Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 18 de 18
Filtrar
1.
Int J Hyg Environ Health ; 250: 114143, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-36907106

RESUMO

OBJECTIVES: We assessed the contamination with Legionella pneumophila (Lp) of the hot water network (HWN) of a hospital, mapped the risk of contamination, and evaluated the relatedness of isolates. We further validated phenotypically the biological features that could account for the contamination of the network. METHODS: We collected 360 water samples from October 2017 to September 2018 in 36 sampling points of a HWN of a building from a hospital in France. Lp were quantified and identified with culture-based methods and serotyping. Lp concentrations were correlated with water temperature, date and location of isolation. Lp isolates were genotyped by pulsed-field gel electrophoresis and compared to a collection of isolates retrieved in the same HWN two years later, or in other HWN from the same hospital. RESULTS: 207/360 (57.5%) samples were positive with Lp. In the hot water production system, Lp concentration was negatively associated with water temperature. In the distribution system, the risk of recovering Lp decreased when temperature was >55 °C (p < 10-3), the proportion of samples with Lp increased with distance from the production network (p < 10-3), and the risk of finding high loads of Lp increased 7.96 times in summer (p = 0.001). All Lp isolates (n = 135) were of serotype 3, and 134 (99.3%) shared the same pulsotype which is found two years later (Lp G). In vitro competition experiments showed that a 3-day culture of Lp G on agar inhibited the growth of a different pulsotype of Lp (Lp O) contaminating another HWN of the same hospital (p = 0.050). We also found that only Lp G survived to a 24h-incubation in water at 55 °C (p = 0.014). CONCLUSION: We report here a persistent contamination with Lp of a hospital HWN. Lp concentrations were correlated with water temperature, season, and distance from the production system. Such persistent contamination could be due to biotic parameters such as intra-Legionella inhibition and tolerance to high temperature, but also to the non-optimal configuration of the HWN that prevented the maintenance of high temperature and optimal water circulation.


Assuntos
Legionella pneumophila , Legionella , Abastecimento de Água , Microbiologia da Água , Legionella pneumophila/genética , Hospitais , Temperatura Alta , Água
2.
Clin Microbiol Infect ; 28(10): 1353-1358, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35597505

RESUMO

OBJECTIVES: To determine prevalence, incidence, and factors associated with Pseudomonas aeruginosa (PA) intestinal carriage in residents of long-term care facilities (LTCFs) and to understand the population structure of this pathogen in LTCFs from two European countries. METHODS: We assessed the prevalence of PA intestinal carriage and the incidence of acquisition by collecting fecal samples from 403 residents of 20 LTCFs. We collected 289 environmental samples from sinks and drinking water. Factors associated with carriage and acquisition of intestinal PA were identified. All PA isolates had their antibiotic phenotypic resistance profile determined and their genome sequenced, from which we assessed the population structure of the collection and identified resistance determinants. RESULTS: We found a high proportion of residents with PA intestinal carriage (51.6%) over the entire study period. Over the follow-up period, 28.6% of the residents acquired intestinal PA. Older age (OR, 1.29; 95% CI, 1.09-1.52; p = 0.002), urinary incontinence (OR, 2.56; 95% CI, 1.37-4.88; p = 0.003), and male sex (OR, 2.55; 95% CI, 1.05-6.18; p = 0.039) were associated with higher probability of carriage. Wheelchair usage (OR, 4.56; 95% CI, 1.38-15.05; p = 0.013) and a body mass index >25 (OR, 3.71; 95% CI, 1.17-11.82; p = 0.026) were associated with higher risk of PA acquisition. Population structure of our isolates was mainly non-clonal with 112 different STs among the 241 isolates. Most represented STs were high risk clones ST253 (n = 26), ST17 (n = 11), ST244 (n = 11), ST309 (n = 10), and ST395 (n = 10). Most PA isolates (86.3%) were susceptible to antibiotics, with no acquired genes conferring resistance to antipseudomonal agents. DISCUSSION: We found an unexpected high prevalence of PA intestinal carriage in LTCF residents mainly associated with individual-level factors. Our study revealed a polyclonal PA population structure suggesting that individual acquisition is more frequent than resident-to-resident transmission.


