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Leijding C, Viken I, Bruton JD, Andersson DC, Cheng AJ, Westerblad H. Increased tetanic calcium in early fatigue of mammalian muscle fibers is accompanied by accelerated force development despite a decreased force. FASEB J 2023; 37:e22978. [PMID: 37191967 DOI: 10.1096/fj.202300401r] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/18/2023] [Accepted: 05/05/2023] [Indexed: 05/17/2023]
Abstract
During the initial phase of fatigue induced by repeated contractions in fast-twitch muscle fibers, tetanic force decreases despite increasing tetanic free cytosolic [Ca2+ ] ([Ca2+ ]cyt ). Here, we hypothesized that the increase in tetanic [Ca2+ ]cyt nevertheless has positive effects on force in early fatigue. Experiments on enzymatically isolated mouse flexor digitorum brevis (FDB) fibers showed that an increase in tetanic [Ca2+ ]cyt during ten 350 ms contractions required trains of electrical pulses to be elicited at short intervals (≤2 s) and at high frequencies (≥70 Hz). Mechanically dissected mouse FDB fibers showed greater decrease in tetanic force when the stimulation frequency during contractions was gradually reduced to prevent the increase in tetanic [Ca2+ ]cyt . Novel analyses of data from previous studies revealed an increased rate of force development in the tenth fatiguing contraction in mouse FDB fibers, as well as in rat FDB and human intercostal fibers. Mouse FDB fibers deficient in creatine kinase showed no increase in tetanic [Ca2+ ]cyt and slowed force development in the tenth contraction; after injection of creatine kinase to enable phosphocreatine breakdown, these fibers showed an increase in tetanic [Ca2+ ]cyt and accelerated force development. Mouse FDB fibers exposed to ten short contractions (43 ms) produced at short intervals (142 ms) showed increased tetanic [Ca2+ ]cyt accompanied by a marked (~16%) increase in the developed force. In conclusion, the increase in tetanic [Ca2+ ]cyt in early fatigue is accompanied by accelerated force development, which under some circumstances can counteract the decline in physical performance caused by the concomitant decrease in maximum force.
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Affiliation(s)
- Cecilia Leijding
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Ida Viken
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Joseph D Bruton
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Daniel C Andersson
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
- Heart, Vascular and Neurology Theme, Cardiology Unit, Karolinska University Hospital, Stockholm, Sweden
| | - Arthur J Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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Ranatunga KW, Geeves MA. Effects of Hydrostatic-Pressure on Muscle Contraction: A Look Back on Some Experimental Findings. Int J Mol Sci 2023; 24:5031. [PMID: 36902460 PMCID: PMC10003533 DOI: 10.3390/ijms24055031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/27/2023] [Accepted: 02/28/2023] [Indexed: 03/08/2023] Open
Abstract
Findings from experiments that used hydrostatic pressure changes to analyse the process of skeletal muscle contraction are re-examined. The force in resting muscle is insensitive to an increase in hydrostatic pressure from 0.1 MPa (atmospheric) to 10 MPa, as also found for force in rubber-like elastic filaments. The force in rigour muscle rises with increased pressure, as shown experimentally for normal elastic fibres (e.g., glass, collagen, keratin, etc.). In submaximal active contractions, high pressure leads to tension potentiation. The force in maximally activated muscle decreases with increased pressure: the extent of this force decrease in maximal active muscle is sensitive to the concentration of products of ATP hydrolysis (Pi-inorganic phosphate and ADP-adenosine diphosphate) in the medium. When the increased hydrostatic pressure is rapidly decreased, the force recovered to the atmospheric level in all cases. Thus, the resting muscle force remained the same: the force in the rigour muscle decreased in one phase and that in active muscle increased in two phases. The rate of rise of active force on rapid pressure release increased with the concentration of Pi in the medium, indicating that it is coupled to the Pi release step in the ATPase-driven crossbridge cycle in muscle. Pressure experiments on intact muscle illustrate possible underlying mechanisms of tension potentiation and causes of muscle fatigue.
