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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.
21

DNA fragmentation in cultured cells exposed to high linear energy transfer radiation

Höglund, Erik January 2000 (has links)
The DNA double-strand break (DSB) is a critical lesion which, if not completely restored, can have serious biological consequences. The relative biological effectiveness (RBE) of many severe end-points are closely related to radiation quality, with increased effectiveness at elevated ionization density. Data presented provide information about the influence of radiation quality on the initial processes causing DNA damage, and the mechanisms leading to its restoration. Such information will increase the understanding of radiation action mechanisms in mammalian cells. Human cells were irradiated with accelerated ions having linear energy transfer (LET) values in the range 40-225 keV/μm, and 60Co-photons. Detailed analyses of the DNA fragment distributions were performed in the size-range 5 kilobasepairs to 6 megabasepairs by pulsed-field gel electrophoresis. A non-random fragmentation of DNA was evident, with an elevated number of small and medium-sized fragments for ion irradiation, and the total number of breaks increased by 80-110% when these fragments were included in the analyses. The RBE for DSB induction was 1.2-1.5. A two-fold increase of the number of breaks induced per nitrogen ion passing the cell nuclues was found when LET was increased from 80 to 225 keV/μm, indicating a possible role of particle track structure in DSB induction. Furthermore, the ability to repair DNA was closely related to radiation quality, with an increased proportion of unrejoined breaks for densely ionizing radiation. Surprisingly, the majority of breaks were rapidly rejoined even following exposure to high-LET radiation. The proportion of breaks restored by the slow phase showed a five-fold increase for the highest LET tested, compared with photons. The results presented nominates the complexity of breaks as one determining factor for reduced reparability reported following high-LET exposure.
22

Radionuclide targeting with particular empahsis on urinary bladder carcinoma

Sjöström, Anna January 2001 (has links)
The incidence of urinary bladder carcinoma is increasing and many patients die every year of this disease despite assumed radical therapy. Thus, there is a need for improved methods of diagnosis and therapy. Radionuclide targeting is based on achieving specific delivery of radioactive nuclides to tumour cells with minimal damage to surrounding normal tissues. Two possible target structures are the epidermal growth factor (EGF) receptor and the related receptor HER-2. Cellular binding and retention of 125I-EGF-dextran conjugates was investigated in two bladder carcinoma cell lines. The conjugate bound specifically to the EGF receptor with delayed maximum binding, limited intracellular degradation and prolonged cellular retention compared to 125I-EGF. EGF was labelled using different radionuclides and methods. All the labelled variants bound specifically to the tumour cells although the cellular binding patterns and retention varied considerably. 111In-DTPA-EGF had highest cellular retention and in decreasing order 211At-benzoyl-EGF and 125I-labelled EGF. Bladder cancer spheroids bound both 125I-EGF-dextran as well as 125I-EGF. Conjugate binding increased during a 48 h incubation period and was most prominent in the outer cell layers. The length of the dextran chain appeared not to alter the binding pattern. The expression of EGF receptors and HER-2 in metastases and primary bladder carcinoma tumours was investigated. Both receptors were expressed in the majority of metastases and primary tumours. Targeting the EGF receptor and/or HER-2 in urinary bladder carcinoma is an exciting new concept.
23

Structural and Functional Studies of the Density Enhanced Receptor-like Protein Tyrosine Phosphatase DEP-1

