Synergism between ammonia and phenols for Hybomitra tabanids in northern and temperate Canada

Baits for tabanids (Diptera: Tabanidae) were tested in the Northwest Territories (60 °N) and Ontario (45 °N) using Nzi traps. Tests targeted ammonia, phenols/cow urine and octenol. About 200 000 tabanids were captured in 15 experiments with a maximum capture of 4182 in one trap in 1 day. In the Northwest Territories, phenols, urine and octenol were effective single baits for only some species. At both locations, adding ammonia to an unbaited or an octenol-baited trap had no effect on catches. By contrast, catches were increased for several species when ammonia was combined with phenols or urine. In Ontario, including ammonia in various baits increased catches by 1.5- to 3.4-fold relative to octenol alone for three Hybomitra and one Tabanus species. Synergism between ammonia and phenols was clearly demonstrated for the dominant Hybomitra species in Ontario (Hybomitra lasiophthalma), but not for the dominant species in the Northwest Territories (Hybomitra epistates). In five other northern Hybomitra species, baits of ammonia and/or octenol in combination with phenols resulted in a 1.7- to 4.1-fold increase in catch relative to an unbaited trap. Further tests of ammonia as a synergist for biting flies may prove useful in, for example, tsetse, which respond strongly to phenols.

Intercellular calcium waves in primary cultured rat mesenteric smooth muscle cells are mediated by connexin43

Intercellular Ca(2+) wave propagation between vascular smooth muscle cells (SMCs) is associated with the propagation of contraction along the vessel. Here, we characterize the involvement of gap junctions (GJs) in Ca(2+) wave propagation between SMCs at the cellular level. Gap junctional communication was assessed by the propagation of intercellular Ca(2+) waves and the transfer of Lucifer Yellow in A7r5 cells, primary rat mesenteric SMCs (pSMCs), and 6B5N cells, a clone of A7r5 cells expressing higher connexin43 (Cx43) to Cx40 ratio. Mechanical stimulation induced an intracellular Ca(2+) wave in pSMC and 6B5N cells that propagated to neighboring cells, whereas Ca(2+) waves in A7r5 cells failed to progress to neighboring cells. We demonstrate that Cx43 forms the functional GJs that are involved in mediating intercellular Ca(2+) waves and that co-expression of Cx40 with Cx43, depending on their expression ratio, may interfere with Cx43 GJ formation, thus altering junctional communication.

The location and nature of general anesthetic binding sites on the active conformation of firefly luciferase; a time resolved photolabeling study

Firefly luciferase is one of the few soluble proteins that is acted upon by a wide variety of general anesthetics and alcohols; they inhibit the ATP–driven production of light. We have used time–resolved photolabeling to locate the binding sites of alcohols during the initial light output, some 200 ms after adding ATP. The photolabel 3-azioctanol inhibited the initial light output with an IC50 of 200 µM, close to its general anesthetic potency. Photoincorporation of [³H]3-azioctanol into luciferase was saturable but weak. It was enhanced 200 ms after adding ATP but was negligible minutes later. Sequencing of tryptic digests by HPLC–MSMS revealed a similar conformation–dependence for photoincorporation of 3-azioctanol into Glu-313, a residue that lines the bottom of a deep cleft (vestibule) whose outer end binds luciferin. An aromatic diazirine analog of benzyl alcohol with broader side chain reactivity reported two sites. First, it photolabeled two residues in the vestibule, Ser-286 and Ile-288, both of which are implicated with Glu-313 in the conformation change accompanying activation. Second, it photolabeled two residues that contact luciferin, Ser-316 and Ser-349. Thus, time resolved photolabeling supports two mechanisms of action. First, an allosteric one, in which anesthetics bind in the vestibule displacing water molecules that are thought to be involved in light output. Second, a competitive one, in which anesthetics bind isosterically with luciferin. This work provides structural evidence that supports the competitive and allosteric actions previously characterized by kinetic studies.

