Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Timothy A. Cross, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed June 9, 2006). Document formatted into pages; contains xv, 98 pages. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 69-72).

Thesis (Ph. D.)--Miami University, Dept. of Chemistry and Biochemistry, 2007. / Title from second page of PDF document. Includes bibliographical references.

The status of the myocardial 'high energy phosphate' metabolism is a sensitive marker of the occurrence and progression of heart failure. Magnetic resonance spectroscopy enables non-invasive, direct and potentially quantitative measurements of the phosphate containing metabolites present in the human myocardium. This thesis is primarily concerned with the creation of measurement techniques for cardiac phosphorus magnetic resonance spectroscopy (³¹P-MRS) at the 7 tesla field strength. Chapter 1 provides an overview of the physical basis of magnetic resonance spectroscopy, the myocardial high energy phosphate metabolism, and the clinical relevance of the technique. Chapter 2 describes the advantage of 7 tesla scanners over lower field strengths. The radio frequency coil hardware is characterised experimentally. The multivoxel spectroscopy methods used throughout the thesis are described. Chapter 3 details the implementation of an open source spectroscopy fitting program. It is validated against previous closed-source implementations. The program's use is demonstrated in several clinical studies of heart failure, and to improve a previously implemented ¹H spectroscopy coil combination method. In Chapter 4 the measurement of inorganic phosphate in the presence of overlapping peaks is attempted. Suppression of overlapping peaks, originating from the blood, is tried using B_o gradients, then saturation transfer. The myocardial pH of hypertrophic cardiomyopathy patients is measured. Chapter 5 describes the effect of creatine kinase catalysed chemical exchange on the ³¹P-MRS spectrum. A survey of methods suitable for measuring creatine kinase kinetics at 7 tesla is made. Multi-parametric fitting of variable repetition time saturation transfer data is explored in simulation and experiment. Chapter 6 describes the re-implementation and extension, for dynamic measurements, of the triple repetition time saturation transfer method for two clinical studies at 3 tesla. The creatine kinase forward rate constant is measured in heart failure and healthy cohorts, at rest, and during cardiac stress. In Chapter 7 a Bloch-Siegert B₁ mapping sequence is implemented for ³¹P-MRS. An optimal Bloch-Siegert method for X-nuclear spectroscopy is calculated. B₁maps are validated in skeletal muscle and collected in 5 volunteer's hearts. Chapter 8 uses the Bloch-Siegert B₁ mapping sequence and the four angle saturation transfer method to implement creatine kinase rate measurement at 7 tesla. The first 3D localised creatine kinase rate measurements in the human myocardium are achieved in 10 volunteers.

