264 research outputs found
Genetic overexpression of eNOS attenuates hepatic ischemia-reperfusion injury
No full textPrevious studies have shown that endothelial nitric oxide (NO) synthase (eNOS)-derived NO is an important signaling molecule in ischemia-reperfusion (I-R) injury. Deficiency of eNOS-derived NO has been shown to exacerbate injury in hepatic and myocardial models of I-R. We hypothesized that transgenic overexpression of eNOS (eNOS-TG) would reduce hepatic I-R injury. We subjected two strains of eNOS-TG mice to 45 min of hepatic ischemia and 5 h of reperfusion. Both strains were protected from hepatic I-R injury compared with wild-type littermates. Because the mechanism for this protection is still unclear, additional studies were performed by using inhibitors and activators of both soluble guanylyl cyclase (sGC) and heme oxygenase-1 (HO-1) enzymes. Blocking sGC with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and HO-1 with zinc (III) deuteroporphyrin IX-2,4-bisethyleneglycol (ZnDPBG) in wild-type mice increased hepatic I-R injury, whereas pharmacologically activating these enzymes significantly attenuated I-R injury in wild-type mice. Interestingly, ODQ abolished the protective effects of eNOS overexpression, whereas ZnDPBG had no effect. These results suggest that hepatic protection in eNOS-TG mice may be mediated in part by NO signaling via the sGC-cGMP pathway and is independent of HO-1 signal transduction pathways
Cardiomyocyte-specific overexpression of NO synthase-3 protects against myocardial ischemia-reperfusion injury
No full textThese results provide evidence that site-specific targeting of eNOS gene therapy may be more advantageous in limiting MI-R injury and subsequent cardiac dysfunction
L-arginine: A unique amino acid for improving depressed wound immune function following hemorrhage
No full textObjective: To determine whether L-arginine has any salutary effects on wound immune cell function following trauma-hemorrhage. Background. Depressed wound immune function contributes to an increased incidence of wound infections following hemorrhage. Although administration of L-arginine has been shown to restore depressed cell-mediated immune responses following hemorrhage potentially by maintaining organ blood flow, it remains unknown whether Larginine has any salutary effects on the depressed local immune response at the wound site. Methods: Male mice were subjected to a midline laparotomy and polyvinyl sponges were implanted subcutaneously in the abdominal wound prior to hemorrhage (35 +/- 5 mm Hg for 90 min and resuscitation) or sham operation. During resuscitation mice received 300 mg/kg body weight L-arginine or saline (vehicle). Sponges were harvested 24 h thereafter, wound fluid collected and wound immune cells cultured for 24 h in the presence of LPS. Pro- (IL-1beta, IL-6) and anti-inflammatory (IL-10) cytokines were determined in the supernatants and the wound fluid. In addition, wounds were stained for IL-6 immunohistochemically. In a separate set of animals, skin and muscle blood flow was determined by microspheres. Results: The capacity of wound immune cells to release IL-1beta and IL-6 in vitro was significantly depressed in hemorrhaged mice receiving vehicle. Administration of L-arginine, however, improved wound immune cell function. In contrast, in vivo the increased IL-6 release at the wound site was decreased in L-arginine-treated mice following hemorrhage. Moreover, IL-10 levels were significantly increased in the wound fluid in hemorrhaged animals receiving L-arginine compared to vehicle-treated mice. In addition, the depressed skin and muscle blood flow after hemorrhage was restored by L-arginine. Conclusions: Thus, L-arginine might improve local wound cell function by decreasing the inflammatory response at the wound site. Since L-arginine protected wound immune cell function this amino acid might represent a novel and useful adjunct to fluid resuscitation for decreasing wound complications following hemorrhage. Copyright beta 2002 S. Karger AG, Basel
Atmospheric Mercury and Methane in the South-Central U.S.
No full textThis study characterized temporal and spatial variations of atmospheric mercury and methane (CH4), and investigated their emission sources. Speciated atmospheric mercury observations collected over the period from 2008 to 2010 at the U.S. Atmospheric Mercury Network sites (AMNet) were analyzed. We found similar median levels of gaseous elemental mercury (GEM) as well as its seasonality at 11 sites. Seasonal and diurnal variations were also observed for gaseous oxidized mercury (GOM) and particulate bound mercury (PBM).
