A novel role of Drosophila cytochrome P450-4e3 in permethrin insecticide tolerance

The exposure of insects to xenobiotics, such as insecticides, triggers a complex defence response necessary for survival. This response includes the induction of genes that encode key Cytochrome P450 monooxygenase detoxification enzymes. Drosophila melanogaster Malpighian (renal) tubules are critical organs in the detoxification and elimination of these foreign compounds, so the tubule response induced by dietary exposure to the insecticide permethrin was examined. We found that expression of the gene encoding Cytochrome P450-4e3 (Cyp4e3) is significantly up-regulated by Drosophila fed on permethrin and that manipulation of Cyp4e3 levels, specifically in the principal cells of the Malpighian tubules, impacts significantly on the survival of permethrin-fed flies. Both dietary exposure to permethrin and Cyp4e3 knockdown cause a significant elevation of oxidative stress-associated markers in the tubules, including H2O2 and lipid peroxidation byproduct, HNE (4-hydroxynonenal). Thus, Cyp4e3 may play an important role in regulating H2O2 levels in the endoplasmic reticulum (ER) where it resides, and its absence triggers a JAK/STAT and NF-κB-mediated stress response, similar to that observed in cells under ER stress. This work increases our understanding of the molecular mechanisms of insecticide detoxification and provides further evidence of the oxidative stress responses induced by permethrin metabolism

Determining the Complex Permittivity of Building Dielectric Materials using a Propagation Constant Measurement

This paper presents a technique to determine the Dielectric constant and dielectric loss of the building dielectric materials using propagation constant measurements. The material sample is loaded in an X-band (8.5GHz-12.5GHz) rectangular waveguide and its two port S-parameters are measured as a function of frequency using a Vector Network Analyzer without TRL Calibration. The results obtained from samples of dielectric materials  (Air, Cellular concrete and  Wood)  on  the  X-band  frequencies show  the  validity  of  the  proposed technique to determine the complex permittivity of the building dielectric materials on the X-band frequencies

Mechanism and function of drosophila capa GPCR: a desiccation stress-responsive receptor with functional homology to human neuromedinU receptor

The capa peptide receptor, capaR (CG14575), is a G-protein coupled receptor (GPCR) for the D. melanogaster capa neuropeptides, Drm-capa-1 and -2 (capa-1 and -2). To date, the capa peptide family constitutes the only known nitridergic peptides in insects, so the mechanisms and physiological function of ligand-receptor signalling of this peptide family are of interest. Capa peptide induces calcium signaling via capaR with EC50 values for capa-1 = 3.06 nM and capa-2 = 4.32 nM. capaR undergoes rapid desensitization, with internalization via a b-arrestin-2 mediated mechanism but is rapidly re-sensitized in the absence of capa-1. Drosophila capa peptides have a C-terminal -FPRXamide motif and insect-PRXamide peptides are evolutionarily related to vertebrate peptide neuromedinU (NMU). Potential agonist effects of human NMU-25 and the insect -PRLamides [Drosophila pyrokinins Drm-PK-1 (capa-3), Drm-PK-2 and hugin-gamma [hugg]] against capaR were investigated. NMU-25, but not hugg nor Drm-PK-2, increases intracellular calcium ([Ca2+]i) levels via capaR. In vivo, NMU-25 increases [Ca2+]i and fluid transport by the Drosophila Malpighian (renal) tubule. Ectopic expression of human NMU receptor 2 in tubules of transgenic flies results in increased [Ca2+]i and fluid transport. Finally, anti-porcine NMU-8 staining of larval CNS shows that the most highly immunoreactive cells are capa-producing neurons. These structural and functional data suggest that vertebrate NMU is a putative functional homolog of Drm-capa-1 and -2. capaR is almost exclusively expressed in tubule principal cells; cell-specific targeted capaR RNAi significantly reduces capa-1 stimulated [Ca2+]i and fluid transport. Adult capaR RNAi transgenic flies also display resistance to desiccation. Thus, capaR acts in the key fluid-transporting tissue to regulate responses to desiccation stress in the fly

A biogenic amine and a neuropeptide act identically: tyramine signals through calcium in drosophila tubule stellate cells

Insect osmoregulation is subject to highly sophisticated endocrine control. In Drosophila, both Drosophila kinin and tyramine act on the Malpighian (renal) tubule stellate cell to activate chloride shunt conductance, and so increase the fluid production rate. Drosophila kinin is known to act through intracellular calcium, but the mode of action of tyramine is not known. Here, we used a transgenically encoded GFP::apoaequorin translational fusion, targeted to either principal or stellate cells under GAL4/UAS control, to demonstrate that tyramine indeed acts to raise calcium in stellate, but not principal cells. Furthermore, the EC(50) tyramine concentration for half-maximal activation of the intracellular calcium signal is the same as that calculated from previously published data on tyramine-induced increase in chloride flux. In addition, tyramine signalling to calcium is markedly reduced in mutants of NorpA (a phospholipase C) and itpr, the inositol trisphosphate receptor gene, which we have previously shown to be necessary for Drosophila kinin signalling. Therefore, tyramine and Drosophila kinin signals converge on phospholipase C, and thence on intracellular calcium; and both act to increase chloride shunt conductance by signalling through itpr. To test this model, we co-applied tyramine and Drosophila kinin, and showed that the calcium signals were neither additive nor synergistic. The two signalling pathways thus represent parallel, independent mechanisms for distinct tissues (nervous and epithelial) to control the same aspect of renal function

