827 resultados para Failure(Mechanics)
Resumo:
BACKGROUND & AIMS: The prognostic value of the different causes of renal failure in cirrhosis is not well established. This study investigated the predictive value of the cause of renal failure in cirrhosis. METHODS: Five hundred sixty-two consecutive patients with cirrhosis and renal failure (as defined by serum creatinine 1.5 mg/dL on 2 successive determinations within 48 hours) hospitalized over a 6-year period in a single institution were included in a prospective study. The cause of renal failure was classified into 4 groups: renal failure associated with bacterial infections, renal failure associated with volume depletion, hepatorenal syndrome (HRS), and parenchymal nephropathy. The primary end point was survival at 3 months. RESULTS: Four hundred sixty-three patients (82.4%) had renal failure that could be classified in 1 of 4 groups. The most frequent was renal failure associated with infections (213 cases; 46%), followed by hypovolemia-associated renal failure (149; 32%), HRS (60; 13%), and parenchymal nephropathy (41; 9%). The remaining patients had a combination of causes or miscellaneous conditions. Prognosis was markedly different according to cause of renal failure, 3-month probability of survival being 73% for parenchymal nephropathy, 46% for hypovolemia-associated renal failure, 31% for renal failure associated with infections, and 15% for HRS (P .0005). In a multivariate analysis adjusted for potentially confounding variables, cause of renal failure was independently associated with prognosis, together with MELD score, serum sodium, and hepatic encephalopathy at time of diagnosis of renal failure. CONCLUSIONS: A simple classification of patients with cirrhosis according to cause of renal failure is useful in assessment of prognosis and may help in decision making in liver transplantation.
Resumo:
PURPOSE: To examine the effects of the world's most challenging mountain ultra-marathon (Tor des Géants(®) 2012) on the energy cost of three types of locomotion (cycling, level and uphill running) and running kinematics. METHODS: Before (pre-) and immediately after (post-) the competition, a group of ten male experienced ultra-marathon runners performed in random order three submaximal 4-min exercise trials: cycling at a power of 1.5 W kg(-1) body mass; level running at 9 km h(-1) and uphill running at 6 km h(-1) at an inclination of +15 % on a motorized treadmill. Two video cameras recorded running mechanics at different sampling rates. RESULTS: Between pre- and post-, the uphill-running energy cost decreased by 13.8 % (P = 0.004); no change was noted in the energy cost of level running or cycling (NS). There was an increase in contact time (+10.3 %, P = 0.019) and duty factor (+8.1 %, P = 0.001) and a decrease in swing time (-6.4 %, P = 0.008) in the uphill-running condition. CONCLUSION: After this extreme mountain ultra-marathon, the subjects modified only their uphill-running patterns for a more economical step mechanics.
Resumo:
Plasma urate levels are higher in humans than rodents (240-360 vs. â^¼30 μM) because humans lack the liver enzyme uricase. High uricemia in humans may protect against oxidative stress, but hyperuricemia also associates with the metabolic syndrome, and urate and uric acid can crystallize to cause gout and renal dysfunctions. Thus, hyperuricemic animal models to study urate-induced pathologies are needed. We recently generated mice with liver-specific ablation of Glut9, a urate transporter providing access of urate to uricase (LG9KO mice). LG9KO mice had moderately high uricemia (â^¼120 μM). To further increase their uricemia, here we gavaged LG9KO mice for 3 days with inosine, a urate precursor; this treatment was applied in both chow- and high-fat-fed mice. In chow-fed LG9KO mice, uricemia peaked at 300 μM 2 h after the first gavage and normalized 24 h after the last gavage. In contrast, in high-fat-fed LG9KO mice, uricemia further rose to 500 μM. Plasma creatinine strongly increased, indicating acute renal failure. Kidneys showed tubule dilation, macrophage infiltration, and urate and uric acid crystals, associated with a more acidic urine. Six weeks after inosine gavage, plasma urate and creatinine had normalized. However, renal inflammation, fibrosis, and organ remodeling had developed despite the disappearance of urate and uric acid crystals. Thus, hyperuricemia and high-fat diet feeding combined to induce acute renal failure. Furthermore, a sterile inflammation caused by the initial crystal-induced lesions developed despite the disappearance of urate and uric acid crystals.
