Thesis (Ph. D.)--University of Virginia, 2008. / Title from title page. Includes bibliographical references. Also available online through Digital Dissertations.

Para desenvolver e avaliar a aplicabilidade de uma escala técnica prognostica das dificuldades no tratamento microcirúrgico dos aneurismas gigantes e complexos da circulação anterior do polígono de Willis, 50 lesões foram operadas. Um valor numérico foi dado a cada uma das 8 variáveis da escala. Somando-se os valores para cada variável, uma nota (de 1 a 14) foi obtida, para cada uma das 50 cirurgias. Dois grupos, portanto, foram definidos: cirurgia difícil (nota de 1 a 8) e cirurgia extremamente difícil (nota de 9 a 14). Foi feita análise estatística comparando-se os 2 grupos em relação a diversas variáveis demográficas e clínicas. Concluiu-se que a escala proposta é útil no planejamento pré-operatório, intra-operatório e prognóstico neste tipo de aneurisma / In order to develop and verify the applicability of a technical and prognostic scale of the difficulties in the microsurgical treatment of giant and complex aneurysms of the anterior circulation of the Cicle of Willis, 50 lesions were operated. A numeric amount was given for each of 8 variants of the scale. By adding each amount for each variant a score(from 1 to 14) was achieved, for each of the 50 surgeries. Two groups, therefore, were established: difficult surgery (scores from 1 to 8) and extremely difficult surgery (scores from 9 to 14). Statistical assessment comparing both groups in relation to several demographic and clinical variants was done. It was concluded that the proposed scale is useful in preoperative, intraoperative and prognostic planning in microsurgery for this kind of aneurysms

Atherosclerosis is an arterial disease that occurs due to the build-up of lipids, cholesterol and other substances in the arterial wall, collectively called plaque, leading to narrowing of the vessel lumen and, in time, disruption to the blood supply. The study of flow through atherosclerotic vessels is especially important since plaques not only cause a reduction in the vessel lumen but can rupture from the arterial wall, causing a blood clot in the vessel that may ultimately lead to heart attack or a stroke. Elevated level of oxidated low density lipoprotein (LDL) is a known risk factor associated with the genesis of atherosclerosis in arterial walls. Previous studies reported in literature have explored the transport of LDL through the arterial wall using analytical and mathematical models. In this work, we have presented a computational framework for the study of LDL transport in the lumen and the porous arterial wall. We have employed a four-layer arterial wall model and used governing equations to model the transport of LDL. We have used physiological parameters for the wall layers from literature and have validated the model based on the calculated filtration velocities and LDL concentration profiles in the arterial wall. We have further used this established model to study the effect of change in permeability and pressure on the LDL concentration. We have also studied the effect of pulsatile flow on the transport of LDL through the porous walls to examine the validity of the initial assumption of steady state and have seen that pulsation increases the time averaged net flux of LDL species by about 20%. We have next modeled a drug-eluting stent (DES), which is one of the popular remedies to cure atherosclerosis. The validation of DES model is followed by a combined study to analyze the effect of stent placement on LDL transport. Although there is no chemical reaction between the drug and LDL, we have noticed recirculation zones near the stent strut which result in accumulation of LDL molecules in the arterial wall. Future studies are aimed at incorporating variable porosity and permeability and a stenosed region in the geometry. The deformation of arterial wall due to pulsatile blood flow may lead to alteration of wall properties, which can give a realistic view of macromolecular transport.

Surgical intervention can result in endothelial denudation, driving growth factor-stimulated vascular smooth muscle cell (VSMC) migration towards the intima, leading to luminal narrowing and restenosis. Clinically approved PGI₂ analogues, including beraprost, activate the cyclic adenosine monophosphate (cAMP) signaling pathway to inhibit VSMC migration in vitro. This pathway is a potential therapeutic target, however the downstream proteins involved in the inhibitory effects of cAMP on migration remain unknown. The aims of this study were to determine the signalling pathways involved in inhibiting VSMC migration through cAMP downstream mediators, protein kinase A (PKA) and the more recently characterised exchange protein activated by cAMP (Epac), and delineate the mechanisms involved. In human saphenous vein VSMCs, Epac activation using an Epac analogue inhibited VSMC migration. Therapeutic concentrations of beraprost (1 nM) also resulted in an inhibition of VSMC migration. The use of fluorescence resonance energy transfer (FRET) confirmed 1 nM beraprost activated Epac, but not PKA. Epac is a guanine nucleotide exchange factor (GEF) for Rap1 thus Rap1 siRNA was used to inhibit the Epac pathway. This blocked the inhibitory effects of beraprost on VSMC migration. Epac1 was localised to the leading edge of migrating VSMCs. Another G-protein, RhoA, was investigated since it is essential for cell migration and is involved in several processes including actin regulation. Epac signaling inhibited PDGF-induced RhoA activation and disassembled F-actin at the leading edge, where Epac1 was previously located. This indicates that beraprost activated the Epac pathway, which inhibited RhoA to decrease VSMC migration. The clinical relevance of this study has discovered the mechanisms of Epac's inhibitory action on VSMC migration and this pathway could be targeted therapeutically to reduce restenosis. In the future the potential use of beraprost on a drug eluting stent might be beneficial to prevent restenosis formation following surgical intervention.

