Relation between Hepatitis B Carrier Status and Antibody against Synthetic Plasmodium falciparum Erythrocyte Surface (pf155 - RESA) Antigen

A survey on Plasmodium infection was carried out in gold mine camps located in the Brazilian Amazon. Antibody against P. falciparum ring-infected erythrocyte surface antigen (RESA) was quantified by an enzyme-immunoassay in order to assess P. falciparum exposure. Hepatitis B, a common infection in this area, was also investigated by serologic markers. Among 520 sampled subjects, 517 (99.4%) admitted previous symptomatic malaria, 106 (20.4%) had positive thick smears for malaria, 82.9% had HBV markers, and 7.1% were HBsAg positive. Anti-RESA titers was significantly lower in HBV carriers than in people with resolved HBV infection suggesting that the anti-RESA immune response could be supressed by HBV carrier status. Moreover, immunedeficient responses to both infections may take place in some subjects causing concomitant lower anti-RESA response and incapacity to clear HBV.

First paleoparasitological study of an embalming rejects jar found in Saqqara, Egypt

For the first time, a jar of embalming rejects was studied in search for helminth parasite eggs. This kind of jar was used to put discarded material by Egyptian embalmers during mummification process. Ascaris lumbricoides and Tænia saginata eggs were found in the linen and strip fragment contents of the jar, dated of 2,715-2,656 years ago.

Schizophrenic delusions: a phenomenological approach.

The issue of specificity of delusions in schizophrenia is still a matter of debate. The authors analyze the delusion formation in schizophrenia from a prototypical, phenomenological point of view, focusing on the subject's experience. This perspective links delusion formation to the autistic predisposition, which is considered here as the elementary phenotypic expression of the vulnerability to schizophrenia. Autism is viewed as a defective preconceptual (i.e., before language) attunement to the world. It impedes the individual's sharing of "common sense" with others and impairs the ability to project into the future. The development of delusions is illustrated, in part, by Klaus Conrad's work on the onset of paranoid schizophrenia. Delusions are viewed as transformations of the structure of experiencing. When threatened in future ability to be, the autistic, vulnerable person looks for the clues to becoming by attributing significance to disparate elements of the environment, which become self-referential. The link established between these disparate elements is based on universal characteristics that give the schizophrenic delusion a metaphysical quality. The transitivistic experience in delusions of control and omnipotence points to a specific way of crossing the border between "mine" and "yours" (disturbances of the experiencing "I"). What strikes a clinician in these delusions is that the normally tacit link between the sense of being and the sense of acting becomes quite apparent. The authors also propose a specificity in the themes of schizophrenic delusions. Delusions acquire a schizophrenic quality when ontological (i.e., universal) elements of the discourse between the locutor and the Other dominate at the expense of the worldly elements. It is emphasized that delusional content and form are dialectically related and hardly distinguishable. The authors consider the delusion formation as a phenomenon of emergence, a situation in which a new qualitative order arises from the reorganization of essentially unchanged elements. To consider schizophrenia as an emergent, particular way of experiencing, related to the autistic defect, has important consequences for research and for treatment. A dialectic exchange is needed between prototypical models generated by phenomenological inquiry and empirical, operational validation of testable aspects of such models.

Distribution and Schistosoma mansoni infection of Biomphalaria glabrata in different habitats in a rural area in the Jequitinhonha Valley, Minas Gerais, Brazil: environmental and epidemiological aspects

This paper examines the distribution and infection of Biomphalaria glabrata with Schistosoma mansoni in all aquatic snail habitats in a rural area in the state of Minas Gerais, Brazil, in relation to physico/biotic and behavioral factors. Snail and environmental surveys were carried out semi-annually between July 2001 and November 2002 at 106 sites. Collected snails were examined in the laboratory for infection. B. glabrata densities were highest in overflow ponds, irrigation ponds, springs, canals and wells, and lowest in fishponds and water tanks. Snail densities were higher during the hot, rainy season except for streams and canals and were statistically associated with the presence of fish, pollution, and vegetation density. Tilapia fish and an unidentified Diptera larva were found to be predators of B. glabrata but ducks were not. Twenty-four of the 25 infected snails were collected in 2001(1.4% infection rate) and only one in 2002, after mass chemotherapy. The occurrence of B. glabrata in all 11 snail habitats both at and away from water contact sites studied indicates widespread risk of human infection in the study area. In spite of the strong association between B. glabrata and tilapia in fishponds we do not recommend its use in schistosomiasis control for ecological reasons and its relative inefficiency in streams and dams.

