93 resultados para function and evolution
em BORIS: Bern Open Repository and Information System - Berna - Suiça
Resumo:
Despite the strong increase in observational data on extrasolar planets, the processes that led to the formation of these planets are still not well understood. However, thanks to the high number of extrasolar planets that have been discovered, it is now possible to look at the planets as a population that puts statistical constraints on theoretical formation models. A method that uses these constraints is planetary population synthesis where synthetic planetary populations are generated and compared to the actual population. The key element of the population synthesis method is a global model of planet formation and evolution. These models directly predict observable planetary properties based on properties of the natal protoplanetary disc, linking two important classes of astrophysical objects. To do so, global models build on the simplified results of many specialized models that address one specific physical mechanism. We thoroughly review the physics of the sub-models included in global formation models. The sub-models can be classified as models describing the protoplanetary disc (of gas and solids), those that describe one (proto)planet (its solid core, gaseous envelope and atmosphere), and finally those that describe the interactions (orbital migration and N-body interaction). We compare the approaches taken in different global models, discuss the links between specialized and global models, and identify physical processes that require improved descriptions in future work. We then shortly address important results of planetary population synthesis like the planetary mass function or the mass-radius relationship. With these statistical results, the global effects of physical mechanisms occurring during planet formation and evolution become apparent, and specialized models describing them can be put to the observational test. Owing to their nature as meta models, global models depend on the results of specialized models, and therefore on the development of the field of planet formation theory as a whole. Because there are important uncertainties in this theory, it is likely that the global models will in future undergo significant modifications. Despite these limitations, global models can already now yield many testable predictions. With future global models addressing the geophysical characteristics of the synthetic planets, it should eventually become possible to make predictions about the habitability of planets based on their formation and evolution.
Resumo:
AIMS: The effect of cardiac resynchronization therapy (CRT) on right ventricular ejection fraction (RVEF) has not been well studied. Furthermore, it is unclear whether baseline RVEF influences response to CRT. To evaluate the acute and chronic effects of CRT on right ventricular systolic function, and to investigate whether baseline RVEF impacts response to CRT. METHODS AND RESULTS: Forty-four patients with a standard indication for CRT underwent radionuclide angiography at baseline and after at least 6 months' follow-up for measuring RVEF, right ventricular synchrony (using phase analysis), and left ventricular ejection fraction (LVEF). In addition, NYHA functional class and 6-min walking distance (6MWD) were evaluated. There were no significant acute changes in RVEF with CRT. After a mean follow-up of 9 +/- 5 months, RVEF was slightly improved (by 1.9 +/- 5.0% in absolute terms, P = 0.016), and to a lesser extent than LVEF (5.1 +/- 9.0%, P = 0.009 compared with RVEF). Right ventricular dyssynchrony was significantly improved at follow-up (P = 0.016). Patients with a baseline RVEF < or = 0.35 (n = 19) were less likely to improve in NYHA class (P = 0.016), and also tended to improve less in 6MWD and LVEF (P < 0.06). CONCLUSION: Cardiac resynchronization therapy has no acute effect on RVEF, and only slightly improves RVEF at follow-up. Patients with reduced RVEF at baseline were less likely to respond to CRT, indicating that right ventricular systolic dysfunction may play a role in patient selection.
