Nutrient cycling in grazed pastures. I. A preliminary investigation of the use of [35S] in gypsum.

1968 ◽  
Vol 19 (4) ◽  
pp. 531 ◽  
Author(s):  
PF May ◽  
AR Till ◽  
AM Downes
Keyword(s):  
Nutrient Cycling ◽  
Isotope Dilution ◽  
Plant Uptake ◽  
Specific Activity ◽  
Preliminary Investigation ◽  
Residual Value ◽  
Grazed Pastures ◽  
Initial Application ◽  
Total Soil

[35S]Gypsum was applied to six strips covering a total of approximately 1/32 of the area of a pasture grazed by sheep. The specific activity of samples of soil, plants, ingesta, faeces, and wool was measured. The results were as would be expected from uniform labelling of the whole paddock, and enabled translocation to untreated areas to be measured. They indicate that doses of the order of 1–10 mc should be detectable on paddocks up to 4 ha in area for periods of up to 1 year. When animals were put onto or removed from the treated pastures, changes in the specific activity of wool indicated that 100–150 days were required for the sulphur in the sheep and pasture to reach equilibrium. Animals continuously maintained on the pasture were still producing wool at 60% of the maximal specific activity after 600 days, which indicated a continuing recycling of the applied sulphur. From calculation of the isotope dilution it appears that only a small fraction of the total soil sulphur was available for plant uptake, and the continuing cycling of this over a period exceeding 600 days indicates a high residual value of the initial application.

Nutrient cycling in grazed pastures. II. Further observations with [35S] gypsum

1970 ◽  
Vol 21 (2) ◽  
pp. 253 ◽  
Author(s):  
AR Till ◽  
PF May
Keyword(s):  
Nutrient Cycling ◽  
Sheep Grazing ◽  
Grazed Pastures ◽  
Grazed Pasture ◽  
Sulphur Cycle ◽  
Total Soil ◽  
Animal System ◽  
Gypsum Application

The incorporation of sulphur-35 (35S) into the wool of sheep grazing radioactive pasture was measured in two successive experiments on the same site following application of [35S]gypsum. Equilibrium between the applied sulphur and sulphur present prior to the application was established at different rates with different rainfall. After 3 years the sulphur from the original gypsum application was still being turned over in the soil-plant-animal system, there had been no change in the total soil sulphur, and a large portion of soil sulphur did not enter the sulphur cycle. A diagram of a proposed sulphur cycle in grazed pasture is given, and the assumptions made are discussed.

Effects of insulin on glucose turnover rates in vivo: Isotope dilution versus constant specific activity technique

Metabolism ◽  
1996 ◽  
Vol 45 (1) ◽  
pp. 82-91 ◽  
Author(s):  
Ole Hother-Nielsen ◽  
Jan Erik Henriksen ◽  
Jens Juul Holst ◽  
Henning Beck-Nielsen
Keyword(s):  
Isotope Dilution ◽  
Specific Activity ◽  
Glucose Turnover ◽  
Turnover Rates ◽  
Constant Specific Activity

Production of volatile fatty acids in the sheep caecum

1969 ◽  
Vol 20 (3) ◽  
pp. 491 ◽  
Author(s):  
GJ Faichney
Keyword(s):  
Fatty Acids ◽  
Steady State ◽  
Fatty Acid ◽  
Production Rate ◽  
Energy Intake ◽  
Isotope Dilution ◽  
Volatile Fatty Acids ◽  
Specific Activity ◽  
Total Production ◽  
Digestible Energy

Acetic, propionic, and butyric acids labelled with 14C were infused into the caecum of continuously fed sheep. The specific activity of the volatile fatty acids (VFA) in the caecum was determined at intervals during the infusion. The production rate was calculated by isotope dilution from the results of those experiments in which steady state conditions were obtained. Substantial interconversions occurred between the fatty acid fractions. The total production of VFA was about 440 mmoles/day, equivalent to 125 kcal/day or 5.3% of the animal's digestible energy intake.

