Thesis (Ph. D.)--Institute of Paper Chemistry, 1966. / Includes bibliographical references (p. 114-117).

No description available.

Phosphate is an essential but often growth-limiting nutrient for bacteria. At low concentrations of phosphate in the growth medium, bacteria induce high-affinity uptake systems for phosphate, and this is usually the ABC-type phosphate specific transport system Pst. In the fully sequenced genomes of pathogenic species of mycobacteria, several copies of the genes encoding for the Pst system (pstSCAB) have been identified and some of these genes have been shown to be virulence factors. The reasons for the presence of multiple copies of pst genes in pathogenic mycobacteria are not understood, and phosphate transport by these bacteria, as well as the gene regulation involved, is poorly characterised. The fast-growing M. smegmatis contains only a single copy of the pst operon, but we recently identified a gene locus containing three genes, phnDCE, which encode for a putative ABC-type phosphate/phosphonate transport system, and a gene, phnF, which encodes for a putative transcriptional regulator of the HutC subfamily of GntR like regulators. To identify a function for the PhnDCE transport system and to characterise high-affinity phosphate transport in M. smegmatis, we created allelic exchange mutants in phnD and pstS, as well as a phnD pstS double deletion mutant. All three mutants failed to grow in minimal medium containing 10 mM phosphate, while the wildtype was able to grow in the presence of micromolar phosphate concentrations. No differences were observed in complex growth medium. Steady-state levels of [��P]-phosphate uptake were approximately 25% lower in all mutant strains as compared to the wildtype. Kinetics of phosphate uptake in the wildtype strain when grown at low phosphate concentrations (50 [mu]M P[i]) were biphasic, suggesting the presence of two inducible transport systems with apparent K[m] values of 16 [mu]M P[i] and 64 [mu]M P[i], respectively. Analysis of the kinetics of phosphate transport in the mutant strains led us to the proposition that the Pst system has an apparent Km value of ca. 16 [mu]M P[i], and the Phn system has an apparent Km of ca. 60 [mu]M P[i]. A third inducible phosphate transport system, which was active in the double mutant strain, had an apparent K[m] of ca. 90 [mu]M P[i]. Uptake of phosphate in all strains was not inhibited by the presence of excess phosphonates or phosphite, suggesting that all three transport systems were specific for phosphate. The study of phosphate transport in the presence of various metabolic inhibitors revealed that uptake by the Phn and Pst systems is driven by ATP-hydrolysis, consistent with ABC-type transport, while the third, unidentified transport system may be driven by the proton motive force. We showed that phnDCE formed an operon, and that the promoter area of the operon lies within 200 bp of the start of phnD. To investigate the regulation of the phn and pst genes, β-galacosidase activities of strains carrying transcriptional lacZ-fusions of the pstSCAB, phnDCE and phnF promoter areas, and levels of mRNA of the phn and pst genes were studied. All genes were induced when phosphate concentrations fell below a threshold value of 30 [mu]M, which coincided with a shift in the growth characteristics of M. smegmatis. Expression of the pst operon appeared to be controlled directly by the PhoPR two-component regulatory system, while the phn operon may be under direct or indirect control by PhoPR. To identify a role for PhnF in the regulation of phn gene expression, we created a phnF deletion mutant. PhnF appeared to repress transcription of phnDCE and phnF under phosphate-replete conditions. We identified two putative binding sequences for PhnF in the intergenic region between phnD and phnF with the sequence TGGTATAGACCA, which is similar to the proposed recognition consensus for HutC-like transcriptional regulators. Using site-directed mutagenesis of these sequences, we demonstrated that they are required for the repression of phnDCE and phnF. To prove PhnF binding to these potential binding sites, we attempted to express the M. smegmatis PhnF protein in E. coli, but could not obtain soluble recombinant protein. Electrophoretic mobility shift assays of the phnDCE promoter fragment using cell-free crude extracts of M. smegmatis were not successful. We propose that Pst and Phn both constitute high-affinity phosphate specific transport systems of M. smegmatis, and that a third inducible phosphate transport system is present in this bacterium. PhnF is required for repression of phnDCE and phnF transcription under phosphate-replete conditions, while induction of the pst operon, and possibly the phn operon, under phosphate-limited conditions involves the PhoPR system.