Opinion Formation Models on a Gradient

Statistical physicists have become interested in models of collective social behavior such as opinion formation, where individuals change their inherently preferred opinion if their friends disagree. Real preferences often depend on regional cultural differences, which we model here as a spatial gradient g in the initial opinion. The gradient does not only add reality to the model. It can also reveal that opinion clusters in two dimensions are typically in the standard (i.e., independent) percolation universality class, thus settling a recent controversy about a non-consensus model. However, using analytical and numerical tools, we also present a model where the width of the transition between opinions scales , not as in independent percolation, and the cluster size distribution is consistent with first-order percolation.     

Carriage of Neisseria meningitidis and Neisseria lactamica in northern Greece

In response to an increase in the number of cases of invasive meningococcal disease (IMD) in northern regions of Greece, a survey was carried out to determine if there was an increase in carriage of Neisseria meningitidis, particularly in areas where there have been increases in immigrant populations from neighbouring countries. The second objective was to determine if there was an increase in the serogroup C:2a:P1.5,2 a phenotype associated with recent outbreaks or changes in antibiotic sensitivities. As carriage of Neisseria lactamica is associated with development of natural immunity to IMD, the third objective was to determine the carriage rate of N. lactamica in this population. Among 3167 individuals tested, meningococci were isolated from 334 (10.5%). Compared with our previous studies, the proportion of meningococcal carriers was significantly increased among children in secondary education (11.3%) (chi2=9.67, P<0.005) and military recruits (37.4%) (chi2=21.11, P<0.000). Only 5/334 (1.5%) isolates expressed the phenotype associated with the increase in IMD in Greece. N. lactamica was isolated from 146/3167 (4.6%) participants. It was isolated from 71/987 (7.2%) children attending primary or nursery schools; however, the highest proportion of carriers (11.3%) was found in the boarding school for young Albanian men. In the 21-59-year age range, the majority of N. lactamica isolates (22/25, 88%) were from women, probably due to closer or more prolonged contact with children in the primary school age range. Smoking was significantly associated with isolation of meningococci from men but not from women. Penicillin-insensitive strains (25/334, 7.5%) were identified in all four regions examined; the majority (14/25, 56%) were obtained from military personnel. We conclude that there was a higher proportion of carriers in the population of northern Greece; however, the increase in carriage rate was not associated with the influx of immigrants from neighbouring countries, and there was not a higher incidence of the C:2a:P1.5,2 strain responsible for increased disease activity in Greece in either the immigrant or local populations.     

STAT-Related Profiles Are Associated with Patient Response to Targeted Treatments in Locally Advanced SCCHN

The anti-epidermal growth factor receptor antibody cetuximab (Erbitux, CTX) is currently used for the treatment of locally advanced squamous cell carcinoma of the head and neck (LA-SCCHN), as yet with modest effectiveness, prompting for the identification of response predictors to this treatment and for the targeting of additional pathways implicated in this disease. Within this scope, we investigated the effect of SRC/STAT pathway components on LA-SCCHN patient outcome. SRC, STAT1, STAT3, STAT5A, STAT5B, ANXA1, CAV1, IGFBP2, EPHA2, EPHB2, and MSN relative gene expression, as well as Stat protein activation, were assessed on LA-SCCHN tumor tissues from 35 patients treated with combined radiotherapy (RT) and CTX-based regimens. Stat1, Stat3, and Stat5 proteins were usually found activated in neoplastic nuclei (70.4%, 85.7%, and 70.8%, respectively). Activated Stat3 and Stat5 were associated with each other (P = .017) and with a CAV1(high)/MSN(high)/IGFBP2(low) profile. All patients with tumors expressing high STAT5A/EPHA2 experienced a complete response on RT-CTX-based treatments (12/15 complete responders, P < .0001) and a longer progression-free survival (P = .024). Few tumors expressed high ANXA1/CAV1/EPHA2 and low IGFBP2, a putative dasatinib response-related profile, whereas high ANXA1 was associated with shorter overall survival (P = .003). In conclusion, Stat activation is common in LA-SCCHN, where overexpression of STAT5A and EPHA2 may predict for response to RT-CTX treatments. The STAT5A/EPHA2 profile seems of particular interest for validation in larger cohorts and in multiple tumor types because markers for the positive selection of patients to benefit from CTX-containing treatments are currently lacking.     