Assuntos
Água Potável , Pseudomonas aeruginosa , Antibacterianos/farmacologia , Humanos , Assistência de Longa Duração , Masculino , Prevalência , Pseudomonas aeruginosa/genética
3.
Clin Microbiol Infect ; 28(3): 447.e7-447.e14, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34325070

RESUMO

OBJECTIVES: To assess the extent to which food items are a source of extended-spectrum ß-lactamase (ESBL) -producing Escherichia coli (ESBL-Ec) and ESBL-producing Klebsiella pneumoniae (ESBL-Kp) for humans in five European cities. METHODS: We sampled 122 human polluted (hp)-environments (sewers and polluted rivers, as a proxy of human contamination) and 714 food items in Besançon (France), Geneva (Switzerland), Sevilla (Spain), Tübingen (Germany) and Utrecht (The Netherlands). A total of 254 ESBL-Ec and 39 ESBL-Kp isolates were cultured. All genomes were fully sequenced to compare their sequence types (ST) and core genomes, along with the distribution of blaESBL genes and their genetic supports (i.e. chromosome or plasmid). RESULTS: Sequence data revealed that ESBL-Ec and ESBL-Kp isolates from hp-environments were genetically different from those contaminating food items. ESBL-Ec ST131 was widespread in the hp-environment (21.5% of the isolates) but absent from the food items tested. ESBL-Ec ST10 was in similar proportions in hp-environments and food items (15 and 10 isolates, respectively) but mostly carried reservoir-specific blaESBL. blaCTX-M-1 and blaSHV-12 predominated in food-related E. coli isolates (32% and 34% of the isolates, respectively), whereas blaCTX-M-15 and blaCTX-M-27 predominated in isolates from hp-environments (52% and 15% of the isolates, respectively). CONCLUSIONS: We found a very limited connection between ESBL-Ec and ESBL-Kp populations retrieved in food items and from hp-environments and blaESBL. This suggests that human-to-human contamination, rather than the food chain, is possibly the most frequent route of ESBL-Ec and ESBL-Kp transmission in high-income countries.


Assuntos
Infecções por Escherichia coli , Infecções por Klebsiella , Antibacterianos , Escherichia coli/genética , Infecções por Escherichia coli/microbiologia , Humanos , Infecções por Klebsiella/microbiologia , Klebsiella pneumoniae/genética , Plasmídeos , beta-Lactamases/genética
4.
Microb Genom ; 7(9)2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34473016

RESUMO

The biological features that allow a pathogen to survive in the hospital environment are mostly unknown. The extinction of bacterial epidemics in hospitals is mostly attributed to changes in medical practice, including infection control, but the role of bacterial adaptation has never been documented. We analysed a collection of Pseudomonas aeruginosa isolates belonging to the Besançon Epidemic Strain (BES), responsible for a 12year nosocomial outbreak, using a genotype-to-phenotype approach. Bayesian analysis estimated the emergence of the clone in the hospital 5 years before its opening, during the creation of its water distribution network made of copper. BES survived better than the reference strains PAO1 and PA14 in a copper solution due to a genomic island containing 13 metal-resistance genes and was specifically able to proliferate in the ubiquitous amoeba Vermamoeba vermiformis. Mutations affecting amino-acid metabolism, antibiotic resistance, lipopolysaccharide biosynthesis, and regulation were enriched during the spread of BES. Seven distinct regulatory mutations attenuated the overexpression of the genes encoding the efflux pump MexAB-OprM over time. The fitness of BES decreased over time in correlation with its genome size. Overall, the resistance to inhibitors and predators presumably aided the proliferation and propagation of BES in the plumbing system of the hospital. The pathogen further spread among patients via multiple routes of contamination. The decreased prevalence of patients infected by BES mirrored the parallel and convergent genomic evolution and reduction that affected bacterial fitness. Along with infection control measures, this may have participated in the extinction of BES in the hospital setting.