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Affiliation(s)
- K. W. Ranatunga
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - M. A. Geeves
- Department of Biosciences, University of Kent, Kent, Canterbury CT2 7NJ, UK
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Kuehn K, Hahn A, Seefried L. Mineral Intake and Clinical Symptoms in Adult Patients with Hypophosphatasia. J Clin Endocrinol Metab 2020; 105:5851912. [PMID: 32502243 DOI: 10.1210/clinem/dgaa324] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 06/02/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Hypophosphatasia (HPP) is a rare inherited metabolic disorder characterized by deficient activity of the tissue-nonspecific alkaline phosphatase entailing impaired turnover of phosphorus metabolites. Dietary mineral intake is suspected to influence clinical symptoms of HPP, but scientific evidence is missing. METHODS Cross-sectional matched-pairs study collecting comprehensive data on nutrient intake in 20 HPP patients and 20 unaffected, age- and gender-matched controls. Dietary information and clinical symptoms were documented in detail over 7 consecutive days using structured diaries. RESULTS Baseline data and type of energy-supplying nutrients were balanced between both groups. Median nutritional intake of phosphorus and calcium were significantly lower in HPP patients versus controls, which is partially attributable to lower energy consumption in HPP patients. Differences regarding phosphorus and calcium (Ca/P) ratio and uptake of magnesium, zinc, and vitamin B6 were not statistically significant. Both high (≥ 1375 mg/d) and low intakes (< 1100 mg/d) of phosphorus were significantly associated with an increased frequency of neuropsychiatric symptoms (P = 0.02). Similarly, very high and very low intake of calcium was significantly associated with musculoskeletal (P < 0.01), gastrointestinal (P = 0.02), and neuropsychiatric (P < 0.001) symptoms. An increased Ca/P ratio was associated with increased tiredness/fatigue (P < 0.01), whereas a decreased Ca/P was associated with gastrointestinal issues (P = 0.01). CONCLUSION Phosphorus and calcium intake seem reduced in HPP patients along with reduced total energy consumption. Particularly high as well as very low absolute or unbalanced phosphorus and calcium intake are associated with an increased frequency of clinical symptoms.
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Affiliation(s)
- Katinka Kuehn
- Faculty of Natural Science, Institute of Food Science and Human Nutrition, Leibniz University Hannover, Hannover, Germany
| | - Andreas Hahn
- Faculty of Natural Science, Institute of Food Science and Human Nutrition, Leibniz University Hannover, Hannover, Germany
| | - Lothar Seefried
- Clinical Trial Unit, Orthopedic Institute, Koenig-Ludwig-Haus, University of Wuerzburg, Wuerzburg, Germany
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MacDougall KB, Devrome AN, Kristensen AM, MacIntosh BR. Force-frequency relationship during fatiguing contractions of rat medial gastrocnemius muscle. Sci Rep 2020; 10:11575. [PMID: 32665563 PMCID: PMC7360560 DOI: 10.1038/s41598-020-68392-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 06/15/2020] [Indexed: 01/26/2023] Open
Abstract
The force–frequency relationship presents the amount of force a muscle can produce as a function of the frequency of activation. During repetitive muscular contractions, fatigue and potentiation may both impact the resultant contractile response. However, both the apparent fatigue observed, and the potential for activity-dependent potentiation can be affected by the frequency of activation. Thus, we wanted to explore the effects that repetitive stimulation had on the force–frequency relationship. The force–frequency relationship of the rat medial gastrocnemius muscle was investigated during consecutive bouts of increasing fatigue with 20 to 100 Hz stimulation. Force was measured prior to the fatiguing protocol, during each of three levels of fatigue, and after 30 min of recovery. Force at each frequency was quantified relative to the pre-fatigued 100 Hz contractions, as well as the percentage reduction of force from the pre-fatigued level at a given frequency. We observed less reduction in force at low frequencies compared to high frequencies, suggesting an interplay of fatigue and potentiation, in which potentiation can “protect” against fatigue in a frequency-dependent manner. The exact mechanism of fatigue is unknown, however the substantial reduction of force at high frequency suggests a role for reduced force per cross-bridge.