Resumo:
PURPOSE: Positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) was used to evaluate treatment response in patients with gastrointestinal stromal tumors (GIST) after administration of sunitinib, a multitargeted tyrosine kinase inhibitor, after imatinib failure. PATIENTS AND METHODS: Tumor metabolism was assessed with FDG-PET before and after the first 4 weeks of sunitinib therapy in 23 patients who received one to 12 cycles of sunitinib therapy (4 weeks of 50 mg/d, 2 weeks off). Treatment response was expressed as the percent change in maximal standardized uptake values (SUV). The primary end point of time to tumor progression was compared with early PET results on the basis of traditional Response Evaluation Criteria in Solid Tumors (RECIST) criteria. RESULTS: Progression-free survival (PFS) was correlated with early FDG-PET metabolic response (P < .0001). Using -25% and +25% thresholds for SUV variations from baseline, early FDG-PET response was stratified in metabolic partial response, metabolically stable disease, or metabolically progressive disease; median PFS rates were 29, 16, and 4 weeks, respectively. Similarly, when a single FDG-PET positive/negative was considered after 4 weeks of sunitinib, the median PFS was 29 weeks for SUVs less than 8 g/mL versus 4 weeks for SUVs of 8 g/mL or greater (P < .0001). None of the patients with metabolically progressive disease subsequently responded according to RECIST criteria. Multivariate analysis showed shorter PFS in patients who had higher residual SUVs (P < .0001), primary resistance to imatinib (P = .024), or nongastric GIST (P = .002), regardless of the mutational status of the KIT and PDGFRA genes. CONCLUSION: Week 4 FDG-PET is useful for early assessment of treatment response and for the prediction of clinical outcome. Thus, it offers opportunities to individualize and optimize patient therapy.
Resumo:
We report a case of neonatal lupus erythematosus (NLE) with congenital heart block and severe myocardial failure, which was followed from the 25th week of gestation because of fetal bradycardia. The child was delivered at the 37th week of gestation by elective cesarean section because of echocardiographically documented heart enlargement, pericardial effusion and moderate insufficiency of the mitral and tricuspid valves. In spite of immediate pacing, intubation and supportive treatment, the newborn developed progressive heart failure. Echocardiography showed endocarditis of the mitral valve and diffuse myocarditis. The heart failure resolved under steroid treatment. Our experience supports the early use of steroids in treating myocarditis due to NLE. Intrauterine steroid treatment in the presence of fetal hydrops and congenital heart block is discussed.
Resumo:
Captopril (SQ 14 225), an orally active inhibitor of angiotensin-converting enzyme, was given to 7 hypertensive patients with chronic renal failure whose plasma-creatinine ranged from 1.5--7.4 mg/dl; whose plasma-renin activity was normal; whose hypertension was not controlled by previous therapy consisting in 5 patients of three or more antihypertensive drugs; and whose blood-pressures averaged 176/111 +/- 11/3 mm Hg. Inhibition of converting enzyme by oral captopril, 200 mg twice daily, reduced blood-pressure to 156/100 +/- 9/5 mm Hg. 5 patients needed additional treatment by frusemide 40--250 mg/day orally. With this combined regimen the blood-pressure of all patients averaged 126/85 +/- 4/3 mm Hg after 8 +/- 2 weeks of captopril. The drug was well tolerated. These results suggest that inhibition of angiotensin-converting enzyme with or without sodium depletion is an efficient treatment for hypertension associated with chronic renal failure. It appears that although renin levels in patients with this condition may be "normal", they are inappropriate in relation to the subtle degree of sodium retention that occurs with this disorder.