Assuntos
Hospitais , Infecções por Pseudomonas/epidemiologia , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa/genética , Teorema de Bayes , DNA Bacteriano , Surtos de Doenças , Farmacorresistência Bacteriana Múltipla/genética , Ilhas Genômicas , Humanos , Fenótipo , Pseudomonas aeruginosa/classificação , Análise de Sequência de DNA
5.
Clin Microbiol Infect ; 27(9): 1322-1329, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33421572

RESUMO

OBJECTIVES: This study aimed to determine rates and risk factors of extended-spectrum ß-lactamase-producing Enterobacteriaceae (ESBL-PE) acquisition and transmission within households after hospital discharge of an ESBL-PE-positive index patient. METHODS: Two-year prospective cohort study in five European cities. Patients colonized with ESBL-producing Escherichia coli (ESBL-Ec) or Klebsiella pneumoniae (ESBL-Kp), and their household contacts were followed up for 4 months after hospital discharge of the index case. At each follow up, participants provided a faecal sample and personal information. ESBL-PE whole-genome sequences were compared using pairwise single nucleotide polymorphism-based analysis. RESULTS: We enrolled 71 index patients carrying ESBL-Ec (n = 45), ESBL-Kp (n = 20) or both (n = 6), and 102 household contacts. The incidence of any ESBL-PE acquisition among household members initially free of ESBL-PE was 1.9/100 participant-weeks at risk. Nineteen clonally related household transmissions occurred (case to contact: 13; contact to case: 6), with an overall rate of 1.18 transmissions/100 participant-weeks at risk. Most of the acquisition and transmission events occurred within the first 2 months after discharge. The rate of ESBL-Kp household transmission (1.16/100 participant-weeks) was higher than of ESBL-Ec (0.93/100 participant-weeks), whereas more acquisitions were noted for ESBL-Ec (1.06/100 participant-weeks) compared with ESBL-Kp (0.65/100 participant-weeks). Providing assistance for urinary and faecal excretion to the index case by household members increased the risk of ESBL-PE transmission (adjusted prevalence ratio 4.3; 95% CI 1.3-14.1). CONCLUSIONS: ESBL-PE cases discharged from the hospital are an important source of ESBL-PE transmission within households. Most acquisition and transmission events occurred during the first 2 months after hospital discharge and were causally related to care activities at home, highlighting the importance of hygiene measures in community settings. CLINICAL STUDY REGISTRATION: German Clinical Trials Register, DRKS-ID: DRKS00013250.


Assuntos
Infecções por Enterobacteriaceae , Alta do Paciente , Infecções por Enterobacteriaceae/epidemiologia , Infecções por Enterobacteriaceae/transmissão , Escherichia coli , Características da Família , Hospitais , Humanos , Klebsiella pneumoniae , Estudos Prospectivos , Fatores de Risco , beta-Lactamases/genética
6.
BMC Med Educ ; 20(1): 313, 2020 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-32943030

RESUMO

BACKGROUND: The evaluation process of French medical students will evolve in the next few years in order to improve assessment validity. Script concordance testing (SCT) offers the possibility to assess medical knowledge alongside clinical reasoning under conditions of uncertainty. In this study, we aimed at comparing the SCT scores of a large cohort of undergraduate medical students, according to the experience level of the reference panel. METHODS: In 2019, the authors developed a 30-item SCT and sent it to experts with varying levels of experience. Data analysis included score comparisons with paired Wilcoxon rank sum tests and concordance analysis with Bland & Altman plots. RESULTS: A panel of 75 experts was divided into three groups: 31 residents, 21 non-experienced physicians (NEP) and 23 experienced physicians (EP). Among each group, random samples of N = 20, 15 and 10 were selected. A total of 985 students from nine different medical schools participated in the SCT examination. No matter the size of the panel (N = 20, 15 or 10), students' SCT scores were lower with the NEP group when compared to the resident panel (median score 67.1 vs 69.1, p < 0.0001 if N = 20; 67.2 vs 70.1, p < 0.0001 if N = 15 and 67.7 vs 68.4, p < 0.0001 if N = 10) and with EP compared to NEP (65.4 vs 67.1, p < 0.0001 if N = 20; 66.0 vs 67.2, p < 0.0001 if N = 15 and 62.5 vs 67.7, p < 0.0001 if N = 10). Bland & Altman plots showed good concordances between students' SCT scores, whatever the experience level of the expert panel. CONCLUSIONS: Even though student SCT scores differed statistically according to the expert panels, these differences were rather weak. These results open the possibility of including less-experienced experts in panels for the evaluation of medical students.


