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)

In respiratory muscles, force generation and shortening depend on the cyclical interaction of actin and myosin (cross-bridge cycling). During cross-bridge cycling, adenosine triphosphate (ATP) is hydrolysed. The globular head region of the myosin heavy chain (MyHC) possesses both the binding site to actin and the site for ATP hydrolysis. Therefore, the MyHC is both a structural and enzymatic protein. Different isoforms of MyHC are expressed in skeletal muscle fibres, and these MyHC isoforms provide mechanical and metabolic diversity. In the present study, the relationships between MyHC isoform expression in single rat diaphragm muscle fibres and their mechanical and energetic properties were evaluated. The expression of MyHC isoforms in single diaphragm muscle fibres was identified using electrophoretic and immunohistochemical techniques. Cross-bridge cycling kinetics in diaphragm muscle fibres clearly depend on MyHC isoform expression, and these differences are interpreted in the context of Huxley's two-state cross-bridge model. It is concluded that the unique mechanical and energetic properties of myosin heavy chain isoforms are designed to accomplish different motor behaviours of the diaphragm muscle, and that, as a result of these unique properties, a selective recruitment of diaphragm muscle fibres is essential to avoid fatigue.
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PMID:Cross-bridge kinetics in respiratory muscles. 931 83

Mechanical and histochemical characteristics of the lateral gastrocnemius (LG) muscle of the rat were examined 21 days after capsaicin injection into the LG muscle. The capsaicin caused a decrease in generation rate of twitch and tetanic tension and an increase in fatigue resistance of LG muscle. The histochemical muscle fiber profile evaluated by myosin adenosine triphosphatase and reduced nicotinamide adenine dinucleotide tetrazolium reductase methods showed an increase of type I and IIC fibers and a decrease of the type IIB in whole muscle, and a decrease of the IIA, IIX fibers in the red part accompanied by their increase in the white part. Therefore the capsaicin treatment, which selectively eliminated fibers belonging to the III and IV groups of muscle afferents, induced muscle fiber transformation from fast contracting fatiguing fibers to slowly contracting nonfatiguing ones.
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PMID:Partial transformation from fast to slow muscle fibers induced by deafferentation of capsaicin-sensitive muscle afferents. 934 57

Muscle catabolism is a characteristic metabolic response to sepsis, severe infection, and injury. In patients with severe and protracted sepsis, the catabolic response results in muscle wasting and fatigue, which may adversely affect the outcome in these patients. An understanding of the regulation of muscle protein breakdown during sepsis and the mechanisms involved is important from a clinical standpoint and is essential for the development of new therapeutic modalities to prevent protein loss from muscle tissue. Studies in septic patients and experimental animals have provided evidence that the myofibrillar proteins actin and myosin are particularly sensitive to the effects of sepsis. Among the factors that regulate muscle protein breakdown during sepsis, the proinflammatory cytokines tumor necrosis factor and interleukin-1, together with glucocorticoids, are the principal mediators. Intracellular protein breakdown is regulated by multiple proteolytic pathways. Among these, the energy-ubiquitin-dependent pathway accounts for a major portion of muscle protein breakdown during sepsis. The development of specific proteasome inhibitors may make it possible in the future to target the molecular mechanisms of sepsis-induced increase in muscle proteolysis. Such treatment may prove an important avenue to reduce the metabolic cost in patients with severe infection or sepsis.
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PMID:Sepsis: stimulation of energy-dependent protein breakdown resulting in protein loss in skeletal muscle. 945 37

