Showing papers by "Aix-Marseille University published in 2006"

Accurate photometric redshifts for the CFHT legacy survey calibrated using the VIMOS VLT deep survey

Abstract: We present photometric redshifts for an uniquely large and deep sample of 522286 objects with i'_{AB}<25 in the Canada-France Legacy Survey ``Deep Survey'' fields, which cover a total effective area of 3.2 deg^2. We use 3241 spectroscopic redshifts with 0

Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum

Abstract: The Palaeocene/Eocene thermal maximum, ~55 million years ago, was a brief period of widespread, extreme climatic warming1, 2, 3, that was associated with massive atmospheric greenhouse gas input4. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition5. We show that sea surface temperatures near the North Pole increased from ~18 °C to over 23 °C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations6, but the absolute polar temperatures that we derive before, during and after the event are more than 10 °C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms—perhaps polar stratospheric clouds7 or hurricane-induced ocean mixing8—to amplify early Palaeogene polar temperatures.

Discovery of an RNA virus 3'->5' exoribonuclease that is critically involved in coronavirus RNA synthesis

Abstract: Replication of the giant RNA genome of severe acute respiratory syndrome (SARS) coronavirus (CoV) and synthesis of as many as eight subgenomic (sg) mRNAs are mediated by a viral replicase-transcriptase of outstanding complexity that includes an essential endoribonuclease activity. Here, we show that the CoV replicative machinery, unlike that of other RNA viruses, also uses an exoribonuclease (ExoN) activity, which is associated with nonstructural protein (nsp) 14. Bacterially expressed forms of SARS-CoV nsp14 were shown to act on both ssRNAs and dsRNAs in a 3′→5′ direction. The activity depended on residues that are conserved in the DEDD exonuclease superfamily. The protein did not hydrolyze DNA or ribose-2′-O-methylated RNA substrates and required divalent metal ions for activity. A range of 5′-labeled ssRNA substrates were processed to final products of ≈8–12 nucleotides. When part of dsRNA or in the presence of nonlabeled dsRNA, the 5′-labeled RNA substrates were processed to significantly smaller products, indicating that binding to dsRNA in cis or trans modulates the exonucleolytic activity of nsp14. Characterization of human CoV 229E ExoN active-site mutants revealed severe defects in viral RNA synthesis, and no viable virus could be recovered. Besides strongly reduced genome replication, specific defects in sg RNA synthesis, such as aberrant sizes of specific sg RNAs and changes in the molar ratios between individual sg RNA species, were observed. Taken together, the study identifies an RNA virus ExoN activity that is involved in the synthesis of multiple RNAs from the exceptionally large genomic RNA templates of CoVs.

Search for neutral MSSM Higgs bosons at LEP

Abstract: The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric standard model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of “benchmark” models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter cosβ and, in some scenarios, on the masses of neutral Higgs bosons.

The upgraded DØ detector

Abstract: The D0 experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to D0.

SRPX2 mutations in disorders of language cortex and cognition

Abstract: The rolandic and sylvian fissures divide the human cerebral hemispheres and the adjacent areas participate in speech processing. The relationship of rolandic (sylvian) seizure disorders with speech and cognitive impairments is well known, albeit poorly understood. We have identified the Xq22 gene SRPX2 as being responsible for rolandic seizures (RSs) associated with oral and speech dyspraxia and mental retardation (MR). SRPX2 is a secreted sushi-repeat containing protein expressed in neurons of the human adult brain, including the rolandic area. The disease-causing mutation (N327S) resulted in gain-of-glycosylation of the secreted mutant protein. A second mutation (Y72S) was identified within the first sushi domain of SRPX2 in a male with RSs and bilateral perisylvian polymicrogyria and his female relatives with mild MR or unaffected carrier status. In cultured cells, both mutations were associated with altered patterns of intracellular processing, suggesting protein misfolding. In the murine brain, Srpx2 protein expression appeared in neurons at birth. The involvement of SRPX2 in these disorders suggests an important role for SRPX2 in the perisylvian region critical for language and cognitive development.

