No / Objective We sought to analyze the effect of a structured, dietitian-led education program on patients' general knowledge of phosphate and phosphate binders, and its impact on serum phosphate concentrations in a single-center hemodialysis population. Design We compared subjects before and after intervention. Setting This study involved two dialysis units operated by a single center. Patients One hundred and fifteen hemodialysis patients consented to participate in this study (54% male; mean age, 61.1 years; 32% Asian). Patients acted as their own controls. One hundred and eight patients completed the study. Intervention All patients completed a questionnaire to assess their knowledge of phosphate and phosphate-binder therapy. Small group teaching sessions were then delivered to patients by a single dietitian, with the aid of a hospital interpreter as required. Patients also received information booklets or audio cassettes translated into Urdu. A second identical questionnaire was completed a month later. Main Outcome Measures Outcome measures involved pre-education and posteducation knowledge scores, monthly measurements of serum phosphate, calcium, and mean Kt/V, and parathyroid hormone concentrations every 3 months during the 5 month run-in period and subsequent 5-month study period. Results The education program significantly improved patients' general knowledge of phosphate and of phosphate-binders (P < .001), especially in patients with a low pretest score and those of South Asian origin. This result was associated with a significant reduction in serum phosphate in patients with hyperphosphatemia (P = .032). Conclusions These findings suggest that a combination of educational initiatives is effective in enhancing patients' knowledge of phosphate and phosphate-binders, and consequently in improving serum phosphate levels in patients with hyperphosphatemia.

<p>Trehalose is a non-reducing disaccharide essential for pathogenic fungal survival and virulence. The biosynthesis of trehalose requires the trehalose-6-phosphate synthase, Tps1, and trehalose-6-phosphate phosphatase, Tps2. More importantly, the trehalose biosynthetic pathway is absent in mammals, conferring this pathway as an ideal target for antifungal drug design. However, lack of germane biochemical and structural information hinders antifungal drug design against these targets. </p><p>In this dissertation, macromolecular X-ray crystallography and biochemical assays were employed to understand the structures and functions of proteins involved in the trehalose biosynthetic pathway. I report here the first eukaryotic Tps1 structures from Candida albicans (C. albicans) and Aspergillus fumigatus (A. fumigatus) with substrates or substrate analogs. These structures reveal the key residues involved in substrate binding and catalysis. Subsequent enzymatic assays and cellular assays highlight the significance of these key Tps1 residues in enzyme function and fungal stress response. The Tps1 structure captured in its transition-state with a non-hydrolysable inhibitor demonstrates that Tps1 adopts an “internal return like” mechanism for catalysis. Furthermore, disruption of the trehalose biosynthetic complex formation through abolishing Tps1 dimerization reveals that complex formation has regulatory function in addition to trehalose production, providing additional targets for antifungal drug intervention. </p><p>I also present here the structure of the Tps2 N-terminal domain (Tps2NTD) from C. albicans, which may be involved in the proper formation of the trehalose biosynthetic complex. Deletion of the Tps2NTD results in a temperature sensitive phenotype. Further, I describe in this dissertation the structures of the Tps2 phosphatase domain (Tps2PD) from C. albicans, A. fumigatus and Cryptococcus neoformans (C. neoformans) in multiple conformational states. The structures of the C. albicans Tps2PD -BeF3-trehalose complex and C. neoformans Tps2PD(D24N)-T6P complex reveal extensive interactions between both glucose moieties of the trehalose involving all eight hydroxyl groups and multiple residues of both the cap and core domains of Tps2PD. These structures also reveal that steric hindrance is a key underlying factor for the exquisite substrate specificity of Tps2PD. In addition, the structures of Tps2PD in the open conformation provide direct visualization of the conformational changes of this domain that are effected by substrate binding and product release. </p><p>Last, I present the structure of the C. albicans trehalose synthase regulatory protein (Tps3) pseudo-phosphatase domain (Tps3PPD) structure. Tps3PPD adopts a haloacid dehydrogenase superfamily (HADSF) phosphatase fold with a core Rossmann-fold domain and a α/β fold