myofilaments and that is capable to capture available experimental data on smooth muscle contraction. This allows a refined study of the effects of myofilament dispersion on the smooth muscle contraction. A classical biochemical model is used to describe the cross-bridge interactions with the thin filament in smooth muscles in which calcium-dependent myosin phosphorylation is the only regulatory mechanism. A novel mechanical model considers the dispersion of the contractile fiber orientations in smooth muscle cells by means of a strain-energy function in terms of one dispersion parameter. All model parameters have a biophysical meaning and may be estimated through comparisons with experimental data. The contraction of the middle layer of a carotid artery is studied numerically. Using a tube the relationships between the internal pressure and the stretches are investigated as functions of the dispersion parameter, which implies a strong influence of the orientation of smooth muscle myofilaments on the contraction response. It is straightforward to implement this model in a finite element code to better analyze more complex boundary-value problems.

  20. Change in fiber type in partially-denervated soleus muscle of the rat.

    PubMed

    Narusawa, M

    1985-10-01

    In 30% or less partially denervated muscle, the reinnervation of denervated muscle fiber may give rise to a change in motor unit size or number of muscle fibers innervated by a single motor neuron. This study was designed to evaluate changes in fiber type and contractibility of partially denervated rat soleus muscle. Partial denervation (by 30% or less) of the soleus nerve does not cause a decrease in the number of muscle fibers. A histochemical study was performed on frozen sections of the muscle. The total number of muscle fibers, atrophied fibers and type II fibers were counted. In the muscle 4 weeks after partial denervation, the number of type II fibers was fewer with a decrease of about 40% which was not significant. The twitch time to peak and half-relaxation time were not changed. The number of type II fibers was significantly decreased (p less than 0.01) after 8 weeks. There was a prolongation of contraction time. The decrease of type II fibers was extensive involving not only the denervated area but also the rest of the muscle area. The transformation of fiber type observed in partially denervated muscle may be attributed to a possible diminution of neurotrophic substances in intact motor neurons.

  1. Memristive Model of the Barnacle Giant Muscle Fibers

    NASA Astrophysics Data System (ADS)

    Sah, Maheshwar Pd.; Kim, Hyongsuk; Eroglu, Abdullah; Chua, Leon

    The generation of action potentials (oscillations) in biological systems is a complex, yet poorly understood nonlinear dynamical phenomenon involving ions. This paper reveals that the time-varying calcium ion and the time-varying potassium ion, which are essential for generating action potentials in Barnacle giant muscle fibers are in fact generic memristors in the perspective of electrical circuit theory. We will show that these two ions exhibit all the fingerprints of memristors from the equations of the Morris-Lecar model of the Barnacle giant muscle fibers. This paper also gives a textbook reference to understand the difference between memristor and nonlinear resistor via analysis of the potassium ion-channel memristor and calcium ion-channel nonlinear resistor. We will also present a comprehensive in-depth analysis of the generation of action potentials (oscillations) in memristive Morris-Lecar model using small-signal circuit model and the Hopf bifurcation theorem.

  2. Imaging of calcium transients in skeletal muscle fibers.

    PubMed Central

    Vergara, J; DiFranco, M; Compagnon, D; Suarez-Isla, B A

    1991-01-01

    Epifluorescence images of Ca2+ transients elicited by electrical stimulation of single skeletal muscle fibers were studied with fast imaging techniques that take advantage of the large fluorescence signals emitted at relatively long wavelengths by the dyes fluo-3 and rhod-2 in response to binding of Ca2+ ions, and of the suitable features of a commercially available CCD video camera. The localized release of Ca2+ in response to microinjection of InsP3 was also monitored to demonstrate the adequate space and time resolutions of the imaging system. The time resolution of the imager system, although limited to the standard video frequency response, still proved to be adequate to investigate the fast Ca2+ release process in skeletal muscle fibers at low temperatures. Images FIGURE 4 FIGURE 5 FIGURE 6 PMID:2015378

  3. Identification of motoneurons supplying multiply- or singly-innervated extraocular muscle fibers in the rat.

    PubMed

    Eberhorn, A C; Büttner-Ennever, J A; Horn, A K E

    2006-02-01

    In mammals, the extraocular muscle fibers can be categorized in singly-innervated and multiply-innervated muscle fibers. In the monkey oculomotor, trochlear and abducens nucleus the motoneurons of multiply-innervated muscle fibers lie separated from those innervating singly-innervated muscle fibers and show different histochemical properties. In order to discover, if this organization is a general feature of the oculomotor system, we investigated the location of singly-innervated muscle fiber and multiply-innervated muscle fiber motoneurons in the rat using combined tract-tracing and immunohistochemical techniques. The singly-innervated muscle fiber and multiply-innervated muscle fiber motoneurons of the medial and lateral rectus muscle were identified by retrograde tracer injections into the muscle belly or the distal myotendinous junction. The belly injections labeled the medial rectus muscle subgroup of the oculomotor nucleus or the greatest part of abducens nucleus, including some cells outside the medial border of abducens nucleus. In contrast, the distal injections labeled only a subset of the medial rectus muscle motoneurons and exclusively cells outside the medial border of abducens nucleus. The tracer detection was combined with immunolabeling using antibodies for perineuronal nets (chondroitin sulfate proteoglycan) and non-phosphorylated neurofilaments. In monkeys both antibodies permit a distinction between singly-innervated muscle fiber and multiply-innervated muscle fiber motoneurons. The experiments revealed that neurons labeled from a distal injection lack both markers and are assumed to represent multiply-innervated muscle fiber motoneurons, whereas those labeled from a belly injection are chondroitin sulfate proteoglycan- and non-phosphorylated neurofilament-immunopositive and assumed to represent singly-innervated muscle fiber motoneurons. The overall identification of multiply-innervated muscle fiber and singly-innervated muscle fiber motoneurons

  4. The effects of cutting or of stretching skeletal muscle in vitro on the rates of protein synthesis and degradation.

    PubMed Central

    Seider, M J; Kapp, R; Chen, C P; Booth, F W

    1980-01-01

    Rates of protein synthesis were significantly lower in the cut soleus and extensor digitorum longus muscles than in their uncut counterparts. Rates of protein degradation were significantly higher in cut soleus muscles, but not in cut extensor digitorum longus muscles as compared with their uncut controls. Concentrations of ATP and phosphocreatine were significantly lower in cut soleus and extensor digitorum longus muscles after incubation in vitro in contrast with respective control uncut muscles. These data indicate that cutting of muscle fibres alters rates of protein synthesis and degradation, in addition to altering concentrations of high-energy phosphates. Since these findings stressed the importance of using intact muscles to study protein metabolism, additional studies were made on intact muscles in vitro. Stretched soleus muscles had higher concentrations of high-energy phosphates at the end of an incubation period than did unstretched muscles. However, the length of the soleus, extensor digitorum longus and diaphragm muscles during incubation did not affect rates of protein degradation.U PMID:7406883

  5. Effect of one stretch a week applied to the immobilized soleus muscle on rat muscle fiber morphology.

    PubMed

    Gomes, A R S; Coutinho, E L; França, C N; Polonio, J; Salvini, T F

    2004-10-01

    We determined the effect of stretching applied once a week to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Twenty-six male Wistar rats weighing 269 +/- 26 g were divided into three groups. Group I, the left soleus was immobilized in the shortened position for 3 weeks; group II, the soleus was immobilized in the shortened position and stretched once a week for 3 weeks; group III, the soleus was submitted only to stretching once a week for 3 weeks. The medial part of the soleus muscle was frozen for histology and muscle fiber area evaluation and the lateral part was used for the determination of number and length of serial sarcomeres. Soleus muscle submitted only to immobilization showed a reduction in weight (44 +/- 6%, P = 0.002), in serial sarcomere number (23 +/- 15%) and in cross-sectional area of the fibers (37 +/- 31%, P < 0.001) compared to the contralateral muscles. The muscle that was immobilized and stretched showed less muscle fiber atrophy than the muscles only immobilized (P < 0.05). Surprisingly, in the muscles submitted only to stretching, fiber area was decreased compared to the contralateral muscle (2548 +/- 659 vs 2961 +/- 806 microm(2), respectively, P < 0.05). In conclusion, stretching applied once a week for 40 min to the soleus muscle immobilized in the shortened position was not sufficient to prevent the reduction of muscle weight and of serial sarcomere number, but provided significant protection against muscle fiber atrophy. In contrast, stretching normal muscles once a week caused a reduction in muscle fiber area.

  6. Prenatal muscle fiber development and bundle structure in beef and dairy cattle.

    PubMed

    Albrecht, E; Lembcke, C; Wegner, J; Maak, S

    2013-08-01

    Muscle fiber development during gestation determines the muscle structure at birth and establishes the conditions for muscle development in growing cattle. Differences in muscle structure among beef cattle breeds and between beef and dairy cattle are obvious already shortly after birth. The objective of the study was to investigate the development of muscle fibers and muscle fiber bundle structure in semitendinosus muscle of divergent cattle breeds from 3 mo of gestation until birth. Fetuses of German Angus (GA), Galloway (GW), Belgian Blue (BB), and Holstein Friesian (HF) were harvested at 3, 4.5, 6, or 9 mo of gestation. Muscle sections were analyzed for fiber size and types as well as for bundle structure. The results confirmed that primary muscle fiber development occurs mainly during the first trimester of gestation. All fibers were initially positive for fetal fast myosin. Slow myosin as a marker for fiber maturation was detected in primary fibers at 3 mo of gestation showing a weak immunostaining. During the second trimester, the intensity of immunostaining strongly increased indicating increased slow myosin protein expression. Concurrently, the shape of primary fibers changed from myotubes to myofibers whereas the size stayed nearly constant. The main increase in muscle mass during the second trimester was caused by secondary fiber development. As an example, the ratio between secondary and primary fibers increased in Holstein Friesian fetuses from 5.9 at 4.5 mo of gestation to 21.6 at 6 mo of gestation. Primary and secondary fibers continued to growth during the third trimester. Regional differences in the density of slow muscle fibers were detected leading to greater variation within the muscle than among breeds. Structural organization of muscle fibers in muscle fiber bundles developed early in fetal life. At first, large main bundles were visible. Smaller structural units defined as primary bundles were measurable at 6 mo of gestation when most fibers

  7. Volume Control by Muscle Fibers of the Blue Crab

    PubMed Central

    Lang, Michael A.; Gainer, Harold

    1969-01-01

    Single isolated muscle fibers from the walking legs of the blue crab, Callinectes sapidus act as Boyle-van't Hoff osmometers with an osmotically inactive volume of 33 %. Fibers in hypotonic salines undergo a spontaneous volume readjustment toward the initial volumes of the cells found in isotonic salines. The volume readjustment is initiated by the increase in cell volume in hypotonic salines and appears to be dependent on the duration of exposure of the fiber to external sodium, the sodium concentration, and the pH of the external medium. The volume-readjusted cells continue to behave as osmometers, but with an increased relative osmotically inactive volume and a decreased internal resistivity. The decreases in cell volumes appear to be, in large part, due to losses of osmotically active nonelectrolytes from the cells. PMID:5767335

  8. Egr3-Dependent Muscle Spindle Stretch Receptor Intrafusal Muscle Fiber Differentiation and Fusimotor Innervation Homeostasis

    PubMed Central

    Oliveira Fernandes, Michelle

    2015-01-01

    Muscle stretch proprioceptors (muscle spindles) are required for stretch reflexes and locomotor control. Proprioception abnormalities are observed in many human neuropathies, but the mechanisms involved in establishing and maintaining muscle spindle innervation and function are still poorly understood. During skeletal muscle development, sensory (Ia-afferent) innervation induces contacted myotubes to transform into intrafusal muscle fibers that form the stretch receptor core. The transcriptional regulator Egr3 is induced in Ia-afferent contacted myotubes by Neuregulin1 (Nrg1)/ErbB receptor signaling and it has an essential role in spindle morphogenesis and function. Because Egr3 is widely expressed during development and has a pleiotropic function, whether Egr3 functions primarily in skeletal muscle, Ia-afferent neurons, or in Schwann cells that myelinate Ia-afferent axons remains unresolved. In the present studies, cell-specific ablation of Egr3 in mice showed that it has a skeletal muscle autonomous function in stretch receptor development. Moreover, using genetic tracing, we found that Ia-afferent contacted Egr3-deficient myotubes were induced in normal numbers, but their development was blocked to generate one to two shortened fibers that failed to express some characteristic myosin heavy chain (MyHC) proteins. These “spindle remnants” persisted into adulthood, remained innervated by Ia-afferents, and expressed neurotrophin3 (NT3), which is required for Ia-afferent neuron survival. However, they were not innervated by fusimotor axons and they did not express glial derived neurotrophic factor (GDNF), which is essential for fusimotor neuron survival. These results demonstrate that Egr3 has an essential role in regulating gene expression that promotes normal intrafusal muscle fiber differentiation and fusimotor innervation homeostasis. PMID:25855173

  9. Egr3-dependent muscle spindle stretch receptor intrafusal muscle fiber differentiation and fusimotor innervation homeostasis.

    PubMed

    Oliveira Fernandes, Michelle; Tourtellotte, Warren G

    2015-04-08

    Muscle stretch proprioceptors (muscle spindles) are required for stretch reflexes and locomotor control. Proprioception abnormalities are observed in many human neuropathies, but the mechanisms involved in establishing and maintaining muscle spindle innervation and function are still poorly understood. During skeletal muscle development, sensory (Ia-afferent) innervation induces contacted myotubes to transform into intrafusal muscle fibers that form the stretch receptor core. The transcriptional regulator Egr3 is induced in Ia-afferent contacted myotubes by Neuregulin1 (Nrg1)/ErbB receptor signaling and it has an essential role in spindle morphogenesis and function. Because Egr3 is widely expressed during development and has a pleiotropic function, whether Egr3 functions primarily in skeletal muscle, Ia-afferent neurons, or in Schwann cells that myelinate Ia-afferent axons remains unresolved. In the present studies, cell-specific ablation of Egr3 in mice showed that it has a skeletal muscle autonomous function in stretch receptor development. Moreover, using genetic tracing, we found that Ia-afferent contacted Egr3-deficient myotubes were induced in normal numbers, but their development was blocked to generate one to two shortened fibers that failed to express some characteristic myosin heavy chain (MyHC) proteins. These "spindle remnants" persisted into adulthood, remained innervated by Ia-afferents, and expressed neurotrophin3 (NT3), which is required for Ia-afferent neuron survival. However, they were not innervated by fusimotor axons and they did not express glial derived neurotrophic factor (GDNF), which is essential for fusimotor neuron survival. These results demonstrate that Egr3 has an essential role in regulating gene expression that promotes normal intrafusal muscle fiber differentiation and fusimotor innervation homeostasis.

  10. Inositol trisphosphate stimulates calcium release from peeled skeletal muscle fibers.

    PubMed

    Donaldson, S K; Goldberg, N D; Walseth, T F; Huetteman, D A

    1987-01-19

    The effects of inositol phosphates (tris (InsP3), bis (InsP2), mono (InsP)) on rabbit adductor magnus and soleus muscles were determined using mechanically peeled fibers (sarcolemma removed). Isometric force generation of each fiber was continuously monitored and was used along with 45Ca to detect calcium release from internal fiber stores. All experiments were conducted at a physiological Mg2+ concentration (10(-3) M) of the bathing solutions. The inositol phosphates did not directly activate the contractile apparatus. At bath concentrations of 100-300 microM, only InsP3 was capable of stimulating Ca2+ release. In contrast, 1 microM InsP3 maximally and selectively stimulated Ca2+ release when microinjected into the myofilament lattice. Calcium releasing effects of InsP2 and InsP were manifested at 10 microM when they were microinjected. The end-to-end internal Ca2+ release and subsequent fiber force generation stimulated by the locally applied microinjected InsP3 suggests that the InsP3-induced Ca2+ release mechanism may involve propagation, but not via the Ca2+-induced Ca2+ release, since procaine did not inhibit this response. These findings support the possibility that InsP3 plays a role in skeletal muscle excitation-contraction coupling.

  11. The effects of femoral neck cut, cable tension, and muscles forces on the greater trochanter fixation.

    PubMed

    Petit, Yvan; Cloutier, Luc P; Duke, Kajsa; Laflamme, G Yves

    2012-04-01

    Greater trochanter (GT) stabilization techniques following a fracture or an osteotomy are still showing high levels of postoperative complications. Understanding the effect of femoral neck cut placement, cable tension and muscles forces on GT fragment displacements could help surgeons optimize their techniques. A 3D finite element model has been developed to evaluate, through a statistical experimental design, the impact of the above variables on the GT fragment gap and sliding displacements. Muscles forces were simulating typical daily activities. Stresses were also investigated. The femoral neck cut placement had the most significant effect on the fragment displacement. Lowering it by 5 mm increased the gap and sliding fragment displacements by 288 and 128 %, respectively. Excessive cable tightening provided no significant reduction in fragment displacement. Muscle activities increased the gap and the sliding displacements for all muscle configurations. The maximum total displacement of 0.41 mm was present with a 10 mm femoral neck cut, a cable tension of 178 N, and stair climbing. Caution must be used not to over tighten the cables as the potential damage caused by the increased stress is more significant than any reduction in fragment displacement. Furthermore, preservation of the contact area is important for GT stabilization.

  12. In-fiber rectangular air fabry-perot strain sensor based on high-precision fiber cutting platform

    NASA Astrophysics Data System (ADS)

    Zhao, Yong; Chen, Mao-qing; Lv, Ri-qing; Xia, Feng

    2017-02-01

    An in-fiber rectangular air Fabry-Perot (FP) strain sensor based on a high-precision fiber cutting platform (HFCP) is proposed. The HFCP consisting of a CCD notation system, a micro-displacement platform, and an optical fiber cleaver can be used to precisely control the length of FP cavity. The microcavity of FP (even only tens of microns) with smooth reflective surface can be realized easily by using this system. The FP structures with different cavity lengths have been fabricated in this paper. Simulation and experimental results prove that the shorter length the cavity has, the higher strain sensitivity and the larger free spectral range (FSR) the sensor obtains. The strain sensitivity and FSR of in-fiber rectangular air FP sensor with a cavity length of 35 μm can be up to 2.23 pm/με and 28.5 nm respectively. Moreover, the proposed FP strain sensor has a negligible temperature sensitivity in the range of 25-75 °C. It is anticipated that such easy making, compact and low-cost fiber-optic strain sensors could find important applications in practice.

  13. Fluctuations in tension during contraction of single muscle fibers.

    PubMed Central

    Borejdo, J; Morales, M F

    1977-01-01

    We have searched for fluctuations in the steady-state tension developed by stimulated single muscle fibers. Such tension "noise" is expected to be present as a result of the statistical fluctuations in the number and/or state of myosin cross-bridges interacting with thin filament sites at any time. A sensitive electro-optical tension transducer capable of resolving the expected fluctuations in magnitude and frequency was constructed to search for the fluctuations. The noise was analyzed by computing the power spectra and amplitude of stochastic fluctuations in the photomultiplier counting rate, which was made proportional to muscle force. The optical system and electronic instrumentation together with the minicomputer software are described. Tensions were measured in single skinned glycerinated rabbit psoas muscle fibers in rigor and during contraction and relaxation. The results indicate the presence of fluctuations in contracting muscles and a complete absence of tension noise in eith rigor or relaxation. Also, a numerical method was developed to simulate the power spectra and amplitude of fluctuations, given the rate constants for association and dissociation of the cross-bridges and actin. The simulated power spectra and the frequency distributions observed experimentally are similar. PMID:922123

  14. Cutting and drilling of carbon fiber reinforced plastics (CFRP) by 70W short pulse nanosecond laser

    NASA Astrophysics Data System (ADS)

    Jaeschke, Peter; Stolberg, Klaus; Bastick, Stefan; Ziolkowski, Ewa; Roehner, Markus; Suttmann, Oliver; Overmeyer, Ludger

    2014-02-01

    Continuous carbon fibre reinforced plastics (CFRP) are recognized as having a significant lightweight construction potential for a wide variety of industrial applications. However, a today`s barrier for a comprehensive dissemination of CFRP structures is the lack of economic, quick and reliable manufacture processes, e.g. the cutting and drilling steps. In this paper, the capability of using pulsed disk lasers in CFRP machining is discussed. In CFRP processing with NIR lasers, carbon fibers show excellent optical absorption and heat dissipation, contrary to the plastics matrix. Therefore heat dissipation away from the laser focus into the material is driven by heat conduction of the fibres. The matrix is heated indirectly by heat transfer from the fibres. To cut CFRP, it is required to reach the melting temperature for thermoplastic matrix materials or the disintegration temperature for thermoset systems as well as the sublimation temperature of the reinforcing fibers simultaneously. One solution for this problem is to use short pulse nanosecond lasers. We have investigated CFRP cutting and drilling with such a laser (max. 7 mJ @ 10 kHz, 30 ns). This laser offers the opportunity of wide range parameter tuning for systematic process optimization. By applying drilling and cutting operations based on galvanometer scanning techniques in multi-cycle mode, excellent surface and edge characteristics in terms of delamination-free and intact fiber-matrix interface were achieved. The results indicate that nanosecond disk laser machining could consequently be a suitable tool for the automotive and aircraft industry for cutting and drilling steps.

  15. Muscle fiber size and function in elderly humans: a longitudinal study.

    PubMed

    Frontera, Walter R; Reid, Kieran F; Phillips, Edward M; Krivickas, Lisa S; Hughes, Virginia A; Roubenoff, Ronenn; Fielding, Roger A

    2008-08-01

    Cross-sectional studies are likely to underestimate age-related changes in skeletal muscle strength and mass. The purpose of this longitudinal study was to assess whole muscle and single muscle fiber alterations in the same cohort of 12 older (mean age: start of study 71.1+/-5.4 yr and end of study 80+/-5.3 yr) volunteers (5 men) evaluated 8.9 yr apart. No significant changes were noted at follow-up in body weight, body mass index, and physical activity. Muscle strength, evaluated using isokinetic dynamometry, and whole muscle specific force of the knee extensors were significantly lower at follow-up. This was accompanied by a significant reduction (5.7%) in cross-sectional area of the total anterior muscle compartment of the thigh as evaluated by computed tomography. Muscle histochemistry showed no significant changes in fiber type distribution or fiber area. Experiments with chemically skinned single muscle fibers (n=411) demonstrated no change in type I fiber size but an increase in IIA fiber diameter. A trend toward an increase in maximal force in both fiber types was observed. Maximum unloaded shortening velocity did not change. In conclusion, single muscle fiber contractile function may be preserved in older humans in the presence of significant alterations at the whole muscle level. This suggests that surviving fibers compensate to partially correct muscle size deficits in an attempt to maintain optimal force-generating capacity.

  16. Elaboration of excimer lasers dosimetry for bone and meniscus cutting and drilling using optical fibers

    NASA Astrophysics Data System (ADS)

    Jahn, Renate; Dressel, Martin; Neu, Walter; Jungbluth, Karl-Heinz

    1991-05-01

    In order to optimize bone and cartilage ablation, various excimer laser systems at 308 nm wavelength (pulse width 28 ns, 60 ns, 300 ns) and tapered fibers (core diameter 400 micrometers , 600 micrometers , 1000 micrometers ) were combined. By varying the major parameters such as fluence, pulselength, repetition rate, fiber diameter, medium, manner of application (drilling, cutting); analysis was made of the interaction of the excimer laser beam with different organic material (meniscus, bone tissue). More than 300 cuts and drillings have been realized with different parameters. The ablation rate mainly depends on fluence, repetition rate and pulse duration. The achieved ablation rate was 3 micrometers /pulse in bone. The drilling speed of the meniscus was 6 mm/s. The samples showed no carbonization at all, when being cut or drilled in liquid medium. This might be a breakthrough in fiber guided excimer laser surgery. From these and further experiments the authors obtained the dosimetry, which will be the basis for the elaboration of necessary operation guidelines for accident surgery.

  17. Energy balance in high-quality cutting of steel by fiber and CO2 lasers

    NASA Astrophysics Data System (ADS)

    Fomin, V. M.; Golyshev, A. A.; Orishich, A. M.; Shulyat'ev, V. B.

    2017-03-01

    The energy balance of laser cutting of low-carbon and stainless steel sheets with the minimum roughness of the cut surface is experimentally studied. Experimental data obtained in wide ranges of cutting parameters are generalized with the use of dimensionless parameters (Peclet number and absorbed laser energy). It is discovered for the first time that the minimum roughness is ensured at a certain value of energy per unit volume of the melt (approximately 26 J/mm3), regardless of the gas type (oxygen or nitrogen) and laser type (fiber laser with a wavelength of 1.07 μm or CO2 laser with a wavelength of 10.6 μm).

  18. Heterogeneity of fiber characteristics in the rat masseter and digastric muscles.

    PubMed

    Sano, R; Tanaka, E; Korfage, J A M; Langenbach, G E J; Kawai, Nobuhiko; van Eijden, T M G J; Tanne, K

    2007-10-01

    The functional requirements in muscle use are related to the fiber type composition of the muscles and the cross-sectional area of the individual fibers. We investigated the heterogeneity in the fiber type composition and fiber cross-sectional area in two muscles with an opposing function, namely the digastric and masseter muscles (n = 5 for each muscle) of adult male rats, by means of immunohistochemical staining according to their myosin heavy chain (MyHC) content. The digastric and masseter muscles were taken from Wistar strain male rats 10 weeks old. In the masseter six predefined sample locations were examined; in the digastric four. Most regions showed dominant proportions of type IIA and IIX fibers. However, both muscles also revealed a regional heterogeneity in their fiber type distribution. In the digastric, type I fibers were detected only at the central and deep areas of the anterior and posterior belly, respectively. Meanwhile, the peripheral area of the anterior belly contained a higher proportion of type IIB fibers. In the masseter, the type I fibers were absent. In the superficial masseter the distribution of IIA and IIB fibers was significantly different between the superior and inferior regions. In the deep masseter, regional differences were observed among all four examined areas, of which the posterolateral region contained the highest proportion of type IIB fibers. The cross-sectional areas of type IIB fibers were always the largest, followed by the type IIX and IIA fibers. Only a few differences in cross-sectional area of corresponding fiber types were detected between the various sites. In conclusion, the masseter and digastric muscles showed an obvious heterogeneity of fiber type composition and fiber cross-sectional area. Their heterogeneity reflects the complex role of the both muscles during function. This detailed description of the fiber type composition can serve as a reference for future studies examining the muscular adaptations after

  19. Experimental investigation on fiber and CO2 inert gas fusion cutting of AZ31 magnesium alloy sheets

    NASA Astrophysics Data System (ADS)

    Scintilla, L. D.; Tricarico, L.

    2013-03-01

    The influence of processing parameters and laser source type on cutting edge quality of AZ31 magnesium alloy sheets and differences in cutting efficiency between fiber and CO2 lasers were studied. A first part of the cutting experiments compared a fiber and CO2 laser source when cutting 1 mm thick sheets in continuous wave mode and using Argon as an assist gas. The effects of cutting speed and assist gas pressure were investigated and optimal conditions were identified. In the second part of the experimental investigation, 3.3 mm thick sheets were cut using fiber laser. Focal position and cutting speed were varied in order to detect the optimal combination of processing parameters to obtain the best edge quality. For both sheet thicknesses investigated, surface roughness, dross height, and striation pattern inclination were measured. Cutting quality assessment and classification was carried out according to UNI EN ISO 9013 standard. Results showed that productivity, process efficiency and cutting edges quality obtained using fiber lasers outperform CO2 laser performances and therefore are considered suitable for application like sheet metal trimming.

  20. Halothane cooling contractures of skinned mammalian muscle fibers.

    PubMed

    Sudo, R T; Zapata-Sudo, G; Suarez-Kurtz, G

    1990-11-01

    The effects of halothane or cooling on Ca2(+)-activated tensions and on the uptake and release of Ca2+ by the sarcoplasmic reticulum were investigated in chemically skinned fibers of the extensor digitorum longus muscle of adult rabbits. At 22 degrees C, halothane (greater than 0.46 mM) induced Ca2+ release from the SR of Ca2(+)-loaded skinned fibers that resulted in transient tensions. Higher concentrations of halothane (greater than 4.65 mM) reduced the steady-state accumulation of Ca2+ in the SR at 22 degrees C. Cooling (to less than 10 degrees C) elicited transient contractures (cooling-induced contractures [CC]) in Ca2(+)-loaded skinned fibers, despite the fact that the tensions elicited by adding Ca2+ to the bath were depressed at these low temperatures. The skinned fibers did not develop CCs at 12-16 degrees C. Halothane cooling contractures could be elicited at these temperatures by exposing the fibers to halothane concentrations that failed to elicit Ca2+ release at 22 degrees C. The halothane cooling contractures were blocked by procaine but not by lidocaine. It was concluded that these contractures resulted from a synergistic interaction between halothane and cooling that stimulates Ca2+ release from, and reduces Ca2+ uptake by, the sarcoplasmic reticulum.

  1. Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle

    PubMed Central

    Castorena, Carlos M.; Arias, Edward B.; Sharma, Naveen; Bogan, Jonathan S.

    2014-01-01

    To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[3H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater (P < 0.05) 2-DG uptake for each of the isolated fiber types (MHC-IIa, MHC-IIax, MHC-IIx, MHC-IIxb, and MHC-IIb). However, 2-DG uptake for E-Stim fibers was not significantly different among these five fiber types. GLUT4, tethering protein containing a UBX domain for GLUT4 (TUG), cytochrome c oxidase IV (COX IV), and filamin C protein levels were significantly greater (P < 0.05) in MHC-IIa vs. MHC-IIx, MHC-IIxb, or MHC-IIb fibers. TUG and COX IV in either MHC-IIax or MHC-IIx fibers exceeded values for MHC-IIxb or MHC-IIb fibers. GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly (P < 0.05) correlated with each other. Differences in GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake. PMID:25491725

  2. Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle.

    PubMed

    Castorena, Carlos M; Arias, Edward B; Sharma, Naveen; Bogan, Jonathan S; Cartee, Gregory D

    2015-02-01

    To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[(3)H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater (P < 0.05) 2-DG uptake for each of the isolated fiber types (MHC-IIa, MHC-IIax, MHC-IIx, MHC-IIxb, and MHC-IIb). However, 2-DG uptake for E-Stim fibers was not significantly different among these five fiber types. GLUT4, tethering protein containing a UBX domain for GLUT4 (TUG), cytochrome c oxidase IV (COX IV), and filamin C protein levels were significantly greater (P < 0.05) in MHC-IIa vs. MHC-IIx, MHC-IIxb, or MHC-IIb fibers. TUG and COX IV in either MHC-IIax or MHC-IIx fibers exceeded values for MHC-IIxb or MHC-IIb fibers. GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly (P < 0.05) correlated with each other. Differences in GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake.

  3. Inactivity, age, and exercise: single-muscle fiber power generation.

    PubMed

    Kim, Jong-Hee; Thompson, Ladora V

    2013-01-01

    We examined the effects of mild therapeutic exercise during a period of inactivity on size and contractile functions of myosin heavy chain (MHC) type I (n = 204) and type II (n = 419) single fibers from the medial gastrocnemius in three age groups. Young adult (5-12 mo), middle-aged (24-31 mo), and old (32-37 mo) F344BNF1 rats were assigned to one of three groups: weight-bearing control, non-weight bearing (NWB), and NWB plus exercise (NWBX). Fourteen days of hindlimb suspension were applied in NWB rats. The NWBX rats exercised on the treadmill for 15 min, four times a day, during the period of NWB. The NWBX did not improve peak power, but increased normalized power of MHC type I fibers in young adult rats. In MHC type II fibers, NWBX did not change peak power, isometric maximal force, V(max), and fiber size from young adult and middle-aged rats. NWBX did not improve peak power and isometric maximal force and showed a dramatic decline in V(max) and normalized power in the old rats. Collectively, mild treadmill exercise during a period of inactivity does not improve peak power of MHC type I or type II fiber from the gastrocnemius in young, middle-aged, and old rats. However, NWBX is beneficial in enhancing normalized power of MHC type I fibers in young adult rats, most likely due to the stimulus intensity and the ability of the individual fibers to adapt to the stimulus. In contrast, several factors, such as impaired adaptation potential, inappropriate exercise intensity, or increased susceptibility to muscle damage, may contribute to the lack of improvement in the older rats.

  4. Muscle-fiber transdifferentiation in an experimental model of respiratory chain myopathy.

    PubMed

    Venhoff, Nils; Lebrecht, Dirk; Pfeifer, Dietmar; Venhoff, Ana C; Bissé, Emmanuel; Kirschner, Janbernd; Walker, Ulrich A

    2012-10-29

    Skeletal muscle fiber composition and muscle energetics are not static and change in muscle disease. This study was performed to determine whether a mitochondrial myopathy is associated with adjustments in skeletal muscle fiber-type composition. Ten rats were treated with zidovudine, an antiretroviral nucleoside reverse transcriptase inhibitor that induces a myopathy by interfering with mitochondrial functions. Soleus muscles were examined after 21 weeks of treatment. Ten untreated rats served as controls. Zidovudine induced a myopathy with mitochondrial DNA depletion, abnormalities in mitochondrial ultrastructure, and reduced cytochrome c oxidase activity. Mitochondrial DNA was disproportionally more diminished in type I compared with type II fibers, whereas atrophy predominated in type II fibers. Compared with those of controls, zidovudine-exposed soleus muscles contained an increased proportion (256%) of type II fibers, whereas neonatal myosin heavy chains remained repressed, indicating fiber-type transformation in the absence of regeneration. Microarray gene-expression analysis confirmed enhanced fast-fiber isoforms, repressed slow-fiber transcripts, and reduced neonatal fiber transcripts in the mitochondrial myopathy. Respiratory chain transcripts were diminished, whereas the enzymes of glycolysis and glycogenolysis were enhanced, indicating a metabolic adjustment from oxidative to glycolytic capacities. A coordinated regulation was found of transcription factors known to orchestrate type II fiber formation (upregulation of MyoD, Six1, Six2, Eya1, and Sox6, and downregulation of myogenin and ERRγ). The type I to type II fiber transformation in mitochondrial myopathy implicates mitochondrial function as a new regulator of skeletal muscle fiber type.

  5. Calcium transients in asymmetrically activated skeletal muscle fibers.

    PubMed Central

    Trube, G; Lopez, J R; Taylor, S R

    1981-01-01

    Skeletal muscle fibers of the frog Rana temporaria were held just taut and stimulated transversely by unidirectional electrical fields. We observed the reversible effects of stimulus duration (0.1-100 ms) and strength on action potentials, intracellular Ca2+ transients (monitored by aequorin), and contractile force during fixed-end contractions. Long duration stimuli (e.g., 10 ms) induced a maintained depolarization on the cathodal side of a cell and a maintained hyperpolarization on its anodal side. The hyperpolarization of the side facing the anode prevented the action potential from reaching mechanical threshold during strong stimuli. Variation of the duration or strength of a stimulus changed the luminescent response from a fiber injected with aequorin. Thus, the intracellular Ca2+ released during excitation-contraction coupling could be changed by the stimulus parameters. Prolongation of a stimulus at field strengths above 1.1 x rheobase decreased the amplitude of aequorin signals and the force of contractions. The decreases in aequorin and force signals from a given fiber paralleled one another and depended on the stimulus strength, but not on the stimulus polarity. These changes were completely reversible for stimulus strengths up to at least 4.2 x rheobase. The graded decreases in membrane depolarization, aequorin signals, and contractile force were correlated with the previously described folding of myofibrils in fibers allowed to shorten in response to the application of a long duration stimulus. The changes in aequorin signals and force suggest an absence of myofilament activation by Ca2+ in the section of the fiber closest to the anode. The results imply that injected aequorin distributes circumferentially in frog muscle with a coefficient of at least 10(-7) cm2/s, which is not remarkably different from the previously measured coefficient of 5 x 10(-8) cm2/s for its diffusion lengthwise. PMID:6976801

  6. Regional variations in intramyocellular lipid concentration correlate with muscle fiber type distribution in rat tibialis anterior muscle.

    PubMed

    De Feyter, Henk M M L; Schaart, Gert; Hesselink, Matthijs K; Schrauwen, Patrick; Nicolay, Klaas; Prompers, Jeanine J

    2006-07-01

    1H MR spectroscopy (MRS) has proved to be a valuable noninvasive tool to measure intramyocellular lipids (IMCL) in research focused on insulin resistance and type II diabetes in both humans and rodents. An important determinant of IMCL is the muscle fiber type, since oxidative type I fibers can contain up to three times more IMCL than glycolytic type II muscle fibers. Because these different muscle fiber types are inhomogeneously distributed in rodent muscle, in the present study we investigated the distribution of IMCL within the rat tibialis anterior muscle (TA) in vivo using single-voxel 1H MRS along with the muscle fiber distribution in the TA ex vivo determined from immunohistological assays. IMCL levels in the TA differed by up to a factor of 3 depending on the position of the voxel. The distribution of IMCL over the TA cross section was not random, but emerged in a pattern similar to the distribution of the predominantly oxidative muscle fiber types. Dietary interventions, such as high-fat feeding and 15 hr of fasting, did not significantly change this typical fiber type-dependent pattern of IMCL content. These results stress the importance of voxel positioning when single-voxel 1H MRS is used to study IMCL in rodent muscle. Copyright (c) 2006 Wiley-Liss, Inc.

  7. Evidence for ACTN3 as a Speed Gene in Isolated Human Muscle Fibers

    PubMed Central

    Broos, Siacia; Malisoux, Laurent; Theisen, Daniel; van Thienen, Ruud; Ramaekers, Monique; Jamart, Cécile; Deldicque, Louise; Thomis, Martine A.; Francaux, Marc

    2016-01-01

    Purpose To examine the effect of α-actinin-3 deficiency due to homozygosity for the ACTN3 577X-allele on contractile and morphological properties of fast muscle fibers in non-athletic young men. Methods A biopsy was taken from the vastus lateralis of 4 RR and 4 XX individuals to test for differences in morphologic and contractile properties of single muscle fibers. The cross-sectional area of the fiber and muscle fiber composition was determined using standard immunohistochemistry analyses. Skinned single muscle fibers were subjected to active tests to determine peak normalized force (P0), maximal unloading velocity (V0) and peak power. A passive stretch test was performed to calculate Young’s Modulus and hysteresis to assess fiber visco-elasticity. Results No differences were found in muscle fiber composition. The cross-sectional area of type IIa and IIx fibers was larger in RR compared to XX individuals (P<0.001). P0 was similar in both groups over all fiber types. A higher V0 was observed in type IIa fibers of RR genotypes (P<0.001) but not in type I fibers. The visco-elasticity as determined by Young’s Modulus and hysteresis was unaffected by fiber type or genotype. Conclusion The greater V0 and the larger fast fiber CSA in RR compared to XX genotypes likely contribute to enhanced whole muscle performance during high velocity contractions. PMID:26930663

  8. Evidence for ACTN3 as a Speed Gene in Isolated Human Muscle Fibers.

    PubMed

    Broos, Siacia; Malisoux, Laurent; Theisen, Daniel; van Thienen, Ruud; Ramaekers, Monique; Jamart, Cécile; Deldicque, Louise; Thomis, Martine A; Francaux, Marc

    2016-01-01

    To examine the effect of α-actinin-3 deficiency due to homozygosity for the ACTN3 577X-allele on contractile and morphological properties of fast muscle fibers in non-athletic young men. A biopsy was taken from the vastus lateralis of 4 RR and 4 XX individuals to test for differences in morphologic and contractile properties of single muscle fibers. The cross-sectional area of the fiber and muscle fiber composition was determined using standard immunohistochemistry analyses. Skinned single muscle fibers were subjected to active tests to determine peak normalized force (P0), maximal unloading velocity (V0) and peak power. A passive stretch test was performed to calculate Young's Modulus and hysteresis to assess fiber visco-elasticity. No differences were found in muscle fiber composition. The cross-sectional area of type IIa and IIx fibers was larger in RR compared to XX individuals (P<0.001). P0 was similar in both groups over all fiber types. A higher V0 was observed in type IIa fibers of RR genotypes (P<0.001) but not in type I fibers. The visco-elasticity as determined by Young's Modulus and hysteresis was unaffected by fiber type or genotype. The greater V0 and the larger fast fiber CSA in RR compared to XX genotypes likely contribute to enhanced whole muscle performance during high velocity contractions.

