Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many athletes and active people have consumed a large variety of supplements in order to get a good shape or a better performance in competitions. Due to this, several studies have been carried out to determine if these supplements are in fact ergogenic aids. Creatine seems to be related to the performance enhance in high intensity intermittent exercises. Carnitine might probably improve the aerobic capacity by stimulating lipid oxidation on muscle cells during long term exercise. Bicarbonate is thought to increase blood pH delaying the onset of peripheral fatigue in high intensity exercises of short duration and strength training. Some other supplements like branched-chain amino acids and chromium are also involved in body composition changes as a gain of fat free mass and loss of fat mass. The effects caused by these supplements during physical activity have not been fully described in literature yet as well as their side effects.
 ...
PMID:[Relation of some nutritional supplements and physical performance]. 1146 29

A comprehensive failure analysis was performed on 6 femoral components and 1 tibial component that fractured in service. All were Whiteside Ortholoc II total knee arthroplasty components, manufactured from cast cobalt-chromium-molybdenum alloy and porous coated. Fracture surface analysis revealed fatigue-induced failure in all cases. Most fractures occurred at regions of high stress concentration, such as sharp corners, sintered beads, and thin sections. Metallurgical examination showed significant variation in grain size, interdendritic carbides, and hardness between samples. In some cases, continuous carbide networks and voids were prominent at the bead-substrate interface. Patient weight and surgical placement were identified as contributory factors in component failure. Limitations of cast cobalt-chromium-molybdenum alloy in weight-bearing applications must be emphasized, particularly when important determinants, such as design, metallurgy, and specific clinical factors, are less than optimal.
 ...
PMID:Fractured Whiteside Ortholoc II knee components. 1160 12

Fracture of dental implants is a rare phenomenon with severe clinical results. In this article, the literature is reviewed and various causative factors that may lead to fracture are presented. Galvanic activity has not been mentioned before as a possible cause for implant fracture, yet, it can occur at the level of contact with the superstructure. This is illustrated by the case of a titanium implant restored with a non-precious porcelain-fused-to-metal cemented crown that fractured 4 years after loading. The radiographs show alveolar bone resorption around the fixture. Metallurgical analysis of the implant indicated that the fracture was caused by metal fatigue and that the crown metal, a nickel-chromium-molybdenum alloy, exhibited corrosion. These findings suggest a new explanation for implant fractures; cytotoxic nickel ions, leaching from the base metal alloy may cause bone resorption. This in turn leads to increased mobility, facilitating washout of the luting cement. Contact of the base metal with titanium in the presence of oral fluids produces galvanic currents that hasten corrosion and leaching out of nickel ions, thus leading to further bone resorption. Loss of bone support allows lateral bending moments that cause metal fatigue, eventually leading to fracture. Therefore, good treatment planning and appropriate case selection might have prevented this fracture. Furthermore, the use of nonprecious metal alloy for the crown's infrastructure had further contribution to the chain of events that led to the implant's fracture.
 ...
PMID:Fracture of dental implants: literature review and report of a case. 1207 95

We report 10 fatigue fractures of a modern, cemented, cobalt chromium alloy stem (Osteonics Omnifit) for total hip arthroplasty occurring between 1995 and 2004. The primary total hip arthroplasties had been performed between 1989 and 1996. The average age at the time of surgery was 54 years (range, 34-70 years), and the average body mass index was 29 (range, 20-38). The time in situ of the prosthesis at the time of fracture averaged 8 years (range, 4-12 years). Intermediate follow-up radiographs before the fracture were available in 7 cases, all of which demonstrated loss of calcar support. Scanning electron microscopy of the fracture surfaces in 3 of the components showed porosity near the initiation site. Metallography of polished and etched cross sections near the fracture surface revealed large grain size. In the presence of a spontaneous onset of thigh pain at intermediate follow-up in patients with this stem, particularly if associated with loss of calcar support, a fatigue fracture should be considered.
 ...
PMID:Late fatigue fracture of a modern cemented [corrected] cobalt chrome stem for total hip arthroplasty: a report of 10 cases. 1702 57

Highly cross-linked ultra-high molecular weight polyethylene (UHMWPE) decreases wear at the hip by more than 50% compared with conventional UHMWPE. However, melted highly cross-linked polyethylene may be susceptible to fatigue cracking, and annealed highly cross-linked polyethylene may be susceptible to in vivo oxidation. The second-generation highly cross-linked UHMWPE (X3 HXPE) uses a sequential irradiation and annealing process. It preserves mechanical strength properties and has the highest survivorship in functional fatigue testing. The free radical content is low, and its performance under accelerated aging is the same as virgin UHMWPE. Hip simulator studies with 32-mm acetabular components demonstrated 97% wear reduction compared with conventional UHMWPE, and 62% compared with a clinically successful first-generation annealed highly cross-linked polyethylene. The crystallinity, density, and tensile strength of the X3 HXPE material was unchanged by oxidative challenge. X3 HXPE material articulating on cobalt-chromium alloy yields a volumetric wear rate very similar to that of metal-on-metal articulations, but eliminates the concerns of metal ion release. Wear particles generated from the X3 HXPE were the same size as those produced from conventional UHMWPE. Preliminary results suggest X3 HXPE can be used for cups larger than 36 mm.
 ...
PMID:The basis for a second-generation highly cross-linked UHMWPE. 1701 28

