STUDIES ON THE METABOLISM OF C-19 STEROIDS IN THE HUMAN FOETO-PLACENTAL UNIT.

1967 ◽  
Vol 55 (2) ◽  
pp. 263-277 ◽  
Author(s):  
E. Lamb ◽  
S. Mancuso ◽  
S. Dell' Acqua ◽  
N. Wiqvist ◽  
E. Diczfalusy
Keyword(s):  
Isotope Ratios ◽  
Arterial Supply ◽  
Homogeneous Form

ABSTRACT Dehydroepiandrosterone sulphate (DHAS) labelled with 3H and dehydroepiandrosterone (DHA) labelled with 14C were simultaneously administered into the arterial supply of four placentas perfused in situ immediately following the removal of the foetus at midpregnancy. From the perfused placentas testosterone (T), androstenedione (A), oestrone (OE1) and 17β-oestradiol (OE2) derived from the metabolism of both DHA and DHAS were isolated in a radiochemically homogeneous form. In addition DHA derived from DHAS was isolated. No labelled 19-hydroxy-androst-4-ene-3,17-dione, or 3β,19-dihydroxy-androst-5-en-17-one was detected. From the perfusates the same steroids were isolated as from the placentas. They contained so small amounts of 3H that their radiochemical homogeneity could be established only on the basis of the 14C label. The 3H/14C ratio of the A isolated from each placenta was higher than that of DHA and OE1 isolated from the same source, indicating a higher contribution of DHAS to A than to DHA or OE1 However, no conjugated or unconjugated intermediates between DHAS and A other than DHA were detected. One possible explanation for the differences in isotope ratios based on the existence of two hypothetical placental compartments, is discussed.

STUDIES ON THE AROMATISATION OF NEUTRAL STEROIDS IN PREGNANT WOMEN

1970 ◽  
Vol 65 (1) ◽  
pp. 69-83 ◽  
Author(s):  
H. Vokal ◽  
D. F. Archer ◽  
N. Wiqvist ◽  
E. Diczfalusy
Keyword(s):  
Pregnant Women ◽  
Placental Perfusion ◽  
Homogeneous Form ◽  
Urine Specimens

ABSTRACT The following steroids, [7α-3H]5-androstene-3β,16α,17β-triol and [4-14C] 5-androstene-3β,16β,17β-triol were biosynthesized and their metabolism was studied in two subjects at midgestation, following placental perfusion in situ. Among the metabolites isolated in a radiochemically homogeneous form, exclusively 3H-labelled 16α,17β-dihydroxy-4-androsten-3-one was isolated from the extracts of placentas and perfusates. Exclusively 14C-labelled 16β,17β-dihydroxy-4-androsten-3-one was isolated from the placentas and perfusates and 16-epioestriol (1,3,5(10)-oestratriene-3,16β,17β-triol) from the placentas, perfusates and urine specimens. The following compounds contained both 3H and 14C-label: oestriol (placentas and urine specimens) and 5β-androstane-3α,16α,17β-triol (urine specimens). The 3H/14C-ratio of oestriol isolated from the urine specimens was much lower than that of urinary 5β-androstane-3α,16α,17β-triol, or that of the oestriol isolated from the placentas. The 3H/14C-ratio of the oestriol isolated from the urine 2–4 days following the perfusion was lower than that of the perfused material. It is concluded that a considerable amount of the 16-epioestriol secreted by the placenta is gradually converted to oestriol by the maternal organism. A limited conversion occurs also in the placenta.

In situ Fe isotopic analyses of fourteen reference materials using a synthetic Cr standard for mass bias and isobaric interference corrections by femtosecond LA-MC-ICP-MS

2021 ◽  
Author(s):  
Lei Xu ◽  
Wen Zhang ◽  
Tao Luo ◽  
Jin-Hui Yang ◽  
Zhaochu Hu
Keyword(s):  
Reference Materials ◽  
Isotope Ratios ◽  
Isobaric Interference ◽  
Analytical Technique ◽  
Mass Bias ◽  
Icp Ms ◽  
Isotopic Analyses

High precise and accurate measurements of Fe isotope ratios for fourteen reference materials from the USGS, MPI-DING and CGSG were successfully carried out using a developed analytical technique by fs...

scholarly journals In-situ determination of antimony isotope ratios in Sb minerals by femtosecond LA-MC-ICP-MS

2021 ◽  
Author(s):  
Andreas Benjamin Kaufmann ◽  
Marina Lazarov ◽  
Stefan Kiefer ◽  
Juraj Majzlan ◽  
Stefan Weyer
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Femtosecond Laser Ablation ◽  
Isotope Ratios ◽  
Icp Ms

Here we present a method for in-situ determination of stable antimony (Sb) isotope compositions by ultraviolet (UV)-femtosecond-laser-ablation-multi-collector-ICP-MS (fs-LA-MC-ICP-MS). Metallic antimony and a number of Sb minerals (stibnite, senarmontite, chalcostibite, tetrahedrite,...

Uranium238U/235U Isotope Ratios as Indicators of Reduction: Results from an in situ Biostimulation Experiment at Rifle, Colorado, U.S.A.

