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Biesiadecki BJ, Brotto MA, Brotto LS, Koch LG, Britton SL, Nosek TM, Jin JP. Rats genetically selected for low and high aerobic capacity exhibit altered soleus muscle myofilament functions. Am J Physiol Cell Physiol 2020; 318:C422-C429. [PMID: 31875694 DOI: 10.1152/ajpcell.00430.2019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aerobic exercise capacity is critical to bodily health. As a model to investigate the mechanisms that determine health and disease, we employed low (LCR) and high (HCR) capacity running rat models selectively bred to concentrate the genes responsible for divergent aerobic running capacity. To investigate the skeletal muscle contribution to this innate difference in running capacity we employed an approach combining examination of the myofilament protein composition and contractile properties of the fast fiber extensor digitorum longus (EDL) and slow fiber soleus (SOL) muscles from LCR and HCR rats. Intact muscle force experiments demonstrate that SOL, but not EDL, muscles from LCR rats exhibit a three times greater decrease in fatigued force. To investigate the mechanism of this increased fatigability in the LCR SOL muscle, we determined the myofilament protein composition and functional properties. Force-Ca2+ measurements demonstrate decreased Ca2+ sensitivity of single skinned SOL muscle fibers from LCR compared with that of HCR rats. Segregating SOL fibers into fast and slow types demonstrates that the decreased Ca2+ sensitivity in LCR SOL results from a specific decrease in slow-type SOL fiber Ca2+ sensitivity such that it was similar to that of fast-type fibers. These results identify that the altered myofilament contractile properties of LCR SOL slow-type fibers result in a fast muscle type Ca2+ sensitivity and the LCR muscle phenotype. Overall our findings demonstrate alterations of the myofilament proteins could contribute to fatigability of the SOL muscle and the decreased innate aerobic running performance of LCR compared with HCR rats.
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Affiliation(s)
- B J Biesiadecki
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio.,Department of Physiology and Cell Biology and Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
| | - M A Brotto
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio.,Bone-Muscle Research Center, University of Texas, Arlington, Texas
| | - L S Brotto
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio.,Bone-Muscle Research Center, University of Texas, Arlington, Texas
| | - L G Koch
- Department of Physiology and Pharmacology, The University of Toledo College of Medicine and Life Sciences, Toledo, Ohio
| | - S L Britton
- Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan.,Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - T M Nosek
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - J-P Jin
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio.,Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
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Robinson-Whelen S, Hughes RB, Taylor HB, Markley R, Vega JC, Nosek TM, Nosek MA. Promoting psychological health in women with SCI: Development of an online self-esteem intervention. Disabil Health J 2019; 13:100867. [PMID: 31757776 DOI: 10.1016/j.dhjo.2019.100867] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 10/01/2019] [Accepted: 10/22/2019] [Indexed: 01/06/2023]
Abstract
BACKGROUND There are no known interventions addressing self-esteem in women following spinal cord injury (SCI). OBJECTIVES To test the feasibility of an online self-esteem intervention for women with disabilities, as modified for women with SCI. METHOD We conducted a randomized, controlled feasibility test of a self-esteem intervention (N = 21). Participants were randomly assigned to the intervention or control group that received intervention materials at the end of the study. Intervention participants met as avatars for 7 weekly real-time group sessions in Second Life (SL), a free online virtual world. Feasibility indicators were study engagement, acceptability of SL and the intervention, and improvements on measures of psychological health promoting behaviors, social support, self-efficacy, self-esteem, and depression. RESULTS Intervention participants (n = 10) were highly engaged, and most described the SL program as more enjoyable and more convenient than in-person programs. All rated the intervention as "good" (n = 4) or "very good" (n = 6), and all 10 rated themselves has having made positive life changes as a result of the program. Intervention participants experienced significantly greater change than controls on two measures of health-promoting behavior (Health Promoting Lifestyle Profile-II Spiritual Growth/Self-actualization; Interpersonal Relations). Examining change in the intervention group using regression analyses, we found medium-to-large effects of the intervention on these behaviors and measures of depression (CESD-10, PHQ-9). The intervention had small effects on remaining measures. CONCLUSION We found preliminary support for the feasibility of this modified self-esteem intervention offered in SL. Such programming may help circumvent barriers to community-based psychological services and may improve psychological health.
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Affiliation(s)
- Susan Robinson-Whelen
- Spinal Cord Injury and Disability Research Center, TIRR Memorial Hermann, Houston, TX, USA; Center for Research on Women with Disabilities, H. Ben Taub Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Houston, TX, USA.
| | - Rosemary B Hughes
- The Rural Institute for Inclusive Communities, University of Montana, Missoula, MT, USA; Department of Psychology, University of Montana, Missoula, MT, USA
| | - Heather B Taylor
- Spinal Cord Injury and Disability Research Center, TIRR Memorial Hermann, Houston, TX, USA; McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), USA
| | - Rachel Markley
- Spinal Cord Injury and Disability Research Center, TIRR Memorial Hermann, Houston, TX, USA
| | - José C Vega
- Spinal Cord Injury and Disability Research Center, TIRR Memorial Hermann, Houston, TX, USA
| | - Thomas M Nosek
- Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, OH, USA
| | - Margaret A Nosek
- Center for Research on Women with Disabilities, H. Ben Taub Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Houston, TX, USA
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3
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Nosek MA, Robinson-Whelen S, Ledoux TA, Hughes RB, O'Connor DP, Lee RE, Goe R, Silveira SL, Markley R, Nosek TM. A pilot test of the GoWoman weight management intervention for women with mobility impairments in the online virtual world of Second Life ®. Disabil Rehabil 2018; 41:2718-2729. [PMID: 29889580 DOI: 10.1080/09638288.2018.1473511] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Objective: Pilot test GoWoman, a small-group weight management intervention for mobility impaired women that was a disability- and gender-responsive adaptation of the Diabetes Prevention Program delivered in the online virtual world of Second Life®. Objectives were to (1) examine pre-/post-intervention differences in weight, waist circumference, diet, physical activity, self-efficacy for diet and physical activity, nutrition knowledge and social support for weight management, (2) determine intervention feasibility (fidelity, attrition, engagement, acceptability). Design: Single-group modified interrupted time series quasi-experimental design whereby participants served as their own controls. Results: Thirteen women attended ≥8 of 16 GoWoman weekly sessions and lost an average of 5.97 pounds (2.71 kg) (3.31%) body weight (Cohen's d = 0.74) and 1.44 inches (3.66 cm) (3.58%) waist circumference (Cohen's d = 0.83). There were significant improvements in physical activity, diet and self-efficacy for diet and physical activity. All benchmarks for feasibility were met. Ratings of intervention content, group interactions and support and virtual world experiences were highly positive. Conclusion: Findings suggest that a disability- and gender-responsive weight management intervention with peer group support delivered in an online virtual world is feasible, meaningful and may assist with weight management for mobility impaired women. Implications for Rehabilitation This study addresses a gap in the general and rehabilitation research literature by addressing the disproportionately high rates of obesity among women with mobility impairments, who are generally excluded from tests of weight management interventions if they have limited ability to engage in vigorous physical activity. The GoWoman program is an adaptation of the Diabetes Prevention Program Lifestyle Change curriculum that is tailored to meet the unique weight management needs of women with mobility impairments, and was created to become a publicly available, disability- and gender-responsive intervention that can be used in community and rehabilitation settings. More rehabilitation and health promotion program should be offered in the free, online, virtual world of Second Life® since participants in this pilot study offered many favorable comments about the new learning and social opportunities available to them there and they did not have to deal with the disability-related environmental and health challenges that often prevent them from participating in face-to-face workshops. Preliminary indications of improvements in body weight, waist circumference, diet and physical activity after attending the GoWoman weight management intervention offered in Second Life® tell us that these strategies are feasible for helping women with mobility impairments manage their weight and should undergo further testing.
