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

Neuromuscular adaptations to a submaximal static contraction for a period of 2 min were investigated using children as subjects to detect changes in the contributing frequency components of the electromyogram (EMG) recorded from surface electrodes. The purpose of this study was to determine the similarity between EMG response patterns of children and published data for adult subjects under similar conditions. Spectral analysis of the EMG signal revealed a shift to lower frequency components and a concurrent increase in total variance of the signal as a response to fatigue. The frequency shift and increase amplitude for the EMG signal were discussed in light of evidence for recruitment and synchronization of motor units and changes in muscle fiber conduction velocity as possible mechanisms.
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PMID:Myoelectric frequency changes in children during static force production. 7 27

During the period 1960 to 1978, 98 patients underwent intracardiac repair of Fallot's tetralogy after palliative operations. Preoperative symptoms were cyanosis, dyspnea, increased fatigue with squatting and hypoxic spells. The hemoglobin concentration varied from 19 to 22 g/100 ml. At correction only 65 of 95 shunts were patent and needed surgical closure. Seventeen early deaths occurred (19%), the main causes being cardiac failure and arrhythmia. One patient died 3 years after correction from pneumonia. The subjective clinical result was excellent or good in all surviving patients. At repeat heart catheterization in 26 patients a high percentage of residual ventricular septal defects and pulmonary stenosis/insufficiency was found. However, the majority of defects were of minimal haemodynamic significance, and so far did not seem to do harm to the patients' subjective function.
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PMID:Correction of Fallot's tetralogy after palliative operations. 8 99

Patterns of breathing at night were recorded in 4 patients with heart-failure. 2 had periodic breathing while awake and in 2 it developed after they fell asleep. In all 4 the phase of hyperventilation disturbed sleep. These cases also illustrate other problems caused by periodic respiration in heart-failure, which range from tiredness during the day to an inability to sleep for more than a few minutes. Nocturnal waking in the hyperventilation phase of Cheyne-Stokes breathing should be differentiated from paroxysmal nocturnal dyspnoea caused by episodes of pulmonary oedema at night.
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PMID:Paroxysmal nocturnal dyspnoea and periodic respiration. 9 69

Using a commercially available television set for stimulation of 78 healthy subjects, the upper limit of normal for the latency of the major positive wave (p 100) of checkerboard pattern reversal evoked potentials is practically the same as that obtained by employing slide projector combined with a rotating mirror. Potentials evoked by a small pattern, for purely foveal stimulation, were often difficult to evaluate exactly. Fixation of a large pattern at the upper border of the stimulus field brought no advantages as compared to the usual fixation in the center. Continuous prolonged recordings, with successive averaging of 64 pattern reversals, confirmed statements that only the major positive wave and its latency are constantly reproducible without being influenced by fatigue or inattention. Repeated examinations in the same subjects at intervals of 2 weeks showed a considerable spread of the latencies from one session to the other but the absolute values always ranged within the normal. More or less large latency differences (up to 12ms with large pattern stimulation) were found in every subject at least once. A longer latency found at a control examination, or a newly appearing latency difference, therefore do not prove a fresh optic nerve lesion as long as the absolute values are still within the limits of normal. From repeated examinations it could also be seen that foveal stimulation with a small pattern is not suitable for routine examinations because of high variation in the results.
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PMID:Pattern reversal evoked cortical responses in normals. A study of different methods of stimulation and potential reproducibility. 9 35

Glutaraldehyde-preserved porcine mitral leaflet tissue has been subjected to extended accelerated fatigue loading in Ringer's solution containing 0.15% glutaraldehyde. Five tissue test pieces were subjected to cyclic tensile stresses of 50 and 200 Gm. per square millimeter and to 300 million to 800 million accumulated fatigue cycles. Tissue disruption occurred in each of the fatigued test pieces. Tensile loading, apart from reducing the acuteness of the collagen waveform and thereby decreasing tissue compliance, does not contribute significantly to the disruption process nor its rate of occurrence. Compressive flexure occurring during the unloading half of the fatigue cycle, however, does induce damage in the tissue. Mechanisms involved in the disruptive processes have been identified by conducting simultaneous morphologic and stress/strain observations on both the fatigued and unfatigued tissues in their wet functional condition. This vulnerability of the preserved tissue to compressive flexure could well affect the long-term durability of the glutaraldehyde-preserved heterograft valve, and this possibility is discussed in relation to the clinical use of these valves.
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PMID:Fatigue-induced damage in glutaraldehyde-preserved heart valve tissue. 9 72