Rural tourism as risk factor for the transmission of schistosomiasis in Minas Gerais, Brazil

Recently, the booming rural tourism in endemic areas of the state of Minas Gerais was identified as a contributing factor in the dissemination of the infection with Schistosoma mansoni. This article presents data from six holiday resorts in a rural district approximately 100 km distant from Belo Horizonte, MG, Brazil, where a possibly new and until now unperceived way of transmission was observed. The infection takes place in swimming pools and little ponds, which are offered to tourists and the local population for fishing and leisure activities. The health authorities of the district reported cases of schistosomiasis among the local population after visiting these sites. As individuals of the non-immune middle class parts of the society of big urban centers also frequent these resorts, infection of these persons cannot be excluded. A malacological survey revealed the presence of molluscs of the species Biomphalaria glabrata and Biomphalaria straminea at the resorts. The snails (B. glabrata) of one resort tested positive for S. mansoni. In order to resolve this complex problem a multidisciplinary approach including health education, sanitation measures, assistance to the local health services, and evolvement of the local political authorities, the local community, the tourism association, and the owners of the leisure resorts is necessary. This evidence emphasizes the urgent need for a participative strategic plan to develop the local tourism in an organized and well-administered way. Only so this important source of income for the region can be ensured on the long term without disseminating the disease and putting the health of the visitors at risk.

Summer School Programme

The Summer School aims to enable and foster a climate of inquiry for critical thinking, quantitative analysis and explore existing relevant data sources. We aim to develop the concepts and tools associated with quantitative research related to child health and wellbeing. Building on participants’ existing knowledge of research, policy and practice, we will focus on the quantitative skills necessary to mine and critique relevant national databases, conduct basic quantitative research and apply these skills to work. The SPSS workshops will provide  participants with a basic understanding of a statistical programme for analysing empirical data and the open clinics will allow participants to discuss their own research issues with experts.

