1,143 research outputs found
Tomography of Electrospun Carbon Nanotube Polymeric Blends by Focus Ion Beam: Alignment and Phase Separation Analysis from Multicontrast Electron Imaging
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Multimodal focused ion beam (FIB) imaging on a polydimethylsiloxane/poly(methyl methacrylate) (PMMA)/multiwall carbon nanotube (MWCNT) electrospun composite has been applied to discriminate the phase-separated polymer blend and identify MWCNT fillers. Upon tomographic reconstruction, this discrimination has been possible through both atomic number and voltage contrast, the latter being enabled by preferential MWCNT segregation to PMMA. This study suggests that electrospinning could be affecting not only MWCNT alignment but also phase separation dynamics of immiscible polymers, yielding a porous structure throughout the fibers. This work opens the door to correlative materials science in polymer nanocomposites through FIB tomography, where voltage contrast is a main actor. (Figure presented.)
Efectos de los ejercicios pliométricos en pacientes postoperatorio de rotura del tendón calcáneo
It is known about the rupture of the Achilleus tendon since ancient Greece, which has been increasing in recent years, therefore, it seeks to implement better tools for its treatment, one of them being plyometric exercises. Meta-analysis type studies, randomized and experimental controlled trials observed that the application of plyometric exercises in most of the participants improved the quality of the tendon, increasing elasticity and decreasing its stiffness (p <0.01) in 14 studies and in the remaining 3 studies. , did not improve the structure of the tendon, however, it did improve its symptoms and functionality in late studies (p <0.01). The application of plyometric exercises is an additional tool to treat subjects undergoing an operation to rupture the Achilles tendon, which must be applied in the final stages of rehabilitation, improving tissue stiffness, increasing functionality and reducing chronic pain.De la ruptura del tendón Aquileo se tiene conocimiento desde la antigua Grecia, la cual ha ido en aumento en los últimos años, por ende, se busca implementar mejores herramientas para el tratamiento de la misma, siendo una de ellas los ejercicios pliométricos. Estudios tipo meta-análisis, ensayos controlados aleatorizados y experimentales observaron que la aplicación de ejercicios pliométricos en la mayoría de los participantes mejoraba la calidad del tendón, aumentando elasticidad y disminuyendo su rigidez (p<0.01) en 14 estudios y en los 3 estudios restantes, no mejoraba la estructura del tendón, sin embargo, mejoraba la sintomatología y funcionalidad del mismo en estudios tardíos (p<0.01). La aplicación de ejercicios pliométricos es una herramienta adicional para tratar a los sujetos sometidos a una operación de ruptura de tendón Aquileo, el cual debe ser aplicado en estadios finales en rehabilitación, mejorando la rigidez del tejido, aumentando la funcionalidad y disminuyendo el dolor crónico
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The matricellular protein TSP1 promotes human and mouse endothelial cell senescence through CD47 and Nox1.
Senescent cells withdraw from the cell cycle and do not proliferate. The prevalence of senescent compared to normally functioning parenchymal cells increases with age, impairing tissue and organ homeostasis. A contentious principle governing this process has been the redox theory of aging. We linked matricellular protein thrombospondin 1 (TSP1) and its receptor CD47 to the activation of NADPH oxidase 1 (Nox1), but not of the other closely related Nox isoforms, and associated oxidative stress, and to senescence in human cells and aged tissue. In human endothelial cells, TSP1 promoted senescence and attenuated cell cycle progression and proliferation. At the molecular level, TSP1 increased Nox1-dependent generation of reactive oxygen species (ROS), leading to the increased abundance of the transcription factor p53. p53 mediated a DNA damage response that led to senescence through Rb and p21cip, both of which inhibit cell cycle progression. Nox1 inhibition blocked the ability of TSP1 to increase p53 nuclear localization and p21cip abundance and its ability to promote senescence. Mice lacking TSP1 showed decreases in ROS production, p21cip expression, p53 activity, and aging-induced senescence. Conversely, lung tissue from aging humans displayed increases in the abundance of vascular TSP1, Nox1, p53, and p21cip Finally, genetic ablation or pharmacological blockade of Nox1 in human endothelial cells attenuated TSP1-mediated ROS generation, restored cell cycle progression, and protected against senescence. Together, our results provide insights into the functional interplay between TSP1 and Nox1 in the regulation of endothelial senescence and suggest potential targets for controlling the aging process at the molecular level
How acceptable are antiretrovirals for the prevention of sexually transmitted HIV? A review of research on the acceptability of oral pre-exposure prophylaxis and treatment as prevention
Recent research has demonstrated how antiretrovirals (ARVs) could be effective in the prevention of sexually transmitted HIV. We review research on the acceptability of oral pre-exposure prophylaxis (PrEP) and treatment as prevention (TasP) for HIV prevention amongst potential users. We consider with whom, where and in what context this research has been conducted, how acceptability has been approached, and what research gaps remain. Findings from 33 studies show a lack of TasP research, PrEP studies which have focused largely on men who have sex with men (MSM) in a US context, and varied measures of acceptability. In order to identify when, where and for whom PrEP and TasP would be most appropriate and effective, research is needed in five areas: acceptability of TasP to people living with HIV; motivation for PrEP use and adherence; current perceptions and management of risk; the impact of broader social and structural factors; and consistent definition and operationalisation of acceptability which moves beyond adherence
Quantitative principles of cis-translational control by general mRNA sequence features in eukaryotes.