cap domain. Despite lack of phosphatase activity, the cleft between the Tps3PPD core domain and cap domain presents a binding pocket for a yet uncharacterized ligand. Identification of this ligand could reveal the cellular function of Tps3 and any interconnection of the trehalose biosynthetic pathway with other cellular metabolic pathways. </p><p>Combined, these structures together with significant biochemical analyses advance our understanding of the proteins responsible for trehalose biosynthesis. These structures are ready to be exploited to rationally design or optimize inhibitors of the trehalose biosynthetic pathway enzymes. Hence, the work described in this thesis has laid the groundwork for the design of Tps1 and Tps2 specific inhibitors, which ultimately could lead to novel therapeutics to treat fungal infections.</p> / Dissertation

Les réactions de phosphorylation / déphosphorylation chez les bactéries régulent plusieurs fonctions cellulaires telles que croissance, différenciation, pathogénie, résistance aux antibiotiques, réponse au stress, formation des biofilms ainsi que plusieurs processus impliqués dans le métabolisme secondaire. Cependant, les signaux qui déclenchent la cascade de signalisation par phosphorylation/déphosphorylation intracellulaire restent encore peu connus. Staphylococcus aureus est une bactérie à Gram-positif pathogène pour l‟homme. Elle est l‟une des principales causes des infections nosocomiales et ce pathogène opportuniste est capable de provoquer de multiples infections allant du furoncle à la septicémie. Nos études se sont basées sur la caractérisation aux niveaux structural et fonctionnel de deux protéines de cette bactérie : une sérine/thréonine kinase nommée Stk1 ainsi que l‟un de ses substrats, la triose phosphate isomérase. Stk1 a déjà été identifiée comme responsable de la phosphorylation de plusieurs enzymes impliquées dans le métabolisme central de la bactérie ainsi que dans les phénomènes de virulence et de résistance à l‟antibiotique phosphomycine. Cependant, à ce jour, aucune caractérisation structurale n‟a été conduite sur cette kinase. Nous avons ainsi mené une étude cristallographique de plusieurs domaines de cette protéine et nous présentons, plus particulièrement, la structure de trois domaines extracellulaires dits « PASTA », ainsi qu‟un modèle tridimensionnel de la protéine entière. Les domaines PASTA sont spécifiques des Ser/Thr kinases et des Penicillin-Binding Proteins et sont impliqués dans la synthèse du peptidoglycane. Par conséquent, la connaissance de la structure de ces domaines chez Stk1 pourrait servir de base à la conception rationnelle de nouveaux inhibiteurs à visée thérapeutique. Enfin, nous avons démontré que l‟activité de l‟un des substrats de Stk1, la triose phosphate isomérase, était régulée par phosphorylation / déphosphorylation, et nous avons décrit le mécanisme qui contrôle son activation/inactivation réversible. / The phosphorylation /dephosphorylation reactions in bacteria regulate various cellular functions such as growth, differentiation, pathogenicity, antibiotic resistance, stress response, biofilm formation as well as several processes involved in secondary metabolism. However, detailed understanding of their complete signaling pathways induced by phosphorylation/dephosphorylation is still unclear. Staphylococcus aureus is a Gram-positive bacterium and a human pathogen. It is one of the primary causes of nosocomial infections and this opportunist pathogen is able to cause multiple infections ranging from furuncle to septicemia. This study is focused on the structural and functional characterizations of two proteins from this bacterium: the serine/threonine kinase Stk1 and one of its substrates, the triose phosphate isomerase. Stk1 has been previously identified as responsible for the phosphorylation of several enzymes involved in the central metabolism of this bacterium as well as virulence and resistance to the antibiotic phosphomycin. However, no structural characterization has been done to date. We have performed a crystallographic study of several domains of this protein. We now present the structure of three extracellular domains designated “PASTA” in addition to the 3D molecular model of the entire protein. PASTA domains are specific to bacterial Ser/Thr kinases and to Penicillin-Binding Proteins which are involved in the peptidoglycan synthesis. Thus, the structural knowledge of PASTA domains from Stk1 could be of particular interest in the rational drug-design of new inhibitors with therapeutic aims. Finally, we have demonstrated that triose phosphate isomerase activity is regulated by phosphorylation/dephosphorylation and we have described the reversible activation/inactivation mechanism.