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Made available in DSpace on 2014-06-11T19:31:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-09Bitstream added on 2014-06-13T20:22:22Z : No. of bitstreams: 1 lima_rkp_dr_arafo.pdf: 692401 bytes, checksum: 6c17d09894639b5d27ecc81f49ce48d5 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este estudo objetivou avaliar a capacidade de liberação e difusão de íons hidroxila, e a atividade antibacteriana de medicações intracanal, in vitro. No primeiro experimento, canais radiculares de dentes bovinos foram instrumentados. Uma cavidade de 4 mm de comprimento, 2 mm de largura e 0,5 mm de profundidade foi confeccionada no terço médio/apical radicular de cada amostra. A abertura coronária e a superfície externa radicular foram seladas com adesivo e esmalte para unhas, exceto a área da cavidade preparada. Os canais radiculares foram preenchidos com as seguintes medicações: G1: hidróxido de cálcio (Ca(OH)2)/soro; G2: Calen; G3: Calen/PMCC; G4: Calen/Clorexidina (CLX) a 0,4%. Os dentes foram armazenados individualmente em frascos contendo água destilada a 37oC. As medições do pH foram realizadas nos períodos de 1, 3, 7, 14, 21, 30 e 60 dias, com utilização de pHmetro digital. Os resultados mostraram aumento significativo do pH a partir de 3 dias para a pasta Calen/CLX e para as demais pastas a partir de 7 até os 14 dias. Para a pasta Calen ocorreu aumento até os 21 dias. A pasta Calen/PMCC apresentou pH mais elevado até 21 dias, sendo os resultados semelhantes para todos grupos aos 30 dias. Aos 60 dias, os maiores valores de pH foram observados para as pastas Calen/PMCC e Calen. Conclui-se que as diferentes composições de pastas à base de Ca(OH)2 proporcionam difusão de íons hidroxila pela dentina radicular. Em outro experimento, 106 dentes humanos unirradiculados tiveram seus canais radiculares contaminados com Enterococcus faecalis e incubados a 37°C por 21 dias. Em seguida, foram divididos de acordo com a medicação intracanal e o período em: G1: Calen - 7 dias; G2: Calen - 14 dias; G3: Calen/PMCC - 7 dias; G4: Calen/PMCC - 14 dias; G5: Calen/CLX a 0,4% - 7 dias; G6: Calen/CLX a 0,4% - 14 dias; G7: Calen/CLX a 1% - 7 dias; G8: Calen/CLX a 1% - 14 dias.... / The aim of this study was to evaluate the release and diffusion of hydroxil ions, and the antibacterial activity of intracanal medication, in vitro. At first study, root canals from bovine teeth were instrumented. A cavity with 4 mm of length, 2 mm of width and 0.5 mm of depth was opened at middle/apical third of each sample. The coronal opening and the external surface of the roots were coated with a nail polish layer and a layer of sticky wax, except on the cavity area. Root canals were filled with the following intracanal medication: G1: calcium hydroxide powder with saline solution (Ca(OH)2); G2: Calen; G3: Calen/PMCC; G4: Calen/Chlorhexidine (CHX) 0.4%. Teeth were stored individually in recipients with distilled water at 37oC. Measurements of pH were made at periods of 1, 3, 5, 7, 14, 21, 30 and 60 days, using a digital pH meter. Results showed a significant increase of pH from 3 days for Calen/PMCC, and from 7 until 14 days for the other medications. For Calen, an increase was observed until 21 days. Calen/PMCC showed the highest pH until 21 days, and all the groups had similar results at 30 days. At 60 days, the highest pH values were observed for Calen/PMCC and Calen. It is possible to conclude that different compositions of calcium hydroxide pastes caused diffusion of hydroxil ions through radicular dentin. In another study, 106 single-rooted human teeth had their root canals contaminated with Enterococcus faecalis and incubated at 37oC for 21 days. Then, these teeth were divided according to intracanal medication and periods: G1: Calen - 7 days; G2: Calen - 14 days; G3: Calen/PMCC - 7 days; G4: Calen/PMCC - 14 days; G5: Calen/CHX 0.4% - 7 days; G6: Calen/CHX 0.4% - 14 days; G7: Calen/CHX 1% - 7 days; G8: Calen/CHX 1% - 14 days. Microbiological samples were collected immediately after intracanal medication removal and after seven days. After serial 10-fold dilutions and culture... (Complete abstract click electronic access below)

