Reduction of acetylene by stationary cultures of free-living Rhizobium sp. under atmospheric oxygen levels

1976 ◽  
Vol 22 (7) ◽  
pp. 949-952 ◽  
Author(s):  
William R. Evans ◽  
Donald L. Keister
Keyword(s):  
Atmospheric Oxygen ◽  
Maximal Activity ◽  
Free Living ◽  
Oxygen Levels ◽  
Specific Activities ◽  
Rhizobium Sp ◽  
Oxygen Concentrations

The reduction of acetylene to ethylene by stationary (non-shaking) cultures of free-living rhizobia under atmospheric oxygen levels has been demonstrated. Under these conditions the development of the activity is inhibited by 10 mM NH4Cl and about 20% of oxygen is required for maximal activity. When the stationary cultures were shaken, oxygen concentrations of 1% and higher were found to be inhibitory. Specific activities of 20 and 40 nmol of acetylene reduced h−1 mg−1 protein were observed.

Ancient Atmospheres and the Evolution of Oxygen Sensing Via the Hypoxia-Inducible Factor in Metazoans

Physiology ◽  
2010 ◽  
Vol 25 (5) ◽  
pp. 272-279 ◽  
Author(s):  
Cormac T. Taylor ◽  
Jennifer C. McElwain
Keyword(s):  
Oxygen Sensing ◽  
Atmospheric Oxygen ◽  
Hypoxia Inducible Factor ◽  
Transcriptional Response ◽  
Oxygen Levels ◽  
Selection Force ◽  
Cellular Oxygen ◽  
Hif Pathway ◽  
Evolution Of Oxygen ◽  
Oxygen Concentrations

Metazoan diversification occurred during a time when atmospheric oxygen levels fluctuated between 15 and 30%. The hypoxia-inducible factor (HIF) is a primary regulator of the adaptive transcriptional response to hypoxia. Although the HIF pathway is highly conserved, its complexity increased during periods when atmospheric oxygen concentrations were increasing. Thus atmospheric oxygen levels may have provided a selection force on the development of cellular oxygen-sensing pathways.

Plasmid replicons of Rhizobium

2005 ◽  
Vol 33 (1) ◽  
pp. 157-158 ◽  
Author(s):  
L.C. Crossman
Keyword(s):  
Short Review ◽  
Nitrogen Fixing ◽  
Rhizobium Etli ◽  
Free Living ◽  
Leguminous Plants ◽  
Symbiotic Plasmid ◽  
Rhizobium Spp ◽  
Plasmid Replicons ◽  
Rhizobium Sp

Rhizobium spp. are found in soil. They are both free-living and found symbiotically associated with the nodules of leguminous plants. Traditionally, studies have focused on the association of these organisms with plants in nitrogen-fixing nodules, since this is regarded as the most important role of these bacteria in the environment. Rhizobium sp. are known to possess several replicons. Some, like the Rhizobium etli symbiotic plasmid p42d and the plasmid pNGR234b of Rhizobium NGR234, have been sequenced and characterized. The plasmids from these organisms are the focus of this short review.

Plants at Sub-Atmospheric Oxygen-Levels

Nature ◽  
1963 ◽  
Vol 198 (4887) ◽  
pp. 1288-1290 ◽  
Author(s):  
S. M. SIEGEL ◽  
L. A. ROSEN ◽  
C. GIUMARRO
Keyword(s):  
Atmospheric Oxygen ◽  
Oxygen Levels

A case for low atmospheric oxygen levels during Earth's middle history

2018 ◽  
Vol 2 (2) ◽  
pp. 149-159 ◽  
Author(s):  
Noah J. Planavsky ◽  
Devon B. Cole ◽  
Terry T. Isson ◽  
Christopher T. Reinhard ◽  
Peter W. Crockford ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Conceptual Framework ◽  
Environmental Conditions ◽  
Atmospheric Oxygen ◽  
Critical Factor ◽  
Planetary Surface ◽  
Surface Oxygen ◽  
Oxygen Levels ◽  
Early Diversification ◽  
Atmospheric Level

The oxygenation of the atmosphere — one of the most fundamental transformations in Earth's history — dramatically altered the chemical composition of the oceans and provides a compelling example of how life can reshape planetary surface environments. Furthermore, it is commonly proposed that surface oxygen levels played a key role in controlling the timing and tempo of the origin and early diversification of animals. Although oxygen levels were likely more dynamic than previously imagined, we make a case here that emerging records provide evidence for low atmospheric oxygen levels for the majority of Earth's history. Specifically, we review records and present a conceptual framework that suggest that background oxygen levels were below 1% of the present atmospheric level during the billon years leading up to the diversification of early animals. Evidence for low background oxygen levels through much of the Proterozoic bolsters the case that environmental conditions were a critical factor in controlling the structure of ecosystems through Earth's history.

