Hydrogen sulfide (H2S) is notable for its toxicity and corrosion is one of the major sources of odor in wastewater treatment plants. Evaluation of existing or potential odor problems requires knowledge of the type of compounds likely to cause such problems and the mechanism of their formation in wastewater systems which is discussed in this paper. For the present study, the East Bank wastewater treatment plant was chosen since it is the largest wastewater treatment facility within Jefferson Parish, Louisiana. To combat the odor problems in this facility, a monitoring program was designed and developed to characterize the severity of the problem. The program involved continuous ambient monitoring followed by careful evaluation of the data obtained from sample collection and analysis. Different instruments were strategically placed within the facility after a hot-spot analysis to determine the major sources of odor generation.

ATP-sensitive potassium (K+) channels (KATP) in vascular smooth muscle cells (VSMC) play a major role in the regulation of vascular tone by coupling cell contractility and K+ fluxes to cellular metabolism. They are composed of the regulatory sulphonylurea receptors (SUR) and the pore-forming inwardly rectifying K+ (Kir) channels. SUR subunits interact closely with Kir subunits by conferring their sensitivity to nucleotide or sulphonylurea. However, the modulatory mechanisms of KATP channels in VSMC are largely unknown. In particular, the effects of hydrogen sulfide (H2S) and hydroxylamine (HA) on KATP channels and underlying mechanisms have not been addressed in VSMC of resistance arteries. The combined approaches including molecular biology, biochemical assays, and patch-clamp techniques were applied. The electrophysiological and pharmacological features of native KATP channels in VSMC and cloned KATP channels in HEK-293 cells, and the modulation of KATP channels by H2S and HA in single freshly isolated VSMC from rat mesenteric arteries were characterized. In the present study, only small conductance KATP channels of 13 pS were found in rat mesenteric artery VSMC. The recorded macroscopic and unitary KATP currents were activated by nucleoside diphosphate in the presence of magnesium and K+ channel openers, inhibited by a specific KATP channel blocker glibenclamide, but were insensitive to ATP inhibition. The reversal potential shifted rightward in response to the elevation of extracellular K+ and matched the calculated K+ equilibrium potential, indicating the basal currents in both VSMC and HEK-293 cells are carried by K+ ions. Heterologous expression of Kir6.1 with SUR2B in HEK-293 cells formed functional channels and elicited whole-cell K+ currents, which shared some similar biophysical characteristics of native KATP channels in VSMC. Basal KATP currents and resting membrane potential in VSMC were reduced by glibenclamide, demonstrating that KATP channels contribute to background K+ conductance and in the setting of resting membrane potential in this resistance artery. Exogenous H2S enhanced macroscopic and unitary KATP currents with an EC50 of 116 ± 8.3 µM and hyperpolarized membrane potential. H2S activated KATP channels by increasing the open probability of single channels, but not single channel conductance. The reduced endogenous H2S production by D, L-propargylglycine resulted in the attenuation of KATP currents. H2S-induced activation of KATP channels and resultant hyperpolarization were not mediated by cGMP signaling pathway. HA enhanced reversibly KATP currents in a dose-dependent fashion with an EC50 of 54±3.4 µM and also hyperpolarized the cell membrane. HA-stimulated KATP currents were blocked by free radical scavengers (superoxide dismutase and N-acetyl-L-cysteine), and KATP channels were stimulated by a free radical generating system (hypoxanthine/xanthine oxidase), indicating the involvement of superoxide (O2-) in HA effects. Sodium nitroprusside and 8-Br-cGMP did not affect basal KATP currents and HA-stimulated KATP currents, disproving the involvement of NO-sGC-cGMP-mediated signaling pathway in the HA effects. Therefore, HA-induced KATP channel activation and hyperpolarization are likely due to the generation of O2-. In conclusion, KATP channels in resistance artery VSMC serve as the regulatory targets of H2S and HA. These two endogenous molecules modulate KATP channels via different mechanisms. H2S may directly act on KATP channel proteins while HA oxidized them via the formation of O2-, leading to the activation of KATP channels.