  9. Preparation of adult muscle fiber-associated stem/precursor cells.

    PubMed

    Conboy, Michael J; Conboy, Irina M

    2010-01-01

    In our studies of muscle regeneration we have developed, modified, and optimized techniques to isolate and study the stem and precursor cells to muscle tissue. Our goals have been to obtain for study muscle fibers in bulk, or the fiber-associated cells, separately from the other cells found in muscle. Using these techniques, myofiber-associated cells may be isolated from neonatal through adult muscle, from resting or from regenerating muscle, thus allowing one to investigate the cellular populations participating during the time course of these events. The protocol is applicable to any age and condition of muscle and may be adapted for other tissues.

  10. Type IIB human skeletal muscle fibers positively correlate with bone mineral density irrespective to age.

    PubMed

    Cheung, Wing-Hoi; Lee, Wing-Sze; Qin, Ling; Tang, Ning; Hung, Vivian Wing-Yin; Leung, Kwok-Sui

    2010-11-01

    Age-associated decrease in type IIA/B human skeletal muscle fibers was detected in human biopsies in our previous study. The relationship between change in muscle fiber typing and bone mineral density (BMD) is, however, unknown either cross-sectionally or longitudinally. We therefore conducted a cross-sectional study to investigate their correlation using human muscle biopsies. Forty human subjects aged (53.4 ± 20.2) years were recruited. Histomorphometric parameters of their muscle biopsies were measured by ATPase staining and image analysis, including average area percentage, fiber number percentage, mean fiber area, and area percentage of connective tissues. Hip and spine BMD was measured by dual-energy X-ray absorptiometry. Partial correlation with adjusting age was performed. Type IIB muscle fiber was found positively correlated with hip BMD irrespective to age and demonstrated significantly stronger relationship with BMD among all fiber types, in terms of its cross-sectional area (r = 0.380, P = 0.029) and size (r = 0.389, P = 0.025). Type IIA muscle fibers associated with hip BMD in mean fiber area only (r = 0.420, P = 0.015). Type IIB muscle fiber may play an important role in maintaining bone quality. This may also be a relatively more sensitive fiber type of sarcopenia and osteoporosis. These findings further consolidate the muscle-bone relationship.

  11. An ultrastructural and histochemical study of the flexor tibialis muscle fiber types in male and female stick insects (Eurycantha calcarata, L).

    PubMed

    Pilehvarian, Ali Asghar

    2015-10-01

    In this study the ultrastructural and histochemical characteristics of the flexor tibialis muscle fibers of the specialized metathoracic legs in the male and those of homologous and unspecialized ones in the female stick insects, Eurycantha calcarata, L, were examined. For the ultrastructural analysis, the muscle was divided longitudinally and vertically to produce a total of 12 sample parts e.g., anterior-dorsal-distal (ADD), posterior-ventral-medial (PVM) and so on. Light and electron microscopes were used to observe the muscle tissue. The methods for myosin adenosine triphosphatase (mATPase) and nicotine adenine dinucleotide- tetrazolium (NADH-TR) staining were modified from the methods of (Stokes et al., '79; Anttila et al., 2009; Anttila and Manttari, 2009). Sections with thickness of 22 μm, were cut from the anterior and the posterior surfaces of the muscle, using a cryostat. The histochemical and ultrastructural results showed that the muscles of both the male and the female were mixtures of physiological fiber types, with predominantly fast fibers. The muscles were composed of fibers with different staining properties for both mATPase and NADH-TR activities. The population of fibers within the muscles was heterogeneous. The differences between the population of the male and that of the female were significant. The means of most criteria e.g., mitochondrial amount and sarcoplasmic reticulum area predicted that the muscle of the male contained more fast fibers than the female. The histochemical examination also showed that the muscle of the male contained more fibers stained darkly for mATPase and lightly for NADH-TR. © 2015 Wiley Periodicals, Inc.

  12. How muscle fiber lengths and velocities affect muscle force generation as humans walk and run at different speeds.

    PubMed

    Arnold, Edith M; Hamner, Samuel R; Seth, Ajay; Millard, Matthew; Delp, Scott L

    2013-06-01

    The lengths and velocities of muscle fibers have a dramatic effect on muscle force generation. It is unknown, however, whether the lengths and velocities of lower limb muscle fibers substantially affect the ability of muscles to generate force during walking and running. We examined this issue by developing simulations of muscle-tendon dynamics to calculate the lengths and velocities of muscle fibers from electromyographic recordings of 11 lower limb muscles and kinematic measurements of the hip, knee and ankle made as five subjects walked at speeds of 1.0-1.75 m s(-1) and ran at speeds of 2.0-5.0 m s(-1). We analyzed the simulated fiber lengths, fiber velocities and forces to evaluate the influence of force-length and force-velocity properties on force generation at different walking and running speeds. The simulations revealed that force generation ability (i.e. the force generated per unit of activation) of eight of the 11 muscles was significantly affected by walking or running speed. Soleus force generation ability decreased with increasing walking speed, but the transition from walking to running increased the force generation ability by reducing fiber velocities. Our results demonstrate the influence of soleus muscle architecture on the walk-to-run transition and the effects of muscle-tendon compliance on the plantarflexors' ability to generate ankle moment and power. The study presents data that permit lower limb muscles to be studied in unprecedented detail by relating muscle fiber dynamics and force generation to the mechanical demands of walking and running.

  13. Contractile activation phenomena in voltage-clamped barnacle muscle fiber

    PubMed Central

    1978-01-01

    Tension development in voltage-clamped barnacle muscle fibers occurs with depolarizing pulses so small as not to activate the potassium and calcium conductance systems. Peak tension and the tension time integral appear to be graded by both amplitude and duration of the depolarizing pulses. Subthreshold depolarizing conditioning pulses shorter than 500 ms potentiate the response to a given test pulse. This effect diminishes and reverts when the duration of the conditioning pulse is increasingly prolonged. The relationship between fiber membrane potential and tension developed in response to depolarizing pulses is described by an S-shaped curve. The tension saturates at a membrane potential of about +10 mV (inside positive). For a given pulse duration the saturation value remains constant even when the fiber interior reaches a value of +230 mV, which is well above what may be estimated to be the equilibrium potential of calcium ions (Eca = +120). In the presence of 5 mM external procaine, the shape of the tension-potential curve changes; the maximum value tension besides being diminished is not sustained by falls when the potential approaches the estimated value for Eca. These results suggest that under physiological conditions the contractile activator is probably released from an internal store, and that the calcium entering the fiber as inward current does not play a direct major role in contractile activation. PMID:660158

  14. Electro-optical property of extremely stretched skinned muscle fibers.

    PubMed Central

    Umazume, Y; Fujime, S

    1975-01-01

    Skinned fibers of frog semitendinosus muscle could easily be stretched up to 8 mum or more in sarcomere length. Such extremely stretched fibers gave quite sharp optical diffraction patterns. The intensities of all observable diffraction lines were found to increase on application of electric field (10 similar to 100 V/cm) parallel to the fiber axis, provided that there was no overlap between thin and thick filaments. By use of a polarizing microscope, it was concluded that I-bands were mainly responsible for this intensity increase. By application of square pulses, the time course of the intensity increase and decay was followed. The analysis based on a simple model suggests: (a) Each thin filament has a permanent dipole movement and the movement directs from Z-bands to the free end of the thin filament. (b) The flexural rigidity of thin filaments is estimated to be similar to 3 with 10-17 dyn with cm-2. The present fibers will provide various applications in physiochemical studies of in vivo thin and thick filaments. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 8 FIGURE 9 FIGURE 10 PMID:1078630

  15. Quantification of muscle fiber strain during in vivo repetitive stretch-shortening cycles.

    PubMed

    Butterfield, Timothy A; Herzog, Walter

    2005-08-01

    Muscles subjected to lengthening contractions exhibit evidence of subcellular disruption, arguably a result of fiber strain magnitude. Due to the difficulty associated with measuring fiber strains during lengthening contractions, fiber length estimates have been used to formulate relationships between the magnitude of injury and mechanical measures such as fiber strain. In such protocols, the series compliance is typically minimized by removing the distal tendon and/or preactivating the muscle. These in vitro and in situ experiments do not represent physiological contractions well where fiber strain and muscle strain may be disassociated; thus the mechanisms of in vivo muscle injury remain elusive. The purpose of this paper was to quantify fiber strains during lengthening contractions in vivo and assess the potential role of fiber strain in muscle injury following repetitive stretch-shortening cycles. Using intact New Zealand White rabbit dorsiflexors, fiber strain and joint torque were measured during 50 stretch-shortening cycles. We were able to show that fiber length changes are disassociated from muscle tendon unit length changes and that complex fiber dynamics during these cycles prevent easy estimates of fiber strains. In addition, fiber strains vary, depending on how they are defined, and vary from repetition to repetition, thereby further complicating the potential relationship between muscle injury and fiber strain. We conclude from this study that, during in vivo stretch-shortening cycles, the relationship between fiber strain and muscle injury is complex. This is due, in part, to temporal effects of repeated loading on fiber strain magnitude that may be explained by an increasing compliance of the contractile element as exercise progresses.

  16. Ultrastructure of mouse striated muscle fibers following pravastatin administration.

    PubMed

    Bergman, Michael; Salman, Hertzel; Djaldetti, Meir; Alexandrova, Svetlana; Punsky, Igor; Bessler, Hanna

    2003-01-01

    To examine the effect of pravastatin administration on striated muscle ultrastructure, 10 BalbC mice were given pravastatin 40 mg/kg/day for 3 weeks. At the end of the study, blood was withdrawn for evaluation of the serum creatine phospho-kinase (CPK) level and the muscles of the hind legs, as well as the heart and liver of the animals were examined with a light and transmission electron microscope. After treatment with pravastatin the results showed a 101% increase in serum CPK level in comparison to untreated controls. Hematoxillin-eosin stained tissues of pravastatin treated mice did not show any abnormal findings. While the ultrastructure of the heart and liver of the treated animals appeared normal, the muscle fibers showed a marked alterations of the mitochondria, which were increased in size compared to those of the controls. The cristae were heavily damaged and even completely destructed, giving the mitochondria appearance of empty vacuoles. The findings are in favor of a specificity of pravastatin for striated muscles.

  17. Reduced muscle fiber force production and disrupted myofibril architecture in patients with chronic rotator cuff tears.

    PubMed

    Mendias, Christopher L; Roche, Stuart M; Harning, Julie A; Davis, Max E; Lynch, Evan B; Sibilsky Enselman, Elizabeth R; Jacobson, Jon A; Claflin, Dennis R; Calve, Sarah; Bedi, Asheesh

    2015-01-01

    A persistent atrophy of muscle fibers and an accumulation of fat, collectively referred to as fatty degeneration, commonly occur in patients with chronic rotator cuff tears. The etiology of fatty degeneration and function of the residual rotator cuff musculature have not been well characterized in humans. We hypothesized that muscles from patients with chronic rotator cuff tears have reduced muscle fiber force production, disordered myofibrils, and an accumulation of fat vacuoles. The contractility of muscle fibers from biopsy specimens of supraspinatus muscles of 13 patients with chronic full-thickness posterosuperior rotator cuff tears was measured and compared with data from healthy vastus lateralis muscle fibers. Correlations between muscle fiber contractility, American Shoulder and Elbow Surgeons (ASES) scores, and tear size were analyzed. Histology and electron microscopy were also performed. Torn supraspinatus muscles had a 30% reduction in maximum isometric force production and a 29% reduction in normalized force compared with controls. Normalized supraspinatus fiber force positively correlated with ASES score and negatively correlated with tear size. Disordered sarcomeres were noted, along with an accumulation of lipid-laden macrophages in the extracellular matrix surrounding supraspinatus muscle fibers. Patients with chronic supraspinatus tears have significant reductions in muscle fiber force production. Force production also correlates with ASES scores and tear size. The structural and functional muscle dysfunction of the residual muscle fibers is independent of the additional area taken up by fibrotic tissue. This work may help establish future therapies to restore muscle function after the repair of chronically torn rotator cuff muscles. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  18. [Validation of cut points of skeletal muscle mass index for identifying sarcopenia in Chilean older people].

    PubMed

    Lera, Lydia; Ángel, Bárbara; Sánchez, Hugo; Picrin, Yaisy; Hormazabal, María José; Quiero, Andrea; Albala, Cecilia

    2014-09-28

    To estimate and validate cut-off points of skeletal muscle mass index (SMI) in Chilean population, for using in an algorithm for a diagnosis of sarcopenia developed by European Working Group on Sarcopenia in Older People (EWGSOP). Secondary analysis of Cross-sectional data in 440 Chilean older subjects to estimate cut-off points of SMI determined by DEXA and predicted by an anthropometric equation. Afterward a cross-sectional validation in a sample of 164 older people was performed. Anthropometric measures, self-reported health status, physical performance tests and DEXA were carried out. Decreased muscle strength was defined as handgrip strength <15 kg in women and <27 kg in male. Cut-off points of SMI were defined as values under 20th percentile for DEXA measures and estimated through ROC curves for the anthropometric model. Biological validity of the algorithm was tested by contrasting the diagnosis with physical performance tests and functionality. Cut-off points of SMI obtained by DEXA were 7.19 kg/m² in men and 5.77 kg/m² in women and 7.45 kg/ m² and 5.88 kg/m², respectively for the predicted by the model. Sensibility and specificity of estimations vs DEXA measures were 80% and 92% in men and 77% and 89% in women. We obtained cut-off points of SMI for DEXA and for a prediction equation for older adults Chilean, with good sensibility and specificity for the measurement by DEXA. It will allow to apply the EWGSOP algorithm to the early diagnosis of sarcopenia and to develop programs for prevention, delay or reversion this syndrome. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

  19. 20-Hydroxyecdysone increases fiber size in a muscle-specific fashion in rat.

    PubMed

    Tóth, Noémi; Szabó, András; Kacsala, Péter; Héger, Júlia; Zádor, Ernö

    2008-09-01

    20-Hydroxyecdysone (20E) is an ecdysteroid hormone that regulates moulting in insects. Interestingly, 20E is also found most abundantly in plant species and has anabolic effects in vertebrates, i.e. increasing muscle size without androgen influence. The effect of 20E on slow and fast fiber types of skeletal muscle has not been reported yet. Here we present that 20E affects the size (cross-sectional area, CSA) of the different fiber types in a muscle-specific manner. The effect on fiber size was modified by the distance from the site of the treatment and the presence of a regenerating soleus muscle in the animal. Besides the fiber size, 20E also increased the myonuclear number in the fibers of normal and regenerating muscles, suggesting the activation of satellite cells. According to our results 20E may provide an alternative for substitution of anabolic-androgenic steroids in therapeutic treatments against muscle atrophy.

  20. Skeletal muscle fiber atrophy: altered thin filament density changes slow fiber force and shortening velocity.

    PubMed

    Riley, D A; Bain, J L W; Romatowski, J G; Fitts, R H

    2005-02-01

    Single skinned fibers from soleus and adductor longus (AL) muscles of weight-bearing control rats and rats after 14-day hindlimb suspension unloading (HSU) were studied physiologically and ultrastructurally to investigate how slow fibers increase shortening velocity (V0) without fast myosin. We hypothesized that unloading and shortening of soleus during HSU reduces densities of thin filaments, generating wider myofilament separations that increase V0 and decrease specific tension (kN/m2). During HSU, plantarflexion shortened soleus working length 23%. AL length was unchanged. Both muscles atrophied as shown by reductions in fiber cross-sectional area. For AL, the 60% atrophy accounted fully for the 58% decrease in absolute tension (mN). In the soleus, the 67% decline in absolute tension resulted from 58% atrophy plus a 17% reduction in specific tension. Soleus fibers exhibited a 25% reduction in thin filaments, whereas there was no change in AL thin filament density. Loss of thin filaments is consistent with reduced cross bridge formation, explaining the fall in specific tension. V0 increased 27% in soleus but was unchanged in AL. The V0 of control and HSU fibers was inversely correlated (R = -0.83) with thin filament density and directly correlated (R = 0.78) with thick-to-thin filament spacing distance in a nonlinear fashion. These data indicate that reduction in thin filament density contributes to an increased V0 in slow fibers. Osmotically compacting myofilaments with 5% dextran returned density, spacing, and specific tension and slowed V0 to near-control levels and provided evidence for myofilament spacing modulating tension and V0.

  1. Constant Fiber Number During Skeletal Muscle Atrophy and Modified Arachidonate Metabolism During Hypertrophy

    NASA Technical Reports Server (NTRS)

    Templeton, G.

    1985-01-01

    A previously documented shift from Type I to IIA predominance of the soleus muscle during rat suspension was further investigated to determine if this shift was by selective reduction of a single fiber type, simultaneous reduction and formation of fibers with different fiber types, or a transformation of fiber type by individual fibers. By partial acid digestion and dissection, average total soleus fiber number was found to be 3022 + or - 80 (SE) and 3008 + or - 64 before and after four-week suspension (n=12). Another area of current research was based on previous studies which indicate that prostaglandins are biosynthesized by skeletal muscle and evoke protein synthesis and degradation.

  2. Constant Fiber Number During Skeletal Muscle Atrophy and Modified Arachidonate Metabolism During Hypertrophy

    NASA Technical Reports Server (NTRS)

    Templeton, G.

    1985-01-01

    A previously documented shift from Type I to IIA predominance of the soleus muscle during rat suspension was further investigated to determine if this shift was by selective reduction of a single fiber type, simultaneous reduction and formation of fibers with different fiber types, or a transformation of fiber type by individual fibers. By partial acid digestion and dissection, average total soleus fiber number was found to be 3022 + or - 80 (SE) and 3008 + or - 64 before and after four-week suspension (n=12). Another area of current research was based on previous studies which indicate that prostaglandins are biosynthesized by skeletal muscle and evoke protein synthesis and degradation.

  3. In vivo simultaneous evaluations of sarcomere imaging and muscle fiber tension.

    PubMed

    Wu, Yi-Ning; Ren, Yupeng; Tsai, Liang-Ching; Gao, Fan; Zhang, Li-Qun

    2016-03-21

    Muscle fiber tension and sarcomere length play critical roles in regulating muscle functions and adaptations under pathological conditions. However, methods are lacking to quantify these two variables simultaneously in vivo. A novel force microscope was developed with the unique capabilities of estimating muscle fiber tension and acquiring sarcomere images simultaneously in vivo. The force microscope consisting of a custom microscopic imaging system and a force sensor was used to quantify in vivo sarcomere length, muscle fiber tension and stress of the tibialis cranialis muscle at plantar-flexed and dorsi-flexed positions from 11 rat hind limbs. Results showed that sarcomere images and fiber tension could be measured together in vivo with significantly higher muscle fiber tension and stress and longer sarcomere length at the plantar-flexed position when compared to their counterparts at the dorsi-flexed position. The fiber tension estimated using the force microscope had close agreement with the direct measurements of the fiber tension. The present force microscope with simultaneous characterizations of fiber tension and sarcomere imaging provides us a useful in vivo tool to investigate the roles of muscle tension in regulating sarcomere and muscle fiber functions under physiological and pathological conditions.

  4. Fiber-type composition of the human jaw muscles--(part 2) role of hybrid fibers and factors responsible for inter-individual variation.

    PubMed

    Korfage, J A M; Koolstra, J H; Langenbach, G E J; van Eijden, T M G J

    2005-09-01

    This is the second of two articles about fiber-type composition of the human jaw muscles. It reviews the functional relationship of hybrid fibers and the adaptive properties of jaw-muscle fibers. In addition, to explain inter-individual variation in fiber-type composition, we discuss these adaptive properties in relation to environmental stimuli or perturbations. The fiber-type composition of the human jaw muscles is very different from that of limb and trunk muscles. Apart from the presence of the usual type I, IIA, and IIX myosin heavy-chains (MyHC), human jaw-muscle fibers contain MyHCs that are typical for developing or cardiac muscle. In addition, much more frequently than in limb and trunk muscles, jaw-muscle fibers are hybrid, i.e., they contain more than one type of MyHC isoform. Since these fibers have contractile properties that differ from those of pure fibers, this relatively large quantity of hybrid fibers provides a mechanism that produces a very fine gradation of force and movement. The presence of hybrid fibers might also reflect the adaptive capacity of jaw-muscle fibers. The capacity for adaptation also explains the observed large inter-individual variability in fiber-type composition. Besides local influences, like the amount of muscle activation and/or stretch, more general influences, like aging and gender, also play a role in the composition of fiber types.

  5. Laser Cutting of Carbon Fiber Reinforced Plastics - Investigation of Hazardous Process Emissions

    NASA Astrophysics Data System (ADS)

    Walter, Juergen; Hustedt, Michael; Staehr, Richard; Kaierle, Stefan; Jaeschke, Peter; Suttmann, Oliver; Overmeyer, Ludger

    Carbon fiber reinforced plastics (CFRP) show high potential for use in lightweight applications not only in aircraft design, but also in the automotive or wind energy industry. However, processing of CFRP is complex and expensive due to their outstanding mechanical properties. One possibility to manufacture CFRP structures flexibly at acceptable process speeds is high-power laser cutting. Though showing various advantages such as contactless energy transfer, this process is connected to potentially hazardous emission of respirable dust and organic gases. Moreover, the emitted particles may be fibrous, thus requiring particular attention. Here, a systematic analysis of the hazardous substances emitted during laser cutting of CFRP with thermoplastic and thermosetting matrix is presented. The objective is to evaluate emission rates for the total particulate and gaseous fractions as well as for different organic key components. Furthermore, the influence of the laser process conditions shall be assessed, and first proposals to handle the emissions adequately are made.

  6. Low myoplasmic Mg2+ potentiates calcium release during depolarization of frog skeletal muscle fibers

    PubMed Central

    1992-01-01

    The role of intracellular free magnesium concentration ([Mg2+]) in modulating calcium release from the sarcoplasmic reticulum (SR) was studied in voltage-clamped frog cut skeletal muscle fibers equilibrated with cut end solutions containing two calcium indicators, fura-2 and antipyrylazo III (AP III), and various concentrations of free Mg2+ (25 microM-1 mM) obtained by adding appropriate total amounts of ATP and magnesium to the solutions. Changes in AP III absorbance were used to monitor calcium transients, whereas fura-2 fluorescence was used to monitor resting calcium. The rate of release (Rrel) of calcium from the SR was calculated from the calcium transient and found to be increased in low internal [Mg2+]. After correcting for effects of calcium depletion from the SR and normalization to SR content, the mean values of the inactivatable and noninactivatable components of Rrel were increased by 163 and 46%, respectively, in low Mg2+. Independent of normalization to SR content, the ratio of inactivatable to noninactivatable components of Rrel was increased in low internal [Mg2+]. Both observations suggest that internal [Mg2+] preferentially modulates the inactivatable component of Rrel, which is thought to be due to calcium-induced calcium release from the SR. This could also explain the observation that, in low internal [Mg2+], the time to the peak of the calcium transient for a 5-ms depolarizing pulse was not very different from the time to the peak of the delta [Ca2+] for a 10- ms pulse of the same amplitude. Finally, in low internal [Mg2+], the calcium transient elicited by a short depolarizing pulse was in some cases clearly followed by a very slow rise of calcium after the end of the pulse. The observed effects of reduced [Mg2+] on calcium release are consistent with a removal of the inhibition that the normal 1 mM myoplasmic [Mg2+] exerts on calcium release in skeletal muscle fibers. PMID:1512555

  7. Can proinflammatory cytokine gene expression explain multifidus muscle fiber changes after an intervertebral disc lesion?

    PubMed

    Hodges, Paul W; James, Gregory; Blomster, Linda; Hall, Leanne; Schmid, Annina B; Shu, Cindy; Little, Chris; Melrose, James

    2014-06-01

    Longitudinal case-controlled animal study. To investigate the effect of an intervertebral disc (IVD) lesion on the proportion of slow, fast, and intermediate muscle fiber types in the multifidus muscle in sheep, and whether muscle fiber changes were paralleled by local gene expression of the proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1-β. Structure and behavior of the multifidus muscle change in acute and chronic back pain, but the mechanisms are surprisingly poorly understood and the link between structure and behavior is tenuous. Although changes in muscle fiber types have the potential to unify the observations, the effect of injury on muscle fiber distribution has not been adequately tested, and understanding of possible mechanisms is limited. The L1-L2, L3-L4, and L5-L6 IVDs of 11 castrated male sheep received anterolateral lesions. Six control sheep underwent no surgical procedures. Multifidus muscle tissue was harvested at L4 for muscle fiber analysis using immunohistochemistry and L2 for cytokine analysis with polymerase chain reaction for local gene expression of TNF-α and interleukin-1β. The proportion of slow muscle fibers in multifidus was significantly less in the lesioned animals both ipsilateral and contralateral to the IVD lesion. The greatest reduction in slow fibers was in the deep medial muscle region. A greater prevalence of intermediate fibers on the uninjured side implies a delayed fiber-type transformation on that side. TNF-α gene expression in multifidus was greater on both sides in the lesion animals than in the muscle of control animals. Interleukin-1β was increased only on the injured side. These data provide evidence of muscle fiber changes after induction of an IVD lesion and a parallel increase in TNF-α expression. Proinflammatory cytokine changes provide a novel mechanism to explain behavioral and structural changes in multifidus. N/A.

  8. Extensive Type II Muscle Fiber Atrophy in Elderly Female Hip Fracture Patients.

    PubMed

    Kramer, Irene Fleur; Snijders, Tim; Smeets, Joey S J; Leenders, Marika; van Kranenburg, Janneau; den Hoed, Marcel; Verdijk, Lex B; Poeze, Martijn; van Loon, Luc J C

    2017-10-01

    Sarcopenia, or the loss of muscle mass and strength, is known to increase the risk for falls and (hip) fractures in older people. The objective of this study was to assess the skeletal muscle fiber characteristics in elderly female hip fracture patients. Percutaneous needle biopsies were collected from the vastus lateralis muscle in 15 healthy young women (20 ± 0.4 years), 15 healthy elderly women (79 ± 1.7 years), and 15 elderly women with a fall-related hip fracture (82 ± 1.5 years). Immunohistochemical analyses were performed to assess Type I and Type II muscle fiber size, and myonuclear and satellite cell content. Type II muscle fiber size was significantly different between all groups (p < .05), with smaller Type II muscle fibers in the hip fracture patients (2,609 ± 185 µm2) compared with healthy elderly group (3,723 ± 322 µm2) and the largest Type II muscle fibers in the healthy young group (4,755 ± 335 µm2). Furthermore, Type I muscle fiber size was significantly lower in the hip fracture patients (4,684 ± 211 µm2) compared with the healthy elderly group (5,842 ± 316 µm2, p = .02). The number of myonuclei per Type II muscle fiber was significantly lower in the healthy elderly and hip fracture group compared with the healthy young group (p = .011 and p = .002, respectively). Muscle fiber satellite cell content did not differ between groups. Elderly female hip fracture patients show extensive Type II muscle fiber atrophy when compared with healthy young or age-matched healthy elderly controls. Type II muscle fiber atrophy is an important hallmark of sarcopenia and may predispose to falls and (hip) fractures in the older population.

  9. Microintegrating smooth muscle cells into a biodegradable, elastomeric fiber matrix.

    PubMed

    Stankus, John J; Guan, Jianjun; Fujimoto, Kazuro; Wagner, William R

    2006-02-01

    Electrospinning permits fabrication of biodegradable elastomers into matrices that can resemble the scale and mechanical behavior of the native extracellular matrix. However, achieving high-cellular density and infiltration with this technique remains challenging and time consuming. We have overcome this limitation by electrospraying vascular smooth muscle cells (SMCs) concurrently with electrospinning a biodegradable, elastomeric poly(ester urethane)urea (PEUU). Trypan blue staining revealed no significant decrease in cell viability from the fabrication process and electrosprayed SMCs spread and proliferated similar to control unprocessed SMCs. The resulting SMC microintegrated PEUU constructs were cultured under static conditions or transmural perfusion. Higher cell numbers resulted with perfusion culture with 131% and 98% more viable cells versus static culture at days 4 and 7 (p<0.05). Fluorescent imaging and hematoxylin and eosin staining further illustrated high cell densities integrated between the elastomeric fibers after perfusion culture. SMC microintegrated PEUU was strong, flexible and anisotropic with tensile strengths ranging from 2.0 to 6.5 MPa and breaking strains from 850 to 1,700% dependent on the material axis. The ability to microintegrate smooth muscle or other cell types into a biodegradable elastomer fiber matrix embodies a novel tissue engineering approach that could be applied to fabricate high cell density elastic tissue mimetics, blood vessels or other cardiovascular tissues.

  10. Microintegrating smooth muscle cells into a biodegradable, elastomeric fiber matrix

    PubMed Central

    Stankus, John J.; Guan, Jianjun; Fujimoto, Kazuro; Wagner, William R.

    2010-01-01

    Electrospinning permits fabrication of biodegradable elastomers into matrices that can resemble the scale and mechanical behavior of the native extracellular matrix. However, achieving high-cellular density and infiltration with this technique remains challenging and time consuming. We have overcome this limitation by electrospraying vascular smooth muscle cells (SMCs) concurrently with electrospinning a biodegradable, elastomeric poly(ester urethane)urea (PEUU). Trypan blue staining revealed no significant decrease in cell viability from the fabrication process and electrosprayed SMCs spread and proliferated similar to control unprocessed SMCs. The resulting SMC microintegrated PEUU constructs were cultured under static conditions or transmural perfusion. Higher cell numbers resulted with perfusion culture with 131% and 98% more viable cells versus static culture at days 4 and 7 (p < 0.05). Fluorescent imaging and hematoxylin and eosin staining further illustrated high cell densities integrated between the elastomeric fibers after perfusion culture. SMC microintegrated PEUU was strong, flexible and anisotropic with tensile strengths ranging from 2.0 to 6.5 MPa and breaking strains from 850 to 1700% dependent on the material axis. The ability to microintegrate smooth muscle or other cell types into a biodegradable elastomer fiber matrix embodies a novel tissue engineering approach that could be applied to fabricate high cell density elastic tissue mimetics, blood vessels or other cardiovascular tissues. PMID:16095685

  11. Dimensions of calcium release domains in frog skeletal muscle fibers

    NASA Astrophysics Data System (ADS)

    Vergara, Julio L.; DiFranco, Marino; Novo, David

    2001-07-01

    The spatiotemporal properties of the Ca2+ release process in skeletal muscle fibers were determined using an improved confocal spot detection system. Muscle fibers were loaded with the low affinity fluorescent Ca2+ indicator OGB-5N and localized action potential-induced fluorescence signals were recorded from consecutive locations separated by 200 nm within a single sarcomere. Three-dimensional reconstructions on the Ca2+ transients illustrate the existence of domains of increased fluorescence around Ca2+ release sites in the neighborhood of the T-tubules. We estimated the dimensions of these domains by drawing isochronal curves ((delta) F/F vs. spot position) and fitting Gaussian profiles to them. It was found that the earliest detectable full-width-at-half- maximum of these profiles was 0.77 +/- 0.25 micrometers and increased rapidly with time to 1.4 +/- 0.2 micrometers at their peak (18 degree(s)C). A brief, but statistically significant delay of 0.8 +/- 0.42ms was observed between the onset of the fluorescent transients at the Z- and M-lines. Our results are compatible with the possibility that, in response to AP stimulation, Ca2+ is not released exclusively from the junctional region of the sarcoplasmic reticulum, but from a broader expanse of the triadic region.

  12. [Action potentials of the fast and slow muscle fibers of the bog turtle Emys orbicularis].

    PubMed

    Lebedinskaia, I I; Nasledov, G A

    1977-01-01

    In skeletal muscles of the tortoise E. orbicularis, fast and slow muscle fibers were found which differ in the lipid content and electrophysiological properties. Fast fibers contain small amounts of lipid inclusions. In response to direct electrical stimulation they produce fast action potentials (AP) which are capable of rhythmic activity during prolonged depolarization. Slow fibers are rich in lipid inclusions. Their AP differs from that of fast fibers by slow onset, and decay, lower gradient of rise, lower amplitude and lower velocity of propagation. These fibers are not capable of rhythmic activity. The data obtained show that with respect to their morphological and physiological properties slow muscle fibers of the tortoise differ from tonic amphibian fibers, but exhibit the most similarity to slow avian fibers.

  13. Human muscle fiber type-specific insulin signaling: impact of obesity and type 2 diabetes.

    PubMed

    Albers, Peter H; Pedersen, Andreas J T; Birk, Jesper B; Kristensen, Dorte E; Vind, Birgitte F; Baba, Otto; Nøhr, Jane; Højlund, Kurt; Wojtaszewski, Jørgen F P

    2015-02-01

    Skeletal muscle is a heterogeneous tissue composed of different fiber types. Studies suggest that insulin-mediated glucose metabolism is different between muscle fiber types. We hypothesized that differences are due to fiber type-specific expression/regulation of insulin signaling elements and/or metabolic enzymes. Pools of type I and II fibers were prepared from biopsies of the vastus lateralis muscles from lean, obese, and type 2 diabetic subjects before and after a hyperinsulinemic-euglycemic clamp. Type I fibers compared with type II fibers have higher protein levels of the insulin receptor, GLUT4, hexokinase II, glycogen synthase (GS), and pyruvate dehydrogenase-E1α (PDH-E1α) and a lower protein content of Akt2, TBC1 domain family member 4 (TBC1D4), and TBC1D1. In type I fibers compared with type II fibers, the phosphorylation response to insulin was similar (TBC1D4, TBC1D1, and GS) or decreased (Akt and PDH-E1α). Phosphorylation responses to insulin adjusted for protein level were not different between fiber types. Independently of fiber type, insulin signaling was similar (TBC1D1, GS, and PDH-E1α) or decreased (Akt and TBC1D4) in muscle from patients with type 2 diabetes compared with lean and obese subjects. We conclude that human type I muscle fibers compared with type II fibers have a higher glucose-handling capacity but a similar sensitivity for phosphoregulation by insulin.

  14. Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth

    PubMed Central

    Farup, Jean; Rahbek, Stine Klejs; Riis, Simon; Vendelbo, Mikkel Holm; de Paoli, Frank

    2014-01-01

    Skeletal muscle satellite cells (SCs) are involved in remodeling and hypertrophy processes of skeletal muscle. However, little knowledge exists on extrinsic factors that influence the content of SCs in skeletal muscle. In a comparative human study, we investigated the muscle fiber type-specific association between emergence of satellite cells (SCs), muscle growth, and remodeling in response to 12 wk unilateral resistance training performed as eccentric (Ecc) or concentric (Conc) resistance training ± whey protein (Whey, 19.5 g protein + 19.5 g glucose) or placebo (Placebo, 39 g glucose) supplementation. Muscle biopsies (vastus lateralis) were analyzed for fiber type-specific SCs, myonuclei, and fiber cross-sectional area (CSA). Following training, SCs increased with Conc in both type I and type II fibers (P < 0.01) and exhibited a group difference from Ecc (P < 0.05), which did not increase. Myonuclei content in type I fibers increased in all groups (P < 0.01), while a specific accretion of myonuclei in type II fibers was observed in the Whey-Conc (P < 0.01) and Placebo-Ecc (P < 0.01) groups. Similarly, whereas type I fiber CSA increased independently of intervention (P < 0.001), type II fiber CSA increased exclusively with Whey-Conc (P < 0.01) and type II fiber hypertrophy correlated with whole muscle hypertrophy exclusively following Conc training (P < 0.01). In conclusion, isolated concentric knee extensor resistance training appears to constitute a stronger driver of SC content than eccentric resistance training while type II fiber hypertrophy was accentuated when combining concentric resistance training with whey protein supplementation. PMID:25103976

  15. Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth.

    PubMed

    Farup, Jean; Rahbek, Stine Klejs; Riis, Simon; Vendelbo, Mikkel Holm; Paoli, Frank de; Vissing, Kristian

    2014-10-15

    Skeletal muscle satellite cells (SCs) are involved in remodeling and hypertrophy processes of skeletal muscle. However, little knowledge exists on extrinsic factors that influence the content of SCs in skeletal muscle. In a comparative human study, we investigated the muscle fiber type-specific association between emergence of satellite cells (SCs), muscle growth, and remodeling in response to 12 wk unilateral resistance training performed as eccentric (Ecc) or concentric (Conc) resistance training ± whey protein (Whey, 19.5 g protein + 19.5 g glucose) or placebo (Placebo, 39 g glucose) supplementation. Muscle biopsies (vastus lateralis) were analyzed for fiber type-specific SCs, myonuclei, and fiber cross-sectional area (CSA). Following training, SCs increased with Conc in both type I and type II fibers (P < 0.01) and exhibited a group difference from Ecc (P < 0.05), which did not increase. Myonuclei content in type I fibers increased in all groups (P < 0.01), while a specific accretion of myonuclei in type II fibers was observed in the Whey-Conc (P < 0.01) and Placebo-Ecc (P < 0.01) groups. Similarly, whereas type I fiber CSA increased independently of intervention (P < 0.001), type II fiber CSA increased exclusively with Whey-Conc (P < 0.01) and type II fiber hypertrophy correlated with whole muscle hypertrophy exclusively following Conc training (P < 0.01). In conclusion, isolated concentric knee extensor resistance training appears to constitute a stronger driver of SC content than eccentric resistance training while type II fiber hypertrophy was accentuated when combining concentric resistance training with whey protein supplementation.

  16. Single muscle fiber adaptations to resistance training in old (>80 yr) men: evidence for limited skeletal muscle plasticity.

    PubMed

    Slivka, Dustin; Raue, Ulrika; Hollon, Chris; Minchev, Kiril; Trappe, Scott

    2008-07-01

    The purpose of this study was to investigate whole muscle and single muscle fiber adaptations in very old men in response to progressive resistance training (PRT). Six healthy independently living old men (82 +/- 1 yr; range 80-86 yr, 74 +/- 4 kg) resistance-trained the knee extensors (3 sets, 10 repetitions) at approximately 70% one repetition maximum 3 days/wk for 12 wk. Whole thigh muscle cross-sectional area (CSA) was assessed before and after PRT using computed tomography (CT). Muscle biopsies were obtained from the vastus lateralis before and after the PRT program. Isolated myosin heavy chain (MHC) I and IIa single muscle fibers (n = 267; 142 pre; 125 post) were studied for diameter, peak tension, shortening velocity, and power. An additional set of isolated single muscle fibers (n = 2,215; 1,202 pre; 1,013 post) was used to identify MHC distribution. One repetition maximum knee extensor strength increased (P < 0.05) 23 +/- 4 kg (56 +/- 4 to 79 +/- 7 kg; 41%). Muscle CSA increased (P < 0.05) 3 +/- 1 cm2 (120 +/- 7 to 123 +/- 7 cm2; 2.5%). Single muscle fiber contractile function and MHC distribution were unaltered with PRT. These data indicate limited muscle plasticity at the single-muscle fiber level with a resistance-training program among the very old. The minor increases in whole muscle CSA coupled with the static nature of the myocellular profile indicate that the strength gains were primarily neurological. These data contrast typical muscle responses to resistance training in young ( approximately 20 yr) and old ( approximately 70 yr) humans and indicate that the physiological regulation of muscle remodeling is adversely modified in the oldest old.