This study also reports continuous measurements of total gaseous mercury (THg = GEM + GOM) for the first time in urban Houston area. We found that the median level of THg was consistent with the current global background level. A predominant feature of THg was the frequent occurrence of large THg spikes. Our measurements revealed that the variability of THg was primarily controlled by nearby mercury sources.
Atmospheric mercury emissions in the Barnett Shale area were studied by employing both stationary measurements and mobile laboratory surveys. The influence of oil and natural gas (ONG) emissions was substantial in this area, as inferred from the i-pentane/n-pentane ratio (= 1.17). However, few THg plumes were captured in our extensive mobile laboratory surveys. Only one compressor station and one natural gas condensate processing facility were found to have significant THg emissions. Our results suggest that the majority of ONG facilities are not significant sources of THg; however, it is highly likely that a small number of these facilities contribute a relatively large amount of the emissions in the ONG sector.
Atmospheric CH4 was also investigated to quantify emissions from ONG operations and landfills in the Barnett Shale area. The background CH4 level (10th percentile) was 1.89 ppmv, which was higher than the northern hemisphere background level. Emission rates were estimated using Inversed Dispersion Models. Model results show that well pad emissions were linearly correlated with gas production, yielding a total well pad emission rate of 1.44×105 kg CH4/hr in the Barnett Shale area. It was found that CH4 emissions from compressor stations and gas processing plants were substantial; several of them have similar emission rates as a major landfill.Earth and Atmospheric Sciences, Department o
Spatial and Temporal Distribution of Speciated Atmospheric Mercury in Southeastern Texas
No full textThe purpose of this study was to investigate and compare the contribution of anthropogenic emissions to the levels of atmospheric mercury in both urban and coastal settings of southeastern Texas. Speciated atmospheric mercury measurements were obtained from the ideally located University of Houston Moody Tower and University of Houston Coastal Center from March 22, 2012- June 6, 2013 and July 26, 2013-June 6, 2013, respectively. The use of key tracer gases from various data sources as well as meteorological data from ground-based stationary monitoring facilities was used in the evaluation of high-mercury pollution plumes, the general direction of the source origin as well as seasonal and diurnal mixing ratios of the three atmospheric mercury species. At the costal site measurements showed consistently lower mixing ratios for all mercury species and had no significant mercury events recorded. The urban University of Houston Moody Tower had much higher and more dramatic fluctuations in mixing ratios for all three mercury species with two major mercury events recorded. Both events were associated with periods of low wind conditions and Houston Ship Channel origins. While the measurements collected at the urban location show consistencies with past studies conducted at the same location, the complexity of atmospheric mercury interactions prevent any indepth interpretations of the results.Earth and Atmospheric Sciences, Department o
Measurements and analysis of ozone production in Houston and Los Angeles
No full textOzone is a respiratory irritant that affects all groups of people, but can be of significant concern to young children, those with respiratory illnesses such as asthma, and the elderly. Repeated exposure can cause permanent lung damage. An estimated 123 million people in the Unites States live in regions designated as non-attainment for the 2008 8-hour ozone standard of 75 ppbv. Nearly 5.9 million people live in the Houston-Galveston-Brazoria non-attainment area, and over 15.7 million live in the Los Angeles-South Coast Air Basin non-attainment area.
The work presents the results and analysis of measurements collected during several field campaigns in Houston, TX between 2006 and 2012, as well as in Pasadena, CA (CalNex) in the summer of 2010. Part one focuses on the comparison of O3, CO, NO, and NO2 measured continuously at two heights on the UH main campus in the fall of 2011 and 2012 and finds that the titration of O3 to NO2 accounts for ~50% of the observed nighttime differences on average, while it accounts for nearly 100% of the differences during some mornings. The second part presents the results of photochemical box modeling of O3 production rates during three campaigns in Houston and during CalNex, which shows the effects of VOC reductions on O3 production and the differences between the spring and fall O3 seasons in Houston. Finally, an examination of the NOy budget during CalNex and the impacts that the choice of classification of days has on the analysis will be discussed reports that the overall agreement between measured NOy and the sum of individual NOy species is good, and that distinctly different results for calculated O3 production efficiencies are found depending on which classification method is applied to the measurements.Earth and Atmospheric Sciences, Department o
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