BackgroundGeneral translational cis-elements are present in the mRNAs of all genes and affect the recruitment, assembly, and progress of preinitiation complexes and the ribosome under many physiological states. These elements include mRNA folding, upstream open reading frames, specific nucleotides flanking the initiating AUG codon, protein coding sequence length, and codon usage. The quantitative contributions of these sequence features and how and why they coordinate to control translation rates are not well understood.ResultsHere, we show that these sequence features specify 42-81% of the variance in translation rates in Saccharomyces cerevisiae, Schizosaccharomyces pombe, Arabidopsis thaliana, Mus musculus, and Homo sapiens. We establish that control by RNA secondary structure is chiefly mediated by highly folded 25-60 nucleotide segments within mRNA 5' regions, that changes in tri-nucleotide frequencies between highly and poorly translated 5' regions are correlated between all species, and that control by distinct biochemical processes is extensively correlated as is regulation by a single process acting in different parts of the same mRNA.ConclusionsOur work shows that general features control a much larger fraction of the variance in translation rates than previously realized. We provide a more detailed and accurate understanding of the aspects of RNA structure that directs translation in diverse eukaryotes. In addition, we note that the strongly correlated regulation between and within cis-control features will cause more even densities of translational complexes along each mRNA and therefore more efficient use of the translation machinery by the cell
Plasma Tau and Neurofilament Light in Frontotemporal Lobar Degeneration and Alzheimer Disease
Objective: To test the hypothesis that plasma total tau (t-tau) and neurofilament light chain (NfL) concentrations may have a differential role in the study of frontotemporal lobar degeneration syndromes (FTLD-S) and clinically diagnosed Alzheimer disease syndromes (AD-S), we determined their diagnostic and prognostic value in FTLD-S and AD-S and their sensitivity to pathologic diagnoses.
Methods: We measured plasma t-tau and NfL with the Simoa platform in 265 participants: 167 FTLD-S, 43 AD-S, and 55 healthy controls (HC), including 82 pathology-proven cases (50 FTLD-tau, 18 FTLD-TDP, 2 FTLD-FUS, and 12 AD) and 98 participants with amyloid PET. We compared cross-sectional and longitudinal biomarker concentrations between groups, their correlation with clinical measures of disease severity, progression, and survival, and cortical thickness.
Results: Plasma NfL, but not plasma t-tau, discriminated FTLD-S from HC and AD-S from HC. Both plasma NfL and t-tau were poor discriminators between FLTD-S and AD-S. In pathology-confirmed cases, plasma NfL was higher in FTLD than AD and in FTLD-TDP compared to FTLD-tau, after accounting for age and disease severity. Plasma NfL, but not plasma t-tau, predicted clinical decline and survival and correlated with regional cortical thickness in both FTLD-S and AD-S. The combination of plasma NfL with plasma t-tau did not outperform plasma NfL alone.
Conclusion: Plasma NfL is superior to plasma t-tau for the diagnosis and prediction of clinical progression of FTLD-S and AD-S.
