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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Efeito da cabodiimida e da clorexidina na longevidade da resistência de união de cimento resinoso à dentina radicular e na composição química e estrutura do colágeno dentinário após radioterapia / Effect of carbodiimide and chlorhexidine on the longevity of resin cement to root dentine bond strength and on the chemical composition and structure of dentin collagen after radiotherapy

Lopes, Fabiane Carneiro 15 June 2018 (has links)
Este estudo avaliou o efeito da carbodiimida (EDC) e da clorexidina (CLX) na longevidade da resistência de união (RU) de cimento resino à dentina radicular e na composição química e estrutura do colágeno de dentes submetidos à radioterapia. 120 caninos superiores foram selecionados e distribuídos em 2 grupos: não irradiados (n=60) e irradiados (30 ciclos de 2Gy, totalizando 60Gy) (n=60). Os dentes foram seccionados, sendo as raízes destinadas à análise da RU e os remanescentes coronários à análise química. 40 fragmentos coronários remanescentes, 20 irradiados e 20 não irradiados, foram seccionados, lixados e polidos para obtenção de blocos de dentina intraradicular (3x3x2mm), distribuídos de acordo com o tratamento da dentina (n=10): CLX 2% e EDC 0,5M. A análise foi realizada em espectroscopia no infravermelho com transformada de Fourier (FTIR) no tempo zero (T0) e após 1(T1), 3(T3) e 5(T5) min de imersão nas soluções para análise das bandas de carbonato (C), amida I (AI) e razão entre as bandas amida III e prolina e hidroxiprolina (AIII/PH). As raízes (16mm) foram instrumentadas com Reciproc (R50) e obturadas com AH Plus. Em seguida, as raízes foram preparadas para pino e redistribuídas de acordo com o tratamento da dentina (n=20): soro fisiológico (SF); CLX 2%; e EDC 0,5M. Após secagem do canal, pinos de fibra de vidro foram cimentados com RelyX U200. Em seguida, obteve-se os slices e, em metade dos espécimes de cada subgrupo (n=10), as análises foram realizadas imediatamente; as demais (n=10) foram armazenadas por 10 meses, para análise da longevidade. O slice mais cervical de cada terço foi submetido ao push-out e padrão de falha (n=10), e o slice mais apical submetido à análise da interface adesiva em microscopia eletrônica de varredura (MEV) (n=5). Os dados de área das bandas e de RU foram submetidos à análise estatística pelos testes de ANOVA e Tukey, já a adaptação da interface adesiva foi submetida aos testes de Kruskal-Wallis e Duns, e o teste qui-quadrado foi utilizado para avaliar o tipo de falha. Não houve diferença estatística para as áreas das bandas de C; para AI houve diferenças entre os tempos experimentais (P<0,0001) independentemente dos fatores radioterapia e tratamento, em que T3 e T5 apresentaram valores maiores que T0 e T1 (P<0,05); já a razão AIII/PH foi reduzida pela radioterapia (P<0,05), sendo que o EDC aumentou os valores de AIII/PH em T1, T3 e T5 em dentes irradiados (P<0,05), sendo esses valores semelhantes aos dentes não irradiados (P>0,05); já para a CLX os valores de AIII/PH foram menores para todos os tempos experimentais tanto em dentes irradiados como não irradiados (P<0,05). Os dentes irradiados apresentaram menores valores de RU (13,8±4,3) comparados aos não irradiados (18,1±3,1)(P<0,001). Para os dentes irradiados, os valores de RU foram menores para o SF e CLX (P<0,001), sendo que o EDC mostrou valores de RU similares aos dentes não irradiados (P=0,215). Para os dentes não irradiados, os valores de RU foram similares para os dentes tratados com SF, CLX e EDC (P>0,05). Ainda, a RU reduziu após 10 meses para o grupo tratado com SF e CLX (P<0,001), sendo que o EDC manteve os valores (P=0,236), de forma que após 10 meses, o EDC apresentou maior RU que a CLX (P<0,001), sendo a CLX superior ao SF (P<0,001). O terço cervical apresentou maior RU quando comparado ao terço médio (P<0,001), que por sua vez foi maior que no terço apical (P<0,001). O padrão de falhas mostrou ocorrência de falhas coesivas na dentina para os espécimes irradiados, e a análise da interface adesiva em MEV mostrou maior desadaptação nos dentes submetidos à radioterapia, além de fraturas e microfraturas na dentina. Em relação aos tratamentos da dentina, observou-se maior adaptação para o EDC. A radioterapia altera a estrutura secundária do colágeno, resultando na redução da RU e maior desadaptação da interface, sendo que o tratamento da dentina com EDC devolveu a integridade do colágeno, se apresentando como melhor alternativa para tratamento da dentina previamente à cimentação de pinos de fibra de vidro em dentes irradiados e não irradiados, uma vez que contribui para a longevidade da interface adesiva / This study evaluated the effect of carbodiimide (EDC) and chlorhexidine (CHX) on the bond strength (BS) of resin cement to root dentin and on the chemical composition and structure of dentin collagen of teeth submitted to radiotherapy. 