Cours de médecine

2023, Carla Vázquez-González, Violeta Quiroga, Lucía Martín-Cacheda, Rasmann, Sergio, Röder, Gregory, Luis Abdala-Roberts, Xoaquín Moreira

Herbivore-damaged plants emit volatile organic compounds (VOCs) that can alert neighbours and boost their resistance. While VOC-mediated plant communication has been shown to be herbivore-specific, we know little about its contingency on variation in herbivore load. To address this knowledge gap, we tested herbivore load effects on VOC-mediated communication between potato plants (Solanum tuberosum) using the generalist herbivore Spodoptera exigua. First, we tested whether herbivore load (three levels: undamaged control, low, and high load) affected total VOC emissions and composition. Second, we matched emitter and receiver plants and subjected emitters to the same herbivore load treatments. Finally, we performed a bioassay with S. exigua on receivers to test for induced resistance due to VOC-mediated communication. We found that herbivory significantly increased total VOC emissions relative to control plants, and that such increase was greater under high herbivore load. In contrast, we found no detectable effect of herbivory, regardless of the load, on VOC composition. The communication experiment showed that VOCs released by herbivore-induced emitters boosted resistance in receivers (i.e., lower leaf damage than receivers exposed to VOCs released by control emitters), but the magnitude of such effect was similar for both levels of emitter herbivore load. These findings suggest that changes in VOCs due to variation in herbivore load do not modify the outcomes of plant communication.

2012, Heng-Yu, L., Théron, R, Röder, Gregory, Turlings, Ted, Lange, R.F.M., Ballif, C., Perret-Aebi, L.-E.

Appropriate encapsulation schemes are essential in protecting the active components of the photovoltaic (PV) module against weathering and to ensure long term reliability. For crystalline cells, poly(ethylene-co-vinyl acetate) (EVA) is the most commonly used PV encapsulant. Additives like peroxides and silanes are formulated in EVA encapsulants to obtain the desired properties, e.g. the desired gel content value and sufficient adhesion after the encapsulation process etc. The identification and control of volatile organic compounds (VOCs) released by the polymeric encapsulant during PV module encapsulation is important for understanding and optimizing processes in order to enhance the encapsulation quality of the manufactured modules. The authors demonstrate how gas chromatography and mass spectrometry (GC-MS) techniques can be used to help understand the curing process, mainly by identifying the VOCs emanating from EVA under the effect of temperature and pressure. The results provide chemical insights into the EVA encapsulation process, which are valuable for further optimisation of the PV module manufacturing process and evaluation of its environmental impact. 26 Refs.

2001, Bischoff, Alexander, Loutan, Louis, Stalder, Hans

Wie steht es mit der Verantwortung, sich mit dem Gesprächspartner communis – «gemein» – zu machen, wenn der fremdsprachig ist? Wie wird die Verantwortung für die Kommunikation wahrgenommen, wenn Sprachbarrieren bestehen? Und wie sieht diese Verantwortung im Gesundheitsbereich aus? Im Universitätsspital Genf wurde dies im Rahmen eines Pflegequalitäts-Projektes untersucht. Die Studie zeigt, dass Französisch nur in 36% aller Fälle die Muttersprache der Patienten war, welche die medizinische Poliklinik während zwei Monaten (1999) aufsuchten. Zudem sprach mehr als ein Drittel der Patienten, entsprechend den Angaben der Ärzte, nicht fliessend französisch. Die Auswertung der von Patienten und Ärzten ausgefüllten Fragebogen ergab folgende Resultate: Fremdsprachige Patienten bewerteten die Kommunikation in der Sprechstunde dann am besten, wenn ein qualifizierter Dolmetscher zugegen war, weniger gut, wenn auf eine Drittsprache ausgewichen wurde, und noch weniger gut, wenn Patientenangehörige Ad-hoc-Übersetzungsdienste verrichteten. Auf der Ärzteseite wird die Kommunikation mit französisch sprechenden Patienten durchwegs besser bewertet. Was die Kommunikation mit fremdsprachigen Patienten angeht, werden oft höhere Bewertungen der Kommunikation angegeben, wenn der Arzt allein dem Patienten gegenübersitzt (d.h. also eine «Verkehrsprache» benützt), im Durchschnitt jedenfalls höher als wenn ein Dolmetscher anwesend ist. Am wenigsten gut kam auch hier, und zwar mit weit grösseren Unterschieden, die Kommunikation mittels Angehöriger weg. Die Zufriedenheit der Ärzte mit den qualifizierten Dolmetschern war sehr gross (8,8 im Durchschnitt, bei einer Skala von 1-10).

