In vitro modulation of reactive oxygen and nitrogen intermediate (ROI/RNI) production in Crassostrea gigas hemocytes

International audienceBivalve hemocyte competence has been measured by quantifying functional characteristics, including reactive oxygen intermediate (ROI) production after activation with zymosan or phorbol myristate acetate (PMA). However, untreated oyster hemocytes also produce ROI and RNI (reactive nitrogen intermediates) after bleeding even if not stimulated by zymosan or PMA. Extensive investigation of this parameter by flow cytometry showed that, in vitro, ROI/RNI production by untreated hemocytes maintained in seawater appeared to be independent of both bacterial burden in the serum and non-self particle phagocytosis. ROI/ RNI production in granulocytes was higher than in hyalinocytes and could be intensified when activated by zymosan but not by PMA. Both cell types used NADPH-oxidase- and NO-synthase-like pathways to produce these molecules; the NO-synthase pathway seemed relatively more dominant in hyalinocytes and NADPH-oxidase appeared more effective in granulocytes. These results provide new insights for interpreting the modulation of ROI/RNI production by untreated hemocytes shown by other studies, relative to environmental conditions or physiological status of the oysters

Analysis of Virion Structural Components Reveals Vestiges of the Ancestral Ichnovirus Genome

Many thousands of endoparasitic wasp species are known to inject polydnavirus (PDV) particles into their caterpillar host during oviposition, causing immune and developmental dysfunctions that benefit the wasp larva. PDVs associated with braconid and ichneumonid wasps, bracoviruses and ichnoviruses respectively, both deliver multiple circular dsDNA molecules to the caterpillar. These molecules contain virulence genes but lack core genes typically involved in particle production. This is not completely unexpected given that no PDV replication takes place in the caterpillar. Particle production is confined to the wasp ovary where viral DNAs are generated from proviral copies maintained within the wasp genome. We recently showed that the genes involved in bracovirus particle production reside within the wasp genome and are related to nudiviruses. In the present work we characterized genes involved in ichnovirus particle production by analyzing the components of purified Hyposoter didymator Ichnovirus particles by LC-MS/MS and studying their organization in the wasp genome. Their products are conserved among ichnovirus-associated wasps and constitute a specific set of proteins in the virosphere. Strikingly, these genes are clustered in specialized regions of the wasp genome which are amplified along with proviral DNA during virus particle replication, but are not packaged in the particles. Clearly our results show that ichnoviruses and bracoviruses particles originated from different viral entities, thus providing an example of convergent evolution where two groups of wasps have independently domesticated viruses to deliver genes into their hosts

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Review and perspectives of physiological mechanisms underlying genetically-based resistance of the Pacific oyster

French oyster farming has been subject to severe mortalities during the summer months. Results from the research program “Morest”, which ran from 2000 to 2006 and examined the possible causes of these mortalities, led to the construction of a model to explain the interaction between environmental factors, oyster physiology and different opportunistic pathogens underlying oyster summer mortality. Temperature, food, reproduction and stress were the main factors required for oyster mortality. Genetically-based resistance (“R” oysters) or susceptibility (“S” oysters) to summer mortality was revealed by divergent selection. Building on these results, a literature search was made in 2007 on the molecular origin of genetic resistance to such a complex mortality risk. The objectives were to lay a foundation for the preparation and orientation of future research directions and to improve understanding of the underlying physiological mechanism leading to summer mortality. Three years later, the resulting conceptual analysis reported here was presented as an introductory lecture to Physiomar 2010, a conference where many new results contributing to this research field were also reported. The literature review highlighted two major review articles: the first dealing with nutrition and reproduction (Schneider 200

Modulation des paramètres hémocytaires par la nutrition chez l'huitre creuse Crassostrea Gigas (Implication dans les mortalités estivales)

Cette étude réalisée dans le cadre des mortalités estivales de l'huître C. gigas montre que l'effort de reproduction, associé à une montée thermique, déprime les paramètres énergétiques (glucides, CEA) et hémocytaires (concentration, phagocytose, adhésion). L'augmentation de la ration alimentaire de 4% à 12% du poids sec de l';huître ne compense pas voir aggrave ces dépressions puisque l'excédant énergétique du régime 12% est alloué en priorité à la gamétogénèse. Par contre, après la gamétogénèse, la ration 12% favorise l'acquisition de réserves et corrélativement augmente la concentration en hémocytes. Les paramètres hémocytaires sont aussi sensibles à la qualité de la nourriture. Ainsi, l'apport de 20:4n-6 et/ou de 20:5n-3 par des microalgues ou aliments artificiels tend à augmenter le nombre d'hémocytes. Lorsque ces acides gras sont apportés séparément, il a été établi que le 20:4n-6 stimule la phagocytose et la production d'espèces actives de l'O2 tandis que le 20:5n-3 les inhibe.RENNES1-BU Sciences Philo (352382102) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

Impacts of Harmful Algal Blooms on physiological and cellular processes of bivalve molluscs