120 maxillary canines were selected and distributed in 2 groups: non-irradiated (n=60) and irradiated (30 cycles of 2Gy, total 60Gy) (n=60). The teeth were sectioned, and the roots were used for BS analysis while the remaining coronary was subjected to chemical analysis. 40 remaining coronal fragments, 20 non irradiated and 20 irradiated, were sectioned and polished to obtain 40 intraradicular dentin blocks (3x3x2mm), distributed according to the dentin treatment (n=10): CHX and EDC. The analysis was carried out in Fourier Transform Infrared Spectroscopy (FTIR) before treatment (T0) and after 1 (T1), 3 (T3) and 5 (T5) minute immersion in solutions for the analysis of carbonate bands (C), amide I (AI), and ratio between the amide III and proline and hydroxyproline (AIII/PH) bands. The roots (16mm) were instrumented with Reciproc (R50) and filled with AH Plus. The post space was prepared and the samples were redistributed according to dentin treatment (n=20): saline solution (SF); CHX 2%; and EDC 0.5M. After drying the post space, fiberglass posts were cemented with RelyX U200. Then, slices were obtained and, in half of the specimens of each subgroup (n=10) the analyses were performed immediately; the others (n=10) were stored for 10 months before analysis. The most cervical slice of each third was subjected to push-out and failure pattern analysis (n=10), and the most apical slice submitted to the analysis of the adhesive interface in scanning electron microscopy (SEM) (n=5). The band areas and BS data were submitted to statistical analysis by the ANOVA and Tukey tests, the adhesive interface adaptation was submitted to the Kruskal-Wallis and Duns tests, and the chi-square test was used to evaluate the type of failure. There was no statistical difference for the areas of the C bands; for AI, there were differences between the experimental times (P<0.0001) independent of the radiotherapy and treatment factors, in which T3 and T5 presented higher values than T0 and T1 (P<0.05); the AIII/PH ratio was reduced by radiotherapy (P<0.05), and the EDC increased the AIII/PH values in T1, T3 and T5 in irradiated teeth (P<0.05), with similar values in non-irradiated teeth (P>0.05); for CHX, AIII/PH values were lower for all experimental times in both irradiated and non-irradiated (P<0.05) teeth. The irradiated specimens presented lower BS values (13.8±4.3) than non-irradiated specimens (18.1±3.1) (P<0.001). For the irradiated teeth, the BS values were lower for the SF and CHX (P<0.001), while EDC showed similar BS values to the non-irradiated teeth (P=0.215). For non-irradiated teeth, BS values were similar for teeth treated with SF, CHX, and EDC (P>0.05). Also, the BS reduced after 10 months for the group treated with SF and CHX (P<0.001), while EDC maintained the BS values (P=0.236), wherein EDC presented higher BS values than CHX (P<0.001), and CHX presented higher values than SF (P<0.001). The cervical third showed higher BS values when compared to the middle third (P<0.001), which in turn was higher than in the apical third (P<0.001). The failure pattern showed the occurrence of cohesive failures in dentin for the irradiated specimens, and the analysis of the adhesive interface in SEM revealed worse adaptation in teeth submitted to radiotherapy, in addition to fractures and microfractures in dentin. Regarding the dentin treatments, a better adaptation of the adhesive interface was observed with EDC treatment. Radiotherapy alters the secondary structure of collagen, resulting in the reduction of BS values and worse adaptation of the adhesive interface; and the dentin treatment with EDC returned the collagen integrity, and was the best alternative for surface treatment prior to the cementation of glass fiber posts in non-irradiated and irradiated teeth, since it contributed to the longevity of the adhesive interface
162

