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

In this study fatigue resistance of experimentally prepared titanium-nickel (50.8% nickel and 49.2% titanium) cast clasps was evaluated in a simulated clinical situation. The change in force required to remove the titanium-nickel clasps was recorded under a repeated placement-and-removal test on steel model abutment teeth. Commercially-pure titanium, cobalt-chromium alloy, and gold-silver-palladium-copper alloy clasps were also tested for comparison. The tips of the clasps were located in the 0.25- and 0.50-mm undercut areas of the abutments. No significant changes in the retentive force were found in titanium-nickel clasps in the 1,010 repeated cycles, whereas the other three types of clasp revealed a significant decrease in the force required for removal during the test procedures (repeated analysis of variance P < 0.001). The results suggest that the cast titanium-nickel clasp may be suitable in removable prosthodontic constructions because of its significantly less permanent deformation during service. This report also discusses clinical applicability and some current problems with this new application.
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PMID:Fatigue resistance of titanium-nickel alloy cast clasps. 949 76

A total of 80 freshly extracted human molars, free from caries, cracks & decalcifications, were used in this study. Conservative class I cavities were prepared in the occlusal surface. Two types of amalgam alloys were used, high copper (Dispersalloy) & conventional (Velvalloy). The prepared cavities were classified into 5 groups, 16 each carve (C), carve & polish (CP), precarve burnish (BC), past-carve (CB) & pre post carve burnish (BCB). The specimens were thermally stressed using the stress fatigue device. The marginal integrity of the amalgam enamel interface were evaluated using SEM, for the four marginal quantities: 1--excellent margin, 2--open margins, 3--enamel fracture, and 4--amalgam fracture. The results of this study revealed that higher copper amalgam demonstrated superior marginal integrity than the conventional one. The pre-post carve burnish group showed the highest percentage of excellent margin than the other groups.
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PMID:Effect of surface treatment on marginal integrity of amalgam restorations (in vitro study). 949 75

The fatigue of copper single crystals, orientated for single slip, has been studied using electron channelling contrast imaging in a scanning electron microscope. With the incident beam set at the Bragg condition, changes in the backscattered electron intensity occur as the beam is scanned over dislocations that cause a local tilting of the diffraction planes. This technique allows the evolution of dislocation structures over large areas to be followed through different stages of the fatigue life. Furthermore, it enables direct imaging of dislocation configurations at crack tips. The technique is compared with transmission electron microscopy and electron backscatter diffraction in its application to fatigue studies.
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PMID:Study of dislocation structures near fatigue cracks using electron channelling contrast imaging technique (ECCI). 1046 Jun 84

Wilson's disease (WD) shows a wide heterogeneity in symptoms. In this case report we present hypersomnia as a symptom of WD. The male patient's complaints as fatigue, decreased level of concentration, and highly increased demand of sleeping started at his age of 21 years. No abnormality was found at physical examination. A moderate elevation in liver function tests was found, but all the other laboratory findings were within the normal range. The marked hypersomnia was verified by 24-h cassette EEG polisomnographic monitoring. No abnormality was found at physical examination. EEG, brain CT and MRI were normal. Neither toxic nor infectious disease was detectable. The diagnosis of WD was based on decreased coeruloplasmin level, increased baseline and forced urinary excretion of copper, and decreased level of serum copper. Kayser-Fleischer ring was not detectable. D-penicillamine (DPA) was introduced. At 8-10 months after the initiation of the therapy the patient's complaints gradually resolved. The control sleep record 14 months after the initiation of the DPA therapy was normal. Five years later the patient is currently on penicillamine treatment and he is free of any symptom.
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PMID:Hypersomnia in Wilson's disease: an unusual symptom in an unusual case. 1077 May 29

