1,720,973 research outputs found
Application of chitosan in the treatment of wastewater from agricultural sources
Full text linkModern agricultural practices is dependent on fertilizers, rich in nitrogen, phosphorus, and potassium. However, not all of the nutrients are absorbed and are usually washed away into rivers and streams. These runoffs accumulate in downstream large water bodies and enhance the growth of algae and unwanted plants, which leads to eutrophication. The consequences of eutrophication are the degradation of water quality and destruction of the affected aquatic eco-system. This study primarily examines the efficacy of metal-complexed chitosan composites in the attenuation of phosphates at three field test sites. In addition to this, chitosan was also studied for its potential use in hydrogen sulfide removal and its application in biological treatment. Metal-chitosan composites used in conjunction with red sand proved most effective in the removal of phosphates reducing it from ~19 μg/ml by 6-30 fold. Furthermore, these composites were capable of attenuating dissolved hydrosulfides from 1mM by 100-fold
Some aspects of glutathione and L-arginine/nitric oxide metabolism in the maintenance of platelet function.
No full textEvidence is presented here for the regulation of platelet activation by intra-platelet levels of glutathione (GSH) and L-arginine. Our data is consistent with the intra-platelet GSH ((GSH) \sb{\rm ip}) modulation through the regulation of the thromboxane A\sb2 (TxA\sb2) biosynthesis. The reduction of (GSH) \sb{\rm ip} by 100 M 1-chloro-2,4-dinitrobenzene (CDNB) enhanced thrombin-induced platelet aggregation and ADP-induced platelet aggregation was inhibited by the elevation of (GSH) \sb{\rm ip} through a facilitative GSH-specific transport system. Platelet facilitative GSH uptake was subsequently characterized as being Na\sp+-independent, concentration dependent (K\sb{\rm M} and V\sb{\rm max} for GSH uptake in platelet plasma membrane vesicles (PPMV) is M and 178 27 pmol/min/mg protein, respectively), inhibited by GSH analogs, enhanced by KCl-induced membrane depolarization and sensitive to the intraplatelet thiol redox status since the K\sb{\rm M} and V\sb{\rm max} for GSH uptake in intact platelets changed from 137 M and 42.2 pmol/min/10\sp9 platelets, respectively, to 31.7 M and 31.3 pmol/min/10\sp9 platelets, respectively, on reducing intra-platelet GSH with 100 M CDNB. Glutathione reductase (GR) was found to be inhibited by physiological levels of GSH with species-dependent differences. With respect to varying GSSG, GSH inhibited GR from human platelets in an apparent uncompetitive manner (K\sb{\rm i} = 6.6 mM), while bovine intestinal mucosa and yeast GRs displayed apparent mixed hyperbolic inhibition (K\sb{\rm i} = 2.9 and 2.4 mM, respectively), and the E. coli enzyme exhibited an apparent, competitive inhibition (K\sb{\rm i} = 12.1 mM). In the course of this study it was observed that 1-(4-chlorophenyl)-4,4-dimethyl-5-diethylamino-1-penten-3-one hydrobromide (CDDP) is an alpha class selective glutathione S-transferase (GST) substrate and that certain analogs of CDDP are GST inhibitors with K\sb{\rm i}s ranging from 7.5 to 53.4 M. Exogenous L-arginine inhibited ADP-induced platelet aggregation which suggests that platelet-derived NO regulates platelet activation. Platelet L-arginine uptake was via the cationic amino acid transporter, system y\sp+, which appears to be regulated by NO. S-nitrosoglutathione (GSNO) was found to be photolyzed by visible light. The release of NO by GSNO photolysis resulted in an enhanced NO-dependent cytotoxicity towards HL-60 cells. GSNO, or related compounds, may therefore find use as photochemotherapeutic agents.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .S49. Source: Dissertation Abstracts International, Volume: 56-11, Section: B, page: 6097. Adviser: Bulent Mutus. Thesis (Ph.D.)--University of Windsor (Canada), 1995
Some biochemical aspects of nitric oxide in biological systems.
