The search operating characteristic as a tool for analyzing performance in dynamic visual search tasks.

A standard data plot for the analysis of eye movement behavior in visual search and related tasks, a Search Operating Characteristic (SOC), is proposed. The SOC plots mean fixation duration (in ms) vs. search span (in items/fixation) for different difficulty levels. It is well specified by a reciprocal power function and this function can be explained with the help of Piéron's law.     

SNP genotypes reveal breed substructure,selection signatures and highly inbred regions in Piétrain pigs

The Piétrain pig originates from the Belgian village Piétrain some time between 1920 and 1950. Owing to its superior conformation, the Piétrain has spread worldwide since the 1960s. As initial population sizes were limited and close inbreeding was commonplace, the breed’s genetic diversity has been questioned. Therefore, this study examines Piétrain breed substructure, diversity and selection signatures using SNP data in comparison with Duroc, Landrace and Large White populations. Principal component analysis indicated three subpopulations, and F_ST analysis showed that US Piétrains differ most from European Piétrains. Average inbreeding based on runs of homozygosity (ROH) segments larger than 4 Mb ranged between 16.7 and 20.9%. The highest chromosomal inbreeding levels were found on SSC8 (42.7%). ROH islands were found on SSC8, SSC15 and SSC18 in all Piétrain populations, but numerous population-specific ROH islands were also detected. Moreover, a large ROH island on SSC8 (34–126 Mb) appears nearly fixed in all Piétrain populations, with a unique genotype. Chromosomal ROH patterns were similar between Piétrain populations. This study shows that Piétrain populations are genetically diverging, with at least three genetically distinct populations worldwide. Increasing genetic diversity in local Piétrain populations by introgression from other Piétrain populations seems to be only limited. Moreover, a unique 90 Mb region on SSC8 appeared largely fixed in the Piétrain breed, indicating that fixation was already present before the 1960s. We believe that strong selection and inbreeding during breed formation fixed these genomic regions in Piétrains. Finally, we hypothesize that independent coat color selection may have led to large ROH pattern similarities on SSC8 between unrelated pig breeds.     

Mechanistic insight from thermal activation parameters for oxygenation reactions of different substrates with biomimetic iron porphyrin models for compounds I and II

Compound I, an oxo–iron(IV) porphyrin π-cation radical species, and its one-electron-reduced form compound II are regarded as key intermediates in reactions catalyzed by cytochrome P450. Although both reactive intermediates can be easily produced from model systems such as iron(III) meso-tetra(2,4,6-trimethylphenyl)porphyrin hydroxide by selecting appropriate reaction conditions, there are only a few thermal activation parameters reported for the reactions of compound I analogues, whereas such parameters for the reactions of compound II analogues have not been investigated so far. Our study demonstrates that ΔH ^≠ and ΔS ^≠ are closely related to the chemical nature of the substrate and the reactive intermediate (viz., compounds I and II) in epoxidation and C–H abstraction reactions. Although most studied reactions appear to be enthalpy-controlled (i.e., ΔH ^≠ > −TΔS ^≠), different results were found for C–H abstractions catalyzed by compound I. Whereas the reaction with 9,10-dihydroanthracene as a substrate is also dominated by the activation enthalpy (ΔH ^≠ = 42 kJ/mol, ΔS ^≠ = 41 J/Kmol), the same reaction with xanthene shows a large contribution from the activation entropy (ΔH ^≠ = 24 kJ/mol, ΔS ^≠ = −100 J/kmol). This is of special interest since the activation barrier for entropy-controlled reactions shows a significant dependence on temperature, which can have an important impact on the relative reaction rates. As a consequence, a close correlation between bond strength and reaction rate—as commonly assumed for C–H abstraction reactions—no longer exists. In this way, this study can contribute to a proper evaluation of experimental and computational data, and to a deeper understanding of mechanistic aspects that account for differences in the reactivity of compounds I and II.     