  17. How muscle fiber lengths and velocities affect muscle force generation as humans walk and run at different speeds

    PubMed Central

    Arnold, Edith M.; Hamner, Samuel R.; Seth, Ajay; Millard, Matthew; Delp, Scott L.

    2013-01-01

    SUMMARY The lengths and velocities of muscle fibers have a dramatic effect on muscle force generation. It is unknown, however, whether the lengths and velocities of lower limb muscle fibers substantially affect the ability of muscles to generate force during walking and running. We examined this issue by developing simulations of muscle–tendon dynamics to calculate the lengths and velocities of muscle fibers from electromyographic recordings of 11 lower limb muscles and kinematic measurements of the hip, knee and ankle made as five subjects walked at speeds of 1.0–1.75 m s−1 and ran at speeds of 2.0–5.0 m s−1. We analyzed the simulated fiber lengths, fiber velocities and forces to evaluate the influence of force–length and force–velocity properties on force generation at different walking and running speeds. The simulations revealed that force generation ability (i.e. the force generated per unit of activation) of eight of the 11 muscles was significantly affected by walking or running speed. Soleus force generation ability decreased with increasing walking speed, but the transition from walking to running increased the force generation ability by reducing fiber velocities. Our results demonstrate the influence of soleus muscle architecture on the walk-to-run transition and the effects of muscle–tendon compliance on the plantarflexors' ability to generate ankle moment and power. The study presents data that permit lower limb muscles to be studied in unprecedented detail by relating muscle fiber dynamics and force generation to the mechanical demands of walking and running. PMID:23470656

  18. Diagnostics, Modeling and Simulation: Three Keys Towards Mastering the Cutting Process with Fiber, Disk and Diode Lasers

    NASA Astrophysics Data System (ADS)

    Petring, Dirk; Molitor, Thomas; Schneider, Frank; Wolf, Norbert

    Even established laser processing technologies such as cutting are far away from being completely understood. Nevertheless, the progress in industrially available laser cutting systems and applications is quite respectable. Fiber and disk laser cutting changed from a debatable newcomer to a serious part of the business while the diode laser appears at the horizon as the next player to be reckoned. Understanding of the process and its performance are continually improved. This paper highlights results of research and development from the recent years. Some speculations, simulations, diagnostics and facts about the process, its properties and capabilities are assessed. Earlier and latest diagnostics and CALCut simulation results of laser beam cutting processes are presented.

  19. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training.

    PubMed

    McCall, G E; Byrnes, W C; Dickinson, A; Pattany, P M; Fleck, S J

    1996-11-01

    Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% (P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 +/- 2.7 to 13.3 +/- 2.6 cm2; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases (P < 0.05) in fiber areas for type I (from 4,196 +/- 859 to 4,617 +/- 1,116 microns2; n = 11) and II fibers (from 6,378 +/- 1,552 to 7,474 +/- 2,017 microns2; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 +/- 61.5 x 10(3) pretraining; 297.5 +/- 69.5 x 10(3) posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly (P < 0.05) for both type I (from 4.9 +/- 0.6 to 5.5 +/- 0.7; n = 10) and II fibers (from 5.1 +/- 0.8 to 6.2 +/- 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.

  20. Metabolic and morphometric profile of muscle fibers in chronic hemodialysis patients

    PubMed Central

    Fournier, Mario; Wang, Huiyuan; Storer, Thomas W.; Casaburi, Richard; Cohen, Arthur H.; Kopple, Joel D.

    2012-01-01

    Muscle weakness and effort intolerance are common in maintenance hemodialysis (MHD) patients. This study characterized morphometric, histochemical, and biochemical properties of limb muscle in MHD patients compared with controls (CTL) with similar age, gender, and ethnicity. Vastus lateralis muscle biopsies were obtained from 60 MHD patients, 1 day after dialysis, and from 21 CTL. Muscle fiber types and capillaries were identified immunohistochemically. Individual muscle fiber cross-sectional areas (CSA) were quantified. Individual fiber oxidative capacities were determined (microdensitometric assay) to measure succinate dehydrogenase (SDH) activity. Mean CSAs of type I, IIA, and IIX fibers were 33, 26, and 28% larger in MHD patients compared with CTL. SDH activities for type I, IIA, and IIX fibers were reduced by 29, 40, and 47%, respectively, in MHD. Capillary to fiber ratio was increased by 11% in MHD. The number of capillaries surrounding individual fiber types were also increased (type I: 9%; IIA: 10%; IIX: 23%) in MHD patients. However, capillary density (capillaries per unit muscle fiber area) was reduced by 34% in MHD patients, compared with CTL. Ultrastuctural analysis revealed swollen mitochondria with dense matrix in MHD patients. These results highlight impaired oxidative capacity and capillarity in MHD patients. This would be expected to impair energy production as well as substrate and oxygen delivery and exchange and contribute to exercise intolerance. The enlarged CSA of muscle fibers may, in part, be accounted for by edema. We speculate that these changes contribute to reduce limb strength in MHD patients by reducing specific force. PMID:22016372

  1. Muscle fiber characteristics of broiler breast fillets with the wooden breast condition.

    USDA-ARS?s Scientific Manuscript database

    Broiler breast fillets exhibiting the wooden breast condition are described as having a rigid feel and abnormal texture attributes; however, changes at the muscle fiber level in wooden breast fillets are not well understood. The objective of this study was to compare the histochemical muscle fiber ...

  2. Cut-off analysis of 19-cell Yb-doped double-cladding rod-type photonic crystal fibers.

    PubMed

    Poli, F; Coscelli, E; Alkeskjold, T T; Passaro, D; Cucinotta, A; Leick, L; Broeng, J; Selleri, S

    2011-05-09

    Yb-doped double-cladding large mode area rod-type photonic crystal fibers are a key component for power scaling in fiber laser systems. Recently, designs with 19-cell core defect, that is with 19 missing air-holes in the center of the photonic crystal cladding, have been proposed, with reported core diameter up to 100 μm. In this paper an analysis of the cut-off wavelength of the first high-order mode in such low-NA fibers is reported, accounting for different approaches for the definition of the cladding effective index. Results have shown that taking into account the finite fiber cross-section and considering the first cladding mode of the actual fiber is mandatory to obtain a correct estimate of the cut-off wavelength.

  3. The effect of resistance training combined with timed ingestion of protein on muscle fiber size and muscle strength.

    PubMed

    Andersen, Lars L; Tufekovic, Goran; Zebis, Mette K; Crameri, Regina M; Verlaan, George; Kjaer, Michael; Suetta, Charlotte; Magnusson, Peter; Aagaard, Per

    2005-02-01

    Acute muscle protein metabolism is modulated not only by resistance exercise but also by amino acids. However, less is known about the long-term hypertrophic effect of protein supplementation in combination with resistance training. The present study was designed to compare the effect of 14 weeks of resistance training combined with timed ingestion of isoenergetic protein vs carbohydrate supplementation on muscle fiber hypertrophy and mechanical muscle performance. Supplementation was administered before and immediately after each training bout and, in addition, in the morning on nontraining days. Muscle biopsy specimens were obtained from the vastus lateralis muscle and analyzed for muscle fiber cross-sectional area. Squat jump and countermovement jump were performed on a force platform to determine vertical jump height. Peak torque during slow (30 degrees s-1) and fast (240 degrees s-1) concentric and eccentric contractions of the knee extensor muscle was measured in an isokinetic dynamometer. After 14 weeks of resistance training, the protein group showed hypertrophy of type I (18% +/- 5%; P < .01) and type II (26% +/- 5%; P < .01) muscle fibers, whereas no change above baseline occurred in the carbohydrate group. Squat jump height increased only in the protein group, whereas countermovement jump height and peak torque during slow isokinetic muscle contraction increased similarly in both groups. In conclusion, a minor advantage of protein supplementation over carbohydrate supplementation during resistance training on mechanical muscle function was found. However, the present results may have relevance for individuals who are particularly interested in gaining muscle size.

  4. Connectin filaments in stretched skinned fibers of frog skeletal muscle

    PubMed Central

    1984-01-01

    Indirect immunofluorescence microscopy of highly stretched skinned frog semi-tendinous muscle fibers revealed that connectin, an elastic protein of muscle, is located in the gap between actin and myosin filaments and also in the region of myosin filaments except in their centers. Electron microscopic observations showed that there were easily recognizable filaments extending from the myosin filaments to the I band region and to Z lines in the myofibrils treated with antiserum against connectin. In thin sections prepared with tannic acid, very thin filaments connected myosin filaments to actin filaments. These filaments were also observed in myofibrils extracted with a modified Hasselbach-Schneider solution (0.6 M KCl, 0.1 M phosphate buffer, pH 6.5, 2 mM ATP, 2 mM MgCl2, and 1 mM EGTA) and with 0.6 M Kl. SDS PAGE revealed that connectin (also called titin) remained in extracted myofibrils. We suggest that connectin filaments play an important role in the generation of tension upon passive stretch. A scheme of the cytoskeletal structure of myofibrils of vertebrate skeletal muscle is presented on the basis of our present information of connectin and intermediate filaments. PMID:6384237

  5. Fiber-type differences in masseter muscle associated with different facial morphologies

    PubMed Central

    Rowlerson, Anthea; Raoul, Gwénaël; Daniel, Yousif; Close, John; Maurage, Claude-Alain; Ferri, Joel; Sciote, James J.

    2013-01-01

    Background The influence of muscle forces and associated physiologic behaviors on dental and skeletal development is well recognized but difficult to quantify because of the limited understanding of the interrelationships between physiologic and other mechanisms during growth. Methods The purpose of this study was to characterize fiber-type composition of masseter muscle in 44 subjects during surgical correction of malocclusion. Four fiber types were identified after immunostaining of biopsy sections with myosin heavy chain-specific antibodies, and the average fiber diameter and percentage of muscle occupancy of the fiber types were determined in each of 6 subject groups (Class II or Class III and open bite, normal bite, or deepbite). A 2 × 3 × 4 analysis of variance was used to determine significant differences between mean areas for fiber types, vertical relationships, and sagittal relationships. Results There were significant differences in percentage of occupancy of fiber types in masseter muscle in bite groups with different vertical dimensions. Type I fiber occupancy increased in open bites, and conversely, type II fiber occupancy increased in deepbites. The association between sagittal jaw relationships and mean fiber area was less strong, but, in the Class III group, the average fiber area was significantly different between the open bite, normal bite, and deepbite subjects. In the Class III subjects, type I and I/II hybrid fiber areas were greatly increased in subjects with deepbite. Conclusions Given the variation between subjects in fiber areas and fiber numbers, larger subject populations will be needed to demonstrate more significant associations between sagittal relationships and muscle composition. However, the robust influence of jaw-closing muscles on vertical dimension allowed us to conclude that vertical bite characteristics vary according to the fiber type composition of masseter muscle. PMID:15643413

  6. Effect of laser incidence angle on cut quality of 4 mm thick stainless steel sheet using fiber laser

    NASA Astrophysics Data System (ADS)

    Mullick, Suvradip; Agrawal, Arpit Kumar; Nath, Ashish Kumar

    2016-07-01

    Fiber laser has potential to outperform the more traditionally used CO2 lasers in sheet metal cutting applications due to its higher efficiency, better beam quality, reliability and ease of beam delivery through optical fiber. It has been however, reported that the higher focusability and shorter wavelength are advantageous for cutting thin metal sheets up to about 2 mm only. Better focasability results in narrower kerf-width, which leads to an earlier flow separation in the flow of assist gas within the kerf, resulting in uncontrolled material removal and poor cut quality. However, the advarse effect of tight focusability can be taken care by shifting the focal point position towards the bottom surface of work-piece, which results in a wider kerf size. This results in a more stable flow within the kerf for a longer depth, which improves the cut quality. It has also been reported that fiber laser has an unfavourable angle of incidence during cutting of thick sections, resulting in poor absorption at the metal surface. Therefore, the effect of laser incidence angle, along with other process parameters, viz. cutting speed and assist gas pressure on the cut quality of 4 mm thick steel sheet has been investigated. The change in laser incidence angle has been incorporated by inclining the beam towards and away from the cut front, and the quality factors are taken as the ratio of kerf width and the striation depth. Besides the absorption of laser radiation, beam inclination is also expected to influence the gas flow characteristics inside the kerf, shear force phenomena on the molten pool, laser beam coupling and laser power distribution at the inclined cut surface. Design of experiment has been used by implementing response surface methodology (RSM) to study the parametric dependence of cut quality, as well as to find out the optimum cut quality. An improvement in quality has been observed for both the inclination due to the combined effect of multiple phenomena.

  7. High Power Laser Cutting of Fiber Reinforced Thermoplastic Polymers with cw- and Pulsed Lasers

    NASA Astrophysics Data System (ADS)

    Schneider, F.; Wolf, N.; Petring, D.

    Glass fiber and carbon fiber reinforced polymers with thermoplastic matrix enable high volume production with short cycle times. Cutting and trimming operations in these production chains require the use of high average laser power for an efficient cutting speed, but employment of high laser power runs the risk to induce a wide heat affected zone (HAZ). This paper deals with investigations with cw and ns-pulsed CO2-laser radiation in the kilowatt range in single-pass and multiple-pass processes. Using multi-pass processing at high processing speeds of 100 m/min and above a reduced heat affected zone in the range of 100 μm to 200 μm could be achieved by the ns-pulsed radiation. With cw radiation at the same average power of 1 kW however, the HAZ was 300-400 μm. Also employing ns-pulses in the kW-range average power leads to heat accumulation in the material. Small HAZ were obtained with sufficient break times between subsequent passes.

  8. Muscle fiber-type changes induced by botulinum toxin injection in the rat larynx.

    PubMed

    Inagi, K; Connor, N P; Schultz, E; Ford, C N; Cook, C H; Heisey, D M

    1999-06-01

    This study examined muscle fiber-type alterations after single or multiple botulinum toxin (BT) injections to better understand possible morphologic changes induced by therapeutic BT injections in patients with spasmodic dysphonia. Muscle fiber staining was accomplished in rat intrinsic laryngeal muscles with antibodies to specific myosin heavy chains. Results indicated that the typical baseline distributions of type II muscle fibers (ie, types IIa, IIb, IIx, and IIL) were altered by BT injection, while no change was observed in type I fibers. Embryonic fibers were observed only along the needle insertion site at 7 days post BT injection. Although inferences from these animal data to human neuromuscular function must be made with caution, our findings provide insight into the possible cellular and molecular changes characterizing BT-injected muscles.

  9. Control of fresh meat quality through manipulation of muscle fiber characteristics.

    PubMed

    Joo, S T; Kim, G D; Hwang, Y H; Ryu, Y C

    2013-12-01

    Variations of fresh meat quality exist because the quality traits are affected by various intrinsic and extrinsic factors. Because the meat quality is basically dependent on muscle fiber characteristics, numerous studies have reported the relationship between quality traits and fiber characteristics. Despite intensive research, the relationship is yet to be fully established, however, the present knowledge suggests several potential ways to manipulate muscle fiber characteristics to improve meat quality. The present paper reviews the definition of fresh meat quality, meat quality traits and variations of meat quality. Also, this review presents recent knowledge underlying the relationship between fresh meat quality traits and muscle fiber characteristics. Finally, the present work proposes several potential factors including breed, genotype, sex, hormone, growth performance, diet, muscle location, exercise and ambient temperature that can be used to manipulate muscle fiber characteristics and subsequently meat quality in animals.

  10. Skeletal muscle fiber, nerve, and blood vessel breakdown in space-flown rats

    NASA Technical Reports Server (NTRS)

    Riley, D. A.; Ilyina-Kakueva, E. I.; Ellis, S.; Bain, J. L.; Slocum, G. R.; Sedlak, F. R.

    1990-01-01

    Histochemical and ultrastructural analyses were performed postflight on hind limb skeletal muscles of rats orbited for 12.5 days aboard the unmanned Cosmos 1887 biosatellite and returned to Earth 2 days before sacrifice. The antigravity adductor longus (AL), soleus, and plantaris muscles atrophied more than the non-weight-bearing extensor digitorum longus, and slow muscle fibers were more atrophic than fast fibers. Muscle fiber segmental necrosis occurred selectively in the AL and soleus muscles; primarily, macrophages and neutrophils infiltrated and phagocytosed cellular debris. Granule-rich mast cells were diminished in flight AL muscles compared with controls, indicating the mast cell secretion contributed to interstitial tissue edema. Increased ubiquitination of disrupted myofibrils implicated ubiquitin in myofilament degradation. Mitochondrial content and succinic dehydrogenase activity were normal, except for subsarcolemmal decreases. Myofibrillar ATPase activity of flight AL muscle fibers shifted toward the fast type. Absence of capillaries and extravasation of red blood cells indicated failed microcirculation. Muscle fiber regeneration from activated satellite cells was detected. About 17% of the flight AL end plates exhibited total or partial denervation. Thus, skeletal muscle weakness associated with spaceflight can result from muscle fiber atrophy and segmental necrosis, partial motor denervation, and disruption of the microcirculation.

  11. Skeletal muscle fiber, nerve, and blood vessel breakdown in space-flown rats

    NASA Technical Reports Server (NTRS)

    Riley, D. A.; Ilyina-Kakueva, E. I.; Ellis, S.; Bain, J. L.; Slocum, G. R.; Sedlak, F. R.

    1990-01-01

    Histochemical and ultrastructural analyses were performed postflight on hind limb skeletal muscles of rats orbited for 12.5 days aboard the unmanned Cosmos 1887 biosatellite and returned to Earth 2 days before sacrifice. The antigravity adductor longus (AL), soleus, and plantaris muscles atrophied more than the non-weight-bearing extensor digitorum longus, and slow muscle fibers were more atrophic than fast fibers. Muscle fiber segmental necrosis occurred selectively in the AL and soleus muscles; primarily, macrophages and neutrophils infiltrated and phagocytosed cellular debris. Granule-rich mast cells were diminished in flight AL muscles compared with controls, indicating the mast cell secretion contributed to interstitial tissue edema. Increased ubiquitination of disrupted myofibrils implicated ubiquitin in myofilament degradation. Mitochondrial content and succinic dehydrogenase activity were normal, except for subsarcolemmal decreases. Myofibrillar ATPase activity of flight AL muscle fibers shifted toward the fast type. Absence of capillaries and extravasation of red blood cells indicated failed microcirculation. Muscle fiber regeneration from activated satellite cells was detected. About 17% of the flight AL end plates exhibited total or partial denervation. Thus, skeletal muscle weakness associated with spaceflight can result from muscle fiber atrophy and segmental necrosis, partial motor denervation, and disruption of the microcirculation.

  12. Contractile properties of rat, rhesus monkey, and human type I muscle fibers

    NASA Technical Reports Server (NTRS)

    Widrick, J. J.; Romatowski, J. G.; Karhanek, M.; Fitts, R. H.

    1997-01-01

    It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

  13. Contractile properties of rat, rhesus monkey, and human type I muscle fibers

    NASA Technical Reports Server (NTRS)

    Widrick, J. J.; Romatowski, J. G.; Karhanek, M.; Fitts, R. H.

    1997-01-01

    It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

  14. [Comparison of force and shortening velocity in fast and slow rabbit muscle fibers at different temperatures].

    PubMed

    Kochubeĭ, P V; Bershitskiĭ, S Iu

    2014-01-01

    The temperature dependence of force, maximal shortening velocity and power of maximally activated single permeabilized fibers from fast and slow muscles of the rabbit were recorded in a temperature range from 10 to 35 degrees C with 5 degrees C step. It was found that temperature dependence of force of both types of fibers is identical. Averaged maximal shortening velocity in the slow fibers, unlike the fast fibers, had no statistically significant temperature dependence that is not in agreement with the data obtained on intact rat muscle fibers and in an in vitro motility assay. However maximal shortening velocity in each individual slow fiber did depend on temperature. The temperature dependence of power of the slow fibers was lower than that of the fast ones. Because of large data scattering the average temperature dependence of power of the slow fibers was significantly lower than that in individual slow fibers.

  15. Non-uniform Distribution of Strain during Stretch of Relaxed Skeletal Muscle Fibers from Rat Soleus Muscle

    PubMed Central

    Palmer, Mark L.; Claflin, Dennis R.; Faulkner, John A.; Panchangam, Appaji

    2011-01-01

    Tension and regional average sarcomere length (Ls) behavior were examined during repeated stretches of single, permeabilized, relaxed muscle fibers isolated from the soleus muscles of rats. We tested the hypothesis that during stretches of single permeabilized fibers, the global fiber strain is distributed non-uniformly along the length of a relaxed fiber in a repeatable pattern. Each fiber was subjected to eight constant-velocity stretch and release cycles with a strain of 32% and strain rate of 54% s−1. Stretch-release cycles were separated by a 4.5 minute interval. Throughout each stretch-release cycle, sarcomere lengths were measured using a laser diffraction technique in which 20 contiguous sectors along the entire length of a fiber segment were scanned within 2 ms. The results revealed that: (1) the imposed length change was not distributed uniformly along the fiber, (2) the first stretch-release cycle differed from subsequent cycles in passive tension and in the distribution of global fiber strain, and (3) a characteristic “signature” for the Ls response emerged after cycle 3. The findings support the conclusions that longitudinal heterogeneity exists in the passive stiffness of individual muscle fibers and that preconditioning of fibers with stretch-release cycles produces a stable pattern of sarcomere strains. PMID:21710358

  16. Effects of polysaccharide-based edible coatings enriched with dietary fiber on quality attributes of fresh-cut apples.

    PubMed

    Moreira, Maria R; Cassani, Lucía; Martín-Belloso, Olga; Soliva-Fortuny, Robert

    2015-12-01

    Little information is available regarding the incorporation of dietary fiber into edible films and coatings. In this work, apple fiber and inulin were incorporated into polysaccharide-based (alginate, pectine and gellan gum) edible coating formulations and their effects on the quality attributes of fresh-cut apples were evaluated. Antioxidant properties, color, firmness, sensory quality and microbial growth of fresh-cut apple were studied during 16 days of storage at 4 °C. Results show that dietary fiber extracts incorporated to gellan gum, pectin and alginate-based coatings together with calcium chloride and ascorbic acid successfully maintained the firmness and color of coated fresh-cut apples in comparison with uncoated control samples, which presented severe texture softening and browning. The firmness of apple pieces coated with polysaccharide-based coating formulations incorporating apple fiber doubled, and sometimes tripled, that of uncoated samples. Any of the assayed coatings exhibited a positive effect on the sensory properties of fresh-cut apples. The incorporation of apple fiber, together with the use of ascorbic acid, contributed to keep the antioxidant potential of the fruit at least during the first week of storage. Furthermore, gellan gum coatings had a marked effect in reducing mesophilic and psychrophilic counts on fresh-cut apples throughout storage regardless the addition of dietary fibers. The results achieved demonstrate the feasibility of the addition of dietary fiber to edible coating formulations for increasing the nutritional value of fresh-cut apples without compromising their fresh-like quality attributes.

  17. Work production and work absorption in muscle strips from vertebrate cardiac and insect flight muscle fibers.

    PubMed

    Maughan, D; Moore, J; Vigoreaux, J; Barnes, B; Mulieri, L A

    1998-01-01

    Stretch activation, which underlies the ability of all striated muscles to do oscillatory work, is a prominent feature of both insect flight and vertebrate cardiac muscle. We have examined and compared work-producing and work-absorbing processes in skinned fibers of Drosophila flight muscle, mouse papillary muscle, and human ventricular strips. Using small amplitude sinusoidal length perturbation analysis, we distinguished viscoelastic properties attributable to crossbridge processes from those attributable to other structures of the sarcomere. Work-producing and work-absorbing processes were identified in Ca(2+)-activated fibers by deconvolving complex stiffness data. An 'active' work-producing process ("B"), attributed to crossbridge action, was identified, as were two work-absorbing processes, one attributable to crossbridge action ("C") and the other primarily to viscoelastic properties of parallel passive structures ("A"). At maximal Ca(2+)-activation (pCa 5, 27 degrees C), maximum net power output (processes A, B and C combined) occurs at a frequency of: 1.3 +/- 0.1 Hz for human, 10.9 +/- 2.2 Hz for mouse, and 226 +/- 9 Hz for fly, comparable to the resting heart rate of the human (1 Hz, 37 degrees C) and mouse (10 Hz, 37 degrees C) and to the wing beat frequency of the fruit fly (200 Hz, 22 degrees C). Process B maximal work production per myosin head is 7-11 x 10(-21) J per perturbation cycle, equivalent to approximately 2 kT of energy. Process C maximal work absorption is about the same magnitude. The equivalence suggests the possibility that a thermal ratchet type mechanism operates during small amplitude length perturbations. We speculate that there may be a survival advantage in having a mechanical energy dissipater (i.e., the C process) at work in muscles if they can be injuriously stretched by the system in which they operate.

  18. Ontogenetic changes in skeletal muscle fiber type, fiber diameter and myoglobin concentration in the Northern elephant seal (Mirounga angustirostris).

    PubMed

    Moore, Colby D; Crocker, Daniel E; Fahlman, Andreas; Moore, Michael J; Willoughby, Darryn S; Robbins, Kathleen A; Kanatous, Shane B; Trumble, Stephen J

    2014-01-01

    Northern elephant seals (Mirounga angustirostris) (NES) are known to be deep, long-duration divers and to sustain long-repeated patterns of breath-hold, or apnea. Some phocid dives remain within the bounds of aerobic metabolism, accompanied by physiological responses inducing lung compression, bradycardia, and peripheral vasoconstriction. Current data suggest an absence of type IIb fibers in pinniped locomotory musculature. To date, no fiber type data exist for NES, a consummate deep diver. In this study, NES were biopsied in the wild. Ontogenetic changes in skeletal muscle were revealed through succinate dehydrogenase (SDH) based fiber typing. Results indicated a predominance of uniformly shaped, large type I fibers and elevated myoglobin (Mb) concentrations in the longissimus dorsi (LD) muscle of adults. No type II muscle fibers were detected in any adult sampled. This was in contrast to the juvenile animals that demonstrated type II myosin in Western Blot analysis, indicative of an ontogenetic change in skeletal muscle with maturation. These data support previous hypotheses that the absence of type II fibers indicates reliance on aerobic metabolism during dives, as well as a depressed metabolic rate and low energy locomotion. We also suggest that the lack of type IIb fibers (adults) may provide a protection against ischemia reperfusion (IR) injury in vasoconstricted peripheral skeletal muscle.

  19. Ontogenetic changes in skeletal muscle fiber type, fiber diameter and myoglobin concentration in the Northern elephant seal (Mirounga angustirostris)

    PubMed Central

    Moore, Colby D.; Crocker, Daniel E.; Fahlman, Andreas; Moore, Michael J.; Willoughby, Darryn S.; Robbins, Kathleen A.; Kanatous, Shane B.; Trumble, Stephen J.

    2014-01-01

    Northern elephant seals (Mirounga angustirostris) (NES) are known to be deep, long-duration divers and to sustain long-repeated patterns of breath-hold, or apnea. Some phocid dives remain within the bounds of aerobic metabolism, accompanied by physiological responses inducing lung compression, bradycardia, and peripheral vasoconstriction. Current data suggest an absence of type IIb fibers in pinniped locomotory musculature. To date, no fiber type data exist for NES, a consummate deep diver. In this study, NES were biopsied in the wild. Ontogenetic changes in skeletal muscle were revealed through succinate dehydrogenase (SDH) based fiber typing. Results indicated a predominance of uniformly shaped, large type I fibers and elevated myoglobin (Mb) concentrations in the longissimus dorsi (LD) muscle of adults. No type II muscle fibers were detected in any adult sampled. This was in contrast to the juvenile animals that demonstrated type II myosin in Western Blot analysis, indicative of an ontogenetic change in skeletal muscle with maturation. These data support previous hypotheses that the absence of type II fibers indicates reliance on aerobic metabolism during dives, as well as a depressed metabolic rate and low energy locomotion. We also suggest that the lack of type IIb fibers (adults) may provide a protection against ischemia reperfusion (IR) injury in vasoconstricted peripheral skeletal muscle. PMID:24959151

  20. Aging alters contractile properties and fiber morphology in pigeon skeletal muscle.

    PubMed

    Pistilli, Emidio E; Alway, Stephen E; Hollander, John M; Wimsatt, Jeffrey H

    2014-12-01

    In this study, we tested the hypothesis that skeletal muscle from pigeons would display age-related alterations in isometric force and contractile parameters as well as a shift of the single muscle fiber cross-sectional area (CSA) distribution toward smaller fiber sizes. Maximal force output, twitch contraction durations and the force-frequency relationship were determined in tensor propatagialis pars biceps muscle from young 3-year-old pigeons, middle-aged 18-year-old pigeons, and aged 30-year-old pigeons. The fiber CSA distribution was determined by planimetry from muscle sections stained with hematoxylin and eosin. Maximal force output of twitch and tetanic contractions was greatest in muscles from young pigeons, while the time to peak force of twitch contractions was longest in muscles from aged pigeons. There were no changes in the force-frequency relationship between the age groups. Interestingly, the fiber CSA distribution in aged muscles revealed a greater number of larger sized muscle fibers, which was verified visually in histological images. Middle-aged and aged muscles also displayed a greater amount of slow myosin containing muscle fibers. These data demonstrate that muscles from middle-aged and aged pigeons are susceptible to alterations in contractile properties that are consistent with aging, including lower force production and longer contraction durations. These functional changes were supported by the appearance of slow myosin containing muscle fibers in muscles from middle-aged and aged pigeons. Therefore, the pigeon may represent an appropriate animal model for the study of aging-related alterations in skeletal muscle function and structure.

  1. Skeletal muscle fiber types in the ghost crab, Ocypode quadrata: implications for running performance.

    PubMed

    Perry, Michael J; Tait, Jennifer; Hu, John; White, Scott C; Medler, Scott

    2009-03-01

    Ghost crabs possess rapid running capabilities, which make them good candidates for comparing invertebrate exercise physiology with that of more extensively studied vertebrates. While a number of studies have examined various aspects of running physiology and biomechanics in terrestrial crabs, none to date have defined the basic skeletal muscle fiber types that power locomotion. In the current study, we investigated skeletal muscle fiber types comprising the extensor and flexor carpopodite muscles in relation to running performance in the ghost crab. We used kinematic analyses to determine stride frequency and muscle shortening velocity and found that both parameters are similar to those of comparably sized mammals but slower than those observed in running lizards. Using several complementary methods, we found that the muscles are divided into two primary fiber types: those of the proximal and distal regions possess long sarcomeres (6.2+/-2.3 microm) observed in crustacean slow fibers and have characteristics of aerobic fibers whereas those of the muscle mid-region have short sarcomeres (3.5+/-0.4 microm) characteristic of fast fibers and appear to be glycolytic. Each fiber type is characterized by several different myofibrillar protein isoforms including multiple isoforms of myosin heavy chain (MHC), troponin I (TnI), troponin T (TnT) and a crustacean fast muscle protein, P75. Three different isoforms of MHC are differentially expressed in the muscles, with fibers of the mid-region always co-expressing two isoforms at a 1:1 ratio within single fibers. Based on our analyses, we propose that these muscles are functionally divided into a two-geared system, with the aerobic fibers used for slow sustained activities and the glycolytic mid-region fibers being reserved for explosive sprints. Finally, we identified subtle differences in myofibrillar isoform expression correlated with crab body size, which changes by several orders of magnitude during an animal's lifetime.

  2. Eccentric exercise increases satellite cell content in type II muscle fibers.

    PubMed

    Cermak, Naomi M; Snijders, Tim; McKay, Bryon R; Parise, Gianni; Verdijk, Lex B; Tarnopolsky, Mark A; Gibala, Martin J; Van Loon, Luc J C

    2013-02-01

    Satellite cells (SCs) are of key importance in skeletal muscle tissue growth, repair, and regeneration. A single bout of high-force eccentric exercise has been demonstrated to increase mixed muscle SC content after 1-7 d of postexercise recovery. However, little is known about fiber type-specific changes in SC content and their activation status within 24 h of postexercise recovery. Nine recreationally active young men (23 ± 1 yr) performed 300 eccentric actions of the knee extensors on an isokinetic dynamometer. Skeletal muscle biopsies from the vastus lateralis were collected preexercise and 24 h postexercise. Muscle fiber type-specific SC content and the number of activated SCs were determined by immunohistochemical analyses. There was no difference between Type I and Type II muscle fiber SC content before exercise. SC content significantly increased 24 h postexercise in Type II muscle fibers (from 0.085 ± 0.012 to 0.133 ± 0.016 SCs per fiber, respectively; P < 0.05), whereas there was no change in Type I fibers. In accordance, activation status increased from preexercise to 24 h postexercise as demonstrated by the increase in the number of DLK1+ SCs in Type II muscle fibers (from 0.027 ± 0.008 to 0.070 ± 0.017 SCs per muscle fiber P < 0.05). Although no significant changes were observed in the number of Ki-67+ SCs, we did observe an increase in the number of proliferating cell nuclear antigen-positive SCs after 24 h of postexercise recovery. A single bout of high-force eccentric exercise increases muscle fiber SC content and activation status in Type II but not Type I muscle fibers.

  3. Changes in skeletal muscle biochemistry and histology relative to fiber type in rats with heart failure

    NASA Technical Reports Server (NTRS)

    Delp, M. D.; Duan, C.; Mattson, J. P.; Musch, T. I.

    1997-01-01

    One of the primary consequences of left ventricular dysfunction (LVD) after myocardial infarction is a decrement in exercise capacity. Several factors have been hypothesized to account for this decrement, including alterations in skeletal muscle metabolism and aerobic capacity. The purpose of this study was to determine whether LVD-induced alterations in skeletal muscle enzyme activities, fiber composition, and fiber size are 1) generalized in muscles or specific to muscles composed primarily of a given fiber type and 2) related to the severity of the LVD. Female Wistar rats were divided into three groups: sham-operated controls (n = 13) and rats with moderate (n = 10) and severe (n = 7) LVD. LVD was surgically induced by ligating the left main coronary artery and resulted in elevations (P < 0.05) in left ventricular end-diastolic pressure (sham, 5 +/- 1 mmHg; moderate LVD, 11 +/- 1 mmHg; severe LVD, 25 +/- 1 mmHg). Moderate LVD decreased the activities of phosphofructokinase (PFK) and citrate synthase in one muscle composed of type IIB fibers but did not modify fiber composition or size of any muscle studied. However, severe LVD diminished the activity of enzymes involved in terminal and beta-oxidation in muscles composed primarily of type I fibers, type IIA fibers, and type IIB fibers. In addition, severe LVD induced a reduction in the activity of PFK in type IIB muscle, a 10% reduction in the percentage of type IID/X fibers, and a corresponding increase in the portion of type IIB fibers. Atrophy of type I fibers, type IIA fibers, and/or type IIB fibers occurred in soleus and plantaris muscles of rats with severe LVD. These data indicate that rats with severe LVD after myocardial infarction exhibit 1) decrements in mitochondrial enzyme activities independent of muscle fiber composition, 2) a reduction in PFK activity in type IIB muscle, 3) transformation of type IID/X to type IIB fibers, and 4) atrophy of type I, IIA, and IIB fibers.

  4. Changes in skeletal muscle biochemistry and histology relative to fiber type in rats with heart failure

    NASA Technical Reports Server (NTRS)

    Delp, M. D.; Duan, C.; Mattson, J. P.; Musch, T. I.

    1997-01-01

    One of the primary consequences of left ventricular dysfunction (LVD) after myocardial infarction is a decrement in exercise capacity. Several factors have been hypothesized to account for this decrement, including alterations in skeletal muscle metabolism and aerobic capacity. The purpose of this study was to determine whether LVD-induced alterations in skeletal muscle enzyme activities, fiber composition, and fiber size are 1) generalized in muscles or specific to muscles composed primarily of a given fiber type and 2) related to the severity of the LVD. Female Wistar rats were divided into three groups: sham-operated controls (n = 13) and rats with moderate (n = 10) and severe (n = 7) LVD. LVD was surgically induced by ligating the left main coronary artery and resulted in elevations (P < 0.05) in left ventricular end-diastolic pressure (sham, 5 +/- 1 mmHg; moderate LVD, 11 +/- 1 mmHg; severe LVD, 25 +/- 1 mmHg). Moderate LVD decreased the activities of phosphofructokinase (PFK) and citrate synthase in one muscle composed of type IIB fibers but did not modify fiber composition or size of any muscle studied. However, severe LVD diminished the activity of enzymes involved in terminal and beta-oxidation in muscles composed primarily of type I fibers, type IIA fibers, and type IIB fibers. In addition, severe LVD induced a reduction in the activity of PFK in type IIB muscle, a 10% reduction in the percentage of type IID/X fibers, and a corresponding increase in the portion of type IIB fibers. Atrophy of type I fibers, type IIA fibers, and/or type IIB fibers occurred in soleus and plantaris muscles of rats with severe LVD. These data indicate that rats with severe LVD after myocardial infarction exhibit 1) decrements in mitochondrial enzyme activities independent of muscle fiber composition, 2) a reduction in PFK activity in type IIB muscle, 3) transformation of type IID/X to type IIB fibers, and 4) atrophy of type I, IIA, and IIB fibers.

  5. Early changes in muscle atrophy and muscle fiber type conversion after spinal cord transection and peripheral nerve transection in rats.

    PubMed

    Higashino, Kosaku; Matsuura, Tetsuya; Suganuma, Katsuyoshi; Yukata, Kiminori; Nishisho, Toshihiko; Yasui, Natsuo

    2013-05-20

    Spinal cord transection and peripheral nerve transection cause muscle atrophy and muscle fiber type conversion. It is still unknown how spinal cord transection and peripheral nerve transection each affect the differentiation of muscle fiber type conversion mechanism and muscle atrophy. The aim of our study was to evaluate the difference of muscle weight change, muscle fiber type conversion, and Peroxisome proliferator-activated receptor-γ coactivatior-1α (PGC-1α) expression brought about by spinal cord transection and by peripheral nerve transection. Twenty-four Wistar rats underwent surgery, the control rats underwent a laminectomy; the spinal cord injury group underwent a spinal cord transection; the denervation group underwent a sciatic nerve transection. The rats were harvested of the soleus muscle and the TA muscle at 0 week, 1 week and 2 weeks after surgery. Histological examination was assessed using hematoxylin and eosin (H&E) staining and immunofluorescent staing. Western blot was performed with 3 groups. Both sciatic nerve transection and spinal cord transection caused muscle atrophy with the effect being more severe after sciatic nerve transection. Spinal cord transection caused a reduction in the expression of both sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection produced an increase in expression of sMHC protein and PGC-1α protein in the soleus muscle. The results of the expression of PGC-1α were expected in other words muscle atrophy after sciatic nerve transection is less than after spinal cord transection, however muscle atrophy after sciatic nerve transection was more severe than after spinal cord transection. In the conclusion, spinal cord transection diminished the expression of sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection enhanced the expression of sMHC protein and PGC-1α protein in the soleus muscle.

