Positioning Improvement for Spaceborne Laser Footprint Based on Precisely Terrain Data

Spaceborne laser altimetry represents a novel active remote sensing technology applicable to earth observation, which together with imaging spectroscopy and synthetic aperture radar as a core technology for data acquisition in the earth observation systems. However, the accuracy of horizontal positioning for laser footprints from spaceborne laser altimeters declines due to various factors such as the changes in the orbital environment and the deterioration of performance. Moreover, the limited frequency of in-orbit calibration of the spaceborne laser altimeters and the non-disclosure of calibration parameters mean that users are heavily reliant on positioning accuracy of the altimetry data provided. To address this issue, a new algorithm is proposed in this study for enhancing the accuracy of horizontal positioning for laser footprints in the absence of satellite altimeter pointing and ranging parameters. In this algorithm, high-resolution DSM is taken as the reference terrain data to take advantage of the higher precision in elevation over horizontal positioning of the laser footprints. By adjusting the horizontal position of the laser footprint within a small area, the algorithm achieves the optimal alignment of laser elevation data with the reference terrain. Then, the resulting shift in the horizontal position of the laser footprints is referenced to correct their horizontal positioning during that period. Based on the high-accuracy DSM data collected from the Xinjiang autonomous region in China and the data collected by the GF-7 satellite, simulation experiments are performed in this study to analyze and validate the proposed algorithm. According to the experimental results, the horizontal accuracy of the laser footprints improves significantly from 12.56 m to 3.11 m after optimization by the proposed method. With the elimination of 9.45 m horizontal error, accuracy is improved by 75.23%. This method is demonstrated as effective in further optimizing the horizontal position of laser altimetry data products in the absence of altimeter parameters and original data, which promotes the application of spaceborne laser data

Epigallocatechin gallate (EGCG) restores 25-hydroxy vitamin D levels in rheumatoid arthritis patients by attenuating ROS-mediated activation of NF-κB

Purpose: To investigate the mechanism by which epigallocatechin gallate (EGCG) attenuates ROS-induced pathogenesis in a rheumatoid arthritis (RA) patients. Methods: Fifty patients (33 male and 17 female) aged between 25 and 60 years who satisfied ACR 1987 criteria for active RA, and thirty healthy individuals were recruited. Total peripheral blood mononuclear cells (PBMCs), neutrophils and monocytes were isolated from the blood samples of RA patients and healthy donors using commercial extraction kits. Levels of reactive oxygen species (ROS) and superoxide radical (O2-) in isolated cells were measured using fluorescence spectroscopy while the levels of the associated inflammatory cytokines (TNF-α and IL-6) were determined in PBMCs isolated from RA patients using enzyme linked immunosorbent assay (ELISA). These parameters were monitored in EGCG-treated and untreated cells. Moreover, the status of 25(OH) vitamin D and NK-κB were investigated in lipopolysaccharide (LPS)-challenged PBMCs in the presence and absence of EGCG. Results: Elevated levels of superoxide radical and ROS were observed in neutrophils from RA patients in the absence of ECGC, but in the presence of EGCG, the levels of the two parameters were significantly reduced (p < 0.05). Similarly, EGCG treatment downregulated the ROS-mediated increases in TNF-α and IL-6 in the PBMCs from RA patients (p < 0.05). Treatment of PBMCs with the ROS-inducing agent, LPS, resulted in the activation of NK-κB via phosphorylation, and also depletion of 25(OH) vitamin D levels (p < 0.05). However, pre-treatment of the LPS-challenged cells with EGCG inhibited NK-κB activation and 25(OH)-vitamin D depletion (p < 0.05). Moreover, 25(OH)vitamin D levels were restored in the presence of NK-κB inhibitor, flavopiridol, thereby confirming the direct regulatory role of NK-κB in 25(OH) vitamin D levels. Conclusion: EGCG restores 25(OH) vitamin D levels by attenuating ROS-mediated NK-κB activation. Thus, EGCG may be a promising drug candidate for RA

Efficiency of Ferritin as an MRI Reporter Gene in NPC Cells Is Enhanced by Iron Supplementation

Background. An emerging MRI reporter, ferritin heavy chain (FTH1), is recently applied to enhance the contrast and increase the sensitivity of MRI in the monitoring of solid tumors. However, FTH1-overexpression-related cytotoxicity is required to be explored. Methods. By using the Tet-Off system, FTH1 overexpression was semi-quantitativiely and dynamicly regulated by doxycycline in a NPC cell line. Effects of FTH1 overexpression on the proliferation, cytotoxicity, apoptosis and migration of NPC cells were investigated in vitro, and MR relaxation rate was measured in vitro and in vivo. Results. In vitro and in vivo overexpression of FTH1 significantly increased the transverse relaxivity (R2), which could be enhanced by iron supplementation. In vitro, overexpression of FTH1 reduced cell growth and migration, which were not reduced by iron supplementation. Furthermore, cells were subcutaneously inoculated into the nude mice. Results showed FTH1 overexpression decreased tumor growth in the absence of iron supplementation but not in the presence of iron supplementation. Conclusion. To maximize R2 and minimize the potential adverse effects, supplementation of iron at appropriate dose is recommended during the application of FTH1 as a reporter gene in the monitoring of NPC by MRI

Alantolactone exerts anti-proliferative and apoptotic effects on BGC823 and SGC7901 cells via activation of p38MAPK and inhibition of NF-κB signaling pathway

Purpose: To investigate the anti-proliferative and apoptotic influences of alantolactone on gastric carcinoma (GC) cell lines, and the mechanism(s) involved. Methods: Human gastric cancer cell line (BGC823) and gastric adenocarcinoma lymph node metastasis cell line (SGC7901) were maintained in Ham’s F12 medium supplemented with 10 % heatinactivated fetal bovine serum (FBS). In each group of cancer cell line, 5 groups of cells were used: control and four alantolactone groups which were treated with increasing concentrations of alantolactone (5 - 30 μM) for varying periods. Proliferation was determined using MTT assay, while realtime quantitative polymerase chain reaction (qRT-PCR) was used to assay the expressions of apoptosis- and metastasis-related genes. The expressions of p38MAPK and nuclear transcription factor-κB (NF-κB) in BGC823 and SGC7901 cells were measured with Western blotting. Results: Phosphorylated protein (p-p38 protein) expression was significantly higher in both groups of GC cells, relative to control (p < 0.05). The expressions of NF-κB in plasma protein were markedly higher in both groups of GC cells than in control group, but the corresponding expressions in nuclear protein were significantly lower in both groups of GC cells, relative to control (p < 0.05). Conclusion: Alantolactone exerts anti-proliferative and apoptotic effects on BGC823 and SGC7901 cells via mechanisms involving activation of the p38MAPK, and inhibition of the NF-κB signaling pathways. Thus, alantolactone may be a new and effective anti-gastric cancer drug