No full textThe role of nitric oxide (NO) in biological systems is becoming increasingly important. Initially, the effect of NO on the transport of L-arginine into human platelets was studied. NO is known to have an effect on this system, and platelets have been shown to possess an isoform of the enzyme nitric oxide synthase. Two NO donors (S-nitrosoglutathione and S-nitroso-N-acetyl penicillamine), a source of NO\sp{+} and a solution of authentic NO were used to measure the effect of NO on the L-arginine transport system. The toxicity of nitric oxide can be due to its direct effects, or more likely through higher oxidation products such as peroxynitrite (\sp{-}OONO). There is evidence for peroxynitrite production in vivo, and this has been linked to an assortment of pathological conditions. An indirect method of peroxynitrite detection is the formation nitrotyrosine. We have found evidence for nitrotyrosine formation in platelet proteins from patients suffering from prolonged hyperglycemia. Calmodulin is one of the proteins implicated in this peroxynitrite modification. The effect of peroxynitrite on the enzyme glutathione S-transferase was also studied. (Abstract shortened by UMI.)Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1997 .H68. Source: Masters Abstracts International, Volume: 37-01, page: 0263. Adviser: Bulent Mutus. Thesis (M.Sc.)--University of Windsor (Canada), 1997
Chemical, biochemical, and cellular aspects of S-nitrosothiols.
No full textNitric oxide is involved in many physiological processes including vascular control, immune responses and neurotransmission under physiological conditions. Many functions of NO are triggered by the formation of its metabolite, S-nitrosothiol. S-nitrosothiols play an important role in the delivery, storage and transport of NO. In addition, they regulate the activity of a variety of proteins and enzymes. The first part of my study is focused on studying the regulatory role of S-nitrosothiol. In this study, S-nitrosothiols including S-nitrosoglutathione (GSNO) have been demonstrated to regulate the activity of a key protein in plasma, fibrinogen, without chemically modifying it. GSNO and a few other RSNO derivatives have demonstrated the ability to inhibit thrombin catalyzed fibrinogen polymerization via their effects on fibrinogen, whereas the activity of thrombin itself remained intact upon incubation with GSNO. The percentage of inhibition obtained ranged from 43% to 68%. Upon incubation with GSNO, the alpha-helix content of fibrinogen increased by 15%. The GSNO fibrinogen interaction was allosteric and reversible with an estimated dissociation constant of 3-10 muM. Fibrinogen has been demonstrated to contain 2 binding sites for GSNO. The second part of my study deals with the chemical and cellular aspects of S-nitrosothiols. I formed a coloured nitrite adduct of sinapinic acid (SA) which has shown the ability to S-nitrosate thiol-containing amino acids and proteins. In addition, this nitrite adduct has demonstrated the potential for spectrophotometric detection of NO derived species, NO+ or peroxynitrite in vitro or under physiological conditions. In addition, I synthesized an S-nitroso derivative of 1-octadecane thiol, S-nitrosooctadecane (SNOD). We also designed SNOD-BSA nanoparticles, which were capable of delivering large amounts of SNOD to human fibroblasts. In preliminary studies, the illumination of SNOD-BSA loaded fibroblasts induced apoptosis in 58% of the fibroblasts. The third part of my study deals with the molecular aspects of S-nitrosothiols. Under physiological conditions, the reaction between NO and O2 •- produces peroxynitrite. I have shown previously that upon exposure to light, an air-saturated GSNO solution can also give rise to peroxynitrite. Peroxynitrite causes inactivation of many proteins and enzymes by nitrating their tyrosine residues. We created three different tyrosine mutants of rat calmodulin namely, CaM Y99A CaM Y138A, and CaM Y99AY138A for assessing the roles of its two tyrosine residues. Mutations of the tyrosine residues apparently affected calmodulin's stability and its Ca2+ binding ability. S-nitrosothiols are also capable of causing DNA damage. For the purpose of decontaminating platelet-rich plasma, we synthesized two fluorophore labelled S-nitrosthiols namely N-dansyl-S-nitrosohomocysteine (Dns-HCysNO) and N-dansyl-S-nitrosoglutathione (Dns-GSNO), which could mediate the cleavage of DNA upon exposure to light. Dns-HcysNO solutions degraded R773 plasmid DNA completely upon exposure to light and the extent of degradation was a function of exposure time. In contrast, only a high concentration of Dns-HCysNO degraded plasmid DNA partially without exposure to light. Thus, Dns-HCysNO could be potentially utilized for light-induced DNA cleavage in order to decontaminate platelet rich plasma.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .A44. Source: Dissertation Abstracts International, Volume: 64-08, Section: B, page: 3800. Adviser: Bulent Mutus. Thesis (Ph.D.)--University of Windsor (Canada), 2003
Peroxynitrite modification of calmodulin: Structural and functional consequences.
