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. The goal of this study was to characterize the fatigability, contractile relaxation properties, electrophysiological responses, and histochemical properties of the human paralyzed soleus muscle to determine its relative plasticity. 2. Acute (< 6 wk, n = 3) and chronic (> 1 yr, n = 10) paralyzed individuals had the tibial nerve activated with a 20-Hz square wave delivered for 330 ms every second for 4 min. The soleus muscle peak torque, one-half relaxation time (1/2RT), normalized maximum rate of relaxation (nMRR), and mass muscle action-potential amplitude (M wave) were computed every 30 s. A soleus muscle biopsy was evaluated for myosin adenosine triphosphatase enzyme (ATPase; pH 9.4, 4.6, and 4.2) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR). 3. In the chronically paralyzed group the torque was significantly reduced within 30 s of the fatigue protocol. The 1/2RT and nMRR were also significantly changed within 30 s, supporting that muscle relaxation was prolonged. No significant changes were present at comparable times during the same 4-min fatigue protocol applied to the acutely paralyzed soleus muscle. M-wave amplitude was significantly reduced in the chronic group, but only at 3 min of the fatigue protocol. Conversely, no significant changes occurred to the M waves of the acute group. 4. The correlation was high between torque and nMRR (r = 0.88-0.97) and torque and 1/2RT (r = 0.88-0.96) for each chronic subject. A close association was also found between 1/2RT and nMRR (r = 0.88-0.92) for each chronic subject. Because these variables changed minimally in the acutely paralyzed group, a lower correlation was present (r = 0.45-0.52). 5. Torque was weakly correlated to M-wave amplitude (r = 0.55) for the chronically paralyzed group. The greatest change in torque occurred at a time (0-65 s) when the least amount of change occurred in the M-wave amplitude, suggesting that the source of fatigue was within the contractile mechanism and not attributable to neuromuscular transmission compromise. 6. Despite a close association between torque and relaxation properties during fatigue of the chronically paralyzed soleus muscle, there was a significant dissociation after 5 min of recovery. Torque recovered to 60%, whereas the relaxation properties were consistently fully recovered. This suggests that the mechanism causing torque reduction covaried with the mechanism leading to prolonged relaxation during fatigue, but during recovery the two mechanisms no longer covaried. M-wave amplitude was also completely recovered at 5 min despite continued torque depression.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Fatigability, relaxation properties, and electromyographic responses of the human paralyzed soleus muscle. 766 32

The diaphragm is a vital respiratory muscle in the sleeping infant. Any changes in diaphragm fiber type number or size could represent either a primary developmental delay or a secondary reaction to increased workload, and could give a clue as to the pathogenesis of sudden infant death syndrome (SIDS). We therefore quantitated by point counting on ATPase histochemistry the numbers and areas of type 1 and 2 fibers in the diaphragm, external intercostal and psoas muscles of 37 SIDS and 20 control infants. The amount of slow, fast and fetal myosin in the diaphragm and psoas muscles was measured by electrophoresis to check the ATPase quantitation. There were fewer type 1 fibers in SIDS (median 30.0%) compared with control (median 40.0%) infants (p < 0.02), whereas the diameter of type 1 fibers in SIDS (median 33.9 microns) was larger than in control (median 30.3 microns) infants (p < 0.007). The total cross-sectional area occupied by type 1 and 2 fibers was similar in both groups. No changes were found in the external intercostal or psoas. The amount of slow and fast myosins correlated well with type 1 and type 2 fibers, respectively. The finding of fewer type 1 (fatigue-resistant) fibers of large diameter in SIDS diaphragms suggests that differences in muscle fiber types may predispose these infants to diaphragm fatigue and respiratory failure.
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PMID:Differences in diaphragm fiber types in SIDS infants. 781 77

