Analyse par HPLC et CG/SM des constituants du carbone organique dissous (COD), du COD biodégradable (CODB) et des composés organohalogénés (TOX) d'un perméat de nanofiltration

Pour limiter la formation de composés organohalogénés des eaux traitées et la reviviscence bactérienne des réseaux, il est important d'éliminer la majeure partie du carbone organique dissous (COD) et du carbone organique dissous biodégradable (CODB) contenus dans les eaux naturelles. Des travaux récents nous ont permis de montrer que la nanofiltration est une technologie de choix pour répondre à ces contraintes.L'objectif de cet article est de présenter à partir de travaux de laboratoire un inventaire détaillé du carbone organique résiduel d'un perméat prélevé le 21/04/93 sur le prototype industriel de nanofiltration de Méry/Oise en banlieue parisienne. Pour atteindre cet objectif il a été nécessaire de mettre en œuvre des 'techniques analytiques impliquant l'utilisation de la chromatographie liquide haute performance (CLHP) et de la chromatographie en phase gazeuse (CG) soit équipée d'un détecteur à ionisation de flamme (FID) ou d'un détecteur à capture d'électrons (ECD), soit couplée à la spectrométrie de masse (SM).Les résultats obtenus ont montré que le COD du perméat étudié est constitué d'environ 60% d'acides aminés libres et combinés, de 7% d'aldéhydes et de 10 à 20% de composés divers identifiables en CG/SM. Ces derniers composés comprennent majoritairement des acides gras aliphatiques et des acides aromatiques de faibles masses. La concentration de chacun de ces composés a été estimée à 0,3 µg l-¹ C. On peut raisonnablement penser, d'après la bibliographie que les hydrates de carbone (non analysés dans cette étude) représenteraient une part importante de COD du perméat. En outre, cette étude a montré que la part prise par les acides aminés totaux dans le CODB du perméat est importante.Seul le tiers des potentiels de formation d'organohalogénés totaux (PFTOX) a été identifié comme étant des trihaloméhanes (THM) et des acides haloascétiques. Toutefois, étant donné que les acides aminés totaux représentent à eux seuls la quasi totalité de la demande en chlore du perméat, les autres sous-produits de chloration non identifiés seraient probablement des nitriles chlorés, des chloramines et des chloroaldéhydes qui sont parmi les principaux intermédiaires réactionnels de la coloration des acides aminés.Removal of dissolved organic carbon (DOC) and biodegradable dissolved organic carbon (BDOC) is one of the most important means to prevent disinfection by-products (DBPs) formation during water treatment and bacterial regrowth in distribution systems. In previous investigations, the authors have shown that nanofiltration, over nine months of operation at industrial scale in Paris suburbs, was an effective technology to meet the new guidelines concerning chlorine DBPs.This paper reports laboratory investigations aimed to identify and quantify the main organic components included in the low DOC, BDOC and TOXFP (Total - Organohalides Formation Potential) residuals of a nanofiltration permeate sampled on April 21, 1993.Details on DOC, BDOC, organohalides, amino acids and aldehydes analysis procedures were described elsewhere (AGBEKODO et al., 1994). Chlorination was undertaken in potential conditions k: 2.5 mg Cl2/mg DOC, pH=7.5 (phosphate buffer), 72 hours contact time, in dark at 20°C. Haloacetic acids determination consisted (after chlorination in potential conditions) in liquid-liquid extraction, methylation with diazomethane and gas chromatography analysis. Extraction procedure based on XAD8/XAD4 adsorption prior to gas chromatography/Mass Spectrometry (GC/MS) analysis (Fig. 3), allowed a 19000 fold concentration of the permeate. To prevent possible contamination of the permeate, the extraction system consisted of four glass columns and teflon materials. The flow through the columns was performed under high purity nitrogen gas pressure.Analysis involving high performance liquid chromatography (HPLC) and gas chromatography (GC) in combination with Mass Spectrometry (MS), showed that the studied permeate DOC (- 0.15 mg l-¹ c) consisted of amino acids at an average of 60% of DOC, aldehydes (7%) and 10 to 20% of several other compounds (analyzed in GC/MS) including primarily fatty and aromatic acids of low molecular weight (Table 4a and Table 4b). The maximum concentration of each compound (identified hy GC/MS) has been roughly assessed to 0.3 µg l-¹ C. According to literature, sugars represent probably an important portion of the remaining DOC of the permeate. Moreover, the authors have shown that amino acids represented a large portion of permeate BDOC.Only 34% of the total organohalide potentials were identified as trihalomethanes and haloacetic acids. However, since amino acids represent almost the entire chlorine demand of the permeate, the non- identified chlorination DBPs are likely chlorinated nitriles, chloramines and chloraldehydes which are known as the main reactionnal intermediates of aminoacid chlorination