Resumo:
Unless effective preventive strategies are implemented, aging of the population will result in a significant worsening of the heart failure (HF) epidemic. Few data exist on whether baseline electrocardiographic (ECG) abnormalities can refine risk prediction for HF. METHODS: We examined a prospective cohort of 2,915 participants aged 70 to 79 years without preexisting HF, enrolled between April 1997 and June 1998 in the Health, Aging, and Body Composition (Health ABC) study. Minnesota Code was used to define major and minor ECG abnormalities at baseline and at year 4 follow-up. Using Cox models, we assessed (1) the association between ECG abnormalities and incident HF and (2) the incremental value of adding ECG to the Health ABC HF Risk Score using the net reclassification index. RESULTS: At baseline, 380 participants (13.0%) had minor, and 620 (21.3%) had major ECG abnormalities. During a median follow-up of 11.4 years, 485 participants (16.6%) developed incident HF. After adjusting for the Health ABC HF Risk Score variables, the hazard ratio (HR) was 1.27 (95% CI 0.96-1.68) for minor and 1.99 (95% CI 1.61-2.44) for major ECG abnormalities. At year 4, 263 participants developed new and 549 had persistent abnormalities; both were associated with increased subsequent HF risk (HR 1.94, 95% CI 1.38-2.72 for new and HR 2.35, 95% CI 1.82-3.02 for persistent ECG abnormalities). Baseline ECG correctly reclassified 10.5% of patients with HF events, 0.8% of those without HF events, and 1.4% of the overall population. The net reclassification index across the Health ABC HF risk categories was 0.11 (95% CI 0.03-0.19). CONCLUSIONS: Among older adults, baseline and new ECG abnormalities are independently associated with increased risk of HF. The contribution of ECG screening for targeted prevention of HF should be evaluated in clinical trials.
Resumo:
Rectangular hollow section (RHS) members are components widely used in engineering applications because of their good-looking, good properties in engineering areas and inexpensive cost comparing to members with other sections. The increasing use of RHS in load bearing structures makes it necessary to analyze the fatigue behavior of the RHS members. In this thesis, concentration will be given to the fatigue behavior of the RHS members under variable amplitude pure torsional loading. For the RHS members, failure will normally occur in the corner region if the welded regions are under full penetration. This is because of the complicated stress components' distributions at the RHScorners, where all of three fracture mechanics modes will happen. Mode I is mainly caused by the residual stresses that caused by the manufacturing process. Modes II and III are caused by the applied torsional loading. Stress based Findleymodel is also used to analyze the stress components. Constant amplitude fatigue tests have been done as well as variable amplitude fatigue tests. The specimens under variable amplitude loading gave longer fatigue lives than those under constant amplitude loading. Results from tests show an S-N curvewith slope around 5.
Resumo:
AbstractMyotonic dystrophy type 1 (DM1), also known as Steinert's disease, is an inherited autosomal dominant disease. DM1 is characterized by myotonia, muscular weakness and atrophy, but it has a multisystemic phenotype. The genetic basis of the disease is the abnormal expansion of CTG repeats in the 3' untranslated region of the DM protein kinase (DMPK) gene on chromosome 19. The size of the expansion correlates to the severity of the disease and the age of onset.Respiratory problems have long been recognized to be a major feature of the disease and are the main factor contributing to mortality ; however the mechanisms are only partly known. The aim of our study is to investigate whether respiratory failure results only from the involvement of the dystrophic process at the level of the respiratory muscles or comes also from abnormalities in the neuronal network that generates and controls the respiratory rhythm. The generation of valid transgenic mice displaying the human DM1 phenotype by the group of Dr. Gourdon provided us a useful tool to analyze the brain stem respiratory neurons, spinal phrenic motoneurons and phrenic nerves. We examined therefore these structures in transgenic mice carrying 350-500 CTGs and displaying a mild form of the disease (DM1 mice). The morphological and morphometric analysis of diaphragm muscle sections revealed a denervation of the end-plates (EPs), characterized by a decrease in size and shape complexity of EPs and a reduction in the density of acetylcholine receptors (AChRs). Also a strong and significant reduction in the number of phrenic unmyelinated fibers was detected, but not in the myelinated fibers. In addition, no pathological changes