Browsing by Subject "nitric oxide"
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Item Confocal Image-Based Computational Modeling of Nitric Oxide Transport in a Rat Mesenteric Lymphatic Vessel(2012-11-15) Wilson, John 1988-The lymphatic system plays an important role in protein and solute transport as well as the immune system. Its functionality is vital to proper homeostasis and fluid balance. Lymphatic fluid (lymph) may be propelled by intrinsic (active) vessel pumping or passively. With regard to the former, nitric oxide (NO) is known to play an important role in lymphatic vessel contraction and vasodilation. Lymphatic endothelial cells (LECs) are sensitive to shear and increases in flow have been shown to cause enhanced production of NO by LECs. Additionally, high concentrations of NO have been experimentally observed in the sinus region of mesenteric lymphatic vessels. The goal of this work was to develop a computational flow and mass transfer model using physiologic geometries obtained from confocal images of a rat mesenteric lymphatic vessel to determine the characteristics of NO transport in the lymphatic flow regime. Both steady and unsteady analyses were performed. Steady models were simulated by prescribing fully developed velocity profiles ranging from 0.5 mm s^-1 to 7 mm s^-1 as the inlet boundary conditions. Unsteady simulations were generated using a velocity profile taken from experimental data from in situ experiments with rats. Production of NO was shear-dependent; basal cases using constant production were also generated. Simulations revealed areas of flow stagnation adjacent to the valve leaflets, suggesting the high concentrations observed here experimentally are due to lack of convection in this region. LEC sensitivity was found to alter the concentration of NO in the vessel, and the convective forces were found to profoundly affect the concentration of NO at a Peclet value greater than or equal to approximately 61. The quasi-steady analysis was able to resolve wall shear stress within 0.15% of the unsteady case. However, the percent error between unsteady and quasi-steady conditions was higher for NO concentration (approximately 6.7%).Item Effects of light-emitting diode photostimulation on burn wound healing(2003-06-23) Mimi Leong; Lisa J. Gould; Massoud Motamedi; Linda G. Phillips; Hal K. Hawkins; Gregory AsimakisAnnually, more than 1.2 million persons in the United States require medical care for burns. Healing of deep burn wounds requires restored perfusion and neoangiogenesis to reestablish blood flow and limit ischemic damage.\r\nWe propose that LED photostimulation, by inducing macrophage proliferation and secretion of pro-angiogenic factors, will restore perfusion by increasing angiogenesis. \r\nAn in vitro inflammatory model and in vivo rodent thermal injury model were treated with LED at 670nm, 730nm, 880nm, or combination-670nm/730nm/880nm. Conditioned media were analyzed for VEGF and NO. Excised burn wounds underwent measurement of surface area, tensile strength, VEGF, nitrites, and immunohistochemical markers (iNOS, VEGF, cyclooxygenase-2, Factor VIII, ED-1) on days 3, 7, and 14.\r\nBoth in vitro and in vivo findings demonstrate that LED therapy has vulnerary effects on angiogenesis, by affecting macrophage production of VEGF and NO. These effects are wavelength and fluence-dependent.\r\nItem Exploration of the Linkage between the A:a gradient and oxygen transfer efficiency as a measure of response to treatment with inhaled nitric oxide in a heterogenous group of newborns treated for acute hypoxic respiratory failure(2008-07-07) Leah Michaelle Best; Alice Hill, RN, PhD.; Sheryl Bishop; Regina Lederman, RN, PhD.; Harvinder Bedi, MD; Daniel Traber, MDAcute hypoxic respiratory failure, (AHRF) is a severe condition associated with high morbidity and mortality rates in neonates. While much is known about the treatment for AHRF, less is understood about the types or degree of physiological shunting which occurs in this condition. Therefore, the purpose of this study was to explore the relationship between intrapulmonary and extra pulmonary shunting and oxygen transfer efficiency in the newborn treated for AHRF using inhaled nitric oxide. The aims of this study were to identify linkages between shunting and oxygenation prior to and during inhaled nitric oxide (iNO) therapy and to determine whether gestational age is predictive of infants’ response to iNO therapy. \r\nA secondary data analysis was conducted on 74 infants who received a treatment protocol of iNO over a one-week period. A:a gradient measures were examined to determine the correlation prior to treatment for baseline measures. Infants’ data were grouped by mode of ventilation to determine whether shunt differed between groups. Infants were then grouped by responders and non responders to examined differences in the A:a gradient over the treatment period. Finally gestational age was examined as a possible predictor of response, followed by examination of other possible predictive variables.