Molecular mechanisms involved in the adenosine A and A receptor-induced neuronal differentiation in neuroblastoma cells and striatal primary cultures

Adenosine A1 receptors (A1Rs) and adenosine A(2A) receptors (A(2A)Rs) are the major mediators of the neuromodulatory actions of adenosine in the brain. In the striatum A1Rs and A(2A)Rs are mainly co-localized in the GABAergic striatopallidal neurons. In this paper we show that agonist-induced stimulation of A1Rs and A(2A)Rs induces neurite outgrowth processes in the human neuroblastoma cell line SH-SY5Y and also in primary cultures of striatal neuronal precursor cells. The kinetics of adenosine-mediated neuritogenesis was faster than that triggered by retinoic acid. The triggering of the expression of TrkB neurotrophin receptor and the increase of cell number in the G1 phase by the activation of adenosine receptors suggest that adenosine may participate in early steps of neuronal differentiation. Furthermore, protein kinase C (PKC) and extracellular regulated kinase-1/2 (ERK-1/2) are involved in the A1R- and A(2A)R-mediated effects. Inhibition of protein kinase A (PKA) activity results in a total inhibition of neurite outgrowth induced by A(2A)R agonists but not by A1R agonists. PKA activation is therefore necessary for A(2A)R-mediated neuritogenesis. Co-stimulation does not lead to synergistic effects thus indicating that the neuritogenic effects of adenosine are mediated by either A1 or A(2A) receptors depending upon the concentration of the nucleoside. These results are relevant to understand the mechanisms by which adenosine receptors modulate neuronal differentiation and open new perspectives for considering the use of adenosine agonists as therapeutic agents in diseases requiring neuronal repair.     

The adaptor protein 3BP2 binds human CD244 and links this receptor to Vav signaling, ERK activation, and NK cell killing

Adaptor proteins, molecules that mediate intermolecular interactions, are crucial for cellular activation. The adaptor 3BP2 has been shown to positively regulate NK cell-mediated cytotoxicity. In this study we present evidence for a physical interaction between 3BP2 and the CD244 receptor. CD244, a member of the CD150 family, is a cell surface protein expressed on NK, CD8+ T, and myeloid cells. CD244 interacts via its Src homology 2 domain with the X-linked lymphoproliferative disease gene product signaling lymphocytic activation molecule-associated protein (SAP)/SH2 domain protein 1A. 3BP2 interacts with human but not murine CD244. CD244-3BP2 interaction was direct and regulated by phosphorylation, as shown by a three-hybrid analysis in yeast and NK cells. Tyr337 on CD244, part of a consensus motif for SAP/SH2 domain protein 1A binding, was critical for the 3BP2 interaction. Although mutation of Tyr337 to phenylalanine abrogated human 3BP2 binding, we still observed SAP association, indicating that this motif is not essential for SAP recruitment. CD244 ligation induced 3BP2 phosphorylation and Vav-1 recruitment. Overexpression of 3BP2 led to an increase in the magnitude and duration of ERK activation, after CD244 triggering. This enhancement was concomitant with an increase in cytotoxicity due to CD244 ligation. However, no differences in IFN-gamma secretion were found when normal and 3BP2-transfected cells were compared. These results indicate that CD244-3BP2 association regulates cytolytic function but not IFN-gamma release, reinforcing the hypothesis that, in humans, CD244-mediated cytotoxicity and IFN-gamma release involve distinct NK pathways.     

Structural requirements of astrovirus virus-like particles assembled in insect cells

