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排序方式: 共有57条查询结果,搜索用时 218 毫秒
1.
Sediment-related growth limitation of Elodea nuttallii as indicated by a fertilization experiment 总被引:4,自引:0,他引:4
1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
2.
E.P.H. BEST H. WOLTMAN & FH.H. JACOBS 《The Plant journal : for cell and molecular biology》2003,36(1):33-44
1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
3.
Kai Hilpert Dirk FH Winkler Robert EW Hancock 《Biotechnology & genetic engineering reviews》2013,29(1):31-106
Spatial organization of metabolic enzymes may represent a general cellular mechanism to regulate metabolic flux. One recent example of this type of cellular phenomenon is the purinosome, a newly discovered multi-enzyme metabolic assembly that includes all of the enzymes within the de novo purine biosynthetic pathway. Our understanding of the components and regulation of purinosomes has significantly grown in recent years. This paper reviews the purine de novo biosynthesis pathway and its regulation, and presents the evidence supporting the purinosome assembly and disassembly processes under the control of G-protein-coupled receptor (GPCR) signaling. This paper also discusses the implications of purinosome and GPCR regulation in drug discovery. 相似文献
4.
The G protein-coupled vasopressin V2 receptor (V2 receptor) contains a pair of conserved cysteine residues (C112 and C192) which are thought to form a disulfide bond between the first and second extracellular loops. The conserved cysteine residues were found to be important for the correct formation of the ligand binding domain of some G protein-coupled receptors. Here we have assessed the properties of the V2 receptor after site-directed mutagenesis of its conserved cysteine residues in transiently transfected human embryonic kidney (HEK 293) cells. Mutant receptors (C112S, C112A and C192S, C192A) were non-functional and located mostly in the cell's interior. The conserved cysteine residues of the V2 receptor are thus not only important for the structure of the ligand binding domain but also for efficient intracellular receptor transport. In addition to the functional significance of the conserved cysteine residues, we have also analyzed the defects of two mutant V2 receptors which cause X-linked nephrogenic diabetes insipidus (NDI) by the introduction of additional cysteine residues into the second extracellular loop (mutants G185C, R202C). These mutations are assumed to impair normal disulfide bond formation. Mutant receptor G185C and R202C were efficiently transported to the plasma membrane but were defective in ligand binding. Only in the case of the mutant receptor R202C, the more sensitive adenylyl cyclase activity assay revealed vasopressin-stimulated cAMP formation with a 35-fold increased EC(50) value and with a reduced EC(max), indicating that ligand binding is not completely abolished. Taking the unaffected intracellular transport of both NDI-causing mutant receptors into account, our results indicate that the observed impairment of ligand binding by the additional cysteine residues is not due to the prevention of disulfide bond formation between the conserved cysteine residues. 相似文献
5.
6.
Miriam YH Ueda Paulo G Alvarenga Juliana M Real Eloisa de Sá Moreira Aripuan? Watanabe Ana Maria Passos-Castilho Matheus Vescovi Yana Novis Vanderson Rocha Adriana Seber Jose SR Oliveira Celso A Rodrigues Celso FH Granato 《Memórias do Instituto Oswaldo Cruz》2015,110(4):461-467
Human herpesvirus 6 (HHV-6) may cause severe complications after haematopoietic stem
cell transplantation (HSCT). Monitoring this virus and providing precise, rapid and
early diagnosis of related clinical diseases, constitute essential measures to
improve outcomes. A prospective survey on the incidence and clinical features of
HHV-6 infections after HSCT has not yet been conducted in Brazilian patients and the
impact of this infection on HSCT outcome remains unclear. A rapid test based on
real-time quantitative polymerase chain reaction (qPCR) has been optimised to screen
and quantify clinical samples for HHV-6. The detection step was based on reaction
with TaqMan® hydrolysis probes. A set of previously described primers and
probes have been tested to evaluate efficiency, sensitivity and reproducibility. The
target efficiency range was 91.4% with linearity ranging from 10-106
copies/reaction and a limit of detection of five copies/reaction or 250 copies/mL of
plasma. The qPCR assay developed in the present study was simple, rapid and
sensitive, allowing the detection of a wide range of HHV-6 loads. In conclusion, this
test may be useful as a practical tool to help elucidate the clinical relevance of
HHV-6 infection and reactivation in different scenarios and to determine the need for
surveillance. 相似文献
7.
