Transfer Constant Research Articles

Glioma grade discrimination with dynamic contrast-enhanced MRI: An accurate analysis based on MRI guided stereotactic biopsy

PurposeTo evaluate the diagnostic performance of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) metrics for glioma grading on a point-to-point basis. MethodsForty patients with treatment-naïve glioma underwent DCE-MR examination and stereotactic biopsy. DCE-derived parameters including endothelial transfer constant (Ktrans), volume of extravascular-extracellular space (ve), fractional plasma volume (fpv), and reflux transfer rate (kep) were measured within ROIs on DCE maps accurately matched with biopsies used for histologic grades diagnosis. Differences in parameters between grades were evaluated by Kruskal-Wallis tests. Diagnostic accuracy of each parameter and their combination was assessed using receiver operating characteristic curve. ResultsEighty-four independent biopsy samples from 40 patients were analyzed in our study. Significant statistical differences in Ktrans and ve were observed between grades except ve between grade 2 and 3. Ktrans showed good to excellent accuracy in discriminating grade 2 from 3, 3 from 4, and 2 from 4 (area under the curve = 0.802, 0.801 and 0.971, respectively). Ve indicated good accuracy in discriminating grade 3 from 4 and 2 from 4 (AUC = 0.874 and 0.899, respectively). The combined parameter demonstrated fair to excellent accuracy in discriminating grade 2 from 3, 3 from 4, and 2 from 4 (AUC = 0.794, 0.899 and 0.982, respectively). ConclusionOur study had identified Ktrans, ve and the combination of parameters to be an accurate predictor for grading glioma.

Diagnostic Accuracy of Arterial Spin-Labeling, Dynamic Contrast-Enhanced, and DSC Perfusion Imaging in the Diagnosis of Recurrent High-Grade Gliomas: A Prospective Study.

For patients with high-grade gliomas, the appearance of a new, enhancing lesion after surgery and chemoradiation represents a diagnostic dilemma. We hypothesized that MR perfusion without and with contrast can differentiate tumor recurrence from radiation necrosis. In this prospective study, we performed 3 MR perfusion methods: arterial spin-labeling, DSC, and dynamic contrast enhancement. For each lesion, we measured CBF from arterial spin-labeling, uncorrected relative CBV, and leakage-corrected relative CBV from DSC imaging. The volume transfer constant and plasma volume were obtained from dynamic contrast-enhanced imaging without and with T1 mapping using modified Look-Locker inversion recovery (MOLLI). The diagnosis of tumor recurrence or radiation necrosis was determined by either histopathology for patients who underwent re-resection or radiologic follow-up for patients who did not have re-resection. There were 26 patients with 32 lesions, 19 lesions with tumor recurrence and 13 lesions with radiation necrosis. Compared with radiation necrosis, lesions with tumor recurrence had higher CBF (P = .033), leakage-corrected relative CBV (P = .048), and plasma volume using MOLLI T1 mapping (P = .012). For differentiating tumor recurrence from radiation necrosis, the areas under the curve were 0.81 for CBF, 0.80 for plasma volume using MOLLI T1 mapping, and 0.71 for leakage-corrected relative CBV. A correlation was found between CBF and leakage-corrected relative CBV (r s = 0.54), volume transfer constant, and plasma volume (0.50 < r s< 0.77) but not with uncorrected relative CBV (r s = 0.20, P = .29). In the differentiation of tumor recurrence from radiation necrosis in a newly enhancing lesion, the diagnostic value of arterial spin-labeling-derived CBF is similar to that of DSC and dynamic contrast-enhancement-derived blood volume.

Quantitative analysis of local microcirculation changes in early osteonecrosis of femoral head: DCE-MRI findings.

