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51.
C L?mmler C Frede K Gürtürk A Hildebrand H Blobel 《Journal of general microbiology》1988,134(8):2317-2323
All 24 cultures of Streptococcus canis examined bound 125I-labelled human albumin, IgG and fibrinogen; but neither IgA nor haptoglobin. Binding of human albumin was time-dependent, saturable and reversible by the addition of unlabelled albumin. The binding of 125I-labelled human albumin could be inhibited completely by unlabelled albumin preparations from humans, mice and dogs, and partly by bovine albumin. In contrast, binding of 125I-labelled human albumin was not inhibited by unlabelled rabbit albumin, human IgG or human fibrinogen. Data from competition experiments of two S. canis cultures with high 125I-labelled albumin-binding activities yielded KD values of 10 and 15 nmol l-1, respectively. The estimated number of binding sites per bacterial cell ranged from 30,000 to 57,000. The binding factor for albumin could be isolated from S. canis by boiling the bacteria at pH 2, and it was purified by affinity chromatography on human albumin-Sepharose. The isolated albumin-binding proteins had a molecular mass of approximately 51 kDa and inhibited binding of 125I-labelled albumin to S. canis. They formed complexes with human albumin that altered its electrophoretic mobility. 相似文献
52.
The importance of isoetids for the exchange of dissolved inorganic nitrogen (DIN) between sediment and water was studied in shallow Lake Kvie, Denmark. Vegetated sediments from the littoral zone (55% of lake area) were compared to unvegetated sediments from the littoral and profundal zone. Clear effects of the isoetids were found on DIN in the porewater. At the vegetated station, NH4
+ showed the highest concentrations just below the surface (< 40 µM) whereas NO3
- was dominating below 5 cm depth with concentrations up to 100 µM during the spring. The unvegetated littoral sediment showed a distinct change between winter where NH4
+ dominated and summer where NO3
- was most abundant. NH4
+ dominated in the profundal sediment and showed increasing concentration with depth. The Eh was high (> 400 mV) in the vegetated sediment, indicating isoetid release of O2 in the rhizosphere. A low DIN uptake was observed at the vegetated station while, based on porewater data, a diffusive release from the sediment was expected. This difference was due to plant assimilation. In general a release of NH4
+ and an uptake of NO3
- was seen in all sediments. The denitrification rate calculated from the mass balance for the entire lake was 0.4 mmol m - 2 d-1 and accounted for removal of 77% of the annual N-input to Lake Kvie. 相似文献
53.
Frede Østergaard Andersen 《Ecography》1981,4(1):66-72
Seasonal measurements of the oxygen and nitrate uptake by a reed swamp sediment were carried out in a shallow, eutrophic Danish lake, Arreskov Sø. The oxidation of organic carbon in the sediment by aerobic and nitrate respiration was 290 and 188 g C m−2 yr−1 respectively. During winter, nitrate respiration amounted to 94% of the total carbon oxidation, whereas it was zero during summer. On an annual basis nitrate respiration constituted 39% of total respiration. Sediment nitrate uptake was correlated to nitrate concentration. In consequence of this the nitrate uptake rates varied during the year from zero in summer to 55 mg N m−2 d−1 in spring.
Oxygen uptake rates varied from 30 to 250 mg O2 m−2 h−1 during the year, with a maximum uptake in August. The oxygen uptake per year was calculated to 860 g O2 m−2 . The oxygen uptake rate was correlated to lake temperature and Kjeldahl nitrogen content of the sediment. The oxygen uptake rate, however, showed no correlation with loss on ignition of the sediment. A Q10 -value of 2.2 was found for lake measurements in the temperature interval of 5–15°C. The corresponding O10 -value in the laboratory was 2.6. A high microbial biomass indicated by the maximum content of Kjeldahl nitrogen and the lowest ratio of loss on ignition on Kjeldahl nitrogen appeared in late August, when the maximum oxygen uptake occurred. The oxygen uptake rate increased during the time interval from sampling to the start of the experiments. 相似文献
Oxygen uptake rates varied from 30 to 250 mg O
54.