A 3D mechanical model of the early mammalian embryo

The early development of the mammalian embryo leads to the formation of a structure composed by an outer layer of polarized cells surrounding an inner mass of nonpolarized cells. Experimental biology has shown that this organization results from changes in cell polarity, cell shape and intercellular contacts at the 8 and 16-cell stages. In order to examine how the physical properties of embryo cells (adhesion, cortical tension) influence the organization of the cells within the embryo, our team has developed a 3D mechanical model of the dividing early embryo, based on cellular Potts models. In this paper we will present the principles of our simulations, the methodology used and we will show that a very simple mechanical model can reproduce the main structural features (geometry, cell arrangement) of the mammalian embryo during its early developmental stages, up to the 16-cell stage

A tyrosine-rich amelogenin peptide promotes neovasculogenesis in vitro and ex vivo

The formation of new blood vessels has been shown to be fundamental in the repair of many damaged tissues, and we have recently shown that the adult human periodontal ligament contains multipotent stem/progenitor cells that are capable of undergoing vasculogenic and angiogenic differentiation in vitro and ex vivo. Enamel matrix protein (EMP) is a heterogeneous mixture of mainly amelogenin-derived proteins produced during tooth development and has been reported to be sometimes effective in stimulating these processes, including in clinical regeneration of the periodontal ligament. However, the identity of the specific bioactive component of EMP remains unclear. In the present study we show that, while the high-molecular-weight Fraction A of enamel matrix derivative (a heat-treated form of EMP) is unable to stimulate the vasculogenic differentiation of human periodontal ligament cells (HPC) in vitro, the low-molecular-weight Fraction C significantly up-regulates the expression of the endothelial markers VEGFR2, Tie-1, Tie-2, VE-cadherin and vWF and markedly increases the internalization of low-density lipoprotein. Furthermore, we also demonstrate, for the first time, that the synthetic homolog of the 45-amino acid tyrosine-rich amelogenin peptide (TRAP) present in Fraction C is likely to be responsible for its vasculogenesis-inducing activity. Moreover, the chemically synthesized TRAP peptide is also shown here to be capable of up-regulating the angiogenic differentiation of the HPC, based on its marked stimulation of in vitro cell migration and tubule formation and of blood vessel formation assay in a chick embryo chorioallantoic membrane model ex vivo. This novel peptide, and modified derivatives, might thereby represent a new class of regenerative drug that has the ability to elicit new blood vessel formation and promote wound healing in vivo. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Vitamin D Supplementation Enhances the Fixation of Titanium Implants in Chronic Kidney Disease Mice

Vitamin D (Vit D) deficiency is a common condition in chronic kidney disease (CKD) patients that negatively affects bone regeneration and fracture healing. Previous study has shown that timely healing of titanium implants is impaired in CKD. This study aimed to investigate the effect of Vit D supplementation on implant osseointegration in CKD mice. Uremia was induced by 5/6 nephrectomy in C57BL mice. Eight weeks after the second renal surgery, animals were given 1,25(OH)2D3 three times a week intraperitoneally for four weeks. Experimental titanium implants were inserted into the distal end of femurs two weeks later. Serum measurements confirmed decreased 1,25(OH)2D levels in CKD mice, which could be successfully corrected by Vit D injections. Moreover, the hyperparathyroidism observed in CKD mice was also corrected. X-ray examination and histological sections showed successful osseointegration in these mice. Histomorphometrical analysis revealed that the bone-implant contact (BIC) ratio and bone volume (BV/TV) around the implant were significantly increased in the Vit D-supplementation group. In addition, resistance of the implant, as measured by a push-in method, was significantly improved compared to that in the vehicle group. These results demonstrate that Vit D supplementation is an effective approach to improve the fixation of titanium implants in CKD

Inhibitory activities of short linear motifs underlie Hox interactome specificity in vivo

International audienceHox proteins are well-established developmental regulators that coordinate cell fate and morphogenesis throughout embryogenesis. In contrast, our knowledge of their specific molecular modes of action is limited to the interaction with few cofactors. Here, we show that Hox proteins are able to interact with a wide range of transcription factors in the live Drosophila embryo. In this context, specificity relies on a versatile usage of conserved short linear motifs (SLiMs), which, surprisingly, often restrains the interaction potential of Hox proteins. This novel buffering activity of SLiMs was observed in different tissues and found in Hox proteins from cnidarian to mouse species. Although these interactions remain to be analysed in the context of endogenous Hox regulatory activities, our observations challenge the traditional role assigned to SLiMs and provide an alternative concept to explain how Hox interactome specificity could be achieved during the embryonic development