Characterization of root apoplastic barriers in Arabidopsis thaliana

In vascular plants, the best-known feature of a differentiated endodermal cell is the "Casparian Strip" (CS). This structure refers to a highly localized cell wall impregnation in the transversal and anticlinal walls of the cell, which surrounds the cell like a belt/ring and is tightly coordinated with respect to neighboring cells. Analogous to tight junctions in animal epithelia, CS in plants act as a diffusion barrier that controls the movement of water and ions from soil into the stele. Since its first description by Robert Caspary in 1865 there have been many attempts to identify the chemical nature of the cell wall deposition in CS. Suberin, lignin, or both have been claimed to be the important components of CS in a series of different species. However, the exact chemical composition of CS has remained enigmatic. This controversy was due to the confusion and lack of knowledge regarding the precise measurement of three developmental stages of the endodermis. The CS represent only the primary stage of endodermal differentiation, which is followed by the deposition of suberin lamellae all around the cellular surface of endodermal cells (secondary developmental stage). Therefore, chemical analysis of whole roots, or even of isolated endodermal tissues, will always find both of the polymers present. It was crucial to clarify this point because this will guide our efforts to understand which cell wall biosynthetic component becomes localized in order to form the CS. The main aim of my work was to find out the major components of (early) CS, as well as their spatial and temporal development, physiological roles and relationship to barrier formation. Employing the knowledge and tools that have been accumulated over the last few years in the model plant Arabidopsis thaliana, various histological and chemical assays were used in this study. A particular feature of my work was to completely degrade, or inhibit formation of lignin and suberin biopolymers by biochemical, classical genetic and molecular approaches and to investigate its effect on CS formation and the establishment of a functional diffusion barrier. Strikingly, interference with monolignol biosynthesis abrogates CS formation and delays the formation of function diffusion barrier. In contrast, transgenic plants devoid of any detectable suberin still develop a functional CS. The combination of all these assays clearly demonstrates that the early CS polymer is made from monolignol (lignin monomers) and is composed of lignin. By contrast, suberin is formed much later as a secondary wall during development of endodermis. These early CS are functionally sufficient to block extracellular diffusion and suberin does not play important role in the establishment of early endodermal diffusion barrier. Moreover, suberin biosynthetic machinery is not present at the time of CS formation. Our study finally concludes the long-standing debate about the chemical nature of CS and opens the door to a new approach in lignin research, specifically for the identification of the components of the CS biosynthetic pathway that mediates the localized deposition of cell walls. I also made some efforts to understand the patterning and differentiation of endodermal passage cells in young roots. In the literature, passage cells are defined as a non- suberized xylem pole associated endodermal cells. Since these cells only contain the CS but not the suberin lamellae, it has been assumed that these cells may offer a continued low-resistance pathway for water and minerals into the stele. Thus far, no genes have been found to be expressed specifically in passage cells. In order to understand the patterning, differentiation, and physiological role of passage it would be crucial to identify some genes that are exclusively expressed in these cells. In order to identify such genes, I first generated fluorescent marker lines of stele-expressed transporters that have been reported to be expressed in the passage cells. My aim was to first highlight the passage cells in a non-specific way. In order to find passage cell specific genes I then adapted a two-component system based on previously published methods for gene expression profiling of individual cell types. This approach will allow us to target only the passage cells and then to study gene expression specifically in this cell type. Taken together, this preparatory work will provide an entry point to understand the formation and role of endodermal passage cells. - Chez les plantes vasculaires, la caractéristique la plus commune des cellules différentiées de l'endoderme est la présence de cadres de Caspary. Cette structure correspond à une imprégnation localisée des parties transversales et anticlinales de la paroi cellulaire. Cela donne naissance, autour de la cellule, à un anneau/cadre qui est coordonné par rapport aux cellules voisines. De manière analogue aux jonctions serrées des épithéliums chez les animaux, les cadres de Caspary agissent chez les plantes comme barrière de diffusion, contrôlant le mouvement de l'eau et des ions à travers la racine entre le sol et la stèle. Depuis leur première description par Robert Caspary en 1865, beaucoup de tentatives ont eu pour but de définir la nature chimique de ces cadres de Caspary. Après l'étude de différentes espèces végétales, à la fois la subérine, la lignine ou les deux ont été revendiquées comme étant des composants importants de ces cadres. Malgré tout, leur nature chimique exacte est restée longtemps énigmatique. Cette controverse provient de la confusion et du manque de connaissance concernant la détermination précise des trois stades de développement de l'endoderme. Les cadres de Caspary représentent uniquement le stade primaire de différentiation de l'endoderme. Celui-ci est suivi par le second stade de différentiation, la déposition de lamelles de subérine tout autour de la cellule endodermal. De ce fait, l'analyse chimique de racines entières ou de cellules d'endoderme isolées ne permet pas de séparer les stades de différentiation primaire et secondaire et aboutit donc à la présence des deux polymères. Il est également crucial de clarifier ce point dans le but de connaître quelle machinerie cellulaire localisée à la paroi cellulaire permet l'élaboration des cadres de Caspary. En utilisant les connaissances et les outils accumulés récemment grâce à la plante modèle Arabidopsis thaliana, divers techniques histologiques et chimiques ont été utilisées dans cette étude. Un point particulier de mon travail a été de dégrader ou d'inhiber complètement la formation de lignine ou de subérine en utilisant des approches de génétique classique ou moléculaire. Le but étant d'observer l'effet de l'absence d'un de ces deux polymères sur la formation des cadres de Caspary et l'établissement d'une barrière de diffusion fonctionnelle. De manière frappante, le fait d'interférer avec la voie de biosynthèse de monolignol (monomères de lignine) abolit la formation des cadres de Caspary et retarde l'élaboration d'une barrière de diffusion fonctionnelle. Par contre, des plantes transgéniques dépourvues d'une quantité détectable de subérine sont quant à elles toujours capables de développer des cadres de Caspary fonctionnels. Mises en commun, ces expériences démontrent que le polymère formant les cadres de Caspary dans la partie jeune de la racine est fait de monolignol, et que de ce fait il s'agit de lignine. La subérine, quant à elle, est formée bien plus tard durant le développement de l'endoderme, de plus il s'agit d'une modification de la paroi secondaire. Ces cadres de Caspary précoces faits de lignine suffisent donc à bloquer la diffusion extracellulaire, contrairement à la subérine. De plus, la machinerie de biosynthèse de la subérine n'est pas encore présente au moment de la formation des cadres de Caspary. Notre étude permet donc de mettre un terme au long débat concernant la nature chimique des cadres de Caspary. De plus, elle ouvre la porte à de nouvelles approches dans la recherche sur la lignine, plus particulièrement pour identifier des composants permettant la déposition localisée de ce polymère dans la paroi cellulaire. J'ai aussi fais des efforts pour mettre en évidence la formation ainsi que le rôle des cellules de passage dans les jeunes racines. Dans la littérature, les cellules de passage sont définies comme de la cellule endodermal faisant face aux pôles xylèmes et dont la paroi n'est pas subérisée. Du fait que ces cellules contiennent uniquement des cadres de Caspary et pas de lamelle de subérine, il a été supposé qu'elles ne devraient offrir que peu de résistance au passage de l'eau et des nutriments entre le sol et la stèle. Le rôle de ces cellules de passage est toujours loin d'être clair, de plus aucun gène s'exprimant spécifiquement dans ces cellules n'a été découvert à ce jour. De manière à identifier de tels gènes, j'ai tout d'abord généré des marqueurs fluorescents pour des transporteurs exprimés dans la stèle mais dont l'expression avait également été signalée dans l'endoderme, uniquement dans les cellules de passage. J'ai ensuite développé un système à deux composants basé sur des méthodes déjà publiées, visant principalement à étudier le profil d'expression génique dans un type cellulaire donné. En recoupant les gènes exprimés spécifiquement dans l'endoderme à ceux exprimés dans la stèle et les cellules de passage, il nous sera possible d'identifier le transriptome spécifique de ces cellules. Pris dans leur ensemble, ces résultats devraient donner un bon point d'entrée dans la définition et la compréhension des cellules de passage.