\r\nThe findings suggest there was a negative moderate relationship between the A:a gradient (r = .33, p=.004) but there was no difference in the degree of shunt based on the use of high frequency vs. conventional ventilation (t = .07, p =.944). Additionally, there were significant main effects for time (F=4.94, p=.009) and groups (F=13.74, p=.001). Although the less mature infants failed to respond twice as often, they failed to reach statistically significant levels (c2=2.79, df=1, p=.095). Race, ventilator type, nor early onset-sepsis was a predictor in response to iNO. In conclusion, the A:a gradient provides useful information relative to oxygen transfer efficiency and it appears useful in trending infant’s response to treatment and degree of shunt. Although the more premature infant is most likely to fail the first iNO course, many survived without serious sequelae. Therefore, gestational age should not be used for exclusion criteria when designing treatment protocols.Item Investigation into the Emissions and Efficiency of Low Temperature Diesel Combustion(2011-10-21) Knight, Bryan MichaelAs global focus shifts towards the health and conservation of the planet, greater importance is placed upon the hazardous emissions of our fossil fuels, as well as their finite supply. These two areas remain intense topics of research in order to reduce green house gas emissions and increase the fuel efficiency of our vehicles. A particular solution to this problem is the diesel engine, with its inherently fuel-lean combustion, which gives rise to low CO2 production and higher efficiencies than its gasoline counterpart. Diesel engines, however, typically exhibit higher nitrogen oxides (NOx [NOx = NO NO2, where NO is nitric oxide and NO2 is nitrogen dioxide]) and soot. There exists the possibility to simultaneously reduce both emissions with the application of low temperature diesel combustion (LTC). While exhibiting great characteristics in simultaneous reductions in nitrogen oxides and soot, LTC faces challenges with higher carbon monoxide (CO) and hydrocarbon (HC) emissions, as well as penalties in fuel efficiency. The following study examines the characteristics of LTC which contribute to the differences in emissions and efficiency compared to typical conventional diesel combustion. More specifically, key engine parameters which are used to enable LTC, such as EGR and fuel pressure are swept through a full range to determine their effects on each combustion regime. Analysis will focus on comparing both combustion regimes to determine how exhaust gas recirculation (EGR) and fuel pressure relate to lowering NO and smoke concentrations, and how these relate to a penalty in fuel efficiency. This study finds that the application of LTC is able to realize a 99 percent reduction in NO while simultaneously reducing smoke by 17 percent compared to the conventional combustion counterpart. Through a sweep increasing EGR, LTC is able to defeat the typical soot ? NO tradeoff; however, brake fuel conversion efficiency decreases 6.8 percent for LTC, while conventional combustion realizes a 4 percent increase in efficiency. The sweep of increasing fuel pressure confirms typical increases in NO and decreases in smoke for both LTC and conventional combustion; however, brake fuel conversion efficiency increases 2.3 percent for LTC and drops 4 percent for conventional combustion.Item Localization and partial immunological characterization of Fasciola hepatica Thioredoxin(Texas A&M University, 2005-02-17) McKown, Richard DwayneThis study reports the localization and partial characterization of thioredoxin from the parasitic trematode Fasciola hepatica. Snails (Pseudosuccinia columella) were raised in culture and infected with F. hepatica so that Western blotting and immunohistochemical techniques could be utilized to determine the presence of thioredoxin in different stages of the parasite?s development. The results of these experiments showed that thioredoxin was present in the tegument, gut epithelium, excretory canal epithelium and sperm, of the adult parasite as well as in the tegument and gut of the redia and cercaria intermediate