were detected in the cervical motoneurons and medullary respiratory centers (Panaite et al., 2008). These results suggest that the breathing rhythm is probably not affected in mice expressing a mild form of DM1, but rather the transmission of action potentials at the level of diaphragm NMJs is deficient.Because size of the mutation increases over generations, new transgenic mice were obtained from the mice with 350-500 CTGs, resulting from a large increase of CTG repeat in successive generations, these mice carry more than 1300 CTGs (DMSXL) and display a severe DM1 phenotype (Gomes-Pereira et al., 2007). Before we study the mechanism underlying the respiratory failure in DMSXL mice, we analyzed the peripheral nervous system (PNS) in these mice by electrophysiological, histological and morphometric methods. Our results provide strong evidence that DMSXL mice have motor neuropathy (Panaite et al., 2010, submitted). Therefore the DMSXL mice expressing severe DM1 features represent for us a good tool to investigate, in the future, the physiological, structural and molecular alterations underlying respiratory failure in DM1. Understanding the mechanism of respiratory deficiency will help to better target the therapy of these problems in DM1 patients. In addition our results may, in the future, orientate pharmaceutical and clinical research towards possible development of therapy against respiratory deficits associated with the DM1.RésuméLa dystrophic myotonique type 1 (DM1), aussi dénommée maladie de Steinert, est une maladie héréditaire autosomique dominante. Elle est caractérisée par une myotonie, une faiblesse musculaire avec atrophie et se manifeste aussi par un phénotype multisystémique. La base génétique de la maladie est une expansion anormale de répétitions CTG dans une région non traduite en 3' du gène de la DM protéine kinase (DMPK) sur le chromosome 19. La taille de l'expansion est corrélée avec la sévérité et l'âge d'apparition de DM1.Bien que les problèmes respiratoires soient reconnus depuis longtemps comme une complication de la maladie et soient le principal facteur contribuant à la mortalité, les mécanismes en sont partiellement connus. Le but de notre étude est d'examiner si l'insuffisance respiratoire de la DM1 est dû au processus dystrophique au niveau des muscles respiratoires ou si elle est entraînée aussi par des anomalies dans le réseau neuronal qui génère et contrôle le rythme respiratoire. La production par le groupe du Dr. Gourdon de souris transgéniques de DM1, manifestant le phénotype de DM1 humaine, nous a fourni un outil pour analyser les nerfs phréniques, les neurones des centres respiratoires du tronc cérébral et les motoneurones phréniques. Par conséquence, nous avons examiné ces structures chez des souris transgéniques portant 350-500 CTG et affichant une forme légère de la maladie (souris DM1). L'analyse morphologique et morphométrique des sections du diaphragme a révélé une dénervation des plaques motrices et une diminution de la taille et de la complexité de la membrane postsynaptîque, ainsi qu'une réduction de la densité des récepteurs à l'acétylcholine. Nous avons aussi détecté une réduction significative du nombre de fibres nerveuses non myélinisées mais pas des fibres myélinisées. Par ailleurs, aucun changement pathologique n'a été détecté pour les neurones moteurs médullaires cervicaux et centres respiratoires du tronc cérébral (Panaite et al., 2008). Ces résultats suggèrent que le iythme respiratoire n'est probablement pas affecté chez les souris manifestant une forme légère du DM1, mais plutôt que la transmission des potentiels d'action au niveau des plaques motrices du diaphragme est déficiente.Comme la taille du mutation augmente au fil des générations, de nouvelles souris transgéniques ont été générés par le groupe Gourdon; ces souris ont plus de 1300 CTG (DMSXL) et manifestent un phénotype sévère du DM1 (Gomes-Pereira et al., 2007). Avant d'étudier le mécanisme sous-jacent de l'insuffisance respiratoire chez les souris DMSXL, nous avons analysé le système nerveux périphérique chez ces souris par des méthodes électrophysiologiques, histologiques et morphométriques. Nos résultats fournissent des preuves solides que les souris DMSXL manifestent une neuropathie motrice (Panaite et al., 2010, soumis). Par conséquent, les souris DMSXL représentent pour nous un bon outil pour étudier, à l'avenir, les modifications physiologiques, morphologiques et moléculaires qui sous-tendent l'insuffisance respiratoire du DM1. La connaissance du mécanisme de déficience respiratoire en DM1 aidera à mieux cibler le traitement de ces problèmes aux patients. De plus, nos résultats pourront, à l'avenir, orienter la recherche pharmaceutique et clinique vers le développement de thérapie contre le déficit respiratoire associé à DM1.