Ce travail porte sur l’élaboration et la caractérisation physico-chimique de nanoparticules hybrides à base d’apatites phosphocalciques biomimétiques proches du minéral osseux, en vue d’applications dans le domaine du diagnostic de cancers voire de thérapeutique. Dans cette étude, une formulation colloïdale a été développée en milieu aqueux à partir de sels aisément manipulables et en présence d’un dérivé phospholipidique (2-aminoéthylphosphate, AEP) jouant le rôle d’agent dispersant et permettant de contrôler la taille moyenne des nanoparticules (dans la gamme 30-100 nm). L’effet de paramètres expérimentaux majeurs (pH, concentrations, température) a été déterminé. La complémentarité des données analytiques (analyses chimiques, spectroscopie FTIR, diffraction des rayons X, diffusion de la lumière, MET, mesures de potentiel zêta) nous a permis de proposer un modèle descriptif des nanoparticules colloïdales mettant en jeu la présence de complexes entre Ca2+ et AEP- en surface de nanocristaux d’apatite. La possibilité de conférer des propriétés de luminescence a été démontrée, par substitution d’ions Ca2+ par des ions europium Eu3+, et une durée de vie de luminescence de l’ordre de la milliseconde permet d’envisager l’étude de matériel biologique. Plus ponctuellement, l’adsorption additionnelle d’acide folique a été étudiée, avec pour objectif final le ciblage de cellules cancéreuses. Divers aspects liés à une potentielle utilisation dans le domaine biomédical ont également été abordés, tels que la purification de telles suspensions par dialyse, la possibilité d’une remise en suspension après lyophilisation, l’évaluation de leur cytotoxicité, l’étude de leur potentiel proinflammatoire par interaction avec des macrophages humains, et une étude préliminaire de l’internalisation de ces nanoparticules par des cellules cancéreuses. Ce travail a permis de développer une « preuve de concept » permettant d’envisager l’utilisation future de tels nano-systèmes colloïdaux dans le domaine biomédical, et en particulier en oncologie. / This work deals with the synthesis and physico-chemical characterization of hybrid nanoparticles based on biomimetic calcium phosphate apatites close to bone mineral, in view of applications in the field of cancer diagnosis, or therapeutics. In this study, a colloidal formulation has been developed in aqueous medium, from easily-handled salts and in the presence of a phospholipid moiety (2-aminoethylphosphate, AEP) acting as dispersing agent and allowing the control of the mean nanoparticle size (in the range 30-100 nm). The effect of major experimental parameters (pH, concentrations, temperature) has been determined. Complementary analytical data (chemical analyses, FTIR spectroscopy, XRD, dynamic light scattering, TEM, zeta potential measurements) enabled us to propose a descriptive model for the colloidal nanoparticles, involving the presence of complexes between Ca2+ and AEP- on the surface of apatite nanocrystals. The possibility to confer luminescence properties was demonstrated by way of ionic substitutions of some Ca2+ ions by europium Eu3+ ions, allowed us to envision the study of biological material. The additional adsorption of folic acid was also addressed, with the final aim to target cancer cell. Other aspects linked to a potential future use of these nano-systems in the biomedical field were also examined, such as the purification of these suspensions by dialysis, the possibility to resuspend the nanoparticles after freeze-drying, the evaluation of their cytotoxicity, the study of the pro-inflammatory potential by following interactions with human macrophages, and a preliminary study of their internalization by cancer cells. This work enabled us to develop a « proof of concept » allowing one to envision the future use of such colloidal nano-systems in the biomedical field, and in particular in oncology.

