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See detailProduction of alarm pheromone by developing aphids varies in response to their social environment
Verheggen, François ULg; Mescher, Mark; Haubruge, Eric ULg et al

Conference (2008)

Aphid alarm pheromone—the volatile sesquiterpene (E)-β-farnesene (Eβf) in most species—is released in response to predation and other stresses and typically causes nearby aphids who receive the signal to ... [more ▼]

Aphid alarm pheromone—the volatile sesquiterpene (E)-β-farnesene (Eβf) in most species—is released in response to predation and other stresses and typically causes nearby aphids who receive the signal to cease feeding, drop from their host plant, and disperse. Because aphid alarm pheromone confers apparent fitness benefits on recipients while its production and release likely entail costs for the emitting aphid, it could be adaptive for aphids to regulate their Eβf production in response to variation in the social environment. To explore this possibility we compared the production of Eβf by Acyrthosiphon pisum (Harris) individuals reared from first-instar larvae to the adult stage in isolation to that of individuals reared among conspecifics or among individuals of a different aphid species, Myzus persicae (Sulzer). Levels of EβF produced in each treatment were assayed by GC-FID quantification of EβF in volatiles collected from crushed aphids. Production of EβF by A. pisum reared in isolation (14.4ng/aphid) was significantly lower than that of aphids reared in a colony of conspecifics (49.1ng/aphid), reared in a M. persicae colony (31.5ng/aphid) or reared among conspecifics of another aaphid clone (52.7ng/aphid). Though A. pisum individuals in our experiments produced less EβF when reared among M. persicae than among conspecifics, this difference was not statistically significant. In a separate experiment we reared A. pisum individuals in isolation and exposed them to the odor of conspecifics. Under these conditions, EβF production was similar to that of aphids reared among conspecifics, suggesting that aphids use volatile cues to assess their social environment and regulate their production of alarm pheromone accordingly. [less ▲]

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See detailProduction of alarm pheromone in aphids and perception by ants and natural enemies
Verheggen, François ULg

Doctoral thesis (2008)

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm ... [more ▼]

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm behaviours. This PhD thesis aims to better understand how aphids manage their production and emission of alarm pheromone (Chapter IV). We also wanted, in a second step, to improve our knowledge on the roles that Eßf could play in the relationships that aphids have with their predators (Chapter V) and tending ants (Chapter VI), in order to better pinpoint the problem in this very tough context. The aphid predators have indeed a real advantage to be able to use the odorant cues emitted by their prey, to locate them and to select an adequate oviposition site. Ants establish with certain aphid species mutualistic relationships, which occurrence could be facilitated by the use of aphids’ odours. In Chapter IV, we have highlighted that aphid colonies non subjected to attack by predators release constantly small quantities of Eßf in their headspace, which means that this molecule could have additional roles than just acting as an alarm pheromone. In a second study, we demonstrated that the release of Eßf was not contagious, and therefore that a non stressed aphid receiving the alarm signal does not release additional Eßf. Since the production of alarm pheromone is likely to entail physiological cost, we tested and validated the hypothesis that aphids regulate their Eßf production according to their social environment. In Chapter V, we studied the ability of the hoverfly predator Episyrphus balteatus (Diptera, Syrphidae) to be used as biological control agent against aphids infesting tomato plants (Lycopersicon esculentum). After identifying the odours emitted by aphid infested plants, we have demonstrated that although this Diptera is able to perceive all the odours released by the system, it mainly uses Eßf to select its oviposition site. However, the E. balteatus larvae are not adapted to the architecture of tomato plants. We also showed that the Asian ladybeetle Harmonia axyridis (Coleoptera, Coccinellidae) olfaction was adapted to the perception of Eßf and that this beetle is also attracted by this sesquiterpene. Finally, in Chapter VI, we characterized the benefits accruing to aphid populations that have established mutualistic relationships with Lasius niger (Hymenoptera, Formicidae), and have demonstrated the role of Eßf and honeydew, respectively in locating aphid colonies and in the persistence of the mutualism. [less ▲]

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See detailProduction of anionic extracellular polysaccharide by Enterobacter A47 using cheese whey as feedstock
Antunes, S; Alves, V.D.; Grandfils, Christian ULg et al

Conference (2013, September)