Mineralização in vitro de matrizes de colágeno aniônico derivadas de tecidos biológicos / In vitro mineralization of anionic collagen matrices

Batista, Thelma Matuura de 07 November 2008 (has links)
A reconstrução de defeitos ósseos é um problema que afeta milhões de pessoas, que a medicina tenta resolver. Uma alternativa para a solução deste problema tem sido o desenvolvimento de biomateriais que atuem no processo de reparação óssea. O colágeno é um polímero de origem natural capaz de promover cicatrização e regeneração óssea e juntamente com a hidroxiapatita são os principais componentes encontrados no tecido ósseo. Vários trabalhos têm sido reportados com matrizes mineralizadas de colágeno tipo I em diferentes formas como em géis, membranas e esponjas, mas a mineralização in vitro de matrizes acelulares obtidas de tecidos biológicos sem a perda da estrutura colagênica não tem sido descrito. Este trabalho teve como objetivo a mineralização in vitro e a caracterização de matrizes de colágeno aniônico obtidas de pele porcina, pericárdio bovino e serosa porcina. Os tecidos foram tratados em temperatura ambiente com solução alcalina por períodos variáveis de 0 à 96h e mineralizados pelo processo de imersão alternada. Os materiais obtidos foram caracterizados pela avaliação preliminar da citotoxicidade in vitro, termogravimetria (TG/DTG), calorimetria exploratória diferencial (DSC), microscopia eletrônica de varredura (MEV), dispersão de raios X (EDS), difração de raios X (DRX) e absorção no infravermelho (FT-IR). Não foi observada citotoxicidade em nenhuma das matrizes avaliadas, contudo foi necessário um pré-tratamento nas matrizes de pele porcina para remoção de gordura. Os resultados de DSC mostraram a integridade da matriz colagênica após o tratamento alcalino. O aumento no tempo desse tratamento diminui a temperatura de desnaturação sendo observado um efeito maior nas matrizes de pele porcina seguidas por pericárdio bovino e serosa porcina. A mineralização induz a um aumento na temperatura de desnaturação em todos os casos. As curvas TG apresentaram perdas de massa relacionadas à água presente no material, decomposição da proteína e carbonização do material orgânico e um resíduo após 750 °C que foi associado ao material inorgânico presente na forma de hidroxiapatita, sendo as matrizes de serosa porcina as de maior teor de mineralização. As matrizes mineralizadas tendem a um aumento na estabilidade térmica do colágeno quando comparadas com as matrizes hidrolisadas. Os espectros FT-IR mostraram a presença de íons fosfatos e a interação de íons cálcio com o colágeno. As relações Ca/P obtidas por EDS foram aquelas esperadas em comparação com o valor teórico para hidroxiapatita (HA) e resultados de DRX confirmaram a obtenção de HA amorfa como principal produto de mineralização. Pelas fotomicrografias obtidas por MEV pôde-se observar que as fibras de colágeno tornam-se mais desestruturadas quando há um aumento no tempo de hidrolise e que a deposição de sais ocorreu de forma heterogênea, disposta em aglomerados esféricos no formato de agulhas por toda a superfície e interior, exceto para matrizes derivadas de pele porcina que