Development of a new approach using mathematical modeling to predict cocktail effects of micropollutants of diverse origins

A wide variety of micropollutants (MP) of diverse origins is present in waste and surface waters without knowing the effect of their combination on ecosystems and human. The impact of chemical mixtures is poorly documented and often limited to binary mixtures using MP of the same category. Knowing that it is not realistic to test every possible combination found in mixtures, we aimed to develop a new method helping to predict cocktail effects. Six chemicals of agriculture, industry or pharmaceutical origin were selected: cyproconazole, diuron, terbutryn, bisphenol A, diclofenac and tramadol. Individual MP were first used in vitro to determine the concentration at which 10% (Effective Concentration EC10) or 25% (EC25) of their maximal effect on human cytotoxicity was observed. Using an Orthogonal Array Composite Design (OACD), relevant complex mixtures were then tested. Multiple linear regression was applied for response surface modeling in order to evaluate and visualize the influence of the different MP in mixtures and their potential interactions. The comparison of the predicted values obtained using the response surface model with those obtained with the model of independent effects, evidenced that the hypothesis of independence was unjustified. The cocktail effect was further investigated by considering micropollutant response surfaces pairwise. It was deduced that there was a neutralizing effect between bisphenol A and tramadol. In conclusion, we propose a new method to predict within a complex mixture of MP the combinations likely involved in cocktail effects. The proposed methodology coupling experimental data acquisition and mathematical modeling can be applied to all kind of relevant bioassays using lower concentrations of MP. Situations at high ecological risk and potentially hazardous for humans will then be identified, which will allow to improve legislation and policies.

Threat of plastic ageing in marine environment. Adsorption/desorption of micropollutants

Ageing of various plastics in marine environment was monitored after immersion of two synthetic (polyvinylchloride, PVC, and polyethylene terephthalate, PET) and one biodegradable (poly(butylene adipate co-terephtalate), PBAT) plastics for 502days in the bay of Lorient (Brittany, France). Data analysis indicates that aged PVC rapidly releases estrogenic compounds in seawater with a later adsorption of heavy metals; PET undergoes a low weakening of the surface whereas no estrogenic activity is detected; PBAT ages faster in marine environment than PVC. Aged PBAT exhibits heterogeneous surface with some cavities likely containing clay minerals from the chlorite group. Besides, this degraded material occasionally shows a high estrogenic activity. Overall, this study reports, for the first time, that some aged plastics, without being cytotoxic, can release estrogenic compounds in marine environment.

Acidic pH resistance of grafted chitosan on dental implant

Over the last decade, access to dental care has increasingly become a service requested by the population, especially in the case of dental implants. However, the major cause of implant failure is an inflammatory disease: peri-implantitis. Currently, the adhesion strength of antibacterial coatings at implant surfaces remains a problem to solve. In order to propose a functionalized implant with a resistant antibacterial coating, a novel method of chitosan immobilization at implant surface has been investigated. Functionalization of the pre-active titanium (Ti) surface was performed using triethoxysilylpropyl succinic anhydride (TESPSA) as a coupling agent which forms a stable double peptide bond with chitosan. The chitosan presence and the chemical resistibility of the coating under acid pH solutions (pH 5 and pH 3) were confirmed by FTIR-ATR and XPS analyses. Furthermore, peel test results showed high adhesive resistance of the TESPSA/chitosan coating at the substrate. Cytocompatibility was evaluated by cell morphology with confocal imaging. Images showed healthy morphology of human gingival fibroblasts (HGF-1). Finally, the reported method for chitosan immobilization on Ti surface via peptide bindings allows for the improvement of its adhesive capacities and resistibility while maintaining its cytocompatibility. Surface functionalization using the TESPSA/chitosan coupling method is noncytotoxic and stable even in drastic environments as found in oral cavity, thus making it a valuable candidate for clinical implantology applications.

Functionalization of titanium surface with chitosan via silanation: 3D CLSM imaging of cell biocompatibility behaviour

INTRODUCTION

Biocompatibility ranks as one of the most important properties of dental materials. One of the criteria for biocompatibility is the absence of material toxicity to cells, according to the ISO 7405 and 10993 recommendations. Among numerous available methods for toxicity assessment; 3-dimensional Confocal Laser Scanning Microscopy (3D CLSM) imaging was chosen because it provides an accurate and sensitive index of living cell behavior in contact with chitosan coated tested implants.

OBJECTIVES

The purpose of this study was to investigate the in vitro biocompatibility of functionalized titanium with chitosan via a silanation using sensitive and innovative 3D CLSM imaging as an investigation method for cytotoxicity assessment.

