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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.
1

The influence of social factors on escape responses of domestic chicks

Miller, Don Edward, January 1962 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 32).
2

Role of hypoxia and hypoxia-inducible factor-1 in tumour immune escape

Li, Xin 20 October 2010 (has links)
Previous studies revealed that, upon exposure to hypoxia, tumour cells acquire resistance to the cytolytic activity of IL-2-activated lymphocytes. The MHC class I chain-related (MIC) molecules – comprised of MICA and MICB – are ligands for the activating NKG2D receptor on Natural Killer (NK) and CD8+ T cells. MIC-NKG2D interactions lead to the activation of NK and CD8+ T cells and the subsequent lysis of the tumour cells. The study also showed that the mechanism of the hypoxia-mediated immune escape involves the shedding of MIC, specifically MICA, from the tumour cell surface. The objective of the present study was to determine whether the shedding of MICA requires the expression of hypoxia inducible factor-1 (HIF-1), a transcription factor that regulates cellular adaptations to hypoxia. Exposure to hypoxia (0.5% O2 vs. 20% O2) led to the shedding of MIC from the surface of MDA-MB-231 human breast cancer cells and DU-145 human prostate cancer cells as determined by flow cytometry. Knockdown of HIF-1α mRNA using siRNA technology resulted in inhibition of HIF-1α accumulation under hypoxic conditions as determined by Western blot analysis. Parallel study revealed that knockdown of HIF-1α also blocked the shedding of MICA from the surface of MDA-MB-231 cells exposed to hypoxia. These results indicate that HIF-1 is required for the hypoxia-mediated shedding of MICA and, consequently, that HIF-1 may play an important role in tumour immune escape. Ongoing studies aim to determine the HIF-1 target genes involved in the shedding of MICA under hypoxia. / Thesis (Master, Anatomy & Cell Biology) -- Queen's University, 2009-08-19 21:09:13.707
3

THE EFFECT OF HYPOXIA INDUCIBLE FACTOR-1 ON THE EXPRESSION OF THE COINHIBITORY LIGANDS B7-H3 AND B7-H1 IN CANCER: RELEVANCE TO CANCER IMMUNE ESCAPE

Smallwood, Chelsea 15 August 2012 (has links)
The interactions between tumour cells and cells of the immune system are important in the natural evolution of cancer, and the acquired immune system plays an integral role in cancer immune escape. B7-H3 and B7-H1 ligands provide coinhibitory signals to T cells resulting in T cell anergy or apoptosis and their expression has been shown to increase in cancer cells. Tumour hypoxia (oxygen concentration below physiological level) is a major contributor to the spread of cancer and resistance to radiation and chemotherapy. We proposed that hypoxia results in the upregulation of the B7 molecules B7-H3 and B7-H1. Furthermore, studies in our laboratory have shown that acquisition of malignant properties in tumour cells exposed to hypoxia can be inhibited by low concentrations of nitric oxide mimetic agents such as glyceryl trinitrate (GTN). Using cultured breast and prostate cancer cells, we investigated whether the hypoxia-inducible factor HIF-1α, would mediate an upregulation of these ligands. Using a mouse model, we investigated the effect of GTN on tumour growth in vivo. For the in vitro studies, we exposed MDA-MB-231 and MCF-7 breast cancer cells and DU-145 prostate cancer cells to standard culture conditions, hypoxic conditions, or 100 μM CoCl2 (stabilizes HIF-1α) for 24 hours. Our findings indicate that B7-H3 mRNA was upregulated in hypoxia (P = 0.0101). Contrary to our hypothesis, B7-H3 protein was not upregulated in hypoxia. Interestingly, increased B7-H1 protein expression correlated with increased HIF-1α expression (r2=0.48, P<0.0001), and HIF-1α bound to the hypoxia response element (HRE) of B7-H1. These results indicate a role for HIF-1α in the upregulation of B7-H1 levels in MDA-MB-231 cells. While in vitro studies indicated no effect of GTN, a study using female BALB/c mice injected with 4T1 mammary carcinoma cells resulted in a decrease in tumour volume in the GTN treated mice. Together, these results indicate a novel role for HIF-1α in the up-regulation of B7-H1 on cancer cells, thus potentially contributing to immune escape of cancer cells and additionally, a role for GTN as a possible breast cancer therapy. / Thesis (Master, Anatomy & Cell Biology) -- Queen's University, 2012-08-15 11:10:06.237
4