This study aims to quantitatively analyze the changes in local microcirculation in early osteonecrosis of the femoral head (ONFH) by dynamic contrast-enhanced (DCE) MRI and to explore the pathophysiological mechanisms of early ONFH. We selected 49 patients (98 hips) aged 21-59years who were clinically diagnosed with early ONFH. A total of 77 femoral heads were diagnosed with different degrees of necrosis according to the Association Research Circulation Osseous (ARCO) staging system, and 21 femoral heads were judged to be completely healthy. All patients underwent DCE-MRI scanning. Pseudocolor images and time-signal intensity curves were generated by Tissue 4D processing software. The volume transfer constant (K trans), extracellular extravascular space, also known as vascular leakage (V e), and transfer rate constant (K ep) of healthy and different areas of necrotic femoral heads were measured on perfusion parameter maps. The differences and characteristics of these parameters in healthy and different areas of necrotic femoral heads were analyzed. The signal accumulation in healthy femoral heads is lower than that of necrotic femoral heads in pseudocolor images. The time-signal intensity curve of healthy femoral heads is along the horizontal direction, while they all have upward trends for different areas of necrotic femoral heads. The mean value of K trans of healthy femoral heads was lower than the integration of necrotic, boundary, and other areas (F = 3.133, P = .036). The K ep value of healthy femoral heads was higher than the integration of lesion areas (F = 6.273, P = .001). The mean V e value of healthy femoral heads was smaller than that of the lesion areas (F = 3.872, P = .016). The comparisons of parameters between different areas and comparisons among healthy areas and lesion areas showed different results. ONFH is a complex ischemic lesion caused by changes in local microcirculation. It mainly manifests as increased permeability of the vascular wall, blood stasis in the posterior circulation, high intraosseous pressure in the femoral head, and decreased arterial blood flow. The application of DCE-MRI scanning to quantitatively analyze the visual manifestations of microcirculation after early ONFH is an ideal method to study the microcirculation changes of necrotic femoral heads.

Epoxy/Graphite Composite Electrode Modified with Recycled Silver Nanoparticles: An Eco-Friendly Strategy to Improve Lead Detection

In this work, silver nanoparticles (AgNPs) obtained from photographic waste were synthesized and electrodeposited via cyclic voltammetry using epoxy-graphite composite as an electrochemical substrate. Both electrodes, unmodified (Epoxy/C) and modified (Epoxy/C/AgNPs), were characterized electrochemically by electrochemical impedance spectroscopy (EIS), charge transfer constant (K0 ), and electroactive area. The modified electrode provided lower charge transfer resistance (275 Ω), more kinetically favored electron transfer (K0 = 1.15 × 10-3 cm s-1), and a 1.7- fold increase in the active area compared to the unmodified electrode. Additional characterizations by scanning electron microscopy (SEM) and Raman spectroscopy confirmed the presence of AgNPs structures on the carbonaceous surface. As a proof of concept, Pb2+ was used as a model analyte, and a square wave anodic stripping voltammetry (SWASV) method was developed to evaluate the analytical performance of both electrodes. A wider linear range (4.0 to 40.0 µg L-1), the appropriate limit of detection (1.2 µg L-1), and a 6-fold increase in sensitivity were found using the modified electrode, suggesting that the AgNPs significantly contributed to the performance of the electrode. The proposed method was applied to three real water samples, where the Pb2+ levels varied from 11.3 to 19.5 µg L-1. The proposed protocol (reuse of silver waste) has proven to be a powerful tool for improving the detection of Pb2+, which can be helpful for other electrochemical sensing applications in locations with minimal infrastructure.

CO2 Emission Control Using Selective Oxidation of Catalytic Zeolite13x

Abstract: For this research, Zeolite 13 x was prepared under high pressure with a mixture of activated charcoal and Natural coconut residue. The isotherms of adsorption and Kinetic curves of the Co2 on the prepared adsorbent materials are measured at 328k, 318 k, 308 k, and 298 K and using the gravimetric adsorption method, and with a pressure range of 0–30 bar[1]. Separately, the mass transfer constants and adsorption activation energy Ea of CO2 on the adsorbents were calculated. The results showed that the amount of CO2 adsorbed on the zeolite 13X was greater. The linear driving force (LDF) model can accurately describe CO2 adsorption kinetics. The mass transfer constants of CO2 adsorption on both samples increased as the temperature increased. The adsorption activation energy Ea for CO2 on the two adsorbents decreased as the concentration increased[2] .

Evaluation of blood-brain barrier integrity by the analysis of dynamic contrast-enhanced MRI - a comparison of quantitative and semi-quantitative methods.

