Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Feb. 17, 2009). PDF text: 105 p. : ill. (some col.) ; 3 Mb. UMI publication number: AAT 3328258. Includes bibliographical references. Also available in microfilm and microfiche formats.

A multidisciplinary hypothesis testing approach is adopted to investigate the intraspecific relationships, and venom evolution within the polytypic species, Crotalus viridis, in western North America. A molecular phylogeny is reconstructed from mitochondrial cytochrome b (678 bp) and NADH dehydrogenase subunit 4 (ND4; 669 bp) DNA sequence information. The phylogeny is not concordant with the conventional subspecies categories, but shows strong geographical structuring corresponding to the major geographic regions of the western U. S. The basal split gives rise to two lineages (5.1-6.4% sequence divergence) corresponding to haplotypes east and west of the Rocky Mountains. Within the western lineage, Crotalus viridis cerberus forms a sister group to the other western haplotypes, and appears to have a long, independent evolutionary history. Multivariate morphometric analysis also reveals regional structuring. Clear eastern and western forms are apparent, although these populations are not totally reproductively isolated. North-south clinal variation in morphology is found among populations east of the Rocky Mountains between Montana and Arizona. Among the western forms, there is clearly a zone of intergradation between the Great Basin and Pacific Coast forms, represented by a morphological cline in Idaho. Clinal variation was also found between the northern and southern Pacific Coast forms. Venom evolution is of interest in C. viridis, since C. v. concolor is the only subspecies of C. viridis to secrete a high toxicity PLA2 phospholipase (Concolor toxin) in its venom in adulthood. Isoelectric focusing of venom proteins revealed 14 variable bands, of which only one was unique (pI 8.52) to C. v. concolor. Principal coordinates analysis revealed three main venom types, corresponding to the Pacific Coast, C. v. concolor, and the remaining populations respectively. However, C. v. concolor tends to cluster with the latter group when the unique venom band is excluded from the analysis. 1 Phylogeny, rather than ecology, appears to be an important cause of geographic variation in both morphology and venom, as revealed by partial Mantel tests. Many characters are influenced by both phylogeny and ecology, however, probably because many causes of variation are intercorrelated. It is suggested that selection on venom composition probably varies according to the function of individual components. The systematics of Crotalus viridis complex is reviewed according the criteria of the general lineage concept of species. Combined evidence from the molecular phylogeny and morphology (and to a lesser extent venom) suggests the existence of three species, to be named Crotalus viridis, Crotalus cerberus, and Crotalus oreganus (including the subspecies C. o. oreganus, C. o. lutosus and C. o. concolor).

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The extent of genetic structuring of a population results from a balance of forces producing local genetic differentiation, and counter-forces producing genetic homogeneity. An understanding of these forces is essential when investigating evolutionary processes in a species. It has been predicted that, when populations experience severe reductions in size, they lose genetic variability. Small population size may occur as a consequence of founder events, such as with the introduction and spread of a pest species. The predictions as described were examined by studying the molecular evolution and population genetics of European rabbit (Oryctolagus cuniculus (L)) populations in Australia, using variation in mitochondrial DNA control region sequences. The results suggest that there is a higher rate of gene flow within populations in semi arid/arid areas, which is attributable to the extreme environmental heterogeneity found in these areas and may be best explained by a process whereby local populations becoming extinct and are recolonised by individuals drawn from other populations. / Master of Science (Hons)

The production of reactive oxygen species by mitochondria is implicated in the mitochondrial dysfunction associated with a range of diseases and ageing. In contrast, reactive oxygen species produced by mitochondria are involved in redox signalling pathways necessary for modulating a number of cell processes. Mitochondrially targeted antioxidants comprised of an antioxidant moiety linked to a lipophilic triphenylphosphonium cation have recently been used to decrease reactive oxygen species-mediated oxidative damage to mitochondria and to investigate the role of mitochondrial reactive oxygen species in redox signalling. These lipophilic cations are selectively accumulated by mitochondria within cells due to the mitochondrial membrane potential. This thesis presents the synthesis and characterization of mitochondrially targeted antioxidant superoxide dismutase and thiol peroxidase mimetics. A mitochondrially targeted derivative of the Mn(II) macrocycle SOD mimetic M40403 (MitoSOD) was synthesized by Mn(II) template synthesis of a chiral tetraamine component and a triphenylphosphonium derivative of 2,6-pyridinedialdehyde. Racemic tetraamine was synthesized by mono-protection of racemic diamine followed by reductive amination of glyoxal and deprotection of di-protected tetraamine but overall this was found to be less efficient than a reported method based on trityl protection. The synthesis of the triphenylphosphonium derivative of 2,6-pyridinedialdehyde involved substitution of protected 4-bromo-2,6-pyridinedialdehyde by the thiolate of 3-mercaptoproanol followed by simultaneous deprotection and alkyl bromide formation, and triphenylphosphine substitution of the thioalkyl bromide substituent. MitoSOD was found to be more lipophilic than M40403 and was kinetically stable to dissociation to Mn(II) and macrocyclic ligand at physiological pH. Pulse radiolysis kinetic studies indicated both MitoSOD and M40403 catalyse the dismutation of superoxide. Fast conductivity and spectrophotometric measurements indicated the mechanism of catalysis involved reaction of the Mn(II) centre with superoxide to give a Mn(III)-peroxide intermediate which reacted with further superoxide to give the parent Mn(II) macrocycle. MitoSOD was significantly accumulated by mitochondria and this was dependent to some extent on the mitochondrial membrane potential. In addition, MitoSOD appeared to react with a product of mitochondrial succinate respiration. A mitochondrially targeted derivative of the organoselenium thiol peroxidase mimetic ebselen (Mitoebselen) was synthesized by O-alkylation of a phenolic ebselen derivative with a triphenylphosphonium derivative of an alkyl iodide. Reaction of excess triphenylphosphine with an ebselen derivative containing an alkyl iodide substituent resulted in substitution of iodide and, unexpectedly, reduction of the isoselenazole moiety to the diselenide redox form. Mitoebselen and its diselenide were both readily reduced to a selenol by an excess of the physiological thiol glutathione. Reaction of the selenol with excess peroxide generated the diselenide, possibly via reaction of unreacted selenol with Mitoebselen formed from a selenenic acid intermediate or with selenenic acid directly. Mitoebselen and its diselenide were both oxidized by excess peroxide to a selenoxide but these reactions were much slower than those between selenol and peroxides, and those between Mitoebselen or its diselenide with glutathione. Together these studies suggested cyclic pathways other than a selenolisoselenazole-selenol cycle could be involved in Mitoebselen or ebselen-catalysed thiol peroxidation.

Thesis (M.S.) in Marine Biology--University of Maine, 2004. / Includes vita. Includes bibliographical references (leaves 70-79).