Comparing peripheral olfactory coding with host preference in the rhagoletis species complex

Recent studies have shown that flies from sympatric populationsof Rhagoletis pomonella infesting hawthorn, apple, and floweringdogwood fruit can distinguish among unique volatile blends identifiedfrom each host. Analysis of peripheral chemoreception in Rhagoletisflies suggests that changes in receptor specificity and/or receptorneuron sensitivity could impact olfactory preference among thehost populations and their hybrids. In an attempt to validatethese claims, we have combined flight tunnel analyses and singlesensillum electrophysiology in F₂ and backcross hybrids displayinga variety of behavioral phenotypes. Results show that differencesin peripheral chemoreception among second-generation adultsdo not provide a direct correlation between peripheral codingand olfactory behavior. We conclude that either the plasticityof the central nervous system in Rhagoletis can compensate forsignificant alterations in peripheral coding or that peripheralchanges present subtle effects on behavior not easily detectablewith current techniques. The results of this study imply thatthe basis for olfactory behavior in Rhagoletis has a complicatedgenetic and neuronal basis, even for populations with a recentdivergence in preference.     

Predicting drug resistance of the HIV-1 protease using molecular interaction energy components

Drug resistance significantly impairs the efficacy of AIDS therapy. Therefore, precise prediction of resistant viral mutants is particularly useful for developing effective drugs and designing therapeutic regimen. In this study, we applied a structure-based computational approach to predict mutants of the HIV-1 protease resistant to the seven FDA approved drugs. We analyzed the energetic pattern of the protease-drug interaction by calculating the molecular interaction energy components (MIECs) between the drug and the protease residues. Support vector machines (SVMs) were trained on MIECs to classify protease mutants into resistant and nonresistant categories. The high prediction accuracies for the test sets of cross-validations suggested that the MIECs successfully characterized the interaction interface between drugs and the HIV-1 protease. We conducted a proof-of-concept study on a newly approved drug, darunavir (TMC114), on which no drug resistance data were available in the public domain. Compared with amprenavir, our analysis suggested that darunavir might be more potent to combat drug resistance. To quantitatively estimate binding affinities of drugs and study the contributions of protease residues to causing resistance, linear regression models were trained on MIECs using partial least squares (PLS). The MIEC-PLS models also achieved satisfactory prediction accuracy. Analysis of the fitting coefficients of MIECs in the regression model revealed the important resistance mutations and shed light into understanding the mechanisms of these mutations to cause resistance. Our study demonstrated the advantages of characterizing the protease-drug interaction using MIECs. We believe that MIEC-SVM and MIEC-PLS can help design new agents or combination of therapeutic regimens to counter HIV-1 protease resistant strains.     

Protected raspberry production accelerates onset of oviposition by vine weevils (Otiorhynchus sulcatus)

• 1 Soft fruit production is increasingly reliant on crops that are grown under the protection of plastic tunnels, which may also affect insect communities as a result of localized climate change and changes to host plant physiology and chemistry. In particular, insect development rates may differ from field populations, making it more difficult to target control measures.
• 2 The present study investigated how protected environments affected adult vine weevil (Otiorhynchus sulcatus) feeding and reproduction on red raspberry (Rubus idaeus). We focused on the period between adult emergence and the onset of oviposition (i.e. the pre‐reproductive period), which represents the optimal period for control.
• 3 Tunnels were up to 4 °C warmer than field plantations in 2008, with plants growing significantly faster (50% increase in height and 16% increase in leaf area) than field grown plants. The carbon/nitrogen ratio in leaves was higher in tunnels (12.07) than the field (10.89) as a result of a significant decrease in nitrogen concentrations (3.40 and 3.90 mg g^?1, respectively).
• 4 Over 4 weeks, weevils consumed significantly more foliage in tunnels (370.89 mg) than weevils in the field (166.68 mg), suggesting compensatory feeding to counteract lower leaf nitrogen concentrations. Weevils in tunnels achieved sexual maturity 8 days earlier than those in the field and produced 20‐fold more eggs by the time they were 5 weeks old.
• 5 Applying a degree‐day model showed good agreement between predicted and observed pre‐reproductive periods for weevils in tunnels (36 and 30 days, respectively) and in field plots (41 and 38 days, respectively).