  6. Early changes in muscle atrophy and muscle fiber type conversion after spinal cord transection and peripheral nerve transection in rats

    PubMed Central

    2013-01-01

    Background Spinal cord transection and peripheral nerve transection cause muscle atrophy and muscle fiber type conversion. It is still unknown how spinal cord transection and peripheral nerve transection each affect the differentiation of muscle fiber type conversion mechanism and muscle atrophy. The aim of our study was to evaluate the difference of muscle weight change, muscle fiber type conversion, and Peroxisome proliferator-activated receptor-γ coactivatior-1α (PGC-1α) expression brought about by spinal cord transection and by peripheral nerve transection. Methods Twenty-four Wistar rats underwent surgery, the control rats underwent a laminectomy; the spinal cord injury group underwent a spinal cord transection; the denervation group underwent a sciatic nerve transection. The rats were harvested of the soleus muscle and the TA muscle at 0 week, 1 week and 2 weeks after surgery. Histological examination was assessed using hematoxylin and eosin (H&E) staining and immunofluorescent staing. Western blot was performed with 3 groups. Results Both sciatic nerve transection and spinal cord transection caused muscle atrophy with the effect being more severe after sciatic nerve transection. Spinal cord transection caused a reduction in the expression of both sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection produced an increase in expression of sMHC protein and PGC-1α protein in the soleus muscle. The results of the expression of PGC-1α were expected in other words muscle atrophy after sciatic nerve transection is less than after spinal cord transection, however muscle atrophy after sciatic nerve transection was more severe than after spinal cord transection. Conclusion In the conclusion, spinal cord transection diminished the expression of sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection enhanced the expression of sMHC protein and PGC-1α protein in the soleus

  7. Contractile properties of single permeabilized muscle fibers from congenital cleft palates and normal palates of Spanish goats

    USDA-ARS?s Scientific Manuscript database

    A goat model in which cleft palate is induced by the plant alkaloid, anabasine was used to determine muscle fiber integrity of the levator veli palatine muscle. It was determined that the muscle fibers of the cleft palate-induced goats were primarily of the type 2 (fast fibers) which fatigue easil...

  8. Immobilization induces carbonic anhydrase III in type II fibers of rat skeletal muscle.

    PubMed

    Laurila, A L; Jeffery, S; Savolainen, J; Takala, T E; Carter, N D; Väänänen, H K

    1991-05-01

    The amount and fiber distribution of carbonic anhydrase III (CA III), a major soluble protein in Type I muscle fibers, were studied during cast immobilization of rat hindlimb with the ankle in plantar or dorsiflexion. The concentration of CA III increased two- (p less than 0.05) and three- (p less than 0.01) fold in the shortened and lengthened tibialis anterior muscle during a 3-weeks immobilization period, respectively. After 6 weeks of immobilization the increase was even greater (p less than 0.001). Concomitantly, the number of CA III positive fibers in the lengthened muscle increased so that almost all fibers were positive. In the soleus muscle no significant change in the CA III concentration was seen. On the basis of actomyosin ATPase staining, the transition of Type IIb fibers towards Type IIa occurred in the tibialis anterior muscle, whereas in the soleus muscle a transformation of Type I fibers towards Type IIa fibers occurred. Therefore, the increase in the muscle CA III concentration seems to be associated with a cell transformation of the muscle towards a more oxidative type.

  9. Ablation of Protein Kinase CK2β in Skeletal Muscle Fibers Interferes with Their Oxidative Capacity

    PubMed Central

    Eiber, Nane; Simeone, Luca; Hashemolhosseini, Said

    2017-01-01

    The tetrameric protein kinase CK2 was identified playing a role at neuromuscular junctions by studying CK2β-deficient muscle fibers in mice, and in cultured immortalized C2C12 muscle cells after individual knockdown of CK2α and CK2β subunits. In muscle cells, CK2 activity appeared to be at least required for regular aggregation of nicotinic acetylcholine receptors, which serves as a hallmark for the presence of a postsynaptic apparatus. Here, we set out to determine whether any other feature accompanies CK2β-deficient muscle fibers. Hind limb muscles gastrocnemius, plantaris, and soleus of adult wildtype and CK2β-deficient mice were dissected, cross-sectioned, and stained histochemically by Gomori trichrome and for nicotinamide adenine dinucleotide (NADH) dehydrogenase and succinate dehydrogenase (SDH) enzymatic activities. A reduction of oxidative enzymatic activity was determined for CK2β-deficient muscle fibers in comparison with wildtype controls. Importantly, the CK2β-deficient fibers, muscle fibers that typically exhibit high NADH dehydrogenase and SDH activities, like slow-type fibers, showed a marked reduction in these activities. Altogether, our data indicate additional impairments in the absence of CK2β in skeletal muscle fibers, pointing to an eventual mitochondrial myopathy. PMID:28106831

  10. Fiber type composition and maximum shortening velocity of muscles crossing the human shoulder.

    PubMed

    Srinivasan, R C; Lungren, M P; Langenderfer, J E; Hughes, R E

    2007-03-01

    A study of the fiber type composition of fourteen muscles spanning the human glenohumeral joint was carried out with the purpose of determining the contribution of fiber types to overall muscle cross-sectional area (CSA) and to estimate the maximum shortening velocity (V(max)) of those muscles. Muscle biopsies were procured from 4 male cadavers (mean age 50) within 24 hr of death, snap frozen, mounted, and transversely sectioned (10 microm). Slides were stained for myofibrillar ATPase after alkaline preincubation. Photoimages were taken of defined areas (100 fibers) using the Bioquant system, and fiber type and CSA were measured from these images. Staining for mATPase produced three different fiber types: slow-oxidative (SO), fast-oxidative-glycolytic (FOG), and fast-glycolytic (FG). On average, the muscle fiber type composition ranged from 22 to 40% of FG, from 17 to 51% of FOG, and from 23 to 56% of SO. Twelve out of the 14 muscles had average SO proportions ranging from 35 to 50%. V(max) was calculated from the fiber type contribution relative to CSA and shortening velocity values taken from the literature. The maximum velocities of shortening presented here provide a physiological basis for the development of human shoulder musculoskeletal models suitable for predicting muscle forces for functionally relevant tasks encompassing conditions of muscle shortening and lengthening.

  11. Persistent Muscle Fiber Regeneration in Long Term Denervation. Past, Present, Future

    PubMed Central

    Carraro, Ugo; Boncompagni, Simona; Gobbo, Valerio; Rossini, Katia; Zampieri, Sandra; Mosole, Simone; Ravara, Barbara; Nori, Alessandra; Stramare, Roberto; Ambrosio, Francesco; Piccione, Francesco; Masiero, Stefano; Vindigni, Vincenzo; Gargiulo, Paolo; Protasi, Feliciano; Kern, Helmut; Pond, Amber

    2015-01-01

    Despite the ravages of long term denervation there is structural and ultrastructural evidence for survival of muscle fibers in mammals, with some fibers surviving at least ten months in rodents and 3-6 years in humans. Further, in rodents there is evidence that muscle fibers may regenerate even after repeated damage in the absence of the nerve, and that this potential is maintained for several months after denervation. While in animal models permanently denervated muscle sooner or later loses the ability to contract, the muscles may maintain their size and ability to function if electrically stimulated soon after denervation. Whether in mammals, humans included, this is a result of persistent de novo formation of muscle fibers is an open issue we would like to explore in this review. During the past decade, we have studied muscle biopsies from the quadriceps muscle of Spinal Cord Injury (SCI) patients suffering with Conus and Cauda Equina syndrome, a condition that fully and irreversibly disconnects skeletal muscle fibers from their damaged innervating motor neurons. We have demonstrated that human denervated muscle fibers survive years of denervation and can be rescued from severe atrophy by home-based Functional Electrical Stimulation (h-bFES). Using immunohistochemistry with both non-stimulated and the h-bFES stimulated human muscle biopsies, we have observed the persistent presence of muscle fibers which are positive to labeling by an antibody which specifically recognizes the embryonic myosin heavy chain (MHCemb). Relative to the total number of fibers present, only a small percentage of these MHCemb positive fibers are detected, suggesting that they are regenerating muscle fibers and not pre-existing myofibers re-expressing embryonic isoforms. Although embryonic isoforms of acetylcholine receptors are known to be re-expressed and to spread from the end-plate to the sarcolemma of muscle fibers in early phases of muscle denervation, we suggest that the MHCemb

  12. Mitochondrial ROS regulate oxidative damage and mitophagy but not age-related muscle fiber atrophy

    PubMed Central

    Sakellariou, Giorgos K.; Pearson, Timothy; Lightfoot, Adam P.; Nye, Gareth A.; Wells, Nicola; Giakoumaki, Ifigeneia I.; Vasilaki, Aphrodite; Griffiths, Richard D.; Jackson, Malcolm J.; McArdle, Anne

    2016-01-01

    Age-related loss of skeletal muscle mass and function is a major contributor to morbidity and has a profound effect on the quality of life of older people. The potential role of age-dependent mitochondrial dysfunction and cumulative oxidative stress as the underlying cause of muscle aging remains a controversial topic. Here we show that the pharmacological attenuation of age-related mitochondrial redox changes in muscle with SS31 is associated with some improvements in oxidative damage and mitophagy in muscles of old mice. However, this treatment failed to rescue the age-related muscle fiber atrophy associated with muscle atrophy and weakness. Collectively, these data imply that the muscle mitochondrial redox environment is not a key regulator of muscle fiber atrophy during sarcopenia but may play a key role in the decline of mitochondrial organelle integrity that occurs with muscle aging. PMID:27681159

  13. Measurements and modeling of multipath interference at wavelengths below cable cut-off in a G.654 optical fiber span.

    PubMed

    Downie, John D; Hurley, Jason; DePedro, Hector; Garner, Steven; Blaker, Jeremy; Zakharian, Aramais; Ten, Sergey; Mills, Greg

    2017-04-17

    Transmission below the cable cut-off wavelength may be a concern in some systems, especially for an optical supervisory channel (OSC) operating below the signal transmission band in systems built with G.654 fiber. In this work, we constructed a cabled span of G.654-compliant fiber and measured the multipath interference (MPI) generated during propagation through the span at a range of wavelengths below the cable cut-offs of the constituent fibers. Measurements were made under a range of conditions including different splice losses and the presence or absence of higher order mode filters placed around the splices. MPI levels were found to be sufficiently low at wavelengths far below the average cable cut-off such that OSC transmission was penalty-free. We compare the experimental results to modeling predictions and find very good agreement.

  14. Influence of muscle fiber type composition on early fat accumulation under high-fat diet challenge.

    PubMed

    Hua, Ning; Takahashi, Hirokazu; Yee, Grace M; Kitajima, Yoichiro; Katagiri, Sayaka; Kojima, Motoyasu; Anzai, Keizo; Eguchi, Yuichiro; Hamilton, James A

    2017-01-01

    To investigate whether differences in muscle fiber types affect early-stage fat accumulation, under high fat diet challenge in mice. Twelve healthy male C57BL/6 mice experienced with short-term (6 weeks) diet treatment for the evaluation of early pattern changes in muscular fat. The mice were randomly divided into two groups: high fat diet (n = 8) and normal control diet (n = 4). Extra- and intra-myocellular lipid (EMCL and IMCL) in lumbar muscles (type I fiber predominant) and tibialis anterior (TA) muscle (type II fiber predominant) were determined using magnetic resonance spectroscopy (MRS). Correlation of EMCL, IMCL and their ratio between TA and lumbar muscles was evaluated. EMCL increased greatly in both muscle types after high fat diet. IMCL in TA and lumbar muscles increased to a much lower extent, with a slightly greater increase in TA muscles. EMCLs in the 2 muscles were positively correlated (r = 0.84, p = 0.01), but IMCLs showed a negative relationship (r = -0.84, p = 0.01). In lumbar muscles, high fat diet significantly decreased type I fiber while it increased type II fiber (all p≤0.001). In TA muscle, there was no significant fiber type shifting (p>0.05). Under short-time high fat diet challenge, lipid tends to initially accumulate extra-cellularly. In addition, compared to type II dominant muscle, Type I dominant muscle was less susceptible to IMCL accumulation but more to fiber type shifting. These phenomena might reflect compensative responses of skeletal muscle to dietary lipid overload in order to regulate metabolic homeostasis.

  15. Green tea extract decreases muscle pathology and NF-κB immunostaining in regenerating muscle fibers of mdx mice

    PubMed Central

    Evans, Nicholas P.; Call, Jarrod A.; Bassaganya-Riera, Josep; Robertson, John L.; Grange, Robert W.

    2009-01-01

    BACKGROUND & AIMS Duchenne muscular dystrophy is a debilitating genetic disorder characterized by severe muscle wasting and early death in afflicted boys. The primary cause of this disease is mutations in the dystrophin gene resulting in massive muscle degeneration and inflammation. The purpose of this study was to determine if dystrophic muscle pathology and inflammation were decreased by pre-natal and early dietary intervention with green tea extract. METHODS Mdx breeder mice and pups were fed diets containing 0.25% or 0.5% green tea extract and compared to untreated mdx and C57BL/6J mice. Serum creatine kinase was assessed as a systemic indicator of muscle damage. Quantitative histopathological and immunohistochemical techniques were used to determine muscle pathology, macrophage infiltration, and NF-κB localization. RESULTS Early treatment of mdx mice with green tea extract significantly decreased serum creatine kinase by ~85% at age 42 days (P≤0.05). In these mice, the area of normal fiber morphology was increased by as much as ~32% (P≤0.05). The primary histopathological change was a ~21% decrease in the area of regenerating fibers (P≤0.05). NF-κB staining in regenerating muscle fibers was also significantly decreased in green tea extract-treated mdx mice when compared to untreated mdx mice. CONCLUSION Early treatment with green tea extract decreases dystrophic muscle pathology potentially by regulating NF-κB activity in regenerating muscle fibers. PMID:19897286

  16. Muscle Fiber Size and Function in Elderly Humans: A Longitudinal Study

    USDA-ARS?s Scientific Manuscript database

    Cross-sectional studies are likely to underestimate age-related changes in skeletal muscle strength and mass. The purpose of this longitudinal study was to assess whole muscle and single muscle fiber alterations in the same cohort of 12 older (mean age: start of study=71.1+/-5.4 yrs and end of study...

  17. Function of longitudinal vs circular muscle fibers in esophageal peristalsis, deduced with mathematical modeling

    PubMed Central

    Brasseur, James G; Nicosia, Mark A; Pal, Anupam; Miller, Larry S

    2007-01-01

    We summarize from previous works the functions of circular vs. longitudinal muscle in esophageal peristaltic bolus transport using a mix of experimental data, the conservation laws of mechanics and mathematical modeling. Whereas circular muscle tone generates radial closure pressure to create a local peristaltic closure wave, longitudinal muscle tone has two functions, one physiological with mechanical implications, and one purely mechanical. Each of these functions independently reduces the tension of individual circular muscle fibers to maintain closure as a consequence of shortening of longitudinal muscle locally coordinated with increasing circular muscle tone. The physiological function is deduced by combining basic laws of mechanics with concurrent measurements of intraluminal pressure from manometry, and changes in cross sectional muscle area from endoluminal ultrasound from which local longitudinal shortening (LLS) can be accurately obtained. The purely mechanical function of LLS was discovered from mathematical modeling of peristaltic esophageal transport with the axial wall motion generated by LLS. Physiologically, LLS concentrates circular muscle fibers where closure pressure is highest. However, the mechanical function of LLS is to reduce the level of pressure required to maintain closure. The combined physiological and mechanical consequences of LLS are to reduce circular muscle fiber tension and power by as much as 1/10 what would be required for peristalsis without the longitudinal muscle layer, a tremendous benefit that may explain the existence of longitudinal muscle fiber in the gut. We also review what is understood of the role of longitudinal muscle in esophageal emptying, reflux and pathology. PMID:17457963

  18. Expression profiling reveals heightened apoptosis and supports fiber size economy in the murine muscles of mastication.

    PubMed

    Evans, Marianna; Morine, Kevin; Kulkarni, Cyelee; Barton, Elisabeth R

    2008-09-17

    Distinctions between craniofacial and axial muscles exist from the onset of development and throughout adulthood. The masticatory muscles are a specialized group of craniofacial muscles that retain embryonic fiber properties in the adult, suggesting that the developmental origin of these muscles may govern a pattern of expression that differs from limb muscles. To determine the extent of these differences, expression profiling of total RNA isolated from the masseter and tibialis anterior (TA) muscles of adult female mice was performed, which identified transcriptional changes in unanticipated functional classes of genes in addition to those attributable to fiber type. In particular, the masseters displayed a reduction of transcripts associated with contractile and cytoskeletal load-sensing and anabolic processes, and heightened expression of genes associated with stress. Associated with these observations was a significantly smaller fiber cross-sectional area in masseters, significantly elevated load-sensing signaling (phosphorylated focal adhesion kinase), and increased apoptotic index in masseters compared with TA muscles. Based on these results, we hypothesize that masticatory muscles may have a fundamentally different strategy for muscle design, compared with axial muscles. Specifically there are small diameter fibers that have an attenuated ability to hypertrophy, but an increased propensity to undergo apoptosis. These results may provide insight into the molecular basis for specific muscle-related pathologies associated with masticatory muscles.

  19. Management of low transsphincteric anal fistula with serial setons and interval muscle-cutting fistulotomy.

    PubMed

    Wang, Chen; Rosen, Lester

    2016-03-01

    This study evaluates low transsphincteric anal fistula managed by serial setons and interval fistulotomy, with attention to healing without recurrence and preservation of continence. Following Institutional Review Board approval, consecutive anal fistula operations performed by a single surgeon from January 1, 2009 to December 31, 2013 were retrospectively reviewed using electronic medical records and telephone interviews for patients lost to follow up. Of the 71 patients, 26 (37%) had low transsphincteric fistula (23 males and 3 females; mean age: 46 years), treated at our institution by seton placement followed by interval surgical muscle cutting and subsequent seton replacement or final fistulotomy. Of the 26 patients, 22 (85%) were initially referred due to previous failed treatment, with a 30.6 month mean duration of fistula prior to referral and a mean of 2.2 (range: 0 -6) prior anorectal surgeries. At a mean follow-up of 11.9 months, none of the 21 patients experienced recurrence or fecal incontinence. Serial seton with interval muscle-cutting sphincterotomy followed by complete fistulotomy is an effective treatment for the management of patients who are either initially seen for low transsphincteric fistula, or referred after failed anorectal surgery for that condition.

  20. Muscle-fiber transdifferentiation in an experimental model of respiratory chain myopathy

    PubMed Central

    2012-01-01

    Introduction Skeletal muscle fiber composition and muscle energetics are not static and change in muscle disease. This study was performed to determine whether a mitochondrial myopathy is associated with adjustments in skeletal muscle fiber-type composition. Methods Ten rats were treated with zidovudine, an antiretroviral nucleoside reverse transcriptase inhibitor that induces a myopathy by interfering with mitochondrial functions. Soleus muscles were examined after 21 weeks of treatment. Ten untreated rats served as controls. Results Zidovudine induced a myopathy with mitochondrial DNA depletion, abnormalities in mitochondrial ultrastructure, and reduced cytochrome c oxidase activity. Mitochondrial DNA was disproportionally more diminished in type I compared with type II fibers, whereas atrophy predominated in type II fibers. Compared with those of controls, zidovudine-exposed soleus muscles contained an increased proportion (256%) of type II fibers, whereas neonatal myosin heavy chains remained repressed, indicating fiber-type transformation in the absence of regeneration. Microarray gene-expression analysis confirmed enhanced fast-fiber isoforms, repressed slow-fiber transcripts, and reduced neonatal fiber transcripts in the mitochondrial myopathy. Respiratory chain transcripts were diminished, whereas the enzymes of glycolysis and glycogenolysis were enhanced, indicating a metabolic adjustment from oxidative to glycolytic capacities. A coordinated regulation was found of transcription factors known to orchestrate type II fiber formation (upregulation of MyoD, Six1, Six2, Eya1, and Sox6, and downregulation of myogenin and ERRγ). Conclusions The type I to type II fiber transformation in mitochondrial myopathy implicates mitochondrial function as a new regulator of skeletal muscle fiber type. PMID:23107834

  1. Glycogen synthesis in muscle fibers during active recovery from intense exercise.

    PubMed

    Fairchild, Timothy J; Armstrong, Alex A; Rao, Arjun; Liu, Hawk; Lawrence, Steve; Fournier, Paul A

    2003-04-01

    There is evidence that active recovery impairs glycogen repletion in skeletal muscles of fasted individuals. Our main goal was to examine the impact of active recovery on the glycogen stores of the different muscle fiber types. Eight endurance-trained individuals cycled for 2.5 min at 130% [OV0312]O(2peak) followed by a 30-s all-out cycling sprint. After exercise, the participants were subjected to either a passive recovery or an active recovery protocol that consisted of pedalling for 45 min at 40% [OV0312]O(2peak). During active recovery, blood lactate and pH returned more rapidly toward preexercise levels than during passive recovery. In contrast, average muscle glycogen content remained at stable levels during active recovery (209 +/- 32 and 202 +/- 30 mmol.kg-1 at 0 and 45 min of recovery, respectively) but increased significantly in response to passive recovery (from 185 +/- 27 to 283 +/- 42 mmol.kg-1). The pattern of change in periodic acid-Schiff staining intensity across muscle fibers suggests that the impact of active recovery on average muscle glycogen content is different from that observed at the levels of the individual muscle fibers, with active recovery having no effect on glycogen resynthesis in Type II muscle fibers but causing glycogen breakdown in Type I muscle fibers. Although active recovery was also associated with higher plasma catecholamines and lower insulin levels, such an unfavorable hormonal environment had no effect on glycogen resynthesis in Type II muscle fibers. Active recovery in comparison to passive recovery does not affect glycogen resynthesis in Type II muscle fibers despite being associated with an unfavorable hormonal environment but results in a marked glycogen mobilization in Type I muscle fibers.

  2. Epaxial muscle fiber architecture favors enhanced excursion and power in the leaper Galago senegalensis.

    PubMed

    Huq, Emranul; Wall, Christine E; Taylor, Andrea B

    2015-10-01

    Galago senegalensis is a habitual arboreal leaper that engages in rapid spinal extension during push-off. Large muscle excursions and high contraction velocities are important components of leaping, and experimental studies indicate that during leaping by G. senegalensis, peak power is facilitated by elastic storage of energy. To date, however, little is known about the functional relationship between epaxial muscle fiber architecture and locomotion in leaping primates. Here, fiber architecture of select epaxial muscles is compared between G. senegalensis (n = 4) and the slow arboreal quadruped, Nycticebus coucang (n = 4). The hypothesis is tested that G. senegalensis exhibits architectural features of the epaxial muscles that facilitate rapid and powerful spinal extension during the take-off phase of leaping. As predicted, G. senegalensis epaxial muscles have relatively longer, less pinnate fibers and higher ratios of tendon length-to-fiber length, indicating the capacity for generating relatively larger muscle excursions, higher whole-muscle contraction velocities, and a greater capacity for elastic energy storage. Thus, the relatively longer fibers and higher tendon length-to-fiber length ratios can be functionally linked to leaping performance in G. senegalensis. It is further predicted that G. senegalensis epaxial muscles have relatively smaller physiological cross-sectional areas (PCSAs) as a consequence of an architectural trade-off between fiber length (excursion) and PCSA (force). Contrary to this prediction, there are no species differences in relative PCSAs, but the smaller-bodied G. senegalensis trends towards relatively larger epaxial muscle mass. These findings suggest that relative increase in muscle mass in G. senegalensis is largely attributable to longer fibers. The relative increase in erector spinae muscle mass may facilitate sagittal flexibility during leaping. The similarity between species in relative PCSAs provides empirical support for

  3. Mitochondrial Dynamics is a Distinguishing Feature of Skeletal Muscle Fiber Types and Regulates Organellar Compartmentalization.

    PubMed

    Mishra, Prashant; Varuzhanyan, Grigor; Pham, Anh H; Chan, David C

    2015-12-01

    Skeletal muscle fibers differentiate into specific fiber types with distinct metabolic properties determined by their reliance on oxidative phosphorylation (OXPHOS). Using in vivo approaches, we find that OXPHOS-dependent fibers, compared to glycolytic fibers, contain elongated mitochondrial networks with higher fusion rates that are dependent on the mitofusins Mfn1 and Mfn2. Switching of a glycolytic fiber to an oxidative IIA type is associated with elongation of mitochondria, suggesting that mitochondrial fusion is linked to metabolic state. Furthermore, we reveal that mitochondrial proteins are compartmentalized to discrete domains centered around their nuclei of origin. The domain dimensions are dependent on fiber type and are regulated by the mitochondrial dynamics proteins Mfn1, Mfn2, and Mff. Our results indicate that mitochondrial dynamics is tailored to fiber type physiology and provides a rationale for the segmental defects characteristic of aged and diseased muscle fibers.

  4. Ryanodine interferes with charge movement repriming in amphibian skeletal muscle fibers.

    PubMed Central

    Gonzalez, A; Caputo, C

    1996-01-01

    Cut twitch muscle fibers mounted in a triple Vaseline-gap chamber were used to study the effects of ryanodine on intramembranous charge movement, and in particular on the repriming of charge 1. Charge 1 repriming was measured either under steady-state conditions or by using a pulse protocol designed to study the time course of repriming. This protocol consisted of repolarizing the fibers to -100 mV from a holding potential of 0 mV, and then measuring the reprimed charge moving in the potential range between -40 and +20 mV. Ryanodine at a high concentration (100 microM) did not affect the maximum amount of movable charge 1 and charge 2, or their voltage dependence. This indicates that the alkaloid does not interact with the voltage sensor molecules. However, ryanodine did reduce the amount of reprimed charge 1 by approximately 60% suggesting the possibility of a retrograde interaction between ryanodine receptors and voltage sensors. PMID:8770214

  5. Morphometric analysis of rat muscle fibers following space flight and hypogravity

    NASA Technical Reports Server (NTRS)

    Chui, L. A.; Castleman, K. R.

    1982-01-01

    The effect of hypogravity on striate muscles, containing both fast twitch glycolytic and slow twitch oxidative fibers, was studied in rats aboard two Cosmos biosatellites. Results of a computer-assisted image analysis of extensor digitorum muscles from five rats, exposed to 18.5 days of hypogravity and processed for the alkaline ATPase reaction, showed a reduction of the mean fiber diameter (41.32 + or - 0.55 microns), compared to synchronous (46.32 + or - 0.55 microns) and vivarium (49 + or - 0.5 microns) controls. A further experiment studied the ratio of fast to slow twitch fibers in 25 rats exposed to 18.5 days of hypogravity and analyzed at four different periods of recovery following the space flight. Using the previous techniques, the gastrocnemius muscle showed a reduction of the total muscle fiber area in square microns and a reduction in the percentage of slow fibers of flight animals compared to the control animals.

  6. Effect of passive stretching on the immobilized soleus muscle fiber morphology.

    PubMed

    Coutinho, E L; Gomes, A R S; França, C N; Oishi, J; Salvini, T F

    2004-12-01

    The aim of the present study was to determine the effect of stretching applied every 3 days to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Eighteen 16-week-old Wistar rats were used and divided into three groups of 6 animals each: a) the left soleus muscle was immobilized in the shortened position for 3 weeks; b) during immobilization, the soleus was stretched for 40 min every 3 days; c) the non-immobilized soleus was only stretched. Left and right soleus muscles were examined. One portion of the soleus was frozen for histology and muscle fiber area evaluation, while the other portion was used to identify the number and length of serial sarcomeres. Immobilized muscles (group A) showed a significant decrease in weight (44 +/- 6%), length (19 +/- 7%), serial sarcomere number (23 +/- 15%), and fiber area (37 +/- 31%) compared to the contralateral muscles (P < 0.05, paired Student t-test). The immobilized and stretched soleus (group B) showed a similar reduction but milder muscle fiber atrophy compared to the only immobilized group (22 +/- 40 vs 37 +/- 31%, respectively; P < 0.001, ANOVA test). Muscles submitted only to stretching (group C) significantly increased the length (5 +/- 2%), serial sarcomere number (4 +/- 4%), and fiber area (16 +/- 44%) compared to the contralateral muscles (P < 0.05, paired Student t-test). In conclusion, stretching applied every 3 days to immobilized muscles did not prevent the muscle shortening, but reduced muscle atrophy. Stretching sessions induced hypertrophic effects in the control muscles. These results support the use of muscle stretching in sports and rehabilitation.

  7. Muscle fiber type distribution in climbing Hawaiian gobioid fishes: ontogeny and correlations with locomotor performance.

    PubMed

    Cediel, Roberto A; Blob, Richard W; Schrank, Gordon D; Plourde, Robert C; Schoenfuss, Heiko L

    2008-01-01

    Three species of Hawaiian amphidromous gobioid fishes are remarkable in their ability to climb waterfalls up to several hundred meters tall. Juvenile Lentipes concolor and Awaous guamensis climb using rapid bursts of axial undulation, whereas juvenile Sicyopterus stimpsoni climb using much slower movements, alternately attaching oral and pelvic sucking disks to the substrate during prolonged bouts of several cycles. Based on these differing climbing styles, we hypothesized that propulsive musculature in juvenile L. concolor and A. guamensis would be dominated by white muscle fibers, whereas S. stimpsoni would exhibit a greater proportion of red muscle fibers than other climbing species. We further predicted that, because adults of these species shift from climbing to burst swimming as their main locomotor behavior, muscle from adult fish of all three species would be dominated by white fibers. To test these hypotheses, we used ATPase assays to evaluate muscle fiber type distribution in Hawaiian climbing gobies for three anatomical regions (midbody, anal, and tail). Axial musculature was dominated by white muscle fibers in juveniles of all three species, but juvenile S. stimpsoni had a significantly greater proportion of red fibers than the other two species. Fiber type proportions of adult fishes did not differ significantly from those of juveniles. Thus, muscle fiber type proportions in juveniles appear to help accommodate differences in locomotor demands among these species, indicating that they overcome the common challenge of waterfall climbing through both diverse behaviors and physiological specializations.

  8. Is fast fiber innervation responsible for increased acetylcholinesterase activity in reinnervating soleus muscles?

    NASA Technical Reports Server (NTRS)

    Misulis, K. E.; Dettbarn, W. D.

    1985-01-01

    An investigation was conducted as to whether the predominantly slow SOL, which is low in AChE activity, is initially reinnervated by axons that originally innervated fast muscle fibers with high AChE activity, such as those of the EDL. Local denervation of the SOL in the guinea pig was performed because this muscle is composed solely of slow (type I) fibers; thereby virtually eliminating the possibility of homologous muscle fast fiber innervation. The overshoot in this preparation was qualitatively similar to that seen with distal denervation in the guinea pig and local and distal denervation in the rat. Thus, initial fast fiber innvervation is not responsible for the patterns of change in AChE activity seen with reinnervation in the SOL. It is concluded that the neural control of AChe is different in these two muscles and may reflect specific differences in the characteristics of AChE regulation in fast and slow muscle.

  9. Fiber Composition of the Grasscutter (Thryonomys swinderianus, Temminck 1827) Thigh Muscle: An Enzyme-histochemical Study

    PubMed Central

    Bakou, Serge Niangoran; Nteme Ella, Gualbert Simon; Aoussi, Serge; Guiguand, Lydie; Cherel, Yannick; Fantodji, Agathe

    2015-01-01

    The aim of this study was to describe de fiber composition in the thigh muscles of grass cutter (Thryonomys swinderianus, Temminck 1827). Ten 4 to 6-month-old (3 to 4 kg) male grasscutter were used in this study. Eleven skeletal muscles of the thigh [M. biceps femoris (BF), M. rectus femoris (RF), M. vastus lateralis (VL), M. vastus medialis (VM), M. tensor fasciae latae (TFL), M. semitendinosus (ST), M. semimembranosus (SM), M. semimembranosus accessorius (SMA), M. Sartorius (SRT), M. pectineus (PCT), M. adductor magnus (AM)] were collected after animals euthanasia and examined by light microscopy. Three muscle fiber types (I, IIB and IIA) were found in these muscles using enzyme histochemical techniques [myosine adenosine triphosphatase (ATPase) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR)]. Ten of these eleven muscles are composed by 89% to 100% of fast contracting fibers (types IIA and IIB), while the SMA was almost exclusively formed by slow contracting fibers. PMID:26167391

  10. The Suppression of the Late After-Potential in Rubidium-Containing Frog Muscle Fibers

    PubMed Central

    Hellam, D. C.; Goldstein, D. A.; Peachey, L. D.; Freygang, W. H.

    1965-01-01

    The late after-potential that follows trains of impulses in frog muscle fibers is virtually absent when most of the intracellular potassium is replaced by rubidium and the muscle is immersed in rubidium-containing Ringer's fluid. Its amplitude is also reduced in freshly dissected, potassium-containing muscle fibers that are immersed directly in Rb-Ringer's fluid. These findings are discussed in terms of the model for muscle membrane of Adrian and Freygang (1962 a, b) and in relation to the report of Adrian (1964) that Rb-containing muscle fibers do not exhibit the variations in potassium permeability as a function of membrane potential that are found in fibers with normal intracellular potassium concentration immersed in Ringer's fluid. PMID:5855505

  11. Supplementing healthy rats with a high-niacin dose has no effect on muscle fiber distribution and muscle metabolic phenotype.

    PubMed

    Scholz, Kristen; Kynast, Anna Marie; Couturier, Aline; Mooren, Frank-Christoph; Krüger, Karsten; Most, Erika; Eder, Klaus; Ringseis, Robert

    2014-08-01

    It was recently shown that niacin prevents the obesity-induced type I to type II fiber switching in skeletal muscle of obese rats and favors the development of a more oxidative metabolic phenotype and thereby increases whole body utilization of fatty acids. Whether niacin also causes type II to type I fiber switching in skeletal muscle of healthy rats has not been investigated yet. Thus, the present study aimed to investigate whether niacin supplementation influences fiber distribution and metabolic phenotype of different skeletal muscles with a distinct type I-to-type II fiber ratio in healthy rats. Twenty-four male, 10-week-old Sprague-Dawley rats were randomly assigned into two groups of 12 rats each and fed either a control diet with 30 mg supplemented niacin/kg diet (control group) or a high-niacin diet with 780 mg supplemented niacin/kg diet (high-niacin group). After 27 days of treatment, the percentage number of type I fibers in rectus femoris, gastrocnemius, and tibialis anterior muscles was 5-10% greater in the niacin group than in the control group, but did not differ between groups in soleus and vastus intermedius muscles. Transcript levels of genes encoding transcription factors regulating fiber switching, fiber-specific myosin heavy chain isoforms, and proteins involved in fatty acid utilization, oxidative phosphorylation, and angiogenesis did not differ between groups. The results show that niacin has only negligible effects on fiber distribution and its regulation as well as the metabolic phenotype of skeletal muscle in healthy rats.

  12. Regeneration of reinnervated rat soleus muscle is accompanied by fiber transition toward a faster phenotype.

    PubMed

    Mendler, Luca; Pintér, Sándor; Kiricsi, Mónika; Baka, Zsuzsanna; Dux, László

    2008-02-01

    The functional recovery of skeletal muscles after peripheral nerve transection and microsurgical repair is generally incomplete. Several reinnervation abnormalities have been described even after nerve reconstruction surgery. Less is known, however, about the regenerative capacity of reinnervated muscles. Previously, we detected remarkable morphological and motor endplate alterations after inducing muscle necrosis and subsequent regeneration in the reinnervated rat soleus muscle. In the present study, we comparatively analyzed the morphometric properties of different fiber populations, as well as the expression pattern of myosin heavy chain isoforms at both immunohistochemical and mRNA levels in reinnervated versus reinnervated-regenerated muscles. A dramatic slow-to-fast fiber type transition was found in reinnervated soleus, and a further change toward the fast phenotype was observed in reinnervated-regenerated muscles. These findings suggest that the (fast) pattern of reinnervation plays a dominant role in the specification of fiber phenotype during regeneration, which can contribute to the long-lasting functional impairment of the reinnervated muscle. Moreover, because the fast II fibers (and selectively, a certain population of the fast IIB fibers) showed better recovery than did the slow type I fibers, the faster phenotype of the reinnervated-regenerated muscle seems to be actively maintained by selective yet undefined cues.

  13. Single skinned muscle fibers in Duchenne muscular dystrophy generate normal force.

    PubMed

    Horowits, R; Dalakas, M C; Podolsky, R J

    1990-06-01

    We measured the intrinsic mechanical properties and protein content of single skinned muscle fibers obtained from patients who had Duchenne muscular dystrophy. To check for possible nonspecific changes caused by muscle disease per se, we also studied the properties of muscle fibers obtained from patients exhibiting severe muscle weakness due to polymyositis. Relative to control fibers obtained from 4 patients with normal or nonmyopathic muscle, we found no significant changes in the ability of muscle fibers from the patients with Duchenne muscular dystrophy or polymyositis to generate active tension in response to calcium or resting tension in response to stretch. In addition, we found no significant changes in the concentrations of the major contractile proteins myosin and actin, of the elastic protein titin, or of the structural proteins nebulin and alpha-actinin. In contrast, immunocytochemical studies showed that dystrophin was absent in the biopsy specimens from the patients with Duchenne muscular dystrophy, but localized at the cell membrane in all of the other muscle biopsy specimens used in this study. These results indicate that myofibrils assemble and function normally in Duchenne muscular dystrophy. Therefore, the absence of dystrophin, which is the primary biochemical defect in this disease, leads to clinical weakness by causing the breakdown of muscle fibers that were once capable of generating normal force, while the surviving fibers exhibit normal contractility.

  14. Rotator cuff tear reduces muscle fiber specific force production and induces macrophage accumulation and autophagy

    PubMed Central

    Gumucio, Jonathan P; Davis, Max E; Bradley, Joshua R; Stafford, Patrick L; Schiffman, Corey J; Lynch, Evan B; Claflin, Dennis R; Bedi, Asheesh; Mendias, Christopher L

    2012-01-01

    Summary Full-thickness tears to the rotator cuff can cause severe pain and disability. Untreated tears progress in size and are associated with muscle atrophy and an infiltration of fat to the area, a condition known as “fatty degeneration.” To improve the treatment of rotator cuff tears, a greater understanding of the changes in the contractile properties of muscle fibers and the molecular regulation of fatty degeneration is essential. Using a rat model of rotator cuff injury, we measured the force generating capacity of individual muscle fibers and determined changes in muscle fiber type distribution that develop after a full thickness rotator cuff tear. We also measured the expression of mRNA and miRNA transcripts involved in muscle atrophy, lipid accumulation, and matrix synthesis. We hypothesized that a decrease in specific force of rotator cuff muscle fibers, an accumulation of type IIb fibers, an upregulation in fibrogenic, adipogenic, and inflammatory gene expression occur in torn rotator cuff muscles. Thirty days following rotator cuff tear, we observed a reduction in muscle fiber force production, an induction of fibrogenic, adipogenic and autophagocytic mRNA and miRNA molecules, and a dramatic accumulation of macrophages in areas of fat accumulation. PMID:22696414

  15. Rotator cuff tear reduces muscle fiber specific force production and induces macrophage accumulation and autophagy.

    PubMed

    Gumucio, Jonathan P; Davis, Max E; Bradley, Joshua R; Stafford, Patrick L; Schiffman, Corey J; Lynch, Evan B; Claflin, Dennis R; Bedi, Asheesh; Mendias, Christopher L

    2012-12-01

    Full-thickness tears to the rotator cuff can cause severe pain and disability. Untreated tears progress in size and are associated with muscle atrophy and an infiltration of fat to the area, a condition known as "fatty degeneration." To improve the treatment of rotator cuff tears, a greater understanding of the changes in the contractile properties of muscle fibers and the molecular regulation of fatty degeneration is essential. Using a rat model of rotator cuff injury, we measured the force generating capacity of individual muscle fibers and determined changes in muscle fiber type distribution that develop after a full thickness rotator cuff tear. We also measured the expression of mRNA and miRNA transcripts involved in muscle atrophy, lipid accumulation, and matrix synthesis. We hypothesized that a decrease in specific force of rotator cuff muscle fibers, an accumulation of type IIb fibers, and an upregulation in fibrogenic, adipogenic, and inflammatory gene expression occur in torn rotator cuff muscles. Thirty days following rotator cuff tear, we observed a reduction in muscle fiber force production, an induction of fibrogenic, adipogenic, and autophagocytic mRNA and miRNA molecules, and a dramatic accumulation of macrophages in areas of fat accumulation. Copyright © 2012 Orthopaedic Research Society.

