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Fogarty MJ. Dendritic morphology of motor neurons and interneurons within the compact, semicompact, and loose formations of the rat nucleus ambiguus. Front Cell Neurosci 2024; 18:1409974. [PMID: 38933178 PMCID: PMC11199410 DOI: 10.3389/fncel.2024.1409974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Accepted: 05/27/2024] [Indexed: 06/28/2024] Open
Abstract
Introduction Motor neurons (MNs) within the nucleus ambiguus innervate the skeletal muscles of the larynx, pharynx, and oesophagus. These muscles are activated during vocalisation and swallowing and must be coordinated with several respiratory and other behaviours. Despite many studies evaluating the projections and orientation of MNs within the nucleus ambiguus, there is no quantitative information regarding the dendritic arbours of MNs residing in the compact, and semicompact/loose formations of the nucleus ambiguus.. Methods In female and male Fischer 344 rats, we evaluated MN number using Nissl staining, and MN and non-MN dendritic morphology using Golgi-Cox impregnation Brightfield imaging of transverse Nissl sections (15 μm) were taken to stereologically assess the number of nucleus ambiguus MNs within the compact and semicompact/loose formations. Pseudo-confocal imaging of Golgi-impregnated neurons within the nucleus ambiguus (sectioned transversely at 180 μm) was traced in 3D to determine dendritic arbourisation. Results We found a greater abundance of MNs within the compact than the semicompact/loose formations. Dendritic lengths, complexity, and convex hull surface areas were greatest in MNs of the semicompact/loose formation, with compact formation MNs being smaller. MNs from both regions were larger than non-MNs reconstructed within the nucleus ambiguus. Conclusion Adding HBLS to the diet could be a potentially effective strategy to improve horses' health.
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Affiliation(s)
- Matthew J. Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
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2
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Sieck GC, Hernandez-Vizcarrondo GA, Brown AD, Fogarty MJ. Sarcopenia of the longitudinal tongue muscles in rats. Respir Physiol Neurobiol 2024; 319:104180. [PMID: 37863156 PMCID: PMC10851598 DOI: 10.1016/j.resp.2023.104180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/29/2023] [Accepted: 10/14/2023] [Indexed: 10/22/2023]
Abstract
The tongue is a muscular hydrostat, with lingual movements occurring during breathing, chewing, swallowing, vocalization, vomiting, coughing and grooming/sexual activities. In the elderly, reduced lingual dysfunction and weakness contribute to increased risks of obstructive sleep apnea and aspiration pneumonia. In Fischer 344 (F344) rats, a validated model of aging, hypoglossal motor neuron death is apparent, although there is no information regarding tongue strength. The intrinsic tongue muscles, the superior and inferior longitudinal, transversalis and verticalis exist in an interdigitated state. Recently, we established a method to measure the specific force of individual intrinsic tongue muscle, accounting for the tissue bulk that is not in the direction of uniaxial force. In the longitudinal muscles of 6- (n = 10), 18- (n = 9) and 24-month-old (n = 12) female and male F344 rats, we assessed specific force, fatigability, fiber type dependent cross-sectional area (CSA) and overall CSA. Muscle force and fatigue was assessed ex vivo using platinum plate simulation electrodes. Tongue muscles were frozen in melting isopentane, and transverse sections cut at 10 µm. Muscle fiber type was classified based on immunoreactivity to myosin heavy chain (MyHC) isoform antibodies. In H&E stained muscle, CSA and uniaxial muscle contributions to total tongue bulk was assessed. We observed a robust ∼30% loss of longitudinal specific force, with reductions in overall longitudinal muscle fiber CSA and specific atrophy of type IIx/IIb fibers. It will be important to investigate the mechanistic underpinnings of hypoglossal motor neuron death and tongue muscle weakness to eventually provide therapies for age-associated lingual dysfunctions.
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Affiliation(s)
- Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Alyssa D Brown
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA.
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3
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Fogarty MJ. Loss of larger hypoglossal motor neurons in aged Fischer 344 rats. Respir Physiol Neurobiol 2023:104092. [PMID: 37331418 DOI: 10.1016/j.resp.2023.104092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/06/2023] [Accepted: 06/15/2023] [Indexed: 06/20/2023]
Abstract
The intrinsic (longitudinal, transversalis and verticalis) and extrinsic (genioglossus, styloglossus, hyoglossus and geniohyoid) tongue muscles are innervated by hypoglossal motor neurons (MNs). Tongue muscle activations occur during many behaviors: maintaining upper airway patency, chewing, swallowing, vocalization, vomiting, coughing, sneezing and grooming/sexual activities. In the tongues of the elderly, reduced oral motor function and strength contribute to increased risk of obstructive sleep apnoea. Tongue muscle atrophy and weakness is also described in rats, yet hypoglossal MN numbers are unknown. In young (6-months, n=10) and old (24-months, n=8) female and male Fischer 344 (F344) rats, stereological assessment of hypoglossal MN numbers and surface areas were performed on 16µm Nissl-stained brainstem cryosections. We observed a robust loss of ~15% of hypoglossal MNs and a modest ~8% reduction in their surface areas with age. In the larger size tertile of hypoglossal MNs, age-associated loss of hypoglossal MNs approached ~30% These findings uncover a potential neurogenic locus of pathology for age-associated tongue dysfunctions.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55905.
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4
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Allen MD, Dalton BH, Gilmore KJ, McNeil CJ, Doherty TJ, Rice CL, Power GA. Neuroprotective effects of exercise on the aging human neuromuscular system. Exp Gerontol 2021; 152:111465. [PMID: 34224847 DOI: 10.1016/j.exger.2021.111465] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 05/31/2021] [Accepted: 06/30/2021] [Indexed: 12/23/2022]
Abstract
Human biological aging from maturity to senescence is associated with a gradual loss of muscle mass and neuromuscular function. It is not until very old age (>80 years) however, that these changes often manifest into functional impairments. A driving factor underlying the age-related loss of muscle mass and function is the reduction in the number and quality of motor units (MUs). A MU consists of a single motoneuron, located either in the spinal cord or the brain stem, and all of the muscle fibres it innervates via its peripheral axon. Throughout the adult lifespan, MUs are slowly, but progressively lost. The compensatory process of collateral reinnervation attempts to recapture orphaned muscle fibres following the death of a motoneuron. Whereas this process helps mitigate loss of muscle mass during the latter decades of adult aging, the neuromuscular system has fewer and larger MUs, which have lower quality connections between the axon terminal and innervated muscle fibres. Whether this process of MU death and degradation can be attenuated with habitual physical activity has been a challenging question of great interest. This review focuses on age-related alterations of the human neuromuscular system, with an emphasis on the MU, and presents findings on the potential protective effects of lifelong physical activity. Although there is some discrepancy across studies of masters athletes, if one considers all experimental limitations as well as the available literature in animals, there is compelling evidence of a protective effect of chronic physical training on human MUs. Our tenet is that high-levels of physical activity can mitigate the natural trajectory of loss of quantity and quality of MUs in old age.
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Affiliation(s)
- Matti D Allen
- Department of Physical Medicine and Rehabilitation, School of Medicine, Faculty of Health Sciences, Queen's University, Kingston, ON K7L 4X3, Canada; School of Kinesiology and Health Studies, Faculty of Arts and Sciences, Queen's University, Kingston, ON K7L 4X3, Canada
| | - Brian H Dalton
- School of Health and Exercise Science, University of British Columbia, Kelowna, BC V1V 1V7, Canada
| | - Kevin J Gilmore
- Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Chris J McNeil
- School of Health and Exercise Science, University of British Columbia, Kelowna, BC V1V 1V7, Canada
| | - Timothy J Doherty
- Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada; Department of Physical Medicine and Rehabilitation, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
| | - Charles L Rice
- School of Kinesiology, The University of Western Ontario, London, ON, Canada; Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada.
