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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.
51

Comparative Treatment Planning in Radiotherapy and Clinical Impact of Proton Relative Biological Effectiveness / Jämförande dosplaneringsstudier inom strålterapi samt betydelsen av relativ biologisk effekt för protoner

Johansson, Jonas January 2006 (has links)
<p>The development of new irradiation techniques is presently a very active field of research with increased availability of more sophisticated modalities such as intensity modulated photons (IMRT), protons and light ions. The primary aim of this work is to evaluate if the dose-distributions using IMRT and protons contribute to clinical advantages. A secondary aim is to investigate the potential clinical implication of the increased relative biological effect (RBE) for protons at the end of the Bragg peak. </p><p>The potential benefits are evaluated using physical dose measures and dose-response models for normal tissue complication probability (NTCP) and tumour control probability (TCP). Comparative treatment planning was performed using three locally advanced tumour types, left-sided node positive breast cancer, hypopharyngeal cancer, and rectal cancer. All studies showed that both IMRT and protons could improve the dose distributions compared to 3D-CRT, and significantly improve treatment results with lower NTCPs and, concerning hypopharyngeal cancer, higher TCP. Protons always resulted in smaller volumes receiving intermediate and low radiation doses.</p><p>Using protons or IMRT for left-sided node-positive breast cancer, the advantage is a significantly decreased risk for cardiac mortality (from 6.7% to 1%) and radiation induced pneumonitis (from 28.2% to less than 3%) compared to 3D-CRT. For hypopharyngeal cancer, protons and IMRT provide more selective treatment plans, higher TCP since a simultaneous boost technique is feasible, and better parotid gland sparing for several patients. For locally advanced rectal cancer, the NTCP for small bowel is potentially reduced by approximately 50% using IMRT or protons; protons have an even greater potential if the structure of the small bowel is parallel.</p><p>A variable RBE correction is developed and applied to a clinical proton treatment plan. A significant difference is obtained compared to the commonly accepted RBE correction of 1.1. This indicates that a variable RBE may be of importance in future proton treatment planning.</p><p>This thesis provides support for increased use both IMRT and proton radiotherapy, although stronger for protons. Therefore, investments in proton facilities with capacity for large clinical trials can be supported.</p>
52

Investigation of Incompatibility Reactions Caused by Biomaterials in Contact with Whole Blood Using a New in vitro Model.

Hong, Jaan January 2001 (has links)
<p>This thesis describes a new <i>in vitro</i> slide chamber model that makes it possible to conduct studies of molecular and cellular interactions between whole blood and biomaterials. The model proved to be a suitable tool for detection of cell and platelet binding to a biomaterial surface. It was possible to monitor activation of the blood cascade systems and cells in the fluid phase and detect surface-bound molecules.</p><p>One finding was that thrombin generation is primarily triggered by FXII on a biomaterial surface since corn trypsin inhibitor, inhibited thrombin generation in blood.</p><p>Another finding was that thrombin generation was dependent on variety types of blood cells, since thrombin generation was almost negligible in platelet-rich plasma. When various preparations of blood cells were used to reconstitute platelet-rich and platelet-poor plasma, erythrocytes were shown to be the most efficient cell type in triggering thrombin generation. Inhibition of platelet aggregation with aspirin and Ro44-9883 was associated with a decrease in thrombin generation, confirming that platelet activation is necessary for normal coagulation activation. These findings suggest that the central events consist of an initial low-grade generation of thrombin that involves erythrocytes and possibly leukocytes which leads to activation of platelets; and a second platelet-dependent amplification loop that produces most of the thrombin.</p><p>Titanium exposed to whole blood produced high amounts of thrombin. Stainless steel and PVC, generated lower amounts. This indicates that titanium might be less suitable as a biomaterial in devices that are in direct contact with blood for prolonged time. Considering the superior osteointegrating properties of titanium and titanium's response to blood, a correlation between high thrombogenicity and good osteointegration seems to exist.</p><p>Compstatin, that binds to complement component C3, effectively inhibited the generation of C3a and sC5b-9 and the binding of C3/C3 fragments to the surface. Our results suggest that a biomaterial is able to activate complement through both the classical and alternative pathways and that the classical pathway alone is able to maintain a substantial bioincompatibility reaction. The results show that complement activation is a prerequisite for activation and binding of PMNs to the surface in the <i>in vitro</i> model.</p>
53

