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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.
341

Ação da polaridade na estimulação elétrica transcutânea para o tratamento de áreas doadoras de enxertos autógenos em pacientes queimados: estudo clínico randomizado cego / Effect of polarity on transcutaneous electrical stimulation for the treatment of autogenous graft donor sites in burn patients: randomized blinded clinical study

Camila Silva de Carvalho 30 August 2017 (has links)
O cuidado com as áreas doadoras de enxertos de pele merece constante atenção, visto que desencadeia desconforto por dor e restrição de movimentos. Existem evidências de que a estimulação elétrica pode acelerar a cicatrização de feridas e produzir analgesia, e que diferentes parâmetros físicos podem interferir nas respostas apresentadas. O objetivo do estudo foi avaliar o efeito da polaridade da corrente na cicatrização e na dor. Para tanto foram comparados os efeitos da estimulação elétrica de alta voltagem (EAV), polarizada, e a estimulação elétrica nervosa transcutânea (ENT), despolarizada, no tratamento das áreas doadoras de pacientes queimados. Para tanto, foram avaliados 48 voluntários do sexo masculino randomizados em três grupos: submetidos à estimulação elétrica de alta voltagem (GEAV), média idade de 34,2(±9,8) anos, n=17; submetidos à estimulação elétrica nervosa transcutânea (GENT), com 34(±9,5) anos, n= 16; e não submetido à estimulação elétrica ou grupo controle (GC) média de idade 35(±9,5 anos), n= 15. Os procedimentos terapêuticos foram aplicados nas extremidades da área doadora, no primeiro pós-operatório, até a epitelização completa. As variáveis avaliadas foram avaliação clínica, o tempo (dias) de epitelização, estimado pelo desprendimento do curativo primário sobre a lesão, avaliação da dor pela escala numérica de dor, a temperatura cutânea pela termografia infravermelha, qualidade da cicatriz (book de fotos, escala ® Vancouver, software Image J ). Após a análise dos dados, foi aplicado o teste de Shapiro-Wilk, em seguida o comportamento pré e pós-intervenção intragrupo foi aplicado o teste Wilcoxon. Para comparação entre os grupos foi efetuado teste de Kruskal-Wallis seguido de post-hoc de Dunn, em todos os casos foi utilizado o nível de significância de 5% (p<0,05). Os achados apontam que o tempo de desprendimento do curativo Rayon das áreas doadoras foi significativamente menor para GEAV apresentando (p<0,033). Houve redução significativa da dor (p<0,05) para o GEAV e para o GENT, quando comparado ao GC. A quantidade relacionada a solicitação de analgésicos foi reduzida para os grupos estimulados, com diferença significativa do GEAV versus GC (p<0,002) e GENT versus GC (p<0,001). Não houve diferença significativa na temperatura cutânea entre os grupos. Não houve diferença significativa no escore final da escala Vancouver e nem quantidade de crostas entre os grupos. A polaridade da corrente pode ter influenciado no tempo de epitelização, porém não interferiu na dor e na qualidade da área doadora. / The cares with donor areas of skin grafts deserve constant attention, since it triggers discomfort due to pain and movement restriction. There are evidences that electric stimulation may accelerate wound healing and produce pain relief. The objective of this study was to evaluate the effect of electric current polarity on the healing and pain. Therefore, the effects of stimulation on high voltage pulsed current (HVPC) and nervous transcutaneous stimulation (TENS) were compared in the treatment of donor areas of burns victims. Therefore, 48 volunteers of the male sex were randomized between three groups: submitted to high voltage pulsed current stimulation (GHVPC), with 34.2 (± 9.8) years, n=17; submitted to nervous transcutaneous stimulation (GTENS), with 34 (±9.5) years, n=16; and nonsubmitted to stimulation group, or control group (GC), average age of 35 (± 9,5) years, n=15. The therapeutic procedures were applied on the edges of the donor area, at the first postoperative, until complete healing. The evaluated variables were ephitelization time (days), estimated by the unfastening of the primary curative on the wound, evaluation of pain by numerical scale of pain, skin temperature by infrared thermography, scar quality (photo book, Vancouver scale and Image J® software). After data analysis, the Shapiro-Wilk test was applied, and the Wilcoxon test was applied to the before and after intervention. Kruskal-Wallis test followed by Dunn post-hoc was used to compare the groups. In all cases, the significance level of 5% (p<0.05) was used. The findings indicate that the time of release of the Rayon dressing from the donor sites was significantly reduced for GEAV (p <0.033). A reduction of pain relief was significant (p<0.05) for the GEAV and for the GENT, when compared to the GC. Amount the number of solitation for analgesic drugs was decreased for the groups stimulated with significant difference of the GEAV verse GC (p<0.002) and GENT verse GC (p <0.001). Change in cutaneous temperature was not significant between groups. There was no difference significant in score of Vancouver scale and in the number of crusts in the groups. The polarity of the current might have influenced the healing time, however not the pain nor the quality of the donor site.
342

