Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Physiological, enzyme-histochemical, biochemical and morphometrical properties of fast-twitch single motor units were compared between young (3-6 months) and old rats (20-24 months) using the glycogen depletion technique. Monoclonal antibodies (mAbs) were used to identify the myosin heavy chain (MHC) composition in the muscle fibres of the motor unit (motor unit fibres) in order to facilitate correlative physiological, histochemical, biochemical and morphometrical studies. 2. Earlier observations on effects of age on contractile properties of fast-twitch motor units were confirmed and extended. That is, the duration of the isometric twitch, and the twitch and tetanus forces, were increased. Further, motor unit fibres were rearranged, occupying a larger territory and displaying an increased innervation ratio in old age, indicating a denervation-reinnervation process. 3. Motor units with muscle fibres expressing the novel IIX myosin heavy chain (MHC) were observed in both young and old animals, and they constituted the predominant motor unity type identified in the old animals. In contrast to the type IIX MHC motor units in the young animals, the type IIX MHC units in old age often contained muscle fibres which expressed either the type IIA or type IIB MHC, although type IIX MHC fibres were in the majority (so called 'IIX' MHC motor units), but motor units containing all these three fibre types were never observed. There were also single fibres co-expressing IIX and IIB MHCs in old age. 4. In the young animals the IIX MHC motor units had a higher (P less than 0.001) resistance to fatigue (fatigue ratio 0.45 +/- 0.11) than the type IIB MHC units (0.03 +/- 0.05), a succinate dehydrogenase (SDH) activity (0.62 +/- .007) intermediate (P less than 0.001) between those of type IIA muscle fibres classified according to myofibrillar ATPase activity after acid pre-incubation, i.e. type IIA ATPase, (0.84 +/- 0.13) and type IIB MHC motor unit fibres (0.20 +/- 0.04), and cross-sectional fibre areas (1650 +/- 320 microns 2) which were similar to those of type IIA ATPase muscle fibres (1460 +/- 150 microns 2) but smaller (P less than 0.001) than type IIB MHC motor unit fibres (4650 +/- 1180 microns 2).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effects of age on physiological, immunohistochemical and biochemical properties of fast-twitch single motor units in the rat. 166 38

Skeletal muscle has an inherent plasticity which allows it to undergo fibre type transformation when induced by a specific stimulus. Electrical stimulation has been used here to induce transformation of a predominantly fast type skeletal muscle towards a slow, more fatigue-resistant phenotype, which is more suitable for use in long-term cardiac assistance. Muscle samples from animals electrically stimulated for periods up to 6 months have been analysed by electrophoresis for myosin heavy chain (MHC) and myosin light chain (MLC) fast and slow isoforms. Densitometry and computer analysis have been used to determine the pattern of transformation of the different myosin subunits over this time period. MHC and MLC 2 fast to slow isoform switching preceded that of the alkali light chains (MLC1 and MLC3). After 3 months of stimulation the MHC slow isoform was found to have doubled in concentration relative to the unstimulated control muscle and by 4 months accounted for almost 50% of the total MHC content. The slow isoform accounted for 75% of the MLC2 after 4 months of stimulation. The protein products of mRNA isolated from stimulated muscle samples, translated in vitro and separated by electrophoresis, showed that transformation at the mRNA level preceded that at the protein level. By 2-4 weeks of stimulation MLC2 slow isoform mRNA represented over 60% of the total MLC2 mRNA population. An understanding of the molecular structure of muscle during transformation provides insight into its haemodynamic performance in cardiac assistance.
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PMID:Electrophoretic and computer analysis of skeletal muscle used for cardiac assistance. 171 52