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See detailProduction of anti-PMSG antibodies and its relation to the productivity of rabbit does
Lebas, F.; Theau-Clement, M.; Remy, Benoît ULg et al

in World Rabbit Science (1996), 4(2), 57-62

Detailed reference viewed: 25 (4 ULg)
See detailProduction of beta-galactosidase from a thermotolerant yeast strain.
Thonart, Philippe ULg; Baijot, B.; Crahay, V.

in Third European Congress on Biotechnology. Munchen, Federal Republic ofGermany, 10-14 September 1984. Vol. I. (1984)

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See detailProduction of biodegradable polyesters from industrial and agricultural by-products
de Almeida, C.; Calvaheiro, J.; Raposo, R. et al

Conference (2011, September)

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See detailProduction of Biopolymers from Sugar Beet Pulp
Meyer, Laurence ULg; Paquot, Michel ULg; Dubois, Philippe

Poster (2009, May)

Sugar beet pulp is an important by-product of the sugar industry. In order to make the most of this waste, pectin extraction can constitute an economical solution. Pectin is commonly used in food industry ... [more ▼]

Sugar beet pulp is an important by-product of the sugar industry. In order to make the most of this waste, pectin extraction can constitute an economical solution. Pectin is commonly used in food industry as a gelling agent. However, in the present study another use of pectin is considered: its potential embedding into biodegradable polymer films which can further be used in plastic industry. At first, different pectin extraction methods have been developed on sugar beet pulp in order to obtain four different types of pectins characterized at the same time by their molecular weight degree of esterification. Acidic extraction leads to pectin of high molecular weight and high degree of esterification. From this pectin, a de-esterification and a de-polymerization allow us to obtain, respectively, a pectin of high molecular weight and low degree of esterification and a pectin of low molecular weight and high degree of esterification. On the other hand, a basic extraction leads to pectin of low molecular weight and degree of esterification. Preliminary, tests have been conducted on mixes comprising 5, 10, 15, 20 % of commercial pectin and PLA (polylactic acid) or PBAT (Polybutylen-adipate terephtalate). In all cases, the products were not stable and therefore the use of a compatibilizing agent was required. Glycerol and D-Sorbitol were thus studied for that purpose, in mixing ratios between 40-80 % with commercial pectin. The best mechanical properties (Young modulus; yield stress and yield strain) were obtained with the pectin/sorbitol 50/50 mix. This proportion was then used with our different sugar beet pulp extracted pectins to produce PLA/pectin/Sorbitol 50/25/25 formulations. The best mechanical properties were reached with the low molecular weight end degree of esterification pectin. Indeed, the relative small size of this pectin with the lack of esterified groups enables interactions between pectin chains plastified by sorbitol and PLA. These interactions lead to a better cohesion of the high pectic content biomaterial. [less ▲]

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See detailProduction of Bovine Herpesvirus Type 1-Seronegative Latent Carriers by Administration of a Live-Attenuated Vaccine in Passively Immunized Calves
Lemaire, Mylène; Meyer, Gilles; Baranowski, Eric et al

in Journal of Clinical Microbiology (2000), 38(11), 4233-8

The consequences of the vaccination of neonatal calves with the widely used live-attenuated temperature-sensitive (ts) bovine herpesvirus type 1 (BHV-1) were investigated. The ts strain established acute ... [more ▼]

The consequences of the vaccination of neonatal calves with the widely used live-attenuated temperature-sensitive (ts) bovine herpesvirus type 1 (BHV-1) were investigated. The ts strain established acute and latent infections in all vaccinated calves either with or without passive immunity. Four of seven calves vaccinated under passive immunity became clearly BHV-1 seronegative by different serological tests, as did uninfected control calves after the disappearance of maternal antibodies, and they remained so for long periods. A cell-mediated immune response was detected by a BHV-1 gamma interferon assay, but this test failed to detect the seronegative latent carriers (SNLCs). While they are not detected, SNLCs represent a threat for BHV-1-free herds or countries. This study demonstrates that SNLCs can be easily obtained by inoculation with a live-attenuated BHV-1 under passive immunity and that latent carrier animals without any antibody do exist. Consequently, this situation could represent a good model to experimentally produce SNLCs. [less ▲]