Les mécanismes de perception du phosphate chez les plantes ainsi que la mise en place des réponses à une carence demeurent relativement méconnus. On explique le nombre restreint d'éléments identifiés jusqu'ici par la complexité des mécanismes mis en jeu, impliquant probablement une redondance fonctionnelle. Ce travail de thèse avait pour but de contourner cet obstacle pour tenter d'apporter de nouveaux éléments de compréhension de la réponse à la carence en phosphate chez la plante modèle Arabidopsis thaliana. Une approche de génétique chimique a donc été utilisée pour isoler une famille de molécules (les Phosphatins) inhibant de nombreuses réponses induites par la carence phosphatée. Elles agissent aussi bien au niveau de la réponse morphologique que métabolique. Ceci révèle l'existence de blocages génétiques limitants la croissance des plantes en condition de carence en phosphate. Cette étude suggère aussi l'existence de « cross talks » potentiels ou de mécanismes redondants ignorés jusqu'ici entre les réponses morphologiques et biochimiques. / The plant mechanism of phosphate perception and responses pathways to a starvation are still poorly understood. We explain that only few elements have been identified so far by the complexity of the mechanisms involved, probably coupled with functional redundancy. The aim of this work was to bypass this obstacle in order to deep our knowledge on the understanding of the phosphate starvation response in the plant model Arabidopsis thaliana. A chemical genetic approach was used to isolate a drug family (the Phosphatins) inhibiting several responses induced by a phosphate starvation. They act both on morphological and metabolic response. This reveals the existence of genetic blocking limiting plant growth under conditions of phosphate deficiency. This study also suggests the existence of potential "cross talks" or redundant mechanisms hitherto unknown between morphological and biochemical responses.

La Phostine (PSN ; PHOSphate STarvation response INductor) est une petite molécule organique de synthèse, identifiée dans une chimiothèque par son effet inducteur de l’expression du gène PHT1;4 codant un transporteur de phosphate chez Arabidopsis thaliana. Au cours de cette thèse, j’ai caractérisé l’effet de la PSN chez Arabidopsis et montré que cette drogue induit plusieurs réponses typiques de la carence en phosphate : expression de gènes régulés localement ou à longue distance, accumulation d’anthocyanes et d’amidon, activité des phosphatases acides, inhibition de la croissance des racines. De plus, la PSN provoque une accumulation de phosphate soluble dans les racines.L’étude d’analogues structuraux de la PSN m’a permis d’identifier un motif commun (#10) nécessaire à son activité biologique. Il apparaît que la PSN et ses analogues actifs sont instables à pH acide, ce qui libère le motif #10. Nous montrons que le motif #10 pénètre dans la plante essentiellement par les racines et qu’il ne circule pas des racines vers les feuilles, et faiblement des feuilles vers les racines. L’accumulation de #10 dans les racines expliquerait l’ensemble des effets observés de la PSN et de ses analogues actifs. Nous avons isolé un mutant d’Arabidopsis dont la croissance racinaire résiste à la PSN. Chez ce mutant, la PSN ne provoque plus l’accumulation d’anthocyanes et d’amidon dans les feuilles, ni celle de phosphate dans les racines. En absence de PSN, et sur un milieu de culture partiellement appauvri en phosphate, les feuilles et les racines de ce mutant accumulent plus de phosphate que celles du type sauvage. Chez les plantes, l’homéostasie du phosphate est soumise à une régulation complexe, la caractérisation approfondie de ce mutant apportera de nouveaux éléments pour sa compréhension. / The Phostin (PSN ; PHOSphate STarvation response INductor) is a small organic synthetic molecule identified in a chemical library by its induction effect on PHT1;4 expression, a gene encoding a phosphate transporter in Arabidopsis thaliana. During my PhD, I characterized the effects of PSN in Arabidopsis and shown that this drug induces several phosphate starvation responses: expression of locally or systemically regulated genes, anthocyanin and starch accumulation, acid phosphatase activity, primary root growth inhibition. Moreover, PSN induces inorganic soluble phosphate accumulation in roots.Thanks to PSN’s structural analogues, we identified a common motif (motif #10) necessary to its biological activity. PSN and its analogues are unstable in acidic conditions, leading to the release of #10 motif. We have shown that #10 motif enters the plant mostly by the roots and do not circulate from roots to shoots, and weakly from shoots to roots. The accumulation of #10 motif in the roots explains all the PSN and analogues observed effects. We characterized an Arabidopsis mutant resistant to PSN for its root growth. In this mutant, PSN does not induce anthocyanin or starch accumulation in leaves, neither phosphate in roots. When growing without PSN, on partially phosphate depleted medium, the mutant presents higher phosphate content than the wild type. Phosphate homeostasis is a very complex process in plant, the deep characterization of this mutant will bring new elements for the comprehension of this pathway.