The intent of this research was to identify if the degenerative changes within arteries in the endometrium (endometrial angiopathies) correlate with degenerative changes in the uterine arteries and can be used as a predictor of increased risk for uterine artery rupture (UAR). With this objective specimens from 20 mares that died from uterine artery rupture and 21 control mares that died from unrelated causes were obtained from cases submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) over a two-year period. Postmortem specimens of each mare were collected from the left and right uterine arteries at the origin, bifurcation, and distal to the bifurcation as well as full thickness uterine wall sections at five different sites. An additional sample was taken from the uterine artery at the site of rupture in the affected mares. Tissue samples were immersed in 10% neutral buffered formalin, routinely processed, and stained with hematoxylin and eosin, Masson’s Trichrome, and Verhoeff´s Van Gieson histochemical stains as well as a smooth muscle-actin immunohistochemical marker. Elastosis, fibrosis, and vascular smooth muscle cell degeneration were identified in this study as potential contributors of vascular degeneration and a scoring system was developed to differentiate the degrees of severity of these specific degenerative changes within the intima and media of the vascular wall. Based on the scoring system, sections of uterine arteries and endometrial arterioles were blindly examined and the scored changes recorded for statistical analysis. Although the degenerative changes in endometrial and uterine arteries were similar within each group, the results could not not be used to predict an increased risk for UAR. Furthermore, we determined the major changes in vascular pathology of the affected uterine arteries and show there is a significant difference in degenerative changes between specific layers of the vascular wall.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

A vast majority of heart attacks occur due to rapid progression of plaque buildup in the coronary arteries that supply blood to the heart muscles. The diseased arteries can be treated with drugs delivered locally to vulnerable plaques—ones that may rupture and release emboli, resulting in the formation of thrombus, or blood clot that can cause blockage of the arterial lumen. In designing these local drug delivery devices, important issues regarding drug distribution and targeting need to be addressed to ensure device design optimization as physiological forces can cause the local concentration to be very different from mean drug tissue concentration estimated from in vitro experiments and animal studies. Therefore, the main objective of this work was to develop a computational tool-set to support the design of a catheter-based local drug delivery system that uses nanoparticles as drug carriers by simulating drug transport and quantifying local drug distribution in coronary artery walls. Toward this end, a three dimensional mathematical model of coupled transport of drug and drug-encapsulated nanoparticles was developed and solved numerically by applying finite element based isogeometric analysis that uses NURBS-based techniques to describe the artery wall geometry. To gain insight into the parametric sensitivity of drug distribution, a study of the effect of Damkohler number and Peclet number was carried out. The tool was then applied to a three-dimensional idealized multilayered model of the coronary artery wall under healthy and diseased condition. Preliminary results indicated that use of realistic geometry is essential in creating physiological flow features and transport forces necessary for developing catheter-based drug delivery design procedures. Hence, simulations were run on a patient-specific coronary artery wall segment with a typical atherosclerotic plaque characterized by a lipid pool encased by a thin fibrous cap. Results show that plaque heterogeneity and artery wall inhomogeneity have a considerable effect on drug distribution. The computational tool-set developed was able to successfully capture trends observed in local drug delivery by incorporating a multitude of relevant physiological phenomena, and thus demonstrated its potential utility in optimizing drug design parameters including delivery location, nanoparticle surface properties and drug release rate. / text