Vigilância de infecção de sítio cirúrgico em pacientes egressas no ambulatório de ginecologia de um hospital de ensino / Surgical site infection surveillance in discharged gynecological patients into teaching hospital ambulatory

Madeira, Maria Zélia de Araújo, 1965- 25 August 2018 (has links)
Orientador: Plínio Trabasso / Texto em português e inglês / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-25T16:43:11Z (GMT). No. of bitstreams: 1 Madeira_MariaZeliadeAraujo_M.pdf: 1405070 bytes, checksum: 92d0a92bffeb8403785ffcb448a2afbb (MD5) Previous issue date: 2014 / Resumo: INTRODUÇÃO: As Infecções do Sítio Cirúrgico (ISC), compreendendo de 14% a 16% das encontradas em pacientes hospitalizados, são classificadas em incisional superficial, incisional profunda ou de órgão/cavidade. Entre 12% e 84% dessas infecções são detectadas depois que o paciente deixa o hospital, daí a importância da realização da vigilância pós-alta hospitalar. OBJETIVOS: Implementar um serviço de vigilância pós-alta de ISC em mulheres que realizaram cirurgia ginecológica em um Hospital de Ensino em Teresina-PI; monitorizar a ocorrência de ISC e sua associação com fatores de risco; caracterizar o perfil sociodemográfico desse contingente; determinar a taxa de incidência de ISC no ambulatório de ginecologia por meio da vigilância; e identificar o perfil das ISC diagnosticadas após a alta hospitalar. MÉTODO: Estudo quantitativo e prospectivo, realizado no ambulatório de ginecologia do Hospital Getúlio Vargas, o qual é de ensino público, geral, de grande porte e de referência em saúde para o Estado do Piauí e demais regiões do Norte e Nordeste do Brasil. A população foi de 1.026 mulheres egressas do hospital de ensino, que realizaram cirurgia ginecológica, no período de junho de 2011 a março de 2013. O projeto foi aprovado pelo Comitê de Ética e Pesquisa da UFPI, sob o CAAE: 0059. 045. 000.11. RESULTADOS: Utilizou-se a vigilância epidemiológica às ISC do tipo busca ativa, por 30 dias, no ambulatório de ginecologia, por meio de contato presencial e telefônico. A taxa de retorno das mulheres para o ambulatório foi de 86,6% e a incidência de ISC foi de 5,8%, destas, 71,7% foram classificadas como incisional superficial e 28,3% como incisional profunda. O tempo médio entre a cirurgia e o diagnóstico de ISC foi de 12,9 dias; a maior incidência se encontra na faixa etária de 25 a 44 anos (44,3%) de idade; procediam da capital 57,8% e, do interior do Estado, 42,2%; 63% são casadas, 61% tinham até o ensino fundamental; economicamente, 46,4% declararam renda familiar de 1 (um) salário mínimo. Os fatores de risco para o desenvolvimento de ISC foram: Tempo PO (dias), Neoplasia e Diabetes mellitus. CONCLUSÃO: Evidenciou-se o incremento da notificação de incidência de ISC, o que aponta para a importância do acompanhamento das mulheres sob vigilância pós-alta, utilizando uma estratégia sistematizada. Palavras chaves: Vigilância epidemiológica, Procedimentos Cirúrgicos em Ginecologia, Infecção de ferida operatória / Abstract: INTRODUCTION: The Surgical Site Infection (SSI) understanding 14% to 16% of those found in intern patients, and be assorted in superficial incisional SSI, deep incisional SSI, or organ or space SSI. Between 12% and 84% those infections are detected after the patient leaves hospital, hence the importance of post-discharge surveillance. OBJECTIVES: The post-discharge surveillance woman service implementation who underwent gynecological surgery in school hospital in Teresina - PI; monitor the occurrence of ISC and association with risk factors; characterizing the socio-demographic profile; appoint incidence rate (SSI) in gynecological ambulatory for surveillance method, and identify the profile of SSI misdiagnosed after discharge. METHODS: Prospective and quantitative study, accomplished in gynecological ambulatory in Getulio Vargas Hospital, which is for public education, and a large general hospital, and the health reference for the state of Piauí and further the North and Northeast regions of Brazil. The population was 1026 patient women which has undergone gynecological surgery in period from june 2011 to march 2013. The project was approved for the UFPI Research Ethics Committee, under the CAAE: 0059 045 000.11. RESULTS: It was used SSI epidemiologic surveillance, type active report for 30 days in gynecological ambulatory, by face or telephonic contact. Return rate of women to gynecological ambulatory was 86,6% and SSI incidence was 5,8%, those 71,1% was classed in superficial incisional and 28,3% deep incisional. The average time betwixt surgery and SSI diagnosis was 12,9 days; the highest incidence is in the age group 25-44 years (44.3%); came from the city (57,8%) e countryside of the State (42,2%), 63% married women, had basic education 61%, 46,4% declare having minimum wage. The risk factors to SSI development was: OP Time (days), neoplasm and Diabetes mellitus. CONCLUSION: Highlighted the increased incidence of SSI notification, pointing to the importance of accompanying the women in post-discharge surveillance, using a systematic strategy. Key words: Epidemiological surveillance, Gynecologic Surgical Procedures, Surgical wound infection / Mestrado / Ciencias Biomedicas / Doutora em Ciências Médicas
343

