Cantor Spectrum for Schr\"odinger Operators with Potentials arising from Generalized Skew-shifts

We consider continuous $SL(2,\mathbb{R})$-cocycles over a strictly ergodic homeomorphism which fibers over an almost periodic dynamical system (generalized skew-shifts). We prove that any cocycle which is not uniformly hyperbolic can be approximated by one which is conjugate to an $SO(2,\mathbb{R})$-cocycle. Using this, we show that if a cocycle's homotopy class does not display a certain obstruction to uniform hyperbolicity, then it can be $C^0$-perturbed to become uniformly hyperbolic. For cocycles arising from Schr\"odinger operators, the obstruction vanishes and we conclude that uniform hyperbolicity is dense, which implies that for a generic continuous potential, the spectrum of the corresponding Schr\"odinger operator is a Cantor set.Comment: Final version. To appear in Duke Mathematical Journa

Mechanisms of escape phenomenon of spinal cord and brainstem in human rabies

BACKGROUND: Rabies virus preferentially involves brainstem, thalamus and spinal cord in human furious and paralytic rabies beginning in the early stage of illness. Nevertheless, rabies patient remains alert until the pre-terminal phase. Weakness of extremities develops only when furious rabies patient becomes comatose; whereas peripheral nerve dysfunction is responsible for weakness in paralytic rabies. METHODS: Evidence of apoptosis and mitochondrial outer membrane permeabilization in brain and spinal cord of 10 rabies patients was examined and these findings were correlated with the presence of rabies virus antigen. RESULTS: Although apoptosis was evident in most of the regions, cytochrome c leakage was relatively absent in spinal cord of nearly all patients despite the abundant presence of rabies virus antigen. Such finding was also noted in brainstem of 5 patients. CONCLUSION: Cell death in human rabies may be delayed in spinal cord and the reticular activating system, such as brainstem, thus explaining absence of weakness due to spinal cord dysfunction and preservation of consciousness

Specific detection of Salmonella enterica and Escherichia coli strains by using ELISA with bacteriophages as recognition agents

The use of bacteriophages, instead of antibodies, in the ELISA-based detection of bacterial strains was tested. This procedure appeared to be efficient, and specific strains of Salmonella enterica and Escherichia coli could be detected. The sensitivity of the assay was about 105 bacterial cells/well (106/ml), which is comparable with or outperforms other ELISA tests detecting intact bacterial cells without an enrichment step. The specificity of the assay depends on the kind of bacteriophage used. We conclude that the use of bacteriophages in the detection and identification of bacteria by an ELISA-based method can be an alternative to the use of specific antibodies. The advantages of the use of bacteriophages are their environmental abundance (and, thus, a possibility to isolate various phages with different specificities) and the availability of methods for obtaining large amounts of phage lysates, which are simple, rapid, cheap, and easy

Validation of the OECD reproduction test guideline with the New Zealand mudsnail Potamopyrgus antipodarum using trenbolone and prochloraz

The Organisation for Economic Cooperation and Development (OECD) provides several standard test methods for the environmental hazard assessment of chemicals, mainly based on primary producers, arthropods, and fish. In April 2016, two new test guidelines with two mollusc species representing different reproductive strategies were approved by OECD member countries. One test guideline describes a 28-day reproduction test with the parthenogenetic New Zealand mudsnail Potamopyrgus antipodarum. The main endpoint of the test is reproduction, reflected by the embryo number in the brood pouch per female. The development of a new OECD test guideline involves several phases including inter-laboratory validation studies to demonstrate the robustness of the proposed test design and the reproducibility of the test results. Therefore, a ring test of the reproduction test with P. antipodarum was conducted including eight laboratories with the test substances trenbolone and prochloraz and results are presented here. Most laboratories could meet test validity criteria, thus demonstrating the robustness of the proposed test protocol. Trenbolone did not have an effect on the reproduction of the snails at the tested concentration range (nominal: 10-1000 ng/L). For prochloraz, laboratories produced similar EC10 and NOEC values, showing the inter-laboratory reproducibility of results. The average EC10 and NOEC values for reproduction (with coefficient of variation) were 26.2 µg/L (61.7%) and 29.7 µg/L (32.9%), respectively. This ring test shows that the mudsnail reproduction test is a well-suited tool for use in the chronic aquatic hazard and risk assessment of chemicals

Irradiation accidentelle et reconstitution lymphocytaire T : données récentes et perspectives

