Techniques used to identify the Brazilian variant of HIV-1 subtype B

The purpose of the present study was to compare the sensitivity and specificity of V3 enzyme immunoassay (solid phase EIA and EIA inhibition) and restriction fragment length polymorphism (RFLP) with the DNA sequencing "gold standard" to identify the Brazilian HIV-1 variants of subtype B and B"-GWGR. Peripheral blood mononuclear cells were collected from 61 HIV-1-infected individuals attending a clinic in São Paulo. Proviral DNA was amplified and sequentially cleaved with the Fok I restriction enzyme. Plasma samples were submitted to a V3-loop biotinylated synthetic peptide EIA. Direct partial DNA sequencing of the env gene was performed on all samples. Based on EIA results, the sensitivity for detecting B-GPGR was 70%, compared to 64% for the Brazilian variant B"-GWGR while, the specificity of B-GPGR detection was 85%, compared to 88% for GWGR. The assessment of RFLP revealed 68% sensitivity and 94% specificity for the B-GPGR strain compared to 84 and 90% for the B"-GWGR variant. Moreover, direct DNA sequencing was able to detect different base sequences corresponding to amino acid sequences at the tip of the V3 loop in 22 patients. These results show a similar performance of V3 serology and RLFP in identifying the Brazilian variant GWGR. However, V3 peptide serology may give indeterminate results. Therefore, we suggest that V3 serology be used instead of DNA sequencing where resources are limited. Samples giving indeterminate results by V3 peptide serology should be analyzed by direct DNA sequencing to distinguish between B-GPGR and the Brazilian variant B"-GWGR

Influence of pulse sequence parameters at 1.5 T and 3.0 T on MRI artefacts produced by metal-ceramic restorations

Objectives: Susceptibility artefacts from dental materials may compromise MRI diagnosis. However, little is known regarding MRI artefacts of dental material samples with the clinical shapes used in dentistry. The present phantom study aims to clarify how pulse sequences and sequence parameters affect MRI artefacts caused by metal-ceramic restorations.Methods: A phantom consisting of nickel-chromium metal-ceramic restorations (i.e. dental crowns and fixed bridges) and cylindrical reference specimens immersed in agar gel was imaged in 1.5 and 3.0 T MRI scanners. Gradient echo (GRE), spin echo (SE) and ultrashort echo time (UTE) pulse sequences were used. The artefact area in each image was automatically calculated from the pixel values within a region of interest. Mean values for similar pulse sequences differing in one parameter at a time were compared. A comparison between mean artefact area at 1.5 and 3.0 T, and from GRE and SE was also carried out. In addition, a parametric correlation between echo time (TE) and artefact area was performed.Results: A significant correlation was found between TE and artefact area in GRE images. Higher receiver bandwidth significantly reduced artefact area in SE images. UTE images yielded the smallest artefact area at 1.5 T. In addition, a significant difference in mean artefact area was found between images at 1.5 and 3.0 T field strengths (p = 0.028) and between images from GRE and SE pulse sequences (p = 0.005).Conclusions: It is possible to compensate the effect of higher field strength on MRI artefacts by setting optimized pulse sequences for scanning patients with metal-ceramic restorations.peer-reviewe

Hidden Charge Order in an Iron Oxide Square-Lattice Compound

Since the discovery of charge disproportionation in the FeO2 square-lattice compound Sr3Fe2O7 by Mössbauer spectroscopy more than fifty years ago, the spatial ordering pattern of the disproportionated charges has remained “hidden” to conventional diffraction probes, despite numerous x-ray and neutron scattering studies. We have used neutron Larmor diffraction and Fe K-edge resonant x-ray scattering to demonstrate checkerboard charge order in the FeO2 planes that vanishes at a sharp second-order phase transition upon heating above 332 K. Stacking disorder of the checkerboard pattern due to frustrated interlayer interactions broadens the corresponding superstructure reflections and greatly reduces their amplitude, thus explaining the difficulty of detecting them by conventional probes. We discuss the implications of these findings for research on “hidden order” in other materials

Influence of receiver bandwidth on MRI artifacts caused by orthodontic brackets composed of different alloys

