Platelets have been shown to be a main contributor to thrombus formation in stenotic arteries leading to acute coronary syndromes. It is thought that increased activation and adhesion of platelets under variable shear and complex flow conditions contribute to thrombosis. The objective of this work was to evaluate the relationship between asymmetric stenosis hemodynamics and platelet adhesion using in-vitro models developed to properly simulate physiological conditions. In this study, platelet rich plasma was circulated through stenotic and straight coronary artery models. Adhesion results were obtained by post-perfusion fluorescent labelling and imaging of adhered platelets. Analysis of platelet area coverage has shown maximum adhesion occurs in the distal region of the stenosis. Most likely this is due to increased exposure time of platelets to the wall of the recirculation zone following the stenosis and that exposure being directly after a period of high shear stress. This result gives us a better understanding of the importance of both shear and flow conditions in coronary artery thrombosis.

Peripherin is a type III intermediate filament protein that is predominately expressed in the peripheral nervous system and in subsets of efferent projections in the central nervous systems. While the exact role of peripherin remains unclear, it is found upregulated after traumatic neuronal injury and in the devastating neurodegenerative disease amyotrophic lateral sclerosis (ALS). Interestingly, peripherin overexpressing transgenic mice succumb to motor neuron disease with pathological hallmarks reminiscent of those found in ALS. Pathological peripherin abnormalities occur with high frequency in both familial and sporadic forms of ALS, with peripherin found associated with the majority intracellular inclusions present within degenerating motor neuron populations. The findings of peripherin mutations in sporadic ALS have reinforced the importance of peripherin as a prospective etiological or propagative factor of disease pathogenesis. Surprisingly, inherited peripherin gene mutations have not been identified; as such, understanding the post-transcriptional mechanism at which peripherin imparts its effect(s) is considered a key goal and represents a pathological point-of-convergence for an otherwise complex, multifaceted disease. Prior to the commencement of this work, our group identified the presence of an abnormal peripherin alternative splice variant upregulated in ALS. In doing so, we consistently observed the presence of a second peripherin species of ~45 kDa on immunoblots of cell lysates derived from full-length peripherin transfections. Here, we identified this protein as a constitutively expressed isoform, termed Per-45, that arises from alternative translation and that is required for normal filament assembly: changes to the normal isoform expression pattern are associated with malformed filaments and intracellular inclusions. In lieu of the possibility of distinct peripherin intra-isoform associations, we identified isoform-specific expression and ratio changes in traumatic neuronal injury, in mouse models of motor neuron disease, and in ALS. Finally, we explored the interrelationships between peripherin isoform expression, protein aggregation, and neuritic outgrowth by linking these phenotypes with major pathogenic features associated with ALS, including in vitro models of oxidation, glutamate excitotoxicity, and neuroinflammation. Overall, this thesis provides exciting new insight into our knowledge of basic IF biology and the role of peripherin isoforms in injury and in motor neuron disease.

Despite the growing number of mobile devices equipped with multiple networking interfaces, they are not using multiple available networks in parallel. The simple network selection techniques only allow for single network to be used at a time and switching between different networks interrupts all existing connections. This work presents system that improves network connectivity in presence of multiple network adapters, not only through better network handovers, smarter network selection and failure detection, but also through increased bandwidth offered to the device over aggregated channels. The biggest challenge such a system has to face is the heterogeneity of networks in mobile environment. Different wireless technologies, and even different networks of the same type offer inconsistent link parameters like available bandwidth, latency or packet loss. The wireless nature of these networks also means, that most of the parameters fluctuate in unpredictable way. Given the intended practicality of designed system, all that complexity has to be hidden from both client-side applications and from the remote servers. These factors combined make the task of designing and implementing an efficient solution difficult. The system incorporates client-side software, as well as network proxy that assists in splitting data traffic, tunnelling it over a number of available network interfaces, and reassembling it on the remote side. These operations are transparent to both applications running on the client, as well as any network servers those applications communicate with. This property allows the system to meet one of the most important requirements, which is the practicality of the solution, and being able to deploy it in real life scenarios, using network protocols available today and on existing devices. This work also studies the most critical cost associated with increased data processing and parallel interface usage - the increase in energy usage, which needs to remain within reasonable values for this kind of solution being usable on mobile devices with limited battery life. The properties of designed and deployed system are evaluated using multiple experiments in different scenarios. Collected results confirm that our approach can provide applications with increased bandwidth when multiple networks are available. We also discover that even though per-second energy usage increases when multiple interfaces are used in parallel, the use of multi-interface connectivity can actually reduce the total energy cost associated with performing specific tasks - effectively saving energy.

