Effect Of High Partial Pressure Research Articles

Effect of High Oxygen Partial Pressure on 4-Hydroxy-2-Nonenal Induced Myoglobin Oxidation, Oxidation-Reduction Potential, and Myoglobin Unfolding

ObjectivesHigh oxygen modified atmosphere packaging (MAP) is often employed by the meat industry to enhance the appearance of fresh meat. 4-hydroxy-2-nonenal (HNE) is an ɑ-, β-unsaturated aldehyde derived from the oxidation of Ɯ6–polyunsaturated fatty acids. Previous research has examined the effect of HNE on oxymyoglobin oxidation at atmospheric oxygen partial pressure (20%). However, limited knowledge is currently available on the effects of HNE on myoglobin redox stability under high oxygen conditions. Therefore, the objective of this study was to examine the effect of high partial pressure of oxygen on HNE induced myoglobin oxidation.Materials and MethodsOxymyoglobin (0.15 mM; pH 5.6) prepared via hydrosulfite-mediated reduction was mixed with HNE (1.05 mM; dissolved in water), whereas controls received an equal volume of water. Following mixing, both samples were assigned to either high oxygen partial pressure (78%) or atmospheric oxygen partial pressure packaging. The samples were incubated either in a coffin-style display case maintained at 2 ± 1°C (under continuous lighting) for 0, 2 or 6 d, or in an incubator for 0, 1, 2, or 3 h at 25°C. Metmyoglobin formation, oxidation–reduction potential, and myoglobin unfolding were evaluated on each of the storage time points. The experiments were replicated 3 times (n = 3) and the data were analyzed using the Mixed Procedure of SAS (SAS Inst. Inc., Cary, NC).ResultsMyoglobin oxidation, oxidation–reduction potential, and protein unfolding properties were not different (P > 0.05) between treatments on time 0 for samples incubated at 4 and 25°C. On d 2 and 6, the high oxygen partial pressure treatment resulted in increased metmyoglobin formation and protein unfolding (P < 0.05) than the atmospheric oxygen partial pressure samples. Moreover, atmospheric oxygen partial pressure treatment had greater oxidation–reduction potential than high oxygen partial pressure treatment. At 25°C, high oxygen partial pressure treatments exhibited greater myoglobin oxidation from 1 to 3 h of incubation (P < 0.05) than atmospheric conditions.ConclusionThe results suggest that high oxygen partial pressure accelerated HNE induced oxidation irrespective of temperature. Further research using molecular protein biomarkers may provide an understanding of the underlying mechanistic steps involved in the interaction of HNE with the myoglobin at higher oxygen partial pressure.

An investigation on the effect of high partial pressure of hydrogen on the nanocrystalline structure of silicon carbide thin films prepared by radio-frequency magnetron sputtering

The aim of the study reported in this paper is to investigate the role of the high partial pressure of hydrogen introduced during the growth of nanocrystalline silicon carbide thin films (nc-SiC:H). For this purpose, we report the preparation as well as spectroscopic studies of four series of nc-SiC:H obtained by radio-frequency magnetron sputtering at high partial pressure of hydrogen by varying the percentage of H2 in the gas mixture from 70% to 100% at common substrate temperature (TS=500°C). The effects of the dilution on the structural changes and the chemical bonding of the different series have been studied using Fourier transform infrared and Raman spectroscopy. For this range of hydrogen dilution, two groups of films were obtained. The first group is characterized by the dominance of the crystalline phase and the second by a dominance of the amorphous phase. This result confirms the multiphase structure of the grown nc-SiC:H thin films by the coexistence of the SiC network, carbon-like and silicon-like clusters. Furthermore, infrared results show that the SiC bond is the dominant absorption peak and the carbon atom is preferentially bonded to silicon. The maximum value obtained of the crystalline fraction is about 77%, which is relatively important compared to other results obtained by other techniques. In addition, the concentration of CHn bonds was found to be lower than that of SiHn for all series.Raman measurements revealed that the crystallization occurs in all series even at 100% H2 dilution suggesting that high partial pressure of hydrogen favors the formation of silicon nanocrystallites (nc-Si). The absence of both the longitudinal acoustic band and the transverse optical band indicate that the crystalline phase is dominant.

Does pneumoperitoneum adversely affect growth, development and liver function in biliary atresia patients after laparoscopic portoenterostomy?

