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

The Na-K-ATPase is the enzymatic basis of a energy-dependent transport of sodium and potassium through the cell membrane and is therefore of importance to the survival of organs during periods of decreased energy supply. In the present paper the influence of various preservation solutions on the activity of this enzyme was examined. It was shown that Na-K-ATPase activity in rat kidneys did remain unchanged after 48 hour preservation in various preservation solutions (Bretschneider, Ross, Collins, Sacks, Belzer). Therefore, its estimation is no valuable for evaluation of preservation solutions.
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PMID:[Na K ATPase activity in rat kidneys following storage at 4 degrees C in various kidney preservative solutions]. 216 14

We studied the changes of histochemical properties of diaphragm in guinea pigs with elastase-induced emphysema. Using myofibrillar ATPase staining, three types of diaphragmatic muscle fibers were classified as slow-twitch, oxidative (SO), fast-twitch, oxidative, glycolytic (FOG), and fast-twitch, glycolytic (FG). Capillaries adjacent to individual fibers were also demonstrated by ATPase reaction. After 24 weeks of tracheal instillation of elastase, both the size and number of SO and FOG fibers were increased, thereby indicating the increase in relative areas occupied by these oxidative fibers in the diaphragm (p less than 0.01 in each case). Moreover, these changes were accompanied by the increased capillary density (p less than 0.01). These results suggest that chronic respiratory load with emphysema may establish the diaphragm more resistant to fatigue by increasing oxidative capacity of the diaphragmatic muscle fibers.
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PMID:Effects of elastase-induced emphysema on histochemical properties of guinea pig diaphragm. 246 17

In rats with adrenaline-induced myocarditis conditionally therapeutic doses of strophanthin (2.7 mg/kg) and digoxin (0.89 mg/kg) were chosen according to performance of the test of swimming until the complete fatigue. The influence of drugs in these doses on enzymatic activity was evaluated by histochemical methods in heart of control and myocarditis rats. It was found out that both of cardiac glycosides decreased lactate dehydrogenase and membrane Na+, K+-ATPase activity and increased succinate dehydrogenase activity in rats with experimental myocarditis.
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PMID:[Effect of strophanthin and digoxin on the activity of succinate and lactate dehydrogenases and membrane Na+, K+-ATPase in the heart of rats with experimental myocarditis]. 254 33

The fields of muscle physiology and biochemistry have already identified some of the key components of ATPase hydrolysis products that are involved in muscle fatigue. The concentration of the relevant chemical species can be readily measured by nuclear magnetic resonance techniques in muscle. Now the question is: is alteration of cellular energy balance and the normal balance between supply and demand disturbed in fibromyalgia? Since these chemical events account for a very large amount of muscle reduced performance as well as reduction in both velocity and force, at the very least one ought to identify how large these changes are in any patient in whom we are trying to assess the degree to which these chemical changes might be associated with muscle fatigue. An objective chemical criteria for muscle performance is possible with modern noninvasive phosphorus magnetic resonance spectroscopy.
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PMID:Muscle energy metabolism, nuclear magnetic resonance spectroscopy and their potential in the study of fibromyalgia. 260 14

There are a number of advantages in using an electrically stimulated autogenous skeletal muscle to construct an auxiliary ventricle to assist a heart. The purpose of this study was to determine the feasibility of biological right ventricular assistance using long-term electrically stimulated skeletal muscle grafts. In fourteen dogs, the latissimus dorsi muscles and the right thoracodorsal nerves were exposed and unipolar pulse generator was implanted. The initial rate of 70 cycle/min. was increased to a rate of 100 cycle/min. Six or 12 months later, the latissimus dorsi was wrapped around a latex pouch equipped with inflow and outflow valved conduit (skeletal muscle ventricles; SMVs). The SMVs were connected to main pulmonary artery and right atrium. These SMVs were stimulated 20 Hz for 200 msec at a fixed rate of 90 cycle/min, the hemodynamic changes with or without skeletal muscle ventricular assistance (SMVA) were measured. In as animals the circulation failed after total right ventricular bypass without SMVA. But the SMVA increased aortic blood pressure, aortic blood flow, left atrial pressure and peak pulmonary pressure significantly. There was a linear correlation between central venous pressure and skeletal muscle ventricular assist flow. Histologic studies showed the conditioned muscles had a greater percentage of slow-twitch, fatigue resistant fibers on ATPase stain. These results suggested the long-term electrical conditioning skeletal muscle could be possible to use SMVs in humans to provide support in children with some types of congenital heart disease.
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PMID:[Skeletal muscle ventricle used for right ventricle assistance]. 279 73