Collection of Culicoides (Diptera: Ceratopogonidae) using CO2 and enantiomers of 1-octen-3-ol in the United Kingdom

The host kairomones carbon dioxide (CO2) and 1-octen-3-ol elicit a host seeking response in a wide range of haematophagous Diptera. This study investigates the response of Culicoides biting midges (Diptera: Ceratopogonidae) to these cues using field-based experiments at two sites in the United Kingdom with very different species complements. Traps used for surveillance (miniature CDC model 512) and control (Mosquito Magnet Pro) were modified to release ratios of (R)- and (S)-1-octen-3-ol enantiomers in combination with CO2 and, in the case of the latter trap type, a thermal cue. Abundance and species diversity were then compared between these treatments and against collections made using a trap with a CO2 lure only, in a Latin square design. In both habitats, results demonstrated that semiochemical lures containing a high proportion of the (R)-enantiomer consistently attracted a greater abundance of host-seeking Culicoides females than any other treatment. Culicoides collected using an optimal stimulus of 500 ml/min CO2 combined with 4.1 mg/h (R)-1-octen-3-ol were then compared with those collected on sheep through the use of a drop trap. While preliminary in nature, this trial indicated Culicoides species complements are similar between collections made using the drop trap in comparison to the semiochemical-baited CDC trap, and that there are advantages in using (R)-1-octen-3-ol.

Disruptive selection maintains variable pheromone blends in the bark beetle Ips pini

The presence of heritable variation is a prerequisite for evolution, but natural selection typically reduces genetic variation. Variation can be maintained in traits under selection through spatial or temporal variation in fitness surfaces, frequency-dependent selection, or disruptive selection. We evaluated the maintenance of variation in the enantiomeric blend of pheromones employed by the bark beetle Ips pini (Say). In natural populations, we quantified fitness surfaces for mating success and progeny production. We investigated the effects of paternal pheromone blend on offspring survival by comparing the spatial scales at which pheromone blends and larval mortality agents vary. Males with extreme pheromone blends obtained up to 1.8 times as many mates who each laid equivalent numbers of eggs, producing strong disruptive selection on male pheromone blend. In combination with imperfect assortative mating that continually produces intermediate genotypes, this fitness surface is sufficient to maintain variation in a heritable trait that is strongly linked to fitness. The ultimate explanation for female preference is unknown but could be because of selection for reduced mortality from specialist predators that prefer common prey pheromone blends. Selection is most likely occurring at the scale of small resource patches within pine stands. Selection at coarser scales (pine stands) is unlikely because pheromone blends did not vary among pine stands. Selection at finer scales (within logs) is unlikely because males of similar enantiomeric blends were not aggregated on logs, and male pheromone blend did not affect the spacing to neighboring galleries. This study documents a rare case of diversifying selection in natural populations.

Semi-field comparison of the BG Lure, nonanal, and 1-octen-3-ol to attract adult mosquitoes in northwestern Florida

The relative attractiveness of Mosquito Magnet-X suction traps baited with various combinations of the BG Lure, nonanal, 1-octen-3-ol (octenol), and carbon dioxide was evaluated against laboratory-reared female Aedes albopictus and Culex quinquefasciatus in semi-field trials in northwestern Florida. In the absence of carbon dioxide, traps baited with the BG Lure (comprised of ammonia, caproic acid, and lactic acid) collected just as many mosquitoes as traps baited with carbon dioxide only. The numbers of mosquitoes caught in traps baited with no carbon dioxide and only nonanal, octenol, or their combination with or without the BG Lure were generally depressed compared with traps baited with carbon dioxide alone. When these chemicals were combined with carbon dioxide, no significant difference existed in the abundance of either mosquito species caught compared with traps baited only with carbon dioxide. However, in one trial, the combination of BG Lure plus octenol and carbon dioxide resulted in nearly a 4-fold depression in Ae. albopictus collections compared with carbon dioxide-only baited traps. The reason for this discordance remains to be investigated.

Enantiomeric selectivity in behavioural and electrophysiological responses of Aedes aegypti and Culex quinquefasciatus mosquitoes

