Vanadium compounds have been reported to cause numerous toxicological effects including NAD(P)H oxidation and lipid peroxidation. The purpose of this thesis is to determine the active form of vanadium in causing these effects, and to determine any possible free radical involvement in these processes. Vanadium-stimulated oxidation of NADH was studied spectrophotometrically and by electron spin resonance spectroscopy. In 25 mM sodium phosphate buffer at pH 7. 4, vanadyl , (V(IV)), is slightly more effective in stimulating NADH oxidation than was vanadate (V(V)). Addition of a superoxide generating system, xanthine/xanthine oxidase, results in a marked increase in NADH oxidation by vanadyl, and to a lesser extent, by vanadate. In contrast, addition of hydrogen peroxide did not change the NADH oxidation by vanadate, but greatly enhanced NADH oxidation by vanadyl. Use of the spin trap DMPO in reaction mixtures containing vanadyl and hydrogen peroxide or a superoxide generating system resulted in the detection by ESR of hydroxyl radical. Hydroxyl radical was also detected in the system containing vanadate plus superoxide. It was found that superoxide is capable of reducing vanadate to vanadyl, and that vanadyl is capable of reaction with hydrogen peroxide in a Fenton-like mechanism to produce hydroxyl radical. Hydroxyl radical is suggested to be the active species involved in NADH oxidation. Other reductants, such as thiols, are also capable of supporting vanadate-stimulated NADH oxidation . The above results indicat that ability of vanadium to act in a Fenton-like mechanism is an important process in the vanadium-stimulated oxidation of NADH. Vanadyl was found to be the active form of vanadium involved in initiating and stimulating lipid peroxidation in purified and partially purified fatty acid micelle preparations. Hydroxyl radicals were shown to be involved in initiating diene conjugation when vanadyl and hydrogen peroxide were added together in the reaction mixture. Furthermore, hydroxyl radicals were shown to be generated in the vanadyl-catalyzed decomposition of fatty acid lipoperoxides. The results of this study indicat that the ability of vanadium compounds to oxidize NADH and to stimulate lipid peroxidation are related by the common mechanism of hydroxyl radical production from the reaction of vanadyl with hydrogen peroxide.

Thesis (M.Sc. (Human Movement Science))--North-West University, Potchefstroom Campus, 2007.

This thesis addresses the mechanisms involved in cellulosedegradation in general and Totally Chlorine Free (TCF) bleachingof pulp in particular. The thesis shows that the cellulosedegradation during high consistency ozone bleaching is explainedby free radical chain reactions. By simulation, it has been shown that the number, weight andviscosity average of liner polymer chain length can be used tocalculate the number of random scissions in a linear polymer ofany molecular weight distribution, provided that there is acalibrated Mark-Houwink equation. A model describing partialdegradation of molecular weight distributions of linear polymersmeasured with viscometry was developed and verifiedexperimentally. The model predicts viscometric measurement ofchemical cellulose degradation by a rapidly reacting reagent tobe strongly dependent on cellulose accessibility. The role of free radical reactions in cellulose degradationwas studied by varying the amount of ferrous ions and ozone addedto the cotton linters. The result was compared to the resultsobtained from cellulose of lower crystallinity (cellulose beads)by measuring average chain length. When a ferryl ion reacted withcotton linters in the presence of ozone, the very formation ofone glycosidic radical was more significant to degradation thanthe final step of forming one oxidised glycoside. The inefficientdegradation observed of the oxidation step is explainable by theamount of accessible glycosides being too small to influenceviscometry. The efficient degradation observed in associationwith the glycosidic radical formation is explained by initiationof free radical chain reactions that are propagated as long asthere is ozone in the system. As none of these phenomena werefound in the less crystalline cellulose, cellulose structureappears to be important for how free radical mediated cellulosedegradation develops. The theory of free radical chain reactions coupled withdiffusion suggests a concentric expansion of the chain reactionsoutwards from the initial site of radical formation duringozonation of carbohydrates. This was confirmed by demonstratingfree radical chain reactions spreading from a spot of initiationoutwards during ozonation of a filter paper, using a pH-indicatorto monitor acid formation. Furthermore, the interior and exteriorof cellulose fibres doped with initiator were shown to bepermeated by small holes after ozonation. Ethylene glycol was shown to improve the selectivity duringozone bleaching of oxygen bleached kraft pulp at pH 3. Optimalconditions were obtained at pH 3 for 25 wt% ethylene glycol. Theinfluence of ethylene glycol on selectivity is explained by aproportion of the free radical chain reactions being carried bythe ethylene glycol instead of the cellulose during ozonebleaching. The observations were summarised in the form of amodel where the observed degradations for pulp, bleached pulp andcotton fibres during both ozone bleaching and ethylene glycolassisted ozone bleaching were shown to agree with each other. From g-irradiation of ozonised aqueous solutions of alcohol,the rate constant of superoxide formation from the peroxylradical of methanol was estimated to be 10 s-1. Rate constants of the reactions between ozone andalkylperoxyl radicals were determined to be around 104M-1s-1. The possibility of the reaction betweenalkylperoxyl radicals and ozone contributing significantly tofree radical chain reactions during ozonation of carbohydratesand alcohols could therefore be ruled out. Cellulose, degradation, free radical, ozone, selectivity,ethylene glycol, alcohol, bleaching, kraft pulp, cotton linters,delignification, fibre, fibril, crystallinity, ferryl ion, freeradical chain reactions, TCF, viscometry, molecular weightdistributions, random scissions.