não são mineralizadas internamente devido a sua espessura. Os resultados obtidos demonstraram que é possível a mineralização in vitro de matrizes de colágeno tipo I obtidas de diferentes tecidos biológicos em diferentes tempos de hidrólise, produzindo um material com potencial de uso para regeneração óssea. / The reconstruction of osseous defects is still a problem that affects millions of people and medicine tries to solve it. One alternative to solve these problems has been the development of biomaterials that can be used as inductors in the osseous repair process. Collagen is a natural polymer able to promote healing and bone regeneration, and among hydroxyapatite (HA) is the main component found in bone tissue. Several mineralized collagen scaffolds are described in literature, in the form of gel, membranes and films, however, in vitro mineralization of acellular matrices, obtained from biological tissues without the loss of collagenic structure, has not been reported. The objective of this work was the mineralization and characterization of anionic collagen matrices obtained from porcine skin, bovine pericardium and porcine serosa. Biological tissues were treated at room temperature for 0-96h in alkaline solution and mineralized by alternate soaking method. Materials were characterized by preliminary assay of in vitro cytotoxicity, differential scanning calorimetry (DSC), termogravimetric analysis (TG/DTG), scanning electronic microscopy (SEM), energy dispersive x-ray analysis (EDS), x-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). No cytotoxicity was observed in any of the evaluated matrices; however, a pre-treatment of porcine skin matrices, for fat removal, was necessary. DSC results showed the integrity of collagen matrices after alkaline treatment. Denaturation temperature is dependent of time of alkaline treatment, and this effect is greater for porcine skin matrix, followed by bovine pericardium and porcine serosa. TG/DTG curves showed weight losses associated with release of water, degradation of protein structure and combustion of residual organic components. Residues were obtained at 750°C and associated to hydroxyapatite, being porcine serosa matrix the most mineralized. All mineralized matrices showed an increase in collagen thermal stability when compared to hydrolyzed matrices. FTIR spectra showed the presence of phosphate ions and the interaction of calcium ions with collagen. Ca/P ratios obtained by EDS were as expected when compared with literature values for HA, and RDX results confirmed amorphous HA as the main mineralization product. MEV analysis showed that collagen fibers were more affected for longer hydrolysis times, and that salt deposition was heterogeneous, with crystals grouped in spherical agglomerates in a needle-like shape throughout surface and inner, except for porcine skin derived matrices that were not internally mineralized due their width. Obtained results demonstrated that in vitro mineralization of type I collagen matrices, using different sources of biological tissues and hydrolysis time was possible, producing a material with potential to be used in bone regeneration.
163