1H-Magnetic Resonance Spectroscopy (MRS) is a MRI paradigm that allows the levels of specific metabolites to be estimated in vivo [1]. This means that insights into the biochemical changes associated with a rare genetic change that raises the risk of mental disorders, and the impact of having a mental disorder, can potentially be made. In this study the levels of glutamate and N-acetyl-aspartate (NAA) were measured at 3T field strength in three separate voxels: right dorsolateral prefrontal cortex (DLPFC), left DLPFC and the anterior cingulate cortex (ACC). This thesis reports that members of a family that carry a unique t(1;11)(q42.2;q14) translocation that affects DISC1 have a substantially raised risk of developing a range of mental disorders, including bipolar affective disorder, schizophrenia and depression. A genetic change that leads to an increase in the susceptibility to a range of mental disorders is in line with other genetic studies that have been recently reported [2, 3]. The translocation was associated with a significant reduction in right DLPFC glutamate (mean difference= -2.11, CI= -0.24: -3.98, p=0.029) and left DLPFC NAA (mean difference= -1.97, CI= -0.34: -3.61, p=0.020). Changes in these metabolites offer some support to studies in cells and rodents trying to understand the impact of the t(1;11) translocation. More specifically the results offer support to studies that have linked alterations in DISC1's molecular biology to changes in glutamate receptors and mitochondrial function [4-6]. The results need to be interpreted with some caution due to the small sample size and the lack of a significant effect in the bilateral DLPFCs. People with a major mental disorder were also found to have significantly lower levels of glutamate in the left DLPFC (F=3.16, p=0.047). When compared to controls the reductions were significant in the people with a diagnosis of schizophrenia (mean difference= -0.86, CI= -0.19: -1.51, p=0.012), but not in people with bipolar affective disorder. Glutamate levels were significantly correlated with negative symptoms in people with schizophrenia (SANS r= -0.44, CI= -0.07: - 0.70, p= 0.024). The effect of experiencing depressive symptoms was also evaluated due to support for a link in previous studies [7, 8]. Whist the participants were not recruited due their experience of depressive symptoms, metabolite levels were found to be significantly associated with depressive symptoms in all participants with a mental disorder (all three voxels, both NAA and glutamate p < 0.05). The experience of depressive symptoms is not the same experiencing a depressive episode though, and further work may offer more insights into the association between metabolite changes and experience of depression. These findings provide insights into the relationship between diagnosis, current psychopathology and genetic risk in major mental disorders. The thesis provides some support that MRS imaging can be used to try understand neurobiological changes that are associated a genetic change, which is in turn linked to range of mental disorders. Interpreting the results of MRS imaging studies in humans remains challenging due to the complexity of the molecular biology that underpins the estimated metabolite levels, but where there has been a wide range of translational study into a specific protein (or genetic change) MRS may offer further information to help understand any effect in vivo.

The pathophysiology of traumatic brain injury (TBI) includes perturbations to energy metabolism. Improving our understanding of cerebral energy metabolism will lead to strategies that improve clinical outcomes. For the studies in my thesis I used microdialysis to deliver carbon-13 labelled substrates to the human brain. I combined this with nuclear magnetic resonance (NMR) spectroscopy of interstitial fluid sampled from the brain to interrogate glucose, lactate and tricarboxylic acid (TCA) cycle metabolism. Study I: I defined the optimal parameters for quantitative proton and carbon-13 NMR of cerebral microdialysates. Study II: I measured baseline microdialysate metabolite concentrations for brain and muscle and investigated the influence of muscle activity and cerebral catheter placement in grey or white matter on metabolite concentrations. Study III: I used 1,2-13C2 glucose to measure glycolysis and pentose phosphate pathway activity. Glycolysis is the dominant lactate-producing pathway but the pentose phosphate pathway also contributes and is increased in some TBI patients. Study IV: I used arterio-venous gradients to measure glucose and lactate delivery to the brain. There are periods after injury when lactate is imported from the circulation despite relatively high brain lactate levels suggesting up-regulation of lactate transport. Study V: I followed the metabolism of 3-13C lactate and demonstrated that lactate is metabolised by the TCA cycle. This occurs in both normal and injured brain but not in muscle. Study VI: I used 2,3-13C2 succinate to investigate the role of the TCA cycle in producing metabolites that are exported into the interstitium. The TCA cycle is found to be a source of lactate. Succinate delivered to the brain improves redox and enhances glutamate uptake into cells. The implications of the findings in my thesis on existing knowledge of cerebral metabolism are discussed. Strategies that might potentiate cerebral metabolism and improve clinical outcomes are suggested.