Hurmful algal blooms (HABs) are increasingly recognized as having profound effects upon economics of fisheries and aquaculture. Further, HABs are included in a list of concerns about changes in marine ecosystems that increase impacts of diseases and parasites on important resource species and the food webs that support them. This research assessed the interactions between HABs and bivalve molluscs. A number of specific HAB-bivalve interactions were studied, measuring fundamental physiological processes such as clearance and filtration rates of bivalves when exposed to pure cultures of HAB species or mixed benign and HAB cultures. Results indicate that clearance and filtration rates, as well as biodeposit production, were species specific. Further studies demonstrated the presence of intact HAB cells in the biodeposits with the ability to recover, suggesting potential risks for bivalves to be vectors of introduction of HABs into new environments. A simple method for mitigating this risk was demonstrated : keeping shellfish out of mater for 24 hr, or depurating at least 24 hr in quarantined seawater renders cells non-viable. Physiological responses of bivalve molluscs to HABs varied according to the algal/mollusc combination. This study further investigated whether these physiologicalRENNES-Agrocampus-CRD (352382323) / SudocRENNES-Agrocampus-Bibl. Linné (352382308) / SudocSudocFranceF

Oyster adenylate energy charge: response to levels of food

Adenylate Energy Charge (AEC) values of Crassostrea gigas (9 and 18 months old) cultured in ponds in Marennes-Oléron Bay (Atlantic coast, France) are reported. Two ponds were loaded with two different initial oyster biomasses in order to obtain different food conditions. The growth of oysters was different in the two ponds which corroborated the effectiveness of attaining different food conditions. AEC level was different depending on the pond and was therefore related to food availability per unit oyster biomass. Well-fed oysters exhibited greater AEC values than poorly-fed oysters, throughout the study. Information on nutritional situations for wild or cultured populations can therefore be obtained by AEC. In each pond, the seasonal AEC variations were similar for both age-groups and were characterized by a minimum value in summer and a maximum value in winter. The influence of reproduction on these variations cannot be ruled out as for all the batches maturation processes were evidenced. Research will be done on a temperature effect to try to distinguish these seasonal variations. A strong correlation between adenylate energy charge (AEC) and guanylate energy charge (GEC) was demonstrated; it was similar for both ponds. The levels of nucleotide concentration were relatively stable during the survey except in September and December for oysters in the low density pond. Among nucleotides, adenylate pool represented the major part (80%). A decrease in the total concentration of adenylates was observed in August. The best growth correlated with the lowest adenylate percentage and a better GTP/ATP ratio, suggesting that this ratio could be a useful index for growth

Fatty acid composition of polar lipid classes during larval development of scallop Pecten maximus (L.)

International audienceThe major phospholipid classes in the larvae of the scallop Pecten maximus were phosphatidylcholine (PC) and plasmalogens (PLSM) (35.5 and 32.1 mol%, respectively). The minor classes were glycosyldiacylglycerol-like (GLY), phosphatidylinositol (PI), phosphatidylserine (PS) and non- plasmalogen phosphatidylethanolamine (PE) at 6.7, 9.1, 8.5 and 8.1 mol%, respectively. Abundance of phospholipid classes and their content of saturated, monounsaturated and polyunsaturated fatty acids remained relatively conserved during the course of larval development. During larval development there was a decrease in the amount of 20-carbon polyunsaturated fatty acids (PUFA) in the polar lipids, while the amount of 22-carbon PUFA remained constant. These changes, which occurred mainly during the lecithotrophic phase, imparted a specificity in PUFA composition to the different classes of polar lipids. During this phase, 20:5(n - 3) replaced 20:4(n - 6) in PI but decreased sharply in PLSM and, to a lesser extent, in PC. After the initial phase of composition changes, the fatty acid composition of the polar lipid classes became stable, with specific associations of some of the PUFA with certain polar lipid classes: 22:6(n - 3) with GLY, 20:5(n - 3) with PE, 20:4(n - 6) with PI. The 22:6(n - 3)/20:5(n - 3) ratio in PLSM during exotrophy was always twice as high as in the PC fraction

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Effect of sediment nearness on the metabolic enzyme activity and energy state of the oyster

This study was designed to assess in situ the effects of sediment nearness on Crassostrea gigas metabolism. One year-old oysters were reared for 5 months (April-August) in plastic bags on metallic frames at 10 and 60 cm off the sediment at the beginning of April. The management of the energetic resources (storage, consumption) was estimated with respect to biochemical changes of proteins, lipids and carbohydrates. In order to evaluate the effect of the sediment nearness at cellular level, the metabolic rate was evaluated by assessing pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK) enzyme activities and electron transport system (ETS) activity. The metabolic pathways were assessed by measuring ATP and intermediary metabolites such as alanine, succinate and aspartate. Despite similar survival and growth at the two rearing levels, the protein, lipid and carbohydrate content were significantly lower in the oysters close to the bottom. In the oysters reared at 10 cm, PK activity was also significantly reduced and a significant negative correlation between alanine content and PK activity was revealed. The sediment nearness decreased significantly the ATP content in the oyster. There was a significant relationship between ATP and aspartate in these oysters. The use of aspartate contributed to complete the metabolic pathways along with carbohydrate allowing to maintain the same biological performance as the oyster reared far from the bottom. The energy state (proteins, lipids, carbohydrates and ATP contents) could suggest that the oysters close to the sediment were fed less but the metabolic enzyme activities allow to suggest an oxygen deficiency. However, the reduced PK activity, the absence of PEPCK activity stimulation and the utilization of aspartate suggest a transition stage to anaerobiosis