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171.
Temporally variable and reciprocal subsidies between ecosystems are ubiquitous. These spatial flows can generate a suite of
direct and indirect effects in local and meta-ecosystems. The focus of most subsidy research, however, has been on the response
of consumers in recipient ecosystems to constant subsidies over very short or very long time scales. We derive a meta-ecosystem
model to explicitly consider the dynamic feedbacks between local ecosystems coupled through reciprocal pulsed subsidies. We
predict oscillating reinforcing and dampening effects of reciprocal pulsed herbivore flows. Maximum reinforcing effects between
reciprocal pulsed herbivore flows occur when these flows are in phase with the dynamics of neighboring predators. This prediction
is robust to a range of pulse quantities and frequencies. Reciprocal pulsed herbivore subsidies lead to spatial and temporal
variability in the strength of trophic cascades in local and meta-ecosystems but these cascading effects are the strongest
when reciprocal pulsed subsidies are temporally concentrated. When predators demonstrate a behavioral response to prey abundance,
reciprocal pulsed subsidies dampen the strength of local trophic cascades but lead to strong trophic cascades across local
ecosystems. The timing of reciprocal pulsed subsidies is a critical component that determines the cascading effects of spatial
flows. We show that spatial and temporal variabilities in resources and consumers can have a significant influence on the
strength of cascading trophic interactions; therefore, our ability to detect and understand trophic cascades may depend on
the scale of inquiry of ecological studies. 相似文献
172.
Kumar P Mohammadi M Viger JF Barriault D Gomez-Gil L Eltis LD Bolin JT Sylvestre M 《Journal of molecular biology》2011,405(2):531-44
The biphenyl dioxygenase of Burkholderia xenovorans LB400 is a multicomponent Rieske-type oxygenase that catalyzes the dihydroxylation of biphenyl and many polychlorinated biphenyls (PCBs). The structural bases for the substrate specificity of the enzyme's oxygenase component (BphAELB400) are largely unknown. BphAEp4, a variant previously obtained through directed evolution, transforms several chlorobiphenyls, including 2,6-dichlorobiphenyl, more efficiently than BphAELB400, yet differs from the parent oxygenase at only two positions: T335A/F336M. Here, we compare the structures of BphAELB400 and BphAEp4 and examine the biochemical properties of two BphAELB400 variants with single substitutions, T335A or F336M. Our data show that residue 336 contacts the biphenyl and influences the regiospecificity of the reaction, but does not enhance the enzyme's reactivity toward 2,6-dichlorobiphenyl. By contrast, residue 335 does not contact biphenyl but contributes significantly to expansion of the enzyme's substrate range. Crystal structures indicate that Thr335 imposes constraints through hydrogen bonds and nonbonded contacts to the segment from Val320 to Gln322. These contacts are lost when Thr is replaced by Ala, relieving intramolecular constraints and allowing for significant movement of this segment during binding of 2,6-dichlorobiphenyl, which increases the space available to accommodate the doubly ortho-chlorinated congener 2,6-dichlorobiphenyl. This study provides important insight about how Rieske-type oxygenases can expand substrate range through mutations that increase the plasticity and/or mobility of protein segments lining the catalytic cavity. 相似文献
173.
