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Université de Fribourg

Host starvation decreases parasite load and mean host size in experimental populations

Pulkkinen, Katja ; Ebert, Dieter

In: Ecology, 2004, vol. 85, p. 823-833

While host stress in vertebrate populations has often been linked to outbreaks of epidemics, which are attributed to the immuno-compromise of the stressed hosts, no predictions have been made about the response of invertebrate host populations to stressful conditions. Experiments conducted on individual invertebrate hosts, however, suggest that starved hosts may be a poor resource for...

Université de Fribourg

An operating cost of learning in Drosophila melanogaster

Mery, Frederic ; Kawecki, Tadeusz J.

In: Animal Behaviour, 2004, vol. 68, p. 589-598

Although the fitness benefits of learning are well understood, we know little about its costs; yet both are essential to understand the evolution of animal learning. We tested the hypothesis that learning has an operating cost, such that an animal repeatedly forced to use its learning ability would show a reduction in some fitness component(s), relative to an animal of the same genotype that does...

Université de Fribourg

Evidence for epistasis: reply to Trouve et al.

Ebert, Dieter ; Salathé, P. ; Kawecki, Tadeusz J.

In: Journal of Evolutionary Biology, 2004, vol. 17, p. 1402-1404

Salathé and Ebert (2003, J. Evol. Biol. 16: 976-985) have shown that the mean logarithmic fitness of Daphnia magna clones declined faster than linearly with increasing inbreeding coefficient F. They interpreted this result as evidence for synergistic epistasis. Trouve et al. (2004, J. Evol. Biol., doi: 10.1111/j.1420-9101.2004.00755.x) suggested that hybrid vigour could be an alternative...

Université de Fribourg

Visual learning in individually assayed Drosophila larvae

Gerber, Bertram ; Scherer, Sabine ; Neuser, K. ; Michels, B. ; Hendel, T. ; Stocker, Reinhard F. ; Heisenberg, M.

In: Journal of Experimental Biology, 2004, vol. 207, p. 179-188

An understanding of associative learning is facilitated if it can be analyzed in a simple animal like the fruit fly Drosophila. Here, we introduce the first visual associative learning paradigm for larval Drosophila; this is remarkable as larvae have an order of magnitude fewer neurons than adult flies. Larvae were subjected to either of two reciprocal training regimes: Light+/Dark- or...

Université de Fribourg

Non-canonical eukaryotic glutaminyl- and glutamyl-tRNA synthetases form mitochondrial aminoacyl-tRNA in Trypanosoma brucei

Rinehart, Jesse ; Horn, Elke K. ; Wei, David ; Söll, Dieter ; Schneider, André

In: Journal of Biological Chemistry, 2004, vol. 279, p. 1161-1166

Glutaminyl-tRNA synthetase is thought to be absent from organelles. Instead, Gln-tRNA is formed via the transamidation pathway, the other route to this essential compound in protein biosynthesis. However, it was previously shown that glutaminyl-tRNA synthetase activity is present in Leishmania mitochondria. This work identifies genes encoding glutaminyl- and glutamyl-tRNA synthetase in the...

Université de Fribourg

Mitochondrial tRNA import in Toxoplasma gondii

Crausaz Esseiva, Anne ; Naguleswaran, Arunasalam ; Hemphill, Andrew ; Schneider, André

In: Journal of Biological Chemistry, 2004, vol. 279, p. 42363-42368

Apicomplexan parasites have the smallest known mitochondrial genome. It consists of a repeated element of ~6–7 kb in length and encodes three mitochondrial proteins, a number of rRNA fragments, but no tRNAs. It has therefore been postulated that in apicomplexans all tRNAs required for mitochondrial translation are imported from the cytosol. To provide direct evidence for this process we have...

Université de Fribourg

Temporal dissection of Bax-induced events leading to fission of the single mitochondrion in Trypanosoma brucei

Crausaz Esseiva, Anne ; Chanez, Anne-Laure ; Bochud-Allemann, Natacha ; Martinou, Jean-Claude ; Hemphill, Andrew ; Schneider, André

In: EMBO reports, 2004, vol. 5, p. 268-273

The protozoan Trypanosoma brucei has a single mitochondrion and lacks an apoptotic machinery. Here we show that expression of the proapoptotic protein Bax in T. brucei causes the release of cytochrome c, the depolarization of the mitochondrial membrane potential and mitochondrial fission. However, in contrast to mammalian cells, the three events are temporally well separated. The release of...

Université de Fribourg

Multiple genetic pathways involving the Caenorhabditis elegans Bloom's syndrome genes him-6, rad-51, and top-3 are needed to maintain genome stability in the germ line

Wicky, Chantal ; Alpi, Arno ; Passannante, Myriam ; Rose, Ann ; Gartner, Anton ; Müller, Fritz

In: Molecular and Cellular Biology, 2004, vol. 24, p. 5016-5027

Bloom's syndrome (BS) is an autosomal-recessive human disorder caused by mutations in the BS RecQ helicase and is associated with loss of genomic integrity and an increased incidence of cancer. We analyzed the mitotic and the meiotic roles of Caenorhabditis elegans him-6, which we show to encode the ortholog of the human BS gene. Mutations in him-6 result in an enhanced irradiation sensitivity, a...

Université de Fribourg

Covariation of mitochondrial genome size with gene lengths: evidence for gene length reduction during mitochondrial evolution

Schneider, André ; Ebert, Dieter

In: Journal of Molecular Evolution, 2004, vol. 59, p. 90-96

Reduction of genome size and gene shortening have been observed in a number of parasitic and mutualistic intracellular symbionts. Reduction of coding capacity is also a unifying principle in the evolutionary history of mitochondria, but little is known about the evolution of gene length in mitochondria. The genes for cytochrome c oxidase subunits I–III, cytochrome b, and the large and small...

Université de Fribourg

The Caenorhabditis elegans ortholog of C21orf80, a potential new protein O-fucosyltransferase, is required for normal development

Menzel, Olivier ; Vellai, Tibor ; Takacs-Vellai, Krisztina ; Reymond, Alexandre ; Müller, Fritz ; Antonarakis, Stylianos E. ; Guipponi, Michel

In: Genomics, 2004, vol. 84, p. 320-330

Down syndrome (DS), as a phenotypic result of trisomy 21, is the most frequent aneuploidy at birth and the most common known genetic cause of mental retardation. DS is also characterized by other phenotypes affecting many organs, including brain, muscle, heart, limbs, gastrointestinal tract, skeleton, and blood. Any of the human chromosome 21 (Hsa21) genes may contribute to some of the DS...