Classification of Evidence: This study provides Class III evidence that plasma NfL has superior diagnostic and prognostic performance vs plasma t-tau in FTLD and AD
Rapid and Accurate Detection of Mycobacterium tuberculosis in Sputum Samples by Cepheid Xpert MTB/RIF Assay-A Clinical Validation Study
Background: A crucial impediment to global tuberculosis control is the lack of an accurate, rapid diagnostic test for detection of patients with active TB. A new, rapid diagnostic method, (Cepheid) Xpert MTB/RIF Assay, is an automated sample preparation and real-time PCR instrument, which was shown to have good potential as an alternative to current reference standard sputum microscopy and culture.Methods: We performed a clinical validation study on diagnostic accuracy of the Xpert MTB/RIF Assay in a TB and HIV endemic setting. Sputum samples from 292 consecutively enrolled adults from Mbeya, Tanzania, with suspected TB were subject to analysis by the Xpert MTB/RIF Assay. The diagnostic performance of Xpert MTB/RIF Assay was compared to standard sputum smear microscopy and culture. Confirmed Mycobacterium tuberculosis in a positive culture was used as a reference standard for TB diagnosis.Results: Xpert MTB/RIF Assay achieved 88.4% (95% CI = 78.4% to 94.9%) sensitivity among patients with a positive culture and 99% (95% CI = 94.7% to 100.0%) specificity in patients who had no TB. HIV status did not affect test performance in 172 HIV-infected patients (58.9% of all participants). Seven additional cases (9.1% of 77) were detected by Xpert MTB/RIF Assay among the group of patients with clinical TB who were culture negative. Within 45 sputum samples which grew non-tuberculous mycobacteria the assay's specificity was 97.8% (95% CI = 88.2% to 99.9%).Conclusions: The Xpert MTB/RIF Assay is a highly sensitive, specific and rapid method for diagnosing TB which has potential to complement the current reference standard of TB diagnostics and increase its overall sensitivity. Its usefulness in detecting sputum smear and culture negative patients needs further study. Further evaluation in high burden TB and HIV areas under programmatic health care settings to ascertain applicability, cost-effectiveness, robustness and local acceptance are required
Reconstruction of sediment-transport pathways on a modern microtidal coast by a new grain-size trend analysis method
A new method for granulometric-parameter-based reconstruction of sediment-transport pathways is proposed and is termed P-GSTA (grain-size trend analysis using principal component analysis) herein. The main advantage of this method is its applicability to depositional environments involving mixed transport processes, for instance, fluvial, tidal, and wave-influenced environments. In the P-GSTA method, a linear function with all significant granulometric parameters that are summed with different weighting factors was used to infer sediment-transport direction (sediment flux pattern); the previous grain-size trend analysis (GSTA) methods considered only three parameters (mean grain size, sorting, and skewness) with equal weighting. This study chose six parameters (namely, median grain size, coefficient of variation, skewness, kurtosis, and mud and gravel log-ratios) for calculation. First, the zero values of mud and gravel fractions are replaced, and their log-ratios are defined. Then, all values are standardized. Thereafter, principal component analysis (PCA) is conducted to determine the weighting factor of each granulometric parameter. Each principal component is then interpreted, and the function best representing a sediment flux pattern is chosen from these components. Trend vectors are calculated, solely on the basis of a map interpolated from the scores of the chosen principal component, as the two-dimensional gradient of this value. The P-GSTA method proposed in this study was applied to a modern microtidal coast (tidal sand flat along the Kushida River Delta, central Japan). Sediment-transport pathways reconstructed by this method were consistent with observed sediment-transport patterns determined by field experiments using tracer sediments and geomorphologic observation; the results of the previous GSTA method were inconsistent with the observations. The proposed method also revealed additional minor depositional processes on the sand flat, namely, the deposition of fluvial-channel lags and muddy particles. Thus, this study demonstrates that the proposed P-GSTA method is a potentially powerful tool to reconstruct sediment-transport patterns even under mixed transport processes, where the estimation of the sediment-transport function is difficult
Genetic Diversity in New Members of the Reticulocyte Binding Protein Family in Thai Plasmodium vivax Isolates
Background Plasmodium vivax merozoites specifically invade reticulocytes. Until recently, two reticulocyte-binding proteins (Pvrbp1 and Pvrbp2) expressed at the apical pole of the P. vivax merozoite were considered to be involved in reticulocyte recognition. The genome sequence recently obtained for the Salvador I (Sal-I) strain of P. vivax revealed additional genes in this family, and in particular Pvrbp2a, Pvrbp2b (Pvrbp2 has been renamed as Pvrbp2c) and two pseudogenes Pvrbp2d and Pvrbp3. It had been previously found that Pvrbp2c is substantially more polymorphic than Pvrbp1. The primary goal of this study was to ascertain the level of polymorphism of these new genes. Methodology/Principal Findings The sequence of the Pvrbp2a, Pvrbp2b, Pvrbp2d and Pvrbp3 genes were obtained by amplification/cloning using DNA purified from four isolates collected from patients that acquired the infection in the four cardinal regions of Thailand (west, north, south and east). An additional seven isolates from western Thailand were analyzed for gene copy number variation. There were significant polymorphisms exhibited by these genes (compared to the reference Sal-I strain) with the ratio of mutations leading to a non-synonymous or synonymous amino acid change close to 3∶1 for Pvrbp2a and Pvrbp2b. Although the degree of polymorphism exhibited by these two genes was higher than that of Pvrbp1, it did not reach the exceptional diversity noted for Pvrbp2c. It was interesting to note that variations in the copy number of Pvrbp2a and Pvrbp2b occurred in some isolates. Conclusions/Significance The evolution of different members of the Pvrbp2 family and their relatively high degree of polymorphism suggests that the proteins encoded by these genes are important for parasite survival and are under immune selection. Our data also shows that there are highly conserved regions in rbp2a and rbp2b, which might provide suitable targets for future vaccine development against the blood stage of P. vivax
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