Sörby, Maria January 2001 (has links)
Tyrosine phosphorylation is a central mechanism in cellular signalling leading to proliferation, migration or differentiation. Protein tyrosine phosphorylation is regulated by the coordinated actions of protein tyrosine kinases and protein tyrosine phosphatases. This thesis investigates the involvement of tyrosine phosphatases in contact-induced growth inhibition of cells. Furthermore, it describes the structure and function of the extracellular domain of the receptor-like tyrosine phosphatase DEP- 1. Tyrosine phosphatases, negatively regulating tyrosine kinases, have been suggested being involved in contact-induced growth inhibition of cells. Both endogenous EGF-receptors and transfected PDGF receptors showed a decreased ligand-induced tyrosine phosphorylation in cells of dense cultures. This difference was found to be due to increased receptor-directed tyrosine phosphatase activity in dense cultures. Density enhanced tyrosine phosphatase-1 (DEP-1) is a receptor-like tyrosine phosphatase. It was found that DEP-1 contains chondroitin sulfate chains, thus identifying DEP-1 as a proteoglycan. Furthermore, DEP-1 was found to interact with a heparan sulfate proteoglycan. No ligands have been identified for DEP-1. We have established a biacore-based assay for the identification of molecules interacting with the extracellular domain of DEP-1. A library of cell conditioned media was screened with the biacore assay. One of the samples was found to contain DEP-1 interacting molecules. Purification of the ligand has been initiated. In an attempt to identify modulators of DEP-1 activity, Matrigell™ , a preparation of extracellular matrix was investigated. Stimulation with Matrigel™ was found to increase the specific activity of DEP-1 through interactions between the extracellular domain of DEP-1 and Matrigel™ component(s).
24

Stem Cell Factor Induced Signal Transduction

Lennartsson, Johan January 2002 (has links)
Stem Cell Factor (SCF) can function as a survival factor, a mitogen or a chemoattractant depending on cell type. Binding of SCF to c-Kit induces dimerization and subsequent autophosphorylation of the receptor. This thesis describes the intracellular signal transduction elicited by c-Kit. In the search for signal transduction molecules binding to activated c-Kit, we identified the adaptor proteins Grb2 and Grb7 as interacting partners. Grb2 could associate to Tyr-703 in the kinase insert as well as to Tyr-936 in the C-terminal tail of c-Kit. However, Grb7 could only bind to Tyr-936. Tyr-568 in c-Kit is essential for SCF induced association and activation of Src family kinases (SFK). A mutated receptor that could not activate SFK (Y568F or Y568/570F) showed reduced Shc phosphorylation, Ras GTP loading, Erk activation and induction of c-fos. However, activation of SFK is not essential for the mitogenic response as measured by DNA synthesis. Tyr-900 in c-Kit was identified as a SFK dependent phosphorylation site. The adaptor protein Crk and the p85 subunit of PI3’-kinase could associate with phosphorylated Tyr-900. In addition, we could demonstrate a constitutive complex between Crk and p85, suggesting indirect binding of Crk to Tyr-900 via p85. Mutation of Tyr-900 (Y900F) led to a reduced phosphorylation of Crk-II, loss of the second wave of Erk phosphorylation and a reduced mitogenic response. In addition the mutated receptor showed an increased ligand-induced degradation as compared to the wild-type receptor. There exist two splice forms of c-Kit that differ in the presence or absence of four amino acids in the extracellular juxtamembrane region. These splice forms bind SCF with similar affinity but display striking differences in signaling characteristics, e.g. in phosphorylation kinetics, ligand-induced c-Kit degradation and activation of Erks. However, other pathways are activated similarly by both splice forms, such as the Ser/Thr kinase Akt which lies downstream of PI3’-kinase. In this study we show that differential phosphorylation of the various tyrosine residues occurs. Interestingly, Tyr-568 is more efficiently phosphorylated in the shorter form leading to stronger binding of SFK, whereas the PI3’-kinase binding site showed a similar degree of phosphorylation consistent with the data on Akt activation.
25

Prognostic Modeling in the Presence of Competing Risks| An Application to Cardiovascular and Cancer Mortality in Breast Cancer Survivors

Leoce, Nicole M. 07 June 2016 (has links)
<p> Currently, there are an estimated 2.8 million breast cancer survivors in the United States. Due to modern screening practices and raised awareness, the majority of these cases will be diagnosed in the early stages of disease where highly effective treatment options are available, leading a large proportion of these patients to fail from causes other than breast cancer. The primary cause of death in the United States today is cardiovascular disease, which can be delayed or prevented with interventions such as lifestyle modifications or medications. In order to identify individuals who may be at high risk for a cardiovascular event or cardiovascular mortality, a number of prognostic models have been developed. The majority of these models were developed on populations free of comorbid conditions, utilizing statistical methods that did not account for the competing risks of death from other causes, therefore it is unclear whether they will be generalizable to a cancer population remaining at an increased risk of death from cancer and other causes. </p><p> Consequently, the purpose of this work is multi-fold. We will first summarize the major statistical methods available for analyzing competing risk data and include a simulation study comparing them. This will be used to inform the interpretation of the real data analysis, which will be conducted on a large, contemporary cohort of breast cancer survivors. For these women, we will categorize the major causes of death, hypothesizing that it will include cardiovascular failure. Next, we will evaluate the existing cardiovascular disease risk models in our population of cancer survivors, and then propose a new model to simultaneously predict a survivor's risk of death due to her breast cancer or due to cardiovascular disease, while accounting for additional competing causes of death. Lastly, model predicted outcomes will be calculated for the cohort, and evaluation methods will be applied to determine the clinical utility of such a model.</p>
26