Isolation and isoenzyme characterization of Leishmania (Viannia) braziliensis from a case of human cutaneous leishmaniasis in northeast centre of the state of São Paulo

The diagnosis of human cutaneous leishmaniasis in small towns is sometimes made without the species identification of the Leishmania, even in areas without previous epidemiological surveys. Here we report the isolation of a Leishmania strain from a patient of Rincão, state of São Paulo, that was identified by isoenzyme characterization as L. (Viannia) braziliensis. Sand fly collections were made in the area where the patient live in order to investigate the likely vector species.

Esteganografia en contingut multimèdia

L'objectiu d'aquest treball fi de carrera és el disseny i la implementació d'un mètode per a amagar, de forma secreta, un missatge en un contingut multimedia (imatge, àudio, vídeo, etc.). El missatge serà una tira de caràcters que caldrà emmagatzemar al contingut multimedia de forma robusta, entenent-se per robust aquell mètode que permet recuperar el missatge tot i haver modificat 'lleugerament' l'objecte.

Field trials of low dose Bayluscide on snail hosts of schistosome and selected non-target organisms in sahelian Cameroon

More than 85% of all cases of schistosomiasis in Cameroon occur in the northern sahelian half of the country representing 20% of the population. Several workers have advocated the integrated approach to schistosomiasis control, including snail control, but the death and decay of aquatic organisms, and fish kill that often follows Bayluscide application at the dose of 1g/m³ decrease its acceptability. The present study was designed to assess the effect of lower Bayluscide doses on snail host and non-target fish, frog, the tadpole kill. Bayluscide was applied to study ponds at concentrations of 0, 0.25, 0.5, and 1 g/m³ (ppm). Pre and post application assessment of snails hosts of schistosomes, fish, frog, and tadpole kill were carried out. All 0.25, 0.5, and 1 g/m³ Bayluscide concentrations reduced snail population significantly. Bayluscide concentration of 0.50 g/m³ applied in two rounds of 0.25 g/m³ resulted in high snail mortality and low lethality to fish, frogs, and tadpoles. Further studies are needed to assess the cost-effectiveness of Bayluscide in the control of schistosomiasis following the simplified approach.

