Functional consequences of Kir2.1/Kir2.2 subunit heteromerization

Kir2 subunits form channels that underlie classical strongly inwardly rectifying potassium currents. While homomeric Kir2 channels display a number of distinct and physiologically important properties, the functional properties of heteromeric Kir2 assemblies, as well as the stoichiometries and the arrangements of Kir2 subunits in native channels, remain largely unknown. Therefore, we have implemented a concatemeric approach, whereby all four cloned Kir2 subunits were linked in tandem, in order to study the effects of Kir2.1 and Kir2.2 heteromerization on properties of the resulting channels. Kir2.2 subunits contributed stronger to single-channel conductance than Kir2.1 subunits, and channels containing two or more Kir2.2 subunits displayed conductances indistinguishable from that of a Kir2.2 homomeric channel. In contrast, single-channel kinetics was a more discriminating property. The open times were significantly shorter in Kir2.2 channels compared with Kir2.1 channels and decreased nearly proportionally to the number of Kir2.2 subunits in the heteromeric channel. Similarly, the sensitivity to block by barium also depended on the proportions of Kir2.1 to Kir2.2 subunits. Overall, the results showed that Kir2.1 and Kir2.2 subunits exert neither a dominant nor an anomalous effect on any of the properties of heteromeric channels. The data highlight opportunities and challenges of using differential properties of Kir2 channels in deciphering the subunit composition of native inwardly rectifying potassium currents.     

Application of the granzyme B ELISPOT assay for monitoring cancer vaccine trials

Granzyme B (GrB) is present in the granules of cytolytic lymphocytes and is a key mediator of cell-mediated target cell death via the granule-mediated pathway. The release of GrB can be used as an indicator of a cytotoxic T lymphocyte response. Herein, we report that the GrB enzyme-linked immunospot assay (ELISPOT) can be used to measure ex vivo antigen-specific cytotoxicity of peripheral blood mononuclear cells from cancer patients vaccinated with a peptide-based cancer vaccine. We compare the reactivity of patients' peripheral blood mononuclear cells in the GrB ELISPOT with reactivity in the tetramer, interferon (IFN)-gamma ELISPOT, and Cr-release assays. Differences in immune response over all assays tested were found between patients and 4 response patterns were observed. Reactivity in the GrB ELISPOT was more closely associated with cytotoxicity in the Cr-release assay than the tetramer or IFN-gamma ELISPOT assays. Moreover, the higher affinity g209-2M peptide (used for vaccination) elicited greater GrB secretion than the native g209 peptide, although this difference was not observed with IFN-gamma secretion. Taken together with the fact that GrB is a specific mediator released by cytotoxic T lymphocytes, these results show that simultaneous use of the GrB ELISPOT assay with other immunologic assays may provide important additional immunologic insight into patient responses to cancer vaccines.     

Bioencapsulation of living bacteria (Escherichia coli) with poly(silicate) after transformation with silicatein-alpha gene

Bioencapsulation is an intriguing way to immobilize biological materials, including cells, in silica, metal-oxides or hybrid sol-gel polymers. Until now only the sol-gel precursor technology was utilized to immobilize bacteria or yeast cells in silica. With the discovery of silicatein, an enzyme from demosponges that catalyzes the formation of poly(silicate), it became possible to synthesize poly(silicate) under physiological (ambient) conditions. Here we show that Escherichia coli can be transformed with the silicatein gene, its expression level in the presence of isopropyl beta-D-thiogalactopyranoside (IPTG) can be efficiently intensified by co-incubation with silicic acid. This effect could be demonstrated on the level of recombinant protein synthesis as well as by immunostaining analysis. The heterologously produced silicatein is enzymatically active, as confirmed by staining with Rhodamine 123 (formation for poly[silicate] from silicic acid) and by reacting free silicic acid with the beta-silicomolybdato color system. Electron microscopic analysis revealed that the bacteria that express silicatein form a viscous cover around them when growing in the presence of silicic acid. Finally, we demonstrate that the growth kinetics of E. coli remains unaffected whether or not the bacteria had been transformed with silicatein or grown in medium, supplemented with silicic acid. It is concluded that silicatein-mediated encapsulation of bacteria with silica might improve, extend and optimize the range of application of bacteria for the production of recombinant protein.     

Metastable States of Glassy Dynamics,Possibly Mimicking Confinement‐Effects in Thin Polymer Films

The impact of the preparation and thermal history on the dynamic glass transition in thin films of poly(methyl methacrylate) and poly(vinyl acetate) is systematically investigated by means of broadband dielectric spectroscopy. Metastable states of glassy dynamics are detected, exhibiting shifts in the mean‐relaxation time from the bulk values. These shifts ‐ possibly mimicking confinement‐effects in thin polymer films ‐ become weaker (or even disappear) after an extensive annealing.

