Is resistance of a muscle to fatigue controlled by its motoneurones?

Edgerton, V. Reggie; Goslow, G. E.; Rasmussen, S. A.; Spector, S. A.

doi:10.1038/285589a0

Cited by 36 publications

(11 citation statements)

References 14 publications

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“…Six months after transection, the soleus mass and force potential are significantly decreased, the maximum rate of shortening is increased, and there is an increase in the percenta e of dark ATPase, presumably in the glycolytic potential occur whether the transection is performed at an early age of devel~p m e n t~, '~ or at an adult ~t a g e .~~~~~ Further, after 4 months of spinal transection in the adult cat, there is an increase in the number of fast fatigue resistant motor units in the so leu^.^^^^ Another consistent finding among studies using cross-reinnervation, 7,11,12 spinali~ation,~*'~ hindlimb suspension, 15,17,19,37,45 and s p a~e f l i g h t~~,~~.~ as models of altered use, is that the oxidative pofast, fiber^.^'^,'^. 8 2s39 In addition, the adaptations tential and/or resistance to fatigue of the soleus is sustained after prolonged periods of reduced neurornuscular activity.…”

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confidence: 89%

Enzyme and size profiles in chronically inactive cat soleus muscle fibers

et al. 1992

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Spinal isolation (SI), i.e., the isolation of the lumbar spinal cord via a rostral and a caudal cord transection and bilateral dorsal rhizotomy, was used to determine the effects of chronic (6 months) inactivity on the size and metabolic properties of fibers in the cat soleus. Fibers were classified as dark or light, based on their staining reactions to myosin ATPase, alkaline preincubation, and immunohistochemically as expressing fast and/or slow myosin heavy chains (MHC). Succinate dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPD) activities were assessed histochemically. Following SI, both the light and the dark ATPase fibers in the SI cats were significantly smaller than the light ATPase fibers in the controls. Normally 100% of the fibers were light ATPase and reacted exclusively with the slow antibody. After SI, approximately 45% of the fibers were dark ATPase fibers, many reacting with both fast and slow MHC antibodies. The total amount and concentration of GPD were higher in the light and dark ATPase fibers in SI compared with light ATPase fibers in controls. In contrast, although the total amount of SDH per fiber was decreased, reflecting the decrease in fiber size, the mean SDH concentration per fiber was unchanged following SI. These data indicate that there is a close coordination in the regulation of GPD activity and the type of myosin. SDH activity, on the other hand, appears to be resistant to decreased levels of activity and unloading, i.e., there seems to be a minimum level of oxidative potential in the soleus that is independent of activity level. Fiber sizes, however, are very sensitive to less-than-normal amounts of neuromuscular activity and/or loading.

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confidence: 89%

Enzyme and size profiles in chronically inactive cat soleus muscle fibers

et al. 1992

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“…These data suggest, then, that the axons of slow twitch, fatigue resistant (s.) and f.r. motoneurones are selectively favoured by the soleus muscle in the process of reinnervation or that the particular phenotypic expression offatigue resistance, which is related to mitochondrial content, is controlled primarily within the muscle and not by the motoneurone (Edgerton, Goslow, Rasmussen & Spector, 1980a). …”

Section: Discussionmentioning

confidence: 99%

Histochemical and physiological properties of cat motor units after self‐ and cross‐reinnervation

Chan

Edgerton

Goslow

et al. 1982

The Journal of Physiology

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SUMMARY1. This report describes selected histochemical and physiological properties of the motor units of adult cat soleus muscle approximately one year after self-and cross-reinnervation with the nerve of the heterogenous flexor hallucis longus (f.h.l.). Self-reinnervated f.h.l. motor units are also considered. Whole muscles were tested for fibre reaction to alkaline pre-incubated ATPase, cz-glycerophosphate dehydrogenase (a-GPD) and reduced nicotinamide adenine dinucleotide diaphorase (NADH-D). Motor units were isolated and studied by splitting the ventral root in acute preparations.2. The histochemical fibre type profile in the self-reinnervated muscle was comparable to normal muscle as was mean twitch contraction time, twitch-tetanus ratio and fatigue index. The mean tetanic tension of the soleus self-and cross-reinnervated motor units appeared close to a normal soleus whereas the mean tetanic tension of the f.h.l. self-reinnervated units was significantly less than a normal f.h.l.3. An average of 14 % of the fibres of the soleus cross-reinnervated muscles had high ATPase and a c-GPD staining intensity in contrast to normal and selfreinnervated soleus in which such fibres are absent. Thus alkaline lability of myofibrillar ATPase increased in some fibres of what was originally a homogeneous population. The small increase in the number of densely staining fibres for ATPase at an alkaline pH (14 %) was associated with a 73 % decrease in (mean) contraction time (41 + 11 ms) of the thirty-three cross-reinnervated muscle units studied, with no unit's contraction time greater than 60 ms. Mean contraction times for the self-reinnervated soleus and f.h.l. muscles were 78 + 31 ms and 27 + 8 ms respectively.4. All fibres of the soleus cross-reinnervated muscles showed intense reaction to NADH-D, as was true of self-reinnervated soleus. This staining pattern is typical of normal soleus. In concordance, these motor units consistently demonstrated a high resistance to fatigue when stimulated for a four-minute period.5. These results suggest that in the adult self-and cross-reinnervated soleus muscle,

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“…However, even though each fibre presumably receives the same amount and type of activation, muscle fibre heterogeneity is still maintained. Moreover, although muscle fibres from a fast muscle become slower when reinnervated by a slow nerve, the biochemical and histochemical conversion is not complete (Buller et al 1960;Edgerton, Goslow, Rasmussen & Spector, 1980;Bagust, Lewis & Westerman, 1981), i.e. the fibres of a cross-reinnervated fast muscle are not identical to those found in a slow muscle.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and morphological properties of chronically inactive cat tibialis anterior motor units.

Pierotti

Roy

Bodine

et al. 1991

The Journal of Physiology

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SUMMARY1. The lumbar spinal cord was functionally isolated in ten cats by cord transection at the junctions of segments T12-T13 and L7-S1 and cutting bilaterally all dorsal roots between the two transections. Two 24 h EMG recording sessions were used to verify that muscles in the lower limb were virtually electrically silent. The cats were maintained in excellent health for 6 months.2. Six months after spinal cord isolation, an acute experiment was performed to isolate a single motor unit from the tibialis anterior of each hindlimb using ventral root splitting techniques. Each motor unit was characterized physiologically as either fast fatigable (FF, n = 11), fast fatigue resistant (FR, n = 4), fast intermediate (Fl, n = 2), or slow (S, n = 1), and repetitively stimulated to deplete the motor unit of its glycogen.3. Maximum tensions of the fast motor units were lower than mean maximum tensions of control, whereas the S motor unit remained within the range observed in controls. In general, the isometric contractile properties, as well as fatigability, were within the ranges for each of the motor unit types in control cats. The mean fibre cross-sectional areas of the fibres within the FR and FF motor units were 40 and 50 % smaller than control, while the mean fibre size of the fibres within the S motor unit was similar to control.4. Innervation ratios and specific tensions for all experimental motor units were within the ranges of those reported for tibialis anterior motor units in control cats. Thus, it appears that the decrease in maximum tension of the fast motor units was primarily related to a reduction in fibre size.5. The spatial distribution of the fibres within fast motor units of a spinally isolated cat, as measured by interfibre distances of the motor unit fibres, was similar to that reported for control tibialis anterior motor units.6. These data suggest that factors independent of activity play a prominent, if not dominant, role in maintaining the complement of motor unit types typical of adult cat muscles. In addition, normal innervation patterns appear to be maintained in the absence of activity. § To whom reprint requests should be sent. MS 8916 D. J. PIEROTTI AND OTHERS

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Is resistance of a muscle to fatigue controlled by its motoneurones?

Cited by 36 publications

References 14 publications

Enzyme and size profiles in chronically inactive cat soleus muscle fibers

Enzyme and size profiles in chronically inactive cat soleus muscle fibers

Histochemical and physiological properties of cat motor units after self‐ and cross‐reinnervation

Mechanical and morphological properties of chronically inactive cat tibialis anterior motor units.

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