Expression of the complete ORF2 of human astrovirus serotype 1 (HAstV-1) in the baculovirus system led to the formation of virus-like particles (VLPs) of around 38 nm. The same kind of VLPs were also obtained either with the expression of a truncated form of ORF2 lacking the first 70 amino acids (aa), or with the same truncated form in which those 70 aa were replaced by the green fluorescent protein. All three kinds of VLPs were equally recognized by an anti-HAstV-1 polyclonal antibody and by two monoclonal antibodies (MAbs; 8E7 and 5B7), indicating a nonessential role of those amino acids neither in the capsid assembly nor in the antigen structure. A second type of structure consisting of 16-nm ring-like units was observed in all of the cases, mostly after disassembling the 38-nm VLPs through the addition of EDTA. The removal of the EDTA and the addition of Mg(2+) ions promoted the reassembly of the 38-nm VLPs. The nature of these 16-nm ring-like structures, capsomers or T = 1 VLPs, still remains unclear. Biochemical analysis revealed no differences between the 38-nm VLPs and the 16-nm structures, whereas antigenically, they shared the 8E7 MAb epitope but differed in the 5B7 MAb epitope, with the latter structures being more readily recognized.     

DNA SEQUENCE DATA DEMONSTRATE THE POLYPHYLY OF THE GENUS CYSTOSEIRA AND OTHER SARGASSACEAE GENERA (PHAEOPHYCEAE)1

Phylogenetic relationships in the Sargassaceae were explored using three DNA markers, and the monophyly of its genera was challenged. Nineteen out of 24 currently recognized genera were sampled, representing 63 species. The variable mt23S‐tRNA Val intergenic spacer could only be aligned within genera and could not be used to infer intergeneric relationships. The partial mt23S was also useful to delineate genera and was alignable at the family level but provided few informative characters. Analysis of mt23S DNA sequences together with chloroplast‐encoded psbA sequences resulted in a better resolved phylogeny. Hormophysa was the first genus to branch off within the Sargassaceae, followed by Myriodesma; then the three genera Caulocystis, Carpoglossum, and Scaberia in unresolved order; and then Acrocarpia. The other taxa studied here were divided over three major clades, but there was no branch support for the monophyly of two of these. The genera Bifurcaria, Cystoseira, Halidrys, and Sargassum appeared polyphyletic. The following taxonomic changes are proposed: a new genus Brassicophycus for Bifurcaria brassicaeformis (Kützing) E. S. Barton; reinstatement of the genus Sargassopsis for Sargassum decurrens (R. Brown ex Turner) C. Agardh; reinstatement of the genus Sirophysalis for Indo‐Pacific Cystoseira trinodis (Forsskål) C. Agardh; reinstatement of the genus Polycladia for the western Indian Ocean species Cystoseira indica (Thivy et Doshi) Mairh, Cystoseira myrica (S. G. Gmelin) C. Agardh, and Acystis heinii Schiffner; and reinstatement of the genus Stephanocystis for the North Pacific Cystoseira species and Halidrys dioica N. L. Gardner. The European Cystoseira species should be split into three genera, but no name changes are proposed yet, because diagnostic characters were found only for the clade including the type species. Some evolutionary trends could be discerned from the mt23S + psbA phylogeny.     

Modulating the expression of aquaporin genes in planta: A key to understand their physiological functions?

Aquaporins (AQPs) are believed to act as "cellular plumbers", allowing plants to rapidly alter their membrane water permeability in response to environmental cues. This study of AQP regulation at both the RNA and protein levels has revealed a large number of possible mechanisms. Currently, modulation of AQP expression in planta is considered the strategy of choice for elucidating the role of AQPs in plant physiology. This review highlights the fact that this strategy is complicated by many factors, such as the incomplete characterization of transport selectivity of the targeted AQP, the fact that AQPs might act as multifunctional channels with multiple physiological roles, and the number of post-translational regulation mechanisms. The classification of AQPs as constitutive or stress-responsive isoforms is also proposed.     

Pollen-mediated gene flow in maize in real situations of coexistence

We present the first study on cross-fertilization between Bt and conventional maize in real situations of coexistence in two regions in which Bt and conventional maize were cultivated. A map was designed and the different crops were identified, as were the sowing and flowering dates, in Bt and conventional maize fields. These data were used to choose the non-transgenic fields for sampling and analysis by the real-time quantification system-polymerase chain reaction (RTQ-PCR) technique. In general, the rate of cross-fertilization was higher in the borders and, in most of the fields, decreased towards the centre of the field. Nine fields had values of genetically modified organism DNA to total DNA of much lower than 0.9%, whereas in three the rate was higher. Some differences were found when comparing our results with those of common field trials. In real conditions of coexistence and in cropping areas with smaller fields, the main factors that determined cross-pollination were the synchronicity of flowering and the distances between the donor and receptor fields. By establishing an index based on these two variables, the rate of the adventitious presence of genetically modified maize could be predicted, as well as the influence of other factors. By applying this index, and in the case of a fully synchronous flowering time, a security distance between transgenic and conventional fields of about 20 m should be sufficient to maintain the adventitious presence of genetically modified organisms as a result of pollen flow below the 0.9% threshold in the total yield of the field.     