Avaliação da ação do uso tópico de heparina encapsulada em nanopartículas poliméricas recobertas com quitosana em modelo de úlcera de pele em ratos / Evaluation of the action of topical use of encapsulated heparin in polymeric nanoparticles recovered by chitosan in rat skin ulcer model

Huber, Stephany Cares, 1988- 22 August 2018 (has links)
Orientador: Joyce Maria Anicchino-Bizzacchi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-22T13:12:37Z (GMT). No. of bitstreams: 1 Huber_StephanyCares_M.pdf: 5877456 bytes, checksum: 79a59ae5e01aa03f9d5a57ca56e58df7 (MD5) Previous issue date: 2013 / Resumo poderá ser visualizado no texto completo da tese digital / Abstract is available with the full electronic document / Mestrado / Clinica Medica / Mestra em Clínica Médica
344

Development of antibiotic loaded liposomal hydrocolloid dressings for application in wound healing

Ntsalu, Vuyiseka January 2017 (has links)
Wound healing, as a normal biological process in the human body, is achieved through four precise and highly programmed phases: hemostasis, inflammation, proliferation, and remodeling. For a wound to heal successfully, all four phases must occur in the proper sequence and time frame. However, many factors can interfere with one or more of these phases, thus causing improper or impaired wound healing. Maintaining a moist wound environment is crucial in facilitating the wound-healing process. The beneficial effects of a moist versus a dry wound environment include re-epithelization, tissue granulation, and repair. The use of hydrocolloid occlusive dressings in maintaining a moist wound environment has proven to be a useful adjunct in facilitating wound healing. Although hydrocolloid dressings have been widely used clinically in wound management, bacterial resistance, poor solubility and sustained drug release remain to be a problem for many of the drugs used in wound therapy. In chronic wound management, where patients normally undergo long treatments and frequent dressing changes, a system that delivers drugs into a wound site in a controlled fashion can improve patient compliance and therapeutic outcomes. Liposomes are small phospholipid vesicles that have been widely investigated as drug carriers for the delivery of therapeutic agents. They are spherical lipid vesicles consisting of phospholipid bilayers that improve the efficacy of the drugs by fusing with biological membranes, and eventually releasing their entrapped content into the cells or bacteria. The aim of this study therefore, is to develop a new bacitracin-based controlled release hydrocolloid dressing, with good absorptive properties for improving the efficacy of antibiotics in wound healing. HPLC (high-pressure liquid chromatography) assay of bacitracin was performed for quantification of the drug. Liposomes were prepared using thin film hydration and extrusion methods. Liposomes were also characterized based on their ideal particle size and encapsulation efficiency, and then incorporated into the different ratios of chitosan/gelatin hydrocolloid films. The films were prepared with increase in gelatin concentration and were evaluated for folding endurance, tensile strength, water absorption capacity, morphology, drug release kinetics, antimicrobial activity and stability. The morphology of these films was found to be very smooth and homogeneous proving a good compatibility between the two polymers. With increase in gelatin concentration, folding endurance, water absorption capacity, tensile strength, drug release kinetics and antimicrobial activity were increased. The antibacterial activity against various bacterial species was improved in the bacitracin loaded hydrocolloid films as compared to the blank films. Based on the findings above, it can be concluded that chitosan/gelatin films at 1:3 proportion is a successful wound dressing for wound management with improved wound healing properties than other formulations. This formulation is a potential candidate for the development of alternative pharmaceutical dosage forms, for the treatment of bacterial infected wounds, based on the activity of the eco-friendly chitosan matrix added to the bacitracin activity. In this work, chitosan also demonstrated a great potential as a dressing for advanced wound therapy and confirmed its good biocompatibility and potential to provide, in combination with liposomes, sustained drug release which is highly beneficial for wound treatment. The addition of gelatin improved the water affinity of the films and facilitated water mediated cross-linking process.
345