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Affiliation(s)
- Margaret A Nosek
- Department of Physical Medicine and Rehabilitation, Center for Research on Women with Disabilities, Baylor College of Medicine , Houston , TX , USA
| | - Susan Robinson-Whelen
- Department of Physical Medicine and Rehabilitation, Center for Research on Women with Disabilities, Baylor College of Medicine , Houston , TX , USA.,TIRR Memorial Hermann , Houston , TX , USA
| | - Tracey A Ledoux
- Department of Health and Human Performance, Texas Obesity Research Center, University of Houston , Houston , TX , USA
| | - Rosemary B Hughes
- Rural Institute for Inclusive Communities, University of Montana , Missoula , MT , USA
| | - Daniel P O'Connor
- Department of Health and Human Performance, Texas Obesity Research Center, University of Houston , Houston , TX , USA
| | - Rebecca E Lee
- Center for Health Promotion and Disease Prevention, College of Nursing and Health Innovation, Arizona State University , Phoenix , AZ , USA
| | - Rebecca Goe
- Rural Institute for Inclusive Communities, University of Montana , Missoula , MT , USA
| | - Stephanie L Silveira
- Department of Physical Medicine and Rehabilitation, Center for Research on Women with Disabilities, Baylor College of Medicine , Houston , TX , USA.,Department of Health and Human Performance, Texas Obesity Research Center, University of Houston , Houston , TX , USA
| | | | - Thomas M Nosek
- School of Medicine, Case Western Reserve University , Cleveland , OH , USA
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4
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Nosek MA, Robinson-Whelen S, Hughes RB, Nosek TM. An Internet-based virtual reality intervention for enhancing self-esteem in women with disabilities: Results of a feasibility study. Rehabil Psychol 2016; 61:358-370. [DOI: 10.1037/rep0000107] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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5
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Nosek MA, Robinson-Whelen S, Hughes RB, Ledoux T, Goe R, Silveira S, Lee RE, O'Connor D, Nosek TM. A Virtual-Reality Weight Loss Program for Women with Mobility Limitations: Results of a Pilot Study. Arch Phys Med Rehabil 2015. [DOI: 10.1016/j.apmr.2015.08.256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Haldar SM, Jeyaraj D, Anand P, Zhu H, Lu Y, Prosdocimo DA, Eapen B, Kawanami D, Okutsu M, Brotto L, Fujioka H, Kerner J, Rosca MG, McGuinness OP, Snow RJ, Russell AP, Gerber AN, Bai X, Yan Z, Nosek TM, Brotto M, Hoppel CL, Jain MK. Kruppel-like factor 15 regulates skeletal muscle lipid flux and exercise adaptation. Proc Natl Acad Sci U S A 2012; 109:6739-44. [PMID: 22493257 PMCID: PMC3340075 DOI: 10.1073/pnas.1121060109] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ability of skeletal muscle to enhance lipid utilization during exercise is a form of metabolic plasticity essential for survival. Conversely, metabolic inflexibility in muscle can cause organ dysfunction and disease. Although the transcription factor Kruppel-like factor 15 (KLF15) is an important regulator of glucose and amino acid metabolism, its endogenous role in lipid homeostasis and muscle physiology is unknown. Here we demonstrate that KLF15 is essential for skeletal muscle lipid utilization and physiologic performance. KLF15 directly regulates a broad transcriptional program spanning all major segments of the lipid-flux pathway in muscle. Consequently, Klf15-deficient mice have abnormal lipid and energy flux, excessive reliance on carbohydrate fuels, exaggerated muscle fatigue, and impaired endurance exercise capacity. Elucidation of this heretofore unrecognized role for KLF15 now implicates this factor as a central component of the transcriptional circuitry that coordinates physiologic flux of all three basic cellular nutrients: glucose, amino acids, and lipids.
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Affiliation(s)
- Saptarsi M Haldar
- Harrington Heart and Vascular Institute and Department of Medicine, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, OH 44106, USA.
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7
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Thornton AM, Zhao X, Weisleder N, Brotto LS, Bougoin S, Nosek TM, Reid M, Hardin B, Pan Z, Ma J, Parness J, Brotto M. Store-operated Ca(2+) entry (SOCE) contributes to normal skeletal muscle contractility in young but not in aged skeletal muscle. Aging (Albany NY) 2011; 3:621-34. [PMID: 21666285 PMCID: PMC3164370 DOI: 10.18632/aging.100335] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Muscle atrophy alone is insufficient to explain the significant decline in contractile force of skeletal muscle during normal aging. One contributing factor to decreased contractile force in aging skeletal muscle could be compromised excitation-contraction (E-C) coupling, without sufficient available Ca2+ to allow for repetitive muscle contractility, skeletal muscles naturally become weaker. Using biophysical approaches, we previously showed that store-operated Ca2+ entry (SOCE) is compromised in aged skeletal muscle but not in young ones. While important, a missing component from previous studies is whether or not SOCE function correlates with contractile function during aging. Here we test the contribution of extracellular Ca2+ to contractile function of skeletal muscle during aging. First, we demonstrate graded coupling between SR Ca2+ release channel-mediated Ca2+ release and activation of SOCE. Inhibition of SOCE produced significant reduction of contractile force in young skeletal muscle, particularly at high frequency stimulation, and such effects were completely absent in aged skeletal muscle. Our data indicate that SOCE contributes to the normal physiological contractile response of young healthy skeletal muscle and that defective extracellular Ca2+ entry through SOCE contributes to the reduced contractile force characteristic of aged skeletal muscle.
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Affiliation(s)
- Angela M Thornton
- Department of Physiology and Biophysics, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
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8
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Brotto MAP, Sherman JA, Nosek TM, Qu CK, Valdivia HH. Effects of PI(3,5)P2 on the Skeletal Muscle Ryanodine Receptor. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.780.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Marco A. P. Brotto
- Schools of Nursing & MedicineUniversity of Missouri‐Kansas CityKansas CityMO
| | | | | | - Cheng Kui Qu
- MedicineCase Western Reserve UniversityClevelandOH
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9
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Nosek TM, Brotto L, Qu C, Brotto M. Loss of muscle‐specific inositol phosphatase (MIP) and increased phosphatidylinositol 3,5‐bisphosphate (PI(3,5)P2) inhibit muscle contractility and produce a Brody's disease phenotype. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.780.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | - Marco Brotto
- University of Missouri at Kansas CityKansas CityMO
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10
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Qu C, Shen J, Yu W, Guo C, Stoddard C, Brotto M, Nosek TM. Discovery and functional characterization of the novel muscle‐specific inositol phosphatase MIP (MTMR14). FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.780.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Wen‐Mei Yu
- Case Western Reserve UniversityClevelandOH
| | - Caiying Guo
- University of Connecticut Health CenterFarmingtonCT
| | | | - Marco Brotto
- University of Missouri at Kansas CityKansas CityMO
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11
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Nosek TM, Cohen M, Matthews A, Papp K, Wolf N, Wrenn G, Sher A, Coulter K, Martin J, Wiesner GL. Pilot test of a serious gaming/immersion environment to teach clinical cancer genetics. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Thomas M. Nosek
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
| | - Mark Cohen
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
- University Hospitals/Case Medical Center10900 Euclid AvenueClevelandOH44106
| | - Anne Matthews
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
| | - Klara Papp
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
| | - Nancy Wolf
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
- University Hospitals/Case Medical Center10900 Euclid AvenueClevelandOH44106
| | - Gregg Wrenn
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
| | - Andrew Sher
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
| | - Kenneth Coulter
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
| | - Jessica Martin
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
| | - Georgia L. Wiesner
- Case Western Reserve University School of Medicine10900 Euclid AvenueClevelandOH44106
- University Hospitals/Case Medical Center10900 Euclid AvenueClevelandOH44106
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12
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Abstract
The conserved central and COOH-terminal regions of troponin T (TnT) interact with troponin C, troponin I, and tropomyosin to regulate striated muscle contraction. Phylogenic data show that the NH2-terminal region has evolved as an addition to the conserved core structure of TnT. This NH2-terminal region does not bind other thin filament proteins, and its sequence is hypervariable between fiber type and developmental isoforms. Previous studies have demonstrated that NH2-terminal modifications alter the COOH-terminal conformation of TnT and thin filament Ca2+-activation, yet the functional core structure of TnT and the mechanism of NH2-terminal modulation are not well understood. To define the TnT core structure and investigate the regulatory role of the NH2-terminal variable region, we investigated two classes of model TnT molecules: (1) NH2-terminal truncated cardiac TnT and (2) chimera proteins consisting of an acidic or basic skeletal muscle TnT NH2-terminus spliced to the cardiac TnT core. Deletion of the TnT hypervariable NH2-terminus preserved binding to troponin I and tropomyosin and sustained cardiac muscle contraction in the heart of transgenic mice. Further deletion of the conserved central region diminished binding to tropomyosin. The reintroduction of differently charged NH2-terminal domains in the chimeric molecules produced long-range conformational changes in the central and COOH-terminal regions to alter troponin I and tropomyosin binding. Similar NH2-terminal charge effects are demonstrated in naturally occurring cardiac TnT isoforms, indicating a physiological significance. These results suggest that the hypervariable NH2-terminal region modulates the conformation and function of the TnT core structure to fine-tune muscle contractility.
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Affiliation(s)
- Brandon J. Biesiadecki
- From the Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106; and
| | - Stephen M. Chong
- Section of Molecular Cardiology, Evanston Northwestern Healthcare and Northwestern University Fienberg School of Medicine, Evanston, Illinois 60201
| | - Thomas M. Nosek
- From the Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106; and
| | - J.-P. Jin
- From the Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106; and
- Section of Molecular Cardiology, Evanston Northwestern Healthcare and Northwestern University Fienberg School of Medicine, Evanston, Illinois 60201
- *To whom correspondence should be addressed: Tel.: 847-570-1960; Fax: 847-570-1865; e-mail:
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13
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Nosek TM, Cohen M, Matthews A, Papp K, Wolf N, Wrenn G, Sher A, Coulter K, Martin J, Wiesner GL. A serious gaming/immersion environment to teach clinical cancer genetics. Stud Health Technol Inform 2007; 125:355-60. [PMID: 17377303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We are creating an interactive, simulated "Cancer Genetics Tower" for the self-paced learning of Clinical Cancer Genetics by medical students (go to: http://casemed.case.edu/cancergenetics). The environment uses gaming theory to engage the students into achieving specific learning objectives. The first few levels contain virtual laboratories where students achieve the basic underpinnings of Cancer Genetics. The next levels apply these principles to clinical practice. A virtual attending physician and four virtual patients, available for questioning through virtual video conferencing, enrich each floor. The pinnacle clinical simulation challenges the learner to integrate all information and demonstrate mastery, thus "winning" the game. A pilot test of the program by 17 medical students yielded very favorable feedback; the students found the Tower a "great way to teach", it held their attention, and it made learning fun. A majority of the students preferred the Tower over other resources to learn Cancer Genetics.
