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Search Results: 1 - 10 of 498761 matches for " Johannes P. H. van de Ven "
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Analysis of Rare Variants in the C3 Gene in Patients with Age-Related Macular Degeneration
Maheswara R. Duvvari, Codrut C. Paun, Gabri?lle H. S. Buitendijk, Nicole T. M. Saksens, Elena B. Volokhina, Tina Ristau, Frederieke E. Schoenmaker-Koller, Johannes P. H. van de Ven, Joannes M. M. Groenewoud, Lambertus P. W. J. van den Heuvel, Albert Hofman, Sascha Fauser, André G. Uitterlinden, Caroline C. W. Klaver, Carel B. Hoyng, Eiko K. de Jong, Anneke I. den Hollander
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0094165
Abstract: Age-related macular degeneration (AMD) is a progressive retinal disorder affecting over 33 million people worldwide. Genome-wide association studies (GWASs) for AMD identified common variants at 19 loci accounting for 15–65% of the heritability and it has been hypothesized that the missing heritability may be attributed to rare variants with large effect sizes. Common variants in the complement component 3 (C3) gene have been associated with AMD and recently a rare C3 variant (Lys155Gln) was identified which exerts a large effect on AMD susceptibility independent of the common variants. To explore whether additional rare variants in the C3 gene are associated with AMD, we sequenced all coding exons in 84 unrelated AMD cases. Subsequently, we genotyped all identified variants in 1474 AMD cases and 2258 controls. Additionally, because of the known genetic overlap between AMD and atypical hemolytic uremic syndrome (aHUS), we genotyped two recurrent aHUS-associated C3 mutations in the entire cohort. Overall, we identified three rare variants (Lys65Gln (P = 0.04), Arg735Trp (OR = 17.4, 95% CI = 2.2–136; P = 0.0003), and Ser1619Arg (OR = 5.2, 95% CI = 1.0–25; P = 0.05) at the C3 locus that are associated with AMD in our EUGENDA cohort. However, the Arg735Trp and Ser1619Arg variants were not found to be associated with AMD in the Rotterdam Study. The Lys65Gln variant was only identified in patients from Nijmegen, the Netherlands, and thus may represent a region-specific AMD risk variant.
Paradigms of Mother Tongue Education: Introduction.
Sawyer, W.,Van de Ven, P.-H.
L1 Educational Studies in Language and Literature , 2007,
Abstract: This edition of L1 is devoted to discussion of debates around paradigms of mother tongue education. In this special issue we have sampled contributions from Belgium, Brazil, Hong Kong and Australia that each take up the kinds of arguments which we have tried to capture in our own chapteron paradigm conflict. Each contribution deals with the polyparadigmatic character of mother tongue education and answers the main question of this issue: MTE paradigms – common? competing? coexisting?
Escitalopram Decreases Cross-Regional Functional Connectivity within the Default-Mode Network
Vincent van de Ven, Marleen Wingen, Kim P. C. Kuypers, Johannes G. Ramaekers, Elia Formisano
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0068355
Abstract: The default-mode network (DMN), which comprises medial frontal, temporal and parietal regions, is part of the brain’s intrinsic organization. The serotonergic (5-HT) neurotransmitter system projects to DMN regions from midbrain efferents, and manipulation of this system could thus reveal insights into the neurobiological mechanisms of DMN functioning. Here, we investigate intrinsic functional connectivity of the DMN as a function of activity of the serotonergic system, through the administration of the selective serotonin reuptake inhibitor (SSRI) escitalopram. We quantified DMN functional connectivity using an approach based on dual-regression. Specifically, we decomposed group data of a subset of the functional time series using spatial independent component analysis, and projected the group spatial modes to the same and an independent resting state time series of individual participants. We found no effects of escitalopram on global functional connectivity of the DMN at the map-level; that is, escitalopram did not alter the global functional architecture of the DMN. However, we found that escitalopram decreased DMN regional pairwise connectivity, which included anterior and posterior cingulate cortex, hippocampal complex and lateral parietal regions. Further, regional DMN connectivity covaried with alertness ratings across participants. Our findings show that escitalopram altered intrinsic regional DMN connectivity, which suggests that the serotonergic system plays an important role in DMN connectivity and its contribution to cognition. Pharmacological challenge designs may be a useful addition to resting-state functional MRI to investigate intrinsic brain functional organization.
Optimal Tradeoff Between Exposed and Hidden Nodes in Large Wireless Networks
P. M. van de Ven,A. J. E. M. Janssen,J. S. H. van Leeuwaarden
Computer Science , 2010,
Abstract: Wireless networks equipped with the CSMA protocol are subject to collisions due to interference. For a given interference range we investigate the tradeoff between collisions (hidden nodes) and unused capacity (exposed nodes). We show that the sensing range that maximizes throughput critically depends on the activation rate of nodes. For infinite line networks, we prove the existence of a threshold: When the activation rate is below this threshold the optimal sensing range is small (to maximize spatial reuse). When the activation rate is above the threshold the optimal sensing range is just large enough to preclude all collisions. Simulations suggest that this threshold policy extends to more complex linear and non-linear topologies.
