Exposure to static electric fields leads to changes in biogenic amine levels in the brains of Drosophila

Natural and anthropogenic static electric fields are commonly found in the environment and can have both beneficial and harmful effects on many animals. Here, we asked how the fruitfly responds to these fields and what the consequences of exposure are on the levels of biogenic amines in the brain. When given a choice in a Y-tube bioassay Drosophila avoided electric fields, and the greater the field strength the more likely Drosophila were to avoid it. By comparing wild-type flies, flies with wings surgically removed and vestigial winged flies we found that the presence of intact wings was necessary to produce avoidance behaviour. We also show that Coulomb forces produced by electric fields physically lift excised wings, with the smaller wings of males being raised by lower field strengths than larger female wings. An analysis of neurochemical changes in the brains showed that a suite of changes in biogenic amine levels occurs following chronic exposure. Taken together we conclude that physical movements of the wings are used by Drosophila in generating avoidance behaviour and are accompanied by changes in the levels of amines in the brain, which in turn impact on behaviour.     

AKAP79-mediated targeting of the cyclic AMP-dependent protein kinase to the beta1-adrenergic receptor promotes recycling and functional resensitization of the receptor

Resensitization of G protein-coupled receptors (GPCR) following prolonged agonist exposure is critical for restoring the responsiveness of the receptor to subsequent challenges by agonist. The 3'-5' cyclic AMP-dependent protein kinase (PKA) and serine 312 in the third intracellular loop of the human beta(1)-adrenergic receptor (beta(1)-AR) were both necessary for efficient recycling and resensitization of the agonist-internalized beta(1)-AR (Gardner, L. A., Delos Santos, N. M., Matta, S. G., Whitt, M. A., and Bahouth, S. W. (2004) J. Biol. Chem. 279, 21135-21143). Because PKA is compartmentalized near target substrates by interacting with protein kinase A anchoring proteins (AKAPs), the present study was undertaken to identify the AKAP involved in PKA-mediated phosphorylation of the beta(1)-AR and in its recycling and resensitization. Here, we report that Ht-31 peptide-mediated disruption of PKA/AKAP interactions prevented the recycling and functional resensitization of heterologously expressed beta(1)-AR in HEK-293 cells and endogenously expressed beta(1)-AR in SK-N-MC cells and neonatal rat cortical neurons. Whereas several endogenous AKAPs were identified in HEK-293 cells, small interfering RNA-mediated down-regulation of AKAP79 prevented the recycling of the beta(1)-AR in this cell line. Co-immunoprecipitations and fluorescence resonance energy transfer (FRET) microscopy experiments in HEK-293 cells revealed that the beta(1)-AR, AKAP79, and PKA form a ternary complex at the carboxyl terminus of the beta(1)-AR. This complex was involved in PKA-mediated phosphorylation of the third intracellular loop of the beta(1)-AR because disruption of PKA/AKAP interactions or small interfering RNA-mediated down-regulation of AKAP79 both inhibited this response. Thus, AKAP79 provides PKA to phosphorylate the beta(1)-AR and thereby dictate the recycling and resensitization itineraries of the beta(1)-AR.     

The importance of myocardial amino acids during ischemia and reperfusion in dilated left ventricle of patients with degenerative mitral valve disease

Taurine, glutamine, glutamate, aspartate, and alanine are the most abundant intracellular free amino acids in human heart. The myocardial concentration of these amino acids changes during ischemia and reperfusion due to alterations in metabolic and ionic homeostasis. We hypothesized that dilated left ventricle secondary to mitral valve disease has different levels of amino acids compared to the right ventricle and that such differences determine the extent of amino acids' changes during ischemia and reperfusion. Myocardial concentration of amino acids was measured in biopsies collected from left and right ventricles before cardioplegic arrest (Custodiol HTK) and 10 min after reperfusion in patients undergoing mitral valve surgery. The dilated left ventricle had markedly higher (P < 0.05) concentrations (nmol/mg wet weight) of taurine (17.0 ± 1.5 vs. 10.9 ± 1.5), glutamine (20.5 ± 2.4 vs. 12.1 ± 1.2), and glutamate (18.3 ± 2.2 vs. 11.4 ± 1.5) when compared to right ventricle. There were no differences in the basal levels of alanine or aspartate. Upon reperfusion, a significant (P < 0.05) fall in taurine and glutamine was seen only in the left ventricle. These changes are likely to be due to transport (taurine) and/or metabolism (glutamine). There was a marked increase in the alanine to glutamate ratio in both ventricles indicative of ischemic stress which was confirmed by global release of lactate during reperfusion. This study shows that in contrast to the right ventricle, the dilated left ventricle had remodeled to accumulate amino acids which are used during ischemia and reperfusion. Whether these changes reflect differences in degree of cardioplegic protection between the two ventricles remain to be investigated.     