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Affiliation(s)
| | - Andrea N Devrome
- Faculty of Medicine, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | | | - Brian R MacIntosh
- Faculty of Kinesiology, University of Calgary, Calgary, AB, T2N 1N4, Canada.
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Degens H, Jones DA. Are Force Enhancement after Stretch and Muscle Fatigue Due to Effects of Elevated Inorganic Phosphate and Low Calcium on Cross Bridge Kinetics? ACTA ACUST UNITED AC 2020; 56:medicina56050249. [PMID: 32443826 PMCID: PMC7279286 DOI: 10.3390/medicina56050249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 05/18/2020] [Indexed: 11/20/2022]
Abstract
Background and Objectives: Muscle fatigue is characterised by (1) loss of force, (2) decreased maximal shortening velocity and (3) a greater resistance to stretch that could be due to reduced intracellular Ca2+ and increased Pi, which alter cross bridge kinetics. Materials and Methods: To investigate this, we used (1) 2,3-butanedione monoxime (BDM), believed to increase the proportion of attached but non-force-generating cross bridges; (2) Pi that increases the proportion of attached cross bridges, but with Pi still attached; and (3) reduced activating Ca2+. We used permeabilised rat soleus fibres, activated with pCa 4.5 at 15 °C. Results: The addition of 1 mM BDM or 15 mM Pi, or the lowering of the Ca2+ to pCa 5.5, all reduced the isometric force by around 50%. Stiffness decreased in proportion to isometric force when the fibres were activated at pCa 5.5, but was well maintained in the presence of Pi and BDM. Force enhancement after a stretch increased with the length of stretch and Pi, suggesting a role for titin. Maximum shortening velocity was reduced by about 50% in the presence of BDM and pCa 5.5, but was slightly increased by Pi. Neither decreasing Ca2+ nor increasing Pi alone mimicked the effects of fatigue on muscle contractile characteristics entirely. Only BDM elicited a decrease of force and slowing with maintained stiffness, similar to the situation in fatigued muscle. Conclusions: This suggests that in fatigue, there is an accumulation of attached but low-force cross bridges that cannot be the result of the combined action of reduced Ca2+ or increased Pi alone, but is probably due to a combination of factors that change during fatigue.
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Affiliation(s)
- Hans Degens
- Department of Life Sciences, Manchester Metropolitan University, Research Centre for Musculoskeletal Sciences & Sport Medicine, Manchester M1 5GD, UK;
- Institute of Sport Science and Innovations, Lithuanian Sports University, LT-44221 Kaunas, Lithuania
- Correspondence: ; Tel.: +44-161-247-5686
| | - David A. Jones
- Department of Life Sciences, Manchester Metropolitan University, Research Centre for Musculoskeletal Sciences & Sport Medicine, Manchester M1 5GD, UK;
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Rockenfeller R, Günther M, Stutzig N, Haeufle DFB, Siebert T, Schmitt S, Leichsenring K, Böl M, Götz T. Exhaustion of Skeletal Muscle Fibers Within Seconds: Incorporating Phosphate Kinetics Into a Hill-Type Model. Front Physiol 2020; 11:306. [PMID: 32431619 PMCID: PMC7214688 DOI: 10.3389/fphys.2020.00306] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 03/19/2020] [Indexed: 12/01/2022] Open
Abstract
Initiated by neural impulses and subsequent calcium release, skeletal muscle fibers contract (actively generate force) as a result of repetitive power strokes of acto-myosin cross-bridges. The energy required for performing these cross-bridge cycles is provided by the hydrolysis of adenosine triphosphate (ATP). The reaction products, adenosine diphosphate (ADP) and inorganic phosphate (P i ), are then used-among other reactants, such as creatine phosphate-to refuel the ATP energy storage. However, similar to yeasts that perish at the hands of their own waste, the hydrolysis reaction products diminish the chemical potential of ATP and thus inhibit the muscle's force generation as their concentration rises. We suggest to use the term "exhaustion" for force reduction (fatigue) that is caused by combined P i and ADP accumulation along with a possible reduction in ATP concentration. On the basis of bio-chemical kinetics, we present a model of muscle fiber exhaustion based on hydrolytic ATP-ADP-P i dynamics, which are assumed to be length- and calcium activity-dependent. Written in terms of differential-algebraic equations, the new sub-model allows to enhance existing Hill-type excitation-contraction models in a straightforward way. Measured time courses of force decay during isometric contractions of rabbit M. gastrocnemius and M. plantaris were employed for model verification, with the finding that our suggested model enhancement proved eminently promising. We discuss implications of our model approach for enhancing muscle models in general, as well as a few aspects regarding the significance of phosphate kinetics as one contributor to muscle fatigue.