Caractérisation et modélisation de l'endommagement des composites bobinés. Application à la prédiction de l'éclatement des réservoirs bobinés hyperbares / Wound composites damage modelling and characterization. Application to burst prediction of hyperbaric wound composite pressure vessels

Berro Ramírez, Juan Pedro 28 November 2013 (has links)
Un modèle d’endommagement dédié aux composites bobinés est développé à partir des outils de lamécanique de l’endommagement continu, de la thermodynamique des processus irréversibles et dela théorie de représentation des fonctions tensorielles. La particularité de ce modèle est l’utilisationd’une approche à directions fixes de l’endommagement qui associe à chaque mode de dégradationdes variables internes scalaires et des tenseurs directionnels. La rupture des fibres (considéréecomme probabiliste), les fissurations tant matricielles, que hors – plan ou provoquées par lecisaillement sont ainsi prises en compte. Le modèle est capable de reproduire, dans un contextetridimensionnel imposé par les fortes épaisseurs de composite, la perte de rigidité, l’interaction entreanisotropies initiale et induite, la non linéarité du comportement, les déformations résiduelles et laviscosité en cisaillement. Afin de valider cette approche, le comportement thermomécaniqued’éprouvettes issues de structures bobinées a été caractérisé grâce à des essais de traction multi –instrumentés (vidéo – traction, émission acoustique,...). On montre que le modèle est capable nonseulement de simuler la réponse mécanique macroscopique de ces échantillons, mais également dereproduire l’émission acoustique enregistrée, de distinguer les différentes formesd’endommagement et de prédire précisément l’éclatement des réservoirs hyperbares. / A damage model dedicated to wound composite is developed by using the tools of continuousdamage mechanics, irreversible processes thermodynamics and the representation theory of tensorfunctions. The particularity of this model is the use of a fixed directions approach of damage whichassociates each degradation mode to internal scalar variables and directional tensors. Fiber breakage(considered probabilistic), matrix cracking (transverse, out-of-plane or caused by shear) are thustaken into account. The model is able to reproduce, in a three-dimensional context imposed bythick composite layers, loss of strength, interaction between initial and induced anisotropy, nonlinearitybehavior, residual strain and shear viscosity. To validate this approach, thermo mechanicalbehavior of specimens from the wound structures was characterized by tensile multi - instrumentedtests (video - traction, acoustic emission, ...). We show that the model is able to simulate not onlythe macroscopic mechanical response of these samples, but also to reproduce the recorded acousticemission to distinguish the various forms of damage and to accurately predict the burst ofhyperbaric tanks.
346

Wound healing in a suction blister model:an experimental study with special reference to healing in patients with diabetes and patients with obstructive jaundice

Koivukangas, V. (Vesa) 23 November 2004 (has links)
Abstract The expression intensities of cytokeratins and tight junction proteins were determined on re-epithelization. Experimental blister wound healing was studied in patients with diabetes mellitus and in patients with obstructive jaundice. Suction blisters were induced on healthy volunteers, and the healing blisters were biopsied at different time points. Cytokeratin expression and the tight junction proteins ZO-1 and occludin were studied immunohistochemically. Blisters were induced on 17 patients with diabetes and 11 control subjects, and the healing process was followed indirectly by measuring water evaporation and blood flow in the wounds. Microvascular reactivity in the diabetic patients was also studied by using non-immunologic contact irritants. Wound healing, skin collagen synthesis and serum levels of procollagen propeptides were studied in 24 patients with obstructive jaundice caused by neoplastic pancreaticobiliary obstruction and in 17 control patients with the corresponding condition without jaundice. Cytokeratin expression was altered in healing epidermis. In the suprabasal layer, K10 was replaced by K14 and, most likely, by K16. K18 keratin, which is not present in normal epidermis, was found in the basal and suprabasal layers. Thus, there was a shift towards lower molecular weight cytokeratins, which is a reflection of immaturity, and probably towards motility. The tight junction proteins ZO-1 and occludin were expressed in the migrating epidermal sheet, where they apparently form an early barrier. Enhanced expression was seen in the hyperproliferative zone of the wound edge. The diabetic patients showed slower restoration of the epidermal barrier and a weaker initial inflammatory response. Obstructive jaundice and its resolution had no effect on healing. Skin collagen synthesis was decreased in jaundiced patients, and it increased slightly after drainage. Serum type III collagen propeptide levels were elevated in patients with biliary obstruction and dropped after drainage. The elevated levels may be related to the increased synthesis due to fibrosis. As a conclusion, diabetes mellitus impairs epidermal wound healing, while obstructive jaundice does not.
347

