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

Volunteers with normal hearing were tested for vegetative balance with the aid of vegetative reflexes and with the aid of the atropine test. The effect of white noise stimulated on hearing thresholds was then investigated together with their recovery. The vegetative system was affected experimentally by intravenous administration of atropine, and the beginning and recession of hearing fatigue was observed. Atropine caused a small change only. In a similarly arranged experiment, 1% pilocarpin administered subcutaneously in a dose of 1.4 minus 1.6 ml, resulted in increased hearing fatigue and retarded recovery at higher frequencies. The effect of pilocarpin is explained by the fact that it supports the inhibitory processes checked by the parasympathetic nervous system on the periphery.
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PMID:The effect of the parasympathetic autonomic nervous system on auditory fatigue. 12 96

A case is presented of a 60-year-old woman with fatigue, dyspnea, and chest pain. A chest x-ray film revealed an abnormal cardiac silhouette. Echocardiography revealed a large, echo-free area with well-demarcated, discrete borders adjacent to the right heart border. This structure decreased in size with inspiration and did not show pulsatile cardiac motion. Cardiac catheterization confirmed the extracardiac nature of the lesion and also showed a "constrictive" pattern with equalization of diastolic pressures. Surgical exploration revealed a large cystic thymoma. With removal of the tumor, intracardiac pressures returned to normal.
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PMID:Cystic thymoma simulating contrictive pericarditis. The role of echocardiography in the differential diagnosis. 12 66

The professional ballet dancer presents all of the problems of any vigorous athlete. The problems include osteochondral fractures, fatigue fractures, sprains, chronic ligamentous instability of the knee, meniscal tears, impingement syndrome, degenerative arthritis of multiple joints and low back pain. Attention to minor problems with sound conservative therapy can avoid many major developments and lost hours. Observations included the extraordinary external rotation of at the hip without demonstrable alteration in the hip version angle and hypertrophy of the femur, tibia and particularly the second metatarsal (in female dancers). Careful evaluation of the range of motion of the extremities, serial roentgenographic examination, and systematic review of previous injuries, training programs and rehearsal techniques have been evaluated in a series of cases to provide the basis for advice to directors and teachers of the ballet.
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PMID:A new consideration in athletic injuries. The classical ballet dancer. 12 36

Slow (m.soleus) and fast (m.tibialis anterior) muscles of the rabbit were subjected to indirect long-term intermittent stimulation (3 weeks, 8 hrs daily) with a frequency pattern of 10 imp/sec. Whereas no changes were observed in case of the slow muscle, stimulation induced profound changes in the fast tibialis anterior muscle. These consisted in a rearrangement of the enzyme activity pattern of energy-supplying metabolism, e.g. decrease in glycogenolytic and glycolytic enzyme activities and severalfold increase in key enzymes of aerobic endoxidation of substrates in beta-oxidation and the citric acid cycle. Concomitant with the increase in aerobic oxidative capacity, there was an increased resistance to fatigue. Histochemical studies revealed a strong increase in mitochondria of all fibres. The bimodal distribution of fibre cross-sectional area in the normal tibialis anterior muscle was changed by stimulation into a more homogeneous population of fibres with a smaller cross-sectional area. Despite a 50% increase in time to peak of isometric twitch contraction no changes were observed in the fibre population with regard to myofibrillar ATPase reaction in quantitative evaluation of whole cross-sections of the muscles. The percentage of fibres histochemically classified as slow amounted to 2.8% and 3.1% in control and stimulated tibialis anterior muscle. Nevertheless the data suggest a transformation of the fibre population under the influence of long-term intermittent stimulation.
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PMID:Influence of intermittent long-term stimulation on contractile, histochemical and metabolic properties of fibre populations in fast and slow rabbit muscles. 12 33

Dehydroepiandrosterone (DEA), a metabolite of steroid hormone in the urine, differed from papaverine in the mode of inhibitory action on the isolated guinea-pig ileum. Papaverine inhibited both phasic and tonic contractions induced by an agonist, while DEA inhibited the phasic contraction without apparent fatigue of the tonic phase. The main action of papaverine seems to be predominatly a metabolic inhibition similar to that of metabolic inhibitors, but the action of DEA could not be ascribed to that of metabolic inhibition. In the presence of papaverine or metabolic inhibitors the height of maximal contraction of an agonist tested by the cumulative method was greatly depressed and less than that by a single method. The longer the time involved in the cumulative doses, the lower was the maximal contraction.
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PMID:Difference between inhibitory actions of papaverine and dehydroepiandrosterone on the isolated guinea-pig ileum. 13 53