Cytoskeleton and calcium. A review

The aim of the present paper was to summarize the main features about cytoskeleton in order to understand the possible interactions between this system of filamentous, microfilaments structures (including microtubules, intermediate filaments, microfilaments) and calcium in mesenchymal cells of the oral cavity.Cet article fait le point des connaissances actuelles sur le cytosquelette et vise à mettre en évidence les interactions possibles entre ce système de structures fibrillaire (microtubules, filaments intermédiaires, microfilaments) et le calcium, pour ce qui concerne les cellules mesenchymateuses de la cavité buccale

Histology of alveolar bone and primary tooth roots in a case of cleidocranial dysplasia

Cleidocranial dysplasia is commonly reported as an autosomal dominant inherited condition with defective formation of clavicles, malformation of the craniofacial bones, very slow exfoliation of the primary teeth and failure of the eruption of the permanent dentition.Lack of clinical resorption of the roots of the deciduous teeth and/or surrounding bone, lead to eruption failure of permanent teeth.Histopathological study (light and scanning electron microscopy), in a case of cleidocranial dysplasia, gives prominence to the hypothesis of abnormal remodelling of bone and cementum.La dysplasie cleïdocrânienne est un syndrome transmis sur le mode autosomique dominant. La maladie se caractérise par des dysplasies des clavicules et des os crânio-faciaux, un retard de la perte des dents temporaires et des anomalies d’évolution des dents permanentes.L’absence de résorption cliniquement décelable des racines des dents temporaires et/ou de l’os environnant, entraîne des anomalies d’éruption des dents permanentes.L’étude, en microscopie photonique et microscopie électronique à balayage de l’os et du cément de dents temporaires, permet d’avancer l’hypothèse d’un remodelage anormal des tissus calcifiés dans les cas de dysplasie cleïdocrânienne

The macroscopic effects of microscopic heterogeneity

Over the past decade, advances in super-resolution microscopy and particle-based modeling have driven an intense interest in investigating spatial heterogeneity at the level of single molecules in cells. Remarkably, it is becoming clear that spatiotemporal correlations between just a few molecules can have profound effects on the signaling behavior of the entire cell. While such correlations are often explicitly imposed by molecular structures such as rafts, clusters, or scaffolds, they also arise intrinsically, due strictly to the small numbers of molecules involved, the finite speed of diffusion, and the effects of macromolecular crowding. In this chapter we review examples of both explicitly imposed and intrinsic correlations, focusing on the mechanisms by which microscopic heterogeneity is amplified to macroscopic effect.Comment: 20 pages, 5 figures. To appear in Advances in Chemical Physic

Influence of gaseous ozone in peri-implantitis: bactericidal efficacy and cellular response. An in vitro study using titanium and zirconia

Dental implants are prone to bacterial colonization which may result in bone destruction and implant loss. Treatments of peri-implant disease aim to reduce bacterial adherence while leaving the implant surface intact for attachment of bone-regenerating host cells. The aims of this study were to investigate the antimicrobial efficacy of gaseous ozone on bacteria adhered to various titanium and zirconia surfaces and to evaluate adhesion of osteoblast-like MG-63 cells to ozone-treated surfaces. Saliva-coated titanium (SLA and polished) and zirconia (acid etched and polished) disks served as substrates for the adherence of Streptococcus sanguinis DSM20068 and Porphyromonas gingivalis ATCC33277. The test specimens were treated with gaseous ozone (140ppm; 33mL/s) for 6 and 24s. Bacteria were resuspended using ultrasonication, serially diluted and cultured. MG-63 cell adhesion was analyzed with reference to cell attachment, morphology, spreading, and proliferation. Surface topography as well as cell morphology of the test specimens were inspected by SEM. The highest bacterial adherence was found on titanium SLA whereas the other surfaces revealed 50-75% less adherent bacteria. P. gingivalis was eliminated by ozone from all surfaces within 24s to below the detection limit (≥99.94% reduction). S. sanguinis was more resistant and showed the highest reduction on zirconia substrates (>90% reduction). Ozone treatment did not affect the surface structures of the test specimens and did not influence osteoblastic cell adhesion and proliferation negatively. Titanium (polished) and zirconia (acid etched and polished) had a lower colonization potential and may be suitable material for implant abutments. Gaseous ozone showed selective efficacy to reduce adherent bacteria on titanium and zirconia without affecting adhesion and proliferation of osteoblastic cells. This in vitro study may provide a solid basis for clinical studies on gaseous ozone treatment of peri-implantitis and revealed an essential base for sufficient tissue regeneratio