Amount of escape vs. no-escape training : a variable in conditioning "learned helplessness"

Ryman, Fred L. January 1973 (has links)
Four groups of rats (10 rats per group), composing an independent subjects design, were exposed to various amounts of escape training (escape contingent upon a fixed-ratio of 3 lever presses) and inescapable shook, prior to being tested on an escape task identical to the one on which they were trained. Interest was focused on the length of time required for, the number of, and the consistency of successful escapes as measures of disruption in responding. The High conditions consisted of 100 escape training trials and 200 seconds of inescapable shock while the Low conditions consisted of 5 escape training trials and 20 seconds of inescapable shock. The four possible combinations of the escape training and inescapable shock composed the four groups. A summary of the results indicated the production of learned helplessness (as measured by the amount of disruption) was not significantly effected by either the amount of escape pretraining or the amount of inescapable shook given the subjects.
5

Escapism in Euripides

Kakkos, Athanasios Tommy January 1995 (has links)
This thesis explores the form, meaning and development of the escapist theme in Euripides' tragedies. The dramatist's corpus reveals an intense preoccupation with escapism and exhibits it in a wide range of escape wishes and escape choral odes. Most of these, because they fail of their objective, point to the inability of the tragic hero to escape his or her fate as determined by the dark forces of tragedy. Escapism intensifies the well-known Euripidean element of pathos, but in some of the plays its use becomes quite sophisticated evoking irony, ambiguity and paradox. In this way, it sheds light upon the tragic event from a different perspective. In the end, however, the Euripidean oeuvre betrays a strong affirmation of reality in spite of its escapist tendencies. Euripides' innovative use of escapism is, in fact, an ingenious modification and adaptation of older poetic, and as this thesis argues, ritual forms. Finally, the pervasive presence of escapism in Euripides is not irrelevant to the wider political and social atmosphere of late fifth-century Athens.
6

A Role for ETA(253-412) in Peptide-based Delivery of Therapeutic Molecules into Cells

Broad, Amaalia 15 February 2010 (has links)
The delivery of biomolecules by cell penetrating peptides (CPPs) is an innovative therapeutic strategy. However delivery efficiency is hindered by the entrapment of CPPs in vesicles, degradation, or recycling out of cells, which limits their delivery into the cell cytoplasm and nucleus. To overcome these barriers, we investigated a bacterial protein domain derived from Pseudomonas aeruginosa, Exotoxin A (ETA, residues 253-412) that is able to exit vesicular compartments. A series of CPP-ETA(253-412) fusion proteins were constructed, expressed, and purified. Confocal microscopy and flow cytometry confirmed the internalization at 37oC of constructs containing CPPs (poly-arginine or TAT). In addition, constructs containing CPP-ETA(253-412)-eGFP were shown to relocate from endosomes to the cytosol. CPP-ETA(253-412) constructs were also able to act as carriers of DNA cargos facilitating their delivery to the cytosol. The ETA(253-412) translocation domain may prove useful for the intracellular delivery of drugs, protein therapeutics, siRNA delivery, and vaccine formulations.
7

A Role for ETA(253-412) in Peptide-based Delivery of Therapeutic Molecules into Cells

