Standardizing Visual Control Devices for Tsetse Flies: East African Species Glossina swynnertoni

Background

Here we set out to standardize long-lasting, visually-attractive devices for Glossina swynnertoni, a vector of both human and animal trypanosomiasis in open savannah in Tanzania and Kenya, and in neighbouring conservation areas used by pastoralists. The goal was to determine the most practical device/material that would induce the strongest landing response in G. swynnertoni for use in area-wide population suppression of this fly with insecticide-impregnated devices.

Methods and Findings

Trials were conducted in wet and dry seasons in the Serengeti and Maasai Mara to measure the performance of traps and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a simple enumerator at these remote locations to compare trapping efficiencies of devices. Independent of season or presence of chemical baits, targets in phthalogen blue or turquoise blue cloth with adhesive film were the best devices for capturing G. swynnertoni in all situations, catching up to 19 times more flies than pyramidal traps. Baiting with chemicals did not affect the relative performance of devices. Fly landings were two times higher on 1 m² blue-black targets as on pyramidal traps when equivalent areas of both were covered with adhesive film. Landings on 1 m² blue-black targets were compared to those on smaller phthalogen blue 0.5 m² all-blue or blue-black-blue cloth targets, and to landings on all-blue plastic 0.32–0.47 m² leg panels painted in phthalogen blue. These smaller targets and leg panels captured equivalent numbers of G. swynnertoni per unit area as bigger targets.

Conclusions

Leg panels and 0.5 m² cloth targets show promise as cost effective devices for management of G. swynnertoni as they can be used for both control (insecticide-impregnated cloth) and for sampling (rigid plastic with insect glue or adhesive film) of populations.     

Visual pigments in a living fossil,the Australian lungfish <Emphasis Type="Italic">Neoceratodus forsteri</Emphasis>

Background  

One of the greatest challenges facing the early land vertebrates was the need to effectively interpret a terrestrial environment. Interpretation was based on ocular adaptations evolved for an aquatic environment millions of years earlier. The Australian lungfish Neoceratodus forsteri is thought to be the closest living relative to the first terrestrial vertebrate, and yet nothing is known about the visual pigments present in lungfish or the early tetrapods.     

Acute toxicity effects of ibuprofen on behaviour and haematological parameters of African catfish Clarias gariepinus (Burchell, 1822)

Indiscriminate discharge of pharmaceutical waste into the aquatic ecosystem may pose serious health challenges to aquatic biota. The effect of acute exposure to ibuprofen was evaluated using changes in behaviour and haematological parameters under static bio-assay method in Clarias gariepinus. Test specimens were exposed to acute concentrations of ibuprofen (0.28, 0.33, 0.38, 0.43 and 0.48 mg l^?1) for 24, 48, 72 and 96 h durations respectively. Behavioural and phenotypic changes were observed in surviving fish. There were significant (p < 0.05) concentration and duration-dependent increases in erythrocyte (RBC), haemoglobin (Hb), pack cell volume (PCV) and leukocytes (WBC) in treated fish compared to the control. Insignificant decreases (p > 0.05) in mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were observed in treated fish compared to the control. Ibuprofen elicited dose and duration- dependent decrease in neutrophil counts with the decreases being significant (p < 0.05) in the higher doses of 0.43 and 0.48 mg l^?1. Ibuprofen did not elicit any significant changes in monocytes, basophils and eosinophils. Changes observed in this study showed that ibuprofen negatively affected the health of the fish and we recommend that discharge of ibuprofen into the aquatic environment should be monitored and controlled.     

The dynamics of the MgATP-driven closure of MalK, the energy-transducing subunit of the maltose ABC transporter

The nucleotide binding domains (NBDs) are the energy supplying subunits of ATP-binding cassette (ABC) proteins. They power transport by binding and hydrolyzing ATP. Tracing the pathway between different conformational states of the NBDs during ATP binding, hydrolysis, and release has, however, proven difficult. We have used molecular dynamics simulations to study the ATP-driven association of the NBDs of the maltose ABC transporter, MalK, based on the crystal structures of its open and semiopen dimers. When MgATP was introduced into the binding pockets, the semiopen dimer transitioned to a closed conformation, whereas the open dimer evolved to a semiopen state. In the absence of docked MgATP, however, the twin NBDs of both the open and semiopen starting configurations drifted further apart. Both the presence of MgATP and direct cross-interface protein-protein hydrogen bonds, primarily involving the D-loop, quite likely play a key role in initiating closure. The simulations of the MgATP-docked semiopen form indicate that completion of closure is driven mainly by cross-interface contacts between the gamma-phosphate of ATP and residues in the signature motif. Our simulations also give insight into possible interactions of MalK with the regulatory proteins MalT and enzyme IIA(glc).     