2014-4, Röder, Gregory, Canestrari, Daniela, Bolopo, Diana, Marcos, José M., Villard, Neil, Baglione, Vittorio, Turlings, Ted

The great spotted cuckoo (Clamator glandarius) is an important brood parasite of carrion crows (Corvus corone corone) in northern Spain. We recently found that, unlike what is commonly known for cuckoo-host interactions, the great spotted cuckoo has no negative impact on average crow fitness in this region. The explanation for this surprising effect is a repulsive secretion that the cuckoo chicks produce when they are harassed and that may protect the brood against predation. Here, we provide details on the chemical composition of the cuckoo secretion, as well as conclusive evidence that the dominating volatile chemicals in the secretion are highly repellent to model species representative of common predators of the crows. These results support the notion that, in this particular system, the production of a repulsive secretion by the cuckoo chicks has turned a normally parasitic interaction into a mutualistic one.

2007, Röder, Gregory, Rahier, Martine, Naisbit, Russell. E.

Adaptation to different hosts plays a central role in the evolution of specialization and speciation in phytophagous insects and parasites, and our ability to experimentally rank hosts by their quality is critical to research to understand these processes. Here we provide a counter-intuitive example in which growth is faster on poor quality hosts. The leaf beetles Oreina elongata and Oreina cacaliae share their host plant with the rust Uromyces cacaliae. Larvae reared on infected Adenostyles alliariae show reduced growth rate, reduced maximum weight and longer development time. However, they normally respond adaptively to the rust's mid-season arrival. When switched during development from healthy to infected leaves, larvae accelerate growth and reduce development time, but pupate at lower body weight. In this novel plant–insect–fungus interaction, infection forms the cue to trade off life-history traits in order to complete development within the brief alpine summer. It represents a novel mode of developmental plasticity, which is likely to be found in other host–parasite systems whenever host quality deteriorates due to multiple infection or ageing. This phenotypic plasticity would modify competition after co-infection and the mutual selection imposed by hosts and parasites, and creates a paradoxical negative correlation between growth rate and environmental quality.

2008, Bischoff, Alexander, Dahinden, Janine

2016-1, Norghauer, Julian M., Röder, Gregory, Glauser, Gaëtan

Small mammals can impede tree regeneration by injuring seedlings and saplings in several ways. One fatal way is by severing their stems, but apparently this type of predation is not well-studied in tropical rain forest. Here, we report on the incidence of stem-cutting' to new, wild seedlings of two locally dominant, canopy tree species monitored in 40 paired forest understorey and gap-habitat areas in Korup, Cameroon following a 2007 masting event. In gap areas, which are required for the upward growth and sapling recruitment of both species, 137 seedlings of the long-lived, light-demanding, fast-growing large tropical tree (Microberlinia bisulcata) were highly susceptible to stem-cutting (83% of deaths) it killed 39% of all seedlings over a c. 2-y period. In stark contrast, seedlings of the more shade-tolerant, slower-growing tree species (Tetraberlinia bifoliolata) were hardly attacked (4.3%). In the understorey, however, stem-cutting was virtually absent. Across the gap areas, the incidence of stem-cutting of M. bisulcata seedlings showed significant spatial variation that could not be explained significantly by either canopy openness or Janzen-Connell type effects (proximity and basal area of conspecific adult trees). To examine physical and chemical traits that might explain the species difference to being cut, bark and wood tissues were collected from a separate sample of seedlings in gaps (i.e. not monitored for stem-cutting). These analyses suggested that, compared with T. bifoliolata, the lower stem density, higher Mg and K and fatty acid concentrations in bark, and fewer phenolic and terpene compounds in M. bisulcata seedlings made them more palatable and attractive to small-mammal predators, likely rodents. We conclude that selective stem-cutting is a potent countervailing force to the current local canopy dominance of the grove-forming M. bisulcata by limiting the recruitment and abundance of its saplings. Given the ubiquity of gaps and ground-dwelling rodents in pantropical forests, it would be surprising if this form of lethal browsing was restricted to Korup.