ATP-sensitive potassium (K+) channels (KATP) in vascular smooth muscle cells (VSMC) play a major role in the regulation of vascular tone by coupling cell contractility and K+ fluxes to cellular metabolism. They are composed of the regulatory sulphonylurea receptors (SUR) and the pore-forming inwardly rectifying K+ (Kir) channels. SUR subunits interact closely with Kir subunits by conferring their sensitivity to nucleotide or sulphonylurea. However, the modulatory mechanisms of KATP channels in VSMC are largely unknown. In particular, the effects of hydrogen sulfide (H2S) and hydroxylamine (HA) on KATP channels and underlying mechanisms have not been addressed in VSMC of resistance arteries. The combined approaches including molecular biology, biochemical assays, and patch-clamp techniques were applied. The electrophysiological and pharmacological features of native KATP channels in VSMC and cloned KATP channels in HEK-293 cells, and the modulation of KATP channels by H2S and HA in single freshly isolated VSMC from rat mesenteric arteries were characterized. In the present study, only small conductance KATP channels of 13 pS were found in rat mesenteric artery VSMC. The recorded macroscopic and unitary KATP currents were activated by nucleoside diphosphate in the presence of magnesium and K+ channel openers, inhibited by a specific KATP channel blocker glibenclamide, but were insensitive to ATP inhibition. The reversal potential shifted rightward in response to the elevation of extracellular K+ and matched the calculated K+ equilibrium potential, indicating the basal currents in both VSMC and HEK-293 cells are carried by K+ ions. Heterologous expression of Kir6.1 with SUR2B in HEK-293 cells formed functional channels and elicited whole-cell K+ currents, which shared some similar biophysical characteristics of native KATP channels in VSMC. Basal KATP currents and resting membrane potential in VSMC were reduced by glibenclamide, demonstrating that KATP channels contribute to background K+ conductance and in the setting of resting membrane potential in this resistance artery. Exogenous H2S enhanced macroscopic and unitary KATP currents with an EC50 of 116 ± 8.3 µM and hyperpolarized membrane potential. H2S activated KATP channels by increasing the open probability of single channels, but not single channel conductance. The reduced endogenous H2S production by D, L-propargylglycine resulted in the attenuation of KATP currents. H2S-induced activation of KATP channels and resultant hyperpolarization were not mediated by cGMP signaling pathway. HA enhanced reversibly KATP currents in a dose-dependent fashion with an EC50 of 54±3.4 µM and also hyperpolarized the cell membrane. HA-stimulated KATP currents were blocked by free radical scavengers (superoxide dismutase and N-acetyl-L-cysteine), and KATP channels were stimulated by a free radical generating system (hypoxanthine/xanthine oxidase), indicating the involvement of superoxide (O2-) in HA effects. Sodium nitroprusside and 8-Br-cGMP did not affect basal KATP currents and HA-stimulated KATP currents, disproving the involvement of NO-sGC-cGMP-mediated signaling pathway in the HA effects. Therefore, HA-induced KATP channel activation and hyperpolarization are likely due to the generation of O2-. In conclusion, KATP channels in resistance artery VSMC serve as the regulatory targets of H2S and HA. These two endogenous molecules modulate KATP channels via different mechanisms. H2S may directly act on KATP channel proteins while HA oxidized them via the formation of O2-, leading to the activation of KATP channels.

No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 139-140). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 139-140). Also available on the Internet.