1-Octen-3-ol is a kairomone for many haematophagous insects including mosquitoes. Numerous studies have examined the effects of racemic 1-octen-3-ol; however, few studies have investigated the role of individual enantiomers in relation to mosquito attraction. In the present study, we investigated the behavioural and electrophysiological responses of two mosquito species, Aedes aegypti and Culex quinquefasciatus, to individual enantiomers and mixtures of 1-octen-3-ol, employing a laboratory Y-tube olfactometer and single sensillum recordings. The olfactory receptor neurons of both Ae. aegypti and Cx. quinquefasciatus had a significantly higher response to the (R)-1-octen-3-ol enantiomer compared to the (S)-1-octen-3-ol enantiomer at 10-9 g μl-1 to 10-6 g μl-1. Behaviourally, Ae. aegypti was more responsive to the (R)-1-octen-3-ol enantiomer, showing an increase in flight activity and relative attraction compared to Cx. quinquefasciatus. The (R)-1-octen-3-ol enantiomer caused an increase in activation for Cx. quinquefasciatus. However, the most notable effect was from an (R:S)-1-octen-3-ol mixture (84:16) that caused significantly more mosquitoes to sustain their flight and reach the capture chambers (demonstrated by a reduced non-sustained flight activity), suggesting that it may have a behaviourally excitatory effect. For Cx. quinquefasciatus, a reduced relative attraction response was also observed for all treatments containing the (R)-1-octen-3-ol enantiomer, either on its own or as part of a mixture, but not with the (S)-1-octen-3-ol enantiomer. This is the first time enantiomeric selectivity has been shown for Ae. aegypti using electrophysiology in vivo. The implications of these results for exploitation in mosquito traps are discussed.

Disruption of gap junctions reduces biomarkers of decidualization and angiogenesis and increases inflammatory mediators in human endometrial stromal cell cultures

CONTEXT

Uterine decidualization is critical to embryonic implantation and sustained pregnancy.

OBJECTIVE

To evaluate the role of gap junction intercellular communications and connexin (Cx) proteins in the morphological and biochemical differentiation of decidualized human endometrial stromal cell (ESC) cultures.

DESIGN

Translational cell biological study.

SETTING

Academic medical center.

PATIENTS

Endometrial tissue was provided by five healthy reproductive age women on no hormonal medication, undergoing laparoscopy in the early proliferative phase of the menstrual cycle.

INTERVENTIONS

Endometrial biopsy under general anesthesia, establishment and decidualization of ESC with 10 nM 17β-estradiol, 100 nM progesterone and 0.5 mM dibutyryl-cAMP (E/P/c), and manipulation of gap junctions in vitro via a combination of pharmacological or transgenic approaches.

MAIN OUTCOME MEASURES

Decidualized ESC evaluated morphologically for epithelioid transformation, gap junctions by dye diffusion and Cx43, prolactin, VEGF and IL-6 expression by RT-PCR, Western and ELISA methods.

RESULTS

Cx43 accumulation and functional gap junctions between decidualized ESC increase concomitantly with morphological differentiation following E/P/c treatment. Disruption of gap junctions using pharmacological inhibitors or Cx43 shRNA prevents morphological differentiation and inhibits prolactin and VEGF secretion. By contrast, IL-6 secretion from decidualized ESC is augmented by both approaches.

CONCLUSIONS

The findings suggest that decidualized ESC function as a coordinated secretory organ to regulate embryonic implantation via intercellular cooperation mediated by gap junctions. When adjacent cells can communicate through these junctions, decidual prolactin and VEGF secretion appears to be optimized for vascular development of the placental bed. Conversely, when intercellular communications are disrupted, angiogenesis is impaired and an inflammatory state is induced.

Semi-field evaluation of several novel alkenol analogs of 1-octen-3-ol as attractants to adult Aedes albopictus and Culex quinquefasciatus

The compound 1-octen-3-ol is a known attractant of some mosquito species, which has led to the hypothesis that olfactory stimulation by this alkenol may be associated with the following structural elements: a terminal site of unsaturation or high electron density; a structural capability for hydrogen bonding, e.g., -OH, -NH2, NHR, NR2, etc.; a saturated hydrocarbon chain of a certain minimum length; and a certain relative distance between the region of high electron density and the alcohol (or other hydrogen-bonding) functional group. Using this logic, we synthesized 20 alkenol analogs based on the octenol double-bonded carbon skeleton. The attraction of female Aedes albopictus and Culex quinquefasciatus to these analogs was compared with 1-octen-3-ol as a standard in semi-field trials. For both species, collections from Mosquito Magnet-X (MMX) suction traps baited with the alkenol analogs in the absence of carbon dioxide were not significantly different from octenol-only baited traps, with the exception of (Z)-3-hepten-1-ol which collected significantly more Ae. albopictus. In the presence of CO2, most of the collections from traps baited with an alkenol were considerably increased for both species but not different from octenol plus CO2, with the exception of Ae. albopictus where (Z)-3-decen-1-ol, (Z)-4-hexen-1-ol, 7-octen-2-ol, and 8-nonen-3-ol significantly depressed trap catches. Although no clearly identifiable structure-activity relationship could be determined from our collected data, we did find that MMX traps baited with carbon dioxide and 4-penten-2-ol or (E)-2-decen-4-ol significantly enhanced Cx. quinquefasciatus collections up to nearly 3-fold compared with octenol plus carbon dioxide.