Biomphalaria spp. (Preston, 1910) snails in the municipality of Juiz de Fora, Zona da Mata Mineira mesoregion, ate of Minas Gerais, Brazil

This study focuses on the geographic distribution of the snail of the genus Biomphalaria and evaluates its infectivity by Schistosoma mansoni in 5264 specimens collected in the municipality of Juiz de Fora, Minas Gerais, Brazil. Of the 31 locations studied, 6 were reservoirs, 11 rudimentary holding ponds, 7 irrigation ditches, 5 lakes, 1 ornamental pond, and 1 waterfall. Intermediate hosts were found only in the rudimentary ponds and ditches, which were 100% positive. Using morphological and molecular analysis techniques, B. tenagophila, B. peregrina, and B. straminea were identified. This is the first report of B. stramínea in the municipality, and evaluation of its infective potential revealed susceptibility of 25.4%. Although we did not find specimens of Biomphalaria infected by S. mansoni, the data obtained indicate the presence of intermediate hosts, especially in the irrigation ditches in Juiz de Fora, and their proximity to contaminated areas.

Contrasted influences of moon phases on the reproduction and movement patterns of four amphibian species inhabiting different habitats in central Italy

Many studies have provided evidence that prey adjust their behaviour to adaptively balance the fitness effects of reproduction and predation risk. Nocturnal terrestrial animals should deal with a range of environmental conditions during the reproductive season at the breeding sites, including a variable amount of natural ambient light. High degrees of illumination are expected to minimize those behaviours that might increase the animal detection by predators. Therefore, under habitat variable brightness conditions and in different ecosystems, the above mentioned behaviours are expected to depend on the variation in predation risk. Although moon effects on amphibian biology have been recognized, the direction of this influence is rather controversial with evidences of both increased and depressed activity under full moon. We tested in four nocturnal amphibian species (Hyla intermedia, Rana dalmatina, Rana italica, Salamandrina perspicillata) the effects of different (i) light conditions and (ii) habitats (open land vs. dense forest) on the reproductive phenology. Our results showed that the effects of the lunar cycle on the study species are associated with the change in luminosity, and there is no evidence of an endogenous rhythm controlled by biological clocks. The habitat type conditioned the amphibian reproductive strategy in relation to moon phases. Open habitat breeders (e. g., ponds with no canopy cover) strongly avoided conditions with high brightness, whereas forest habitat breeders were apparently unaffected by the different moon phases. Indeed, for all the studied species no effects of the moon phase itself on the considered metrics were found. Rather, the considered amphibian species seem to be conditioned mainly by moonlight irrespective of the moon phase. The two anurans spawning in open habitat apparently adjust their oviposition timing by balancing the fitness effects of the risk to be detected by predators and the reproduction.

Hirschsprung's disease: the "Swiss roll" technique revisited.

PURPOSE: During pull-through for Hirschsprung's disease (HSCR), the assessment of innervation is mainly based on the presence of ganglion cells when conventional Hematoxylin and Eosin (HE) staining is used. In hypoganglionosis, the evaluation is difficult. We adapted a standardized methodology for the examination of resected bowel after HSCR surgery, using the technique described by Moolenbeek on rodent intestine and later by Meier-Ruge in children. We have analysed the entire innervation of surgically resected bowels and compared the results with the follow up of patients. METHODS: Three longitudinal strips of colon were harvested from the mesenteric, anti-mesenteric and intermediate part in the whole length of resected colon of six patients with HSCR. Each strip was divided into two parts. One of the contiguous strips was assessed with HE and Hematoxylin-Phloxin-Safran, and the other one with acetylcholinesterase (AChE) histochemistry. We analyzed the distribution of ganglion cells and nerve arrangement along the strips with both techniques and compared the results obtained in the three different regions of the bowel. RESULTS: There was no significant difference in the pattern of innervation circumferentially. There was a correlation between a progressive increase of AChE activity and nerve hypertrophy and a decrease of ganglion cells from the proximal to the distal part of the resected colon in the submucosa and the myenteric plexus. Nerve hypertrophy and AChE-positive reaction in the mucosa were found at the resection border in patients who presented postoperative complications. CONCLUSIONS: Simultaneous assessment of nerve cells, nerve fibers and AChE activity is important in the evaluation of the innervation of the bowel segment proximal to the aganglionic zone. The method described is feasible and can be adapted to older children and adults with larger bowels. These results point out the importance of assessing nerve fibers in intraoperative biopsies during pull-through procedures to prevent uncomplete surgical bowel resection.