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Affiliation(s)
| | - Michael Günther
- Institute for Modelling and Simulation of Biomechanical Systems, Computational Biophysics and Biorobotics, University of Stuttgart, Stuttgart, Germany
- Friedrich-Schiller-University, Jena, Germany
| | - Norman Stutzig
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - Daniel F. B. Haeufle
- Hertie-Institute for Clinical Brain Research and Center for Integrative Neuroscience, Eberhard-Karls-University, Tübingen, Germany
| | - Tobias Siebert
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - Syn Schmitt
- Institute for Modelling and Simulation of Biomechanical Systems, Computational Biophysics and Biorobotics, University of Stuttgart, Stuttgart, Germany
| | - Kay Leichsenring
- Institute of Solid Mechanics, Technical University Braunschweig, Braunschweig, Germany
| | - Markus Böl
- Institute of Solid Mechanics, Technical University Braunschweig, Braunschweig, Germany
| | - Thomas Götz
- Mathematical Institute, University of Koblenz-Landau, Koblenz, Germany
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7
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Muangkram Y, Honda M, Amano A, Himeno Y, Noma A. Exploring the role of fatigue-related metabolite activity during high-intensity exercise using a simplified whole-body mathematical model. INFORMATICS IN MEDICINE UNLOCKED 2020. [DOI: 10.1016/j.imu.2020.100355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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Bagni MA, Colombini B, Nocella M, Pregno C, S Cornachione A, Rassier DE. The effects of fatigue and oxidation on contractile function of intact muscle fibers and myofibrils isolated from the mouse diaphragm. Sci Rep 2019; 9:4422. [PMID: 30872655 PMCID: PMC6418105 DOI: 10.1038/s41598-019-39353-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 01/18/2019] [Indexed: 11/09/2022] Open
Abstract
The goal of this study was to investigate the effects of repetitive stimulation and the oxidant H2O2 on fatigue of diaphragm intact fibers and in myofibrils measured with different Ca2+ concentrations. Intact fibers were isolated from mice diaphragm, and twitch and tetanic contractions (500 ms duration) were performed at different frequencies of stimulation ranging from 15 Hz to 150 Hz to establish a force-frequency relation before and after a fatigue and recovery protocol, without or after a treatment with H2O2. Fatigue was induced with isometric contractions (500 ms, 40 Hz) evoked every 0.8 seconds, with a total of 625 tetani. After the fatigue, the force recovery was followed by invoking tetanic contractions (500 ms, 40 Hz) every 1 min, with a total duration of 30 min. Individual myofibrils were also isolated from the mouse diaphragm and were tested for isometric contractions before and after treatment with H2O2 and NAC. In a second series of experiments, myofibrils were activated at different pCa (pCa = -log10 [Ca2+]), before and after H2O2 treatment. After 15 minutes of H2O2 treatment, the myofibrillar force was decreased to 54 ± 12% of its control, maximal value, and a result that was reversed by NAC treatment. The force was also decreased after myofibrils were treated with H2O2 and activated in pCa ranging between 4.5 and 5.7. These results suggest that fatigue in diaphragm intact fibers and at the myofibrils level is caused partially by oxidation of the contractile proteins that may be responsible for changing the force in various levels of Ca2+ activation.