Bark beetle pheromones and pine volatiles: attractant kairomone lure blend for longhorn beetles (Cerambycidae) in pine stands of the southeastern United States

In 2006, we examined the flight responses of 43 species of longhorn beetles (Coleoptera: Cerambycidae) to multiple-funnel traps baited with binary lure blends of (1) ipsenol + ipsdienol, (2) ethanol + alpha-pinene, and a quaternary lure blend of (3) ipsenol + ipsdienol + ethanol + alpha-pinene in the southeastern United States. In addition, we monitored responses of Buprestidae, Elateridae, and Curculionidae commonly associated with pine longhorn beetles. Field trials were conducted in mature pine (Pinus pp.) stands in Florida, Georgia, Louisiana, and Virginia. The following species preferred traps baited with the quaternary blend over those baited with ethanol + alpha-pinene: Acanthocinus nodosus (F.), Acanthocinus obsoletus (Olivier), Astylopsis arcuata (LeConte), Astylopsis sexguttata (Say), Monochamus scutellatus (Say), Monochamus titillator (F.) complex, Rhagium inquisitor (L.) (Cerambycidae), Buprestis consularis Gory, Buprestis lineata F. (Buprestidae), Ips avulsus (Eichhoff), Ips calligraphus (Germar), Ips grandicollis (Eichhoff), Orthotomicus caelatus (Eichhoff), and Gnathotrichus materiarus (Fitch) (Curculionidae). The addition ofipsenol and ipsdienol had no effect on catches of 17 other species of bark and wood boring beetles in traps baited with ethanol and a-pinene. Ethanol + alpha-pinene interrupted the attraction of Ips avulsus, I. grandicollis, and Pityophthorus Eichhoff spp. (but not I. calligraphus) (Curculionidae) to traps baited with ipsenol + ipsdienol. Our results support the use of traps baited with a quaternary blend of ipsenol + ipsdienol + ethanol + alpha-pinene for common saproxylic beetles in pine forests of the southeastern United States.

Variation in enantiospecific attraction of Ips avulsus (Coleoptera: Curculionidae) to the pheromone ipsdienol in Georgia

In 2006, we tested the responses of the small southern pine engraver, Ips avulsus (Eichhoff) (Coleoptera: Curculionidae), to multiple-funnel traps baited with (+)-, (-)-, and (+/-)-ipsdienol. Three experiments were conducted in Georgia with all traps co-baited with one of the following lure combinations, respectively: experiment 1, ipsenol; experiment 2, lanierone and (-)-alpha-pinene; and experiment 3, ipsenol, lanierone, and (-)-alpha-pinene. Ipsdienol and lanierone are aggregation pheromones used by I. avulsus, whereas ipsenol is an aggregation pheromone used by the eastern fivespined ips, Ips grandicollis (Eichhoff), a sympatric species also breeding in pines. In all experiments, the highest catches of I. avulsus were obtained in traps baited with (+/-)-ipsdienol. The relative attractiveness of (+)-ipsdienol varied across the three experiments. When traps were co-baited with ipsenol, lanierone, and (-)-alpha-pinene, catches of I. avulsus in traps baited with (+)-ipsdienol were high and no different from those in traps baited with (+/-)-ipsdienol. When traps were co-baited with lanierone and (-)-alpha-pinene, catches in traps baited with (+)-ipsdienol were lower than those in traps baited with (+/-)-ipsdienol by approximately 40%, whereas catches were reduced by approximately 95% when traps were co-baited with ipsenol alone. We hypothesize that the observed variation in enantiospecific responses of I. avulsus to ipsdienol may be explained by variation in semiochemical context (i.e., different co-baits among the experiments) or seasonal variation.