Worldwide research devotes significant effort to identify new, targetable molecular mechanisms in the field of angiogenesis, since therapeutic modulation of angiogenesis can critically alter the progression of a number of diseases. Stimulation of angiogenesis is desirable in situations characterized by tissue-damaging ischemia where blood supply is severely reduced, such as lower limb diabetic arteriopathy or following myocardial infarct. In contradistinction, stemming excessive or ectopic angiogenesis can be beneficial in situations such as solid tumor growth or in neovascular age-related macular degeneration. It has been previously shown that Hydrogen Sulfide (H2S), a new vasoactive gasotransmitter, can initiate angiogenic responses which depend on the activation of ATP-sensitive potassium channels (KATP). Intriguingly, C-type Natriuretic Peptide (CNP), which is also known to activate KATP, has been reported to promote endothelial cell growth; however, its angiogenic properties have not been explored at any depth. This pattern prompted us to investigate whether direct KATP activation induces angiogenic responses and whether endothelial responses to CNP or Vascular Endothelial Growth Factor (VEGF) indeed require KATP activation. We undertook a dual-pronged approach, based on both in vivo and in vitro experimental approaches. In vivo, chick embryo chorioallantoic membrane (CAM) angiogenesis was similarly enhanced by the direct KATP channel activator SG-209 and by the polypeptides CNP or VEGF. Two KATP inhibitors, Glibenclamide and 5-Hydroxydecanoate (5-HD), abrogated both basal and CNP-induced CAM angiogenesis. In vitro, direct activators of KATP such as Nicorandil and SG- 209 and receptor-acting agonists such as VEGF and CNP, increased proliferation and migration in the mouse brain endothelial cell line bEnd.3. In addition, VEGF and CNP induced comparable capillary tube-like formation by Human Umbilical Vein Endothelial cells (HUVECs) in low growth factor Matrigel. All these in vitro pro-angiogenic endothelial responses were effectively abrogated by Glibenclamide or by 5-HD. Transfection of HUVECs with a siRNA specifically targeting the inwardly rectifying potassium channel (Kir) 6.1 subunit decreased the expression of this subunit at both the mRNA and the protein level. The resulting knock-down of the Kir6.1 KATP subunit impaired HUVEC migration through transwells in vitro and substantially decreased tubular network formation in Matrigel in response to either the direct KATP activator SG-209 or the receptor-operating KATP activator CNP. Furthermore, the bEnd.3 endothelial cell proliferation and migration responses to SG-209 required mobilization of the “classic” endothelial pro-angiogenesis kinases Erk1/2, p38 and Akt, since the responses to SG-209 were all abolished by each of the respective kinase inhibitors. This work allows us to firmly conclude that: a) direct pharmacological modulation of KATP channels affects angiogenic responses in vitro and in vivo, b) CNP is a bona fide angiogenic factor, as potent and efficient to mobilize endothelial cells as VEGF, c) the angiogenic effects of CNP and VEGF depend on the activation of endothelial KATP channels and specifically require the expression of the Kir6.1 