1,039 research outputs found
Diminished Virulence Of A Sar-lagr- Mutant Of Staphylococcus Aureus In The Rabbit Model Of Endocarditis
Microbial pathogenicity in Staphylococcus aureus is a complex process involving a number of virulence genes that are regulated by global regulatory systems including sar and agr. To evaluate the roles of these two loci in virulence, we constructed sar-lagr- mutants of strains RN6390 and RN450 and compared their phenotypic profiles to the corresponding single sar- and agr- mutants and parents. The secretion of all hemolysins was absent in the sar-lagr- mutants while residual β-hemolysin activity remained in single agr- mutants. The fibronectin binding capacity was significantly diminished in both single sar- mutants and double mutants when compared with parents while the reduction in fibrinogen binding capacity in the double mutants was modest. In the rabbit endocarditis model, there was a significant decrease in both infectivity rates and intravegetation bacterial densities with the double mutant as compared to the parent (RN6390) at 103-106 CFU inocula despite comparable levels of early bacteremia among various challenge groups. Notably, fewer bacteria in the double mutant group adhered to valvular vegetations at 30 min after challenge (106 CFU) than the parent group. These studies suggest that both the sar and agr loci are involved in initial valvular adherence, intravegetation persistence and multiplication of S. aureus in endocarditis.94518151822Waldvogel, F.A., Staphylococcus aureus (1985) Principles and Practice of Infectious Diseases, pp. 1097-1116. , G. L. Mandell, R. G. Douglas, Jr., and J. E. Bennett, editors. John Wiley & Sons, New YorkNeu, H.C., The crisis in antibiotic resistance (1992) Science (Wash. DC), 257, pp. 1064-1072Cohen, M.L., Epidemiology of drug resistance: Implications for a post-antibiotic era (1992) Science (Wash. DC), 257, pp. 1050-1055Easmon, C.S.F., Adlam, C., (1983) Staphylococci and Staphylococcal Infections, pp. 705-740. , Academic Press, New YorkCheung, A.L., Krishnan, M., Jaffe, E.A., Fischetti, V.A., Fibrinogen acts as a bridging molecule in the adherence of Staphylococcus aureus to cultured human endothelial cells (1991) J. Clin. Invest., 87, pp. 2236-2245Herrmann, M., Vaudaux, P.E., Pittet, D., Auckenthaler, R., Lew, P.D., Schumacher Perdreau, F., Peters, G., Waldvogel, F.A., Fibronectin, fibrinogen, and laminin act as mediators of adherence of clinical staphylococcal isolates to foreign material (1988) J. Infect. Dis., 158, pp. 693-701Kuypers, J.M., Proctor, R.A., Reduced adherence to traumatized rat heart valves by a low-fibronectin-binding mutant of Staphylococcus aureus (1989) Infect. Immun., 57, pp. 2306-2312DeRita, V.J., Mekalanos, J.J., Genetic regulation of bacterial virulence (1989) Annu. Rev. Genet., 23, pp. 455-482Kornblum, J., Kreiswirth, B., Projan, S.J., Ross, H., Novick, R.P., Agr: A polycistronic locus regulating exoprotein synthesis in Staphylococcus aureus (1990) Molecular Biology of the Staphylococci, pp. 373-402. , R. P. Novick, editor. VCH Publishers, New YorkNixon, B.T., Ronson, C.W., Ausubel, R.M., Two component regulatory systems responsive to environmental stimuli share strongly conserved domains with the nitrogen assimilation regulatory genes ntrB and btrC (1986) Proc. Natl. Acad. Sci. USA, 