The RhoA-associated protein Citron-N controls dendritic spine maintenance by interacting with spine-associated Golgi compartments

Dendritic spines are highly dynamic protuberances that are thought to be crucial for learning and memory. Although it is well known that actin filaments and membrane dynamics regulate spine plasticity, how these two events are linked locally is less clear. Here, we provide evidence that Citron-N (CIT-N), a binding partner of the small GTPase RhoA, is associated with the actin filaments and Golgi compartments of dendritic spines. We also show that CIT-N is required for recruiting F-actin and Golgi membranes at spines of in vitro-grown neurons. Studies in knockout mice show that this protein is essential for the maturation of dendritic spines. We suggest that CIT-N might function as a scaffold protein in spine organization through its ability to bind to Golgi membranes and by affecting actin remodelling.     

Stimulation of the proximal tubule Na+-ATPase activity by adenosine A(2A) receptor

The aim of this work was to determine the molecular mechanism involved in the stimulation of the pig kidney proximal tubule Na+-ATPase by adenosine (Ado). To study the role of A2 Ado receptors, we added in all experiments 10(-6)M DPCPX, an A1 receptor-selective antagonist, since we have previously shown that Ado inhibits the enzyme activity through this receptor. Ado increased the Na+-ATPase activity with maximal effect observed at 10(-6)M. The presence of both A(2A) and A(2B) receptors were demonstrated by immunoblotting using specific polyclonal antibodies. The stimulatory effect of Ado was completely abolished by 5 x 10(-9)M DMPX, an antagonist of A2 receptor, and 10(-7)M SCH 58261, an A(2A) receptor-selective antagonist. DMPA (10(-7)M), a specific agonist of A(2A) receptor mimicked the stimulatory effect of Ado. Involvement of a Gs protein/adenylate cyclase/PKA pathway was evidenced by: (a) the reversion of Ado-induced effect by GDPbetaS; (b) stimulation of the Na+-ATPase activity in a similar and non-additive manner to Ado by 10(-8)M cholera toxin, 10(-7)M GTPgammaS, 10(-6)M forskolin, 10(-7)M cAMP or 1.25 U catalytic subunit of PKA; (c) the reversion of the stimulatory effect of Ado by 10(-8)M PKA inhibitor peptide; (d) Ado-produced two-fold increase of the PKA activity, which was completely reversed by 10(-6)M DMPX. These are the first evidences showing the modulation of a renal primary active sodium transporter by Ado through A(2A) receptor.     

Organic aggregates formed by benthopleustophyte brown alga Acinetospora crinita (Acinetosporaceae,Ectocarpales)

This work presents the elemental, polysaccharide, and fatty acid compositions of benthic aggregates formed by the filamentous brown alga Acinetospora crinita, which are widely spread on the rocky bottoms of the Mediterranean Sea. The aggregates can be characterized as mineralized centers in which regeneration of nutrients and recycling of dissolved organic matter actively occur and favor the development of an abundant phytoplankton community. Analyses of the stable isotopes of C and N display their marine origin and could provide evidence of the processes that occur inside/outside of the aggregates. The monosaccharide compositions of Adriatic and Tyrrhenian mucilages produced by brown alga A. crinita were quite similar. In particular, the Adriatic sample compositions resembled the average composition of the Tyrrhenian high molecular weight exopolymers, and the observed differences could be ascribed to different degradation stages. The fatty acid patterns found for the aggregates were similar to those observed in the isolated A. crinita algae with variable contributions from embedded diatom species. The bacterial contribution to the fatty acid pool was quite low, most likely due to the known poor conditions for their heterotrophic growth.     

Redescription and molecular identification of Isospora feroxis Berto,Luz, Flausino,Ferreira & Lopes, 2009 (Eimeriidae) from tyrant-flycatchers (Tyrannoidea) in South America

Systematic Parasitology - In the present study Isospora feroxis Berto, Luz, Flausino, Ferreira & Lopes, 2009 is redescribed from the photosyntypes and from new samples from a short-crested...     

Three new species of <Emphasis Type="Italic">Isospora</Emphasis> Schneider, 1881 (Apicomplexa: Eimeriidae) from the buffy-fronted seedeater <Emphasis Type="Italic">Sporophila frontalis</Emphasis> Verreaux (Passeriformes: Emberizidae) in South America

Three new coccidian (Apicomplexa: Eimeriidae) species from the buffy-fronted seedeater Sporophila frontalis Verraux in Brazil are reported in the current study. Isospora frontalis n. sp. oöcysts are spherical to sub-spherical, 27.9 × 26.9 μm, with a smooth, bi-layered wall c.1.4 μm thick. A micropyle and an oöcyst residuum are absent, but polar granules are present. Sporocysts are elongate ellipsoidal, 19.6 × 11.1 μm. The Stieda body is knob-like and the substieda body is slight. The sporocyst residuum is composed of scattered granules, and the sporozoites are vermiform with a refractile body and a nucleus. Isospora teresopoliensis n. sp. oöcysts are spherical to sub-spherical, 25.7 × 24.3 μm, with a smooth, bi-layered wall 1.3 μm thick. A micropyle, oöcyst residuum and polar granule are absent. Sporocysts are ovoid, 18.8 × 11.2 μm. The Stieda body is nipple-shaped and the substieda body is large and prominent. The sporocyst residuum is composed of scattered granules, and the sporozoites are large and elongate, with a refractile body and nucleus. Oöcysts of Isospora chanchaoi n. sp. are spherical to sub-spherical or ovoid, 24.2 × 22.0 μm, with a smooth, bi-layered wall c.1.2 μm thick. Both a micropyle and an oöcyst residuum are absent, but one or two polar granules are present. The sporocysts are ellipsoidal, 16.1 × 10.3 μm. The Stieda body is nipple-shaped and the substieda body is small but prominent. The sporocyst residuum forms a compact mass of granules, and the sporozoites are large and elongate, with a refractile body and a nucleus.     