No full textNitric oxide (NO), a free radical species is an important retrograde messenger in cell regulation, but is cytotoxic in higher concentrations. Superoxide (O\sb2\sp{{\cdot}-}) and NO react yielding peroxynitrite anion (OONO\sp-) which is a potent and toxic oxidant that can attack a wide range of biological targets, for eg. in regulation of blood flow, neurotransmission, sepsis etc. In proteins, peroxynitrite mediated damage occurs via nitration of the aromatic side chains. In the present study, we examined the susceptibility of the two Tyr residues of calmodulin (CaM) to OONO\sp- mediated nitration in vitro as indicated by the amino acid analysis. CaM and OONO\sp- modified CaM were compared with respect to the activation of the CaM dependent enzymes calcineurin phosphatase (CaN) and phosphodiesterase (PDE). Upon modification, the estimated K\sb{\rm activity} for CaN was 60 fold lower than that observed with the native CaM. There were no apparent change in the K\sb{\rm activity} of PDE, but the extent of activation was reduced by 79% of that of native CaM. We assessed the binding patterns of CaM (bovine and octopus) with a peptide analog of smMLCK which is the CaM binding domain of smMLCK enzyme, but the OONO\sp- modified CaM failed to bind the same peptide. The effect of peroxynitrite modification on the metal binding properties of CaM were probed by aromatic energy transfer Tb\sp{3+}-fluorescence spectroscopy. Energy transfer efficiency of a 14 mer peptide containing 3-nitro-Tyr analogous to the 3\rm\sp{rd}\ Ca\sp{2+} binding loop of CaM was diminished by 3 fold in comparison to the peptide containing Tyr side chain. The Tb\sp{3+} binding data from nitrated CaM, when normalized was sensitive to the occupation of all four Ca\sp{2+} binding sites whereas with native CaM, the occupation of the 3\sp{\rm rd} and 4\sp{\rm th} sites were detected. This suggests that OONO\sp- modification induced a conformational change on CaM.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1997 .P379. Source: Masters Abstracts International, Volume: 37-01, page: 0264. Adviser: Bulent Mutus. Thesis (M.Sc.)--University of Windsor (Canada), 1997
Intraplatelet abnormalities in diabetes mellitus.