Spatial fairness in linear wireless multi-access networks
P. M. van de Ven,J. S. H. van Leeuwaarden,D. Denteneer,A. J. E. M. Janssen
Computer Science , 2010,
Abstract: Multi-access networks may exhibit severe unfairness in throughput. Recent studies show that this unfairness is due to local differences in the neighborhood structure: Nodes with less neighbors receive better access. We study the unfairness in saturated linear networks, and adapt the multi-access CSMA protocol to remove the unfairness completely, by choosing the activation rates of nodes appropriately as a function of the number of neighbors. We then investigate the consequences of this choice of activation rates on the network-average saturated throughput, and we show that these rates perform well in a non-saturated setting.
A study of rotating globular clusters - the case of the old, metal-poor globular cluster NGC 4372
N. Kacharov,P. Bianchini,A. Koch,M. J. Frank,N. F. Martin,G. van de Ven,T. H. Puzia,I. McDonald,C. I. Johnson,A. A. Zijlstra
Physics , 2014, DOI: 10.1051/0004-6361/201423709
Abstract: Aims: We present the first in-depth study of the kinematic properties and derive the structural parameters of NGC 4372 based on the fit of a Plummer profile and a rotating, physical model. We explore the link between internal rotation to different cluster properties and together with similar studies of more GCs, we put these in the context of globular cluster formation and evolution. Methods: We present radial velocities for 131 cluster member stars measured from high-resolution FLAMES/GIRAFFE observations. Their membership to the GC is additionally confirmed from precise metallicity estimates. Using this kinematic data set we build a velocity dispersion profile and a systemic rotation curve. Additionally, we obtain an elliptical number density profile of NGC 4372 based on optical images using a MCMC fitting algorithm. From this we derive the cluster's half-light radius and ellipticity as r_h=3.4'+/-0.04' and e=0.08+/-0.01. Finally, we give a physical interpretation of the observed morphological and kinematic properties of this GC by fitting an axisymmetric, differentially rotating, dynamical model. Results: Our results show that NGC 4372 has an unusually high ratio of rotation amplitude to velocity dispersion (1.2 vs. 4.5 km/s) for its metallicity. This, however, puts it in line with two other exceptional, very metal-poor GCs - M 15 and NGC 4590. We also find a mild flattening of NGC 4372 in the direction of its rotation. Given its old age, this suggests that the flattening is indeed caused by the systemic rotation rather than tidal interactions with the Galaxy. Additionally, we estimate the dynamical mass of the GC M_dyn=2.0+/-0.5 x 10^5 M_Sun based on the dynamical model, which constrains the mass-to-light ratio of NGC 4372 between 1.4 and 2.3 M_Sun/L_Sun, representative of an old, purely stellar population.
Surgical Treatment for Unexplained Severe Pain of the Thyroid Gland: Report of Three Cases and Concise Review of the Literature
Jan van Schaik,Olaf M. Dekkers,Eleonora P. M. van der Kleij-Corssmit,Johannes A. Romijn,Hans Morreau,Cornelis J. H. van de Velde
Case Reports in Medicine , 2011, DOI: 10.1155/2011/349756
Abstract: Painful thyroid has a limited differential diagnosis. In rare cases, no clear cause can be found after careful clinical, biochemical, and radiological analysis. This may lead to extensive patient morbidity and frustration when symptomatic treatment proves insufficient. Hemithyroidectomy or total thyroidectomy may then be the last resort for doctor and patient. Three cases of unexplained painful thyroid which were successfully treated with hemi or total thyroidectomy are presented. In two cases extensive histological evaluation did not yield a satisfactory explanation for the extreme thyroid pain. In one case histological evaluation of the thyroid revealed Hashimoto's thyroiditis. Review of the literature does not mention surgical treatment for unexplained painful thyroid, and only 15 cases of surgical treatment for painful Hashimoto's thyroiditis are presented. Surgical therapy is a successful final option in the treatment of unexplained painful thyroid and painful Hashimoto's thyroiditis.
