Measurement of extracellular pH,K(+), and lactate in ischemic heart

Simultaneous and continuous measurements of extracellular pH, potassium (K(+)), and lactate (L(-)) in ischemic rabbit papillary muscle are presented for the first time. Potentiometric pH and K(+) sensors and an amperometric lactate biosensor were used. These miniature electrodes were previously developed and individually tested for this purpose. The pH sensor was based on an iridium oxide layer electrodeposited on a planar platinum electrode fabricated on a flexible substrate. The potentiometric K(+) sensor was based on a polymeric membrane and valinomycin ionophore. The L(-) biosensor was based on lactate oxidase and an organic conducting salt polarized at 0.15V vs Ag/AgCl reference electrode. The utility of this novel analytical system to cardiovascular research was demonstrated by using the system to study the interrelationship of cellular K(+) and lactate loss in ischemic myocardium, and the role of extracellular pH and buffer capacity on this relationship. The results indicated: (i) sequential brief episodes of ischemia produced reproducible trends of L(-), pH, and K(+) changes during the first three episodes, (ii) extracellular L(-) increased with increasing buffer capacity of extracellular compartment, (iii) the patterns of extracellular L(-) and K(+) changes were not related directly, and (iv) L(-) transport and lactic acid diffusion were not the primary cause of extracellular acidosis during ischemia.     

Bayesian analysis for nonlinear regression model under skewed errors,with application in growth curves

We have considered a Bayesian approach for the nonlinear regression model by replacing the normal distribution on the error term by some skewed distributions, which account for both skewness and heavy tails or skewness alone. The type of data considered in this paper concerns repeated measurements taken in time on a set of individuals. Such multiple observations on the same individual generally produce serially correlated outcomes. Thus, additionally, our model does allow for a correlation between observations made from the same individual. We have illustrated the procedure using a data set to study the growth curves of a clinic measurement of a group of pregnant women from an obstetrics clinic in Santiago, Chile. Parameter estimation and prediction were carried out using appropriate posterior simulation schemes based in Markov Chain Monte Carlo methods. Besides the deviance information criterion (DIC) and the conditional predictive ordinate (CPO), we suggest the use of proper scoring rules based on the posterior predictive distribution for comparing models. For our data set, all these criteria chose the skew‐t model as the best model for the errors. These DIC and CPO criteria are also validated, for the model proposed here, through a simulation study. As a conclusion of this study, the DIC criterion is not trustful for this kind of complex model.     

Estimation of anisotropy coefficient of swine pancreas,liver and muscle at 1064 nm based on goniometric technique

Optical properties of tissues are required for theoretical modeling of Laser Ablation in tumor therapy. The light scattering characteristic of tissues is described by the anisotropy coefficient, g. The relationship between the angular distribution of scattered light and g is given by the Henyey‐Greenstein (HG) phase function. This work describes the estimation of anisotropy coefficients of ex vivo swine pancreas, liver and muscle at 1064 nm. The intensities of scattered light at fixed angles were measured under repeatability conditions. Experimental data were fitted with a two‐term HG, estimating the anisotropy coefficients for the forward (e.g., 0.956 for pancreas, 0.964 for liver and 0.968 for muscle) and the backward (e.g., –0.481 for pancreas, –0.414 for liver and –0.372 for muscle) scattering.

Experimental set up employed to estimate the anisotropy coefficient of biological tissues. The image on the left depicts the holder used to house tissue, laser fiber and photodetector; on the left an example of scattered light beam is shown, as well as the effect due to Snell's law.     