Sensores com material magnetoelástico vêm sendo desenvolvidos pois possibilitam medidas sem contato de fios (wireless). Apresentam variação da frequência de ressonância (redução) quando submetidos a um carregamento de massa. Podem ser empregados para detecção e determinação de grandezas físicas através de instrumentação remota que vem se tornando cada vez mais importante. As grandezas podem ser desde a quantificação de pH até a detecção da presença de microrganismos. Neste trabalho descrevemos um sistema de detecção rápida e wireless de grandezas físicas como pH e a presença de microorganismos. São utilizados como substrato tiras de material magnetoelástico amorfo Metglas 2826MB3. O material foi cortado em tamanhos de 30 mm x 6 mm e 5 mm x 1 mm, através de uma serra de micro corte, sendo parte destas logo em seguida foram revestidas com finas camadas de Cr e Au através de sputtering. Foi desenvolvido um dispositivo portátil com a função de análise de frequência de ressonância das fitas magnetoelásticas. Este dispositivo pode operar completamente de forma autônomo ou em conjunto com computador. Ele é composto de um central de processamento, circuitos auxiliares e interface de entrada e saída de dados. A operação do dispositivo portátil está em expor o material magnetoelástico (transdutor/sensor) a um campo magnético variável com o tempo, que por sua vez responde com uma onda elástica longitudinal que é detectada de forma magnética. Foram realizados ensaios com o transdutor (superfície livre) e também após a aplicação de camadas sensíveis ao pH e bem como a captura de microrganismo. Para os sensores detectores de pH foram utilizadas tiras do transdutor revestidas com Cr e Au sendo nestas aplicada uma camada de cistamina (CYS) para gerar aderência do polímero de pH sintetizado a partir de monómeros de ácido acrílico e acrilato de isooctilo. O sensor de pH foi exposto a uma faixa de pH (1,5 a 7,5) sendo analisado através do dispositivo portátil e comparado com analisador de rede Agilent E5061B. As medidas da frequência de ressonância do sensor de pH apresentaram uma variação de 70 Hz/pH para sensores 30 mm x 5 mm e para sensores de 5 mm x 1 mm foi de 1000 Hz/pH. Também foram realizadas medidas com o transdutor funcionalizado com Poli- L-Lisina para captura de S. cerevisiae. Com a aderência da S. cerevisiae à superfície do sensor, houve uma redução da frequência de ressonância em 531 Hz, que concorda quantitativamente com valores calculados para este carregamento de massa. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-08-09T17:17:16Z No. of bitstreams: 1 Dissertacao Mateus Beltrami.pdf: 5990387 bytes, checksum: 8b30dc1a304d4ed66593186686b04ee2 (MD5) / Made available in DSpace on 2016-08-09T17:17:16Z (GMT). No. of bitstreams: 1 Dissertacao Mateus Beltrami.pdf: 5990387 bytes, checksum: 8b30dc1a304d4ed66593186686b04ee2 (MD5) Previous issue date: 2016-08-09 / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS / Sensors with magnetoelastic materials are being developed for possible wireless measurements. They show variation of the resonance frequency (decrease) when subjected to a loading mass. May be employed for detection and determination of physical quantities via remote instrumentation that is becoming increasingly important. These quantities could be the pH of a solution or the detection of the presence of microorganisms. In this work, we describe a rapid and wireless detection system for physical quantities such as pH and the presence of microorganisms. We used as substrates strips of amorphous magnetoelastic material Metglas 2826MB3. The material was cut into strips with sizes of 30 mm