Stimulus-secretion coupling of arginine-induced insulin release. Insulinotropic action of agmatine.

Agmatine causes a concentration-related (0.1-1.0 mM) stimulation of insulin secretion by rat pancreatic islets exposed to D-glucose (5.6-11.1 mM) but, like L-arginine, fails to affect insulin release either in the absence of glucose or at a high concentration (16.7 mM) of the hexose. Agmatine, which accumulates in islet cells, also stimulates 45Ca net uptake by the islets. The secretory response to agmatine represents a delayed process. It is enhanced by theophylline and suppressed by antimycin A or the absence of extracellular Ca2+. The insulinotropic action of agmatine is compatible with the view that endogenously formed polyamines may play a role in the secretory response of islet cells to L-arginine.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Ketone bodies and islet function: 86Rb handling and metabolic data.

The metabolism of ketone bodies was investigated in rat pancreatic islets incubated in the absence or presence of D-glucose. The generation of 14CO2 from 3-14C-labeled ketone bodies, the interconversion of D-(-)-beta-hydroxybutyrate and acetoacetate (AcAc), the reciprocal effects of ketone bodies and D-glucose on their respective catabolism, and the influence of these exogenous nutrients on the output of 14CO2 from islets preincubated with either L-[U-14C]glutamine or [U-14C]palmitate provided an estimation of the nutrient-induced changes in O2 uptake that was in fair agreement with the observed modifications of islet respiration. There was a close correlation between such changes and the corresponding values for insulin output. Because the stimulation of insulin release by ketone bodies also coincided with a decrease in 86Rb outflow from prelabeled islets, these findings suggest that the insulinotropic action of ketone bodies is causally linked to their catabolism through an increase in ATP generation rate and a subsequent decrease in K+ conductance. A complementary participation of changes in mitochondrial redox state to stimulus-secretion coupling is considered, however, in the light of comparisons between the effects of D-(-)-beta-hydroxybutyrate and AcAc, respectively, on mitochondrial NADH generation, 45Ca net uptake, and D-[6-14C]glucose oxidation.In VitroJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Ostreid Herpesvirus 1 Infection among Pacific Oyster (Crassostrea gigas) Spat: Relevance of Water Temperature to Virus Replication and Circulation Prior to the Onset of Mortality

number of bivalve species worldwide, including the Pacific oyster, Crassostrea gigas, have been affected by mass mortality events associated with herpesviruses, resulting in significant losses. A particular herpesvirus was purified from naturally infected larval Pacific oysters, and its genome was completely sequenced. This virus has been classified as Ostreid herpesvirus 1 (OsHV-1) within the family Malacoherpesviridae. Since 2008, mass mortality outbreaks among C. gigas in Europe have been related to the detection of a variant of OsHV-1 called µVar. Additional data are necessary to better describe mortality events in relation to environmental-parameter fluctuations and OsHV-1 detection. For this purpose, a single batch of Pacific oyster spat was deployed in 4 different locations in the Marennes-Oleron area (France): an oyster pond (“claire”), a shellfish nursery, and two locations in the field. Mortality rates were recorded based on regular observation, and samples were collected to search for and quantify OsHV-1 DNA by real-time PCR. Although similar massive mortality rates were reported at the 4 sites, mortality was detected earlier in the pond and in the nursery than at both field sites. This difference may be related to earlier increases in water temperature. Mass mortality was observed among oysters a few days after increases in the number of PCR-positive oysters and viral-DNA amounts were recorded. An initial increment in the number of PCR-positive oysters was reported at both field sites during the survey in the absence of significant mortality. During this period, the water temperature was below 16°C

Claire ponds as an experimental model for <I>Marteilia refringens</I> life-cycle studies: new perspectives

International audienceSince its first description, the paramyxean parasite Marteilia refringens (Grizel et al.) has been recognised as a significant pathogen of the European flat oyster Ostrea edulis L. The existence of a complex life-cycle involving several hosts was postulated early on by many authors, although it remains unsolved. Recent developments in the DNA-based diagnosis of M. refringens provides new prospects for the detection of the parasite in potential hosts. However, this screening remains impeded by the number of species living in the vicinity of oyster beds. We report here on the use of semi-closed oyster ponds (so called ‘claire’ in Marennes-Oléron Bay) as a study model for the life-cycle of M. refringens. Claires are located in an endemic area for M. refringens and transmission of the disease to healthy oysters has been shown to be effective during the course of this study. The environmental characteristics of the claires strongly limit the number of species compared with intertidal areas and oyster beds. Consequently, extensive sampling of a limited number of species cohabiting with oysters was possible. These were preserved for future screening of M. refringens. The experimental model should bring new insights to the life-cycle of M. refringens, as it enables us to propose new conceptual schemes of M. refringens transmission. The role of species as potential hosts is discussed regarding their biology and geographical distribution

Anti-spike protein to determine SARS-CoV-2 antibody levels: Is there a specific threshold conferring protection in immunocompromised patients?