The purpose of the research was to develop a quantitative method which could be used to obtain a clearer understanding of the time-dependent fluid filteration and load-deformation behavior of soft, porous, fluid filled materials (e.g. biological tissues, soil). The focus of the study was on the development of a finite strain theory for multiphasic media and associated computer models capable of predicting the mechanical stresses and the fluid transport processes in porous structures (e.g. across the large blood vessels walls). The finite element (FE) formulation of the nonlinear governing equations of motion was the method of solution for a poroelastic (PE) media. This theory and the FE formulations included the anisotropic, nonlinear material; geometric nonlinearity; compressibility and incompressibility conditions; static and dynamic analysis; and the effect of chemical potential difference across the boundaries (known as swelling effect in biological tissues). The theory takes into account the presence and motion of free water within the biological tissue as the structure undergoes finite straining. Since it is well known that biological tissues are capable of undergoing large deformations, the linear theories are unsatisfactory in describing the mechanical response of these tissues. However, some linear analyses are done in this work to help understand the more involved nonlinear behavior. The PE view allows a quantitative prediction of the mechanical response and specifically the pore pressure fluid flow which may be related to the transport of the macromolecules and other solutes in the biological tissues. A special mechanical analysis was performed on a representative arterial walls in order to investigate the effects of nonlinearity on the fluid flow across the walls. Based on a finite strain poroelastic theory developed in this work; axisymmetric, plane strain FE models were developed to study the quasi-static behavior of large arteries. The accuracy of the FE models was verified by comparison with analytical solutions wherever is possible. These numerical models were used to evaluate variables and parameters, that are difficult or may be impossible to measure experimentally. For instance, pore pressure distribution within the tissue, relative fluid flow; deformation of the wall; and stress distribution across the wall were obtained using the poroelastic FE models. The effect of hypertension on the mechanical response of the arterial wall was studied using the nonlinear finite element models. This study demonstrated that the finite element models are powerful tools for the study of the mechanics of complicated structures such as biological tissue. It is also shown that the nonlinear multiphasic theory, developed in this thesis, is valid for describing the mechanical response of biological tissue structures under mechanical loadings.

INTRODUÇÃO: O acometimento de artérias ou veias tronculares periféricas por neoplasias malignas é raro. Quando o tratamento cirúrgico é realizado sendo constatado o acometimento arterial pela neoplasia, a melhor conduta é a ressecção conjunta seguida de reconstrução arterial imediata, restabelecendo o eixo vascular e evitando a isquemia de tecidos nobres com suas possíveis conseqüências. OBJETIVOS: O objetivo desse trabalho é analisar os resultados do tratamento cirúrgico de pacientes portadores de neoplasias malignas, submetidos a ressecções tumoral e vascular associadas à reconstrução vascular, avaliando principalmente a morbidade, a mortalidade e a perviedade primária relacionadas às reconstruções arteriais. MÉTODOS: Foram acompanhados os pacientes portadores de neoplasias malignas em regiões cervical, abdominal ou extremidades inferiores, operados eletivamente no período de setembro de 1997 a setembro de 2004 no Hospital do Câncer A.C.Camargo em São Paulo, submetidos à ressecções tumoral e vascular associadas à reconstrução arterial (associada ou não à reconstrução venosa de segmento venoso ressecado no mesmo feixe). O seguimento vascular foi em ambiente ambulatorial, realizando-se exame clínico vascular e exames de imagem para o acompanhamento das reconstruções. Foram analisadas: as características clínicas dos pacientes, as reconstruções vasculares, as complicações vasculares e não vasculares precoces (até 30 dias); as complicações vasculares e não vasculares tardias (após 30 dias), a perviedade primária das reconstruções arteriais e a sobrevida dos pacientes. RESULTADOS: foram operados 36 pacientes, sendo divididos em grupos de acordo com a localização das neoplasias: Cervical (14), Extremidade (13) e Abdome (9). No grupo Cervical, foram realizadas 17 reconstruções (16 arteriais e 1 venosa) nos 14 pacientes, predominantemente com a veia safena. Houve uma oclusão sintomática precoce do enxerto carotídeo com seqüelas importantes e uma oclusão sintomática tardia de enxerto carotídeo sem seqüelas (esse paciente também apresentou oclusão de enxerto arterial para o membro superior sem isquemia grave). No grupo Extremidade, foram realizadas 23 reconstruções (13 arteriais e 10 venosas) nos 13 pacientes, predominantemente com a safena. Houve uma rotura precoce de enxerto arterial femoral, tratada por meio de ligadura e evoluindo sem seqüelas. No grupo Abdome, foram realizadas 13 reconstruções (9 arteriais e 4 venosas) nos 9 pacientes, predominantemente com prótese. Uma paciente apresentou oclusão tardia sintomática de ramo do enxerto aorto-bifemoral, sendo realizado enxerto femoral cruzado, evoluindo sem seqüelas. Não houve diferença estatística entre os índices de perviedade arterial primária entre os grupos (p=0,593). Em relação às reconstruções venosas, houve