A single mutation in the glycophorin A binding site of hepatitis A virus enhances virus clearance from the blood and results in a lower fitness variant

Hepatitis A virus (HAV) has previously been reported to bind to human red blood cells through interaction with glycophorin A. Residue K221 of VP1 and the surrounding VP3 residues are involved in such an interaction. This capsid region is specifically recognized by the monoclonal antibody H7C27. A monoclonal antibody-resistant mutant with the mutation G1217D has been isolated. In the present study, the G1217D mutant was characterized physically and biologically in comparison with the parental HM175 43c strain. The G1217D mutant is more sensitive to acid pH and binds more efficiently to human and rat erythrocytes than the parental 43c strain. In a rat model, it is eliminated from serum more rapidly and consequently reaches the liver with a certain delay compared to the parental 43c strain. In competition experiments performed in vivo in the rat model, the G1217D mutant was efficiently outcompeted by the parental 43c strain. Only in the presence of antibodies reacting specifically with the parental 43c strain could the G1217D mutant outcompete the parental 43c strain in serum, although the latter still showed a remarkable ability to reach the liver. Altogether, these results indicate that the G1217D mutation induces a low fitness phenotype which could explain the lack of natural antigenic variants of the glycophorin A binding site.     

Fertilizing Methods and Nutrient Balance at the End of Traditional Organic Agriculture in the Mediterranean Bioregion: Catalonia (Spain) in the 1860s

By reconstructing the nutrient balance of a Catalan village circa 1861–65 we examine the sustainability of organic agricultural systems in the northwest Mediterranean bioregion prior to the green revolution and the question of whether the nutrients extracted from the soil were replenished. With a population density of 59 inhabitants per square km, similar to other northern European rural areas at that time, and a lower livestock density per cropland unit, this village experienced a manure shortage. The gap was filled by other labour-intensive ways of transferring nutrients from uncultivated areas into the cropland. Key elements in this agricultural system were vineyards because they have few nutrient requirements, and woodland and scrublands as sources of relevant amounts of nutrients collected in several ways.     

Biochemical behaviour of an incidentally diagnosed silent corticotroph adenoma

Silent corticotroph adenoma (SCA) is a non-functioning macroadenoma that has positive immunoreactivity for ACTH. Few studies have evaluated the biochemical behaviour of these tumours. We present the case of a 65-year-old male incidentally diagnosed with SCA, in which an exhaustive study of the corticotroph axis was conducted.     

Using successional theory to measure marine ecosystem health

Marine ecosystems are diverse and complex, providing significant challenges to the development of generalizable metrics of ecosystem health. Of particular concern is the varied form of change caused by multiple human activities, which limits the capacity to generate a single measure to encapsulate the overall condition of the ecosystem. Here we consider how successional theory can help to simplify our understanding of marine community structure, especially when viewed in context of human disturbance. During succession, the emergent properties of communities change in predictable ways. As communities mature, there is an increase in total production and biomass, the mean size of organisms, the level of internal recycling of food and nutrients, and the mean trophic level. Using a set of multi-species trophic models, we explore the changes in community structure that are likely to occur during succession. These changes include increases in biomass within trophic levels due to decreased rates of energy and food loss through trophic and production inefficiencies, and potential shifts from top-down control early in succession to bottom-up later. Because human activities disproportionately favor early-successional species, we can gain insights by considering community degradation in the context of succession being played in reverse. Indicators of health based on ecological succession thus provide a mechanistic view to measure the impact of human activities (both positive and negative) on marine ecosystems.