Three new cases of chronic vitamin A intoxication are reported and a review of the literature with special reference to chronic intoxication in adolescents and adults is presented. The most prominent features are intracranial hypertension, skin and hair deviations, pain in the musculoskeletal system, and fatigue. Intracranial hypertension occurs in 50% of chronic intoxications, but is not invariably linked with the other symptoms. Young women are the major age group represented. There seems to be no relation between the severity of the clinical picture and the vitamin A serum level. Discontinuance of vitamin A intake is sufficient for cure.
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PMID:Benign intracranial hypertension due to A-hypervitaminosis in adults and adolescents. 13 26

1. The servo-like properties of muscle in healthy human subjects have been studied by interfering unexpectedly with flexion movements of the top joint of the thumb. This movement is carried out by the flexor pollicis longus muscle only. 2. The movements were standardized in rate by giving the subject a tracking task. They started off against a constant torque load offered by an electric motor. 3. In some movements the load remained constant, but in others, in mid-course, perturbations were introduced at random. Either the movement was halted, or released and allowed to accelerate by reducing the load, or reversed by suddenly increasing the current in the motor, so stretching the muscle. 4. Usually eight or sixteen responses to each kind of perturbation and a similar number of controls against a constant load were averaged. 5. Muscle activity was recorded as the electromyogram from surface electrodes over the belly of the long flexor in the lower forearm. Action potentials were usually full-wave rectified and integrated. 6. About 50 msec after a perturbation the muscle's activity alters in such a sense as to tend to compensate for the perturbation, i.e. it increases after a halt or a stretch and decreases after a release. The latency is similar in each case. 7. These responses are interpreted as manifestations of automatic servo action based on the stretch reflex. They are considered to be too early to be voluntary. 8. This interpretation was supported by measuring voluntary reaction times to perturbations under tracking conditions. They were found to be 90 msec or longer. 9. When the initial load was increased by a factor of 10, the servo responses were all scaled up likewise. Thus to a first approximation the gain of the servo is proportional to initial load. 10. It follows that in relaxed muscle the gain should be zero. This was confirmed by showing that stretching a relaxed muscle gives no reflex, or only a small one. 11. Gain appears to be determined by the level of muscle activation as determined by the effort made by the subject, rather than by the actual pressure exerted by the thumb. 12. Thus in fatigued muscle gain is boosted as the muscle has to be activated more strongly to keep up the same force output. The net effect is to compensate for fatigue and maintain the performance of the servo. 13. The Discussion centres on the implications of gain control in the servo. For a start, if the gain of the stretch reflex arc is zero in relaxed muscle, contractions cannot be initiated via the stretch reflex by simply causing the spindles to contract, as proposed on the original 'follow-up' servo theory.
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PMID:Servo action in the human thumb. 13 38

The effect of dipeptides (carnosine and anserine) on a neuromuscular preparation under fatigue or diplacine blocking is shown to result in a significant restoration of the muscle contraction. The analysis of this phenomenon evidences that synaptic processes are not responsible for the restoration, at least under the given experimental conditions. At the same time, the absence of any effect of the compounds studied on the maximal rate of isotonic shortening and on the tension of glycerinized fibres and ATPPase of native and desenitized actomyosine indicates that the contractile mechanism is not involved in the effect described. On the other hand, the dipeptides restore the value of the transmembrane potential depolarized by exhaustion, increase the amplitude of isometric twitch and the value of maximal load under isotonic conditions. Moreover, the time of the contractile cycle in the presence of the dipeptides is considcted to the processes of electromechanical coupling in skeletal muscles.
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PMID:[Effect of carnosine and anserine on excitation and contraction of fatigued skeletal muscle]. 13 81

The fatiguability of the quadriceps muscle was investigated in 10 male subjects (25-40 yrs), with inter-individual differences in fibre composition of their vastus lateralis muscles (range 25-65% fast twitch, FT, muscle fibres). Fatiguability was assessed as the decline in maximal force (in % of initial values) with 50 repeated isokinetic knee-extensions at fast angular velocity (3.14 rad/s). Each contraction lasted 0.5 s and the rest periods were about 0.7 s. Every subject was tested on two occasions and the standard deviation for a single determination of fatiguability was 1.4%. The decline in force after 50 contractions was on the average about 45%. The individual values varied, however, and a linear correlation was present between fatiguability and % FT fibres (r = 0.86, p less than 0.01). It was concluded that development of fatigue in human skeletal muscle performing repeated fast dynamic contractions with maximal effort was most marked in muscles with a high proportion FT fibres. This finding was in conformity with earlier results from animal skeletal muscle preparations.
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PMID:Fatiguability and fibre composition of human skeletal muscle. 13 65

A case of bilateral aneurysmatic widening of the Dacron graft after aorto-femoral bypass is described. The probable cause of an aneurysm in Dacron graft without any involvement of the host vessels may be the rupture of the Dacron fibres due to fatigue of the material. Furthermore, a contributory cause of aneurysm in our case may be the fact that both anastomoses were performed at nearly right angles causing turbulence.
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PMID:Bilateral aneurysm of dacron graft following aorto-femoral graft operation. A case report. 13 44


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