Frede Frihagen Lars Nordsletten Jan Erik Madsen 《BMJ (Clinical research ed.)》2007,335(7632):1251-1254
Objective To compare the functional results after displaced fractures of the femoral neck treated with internal fixation or hemiarthroplasty.Design Randomised trial with blinding of assessments of functional results.Setting University hospital.Participants 222 patients; 165 (74%) women, mean age 83 years. Inclusion criteria were age above 60, ability to walk before the fracture, and no major hip pathology, regardless of cognitive function.Interventions Closed reduction and two parallel screws (112 patients) and bipolar cemented hemiarthroplasty (110 patients). Follow-up at 4, 12, and 24 months.Main outcome measures Hip function (Harris hip score), health related quality of life (Eq-5d), activities of daily living (Barthel index). In all cases high scores indicate better function.Results Mean Harris hip score in the hemiarthroplasty group was 8.2 points higher (95% confidence interval 2.8 to 13.5 points, P=0.003) at four months and 6.7 points (1.5 to 11.9 points, P=0.01) higher at 12 months. Mean Eq-5d index score at 24 months was 0.13 higher in the hemiarthroplasty group (0.01 to 0.25, P=0.03). The Eq-5d visual analogue scale was 8.7 points higher in the hemiarthroplasty group after 4 months (1.9 to 15.6, P=0.01). After 12 and 24 months the percentage scoring 95 or 100 on the Barthel index was higher in the hemiarthroplasty group (relative risk 0.67, 0.47 to 0.95, P=0.02. and 0.63, 0.42 to 0.94, P=0.02, respectively). Complications occurred in 56 (50%) patients in the internal fixation group and 16 (15%) in the hemiarthroplasty group (3.44, 2.11 to 5.60, P<0.001). In each group 39 patients (35%) died within 24 months (0.98, 0.69 to 1.40, P=0.92)Conclusions Hemiarthroplasty is associated with better functional outcome than internal fixation in treatment of displaced fractures of the femoral neck in elderly patients.Trial registration . NCT00464230相似文献
55.
D. L. Butler N. Juncosa-Melvin G. P. Boivin M. Galloway C. Gooch J. T. Shearn V. S. Nirmalanandhan S. A. Hunter K. Chokalingam C. Frede J. Florer R. Wenstrup 《Molecular & cellular biomechanics : MCB》2006,3(4):127-130
This article has no abstract. 相似文献
56.
Simple models combining competition,defence and resource availability have broad implications in pelagic microbial food webs
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Selina Våge Gunnar Bratbak Jorun Egge Mikal Heldal Aud Larsen Svein Norland Maria Lund Paulsen Bernadette Pree Ruth‐Anne Sandaa Evy Foss Skjoldal Tatiana M. Tsagaraki Lise Øvreås T. Frede Thingstad 《Ecology letters》2018,21(9):1440-1452
In food webs, interactions between competition and defence control the partitioning of limiting resources. As a result, simple models of these interactions contain links between biogeochemistry, diversity, food web structure and ecosystem function. Working at hierarchical levels, these mechanisms also produce self‐similarity and therefore suggest how complexity can be generated from repeated application of simple underlying principles. Reviewing theoretical and experimental literature relevant to the marine photic zone, we argue that there is a wide spectrum of phenomena, including single cell activity of prokaryotes, microbial biodiversity at different levels of resolution, ecosystem functioning, regional biogeochemical features and evolution at different timescales; that all can be understood as variations over a common principle, summarised in what has been termed the ‘Killing‐the‐Winner’ (KtW) motif. Considering food webs as assemblages of such motifs may thus allow for a more integrated approach to aquatic microbial ecology. 相似文献
57.
T. Frede Thingstad Lise Øvreås Jorun K. Egge Trond Løvdal Mikal Heldal 《Ecology letters》2005,8(7):675-682
Coexistence of two organisms competing for the same nutrient is possible if one is an ‘uptake’, and the other a ‘predation defence’ specialist. In pelagic food webs this principle has been linked to cell size. Small osmotroph cells, with their high surface : volume ratio, have been argued to be uptake specialists, while larger osmotrophs avoiding the intense grazing pressure from small protozoan predators might represent ‘predation defence’ specialists. This may seem like an obligatory trade‐off situation that necessitates a choice of either being small or being large, and thus being potentially dominant in oligotrophic or in eutrophic environments, respectively. However, in a more precise form, the theory for nutrient diffusion states that it is the ‘surface : cell requirement of limiting element’ ratio, rather than the ‘surface : volume’ ratio, that is important. The distinction is crucial, since it opens up the possibility of there being life strategies that use a non‐limiting element to increase size. Hypothesized to maximize uptake and predator defence simultaneously, such strategies should be particularly successful. We suggest that this strategy is exploited by osmotrophs with different size and physiology, such as heterotrophic bacteria, unicellular cyanobacteria and diatoms. Since the strategy implies a shift in organism stoichiometry, the biogeochemical implications are strong, illustrating the tight relationships between physical micro‐scale processes, organism life strategies, biodiversity, food web structure, and biogeochemistry. 相似文献
58.