Quantitation of renal uric acid synthesis in the chicken

1978 ◽  
Vol 234 (5) ◽  
pp. F446-F451 ◽  
Author(s):  
Theodore Y. Chin ◽  
A. J. Quebbemann
Keyword(s):  
Uric Acid ◽  
Isotope Dilution ◽  
Activity Ratio ◽  
Specific Activity ◽  
Acid Synthesis ◽  
Systemic Circulation ◽  
Portal Circulation ◽  
Dilution Technique ◽  
Renal Metabolism ◽  
Isotope Dilution Technique

The contribution of uric acid synthesized in the kidney (nephrogenic uric acid) to the total uric acid excreted in the urine was studied in the chicken by use of the isotope-dilution technique. In the nonfasted chicken the urine-to-plasma specific activity ratio (SAR) of [14C]uric acid was 0.83, suggesting that a minimum of 17% of the uric acid excreted in the urine is synthesized in the kidney. During allopurinol infusion into the renal portal circulation of one kidney the SAR increased to 0.99, indicating that the renal synthesis of uric acid was almost completely inhibited and that the SAR is a valid indicator of the contribution of nephrogenic uric acid excreted into the urine without first entering the circulation. Chickens fasted for 18 h showed a lower rate of renal synthesis of uric acid. Hypoxanthine infusion into the systemic circulation increased the rate of renal synthesis of uric acid in both fasted and nonfasted chickens, suggesting that circulating precursor levels may in part regulate the renal synthesis of uric acid. kidney; specific activity ratio; allopurinol; renal metabolism Submitted on July 14, 1977

GLUCOCORTICOID SYNTHESIS FROM PREGNENOLONE BY SHEEP FOETAL ADRENALS IN VITRO

1973 ◽  
Vol 58 (3) ◽  
pp. 485-491 ◽  
Author(s):  
I. J. DAVIES ◽  
K. J. RYAN
Keyword(s):  
Isotope Dilution ◽  
Adrenal Glands ◽  
Specific Activity ◽  
Newborn Period ◽  
Adult Sheep ◽  
Age Related ◽  
Period Of Gestation ◽  
Constant Specific Activity

SUMMARY [7-3H]Pregnenolone was incubated with homogenates of adrenal glands from two 100-day-old sheep foetuses. Cortisol and corticosterone were isolated and identified by reverse isotope dilution and recrystallization to constant specific activity. Together these two compounds accounted for 12% and 17% of the substrate with the two tissue preparations. Other C21 and C19 metabolites which were sought were not present in appreciable quantities. Additional incubations were done with the adrenals of lamb foetuses ranging in age from 110 days of gestation to the immediate newborn period. Glucocorticoidogenic capacity similar to that of the 100-day-old foetuses was demonstrated throughout this period and no age-related change was evident. These results demonstrate that the lamb foetal adrenal has a substantial enzymic capacity for glucocorticoid synthesis throughout at least the last third of gestation. In conjunction with the observations of others, these experiments support the hypothesis that during this period of gestation the lamb foetal adrenal is actively synthesizing glucocorticoids in a manner which is similar to the lamb at term and the adult sheep.

Bestimmung der Halbwertszeit von 210Pb

1969 ◽  
Vol 24 (4) ◽  
pp. 612-615 ◽  
Author(s):  
A. Höhndorf
Keyword(s):  
Isotope Dilution ◽  
Half Life ◽  
Specific Activity ◽  
Mass Spectrometric ◽  
Isotope Dilution Analysis ◽  
Isotope Dilution Method ◽  
Dilution Method ◽  
Daughter Product ◽  
Pb Concentration

Abstract The half-life of 210Pb has been calculated from measurements of the specific activity and the 210Pb-concentration of a 210Pb-solution. The specific 210Pb-activity was determined by measuring the daughter product 210Po using an α-spectrometric isotope dilution method with 208Po as tracer. The 210Pb-concentration was measured by mass-spectrometric isotope dilution analysis. A half-life of 22.26 ± 0.22 ( = 2 σ) years has been obtained.