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Affiliation(s)
- M Angela Bagni
- Dept Experimental and Clinical Medicine, University of Firenze, Florence, Italy
| | - Barbara Colombini
- Dept Experimental and Clinical Medicine, University of Firenze, Florence, Italy
| | - Marta Nocella
- Dept Experimental and Clinical Medicine, University of Firenze, Florence, Italy
| | - Claudio Pregno
- Dept Experimental and Clinical Medicine, University of Firenze, Florence, Italy
| | - Anabelle S Cornachione
- Dept Kinesiology and Physical Education, Faculty of Education, McGill University, Montreal, Canada
| | - Dilson E Rassier
- Dept Kinesiology and Physical Education, Faculty of Education, McGill University, Montreal, Canada.
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9
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Assessing the role of Ca2+ in skeletal muscle fatigue using a multi-scale continuum model. J Theor Biol 2019; 461:76-83. [DOI: 10.1016/j.jtbi.2018.10.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 10/09/2018] [Accepted: 10/13/2018] [Indexed: 11/16/2022]
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10
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Spainhower KB, Cliffe RN, Metz AK, Barkett EM, Kiraly PM, Thomas DR, Kennedy SJ, Avey-Arroyo JA, Butcher MT. Cheap labor: myosin fiber type expression and enzyme activity in the forelimb musculature of sloths (Pilosa: Xenarthra). J Appl Physiol (1985) 2018; 125:799-811. [PMID: 29722617 DOI: 10.1152/japplphysiol.01118.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sloths are canopy-dwelling inhabitants of American neotropical rainforests that exhibit suspensory behaviors. These abilities require both strength and muscular endurance to hang for extended periods of time; however, the skeletal muscle mass of sloths is reduced, thus requiring modifications to muscle architecture and leverage for large joint torque. We hypothesize that intrinsic muscle properties are also modified for fatigue resistance and predict a heterogeneous expression of slow/fast myosin heavy chain (MHC) fibers that utilize oxidative metabolic pathways for economic force production. MHC fiber type distribution and energy metabolism in the forelimb muscles of three-toed ( Bradypus variegatus, n = 5) and two-toed ( Choloepus hoffmanni, n = 4) sloths were evaluated using SDS-PAGE, immunohistochemistry, and enzyme activity assays. The results partially support our hypothesis by a primary expression of the slow MHC-1 isoform as well as moderate expression of fast MHC-2A fibers, whereas few hybrid MHC-1/2A fibers were found in both species. MHC-1 fibers were larger in cross-sectional area (CSA) than MHC-2A fibers and comprised the greatest percentage of CSA in each muscle sampled. Enzyme assays showed elevated activity for the anaerobic enzymes creatine kinase and lactate dehydrogenase compared with low activity for aerobic markers citrate synthase and 3-hydroxyacetyl CoA dehydrogenase. These findings suggest that sloth forelimb muscles may rely heavily on rapid ATP resynthesis pathways, and lactate accumulation may be beneficial. The intrinsic properties observed match well with suspensory requirements, and these modifications may have further evolved in unison with low metabolism and slow movement patterns as means to systemically conserve energy. NEW & NOTEWORTHY Myosin heavy chain (MHC) fiber type and fiber metabolic properties were evaluated to understand the ability of sloths to remain suspended for extended periods without muscle fatigue. Broad distributions of large, slow MHC-1 fibers as well as small, fast MHC-2A fibers are expressed in sloth forelimbs, but muscle metabolism is generally not correlated with myosin fiber type or body size. Sloth muscles rely on rapid, anaerobic pathways to resist fatigue and sustain force production.