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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Chugh D, Iyer CC, Bobbili P, Blatnik AJ, Kaspar BK, Meyer K, Burghes AH, Clark BC, Arnold WD. Voluntary wheel running with and without follistatin overexpression improves NMJ transmission but not motor unit loss in late life of C57BL/6J mice. Neurobiol Aging 2021; 101:285-296. [PMID: 33678425 PMCID: PMC8122043 DOI: 10.1016/j.neurobiolaging.2021.01.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 12/23/2020] [Accepted: 01/16/2021] [Indexed: 01/17/2023]
Abstract
Sarcopenia, or pathological loss of muscle mass and strength during aging, is an important contributor to loss of physical function in older adults. Sarcopenia is a multifactorial syndrome associated with intrinsic muscle and upstream neurological dysfunction. Exercise is well-established as an effective intervention for sarcopenia, but less is known about the long-term neurobiological impact of exercise. The goals of this study were to investigate the effects of exercise, alone or in combination with follistatin (FST) overexpression (antagonist of myostatin), on neuromuscular junction transmission and motor unit numbers in mice between the age of 22 and 27 months, ages at which prior studies have demonstrated that some motor unit loss is already evident. C57BL/6J mice underwent baseline assessment and were randomized to housing with or without voluntary running wheels and injection with adeno-associated virus to overexpress FST or vehicle. Groups for comparison included sedentary and running with and without FST. Longitudinal assessments showed significantly increased muscle mass and contractility in the 'running plus FST' group, but running, with and without FST, showed no effect on motor unit degeneration. In contrast, running, with and without FST, demonstrated marked improvement of neuromuscular junction transmission stability.
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Affiliation(s)
- Deepti Chugh
- Department of Neurology, Neuromuscular Division, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Chitra C Iyer
- Department of Neurology, Neuromuscular Division, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Prameela Bobbili
- Department of Neurology, Neuromuscular Division, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Anton J Blatnik
- Department of Biological Chemistry and Pharmacology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Brian K Kaspar
- The Research Institute, Nationwide Children's Hospital, Columbus, OH, USA
| | - Kathrin Meyer
- The Research Institute, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University, Columbus, OH, USA
| | - Arthur Hm Burghes
- Department of Biological Chemistry and Pharmacology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Brian C Clark
- Ohio Musculoskeletal and Neurological Institute & the Department of Biomedical Sciences, Athens, OH, USA
| | - W David Arnold
- Department of Neurology, Neuromuscular Division, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Physical Medicine and Rehabilitation, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
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Tanaka H, Tarumi T, Rittweger J. Aging and Physiological Lessons from Master Athletes. Compr Physiol 2019; 10:261-296. [PMID: 31853968 DOI: 10.1002/cphy.c180041] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Sedentary aging is often characterized by physical dysfunction and chronic degenerative diseases. In contrast, masters athletes demonstrate markedly greater physiological function and more favorable levels of risk factors for cardiovascular disease, osteoporosis, frailty, and cognitive dysfunction than their sedentary counterparts. In many cases, age-related deteriorations of physiological functions as well as elevations in risk factors that are typically observed in sedentary adults are substantially attenuated or even absent in masters athletes. Older masters athletes possess greater functional capacity at any given age than their sedentary peers. Impressive profiles of older athletes provide insight into what is possible in human aging and place aging back into the domain of "physiology" rather than under the jurisdiction of "clinical medicine." In addition, these exceptional aging athletes can serve as a role model for the promotion of physical activity at all ages. The study of masters athletes has provided useful insight into the positive example of successful aging. To further establish and propagate masters athletics as a role model for our aging society, future research and action are needed. © 2020 American Physiological Society. Compr Physiol 10:261-296, 2020.
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Affiliation(s)
- Hirofumi Tanaka
- Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas, USA
| | - Takashi Tarumi
- Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.,Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
| | - Jörn Rittweger
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany.,Department of Pediatrics and Adolescent Medicine, University of Cologne, Cologne, Germany
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McArdle A, Pollock N, Staunton CA, Jackson MJ. Aberrant redox signalling and stress response in age-related muscle decline: Role in inter- and intra-cellular signalling. Free Radic Biol Med 2019; 132:50-57. [PMID: 30508577 PMCID: PMC6709668 DOI: 10.1016/j.freeradbiomed.2018.11.038] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 11/29/2018] [Accepted: 11/29/2018] [Indexed: 12/22/2022]
Abstract
Age-associated frailty is predominantly due to loss of muscle mass and function. The loss of muscle mass is also associated with a greater loss of muscle strength, suggesting that the remaining muscle fibres are weaker than those of adults. The mechanisms by which muscle is lost with age are unclear, but in this review we aim to pull together various strands of evidence to explain how muscle contractions support proteostasis in non-muscle tissues, particularly focussed on the production and potential transfer of Heat Shock Proteins (HSPs) and how this may fail during ageing, Furthermore we will identify logical approaches, based on this hypothesis, by which muscle loss in ageing may be reduced. Skeletal muscle generates superoxide and nitric oxide at rest and this generation is increased by contractile activity. In adults, this increased generation of reactive oxygen and nitrogen species (RONS) activate redox-sensitive transcription factors such as nuclear factor κB (NFκB), activator protein-1 (AP1) and heat shock factor 1 (HSF1), resulting in increases in cytoprotective proteins such as the superoxide dismutases, catalase and heat shock proteins that prevent oxidative damage to tissues and facilitate remodelling and proteostasis in both an intra- and inter-cellular manner. During ageing, the ability of skeletal muscle from aged organisms to respond to an increase in ROS generation by increased expression of cytoprotective proteins through activation of redox-sensitive transcription factors is severely attenuated. This age-related lack of physiological adaptations to the ROS induced by contractile activity appears to contribute to a loss of ROS homeostasis, increased oxidative damage and age-related dysfunction in skeletal muscle and potentially other tissues.
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Affiliation(s)
- Anne McArdle
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom.
| | - Natalie Pollock
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom
| | - Caroline A Staunton
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom
| | - Malcolm J Jackson
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom
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8
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Abstract
Even in the absence of disease or disability, aging is associated with marked physiological adaptations within the neuromuscular system. An ability to perform activities of daily living and maintain independence with advanced age is reliant on the health of the neuromuscular system. Hence, it is critical to elucidate the age-related adaptations that occur within the central nervous system and the associated muscles to design interventions to maintain or improve neuromuscular function in the elderly. This brief review focuses on the neural alterations observed at both spinal and supraspinal levels in healthy humans in their seventh decade and beyond. The topics addressed are motor unit loss and remodelling, neural drive, and responses to transcranial magnetic stimulation of the motor cortex.