Octenol as attractant to Nyssomyia neivai (Diptera:Psychodidae:Phlebotominae) in the field

The kairomone octenol is known as attractive to hematophagous Diptera such as mosquitoes, tsetse flies, and midges. There is little evidence that traps baited with octenol are also effective in attracting phlebotomine sand flies. The present report evaluated octenol in modified Centers for Disease Control and Prevention (CDC) traps in two experiments: 1) modified CDC trap without light and 2) modified CDC trap with light. The traps were baited with octenol at concentrations of 0.5, 27, and 43 mg/h in Rincão locality, São Paulo, Brazil. Traps without octenol were used as controls. The sand fly Nyssomyia neivai (Pinto) (= Lutzomyia neivai) (Diptera: Psychodidae: Phlebotominae) was the prevalent species (99.9%) in both experiments. The results of the experiments showed that traps baited with octenol at 27 and 43 mg/h caught significantly more N. neivai than control and octenol at 0.5 mg/h with and without light. This is the first report that shows that octenol itself is attractive to N. neivai and associated with light traps significantly increases the catches.

Evaluation of octenol and Lurex as baits in Mosquito Magnet Pro traps to collect vector mosquitoes in China

The effectiveness of the attractants 1-octen-3-ol (octenol) and L-lactic acid (Lurex) on the collection of Aedes albopictus, Culex tritaeniorhynchus, Cx. pipiens pallens, and Anopheles sinensis was first evaluated in Mosquito Magnet Pro traps in Yamenkou and Badachu residential areas, Beijing City, and Lishui area, Zhejiang Province, China. The Mosquito Magnet Pro traps baited with octenol collected significantly more Ae. albopictus, Cx. tritaeniorhynchus, and An. sinensis, but fewer Cx. pipiens pallens than collection by the traps alone. There were no significant differences in the numbers of Cx. pipiens pallens, Cx. tritaeniorhynchus, and An. sinensis collected by Mosquito Magnet Pro traps baited with Lurex compared to the traps alone, but the Mosquito Magnet Pro traps baited with Lurex collected significantly more Ae. albopictus than the number collected by the traps alone at 2 areas in Beijing.

Evaluation of lurex 3, octenol, and CO2 sachet as baits in Mosquito Magnet Pro traps against floodwater mosquitoes

Field evaluation of Lurex 3, 1-octen-3-ol (octenol), and CO2 sachet as baits in Mosquito Magnet Pro traps (MMP) for collecting adult mosquitoes was conducted at 2 different locations in northeast Florida. A total of 18 species of mosquitoes were collected by the MMP baited with the 3 attractant baits in St. Augustine, FL. The MMP baited with octenol collected significantly more mosquitoes than the traps baited with Lurex 3 and the CO2 sachet. A total of 6 floodwater mosquito species were collected by the MMP baited with the 3 attractant baits in Elkton, FL. The MMP baited with Lurex 3 or octenol collected more mosquitoes than the MMP baited with CO2 sachet or MMP alone.

Insect repellents: modulators of mosquito odorant receptor activity

Background

DEET, 2-undecanone (2-U), IR3535 and Picaridin are widely used as insect repellents to prevent interactions between humans and many arthropods including mosquitoes. Their molecular action has only recently been studied, yielding seemingly contradictory theories including odorant-dependent inhibitory and odorant-independent excitatory activities on insect olfactory sensory neurons (OSNs) and odorant receptor proteins (ORs).

Methodology/Principal Findings

Here we characterize the action of these repellents on two Aedes aegypti ORs, AaOR2 and AaOR8, individually co-expressed with the common co-receptor AaOR7 in Xenopus oocytes; these ORs are respectively activated by the odors indole (AaOR2) and (R)-(−)-1-octen3-ol (AaOR8), odorants used to locate oviposition sites and host animals. In the absence of odorants, DEET activates AaOR2 but not AaOR8, while 2-U activates AaOR8 but not AaOR2; IR3535 and Picaridin do not activate these ORs. In the presence of odors, DEET strongly inhibits AaOR8 but not AaOR2, while 2-U strongly inhibits AaOR2 but not AaOR8; IR3535 and Picaridin strongly inhibit both ORs.