We assessed the effect of high partial pressure of arterial carbon dioxide (PaCO2) due to pneumoperitoneum (PP) on growth (height/weight) and development (gross/fine motor function, receptive/expressive communication, and social interaction), by comparing outcome after portoenterostomy (PE) for biliary atresia (BA) using laparoscopic PE (LPE: n = 13) and open PE (OPE: n = 13) cases performed between 2005 and 2014. Our PE is based on Kasai's original PE. All data were collated prospectively. Differences in duration of follow-up (LPE: 38.8 months; OPE: 38.1 months), jaundice clearance (LPE: 12/13 = 92.3 %; OPE: 9/13 = 69.2 %), survival with the native liver (LPE: 10/13 = 76.9 %; OPE: 9/13 = 69.2 %), incidence of cholangitis, hypersplenism, and incidence of esophageal varices were not significant. Mean intraoperative PaCO2 was significantly higher in LPE (LPE: 50.1 mmHg; OPE: 40.7 mmHg, p < 0.05). Liver function impairment was not statistically different, although LPE results were slightly worse. There was no overall delay in growth observed, although height/weight gain was more consistent in LPE. The pattern of developmental delay observed was similar for LPE and OPE suggesting that developmental delay is not PE-related; in other words, PP is not implicated in developmental delay. PP during LPE would appear to have no adverse effects on overall growth/development and liver function in BA patients.

Hyperoxia: A Review of the Risks and Benefits in Adult Cardiac Surgery

Perioperative hyperoxia has been claimed to have a number of therapeutic advantages. However, in the setting of cardiac surgery and cardiopulmonary bypass (CPB), enthusiasm for its use has been tempered by concerns regarding the effect of high partial pressures of oxygen on cardiac, vascular, and respiratory function and the potential for exacerbation of ischemia–reperfusion injury. There is encouraging evidence from animal studies that hyperoxia is effective in myocardial preconditioning, at least in nondiseased hearts. There is also evidence that hyperoxia reduces gas microemboli production and longevity during CPB, although it is unclear whether this translates into a clinical benefit in terms of a reduction in postoperative neurological morbidity. Hyperoxia leads to changes in cardiovascular function. However, the effects of these changes remain unclear. At a tissue level, there is evidence that hyperoxia does not lead to improvement in partial pressure of oxygen. Indeed, the opposite may be the case with reductions in capillary density leading to areas of reduced tissue oxygenation. The risks of hyperoxia in association with CPB include lung injury, increased systemic reactive oxygen species generation, and exacerbation of reactive oxygen species-mediated myocardial injury at the time of reperfusion. Again, it is difficult to know whether the changes demonstrated are temporary or if they translate into a worsening of clinical outcomes. In conclusion, perhaps the key to the use of hyperoxia is in the timing. In the period pre-CPB, hyperoxia may precondition the myocardium and, paradoxically, confer a degree of protection against reactive oxygen species-induced injury at the time of reperfusion. Hyperoxia during CPB is probably harmful and should be avoided unless the risk from gas microemboli is thought to be significant, in which case the risks and benefits to the individual patient must be weighed.

The influence of calcite loading on producer gas composition and tar concentration of radiata pine pellets in a dual fluidised bed steam gasifier

This study has investigated the influence of calcite loading on the producer gas composition and the tar concentrations on a 100kWth dual fluidised bed (DFB) steam gasifier. In the experiments, wood pellets of radiata pine were used as the feedstock and the operating temperature in the bubbling fluidised bed reactor (BFB) was set at 710–750°C while that in the fast fluidised bed reactor (FFB) was controlled at 800°C. In the first part of the experiments, the calcite loading was varied at 0%, 50% and 100% at constant steam to biomass (S/B) ratio of 0.8kg/kgdry. In the second part of the experiment, the influence of S/B ratio was examined at 50% and 100% calcite loadings. The present study has concluded that the ratio of H2/CO can be varied from 0.9 to 4.2 by increasing the calcite loading and the S/B ratio only at 100% calcite loading. In addition, the total tar concentration decreased exponentially from 5.0 to 0.7g/Nm3 with the calcite loading. This method provides the flexibility to meet the required H2/CO in target downstream applications. However, the disadvantage of increasing calcite loading was that the attrition rate increased exponentially from 0.5% at 0% loading to 4.1kg/h at 100% loading. The tar reduction from 0% to 50% calcite loading was found to be higher than that from 50% to 100% calcite loading. This could be mainly due to the suppressing effect of high partial pressure of H2 on the steam reforming of those tar compounds.