Formulation of ‘ready-to-use’ human clinical doses of 177Lu-labeled bisphosphonate amide of DOTA using moderate specific activity 177Lu and its preliminary evaluation in human patient

2020 ◽  
Vol 108 (8) ◽  
pp. 661-672
Author(s):  
Sudipta Chakraborty ◽  
Priyalata Shetty ◽  
Rubel Chakravarty ◽  
K. V. Vimalnath ◽  
Chandan Kumar ◽  
...  
Keyword(s):  
Specific Activity ◽  
Specific Binding ◽  
Preliminary Investigation ◽  
Skeletal Metastases ◽  
Preliminary Evaluation ◽  
Binding Studies ◽  
Human Patient ◽  
Biodistribution Studies ◽  
Target Organs

AbstractRadiolabeled macrocyclic bisphosphonate ligands have recently been demonstrated to be highly efficacious in treatment of patients with painful bone metastases. Herein, we report a robust protocol for formulation of therapeutically relevant doses of 177Lu-labeled bisphosphonate amide of DOTA (BPAMD) using moderate specific activity 177Lu produced by direct (n,γ) route and its preliminary investigation in human patients. Doses (2.8 ± 0.2 GBq) were formulated with high radiochemical purity (98.3 ± 0.4 %) using a protocol optimized after extensive radiochemical studies. In vitro binding studies with mineralized osteosarcoma cells demonstrated specific binding of the radiotracer. Biodistribution studies in healthy Wistar rats demonstrated rapid skeletal accumulation with fast clearance from the non-target organs. In a patient administered with 555 MBq dose of 177Lu-BPAMD, intense radiotracer uptake was observed in the metastatic skeletal lesions with insignificant uptake in any other major non-targeted organs. Preliminary clinical investigations carried out after administration of 2.6 GBq of 177Lu-BPAMD revealed significant reduction in pain after 1 week without any adverse effects. The developed protocol for formulation of 177Lu-BPAMD doses using moderate specific activity carrier added 177Lu has been found to be effective and warrants wider investigations in patients with painful skeletal metastases.

Nutrient cycling in grazed pastures. III. Studies on labelling of the grazed pasture system by solid [35S]gypsum and aqueous Mg35S04

1970 ◽  
Vol 21 (3) ◽  
pp. 455 ◽  
Author(s):  
AR Till ◽  
PF May
Keyword(s):  
Steady State ◽  
Nutrient Cycling ◽  
Specific Radioactivity ◽  
Sulphur Content ◽  
Sheep Grazing ◽  
Plant Materials ◽  
Grazed Pastures ◽  
Grazed Pasture ◽  
Sulphur Cycle

35S was applied to eight paddocks either onto strips that comprised 1/30 of the area of the paddock or uniformly over the paddock. It was applied as solid [35S]gypsum or aqueous Mg35SO4 at sulphur levels of either 130 mg/ha or 7.8 kg/ha. The specific radioactivity of wool grown by sheep grazing the paddocks showed that strip and uniform labelling gave similar results, that there was no retention of the applied sulphur in forms that were not eventually available to plants, and that after about 260 days the effective specific radioactivity of the cycling sulphur had approached a steady state. There were significant differences between the specific radioactivities of sulphur in phalaris and clover. The differences in the sulphur application levels produced plant materials having slightly different sulphur contents but the major changes in sulphur content were due to the natural sulphur cycle.

Does the Amount of Stable Isotope Dose Influence Retinol Kinetic Responses and Predictions of Vitamin A Total Body Stores by the Retinol Isotope Dilution Method in Theoretical Children and Adults?