BackgroundIdentifying a specific threshold level of SARS-CoV-2 antibodies that confers protection in immunocompromised patients has been very challenging. The aim was to assess the threshold of 264 binding antibody units (BAU)/ml using four different SARS-CoV-2 antibody assays (Abbott, Beckman, Roche, and Siemens) and to establish a new optimal threshold of protection for each of the four antibody assays.MethodsThis study was performed on data retrieved from 69 individuals, who received at least one dose of the Pfizer/BioNTech BNT162b2 or Moderna COVID-19 vaccine (Spikevax) at the Alphabio Laboratory in Marseille, France (European Hospital, Alphabio-Biogroup). The results were compared to the percent inhibition calculated using a functional surrogate of a standardized virus neutralization test (Genscript).ResultsSamples from 69 patients were analyzed. For a reference cutoff of 264 BAU/ml, assays showed moderate to good overall concordance with Genscript: 87% concordance for Abbott, 78% for Beckman, 75% for Roche, and 88% for Siemens. Overall concordance increased consistently after applying new thresholds, i.e., 148 BAU/ml (Abbott), 48 (Beckman), 559 (Roche), and 270 (Siemens).ConclusionWe suggest specific adjusted thresholds (BAU/ml) for the four commercial antibody assays that are used to assess pre-exposure prophylaxis in immunocompromised patients

A Joint European Certification System for Sustainable Non-Intensive Aquaculture: a proposal from the SEACASE project

The European project Sustainable extensive and semi-intensive coastal aquaculture in Southern Europe (SEACASE) included the proposal of 6 Codes of Conduct for the aquaculture systems studied during the project work. These case studies are typical of the countries involved, namely semi-intensive polyculture (Portugal and Spain), extensive polyculture in esteros (Spain), integrated systems (France), valliculture (Italy), nursery ponds (Greece, Portugal, France and Italy) and eel ponds (France). This article was written having as objective the providing of a concise summary of the characteristics that SEACASE collaborators found to be central to build a complete and trustable Certification system for products of sustainable non-intensive aquaculture (for “certification of sustainability”, see Ojeda, 2008). The 6 Codes of Conduct are the basic information to build such a system in the future.This study has been carried out with the financial support from the Commission of the European Communities, specific RTD programme “Specific Support to Policies”, SSP-2005-44483 “SEACASE - Sustainable extensive and semi-intensive coastal aquaculture in Southern Europe”, and does not necessarily reflect the European Commission views and in no way anticipates the Commission’s future policy in this area.Peer reviewe

Recruitment in pediatric clinical research was influenced by study characteristics and pediatricians' perceptions: a multicenter survey.

International audienceOBJECTIVES: The aim of this survey was to quantify refusal rates and identify factors of refusal pertaining to studies and recruiting pediatricians in the research recruitment process. STUDY DESIGN AND SETTING: We performed a cross-sectional survey on all clinical studies conducted in six pediatric Clinical Investigation Centers in France over an 18-month period. Data were retrieved using a data collection form for the characteristics of each of the studies included in the survey and a questionnaire addressed to recruiting pediatricians. Multilevel models were used for the statistical analysis. RESULTS: Overall, 145 pediatricians approached the families of 999 children and adolescents for participation in 44 studies. In the 36 of the 44 studies that enrolled subjects, median refusal rate was 12.5% (Q1-Q3, 0-28%). Lower refusal rates were associated with therapeutic drug use as the focus of the study [odds ratio (OR), 0.51; 95% CI: 0.25, 1.05], additional hospital stays required for the study (OR, 0.53; 95% CI: 0.28, 0.99), longer duration of the inclusion visit (OR, 0.93/10 min; 95% CI: 0.87, 1), and recruitment by a pediatrician with university teaching responsibilities (OR, 0.26; 95% CI: 0.10, 0.68). Refusal rate was higher when the recruiting pediatrician perceived the study as generating heavy practical burden for the subject and/or its family (OR, 1.3; 95% CI: 1.17, 1.45). CONCLUSION: Refusal to participate in clinical research was low and was influenced by factors associated to the objectives and conduct of the studies and factors related to the characteristics and perceptions of the recruiting pediatricians

Does the site of magnetic resonance imaging abnormalities match the site of recent-onset inflammatory back pain? The DESIR cohort.