CO2 Capture from Simulated Syngas via Cyclic Carbonation/Calcination for a Naturally Occurring Limestone: Pilot-Plant Testing

Experiments were performed using a dual fluidized bed reactor system, operated in a batch mode, in order to investigate the effects of steam and simulated syngas on CO{sub 2} capture and sorbent conversion efficiency for a naturally occurring Polish calcitic limestone. In addition, the effect of high partial pressures of CO{sub 2} on the calcination process was examined using either oxygen-enriched air or oxy-fuel combustion in the calciner. As expected, calcination under oxy-fuel conditions resulted in decreased carbonation conversion due primarily to particle sintering and pore pluggage. On average there was a decrease in carbonation conversion of approximately 36.5 and 33.4% for carbonation with steam and steam/simulated syngas, respectively, compared to similar experiments using oxygen-enriched air. However, during the carbonation of the limestone with steam present in the feed gas, it was observed that the high CO{sub 2} capture efficiency period was significantly extended compared to carbonation with only CO{sub 2} present. This resulted in increased CaO conversion from approximately 16.1 to 29.7% for the initial carbonation cycle. A further increase in carbonation conversion from 29.7 to 46.9%, was also observed when simulated syngas conditions (CO, H{sub 2}) were used in the carbonator. Analysis of the outlet gases also confirmedmore » that the calcined limestone catalyzes the water gas shift reaction, which we believe results in enhanced CO{sub 2} concentration levels at the grain surfaces of the sorbent.« less

Novel active dirhodium complexes for the low pressure hydroformylation reaction. Unexpected inhibiting effect of high partial pressures of hydrogen

Abstract The complex [Rh 2 (μ-S t Bu) 2 (CO) 2 (PPh 3 ) 2 ] was shown to be an active precursor for the low pressure hydroformylation of terminal alkenes in the presence of an excess of triphenylphosphine. Preliminary kinetic studies have shown that as usual has CO an inhibiting effect, but unexpectedly the reaction was also inhibited by high H 2 /CO ratios.

Influence of partial pressure of oxygen and carbon dioxide on Methylomonas clara in continuous culture

The inhibitory effect of high partial pressures of O2 and CO2 on Methylomonas clara growing on methanol was assessed. Above a pO2 of 700 mbar and a pCO2 of 330 mbar the cell mass yield decreased with increasing pO2 and pCO2. No washout was observed even when pure oxygen was used, but the cell mass yield was very low. High pCO2 increased the aminoacid and nucleic acid content. CO2 fixation by this organism seems to be feasible, but it was not possible to determine if high pCO2 stimulates CO2 assimilation.

Effect of oxygen exposure on lung clearance of amines.

Depression of 5-hydroxytryptamine (5-HT) clearance by the endothelial cells of the lung has been shown to be a sensitive index of oxygen (O2) induced pulmonary dysfunction. In the present study, we evaluated the effect of high partial pressures of O2 on the pulmonary clearance of two other bioactive amines, norepinephrine (NE) and imipramine (IMP), which are removed from the circulation by interaction with the pulmonary endothelial cell. Lungs from rats previously exposed to either air or 100% O2 at 1 ATA for 12 to 48 h were isolated, ventilated and perfused via the pulmonary artery. Clearances of NE and IMP were calculated from the arteriovenous difference of radiolabeled amine across the lung. There was a progressive reduction in the clearance of NE with increasing duration of O2 exposure. Compared to control lungs, clearance was depressed 7% after 12 h, 39% (P < 0.001) after 24 h, and 51% (P < 0.001) after 48 h O2 exposure. In contrast, pulmonary clearance of IMP was not altered by exposure to 100% O2. These results indicate that high partial pressures of O2 depress clearance of NE but not IMP in the isolated, perfused rat lung. The most likely mechanism for the depression of NE clearance is interference with the transport properties of lung endothelium.

The effect of high partial pressures of oxygen on photosynthesis in Chlorella—I. : The effect on end products of photosynthesis

During periods of photosynthesis in 14CO 2 of up to 70 min at concentrations of carbon dioxide up to 4 per cent, the major end products were sucrose and a polyglucan. At the lower concentrations of carbon dioxide the addition of isonicotinyl hydrazide (INH) stimulated the production of glycollate and glycine but did not affect the total fixation. Raising the partial pressure of oxygen or the addition of iodoacetamide increased the production of glycollate but decreased the total fixation. At higher concentrations of carbon dioxide both the inhibition of photosynthesis by oxygen and the stimulation in production of glycollate were decreased; whereas the inhibition of photosynthesis by iodoacetamide increased. Carbon-14 was incorporated into the sugar phosphates of the photosynthetic cycle during short term photosynthesis and the further metabolism of this carbon studied during photosynthesis in 12CO 2. The main radioactive products were sucrose and polyglucan. At low concentrations of carbon dioxide, raising the partial pressure of oxygen or the addition of INH led to an accumulation of glycollate. Similar effects of high partial pressure of oxygen and addition of INH were found on the products of photometabolism of exogenous [U- 14C]glucose in carbon dioxide free conditions.