2021 ◽  
Author(s):  
Michael H Green ◽  
Veronica Lopez-Teros ◽  
Joanne Balmer Green
Keyword(s):  
Stable Isotope ◽  
Vitamin A ◽  
Isotope Dilution ◽  
Specific Activity ◽  
Simulated Data ◽  
Compartmental Analysis ◽  
Isotope Dilution Method ◽  
Dilution Method ◽  
Plasma Retinol ◽  
Total Body

Abstract Background To minimize both cost and perturbations to the vitamin A system, investigators limit the amount of stable isotope administered when estimating vitamin A total body stores (TBS) by retinol isotope dilution (RID). Objectives We hypothesized that reasonable increases in the mass of stable isotope administered to theoretical subjects would have only transient impacts on vitamin A kinetics and minimal effects on RID-predicted TBS. Methods We adapted previously-used theoretical subjects (3 children, 3 adults) with low, moderate, or high assigned TBS and applied compartmental analysis to solve a steady state model for tracer and tracee using assigned values for retinol kinetic parameters and plasma retinol. To follow retinol trafficking when increasing amounts of stable isotope were administered [1.39-7 (children) and 2.8-14 µmol retinol (adults)], we added assumptions to an established compartmental model so that plasma retinol homeostasis was maintained. Using model-simulated data, we plotted retinol kinetics versus time and applied the RID equation TBS = FaS/SAp [Fa, fraction of dose in stores; S, retinol specific activity (SA) in plasma/SA in stores; SAp, SA in plasma] to calculate vitamin A stores. Results The model predicted that increasing the stable isotope dose caused transient early increases in hepatocyte total retinol; increases in plasma tracer were accompanied by decreases in tracee to maintain plasma retinol homeostasis. Despite changes in kinetic responses, RID accurately predicted assigned TBS (98-105%) at all loads for all theoretical subjects from 1-28 d postdosing. Conclusions Results indicate that, compared with doses of 1.4–3.5 µmol used in recent RID field studies, doubling the stable isotope dose should not affect accuracy of TBS predictions, thus allowing for experiments of longer duration when including a super-subject design (Ford et al., J Nutr 2020;150:411–8) and/or studying retinol kinetics.

Influence of Vitamin A Status on the Choice of Sampling Time for Application of the Retinol Isotope Dilution Method in Theoretical Children

2021 ◽  
Author(s):  
Veronica Lopez-Teros ◽  
Michael H Green ◽  
Marjorie J Haskell ◽  
Joanne Balmer Green
Keyword(s):  
Vitamin A ◽  
Isotope Dilution ◽  
Specific Activity ◽  
Geometric Mean ◽  
Sampling Time ◽  
Percentage Error ◽  
Isotope Dilution Method ◽  
Dilution Method ◽  
Individual Subject ◽  
Vitamin A Status

ABSTRACT Background Vitamin A status may influence the choice of a blood sampling time for applying the retinol isotope dilution (RID) equation to predict vitamin A total body stores (TBS) in children. Objectives We aimed to identify time(s) after administration of labeled vitamin A that provide accurate estimates of TBS in theoretical children with low or high TBS. Methods We postulated 2- to 5-y-old children (12/group) with low (<200 μmol) or high TBS (≥700 μmol) and used compartmental analysis to simulate individual subject values for the RID equation TBS =   FaS/SAp (Fa, fraction of dose in stores; S, retinol specific activity in plasma/in stores; SAp, retinol specific activity in plasma). Using individual SAp and group geometric mean FaS values from 1–28 d, we calculated individual and group mean TBS and compared them to assigned values. Results Mean TBS was accurately predicted for both groups at all times. For individuals, predicted and assigned TBS were closest when the CV% for FaS was low [12–14%; 4–13 d (low), 12–28 d (high)]. The mean percentage error for TBS was <10% from 2–19 d (low) and 7–28 d (high). Predicted TBS was within 25% of assigned TBS for ≥80% of children from 3–23 d (low) and 9–28 d (high). Within groups, RID tended to overestimate lower TBS and underestimate higher TBS. Conclusions Using a good estimate for FaS, accurate RID predictions of TBS for individuals will be obtained at many times. If vitamin A status is low, results indicate that early sampling (e.g., 4–13 d) is optimal; if vitamin A status is high, sampling at 12–28 d is indicated. When vitamin A status is unknown, sampling at 14 d is recommended, or a super-subject design can be used to obtain the group mean FaS at various times for RID prediction of TBS in individuals.

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