The origin and evolution of Archaea: a state of the art

Abstract: Environmental surveys indicate that the Archaea are diverse and abundant not only in extreme environments, but also in soil, oceans and freshwater, where they may fulfil a key role in the biogeochemical cycles of the planet. Archaea display unique capacities, such as methanogenesis and survival at temperatures higher than 90 °C, that make them crucial for understanding the nature of the biota of early Earth. Molecular, genomics and phylogenetics data strengthen Woese's definition of Archaea as a third domain of life in addition to Bacteria and Eukarya. Phylogenomics analyses of the components of different molecular systems are highlighting a core of mainly vertically inherited genes in Archaea. This allows recovering a globally well-resolved picture of archaeal evolution, as opposed to what is observed for Bacteria and Eukarya. This may be due to the fact that no rapid divergence occurred at the emergence of present-day archaeal lineages. This phylogeny supports a hyperthermophilic and non-methanogenic ancestor to present-day archaeal lineages, and a profound divergence between two major phyla, the Crenarchaeota and the Euryarchaeota, that may not have an equivalent in the other two domains of life. Nanoarchaea may not represent a third and ancestral archaeal phylum, but a fast-evolving euryarchaeal lineage. Methanogenesis seems to have appeared only once and early in the evolution of Euryarchaeota. Filling up this picture of archaeal evolution by adding presently uncultivated species, and placing it back in geological time remain two essential goals for the future.

Role of SGT1 in resistance protein accumulation in plant immunity

Abstract: A highly conserved eukaryotic protein SGT1 binds specifically to the molecular chaperone, HSP90. In plants, SGT1 positively regulates disease resistance conferred by many Resistance (R) proteins and developmental responses to the phytohormone, auxin. We show that silencing of SGT1 in Nicotiana benthamiana causes a reduction in steady-state levels of the R protein, Rx. These data support a role of SGT1 in R protein accumulation, possibly at the level of complex assembly. In Arabidopsis, two SGT1 proteins, AtSGT1a and AtSGT1b, are functionally redundant early in development. AtSGT1a and AtSGT1b are induced in leaves upon infection and either protein can function in resistance once a certain level is attained, depending on the R protein tested. In unchallenged tissues, steady-state AtSGT1b levels are at least four times greater than AtSGT1a. While the respective tetratricopeptide repeat (TPR) domains of SGT1a and SGT1b control protein accumulation, they are dispensable for intrinsic functions of SGT1 in resistance and auxin responses.

Drilling to gabbro in intact ocean crust

Abstract: Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.

A 12-28-year followup study of closing wedge high tibial osteotomy

Abstract: Current indications for high tibial osteotomy (HTO) are controversial although several risk factors have been associated with HTO survival. We ascertained the influence of preoperative variables in a consecutive series of patients who had closing wedge HTO at a minimum of 12 year followup (mean 18-year, range 12 to 28 years). Three hundred one of an initial 372 high tibial osteotomies (313 patients) were included (81% followup); 71 knees were eliminated because patients died (30 knees) or were lost to followup (41 knees). The mean age was 42 years (range, 15-76 years), 194 were men and 119 were women. The osteotomy was fixed by a Blount staple and an AO half-tube plate with three screws. Forty-three knees (14%) in 39 patients were revised for progression of osteoarthritis at an average of 102 months. Survival was 85% at 20 years with revision as the endpoint. Knee function was considered satisfactory by 77% of patients. At final followup, 1/2 of the knees showed radiographic signs of medial osteoarthritis. The most important risk factors predicting revision were age greater than 50 years and a preoperative arthritis Ahlback grade of 3 or more.

The desert of Tataouine: an extreme environment that hosts a wide diversity of microorganisms and radiotolerant bacteria

Abstract: The phylogenetic diversity of prokaryotic communities exposed to arid conditions in the hot desert of Tataouine (south Tunisia) was estimated with a combination of a culture and – molecular-based analysis. Thirty-one isolates, representative of each dominant morphotypes, were affiliated to Actinobacteria , Firmicutes , Proteobacteria and the CFB group while none related to Archaea. Analysis of 16S rRNA gene libraries revealed the presence of species related to Bacteria and Archaea . Sequences related to Archaea were all affiliated to the non-thermophilic Crenarchaeota subgroup. Bacterial sequences were dominated by Proteobacteria , Actinobacteria and Acidobacteria ; a few sequences were distributed among eight others phyla, including Thermus/Deinococcus relatives. A correlation between tolerance to desiccation and to radiation has been demonstrated for the radiotolerant bacteria Deinococcus radiodurans. Because bacteria living in the hot desert of Tataouine are one way or another tolerant to desiccation, we investigate whether they could also be tolerant to radiation. Exposition of soil samples to intense gamma radiation yields Bacillus , Thermus/Deinococcus and αα - Proteobacteria relatives. Four of these strains correspond to radiotolerant species as revealed by evaluation of the resistance levels of the individual cultures. A detailed analysis of the resistance levels for two Thermus/ Deinococcus and two αα - Proteobacteria relatives revealed that they correspond to new radiotolerant species.

