Recent studies on Schistosoma intercalatum: taxonomic status, puzzling distribution and transmission foci revisited

Schistosoma intercalatum, which causes human rectal schistosomiasis in Africa, still presents a great interest for its imprecise taxonomic status and its puzzling distribution in Africa. Two geographically isolated strains of S. intercalatum are recognized, the Lower Guinea strain and the Congo strain, which differ from each other in a number of morphological, biological and biochemical characteristics. Recent molecular data using RAPD markers indicate high divergence between the two strains, with values of Nei and Li's similarity indice allowing recognition of two genetically distinct taxa: experiments on pre- and post-isolating mechanisms are in progress in order to re-evaluate the taxonomic status of this polytypic species. With regard to its geographical distribution, S. intercalatum is characterized by the existence of two stable endemic areas (localized in Lower Guinea and North East of Democratic Republic of Congo) which correspond to the historical areas of species discovery, and the emergence during the last 15 years of new foci of the Lower Guinea strain outside previously known endemic areas. The absence of local adaptation of the Lower Guinea strain to its intermediate host, supported by experimental studies, may help to facilitate the spread of this strain. Nevertheless, the present restricted distribution of this species remains puzzling, because its potential snail hosts (bulinids) are widely distributed throughout much of Africa. Recent experimental and epidemiological studies suggest that interspecific sexual interactions between human schistosomes could have a role in limiting the distribution of S. intercalatum: the competitive sexual processes acting among human schistosomes show that S. haematobium and S. mansoni are always competitively dominant over S. intercalatum. These epidemiological observations lead the authors to distinguish three kinds of transmission foci for S. intercalatum.

RADIC: un middleware de tolerancia a fallos que preserva el rendimiento

La tolerancia a fallos es una línea de investigación que ha adquirido una importancia relevante con el aumento de la capacidad de cómputo de los súper-computadores actuales. Esto es debido a que con el aumento del poder de procesamiento viene un aumento en la cantidad de componentes que trae consigo una mayor cantidad de fallos. Las estrategias de tolerancia a fallos actuales en su mayoría son centralizadas y estas no escalan cuando se utiliza una gran cantidad de procesos, dado que se requiere sincronización entre todos ellos para realizar las tareas de tolerancia a fallos. Además la necesidad de mantener las prestaciones en programas paralelos es crucial, tanto en presencia como en ausencia de fallos. Teniendo en cuenta lo citado, este trabajo se ha centrado en una arquitectura tolerante a fallos descentralizada (RADIC – Redundant Array of Distributed and Independant Controllers) que busca mantener las prestaciones iniciales y garantizar la menor sobrecarga posible para reconfigurar el sistema en caso de fallos. La implementación de esta arquitectura se ha llevado a cabo en la librería de paso de mensajes denominada Open MPI, la misma es actualmente una de las más utilizadas en el mundo científico para la ejecución de programas paralelos que utilizan una plataforma de paso de mensajes. Las pruebas iniciales demuestran que el sistema introduce mínima sobrecarga para llevar a cabo las tareas correspondientes a la tolerancia a fallos. MPI es un estándar por defecto fail-stop, y en determinadas implementaciones que añaden cierto nivel de tolerancia, las estrategias más utilizadas son coordinadas. En RADIC cuando ocurre un fallo el proceso se recupera en otro nodo volviendo a un estado anterior que ha sido almacenado previamente mediante la utilización de checkpoints no coordinados y la relectura de mensajes desde el log de eventos. Durante la recuperación, las comunicaciones con el proceso en cuestión deben ser retrasadas y redirigidas hacia la nueva ubicación del proceso. Restaurar procesos en un lugar donde ya existen procesos sobrecarga la ejecución disminuyendo las prestaciones, por lo cual en este trabajo se propone la utilización de nodos spare para la recuperar en ellos a los procesos que fallan, evitando de esta forma la sobrecarga en nodos que ya tienen trabajo. En este trabajo se muestra un diseño propuesto para gestionar de un modo automático y descentralizado la recuperación en nodos spare en un entorno Open MPI y se presenta un análisis del impacto en las prestaciones que tiene este diseño. Resultados iniciales muestran una degradación significativa cuando a lo largo de la ejecución ocurren varios fallos y no se utilizan spares y sin embargo utilizándolos se restablece la configuración inicial y se mantienen las prestaciones.