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Affiliation(s)
- Chris J. McNeil
- School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC V1V 1V7, Canada
- Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, University of British Columbia, Kelowna, BC V1V 1V7, Canada
| | - Charles L. Rice
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6A 3K7, Canada
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 3K7, Canada
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9
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Causes and consequences of age-related changes at the neuromuscular junction. CURRENT OPINION IN PHYSIOLOGY 2018. [DOI: 10.1016/j.cophys.2018.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Krause Neto W, Silva WDA, Ciena AP, de Souza RR, Anaruma CA, Gama EF. Aging Induces Changes in the Somatic Nerve and Postsynaptic Component without Any Alterations in Skeletal Muscles Morphology and Capacity to Carry Load of Wistar Rats. Front Neurosci 2017; 11:688. [PMID: 29326543 PMCID: PMC5741656 DOI: 10.3389/fnins.2017.00688] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 11/22/2017] [Indexed: 01/09/2023] Open
Abstract
The present study aimed to analyze the morphology of the peripheral nerve, postsynaptic compartment, skeletal muscles and weight-bearing capacity of Wistar rats at specific ages. Twenty rats were divided into groups: 10 months-old (ADULT) and 24 months-old (OLD). After euthanasia, we prepared and analyzed the tibial nerve using transmission electron microscopy and the soleus and plantaris muscles for cytofluorescence and histochemistry. For the comparison of the results between groups we used dependent and independent Student's t-test with level of significance set at p ≤ 0.05. For the tibial nerve, the OLD group presented the following alterations compared to the ADULT group: larger area and diameter of both myelinated fibers and axons, smaller area occupied by myelinated and unmyelinated axons, lower numerical density of myelinated fibers, and fewer myelinated fibers with normal morphology. Both aged soleus and plantaris end-plate showed greater total perimeter, stained perimeter, total area and stained area compared to ADULT group (p < 0.05). Yet, aged soleus end-plate presented greater dispersion than ADULT samples (p < 0.05). For the morphology of soleus and plantaris muscles, density of the interstitial volume was greater in the OLD group (p < 0.05). No statistical difference was found between groups in the weight-bearing tests. The results of the present study demonstrated that the aging process induces changes in the peripheral nerve and postsynaptic compartment without any change in skeletal muscles and ability to carry load in Wistar rats.
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Affiliation(s)
- Walter Krause Neto
- Laboratory of Morphoquantitative Studies and Immunohistochemistry, Department of Physical Education, São Judas Tadeu University, São Paulo, Brazil
| | - Wellington de Assis Silva
- Laboratory of Morphoquantitative Studies and Immunohistochemistry, Department of Physical Education, São Judas Tadeu University, São Paulo, Brazil
| | - Adriano P Ciena
- Laboratory of Morphology and Physical Activity, Department of Physical Education, São Paulo State University, Rio Claro, Brazil
| | - Romeu R de Souza
- Laboratory of Morphoquantitative Studies and Immunohistochemistry, Department of Physical Education, São Judas Tadeu University, São Paulo, Brazil
| | - Carlos A Anaruma
- Laboratory of Morphology and Physical Activity, Department of Physical Education, São Paulo State University, Rio Claro, Brazil
| | - Eliane F Gama
- Laboratory of Morphoquantitative Studies and Immunohistochemistry, Department of Physical Education, São Judas Tadeu University, São Paulo, Brazil
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Krause Neto W, Silva WDA, Ciena AP, Nucci RAB, Anaruma CA, Gama EF. Effects of Strength Training and Anabolic Steroid in the Peripheral Nerve and Skeletal Muscle Morphology of Aged Rats. Front Aging Neurosci 2017; 9:205. [PMID: 28713262 PMCID: PMC5491539 DOI: 10.3389/fnagi.2017.00205] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 06/07/2017] [Indexed: 01/12/2023] Open
Abstract
Thirty male 20-month-old Wistar rats were divided into groups: IC—initial control (n = 6), FC—final control (n = 6), AC—anabolic hormone control (n = 6), ST—strength trained (n = 6) and STA—strength trained with anabolic hormone (n = 6). All groups were submitted to adaptation, familiarization and maximum load carrying test (MLCT). Strength training (6–8×/session with loads of 50%–100% MLCT, 3×/week and pause of 120 s) was performed in ladder climbing (LC) for 15 weeks. The administration of testosterone propionate (TP) was performed 2×/week (10 mg/kg) in animals in the AC and STA groups. After the experimental period, animals were euthanized and the tibial nerve and plantaris muscle removed and prepared for electron transmission and histochemistry. To compare the groups we used one-way ANOVA (post hoc Bonferroni), student’s t-tests for pre vs. post (dependent and independent variables) comparisons and significance level set at p ≤ 0.05. The following significant results were found: (a) aging decreased the number of myelinated axon fibers; (b) use of isolated TP increased the diameter of myelinated fibers, along with increased thickness of myelin sheath; (c) ST increased area of myelinated and unmyelinated fibers, together with the myelin sheath. These changes made it possible to increase the area occupied by myelinated fibers keeping their quantity and also reduce the interstitial space; and (d) association of anabolic steroid and ST increased the area of unmyelinated axons and thickness of the myelin sheath. Compared to ST, both strategies have similar results. However, Schwann cells increased significantly only in this strategy.
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Affiliation(s)
- Walter Krause Neto
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu UniversitySão Paulo, Brazil
| | - Wellington de A Silva
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu UniversitySão Paulo, Brazil
| | - Adriano P Ciena
- Department of Physical Education, Laboratory of Morphology and Physical Activity, São Paulo State University "Júlio de Mesquita Filho"Rio Claro, Brazil
| | - Ricardo Aparecido Baptista Nucci
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu UniversitySão Paulo, Brazil
| | - Carlos A Anaruma
- Department of Physical Education, Laboratory of Morphology and Physical Activity, São Paulo State University "Júlio de Mesquita Filho"Rio Claro, Brazil
| | - Eliane F Gama
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu UniversitySão Paulo, Brazil
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Resistance wheel exercise from mid-life has minimal effect on sciatic nerves from old mice in which sarcopenia was prevented. Biogerontology 2017; 18:769-790. [PMID: 28597407 DOI: 10.1007/s10522-017-9714-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 05/31/2017] [Indexed: 12/16/2022]
Abstract
The ability of resistance exercise, initiated from mid-life, to prevent age-related changes in old sciatic nerves, was investigated in male and female C57BL/6J mice. Aging is associated with cellular changes in old sciatic nerves and also loss of skeletal muscle mass and function (sarcopenia). Mature adult mice aged 15 months (M) were subjected to increasing voluntary resistance wheel exercise (RWE) over a period of 8 M until 23 M of age. This prevented sarcopenia in the old 23 M aged male and female mice. Nerves of control sedentary (SED) males at 3, 15 and 23 M of age, showed a decrease in the myelinated axon numbers at 15 and 23 M, a decreased g-ratio and a significantly increased proportion of myelinated nerves containing electron-dense aggregates at 23 M. Myelinated axon and nerve diameter, and axonal area, were increased at 15 M compared with 3 and 23 M. Exercise increased myelinated nerve profiles containing aggregates at 23 M. S100 protein, detected with immunoblotting was increased in sciatic nerves of 23 M old SED females, but not males, compared with 15 M, with no effect of exercise. Other neuronal proteins showed no significant alterations with age, gender or exercise. Overall the RWE had no cellular impact on the aging nerves, apart from an increased number of old nerves containing aggregates. Thus the relationship between cellular changes in aging nerves, and their sustained capacity for stimulation of old skeletal muscles to help maintain healthy muscle mass in response to exercise remains unclear.
