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

1. Longitudinal movements of marked segments of single fibres from the anterior tibialis muscle were recorded during tetanus and relaxation under isometric (fixed-end) conditions. 2. During relaxation, shortening and lengthening of different segments occurred simultaneously, starting at about the same time as the end of the linear fall of force (shoulder on the force record). 3. Variations in intracellular pH, measured with pH-sensitive microelectrodes, along the length of fibres were not statistically significant, and are unlikely to be responsible for the non-uniform behaviour of different segments. 4. As expected from earlier studies, both fatigue (produced by increasing tetanus duration or decreasing the time between tetani) and intracellular acidification (produced by raised extracellular CO2), reduced the tetanus force and prolonged the linear phase of force decline in relaxation. Each treatment delayed the start and markedly reduced the amount of segment movement in relaxation. 5. Fatigue and intracellular acidification have a smaller effect on force during stretching than on force produced under isometric conditions. This may contribute to making the segments behave in a more uniform way during relaxation under these conditions. 6. Changes in the Ca2+ uptake mechanisms are also discussed as possible causes for the changes in segment behaviour in relaxation.
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PMID:Effects of fatigue and reduced intracellular pH on segment dynamics in 'isometric' relaxation of frog muscle fibres. 260 Aug 46

Fatigue of tibialis anterior (TA) was induced by repetitive electrical stimulation. Using this test, patients with upper motor neuron muscle weakness owing to multiple sclerosis (MS) and injuries to the spinal cord showed greater fatigability of their TA muscles, suggesting that the muscle fiber population changed toward that typical of fatigable motor units. During repetitive stimulation, in addition to the decrement in tension there was an increase in half-relaxation time of tetanic contractions at 40 Hz in both subjects and patients. The increase in half relaxation during repeated activity was greater in patients with MS and spinal cord injury than in healthy subjects, suggesting that the long-term inactivity affected the efficiency of the Ca2+ uptake mechanism of their muscle fibers. Thus long-term inactivity of patients with upper motoneuron dysfunction leads to increased fatigability of their muscles and exaggerates the slowing of muscle relaxation after prolonged exercise.
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PMID:Muscle fatigue in some neurological disorders. 260 89

Psychiatric symptoms are well recognized as a feature of patients with primary hyperparathyroidism. We have applied a standardized psychiatric interview to 15 patients before and after surgery. Thirteen had a lower 'psychiatric score' (less psychiatric morbidity) after surgery and improvements were particularly seen in symptoms of fatigue, depression, irritability, sleep disturbance and lack of concentration. The levels of intellectual impairment and of anxiety were unchanged after surgery. The 'psychiatric scores' in an additional group of 21 hyperparathyroid patients, in whom a decision to treat conservatively had been made independently, were similar to those in the surgically treated patients after surgery. Among all the untreated patients no relationship was found between overall 'psychiatric score' and serum levels of calcium or parathyrin.
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PMID:Psychiatric morbidity in primary hyperparathyroidism. 260 90

Muscular fatigue is of critical importance to performance and as such has been the subject of numerous investigations. However, a clear cause remains elusive. Although many factors have been identified, this review deals only with those which occur distal to the neuromuscular junction. Factors discussed include: energy supply (ATP/creatine phosphate, glycogen, oxygen, and free fatty acids); the accumulation of metabolites (lactate/hydrogen ions, calcium, ammonium, electrolyte and water shifts); and, the special case of eccentric work. The results of many studies using various methodologies are examined. Peripheral fatigue appears to be a complex series of interactions with variable influence on the development of fatigue depending upon the nature of the work performed.
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PMID:Biochemical aspects of peripheral muscle fatigue. A review. 264 71

Recent work has now clearly established that coronary arterial thrombosis is the direct cause of acute myocardial infarction. This thrombotic event occurs when a pre-existing atherosclerotic plaque ruptures or fissures, thereby exposing underlying thrombogenic material to the circulation. Platelets are thus activated and the clotting cascade is initiated. It is as yet unclear why a previously stable atherosclerotic plaque should fissure or rupture. However, suggested mechanisms include release of vasoactive substances from activated platelets, coronary arterial vasomotion, mechanical stress fatigue of the atherosclerotic plaque, and rupture of vasa vasorum within the atherosclerotic plaque. The resultant cessation of myocardial blood flow produces specific biochemical and physiological alterations secondary to myocardial ischemia. Intracellular acidosis, loss of high-energy phosphates, reduced sensitivity of contractile proteins to calcium, and accumulation of inorganic phosphate and lipid, all occur within the ischemic myocyte. Diastolic compliance is markedly reduced by ischemia followed by cessation of systolic contractile activity. Most of these alterations are reversible if ischemia is relieved promptly. Prolonged ischemia leads to delayed biochemical and physiological recovery and/or cell necrosis.
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PMID:The pathophysiology of acute myocardial infarction. 266 57

