181 research outputs found
Analysis on recent changes of water area in China's Poyang lake region using Sentinel-1 data
No full textPoyang Lake is the largest fresh water lake in China. Monitoring water area changes of Poyang Lake is essential for flood mitigation and control in the middle and lower part of Yangtze River. It helps to better conserve wetland and ecological resources, and plays an important role for sustainable water use and management. Landsat and MODIS sensor images are widely used for mapping water body with their sensitivity for spectral reflectance of water bodies and relatively high spatial resolution and temporal resolution. Studies using Landsat images mainly investigate changes of Poyang Lake in dry season because of its 16 days revisit cycle and effect of cloud cover. It builds on the assumption that Poyang Lake undergone relatively small changes in dry season. However, this assumption may not be reliable. MODIS images with very short revisit period, on the other hand, has been proven not be able to assess water area of Poyang Lake accurately in dry season. The contribution of this study is to investigate recent Poyang Lake water area changes with unforeseen temporal resolution in high water period and spatial resolution in low water period using Sentinel-1 satellite, with the specific objective of investigating recent Poyang Lake water area changes in intra-month scales. After preprocessing, calibration, speckle filtering and terrain correction, water bodies were extracted using the histogram-based threshold method. Binarization results were imported into Google Earth for visualization. Shape and area information of Poyang Lake were extracted in ArcGIS. Results show that significant intra-month variability exists, even in dry season. During the observation period from October 2014 to March 2016, October 2014 was the month with the largest max/min water coverage ratio. Water coverage of winter in 2014 and 2015 was completely different, with severe drought happened in 2014 and unusual winter flood in 2015. Parts covered by water in the whole year were identified. Sequence exists for marshland to emerge during water retreat. This study demonstrated the value of Sentinel-1 SAR data to reveal intra-month variation with its regular observation independent of weather conditions. Sentinel-1 SAR data, with near real-time and free of charge distributing policy, relatively high spatial and temporal resolution, is bound to be an important data source for early warning, monitoring, assessment of drought disaster, and will plays an important role for mapping flood extent during the flood, enabling better disaster management. The approach used here can also be applied to other large lakes or wetlands research
Role of histone deacetylases in vascular cell homeostasis and arteriosclerosis
No full textHistone deacetylases (HDACs) are a family of enzymes that remove acetyl groups from lysine residues of histone proteins, a modification that results in epigenetic modulation of gene expression. Although originally shown to be involved in cancer and neurological disease, HDACs are also found to play crucial roles in arteriosclerosis. This review summarizes the effects of HDACs and HDAC inhibitors on proliferation, migration, and apoptosis of endothelial and smooth muscle cells. In addition, an updated discussion of HDACs' recently discovered effects on stem cell differentiation and atherosclerosis is provided. Overall, HDACs appear to be promising therapeutic targets for the treatment of arteriosclerosis and other cardiovascular diseases
X-Box-Binding Protein 1 Splicing Induces an Autophagic Response in Endothelial Cells:Molecular Mechanisms in ECs and Atherosclerosis
No full textAtherosclerosis is the leading cause of death in the developed world and involves the production of an atherosclerotic plaque in the artery wall, limiting blood flow and resulting in conditions such as peripheral artery disease, coronary heart disease, myocardial infarction, and stroke. Autophagy is a method of self-digestion, primarily a survival pathway for the cell, to remove and/or recycle old and damaged proteins in the cytoplasm. There is increasing evidence that autophagy takes place in severe atherosclerotic plaques implicating macrophages and vascular smooth muscle cells. In addition, oxidized low-density lipoprotein (Ox-LDL) can also trigger autophagy in endothelial cells (ECs) through LC3β/BECLIN-1, leading to the lysosome-mediated degradation of Ox-LDL. However the role of autophagy in atherosclerosis still remains shrouded in mystery, as it is still debated whether autophagy is a damaging or a protective mechanism or a balance of both is needed for normal cellular function. X-Box binding protein 1 (XBP1) mRNA splicing is involved in the regulation of autophagy in ECs through BECLIN-1 transcriptional activation. It has recently been shown that sustained activation of XBP1 results in EC apoptosis and development of atherosclerosis. More evidence has shown the importance of XBP1 in eliciting an autophagic response in ECs. Therefore, it seems that the threshold of the autophagic responses could be determined through the tight regulation of the expression and duration of splicing activation of molecules, such as XBP1s, in a cell-specific manner.</p
Blood flow and stem cells in vascular disease
No full textIt is well known that the altered blood flow is related to vascular diseases, including atherosclerosis, restenosis, and arteriosclerosis, which preferentially located at areas with the disturbed blood flow, suggesting that altered biomechanical stress may exert their effect on the vascular disease. Recent evidence indicated the presence of abundant stem/progenitor cells in the vessel wall, in which laminar shear stress can stimulate these cells to differentiate towards endothelial lineage, while cyclic strain results in smooth muscle differentiation. In line with this, it was evidenced that altered biomechanical stress in stented vessels may lead to 'wrong' direction of vascular stem cell differentiation resulting in restenosis. However, the underlying mechanisms are not well understood. In this article, we will give an overview of the effect of the local flow pattern on stem/progenitor cell differentiation and the possible mechanism on how the blood flow influences stem cell behaviours in the development of vascular diseases
Analysis of Histone Deacetylase 7 (HDAC7) Alternative Splicing and Its Role in Embryonic Stem Cell Differentiation Toward Smooth Muscle Lineage
No full textHistone deacetylases (HDACs) have a central role in the regulation of gene expression, which undergoes alternative splicing during embryonic stem cell (ES) cell differentiation. Alternative splicing gives rise to vast diversity over gene information, arousing public concerns in the last decade. In this chapter, we describe a strategy to detect HDAC7 alternative splicing and analyze its function on ES cell differentiation.</p
- …