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Kern H, Hofer C, Loefler S, Zampieri S, Gargiulo P, Baba A, Marcante A, Piccione F, Pond A, Carraro U. Atrophy, ultra-structural disorders, severe atrophy and degeneration of denervated human muscle in SCI and Aging. Implications for their recovery by Functional Electrical Stimulation, updated 2017. Neurol Res 2017; 39:660-666. [PMID: 28403681 DOI: 10.1080/01616412.2017.1314906] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
OBJECTIVES Long-term lower motor neuron denervation of skeletal muscle is known to result in degeneration of muscle with replacement by adipose and fibrotic tissues. However, long-term survival of a subset of skeletal myofibers also occurs. METHODS We performed transverse and longitudinal studies of patients with spinal cord injury (SCI), patients specifically complete Conus and Cauda Equina Syndrome and also of active and sedentary seniors which included analyses of muscle biopsies from the quadriceps m. RESULTS Surprisingly, we discovered that human denervated myofibers survive years of denervation after full and irreversible disconnection from their motor neurons. We found that atrophic myofibers could be rescued by home-based Functional Electrical Stimulation (h-bFES), using purpose developed stimulators and electrodes. Although denervated myofibers quickly lose the ability to sustain high-frequency contractions, they respond to very long impulses that are able to allow for re-emergence of tetanic contractions. A description of the early muscle changes in humans are hampered by a paucity of patients suffering complete Conus and Cauda Equina Syndrome, but the cohort enrolled in the EU RISE Project has shown that even five years after SCI, severe atrophic myofibers with a peculiar cluster reorganization of myonuclei are present in human muscles and respond to h-bFES. CONCLUSIONS Human myofibers survive permanent denervation longer than generally accepted and they respond to h-bFES beyond the stage of simple atrophy. Furthermore, long-term denervation/reinnervation events occur in elderly people and are part of the mechanisms responsible for muscle aging and again h-bFES was beneficial in delaying aging decay.
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Affiliation(s)
- Helmut Kern
- a Physiko- und Rheumatherapie , St. Poelten , Austria
| | - Cristian Hofer
- b Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation , Vienna , Austria
| | | | - Sandra Zampieri
- a Physiko- und Rheumatherapie , St. Poelten , Austria.,c Department of Biomedical Sciences , University of Padova , Padova , Italy
| | - Paolo Gargiulo
- d Instutute for Biomedical and Neural Engineering/Biomedical Technology Centre , Reykjavik University and Landspitali , Reykjavik , Iceland
| | - Alfonc Baba
- e IRCCS Fondazione Ospedale San Camillo , Venice , Italy
| | | | | | - Amber Pond
- f Anatomy Department , Southern Illinois University School of Medicine , Carbondale , IL , USA
| | - Ugo Carraro
- e IRCCS Fondazione Ospedale San Camillo , Venice , Italy
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Power GA, Dalton BH, Gilmore KJ, Allen MD, Doherty TJ, Rice CL. Maintaining Motor Units into Old Age: Running the Final Common Pathway. Eur J Transl Myol 2017; 27:6597. [PMID: 28458809 PMCID: PMC5391523 DOI: 10.4081/ejtm.2017.6597] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Invited Letter to the Editor. This article is a commentary on the recently published manuscript "Use it or lose it: tonic activity of slow motoneurons promotes their survival and preferentially increases slow fiber-type groupings in muscles of old lifelong recreational sportsmen". Mosole S, Carraro U, Kern H, Loefler S, Zampieri S. Use it or lose it: tonic activity of slow motoneurons promotes their survival and preferentially increases slow fiber-type groupings in muscles of old lifelong recreational sportsmen. Eur J Transl Myol 2016;26:5972. doi: 10.4081/ejtm.2016.5972. We offer some unique perspectives on masters athletes and the role of physical activity in maintaining the number and function of motor units into old age.
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Affiliation(s)
- Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Brian H Dalton
- School of Health and Exercise Sciences, The University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Kevin J Gilmore
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada
| | - Matti D Allen
- Schools of Medicine and Kinesiology and Health Studies, Faculty of Health Sciences, Queen's University, Kingston, Ontario, Canada
| | - Timothy J Doherty
- Departments of Physical Medicine and Rehabilitation and Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Charles L Rice
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada.,Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
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Carbone PO, Krause Neto W, Gama EF, Silva WDA, Nobre TL, Caperuto EC, Mascaro MB, Souza RRD. MORPHOLOGICAL ADJUSTMENTS OF THE RADIAL NERVE ARE INTENSITY-DEPENDENT. REV BRAS MED ESPORTE 2017. [DOI: 10.1590/1517-869220172301157903] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
ABSTRACT Introduction: Peripheral nerve adaptation is critical for strength gains. However, information about intensity effects on nerve morphology is scarce. Objective: To compare the effects of different intensities of resistance training on radial nerve structures. Methods: Rats were divided into three groups: control (GC), training with 50% (GF1) and training 75% (GF2) of the animal’s body weight. The morphological analysis of the nerve was done by light and transmission electron microscopy. One-way ANOVA and the Tukey’s post hoc test were applied and the significance level was set at p≤0.05. Results: Training groups had an increase of strength compared to GC (p≤0.05). All measured nerve components (mean area and diameter of myelin fibers and axons, mean area and thickness of the myelin sheath, and of neurofilaments and microtubules) were higher in GF2 compared to the other (p≤0.05). Conclusion: Results demonstrated greater morphological changes on radial nerve after heavier loads. This can be important for rehabilitation therapies, training, and progression.
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Unhjem R, Nygård M, van den Hoven LT, Sidhu SK, Hoff J, Wang E. Lifelong strength training mitigates the age-related decline in efferent drive. J Appl Physiol (1985) 2016; 121:415-23. [DOI: 10.1152/japplphysiol.00117.2016] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 06/17/2016] [Indexed: 12/31/2022] Open
Abstract
Recently, we documented age-related attenuation of efferent drive to contracting skeletal muscle. It remains elusive if this indication of reduced muscle strength is present with lifelong strength training. For this purpose, we examined evoked potentials in the calf muscles of 11 [71 ± 4 (SD) yr] strength-trained master athletes (MA) contrasted with 10 (71 ± 4 yr) sedentary (SO) and 11 (73 ± 6 yr) recreationally active (AO) old subjects, as well as 9 (22 ± 2 yr) young controls. As expected, MA had higher leg press maximal strength (MA, 185 ± 32 kg; AO, 128 ± 15 kg; SO, 106 ± 11 kg; young, 147 ± 22 kg, P < 0.01) and rate of force development (MA, 5,588 ± 2,488 N/s; AO, 2,156 ± 1,100 N/s; SO, 2,011 ± 825 N/s; young, 3,663 ± 1,140 N/s, P < 0.05) than the other groups. MA also exhibited higher musculus soleus normalized V waves during maximal voluntary contractions (MVC) [maximal V wave amplitude/maximal M wave during MVC (Vsup/Msup); 0.28 ± 0.15] than AO (0.13 ± 0.06, P < 0.01) and SO (0.11 ± 0.05, P < 0.01), yet lower than young (0.45 ± 0.12, P < 0.01). No differences were apparent between the old groups in H reflex recorded at rest or during MVC [maximal H reflex amplitude/maximal M wave during rest (Hmax/Mmax); maximal H reflex amplitude during MVC/maximal M wave during MVC (Hsup/Msup)], and all were lower ( P < 0.01) than young. MA (34.4 ± 2.1 ms) had shorter ( P < 0.05) H reflex latency compared with AO (36.4 ± 3.7 ms) and SO (37.3 ± 3.2 ms), but longer ( P < 0.01) than young (30.7 ± 2.0 ms). Using interpolated twitch analysis, MA (89 ± 7%) had plantar flexion voluntary activation similar to young (90 ± 6%), and this was higher ( P < 0.05), or tended to be higher ( P = 0.06–0.09), than SO (83 ± 10%) and AO (84 ± 5%). These observations suggest that lifelong strength training has a protective effect against age-related attenuation of efferent drive. In contrast, no beneficial effect seems to derive from habitual recreational activity, indicating that strength training may be particularly beneficial for counteracting age-related loss of neuromuscular function.
