879 resultados para Long-Life Fatigue


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1. Parasitism is a non-negligible cost of reproduction in wild organisms, and hosts are selected to partition resources optimally between current and future reproduction. While parents can compensate for the cost of parasitism by increasing their current reproductive investment, such change in resource allocation is expected to carry-over costs on future reproduction. 2. Life history theory predicts that because long-lived organisms have a high residual reproductive value, they should be more reluctant to increase parental effort in response to parasites. Also, when rearing successive infested broods, the cost of parasitism can cumulate over the years and hence be exacerbated by past infestations. 3. We tested these two predictions in the alpine swift Apus melba, a long-lived colonial bird that is infested intensely by the nest-based blood sucking louse-fly Crataerina melbae. For this purpose, we manipulated ectoparasite load over 3 consecutive years and measured reproductive parameters in successive breeding attempts of adults assigned randomly to 'parasitized' and 'deparasitized' treatments. 4. In current reproduction, fathers of experimentally parasitized broods produced a similar number of offspring as fathers from the deparasitized treatment, but the rearing period was prolonged by 4 days. Fathers that were assigned to the parasitized treatment in year x produced significantly fewer fledglings the following year x + 1 than those of the deparasitized treatment. The number of young produced by fathers in year x + 1 was correlated negatively with the number of days they cared for their brood in the previous year x. We also found a significant interaction between treatments performed over 2 successive years, with fathers of parasitized broods suffering a larger fitness loss if in the past they had already cared for a parasitized brood rather than for a deparasitized one. Similar effects of parasitism, although partly non-significant (0.05 < P-values > 0.10), were found in mothers. 5. Altogether, our results show that parasites can modify resource allocation between current and future reproduction in long-lived hosts, and that the cost of parasitism can cumulate over the years. It emphasizes the fact that effects of parasites can depend on past infestations and become apparent in future reproduction only.

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Glucagon-like peptide-1(7-37) (GLP-1) is the most potent insulinotropic hormone characterized thus far. Because its activity is preserved in non-insulin-dependent diabetes mellitus (NIDDM) patients, it is considered a potential new drug for the treatment of this disease. One limitation in its therapeutic use is a short half-life in vivo (5 minutes), due in part to a fast degradation by the endoprotease dipeptidylpeptidase IV (DPPIV). Recently, it was reported that GLP-1 became resistant to DPPIV when the alanine residue at position 8 was replaced by a glycine (GLP-1-Gly8). We report here that this change slightly decreased the affinity of the peptide for its receptor (IC50, 0.41 +/- 0.14 and 1.39 +/- 0.61 nmol/L for GLP-1 and GLP-1-Gly8, respectively) but did not change the efficiency to stimulate accumulation of intracellular cyclic adenosine monophosphate (cAMP) (EC50, 0.25 +/- 0.05 and 0.36 +/- 0.06 nmol/L for GLP-1 and GLP-1-Gly8, respectively). Second, we demonstrate for the first time that this mutant has an improved insulinotropic activity compared with the wild-type peptide when tested in vivo in an animal model of diabetes. A single injection of 0.1 nmol GLP-1-Gly8 in diabetic mice fed a high-fat diet can correct fasting hyperglycemia and glucose intolerance for several hours, whereas the activity of 1 nmol GLP-1 vanishes a few minutes after injection. These actions were correlated with increased insulin and decreased glucagon levels. Interestingly, normoglycemia was maintained over a period that was longer than the predicted peptide half-life, suggesting a yet undescribed long-term effect of GLP-1-Gly8. GLP-1-Gly8 thus has a markedly improved therapeutic potential compared with GLP-1, since it can be used at much lower doses and with a more flexible schedule of administration.

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BACKGROUND: The occurrence of depression in younger adults is related to the combination of long-standing factors such as personality traits (neuroticism) and more acute factors such as the subjective impact of stressful life events. Whether an increase in physical illnesses changes these associations in old age depression remains a matter of debate. METHODS: We compared 79 outpatients with major depression and 102 never-depressed controls; subjects included both young (mean age: 35 years) and older (mean age: 70 years) adults. Assessments included the Social Readjustment Rating Scale, NEO Personality Inventory and Cumulative Illness Rating Scale. Logistic regression models analyzed the association between depression and subjective impact of stressful life events while controlling for neuroticism and physical illness. RESULTS: Patients and controls experienced the same number of stressful life events in the past 12 months. However, in contrast to the controls, patients associated the events with a subjective negative emotional impact. Negative stress impact and levels of neuroticism, but not physical illness, significantly predicted depression in young age. In old age, negative stress impact was weakly associated with depression. In this age group, depressive illness was also determined by physical illness burden and neuroticism. CONCLUSIONS: Our data suggest that the subjective impact of life stressors, although rated as of the same magnitude, plays a less important role in accounting for depression in older age compared to young age. They also indicate an increasing weight of physical illness burden in the prediction of depression occurrence in old age.