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See detailProduction of clusters (up to A=10) during the intranuclear cascade phase of spallation reactions
Cugnon, Joseph ULg; Boudard, A; David, J-C et al

in Proceedings of the Tenth International Topical Meeting on Nuclear Applications of Accelerators (2012)

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See detailProduction of dissolved organic matter by phytoplankton and its uptake by heterotrophic prokaryotes in large tropical lakes
Morana, C; Sarmento, H; Descy, J-P et al

Poster (2014, April 27)

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See detailProduction of dissolved organic matter by phytoplankton and its uptake by heterotrophic prokaryotes in large tropical lakes
Morana, Cédric; Sarmento, Hugo; Descy, Jean-Pierre et al

in Limnology & Oceanography (2014), 59(4), 1364-1375

In pelagic ecosystems, phytoplankton extracellular release can extensively subsidize the heterotrophic prokaryotic carbon demand. Time-course experiments were carried out to quantify primary production ... [more ▼]

In pelagic ecosystems, phytoplankton extracellular release can extensively subsidize the heterotrophic prokaryotic carbon demand. Time-course experiments were carried out to quantify primary production, phytoplankton excretion, and the microbial uptake of freshly released dissolved organic carbon (DOC) derived from phytoplankton extracellular release (DOCp) in four large tropical lakes distributed along a productivity gradient: Kivu, Edward, Albert, and Victoria. The contributions of the major heterotrophic bacterial groups to the uptake of DOCp was also analyzed in Lake Kivu, using microautoradiography coupled to catalyzed reporter deposition fluorescent in situ hybridization. The percentage of extracellular release (PER) varied across the productivity gradient, with higher values at low productivity. Furthermore, PER was significantly related to high light and low phosphate concentrations in the mixed layer and was comparatively higher in oligotrophic tropical lakes than in their temperate counterparts. Both observations suggest that environmental factors play a key role in the control of phytoplankton excretion. Standing stocks of DOCp were small and generally contributed less than 1% to the total DOC because it was rapidly assimilated by prokaryotes. In other words, there was a tight coupling between the production and the heterotrophic consumption of DOCp. None of the major phylogenetic bacterial groups that were investigated differed in their ability to take up DOCp, in contrast with earlier results reported for standard labeled single-molecule substrates (leucine, glucose, adenosine triphosphate). It supports the idea that the metabolic ability to use DOCp is widespread among heterotrophic prokaryotes. Overall, these results highlight the importance of carbon transfer between phytoplankton and bacterioplankton in large African lakes. [less ▲]

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See detailProduction of essential oil by in vitro culture of Anthemis nobilis L. and characterization by GC-MS.
Marlier, M.; Fauconnier, Marie-Laure ULg; Jaziri, M. et al

Poster (1992, September 21)

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See detailProduction of four amyloidogenic variants of human lysozyme as inclusion bodies in Escherichia coli
Dumont, Janice ULg; Menzer, Linda ULg; Scarafone, Natacha ULg et al

Poster (2009)

Six variants of human lysozyme (I56T, F57I, W64R, D67H, F57I/T70N and W112R/T70N) are associated with a hereditary non-neuropathic systemic amyloidosis. This disease involved an extra cellular deposition ... [more ▼]

Six variants of human lysozyme (I56T, F57I, W64R, D67H, F57I/T70N and W112R/T70N) are associated with a hereditary non-neuropathic systemic amyloidosis. This disease involved an extra cellular deposition of amyloid fibrils made of lysozyme variants in a wide range of organs such as liver, spleen and kidneys [1]. The characterisation at the molecular level of two variants, I56T and D67H, has shown that these mutations reduce the stability and more particularly the global cooperativity of the protein. Consequently, under physiologically relevant conditions, these variants can transiently populate a partially unfolded state in which the beta-domain and the C-helix are cooperatively unfolded while the rest of the protein remains native like [1]. The formation of intermolecular interactions between the regions that are unfolded in this intermediate state is likely to be a fundamental trigger of the aggregation process that ultimately leads to the formation and deposition of fibrils in tissues. In order to study the effects of the other amyloidogenic mutations on the properties of lysozyme and thus to get more insight in the mechanism of amyloid formation, it is necessary to produce them in large quantities. The D67H, I56T and F57I variants are currently produced in Aspergillus niger; the expression in this organism is, however, time consuming and the yield is very low. The attempts to use alternative systems such as Pichia pastoris [2], Saccharomyces cerevisiae, and Arabidopsis thaliana have not been conclusive so far. In this work, we have produced the four single-point lysozyme variants as inclusion bodies in Escherichia coli and explored the possibility to refold them. [1] Dumoulin & al., (2006) Acc. Chem. Res., 39, 603 - 610 [2] Kumita & al., (2006) FEBS J., 273, 711-720 [less ▲]

