Studies on the oyster pathogen Perkinsus marinus (Apicomplexa): Interactions with host defenses of Crassostrea virginica and Crassostrea gigas, and in vitro propagation

The disease caused by the protozoan Perkinsus marinus has been a major source of mortality in the eastern oyster, Crassostrea virginica. Variations in susceptibility to P. marinus infection among eastern oysters collected from the Chesapeake Bay and Gulf of Mexico, as well as between eastern and Pacific (Crassostrea gigas) oysters were determined. Since oyster host defense may play a role in determining susceptibility to pathogen infection, cellular and humoral defense activities of the oyster and their interactions with P. marinus were investigated. Procedures also had to be established to isolate, purify, and propagate in vitro, P. marinus. Eastern oysters from all sites were found to be highly susceptible to the pathogen. Cellular and humoral activities were significantly affected by heavy intensity of P. marinus infection. Prevalence and intensity of P. marinus infection were lower in Pacific oysters than in eastern oysters. Pacific oysters may offer a less favorable environment for the development of P. marinus compared to eastern oysters for at least two possible reasons: the elevated cellular and humoral activities may degrade the parasite more effectively, and lower plasma protein levels may limit parasite growth. Incubation of merozoites with hemocytes of eastern and Pacific oysters in vitro suggested that limited intracellular killing of P. marinus occurred but that killing was not mediated by oxygen metabolites. Perkinsus marinus was successfully propagated in vitro in a culture medium containing most of the known constituents of cell-free oyster hemolymph. Cultures of the parasite were initiated from heart fragments of infected oysters. The cultured protozoan was similar in morphology to P. marinus, enlarged in fluid thioglycollate medium, reacted with polyclonal antibodies raised against hypnospores and was infective. Continuous cultures of P. marinus could also be initiated from hypnospores. Two types of division, progressive cleavage and successive bipartition of the mother cell protoplast, were observed

Predicting the impacts of Mississippi River diversions and sea-level rise on spatial patterns of eastern oyster growth rate and production

© 2017 There remains much debate regarding the perceived tradeoffs of using freshwater and sediment diversions for coastal restoration in terms of balancing the need for wetland restoration versus preserving eastern oyster (Crassostrea virginica) production. Further complicating the issue, climate change-induced sea-level rise (SLR) and land subsidence are also expected to affect estuarine water quality. In this study, we developed a process-based numerical modeling system that couples hydrodynamic, water quality, and oyster population dynamics. We selected Breton Sound Estuary (BSE) (∼2740 km2) in the eastern Mississippi River Deltaic Plain since it is home to several of the largest public oyster seed grounds and private leases for the Gulf coast. The coupled oyster population model was calibrated and validated against field observed oyster growth data. We predicted the responses of oyster population in BSE to small- (142 m3 s−1) and large-scale (7080 m3 s−1) river diversions at the Caernarvon Freshwater Diversion structure planned in the 2012 Coastal Master Plan (Louisiana) under low (0.38 m) and high (1.44 m) relative sea-level rise (RSLR = eustatic SLR + subsidence) compared to a baseline condition (Year 2009). Model results showed that the large-scale diversion had a stronger negative impact on oyster population dynamics via freshening of the entire estuary, resulting in reduced oyster growth rate and production than RSLR. Under the large-scale diversion, areas with optimal oyster growth rates (\u3e15 mg ash-free dry weight (AFDW) oyster−1 wk−1) and production (\u3e500 g AFDW m−2 yr−1) would shift seaward to the southeastern edge of the estuary, turning the estuary into a very low oyster production system. RSLR however played a greater role than the small-scale diversion on the magnitude and spatial pattern of oyster growth rate and production. RSLR would result in an overall estuary-wide decrease in oyster growth rate and production as a consequence of decreased salinities in the middle and lower estuary because rising sea level likely causes increased stage and overbank flow downstream along the lower Mississippi River