Interaction of Diocleinae Lectins with Glycoproteins Based in Surface Plasmon Resonance

Interaction of glucose/mannose-binding lectins in solution with immobilized glycoproteins was followed in real time using surface plasmon resonance technology. The lectins which share many biochemical and structural features could be clearly differentiated in terms of their specificity for complex glycoconjugates. The most prominent interaction of the lectins with PHA-E comparing with soybean agglutinin, both glycoproteins exhibiting high mannose oligosaccharides, suggests that the whole structure of the glycoproteins themselves, may interfere in affinity. These findings also support the hypothesis that minor amino acid replacements in the primary sequence of the lectins might be responsible for their divergence in fine specificity and biological activities. This is the first report using surface plasmon resonance technology that evidences differences of Diocleinae lectins in respect their fine glycan-specificity.

Clinical application of differential time to positivity of blood cultures as a diagnostic method for catheter-related bloodstream infection.

La sospita de bacterièmia relacionada a catèter (BRC) necessita la retirada d’aquest, confirmant-se a posteriori només en un 15-25%. La diferencia en el temps de positivització d´ hemocultius (DTP) ha demostrat ser un mètode fiable per el diagnòstic de BRC evitant la retirada del catèter. Amb la intenció de comprovar la utilitat clínica de la DTP, l’hem comparada amb un mètode diagnòstic estàndard. Hem inclòs 133 pacients ingressats a una unitat de cures intensives portadors de catèters venosos centrals. 56 pacients s’han aleatoritzats. No hem trobat diferències significatives en quant a morbi-mortalitat en els 2 grups havent evitat 70% de retirada innecessària de catèters en el grup de DTP.

X-ray mosaic nanotomography of large microorganisms.

Full-field X-ray microscopy is a valuable tool for 3D observation of biological systems. In the soft X-ray domain organelles can be visualized in individual cells while hard X-ray microscopes excel in imaging of larger complex biological tissue. The field of view of these instruments is typically 10(3) times the spatial resolution. We exploit the assets of the hard X-ray sub-micrometer imaging and extend the standard approach by widening the effective field of view to match the size of the sample. We show that global tomography of biological systems exceeding several times the field of view is feasible also at the nanoscale with moderate radiation dose. We address the performance issues and limitations of the TOMCAT full-field microscope and more generally for Zernike phase contrast imaging. Two biologically relevant systems were investigated. The first being the largest known bacteria (Thiomargarita namibiensis), the second is a small myriapod species (Pauropoda sp.). Both examples illustrate the capacity of the unique, structured condenser based broad-band full-field microscope to access the 3D structural details of biological systems at the nanoscale while avoiding complicated sample preparation, or even keeping the sample environment close to the natural state.

Isoenzymatic variability among five Anopheles species belonging to the Nyssorhynchus and Anopheles subgenera of the Amazon region, Brazil

An isoenzymatic comparative analysis of the variability and genetics differentiation among Anopheles species was done in populations of An. (Nys.) intermedius and An. (Ano.) mattogrossensis of the Anopheles subgenus, and of An. darlingi, An. albitarsis and An. triannulatus of the Nyssorhynchus subgenus, with the aim of detecting differences between both subgenera and of estimating the degree of genetic intere specific divergence. Samples from Macapá, State of Amapá and Janauari Lake, near Manaus, State of Amazonas, were analyzed for eight isoenzymatic loci. Analysis revealed differences in the average number of alleles per locus (1.6-2.3) and heterozygosity (0.060-0.284). However, the proportion of polymorphic loci was the same for An. (Nys.) darlingi, An. (Nys.) triannulatus and An. (Ano.) mattogrossensis (50%), but differed for An. (Nys.) albitarsis (62.5%) and An. (Ano.) intermedius (25%). Only the IDH1 (P > 0.5) locus in all species studied was in Hardy-Weinberg equilibrium. The fixation index demonstrated elevated genetic structuring among species, based on values of Fst = 0.644 and genetic distance (0.344-0.989). Genetic difference was higher between An. (Nys.) triannulatus and An. (Ano.) intermedius (0.989) and smaller between An. (Nys.) albitarsis sensu lato and An. (Nys.) darlingi (0.344). The data show interspecific genetic divergence which differs from the phylogenetic hypothesis based on morphological characters.