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Background: Gouty arthritis is a painful inflammatory disease with a significant impact on patients' HRQoL. In gouty arthritis, the inflammatory response is initiated by interleukin-1b (IL-1b) release, due to activation of the NALP3 inflammasome by MSU crystals. Canakinumab, a fully human anti-IL-1b antibody has a long half-life and has been shown to control inflammation in gouty arthritis. This study evaluated changes in HRQoL in gouty arthritis patients following treatment with canakinumab or triamcinolone acetonide (TA).Methods: This was an 8-week, dose-ranging, multi-center, active controlled, single-blind study. Patients (>=18 to <=80 years) experiencing an acute gouty arthritis flare, refractory to or contraindicated to NSAlDs and/or colchicine, were randomized to canakinumab 10, 25, 50, 90, 150 mg sc or TA 40 mg im. HRQoL was assessed as an exploratory endpoint at baseline and different pre-specified time-points using patient reported outcomes evaluating general mental and physical component summary scores and subscale scores of SF-36® (acute version 2) and functional disability (HAQ-DI©). We report HRQoL results for canakinumab 150 mg, the dose that was selected for the Phase III studies.Results: Baseline assessments showed a major impact on the HRQoL during acute gouty arthritis. Compared to TA, canakinumab 150 mg showed greater improvements in SF-36® physical and mental component summary and subscale scores at 7 days post-dose.In the canakinumab 150 mg group, the most severe impairment at baseline was reported for physical functioning and bodily pain; levels of 41.5 and 36.0, respectively, which improved within 7 days to 80.0 and 72.2 (mean increases of 39.0 and 35.6) approaching levels of the general US population (84.2 and 75.2). 8 weeks post-dose patients reached levels of 86.1 and 86.6 (mean increases of 44.6 and 50.6 for physical functioning and bodily pain, respectively) and these were higher than levels seen in the general US population. This was in contrast to patients treated with TA, who showed less improvement within 7 days (mean increases of 23.3 and 21.3 for physical function and bodily pain, respectively). None of the scores reached levels of the general US population 8 weeks post-dose. Functional disability scores, as measured by the HAQ-DI© decreased in both treatment groupsConclusions: All canakinumab doses showed a rapid improvement in physical and mental well-being of gouty arthritis patients based on SF-36® scores, in particular the 150 mg dose. In contrast to the TA group, patients treated with canakinumab showed improvement within 7 days in physical function and bodily pain approaching levels of the general population. The 150 mg dose of canakinumab was selected for further development in Phase III studies.

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This report is formatted to independently present four individual investigations related to similar web gap fatigue problems. Multiple steel girder bridges commonly exhibit fatigue cracking due to out-of-plane displacement of the web near the diaphragm connections. This fatigue-prone web gap area is typically located in negative moment regions of the girders where the diaphragm stiffener is not attached to the top flange. In the past, the Iowa Department of Transportation has attempted to stop fatigue crack propagation in these steel girder bridges by drilling holes at the crack tips. Other nondestructive retrofits have been tried; in a particular case on a two-girder bridge with floor beams, angles were bolted between the stiffener and top flange. The bolted angle retrofit has failed in the past and may not be a viable solution for diaphragm bridges. The drilled hole retrofit is often only a temporary solution, so a more permanent and effective retrofit is required. A new field retrofit has been developed that involves loosening the bolts in the connection between the diaphragm and the girders. Research on the retrofit has been initiated; however, no long-term studies of the effects of bolt loosening have been performed. The intent of this research is to study the short-term effects of the bolt loosening retrofit on I-beam and channel diaphragm bridges. The research also addressed the development of a continuous remote monitoring system to investigate the bolt loosening retrofit on an X-type diaphragm bridge over a number of months, ensuring that the measured strain and displacement reductions are not affected by time and continuous traffic loading on the bridge. The testing for the first three investigations is based on instrumentation of web gaps in a negative moment region on Iowa Department of Transportation bridges with I-beam, channel, and X-type diaphragms. One bridge of each type was instrumented with strain gages and deflection transducers. Field tests, using loaded trucks of known weight and configuration, were conducted on the bridges with the bolts in the tight condition and after implementing the bolt loosening retrofit to measure the effects of loosening the diaphragm bolts. Long-term data were also collected on the X-diaphragm bridge by a data acquisition system that collected the data continuously under ambient truck loading. The collected data were retrievable by an off-site modem connection to the remote data acquisition system. The data collection features and ruggedness of this system for remote bridge monitoring make it viable as a pilot system for future monitoring projects in Iowa. Results indicate that loosening the diaphragm bolts reduces strain and out-of-plane displacement in the web gap, and that the reduction is not affected over time by traffic or environmental loading on the bridge. Reducing the strain in the web gap allows the bridge to support more cycles of loading before experiencing fatigue, thus increase the service life of the bridge. Two-girder floor beam bridges may also exhibit fatigue cracking in girder webs.