The VIMOS VLT Deep Survey: The build-up of the colour-density relation

Abstract: We investigate the redshift and luminosity evolution of the galaxy colour-density relation using the data from the First Epoch VIMOS-VLT Deep Survey (VVDS). The size (6582 galaxies), depth (I_AB<=24) and redshift sampling rate of the survey enable us to reconstruct the 3D galaxy environment on relatively local scales (R=5 Mpc) up to z~1.5. Particular attention has been devoted to calibrate a density reconstruction scheme, which factors out survey selection effects and reproduces in an unbiased way the underlying 'real' galaxy environment. While at lower redshift we confirm the existence of a steep colour-density relation, with the fraction of the reddest(/bluest) galaxies of the same luminosity increasing(/decreasing) as a function of density, this trend progressively disappears and eventually reverses in the highest redshift bins investigated. The rest frame U-V colour-magnitude diagram shows a bimodal pattern in both low and high density environments up to z ~ 1.5. The bimodal distribution is not universal but strongly depends upon environment: at lower redshifts the colour-magnitude diagrams in low and high density regions are significantly different while the progressive weakening of the colour-density relation causes the two bimodal distributions to nearly mirror each other in the highest redshift bin investigated. Both the colour-density and colour-magnitude relations appear to be a transient, cumulative product of genetic and environmental factors operating over at least a period of 9 Gyr. These findings support an evolutionary scenario in which star formation/gas depletion processes are accelerated in more luminous objects and in high density environments.

Molecular Interaction between Projection Neuron Precursors and Invading Interneurons via Stromal-Derived Factor 1 (CXCL12)/CXCR4 Signaling in the Cortical Subventricular Zone/Intermediate Zone

Abstract: Most cortical interneurons are generated in the subpallial ganglionic eminences and migrate tangentially to their final destinations in the neocortex. Within the cortex, interneurons follow mainly stereotype routes in the subventricular zone/intermediate zone (SVZ/IZ) and in the marginal zone. It has been suggested that interactions between invading interneurons and locally generated projection neurons are implicated in the temporal and spatial regulation of the invasion process. However, so far experimental evidence for such interactions is lacking. We show here that the chemokine stromal-derived factor 1 (SDF-1; CXCL12) is expressed in the main invasion route for cortical interneurons in the SVZ/IZ. Most SDF-1-positive cells are proliferating and express the homeodomain transcription factors Cux1 and Cux2. Using MASH-1 mutant mice in concert with the interneuron marker DLX, we exclude that interneurons themselves produce the chemokine in an autocrine manner. We conclude that the SDF-1-expressing cell population represents the precursors of projection neurons during their transition and amplification in the SVZ/IZ. Using mice lacking the SDF-1 receptor CXCR4 or Pax6, we demonstrate that SDF-1 expression in the cortical SVZ/IZ is essential for recognition of this pathway by interneurons. These results represent the first evidence for a molecular interaction between precursors of projection neurons and invading interneurons during corticogenesis.

A survey of algebraic properties used in cryptographic protocols

Abstract: Cryptographic protocols are successfully analyzed using formal methods. However, formal approaches usually consider the encryption schemes as black boxes and assume that an adversary cannot learn anything from an encrypted message except if he has the key. Such an assumption is too strong in general since some attacks exploit in a clever way the interaction between protocol rules and properties of cryptographic operators. Moreover, the executability of some protocols relies explicitly on some algebraic properties of cryptographic primitives such as commutative encryption. We give a list of some relevant algebraic properties of cryptographic operators, and for each of them, we provide examples of protocols or attacks using these properties. We also give an overview of the existing methods in formal approaches for analyzing cryptographic protocols.