A simple approach improving the performance of urine reagent strips for rapid diagnosis of urinary schistosomiasis in Nigerian schoolchildren

In Nigeria, schistosomiasis, caused predominantly by the species Schistosoma haematobium, is highly endemic in resource-poor communities. We performed a school-based survey in two rural communities in Osun State (Southwestern Nigeria) and assessed macrohaematuria, microhaematuria and proteinuria as indirect indicators for the presence of disease. Urine samples were inspected macroscopically for haematuria and screened for microhaematuria and proteinuria using urine reagent strips. The microscopic examination of schistosome eggs was used as the gold standard for diagnosis. In total, 447 schoolchildren were included in this study and had a 51% prevalence of urinary schistosomiasis. The sensitivity of microhaematuria (68%) and proteinuria (53%) for infection with S. haematobium was relatively low. In patients with a heavy infection (>500 eggs/10 mL), the sensitivity of microhaematuria was high (95%). When the presence of macrohaematuria and the concomitant presence of microhaematuria and proteinuria were combined, it revealed a sensitivity of 63%, a specificity of 93% and a positive predictive value of 91%. Macrohaematuria also showed high specificity (96%) and a positive predictive value of 92%, while sensitivity was < 50%. These data show that combining urine reagent strip tests (presence of proteinuria and microhaematuria) and information on macrohaematuria increased the accuracy of the rapid diagnosis of urinary schistosomiasis in an endemic rural West African setting. This simple approach can be used to increase the quality of monitoring of schistosomiasis in schoolchildren.

Molecular dissection of Arabidopsis thaliana endodermis development, structure and function