In this work, we have analyzed the pathways by which lipophorin (Lp) delivers its lipid cargo to developing oocytes of Panstrongylus megistus, a hematophagous vector of Chagas’ disease. Lp, vitellin, total lipids and proteins were measured in ovarian tissues at different stages of the reproductive cycle. Localization of Lp in developing oocytes, mainly at their cortical area, was demonstrated by immunofluorescence assays using an anti-Lp antibody labeled with FITC. In vivo approaches injecting fluorescently labeled Lp to follow the course of the entire particle (Lp-DiI or Lp-Oregon Green) or its lipid cargo (Lp-Bodipy-FA) were monitored by laser scanning confocal microscopy. Significant increases in the amounts of lipids, proteins and vitellin were observed in ovarian tissue with the progress of vitellogenesis. Unexpectedly, an increase in the amount of Lp was also observed. The experiments in vivo demonstrated that the uptake of fluorescent Lp labeled on its protein or lipid moiety by developing oocytes occurred very fast, being impaired at low temperatures. The co-injection of fluorescent Lp and vitellogenin (Vg) showed that both particles co-localized inside yolk bodies, confirming the endocytic pathway for Lp. When the fate of lipids transferred to oocytes was evaluated in vitellogenic females by co-injecting Lp-Bodipy-FA and Lp-DiI, the signal for Bodipy-FA was found in both lipid droplets and yolk bodies. In contrast, in injected females kept at 4 °C the fluorescence was reduced, being observed exclusively in lipid droplets, implying that lipid transfer to the oocyte was diminished but not abolished. Taken together, the results demonstrate that in the hematophagous P. megistus, the storage of lipid resources by developing oocytes occurs by the convergence of different pathways by which Lp maximizes the delivery of its lipid cargo. In addition, it was also shown that, to some extent, lipids stored in the oocyte lipid droplets can also originate from endocytosed Vg. The relevance of these events in the context of the physiology of reproduction in P. megistus is discussed. 相似文献
59.
Bodil Korsgaard Frede Østergaard Andersen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,155(4):437-444
Summary The embryos ofZoarces viviparus (L.) show linear growth during their intraovarian development. In early gestation before hatching, the embryos take up very small amounts of low molecular tracer compounds such as glucose, glycine or taurine. Later in gestation (two months after hatching), the embryos accumulate substantial amounts of the tracer compounds. The uptake rates of the tracer compounds in vitro are correlated with ambient concentrations of unlabelled compounds within the natural concentration range of the ovarian fluid. The highest uptake rates are found for glucose and the lowest for taurine. Release of14CO2 and dissolved organic carbon (DO14C) from assimilated tracers in the embryos is low. Oxygen uptake and body weight of the embryos appear to be linearly correlated, and the average oxygen uptake is 4.20 (SD 0.73) mol O2 g–1 h–1 WW at 11°C. The contribution of glucose respiration to total aerobic respiration is 13.9%. A growth to respiration ratio of 0.91 indicates a relatively high efficiency for converting food to growth.Symbols and abbreviations
DW
dry weight
-
WW
wet weight
-
DO
14
C
dissolved organic carbon (14C-labelled)
-
t
1/2
half life time
-
turnover time (replacement time) 相似文献
60.
Regeneration of inorganic phosphorus and nitrogen from decomposition of seston in a freshwater sediment 总被引:6,自引:2,他引:4
The mineralization of phosphorus and nitrogen from seston was studied in consolidated sediment from the shallow Lake Arreskov (July and November) and in suspensions without sediment (July). In the suspension experiment, phosphorus and nitrogen were mineralized in the same proportions as they occurred in the seston. During the 30 days suspension experiment, 47 and 43% of the particulate phosphorus and nitrogen, respectively, was mineralized with constant rates.Addition of seston to the sediment had an immediate enhancing effect on oxygen uptake, phosphate and ammonia release, whereas nitrate release decreased due to denitrification. The enhanced rates lasted for 2–5 weeks, while the decrease in nitrate release persisted throughout the experiment. The increase in oxygen uptake (equivalent to 21% of the seston carbon) was, however, only observed in the July experiment. The release of phosphorus and nitrogen from seston decomposing on the sediment surface differed from the suspension experiments. Thus, between 91 and 111% of the phosphorus in the seston was released during the experiments. Due to opposite directed effects on ammonium and nitrate release, the resulting net release of nitrogen was relatively low.A comparison of C/N/P ratios in seston, sediment and flux rates indicated that nitrogen was mineralized faster than phosphorus and carbon. Some of this nitrogen was lost through denitrification and therefore not measurable in the flux of inorganic nitrogen ions. This investigation also suggests that decomposition of newly settled organic matter in sediments have indirect effects on sediment-water exchanges (e.g. by changing of redox potentials and stimulation of denitrification) that modifies the release of mineralized phosphate and nitrogen from the sediment. 相似文献