Oxygen Concentration In Medium Research Articles

Chemical Stability and Characterization of Degradation Products of Blends of 1-(2-Hydroxyethyl)pyrrolidine and 3-Amino-1-propanol.

Aqueous amine solvents are used to capture CO2 from various flue gas sources. In this work, the chemical stability of a blend of 3-amino-1-propanol (3A1P) and 1-(2-hydroxyethyl)pyrrolidine [1-(2HE)PRLD] was studied. The chemical stability tests were conducted both in batch and cycled systems using various oxygen and NOx concentrations, additives (iron), and temperatures. In the thermal degradation experiments with CO2 present, the blend was more stable than the primary amines [(3A1P or monoethanolamine (MEA)] but less stable than the tertiary amine 1-(2HE)PRLD alone. Similar stability was observed between MEA, 3A1P, and the blend in the batch experiments at medium oxygen concentration (21% O2) and no iron present. 1-(2HE)PRLD was more stable. However, the presence of high oxygen concentration (96% O2) and iron reduced the stability of 1-(2HE)PRLD significantly. Furthermore, in the case of the blend, the chemical stability increased with increasing promoter concentration in batch experiments. During the cyclic experiment, the amine loss for the blend was similar to what was previously observed for MEA (30 wt %) under the same conditions. A thorough mapping of degradation compounds in the solvent and condensate samples resulted in the identification and quantification of 30 degradation compounds. The major components in batch and cycled experiments varied somewhat, as expected. In the cyclic experiments, the major components were ammonia, 3-(methylamino)-1-propanol (methyl-AP), N,N'-bis(3-hydroxypropyl)-urea (AP-urea), pyrrolidine, formic acid (formate), and N-(3-hydroxypropyl)-glycine (HPGly). Finally, in this paper, formation pathways for the eight degradation compounds (1,3-oxazinan-2-one, AP-urea, 3-[(3-aminopropyl)amino]-1-propanol, tetrahydro-1-(3-hydroxypropyl)-2(1H)-pyrimidinone, methyl-AP, N-(3-hydroxypropyl)-formamide, N-(3-hydroxypropyl)-β-alanine, and HPGly) are suggested.

Suitability of methods for Plasmodium falciparum cultivation in atmospheric air.

BACKGROUND One of the most controversial factors about malaria parasite culture is the gaseous composition used. The most commonly used one consists of a mixture poor in O2 and rich in CO2.OBJECTIVES The present study aimed to share standard methods from our research group simplifying Plasmodium falciparum cultures by employing atmospheric air (ATM) and reusable glass bottles under agitation.METHODS Here, it was compared the parasite viability, free oxygen in media, and drug sensitivity between different strains and isolates maintained for long periods under ATM or classic conditions.FINDINGS The oxygen concentration in media under ATM was slightly superior to that observed in human blood and the media under the classic gaseous mixture. However, ATM or the use of glass bottles did not affect parasitic proliferation after several years of culture. Noticeably, the introduction of ATM altered reversibly the efficacy of several antimalarials. This influence was different between the strains and isolate.CONCLUSIONS ATM conditions and shaken flasks could be used as a standard method condition for culture manutention since they do not differ greatly from classical 5% O2 gas mixtures in terms of parasite proliferation and do not impose non-reversible changes to P. falciparum physiology.

Power saving by a smart breath sensor working in non-connectable advertising mode

The paper presents an energy-saving breath monitoring system based on smart sensors. The current consumption by BLE modules was limited by reducing transmission frequency, which was related to the number of PDUs transmitted per unit of time. Each time 20 consecutive measurement results were saved in the PDUs. Therefore, the measurement frequency was 20 times higher than the transmission frequency. Appropriate configuration of the PDU transmission interval allows to extend the working time of battery-powered sensors by approx. 45 %, without reducing the accuracy of mapping individual breathing cycle curves, both for normal (10−20BPM) and highly accelerated (even over 100BPM) breathing. Statistical analysis showed that a 10-fold reduction of the measurement frequency (from 200 Hz to 20 Hz), allowing to extend the system working time by the mentioned 45 %, does not significantly (p > 0.05) affect the shape of the recorded breathing cycle curves, both for normal and highly accelerated breathing. The paper also presents the design of the wearable sensor, intended for cooperation with medium oxygen concentration masks.

