University of Amsterdam

About: University of Amsterdam is a education organization based out in Amsterdam, Noord-Holland, Netherlands. It is known for research contribution in the topics: Population & Randomized controlled trial. The organization has 59309 authors who have published 140894 publications receiving 5984137 citations. The organization is also known as: UvA & Universiteit van Amsterdam.

Exploring the phenotypic consequences of tissue specific gene expression variation inferred from GWAS summary statistics.

Abstract: Scalable, integrative methods to understand mechanisms that link genetic variants with phenotypes are needed. Here we derive a mathematical expression to compute PrediXcan (a gene mapping approach) results using summary data (S-PrediXcan) and show its accuracy and general robustness to misspecified reference sets. We apply this framework to 44 GTEx tissues and 100+ phenotypes from GWAS and meta-analysis studies, creating a growing public catalog of associations that seeks to capture the effects of gene expression variation on human phenotypes. Replication in an independent cohort is shown. Most of the associations are tissue specific, suggesting context specificity of the trait etiology. Colocalized significant associations in unexpected tissues underscore the need for an agnostic scanning of multiple contexts to improve our ability to detect causal regulatory mechanisms. Monogenic disease genes are enriched among significant associations for related traits, suggesting that smaller alterations of these genes may cause a spectrum of milder phenotypes.

Extended transthoracic resection compared with limited transhiatal resection for adenocarcinoma of the mid/distal esophagus: five-year survival of a randomized clinical trial.

Abstract: Objective: To determine whether extended transthoracic esophagectomy for adenocarcinoma of the mid/distal esophagus improves long-term survival. Background: A randomized trial was performed to compare surgical techniques. Complete 5-year survival data are now available. Methods: A total of 220 patients with adenocarcinoma of the distal esophagus (type I) or gastric cardia involving the distal esophagus (type II) were randomly assigned to limited transhiatal esophagectomy or to extended transthoracic esophagectomy with en bloc lymphadenectomy. Patients with peroperatively irresectable/incurable cancer were excluded from this analysis (n = 15). A total of 95 patients underwent transhiatal esophagectomy and 110 patients underwent transthoracic esophagectomy. Results: After transhiatal and transthoracic resection, 5-year survival was 34% and 36%, respectively (P = 0.71, per protocol analysis). In a subgroup analysis, based on the location of the primary tumor according to the resection specimen, no overall survival benefit for either surgical approach was seen in 115 patients with a type II tumor (P = 0.81). In 90 patients with a type I tumor, a survival benefit of 14% was seen with the transthoracic approach (51% vs. 37%, P = 0.33). There was evidence that the treatment effect differed depending on the number of positive lymph nodes in the resection specimen (test for interaction P = 0.06). In patients (n = 55) without positive nodes locoregional disease-free survival after transhiatal esophagectomy was comparable to that after transthoracic esophagectomy (86% and 89%, respectively). The same was true for patients (n = 46) with more than 8 positive nodes (0% in both groups). Patients (n = 104) with 1 to 8 positive lymph nodes in the resection specimen showed a 5-year locoregional disease-free survival advantage if operated via the transthoracic route (23% vs. 64%, P = 0.02). Conclusion: There is no significant overall survival benefit for either approach. However, compared with limited transhiatal resection extended transthoracic esophagectomy for type I esophageal adenocarcinoma shows an ongoing trend towards better 5-year survival. Moreover, patients with a limited number of positive lymph nodes in the resection specimen seem to benefit from an extended transthoracic esophagectomy.

Recurrent somatic alterations of FGFR1 and NTRK2 in pilocytic astrocytoma

Abstract: Pilocytic astrocytoma, the most common childhood brain tumor, is typically associated with mitogen-activated protein kinase (MAPK) pathway alterations. Surgically inaccessible midline tumors are therapeutically challenging, showing sustained tendency for progression and often becoming a chronic disease with substantial morbidities. Here we describe whole-genome sequencing of 96 pilocytic astrocytomas, with matched RNA sequencing (n = 73), conducted by the International Cancer Genome Consortium (ICGC) PedBrain Tumor Project. We identified recurrent activating mutations in FGFR1 and PTPN11 and new NTRK2 fusion genes in non-cerebellar tumors. New BRAF-activating changes were also observed. MAPK pathway alterations affected all tumors analyzed, with no other significant mutations identified, indicating that pilocytic astrocytoma is predominantly a single-pathway disease. Notably, we identified the same FGFR1 mutations in a subset of H3F3A-mutated pediatric glioblastoma with additional alterations in the NF1 gene. Our findings thus identify new potential therapeutic targets in distinct subsets of pilocytic astrocytoma and childhood glioblastoma.