Caractérisation de deux neuropeptides chez Drosophila melanogaster : la Leucokinine et l'IFamide

Nous avons isolé et identifié deux neuropeptides de la mouche du vinaigre, Drosophila melanogaster, la leucokinine et l'IFamide. La leucokinine, NSVVLGKKQRFHSWGamide, agit comme une hormone diurétique à une concentration seuil de 0,1 nM en utilisant le calcium comme second messager. L'IFamide, AYRKPPFNGSIFamide, est produit par quatre cellules dans le cerveau et nous avons démontré que des mâles dépourvus de ces quatre neurones sont bisexuels. Nous avons construit un gène artificiel codant un précurseur contenant plusieurs copies de neuropeptides et créé des mouches qui surexpriment ces neuropeptides artificiels.We have isolated and identified two neuropeptides from the fruitfly, Drosophila melanogaster , leucokinin and IFamide. Drosophila leucokinin, NSVVLGKKQRFHSWGamide, acts as a diuretic hormone with a threshold concentration of 0,1 nM and uses calcium as a second messenger. IFamide, AYRKPPFNGSIFamide, is produced by four neurons in the brain and males lacking these four peptidergic neurons are bisexuals. We have constructed an artificial precursor gene encoding several copies of neuropeptides and have made flies that over express the artificial neuropeptide gene

Chloride channels in stellate cells are essential for uniquely high secretion rates in neuropeptide-stimulated Drosophila diuresis

Epithelia frequently segregate transport processes to specific cell types, presumably for improved efficiency and control. The molecular players underlying this functional specialization are of particular interest. In Drosophila, the renal (Malpighian) tubule displays the highest per-cell transport rates known and has two main secretory cell types, principal and stellate. Electrogenic cation transport is known to reside in the principal cells, whereas stellate cells control the anion conductance, but by an as-yet-undefined route. Here, we resolve this issue by showing that a plasma membrane chloride channel, encoded by ClC-a, is exclusively expressed in the stellate cell and is required for Drosophila kinin-mediated induction of diuresis and chloride shunt conductance, evidenced by chloride ion movement through the stellate cells, leading to depolarization of the transepithelial potential. By contrast, ClC-a knockdown had no impact on resting secretion levels. Knockdown of a second CLC gene showing highly abundant expression in adult Malpighian tubules, ClC-c, did not impact depolarization of transepithelial potential after kinin stimulation. Therefore, the diuretic action of kinin in Drosophila can be explained by an increase in ClC-a–mediated chloride conductance, over and above a resting fluid transport level that relies on other (ClC-a–independent) mechanisms or routes. This key segregation of cation and anion transport could explain the extraordinary fluid transport rates displayed by some epithelia

Functional correlates of positional and gender-specific renal asymmetry in drosophila

Accordingly, the physical asymmetry of the tubules in the body cavity is directly adaptive. Now that the detailed machinery underlying internal asymmetry is starting to be delineated, our work invites the investigation, not just of tissues in isolation, but in the context of their unique physical locations and milieux

Renal neuroendocrine control of desiccation and cold tolerance by Drosophila suzukii

Background: Neuropeptides are central to the regulation of physiological, and behavioural processes in insects, directly impacting cold and desiccation survival. However, little is known about the control mechanisms governing these responses in D. suzukii. The close phylogenetic relationship of D. suzukii with D. melanogaster allows, through genomic and functional studies, an insight into the mechanisms directing stress tolerance in D. suzukii. Results: Capa, Leucokinin, DH44 and DH31 neuropeptides demonstrate a high level of conservation between D. suzukii and D. melanogaster with respect to peptide sequences, neuronal expression, receptor localisation, and diuretic function in the Malpighian tubules. Despite D. suzukii’s ability to populate cold environments, they proved sensitive to both cold and desiccation. Furthermore, in D. suzukii, Capa acts as a desiccation-and cold stress-responsive gene, while DH44 gene expression is increased only after desiccation exposure, and the LK gene after nonlethal cold stress recovery. Conclusion: This study provides a comparative investigation into stress tolerance mediation by neuroendocrine signalling in two Drosophila species, providing evidence that similar signalling pathways control fluid secretion in the Malpighian tubules. Identifying processes governing specific environmental stresses affecting D. suzukii could lead to the development of targeted integrated management strategies to control insect pest populations

2D-FDTD method to estimate the complex permittivity of a multilayer dielectric materials at Ku-band frequencies

In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a multi-layer dielectric material using a Ku-band rectangular waveguide WR62. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a multi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the two dimensional finite difference in time domain (2D-FDTD), the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated Sij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer and one tri-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from multi-layer measurements and mono-layer measurements is presented

Complex permittivity estimation for each layer in a bi-layer dielectric material at Ku-band frequencies

In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a bi-layer dielectric material using a Ku-band rectangular waveguide WR62. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a bi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the transmission lines theory, the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated the Sij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from bi-layer measurements and mono-layer measurements is presented