cinco oclusões sintomáticas. O tempo de seguimento mediano nos grupos Cervical, Extremidade e Abdome foi respectivamente de 11,5, 25 e 18 meses, sendo significantemente menor no grupo Cervical (p=0,034). Houve duas amputações de membro não relacionados às complicações dos enxertos. Não houve óbitos no período intra-hospitalar, sendo todos decorrentes da evolução da doença neoplásica (11 do grupo Cervical, 8 do Extremidade e 3 do Abdome). CONCLUSÕES: 1. as reconstruções arteriais associadas à ressecção de tumores malignos com acometimento arterial em segmentos cervical, abdominal ou extremidades inferiores podem ser realizadas com baixos índices de morbi-mortalidade; 2. não houve diferença entre os índices de perviedade primária das reconstruções arteriais realizadas nos grupos estudados / INTRODUCTION: Arteries or peripheral truncular veins are rarely affected by malignant neoplasias. When arteries affected by neoplasia are observed during surgical treatment, the best approach is in bloc resection followed immediately by arterial reconstruction to reestablish the vascular axis and avoid ischemia of important tissues with the possible consequences. OBJECTIVES: The objectives of this study were to analyze the surgical treatment results from patients with malignant neoplasias who underwent tumor and vascular resection associated with vascular reconstruction and, in particular, to evaluate morbidity, mortality and primary patency relating to arterial reconstruction. METHODS: Patients with malignant neoplasias in the cervical, abdominal or lower extremity regions who underwent elective surgery between September 1997 and September 2004 at Hospital do Câncer A.C. Camargo, São Paulo, were followed up. These patients underwent tumor and vascular resections associated with arterial reconstruction (with or without reconstruction of the venous segment resected in the same bundle). The vascular follow-up was in an outpatient environment, through clinical vascular examination and imaging examinations to monitor the reconstructions. The patients\' clinical characteristics, vascular reconstructions, early vascular and non-vascular complications (within 30 days), late vascular and non-vascular complications (beyond 30 days), primary patency of arterial reconstructions and survival were analyzed. RESULTS: Thirty-six patients underwent surgery and were grouped according to neoplasia location: Cervical (14), Extremity (13) and Abdomen (9). In the Cervical group, 17 reconstructions were performed (16 arterial and 1 venous) in 14 patients, predominantly using the saphenous vein. There were one early symptomatic occlusion of the carotid graft with significant sequelae and one late symptomatic occlusion of the carotid graft without sequelae (this patient also presented arterial graft occlusion to the upper limb, without severe ischemia). In the Extremity group, 23 reconstructions were performed (13 arterial and 10 venous) in 13 patients, predominantly using the saphenous vein. There was one early rupture of a femoral arterial graft, with treatment by means of ligature and evolution without sequelae. In the Abdomen group, 13 reconstructions were performed (9 arterial and 4 venous) in 9 patients, predominantly using a prosthesis. One patient presented a late symptomatic occlusion in a branch of the aortobifemoral graft, for which a femoral crossover graft was performed, which evolved without sequelae. There was no statistical difference in primary arterial patency rates between the groups (p=0,593). Five symptomatic occlusions relating to venous reconstructions occurred. The median follow-up for the Cervical, Extremity and Abdomen groups were 11,5, 25 and 18 months, respectively: significantly shorter in the Cervical group (p=0,034). There were two limb amputations, unrelated to graft complications. There were no deaths while in hospital. Deaths occurred only as a result of neoplastic disease evolution (11 Cervical, 8 Extremity and 3 Abdomen patients). CONCLUSIONS: 1. arterial reconstructions associated with resection of malignant tumors affecting arteries in the cervical, abdominal or lower extremity segments can be performed with low morbidity-mortality rates; 2. there is no difference between primary patency rates of the arterial reconstructions performed, regarding the groups studied