Human secretoglobins in normal and neoplastic cells and tissues

Sjödin, Anna January 2005 (has links)
Secretoglobins is a newly described polypeptide family that has gained a lot of interest in human cancer and inflammation research. Although the first secretoglobin polypeptide was discovered more than 30 years ago, their physiological function is still not known. The aim of this thesis was to study the expression of secretoglobins in normal and neoplastic human cells and tissues, and to clarify their possible involvement in human cancer. We established sensitive and specific quantitative real-time RT-PCR assays for uteroglobin, lipophilins A, B, C, mammaglobin, HIN-1, and UGRP1, and developed specific antibodies for lipophilin B and mammaglobin. By using quantitative real-time RT-PCR, immunohistochemistry, Western blotting, and in situ hybridization, we studied secretoglobin expression in normal and neoplastic cells and tissues. In normal tissues, real-time RT-PCR analysis showed high expression of mammaglobin in skin. The mammaglobin expression in skin tissue was further confirmed by in situ hybridization and immunohistochemistry, and the expression was shown to be localized to the coiled gland cells of the eccrine sweat glands and the apocrine sweat glands. In addition, we showed by using Western blotting, that mammaglobin was secreted into perspiration from the eccrine sweat glands. In pituitary gland, immunohistochemical analysis showed that lipophilin B was expressed by approximately half of the cells in the anterior pituitary. By using quantitative real-time RT-PCR it was shown that both lipophilins B and C mRNA were expressed in the pituitary gland, therefore we suggested that lipophilins B and C form heterodimers in human pituitary. In neoplastic tissues, real-time RT-PCR analysis showed dysregulated secretoglobin expression in lung tumors, with down-regulation of uteroglobin and frequent up-regulation of lipophilins A, B, C, and mammaglobin. Immunohistochemical analyses showed down-regulation of mammaglobin in cylindromas versus non-neoplastic eccrine sweat glands and of lipophilin B in pituitary adenomas versus non-neoplastic anterior pituitary. The majority of investigated cell lines showed low, or most often, lack of secretoglobin expression. Nevertheless, it has been shown that mammaglobin is over-expressed in human breast carcinomas. However, ectopic over-expression of mammaglobin and/or lipophilin B had no appreciable effect on cell proliferation rates of Hs578T breast carcinoma cells in vitro. This does not exclude the possibility that secretoglobins could confer some advantage to tumor cells in vivo, but, it indicates that the reported over-expression of mammaglobin is an epiphenomenon not causally involved in breast carcinogenesis. In summary, our major findings were that mammaglobin was expressed and secreted by the sweat glands of the skin and lipophilin B was expressed by the anterior pituitary gland; and, that expression of mammaglobin and lipophilin B were down-regulated in tumors derived from the same tissues, i.e, in cylindromas and pituitary adenomas, respectively. Furthermore, ectopic over-expression of mammaglobin and lipophilin B in breast carcinoma cells had no appreciable effect on cell proliferation rates in vitro.
54

Experimental studies in brain tumours : with special regard to multidrug resistance and the ErbB-family