Caracterização térmica e reológica de blendas de glicerol:colágeno tipo I de diferentes tecidos / Thermal and rheological characterization of glycerol: type I collagen blends

Egawa, Edgar Yuji 20 September 2007 (has links)
O colágeno possui características que fazem com seja amplamente utilizado como biomaterial. A termo-estabilidade do colágeno está diretamente relacionada a mudanças na sua estrutura (hélice tripla) via de regra quanto mais estável termicamente uma matriz, mais estável biologicamente será. Vários poliálcoois incluindo o glicerol têm apresentado um aumento na estabilidade térmica do colágeno tipo I, embora o tipo de interação não seja evidente. Este trabalho tem como objetivo estudar o efeito da adição de glicerol sobre o colágeno aniônico obtido por tratamento alcalino (24 H) em três diferentes tecidos: pericárdio e tendão bovinos e serosa porcina. Para isto são utilizados a espectroscopia na região do infravermelho (FTIR), termogravimetria e reologia. Os espectros mostraram que o tratamento alcalino e a adição de glicerol não causam desnaturação da proteína de colágeno. A partir dos resultados das curvas termogravimétricas foi observado que o glicerol aumenta a temperatura de decomposição térmica do colágeno. Os resultados dos ensaios de reologia mais precisamente a varredura de deformação mostrou que as soluções de colágeno apresentam G\' maior que G\'\' independente do tecido de origem, e a adição de glicerol não causa mudanças nesta propriedade das soluções. A varredura de freqüência mostrou que as amostras têm características de um gel, sendo G\' maior que G\'\' nas condições de estudo. O ensaio de escoamento a temperatura constante determinou o comportamento pseudoplástico das soluções, e a adição de glicerol causou aumento na viscosidade das soluções sem alterar tal característica. Os ensaios de escoamento com variação de temperatura permitiram determinar a temperatura de desnaturação do colágeno. A adição de glicerol aumentou apenas a temperatura de desnaturação do colágeno obtido por serosa porcina, sugerindo que esta solução é a mais sensível à adição de glicerol. / Several characteristics make collagen widely applied as a biomaterial. The collagen thermal stability is directly related with its structure changes (triple helix), generally, the better is the thermal stability the better is the biological stability. Several polyols including glycerol, has shown a increasing on type I collagen denaturation. The objective of this work is to study the effect of glycerol when mixed with anionic collagen. Type I anionic collagen was obtained after alkaline treatment (24h) of bovine pericardium, bovine tendon and porcine serosa. FT-IR, thermogravimetry and rheology were used. The results of thermal analysis showed that glycerol indeed increases the collagen decomposition temperature. The reologycal tests, precisely strain sweep, revealed that collagen samples have modulus G\' prevailed on modulus G\'\' independent of tissue origin, and glycerol addiction did not change these. The frequency sweep revealed that collagen and collagen:glycerol samples behave like a gel-like substance since both the storage and loss modulus showed dependence with frequency sweep and G\' > G\'\' in all cases. Flow tests at constant temperature revealed that collagen solution behave like a pseudoplastic substance, and glycerol addiction increase solution viscosity and did not change the pseudoplastic characteristic. Flow tests in function of temperature revealed collagen denaturation temperature, but glycerol addiction alters thermal stability (increase of denaturation temperature) only for collagen obtained from porcine serosa.
164

Development of Recombinant Human Collagen Type I and Type III Injectable Hydrogels for Cardiac Therapy

Podrebarac, James January 2017 (has links)
Functional biomaterials are being developed as scaffolds to support endogenous cells and to promote the regeneration of ischemic tissue. The aim for this study was to develop a new translational platform for injectable hydrogels using recombinant human collagen (rHC) of two types: type I (TI) and type III (TIII). The collagen solutions were characterized to ensure batch-to-batch consistency and protein integrity. The hydrogel preparation protocol was extensively monitored to ensure ease of use and high-quality production. Post-gelation, rHC TIII have a higher viscosity compared to rHC TI, yet water content was high for both hydrogels. The cross-linking degree is similar for both rHC hydrogels, which are stable well above physiological temperatures, but rHC TI is more susceptible to enzymatic degradation than rHC TIII. Furthermore, the micro-architecture differed with pore size dimensions of rHC TIII being significantly larger than that of rHC TI. Cardiac fibroblasts were cultured on the rHC hydrogels, and cells attached readily to the scaffold environment, which promoted proliferation. The rHC matrices mechanical and biological properties provide structural support, and demonstrate biodegradability and biocompatibility. The intrinsic physical differences between the rHC hydrogels will likely have implications in future studies. In conclusion, the rHC TI and TIII hydrogels are proven to be suitable matrices for continued investigation towards future translational applications.
165

Mineralização in vitro de matrizes colagênicas derivadas de tendões calcâneos bovinos e de avestruz / In vitro mineralization of anionic collagen scaffolds prepared from bovine and ostrich calcaneous tendons

