published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

No description available.

No description available.

Our study shows that the secretion of a major glycosylated, phosphoprotein with a molecular weight of 69kDa (pp69) is a specific marker for non-transformed NRK-49F cells. Antibody raised against pp69 recognizes, in addition to pp69, another major phosphoprotein with a molecular weight of 62kDa (pp62) secreted by RR1022 and spontaneously transformed NRK-49F cells (spt-NRK-49F). Immunoprecipitation of total cell lysates from both NRK-49F and RR1022 cells with anti-pp69 antibody detected only pp69. Treatments with: epidermal growth factor (EGF), transforming growth factor-$ beta$ (TGF-$ beta$) retinoic acid (RA), and TPA modulate the levels of pp69 present in the conditioned media. Furthermore, TPA and EGF induce the synthesis of 3 internal peptides with molecular weights of 58, 54, and 44 kDa which appear to be pre-processed forms of pp69. / Treatment of NRK-49F cells with insulin, EGF, TGF-$ beta$, PPA, levamisole and spermine clearly demonstrate alterations in the phosphorylation of pp69, concomitant with changes in extracellular phosphatase activity.

Arterial smooth muscle cells (SMCs) from the systemic and pulmonary circulations experience a broad range of oxygen concentrations under physiological conditions. The hypoxic response, however, has been inconsistent, with both enhanced proliferation and growth arrest being reported. This variability precludes a definitive conclusion regarding the role of oxygen tension in arterial disease. In the first part of this study, we determined if hypoxia elicits different proliferative and apoptotic responses in human aortic SMCs (HASMCs) incubated under conditions which do or do not result in cellular ATP depletion and whether these effects are relevant to vascular remodeling in vivo. Gene expression profiling was used to identify potential regulatory pathways. In HASMCs incubated at 3% O2, proliferation and progression through G1/S interphase are enhanced. Incubation at 1% O2 reduced proliferation, delayed G1/S transition, increased apoptosis and cellular ATP levels were reduced. In aorta and mesenteric artery from hypoxia exposed rats, both proliferation and apoptosis are increased after 48hrs. p53 and p21expression is differentially affected in HASMCs incubated at 1% and 3% O2. Hypoxia induces a state of enhanced cell turnover, conferring the ability to remodel the vasculature in response to changing tissue metabolic needs while avoiding the accumulation of mutations that may lead to malignant transformation or abnormal vascular structure formation. A unifying hypothesis in which events at the G1/S transition and apoptosis activation are coordinated by effects on p53, p21, their downstream effector genes and regulatory factors is proposed. Differences in the contractile responses of systemic and pulmonary arterial smooth muscle cells to hypoxia are well studied. Differences in proliferation and survival are anticipated because of differences in embryonal cell origin, oxygen concentrations within their respective microenvironments and in cellular energetics but these responses have not been directly compared. In the second part of the study, human pulmonary arterial SMCs (HPASMCs) proliferated at oxygen concentrations which inhibited cell growth in HASMCs. HPASMCs survived and maintained their intracellular ATP levels at levels of hypoxia sufficient to deplete ATP and induce apoptosis in HASMCs. In vivo studies in rats show proliferation and apoptosis in main or branch PASMCs only after 7 days of hypoxia. VSMCs are able to proliferate under hypoxic conditions as long as cellular ATP levels are maintained. HPASMCs have an enhanced capacity to maintain cellular energy status compared to HASMCs and hence their viability is preserved and the proliferative response predominates at lower oxygen concentrations.

Optic nerve section (ONS) is an experimental model for damage of the optic nerve associated with diseases such as glaucoma and optic neuritis. Damage to the optic nerve causes loss of retinal ganglion cells that are attached, once the cells are damaged, they are not typically replaced. Recently, Fischer and Reh (2003) found that Müller glia have the potential to adopt phenotypes and functional capabilities similar to those of retinal progenitors, a potential source of retinal regeneration. In the chick, when the specific retinal cells are targeted for damage by chemotoxins, there is widespread apoptosis but also mitotically active cells that label with retinal progenitor markers. Fischer and Reh (2002) also discovered that the combination of growth factors FGF2 and insulin is capable of stimulating the regenerative response of the Müller glia to retinal progenitor cells in chick eyes. This study was conducted to analyse damage to the ganglion cells by optic nerve section in chicks to determine the effect of age on the cell death timeline, the proliferative qualities of the retina and to see if injections of growth factors had the ability to increase the proliferation. Histological methods were used to analyse cellular changes and ultrasound to monitor eye growth. Apoptotic activity preceded retinal thinning and ganglion cell loss, indicating that ONS-related cell death is mediated at least in part by apoptotic mechanisms and age did not affect the time course, although, age did affect the eye growth changes, which may be attributed to the plasticity of the younger eyes. ONS damage elicited proliferative activity in the retina as did growth factor injections alone. The combination of ONS damage and growth factor injections increased the proliferative activity and the overall total number of cells in the ganglion cell layer. These findings can potentially lead to the development of therapeutic strategies for the preservation or restoration of retinal cells in diseased eyes.