The aetiology and pathogenesis of the Chronic Fatigue Syndrome (CFS) are still largely unresolved. Accompanying metabolic disorders such as selective n-6 fatty acid depletion suggest that oxidative stress and more specifically lipid peroxidation might play a role in its pathogenesis. In order to investigate this hypothesis, oxidant-antioxidant status and its impact on lipoprotein peroxidation in vitro was examined in 61 patients with unexplained fatigue lasting more than 1 month. They were subdivided into 2 groups: group CFS+ (33 subjects) fulfilled the 1988 Center of Disease Control criteria for CFS and group CFS- did not but was similar as regards age, sex distribution and clinical characteristics. Antioxidant status was similar in the 2 groups except for lower serum transferrin in the CFS + (mean (95 % CI) 2.41 (2.28-2.54) versus 2.73 (2.54-2.92) g/L in the CFS-, p = 0.009) and higher lipoprotein peroxidation in vitro: 6630 (5949-7312) versus 5581 (4852-6310) nmol MDA/mg LDL and VLDL cholesterol x minutes, p = 0.035). CFS intensified the influence of LDL cholesterol (p = 0.012) and of transferrin (p = 0.045) on peroxidation in vitro, suggesting additional pro-oxidant effects. These results indicate that patients with CFS have increased susceptibility of LDL and VLDL to copper-induced peroxidation and that this is related both to their lower levels of serum transferrin and to other unidentified pro-oxidising effects of CFS.
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PMID:Antioxidant status and lipoprotein peroxidation in chronic fatigue syndrome. 1138 5

The transformation behaviour, mechanical properties and cytotoxicity of a binary NiTi42 and a ternary NiTi42Cu7 alloy have been investigated. The transformation temperatures were determined via differential scanning calorimetry, the mechanical properties have been investigated in 3-point bending tests in the temperature range between 6 and 60 degrees C. The cytotoxicity tests were performed on both alloys in cultured epithelial cells from human gingiva. The cytotoxicity investigations included both MTT tests and morphological observations. It is shown that although the ternary alloy is characterised by a narrower hysteresis and superior mechanical properties, including fatigue resistance, its cytotoxicity is higher than that of the binary alloy. This is thought to arise from the release of copper ions in the medium, which upon atomic absorption spectroscopy measurements amount to approximately 2.8 microg cm(-2) for an incubation period of 7 days.
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PMID:On the transformation behaviour, mechanical properties and biocompatibility of two niti-based shape memory alloys: NiTi42 and NiTi42Cu7. 1143 95

Chronic fatigue syndrome is defined by the Atlanta Centers for Disease Control (Atlanta, GA, USA) as debilitating fatigue lasting for longer than 6 months. Symptoms include disturbances of cognition. Certain factors have in the past been shown to influence cognition, including metals such as aluminum, iron, and zinc; and steroids such as dehydroepiandrosterone. In the present study, concentrations of these factors were determined in the serum and plasma of patients and their age- and gender-matched healthy controls (10 women and 5 men in each group). In addition, copper, dehydroepiandrosterone sulphate, cortisol, cholesterol, hemoglobin, ferritin and transferrin concentrations, as well as transferrin genetic subtypes were determined in both groups. The results indicate that patients had significantly increased serum aluminum and decreased iron compared to controls. In the females, serum iron and dehydroepiandrosterone sulphate were significantly decreased and correlated. Total cholesterol was significantly increased, and significantly negatively correlated with dehydroepiandrosterone sulphate. There were no differences in zinc, copper, cortisol, hemoglobin, transferrin and ferritin concentrations, or in transferrin genetic subtypes.
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PMID:Serum concentrations of some metals and steroids in patients with chronic fatigue syndrome with reference to neurological and cognitive abnormalities. 1147 Mar 34

A 27-year-old man with a history of acne presented to his primary care physician because of fatigue and dyspnea on exertion of 4 weeks' duration. He was remarkably pale, orthostatic pulse changes were noted, and a systolic ejection murmur was heard. The patient had profound anemia (hemoglobin concentration, 5.0 g/dL) and neutropenia (neutrophil count, 0.06 x 10(9)/L); he was admitted for further evaluation. A detailed inquiry into his medication history revealed that he was taking several vitamins and zinc gluconate, 850 to 1000 mg/d for 1 year (US recommended daily allowance, 15 mg), as therapy for acne. A zinc toxic and copper-deficient state was confirmed by laboratory studies. The patient was treated with intravenous copper sulfate, followed by 3 months of oral therapy. The complete blood cell count, serum copper level, and serum zinc level returned to normal.
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PMID:Toxic effects associated with consumption of zinc. 1210 10