x 6 mm and 5 mm x 1 mm, using a micro-dicing saw. Part of these were coated with thin layers of Cr and Au through sputtering. We developed a portable electronic device with the function of determining the resonance frequency of the magnetoelastic strips. This device can operate completely standalone or in conjunction with a computer. It is composed of a central processing, auxiliary circuits and input and output interface of data. The portable device produces a variable magnetic field, which in turn produces a longitudinal elastic wave which is detected magnetically. Tests were carried out with the bare transducer as well as after the application of pH-sensitive layers or material for the capture of microorganisms. For pH sensors we used transducer strips coated with Cr and Au and then applied a layer of cystamine (CYS) to promote adherence to the copolymer of acrylic acid and iso-octyl acrylate. The pH sensor was exposed to a range of pH (1.5 to 7.5) and was measured using the portable device and compared with results from an Agilent E5061B Network Analyzer. The measurements of the resonance frequency of the pH sensor showed a 70 Hz/pH variation for strips of 30 mm x 6 mm and 1000 Hz/pH for strips measuring 5 mm x 1 mm. Measurements were also carried out with the transducer functionalized using poly-l-lysine to capture S. cerevisiae. With the adherence of S. cerevisiae on the sensor surface, there was a reduction of the resonance frequency 531 Hz, which agrees quantitatively with values calculated for mass loading.

Orientador: Jaime Aparecido Cury / Dissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-16T04:46:21Z (GMT). No. of bitstreams: 1 Correia_MariliaFerreira_M.pdf: 14739894 bytes, checksum: a66d446ede854332c287fe24fbc20a31 (MD5) Previous issue date: 2018-08-16T01:46:07Z / Resumo: O biofilme dental apresenta reservatórios orgânicos e inorgânicos de cálcio (Ca), fosfato (Pi) e fluoreto (F) que se liberados para o fluido do biofilme mediante quedas de pH, interfeririam com o grau de saturação do fluido, reduzindo a desmineralização dental. Entretanto, ainda se desconhece a origem responsável pelas mudanças observadas na concentração de Ca, Pi e F no fluido após queda de pH: se derivadas dos reservatórios ou da desmineralização do próprio substrato dental. Em acréscimo, ainda não se determinou a solubilidade desses reservatórios em pHs considerados importantes para interferir com o processo de desmineralização dental. Assim, este trabalho de dissertação teve como objetivos avaliar a influência que a solubilidade dos substratos e dos reservatórios do biofilme exercem na concentração inorgânica do fluido do biofilme, avaliando a cinética dos íons Ca, Pi e F para o fluido após desafio acidogênico. Para isto foram realizados dois estudos in situ, ambos cegos e cruzados. No primeiro foi contemplada a hipótese de que a concentração inorgânica do fluido do biofilme seria influenciada pela desmineralização do substrato, refletindo o grau de solubilidade do mineral que o compõe. Para isto, blocos de esmalte (menos solúvel), dentina (mais solúvel) e acrílico (não solúvel) foram expostos, durante 4 dias, a desafios cariogênicos utilizando glicose a 20%, 8x/ao dia; as variáveis analisadas ao final de cada fase foram composição microbiológica, pH no fluido, Ca, Pi e F no fluido e no estroma (parte sólida) do biofilme antes e 5 min após desafio acidogênico. A influência da quantidade dos reservatórios na concentração inorgânica do fluido foi avaliada no segundo in situ, onde em acréscimo, determinou-se a solubilidade dos mesmos em função de pHs decrescentes. Assim, biofilme dental foi formado, durante 14 dias, sobre blocos de esmalte e acrílico, utilizando diferentes freqüências de exposição a glicose a 20% (0, 2 e 8x/dia), para obtenção de biofilmes com diferentes quantidades de reservatórios. O pH, Ca, Pi e F foram determinados no fluido antes e 5 min após desafio acidogênico, enquanto a solubilidade dos reservatórios foi determinada através da extração de Ca, Pi e F no estroma do biofilme, utilizando tampões com pHs decrescentes (6,5; 5,5; 4,5 e ácido forte). Os resultados desses estudos permitiram observar que houve um aumento significativo de Ca no fluido após