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Affiliation(s)
- Thomas M Nosek
- Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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14
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Nosek TM, Cohen M, Matthews A, Papp K, Wolf N, Wrenn G, Wiesner GL. Next Generation Computer Assisted Instruction: A Serious Gaming/Immersion Environment for Medical Education. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a13-d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | | | | | - Gregg Wrenn
- Case Western Reserve University10900 Euclid AvenueClevelandOhio44106‐4963
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15
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Nosek TM, Medvedev I, Wang W, Baptista CA. Long Distance Collaborative Use of the Case Western Reserve School of Medicine eAssessment System by the Medical University of Ohio at Toledo. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a13-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Irene Medvedev
- Academic ComputingCase Western Reserve University10900 Euclid AvenueClevelandOhio44106‐4963
| | - Wei Wang
- Academic ComputingCase Western Reserve University10900 Euclid AvenueClevelandOhio44106‐4963
| | - Carlos A.C. Baptista
- NeurosciencesMedical University of Ohio at Toledo3035 Arlington AvenueToledoOhio43614‐5804
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16
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Pelaez NJ, Kay I, Nosek TM. Instructional technology (IT) impacts physiology teaching and learning. FASEB J 2006. [DOI: 10.1096/fasebj.20.5.a864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Nancy J Pelaez
- Biological ScienceCalifornia State University Fullerton800 N State College BlvdFullertonCA92834‐6850
| | - Ian Kay
- Biological SciencesManchester Metropolitan UniversityJohn Dalton Building, Chester StreetManchesterMI 5GDUnited Kingdom
| | - Thomas M Nosek
- Physiology and BiophysicsCase Western Reserve University10900 EuclidClevelandOH44106‐7001
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17
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Brotto MA, Biesiadecki BJ, Brotto LS, Nosek TM, Jin JP. Coupled expression of troponin T and troponin I isoforms in single skeletal muscle fibers correlates with contractility. Am J Physiol Cell Physiol 2005; 290:C567-76. [PMID: 16192301 PMCID: PMC1409758 DOI: 10.1152/ajpcell.00422.2005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Striated muscle contraction is powered by actin-activated myosin ATPase. This process is regulated by Ca(2+) via the troponin complex. Slow- and fast-twitch fibers of vertebrate skeletal muscle express type I and type II myosin, respectively, and these myosin isoenzymes confer different ATPase activities, contractile velocities, and force. Skeletal muscle troponin has also diverged into fast and slow isoforms, but their functional significance is not fully understood. To investigate the expression of troponin isoforms in mammalian skeletal muscle and their functional relationship to that of the myosin isoforms, we concomitantly studied myosin, troponin T (TnT), and troponin I (TnI) isoform contents and isometric contractile properties in single fibers of rat skeletal muscle. We characterized a large number of Triton X-100-skinned single fibers from soleus, diaphragm, gastrocnemius, and extensor digitorum longus muscles and selected fibers with combinations of a single myosin isoform and a single class (slow or fast) of the TnT and TnI isoforms to investigate their role in determining contractility. Types IIa, IIx, and IIb myosin fibers produced higher isometric force than that of type I fibers. Despite the polyploidy of adult skeletal muscle fibers, the expression of fast or slow isoforms of TnT and TnI is tightly coupled. Fibers containing slow troponin had higher Ca(2+) sensitivity than that of the fast troponin fibers, whereas fibers containing fast troponin showed a higher cooperativity of Ca(2+) activation than that of the slow troponin fibers. These results demonstrate distinct but coordinated regulation of troponin and myosin isoform expression in skeletal muscle and their contribution to the contractile properties of muscle.
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Affiliation(s)
- Marco A Brotto
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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18
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Zhao X, Yoshida M, Brotto L, Takeshima H, Weisleder N, Hirata Y, Nosek TM, Ma J, Brotto M. Enhanced resistance to fatigue and altered calcium handling properties of sarcalumenin knockout mice. Physiol Genomics 2005; 23:72-8. [PMID: 15998745 DOI: 10.1152/physiolgenomics.00020.2005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sarcalumenin is a Ca2+-binding protein located in the sarcoplasmic reticulum of striated muscle cells, the physiological function of which has not been fully determined yet. Using sarcalumenin knockout ( sar−/−) mice, we showed that sar ablation altered store-operated Ca2+entry (SOCE) and enhanced muscle fatigue resistance. Sar−/−mice fatigued less with treadmill exercise, and intact isolated soleus and extensor digitorum longus muscles from sar−/−mice were more resistant to intermittent fatiguing stimulation than those from wild-type mice. Enhanced SOCE was observed in the sar−/−muscles. Biochemical analysis revealed that sar−/−muscles contained significantly elevated expression of mitsugumin 29 (MG29), a synaptophysin-related membrane protein located in the triad junction of skeletal muscle. Because the ablation of mg29 has been shown to cause increased fatigability and dysfunction of SOCE, the enhanced SOCE activity seen in sar−/−muscle may be correlated with the increased expression of MG29. Our data suggest that systemic ablation of sarcalumenin caused enhanced resistance to muscle fatigue by compensatory changes in Ca2+regulatory proteins that effect SOCE.
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Affiliation(s)
- Xiaoli Zhao
- Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
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19
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Abstract
Although it is well established that patients suffering from malaria experience skeletal muscle problems (contracture, aches, fatigue, weakness), detailed studies have not been performed to investigate changes in the contractile function and biochemical properties of intact and skinned skeletal muscles of mammals infected with malaria. To this end, we investigated such features in the extensor digitorium longus (EDL, fast-twitch, glyocolytic) and in the soleus (SOL, slow-twitch, oxidative) muscles from mice infected with Plasmodium berghei. We first studied maximal tetanic force (T(max)) produced by intact control and malaria-infected muscles before, during and after fatigue. Triton-skinned muscle fibres were isolated from these muscles and used to determine isometric contractile features as well as a basic biochemical profile as analysed by silver-enhanced SDS-PAGE. We found that the T(max) of intact muscles and the maximal Ca2+-activated force (F(max)) of Triton-skinned muscle fibres were reduced by approximately 50% in malarial muscles. In addition, the contractile proteins of Triton-skinned muscle fibres from malarial muscles were significantly less sensitive to Ca2+. Biochemical analysis revealed that there was a significant loss of essential contractile proteins (e.g. troponins and myosin) in Triton-skinned muscle fibres from malarial muscles as compared to controls. The biochemical alterations (i.e., reduction of essential contractile proteins) seem to explain well the functional modifications resolved in both intact muscles and Triton-skinned muscle fibres and may provide a suitable paradigm for the aetiology of muscle symptoms associated with malaria.
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Affiliation(s)
- Marco A P Brotto
- Department of Physiology and Biophysics, University of Medicine & Dentistry of New Jersey-Robert Wood Johnson School of Medicine, Piscataway, NJ 08854, USA.
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20
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Brotto MAP, Nagaraj RY, Brotto LS, Takeshima H, Ma JJ, Nosek TM. Defective maintenance of intracellular Ca2+ homeostasis is linked to increased muscle fatigability in the MG29 null mice. Cell Res 2005; 14:373-8. [PMID: 15538969 DOI: 10.1038/sj.cr.7290237] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mitsugumin 29 (MG29) is a transmembrane protein that is normally found in the triad junction of skeletal muscle. Our previous studies have shown that targeted deletion of mg29 from the skeletal muscle resulted in abnormality of the triad junction structure, and also increased susceptibility to muscle fatigue. To elucidate the basis of these effects, we investigated the properties of Ca2+-uptake and -release in toxin-skinned Extensor Digitorium Longus (EDL) muscle fibers from control and mg29 knockout mice. Compared with the control muscle, submaximal Ca2+-uptake into the sarcoplasmic reticulum (SR) was slower and the storage of Ca2+ inside the SR was less in the mutant muscle, due to increased leakage process of Ca2+ movement across the SR. The leakage pathway is associated with the increased sensitivity of Ca2+/caffeine -induced Ca2+ release to myoplasmic Ca2+. Therefore, the increased fatigability of mutant EDL muscles can result from a combination of a slowing of Ca2+ uptake, modification of Ca2+-induced Ca2+ release (CICR), and a reduction in total SR Ca2+ content.
