148 research outputs found

    Scanning electrochemical microscopy as a local probe of oxygen permeability in cartilage

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    The use of scanning electrochemical microscopy, a high-resolution chemical imaging technique, to probe the distribution and mobility of solutes in articular cartilage is described. In this application, a mobile ultramicroelectrode is positioned close (not, vert, similar1 μm) to the cartilage sample surface, which has been equilibrated in a bathing solution containing the solute of interest. The solute is electrolyzed at a diffusion-limited rate, and the current response measured as the ultramicroelectrode is scanned across the sample surface. The topography of the samples was determined using Ru(CN)64−, a solute to which the cartilage matrix was impermeable. This revealed a number of pit-like depressions corresponding to the distribution of chondrocytes, which were also observed by atomic force and light microscopy. Subsequent imaging of the same area of the cartilage sample for the diffusion-limited reduction of oxygen indicated enhanced, but heterogeneous, permeability of oxygen across the cartilage surface. In particular, areas of high permeability were observed in the cellular and pericellular regions. This is the first time that inhomogeneities in the permeability of cartilage toward simple solutes, such as oxygen, have been observed on a micrometer scale

    Dolutegravir Monotherapy as Maintenance Strategy: A Meta-Analysis of Individual Participant Data From Randomized Controlled Trials

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    Background Dolutegravir monotherapy (DTG-m) results in virological failure (VF) in some people with human immunodeficiency virus (PWH). We sought to identify the independent factors associated with the risk of VF and to explore the effect size heterogeneity between subgroups of PWH enrolled in DTG-m trials. Methods We searched for randomized clinical trials (RCTs) evaluating DTG-m versus combined antiretroviral therapy (cART) among PWH virologically controlled for at least 6 months on cART. We performed an individual participant data meta-analysis of VF risk factors and quantified their explained heterogeneity in random-effect models. Definition of VF was a confirmed plasma human immunodeficiency virus (HIV)-1 ribonucleic acid (RNA) >50 copies/mL by week 48. Results Among 416 PWH from 4 RCTs, DTG-m significantly increased the risk of VF (16 of 227 [7%] versus 0 of 189 for cART; risk difference 7%; 95% confidence interval [CI], 1%-2%; P = .02; I2^{2} = 51%). Among 272 participants exposed to DTG-m, VF were more likely in participants with the following: first cART initiated ≥90 days from HIV acute infection (adjusted hazard ratio [aHR], 5.16; 95% 95% CI, 1.60-16.65), CD4 T cells nadir <350/mm3^{3} (aHR, 12.10; 95% CI, 3.92-37.40), HIV RNA signal at baseline (aHR, 4.84; 95% CI, 3.68-6.38), and HIV-deoxyribonucleic acid (DNA) copy number at baseline ≥2.7 log/106^{6} peripheral blood mononuclear cells (aHR, 3.81; 95% CI, 1.99-7.30). Among these independent risk factors, the largest effect size heterogeneity was found between HIV DNA subgroups (I2^{2} = 80.2%; P for interaction = .02). Conclusions Our study supports the importance of a large viral reservoir size for explaining DTG-m simplification strategy failure. Further studies are needed to link size and genetic diversity of the HIV-1 reservoir

    Reassessment of the Lineage Fusion Hypothesis for the Origin of Double Membrane Bacteria

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    In 2009, James Lake introduced a new hypothesis in which reticulate phylogeny reconstruction is used to elucidate the origin of Gram-negative bacteria (Nature 460: 967–971). The presented data supported the Gram-negative bacteria originating from an ancient endosymbiosis between the Actinobacteria and Clostridia. His conclusion was based on a presence-absence analysis of protein families that divided all prokaryotes into five groups: Actinobacteria, Double Membrane bacteria (DM), Clostridia, Archaea and Bacilli. Of these five groups, the DM are by far the largest and most diverse group compared to the other groupings. While the fusion hypothesis for the origin of double membrane bacteria is enticing, we show that the signal supporting an ancient symbiosis is lost when the DM group is broken down into smaller subgroups. We conclude that the signal detected in James Lake's analysis in part results from a systematic artifact due to group size and diversity combined with low levels of horizontal gene transfer.Exobiology Program (U.S.) (Grant NNX08AQ10G)Assembling the Tree of Life (Program) (Grant DEB 0830024