Perkinsus marinus susceptibility and defense-related activities in eastern oysters Crassostrea virginica: temperature effects

he relationship of potential defense-related cellular and humoral activities and the sus- ceptibility of eastern oysters Crassostrea virginica to the parasite Perkinsus marinus were examined at 10, 15, 20 and 25 C. Oysters were acclimated at experimental temperatures for 20 d and then chal- lenged with R marinus. Total hemocyte counts (TC) and percentage of granulocytes (PG) 20 d after temperature acclimation were higher in oysters at high than at low acclimation temperature. Higher protein (P) and lysozyme (L) concentrations were found in oysters at 10 and 15 C. No significant differ- ences in hemagglutination (H) titers due to temperature acclimation were observed. Infection preva- lence 46 d after challenge by R marinus was 100, 91, 46 and 23 % respectively, for oysters at 25, 20, 15 and 10 C. Disease intensity increased with temperature. Oysters at higher temperatures had greater PG and TC and hemocyte phagocytic activity. No difference was found in TC and PG between control and challenged oysters within each temperature treatment. Bleeding may to some extent reduce TC and PG in oysters. P did not vary much among temperatures. No reduction of P in oysters was found due to P. marinuschallenge and infection. L tended to be higher in oysters at lower than at higher treat- ment temperatures. The oysters at 10 C had the highest L concentration and lowest P marinus infec- tion. But, it is not known whether the high extracellular L in oysters at 10 DC is attributable to the low R marinus susceptibility in these oysters. There was no significant difference in condition index (Cl) between control and challenged oysters and between infected and uninfected oysters. However, C1 de- creased with increasing temperatures. The H titers were not associated with any measured variables. The greater TC, PG, and phagocytic capability in oysters at higher temperatures did not result in fewer or less intense P marinus infections

Swine influenza surveillance in East and Southeast Asia: a systematic review

East and Southeast Asia are important pig- and poultry-producing areas, where the majority of production takes place on small-scale farms with low biosecurity levels. This systematic review synthesizes data on swine influenza virology, serology and epidemiology in East and Southeast Asia. A total of 77 research articles, literature reviews and conference papers were selected and analyzed from 510 references retrieved from PubMed and ISI Web of KnowledgeSM. The number of published articles increased in the last 3 years, which may be attributed to improvement in monitoring and/or a better promotion of surveillance data. Nevertheless, large inequalities in surveillance and research among countries are underlined. Virological results represent the largest part of published data, while the serological and epidemiological features of swine influenza in East and Southeast Asia remain poorly described. The literature shows that there have been several emergences of swine influenza in the region, and also considerable evidence of multiple introductions of North American and avian-like European strains. Furthermore, several avian-origin strains are isolated from pigs, including H5 and H9 subtypes. However, their low seroprevalence in swine also shows that pigs remain poorly infected by these subtypes. We conclude that sero-epidemioligical investigations have been neglected, and that they may help to improve virological surveillance. Inter- and intra-continental surveillance of gene flows will benefit the region. Greater investment is needed in swine influenza surveillance, to improve our knowledge of circulating strains as well as the epidemiology and disease burden in the region.published_or_final_versio

Towards a numerical simulation of direct manufacturing of thermoplastic parts by powder laser sintering COMPLAS XI

Direct manufacturing technology using Selective Laser Sintering (SLS) on thermoplastic powders allows obtaining final parts in a short time, with classical polymer density and a high flexibility of shape and evolution of parts. The physical base of this process is the coalescence of grains, which initiates the densification of powder during SLS. This study presents a 2D C-NEM simulation of the whole process. We firstly focus on the chosen method and its advantages. We present the simulation details and validate the modeling through a 2D infinite cylinders coalescence simulation. The mesh of the grain interface is continuously adapted to the local curvature to better capture the coalescence phenomenon. We are able to simulate the sintering of twelve particles laying on a support within some hours

Derivatives with respect to metrics and applications: subgradient marching algorithm

This paper introduces a subgradient descent algorithm to compute a Riemannian metric that minimizes an energy involving geodesic distances. The heart of the method is the Subgradient Marching Algorithm to compute the derivative of the geodesic distance with respect to the metric. The geodesic distance being a concave function of the metric, this algorithm computes an element of the subgradient in O(N (2) log(N)) operations on a discrete grid of N points. It performs a front propagation that computes a subgradient of a discrete geodesic distance. We show applications to landscape modeling and to traffic congestion. Both applications require the maximization of geodesic distances under convex constraints, and are solved by subgradient descent computed with our Subgradient Marching. We also show application to the inversion of travel time tomography, where the recovered metric is the local minimum of a non-convex variational problem involving geodesic distances

