Bioavailability of Quercetin in Humans with a Focus on Interindividual Variation

After consumption of plant‐derived foods or beverages, dietary polyphenols such as quercetin are absorbed in the small intestine and metabolized by the body, or they are subject to catabolism by the gut microbiota followed by absorption of the resulting products by the colon. The resulting compounds are bioavailable, circulate in the blood as conjugates with glucuronide, methyl, or sulfate groups attached, and they are eventually excreted in the urine. In this review, the various conjugates from different intervention studies are summarized and discussed. In addition, the substantial variation between different individuals in the measured quercetin bioavailability parameters is assessed in detail by examining published human intervention studies where sources of quercetin have been consumed in the form of food, beverages, or supplements. It is apparent that most reported studies have examined quercetin and/or metabolites in urine and plasma from a relatively small number of volunteers. Despite this limitation, it is evident that there is less interindividual variation in metabolites which are derived from absorption in the small intestine compared to catabolites derived from the action of microbiota in the colon. There is also some evidence that a high absorber of intact quercetin conjugates could be a low absorber of microbiota‐catalyzed phenolics, and vice versa. From the studies reported so far, the reasons or causes of the interindividual differences are not clear, but, based on the known metabolic pathways, it is predicted that dietary history, genetic polymorphisms, and variations in gut microbiota metabolism would play significant roles. In conclusion, quercetin bioavailability is subject to substantial variation between individuals, and further work is required to establish if this contributes to interindividual differences in biological responses.     

Determination of cadmium at ultra-trace levels by CPE–molecular fluorescence combined methodology

A highly sensitive micelle-mediated extraction methodology for the preconcentration and determination of trace levels of cadmium by molecular fluorescence has been developed. Metal was complexed with o-phenanthroline (o-phen) and eosin (eo) at pH 7.6 in buffer Tris medium and quantitatively extracted into a small volume of surfactant-rich phase of PONPE 7.5 after centrifugating. The chemical variables affecting cloud point extraction (CPE) were evaluated and optimized. The RSD for six replicates of cadmium determinations at 0.84 μg L⁻¹ level was 1.17%. The linearity range using the preconcentration system was between 2.79 × 10⁻³ μg L⁻¹ and 2.81 μg L⁻¹ with a correlation coefficient of 0.99. Under the optimal conditions, it obtained a LOD of 8.38 × 10⁻⁴ μg L⁻¹ and LOQ of 2.79 × 10⁻³ μg L⁻¹. The method presented good sensitivity and selectivity and was applied to the determination of trace amounts of cadmium in commercially bottled mineral water, tap water and water well samples with satisfactory results. The proposed method is an innovative application of CPE-luminescence to metal analysis comparable in sensitivity and accuracy with atomic spectroscopies.     

What every psychologist should know about the Food and Drug Administration’s black box warning label for antidepressants.

In 2004, the Food and Drug Administration released a black box warning label for all antidepressants, indicating an increased risk for suicidality in children and adolescents. The label was subsequently updated in 2007 to include those up to 24 years of age. Data have since emerged to indicate changes in clinical practice patterns of nonspecialists (i.e., nonpsychiatrists) prescribing medications. Among the changes reported in practice patterns are an increased likelihood of referral and a decreased willingness to prescribe antidepressants. Findings also indicate marked reductions in ambulatory visits for depression among children and adolescents, lower rates of diagnosis of depression in this age group, a spillover effect to adults, inaccurate understanding of the actual risk communicated on the warning label (on the part of primary care practitioners), and increased suicide rates among children and adolescents. Recent findings have important implications for practicing psychologists, and specific recommendations are offered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermodynamic evaluation of hydrogen production for fuel cells by using bio-ethanol steam reforming: Effect of carrier gas addition

Omitting the influence of the addition of carrier gas to the reaction system for hydrogen production by bio-ethanol steam reforming can lead to wrong conclusions, especially when it is going to be made to scale. The effect of carrier gas addition to produce hydrogen using bio-ethanol steam reforming to feed fuel cells was evaluated. Thermodynamic calculations in equilibrium conditions were made, however the analysis derived from them can also be applied to kinetic conditions. These calculations were made by using the Aspen-HYSYS software at atmospheric pressure and different values of temperature, water/ethanol molar ratios, and inert (argon)/(water/ethanol) molar ratios. The addition of inert carrier gas modifies the concentrations of the reaction products in comparison to those obtained without its presence. This behavior occurs because most of the reactions which take place in bio-ethanol steam reforming have a positive difference of moles. This fact enhances the system sensitivity to inert concentration at low and moderated temperatures (<700 °C). At high values of temperature, the inert addition does not influence the composition of the reaction products because of the predominant effect of inverse WGS reaction.     