Conclusions/Significance

These data demonstrate that repellents can act as olfactory agonists or antagonists, thus modulating OR activity, bringing concordance to conflicting models.

Evaluation for attractiveness of four chemicals to the biting midge, Forcipomyia taiwana (Diptera: Ceratopogonidae)

Four chemicals (1-octen-3-ol [octenol], lactic acid, acetone, and carbon dioxide) were evaluated for their attractiveness to the biting midge, Forcipomyia taiwana. The attractiveness was based on the number of adult biting midges attracted to each chemical. Results showed that the attractiveness of each chemical changed with different release rates. The optimal attractive release rates for octenol, lactic acid, and acetone fell in the range 0.5-0.9 mg/h, 0.2-1.4 mg/h, and 3.4-10.9 mg/h, respectively. The most attractive release rates were 0.7 mg/h, 0.2 mg/h, and 4.8 mg/h, respectively. Octenol, lactic acid, and acetone were evaluated simultaneously but in separate traps, at the best attractive release rate mentioned above to compare their attractiveness efficacies. Octenol was the most attractive to F. taiwana, followed by lactic acid and acetone; however, there was no significant difference between the mean numbers of adults attracted by the 3 attractants. Carbon dioxide (CO2) with release rates of 100, 250, and 500 ml/min showed no differences in attractiveness. When combinations of CO2, octenol, and blue light (BL, lamda max = 405 nm) were evaluated, the number of adults attracted by the treatment of CO2 + BL was the lowest, and that of the CO2 + octenol + BL was the highest.

Comparison of octenol- and BG Lure-baited biogents sentinel traps and an encephalitis virus surveillance trap in Portland, OR

Two types of mosquito trap were tested near Smith Lake in Portland, Multnomah County, OR: 2 Biogents Sentinel (BGS) traps baited with carbon dioxide (CO2) and an octenol sachet or a BG Lure, and an encephalitis virus surveillance (EVS) trap with CO2 but without an odor sachet. After 6 trap-nights, the 2 BGS traps caught significantly more mosquitoes than the EVS trap. More Culex tarsalis and an overall greater number of species were caught in the BGS traps. A BGS trap and an EVS trap, both baited with CO2 alone, were compared to investigate whether the difference was due to the attractants or the difference in trap type. The BGS trap caught more mosquitoes but the difference was not significant. The BGS trap, when baited with CO2 and other lures, can be an effective mosquito sampling tool, but further research is needed to understand the importance of the attractants.

Field evaluation of CDC and Mosquito Magnet X traps baited with dry ice, CO2 sachet, and octenol against mosquitoes

The Centers for Disease Control and Prevention (CDC) light traps and Mosquito Magnet X (MMX) traps baited with dry ice, octenol, and a new formulation (granular) of carbon dioxide (CO2) were evaluated against adult mosquitoes in the field. The results showed that the MMX traps (68.6%) baited with dry ice collected more mosquitoes compared to the CDC light traps (32.4%) only. The CDC traps baited with dry ice (64%) collected significantly more mosquitoes than traps baited with CO2 sachets (11%) or octenol (23%). The MMX traps baited with dry ice (85.5%) collected significantly more mosquitoes than traps baited with CO2 sachets (6.5%) or octenol (9%). The CDC traps baited with the formulations of normal and slow release CO2 sachets collected more mosquitoes than the formulation of fast release sachets. The CDC traps baited with fresh sachets and 24-h-exposed sachets collected significantly more mosquitoes than the traps baited with 48-h- and 72-h-exposed sachets.

A comparison of trapping methods for Tabanidae (Diptera) in North Queensland, Australia

The ability to monitor the abundance and diversity of tabanid flies over wide areas requires effective and low-cost surveillance methods. Such monitoring activities help to quantify the risk of transmission of pathogens by tabanids. Here we examine the effectiveness and practicality of two types of trap (canopy traps and Nzi traps) and two types of attractant (octenol and carbon dioxide) for monitoring tabanid flies in tropical Australia. The Nzi trap consistently caught more tabanids and more species of tabanids than the canopy trap. It was also more robust and therefore required less maintenance in remote locations. The use of attractants substantially increased capture rates, both of individuals and species, and traps using both attractants were consistently the most effective. However, in remote locations, where it is not possible to check traps frequently, the use of attractants may not be feasible. When attractants were not used, the canopy trap caught very few tabanids, but the Nzi trap remained effective enough to be useful as a monitoring device. In addition, the number of tabanid species caught by the Nzi traps remained high, and included those that were most abundant. We therefore conclude that, in this region, Nzi traps are preferable for tabanid monitoring and that attractants greatly improve their effectiveness. However, for longterm monitoring, especially in remote locations, Nzi traps without attractants are a satisfactory option.