Assuntos
Estudantes de Medicina , Competência Clínica , Avaliação Educacional , Humanos , Estatísticas não Paramétricas , Incerteza
7.
Syst Biol ; 69(3): 445-461, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-31589325

RESUMO

C$_{4}$ photosynthesis is a complex trait that sustains fast growth and high productivity in tropical and subtropical conditions and evolved repeatedly in flowering plants. One of the major C$_{4}$ lineages is Andropogoneae, a group of $\sim $1200 grass species that includes some of the world's most important crops and species dominating tropical and some temperate grasslands. Previous efforts to understand C$_{4}$ evolution in the group have compared a few model C$_{4}$ plants to distantly related C$_{3}$ species so that changes directly responsible for the transition to C$_{4}$ could not be distinguished from those that preceded or followed it. In this study, we analyze the genomes of 66 grass species, capturing the earliest diversification within Andropogoneae as well as their C$_{3}$ relatives. Phylogenomics combined with molecular dating and analyses of protein evolution show that many changes linked to the evolution of C$_{4}$ photosynthesis in Andropogoneae happened in the Early Miocene, between 21 and 18 Ma, after the split from its C$_{3}$ sister lineage, and before the diversification of the group. This initial burst of changes was followed by an extended period of modifications to leaf anatomy and biochemistry during the diversification of Andropogoneae, so that a single C$_{4}$ origin gave birth to a diversity of C$_{4}$ phenotypes during 18 million years of speciation events and migration across geographic and ecological spaces. Our comprehensive approach and broad sampling of the diversity in the group reveals that one key transition can lead to a plethora of phenotypes following sustained adaptation of the ancestral state. [Adaptive evolution; complex traits; herbarium genomics; Jansenelleae; leaf anatomy; Poaceae; phylogenomics.].


Assuntos
Adaptação Fisiológica/genética , Fotossíntese/genética , Poaceae/classificação , Poaceae/genética , Biodiversidade , Evolução Biológica , Especificidade da Espécie
8.
Surg Endosc ; 34(9): 4157-4165, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-31641913

RESUMO

INTRODUCTION: Postoperative pain following colorectal surgery is associated with a significant use of opioids. Recently, regional anesthesia, such as the posterior quadratus lumborum block (QL2), has been proposed to improve pain relief and reduce opioid use. However, the benefit of the QL2 on postoperative pain control remains controversial. METHODS: We conducted a randomized controlled trial of patients undergoing colorectal surgery at the CHU de Québec-Université Laval. Patients were randomized to regional QL2 anesthesia with 150 mg of ropivacaine combined with standard analgesia or to QL2 with a sham intervention and standard analgesia. Our primary outcome was postoperative opioid administration at 24 h. Secondary outcomes included opioid administration in the post-anesthesia care unit (PACU), at 48 h and at hospital discharge, postoperative pain scores, delay in resumption of intestinal transit, nausea and vomiting, and hospital length of stay. RESULTS: A total of 62 patients were enrolled from November 2017 to February 2018. QL2 regional anesthesia compared with a sham intervention was not associated with a reduction in postoperative morphine dose equivalent (100.2 mg, 95% CI 68.9-131.5 versus 88.7 mg, 95% CI 59.3-118.0, p = 0.81, respectively). Compared to QL2 regional anesthesia, postoperative pain scores in the control group were lower although statistical significance was not consistent for all postoperative time points. Other secondary outcomes were comparable between both groups. CONCLUSION: We did not observe a reduction in postoperative opioid administration at 24 h with a posterior quadratus lumborum block regional anesthesia in patients undergoing elective colorectal surgery.