Non-invasive imaging of mouse embryo metabolism in response to induced hypoxia.

This study used noninvasive, fluorescence lifetime imaging microscopy (FLIM)-based imaging of NADH and FAD to characterize the metabolic response of mouse embryos to short-term oxygen deprivation. We investigated the response to hypoxia at various preimplantation stages. Mouse oocytes and embryos were exposed to transient hypoxia by dropping the oxygen concentration in media from 5-0% over the course of ~1.5 h, then 5% O2 was restored. During this time, FLIM-based metabolic imaging measurements of oocyte/embryo cohorts were taken every 3 minutes. Experiments were performed in triplicate for oocytes and embryos at the 1- to 8-cell, morula, and blastocyst stages. Maximum hypoxia response for each of eight measured quantitative FLIM parameters was taken from the time points immediately before oxygen restoration. Metabolic profiles showed significant changes in response to hypoxia for all stages of embryo development. The response of the eight measured FLIM parameters to hypoxia was highly stage-dependent. Of the eight FLIM parameters measured, NADH and FAD intensity showed the most dramatic metabolic responses in early developmental stages. At later stages, however, other parameters, such as NADH fraction engaged and FAD lifetimes, showed greater changes. Metabolic parameter values generally returned to baseline with the restoration of 5% oxygen. Quantitative FLIM-based metabolic imaging was highly sensitive to metabolic changes induced by hypoxia. Metabolic response profiles to oxygen deprivation were distinct at different stages, reflecting differences in metabolic plasticity as preimplantation embryos develop.

Nitrogen fixation in Rhodopseudomonas palustris co-cultured with Bacillus subtilis in the presence of air

Nitrogen fixation in purple non-sulfur bacteria (PNSB) does not take place even in N-free medium when they are cultured under aerobic conditions. It is assumed that PNSB might possess inadequate capability to protect their cellular components from exposure to air (20.95 vol.% oxygen). In this study, therefore, Bacillus subtilis was inoculated together with a purple non-sulfur bacterium Rhodopseudomonas palustris in N-free medium in order to examine whether nitrogen fixation in Rps. palustris takes place when the co-culture is exposed to 20.95 vol.% oxygen. Rps. palustris grew and formed biofilm only when it was inoculated together with B.subtilis. When the biofilm formed in the co-culture was inoculated in N-free medium, diazotrophic growth was observed in the sequential subcultures. Expression of nifH gene, derepression of nitrogenase activity, an increase of total nitrogen, and a decrease of C/N in the co-culture of Rps. palustris and B.subtilis demonstrated the occurrence of nitrogen fixation under aerobic conditions. The diazotrophic growth was suppressed at a lower medium-to-air ratio in a sealed culture vessel, and growth of B.subtilis preceded growth of Rps. palustris in the co-culture. These results suggest that growth of B.subtilis, which is usually accompanied with oxygen consumption, might cause a decrease of dissolve oxygen concentration in medium and contribute to the occurrence of nitrogenase activity in Rps. palustris.

Increased root zone oxygen by a capillary barrier is beneficial to bell pepper irrigated with brackish water in an arid region

Limitations to growth and biomass production are expected under high (>30°C) soil temperatures due to low soil oxygen levels and insufficient oxygen transport to roots. These limitations will be exacerbated when irrigation with brackish water dictates large amounts of water application for leaching salts. We hypothesized that the introduction of an artificial capillary barrier (CB), in the form of a gravel layer at the lower root-zone boundary, can increase yields of irrigated horticultural crops due to better soil aeration and improved oxygen supply to roots. The specific objectives of the study were (1) to isolate scenarios where insufficient oxygen concentrations may limit pepper plant growth, (2) to measure oxygen concentrations in media under varied scenarios of CB placement below the active root zone and (3) to understand the environmental factors leading to sub-optimum oxygen concentrations in horticultural soils in a desert environment where supra-optimal soil temperatures are prevalent. At high root-zone temperatures oxygen flux to the roots was lower than the potential uptake rate and therefore soil oxygen concentrations were sub-optimal. These conditions led to reduced plant biomass and fruit yield. Fruit yield was found to decrease by 1% for every soil oxygen concentration decrease of 700ppm. In a fine textured Reg soil, allowing roots to penetrate into the capillary barrier gravel layer increased oxygen concentration in the root zone by 5% and improved biomass and fruit yield by 16% and 18%, respectively.

Effect of oxygen at low and high light intensities on the growth of Neochloris oleoabundans

The effect of partial oxygen pressure on growth of Neochloris oleoabundans was studied at near-saturating light intensity in a fully-controlled photobioreactor. At the partial oxygen pressures tested (PO2=0.24; 0.42; 0.63; 0.84bar), the specific growth rate was 1.36; 1.16; 0.93 and 0.68day−1, respectively. An increase of the PCO2 from 0.007 to 0.02bar at PO2 of 0.84bar did not show any positive effect on the overall growth of the algae, contrary to what happens at sub-saturating light intensities. These results indicate that at near-saturating light intensity the inhibitory effect of oxygen by photorespiration cannot be overcome. The chlorophyll content of N. oleoabundans grown at 200μmolm−2s−1 is about 1.9 times higher than when cultivated at 500μmolm−2s−1, whereas the carotenoid content was about 1.5 lower, both demonstrating photoacclimation effects. The elevated oxygen concentration in the growth medium does not affect the pigment content both at sub- and near-saturating light conditions. This indicates that elevated oxygen concentrations in the medium do not contribute to photooxidative damage at the light conditions that are predominantly experienced by algae in closed photobioreactors, but only inhibit the growth via photorespiration effects.

Pericellular oxygen concentration of cultured primary human trophoblasts

IntroductionOxygen is pivotal in placental development and function. In vitro culture of human trophoblasts provides a useful model to study this phenomenon, but a hotly debated issue is whether or not the oxygen tension of the culture conditions mimics in vivo conditions. We tested the hypothesis that ambient oxygen tensions in culture reflect the pericellular oxygen levels. MethodsWe used a microelectrode oxygen sensor to measure the concentration of dissolved oxygen in the culture medium equilibrated with 21%, 8% or <0.5% oxygen. ResultsThe concentration of oxygen in medium without cells resembled that in the ambient atmosphere. The oxygen concentration present in medium bathing trophoblasts was remarkably dependent on the depth within the medium where sampling occurred, and the oxygen concentration within the overlying atmosphere was not reflected in medium immediately adjacent to the cells. Indeed, the pericellular oxygen concentration was in a range that most would consider severe hypoxia, at ≤0.6% oxygen or about 4.6 mm Hg, when the overlying atmosphere was 21% oxygen. ConclusionsWe conclude that culture conditions of 21% oxygen are unable to replicate the pO2 of 40–60 mm Hg commonly attributed to the maternal blood in the intervillous space in the second and third trimesters of pregnancy. We further surmise that oxygen atmospheres in culture conditions between 0.5% and 21% provide different oxygen fluxes in the immediate pericellular environment yet can still yield insights into the responses of human trophoblast to different oxygen conditions.

Impact of medium volume and oxygen concentration in the incubator on pericellular oxygen concentration and differentiation of murine chondrogenic cell culture

Previous studies have demonstrated that oxygen environment is an important determinate factor of cell phenotypes and differentiation, although factors which affect pericellular oxygen concentration (POC) in murine chondrogenic cell culture remain unidentified. Oxygen concentrations in vivo were measured in rabbit musculoskeletal tissues, which were by far hypoxic compared to 20% O(2) (ranging from 2.29 ± 1.16 to 4.36 ± 0.51%). Oxygen concentrations in murine chondrogenic cell (C3H10T1/2) culture medium were monitored in different oxygen concentrations (20% or 5%) in the incubator and in different medium volumes (3,700 or 7,400μl) within 25-cm(2) flasks. Chondrogenic differentiation was assessed by glycosaminoglycan production with quantitative evaluation of Alcian blue staining in 12-well culture dishes. Expression of chondrogenic genes, aggrecan, and type II collagen α1, was examined by quantitative real-time polymerase chain reaction. Oxygen concentrations in medium decreased accordingly with the depth from medium surface, and POC at Day 6 was 18.99 ± 0.81% in 3,700-μl medium (1,480-μm depth) and 13.26 ± 0.23% in 7,400-μl medium (2,960-μm depth) at 20% O(2) in the incubator, which was 4.96 ± 0.08% (1,480-μm depth) and 2.83 ± 0.42% (2,960-μm depth) at 5% O(2), respectively. The differences of POC compared by medium volume were statistically significant (p = 0.0003 at 20% and p = 0.001 at 5%). Glycosaminoglycan production and aggrecan gene expression were most promoted when cultured in moderately low POC, 1,000μl (2,960-μm depth) at 20% O(2) and 500μl (1,480-μm depth) at 5% O(2) in 12-well culture dishes. We demonstrate that medium volume and oxygen concentration in the incubator affect not only POC but also chondrogenic differentiation.

SEASONAL CHANGES OF THE CONDITION INDICES AND HAEMOCYTE COUNTS OF THE AUSTROPOTAMOBIUS TORRENTIUM POPULATION IN KRALJEVEC STREAM, CROATIA

The stone crayfish, Austropotamobius torrentium is one of the four native European crayfish living in Croatian freshwaters. Kraljevec Stream is situated on the southern slopes of Medvednica Mountain (north-west Croatia) at 400m above the sea level. Our research was conducted during one year, from May 2003 to April 2004. Temperature varied between 2 to 17, 2 oC, medium oxygen concentration was 12, 12 mg/L, medium pH was 8, 27 and alkalinity was between 100 and 200 mg CaCO3/L. Crayfish were trapped by baited hand made traps which were secured in a stream current with the stones and roots of the surrounding trees. We caught 100 crayfishes, 68 males and 32 females. Hemolymph was sampled 10 to 15 min after catch. EDTA anticoagulant was used to prevent hemolymph coagulation and 10% formaline was used to fix haemocyte for differential counts. Each month five to six animals were sacrificed and hepatosomatic, gonadosomatic and muscle indices were measured. We found statistically significant differences in hepatosomatic and gonadosomatic indices between months and between sexes. Muscle indices were significantlly different between males and females. Average total haemocyte count for males was 7, 6 x 105 cells/ml hemolymph and for females was 6, 5 x 105 cells/ml. Average hyalinocyte, granulocyte and semigranulocyte ratio was 77:14, 5:8, 5%, respectively. There were no statisticaly significant differences in total and differential counts between months and between sexes.

Synthesis of alpha-ketoglutaric acid by Yarrowia lipolytica yeast grown on ethanol.

The ability of yeast to synthesize alpha-ketoglutaric acid (KGA) from ethanol has been studied. Thiamine-auxotrophic yeasts of different genera and species may be able to produce KGA; the main condition of synthesis is growth limitation by thiamine. Using a model culture, mutant Yarrowia lipolytica N 1, the principal conditions affecting KGA oversynthesis were identified. These were: thiamine concentration in medium and in cells, nitrogen and oxygen concentration in medium, and pH level. A KGA concentration of 49 g/l and a yield from ethanol consumed of 42% were achieved. Based on the results of the analysis of the activities of the key enzymes participating in ethanol metabolism and KGA synthesis, a concept of the mechanism of KGA biosynthesis by Y. lipolytica yeast is suggested and discussed.

Effects of high oxygen concentrations on microbial biosensor signals. Hyperoxygenation by means of perfluorodecalin

Amperometric biosensors register oxygen depletion in response to analyte catabolism, and thus are limited by the availability of dissolved oxygen. Microbial sensors containing immobilized cells of Gluconobacter oxydans were hyperoxygenated to 400% of control levels and the effects on sensor responses to glucose were determined. Oxygenated perfluorodecalin (a completely fluorinated organic substance) was as effective in hyperoxygenation as direct sparging with O 2, increasing sensor base medium oxygen concentrations from 9.3 to 37 mg/l. Hyperoxygenation enhanced maximal biosensor response amplitudes, particularly at high cell loading densities. Maximal response rates were also improved, although less dramatically. Results suggest that hyperoxygenation may be a new general approach for modulating biosensor responses.

Early Development of Bovine Embryos

安定して高い発生率が得られるウシ初期胚の培養系を確立することを目的として，ウシ体外成熟・体外受精卵の胚盤胞への発生に及ぼす卵管上皮細胞（BOET）との共培養，培養液への血清（FCS）添加，培養気相中の酸素濃度，培養液の水質，培養液の種類および培養液へのグルコース添加の影響について検討した．得られた結果は以下の通りである．1)ウシ初期胚とBOETとの共培養に血清添加は必要ない．2)共培養におけるBOETの発生促進作用の一つは，培養液中の酸素濃度を低下させることである．低酸素濃度（5%）環境は，共培養を用いないウシ胚の培養において，胚盤胞への発生を促進する．3)蛋白・細胞無添加培養におけるウシ初期胚の発生は培養液の水質に影響されており，超純水レベルの高い精製度の水（Milli-Q水）が必要である．4)蛋白・細胞無添加培養における胚盤胞への発生率は，m-SOFを用いた場合に47%と，m-TCM199（31%）より高かった．5)発生および受精培養液中の高濃度のグルコース（5.6 mMあるいは13.9 mM）は，胚発生を抑制する．以上により，培養気相中の酸素濃度を低下させ，低グルコ-ス濃度の培養液を用い，培養液作製に高純度の水を使用することで，共培養や蛋白の添加を行うことなく，ウシ1細胞期胚を効率的に胚盤胞期へ発生させることが可能となった．

Wet thermal oxidation of AlxGa1−xAs compounds

Results are presented on the wet thermal oxidation of AlxGa1−xAs. The growth of wet thermal oxides of AlxGa1−xAs is shown to be linear with time. An O2 carrier gas was found to form a self-terminating oxide for compositions investigated (x≳0.4), but required elevated temperatures for substantial growth. The use of a medium oxygen concentration (∼20%) in a N2 carrier formed nonuniform oxides for all compositions investigated. A low O2 concentration (0.1%) in the N2 carrier was found to reduce the activation energy of the oxidation process for Al0.6Ga0.4As from 1.9 to 1.0 eV while increasing the activation energy of Al0.8Ga0.2As from 1.6 to 1.75 eV. For these wet thermal oxides it is observed that lateral oxidation at heterojunction interfaces is enhanced. This enhanced lateral oxidation can be attributed to local stress due to the smaller volume of the growing oxide compared to the volume of the consumed semiconductor.

The relationship between dissimilatory nitrate reduction and oxygen uptake by cells of an Alcaligenes strain in flocs and in suspension and by activated sludge flocs

The oxygen uptake and the dissimilatory nitrate reduction by anaerobically grown cells of a denitrifying Alcaligenes strain, occurring in floc form or in suspension, were studied at different oxygen concentrations in the surrounding medium. When the oxygen concentration in the medium fell below 1·5 mg l −1, the nitrate reduction by the cells within flocs increased considerably. The cells in suspension showed an increased nitrate reduction when the oxygen concentration was below 0·1 mg l −1. When anaerobically grown cells had been aerated for 24 h in a nitrogen-free medium, the cells became sensitive to respiration inhibition by nitric oxide, resulting from nitrate reduction. This gave rise to an increased nitrate reduction below 2·5 mg oxygen l −1 when the cells were aggregated in flocs and below 0·1 mg oxygen per litre when the cells were in suspension. The nitrate reduction by the denitrifying, floc-forming pure culture was compared with that of activated sludge flocs.