Collagenase-2 (matrix metalloproteinase-8) in tongue squamous cell carcinoma, bone osteosarcoma, and wound repair

Korpi, J. (Jarkko) 02 February 2010 (has links)
Abstract Degradation of extracellular matrix (ECM) and basement membrane (BM) are required both in normal physiological conditions such as wound healing and in pathological tissue remodelling such as chronic ulcers and cancers. Matrix metalloproteinases (MMPs) are an enzyme family, which can cleave most ECM and BM components. They are associated with physiological and pathological processes but their exact roles are still largely unknown. The expression of MMP-8 and MMP-26 in acute and chronic human cutaneous wounds using histological and cell culture methods were investigated. MMP-8 was expressed in epithelial cells, neutrophils, and other inflammatory cells especially in chronic ulcers while in acute wounds MMP-8 expression was weak or absent. MMP-26 was temporarily present in acute wounds while it was strongly expressed in close vicinity to the BM in multiple cell types of most chronic ulcers. In vitro keratinocyte wound assay showed that MMP-8 and -26 were expressed in migrating cells. Bone formation, collagen metabolism, and inflammation in MMP8-/- mice tooth extraction wounds and also periapical lesion formation were analysed. No differences between wild type or MMP-8-deficient mice in the new bone area or periapical lesion size were found. However, type III procollagen production was increased and inflammatory cell influx was decreased in MMP8-/- mice. In addition, Fas ligand (FasL) production was increased in mandibular alveolar mucosa but decreased in alveolar bone of MMP-8 deficient mice. MMP-8 was also found to cleave FasL in vitro. A total of 90 human mobile tongue squamous cell carcinoma (SCC) samples were collected. Bryne’s malignancy scores, thickness of the SCCs, expression of microvessel density (CD31 and factor VIII), cyclooxygenase-2 (COX-2), the laminin-5 (currently termed laminin-332) γ2-chain, integrin αvβ6, estrogen receptor-α (ER-α), estrogen receptor-β (ER-β), and MMPs (-2, -7, -8, -9, -20, and -28) were analysed. The high expression of MMP-8 was associated with a better prognosis for the patients, particularly in females. In addition, tongue carcinoma formation in MMP8-/- mice was investigated. Tongue SCC developed more often in MMP8-/- female mice than wild type littermates. In addition, MMP-8 can cleave ER- α and -β and estrogen can induce MMP-8 production in vitro. A total of 22 biopsies, 10 resection sections, and three lung metastases of 25 osteosarcoma patients samples were stained with MMP-2, -8, -13, -26, and tissue inhibitor of metalloproteinase-1 (TIMP-1) using immunohistological methods. Expression of these markers was mostly present in sarcoma cells but MMP-8 was not present in lung metastases. In resection sections, chemotherapy altered MMP-2, -8, and -13 expressions compared to biopsies. However, an association between the expression and prognosis of osteosarcoma patients could not been found. In conclusion, MMP-8 seems to be an estrogen-related protective factor in tongue SCC and can regulate ECM and BM components and inflammation during wound healing. Further studies are needed to evaluate the exact function especially of MMP-8 in human osteosarcoma.
348

An investigation of the anti-oxidant, antimicrobial and wound healing properties of whole leave juice and gelpowders of Aloe ferox and Aloe vera