Andersson, Ulrika January 2005 (has links)
Primary brain tumours, and especially the most common form malignant gliomas, usually display a pronounced resistance to other treatment modalities when surgery fails to cure. Growth factors, such as EGF and its receptor, frequently amplified and overexpressed in malignant gliomas, and factors associated with multidrug resistance have been suggested to at least partially explain the poor outcome. The aim of this thesis was to characterise factors in primary brain tumours associated with the development of resistance with focus on the epidermal growth factor receptor (ErbB) family, and multidrug resistance (MDR). Influences of irradiation on the expression and activity of P-glycoprotein (Pgp) in malignant gliomas was evaluated. The effects showed that irradiation increased the efflux activity of Pgp in rat brain vascular endothelial cells, but not in glioma cells. In the intracranial BT4C glioma model, Pgp was detected in the capillary endothelium in the tumour tissue but not in glioma cells. Expression of several factors coupled to MDR (Pgp, MRP1, LRP, and MGMT) in primary brain tumours were analysed and correlated to clinical data. In gliomas, Pgp and MRP1 were predominantly observed in capillary endothelium and in scattered tumour cells, whereas LRP occurred only in tumour cells. In meningiomas, expression of the analysed markers was demonstrated in the capillary endothelium, with a higher expression of Pgp and MRP1 in transitional compared to meningothelial meningiomas. A pronounced expression of MGMT was found independently of the histopathological grade or tumour type. Survival analysis indicated a shorter overall survival for patients suffering from low-grade gliomas with high expression of Pgp. To explore the importance of the epidermal growth factor receptor (EGFR), expression levels of the family members (EGFR, ErbB2-4) were analysed and their relations to various clinical parameters were evaluated in gliomas and meningiomas. In gliomas, the highest EGFR expression was observed in high-grade tumours, while ErbB4 expression was most pronounced in low-grade tumours. In meningiomas, expression of EGFR, ErbB2, and ErbB4 was observed in the majority of the tumours. An intriguing observation in low-grade gliomas was a significantly decreased overall survival for patients with high EGFR protein expression. The effects of different time schedules for administration of the selective EGFR inhibitor ZD1839 in relation to irradiation of glioma cells were analysed. The analyses showed a heterogeneity in the cytotoxic effects of ZD1839 between cell lines, and it was obvious that some of the cell lines showed sensitivity to ZD1839 despite no or low expression of EGFR. The study also demonstrated the importance of timing of ZD1839 administration when this agent is combined with irradiation. In conclusion, in order to enhance the efficacy of radiotherapy by various drugs in malignant gliomas it may be essential to inhibit drug efflux activity in endothelial cells and to deliver drugs in an optimal timing in relation to radiotherapy. The heterogeneity in expression of drug resistance markers, as well as the ErbB family reflects the complexity in classification of primary brain tumours, and indicates that subgroups of patients with low-grade gliomas expressing Pgp and EGFR might benefit from more aggressive and individualised treatment.
55

Expressions of mercury-selenium interaction in vitro

Frisk, Peter January 2001 (has links)
Interaction between mercury and selenium has previously been observed both in man and in animals. The aim of this work was to study expressions of interaction between mercury and selenium in human K-562 cells. Inorganic and organic forms of mercury and selenium were used and cells were either pre-treated with selenium or simultaneously exposed to selenium and mercury. Concentrations of selenium and mercury chosen were indicated by a study of growth inhibition in the individual compounds: a low concentration of selenium and selenomethionine induced slight cell growth inhibition, while a high concentration resulted in a notable growth inhibition. Two mercury concentrations were chosen: one with minimal toxicity and another with high cell toxicity. In addition, uptake and retention patterns of selenomethionine and selenite differed in both selenocompounds. All simultaneous treatments with 3.5 μM methylmercury produced a reduction in cellular mercury with increased selenium concentration. This was particularly obvious in selenite treatments. Growth curves from the simultaneous 3.5 μM methylmercury and selenite treatments indicated protection with increased selenite concentrations. In both exposure protocols, the 5 μM methylmercury treatments were toxic to the cells. In both study protocols, cells exposed to selenite and mercuric chloride manifested increased cellular mercury uptake with increased selenium concentration. In all selenite and 35 μM mercuric chloride treatments, no inhibition of growth was observed, while the 50 μM mercuric chloride treatments were toxic to the cells. Selenite-dependent protection was achieved in both exposure protocols when considering the cellular uptake of mercury. With few exceptions, selenomethionine produced similar effects as selenite on mercuric chloride uptake and growth inhibition.
56

Investigation of Incompatibility Reactions Caused by Biomaterials in Contact with Whole Blood Using a New in vitro Model.