Black widow spider (Latrodectus mactans) envenomation is found throughout both the temperate and tropical latitudes, and is one of the leading causes of death from arthropod envenomations worldwide. The venom is highly neurotoxic, affecting the presynaptic motor endplate to allow massive noradrenaline (norepinephrine) and acetylcholine release into synapses causing excessive stimulation and fatigue of the motor end plate and muscle. Clinically, patients develop a bite site lesion and pain, abdominal pain and tenderness, and lower extremity pain and weakness within minutes to hours of envenomation. Symptoms progress over several hours, then subside over 2 to 3 days. The recommended treatment of 'common' envenomation is calcium gluconate 10% intravenously, titrated to relief of symptoms; antivenin, although effective, may cause hypersensitivity and serum sickness reactions, and should be restricted to life-threatening envenomations only. Brown recluse spider (Loxosceles reclusa) envenomations are seen in the Americas and in Europe, and are endemic to the south and central United States. The venom contains at least 8 enzymes, consisting of various lysins (facilitating venom spread) and sphingomyelinase D, which causes cell membrane injury and lysis, thrombosis, local ischaemia, and chemotaxis. Local envenomations begin as pain and itching that progresses to vesiculation with violaceous necrosis and surrounding erythema, and ultimately ulcer formation. Systemic envenomations may be life threatening, and present with fever, constitutional symptoms, petechial eruptions, thrombocytopenia, and haemolysis with haemoglobinuric renal failure. Treatment of local envenomations is conservative (local wound care, cryotherapy, elevation, tetanus prophylaxis, and close follow-up); systemic envenomation requires supportive care and treatment of arising complications, corticosteroids to stabilise red blood cell membranes, and support of renal function. Dapsone 100mg daily has emerged as a promising therapeutic agent in both animal studies and clinical trials. Over 650 species of scorpions are known to cause envenomation (mostly in children under 10 years); they are endemic mostly in arid and tropical areas. Different venoms and clinical presentations are seen across the different species. Most commonly, an inflammatory local reaction occurs with envenomation, which is treated with wound debridement and cleaning, tetanus prophylaxis, and antihistamines. Occasionally the venom is allergenic, and the resultant allergic reaction is treated in a standard fashion.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Acute arthropod envenomation. Incidence, clinical features and management. 266 28

Felodipine is a new dihydropyridine calcium antagonist which selectively relaxes vascular smooth muscle. It lovers dose-dependently blood pressure in hypertensives patients. In this multicentre double-blind study, 113 patients (mean age 50 +/- 14 years) whose diastolic blood pressure was higher than 95 mmHg after withdrawal of an eventual antihypertensive therapy and a week of placebo administration. The patients received randomly either felodipine (5 mg x 2/j during two weeks and then 10 mg x 2/day) either atenolol (100 mg/day) during two months. Antihypertensive effects of these two drug regimens were not significantly different. Supine blood pressure decreased from 177 +/- 22/107 +/- 8 mmHg to 152 +/- 27/91 +/- 13 mmHg with felodipine and from 176 +/- 19/107 +/- 8 to 152 +/- 24/91 +/- 12 with atenolol. Side effects recorded by means of active questioning were ankle oedemas and headache with felodipine and fatigue and headache with atenolol.
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PMID:[Felodipine in arterial hypertension. Double-blind comparison with atenolol]. 267 77

Pharmacotherapy of hypertension in the aged does not differ qualitatively but only quantitatively from that in use for younger patients. Adjusted, usually lower doses of diuretics, beta-blocking agents, ACE-inhibitors and calcium-channel blockers are the basic drugs. Individual aging processes and concomitant diseases determine the choice of drugs in the elderly (individualized therapy). All substances are initially prescribed at very low dose. The increasing infirmity of the aged often associated with tiredness, dyspnea and dizziness even without treatment requires careful instruction of the patient about effects and side effects of the prescribed medication. The old WHO-guidelines (systolic BP greater than or equal to 160, diastolic BP greater than or equal to 95 mm mercury) should be maintained for diagnosis and treatment of hypertension. However antihypertensive therapy in patients over 80 years of age and in those with marginally elevated diastolic or solely elevated systolic pressure is controversial today.
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PMID:[Hypertension and old age]. 268 25

A 50-year-old man presented with knee pain and general fatigue and was found to have severe hypercalcemia and renal failure. Hyperparathyroidism was suspected by hypercalcemia and a nodular lesion of the thyroid gland with CT-scan of the patient's neck. Exploration of the neck disclosed two slightly enlarged parathyroid glands. After surgery, the patient's serum calcium levels remained normal for two weeks, but after that his serum calcium levels rose again and renal failure continued. So needle biopsy of the kidney was enforced, and myeloma of the kidney was suspected. Multiple myeloma was diagnosed by bone marrow puncture.
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PMID:[Multiple myeloma in a patient with primary hyperparathyroidism]. 268 49

Despite decreasing cardiac mortality rates in the elderly since 1968, rates of health care service use by persons over age 65 years have progressively increased. The growing availability of potent and effective cardiovascular drugs, together with the high prevalence of untoward side effects in the elderly, make it important that we consider the influence of age on cardiovascular response to the calcium entry blockers. The age-related structural, functional, pharmacokinetic, and pharmacodynamic changes that occur in elderly patients suggest that careful monitoring, adjustment, and frequent reassessment of the medical regimen should be performed to minimize untoward effects. Nifedipine, diltiazem, and verapamil are all well absorbed orally, are extensively protein bound, and are metabolized by the liver. The age-associated attenuation in rates of hepatic metabolism and hepatic blood flow contribute to the decreased clearance and prolonged elimination half-lives of these drugs in the elderly. Advanced age can be associated with increased susceptibility to sinoatrial depression, fatigue, constipation, hypotension, and peripheral edema after calcium entry blockade, even at modest doses. It would be prudent, therefore, to administer these agents at lower doses and at less frequent intervals.
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PMID:Use of calcium entry blockers in elderly patients. Special considerations. 268 81


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