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91.
92.
This study focuses on relationships between the phenological growing season of plant communities and the seasonal metrics
of Normalized Difference Vegetation Index (NDVI) at sample stations and pixels overlying them, and explores the procedure
for determining the growing season of terrestrial vegetation at the regional scale, using threshold NDVI values obtained by
surface–satellite analysis at individual stations/pixels. The cumulative frequency of phenophases has been calculated for
each plant community and each year in order to determine the growing season at the three sample stations from 1982 to 1993.
The precise thresholds were arbitrarily set as the dates on which the phenological cumulative frequency reached 5% and 10%
(for the beginning) and 90% and 95% (for the end). The beginning and end dates of the growing season were then applied each
year as time thresholds, to determine the corresponding 10-day peak greenness values from NDVI curves for 8-km2 pixels overlying the phenological stations. According to a trend analysis, a lengthening of the growing seasons and an increase
of the integrated growing season NDVI have been detected in the central part of the research region. The correlation between
the beginning dates of the growing season and the corresponding threshold NDVI values is very low, which indicates that the
satellite-sensor-derived greenness is independent of the beginning time of the growing season of local plant communities.
Other than in spring, the correlation between the end dates of the growing season and the corresponding threshold NDVI values
is highly significant. The negative correlation shows that the earlier the growing season terminates, the larger the corresponding
threshold NDVI value, and vice versa. In order to estimate the beginning and end dates of the growing season using the threshold
NDVI values at sites without phenological data from 1982 to 1993, we calculated the spatial correlation coefficients between
NDVI time-series at each sample station and other contiguous sites year by year. The results provide the spatial extrapolation
area of the growing season for each sample station. Thus, we can use the threshold NDVI value obtained at one sample station/pixel
for a year to determine the growing season at the extrapolation sites with a similar vegetation type for the same year.
Received: 25 October 2000 / Revised: 19 June 2001 / Accepted: 19 June 2001 相似文献
93.
94.
本文根据MTT只能被活的增殖细胞中线粒体切断形成紫色甲(?)的原理,测定了8—甲氧基补骨脂素(8—MOP)对体外培养人癌细胞系HCT、KB和BEL细胞的光敏灭活作用。结果表明,8—MOP和UVA光照对这几种人癌细胞有肯定的灭活作用,该作用与8—MOP剂量和光照时间以及细胞种类有关;MTT法可以作为光敏剂活性检测的一种快捷方法。 相似文献
95.
96.
Overexpression of Jatropha curcas Defensin (JcDef) Enhances Sheath Blight Disease Resistance in Tobacco 下载免费PDF全文
Qingwei Wang Shuhua Zhu Yao Liu Rui Li Shancai Tan Shenghua Wang Lin Tang Fang Chen 《Journal of Phytopathology》2017,165(1):15-21
Plant defensins are small, basic, cysteine‐rich peptides, belonging to the antimicrobial peptide superfamily, commonly found in the plant kingdom. In this study, we cloned and characterized a plant defensin gene from Jatropha curcas (JcDef). JcDef carried conserved receptor binding sites and a cysteine motif, and it was phylogenetically grouped together with defensin Ec‐AMP‐D2‐like in Elaeis guineensis. JcDef is localized to cytoplasm and highly expressed in young tissues with fast metabolism such as cotyledons and stem apexes. Transgenic expression of JcDef in tobacco showed enhanced resistance against sheath blight disease caused by R. solani, indicating the antibacterial function. 相似文献
97.
Interleukin-15 rescues tolerant CD8+ T cells for use in adoptive immunotherapy of established tumors 总被引:10,自引:0,他引:10
Teague RM Sather BD Sacks JA Huang MZ Dossett ML Morimoto J Tan X Sutton SE Cooke MP Ohlén C Greenberg PD 《Nature medicine》2006,12(3):335-341
CD8+ T cells can mediate eradication of established tumors, and strategies to amplify tumor-reactive T-cell numbers by immunization or ex vivo expansion followed by adoptive transfer are currently being explored in individuals with cancer. Generating effective CD8+ T cell-mediated responses to tumors is often impeded by T-cell tolerance to relevant tumor antigens, as most of these antigens are also expressed in normal tissues. We examined whether such tolerant T cells could be rescued and functionally restored for use in therapy of established tumors. We used a transgenic T-cell receptor (TCR) mouse model in which peripheral CD8+ T cells specific for a candidate tumor antigen also expressed in liver are tolerant, failing to proliferate or secrete interleukin (IL)-2 in response to antigen. Molecular and cellular analysis showed that these tolerant T cells expressed the IL-15 receptor alpha chain, and could be induced to proliferate in vitro in response to exogenous IL-15. Such proliferation abrogated tolerance and the rescued cells became effective in treating leukemia. Therefore, high-affinity CD8+ T cells are not necessarily deleted by encounter with self-antigen in the periphery, and can potentially be rescued and expanded for use in tumor immunotherapy. 相似文献
98.
Cholesterol efflux is the first step in the reverse cholesterol transport (RCT) pathway, removing excess cholesterol from
tissues, including the arterial wall, thus preventing the development of atherosclerosis. Adeno-associated virus (rAAV) has
demonstrated significant promise as a DNA-delivery vector to treat serious human diseases. In this study, we constructed recombinant
adeno-associated viruses coexpressing apoAI and SR-BI successfully, the double gene mRNA and protein were both strongly expressed
in transduced HepG2 cells. A novel safe and efficient method of promoting the reverse cholesterol transport (RCT) may be established.
These results may provide a new method for gene therapy of Arteriosclerosis. 相似文献
99.
xCT is the functional subunit of the cystine/glutamate antiporter system xc-, which exchanges intracellular glutamate with extracellular cystine. xCT has been reported to play roles in the maintenance of intracellular redox and ambient extracellular glutamate, which may affect neuronal function. To assess a potential role of xCT in the mouse hippocampus, we performed fear conditioning and passive avoidance for long-term memories and examined hippocampal synaptic plasticity in wild-type mice and xCT-null mutants, sut mice. Long-term memory was impaired in sut mice. Normal basal synaptic transmission and short-term presynaptic plasticity at hippocampal Schaffer collateral-CA1 synapses were observed in sut mice. However, LTP (long-term potentiation) was significantly reduced in sut mice compared with their wild-type counterparts. Supplementation of extracellular glutamate did not reverse the reduction in LTP. Taken together, our results suggest that xCT plays a role in the modulation of hippocampal long-term plasticity. 相似文献
100.
Judith Zhi-Yie Tan Stephen M Schlicht Gerard J Powell David Thomas John L Slavin Peter J Smith Peter FM Choong 《International Seminars in Surgical Oncology : ISSO》2006,3(1):38