Multivariate QST-FST comparisons: a neutrality test for the evolution of the g matrix in structured populations.

Neutrality tests in quantitative genetics provide a statistical framework for the detection of selection on polygenic traits in wild populations. However, the existing method based on comparisons of divergence at neutral markers and quantitative traits (Q(st)-F(st)) suffers from several limitations that hinder a clear interpretation of the results with typical empirical designs. In this article, we propose a multivariate extension of this neutrality test based on empirical estimates of the among-populations (D) and within-populations (G) covariance matrices by MANOVA. A simple pattern is expected under neutrality: D = 2F(st)/(1 - F(st))G, so that neutrality implies both proportionality of the two matrices and a specific value of the proportionality coefficient. This pattern is tested using Flury's framework for matrix comparison [common principal-component (CPC) analysis], a well-known tool in G matrix evolution studies. We show the importance of using a Bartlett adjustment of the test for the small sample sizes typically found in empirical studies. We propose a dual test: (i) that the proportionality coefficient is not different from its neutral expectation [2F(st)/(1 - F(st))] and (ii) that the MANOVA estimates of mean square matrices between and among populations are proportional. These two tests combined provide a more stringent test for neutrality than the classic Q(st)-F(st) comparison and avoid several statistical problems. Extensive simulations of realistic empirical designs suggest that these tests correctly detect the expected pattern under neutrality and have enough power to efficiently detect mild to strong selection (homogeneous, heterogeneous, or mixed) when it is occurring on a set of traits. This method also provides a rigorous and quantitative framework for disentangling the effects of different selection regimes and of drift on the evolution of the G matrix. We discuss practical requirements for the proper application of our test in empirical studies and potential extensions.

Exogenous selection shapes germination behaviour and seedling traits of populations at different altitudes in a Senecio hybrid zone.

BACKGROUND AND AIMS: The Senecio hybrid zone on Mt Etna, Sicily, is characterized by steep altitudinal clines in quantitative traits and genetic variation. Such clines are thought to be maintained by a combination of 'endogenous' selection arising from genetic incompatibilities and environment-dependent 'exogenous' selection leading to local adaptation. Here, the hypothesis was tested that local adaptation to the altitudinal temperature gradient contributes to maintaining divergence between the parental species, S. chrysanthemifolius and S. aethnensis. METHODS: Intra- and inter-population crosses were performed between five populations from across the hybrid zone and the germination and early seedling growth of the progeny were assessed. KEY RESULTS: Seedlings from higher-altitude populations germinated better under low temperatures (9-13 °C) than those from lower altitude populations. Seedlings from higher-altitude populations had lower survival rates under warm conditions (25/15 °C) than those from lower altitude populations, but also attained greater biomass. There was no altitudinal variation in growth or survival under cold conditions (15/5 °C). Population-level plasticity increased with altitude. Germination, growth and survival of natural hybrids and experimentally generated F(1)s generally exceeded the worse-performing parent. CONCLUSIONS: Limited evidence was found for endogenous selection against hybrids but relatively clear evidence was found for divergence in seed and seedling traits, which is probably adaptive. The combination of low-temperature germination and faster growth in warm conditions might enable high-altitude S. aethnensis to maximize its growth during a shorter growing season, while the slower growth of S. chrysanthemifolius may be an adaptation to drought stress at low altitudes. This study indicates that temperature gradients are likely to be an important environmental factor generating and maintaining adaptive divergence across the Senecio hybrid zone on Mt Etna.