By means of histological method and ultrasound cardiographic (UCG) examination, the left-right ratio of transectional area of muscle fiber of latissimus dorsi muscle (LDM) after non-dynamic cardiomyoplasty was 77.4 +/- 11.7% in Group I (3 weeks after operation), and 78.4 +/- 11.6% atrophy and hyperplasia of LDM, but the basical structure was retained. The ejection fraction (EF) decreased significantly after operation (P < 0.05), but the difference between two groups was non- significant. Also, dynamic cardiomyoplasty was performed on a sheep. UCG showed the increased cardiac systolic function after operation. ATPase, succinodehydrogenase (SDH) and PAS examination implied the strengthening of fatigue-resistant ability in skeletal muscles after long-term electrical stimulation. So cardiomyoplasty is suggested to be a supplementary measure in treating end-stage heart failure.
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PMID:Cardiac function and histological changes after non-dynamic cardiomyoplasty and preliminary study of dynamic cardiomyoplasty. 786 91

To examine the effect of exercise on sarcoplasmic reticulum function in muscle tissue of different fibre composition, adult male Wistar rats weighing 388 +/- 23 g (x +/- SE) ran intermittently on a treadmill until fatigue. Fatigue was induced by 15-20 min of running performed at 52 m/min on an 8 degrees incline in periods of 2.5 min of exercise separated by 2 min of recovery. Analysis of sarcoplasmic reticulum Ca2+ ATPase activity determined in homogenates indicated no difference (p > 0.05) between age-matched control and exercised tissue for the soleus (SOL; 0.121 +/- 0.012 vs. 0.156 +/- 0.018 mumol.mg-1 protein.min-1), red gastrocnemius (RG; 0.381 +/- 0.022 vs. 0.354 +/- 0.022), or white gastrocnemius (WG; 0.526 +/- 0.05 vs. 0.471 +/- 0.031). Similarly, both total ATPase and Mg2+ ATPase activities were unaffected by the exercise in any of the tissues examined. Exercise also failed to alter sarcoplasmic reticulum Ca2+ uptake in homogenates of the SOL (1.43 +/- 0.15 vs. 1.38 +/- 0.19 nmol.mg-1 protein.min-1), RG (3.74 +/- 0.29 vs. 3.59 +/- 0.24), and WG (5.98 +/- 0.48 vs. 5.41 +/- 0.50). At fatigue, glycogen depletion was similar in all tissue types and amounted to 65.1% in the SOL (172 +/- 9 vs. 60 +/- 16 mmol.glucosyl units-1.kg-1 dry weight), 74.4% in RG (164 +/- 8 vs. 42 +/- 6), and 79% in the WG (167 +/- 9 vs. 35 +/- 9). It is concluded that exercise by itself does not alter sarcoplasmic reticulum Ca2(+)-sequestering function in tissues of primarily different fibre composition when determined in homogenates in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Preservation of sarcoplasmic reticulum Ca2(+)-sequestering function in homogenates of different type composition following sprint activity. 788 89

We analyzed the masticatory muscles (masseter, temporal, medial pterygoid and lateral pterygoid muscles) of Bovidae and Cervidae (Artiodactyla) for the histochemical characteristics of their fiber types. Analysis of muscle fiber types in the present study was based on the staining reaction for SDH, Sudan black B, alpha-GPDH, and myosin-ATPase after alkaline preincubations. Histochemical properties were found to contribute to masticatory function, including a slow-twitch fatigue resistant activity derived from the high percentage of red fibers, in spite of the differences in the distributions of fiber types in three portions (superficial, medial and profound portions) of each masticatory muscle. These results indicate a correlation between the histochemical profiles of individual masticatory muscles in these species and their functions during jaw movements.
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PMID:Differentiation of histochemical properties of masticatory muscles in Bovidae and Cervidae (Artiodactyla). 804 63

