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1. River flow alterations due to climate change and increasing water usage affect freshwater biodiversity including fish species richness. Here, we statistically explored the relationships of fish species richness to 14 ecologically relevant flow metrics as well as basin area and latitude in 72 rivers worldwide. 2. The statistical models best supported by the data included three variables with positive coefficients (mean river discharge, basin area and the maximum proportion of no‐flooding period) and three variables with negative coefficients (latitude, coefficients of variation in the frequency of low flow and the Julian date of annual minimum flow). 3. The model outputs have provided the first empirical indication that specific low‐ and high‐flow characteristics may be important in explaining variations in basin‐scale fish species richness. Our findings can be useful in identifying high‐risk basins for conservation of fish species diversity. 4. The results not only support the adoption of mean discharge as a predictor, but also suggest the importance of basin area in predicting basin‐scale fish species richness around the world. 相似文献
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TATSUOMI MATSUOKA SETSUKO MATSUOKA YUMIKO YAMAOKA TOSHIHIKO KURIU YOSHIYA WATANABE MIYUKI TAKAYANAGI YOJI KATO KOJI TANEDA 《The Journal of eukaryotic microbiology》1992,39(4):498-502
ABSTRACT The cells of Blepharisma which possess red pigment (blepharismin) show step-up photophobic response (temporal ciliary reversal induced by a sudden increase in light intensity). Bleaching of the cells by cold shock raised a threshold light intensity for the response, Oxidation of red pigment that produced blue pigment did not raise the threshold for the response. The action spectrum for the step-up photophobic response of the cells which possess normal red pigment had peaks at about 580, 540 and 490 nm, a value which coincided with peaks of an absorption spectrum of the red pigment. The absorption spectrum of oxidized pigment (blue pigment) shifted 20 nm toward infrared light. The action spectrum for the response of the cells which possess blue pigment also shifted 20 nm toward infrared light. Results suggest that red pigment might be involved in the step-up photophobic response. Key words. Blepharismin, ciliary reversal, photoreceptors, photoresponse. 相似文献
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Nitrogen assimilation by a Citrus tree 总被引:1,自引:0,他引:1
TADASHI KATO 《Physiologia plantarum》1980,50(3):304-308
Primary assimilation of 15N-ammonium or 15N-nitrate by excised leaves of satsuma mandarin (Citrus unshiu Markovitch) was examined under light and dark conditions. Under both conditions both types of nitrogen were most markedly incorporated into glutamine-amide nitrogen in the primary step of the assimilation, and into proline in the later steps. Incorporation of ammonium or nitrate into amino acids was more active in the light than in the dark, although the stimulating effect of light on the incorporation was relatively small in both cases. 相似文献
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TZUHUA LIN JUKKA PAJARINEN YUSUKE KOHNO MASAHIRO MARUYAMA MONICA ROMERO-LOPEZ JHIH-FONG HUANG KARTHIK NATHAN TAHSIN N. KHAN ZHENYU YAO STUART B. GOODMAN 《Cytotherapy》2018,20(8):1028-1036
Background
Mesenchymal stromal cell (MSC)–based therapy has great potential to modulate chronic inflammation and enhance tissue regeneration. Crosstalk between MSC-lineage cells and polarized macrophages is critical for bone formation and remodeling in inflammatory bone diseases. However, the translational application of this interaction is limited by the short-term viability of MSCs after cell transplantation.Methods
Three types of genetically modified (GM) MSCs were created: (1) luciferase-expressing reporter MSCs; (2) MSCs that secrete interleukin (IL)-4 either constitutively; and (3) MSCs that secrete IL-4 as a response to nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) activation. Cells were injected into the murine distal femoral bone marrow cavity. MSC viability and bone formation were examined in vivo. Cytokine secretion was determined in a femoral explant organ culture model.Results
The reporter MSCs survived up to 4 weeks post-implantation. No difference in the number of viable cells was found between high (2.5?×?106) and low (0.5?×?106) cell-injected groups. Injection of 2.5?×?106 reporter MSCs increased local bone mineral density at 4 weeks post-implantation. Injection of 0.5?×?106 constitutive IL-4 or NFκB-sensing IL-4–secreting MSCs increased bone mineral density at 2 weeks post-implantation. In the femoral explant organ culture model, LPS treatment induced IL-4 secretion in the NFκB-sensing IL-4–secreting MSC group and IL-10 secretion in all the femur samples. No significant differences in tumor necrosis factor (TNF)α and IL-1β secretion were observed between the MSC-transplanted and control groups in the explant culture.Discussion
Transplanted GM MSCs demonstrated prolonged cell viability when transplanted to a compatible niche within the bone marrow cavity. GM IL-4–secreting MSCs may have great potential to enhance bone regeneration in disorders associated with chronic inflammation. 相似文献69.
Properties of Invertases in Sugar Storage Tissues of Citrus Fruit and Changes in Their Activities during Maturation 总被引:4,自引:0,他引:4
Both acid and alkaline invertases were present in immature juice sacs of satsuma mandarin (Citrus‘Unshu Marcovitch”) fruit, in which sugar content was low. Maturing and mature juice sacs, in which sugar content increased steadily with time, were characterized by the presence of alkaline invertase and the absence of acid invertase. When the immature juice sacs were homogenized with 0.2 M sodium phosphate-citrate buffer (pH 8.0), almost all of the acid invertase activity was found in the solubilized fraction, whereas almost all of the alkaline invertase activity was present in the insoluble fraction. The distribution of alkaline invertase between the solubilized and insoluble fractions changed with the development of fruit. The acid invertase had a molecular weight of 69,000, optimum pH of 4.8–5.3, and Km value for sucrose of 7.3 mM. The alkaline invertase had a molecular weight of 200,000, pH optimum of 7.2–7.7, and Km value of 35.7 mM. The hydrolysing activities of both enzymes for raffinose were considerably less than those for sucrose. The alkaline invertase had lower activity for raffinose than the acid invertase. 相似文献
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