Michel de Bandt Bruno Fautrel Jean Francis Maillefert Jean Marie Berthelot Bernard Combe René-Marc Flipo Frédéric Lioté Olivier Meyer Alain Saraux Daniel Wendling Xavier Le Loët Francis Guillemin 《Arthritis research & therapy》2009,11(5):1-8
Introduction
The aim of this study was to determine a low disease activity threshold - a 28-joint disease activity score (DAS28) value - for the decision to maintain unchanged disease-modifying antirheumatic drug (DMARD) treatment in rheumatoid arthritis patients, based on expert opinion.Methods
Nine hundred and sixty-seven case scenarios with various levels for each component of the DAS28 (resulting in a disease activity score between 2 and 3.2) were presented to 44 panelists. For each scenario, panelists had to decide whether or not DMARD treatment (excluding steroids) could be maintained unchanged. In each scenario, for decision, the participants were given the DAS28 parameters, without knowledge of the resultant DAS28. The relationship between panelists' decision, DAS28 value, and components of the score were analysed by multiple logistic regression analysis. Each panelist analysed 160 randomised scenarios. Intra-rater and inter-rater reproducibility were assessed.Results
Forty-four panelists participated in the study. Inter-panelist agreement was good (κ = 0.63; 95% confidence interval = 0.61 to 0.65). Intra-panelist agreement was excellent (κ = 0.87; 95% confidence interval = 0.82 to 0.92). Quasi-perfect agreement was observed for DAS28 ≤ 2.4, less pronounced between 2.5 and 2.9, and almost no agreement for DAS28 > 3.0. For values below 2.5, panelists agreed to maintain unchanged DMARDs; for values above 2.5, discrepancies occurred more frequently as the DAS28 value increased. Multivariate analysis confirmed the relationship between panelist's decision, DAS28 value and components of the DAS28. Between DAS28 of 2.4 and 3.2, a major determinant for panelists' decision was swollen joint count. Female and public practice physicians decided more often to maintain treatment unchanged.Conclusions
As a conclusion, panelists suggested that in clinical practice there is no need to change DMARD treatment in rheumatoid arthritis patients with DAS28 ≤ 2.4. 相似文献174.
Marcia R. Cominetti Ana Carolina B.M. Martin Juliana U. Ribeiro Ibtissem Djaafri Françoise Fauvel-Lafève Michel Crépin Heloisa S. Selistre-de-Araujo 《Biochimie》2009
This work aimed to investigate the role of the disintegrin domain of the human ADAM9 (ADAM9D) on the adhesion of breast tumor cells and platelets to collagen I, in a dynamic flow assay to simulate in vivo shear conditions. Recombinant ADAM9D was able to support tumor cell adhesion through binding to the β1 integrin subunit and also to inhibit the invasion through matrigel in vitro. In a dynamic flow assay ADAM9D inhibited about 75% and 65% of MDA-MB-231 tumor cells and platelet adhesion to collagen I, respectively. In addition, it was demonstrated that αVβ3 integrin is new interacting partner for ADAM9D. In conclusion, these results suggest a role for the disintegrin domain of ADAM9 in the metastatic process. Also, ADAM9D may be a tool for investigating the role of ADAMs in metastasis and cancer progression and for the design of selective inhibitors against the adhesion and extravasation of cancer cells. 相似文献
175.
Cossard R Viard T Lamour V Duguet M Bouthier de La Tour C 《Biochimica et biophysica acta》2004,1700(2):161-170
Using limited proteolysis, we show that the hyperthermophilic topoisomerase I from Thermotoga maritima exhibits a unique hot spot susceptible to proteolytic attack with a variety of proteases. The remaining of the protein is resistant to further proteolysis, which suggests a compact folding of the thermophilic topoisomerase, when compared to its mesophilic Escherichia coli homologue. We further show that a truncated version of the T. maritima enzyme, lacking the last C-terminal 93 amino acids is more susceptible to proteolysis, which suggests that the C-terminal region of the topoisomerase may be important to maintain the compact folding of the enzyme. The hot spot of cleavage is located around amino acids 326-330 and probably corresponds to an exposed loop of the protein, near the active site tyrosine in charge of DNA cleavage and religation. Location of this protease sensitive region in the vicinity of bound DNA is consistent with the partial protection observed in the presence of different DNA substrates. Unexpectedly, although proteolysis splits the enzyme in two halves, each containing part of the motifs involved in catalysis, trypsin-digested topoisomerase I retains full DNA binding, cleavage, and relaxation activities, full thermostability and also the same hydrodynamic and spectral properties as undigested samples. This supports the idea that the two fragments which are generated by proteolysis remain correctly folded and tightly associated after proteolytic cleavage. 相似文献
176.