2010 ◽  
Vol 44 (15) ◽  
pp. 5927-5933 ◽  
Author(s):  
Charles John Bopp ◽  
Craig C. Lundstrom ◽  
Thomas M. Johnson ◽  
Robert A. Sanford ◽  
Philip E. Long ◽  
...  
Keyword(s):  
Isotope Ratios

In situ determination of precise stable Si isotope ratios by UV-femtosecond laser ablation high-resolution multi-collector ICP-MS

2008 ◽  
Vol 249 (1-2) ◽  
pp. 155-166 ◽  
Author(s):  
Jérôme Chmeleff ◽  
Ingo Horn ◽  
Grit Steinhoefel ◽  
Friedhelm von Blanckenburg
Keyword(s):  
Laser Ablation ◽  
High Resolution ◽  
Femtosecond Laser ◽  
Femtosecond Laser Ablation ◽  
Isotope Ratios ◽  
Icp Ms ◽  
Si Isotope

Blood flow elevation increases VO2 maximum during repetitive tetanic contractions of dog muscle in situ

1993 ◽  
Vol 74 (4) ◽  
pp. 1499-1503 ◽  
Author(s):  
W. F. Brechue ◽  
B. T. Ameredes ◽  
G. M. Andrew ◽  
W. N. Stainsby
Keyword(s):  
Blood Flow ◽  
Perfusion Pressure ◽  
Power Production ◽  
Arterial Supply ◽  
O2 Uptake ◽  
Plantaris Muscle ◽  
Control Series ◽  
Flow Through ◽  
Series Of Experiments

Blood flow through the gastrocnemius-plantaris muscle of the dog in situ was increased by a pump in the arterial supply during a 30-min period of 1/s isotonic tetanic contractions. Compared with a control series of experiments with normoxemia and spontaneous flow, the pump increased flow 84%, from 1.51 +/- 0.08 to 2.78 +/- 0.15 ml.g-1.min-1. The perfusion pressure was increased from 125 to 196 mmHg. The pump hyperemia increased maximal O2 uptake (VO2) at 5 min of contractions by 31%, from 8.97 +/- 0.44 to 12.89 +/- 0.30 mumol.g-1.min-1. The extraction was decreased, and venous PO2 (PVO2) was increased. Fatigue, measured as a drop in power production from the highest level at 10 s to 30 min, was 49% during pump hyperemia and 54% in the control conditions. VO2 decreased 30% from the 5-min value to the 30-min value with pump hyperemia and 28% over the same time in the control conditions. At maximal VO2, the ratio VO2/PVO2 was increased by pump hyperemia compared with control conditions, suggesting an increased O2 diffusing conductance of the muscles. We conclude that the elevated perfusion pressure of pump hyperemia increased flow to raise maximal VO2 mainly in areas of the muscle that had restricted flow under control conditions.

scholarly journals Nitrogen and Oxygen Isotope Effects of Ammonia Oxidation by Thermophilic Thaumarchaeota from a Geothermal Water Stream

2016 ◽  
Vol 82 (15) ◽  
pp. 4492-4504 ◽  
Author(s):  
Manabu Nishizawa ◽  
Sanae Sakai ◽  
Uta Konno ◽  
Nozomi Nakahara ◽  
Yoshihiro Takaki ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Ammonia Oxidation ◽  
Isotope Effects ◽  
Isotope Ratios ◽  
Oxidation Activity ◽  
Content Type ◽  
Ammonia Oxidizing Archaea ◽  
Nitrogen Pools ◽  
Archaeal Ammonia Oxidation

ABSTRACTAmmonia oxidation regulates the balance of reduced and oxidized nitrogen pools in nature. Although ammonia-oxidizing archaea have been recently recognized to often outnumber ammonia-oxidizing bacteria in various environments, the contribution of ammonia-oxidizing archaea is still uncertain due to difficulties in thein situquantification of ammonia oxidation activity. Nitrogen and oxygen isotope ratios of nitrite (δ15NNO2−and δ18ONO2−, respectively) are geochemical tracers for evaluating the sources and thein siturate of nitrite turnover determined from the activities of nitrification and denitrification; however, the isotope ratios of nitrite from archaeal ammonia oxidation have been characterized only for a few marine species. We first report the isotope effects of ammonia oxidation at 70°C by thermophilicThaumarchaeotapopulations composed almost entirely of “CandidatusNitrosocaldus.” The nitrogen isotope effect of ammonia oxidation varied with ambient pH (25‰ to 32‰) and strongly suggests the oxidation of ammonia, not ammonium. The δ18O value of nitrite produced from ammonia oxidation varied with the δ18O value of water in the medium but was lower than the isotopic equilibrium value in water. Because experiments have shown that the half-life of abiotic oxygen isotope exchange between nitrite and water is longer than 33 h at 70°C and pH ≥6.6, the rate of ammonia oxidation by thermophilicThaumarchaeotacould be estimated using δ18ONO2−in geothermal environments, where the biological nitrite turnover is likely faster than 33 h. This study extended the range of application of nitrite isotopes as a geochemical clock of the ammonia oxidation activity to high-temperature environments.IMPORTANCEBecause ammonia oxidation is generally the rate-limiting step in nitrification that regulates the balance of reduced and oxidized nitrogen pools in nature, it is important to understand the biological and environmental factors underlying the regulation of the rate of ammonia oxidation. The discovery of ammonia-oxidizing archaea (AOA) in marine and terrestrial environments has transformed the concept that ammonia oxidation is operated only by bacterial species, suggesting that AOA play a significant role in the global nitrogen cycle. However, the archaeal contribution to ammonia oxidation in the global biosphere is not yet completely understood. This study successfully identified key factors controlling nitrogen and oxygen isotopic ratios of nitrite produced from thermophilicThaumarchaeotaand elucidated the applicability and its limit of nitrite isotopes as a geochemical clock of ammonia oxidation rate in nature. Oxygen isotope analysis in this study also provided new biochemical information on archaeal ammonia oxidation.

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