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See detailProduction of free radicals and oxygen consumption by primary equine endothelial cells during anoxia-reoxygenation.
de la Rebière de Pouyade, Geoffroy ULg; Salciccia, Alexandra ULg; Ceusters, Justine ULg et al

in Open Biochemistry Journal (The) (2011), 5

The endothelium plays an active role in ischemia/reperfusion injuries. Herein, we report the effect of a single or successive cycles of anoxia/reoxygenation (A/R) on the mitochondrial respiratory function ... [more ▼]

The endothelium plays an active role in ischemia/reperfusion injuries. Herein, we report the effect of a single or successive cycles of anoxia/reoxygenation (A/R) on the mitochondrial respiratory function of equine endothelial cells (cultured from carotids) monitored by high resolution oxymetry, and on their production of reactive oxygen species (ROS). ROS were measured by electron paramagnetic resonance (ESR) using POBN and DMPO spin traps, and by gas chromatography (GC) of ethylene released by ROS-induced alpha-keto-gamma-(methylthio)butyric acid (KMB) oxidation. The oxygen consumption significantly decreased with the number of A/R cycles, and POBN-ESR spectra were specific of adducts formed in the cells from superoxide anion. After a one-hour A/R cycle, high intensity DMPO-ESR spectra were observed and assigned to superoxide anion trapping; the GC results confirmed an important production of ROS compared to normoxic cells. These results show that A/R induces mitochondrial alterations in endothelial cells, and strongly stimulates their oxidative activity as demonstrated by ESR and GC methods. [less ▲]

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See detailProduction of freeze-dried lactic acid bacteria starter culture for cassava fermentation into gari.
Yao, Amenan Anastasie ULg; Dortu, Carine; Egounlety, Moutairu et al

in African Journal of Biotechnology (2009), 8(19), 4996-5004

Sixteen lactic acid bacteria, eight Lactobacillus plantarum, three L. pentosus, 2 Weissella paramesenteroides, two L. fermemtum and one Leuconostoc mesenteroides ssp. mesenteroides were previously ... [more ▼]

Sixteen lactic acid bacteria, eight Lactobacillus plantarum, three L. pentosus, 2 Weissella paramesenteroides, two L. fermemtum and one Leuconostoc mesenteroides ssp. mesenteroides were previously isolated from cassava fermentation and selected on the basis of their biochemical properties with a view to selecting appropriate starter cultures during cassava fermentation for gari production. In this study, the potential of these pre-selected strains as suitable freeze-dried cultures was evaluated. Their ability to tolerate the freeze-drying process was assessed by dehydration in a glycerol solution of increasing concentration, followed by staining with two fluorescent markers: rhodamine 123 and propydium iodide. Twelve strains that recovered more than 50% of their population value after visualisation on an epi-fluorescent microscope were produced in a bioreactor and freeze-dried. The technological characteristics identified after the freeze-drying process, were a high cell concentration or high survival rate. The ability of the freeze-dried strains to recover their acidification activity was evaluated through the determination of the pH, titratable acidity (% lactic acid/g Dry Weight) and cell count over 24 h on MRS broth. Ultimately, the strains L. plantarum VE36, G2/25, L. fermentum G2/10 and W. paramesenteroides LC11 were selected to be developed as freeze-dried starter cultures for gari production. [less ▲]

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See detailProduction of glycerol by immobilized Saccharomyces cerevisiae in stirred bioreactor.
Destain, Jacqueline ULg; Renault, M.; Rikir, R. et al

Poster (1990, July)

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See detailProduction of heavy clusters (up to A=10) by coalescence during the intranuclear cascade phase of spallation reactions
Cugnon, Joseph ULg; Boudard, A; David, J-C et al

in J. Phys.: Conf. Ser. (2011), 312

Detailed reference viewed: 5 (0 ULg)