Use Of Radioactive Tracers Research Articles

Use of gas chromatography-combustion-isotope ratio mass spectrometry in nutrition and metabolic research

Linking gas chromatography via an on-line combustion interface to isotope ratio mass spectrometry has opened the door to high-precision compound-specific isotope analysis. For this reason, gas chromatography-combustion-isotope ratio mass spectrometry is now increasingly employed in metabolic and nutritional research because it offers a reliable and risk-free alternative to the use of radioactive tracers.

Mechanisms of apomorphine cytoxicity towards rat glioma C6 cells: protection by bovine serum albumin and formation of apomorphine-protein conjugates

Apomorphine cytotoxicity towards rat glioma C6 cells was recently demonstrated to be time- and concentration-dependent. In the present work, the mechanism of cytotoxicity of apomorphine was further studied in the C6 cell line. We showed that bovine serum albumin partially protects C6 cells against apomorphine cytotoxicity. However, serum albumin did not prevent apomorphine autoxidation and melanin formation, suggesting that this protein scavenges apomorphine reactive products formed during its oxidation. The use of radioactive tracers, fluorimetry and protein electrophoresis showed that apomorphine autoxidation products covalently and nonspecifically bind to serum albumin and to rat liver microsomes. l-Cysteine, which is a thiol reagent that inhibits apomorphine autoxidation also prevented the formation of apomorphine-serum albumin adducts. These results suggest that quinone derivatives formation and oxidative stress should be responsible for apomorphine cytotoxicity.

Development of compartmental models in stable-isotope experiments: application to lipid metabolism.

Kinetic experiments are of great importance in lipid research because they further the understanding of lipid metabolism in vivo and help to explain the physiopathology of lipid disorders in humans. At present, due to species specificity, no valid animal model can efficiently replace a study in humans to explore lipid metabolism, and the use of radioactive tracers is restricted in humans. Thus, stable-isotope tracer kinetic studies have become an important component of research programs to achieve in humans a quantitative understanding of the dynamics of metabolic processes in vivo. The aim of this review is to describe the practical aspects of compartmental model development in stable-isotope experiments. The recent development of computer hardware and modeling software has dramatically facilitated the task of the modeler in his or her calculations. In the current review, we show that the model may be considered an integral component of the experimental design and that model development must obey strict rules to provide a rigorous solution. The main difficulties of model development in tracer experiments, such as experiment design, model identifiability, data expression, comparison of models, or tracer recycling, are presented with extensive references. We have paid particular attention to kinetic modeling in stable-isotope experiments because they have shown the greatest development in recent years.

Use of radioactive tracers in the evaluation of penile hemodynamics: history, methodology and measurements.

Radionuclide tracer techniques are intimately associated with some of the early ground-breaking investigations in erectile dysfunction and have evolved along with the field. At the present time, the various investigations can be grouped into four categories: labeled blood-pool; tracer washout; tracer washin and combined blood-pool/tracer and tracer washout examinations. Blood pool studies are most useful in assessing the integrity of arterial inflow, but may also be used to generate indices of venous leak. A non-imaging version of the blood-pool test may represent a simple and cost-effective alternative. Washout of intracavernosal xenon during erection seems the most rigorous method of testing venous integrity. Washout using 99mTc-labeled substances may emerge as a convenient alternative to the more technically difficult xenon examinations. Dual-isotope blood pool and washout examinations, though complicated, represent an ideal method of analyzing penile hemodynamics, with potential to contribute significantly to the understanding of penile physiology. Development of improved pharmacologic stimuli and augmentation of testing protocols by intracavernosal pressure monitoring may further improve the utility of quantitative and physiologic nuclear medicine examinations in erectile dysfunction.

Biosynthesis of Vitamin B1 (Thiamin): An Instance of Biochemical Diversity

AbstractThe elucidation of the biosynthetic pathway to thiamin (Vitamin B1) and its pyrophosphate ester, the important coenzyme “cocarboxylase”, has challenged researchers for many years and continues to do so. The problem of the origin of thiamin can be separated into three parts: the independent pathways to the pyrimidine moiety 4‐amino‐5‐hy‐droxymethyl‐2‐methylpyrimidine and to the thiazole moiety 5‐(2‐hydroxyethyl)‐4‐methylthiazole, and the route from these subunits to the vitamin. The steps in the latter process were fully established some twenty years ago, and it was shown that the route in aerobic bacteria and yeast differs to some extent from that in enteric bacteria. The pathways to the subunits, on the other hand, are still not clarified. Significant differences exist in the routes whereby each of the two subunits, the pyrimidine moiety and the thiazole moiety, originate in bacteria and yeast. One difficulty that delayed progress was that the incorporation patterns of labeled precursors, which were observed by different research groups in different microorganisms, could not be reconciled on the basis of a single pathway to each of the two subunits. It is now accepted that in each case different pathways exist in enteric bacteria and yeast, and that the biosynthesis of Vitamin B1 represents an instance of biochemical diversity. A second factor that added to the difficulties is the minute amount of thiamin synthesized in microbiological cultures (about 15 μg per L culture). This limited the investigations until very recently either to the use of radioactive tracers or to the use of stable isotopes in conjunction with mass spectrometric analysis. It is widely recognized that both methods are associated with pitfalls in the interpretation of results. High‐field 13C NMR, the most powerful modern method available for the determination of incorporation patterns, has only very recently been successfully employed in investigations of thiamin biosynthesis. As a result of the conceptual and experimental problems, even the primary precursors of each of the two relatively simple heterocyclic subunits of thiamin are still not completely established. A search for committed intermediates, the study of the enzymes, and identification of the genes that are involved are the matter of current research.

