Community replacement of neritic carbonate organisms during the late Valanginian platform demise: A new record from the Provence Platform

The Valanginian is marked by a major platform demise inducing a hiatus in the northern Tethyan neritic carbonate record from the top of the lower Valanginian to the lower Hauterivian. New biostratigraphic and chemostratigraphic data from the Ollioules section (Provence Platform, southern France) are presented here, demonstrating that a large part of the upper Valanginian is preserved in an inner platform environment. The thick, upper Valanginian, aggrading carbonate succession is observed in an aborted rift domain, implying relatively low subsidence. In this context, a relatively long-term sea-level rise was required to sustain a keep-up style of carbonate production. Like the Apulian Platform, the remarkable preservation of the Provence Platform may have been favored by its remoteness from terrigenous source areas, as suggested by the low clastic inputs and low P-accumulation rates. Two main biotic community replacements are observed in Ollioules. The first saw the development of abundant microbialites and algae at the onset of the late Valanginian. A Tubiphytes concentration occurred during the coolest climatic conditions and the transition towards arid conditions, whereas the subsequent Lithocodium-Bacinella and orbitolinids assemblages developed under low nutrient conditions during a warmer interval. Both assemblages may have been triggered by increased alkalinity. The second community replacement saw the installation of coral- and rudist-dominated communities during the latest Valanginian to early Hauterivian. They indicate a change to oligotrophic, open marine conditions. Six medium-scale sequences have been defined in Ollioules, indicating short-term transgressive-regressive trends superimposed on a long-term transgression. Low nutrient inputs and relatively low subsidence in an aggradational context may explain the survival of the isolated Provence Carbonate Platform during a time of widespread drowning episodes and platform demise in the northern Tethyan domain. (c) 2012 Elsevier B.V. All rights reserved.

Usefulness of betalactam therapy for community-acquired pneumonia in the era of drug-resistant Streptococcus pneumoniae: a randomized study of amoxicillin-clavulanate and ceftriaxone

Empirical antibiotic therapy of community-acquired pneumonia (CAP) has been complicated by the worldwide emergence of penicillin resistance among Streptococcus pneumoniae. The impact of this resistance on the outcome of patients hospitalized for CAP, empirically treated with betalactams, has not been evaluated in a randomized study. We conducted a prospective, randomized trial to assess the efficacy of amoxicillin-clavulanate (2 g/200 mg/8 hr) and ceftriaxone (1 g/24 hr) in a cohort of patients hospitalized for moderate-to-severe CAP. Three-hundred seventy-eight patients were randomized to receive amoxicillin-clavulanate (184 patients) or ceftriaxone (194 patients). Efficacy was assessed on Day 2, after completion of therapy and at long term follow-up. There were no significant differences in outcomes between treatment groups, both in intention-to-treat and per-protocol analysis. Overall mortality was 10.3% for amoxicillin-clavulanate and 8.8% for ceftriaxone (NS). There were 116 evaluable patients with proven pneumococcal pneumonia. Rates of high-level penicillin resistance (MIC of penicillin ≥2 µg/mL) were similar in the two groups (8.2 and 10.2%). Clinical efficacy at the end of therapy was 90.6% for amoxicillin-clavulanate and 88.9% for ceftriaxone (95% C.I. of the difference: -9.3 to +12.7%). No differences in outcomes were attributable to differences in penicillin susceptibility of pneumococcal strains. Sequential i.v./oral amoxicillin-clavulanate and parenteral ceftriaxone were equally safe and effective for the empirical treatment of acute bacterial pneumonia, including penicillin and cephalosporin-resistant pneumococcal pneumonia. The use of appropriate betalactams in patients with penumococcal pneumonia and in the overall CAP population, is reliable at the current level of resistance

Polarized cell growth in Arabidopsis requires endosomal recycling mediated by GBF1-related ARF exchange factors.

Polarized tip growth is a fundamental cellular process in many eukaryotic organisms, mediating growth of neuronal axons and dendrites or fungal hyphae. In plants, pollen and root hairs are cellular model systems for analysing tip growth. Cell growth depends on membrane traffic. The regulation of this membrane traffic is largely unknown for tip-growing cells, in contrast to cells exhibiting intercalary growth. Here we show that in Arabidopsis, GBF1-related exchange factors for the ARF GTPases (ARF GEFs) GNOM and GNL2 play essential roles in polar tip growth of root hairs and pollen, respectively. When expressed from the same promoter, GNL2 (in contrast to the early-secretory ARF GEF GNL1) is able to replace GNOM in polar recycling of the auxin efflux regulator PIN1 from endosomes to the basal plasma membrane in non-tip growing cells. Thus, polar recycling facilitates polar tip growth, and GNL2 seems to have evolved to meet the specific requirement of fast-growing pollen in higher plants.