Vários mecanismos controlam os processos de contração e relaxamento das células musculares lisas vasculares (CMLVs). Receptores e moléculas sinalizadoras intracelulares, os quais controlam os processos de contração e relaxamento das CMLVs, são alvo de modificações pós-traducionais, como a O-GlcNAcilação que modula respostas vasculares. O aumento de proteínas modificadas por O-GlcNAc apresenta efeito ambíguo sobre as CMLVs, sendo protetor em situações de aumento agudo, mas lesivo quando mantido cronicamente. O aumento crônico de O-GlcNAc em animais está associado a repostas contráteis mais intensas e redução do relaxamento vascular, assim como o aumento da produção de espécies reativas de oxigênio (EROs), denominado estresse oxidativo, alterações constantemente descritas em doenças crônicas como diabetes e hipertensão arterial. Considerando que algumas proteínas que controlam a contratilidade vascular são modificadas por O-GlcNAc e que pouco se sabe a respeito da via de Biossíntese das Hexosaminas (VBH) e sua relação com o sistema vascular em humanos, nós investigamos a hipótese de que modificações de proteínas por O-GlcNAc estão relacionadas a alterações vasculares na hipertensão arterial em humanos. Durante a realização de nossos experimentos, demonstramos que os principais componentes da VBH estão presentes em CMLVs humanas. O tratamento com Thiamet G (TMG) por 24 h aumentou os níveis de proteínas modificadas por O-GlcNAc nas CMLVs pela redução da atividade de OGA, assim como induziu efeito compensatório de aumento da expressão dessa enzima. TMG reduziu a atividade de OGA em CMLVs no grupo Controle, mas não promoveu alteração na geração de EROs. Após tratamento com TMG, artérias de grupo Controle apresentaram maior sensibilidade à noradrenalina (NA) e maior relaxamento ao nitroprussiato de sódio (NPS); enquanto o grupo Hipertenso não apresentou alterações na contratilidade ou no relaxamento arterial. Artérias do grupo Hipertenso apresentaram maior sensibilidade à NA que o grupo Controle antes de qualquer tratamento, além de deficiência no relaxamento, com menor sensibilidade e menor resposta máxima ao NPS em comparação ao grupo Controle. O grupo Hipertenso apresentou aumento da pressão arterial média de internação (PAMi), assim como da idade, quando comparado com o grupo Controle. Em conclusão, a VBH está presente nas CMLVs humanas. A inibição da atividade da OGA por TMG aumenta os níveis de proteínas modificadas por O-GlcNAc, a expressão de OGA e modula a reatividade vascular no grupo Controle, mas não no grupo Hipertenso. Os resultados demonstram que pacientes hipertensos apresentam respostas vasculares a drogas vasoativas diferentes daquelas observadas em pacientes controle, antes e após o aumento dos níveis de proteínas modificadas por O-GlcNAc nas CMLVs. Novos estudos serão necessários para determinar se as alterações observadas são decorrentes da hipertensão arterial e/ou do tratamento farmacológico aos quais os pacientes estão submetidos. / Several mechanisms control the contraction and relaxation processes in the vascular smooth muscles cells (VSMC). Intracellular receptors and signaling molecules involved in contraction and relaxation mechanisms are targets of post-translational modifications (PTM), such as O-GlcNAcylation, which modulates vascular responses. Augmented levels of O-GlcNAc-modified proteins show a dual effect in VSMC, being protective during acute stressful events and deleterious when O-GlcNAc is chronically augmented. In animals, chronic increases in O-GlcNAc-modified proteins are linked to increased vascular responses to constrictor agents, to reduced vascular relaxation in response to dilator drugs, and to increased production of reactive oxygen species (ROS), named oxidative stress. All these changes are frequently described in chronic diseases such as diabetes and arterial hypertension. Since proteins involved in vascular contractility are modified by O-GlcNAc, and our knowledge on the influence of the hexosamine biosynthesis pathway (HBP) in the human vascular system is limited, we tested the hypothesis that proteins modified by O-GlcNAc contribute to vascular changes in hypertensive patients. Our data show that human VSMC express the main components of the HBP; the treatment of human VSMC with Thiamet G (TMG) for 24 h augmented O-GlcNAc levels, decreased OGA activity and induced a compensatory increase in OGA\'s expression. TMG reduced OGA activity, increased levels of O-GlcNAc-modified proteins but did not change ROS generation in human arteries from the Control group. After treatment with TMG, arteries from the Control group exhibited increased sensitivity to norepinephrine (NE) and to sodium nitroprusside (SNP), as well as increased maximum relaxation to SNP. Augmented O-GlcNAc levels produced no changes in contractile or relaxation responses in the Hypertensive group. Arteries from the Hypertensive group exhibited an increased sensitivity to NE as well as decreased sensitivity and maximum relaxation to SNP when compared to arteries from the Control group. Mean arterial blood pressure (hMABP) and the average age were increased in patients from the Hypertensive group. In conclusion, the HBP is present in human VSMC and the inhibition of OGA activity with TMG increases O-GlcNAc levels, increases OGA expression and modifies vascular responses to constrictor and dilator stimuli in human arteries from the Control group, but not from the Hypertensive group. These results indicate that hypertensive patients have altered vascular responses to vasoactive drugs both in the absence and in the presence of augmented O-GlcNAc levels. Further research is needed to explain whether these differences are due to the hypertensive disease and/or to the patient\'s medical treatment.