O presente trabalho constou de dois experimentos, ambos realizados em casa de vegetação do Departamento de Solos e Nutrição de Plantas da ESALQ/USP com delineamento experimental de blocos ao acaso, nos quais utilizaram-se amostras de um Latossolo Amarelo adicionando-se ou não um gel de ferro (Fe), estabelecendo assim condições distintas de capacidade de fixação de fósforo (CFF) para um mesmo solo. As fontes de P testadas foram: (i) fosfato monocálcio p.a. (FMC), que foi utilizado como fonte padrão, (ii) superfosfato simples com baixa solubilidade em água ("low-grade SSP", LG SSP), (iii) multifosfato magnesiano (MFM), (iv) termofosfato (TERMO), e (v) fosfato natural de Arad (FN). A hipótese central estudada foi a de que "algumas fontes de fósforo com baixa solubilidade em água utilizadas no Brasil possuem maior eficiência agronômica relativa em solos de elevada capacidade de fixação de P". O experimento 1 teve como objetivo comparar e avaliar a liberação de P das fontes em diferentes situações de acidez e fixação de P. Neste estudo não foi utilizado planta. Os tratamentos envolveram cinco fontes de P (FMC; LG SSP; MFM; TERMO; FN), seis doses (0, 12,5; 25; 50; 100 e 200 mg kg-1 P), duas condições de solo (sem e com aplicação de gel de Fe) e dois níveis de acidez (pHCaCl2 4,6 e 5,6). O número total de tratamentos foi de 120 (5 fontes x 6 doses x 2 condições de CFF x 2 níveis de acidez), com três repetições, totalizando assim, 360 unidades experimentais. Amostras de terra foram coletadas 30 dias após a montagem do experimento para avaliar o teor de fósforo no solo, utilizando a resina trocadora de íons como extrator. De forma geral observaram-se maiores valores do índice de eficiência relativa das fontes de baixa solubilidade em água nos solos com indução da CFF. No experimento 2 o objetivo principal foi avaliar a eficiência agronômica relativa (EAR) das fontes de P. Realizaram-se dois cultivos de milho que seguiram o esquema [(2 x 5 ) + 2 ], ou seja, duas condições de solo (sem e com gel de Fe), cinco fontes de P (FMC; LG SSP; MFM; TERMO; FN), duas testemunhas sem P e três repetições (36 unidades experimentais). Nos dois cultivos observou-se um decréscimo na produção de matéria seca, e P acumulado, com o FMC na condição de alta CFF, além disso, ocorreu o aumento da EAR das fontes de baixa solubilidade em água com a indução da CFF. Os resultados dos dois estudos sugerem que geralmente as fontes com baixa solubilidade em água apresentam maiores valores de eficiência relativa quando se induziu o aumento da CFF. Esta informação, adaptada através de experimentação regional adequada de campo, poderá levar a um melhor manejo das fontes de fósforo e ainda auxiliar na tomada de decisão por parte dos empresários rurais com relação a fontes disponíveis de P. / The study was carried out through two experiments conducted at the greenhouse of the Soil and Plant Nutrition Department, ESALQ/USP, utilizing experimental outline as blocks and a Yellow Latossol, with the addition or not of an iron gel to vary the soil phosphorus (P) fixation capacity (PFC). The P sources tested were: (i) reagent grade monocalcium phosphate (MCP), used as the standard source of P, (ii) low-grade single superphosphate with medium water solubility (LG SSP), (iii) magnesium multiphosphate (MMP), (iv) termophosphate (TERMO), and (v) Arad phosphate rock (PR). The hypothesis tested was that "some P sources, with low water solubility, may have higher relative agronomic effectiveness (RAE) in soils with high PFC". Experiment 1 aimed to evaluate and compare the P released from the sources in different scenarios of soil acidity and PFC. In this study plants were not used as indicators but an extractor of bioavailable P. The treatments consisted of five P sources, six rates of P (0, 12,5; 25; 50; 100 e 200 mg P Kg-1 of soil), two soil