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<p> Major Depressive Disorder (MDD) is a common affective disorder associated with persistent states of negative mood and selective cognitive impairments. Fronto-temporal dysregulation in MDD patients is thought to contribute to the symptoms seen in these patients.</p> <p> Based on prior evidence of structural and functional alterations in the hippocampus (Hc) and prefrontal cortex (PFC) in MDD patients, we were interested in examining the changes in cerebral function that underlie the cognitive dysfunction seen in two different MDD populations. We studied psychotropically naïve depressed patients experiencing their first treated episode (FTE) of depression, MDD patients who had experienced multiple past treated episodes (MTE) of MDD and healthy controls.</p> <p> Two functional magnetic resonance imaging studies (fMRI) were conducted. The first study used an Hc dependent process dissociation task to examine Hc activation during recollection memory. The second fMRI study examined the activation in the PFC during reward and punishment conditions of a reversal-learning paradigm. Finally, we conducted magnetic resonance spectroscopy scans to measure levels of metabolites indicative of neuronal and glial cell integrity in the Hc of depressed patients and controls. </p> <p> We observed differing results across all three studies in our FTE and MTE depression groups. Our studies examining the Hc suggest that MTE patients have decreased activation in this region as well as corresponding memory errors during recollection memory. Additionally, these patients have smaller Hc volume and signs of increased neuronal membrane turnover. Conversely, our FTE patients displayed heightened Hc activation without memory deficits. Moreover, FTE patients had signs of increased glial cell density in the Hc without volumetric differences in this region. Our examination of reward processing revealed several health-to-illness gradients of activation in areas as the nucleus accumbens, anterior cingulate and ventral prefrontal cortices during the processing of rewards and punishers. </p> <p> These findings suggest that several regions in the brain may be sensitive to the impact of disease burden and repeated episodes of MDD. In the Hc, first treatment patients may engage in compensatory processes during the early stages of illness that are attenuated with repeated episodes of illness. Moreover, reward processing may be affected in the early course of the disorder, however with a protracted course of illness these regional alterations in activation become more pronounced.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The goal of this research project was the development of a protocol for preparation of optically clear organic/inorganic hybrid materials that was amenable to entrapment of lipophilic biomolecules. The protocol involved the acid-catalyzed hydrolysis of mixtures of tetraethylorthosilicate (TEOS) with organosilane precursors, including methyltriethoxysilane (MTES), dimethyldimethoxysilane (DMDMS) and propyltrimethoxysilane (PTMS) in the presence and absence of the polymer additives poly(ethylene glycol) or poly(vinyl alcohol).</p> <p> The effect of organosilane precursors and polymer additives on the optical clarity, hardness and hydration stability of the resulting materials was characterized. It was determined that there was a limit to the amount of organosilane that could be added before the materials exhibited unacceptable characteristics. These limits were 20.0% (v/v) for MTES, 10.0% (v/v) for PTMS, and 5.0% (v/v) for DMDMS. Addition of PEG to these materials at levels up to 10.0% (w/v) resulted in good material characteristics. However, addition of PVA produced opaque materials with poor material properties. The internal environment of the materials was also probed using the environmentally sensitive fluorescent probes 7-azaindole (7AI) and prodan. These studies showed that the method of hydrolysis of the silane precursors and the aging conditions had a dramatic effect on the resulting material.</p> <p> The hybrid materials were used to entrap human serum albumin (HSA) and lipase to determine the effect of organic content on the biological function of these biomolecules. Both biomolecules retained a portion of their native function when entrapped in sol-gel-derived materials, and it was found that both proteins showed enhanced function in the presence of MTES. In the case of lipase, it was also determined that addition of PEG 600 at 10.0% (w/v in the gelation buffer) provided a dramatic increase in activity compared to materials without this additive, likely owing to a direct effect of the PEG on the stability of the entrapped protein.</p> <p> Following studies using bulk glasses, a protocol was developed for the preparation of optically clear sol-gel-derived thin films that was amenable to entrapment of biomolecules. The optimal method involved dipcasting of co-hydrolyzed materials containing 1.0 to 3.0% PEG. By careful control of the viscosity of the casting solution and the rate of film deposition, it was possible to form very stable thin films with excellent physical characteristics. These films were used to entrap the pH-sensitive, ratiometric fluorescent probe dextran-SNARF-1, resulting in a prototype of a fluorimetric pH sensor. Co-entrapment of the probe and lipase into sol-gel-derived thin films resulted in a rapid, reagentless biosensor prototype that could monitor changes in pH due to the enzyme-catalyzed hydrolysis of triglycerides. These results demonstrate that species entrapped in sol-gel derived thin films are suitable for biosensor development.</p> / Thesis / Master of Science (MSc)

<p> Treatment of chromium hexacarbonyl with a series of benzyl alcohols yields the corresponding (R-C6H4CH2OH)Cr(CO)3 complexes, where R = 3-methoxy, 3-methyl, 4-methoxy or 4-methyl. These complexes were characterized by NMR spectroscopy.</p> <p> Protonation of the tricarbonylchromium alcohols with CF3SO3H at low temperature yields a benzyl cation complex which can be isolated and examined by variable-temperature 13C NMR spectroscopy. The spectra show a splitting of the carbonyl carbons at low temperature, providing evidence of electronically restricted rotation of the tripodal ligand. Evaluation of the simulated spectra provides the rotational barrier for this dynamic process. These results are rationalized by means of EHMO calculations.</p> <p> Evidence suggests tripodal rotation was also electronically hindered in the analogous fulvene complexes. Variable-temperature 13C NMR spectra of (6,6-Diphenylfulvene)Cr(CO)3 and (6-Methyl-6-phenylfulvene)Cr(CO)3 show respective 2:1 and 1:1:1 splitting of the carbonyl carbons a low temperature. Barriers of 8.3 kcal/mol and 8.8 kcal/mol were obtained by spectral simulation and were explained by using EHMO calculations.</p> <p> The calculated rotational barrier for the [α-(C5H5CH2)Cr(CO)2NO]+ cation suggests that NMR spectral evidence for hindered rotation may be difficult to obtain.</p> / Thesis / Master of Science (MSc)

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