Resumo:
Myotonic dystrophy (DM1) is a multisystemic disease caused by an expansion of CTG repeats in the region of DMPK, the gene encoding DM protein kinase. The severity of muscle disability in DM1 correlates with the size of CTG expansion. As respiratory failure is one of the main causes of death in DM1, we investigated the correlation between respiratory impairment and size of the (CTG)n repeat in DM1 animal models. Using pressure plethysmography the respiratory function was assessed in control and transgenic mice carrying either 600 (DM600) or >1300 CTG repeats (DMSXL). The statistical analysis of respiratory parameters revealed that both DM1 transgenic mice sub-lines show respiratory impairment compared to control mice. In addition, there is no significant difference in breathing functions between the DM600 and DMSXL mice. In conclusion, these results indicate that respiratory impairment is present in both transgenic mice sub-lines, but the severity of respiratory failure is not related to the size of the (CTG)n expansion.
Resumo:
Previous studies assessed the outcome of ankle arthrodesis (AA) and total ankle replacement (TAR) surgeries; however, the extent of postoperative recovery towards bilateral gait mechanics (BGM) is unknown. We evaluated the outcome of the two surgeries at least 2 years post rehabilitation, focusing on BGM. 36 participants, including 12 AA patients, 12 TAR patients, and 12 controls were included. Gait assessment over 50 m distance was performed utilizing pressure insoles and 3D inertial sensors, following which an intraindividual comparison was performed. Most spatiotemporal and kinematic parameters in the TAR group were indicative of good gait symmetry, while the AA group presented significant differences. Plantar pressure symmetry among the AA group was also significantly distorted. Abnormality in biomechanical behavior of the AA unoperated, contralateral foot was observed. In summary, our results indicate an altered BGM in AA patients, whereas a relatively fully recovered BGM is observed in TAR patients, despite the quantitative differences in several parameters when compared to a healthy population. Our study supports a biomechanical assessment and rehabilitation of both operated and unoperated sides after major surgeries for ankle osteoarthrosis.
Resumo:
This research has been focused at the development of a tuned systematic design methodology, which gives the best performance in a computer aided environment and utilises a cross-technological approach, specially tested with and for laser processed microwave mechanics. A tuned design process scheme is also presented. Because of the currently large production volumes of microwave and radio frequency mechanics even slight improvements of design methodologies or manufacturing technologies would give reasonable possibilities for cost reduction. The typical number of required iteration cycles could be reduced to one fifth of normal. The research area dealing with the methodologies is divided firstly into a function-oriented, a performance-oriented or a manufacturability-oriented product design. Alternatively various approaches can be developed for a customer-oriented, a quality-oriented, a cost-oriented or an organisation-oriented design. However, the real need for improvements is between these two extremes. This means that the effective methodology for the designers should not be too limited (like in the performance-oriented design) or too general (like in the organisation-oriented design), but it should, include the context of the design environment. This is the area where the current research is focused. To test the developed tuned design methodology for laser processing (TDMLP) and the tuned optimising algorithm for laser processing (TOLP), seven different industrial product applications for microwave mechanics have been designed, CAD-modelled and manufactured by using laser in small production series. To verify that the performance of these products meets the required level and to ensure the objectiveness ofthe results extensive laboratory tests were used for all designed prototypes. As an example a Ku-band horn antenna can be laser processed from steel in 2 minutes at the same time obtaining a comparable electrical performance of classical aluminium units or the residual resistance of a laser joint in steel could be limited to 72 milliohmia.
Resumo:
BACKGROUND: Recurrent hepatitis C virus infection after liver transplantation is associated with reduced graft and patient survival. Re-transplantation for graft failure due to recurrent hepatitis C is controversial and not performed in all centers. CASE PRESENTATION: We describe a 54-year-old patient with hepatitis C virus genotype 1b infection and a null response to pegylated interferon-α and ribavirin who developed decompensated graft cirrhosis 6 years after a first liver transplantation. Treatment with sofosbuvir and ribavirin allowed for rapid negativation of serum HCV RNA and was well tolerated despite advanced liver and moderate renal dysfunction. Therapeutic drug monitoring did not reveal any clinically significant drug-drug interactions. Despite virological response, the patient remained severely decompensated and re-transplantation was performed after 46 days of undetectable serum HCV RNA. The patient is doing well 12 months after his second liver transplantation and remains free of hepatitis C virus. CONCLUSIONS: The use of directly acting antivirals may allow for successful liver re-transplantation for recipients who remain decompensated despite virological response and is likely to improve the outcome of liver re-transplantation for end-stage recurrent hepatitis C.