Josée Doyon

Endothelin-1 (ET-1) promotes MMP-2 and MMP-9 induction involving the transcription factor NF-κB in human osteosarcoma

In the present study, we have investigated the effect of (i) ET-1 (endothelin-1) and its precursor, big ET-1, on MMP (matrix metalloproteinase)-2 and MMP-9 synthesis and activity in osteosarcoma tissue, and (ii) ET-1 receptor antagonists on cell invasion. Using Western blotting, zymography, RT-PCR (reverse transcription-PCR), immunohistochemistry, immunofluorescence and Northern blotting, we have shown that ET-1 and ET-1 receptors (ET(A) and ET(B)) were expressed in these cells. Additionally, we have demonstrated that ET-1 markedly induced the synthesis and activity of MMP-2, which was significantly increased when compared with MMP-9. Furthermore, inhibition of NF-kappaB (nuclear factor kappaB) activation blocked MMP-2 production and activity, indicating the involvement of NF-kappaB, a ubiquitous transcription factor playing a central role in the differentiation, proliferation and malignant transformation. Since ET-1 acts as an autocrine mediator through gelatinase induction and because inhibition of ET(A) receptor is beneficial for reducing both basal and ET-1-induced osteosarcoma cell invasion, targeting this receptor could be an attractive therapeutic alternative for the successful treatment of osteosarcoma.

Prey DNA detection success following digestion by intraguild predators: influence of prey and predator species

Intraguild predation (IGP) has been increasingly recognized as an important interaction in ecological systems over the past two decades, and remarkable insights have been gained into its nature and prevalence. We have developed a technique using molecular gut‐content analysis to compare the rate of IGP between closely related species of coccinellid beetles (lady beetles or ladybirds), which had been previously known to prey upon one another. We first developed PCR primers for each of four lady beetle species: Harmonia axyridis, Coccinella septempunctata, Coleomegilla maculata and Propylea quatuordecimpunctata. We next determined the prey DNA detection success over time (DS50) for each combination of interacting species following a meal. We found that DS50 values varied greatly between predator–prey combinations, ranging from 5.2 to 19.3 h. As a result, general patterns of detection times based upon predator or prey species alone are not discernable. We used the DS50 values to correct field data to demonstrate the importance of compensation for detection times that are specific to particular predator–prey combinations.

Who is the puppet master? Replication of a parasitic wasp-associated virus correlates with host behaviour manipulation.

Many parasites modify their host behaviour to improve their own transmission and survival, but the proximate mechanisms remain poorly understood. An original model consists of the parasitoid Dinocampus coccinellae and its coccinellid host, Coleomegilla maculata; during the behaviour manipulation, the parasitoid is not in contact with its host anymore. We report herein the discovery and characterization of a new RNA virus of the parasitoid (D. coccinellae paralysis virus, DcPV). Using a combination of RT-qPCR and transmission electron microscopy, we demonstrate that DcPV is stored in the oviduct of parasitoid females, replicates in parasitoid larvae and is transmitted to the host during larval development. Next, DcPV replication in the hosts nervous tissue induces a severe neuropathy and antiviral immune response that correlate with the paralytic symptoms characterizing the behaviour manipulation. Remarkably, virus clearance correlates with recovery of normal coccinellid behaviour. These results provide evidence that changes in ladybeetle behaviour most likely result from DcPV replication in the cerebral ganglia rather than by manipulation by the parasitoid. This offers stimulating prospects for research on parasitic manipulation by suggesting for the first time that behaviour manipulation could be symbiont-mediated.

The cost of a bodyguard

Host manipulation by parasites not only captures the imagination but has important epidemiological implications. The conventional view is that parasites face a trade-off between the benefits of host manipulation and their costs to fitness-related traits, such as longevity and fecundity. However, this trade-off hypothesis remains to be tested. Dinocampus coccinellae is a common parasitic wasp of the spotted lady beetle Coleomegilla maculata. Females deposit a single egg in the haemocoel of the host, and during larval development the parasitoid feeds on host tissues. At the prepupal stage, the parasitoid egresses from its host by forcing its way through the coccinellids abdominal segments and begins spinning a cocoon between the ladybirds legs. Remarkably, D. coccinellae does not kill its host during its development, an atypical feature for parasitoids. We first showed under laboratory conditions that parasitoid cocoons that were attended by a living and manipulated ladybird suffered less predation than did cocoons alone or cocoons under dead ladybirds. We then demonstrated that the length of the manipulation period is negatively correlated with parasitoid fecundity but not with longevity. In addition to documenting an original case of bodyguard manipulation, our study provides the first evidence of a cost required for manipulating host behaviour.

Host behaviour manipulation as an evolutionary route towards attenuation of parasitoid virulence

By definition, insect parasitoids kill their host during their development. Data are presented showing that ladybirds not only can survive parasitism by Dinocampus coccinellae, but also can retain their capacity to reproduce following parasitoid emergence. We hypothesize that host behaviour manipulation constitutes a preadaptation leading to the attenuation of parasitoid virulence. Following larval development, the parasitoid egresses from the host and spins a cocoon between the ladybirds legs. Throughout parasitoid pupation, the manipulated host acts as a bodyguard to protect the parasitoid cocoon from predation. The parasitoid has evolved mechanisms to avoid killing the host prematurely so that its own survival is not compromised. Bodyguard manipulation may thus constitute a selective trait for the evolution of true parasitism in some host–parasitoid associations.