Drainage of fluorescent liposomes from the vitreous to cervical lymph nodes via conjunctival lymphatics.

The use of liposomes as carriers for the delivery of biologically active molecules into the eye is of major interest. Indeed, encapsulation of biologically active molecules in liposomes may increase their bioavailability and may induce a sustained release, thus avoiding repeated intraocular injections and reducing side effects. We describe here the fate of rhodamine-conjugated liposomes (Rh-Lip) injected into the vitreous of normal Lewis rats. Twenty-four hours after intravitreal injection fluorescent liposomes were detected in the vitreous, the inner layer of the retina and to a lesser extent in the anterior segment of the eye. In addition, numerous Rh-Lip were also observed in the episclera and conjunctival stroma, in conjunctival lymphatic vessels and cervical lymph nodes (LN) draining the conjunctiva and the eye. In the LN, Rh-Lip were taken up by resident macrophages adjacent to CD4+ and CD8+ T cells. Thus, intravitreal injection of anti-inflammatory drugs loaded in liposomes could modulate the ocular immune microenvironment. In addition the passage of drugs into the cervical LN could alter the immune status of these LN and contribute to the regulation of intraocular inflammation. Our results suggest that this phenomenon should be taken into account to design new therapies based on intraocular drug administration.

Phylogeny of subtribe Gentianinae (Gentianaceae): biogeographic inferences despite limitations in temporal calibration points

The subtribe Gentianinae comprises ca. 425 species, most of them within the well-studied genus Gentiana and mainly distributed over the Eurasian continent. Phylogenetic relationships between Gentiana and its closest relatives, the climbing gentians (Crawfurdia, Tripterospermum) and the new genus Metagentiana, remain unclear. All three genera were recently found to be polyphyletic, possibly because of poor sampling of Tripterospermum and Crawfurdia. Highest diversity of Gentianinae occurs in the western Himalaya, but the absence of uncontroversial fossil evidence limits our understanding of its biogeography. In the present study, we generated ITS and atpB-rbcL sequences for 19 species of Tripterospermum, 9 of Crawfurdia and 11 of Metagentiana, together representing about 60 percent of the species diversity of these genera. Our results show that only Metagentiana is polyphyletic and divided into three monophyletic entities. No unambiguous synapomorphies were associated with the three Metagentiana entities. Different combinations of three approximate calibration points were used to generate three divergence time estimation scenarios. Although dating hypotheses were mostly inconsistent, they concurred in associating radiation of Gentiana to an orogenic phase of the Himalaya between 15 and 10 million years ago. Our study illustrates the conceptual difficulties in addressing the time frame of diversification in a group lacking sufficient fossil number and quality.