stages. In situ hybridization was used to determine the localization and possible differential mRNA expression of two different F. hepatica thioredoxin isotypes (Fh2020.A and Fh2020.SL) in the adult parasite. The in situ hybridization results showed that both isotypes are expressed in the tegument and gut epithelium. Fh2020.A stains with a greater intensity possibly demonstrating a difference in the amount of expression between the two isotypes. Recombinant F. hepatica thioredoxin expressed in bacteria using the pMAL? Protein Fusion and Expression System was used to test its affects on the production of super oxide anion by murine peritoneal macrophages, bovine monocyte-derived macrophages and bovine whole blood neutrophils, and nitric oxide production by mouse peritoneal macrophages and bovine monocyte-derived macrophages. The results of the cellular assays were not definitive due to the fact that the maltose binding protein (MBP) moiety of the recombinant thioredoxin, when tested alone, increased production of nitric oxide by bovine monocyte-derived macrophages. Consequently, since the MBP could not be effectively separated from the thioredoxin portion of the recombinant, allowing the thioredoxin affects to be tested independently, no true conclusions regarding its affects on the host immune cells tested could be drawn. This is the first report of the localization of thioredoxin in both the adult F. hepatica as well as in specific intermediate stages of the parasite. These studies demonstrate the possible affects that a protein tag can have on experimental results and demonstrate how such data may be interpreted when a non-cleaved recombinant protein is used in cellular or other assays when compared to native or cleaved recombinant proteins.Item The relationship between nitric oxide synthase (NOS) and cyclooxygenase (COX) in the control of cervical ripening and parturition(2005-03-14) Stephen Gureasko Marx; Robert E. Garfield, Ph.D., Supervisor; Yurij Vedernikov, M.D., Ph.D.; Thomas Collins, Ph.D.; Randall Given, Ph.D.; Gwendoly V. Childs, Ph.D.; George Saade, M.D.Stephen G. Marx\r\nThe University of Texas Medical Branch at Galveston, April 2005\r\n\r\nSupervisor: Robert E. Garfield\r\n\r\nThe purpose of these studies is to examine if there is relationship between iNOS and COX-2 in the control of cervical ripening and parturition. Cervices were obtained from estrus and timed pregnant Sprague-Dawley rats (n = 4-10 per group) under normal conditions; or after treating with LPS (100ƒÝg i.p.), Onapristone (3mg/rat), progesterone (2.5 mg, twice daily), L-NAME (50mg/day), or SNP (0.3mg/rat). Collagen changes were measured and visualized with the picrosirius polarization method. Expression of iNOS and COX-2 mRNA was determined using RT-PCR. Immunohistochemistry (IHS) was performed for localization of the iNOS and COX-2 enzymes (significance: P<0.05). Picrosirius polarization showed a decrease in the organization and birefringence of the cervical collagen from the non-pregnant state through pregnancy and is supported by changes in the luminosity (P<0.001). The iNOS and COX-2 enzymes were mainly localized in the cervical muscle with labeling also in the vascular smooth muscle and epithelium. Under normal term pregnant conditions, iNOS mRNA levels decrease as COX-2 mRNA levels increased demonstrating an inverse correlation (Spearman r = -0.497; P = 0.00295). Onapristone stimulated preterm labor and/or birth causing a parallel increase in iNOS and COX-2 mRNA demonstrating a positive correlation (Spearman r = 0.456; P = 0.03). Progesterone prolonged pregnancy stimulating a decrease in the iNOS and COX-2 (P=0.036) mRNA. In comparing term to preterm laboring conditions, there is a significant increase in the iNOS mRNA (P=0.004) but not the COX-2 mRNA. LPS enhanced the iNOS mRNA (P<0.001) but had no effect on the COX-2 mRNA. L-NAME had no effect on the COX-2 or iNOS mRNA. SNP decreased the COX-2 and iNOS with the decrease in the iNOS being significant (P=0.007). In conclusion, under normal term pregnant conditions iNOS and COX-2 play an important role in regulating cervical ripening and parturition but the pathways appear to act independently of one another in regulating iNOS and COX-2 expression at the mRNA level. Under preterm laboring conditions, when NO is up regulated and/or over expressed, there may be an interaction between the NO and PG pathways in the control of cervical ripening and parturition. \r\n\r\nItem Selective Catalytic Reduction (SCR) of nitric oxide with ammonia using Cu-ZSM-5 and Va-based honeycomb monolith catalysts: effect of H2 