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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

On the basis of the histochemical activity of succinic dehydrogenase, only two fibre-types are distinguished in pigeon pectoralis major muscle. These are narrow "Red" and broad "White". The histochemical activity of myofibrillar ATPase was studied in these two distinct fibre-types. Both fibre-types showed high activity for the ATPase. "Red" fibres of pigeon pectoralis were not alkali-labile, at incubation pH 9.4, as were the "Type I" fibres of both avian and mammalian muscles. Again unlike "Type I" fibres, the "Red" fibres of pigeon pectoralis lacked the characteristic activation of acid-preincubated ATPase reaction. Pigeon pectoralis "Red" fibres are known to possess some characteristics of fast-twitch fibres (e.g. high fat, considerable phosphorylase, fibrillenstruktur myofibrillar arrangement, focal "en plaque" pattern of nerve endings). It is emphasized, therefore, that the pigeon pectoralis "Red" fibres are not equivalent to "Type I or slow-twitch", muscle fibres, but they are possibly "fast-twitch fatigue resistent or Type II Red" muscle fibres.
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PMID:"Red" fibres of pigeon pectoralis major muscle are "type II red". 14 61

The effects of up to 4 months dietary supplementation with 40% galactose on muscle and nerve function were examined in rats. Galactitol, a polyol pathway metabolite, accumulated to high levels in both tissues. This led to changes similar to those found in experimental diabetes, which were largely prevented by treatment with an inhibitor of the first enzyme in the pathway, aldose reductase. For fast twitch extensor digitorum longus muscle there was weight loss, fibre damage, slowing of twitch time to peak, increased twitch tension, and reduced tetanic tension. There were no relaxation deficits. For slow twitch soleus there were no changes in tension production. However, contraction and relaxation for both twitch and tetanus were prolonged. Fatigue resistance was reduced after 1 week. Damage in soleus led to a reduction in mean fibre area after 2 months, which largely recovered by 4 months. There was a selective loss of fast oxidative glycolytic fibres. Histochemical staining for succinic dehydrogenase was normal in galactosaemic soleus, in contrast to the marked reduction seen in diabetes. Sciatic nerve conduction velocity was reduced after 2 months, particularly in normally fast conducting motor and sensory fibres. Resistance to hypoxic conduction block was increased in galactosaemic nerves to diabetic levels. It was concluded that polyol pathway hyperactivity is likely to contribute to the aetiology of diabetic myopathy and neuropathy, and that experimental galactosaemia provides a good model in which to study pathway effects without the complicated hormonal changes found in diabetes.
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PMID:Muscle and nerve dysfunction in rats with experimental galactosaemia. 153 21

1. Transmitter release at neuromuscular junctions of extensor digitorum longus (EDL) muscle in mice was studied after 2-8 month periods of unforced running in wheels. 2. Intracellular recordings at 10 Hz stimulation revealed that the quantal content of endplate potentials (EPPs) in Mg(2+)-blocked preparations was larger by 30% in trained (mean number of quanta, m = 1.75 +/- 0.19, n = 7) than in untrained control EDL muscles (m = 1.35 +/- 0.35, n = 7). Similarly the amplitudes of the first, maximum and plateau EPPs during tetanic stimulation (100 Hz for 1 s or 400 ms) in curare-blocked preparations were increased by 28% each; muscle fibre diameters did not differ while other postsynaptic effects were not excluded. 3. Training effects became particularly evident in two pairs of monozygotic twins, in which the time courses of facilitation and depression were changed as well: at 100 Hz stimulation the maximum EPP amplitude was reached on average at 2.6 impulses in controls but at 2.0 impulses in runners, and the following decline below the value of the first EPP at 5.0 and 3.8 impulses respectively. 4. Block resistance, as monitored by isometric tension measurements in different presynaptic (Mg2+) and postsynaptic (curare) blocking solutions, was higher in trained than in control EDL muscles. Depression in a train of four nerve-evoked single twitches at 2 Hz was lower. 5. As expected from the unchanged fibre diameters (see above) isometric tetanic force was similar in trained and control EDL muscles. Muscle fatigue resistance was larger in trained animals and succinic dehydrogenase activity was higher in fibres of trained muscles indicating an endurance training of the EDL muscle. 6. It is concluded that besides changes in muscle fibre properties, prolonged elevated activity causes increased transmitter release in EDL muscles. As a consequence, the safety margin of transmission in trained EDL muscles is markedly elevated.
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PMID:Effects of enhanced activity on synaptic transmission in mouse extensor digitorum longus muscle. 164 30