Survey of electromagnetic field exposure in bedrooms of residences in lower Austria

Previous investigations of exposure to electric, magnetic, or electromagnetic fields (EMF) in households were either about electricity supply EMFs or radio frequency EMFs (RF‐EMFs). We report results from spot measurements at the bedside that comprise electrostatic fields, extremely low‐frequency electric fields (ELF‐EFs), extremely low‐frequency magnetic fields (ELF‐MFs), and RF‐EMFs. Measurements were taken in 226 households throughout Lower Austria. In addition, effects of simple reduction measures (e.g., removal of clock radios or increasing their distance from the bed, turning off Digital Enhanced Cordless Telecommunication (DECT) telephone base stations) were assessed. All measurements were well below International Commission on Non‐Ionizing Radiation Protection (ICNIRP) guideline levels. Average night‐time ELF‐MFs (long‐term measurement from 10 pm to 6 am, geometric mean over households) above 100 nT were obtained in 2.3%, and RF‐EMFs above 1000 µW/m² in 7.1% of households. Highest ELF‐EFs were primarily due to lamps beside the bed (max = 166 V/m), and highest ELF‐MFs because of transformers of devices (max = 1030 nT) or high current of power lines (max = 380 nT). The highest values of RF‐EMFs were caused by DECT telephone base stations (max = 28979 µW/m²) and mobile phone base stations (max = 4872 µW/m²). Simple reduction measures resulted in an average decrease of 23 nT for ELF‐MFs, 23 V/m for ELF‐EFs, and 246 µW/m² for RF‐EMFs. A small but statistically significant correlation between ELF‐MF exposure and overall RF‐EMF levels of R = 0.16 (P = 0.008) was computed that was independent of type (flat, single family) and location (urban, rural) of houses. Bioelectromagnetics 31:200–208, 2010. © 2009 Wiley‐Liss, Inc.     

Spectral analysis of Delayed Luminescence from human skin as a possible non-invasive diagnostic tool

In vivo measurements of Delayed Luminescence (DL), the low-level photo-induced emission which lasts for a longer time after switching off the excitation light, have been performed on human skin, with the aim to develop a technique for optical biopsy. Preliminary tests have been performed on healthy volunteers, measuring the time decays of the spectral components (λ_emiss = 400–800 nm) starting 10 μs after switching off the excitation (λ_exc = 337 nm). Significant differences in the decay trends of DL from different subjects were revealed and quite a good reproducibility for the same subject was observed. The modeling of experimental data has been examined in detail in order to get parameters, characterizing the theoretical fit, whose changes may be correlated with age differences and seasonal variations. Proceedings of the XVIII Congress of the Italian Society of Pure and Applied Biophysics (SIBPA), Palermo, Sicily, September 2006.     

Technical note: compatibility of microtomographic imaging systems for dental measurements

Modern micro-computed tomography techniques allow the accurate visualization of internal dental structures, and are becoming widely used within (paleo-) anthropological dental studies. There exist several types and name brands of microtomographic systems, however, which have been demonstrated to produce images that vary in resolution and signal-to-noise ratio. As a growing body of dental research using disparate microtomographic techniques is likely to continue accumulating, it is imperative that different systems are compared to ensure that results are comparable and not machine-dependent. In the present study, we compare volume, surface area, and linear measurements recorded on a sample of modern and fossil teeth using four microtomographic systems (three laboratory scanners, and the ID19 beamline of the European Synchrotron Radiation Facility). Results indicate that measurements are comparable between systems (within 3%), but that synchrotron radiation is superior to the other systems because its monochromatic X-rays prevent beam hardening and its parallel beam prevents geometric artifacts in the resultant images, making it easier to record measurements and see fine details at the enamel cervix or dentine horn tips. Although the synchrotron produces higher resolution images with less artifacts, results indicate that for gross morphological measurements (e.g., enamel cap volume, intercuspal distances), each of the scanners produces approximately the same measurements. Combining measurements of teeth from multiple microCT systems presupposes that measurements from each system are comparable; the research presented here indicates that this is the case when teeth are not severely diagenetically remineralized.     