2010, Dahinden, Janine, Bischoff, Alexander, Dahinden, Janine, Bischoff, Alexander

2014-7-21, Gotlieb, Ariella, Pisanty, Gideon, Rozen, Jerome G, Gideon, Mueller, Andreas, Röder, Gregory, Sedivy, Claudio, Praz, Christophe

Herein we describe the nests (including structure, closure, orientation, and depth of cells) of the bee Haetosmia vechti Peters found nesting in Rehovot, Israel. The nesting biology of H. vechti mirrors the ancestral nesting biology within the Osmia group of the Osmiini. Nests in sandy soil consist of an excavated burrow, ending below in a small cluster of vertical cells. The cells possess firm walls of masticated leaf pulp of Centaurea procurrens Spreng. and Heliotropium suaveolens M. Bieb., and are covered with pebbles and sand grains. The last larval instar and pupa of Haetosmia vechti are described, as is its cocoon. The "immature stages exhibit the basic features of megachilid bees, but tend to have a thinner body vestiture compared to other studied taxa. In addition, we report new information on and review published accounts concerning the pollen collecting behavior of the genus Haetosmia Popov, which contains three species. Pollen taken from scopal hairs of 68 females collected at 17 sites in Turkestan, Morocco, Israel, and the United Arab Emirates was identified as originating solely from Heliotropium L. (Boraginaceae), which strongly suggests that all three Haetosmia species are narrowly oligolectic on this plant genus. In females of all three species, the second segment of the labial palpus is densely covered with rather long, apically curved and capitate bristles, an adaptation to collect Heliotropium pollen from anthers that are hidden inside the narrow corolla tube. Similar pollen-harvesting bristles specifically adapted to exploit flowers of He/iotropium seem to have evolved independently a number of times on different continents, in bees of four families.

2019-3-28, Xu, Hao, Dötterl, Stefan, Zhou, Guoxin, Schäffler, Irmgard, von Arx, Martin, Röder, Gregory, Degen, Thomas, Chen, Li, Turlings, Ted

Gregarious parasitoids usually clump their cocoons together and the adults emerge in a synchronized fashion. This makes it easy for them to find mating partners and most copulations indeed take place at the natal patch. Yet, males should leave such sites when females are no longer receptive. As yet, this decision-making process and the possible involvement of pheromones were poorly understood. Here we report on a remarkable use of attractive and repellent pheromones of the well-studied gregarious parasitoid species Cotesia glomerata (L.) (Hymenoptera: Braconidae). Virgin C. glomerata females were found to release an attractive as well as a repellent compound, which in combination arrest males on the natal patch, but after mating the females stop the production of the attractant and the males are repelled. The repellent compound was identified as heptanal, which was also released by males, probably reducing male-male competition on the natal patch. We also confirmed that the sex ratio of the emerging wasps can vary considerably among patches, depending on the relative quality of hosts and the number of females that parasitize a host. The newly revealed use of attractive and repellent pheromone compounds by C. glomerata possibly helps maximize mating success under these variable conditions.