The distribution of elastic strains (and thus stresses) at the submicrometre length scale within deformed metal single crystals has remarkably broad implications for our understanding of important physical phenomena. These include the evolution of the complex dislocation structures that govern mechanical behaviour within individual grains, the transport of dislocations through such structures, changes in mechanical properties that occur during reverse loading (for example, sheet-metal forming and fatigue), and the analyses of diffraction line profiles for microstructural studies of these phenomena. We present the first direct, spatially resolved measurements of the elastic strains within individual dislocation cells in copper single crystals deformed in tension and compression along <001> axes. Broad distributions of elastic strains are found, with important implications for theories of dislocation structure evolution, dislocation transport, and the extraction of dislocation parameters from X-ray line profiles.
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PMID:X-ray microbeam measurements of individual dislocation cell elastic strains in deformed single-crystal copper. 1688 Aug 2

The objective of this update is to give an overview of the effects of dietary nutrients on the structure and certain functions of the brain. As any other organ, the brain is elaborated from substances present in the diet (sometimes exclusively, for vitamins, minerals, essential amino-acids and essential fatty acids, including omega- 3 polyunsaturated fatty acids). However, for long it was not fully accepted that food can have an influence on brain structure, and thus on its function, including cognitive and intellectuals. In fact, most micronutrients (vitamins and trace-elements) have been directly evaluated in the setting of cerebral functioning. For instance, to produce energy, the use of glucose by nervous tissue implies the presence of vitamin B1; this vitamin modulates cognitive performance, especially in the elderly. Vitamin B9 preserves brain during its development and memory during ageing. Vitamin B6 is likely to benefit in treating premenstrual depression. Vitamins B6 and B12, among others, are directly involved in the synthesis of some neurotransmitters. Vitamin B12 delays the onset of signs of dementia (and blood abnormalities), provided it is administered in a precise clinical timing window, before the onset of the first symptoms. Supplementation with cobalamin improves cerebral and cognitive functions in the elderly; it frequently improves the functioning of factors related to the frontal lobe, as well as the language function of those with cognitive disorders. Adolescents who have a borderline level of vitamin B12 develop signs of cognitive changes. In the brain, the nerve endings contain the highest concentrations of vitamin C in the human body (after the suprarenal glands). Vitamin D (or certain of its analogues) could be of interest in the prevention of various aspects of neurodegenerative or neuroimmune diseases. Among the various vitamin E components (tocopherols and tocotrienols), only alpha-tocopherol is actively uptaken by the brain and is directly involved in nervous membranes protection. Even vitamin K has been involved in nervous tissue biochemistry. Iron is necessary to ensure oxygenation and to produce energy in the cerebral parenchyma (via cytochrome oxidase), and for the synthesis of neurotransmitters and myelin; iron deficiency is found in children with attention-deficit/hyperactivity disorder. Iron concentrations in the umbilical artery are critical during the development of the foetus, and in relation with the IQ in the child; infantile anaemia with its associated iron deficiency is linked to perturbation of the development of cognitive functions. Iron deficiency anaemia is common, particularly in women, and is associated, for instance, with apathy, depression and rapid fatigue when exercising. Lithium importance, at least in psychiatry, is known for a long time. Magnesium plays important roles in all the major metabolisms: in oxidation-reduction and in ionic regulation, among others. Zinc participates among others in the perception of taste. An unbalanced copper metabolism homeostasis (due to dietary deficiency) could be linked to Alzheimer disease. The iodine provided by the thyroid hormone ensures the energy metabolism of the cerebral cells; the dietary reduction of iodine during pregnancy induces severe cerebral dysfunction, actually leading to cretinism. Among many mechanisms, manganese, copper, and zinc participate in enzymatic mechanisms that protect against free radicals, toxic derivatives of oxygen. More specifically, the full genetic potential of the child for physical growth ad mental development may be compromised due to deficiency (even subclinical) of micronutrients. Children and adolescents with poor nutritional status are exposed to alterations of mental and behavioural functions that can be corrected by dietary measures, but only to certain extend. Indeed, nutrient composition and meal pattern can exert either immediate or long-term effects, beneficial or adverse. Brain diseases during aging can also be due to failure for protective mechanism, due to dietary deficiencies, for instance in anti-oxidants and nutrients (trace elements, vitamins, non essential micronutrients such as polyphenols) related with protection against free radicals. Macronutrients are presented in the accompanying paper.
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PMID:Effects of nutrients (in food) on the structure and function of the nervous system: update on dietary requirements for brain. Part 1: micronutrients. 1706 9


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