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A 59-year-old kidney recipient was diagnosed with a late onset of severe chronic inflammatory demyelinating polyradiculoneuropathy and almost fully recovered after stopping tacrolimus and one course of intravenous immunoglobulin treatment. Unique features of this patient are the unusually long time lapse between initiation of tacrolimus and the adverse effect (10 years), a strong causality link and several arguments pointing toward an inflammatory etiology. When facing new neurological signs and symptoms in graft recipients, it is important to bear in mind the possibility of a drug-induced adverse event. Discontinuation of the suspect drug and immunomodulation are useful treatment options.

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About 30 million people live above 2500 m in the Andean Mountains of South America. Among them are 5.5 million Aymaras, an ethnic group with its own language, living on the altiplano of Bolivia, Peru, and northern Chile at altitudes of up to 4400 m. In this high altitude region traces of human population go back for more than 2000 years with constant evolutionary pressure on its residents for genetic adaptation to high altitude. Aymaras as the assumed direct descendents of the ancient cultures living in this region were the focus of much research interest during the last decades and several distinctive adaptation patterns to life at high altitude have been described in this ethnic group. The aim of this article was to review the physiology and pathophysiology of circulatory adaptation and maladaptation to longtime altitude exposure in Aymaras and Caucasians.

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Conjugated linoleic acid (CLA) has been reported to exert beneficial physiological effects on body composition and the immune system. However, little information is available on the influence of CLA on immune function during early life periods. The present study evaluates the effect of feeding an 80:20 mixture of cis-9,trans-11- and trans-10,cis-12-CLA isomers duringgestation, suckling and early infancy on the systemic and mucosal immune responses of Wistar rats at three different time points: at the end of the suckling period (21-day-old rats), in early infancy (28-day-old rats), and later in life (adulthood). Cis-9,trans-11- and trans-10,cis-12-CLA isomers were detected in the milk of CLA-fed dams and in the plasma of all CLA-supplemented pups, and the highest content was achieved in those rats supplemented over the longest period. Dietary supplementation with that CLA mix enhances the systemic production of the main in vivo and ex vivo immunoglobulin (Ig) isotypes in 21- and 28-day-old rats. Moreover, CLA supplementation during suckling and early infancy also enhances the humoral immune defenses at intestinal level, by means of mucosal IgA increase, whereas down-regulates thesystemic lymphoproliferative response. Finally, we described herein how feeding a diet enriched with the same isomer mix of cis9,trans11- and trans10,cis12-CLA from gestation to adulthood improves the capacity of adult rats to achieve a specific systemic and mucosal immune responses. All these data support the immunomodulatory effects of dietary supplementation of CLA, particularly of the cis9,trans11-CLA isomer, during early stages of life on immune system development, as well as the long-term effects on the specific immune response in adult age.

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The AASHTO strategic plan in 2005 for bridge engineering identified extending the service life of bridges and accelerating bridge construction as two of the grand challenges in bridge engineering. These challenges have the objective of producing safer and more economical bridges at a faster rate with a minimum service life of 75 years and reduced maintenance cost to serve the country’s infrastructure needs. Previous studies have shown that a prefabricated full-depth precast concrete deck system is an innovative technique that accelerates the rehabilitation process of a bridge deck, extending its service life with reduced user delays and community disruptions and lowering its life-cycle costs. Previous use of ultra-high performance concrete (UHPC) for bridge applications in the United States has been considered to be efficient and economical because of its superior structural characteristics and durability properties. Full-depth UHPC waffle deck panel systems have been developed over the past three years in Europe and the United States. Subsequently, a single span, 60-ft long and 33-ft wide prototype bridge with full-depth prefabricated UHPC waffle deck panels has been designed and built for a replacement bridge in Wapello County, Iowa. The structural performance characteristics and the constructability of the UHPC waffle deck system and its critical connections were studied through an experimental program at the structural laboratory of Iowa State University (ISU). Two prefabricated full-depth UHPC waffle deck (8 feet by 9 feet 9 inches by 8 inches) panels were connected to 24-ft long precast girders, and the system was tested under service, fatigue, overload, and ultimate loads. Three months after the completion of the bridge with waffle deck system, it was load tested under live loads in February 2012. The measured strain and deflection values were within the acceptable limits, validating the structural performance of the bridge deck. Based on the laboratory test results, observations, field testing of the prototype bridge, and experience gained from the sequence of construction events such as panel fabrication and casting of transverse and longitudinal joints, a prefabricated UHPC waffle deck system is found to be a viable option to achieve the goals of the AASHTO strategic plan.