Metabolism of tritium- and 14C-labeled alanine in rats

1981 ◽  
Vol 241 (2) ◽  
pp. E121-E128 ◽  
Author(s):  
S. Golden ◽  
M. Chenoweth ◽  
A. Dunn ◽  
F. Okajima ◽  
J. Katz
Keyword(s):  
Continuous Infusion ◽  
Transit Time ◽  
Bolus Injection ◽  
Specific Activity ◽  
Mean Transit Time ◽  
Vena Cava ◽  
Maximal Activity ◽  
Total Body Mass ◽  
Arterial Blood ◽  
Specific Activities

[3-3H]- and [U-14C]alanine were administered to starved rats by bolus injection and by continuous infusion. The specific activities of alanine, glucose, and lactate in blood were followed. The tracer kinetics of alanine depended on the site of tracer administration and sampling. Tracer was either administered into the aorta and blood sampled from the vena cava (A-VC mode) or tracer was administered into the vena cava and arterial blood sampled (V-A mode) (Katz, J. F. Okajima, and A. Dunn. Biochem J. 194: 513-524, 1981). When tracer was infused in the A-VC mode the plateau specific activity of alanine was about half that obtained in the V-A mode. The parameters of alanine turnover were calculated from the specific activities obtained in the A-VC mode. The calculated apparent replacement rate averaged 1.9 mg.min-1.kg-1 for [U-14C]- and 3.9 mg.min-1.kg-1 for [3-3H]alanine, indicating a carbon recycling of about 50%. The apparent contribution of alanine carbon to that of glucose is 15%. The maximal activity in plasma water is attained at about 5 min after bolus injection of [3-3H]alanine and that of [14C]glucose in blood is attained about 10 min after the injection of [U-14C]alanine. Maximal specific activity of [3H]- and [14C]lactate is attained within about 1 min after injection. The apparent mean transit time and alanine mass were calculated from the areas of washout curves after the continuous infusion was terminated. The mean transit time for [3H]alanine was 10 min and apparent total body mass of alanine of the order of 40 mg/kg. The apparent means transit time for [U-14C]alanine ranged from 33 to 66 min corresponding to a mass of the order of 100 mg/kg of alanine or 40 mg/kg of alanine carbon.

scholarly journals Metabolic Activity of Human Embryos after Thawing Differs in Atmosphere with Different Oxygen Concentrations

2020 ◽  
Vol 9 (8) ◽  
pp. 2609
Author(s):  
Michal Ješeta ◽  
Andrea Celá ◽  
Jana Žáková ◽  
Aleš Mádr ◽  
Igor Crha ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Oxygen Concentration ◽  
Atmospheric Oxygen ◽  
Blastocyst Stage ◽  
Human Embryos ◽  
Total Amino Acid ◽  
Oxygen Levels ◽  
Amino Acid Turnover ◽  
Cultivation Environment

The vitrification of human embryos is more and more frequently being utilized as a method of assisted reproduction. For this technique, gentle treatment of the embryos after thawing is crucial. In this study, the balance of amino acids released to/consumed from the cultivation media surrounding the warmed embryos was observed in the context of a cultivation environment, which was with the atmospheric oxygen concentration ≈20% or with a regulated oxygen level—hysiological (5%). It is the first time that total amino acid turnover in human embryos after their freezing at post compaction stages has been evaluated. During this study, progressive embryos (developed to blastocyst stage) and stagnant embryos (without developmental progression) were analyzed. It was observed that the embryos cultivated in conditions of physiological oxygen levels (5% oxygen) showed a significantly lower consumption of amino acids from the cultivation media. Progressively developing embryos also had significantly lower total amino acid turnovers (consumption and production of amino acids) when cultured in conditions with physiological oxygen levels. Based on these results it seems that a cultivation environment with a reduced oxygen concentration decreases the risk of degenerative changes in the embryos after thawing. Therefore, the cultivation of thawed embryos in an environment with physiological oxygen levels may preclude embryonal stagnation, and can support the further development of human embryos after their thawing.

scholarly journals A modeling case for high atmospheric oxygen concentrations during the Mesozoic and Cenozoic

Geology ◽  
2016 ◽  
Vol 44 (12) ◽  
pp. 1023-1026 ◽  
Author(s):  
Benjamin J.W. Mills ◽  
Claire M. Belcher ◽  
Timothy M. Lenton ◽  
Robert J. Newton
Keyword(s):  
Atmospheric Oxygen ◽  
Oxygen Concentrations

scholarly journals No evidence for high atmospheric oxygen levels 1,400 million years ago

2016 ◽  
Vol 113 (19) ◽  
pp. E2550-E2551 ◽  
Author(s):  
Noah J. Planavsky ◽  
Devon B. Cole ◽  
Christopher T. Reinhard ◽  
Charles Diamond ◽  
Gordon D. Love ◽  
...  
Keyword(s):  
Atmospheric Oxygen ◽  
Oxygen Levels
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