Hong, Jaan January 2001 (has links)
This thesis describes a new in vitro slide chamber model that makes it possible to conduct studies of molecular and cellular interactions between whole blood and biomaterials. The model proved to be a suitable tool for detection of cell and platelet binding to a biomaterial surface. It was possible to monitor activation of the blood cascade systems and cells in the fluid phase and detect surface-bound molecules. One finding was that thrombin generation is primarily triggered by FXII on a biomaterial surface since corn trypsin inhibitor, inhibited thrombin generation in blood. Another finding was that thrombin generation was dependent on variety types of blood cells, since thrombin generation was almost negligible in platelet-rich plasma. When various preparations of blood cells were used to reconstitute platelet-rich and platelet-poor plasma, erythrocytes were shown to be the most efficient cell type in triggering thrombin generation. Inhibition of platelet aggregation with aspirin and Ro44-9883 was associated with a decrease in thrombin generation, confirming that platelet activation is necessary for normal coagulation activation. These findings suggest that the central events consist of an initial low-grade generation of thrombin that involves erythrocytes and possibly leukocytes which leads to activation of platelets; and a second platelet-dependent amplification loop that produces most of the thrombin. Titanium exposed to whole blood produced high amounts of thrombin. Stainless steel and PVC, generated lower amounts. This indicates that titanium might be less suitable as a biomaterial in devices that are in direct contact with blood for prolonged time. Considering the superior osteointegrating properties of titanium and titanium's response to blood, a correlation between high thrombogenicity and good osteointegration seems to exist. Compstatin, that binds to complement component C3, effectively inhibited the generation of C3a and sC5b-9 and the binding of C3/C3 fragments to the surface. Our results suggest that a biomaterial is able to activate complement through both the classical and alternative pathways and that the classical pathway alone is able to maintain a substantial bioincompatibility reaction. The results show that complement activation is a prerequisite for activation and binding of PMNs to the surface in the in vitro model.
57

Infrainguinal Percutaneous Transluminal Angioplasty in Limbs with Severe Lower Limb Ischaemia

Löfberg, Anne-Marie January 2001 (has links)
Infrainguinal bypass grafting is an established method in the treatment of patients with femoropopliteal and crural occlusive disease leading to critical lower limb ischaemia (CLI). However, complications related to surgical procedure are not negligible and percutaneous transluminal angioplasty (PTA) has emerged as an alternative. The present thesis covers some aspects of infrainguinal PTA in patients with chronic severe lower limb ischaemia. The records of 217 patients undergoing 272 PTA procedures at various infrainguinal arterial segments were analysed. The indication for intervention was subcritical ischaemia in 76 limbs and critical ischaemia in 177 limbs. The role of duplex ultrasound examination in the selection of patients for PTA was retrospectively evaluated following a prospective validation of the method against angiography. A technically successful PTA was achieved in 89%. The overall 30-day mortality was 2.7%. No patient underwent amputation directly related to failed PTA. The primary success rates at 12 and 60 months following femoropopliteal PTA were 40% and 27% compared, to 51% and 36% in limbs undergoing crural artery PTA. Primary success rate in limbs with SFA occlusion longer than 5 cm was only 12% after 5 years, compared to 32% if the occlusion was equal or less than 5 cm in length (p&lt;0.01). In patients undergoing distal PTA through patent infrainguinal grafts, the primary and primary assisted patency rates at 3 years were 32% and 53%, respectively. The sensitivity of duplex scanning in the selection of lesions for PTA was less satisfactory in the popliteal and crural arteries compared to the superficial femoral arteries. In conclusion, the results of infrainguinal PTA performed for treatment of subcritical or CLI seemed to be inferior to the results of surgical interventions reported in the literature. However, due to the fact that the PTA procedure does not preclude the performance of bypass grafting, it might be an alternative to surgical intervention in limbs with stenotic or short occlusive lesions.
58

Improved Nutritional Support in Cancer Patients

Persson, Christina January 2002 (has links)
Weight loss and other nutritional problems are common in cancer patients. The problems are of importance for response to treatment and survival and the well-being of the patients. Nutritional support can be carried out in different ways. The efforts considered in this thesis are; assessment of nutritional status to find the patients who are at risk to become or already are malnourished, assessment of dietary intake, dietary advice, information and support to the families, information and education to the caregivers, and supplementation with drugs that possibly could influence the weight development. The Swedish version of the Patient Generated Subjective Global assessment of nutritional status, PG-SGA, is useful in assessment of nutritional status in cancer patients. Dietary advice and support to patients and their families combined with information and education to the staff, at the hospital and in the home care, turned out to have a positive influence at the weight development and other parameters related to nutrition. The effects were seen in consecutive patients with small cell lung cancer in comparison with a historical control group, and in patients in a randomised trial. Fish oil and melatonin could stabilise weight development in patients with advanced gastrointestinal cancer, but had no marked influence on factors reflecting cachexia. Problems with nutrition in cancer patients are possible to recognise and various interventions may be beneficial.
59