Oxidative stress has been associated with many disease conditions in adults and neonates based on clinical and post mortem studies. Trauma is the commonest cause of oxidative stress. However a gap in knowledge of the natural history of oxidative stress in humans was identified as most studies have been post mortem or in animals. <p>The aim of this research is to understand treat and oxidative stress in trauma and surgical patients. The study involved three components including: the development and evaluation of the novel oxistress assay; study of clinical trauma and oxidative stress; and clinical trial of alanyl-glutamine supplementation following major surgery. The novel oxistress assay was used on urine samples in the normal population to determine reference values and subsequently on hospital patients to determine sensitivity and specificity. The study of clinical trauma and oxidative stress evaluated plasma antioxidants (FRAP assay), red cell glutathione (Asensis method), plasma and urine protein carbonyl (Levines method) and total oxidants in plasma and urine (oxistress assay) over 7 day period following trauma. The clinical trial was a double blind study of 69 major surgery patients evaluating biochemical and clinical parameters over 7 day period in comparison with pre-operative status. <p>The novel oxistress assay proves to be a sensitive and accurate bedside diagnostic tool for oxidative stress. It can also be used in the laboratory setting. Oxidative stress is associated with increased trauma severity resulting in antioxidant depletion, strong oxidant production and protein degradation. The presence of pre-morbid medical factors also increased oxidative stress in trauma patients. Oral alanyl-glutamine supplementation (0.3 g/kg) increased plasma glutamine and antioxidant levels while decreasing urine oxidant levels. It significantly reduced hospital stay in non-cancer and higher disease complexity patients. The intervention also reduced the resource intensity weighting (RIW) score. <p>Oxidative stress is a clinical problem in surgery and trauma patients that can now be easily diagnosed at the bedside using the novel oxistress assay. Treatment with alanyl-glutamine is effective in reducing oxidative stress and improving clinical outcome. It is highly recommended probably at a higher dose in order to achieve optimal results.