Assuntos
Anestésicos Locais/administração & dosagem , Doenças do Colo/cirurgia , Bloqueio Nervoso , Dor Pós-Operatória/prevenção & controle , Doenças Retais/cirurgia , Músculos Abdominais , Adulto , Idoso , Analgésicos Opioides/administração & dosagem , Analgésicos Opioides/efeitos adversos , Anestésicos Locais/efeitos adversos , Neoplasias Colorretais/cirurgia , Método Duplo-Cego , Procedimentos Cirúrgicos Eletivos/efeitos adversos , Feminino , Trânsito Gastrointestinal/efeitos dos fármacos , Humanos , Tempo de Internação , Masculino , Pessoa de Meia-Idade , Morfina/administração & dosagem , Morfina/efeitos adversos , Náusea/induzido quimicamente , Bloqueio Nervoso/efeitos adversos , Medição da Dor , Ropivacaina/administração & dosagem , Ropivacaina/efeitos adversos , Vômito/induzido quimicamente
9.
Water Res ; 157: 579-586, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30999256

RESUMO

BACKGROUND: Pseudomonas aeruginosa (PA) is an important opportunistic pathogen that thrives best in the distal elements of plumbing and waste-water systems. Although nosocomial outbreaks of PA have been associated with water sources, the role of the plumbing system of healthcare premises as a reservoir for this pathogen is still unclear. MATERIALS AND METHODS: We collected water samples from 12 technical areas, distant from any medical activity, in a teaching hospital in France once a week for 11 weeks. We used a method that resuscitates persister cells because of the nutrient-poor conditions and the presence of inhibitors (e.g. chlorine and copper ions). Briefly, water was sampled in sterile bottles containing 100 µM of the copper-ion chelating agent diethyldithiocarbamate (DDTC). A portion of the samples was immediately filtered through 0.45-µm membranes, deposited on R2A agar plates, and incubated seven days at 22 °C (following European recommendations). The remaining water was incubated 14 days at 22 °C and then filtered and cultured on R2A, blood-, or cetrimide-containing agar plates. PA isolates were identified by MS MALDI-TOF, genotyped by PFGE and WGS, and tested for survival in a 150 µg/L copper (II) sulphate solution. RESULTS: Although the 12 water sampling points always tested negative with the recommended method, 67% were positive at least once for PA with the adapted method (i.e. with DDTC). The 14 PA persister isolates found throughout the plumbing system were clonal and belong to the high-risk clone ST308. Their genome harbours a 37-kb genomic island (GI-7) containing 13 genes linked to copper resistance. ST308 survived better in the copper solution than comparators that did not harbour GI-7 (P. aeruginosa strains PAO1, PA14, and ST235). The deletion of GI-7 in ST308 abrogated its tolerance to copper. The GI-7 nucleotide sequence shares 98% and 72% identity with sequences from the environmental species Pseudomonas putida and the phytopathogenic species Pseudomonas syringae, respectively. CONCLUSION: We report the contamination of the plumbing system of a healthcare premises by persister cells of the high-risk clone P. aeruginosa ST308. New recommendations for the monitoring of water contamination should consider persister cells. The genomic island GI-7, which confers tolerance to copper, probably originates from Pseudomonas species found in copper-contaminated soils and plants. Agricultural practices may have an unexpected consequence, allowing copper-tolerant pathogens to survive in the hospital environment and contaminate fragile patients.