queda de pH, ocorrendo de modo semelhante independentemente do substrato onde o biofilme foi formado e da quantidade de reservatórios presentes no seu estroma. Além disso, a solubilidade dos reservatórios demonstrou ser função inversa do pH e direta da concentração de Ca e PI presente. Assim, sugere-se que os reservatórios representam uma importante fonte de mobilização iônica para o fluido do biofilme, porém o fluido não refletiu, na condição analisada, a diferença de solubilidade dos substratos utilizados e dos reservatórios presentes. / Abstract: Dental biofilm presents organic and inorganic reservoirs of calcium (Ca), phosphate (PI) and fluoride (F) that could act as a source of these ions to biofilm fluid during pH drops, reducing dental demineralization. It's still unknown the source responsible for the increase of such ions in biofilm fluid after pH drop, since they could be also derived from mineral dissolution of dental structure. In addiction, there's no clear evidence about the solubility of these reservoirs according to the pHs considered important to interfere with dental demineralization. Thus, this study aimed to evaluate the influence of mineral dissolution of dental structure and also of biofilm reservoirs in the inorganic composition of biofilm fluid, analyzing the kinetics of Ca, PI and F to fluid just after pH drop. Two crossover and blind in situ studies were performed, which the aim of the first one was to evaluate the hypothesis of the inorganic composition of biofilm fluid after pH drop would reflect the mineral solubility of substrate where biofilm was formed. Thus, dental biofilm was formed during 4 days on enamel (less soluble), dentine (more soluble) and acrylic (not soluble) slabs, which were exposed to 8 times/day to 20% glucose solution. In the end of each phase, the acidogenicity, microbiological composition and inorganic concentration of these biofilms were analyzed. The second in situ study evaluated the relation between the amount of Ca, Pi and F reservoirs with the inorganic composition of biofilm fluid and moreover, the potential of these reservoirs to release Ca, Pi and F was estimated according to decreasing pHs (6.5; 5.5; 4.5 and acid). Therefore during 14 days, dental biofilm was formed on enamel and acrylic slabs, which were exposed to different frequencies of 20% glucose (0, 2 and 8 times/day) to form biofilms with different amounts of Ca, Pi and F reservoirs. The biofilm fluid analyses were the same performed in the first study, however the concentration of Ca, Pi and F in biofilm solids were determined after extraction with buffers of 6.5, 5.5 and 4.5 and with acid. A significant increase in Ca concentration was observed after pH fell; nevertheless this increase was the same regardless of the substrate where biofilm was formed and regardless of the amount of Ca, Pi and F reservoirs. Furthermore, biofilm reservoirs showed potential to release Ca, Pi and F at those pHs analyzed, although their solubility were inversely related with the frequency of glucose exposure that biofilm was formed. These findings suggest that biofilm reservoirs are important source of Ca, Pi and F to biofilm fluid after pH drop, however the inorganic concentration of fluid does not reflect the mineral solubility of substrates, the amount and solubility potential of biofilm reservoirs. / Mestrado / Cariologia / Mestre em Odontologia

Orientadores: Marinês Nobre dos Santos Uchôa, Regina Célia Rocha Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-17T19:37:13Z (GMT). No. of bitstreams: 1 Frasseto_Fernanda_M.pdf: 2583603 bytes, checksum: 24da915e364fd5a9767488a99e21f068 (MD5) Previous issue date: 2011 / Resumo: Este estudo teve como objetivos determinar a atividade da anidrase carbônica VI (ACVI) na saliva de pré-escolares com cárie e investigar a relação entre a experiência cárie (dmfs) e a atividade da ACVI, o fluxo salivar e pH do biofilme antes e após o bochecho com sacarose a 20% em pré-escolares. Trinta pré-escolares com idade entre 45,3 e 80,3 meses foram divididos em 2 grupos: grupo livres de cárie (LC) e grupo com cárie (C). Exames clínicos foram realizados por um examinador de acordo com os critérios da OMS + lesões iniciais de cárie. Em cada individuo, foi determinada a atividade da ACVI, o fluxo salivar e o pH do biofilme dental tanto antes quanto após o bochecho com sacarose. Os resultados foram submetidos aos testes de Wilcoxon, Mann-Whitney e correlação de Spearman (?