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61.
AbstractAn evaluation of nitrite determination in marine lake sediments has shown that spectrophotometric measurements can be in error due to light scattering by colloidal (<0.2 μm) matter in extract solutions and incomplete nitrite recovery. The scatter error can be minimised by using uncoloured extract in the reference beam but precision at low levels remains poor (RSD 25 to 100%). Recovery tests on ‘spiked’ sediment indicated that optimum retrieval (~85%) occurred with 30 minute mixing with 0.2 M NH4Cl, using a sediment to extractant ratio of 1:30. To counter this variable, calibration based on standard addition to sample suspensions is recommended. Modified procedure proposed is suitable for measuring up to 10 μg g?1 of nitrite N; the lake sediments tested contained <100 ng g?1 相似文献
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Inactivation of nitrate reductase alters metabolic branching of carbohydrate fermentation in the cyanobacterium Synechococcus sp. strain PCC 7002 下载免费PDF全文
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Suchandan Bemal 《欧洲藻类学杂志》2016,51(4):469-481
The novel phycoerythrin-containing Synechococcus strain CSIRNIO1 belonging to phylogenetic clade II was isolated from the coastal Arabian Sea. Chromophore characteristics of this isolate revealed the presence of phycoerythrin I (PEI), which allows it to utilize green light efficiently. The DNA distribution data indicate a bimodal slow growth model synchronized with the light/dark cycle. The duration of the cell cycle was regulated by spectral wavelength and nutrient concentration. Nitrate and phosphate enrichment shortened G1 phase duration when cells were exposed to equal doses of photosynthetically usable radiation (PUR) of different spectral wavelengths. G2 phase duration was influenced by spectral quality and phosphate concentration. S phase duration was not affected by the spectral wavelength. However, a shorter doubling time corresponding to shortened G1 and S phases was observed under nitrate enrichment. Phosphate enrichment resulted in shortening of all three phases (G1, S and G2). More efficient utilization of green and red light than blue light regulated the duration of the cell cycle as well as the doubling time, suggesting spectral selectivity in this strain. The effects of spectral wavelengths under varying nutrient concentrations will determine the proliferation of Synechococcus and its adaptation to different environmental conditions. 相似文献
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Bhanupriya Madarampalli Gerald F.M. Watts Paul M. Panipinto Hung N. Nguygen Michael B. Brenner Erika H. Noss 《生物化学与生物物理学报:疾病的分子基础》2019,1865(6):1516-1524
Cadherins are homophilic cell-to-cell adhesion molecules that help cells respond to environmental changes. Newly formed cadherin junctions are associated with increased cell phosphorylation, but the pathways driving this signaling response are largely unknown. Since cadherins have no intrinsic signaling activity, this phosphorylation must occur through interactions with other signaling molecules. We previously reported that cadherin-11 engagement activates joint synovial fibroblasts, promoting inflammatory and degradative pathways important in rheumatoid arthritis (RA) pathogenesis. Our objective in this study was to discover interacting partners that mediate cadherin-11 signaling. Protein array screening showed that cadherin-11 extracellular binding domains linked to an Fc domain (cad11Fc) induced platelet-derived growth factor (PDGFR)-α phosphorylation in synovial fibroblasts and glioblastoma cells. PDGFRs are growth factor receptor tyrosine kinases that promote cell proliferation, survival, and migration in mesodermally derived cells. Increased PDGFR activity is implicated in RA pathology and associates with poor prognosis in several cancers, including sarcoma and glioblastoma. PDGFRα activation by cadherin-11 signaling promoted fibroblast proliferation, a signaling pathway independent from cadherin-11-stimulated IL-6 or matrix metalloproteinase (MMP)-3 release. PDGFRα phosphorylation mediated most of the cad11Fc-induced phosphatidyl-3-kinase (PI3K)/Akt activation, but only part of the mitogen-activated protein kinase (MAPK) response. PDGFRα-dependent signaling did not require cell cadherin-11 expression. Rather, cad11Fc immunoprecipitated PDGFRα, indicating a direct interaction between cadherin-11 and PDGFRα extracellular domains. This study is the first to report an interaction between cadherin-11 and PDGFRα and adds to our growing understanding that cadherin-growth factor receptor interactions help balance the interplay between tissue growth and adhesion. 相似文献
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Zoltan Mastala Sndor Herodek Katalin V.-Balogh Gyrgy Borbly Hesham Mohamed Shafik Lajos Vrs 《International Review of Hydrobiology》1996,81(4):503-512
A pico sized Synechococcus species isolated from Lake Balaton was studied in batch and continuous cultures. This picocyanobacterium had a pH optimum at 8.5 and a temperature optimum at 28-30°C. The Ik value for growth was 52 μEinstein m−2 S−1, the maximum growth rate 2.27 d−1, the half saturation Constant of growth 1.2 μg PO4-P I−1 and the minimal cell quota 1.74 nig P g dry weight−1. The dry weight of cells showed a minimum, the chlorophyll-a/biomass ratio a maximum as a function of growth rate. Above the quota of 3.4 fg P Cell−1 significant amounts of non-reactive dissolved Phosphorous were released. 相似文献
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