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Affiliation(s)
- Marco A P Brotto
- Department of Physiology and Biophysics, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
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21
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Nosek TM, Brotto MA, Jin JP. Troponin T isoforms alter the tolerance of transgenic mouse cardiac muscle to acidosis. Arch Biochem Biophys 2004; 430:178-84. [PMID: 15369816 DOI: 10.1016/j.abb.2004.07.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2004] [Revised: 07/14/2004] [Indexed: 11/20/2022]
Abstract
Troponin T (TnT) is an essential protein in the Ca2+ regulatory system of striated of muscle. Three fiber type-specific TnT genes have evolved in higher vertebrates to encode cardiac, slow and fast skeletal muscle TnT isoforms. To understand the functional significance of TnT isoforms, we studied the effects of acidosis on the contractility of transgenic mouse cardiac muscle that expresses fast skeletal muscle TnT. Contractility analysis of intact cardiac muscle strips showed that while no differences were detected at physiological pH, the transgenic cardiac muscle had significantly greater decreases in +dF/dtmax at acidic pH than that of the wild-type control. Contractility of skinned cardiac muscles demonstrated that the presence of fast TnT resulted in significantly larger decreases in force and Ca2+ sensitivity at acidic pH than that of the wild-type control. The effect of TnT isoforms on the tolerance of muscle to acidosis may explain the higher tolerance of embryonic versus adult cardiac muscles. The results are consistent with the hypothesis that charge differences in TnT isoforms contribute to the contractility of muscle. The data further support a hypothesis that slow TnT is similar to the cardiac, but not fast, and TnT may contribute to the higher tolerance of slow muscles to stress conditions. Therefore, TnT isoform diversity may contribute to the compatibility of muscle thin filaments to cellular environments in different fiber types, during development and functional adaptation.
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Affiliation(s)
- Thomas M Nosek
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4970, USA
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22
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Kingsberg SA, Malemud CJ, Novak T, Cole-Kelly K, Wile MZ, Spanos P, Nosek TM. A comprehensive approach to enhancing sexual health education in the Case Western Reserve University School of Medicine. Int J Impot Res 2003; 15 Suppl 5:S51-7. [PMID: 14551578 DOI: 10.1038/sj.ijir.3901073] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We report on the Sexual Health Curriculum Enhancement project at Case Western Reserve University School of Medicine. Using a US dollars 100000 grant from Pfizer Pharmaceuticals, Inc., we have developed and are in the process of implementing a comprehensive, cross-disciplinary and innovative curriculum that is based on three primary objectives for teaching sexual health: attitude change, behavior change, and knowledge acquisition. Five general strategies to incorporate specific sexual health content into the medical school curriculum have been implemented: (1). Faculty Development; (2). Additional Didactics; (3). Cased-Based Learning; (4). Testing and Assessment; and (5). Electronic (Computer/Web-Based Enhancements).
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Affiliation(s)
- S A Kingsberg
- Department of Obstetrics/Gynecology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
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23
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Jin JP, Brotto MA, Hossain MM, Huang QQ, Brotto LS, Nosek TM, Morton DH, Crawford TO. Truncation by Glu180 nonsense mutation results in complete loss of slow skeletal muscle troponin T in a lethal nemaline myopathy. J Biol Chem 2003; 278:26159-65. [PMID: 12732643 DOI: 10.1074/jbc.m303469200] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A lethal form of nemaline myopathy, named "Amish Nemaline Myopathy" (ANM), is linked to a nonsense mutation at codon Glu180 in the slow skeletal muscle troponin T (TnT) gene. We found that neither the intact nor the truncated slow TnT protein was present in the muscle of patients with ANM. The complete loss of slow TnT is consistent with the observed recessive pattern of inheritance of the disease and indicates a critical role of the COOH-terminal T2 domain in the integration of TnT into myofibrils. Expression of slow and fast isoforms of TnT is fiber-type specific. The lack of slow TnT results in selective atrophy of type 1 fibers. Slow TnT confers a higher Ca2+ sensitivity than does fast TnT in single fiber contractility assays. Despite the lack of slow TnT, individuals with ANM have normal muscle power at birth. The postnatal onset and infantile progression of ANM correspond to a down-regulation of cardiac and embryonic splice variants of fast TnT in normal developing human skeletal muscle, suggesting that the fetal TnT isoforms complement slow TnT. These results lay the foundation for understanding the molecular pathophysiology and the potential targeted therapy of ANM.
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MESH Headings
- Adult
- Age Factors
- Animals
- Biopsy
- Blotting, Western
- Calcium/metabolism
- Codon
- Codon, Nonsense
- Electrophoresis, Polyacrylamide Gel
- Escherichia coli/metabolism
- Heart/embryology
- Humans
- Immunohistochemistry
- Infant
- Infant, Newborn
- Models, Biological
- Models, Genetic
- Muscle Fibers, Slow-Twitch/metabolism
- Muscle, Skeletal/metabolism
- Myocardium/metabolism
- Myopathies, Nemaline/genetics
- Myopathies, Nemaline/metabolism
- Phenotype
- Phylogeny
- Protein Isoforms
- Protein Structure, Tertiary
- Silver Staining
- Troponin T/chemistry
- Troponin T/genetics
- Troponin T/physiology
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Affiliation(s)
- Jian-Ping Jin
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
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24
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Abstract
We investigated the influence of ageing on the fatiguing characteristics of the mouse extensor digitorum longus (EDL) muscle as compared to those of the soleus muscle. Fatigue was produced by an intermittent stimulation protocol. We report for mature and aged animals the effects of fatigue on force produced during stimulation patterns that in non-fatigued muscle gave maximum force (T(max), high frequency stimulation) and approximately half-maximum force (1/2T(max), low frequency stimulation). In 15-month-old (mature) mice, fatiguing stimulation decreased T(max) in EDL and soleus muscle to 10.3 +/- 1.0 % and 33.4 +/- 3.0 % of control, respectively. In 30-month-old (aged) mice, the decrease in T(max) in EDL and soleus was statistically equal to that of the younger animals. Fatiguing stimulation decreased 1/2T(max) in EDL and soleus from 15-month-old animals to 22.5 +/- 2.9 % and 45.7 +/- 0.3 % of control, respectively. In 30-month-old animals, the 1/2T(max) in EDL and soleus muscle decreased to 18.2 +/- 1.3 % and 35.0 +/- 3.6 % of control, respectively. Under all conditions, the soleus fatigued significantly less. Contractile recovery from fatiguing stimulation was complete for the soleus in both age groups after 30 min, but incomplete for the EDL. The 1/2T(max)/T(max) ratio significantly increased in EDL and soleus muscle from 15-month-old animals after fatiguing stimulation. This increase was less significant in EDL, and absent in soleus muscle, from 30-month-old animals. These results indicate that fatiguing stimulation induces a leftward shift in the force-frequency relationship in the young animals; this shift is either significantly less (EDL) or absent (soleus) in the older animals. We speculate that the leftward shift of the force-frequency relationship may reflect a protective mechanism in younger animals against some of the damaging effects of fatiguing stimulation (i.e. oxidative stress).
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Affiliation(s)
- Marco A de Paula Brotto
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4963, USA
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25
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de Paula Brotto M, van Leyen SA, Brotto LS, Jin JP, Nosek CM, Nosek TM. Hypoxia/fatigue-induced degradation of troponin I and troponin C: new insights into physiologic muscle fatigue. Pflugers Arch 2001; 442:738-44. [PMID: 11512030 DOI: 10.1007/s004240100587] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2001] [Accepted: 03/22/2001] [Indexed: 10/27/2022]
Abstract
Conditions such as respiratory failure and cardiopulmonary arrest can expose the diaphragm to hypoxemia. In skeletal muscles, fatiguing stimulation renders muscles hypoxic, which has long been known to dramatically reduce muscle function. We have previously demonstrated that fatiguing stimulation under hypoxic conditions disrupts both the excitation-contraction coupling (ECC) process and the isometric contractile properties (ICP) in intact diaphragm muscle strips and the contractile properties of skinned fibers isolated from these muscles. Here we have analyzed the effects of intermittent fatiguing stimulation on specific muscle proteins in muscle strips from mouse diaphragms that have been exposed to hypoxia. We report for the first time that the effects of hypoxia-fatigue, namely to decrease maximal tetanic force, maximal calcium-activated force and calcium sensitivity of the mouse diaphragm muscle, are associated with the degradation of troponins TnI and TnC (Western blot analysis). The concentrations of TnT and actin did not change under these same conditions. Because troponins are integrally involved in regulating the interaction between actin and myosin during the cross-bridge cycle, the degradation of TnI and TnC may explain the effects of hypoxia-fatigue on the ICP. This interpretation is supported by the observations that extraction of troponins from control skinned fibers mimics the effects of hypoxia-fatigue on contractile function and that incorporation of native troponins into fibers isolated from hypoxic-fatigued muscles partially restores function.