conditions as related to PFC (without and with the addition of an iron gel) and two soil pH levels. The total number of treatments was 120, with three replicates, totalizing 360 experimental units. Soil samples were collected 30 days after soil incubation with the P sources and analyzed following the exchange resin as the extractor. In general, higher relative index were observed for the alternative sources of P (low water solubility) in the soil with induced PFC. Experiment 2 was designed to provide information related to the RAE utilizing two short corn plant crops as indicator. The experimental outline was of two soil condition as related to PFC (without and with addition of the iron gel), five P sources, two controls, and three replicates, totalizing 36 experimental units. Only one soil pH condition was tested in this case (with lime added to pH CaCl2 5.6). Both corn crops showed a decrease in dry-matter yield and P uptake by the plants with the MCP applied in the soil with higher PFC. The RAE was in general higher for the lower water soluble P sources in the soil with induced PFC. The results of both experiments suggested that, in general, P sources with lower water solubility present higher relative effectiveness when the soil PFC was induced by the addition of the iron gel. The information, once adapted to local field experimentation, can lead to a more adequate management of the P sources, as well may serve to guide farmers in taking decisions as related to sources to be utilized in their agricultural fields.

Apesar de ser utilizado na indústria de Fosfato Bicácico (DCP) há vários anos, a microgranulação a partir de misturados horizontais de alto cisalhamento possui fundamentos pouco conhecidos, de maneira que as operações das unidades industriais sejam baseadas em conhecimentos empíricos. Este trabalho busca determinar os mecanismos de granulação associados com o processo de microgranulação de DCP e o perfil de crescimento dos grãos em função dos seguintes parâmetros operacionais: a quantidade de fase líquida, acidez do meio reacional e a velocidade de rotação do eixo central do granulador. Após a análise estatística de dados coletados a partir de um ano de operação em uma unidade industrial, conclui-se que a aglomeração do DCP em ambientes com alta umidade geram preferencialmente partículas grosseiras, que não contribuem para o aumento da eficiência de granulação. O processo de microgranulação de DCP deve ser controlado em uma estreita faixa de condições operacionais, balanceando a quantidade de fase líquida adicionada e a taxa de reciclo de material seco praticada. A redução na umidade de operação, aumenta a qualidade granulométrica do material produzido por este processo. / Despite being used by the Dicalcium Phosphate (DCP) Industry for many years, the fundaments of high shear horizontal mixer microgranulation are poorly known, so the industrial operations are based on empirical knowledge. The goal of this work was to determine the granulation mechanisms associated with the DCP microgranulation process and the particle size enlargement pattern, according with the following operational parameters: the amount of liquid phase, reaction media acidity and the mixer paddles` rotational speed. After statistically analysing one year operational data collected from an industrial facility, it was concluded that the agglomeration of DCP at a high moisture environment promotes preferable formation of coarse particles, which dont increase the overall granulation efficiency. The DCP microgranulated process has to be controlled in very narrow operational condition, balancing the liquid phase and the recycle material returned during the granulation process. The reduction of the process moisture increased the quality of physical quality of the material produced by this process route.