The [4Fe–4S]-cluster coordination of [FeFe]-hydrogenase maturation protein HydF as revealed by EPR and HYSCORE spectroscopies

[FeFe] hydrogenases are key enzymes for bio(photo)production of molecular hydrogen, and several efforts are underway to understand how their complex active site is assembled. This site contains a [4Fe–4S]-2Fe cluster and three conserved maturation proteins are required for its biosynthesis. Among them, HydF has a double task of scaffold, in which the dinuclear iron precursor is chemically modified by the two other maturases, and carrier to transfer this unit to a hydrogenase containing a preformed [4Fe–4S]-cluster. This dual role is associated with the capability of HydF to bind and dissociate an iron–sulfur center, due to the presence of the conserved FeS-cluster binding sequence CxHx_46–53HCxxC. The recently solved three-dimensional structure of HydF from Thermotoga neapolitana described the domain containing the three cysteines which are supposed to bind the FeS cluster, and identified the position of two conserved histidines which could provide the fourth iron ligand. The functional role of two of these cysteines in the activation of [FeFe]-hydrogenases has been confirmed by site-specific mutagenesis. On the other hand, the contribution of the three cysteines to the FeS cluster coordination sphere is still to be demonstrated. Furthermore, the potential role of the two histidines in [FeFe]-hydrogenase maturation has never been addressed, and their involvement as fourth ligand for the cluster coordination is controversial. In this work we combined site-specific mutagenesis with EPR (electron paramagnetic resonance) and HYSCORE (hyperfine sublevel correlation spectroscopy) to assign a role to these conserved residues, in both cluster coordination and hydrogenase maturation/activation, in HydF proteins from different microorganisms.     

The cyanobacterium Synechocystis sp. PCC 6803 is able to express an active [FeFe]-hydrogenase without additional maturation proteins

[FeFe]-hydrogenases have been claimed as the most promising catalysts of hydrogen bioproduction and several efforts have been accomplished to express and purify them. However, previous attemps to obtain a functional recombinant [FeFe]-hydrogenase in heterologous systems such as Escherichia coli failed due to the lack of the specific maturation proteins driving the assembly of its complex active site. The unique exception is that of [FeFe]-hydrogenase from Clostridium pasteurianum that has been expressed in active form in the cyanobacterium Synechococcus PCC 7942, which holds a bidirectional [NiFe]-hydrogenase with a well characterized maturation system, suggesting that the latter is flexible enough to drive the synthesis of a [FeFe]-enzyme. However, the capability of cyanobacteria to correctly fold a [FeFe]-hydrogenase in the absence of its auxiliary maturation proteins is a debated question. In this work, we expressed the [FeFe]-hydrogenase from Chlamydomonas reinhardtii as an active enzyme in the cyanobacterium Synechocystis sp. PCC 6803. Our results, using a different experimental system, confirm that cyanobacteria are able to express a functional [FeFe]-hydrogenase even in the absence of additional chaperones.     

Coccidia of New World passerine birds (Aves: Passeriformes): a review of <Emphasis Type="Italic">Eimeria</Emphasis> Schneider, 1875 and <Emphasis Type="Italic">Isospora</Emphasis> Schneider, 1881 (Apicomplexa: Eimeriidae)

In the New World, the avian order Passeriformes comprises 47 families and 2,453 species, yet to date only 21 (45%) of the families and 58 (2%) of the species have been examined for coccidia, and from these only two species of Eimeria Schneider, 1875 and 81 species of Isospora Schneider, 1881 have been described. This review contributes to our understanding of the morphology and systematics of coccidian parasites of passeriforms, providing a scientific basis for the identification of sporulated oöcysts recovered from the faeces of passerine birds from North, Central and South America. To this end, the coccidia were organised and grouped according to the family of the host, following the widely recognised concept of family-specificity and the updated systematics of the class Aves. Details of 83 eimeriid species are presented along with an illustration and tabulated data.     

Prevalence and transmission of hepatitis E virus in domestic swine populations in different European countries

ABSTRACT: BACKGROUND: Hepatitis E virus (HEV) genotype 3 and 4 can cause liver disease in human and has its main reservoir in pigs. HEV investigations in pigs worldwide have been performed but there is still a lack of information on the infection dynamics in pig populations. FINDINGS: The HEV transmission dynamics in commercial pig farms in six different European countries was studied. The data collected show prevalence in weaners ranging from 8% to 30%. The average HEV prevalence in growers was between 20% and 44%. The fatteners prevalence ranged between 8% and 73%. Sows prevalence was similar in all countries. Boar faeces were tested for HEV only in Spain and Czech Republic, and the prevalence was 4.3% and 3.5% respectively. The collected data sets were analyzed using a recently developed model to estimate the transmission dynamics of HEV in the different countries confirming that HEV is endemic in pig farms. CONCLUSIONS: This study has been performed using similar detection methods (real time RT-PCR) for all samples and the same model (SIR model) to analyse the data. Furthermore, it describes HEV prevalence and within-herd transmission dynamics in European Countries (EU): Czech Republic, Italy, Portugal, Spain, The Netherlands and United Kingdom, confirming that HEV is circulating in pig farms from weaners to fatteners and that the reproductive number mathematical defined as R0 is in the same range for all countries studied.