pore-forming KATP subunit, and finally d) KATP activation may be a common molecular mechanism that underpins angiogenesis to a wide variety of endogenous vasoactive stimuli that includes H2S, VEGF and CNP. The therapeutic implications of this work are significant: Sulfonylurea-type KATP channel inhibitors, with questionable selectivity for pancreatic β-cells, are widely used drugs to treat type II diabetes, a disease characterized by arterial dysfunction and higher incidence of myocardial and lower limb ischemia. The outcome of cardiac ischemia in diabetic patients is worse if they have been treated with sulfonylureas, indicating some, until now unresolved, deleterious cardiovascular activity of this class of compounds. The present demonstration that endothelial KATP channel activation is a common pro-angiogenic mechanism, may in part explain this unfavorable outcome of sulfonylurea treatment in diabetics. Furthermore, it raises the need to design new molecules which, while inhibiting the pancreatic KATP channels, should spare the endothelial KATP channels and the ensuing angiogenesis, thus exhibiting increased therapeutic benefit. / Σε πολλά εργαστήρια, σε παγκόσμιο επίπεδο, συντελείται σημαντική ερευνητική προσπάθεια για την ταυτοποίηση νέων μοριακών μηχανισμών στο πεδίο της αγγειογένεσης ως στόχων ανάπτυξης φαρμάκων, καθώς η θεραπευτική ρύθμιση της αγγειογένεσης μπορεί να επηρεάσει σημαντικά την εξέλιξη πολλών ασθενειών. Η διέγερση της αγγειογένεσης είναι επιθυμητή σε καταστάσεις ισχαιμίας όπου η παροχή αίματος μειώνεται σοβαρά, με αποτέλεσμα δυσλειτουργία ή νέκρωση ιστών, όπως πχ συμβαίνει κατά την εμφάνιση αρτηριοπάθειας στο διαβητικό κάτω άκρο ή μετά από έμφραγμα του μυοκαρδίου. Σε αντιδιαστολή, η αναστολή υπερβολικής ή έκτοπης αγγειογένεσης μπορεί να είναι επωφελής σε καταστάσεις όπως κατά την ανάπτυξη συμπαγούς όγκου ή σε νεοαγγειακή εκφύλιση της ωχράς κηλίδας σχετιζόμενη με την ηλικία. Έχει δειχθεί ότι το Υδρόθειο (H2S), ένας νέος αγγειοδραστικός αέριος διαβιβαστής (gasotransmitter), μπορεί να εκκινήσει αγγειογόνες αποκρίσεις που εξαρτώνται από την ενεργοποίηση των ευαίσθητων στο ΑΤΡ διαύλων καλίου (ΚΑTP). Μας κίνησε επίσης το ενδιαφέρον η αναφορά οτι το C-νατριουρητικό πεπτίδιο (CNP), που είναι γνωστό ότι ενεργοποιεί τους ίδιους διαύλους καλίου, δύναται να προάγει τον πολλαπλασιασμό των ενδοθηλιακών κυττάρων. Ωστόσο, οι αγγειογενετικές ιδιότητες του CNP δεν έχουν διερευνηθεί σε βάθος. Αυτή η σύγκλιση μας ώθησε στη διερεύνηση του κατά πόσον η άμεση ενεργοποίηση των ΚΑTP διαύλων καλίου προκαλεί αγγειογενετική απόκριση και επίσης εάν η απόκριση των ενδοθηλιακών κυττάρων στο CNP ή στον αγγειακό ενδοθηλιακό αυξητικό παράγοντα (VEGF) απαιτούν πράγματι ενεργοποίηση των διαύλων ΚΑTP. Η πειραματική προσέγγιση σχεδιάστηκε με βάση τόσο in vivo, όσο και in vitro μεθόδους. In vivo, η φυσιολογικά συντελλούμενη αγγειογένεση στην χοριοαλλαντοϊκή μεμβράνη εμβρύου όρνιθας (CAM) ενισχύθηκε απο τον άμεσο ενεργοποιητή των διαύλων ΚΑTP, το μόριο SG-209, καθώς και απο τα πολυπεπτίδια CNP και VEGF. Δύο αναστολείς των διαύλων ΚΑTP, η γλιβενκλαμίδη (glibenclamide) και το 5-υδροξυδεκανοϊκό οξύ (5-HD), ανέστειλαν τόσο την αγγειογένεση υποβάθρου (basal) της χοριοαλλαντοϊκής μεμβράνης, όσο και την επαγόμενη απο το CNP αγγειογένεση