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Affiliation(s)
- M de Paula Brotto
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
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26
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Callahan LA, She ZW, Nosek TM. Superoxide, hydroxyl radical, and hydrogen peroxide effects on single-diaphragm fiber contractile apparatus. J Appl Physiol (1985) 2001; 90:45-54. [PMID: 11133892 DOI: 10.1152/jappl.2001.90.1.45] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Reactive oxygen species contribute to diaphragm dysfunction in certain pathophysiological conditions (i.e., sepsis and fatigue). However, the precise alterations induced by reactive oxygen species or the specific species that are responsible for the derangements in skeletal muscle function are incompletely understood. In this study, we evaluated the effect of the superoxide anion radical (O(2)(-).), hydroxyl radical (.OH), and hydrogen peroxide (H(2)O(2)) on maximum calcium-activated force (F(max)) and calcium sensitivity of the contractile apparatus in chemically skinned (Triton X-100) single rat diaphragm fibers. O(2)(-). was generated using the xanthine/xanthine oxidase system;.OH was generated using 1 mM FeCl(2), 1 mM ascorbate, and 1 mM H(2)O(2); and H(2)O(2) was added directly to the bathing medium. Exposure to O(2)(-). or.OH significantly decreased F(max) by 14.5% (P < 0.05) and 43.9% (P < 0. 005), respectively.OH had no effect on Ca(2+) sensitivity. Neither 10 nor 1,000 microM H(2)O(2) significantly altered F(max) or Ca(2+) sensitivity. We conclude that the diaphragm is susceptible to alterations induced by a direct effect of.OH and O(2)(-)., but not H(2)O(2), on the contractile proteins, which could, in part, be responsible for prolonged depression in contractility associated with respiratory muscle dysfunction in certain pathophysiological conditions.
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Affiliation(s)
- L A Callahan
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109, USA.
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27
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Nosek TM, Brotto MA, Essig DA, Mestril R, Conover RC, Dillmann WH, Kolbeck RC. Functional properties of skeletal muscle from transgenic animals with upregulated heat shock protein 70. Physiol Genomics 2000; 4:25-33. [PMID: 11074010 DOI: 10.1152/physiolgenomics.2000.4.1.25] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The influence of inducible heat stress proteins on protecting contracting skeletal muscle against fatigue-induced injury was investigated. A line of transgenic mice overexpressing the inducible form of the 72-kDa heat shock protein (HSP72) in skeletal muscles was used. We examined the relationship between muscle contractility and levels of the constitutive (HSC73) and inducible (HSP72) forms of the 72-kDa heat shock protein in intact, mouse extensor digitorum longus (EDL), soleus (SOL), and the diaphragm (DPH). In all transgenic muscles, HSP72 was expressed at higher levels compared with transgene-negative controls, where HSP72 was below the level of detection. At the same time, HSC73 levels were downregulated in all transgenic muscle types. Shipment-related stress caused an elevation in the levels of HSP72 in all muscles for 1 wk after arrival of the animals. We also found that, although no statistical differences in response to intermittent fatiguing stimulation in the contractile properties of intact transgene-positive muscles compared with their transgene-negative counterparts were observed, the response of intact transgene-positive EDL muscles to caffeine was enhanced. These findings demonstrate that elevated HSP72 does not protect EDL, SOL, or DPH muscles from the effects of intermittent fatiguing stimulation. However, HSP72 may influence the excitation-contraction coupling (ECC) process, either directly or indirectly, in EDL muscle. If the effects on ECC were indirect, then these results would suggest that manipulation of a specific gene might cause functional effects that seem independent of the manipulated gene/protein.
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Affiliation(s)
- T M Nosek
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4963, USA
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28
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Nagaraj RY, Nosek CM, Brotto MA, Nishi M, Takeshima H, Nosek TM, Ma J. Increased susceptibility to fatigue of slow- and fast-twitch muscles from mice lacking the MG29 gene. Physiol Genomics 2000; 4:43-9. [PMID: 11074012 DOI: 10.1152/physiolgenomics.2000.4.1.43] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mitsugumin 29 (MG29), a major protein component of the triad junction in skeletal muscle, has been identified to play roles in the formation of precise junctional membrane structures important for efficient signal conversion in excitation-contraction (E-C) coupling. We carried out several experiments to not only study the role of MG29 in normal muscle contraction but also to determine its role in muscle fatigue. We compared the in vitro contractile properties of three muscles types, extensor digitorum longus (EDL) (fast-twitch muscle), soleus (SOL) (slow-twitch muscle), and diaphragm (DPH) (mixed-fiber muscle), isolated from mice lacking the MG29 gene and wild-type mice prior to and after fatigue. Our results indicate that the mutant EDL and SOL muscles, but not DPH, are more susceptible to fatigue than the wild-type muscles. The mutant muscles not only fatigued to a greater extent but also recovered significantly less than the wild-type muscles. Following fatigue, the mutant EDL and SOL muscles produced lower twitch forces than the wild-type muscles; in addition, fatiguing produced a downward shift in the force-frequency relationship in the mutant mice compared with the wild-type controls. Our results indicate that fatiguing affects the E-C components of the mutant EDL and SOL muscles, and the effect of fatigue in these mutant muscles could be primarily due to an alteration in the intracellular Ca homeostasis.
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Affiliation(s)
- R Y Nagaraj
- Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106-4963, USA
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29
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Brotto MA, Andreatta-van Leyen S, Nosek CM, Brotto LS, Nosek TM. Hypoxia and fatigue-induced modification of function and proteins in intact and skinned murine diaphragm muscle. Pflugers Arch 2000; 440:727-34. [PMID: 11007314 DOI: 10.1007/s004240000327] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fatigue studies of isolated, intact muscles typically utilize solutions saturated with O2. However, under in vivo fatiguing conditions, less oxygen is delivered to the muscles and they actually experience hypoxia. No studies to date have correlated the effects of acute hypoxia on the isometric contractile properties of intact muscles, skinned fibers isolated from the same muscles, and the cellular content of specific muscle proteins. Therefore, we have studied the effects of in vitro acute hypoxia on the fatigability of intact diaphragm muscle strips and on the isometric contractile properties of single Triton-skinned fibers isolated from control and hypoxic diaphragm muscles. We found that hypoxia and fatiguing stimulation per se affect the tetanic force of intact muscle strips without exhibiting any significant deleterious effects on the calcium-activated force of skinned muscle fibers dissected from the intact muscles. In contrast, fatiguing stimulation under hypoxic conditions decreased both the tetanic force of muscle strips and the calcium-activated force of skinned muscle fibers. Gel electrophoresis of muscles subjected to hypoxia and hypoxic-fatigue revealed that there is a significant reduction in three protein bands when compared to control muscles. Protein modification may be the underlying mechanism of muscle fatigue under physiologic conditions.
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Affiliation(s)
- M A Brotto
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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30
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Supinski G, Nethery D, Nosek TM, Callahan LA, Stofan D, DiMarco A. Endotoxin administration alters the force vs. pCa relationship of skeletal muscle fibers. Am J Physiol Regul Integr Comp Physiol 2000; 278:R891-6. [PMID: 10749776 DOI: 10.1152/ajpregu.2000.278.4.r891] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent work indicates that endotoxemia elicits severe reductions in skeletal muscle force-generating capacity. The subcellular alterations responsible for these decrements have not, however, been fully characterized. One possibility is that the contractile proteins per se are altered in endotoxemia and another is that the mechanism by which these proteins are activated is affected. The purpose of the present study was to assess the effects of endotoxin administration on the contractile proteins by examining the maximum calcium-activated force (F(max)) and calcium sensitivity of single Triton-skinned fibers of diaphragm, soleus, and extensor digitorum longus (EDL) muscles taken from control and endotoxin-treated (8 mg/kg) rats. Fibers were mounted on a force transducer and sequentially activated by serial immersion in solutions of increasing Ca(2+) concentration (i.e., pCa 6.0 to pCa 5.0); force vs. pCa data were fit to the Hill equation. All fibers were typed at the conclusion of studies using gel electrophoresis. F(max), the calcium concentration required for half-maximal activation (Ca(50)), and the Hill coefficient were compared as a function of muscle and fiber type for the control and endotoxin-treated animals. Control group F(max) was similar for diaphragm, soleus, and EDL fibers, i.e., 112.34 +/- 2.64, 111.55 +/- 3.66, and 104.05 +/- 4.33 kPa, respectively. Endotoxin administration reduced the average F(max) for fibers from all three muscles to 80.25 +/- 2.30, 72.47 +/- 2.97, and 78.32 +/- 2.43 kPa, respectively (P < 0.001 for comparison of each to control). All fiber types in diaphragm, soleus, and EDL muscles manifested similar endotoxin-related reductions in F(max). The Ca(50) and the Hill coefficient for all fiber types and all muscles were unaffected by endotoxin administration. We speculate that these alterations in the intrinsic properties of the contractile proteins represent a major mechanism by which endotoxemia reduces muscle force-generating capacity.