     

Attraction of the sandfly Lutzomyia longipalpis to possible biomarker compounds from dogs infected with Leishmania infantum

Lutzomyia longipalpis (Diptera: Psychodidae) is the primary vector of Leishmania infantum (Kinetoplastida: Trypanosomatidae) in the Americas. Studies have been carried out to identify new alternatives for monitoring and controlling this sandfly species, particularly with the use of chemical baits. The attractiveness of odours emitted by foxes and alcohols found in some plants has already been demonstrated in laboratory tests with Lu. longipalpis. However, no studies have evaluated the responses of these insects to volatile organic compounds (VOCs) emitted by dogs. The present study was carried out to investigate the effects on Lu. longipalpis of individual and blends of VOCs identified in hair from dogs infected with L. infantum. Effects in male and female Lu. longipalpis were assessed using wind tunnel methodology. Individual compounds including octanal, nonanal, decanal and heptadecane showed capacity for activating and/or attracting male Lu. longipalpis. Only decanal and nonanal showed effects on females. The combination of octanal, decanal and heptadecane increased activation and attraction behaviour in male sandflies, as did the blend of octanal and decanal. These findings indicate that VOCs emitted by dogs may be an interesting source of new attractants of sandflies.     

Effects of methoxyfenozide-treated surfaces on the attractiveness and responsiveness of adult leafrollers

Abstract The attractiveness and responsiveness of the adult redbanded leafroller, Argyrotaenia velutinana (Walker), and obliquebanded leafroller, Choristoneura rosaceana (Harris), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide were investigated in wind tunnel and orientation tube assays. For both species, when males were exposed to water‐treated surfaces for 48 h, and regardless of what treatment surfaces the females had been exposed to, the mean percentage recaptures of such treated males in the wind tunnel assays were always significantly greater than the recaptures of males that had been exposed to methoxyfenozide. However, exposure to surfaces treated with surfactant (Latron B‐1956) also negatively affected the responsiveness (or attractiveness) of both moth species. In the orientation tube assays, males exposed to methoxyfenozide‐treated surfaces always had significantly lower mean levels of individuals exhibiting sexual excitability, and the mean distances traveled upwind, regardless of females’ exposure. In addition, exposure to surfactant‐treated surfaces did not affect mean levels of sexual excitibility and distances traveled upwind. The two bioassays demonstrated that male A. velutinana and C. rosaceana exposed to methoxyfenozide‐treated surfaces were not as responsive to calling females (treated and non‐treated) as were the non‐treated males. Conversely, females exposed to methoxyfenozide‐treated surfaces were just as attractive to non‐treated males as water‐treated females. It appears that a male's ability to respond to a calling female is more negatively affected by the ecdysone agonist than a female's ability to call and attract males.     

Elevated CO2 may alter pheromonal communication in Helicoverpa armigera (Lepidoptera: Noctuidae)

Carbon dioxide (CO₂) as a greenhouse gas has been increasing in recent decades. Because an elevated atmospheric CO₂ influences insect physiology and behaviour, we hypothesize that pheromone–mediated communication in the moth is affected by an increased CO₂ level. We test the behavioural responses of male Helicoverpa armigera to sex pheromone in a wind tunnel, demonstrating a significant reduction of approaching behaviour to the odour source at a high CO₂ level (1000 ppm). Electroantennogram (EAG) responses of male to the pheromone component are also significantly suppressed in high CO₂ environments (600 and 1000 ppm), indicating that a high CO₂ level inhibits both behavioural and electrophysiological responses of male to the sex pheromone. Interestingly, the EAG response of the whole head preparation of males is influenced more by the elevated CO₂ level than that of the antenna‐cut preparation. A sequential increase of CO₂ levels from an ambient CO₂ level also decreases the EAG response of the whole head but not of the labial palp‐removed head, implying a potential mediation of labial palp in the head where the CO₂ receptor is located. By contrast, sex pheromone production in females reared under or shifted to an elevated CO₂ condition is increased, and the putative underlying mechanism for this is discussed. The present study provides an insight into the adaptive strategy of moth pheromone communication in a changing environment.     