On the quantum origin of the seeds of cosmic structure

Abstract: The current understanding of the quantum origin of cosmic structure is discussed critically. We point out that in the existing treatments a transition from a symmetric quantum state to an (essentially classical) non-symmetric state is implicitly assumed, but not specified or analysed in any detail. In facing this issue, we are led to conclude that new physics is required to explain the apparent predictive power of the usual schemes. Furthermore, we show that the novel way of looking at the relevant issues opens new windows from where relevant information might be extracted regarding cosmological issues and perhaps even clues about aspects of quantum gravity.

Definitions of equilibrium in network formation games

Abstract: We examine a variety of stability and equilibrium definitions that have been used to study the formation of social networks among a group of players. In particular we compare variations on three types of definitions: those based on a pairwise stability notion, those based on the Nash equilibria of a link formation game, and those based on equilibria of a link formation game where transfers are possible.

Direct limits on the B-s(0) oscillation frequency

Abstract: We report the first direct two-sided bound on the $B^0_s$ oscillation frequency using a large sample of $B^0_s$ semileptonic decays corresponding to approximately 1 fb$^{-1}$ of integrated luminosity collected by the \dzer\ experiment in 2002--2006 during Run II of the Fermilab Tevatron Collider. The flavor (i.e., $B^0_s$ or $\bar{B}^0_s$) of the \bs meson at the time of production was found using an opposite-side tagging technique, and the flavor at the time of decay was determined from the charge of the muon in the partially reconstructed decay $\bs\to \mu^{+}D_{s}^{-}X$, $D_{s}^{-}\to \phi \pi^{-}$, $\phi\to K^{+}K^{-}$. A likelihood scan over the oscillation frequency, $\Delta m_s$, gives a most probable value of 19 ps$^{-1}$ and a range of $17 < \Delta m_s < 21$ ps$^{-1}$ at the 90% C.L. At $\Delta m_s=19$ ps$^{-1}$, the amplitude method yields a result that deviates from the hypothesis of an oscillation amplitude of zero by 2.5 standard deviations, corresponding to a two-sided C.L. of 1%.

Crystal structure and mechanistic determinants of SARS coronavirus nonstructural protein 15 define an endoribonuclease family

Abstract: The ≈30-kb coronavirus (+)RNA genome is replicated and transcribed by a membrane-bound replicase complex made up of 16 viral nonstructural proteins (nsp) with multiple enzymatic activities. The complex includes an RNA endonuclease, NendoU, that is conserved among nidoviruses but no other RNA virus, making it a genetic marker of this virus order. NendoU (nsp15) is a Mn2+-dependent, uridylate-specific enzyme, which leaves 2′–3′-cyclic phosphates 5′ to the cleaved bond. Neither biochemical nor sequence homology criteria allow a classification of nsp15 into existing endonuclease families. Here, we report the crystal structure of the severe acute respiratory syndrome coronavirus nsp15 at 2.6-A resolution. Nsp15 exhibits a unique fold and assembles into a toric hexamer with six potentially active, peripheric catalytic sites. The structure and the spatial arrangement of the catalytic residues into an RNase A-like active site define a separate endonuclease family, endoU, and represent another spectacular example of convergent evolution toward an enzymatic function that is critically involved in the coronavirus replication cycle.

Space-time clustering of childhood malaria at the household level: a dynamic cohort in a Mali village