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Affiliation(s)
- G Supinski
- Pulmonary Division, Department of Medicine, Case Western Reserve University and Metrohealth Medical Center, Cleveland, Ohio 44109, USA
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31
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Matar W, Nosek TM, Wong D, Renaud J. Pinacidil suppresses contractility and preserves energy but glibenclamide has no effect during muscle fatigue. Am J Physiol Cell Physiol 2000; 278:C404-16. [PMID: 10666037 DOI: 10.1152/ajpcell.2000.278.2.c404] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of 10 microM glibenclamide, an ATP-sensitive K(+) (K(ATP)) channel blocker, and 100 microM pinacidil, a channel opener, were studied to determine how the K(ATP) channel affects mouse extensor digitorum longus (EDL) and soleus muscle during fatigue. Fatigue was elicited with 200-ms-long tetanic contractions every second. Glibenclamide did not affect rate and extent of fatigue, force recovery, or (86)Rb(+) fractional loss. The only effects of glibenclamide during fatigue were: an increase in resting tension (EDL and soleus), a depolarization of the cell membrane, a prolongation of the repolarization phase of action potential, and a greater ATP depletion in soleus. Pinacidil, on the other hand, increased the rate but not the extent of fatigue, abolished the normal increase in resting tension during fatigue, enhanced force recovery, and increased (86)Rb(+) fractional loss in both the EDL and soleus. During fatigue, the decreases in ATP and phosphocreatine of soleus muscle were less in the presence of pinacidil. The glibenclamide effects suggest that fatigue, elicited with intermittent contractions, activates few K(ATP) channels that affect resting tension and membrane potentials but not tetanic force, whereas opening the channel with pinacidil causes a faster decrease in tetanic force, improves force recovery, and helps in preserving energy.
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Affiliation(s)
- W Matar
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
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32
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Shi B, Bhat G, Mahesh VB, Brotto M, Nosek TM, Brann DW. Bradykinin receptor localization and cell signaling pathways used by bradykinin in the regulation of gonadotropin-releasing hormone secretion. Endocrinology 1999; 140:4669-76. [PMID: 10499524 DOI: 10.1210/endo.140.10.7069] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In a previous publication we provided evidence of a novel neuronal pathway for the control of GnRH secretion by bradykinin. The action of bradykinin appeared to be exerted through the bradykinin B2 receptor. In this study we demonstrated that the bradykinin B2 receptor is densely localized in the arcuate nucleus, median eminence, organum vasculosum of the lamina terminalis, and preoptic area, regions known to be critical for the control of GnRH secretion. To determine the mechanism of action of bradykinin in stimulating GnRH release, we used immortalized GnRH (GT1-7) cells in vitro. Bradykinin stimulation of GnRH secretion from GT1-7 cells appears to involve activation of the phospholipase C signaling pathway and mobilization of extracellular and intracellular calcium stores. Evidence to support this contention was derived from the observations that incubation of the phospholipase C inhibitor, U-73122 with bradykinin, blocked the ability of bradykinin to stimulate release from GT1-7 cells. This effect was specific, as a nitric oxide synthase inhibitor and a cyclooxygenase inhibitor were found to have no effect on bradykinin-induced GnRH secretion, suggesting that nitric oxide and PGs do not mediate bradykinin effects. Pertussis toxin also had no effect on bradykinin action. This suggests that the bradykinin B2 receptor may be coupled to a pertussis toxin-insensitive G protein in GT1-7 cells. With respect to calcium involvement in bradykinin action, fura-2 calcium indicator studies revealed that bradykinin can rapidly increase intracellular Ca2+ levels in GT1-7 cells. A role for intracellular Ca2+ in bradykinin action was further suggested by the finding that an intracellular calcium chelator, 1,2-bis(O-aminophenoxy)]ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester, significantly attenuated the effects of bradykinin on GnRH release. The elevation of intracellular calcium by bradykinin appears to be due to mobilization of calcium from the endoplasmic reticulum, as incubation of the Ca2+-adenosine triphosphatase inhibitor thapsigarin, which depletes endoplasmic reticulum Ca2+ stores, significantly attenuated bradykinin action on GnRH release. Extracellular calcium may also be involved in bradykinin action, as the L-type Ca2+ channel blockers verapamil and nifedipine had no effect on bradykinin-induced GnRH release, whereas the nonselective Ca2+ channel blocker, nickel chloride, attenuated bradykinin-induced GnRH release. Taken as a whole, these studies demonstrate that the bradykinin B2 receptor is densely localized in key hypothalamic nuclei responsible for regulation of GnRH release, and that the mechanism of bradykinin stimulation of GnRH secretion involves activation of the phospholipase C signaling pathway, with a critical role implicated for calcium in bradykinin action in GT1-7 cells.
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Affiliation(s)
- B Shi
- Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912, USA
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Hatcher CJ, Godt RE, Nosek TM. Excessive microtubules are not responsible for depressed force per cross-bridge in cardiac neural-crest-ablated embryonic chick hearts. Pflugers Arch 1999; 438:307-13. [PMID: 10398860 DOI: 10.1007/s004240050914] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ablation of the cardiac neural crest (CNCA) in embryonic chicks results in a high incidence of persistent truncus arteriosus, a congenital heart defect associated with decreased myocardial contractility. Using left ventricular trabeculae from chicks at embryonic day (ED) 15, we have previously shown that the twitch force of intact preparations is significantly reduced whereas the maximal calcium-activated force of skinned preparations is not significantly different in CNCA and sham-operated animals. We also previously found that the ventricular content of myosin, as well as of actin and tropomyosin, was nearly doubled in ED 15 hearts after CNCA. Since the number of cross-bridges is proportional to the myosin concentration, these data suggest that the force exerted per cross-bridge is decreased in CNCA hearts. We investigated the possibility that the decrease in force per cross-bridge is caused by inhibition of the contractile apparatus by excessive microtubules. To the contrary, we found that the total beta-tubulin content and the fraction of beta-tubulin polymerized in microtubules measured by Western blotting was the same in ventricular muscle strips from CNCA and sham-operated embryos. Furthermore, exposure to microtubule-destabilizing agents did not improve the force-producing capability of the contractile apparatus in CNCA embryos. We conclude that depression of force per cross-bridge in hearts from CNCA embryos is not due to an excess of microtubules.
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Affiliation(s)
- C J Hatcher
- Cornell University Medical College, Department of Medicine, Division of Cardiology, New York, NY 10021, USA
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Supinski G, Stofan D, Callahan LA, Nethery D, Nosek TM, DiMarco A. Peroxynitrite induces contractile dysfunction and lipid peroxidation in the diaphragm. J Appl Physiol (1985) 1999; 87:783-91. [PMID: 10444640 DOI: 10.1152/jappl.1999.87.2.783] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Peroxynitrite may be generated in and around muscles in several pathophysiological conditions (e.g., sepsis) and may induce muscle dysfunction in these disease states. The effect of peroxynitrite on muscle force generation has not been directly assessed. The purpose of the present study was to assess the effects of peroxynitrite administration on diaphragmatic force-generating capacity in 1) intact diaphragm muscle fiber bundles (to model the effects produced by exposure of muscles to extracellular peroxynitrite) and 2) single skinned diaphragm muscle fibers (to model the effects of intracellular peroxynitrite on contractile protein function) by examining the effects of both peroxynitrite and a peroxynitrite-generating solution, 3-morpholinosydnonimine, on force vs. pCa characteristics. In intact diaphragm preparations, peroxynitrite reduced diaphragm force generation and increased muscle levels of 4-hydroxynonenal (an index of lipid peroxidation). In skinned fibers, both peroxynitrite and 3-morpholinosydnonimine reduced maximum calcium-activated force. These data indicate that peroxynitrite is capable of producing significant diaphragmatic contractile dysfunction. We speculate that peroxynitrite-mediated alterations may be responsible for much of the muscle dysfunction seen in pathophysiological conditions such as sepsis.
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Affiliation(s)
- G Supinski
- Pulmonary Division, Department of Medicine, Case Western Reserve University, Cleveland 44106; and Metrohealth Medical Center, Cleveland, Ohio 44109, USA
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35
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Godt RE, Fogaça RT, Nosek TM. Alterations of myocardial contraction associated with a structural heart defect in embryonic chicks. Adv Exp Med Biol 1999; 453:453-8; discussion 459. [PMID: 9889857 DOI: 10.1007/978-1-4684-6039-1_50] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ablation of cardiac neural crest at stages 8-10 produces a structural heart defect (persistent truncus arteriosus, PTA) in embryonic chicks. PTA is associated with decreased myocardial contractility, as indicated by decreased left ventricular ejection fraction. We compared the force of small ventricular strips from normal and defective chick hearts. In intact muscle, ablation of the neural crest leads to a 30-50% decrease in twitch force at any level of extracellular Ca2+ (0.45-20 mM) at embryonic days (ED) 7 and 15, relative to sham-operated controls. These differences could reflect defects at the level of the contractile apparatus and/or in the excitation-contraction coupling process. To distinguish changes of the contractile apparatus, we used detergent skinned preparations. The maximal Ca(2+)-activated force (Fmax) at ED15 was not significantly different between control and experimental embryos. At ED 7, however, Fmax was reduced by 36% in experimental preparations. Electron-micrographs showed that the organization and orientation of the myofibrils was similar in experimental and control ventricles. At ED 14, however, the average myofibrillar diameter was significantly increased in experimental ventricles. The content of the major myofibrillar proteins (myosin heavy chain, actin, and tropomyosin), determined from polyacrylamide gel electrophoresis and Coomassie Blue staining, normalized to total protein, was not statistically different in experimental and control ventricles at ED7. At ED15, however, content of these proteins was doubled in experimental ventricles. These data suggest a possible defect of the contractile apparatus at both ED 7 and 15, since the ratio of Fmax/myosin is reduced in the experimental hearts.