Disruption of the blood-brain barrier (BBB) is a key feature of various brain disorders. To assess its integrity a parametrization of dynamic magnetic resonance imaging (DCE MRI) with a contrast agent (CA) is broadly used. Parametrization can be done quantitatively or semi-quantitatively. Quantitative methods directly describe BBB permeability but exhibit several drawbacks such as high computation demands, reproducibility issues, or low robustness. Semi-quantitative methods are fast to compute, simply mathematically described, and robust, however, they do not describe the status of BBB directly but only as a variation of CA concentration in measured tissue. Our goal was to elucidate differences between five semi-quantitative parameters: maximal intensity (Imax), normalized permeability index (NPI), and difference in DCE values between three timepoints: baseline, 5 min, and 15 min (delta5-0, delta15-0, delta15-5) and two quantitative parameters: transfer constant (Ktrans) and an extravascular fraction (Ve). For the purpose of comparison, we analyzed DCE data of four patients 12-15 days after the stroke with visible CA enhancement. Calculated parameters showed abnormalities spatially corresponding with the ischemic lesion, however, findings in individual parameters morphometrically differed. Ktrans and Ve were highly correlated. Delta5-0 and delta15-0 were prominent in regions with rapid CA enhancement and highly correlated with Ktrans. Abnormalities in delta15-5 and NPI were more homogenous with less variable values, smoother borders, and less detail than Ktrans. Moreover, only delta15-5 and NPI were able to distinguish vessels from extravascular space. Our comparison provides important knowledge for understanding and interpreting parameters derived from DCE MRI by both quantitative and semi-quantitative methods.

Исследование влияния катионов щелочноземельных металлов на электрохимическое поведение редокс-пары Ti (IV) / Ti (III) в расплаве CsCl — CsF

The influence of the alkaline earth metal cations (Mg2+, Ca2+, Sr2+ и Ва2+) on the charge transfer kinetics of the Ti (IV) / Ti (III) redox couple in melts of alkali metal halides was studied by cyclic voltammetry method. Standard rate constants of charge transfer have been determined by the Nicholson method. The activation energies of the charge transfer process in the CsCl — CsF (10 wt. %) — K2TiF6 melt with the addition of alkaline earth metal cations were calculated.

Arylene Diimide Derivatives as Anolyte Materials with Two-Electron Storage for Ultrastable Neutral Aqueous Organic Redox Flow Batteries

Arylene Diimide Derivatives as Anolyte Materials with Two-Electron Storage for Ultrastable Neutral Aqueous Organic Redox Flow Batteries

Spectroscopic characterization and assessment of microbiological potential of 1,3,4-thiadiazole derivative showing ESIPT dual fluorescence enhanced by aggregation effects

In the presented study, advanced experimental techniques, including electronic absorption and fluorescence spectroscopies [with Resonance Light Scattering (RLS)], measurements of fluorescence lifetimes in the frequency domain, calculations of dipole moment fluctuations, quantum yields, and radiative and non-radiative transfer constants, were used to characterize a selected analogue from the group of 1,3,4-thiadiazole, namely: 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol (NTBD), intrinsically capable to demonstrate enol → keto excited-states intramolecular proton transfer (ESIPT) effects. The results of spectroscopic analyses conducted in solvent media as well as selected mixtures were complemented by considering biological properties of the derivative in question, particularly in terms of its potential microbiological activity. The compound demonstrated a dual fluorescence effect in non-polar solvents, e.g. chloroform and DMSO/H2O mixtures, while in polar solvents only a single emission maximum was detected. In the studied systems, ESIPT effects were indeed observed, as was the associated phenomenon of dual fluorescence, and, as demonstrated for the DMSO: H2O mixtures, the same could be relatively easily induced by aggregation effects related to aggregation-induced emission (AIE). Subsequently conducted quantum-chemical (TD-)DFT calculations supported further possibility of ESIPT effects. The following article provides a comprehensive description of the spectroscopic and biological properties of the analyzed 1,3,4-thiadiazole derivatives, highlighting its potential applicability as a very good fluorescence probes as well as a compound capable of high microbiological activity.

Microenvironmental Factors in Oral Cavity Squamous Cell Carcinoma Undergoing Surgery: Correlation with Diffusion Kurtosis Imaging and Dynamic Contrast-Enhanced MRI.

