G-substrate is a 23 kDa protein named as a specific substrate of cGMP-dependent protein kinase and found predominantly in cerebellar Purkinje cells. As a component of the NO/cGMP/PKG pathway, G-substrate is potentially involved in several important cellular processes and has so far been associated with a number of disease conditions: a single point mutation in G-substrate has been linked to hypercholesterolaemia, while the potent inhibition of PP2A by phosphorylated Gsubstrate possibly influences Tau protein hyperphosphorylation and contributes to Alzheimer's disease pathology. Conversely, overexpression of G-substrate protein in dopaminergic neurons has been found to protect neurons from Parkinson's disease toxins, making G-substrate a possible target of interventions for mitigating the debilitating effects of Parkinson's disease on patients. A shorter splice variant, which only retains one of the phosphorylatable threonine motifs, has recently been described for G-substrate and given the importance of phosphorylation to its action as a phosphatase inhibitor, this study focuses on determining whether both variants of the protein exhibit similar levels of phosphatase inhibition and interact with the same/similar proteins in vivo. We were also interested in determining whether the 51 amino acid section absent from short G-substrate resulted in any significant differences in protein structure, which potentially has implications on functions in vivo. My results indicate the association of G-substrate with a wide range of proteins involved in processes including cell cycle regulation, endocytosis and signalling and the two variants do not always interact with the same proteins. Among these interactors is the PARK 7/ DJ-1 protease, which like G-substrate has been shown to be neuroprotective. I have found that G-substrate is proteolysed by DJ-1 in its active form and interactions between these two proteins is affected by the anti-vertigo drug Tanganil. Phosphatase inhibition studies suggest that the G-substrate variants affect phosphatase activity to different extents under similar conditions, while NMR and circular dichroism structural studies suggest that in solution, the full length Gsubstrate variant is slightly more compactly folded. Understanding the details of G-substrate action in the cell will lead to a better understanding of its roles including the protection of dopaminergic neurons from Parkinson's disease toxins and shed more light on the intricacies of the NO/cGMP/PKG signalling pathway as a whole, thus providing important information that might help improve strategies for dealing with conditions involving this pathway and help develop interventions for diseases such as Alzheimer's and Parkinson's.

According to statistics from the American Heart Association, valvular heart disease directly leads to about 20,000 deaths a year and contributes to an additional 50,000. While significant advancements have been made in the treatment options available for valvular heart disease, complications still occur. For this reason, the future of valvular heart disease treatment lies in understanding the physiology of the heart valve, and subsequently bioengineering a valve from one's own tissue to mimic native valve processes. Valvular interstitial cells (VICs) are the major cell type populating the valve matrix. In the inactive fibroblast-like state, these cells are responsible for extracellular matrix deposition. Activated VICs display a myofibroblast morphology characterized by the expression of alpha smooth muscle actin and are responsible for valve maintenance and repair. The activation of VICs is hypothesized to be stimulated by mechanical tension, which, in the presence of TGF-â1 allows the complete differentiation of VICs from the inactive to the active form. However, little is known about the potential for reversal or dedifferentiation from the active to inactive state. The purpose of this study was to determine whether substrate stiffness, the mechanical tension hypothesized to initiate VIC activation, modulates alpha smooth muscle actin expression in the presence and absence of TGF-â1. To mimic conditions found in vivo, substrates were varied from physiologic to pathological stiffness levels. Results showed that when freshly isolated VICs are cultured in the presence of serum, alpha smooth muscle actin expression increased on all substrate stiffnesses. In TGF-â-free medium, there was an apparent increase on all stiffness levels as well, but a statistical significance between groups could not be demonstrated. Immunoblots used to detect TGF-â1 showed that intracellular TGF-â1 was upregulated in VICs cultured in the presence of serum compared to those cultured in TGF-â-free medium. Taken together, these results suggest that freshly isolated VICs become activated, as indicated by increased expression of alpha smooth muscle actin, on all substrate levels in the presence of serum. It also appears as though unknown factors which are present in serum are required to stimulate significant autocrine production of TGF-â1. To determine whether VICs which had transitioned to the myofibroblast phenotype had the ability to dedifferentiate, cells were cultured on polystyrene for a minimum of four days then replated on substrates of varying stiffness. Analysis of alpha smooth muscle actin expression showed that, in the presence of serum and when replated on all of substrates used, alpha smooth muscle actin expression decreased, suggesting that these cells indeed have the potential to dedifferentiate. A change in cell morphology to a more rounded phenotype as well as the loss of visible stress fibers further supported this possibility. These studies represent a unique approach to studying phenotypic differentiation of valvular interstitial cells. Using acrylamide substrates of varying stiffness, and growth factor free media, we have shown that by altering substrate stiffness, changes in alpha smooth muscle actin expression consistent with differentiation and dedifferentiation can be induced. This potential for dedifferentiation suggests that in engineering the next generation of bioartificial valves, it may be possible to use the patient's own cells to seed the manufactured scaffold. This would avoid complications associated with current treatments, including immune rejections.