Broad, Amaalia 15 February 2010 (has links)
The delivery of biomolecules by cell penetrating peptides (CPPs) is an innovative therapeutic strategy. However delivery efficiency is hindered by the entrapment of CPPs in vesicles, degradation, or recycling out of cells, which limits their delivery into the cell cytoplasm and nucleus. To overcome these barriers, we investigated a bacterial protein domain derived from Pseudomonas aeruginosa, Exotoxin A (ETA, residues 253-412) that is able to exit vesicular compartments. A series of CPP-ETA(253-412) fusion proteins were constructed, expressed, and purified. Confocal microscopy and flow cytometry confirmed the internalization at 37oC of constructs containing CPPs (poly-arginine or TAT). In addition, constructs containing CPP-ETA(253-412)-eGFP were shown to relocate from endosomes to the cytosol. CPP-ETA(253-412) constructs were also able to act as carriers of DNA cargos facilitating their delivery to the cytosol. The ETA(253-412) translocation domain may prove useful for the intracellular delivery of drugs, protein therapeutics, siRNA delivery, and vaccine formulations.
8

Utility of envelope T cells in preventing AIDS: HIV-1 and SIV envelope-specific T cells: controlling HIV-1 and SIV infection in pigtail macaques and their utility as a T cell immunogen

Peut, Vivienne Mary January 2008 (has links)
HIV/AIDS annually kills millions of people worldwide. Those claimed by the disease are quickly replaced by those newly infected. Three times as many new infections occur globally, as patients who are likely to have access to antiretroviral therapy. We need a HIV vaccine. However, the better HIV protein to target for this vaccine in unknown. Structural proteins such as Group specific antigen (Gag) and Envelope (Env) were thought likely candidates due to viral structural proteins usually being highly conserved and constrained in their ability to mutate to escape T cell attack. To establish if Env-specific T cells could control viraemia, 2 large vaccine trials were conducted with 66 pigtail macaques participating. Also, 2 reversion trials involving 4 pigtail macaques were undertaken. Env-specific T cell epitopes were mapped in both SHIV (simian/human immunodeficiency virus) and SIV (simian immunodeficiency virus)-infected macaques using IFNγ intracellular cytokine staining and flow cytometry.
9

Escape of hydrogen from the exosphere of Mars

Bhattacharyya, Dolon 12 August 2016 (has links)
After decades of exploration, the martian neutral hydrogen exosphere has remained poorly characterized. The first measurements of this layer by Mariner 6 and 7 revealed it to be optically thick in Lyman α emission, along with a characteristic temperature that was higher than the majority of the collisional atmosphere of Mars. Further exploration revealed that the hydrogen in the martian exosphere was formed from photodissociation of water vapor by solar UV light, and that its escape can be directly linked to the escape of water from Mars. Theoretical analysis of hydrogen transport in the martian atmosphere suggested a steady escape rate limited by diffusion of hydrogen through the martian atmosphere. Subsequent missions to Mars provided a wide range of values for the temperature and density of hydrogen at Mars. It is important to determine the properties of the martian hydrogen exosphere in order to constrain the escape flux, which can then be used to calculate the total amount of water lost by Mars during its evolutionary history. In this dissertation the characteristics of the martian hydrogen exosphere are constrained using data from the Hubble Space Telescope (HST). HST observations of this layer reveal short-term seasonal changes, thereby disproving the theory of constant escape rate for H from Mars. Analysis of these datasets using a radiative transfer model constructed at Boston University revealed a large seasonal variation in the hydrogen escape flux, making it difficult to easily backtrack the martian water loss history. Results also indicate the possible presence of a superthermal population created by non-thermal processes at Mars. Exploration of the latitudinal symmetry of the martian exosphere indicates that it is symmetric above 2.5 martian radii and asymmetric below this altitude, which could be due to temperature differences between the day and night side. Finally, there are large uncertainties in determining the characteristics of the martian exosphere after decades of exploration, due to various assumptions about the intrinsic characteristics of the martian exosphere in the modeling process, degeneracy in the two modeling parameters for hydrogen -i.e. its temperature and density, unaccounted seasonal effects and uncertainties introduced from spacecraft instrumentation and viewing geometry.
10

Escapism in Euripides

Kakkos, Athanasios Tommy January 1995 (has links)
No description available.

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