Contact angle of a hemispherical bubble: an analytical approach

We have calculated the equilibrium shape of the axially symmetric Plateau border along which a spherical bubble contacts a flat wall, by analytically integrating Laplace’s equation in the presence of gravity, in the limit of small Plateau border sizes. This method has the advantage that it provides closed-form expressions for the positions and orientations of the Plateau border surfaces. Results are in very good overall agreement with those obtained from a numerical solution procedure, and are consistent with experimental data. In particular we find that the effect of gravity on Plateau border shape is relatively small for typical bubble sizes, leading to a widening of the Plateau border for sessile bubbles and to a narrowing for pendant bubbles. The contact angle of the bubble is found to depend even more weakly on gravity

Synergy of farnesol and antibiotics against planktonic versus biofilm cells of Staphylococcus epidermidis

Staphylococcus epidermidis is the most frequent cause of nosocomial sepsis and catheter-related infections, in which biofilm formation is considered to be one of the main virulence mechanisms. Moreover, their increased resistance to conventional antibiotic therapy enhances the need to develop new therapeutical agents. Farnesol, a quorum-sensing molecule in Candida albicans, has been described as impairing bacterial growth. The goal of this study was to evaluate the synergistic effect of farnesol and antibiotics on planktonic and biofilm cells of S. epidermidis strains (1457 and 9142). To accomplish that, three antibiotics with different mechanisms of action were tested: vancomycin (cell wall synthesis inhibitor), tetracycline (Protein synthesis inhibitor) and rifampicin (RNA synthesis inhibitor). A 24 h kinetic study was performed using these antibiotics at the peak serum concentration along with farnesol at concentrations of 30, 100, 200 and 300 μM. To evaluate planktonic cells viability, it was used two tests: a rapid colorimetric method that is based on the reduction of tetrazolium salt (XTT) to measure mitochondrial cellular activity and standard colony forming units enumeration (CFU). The growth inhibition effect of farnesol and/or antibiotics on biofilm cells of S. epidermidis was assessed by XTT, CFU enumeration and Crystal Violet, which measures total biomass of biofilm. In planktonic as well as in biofilm cells, both strains of S. epidermidis studied were much less susceptible to farnesol than to all the antibiotics tested. All the antibiotics were highly effective against planktonic cells. Biofilm cells were much less susceptible than planktonic cultures to vancomycin, tetracycline and rifampicin. In planktonic cells it was not observed a synergistic effect of farnesol and any of the antibiotics used, except for the strain 9142 when treated with vancomycin. In biofilms, there was a synergistic effect of farnesol and all antibiotics, expressed by the reduction of biomass and mitochondrial cellular activity of biofilm cells. The susceptibility of biofilm cells to farnesol and antibiotics was higher when the antibiotic tested was rifampicin, followed by tetracycline and finally by vancomycin

Farnesol as a prospective antimicrobial agent against Staphylococcus epidermidis

Objectives: Staphylococcus epidermidis is now among the most important pathogenic agents responsible for bloodstream nosocomial infections and for biofilm formation on indwelling medical devices. Its increasing resistance to common antibiotics is a challenge for the development of new antimicrobial agents. Accordingly, the goal of this study was to evaluate the effect of farnesol, a natural sesquiterpenoid, on Staphylococcus epidermidis biofilm cells and compare this one with the effect of vancomycin, one of the most frequently used antibiotics to treat resistant nosocomial infections. Another aim of this work was to determine if subjecting S. epidermidis cells to farnesol they acquire resistance. Methods: A 24 h kinetic study was performed using vancomycin at the peak serum concentration (40mg/L) and farnesol at concentrations of 30, 100, 200 and 300 microM. The growth inhibition effect of farnesol and vancomycin on biofilm cells of S. epidermidis was assessed by XTT (the reduction of this tetrazolium salt is a measure of cellular activity and is easily assessed by colorimetry) and Crystal Violet, which measures total biomass of biofilm. The biofilm cells were analysed by confocal laser scanning microscopy after being stained with Live/Dead. Resistance to farnesol and vancomycin was tested growing S. epidermidis planktonic cells in sub-inhibitory concentrations of farnesol and vancomycin and then subjecting these cells to inhibitory concentrations of both antimicrobial agents during 24 hours. After that, cellular activity was assessed by XTT. This was repeated for 5 consecutive days. Results: Both tested agents act at the cell wall level, vancomycin inhibits the biosynthesis of bacterial cell wall, while farnesol is considered to disrupt the normal barrier function of the cell membrane. Interestingly, farnesol at a concentration higher than 200 microM displayed the same or higher effectiveness of vancomycin at peak serum concentration. In fact, the response of the strains tested was very similar for both farnesol (>200 microM) and vancomycin. Regarding cells resistance to farnesol, the results point out to a slight increase of tolerance but not to an acquired resistance, because the percentage of inhibition was steady along the time. Conclusions: Overall, the results indicate a potential antibacterial effect of farnesol against S. epidermidis, and therefore the possible action of this molecule on the prevention of S. epidermidis related infections