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Affiliation(s)
- R E Godt
- Department of Physiology and Endocrinology, Medical College of Georgia, Augusta, USA
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Affiliation(s)
- M A Andrews
- Department of Medical Physiology, New York College of Osteopathic, Medicine of NYIT, Old Westbury 11568-8000, USA.
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Abstract
We investigated the inhibitory effects of increased salt concentrations on maximal calcium-activated force (Fmax) of rabbit cardiac papillary muscle bundles skinned with Triton X-100. While other studies have reported a lack of ion-specific effects on Fmax of cardiac muscle, we clearly demonstrated the presence of such effects when a wider variety of salts was investigated. In addition, like skeletal muscle, cardiac muscle was found to be sensitive to ionic strength and not to ionic equivalence. In support of our hypothesis that the ion-specific effects are due to protein destabilization, we found that a protein stabilizer (trimethylamine N-oxide, TMAO) completely abolished the ion-specific effects on Fmax. The ion-specific effect is probably due to binding of ions to the contractile proteins. The general ionic effect is most likely due to electrostatic shielding that remains in the presence of TMAO. Neither 300 mM sucrose nor TMAO significantly altered Fmax at physiological ionic strength indicating that the ion-specific depression of Fmax was not due to a colligative/osmotic effect. Furthermore, adding sucrose to solutions with a supraphysiological ionic strength caused a further decrease in Fmax indicating that certain osmolytes can alter Fmax if the contractile proteins are initially destabilized.
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Affiliation(s)
- T M Nosek
- Department of Physiology, New York College of Osteopathic Medicine, Old Westbury, NY 11568, USA
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Essig DA, Nosek TM. Muscle fatigue and induction of stress protein genes: a dual function of reactive oxygen species? Can J Appl Physiol 1997; 22:409-28. [PMID: 9356761 DOI: 10.1139/h97-026] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Definitive characterization of the mechanisms of skeletal muscle fatigue is still an area of active investigation. One emerging theory concerns a role for the reactive oxygen species (ROS) produced primarily as a consequence of elevated rates of mitochondrial respiration. It has been theorized that the long-lasting effects of low-frequency fatigue (LFF) can be attributed to disruption of some stage of the excitation contraction coupling (ECC) process. Recent evidence suggests that ROS likely denature one or more proteins directly associated with the sarcoplasmic reticulum (SR) Ca2+ release mechanism. Given the potential of ROS to damage intracellular proteins during subsequent bouts of muscle contractions, the capacity of preexisting antioxidant pathways may be complemented by the synthesis of inducible heat-stress proteins (HSPs). HSPs collectively function to maintain cellular protein conformation during stressful proteotoxic insults. The goal of this article is to illustrate how recent findings suggest a dual role of ROS generated during muscle contractions.
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Affiliation(s)
- D A Essig
- Department of Exercise Science, Blatt Center, University of South Carolina, Columbia 29208, USA
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Nosek TM, Fogaça RT, Hatcher CJ, Brotto MA, Godt RE. Effect of cardiac neural crest ablation on contractile force and calcium uptake and release in chick heart. Am J Physiol 1997; 273:H1464-71. [PMID: 9321838 DOI: 10.1152/ajpheart.1997.273.3.h1464] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cardiac neural crest ablation (CNCA) in the chick embryo at stages 8-10 results in reduced contractility of the heart that can be observed as early as stage 14. We found that intact trabeculae from embryonic day (E) 15 experimental animals after CNCA display an approximately 50% decrease in twitch force relative to sham-operated E15 control animals. In control and CNCA trabeculae skinned in Triton X-100 and bathed in our standard solutions, neither maximum Ca(2+)-activated force nor Ca2+ sensitivity of the contractile apparatus was significantly different. CNCA resulted in a marked reduction in the magnitude of the Ca2+ transient in trabeculae, estimated using fura 2 acetoxymethyl ester. CNCA had no effect on the half-time of Ca2+ loading by the sarcoplasmic reticulum (SR) of saponin skinned trabeculae at fixed Ca2+. However, it slightly reduced the Ca2+ sensitivity of Ca2+ uptake by the SR. Its most dramatic effect was to essentially abolish Ca(2+)-induced Ca2+ release from the SR. These effects on Ca2+ metabolism explain, in part, the decrease in the intracellular Ca2+ transient and myocardial contractility observed with CNCA.
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Affiliation(s)
- T M Nosek
- Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000, USA
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40
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Abstract
This study test the hypothesis that a temporal relationship exists between the production of superoxide anion (O2-) and the contractile activity of perfused rat diaphragm. O2- levels were determined minute to minute by measuring the reduction of cytochrome c in the perfusate as the diaphragms were subjected to various levels of contractile activity. After equilibrating at low contractile rates (one 500 ms 80 Hz train/min), diaphragms were fatigued by increasing their contractile activity for 5 min (one 500 ms 80 Hz train/s) and then allowed to recover for 30 min (one 500 ms 80 Hz train/min). During equilibration, diaphragms did not produce O2- above the background level measured in the presence of superoxide dismutase (SOD). Within the first minute of fatigue-inducing stimulation, however, the rate of O2- production increased to 0.70 +/- 0.17 nmol/min and remained elevated until the recovery period when production returned towards baseline. SOD blocked this stimulation-related increase of O2-. Tension (+/-SOD) fell to 12% of the control value during the fatigue-inducing stimulation. During recovery the contractile response returned to 51% of control, indicating long-lasting effects on the contractile machinery. SOD did not limit fatigue or improve recovery, probably because it is a large protein that cannot cross cell membranes and protect the cells by scavenging O2- at its site of production.
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Affiliation(s)
- R C Kolbeck
- Department of Medicine, Medical College of Georgia, Augusta 30912, USA
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Abstract
Reactive oxygen species such as superoxide (O2-) and H2O2 are produced at low levels in resting muscles and at substantially higher levels in exercising muscles. Increased respiratory activity with exercise leads to O2- production by the NADPH oxidase reaction and the subsequent generation of H2O2 from O2- by spontaneous dismutation or by the superoxide dismutase reaction. The long-lasting (24-h) depression of contractile function after exercise has been linked to damage of one or more proteins important in the excitation-contraction coupling process. We studied mechanically and chemically skinned fibers from the extensor digitorum longus muscle of the rat to evaluate the effects of a 5-min exposure to 1.0 mM H2O2 on muscle function. We found that H2O2 had no effect on the isometric force-producing properties of the contractile apparatus or on Ca2+ uptake by the sarcoplasmic reticulum. It did, however, significantly affect Ca2+ release from the sarcoplasmic reticulum. Maximum depolarization-induced Ca2+ release was inhibited, and the sensitivity to depolarization was decreased. Ca(2+)-induced release was completely blocked. We conclude that elevated levels of H2O2 with exercise are capable of damaging one or more proteins of the excitation-contraction coupling process to produce a disruption in function that can account, at least in part, for the long-lasting effects of fatiguing stimulation.
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Affiliation(s)
- M A Brotto
- Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000, USA
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Andrews MA, Godt RE, Nosek TM. Influence of physiological L(+)-lactate concentrations on contractility of skinned striated muscle fibers of rabbit. J Appl Physiol (1985) 1996; 80:2060-5. [PMID: 8806914 DOI: 10.1152/jappl.1996.80.6.2060] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
These experiments investigated the effects of physiological concentrations of L(+)-lactate on the contractility of chemically skinned rabbit fast-twitch psoas, slow-twitch soleus, and cardiac muscles at pH 7.L(+)-Lactate depressed maximal calcium-activated force (Fmax) of all muscles studied within the range of 5-20 (slow-twitch muscle) or 5-25 mM (fast-twitch and cardiac muscles). Fmax of fast-twitch fibers was inhibited to the greatest degree (9% in K2 creatine phosphate solutions). In all of these muscle types, Fmax returned to control levels as L(+)-lactate was increased to 30-50 mM. Substitution of neither D-lactate nor propionate for L(+)-lactate significantly altered Fmax. In addition, with the exception of fast-twitch muscle (where the Hill coefficient decreased), L(+)-lactate concentrations, which maximally inhibited Fmax, did not affect the force vs. pCa relationship of muscles tested. These results demonstrate that L(+)-lactate significantly contributes to the depression of muscle function noted during lactic acidosis, directly inhibiting Fmax of the contractile apparatus. This contribution is maximal in fast-twitch muscle where L(+)-lactate is responsible for as much as one-third of the depressant effect on Fmax of the contractile apparatus noted during lactic acidosis.
