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| 2. |
- Reddy, Pradeep, et al.
(författare)
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Formation of E-cadherin-mediated cell-cell adhesion activates AKT and mitogen activated protein kinase via phosphatidylinositol 3 kinase and ligand-independent activation of epidermal growth factor receptor in ovarian cancer cells
- 2005
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Ingår i: Mol Endocrinol. - : The Endocrine Society. - 0888-8809. ; 19:10, s. 2564-2578
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Tidskriftsartikel (refereegranskat)abstract
- E-cadherin is a well characterized adhesion molecule that plays a major role in epithelial cell adhesion. Based on findings that expression of E-cadherin is frequently lost in human epithelial cancers, it has been implicated as a tumor suppressor in carcinogenesis of most human epithelial cancers. However, in ovarian cancer development, our data from the current study showed that E-cadherin expression is uniquely elevated in 86.5% of benign, borderline, and malignant ovarian carcinomas irrespective of the degree of differentiation, whereas normal ovarian samples do not express E-cadherin. Thus, we hypothesize that E-cadherin may play a distinct role in the development of ovarian epithelial cancers. Using an E-cadherin-expressing ovarian cancer cell line OVCAR-3, we have demonstrated for the first time that the establishment of E-cadherin mediated cell-cell adhesions leads to the activation of Akt and MAPK. Akt activation is mediated through the activation of phosphatidylinositol 3 kinase, and both Akt and MAPK activation are mediated by an E-cadherin adhesion-induced ligand-independent activation of epidermal growth factor receptor. We have also demonstrated that suppression of E-cadherin function leads to retarded cell proliferation and reduced viability. We therefore suggest that the concurrent formation of E-cadherin adhesion and activation of downstream proliferation signals may enhance the proliferation and survival of ovarian cancer cells. Our data partly explain why E-cadherin is always expressed during ovarian tumor development and progression.
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| 3. |
- Zhang, Qiang, et al.
(författare)
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Changing properties of precipitation concentration in the Pearl River basin, China
- 2009
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Ingår i: Stochastic environmental research and risk assessment (Print). - : Springer Science and Business Media LLC. - 1436-3240 .- 1436-3259. ; 23:3, s. 377-385
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, precipitation concentrations across the Pearl River basin and the associated spatial patterns are analyzed based on daily precipitation data of 42 rain gauging stations during the period 1960-2005. Regions characterized by the different changing properties of precipitation concentration index (CI) are identified. The southwest and northeast parts of the Pearl River basin are characterized by lower and decreasing precipitation CI; the northwest and south parts of the study river basin show higher and increasing precipitation CI. Higher but decreasing precipitations CI are found in the West and East River basin. Comparison of precipitation CI trends before and after 1990 shows that most parts of the Pearl River basin are characterized by increasing precipitation CI after 1990. Decreasing precipitation CI after 1990 (compared to precipitation CI changes before 1990) is observed only in a few stations located in the lower Gui River and the lower Yu River. Significant increasing precipitation CI after 1990 is detected in the West River, lower North River and upper Beipan River. These changes of precipitation CI in the Pearl River basin are likely to be associated with the consequences of the well-evidenced global warming. These findings can contribute to basin-scale water resource management and conservation of ecological environment in the Pearl River basin.
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| 4. |
- Zhang, Qiang, et al.