The tick saliva immunosuppressor, Salp15, contributes to Th17-induced pathology during Experimental Autoimmune Encephalomyelitis

Salp15 is a tick saliva protein that inhibits CD4⁺ T cell differentiation through its interaction with CD4. The protein inhibits early signaling events during T cell activation and IL-2 production. Because murine Experimental Autoimmune Encephalomyelitis development is mediated by central nervous system-infiltrating CD4⁺ T cells that are specific for myelin-associated proteins, we sought to determine whether the treatment of mice with Salp15 during EAE induction would prevent the generation of proinflammatory T cell responses and the development of the disease. Surprisingly, Salp15-treated mice developed more severe EAE than control animals. The treatment of EAE-induced mice with the tick saliva protein did not result in increased infiltration of T cells to the central nervous system, indicating that Salp15 had not affected the permeability of the blood-brain barrier. Salp15 treatment did not affect the development of antibody responses against the eliciting peptide or the presence of IFNγ in the sera. The treatment with Salp15 resulted, however, in the increased differentiation of Th17 cells in vivo, as evidenced by higher IL-17 production from PLP_139-151-specific CD4⁺ T cells isolated from the central nervous system and the periphery. In vitro, Salp15 was able to induce the differentiation of Th17 cells in the presence of IL-6 and the absence of TGFβ These results suggest that a conductive milieu for the differentiation of Th17 cells can be achieved by restriction of the production of IL-2 during T cell differentiation, a role that may be performed by TGFβ and other immunosuppressive agents.     

Influence of Primary Producers on Bioavailability of Desorption Resistant Organic Pollutants in the Sediments

The experiments were conducted on three freshwater microalgal strains, which were grown in the top chambers of retrofitted filter assemblies. The bottom receivers contained control sediments and two types of ¹⁴C-labeled, phenanthrene contaminated sediments. The first contaminated sediment had both the reversible and desorption resistant fractions (referred to as partially washed sediment), while the second contaminated sediment had the desorption resistant fraction only (completely washed sediment). A second set of controls was added to isolate the effect of microalgae. Despite minor variations in toxicity, there was no significant difference (P > 0.05) between the growth curves of the three algal strains. From a bioavailability perspective, there was a significant difference (P < 0.05) in desorption rates in chambers containing microalgae. Pooled data from the three cultures indicated that, for assemblies with desorption resistant sediment (completely washed) and microalgae, the top chamber phenanthrene concentrations were approximately 90–100% of the theoretical maximum concentrations. However, filter assemblies without microalgae had only 5–6% of the theoretical maximum. Results also indicated that approximately 91.7–92.4% of the desorbed phenanthrene is directly sequestered by the microalgae in assemblies with the completely washed sediment. These results indicated that the term “desorption-resistant” fraction from a purely physical perspective may not be truly desorption-resistant in presence of microalgae.     

Influence de i’acide abscissique sur le transport d’ions inorganiques chez la pomme de terre (solanum tuberosum cv. Bintje). etude comparée avec quelques autres phytohormones

Using detached leaves of potato plants (Solanum tuberosum cv. Bintje) it was shown that abscisic acid (ABA) induced an oriented transport of ions (⁸⁶Rb,³²P and^3SS) towards the hormone-treated leaflet. In order to understand the hormone effect on cell permeability, pretreatment of discs with hormonal solution was conducted. The pretreatment with ABA stimulated the uptake of K⁺ simultaneously with the decrease of efflux. The effect of ABA on ion uptake is compared with the action of other hormones, benzylaminopurine (BAP), gibberellic acid (GA₃) known to act over a long distance transport, too. Three kinds of specificity are underlined: - hormonal specificity (stimulation by ABA and inhibiton by BAP of K⁺ uptake by foliar tissues); - ionic specificity (ABA increase⁸⁶Rb influx, but inhibits³²P and^3SS influx); - tissue specificity shown by a comparative study between foliar tissues (source) and tuber tissues (sink). The autoradiography of foliar discs demonstrated that a treatment of foliar discs can be used, at least for Rb⁺ (K), to study role of ABA in long-distance transport.      

Optimisation of the Photonic Efficiency of TiO2 Decorated on MWCNTs for Methylene Blue Photodegradation

MWCNTs/TiO₂ nanocomposite was prepared by oxidising MWCNT in H₂SO₄/HNO₃ then decorating it with TiO₂-p25 nanopowder. The composites were characterised using XRD, TEM, FT-IR PL and UV−vis spectroscopy. The TEM images have shown TiO₂ nanoparticles immobilised onto the sidewalls of the MWCNTs. The UV-vis spectrum confirms that the nanocomposites can significantly absorb more light in the visible regions compared with the commercial TiO₂ (P25). The catalytic activity of these nanocomposites was determined by photooxidation of MB aqueous solution in the presence of visible light. The MWCNTs/TiO₂ (1:3) mass ratio showed maximum degradation efficiency. However, its activity was more favourable in alkaline and a neutral pH than an acidic medium.