Assuntos
Pseudomonas aeruginosa , Engenharia Sanitária , Cobre , França , Hospitais , Humanos
10.
J Antimicrob Chemother ; 74(6): 1572-1577, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-30789224

RESUMO

BACKGROUND: Infections with antibiotic-resistant pathogens in cancer patients are a leading cause of mortality. Cancer patients are treated with compounds that can damage bacterial DNA, potentially triggering the SOS response, which in turn enhances the bacterial mutation rate. Antibiotic resistance readily occurs after mutation of bacterial core genes. Thus, we tested whether cancer chemotherapy drugs enhance the emergence of resistant mutants in commensal bacteria. METHODS: Induction of the SOS response was tested after the incubation of Escherichia coli biosensors with 39 chemotherapeutic drugs at therapeutic concentrations. The mutation frequency was assessed after induction with the SOS-inducing chemotherapeutic drugs. We then tested the ability of the three most highly inducing drugs to drive the emergence of resistant mutants of major bacterial pathogens to first-line antibiotics. RESULTS: Ten chemotherapeutic drugs activated the SOS response. Among them, eight accelerated the evolution of the major commensal E. coli, mostly through activation of the SOS response, with dacarbazine, azacitidine and streptozotocin enhancing the mutation rate 21.3-fold (P < 0.001), 101.7-fold (P = 0.01) and 1158.7-fold (P = 0.02), respectively. These three compounds also spurred the emergence of imipenem-resistant Pseudomonas aeruginosa (up to 6.21-fold; P = 0.05), ciprofloxacin-resistant Staphylococcus aureus (up to 57.72-fold; P = 0.016) and cefotaxime-resistant Enterobacteria cloacae (up to 4.57-fold; P = 0.018). CONCLUSIONS: Our results suggest that chemotherapy could accelerate evolution of the microbiota and drive the emergence of antibiotic-resistant mutants from bacterial commensals in patients. This reveals an additional level of complexity of the interactions between cancer, chemotherapy and the gut microbiota.


Assuntos
Antibacterianos/farmacologia , Antineoplásicos/uso terapêutico , Farmacorresistência Bacteriana , Enterobacter cloacae/efeitos dos fármacos , Pseudomonas aeruginosa/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Resposta SOS em Genética
11.
Bioinformatics ; 34(22): 3795-3800, 2018 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-29931098

RESUMO

Motivation: The advent of next-generation sequencing has boosted the analysis of bacterial genome evolution. Insertion sequence (IS) elements play a key role in prokaryotic genome organization and evolution, but their repetitions in genomes complicate their detection from short-read data. Results: PanISa is a software pipeline that identifies IS insertions ab initio in bacterial genomes from short-read data. It is a highly sensitive and precise tool based on the detection of read-mapping patterns at the insertion site. PanISa performs better than existing IS detection systems as it is based on a database-free approach. We applied it to a high-risk clone lineage of the pathogenic species Pseudomonas aeruginosa, and report 43 insertions of five different ISs (among which three are new) and a burst of ISPa1635 in a hypermutator isolate. Availability and implementation: PanISa is implemented in Python and released as an open source software (GPL3) at https://github.com/bvalot/panISa. Supplementary information: Supplementary data are available at Bioinformatics online.


Assuntos
Elementos de DNA Transponíveis , Genoma Bacteriano , Sequenciamento de Nucleotídeos em Larga Escala , Análise de Sequência de DNA , Software
12.
Biochimie ; 94(4): 1069-73, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22210492

RESUMO

FMRP, a RNA-binding protein, was shown in association with polyribosomes in every cell types studied so far, suggesting a ubiquitous role as a translational regulator. Platelets are known for their limited protein synthesis potential. However, current investigations put forward that RNA metabolism is more developed than previously thought. Unexpectedly, our results provide evidence that FMRP, in platelets, is not constitutively associated with heavy particles, such as polyribosomes, and possesses a sedimentation coefficient of less than 10S contrasting with values of 150 to 500S as reported in other cell types. In summary, this report brings to light platelets as a simple human biological system to delineate novel FMRP functions as well as strengthening our comprehension of the pathophysiology of the fragile X syndrome which results from the absence of FMRP.