A Multi-Approach Study to Delineate Interactions Between Carabid Beetles and Soybean Aphids

ABSTRACT In recent years, the soybean aphid, Aphis glycines Matsumura, has become the most important exotic pest of soybean, Glycine max (L.) Merrill, in North America. Given the significant yield losses that are reported, considerable effort has been expended to characterize the natural enemy community associated with this pest. Several indigenous and naturalized predators have been identified as potential biological control agents, and these include carabid beetles, an abundant and important family of aphid predators. The objectives of this study were to assess the incidence of field predation by Pterostichus melanarius (Illiger), the most common carabid species in Québec soybeans, using molecular gut-content analysis, and to quantify its impact on A. glycines populations through laboratory and field cage experiments. Throughout the growing season between 16.8% (during low aphid density) and 33.7% (at times of high aphid density) of P. melanarius tested positive for aphid DNA. Furthermore, although laboratory feeding trials confirmed that P. melanarius prey on A. glycines, short-term field cage experiments failed to demonstrate a significant reduction of A. glycines populations by carabid beetles. These results suggest a relatively weak interaction between P. melanarius and A. glycines when pest densities are high, but the high predation rate when aphid densities are particularly low suggests these natural enemies may function as important early-season predators.

Bodyguard manipulation in a multipredator context: Different processes, same effect

Parasites have evolved various strategies to exploit hosts to their own advantage. Bodyguard manipulations consist of usurping the behaviour of the host to confer some protection to the parasite and/or its offspring. Dinocampus coccinellae Schrank is a solitary endoparasitoid of the spotted lady beetle Coleomegilla maculata lengi Timberlake. The parasitoid larva grows inside the host until mature, then egresses and spins a cocoon between the ladybirds legs. Unlike most parasitoids, D. coccinellae does not kill its host during development, but keeps the coccinellid partially paralysed on top of the cocoon, where it acts as a bodyguard against natural enemies. As recently shown, the presence of a living ladybird on the parasitoid cocoon provides efficient protection against a predator, lacewing larvae. In the present study, we used predators with different foraging behaviours--jumping spiders and crickets--to explore the relevance of the bodyguard strategy for D. coccinellae in a multipredator context. Although the manner of the protection differs among the different tested predators, the presence of the ladybird always enhances parasitoid survival, even when it first increases detection of the cocoon-ladybird complex, as is the case with jumping spiders. Furthermore, although a dead bodyguard is sufficient to passively defend parasitoid cocoons against crickets, it provides only partial protection against jumping spiders. Altogether, these results support the bodyguard hypothesis in a multipredator context, since the presence of a living coccinellid significantly reduces cocoon predation by predators having different prey specificities, morphologies, and hunting behaviours.

Plasmodium infections and fluctuating asymmetry among children and teenagers from Senegal

Although fluctuating asymmetry is a sensitive indicator of stress, its links with health remains controversial, especially in humans. Here, we explored for the first time the association between fluctuating asymmetry and malaria infections in humans, from 107 participants involved in a long term medical survey in Senegal. No clear relationship was detected. Depending on traits considered, associations were not significant, or (marginally) significant but not in the same directions. We discuss the possible reasons for the global weakness of the signals detected in this study.

Malignant perineurioma (malignant peripheral nerve sheath tumor with perineural differentiation).

The great majority of malignant peripheral nerve sheath tumors (MPNST) exhibit Schwannian differentiation. In recent years, a subset of perineurial MPNST (malignant perineurioma) has been identified based on their histologic, immunohistochemical and ultrastructural features. Immunopositivity for epithelial membrane antigen (EMA), glut-1 and claudin-1, is characteristic. Such tumors must be distinguished from benign perineurioma and a variety of atypical or malignant soft tissue tumors featuring EMA positivity. Herein, we report a perineurial MPNST involving the buttock of a 42-year-old woman. Nerve involvement was noted. The clinicopathologic features of reported examples are ummarized and key differential diagnoses are discussed.

Thrips-induced damage of chrysanthemum inflorescences: evidence for enhanced leakage of carotenoid pigments

The present study quantifies the leakage of carotenoid pigments in senescing inflorescences of chrysanthemum, Dendranthema grandiflora Tzelev (Asteraceae), infested or not with western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). The extractability of pigments was evaluated at repeated intervals by measuring the absorbance of immersion and crude extracts of inflorescences, using 447 nm as a diagnostic wavelength (absorption peak of lutein, a predominant carotenoid pigment in chrysanthemum with yellow inflorescences). The absorbance of immersion extracts increased over time and was higher for inflorescences infested with thrips than control inflorescences; the opposite trends were observed for crude extracts of inflorescences. These results suggest that both natural and thrips‐induced senescence of chrysanthemum inflorescences are characterized by enhanced extractability of pigments in organic solvents, most likely resulting from a disruption of cellular membranes. Thin layer chromatography analysis confirmed the presence of lutein in immersion extracts of thrips‐infested inflorescences, providing further support to the hypothesis that the mechanical damage caused by thrips is linked with a leakage of cellular content. An enhanced extractability of pigments in organic solvents may be a widespread phenomenon characterizing floral senescence in non‐climacteric plants.