The extensor carpi radialis muscle of the horse is deceptive at first appearance. It has a fusiform shape similar to other forearm extensor muscles. The fiber arrangement also appears long and relatively parallel. However, it may contain two or more compartments that correlate with differing functional roles. Histochemical and immunocytochemical analysis of proximal and distal regions of the muscle (n = 9) demonstrate that the proximal portion of the muscle is composed of a mean of 13% type I, presumed slow twitch, and 61% type IIb, presumed fast twitch fibers. In contrast, the distal compartment is composed of a mean of about 43% type I and only 22% type IIB fibers. The type I and IIa fibers are all highly aerobic based on nicotinamide dinucleotide tetrazolium reductase reactions. Correlative data regarding the myosin isoforms has been obtained with 4% SDS-PAGE analysis of myosin heavy chain isoforms which demonstrate isoforms migrating at rates similar to rat type I, IIa, and IIx. The latter has been referred to as type IIB/X in a study of the horse's gluteus medius muscle. We propose that the in-series 'compartmentalization' of the muscle, while not conforming strictly to the definitions of neuromuscular compartments, relates to the insertion of the lacertus fibrosus, a distal slip of the biceps brachii, upon the extensor carpi radialis. Earlier studies demonstrated a high proportion of type I fibers in the equine lateral biceps brachii which were thought to stabilize the shoulder during long periods of quiet standing. Because of action imposed on the distal compartment by the biceps brachii, slow and fatigue-resistant functions are part of the limb's passive stay apparatus to effect long-term standing by the horse. Thus, the fatigue-resistant compartments of biceps brachii and extensor carpi radialis may constitute an in-series arrangement of the two muscles. The proximal compartment is suited to provide powerful, more fatigable contractions during locomotion and likely affects stress or strain within the distal postural compartment.
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PMID:Architecture and the division of labor in the extensor carpi radialis muscle of horses. 957 63

This study examined the effects of fatigue on the functional aspects of the contractile apparatus and sarcoplasmic reticulum (SR). Frog semitendinosus muscles were stimulated to fatigue, and skinned fibers or a homogenate fraction was prepared from both fatigued and rested contralateral muscles. In fatigued fibers, maximal Ca2+-activated force of the contractile apparatus was unaltered, whereas maximal actomyosin-ATPase activity was depressed by 20%. The Ca2+ sensitivity of force was increased, whereas that of actomyosin-ATPase was not altered. Also, the rate constant for tension redevelopment was decreased at submaximal Ca2+ concentration. These latter findings suggest that fatigue slows the dissociation of force-generating myosin cross bridges. Ca2+ uptake and Ca2+-ATPase activity of the SR were depressed by 46 and 21%, respectively, in the fatigued muscles. Fatigue also reduced the rates of SR Ca2+ release evoked by AgNO3 and 4-chloro-m-cresol by 38 and 45%, respectively. During fatigue, the contractile apparatus and SR undergo intrinsic functional alterations. These changes likely result in altered force production and energy consumption by the intact muscle.
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PMID:Functional aspects of skeletal muscle contractile apparatus and sarcoplasmic reticulum after fatigue. 968 40

Rabbit tibialis anterior muscles were stimulated continuously at 2.5 Hz, 5 Hz, or 10 Hz for 10 months. The resulting adaptive transformation was dose-related for contractile speed, myosin isoform composition, and enzyme activities. The "fast-oxidative" state produced by stimulation at 2.5 Hz was stable: even after 10 months, 84% of the fibers were of type 2A. Absence of a secondary decline in oxidative activity in these muscles provided strong evidence of a causal link between myosin transitions and metabolic adaptation. Significant fiber loss occurred only after prolonged stimulation at 10 Hz. The myosin isoform composition of individual muscles stimulated at 5 Hz resembled that of muscles stimulated at either the lower or the higher frequency, behavior consistent with a threshold for fiber type change. In clinical applications such as cardiomyoplasty, muscles could be used more effectively by engineering their properties to combine speed and power of contraction with the necessary resistance to fatigue.
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PMID:The dose-related response of rabbit fast muscle to long-term low-frequency stimulation. 984 63

Using telemetered electromyography and immunocytochemical fibre typing (of both fresh frozen and preserved specimens), the present paper demonstrates clearly that at the elbow, knee, and ankle joints, the rhesus monkey (Macaca mulatta) is endowed with one extensor-muscle head specialized for posture. These postural heads are distinguished by (a) recruitment at low levels to maintain joint position against the effect of gravity, (b) recruitment near maximum levels during walking, and (c) high content and relatively large size of slow, fatigue-resistant (type I) muscle fibres. The nonpostural heads of the investigated muscles were recruited at levels correlated to the strenuousness of the effort and are notable by the small percentage and size of slow muscle fibres. The postmortem stability of the structural properties of myosin makes immunocytochemical fibre typing suitable for the study of preserved cadavers.
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PMID:Function and cytochemical characteristics of postural limb muscles of the rhesus monkey: A telemetered EMG and immunofluorescence study. 1056 29