Quinacrine in endometrial cancer| Repurposing an old antimalarial drug

Kalogera, Eleftheria 07 June 2016 (has links)
<p> <u>Background and Rationale:</u> Although the majority of patients with endometrial cancer (EC) are diagnosed early when disease is confined in the uterus and prognosis is excellent, there is a subset of patients with dismal prognosis. Carboplatin and paclitaxel is the standard chemotherapeutic regimen for EC. Given that response to chemotherapy impacts disease prognosis, especially in advanced, recurrent and metastatic disease, novel chemotherapeutic agents with improved safety profile are necessary to improve response rates and outcomes in these patients. Quinacrine (QC) is an inexpensive antimalarial drug with a predictable safety profile which recently surfaced as a promising anticancer agent thought to be associated with decreased risk of developing chemo-resistance through targeting multiple pathways simultaneously. </p><p> <u>Objective:</u> To generate preclinical data on the effect of QC in inhibiting tumorigenesis in EC both <i>in vitro</i> and <i>in vivo</i> as well as explore its role as an adjunct to standard chemotherapy <i>in vivo</i> in an EC mouse xenograft model. </p><p> <u>Methods:</u> Five different EC cell lines (Ishikawa, Hec-1B, KLE, ARK-2, and SPEC-2) representing different histologies, grades of EC, sensitivity to cisplatin and p53 status were used for the <i> in vitro</i> studies. MTT and colony formation assays were used to examine QC&rsquo;s ability to inhibit cell viability <i>in vitro.</i> Drug combination studies were performed and the Chou-Talalay methodology was employed in order to examine synergism between QC and cisplatin, carboplatin or paclitaxel. A cisplatin-resistant EC subcutaneous mouse xenograft model was used in order to explore QC&rsquo;s anticancer activity <i>in vivo</i> and assess its role as maintenance therapy. </p><p> <u>Results:</u> QC exhibited strong synergism <i> in vitro</i> when combined with cisplatin, carboplatin or paclitaxel with the highest level of the synergism being observed in the most chemo-resistant EC cell line. Neither QC monotherapy nor standard chemotherapy significantly delayed tumor growth in the mouse xenografts. Co-administration of QC with standard chemotherapy significantly augmented the antiproliferative ability of these chemotherapeutic agents as evidenced by the significant decrease in tumor burden. Combination treatment was associated with a 14-week prolongation of median survival compared to standard chemotherapy alone. Maintenance therapy with QC following standard chemotherapy was proven superior to standard chemotherapy as it resulted in long-term stabilization of disease evidenced by lack of significant tumor progression and further prolongation of overall survival. QC treatment alone, in combination with standard chemotherapy or as maintenance therapy was well-tolerated and was not associated with weight loss compared to control mice. A yellow skin discoloration was noted during active treatment with QC which was entirely reversible within a few days upon discontinuation of treatment. </p><p> <u>Conclusions:</u> QC exhibited significant antitumor activity against EC cell lines <i>in vitro</i> and was successful as maintenance therapy in chemo-resistant EC mouse xenografts. This preclinical data suggest that QC may be an important adjunct to standard platinum-based chemotherapeutic regimens for patients with recurrent EC.</p>
27