1. The effects of phosphate and protons on the mechanics and energetics of muscle contraction have been investigated using glycerinated rabbit psoas muscle. 2. Fibres were fully activated by addition of Ca2+ (pCa 4-5) at 10 degrees C. The velocities of contraction were measured in isotonic load clamps, and the velocities of unloaded fibres were measured by applying a series of step changes in fibre length. Fibre ATPase activity was monitored using an enzyme system to couple ADP production to reduced nicotinamide-adenine dinucleotide (NADH) and measuring the depletion of NADH by optical density. 3. At pH 7.0 and 3 mM-phosphate, isometric tension (P0) was 13.2 +/- 0.9 N/cm (mean +/- S.E.M., n = 10 observations), the maximum contraction velocity (Vmax) was 1.63 +/- 0.05 lengths/s (n = 5) and the ATPase activity was 1.27 +/- 0.12 s-1 myosin head-1 (n = 35). Increasing phosphate from 3 to 20 mM at pH 7.0 does not affect Vmax, causes a small decrease in the ATPase activity (15-20%) and decreases P0 by approximately 20%. Changing pH from 7 to 6 at 3 mM-phosphate decreases P0 by 45% and both Vmax and ATPase activity by 25-30%. The effects of changing both pH and phosphate were approximately additive for all parameters measured. The inhibition of these parameters by low pH and high concentration of phosphate was reversible. 4. The force-velocity relation was fitted by the Hill equation using a non-linear least-squares method. The value of the parameter which describes the curvature, a/P0, was 0.20. The curvature of the force-velocity relation was not changed by addition of phosphate or by changes in pH. 5. These data provide information on both the kinetics of the actomyosin interaction and on the process of muscle fatigue. The data are consistent with models of cross-bridge kinetics in which phosphate is released within the powerstroke in a step involving a rapid equilibrium between states. The inhibition by protons is more complex, and may involve less specific effects on protein structure. 6. During moderate fatigue of living skeletal muscle, MgATP concentration is known to remain approximately constant at 4 mM, phosphate to increase from 3 to 20 mM, and protons from 0.1 to 1 microM. The data suggest that much of the inhibition of P0 observed during moderate fatigue can be explained by the increased levels of phosphate and protons, and that much of the inhibition of fibre Vmax and ATPase activity can be explained by the increase in protons.
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PMID:The inhibition of rabbit skeletal muscle contraction by hydrogen ions and phosphate. 284 89

The effect of hyperthyroidism on the fatigue properties of the soleus muscle was investigated in rats treated with T3 (20 micrograms/100 g bw) for 14 (14 d T3) and 30 (30 d T3) days. Maximum tetanic force (Po) was identical in all groups. During 15 minutes of stimulation with 600 ms pulsetrains of 100 Hz at a rate of 60/min, Po declined by 50%, 54%, and 70% in euthyroid, 14 d T3, and 30 d T3 rats, respectively. The results were similar when indirect or direct stimulation was applied. Force recovered to 80% of Po in all groups within five minutes. Whereas relaxation rate and Ca++ transport activity were increased twofold already after 14 days of T3 treatment, myofibrillar ATPase activity (M-ATPase) was only increased in the 30 d T3 group. The decrease in phosphorylation potential ([ATP]/[ADP]f[Pi]) (PP) during stimulation was similar in euthyroid and 14 d T3 rats, but 50% larger in 30 d T3 rats. The latter indicated a higher energy consumption, presumably caused by the M-ATPase. Nevertheless, the PP during fatigue was equal in all groups. The decrease in ATP and the increase in lactate content during fatigue were larger in 14 d T3 and 30 d T3 rats as compared to euthyroid rats, but did not differ between the two hyperthyroid groups. It is concluded that the higher fatigability in the 30 d T3 group cannot be explained by impaired neuromuscular transmission, nor by shortage of energy supply.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fatigability and recovery of rat soleus muscle in hyperthyroidism. 295 65