Cadmium Selenide is a binary compound. It has a band gap of 1.7 eV. This is one of the suitable materials for an absorber layer in the top cell of a tandem solar cell. CIGS with a low Gallium content has a band gap of 1 eV suits well as an absorber layer for the bottom cell. CIGS cells have already attained an efficiency of 15% [1,2]. Since years, research has been done in developing the bottom cell. The results of the bottom cell are promising. So the fabrication of an efficient top cell in a tandem solar cell is a challenge. To achieve a high tandem efficiency of above 25 %, the top cell has to contribute at least 2/3 of the total efficiency, which necessitates the top cell to have at least 16 to 18 % efficiency [3]. Development of a defect free absorber layer is a crucial step in this process to achieve the above goals besides optimizing other layers. Selenium vacancies in CdSe make the absorber layer n-type. CdSe is deposited by closed space sublimation. Deposition of CdSe at higher substrate temperatures in comparison to the standard conditions was studied. ZnSe acts as an insulating layer. It is thermally evaporated in an Evaporation system. Copper acts as a metal contact on top of the insulator resulting in a MIS structure. Copper is also deposited by Thermal Evaporation. Devices are fabricated on different substrates like SnO2: F, AZO etc. Fabricated cells are characterized by J-V and Spectral response measurements. Devices fabricated on SnO2: F substrates show typical open circuit voltages of around 220 mV, short circuit current densities of 10.02 mA/cm2 and fill factors around 33 %. N-type CdS when deposited on SnO2: F below the absorber layer further improved Voc's to around 330 mV. Annealing of these devices improved Voc's to about 350 mV but Jsc's remained 7.21 mA/cm2.

Graduation date: 2004

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 53-54). Also available on the World Wide Web.

An increasing amount of people have their work hours displaced to the night and there are indications that shift work and other irregular working schedules are associated with an increased risk of developing the metabolic syndrome and other pathological conditions. It is therefore important to address the consequences of eating at irregular hours, especially nighttime. Papers I-III refer to a study in which 7 males were given a high-carbohydrate diet (HC) or a high-fat diet (HF), using a cross-over design. Subjects were kept awake for 24 h and food was provided as 6 equally spaced isocaloric meals. Higher energy expenditure and non-esterified fatty acids (NEFA) concentration, as well as lower glucose and triacylglycerol (TAG) concentrations were observed with the HF-diet, compared to the HC-diet. With the HF-diet, fat oxidation, heat release, heart rate, glucose, NEFA and TAG concentrations differed depending on time of day. The highest postprandial TAG concentrations were seen after the 04.00 meal with both diets. Insulin and leptin responses to meal intake differed with respect to diet and time of day. Time of day affected glucagon, thyroid stimulating hormone, free thyroxin, total triiodothyronine (tT3), cortisol, chromogranin A and pancreatic polypeptide (PP) concentrations. PP’s postprandial increase was greater during 08.00 – 16.00 compared to 20.00 – 08.00. Furthermore, the subjects felt less irritated when eating the HF-diet but hunger was not related to macronutrient composition. Hunger and thirst decreased throughout the 24 h period despite constant activity and energy intake; and were correlated with several endocrine and metabolic variables. In paper IV 7 males were studied twice during 24-h either given 6 isocaloric meals throughout the 24-h period, or 4 isocaloric meals from 08.00 to 20.00, followed by a nocturnal fast. Energy expenditure, glucose, TAG, insulin and glucagon concentrations were lower; and NEFA concentrations were higher during the nocturnal fast compared to nocturnal eating; although no 24 h differences between the protocols were apparent. The subjects were more passive during the fasting period compared to when food was given. Stepwise regression showed that correlations between metabolic variables and hormones differed between daytime and nighttime. The decreased evening/nocturnal responses of cortisol and PP to meal intake suggest that nocturnal eating might have health implications and that the body reacts unfavorably to nocturnal eating. Smaller meals around the clock, however, showed marginally better effects on postprandial TAG concentrations and mental energy compared to larger meals during daytime. Further studies (long term) are needed before dietary guidelines can be given to shift workers, especially regarding the impact of nocturnal eating on gastrointestinal response and cortisol.