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Background: Declining physical activity is associated with a rising burden of global disease. There is little evidence about effective ways to increase adherence to physical activity. Therefore, interventions are needed that produce sustained increases in adherence to physical activity and are cost-effective. The purpose is to assess the effectiveness of a primary care physical activity intervention in increasing adherence to physical activity in the general population seen in primary care. Method and design: Randomized controlled trial with systematic random sampling. A total of 424 subjects of both sexes will participate; all will be over the age of 18 with a low level of physical activity (according to the International Physical Activity Questionnaire, IPAQ), self-employed and from 9 Primary Healthcare Centres (PHC). They will volunteer to participate in a physical activity programme during 3 months (24 sessions; 2 sessions a week, 60 minutes per session). Participants from each PHC will be randomly allocated to an intervention (IG) and control group (CG). The following parameters will be assessed pre and post intervention in both groups: (1) health-related quality of life (SF-12), (2) physical activity stage of change (Prochaska's stages of change), (3) level of physical activity (IPAQ-short version), (4) change in perception of health (vignettes from the Cooperative World Organization of National Colleges, Academies, and Academic Associations of Family Physicians, COOP/WONCA), (5) level of social support for the physical activity practice (Social Support for Physical Activity Scale, SSPAS), and (6) control based on analysis (HDL, LDL and glycated haemoglobin).Participants' frequency of visits to the PHC will be registered over the six months before and after the programme. There will be a follow up in a face to face interview three, six and twelve months after the programme, with the reduced version of IPAQ, SF-12, SSPAS, and Prochaska's stages. Discussion: The pilot study showed the effectiveness of an enhanced low-cost, evidence-based intervention in increased physical activity and improved social support. If successful in demonstrating long-term improvements, this randomised controlled trial will be the first sustainable physical activity intervention based in primary care in our country to demonstrate longterm adherence to physical activity. Trial Registration: A service of the U.S. National Institutes of Health. Developed by the National Library of Medicine. ClinicalTrials.gov ID: NCT00714831.

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Resveratrol is a polyphenol that is mainly found in grapes and red wine and has been reported to be a caloric restriction (CR) mimetic driven by Sirtuin 1 (SIRT1) activation. Resveratrol increases metabolic rate, insulin sensitivity, mitochondrial biogenesis and physical endurance, and reduces fat accumulation in mice. In addition, resveratrol may be a powerful agent to prevent age-associated neurodegeneration and to improve cognitive deficits in Alzheimer's disease (AD). Moreover, different findings support the view that longevity in mice could be promoted by CR. In this study, we examined the role of dietary resveratrol in SAMP8 mice, a model of age-related AD. We found that resveratrol supplements increased mean life expectancy and maximal life span in SAMP8 and in their control, the related strain SAMR1. In addition, we examined the resveratrol-mediated neuroprotective effects on several specific hallmarks of AD. We found that long-term dietary resveratrol activates AMPK pathways and pro-survival routes such as SIRT1 in vivo. It also reduces cognitive impairment and has a neuroprotective role, decreasing the amyloid burden and reducing tau hyperphosphorylation.

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Resveratrol is a polyphenol that is mainly found in grapes and red wine and has been reported to be a caloric restriction (CR) mimetic driven by Sirtuin 1 (SIRT1) activation. Resveratrol increases metabolic rate, insulin sensitivity, mitochondrial biogenesis and physical endurance, and reduces fat accumulation in mice. In addition, resveratrol may be a powerful agent to prevent age-associated neurodegeneration and to improve cognitive deficits in Alzheimer's disease (AD). Moreover, different findings support the view that longevity in mice could be promoted by CR. In this study, we examined the role of dietary resveratrol in SAMP8 mice, a model of age-related AD. We found that resveratrol supplements increased mean life expectancy and maximal life span in SAMP8 and in their control, the related strain SAMR1. In addition, we examined the resveratrol-mediated neuroprotective effects on several specific hallmarks of AD. We found that long-term dietary resveratrol activates AMPK pathways and pro-survival routes such as SIRT1 in vivo. It also reduces cognitive impairment and has a neuroprotective role, decreasing the amyloid burden and reducing tau hyperphosphorylation.