In this prospective study, we hypothesized that magnetic resonance imaging (MRI) may represent not only the tumor but also the microenvironment, reflecting the heterogeneity and microstructural complexity of neoplasms. We investigated the correlation between both diffusion kurtosis imaging (DKI) and dynamic contrast-enhanced (DCE)-MRI with the pathological factors in oral cavity squamous cell carcinomas (OSCCs). A total of 37 patients with newly diagnosed OSCCs underwent an MR examination on a 3T system. The diffusion coefficient (D), the kurtosis parameter (K), the transfer constants Ktrans and Kep and the volume of extravascular extracellular space ve were quantified. A histogram-based approach was proposed to investigate the associations between the imaging and the pathological factors based on the histology and immunochemistry. Significant differences in the DCE-MRI and DKI parameters were found in relation to the inflammatory infiltrate, tumor grading, keratinization and desmoplastic reaction. Relevant relationships emerged between tumor-infiltrating lymphocytes (TILs) and DKI, with lower D and higher K values being associated with increased TILs. Although a further investigation is needed, these findings provide a more comprehensive biological characterization of OSCCs and may contribute to a better understanding of DKI-derived parameters, whose biophysical meaning is still not well-defined.

Dynamic Contrast-Enhanced MRI Parameters and Normalized ADC Values Could Aid Differentiation of Skull Base Osteomyelitis from Nasopharyngeal Cancer.

The skull base osteomyelitis sometimes can be difficult to distinguish from nasopharyngeal cancer. This study aimed to investigate the differences between skull base osteomyelitis and nasopharyngeal cancer using dynamic contrast-enhanced MR imaging and normalized ADC values. This study included 8 and 12 patients with skull base osteomyelitis and nasopharyngeal cancer, respectively, who underwent dynamic contrast-enhanced MR imaging and DWI before primary treatment. Quantitative dynamic contrast-enhanced MR imaging parameters and ADC values of the ROIs were analyzed. Normalized ADC parameters were calculated by dividing the ROIs of the lesion by that of the spinal cord. The rate transfer constant between extravascular extracellular space and blood plasma per minute (Kep) was significantly lower in patients with skull base osteomyelitis than in those with nasopharyngeal cancer (median, 0.43 versus 0.57; P = .04). The optimal cutoff value of Kep was 0.48 (area under the curve, 0.78; 95% CI, 0.55-1). The normalized mean ADC was significantly higher in patients with skull base osteomyelitis than in those with nasopharyngeal cancer (median, 1.90 versus 0.87; P < .001). The cutoff value of normalized mean ADC was 1.55 (area under the curve, 0.96; 95% CI, 0.87-1). The area under the curve of the combination of dynamic contrast-enhanced MR imaging parameters (Kep and extravascular extracellular space volume per unit tissue volume) was 0.89 (95% CI, 0.73-1), and the area under the curve of the combination of dynamic contrast-enhanced MR imaging parameters and normalized mean ADC value was 0.98 (95% CI, 0.93-1). Quantitative dynamic contrast-enhanced MR imaging parameters and normalized ADC values may be useful in differentiating skull base osteomyelitis and nasopharyngeal cancer. The combination of dynamic contrast-enhanced MR imaging parameters and normalized ADC values outperformed each measure in isolation.

DCE-MRI and DWI can differentiate benign from malignant prostate tumors when serum PSA is ≥10 ng/ml.

This study investigated the diagnostic utility of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted imaging (DWI) parameters for distinguishing between benign and malignant prostate tumors when serum prostate-specific antigen (PSA) level is ≥10 ng/ml. Patients with prostate cancer (PCa) and benign prostatic hyperplasia (BPH) with serum PSA ≥10 ng/ml before treatment were recruited. Transrectal ultrasound-guided biopsy or surgery was performed for tumor classification and patients were stratified accordingly into PCa and BPH groups. Patients underwent DCE-MRI and DWI scanning and the transfer constant (Ktrans), rate constant (Kep), fractional volume of the extravascular extracellular space, plasma volume (Vp), and Prostate Imaging Reporting and Data System Version 2 (PI-RADS v2) score were determined. The apparent diffusion coefficient (ADC) was calculated from DWI. The diagnostic performance of these parameters was assessed by receiver operating characteristic (ROC) curve analysis, and those showing a significant difference between the PCa and BPH groups were combined into a multivariate logistic regression model for PCa diagnosis. Spearman's correlation was used to analyze the relationship between Gleason score and imaging parameters. The study enrolled 65 patients including 32 with PCa and 33 with BPH. Ktrans (P=0.006), Kep (P=0.001), and Vp (P=0.009) from DCE-MRI and ADC (P<0.001) from DWI could distinguish between the 2 groups when PSA was ≥10 ng/ml. PI-RADS score (area under the ROC curve [AUC]=0.705), Ktrans (AUC=0.700), Kep (AUC=0.737), Vp (AUC=0.688), and ADC (AUC=0.999) showed high diagnostic performance for discriminating PCa from BPH. A combined model based on PI-RADS score, Ktrans, Kep, Vp, and ADC had a higher AUC (1.000), with a sensitivity of 0.998 and specificity of 0.999. Imaging markers showed no significant correlation with Gleason score in PCa. DCE-MRI and DWI parameters can distinguish between benign and malignant prostate tumors in patients with serum PSA ≥10 ng/ml.