Gregan B Jürgensen J Papsdorf G Furkert J Schaefer M Beyermann M Rosenthal W Oksche A 《The Journal of biological chemistry》2004,279(26):27679-27687
Endothelin-1 (ET-1) is a potent vasoactive peptide that acts on endothelin A (ET(A)) and endothelin B (ET(B)) receptors. Although both receptor subtypes are co-expressed in numerous cells, little is known about their ability to form heterodimers. Here we show that both receptors were co-immunoprecipitated with an ET(B)-specific antibody using extracts from HEK293 cells stably co-expressing a fusion protein consisting of a myc-tagged ET(A) receptor and CFP (ET(A)myc.CFP) and a fusion protein consisting of an ET(B) receptor and YFP (ET(B).YFP). Co-immunoprecipitation was also observed with extracts from HEK293 cells transiently co-expressing FLAG-tagged ET(B) and myc-tagged ET(A) receptors, thereby excluding that heterodimerization is mediated by the CFP/YFP moieties. Heterodimerization was further confirmed in fluorescence resonance energy transfer (FRET) analysis of HEK293 cells transiently co-expressing ET(A)myc.CFP and ET(B).YFP receptors. FRET efficiencies were between 12 and 18% in untreated and antagonist- or ET-1-treated cells, indicating constitutive heterodimerization. Prolonged stimulation (30 min) with the ET(B) receptor-selective agonist BQ3020 decreased FRET efficiency by 50%. This decrease was not observed when internalization was inhibited by co-expression of dominant-negative K44A.dynamin I or incubation with 450 mm sucrose. Enzyme-linked immunosorbent assay and laser scanning microscopy of cell clones stably co-expressing ET(A)myc.CFP/ET(B)flag.YFP receptors revealed a slower sequestration of the ET(B)flag.YFP receptors upon stimulation with ET-1 than with BQ3020. No difference in ET-1 or BQ3020-mediated sequestration was observed with cell clones expressing ET(B)flag.YFP receptors alone. The data suggest that ET(A) and ET(B) receptors form constitutive heterodimers, which show a slower sequestration upon stimulation with ET-1 than with BQ3020. Heterodimer dissociation along the endocytic pathway only occurs upon ET(B)-selective stimulation. 相似文献
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10.
Obesity is a major health problem. We investigated the effects of forskolin and rolipram in the diet of animals in which obesity had been induced. We used 50 female albino Wistar rats that were assigned randomly into five groups as follows: group 1, control; group 2, high fat diet; group 3, high fat diet + forskolin; group 4, high fat diet + rolipram; and group 5, high fat diet + rolipram + forskolin. The rats were fed for 10 weeks and rolipram and forskolin were administered during last two weeks. The animals were sacrificed and blood samples were obtained. Serum cAMP, cGMP and free fatty acids (FFA) levels were measured using ELISA assays. We also measured weight gain during the 10 week period. cAMP and FFA levels of groups 3, 4 and 5 were significantly higher than those of groups 1 and 2. We found no significant differences in serum cGMP levels among the groups. The weight gain in groups 3, 4 and 5 was significantly less than for group 2. We also found that the weight gain in group 5 was significantly less than in groups 3 and 4. We found that both forskolin and rolipram stimulated lipolysis and inhibited body weight increase by increasing cAMP levels. Also, combination therapy using the two agents may be more effective in preventing diet induced obesity than either agent alone. We found also that these agents did not effect cellular cGMP levels in diet induced obesity. 相似文献