Indirect plant-mediated interactions among parasitoid larvae

Communities are riddled with indirect species interactions and these interactions can be modified by organisms that are parasitic or symbiotic with one of the indirectly interacting species. By inducing plant responses, herbivores are well known to alter the plant quality for subsequent feeders. The reduced performance of herbivores on induced plants cascades into effects on the performance of higher trophic level organisms such as parasitoids that develop inside herbivores. Parasitoids themselves may also, indirectly, interact with the host plant by affecting the behaviour and physiology of their herbivorous host. Here, we show that, through their herbivorous host, larvae of two parasitoid species differentially affect plant phenotypes leading to asymmetric interactions among parasitoid larvae developing in different hosts that feed on the same plant. Our results show that temporally separated parasitoid larvae are involved in indirect plant-mediated interactions by a network of trophic and non-trophic relationships.     

Bone Suppression Increases the Visibility of Invasive Pulmonary Aspergillosis in Chest Radiographs

Objective

Chest radiographs (CXR) are an important diagnostic tool for the detection of invasive pulmonary aspergillosis (IPA) in critically ill patients, but their diagnostic value is limited by a poor sensitivity. By using advanced image processing, the aim of this study was to increase the value of chest radiographs in the diagnostic work up of neutropenic patients who are suspected of IPA.

Methods

The frontal CXRs of 105 suspected cases of IPA were collected from four institutions. Radiographs could contain single or multiple sites of infection. CT was used as reference standard. Five radiologists and two residents participated in an observer study for the detection of IPA on CXRs with and without bone suppressed images (ClearRead BSI 3.2; Riverain Technologies). The evaluation was performed separately for the right and left lung, resulting in 78 diseased cases (or lungs) and 132 normal cases (or lungs). For each image, observers scored the likelihood of focal infectious lesions being present on a continuous scale (0–100). The area under the receiver operating characteristics curve (AUC) served as the performance measure. Sensitivity and specificity were calculated by considering only the lungs with a suspiciousness score of greater than 50 to be positive.

Results

The average AUC for only CXRs was 0.815. Performance significantly increased, to 0.853, when evaluation was aided with BSI (p = 0.01). Sensitivity increased from 49% to 66% with BSI, while specificity decreased from 95% to 90%.

Conclusion

The detection of IPA in CXRs can be improved when their evaluation is aided by bone suppressed images. BSI improved the sensitivity of the CXR examination, outweighing a small loss in specificity.     

Silent or Vocalizing Rats Copulate in a Similar Manner

Both male and female rats produce 50 kHz ultrasonic vocalizations (USVs) in the presence of a sexual partner and during copulation. Previous studies showed that USVs have no incentive value for rats. In this study, we evaluated the role of USVs in behavior during copulation. Three groups of rats were used: sham males paired with sham females, devocalized females paired with sham males, and sham females paired with devocalized males. During the copulation test, the USVs emitted by the sham rat were recorded and the sexual behavior of both the male and the female were observed. The results revealed that devocalized and sham females showed similar patterns of sexual behavior and no difference was found in the copulatory behavior of devocalized and sham males. Also the behavior of the partner of a sham rat was comparable to the partner of a devocalized rat. In addition, almost no changes in USVs emission were found in the 5 seconds before and/or after a copulatory behavior. It can be concluded that USVs play no important role in rat copulatory behavior at least in sexually naïve rats.     

Virus infection decreases the attractiveness of white clover plants for a non-vectoring herbivore

Plant pathogens and insect herbivores are prone to share hosts under natural conditions. Consequently, pathogen-induced changes in the host plant can affect herbivory, and vice versa. Even though plant viruses are ubiquitous in the field, little is known about plant-mediated interactions between viruses and non-vectoring herbivores. We investigated the effects of virus infection on subsequent infestation by a non-vectoring herbivore in a natural genotype of Trifolium repens (white clover). We tested whether infection with White clover mosaic virus (WClMV) alters (1) the effects of fungus gnat feeding on plant growth, (2) the attractiveness of white clover for adult fungus gnat females, and (3) the volatile emission of white clover plants. We observed only marginal effects of WClMV infection on the interaction between fungus gnat larvae and white clover. However, adult fungus gnat females clearly preferred non-infected over WClMV-infected plants. Non-infected and virus-infected plants could easily be discriminated based on their volatile blends, suggesting that the preference of fungus gnats for non-infected plants may be mediated by virus-induced changes in volatile emissions. The compound β-caryophyllene was exclusively detected in the headspace of virus-infected plants and may hence be particularly important for the preference of fungus gnat females. Our results demonstrate that WClMV infection can decrease the attractiveness of white clover plants for fungus gnat females. This suggests that virus infections may contribute to protecting their hosts by decreasing herbivore infestation rates. Consequently, it is conceivable that viruses play a more beneficial role in plant-herbivore interactions than generally thought.     

Physicochemical investigation of k-carrageenan in the random state

Light-scattering, viscosity, and sedimentation experiments on aqueous solutions of k-carrageenan show that this sulfated polygalactose is an expanded flexible random coil. This expansion is due to long-range interactions that are predominantly electrostatic. Extrapolation of viscosity data to infinite ionic strength provided values for the intrinsic viscosity which were subjected to the Stockmayer-Fixman analysis, giving a value for the Mark-Houwink coefficient under theta-conditions, K_θ, of 0.27. The characteristic ratio, C_∞, under these conditions is 7.8, and the conformation factor σ is 2. In a solution of 0.118 ionic strength, where a Mark-Houwink exponent a_η of 0.86 is found, the radii of gyration calculated from viscosity data are lower than those found from the angular dependence of scattered light. On the other hand, the radius of gyration found from the sedimentation rate agrees well with the light-scattering radius. The relations between molecular parameters are corrected for the poly-dispersity of the sample.     

On the sol-gel transition in solutions of Kappa-carrageenan

The disorder-order transition, which takes place at the gelpoint of κ-carrageenan solutions was monitored by optical rotation and light scattering measurements. The coincidence of both sets of experimental data affords good evidence that the sol-gel transition is accompanied by a conformational change. Transition temperatures were observed to be linearly dependent on the logarithm of the salt concentration and this result is explained by the formation of double helices.Heats of gelation were measured by differential scanning calorimetry. It was found that the enthalpy increases with ionic strength, which was ascribed to the occurrence of a secondary process in which double helices are assembled into larger aggregates.     

Heterogeneous bone-marrow stromal progenitors drive myelofibrosis via a druggable alarmin axis

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