<Emphasis Type="Italic">Pneumocystis jirovecii</Emphasis> and Cystic Fibrosis in Brittany,France

Pneumocystis jirovecii is a transmissible fungus with a high pulmonary tropism. The prevalence of P. jirovecii in patients with cystic fibrosis (CF) has been estimated in Germany at 7.4%, in Spain at 21.5% and in Brazil at 38.2%. Data on the prevalence of P. jirovecii in CF patients in France remain scarce, particularly in Brittany, where the prevalence of CF is high (from 1/1600 to 1/4500). Our objectives were to determine the prevalence of colonization of the airways by P. jirovecii in Brittany in CF patients monitored at the “Centre de Ressources et de Compétences de la Mucoviscidose (CRCM)” of Rennes compared to that previously observed at the CRCM of Roscoff–Brest. Sputa from 86 patients (178 specimens) followed in Rennes were analyzed retrospectively. The detection of P. jirovecii was performed using real-time PCR targeting the gene encoding the mitochondrial large subunit of ribosomal RNA. Pneumocystis jirovecii DNA was detected in 3/86 patients (3.5%) monitored at Rennes, whereas it had previously been detected in 1/76 patients (1.3%) monitored at Roscoff–Brest, thus showing an overall prevalence of 2.5% in Brittany. These results obtained from two Breton centers taken together show that P. jirovecii prevalence in patients with CF in Brittany is lower than those observed in Germany, Spain, Brazil or in other regions of France. This study is a preliminary step in determining the risk factors for P. jirovecii acquisition, its epidemiological and clinical significance in CF patients through a prospective multicenter study.     

The Endoplasmic Reticulum Is the Main Membrane Source for Biogenesis of the Lytic Vacuole in Arabidopsis

Vacuoles are multifunctional organelles essential for the sessile lifestyle of plants. Despite their central functions in cell growth, storage, and detoxification, knowledge about mechanisms underlying their biogenesis and associated protein trafficking pathways remains limited. Here, we show that in meristematic cells of the Arabidopsis thaliana root, biogenesis of vacuoles as well as the trafficking of sterols and of two major tonoplast proteins, the vacuolar H⁺-pyrophosphatase and the vacuolar H⁺-adenosinetriphosphatase, occurs independently of endoplasmic reticulum (ER)–Golgi and post-Golgi trafficking. Instead, both pumps are found in provacuoles that structurally resemble autophagosomes but are not formed by the core autophagy machinery. Taken together, our results suggest that vacuole biogenesis and trafficking of tonoplast proteins and lipids can occur directly from the ER independent of Golgi function.     

Labeling of Bifidobacterium longum cells with 13C-substituted leucine for quantitative proteomic analyses

Stable isotope labeling of amino acids in cell culture was used for Bifidobacterium longum. A comprehensive proteomic strategy was developed and validated by designing an appropriate semidefined medium that allows stable replacement of natural leucine by [(13)C6]leucine. Using this strategy, proteins having variations of at least 50% in their expression rates can be quantified with great confidence.     

Olive Oil and Vitamin D Synergistically Prevent Bone Loss in Mice

As the Mediterranean diet (and particularly olive oil) has been associated with bone health, we investigated the impact of extra virgin oil as a source of polyphenols on bone metabolism. In that purpose sham-operated (SH) or ovariectomized (OVX) mice were subjected to refined or virgin olive oil. Two supplementary OVX groups were given either refined or virgin olive oil fortified with vitamin D3, to assess the possible synergistic effects with another liposoluble nutrient. After 30 days of exposure, bone mineral density and gene expression were evaluated. Consistent with previous data, ovariectomy was associated with increased bone turnover and led to impaired bone mass and micro-architecture. The expression of oxidative stress markers were enhanced as well. Virgin olive oil fortified with vitamin D3 prevented such changes in terms of both bone remodeling and bone mineral density. The expression of inflammation and oxidative stress mRNA was also lower in this group. Overall, our data suggest a protective impact of virgin olive oil as a source of polyphenols in addition to vitamin D3 on bone metabolism through improvement of oxidative stress and inflammation.     