Resumo:
Duchenne muscular dystrophy (DMD) is a hereditary X-linked recessive disorder affecting the synthesis of dystrophin, a protein essential for structural stability in muscle. Dystrophin also occurs in the central nervous system, particularly in the neocortex, hippocampus and cerebellum. Quantitative metabolic analysis by localized (1) H MRS was performed in the cerebellum (12 patients and 15 controls) and a temporo-parietal location (eight patients and 15 controls) in patients with DMD and healthy controls to investigate possible metabolic differences. In addition, the site of individual mutations on the dystrophin gene was analyzed and neuropsychological cognitive functions were examined. Cognitive deficits in the patient group were found in line with earlier investigations, mainly concerning verbal short-term memory, visuo-spatial long-term memory and verbal fluency, but also the full-scale IQ. Causal mutations were identified in all patients with DMD. Quantitative MRS showed consistent choline deficits, in both cerebellar white matter and temporo-parietal cortex, as well as small, but significant, metabolic abnormalities for glutamate and total N-acetyl compounds in the temporo-parietal region. Compartment water analysis did not reveal any abnormalities. In healthy subjects, choline levels were age related in the cerebellum. The choline deficit contrasts with earlier findings in DMD, where a surplus of choline was postulated for the cerebellum. In patients, total N-acetyl compounds in the temporo-parietal region were related to verbal IQ and verbal short-term memory. However, choline, the putative main metabolic abnormality, was not found to be associated with cognitive deficits. Furthermore, in contrast with the cognitive performance, the metabolic brain composition did not depend significantly on whether or not gene mutations concerned the expression of the dystrophin isoform Dp140, leading to the conclusion that the effect of the missing Dp140 isoform on cognitive performance is not mediated through the observed metabolite composition, or is caused by local effects beyond the resolution accessible to MRS investigations.
Resumo:
Olfactory impairment has been reported in drug-induced parkinsonism (DIP), but the relationship between dopaminergic dysfunction and smell deficits in DIP patients has not been characterized. To this end, we studied 16 DIP patients and 13 patients affected by Parkinson's disease (PD) using the "Sniffin' Sticks" test and [(123)I] FP-CIT SPECT (single-photon emission computed tomography). DIP patients were divided based on normal (n = 9) and abnormal (n = 7) putamen dopamine transporter binding. Nineteen healthy age- and sex-matched subjects served as controls of smell function. Patients with DIP and pathological putamen uptake had abnormal olfactory function. In this group of patients, olfactory TDI scores (odor threshold, discrimination and identification) correlated significantly with putamen uptake values, as observed in PD patients. By contrast, DIP patients with normal putamen uptake showed odor functions-with the exception of the threshold subtest-similar to control subjects. In this group of patients, no significant correlation was observed between olfactory TDI scores and putamen uptake values. The results of our study suggest that the presence of smell deficits in DIP patients might be more associated with dopaminergic loss rather than with a drug-mediated dopamine receptor blockade. These preliminary results might have prognostic and therapeutic implications, as abnormalities in these individuals may be suggestive of an underlying PD-like neurodegenerative process.
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Recent data have suggested a relation among long-term endurance sport practice, left atrial remodeling, and atrial fibrillation. We investigated the influence of an increased vagal tone, represented by the early repolarization (ER) pattern, on diastolic function and left atrial size in professional soccer players. Fifty-four consecutive athletes underwent electrocardiography, echocardiography, and exercise testing as part of their preparticipation screening. Athletes were divided into 2 groups according to presence or absence of an ER pattern, defined as a ST-segment elevation at the J-point (STE) > or =0.1 mm in 2 leads. For linear comparisons average STE was calculated. Mean age was 24 +/- 4 years. Twenty-five athletes (46%) showed an ER pattern. Athletes with an ER pattern had a significant lower heart rate (54 +/- 9 vs 62 +/- 11 beats/min, p = 0.024), an increased E/e' ratio (6.1 +/- 1.2 vs 5.1 +/- 1.0, p = 0.002), and larger volumes of the left atrium (25.6 +/- 7.3 vs 21.8 +/- 5.0 ml/m(2), p = 0.031) compared to athletes without an ER pattern. There were no significant differences concerning maximum workload, left ventricular dimensions, and systolic function. Univariate regression analysis revealed significant correlations among age, STE, and left atrial volume. In a stepwise multivariate regression analysis age, STE and e' contributed independently to left atrial size (r = 0.659, p <0.001). In conclusion, athletes with an ER pattern had an increased E/e' ratio, reflecting a higher left atrial filling pressure, contributing to left atrial remodeling over time.
