Bio-accumulation des métaux lourds chez l'oursin Paracentrotus lividus (Lamarck) sur la côte Est de la Méditerranée marocaine

La composition minérale de l’oursin (Paracentrotus lividus), échinoderme benthique fréquent dans la côte Est de la Méditerranée marocaine, concorde avec celle de l’eau du site de prélèvement. En outre, la comparaison des valeurs obtenues sur des oursins récoltés en automne avec celles élevées qui sont obtenues sur des oursins récoltés au printemps suppose l’existence d’un cycle métabolique saisonnier. Les teneurs observées dans l’épithélium digestif et dans les gonades laissent présager les possibilités d’échanges métaboliques entre les systèmes digestif et reproducteur. Ce phénomène est non étudié jusqu’à présent chez les Échinides. Les lysosomes sont les organites cibles où la plupart des éléments, absorbés à l’état de traces sous forme soluble, se concentrent sous forme de précipités de phosphates insolubles

Étude expérimentale de la bio-accumulation des lanthanides chez la moule Mytilus galloprovincialis (Lamarck) du littoral méditerranéen marocain

La microscopie ionique et la microanalyse X ont été utilisées pour détecter in situ, sur coupes histologiques, les éléments bio-accumulés dans la moule Mytilus galloprovincialis, contaminée expérimentalement in vitro par le cérium, le thulium et le lanthane. Les éléments absorbés, sous forme soluble à l’état de traces dans les organites cibles (les lysosomes), sont concentrés sous forme de précipités de phosphate insolubles dans les cellules épithéliales des branchies, des glandes digestives et des palpes labiaux

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.This study was carried out under a MNT ERA-Net Project named NANOMED. The authors gratefully thank the Midi-Pyrénées region (MNT ERA Net Midi-Pyrénées Région, NANOMED2 project) and the Institute National Polytechnique de Toulouse (BQR INPT 2011, BIOREVE project) for supporting this research work, especially the financial support for research carried out in the CIRIMAT and the LGP laboratories (France), and the Basque government and Tratamientos Superficiales Iontech, S.A. for their financial and technical support under the IG-2007/0000381 grant for the development of the LEPS device and deposition of the coatings carried out in Inasmet-Tecnalia. The French industrial collaborators (TEKNIMED SA and 2PS SA) were financed by the OSEO programs

Crude incidence in two-phase designs in the presence of competing risks.

BackgroundIn many studies, some information might not be available for the whole cohort, some covariates, or even the outcome, might be ascertained in selected subsamples. These studies are part of a broad category termed two-phase studies. Common examples include the nested case-control and the case-cohort designs. For two-phase studies, appropriate weighted survival estimates have been derived; however, no estimator of cumulative incidence accounting for competing events has been proposed. This is relevant in the presence of multiple types of events, where estimation of event type specific quantities are needed for evaluating outcome.MethodsWe develop a non parametric estimator of the cumulative incidence function of events accounting for possible competing events. It handles a general sampling design by weights derived from the sampling probabilities. The variance is derived from the influence function of the subdistribution hazard.ResultsThe proposed method shows good performance in simulations. It is applied to estimate the crude incidence of relapse in childhood acute lymphoblastic leukemia in groups defined by a genotype not available for everyone in a cohort of nearly 2000 patients, where death due to toxicity acted as a competing event. In a second example the aim was to estimate engagement in care of a cohort of HIV patients in resource limited setting, where for some patients the outcome itself was missing due to lost to follow-up. A sampling based approach was used to identify outcome in a subsample of lost patients and to obtain a valid estimate of connection to care.ConclusionsA valid estimator for cumulative incidence of events accounting for competing risks under a general sampling design from an infinite target population is derived

The role of γδ T cells in airway epithelial injury and bronchial responsiveness after chlorine gas exposure in mice

BACKGROUND: Acute exposure to chlorine (Cl(2)) gas causes epithelial injury and airway dysfunction. γδ T cells are present in the mucosal surface of the airways and may contribute to the injury/repair response of the epithelium. METHODS: C57Bl/6J (wild type) and TCR-δ(-/- )mice exposed to Cl(2 )(400 ppm) for 5 minutes underwent measurements of airway responses to i.v. methacholine (MCh) at 1, 3, and 5 days after exposure. Bronchoalveolar lavage was performed to determine epithelial and leukocyte counts, and protein content. Tissue repair was assessed by proliferating cell nuclear antigen (PCNA) immunoreactivity and by expression of keratinocyte growth factor (KGF) mRNA by real-time PCR. RESULTS: Wild type mice developed a greater degree of airway hyperresponsiveness to MCh at 1 day post exposure to Cl(2 )compared with TCR-δ(-/- )mice. Epithelial cell counts in BAL after Cl(2 )exposure were greater in TCR-δ(-/- )mice, but macrophages showed a later peak and granulocyte numbers were lower in TCR-δ(-/- )than in wild type mice. Both groups had increased levels of total protein content in BAL after Cl(2 )exposure that resolved after 3 and 5 days, respectively. Epithelial proliferating cell nuclear antigen staining was increased at 1 and 3 days post exposure and was similar in the two groups. KGF mRNA was constitutively expressed in both groups and did not increase significantly after Cl(2 )but expression was lower in TCR-δ(-/- )mice. CONCLUSION: The severity of airway epithelial injury after Cl(2 )is greater in TCR-δ(-/- )mice but the inflammatory response and the change in airway responsiveness to methacholine are reduced. The rates of epithelial regeneration are comparable in both groups