Mapping QTL for production traits in segregating Piétrain pig populations using genome‐wide association study results of F2 crosses

In this study, genome‐wide association study (GWAS) results of porcine F2 crosses were used to map QTL in outcross Piétrain populations. For this purpose, two F2 crosses (Piétrain × Meishan, n = 304; Piétrain × Wild Boar, n = 291) were genotyped with the PorcineSNP60v2 BeadChip and phenotyped for the dressing yield, carcass length, daily gain and drip loss traits. GWASs were conducted in the pooled F2 cross applying single marker mixed linear models. For the investigated traits, between two and five (in total 15) QTL core regions, spanning 250 segregating SNPs around a significant trait‐associated peak SNP, were identified. The SNPs within the QTL core regions were subsequently tested for trait association in two outcross Piétrain populations consisting of 771 progeny‐tested boars and 210 sows with their own performance records. In the sow (boar) dataset, five (eight) of the 15 mapped QTL were validated. Hence, many QTL mapped in the F2 crosses (with Piétrain as a common founder breed) are still segregating in the current Piétrain breed. This confirms the usefulness of existing F2 crosses for mapping QTL that are still segregating in the recent founder breed generation. The approach utilizes the high power of an F2 cross to map QTL in a breeding population for which it is not guaranteed that they would be found using a GWAS in this population.     

DNA microsatellite analysis for parentage control in Austrian pigs.

We present an efficient parentage control for pigs based on ten polymorphic microsatellite markers analyzed in a single PCR reaction. Assuming one known parent ("paternity control"), combined exclusion probabilities (CEPs) ranged from 99.18% (Landrace), 99.74% (Piétrain) to 99.76% (Large White) for the most important Austrian breeds. Assuming a known parent-pair ("parentage control", e.g. a substituted offspring), the CEP of the 10-plex PCR increased to 99.97% (Landrace) and 99.99% (Piétrain and Large White). We developed an additional standby battery of 5 markers, which might be applied in those cases, where the CEP of the 10-plex PCR is not sufficient. Therefore an automated, cost and time reduced genotype analysis for pigs is available.     

Citrate Uptake into Tonoplast Vesicles from Acid Lime (Citrus aurantifolia) Juice Cells

Citrate transport into the vacuoles of acid lime juice cells was investigated using isolated tonoplast vesicles. ATP stimulated citrate uptake in the presence or in the absence of a ΔμH⁺. Energization of the vesicles only by an artificial K⁺ gradient (establishing an inside-positive Δψ) also resulted in citrate uptake as was the case of a ΔpH dominated ΔμH⁺. Addition of inhibitors to endomembrane ATPases showed no direct correlation between the inhibition to the tonoplast bound H⁺/ATPase and citrate uptake. The data indicated that, although some citrate uptake can be accounted for by Δψ and by a direct primary active transport mechanism involving ATP, under in vivo conditions of vacuolar pH of 2.0, citrate uptake is driven by ΔpH. Received: 27 April 1998/Revised: 8 September 1998     

Thermodynamic and kinetic analysis of the H2 threshold for Methanobacterium bryantii M.o.H

H₂ thresholds, concentrations below which H₂ consumption by a microbial group stops, have been associated with microbial respiratory processes such as dechlorination, denitrification, sulfate reduction, and methanogenesis. Researchers have proposed that observed H₂ thresholds occur when the available Gibbs free energy is minimal (ΔG ≈ 0) for a specific respiratory reaction. Others suggest that microbial kinetics also may play a role in controlling the thresholds. Here, we comprehensively evaluate H₂ thresholds in light of microbial thermodynamic and kinetic principles. We show that a thermodynamic H₂ threshold for Methanobacterium bryantii M.o.H. is not controlled by ΔG for methane production from H₂ + HCO₃⁻. We repeatedly attain a H₂ threshold near 0.4 nM, with a range of 0.2–1 nM, and ΔG for methanogenesis from H₂ + HCO₃⁻ is positive, +5 to +7 kJ/mol-H_2, at the threshold in most cases. We postulate that the H₂ threshold is controlled by a separate reaction other than methane production. The electrons from H₂ oxidation are transferred to an electron sink that is a solid-phase component of the cells. We also show that a kinetic threshold (S _min) occurs at a theoretically computed H₂ concentration of about 2400 nM at which biomass growth shifts from positive to negative.     