Kirschbauer, Klaus Giovanelli 26 November 2009 (has links)
Um dos maiores desafios da ortopedia moderna é recuperar o tecido ósseo que tenha sido perdido por motivo de doença ou acidente. Na busca de substitutos para os enxertos, tem-se utilizado comumente biomateriais para recuperação desse tecido. Um dos vários tipos de biomateriais usados são os preparados à base de colágeno. Além de desempenhar papel importante na estrutura dos tecidos, o colágeno é capaz de orientar a formação de tecidos em desenvolvimento fato altamente favorável na sua utilização como biomaterial. Uma nova vertente de pesquisa do processo de mineralização de matrizes colagênicas que vem sendo desenvolvida é a analise de como a organização do tecido interfere no modo como ocorre esse processo de deposição. O uso do tendão vem sido pesquisado devido ao fato de ser um tecido extremamente organizado, com as fibras colagênicas alinhadas por toda a sua extensão. Este trabalho teve como objetivo a preparação e caracterização de matrizes de colágeno tipo I, oriundas de tendão bovino (TB) e avestruz (TA) após a hidrólise alcalina e mineralização. Os tendões foram colocados em solução alcalina contendo sais de K+, Na+ e Ca2+ por 72, 96 e 120 h a 25&deg;C e depois equilibrados em solução de sais, lavados em H3BO3, EDTA e água. As matrizes resultantes foram então mineralizadas em soluções de CaCl2 0,2 mol L-1, pH = 7,4 e de Na2HPO4 0,12 mol L-1 pH = 9,0 durante 6 h, ocorrendo a troca de soluções a cada 30 min. As matrizes antes e após mineralização foram congeladas, liofilizadas e submetidas à análise termogravimétrica (TG), calorimetria exploratória diferencial (DSC), microscopia eletrônica de varredura (MEV), espectroscopia no infra-vermelho (FT-IR) e dispersão de energia por raios-X (EDX). DSC mostrou que não houve desnaturação do colágeno durante o processo de tratamento alcalino e mineralização. A análise termogravimétrica mostrou que houve deposição de fosfato de cálcio, com o valor dependendo do número de ciclos de mineralização. MEV mostrou que essa mineralização não é uniforme, ocorrendo a formação de aglomerados. FT-IR e EDX mostrou que o fosfato de cálcio depositado provavelmente seja hidroxiapatita, mas não em sua estrutura estequiométrica. / One of greatest challenges of modern orthopedics is to restore bone tissue that has been lost due to sickness or accident. Searching for substitutes for grafts, biomaterials have been commonly used for recovery of bone tissue. Between different types of biomaterials, several are based on collagen. In addition to have important role in tissue structure, collagen is able to guide the formation of tissues, a highly favorable fact in its use as biomaterial. A possible research in collagen scaffolds mineralization is the analysis of how tissue organization interferes in deposition process. The tendon has been used because it is a highly organized tissue, with collagen fibers lined on its structure. This research aims the preparation and characterization of type I collagen scaffolds, prepared from bovine tendon (TB) and ostrich tendon (TA) after alkaline hydrolysis and mineralization. Tendons were maintained in alkaline solution containing K+, Na+ and Ca2+ ions for 72, 96 and 120 hours at 25&deg;C and then equilibrated in salt solution, washed with H3BO3, EDTA and water. The resulting matrices were then mineralized in 0.2 mol L-1, pH = 7.4 CaCl2 solution and 0.12 mol L-1 Na2HPO4 pH = 9.0 for 6 h, changing solutions after 30 minutes. The matrices before and after mineralization were frozen, lyophilized and subjected to thermogravimetric analysis (TG), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) and energy dispersive X-ray spectroscopy (EDS). DSC showed that the collagen was not denaturated by alkaline treatment process and mineralization. TG analysis showed deposition of calcium phosphate on the scaffolds, with values depending on the number of mineralization cycles. SEM showed that the mineralization is not uniform, forming clusters of phosphate crystals. FT-IR and EDS showed that the deposited calcium phosphate is probably hydroxyapatite, but not in its stoichiometric structure.
166

Estudo comparativo de colágeno hidrolisado e comercial com adição de PVA / Comparative study of commercial and anionic collagen blended with PVA