    Variations of Plasmid Content in Rickettsia felis

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    Background: Since its first detection, characterization of R. felis has been a matter of debate, mostly due to the contamination of an initial R. felis culture by R. typhi. However, the first stable culture of R. felis allowed its precise phenotypic and genotypic characterization, and demonstrated that this species belonged to the spotted fever group rickettsiae. Later, its genome sequence revealed the presence of two forms of the same plasmid, physically confirmed by biological data. In a recent article, Gillespie et al. ( PLoS One. 2007; 2( 3): e266.) used a bioinformatic approach to refute the presence of the second plasmid form, and proposed the creation of a specific phylogenetic group for R. felis. Methodology/ Principal Findings: In the present report, we, and five independent international laboratories confirmed unambiguously by PCR the presence of two plasmid forms in R. felis strain URRWXCal(2)(T), but observed that the plasmid content of this species, from none to 2 plasmid forms, may depend on the culture passage history of the studied strain. We also demonstrated that R. felis does not cultivate in Vero cells at 37 degrees C but generates plaques at 30 degrees C. Finally, using a phylogenetic study based on 667 concatenated core genes, we demonstrated the position of R. felis within the spotted fever group. Significance: We demonstrated that R. felis, which unambiguously belongs to the spotted fever group rickettsiae, may contain up to two plasmid forms but this plasmid content is unstable

    Menstrual factors, reproductive history, hormone use, and Urothelial carcinoma risk: A prospective study in the EPIC cohort

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    Background: Urothelial carcinoma (UC) is the predominant (95%) bladder cancer subtype in industrialised nations. Animal and epidemiological human studies suggest that hormonal factors may influence UC risk. Methods: We used an analytic cohort of 333,919 women from the European Prospective Investigation into Cancer and Nutrition Cohort (EPIC). Associations between hormonal factors and incident UC (overall and by tumour grade, by tumour aggressiveness, and by non-muscle invasive UC) risk were evaluated using Cox proportional hazards models. All models were stratified by age at recruitment and study centre, and adjusted for smoking status and intensity, and fruit and vegetable intakes. Results: During a mean of 15 years of follow-up, 529 women developed UC. In a model including number of full-term pregnancies (FTP), menopausal status, and menopausal hormone therapy (MHT) showed an inverse association between, number of FTP was inversely associated with UC risk (HR≥5vs1=0.48, 0.25-0.90; P-trend in parous women=0.010) and MHT-use (compared to non-use) was positively associated with UC risk (HR=1.27, 1.03-1.57), but no dose-response by years of MHT-use was observed. No modification of HRs by smoking status was observed. Finally, sensitivity analysis in never-smokers showed similar HR patterns for number of FTP and no association between MHT-use and UC risk. Association between MHT-use and UC risk only remained significant in current-smokers. No heterogeneity of the risk estimations in the final model was observed by tumour aggressiveness or by tumour grade. A positive association between the MTH-use and non-muscle invasive UC risk was observed. Conclusion: Increasing number of FTP may reduce UC risk. Our results provided limited evidence for a role of MHT-use in UC risk due to residual confounding by tobacco. Impact: More detailed studies on parity are needed to understand the possible effects of perinatal hormone changes in urothelial cells

    Specialist laboratory networks as preparedness and response tool - The emerging viral diseases-expert laboratory network and the chikungunya outbreak, Thailand, 2019

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    We illustrate the potential for specialist laboratory networks to be used as preparedness and response tool through rapid collection and sharing of data. Here, the Emerging Viral Diseases-Expert Laboratory Network (EVD-LabNet) and a laboratory assessment of chikungunya virus (CHIKV) in returning European travellers related to an ongoing outbreak in Thailand was used for this purpose. EVD-LabNet rapidly collected data on laboratory requests, diagnosed CHIKV imported cases and sequences generated, and shared among its members and with the European Centre for Disease Prevention and Control. Data across the network showed an increase in CHIKV imported cases during 1 October 2018-30 April 2019 vs the same period in 2018 (172 vs 50), particularly an increase in cases known to be related to travel to Thailand (72 vs 1). Moreover, EVD-LabNet showed that strains were imported from Thailand that cluster with strains of the ECSA-IOL E1 A226 variant emerging in Pakistan in 2016 and involved in the 2017 outbreaks in Italy. CHIKV diagnostic requests increased by 23.6% between the two periods. The impact of using EVD-LabNet or similar networks as preparedness and response tool could be improved by standardisation of the collection, quality and mining of data in routine laboratory management systems

    Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk

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    BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7×10-8, HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4×10-8, HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4×10-8, HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific associat
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