UDP-galactopyranose mutase (UGM) is a flavoenzyme which catalyzes the interconversion of UDP-galactopyranose (UDP-Galp) and UDP-galactofuranose (UDPGalf). UDP-Galf is the active precursor of Galf residues. Glycoconjugates of Galf residues are found in the cell wall of bacteria and on the cell surface of higher eukaryotes. Galf residues have not been found in humans and the fact that they are essential for the growth of pathogenic bacteria makes UGM a potential antibacterial target. In the present study, crystal structures of UGM from Deinocococcus radiodurans (drUGM) in complex with substrate (UDP-Galp) were determined. UDP-Galp is buried in the active site and bound in a U-shaped conformation. The binding mode and active site interactions of UDP-Galp are consistent with the previous biochemical and mechanistic studies. The mobile loops in the substrate complex structures exist in a closed conformation and Arg198 on one of the mobile loops stabilizes the phosphate groups of the substrate. The anomeric carbon of galactose is 2.8 Å from the N5 of FAD (in the reduced complex) favorable to form FAD-galactosyl adduct. In addition to substrate complex structures, the crystal structures of drUGM in complex with UDP, UMP, and UDP-Glc have been determined. The mobile loops in all these complexes exist in a closed conformation. Inhibitors for UGM were identified by ligand-based and structure-based methods. The phosphonate analog of UDP-Galp (GCP) showed only weak inhibition against various bacterial UGMs. The structure of drUGM in complex with GCP provided a basis for its inhibitory activity. Poor stabilization of the phosphate groups by conserved arginines (Arg198 and Arg305) and altered sugar binding mode account for its activity. Novel indole-based (LQ1, LQ6 and LQ10) inhibitors of UGM were identified through structure-based virtual screening (SBVS) of a chemical library. Inhibition studies also allowed the identification of an active site aspartic acid that plays role in inhibitor binding. The structural studies on drUGM provided a basis for understanding substrate binding to UGM. In vitro enzyme inhibition studies allowed the identification of novel indole-based inhibitors. The structural and inhibition studies reported here enhance the understanding of UGM-ligand interactions and will assist in the development of more potent inhibitors of UGM.

Research investigating the effects of pre-exercise meals with varying glycemic indices on exercise performance in intermittent sports is scarce. This study determined whether whole foods of low glycemic index (GI) resulted in a metabolic and performance advantage, in comparison to high GI foods, when eaten prior to extended intermittent cardiovascular exercise, such as tournament soccer play. Consenting trained participants (10 males, 4 females, 25.8 ± 7.3 y) completed two simulated soccer tournaments separated by at least seven days. Each testing day included two 90-minute soccer matches separated by a three hour break. Using a randomized cross-over design, low-GI, lentil-based meals (GI~42) or high-GI, potato-based meals (GI~78) matched for caloric value were consumed two hours prior to and then within one hour after the first soccer match. Blood glucose, lactate, insulin, free fatty acids, and respiratory gases were measured throughout the post-prandial and testing periods. Ratings of perceived exertion (RPE) and gastrointestinal symptoms were also recorded. Performance was measured by the distance covered during five one-minute sprints, separated by two minute and thirty second rest intervals, at the end of each match. Peak post-prandial blood glucose was higher (p<0.05) in the high-GI trial (8.9 ± 2.2 molL-1 [SD]) compared to the low GI trial (5.9 ± 1.3 mmolL-1) as was insulin prior to the start of exercise (19.4 ± 2.0 versus 9.2 ¬± 1.3 umolL-1, p<0.05). Blood lactate levels were significantly higher (p<0.05) at the end of the second match during the high-GI trial (6.1 ± 1.2 mmolL-1) compared to the low-GI trial (2.5 ± 0.4 mmolL-1). Breath-by-breath analysis showed lower (p<0.05) carbohydrate oxidation during the low-GI trials compared to the high-GI at the start of the first soccer match (p<0.05). Subjects reported greater feelings of hunger during the high-GI trial versus greater feelings of fullness during the low-GI trial (p<0.05), but RPE during the low-GI (14.1 ± 0.3) was similar to the high-GI meal (14.2 ± 0.3). Sprint distance was not significantly different between treatments (p=0.27). Overall, these findings suggest that lentil-based, low-GI foods are a comparable alternative to traditional high-GI pre-exercise meals, as they result in similar performance outcomes but improved metabolic profiles. Over the long-term, improving metabolic conditions during exercise may be beneficial to the health of athletes.

Serine proteases are a family of enzymes with a wide array of functions across both eukaryotes and prokaryotes. Here we have attempted to produce the serine proteases rat mast cell protease 2 and mouse mast cell protease 5 in a culture of HEK 293 cells; and mouse mast cell protease 4, platypus granzyme B-like protease and platypus hypothetical protease in a baculovirus expression system. Following production we wanted to analyse these serine proteases using a phage display assay and a battery of chromogenic substrates.

Local differentiation may occur during a short period of time and is part of the formation of new species. The isopod Asellus aquaticus is an example of a species in which local adaptation has occurred during a short period of time. An establishment of stonewort (Chara spp.) vegetation in Lake Tåkern (in the 2000) resulted in two different Asellus ecotypes; a lighter pigmented, smaller one that lives among stoneworts grazing periphytic algae, and a darker, larger ecotype that feeds on decaying leaves in reed (Phragmites australis vegetation. The purpose of this study was to examine whether there are differences in growth between ecotypes, depending on whether the food was periphytic algae or leaves, and to study the choice of substrates between the two food types. For the study, animals from both habitats were brought in from Lake Tåkern to the laboratory. I found that both the reed and the stonewort animals grew better when feeding on periphytic algae than on leaves, but that there was no difference in weight gain between the two ecotypes. There was no indication that the animals preferred any of the substrates. Results suggest that despite earlier noted differences in behavior, size and pigmentation (which differentiation had brought), there is no evidence that Asellus aquaticus has adapted to feed on plant matter prevailing in their original habitat. The animals grew better when the food was algae maybe due to that the algae, as previous studies show, are easier assimilated, whereas Asellus has to eat a larger amount of leaves to reach the same energy intake.