Monoclinic-rich CsPbBr3/α-Fe2O3 S-scheme heterojunction for highly efficient thermal-assisted CO2 photoreduction

A new monoclinic-rich CsPbBr3/porous α-Fe2O3 with 3D/3D heterojunction has been prepared by a facile one-step ligand-assisted reprecipitation (LARP) under low temperature and air atmosphere. The morphologies (i.e., cubic and monoclinic phases) of CsPbBr3 are easily tuned by varying the ratios of precursor solution during the LARP process. We observed that monoclinic-rich CsPbBr3 is favorable to the photocatalytic reduction of CO2 with the superior electron consumption rate of 1.42 mmol g−1 h−1. Upon the heterojunction of monoclinic-rich CsPbBr3 with porous α-Fe2O3, the electron consumption rate is further enhanced to 3.38 mmol g−1 h−1, which is ca. 2.4-fold improvements of pristine monoclinic-rich CsPbBr3. More importantly, the activity can maintain ca. 90% after three consecutive cycles of photocatalytic CO2 reduction. The surpassing performance could be attributed to the higher CO2 uptakes, superior charge separation properties of the CsPbBr3/α-Fe2O3 heterojunction. The apparent activation energies of CO and H2 production calculated by the Arrhenius equation are 26.67 and 31.95 kJ mol−1, respectively. Time-resolved photoluminescence and ultraviolet photoelectron spectroscopy were used to evidence that the S-scheme pathway with an interfacial charge transfer constant of 2.53 × 108 s−1 occurs at the interface of monoclinic-rich CsPbBr3/porous α-Fe2O3. This study demonstrates a very simple wet-chemistry route to synthesize efficient morphology-dependent perovskite/α-Fe2O3 heterojunctions with 3D/3D construction which may provide the promising applications in the solar conversions of CO2.

Inhibition of calcium‐dependent phospholipase A2 improves blood‐brain barrier integrity in ApoE4 carrying mice

AbstractBackgroundBlood‐brain barrier (BBB) is essential for neural health and function. Degradation of BBB is observed in Alzheimer’s disease (AD) and is more pronounced in individuals carrying the apolipoprotein E4 (ApoE4) allele, which is a major genetic risk factor for AD. ApoE4 increases the activation of calcium‐dependent phospholipase A2 (cPLA2), which is linked to BBB function. Here, we asked if cPLA2 inhibition in ApoE4 carrying mice could repair BBB integrity and if the changes could be observed in vivo by dynamic contrast‐enhanced MRI (DCE‐MRI).Method16‐month‐old ApoE4 targeted replacement (ApoE4‐TR) mice were divided into a control group treated with vehicle (n=4) and an experimental group treated with a cPLA2 inhibitor ASB‐14780 (n=4). All imaging was performed using a 7T MRI scanner. DCE‐MRI protocol involved acquisition of baseline images (5min), mice receiving a bolus of gadolinium diethylenetriaminepentaacetic acid (Gd‐DTPA, 0.3mmol/kg, i.v.)) and followed by post‐bolus scans for 20min. Regions of interest (ROIs), such as the hippocampus and isocortex, were manually defined using T2‐weighted (FSE) anatomical scans in ImageJ. Volume transfer constants (KTrans) of the contrast agent uptake were calculated for each subject from the dynamic DCE‐MRI scan using the Patlak model on the Rocketship software (MATLAB).ResultKTrans values for the isocortex and the hippocampus were calculated for two animals from the control group and three animals from the experimental group. The mean KTrans value in the hippocampus region was 60% lower for the mice treated with cPLA2 inhibitor than controls (p=0.056), 0.0459 ± 0.0168 min‐1 and 0.117 ± 0.030 min‐1 respectively. Similarly, the mean KTrans value in the isocortex for the treated mice was 50% lower than the controls (p=0.89), 0.0554 ± 0.018 min‐1 and 0.110 ± 0.028 min‐1 respectively.ConclusionWe observed that cPLA2 inhibition decreased KTrans values implying increased BBB function. Thus, cPLA2 inhibition can be a possible therapeutic path towards reversing some of the damage to the brain due to AD. Currently, we are validating this observation with larger sample sizes and by analyzing the brains of these mice for changes in molecular signatures of BBB.