Provider weight bias| Experiences of overweight and obese cancer survivors

Wyrick, Sandra Lee 19 July 2016 (has links)
<p> Declared a disease by the AMA in 2013, obesity claims the lives of over 2.8 million people annually in the U.S. Mounting evidence indicates weight bias is encountered in the interactions with health care professionals; resulting in a decreased health-related quality of life and shorter survival rates. Knowingly or unknowingly, healthcare providers communicate forms of weight bias when they associate negative traits and assumptions with obesity to their patients. Using a descriptive phenomenology methodology, the purpose of this research study is to explore and describe the phenomenon of weight bias as experienced by overweight and obese cancer survivors in their interactions with oncology nurses and physicians. </p><p> The study findings report heavy underlying implications related to the psychosocial and cultural aspects related to the overweight and obese cancer survivor population that oncology nurses and doctors are not addressing in their clinical practice. There are strong implications related to the coexisting factors including large body size and increased risks of many types of cancer, yet often nurses and doctors fail to contemplate what constitutes health outcomes for overweight and obese cancer survivors. Findings from this study explicate and illuminate disparities within the oncological healthcare settings. Evidence from this study found oncologists simply do not &ldquo;want to get involved&rdquo; in the weight-related implications of cancer. One participant called it a disservice and others simply described it as ignoring the <i>elephant in the room</i>. Additionally, the study findings discovered emerging themes denoting the <i>participants&rsquo; positive experiences</i> with their cancer care. </p><p> The current study advanced the understanding of how overweight and obese cancer survivors experience oncology health care. Given the prevalence of obesity in the U. S. and permeation of weight bias throughout the healthcare industry, meaningful remedies are needed to protect patients against weight bias. Findings may be used to further the state-of-the-knowledge by informing oncology healthcare nurses and physicians of tactics to change current practice to include culturally sensitive, holistic, and respectful delivery of care for the overweight and obese cancer survivor.</p>
28

Fibroblast growth factor 8 as a model of androgen receptor mediated carcinogenesis in human prostate cancer

Gnanapragasam, Vincent Jeyaseelan January 2002 (has links)
No description available.
29

An investigation of the experience of patients with oral and oropharyngeal cancer : from diagnosis to three months post treatment

Shepherd, Karen Louise January 2002 (has links)
No description available.
30

Some effects of two drugs on lysosomal enzymes and their potential value as antimetastatic agents in the treatment of cancer

Stewart, P. S. January 1975 (has links)
The case for the involvement of lysosomal enzymes in the metastatic spread of cancer has been examined. A study of the effects of two potentially inhibitory compounds on a selection of these enzymes has been made both in vivo and in vitro. The two compounds, glucosaccharo-1,4-lactone (GSL) and the sodium salt of 1-(3-benzamino-4-methylbenzamido)-naphthalene-4,6,8-trisulphonic acid (Suramin), have been tested for their effects on hydrolytic lysosomal enzymes. GSL is a very powerful and specific inhibitor of beta-glucuronidase (BGD), (E.C.3.2.1.31): The Ki of this inhibitor was found to be in the order of 10 to 10 M, depending on the enzyme source. Suramin, though a less powerful inhibitor, has been shown to inhibit BGD, acid phosphatase (APT) (E.C.3.1.3.2) and N-acetylneuraminidase (E.C.3.2.1.18), while showing a less marked effect on aryl sulphatase (E.C.3.1.6.1.). In order to determine the effects of these compounds in vivo, experiments were made to observe the effect of GSL and Suramin on lysosomal enzyme activity and the composition of liver after 24-hour and 4-week administrations. Suramin, which appeared to have the more profound influences on the lysosomal enzymes and which, according to the literature, is metabolically inert, was also tested for its effects on the Ehrlich ascites tumour (EAT) and on involution of the rat uterus. The drug's effect on EAT was dramatic: tumour development was markedly inhibited and levels of BGD, APT and N-acetyl-neuraminidase activity were reduced to those found in normal, healthy animals. The influence of these enzymes on EAT cell surfaces is discussed in relation to surface electrical charges and intercellular binding of malignant cells. The effect of Suramin on rat uterus involution was also marked: the rate of involution was reduced, BGD and APT activities were lowered, and the rate of change found in tissue proteins was modified. The significance of these findings is discussed and further relevant studies are suggested which might contribute to a clearer understanding of the process of metastasis and to a prediction of the usefulness of these compounds as antimetastatic agents.

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