Association of LDL Cholesterol, Non–HDL Cholesterol, and Apolipoprotein B Levels With Risk of Cardiovascular Events Among Patients Treated With Statins: A Meta-analysis

Abstract: Context The associations of low-density lipoprotein cholesterol (LDL-C), non–high-density lipoprotein cholesterol (non–HDL-C), and apolipoprotein B (apoB) levels with the risk of cardiovascular events among patients treated with statin therapy have not been reliably documented. Objective To evaluate the relative strength of the associations of LDL-C, non–HDL-C, and apoB with cardiovascular risk among patients treated with statin therapy. Design Meta-analysis of individual patient data from randomized controlled statin trials in which conventional lipids and apolipoproteins were determined in all study participants at baseline and at 1-year follow-up. Data Sources Relevant trials were identified by a literature search updated through December 31, 2011. Investigators were contacted and individual patient data were requested and obtained for 62 154 patients enrolled in 8 trials published between 1994 and 2008. Data Extraction Hazard ratios (HRs) and corresponding 95% CIs for risk of major cardiovascular events adjusted for established risk factors by 1-SD increase in LDL-C, non–HDL-C, and apoB. Results Among 38 153 patients allocated to statin therapy, 158 fatal myocardial infarctions, 1678 nonfatal myocardial infarctions, 615 fatal events from other coronary artery disease, 2806 hospitalizations for unstable angina, and 1029 fatal or nonfatal strokes occurred during follow-up. The adjusted HRs for major cardiovascular events per 1-SD increase were 1.13 (95% CI, 1.10-1.17) for LDL-C, 1.16 (95% CI, 1.12-1.19) for non–HDL-C, and 1.14 (95% CI, 1.11-1.18) for apoB. These HRs were significantly higher for non–HDL-C than LDL-C (P = .002) and apoB (P = .02). There was no significant difference between apoB and LDL-C (P = .21). Conclusion Among statin-treated patients, on-treatment levels of LDL-C, non–HDL-C, and apoB were each associated with risk of future major cardiovascular events, but the strength of this association was greater for non–HDL-C than for LDL-C and apoB.

The relationship between ethical leadership and core job characteristics.

Abstract: Summary In the current study, we draw on the original job characteristics model (JCM) and on an elaborated model of work design to examine relationships between ethical leadership, task significance, job autonomy, effort, and job performance. We suggest that leaders with strong ethical commitments who regularly demonstrate ethically normative behavior can have an impacton the JCM elementsof tasksignificance and autonomy, thereby affecting anemployee’s motivation (willingness to exert effort), which in turn will be evidenced by indications of enhanced task performance and organizational citizenship behavior. We conducted a field study by surveying pairs of co-workers in a diverse set of organizations. Results provide support for a fully mediated model whereby task significance and effort fully mediate relationships between ethical leadership and subordinates’ job performance. Implications for future research on job design are discussed. Copyright # 2010 John Wiley & Sons, Ltd. At the heart of the job characteristics model (JCM, Hackman & Oldham, 1976) is the premise that leaders canshape intrinsic motivation bytheway inwhich theystructuretheobjectivecharacteristics of the work itself. 1 The theoretical model of job design was rooted in an examination of the ‘‘basic conditions that promote high performance motivation and satisfaction at work,’’ in order ‘‘to determine how those conditions can be created’’ (Hackman & Oldham, 1976; p. 71). We argue that the conceptual and empirical developments of the JCM to date can be expanded to encompass a broader role for leaders. In particular, we suggest that leaders with strong ethical commitments who regularly demonstrate ethically normative behavior can have an impact on the JCM elements of task significance and autonomy, thereby affecting an employee’s motivation (willingness to exert effort), which in turn will be evidenced by indications of enhanced task performance and organizational citizenship behaviors.