=0,05). Os resultados mostraram que a atividade da ACVI antes do bochecho e a variação da atividade da ACVI foram maiores na saliva do grupo com cárie que do livres de cárie. Não houve diferença significativa entre os dois grupos após o bochecho. Porém, após o bochecho, a variação do pH do biofilme foi menor em ambos os grupos (p=0,0012 e p=0,0037 para C e LC, respectivamente). E, após o bochecho, houve um aumento significativo do fluxo salivar nos dois grupos (p=0,0003 e p=0,0037 para C e LC, respectivamente). Houve uma correlação negativa da variação entre a atividade da ACVI e a cárie (r=-0,501 e p=0,005). E uma correlação positiva entre a idade das crianças e a experiência de cárie (r=0,456 e p=0,011). Assim, os resultados sugerem que a variação da atividade da ACVI e a idade das crianças está associada com a cárie dentária em pré-escolares / Abstract: This study aimed to determine the activity of the carbonic anhydrase isoenzyme VI (CAVI) in saliva of preschool children with caries and investigate the relationship between caries and the salivary CAVI activity, salivary flow rate (SFR) and biofilm pH before and after a 20% sucrose mouthrinse in preschool children with caries. Thirty preschool children aging from 45.3 to 80.3 months were divided into two groups: caries-free group (CF) and caries group (C). Clinical examinations were conducted by one examiner (kappa=0.95) according to WHO criteria (dmfs) + early caries lesions. From each subject, CAVI activity, SFR and plaque pH were determined before and after a sucrose rinse. The results were submitted to Wilcoxon and Spearman correlation tests (?=0.05). The results showed that the pre-rinse CAVI activity and its variation were higher in saliva from caries children than from CF children. No difference was found between the two groups in the post- rinse salivary CAVI activity. After mouthrinse, the biofilm pH difference were lower in both groups (p=0.0012 and p=0.0037 for the C and CF group respectively). Also, after the sucrose rinse, SFR significantly increased in C and CF groups, (p=0.0003 and p=0.0037). The variation of salivary CA VI activity was negatively correlated with caries (r= -0.501 p=0.005). Child's age showed a positive correlation with caries (r=0.456 and p=0.011). These results suggest that variation of salivary CA VI activity and child's age are associated with dental caries of preschool children / Mestrado / Odontopediatria / Mestre em Odontologia

Orientador: Wander José da Silva / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-23T21:32:32Z (GMT). No. of bitstreams: 1 Vasconcellos_AndreaAraujode_D.pdf: 1848121 bytes, checksum: 942c0eb282415b9184ea64e02add85a8 (MD5) Previous issue date: 2013 / Resumo: A colonização da prótese dental por Candida albicans pode contribuir para o desenvolvimento de candidose associada ao seu uso. As variações de pH que ocorrem no biofilme formado sobre a prótese dental podem influenciar a quantidade de matriz extracelular e a estrutura do biofilme de C. albicans. Entretanto, não está claro como o pH pode interferir na matriz extracelular e em determinados parâmetros estruturais nos biofilmes de C. albicans. O objetivo neste estudo foi avaliar a influência do pH na quantidade de matriz extracelular e na estrutura de biofilmes de C. albicans. Discos de resina à base de poli (metilmetacrilato) com a rugosidade de superfície padronizada foram utilizados como substrato para a formação dos biofilmes. Os discos foram cobertos por uma película de saliva e biofilmes de C. albicans ATCC 90028 foram desenvolvidos em meio de cultura RPMI 1640 tamponado em diferentes valores de pH (4,0, 5,5 e 7,0) por 48 horas como grupos experimentais, e meio de cultura sem o tamponamento (pH inicial de 7,4) como grupo controle. O número de células viáveis foi quantificado por diluição seriada, e a quantidade de matriz de polissacarídeos foi analisada pelo método fenol-sulfúrico (n = 9). As características morfológicas dos biofilmes foram observadas