The critical swimming speed of Iberian barbel Barbus bocagei in relation to size and sex

The swimming capacity of Barbus bocagei was measured with the critical swimming speed (U_crit) standard test in a modified Bla?ka‐type swim tunnel. Sixty B. bocagei were tested and they exhibited a mean ±s .d . U_crit of 0·81 ± 0·11 m s^?1 or 3·1 ± 0·86 total lengths per second (L_T s^?1). Sex had no effect on U_crit but significant differences were found between the swimming performance of fish with distinct sizes.     

Berberine produces antidepressant-like effects in the forced swim test and in the tail suspension test in mice

This study investigated the effect of berberine (BER) in the mouse forced swim test (FST) and in the tail suspension test (TST), two models predictive of antidepressant activity. We also investigated the antidepressant-like mechanism of BER by the combination of the desipramine [DES, an inhibitor of reuptake of noradrenaline (NA) and serotonin (5-HT)], maprotiline (MAP, selective NA reuptake inhibitor), fluoxetine (FLU, selective 5-HT reuptake inhibitor) and moclobemide [MOC, monoamine oxidase (MAO) A inhibitor). Then we further measured the levels of monoamines [NA, dopamine (DA) and 5-HT) in mice striatum, hippocampus and frontal cortex. The results show that BER (10, 20 mg/kg, p.o.), significantly reduced the immobility time during the FST and the TST. The immobility time after treatment with BER (20 mg/kg, p.o.) in FST was augmented by DES, FLU and MOC, and not affected by MAP. Furthermore, BER (20 mg/kg, p.o.) increased NA and 5-HT levels in the hippocampus and frontal cortex. Our findings support the view that BER exerts antidepressant-like effect. The antidepressant-like mechanism of BER may be related to the increase in NA and 5-HT levels in the hippocampus and frontal cortex.     

Sub-atomic resolution crystal structure of cholesterol oxidase: what atomic resolution crystallography reveals about enzyme mechanism and the role of the FAD cofactor in redox activity

The crystal structure of cholesterol oxidase, a 56kDa flavoenzyme was anisotropically refined to 0.95A resolution. The final crystallographic R-factor and R(free) value is 11.0% and 13.2%, respectively. The quality of the electron density maps has enabled modeling of alternate conformations for 83 residues in the enzyme, many of which are located in the active site. The additional observed structural features were not apparent in the previous high-resolution structure (1.5A resolution) and have enabled the identification of a narrow tunnel leading directly to the isoalloxazine portion of the FAD prosthetic group. The hydrophobic nature of this narrow tunnel suggests it is the pathway for molecular oxygen to access the isoalloxazine group for the oxidative half reaction. Resolving the alternate conformations in the active site residues provides a model for the dynamics of substrate binding and a potential oxidation triggered gating mechanism involving access to the hydrophobic tunnel. This structure reveals that the NE2 atom of the active site histidine residue, H447, critical to the redox activity of this flavin oxidase, acts as a hydrogen bond donor rather than as hydrogen acceptor. The atomic resolution structure of cholesterol oxidase has revealed the presence of hydrogen atoms, dynamic aspects of the protein and how side-chain conformations are correlated with novel structural features such as the oxygen tunnel. This new structural information has provided us with the opportunity to re-analyze the roles played by specific residues in the mechanism of the enzyme.     

A wind tunnel comparison of the rotorod and samplair pollen samplers

Summary The relative sampling efficiency of the Samplair (Allergenco Inc.) and Rotorod samplers (Sampling Technologies Inc.) were compared for different conifer pollen sizes and at different wind speeds. The wind tunnel experiments conducted with the two samplers are valid for the range of wind speeds and conifer pollen types which might be expected in seed orchards in Canada. A Quadratic relationship was established between the two samplers which revealed a decrease in relative efficiency on the part of the Samplair as compared to the Rotorod at wind speeds less than 5 m/s. An apparent increase in the efficiency of the samplair at higher wind speeds resulted from a decrease in the sampling ability of the rotorod.