Characterizing the Epigenetic and Transcriptomic Responses to Perkinsus marinus Infection in the Eastern Oyster Crassostrea virginica

© Copyright © 2020 Johnson, Sirovy, Casas, La Peyre and Kelly. Eastern oysters in the northern Gulf of Mexico are routinely infected with the protistan parasite Perkinsus marinus, the cause of the disease commonly known as dermo. Recent experimental challenges among Atlantic coast populations have identified both resistant and susceptible genotypes using comparative transcriptomics. While controlled experimental challenges are essential first assessments, expanding this analysis to field reared individuals provides an opportunity to identify key genomic signatures of infection that appear both in the laboratory and in the field. In this study we combined reduced representation bisulfite sequencing with 3′ RNA sequencing (Tag-seq) to describe two molecular phenotypes associated with infection in oysters outplanted at a common garden field site. These combined approaches allowed us to examine changes in DNA methylation and gene expression for a large number of individuals (n = 40) that developed infections during the course of a common garden outplant experiment. Our epigenetic analysis of DNA methylation identified significant changes in gene body methylation associated with increasing infection intensity, across genes associated with immune responses. There was a smaller transcriptomic response to increasing infection intensities with 32 genes showing differential expression; however, only 40% of these genes were found to also be differentially methylated. While there was no clear pattern between direction of differential methylation and gene expression, there was a significant effect of percent methylation on gene-by-gene expression levels and the coefficient of variation in gene body methylation between treatments. These results show that in C. virginica, heavily methylated genes have high levels of gene expression with low levels of variation. Comparing our differential expression results with previously published experimental P. marinus challenges identified overlapping expression patterns for genes associated with C1q-domain-containing and V-type proton ATPase proteins. Through our comparative transcriptomic approach using field reared individuals and co-expression network analysis we have also been able to identify a network of genes that change in expression in response to infection. These combined analyses provide evidence for a conserved response to P. marinus infections across infection intensities and suggest that DNA methylation may not be a reliable predictor of differential gene expression in long-term infections

Estudio de validación de la escala de depresión de Montgomery y Asberg.

Derivada del cuestionario psicopatológico C.P.R.S., aparece en 1979 la "Montgomery Asberg Depression Rating Scale" concebida por sus autores como un instrumento altamente sensible para detectar los cambios en la sintomatología depresiva de los pacientes. Validada por sus autores originales en Inglaterra y Suecia, presentamos en este artículo un estudio de validación realizado sobre 147 pacientes franceses hospitalizados y diagnosticados de un trastorno afectivo según el DSM III. Obtuvimos resultados similares a los estudios precedentes que confirman una validez superior (sensibilidad = 94%, especificidad = 75% y mal clasificados = 6%), una más alta fiabilidad interexaminadores (K = 0,41 KW = 0,81) y sobre todo una mayor sensibilidad al cambio (S = 0,64 y 0,59) que las escalas de Hamilton y Beck consideradas hasta ahora como de referencia en su géner

A Shell-Neutral Modeling Approach Yields Sustainable Oyster Harvest Estimates: A Retrospective Analysis of the Louisiana State Primary Seed Grounds

A numerical model is presented that defines a sustainability criterion as no net loss of shell, and calculates a sustainable harvest of seed (\u3c75 mm) and sack or market oysters (\u3e= 75 mm). Stock assessments of the Primary State Seed Grounds conducted east of the Mississippi from 2009 to 2011 show a general trend toward decreasing abundance of sack and seed oysters. Retrospective simulations provide estimates of annual sustainable harvests. Comparisons of simulated sustainable harvests with actual harvests show a trend toward unsustainable harvests toward the end of the time series. Stock assessments combined with shell-neutral models can be used to estimate sustainable harvest and manage cultch through shell planting when actual harvest exceeds sustainable harvest. For exclusive restoration efforts (no fishing allowed), the model provides a metric for restoration success namely, shell accretion. Oyster fisheries that remove shell versus reef restorations that promote shell accretion, although divergent in their goals, are convergent in their management; both require vigilant attention to shell budgets