Effect of Cooling and Heating Rates on Polymorphic Transformations and Gelation of Tripalmitin Solid Lipid Nanoparticle (SLN) Suspensions

Solid lipid nanoparticle (SLN) suspensions undergo a phase transition from the α- to β-polymorphic forms, which is accompanied by particle aggregation and gel formation. These processes are both time and temperature dependent, and so it is important to study the impact of cooling rates (CRs) and heating rates (HRs) on polymorphic transformations, particle aggregation, and gelation. Rheology measurements indicated that the temperature where gelation was first observed during cooling (T _gel) decreased with increasing CRs, with SLN suspensions remaining fluid at HR ≥ 5 °C/min. On the other hand, the temperature where gelation was first observed during heating of stable SLN suspensions increased with increasing HRs: 18, 24, 31, and 45 °C at 2, 5, 10, and 20 °C/min, respectively. When the melted SLN suspensions were cooled again, two exothermic peaks were observed in the differential scanning calorimetry scans at 39 (which was attributed to coalesced oil) and 19 °C (which was attributed to stable SLN). With increasing CR, the enthalpy of the coalescence peak (ΔH _CO) decreased, while that of the supercooled SLN (ΔH _SLN) increased. With increasing HR, ΔH _CO decreased and ΔH _SLN increased, with no coalescence being observed at HR ≥ 10 °C/min. These results show that increasing the CRs or HRs retard the α→β polymorphic transformation, which increased the stability of SLN against aggregation and retarded gelation. In addition, this study shows that the careful selection of HRs and CRs is required to examine polymorphic transformations and the stability of SLN suspensions.     

Affinity and Specificity of Ciprofloxacin-Bovine Serum Albumin Interactions: Spectroscopic Approach

Fluorescence spectroscopy in combination with UV–Vis absorption spectroscopy were employed to investigate the binding of an antibacterial drug Ciprofloxacin (CPFX) to bovine serum albumin (BSA) under the physiological conditions. In the discussion of the quenching mechanism, it was proved that the fluorescence quenching of BSA by CPFX is a result of the formation of CPFX-BSA complex. Binding parameters were determined using the modified Stern-Volmer equation and Scatchard equation to provide a measure of the binding affinity between CPFX and BSA. The results of thermodynamic parameters ΔG, ΔH, ΔS, at different temperatures indicate that the electrostatic interactions play a major role for CPFX-BSA association. Site marker competitive experiments indicated that the binding of CPFX to BSA primarily took place in site I. Furthermore, the effect of metal ions to CPFX-BSA system was studied, and the distance r between donor (BSA) and acceptor (CPFX) was obtained according to fluorescence resonance energy transfer (FRET). The conformation of BSA upon CPFX binding was evaluated by measuring synchronous fluorescence properties of the CPFX-BSA complex.     

Energization of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> membrane vesicles increases catalytic activity of succinate: Menaquinone oxidoreductase

In this work, high ΔμH⁺-dependent succinate oxidase activity has been demonstrated for the first time with membrane vesicles isolated from Bacillus subtilis. The maximal specific rate of succinate oxidation by coupled inside-out membrane vesicles isolated from a B. subtilis strain overproducing succinate:menaquinone oxidoreductase approaches the specific rate observed with the intact cells. Deenergization of the membrane vesicles with ionophores or alamethicin brings about an almost complete inhibition of succinate oxidation. An apparent K _m for succinate during the energy-dependent succinate oxidase activity of the vesicles (2.2 mM) is higher by an order of magnitude than the K _m value measured for the energy-independent reduction of 2,6-dichlorophenol indophenol. The data reveal critical importance of ΔμH⁺ for maintaining active electron transfer by succinate:menaquinone oxidoreductase. The role of ΔμH⁺ might consist in providing energy for thermodynamically unfavorable menaquinone reduction by succinate by virtue of transmembrane electron transport within the enzyme down the electric field; alternatively, ΔμH⁺ could play a regulatory role by maintaining the electroneutrally operating enzyme in a catalytically active conformation.     