Most crude oils contain traces of vanadyl porphyrins within their asphaltene fraction. Although these metals are only present in trace quantities, they have a significant detrimental impact on crude oil processing units; therefore, their selective removal is highly desirable. The current work studied the interaction of these vanadyl porphyrins with asphaltenes using two approaches: 1) equilibrium solubility measurements of model porphyrins and 2) membrane diffusion measurements in dilute solution. Solubility measurements with model porphyrins showed that simple model porphyrins fit the operational definition for asphaltenes, exhibiting negligible solubility in n-heptane and orders of magnitude higher solubility in toluene. Measurement of the melting point properties enabled modeling of their solubility behaviour and showed that simple models incorporating solubility parameters (Regular solution and Flory-Huggins) were not capable of describing the observed behaviour. Diffusion measurements were done using model vanadyl porphyrins, asphaltenes, and petroporphyrins in toluene using a stirred diffusion cell equipped with ultrafiltration membranes (Ultracel YM and Anopore). The pore sizes were varied between 3-20 nm to retain aggregates while allowing free molecules to diffuse. The permeate was continuously monitored using in situ UV/Visible spectroscopy. These experiments determined that the size of the asphaltene aggregates at 1 g/L in toluene at 25C were in the range of 5-9 nm. An increase in temperature results in an increase in asphaltene mobility but does not reduce the size of the asphaltene structures below 5 nm. Likewise, a decrease in concentration to 0.1 g/L did not result in a decrease in size. It was also observed that the exclusion of a large portion of the total asphaltenes by pores < 5 nm eliminates the absorbance of visible light (>600 nm) indicating the presence of Rayleigh scattering for the aggregated species in solution. The petroporphyrins are larger than the model vanadyl porphyrins as indicated by pore hindrance effects within smaller pores. An increase in temperature results in an increase in petroporphyrin mobility, although decreasing the asphaltene concentration does not. The mobility of the vanadyl petroporphyrins is affected by the origin of the sample (Safaniya, Venezuela, Athabasca) and is therefore not universal. / Chemical Engineering

Catheter-associated urinary tract infection (CAUTI) is one of the most common nosocomial infections and is caused by a range of different uropathogens, particularly by uropathogenic Escherichia coli (UPEC). Amongst the different virulence factors, biofilm formation and bacterial aggregation, often mediated by cell surface structures such as fimbriae, are common traits among uropathogens that cause CAUTI. In this study, a collection of UPEC isolates were screened for virulence genes and phenotypes associated with urinary tract infections such as biofilm formation and mannose-sensitive haemagglutination. Two strains, E. coli MS2027 (which formed a strong biofilm) and E. coli M184 (which aggregated strongly) were analysed in detail to determine the molecular mechanisms associated with these phenotypes. Transposon mutagenesis of E. coli MS2027 identified type 3 fimbriae as the factor responsible for its strong biofilm growth. Further screening revealed the presence of type 3 fimbriae in uropathogenic Citrobacter freundii, Citrobacter koseri, Klebsiella oxytoca, Klebsiella pneumoniae and other E. coli. Phylogenetic analysis of the type 3 fimbrial (mrkABCD) genes from these strains revealed they clustered into five distinct clades (A-E) ranging from one to twenty-three members. The majority of the sequences grouped in clade A, which was represented by the mrk gene cluster from the genome sequenced K. pneumoniae strain MGH78578. We demonstrated that type 3 fimbriae are functionally expressed by different Gram negative nosocomial pathogens and present evidence to suggest that they contribute significantly to catheter colonisation. The type 3 fimbrial genes from E. coli MS2027 were found to be located on a conjugative plasmid. Sequencing and annotation revealed that this 42,644 bp plasmid, named pMAS2027, contains 58 putative genes. Bioinformatic analysis identified pMAS2027 as an incompatibility X (IncX1) plasmid. Plasmid pMAS2027 contained genes encoding two important virulence factors, type 3 fimbriae and a type IV secretion (T4S) system. The biofilm ability was solely based on the expression of type 3 fimbriae and not the T4S system. The T4S system, however, accounted for the conjugative ability of pMAS2027. Differential tagging with fluorescent reporter genes demonstrated conjugative transfer of pMAS2027 between cells during biofilm growth. Finaly, transposon mutagenesis of E. coli M184 revealed a number of putative genes potentially responsible for bacterial aggregation. Of these, genes involved in the synthesis of the enterobacterial common antigen (ECA) were shown to be associated with an aggregation phenotype.