Tight Regulation of the intS Gene of the KplE1 Prophage: A New Paradigm for Integrase Gene Regulation

Temperate phages have the ability to maintain their genome in their host, a process called lysogeny. For most, passive replication of the phage genome relies on integration into the host''s chromosome and becoming a prophage. Prophages remain silent in the absence of stress and replicate passively within their host genome. However, when stressful conditions occur, a prophage excises itself and resumes the viral cycle. Integration and excision of phage genomes are mediated by regulated site-specific recombination catalyzed by tyrosine and serine recombinases. In the KplE1 prophage, site-specific recombination is mediated by the IntS integrase and the TorI recombination directionality factor (RDF). We previously described a sub-family of temperate phages that is characterized by an unusual organization of the recombination module. Consequently, the attL recombination region overlaps with the integrase promoter, and the integrase and RDF genes do not share a common activated promoter upon lytic induction as in the lambda prophage. In this study, we show that the intS gene is tightly regulated by its own product as well as by the TorI RDF protein. In silico analysis revealed that overlap of the attL region with the integrase promoter is widely encountered in prophages present in prokaryotic genomes, suggesting a general occurrence of negatively autoregulated integrase genes. The prediction that these integrase genes are negatively autoregulated was biologically assessed by studying the regulation of several integrase genes from two different Escherichia coli strains. Our results suggest that the majority of tRNA-associated integrase genes in prokaryotic genomes could be autoregulated and that this might be correlated with the recombination efficiency as in KplE1. The consequences of this unprecedented regulation for excisive recombination are discussed.     

A thermodynamic view of networks

Networks can be described by the frequency distribution of the number of links associated with each node (the degree of the node). Of particular interest are the power law distributions, which give rise to the so-called scale-free networks, and the distributions of the form of the simplified canonical law (SCL) introduced by Mandelbrot, which give what we shall call the Mandelbrot networks. Many dynamical methods have been obtained for the construction of scale-free networks, but no dynamical construction of Mandelbrot networks has been demonstrated. Here we develop a systematic technique to obtain networks with any given distribution of the degrees of the nodes. This is done using a thermodynamic approach in which we maximise the entropy associated with degree distribution of the nodes of the network subject to certain constraints. These constraints can be chosen systematically to produce the desired network architecture. For large networks we therefore replace a dynamical approach to the stationary state by a thermodynamical viewpoint. We use the method to generate scale-free and Mandelbrot networks with arbitrarily chosen parameters. We emphasise that this approach opens the possibility of insights into a thermodynamics of networks by suggesting thermodynamic relations between macroscopic variables for networks.     

Silver potentiates aminoglycoside toxicity by enhancing their uptake

The predicted shortage in new antibiotics has prompted research for chemicals that could act as adjuvant and enhance efficacy of available antibiotics. In this study, we tested the effects of combining metals with aminoglycosides on Escherichia coli survival. The best synergizing combination resulted from mixing aminoglycosides with silver. Using genetic and aminoglycoside uptake assays, we showed that silver potentiates aminoglycoside action in by‐passing the PMF‐dependent step, but depended upon protein translation. We showed that oxidative stress or Fe–S cluster destabilization were not mandatory factors for silver potentiating action. Last, we showed that silver allows aminoglycosides to kill an E. coli gentamicin resistant mutant as well as the highly recalcitrant anaerobic pathogen Clostridium difficile. Overall this study delineates the molecular basis of silver's potentiating action on aminoglycoside toxicity and shows that use of metals might offer solutions for battling against increased bacterial resistance to antibiotics.     

The molecular triad OPG/RANK/RANKL: involvement in the orchestration of pathophysiological bone remodeling

The past decade has seen an explosion in the field of bone biology. The area of bone biology over this period of time has been marked by a number of key discoveries that have opened up entirely new areas for investigation. The recent identification of the receptor activator of nuclear factor κB ligand (RANKL), its cognate receptor RANK, and its decoy receptor osteoprotegerin (OPG) has led to a new molecular perspective on osteoclast biology and bone homeostasis. Specifically, the interaction between RANKL and RANK has been shown to be required for osteoclast differentiation. The third protagonist, OPG, acts as a soluble receptor antagonist for RANKL that prevents it from binding to and activating RANK. Any dysregulation of their respective expression leads to pathological conditions such as bone tumor-associated osteolysis, immune disease, or cardiovascular pathology. In this context, the OPG/RANK/RANKL triad opens novel therapeutic areas in diseases characterized by excessive bone resorption. The present article is an update and extension of an earlier review published by Kwan Tat et al. [Kwan Tat S, Padrines M, Théoleyre S, Heymann D, Fortun Y. IL-6, RANKL, TNF-/IL-1: interrelations in bone resorption pathophysiology. Cytokine Growth Factor Rev 2004;15:49–60].