With the advent of functional electrical stimulation (FES) there is the possibility of paraplegic patients regaining some degree of locomotor activity. It is of interest to document the changes in composition histochemistry and size of muscle fibres in such patients both before and after such therapy. We have examined biopsy specimens from quadriceps muscles obtained from 7 male patients, age range 24-47 years, who had been paraplegic for times ranging from 11 months to 9 years and we report the histochemical appearance of the muscle the fibre type composition and the mean fibre areas. In 5 of the 7 subjects there was a marked or complete predominance of fibres which stained as type 2 with the ATPase reaction at pH 9.4. At acid pH these fibres were seen to be predominantly 2B (fast fatigable). The 2 subjects who had been paralysed for the shortest periods had proportions of type 1 fibres which were relatively well preserved. The mean fibre areas of type 2 fibres were below the normal range (2500-7500 microns 2) in every case as were the type 1 fibres in the 4 patients in which these were still present. There was no relationship between the length of time the patient had been paralysed and the mean fibre areas which suggests that atrophy occurs fairly quickly following loss of voluntary control and precedes the loss of type 1 characteristics. Our findings provide an explanation for the rapid onset of fatigue in paraplegic patients taking part in FES programmes since muscles deficient in type 1 fibres will be unable to maintain force for any length of time.
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PMID:Fibre areas and histochemical fibre types in the quadriceps muscle of paraplegic subjects. 833 67

In order to use functional electrical stimulation effectively in paralyzed muscle treatment, changes in the maximal muscle force, muscle fatigue, and histological changes were evaluated in electrically stimulated muscles. Study 1. Tissue damage by percutaneous intramuscular electrodes implanted into the quadriceps muscle was examined in rat. Stimulation was conducted at various output voltages, and for various durations of time, in order to assess the histological changes in the muscle around the electrodes. Study 2. Electrodes were implanted into the bilateral quadriceps and gastrocnemius muscles of adult cat, and the unilateral muscles were then stimulated from 3 weeks following the transection of the spinal cord at the T9 level. Stimulus parameters were divided into two groups; as "A" stimulation: at -8V for 15min twice/week, and as "B" stimulation: at -16V for 30 min 4 times/week. The histological changes were examined using the myofibrillar ATPase method to determine the diameters and occupation ratios for each muscle fiber type. RESULTS. Study 1. Significant tissue damage began to occur when the voltage output created the maximum muscle contraction force. Until that critical voltage point was reached, tissue damage was not significant, regardless of the duration of the stimulation. Study 2. The maximum muscle force decreased until 4 weeks after the transection, then increased regardless of the presence of electrical stimulation. The muscle fatigability of the non-stimulated muscle was greater than that of the stimulated muscle. High voltage, long duration, and frequent stimulation was effective in controlling fatigue. The ratio of type I fibers was higher in the stimulated muscle. There was no evidence, however, of suppressing muscle fiber atrophy after electrical stimulation. These results suggested that electrically stimulating paralyzed muscles was effective for suppressing muscle fatigue, and for reducing the ratio of type I fibers. In clinical use, the output voltage should be kept below the voltage that induces the maximum muscle contraction to prevent tissue damage.
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PMID:[Histological changes, muscle force and fatigability after electrical stimulation to experimentally paralyzed muscles]. 853 Aug 86

The role of prolonged electrical stimulation on sarcoplasmic reticulum (SR) Ca2+ sequestration measured in vitro and muscle energy status in fast white and red skeletal muscle was investigated. Fatigue was induced by 90 min intermittent 10-Hz stimulation of rat gastrocnemius muscle, which led to reductions (p < 0.05) in ATP, creatine phosphate, and glycogen of 16, 55, and 49%, respectively, compared with non-stimulated muscle. Stimulation also resulted in increases (p < 0.05) in muscle lactate, creatine, Pi, total ADP, total AMP, IMP, and inosine. Calculated free ADP (ADPf) and free AMP (AMPf) were elevated 3- and 15-fold, respectively. No differences were found in the metabolic response between tissues obtained from the white (WG) and red (RG) regions of the gastrocnemius. No significant reductions is SR Ca2+ ATPase activity were observed in homogenate (HOM) or a crude SR fraction (CM) from WG or RG muscle following exercise. Maximum Ca2+ uptake in HOM and CM preparations was similar in control (C) and stimulated (St) muscles. However, Ca2+ uptake at 400 nM free Ca2+ was significantly reduced in CM from RG (0.108 +/- 0.04 to 0.076 +/- 0.02 mumol.mg-1 protein.min-1 in RG - C and RG - St, respectively). Collectively, these data suggest that reductions in muscle energy status are dissociated from changes in SR Ca2+ ATPase activity in vitro but are related to Ca2+ uptake at physiological free [Ca2+ bd in fractionated SR from highly oxidative muscle. Dissociation of SR Ca2+ ATPase activity from Ca2+ uptake may reflect differences in the mechanisms evaluated by these techniques.
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PMID:Effects of prolonged low frequency stimulation on skeletal muscle sarcoplasmic reticulum. 856 84

