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排序方式: 共有414条查询结果,搜索用时 15 毫秒
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Kornelia Neveling Lilian?A. Martinez-Carrera Irmgard H?lker Angelien Heister Aad Verrips Seyyed?Mohsen Hosseini-Barkooie Christian Gilissen Sascha Vermeer Maartje Pennings Rowdy Meijer Margot te?Riele Catharina?J.M. Frijns Oksana Suchowersky Linda MacLaren Sabine Rudnik-Sch?neborn Richard?J. Sinke Klaus Zerres R.?Brian Lowry Henny?H. Lemmink Lutz Garbes Joris?A. Veltman Helenius?J. Schelhaas Hans Scheffer Brunhilde Wirth 《American journal of human genetics》2013,92(6):946-954
Spinal muscular atrophy (SMA) is a heterogeneous group of neuromuscular disorders caused by degeneration of lower motor neurons. Although functional loss of SMN1 is associated with autosomal-recessive childhood SMA, the genetic cause for most families affected by dominantly inherited SMA is unknown. Here, we identified pathogenic variants in bicaudal D homolog 2 (Drosophila) (BICD2) in three families afflicted with autosomal-dominant SMA. Affected individuals displayed congenital slowly progressive muscle weakness mainly of the lower limbs and congenital contractures. In a large Dutch family, linkage analysis identified a 9q22.3 locus in which exome sequencing uncovered c.320C>T (p.Ser107Leu) in BICD2. Sequencing of 23 additional families affected by dominant SMA led to the identification of pathogenic variants in one family from Canada (c.2108C>T [p.Thr703Met]) and one from the Netherlands (c.563A>C [p.Asn188Thr]). BICD2 is a golgin and motor-adaptor protein involved in Golgi dynamics and vesicular and mRNA transport. Transient transfection of HeLa cells with all three mutant BICD2 cDNAs caused massive Golgi fragmentation. This observation was even more prominent in primary fibroblasts from an individual harboring c.2108C>T (p.Thr703Met) (affecting the C-terminal coiled-coil domain) and slightly less evident in individuals with c.563A>C (p.Asn188Thr) (affecting the N-terminal coiled-coil domain). Furthermore, BICD2 levels were reduced in affected individuals and trapped within the fragmented Golgi. Previous studies have shown that Drosophila mutant BicD causes reduced larvae locomotion by impaired clathrin-mediated synaptic endocytosis in neuromuscular junctions. These data emphasize the relevance of BICD2 in synaptic-vesicle recycling and support the conclusion that BICD2 mutations cause congenital slowly progressive dominant SMA. 相似文献
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C. Scheffer T. Cloete 《Computer methods in biomechanics and biomedical engineering》2013,16(3):285-294
Clinical gait analysis has proven to reduce uncertainties in selecting the appropriate quantity and type of treatment for patients with neuromuscular disorders. However, gait analysis as a clinical tool is under-utilised due to the limitations and cost of acquiring and managing data. To overcome these obstacles, inertial motion capture (IMC) recently emerged to counter the limitations attributed to other methods. This paper investigates the use of IMC for training and testing a back-propagation artificial neural network (ANN) for the purpose of distinguishing between hemiparetic stroke and able-bodied ambulation. Routine gait analysis was performed on 30 able-bodied control subjects and 28 hemiparetic stroke patients using an IMC system. An ANN was optimised to classify the two groups, achieving a repeatable network accuracy of 99.4%. It is concluded that an IMC system and appropriate computer methods may be useful for the planning and monitoring of gait rehabilitation therapy of stroke victims. 相似文献
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Vasilis Dakos Stephen R. Carpenter Egbert H. van Nes Marten Scheffer 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2015,370(1659)
In the vicinity of tipping points—or more precisely bifurcation points—ecosystems recover slowly from small perturbations. Such slowness may be interpreted as a sign of low resilience in the sense that the ecosystem could easily be tipped through a critical transition into a contrasting state. Indicators of this phenomenon of ‘critical slowing down (CSD)’ include a rise in temporal correlation and variance. Such indicators of CSD can provide an early warning signal of a nearby tipping point. Or, they may offer a possibility to rank reefs, lakes or other ecosystems according to their resilience. The fact that CSD may happen across a wide range of complex ecosystems close to tipping points implies a powerful generality. However, indicators of CSD are not manifested in all cases where regime shifts occur. This is because not all regime shifts are associated with tipping points. Here, we review the exploding literature about this issue to provide guidance on what to expect and what not to expect when it comes to the CSD-based early warning signals for critical transitions. 相似文献
6.