International audienceOBJECTIVES: To assess whether the site of axial pain (thoracic spine, lumbar spine or buttock(s)) was associated with the site of MRI lesions in patients with recent inflammatory back pain (IBP) suggesting spondyloarthritis. METHODS: We conducted a cross-sectional study of baseline data in 708 patients with recent IBP from the DESIR cohort. Radiographs of the sacroiliac joints (SIJs) and MRI scans of the SIJs and thoracic and lumbar spine were obtained routinely. Associations between pain sites and sites of inflammatory and structural MRI changes were evaluated using separate multivariate logistic regressions. RESULTS: Of the 648 patients with complete data, 61% had thoracic pain, 91.6% lumbar pain and 79.2% buttock pain. MRI inflammation was seen in 19%, 21% and 46% of patients at the thoracic, lumbar and SIJ sites, respectively. By multivariate analysis, pain was significantly associated with MRI inflammation only at the same site (adjusted OR (aOR)(thoracic) (pain) 1.71; 95% CI 1.09 to 2.67; p=0.02; aOR(lumbar pain) 2.53; 95% CI 1.03 to 6.20; p=0.04; aOR(buttock pain) 2.86; 95% CI 1.84 to 4.46; p<0.0001). Pain site was not significantly associated with the site of structural MRI changes, except for buttock pain and SIJ structural MRI changes (aOR(buttock pain) 1.89; 95% CI 1.22 to 2.90; p=0.004). The association between pain site and site of MRI inflammation persisted in the subgroups with normal or doubtful SIJ radiographs or with Assessment of SpondyloArthritis international Society criteria for axial spondyloarthritis. CONCLUSIONS: The site of pain (thoracic spine, lumbar spine or buttock(s)) is associated with MRI inflammation at the same site in patients with recent IBP

Factors associated with radiographic lesions in early axial spondyloarthritis. Results from the DESIR cohort.

International audienceOBJECTIVE: To assess whether factors such as inflammation by laboratory tests and MRI differ between early axial SpA with and without radiographic lesions. METHODS: Cross-sectional analysis of baseline data from Devenir des Spondylarthropathies Indifferenciées Récentes (DESIR) cohort patients having recent-onset inflammatory back pain and meeting Assessment of SpondyloArthritis international Society criteria. The baseline evaluation included radiographs and MRI of the SI joints (SIJs) and spine. Patients were classified as having radiographic lesions if they had at least one obvious sacroiliitis, grade 2 for at least one vertebral corner or grade 1 for at least two vertebral corners (at the cervical or lumbar level, according to the modified Stoke Ankylosing Spondylitis Spine Score). Associations between baseline characteristics and the presence of radiographic lesions were evaluated by estimating multi-adjusted odd ratios (aORs) and their 95% CIs using a logistic regression model. RESULTS: Of 475 patients, 180 (37.9%) had radiographic lesions. Factors positively associated with radiographic lesions were alcohol use (aOR 2.42; 95% CI 1.31, 4.44; P = 0.005), CRP level (aOR 1.44; 95% CI 1.13, 1.84; P = 0.003) and SIJ inflammation by MRI (aOR 2.25; 95% CI 1.40, 3.60; P = 0.001); negative associations occurred with good NSAID responsiveness (aOR 0.44; 95% CI 0.24, 0.81; P = 0.008); spinal MRI inflammation was associated with radiographic lesions only in smokers (aOR 1.99; 95% CI 1.01, 3.92; P = 0.048). CONCLUSION: Alcohol use, poor responsiveness to NSAIDs, CRP elevation, SIJ MRI inflammation and spinal MRI inflammation in smokers were independently associated with radiographic lesions in early axial SpA

Tracking receptor motions at the plasma membrane reveals distinct effects of ligands on CCR5 dynamics depending on its dimerization status

International audienceG-protein-coupled receptors (GPCR) are present at the cell surface in different conformational and oligomeric states. However, how these states impact GPCRs biological function and therapeutic targeting remains incompletely known. Here, we investigated this issue in living cells for the CC chemokine receptor 5 (CCR5), a major receptor in inflammation and the principal entry co-receptor for Human Immunodeficiency Viruses type 1 (HIV-1). We used TIRF microscopy and a statistical method to track and classify the motion of different receptor subpopulations. We showed a diversity of ligand-free forms of CCR5 at the cell surface constituted of various oligomeric states and exhibiting transient Brownian and restricted motions. These forms were stabilized differently by distinct ligands. In particular, agonist stimulation restricted the mobility of CCR5 and led to its clustering, a feature depending on β-arrestin, while inverse agonist stimulation exhibited the opposite effect. These results suggest a link between receptor activation and immobilization. Applied to HIV-1 envelope glycoproteins gp120, our quantitative analysis revealed agonist-like properties of gp120s. Distinct gp120s influenced CCR5 dynamics differently, suggesting that they stabilize different CCR5 conformations. Then, using a dimerization-compromized mutant, we showed that dimerization (i) impacts CCR5 precoupling to G proteins, (ii) is a pre-requisite for the immobilization and clustering of receptors upon activation, and (iii) regulates receptor endocytosis, thereby impacting the fate of activated receptors. This study demonstrates that tracking the dynamic behavior of a GPCR is an efficient way to link GPCR conformations to their functions, therefore improving the development of drugs targeting specific receptor conformations