Parathymosin affects the binding of linker histone H1 to nucleosomes and remodels chromatin structure

Linker histone H1 is the major factor that stabilizes higher order chromatin structure and modulates the action of chromatin-remodeling enzymes. We have previously shown that parathymosin, an acidic, nuclear protein binds to histone H1 in vitro and in vivo. Confocal laser scanning microscopy reveals a nuclear punctuate staining of the endogenous protein in interphase cells, which is excluded from dense heterochromatic regions. Using an in vitro chromatin reconstitution system under physiological conditions, we show here that parathymosin (ParaT) inhibits the binding of H1 to chromatin in a dose-dependent manner. Consistent with these findings, H1-containing chromatin assembled in the presence of ParaT has reduced nucleosome spacing. These observations suggest that interaction of the two proteins might result in a conformational change of H1. Fluorescence spectroscopy and circular dichroism-based measurements on mixtures of H1 and ParaT confirm this hypothesis. Human sperm nuclei challenged with ParaT become highly decondensed, whereas overexpression of green fluorescent protein- or FLAG-tagged protein in HeLa cells induces global chromatin decondensation and increases the accessibility of chromatin to micrococcal nuclease digestion. Our data suggest a role of parathymosin in the remodeling of higher order chromatin structure through modulation of H1 interaction with nucleosomes and point to its involvement in chromatin-dependent functions.     

Cholesterol-dependent lipid assemblies regulate the activity of the ecto-nucleotidase CD39

CD39 (ecto-nucleoside triphosphate diphosphohydrolase-1; E-NTPDase1) is a plasma membrane ecto-enzyme that regulates purinergic receptor signaling by controlling the levels of extracellular nucleotides. In blood vessels this enzyme exhibits a thromboregulatory role through the control of platelet aggregation. CD39 is localized in caveolae, which are plasma membrane invaginations with distinct lipid composition, similar to dynamic lipid microdomains, called rafts. Cholesterol is enriched together with sphingolipids in both rafts and caveolae, as well as in other specialized domains of the membrane, and plays a key role in their function. Here, we examine the potential role of cholesterol-enriched domains in CD39 function. Using polarized Madin-Darby canine kidney (MDCK) cells and caveolin-1 gene-disrupted mice, we show that caveolae are not essential either for the enzymatic activity of CD39 or for its targeting to plasma membrane. On the other hand, flotation experiments using detergent-free or detergent-based approaches indicate that CD39 associates, at least in part, with distinct lipid assemblies. In the apical membrane of MDCK cells, which lacks caveolae, CD39 is localized in microvilli, which are also cholesterol and raft-dependent membrane domains. Interfering with cholesterol levels using drugs that either deplete or sequester membrane cholesterol results in a strong inhibition of the enzymatic and anti-platelet activity of CD39. The effects of cholesterol depletion are completely reversed by replenishment of membranes with pure cholesterol, but not by cholestenone. These data suggest a functional link between the localization of CD39 in cholesterol-rich domains of the membrane and its role in thromboregulation.     