Copies of author's previously published articles inserted. / Bibliography: leaves 267-303. / xviii, 304 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Experiments described in the thesis address the anti-aggregatory effects and mechanism of action of the prophylactic anti-anginal agent perhexiline maleate. In particular, it was sought to examine if perhexiline had an anti-aggregatory effect which may contribute to its proven therapeutic efficacy. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 2000

Catheter-associated urinary tract infection (CAUTI) is one of the most common nosocomial infections and is caused by a range of different uropathogens, particularly by uropathogenic Escherichia coli (UPEC). Amongst the different virulence factors, biofilm formation and bacterial aggregation, often mediated by cell surface structures such as fimbriae, are common traits among uropathogens that cause CAUTI. In this study, a collection of UPEC isolates were screened for virulence genes and phenotypes associated with urinary tract infections such as biofilm formation and mannose-sensitive haemagglutination. Two strains, E. coli MS2027 (which formed a strong biofilm) and E. coli M184 (which aggregated strongly) were analysed in detail to determine the molecular mechanisms associated with these phenotypes. Transposon mutagenesis of E. coli MS2027 identified type 3 fimbriae as the factor responsible for its strong biofilm growth. Further screening revealed the presence of type 3 fimbriae in uropathogenic Citrobacter freundii, Citrobacter koseri, Klebsiella oxytoca, Klebsiella pneumoniae and other E. coli. Phylogenetic analysis of the type 3 fimbrial (mrkABCD) genes from these strains revealed they clustered into five distinct clades (A-E) ranging from one to twenty-three members. The majority of the sequences grouped in clade A, which was represented by the mrk gene cluster from the genome sequenced K. pneumoniae strain MGH78578. We demonstrated that type 3 fimbriae are functionally expressed by different Gram negative nosocomial pathogens and present evidence to suggest that they contribute significantly to catheter colonisation. The type 3 fimbrial genes from E. coli MS2027 were found to be located on a conjugative plasmid. Sequencing and annotation revealed that this 42,644 bp plasmid, named pMAS2027, contains 58 putative genes. Bioinformatic analysis identified pMAS2027 as an incompatibility X (IncX1) plasmid. Plasmid pMAS2027 contained genes encoding two important virulence factors, type 3 fimbriae and a type IV secretion (T4S) system. The biofilm ability was solely based on the expression of type 3 fimbriae and not the T4S system. The T4S system, however, accounted for the conjugative ability of pMAS2027. Differential tagging with fluorescent reporter genes demonstrated conjugative transfer of pMAS2027 between cells during biofilm growth. Finaly, transposon mutagenesis of E. coli M184 revealed a number of putative genes potentially responsible for bacterial aggregation. Of these, genes involved in the synthesis of the enterobacterial common antigen (ECA) were shown to be associated with an aggregation phenotype.

Catheter-associated urinary tract infection (CAUTI) is one of the most common nosocomial infections and is caused by a range of different uropathogens, particularly by uropathogenic Escherichia coli (UPEC). Amongst the different virulence factors, biofilm formation and bacterial aggregation, often mediated by cell surface structures such as fimbriae, are common traits among uropathogens that cause CAUTI. In this study, a collection of UPEC isolates were screened for virulence genes and phenotypes associated with urinary tract infections such as biofilm formation and mannose-sensitive haemagglutination. Two strains, E. coli MS2027 (which formed a strong biofilm) and E. coli M184 (which aggregated strongly) were analysed in detail to determine the molecular mechanisms associated with these phenotypes. Transposon mutagenesis of E. coli MS2027 identified type 3 fimbriae as the factor responsible for its strong biofilm growth. Further screening revealed the presence of type 3 fimbriae in uropathogenic Citrobacter freundii, Citrobacter koseri, Klebsiella oxytoca, Klebsiella pneumoniae and other E. coli. Phylogenetic analysis of the type 3 fimbrial (mrkABCD) genes from these strains revealed they clustered into five distinct clades (A-E) ranging from one to twenty-three members. The majority of the sequences grouped in clade A, which was represented by the mrk gene cluster from the genome sequenced K. pneumoniae strain MGH78578. We demonstrated that type 3 fimbriae are functionally expressed by different Gram negative nosocomial pathogens and present evidence to suggest that they contribute significantly to catheter colonisation. The type 3 fimbrial genes from E. coli MS2027 were found to be located on a conjugative plasmid. Sequencing and annotation revealed that this 42,644 bp plasmid, named pMAS2027, contains 58 putative genes. Bioinformatic analysis identified pMAS2027 as an incompatibility X (IncX1) plasmid. Plasmid pMAS2027 contained genes encoding two important virulence factors, type 3 fimbriae and a type IV secretion (T4S) system. The biofilm ability was solely based on the expression of type 3 fimbriae and not the T4S system. The T4S system, however, accounted for the conjugative ability of pMAS2027. Differential tagging with fluorescent reporter genes demonstrated conjugative transfer of pMAS2027 between cells during biofilm growth. Finaly, transposon mutagenesis of E. coli M184 revealed a number of putative genes potentially responsible for bacterial aggregation. Of these, genes involved in the synthesis of the enterobacterial common antigen (ECA) were shown to be associated with an aggregation phenotype.

Techn. Universiẗat, Diss., 2005--Darmstadt.

Universiẗat, Diss.--Dortmund, 2007.