Regional blood‐brain barrier breakdown and Alzheimer’s disease pathology in aging

AbstractBackgroundAlthough blood‐brain barrier disruption (BBBd) is described in aging and AD, its regional characteristics and relationship with AD pathology have not been fully characterized. We aimed to determine whether there are age‐related regional differences in BBBd in cognitively normal adults and if regional BBBd is related to Aβ, tau, and neurodegeneration.MethodBBBd was measured using DCE‐MRI in 9 older adults (OA; 78±6 years, 7M) and 10 young adults (YA; 24±2 years, 7M). The Patlak model was used to generate BBB permeability volume transfer constant (Ktrans) maps in FreeSurfer regions of interest (ROIs). In the OA, PiB‐PET was used to measure global amyloid burden, FTP‐PET to measure tau in medial temporal lobe (MTL) regions, and T1 MRI to measure cortical thickness. We conducted repeated measures ANOVA (group, region, and group x region) with post‐hoc tests to investigate regional differences in Ktrans values between OA/YA and Aβ+/Aβ‐. Linear regressions were used to evaluate the relationships of tau and thickness with Ktrans.ResultsThere was a significant region by age interaction (p&lt; 0.001). OA had greater Ktrans than YA in the entorhinal cortex, parahippocampus, cuneus, fusiform, inferior temporal gyrus (IT), and the lateral occipital cortex (independent sample t‐tests, ps &lt; 0.05; Fig 1). YA had greater Ktrans in the superior and transverse temporal lobe (ps &lt;0.05). In the OA, a trend‐level region by Aβ status interaction (p=0.09) was found for the same ROIs (Fig 2). There were no significant relationships between MTL tau and Ktrans. There was a significant negative relationship between thickness and Ktrans in an averaged ROI consisting of the six regions where OA showed greater Ktrans than YA (p=0.025; Fig 3).ConclusionThese findings show that greater BBBd in OA is relatively specific to the MTL and IT, which are regions affected early in AD. They also suggest that increased BBBd in these regions may be related to amyloid accumulation and neurodegeneration. These findings require extension in larger samples, but implies BBBd as a potentially important event in aging and in the pathophysiology of AD.

Evaluation of the electrochemical response of Saccharomyces cerevisiae using screen-printed carbon electrodes (SPCE) modified with oxidized multi-walled carbon nanotubes dispersed in water – Nafion®

The evaluation of the electrochemical determination of Saccharomyces cerevisiae was carried out using a screen-printed carbon electrode (SPCE) modified with Nafion-dispersed oxidized multi-walled carbon nanotubes (OMWCNT). The morphology was studied using scanning electron microscopy (SEM), showing a complete modification of the surface with the nanotubes and yeast interaction with them instead of the graphite surface. The redox couple Fe(CN)64−/Fe(CN)63− was used to determine the electroactive area, the heterogeneous transfer constant, and the Nafion® effect. Results showed increases in electroactive area and heterogeneous transfer constant of 146% and 20.4%, respectively, due to the presence of nanotubes. Studies of the Nafion® effect showed that the polymeric membrane affects the electroactive area but not the heterogeneous transfer constant. Studies of the scan rate effect show that yeast oxidation is an irreversible mixed control process. As the concentration and scan rate increased, the anodic potential shifted toward more anodic values. The relationship between yeast concentration and the anodic current density (current/electroactive area) of yeast showed a linear range between 0.61 and 7.69 g L−1, the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 g L−1, and 0.61 g L−1, respectively, and the sensibility obtained was 0.03 μA L g−1 mm−2. These results show that with the screen-printed carbon electrodes it is possible to improve the electrochemical determination of this microorganism, enhancing the analytical parameters and quantification, allowing greater portability and decreasing measurement times and associated waste.