  16. Muscle Degeneration in Neuramindase 1 Deficient Mice Results from Infiltration of the Muscle Fibers by Expanded Connective Tissue

    PubMed Central

    Zanoteli, Edmar; van de Vlekkert, Diantha; Bonten, Erik J.; Hu, Huimin; Mann, Linda; Gomero, Elida M.; Harris, A. John; Ghersi, Giulio; d’Azzo, Alessandra

    2010-01-01

    SUMMARY Neuraminidase 1 (NEU1) regulates the catabolism of sialoglycoconjugates in lysosomes. Congenital NEU1 deficiency in children is the basis of sialidosis, a severe neurosomatic disorder in which patients experience a broad spectrum of clinical manifestations varying in the age of onset and severity. Osteoskeletal deformities and muscle hypotonia have been described in patients with sialidosis. Here we present the first comprehensive analysis of the skeletal muscle pathology associated with loss of Neu1 function in mice. In this animal model, skeletal muscles showed an expansion of the epimysial and perimysial spaces, associated with proliferation of fibroblast-like cells and abnormal deposition of collagens. Muscle fibers located adjacent to the expanded connective tissue underwent extensive invagination of their sarcolemma, which resulted in the infiltration of the fibers by fibroblast-like cells and extracellular matrix, and in their progressive cytosolic fragmentation. Both the expanded connective tissue and the juxtaposed infiltrated muscle fibers were strongly positive for lysosomal markers, and displayed increased proteolytic activity of lysosomal cathepsins and metalloproteinases. These combined features could lead to abnormal remodeling of the extracellular matrix that could be responsible for sarcolemmal invagination and progressive muscle fiber degeneration, ultimately resulting in an overt atrophic phenotype. This unique pattern of muscle damage, which has never been described in any myopathy, might explain the neuromuscular manifestations reported in patients with the type II severe form of sialidosis. More broadly, these findings point to a potential role of NEU1 in cell proliferation and extracellular matrix remodeling. PMID:20388541

  17. Distinct muscle apoptotic pathways are activated in muscles with different fiber types in a rat model of critical illness myopathy.

    PubMed

    Barnes, Benjamin T; Confides, Amy L; Rich, Mark M; Dupont-Versteegden, Esther E

    2015-06-01

    Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles showed severe muscle atrophy (40-60% of control muscle weight) and significant apoptosis in interstitial as well as myofiber nuclei that was similar between the two muscles with DSIM. Caspase-3 and -8 activities, but not caspase-9 and -12, were elevated in TA and not in soleus muscle, while the caspase-independent proteins endonuclease G (EndoG) and apoptosis inducing factor (AIF) were not changed in abundance nor differentially localized in either muscle. Anti-apoptotic proteins HSP70, -27, and apoptosis repressor with a caspase recruitment domain (ARC) were elevated in soleus compared to TA muscle and ARC was significantly decreased with induction of DSIM in soleus. Results indicate that apoptosis is a significant process associated with DSIM in both soleus and TA muscles, and that apoptosis-associated processes are differentially regulated in muscles of different function and fiber type undergoing atrophy due to DSIM. We conclude that interventions combating apoptosis with CIM may need to be directed towards inhibiting caspase-dependent as well as -independent mechanisms to be able to affect muscles of all fiber types.

  18. Distinct muscle apoptotic pathways are activated in muscles with different fiber types a rat model of critical illness myopathy

    PubMed Central

    Barnes, Benjamin T.; Confides, Amy L.; Rich, Mark M.; Dupont-Versteegden, Esther E.

    2015-01-01

    Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles showed severe muscle atrophy (40–60% of control muscle weight) and significant apoptosis in interstitial as well as myofiber nuclei that was similar between the two muscles with DSIM. Caspase-3 and −8 activities, but not caspase-9 and −12, were elevated in TA and not in soleus muscle, while the caspase-independent proteins endonuclease G (EndoG) and apoptosis inducing factor (AIF) were not changed in abundance nor differentially localized in either muscle. Anti-apoptotic proteins HSP70, −27, and apoptosis repressor with a caspase recruitment domain (ARC) were elevated in soleus compared to TA muscle and ARC was significantly decreased with induction of DSIM in soleus. Results indicate that apoptosis is a significant process associated with DSIM in both soleus and TA muscles, and that apoptosis-associated processes are differentially regulated in muscles of different function and fiber type undergoing atrophy due to DSIM. We conclude that interventions combating apoptosis with CIM may need to be directed towards inhibiting caspase-dependent as well as -independent mechanisms to be able to affect muscles of all fiber types. PMID:25740800

  19. Comparison of hemp and cotton fiber implants in muscle rat tissue. Study of the inflammatory response.

    PubMed

    Dorfman, S; Dorfman, D; Leonardi, R; Maroso, J; Cardozo, J; Durán, A

    1994-03-01

    Hemp fiber is obtained from the plant Musa textilis. The cost of preparation of its raw fibers is low. The purpose of this paper was to compare the inflammatory response in the rat muscle tissue originated by both hemp and cotton fibers. Both types of fibers, were implanted in gluteal muscles of Sprague Dawley rats. The rats were sacrificed at 15, 30 and 60 postoperative days. Muscle tissue sections were stained with hematoxilyneosin. The inflammatory response was measured by subtracting the suture surface area from the total granulomatous area. At 15 days, the inflammatory response was more conspicuous for hemp than for cotton fiber (P < 0.05). At 30 and 60 days, responses were similar (P > 0.05). We cannot conclude that the hemp fiber is superior to cotton, nevertheless, they behave the same. Therefore, hemp constitutes an alternative as suture material.

  20. Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta(2)-receptor agonist

    NASA Technical Reports Server (NTRS)

    Zeman, Richard J.; Ludemann, Robert; Easton, Thomas G.; Etlinger, Joseph D.

    1988-01-01

    The effects of a beta(2)-receptor agonist, clenbuterol, and a beta(2) antagonist, butoxamine, on the skeletal muscle fibers of rats were investigated. It was found that chronic treatment of rats with clenbuterol caused hypertrophy of histochemically identified fast-twitch, but not slow-twitch, fibers within the soleus, while in the extensor digitorum longus the mean areas of both fiber types were increased; in both muscles, the ratio of the number of fast-twitch to slow-twitch fibers was increased. In contrast, a treatment with butoxamine caused a reduction of the fast-twitch fiber size in both muscles, and the ratio of the fast-twitch to slow-twitch fibers was decreased.

  1. Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta(2)-receptor agonist

    NASA Technical Reports Server (NTRS)

    Zeman, Richard J.; Ludemann, Robert; Easton, Thomas G.; Etlinger, Joseph D.

    1988-01-01

    The effects of a beta(2)-receptor agonist, clenbuterol, and a beta(2) antagonist, butoxamine, on the skeletal muscle fibers of rats were investigated. It was found that chronic treatment of rats with clenbuterol caused hypertrophy of histochemically identified fast-twitch, but not slow-twitch, fibers within the soleus, while in the extensor digitorum longus the mean areas of both fiber types were increased; in both muscles, the ratio of the number of fast-twitch to slow-twitch fibers was increased. In contrast, a treatment with butoxamine caused a reduction of the fast-twitch fiber size in both muscles, and the ratio of the fast-twitch to slow-twitch fibers was decreased.

  2. Catalase-positive microperoxisomes in rat soleus and extensor digitorum longus muscle fiber types

    NASA Technical Reports Server (NTRS)

    Riley, Danny A.; Bain, James L. W.; Ellis, Stanley

    1988-01-01

    The size, distribution, and content of catalase-reactive microperoxisomes were investigated cytochemically in three types of muscle fibers from the soleus and the extensor digitorum longus (EDL) of male rats. Muscle fibers were classified on the basis of the mitochondrial content and distribution, the Z-band widths, and the size and shape of myofibrils as the slow-twitch oxidative (SO), the fast-twitch oxidative glycolytic (FOG), and the fast-twitch glycolytic (FG) fibers. It was found that both the EDL and soleus SO fibers possessed the largest microperoxisomes. A comparison of microperoxisome number per muscle fiber area or the microperoxisome area per fiber area revealed following ranking, starting from the largest number and the area-ratio values: soleus SO, EDL SO, EDL FOG, and EDL FG.

  3. Catalase-positive microperoxisomes in rat soleus and extensor digitorum longus muscle fiber types

    NASA Technical Reports Server (NTRS)

    Riley, Danny A.; Bain, James L. W.; Ellis, Stanley

    1988-01-01

    The size, distribution, and content of catalase-reactive microperoxisomes were investigated cytochemically in three types of muscle fibers from the soleus and the extensor digitorum longus (EDL) of male rats. Muscle fibers were classified on the basis of the mitochondrial content and distribution, the Z-band widths, and the size and shape of myofibrils as the slow-twitch oxidative (SO), the fast-twitch oxidative glycolytic (FOG), and the fast-twitch glycolytic (FG) fibers. It was found that both the EDL and soleus SO fibers possessed the largest microperoxisomes. A comparison of microperoxisome number per muscle fiber area or the microperoxisome area per fiber area revealed following ranking, starting from the largest number and the area-ratio values: soleus SO, EDL SO, EDL FOG, and EDL FG.

  4. Sarcomere Length and Tension Changes in Tetanized Frog Muscle Fibers after Quick Stretches and Releases

    NASA Astrophysics Data System (ADS)

    Sugi, Haruo; Kobayashi, Takakazu

    1983-10-01

    The sarcomere length changes in tetanized frog muscle fibers in response to quick fiber length changes were examined along the fiber length with a high-sensitivity laser diffraction technique. The experiments were only performed with muscle fibers in which the uniform orientation and sarcomere length of the component myofibrils were well preserved during a tetanus. When the sarcomere length changes were recorded near the fixed fiber end, the delay of the onset of sarcomere length change in response to the applied fiber length change tended to be longer than that of the onset of tension changes recorded at the fixed fiber end. The magnitude of sarcomere length changes was larger near the moving fiber end than near the fixed fiber end. In the case of quick releases, the resulting sarcomere shortening tended to outlast the fiber shortening, so that the quick tension recovery started during the sarcomere shortening. These results indicate (i) that the tension changes in response to quick fiber length changes may not give direct information about the cross-bridge properties and (ii) that the viscoelastic multisegmental nature of muscle fibers should be taken into consideration in interpreting the tension responses to quick length changes.

  5. Changes in fiber composition of soleus muscle during rat hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Templeton, G. H.; Sweeney, H. L.; Timson, B. F.; Padalino, M.; Dudenhoeffer, G. A.

    1988-01-01

    A technique in which the gravitational load in the rear limbs of rats was chronically reduced is used to study soleus muscle atrophy in near-zero-gravity conditions. The results show a decline in the number of fibers in groups that contained the slow isoenzyme of myosin and which were classified as type I. The total number of fibers did not change, and fibers containing the intermediate isoenzyme and those classified as type IIa increased. The results are consistent with either a change in the composition within existing fibers or a simultaneous loss of slow fibers accompanied by de novo synthesis of intermediate and fast fibers.

  6. Denervation Causes Fiber Atrophy and Myosin Heavy Chain Co-Expression in Senescent Skeletal Muscle

    PubMed Central

    Rowan, Sharon L.; Rygiel, Karolina; Purves-Smith, Fennigje M.; Solbak, Nathan M.; Turnbull, Douglas M.; Hepple, Russell T.

    2012-01-01

    Although denervation has long been implicated in aging muscle, the degree to which it is causes the fiber atrophy seen in aging muscle is unknown. To address this question, we quantified motoneuron soma counts in the lumbar spinal cord using choline acetyl transferase immunhistochemistry and quantified the size of denervated versus innervated muscle fibers in the gastrocnemius muscle using the in situ expression of the denervation-specific sodium channel, Nav1.5, in young adult (YA) and senescent (SEN) rats. To gain insights into the mechanisms driving myofiber atrophy, we also examined the myofiber expression of the two primary ubiquitin ligases necessary for muscle atrophy (MAFbx, MuRF1). MN soma number in lumbar spinal cord declined 27% between YA (638±34 MNs×mm−1) and SEN (469±13 MNs×mm−1). Nav1.5 positive fibers (1548±70 μm2) were 35% smaller than Nav1.5 negative fibers (2367±78 μm2; P<0.05) in SEN muscle, whereas Nav1.5 negative fibers in SEN were only 7% smaller than fibers in YA (2553±33 μm2; P<0.05) where no Nav1.5 labeling was seen, suggesting denervation is the primary cause of aging myofiber atrophy. Nav1.5 positive fibers had higher levels of MAFbx and MuRF1 (P<0.05), consistent with involvement of the proteasome proteolytic pathway in the atrophy of denervated muscle fibers in aging muscle. In summary, our study provides the first quantitative assessment of the contribution of denervation to myofiber atrophy in aging muscle, suggesting it explains the majority of the atrophy we observed. This striking result suggests a renewed focus should be placed on denervation in seeking understanding of the causes of and treatments for aging muscle atrophy. PMID:22235261

  7. Denervation causes fiber atrophy and myosin heavy chain co-expression in senescent skeletal muscle.

    PubMed

    Rowan, Sharon L; Rygiel, Karolina; Purves-Smith, Fennigje M; Solbak, Nathan M; Turnbull, Douglas M; Hepple, Russell T

    2012-01-01

    Although denervation has long been implicated in aging muscle, the degree to which it is causes the fiber atrophy seen in aging muscle is unknown. To address this question, we quantified motoneuron soma counts in the lumbar spinal cord using choline acetyl transferase immunhistochemistry and quantified the size of denervated versus innervated muscle fibers in the gastrocnemius muscle using the in situ expression of the denervation-specific sodium channel, Nav₁.₅, in young adult (YA) and senescent (SEN) rats. To gain insights into the mechanisms driving myofiber atrophy, we also examined the myofiber expression of the two primary ubiquitin ligases necessary for muscle atrophy (MAFbx, MuRF1). MN soma number in lumbar spinal cord declined 27% between YA (638±34 MNs×mm⁻¹) and SEN (469±13 MNs×mm⁻¹). Nav₁.₅ positive fibers (1548±70 μm²) were 35% smaller than Nav₁.₅ negative fibers (2367±78 μm²; P<0.05) in SEN muscle, whereas Nav₁.₅ negative fibers in SEN were only 7% smaller than fibers in YA (2553±33 μm²; P<0.05) where no Nav₁.₅ labeling was seen, suggesting denervation is the primary cause of aging myofiber atrophy. Nav₁.₅ positive fibers had higher levels of MAFbx and MuRF1 (P<0.05), consistent with involvement of the proteasome proteolytic pathway in the atrophy of denervated muscle fibers in aging muscle. In summary, our study provides the first quantitative assessment of the contribution of denervation to myofiber atrophy in aging muscle, suggesting it explains the majority of the atrophy we observed. This striking result suggests a renewed focus should be placed on denervation in seeking understanding of the causes of and treatments for aging muscle atrophy.

  8. Calcium-activated force of human muscle fibers following a standardized eccentric contraction.

    PubMed

    Choi, Seung Jun; Widrick, Jeffrey J

    2010-12-01

    Peak Ca(2+)-activated specific force (force/fiber cross-sectional area) of human chemically skinned vastus lateralis muscle fiber segments was determined before and after a fixed-end contraction or an eccentric contraction of standardized magnitude (+0.25 optimal fiber length) and velocity (0.50 unloaded shortening velocity). Fiber myosin heavy chain (MHC) isoform content was assayed by SDS-PAGE. Posteccentric force deficit, a marker of damage, was similar for type I and IIa fibers but threefold greater for type IIa/IIx hybrid fibers. A fixed-end contraction had no significant effect on force. Multiple linear regression revealed that posteccentric force was explained by a model consisting of a fiber type-independent and a fiber type-specific component (r(2) = 0.91). Preeccentric specific force was directly associated with a greater posteccentric force deficit. When preeccentric force was held constant, type I and IIa fibers showed identical susceptibility to damage, while type IIa/IIx fibers showed a significantly greater force loss. This heightened sensitivity to damage was directly related to the amount of type IIx MHC in the hybrid fiber. Our model reveals a fiber-type sensitivity of the myofilament lattice or cytoskeleton to mechanical strain that can be described as follows: type IIa/IIx > type IIa = type I. If these properties extend to fibers in vivo, then alterations in the number of type IIa/IIx fibers may modify a muscle's susceptibility to eccentric damage.

  9. Comparative Study of Remote Fiber Laser and Water-Jet Guided Laser Cutting of Thin Metal Sheets

    NASA Astrophysics Data System (ADS)

    Hock, Klaus; Adelmann, Benedikt; Hellmann, Ralf

    This article presents a comparison between remote laser cutting with a fiber laser and water-jet guided laser cutting using a 532 nm solid state laser. Complex contours are processed in stainless steel and brass sheets (thickness ≤ 100 μm), respectively. Results for achievable quality and productivity as well as possible applications for both systems are shown and discussed. We sustained dross free cuts with almost no heat affected zone and small kerf width for the water-jet guided process, whereas small dross, notable heat affected zone and varying kerf width where observed for remote cutting. However, process times for the water-jet guided process where considerably higher than those for remote cutting.

  10. Metabolic and morphologic properties of single muscle fibers in the rat after spaceflight, Cosmos 1887

    NASA Technical Reports Server (NTRS)

    Miu, B.; Martin, T. P.; Roy, R. R.; Oganov, V.; Ilyina-Kakueva, E.; Marini, J. F.; Leger, J. J.; Bodine-Fowler, S. C.; Edgerton, V. R.

    1990-01-01

    The adaptation of a slow (soleus, Sol) and a fast (medial gastrocnemius, MG) skeletal muscle to spaceflight was studied in five young male rats. The flight period was 12.5 days and the rats were killed approximately 48 h after returning to 1 g. Five other rats that were housed in cages similar to those used by the flight rats were maintained at 1 g for the same period of time to serve as ground-based controls. Fibers were classified as dark or light staining for myosin adenosine triphosphatase (ATPase). On the average, the fibers in the Sol of the flight rats atrophied twice as much as those in the MG. Further, the fibers located in the deep (close to the bone and having the highest percentage of light ATPase and high oxidative fibers in the muscle cross section) region of the MG atrophied more than the fibers located in the superficial (away from the bone and having the lowest percentage of light ATPase and high oxidative fibers in the muscle cross-section) region of the muscle. Based on quantitative histochemical assays of single muscle fibers, succinate dehydrogenase (SDH) activity per unit volume was unchanged in fibers of the Sol and MG. However, in the Sol, but not the MG, the total amount of SDH activity in a 10-microns-thick section of a fiber decreased significantly in response to spaceflight. Based on population distributions, it appears that the alpha-glycerophosphate dehydrogenase (GPD) activities were elevated in the dark ATPase fibers in the Sol, whereas the light fibers in the Sol and both fiber types in the MG did not appear to change. The ratio of GPD to SDH activities increased in the dark (but not light) fibers of the Sol and was unaffected in the MG. Immunohistochemical analyses indicate that approximately 40% of the fibers in the Sol of flight rats expressed a fast myosin heavy chain compared with 22% in control rats. Further, 31% of the fibers in the Sol of flight rats expressed both fast and slow myosin heavy chains compared with 8% in

  11. Metabolic and morphologic properties of single muscle fibers in the rat after spaceflight, Cosmos 1887

    NASA Technical Reports Server (NTRS)

    Miu, B.; Martin, T. P.; Roy, R. R.; Oganov, V.; Ilyina-Kakueva, E.; Marini, J. F.; Leger, J. J.; Bodine-Fowler, S. C.; Edgerton, V. R.

    1990-01-01

    The adaptation of a slow (soleus, Sol) and a fast (medial gastrocnemius, MG) skeletal muscle to spaceflight was studied in five young male rats. The flight period was 12.5 days and the rats were killed approximately 48 h after returning to 1 g. Five other rats that were housed in cages similar to those used by the flight rats were maintained at 1 g for the same period of time to serve as ground-based controls. Fibers were classified as dark or light staining for myosin adenosine triphosphatase (ATPase). On the average, the fibers in the Sol of the flight rats atrophied twice as much as those in the MG. Further, the fibers located in the deep (close to the bone and having the highest percentage of light ATPase and high oxidative fibers in the muscle cross section) region of the MG atrophied more than the fibers located in the superficial (away from the bone and having the lowest percentage of light ATPase and high oxidative fibers in the muscle cross-section) region of the muscle. Based on quantitative histochemical assays of single muscle fibers, succinate dehydrogenase (SDH) activity per unit volume was unchanged in fibers of the Sol and MG. However, in the Sol, but not the MG, the total amount of SDH activity in a 10-microns-thick section of a fiber decreased significantly in response to spaceflight. Based on population distributions, it appears that the alpha-glycerophosphate dehydrogenase (GPD) activities were elevated in the dark ATPase fibers in the Sol, whereas the light fibers in the Sol and both fiber types in the MG did not appear to change. The ratio of GPD to SDH activities increased in the dark (but not light) fibers of the Sol and was unaffected in the MG. Immunohistochemical analyses indicate that approximately 40% of the fibers in the Sol of flight rats expressed a fast myosin heavy chain compared with 22% in control rats. Further, 31% of the fibers in the Sol of flight rats expressed both fast and slow myosin heavy chains compared with 8% in

  12. Effects of fiber type and size on the heterogeneity of oxygen distribution in exercising skeletal muscle.

    PubMed

    Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S

    2012-01-01

    The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles.

  13. Effects of Fiber Type and Size on the Heterogeneity of Oxygen Distribution in Exercising Skeletal Muscle

    PubMed Central

    Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S.

    2012-01-01

    The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles. PMID:23028531

  14. Efficient single muscle fiber isolation from alcohol-fixed adult muscle following β-galactosidase staining for satellite cell detection.

    PubMed

    Verma, Mayank; Asakura, Atsushi

    2011-01-01

    Staining for β-galactosidase activity for whole tissues, sections, and cells is a common method to detect expression of β-galactosidase reporter transgene as well as senescence-dependent β-galactosidase activity. Choice of fixatives is a critical step for detection of β-galactosidase activity, subsequent immunostaining, and enzymatic digestion of tissue to dissociate cells. In this report, the authors examined several aldehyde and alcohol fixatives in mouse skeletal muscle tissues for their efficiency at improving detection of β-galactosidase activity as well as detection by immunostaining. In addition, fixatives were also analyzed for their efficiency for collagenase digestion to isolate single muscle fibers on postfixed β-galactosidase-stained whole skeletal muscle tissues. The results show that fixing cells with isopropanol yields the greatest reliability and intensity in both β-galactosidase staining as well as double staining for β-galactosidase activity and antibodies. In addition, isopropanol and ethanol, but not glutaraldehyde or paraformaldehyde, allow for the isolation of single muscle fibers from the diaphragm and tibialis anterior muscles following postfixed β-galactosidase staining. Using this method, it is possible to identify the amount of cells that occupy the satellite cell compartment in single muscle fibers prepared from any muscle tissues, including tibialis anterior muscle and diaphragm.

  15. Lumped Parameter experiments for Single Mode Fiber Laser Cutting of Thin Stainless Steel Plate

    NASA Astrophysics Data System (ADS)

    Lai, Shengying; Jia, Ye; Han, Bing; Wang, Jun; Liu, Zongkai; Ni, Xiaowu; Shen, Zhonghua; Lu, Jian

    2017-06-01

    The present work reports the parameters on laser cutting stainless steel including workpiece thickness, cutting speed, defocus length and assisting gas pressure. The cutting kerf width, dross attachment and cut edge squareness deviation are examined to provide information on cutting quality. The results show that with the increasing thickness, the cutting speed decrease rate is about 27%. The optimal ranges of cutting speed, defocus length and gas pressure are obtained with maximum quality. The first section in your paper

  16. Muscle fatigue examined at different temperatures in experiments on intact mammalian (rat) muscle fibers

    PubMed Central

    Roots, H.; Ball, G.; Talbot-Ponsonby, J.; King, M.; McBeath, K.; Ranatunga, K. W.

    2009-01-01

    In experiments on small bundles of intact fibers from a rat fast muscle, in vitro, we examined the decline in force in repeated tetanic contractions; the aim was to characterize the effect of shortening and of temperature on the initial phase of muscle fatigue. Short tetanic contractions were elicited at a control repetition rate of 1/60 s, and fatigue was induced by raising the rate to 1/5 s for 2–3 min, both in isometric mode (no shortening) and in shortening mode, in which each tetanic contraction included a ramp shortening at a standard velocity. In experiments at 20°C (n = 12), the force decline during a fatigue run was 25% in the isometric mode but was significantly higher (35%) in the shortening mode. In experiments at different temperatures (10–30°C, n = 11), the tetanic frequency and duration were adjusted as appropriate, and for shortening mode, the velocity was adjusted for maximum power output. In isometric mode, fatigue of force was significantly less at 30°C (∼20%) than at 10°C (∼30%); the power output (force × velocity) was >10× higher at 30°C than at 10°C, and power decline during a fatigue run was less at 30°C (∼20–30%) than at 10°C (∼50%). The finding that the extent of fatigue is increased with shortening contractions and is lower at higher temperatures is consistent with the view that force depression by inorganic phosphate, which accumulates within fibers during activity, may be a primary cause of initial muscle fatigue. PMID:19057001

  17. Experiment K-6-21. Effect of microgravity on 1) metabolic enzymes of type 1 and type 2 muscle fibers and on 2) metabolic enzymes, neutransmitter amino acids, and neurotransmitter associated enzymes in motor and somatosensory cerebral cortex. Part 1: Metabolic enzymes of individual muscle fibers; part 2: metabolic enzymes of hippocampus and spinal cord

    NASA Technical Reports Server (NTRS)

    Lowry, O.; Mcdougal, D., Jr.; Nemeth, Patti M.; Maggie, M.-Y. Chi; Pusateri, M.; Carter, J.; Manchester, J.; Norris, Beverly; Krasnov, I.

    1990-01-01

    The individual fibers of any individual muscle vary greatly in enzyme composition, a fact which is obscured when enzyme levels of a whole muscle are measured. The purpose of this study was therefore to assess the changes due to weightless on the enzyme patterns composed by the individual fibers within the flight muscles. In spite of the limitation in numbers of muscles examined, it is apparent that: (1) that the size of individual fibers (i.e., their dry weight) was reduced about a third, (2) that this loss in dry mass was accompanied by changes in the eight enzymes studied, and (3) that these changes were different for the two muscles, and different for the two enzyme groups. In the soleus muscle the absolute amounts of the three enzymes of oxidative metabolism decreased about in proportion to the dry weight loss, so that their concentration in the atrophic fibers was almost unchanged. In contrast, there was little loss among the four enzymes of glycogenolysis - glycolysis so that their concentrations were substantially increased in the atrophic fibers. In the TA muscle, these seven enzymes were affected in just the opposite direction. There appeared to be no absolute loss among the oxidative enzymes, whereas the glycogenolytic enzymes were reduced by nearly half, so that the concentrations of the first metabolic group were increased within the atrophic fibers and the concentrations of the second group were only marginally decreased. The behavior of hexokinase was exceptional in that it did not decrease in absolute terms in either type of muscle and probably increased as much as 50 percent in soleus. Thus, their was a large increase in concentration of this enzyme in the atrophied fibers of both muscles. Another clear-cut finding was the large increase in the range of activities of the glycolytic enzymes among individual fibers of TA muscles. This was due to the emergence of TA fibers with activities for enzymes of this group extending down to levels as low as

  18. Experiment K-308: Automatic analysis of muscle fibers from rats subjected to spaceflight

    NASA Technical Reports Server (NTRS)

    Castleman, K. R.; Chui, L. A.; Vandermeullen, J. P.

    1981-01-01

    The morphology of histochemically prepared muscle sections from the gastrocnemius and plantaris muscles of flight and vivarium control rats was studied quantitatively. Both fast-twitch and slow-twitch fibers were significantly smaller in flight groups than in control groups. Fibers in group 4F were somewhat larger than in 1F, presumably due to growth after recovery. Fibers in 4V were slightly larger than in 1V, presumably due to age. The slow fibers showed more spaceflight induced size loss than fast fibers, suggesting they suffered more from hypogravity. The proportion of slow fibers was also lower in the flight groups, suggesting spaceflight induced fiber type conversion from slow to fast.

  19. Contributions of dynamic phosphorus-31 magnetic resonance spectroscopy to the analysis of muscle fiber distribution.

    PubMed

    Schunk, K; Losch, O; Kreitner, K F; Kersjes, W; Schadmand-Fischer, S; Thelen, M

    1999-05-01

    In high-performance athletes, conclusions regarding the muscle fiber distribution were to be drawn from dynamic 31phosphorus magnetic resonance spectroscopy (31P MRS). Eleven volleyball players (V), eight bodybuilders (B), and 22 nonathletic volunteers (N) were examined by dynamic 31P MRS. During rest, exhaustive exercise, and recovery, respectively, up to 60 consecutive phosphorus spectra of the quadriceps muscle were acquired by "time series" in 36 s each. Two main spectroscopic approaches to the spectroscopic analysis of muscle fiber distribution were applied: evaluation of the ratio Pi/PCr at rest and the computer-assisted analysis of the Pi-peak at its exercise-induced line width maximum. At rest, the bodybuilders showed a significant lower Pi/PCr (0.07 +/- 0.03), in comparison with the volleyball players (0.11 +/- 0.03) and the nonathletic volunteers (0.11 +/- 0.02). The computer-assisted analysis of the Pi-peak at its line width maximum revealed a significantly lower pH of both of the subpeaks in the bodybuilders [6.30 versus 6.37 (V) and 6.38 (N); 6.89 versus 6.92 (V, N)], whereas the volleyball players provided the largest proportion of oxidative muscle fibers (68%), compared to bodybuilders (64%) and nonathletic volunteers (59%). A correlation between the ratio Pi/PCr and the area of the subpeak with the high pH (representing oxidative fibers) could not be demonstrated. Spectroscopic results during rest and exercise may be influenced by the muscle fiber distribution of the respective volunteer. The applied spectroscopic approaches to the analysis of muscle fiber composition are not compatible with each other; depending on the applied method, the classification of a muscle fiber as type I or type II fiber may change. The influence of physiologic factors like muscle fiber distribution on spectroscopic results has to be considered in the interpretation of pathological conditions.

  20. Differences in muscle fiber size and associated energetic costs in phylogenetically paired tropical and temperate birds.

    PubMed

    Jimenez, Ana Gabriela; Williams, Joseph B

    2014-01-01

    Tropical and temperate birds provide a unique system to examine mechanistic consequences of life-history trade-offs at opposing ends of the pace-of-life spectrum; tropical birds tend to have a slow pace of life whereas temperate birds the opposite. Birds in the tropics have a lower whole-animal basal metabolic rate and peak metabolic rate, lower rates of reproduction, and longer survival than birds in temperate regions. Although skeletal muscle has a relatively low tissue-specific metabolism at rest, it makes up the largest fraction of body mass and therefore contributes more to basal metabolism than any other tissue. A principal property of muscle cells that influences their rate of metabolism is fiber size. The optimal fiber size hypothesis attempts to link whole-animal basal metabolic rate to the cost of maintaining muscle mass by stating that larger fibers may be metabolically cheaper to maintain since the surface area∶volume ratio (SA∶V) is reduced compared with smaller fibers and thus the amount of area to transport ions is also reduced. Because tropical birds have a reduced whole-organism metabolism, we hypothesized that they would have larger muscle fibers than temperate birds, given that larger muscle fibers have reduced energy demand from membrane Na(+)-K(+) pumps. Alternatively, smaller muscle fibers could result in a lower capacity for shivering and exercise. To test this idea, we examined muscle fiber size and Na(+)-K(+)-ATPase activity in 16 phylogenetically paired species of tropical and temperate birds. We found that 3 of the 16 paired comparisons indicated that tropical birds had significantly larger fibers, contrary to our hypothesis. Our data show that SA∶V is proportional to Na(+)-K(+)-ATPase activity in muscles of birds.

  1. Gravitational unloading effects on muscle fiber size, phenotype and myonuclear number

    NASA Technical Reports Server (NTRS)

    Ohira, Y.; Yoshinaga, T.; Nomura, T.; Kawano, F.; Ishihara, A.; Nonaka, I.; Roy, R. R.; Edgerton, V. R.

    2002-01-01

    The effects of gravitational unloading with or without intact neural activity and/or tension development on myosin heavy chain (MHC) composition, cross-sectional area (CSA), number of myonuclei, and myonuclear domain (cytoplasmic volume per myonucleus ratio) in single fibers of both slow and fast muscles of rat hindlimbs are reviewed briefly. The atrophic response to unloading is generally graded as follows: slow extensors > fast extensors > fast flexors. Reduction of CSA is usually greater in the most predominant fiber type of that muscle. The percentage of fibers expressing fast MHC isoforms increases in unloaded slow but not fast muscles. Myonuclear number per mm of fiber length and myonuclear domain is decreased in the fibers of the unloaded predominantly slow soleus muscle, but not in the predominantly fast plantaris. Decreases in myonuclear number and domain, however, are observed in plantaris fibers when tenotomy, denervation, or both are combined with hindlimb unloading. All of these results are consistent with the view that a major factor for fiber atrophy is an inhibition or reduction of loading of the hindlimbs. These data also indicate that predominantly slow muscles are more responsive to unloading than predominantly fast muscles. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  2. Fiber type composition of the sternomastoid and diaphragm muscles of dystrophin-deficient mdx mice.

    PubMed

    Guido, Anderson Neri; Campos, Gerson Eduardo Rocha; Neto, Humberto Santo; Marques, Maria Julia; Minatel, Elaine

    2010-10-01

    The muscle fiber phenotype is mainly determined by motoneuron innervation and changes in neuromuscular interaction alter the muscle fiber type. In dystrophin-deficient mdx mice, changes in the molecular assembly of the neuromuscular junction and in nerve terminal sprouting occur in the sternomastoid (STN) muscle during early stages of the disease. In this study, we were interested to see whether early changes in neuromuscular assembly are correlated with alterations in fiber type in dystrophic STN at 2 months of age. A predominance of hybrid fast myofibers (about 52% type IIDB) was observed in control (C57Bl/10) STN. In mdx muscle, the lack of dystrophin did not change this profile (about 54% hybrid type IIDB). Pure fast type IID fibers predominated in normal and dystrophic diaphragm (DIA; about 39% in control and 30% in mdx muscle) and a population of slow Type I fibers was also present (about 10% in control and 13% in mdx muscle). In conclusion, early changes in neuromuscular assembly do not affect the fiber type composition of dystrophic STN. In contrast to the pure fast fibers of the more affected DIA, the hybrid phenotype of the STN may permit dynamic adaptations during progression of the disease.

  3. High endocytotic activity occurs periodically in the endplate region of denervated mouse striated muscle fibers.

    PubMed

    Lawoko, G; Tågerud, S

    1995-08-01

    High endocytotic activity after denervation of skeletal muscle occurs in a proportion of muscle fibers (both slow and fast fiber types) in the endplate region. The present study was performed in order to examine if a periodicity in the endocytotic activity could explain why the process is not observed in all fibers at a given time. Three markers, horseradish peroxidase (HRP), rhodamine B isothiocyanate-labeled dextran, and fluorescein isothiocyanate-labeled dextran were used to demonstrate endocytotic activity of muscle fibers of the denervated mouse hemidiaphragm in vivo. Acetylcholine esterase staining was used in conjunction with HRP uptake to determine the proportion of denervated muscle fibers with endocytotic activity in the endplate region at any one time. The results show that 25-50% of the muscle fibers display high endocytotic activity in the endplate region at a given time 10 days after denervation. The existence of a periodicity in this endocytotic activity is suggested by results obtained using two different endocytotic markers administered at time intervals of 0-7 days. We conclude that loss of contact with the innervating motorneuron induces a high endocytotic activity which occurs periodically in the perisynaptic region of skeletal muscle fibers.

  4. Effects of muscle fiber type and size on EMG median frequency and conduction velocity.

    PubMed

    Kupa, E J; Roy, S H; Kandarian, S C; De Luca, C J

    1995-07-01

    This paper describes an in vitro method for comparing surface-detected electromyographic median frequency (MF) and conduction velocity (CV) parameters with histochemical measurements of muscle fiber type composition and cross-sectional area (CSA). Electromyographic signals were recorded during electrically elicited tetanic contractions from rat soleus, extensor digitorum longus, and diaphragm muscles placed in an oxygenated Krebs bath. Fibers were typed as slow oxidative, fast oxidative glycolytic, and fast glycolytic based on histochemical enzyme stains. Muscles with a greater percentage of fast glycolytic and fast oxidative glycolytic fibers exhibited greater initial values of MF and CV as well as a greater reduction in these variables over the course of the contraction. Regression indicated that fiber type composition could be predicted based on two MF parameters. A weighted measure of muscle fiber CSA was found to be linearly related to both initial MF and CV. The results of this study suggest that MF and CV parameters recorded during a muscular contraction are related to muscle fiber type composition and muscle fiber CSA.

  5. Gravitational unloading effects on muscle fiber size, phenotype and myonuclear number

    NASA Technical Reports Server (NTRS)

    Ohira, Y.; Yoshinaga, T.; Nomura, T.; Kawano, F.; Ishihara, A.; Nonaka, I.; Roy, R. R.; Edgerton, V. R.

    2002-01-01

    The effects of gravitational unloading with or without intact neural activity and/or tension development on myosin heavy chain (MHC) composition, cross-sectional area (CSA), number of myonuclei, and myonuclear domain (cytoplasmic volume per myonucleus ratio) in single fibers of both slow and fast muscles of rat hindlimbs are reviewed briefly. The atrophic response to unloading is generally graded as follows: slow extensors > fast extensors > fast flexors. Reduction of CSA is usually greater in the most predominant fiber type of that muscle. The percentage of fibers expressing fast MHC isoforms increases in unloaded slow but not fast muscles. Myonuclear number per mm of fiber length and myonuclear domain is decreased in the fibers of the unloaded predominantly slow soleus muscle, but not in the predominantly fast plantaris. Decreases in myonuclear number and domain, however, are observed in plantaris fibers when tenotomy, denervation, or both are combined with hindlimb unloading. All of these results are consistent with the view that a major factor for fiber atrophy is an inhibition or reduction of loading of the hindlimbs. These data also indicate that predominantly slow muscles are more responsive to unloading than predominantly fast muscles. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  6. Effects of fiber type and training on beta-adrenoceptor density in human skeletal muscle.

    PubMed

    Martin, W H; Coggan, A R; Spina, R J; Saffitz, J E

    1989-11-01

    The density and distribution of beta-adrenergic receptors in type I and II fibers of human gastrocnemius and quadriceps muscles were characterized in ten healthy sedentary subjects and in a subgroup of six subjects before and after 12 wk of endurance exercise training. Total tissue content of beta-receptors was measured in frozen sections of skeletal muscle biopsies incubated with 125I-labeled cyanopindolol in the presence and absence of 10(-5) M L-propranolol. The relative beta-receptor densities of type I and II fibers were delineated autoradiographically. Muscle fiber types were identified in adjacent serial sections by histochemical staining of myofibrillar adenosine-triphosphatase (ATPase) activity. Type I fibers had a threefold greater beta-receptor density than type II fibers of the same muscle [P less than 0.001; type I-to-type II fiber ratio of beta-receptor density was 3.06 +/- 0.43 (SD)]. Exercise training elicited a change in muscle fiber subtype composition (+34% type IIa and -42% type IIb; P less than 0.05 and P = 0.066, respectively), a 40% increase in citrate synthase activity of skeletal muscle (P = 0.01), and a 23% rise in peak oxygen uptake (P less than 0.001). However, no change in total tissue content of beta-receptors was observed after exercise training, even when receptor density was adjusted for preconditioning fiber type composition. Thus beta-receptor density of type I fibers of human skeletal muscle is threefold greater than that of type II fibers. Enhanced capacity for aerobic metabolism after endurance exercise training is not associated with upregulation of total beta-receptor density.