<i>In vivo</i> and <i>in vitro</i> studies on numerous types of blood vessels obtained from a variety of vascular beds and species have demonstrated that oxygen free radicals (OFRs) can evoke both vasodilation and vasoconstriction. Specific OFRs have been shown to elicit different and often times opposite effects on vascular smooth muscle. Therefore, this thesis attempts to define the vascular actions and mechanism of oxygen free radicals (OFRs) [superoxide anion (O₂^-), hydrogen peroxide (HO₂) and hydroxyl radical (OH)] on isolated rabbit aorta. This thesis will examine the role of OH in Ach- and nitroglycerin (NTG)-induced relaxation of isolated rabbit aorta. Superoxide anions generated by xanthine (X) plus xanthine oxidase (XO) produced concentration-dependent contractions of isolated rabbit aorta. The contractile response to O₂^- was completely abolished in preparations denuded of endothellum or pretreated with superoxide dismutase (SOD), a scavenger of O₂^-. The contractile response was reduced by indomethacin (I), a cyclooxygenase inhibitor. These results suggest that O₂^- mediated by vasoconstrictor arachidonic acid metabolites. Hydrogen peroxide generated by glucose and glucose oxidase produced contraction (low concentrations) and relaxation followed by contraction (high concentrations) in isolated rabbit aorta. The contractile response was abolished in the presence of catalase, a scavenger of H₂O₂ however the relaxant effect was exaggerated. Indomethacin markedly reduced the H₂O₂-induced contraction. Relaxation was completely prevented by de-endothelialization or pretreatment with N^G-monomethyl-L-arginine (LNMMA), an inhibitor of nitric oxide synthetase. These results suggest that H₂O₂ in large concentrations produces a biphasic response, relaxation followed by contraction. Relaxation is endothelium dependent and is mediated by endothelium-derived relaxing factor (EDRF), nitric oxide (NO). The contractile response is endothelium independent and is mediated by vasoconstrictor arachidonic acid metabolites of smooth muscle. Hydroxyl radicals generated by dihydroxyfumarate (DHF), ferric chloride (FeCl₃) and adenosine diphosphate (ADP) (DHF/FeCl₃-ADP) produced concentration dependent relaxations of NE-precontracted rabbit aorta. Mannitol (Ml) completely inhibited OH-induced relaxation. Relaxation was markedly reduced in aortic rings mechanically denuded of endothelium. The relaxant effect was reduced by an inhibitor of NO synthesis (LNMMA), by an inhibitor of guanylate cyclase (methylene blue), by an inhibitor of cyclooxygenase (indomethacin) and by an inhibitor of an ATP-sensitive K⁺ channel blocker (glyburide). These results indicate that OH produces relaxation that is endothelium-dependent and partially mediated by an endothelium-derived relaxing factor (NO), vasodilatory arachidonic acid metabolites and an ATP-sensitive K⁺ channel. We hypothesized that Ach-induced vascular relaxation is mediated by OH derived from the interaction of NO and O₂^-. To test this hypothesis we investigated the effect of Ach and NTG on NE-precontracted isolated rabbit aortic preparations in the absence or presence of scavengers of O₂^- (SOD), and OH (dimethylthiourea (DMTU) or mannitol or Garlicin). The OFR scavengers (SOD, dimethylthiourea, mannitol, garlicin and histidine) alone or the combination of SOD and DMTU markedly reduced Ach- or NTG-induced relaxation. However, the combination of histidine, (a ¹O₂ scavenger) SOD and DMTU completely abolished Ach-induced relaxation.

Oxidative stress has been associated with many disease conditions in adults and neonates based on clinical and post mortem studies. Trauma is the commonest cause of oxidative stress. However a gap in knowledge of the natural history of oxidative stress in humans was identified as most studies have been post mortem or in animals. <p>The aim of this research is to understand treat and oxidative stress in trauma and surgical patients. The study involved three components including: the development and evaluation of the novel oxistress assay; study of clinical trauma and oxidative stress; and clinical trial of alanyl-glutamine supplementation following major surgery. The novel oxistress assay was used on urine samples in the normal population to determine reference values and subsequently on hospital patients to determine sensitivity and specificity. The study of clinical trauma and oxidative stress evaluated plasma antioxidants (FRAP assay), red cell glutathione (Asensis method), plasma and urine protein carbonyl (Levines method) and total oxidants in plasma and urine (oxistress assay) over 7 day period following trauma. The clinical trial was a double blind study of 69 major surgery patients evaluating biochemical and clinical parameters over 7 day period in comparison with pre-operative status. <p>The novel oxistress assay proves to be a sensitive and accurate bedside diagnostic tool for oxidative stress. It can also be used in the laboratory setting. Oxidative stress is associated with increased trauma severity resulting in antioxidant depletion, strong oxidant production and protein degradation. The presence of pre-morbid medical factors also increased oxidative stress in trauma patients. Oral alanyl-glutamine supplementation (0.3 g/kg) increased plasma glutamine and antioxidant levels while decreasing urine oxidant levels. It significantly reduced hospital stay in non-cancer and higher disease complexity patients. The intervention also reduced the resource intensity weighting (RIW) score. <p>Oxidative stress is a clinical problem in surgery and trauma patients that can now be easily diagnosed at the bedside using the novel oxistress assay. Treatment with alanyl-glutamine is effective in reducing oxidative stress and improving clinical outcome. It is highly recommended probably at a higher dose in order to achieve optimal results.

No description available.