Different types of malformations are likely to affect the morphology of diatoms when exposed to particularly unstable environmental conditions, the most easily identifiable being distortion of the whole frustule. In the present study, we investigated, by means of SEM, valve abnormalities induced by high cadmium contamination (100 μg · L?1) in small pennate diatoms. Changes in the shape of Amphora pediculus (Kütz.) Grunow and anomalous sculpturing of the cell wall of many species, such as Encyonema minutum (Hilse) D. G. Mann, Mayamaea agrestris (Hust.) Lange‐Bert., Gomphonema parvulum (Kütz.) Kütz., or Eolimna minima (Grunow) Lange‐Bert., were observed, which were not, or almost not, noticeable in the LM. With consideration to current knowledge of diatom morphogenesis, metal uptake by the cell would induce, directly or indirectly, damage to many cytoplasmic components (e.g., microtubules, cytoskeleton, Golgi‐derived vesicles) involved in the precisely organized silica deposition. This study confirms that many species, whatever their size, are likely to exhibit morphological abnormalities under cadmium stress, and that this indicator may be valuable for the biomonitoring of metal contamination, even if SEM observations are not necessary for routine studies. 相似文献
177.
Yamazaki S Dudziak D Heidkamp GF Fiorese C Bonito AJ Inaba K Nussenzweig MC Steinman RM 《Journal of immunology (Baltimore, Md. : 1950)》2008,181(10):6923-6933
Foxp3(+)CD25(+)CD4(+) regulatory T cells (Treg) mediate immunological self-tolerance and suppress immune responses. A subset of dendritic cells (DCs) in the intestine is specialized to induce Treg in a TGF-beta- and retinoic acid-dependent manner to allow for oral tolerance. In this study we compare two major DC subsets from mouse spleen. We find that CD8(+) DEC-205/CD205(+) DCs, but not the major fraction of CD8(-) DC inhibitory receptor-2 (DCIR2)(+) DCs, induce functional Foxp3(+) Treg from Foxp3(-) precursors in the presence of low doses of Ag but without added TGF-beta. CD8(+)CD205(+) DCs preferentially express TGF-beta, and the induction of Treg by these DCs in vitro is blocked by neutralizing Ab to TGF-beta. In contrast, CD8(-)DCIR2(+) DCs better induce Foxp3(+) Treg when exogenous TGF-beta is supplied. In vivo, CD8(+)CD205(+) DCs likewise preferentially induce Treg from adoptively transferred, Ag-specific DO11.10 RAG(-/-) Foxp3(-)CD4(+) T cells, whereas the CD8(-)DCIR2(+) DCs better stimulate natural Foxp3(+) Treg. These results indicate that a subset of DCs in spleen, a systemic lymphoid organ, is specialized to differentiate peripheral Foxp3(+) Treg, in part through the endogenous formation of TGF-beta. Targeting of Ag to these DCs might be useful for inducing Ag-specific Foxp3(+) Treg for treatment of autoimmune diseases, transplant rejection, and allergy. 相似文献
178.
Farshid Bahrami Mathieu Maisonneuve Michel Meunier Arthur O. Montazeri Yujin Kim Nazir P. Kherani J. Stewart Aitchison Mo Mojahedi 《Journal of biophotonics》2017,10(2):271-277
A plasmon waveguide resonance (PWR) sensor is proposed for studying the interaction between gold nanoparticles and proteins. The ability of the PWR sensor to operate in both TM and TE Polarizations, i.e. its polarization diversity, facilitates the simultaneous spectroscopy of the nanoparticles surface reactions using both polarizations. The response of each polarization to streptavidin‐biotin binding at the surface of gold nanoparticles is investigated in real time. Finally, using the principles of multimode spectroscopy, the nanoparticle's surface reactions are decoupled from the bulk solution refractive index variations.
179.