Alzheimer’s disease (AD) is a progressive neurodegenerative disease resulting in alterations in memory, language, executive function and emotional behaviour. Although it can be characterised by symptoms, by the time they arise significant pathological alterations have already emerged in the central nervous system, namely increased amyloid plaques, neurofibrillary tangles and neuronal loss. Despite known pathological hallmarks the exact aetiology of AD is poorly understood and no current treatments are available. However, there is growing interest in the role of neuroinflammation in AD, with increases observed in the early stages of disease and with disease progression. Moreover, it has been suggested that peripheral inflammation can influence neuroinflammation and worsen neurodegeneration. Using Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRS) we can non-invasively measure biomarkers of neuroinflammation and degeneration allowing multi-modal investigation of its role in normal aging and AD. Considering this the objectives of this study were to (i) Use PET and MRS to investigate neuroinflammatory and metabolite alterations in transgenic (TG) models of AD and their wildtype (WT) animals. (ii) Assess rates of cognitive decline in these models using memory based tests. (iii) Investigate relatively new TgF344AD rat as an AD model by characterising younger time-points than previously reported. (iv) Investigate the contribution of peripheral inflammation on AD progression. PET and MRS imaging was carried out longitudinally in the APPswe×PS1de9 mouse. Neuroinflammation was confirmed ex vivo and cognitive ability was assessed by behavioural tests. Results revealed significantly increase hippocampal and thalamic neuoinflammation in old TG mice as assessed by [18F]DPA-714 PET and supported by immunohistochemistry. Reduced neuronal marker N-acetlyaspartate was seen with age and was exacerbated in the TG mice. Accelerated cognitive decline was also seen in TG mice. PET and MRS imaging was carried out at 6 and 12 months in the TgF344AD model, which expresses amyloid and tau pathology as well as neuronal loss. No cognitive decline was observed in TG rats; however increased anxiety behaviour was seen. Increased [18F]DPA-714 PET was observed as an effect of gene in the thalamus at 6 months and the hypothalamus at 12 months. Increases in glutamate were seen with age in the TG rats but not the WTs. Increased inflammation and metabolite alterations were seen with aging. The effect of peripheral urinary tract infection (UTI) on cognition and imaging out was assessed. Imaging was carried out prior to and after re-current UTI. Infection induced cognitive decline in infected TG but not WT rats. Infection had an increasing effect on hypothalamic neuroinflammation in WT rats but a decreasing effect on TG rats, which masked the original gene differences. This thesis is set out in the alternative format with each experimental study represented as a chapter. Results in this thesis implicate neuroinflammation in AD development and progression. In addition, we report systemic infection-CNS interactions accelerating cognitive decline in AD and highlight the importance of understanding the effects of comorbidities in disease.

Abstract The present thesis describes the development of a novel method, referred to as xenon porometry, for the determination of the structural properties of porous materials by means of xenon NMR spectroscopy. The method exploits the high sensitivity of the chemical shift of the ¹²⁹Xe isotope to its local environment. The purpose of the medium added to the sample is to slow down the diffusion of xenon so that the NMR signal of a xenon atom is characteristic of the properties of one pore, and the signals of all the atoms in the sample represent the distribution of the properties. Two types of porous materials (controlled pore glasses and silica gels) with well-known properties and three different media (acetonitrile, cyclohexane, and naphthalene) were used in the studies. The behavior of the medium and dissolved xenon at different temperatures around the melting point of the medium was explained. By varying the pore size of the material, three different correlations that make it possible to measure the pore sizes of unknown materials were experimentally determined. The chemical shift of xenon inside pockets built up in the pores during solidification of the medium turned out to be especially sensitive to pore size, and this correlation makes it possible to determine the pore size distribution. The curious behavior of the chemical shift as a function of pore size was explained by using a model based on the fast exchange between xenon adsorbed on the walls of the pockets and free xenon in the middle of the pockets. It was also proved that the porosity of the materials can be determined by comparing the intensities of two signals originating from xenon dissolved in a liquid medium. A comparison of the xenon porometry method with other methods used for pore size characterization leads to the following conclusions: The range of applications of the method is relatively wide, the measurements are fast and easy to do, the analysis of the spectra is simple on the basis of the information presented in this thesis, and the properties of the materials can be extracted from the spectral data with basic mathematical conversions. Because there are several different types of correlations available in the same spectra that represent the properties of the porous material, the complementary information of all the correlations make it possible to obtain a picture of the structures of very complex systems.

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