Assuntos
Plaquetas/metabolismo , Proteína do X Frágil da Deficiência Intelectual/sangue , Polirribossomos/metabolismo , Animais , Linhagem Celular , Proteína do X Frágil da Deficiência Intelectual/isolamento & purificação , Proteína do X Frágil da Deficiência Intelectual/metabolismo , Humanos , Masculino , Camundongos , Proteína I de Ligação a Poli(A)/metabolismo , Proteínas de Ligação a RNA/metabolismo , Frações Subcelulares/química
13.
J Comput Aided Mol Des ; 24(4): 361-72, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20354893

RESUMO

This paper reports the results of our attempt to predict hydration free energies on the SAMPL2 blind challenge dataset. We mostly examine the effects of the solute electrostatic component on the accuracy of the predictions. The usefulness of electronic polarization in predicting hydration free energies is assessed by comparing the Electronic Polarization from Internal Continuum model and the self consistent reaction field IEF-PCM to standard non-polarizable charge models such as RESP and AM1-BCC. We also determine an optimal restraint weight for Dielectric-RESP atomic charges fitting. Statistical analysis of the results could not distinguish the methods from one another. The smallest average unsigned error obtained is 1.9 +/- 0.6 kcal/mol (95% confidence level). A class of outliers led us to investigate the importance of the solute-solvent instantaneous induction energy, a missing term in PB continuum models. We estimated values between -1.5 and -6 kcal/mol for a series of halo-benzenes which can explain why some predicted hydration energies of non-polar molecules significantly disagreed with experiment.


Assuntos
Modelos Químicos , Solventes/química , Termodinâmica , Benzeno/química , Glucose/química , Modelos Moleculares , Solubilidade , Soluções/química , Eletricidade Estática , Xilose/química
14.
Org Lett ; 12(9): 1896-9, 2010 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-20349943

RESUMO

Formation of stable glassy phases can be induced through rational design in compounds which otherwise readily crystallize, such as tetraphenylporphyrin, by simple functionalization with moieties known to promote glass formation such as mexylaminotriazine units.

15.
J Biol Chem ; 285(9): 6538-51, 2010 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-20048162

RESUMO

The activation of several G protein-coupled receptors is known to regulate the adhesive properties of cells in different contexts. Here, we reveal that Gbetagamma subunits of heterotrimeric G proteins regulate cell-matrix adhesiveness by activating Rap1a-dependent inside-out signals and integrin activation. We show that Gbetagamma subunits enter in a protein complex with activated Rap1a and its effector Radil and establish that this complex is required downstream of receptor stimulation for the activation of integrins and the positive modulation of cell-matrix adhesiveness. Moreover, we demonstrate that Gbetagamma and activated Rap1a promote the translocation of Radil to the plasma membrane at sites of cell-matrix contacts. These results add to the molecular understanding of how G protein-coupled receptors impinge on cell adhesion and suggest that the Gbetagamma x Rap1 x Radil complex plays important roles in this process.


Assuntos
Proteínas de Transporte/metabolismo , Subunidades beta da Proteína de Ligação ao GTP/fisiologia , Subunidades gama da Proteína de Ligação ao GTP/fisiologia , Proteínas rap1 de Ligação ao GTP/metabolismo , Adesão Celular , Linhagem Celular , Matriz Extracelular/metabolismo , Humanos , Integrinas/metabolismo , Complexos Multiproteicos/metabolismo , Proteínas do Tecido Nervoso , Transporte Proteico
16.
J Gen Virol ; 86(Pt 10): 2897-2911, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16186246