Determinations of fatigue ratio, twitch and tetanus tension, and contraction and half-relaxation times of the isometric twitch were made in 21 single fast-twitch motor units from the rat tibialis anterior muscle. Single motor units were functionally isolated by microdissection of the ventral root, and the glycogen depletion technique was used to demonstrate the muscle fibers in the unit. Morphological and immuno- and enzyme-histochemical methods were applied to serial muscle cross sections to characterize the muscle fibers in the unit. Three of the units had muscle fibers of the IIa type according to staining both for myofibrillar adenosinetriphosphatase after acid preincubation and with the use of monoclonal antibodies specific for myosin heavy chains (MHCs), i.e., the IIa-MHC isoform. The other 18 units were of the IIb type according to enzyme-histochemistry, but immunohistochemistry showed that in six of these units the muscle fibers exhibited the novel type IIx-MHC isoform and in the other 12 units the IIb-MHC isoform. It was found that the IIx motor units have contraction and half-relaxation times similar to those of types IIa and IIb units but have morphological, physiological, and biochemical properties that distinguish them from the latter two types.
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PMID:MHC composition and enzyme-histochemical and physiological properties of a novel fast-twitch motor unit type. 185 63

This study was designed to determine the effects of reduced neuromuscular activity on the expression of proteins associated with contractile and metabolic functions and the size of single muscle fibers in the cat soleus. Adult cats were spinalized (Sp) at T12-T13 and maintained in a healthy condition for 6 months. Some of the cats were trained to weight-support (Sp-WS) for 30 minutes per day beginning one month posttransection. Cross-sectional area (CSA), succinate dehydrogenase (SDH), alpha-glycerophosphate dehydrogenase (GPD), and myofibrillar adenosine triphosphatase (ATPase) activities were determined in a population of single fibers identified in frozen serial cross-sections. Each fiber was categorized as either light or dark based on its staining density for qualitative myosin ATPase, alkaline preincubation (pH 8.75). The Sp (45%) and Sp-WS (31%) groups had significantly higher percentages of dark ATPase fibers than control (less than 1%). All dark ATPase fibers were shown to react positively for a fast myosin heavy chain monoclonal antibody, while some of these fibers showed a reaction to both fast and slow myosin heavy chain antibodies. Overall mean fiber CSA were significantly smaller (approximately 25%) than control in both Sp groups. In the Sp-WS, but not the Sp cats, the dark fibers were larger than the light fibers (P less than 0.05), suggesting a preferential effect of postural training on the ATPase converted fibers. There were no significant differences among the three groups in any of the mean enzyme activities for either ATPase type fiber. However, there was a general tendency for the Sp cats to have elevated GPD and ATP activities per muscle; this appeared to be directly related to the percentage of fibers staining darkly for myosin ATPase. These data indicate that 6 months after spinalization some of the fibers of the slow muscle developed fast myosin staining patterns and oxidative and glycolytic enzyme profiles that are normally exhibited in fast fatigue-resistant motor units. Periods of daily weight-support appear to ameliorate some of these adaptations to spinalization. Further, the observation that SDH activities are maintained at control values in spinalized adult cats as well as in spinalized kittens (unpublished observations) suggest that, at least in the soleus, skeletal muscle fibers can maintain their oxidative potential even though there is a marked reduction in neuromuscular activity for 6 months.
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PMID:Expression of a fast fiber enzyme profile in the cat soleus after spinalization. 214 97

Isomyosin analyses by biochemical, immunochemical, and histochemical investigations have been carried out in five sheep following unilateral recurrent laryngeal nerve paralysis and direct functional electrostimulation of the denervated cricoarytenoid posterior muscle. Myosin light chains were identified by two-dimensional gel electrophoresis. Myosin heavy chains were analyzed by one-dimensional SDS-polyacrylamide gel electrophoresis. Slow myosin heavy chain was identified by orthogonal peptide mapping and immunochemistry. The stimulation effect at cellular level was determined using adenosine triphosphatase (ATPase) histochemistry. A dramatic increase of the type 1 fiber area (slow, fatigue-resistant fibers) could be seen after many weeks of an increasing regime of low-frequency direct electrical stimulation. Biochemically, the amount of slow myosin was always higher than in normal muscles. Some muscles were transformed almost completely to the slow type. At the time they were studied and with the methods employed, the expression of embryonic isomyosin was not observed. In conclusion, after numerous weeks of maintained functional activity, elicited by direct electrostimulation, the denervated muscle regionally showed areas of hypertrophy or at least lack of atrophy of slow myofibers without major signs of muscle damage.
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PMID:Isomyosin changes after functional electrostimulation of denervated sheep muscle. 297 27