Digitalis and diuretics constitute conventional therapy of congestive heart failure, but systemic vasodilators offer an innovative approach in acute and chronic heart failure of decreasing increased left ventricular systolic wall tension (ventricular afterload) by reducing aortic impedance and/or by reducing cardiac venous return. Thus, vasodilators increase cardiac output (CO) by diminishing peripheral vascular resistance (PVR) and/or decrease increased left ventricular end-diastolic pressure (LVEDP) (ventricular preload) by diminishing venous tone. Concomitantly, there is reduction of myocardial oxygen demand, thereby reliably reducing angina pectoris in coronary disease, and potentially limiting infarct size and ischemia provided systemic arterial pressure remains normal. The vasodilators produce disparate modifications of cardiac function depending upon their differing alterations of preload versus impedance: nitrates principally cause venodilation (decrease LVEDP); nitroprusside, phentolamine and prazosin produce balanced arterial and venous dilation (decrease LVEDP and increase CO) provided left ventricular filling pressure is maintained at the upper limit of normal; whereas hydralazine predominantly effects arteriolar dilation (increases CO). With depressed CO plus highly increased LVEDP and increased PVR, nitrates also induce some increase of CO by reducing PVR. Combined nitroprusside and dopamine synergistically enhance CO and decrease LVEDP. Mechanical counterpulsation aids nitroprusside in acute myocardial infarction. The 30-minute venodilator action of sublingual nitroglycerin is extended for 4 to 6 hours by cutaneous nitroglycerin ointment, by sublingual and oral isosorbide dintrate, and by oral pentaerythritol tetranitrate and sustained-release nitroglycerin capsules. Ambulatory oral vasodilator therapy is provided by long-acting nitrates (relieve pulmonary congestion); hydralazine (improves fatigue); prazosin alone, combined nitrate-hydralazine combined prazosin-hydralazine (improve both dyspnea and fatigue).
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PMID:Afterload reduction and cardiac performance. Physiologic basis of systemic vasodilators as a new approach in treatment of congestive heart failure. 9 30

A technique is described for measuring the propagation velocity of a mechanical pulse along a muscle. The pulse is generated and detected by piezoelectric crystals (bimorph benders). Measurement of the time delay for a known crystal separation gives the propagation velocity v (of the order of 100 m s-1) from which the Young's modulus is calculated. Primary results for elastic moduli of frog and toad muscles at 5 degrees C are: 2.6 X 10(6) N m-2 at rest, 3.1 X 10(7) N m-2 in tetanus and 2.1 X 10(7) N m-2 in rigor. Exploratory experiments are also described showing the application of the technique to (i) the development of tetanus, (ii) variation with sarcomere length and (iii) the mechanics of rigor. The pulse technique gives an almost instantaneous measurement of the purely elastic response of a muscle and is thereby of value in basic studies of the mechanism of contraction. It is also a useful non-destructive probe in following the effects of such variables as temperature, fatigue or chemical treatments.
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PMID:Pulse propagation in muscle. 10 92

The interaction between effects of ethanol ingestion and those of infrasound on neuro-muscular fatigue in the animal is abolished by ascorbic acid. The relevant mechanism is in acetaldehyde detoxification.
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PMID:[Suppression by ascorbic acid of neuromuscular fatigue due to sound-alcohol synergy]. 10 54

A woman with multiple myeloma relapsed after 6 years of satisfactory tumor control with melphalan therapy. When progression then occurred, she was given exogenous human leukocyte interferon, 3 x 10(6) reference units twice daily i.m., as the sole therapy. Side-effects of the interferon therapy consisted of fever reactions and thrombocytopenia. One month after the initiation of interferon therapy there was 1) improvement of general health with less pain and tiredness, 2) reduction of the M-component, IgG-lambda, in the serum, and 3) a reduced plasma cell concentration in the bone marrow. After 5 months of interferon therapy tumor progression occurred despite continuous interferon treatment. At the same time, the tumor cells were less sensitive to interferon in in vitro tests than prior to interferon therapy. It is suggested that interferon therapy should be given as initial treatment to a few patients with multiple myeloma in a phase I trial.
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PMID:Interferon therapy in multiple myeloma. 10 25

An inventory of 69 somatic discomforts was used to identify those discomforts most likely to be concurrent with a clinically severe depression in a sample of 223 recently hospitalized women. The inventory provided scores for each of 15 classes of discomfort. The classes of discomfort with the highest average score for the depressed sample at admission also yielded significantly lower scores for a nonpatient control sample (P less than .05). The four classes of discomfort most pertinent to depression were designated autonomic, wakefulness, dry mouth, and fatigue. The items of discomfort contributing to these classes showed a statistically significant diminution in severity during treatment (P less than .05).
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PMID:Somatic discomforts among depressed women. 10 3


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