METHODS

The biocompatibility of four samples (controls cells, TA6V, TA6V-TESBA and TA6V-TESBAChitosan) was compared in vitro after 24h of exposure. Confocal imaging was performed on cultured human gingival fibroblast (HGF1) like cells using Live/Dead® staining. Image series were obtained with a FV10i confocal biological inverted system and analyzed with FV10-ASW 3.1 Software (Olympus France).

RESULTS

Image analysis showed no cytotoxicity in the presence of the three tested substrates after 24 h of contact. A slight decrease of cell viability was found in contact with TA6V-TESBA with and without chitosan compared to negative control cells.

CONCLUSION

Our findings highlighted the use of 3D CLSM confocal imaging as a sensitive method to evaluate qualitatively and quantitatively the biocompatibility behavior of functionalized titanium with chitosan via a silanation. The biocompatibility of the new functionalized coating to HGF1 cells is as good as the reference in biomedical device implantation TA6V.

[Drug eruptions in children in Cotonou, Benin]

INTRODUCTION

The aim of this study was to investigate the epidemiological aspects of drug eruptions in children in hospital area in Cotonou.

PATIENTS AND METHOD

A retrospective study was carried out in the Department of Dermatology of Cotonou (Benin) from 1998 to 2009. All cases of drug eruption occurred, during the study period, in children under 16 years old were selected for the study. The diagnosis of the drug eruption was based on clinical findings. The Identification of culprit drugs was based on the criteria as defined by the French Group of Pharmaco-vigilance.

RESULTS

From 1998 to 2009, 232 cases of drug eruption were diagnosed in the Department of Dermatology. Of this, 35 cases occurred in children under 16 years old. The patient mean age was 6.6 years with a sex ratio of 0.94. 4 patients were HIV positive. The culprit drug was identified in 21 patients (60%): sulfonamides 52.38% (11/21 cases), penicillin 9.52% (2 cases), vaccine 9.52% (2 cases), acetaminophen 9.52% (2 cases), acetyl salicylic acid 4.76% (n = 1), quinine 4.76% (n = 1), phenobarbital 4.76% (n = 1) and ceftriaxone 4.76% (n = 1). The main clinical patterns were: fixed drug eruption 45.71% (16/35), maculopapular rash 17.14% (n = 6), Stevens-Johnson syndrome 17.14% (n=6), and urticaria 8.57% (n = 3), 1 case of toxic epidermal necrolysis was seen and one patient died.

CONCLUSION

Skin reactions caused by drug intake are a rare disorder among children and fixed drug eruption is the main clinical presentation of the disease in Cotonou (Benin).

Effects of FI(O(2)) on hemodynamic responses and O(2) transport during RSR13-induced reduction in P(50)

Reduced Hb-O(2) affinity facilitates O(2) release to tissue but may impair pulmonary O(2) uptake, affecting cardiac output and systemic vascular resistance (SVR). We studied the effects of shifting the O(2)-dissociation curve (ODC) to the right with a continuous infusion of RSR13, an allosteric modifier of Hb, and of different inspired O(2) fractions (FI(O(2))) on arterial O(2) saturations (Sa(O(2))) in Hb and on hemodynamics in nonanesthetized rats. At an FI(O(2)) of 0.21, Sa(O(2)) fell during RSR13 from 95 to 81%. Elevation of FI(O(2)) to 0.30 returned Sa(O(2)) to baseline in the RSR13 group. The decrease in mean arterial pressure (MAP) was significantly greater in the control than in the RSR13 group at 30% O(2). Cardiac index (CI) increased only during RSR13 at 21% O(2) and returned to baseline at 30% O(2). In contrast, SVR decreased after RSR13 was infused at 21% O(2) but returned to baseline at 30%O(2), whereas controls showed the opposite, a sustained SVR. In the follow-up period, when 21 O(2)% was reestablished and mild anemia was present, MAP and SVR fell significantly more in controls, whereas CI only increased in controls. Lactate was significantly lower in the RSR13 than in the control group during RSR13 and the follow-up period. These results demonstrate that 1) continuous infusion of RSR13 produces a constant shift in the O(2) tension at which Hb is 50% saturated (P(50)), 2) FI(O(2)) of 0.30 compensates for the effects of increased P(50) on pulmonary O(2) loading, and 3) right-shifted ODC combined with supplemental O(2) may improve tissue O(2) availability.