1. We studied isometric twitch peak force (TPF) and twitch contraction time (TCT) of 249 motor units of the masseter muscle in 41 rabbits after extracellular electrical stimulation of single trigeminal motoneurons in the brain stem. In 41 of these units we determined the amount of tension decrease during a partially fused tetanus (sag) and the ratio between peak tetanic force after 2 min of intermittent tetanic stimulation and initial tension (fatigue index). Muscle fibers of 24 motor units were identified by the glycogen depletion method and characterized in serial sections with monoclonal antibodies against type IID, IIA, "cardiac" alpha, and I isoforms of myosin heavy chain (MHC). 2. The motor units had TCTs ranging from 13 to 32 ms. The majority of the units showed forces < 35 mN. The TPFs were larger and varied more for motor units with short and intermediate TCTs than for units with long TCTs. There is a small but statistically significant negative correlation between the motor unit TPF and the TCT. 3. All units exhibited "sag" and, with the exeption of one, had fatigue indexes > 0.75. The studied rabbit masseter motor units can therefore be classified as fast, fatigue-resistant, except for one that belonged to the FF (fast, fatigable) category. No slow units were represented in the sample pool. Significant correlations were not found either between TCT and the amount of sag or between TCT and the fatigue index. 4. Immunohistochemical analysis showed that the FF unit had fibers containing only IID-MHC. Five other units were found with a single MHC--three with IIA-MHC and two with alpha-MHC. In three other units all fibers showed one combination of two MHCs (1 IIA/IID, 1 IIA/alpha, and 1 alpha/I). The remaining 15 units contained two MHCs spread unevenly over the constituting fibers. Large variations in myosin composition of fibers within one motor unit cast doubts on the presumed dominant neuronal influence on myosin expression in the adult animal. 5. We found a close, statistically significant correlation between the TCT and the estimated MHC content of the units: the TCT was 13 ms for the IID unit, 18 ms for the pure IIA units, and 28 ms for the pure alpha units. Units with two MHCs had intermediate TCTs; units with alpha/I-MHC mixtures had TCTs of 29-30 ms. No pure MHC-I units were identified.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Contraction characteristics and myosin heavy chain composition of rabbit masseter motor units. 753 59

Red-toothed shrews of subfamily Soricinae are small mammals with very high mass-specific metabolic rate. Owing to their high aerobic power they are interesting objects for studies concerning the limits and constraints of skeletal muscle adaptation. In order to clarify the correlation between metabolic rate and muscle properties, we have analyzed fiber types, fiber size, and myosin heavy chain composition of the common shrew (Sorex araneus) and compared them to those of rat (Rattus norvegicus). Three distinct differences between shrew and rat muscles were noted. 1) The fibers of shrew muscles are exceptionally small in comparison to rat myofibers. 2) Electrophoretic and histochemical analysis showed that shrew muscles are composed of only fast fibers (fiber types IIB and IID), the slow type I fibers being totally absent. 3) The shrew muscles are much more homogenous than rat muscles in regard to myosin heavy chain and fiber type composition. The shrew diaphragm consists exclusively myosin heavy chain type IId (MHCIId), while masseter and soleus are composed 95% and 87% of MHCIId, respectively. Other four studied muscles contain MHCIIb and MHCIId approximately in equal proportions. The present findings show that shrew muscles are composed of small, highly aerobic, fast type II fibers, which may be sufficiently fatigue-resistant to function both as postural muscles and to power fast and high frequency movements of limbs and diaphragm.
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PMID:Fiber types and myosin heavy chain composition in muscles of common shrew (Sorex araneus). 785 46