É amplamente conhecida a importância do fósforo (P) para a obtenção de boa produtividade de culturas. Sabe-se, também, que a matéria prima para produção de adubos fosfatados é um recurso escasso e não renovável. Utilizações adequadas e alternativas que busquem melhorias da eficiência das fontes de P são de grande importância para o manejo da fertilização fosfatada. Os fosfatos naturais (FNs) podem ser fontes alternativas aos fosfatos acidulados para adubação fosfatada. Entretanto, faz-se necessário buscar opções para melhorar a eficiência dessas fontes, sendo uma delas a aplicação junto com enxofre elementar (S0), que, durante o processo de oxidação a sulfato no solo, libera prótons (H+) necessários para solubilização dos FNs. Deste modo, objetivou-se por meio desse trabalho estudar esse efeito do S0. O trabalho constou de dois estudos conduzidos em casa de vegetação: (i) aplicação de FNs associados a S0 nas culturas do arroz e feijão, e (ii) efeitos de doses de S0 e de FNs no aproveitamento do P dessas fontes pelo feijoeiro. Em ambos os estudos, para contabilizar o efeito do S0 no aumento da absorção de P dos FNs pelas culturas, foi utilizado o método da diluição isotópica com 32P. No estudo 1 o objetivo foi avaliar o efeito do modo de aplicação do fosfato natural reativo de Gafsa (FNG) e do fosfato natural de Patos de Minas (FNP) aplicados isoladamente ou em associação com S0 e tendo como referência o superfosfato triplo (SFT), nas culturas do arroz e feijão. Os tratamentos consistiram de 5 fontes de P: SFT, FNP, FNG e das associações do FNP + S0 e FNG + S0, 2 modos de aplicação: área total e localizada, mais um tratamento controle, sem aplicação de P, constituindo um fatorial (5 x 2 + 1). A acidez gerada na oxidação do S0 promoveu aumento da solubilização do FNG e do FNP, melhorando a disponibilidade de P dessas fontes, com maior efeito quando os fertilizantes foram aplicados em contato, localizados no solo. No estudo 2 objetivou-se avaliar o efeito de doses de S0 e de doses de P de FNG e FNP para a cultura do feijoeiro. Os tratamentos foram arranjados em esquema fatorial 3 x 5 x 4, sendo 3 fontes de P: SFT, FNG e FNP, 5 doses de P (0, 30, 60, 90 e 120 mg kg-1) e 4 doses de S com S0 (0, 30, 60, 90 mg kg-1). A associação do S0 com FNG e FNP promoveu aumento da solubilização dessas fontes e consequentemente da absorção de P pelo feijão, sendo o efeito mais expressivo no FNG, comparado ao FNP. Quando aplicados sem a presença do S0, o FNG e o FNP foram equivalentes em fornecer P para a cultura do feijão. A absorção de P do FNG aumentou com as doses de S0 e esse efeito foi mais expressivo na dose inicial, não mantendo proporcionalidade com as demais doses. O efeito sobre o fosfato natural de Patos de Minas foi pouco expressivo. / It is well known the importance of phosphorus (P) for obtaining good crop yield. It is also known that the raw material for obtaining phosphate fertilizers is a scarce and non renewable resource. Appropriate use and searching alternatives for improving the efficiency of P sources are of great importance for the management of phosphate fertilization. The phosphates rocks (PRs) may be the alternative sources for soluble P fertilization. However, it is necessary to find the ways to improve the efficiency of these sources, being one of them taking advantage of elemental sulfur (S0) oxidation, which, during the process, releases protons (H+), necessary for PRs solubilization. The objective of this research was to study this effect of S0. Two studies were carried out in the greenhouse: (i) application of PRs associated with S0 in rice and beans crops, and (ii) effects of So rates and of the PRs on the utilization of P from these sources by the bean crop. In both studies, to account the increasing effect of S0 on the PR-P uptake by the crops, the 32P dilution technique was used. The object of the study 1 was to evaluate the effect of applying methods of Gafsa reactive phosphate rock (GPR) and the Patos de Minas (PPR), sole or in combination with S0 compared to the triple superphosphate (TSP) for rice and bean crops. The treatments consisted of five P sources: TSP, PPR, GPR, PPR+ S0 and GPR + S0, application methods: total area or located, plus a control without P application, constituting a factorial (5 x 2 + 1). The acidity generated by oxidation of S0 increased the solubilization of GPR and PPR, increasing the availability of P from these sources, the effect being greater when fertilizers were applied in contact, located on the soil. The object of second study was to evaluate the effect of P rates associated with S rates as S0 in bean crop. The treatments were arranged in a 3 x 5 x 4 factorial, with 3 P sources: TSP, GPR and PPR, five P rates (0, 30, 60, 90 and 120 mg kg-1) and four rates of the S (0, 30, 60, 90 mg kg-1). The association of S0 with GPR and PPR promoted an increase in solubilisation of these P sources and consequently the absorption of P by the bean plants, being the effect stronger in the GPR, compared to PPR. When applied without S0 the PPR and GPR were equivalent in providing P to the bean crop. The absorption of P from GPR increased with increasing sulfur rate and this effect was more expressive in the initial rate, not maintaining the proportionality with other rates. The effect on the PPR was small.