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Affiliation(s)
- Kyle B Spainhower
- Department of Biological Sciences, Youngstown State University, Youngstown, Ohio
| | - Rebecca N Cliffe
- Department of Biosciences, Swansea University, Wales, United Kingdom
| | - Allan K Metz
- Department of Biological Sciences, Youngstown State University, Youngstown, Ohio
| | - Ernest M Barkett
- Department of Biological Sciences, Youngstown State University, Youngstown, Ohio
| | - Paije M Kiraly
- Department of Biological Sciences, Youngstown State University, Youngstown, Ohio
| | - Dylan R Thomas
- Department of Biological Sciences, Youngstown State University, Youngstown, Ohio
| | - Sarah J Kennedy
- Sloth Conservation Foundation, Puerto Viejo de Talamanca, Limon, Costa Rica
| | | | - Michael T Butcher
- Department of Biological Sciences, Youngstown State University, Youngstown, Ohio
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11
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Ranatunga KW. Temperature Effects on Force and Actin⁻Myosin Interaction in Muscle: A Look Back on Some Experimental Findings. Int J Mol Sci 2018; 19:E1538. [PMID: 29786656 PMCID: PMC5983754 DOI: 10.3390/ijms19051538] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/14/2018] [Accepted: 05/16/2018] [Indexed: 01/23/2023] Open
Abstract
Observations made in temperature studies on mammalian muscle during force development, shortening, and lengthening, are re-examined. The isometric force in active muscle goes up substantially on warming from less than 10 °C to temperatures closer to physiological (>30 °C), and the sigmoidal temperature dependence of this force has a half-maximum at ~10 °C. During steady shortening, when force is decreased to a steady level, the sigmoidal curve is more pronounced and shifted to higher temperatures, whereas, in lengthening muscle, the curve is shifted to lower temperatures, and there is a less marked increase with temperature. Even with a small rapid temperature-jump (T-jump), force in active muscle rises in a definitive way. The rate of tension rise is slower with adenosine diphosphate (ADP) and faster with increased phosphate. Analysis showed that a T-jump enhances an early, pre-phosphate release step in the acto-myosin (crossbridge) ATPase cycle, thus inducing a force-rise. The sigmoidal dependence of steady force on temperature is due to this endothermic nature of crossbridge force generation. During shortening, the force-generating step and the ATPase cycle are accelerated, whereas during lengthening, they are inhibited. The endothermic force generation is seen in different muscle types (fast, slow, and cardiac). The underlying mechanism may involve a structural change in attached myosin heads and/or their attachments on heat absorption.
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Affiliation(s)
- K W Ranatunga
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, UK.
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12
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Abstract
PURPOSE We examined how muscle length and time between stimuli (inter-pulse interval, IPI) influence declines in force (sag) seen during unfused tetani in the human adductor pollicis muscle. METHODS A series of 16-pulse contractions were evoked with IPIs between 1 × and 5 × the twitch time to peak tension (TPT) at large (long muscle length) and small (short muscle length) thumb adduction angles. Unfused tetani were mathematically deconstructed into a series of overlapping twitch contractions to examine why sag exhibits length- and IPI-dependencies. RESULTS Across all IPIs tested, sag was 62% greater at short than long muscle length, and sag increased as IPI was increased at both muscle lengths. Force attributable to the second stimulus increased as IPI was decreased. Twitch force declined from maximal values across all IPI tested, with the greatest reductions seen at short muscle length and long IPI. At IPI below 2 × TPT, the twitch with highest force occurred earlier than the peak force of the corresponding unfused tetani. Contraction-induced declines in twitch duration (TPT + half relaxation time) were only observed at IPI longer than 1.75 × TPT, and were unaffected by muscle length. CONCLUSIONS Sag is an intrinsic feature of healthy human adductor pollicis muscle. The length-dependence of sag is related to greater diminution of twitch force at short relative to long muscle length. The dependence of sag on IPI is related to IPI-dependent changes in twitch duration and twitch force, and the timing of peak twitch force relative to the peak force of the associated unfused tetanus.