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To provide insight into subgrade non-uniformity and its effects on pavement performance, this study investigated the influence of non-uniform subgrade support on pavement responses (stress and deflection) that affect pavement performance. Several reconstructed PCC pavement projects in Iowa were studied to document and evaluate the influence of subgrade/subbase non-uniformity on pavement performance. In situ field tests were performed at 12 sites to determine the subgrade/subbase engineering properties and develop a database of engineering parameter values for statistical and numerical analysis. Results of stiffness, moisture and density, strength, and soil classification were used to determine the spatial variability of a given property. Natural subgrade soils, fly ash-stabilized subgrade, reclaimed hydrated fly ash subbase, and granular subbase were studied. The influence of the spatial variability of subgrade/subbase on pavement performance was then evaluated by modeling the elastic properties of the pavement and subgrade using the ISLAB2000 finite element analysis program. A major conclusion from this study is that non-uniform subgrade/subbase stiffness increases localized deflections and causes principal stress concentrations in the pavement, which can lead to fatigue cracking and other types of pavement distresses. Field data show that hydrated fly ash, self-cementing fly ash-stabilized subgrade, and granular subbases exhibit lower variability than natural subgrade soils. Pavement life should be increased through the use of more uniform subgrade support. Subgrade/subbase construction in the future should consider uniformity as a key to long-term pavement performance.

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As a result of the collapse of a 140 foot high-mast lighting tower in Sioux City, Iowa in November of 2003, a thorough investigation into the behavior and design of these tall, yet relatively flexible structures was undertaken. Extensive work regarding the root cause of this failure was carried out by Robert Dexter of The University of Minnesota. Furthermore, a statewide inspection of all the high-mast towers in Iowa revealed fatigue cracks and loose anchor bolts on other existing structures. The current study was proposed to examine the static and dynamic behavior of a variety of towers in the State of Iowa utilizing field testing, specifically long-term monitoring and load testing. This report presents the results and conclusions from this project. The field work for this project was divided into two phases. Phase 1 of the project was conducted in October 2004 and focused on the dynamic properties of ten different towers in Clear Lake, Ames, and Des Moines, Iowa. Of those ten, two were also instrumented to obtain stress distributions at various details and were included in a 12 month long-term monitoring study. Phase 2 of this investigation was conducted in May of 2005, in Sioux City, Iowa, and focused on determining the static and dynamic behavior of a tower similar to the one that collapsed in November 2003. Identical tests were performed on a similar tower which was retrofitted with a more substantial replacement bottom section in order to assess the effect of the retrofit. A third tower with different details was dynamically load tested to determine its dynamic characteristics, similar to the Phase 1 testing. Based on the dynamic load tests, the modal frequencies of the towers fall within the same range. Also, the damping ratios are significantly lower in the higher modes than the values suggested in the AASHTO and CAN/CSA specifications. The comparatively higher damping ratios in the first mode may be due to aerodynamic damping. These low damping ratios in combination with poor fatigue details contribute to the accumulation of a large number of damage-causing cycles. As predicted, the stresses in the original Sioux City tower are much greater than the stresses in the retrofitted towers at Sioux City. Additionally, it was found that poor installation practices which often lead to loose anchor bolts and out-of-level leveling nuts can cause high localized stresses in the towers, which can accelerate fatigue damage.

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The current study was initiated to quantify the stresses induced in critical details on the reinforcing jacket and the tower itself through the use of field instrumentation, load testing, and long-term monitoring. Strain gages were installed on the both the tower and the reinforcing jacket. Additional strain gages were installed on two anchor rods. Tests were conducted with and without the reinforcing jacket installed. Data were collected from all strain gages during static load testing and were used to study the stress distribution of the tower caused by known loads, both with and without the reinforcing jacket. The tower was tested dynamically by first applying a static load, and then quickly releasing the load causing the tower to vibrate freely. Furthermore, the tower was monitored over a period of over 1 year to obtain stress range histograms at the critical details to be used for a fatigue evaluation. Also during the long-term monitoring, triggered time-history data were recorded to study the wind loading phenomena that excite the tower.