Acute haemodynamic responses and inhibition of tumour necrosis factor-alpha by pentoxifylline in rats with cirrhosis

1. Although pentoxifylline has been shown to reduce portal hypertension, the mechanism for this is unclear. Since pentoxifylline decreases tumour necrosis factor-alpha production and since this cytokine may induce vasodilatation per se, a pentoxifylline-induced decrease in tumour necrosis factor-alpha production may limit arterial vasodilatation and decrease portal pressure. The aim of the present study was to examine the effects of pentoxifylline administration on plasma tumour necrosis factor-alpha concentration and haemodynamics in normal and cirrhotic rats. 2. In both groups, systemic and splanchnic haemodynamics and plasma tumour necrosis factor-alpha concentrations were measured before and 120 min after the administration of saline or pentoxifylline (20 mg/kg intravenous bolus). 3. In cirrhotic rats, pentoxifylline significantly decreased portal pressure (24 +/- 13%) and tributary blood flow (33 +/- 30%). On the other hand, pentoxifylline significantly increased vascular resistance in portal and hepatic arterial territories. Systemic haemodynamics were not altered. In normal rats, pentoxifylline significantly decreased portal pressure but induced no other significant changes in splanchnic or systemic haemodynamics. In cirrhotic rats, plasma tumour necrosis factor-alpha concentrations were significantly reduced after pentoxifylline administration but not after saline administration. No significant correlations were found between pentoxifylline-induced changes in tumour necrosis factor-alpha levels and changes in splanchnic haemodynamics. In normal rats, plasma tumour necrosis factor-alpha concentrations significantly decreased after pentoxifylline or saline administration. 4. This study shows that in rats with cirrhosis, pentoxifylline induces a decrease in both portal pressure and plasma tumour necrosis factor-alpha concentrations. These reductions were not correlated however.

Differences between human sperm and somatic cell DNA in CpG methylation within the HLA class I chromosomal region

PROBLEM

We investigated the possible negative regulatory mechanisms that repress classical human leukocyte antigen (HLA) class I gene expression in human spermatozoa and searched for novel testis-specific coding sequences that might be present in MHC class I chromosomal region.

METHOD

We performed a comparative DNA methylation analysis of this genomic region in both purified human spermatozoa and mononuclear blood cells from the same donors, using methylation-sensitive restriction enzymes followed by classical or pulsed field gel electrophoresis and hybridization with HLA class I locus-specific probes.

RESULTS

Unmethylated CpG sites were detected in the 3' part of HpaII tiny fragments of the HLA-F and HLA-G genes in spermatozoal DNA. In contrast, no difference was observed in the methylation status of the HLA-B, HLA-C, and HLA-E genes between germ and somatic cells. CpG unmethylation events were also detected in several parts of this chromosomal region (outside the known loci) in spermatozoal DNA.

CONCLUSIONS

These results suggest that this genomic region undergoes changes in its DNA methylation pattern during the developmental process. We hypothesize that these dynamic changes have functional importance, including a possible transcriptional activity of nonclassical class I genes and/or as yet undescribed testis-specific coding sequences.

Spermatozoa as potential carriers of HIV

In order to investigate the role of germ cells in the sexual transmission of immunodeficiency virus (HIV), spermatozoa from healthy HIV-seronegative men were incubated in vitro with HIV1. After washing, they were cocultured with peripheral blood leukocytes from seronegative blood donors. Reverse transcriptase assays and p24 antigen tests were performed in culture supernatants. Electron microscopy examination of these HIV-incubated spermatozoa was carried out, as well as the search for CD4 molecules on their surface. Although virus bound to and seemed to enter spermatozoa despite the absence of detectable CD4 epitopes on their surface, no replication of HIV was apparent. However, HIV particles on the surface of spermatozoa were capable of infecting CD4 T lymphocytes. Present results would seem to preclude artificial insemination between an HIV-seropositive man and an HIV-seronegative woman.

Antibodies to spermatozoa and seminal plasma antigens detected by various enzyme-linked immunosorbent (ELISA) assays

Various ELISA methods have been applied by different research centers to test the efficiency of this approach for the diagnosis of sperm-immune infertility cases. The antigens used were either whole spermatozoa or solubilized spermatozoal membrane preparations and were immobilized on microtiter plates, except in one case where plastic beads were employed. Polyvalent second antibodies or protein-A labelled with enzymes served as tracers. A high frequency of positive sera was found in all groups including fertile controls with tests using whole spermatozoa as antigen. The methods using solubilized antigen preparations showed fewer positives on the whole and correlated better with the various clinical categories of the WHO sera. Whilst there was some agreement in the results between the various laboratories on a few sera, most of the positive sera found by one laboratory were reported as negative by others. More investigative work is needed to improve reproducibility between different laboratories and to reduce non-specific reactions with normal controls. A more precise definition of the proper cut-off levels for positives and negatives is also needed. Despite these short-comings, the development of an ELISA for the diagnosis of sperm-immune infertility cases seems to be justified in the long term.