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Affiliation(s)
- Ian C Smith
- Human Performance Lab, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
| | - Jahaan Ali
- Human Performance Lab, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - Geoffrey A Power
- Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Rd E, Guelph, ON, N1G 2W1, Canada
| | - Walter Herzog
- Human Performance Lab, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
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13
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Exploring the Link between Serum Phosphate Levels and Low Muscle Strength, Dynapenia, and Sarcopenia. Sci Rep 2018; 8:3573. [PMID: 29476104 PMCID: PMC5824959 DOI: 10.1038/s41598-018-21784-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 02/09/2018] [Indexed: 11/09/2022] Open
Abstract
Emerging evidences addressed an association between phosphate and muscle function. Because little attention was focused on this issue, the objective of our study was to explore the relationship of phosphate with muscle strength, dynapenia, and sarcopenia. From the National Health and Nutrition Examination Survey, a total of 7421 participants aged 20 years or older were included in our study with comprehensive examinations included anthropometric parameters, strength of the quadriceps muscle, and appendicular lean masses. Within the normal range of serum phosphate, we used quartile-based analyses to determine the potential relationships of serum phosphate with dynapenia, and sarcopenia through multivariate regression models. After adjusting for the pertinent variables, an inverse association between the serum phosphate quartiles and muscle strength was observed and the linear association was stronger than other anthropometric parameters. Notably, the significant association between phosphate and muscle strength was existed in >65 years old age group, not in 20-65 years old. The higher quartiles of phosphate had higher likelihood for predicting the presence of dynapenia rather than sarcopenia in entire population. Our study highlighted that higher quartiles of phosphate had significant association with lower muscle strength and higher risks for predicting the presence of dynapenia.
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14
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Ranatunga KW, Offer G. The force-generation process in active muscle is strain sensitive and endothermic: a temperature-perturbation study. ACTA ACUST UNITED AC 2017; 220:4733-4742. [PMID: 29084851 DOI: 10.1242/jeb.167197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 10/26/2017] [Indexed: 11/20/2022]
Abstract
In experiments on active muscle, we examined the tension decline and its temperature sensitivity at the onset of ramp shortening and at a range of velocities. A segment (∼1.5 mm long) of a skinned muscle fibre isolated from rabbit psoas muscle was held isometrically (sarcomere length ∼2.5 µm) at 8-9°C, maximally Ca2+-activated and a ramp shortening applied. The tension decline with a ramp shortening showed an early decrease of slope (the P1 transition) followed by a slower decrease in slope (the P2 transition) to the steady (isotonic) force. The tension level at the initial P1 transition and the time to that transition decreased as the velocity was increased; the length change to this transition increased with shortening velocity to a steady value of ∼8 nm half-sarcomere-1 A small, rapid, temperature jump (T-jump) (3-4°C, <0.2 ms) applied coincident with the onset of ramp shortening showed force enhancement by T-jump and changed the tension decline markedly. Analyses showed that the rate of T-jump-induced force rise increased linearly with increase of shortening velocity. These results provide crucial evidence that the strain-sensitive cross-bridge force generation, or a step closely coupled to it, is endothermic.
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Affiliation(s)
- K W Ranatunga
- Muscle Contraction Group, School of Physiology, Pharmacology & Neurosciences, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Gerald Offer
- Muscle Contraction Group, School of Physiology, Pharmacology & Neurosciences, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
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Smith IC, Vandenboom R, Tupling AR. Contraction-induced enhancement of relaxation during high force contractions of mouse lumbrical muscle at 37°C. J Exp Biol 2017; 220:2870-2873. [PMID: 28576821 DOI: 10.1242/jeb.158998] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 05/28/2017] [Indexed: 11/20/2022]
Abstract
Repeated stimulation of unfatigued rodent fast-twitch skeletal muscle accelerates the kinetics of tension relaxation through an unknown mechanism. This effect varies with muscle type and stimulation parameters, and has been observed at physiological temperatures for submaximal but not maximal contractions. The purpose of this study was to compare relaxation kinetics of C57BL/6 mouse lumbrical muscles ex vivo from maximal isometric force (500 Hz for 20 ms) when evoked before (pre) and after (post) an intervening tetanic contraction at 37°C. During post contractions, we noted significant increases in the rate of tension decline during both the slow linear phase and the fast exponential phase of relaxation, as well as a reduced duration of the slow phase of relaxation compared with pre contractions (all P<0.05). This is the first demonstration of enhanced slow and fast relaxation phases from maximal isometric tension induced by prior stimulation in intact muscle at a physiological temperature.
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Affiliation(s)
- Ian C Smith
- Human Performance Lab, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada, T2N 1N4 .,Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada, N2L 3G1
| | - Rene Vandenboom
- Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada, L2S 3A1
| | - A Russell Tupling
- Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada, N2L 3G1
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