Myofibrillar proteins in muscles of the claws and abdomen of lobster, Homarus americanus, and the claws of fiddler crab, Uca pugnax, and land crab, Gecarcinus lateralis, have been analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fibers contained numerous isoforms of structural and regulatory proteins in assemblages correlated with fiber type. One fast (F) and two slow (S1 and S2) fibers were identified. All F fibers possessed two isoforms of paramyosin (P1 and P2), while all slow fibers, with the exception of Uca major claw, contained only the P2 variant. S1 and S2 fibers were distinguished by the distribution of a large isoform of troponin-T (T1; Mr = 55,000); S2 fibers in all three species contained T1 in addition to one or two smaller-molecular-weight variants usually associated with S1 fibers. In order to determine whether the slow fibers differed in histochemical properties, land crab claw closer muscle was cryosectioned and stained for myofibrillar ATPase and NADH diaphorase activities. Most S2 fibers had lower ATPase and higher NADH diaphorase activities than S1 fibers, which indicated that S2 fibers had a lower rate of contraction and were more fatigue-resistant than S1 fibers. It is proposed that the S1 and S2 fibers defined by biochemical and histochemical criteria are identical to the slow-twitch and tonic fibers, respectively characterized physiologically.
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PMID:Histochemical and biochemical characterization of two slow fiber types in decapod crustacean muscles. 296 38

The purpose of this study was to examine the Ca2+-Mg2+ myofibrillar ATPase and protein composition of cardiac and skeletal muscle following strenuous activity to voluntary exhaustion. Sprague-Dawley rats (200 g) were assigned to a control and exercised group, with the run group completing 25 m.min-1 and 8% grade for 1 hour. Following activity, the myocardial Ca2+-Mg2+ myofibrillar ATPase activity -pCa relationship had undergone a rightward shift in the curve. Electrophoretic analysis revealed a change in the pattern of cardiac myofibrillar protein bands, particularly in the 38-42 Kdalton region. Enzymatic analysis of myofibrillar proteins from plantaris muscle, revealed no change in Ca2+ regulation following exercise. Electronmicrographic and electrophoretic analysis revealed extensively disrupted sarcomeric structure and a change in the ratio of several plantaris myofibrillar proteins. No difference was observed for myosin: Actin: tropomyosin ratios; however a dramatic reduction in 58 and 95 Kdalton proteins were evident. The results indicate that prolonged running is associated with similar responses in cardiac and skeletal muscle myofibrillar protein compositions. The abnormalities in myofibrillar ultrastructure may implicate force transmission failure as a factor in exercised-induced muscle damage and/or fatigue.
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PMID:Influence of exercise on cardiac and skeletal muscle myofibrillar proteins. 297 50

1. Rat plantaris muscles were subjected to chronic overload by the surgical removal of the soleus and most of the gastrocnemius muscles. Twelve to 16 wk later whole muscle and motor unit (ventral root dissection technique) contractile properties as well as histochemistry were determined. 2. Motor units were categorized as fast, fatigable (FF), fast, intermediate fatigue-resistant (FI), fast, fatigue-resistant (FR), and slow (S) based on contractile characteristics. Muscle fibers were identified as type I and type II according to myofibrillar ATPase staining. 3. Whole muscles demonstrated increases in wet weight, tetanic force, proportion of type I fibers, and mean cross-sectional areas of both type I and II fibers, as a result of chronic overload. 4. Tetanic tension increased by the same relative magnitude in all motor units whereas twitch tension remained unchanged. A significant change in the proportions of the motor unit types occurred in overloaded muscles, such that the latter contained higher proportions of FF and S units, and lower proportions of FI and FR units, than normal muscles. 5. The fatigue profile of a composite constructed from a summation of motor unit responses revealed that the overloaded plantaris displayed fatigue resistance similar to that of the normal plantaris for a given absolute force output. 6. Glycogen-depleted fibers of hypertrophied single motor units demonstrated uniform myofibrillar ATPase and SDH staining characteristics suggesting that metabolic adaptations among fibers of the same unit were similar after 12-16 wk of overload. 7. The finding that overload caused a uniform increase in the tetanic strength of all motor units, whereas alterations in fatigue resistance varied in degree and direction among unit types, demonstrate that these two properties are not controlled in parallel in this model. The smallest units maintain or even increase their fatigue resistance during the hypertrophic process, whereas high threshold units actually decrease in fatigue resistance.
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PMID:Physiological responses of rat plantaris motor units to overload induced by surgical removal of its synergists. 297 14


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