  7. A multiscale chemo-electro-mechanical skeletal muscle model to analyze muscle contraction and force generation for different muscle fiber arrangements

    PubMed Central

    Heidlauf, Thomas; Röhrle, Oliver

    2014-01-01

    The presented chemo-electro-mechanical skeletal muscle model relies on a continuum-mechanical formulation describing the muscle's deformation and force generation on the macroscopic muscle level. Unlike other three-dimensional models, the description of the activation-induced behavior of the mechanical model is entirely based on chemo-electro-mechanical principles on the microscopic sarcomere level. Yet, the multiscale model reproduces key characteristics of skeletal muscles such as experimental force-length and force-velocity data on the macroscopic whole muscle level. The paper presents the methodological approaches required to obtain such a multiscale model, and demonstrates the feasibility of using such a model to analyze differences in the mechanical behavior of parallel-fibered muscles, in which the muscle fibers either span the entire length of the fascicles or terminate intrafascicularly. The presented results reveal that muscles, in which the fibers span the entire length of the fascicles, show lower peak forces, more dispersed twitches and fusion of twitches at lower stimulation frequencies. In detail, the model predicted twitch rise times of 38.2 and 17.2 ms for a 12 cm long muscle, in which the fibers span the entire length of the fascicles and with twelve fiber compartments in series, respectively. Further, the twelve-compartment model predicted peak twitch forces that were 19% higher than in the single-compartment model. The analysis of sarcomere lengths during fixed-end single twitch contractions at optimal length predicts rather small sarcomere length changes. The observed lengths range from 75 to 111% of the optimal sarcomere length, which corresponds to a region with maximum filament overlap. This result suggests that stability issues resulting from activation-induced stretches of non-activated sarcomeres are unlikely in muscles with passive forces appearing at short muscle length. PMID:25566094

  8. Automated muscle fiber type population analysis with ImageJ of whole rat muscles using rapid myosin heavy chain immunohistochemistry.

    PubMed

    Bergmeister, Konstantin D; Gröger, Marion; Aman, Martin; Willensdorfer, Anna; Manzano-Szalai, Krisztina; Salminger, Stefan; Aszmann, Oskar C

    2016-08-01

    Skeletal muscle consists of different fiber types which adapt to exercise, aging, disease, or trauma. Here we present a protocol for fast staining, automatic acquisition, and quantification of fiber populations with ImageJ. Biceps and lumbrical muscles were harvested from Sprague-Dawley rats. Quadruple immunohistochemical staining was performed on single sections using antibodies against myosin heavy chains and secondary fluorescent antibodies. Slides were scanned automatically with a slide scanner. Manual and automatic analyses were performed and compared statistically. The protocol provided rapid and reliable staining for automated image acquisition. Analyses between manual and automatic data indicated Pearson correlation coefficients for biceps of 0.645-0.841 and 0.564-0.673 for lumbrical muscles. Relative fiber populations were accurate to a degree of ± 4%. This protocol provides a reliable tool for quantification of muscle fiber populations. Using freely available software, it decreases the required time to analyze whole muscle sections. Muscle Nerve 54: 292-299, 2016. © 2016 Wiley Periodicals, Inc.

  9. Effect of physical training on the proportion of slow-twitch type I muscle fibers, a novel nonimmune-mediated mechanism for muscle impairment in polymyositis or dermatomyositis.

    PubMed

    Dastmalchi, Maryam; Alexanderson, Helene; Loell, Ingela; Ståhlberg, Marcus; Borg, Kristian; Lundberg, Ingrid E; Esbjörnsson, Mona

    2007-10-15

    To compare muscle fiber type composition and muscle fiber area in patients with chronic polymyositis or dermatomyositis and healthy controls, and to determine whether physical training for 12 weeks could alter these muscle characteristics. Muscle fiber type composition and muscle fiber area were investigated by biochemical and immunohistochemistry techniques in repeated muscle biopsy samples obtained from 9 patients with chronic myositis before and after a 12-week exercise program and in healthy controls. Muscle performance was evaluated by the Functional Index (FI) in myositis and by the Short Form 36 (SF-36) quality of life instrument. Before exercise, the proportion of type I fibers was lower (mean +/- SD 32% +/- 10%) and the proportion of type IIC fibers was higher (3% +/- 3%) in patients compared with healthy controls. After exercise, percentage of type I fiber increased to 42% +/- 13% (P < 0.05), and type IIC decreased to 1% +/- 1%. An exercise-induced 20% increase of the mean fiber area was also observed. The functional capacity measured by the FI in myositis and the physical functioning subscale of the SF-36 increased significantly. Improved physical functioning was positively correlated with the proportion of type I fibers (r = 0.88, P < 0.01) and type II muscle fiber area (r = 0.70, P < 0.05). Low muscle endurance in chronic polymyositis or dermatomyositis may be related to a low proportion of oxidative, slow-twitch type I fibers. Change in fiber type composition and increased muscle fiber area may contribute to improved muscle endurance and decreased muscle fatigue after a moderate physical training program.

  10. [New formation of elastic fiber material in aortic defects covered with muscle flaps].

    PubMed

    Klima, G; Papp, C

    1985-01-01

    The examination of the coverage of vascular defects with intercostal muscles showed during an observation period of 7 weeks the development of cartilage tissue with thick elastic fiber nettings running between the chondroma.

  11. Degeneration of oxidative muscle fibers in HTLV-1 tax transgenic mice.

    PubMed

    Nerenberg, M I; Wiley, C A

    1989-12-01

    The HTLV-1 tax gene under control of the HTLV-1 long terminal repeat (LTR) was introduced into transgenic mice. Previously tax protein expression in the muscle and peripheral nerves of three independent mouse lines was reported. Here the localization of this transgenic protein at a cellular and subcellular level is described. Tax protein was expressed in oxidative muscle fibers that developed severe progressive atrophy. It localized to the cytoplasma where it was associated with structures resembling degenerating Z bands. This pattern of muscle fiber involvement is similar to that observed in human retroviral associated myopathy. This transgenic mouse model suggests that preferential expression of the HTLV-1 viral promoter in oxidative muscle fibers may explain the productive infection of these fibers in HTLV-1 myopathy.

  12. Further study of the electrical and machanical responses of slow fibers in cat extraocular muscles.

    PubMed

    Pilar, G

    1967-10-01

    Electrical and mechanical responses have been obtained in situ and in vitro from the superior oblique muscle stimulated by single and repetitive electrical pulses, applied to the trochlear nerve. Two different types of muscle fibers are described, the twitch and the slow. The slow type is characterized electrically by the presence of junctional potentials, which have reversal potentials between -10 and -20 mv, and do not show propagated responses or spikes, during nerve stimulation. When the slow muscle fibers are repetitively stimulated in situ, a prolonged contraction is maintained during stimulation. At the time, the recorded electrical activity is produced locally, at the level of the neuromuscular junctions of the slow fibers. These results indicate that the contractile mechanism of the slow muscle fibers is activated locally and segmentally.

  13. Skeletal muscle architecture and fiber-type distribution with the multiple bellies of the mouse extensor digitorum longus muscle.

    PubMed

    Chleboun, G S; Patel, T J; Lieber, R L

    1997-01-01

    The purpose of this study was to describe the extent to which architectural and fiber-type characteristics of the four bellies of the mouse extensor digitorum longus (EDL) suggest specialization of the digits, and to mathematically model the functional effects of the structural properties. Six mice were perfused in situ with glutaraldehyde while the lower limb was positioned approximately in the neutral position. After perfusion, lower limbs were removed and placed in glutaraldehyde until the EDL was dissected from the limb and separated into individual muscle bellies corresponding to each digit for architectural determination. The results showed that the muscle belly of digit 5 tended to be different from the muscle bellies of digits 2-4 for many architectural characteristics. Muscle mass, physiological cross-sectional area, muscle length, and fiber length were all significantly greater in digit 5. Proximal tendon length was also significantly longer in digit 5, and distal tendon length, as well as total tendon length, were significantly shorter in digit 5. Sarcomere length was shortest at the proximal end of the muscle and longest, 60-80%, toward the distal end. Fiber type distribution was about 60% FOG, 39% FG with only 1% SO fibers in all muscle bellies. Muscle-tendon modeling illustrated that peak force and maximal shortening velocity were greatest in digit 5. Inclusion of the tendon in the model resulted in a 10% shift of the force-length curve to longer lengths. Assuming muscle structure is matched to function, we speculate that digit 5 of the mouse EDL bears higher loads over a greater excursion during locomotion compared to the remaining digits.

  14. Effects of chronic centrifugation on skeletal muscle fibers in young developing rats

    NASA Technical Reports Server (NTRS)

    Martin, W. D.

    1980-01-01

    Three groups of 30-d old male and female rats were centrifuged for 2, 4, 8, and 16 weeks, after which their soleus and plantaris muscles were analysed for changes in proportions of muscle fiber types. The groups were: earth control, maintained at earth gravity without rotation; rotation control, subjected to a gravitational force of 1.05 G and 28 rpm; and rotation experimental, subjected to a gravitational force of 2 G and 28 rpm. Muscle fibers were classified into four fiber types on the basis of actomyosin ATPase activity as slow oxidative, fast oxidative glycolytic and either fast glycolytic (plantaris) or intermediate (soleus). Hypergravity resulted in an increase in slow oxidative fibers in soleus relative to the earth control, but not of females treated similarly. The relationship of body weight to the changes in proportion of slow oxidative fibers is discussed.

  15. Effects of chronic centrifugation on skeletal muscle fibers in young developing rats

    NASA Technical Reports Server (NTRS)

    Martin, W. D.

    1980-01-01

    Three groups of 30-d old male and female rats were centrifuged for 2, 4, 8, and 16 weeks, after which their soleus and plantaris muscles were analysed for changes in proportions of muscle fiber types. The groups were: earth control, maintained at earth gravity without rotation; rotation control, subjected to a gravitational force of 1.05 G and 28 rpm; and rotation experimental, subjected to a gravitational force of 2 G and 28 rpm. Muscle fibers were classified into four fiber types on the basis of actomyosin ATPase activity as slow oxidative, fast oxidative glycolytic and either fast glycolytic (plantaris) or intermediate (soleus). Hypergravity resulted in an increase in slow oxidative fibers in soleus relative to the earth control, but not of females treated similarly. The relationship of body weight to the changes in proportion of slow oxidative fibers is discussed.

  16. Electrophysiology and dye-coupling are sexually dimorphic characteristics of individual laryngeal muscle fibers in Xenopus laevis.

    PubMed

    Tobias, M L; Kelley, D B

    1988-07-01

    Sex differences at the laryngeal neuromuscular junction of Xenopus laevis were examined by recording intracellularly from muscle fibers in response to nerve stimulation. Male laryngeal muscle contains 2 physiologically distinct fiber types. Type I fibers generate postsynaptic potentials in response to low-magnitude stimulus pulses and action potentials in response to higher-magnitude stimulus pulses. Type II muscle fibers require repetitive stimulation for action potential production, probably because of facilitation. Subthreshold events in type I and II fibers suggest that these neuromuscular synapses have low safety factor junctions. Female laryngeal muscle contains one fiber type (III), which is physiologically distinct from those found in the male. Type III fibers produce an action potential in response to a single-stimulus pulse of suprathreshold voltage delivered to the laryngeal nerve; subthreshold events were not observed. Iontophoretic injection of Lucifer yellow into a single female muscle fiber resulted in as many as 43 labeled fibers. In males, only one fiber was labeled. Dye-coupling was not observed in adult females treated with the androgenic steroid hormone, testosterone. We have previously reported that laryngeal muscle fibers are recruited throughout a stimulus train presented to the laryngeal nerve in males, but are not recruited in females (Tobias and Kelly, 1987). Sex differences in the frequency of electrophysiological fiber types described here may account for sex differences in fiber recruitment. Synchronous activity of dye-coupled fibers may increase the effectiveness of muscle contraction in females.

  17. Spermine oxidase maintains basal skeletal muscle gene expression and fiber size and is strongly repressed by conditions that cause skeletal muscle atrophy.

    PubMed

    Bongers, Kale S; Fox, Daniel K; Kunkel, Steven D; Stebounova, Larissa V; Murry, Daryl J; Pufall, Miles A; Ebert, Scott M; Dyle, Michael C; Bullard, Steven A; Dierdorff, Jason M; Adams, Christopher M

    2015-01-15

    Skeletal muscle atrophy is a common and debilitating condition that remains poorly understood at the molecular level. To better understand the mechanisms of muscle atrophy, we used mouse models to search for a skeletal muscle protein that helps to maintain muscle mass and is specifically lost during muscle atrophy. We discovered that diverse causes of muscle atrophy (limb immobilization, fasting, muscle denervation, and aging) strongly reduced expression of the enzyme spermine oxidase. Importantly, a reduction in spermine oxidase was sufficient to induce muscle fiber atrophy. Conversely, forced expression of spermine oxidase increased muscle fiber size in multiple models of muscle atrophy (immobilization, fasting, and denervation). Interestingly, the reduction of spermine oxidase during muscle atrophy was mediated by p21, a protein that is highly induced during muscle atrophy and actively promotes muscle atrophy. In addition, we found that spermine oxidase decreased skeletal muscle mRNAs that promote muscle atrophy (e.g., myogenin) and increased mRNAs that help to maintain muscle mass (e.g., mitofusin-2). Thus, in healthy skeletal muscle, a relatively low level of p21 permits expression of spermine oxidase, which helps to maintain basal muscle gene expression and fiber size; conversely, during conditions that cause muscle atrophy, p21 expression rises, leading to reduced spermine oxidase expression, disruption of basal muscle gene expression, and muscle fiber atrophy. Collectively, these results identify spermine oxidase as an important positive regulator of muscle gene expression and fiber size, and elucidate p21-mediated repression of spermine oxidase as a key step in the pathogenesis of skeletal muscle atrophy.

  18. Spermine oxidase maintains basal skeletal muscle gene expression and fiber size and is strongly repressed by conditions that cause skeletal muscle atrophy

    PubMed Central

    Bongers, Kale S.; Fox, Daniel K.; Kunkel, Steven D.; Stebounova, Larissa V.; Murry, Daryl J.; Pufall, Miles A.; Ebert, Scott M.; Dyle, Michael C.; Bullard, Steven A.; Dierdorff, Jason M.

    2014-01-01

    Skeletal muscle atrophy is a common and debilitating condition that remains poorly understood at the molecular level. To better understand the mechanisms of muscle atrophy, we used mouse models to search for a skeletal muscle protein that helps to maintain muscle mass and is specifically lost during muscle atrophy. We discovered that diverse causes of muscle atrophy (limb immobilization, fasting, muscle denervation, and aging) strongly reduced expression of the enzyme spermine oxidase. Importantly, a reduction in spermine oxidase was sufficient to induce muscle fiber atrophy. Conversely, forced expression of spermine oxidase increased muscle fiber size in multiple models of muscle atrophy (immobilization, fasting, and denervation). Interestingly, the reduction of spermine oxidase during muscle atrophy was mediated by p21, a protein that is highly induced during muscle atrophy and actively promotes muscle atrophy. In addition, we found that spermine oxidase decreased skeletal muscle mRNAs that promote muscle atrophy (e.g., myogenin) and increased mRNAs that help to maintain muscle mass (e.g., mitofusin-2). Thus, in healthy skeletal muscle, a relatively low level of p21 permits expression of spermine oxidase, which helps to maintain basal muscle gene expression and fiber size; conversely, during conditions that cause muscle atrophy, p21 expression rises, leading to reduced spermine oxidase expression, disruption of basal muscle gene expression, and muscle fiber atrophy. Collectively, these results identify spermine oxidase as an important positive regulator of muscle gene expression and fiber size, and elucidate p21-mediated repression of spermine oxidase as a key step in the pathogenesis of skeletal muscle atrophy. PMID:25406264

  19. Ultrastructural study of muscles fibers in tick Hyalomma (Hyalomma) anatolicum anatolicum (Ixodoidea: Ixodidae).

    PubMed

    Bughdadi, Faisal A

    2010-09-01

    In the present study, ticks were obtained from a colony maintained at 28 degrees C and 75% relative humidity in at the Department of Biology, University College Umm Al-Qura University, Saudi Arabia and the Transmission Electron Microscope technique (TEM) was used to describes the ultrastructure and description of muscle of the of ixodid tick Hyalomma (Hyalomma) anatolicum anatolicum. The results showed that muscles of the unfed ticks Hyalomma (Hyalomma) anatolicum anatolicum in longitudinal sections are spindle-shaped to cylindrical muscle fibers. In the unfed nymph Hyalomma (Hyalomma) anatolicum anatolicum skeletal and visceral muscles are distinguished according to structure, function and position. These muscles include the capitulum, dorsoventral and leg oblique muscles. All muscle fibers are ensheathed (covered by sheath) in a sarcolemma. Their muscle fibers have striated pattern of successive sarcomeres whose thick myosin filaments are surrounded by orbitals of up to 12 thin actin filaments. The cytoplasm of the epidermal cell appears largely devoted with complicated microtubules present in parallel with long axis of adjacent muscle fibers. The cell membrane invaginates into tubular system extending deeply into the sarcoplasm and closely associated to cisternae of sarcoplasmic reticulum. The tubular system and sarcoplasmic reticulum forming two-membered (dyads) are considered to be the main route of calcium ions whose movement are synchronized with the motor impulse to control muscles contraction. In the sarcoplasm two types of muscle fibers are recognized according to thickness and density and mitochondrial size, distribution and population. Both skeletal and visceral muscles are invaginated by tracheoles and innervated by nerve axons containing synaptic vesicles. The actin and myosin filaments are slightly interrupted and the tubular system sarcoplasmic reticulum is well demonstrated.

  20. Effects of cannabinoids on caffeine contractures in slow and fast skeletal muscle fibers of the frog.

    PubMed

    Huerta, Miguel; Ortiz-Mesina, Mónica; Trujillo, Xóchitl; Sánchez-Pastor, Enrique; Vásquez, Clemente; Castro, Elena; Velasco, Raymundo; Montoya-Pérez, Rocío; Onetti, Carlos

    2009-05-01

    The effect of cannabinoids on caffeine contractures was investigated in slow and fast skeletal muscle fibers using isometric tension recording. In slow muscle fibers, WIN 55,212-2 (10 and 5 microM) caused a decrease in tension. These doses reduced maximum tension to 67.43 +/- 8.07% (P = 0.02, n = 5) and 79.4 +/- 14.11% (P = 0.007, n = 5) compared to control, respectively. Tension-time integral was reduced to 58.37 +/- 7.17% and 75.10 +/- 3.60% (P = 0.002, n = 5), respectively. Using the CB(1) cannabinoid receptor agonist ACPA (1 microM) reduced the maximum tension of caffeine contractures by 68.70 +/- 11.63% (P = 0.01, n = 5); tension-time integral was reduced by 66.82 +/- 6.89% (P = 0.02, n = 5) compared to controls. When the CB(1) receptor antagonist AM281 was coapplied with ACPA, it reversed the effect of ACPA on caffeine-evoked tension. In slow and fast muscle fibers incubated with the pertussis toxin, ACPA had no effect on tension evoked by caffeine. In fast muscle fibers, ACPA (1 microM) also decreased tension; the maximum tension was reduced by 56.48 +/- 3.4% (P = 0.001, n = 4), and tension-time integral was reduced by 57.81 +/- 2.6% (P = 0.006, n = 4). This ACPA effect was not statistically significant with respect to the reduction in tension in slow muscle fibers. Moreover, we detected the presence of mRNA for the cannabinoid CB(1) receptor on fast and slow skeletal muscle fibers, which was significantly higher in fast compared to slow muscle fiber expression. In conclusion, our results suggest that in the slow and fast muscle fibers of the frog cannabinoids diminish caffeine-evoked tension through a receptor-mediated mechanism.

  1. Cycle Training Increased GLUT4 and Activation of mTOR in Fast Twitch Muscle Fibers

    PubMed Central

    Stuart, Charles A.; Howell, Mary E.A.; Baker, Jonathan D.; Dykes, Rhesa J.; Duffourc, Michelle M.; Ramsey, Michael W.; Stone, Michael H.

    2009-01-01

    Purpose To determine if cycle training of sedentary subjects would increase the expression of the principle muscle glucose transporters, six volunteers completed six weeks of progressively increasing intensity stationary cycle cycling. Methods In vastus lateralis muscle biopsies, changes in expression of GLUT1, GLUT4, GLUT5, and GLUT12 were compared using quantitative immunoblots with specific protein standards. Regulatory pathway components were evaluated by immunoblots of muscle homogenates and immunohistochemistry of microscopic sections. Results GLUT1 was unchanged, GLUT4 increased 66%, GLUT12 increased 104%, and GLUT5 decreased 72%. A mitochondrial marker (cytochrome c) and regulators of mitochondrial biogenesis (PGC-1α and phospho-AMPK) were unchanged, but the muscle hypertrophy pathway component, phospho-mTOR increased 83% after the exercise program. In baseline biopsies, GLUT4 by immunohistochemical techniques was 37% greater in Type I (slow twitch, red) muscle fibers, but the exercise training increased GLUT4 expression in Type II (fast twitch, white) fibers by 50%, achieving parity with the Type I fibers. Baseline phospho-mTOR expression was 50% higher in Type II fibers and increased more in Type II fibers (62%) with training, but also increased in Type I fibers (34%). Conclusion Progressive intensity stationary cycle training of previously sedentary subjects increased muscle insulin-responsive glucose transporters (GLUT4 and GLUT12) and decreased the fructose transporter (GLUT5). The increase in GLUT4 occurred primarily in Type II muscle fibers and this coincided with activation of the mTOR muscle hypertrophy pathway. There was little impact on Type I fiber GLUT4 expression and no evidence of change in mitochondrial biogenesis. PMID:20010125

  2. Fnip1 regulates skeletal muscle fiber type specification, fatigue resistance, and susceptibility to muscular dystrophy.

    PubMed

    Reyes, Nicholas L; Banks, Glen B; Tsang, Mark; Margineantu, Daciana; Gu, Haiwei; Djukovic, Danijel; Chan, Jacky; Torres, Michelle; Liggitt, H Denny; Hirenallur-S, Dinesh K; Hockenbery, David M; Raftery, Daniel; Iritani, Brian M

    2015-01-13

    Mammalian skeletal muscle is broadly characterized by the presence of two distinct categories of muscle fibers called type I "red" slow twitch and type II "white" fast twitch, which display marked differences in contraction strength, metabolic strategies, and susceptibility to fatigue. The relative representation of each fiber type can have major influences on susceptibility to obesity, diabetes, and muscular dystrophies. However, the molecular factors controlling fiber type specification remain incompletely defined. In this study, we describe the control of fiber type specification and susceptibility to metabolic disease by folliculin interacting protein-1 (Fnip1). Using Fnip1 null mice, we found that loss of Fnip1 increased the representation of type I fibers characterized by increased myoglobin, slow twitch markers [myosin heavy chain 7 (MyH7), succinate dehydrogenase, troponin I 1, troponin C1, troponin T1], capillary density, and mitochondria number. Cultured Fnip1-null muscle fibers had higher oxidative capacity, and isolated Fnip1-null skeletal muscles were more resistant to postcontraction fatigue relative to WT skeletal muscles. Biochemical analyses revealed increased activation of the metabolic sensor AMP kinase (AMPK), and increased expression of the AMPK-target and transcriptional coactivator PGC1α in Fnip1 null skeletal muscle. Genetic disruption of PGC1α rescued normal levels of type I fiber markers MyH7 and myoglobin in Fnip1-null mice. Remarkably, loss of Fnip1 profoundly mitigated muscle damage in a murine model of Duchenne muscular dystrophy. These results indicate that Fnip1 controls skeletal muscle fiber type specification and warrant further study to determine whether inhibition of Fnip1 has therapeutic potential in muscular dystrophy diseases.

  3. Dystrophic skeletal muscle fibers display alterations at the level of calcium microdomains

    PubMed Central

    DiFranco, Marino; Woods, Christopher E.; Capote, Joana; Vergara, Julio L.

    2008-01-01

    The spatiotemporal properties of the Ca2+-release process in skeletal muscle fibers from normal and mdx fibers were determined using the confocal-spot detection technique. The Ca2+ indicator OGB-5N was used to record action potential-evoked fluorescence signals at consecutive locations separated by 200 nm along multiple sarcomeres of FDB fibers loaded with 10- and 30-mM EGTA. Three-dimensional reconstructions of fluorescence transients demonstrated the existence of microdomains of increased fluorescence around the Ca2+-release sites in both mouse strains. The Ca2+ microdomains in mdx fibers were regularly spaced along the fiber axis, displaying a distribution similar to that seen in normal fibers. Nevertheless, both preparations differed in that in 10-mM EGTA Ca2+ microdomains had smaller amplitudes and were wider in mdx fibers than in controls. In addition, Ca2+-dependent fluorescence transients recorded at selected locations within the sarcomere of mdx muscle fibers were not only smaller, but also slower than their counterparts in normal fibers. Notably, differences in the spatial features of the Ca2+ microdomains recorded in mdx and normal fibers, but not in the amplitude and kinetics of the Ca2+ transients, were eliminated in 30-mM EGTA. Our results consistently demonstrate that Ca2+-release flux calculated from release sites in mdx fibers is uniformly impaired with respect to those normal fibers. The Ca2+-release reduction is consistent with that previously measured using global detection techniques. PMID:18787128

  4. Temperature dynamics of soft tissues during diode laser cutting by different types of fiber opto-thermal converters

    NASA Astrophysics Data System (ADS)

    Belikov, Andrey V.; Skrypnik, Alexei V.; Smirnov, Sergey N.; Semyashkina, Yulia V.

    2017-03-01

    The results of in vitro study of the soft tissue temperature dynamics during 980 nm diode laser cutting by different types (CLEAR, FILM, VOLUMETRIC) of fiber opto-thermal converters (FOTC) are presented. It was found that the use of CLEAR fiber end (tip) at the laser power below 8.5 W doesn't lead to the soft tissue (chicken meat) destruction. The chicken meat destruction (cutting) begins when irradiated by 8.5 W laser radiation for approximately 9.0 s. At the power of 9.0 W this time decreases up to 7.0 s, at 9.5 W - to 6.0 s, at 10.0 W - to 3.5 s. The moment of soft tissue cutting start correlates with the moment of black layer (absorber) formation at the fiber end and appearance of visually identifiable laser cut walls on the photos; the temperature in this case rapidly increases up to 850 °C. It was determined that the FILM FOTC begins to cut the soft tissue immediately after exposure of laser radiation with power of 4.0 W, the temperature in this case reaches 900 °C. It was determined that the VOLUMETRIC FOTC begins to cut the tissue immediately after exposure at the power of 1.0 W, the temperature in this case reaches 600 °C. VOLUMETRIC FOTC can produce more effective cuts of the soft tissue at the laser power of 4.0 W, in this case, the temperature is above 1200 °C.

  5. Myosin types and fiber types in cardiac muscle. I. Ventricular myocardium

    PubMed Central

    1981-01-01

    Antisera against bovine atrial myosin were raised in rabbits, purified by affinity chromatography, and absorbed with insolubilized ventricular myosin. Specific anti-bovine atrial myosin (anti-bAm) antibodies reacted selectively with atrial myosin heavy chains, as determined by enzyme immunoassay combined with SDS-gel electrophoresis. In direct and indirect immunofluorescence assay, anti-bAm was found to stain all atrial muscle fibers and a minor proportion of ventricular muscle fibers in the right ventricle of the bovine heart. In contrast, almost all muscle fibers in the left ventricle were unreactive. Purkinje fibers showed variable reactivity. In the rabbit heart, all atrial muscle fibers were stained by anti-bAm, whereas ventricular fibers showed a variable response in both the right and left ventricle, with a tendency for reactive fibers to be more numerous in the right ventricle and in subepicardial regions. Diversification of fiber types with respect to anti-bAm reactivity was found to occur during late stages of postnatal development in the rabbit heart and to be influenced by thyroid hormone. All ventricular muscle fibers became strongly reactive after thyroxine treatment, whereas they became unreactive or poorly reactive after propylthiouracil treatment. These findings are consistent with the existence of different ventricular isomyosins whose relative proportions can vary according to the thyroid state. Variations in ventricular isomyosin composition can account for the changes in myosin Ca2+-activated ATPase activity previously observed in cardiac muscle from hyper- and hypothyroid animals and may be responsible for the changes in the velocity of contraction of ventricular myocardium that occur under these conditions. The differential distribution of ventricular isomyosins in the normal heart suggests that fiber types with different contractile properties may coexist in the ventricular myocardium. PMID:7009623

  6. Contractile properties of muscle fibers from the deep and superficial digital flexors of horses.

    PubMed

    Butcher, M T; Chase, P B; Hermanson, J W; Clark, A N; Brunet, N M; Bertram, J E A

    2010-10-01

    Equine digital flexor muscles have independent tendons but a nearly identical mechanical relationship to the main joint they act upon. Yet these muscles have remarkable diversity in architecture, ranging from long, unipennate fibers ("short" compartment of DDF) to very short, multipennate fibers (SDF). To investigate the functional relevance of the form of the digital flexor muscles, fiber contractile properties were analyzed in the context of architecture differences and in vivo function during locomotion. Myosin heavy chain (MHC) isoform fiber type was studied, and in vitro motility assays were used to measure actin filament sliding velocity (V(f)). Skinned fiber contractile properties [isometric tension (P(0)/CSA), velocity of unloaded shortening (V(US)), and force-Ca(2+) relationships] at both 10 and 30°C were characterized. Contractile properties were correlated with MHC isoform and their respective V(f). The DDF contained a higher percentage of MHC-2A fibers with myosin (heavy meromyosin) and V(f) that was twofold faster than SDF. At 30°C, P(0)/CSA was higher for DDF (103.5 ± 8.75 mN/mm(2)) than SDF fibers (81.8 ± 7.71 mN/mm(2)). Similarly, V(US) (pCa 5, 30°C) was faster for DDF (2.43 ± 0.53 FL/s) than SDF fibers (1.20 ± 0.22 FL/s). Active isometric tension increased with increasing Ca(2+) concentration, with maximal Ca(2+) activation at pCa 5 at each temperature in fibers from each muscle. In general, the collective properties of DDF and SDF were consistent with fiber MHC isoform composition, muscle architecture, and the respective functional roles of the two muscles in locomotion.

  7. Enzymatically modified isoquercitrin supplementation intensifies plantaris muscle fiber hypertrophy in functionally overloaded mice.

    PubMed

    Kohara, Akiko; Machida, Masanao; Setoguchi, Yuko; Ito, Ryouichi; Sugitani, Masanori; Maruki-Uchida, Hiroko; Inagaki, Hiroyuki; Ito, Tatsuhiko; Omi, Naomi; Takemasa, Tohru

    2017-01-01

    Enzymatically modified isoquercitrin (EMIQ) is produced from rutin using enzymatic hydrolysis followed by treatment with glycosyltransferase in the presence of dextrin to add glucose residues. EMIQ is absorbed in the same way as quercetin, a powerful antioxidant reported to prevent disused muscle atrophy by targeting mitochondria and to have ergogenic effects. The present study investigated the effect of EMIQ on skeletal muscle hypertrophy induced by functional overload. In Study 1, 6-week-old ICR male mice were divided into 4 groups: sham-operated control, sham-operated EMIQ, overload-operated control, and overload-operated EMIQ groups. In Study 2, mice were divided into 3 groups: overload-operated whey control, overload-operated whey/EMIQ (low dose), and overload-operated whey/EMIQ (high dose) groups. The functional overload of the plantaris muscle was induced by ablation of the synergist (gastrocnemius and soleus) muscles. EMIQ and whey protein were administered with food. Three weeks after the operation, the cross-sectional area and minimal fiber diameter of the plantaris muscle fibers were measured. In Study 1, functional overload increased the cross-sectional area and minimal fiber diameter of the plantaris muscle. EMIQ supplementation significantly increased the cross-sectional area and minimal fiber diameter of the plantaris muscle in both the sham-operated and overload-operated groups. In Study 2, EMIQ supplementation combined with whey protein administration significantly increased the cross-sectional area and minimal fiber diameter of the plantaris muscle. EMIQ, even when administered as an addition to whey protein supplementation, significantly intensified the fiber hypertrophy of the plantaris muscle in functionally overloaded mice. EMIQ supplementation also induced fiber hypertrophy of the plantaris in sham-operated mice.

  8. Mechanical and/or neural activity-dependent regulation of soleus muscle fibers of mdx mice

    NASA Astrophysics Data System (ADS)

    Terada, Masahiro; Kawano, Fuminori; Lan, Yong Bo; Matsuoka, Yoshikazu; Wang, Xiao Dong; Ohira, Yoshinobu

    2005-08-01

    Roles of mechanical and/or neural activity in the necrosis -regeneration cycle in the soleus muscle fibers of mdxmicewerestudied. Five-weeks-oldmalemdxand wild type (WT) mice were separated into tenotomy (T), denervation (D), and T+D groups. The distal tendons of the left plantarflexors (soleus, plantaris, and gastrocnemius) were ablated in the T group. The left sciatic nerve was transected at the gluteal region in the D group. The right limb was kept intact as the normal control. Ambulation was allowed after the surgery. Soleus muscle was sampled 14 days after the surgery and analyses were performed in cross-section of whole muscle and in single fibers removed longitudinally. The total fiber number of the untreated muscle was 913±19 (Mean±SEM) and 872±45 in WT and mdx mice, respectively. The fiber number in mdx mice was decreased 48% by T and 31-35% by D and T+D, which induced fiber atrophy, may be due to either inhibited regeneration or stimulated necrosis. Although fibers with central nuclei or necrosis were not observed in WT muscle, 25-40% of fibers (vs. 40% in the contralateral control side) in treated muscles of mdx mice, analyzed cross-sectionally, were central-nucleated. However, fibers with only central nuclei were not detected in the longitudinally isolated fibers of treated groups, may be due to the phenomenon that the fibers with necrosis were lost in the relaxing solution. But % fibers with both central and peripheral nuclei were decreased and those with peripheral nuclei alone were increased by T. In both cross-sectional and longitudinal analyses, the % distribution of the central-nucleated relative to total fiber number was not affected by D, but decreased by T in mdx mice (p>0.05). Myonuclear number per mm of fiber length was identical generally, although the number was increased by T. Furthermore, DNA fragmentation was noted in the mdx fibers with necrosis. These data suggested that the localization of myonuclei, as well as either necrosis or

  9. Effects of External Calcium Deprivation on Single Muscle Fibers

    PubMed Central

    Caputo, Carlo; Gimenez, Maximo

    1967-01-01

    Deprivation of external calcium causes sudden potentiation of the twitch response of single muscle fibers. The potentiation was 64 ± 8%. Potentiation is simultaneous with membrane depolarization occurring after Ca++ removal. This depolarization amounted to 9 ± 2 mv. Ca++ removal also alters the action potential. 3 min after calcium withdrawal, action potential amplitude fell by 36 ± 3 mv; maximum rates of rise and fall of the spike decreased by 55 ± 5 and 63 ± 5% respectively. Changes in shape of the A. P. differ from those seen with other potentiators of the twitch response, such as Zn++. After short exposure to calcium-free media, potassium-induced contractures show potentiation of peak tension. The S-shaped curve relating potassium contracture tension to log [K]o shifts to the left after such treatment. Calcium deprivation also increased the rate of relaxation of the contractures. This effect depends on the duration of calcium deprivation, and is probably related to the effect of calcium lack on the membrane. The change in relaxation occurred immediately after calcium deprivation, and was reversed by sudden readmission of calcium. Relaxation of twitch and tetanus responses also were affected by Ca lack, but not as rapidly as potassium contractures. The results suggest that external calcium is not directly involved in the process responsible for tension development, supporting the view that this process is mediated by translocation of intracellular calcium. The relaxation process, however, appears to be rapidly affected by deprivation of external calcium. PMID:6064147

  10. [Myoplasmic fixed charges of the barnacle muscle fiber (author's transl)].

    PubMed

    Caillé, J P

    1979-06-12

    The experimental model used to study diffusion and electrical conduction in the cytoplasm of large muscle fibers was adapted to evaluate the myoplasmic density of fixed charges. Membranes of myoplasm were prepared and phi X, the myoplasmic thermodynamically effective charge density, was calculated from the membrane potential (Kamo, N., Toyoshima, Y. and Kobatake, Y. (1971) Kolloid Z.u.Z. Polymère 1061--1068) when these membranes were used as the partition between two electrolyte solutions. The dilution of KCl in the external solutions reduced phi X, which increases with the reduction of the water content in the membrane of myoplasm. With a water content of 73.0 ml/100 g KCl concentration in the external medium equal to 0.15 M, phi X was evaluated to 0.058 equiv/l. The substitution of KCl by NaCl introduces a reduction in phi X of 20--50% depending on E1KCl] in the external solutions. The addition of ATP, Mg2+, and Ca2+ also causes a reduction of phi B by 30--50% according to the experimental conditions. These results indicate that the fraction of counterions dissociated from the myoplasmic macromolecules is reduced when the concentration of the counterions is diminished or when CKl is replaced by Nal. It also suggests a reduction of phi X during muscular contraction.

  11. A One-Step Immunostaining Method to Visualize Rodent Muscle Fiber Type within a Single Specimen

    PubMed Central

    Sawano, Shoko; Komiya, Yusuke; Ichitsubo, Riho; Ohkawa, Yasuyuki; Nakamura, Mako; Tatsumi, Ryuichi; Ikeuchi, Yoshihide; Mizunoya, Wataru

    2016-01-01

    In this study, we present a quadruple immunostaining method for rapid muscle fiber typing of mice and rats using antibodies specific to the adult myosin heavy chain (MyHC) isoforms MyHC1, 2A, 2X, and 2B, which are common marker proteins of distinct muscle fiber types. We developed rat monoclonal antibodies specific to each MyHC isoform and conjugated these four antibodies to fluorophores with distinct excitation and emission wavelengths. By mixing the four types of conjugated antibodies, MyHC1, 2A, 2X, and 2B could be distinguished within a single specimen allowing for facile delineation of skeletal muscle fiber types. Furthermore, we could observe hybrid fibers expressing MyHC2X and MyHC2B together in single longitudinal muscle sections from mice and rats, that was not attained in previous techniques. This staining method is expected to be applied to study muscle fiber type transition in response to environmental factors, and to ultimately develop techniques to regulate animal muscle fiber types. PMID:27814384

  12. MOUSE TRANSGENIC LINES THAT SELECTIVELY LABEL TYPE I, TYPE IIA AND TYPES IIX+B SKELETAL MUSCLE FIBERS

    PubMed Central

    Chakkalakal, Joe V.; Kuang, Shihuan; Buffelli, Mario; Lichtman, Jeff W.; Sanes, Joshua R.