The effects of global warming raise demands for reduced CO2 emissions, whereas at the same time the world’s need for energy increases. With the aim to resolve some of the difficulties facing today’s nuclear power, striving for safety, sustainability and waste minimization, a new generation of nuclear energy systems is being pursued: Generation IV. New reactor concepts and new nuclear facilities should be at least as resistant to diversion of nuclear material for weapons production, as were the previous ones. However, the emerging generation of nuclear power will give rise to new challenges to the international safeguards community, due to new and increased flows of nuclear material in the nuclear fuel cycle. Before a wide implementation of Generation IV nuclear power facilities takes place, there lies still an opportunity to formulate safeguards requirements for the next generation of nuclear energy systems. In this context, this thesis constitutes one contribution to the global efforts to make future nuclear energy systems increasingly resistant to nuclear material diversion attempts. This thesis comprises three papers, all of which concern safeguards and proliferation resistance in Generation IV nuclear energy systems and especially recycling facilities: In Paper I, proliferation resistances of three fuel cycles, comprising different reprocessing techniques, are investigated. The results highlight the importance of making group actinide extraction techniques commercial, due to the inherently less vulnerable isotopic and radiological properties of the materials in such processes. Paper II covers the schematic design and safeguards instrumentation of a Generation IV recycling facility. The identification of the safeguards needs of planned facilities can act as a guide towards the development of new instrumentation suitable for Generation IV nuclear energy systems. Finally, Paper III describes a mode of procedure for assessing proliferation resistance of a recycling facility for fast reactor fuel. The assessments may be used, as in this case, as an aid to maintain or increase the inherent proliferation resistance when performing facility design changes and upgrades.

Arterial smooth muscle cells (SMCs) from the systemic and pulmonary circulations experience a broad range of oxygen concentrations under physiological conditions. The hypoxic response, however, has been inconsistent, with both enhanced proliferation and growth arrest being reported. This variability precludes a definitive conclusion regarding the role of oxygen tension in arterial disease. In the first part of this study, we determined if hypoxia elicits different proliferative and apoptotic responses in human aortic SMCs (HASMCs) incubated under conditions which do or do not result in cellular ATP depletion and whether these effects are relevant to vascular remodeling in vivo. Gene expression profiling was used to identify potential regulatory pathways. In HASMCs incubated at 3% O2, proliferation and progression through G1/S interphase are enhanced. Incubation at 1% O2 reduced proliferation, delayed G1/S transition, increased apoptosis and cellular ATP levels were reduced. In aorta and mesenteric artery from hypoxia exposed rats, both proliferation and apoptosis are increased after 48hrs. p53 and p21expression is differentially affected in HASMCs incubated at 1% and 3% O2. Hypoxia induces a state of enhanced cell turnover, conferring the ability to remodel the vasculature in response to changing tissue metabolic needs while avoiding the accumulation of mutations that may lead to malignant transformation or abnormal vascular structure formation. A unifying hypothesis in which events at the G1/S transition and apoptosis activation are coordinated by effects on p53, p21, their downstream effector genes and regulatory factors is proposed. Differences in the contractile responses of systemic and pulmonary arterial smooth muscle cells to hypoxia are well studied. Differences in proliferation and survival are anticipated because of differences in embryonal cell origin, oxygen concentrations within their respective microenvironments and in cellular energetics but these responses have not been directly compared. In the second part of the study, human pulmonary arterial SMCs (HPASMCs) proliferated at oxygen concentrations which inhibited cell growth in HASMCs. HPASMCs survived and maintained their intracellular ATP levels at levels of hypoxia sufficient to deplete ATP and induce apoptosis in HASMCs. In vivo studies in rats show proliferation and apoptosis in main or branch PASMCs only after 7 days of hypoxia. VSMCs are able to proliferate under hypoxic conditions as long as cellular ATP levels are maintained. HPASMCs have an enhanced capacity to maintain cellular energy status compared to HASMCs and hence their viability is preserved and the proliferative response predominates at lower oxygen concentrations.

No description available.

Despite their undisputed importance to embryonic growth, the role of mRNA transport proteins in the developing visual system has been widely uncharacterized. Through RNA interference, this study aims to discover the function of Staufen 2 (Stau2), an mRNA transport protein, in chick eye development. When Stau2-miRNA was electroporated into the E1.5 primary optic vesicle, two days later they exhibited a reduction of eye size by 47%, whereas control miRNA did not significantly change eye size. TUNEL, β-III tubulin and BrdU staining were used to analyze the retinal apoptotic, differentiation and proliferative levels respectively, in response to Stau2 knockdown. These data suggest that the small eye is a result of a decrease in proliferation, and not cell death or pre-mature differentiation. Rescue experiments were done with each of the three Stau2 isoforms and confirmed both the direct effect of Stau2-miRNA and the involvement of these isoforms in eye development.