The present study sought to examine the effects of aging on the isometric contractile and fatigue properties as well as the myosin heavy chain (MCH) isoform composition of the rat diaphragm muscle. Male Fischer 344 (F344) specific pathogen-free rats 6 and 24 mo old were used in the study. Peak twitch force was approximately 23% lower (p < 0.05) in the senescent diaphragm compared with the young. Time to peak twitch force and one-half relaxation time of twitch force did not differ between groups. There was a significant decrease (15 to 18%, p < 0.05) in the specific force (N/cm2) of the senescent diaphragm at all stimulation frequencies (10 to 100 Hz) examined. In addition, the fatigability of the diaphragm did not significantly differ between the two groups. No significant changes in the distribution of MHC 1 and 2A isoforms were observed with aging. However, the contribution of MHC 2X significantly decreased with senescence (young, 37.5%; senescent, 30.5%), whereas the contribution of MHC 2B in the senescent diaphragm was significantly higher (young, 6.5%; senescent, 15.0%; p < 0.05). We conclude that the age-related decline in diaphragm muscle specific force is caused by intrinsic factors other than changes in MHC composition.
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PMID:Age-related changes in diaphragm muscle contractile properties and myosin heavy chain isoforms. 802 46

This study examined changes in contractile, biochemical, and histochemical properties of slow antigravity skeletal muscle after a 6-day spaceflight mission. Twelve male Sprague-Dawley rats were randomly divided into two groups: flight and ground-based control. Approximately 3 h after the landing, in situ contractile measurements were made on the soleus muscles of the flight animals. The control animals were studied 24 h later. The contractile measurements included force-velocity relationship, force-frequency relationship, and fatigability. Biochemical measurements focused on the myosin heavy chain (MHC) and myosin light chain profiles. Adenosine-triphosphatase histochemistry was performed to identify cross-sectional area of slow and fast muscle fibers and to determine the percent fiber type distribution. The force-velocity relationships of the flight muscles were altered such that maximal isometric tension (Po) was decreased by 24% and maximal shortening velocity was increased by 14% (P < 0.05). The force-frequency relationship of the flight muscles was shifted to the right of the control muscles. At the end of the 2-min fatigue test, the flight muscles generated only 34% of Po, whereas the control muscles generated 64% of Po. The flight muscles exhibited de novo expression of the type IIx MHC isoform as well as a slight decrease in the slow type I and fast type IIa MHC isoforms. Histochemical analyses of flight muscles demonstrated a small increase in the percentage of fast type II fibers and a greater atrophy of the slow type I fibers. The results demonstrate that contractile properties of slow antigravity skeletal muscle are sensitive to the microgravity environment and that changes begin to occur within the 1st wk. These changes were at least, in part, associated with changes in the amount and type of contractile protein expressed.
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PMID:Effect of spaceflight on skeletal muscle: mechanical properties and myosin isoform content of a slow muscle. 804 58

We correlated the fatigue resistance (FR) of the costal diaphragm (DIA) and external abdominal oblique (EAO) of the rat during postnatal development with their respective 1) myosin heavy chain (MHC) phenotypes and 2) oxidative capacities [indexed by quantitative measurements of succinic dehydrogenase (SDH) enzyme activity]. FR was measured in vitro during isometric contractions with the use of the Burke fatigue test. FR of the DIA and EAO was high in newborns and declined during postnatal development. SDH activity was uniformly low in neonatal DIA and EAO and increased during early postnatal development before declining to adult levels. FR did not significantly correlate with SDH activity (r2 = 0.01) but did relate to the MHC phenotype as indexed by the ratio of adult MHC isoform content (slow + IIa + IIx + IIb) to developmental MHC isoform content (slow + neonatal; r2 = 0.88, P < 0.01). Stepwise regression revealed that neonatal MHC expression alone accounted for 60% of the developmental variance in FR. The correlation between FR and MHC phenotype was improved if SDH was also considered, i.e., the ratio of SDH to MHC phenotype (r2 = 0.99, P < 0.01). We conclude that FR of respiratory muscle during development relates to a balance between the energetic demands of the muscle contractile proteins as reflected by MHC isoform composition and its oxidative capacity with MHC phenotype alone exerting a strong predictive effect on FR.
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PMID:Respiratory muscle fatigue resistance relates to myosin phenotype and SDH activity during development. 822 49


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