     

Learned integration of visual,vestibular, and motor cues in multiple brain regions computes head direction during visually guided navigation

Effective navigation depends upon reliable estimates of head direction (HD). Visual, vestibular, and outflow motor signals combine for this purpose in a brain system that includes dorsal tegmental nucleus, lateral mammillary nuclei, anterior dorsal thalamic nucleus, and the postsubiculum. Learning is needed to combine such different cues to provide reliable estimates of HD. A neural model is developed to explain how these three types of signals combine adaptively within the above brain regions to generate a consistent and reliable HD estimate, in both light and darkness, which explains the following experimental facts. Each HD cell is tuned to a preferred head direction. The cell's firing rate is maximal at the preferred direction and decreases as the head turns from the preferred direction. The HD estimate is controlled by the vestibular system when visual cues are not available. A well‐established visual cue anchors the cell's preferred direction when the cue is in the animal's field of view. Distal visual cues are more effective than proximal cues for anchoring the preferred direction. The introduction of novel cues in either a novel or familiar environment can gain control over a cell's preferred direction within minutes. Turning out the lights or removing all familiar cues does not change the cell's firing activity, but it may accumulate a drift in the cell's preferred direction. The anticipated time interval (ATI) of the HD estimate is greater in early processing stages of the HD system than at later stages. The model contributes to an emerging unified neural model of how multiple processing stages in spatial navigation, including postsubiculum head direction cells, entorhinal grid cells, and hippocampal place cells, are calibrated through learning in response to multiple types of signals as an animal navigates in the world. © 2012 Wiley Periodicals, Inc.     

Genetic Influences on CHD-Death and the Impact of Known Risk Factors: Comparison of Two Frailty Models

The importance of some recognized risk factors on genetic influences for coronary heart disease (CHD) needs further clarification. The aim of the present study was therefore to study the impact of known risk factors on genetic influences for CHD-death. Both twin (correlated gamma-frailty) and non-twin models (univariate gamma-frailty) were utilized and compared regarding their suitability for genetic analyses. The study population consisted of twins born in Sweden between 1886 and 1925. As expected, our findings indicate that genetic influences are important for CHD-death. Inclusion of risk factors in the twin-model increased heritability estimates, primarily due to a substantial reduction in non-shared environmental variances. The genetic influences for CHD-death are only marginally mediated through the risk factors among males, but more so among females. Although the outcome phenotype used in the present study is not behavioral, the analyses demonstrate the potential of frailty models for quantitative genetic analyses of categorical phenotypes.     

A universal cell-free DNA approach for response prediction to preoperative chemoradiation in rectal cancer

The standard treatment approach for stage II/III rectal cancer is neoadjuvant chemoradiation therapy (nCRT) followed by surgery. In recent years, new treatment approaches have led to higher rates of complete tumor eradication combined with organ-preservation strategies. However, better tools are still needed to personalize therapy for the individual patient. In this prospective observational study, we analyzed colon-derived cell-free (cf)DNA (c-cfDNA) using a tissue-specific DNA methylation signature, and its association with therapy outcomes. Analyzing plasma samples (n = 303) collected during nCRT from 37 patients with locally advanced rectal cancer (LARC), we identified colon-specific methylation markers that discriminated healthy individuals from patients with untreated LARC (area under the curve, 0.81; 95% confidence interval, 0.70-0.92; P < .0001). Baseline c-cfDNA predicted tumor response, with increased levels linked to larger residual cancer. c-cfDNA measured after the first week of therapy identified patients with maximal response and complete cancer eradication, who had significantly lower c-cfDNA compared with those who had residual disease (8.6 vs 57.7 average copies/ml, respectively; P = .013). Increased c-cfDNA after 1 week of therapy was also associated with disease recurrence. Methylation-based liquid biopsy can predict nCRT outcomes and facilitate patient selection for escalation and de-escalation strategies.     

Effects of Periodic Religious Fasting for Decades on Nutrient Intakes and the Blood Biochemical Profile

The aim of the present study was to examine differences and correlations in nutrient intakes and serum parameters related to nutrient intake (lipid profile, vitamins, and trace elements) in 200 lifelong Christian Orthodox Church (COC) fasters with periodic abstinence from certain foods (predominantly of animal origin) for approximately half of the year and 200 non-fasting controls, all of whom did not take dietary supplements. Nutrient intakes were assessed through three-day dietary recalls. Blood samples were drawn for the analysis of potential biomarkers of nutrient intake. Fasters had lower energy intake, due to lower fat and protein intake, compared to non-fasters (p < 0.05). Fasters also had lower intakes of vitamins A, B₁, B₂, B₆, B₁₂, D, folate, pantothenate, sodium, calcium, zinc, and phosphorus. Most participants (in both groups) did not meet the recommended dietary allowances of most vitamins and elements. Most serum biochemical parameters did not reflect the differences in nutrient intakes between groups, and none exhibited a correlation coefficient above 0.5 with nutrient intakes. Our findings suggest that COC fasting is associated with reduced intake of many nutrients, although this does not seem to have an impact on the blood biochemical profile.     

Vacancy Defects in Ga2O3: First-Principles Calculations of Electronic Structure

First-principles density functional theory (DFT) is employed to study the electronic structure of oxygen and gallium vacancies in monoclinic bulk β-Ga₂O₃ crystals. Hybrid exchange–correlation functional B3LYP within the density functional theory and supercell approach were successfully used to simulate isolated point defects in β-Ga₂O₃. Based on the results of our calculations, we predict that an oxygen vacancy in β-Ga₂O₃ is a deep donor defect which cannot be an effective source of electrons and, thus, is not responsible for n-type conductivity in β-Ga₂O₃. On the other hand, all types of charge states of gallium vacancies are sufficiently deep acceptors with transition levels more than 1.5 eV above the valence band of the crystal. Due to high formation energy of above 10 eV, they cannot be considered as a source of p-type conductivity in β-Ga₂O₃.