por meio de microscopia eletrônica de varredura e por microscopia confocal (n = 3). Os resultados foram submetidos à análise de variância com um fator, seguido pelo teste de Tukey, com nível de significância de 5%. Observou-se aumento significativo no número de células viáveis nos biofilmes desenvolvidos em pH 4,0 e 5,5 (p < 0,001). A quantidade de polissacarídeos foi maior em pH 5,5, seguida por biofilmes desenvolvidos em pH 4,0 (p < 0,05). As imagens obtidas por microscopia eletrônica de varredura e por microscopia confocal mostram maior formação de hifas pelos biofilmes quando desenvolvidos em pH 7,0 e no grupo controle. Pode ser concluído que condições de pH ácidos influenciaram a formação de biofilmes com o maior número de células viáveis e, consequentemente, maior quantidade de matriz extracelular. Além disso, o pH afetou consideravelmente a morfologia dos biofilmes de C. albicans / Abstract: The colonization of dental prosthesis by Candida albicans may contribute to the development of Candida-associated denture stomatitis. The pH changes that occur in the biofilm developed over the dental prosthesis may influence the amount of extracellular matrix and the structure of C. albicans biofilms. However, it is not clear how the pH could interfere in the extracellular matrix and specifically structural parameters of C. albicans biofilms. The object of this study was to evaluate the influence of environmental pH on the amount of extracellular matrix and structure in C. albicans biofilms. Poly (methylmethacrylate) resin discs with surface roughness standardized were used as substrate for biofilm formation. The discs were covered by the salivary pellicle, and C. albicans ATCC 90028 biofilms were developed in RPMI 1640 culture medium buffered at different pH values (4.0, 5.5 and 7.0) for 48 hours as experimental groups, and unbuffered culture medium (initial pH of 7.4) as control. The number of viable cells was quantified by serial dilution, and the amount of polysaccharide matrix was analyzed by phenol sulfuric method (n = 9). The morphological characteristics of biofilms were observed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) (n = 3). Data were analyzed by one-way ANOVA, followed by Tukey's test, with significance set at 5%. It was observed a significant increase in the number of viable cells in biofilms developed at pH 4.0 and 5.5 (p < 0.001). The amount of polysaccharides was higher at pH 5.5, followed by biofilms developed at pH 4.0 (p < 0.05). The images obtained by SEM and CLSM showed higher hyphae formation by biofilms developed at pH 7.0 and in the control group. It can be concluded that acidic pH conditions influenced the formation of C. albicans biofilms, with higher viable cells and, consequently, higher amount of extracellular matrix. Furthermore, the pH significantly affected the morphology of C. albicans biofilms / Doutorado / Protese Dental / Doutora em Clínica Odontológica

In this work tunability, implantation damage and recovery of GaAs doping superlattices implanted with hydrogen ions were studied. The applicability of two models of the optical properties of semiconductors was also investigated. GaAs doping superlattices were implanted with 0.5 MeV hydrogen ions at doses of 1012 cm-2, 1014 cm-2 and 1016 cm-2. This gradually modifies their optical characteristics from superlattice behaviour to something resembling the bulk material and beyond. Such a processing technique therefore provides a convenient way of tuning the optical properties of a superlattice semi-permanently. A combined result of ellipsometry and near infrared reflectance measurements showed that a single effective oscillator as well as a more advanced three-parameter model could be applied to the virgin and ion-implanted doping superlattices. This allowed us to determine the dose dependent effective band gap as well as other model parameters. Photoluminescence as well as normal and resonance Raman techniques were applied to study hydrogen ion implantation damage and its recovery. These techniques showed that implantation damage could be reversed to a large extent by a simple thermal annealing step. / Dissertation (MSc)--University of Pretoria, 2006. / Physics / unrestricted