Computer calculation-based quantitative structure-activity relationships for the oxidation of phenol derivatives horseradish peroxidase compound II

 The second-order rate constants for the oxidation of a series of phenol derivatives by horseradish peroxidase compound II were compared to computer-calculated chemical parameters characteristic for this reaction step. The phenol derivatives studied were phenol, 4-chlorophenol, 3-hydroxyphenol, 3-methylphenol, 4-methylphenol, 4-hydroxybenzoate, 4-methoxyphenol and 4-hydroxybenzaldehyde. Assuming a reaction of the phenolic substrates in their non-dissociated, uncharged forms, clear correlations (r = 0.977 and r = 0.905) were obtained between the natural logarithm of the second-order rate constants (ln k _app and ln k ₂ respectively) for their oxidation by compound II and their calculated ionisation potential, i.e. minus the energy of their highest occupied molecular orbital [E(HOMO)]. In addition to this first approach in which the quantitative structure-activity relationship (QSAR) was based on a calculated frontier orbital parameter of the substrate, in a second and third approach the relative heat of formation (ΔΔHF) calculated for the process of one-electron abstraction and H^• abstraction from the phenol derivatives was used as a parameter. Plots of the natural logarithms of the second-order rate constants (k _app and k ₂) for the reaction and the calculated ΔΔHF values for the process of one-electron abstraction also provide clear QSARs with correlation coefficients of –0.968 and –0.926 respectively. Plots of the natural logarithms of the second-order rate constants (k _app and k ₂) for the reaction and the calculated ΔΔHF values for the process of H^• abstraction provide QSARs with correlation coefficients of –0.989 and –0.922 respectively. Since both mechanisms considered, i.e. initial electron abstraction versus initial H^• abstraction, provided clear QSARs, the results could not be used to discriminate between these two possible mechanisms for phenol oxidation by horseradish peroxidase compound II. The computer calculation-based QSARs thus obtained for the oxidation of the various phenol derivatives by compound II from horseradish peroxidase indicate the validity of the approaches investigated, i.e. both the frontier orbital approach and the approach in which the process is described by calculated relative heats of formation. The results also indicate that outcomes from computer calculations on relatively unrelated phenol derivatives can be reliably compared to one another. Furthermore, as the actual oxidation of peroxidase substrates by compound II is known to be the rate-limiting step in the overall catalysis by horseradish peroxidase, the QSARs of the present study may have implications for the differences in the overall rate of substrate oxidation of the phenol derivatives by horseradish peroxidase. Received: 29 March 1996 / Accepted: 17 July 1996     

Estimation of seasonal changes in translocation rates in leaves of a Japanese larch stand

To estimate the net rate of translocation in leaves of a larch stand, a new approach based on the summation method was proposed and given by a compartment model. The difference between the rate of translocation into and out of leaf biomass, namely, the net translocation rate (ΔT _r /Δt), was usually expressed by the difference between the growth rate of leaf biomass and the surplus production rate provided that the rate of leaf loss due to leaffall and grazing can be considered negligible. The rate, ΔT _r /Δt in a 19-yr-old larch stand, showed characteristic changes; it was positive from early April to late May, but after that it was negative until leaffall in late October. Our results confirmed that for the growth phase of positive ΔT _r /Δt translocation of assimilate stored in non-photosynthetic organs was indispensable for the growth. To quantify this, the ratio of ΔT _r /Δt to growth rate of leaf biomass was proposed.     

Association of the melanocortin 4 receptor with feed intake and daily gain in F2 Mangalitsa x Piétrain pigs

The melanocortin 4 receptor (MC4R) is a key factor in the regulation of energy balance and body weight. Hence it is a candidate for feed intake and energy homeostasis-related traits. Studies in humans and swine have revealed several sequence variants in the gene that are associated with some of these traits. In pigs the coding non-synonymous missense variant Asp298Asn in MC4R has been associated with feed intake, fatness and growth. Here we confirm the association of this Piétrain-derived polymorphism with feed intake and daily gain in the F2 generation of a Mangalitsa x Piétrain cross. In one Piétrain founder animal, we detected an additional non-synonymous missense variant Arg236His. Thus, the MC4R gene could be a useful marker for increased growth in the relatively slow-growing Piétrain breed.     

Neural adaptation to tone sequences in the songbird forebrain: patterns, determinants, and relation to the build-up of auditory streaming

Neural responses to tones in the mammalian primary auditory cortex (A1) exhibit adaptation over the course of several seconds. Important questions remain about the taxonomic distribution of multi-second adaptation and its possible roles in hearing. It has been hypothesized that neural adaptation could explain the gradual “build-up” of auditory stream segregation. We investigated the influence of several stimulus-related factors on neural adaptation in the avian homologue of mammalian A1 (field L2) in starlings (Sturnus vulgaris). We presented awake birds with sequences of repeated triplets of two interleaved tones (ABA–ABA–…) in which we varied the frequency separation between the A and B tones (ΔF), the stimulus onset asynchrony (time from tone onset to onset within a triplet), and tone duration. We found that stimulus onset asynchrony generally had larger effects on adaptation compared with ΔF and tone duration over the parameter range tested. Using a simple model, we show how time-dependent changes in neural responses can be transformed into neurometric functions that make testable predictions about the dependence of the build-up of stream segregation on various spectral and temporal stimulus properties.     

Molecular Characterization of Five Porcine Candidate Genes for Drip Loss in Pork

Drip loss is the loss of fluid from a piece of meat without mechanical force and represents an important meat quality trait. Previous work revealed a quantitative trait locus (QTL) for drip loss in pork in an experimental Duroc x Piétrain (DUPI) F2 family on SSC 5. Based on functional data indicating their possible involvement in water holding capacity and their expression in skeletal muscle, we selected five positional candidates (ACO2, ADSL, CBY1, KCNJ4, PLA2AG6) out of 130 predicted genes in the QTL interval for further analysis. We performed a mutation analysis of all coding exons and discovered 204 polymorphisms. We genotyped 39 single nucleotide polymorphisms (SNPs) in 192 Piétrain pigs with extreme drip loss phenotypes and detected a possible association with drip loss for one non-coding SNP in the ADSL gene (ss107793818, p_raw = 0.021). Correspondingly, ADSL diplotypes were associated with drip loss and pH1 of M. longissimus dorsi. However, after correction for multiple testing, none of the tested SNPs were significantly associated with drip loss. One possible explanation for these results is that one of the QTL-alleles from the experimental DUPI family may be fixed or nearly fixed in the tested Piétrain population.     

Spectroscopic and Molecular Modeling Studies on the Interaction Between a Fluorine-Containing Triazole Derivative and Human Serum Albumin

The interaction between 4-(4-fluorobenzylideneamino)-5-propyl-4H-1,2,4-triazole-3-thiol (FBTZ) and human serum albumin (HSA) under simulative physiological conditions was investigated by fluorescence, UV–vis absorption and circular dichroism (CD) spectroscopy as well as molecular modeling method. Fluorescence spectroscopic data showed that the fluorescence quenching of HSA was a result of the formation of FBTZ–HSA complex. According to the modified Stern–Volmer equation, the effective quenching constants (K _a) of FBTZ to HSA were obtained at three different temperatures. The enthalpy change (ΔH) and entropy change (ΔS) were calculated on the basis of van′t Hoff equation, and the results showed that hydrogen-bonding and van der Waals forces were the dominant intermolecular forces to stabilize the complex. Site marker competitive replacement experiments demonstrated that the binding of FBTZ to HSA primarily took place in sub-domain IIA (Sudlow’s site I). The binding distance (r) between FBTZ and the tryptophan residue of HSA was estimated according to the theory of fluorescence resonance energy transfer. The conformational investigation showed that the presence of FBTZ induced some changes of secondary structure of HSA. Molecular modeling study further confirmed the binding mode obtained by experimental study.     

Inhibition of colicin synthesis by the antibiotic globomycin

Wolinella succinogenes can grow by anaerobic respiration with fumarate or polysulfide as the terminal electron acceptor, and H₂ or formate as the electron donor. A ΔhydABC mutant lacking the hydrogenase structural genes did not grow with H₂ and either fumarate or polysulfide. In contrast to the wild-type strain, the mutant grown with fumarate and with formate instead of H₂ did not catalyze the reduction of fumarate, polysulfide, dimethylnaphthoquinone, or benzyl viologen by H₂. Growth and enzymic activities were restored upon integration of a plasmid carrying hydABC into the genome of the ΔhydABC mutant. The ΔhydABC mutant was complemented with hydABC operons modified by artificial stop codons in hydA (StopA) or at the 5′-end of hydC (StopC). The StopC mutant lacked HydC, and the hydrophobic C-terminus of HydA was missing in the hydrogenase of the StopA mutant. The two mutants catalyzed benzyl viologen reduction by H₂. The enzyme activity was located in the membrane of the mutants. A mutant with both modifications (StopAC) contained the activity in the periplasm. The three mutants did not grow with H₂ and either fumarate or polysulfide, and did not catalyze dimethylnaphthoquinone reduction by H₂. We conclude that the same hydrogenase serves in the anaerobic respiration with fumarate and with polysulfide. HydC and the C-terminus of HydA appear to be required for both routes of electron transport and for dimethylnaphthoquinone reduction by H₂. The hydrogenase is anchored in the membrane by HydC and by the C-terminus of HydA. The catalytic subunit HydB is oriented towards the periplasmic side of the membrane. Received: 29 December 1997 / Accepted: 6 March 1998     

Time Course and Action Spectrum of Vibrotactile Adaptation

In a series of experiments designed to explore the processes underlying adaptation of the sense of flutter-vibration, vibrotactile threshold was measured on the pad of the index finger, using Békésy tracking. Unadapted thresholds were first measured, for a number of frequencies (4-90 Hz) and contactor sizes (1-8 mm diameter). As expected, these measurements indicated the presence of (1) a Pacinian system possessing spatial summation and increasing in sensitivity, as frequency was raised, at the rate of 12 dB/octave; and (2) a non-Pacinian system showing little spatial summation, and with a frequency characteristic matching that of the NP I mechanism of Bolanowski et al. (1988). These baseline data of Experiment 1 guided the selection of stimulus parameters for subsequent experiments, in which threshold for a test stimulus was measured before, during, and after periods of vibrotactile adaptation.

In Experiment 2, test stimuli of 10 H_z and 50 H_z were combined factorially with 30-dB SL adapting stimuli of the same two frequencies. When the test stimulus was 10 Hz, the two adapting frequencies were equally effective in raising threshold; however, when the 50-Hz test stimulus was used, the 50-Hz adapting stimulus raised threshold by a greater amount than did the 10-Hz adapter. These results confirm on the finger the independence of adaptation in Pacinian and non-Pacinian channels, a result previously established on the thenar by other workers. For all four frequency combinations, threshold rose exponentially with a time constant of 1.5-2 min.

In Experiment 3, an action spectrum was determined, showing the adapting amplitude needed at each of a series of frequencies to raise the threshold of a 10-Hz stimulus by 10 dB; this spectrum was essentially flat from 30 to 90 Hz. The results, taken in conjunction with what is known about rapidly adapting cutaneous mechanoreceptors, imply that the effectiveness of an adapting stimulus is not determined solely by the amount of activity it generates in first-order afferents.     

Mechanosensitive ion channels in chara: influence of water channel inhibitors, HgCl2 and ZnCl2, on generation of receptor potential

Characean internodal cells generate receptor potential (ΔE _m) in response to mechanical stimuli. Upon a long-lasting stimulus, the cells generated ΔE _m at the moment of both compression and decompression, and the amplitude of ΔE _m at the moment of decompression, (ΔE _m)_E, was larger than that at compression. The long-lasting stimulus caused a membrane deformation (ΔD _m) having two components, a rapid one, (ΔD _m)_rapid, at the moment of compression and a slower one, (ΔD _m)_slow, during the long-lasting compression. We assumed that (ΔD _m)_slow might have some causal relation with the larger ΔE _m at (ΔE _m)_E. We treated internodal cells with either HgCl₂ or ZnCl₂, water channel inhibitors, to decrease (ΔD _m)_slow. Both inhibitors attenuated (ΔD _m)_slow during compression. Cells treated with HgCl₂ generated smaller (ΔE _m)_E compared to nontreated cells. On the other hand, cells treated with ZnCl₂ never attenuated (ΔE _m)_E but, rather, amplified it. Thus, the amplitude of (ΔD _m)_slow did not always show tight correlation with the amplitude of (ΔE _m)_E. Furthermore, when a constant deformation was applied to an internodal cell in a medium with higher or lower osmotic value, a cell having higher turgor always showed a larger (ΔE _m)_E. Thus, we concluded that changes in tension at the membrane may be the most important factor to induce activation of mechanosensitive Ca²⁺ channel.