Gall midge olfaction and its role in speciation

With the swede midge (Contarinia nasturtii) as our main model species, we study two types of olfactory cues that are of importance for gall midges: 1) the pheromones emitted by the female to attract the male; 2) and the host plant volatiles that the females use when finding a host for oviposition. We found that both the blend of compounds and the enantioisomeric form are important for male attraction in the wind tunnel and in the field. For pheromone reception, the gall midges use the sensillum type that display sexual dimorphism, male swede midge use the gall midge specific sensilla circumfila while the Hessian fly (Mayetiola destructor) use s. trichodea. In a detailed study of the female host finding behavior, we found that olfactory cues are important for the swede midge host selection. However, this "first impression" can be modulated by later plant characters, such as the physical defense of the host plant, or which host plants are available. By using the electrophysiological technique GC-EAD, we compared the response of 12 gall midge species, including the swede midge, to a blend of 45 plant volatiles to explore the relative impact of host plant chemistry, life-history strategies and the midge phylogeny on the gall midge host plant recognition system

Engineering med vokseværk

Kommentar til Jan Sølberg & Nina Waaddegaard “Hvad ved vi om indsatser inden for engineering i den danske grundskole gennem de sidste 10 år?”, MONA 2019(2)

Ecological and Phylogenetic Relationships Shape the Peripheral Olfactory Systems of Highly Specialized Gall Midges (Cecidomiiydae)

Insects use sensitive olfactory systems to detect relevant host volatiles and avoid un-suitable hosts in a complex environmental odor landscape. Insects with short lifespans, such as gall midges (Diptera: Cecidomyiidae), are under strong selection pressure to detect and locate suitable hosts for their offspring in a short period of time. Ephemeral gall midges constitute excellent models for investigating the role of olfaction in host choice, host shift and speciation. Midges mate near their site of emergence and females migrate in order to locate hosts for oviposition, thus females are expected to be more responsive to olfactory cues emitted by the host compared to males. In this study, we explored the correlation between host choice and the func-tion of the peripheral olfactory system in twelve species of gall midges, including species with close phylogenetic relationships that use widely different host plants and more distantly related gall midge species that use similar hosts. We tested the anten-nal responses of males and females of the twelve species to a blend of 45 known insect attractants using coupled gas chromatographic–electroantennographic detec-tion. When the species-specific response profiles of the gall midges were compared to a newly generated molecular-based phylogeny, we found they responded to the com-pounds in a sex- and species-specific manner. We found the physiological response profiles of species that use annual host plants, and thus have to locate their host every season, are similar for species with similar hosts despite large phylogenetic distances. In addition, we found closely related spe-cies with perennial hosts demonstrated odor response profiles that were consistent with their phylogenetic history. The ecology of the gall midges affects the tuning of the peripheral olfactory system, which in turn demonstrates a correlation between olfaction and speciation in the context of host use

Astrocytic GABA transporter activity modulates excitatory neurotransmission

Astrocytes are ideally placed to detect and respond to network activity. They express ionotropic and metabotropic receptors, and can release gliotransmitters. Astrocytes also express transporters that regulate the extracellular concentration of neurotransmitters. Here we report a previously unrecognized role for the astrocytic GABA transporter, GAT-3. GAT-3 activity results in a rise in astrocytic Na(+) concentrations and a consequent increase in astrocytic Ca(2+) through Na(+)/Ca(2+) exchange. This leads to the release of ATP/adenosine by astrocytes, which then diffusely inhibits neuronal glutamate release via activation of presynaptic adenosine receptors. Through this mechanism, increases in astrocytic GAT-3 activity due to GABA released from interneurons contribute to 'diffuse' heterosynaptic depression. This provides a mechanism for homeostatic regulation of excitatory transmission in the hippocampus

Seizure control by decanoic acid through direct AMPA receptor inhibition

The medium chain triglyceride ketogenic diet is an established treatment for drug-resistant epilepsy that increases plasma levels of decanoic acid and ketones. Recently, decanoic acid has been shown to provide seizure control in vivo, yet its mechanism of action remains unclear. Here we show that decanoic acid, but not the ketones β-hydroxybutryate or acetone, shows antiseizure activity in two acute ex vivo rat hippocampal slice models of epileptiform activity. To search for a mechanism of decanoic acid, we show it has a strong inhibitory effect on excitatory, but not inhibitory, neurotransmission in hippocampal slices. Using heterologous expression of excitatory ionotropic glutamate receptor AMPA subunits in Xenopus oocytes, we show that this effect is through direct AMPA receptor inhibition, a target shared by a recently introduced epilepsy treatment perampanel. Decanoic acid acts as a non-competitive antagonist at therapeutically relevant concentrations, in a voltage- and subunit-dependent manner, and this is sufficient to explain its antiseizure effects. This inhibitory effect is likely to be caused by binding to sites on the M3 helix of the AMPA-GluA2 transmembrane domain; independent from the binding site of perampanel. Together our results indicate that the direct inhibition of excitatory neurotransmission by decanoic acid in the brain contributes to the anti-convulsant effect of the medium chain triglyceride ketogenic diet