83, pp. 7850-7854Smeltzer, M.S., Hart, M.E., Iandolo, J.J., Phenotypic characterization of xpr, a global regulator of extracellular virulence factors in Staphylococcus aureus (1993) Infect. Immun., 61, pp. 919-925Cheung, A.L., Koomey, J.M., Butler, C.A., Projan, S.J., Fischetti, V.A., Regulation of exoprotein expression in Staphylococcus aureus by a locus (sar) distinct from agr (1992) Proc. Natl. Acad. Sci. USA, 89, pp. 6462-6466Cheung, A.L., Yeaman, M., Bayer, A.S., The role of the sar locus of Staphylococcus aureus in the induction of endocarditis in rabbits (1994) Infect. Immun., 62, pp. 1719-1725Vandenesch, F., Kornblum, J., Novick, R.P., A temporal signal, independent of agr, is required for hla but not spa transcription in Staphylococcus aureus (1991) J. Bacteriol., 173, pp. 6313-6320Cheung, A.L., Ying, P., Regulation of α and β hemolysins by the sar locus of Staphylococcus aureus (1994) J. Bacteriol., 176, pp. 580-585Rescei, P., Kreiswirth, B., O'Reilly, M., Schlievert, P., Gruss, A., Novick, R.P., Regulation of exoprotein gene expression in Staphylococcus aureus by agr (1986) Mol. & Gen. 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Bacteriol., 176, pp. 4168-4172Scheld, W.M., Strunk, R.W., Balian, G., Calderone, R.A., Microbial adhesion to fibronectin in vitro correlates with production of endocarditis in rabbits (1985) Proc. Soc. Exp. Biol. Med., 180, pp. 474-482Durack, D.T., Beeson, P.B., Pathogenesis of infective endocarditis (1980) Infective Endocarditis, pp. 1-53. , S. H. Rahimtoola, editor. Grune and Stratton, Inc., New YorkJaffe, E., Cell biology of endothelial cells (1987) Hum. Pathol., 18, pp. 234-239Lopes, J.D., Reis, M.D., Bretani, R.R., Presence of laminin receptors in Staphylococcus aureus (1985) Science (Wash. DC), 229, pp. 275-277Patti, J.M., Bremell, T., Krajewska-Paetrasik, D., Adelnour, A., Tarkowski, A., Ryden, C., Höök, M., The Staphylococcus aureus collagen adhesin is a virulence determinant in experimental septic arthritis Infect. 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Synthesis of chitosan oligomers/propolis/silver-nanoparticles composite systems and study of their activity against Diplodia seriata
The synthesis and characterization of composites of oligomeric chitosan with propolis extract which allow the incorporation of a third component (silver nanoparticles) are reported, together with their application in aqueous or hydroalcoholic solutions with a view to the formation of adhesive substances or nanofilms for the protection of vineyards against harmful xylophagous fungi. The antimicrobial properties of the association of the two biological products or those resulting from the incorporation of silver nanoparticles (NPs) are studied and discussed. The efficacy of the chitosan oligomers/propolis/silver NPs ternary system is assessed in vitro for Diplodia fungi. A preliminary study on the convenience of replacing propolis with gentisic acid is also presented
Two-soliton collisions in a near-integrable lattice system
We examine collisions between identical solitons in a weakly perturbed
Ablowitz-Ladik (AL) model, augmented by either onsite cubic nonlinearity (which
corresponds to the Salerno model, and may be realized as an array of strongly
overlapping nonlinear optical waveguides), or a quintic perturbation, or both.