No full textIntraplatelet abnormalities in the platelets from diabetics have been evaluated with a view of understanding diabetes related platelet hyperaggregation. Three of the modulators involved in the platelet regulatory mechanism namely glutathione (GSH), calmodulin (CaM) and nitric oxide (NO) have been assessed in platelets from both normal and diabetic subjects. GSH and NO levels in the platelets from diabetics were lower (50% & 57% respectively) when compared to platelets from normal subjects, whereas there was no change in the level of total CaM in platelets from diabetics. Estimates of steady state kinetic parameters (apparent K\sb{\rm M} and apparent V\sb\max) for the platelet enzymes glutathione reductase, -glutamyl transpeptidase, glutathione-S-transferase and glutathione peroxidase have been reported for the first time. The kinetic parameters of platelet glutathione reductase, -glutamyl transpeptidase and glutathione S-transferase were essentially independent of the glycemic state of the subjects. However, the apparent K\sb{\rm M} (t-BuOOH) of glutathione peroxidase was fold higher in platelets from uncontrolled diabetics in comparison to platelets from normal subjects. Further, in vitro and in vivo study established that nonenzymatic glycation of the GSH metabolic enzyme glutathione peroxidase (GSH-Px) resulted in a decrease (4 fold) in affinity for its substrate and thereby a loss in the catalytic efficiency of up to 33%. The loss in GSH-Px catalytic efficiency and lowered level of GSH in platelets from diabetics provided new evidence for the previously observed elevation in peroxide levels in diabetic platelets. The impairment in GSH-Px activity due to nonenzymatic glycation has been discussed as a potential contributor to the platelet hyperaggregability in diabetics. The study also showed that intraplatelet calmodulin is susceptible to a nonenzymatic glycation reaction and that there is a 3 fold increase in the glycation of CaM in platelets from diabetics (21.6%) when compared to platelets from normal subjects (7.71%). As part of the study an enzyme linked immunosorbent assay system was devised to detect nanogram levels of glycated calmodulin in blood platelets for use in clinical settings as a short time-window index of glycemic status. Subsequently, a distinct isoform of the CaM dependent nitric oxide producing enzyme nitric oxide synthase was purified to homogeneity from human platelets. The native enzyme appears to be dimeric, with an estimated molecular weight of 150 kDa. The platelet nitric oxide synthase exhibited cofactor and kinetic characteristics similar to those from other cells and tissues but most interestingly possessed a distinct subunit molecular weight ( kDa). The underproduction of NO (57%) in platelets from diabetics when compared to the platelets from normal subjects is discussed in terms of a possible contribution to the diabetes related platelet hyperaggregation.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .M87. Source: Dissertation Abstracts International, Volume: 56-11, Section: B, page: 6095. Adviser: Bulent Mutus. Thesis (Ph.D.)--University of Windsor (Canada), 1994
Protein disulfide isomerase may facilitate the efflux of nitrite derived S-nitrosothiols from red blood cells
No full textProtein disulfide isomerase (PDI) is an abundant protein primarily found in the endoplasmic reticulum and also secreted into the blood by a variety of vascular cells. The evidence obtained here, suggests that PDI could directly participate in the efflux of NO from red blood cells (RBC). PDI was detected both in RBC membranes and in the cytosol. PDI was S-nitrosylated when RBCs were exposed to nitrite under similar to 50% oxygen saturation but not under similar to 100% oxygen saturation. Furthermore, it was observed that hemoglobin (Hb) could promote PDI S-nitrosylation in the presence of similar to 600 nM nitrite. In addition, three lines of evidence were obtained for PDI-Hb interactions: (1) Hb co-immunoprecipitated with PDI; (2) Hb quenched the intrinsic PDI fluorescence in a saturable manner; and (3) Hb-Fe(II)-NO absorption spectrum decreased in a [PDI]-dependent manner. Finally. PDI was detected on the surface RBC under similar to 100% oxygen saturation and released as soluble under similar to 50% oxygen saturation. The soluble PDI detected under similar to 50% oxygen saturation was S-nitrosylated. Based on these data it is proposed that PDI is taken up by RBC and forms a complex with Hb. Hb-Fe(II)-NO that is formed from nitrite reduction under similar to 50% 02, then transfers NO+ to either Hb-Cys beta 93 or directly to PDI resulting in S-nitroso-PDI which transverses the RBC membrane and attaches to the RBC surface. When RBCs enter tissues the S-nitroso-PDI is released from the RBC-surface into the blood where its NO is transferred into the endothelium thereby inducing vasodilation, suggesting local oxygen-dependent dynamic interplays between nitrite, NO and S-nitrosylation. (C) 2013 The Authors. Published by Elsevier By. Open access under CC BY-NC-ND licens
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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