RESUMO

A study of molecular diversity was carried out on 136 sugar beets infected with Beet necrotic yellow vein virus (BNYVV, Benyvirus) collected worldwide. The nucleotide sequences of the RNA-2-encoded CP, RNA-3-encoded p25 and RNA-5-encoded p26 proteins were analysed. The resulting phylogenetic trees allowed BNYVV to be classified into groups that show correlations between the virus clusters and geographic origins. The selective constraints on these three sequences were measured by estimating the ratio between synonymous and non-synonymous substitution rates (omega) with maximum-likelihood models. The results suggest that selective constraints are exerted differently on the proteins. CP was the most conserved, with mean omega values ranging from 0.12 to 0.15, while p26 was less constrained, with mean omega values ranging from 0.20 to 0.33. Selection was detected in three amino acid positions of p26, with omega values of about 5.0. The p25 sequences presented the highest mean omega values (0.36-1.10), with strong positive selection (omega=4.7-54.7) acting on 14 amino acids, and particularly on amino acid 68, where the omega value was the highest so far encountered in plant viruses.


Assuntos
Beta vulgaris/virologia , Variação Genética , Filogenia , Vírus de RNA/classificação , Proteínas do Capsídeo/genética , Vírus de Plantas/genética , Vírus de RNA/genética , RNA Viral/análise , Homologia de Sequência do Ácido Nucleico
17.
Virus Res ; 108(1-2): 15-22, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15681050

RESUMO

RNA-2 P75 open reading frame sequencing was conducted on BNYVV-infected sugar beet plants originating from 10 Belgian sources and was compared with sequences originating from France, Kazakhstan, Japan and China. This allowed the characterization of types A and B in Belgium. Sequence analysis confirmed that type A is intermediate between types P and B. The analysis of nucleotide sequences of the capsid protein epitopes and of different motifs involved in the transmission of the virus to the plant by Polymyxa betae reveals that they are well conserved among the different sequences analysed. In silico analysis showed that a potential dimerization/dsRNA-binding domain is present on P75. Finally, in order to compare the different BNYVV types, a real-time quantitative (RT)-PCR targeting the readthrough domain of P75 was developed and assessed over a period of 40 days on BNYVV susceptible sugar beet cv. Cadyx.


Assuntos
Fases de Leitura Aberta , Vírus de Plantas/classificação , Vírus de Plantas/genética , Vírus de RNA/classificação , Vírus de RNA/genética , RNA Viral/genética , Sequência de Aminoácidos , Substituição de Aminoácidos , Bélgica , Proteínas do Capsídeo/genética , Sequência Conservada , DNA Complementar/química , Dimerização , Genes Virais , Genótipo , Dados de Sequência Molecular , Filogenia , Vírus de Plantas/isolamento & purificação , Reação em Cadeia da Polimerase , Estrutura Terciária de Proteína , Vírus de RNA/isolamento & purificação , RNA Viral/isolamento & purificação , Alinhamento de Sequência , Análise de Sequência de RNA
18.
Appl Environ Microbiol ; 69(4): 2356-60, 2003 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-12676720

RESUMO

Three soilborne viruses transmitted by Polymyxa betae KESKIN in sugar beet have been described: Beet necrotic yellow vein virus (BNYVV), the agent of rhizomania, Beet soilborne virus (BSBV), and Beet virus Q (BVQ). A multiplex reverse transcription-PCR technique was developed to simultaneously detect BNYVV, BSBV, and BVQ, together with their vector, P. betae. The detection threshold of the test was up to 128 times greater than that of an enzyme-linked immunosorbent assay. Systematic association of BNYVV with one or two different pomoviruses was observed. BVQ was detected in samples from Belgium, Bulgaria, France, Germany, Hungary, Italy, Sweden, and The Netherlands but not in samples from Turkey.


Assuntos
Beta vulgaris/microbiologia , Fungos/isolamento & purificação , Vírus de Plantas/isolamento & purificação , Vírus de RNA/isolamento & purificação , Animais , Fungos/genética , Fungos/virologia , Doenças das Plantas/microbiologia , Vírus de Plantas/genética , Vírus de RNA/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sensibilidade e Especificidade , Microbiologia do Solo , Esporos Fúngicos/genética , Esporos Fúngicos/isolamento & purificação , Esporos Fúngicos/virologia , Transcrição Gênica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA