Alleviating social avoidance: Effects of single dose testosterone administration on approach–avoidance action

Testosterone is an important regulator of social–motivational behavior and is known for its dominance-enhancing and social-anxiolytic properties. However, to date no studies have systematically investigated the causal effect of testosterone on actual social approach–avoidance behavior in humans. The present study sets out to test the effects of testosterone administration in healthy female volunteers using an objective implicit measure of social motivational behavior: the social Approach–Avoidance Task, a reaction time task requiring participants to approach or avoid visually presented emotional (happy, angry, and neutral) faces. Participants showed significantly diminished avoidance tendencies to angry faces after testosterone administration. Testosterone did not affect approach–avoidance tendencies to social affiliation (happy) faces. Thus, a single dose testosterone administration reduces automatic avoidance of social threat and promotes relative increase of threat approach tendencies in healthy females. These findings further the understanding of the neuroendocrine regulation of social motivational behavior and may have direct treatment implications for social anxiety, characterized by persistent social avoidance.     

Proteomic analysis to identify early molecular targets of pregabalin in C6 glial cells

Pregabalin is a lipophilic amino acid derivative of γ‐amino butyric acid that displays anticonvulsant and analgesic activities against neuropathic pain. Although a role for glial cells as an important player in pain control and also as a new target for pain medicine has been suggested, the effect of pregabalin on glial cells has not been elucidated. In the present study, we have investigated the action of pregabalin on the glial cell proteome. To identify immediate early protein targets of pregabalin in glial cells, a differential proteomics approach in C6 rat glioma cells treated with pregabalin was used. Seven proteins that sensitively reacted to pregabalin treatment were identified using two‐dimensional gel electrophoresis and MALDI–TOF‐MS (matrix‐assisted laser‐desorption ionization–time‐of‐flight MS). The calcium‐ion‐binding chaperone, calreticulin, and the oxidative response protein, DJ‐1, were up‐regulated after pregabalin treatment. Hsp (heat‐shock protein)‐90‐β, cytoskeleton protein actin and myosin also showed quantitative expression profile differences. Functionally relevant to the proteome result, immediate actin depolymerization was observed after treatment with pregabalin. These results suggest a previously undefined role of pregabalin in the regulation of chaperone activity and cytoskeleton remodelling in glial cells.     

How different from random are docking predictions when ranked by scoring functions?

Docking algorithms predict the structure of protein–protein interactions. They sample the orientation of two unbound proteins to produce various predictions about their interactions, followed by a scoring step to rank the predictions. We present a statistical assessment of scoring functions used to rank near‐native orientations, applying our statistical analysis to a benchmark dataset of decoys of protein–protein complexes and assessing the statistical significance of the outcome in the Critical Assessment of PRedicted Interactions (CAPRI) scoring experiment. A P value was assigned that depended on the number of near‐native structures in the sampling. We studied the effect of filtering out redundant structures and tested the use of pair‐potentials derived using ZDock and ZRank. Our results show that for many targets, it is not possible to determine when a successful reranking performed by scoring functions results merely from random choice. This analysis reveals that changes should be made in the design of the CAPRI scoring experiment. We propose including the statistical assessment in this experiment either at the preprocessing or the evaluation step. Proteins 2010. © 2010 Wiley‐Liss, Inc.     

Postnatal handling reverses social anxiety in serotonin receptor 1A knockout mice

Mice lacking the serotonin receptor 1A (Htr1a knockout, Htr1a ^KO ) show increased innate and conditioned anxiety. This phenotype depends on functional receptor activity during the third through fifth weeks of life and thus appears to be the result of long-term changes in brain function as a consequence of an early deficit in serotonin signaling. To evaluate whether this phenotype can be influenced by early environmental factors, we subjected Htr1a knockout mice to postnatal handling, a procedure known to reduce anxiety-like behavior and stress responses in adulthood. Offspring of heterozygous Htr1a knockout mice were separated from their mother and exposed 15 min each day from postnatal day 1 (PD1) to PD14 to clean bedding. Control animals were left undisturbed. Maternal behavior was observed during the first 13 days of life. Adult male offspring were tested in the open field, social approach and resident–intruder tests and assessed for corticosterone response to restraint stress. Knockout mice showed increased anxiety in the open field and in the social approach test as well as an enhanced corticosterone response to stress. However, while no effect of postnatal handling was seen in wild-type mice, handling reduced anxiety-like behavior in the social interaction test and the corticosterone response to stress in knockout mice. These findings extend the anxiety phenotype of Htr1a ^KO mice to include social anxiety and demonstrate that this phenotype can be moderated by early environmental factors.     

Community structures of ammonia‐oxidising archaea and bacteria in high‐altitude lakes on the Tibetan Plateau

1. Community structures of planktonic ammonia‐oxidising archaea (AOA) and bacteria (AOB) were investigated for five high‐altitude Tibetan lakes, which could be classified as freshwater, oligosaline or mesosaline, to develop a general view of the AOA and AOB in lakes on the Tibetan Plateau. 2. Based on PCR screening of the ammonia monooxygenase α‐subunit (amoA) gene, AOA were present in 14 out of 17 samples, whereas AOB were detected in only four samples. Phylogenetic analyses indicated that the AOB communities were dominated by a unique monophylogenetic lineage within Nitrosomonas, which may represent a novel cluster of AOB. AOA, on the other hand, were distinct among lakes with different salinities. 3. Multivariate statistical analyses indicated a heterogeneous distribution of the AOA communities among lakes largely caused by lake salinity, whereas the uniform chemical properties within lakes and their geographical isolation may favour relatively homogeneous AOA communities within lakes. 4. Our results suggest a wide occurrence of AOA in Tibetan lakes and provide the first evidence of salinity‐related differentiation of AOA community composition as well as potential geographical isolation of AOA in inland aquatic environments.     

Redox potential of the Rieske iron-sulfur protein: Quantum-chemical and electrostatic study

Quantum-chemical study of structures, energies, and effective partial charge distribution for several models of the Rieske protein redox center is performed in terms of the B3LYP density functional method in combination with the broken symmetry approach using three different atomic basis sets. The structure of the redox complex optimized in vacuum differs markedly from that inside the protein. This means that the protein matrix imposes some stress on the active site resulting in distortion of its structure. The redox potentials calculated for the real active site structure are in a substantially better agreement with the experiment than those calculated for the idealized structure. This shows an important role of the active site distortion in tuning its redox potential. The reference absolute electrode potential of the standard hydrogen electrode is used that accounts for the correction caused by the water surface potential. Electrostatic calculations are performed in the framework of the polarizable solute model. Two dielectric permittivities of the protein are employed: the optical permittivity for calculation of the intraprotein electric field, and the static permittivity for calculation of the dielectric response energy. Only this approach results in a reasonable agreement of the calculated and experimental redox potentials.     

Association of permanent arterial hypertension with the renin-angiotensin and kinin-bradykinin system genes in children

A new approach, based on scoring, was proposed for a more objective estimation of the contribution of several genetic variants to a multifactorial disease. Two variants of the approach—genotype scoring and unfavorable factor scoring—were tested by analyzing the polymorphisms of REN (I9–83G>A), AGT (M235T), ACE (I/D), AGTR1 (1166A>C), ATGR2 (3123C>A), and BKR2 (?58T>C and I/D) in children with arterial hypertension (AH). Each of the two variants reported that the genes of the renin-angiotensin and kinin-brady-kinin systems play an important role in permanent AH in girls.     

Model-free analysis of binding at lipid membranes employing micro-calorimetric measurements

Based on universal thermodynamic principles (Schwarz in Biophys Chem 86:119–129, 2000) it is shown how measured enthalpy changes can be utilized to determine the relevant binding isotherm as well as the variation of the molar enthalpy change. This is carried out in a novel way involving multiple titration experiments whose evaluation requires no beforehand assumptions or models whatever. An appropriate specific model mechanism may be discussed afterwards and developed in view of the given experimental results. The pertinent procedure is demonstrated using micro-calorimetric data obtained in the case of the local anesthetic dibucaine as it associates with POPC liposomes. Mutual interactions of the bound ligand molecules could be described in terms of repulsive enthalpic and entropic activity coefficients. Apparently these are induced by electrostatic forces and by the finite size of binding sites, respectively.     

Allosteric communication in dihydrofolate reductase: signaling network and pathways for closed to occluded transition and back

Escherichia coli dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate to tetrahydrofolate. During the catalytic cycle, DHFR undergoes conformational transitions between the closed (CS) and occluded (OS) states that, respectively, describe whether the active site is closed or occluded by the Met20 loop. The CS→OS and the reverse transition may be viewed as allosteric transitions. Using a sequence-based approach, we identify a network of residues that represents the allostery wiring diagram. Many of the residues in the allostery wiring diagram, which are dispersed throughout the adenosine-binding domain as well as the loop domain, are not conserved. Several of the residues in the network have been previously shown by NMR experiments, mutational studies, and molecular dynamics simulations to be linked to equilibration conformational fluctuations of DHFR. To further probe the nature of events that occur during conformational fluctuations, we use a self-organized polymer model to monitor the kinetics of the CS→OS and the reverse transitions. During the CS→OS transition, coordinated changes in a number of residues in the loop domain enable the Met20 loop to slide along the α-helix in the adenosine-binding domain. Sliding is triggered by pulling of the Met20 loop by the βG-βH loop and the pushing action of the βG-βH loop. The residues that facilitate the Met20 loop motion are part of the network of residues that transmit allosteric signals during the CS→OS transition. Replacement of M16 and G121, whose C^α atoms are about 4.3 Å in the CS, by a disulfide cross-link impedes that CS→OS transition. The order of events in the OS→CS transition is not the reverse of the forward transition. The contact Glu18-Ser49 in the OS persists until the sliding of the Met20 loop is nearly complete. The ensemble of structures in the transition state in both the allosteric transitions is heterogeneous. The most probable transition-state structure resembles the OS (CS) in the CS→OS (OS→CS) transition, which is in accord with the Hammond postulate. Structures resembling the OS (CS) are present as minor (∼ 1-3%) components in equilibrated CS (OS) structures.     

Genetic diversity assessment of anoxygenic photosynthetic bacteria by distance-based grouping analysis of pufM sequences

AIM: To assess how completely the diversity of anoxygenic phototrophic bacteria (APB) was sampled in natural environments. METHODS AND RESULTS: All nucleotide sequences of the APB marker gene pufM from cultures and environmental clones were retrieved from the GenBank database. A set of cutoff values (sequence distances 0.06, 0.15 and 0.48 for species, genus, and (sub)phylum levels, respectively) was established using a distance-based grouping program. Analysis of the environmental clones revealed that current efforts on APB isolation and sampling in natural environments are largely inadequate. Analysis of the average distance between each identified genus and an uncultured environmental pufM sequence indicated that the majority of cultured APB genera lack environmental representatives. CONCLUSIONS: The distance-based grouping method is fast and efficient for bulk functional gene sequences analysis. The results clearly show that we are at a relatively early stage in sampling the global richness of APB species. Periodical assessment will undoubtedly facilitate in-depth analysis of potential biogeographical distribution pattern of APB. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first attempt to assess the present understanding of APB diversity in natural environments. The method used is also useful for assessing the diversity of other functional genes.