Pedroso, Maitê Golinelli Vanella 23 October 2009 (has links)
O desenvolvimento de novos materiais tem sido baseado na mistura de dois ou mais polímeros ou biopolímeros, onde soluções destes são misturadas em diferentes proporções na tentativa de se obter materiais com propriedades distintas das de seus precursores. Neste trabalho foram analisadas blendas colágeno:PVA. O colágeno utilizado foi o tipo I, porem proveniente de duas formas diferentes, o colágeno comercial que foi cedido pela Novaprom Food Ingredients Ltda e o colágeno obtido a partir de tendão bovino por meio de hidrólise alcalina em diferentes tempos (24h e 96h). As blendas e os colágenos foram caracterizados por análise térmica (DTG e DSC), microscopia eletrônica de varredura (MEV), espectroscopia de absorção no infravermelho (FT-IR) e analises reológicas. As curvas DSC mostraram que o colágeno comercial é o de maior temperatura de desnaturação e que a adição de PVA não altera essa temperatura. Já as curvas TG mostraram que o PVA, seja qual for sua massa molecular, aumenta a estabilidade térmica do colágeno. A microscopia eletrônica mostrou que os colágenos com tratamento alcalino apresentam uma estrutura fibrilar e pouco desorganizada, enquanto o colágeno comercial apresenta uma estrutura uma pouco mais compacta. Através do FT-IR foi possível observar que a presença de PVA nas blendas não influencia na presença dos picos, sugerindo que não há interação química entre os mesmos. A análise reológica permitiu comparar os módulos elástico (G\') e viscoso (G\") dos géis em diferentes proporções, tendo todos eles valores de G\' maior do que G\", ou seja, podemos concluir que os materiais são mais elásticos do que viscosos. Observa-se também a influência na viscosidade dos géis com a adição de PVA ao mesmo, sendo a viscosidade maior com o aumento da massa de PVA adicionado. / The development of new materials has been based on the mix of two or more polymers or biopolymers where solutions are mixed in different portions trying to get materials with distinct properties from their precursors. In this work different collagen solutions and collagen-PVA blends were analyzed. The used collagen was the type I, however obtained from two different forms, the commercial collagen that was provided by Novaprom Food Ingredients Ltda and the collagen obtained from bovine tendon by alkaline hydrolysis in different times (24h and 96h). The blends and collagen were characterized by thermal analysis (DTG and DSC), electronic scan microscopy (ESM), infrared absorption spectroscopy (FT-IR) and rheological analysis. DSC curves showed that the commercial collagen has the highest denaturing temperature and that the addition of PVA does not change this temperature. In other hand, TG curves showed that PVA, in any given molecular weight, increases collagen thermal stability. Electronic microscopy shows that collagen with alkali treatment have a fibrillar and little disorganized structure, insofar, the commercial collagen have a little more compact structure. By FT-IR it was to possible observe that the presence of PVA on blends have no influence on the peaks, suggesting that there is no chemical interaction between then. Rheological analysis allow to compare the elastic module (G\') and the viscous module (G\'\') from blends in different proportions. All the obtained values for G\' are higher than G\'\', so it can be conclude that samples are more elastic than viscous.
167

Collagen solubility of A-maturity bovine Longissimus muscle as affected by nutritional regimen

Hall, James Brian January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
168

The development of collagen-fibrinogen scaffolds to replicate the hematopoietic microenvironment

Inns, Edward James Scott January 2015 (has links)
No description available.
169

Stimulation of intracellular proteolytic degradation as a means of reducing ER stress in a model of skeletal dysplasia