Drying kinetics of guabiju pulp (Myrcianthes pungens): Mass transfer parameters, mathematical modeling and evaluation of bioactive compounds

AbstractThis work aimed to estimate the mass transfer parameters of guabiju pulp under different temperatures of drying, modeling the kinetic curves using Fick's second law and the Lewis, Henderson–Pabis, Page, Modified Page, Logarithmic and Midilli models and to evaluate their biological properties and color. Guabiju pulp were dried at 313.15–373.15 K. The drying rate decreases over time, showing an exponential behavior with a significant influence of the operating temperature. Values of the effective diffusivity coefficient (Deff) between 1.578 and 10.755 × 10−9 m2 s−1were observed, with an activation energy of 30.77 kJ mol−1and an Arrhenius factor of 1962 × 10−4 m2 s−1. All models used showed good fit quality parameters (coefficient of determination—R2(&gt;0.9521), sum of squared error—SSE (&lt;0.0049), root mean square error—RMSE (&lt;0.0699) and chi‐square test—X2(&lt;0.0052)). The Midilli model showed the smallest deviations in relation to the experimental data. The values of the mass transfer constant (k6) ranged from 0.00036 to 0.01232 for the Midilli model. The best results for antioxidant activity, phenolic compounds and flavonoids were obtained at 353.15 K. The dehydrated guabiju pulp can be considered promising for human consumption and for food supplementation due to its biological activities, since the phenolic compounds act as pigments, flavor precursors and natural antioxidants.Practical applicationsDrying systems have proved to be an important strategy for the conservation of natural resources. However, they still lack studies by society. In line with drying systems, the kinetic modeling of the data allows simulating and optimizing the process, reaching the maximum potential of the process and making the process viable, reducing losses and errors and increasing product quality, facilitating industrial implementation and scale‐up. Thus, studies on the drying of guabiju pulp (Myrcianthes pungens) help to understand the process. Considering that the fruit has bioactive compounds and can be used in a certain product within the pharmaceutical, chemical or food industry.

11C]glyburide PET imaging for quantitative determination of the importance of Organic Anion-Transporting Polypeptide transporter function in the human liver and whole-body

Organic Anion-Transporting Polypeptides (OATPs) are known to control the liver uptake of many drugs. Non-hepatic expression of OATPs has been reported although functional importance for whole-body pharmacokinetics (WBPK) remains unknown. Glyburide is a well described substrate of several hepatic and non-hepatic OATPs. Dynamic whole-body positron emission tomography (DWB-PET) with [11C]glyburide was performed in humans for determination of the importance of OATPs for liver uptake and WBPK. Seven healthy male subjects (24.7 ± 3.2 years) underwent [11C]glyburide PET scan with concomitant blood sampling. All subjects underwent baseline [11C]glyburide PET scan. Five subjects underwent a subsequent [11C]glyburide PET scan after infusion of the potent OATP inhibitor rifampicin (9 mg/kg i.v.). The transfer constant (kuptake) of [11C]glyburide from blood to the liver was estimated using the integration plot method. The tissue exposure of [11C]glyburide was described by the area under the time-activity curve (AUC) and corresponding tissue/blood ratio (AUCR). [11C]glyburide was barely metabolized in both the baseline and rifampicin conditions. Parent (unmetabolized) [11C]glyburide accounted for > 90 % of the plasma radioactivity. Excellent correlation was found between radioactive counting in arterial blood samples and in the image-derived input function, in both the baseline and rifampicin conditions (R2 = 97.9 %, p < 0.01). [11C]glyburide predominantly accumulated in the liver. Rifampicin decreased liver kuptake by 77.3 ± 7.3 %, which increased exposure in blood, kidneys, spleen, myocardium and brain (p < 0.05). No significant change in AUCR was observed except in the liver (p < 0.01). [11C]glyburide benefits from metabolic stability and high sensitivity to OATP inhibition which enables quantitative determination of OATP function. DWB-PET suggests negligible role for non-hepatic OATPs in controlling the tissue distribution of [11C]glyburide.