    2014-01-01

    Skeletal muscle fibers vary in contractile and metabolic properties. Four main fiber types are present in mammalian trunk and limb muscles; they are called I, IIA, IIX and IIB, ranging from slowest- to fastest-contracting. Individual muscles contain stereotyped proportions of two or more fiber types. Fiber type is determined by a combination of nerve-dependent and –independent influences, leading to formation of “homogeneous motor units” in which all branches of a single motor neuron form synapses on fibers of a single type. Fiber type composition of muscles can be altered in adulthood by multiple factors including exercise, denervation, hormones and aging. To facilitate analysis of muscle development, plasticity and innervation, we generated transgenic mouse lines in which Type I, Type IIA, and Type IIX+B fibers can be selectively labeled with distinguishable fluorophores. We demonstrate their use for motor unit reconstruction and live imaging of nerve-dependent alterations in fiber type. PMID:21898764

  13. Embryonic arsenic exposure reduces the number of muscle fibers in killifish (Fundulus heteroclitus).

    PubMed

    D'Amico, Angela R; Gibson, Alec W; Bain, Lisa J

    2014-01-01

    Arsenic is a contaminant of drinking water and has been correlated with adverse developmental outcomes such as low birth weight, reduced weight gain, and altered locomotor activity. Previous research has shown that killifish (Fundulus heteroclitus) exposed to high arsenic levels during embryogenesis had smaller muscle fiber diameters. The current study was designed to determine whether changes in muscle fibers persisted, were exacerbated, or resolved over time. Killifish embryos were exposed to 0-5 ppm arsenite and, upon hatching, were transferred into either clean water or continued receiving the same exposure to arsenic for up to 16 weeks. Arsenic significantly decreased the weight of both embryonic-only exposed juveniles and continuously exposed juveniles between 4 and 16 weeks of development at concentrations as low as 0.8 ppm. Although arsenite exposure increased the percentage of small diameter fibers during the early weeks, fiber diameters returned to control levels in the embryonic-only exposed fish. However, muscle fiber density was still reduced to 85.7%, 80.3%, and 73.8% of control for the 0.8, 2, and 5 ppm embryonic-only exposure groups, respectively, even after 16 weeks of development. These results indicate that while continuous exposure to arsenic may alter the size of muscle fibers, embryonic-only exposure to arsenic has lasting effects on the number of muscle fibers formed.

  14. Myosin content of individual human muscle fibers isolated by laser capture microdissection

    PubMed Central

    Stone, William L.; Howell, Mary E. A.; Brannon, Marianne F.; Hall, H. Kenton; Gibson, Andrew L.; Stone, Michael H.

    2015-01-01

    Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniques allow assessment of mRNA and protein content in individual fibers. We found that specific human fiber types contain different mixtures of myosin heavy and light chains. Fast-twitch (type IIx) fibers consistently contained myosin heavy chains 1, 2, and 4 and myosin light chain 1. Type I fibers always contained myosin heavy chains 6 and 7 (MYH6 and MYH7) and myosin light chain 3 (MYL3), whereas MYH6, MYH7, and MYL3 were nearly absent from type IIx fibers. In contrast to cardiomyocytes, where MYH6 (also known as α-myosin heavy chain) is seen solely in fast-twitch cells, only slow-twitch fibers of skeletal muscle contained MYH6. Classical fast myosin heavy chains (MHC1, MHC2, and MHC4) were present in variable proportions in all fiber types, but significant MYH6 and MYH7 expression indicated slow-twitch phenotype, and the absence of these two isoforms determined a fast-twitch phenotype. The mixed myosin heavy and light chain content of type IIa fibers was consistent with its role as a transition between fast and slow phenotypes. These new observations suggest that the presence or absence of MYH6 and MYH7 proteins dictates the slow- or fast-twitch phenotype in skeletal muscle. PMID:26676053

  15. Myosin content of individual human muscle fibers isolated by laser capture microdissection.

    PubMed

    Stuart, Charles A; Stone, William L; Howell, Mary E A; Brannon, Marianne F; Hall, H Kenton; Gibson, Andrew L; Stone, Michael H

    2016-03-01

    Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniques allow assessment of mRNA and protein content in individual fibers. We found that specific human fiber types contain different mixtures of myosin heavy and light chains. Fast-twitch (type IIx) fibers consistently contained myosin heavy chains 1, 2, and 4 and myosin light chain 1. Type I fibers always contained myosin heavy chains 6 and 7 (MYH6 and MYH7) and myosin light chain 3 (MYL3), whereas MYH6, MYH7, and MYL3 were nearly absent from type IIx fibers. In contrast to cardiomyocytes, where MYH6 (also known as α-myosin heavy chain) is seen solely in fast-twitch cells, only slow-twitch fibers of skeletal muscle contained MYH6. Classical fast myosin heavy chains (MHC1, MHC2, and MHC4) were present in variable proportions in all fiber types, but significant MYH6 and MYH7 expression indicated slow-twitch phenotype, and the absence of these two isoforms determined a fast-twitch phenotype. The mixed myosin heavy and light chain content of type IIa fibers was consistent with its role as a transition between fast and slow phenotypes. These new observations suggest that the presence or absence of MYH6 and MYH7 proteins dictates the slow- or fast-twitch phenotype in skeletal muscle. Copyright © 2016 the American Physiological Society.

  16. Testosterone-induced increase in muscle size in healthy young men is associated with muscle fiber hypertrophy.

    PubMed

    Sinha-Hikim, Indrani; Artaza, Jorge; Woodhouse, Linda; Gonzalez-Cadavid, Nestor; Singh, Atam B; Lee, Martin I; Storer, Thomas W; Casaburi, Richard; Shen, Ruoquing; Bhasin, Shalender

    2002-07-01

    Administration of replacement doses of testosterone to healthy hypogonadal men and supraphysiological doses to eugonadal men increases muscle size. To determine whether testosterone-induced increase in muscle size is due to muscle fiber hypertrophy, 61 healthy men, 18-35 yr of age, received monthly injections of a long-acting gonadotropin-releasing hormone (GnRH) agonist to suppress endogenous testosterone secretion and weekly injections of 25, 50, 125, 300, or 600 mg testosterone enanthate (TE) for 20 wk. Thigh muscle volume was measured by magnetic resonance imaging (MRI) scan, and muscle biopsies were obtained from vastus lateralis muscle in 39 men before and after 20 wk of combined treatment with GnRH agonist and testosterone. Administration of GnRH agonist plus TE resulted in mean nadir testosterone concentrations of 234, 289, 695, 1,344, and 2,435 ng/dl at the 25-, 50-, 125-, 300-, and 600-mg doses, respectively. Graded doses of testosterone administration were associated with testosterone dose and concentration-dependent increase in muscle volume measured by MRI (changes in vastus lateralis volume, -4, +7, +15, +32, and +48 ml at 25-, 50-, 125-, 300-, and 600-mg doses, respectively). Changes in cross-sectional areas of both type I and II fibers were dependent on testosterone dose and significantly correlated with total (r = 0.35, and 0.44, P < 0.0001 for type I and II fibers, respectively) and free (r = 0.34 and 0.35, P < 0.005) testosterone concentrations during treatment. The men receiving 300 and 600 mg of TE weekly experienced significant increases from baseline in areas of type I (baseline vs. 20 wk, 3,176 +/- 186 vs. 4,201 +/- 252 microm(2), P < 0.05 at 300-mg dose, and 3,347 +/- 253 vs. 4,984 +/- 374 microm(2), P = 0.006 at 600-mg dose) muscle fibers; the men in the 600-mg group also had significant increments in cross-sectional area of type II (4,060 +/- 401 vs. 5,526 +/- 544 microm(2), P = 0.03) fibers. The relative proportions of type I and type II

  17. Fiber transformations in multifidus muscle of young patients with idiopathic scoliosis.

    PubMed

    Meier, M P; Klein, M P; Krebs, D; Grob, D; Müntener, M

    1997-10-15

    In this study, the authors investigated the superficial multifidus muscle in patients with idiopathic scoliosis. During spinal fusion, biopsies were taken bilaterally at the apex of the curve, and at the upper and lower end vertebrae. To analyze the muscular reactions in response to bracing in patients with idiopathic scoliosis. The extent to which intervertebral mobility is restricted by an orthosis is still controversial. In addition, the effect of bracing on the erector spinae has not been investigated. Of a total 30 patients, 11 had been treated with a corset for a year or more before surgery. Biopsies were investigated histochemically and the muscle fibers classified as Type I, IIA, IIB, or IIC (transitional fibers). The relative distribution of the fibers was calculated and their diameter was measured. In unbraced patients, a shift in the fiber distribution (from "slow" to "fast") was observed exclusively at the concave side of the apex. This shift was paralleled by an increased percentage of the intermediate Type IIC fiber (indicative of fiber transformation). In patients who always wore a corset, the relative amount of Type IIC fibers was increased, without preference for a specific location. Corset treatment elicits muscle fiber transformation processes at different levels along the scoliosis. This general reaction of the paraspinal muscles provides strong evidence against the existence of muscular disorders that are restricted to the area of the apex and are thus causing the scoliosis. As such, it must be assumed that the muscular changes in the apical region are secondary.

  18. Nerve terminal growth remodels neuromuscular synapses in mice following regeneration of the postsynaptic muscle fiber.

    PubMed

    Li, Yue; Thompson, Wesley J

    2011-09-14

    Muscle fibers degenerate and regenerate in response to contractile damage, during aging, and in various muscle diseases that weaken the fibers. It is known that degeneration and regeneration of the segment of the postsynaptic fiber produces dramatic alterations in the neuromuscular junction (NMJ) that forms on the regenerated fiber, but the mechanisms here are incompletely understood. We have used a laser microbeam to damage the postsynaptic fibers at individual NMJs in the sternomastoid muscle of living young adult mice and then followed the synapses vitally over time using fluorescent proteins expressed in motor neurons and glial cells and staining of postsynaptic acetylcholine receptors. We find, in contrast to previous reports, that the mouse nerve terminal retains contact with the synaptic basal lamina marked by cholinesterase staining even in the absence of the target, showing that this terminal does not require a continuous supply of target-derived molecules for its maintenance. Thus, remodeling of the nerve terminal during the period of target absence does not explain the subsequent changes in the new NMJ. Rather, we see that the synapse becomes altered as the new fiber segment regenerates. Mechanisms for remodeling the synapse include failure of the regenerating muscle fiber to contact the old basal lamina and nerve terminal, growth of the nerve terminal and its glia toward the regenerating fiber, and remodeling of the initial contact as the nerve terminal becomes varicose.

  19. Immunohistochemical detection of interleukin-6 in human skeletal muscle fibers following exercise.

    PubMed

    Penkowa, Milena; Keller, Charlotte; Keller, Pernille; Jauffred, Sune; Pedersen, Bente Klarlund

    2003-11-01

    Interleukin-6 (IL-6) is produced by many different cell types. Human skeletal muscles produce and release high amounts of IL-6 during exercise; however, the cell source of origin in the muscle is not known. Therefore, we studied the protein expression of IL-6 by immunohistochemistry in human muscle tissue from biopsies obtained at time points 0, 3, 4.5, 6, 9, and 24 h in relation to 3 h of bicycle exercise performed by healthy young males (n=12) and in resting controls (n=6). The IL-6 expression was clearly increased after exercise and remained high even by 24 h, relative to pre-exercise or resting individuals. The IL-6 immunostainings of skeletal muscle cells were homogeneous and without difference between muscle fiber types. The IL-6 mRNA peaked immediately after the exercise, and, in accordance, the IL-6 protein expression within muscle cells was most pronounced around 3 h post-exercise. However, the finding that plasma IL-6 concentration peaked in the end of exercise indicates a high turnover of muscle-derived IL-6. In conclusion, the finding of marked IL-6 protein expression exclusively within skeletal muscle fibers following exercise demonstrates that skeletal muscle fibers of all types are the dominant cell source of exercise-induced release of IL-6 from working muscle.

  20. Exercise type and muscle fiber specific induction of caveolin-1 expression for insulin sensitivity of skeletal muscle.

    PubMed

    Oh, Yoon Sin; Kim, Hyo Jeong; Ryu, Sung Jin; Cho, Kyung A; Park, Young Sik; Park, Hyon; Kim, MiJung; Kim, Chang Keun; Park, Sang Chul

    2007-06-30

    It is well known that exercise can have beneficial effects on insulin resistance by activation of glucose transporter. Following up our previous report that caveolin-1 plays an important role in glucose uptake in L6 skeletal muscle cells, we examined whether exercise alters the expression of caveolin-1, and whether exercise-caused changes are muscle fiber and exercise type specific. Fifty week-old Sprague Dawley (SD) rats were trained to climb a ladder and treadmill for 8 weeks and their soleus muscles (SOL) and extensor digitorum longus muscles (EDL) were removed after the last bout of exercise and compared with those from non-exercised animals. We found that the expression of insulin related proteins and caveolins did not change in SOL muscles after exercise. However, in EDL muscles, the expression of insulin receptor beta (IR beta) and glucose transporter-4 (GLUT-4) as well as phosphorylation of AKT and AMPK increased with resistance exercise but not with aerobic exercise. Also, caveolin-1 and caveolin-3 increased along with insulin related proteins only in EDL muscles by resistance exercise. These results suggest that upregulation of caveolin-1 in the skeletal muscle is fiber specific and exercise type specific, implicating the requirement of the specific mode of exercise to improve insulin sensitivity.

  1. Size and myonuclear domains in Rhesus soleus muscle fibers: short-term spaceflight

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Talmadge, R. J.; Bodine, S. C.; Fanton, J. W.; Koslovskaya, I.; Edgerton, V. R.

    2001-01-01

    The cross-sectional area (CSA), myonuclear number per mm of fiber length, and myonuclear domain (cytoplasmic volume/myonucleus) of mechanically isolated single fibers from biopsies of the soleus muscle of 5 vivarium control, 3 flight simulation and 2 flight (BION 11) Rhesus monkeys (Macaca [correction of Macacca] mulatta) were determined using confocal microscopy before and after a 14-day experimental period. Simulation monkeys were confined in chairs placed in capsules identical to those used during the flight. Fibers were classified as type I, type II or hybrid (containing both types I and II) based on myosin heavy chain (MHC) gel electrophoresis. A majority of the fibers sampled contained only type I MHC, i.e. 89, 62 and 68% for the control, simulation and flight groups, respectively. Most of the remaining fibers were hybrids, i.e. 8, 36 and 32% for the same groups. There were no significant pre-post differences in the fiber type composition for any of the experimental groups. There also were no significant pre-post differences in fiber CSA, myonuclear number or myonuclear domain. There was, however, a tendency for the fibers in the post-flight biopsies to have a smaller mean CSA and myonuclear domain (approximately 10%, p=0.07) than the fibers in the pre-flight biopsy. The combined mean cytoplasmic volume/myonucleus for all muscle fiber phenotypes in the Rhesus soleus muscle was approximately 25,000 micrometers3 and there were no differences in pre-post samples for the control and simulated groups. The cytoplasmic domains tended to be lower (p=0.08) after than before flight. No phenotype differences in cytoplasmic domains were observed. These data suggest that after a relatively short period of actual spaceflight, modest fiber atrophy occurs in the soleus muscle fibers without a concomitant change in myonuclear number.

  2. Size and myonuclear domains in Rhesus soleus muscle fibers: short-term spaceflight

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Talmadge, R. J.; Bodine, S. C.; Fanton, J. W.; Koslovskaya, I.; Edgerton, V. R.

    2001-01-01

    The cross-sectional area (CSA), myonuclear number per mm of fiber length, and myonuclear domain (cytoplasmic volume/myonucleus) of mechanically isolated single fibers from biopsies of the soleus muscle of 5 vivarium control, 3 flight simulation and 2 flight (BION 11) Rhesus monkeys (Macaca [correction of Macacca] mulatta) were determined using confocal microscopy before and after a 14-day experimental period. Simulation monkeys were confined in chairs placed in capsules identical to those used during the flight. Fibers were classified as type I, type II or hybrid (containing both types I and II) based on myosin heavy chain (MHC) gel electrophoresis. A majority of the fibers sampled contained only type I MHC, i.e. 89, 62 and 68% for the control, simulation and flight groups, respectively. Most of the remaining fibers were hybrids, i.e. 8, 36 and 32% for the same groups. There were no significant pre-post differences in the fiber type composition for any of the experimental groups. There also were no significant pre-post differences in fiber CSA, myonuclear number or myonuclear domain. There was, however, a tendency for the fibers in the post-flight biopsies to have a smaller mean CSA and myonuclear domain (approximately 10%, p=0.07) than the fibers in the pre-flight biopsy. The combined mean cytoplasmic volume/myonucleus for all muscle fiber phenotypes in the Rhesus soleus muscle was approximately 25,000 micrometers3 and there were no differences in pre-post samples for the control and simulated groups. The cytoplasmic domains tended to be lower (p=0.08) after than before flight. No phenotype differences in cytoplasmic domains were observed. These data suggest that after a relatively short period of actual spaceflight, modest fiber atrophy occurs in the soleus muscle fibers without a concomitant change in myonuclear number.

  3. Size and myonuclear domains in Rhesus soleus muscle fibers: short-term spaceflight.

    PubMed

    Roy, R R; Zhong, H; Talmadge, R J; Bodine, S C; Fanton, J W; Koslovskaya, I; Edgerton, V R

    2001-12-01

    The cross-sectional area (CSA), myonuclear number per mm of fiber length, and myonuclear domain (cytoplasmic volume/myonucleus) of mechanically isolated single fibers from biopsies of the soleus muscle of 5 vivarium control, 3 flight simulation and 2 flight (BION 11) Rhesus monkeys (Macaca [correction of Macacca] mulatta) were determined using confocal microscopy before and after a 14-day experimental period. Simulation monkeys were confined in chairs placed in capsules identical to those used during the flight. Fibers were classified as type I, type II or hybrid (containing both types I and II) based on myosin heavy chain (MHC) gel electrophoresis. A majority of the fibers sampled contained only type I MHC, i.e. 89, 62 and 68% for the control, simulation and flight groups, respectively. Most of the remaining fibers were hybrids, i.e. 8, 36 and 32% for the same groups. There were no significant pre-post differences in the fiber type composition for any of the experimental groups. There also were no significant pre-post differences in fiber CSA, myonuclear number or myonuclear domain. There was, however, a tendency for the fibers in the post-flight biopsies to have a smaller mean CSA and myonuclear domain (approximately 10%, p=0.07) than the fibers in the pre-flight biopsy. The combined mean cytoplasmic volume/myonucleus for all muscle fiber phenotypes in the Rhesus soleus muscle was approximately 25,000 micrometers3 and there were no differences in pre-post samples for the control and simulated groups. The cytoplasmic domains tended to be lower (p=0.08) after than before flight. No phenotype differences in cytoplasmic domains were observed. These data suggest that after a relatively short period of actual spaceflight, modest fiber atrophy occurs in the soleus muscle fibers without a concomitant change in myonuclear number.

  4. Regeneration and change of muscle fiber types after injury induced by a hemorrhagic fraction isolated from Agkistrodon contortrix laticinctus venom.

    PubMed

    Salvini, T F; Belluzzo, S S; Selistre de Araújo, H S; Souza, D H

    2001-05-01

    Tibialis anterior (TA) muscles of rats were evaluated 3h, 3 and 30days after intramuscular injection of ACL hemorrhagic toxin I (ACLHT-I, 5mg/kg), partially purified from the venom of Agkistrodon contortrix laticinctus. Contralateral muscles were injected with saline. Three hours after ACLHT-1 injection: presence of hemorrhagic areas and myonecrotic muscle fibers. Three days: injured muscles showed areas in regeneration, some regions with delay of regeneration and bundles of normal fibers. An increased TA muscle weight was found when compared with the contralateral (0.45+/-0.03g versus 0.36+/-0.04g, p=0.04). Thirty days: areas of regenerated muscle fibers presented splits and centralized nuclei. Some regions were replaced by connective tissue. All muscle fiber types were injured but only the incidence of type IIC increased (3.4+/-2.0% versus 0.2+/-0.2%, p=0.0005). Regenerated areas of muscles were exclusively composed by fiber types II and IIC. Regenerated muscles decreased the muscle weight (0.49+/-0.1g versus 0.66+/-0.05g, p=0. 03). In conclusion, ACLHT-I: (a) caused hemorrhage and muscle fiber injury; (b) injured both fiber types I and II; (c) increased the incidence of fiber type IIC and; (d) some muscle regions were replaced by connective tissue.

  5. Contraction-induced injury to single permeabilized muscle fibers from normal and congenitally-clefted goat palates

    USDA-ARS?s Scientific Manuscript database

    A goat model in which cleft palate is induced by the plant alkaloid, anabasine was used to determine muscle fiber integrity of the levator veli palatine (LVP) muscle. It was determined that muscle fiber type, size, and sensitivity to contraction-induced injury was different between cleft palate ind...

  6. Grb2-associated binder-1 is required for extrafusal and intrafusal muscle fiber development.

    PubMed

    Park, So Y; Jang, So Y; Shin, Yoon K; Yoon, Byeol A; Lee, Hye J; Park, Hwan T

    2017-07-05

    The neuregulin-1 (NRG1) signaling pathway plays an important role in the development of the peripheral neuromuscular system, including in muscle spindle and postnatal myelination. We previously showed that NRG1 on the axonal membrane regulates peripheral nerve myelination through Grb2-associated binder 1 (Gab1), a scaffolding mediator of receptor tyrosine kinase signaling. Here, we determined the role of Gab1 in the development of muscles and the muscle spindle using muscle-specific conditional Gab1 knockout mice. The mutant mice showed general retardation in muscular growth and hypotrophy of extrafusal muscle fibers. In addition, the muscle-specific Gab1 knockout mutant exhibited significant underdevelopment of muscle spindles, which are normally regulated by NRG1, and abnormal proprioceptive behavior. Furthermore, the selective knockdown of Gab1 in C2C12 muscle cells reduced NRG1-induced expression of Egr3, a critical transcription factor for muscle spindle development. However, Gab2 knockout mice did not show any defects in the development of muscles or muscle spindles. Our findings suggest that Gab1 is an essential signaling molecule in mediating axonal NRG1 signaling for the development of both extrafusal and intrafusal muscle fibers.

  7. A mathematical model of force transmission from intrafascicularly terminating muscle fibers.

    PubMed

    Sharafi, Bahar; Blemker, Silvia S

    2011-07-28

    Many long skeletal muscles are comprised of fibers that terminate intrafascicularly. Force from terminating fibers can be transmitted through shear within the endomysium that surrounds fibers or through tension within the endomysium that extends from fibers to the tendon; however, it is unclear which pathway dominates in force transmission from terminating fibers. The purpose of this work was to develop mathematical models to (i) compare the efficacy of lateral (through shear) and longitudinal (through tension) force transmission in intrafascicularly terminating fibers, and (ii) determine how force transmission is affected by variations in the structure and properties of fibers and the endomysium. The models demonstrated that even though the amount of force that can be transmitted from an intrafascicularly terminating fiber is dependent on fiber resting length (the unstretched length at which passive stress is zero), endomysium shear modulus, and fiber volume fraction (the fraction of the muscle cross-sectional area that is occupied by fibers), fibers that have values of resting length, shear modulus, and volume fraction within physiologic ranges can transmit nearly all of their peak isometric force laterally through shearing of the endomysium. By contrast, the models predicted only limited force transmission ability through tension within the endomysium that extends from the fiber to the tendon. Moreover, when fiber volume fraction decreases to unhealthy ranges (less than 50%), the force-transmitting potential of terminating fibers through shearing of the endomysium decreases significantly. The models presented here support the hypothesis that lateral force transmission through shearing of the endomysium is an effective mode of force transmission in terminating fibers.

  8. Effects of fiber type and diet on nuclear magnetic resonance (NMR) relaxation times of skeletal muscle

    SciTech Connect

    Mardini, I.A.; McCarter, R.J.; Fullerton, G.D.

    1986-03-01

    NMR studies of muscle have typically used muscles of mixed fiber composition and have not taken into account the metabolic state of the host. Samples of psoas (type IIB fibers) and soleus (type I fibers) muscles were obtained from 3 groups of rabbits: group C, fed regular chow; group DK fed a potassium deficient diet; and group HC fed a high cholesterol diet. The T/sub 1/ and T/sub 2/ relaxation times of psoas and soleus muscles were not significantly different for group C. Following dietary manipulation, (groups KD and HC), however, the relaxation times of the psoas and soleus muscles were significantly different. There was also a significant difference in water content of psoas muscles in groups KD and HC vs. group C but the observed differences in NMR results could be only partially accounted for by the shift in water content. The authors results suggest that (1) changes in ion or cholesterol concentration are capable of inducing changes in water bonding and structuring in muscle tissues; (2) diet must be added to the growing list of environmental factors that can cause NMR contrast changes; (3) selective use of muscles rich in one fiber type or another for NMR measurements could provide either control or diagnostic information, related to changes in body composition.

  9. Muscle Fiber Type-Predominant Promoter Activity in Lentiviral-Mediated Transgenic Mouse

    PubMed Central

    Suga, Tomohiro; Kimura, En; Morioka, Yuka; Ikawa, Masahito; Li, Sheng; Uchino, Katsuhisa; Uchida, Yuji; Yamashita, Satoshi; Maeda, Yasushi; Chamberlain, Jeffrey S.; Uchino, Makoto

    2011-01-01

    Variations in gene promoter/enhancer activity in different muscle fiber types after gene transduction was noticed previously, but poorly analyzed. The murine stem cell virus (MSCV) promoter drives strong, stable gene expression in hematopoietic stem cells and several other cells, including cerebellar Purkinje cells, but it has not been studied in muscle. We injected a lentiviral vector carrying an MSCV-EGFP cassette (LvMSCV-EGFP) into tibialis anterior muscles and observed strong EGFP expression in muscle fibers, primary cultured myoblasts, and myotubes isolated from injected muscles. We also generated lentiviral-mediated transgenic mice carrying the MSCV-EGFP cassette and detected transgene expression in striated muscles. LvMSCV-EGFP transgenic mice showed fiber type-dependent variations in expression: highest in types I and IIA, intermediate in type IID/X, and lowest in type IIB fibers. The soleus and diaphragm muscles, consisting mainly of types I and IIA, are most severely affected in the mdx mouse model of muscular dystrophy. Further analysis of this promoter may have the potential to achieve certain gene expression in severely affected muscles of mdx mice. The Lv-mediated transgenic mouse may prove a useful tool for assessing the enhancer/promoter activities of a variety of different regulatory cassettes. PMID:21445245

  10. Thyroid hormone regulates muscle fiber type conversion via miR-133a1

    PubMed Central

    Zhang, Duo; Wang, Xiaoyun; Li, Yuying; Zhao, Lei; Lu, Minghua; Yao, Xuan; Xia, Hongfeng; Wang, Yu-cheng; Liu, Mo-Fang; Jiang, Jingjing; Li, Xihua

    2014-01-01

    It is known that thyroid hormone (TH) is a major determinant of muscle fiber composition, but the molecular mechanism by which it does so remains unclear. Here, we demonstrated that miR-133a1 is a direct target gene of TH in muscle. Intriguingly, miR-133a, which is enriched in fast-twitch muscle, regulates slow-to-fast muscle fiber type conversion by targeting TEA domain family member 1 (TEAD1), a key regulator of slow muscle gene expression. Inhibition of miR-133a in vivo abrogated TH action on muscle fiber type conversion. Moreover, TEAD1 overexpression antagonized the effect of miR-133a as well as TH on muscle fiber type switch. Additionally, we demonstrate that TH negatively regulates the transcription of myosin heavy chain I indirectly via miR-133a/TEAD1. Collectively, we propose that TH inhibits the slow muscle phenotype through a novel epigenetic mechanism involving repression of TEAD1 expression via targeting by miR-133a1. This identification of a TH-regulated microRNA therefore sheds new light on how TH achieves its diverse biological activities. PMID:25512392

  11. Fiber type composition of the muscle responsible for throat fan extension in green anole lizards.

    PubMed

    Rosen, G J; O'Bryant, E L; Swender, D; Wade, J

    2004-01-01

    Throat fan (dewlap) extension is sexually dimorphic in green anole lizards (Anolis carolinensis). Males have larger dewlaps which they display more frequently than females. Correlated with the behavior, sexual dimorphisms occur in the skeletal, muscular and neural structures responsible for dewlap extension in green anoles. We used histochemical techniques to stain for myosin ATPase and succinate dehydrogenase (SDH) to determine whether sex differences also exist in fiber type composition of the ceratohyoideus, the muscle that extends the dewlap. Based on the staining pattern for the two enzymes, four fiber types were identified: fast-oxidative-glycolytic (FOG), fast-glycolytic (FG), slow-oxidative (SO), and tonic. In the ceratohyoideus of both sexes, the predominate fiber types were FOG (approximately 43%) and FG (approximately 34%). Also in both males and females, the FOG and FG fibers had approximately twice the cross-sectional area of the SO and tonic fibers. No sex differences occurred in the percentages of FOG and FG fibers. However, males had a greater percentage of tonic fibers than females, whereas females had a greater percentage of SO fibers than males. The high proportion of FOG fibers in the anole ceratohyoideus makes it similar to other relatively fatigue-resistant muscles used in movements of moderate speed and duration. Although the precise role of tonic fibers in dewlap extension is not known, the greater percentage of these fibers in the male ceratohyoideus might be required to stabilize or maintain extension of the large dewlap apparatus in males.

  12. Diet‐induced obesity alters skeletal muscle fiber types of male but not female mice

    PubMed Central

    DeNies, Maxwell S.; Johnson, Jordan; Maliphol, Amanda B.; Bruno, Michael; Kim, Annabelle; Rizvi, Abbas; Rustici, Kevyn; Medler, Scott

    2014-01-01

    Abstract Skeletal muscles are highly plastic tissues capable dramatic remodeling in response to use, disuse, disease, and other factors. Growing evidence suggests that adipose tissues exert significant effects on the basic fiber‐type composition of skeletal muscles. In the current study, we investigated the long‐term effects of a high‐fat diet and subsequent obesity on the muscle fiber types in C57 BLK/6J mice. Litters of mice were randomly assigned to either a high‐fat diet or a control group at the time of weaning, and were maintained on this diet for approximately 1 year. Single fibers were harvested from the soleus and plantaris muscles, and fiber types were determined using SDS‐PAGE. The high‐fat diet mice were significantly heavier than the control mice (39.17 ± 2.7 g vs. 56.87 ± 3.4 g; P < 0.0003), but muscle masses were not different. In male mice, the high‐fat diet was associated with a significantly lower proportion of slow, type I fibers in the soleus muscle (40.4 ± 3.5% vs. 29.33 ± 2.6%; P < 0.0165). Moreover, the proportion of type I fibers in the soleus of male mice was inversely proportional to the relative fatness of the male mice (P < 0.003; r2 = 0.65), but no association was observed in female mice. In male mice, the decline in type I fibers was correlated with an increase in type I/IIA hybrid fibers, suggesting that the type I fibers were transformed primarily into these hybrids. The reported trends indicate that type I fibers are most susceptible to the effects of obesity, and that these fiber‐type changes can be sex specific. PMID:24744883

  13. Analysis of key factors influencing the evaporation performances of an oriented linear cutting copper fiber sintered felt

    NASA Astrophysics Data System (ADS)

    Pan, Minqiang; Zhong, Yujian

    2017-07-01

    Porous structure can effectively enhance the heat transfer efficiency. A kind of micro vaporizer using the oriented linear cutting copper fiber sintered felt is proposed in this work. Multiple long cutting copper fibers are firstly fabricated with a multi-tooth tool and then sintered together in parallel to form uniform thickness metal fiber sintered felts that provided a characteristic of oriented microchannels. The temperature rise response and thermal conversion efficiency are experimentally investigated to evaluate the influences of porosity, surface structure, feed flow rate and input power on the evaporation characteristics. It is indicated that the temperature rise response of water is mainly affected by input power and feed flow rate. High input power and low feed flow rate present better temperature rise response of water. Porosity rather than surface structure plays an important role in the temperature rise response of water at a relatively high input power. The thermal conversion efficiency is dominated by the input power and surface structure. The oriented linear cutting copper fiber sintered felts for three kinds of porosities show better thermal conversion efficiency than that of the oriented linear copper wire sintered felt when the input power is less than 115 W. All the sintered felts have almost the same performance of thermal conversion at a high input power.

  14. Jaw-muscle fiber architecture in tufted capuchins favors generating relatively large muscle forces without compromising jaw gape.

    PubMed

    Taylor, Andrea B; Vinyard, Christopher J

    2009-12-01

    Tufted capuchins (sensu lato) are renowned for their dietary flexibility and capacity to exploit hard and tough objects. Cebus apella differs from other capuchins in displaying a suite of craniodental features that have been functionally and adaptively linked to their feeding behavior, particularly the generation and dissipation of relatively large jaw forces. We compared fiber architecture of the masseter and temporalis muscles between C. apella (n=12) and two "untufted" capuchins (C. capucinus, n=3; C. albifrons, n=5). These three species share broadly similar diets, but tufted capuchins occasionally exploit mechanically challenging tissues. We tested the hypothesis that tufted capuchins exhibit architectural properties of their jaw muscles that facilitate relatively large forces including relatively greater physiologic cross-sectional areas (PCSA), more pinnate fibers, and lower ratios of mass to tetanic tension (Mass/P(0)). Results show some evidence supporting these predictions, as C. apella has relatively greater superficial masseter and temporalis PCSAs, significantly so only for the temporalis following Bonferroni adjustment. Capuchins did not differ in pinnation angle or Mass/P(0). As an architectural trade-off between maximizing muscle force and muscle excursion/contraction velocity, we also tested the hypothesis that C. apella exhibits relatively shorter muscle fibers. Contrary to our prediction, there are no significant differences in relative fiber lengths between tufted and untufted capuchins. Therefore, we attribute the relatively greater PCSAs in tufted capuchins primarily to their larger muscle masses. These findings suggest that relatively large jaw-muscle PCSAs can be added to the suite of masticatory features that have been functionally linked to the exploitation of a more resistant diet by C. apella. By enlarging jaw-muscle mass to increase PCSA, rather than reducing fiber lengths and increasing pinnation, tufted capuchins appear to have

  15. Jaw-muscle fiber architecture in tufted capuchins favors generating relatively large muscle forces without compromising jaw gape

    PubMed Central

    Taylor, Andrea B.; Vinyard, Christopher J.

    2009-01-01

    Cebus apella is renowned for its dietary flexibility and capacity to exploit hard and tough objects. Cebus apella differs from other capuchins in displaying a suite of craniodental features that have been functionally and adaptively linked to their feeding behavior, particularly the generation and dissipation of relatively large jaw forces. We compared fiber architecture of the masseter and temporalis muscles between the tufted capuchin (C. apella; n = 12 ) and two “untufted” capuchins (C. capuchinus, n = 3; C. albifrons, n = 5). These three species share broadly similar diets, but tufted capuchins occasionally exploit mechanically challenging tissues. We tested the hypothesis that C. apella exhibits architectural properties of their jaw muscles that facilitate relatively large forces, including relatively greater physiologic cross-sectional areas (PCSA), more pinnate fibers, and lower ratios of mass to tetanic tension (Mass/P0). Results show some evidence supporting these predictions, as C. apella has relatively greater superficial masseter, whole masseter, and temporalis PCSAs, significantly so only for the temporalis following Bonferroni adjustment. Capuchins did not differ in pinnation angle or Mass/P0. As an architectural trade-off between maximizing muscle force and muscle excursion/contraction velocity, we also tested the hypothesis that C. apella exhibits relatively shorter muscle fibers. Contrary to our prediction, there are no significant differences in relative fiber lengths between tufted and untufted capuchins. Therefore, we attribute the relatively greater PCSAs in C. apella primarily to their larger muscle masses. These findings suggest that relatively large jaw-muscle PCSAs can be added to the suite of masticatory features that have been functionally linked to the exploitation of a more resistant diet by C. apella. By enlarging jaw-muscle mass to increase PCSA, rather than reducing fiber lengths and increasing pinnation, tufted capuchins appear

  16. Quantitative diffusion tensor MRI-based fiber tracking of human skeletal muscle.

    PubMed

    Lansdown, Drew A; Ding, Zhaohua; Wadington, Megan; Hornberger, Jennifer L; Damon, Bruce M

    2007-08-01

    Diffusion-tensor magnetic resonance imaging (DT-MRI) offers great potential for understanding structure-function relationships in human skeletal muscles. The purposes of this study were to demonstrate the feasibility of using in vivo human DT-MRI fiber tracking data for making pennation angle measurements and to test the hypothesis that heterogeneity in the orientation of the tibialis anterior (TA) muscle's aponeurosis would lead to heterogeneity in pennation angle. Eight healthy subjects (5 male) were studied. T(1)-weighted anatomical MRI and DT-MRI data were acquired of the TA muscle. Fibers were tracked from the TA's aponeurosis by following the principal eigenvector. The orientations of the aponeurosis and muscle fiber tracts in the laboratory frame of reference and the orientation of the fiber tracts with respect to the aponeurosis [i.e., the pennation angle (theta)] were determined. The muscle fiber orientations, when expressed relative to the laboratory frame of reference, did not change as functions of superior-to-inferior position. The sagittal and coronal orientations of the aponeurosis did not change in practically significant manners either, but the aponeurosis' axial orientation changed by approximately 40 degrees . As a result, the mean value for theta decreased from 16.3 (SD 6.9) to 11.4 degrees (SD 5.0) along the muscle's superior-to-inferior direction. The mean value of theta was greater in the deep than in the superficial compartment. We conclude that pennation angle measurements of human muscle made using DT-MRI muscle fiber tracking are feasible and reveal that in the foot-head direction, there is heterogeneity in the pennation properties of the human TA muscle.

  17. Contractile function of single muscle fibers after hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Gardetto, P. R.; Schluter, J. M.; Fitts, R. H.

    1989-01-01

    The effects of two weeks of hind-limb suspension (HS) on the functional properties of slow-twitch and fast-twitch single fibers isolated from the predominantly slow-twitch soleus and fast-twitch gastrocnemius of the suspended leg of rats were investigated. Single fibers were suspended between a motor arm and force transducer, and, after their functional properties were studied, the fiber type was established by the myosin heavy chain analysis. It was found that, after HS, the greatest decrease in diameter and a reduction in peak tension occurred in slow-twitch fibers from soleus, followed by slow-twitch fibers from gastrocnemius. Fast-twitch fibers from the red gastrocnemius showed a significant reduction in diameter but no change in peak tension. No effect of HS was observed on the diameter of the fast-twitch fibers from the white gastsrocnemius (which is known to contain 87 percent fast glycolytic fibers).

  18. Multiple isoforms of myofibrillar proteins in crustacean muscle: evidence for two slow fiber types

    SciTech Connect

    Mykles, D.L.

    1986-01-01

    Four distinct patterns of myofibrillar proteins, extracted from fast and slow muscles of the lobster, Homarus americanus, are distinguished by different assemblages of regulatory and contractile protein variants. Multiple isoforms of troponin-T, -I, and -C, paramyosin, and myosin light chains occur in six muscles of the claws and abdomen. Analysis of glycerinated fibers from the claws of lobster and land crab, Gecarcinus lateralis, show that more than one isoform is expressed in a single fiber, forming unique assemblages by which subgroups can be discriminated within the broader categories of fast and slow fibers. 9 refs., 3 figs.