pretreatment, NH3-to-NO ratio, O2, and space velocity(Texas A&M University, 2004-09-30) Gupta, SaurabhIn this work, the steady-state performance of zeolite-based (Cu-ZSM-5) and vanadium-based honeycomb monolith catalysts was investigated in the selective catalytic reduction process (SCR) for NO removal using NH3. The aim was to delineate the effect of various parameters including pretreatment of the catalyst sample with H2, NH3-to-NO ratio, inlet oxygen concentration, and space velocity. The concentrations of the species (e.g. NO, NH3, and others) were determined using a Fourier Transform Infrared (FTIR) spectrometer. The temperature was varied from ambient (25 C) to 500 C. The investigation showed that all of the above parameters (except pre-treatment with H2) significantly affected the peak NO reduction, the temperature at which peak NO reduction occurred, and residual ammonia left at higher temperatures (also known as 'NH3 slip'). Depending upon the particular values of the parameters, a peak NO reduction of around 90% was obtained for both the catalysts. However, an accompanied generation of N2O and NO2 species was observed as well, being much higher for the vanadium-based catalyst than for the Cu-ZSM-5 catalyst. For both catalysts, the peak NO reduction decreased with an increase in space velocity, and did not change significantly with an increase in oxygen concentration. The temperatures at which peak NO reduction and complete NH3 removal occurred increased with an increase in space velocity but decreased with an increase in oxygen concentration. The presence of more ammonia at the inlet (i.e. higher NH3-to-NO ratio) improved the peak NO reduction but simultaneously resulted in an increase in residual ammonia. Pretreatment of the catalyst sample with H2 (performed only for the Cu-ZSM-5 catalyst) did not produce any perceivable difference in any of the results for the conditions of these experiments.Item The development and application of a diode-laser-based ultraviolet absorption sensor for nitric oxide(Texas A&M University, 2004-09-30) Anderson, Thomas NathanThis thesis describes the development of a new type of sensor for nitric oxide (NO) that can be used in a variety of combustion diagnostics and control applications. The sensor utilizes the absorption of ultraviolet (UV) radiation by the NO molecule to determine the concentration via optical absorption spectroscopy. UV radiation at 226.8 nm is generated by sum frequency mixing the outputs from a 395-nm external cavity diode laser (ECDL) and a 532-nm diode-pumped, intracavity frequency doubled Nd:YAG laser in a beta-barium borate (BBO) crystal. This radiation is used to probe the (v'=0, v"=0) band of the ?*?+ - ?*? electronic transition of NO. The ECDL is tuned so that the UV radiation is in resonance with a specific energy level transition, and it is then scanned across the transition to produce a fully resolved absorption spectrum. Preliminary experiments were performed in a room-temperature gas cell in the laboratory to determine the accuracy of the sensor. Results from these experiments indicated excellent agreement between theoretical and experimental absorption line shapes as well as NO concentrations. Further experiments were performed at two actual combustion facilities to demonstrate the operation of the sensors in realistic combustion environments. Tests on a gas turbine auxiliary power unit (APU) at Honeywell Engines and Systems and on a well-stirred reactor (WSR) at Wright-Patterson Air Force Base produced excellent results despite the harsh temperatures and vibrations present. Overall, the sensitivity was estimated to be 0.8 parts per million (ppm) of NO (at 1000 K) for a 1 meter path length and the measurement uncertainty was estimated to be ?10%.Item The effects of cycle-to-cycle variations on nitric oxide (NO) emissions for a spark-ignition engine: Numerical results(Texas A&M University, 2004-11-15) Villarroel, MilivoyThe objectives of this study were to 1) determine the effects of cycle-to-cycle variations (ccv) on nitric oxide (NO) emissions, and 2) determine if the consideration of ccv affects the average NO emission as compared to the mean cycle NO emission. To carry out the proposed study, an engine simulation model was used. The simulation determines engine performance and NO emissions as functions of engine operating conditions, engine design parameters, and combustion parameters. An automotive, spark-ignition engine at part load and 1400 rpm was examined in this study. The engine cycle simulation employed three zones for the combustion process: (1) unburned