Inhibition of lipoxygenase by soy isoflavones: evidence of isoflavones as redox inhibitors

Hydroperoxides, the products of lipoxygenase mediated pathways, play a major role in the manifestation of chronic inflammatory diseases. Soy isoflavones act as antioxidants due to their ability to scavenge free radicals. Isoflavones inhibit the activity of soy lipoxygenase-1 and 5-lipoxygenase, from human polymorph nuclear lymphocyte in a concentration dependent manner. Spectroscopic and enzyme kinetic measurements have helped to understand the nature and mechanism of inhibition. Genistein is the most effective inhibitor of soy lipoxygenase 1 and 5-lipoxygenase with IC(50) values of 107 and 125 microM, respectively. Genistein and daidzein are noncompetitive inhibitors of soy lipoxygenase 1 with inhibition constants, K(i), of 60 and 80 microM, respectively. Electron paramagnetic resonance and spectroscopic studies confirm that isoflavones reduce active state iron to ferrous state and prevent the activation of the resting enzyme. A model for the inhibition of lipoxygenase by isoflavones is suggested.     

Identification of hairs found in leopard seal (<Emphasis Type="Italic">Hydrurga leptonyx</Emphasis>) scats

The leopard seal is a top-order predator in the Southern Ocean ecosystem and preys on a wide variety of vertebrate species including seals and penguins. We assessed the use of hairs found in leopard seal scats to identify the species of pinniped consumed. A reference collection of hairs was obtained from four potential leopard seal prey species including crabeater, Weddell, Ross, and Southern elephant seals. Discrimination techniques applied to terrestrial mammals did not allow for identification of the seal hairs. Instead, a 2-dimensional (2-D) and 6-dimensional (6-D) analysis technique utilising Mahalanobis distances (D ²) was used. The smallest Mahalanobis distance together with the largest value of p(F) positively identified hairs from each species. The 6-D analysis was more accurate and applied to hairs found in the leopard seal scats. The majority of prey species were identified as crabeater seals, which are a known prey item of the leopard seal.     

Fractional <Superscript>13</Superscript>C enrichment of isolated carbons using [1-<Superscript>13</Superscript>C]- or [2-<Superscript>13</Superscript>C]-glucose facilitates the accurate measurement of dynamics at backbone C<Superscript>α</Superscript> and side-chain methyl positions in proteins

A simple labeling approach is presented based on protein expression in [1-¹³C]- or [2-¹³C]-glucose containing media that produces molecules enriched at methyl carbon positions or backbone C^α sites, respectively. All of the methyl groups, with the exception of Thr and Ile(δ1) are produced with isolated ¹³C spins (i.e., no ¹³C–¹³C one bond couplings), facilitating studies of dynamics through the use of spin-spin relaxation experiments without artifacts introduced by evolution due to large homonuclear scalar couplings. Carbon-α sites are labeled without concomitant labeling at C^β positions for 17 of the common 20 amino acids and there are no cases for which ¹³C^α−¹³CO spin pairs are observed. A large number of probes are thus available for the study of protein dynamics with the results obtained complimenting those from more traditional backbone ¹⁵N studies. The utility of the labeling is established by recording ¹³C R _1ρ and CPMG-based experiments on a number of different protein systems.     

Key mutations stabilize antigen‐binding conformation during affinity maturation of a broadly neutralizing influenza antibody lineage

Affinity maturation, the process in which somatic hypermutation and positive selection generate antibodies with increasing affinity for an antigen, is pivotal in acquired humoral immunity. We have studied the mechanism of affinity gain in a human B‐cell lineage in which two main maturation pathways, diverging from a common ancestor, lead to three mature antibodies that neutralize a broad range of H1 influenza viruses. Previous work showed that increased affinity in the mature antibodies derives primarily from stabilization of the CDR H3 loop in the antigen‐binding conformation. We have now used molecular dynamics simulations and existing crystal structures to identify potentially key maturation mutations, and we have characterized their effects on the CDR H3 loop and on antigen binding using further simulations and experimental affinity measurements, respectively. In the two maturation pathways, different contacts between light and heavy chains stabilize the CDR H3 loop. As few as two single‐site mutations in each pathway can confer substantial loop stability, but none of them confers experimentally detectable stability on its own. Our results support models of the germinal center reaction in which two or more mutations can occur without concomitant selection and show how divergent pathways have yielded functionally equivalent antibodies. Proteins 2014; 83:771–780. © 2014 The Authors. Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc.