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Diversity and complexity of flavodiiron NO/O2 reductases.
Folgosa, F, Martins, MC, Teixeira, M
FEMS microbiology letters. 2018;(3)
Abstract
Flavodiiron proteins (FDPs) are a family of enzymes endowed with nitric oxide (NO) or oxygen reductase activities, forming the innocuous nitrous oxide (N2O) or water molecules, respectively. FDPs are widespread in the three life kingdoms, and have a modular nature, being each monomer minimally constituted by a metallo-β-lactamase-like domain containing a catalytic diiron centre, followed by a flavodoxin one, with a flavin mononucleotide. Since their discovery, additional domains have been found in FDPs, attached to the C-terminus, and containing either extra metal (iron) centers or extra flavin binding modules. Following an extensive analysis of genomic databases, we identified novel domain compositions, and proposed a new classification of FDPs in eight classes based on the nature and number of extra domains.
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2.
Oxygen uptake rate as a tool for on-line estimation of cell biomass and bed temperature in a novel solid-state fermentation bioreactor.
Arora, S, Singh, P, Rani, R, Ghosh, S
Bioprocess and biosystems engineering. 2018;(7):917-929
Abstract
Direct measurement of cell biomass is difficult in a solid-state fermentation (SSF) process involving filamentous fungi since the mycelium and the solid substrate are often inseparable. However, respiratory data are rich in information for real-time monitoring of microbial biomass production. In this regard, a correlation was obtained between oxygen uptake rate (OUR) and biomass concentration (X) of Rhizopus oryzae MTCC 1987, during phytase production, in an intermittently mixed novel SSF bioreactor. To obtain the correlation, various models describing sigmoidal growth were tested, namely the logistic, Gompertz, Stannard, and Schnute models. Regression analysis of experimental results, at different operating conditions of inlet air flow rate and relative humidity suggested that OUR and X were correlated well by the logistic model (R2 > 0.90). To corroborate the use of respiratory data for on-line measurement of metabolic activity, OUR was related to metabolic heat generation rate (Rq), and the logistic model was found to satisfactorily correlate Rq and X as well. The model parameter, YQ/X, when substituted into a heat transfer design equation, along with the values of other parameters and operating variables, gave reliable estimates of bed temperature. The correlations developed in the present study, between respiratory activity and biomass concentration may be extended on to other SSF processes for further validation and real-time monitoring of cell biomass and bed temperature.
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3.
Splanchnic-Cerebral Oxygenation Ratio Decreases during Enteral Feedings in Anemic Preterm Infants: Observations under Near-Infrared Spectroscopy.
Braski, K, Weaver-Lewis, K, Loertscher, M, Ding, Q, Sheng, X, Baserga, M
Neonatology. 2018;(1):75-80
Abstract
BACKGROUND Anemia is common in premature infants. Due to risks with red blood cell transfusions, many anemic infants are not transfused. The implications of this pathophysiologic status, especially at times of increased metabolic demand (enteral feedings), is not well understood. Near-infrared spectroscopy (NIRS) allows for the noninvasive determination of regional oxygen saturations (rSO2) in tissues such as the brain and mesentery, giving insight into their oxygen sufficiency. OBJECTIVE We tested the hypothesis that during enteral feedings very low birth weight (VLBW) infants with a hematocrit ≤28% will experience a decrease in splanchnic rSO2 and splanchnic-cerebral oxygenation ratio (SCOR). METHODS This prospective, observational, 2-centered study included VLBW infants receiving full enteral feedings with a hematocrit ≤28%. Cerebral and splanchnic rSO2 were monitored via NIRS for 24 h. Average values were calculated for periods immediately preceding, during, and after each feeding. SCOR was calculated from these values (rSO2 splanchnic/rSO2 cerebral), and data were analyzed using a linear mixed effect model. RESULTS Fifty neonates with a median gestational age of 28 weeks (range 23-32), a birth weight of 1,118 ± 284 g (mean ± SD), and a hematocrit of 26 ± 2% (mean ± SD) were studied. During feedings, SCOR decreased significantly from baseline (0.72 ± 0.17 to 0.69 ± 0.17, p = 0.043). With feedings, there was a trend of decreased splanchnic rSO2 (47 ± 11 to 45 ± 10, p = 0.057) and no change in cerebral rSO2 (66 ± 8 to 66 ± 7, p = 0.597). CONCLUSIONS VLBW infants with a hematocrit ≤28% had a decrease in SCOR and a trend towards decreased splanchnic rSO2 with enteral feedings.
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4.
Beetroot juice ingestion during prolonged moderate-intensity exercise attenuates progressive rise in O2 uptake.