The stapedius muscle (SM) is supposed to prevent cochlear damage by noise. Consequently functional demands are the ability of fast contraction with long endurance. This implies the presence of a large fraction of myosin type II fibres with an appreciable oxidative capacity. We determined the myosin composition of SM fibres using consecutive complete SM cross-sections (6 week old rats) which were processed by enzyme histochemistry (EHC) to determine acid/alkali lability of myofibrillar adenosine triphosphatase (mATPase) or by immunohistochemistry (IHC) using myosin heavy chain (MyHC) antibodies. Method accuracy was determined in co-processed extensor digitorum longus (EDL). Four hundred SM and 200 EDL fibres were assigned to mATPase type I, IIA, IIB, IIX or 'miscellaneous' ('Misc') categories. Per mATPase category the fibres were attributed to groups with specific MyHC composition. In the EDL, mATPase type I and IIB fibres expressed only MyHC I and IIB respectively, whereas about 10% of the type IIA and 40% of the type IIX fibres expressed more than one MyHC. Thus IHC detects amounts of myosin isoforms which are not detected by EHC. The mATPase IIX category criterion leaves the possibility that this category contains fibres with myosin type IIA and/or IIB in larger amounts. The criteria of the mATPase categories type I, IIA or IIB preclude assignment to these categories of fibres which also contain other myosin isoforms in larger amounts. Such fibres were classified in one of the mATPase 'Misc' categories. Thus in the EDL the capability of the EHC criteria to select 'pure' fibres in terms of myosin differs per mATPase category. None of the SM fibres were assigned to the mATPase type I or IIB categories, about 25% to the type IIA, 60% to type IIX and 15% (including most fibres which expressed MyHC I) to a 'Misc' category. All SM fibres expressed two or more MyHC isoforms, MyHC IIB occurring in all fibres and substantial amounts of MyHC IIA and/or IIX in most. These findings confirm the hypothesis that such fibres have the capacity to contract fast and have the better fatigue resistance.
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PMID:Stapedius muscle fibre composition in the rat. 1071 5

Twitch potentiation and fatigue in skeletal muscle are two conditions in which force production is affected by the stimulation history. Twitch potentiation is the increase in the twitch active force observed after a tetanic contraction or during and following low-frequency stimulation. There is evidence that the mechanism responsible for potentiation is phosphorylation of the regulatory light chains of myosin, a Ca2+-dependent process. Fatigue is the force decrease observed after a period of repeated muscle stimulation. Fatigue has also been associated with a Ca2+-related mechanism: decreased peak Ca2+ concentration in the myoplasm is observed during fatigue. This decrease is probably due to an inhibition of Ca2+ release from the sarcoplasmic reticulum. Although potentiation and fatigue have opposing effects on force production in skeletal muscle, these two presumed mechanisms can coexist. When peak myoplasmic Ca2+ concentration is depressed, but myosin light chains are relatively phosphorylated, the force response can be attenuated, not different, or enhanced, relative to previous values. In circumstances where there is interaction between potentiation and fatigue, care must be taken in interpreting the contractile responses.
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PMID:Coexistence of potentiation and fatigue in skeletal muscle. 1077 80

Muscle fatigue induced by consecutive twitches or tetani was studied in single skeletal muscle fibers of the frog, Rana japonica. The fatigue by twitch appeared sooner after the start of stimulation at lower temperatures (2-5 degrees C) than at higher ones (15-20 degrees C), while the fatigue by tetanus appeared sooner at higher temperatures. When a twitch-fatigued fiber was bathed in a solution with caffeine (15 mM), the contracture force was much higher than the fatigued force, while in tetanus fatigue, the force by caffeine was not different from the fatigued force. The length-force relation in fatigued fibers was compared with that in pre-fatigue at low and high temperatures. It was noticed that the ascending limb of the length-force curve in fatigued fibers by twitch was lower than that in pre-fatigue at the low temperatures; namely, the fatigue by twitch was more marked in shorter muscle length, while no marked change in the length-force relation was detected in the tetanus fatigue at the low and high temperatures. The maximum shortening velocity, measured by the slack test, decreased in both types of fatigue. These results suggest that the fatigue by twitch may be mainly due to the failure of activation of the contractile system, while in the fatigue by tetanus, the rate of the interaction between actin and myosin may be impaired due to the change in intracellular chemical environment.
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PMID:The effects of temperature on the mechanical performance in fatigued single muscle fibers of the frog induced by twitch and tetanus. 1086 97


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