Effects of Ageing on the Motor Unit: A Brief Review

Doherty, Timothy J.; Vandervoort, Anthony A.; Brown, William F.

doi:10.1139/h93-029

Cited by 296 publications

(212 citation statements)

References 102 publications

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“…The high frequency of type II fibres in this subject may be related to a special usage of the palate muscles or be a consequence of an ageing process. Previous morphological and electrophysiological investigations have reported that a shift in fibre type proportions occurs during ageing, probably due to degeneration of motor neurons, both in limb (Gollnick et al 1972 ;Larsson et al 1978 ;Aniansson, 1981 ;Larsson, 1983 ;Doherty et al 1993 ;Larsson & Ansved, 1995 ;Trappe et al 1995) and masticatory (Monemi et al 1998) muscles. In limb muscles the atrophy and fibre loss preferentially affect the fast type II fibre population and particularly the type IIB fibres, whereas in one of the human jaw muscles, masseter, the muscle fibre degeneration preferentially affects type I fibres.…”

Section: Fibre Type Compositionmentioning

confidence: 95%

Characterisation of human soft palate muscles with respect to fibre types, myosins and capillary supply

Stål

Lindman

2000

Journal of Anatomy

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Four human soft palate muscles, and palatopharyngeus, the uvula, the levator and tensor veli palatini were examined using enzyme-histochemical, immunohistochemical and biochemical methods and compared with human limb and facial muscles. Our results showed that each palate muscle had a distinct morphological identity and that they generally shared more similarities with facial than limb muscles. The palatopharyngeus and uvula muscles contained 2 of the highest proportions of type II fibres ever reported for human muscles. In contrast, the levator and tensor veli palatini muscles contained predominantly type I fibres. A fetal myosin heavy chain isoform (MyHC), not usually found in normal adult limb muscles, was present in a small number of fibres in all palate muscles. The mean muscle fibre diameter was smaller than in limb muscles and the individual and intramuscular variability in diameter and shape was considerable. All palate muscles had a high capillary density and an unusually high mitochondrial enzyme activity in the type II fibres, in comparison with limb muscles. No ordinary muscle spindles were observed. The fibre type and MyHC composition indicate that the palatopharyngeus and uvula muscles are functionally involved in quick movements whereas the levator and tensor veli palatini muscles perform slower and more continuous contractions. The high aerobic capacity and the rich capillarisation suggest that the palate muscles are relatively fatigue resistant. Absence of ordinary muscle spindles indicates a special proprioceptive control system. The special morphology of the palate muscles may be partly related to the unique anatomy with only one skeletal insertion, a feature consistent with muscle work at low load and tension and which may influence the cytoarchitecture of these muscles. Other important factors determining the special morphological characteristics might be specific functional requirements, distinct embryological origin and phylogenetic factors.

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Section: Fibre Type Compositionmentioning

confidence: 95%

Characterisation of human soft palate muscles with respect to fibre types, myosins and capillary supply

Stål

Lindman

2000

Journal of Anatomy

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“…Analyses from human muscle biopsy samples have consistently demonstrated that type II fibers are more susceptible to aging-related atrophy when compared to type I fibers [3,50]. Doherty [51] reported that the loss of type II fiber area was 20-50%, whereas type I area loss was much less (1-25%).…”