A processing technology has been developed that can be applied to many different fine wire medical alloys to improve their fatigue properties. This technology has been used to process a low inclusion alloy, 35 cobalt-35 nitinol-20 chromium-10 Molybdenum (ASTM F562 chemistry), hereinafter referred to as System A. After processing, this ultra fine microstructure exhibited relatively high yield strength, good axial ductility and a fatigue limit of 1 GPa at a fatigue lifetime that exceeded 100 million cycles, as reported here.
 ...
PMID:Nanocrystalline material with gigacycle fatigue life. 1807 28

The influence of low temperature ultrasonic deformation on the electrical resistivity and magnetic properties of nickel-chromium dilute solid solutions is examined. It is shown that changes in the electrical resistivity and magnetic properties of prequenched samples after ultrasonic fatigue can be explained by order-disorder processes during fatigue. It is concluded that ordering at low temperatures during the ultrasonic deformation is associated with high strain rate and high vacancy concentration produced by deformation.
 ...
PMID:Ultrasonic fatigue of nickel-chromium alloys at low temperatures. 1826 33

The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behavior of endodontically treated bovine incisors restored with zirconium dioxide posts and crowns. Forty-eight endodontically treated bovine primary incisors were restored with zirconium dioxide posts (Cerapost, Brasseler), composite build-ups, and crowns cast from a chromium cobalt alloy. In 16 teeth, each of the posts was cemented conventionally with KetacCem (3M ESPE) or adhesively with Panavia F (Kuraray) or RelyX UniCem (3M ESPE). One-half of the specimens in each group were subjected to thermocycling with 10,000 cycles at 5-55 degrees C and mechanical aging, loading the specimens at an angle of 45 degrees in 1,200,000 cycles with 50 N. Fracture resistance was determined by loading the specimens until fracture at an angle of 45 degrees to the long axis of the teeth. The loading test showed that neither cementation mode nor fatigue testing had an influence on the load bearing capability. Most specimens fractured in a favorable way, independent from the type of cementation.
 ...
PMID:Influence of fatigue testing and cementation mode on the load-bearing capability of bovine incisors restored with crowns and zirconium dioxide posts. 1853 45

During normal breathing, the kidneys move up and down due to the diaphragm motion and the renal artery subsequently experiences bending at or close to its point of fixation to the aorta. The impact of this kidney motion on implanted stent fatigue performance was not well understood in the past. Previous study from the authors on an 18-mm long single cobalt-chromium stent showed that the change in bending angle was minor during simulated respiration-induced kidney motion on cadavers. Finite Element Analysis revealed excellent fatigue resistance of the studied cobalt-chromium stent under simulated respiratory motion for the single stent configuration. In this article, the study was extended further to the overlapped stent configuration where a physician deploys two stents overlapping at the stent ends to fully cover a long lesion. Fluoroscopic images showed that the change in bending angle during simulated respiration-induced kidney motion on cadavers was more significant when two cobalt-chromium stents were overlapped. Calculated data of the Goodman analysis for the overlapped stents migrated toward the Goodman diagram failure line, indicating lower fatigue resistance during respiration when compared to a single stent.
 ...
PMID:Respiration-induced kidney motion on cobalt-chromium stent fatigue resistance. 1950 42

Over 35 million adults suffer from fatigue or lack of energy. In this study, we assessed the safety of a novel niacin-bound chromium-based Energy Formulation, which also contained caffeine, D-ribose, Withania somnifera extract, and selected amino acids. Niacin-bound chromium is a novel source of bioavailable chromium (III), and known to promote healthy lipid profile. Male and female Sprague-Dawley rats were fed 125 ppm Energy Formulation for 90 consecutive days. Body weight, feed, and water intake were monitored over the period of 90 days. No significant changes were observed between the control and treatment groups following subchronic supplementation with this Energy Formulation. Furthermore, no significant changes were observed in selected organ weights individually and as percentages of body and brain weights. The Energy Formulation supplementation did not cause changes in hepatic lipid peroxidation or DNA fragmentation after 30, 60, or 90 days of treatment. Hematology, clinical chemistry, and histopathological evaluations revealed no adverse effects in the treatment group. These findings demonstrate the safety of this Energy Formulation.
 ...
PMID:Safety assessment of a novel niacin-bound chromium-based energy formulation. 2002 Oct 19


<< Previous 1 2 3 4 5 6 7 Next >>