Field evaluation of 3-hydroxy-2-hexanone and ethanol as attractants for the cerambycid beetle pest of vineyards, Xylotrechus arvicola

BACKGROUND: The beetle Xylotrechus arvicola (Coleoptera: Cerambycidae) is a serious pest of vineyards in the Iberian Peninsula. In previous work, the male beetles, but not females, were shown to produce (R)-3-hydroxy-2-hexanone, and female beetles were attracted to this compound in a laboratory bioassay. In this study, release rates of 3-hydroxy-2-hexanone from different dispensers were measured in the laboratory and the attractiveness of these to X. arvicola adults determined in trapping tests in three traditional wine-growing regions in Spain. RESULTS: As a result of laboratory experiments, for field experiments 3-hydroxy-2-hexanone was formulated as 100 µl in a polyethylene sachet (50 mm x 50 mm x 250 µ) and ethanol was formulated as 1 ml in a polyethylene press-seal bag (76 mm x 57 mm x 50 µ). Field catches were similar at all three study sites. Catches in traps baited with 3-hydroxy-2-hexanone alone were not significantly different from those in unbaited control traps, but catches in traps baited with 3-hydroxy-2-hexanone and ethanol in separate sachets, with 3-hydroxy-2-hexanone and ethanol in the same sachet, or with ethanol alone, were significantly greater than those in control traps. These results confirm that the beetles are attracted to ethanol and addition of 3-hydroxy-2-hexanone does not seem to make any difference. CONCLUSIONS: Attraction of females for the male-produced compound, (R)-3-hydroxy-2-hexanone, has been observed in laboratory but not in field experiments. Traps baited with ethanol are highly attractive to both sexes of adults of X. arvicola, and these can be used for improved monitoring of the adult emergence and for population control by mass trapping

Stability of Circulating Blood-Based MicroRNAs - Pre-Analytic Methodological Considerations

Background and aim The potential of microRNAs (miRNA) as non-invasive diagnostic, prognostic, and predictive biomarkers, as well as therapeutic targets, has recently been recognized. Previous studies have highlighted the importance of consistency in the methodology used, but to our knowledge, no study has described the methodology of sample preparation and storage systematically with respect to miRNAs as blood biomarkers. The aim of this study was to investigate the stability of miRNAs in blood under various relevant clinical and research conditions: different collection tubes, storage at different temperatures, physical disturbance, as well as serial freeze-thaw cycles. Methods Blood samples were collected from 12 healthy donors into different collection tubes containing anticoagulants, including EDTA, citrate and lithium-heparin, as well as into serum collection tubes. MiRNA stability was evaluated by measuring expression changes of miR-1, miR21 and miR-29b at different conditions: varying processing time of whole blood (up to 72 hours (h)), long-term storage (9 months at -80 degrees C), physical disturbance (1 and 8 h), as well as in a series of freeze/thaw cycles (1 and 4 times). Results Different collection tubes revealed comparable concentrations of miR-1, miR-21 and miR-29b. Tubes with lithium-heparin were found unsuitable for miRNA quantification. MiRNA levels were stable for at least 24 h at room temperature in whole blood, while separated fractions did show alterations within 24 h. There were significant changes in the miR-21 and miR-29b levels after 72 h incubation of whole blood at room temperature (p< 0.01 for both). Both miR-1 and miR-21 showed decreased levels after physical disturbance for 8 h in separated plasma and miR-1 in serum whole blood, while after 1 h of disturbance no changes were observed. Storage of samples at -80 degrees C extended the miRNA stability remarkably, however, miRNA levels in long-term stored (9 months) whole blood samples were significantly changed, which is in contrast to the plasma samples, where miR-21 or miR-29b levels were found to be stable. Repetitive (n = 4) freeze-thaw cycles resulted in a significant reduction of miRNA concentration both in plasma and serum samples. Conclusion This study highlights the importance of proper and systematic sample collection and preparation when measuring circulating miRNAs, e.g., in context of clinical trials. We demonstrated that the type of collection tubes, preparation, handling and storage of samples should be standardized to avoid confounding variables influencing the results