Abstract: Spatial and temporal heterogeneities in the risk of malaria have led the WHO to recommend fine-scale stratification of the epidemiological situation, making it possible to set up actions and clinical or basic researches targeting high-risk zones. Before initiating such studies it is necessary to define local patterns of malaria transmission and infection (in time and in space) in order to facilitate selection of the appropriate study population and the intervention allocation. The aim of this study was to identify, spatially and temporally, high-risk zones of malaria, at the household level (resolution of 1 to 3 m). This study took place in a Malian village with hyperendemic seasonal transmission as part of Mali-Tulane Tropical Medicine Research Center (NIAID/NIH). The study design was a dynamic cohort (22 surveys, from June 1996 to June 2001) on about 1300 children (<12 years) distributed between 173 households localized by GPS. We used the computed parasitological data to analyzed levels of Plasmodium falciparum, P. malariae and P. ovale infection and P. falciparum gametocyte carriage by means of time series and Kulldorff's scan statistic for space-time cluster detection. The time series analysis determined that malaria parasitemia (primarily P. falciparum) was persistently present throughout the population with the expected seasonal variability pattern and a downward temporal trend. We identified six high-risk clusters of P. falciparum infection, some of which persisted despite an overall tendency towards a decrease in risk. The first high-risk cluster of P. falciparum infection (rate ratio = 14.161) was detected from September 1996 to October 1996, in the north of the village. This study showed that, although infection proportions tended to decrease, high-risk zones persisted in the village particularly near temporal backwaters. Analysis of this heterogeneity at the household scale by GIS methods lead to target preventive actions more accurately on the high-risk zones identified. This mapping of malaria risk makes it possible to orient control programs, treating the high-risk zones identified as a matter of priority, and to improve the planning of intervention trials or research studies on malaria.

Simultaneous mutations in translation initiation factors eIF4E and eIF(iso)4E are required to prevent pepper veinal mottle virus infection of pepper.

Abstract: Capsicum resistance to Pepper veinal mottle virus (PVMV) results from complementation between the pvr2 and pvr6 resistance genes: recessive alleles at these two loci are necessary for resistance, whereas any dominant allele confers susceptibility. In line with previous results showing that pvr2 resistance alleles encode mutated versions of the eukaryotic translation initiation factor 4E (eIF4E), the involvement of other members of the eIF4E multigenic family in PVMV resistance was investigated. It was demonstrated that pvr6 corresponds to an eIF(iso)4E gene, predicted to encode the second cap-binding isoform identified in plants. Comparative genetic mapping in pepper and tomato indicated that eIF(iso)4E maps in the same genomic region as pvr6. Sequence analysis revealed an 82 nt deletion in eIF(iso)4E cDNAs from genotypes with the pvr6 resistance allele, leading to a truncated protein. This deletion was shown to co-segregate with pvr6 in doubled haploid and F2 progeny. Transient expression in a PVMV-resistant genotype of eIF(iso)4E derived from a genotype with the pvr6 + susceptibility allele resulted in loss of resistance to subsequent PVMV inoculation, confirming that pvr6 encodes the translation factor eIF(iso)4E. Similarly, transient expression of eIF4E from a genotype with the pvr2 + -eIF4E susceptibility allele also resulted in loss of resistance, demonstrating that wild-type eIF4E and eIF(iso)4E are susceptibility factors for PVMV and that resistance results from the combined effect of mutations in the two cap-binding isoforms. Thus, whilst most potyviruses specifically require one eIF4E isoform to perform their replication cycle, PVMV uses either eIF4E or eIF(iso)4E for infection of pepper.

Early Reactivation of European Rivers During the Last Deglaciation

Abstract: During the Last Glacial Maximum, the sea-level lowstand combined with the large extent of the Fennoscandian and British ice sheets led to the funneling of European continental runoff, resulting in the largest river system that ever drained the European continent. Here, we show an abrupt and early reactivation of the European hydrological cycle at the onset of the last deglaciation, leading to intense discharge of the Channel River into the Bay of Biscay. This freshwater influx, probably combined with inputs from proglacial or ice-dammed lakes, dramatically affected the hydrology of the region, both on land and in the ocean.

Improvement of gait by chronic, high doses of methylphenidate in patients with advanced Parkinson’s disease

Abstract: Background: Therapeutic management of gait disorders in patients with advanced Parkinson’s disease (PD) can sometimes be disappointing, since dopaminergic drug treatments and subthalamic nucleus (STN) stimulation are more effective for limb-related parkinsonian signs than for gait disorders. Gait disorders could also be partly related to norepinephrine system impairment, and the pharmacological modulation of both dopamine and norepinephrine pathways could potentially improve the symptomatology. Aim: To assess the clinical value of chronic, high doses of methylphenidate (MPD) in patients with PD having gait disorders, despite their use of optimal dopaminergic doses and STN stimulation parameters. Methods: Efficacy was blindly assessed on video for 17 patients in the absence of l-dopa and again after acute administration of the drug, both before and after a 3-month course of MPD, using a Stand–Walk–Sit (SWS) Test, the Tinetti Scale, the Unified Parkinson’s Disease Rating Scale (UPDRS) part III score and the Dyskinesia Rating Scale. Results: An improvement was observed in the number of steps and time in the SWS Test, the number of freezing episodes, the Tinetti Scale score and the UPDRS part III score in the absence of l-dopa after 3 months of taking MPD. The l-dopa-induced improvement in these various scores was also stronger after the 3-month course of MPD than before. The Epworth Sleepiness Scale score fell dramatically in all patients. No significant induction of adverse effects was found. Interpretation: Chronic, high doses of MPD improved gait and motor symptoms in the absence of l-dopa and increased the intensity of response of these symptoms to l-dopa in a population with advanced PD.

