Chronic Progressive External Ophthalmoplegia Is Associated with a Novel Mutation in the Mitochondrial tRNA(Asn) Gene

Chronic progressive external ophthalmoplegia (CPEO) is caused by a decreased oxidative phosphorylation (OXPHOS) activity due to large-scale deletions of the mitochondrial genome in 50 % of the patients. The deletions encompass structural OXPHOS genes as well as tRNA genes, required for their expression so that the pathogenesis could be due to the deleted OXPHOS subunits or to an impaired mitochondrial translation. We have analyzed the mitochondrial genome of a patient presenting with CPEO for single base substitutions and discovered a novel heteroplasmic mutation in the tRNAAsn gene at position 5692 that converts a highly conserved adenine into a guanine. This mutation is unique because it is located at the transition of the anticodon loop to the anticodon stem and it leads to an additional base pair, thus reducing the number of loop-forming nucleotides from seven to five. Our findings suggest that CPEO can be caused by a single base substition in a mitochondrial tRNA gene so that the mitochondrial protein synthesis becomes the rate limiting step in OXPHOS fidelity

A dissipated energy comparison to evaluate fatigue resistance using 2PB

Flexural fatigue due to repeated traffic loading is a process of cumulative damage and one of the main failure modes of flexible pavement structures. Typically, micro-cracks originate at the bottom of an asphalt concrete layer due to horizontal tensile strains. Micro-cracking starts to propagate towards the upper layers under repeated loading which can lead to pavement failure. Different approaches are usually used to characterise fatigue resistance in asphalt mixtures including the phenomenological approach, the fracture mechanics approach and the dissipated energy approach. This paper presents a comparison of fatigue resistance calculated for different dissipated energy models using 2 Point Bending (2PB) at IFSTTAR in Nantes. 2PB tests have been undertaken under different loading and environmental conditions in order to evaluate the properties of the mixtures (stiffness, dissipated energy, fatigue life and healing effect)

Première évaluation du risque toxique lié aux cyanobactéries d'eau douce en France : le programme " EFFLOCYA "

Une enquête menée à l'aide d'un questionnaire couvrant l'ensemble du territoire français ainsi que l'étude spécifique d'écosystèmes aquatiques de type lacs et réservoirs ont permis de montrer que les proliférations de cyanobactéries toxiques pouvaient a priori affecter n'importe quel plan d'eau de l'Héxagone. Les genres rencontrés responsables de la production de toxines, le plus souvent hépatiques, sont Microcystis, Planktothrix, Anabœna et Cylindrospermopsis.Les efflorescences peuvent se produire tout au long de l'année car certaines espèces sont adaptées aux eaux froides et elles ne sont pas liées de manière univoque à un état eutrophe de l'écosystème.La production toxinique est la plus élevée lorsque les populations cyanobactériennes sont peu ou pas diversifiées et à la lumière de travaux récents, cette production serait favorisée, en ce qui concerne les microcystines, par un milieu riche en nitrate, pauvre en ammonium et fortement carencé en fer.La suite à donner à ce travail pourrait être la création d'un observatoire national des efflorescences toxiques.An inquiry covering the whole French territory together with specific studies of natural and artificial reservoirs has been made to assess the human health risk related to the prolifération of toxin producing blue green algae (cyanobacteria). The conclusions show that any lentic ecosystem can be affected like it has been shown already in other countries all over the world and more specifically within the EU. The main genus concemed are: Microcystis, Planktothrix, Anabœna and Cylindrospermopsis.Blooms can occur juring the whole year since some species are well adapted to cold water and are not clearly linked with the trophic status of the aquatic ecosystem.The toxinic production is the largest when the cyanobacteria populations contain only a few number of species. The results of recent works are well correlated with our findings which show that the production of toxic heptapeptides (microcystins) could be correlated with high levels of nitrate and depletions of ammonium and iron.The follow up of this work should now include the set up of a national observatory of toxic algal blooms

Fatigue resistance: is it possible having a unique response?

The mechanical characterisation of the asphalt concrete in terms of both the fatigue resistance and the stiffness modulus is necessary to use any design method of the flexible road pavements. Different kinds of test are usually used in experimental work such as bending tests, uniaxial tests, etc., but sometimes they do not give the same answer. In this paper mechanical characterization was carried out by means of fatigue tests undertaken with two most used testing machines for asphalt material: two point bending (2PB) test at IFSTTAR in Nantes (France) and four point bending (4PB) test at University of Palermo, in Palermo (Italy). Different strain controlled tests were undertaken for the same material under the same loading conditions, frequency and temperature (15 Hz and 20˚C), according to the European standard 12697 part 24 and 26. The first results of this interlaboratory activity are showed in this paper