<strong>Aims:</strong> The purpose of the research presented in this thesis is to elucidate the mechanism of the stimulation of oxidative metabolism and contractile function that occurs in vascular smooth muscle during cerebral vasospasm (CV) after subarachnoid haemorrhage (SAH). The biochemical mechanisms leading to CV were investigated using an in vitro model of CV developed for this research. CSF (cerebrospinal fluid) from SAH patients at risk of vasospasm which stimulated oxygen consumption (CSF S ) was used to model vasospasm. The hypothesis is CSF_S contains a substance which stimulates tension generation over that of CSF_N ,(non-stimulatory cerebrospinal fluid) and also inhibits the myosin light chain phosphatase. <strong>Methods:</strong> The porcine carotid artery was used as a model for the human basilar artery. The rate of oxygen consumption (JO₂) was measured in response to CSF_S and tension generation was also examined. Various agents were used to treat or pretreat the tissue such as magnesium and andalpha;₁-adrenergic receptor agonists. Their effects on the CSF_S-induced stimulation were measured to study the mechanism of vasospasm. A myosin light chain phosphatase (MLCP) assay was developed to study the mechanisms leading to CV. <strong>Results and conclusion:</strong> Addition of CSF_S to the porcine carotid artery is a reliable and reproducible in vitro model of CV. Using this model, it was found that Mg⁺⁺ loading and andalpha;₁-adrenergic receptor agonists attenuated the vasospasm, but a non-specific endothelin antagonist had no effect. Acute addition of 12mM Mg⁺⁺ relaxed the tissue from a CSF_S induced contraction significantly and rendered the contraction rinsible. Okadaic acid (InM), a phosphatase inhibitor, had very similar effects to CSF_S because it stimulated JO₂ and slowed relaxation after a stretch. There was also significant inhibition of phosphatase caused by the CSF_S. Vasospasm appears to be caused by a combination of a contractile stimulus, and inhibition of MLCP activity.

国立情報学研究所で電子化したコンテンツを使用している。

Forage growth in the subarctic is sub-optimal due to low soil nutrient levels. Forage crops in the Yukon Territory consistently require nitrogen (N) and phosphorus fertilization to meet plant requirements. Fertilization is expensive due to transportation costs and potentially harmful to the environment so alternative, more sustainable, sources of nutrients are being sought. Alfalfa is an alternative, but there is limited knowledge in the Yukon of the benefits and management of this crop as a replacement for fertilizer N. Experiments were carried out in south central Yukon during the 2005 and 2006 field seasons to examine the potential of co-inoculation of alfalfa with N-fixing Ensifer meliloti and phosphate-solubilizing Penicillium bilaii to increase the dry matter yield and N fixation of monoculture alfalfa (Medicago sativa) cv Peace and binary mixed alfalfa with smooth bromegrass (Bromus inermis) cv Carlton or timothy (Phleum pratense) cv Climax forage swards. Interactions between alfalfa inoculation and N fertilization and late season harvest treatments were assessed. The TagTeam® inoculant from Philom Bios was used as the rhizobium source which contains both Ensifer meliloti isolate NRG-34 and Penicillium bilaii isolate PB-50. Nitrogen fixation was determined using the total plant N difference method. Alfalfa growth and nodulation was successful in the trials. Inoculation had a positive impact on N fixation, whereas urea fertilizer at 25 kg N/ha had a negative impact in most cases. In the mixed alfalfa and smooth bromegrass stand there was a positive contribution from the alfalfa in both the establishment and second year with N fixation rates of up to 14 kg/ha. In the mixed timothy and alfalfa stand the N fixation reached 35 kg/ha in the establishment year and 102 kg/ha in the second year. In the establishment year the dry matter yield and N fixation of the TagTeam® inoculated, monoculture alfalfa plots were 3.1 t/ha and 77 kg N/ha. In the second year, the unharvested inoculated alfalfa treatment yielded 3.4 t/ha with N fixation of 66 kg/ha compared to the late harvest treatment which yielded only 1.5 t/ha and an N fixation rate of 20 kg/ha. The effects of the late season harvest are startling and reflect the importance of removing grazing animals during the fall to allow plant energy reserves to accumulate in the roots. Fertilizer N replacement is possible with the seeding of alfalfa into existing hay stands or in monoculture.

Platelet-derived growth factor D-chain (PDGF-D) is the newest member of the PDGF family of mitogens and chemo-attractants; it is expressed in a wide variety of cell types, including vascular smooth muscle cells (SMCs). The molecular mechanisms regulating PDGF-D transcription are unknown. Here I investigated the effects of angiotensin II (ATIl) and IL-1 beta on the transcription of PDGF-D and changes in vascular SMCs phenotype. Primer extension analysis mapped a single transcriptional start site to the ccAG CGC motif of PDGF-D promoter. Several potential transcription factor binding sites such as SpI, Ets-1, NF-??B, IRF-1, p53, Smad4 and AP1 were located in the proximal 1168bp of the PDGF-D promoter. ATII-inducible Ets-1 and PDGF-D gene expression is mediated via H202. IL-I beta supresses PDGF-D promoter activity, mRNA and protein expression in SMCs through NF-??B p65, IRF-1 and HDAC1, which form complex in the PDGF-D promoter. This study provides the first direct link between NF-KB and the PDGF-D promoter, IRF-1 with any member of the PDGF family and a new example of HDAC mediated inhibition of gene expression. In summary, this study investigates for the first time the mechanisms mediating the transcriptional regulation of PDGF-D in vascular SMCs. This provides valuable insights into the molecular control of vascular phenotype, and opens up potential opportunities for therapeutic intervention.

Diss. (sammanfattning) Göteborg : Univ. , 2007. / Härtill 3 uppsatser.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. "August 2007" Includes bibliographical references.

Thesis (M. Med. Sc.)--University of Hong Kong, 2007.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "December, 2008." Includes bibliographical references (leaves 227-270). Online version available on the World Wide Web.

Thesis (Ph.D.) - University of St Andrews, May 2007.