Les lymphocytes T sont l'une des populations les plus radiosensibles de l'organisme. La reconstitution des lymphocytes T est lente, et des déficits quantitatifs et qualitatifs apparaissent à long terme chez les personnes irradiées. Les mécanismes de la reconstitution lymphocytaire T sont mal connus, et en particulier le rôle joué par le thymus dans cette reconstitution reste peu clair. Le thymus est l'organe lymphode primaire dans lequel se différencie l'ensemble des populations lymphocytaires T durant la vie foetale et post-natale. Le thymus a été considéré pendant longtemps comme étant inactif à l'age adulte. Cependant, des données récentes montrent que le thymus reste, au moins en partie, fonctionnel à l'age adulte. Ceci suggère un rôle important du thymus dans l'homostasie des populations lymphocytaires T, mais aussi dans la reconstitution des lymphocytes T aprés irradiation, y compris à l'age adulte. Par ailleurs, des études récentes révèlent que les effets des rayonnements ionisants sont, au moins en partie, responsables des déficits quantitatifs des lymphocytes T observés à long terme après irradiation. Ces données montrent la nécessité de poursuivre l'étude des effets des rayonnements ionisants sur le thymus, en particulier par la recherche de bio-indicateurs du fonctionnement du thymus en situation physiologique normale, mais aussi en situation physiopathologique d'irradiation accidentelle

Bio-indicateurs potentiels d'atteinte multi-organe : application au cas des victimes d'irradiation accidentelles

Accidental irradiations induce a complex pathological situation, difficult to assess and to treat. However, recent results describing new biological indicators of radiation-induced damages such as Flt3-ligand, citrulline and oxysterol concentration in the plasma, together with results obtained in large animal models of high dose irradiation, allowed a better understanding of pathophysiological mechanisms induced by uncontrolled irradiations. This conducted to leave the classical paradigm of the acute radiation syndrome, described as the association of three individual syndromes, the hematopoietic syndrome, the gastro-intestinal syndrome and the cerebrovascular syndrome, in favour of a multiple organ dysfunction syndrome, with the implication of other organs and systems. Follow-up of victims from two recent radiation accidents brings a confirmation of the usefulness of the newly described biological indicators, and also a partial confirmation of this new concept of a multiple organ dysfunction syndrome. © 2009 Elsevier Masson SAS. All rights reserved.Les irradiations accidentelles conduisent à des situations pathologiques complexes, difficiles à évaluer et à traiter. Cependant, des résultats récents ont permis de définir de nouveaux bio-indicateurs de dommages radio-induits comme le Flt3-ligand, la citrulline ou les oxystérols plasmatiques. Par ailleurs, des études sur des modèles animaux ont permis une évolution de la compréhension des mécanismes physiopathologiques des irradiations complexes à forte dose. Cette évolution conduit à abandonner le concept de syndrome aigu d’irradiation comme étant une association de trois syndromes bien individualisés, le syndrome hématopoïétique, le syndrome gastro-intestinal et le syndrome cérébrovasculaire au profit d’un concept de syndrome de dysfonctionnement multi-organes, avec l’implication d’autres systèmes physiologiques. Le suivi des victimes de deux accidents d’irradiation récents a permis de confirmer la validité des nouveaux bio-indicateurs utilisés, mais a apporté aussi un début de confirmation de ce concept de syndrome de dysfonctionnement multi-organes induit par une irradiation accidentelle

Modifications of Cerebral Cholesterol Metabolism in Rats Following Internal Contamination by Depleted Uranium

The occurrence of uranium in the environment results from both natural and human origins. Its enrichment in nuclear power plants produces two compounds: enriched uranium (EU) and depleted uranium (DU). The dispersion of uranium in the environment sets human populations at risk of being contaminated mainly through ingestion. After entering the body, uranium builds up in several organs including the brain, where it can induce behaviour disorders after chronic contamination. Brain is the most lipidic organ of the body: half of its weight is due to phospholipids and it contains about 25% of the bodys cholesterol. Cholesterol is essential to brain function due to its various roles, ranging from membrane structure and myelin sheath constitution to synthesis of active molecules such as neurosteroids. Moreover, it is well known that some disruptions in cholesterol metabolism are involved in neurological pathologies, such as Alzheimers disease or Niemann-Pick C disease. Considering the importance of cerebral cholesterol and the susceptibility of brain to uranium exposure, we studied the effect of uranium contamination on cerebral cholesterol metabolism. Therefore, rats were exposed during 9 months to DU through drinking water at a concentration of 40 mg/l (twice the highest environmental level, equivalent to 1 mg/rat/day). After DU contamination, the HDL-cholesterol level in plasma decreased (25%) whereas plasma level of 27-hydroxycholesterol increased (200%). The mRNA levels of several proteins involved in cerebral cholesterol metabolism were modified. Gene expression of CYP46A1, involved in cholesterol catabolism, was increased by 39%. HMGCoA Synthase (HMGS) mRNA levels rose from 91%. Gene expression of three proteins involved in cholesterol transport was also modified: SR-B1 (+34%), ABC A1 (+34%) and Apo E (+75%). Finally, mRNA levels of nuclear receptors PPAR? and PPAR? were increased (46% and 36% respectively). Conversely, gene expression of RXR was reduced by 29%. DU contamination enhances at the same time pathways that increase the cholesterol pool in the cell (uptake and synthesis) and pathways that lead cholesterol out of the cell (detoxification and efflux). This would lead to an overall balanced cholesterol pool in the brain: whatever pathways are primarily altered by DU, the compensatory pathways are also activated. Besides, it is noteworthy that the modification of HDL-cholesterol and 27-hydroxycholesterol plasma levels might foreshadow a disruption of cholesterol metabolism at body level