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Affiliation(s)
- M A Andrews
- Division of Physiology, New York College of Osteopathic Medicine, Old Westbury 11568, USA
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Brotto MA, Fogaça RT, Creazzo TL, Godt RE, Nosek TM. The effect of 2,3-butanedione 2-monoxime (BDM) on ventricular trabeculae from the avian heart. J Muscle Res Cell Motil 1995; 16:1-10. [PMID: 7751400 DOI: 10.1007/bf00125305] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
2,3-butanedione 2-monoxime (BDM, 3-30 mM) decreased twitch force of intact ventricular trabeculae isolated from 19-day embryonic chick hearts in a dose-dependent manner. The responses to BDM were rapid and reversible. In an attempt to determine the cellular basis for the inhibitory effect of BDM, experiments were carried out on skinned muscle fibres and isolated myocytes. In trabeculae skinned with Triton X-100, BDM depressed maximum calcium activated force (Fmax) with an IC50 of 14 mM. At 3 mM BDM, the proportional decrease in twitch force in intact tissue was similar to that of Fmax in skinned tissue. At higher BDM concentrations (10 and 30 mM), however, the proportional decrease in twitch force was greater than that of Fmax. BDM (up to 10 mM) had no effect on the normalized force-pCa relationship. In saponin-skinned preparations, BDM (3 and 30 mM) released calcium from the fully loaded sarcoplasmic reticulum to a slightly greater extent in the absence of calcium (pCa 8.5) than in the presence of a fixed level of free calcium (pCa 5.5). Whole cell patch clamping of freshly isolated chick myocytes demonstrated that BDM caused a dose-dependent decrease in the T- and L-type calcium current. Therefore, at low BDM concentrations (3 mM), the decrease in twitch force can be ascribed predominantly to depression of the contractile apparatus while, at higher concentrations of BDM, there is an additional inhibitory effect of BDM on excitation-contraction coupling.
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Affiliation(s)
- M A Brotto
- Department of Physiology, Medical College of Georgia, Augusta 30912, USA
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Abstract
Muscle fatigue was studied in the isolated perfused rat (66% oxidative fibers) and mouse (99% oxidative fibers) diaphragms. Both muscles displayed two fatigue patterns when exposed to 333-ms trains of 20-Hz stimulation. A rapid fatigue pattern appeared within each contractile train as an immediate progressive twitch-by-twitch diminution in contractility [a decrease in maximal isometric twitch tension (T) and maximal rate of T development]. An intertrain slow fatigue pattern also appeared as a progressive train-by-train diminution in contractility and an increased maximal rate of relaxation normalized to T. A reduction in the stimulatory frequency from 20 to 2 Hz caused a considerable diminution in the rapid fatigue pattern. These data suggest that rapid fatigue results from the time course of mechanical restitution, the time necessary for the Ca2+ channels of the sarcoplasmic reticulum to recover from inactivation. The slow fatigue pattern, on the other hand, is thought to be due to changes in the intracellular milieu. The difference in sensitivity of the rat and mouse diaphragms to rapid and slow fatigue is apparently related to differences in their fiber type composition. Thus, as would be expected, the mouse diaphragm, composed of only oxidative fibers, is less susceptible to slow fatigue compared with the rat diaphragm. On the other hand, it is more susceptible to rapid fatigue.
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Affiliation(s)
- R C Kolbeck
- Department of Medicine, Medical College of Georgia, Augusta 30912
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Abstract
1. Developmental changes in contraction of chick heart show strong similarities with those of the mammalian myocardium. 2. Normalized twitch force of intact trabeculae from chick left ventricle increases most markedly during the 3-day period around the time of hatching. 3. At any age, elevation of extracellular [Ca2+] to 10-20 mM increases twitch force to a maximum. 4. Studies using membrane-free ("skinned") trabeculae demonstrate that the developmental increase in twitch force is paralleled by an increase in the maximal contractile capability of the muscle, that is probably due to proliferation of contractile proteins. 5. At all ages studied, maximal twitch force of intact trabeculae at 10-20 mM extracellular [Ca2+] is similar to maximal Ca(2+)-activated force of the trabeculae after skinning. 6. Calcium sensitivity of the contractile apparatus in chick heart decreases with development in parallel with isoform switching in troponin T. 7. The depressant effect of acidosis on calcium sensitivity of the contractile apparatus increases with development in parallel with isoform switching in troponin I. 8. As in mammalian heart, both acidosis and inorganic phosphate (Pi) depress force generation by the contractile machinery of chick heart.
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Affiliation(s)
- R E Godt
- Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000
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Godt RE, Fogaça RT, Andrews MA, Nosek TM. Influence of ionic strength on contractile force and energy consumption of skinned fibers from mammalian and crustacean striated muscle. Adv Exp Med Biol 1993; 332:763-73; discussion 773-4. [PMID: 8109386 DOI: 10.1007/978-1-4615-2872-2_67] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Increased ionic strength decreases maximal calcium-activated force (Fmax) of skinned muscle fibers via mechanisms that are incompletely understood. In detergent-skinned fibers from either rabbit (psoas) or lobster (leg or abdomen), Fmax in KCl-containing solutions was less than in potassium methanesulfonate (KMeSO3), which we showed previously was the least deleterious salt for adjusting ionic strength. In either salt, lobster fibers were considerably less sensitive to elevated ionic strength than rabbit fibers. Trimethylamine N-oxide (TMAO, a zwitterionic osmolyte found in high concentration in cells of salt-tolerant animals) increased Fmax, especially in high KCl solutions. In this regard, TMAO was more effective than a variety of other natural or synthetic zwitterions. In rabbit fibers, increasing ionic strength decreases Fmax but has little effect on contractile ATPase rate measured simultaneously using a linked-enzyme assay. Thus high salt increases the tension-cost of contraction (i.e. ratio ATPase/Fmax). At both high and low salt, TMAO decreases tension-cost. Given a simple two-state model of the cross-bridge cycle, these data indicate that ionic strength and TMAO affect the apparent detachment rate constant. High ionic strength KCl solutions extract myosin heavy- and light-chains, and troponin C from rabbit fibers. This extraction is virtually abolished by TMAO. Natural zwitterions, such as TMAO, have been shown to protect proteins against destabilization by high salt or other denaturatants. Our data indicate that, even in the best of salts, destabilization of the actomyosin complex may play a role in the effect of high ionic strength on the contractile process.
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Affiliation(s)
- R E Godt
- Dept. of Physiology & Endocrinology, Medical College of Georgia, Augusta 30912
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48
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Abstract
Incubated guinea pig tracheal smooth muscle exhibited both positive and negative inotropic responses to a variety of crown ether analogs that ranged in size from 12-crown-4 to 30-crown-10 and included molecules whose lipophilicity was modified by the addition of benzo- and cyclohexo-substituents on the basic molecular framework. The inotropic influence of crown ethers may not only be due to their ionophoretic capabilities but may result from their ability to affect alterations in membrane physiology.
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Affiliation(s)
- R C Kolbeck
- Department of Medicine, Medical College of Georgia, Augusta 30912-3135
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Abstract
Ruthenium red has been shown to have a positive inotropic effect on isolated perfused hearts. The cellular mechanism of this action is not clear. Ruthenium red is able to block the Ca2+ release channel in isolated sarcoplasmic reticulum (SR) vesicle and reconstituted channel preparations. However, the effect of ruthenium red on SR Ca2+ release has not been studied in skinned cardiac muscle preparations. In the present study we investigated the actions of ruthenium red on both the characteristics of force generation by the contractile apparatus and Ca2+ release from the SR in chemically skinned rat papillary muscle. Ruthenium red (2 and 10 microM) significantly increased the Ca2+ sensitivity of the contractile apparatus (decreasing Ca2+ required for the half-maximal response from 1.56 +/- 0.04 microM to 1.46 +/- 0.05 microM) but had no effect on the maximal Ca(2+)-activated force in triton X-100 treated fibers. This result may suggest one explanation for the positive inotropic effect of ruthenium red on the heart. On the other hand, ruthenium red had no significant effect on either caffeine-induced Ca2+ release or Ca(2+)-induced Ca2+ release from the SR in saponin-skinned muscle fibers. Lack of a blocking effect on SR Ca2+ release by ruthenium red in skinned fibers suggests that the SR Ca2+ channels in intact preparations have characteristics that are different from those of either vesicular or reconstituted channel preparations.
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Affiliation(s)
- Y Zhu
- Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000
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50
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Andrews MA, Maughan DW, Nosek TM, Godt RE. Ion-specific and general ionic effects on contraction of skinned fast-twitch skeletal muscle from the rabbit. J Gen Physiol 1991; 98:1105-25. [PMID: 1664455 PMCID: PMC2229068 DOI: 10.1085/jgp.98.6.1105] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We used single fibers from rabbit psoas muscle, chemically skinned with Triton X-100 nonionic detergent, to determine the salts best suited for adjusting ionic strength of bathing solutions for skinned fibers. As criteria we measured maximal calcium-activated force (Fmax), fiber swelling estimated optically, and protein extraction from single fibers determined by polyacrylamide gel electrophoresis with ultrasensitive silver staining. All things considered, the best uni-univalent salt was potassium methanesulfonate, while a number of uni-divalent potassium salts of phosphocreatine, hexamethylenediamine N,N,N',N'-tetraacetic acid, sulfate, and succinate were equally acceptable. Using these salts, we determined that changes in Fmax correlated best with variations of ionic strength (1/2 sigma ci z2i, where ci is the concentration of ion i, and zi is its valence) rather than ionic equivalents (1/2 sigma ci magnitude of zi). Our data indicate that increased ionic strength per sc decreases Fmax, probably by destabilizing the cross-bridge structure in addition to increasing electrostatic shielding of actomyosin interactions.
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Affiliation(s)
- M A Andrews
- Department of Physiology & Endocrinology, Medical College of Georgia, Augusta 30912-3000
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