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Affiliation(s)
- Runar Unhjem
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Mona Nygård
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Lene T. van den Hoven
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Simranjit K. Sidhu
- Discipline of Physiology, School of Medicine, The University of Adelaide, Adelaide, Australia
| | - Jan Hoff
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Physical Medicine and Rehabilitation, St. Olav's University Hospital, Trondheim, Norway
| | - Eivind Wang
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Research and Development, St. Olav's University Hospital, Trondheim, Norway; and
- Department of Medicine, University of Utah, Salt Lake City, Utah
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Power GA, Allen MD, Gilmore KJ, Stashuk DW, Doherty TJ, Hepple RT, Taivassalo T, Rice CL. Motor unit number and transmission stability in octogenarian world class athletes: Can age-related deficits be outrun? J Appl Physiol (1985) 2016; 121:1013-1020. [PMID: 27013605 DOI: 10.1152/japplphysiol.00149.2016] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 03/18/2016] [Indexed: 11/22/2022] Open
Abstract
Our group has shown a greater number of functioning motor units (MU) in a cohort of highly active older (∼65 yr) masters runners relative to age-matched controls. Because of the precipitous loss in the number of functioning MUs in the eighth and ninth decades of life it is unknown whether older world class octogenarian masters athletes (MA) would also have greater numbers of functioning MUs compared with age-matched controls. We measured MU numbers and neuromuscular transmission stability in the tibialis anterior of world champion MAs (∼80 yr) and compared the values with healthy age-matched controls (∼80 yr). Decomposition-enhanced spike-triggered averaging was used to collect surface and intramuscular electromyography signals during dorsiflexion at ∼25% of maximum voluntary isometric contraction. Near fiber (NF) MU potential analysis was used to assess neuromuscular transmission stability. For the MAs compared with age-matched controls, the amount of excitable muscle mass (compound muscle action potential) was 14% greater (P < 0.05), there was a trend (P = 0.07) toward a 27% smaller surface-detected MU potential representative of less collateral reinnervation, and 28% more functioning MUs (P < 0.05). Additionally, the MAs had greater MU neuromuscular stability than the controls, as indicated by lower NF jitter and jiggle values (P < 0.05). These results demonstrate that high-performing octogenarians better maintain neuromuscular stability of the MU and mitigate the loss of MUs associated with aging well into the later decades of life during which time the loss of muscle mass and strength becomes functionally relevant. Future studies may identify the concomitant roles genetics and exercise play in neuroprotection.
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Affiliation(s)
- Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph Ontario, Canada;
| | - Matti D Allen
- School of Medicine and School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Kevin J Gilmore
- Faculty of Health Sciences, School of Kinesiology, Canadian Centre for Activity and Aging, The University of Western Ontario, Ontario, Canada
| | - Daniel W Stashuk
- Department of Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Timothy J Doherty
- Faculty of Health Sciences, School of Kinesiology, Canadian Centre for Activity and Aging, The University of Western Ontario, Ontario, Canada.,Department of Physical Medicine and Rehabilitation, The University of Western Ontario, London, Ontario, Canada
| | - Russell T Hepple
- Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada.,Department of Medicine, McGill University, Montreal, Quebec, Canada.,Meakins Christie Laboratories, McGill University, Montreal, Quebec, Canada; and
| | - Tanja Taivassalo
- Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada
| | - Charles L Rice
- Faculty of Health Sciences, School of Kinesiology, Canadian Centre for Activity and Aging, The University of Western Ontario, Ontario, Canada.,Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
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18
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Power GA, Dalton BH, Doherty TJ, Rice CL. If you don't use it you'll likely lose it. Clin Physiol Funct Imaging 2015; 36:497-498. [PMID: 25944085 DOI: 10.1111/cpf.12248] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 02/23/2015] [Indexed: 11/27/2022]
Abstract
This article is a commentary on the recently published manuscript by Drey et al. (2014). The age-related loss of motor units (MU) is an immutable process and understanding the possible role of physical activity in maintaining functional MUs is an important topic. Dysfunctional remodelling of a MU is associated with denervation of the muscle and ultimate death of the spinal motoneurone. Conversely, in cross-sectional studies, high levels of physical activity in humans report a maintenance in the number of functional MUs in older master runners. However, it seems that only those MUs directly associated with the elevated long-term physical activity appear to benefit from any exercise-induced neuroprotective effect.
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Affiliation(s)
- Geoffrey A Power
- Human Performance Laboratory, University of Calgary, Calgary, AB, Canada.
| | - Brian H Dalton
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
| | - Timothy J Doherty
- Departments of Physical Medicine and Rehabilitation and Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
| | - Charles L Rice
- Faculty of Health Sciences, Canadian Centre for Activity and Aging, School of Kinesiology, The University of Western Ontario, London, ON, Canada.,Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
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19
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Drey M, Sieber CC, Degens H, McPhee J, Korhonen MT, Müller K, Ganse B, Rittweger J. Relation between muscle mass, motor units and type of training in master athletes. Clin Physiol Funct Imaging 2014; 36:70-6. [DOI: 10.1111/cpf.12195] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 09/09/2014] [Indexed: 12/14/2022]
Affiliation(s)
- Michael Drey
- Institute for Biomedicine of Ageing; University of Erlangen-Nürnberg; Nürnberg Germany
| | - Cornel C. Sieber
- Institute for Biomedicine of Ageing; University of Erlangen-Nürnberg; Nürnberg Germany
| | - Hans Degens
- School of Healthcare Science; Manchester Metropolitan University; Manchester UK
| | - Jamie McPhee
- School of Healthcare Science; Manchester Metropolitan University; Manchester UK
| | - Marko T. Korhonen
- Gerontology Research Center; Department of Health Sciences; University of Jyväskylä; Jyväskylä Finland
| | - Klaus Müller
- German Aerospace Center; Institute of Aerospace Medicine; Cologne Germany
| | - Bergita Ganse
- German Aerospace Center; Institute of Aerospace Medicine; Cologne Germany
| | - Jörn Rittweger
- German Aerospace Center; Institute of Aerospace Medicine; Cologne Germany
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20
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Nishimune H, Stanford JA, Mori Y. Role of exercise in maintaining the integrity of the neuromuscular junction. Muscle Nerve 2013; 49:315-24. [PMID: 24122772 DOI: 10.1002/mus.24095] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2013] [Indexed: 01/16/2023]
Abstract
Physical activity plays an important role in preventing chronic disease in adults and the elderly. Exercise has beneficial effects on the nervous system, including at the neuromuscular junction (NMJ). Exercise causes hypertrophy of NMJs and improves recovery from peripheral nerve injuries, whereas decreased physical activity causes degenerative changes in NMJs. Recent studies have begun to elucidate molecular mechanisms underlying the beneficial effects of exercise. These mechanisms involve Bassoon, neuregulin-1, peroxisome proliferator-activated receptor gamma coactivator 1α, insulin-like growth factor-1, glial cell line-derived neurotrophic factor, neurotrophin 4, Homer, and nuclear factor of activated T cells c1. For example, NMJ denervation and active zone decreases have been observed in aged NMJs, but these age-dependent degenerative changes can be ameliorated by exercise. In this review we assess the effects of exercise on the maintenance and regeneration of NMJs and highlight recent insights into the molecular mechanisms underlying these exercise effects.
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Affiliation(s)
- Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, 3901 Rainbow Boulevard, MS 3051, HLSIC Room 2073, Kansas City, Kansas, 66160, USA
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21
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Power GA, Dalton BH, Rice CL. Human neuromuscular structure and function in old age: A brief review. JOURNAL OF SPORT AND HEALTH SCIENCE 2013; 2:215-226. [PMID: 27011872 PMCID: PMC4801513 DOI: 10.1016/j.jshs.2013.07.001] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Natural adult aging is associated with many functional impairments of the human neuromuscular system. One of the more observable alterations is the loss of contractile muscle mass, termed sarcopenia. The loss of muscle mass occurs primarily due to a progressive loss of viable motor units, and accompanying atrophy of remaining muscle fibers. Not only does the loss of muscle mass contribute to impaired function in old age, but alterations in fiber type and myosin heavy chain isoform expression also contribute to weaker, slower, and less powerful contracting muscles. This review will focus on motor unit loss associated with natural adult aging, age-related fatigability, and the age-related differences in strength across contractile muscle actions.