KIAA1985, a Protein Mutant in Charcot-Marie-Tooth Neuropathy, Links Peripheral Nerve Myelination to Endosomal Recycling Pathways

Charcot-Marie-Tooth neuropathy (CMT) represents a heterogenous group of inherited disorders of the peripheral nervous system. One form of autosomal recessive demyelinating CMT (CMT4C, 5q32) is caused by mutations in the gene encoding KIAA1985, a protein of so far unknown function. Here we show that KIAA1985 is exclusively expressed in Schwann cells. KIAA1985 is tethered to cellular membranes through an N-terminal myristic acid anchor and localizes to the perinuclear recycling compartment. A search for proteins that interact with KIAA1985 identified the small GTPase Rab11, a key regulator of recycling endosome functions. CMT4C-related missense mutations disrupt the KIAA1985/Rab11 interaction. Protein binding studies indicate that KIAA1985 functions as a Rab11 effector, as it interacts only with active forms of Rab11 (WT and Q70L) and does not interact with the GDP locked mutant (S25N). Consistent with a function of Rab11 in Schwann cell myelination, myelin formation was strongly impaired when dorsal root ganglion neurons were co-cultured with Schwann cells infected with Rab11 S25N. Our data indicate that the KIAA1985/Rab11 interaction is relevant for peripheral nerve pathophysiology and place endosomal recycling on the list of cellular mechanisms involved in Schwann cell myelination.

Survey of management of first-ever seizures in a hospital based community

Résumé Contexte: Bon nombre d'études épidémiologiques concernant les premières crises comitiales ont été effectuées principalement sur des populations générales. Cependant, les patients admis dans un hôpital peuvent présenter des éléments cliniques différents. Nous avons donc mené une étude prospective auprès de sujets dans une population hospitalière ayant subi une première crise d'épilepsie, afin d'étudier leur pronostic et le rôle des examens complémentaires (examen neurologique, imagerie cérébrale, examens sanguins, EEG) dans le choix de l'administration d'une médication antiépileptique. Méthodes : Sur une période d'une année, nous avons suivi 177 patients adultes, admis consécutivement, ayant présenté une crise d'épilepsie dont l'évaluation aiguë a été effectuée dans notre hôpital. Pendant 6 mois, nous avons pratiqué pour chaque patient un suivi du traitement antiépileptique, des récidives de crises et d'un éventuel décès. Résultats : L'examen neurologique était anormal dans 72.3% des cas, l'imagerie cérébrale dans 54.8% et les examens sanguins dans 57.1%. L'EEG a montré des éléments épileptiformes dans 33.9% des cas. L'étiologie la plus fréquemment représentée était constituée par des intoxications. Un traitement antiépileptique a été prescrit chez 51% des patients. 31.6% des sujets suivis à six mois ont subi une récidive ; la mortalité s'est élevée à 17.8%. Statistiquement, l'imagerie cérébrale, l'EEG et l'examen neurologique étaient des facteurs prédictifs indépendants pour l'administration d'antiépileptiques, et l'imagerie cérébrale le seul facteur associé au pronostic. Conclusions : Les patients évalués en aigu dans un hôpital pour une première crise comitiale présentent un profil médical sous-jacent, qui explique probablement leur mauvais pronostic. L'imagerie cérébrale s'est avérée être le test paraclinique le plus important dans la prévention du traitement et du pronostic. Mots-clés : première crise d'épilepsie, étiologie, pronostic, récidive, médication antiépileptique, population hospitalière Summary Background: Epidemiological studies focusing on first-ever seizures have been carried out mainly on community based populations. However, since hospital populations may display varying clinical features, we prospectively analysed patients with first-ever seizure in a hospital based community to evaluate prognosis and the role of complementary investigations in the decision to administer antiepileptic drugs (AED). Methods: Over one year, we recruited 177 consecutive adult patients with a first seizure acutely evaluated in our hospital. During six months' follow-up data relating to AED treatment, recurrence of seizures and death were collected for each patient. Results:. Neurological examination was abnormal in 72.3%, neuroimaging in 54.8% and biochemical tests in 57.1%. Electroencephalogram (EEG) showed epileptiform features in 33.9%. Toxicity represented the most common aetiology. AED was prescribed in 51% of patients. Seizure recurrence at six months involved 31.6% of patients completing the follow-up; mortality was 17.8%. Statistical analysis showed that brain CT, EEG and neurological examination are independent predictive factors for AED administration, but only CT scan is associated with outcome. Conclusions: Patients evaluated acutely for first- ever seizure in a hospital setting have severe underlying clinical conditions apparently related to their relatively poor prognosis. Neuroimaging represents the most important paraclinical test in predicting both treatment administration and outcome.