Purpose: The aim of this in vitro study was to assess the role of bandwidth on the area of magnetic resonance imaging (MRI) artifacts caused by orthodontic appliances composed of different alloys, using different pulse sequences in 1.5 T and 3.0 T magnetic fields. Materials and methods: Different phantoms containing orthodontic brackets (ceramic, ceramic bracket with a stainless-steel slot, and stainless steel) were immersed in agar gel and imaged in 1.5 T and 3.0 T MRI scanners. Pairs of gradient-echo (GE), spin-echo (SE), and ultrashort echo time (UTE) pulse sequences were used differing in bandwidth only. The area of artifacts from orthodontic devices was automatically estimated from pixel value thresholds within a region of interest (ROI). Mean values for similar pulse sequences differing in bandwidth were compared at 1.5 T and 3.0 T using analysis of variance. Results: The comparison of groups revealed a significant inverse association between bandwidth values and artifact areas of the stainless-steel bracket and the self-ligating ceramic bracket with a stainless-steel slot (P<0.05). The areas of artifacts from the ceramic bracket were the smallest, but were not reduced significantly in pulse sequences with higher bandwidth values (P<0.05). Significant differences were also observed between 1.5 T and 3.0 T MRI using SE and UTE, but not using GE 2-dimensional or 3-dimensional pulse sequences. Conclusion: Higher receiver bandwidth might be indicated to prevent artifacts from orthodontic appliances in 1.5 T and 3.0 T MRI using SE and UTE pulse sequences.peer-reviewe

Correlation among alveolar bone assessments provided by CBCT, micro-CT, and 14 T MRI

Objectives: The aim of this study was to evaluate bone mineral adipose tissue (BMAT) volume in 21 alveolar bone specimens, as determined by 14 T MRI, and correlate them to the radiodensity values obtained pre-operatively of regions of interest (ROIs) by cone beam computed tomography (CBCT), and to the bone-volume-to-tissue-volume ratio values obtained by micro-CT, the gold-standard for morphometric data collection. Methods: Partially edentulous patients were submitted to a CBCT scan, and the radiographic bone densities in each ROI were automatically calculated using coDiagnostiX software. Based on the CBCT surgical planning, a CAD/CAM stereolithographic surgical guide was fabricated to retrieve a bone biopsy from the same ROIs scanned preoperatively, and then to orientate the subsequent implant placement. The alveolar bone biopsies were then collected and scanned using the micro-CT and 14 T MRI techniques. Pearson’s correlation test was performed to correlate the results obtained using the three different techniques. Results: In the 21 eligible bone specimens (6 females, 15 males), age (mean age 52.9 years), micro-CT, and 14 T MRI variables were found to be normally distributed (p > 0.05). The strongest—and only statistically significant (p < 0.05)—correlation was found between micro-CT and 14 T MRI values (r = 0.943), and the weakest, between 14 T MRI and CBCT values (r =–0.068). Conclusions: The findings suggest that 14 T MRI can be used to evaluate BMAT as an indirect marker for bone volume, and that CBCT is not a reliable technique to provide accurate bone density values.peer-reviewe

Prediction models for carbapenem-resistant Enterobacterales carriage at liver transplantation: A multicenter retrospective study

Background: Carbapenem-resistant Enterobacterales (CRE) colonisation at liver transplantation (LT) increases the risk of CRE infection after LT, which impacts on recipients’ survival. Colonization status usually becomes evident only near LT. Thus, predictive models can be useful to guide antibiotic prophylaxis in endemic centres. Aims: This study aimed to identify risk factors for CRE colonisation at LT in order to build a predictive model. Methods: Retrospective multicentre study including consecutive adult patients who underwent LT, from 2010 to 2019, at two large teaching hospitals. We excluded patients who had CRE infections within 90 days before LT. CRE screening was performed in all patients on the day of LT. Exposure variables were considered within 90 days before LT and included cirrhosis complications, underlying disease, time on the waiting list, MELD and CLIF-SOFA scores, antibiotic use, intensive care unit and hospital stay, and infections. A machine learning model was trained to detect the probability of a patient being colonized with CRE at LT. Results: A total of 1544 patients were analyzed, 116 (7.5%) patients were colonized by CRE at LT. The median time from CRE isolation to LT was 5 days. Use of antibiotics, hepato-renal syndrome, worst CLIF sofa score, and use of beta-lactam/beta-lactamase inhibitor increased the probability of a patient having pre-LT CRE. The proposed algorithm had a sensitivity of 66% and a specificity of 83% with a negative predictive value of 97%. Conclusions: We created a model able to predict CRE colonization at LT based on easy-to-obtain features that could guide antibiotic prophylaxis (Figure presented.)