Simulated-Physiological Loading Conditions Preserve Biological and Mechanical Properties of Caprine Lumbar Intervertebral Discs in Ex Vivo Culture
Cornelis P. L. Paul, Hendrik A. Zuiderbaan, Behrouz Zandieh Doulabi, Albert J. van der Veen, Peter M. van de Ven, Theo H. Smit, Marco N. Helder, Barend J. van Royen, Margriet G. Mullender
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033147
Abstract: Low-back pain (LBP) is a common medical complaint and associated with high societal costs. Degeneration of the intervertebral disc (IVD) is assumed to be an important causal factor of LBP. IVDs are continuously mechanically loaded and both positive and negative effects have been attributed to different loading conditions. In order to study mechanical loading effects, degeneration-associated processes and/or potential regenerative therapies in IVDs, it is imperative to maintain the IVDs' structural integrity. While in vivo models provide comprehensive insight in IVD biology, an accompanying organ culture model can focus on a single factor, such as loading and may serve as a prescreening model to reduce life animal testing. In the current study we examined the feasibility of organ culture of caprine lumbar discs, with the hypothesis that a simulated-physiological load will optimally preserve IVD properties. Lumbar caprine IVDs (n = 175) were cultured in a bioreactor up to 21 days either without load, low dynamic load (LDL), or with simulated-physiological load (SPL). IVD stiffness was calculated from measurements of IVD loading and displacement. IVD nucleus, inner- and outer annulus were assessed for cell viability, cell density and gene expression. The extracellular matrix (ECM) was analyzed for water, glycosaminoglycan and total collagen content. IVD biomechanical properties did not change significantly with loading conditions. With SPL, cell viability, cell density and gene expression were preserved up to 21 days. Both unloaded and LDL resulted in decreased cell viability, cell density and significant changes in gene expression, yet no differences in ECM content were observed in any group. In conclusion, simulated-physiological loading preserved the native properties of caprine IVDs during a 21-day culture period. The characterization of caprine IVD response to culture in the LDCS under SPL conditions paves the way for controlled analysis of degeneration- and regeneration-associated processes in the future.
Dynamic and Static Overloading Induce Early Degenerative Processes in Caprine Lumbar Intervertebral Discs
Cornelis P. L. Paul, Tom Schoorl, Hendrik A. Zuiderbaan, Behrouz Zandieh Doulabi, Albert J. van der Veen, Peter M. van de Ven, Theo H. Smit, Barend J. van Royen, Marco N. Helder, Margriet G. Mullender
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062411
Abstract: Mechanical overloading of the spine is associated with low back pain and intervertebral disc (IVD) degeneration. How excessive loading elicits degenerative changes in the IVD is poorly understood. Comprehensive knowledge of the interaction between mechanical loading, cell responses and changes in the extracellular matrix of the disc is needed in order to successfully intervene in this process. The purpose of the current study was to investigate whether dynamic and static overloading affect caprine lumbar discs differently and what mechanisms lead to mechanically induced IVD degeneration. Lumbar caprine IVDs (n = 175) were cultured 7, 14 and 21 days under simulated-physiological loading (control), high dynamic or high static loading. Axial deformation and stiffness were continuously measured. Cell viability, cell density, and gene expression were assessed in the nucleus, inner- and outer annulus. The extracellular matrix (ECM) was analyzed for water, glycosaminoglycan and collagen content. IVD height loss and changes in axial deformation were gradual with dynamic and acute with static overloading. Dynamic overloading caused cell death in all IVD regions, whereas static overloading mostly affected the outer annulus. IVDs expression of catabolic and inflammation-related genes was up-regulated directly, whereas loss of water and glycosaminoglycan were significant only after 21 days. Static and dynamic overloading both induced pathological changes to caprine lumbar IVDs within 21 days. The mechanism by which they inflict biomechanical, cellular, and extracellular changes to the nucleus and annulus differed. The described cascades provide leads for the development of new pharmacological and rehabilitative therapies to halt the progression of DDD.
Discomfort and factual recollection in intensive care unit patients
Johannes P van de Leur, Cees P van der Schans, Bert G Loef, Betto G Deelman, Jan HB Geertzen, Jan H Zwaveling
Critical Care , 2004, DOI: 10.1186/cc2976
Abstract: All ICU patients older than 18 years who had needed prolonged (>24 hour) admission with tracheal intubation and mechanical ventilation were consecutively included. Within three days after discharge from the ICU, a structured, in-person interview was conducted with each individual patient. All patients were asked to complete a questionnaire consisting of 14 questions specifically concerning the environment of the ICU they had stayed in. Furthermore, they were asked whether they remembered any discomfort during their stay; if they did then they were asked to specify which sources of discomfort they could recall. A reference group of surgical ward patients, matched by sex and age to the ICU group, was studied to validate the questionnaire.A total of 125 patients discharged from the ICU were included in this study. Data for 123 ICU patients and 48 surgical ward patients were analyzed. The prevalence of recollection of any type of discomfort in the ICU patients was 54% (n = 66). These 66 patients were asked to identify the sources of discomfort, and presence of an endotracheal tube, hallucinations and medical activities were identified as such sources. The median (min–max) score for factual recollection in the ICU patients was 15 (0–28). The median (min–max) score for factual recollection in the reference group was 25 (19–28). Analysis revealed that discomfort was positively related to factual recollection (odds ratio 1.1; P < 0.001), especially discomfort caused by the presence of an endotracheal tube, medical activities and noise. Hallucinations were reported more often with increasing age. Pain as a source of discomfort was predominantly reported by younger patients.Among postdischarge ICU patients, 54% recalled discomfort. However, memory was often impaired: the median factual recollection score of ICU patients was significantly lower than that of matched control patients. The presence of an endotracheal tube, hallucinations and medical activities were most frequentl
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