Computer simulations of membrane proteins

Computer simulations are rapidly becoming a standard tool to study the structure and dynamics of lipids and membrane proteins. Increasing computer capacity allows unbiased simulations of lipid and membrane-active peptides. With the increasing number of high-resolution structures of membrane proteins, which also enables homology modelling of more structures, a wide range of membrane proteins can now be simulated over time spans that capture essential biological processes. Longer time scales are accessible by special computational methods. We review recent progress in simulations of membrane proteins.     

Computer simulations of ABC transporter components.

Current computer simulation techniques provide robust tools for studying the detailed structure and functional dynamics of proteins, as well as their interaction with each other and with other biomolecules. In this minireview, we provide an illustration of recent progress and future challenges in computer modeling by discussing computational studies of ATP-binding cassette (ABC) transporters. ABC transporters have multiple components that work in a well coordinated fashion to enable active transport across membranes. The mechanism by which members of this superfamily execute transport remains largely unknown. Molecular dynamics simulations initiated from high-resolution crystal structures of several ABC transporters have proven to be useful in the investigation of the nature of conformational coupling events that may drive transport. In addition, fruitful efforts have been made to predict unknown structures of medically relevant ABC transporters, such as P-glycoprotein, using homology-based computational methods. The various techniques described here are also applicable to gaining an atomically detailed understanding of the functional mechanisms of proteins in general.     

Bionomics ofTetrastichus sesamiae [Hymenoptera: Eulophidae], a pupal endo-parasitoid ofMaruca testulalis [Lepidoptera: Pyralidae]

The biology and behaviour ofTetrastichus sesamiae Risbec, a pupal endoparasitoid ofMaruca testulalis Geyer, were studied under laboratory conditions. Most adults emerged from the host pupae between 08.00 h and 09.00 h and mating and oviposition started almost immediately. Both ♂♂ and ♀♀ mated repeatedly, and each ♀ could lay eggs for up to 6 days and in up to 5 host pupae. Progeny production ranged from 0–263 offspring per ♀ and adult longevity was from 4.3–13.9 days. The quality of food available to the adults was a major factor influencing progeny production, and longevity. The species was capable of parasitizing and completing development on pupae of such other major Lepidopteran crop pests asChilo partellus Swinhoe,Busseola fusca Fuller,Eldana saccharina Wlk andSpodoptera exempta Wlk, an important finding for biological control of these pests under intercropped agro ecosystems. Apart from parasitism, ♀♀ ofT. sesamiae also caused considerable mortality by stinging, and presumably paralyzing, host pupae without ovipositing.      

Conformational transitions induced by the binding of MgATP to the vitamin B12 ATP-binding cassette (ABC) transporter BtuCD

ATP-binding cassette transporters use the free energy of ATP hydrolysis to transport structurally diverse molecules across prokaryotic and eukaryotic membranes. Computer simulation studies of the "real-time" dynamics of the ATP binding process in BtuCD, the vitamin B12 importer from Escherichia coli, demonstrate that the docking of ATP to the catalytic pockets progressively draws the two cytoplasmic nucleotide-binding cassettes toward each other. Movement of the cassettes into closer opposition in turn induces conformational rearrangement of alpha-helices in the transmembrane domain. The shape of the translocation pathway consequently changes in a manner that could aid the vectorial movement of vitamin B12. These results suggest that ATP binding may indeed represent the power stroke in the catalytic mechanism. Moreover, occlusion of ATP at one catalytic site is mechanically coupled to opening of the nucleotide-binding pocket at the second site. We propose that this asymmetry in nucleotide binding behavior at the two catalytic pockets may form the structural basis by which the transporter is able to alternate ATP hydrolysis from one site to the other.     

Life tables and intrinsic rate of natural increase ofPediobius furvus [Hym.: Eulophidae] onChilo partellus [Lep.: Pyralidae]

In the present studies, life table data and intrinsic rate of natural increase (r_m) of the eulophid pupal parasitoid,P. furvus (Gahan) were obtained fromChilo partellus (Swinhoe) at a constant temperature of 26.7±0.6°C, 52.3±2.7% RH in the laboratory. Development of immature stages took 19.1±0.3 days; adult females lived for 7.9±3.3 (range, 2–13) days and produced a mean of 91.9±22.4 progeny per female, with a sex ratio of 1:2.9 (♂:♀). The intrinsic rate of natural increase (rm) was 0.2558/female/day; the net reproductive rate (R₀), 237.25; the capacity for increase (r_c) of 0.252; and the finite rate of increase (λ) of 1.29/female/day; thus, each female contributed 231.42 individuals to the population in a mean generation time of 21.38 days.