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151.
Blanchard C 《Canadian journal of physiology and pharmacology》2008,86(1-2):8-15
Although home-based cardiac rehabilitation (CR) programs have been shown to produce significant increases in exercise capacity, obtaining patient adherence to these programs has been challenging. It is therefore critical to identify key theoretical determinants of exercise during home-based CR in order to inform the development of behavioural interventions that improve adherence. The present study examined the utility of the theory of planned behaviour (TPB) in explaining exercise behaviour during home-based CR. Seventy-six patients who were receiving 6 months of home-based CR completed a TPB questionnaire at the beginning and mid-point of the program and a physical activity scale at the mid-point and end of the program. Path analyses showed that attitude and perceived behavioural control significantly predicted intention for both time intervals (baseline to 3 months, and 3 months to 6 months), whereas subjective norm only predicted intention within the 1st 3 months. Intention significantly predicted implementation intention, which, in turn, significantly predicted exercise for both time intervals. Finally, several underlying accessible beliefs were significantly related to exercise for both time intervals. Therefore, results suggest that the TPB is a potentially useful framework for understanding exercise behaviour during home-based CR. 相似文献
152.
Candida albicans is a causative agent in mycoses of the skin, oral cavity, and gastrointestinal tract. Identification of receptors, and their respective ligands, that are engaged by immune cells when in contact with C. albicans is crucial for understanding inflammatory responses leading to invasive candidiasis. Mincle is a recently identified macrophage-expressed receptor that is important for host responses to C. albicans. The carbohydrate-recognition domain of human and mouse Mincle were expressed, purified under denaturing conditions, and successfully refolded. In addition to oligomers, there are isolatable monomeric and dimeric forms of the protein that occur under two different buffer solutions. The human and mouse homologues bound yeast extract, and the isolated dimeric and monomeric species also demonstrated the recognition of whole C. albicans yeast cells. The data are indicative of several functional states mediating the interaction of Mincle and yeast at the surface of the macrophage. 相似文献
153.
We examined the dynamics of fish species and how they relate to species assemblage coherence in the heavily exploited Georges
Bank fish community. Coherence is defined as reduced temporal variability of total assemblage biomass. We assumed that a higher
degree of compensation hence coherence occurs within competitively coupled species assemblages; therefore, fisheries may directly
alter the dynamics of certain targeted species sizes but assemblage structure will be relatively more stable owing to compensatory
interactions. Species-sizes were grouped, based on negative covariance coupling in biomass time series from survey data. Assemblages
representing benthic feeders were clearly identified by this method; furthermore, the most heavily exploited species-sizes
were decoupled from other species-sizes suggesting that fisheries have diminished their potential to compensate or to be compensated
for by competitive interactions. Biomass of species-sizes within known trophic guilds strongly compensated other guild-member
biomass fluctuations if the diet of guild members was more specialized. This is an indication that more competitive conditions
(more specialization) foster greater compensatory responses between competitors biomass fluctuations. 相似文献
154.
Dendritic cells are prime antigen presenting cells for stimulation of T cell immune responses. These cells are present in
trace amounts in normal tissue. At sites of disease the increased frequency of these cells interacting with T cells may provide
the basis for the release of pro-inflammatory mediators and contribute to localised cell and tissue damage. Studies on dendritic
cells in the colon lamina propria of inflammatory bowel disease (IBD) mice have been limited due to the difficulties encountered
in the isolation and purification of sufficient numbers of these cells. This is the first detailed, reproducible method provided
in the literature for the isolation of colon lamina propria dendritic cells from mice with colitis, yielding optimum purity
of cells and sufficient numbers to advance the study of dendritic cell function in the colons of mice. The most frequently
used identification marker of murine DC is the CD11c surface antigen. We have adapted, combined, and improved procedures developed
for the isolation of other cell types, to develop an efficient procedure for the isolation of dendritic cells from colon tissue.
This protocol describes a step-by-step method for optimising the purity and recovery of lamina propria CD11c+ dendritic cells
from mice colons. 相似文献
155.
Mycobactin acylation plays a crucial role in the ability of Mycobacterium tuberculosis to acquire intracellular iron during infection. M. tuberculosis Rv1347c, the lysine Nε-acyltransferase responsible for mycobactin acylation, represents a valid target for the development of novel anti-tubercular agents. Here we investigate the substrate specificity of Rv1347c, evaluate its kinetic mechanism and probe the contributions of active-site residues to catalysis. Our results confirm that Rv1347c demonstrates a preference for longer acyl-chains and suggest that mycobactin acylation occurs subsequent to mycobactin core assembly. Steady-state bisubstrate kinetics and dead-end inhibitor studies support a random sequential kinetic mechanism. Analysis of the pH dependence of kcat/Km revealed the presence of two groups that must be deprotonated for efficient catalysis. Mutagenesis of His130 and Asp168 indicated that both residues are critical for acyltransferase activity and suggests that His130 is responsible for general base activation of the ε-amino group of lysine. 相似文献
156.