Finite element analysis to predict temperature distribution in the human neck with abnormal thyroid: A proof of concept

Background and ObjectiveHyperthyroidism, hypothyroidism, goiter and cancer are some of the dysfunctions that can occur concerning the thyroid, an important body homeostasis regulatory gland located in the cervical region. These disorders are mostly caused by changes in metabolism and can impair quality of life. This study presents a non-invasive approach that can detect changes in thyroid metabolism through the finite element analysis and medical images. The objective of this work was to develop a numerical model to represent the temperature distribution in the human neck with and without the presence of thyroid nodules. The patient-specific computational model for the case with thyroid nodules was calibrated with infrared thermography. MethodsA three-dimensional geometrical model of the neck was constructed based on the segmentation of magnetic resonance (MR) images. The Finite Element Method (FEM) was used to simulate heat diffusion and convection in the cervical region. The infrared thermography image was used to calibrate the heat transfer constants to obtain the surface temperature of the human neck model containing the enlarged thyroid with nodules. Subsequently, another case for the entire neck with an abnormally large thyroid without the nodules was simulated using the calibrated physical constants. ResultsResults of the simulations with and without the presence of thyroid nodules were compared, showing the influence of the generation of heat from the nodules, allowing observation of the thermal differences on the cervical surface and at the thyroid itself. The model with nodules presented higher skin temperature distribution in the anterior triangle region when compared to the case without nodules. An average of 0.36∘C of absolute error and 1% of relative error was obtained for the calibration between the simulated model and the infrared image. ConclusionsThis research consists of an innovative approach by comparing the results obtained via FEM simulation and the corresponding infrared image of the same neck region under study. Since there are great variability and uncertainties in the determination of the thermal constants, we applied a procedure for calibrating them based on a patient-specific case, which involves a multinodular goiter accompanied by hyperthyroidism. This proof-of-concept study allows the creation of comparative scenarios between the FEM simulations and the corresponding infrared image. Thus, it is expected that, in the future, this approach could be used to include the effect of drugs in the treatment strategies of thyroid diseases and disorders.

Quantitative multiparametric MRI as a promising tool for the assessment of early response to neoadjuvant chemotherapy in bladder cancer

PurposeMagnetic resonance imaging (MRI) has been applied to predict the neoadjuvant chemotherapy (NAC) response of bladder cancer at an early stage, but the performance remains poor. A tool for the selection of patients with muscle-invasive bladder cancer (MIBC) with high probability of benefitting from NAC is not yet available. We designed a prospective study to assess a quantitative MRI for predicting the early response of MIBC to NAC. MethodsAll individuals underwent a time-course MRI at pre-NAC, 24 h after initial cisplatin medication (24 h-NAC) and post-NAC.Chemosensitivity was evaluated according to pathological response.The transfer constant (Ktrans), plasma volume (Vp), extravascular extracellular space (Ve), and apparent diffusion coefficient (ADC) were quantitated based on dynamic contrast-enhanced and diffusion-weighted imaging.Quantitative RECIST criteria were constructed by modelling pre-NAC and 24 h-NAC MRI measures, and then compared with conventional RECIST by using pre- and post-NAC MRI measures. ResultsIn this pilot study, a total of 24 patients were enrolled into the study. Eight patients were pathologically confirmed to be NAC-responders. After a thorough evaluation of these parameters, different parameters showed good discrimination at different point in time. ROC curves showed quantitative MRI can predict the response to NAC, especially ADC_M (AUC = 0.859, P = 0.005) and ADC index (AUC = 0.844, P = 0.007) at pre-NAC timing and ADC_M (AUC = 0.816, P = 0.013) at 24 h-NAC timing. Then, a qRECIST model was established for predicting NAC sensitivity, with AUC of 0.91, TP rate of 0.8, and accuracy of 0.75. ConclusionThe diagnostic performance of mpMRI parameters for NAC response is excellent. The qRECIST derived between pre- and 24 h NAC MRI could predict the early response of MIBC to NAC and help for candidate selection.