  19. Comparison of Characteristics of Myosin Heavy Chain-based Fiber and Meat Quality among Four Bovine Skeletal Muscles

    PubMed Central

    Kim, Gap-Don; Yang, Han-Sul; Jeong, Jin-Yeon

    2016-01-01

    Muscle fiber characteristics account for meat quality and muscle fibers are mainly classified into three or more types according to their contractile and metabolic properties. However, the majority of previous studies on bovine skeletal muscle are based on myosin ATPase activity. In the present study, the differences in the characteristics of muscle fibers classified by the expression of myosin heavy chain (MHC) among four bovine skeletal muscles such as longissimus thoracis (LT), psoas major (PM), semimembranosus (SM) and semitendinosus (ST) and their relationships to beef quality were investigated. MHCs 2x, 2a and slow were identified by LC-MS/MS and IIX, IIA and I fiber types were classified. PM, which had the smallest size and highest density of fibers regardless of type, showed the highest myoglobin content, CIE L*, a*, b* and sarcomere length (p<0.05), whereas ST with the highest composition of IIX, showed high shear force and low sarcomere length (p<0.05). The correlation coefficients between muscle fiber characteristics and meat quality showed that type IIX is closely related to poor beef quality and that a high density of small-sized fibers is related to redness and tenderness. Therefore, the differences in meat quality between muscles can be explained by the differences in muscle fiber characteristics, and especially, the muscles with good quality are composed of more small-sized fibers regardless of fiber type. PMID:28115894

  20. Fiber size and myosin phenotypes of selected rhesus lower limb muscles after a 14-day spaceflight

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Bodine, S. C.; Pierotti, D. J.; Talmadge, R. J.; Barkhoudarian, G.; Kim, J.; Fanton, J. W.; Kozlovskaya, I. B.; Edgerton, V. R.

    2000-01-01

    Muscle biopsies were taken from the rhesus (Macaca mulatta) soleus (Sol, a slow ankle extensor), medial gastrocnemius (MG, a fast ankle extensor), tibialis anterior (TA, a fast ankle flexor), and vastus lateralis (VL, a fast knee extensor) muscles in vivarium controls (n=5) before and after either a 14-day spaceflight (Bion 11, n=2) or a 14-day ground-based flight simulation (n=3). Myosin heavy chain (MHC) composition (gel electrophoresis), fiber type distribution (immunohistochemistry), and fiber size were determined. Although there were no significant changes, each muscle showed trends towards adaptation.

  1. Fiber size and myosin phenotypes of selected rhesus lower limb muscles after a 14-day spaceflight

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Bodine, S. C.; Pierotti, D. J.; Talmadge, R. J.; Barkhoudarian, G.; Kim, J.; Fanton, J. W.; Kozlovskaya, I. B.; Edgerton, V. R.

    2000-01-01

    Muscle biopsies were taken from the rhesus (Macaca mulatta) soleus (Sol, a slow ankle extensor), medial gastrocnemius (MG, a fast ankle extensor), tibialis anterior (TA, a fast ankle flexor), and vastus lateralis (VL, a fast knee extensor) muscles in vivarium controls (n=5) before and after either a 14-day spaceflight (Bion 11, n=2) or a 14-day ground-based flight simulation (n=3). Myosin heavy chain (MHC) composition (gel electrophoresis), fiber type distribution (immunohistochemistry), and fiber size were determined. Although there were no significant changes, each muscle showed trends towards adaptation.

  2. The Regulation of Skeletal Muscle Active Hyperemia: The Differential Role of Adenosine in Muscles of Varied Fiber Types

    DTIC Science & Technology

    1986-04-21

    0.2 Hz and three mnscles ~;timulated to contract at 0.4 Hz during BADA infuston. These m~tabolites were also mea~•1red in two muscles contractin ~ at...APR 1986 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE The Regulation of Skeletal Muscle Active Hyperemia: The Differential...Role of Adenosine in Muscles of Varied Fiber Types 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER

  3. Heat accumulation effects in short-pulse multi-pass cutting of carbon fiber reinforced plastics

    NASA Astrophysics Data System (ADS)

    Kononenko, T. V.; Freitag, C.; Komlenok, M. S.; Onuseit, V.; Weber, R.; Graf, T.; Konov, V. I.

    2015-09-01

    The formation of a matrix evaporation zone (MEZ) in carbon fiber reinforced plastics during multi-pass laser cutting with picosecond laser pulses is studied for a wide range of pulse frequencies (fp = 10-800 kHz) and feed rates (vf = 0.002-10 m/s). Three regimes of the formation of the MEZ are found and related with different heat accumulation effects: (i) small MEZ (<2 μm) with negligible heat accumulation, (ii) moderate-size MEZ (up to a few hundred microns) determined by heat accumulation between pulses, and (iii) large MEZ (up to a few millimeters) caused by heat accumulation between scans. The dependence of the size of the MEZ on the number of scans and the scan frequency was studied to distinguish the two heat accumulation effects (between pulses and between scans), which occur on different time-scales. A diagram to illustrate the boundaries between the three regimes of the formation of the MEZ as a function of feed rate and pulse frequency is proposed as a promising base for further studies and as a useful tool to optimize the processing parameters in practice.

  4. Nuclear receptor/microRNA circuitry links muscle fiber type to energy metabolism.

    PubMed

    Gan, Zhenji; Rumsey, John; Hazen, Bethany C; Lai, Ling; Leone, Teresa C; Vega, Rick B; Xie, Hui; Conley, Kevin E; Auwerx, Johan; Smith, Steven R; Olson, Eric N; Kralli, Anastasia; Kelly, Daniel P

    2013-06-01

    The mechanisms involved in the coordinate regulation of the metabolic and structural programs controlling muscle fitness and endurance are unknown. Recently, the nuclear receptor PPARβ/δ was shown to activate muscle endurance programs in transgenic mice. In contrast, muscle-specific transgenic overexpression of the related nuclear receptor, PPARα, results in reduced capacity for endurance exercise. We took advantage of the divergent actions of PPARβ/δ and PPARα to explore the downstream regulatory circuitry that orchestrates the programs linking muscle fiber type with energy metabolism. Our results indicate that, in addition to the well-established role in transcriptional control of muscle metabolic genes, PPARβ/δ and PPARα participate in programs that exert opposing actions upon the type I fiber program through a distinct muscle microRNA (miRNA) network, dependent on the actions of another nuclear receptor, estrogen-related receptor γ (ERRγ). Gain-of-function and loss-of-function strategies in mice, together with assessment of muscle biopsies from humans, demonstrated that type I muscle fiber proportion is increased via the stimulatory actions of ERRγ on the expression of miR-499 and miR-208b. This nuclear receptor/miRNA regulatory circuit shows promise for the identification of therapeutic targets aimed at maintaining muscle fitness in a variety of chronic disease states, such as obesity, skeletal myopathies, and heart failure.

  5. Muscle fibers in the central nervous system of nemerteans: spatial organization and functional role.

    PubMed

    Petrov, A A; Zaitseva, O V

    2012-08-01

    The system of muscle fibers associated with the brain and lateral nerve cords is present in all major groups of enoplan nemerteans. Unfortunately, very little is known about the functional role and spatial arrangement of these muscles of the central nervous system. This article examines the architecture of the musculature of the central nervous system in two species of monostiliferous nemerteans (Emplectonema gracile and Tetrastemma cf. candidum) using phalloidin staining and confocal microscopy. The article also briefly discusses the body-wall musculature and the muscles of the cephalic region. In both species, the lateral nerve cords possess two pairs of cardinal muscles that run the length of the nerve cords and pass through the ventral cerebral ganglia. A system of peripheral muscles forms a meshwork around the lateral nerve cords in E. gracile. The actin-rich processes that ramify within the nerve cords in E. gracile (transverse fibers) might represent a separate population of glia-like cells or sarcoplasmic projections of the peripheral muscles of the central nervous system. The lateral nerve cords in T. cf. candidum lack peripheral muscles but have muscles similar in their position and orientation to the transverse fibers. The musculature of the central nervous system is hypothesized to function as a support system for the lateral nerve cords and brain, preventing rupturing and herniation of the nervous tissue during locomotion. The occurrence of muscles of the central nervous system in nemerteans and other groups and their possible relevance in taxonomy are discussed.

  6. Pubovisceralis Muscle Fiber Architecture Determination: Comparison Between Biomechanical Modeling and Diffusion Tensor Imaging.

    PubMed

    Brandão, Sofia; Parente, Marco; Silva, Elisabete; Da Roza, Thuane; Mascarenhas, Teresa; Leitão, João; Cunha, João; Natal Jorge, Renato; Nunes, Rita Gouveia

    2017-01-17

    Biomechanical analysis of pelvic floor dysfunction requires knowledge of certain biomechanical parameters, such as muscle fiber direction, in order to adequately model function. Magnetic resonance (MR) diffusion tensor imaging (DTI) provides an estimate of overall muscle fiber directionality based on the mathematical description of water diffusivity. This work aimed at evaluating the concurrence between pubovisceralis muscle fiber representations obtained from DTI, and the maximum principal stress lines obtained through the finite element method. Seven datasets from axial T2-weighted images were used to build numerical models, and muscle fiber orientation estimated from the DT images. The in-plane projections of the first eigenvector of both vector fields describing muscle fiber orientation were extracted and compared. The directional consistency was evaluated by calculating the angle between the normalized vectors for the entire muscle and also for the right and left insertions, middle portions, and anorectal area. The values varied between 28° ± 6 (right middle portion) and 34° ± 9 (anorectal area), and were higher than the angular precision of the DT estimates, evaluated using wild bootstrapping analysis. Angular dispersion ranged from 17° ± 4 (left middle portion) to 23° ± 5 (anorectal area). Further studies are needed to examine acceptability of these differences when integrating the vectors estimated from DTI in the numerical analysis.

  7. Spaceflight and growth effects on muscle fibers in the rhesus monkey

    NASA Technical Reports Server (NTRS)

    Bodine-Fowler, Sue C.; Roy, Roland R.; Rudolph, William; Haque, Naz; Kozlovskaia, Inessa B.; Edgerton, V. R.

    1992-01-01

    The effect of a 14-day spaceflight onboard Cosmos 2044 on selected morphological and metabolic properties of single muscle fibers was investigated in a nonhuman primate, Macaca mulatta. It is concluded that the 14-day spaceflight had little impact on fiber size in the soleus (S) and medial gastrocnemius (MG) muscles, whereas it appeared to be a slight decrease in sized in the tibialis anterior (TA). The mean fiber size in the postflight biopsies increased relative to preflight values. The mean fiber succinate dehydrogenase activity was found to decrease in the MG, whereas there was no apparent effect of spaceflight on the s and ta muscles. The differences in response of the S, MG, and TA to spaceflight in monkeys vs rats may be related to a species responsiveness to spaceflight, the manner in which the animals were restrained, and/or the possibility that the ankle musculature was able to function against a load while in space.

  8. Spaceflight and growth effects on muscle fibers in the rhesus monkey

    NASA Technical Reports Server (NTRS)

    Bodine-Fowler, Sue C.; Roy, Roland R.; Rudolph, William; Haque, Naz; Kozlovskaia, Inessa B.; Edgerton, V. R.

    1992-01-01

    The effect of a 14-day spaceflight onboard Cosmos 2044 on selected morphological and metabolic properties of single muscle fibers was investigated in a nonhuman primate, Macaca mulatta. It is concluded that the 14-day spaceflight had little impact on fiber size in the soleus (S) and medial gastrocnemius (MG) muscles, whereas it appeared to be a slight decrease in sized in the tibialis anterior (TA). The mean fiber size in the postflight biopsies increased relative to preflight values. The mean fiber succinate dehydrogenase activity was found to decrease in the MG, whereas there was no apparent effect of spaceflight on the s and ta muscles. The differences in response of the S, MG, and TA to spaceflight in monkeys vs rats may be related to a species responsiveness to spaceflight, the manner in which the animals were restrained, and/or the possibility that the ankle musculature was able to function against a load while in space.

  9. Measurement of the Impedance of Frog Skeletal Muscle Fibers

    PubMed Central

    Valdiosera, R.; Clausen, C.; Eisenberg, R. S.

    1974-01-01

    Impedance measurements are necessary to determine the passive electrical properties of cells including the equivalent circuits of the several pathways for current flow. Such measurements are usually made with microelectrodes of high impedance (some 15 MΩ) over a wide frequency range (1-10,000 Hz) and so are subject to many errors. An input amplifier has been developed which has negligible phase shift in this frequency range because it uses negative feedback to keep tiny the voltage on top of the microelectrode. An important source of artifact is the extracellular potential produced by capacitive current flow through the wall of the microelectrodes and the effective resistance of the bathing solution. This artifact is reduced some 10 times by shielding the current microelectrode with a conductive paint. The residual artifact is analyzed, measured, and subtracted from our results. The interelectrode coupling capacitance is reduced below 2 × 10-17 F and can be neglected. Phase and amplitude measurements are made with phase-sensitive detectors insensitive to noise. The entire apparatus is calibrated at different signal to noise ratios and the nature of the extracellular potential is investigated. The phase shift in the last 5-20 μm of the microelectrode tip is shown to be small and quite independent of frequency under several conditions. Experimental measurements of the phase characteristic of muscle fibers in normal Ringer are presented. The improvements in apparatus and the physiological significance of impedance measurements are discussed. It is suggested that the interpretation of impedance measurements is sensitive to small errors and so it is necessary to present objective evidence of the reliability of one's apparatus and measurements. PMID:4857358

  10. In Vivo Microscopy Reveals Extensive Embedding of Capillaries within the Sarcolemma of Skeletal Muscle Fibers

    PubMed Central

    Glancy, Brian; Hsu, Li-Yueh; Dao, Lam; Bakalar, Matthew; French, Stephanie; Chess, David J.; Taylor, Joni L.; Picard, Martin; Aponte, Angel; Daniels, Mathew P.; Esfahani, Shervin; Cushman, Samuel; Balaban, Robert S.

    2013-01-01

    Objective To provide insight into mitochondrial function in vivo, we evaluated the 3D spatial relationship between capillaries, mitochondria, and muscle fibers in live mice. Methods 3D volumes of in vivo murine Tibialis anterior muscles were imaged by multi-photon microscopy (MPM). Muscle fiber type, mitochondrial distribution, number of capillaries, and capillary-to-fiber contact were assessed. The role of myoglobin-facilitated diffusion was examined in myoglobin knockout mice. Distribution of GLUT4 was also evaluated in the context of the capillary and mitochondrial network. Results MPM revealed that 43.6 ± 3.3% of oxidative fiber capillaries had ≥ 50% of their circumference embedded in a groove in the sarcolemma, in vivo. Embedded capillaries were tightly associated with dense mitochondrial populations lateral to capillary grooves and nearly absent below the groove. Mitochondrial distribution, number of embedded capillaries, and capillary-to-fiber contact were proportional to fiber oxidative capacity and unaffected by myoglobin knockout. GLUT4 did not preferentially localize to embedded capillaries. Conclusions Embedding capillaries in the sarcolemma may provide a regulatory mechanism to optimize delivery of oxygen to heterogeneous groups of muscle fibers. We hypothesize that mitochondria locate to paravascular regions due to myofibril voids created by embedded capillaries, not to enhance the delivery of oxygen to the mitochondria. PMID:25279425

  11. Muscle fiber hypotrophy with intact neuromuscular junctions. A study of a patient with congenital neuromuscular disease and ophthalmoplegia.

    PubMed

    Bender, A N; Bender, M B

    1977-03-01

    An infant born with severe but nonprogressive somatic and cranial muscle weakness including bilateral external ophthalmoplegia was studied with a motor-point muscle biopsy. There was a strinking generalized decrease in the size of muscle fibers (hypotrophy), most marked in the type I fibers. Many of the small fibers were immature, resembling myotubes. Neuromuscular junctions on severely hypotrophic fibers were normal with esterase staining and by ultrastructural criteria. Although these are unusual clinical and biopsy characteristics, this infant's condition bears a resemblance to two other congenital nonprogressive neuromuscular diseases:myotubular myopathy and congenital fiber type disproportion. In these conditions and in our patient, there is no primary degenerative process affecting nerve or muscle but, rather, an apparent lack of maturation of fetal muscle fibers, indicating a defective normal trophic interaction between nerve and muscle.

  12. The role of nitric oxide in muscle fibers with oxidative phosphorylation defects

    SciTech Connect

    Tengan, Celia H. . E-mail: chtengan@neuro.epm.br; Kiyomoto, Beatriz H.; Godinho, Rosely O.; Gamba, Juliana; Neves, Afonso C.; Schmidt, Beny; Oliveira, Acary S.B.; Gabbai, Alberto A.

    2007-08-03

    NO has been pointed as an important player in the control of mitochondrial respiration, especially because of its inhibitory effect on cytochrome c oxidase (COX). However, all the events involved in this control are still not completely elucidated. We demonstrate compartmentalized abnormalities on nitric oxide synthase (NOS) activity on muscle biopsies of patients with mitochondrial diseases. NOS activity was reduced in the sarcoplasmic compartment in COX deficient fibers, whereas increased activity was found in the sarcolemma of fibers with mitochondrial proliferation. We observed increased expression of neuronal NOS (nNOS) in patients and a correlation between nNOS expression and mitochondrial content. Treatment of skeletal muscle culture with an NO donor induced an increase in mitochondrial content. Our results indicate specific roles of NO in compensatory mechanisms of muscle fibers with mitochondrial deficiency and suggest the participation of nNOS in the signaling process of mitochondrial proliferation in human skeletal muscle.

  13. Muscle function-dependent sarcopenia and cut-off values of possible predictors in community-dwelling Turkish elderly: calf circumference, midarm muscle circumference and walking speed.

    PubMed

    Akın, S; Mucuk, S; Öztürk, A; Mazıcıoğlu, M; Göçer, Ş; Arguvanlı, S; Şafak, E D

    2015-10-01

    The aim of this study was to determine the prevalence of muscle strength-based sarcopenia and to determine possible predictors. This is a cross-sectional population-based study in the community-dwelling Turkish elderly. Anthropometric measurements, namely body height, weight, triceps skin fold (TSF), mid upper arm circumference (MUAC), waist circumference (WC) and calf circumference (CC), were noted. The midarm muscle circumference (MAMC) was calculated by using MUAC and TSF measurement. Sarcopenia was assessed, adjusted for body mass index (BMI) and gender, according to muscle strength. Physical performance was determined by 4 m walking speed (WS; m/s). The receiver operating curve analysis was performed to determine cut-offs of CC, MAMC and 4 m WS. A total of 879 elderly subjects, 50.1% of whom were female, were recruited. The mean handgrip strength (HGS) and s.d. was 24.2 (8.8) kg [17.9 (4.8) female, 30.6 (7.1) male]. The muscle function-dependent sarcopenia was 63.4% (female 73.5%, male 53.2%). The muscle mass-dependent sarcopenia for CC (<31 cm) and MAMC(<21.1 cm in males, <19.9 cm in females) was 6.7% and 7.3%, respectively. The prevalence of low 4 m WS (≤ 0.8 m/s) was 81.8% (91.3% in females and 72.3% in males, respectively). We compared MAMC, CC and 4 m WS and found that AUC for 4 m WS was the best predictor of sarcopenia. An adequate muscle mass may not mean a reliable muscle function. Muscle function may describe sarcopenia better compared with muscle mass. The CC, MAMC and 4 m WS cut-offs may be used to assess sarcopenia in certain age groups.

  14. Artificial muscles of dielectric elastomers attached to artificial tendons of functionalized carbon fibers

    NASA Astrophysics Data System (ADS)

    Ye, Zhihang; Faisal, Md. Shahnewaz Sabit; Asmatulu, Ramazan; Chen, Zheng

    2014-03-01

    Dielectric elastomers are soft actuation materials with promising applications in robotics and biomedical de- vices. In this paper, a bio-inspired artificial muscle actuator with artificial tendons is developed for robotic arm applications. The actuator uses dielectric elastomer as artificial muscle and functionalized carbon fibers as artificial tendons. A VHB 4910 tape is used as the dielectric elastomer and PDMS is used as the bonding material to mechanically connect the carbon fibers to the elastomer. Carbon fibers are highly popular for their high electrical conductivities, mechanical strengths, and bio-compatibilities. After the acid treatments for the functionalization of carbon fibers (500 nm - 10 μm), one end of carbon fibers is spread into the PDMS material, which provides enough bonding strength with other dielectric elastomers, while the other end is connected to a DC power supply. To characterize the actuation capability of the dielectric elastomer and electrical conductivity of carbon fibers, a diaphragm actuator is fabricated, where the carbon fibers are connected to the actuator. To test the mechanical bonding between PDMS and carbon fibers, specimens of PDMS bonded with carbon fibers are fabricated. Experiments have been conducted to verify the actuation capability of the dielectric elastomer and mechanical bonding of PDMS with carbon fibers. The energy efficiency of the dielectric elastomer increases as the load increases, which can reach above 50%. The mechanical bonding is strong enough for robotic arm applications.

  15. Vestigial-like 2 contributes to normal muscle fiber type distribution in mice.

    PubMed

    Honda, Masahiko; Hidaka, Kyoko; Fukada, So-Ichiro; Sugawa, Ryo; Shirai, Manabu; Ikawa, Masahito; Morisaki, Takayuki

    2017-08-02

    Skeletal muscle is composed of heterogeneous populations of myofibers that are classified as slow- and fast-twitch fibers. The muscle fiber-type is regulated in a coordinated fashion by multiple genes, including transcriptional factors and microRNAs (miRNAs). However, players involved in this regulation are not fully elucidated. One of the members of the Vestigial-like factors, Vgll2, is thought to play a pivotal role in TEA domain (TEAD) transcription factor-mediated muscle-specific gene expression because of its restricted expression in skeletal muscles of adult mice. Here, we generated Vgll2 null mice and investigated Vgll2 function in adult skeletal muscles. These mice presented an increased number of fast-twitch type IIb fibers and exhibited a down-regulation of slow type I myosin heavy chain (MyHC) gene, Myh7, which resulted in exercise intolerance. In accordance with the decrease in Myh7, down-regulation of miR-208b, encoded within Myh7 gene and up-regulation of targets of miR-208b, Sox6, Sp3, and Purβ, were observed in Vgll2 deficient mice. Moreover, we detected the physical interaction between Vgll2 and TEAD1/4 in neonatal skeletal muscles. These results suggest that Vgll2 may be both directly and indirectly involved in the programing of slow muscle fibers through the formation of the Vgll2-TEAD complex.

  16. Maximal sprint speeds and muscle fiber composition of wild and laboratory house mice.

    PubMed

    Garland, T; Gleeson, T T; Aronovitz, B A; Richardson, C S; Dohm, M R

    1995-11-01

    We compared males from four groups of house mice (Mus domesticus), all bred and raised under common conditions in the laboratory: randombred Hsd:ICR; a wild population from Wisconsin; hybrids from lab dams; hybrids from wild dams. Wild mice were much faster sprinters (maximal forced sprint speeds over 1.0 m ranged from 2.38 to 3.34 m/s) than were lab mice (range = 0.89-1.68 m/s). Hybrids exhibited intermediate speeds (range = 1.54-2.70 m/s) and body masses, indicating largely additive inheritance. Type-specific mean muscle fiber cross-sectional areas of the gastrocnemius muscle did not differ significantly among groups. Percentage cross-sectional areas occupied by each of the three identified fiber types also did not differ significantly among groups, nor did they covary with body mass. For their body mass, however, lab mice had smaller gastrocnemius muscles than did wild and hybrid mice, which had muscles of similar size. Although we cannot rule out the possibility that smaller gastrocnemius muscles or slight differences in fiber composition account for the lower sprint speeds of the lab mice, we suggest that differences in unmeasured physiological, behavioral or motivational factors are probably the primary cause. This interpretation is supported by a lack of correlation between individual differences in sprint speed and either relative gastrocnemius muscle mass or muscle fiber type composition.

  17. Adaptation of fibers in fast-twitch muscles of rats to spaceflight and hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Jiang, Bian; Ohira, Yoshi; Roy, Roland R.; Nguyen, Quyet; Il'ina-Kakueva, E. I.; Oganov, V.; Edgerton, V. R.

    1992-01-01

    The adaptation of single fibers in medial gastrocnemius (MG), a fast-twitch extensor, and in tibialis anterior (TA), a fast-twitch flexor, was studied after 14 days of spaceflight onboard Cosmos 2044 or hindlimb suspension. Quantitative myosin ATPase activities of single fibers were measured in flight and suspended rats. Each of the enzyme and size measurements were directly correlated within each fiber with respect to its qualitative myosin ATPase staining properties and its expression of fast, slow, or both myosin heavy chains (MHC). The percentage of slow- and fast-twitch fibers of the MG and TA were found to be unchanged. Mean fiber size of all fibers was unaffected after flight or suspension. The ATPase activity in the MG was higher in flight than in control or suspended rats. In comparison to Cosmos 1887 spaceflight, the adaptations in the muscle fibers of the MG were more moderate.

  18. Negative-pressure wound therapy after fasciotomy reduces muscle-fiber regeneration in a pig model.

    PubMed

    Wilkin, Geoffrey; Khogali, Shiemaa; Garbedian, Shawn; Slagel, Bradley; Blais, Simon; Gofton, Wade; Liew, Allan; Renaud, Jean-Marc; Papp, Steven

    2014-08-20

    Negative-pressure wound therapy (NPWT) can improve fasciotomy wound closure, but its effects on skeletal muscle are largely unknown. The purpose of this study was to evaluate NPWT effects on skeletal muscle after fasciotomy for compartment syndrome in an animal model and to assess regional variability in muscle fiber regeneration. Compartment syndrome was induced in the hindlimb of twenty-two adult female pigs with use of a continuous intracompartmental serum-infusion model. Fasciotomy was performed after six hours, and animals were randomized to receive either wet-to-dry gauze dressings (control group) or NPWT dressings (-125 mm Hg, continuous suction) for seven days. Delayed primary wound closure was attempted at seven days, and the peroneus tertius was harvested for analysis seven days or twenty-one days after fasciotomy. Muscles were weighed, and hematoxylin and eosin-stained samples from four regions of the muscle (superficial central, deep central, lateral, and proximal) were mapped for different cellular morphologies. Muscle weight was greater in the affected limb at all time points with no difference between treatment groups. At seven days, only the deep central samples in the NPWT group had a significantly greater cross-sectional area containing normal fibers as compared with that found in the controls. By twenty-one days, the deep central, lateral, and proximal regions of the NPWT-treated muscles had a smaller cross-sectional area containing normal fiber morphology and a greater cross-sectional area containing only mononucleated cells as compared with the controls. NPWT did not decrease muscle weight. At twenty-one days, the extent of muscle fiber regeneration after fasciotomy for compartment syndrome was reduced in muscles treated with NPWT for seven days compared with the values in the control group treated with wet-to-dry gauze dressings. NPWT may be harmful to skeletal muscle after compartment syndrome requiring fasciotomy and local wound care

  19. Fiber Phenotype and Coenzyme Q10 Content in Turkey Skeletal Muscles

    PubMed Central

    Nierobisz, L.S.; Hentz, N.G.; Felts, J.V.; Mozdziak, P.E.

    2010-01-01

    Phenotypical differences between muscle fibers are associated with a source of cellular energy. Coenzyme Q10 (CoQ10) is a major component of the mitochondrial oxidative phosphorylation process, and it significantly contributes to the production of cellular energy in the form of ATP. The objective of this study was to determine the relationship between whole-tissue CoQ10 content, mitochondrial CoQ10 content, mitochondrial protein, and muscle phenotype in turkeys. Four specialized muscles (anterior latissimus dorsi, ALD; posterior latissimus dorsi, PLD; pectoralis major, PM, and biceps femoris, BF) were evaluated in 9- and 20-week-old turkey toms. The amount of muscle mitochondrial protein was determined using the Bradford assay and CoQ10 content was measured using HPLC-UV. The amount of mitochondrial protein relative to total protein was significantly lower (p < 0.05) at 9 compared to 20 weeks of age. All ALD fibers stained positive for anti-slow (S35) MyHC antibody. The PLD and PM muscle fibers revealed no staining for slow myosin heavy chain (S35 MyHC), whereas half of BF muscle fibers exhibited staining for S35 MyHC at 9 weeks and 70% at 20 weeks of age. The succinate dehydrogenase (SDH) staining data revealed that SDH significantly increases (p < 0.05) in ALD and BF muscles and significantly decreases (p < 0.05) in PLD and PM muscles with age. The study reveals age-related decreases in mitochondrial CoQ10 content in muscles with fast/glycolytic profile, and demonstrates that muscles with a slow/oxidative phenotypic profile contain a higher proportion of CoQ10 than muscles with a fast/glycolytic phenotypic profile. Copyright © 2010 S. Karger AG, Basel PMID:20664252

  20. Novel demonstration of amyloid-β oligomers in sporadic inclusion-body myositis muscle fibers.

    PubMed

    Nogalska, Anna; D'Agostino, Carla; Engel, W King; Klein, William L; Askanas, Valerie

    2010-11-01

    Accumulation of amyloid-β (Aβ) within muscle fibers has been considered an upstream step in the development of the s-IBM pathologic phenotype. Aβ42, which is considered more cytotoxic than Aβ40 and has a higher propensity to oligomerize, is preferentially increased in s-IBM muscle fibers. In Alzheimer disease (AD), low-molecular weight Aβ oligomers and toxic oligomers, also referred to as "Aβ-Derived Diffusible Ligands" (ADDLs), are considered strongly cytotoxic and proposed to play an important pathogenic role. ADDLs have been shown to be increased in AD brain. We now report for the first time that in s-IBM muscle biopsies Aβ-dimer, -trimer, and -tetramer are identifiable by immunoblots. While all the s-IBM samples we studied had Aβ-oligomers, their molecular weights and intensity varied between the patient samples. None of the control muscle biopsies had Aβ oligomers. Dot-immunoblots using highly specific anti-ADDL monoclonal antibodies also showed highly increased ADDLs in all s-IBM biopsies studied, while controls were negative. By immunofluorescence, in some of the abnormal s-IBM muscle fibers ADDLs were accumulated in the form of plaque-like inclusions, and were often increased diffusely in very small fibers. Normal and disease-controls were negative. By gold-immuno-electron microscopy, ADDL-immunoreactivities were in close proximity to 6-10 nm amyloid-like fibrils, and also were immunodecorating amorphous and floccular material. In cultured human muscle fibers, we found that inhibition of autophagy led to the accumulation of Aβ oligomers. This novel demonstration of Aβ42 oligomers in s-IBM muscle biopsy provides additional evidence that intra-muscle fiber accumulation of Aβ42 oligomers in s-IBM may contribute importantly to s-IBM pathogenic cascade.

  1. Effects of high-intensity resistance training on untrained older men. II. Muscle fiber characteristics and nucleo-cytoplasmic relationships.

    PubMed

    Hikida, R S; Staron, R S; Hagerman, F C; Walsh, S; Kaiser, E; Shell, S; Hervey, S

    2000-07-01

    During growth and repair of skeletal muscle fibers, satellite cells become activated, undergo mitosis, and a daughter nucleus becomes incorporated into the muscle fiber to increase myonuclear numbers. An increase in myonuclei appears to be required for this postnatal growth. This study examined whether muscle fibers of elderly men can hypertrophy with strength training and, if so, whether they have the capacity to incorporate nuclei into the fibers. The sarcoplasmic area associated with each myonucleus was calculated in nine elderly men before and after 16 weeks of strength training, and compared to nine elderly control men. Muscle fiber type changes and myosin heavy chain composition were also compared. All major fiber types (I, IIA, IIB) became significantly larger after training, and a transition of type IIB fibers to IIA occurred with training. The area occupied by each fiber type correlated with myosin heavy chain percentage, and both of these changed similarly with strength training. The cytoplasm-to-myonucleus ratio increased, but not significantly (p = .07), with muscle fiber hypertrophy. Number of myonuclei per fiber and myonuclei per unit length of muscle fiber increased, but not significantly. Cross-sectional areas of the muscle fibers in untrained elderly men were much smaller than in untrained young men (when compared with our earlier studies). Training increased the sizes of the elderly muscle fibers to that of the untrained young men. This hypertrophy of muscle fibers by 30% with training resulted in no change in the cytoplasm-to-myonucleus ratio. This suggests that the myonuclear population continues to adapt to growth stimuli in the elderly muscles.

  2. Altered distribution of mitochondria in rat soleus muscle fibers after spaceflight

    NASA Technical Reports Server (NTRS)

    Bell, Gordon J.; Martin, Thomas P.; Il'ina-Kakueva, E. I.; Oganov, V. S.; Edgerton, V. R.

    1992-01-01

    The effect of an exposure to microgravity on the distribution of the succinate dehydrogenase (SDH) activity throughout the soleus muscle fibers was investigated by measuring SDH activity throughout the cross section of 20-30 fibers each of the slow-twitch oxidative and fast-twitch oxidative-glycolytic types of fibers in rats exposed to 12.5 days in space aboard Cosmos 1887. It was found that, after the spaceflight, the entire regional distribution of SDH activity was significantly altered (as compared to ground controls) in the slow-twitch oxidative fibers, whereas the fast-twitch oxidative-glycolytic fibers from muscles of flown rats exhibited a significantly lower SDH activity only in their subsarcolemmal region.

  3. Clustering of the human skeletal muscle fibers using linear programming and angular Hilbertian metrics.

    PubMed

    Neji, Radhouène; Besbes, Ahmed; Komodakis, Nikos; Deux, Jean-François; Maatouk, Mezri; Rahmouni, Alain; Bassez, Guillaume; Fleury, Gilles; Paragios, Nikos

    2009-01-01

    In this paper, we present a manifold clustering method fo the classification of fibers obtained from diffusion tensor images (DTI) of the human skeletal muscle. Using a linear programming formulation of prototype-based clustering, we propose a novel fiber classification algorithm over manifolds that circumvents the necessity to embed the data in low dimensional spaces and determines automatically the number of clusters. Furthermore, we propose the use of angular Hilbertian metrics between multivariate normal distributions to define a family of distances between tensors that we generalize to fibers. These metrics are used to approximate the geodesic distances over the fiber manifold. We also discuss the case where only geodesic distances to a reduced set of landmark fibers are available. The experimental validation of the method is done using a manually annotated significant dataset of DTI of the calf muscle for healthy and diseased subjects.

  4. Altered distribution of mitochondria in rat soleus muscle fibers after spaceflight

    NASA Technical Reports Server (NTRS)

    Bell, Gordon J.; Martin, Thomas P.; Il'ina-Kakueva, E. I.; Oganov, V. S.; Edgerton, V. R.

    1992-01-01

    The effect of an exposure to microgravity on the distribution of the succinate dehydrogenase (SDH) activity throughout the soleus muscle fibers was investigated by measuring SDH activity throughout the cross section of 20-30 fibers each of the slow-twitch oxidative and fast-twitch oxidative-glycolytic types of fibers in rats exposed to 12.5 days in space aboard Cosmos 1887. It was found that, after the spaceflight, the entire regional distribution of SDH activity was significantly altered (as compared to ground controls) in the slow-twitch oxidative fibers, whereas the fast-twitch oxidative-glycolytic fibers from muscles of flown rats exhibited a significantly lower SDH activity only in their subsarcolemmal region.

  5. Mitochondrial specialization revealed by single muscle fiber proteomics: focus on the Krebs cycle.

    PubMed

    Schiaffino, S; Reggiani, C; Kostrominova, T Y; Mann, M; Murgia, M

    2015-12-01

    We have developed a highly sensitive mass spectrometry-based proteomic workflow to examine the proteome of single muscle fibers. This study revealed significant differences in the mitochondrial proteome of the four major fiber types present in mouse skeletal muscle. Here, we focus on Krebs cycle enzymes and in particular on the differential distribution of the two mitochondrial isocitrate dehydrogenases, IDH2 and IDH3. Type 1/slow fibers contain high levels of IDH2 and relatively low levels of IDH3, whereas fast 2X and 2B fibers show an opposite expression pattern. The findings suggest that in skeletal muscle, IDH2 functions in the forward direction of the Krebs cycle and that substrate flux along the cycle occurs predominantly via IDH2 in type 1 fibers and via IDH3 in 2X and 2B fibers. IDH2-mediated conversion of isocitrate to α-ketoglutarate leads to the generation of NADPH, which is critical to buffering the H2O2 produced by the respiratory chain. Nicotinamide nucleotide transhydrogenase (NNT), the other major mitochondrial enzyme involved in NADPH generation, is also more abundant in type 1 fibers. We suggest that the continuously active type 1 fibers are endowed with a more efficient H2O2 scavenging capacity to cope with the higher levels of reactive oxygen species production. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Weekly versus monthly testosterone administration on fast and slow skeletal muscle fibers in older adult males.

    PubMed

    Fitts, Robert H; Peters, James R; Dillon, E Lichar; Durham, William J; Sheffield-Moore, Melinda; Urban, Randall J

    2015-02-01

    In older adults, loss of mobility due to sarcopenia is exacerbated in men with low serum T. T replacement therapy is known to increase muscle mass and strength, but the effect of weekly (WK) vs monthly (MO) administration on specific fiber types is unknown. To determine the efficacy of WK vs MO T replacement on the size and functional capacity of individual fast and slow skeletal muscle fiber types. Subjects were randomized into a 5-month, double-blind, placebo-controlled trial. All subjects (ages, 61-71 y) were community-dwelling men who had T levels < 500 ng/dL. Subjects were dosed weekly for 5 months, receiving continuous T (WK, n = 5; 100 mg T enanthate, im injection), monthly cycled T (MO, n = 7; alternating months of T and placebo), or placebo (n = 7). Muscle biopsies of the vastus lateralis were obtained before and after treatment. Main outcomes for individual slow and fast fibers included fiber diameter, peak force (P0), rate of tension development, maximal shortening velocity, peak power, and Ca(2+) sensitivity. Both treatments increased fiber diameter and peak power, with WK treatment 5-fold more effective than MO in increasing type I fiber P0. WK effects on fiber diameter and force were 1.5-fold higher in slow fibers compared to fast fibers. In fast type II fibers, diameter and P0 increased similarly between treatments. The increased power was entirely due to increased fiber size and force. In conclusion, T replacement effects were fiber-type dependent, restricted to increases in cell size, P0, and peak power, and dependent on the paradigm selected (WK vs MO).

  7. Skeletal muscle fiber analysis by atmospheric pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometric imaging at high mass and high spatial resolution.

    PubMed

    Tsai, Yu-Hsuan; Bhandari, Dhaka Ram; Garrett, Timothy J; Carter, Christy S; Spengler, Bernhard; Yost, Richard A

    2016-06-01

    Skeletal muscles are composed of heterogeneous muscle fibers with various fiber types. These fibers can be classified into different classes based on their different characteristics. MALDI mass spectrometric imaging (MSI) has been applied to study and visualize different metabolomics profiles of different fiber types. Here, skeletal muscles were analyzed by atmospheric pressure scanning microprobe MALDI-MSI at high spatial and high mass resolution.

  8. [Pathophysiology of muscular atrophy due to disuse--with special reference to a single muscle fiber and its ultrastructure].

    PubMed

    Sukegawa, T

    1983-08-01

    Immobilization muscule atrophy was experimentally induced by fixing one ankle joint with a K-wire in an extended position in rats. The animals were sacrificed at designated intervals to obtain the soleus muscle from the fixed (or disused) side and the free side; the muscles were weighed wet, evaluated (musculo) physiologically using a single-skinned muscle fiber method, and further examined histochemically and electron-microscopically. The wet weight of the disused soleus muscle was reduced to 54% of that of the healthy (used) muscle. According to classification by types of muscle fibers stained for ATPase, conversion of muscle fiber type, i.e., conversions of type 1 (red muscle) into type 2 (white muscle) was noted on the disused side, and similar findings were also observed by examination using a single skinned muscle fiber method. The maximal tension developed by the disused single muscle fiber was lower. This may be attributable to structural changes in the myofilament arrangement observed under an electron microscope. No abnormalities were found in calcium ion uptake by the sarcoplasmic reticulum. Under the present experimental conditions, it was clarified that the disuse atrophy of skeletal muscle induces not only reduction of muscle fibers in diameter but also their dedifferentiation and redifferentiation.

  9. <