Copper-treated rice seeding (Oryza sativa cv. Tainung 67 and Taichung native 1) showed significant inhibition in rice root growth, and an enhancement in POD activity. POD within Tainung 67 rice roots might synthesize more lignin in Cu-treated tissue. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POD activity in Cu-treated tissues. The increase in POD activity induced by Cu might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung native 1 rice cultivar, high amounts of H2O2 accumulated in Cu-treated tissues could be due to the less amounts of POD induced by Cu. In response to Cu treatment, the Taichung native 1 cultivar also synthesizes a little lignin, and is more Cu-sensitive. Therefore, The Tainung 67 cultivar is more tolerant to Cu than Taichung native 1.

Cadmium-treated rice seeding (Oryza sativa L. cv. Taichung Native 1 and O. sativa L. cv. Tainung 67) showed inhibition in the growth of rice roots or leaves, and an enhancement in POX activity. In Tainung 67 cultivar, Cd treatment may have influence over cis-regulatory elements in POX promoter region and enhanced transcription of POX or enhance glycosylation of POX. The increase in POX activity induced by Cd might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung Native 1 cultivar, high amounts of H2O2 accumulated in Cd-treated tissues could be due to the less amounts of POX induced by Cd. In response to Cd treatment, the Taichung Native 1 cultivar also synthesizes a little lignin, and is more Cd-sensitive. Therefore, the Tainung 67 cultivar is more tolerant to Cd than Taichung Native 1.

The adverse effect of Cd on growth is apparent from the reduction in root length of the Cd-treated Arabidopsis thaliana roots. The increase of the levels of H2O2 was observed in Cd-treated A. thaliana roots. The lignin biosynthesis related enzymes, POXs and laccases were enhanced during the Cd treatments. The lignin contents slightly increased in Cd-treated A. thaliana roots¡]48 h¡^. The A. thaliana can be tolerant to high concentration of Cd (500 µM), and only part of high levels of H2O2 accumulated in Cd-treated tissues are used by POXs to synthesize the lignin.

The adverse effect of Zn on growth is apparent from the reduction in root length of the Zn-treated Arabidopsis roots. The levels of H2O2 were increased rapidly in Zn-treated Arabidopsis roots. The lignin biosynthesis realated enzymes, peroxidases and laccases were enhanced during the Zn treatments. The lignin contents increased in Zn-treated Arabidopsis roots. Arabidopsis can be tolerant to high concentration of Zn (4 mM), because part of high levels of H2O2 accumulated in Zn-treated tissues are utilized by peroxidases to synthesize the lignin.

The E. coli ArsA is involved in arsenic detoxification but the role of yArsA (ArsA homologue of Saccharomyces cerevisiae, encoded by YDL100C ORF) in yeast is still undefined. Disruption of YDL100C ORF is not lethal. To study the role of yArsA in oxidative tolerance, wild type and knock out strain were grown in presence or absence of 1 mM H2O2 and assayed the expression of anti-oxidation machanisms . The results show that molecular oxidation is higher and catalase activity is lower in KO compared with WT. It suggests that increased ROS and decreased catalase activity are the cause of cell death. Further analysis of the expression of ROS defense mechanisms by RT-PCR show that there is no significant difference in TRR1, GSH1, and SOD1 expression in WT and KO grown in presence of 1 mM H2O2 but the CTT1, TPS1, NTH1 expression in KO are less than WT grown under oxidative stress. GSH contents is consistent with the result of RT-PCR, and trehalose contents is higher in KO strain under oxidative stress. Loss of catalase activity and decreased efficiency of degrading trehalose suggest that the deficiency in activation of general stress response in KO when grown in the presence of H2O2. Therefore, yArsA would be involved in expressing the general stress response in oxidative tolerance.

Aluminum-treated rice seeding (Oryza sativa L. cv. Taichung Native 1 and O. sativa L. cv. Tainung 67) showed significant inhibition in rice root growth, and an enhancement of POX activity. In Tainung 67 cultivar rice synthesizes more lignin in Al-treated tissue. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POX activity in Al-treated tissue. The increase in POX activity induced by Al might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung native 1 cultivar, high amounts of H2O2 accumulated in Al-treated tissues could be due to the less amounts of POX induced by Al. In response to Al treatment, the Taichung native 1 cultivar synthesizes less lignin in comparison with that of Tainung 67, and is more Al-less tolerant. Therefore, the Tainung 67 cultivar is more tolerant to Al than Taichung native 1.