Low C-reactive protein values at admission predict mortality in patients with severe community-acquired pneumonia caused by Streptococcus pneumoniae that require intensive care management.

PURPOSE: To identify risk factors associated with mortality in patients with severe community-acquired pneumonia (CAP) caused by S. pneumoniae who require intensive care unit (ICU) management, and to assess the prognostic values of these risk factors at the time of admission. METHODS: Retrospective analysis of all consecutive patients with CAP caused by S. pneumoniae who were admitted to the 32-bed medico-surgical ICU of a community and referral university hospital between 2002 and 2011. Univariate and multivariate analyses were performed on variables available at admission. RESULTS: Among the 77 adult patients with severe CAP caused by S. pneumoniae who required ICU management, 12 patients died (observed mortality rate 15.6 %). Univariate analysis indicated that septic shock and low C-reactive protein (CRP) values at admission were associated with an increased risk of death. In a multivariate model, after adjustment for age and gender, septic shock [odds ratio (OR), confidence interval 95 %; 4.96, 1.11-22.25; p = 0.036], and CRP (OR 0.99, 0.98-0.99 p = 0.034) remained significantly associated with death. Finally, we assessed the discriminative ability of CRP to predict mortality by computing its receiver operating characteristic curve. The CRP value cut-off for the best sensitivity and specificity was 169.5 mg/L to predict hospital mortality with an area under the curve of 0.72 (0.55-0.89). CONCLUSIONS: The mortality of patients with S. pneumoniae CAP requiring ICU management was much lower than predicted by severity scores. The presence of septic shock and a CRP value at admission <169.5 mg/L predicted a fatal outcome.

The role of community and population ecology in applying mycorrhizal fungi for improved food security.

The global human population is expected to reach ∼9 billion by 2050. Feeding this many people represents a major challenge requiring global crop yield increases of up to 100%. Microbial symbionts of plants such as arbuscular mycorrhizal fungi (AMF) represent a huge, but unrealized resource for improving yields of globally important crops, especially in the tropics. We argue that the application of AMF in agriculture is too simplistic and ignores basic ecological principals. To achieve this challenge, a community and population ecology approach can contribute greatly. First, ecologists could significantly improve our understanding of the determinants of the survival of introduced AMF, the role of adaptability and intraspecific diversity of AMF and whether inoculation has a direct or indirect effect on plant production. Second, we call for extensive metagenomics as well as population genomics studies that are crucial to assess the environmental impact that introduction of non-local AMF may have on native AMF communities and populations. Finally, we plead for an ecologically sound use of AMF in efforts to increase food security at a global scale in a sustainable manner.

Using a blog to create and support a Community of Inquiry in Secondary Education

Understanding how blogs can support collaborative learning is a vital concern for researchers and teachers. This paper explores how blogs may be used to support Secondary Education students’ collaborative interaction and how such an interaction process can promote the creation of a Community of Inquiry to enhance critical thinking and meaningful learning. We designed, implemented and evaluated a science case-based project in which fifteen secondary students participated. Students worked in the science blogging project during 4 months. We asked students to be collaboratively engaged in purposeful critical discourse and reflection in their blogs in order to solve collectively science challenges and construct meaning about topics related to Astronomy and Space Sciences. Through student comments posted in the blog, our findings showed that the blog environment afforded the construction of a Community of Inquiry and therefore the creation of an effective online collaborative learning community. In student blog comments, the three presences for collaborative learning took place: cognitive, social, and teaching presence. Moreover, our research found a positive correlation among the three presences –cognitive, social and teaching– of the Community of Inquiry model with the level of learning obtained by the students. We discuss a series of issues that instructors should consider when blogs are incorporated into teaching and learning. We claim that embedded scaffolds to help students to argue and reason their comments in the blog are required to foster blog-supported collaborative learning.

A modular tethering complex for endosomal recycling.

How proteins migrate through the interconnected organelles of the endolysosomal system is poorly understood. A piece of the puzzle has been added with the identification of a complex of tethering factors that functions in the recycling of proteins towards the cell surface.