In response to patterns of chronic electrical stimulation that increase its overall level of use, mammalian skeletal muscle becomes highly resistant to fatigue. The metabolic basis for this adaptation is well documented in the rabbit, but up to now it has not been possible to identify analogous changes in the dog. In this study, canine latissimus dorsi muscles were stimulated in situ for 2, 6 and 12 mo. Marked increases in fatigue resistance were consistently demonstrated. Citrate synthase and succinic dehydrogenase, conventionally used as markers of oxidative metabolism, did not increase in activity, but enzymes involved in major pathways supplying substrates to the tricarboxylic acid cycle increased up to threefold. Stimulation elevated the volume fraction of mitochondria 1.5-fold and that of lipid droplets 4.5-fold. After 6 mo of stimulation, mean fiber diameter had decreased by 30% and the area occupied by nonmuscle tissue had increased by 11%; these changes showed no further progression at 12 mo. Thus stimulated muscle becomes stably adapted to an increase in use, but the metabolic strategies for achieving increased fatigue resistance vary between species.
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PMID:Correlates of fatigue resistance in canine skeletal muscle stimulated electrically for up to one year. 187 71

The muscle fiber types and sizes in the M. stapedius (middle ear muscle) of the domestic chicken, Gallus gallus were determined histochemically on the basis of their reactions to myofibrillar adenosine triphosphatase (mATPase), succinic dehydrogenase and NADH diaphorase. Only type II fibers were identified at pH 9.4 and 4.2. At pH 4.6 three levels of activity were seen: high, intermediate and low. With the staining techniques three subtypes of fibers for oxidative enzymes, Types II1 (highly glycolytic), II12 (intermediately glycolytic and lipolytic) and II123 (highly lipolytic) were identified. Fiber diameter was also measured for the different fiber types. The average fiber diameter was around 20 micron for each fiber type. Although similar in size, the fiber types were markedly different in their histochemical properties. These findings plus those of earlier physiological studies suggest that the M. stapedius of G. gallus is a fast twitch, muscle with fibers of similar diameter showing mainly fatigue resistance characteristics.
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PMID:A histochemical characterization of muscle fiber types in the avian M. stapedius. 288 51

The contractile properties, morphology, and the distribution of striated muscle fiber types of the external and sphincter (EAS) were determined using axial force measurements, fiber size cross-sectional area measurements, and histochemistry. Electrical stimulation of motor axons in pudendal nerve at supramaximal intensities (10 V, 0.05 ms duration) elicited twitch contractions of EAS. The time to peak force after a single pulse ranged from 37 to 42 ms. The time for relaxation to half-maximal twitch force ranged from 20 to 29 ms. Repetitive stimulation of motor axons (0.1-3.0 Hz) produced potentiation and fatigue of single twitch contractile force, suggesting that the EAS of the cat is comprised predominantly of fast-twitch muscle fibers. Confirmation of skeletal muscle fiber types was determined by histochemistry. Frozen serial cross sections of EAS were incubated to demonstrate succinic dehydrogenase (SDH) and myosin adenosine triphosphatase after alkaline preincubation (pH 10.4). Based on these reactions, muscle fibers were classified as fast glycolytic (FG) (high ATPase, low SDH), fast oxidative-glycolytic (FOG) (high ATPase, high SDH), and slow oxidative (SO) (low ATPase, high SDH). The mean percentage +/- SE of each histochemical type was the following: FG, 73.5 +/- 3.9; FOG, 22.8 +/- 3.7; and SO, 3.7 +/- 0.6. These results indicate that the predominant fiber type for the EAS is FG. The EAS of the cat is considered a nominally fast-twitch muscle.
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PMID:Physiological, morphological, and histochemical properties of cat external anal sphincter. 320 71