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Affiliation(s)
- Geoffrey A. Power
- Human Performance Laboratory, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Brian H. Dalton
- School of Kinesiology, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Charles L. Rice
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario N6A 5B1, Canada
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada
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22
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Mierzejewska-Krzyżowska B, Bukowska D, Taborowska M, Celichowski J. Sex differences in the number and size of motoneurons innervating rat medial gastrocnemius muscle. Anat Histol Embryol 2013; 43:182-9. [PMID: 23617786 DOI: 10.1111/ahe.12060] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/20/2013] [Indexed: 11/29/2022]
Abstract
The sex differences in the number and morphometric parameters of motoneurons in motor nuclei are poorly known. The aim of this study was to determine the differences in the number and size of alpha and gamma motoneurons of the medial gastrocnemius (MG) muscle in male and female Wistar rats. Retrogradely labelled cell bodies of motoneurons of 6 months old animals were studied following a bath of the proximal stump of the transected MG nerve in a horseradish peroxidase solution. The number and soma diameters of male and female MG motoneurons were determined from serial microscopic images of sections. The weight of the brain and spinal cord was on average 17% higher in males than in females. The mean number of motoneurons was 13% higher in males than in females and amounted to 94 and 83 motoneurons, respectively. In each case, the average soma diameters and cross-section areas of motoneurons in motor nucleus were distributed bimodally: motoneurons smaller than 27.5 μm in diameter were recognized as gamma and greater ones as alpha motoneurons. In males, the motor nucleus contained on the average 66 alpha motoneurons, whereas in females, 56 alpha motoneurons, that is the mean number of alpha motoneurons was 17% higher in males. Moreover, the soma diameters of gamma and alpha motoneurons were significantly bigger in males and the difference amounted 9 and 6%, respectively. It is concluded that the number as well as size of alpha and size of gamma motoneurons in the MG motor nucleus are greater in males.
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Affiliation(s)
- B Mierzejewska-Krzyżowska
- Department of Anatomy, Biology and Health Sciences, Gorzów Wlkp., University School of Physical Education, Poznań, Poland
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Total daily activity measured with actigraphy and motor function in community-dwelling older persons with and without dementia. Alzheimer Dis Assoc Disord 2013; 26:238-45. [PMID: 21946015 DOI: 10.1097/wad.0b013e31822fc3cb] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Actigraphic measures of physical activity do not rely on participants' self-report and may be of particular importance for examining the health benefits of physical activity across the full spectrum of older individuals, especially those with dementia, a group in which loss of motor function is particularly salient. We tested whether actigraphy could be used to examine the relationship between total daily physical activity and motor function in community-dwelling older persons both with (n = 70) and without (n = 624) clinical dementia. Total daily activity was measured using actigraphy for a median of 9 (range: 2-16) days. All participants also underwent a structured examination, including 9 muscle strength and 9 motor performance measures summarized as a composite measure. In linear regression models controlling for age, sex, and education, total daily activity was associated with global motor scores (β = 0.13, SD = 0.01, P < 0.001). This association remained significant after adjusting for body composition, cognition, depressive symptoms, disability, vascular risk factors, and diseases (β = 0.07, SD = 0.01, P < 0.001). The association did not vary by dementia status (interaction P = 0.53). In persons without dementia, the association was independent of self-reported physical activity. Total daily activity was associated with both muscle strength (β = 0.10, SD = 0.02, P < 0.001) and motor performance (β = 0.16, SD = 0.02, P < 0.001). Actigraphy can be used in the community setting to provide objective measures of total daily activity that are associated with a broad range of motor performances. These associations did not vary by dementia status. Actigraphy may provide a means to more fully explicate the nature and course of motor impairment in old age.
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Power GA, Dalton BH, Behm DG, Doherty TJ, Vandervoort AA, Rice CL. Motor unit survival in lifelong runners is muscle dependent. Med Sci Sports Exerc 2012; 44:1235-42. [PMID: 22246219 DOI: 10.1249/mss.0b013e318249953c] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
UNLABELLED A contributing factor to the loss of muscle mass and strength with adult aging is the reduction in the number of functioning motor units (MUs). Recently, we reported that lifelong competitive runners (master runners = ~66 yr) had greater numbers of MUs in a leg muscle (tibialis anterior) than age-matched recreationally active controls. This suggested that long-term exposure to high levels of physical activity may limit the loss of MU numbers with adult aging. However, it is unknown if this finding is the result of long-term activation of the specifically exercised motoneuron pool (i.e., tibialis anterior) or an overall systemic neuroprotective effect of high levels of physical activity. PURPOSE The purpose was to estimate the number of functioning MUs (MUNEs) in the biceps brachii (an upper body muscle not directly loaded by running) of nine young (27 ± 5 yr) and nine old (70 ± 5 yr) men and nine lifelong competitive master runners (67 ± 4 yr). METHODS Decomposition-enhanced spike-triggered averaging was used to measure surface and intramuscular EMG signals during elbow flexion at 10% of maximum voluntary isometric contraction. RESULTS Derived MUNEs were lower in the biceps brachii of runners (185 ± 69 MUs) and old men (133 ± 69 MUs) than the young (354 ± 113 MUs), but the old and master runners were similar. CONCLUSIONS Although there were no significant differences in MUNE between both older groups in the biceps brachii muscle, with the number of subjects tested here, we cannot eliminate the possibility of some whole-body neuroprotective effect. However, when compared with the remote biceps muscle, a greater influence on age-related spinal motoneuron survival was found in a chronically activated MN pool specific to the exercised muscle.
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Affiliation(s)
- Geoffrey A Power
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada
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25
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Sions JM, Tyrell CM, Knarr BA, Jancosko A, Binder-Macleod SA. Age- and stroke-related skeletal muscle changes: a review for the geriatric clinician. J Geriatr Phys Ther 2012; 35:155-61. [PMID: 22107952 PMCID: PMC3290755 DOI: 10.1519/jpt.0b013e318236db92] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Independently, aging and stroke each have a significant negative impact on skeletal muscle, but the potential cumulative effects of aging and stroke have not been explored. Optimal interventions for individuals post stroke may include those that specifically target skeletal muscle. Addressing changes in muscles may minimize activity limitations and enhance participation post stroke. This article reviews the impact of aging and stroke on muscle morphology and composition, including fiber atrophy, reductions in muscle cross-sectional area, changes in muscle fiber distributions, and increases in intramuscular fat. Relationships between changes in muscle structure, muscle function, and physical mobility are reviewed. Clinical recommendations that preserve and enhance skeletal muscle in the aging adult and individuals post stroke are discussed. Future research directions that include systematic comparison of the differences in skeletal muscle between younger and older adults who have sustained a stroke are suggested.
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Affiliation(s)
- Jaclyn Megan Sions
- Biomechanics and Movement Science Program, University of Delaware, Newark, USA.