Studies on human spermatozoa autoantigens. I. Fractionation of sperm membrane antigens: evidence of three antigenic systems

In order to identify human spermatozoal surface autoantigens, suspensions of previously frozen washed sperm were ground and ultracentrifuged (170,000 g for 60 min). The antigenicity of the fast supernatant (FS) and the fast pellet (FP) were defined by specific inhibition of spermotoxic and various sperm-agglutinating activities of autoimmune human sera (WHO Reference Bank). The FS and the urea-soluble extract of FP were fractionated on Sephadex G-200 columns, and the antigenicity of these fractions was similarly defined. Both FS and FP inhibited, to variable extents, the anti-sperm activities. Inhibition of head-to-head (H-H) agglutination by FS was twice as strong as by FP. The reverse was observed with tail-to-tail (T-T) agglutination. Ten times more FS than FP was necessary to inhibit the spermotoxicity of all tested sera. Four fractions were collected after FS filtration on Sephadex G-200. F1, a homogeneous protein, inhibited spermotoxicity and H-H agglutination F2 inhibited all activities (including T-T agglutination). F3, a low molecular weight fraction, selectively inhibited H-H agglutination. F4 was inactive. Treatment by 8 M urea allowed a partial solubilization of FP antigenicity. Urea-soluble fractions inhibited spermotoxicity and H-H but not T-T agglutination. The antigen(s) involved in T-T agglutination is (are) destroyed by urea since the urea-treated FP was no longer able significantly to decrease T-T agglutination. These results suggest that at least three different autoantigens are responsible for H-H sperm agglutination, T-T sperm agglutination and spermotoxicity respectively.

Resistance of female guinea pig fertility to efficient iso-immunization with spermatozoa autoantigens

Virgin female guinea pigs received two courses of immunization with S, P or T spermatozoa autoantigens and Freund's complete adjuvant and were mated from 1 up to 18 weeks after the end of each course. The immunizations were efficient as judged by the titers of circulating antibodies to S, P or T, the existence of antibodies to the corresponding immunizing antigen in cervico-vaginal secretions and by cutaneous reactions of delayed hypersensitivity. In spite of this successful immunization, the fertility rate was 100% after the first course and only slightly decreased after the second one. The only significant events were a delay in the time of fertilization and a high rate of intrauterine death (as already observed following anti-S immunization). The absence of fertility impairment was not due to a lack of a relevant antigen in the injected preparations since immunizing female guinea pigs with either epididymal spermatozoa or crude water-soluble extract also did not decrease the fertility. The mechanisms responsible for such a resistance remain to be elucidated; they may involve spermatozoa coating substances, enhancing antibodies or sperm immunosuppressive factors.

Characterization of spermatozoal auto-, iso- and allo-antigens

Three approaches are utilized to study and characterize spermatozoal antigens. An immunological approach has demonstrated the presence of spermatozoal auto-, iso- and allo-antigens. Spermatozoal auto-antigens studies by several authors are able to induce the whole spectrum of immune reactions (delayed hypersensitivity, complement-fixing antibodies and anaphylactic antibodies0 as well as of autoimmune aspermatogenic orchiepididymitis (AIAO). Different extraction procedures result in various preparations and even in different independent autoantigens (at least four), one protein, one membrane-linked antigen and at least two glyco-proteins. Spermatozoal iso-antigens stricto sensu are determined by the Y chromosome and present on at least 50% of the spermatozoa. Spermatozoal allo-antigens are also present at the surface of spermatozoa, especially blood group antigens (ABO and MNS systems), transplantation antigens (HL-A, H-2) and also some other unidentified ones. A biochemical approach has mainly been directed towards spermatozoal enzymes that have been directed towards spermatozoal enzymes that have been shown to be antigenic even in the species of origin. This is the case for lactic dehydrogenase LDH-X (a mid-piece enzyme) and for acrosomal enzymes, e.g., hyaluronidase, possibly sorbitol dehydrogenase and trypsin-like acrosomal proteinase (the auto- and allo-antigenicity of the latter having not been established). At least three of these enzymes are known or supposed to play a role in the process of fertilization. A clinical approach has described the presence of spermatozoal-coating antigen(s), such as transferrin or blood group substances from secretors obtained following the admixture of the secretions of the seminal vesicles. Indications were also obtained for the existence of antibodies directed against defined antigens. Several types of localization of antibodies on spermatozoa were described: acrosome (front part), equatorial segment, post-nuclear region, mid-piece and tail. Attempts at fractionation of human psermatozoal antigens are still at a preliminary stage. Whatever the approach, the main interest of these antigens is that they are able to induce, in the species of origin or in a related species antibodies capable of interfering with the normal process of reproduction, especially fertilization..