Gas holdup and mass transfer in solid suspended bubble columns in presence of structured packings

Electrochemical gas absorption or biotechnical purification processes using structured packing as electrode or as biological support, respectively, may operate in bubble columns in presence of suspended solids. In both systems the knowledge of mass transfer rates from the liquid to the packing is important for the design of equipment. In the present investigation, the fluid dynamic behavior of a simple bubble column and a bubble column containing small size particles, both in presence of structured packing, was studied. Furthermore, mass transfer coefficients between the liquid and the structured packing were obtained by the electrochemical method. The influence of physical properties of the liquid phase, gas flow rate, kind and concentration of the suspended particles on both gas holdup and mass transfer was investigated. Correlations of the experimental data of mass transfer using dimensionless groups were derived and compared to previous correlations. Similarity with a heat transfer expression already used in two-phase systems was found.     

Modified sum-product algorithms for decoding low-density parity-check codes

The authors deal with the sum-product algorithm (SPA) based on the hyperbolic tangent (tanh) rule when it is applied for decoding low-density parity-check (LDPC) codes. Motivated by the finding that, because of the large number of multiplications required by the algorithm, an overflow in the decoder may occur, two novel modifications of the tanh function (and its inverse) are proposed. By means of computer simulations, both methods are evaluated using random-based LDPC codes with binary phase shift keying (BPSK) signals transmitted over the additive white Gaussian noise (AWGN) channel. It is shown that the proposed modifications improve the bit error rate (BER) performance up to 1 dB with respect to the conventional SPA. These results have also shown that the error floor is removed at BER lower than 10^-6. Furthermore, two novel approximations are presented to reduce the computational complexity of the tanh function (and its inverse), based on either a piecewise linear function or a quantisation table. It is shown that the proposed approximations can slightly improve the BER performance (up to 0.13 dB) in the former case, whereas small BER performance degradation is observed (<0.25 dB) in the latter case. In both cases, however, the decoding complexity is reduced significantly     

Channeling characterization of defects in silicon: an atomistic approach

We review here the possibilities opened by a recent development of the Monte Carlo binary collision approximation (MC-BCA) simulation of Rutherford backscattering spectrometry-channeling (RBS-C) spectra for the study of radiation damage in monocrystalline materials. The ion implantation of silicon has been chosen as a case study. Atomic-scale modeling of defect structures was used to determine the location of interstitial atoms in the host lattice. Among possible candidate defects, we have considered the elementary hexagonal, tetrahedral, 1 1 0-split interstitials, the Bond-defect and one type of tetra-interstitial cluster. For each defect model a large Si supercell was populated with a proper defect depth distribution and then it was structurally relaxed by the application of the classical EDIP potential. This model system was then given as an input to the MC-BCA simulation code and the spectra corresponding to nine different axial and planar alignments were calculated. For low defect concentration (a few atomic percent), the scattering yields are strongly dependent on the orientation and a distinct signature characteristic of the limited number of allowed interstitial positions in Si could be found. The comparison of simulations and experiments in the case of 180 keV self ion implantation allowed the identification of the dominant interstitial defect whose structural properties are represented by the split-1 1 0 interstitial. By increasing the concentration of defects (and their mutual interaction) the technique looses sensitivity and, at the same time, the contribution of lattice relaxation becomes important. Under these conditions, although the RBS-C response becomes similar to the one obtained from a random distribution of displaced atoms, the major structural features of a heavily damaged sample could be still observed.     

Contributions of Microdialysis to New Alternative Therapeutics for Hepatic Encephalopathy

Hepatic encephalopathy (HE) is a common complication of cirrhosis, of largely reversible impairment of brain function occurring in patients with acute or chronic liver failure or when the liver is bypassed by portosystemic shunts. The mechanisms causing this brain dysfunction are still largely unclear. The need to avoid complications caused by late diagnosis has attracted interest to understand the mechanisms underlying neuronal damage in order to find markers that will allow timely diagnosis and to propose new therapeutic alternatives to improve the care of patients. One of the experimental approaches to study HE is microdialysis; this technique allows evaluation of different chemical substances in several organs through the recollection of samples in specific places by semi-permeable membranes. In this review we will discuss the contributions of microdialysis in the understanding of the physiological alterations in human hepatic encephalopathy and experimental models and the studies to find novel alternative therapies for this disease.     

Density estimation for spatial-temporal models

In this paper a k-nearest neighbor type estimator of the marginal density function for a random field which evolves with time is considered. Considering dependence, the consistency and asymptotic distribution are studied for the stationary and nonstationary cases. In particular, the parametric rate of convergence $\sqrt{T}$ is proven when the random field is stationary. The performance of the estimator is shown by applying our procedure to a real data example.