Rapid sea-level movements and noneruptive crustal deformations in the Phlegrean Fields caldera, Italy

Abstract: The importance of Pozzuoli9s archaeological ruins in linking sea-level change and Earth deformation with volcanic activity has been recognized since the nineteenth century. The pillars of the Roman market were used as a paleotide gauge by pioneer geologists such as Lyell. For the first time, we have radiocarbon dated biological indicators on these remains, showing three 7 m relative sea-level highstands during the fifth century A.D., the early Middle Ages, and before the 1538 eruption of Monte Nuovo. These repeated uplift and subsidence cycles, not always followed by volcanic activity, have important implications for the evaluation of volcanic hazard.

The VIMOS VLT Deep Survey. Evolution of the luminosity functions by galaxy type up to z = 1.5 from first epoch data

Abstract: From the first epoch observations of the VVDS up to z=15 we have derived luminosity functions (LF) of different spectral type galaxies The VVDS data, covering ~70% of the life of the Universe, allow for the first time to study from the same sample and with good statistical accuracy the evolution of the LFs by galaxy type in several rest frame bands from a purely magnitude selected sample The magnitude limit of the VVDS allows the determination of the faint end slope of the LF with unprecedented accuracy Galaxies have been classified in four spectral classes, using their colours and redshift, and LFs have been derived in the U, B, V, R and I rest frame bands from z=005 to z=15 We find a significant steepening of the LF going from early to late types The M* parameter is significantly fainter for late type galaxies and this difference increases in the redder bands Within each of the galaxy spectral types we find a brightening of M* with increasing redshift, ranging from =< 05 mag for early type galaxies to ~1 mag for the latest type galaxies, while the slope of the LF of each spectral type is consistent with being constant with redshift The LF of early type galaxies is consistent with passive evolution up to z~11, while the number of bright early type galaxies has decreased by ~40% from z~03 to z~11 We also find a strong evolution in the normalization of the LF of latest type galaxies, with an increase of more than a factor 2 from z~03 to z~13: the density of bright late type galaxies in the same redshift range increases of a factor ~66 These results indicate a strong type-dependent evolution and identifies the latest spectral types as responsible for most of the evolution of the UV-optical luminosity function out to z=15

Chronic activation in presymptomatic amyotrophic lateral sclerosis (ALS) mice of a feedback loop involving Fas, Daxx, and FasL

Abstract: The reasons for the cellular specificity and slow progression of motoneuron diseases such as ALS are still poorly understood. We previously described a motoneuron-specific cell death pathway downstream of the Fas death receptor, in which synthesis of nitric oxide (NO) is an obligate step. Motoneurons from ALS model mice expressing mutant SOD1 showed increased susceptibility to exogenous NO as compared with controls. Here, we report a signaling mechanism whereby NO leads to death of mutant, but not control, motoneurons. Unexpectedly, exogenous NO triggers expression of Fas ligand (FasL) in cultured motoneurons. In mutant SOD1(G93A) and SOD1(G85R), but not in control motoneurons, this up-regulation results in activation of Fas, leading through Daxx to phosphorylation of p38 and further NO synthesis. This Fas/NO feedback amplification loop is required for motoneuron death in vitro. In vivo, mutant SOD1(G93A) and SOD1(G85R) mice show increased numbers of positive motoneurons and Daxx nuclear bodies weeks before disease onset. Moreover, FasL up-regulation is reduced in the presence of transgenic dominant-negative Daxx. We propose that chronic low-level activation of the Fas/NO feedback loop may underlie the motoneuron loss that characterizes familial ALS and may help to explain its slowly progressive nature.