Koma, Seboeng Portia January 2014 (has links)
Aloe vera is found in the Northern Africa and the Mediterranean areas while Aloe ferox is found in Southern Africa. Aloe ferox and Aloe vera prepared by different methods have been shown to possess the following properties: Stimulatory effects on different cell types (e.g human fibroblasts, rat adrenal cells, calf pulmonary artery endothelial cells etc.), wound healing, antimicrobial, antioxidant, antidiabetics etc. In this study solvent extracted gel powders and whole leaf juice of Aloe ferox and Aloe vera prepared specifically without bitter components were tested. The aim was to assess if the samples could be used orally for therapeutic purposes with regards to wound healing, antimicrobial and antioxidant properties avoiding the laxative effects of the bitter components. The following were used: Human lymphocytes cells to determine cytotoxicity effects, chicken fibroblasts cells for potential wound healing properties, Candida albicans, Staphylococcus aureus and Pseudomona aeruginosa microorganisms for antimicrobial properties and ORAC, DPPH, TEAC and chemiluminescence assays for antioxidant properties. Most of the results obtained were contrary to the bulk of the literature available about these beneficial plants’ extract. Bitter components have been reported to stimulate different cell types and to have antimicrobial and antioxidant properties. Thus the removal has been suggested as the main reason why the effects of the tested extracts did not correspond to much of the reported literature. From the results obtained from various aspects of this study it could be concluded that the removal of bitter components contributed to the apparently contradictory results. From this study it might be concluded that the four Aloe extract samples tested could not be used therapeutically for wound healing, antimicrobial or antioxidant properties. However they could still be effective for cosmetics purposes as obtained from the literature. / Dissertation (MSc)--University of Pretoria, 2014. / gm2014 / Pharmacology / unrestricted
349

In vitro toxicological assessment of amorphous silica particles in relation to their characteristics and mode of action in human skin cells

Moia, Claudia January 2015 (has links)
Background: Silica is the common name for silicon dioxide (SiO2) materials and exists in both crystalline and amorphous forms. While crystalline silica is known for its severe health effects, amorphous silica has been considered safe and applied in many areas. However, some recent studies have showed evidence of their toxicity, raising concerns about its use as nanomaterial for biomedical applications. When nanomaterials enter the body, they are enveloped in biological fluids rich in biomolecules, which compete for binding to the nanomaterial. Such effect could alter their surface chemistry and therefore affect their bio-distribution and interaction with cells. Aim and objectives: As part of the EU-funded NANODRUG network programme, the aim of this project was the in vitro toxicity assessment of commercially-sourced fumed and colloidal amorphous silica particles in relation to their physico-chemical properties and potential application as carriers for drug delivery. The objectives were 1) characterization of silica particles hydrodynamic (Hd) size and dispersity in different cell culture media; 2) in vitro toxicological assessment of silica particles in human skin cells; 3) delineation of toxicity mechanisms in relation to their size; 4) assessment of the influence of Foetal Bovine Serum (FBS) on particle Hd size and toxicity; and 5) contributing to the overall objective of the NANODRUG programme - development of safe nanodrugs for skin application - through collaborations with different partners.
350

Towards an understanding of the mechanisms of acellular zone formation in sutured tendons

Al Youha, Sarah January 2011 (has links)
Fibrotic diseases account for an estimated 45% of the total number of deaths in the developed world (Wynn 2007). Tendons are an excellent model for studying the dysregulated response which leads to fibrosis, as tendons have an organized, parallel matrix, in which tissue defects could easily be distinguished. Wong et al. (2006b) demonstrated the presence of a bell-shaped region around sutures in tendons that was devoid of cells in histological sections. The mechanisms of the formation of this acellular zone, that was also noted in cornea and cartilage (Matsuda et al. 1999; Hunziker and Stähli 2008), were unknown. It was hypothesized that the acellular zone was formed by cell death and that suturing caused alterations to the extracellular matrix of sutured regions of tendon, which made the acellular zone refractory to cellular re-population. The acellular zone was tracked in sutured tendons for up to a year to determine the temporal properties of the acellular zone. Electron microscopic and time lapse studies were carried out to determine if the acellular zone formed by cell migration or cell death. Microarray analysis was conduced to confirm this and to reveal potential molecular targets for future studies. The extracellular matrix of sutured tendons was studied by electron, atomic, scanning and polarized light microscopy and mechanical measurements were obtained using nanoindentation. It was concluded that the acellular zone formed within 24 hours and persisted for up to a year. Tension and size of the suture's grasp were also shown to be important for acellular zone formation. Cell death was the main effector of acellular zone formation. Microarray analysis showed evidence of upregulation of inflammatory mediators and programmed necrosis pathways. The sutured extracellular matrix was denser, more disorganized and had a lower Young's modulus than unsutured regions of the same tendon. These differences in the properties of the extracellular matrix of sutured tendons may be the cause of the persistence of the acellular zone.

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