On the Use of 76Br-labelled Monoclonal Antibodies for PET : Preclinical Evaluation of Halogenated Antibodies for Diagnosis and Treatment of Cancer

Höglund, Johanna January 2002 (has links)
Radioactive substances are used in vivo to localize and characterize malignant tumours, generally by scintigraphic methods. In this context positron emission tomography (PET) in combination with radiolabelled monoclonal antibodies (mAbs) may provide a sensitive and specific method for detection of cancer. Individual dose calculations, based on such PET measurements, may be carried out to predict the possible use of mAbs labelled with therapeutic nuclides. The positron emitter 76Br, with a half-life of 16 h, is a well-suited candidate for radiolabelling and PET imaging. One drawback of radiobromine is that bromide, the ultimate catabolite after degradation of brominated mAb, is only tardily excreted from the body and is evenly distributed throughout the extracellular space, thereby increasing the background radioactivity. The aim of this work was to produce 76Br-mAb preparations with high accumulation and retention in tumour tissue together with a quick clearance of 76Br-labelled catabolites. Furthermore, the possibility to use brominated or iodinated mAbs in combination with PET to predict 211At-mAb dosimetry was evaluated. Monoclonal Abs directed against colorectal cancer were labelled with 76Br using the direct Chloramine-T-method or indirectly by labelling the precursor molecule N-succinimidyl para-(tri-methylstannyl) benzoate with 76Br, which was subsequently conjugated to the mAbs. Monoclonal Ab A33 labelled with 76Br using the two labelling protocols was characterized in vitro and in vivo in a rat tumour xenograft model. The mAb A33 was also labelled with 125I for comparison. In addition, mAb A33 was labelled with 211At, 125I and 76Br using the indirect labelling protocol and the mAb pharmacokinetics was studied in normal rats in order to estimate if data from brominated or iodinated mAb could be used for dosimetry of 211At in healthy organs and tissue. In conclusion, both direct and indirect labelling resulted in high yields and mAbs with preserved immunoreactivity. In vivo characterization of 76Br-brominated mAb A33 showed that the indirect labelling method makes 76Br-brominated mAb A33 a promising candidate for tumour imaging with PET due to the faster excretion of radiolabelled catabolites compared with direct bromination. Finally, mAb A33 labelled with 76Br and 124/125I can be used to predict the 211At dose of astatinated mAb A33 in most organs given that a correction factor is applied for organs with varying uptake.
60

Hodgkin Lymphoma : Studies of Advanced Stages, Relapses and the Relation to Non-Hodgkin Lymphomas

Amini, Rose-Marie January 2002 (has links)
The relationship between Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) is not entirely elucidated and a clonal relation may be present more often than previously believed. Mechanisms of tumour progression and resistance to therapy are poorly understood. Between 1974 and 1994 all individuals in Sweden with both HL and NHL were identified. Thirty-two cases were studied using clinical, histopathological and immunohistochemical methods. The second lymphoma often appeared in an aggressive clinical form and a significant correlation between the expression of p53 and LMP-1 in the first and second lymphoma was demonstrated. The treatment outcome for 307 patients with advanced stages of HL, in an unselected population was in accordance with the treatment results of large centres world-wide. Some patients were successfully selected for a shorter chemotherapy-regimen without inferior treatment results. In 124 patients with relapse, the survival of those primarily treated with radiotherapy according to the National guidelines was in accordance with the survival of patients of initially advanced stages. A worse outcome was found for those who received both chemotherapy and radiotherapy initially, probably because of a higher frequency of bulky disease in this group. Immunohistochemical analysis of the tumour suppressor protein p53 and retinoblastoma protein (Rb) of paired samples at diagnosis and at relapse in 81 patients did not reveal any specific staining pattern affecting survival. A novel B-cell line (U-2932) was established from a patient with a diffuse large B-cell lymphoma previously treated for advanced stage and subsequent relapses of HL. An identical rearranged IgH gene was demonstrated in tumour cells from the patient and in U-2932. A p53 point mutation was detected and over-expression of the p53 protein was found. A complex karyotype with high-level amplifications of the chromosomal regions 18q21 and 3q27, i.e. the loci for bcl-2 and bcl-6 were demonstrated.

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