Enzymatic modification of aminoglycoside antibiotics mediated by regioselective aminoglycoside N-acetyltransferases is the predominant cause of bacterial resistance to aminoglycosides. A recently discovered bifunctional aminoglycoside acetyltransferase (AAC(6')-Ib variant, AAC(6')-Ib-cr) has been shown to catalyze the acetylation of fluoroquinolones as well as aminoglycosides. We have expressed and purified AAC(6')-Ib-wt and its bifunctional variant AAC(6')-Ib-cr in Escherichia coli and characterized their kinetic and chemical mechanism. Initial velocity and dead-end inhibition studies support an ordered sequential mechanism for the enzyme(s). The three-dimensional structure of AAC(6')-Ib-wt was determined in various complexes with donor and acceptor ligands to resolutions greater than 2.2 A. Observation of the direct, and optimally positioned, interaction between the 6'-NH 2 and Asp115 suggests that Asp115 acts as a general base to accept a proton in the reaction. The structure of AAC(6')-Ib-wt permits the construction of a molecular model of the interactions of fluoroquinolones with the AAC(6')-Ib-cr variant. The model suggests that a major contribution to the fluoroquinolone acetylation activity comes from the Asp179Tyr mutation, where Tyr179 makes pi-stacking interactions with the quinolone ring facilitating quinolone binding. The model also suggests that fluoroquinolones and aminoglycosides have different binding modes. On the basis of kinetic properties, the pH dependence of the kinetic parameters, and structural information, we propose an acid/base-assisted reaction catalyzed by AAC(6')-Ib-wt and the AAC(6')-Ib-cr variant involving a ternary complex. 相似文献
157.
The intrinsic resistance of Mycobacterium tuberculosis to the beta-lactam class of antibiotics arises from a chromosomally encoded, extended spectrum, class A beta-lactamase, BlaC. Herein, we report the X-ray crystallographic structure of BlaC inhibited with clavulanate at a resolution of 1.7 A with an R-factor value of 0.180 and R-free value of 0.212 for the m/ z +154 clavulanate-derived fragment observed in the active site. Structural evidence reveals the presence of hydrogen bonds to the C1 carbonyl along with a coplanar arrangement of C1, C2, C3, and N4, which favors enolization to generate a trans-alpha,beta-eneamine, stabilizing the +154 adduct from hydrolysis. The irreversible inhibition of BlaC suggests that treatment of M. tuberculosis with a combination of a beta-lactam antibiotic and clavulanate may lead to rapid bactericidal activity. 相似文献
158.
CONSEQUENCES OF ALTERNATIVE FUNCTIONAL RESPONSE FORMULATIONS IN MODELS EXPLORING WHALE-FISHERY INTERACTIONS 总被引:1,自引:0,他引:1
Steven Mackinson Julia L. Blanchard John K. Pinnegar Robert Scott 《Marine Mammal Science》2003,19(4):661-681
We evaluated the utility of Ecosim for exploring interactions between cetacean predators, their prey, and fisheries. We formulated six Ecosim parameterizations, representing alternative hypotheses of feeding interactions (functional response) between cetaceans and their main fish prey, and examined differences in the predicted responses to simulated harvesting regimes for minke whales and their prey. Regardless of the type of function response formulated, intense fishing on the main fish prey of minke whales had a longer-lasting negative impact on minke whales than when minke whale biomass was removed directly by harvesting. Consumption rate, biomass, feeding time and mortality of minke whales were all sensitive to the type of functional response specified. Inclusion of "handling time" limited minke whales consumption at high prey densities and predicted higher consumption at low prey densities; features characteristic of a type II functional response. Predicted decline and recovery rates of minke whales were slower than when consumption rates were not limited. Addition of "foraging time" adjustments resulted in more conservative estimates of decline and recovery. However, when "other mortality" was linked to time spent foraging, exposure to higher mortality at low prey densities, and reduced mortality at high prey densities resulted in dramatic differences in predicted biomass trajectory. Sensitivity to the "other mortality" assumption is important for cetaceans whose predation mortality is only a small proportion of total mortality. Differences in the feeding and biomass dynamics were also observed when prey availability to predators was represented by changes in prey vulnerability, confirming earlier reports that Ecosim predictions are sensitive to this parameter. 相似文献
159.
160.
W Dahr D Blanchard S Kiedrowski A Poschmann J P Cartron J J Moulds 《Biological chemistry Hoppe-Seyler》1989,370(8):849-854
The epitopes of seven mouse monoclonal antibodies which are related to the Gerbich blood group system were investigated. BRIC4, BRIC10, GERO and MR4-130 have been published earlier. The three others (APO1, APO2, APO3) were prepared by immunization with normal human erythrocytes and detected by screening with red blood cells that lack glycophorins C and D. Using immunoblotting and hemagglutination inhibition assays, the epitopes for all antibodies were found to be located on glycophorin C. Hemagglutination inhibition experiments with peptides and chemically modified glycophorins revealed that MR4-130, GERO, BRIC10 and APO2 are all directed against identical or rather similar epitopes comprising the N-terminal three or four residues of glycophorin C. Modification of the N-terminal methionine residue or release of sialic acid attached to oligosaccharide(s) at the third and/or fourth position(s) destroyed all these antigens. The epitope of APO3 was found to comprise glutamic acid17 and/or aspartic acid19 as well as the oligosaccharide attached to serine15. The antigens of BRIC4 and APO1 were found to be located within the residues 2-21 and to comprise sialic acid attached to O-glycosidically linked oligosaccharide(s). However, these epitopes could not be elucidated further. Radio-iodinated MR4-130 bound to 39,000 receptor sites per normal red blood cell. Binding of the labelled antibody was completely inhibited by unlabelled MR4-130, BRIC10, APO2 and GERO. APO1 caused partial inhibition suggesting that it is directed against an adjacent site. BRIC4, APO3 and anti-Ge3 did not inhibit the binding of labelled MR4-130 to any significant extent. 相似文献