Fatigue indices and succinic dehydrogenase (SDH) activities were determined in the extensor digitorum longus (EDL) and soleus muscles of the hind limb and the extensor carpi radialis longus of the forelimb in control and dystrophic mice aged 4 to 26 weeks. A good correlation was found between SDH activities and fatigue indices in muscles from normal mice. In the dystrophic (dy2J) mice, however, this correlation was not present. The EDL muscles from 26-week-old dy2J mice showed a much higher resistance to fatigue than age-matched controls but this was not accompanied by a significant change in SDH. The increased fatigue resistance in dy2J EDL appeared between 8 and 12 weeks of age and was temporally correlated with the onset of fused bursts of spontaneous activity in the hind limb muscles. Nevertheless, there was no conclusive evidence for a link among this spontaneous activity, oxidative enzyme capacity, and fatigue resistance.
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PMID:Fatiguability and oxidative capacity of forelimb and hind limb muscles of dystrophic mice. 396 20

A continuous electrical 8 Hz impulse pattern imposed directly via implanted electrodes on denervated fast twitch muscle induced changes in its contractile characteristics. Compared with non-stimulated denervated muscle, stimulated muscle showed slowing of contraction time and improved fatigue resistance. The reaction for succinic dehydrogenase was more intense in the denervated stimulated muscle, indicating an increased capacity of oxidative enzymes. The rate of atrophy was not influenced by stimulation. The 8 Hz frequency pattern is the mediator for these changes in the characteristics of denervated muscles. It demonstrates a comparable effect on innervated muscle. The contralateral normal innervated muscle was also influenced by the electrical stimulation. Contraction time as well as twitch tension were increased. This finding is important when using the normal muscle as intraindividual control.
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PMID:Influence of direct low frequency stimulation on contractile properties of denervated fast-twitch rabbit muscle. 405 36

Alterations in enzyme activities involved in muscle energy metabolism and the muscle fiber type distribution were investigated in six subjects, ranging in age from 19-23 years, following short-term, high intensity exercise. Changes in the vastus lateralis muscle were studied prior to exercise and approximately 24 h after each of 2 consecutive days of supramaximal cycling exercise (120% VO2 max) performed intermittently as 1-min work to 4-min rest until fatigue or until 24 repetitions had been completed. The results indicated that there were no changes (P greater than 0.05) in maximal in vitro activities for representative enzymes of beta-oxidation (3-hydroxyacyl CoA dehydrogenase, HAD), the citric acid cycle (succinic dehydrogenase, SDH), glucose phosphorylation (hexokinase, HK), glycogenolysis (total phosphorylase, PHOSPH), or glycolysis (phosphofructokinase, PFK; pyruvate kinase, PK; lactate dehydrogenase, LDH) in spite of the large increase in carbohydrate utilization and glycolytic flux rate. In addition, although no change in fiber type distribution was found in the pre-exercise biopsy between days, an acute reduction (P less than 0.05) in type I fiber distribution occurred with exercise. It is concluded that supramaximal exercise performed on a short-term basis does not alter the enzymatic profile or the fiber type distribution when measured 24 h following the activity.
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PMID:Fiber type distribution and maximal activities of enzymes involved in energy metabolism following short-term supramaximal exercise. 609 Mar 24

The contractile, histochemical, morphological and electrophysiological properties of two rat laryngeal muscles, the cricothyroid and posterior cricoarytenoid, have been measured. Both muscles act during respiration to maintain upper airway patency and an even distribution of air in the lungs. The cricothyroid and posterior cricoarytenoid are fast-twitch muscles, having contraction times of 3.4 and 7.2 ms respectively, high myosin ATPase activity, abundant sarcoplasmic reticulum (with average volumes of 9% and 15%, respectively, of the fibre volume) and T-system membrane (with average areas of 0.4 and 0.5 micron 2 micron -3 of fibre). The large areas of T-tubule membrane are reflected in the average specific membrane capacities of 6.5 muF cm-2 to 10.5 muF cm-2, which are high considering the small diameter of the fibres (20-30 micron). Of the two muscles, the posterior cricoarytenoid has the faster contraction time and the more abundant sarcoplasmic reticulum content. In addition, the posterior cricoarytenoid is less resistant to fatigue and demonstrates lower succinic dehydrogenase activity. The fatigability of this muscle, coupled with its general lack of functional reserve, suggest that its failure may contribute to upper airway obstruction during respiratory distress.
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PMID:The contractile properties, histochemistry, ultrastructure and electrophysiology of the cricothyroid and posterior cricoarytenoid muscles in the rat. 621 35


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