Tricholoma matsutake 1-Ocen-3-ol and methyl cinnamate repel mycophagous Proisotoma minuta (Collembola: Insecta)

Two major volatiles produced by the mycelia and fruiting bodies of Tricholoma matsutake (1-octen-3-ol and methyl cinnamate) repel a mycophagous collembolan, Proisotoma minuta. Aggregation of the collembolans on their diet was significantly inhibited by exposure to 1 ppm methyl cinnamate or 10 to 100 ppm 1-octen-3-ol. The aggregation activity decreased dose-dependently upon exposure to 1-octen-3-ol at concentrations higher than 0.01 ppm. Aggregation in the presence of methyl cinnamate exhibited three phases: no significant effect at concentrations ranging from 0.001 to 0.1 ppm, significant inhibition from 1 to 100 ppm, and strong inhibition at 1,000 ppm. These results may explain why certain collembolan species do not prefer T. matsutake fruiting bodies.

Evaluation of the enantiomers of 1-octen-3-ol and 1-octyn-3-ol as attractants for mosquitoes associated with a freshwater swamp in Florida, U.S.A

Field studies were conducted at wooded wetlands in Gainesville, FL, U.S.A., to assess responses of natural populations of adult mosquitoes (Diptera: Culicidae) to American Biophysics MM-X and Coleman MD-2500 traps baited with enantiomers of 1-octen-3-ol, a naturally occurring compound, and 1-octyn-3-ol, a closely related synthetic compound. Overall, the same species of mosquitoes were attracted by all enantiomers, although the (R)-(+) isomer of octenol generally attracted more species, and it is the isomer produced in greatest proportion in nature. Traps baited with the R-enantiomer caught greater numbers of mosquitoes than those baited with the S-enantiomer of each compound, whereas traps baited with S-enantiomers were equally or slightly less attractive than those baited with carbon dioxide only.

Photoactivated 3-azioctanol irreversibly desensitizes muscle nicotinic ACh receptors via interactions at alphaE262

3-Azioctanol is a photoactivatable analogue of octanol that noncompetitively inhibits nicotinic acetylcholine receptors (nAChRs). Photolabeling studies using [3H]-3-azioctanol in Torpedo nAChR identified alphaE262 as a site of desensitization-dependent incorporation. However, it is unknown whether photolabeling of alphaE262 causes functional effects in nAChRs and what other roles this residue plays in gating, desensitization, and channel block. We used ultrafast patch-perfusion electrophysiology and ultraviolet (UV) irradiation to investigate the state-dependence of both reversible nAChR inhibition by 3-azioctanol and the irreversible effects of photoactivated 3-azioctanol. Channels with mutations at alphaE262 were studied to determine ACh EC50s, desensitization rates, and sensitivities to reversible and photoirreversible 3-azioctanol inhibition. Exposure to 3-azioctanol in the presence of 365 nm UV light produced irreversible inhibition of wild-type nAChRs. Desensitization with ACh dramatically increased the degree of irreversible inhibition by photoactivated 3-azioctanol. Mutations at alphaE262 that reduce diazirine photomodification decreased the irreversible inhibition induced by photoactivated 3-azioctanol. Hydrophobic mutations at alphaE262 significantly slowed rapid ACh-induced desensitization and dramatically slowed fast resensitization. In contrast, alphaE262 mutations minimally affected 3-azioctanol channel block, and a half blocking concentration of 3-azioctanol did not alter the rate of ACh-induced fast desensitization. Our results indicate that position alphaE262 on muscle nAChRs contributes to an allosteric modulator site that is strongly coupled to desensitization. Occupation of this pocket by hydrophobic molecules stabilizes a desensitized state by slowing resensitization.