Resumo:
Despite association with lung growth and long-term respiratory morbidity, there is a lack of normative lung function data for unsedated infants conforming to latest European Respiratory Society/American Thoracic Society standards. Lung function was measured using an ultrasonic flow meter in 342 unsedated, healthy, term-born infants at a mean ± sd age of 5.1 ± 0.8 weeks during natural sleep according to the latest standards. Tidal breathing flow-volume loops (TBFVL) and exhaled nitric oxide (eNO) measurements were obtained from 100 regular breaths. We aimed for three acceptable measurements for multiple-breath washout and 5-10 acceptable interruption resistance (R(int)) measurements. Acceptable measurements were obtained in ≤ 285 infants with high variability. Mean values were 7.48 mL·kg⁻¹ (95% limits of agreement 4.95-10.0 mL·kg⁻¹) for tidal volume, 14.3 ppb (2.6-26.1 ppb) for eNO, 23.9 mL·kg⁻¹ (16.0-31.8 mL·kg⁻¹) for functional residual capacity, 6.75 (5.63-7.87) for lung clearance index and 3.78 kPa·s·L⁻¹ (1.14-6.42 kPa·s·L⁻¹) for R(int). In males, TBFVL outcomes were associated with anthropometric parameters and in females, with maternal smoking during pregnancy, maternal asthma and Caesarean section. This large normative data set in unsedated infants offers reference values for future research and particularly for studies where sedation may put infants at risk. Furthermore, it highlights the impact of maternal and environmental risk factors on neonatal lung function.
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We examined the possible role of H(+) activated acid-sensing ion channels in pain perception. We characterized expression in bladder dome biopsies from patients with bladder pain syndrome and controls, in cultured human urothelium and in urothelial TEU-2 cells.
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The impact of abnormal spirometric findings on risk for incident heart failure among older adults without clinically apparent lung disease is not well elucidated.
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Both subclinical hypothyroidism and the metabolic syndrome have been associated with increased risk of coronary heart disease events. It is unknown whether the prevalence and incidence of metabolic syndrome is higher as TSH levels increase, or in individuals with subclinical hypothyroidism. We sought to determine the association between thyroid function and the prevalence and incidence of the metabolic syndrome in a cohort of older adults.
Resumo:
Primary aim of this study was to evaluate the effect of our therapeutical management in patients with painful bladder syndrome (PBS)/interstitial cystitis (IC) on sexual function, quality of life and bladder symptoms using validated tools prospectively
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To evaluate the prevalence of prolapse and related bladder, bowel, and sexual problems in transsexual patients (TS) after sex reassignment surgery.
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The risk of Hodgkin lymphoma (HL) is increased in patients infected with HIV-1. We studied the incidence and outcomes of HL, and compared CD4⁺ T-cell trajectories in HL patients and controls matched for duration of combination antiretroviral therapy (cART). A total of 40 168 adult HIV-1-infected patients (median age, 36 years; 70% male; median CD4 cell count, 234 cells/μL) from 16 European cohorts were observed during 159 133 person-years; 78 patients developed HL. The incidence was 49.0 (95% confidence interval [CI], 39.3-61.2) per 100,000 person-years, and similar on cART and not on cART (P = .96). The risk of HL declined as the most recent (time-updated) CD4 count increased: the adjusted hazard ratio comparing more than 350 with less than 50 cells/μL was 0.27 (95% CI, 0.08-0.86). Sixty-one HL cases diagnosed on cART were matched to 1652 controls: during the year before diagnosis, cases lost 98 CD4 cells (95% CI, -159 to -36 cells), whereas controls gained 35 cells (95% CI, 24-46 cells; P < .0001). The incidence of HL is not reduced by cART, and patients whose CD4 cell counts decline despite suppression of HIV-1 replication on cART may harbor HL.