Mullan, Lorna A. January 2015 (has links)
MCDS is an autosomal dominant skeletal dysplasia disorder caused by mutations in collagen X. In most cases, mutations in collagen X result in a misfolded protein which is retained within the ER of hypertrophic chondrocytes, causing increased ER stress. It has previously been demonstrated that increased ER stress causes hypertrophic chondrocytes to de-differentiate in an attempt to avoid the stress. The altered differentiation results in reduced cell hypertrophy and impaired vascular invasion accounting for reduced bone growth. The presence of increased ER stress in hypertrophic chondrocytes is sufficient to cause the MCDS pathology; therefore reducing ER stress may be beneficial in terms of improving the associated pathology. The autophagy enhancing drug carbamazepine (CBZ) has been shown to be capable of reducing ER stress in cells expressing the MCDS-causing p.N617K collagen X mutation. I show in this thesis that CBZ treatment reduced ER stress in HeLa cells transiently expressing a further 3 MCDS-causing collagen X mutations. I have also demonstrated that CBZ treatment induced the degradation of mutant collagen X proteins either through autophagy or proteasomal degradation depending on the nature of the mutation. The drug was tested in vivo using the p.N617K collagen X mouse model of MCDS. In MCDS mice, CBZ reduced the severity of the disease pathology based on histological analyses, restored hypertrophic chondrocyte differentiation toward normal, increased long bone growth rates and decreased the severity of the hip dysplasia. Gene expression analyses on RNA isolated from microdissected hypertrophic chondrocytes revealed that CBZ shifted the pattern of hypertrophic differentiation markers in MCDS mice toward the wild-type pattern, most likely through its stimulation of gene expression associated with intracellular proteolytic pathways. The results presented in this thesis have contributed to the identification of a potential treatment strategy for MCDS- the stimulation of intracellular proteolysis of mutant collagen X. CBZ is FDA approved for the use of epilepsy and bipolar disorder and has a strong safety record in humans. Therefore CBZ could be a potential treatment strategy for MCDS.
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Compressive Mechanical Properties and Collagen Fiber Orientation and Dispersion in the Cervix of Non-Pregnant and Pregnant Women

Yao, Wang January 2017 (has links)
The cervix serves as the passage for the fetus during birth. The mechanical function of the cervix is crucial for a healthy term pregnancy: 1) prior to term it must remain closed and resist the increasing mechanical load from the growing pregnancy and 2) at time of parturition it must soften, deform and dilate to allow for delivery of the fetus. After delivery, the cervix must repair and close. The timing and characteristics of this remodeling behavior is currently an active research focus because it is hypothesized that premature remodeling in pregnancy can lead to preterm birth, a leading cause of neonatal death or significant neonatal morbidity. The research goal was to measure and characterize anisotropic material properties because they contribute to keeping cervix shut. In this thesis, the collagen fiber network orientation and dispersion of non-pregnant and pregnant human cervical tissue samples were analyzed using optical coherence tomography, and the samples were tested using mechanical indentation and digital image correlation techniques. Human cervices were acquired from non-pregnant and pregnant consented patients that went through hysterectomy. Axial cervical slices were imaged using optical coherence tomography and fiber orientation and dispersion data was analyzed using a new pixel-wise fiber orientation algorithm and was compared among four anatomical quadrants and among patients with different obstetric backgrounds. Two radial zones with different fiber orientations were found. The posterior and anterior quadrants of the outer zone were found to have distinct fiber dispersion features and their fiber dispersion shifted most dramatically from non-pregnant to pregnant. In an effort to characterize the compressive mechanical behavior of human cervical tissue, we present a novel indentation test with digital correlation imaging to visualize the real-time deformation of cervical slice during indentation and measure the compressive mechanical properties through coupled finite element analysis with collagen fiber orientation and dispersion information informed by OCT of non-pregnant and term pregnant cervical tissue. Heterogeneity within the same cervix and difference between non-pregnant and pregnant cervices were found. The upper cervix was found to have a stronger ground substance. The anterior and posterior quadrants were less compressible than the left and right quadrants for non-pregnant specimens. The upper cervix of non-pregnant patients had a stronger ground substance than that of pregnant patients. A workflow of optical, mechanical, and chemical experiments on the same piece of specimen with most fibers intact was also proposed in this thesis and these experiments would validate and inform each other.

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