Isotope exchange between mercuric [Hg(II)] chloride and Hg(II) bound to minerals and thiolate ligands: Implications for enriched isotope tracer studies

The advent of accelerator mass spectrometry (AMS) now permits the ultrasensitive detection of extremely long-lived isotopes, including 14C, 26Al, and 41Ca. Until now, tracer studies of aluminum kinetics have not been possible because aluminum has only two isotopes, with half-lives of 6.5 min (29Al) and 7 x 10(5) yr (26Al), neither of which is suitable for conventional studies. In a novel experiment we have employed AMS to study aluminum kinetics in a normal rat and a 5/6-nephrectomized rat over a 3-wk period of intravenous injection of a tracer dose of 26Al. Kinetics were similar in the two animals; approximately 75% of intravenously injected tracer 26Al was excreted in the urine in the first 24 h as was approximately 80% after 3 wk. Renal clearance of 26Al was approximately 0.75 ml.min-1.kg body wt-1 in both rats. The results clearly demonstrate the potential of this technique for isotope tracer studies in animals as well as in humans.

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Rapid sample throughput for biomedical stable isotope tracer studies

Biological Mass Spectrometry ◽

10.1002/bms.1200160142 ◽

1988 ◽

Vol 16 (1-12) ◽

pp. 229-235 ◽

Cited By ~ 58

Author(s):

T. Preston ◽

D. C. McMillan

Keyword(s):

Stable Isotope ◽

Tracer Studies ◽

Stable Isotope Tracer ◽

Isotope Tracer ◽

Sample Throughput

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Isotope tracer studies on the carbon dioxide exchange in pregnant primates

American Journal of Obstetrics and Gynecology ◽

10.1016/0002-9378(62)90517-3 ◽

1962 ◽

Vol 84 (9) ◽

pp. 1242-1252 ◽

Cited By ~ 11

Author(s):

Albert A. Plentl ◽

Emanuel A. Friedman

Keyword(s):

Carbon Dioxide ◽

Carbon Dioxide Exchange ◽

Tracer Studies ◽

Isotope Tracer

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Simulation of the dynamics of nitrogen metabolism in sheep

British Journal Of Nutrition ◽

10.1079/bjn19760017 ◽

1976 ◽

Vol 35 (1) ◽

pp. 149-174 ◽

Cited By ~ 20

Author(s):

A. Mazanov ◽

J. V. Nolan

Keyword(s):

Mathematical Model ◽

Nitrogen Metabolism ◽

Transport Processes ◽

Simulation Studies ◽

Tracer Studies ◽

First Order ◽

Isotope Tracer ◽

First Order Kinetics ◽

Pool Model ◽

N Metabolism

1. The results of isotope tracer studies of the dynamics of nitrogen metabolism in mature sheep were used to construct a seven-pool mathematical model.2. The model was extended to a nine-pool model, which incorporates lags describing the time taken for the passage of digesta through the gut of sheep.3. Simulation studies using these models satisfactorily predicted results of independent experiments.4. The dynamics of N metabolism in sheep appear to be best approximated by first-order kinetics; that is, many of the important N transport processes are substantially linear or concentration-dependent.

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How to Convert Biological Carbon Into Graphite for AMS

Radiocarbon ◽

10.1017/s0033822200038789 ◽

2006 ◽

Vol 48 (3) ◽

pp. 325-336 ◽

Cited By ~ 21

Author(s):

Girma Getachew ◽

Seung-Hyun Kim ◽

Betty J Burri ◽

Peter B Kelly ◽

Kurt W Haack ◽

...

Keyword(s):

Sample Preparation ◽

Detection Method ◽

Kinetic Studies ◽

Environmental Research ◽

Educational Materials ◽

Tracer Studies ◽

Isotope Tracer ◽

Biological And Environmental Samples ◽

Multistep Procedure ◽

The Cost

Isotope tracer studies, particularly radiocarbon measurements, play a key role in biological, nutritional, and environmental research. Accelerator mass spectrometry (AMS) is now the most sensitive detection method for 14C, but AMS is not widely used in kinetic studies of humans. Part of the reason is the expense, but costs would decrease if AMS were used more widely. One component in the cost is sample preparation for AMS. Biological and environmental samples are commonly reduced to graphite before they are analyzed by AMS. Improvements and mechanization of this multistep procedure is slowed by a lack of organized educational materials for AMS sample preparation that would allow new investigators to work with the technique without a substantial outlay of time and effort. We present a detailed sample preparation protocol for graphitizing biological samples for AMS and include examples of nutrition studies that have used this procedure.

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Statins, PCSK9 inhibitors and cholesterol homeostasis: a view from within the hepatocyte

Clinical Science ◽

10.1042/cs20160872 ◽

2017 ◽

Vol 131 (9) ◽

pp. 791-797 ◽

Cited By ~ 3

Author(s):

Allan D. Sniderman ◽

Robert Scott Kiss ◽

Thomas Reid ◽

George Thanassoulis ◽

Gerald F. Watts

Keyword(s):

Channel Model ◽

Ldl Receptor ◽

Cholesterol Homeostasis ◽

Lower Plasma ◽

Pcsk9 Inhibitors ◽

Tracer Studies ◽

Conventional Model ◽

Isotope Tracer ◽

Ldl Particles ◽

Receptor Number

Statins and PCSK9 inhibitors dramatically lower plasma LDL levels and dramatically increase LDL receptor number within hepatocyte cell membranes. It seems self-evident that total clearance of LDL particles from plasma and total delivery of cholesterol to the liver must increase in consequence. However, based on the results of stable isotope tracer studies, this analysis demonstrates the contrary to be the case. Statins do not change the production rate of LDL particles. Accordingly, at steady state, the clearance rate cannot change. Because LDL particles contain less cholesterol on statin therapy, the delivery of cholesterol to the liver must, therefore, be reduced. PCSK9 inhibitors reduce the production of LDL particles and this further reduces cholesterol delivery to the liver. With both agents, a larger fraction of a smaller pool is removed per unit time. These findings are inconsistent with the conventional model of cholesterol homeostasis within the liver, but are consistent with a new model of regulation, the multi-channel model, which postulates that different lipoprotein particles enter the hepatocyte by different routes and have different metabolic fates within the hepatocyte. The multi-channel model, but not the conventional model, may explain how statins and PCSK9 inhibitors can produce sustained increases in LDL receptor number.

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