Policy Diffusion: An Agent-Based Approach

Methods like Event History Analysis can show the existence of diffusion and part of its nature, but do not study the process itself. Nowadays, thanks to the increasing performance of computers, processes can be studied using computational modeling. This thesis presents an agent-based model of policy diffusion mainly inspired from the model developed by Braun and Gilardi (2006). I first start by developing a theoretical framework of policy diffusion that presents the main internal drivers of policy diffusion - such as the preference for the policy, the effectiveness of the policy, the institutional constraints, and the ideology - and its main mechanisms, namely learning, competition, emulation, and coercion. Therefore diffusion, expressed by these interdependencies, is a complex process that needs to be studied with computational agent-based modeling. In a second step, computational agent-based modeling is defined along with its most significant concepts: complexity and emergence. Using computational agent-based modeling implies the development of an algorithm and its programming. When this latter has been developed, we let the different agents interact. Consequently, a phenomenon of diffusion, derived from learning, emerges, meaning that the choice made by an agent is conditional to that made by its neighbors. As a result, learning follows an inverted S-curve, which leads to partial convergence - global divergence and local convergence - that triggers the emergence of political clusters; i.e. the creation of regions with the same policy. Furthermore, the average effectiveness in this computational world tends to follow a J-shaped curve, meaning that not only time is needed for a policy to deploy its effects, but that it also takes time for a country to find the best-suited policy. To conclude, diffusion is an emergent phenomenon from complex interactions and its outcomes as ensued from my model are in line with the theoretical expectations and the empirical evidence.Les méthodes d'analyse de biographie (event history analysis) permettent de mettre en évidence l'existence de phénomènes de diffusion et de les décrire, mais ne permettent pas d'en étudier le processus. Les simulations informatiques, grâce aux performances croissantes des ordinateurs, rendent possible l'étude des processus en tant que tels. Cette thèse, basée sur le modèle théorique développé par Braun et Gilardi (2006), présente une simulation centrée sur les agents des phénomènes de diffusion des politiques. Le point de départ de ce travail met en lumière, au niveau théorique, les principaux facteurs de changement internes à un pays : la préférence pour une politique donnée, l'efficacité de cette dernière, les contraintes institutionnelles, l'idéologie, et les principaux mécanismes de diffusion que sont l'apprentissage, la compétition, l'émulation et la coercition. La diffusion, définie par l'interdépendance des différents acteurs, est un système complexe dont l'étude est rendue possible par les simulations centrées sur les agents. Au niveau méthodologique, nous présenterons également les principaux concepts sous-jacents aux simulations, notamment la complexité et l'émergence. De plus, l'utilisation de simulations informatiques implique le développement d'un algorithme et sa programmation. Cette dernière réalisée, les agents peuvent interagir, avec comme résultat l'émergence d'un phénomène de diffusion, dérivé de l'apprentissage, où le choix d'un agent dépend en grande partie de ceux faits par ses voisins. De plus, ce phénomène suit une courbe en S caractéristique, poussant à la création de régions politiquement identiques, mais divergentes au niveau globale. Enfin, l'efficacité moyenne, dans ce monde simulé, suit une courbe en J, ce qui signifie qu'il faut du temps, non seulement pour que la politique montre ses effets, mais également pour qu'un pays introduise la politique la plus efficace. En conclusion, la diffusion est un phénomène émergent résultant d'interactions complexes dont les résultats du processus tel que développé dans ce modèle correspondent tant aux attentes théoriques qu'aux résultats pratiques.

Viremic blood donor found by a rapid screening method in a season of high human parvovirus B19 activity in Niterói, Rio de Janeiro, Brazil

Erythrovirus B19 infection is usually benign but may have serious consequences in patients with hemolytic anemia (transient aplastic crisis), immunodeficiency (in whom persistent infection can lead to chronic bone marrow failure with anemia), or who are in the first or second trimester of gestation (spontaneous abortion, hydrops fetalis, and fetal death). Being non-enveloped, B19 resists most inactivation methods and can be transmitted by transfusion. B19 is difficult to cultivate and native virus is usually obtained from viremic blood. As specific antibodies may be absent, and there is no reliable immunological method for antigen detection, hybridization or polymerase chain reaction are needed for detecting viremia. A rapid method, gel hemagglutination (Diamed ID-Parvovirus B19 Antigen Test), can disclose highly viremic donations, whose elimination lessens the viral burden in pooled blood products and may even render them non-infectious. In order to obtain native antigen and to determine the frequency of viremic donors, we applied this test to blood donors in a period of high viral activity in our community. Positive or indeterminate results were re-tested by dot-blot hybridization. We tested 472 donors in 1998 and 831 ones in 1999. One viremic donor was found in 1999. We suggest that in periods of high community viral activity the gel hemagglutination test may be useful in avoiding highly viremic blood being added to plasma pools or directly transfused to patients under risk.