Modeling of longitudinal polytomous outcome from complex survey data - application to investigate an association between mental distress and non-malignant respiratory diseases

<p>Abstract</p> <p>Background</p> <p>The data from longitudinal complex surveys based on multi-stage sampling designs contain cross-sectional dependencies among units due to clustered nature of the data and within-subject dependencies due to repeated measurements. Special statistical methods are required to analyze longitudinal complex survey data.</p> <p>Methods</p> <p>Statistics Canada's longitudinal National Population Health Survey (NPHS) dataset from the first five cycles (1994/1995 to 2002/2003) was used to investigate the effects of demographic, social, life-style, and health-related factors on the longitudinal changes of mental distress scores among the NPHS participants who self-reported physician diagnosed respiratory diseases, specifically asthma and chronic bronchitis. The NPHS longitudinal sample includes 17,276 persons of all ages. In this report, participants 15 years and older (n = 14,713) were considered for statistical analysis. Mental distress, an ordinal outcome variable (categories: no/low, moderate, and high) was examined. Ordered logistic regression models based on the weighted generalized estimating equations approach were fitted to investigate the association between respiratory diseases and mental distress adjusting for other covariates of interest. Variance estimates of regression coefficients were computed by using bootstrap methods. The final model was used to predict the probabilities of prevalence of no/low, moderate or high mental distress scores.</p> <p>Results</p> <p>Accounting for design effects does not vary the significance of the coefficients of the model. Participants suffering with chronic bronchitis were significantly at a higher risk (OR_adj= 1.37; 95% CI: 1.12-1.66) of reporting high levels of mental distress compared to those who did not self-report chronic bronchitis. There was no significant association between asthma and mental distress. There was a significant interaction between sex and self-perceived general health status indicating a dose-response relationship. Among females, the risk of mental distress increases with increasing deteriorating (from excellent to very poor) self-perceived general health.</p> <p>Conclusions</p> <p>A positive association was observed between the physician diagnosed self-reported chronic bronchitis and an increased prevalence of mental distress when adjusted for important covariates. Variance estimates of regression coefficients obtained from the sandwich estimator (i.e. not accounting for design effects) were similar to bootstrap variance estimates (i.e. accounting for design effects). Even though these two sets of variance estimates are similar, it is more appropriate to use bootstrap variance estimates.</p

Correlates of weapon carrying among high school students in the United States

Abstract Background Deaths and injuries arising from interpersonal violence among adolescents are major public health concerns in the United States. The bearing of weapons among adolescents is a critical factor in many of these deaths and injuries. Methods A secondary analysis of the 2005 United States Youth Risk Behavior Surveillance System Survey data was carried out to examine the variables associated with self-reported history of weapon carrying on school property among high school students. We used logistic regression analysis to assess the associations. Results Of the 13,707 respondents who participated in the survey, 10.2% of males and 2.6% of females reported carrying a weapon on school property. In multivariate logistic regression analysis, males were more likely to report having carried a weapon than females (odds ratio (OR) = 5.58; 95% confidence interval (CI) [4.23, 7.62]). Self-reported race/ethnicity was also associated with weapon carrying. Other variables positively associated with weapon carrying at school were substance use (OR = 1.77; 95% CI [1.16, 2.68]), depression (OR = 1.44; 95% CI [1.10, 1.89]), suicidal ideation (OR = 1.64; 95% CI [1.23, 2.19]), having had property stolen or deliberately damaged at school (OR = 1.55; 95% CI [1.21, 1.98]), having been raped (OR = 1.70; 95% CI [1.22, 2.37]), having been threatened or injured with a weapon on school property (OR = 2.19; 95% CI [1.63, 2.95]), and having engaged in physical fighting (OR = 2.02; 95% CI [1.56, 2.63]). Conclusion This research identifies factors that are associated with weapon bearing among adolescents in the United States. These factors may be important in the design of interventions aimed at improving school safety and adolescent health