This study was designed to investigate Plantago major leaves, which is widely used in ethnobotanical uses in Turkey as is the case in all over the world, for their antioxidant capacities and antimicrobial effect on two gram-positive and two gramnegative bacteria. Extracts of P. major leaves prepared in the methanol and fraction samples were collected in solvents in increasing polarity, from non-polar to polar, to separate bioactive compound in crude extract. Antioxidant capacities of the crude extracts and fractions were examined by radical scavenging methods, namely 2,2-azinobis(3- ethylbenzothiazoline-6-sulfonic acid) ABTS and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) / as well, total phenolic and total flavonoid contents were determined. Furthermore, antimicrobial activities of crude extract and fractions were calculated in terms of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods together with disc diffusion method. v Among the investigated samples, ethyl acetate phase had the highest radical scavenging capacity with the ABTS value of 2130.4&plusmn / 9.845 &mu / mol equivalents of trolox/ g of ethyl acetate fraction DW, and with EC50 value of 0.011&plusmn / 0.001 mg/mL / further, the highest phenolic content was found in ethyl acetate phase with values of 0.452 GAE mg/mg of ethyl acetate fraction DW and 0.434&plusmn / 0.0017 mg catechin equivalent in per mg of ethyl acetate fraction DW. In general, it was found that the crude extract and aqueous phase of Plantago major had a weak antimicrobial effect on S. aureus, P.mirabilis, S.pyogenes and E. coli, along with the highest bacteriostatic and bactericidal upshot on selected bacterial populations in ethyl acetate fraction.

<p>This thesis addresses the mechanisms involved in cellulosedegradation in general and Totally Chlorine Free (TCF) bleachingof pulp in particular. The thesis shows that the cellulosedegradation during high consistency ozone bleaching is explainedby free radical chain reactions.</p><p>By simulation, it has been shown that the number, weight andviscosity average of liner polymer chain length can be used tocalculate the number of random scissions in a linear polymer ofany molecular weight distribution, provided that there is acalibrated Mark-Houwink equation. A model describing partialdegradation of molecular weight distributions of linear polymersmeasured with viscometry was developed and verifiedexperimentally. The model predicts viscometric measurement ofchemical cellulose degradation by a rapidly reacting reagent tobe strongly dependent on cellulose accessibility.</p><p>The role of free radical reactions in cellulose degradationwas studied by varying the amount of ferrous ions and ozone addedto the cotton linters. The result was compared to the resultsobtained from cellulose of lower crystallinity (cellulose beads)by measuring average chain length. When a ferryl ion reacted withcotton linters in the presence of ozone, the very formation ofone glycosidic radical was more significant to degradation thanthe final step of forming one oxidised glycoside. The inefficientdegradation observed of the oxidation step is explainable by theamount of accessible glycosides being too small to influenceviscometry. The efficient degradation observed in associationwith the glycosidic radical formation is explained by initiationof free radical chain reactions that are propagated as long asthere is ozone in the system. As none of these phenomena werefound in the less crystalline cellulose, cellulose structureappears to be important for how free radical mediated cellulosedegradation develops.</p><p>The theory of free radical chain reactions coupled withdiffusion suggests a concentric expansion of the chain reactionsoutwards from the initial site of radical formation duringozonation of carbohydrates. This was confirmed by demonstratingfree radical chain reactions spreading from a spot of initiationoutwards during ozonation of a filter paper, using a pH-indicatorto monitor acid formation. Furthermore, the interior and exteriorof cellulose fibres doped with initiator were shown to bepermeated by small holes after ozonation.</p><p>Ethylene glycol was shown to improve the selectivity duringozone bleaching of oxygen bleached kraft pulp at pH 3. Optimalconditions were obtained at pH 3 for 25 wt% ethylene glycol. Theinfluence of ethylene glycol on selectivity is explained by aproportion of the free radical chain reactions being carried bythe ethylene glycol instead of the cellulose during ozonebleaching. The observations were summarised in the form of amodel where the observed degradations for pulp, bleached pulp andcotton fibres during both ozone bleaching and ethylene glycolassisted ozone bleaching were shown to agree with each other.</p><p>From g-irradiation of ozonised aqueous solutions of alcohol,the rate constant of superoxide formation from the peroxylradical of methanol was estimated to be 10 s^-1. Rate constants of the reactions between ozone andalkylperoxyl radicals were determined to be around 10⁴M^-1s^-1. The possibility of the reaction betweenalkylperoxyl radicals and ozone contributing significantly tofree radical chain reactions during ozonation of carbohydratesand alcohols could therefore be ruled out.</p><p>Cellulose, degradation, free radical, ozone, selectivity,ethylene glycol, alcohol, bleaching, kraft pulp, cotton linters,delignification, fibre, fibril, crystallinity, ferryl ion, freeradical chain reactions, TCF, viscometry, molecular weightdistributions, random scissions.</p>

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains x, 210 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 154-185).