gas, (2) adiabatic core region, and (3) boundary-layer gas. The use of the adiabatic core region has been shown to be especially necessary to capture the production of nitric oxides which are highly temperature dependent. Past research has shown that cyclic variations in combustion cause ccv of burn duration, ignition delay and equivalence ratio. Furthermore, literature has shown that variations of these three input parameters may be approximated by a normal frequency distribution. Using the mean and standard deviation, and a random number generator, input values were tabulated for the ignition delay, burn duration and equivalence ratio. These three input parameters were then used to simulate cyclic variations in the combustion process. Calculated results show that cyclic variations of the input parameters cause the cycle-by-cycle NO emissions to increase and decrease by as much as 59% from the mean cycle NO of 3,247 ppm. The average NO emission resulting from ccv was 4.9% less than the mean cycle NO emission. This result indicates that cyclic variations must be considered when calculating the overall NO emissions.Item The Role of Nitric Oxide Signaling in Learning-Induced Behavioral Plasticity and Neural Circuit Dynamics in the Sea Hare Aplysia californica(2014-08-07) Farruggella, JesseAnimals constantly regulate their behaviors in response to environmental stimuli. These adjustments involve an active and dynamic balance between defensive and non-defensive behaviors, and underlying each change are the fundamental alterations within the neural circuits that form the cellular bases for those behaviors. The marine mollusk Aplysia californica provides an ideal model system for examining plasticity at both the behavioral and neural levels following exposure to aversive stimuli. After receiving a noxious stimulus, Aplysia elicit the learned behavioral change known as sensitization through which their defensive responses are enhanced, in particular the tail-siphon withdrawal reflex (TSWR). Sensitization of the TSWR manifests from an increase in facilitation at the neuronal synapses that govern the reflex. Sensitization training induces a concurrent suppression of non-defensive behaviors, particularly feeding behavior. The suppression of feeding results from a decrease in excitability of neuron B51, which is a key decision-making neuron in the feeding neural circuit that is critical to the production of feeding behavior. The neurotransmitter serotonin has been shown to mediate and induce the sensitization of the TSWR, but it is not involved in the concomitant suppression of feeding behavior. This study proposed the neurotransmitter nitric oxide (NO) as the signaling molecule that mediates the modification of feeding. The goal of this study was to examine the roles of NO signaling in the enhancement of the TSWR produced by sensitization training, the sensitization training-induced suppression of feeding, and the modulation of the feeding neural circuit. NO signaling was found to be necessary for sensitization training-induced behavioral plasticity. When NO signaling was pharmacologically blocked by in vivo application of the NO synthase inhibitor N?-nitro-L-arginine methyl ester (L-NAME), sensitization training failed to produce the sensitization of the TSWR. L-NAME also prevented sensitization training from inducing the suppression of feeding behavior known to occur concomitantly with the sensitization of the TSWR. These results suggested that modifications of both defensive and non-defensive behaviors via aversive learning were prevented when NO signaling was blocked. NO signaling was also found to modulate the Aplysia feeding neural circuit. NO is known to tonically inhibit feeding behavior in vivo. The application of L-NAME in vitro to isolated preparations of the feeding circuit caused the excitability and activity of neuron B51 to increase. Conversely, when NO signaling was augmented by in vitro application of the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) to the isolated feeding circuit, the excitability of B51 decreased in a manner analogous to that produced by sensitization training. Neither L-NAME nor SNAP treatments affected the resting membrane properties of B51, indicating that the bidirectional modulation of B51 excitability by NO signaling acts through voltage-dependent channels. Based on these results, it is evident that NO signaling modulates the changes in multiple behaviors following exposure to aversive stimuli, and that NO signaling is significantly involved in and essential for behavioral and cellular plasticity in Aplysia.