A new Triassic decapod, Platykotta akaina , from the Arabian shelf of the northern United Arab Emirates: earliest occurrence of the Anomura

A Triassic decapod crustacean is described here for the first time from the Norian-Rhaetian Ghalilah Formation of the Musandam Peninsula, United Arab Emirates. The single specimen Platykotta akaina n. gen n. sp. is referred to a new family Platykottidae. The studied crustacean, initially with only the ventral exposure preserved, was collected from shallow-water, burrowed limestones. Using a chemical preparation, the dorsal view revealed a well-preserved, chitinous, granular carapace exhibiting characteristic carapace morphology and groove pattern of the Eocarcinoidea, the superfamily to which the new family is assigned. The dorsal view together with the ventral surface, rarely seen in the fossil record, provide new insight into the morphology of representatives of the Eocarcinoide

Défaut cytotoxique perturbant l'homéostasie lymphocytaire (implication d'un nouvel effecteur, Munc13-4)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Depicting architecture and sedimentology of a hypertidal point bar through Lidar and sedimentary-core data

International audienceMorphodynamic behaviour of tidal meanders and internal architecture of related sedimentary bodies havereceived scarce attention, although they are ubiquitous features of coastal landscapes. Expansion of tidalmeanders is known to produce a progressive increase of bend sinuosity, along with accretion of point-bardeposits and formation of inclined heterolithic strata. These deposits are considered to be rich in fine-grainedsediments and tend to record tidal rhythmic deposition in the upper part of the bar, being the lower bar depositsdominated by erosional and bypass processes. Although these criteria are widely accepted, faciesmodels for tidal point bars still lack a 3D perspective and overlook the along-bend variability of sedimentaryprocesses. This knowledge gap can have a direct impact on understanding intra-point-bar heterogeneitiesand connectivity, with implications for reservoir production. The present study focuses on a 3 m deep tidalmeandering channel located in the salt marshes of the hypertidal Mont-Saint-Michel Bay (France), and investigatessedimentology of a time-framed bar accretionary package by means of Lidar-topographic data,geomorphological-field surveys and sedimentary cores. The studied accretionary package was accretedalong the bar between 28/03/2012 and 29/11/2012. Integration between Lidar and sedimentary-core datashows that over this time the bar expanded alternating depositional phases along its seaward and landwardside. The maximum thickness of deposits was accumulated in the bar apex zone, and just landwardof it, where the largest amount of mud was also stored. High accretion rate of the bar apex zone endorsedalso a better preservation of rhythmites, which are almost missing from deposits accumulated along thebar sides (i.e. close to riffles). We suggest that alternating depositional loci and high sediment accretion atthe bend apex zone emerge due to a combination of factors, including: i) the spatio-temporal asymmetricnature of tidal currents, which influenced deposition and preservation of flood and ebb deposits along thebend; and ii) the development of low-energy conditions at the apex due to ebb and flood flow configuration,which also promoted mud settling.This study highlights that mud and tidal rhythmites are not uniformly distributed within point-bar deposits,and their occurrence is strongly controlled by the asymmetric and mutually evasive nature of ebb and floodtides

Downregulation of the T-Cell Receptor by Human Immunodeficiency Virus Type 2 Nef Does Not Protect against Disease Progression▿

Chronic immune activation is thought to play a major role in human immunodeficiency virus (HIV) pathogenesis, but the relative contributions of multiple factors to immune activation are not known. One proposed mechanism to protect against immune activation is the ability of Nef proteins from some HIV and simian immunodeficiency virus strains to downregulate the T-cell receptor (TCR)-CD3 complex of the infected cell, thereby reducing the potential for deleterious activation. HIV type 1 (HIV-1) Nef has lost this property. In contrast to HIV-1, HIV-2 infection is characterized by a marked disparity in the disease course, with most individuals maintaining a normal life span. In this study, we examined the relationship between the ability of HIV-2 Nef proteins to downregulate the TCR and immune activation, comparing progressors and nonprogressors. Representative Nef variants were isolated from 28 HIV-2-infected individuals. We assessed their abilities to downregulate the TCR from the surfaces of CD4 T cells. In the same individuals, the activation of peripheral lymphocytes was evaluated by measurement of the expression levels of HLA-DR and CD38. We observed a striking correlation of the TCR downregulation efficiency of HIV-2 Nef variants with immune activation in individuals with a low viral load. This strongly suggests that Nef expression can influence the activation state of the immune systems of infected individuals. However, the efficiency of TCR downregulation by Nef was not reduced in progressing individuals, showing that TCR downregulation does not protect against progression in HIV-2 infection

Simultaneous cell-to-cell transmission of human immunodeficiency virus to multiple targets through polysynapses.

International audienceHuman immunodeficiency virus type 1 (HIV-1) efficiently propagates through cell-to-cell contacts, which include virological synapses (VS), filopodia, and nanotubes. Here, we quantified and characterized further these diverse modes of contact in lymphocytes. We report that viral transmission mainly occurs across VS and through "polysynapses," a rosette-like structure formed between one infected cell and multiple adjacent recipients. Polysynapses are characterized by simultaneous HIV clustering and transfer at multiple membrane regions. HIV Gag proteins often adopt a ring-like supramolecular organization at sites of intercellular contacts and colocalize with CD63 tetraspanin and raft components GM1, Thy-1, and CD59. In donor cells engaged in polysynapses, there is no preferential accumulation of Gag proteins at contact sites facing the microtubule organizing center. The LFA-1 adhesion molecule, known to facilitate viral replication, enhances formation of polysynapses. Altogether, our results reveal an underestimated mode of viral transfer through polysynapses. In HIV-infected individuals, these structures, by promoting concomitant infection of multiple targets in the vicinity of infected cells, may facilitate exponential viral growth and escape from immune responses