Section: Type II Muscle Fibers and Agingmentioning

confidence: 99%

Death receptor-associated pro-apoptotic signaling in aged skeletal muscle

2006

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Tumor necrosis factor-alpha (TNF-α) is elevated in the serum as a result of aging and it promotes pro-apoptotic signaling upon binding to the type I TNF receptor. It is not known if activation of this apoptotic pathway contributes to the well-documented age-associated decline in muscle mass (i.e. sarcopenia). We tested the hypothesis that skeletal muscles from aged rodents would exhibit elevations in markers involved in the extrinsic apoptotic pathway when compared to muscles from young adult rodents, thereby contributing to an increased incidence of nuclear apoptosis in these muscles. The plantaris (fast) and soleus (slow) muscles were studied in young adult (5-7 mo, n = 8) and aged (33 mo, n = 8) Fischer 344 × Brown Norway rats. Muscles from aged rats were significantly smaller while exhibiting a greater incidence of apoptosis. Furthermore, muscles from aged rats had higher type I TNF receptor and Fas associated death domain protein (FADD) mRNA, protein contents for FADD, BCL-2 Interacting Domain (Bid), FLICE-inhibitory protein (FLIP), and enzymatic activities of caspase-8 and caspase-3 than muscles from young adult rats. Significant correlations were observed in the plantaris muscle between caspase activity and muscle weight and the apoptotic index, while similar relationships were not found in the soleus. These data demonstrate that pro-apoptotic signaling downstream of the TNF receptor is active in aged muscles. Furthermore, our data extend the previous demonstration that type II fibers are preferentially affected by aging and support the hypothesis that type II fiber containing skeletal muscles may be more susceptible to muscle mass loses via the extrinsic apoptotic pathway.

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“…(21) It is well established that the human aging process is associated with a signiicant decline in neuromuscular function and performance. (22)(23)(24) Characteristic of this decline is the inevitable reduction in skeletal muscle mass and associated loss of strength, so-called sarcopenia, that occurs even in the absence of disease speciically affecting the neuromuscular system. Strength decline in upper and lower limb muscles is typically 20-40% by the 7 th decade and greater in older adults.…”

Section: Indones Biomed J 2015; 7(2): 73-86mentioning

confidence: 99%

Molecular Regulation and Rejuvenation of Muscle Stem (Satellite) Cell Aging

2015

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BACKGROUND: Age-related muscle loss leads to lack of muscle strength, resulting in reduced posture and mobility and an increased risk of falls, all of which contribute to a decrease in quality of life. Skeletal muscle regeneration is a complex process, which is not yet completely understood.CONTENT: Skeletal muscle undergoes a progressive agerelated loss in mass and function. Preservation of muscle mass depends in part on satellite cells, the resident stem cells of skeletal muscle. Reduced satellite cell function may contribute to the age-associated decrease in muscle mass. Recent studies have delineated that the aging process in organ stem cells is largely caused by age-speciic changes in the differentiated niches, and that regenerative outcomes often depend on the age of the niche, rather than on stem cell age. It is likely that epigenetic states will be better deine such key satellite cell features as prolonged quiescence and lineage idelity. It is also likely that DNA and histone modiications will underlie many of the changes in aged satellite cells that account for age-related declines in functionality and rejuvenation through exposure to the systemic environment. SUMMARY:Skeletal muscle aging results in a gradual loss of skeletal muscle mass, skeletal muscle function and regenerative capacity, which can lead to sarcopenia and increased mortality. Although the mechanisms underlying sarcopenia remain unclear, the skeletal muscle stem cell, or satellite cell, is required for muscle regeneration. Decreased muscle stem cell function in aging has long been shown to depend on altered environmental cues, whereas the contribution of intrinsic mechanisms remained less clear. Signals in the aged niche were shown to cause permanent defects in the ability of satellite cells to return to quiescence, ultimately also impairing the maintenance of self-renewing satellite cells. Therefore, only anti-aging strategies taking both factors, the stem cell niche and the stem cells per se, into consideration may ultimately be successful.

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Effects of Ageing on the Motor Unit: A Brief Review

Cited by 296 publications

References 102 publications

Characterisation of human soft palate muscles with respect to fibre types, myosins and capillary supply

Characterisation of human soft palate muscles with respect to fibre types, myosins and capillary supply

Death receptor-associated pro-apoptotic signaling in aged skeletal muscle

Molecular Regulation and Rejuvenation of Muscle Stem (Satellite) Cell Aging

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