Tan, R, Wylie, LJ, Thompson, C, Blackwell, JR, Bailey, SJ, Vanhatalo, A, Jones, AM
Journal of applied physiology (Bethesda, Md. : 1985). 2018;(5):1254-1263
Abstract
Nitrate-rich beetroot juice (BR) supplementation has been shown to increase biomarkers of nitric oxide availability with implications for the physiological responses to exercise. We hypothesized that BR supplementation before and during prolonged moderate-intensity exercise would maintain an elevated plasma nitrite concentration ([[Formula: see text]]), attenuate the expected progressive increase in V̇o2 over time, and improve performance in a subsequent time trial (TT). In a double-blind, randomized, crossover design, 12 men completed 2 h of moderate-intensity cycle exercise followed by a 100-kJ TT in three conditions: 1) BR before and 1 h into exercise (BR + BR); 2) BR before and placebo (PL) 1 h into exercise (BR + PL); and 3) PL before and 1 h into exercise (PL + PL). During the 2-h moderate-intensity exercise bout, plasma [[Formula: see text]] declined by ~17% in BR + PL but increased by ~8% in BR + BR such that, at 2 h, plasma [[Formula: see text]] was greater in BR + BR than both BR + PL and PL + PL ( P < 0.05). V̇o2 was not different among conditions over the first 90 min of exercise but was lower at 120 min in BR + BR (1.73 ± 0.24 l/min) compared with BR + PL (1.80 ± 0.21 l/min; P = 0.08) and PL + PL (1.83 ± 0.27 l/min; P < 0.01). The decline in muscle glycogen concentration over the 2-h exercise bout was attenuated in BR + BR (~28% decline) compared with BR + PL (~44% decline) and PL + PL (~44% decline; n = 9, P < 0.05). TT performance was not different among conditions ( P > 0.05). BR supplementation before and during prolonged moderate-intensity exercise attenuated the progressive rise in V̇o2 over time and appeared to reduce muscle glycogen depletion but did not enhance subsequent TT performance. NEW & NOTEWORTHY We show for the first time that ingestion of nitrate during exercise preserves elevated plasma [nitrite] and negates the progressive rise in O2 uptake during prolonged moderate-intensity exercise.
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A randomized pilot study comparing the role of PEEP, O2 flow, and high-flow air for weaning of ventilatory support in very low birth weight infants.
Yang, CY, Yang, MC, Chu, SM, Chiang, MC, Lien, R
Pediatrics and neonatology. 2018;(2):198-204
Abstract
BACKGROUND There is a lack of evidence to guide step-wise weaning of positive pressure respiratory support for premature infants. This study sought to compare the efficacy of three weaning protocols we designed to facilitate weaning of very low birth weight (VLBW, less than 1500 g) preterm infants from nasal continuous positive airway pressure (NCPAP) support. METHODS This was a prospective, randomized, controlled trial of VLBW preterm infants who received positive pressure ventilatory support in our neonatal intensive care unit (NICU) from April 2008 through March 2009. When these infants were weaned to CPAP as their last step of respiratory support, they would be randomly assigned to one of the following three groups as their further weaning methods (M): (M1) CPAP group, (M2) O2 flow group, and (M3) air flow group. The time period they needed to wean off any kind of respiratory support, as well as the likelihood of developing relevant prematurity related morbidities, were compared among patients using different weaning modalities. RESULTS 181 patients were enrolled in the study. Their gestational age (GA) and birth weight (BW) were 29.1 ± 2.5, 28.7 ± 2.4, 28.7 ± 2.4 (mean ± SD) weeks and 1142 ± 232, 1099 ± 234, 1083 ± 219 g, in M1, M2 and M3, respectively. The time (period) needed to wean off support was 16.0 ± 10.0 days (M1), 11.6 ± 6.4 days (M2), and 15.0 ± 8.9 days (M3), respectively (p = .033). Incidence of retinopathy of prematurity (ROP) and bronchopulmonary dysplasia (BPD) were both significantly higher in the O2 flow group (p = .048). CONCLUSIONS Although using low oxygen flow significantly shortens CPAP weaning time, it may increase risks of BPD and ROP, both known to be related to oxygen toxicity. Unless the infant has BPD and is O2-dependent, clinicians should consider using air flow or just splinting with no support at all when weaning NCPAP.
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6.
[Recipe and application of new oxygen cocktail with high protein content in nutrition of cardiological patients].
Nepovinnykh, NV, Novokshanova, AL, Mogilny, MP, Lyamina, NP, Semina, AI, Ababkova, AA, Shirokov, AA, Grinev, VS, Ptichkina, NM
Voprosy pitaniia. 2018;(2):94-102
Abstract
The aims of this study was to develop recipe composition and to evaluate the use of new oxygen cocktail with high protein content in the dietary therapy of cardiological patients. Objects of the study were: the control sample - an oxygen-containing product prepared using dairy whey, fruit and berry juice, highly esterified pectin; experimental samples - oxygen-containing products, which differed from the control sample by additional introduction of whey protein hydrolysate. Experimental samples have been modified by adding to them whey protein hydrolysate in the amount of 1-3% from the total weight of composition. Technological scheme to produce protein-carbohydrate basis with high content of protein 3% has been developed, parameters of the production process were worked out. Analysis of product chemical composition has shown that 100 g contained 3.4-3.6 g of protein, 0.2-0.3 g of fat, 6.0-8.0 g of carbohydrates. Food value of the product made up 34-46 kcal (162-196 kJ). Assessment of effectiveness of new oxygen-containing product in the diet in conditions of cardiological hospital was carried out. 30 patients aged 60-75 years were included in local open prospective study, meeting the following criteria: patients with chronic heart failure I-IIА stage I-II functional classes, were hospitalized in the cardiology department, not having contraindications to enteral oxygen therapy and signed an informed consent form. In combination with standard therapy patients received new oxygenated product with high content of protein in the dose 250 ml (from 100 g of the basis) daily for 10 days during the second breakfast. By the end of the observation period, according to results of the survey, the psycho-emotional state of patients improved. It has been found that the developed oxygen-containing product with high protein content in combination with a standard diet and drug therapy of the disease was well tolerated by patients.
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7.
Dietary Nitrate Increases VO2peak and Performance but Does Not Alter Ventilation or Efficiency in Patients With Heart Failure With Reduced Ejection Fraction.
Coggan, AR, Broadstreet, SR, Mahmood, K, Mikhalkova, D, Madigan, M, Bole, I, Park, S, Leibowitz, JL, Kadkhodayan, A, Thomas, DP, et al
Journal of cardiac failure. 2018;(2):65-73
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Abstract
BACKGROUND Patients with heart failure with reduced ejection fraction (HFrEF) exhibit lower efficiency, dyspnea, and diminished peak oxygen uptake (VO2peak) during exercise. Dietary nitrate (NO3-), a source of nitric oxide (NO), has improved these measures in some studies of other populations. We determined the effects of acute NO3- ingestion on exercise responses in 8 patients with HFrEF using a randomized, double-blind, placebo-controlled, crossover design. METHODS AND RESULTS Plasma NO3-, nitrite (NO2-), and breath NO were measured at multiple time points and respiratory gas exchange was determined during exercise after ingestion of beetroot juice containing or devoid of 11.2 mmol of NO3-. NO3- intake increased (P < .05-0.001) plasma NO3- and NO2- and breath NO by 1469 ± 245%, 105 ± 34%, and 60 ± 18%, respectively. Efficiency and ventilation during exercise were unchanged. However, NO3- ingestion increased (P < .05) VO2peak by 8 ± 2% (ie, from 21.4 ± 2.1 to 23.0 ± 2.3 mL.min-1.kg-1). Time to fatigue improved (P < .05) by 7 ± 3 % (ie, from 582 ± 84 to 612 ± 81 seconds). CONCLUSIONS Acute dietary NO3- intake increases VO2peak and performance in patients with HFrEF. These data, in conjunction with our recent data demonstrating that dietary NO3- also improves muscle contractile function, suggest that dietary NO3- supplementation may be a valuable means of enhancing exercise capacity in this population.
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[Characteristics of Sediment Oxygen Demand in a Drinking Water Reservoir].
Su, L, Huang, TL, Li, N, Zhang, HH, Wen, G, Li, Y, Chen, JW, Wang, XJ
Huan jing ke xue= Huanjing kexue. 2018;(3):1159-1166
Abstract
Depletion of dissolved oxygen (DO) in the hypolimnetic layer during stratification periods and its deleterious effects on water quality have been widely observed. However, it is still difficult to comprehend conceptually the processes of oxygen consumption at the sediment-water interface. The research presented here is, therefore, based on an areal hypolimnetic oxygen demand (AHOD) model to address three key themes related to the sediment oxygen demand (SOD):① the characteristics of sediment and its influences on SOD; ② evaluation of SOD with different turbulence levels overlying the sediment; and ③ the influence of microbial metabolic activity on SOD. Sediment samples were collected at the entrance to and over the basin area of Jinpen Reservoir, and a sediment-water experimental chamber was designed to achieve these goals. The results showed that, under quiescent conditions, the SOD5area(SOD at DO of 5 mg·L-1) were 0.13 g·(m2·d)-1 and 0.36 g·(m2·d)-1 in the arm and basin, respectively. Under dynamic conditions, the slight mixing of the water column near the sediment induced an increase in SOD and resulted in a gradual shift from first-order to zero-order DO uptake. The organic matter content in the reservoir arm and profundal sediment were 44.43 mg·g-1 and 45.12 mg·g-1, respectively. The microbial metabolic activity in the basin was stronger, and the total fluorescence intensity of the dissolved organic matter (DOM) in the profundal sediments was about 1.5 times that in the reservoir arm. These results suggest that SOD will be higher when microbial metabolic activity is stronger and organic matter content is higher in sediments. The oxygenation aeration techniques should be designed to meet the oxygen demand of the deep reservoir to provide a theoretical basis for improving the oxygenation efficiency.