Ce travail porte sur la recherche et le développement d'un matériau de substitution osseuse permettant une implantation par chirurgie mini invasive, limitant les infections post-opératoires et dont la résorbabilité serait adaptée à la cinétique de régénération osseuse. Nous nous sommes intéressés à un ciment à base de carbonate et de phosphate de calcium (CaCO3 – CaP) dont la réaction de prise conduit à la formation d'une apatite nanocristalline analogue au minéral osseux. Dans une première partie la cinétique de prise et le produit de réaction ont été caractérisés par différentes techniques, notamment la diffraction des RX et les spectroscopies FTIR et RMN du solide. Un sel d'argent – Ag3PO4 ou AgNO3, choisis pour leurs propriétés antibactériennes – a été ensuite introduit dans la formulation. Son effet sur la cinétique de la réaction chimique de prise a été mis en évidence par traitement des spectres FTIR et RMN et un mécanisme réactionnel original impliquant les ions argent et nitrate dans la formation de l'apatite a été proposé. L'ajout d'un polysaccharide, la carboxyméthylcellulose (CMC), dans la phase solide du ciment a montré une très nette amélioration de l'injectabilité de la pâte, avec la disparition du phénomène de séparation des phases qui limite généralement l'injectabilité des ciments minéraux. La résistance à la compression et le module élastique des ciments composites ont été par ailleurs augmentés, parallèlement à une diminution de leur porosité. Différentes études in vitro en présence de cellules ou de bactéries ont enfin été réalisées et ont mis en évidence respectivement la cytocompatibilité des différentes compositions de ciments étudiées et le caractère antibactérien de ces matériaux à partir d'une certaine concentration en argent. L'implantation in vivo de compositions choisies a présenté des résultats très prometteurs quant à la résorbabilité d'un ciment composite CaCO3 - CaP/CMC/Ag et à la néoformation osseuse. / The present work concerns research and development of a material for bone substitution, enabling implantation through a mini-invasive surgery, limiting post-operative infections and whose resorbability is adapted to bone regeneration kinetics. This study focused on a calcium carbonate and phosphate based cement, whose setting reaction leads to the formation of a nanocrystalline apatite, similar to bone mineral. First, the setting kinetics and the reaction products were characterised using different techniques, especially X-ray diffraction and FTIR and solid-state NMR spectroscopies. A silver salt – Ag3PO4 or AgNO3, chosen for their antibacterial properties – was then introduced in the formulation. Its effect on the setting reaction kinetics was revealed by data processing of FTIR and NMR spectra and an original reaction mechanism which involves silver and nitrates in the formation of apatite was proposed. The addition of a polysaccharide, carboxymethylcellulose (CMC), in the solid phase of the cement showed a clear improvement of the injectability of the paste, preventing the occurrence of filter-pressing phenomenon, often limiting the injectability of mineral cements. The resistance to compressive strength and elastic modulus of the composite cement were also improved together with a decrease in their porosity. Different in vitro studies were carried out in the presence of cells or bacteria and demonstrated the cytocompatibility of different cement compositions and their antibacterial properties starting at a certain silver concentration, respectively. In vivo implantation of selected compositions showed promising results concerning resorbability of a composite CaCO3 - CaP/CMC/Ag cement and the associated bone neoformation.