το σύστημα αυτό. In vitro, άμεσοι ενεργοποιητές των διαύλων ΚΑTP όπως η νικορανδίλη (nicorandil) και το SG-209, καθώς και έμμεσοι ενεργοποιητές, μέσω αρχικής αγωνιστικής δράσης τους σε ειδικούς υποδοχείς, όπως ο VEGF και το CNP, αύξησαν τον πολλαπλασιασμό και τη μετανάστευση εγκεφαλικών ενδοθηλιακών κυττάρων ποντικού της κυτταρικής σειράς bEnd.3. Επιπλέον, ο VEGF και το CNP επάγουν με παρόμοιο τρόπο το σχηματισμό τριχοειδών αγγείων απο ενδοθηλιακά κύτταρα απομονωμένα απο φλέβα ανθρώπινου ομφάλιου λώρου (HUVEC) που δημιουργούνται σε Matrigel με χαμηλή περιεκτικότητα σε αυξητικούς παράγοντες. Όλες αυτές οι in vitro θετικές αγγειογενετικές ενδοθηλιακές αποκρίσεις αναστέλλονται παρουσία της γλιβενκλαμίδης και του 5-HD. Διαμόλυνση κυττάρων HUVECs με siRNA που στοχεύει ειδικά την υπομονάδα του δίαυλου καλίου Kir 6.1 μείωσε αποτελεσματικά την έκφραση αυτής της υπομονάδας τόσο σε επίπεδο mRNA όσο και σε πρωτεϊνικό επίπεδο. Η μείωση στην έκφραση της υπομονάδας Kir6.1 των διαύλων καλίου προκάλεσε καταστολή της μετανάστευσης των κυττάρων HUVECs σε θαλάμους τύπου φρέατος (transwells) καθώς και σημαντική απομείωση στο σχηματισμό δικτύου τριχοειδών αγγείων σε Matrigel, όταν αυτές οι αποκρίσεις επάγονται είτε απο τον άμεσο ενεργοποιητή των διαύλων ΚΑTP, το μόριο SG-209, είτε απο τον έμμεσο ενεργοποιητή των διαύλων ΚΑTP (μέσω δράσης σε ειδικούς υποδοχείες), το πεπτίδιο CNP. Επιπλέον, ο πολλαπλασιασμός και η μετανάστευση των ενδοθηλιακών κυττάρων bEnd.3 που διεγείρονται ως απόκριση στο μόριο SG-209 απαιτούν κινητοποίηση των "κλασσικών" ενδοθηλιακών προ-αγγειογενετικών κινασών Erk1 / 2, p38 και Akt, δεδομένου ότι οι αποκρίσεις αυτές στον SG-209 καταστάλθηκαν απο κάθε ένα από τους αντίστοιχους αναστολείς των κινασών. Η παρούσα μελέτη μας επιτρέπει να συμπεράνουμε ότι: α) άμεση φαρμακολογική τροποποίηση της λειτουργίας των διαύλων ΚATP επηρεάζει σημαντικά τις αγγειογόνες αποκρίσεις τόσο in vitro όσο και in νίνο, β) το CNP είναι όντως ένας αγγειογενετικός παράγοντας, τόσο ισχυρός και αποτελεσματικός για την κινητοποίηση ενδοθηλιακών κυττάρων όσο και ο VEGF, γ) οι αγγειογόνες επιδράσεις του CNP και του VEGF εξαρτώνται από την ενεργοποίηση των ενδοθηλιακών διαύλων ΚΑTP και συγκεκριμένα απαιτούν την έκφραση της υπομονάδας Kir6.1 του διαύλου ΚΑTP, και τέλος δ) η ενεργοποίηση των διαύλων ΚΑTP φαίνεται οτι είναι ένας κοινός μοριακός μηχανισμός που υποστηρίζει την αγγειογένεση που διεγείρεται απο ένα ευρύ φάσμα ενδογενών αγγειοδραστικών χυμικών ερεθισμάτων, που περιλαμβάνουν το H2S, τον VEGF και το CNP. Οι επιπτώσεις της μελέτης αυτής στην θεραπευτική πράξη είναι πιθανώς σημαντικές: Οι τύπου σουλφονυλουρίας αναστολείς διαύλων των διαύλων ΚΑTP, που στοχεύουν μη-επαρκώς επιλεκτικά σε β-παγκρεατικά κύτταρα, χρησιμοποιούνται ευρέως ως φάρμακα για τη θεραπεία του διαβήτη τύπου II, μια ασθένεια που χαρακτηρίζεται από γενικευμένη δυσλειτουργία του αρτηριακού συστήματος, με συνέπεια υψηλή επίπτωση εμφράγματος του μυοκαρδίου και ισχαιμίας των κάτω άκρων. Η εξέλιξη ενός επεισοδίου μυοκαρδιακής ισχαιμίας σε διαβητικούς ασθενείς είναι χειρότερη εάν αυτοί ακολουθούσαν φαρμακολογική θεραπεία με σουλφονυλουρίες, υποδεικνύοντας κάποια, μέχρι τώρα σε σημαντικό βαθμό ανεξήγητη, επιβλαβή καρδιαγγειακή επίδραση αυτής της κατηγορίας ενώσεων. Η παρούσα μελέτη