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Transposable elements are an almost ubiquitous feature in all three domains of life, and are a significant driver of genomic evolution. These discrete genetic elements are capable of mobilisation and amplification, which allows them to multiply. A subset of these elements, the cut-and-paste transposons, excise themselves entirely from the surrounding DNA and integrate themselves elsewhere in the genome. Hsmar1, a cut-and-paste element of the mariner transposon family, was recently investigated to examine the kinetics of the complex formation pathway. This transposase forms a dimer in solution before binding to first one transposon end, then recruiting the other. This pathway, Synapsis by Naked End Capture (S-NEC), is found in both prokaryotes and eukaryotes. Tn5, of the IS4 family, is an example of the alternative pathway, Synapsis by Protein Dimerisation (S-PD). In this pathway, the transposase is monomeric in solution. Each monomer binds to a transposon end independently, before combining to form a synaptic complex. This pathway has been seen widely in prokaryotes, but no eukaryotic elements tested to date employ it. To understand what limitations the complex formation pathway might place upon an S-PD transposase in a eukaryotic genome, the Tn5 transposase was manipulated. Forming the transposase into a single-chain dimer allowed it to mimic S-NEC, an alteration that made it hyperactive in prokaryotes and eukaryotes. As the eukaryotic genome contains chromatin, adapting the Tn5 transposase to this might overcome some of the low activity seen. The fusion of a chromatin binding domain to the transposase was not able to enhance the frequency of transposition, which may suggest that the presence of chromatin is not causing significant inhibition. The results presented in this work suggest two significant conclusions. The first is that the S-NEC reaction dynamics are significantly preferable to S-PD within eukaryotes. The second is that S-PD itself may be a system of regulation of transposition, to prevent activity levels that could be detrimental to the host.

Throughout the 1970's, the integration of computers with radiological instruments was used to improve the ability of these instruments to visualize cardiovascular anatomy. Prototype machines that relied on computer technology came to fruition as usable commercial units circa 1982. For many years prior to this commercial availability, however, the measurement of absolute arterial blood flow had been possible with the aid of computer-assisted cine film and videodensitometric time-of-flight methods. The advent of digital subtraction angiography (DSA), as computerized fluoroscopy came to be known, allowed the feasibility of routine applications of videodensitometry to be reevaluated for the case of a DSA image series used as the source of both timing and spatial information. Anatomical imaging of some arterial structures is usually adequate following intravenous injection and of highest quality after the direct arterial injection of contrast material. Simultaneously with anatomical data, timing information can be extracted from the known time of image exposure and its acquisition. This allows functional or physiological imaging to be coupled with anatomical data. In this thesis, two principle applications of DSA are discussed, i) absolute volume blood flow and ii) relative blood flow and organ perfusion. Fourier transform methods are described for the measurement of time-of-flight and compared with existing curve fitting algorithms. The methods are analysed by using statistical modelling techniques (Monte-Carlo theory), and then validated in an animal model by using calibrated electromagnetic flow probes as the Gold Standard of volume blood flow. Clinical applicability of this technique is described and discussed in the context of relative organ perfusion and contrasted with methods of absolute flow estimation. The principal conclusion, supported by the animal validation, is that the Fourier method is more accurate than existing techniques in the presence of noisy data. Nevertheless, the much simpler relative flow techniques have a useful role in routine clinical practice, as exemplified by the parametric assessment of myocardial perfusion reserve.