Chi Xu Milena Holmgren Egbert H. Van Nes Marina Hirota F. Stuart Chapin III Marten Scheffer 《PloS one》2015,10(11)
Publicly available remote sensing products have boosted science in many ways. The openness of these data sources suggests high reproducibility. However, as we show here, results may be specific to versions of the data products that can become unavailable as new versions are posted. We focus on remotely-sensed tree cover. Recent studies have used this public resource to detect multi-modality in tree cover in the tropical and boreal biomes. Such patterns suggest alternative stable states separated by critical tipping points. This has important implications for the potential response of these ecosystems to global climate change. For the boreal region, four distinct ecosystem states (i.e., treeless, sparse and dense woodland, and boreal forest) were previously identified by using the Collection 3 data of MODIS Vegetation Continuous Fields (VCF). Since then, the MODIS VCF product has been updated to Collection 5; and a Landsat VCF product of global tree cover at a fine spatial resolution of 30 meters has been developed. Here we compare these different remote-sensing products of tree cover to show that identification of alternative stable states in the boreal biome partly depends on the data source used. The updated MODIS data and the newer Landsat data consistently demonstrate three distinct modes around similar tree-cover values. Our analysis suggests that the boreal region has three modes: one sparsely vegetated state (treeless), one distinct ‘savanna-like’ state and one forest state, which could be alternative stable states. Our analysis illustrates that qualitative outcomes of studies may change fundamentally as new versions of remote sensing products are used. Scientific reproducibility thus requires that old versions remain publicly available. 相似文献
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Sarian Kosten Gissell Lacerot Erik Jeppesen David da Motta Marques Egbert H. van Nes Nestor Mazzeo Marten Scheffer 《Ecosystems》2009,12(7):1117-1129
A positive feedback between submerged vegetation and water clarity forms the backbone of the alternative state theory in shallow
lakes. The water clearing effect of aquatic vegetation may be caused by different physical, chemical, and biological mechanisms
and has been studied mainly in temperate lakes. Recent work suggests differences in biotic interactions between (sub)tropical
and cooler lakes might result in a less pronounced clearing effect in the (sub)tropics. To assess whether the effect of submerged
vegetation changes with climate, we sampled 83 lakes over a gradient ranging from the tundra to the tropics in South America.
Judged from a comparison of water clarity inside and outside vegetation beds, the vegetation appeared to have a similar positive
effect on the water clarity across all climatic regions studied. However, the local clearing effect of vegetation decreased
steeply with the contribution of humic substances to the underwater light attenuation. Looking at turbidity on a whole-lake
scale, results were more difficult to interpret. Although lakes with abundant vegetation (>30%) were generally clear, sparsely
vegetated lakes differed widely in clarity. Overall, the effect of vegetation on water clarity in our lakes appears to be
smaller than that found in various Northern hemisphere studies. This might be explained by differences in fish communities
and their relation to vegetation. For instance, unlike in Northern hemisphere studies, we find no clear relation between vegetation
coverage and fish abundance or their diet preference. High densities of omnivorous fish and coinciding low grazing pressures
on phytoplankton in the (sub)tropics may, furthermore, weaken the effect of vegetation on water clarity. 相似文献
9.
JF Yuan SJ Zhang O Jafer RA Furlong OE Chausiaux CA Sargent GH Zhang NA Affara 《BMC microbiology》2009,9(1):246
Background
Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult. 相似文献10.
Karen E. van de Wolfshaar Reinier HilleRisLambers Kees P. C. Goudswaard Adriaan D. Rijnsdorp Marten Scheffer 《Theoretical Ecology》2014,7(3):253-261
The invasion of Nile perch into Lake Victoria is one of the iconic examples of the destructive effect of an introduced species on an ecosystem but no convincing explanation exists of why Nile perch only increased dramatically after a 25 year lag. Here, we consider this problem using a mathematical model that takes into account interactions between Nile perch and its cichlid prey. We examined competing hypotheses to explain Nile perch invasion and show that suppression of juvenile Nile perch by cichlids may cause the system to have two alternative stable states: one with only cichlids and one with coexistence of cichlids and Nile perch. Without cichlid predation on Nile perch, alternative stable states did not occur. Our analysis indicates that cichlid mortality, for example fishing mortality, may have induced the observed shift between the states. 相似文献