αποδεικνύει ότι η ενεργοποίηση ενδοθηλιακών διαύλων ΚΑTP είναι ένας κοινός προ- αγγειογενετικός μηχανισμός, που μπορεί εν μέρει να εξηγήσει αυτή την αρνητική έκβαση της πρότερης θεραπείας με σουλφονυλουρίες σε διαβητικούς. Επιπλέον, η έρευνα αυτή υποστηρίζει την ανάγκη για το σχεδιασμό νέων μορίων, τα οποία, ενώ θα αναστέλλουν τους διαύλους ΚΑTP στο πάγκρεας, δεν θα επηρεάζουν τους ενδοθηλιακούς διαύλους ΚΑTP και την εξαρτώμενη απο αυτούς αγγειογένεση, και έτσι θα παρουσιάζουν, βάσει των ανωτέρω, βελτιωμένη θεραπευτική δράση.

The production of biogas through the anaerobic digestion of cattle manure and its subsequent use in the generation of electricity on large Ontario farms is currently economically attractive. While larger farms have advantages of scale, there are substantially more small farms for which individually designed and engineered biogas systems are prohibitively expensive. Although biogas has numerous benefits, it contains hydrogen sulfide, an odourous, poisonous and corrosive gas, which emits sulfur oxides upon combustion. Larger systems can afford to use specialized biogas engines which tolerate some levels of hydrogen sulfide. For smaller scale systems to be financially attractive the hydrogen sulfide needs to be removed inexpensively, allowing for more flexibility in engine choice for electricity generation. In this work, the solid by-products from the anaerobic digestion process were used to create activated carbon, which has a high capacity for hydrogen sulfide. Not only does the carbon adsorb hydrogen sulfide, it allows for the surface oxidation of hydrogen sulfide to elemental sulfur and sulfate. Since the sulfur is in a beneficial form for fertilizer use, and there are no chemicals added to create the carbon, the spent sulfur-containing carbon can be land applied, eliminating any spent carbon disposal costs.

The production of biogas through the anaerobic digestion of cattle manure and its subsequent use in the generation of electricity on large Ontario farms is currently economically attractive. While larger farms have advantages of scale, there are substantially more small farms for which individually designed and engineered biogas systems are prohibitively expensive. Although biogas has numerous benefits, it contains hydrogen sulfide, an odourous, poisonous and corrosive gas, which emits sulfur oxides upon combustion. Larger systems can afford to use specialized biogas engines which tolerate some levels of hydrogen sulfide. For smaller scale systems to be financially attractive the hydrogen sulfide needs to be removed inexpensively, allowing for more flexibility in engine choice for electricity generation. In this work, the solid by-products from the anaerobic digestion process were used to create activated carbon, which has a high capacity for hydrogen sulfide. Not only does the carbon adsorb hydrogen sulfide, it allows for the surface oxidation of hydrogen sulfide to elemental sulfur and sulfate. Since the sulfur is in a beneficial form for fertilizer use, and there are no chemicals added to create the carbon, the spent sulfur-containing carbon can be land applied, eliminating any spent carbon disposal costs.

Thesis (Ph.D.)--University of Tulsa, 1990. / Bibliography: leaves 86-91.