Simple steps to a healthy heart

The number of deaths from coronary heart disease in Northern Ireland has dropped significantly, according to recent figures. However, the Public Health Agency is urging everyone to take steps to protect their heart and reduce their chances of developing the disease during National Heart Month (February).Despite the number of deaths dropping significantly in recent years, coronary heart disease is still the number one killer across the country. Over 2,200 people died in Northern Ireland from coronary heart disease in 2010 compared to just over 2,300 people in 2009 - an overall reduction of 100 province-wide. The latest figure reveals the positive downward trend is continuing - in 2008, there were 2,410 deaths, 2,493 in 2007 and 2,554 in 2006, while in 1979 there were nearly 5,000 deaths. Throughout National Heart Month in February, the PHA is calling for people to follow a number of steps in a bid to reduce their chances of developing the disease.Smoking is a major risk factor and, the more cigarettes you smoke, the higher the risk, according to Dr Christine McMaster, Consultant in Public Health Medicine, with responsibility for cardiovascular disease in the PHA."The reduction in smoking over the past number of years through public education, stop smoking programmes and smoke free legislation has had a major impact on reducing deaths from heart disease. However, 24% of the population in Northern Ireland still smoke, putting them at risk of developing the disease."People who suffer from high blood pressure also run an increased risk of developing coronary heart disease. High blood pressure is a silent, but treatable condition. In order to minimise the risk, I would urge everyone over the age of 45 to have their blood pressure measured every five years by their GP," said Dr McMaster.Simple lifestyle changes will also reduce the risk of heart disease, including eating at least five servings of fruit and vegetables a day, avoiding saturated fats, limiting alcohol intake and taking at least 30 minutes of exercise a day, five days a week.Dr McMaster described the reduction in deaths from coronary heart disease over the past few years as "a big success story". "It shows that people can take very positive steps to reduce their risk of heart disease by getting their blood pressure checked and adopting a healthier lifestyle; in particular by not smoking," he added. "The message is clear during National Heart Month - you only have one heart and you can take steps to keep it healthy."

Stage-specific activity of potential antimalarial compounds measured in vitro by flow cytometry in comparison to optical microscopy and hypoxanthine uptake

The evaluation of new antimalarial agents using older methods of monitoring sensitivity to antimalarial drugs are laborious and poorly suited to discriminate stage-specific activity. We used flow cytometry to study the effect of established antimalarial compounds, cysteine protease inhibitors, and a quinolone against asexual stages of Plasmodium falciparum. Cultured P. falciparum parasites were treated for 48 h with different drug concentrations and the parasitemia was determined by flow cytometry methods after DNA staining with propidium iodide. P. falciparum erythrocytic life cycle stages were readily distinguished by flow cytometry. Activities of established and new antimalarial compounds measured by flow cytometry were equivalent to results obtained with microscopy and metabolite uptake assays. The antimalarial activity of all compounds was higher against P. falciparum trophozoite stages. Advantages of flow cytometry analysis over traditional assays included higher throughput for data collection, insight into the stage-specificity of antimalarial activity avoiding use of radioactive isotopes.

Chromosomal gene movements reflect the recent origin and biology of therian sex chromosomes

Mammalian sex chromosomes stem from ancestral autosomes and have substantially differentiated. It was shown that X-linked genes have generated duplicate intronless gene copies (retrogenes) on autosomes due to this differentiation. However, the precise driving forces for this out-of-X gene "movement" and its evolutionary onset are not known. Based on expression analyses of male germ-cell populations, we here substantiate and extend the hypothesis that autosomal retrogenes functionally compensate for the silencing of their X-linked housekeeping parental genes during, but also after, male meiotic sex chromosome inactivation (MSCI). Thus, sexually antagonistic forces have not played a major role for the selective fixation of X-derived gene copies in mammals. Our dating analyses reveal that although retrogenes were produced ever since the common mammalian ancestor, selectively driven retrogene export from the X only started later, on the placental mammal (eutherian) and marsupial (metatherian) lineages, respectively. Together, these observations suggest that chromosome-wide MSCI emerged close to the eutherian-marsupial split approximately 180 million years ago. Given that MSCI probably reflects the spread of the recombination barrier between the X and Y, crucial for their differentiation, our data imply that these chromosomes became more widely differentiated only late in the therian ancestor, well after the divergence of the monotreme lineage. Thus, our study also provides strong independent support for the recent notion that our sex chromosomes emerged, not in the common ancestor of all mammals, but rather in the therian ancestor, and therefore are much younger than previously thought