Impact of pelvic radiotherapy on female sexuality

PURPOSE: To assess physical and psychological morbidity, sexual functioning and social and relationship satisfaction among women treated with pelvic radiotherapy. METHODS: Observational (case-control) study of 199 women: 98 submitted to pelvic radiotherapy for the treatment of uterine, rectal or anal cancers and 101 without a personal history of cancer and similar socio-demographic variables. These completed a socio-demographic and clinical questionnaire, and validated measures of psychological health (DASS: Lovibond and Lovibond in Behav Res Ther 33:353-343, 1995), sexual function (FSFI: Rosen et al. in J Sex Marital Ther 26:191-208, 2007), social support (ESSS: Ribeiro in Analise Psicologica 3:547-558, 1999) and relationship satisfaction (IMS: Hudson in The WALMYR assessment scales scoring manual 1992). RESULTS: Women submitted to pelvic irradiation reported a higher rate of adverse physical symptoms in the last month: fatigue 59 versus 25% (p < 0.001), lack of strength 42 versus 20% (p = 0.001), diarrhoea 24 versus 12% (p = 0.032), vaginal discharge 17 versus 7% (p = 0.024), skin erythema 9 versus 2% (p = 0.026). Levels of depression, anxiety and stress were higher among radiotherapy patients, but only reach statistical significance for the stress parameter (6.1 vs. 4.0, p = 0.012). Also these women reported lower scores of satisfaction with social support (57.2 vs. 62.2, p = 0.005) and sexual function (8.5 vs. 13.5, p = 0.049). No statistically significant differences occurred between the two groups regarding scores of relationship satisfaction (20.8 vs. 19.9, p = n.s.). CONCLUSIONS: Our results suggested that pelvic radiotherapy had a negative impact on female sexuality. Thus, interventions that would help to reduce this impact need to be designed and integrated into routine clinical practice

Atividades experimentais e computacionais como recursos instrucionais que se complementam : um estudo exploratório no ensino de eletromagnetismo em física geral

Neste trabalho relatamos um estudo exploratório que teve como objetivo o levantamento de proposições norteadoras para embasar um estudo mais amplo, que visa investigar a integração entre atividades computacionais e experimentais no ensino de Eletromagnetismo em Física Geral como meio de propiciar condições favoráveis para uma aprendizagem significativa (Ausubel, 2003) e vivência com atividades práticas que propiciem aos alunos uma visão adequada de modelos teóricos (Bunge, 1974). Trabalhamos com 32 alunos matriculados na disciplina de Física III (Eletromagnetismo) do curso de Física da UFRGS, no 1° semestre de 2008. Os resultados mostram que as atividades integradas tornam os alunos mais ativos e participativos em comparação com as tradicionais aulas de laboratório, principalmente em discussões sobre questões conceituais e no auxílio a seus parceiros de grupo

A Comprehensive Metabolic Profile of Cultured Astrocytes Using Isotopic Transient Metabolic Flux Analysis and 13C-Labeled Glucose

Metabolic models have been used to elucidate important aspects of brain metabolism in recent years. This work applies for the first time the concept of isotopic transient 13C metabolic flux analysis (MFA) to estimate intracellular fluxes in primary cultures of astrocytes. This methodology comprehensively explores the information provided by 13C labeling time-courses of intracellular metabolites after administration of a 13C-labeled substrate. Cells were incubated with medium containing [1-13C]glucose for 24 h and samples of cell supernatant and extracts collected at different time points were then analyzed by mass spectrometry and/or high performance liquid chromatography. Metabolic fluxes were estimated by fitting a carbon labeling network model to isotopomer profiles experimentally determined. Both the fast isotopic equilibrium of glycolytic metabolite pools and the slow labeling dynamics of TCA cycle intermediates are described well by the model. The large pools of glutamate and aspartate which are linked to the TCA cycle via reversible aminotransferase reactions are likely to be responsible for the observed delay in equilibration of TCA cycle intermediates. Furthermore, it was estimated that 11% of the glucose taken up by astrocytes was diverted to the pentose phosphate pathway. In addition, considerable fluxes through pyruvate carboxylase [PC; PC/pyruvate dehydrogenase (PDH) ratio = 0.5], malic enzyme (5% of the total pyruvate production), and catabolism of branched-chained amino acids (contributing with ∼40% to total acetyl-CoA produced) confirmed the significance of these pathways to astrocytic metabolism. Consistent with the need of maintaining cytosolic redox potential, the fluxes through the malate–aspartate shuttle and the PDH pathway were comparable. Finally, the estimated glutamate/α-ketoglutarate exchange rate (∼0.7 μmol mg prot−1 h−1) was similar to the TCA cycle flux. In conclusion, this work demonstrates the potential of isotopic transient MFA for a comprehensive analysis of energy metabolism

Antibiotic resistance of Enterobacteriaceae isolated from the domestic food related environments

Background: Multidrug resistant Enterobacteriaceae which was confined to the hospital environments is now emerging in the domestic food related environments as well. The main objective of the present study was to investigate the prevalence of antibiotic re-sistant Enterobacteriaceae in the domestic food related environments. Methods: Resistance to ampicillin, chloramphenicol, ciprofloxacin, gentamicin, tetracy-cline, nalidixic acid, nitrofurantoin, and trimethoprim was evaluated in 125 isolates; col-lected in domestic food related environments using agar micro dilution method. Results: Results indicated that 49.6% of the isolates were resistant to at least one antibi-otic (32.8% to ampicillin, 6.4% to nitrofurantoin, 4% to tetracycline, 3.2% to nalidixic acid, 2.4% to chloramphenicol and 1.7% to trimethoprim). Resistance to multiple antibi-otics was observed in 6.4% of the isolates. Conclusion: This study implicates existence of antibiotic resistant Enterobactericeae in the domestic food related environments. This resistance phenomenon requires continual vigilance; and further studies are required to evaluate the role of domestic surfaces in the transmission of resistant pathogens and spread of infectious diseases.info:eu-repo/semantics/publishedVersio