Dopamine mimics the cardioprotective effect of ischemic preconditioning via activation of alpha1-adrenoceptors in the isolated rat heart

The aim of the present study was to clarify whether pharmacological preconditioning with dopamine protects the heart against ischemia and whether this effect is mediated through dopaminergic receptors (D1 and D2) or alpha1-adrenoceptors. Isolated perfused rat hearts were either non-preconditioned, preconditioned with 5 min ischemia, or treated for 5 min with dopamine (1, 5 or 10 microM) before being subjected to 45 min of sustained ischemia followed by 60 min reperfusion. Postischemic functional recovery and infarct size were used as indices of the effects of ischemia. Treatment with the lower concentration of dopamine (1 microM), did not provide any protection to the ischemic myocardium. On the other hand, treatment with 5 microM dopamine resulted in significantly improved functional recovery, whereas administration of dopamine (10 microM) resulted in significantly improved functional recovery as well as reduction of infarct size. Pretreatment with the mixed D1/D2 dopaminergic receptor antagonist haloperidol or the beta-adrenoceptor selective antagonist propranolol did not attenuate the protective effect of pharmacological preconditioning with 10 microM dopamine with respect to both functional recovery and infarct size reduction. On the other hand, the cardioprotective effect of dopamine was blocked when the alpha1-adrenoceptor selective antagonist, prazosin, was administered. In conclusion, pharmacological preconditioning with dopamine protects the myocardium against ischemia and this effect seems to be mediated through activation of alpha1-adrenoceptors.     

Effects of phosphorus concentration and light intensity on the biomass composition of Arthrospira (Spirulina) platensis

This paper presents the effects of various phosphorus concentrations (10, 50, 250 and 500 mg l(-1) K(2)HPO(4)) on the biomass production and composition of Arthrospira (Spirulina) platensis in relation to light intensity (24, 42 and 60 μE m(-2) s(-1)). The maximum biomass production was 3,592 ± 392 mg l(-1) and this was observed in 250 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1) light intensity after 32 days of cultivation. A maximum specific growth rate (μ(max)) of 0.55 d(-1) was obtained in 500 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1). The protein, lipid and chlorophyll contents of the biomass varied from 33.59 to 60.57 %, 5.34 to 13.33 % and 0.78 to 2.00 %, respectively. The most significant finding was that phosphorus limitation (10 mg l(-1) K(2)HPO(4)) caused a drastic increase of the carbohydrate content (59.64 %). The effect of phosphorus limitation on the carbohydrate content was independent of the light intensity. The accumulated carbohydrates are proposed to be used as substrate for biofuel generation via one of the appropriate biomass energy conversion technologies. Also, it was observed that phosphorus removal is a function of biomass density, phosphorus concentration and light intensity.     

The ENPI Horizon 2020 Capacity Building/Mediterranean Environment Programme to de-pollute the Mediterranean by the year 2020 (ENPI H2020 CB/MEP)

The paper explains the content, structure, activities and contribution of the capacity building component of the Horizon 2020 Initiative, a major undertaking supported by the EU Neighbourhood policy instrument. The Mediterranean environment is one of the richest and at the same time most vulnerable in the world. A staggering 80% of its pollution comes from land based sources: municipal waste, urban waste and water, and industrial emissions. In 2006, the European Mediterranean Environment Ministers meeting in Cairo committed themselves to a targeted de-pollution of the Mediterranean Sea by 2020, known as the “Horizon 2020 Initiative”. Within this framework, the Horizon 2020 Capacity Building/Mediterranean Environment Programme (H2020 CB/MEP) is one of its three operational components (the other two include the investments for pollution reduction infrastructures and pollution monitoring). It aims at supporting the implementation of the Horizon 2020 Initiative Road Map and Work Plan through a large number (~140) of capacity building and awareness raising activities, while strengthening institutions on environmental mainstreaming and H2020 priority areas. Environmental mainstreaming acts as an umbrella under which the three H2020 priorities are developed horizontally, cross cutting all capacity building activities so as to facilitate and create the enabling environment for the proper implementation, not only of the capacity building component of H2020 but also of the entire Initiative. It is expected that the H2020 CB/MEP will provide by the end of 2012 capacity building for an average of 200–300 persons per country, which means about 3500 individuals in the entire region.