In vascular plants, the endodermis establishes a protective diffusion barrier surrounding the vasculature preventing the passive, uncontrolled entry of nutrients absorbed by the plant. It does so by means of a differentiation feature, the "Casparian Strip" (CS), a highly localized cell wall impregnation made of lignin, which seals the extracellular space. Although the existence of this differentiation feature has been intensively described, the mechanisms establishing this hallmark remain obscure. In this work I report, the developmental sequence of events that leads to a differentiated endodermis, in the plant model Arabidopsis thaliana. In addition, my descriptive approach gave important insights as to how these cells define membrane domains involved in the directional transport of nutrients. I also participated in characterizing a new transmembrane protein family, the CASPs, localized to the membrane domain underlying the CS, which we accordingly named the Casparian Strip membrane Domain (CSD). Our molecular analysis indicates that these proteins drive CS establishment. To identify more molecular factors of CS establishment, I performed a forward genetic screen. This screen led to the identification of 11 endodermis permissive mutants, which we named schengen (sgn) mutants. The causative mutations have been mapped to 5 independent loci: SGN1 to SGN5. SGN1 and SGN3 encode Receptor Like Kinases involved in the correct establishment of the CSD. A lack of those kinases leads to an incomplete CSD, which gives rise to interrupted CS barriers. Interestingly, SGN1 seems to also regulate CSD positioning to the middle of endodermal transversal walls. SGN4 encodes an NADPH oxidase involved in lignin polymerization essential for CS formation. The sgn5 mutant induces extra divisions of cortical cells strongly affecting the cell identity, but also leading to incorrect differentiation. A thorough characterization of the sgn2 mutant will follow elsewhere, yet preliminary results indicate that SGN2 encodes an Acyl-CoA N-acyltransferase. . In summary, with my work I have contributed a first set of molecular players of Casparian strip formation and initiated their characterization. Eventually, this might lead to an understanding of the molecular mechanisms of CS establishment in A.thaliana . This in turn will hopefully help to better understand nutrient uptake in higher plants and their response to environmental stresses. - Au sein des plantes vasculaires, l'endoderme représente un tissu protecteur mettant en place une barrière imperméable, empêchant n'importe quel élément de rejoindre les tissus conducteurs par simple diffusion. Cette barrière, appelée « Cadre de Caspary », correspond à une lignification de la paroi de l'endoderme et donne lieu à un cloisonnement de l'espace intercellulaire. Bien que cet élément de différenciation soit décrit en détail, sa mise en place reste incomprise. Cette étude indique la suite d'événements aboutissant à l'établissement du cadre de Caspary chez la plante modèle Arabidopsis thaliana. De plus, ce travail apporte de nouvelles connaissances expliquant comment ces cellules définissent des domaines membranaires importants pour le transport des nutriments. Nous décrivons une nouvelle famille de protéines membranaires, les CASPs (« CAparian Strip membrane domain Proteins »), localisées dans un domaine membranaire longeant le cadre de Caspary : le domaine de Caspary (CSD). L'analyse moléculaire des CASPs indique qu'elles dirigent la formation du cadre de Caspary. Par ailleurs, une approche génétique directe nous a permis d'identifier 11 mutants ayant un endoderme perméable. Nous avons nommé ces mutants Schengen, en référence à la zone de libre échange européenne. Les mutations impliquées dans ces mutants affectent 5 gènes désignés de SGN1 à SGN5. SGN1 et SGN3 produisent des protéines de type kinases (« Receptor-like Kinases », RLK) qui participent à la délimitation du CSD. L'absence de ces kinases aboutit à un domaine CSD incomplet, se traduisant par un cadre de Caspary discontinu. De plus, SGN1 semble réguler le positionnement du CSD au milieu de la paroi transversale de l'endoderme. SGN4 produit une enzyme de type NADPH oxydase impliquée dans la polymérisation du cadre de Caspary. Dans le mutant sgn5, on observe une division anormale des cellules du cortex créant ainsi une nouvelle couche cellulaire incapable d'achever sa différenciation en endoderme. Quant à la mutation sgn2, bien que nous pensons qu'elle affecte une Acyl-CoA N-acyltransferase, sa caractérisation ne sera réalisée que prochainement. Au final, ce travail procure de nouveaux éléments sur l'établissement du cadre de Caspary qui pourraient être importants afin de comprendre comment les plantes sélectionnent leurs nutriments et résistent à des conditions environnementales parfois hostiles. - De par leur immobilité, les plantes terrestres n'ont pas d'autre choix que de puiser leurs ressources dans leur environnement direct. La plante extrait du sol les nutriments qui lui sont nécessaires et les redistribue grâce à des tissus conducteurs. Afin de ne pas s'intoxiquer, il est donc essentiel de pouvoir sélectionner les éléments entrant dans la racine. Etonnement, ce n'est pas la surface des racines qui permet ce contrôle mais un tissu interne appelé endoderme. Ce dernier forme une barrière imperméable qui entoure chaque cellule et crée une jointure permettant de bloquer le passage des éléments entre les cellules. Cette structure, appelée « cadre de Caspary », oblige les éléments à entrer dans les cellules de l'endoderme et à être ainsi sélectionnés. Bien que cette structure soit décrite en détail, sa mise en place reste incomprise. Cette étude indique la suite d'événements qui aboutit à la formation du cadre de Caspary chez la plante modèle Arabidopsis thaliana. Ce travail apporte également de nouvelles connaissances expliquant comment ces cellules définissent, organisent et dirigent le transport des nutriments. Nous décrivons comment certains éléments de la cellule, les protéines CASPs (CAsparian Strip membrane domain Proteins), sont organisées un domaine particulier des membranes afin de créer une plateforme de construction longeant le cadre de Caspary : le domaine de Caspary (CSD). Afin de déterminer ce qu'il se passerait si une plante ne possédait pas de cadre de Caspary, nous avons réalisé une mutagénèse, ou approche génétique directe, et identifié 11 mutants (individu ayant un gène défectueux conduisant à la perte d'une fonction) ayant un endoderme perméable. Nous avons nommé ces mutants schengen, en référence à la zone de libre échange européenne. Les mutations impliquées dans ces mutants affectent 5 gènes désignés de SGN1 à SGN5. Les gènes SGN1 et SGN3 produisent des protéines de type kinases (« Receptor-like Kinases », RLK) servant à l'établissement de la plateforme de construction. L'absence de ces kinases aboutit à une base incomplète, se traduisant par un cadre de Caspary discontinu. Qui plus est, la kinase SGN1 semble réguler le positionnement de la plateforme au milieu de l'endoderme. Le gène SGN4 est par contre, impliqué dans la construction à proprement dite du cadre de Caspary. Dans le mutant sgn5, on observe une nouvelle couche de cellules ressemblant à de l'endoderme mais incapable de former correctement une barrière identique au cadre de Caspary. Quant au dernier mutant, sgn2, bien que cette étude fournisse des indices permettant de comprendre pourquoi le mutant sgn2 est défectueux, nous n'expliquerons ce cas que prochainement. En résumé, ce travail procure de nouvelles connaissances sur l'établissement du cadre de Caspary qui pourraient être importantes afin de comprendre comment les plantes sélectionnent leurs nutriments et résistent à des conditions environnementales parfois hostiles.