Passage of 17kDa calmodulin through gap junctions of three vertebrate species

Gap junctions of some vertebrates are capable of passing the elongate molecule, calmodulin, with a molecular weight 8-17 times greater than the previously recognized size limits. Fluorescently labeled calmodulin (FCaM) (17.34 kDa) microinjected into oocytes of ovarian follicles from an amphibian, Xenopus laevis, and from two species of teleost fish, Danio rerio (Zebrafish) and Oryzias latipes (Medaka), is shown to transit their gap junctions and enter the surrounding epithelial cells. Passage of FCaM was terminated when follicles were first treated with 1 mM octanol, a molecule known to down-regulate gap junctions. There was no FCaM detected in the surrounding medium, nor did epithelial cells become fluorescent when follicles were incubated in medium containing dye. Calmodulin is well known to modulate many cytoplasmic reactions; thus, its passage through gap junctions opens possibilities of additional means by which cells may be supplied with this signaling molecule, and by which their supply may be regulated.

Odor coding in the maxillary palp of the malaria vector mosquito Anopheles gambiae

BACKGROUND

Many species of mosquitoes, including the major malaria vector Anopheles gambiae, utilize carbon dioxide (CO(2)) and 1-octen-3-ol as olfactory cues in host-seeking behaviors that underlie their vectorial capacity. However, the molecular and cellular basis of such olfactory responses remains largely unknown.

RESULTS

Here, we use molecular and physiological approaches coupled with systematic functional analyses to define the complete olfactory sensory map of the An. gambiae maxillary palp, an olfactory appendage that mediates the detection of these compounds. In doing so, we identify three olfactory receptor neurons (ORNs) that are organized in stereotyped triads within the maxillary-palp capitate-peg-sensillum population. One ORN is CO(2)-responsive and characterized by the coexpression of three receptors that confer CO(2) responses, whereas the other ORNs express characteristic odorant receptors (AgORs) that are responsible for their in vivo olfactory responses.

CONCLUSIONS

Our results describe a complete and highly concordant map of both the molecular and cellular olfactory components on the maxillary palp of the adult female An. gambiae mosquito. These results also facilitate the understanding of how An. gambiae mosquitoes sense olfactory cues that might be exploited to compromise their ability to transmit malaria.

Can chemical communication be cryptic? Adaptations by herbivores to natural enemies exploiting prey semiochemistry

Predators and parasites commonly use chemical cues associated with herbivore feeding and reproduction to locate prey. However, we currently know little about mechanisms by which herbivores may avoid such natural enemies. Pheromones are crucial to many aspects of herbivore life history, so radical alterations of these compounds could be disadvantageous despite their exploitation by predators. Instead, minor modifications in pheromone chemistry may facilitate partial escape while maintaining intraspecific functionality. We tested this hypothesis using Ips pini, an endophytic beetle that develops in the phloem tissue of pine trees. Its predominant predators in the Great Lakes region of North America are Thanasimus dubius and Platysoma cylindrica, both of which are highly attracted to I. pini's pheromones. However, there are significant disparities between prey and predator behaviors that relate to nuances of pheromone chemistry. Thanasimus dubius is most attracted to the (+) stereoisomer of ipsdienol, and P. cylindrica is most attracted to the (-) form; Ips pini prefers racemic mixtures intermediate between each predator's preferences. Further, a component that is inactive by itself, lanierone, greatly synergizes the attraction of I. pini to ipsdienol, but has a weak or no effect on its predators. A temporal component adds to this behavioral disparity: lanierone is most important in the communication of I. pini during periods when its predators are most abundant. The difficulties involved in tracking prey are further compounded by spatial and temporal variation in prey signaling on a local scale. For example, the preferences of I. pini vary significantly among sites only 50 km apart. This chemical crypsis is analogous to morphological forms of camouflage, such as color and mimicry, that are widely recognized as evasive adaptations against visually searching predators. Presumably these relationships are dynamic, with predators and prey shifting responses in microevolutionary time. However, several factors may delay predator counter adaptations. The most important appears to be the availability of alternate prey, specifically I. grandicollis, whose pheromone ipsenol is highly attractive to the above predators but not cross-attractive with I. pini. Consistent with this view, the specialist parasitoid, Tomicobia tibialis, has behavioral preferences for pheromone components that closely correspond with those of I. pini. These results are discussed in terms of population dynamics and coevolutionary theory.