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26
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POWER GEOFFREYA, DALTON BRIANH, BEHM DAVIDG, VANDERVOORT ANTHONYA, DOHERTY TIMOTHYJ, RICE CHARLESL. Motor Unit Number Estimates in Masters Runners. Med Sci Sports Exerc 2010; 42:1644-50. [DOI: 10.1249/mss.0b013e3181d6f9e9] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Deschenes MR, Roby MA, Eason MK, Harris MB. Remodeling of the neuromuscular junction precedes sarcopenia related alterations in myofibers. Exp Gerontol 2010; 45:389-93. [PMID: 20226849 DOI: 10.1016/j.exger.2010.03.007] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 02/08/2010] [Accepted: 03/05/2010] [Indexed: 11/27/2022]
Abstract
Several mechanisms contributing to the etiology of sarcopenia (age-related loss of muscle size) have been postulated. One of these attributes the loss of muscle mass to a preceding age-related denervation of myofibers. The aim of this study was to determine if signs of denervation were apparent at the neuromuscular junction (NMJ) before fiber atrophy, or fiber type conversion could be documented, and to reveal if a muscle's activity level impacts its sensitivity to age-related denervation. Plantaris and soleus muscles were obtained from young adult (10 months) and early aged (21 months) rats. Pre- and post-synaptic NMJ morphology was quantified with cytofluorescent staining of nerve terminal branches and endplate regions, respectively. Myofiber profiles (fiber size and fiber type composition) were assessed with histochemical procedures. Results show that in the lightly recruited plantaris, significant (P<0.05) signs of denervation were noted in aged rats, while the same muscles displayed no change in myofiber profile. In the heavily recruited soleus, however, there was little evidence of denervation, and again no alterations in myofiber profile. These results indicate that age-related denervation occurs before myofiber atrophy, and that high amounts of neuromuscular activity may delay the onset of age-related denervation and sarcopenia.
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Affiliation(s)
- Michael R Deschenes
- Department of Kinesiology and Health Sciences, The College of William & Mary, Williamsburg, VA 23187-8795, USA.
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28
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Dalton BH, Harwood B, Davidson AW, Rice CL. Triceps surae contractile properties and firing rates in the soleus of young and old men. J Appl Physiol (1985) 2009; 107:1781-8. [PMID: 19797692 DOI: 10.1152/japplphysiol.00464.2009] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mean maximal motor unit firing rates (MUFRs) of the human soleus are lower (5-20 Hz) than other limb muscles (20-50 Hz) during brief sustained contractions. With healthy adult aging, maximal MUFRs are 20-40% lower and twitch contractile speed of lower limb muscles are 10-40% slower compared with young adults. However, it is unknown whether the inherently low maximal MUFRs for the soleus are further reduced with aging in association with age-related slowing in contractile properties. The purpose of the present study was to compare the changes in triceps surae contractile properties and MUFRs of the soleus throughout a variety of contraction intensities in six old ( approximately 75 yr old) and six young ( approximately 24 yr old) men. Neuromuscular measures were collected from the soleus and triceps surae during repeated sessions (2-6 sessions). Populations of single MUFR trains were recorded from the soleus with tungsten microelectrodes during separate sustained 6- to 10-s isometric contractions of varying intensities [25%, 50%, 75%, and 100% maximal voluntary isometric contraction (MVC)]. The old men had weaker triceps surae strength (MVC; 35% lower) and slower contractile properties (contraction duration; 20% longer) than the young men. However, there was no difference in average MUFRs of the soleus at 75% and 100% MVC ( approximately 14.5 Hz and approximately 16.5 Hz, respectively). At 25% and 50% MVC, average rates were 10% and 20% lower in the old men compared with young, respectively. Despite a significant slowing in triceps surae contraction duration, there was no age-related change in MUFRs recorded at high contractile intensities in the soleus. Thus the relationship between the whole muscle contractile properties and MUFRs found in other muscle groups may not exist between the triceps surae and soleus and may be muscle dependent.
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Affiliation(s)
- Brian H Dalton
- Canadian Centre for Activity and Aging, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
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Dalton BH, McNeil CJ, Doherty TJ, Rice CL. Age-related reductions in the estimated numbers of motor units are minimal in the human soleus. Muscle Nerve 2008; 38:1108-15. [DOI: 10.1002/mus.20984] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Suzuki I, Kitagawa J, Noma N, Tsuboi Y, Kondo M, Honda K, Kanda K, Hasegawa M, Saito K, Okamoto R, Iwata K. Attenuation of naloxone-induced Vc pERK hyper-expression following capsaicin stimulation of the face in aged rat. Neurosci Lett 2008; 442:39-43. [DOI: 10.1016/j.neulet.2008.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 06/28/2008] [Accepted: 07/01/2008] [Indexed: 11/28/2022]
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Ilha J, Araujo RT, Malysz T, Hermel EES, Rigon P, Xavier LL, Achaval M. Endurance and resistance exercise training programs elicit specific effects on sciatic nerve regeneration after experimental traumatic lesion in rats. Neurorehabil Neural Repair 2008; 22:355-66. [PMID: 18326889 DOI: 10.1177/1545968307313502] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To evaluate the effects of endurance, resistance, and a combination of both types of exercise training on hindlimb motor function recovery and nerve regeneration after experimental sciatic nerve lesion in rats. METHODS Sciatic nerve crush was performed on adult male rats, and after 2 weeks of the nerve lesion, the animals were submitted to endurance, resistance, and a combination of endurance-resistance training programs for 5 weeks. Over the training period, functional recovery was monitored weekly using the Sciatic Functional Index (SFI) and histological and morphometric nerve analyses were used to assess the nerve regeneration at the end of the trainings. RESULTS The SFI values of the endurance-trained group reached the control values from the first posttraining week and were significantly better than both the resistance-trained group at the first, second, and third posttraining weeks and the concurrent training group at the first posttraining week. At the distal portion of the regenerating sciatic nerve, the endurance-trained group showed a greater degree of the myelinated fiber maturation than the sedentary, resistance-trained, and concurrent training groups. Furthermore, the endurance-trained group showed a smaller percentage area of endoneurial connective tissue and a greater percentage area of myelinated fibers than the sedentary group. CONCLUSION These data provide evidence that endurance training improves sciatic nerve regeneration after an experimental traumatic injury and that resistance training or the combination of 2 strategies may delay functional recovery and do not alter sciatic nerve fiber regeneration.
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Affiliation(s)
- Jocemar Ilha
- Programa de Pós-Graduação em Neurociências, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, RS, Brazil
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Buchman AS, Boyle PA, Wilson RS, Bienias JL, Bennett DA. Physical activity and motor decline in older persons. Muscle Nerve 2007; 35:354-62. [PMID: 17143881 DOI: 10.1002/mus.20702] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We tested the hypothesis that physical activity modifies the course of age-related motor decline. More than 850 older participants of the Rush Memory and Aging Project underwent baseline assessment of physical activity and annual motor testing for up to 8 years. Nine strength measures and nine motor performance measures were summarized into composite measures of motor function. In generalized estimating equation models, global motor function declined during follow-up (estimate, -0.072; SE, 0.008; P < 0.001). Each additional hour of physical activity at baseline was associated with about a 5% decrease in the rate of global motor function decline (estimate, 0.004; SE, 0.001; P = 0.007). Secondary analyses suggested that the association of physical activity with motor decline was mostly due to the effect of physical activity on the rate of motor performance decline. Thus, higher levels of physical activity are associated with a slower rate of motor decline in older persons.
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Affiliation(s)
- A S Buchman
- Rush Alzheimer's Disease Center, Rush University Medical Center, Armour Academic Facility, Suite 1038, 600 South Paulina Street, Chicago, Illinois 60612, USA.