(författare)
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Multifractal analysis of streamflow records of the East River basin (Pearl River), China
- 2009
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Ingår i: Physica A. - : Elsevier BV. - 0378-4371 .- 1873-2119. ; 388:6, s. 927-934
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Tidskriftsartikel (refereegranskat)abstract
- Scaling behaviors of the long daily streamflow series of four hydrological stations (Longchuan (1952-2002), Heyuan (1951-2002), Lingxia (1953-2002) and Boluo (1953-2002)) in the mainstream East River, one of the tributaries of the Pearl River (Zhujiang River) basin, were analyzed using multifractal detrended fluctuation analysis (MF-DFA). The research results indicated that streamflow series of the East River basin are characterized by anti-persistence. MF-DFA technique showed similar scaling properties in the streamflow series of the East River basin on shorter time scales, indicating universal scaling properties over the East River basin. Different intercept values of the fitted lines Of log-log Curve of F-q(s) versus s implied hydrological regulation of water reservoirs. Based on the numerical results, we suggested that regulation activities by water reservoirs Could not impact the scaling properties of the streamflow series. The regulation activities by water reservoir only influenced the fluctuation magnitude. Therefore, we concluded that the streamflow variations were mainly the results of climate changes, and precipitation variations in particular. Strong dependence of generalized Hurst exponent h(q) on q demonstrated multifractal behavior of streamflow series of the East River basin, showing ‘universal’ multifractal behavior of river runoffs. The results of this study may provide valuable information for prediction and assessment of water resources under impacts of climatic changes and human activities in the East River basin. (C) 2008 Elsevier B.V. All rights reserved.
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| 5. |
- Zhang, Q., et al.
(författare)
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Observed trends of annual maximum water level and streamflow during past 130 years in the Yangtze River basin, China
- 2006
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 324:1-4, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Annual maximum streamflow and annual maximum water level and their variations exert most serious influences on human society. In this paper, temporal trends and frequency changes at three major stations of Yangtze River, i.e. Yichang, Hankou and Datong representing upper, middle and lower reaches, respectively, were detected with the help of parametric t-test, Mann-Kendall (MK) analysis and wavelet transform methods. The results show that: (1) there is a significant upward trend in streamflow at middle Yangtze River, indicating that flood hazard in the middle reach of the river, the flood rich region, will be more serious; (2) there is a consistent increase of water level from upper to lower reaches of the river which does not always coincide with the maximum streamflow variations; and (3) the periods of water level changes are decreasing over time, indicating the increasing occurrence frequency of annual maximum water level over time. This phenomenon is more obvious from upper Yangtze River to the lower Yangtze River. Human activities like destruction of vegetation, land reclamation and construction of levees reduced lake sizes and filled up the river bed, reducing the flood storage capacity of lakes and fluvial channel. These factors led to higher water level even some times the streamflow is small. Human should adjust his activity to enhance his adaptive capacity to flood hazard in the future.
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| 6. |
- Zhang, Qiang, et al.
(författare)
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Spatial and temporal variability of precipitation maxima during 1960-2005 in the Yangtze River basin and possible association with large-scale circulation
- 2008
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 353:3-4, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated spatial and temporal patterns of trends of the precipitation maxima (defined as the annual./seasonal. maximum precipitation) in the Yangtze River basin for 1960-2005 using Mann-Kendall trend test, and explored association of changing patterns of the precipitation maxima with large-scale circulation using NCEP/NCAR reanalysis data. The research results indicate changes of precipitation maxima from relative stable patterns to the significant increasing/decreasing trend in the middle 1970s. With respect to annual variability, the rainy days are decreasing and precipitation intensity is increasing, and significant increasing trend of precipitation intensity was detected in the middle and lower Yangtze River basin. Number of rain days with daily precipitation exceeding 95th and 99th percentiles and related precipitation intensities are in increasing tendency in summer. Large-scale atmospheric circulation analysis indicates decreasing strength of East Asian summer monsoon during 1975-2005 as compared to that during 1961-1974 and increasing geopotential height in the north China, South China Sea and west Pacific regions, all of which combine to negatively impact the northward propagation of the vapor flux. This circulation pattern will be beneficial for the longer stay of the Meiyu front in the Yangtze River basin, leading to more precipitation in the middle and lower Yangtze River basin in summer months. The significant increasing summer precipitation intensity and changing frequency in the rain/no-rain days in the middle and lower Yangtze River basin have potential to result in higher occurrence probability of flood and drought hazards in the region.
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