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Kinetic and stoichiometric constraints determine the pathway of H2O2 consumption by red blood cells.
Orrico, F, Möller, MN, Cassina, A, Denicola, A, Thomson, L
Free radical biology & medicine. 2018;:231-239
Abstract
Red blood cells (RBC) are considered as a circulating sink of H2O2, but a significant debate remains over the role of the different intraerythocyte peroxidases. Herein we examined the kinetic of decomposition of exogenous H2O2 by human RBC at different cell densities, using fluorescent and oxymetric methods, contrasting the results against a mathematical model. Fluorescent measurements as well as oxygen production experiments showed that catalase was responsible for most of the decomposition of H2O2 at cell densities suitable for both experimental settings (0.1-10 × 1010 cell L-1), since sodium azide but not N-ethylmaleimide (NEM) inhibited H2O2 consumption. Oxygen production decreased at high cell densities until none was detected above 1.1 × 1012 cell L-1, being recovered after inhibition of the thiol dependent systems by NEM. This result underlined that the consumption of H2O2 by catalase prevail at RBC densities regularly used for research, while the thiol dependent systems predominate when the cell density increases, approaching the normal number in blood (5 × 1012 cell L-1). The mathematical model successfully reproduced experimental results and at low cell number it showed a time sequence involving Prx as the first line of defense, followed by catalase, with a minor role by Gpx. The turning points were given by the total consumption of reduced Prx in first place and reduced GSH after that. However, Prx alone was able to account for the added H2O2 (50 µM) at physiological RBC density, calling attention to the importance of cell density in defining the pathway of H2O2 consumption and offering an explanation to current apparently conflicting results in the literature.
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10.
11-Oxygenated androgen precursors are the preferred substrates for aldo-keto reductase 1C3 (AKR1C3): Implications for castration resistant prostate cancer.
Barnard, M, Quanson, JL, Mostaghel, E, Pretorius, E, Snoep, JL, Storbeck, KH
The Journal of steroid biochemistry and molecular biology. 2018;:192-201
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Abstract
The progression of castration resistant prostate cancer (CRPC) is driven by the intratumoral conversion of adrenal androgen precursors to potent androgens. The expression of aldo-keto reductase 1C3 (AKR1C3), which catalyses the reduction of weak androgens to more potent androgens, is significantly increased in CRPC tumours. The oxidation of androgens to their inactive form is catalysed by 17β-hydroxysteroid dehydrogenase type 2 (17βHSD2), but little attention is given to the expression levels of this enzyme. In this study, we show that the 11-oxygenated androgen precursors of adrenal origin are the preferred substrate for AKR1C3. In particular we show that the enzymatic efficiency of AKR1C3 is 8- and 24-fold greater for 11-ketoandrostenedione than for the classic substrates androstenedione and 5α-androstanedione, respectively. Using three independent experimental systems and a computational model we subsequently show that increased ratios of AKR1C3:17βHSD2 significantly favours the flux through the 11-oxygenated androgen pathway as compared to the classical or 5α-androstanedione pathways. Our findings reveal that the flux through the classical and 5α-androstanedione pathways are limited by the low catalytic efficiently of AKR1C3 towards classical androgens combined with the high catalytic efficiency of 17βHSD2, and that the expression of the oxidative enzyme therefore plays a vital role in determining the steady state concentration of active androgens. Using microarray data from prostate tissue we confirm that the AKR1C3:17βHSD2 ratio is significantly increased in patients undergoing androgen deprivation therapy as compared to benign tissue, and further increased in patients with CRPC. Taken together this study therefore demonstrates that the ratio of AKR1C3:17βHSD2 is more important than AKR1C3 expression alone in determining intratumoral androgen levels and that 11-oxygenated androgens may play a bigger role in CRPC than previously anticipated.