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Aging thyroarytenoid and limb skeletal muscle: lessons in contrast. J Voice 2007; 22:430-50. [PMID: 17241767 DOI: 10.1016/j.jvoice.2006.11.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Accepted: 11/29/2006] [Indexed: 01/07/2023]
Abstract
Voice production is vital throughout life because it allows for the communication of basic needs as well as the pursuit and enjoyment of social encounters. Unfortunately, for many older individuals the ability to produce voice is altered. Structural and functional declines in the neuromuscular system occur with aging and likely contribute to the modification of voice. One specific target of the aging process is the thyroarytenoid (TA) muscle, the primary muscle of voice production. The objectives of this overview article are to (1) share current findings related to the aging of limb skeletal muscle, (2) identify age-related morphological and physiological features of TA muscle, (3) compare and contrast age-related changes in TA with those in limb skeletal muscle, and (4) describe therapies for reversing sarcopenia in limb muscle and consider the applicability of these therapies for addressing vocal fold atrophy and age-related voice changes. The article shares current knowledge from the basic sciences related to skeletal muscle aging and compares/contrasts typical muscle aging to TA aging. Current evidence suggests that (1) the TA muscle undergoes notable remodeling with age, (2) aging of the TA is multifactorial, resulting from a myriad of neurologic, metabolic, and hormonal changes, many of which are distinct from the age-related processes of typical limb skeletal muscle, (3) investigation of the aging of the TA and its role in the aging of voice is in its infancy, and (4) potential behavioral and nonbehavioral therapies for reversing aging of the TA must be further examined.
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Liebermann DG, Buchman AS, Franks IM. Enhancement of motor rehabilitation through the use of information technologies. Clin Biomech (Bristol, Avon) 2006; 21:8-20. [PMID: 16198463 DOI: 10.1016/j.clinbiomech.2005.08.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Accepted: 08/10/2005] [Indexed: 02/07/2023]
Abstract
The recent development of information technologies has dramatically increased the tools available for facilitating motor rehabilitation. This review focuses on technologies which can be used to augment movement-related information both to patients as well as to their therapists. A brief outline of the motor system emphasizes the role of spinal motor neurons in the control of voluntary movement and rehabilitative efforts. Technologies which induce passive motion to stimulate spinal motor output as well as technologies that stimulate active voluntary movements are discussed. Finally, we review technologies and notational methods that can be used to quantify and assess the quality of movement for evaluating the efficacy of motor rehabilitation efforts. We conclude that stronger evidence is necessary to determine the applicability of the wide range of technologies now available to clinical rehabilitation efforts.
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Affiliation(s)
- Dario G Liebermann
- Department of Physical Therapy, Sackler Faculty of Medicine, University of Tel Aviv, Israel.
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35
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Abstract
Functional and structural decline in the neuromuscular system with aging has been recognized as a cause of impairment in physical performance and loss of independence in the elderly. Alterations in spinal cord motor neurones and at the neuromuscular junction have been identified as evidence of denervation in skeletal muscles from aging mammals, including humans. However, the reciprocal influences of neurones on gene expression in muscle and of muscle on age-related neurodegeneration are poorly understood, and, as a result, interventions aimed at delaying or preventing degeneration of the neural component in aging muscle have been largely unsuccessful. The present article discusses the evidence for neural influence on age-related impairments of skeletal muscle, including a role in excitation-contraction uncoupling. The role of nerves in regulating the trophic actions of insulin-like growth factor-1 (IGF-1) and other neurotrophic factors is considered as a novel influence on the effects of aging on the neuromuscular junction. A better understanding of nerve-muscle interactions will allow for more rational interventions in the aging neuromuscular system.
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Affiliation(s)
- Osvaldo Delbono
- Department of Physiology and Pharmacology, Neuroscience Program, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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Kanda K. Effects of food restriction on motoneuronal loss with advancing age in the rat. Microsc Res Tech 2002; 59:301-5. [PMID: 12424792 DOI: 10.1002/jemt.10208] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The effects of life-long food restriction on motoneuronal cell death with advancing age was studied in male Fischer rats, which had access to food only 3 days a week after weaning (FR rats). Motoneurons innervating the medial gastrocnemius muscle were labeled with retrogradely transported HRP. The number of labeled motoneurons in FR rats and rats fed ad libitum (AL rats) was similar at the age of 16 months (131.8 +/- 1.7 for FR rats vs. 133.8 +/- 4.5 for AL rats). However, at 28 months of age, AL rats had less labeled motoneurons compared to FR rats (117.0 +/- 2.4 for FR rats vs. 124.3 +/- 7.0 for FR rats). The number of type I muscle fibers in the medial gastrocnemius muscle increased significantly in AL rats during the period from 16 to 28 months of age, which might reflect motor unit reorganization following retraction of axons and/or death of innervating motoneurons. FR rats did not show statistically significant alteration. These findings were also true for the data compiled from several different experiments including those conducted for primarily different purposes in our laboratory. The results suggest that life-long food restriction retards motoneuronal cell death occurring with advancing age.
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Affiliation(s)
- Kenro Kanda
- Department of Central Nervous System, Tokyo Metropolitan Institute of Gerontology, Tokyo 173-0015, Japan.
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Latorre E, Morán M, Aragonés MD, Saborido A, Fernández I, Delgado J, Catalán RE, Megías A. Exercise training-induced changes in sensitivity to endothelin-1 and aortic and cerebellum lipid profile in rats. Lipids 2002; 37:43-52. [PMID: 11876262 DOI: 10.1007/s11745-002-0862-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The purpose of this work was to study whether exercise training induces changes in the lipid profile of rat aorta and nervous system and in the in vitro intrinsic responsiveness of these tissues to endothel in-1 (ET-1) treatment. The exercise program performed successfully produced the characteristic metabolic alterations of the trained state. Exercise training induced a large and significant increase in the levels of both aortic ethanolamine plasmalogens (PlasEtn) and glucosylceramides. In contrast, a decrease of aortic ceramide and cholesterol levels was evoked by exercise training. ET-1 increased PlasEtn content only in sedentary animals. An exercise-induced increase in cerebellum levels of ceramides and ceramide monohexosides was found. The cerebellum ceramide content was increased by ET-1 more noticeably in sedentary rats than in trained animals. In contrast, cerebral cortex was observed to be largely insensitive to both exercise training and ET-1 treatment. It was concluded that exercise training (i) induces changes in both vascular and cerebellar lipid profiles, the former being much more pronounced than the latter, and (ii) diminishes the aortic and cerebellar sensitivity to ET-1 action.
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Affiliation(s)
- Eduardo Latorre
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Spain
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Hirofuji C, Ishihara A, Roy RR, Itoh K, Itoh M, Edgerton VR, Katsuta S. SDH activity and cell size of tibialis anterior motoneurons and muscle fibers in SAMP6. Neuroreport 2000; 11:823-8. [PMID: 10757527 DOI: 10.1097/00001756-200003200-00033] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Succinate dehydrogenase (SDH) activities and cross-sectional areas (CSAs) of tibialis anterior motoneurons and muscle fibers were determined in 20-, 40-, and 60-week-old male senescence-accelerated mice (SAMP6), and compared with those in age-matched accelerated-senescence resistant mice (SAMR1). The mean CSA of motoneurons in SAMP6 decreased at 60 weeks, primarily due to a selective loss of large (>400 microm2) motoneurons. The mean SDH activity of motoneurons with CSAs between 100 and 400 microm2 decreased in SAMP6, but not SAMR1, at 60 weeks. The mean muscle fiber SDH activities and CSAs in SAMP6 decreased at 60 weeks. There were no differences in the mean SDH activity or CSA of motoneurons or muscle fibers among 20-, 40-, and 60-week-old SAMR1. These results demonstrate that mice which have been shown to have a variety of accelerated-senescent features also have an earlier onset of age-related changes in motoneurons and the muscle fibers that they innervate when compared with age-matched accelerated-senescence resistant mice.
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Affiliation(s)
- C Hirofuji
- Laboratory of Neurochemistry, Faculty of Integrated Human Studies, Kyoto University, Japan
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