Complex dependences of the outcomes of the collisions on the initial phase
difference between the solitons and location of the collision point are
observed. Large changes of amplitudes and velocities of the colliding solitons
are generated by weak perturbations, showing that the elasticity of soliton
collisions in the AL model is fragile (for instance, the Salerno's perturbation
with the relative strength of 0.08 can give rise to a change of the solitons'
amplitudes by a factor exceeding 2). Exact and approximate conservation laws in
the perturbed system are examined, with a conclusion that the small
perturbations very weakly affect the norm and energy conservation, but
completely destroy the conservation of the lattice momentum, which is explained
by the absence of the translational symmetry in generic nonintegrable lattice
models. Data collected for a very large number of collisions correlate with
this conclusion. Asymmetry of the collisions (which is explained by the
dependence on the location of the central point of the collision relative to
the lattice, and on the phase difference between the solitons) is investigated
too, showing that the nonintegrability-induced effects grow almost linearly
with the perturbation strength. Different perturbations (cubic and quintic
ones) produce virtually identical collision-induced effects, which makes it
possible to compensate them, thus finding a special perturbed system with
almost elastic soliton collisions.Comment: Phys. Rev. E, in pres
Colonic transit in children and adolescents with chronic constipation
AbstractObjectiveThe aim of this study was to assess clinical features and colonic transit patterns in Brazilian children with refractory constipation.MethodsFrom 2010 to 2013, 79 constipated patients received follow-up care in a tertiary hospital. Of these patients, 28 (aged 8–14 years) were refractory to conventional therapy and underwent a simplified visual method of nuclear colonic transit study, by ingestion of a liquid meal containing 9.25MBq/kg of 99mTc-phytate. Abdominal static images were taken immediately and at two, six, 24, 30, and 48h after ingestion for qualitative analysis of the radio marker progression through the colon.ResultsTwo patterns of colonic transit were found: slow colonic transit (SCT, n=14), when images at 48h showed a larger part of the tracer remained in proximal and transverse colon, and distal retention (DR, n=14), when after 30h, the radio isotope passed the transverse colon and was retained in the rectosigmoid up to 48h. The SCT and DR group included, respectively, nine and ten males; median ages in the nuclear study of 11 and 10 years, p=0.207; median duration of constipation of seven and six years, p=0.599. Constipation appearing during first year age (p=0.04) and report of soft stools (p=0.02) were more common in SCT patients. Palpable abdominal fecal impaction was found only in DR group. Appendicostomy for antegrade continence enema was successful in 4/12 (30%) of SCT patients (median follow-up: 2.4 years).ConclusionNuclear transit study distinguished two colonic dysmotility patterns and was useful for guiding refractory patients to specific therapies
Improving the performance of a preference-based multi-objective algorithm to optimize food treatment processes
This work focuses on the optimization of some high-pressure and temperature food treatments. When dealing with real--life multi-objective optimization problems, the computational cost of evaluating the considered objective functions is usually quite high. Therefore, only a reduced number of iterations is affordable for the optimization algorithm. However, using fewer iterations can lead to inaccurate solutions far from the real Pareto optimal front. In this work, we analyze and compare different mechanisms to improve the convergence of a preference-based multi-objective optimization algorithm called Weighting Achievement Scalarizing Function Genetic Algorithm. The combination of these techniques has been applied for optimizing a particular food treatment process. In particular, the proposed method based on the introduction of an advanced population achieves important improvements in the considered quality indicator measures
Higher Order Evaluation of the Critical Temperature for Interacting Homogeneous Dilute Bose Gases
We use the nonperturbative linear \delta expansion method to evaluate
analytically the coefficients c_1 and c_2^{\prime \prime} which appear in the
expansion for the transition temperature for a dilute, homogeneous, three
dimensional Bose gas given by T_c= T_0 \{1 + c_1 a n^{1/3} + [ c_2^{\prime}
\ln(a n^{1/3}) +c_2^{\prime \prime} ] a^2 n^{2/3} + {\cal O} (a^3 n)\}, where
T_0 is the result for an ideal gas, a is the s-wave scattering length and n is
the number density. In a previous work the same method has been used to
evaluate c_1 to order-\delta^2 with the result c_1= 3.06. Here, we push the
calculation to the next two orders obtaining c_1=2.45 at order-\delta^3 and
c_1=1.48 at order-\delta^4. Analysing the topology of the graphs involved we
discuss how our results relate to other nonperturbative analytical methods such
as the self-consistent resummation and the 1/N approximations. At the same
orders we obtain c_2^{\prime\prime}=101.4, c_2^{\prime \prime}=98.2 and
c_2^{\prime \prime}=82.9. Our analytical results seem to support the recent
Monte Carlo estimates c_1=1.32 \pm 0.02 and c_2^{\prime \prime}= 75.7 \pm 0.4.Comment: 29 pages, 3 eps figures. Minor changes, one reference added. Version
in press Physical Review A (2002
Asymptotically Improved Convergence of Optimized Perturbation Theory in the Bose-Einstein Condensation Problem
We investigate the convergence properties of optimized perturbation theory,
or linear expansion (LDE), within the context of finite temperature
phase transitions. Our results prove the reliability of these methods, recently
employed in the determination of the critical temperature T_c for a system of
weakly interacting homogeneous dilute Bose gas. We carry out the explicit LDE
optimized calculations and also the infrared analysis of the relevant
quantities involved in the determination of in the large-N limit, when
the relevant effective static action describing the system is extended to O(N)
symmetry. Then, using an efficient resummation method, we show how the LDE can
exactly reproduce the known large-N result for already at the first
non-trivial order. Next, we consider the finite N=2 case where, using similar
resummation techniques, we improve the analytical results for the
nonperturbative terms involved in the expression for the critical temperature
allowing comparison with recent Monte Carlo estimates of them. To illustrate
the method we have considered a simple geometric series showing how the
procedure as a whole works consistently in a general case.Comment: 38 pages, 3 eps figures, Revtex4. Final version in press Phys. Rev.