In the rat diaphragm muscle, the histochemical classification of type I, IIa, IIb, or IIx fibers was correlated with myosin heavy chain (MHC) immunoreactivity. Expression of MHC isoforms in single dissected fibers was also assessed electrophoretically. Most fibers (approximately 86%) expressed a single MHC isoform, and when present, coexpression of MHC-2X and MHC-2B isoforms was most prevalent. Type I and IIa fibers were the smallest, type IIb fibers were the largest, and type IIx fibers were intermediate. Succinate dehydrogenase (SDH) and calcium-activated myosin adenosinetriphosphatase (actomyosin ATPase) activities were measured with quantitative histochemical procedures. Type I and IIa fibers had the highest SDH activities, followed in rank order by type IIx and IIb fibers. Type I fibers had the lowest actomyosin ATPase activity, followed in rank order by type IIa, IIx, and IIb fibers. Across all fibers, there was an inverse relationship between fiber SDH activity and cross-sectional area and a positive correlation between fiber actomyosin ATPase activity and cross-sectional area. The SDH and actomyosin ATPase activities of muscle fibers were also inversely correlated. These phenotypic differences in SDH and ATPase activities may be important in determining the contractile and fatigue properties of different fiber types in the rat diaphragm muscle.
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PMID:SDH and actomyosin ATPase activities of different fiber types in rat diaphragm muscle. 859 23

Ionic regulation is critical to muscle excitation, contraction and metabolism, and thus for muscle function during exercise. This review focuses on the effects of training upon K+, Ca2+ and H+ ion regulation in muscle and K+ regulation in blood during exercise. Training enhances K+ regulation in muscle and blood and reduces muscular fatiguability. Endurance, sprint and strength training in humans induce an increased muscle Na+, K+ pump concentration, usually associated with a reduced rise in plasma [K+] during exercise. Although impaired muscle Ca2+ regulation plays a vital role in fatigue, little is known about possible training effects. In rat fast-twitch muscle, overload-induced hypertrophy and endurance training were associated with reduced sarcoplasmic reticulum Ca2+ uptake, consistent with fast-to-slow fibre transition. In human muscle, endurance and strength training had no effect on muscle Ca2+ ATPase concentration. Whilst muscle Ca2+ uptake, release and Ca2+ ATPase activity were depressed by fatigue, no differences were found between strength athletes and untrained individuals. Muscle H+ accumulation may contribute to fatigue during intense exercise and is also modified by sprint training. Sprint training may increase muscle Lac- and work output with exhaustive exercise, but the rise in muscle [H+] is unchanged or attenuated, indicating a reduced rise in muscle [H+] relative to work performed. Muscle buffering capacity can be dissociated from this improved H+ regulatory capacity after training. Thus, training enhances muscle and blood K+ and muscle H+ regulation during exercise, consistent with improved muscular performance and reduced fatiguability; however, little is known about training effects on muscle Ca2+ regulation during contraction.
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PMID:Effects of training on potassium, calcium and hydrogen ion regulation in skeletal muscle and blood during exercise. 872 94


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