Injuries to the central nervous system are irreversible and debilitating due to the limited regrowth of damaged or severed neurons. Two small molecules, xanthofulvin and vinaxanthone, isolated from P. vinaceum and P. glabrum promote spinal cord regeneration in animal models. It is speculated that these natural products inhibit semaphorin 3A, a chemorepellent that mitigates axonal growth-cone formation. In addition to promoting axonal growth, rats treated with vinaxanthone and xanthofulvin following complete spinal cord transection experienced greater remyelination, increased angiogenesis, attenuated apoptosis, and depressed scaring of the lesion site. The only prior synthesis of vinaxanthone speculated that the xanthone core is constructed via enzyme-catalyzed intermolecular Diels-Alder reaction. We have demonstrated, however, that warming a functionalized acetoacetyl chromone in water, furnishes vinaxanthone in good yield, providing an alternative biosynthetic pathway. With a robust syntheses of both natural products, we determined the protein target of the observed regeneration: succinate receptor 1, providing a new therapeutic target to promote neuronal regeneration. Among the various methods of incorporating oxygen into aryl rings, the direct conversion of a C-H bond into a C-OH bond is ideal. The metal-free hydroxylation of arenes developed in our laboratory, utilizing phthaloyl peroxide, marks the first disclosure of this transformation using mild conditions. Computational and experimental evidence obtained thus far has supported a mechanism involving a diradical intermediate. The reactivity of phthaloyl peroxide was increased by the incorporation of two chlorine atoms onto the ring. To minimize the accumulation of large quantities of peroxide, the optimization of the preparation of the peroxide in flow has been developed. This protocol immediately consumes the peroxide as it is generated. Finally, a new dearomatization reaction has been optimized. This reaction forms two carbon-oxygen bonds and dearomatizes the ring system.

No description available.

Contraction of cardiac muscle is a highly regulated event that relies on a delicate balance of ions entering and leaving the cell through ion channels. In particular, voltage gated sodium channels are responsible for the rapid depolarization that leads to a contraction. During an oxidative challenge, sodium channels rapidly activate, but do not fully turn off. This alters the rate of cardiac repolarization and can induce cardiac arrhythmias. It is currently unknown whether the most common sodium channel isoform found in the heart, NaV1.5, generates this oxidant-induced persistent current or if other isoforms are responsible. Therefore, I sought to further explore the biophysical properties NaV1.5, and determine if it can enter this persistent mode. I tested the biophysical properties of native INa in cardiac myocytes and in NaV1.5 transfected HEK293 cells under macro cell-attached voltage-clamp. I used a sodium channel enhancer (Anemonia sulcata toxin II; 10 nM), a sodium channel blocker (tetrodotoxin; 10 nM) and a model of oxidative stress (H2O2; 100 µM, 200 µM, 1000 µM) to compare and contrast the cellular responses between both cell types. I observed that transfected HEK293 cells and cardiac myocytes were unaffected by H2O2 at various concentrations. Given the lack of other isoforms in transfected HEK293 cells, and the low abundance (<5%) of other isoforms in cardiac myocytes, I propose that NaV1.5 function is unaffected by H2O2. Furthermore, ATX II prolonged the inactivation process in both HEK293 cells and cardiac myocytes in a voltage-dependent manner, indicating that NaV1.5 can give rise to persistent sodium current. Finally, by comparing both cell types under control settings, I found that transfected HEK293 cells inactivated at a much slower rate and at more negative potentials compared to the current in cardiac myocytes. My results suggest that NaV1.5 does not underlie oxidant-induced persistent current and that β subunits likely play a significant role in the inactivation process. / Thesis (Master, Physiology) -- Queen's University, 2011-08-19 14:46:42.665

Macromonomers bearing oligomerizable C=C functionality have been prepared by the nucleophilic displacement of allylic bromide functionality on brominated poly(isobutylene-co-isoprene) (BIIR). Whereas commercial grades of isobutylene-rich elastomers do not cure under the action of peroxides, these materials undergo simultaneous cross-linking and degradation when activated by radical initiators, with the competitive balance dictated by the reactivity of the oligomerizable group. Vinyl benzoate, vinyl imidazolium, and acrylate functionalities cure rapidly to high cross-link density whereas the maleimide graft is too reactive and unstable for any utility. Methacrylate and itaconate macromonomers cure to moderate extent while maleate esters and unactivated terminally unsaturated groups are unable to significantly counteract the degradation mechanism and do not afford any appreciable cross-link density to BIIR. The most reactive macromonomers display the potential for scorch, an effect that is efficiently mitigated with the introduction of (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO) to quench free radical cure activity. Furthermore, an acrylated adduct, AOTEMPO, is able to recover more of the cross-link density that would otherwise be lost to irreversible free radical coupling. These nitroxyls display longer than expected induction times, likely due to the catalytic nature of TEMPO when alkoxyamine decomposition is significant. A suite of elastomeric ionomers bearing N-functional imidazolium bromide functionality have been prepared in order to investigate the N-alkylation dynamics with brominated poly(isobutylene-co-para-methylstyrene) (BIMS) as well as the subsequent peroxide cure activity of the reactive ionomer. A functional imidazole bearing a methacrylate group displayed moderate alkylation rate and good cure activity whereas a 4-vinylbenzyl analogue provides fast alkylation at the expense of storage stability. N-Allylimidazole is rapidly alkylated by BIMS in both solution and solvent free processes and the resulting ionomer displays unique cure dynamics. This phenomenon is investigated by model compound polymerization and is likely due to the unique free radical reactivity of allyl imidazolium moieties. The cross-linked ionomer displays many of the beneficial physical properties associated with a hybrid ionic/covalent network including good resistance to stress relaxation and thermal stability. / Thesis (Master, Chemical Engineering) -- Queen's University, 2014-01-29 17:09:42.428