Mechanical stress and inflammation have opposite effects on Wnt signaling in human chondrocytes
Dysregulation of Wingless and Int-1 (Wnt) signaling has been strongly associated with development and progression of osteoarthritis (OA). Here, we set out to investigate the independent effects of either mechanical stress (MS) or inflammation on Wnt signaling in human neocartilage pellets, and to relate this Wnt signaling to OA pathophysiology. OA synovium-conditioned media (OAS-CM) was collected after incubating synovium from human end-stage OA joints for 24 h in medium. Cytokine levels in the OAS-CM were determined with a multiplex immunoassay (Luminex). Human neocartilage pellets were exposed to 20% MS, 2% OAS-CM or 1 ng/mL Interleukin-1 & beta; (IL-1 & beta;). Effects on expression levels of Wnt signaling members were determined by reverse transcription-quantitative polymerase chain reaction. Additionally, the expression of these members in articular cartilage from human OA joints was analyzed in association with joint space narrowing (JSN) and osteophyte scores. Protein levels of IL-1 & beta;, IL-6, IL-8, IL-10, tumor necrosis factor & alpha;, and granulocyte-macrophage colony-stimulating factor positively correlated with each other. MS increased noncanonical WNT5A and FOS expression. In contrast, these genes were downregulated upon stimulation with OAS-CM or IL-1 & beta;. Furthermore, Wnt inhibitors DKK1 and FRZB decreased in response to OAS-CM or IL-1 & beta; exposure. Finally, expression of WNT5A in OA articular cartilage was associated with increased JSN scores, but not osteophyte scores. Our results demonstrate that MS and inflammatory stimuli have opposite effects on canonical and noncanonical Wnt signaling in human neocartilage. Considering the extent to which MS and inflammation contribute to OA in individual patients, we hypothesize that targeting specific Wnt pathways offers a more effective, individualized approach.Orthopaedics, Trauma Surgery and Rehabilitatio
An altered microbiota pattern precedes Type 2 diabetes mellitus development: From the CORDIOPREV study
Introduction. A distinctive gut microbiome have been linked to type 2 diabetes mellitus (T2DM). We aimed to evaluate whether gut microbiota composition, in addition to clinical biomarkers, could improve the prediction of new incident cases of diabetes in patients with coronary heart disease. Methods All the patients from the CORDIOPREV (Clinical Trials.gov.Identifier: NCT00924937) study without T2DM at baseline were included (n = 462). Overall, 107 patients developed it after a median of 60 months. The gut microbiota composition was determined by 16S rRNA gene sequencing and predictive models were created using hold-out method. Results. A gut microbiota profile associated with T2DM development was determined through a microbiome-based predictive model. The addition of microbiome data to clinical parameters (variables included in FINDRISC risk score and the diabetes risk score of the American Diabetes Association, HDL, triglycerides and HbA1c) improved the prediction increasing the area under the curve from 0.632 to 0.946. Furthermore, a microbiome-based risk score including the ten most discriminant genera, was associated with the probability of develop T2DM. Conclusión. These results suggest that a microbiota profile is associated to the T2DM development. An integrate predictive model of microbiome and clinical data that can improve the prediction of T2DM is also proposed, if is validated in independent populations to prevent this disease
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