Use of stable isotopically labeled tracers for studies of metabolic kinetics: An overview

Stable isotopically labeled tracers offer a reliable and safe alternative to the use of radioactive tracers for studies of metabolic kinetics. This overview examines some of the principles and technical issues regarding mass spectrometry instrumentation, and reviews some of the approaches used in the application of stable isotopically labeled tracers to studies of protein, lipid, and carbohydrate metabolic kinetics.

A novel method for the production of antibodies against ACTH: their characterization and use in epitope mapping

Our earlier attempts at immunization with human adrenocorticotropin hormone (ACTH) were unsuccessful and we therefore developed a new strategy including the chemical modification of the hormone by succinic anhydride in order to increase its immunogenicity. This process allowed us to obtain antisera with titers of up to 1 1000 and yielded 39 anti-succinylated ACTH (sACTH)-secreting hybridomas. Subsequently, the epitopes of sACTH were mapped by testing monoclonal antibodies two by two for simultaneous binding to sACTH and for their capacity to recognize its succinylated fragments 1–13, 1–17 and 1–24. The results, obtained with the use of radioactive tracers, were confirmed by and complemented with experiments conducted with biosensor technology. Seven groups of antibodies were defined on the basis of their pattern of reactivity and it was shown that four monoclonal antibodies could bind simultaneously to sACTH. Their dissociation constants ( K d) for sACTH were calculated and ranged from 10 −8 M to 10 −11 M. In order to obtain a fast and sensitive immunoassay for the hormone, we developed a protocol for the chemical modification of ACTH in serum and the most efficient monoclonal antibodies were selected on the basis of the epitope map and of their dissociation constants.

The use of stable tracers to study intestinal calcium absorption. The Italian Society of Osteoporosis.

This paper represents the final document released by the Italian Society of Osteoporosis (S.I.OP.), on the occasion of its fifth annual meeting held in Padova, Italy (November 30-December 3, 1993). The S.I.OP. has in fact planned to periodically organize a conference on still-debated, controversial issues. After an exhaustive discussion of the various aspects of the problem by qualified experts in the field, a solution will be proposed by the members of the Society. The problems related to the use of radioactive tracers to study intestinal calcium absorption and the possible ways to over-come them were the issues discussed last year, by four panelists (R. P. Heaney, C. Gennari, G. Mioni, and S. Minisola) coordinated by G. F. Mazzuoli.

Intestinal absorption of radioactive long-chain saturated fatty acids by the larval dragon-fly Aeshna cyanea and co-absorptive effects of other stable fatty acids

In contrast with unsaturated fatty acids, ingestions of long-chain saturated fatty acids by Aeshna cyanea larvae failed to induce an accumulation of lipid droplets in the intestinal absorptive cells, so that it remained questionable whether they were absorbed or not (Bauerfeind and Komnick, 1989). Therefore, we reinvestigated the question with the use of radioactive tracers, which were orally infused under two conditions: at low doses and at high doses prepared by the addition of other stable fatty acids. We found that carboxyl- 14C labelled long-chain stearic and palmitic acids, as well as the medium-chain lauric acid studied for comparison, were indeed absorbed from low doses of 7 nmol. They were incorporated predominantly into the phospholipids of the midgut wall and released into the haemolymph mainly as diacylglycerols. A substantial part was also transported as cholesterylester. The increase in total fatty acids of the infusates by the addition of 1.8 μmol stable oleic, arachidonic, myristoleic acids and lauric acid ethylester, which at high doses induce the formation of triacylglycerol droplets within the midgut enterocytes, markedly reduced the absorption rates of the radioactive saturated fatty acids and greatly favoured their incorporation into di- and triacylglycerols on the expense of the phospholipids and, at a minor part, on the expense of cholesterylester. By contrast, the addition of 1.8 μmol stable caproic acid yielded little, if any, effect on the absorption pattern of the radioactive palmitic acid. The results suggest that the co-absorption of medium- and long-chain saturated and unsaturated fatty acids is interdependent utilizing the same or similar uptake mechanisms and dose-dependent esterification pathways, while it is largely independent of and probably different from the absorption of short-chain fatty acids.

In Vivo Evaluation of Dosage Forms: Application of Gamma Scintigraphy to Non-enteral Routes of Administration

The trend to deliver drugs to defined areas of the body involves sophisticated carriers systems. In addition to the in vitro drug release profile one must be aware of the in vivo behaviour of the dosage form and the drug. Gamma scintigraphy is an elegant way to gain insights of the actual in vivo distribution pattern of dosage forms. This technique relies on the use of radioactive tracers included into the medicament and selected so as to enable an optimum detection by a gamma ray camera. The choice of a convenient label enables the in vivo determination of the targeting of the formulation administered through a large number of routes. The present paper reviews applications of gamma scintigraphy for the evaluation of dosage forms administered by the parenteral, rectal, buccal, nasal, pulmonary, and ophthalmic routes.

Use of cyclotrons for trace element analysis in biological samples and related metabolism studies

In this work metabolic studies based on proton nuclear activation (PNA) are described. For such kind of experiments a very high sensitivity in concentration determination of adequate tracers in biological tissues is needed and the contemporary use of more than one isotope of some element is often necessary. Moreover the use of radioactive tracers is normally forbidden in healthy persons. PNA is usually obtained inducing (p, xn) reactions on the target nuclei by means of a proton beam of adequate energy. The large power released by the charged particle beam in biological targets (dried serum samples) requires an efficient cooling system and imposes a limitation in the beam intensity. The special irradiation chamber built to irradiate 30 samples at a time is described. An account will be given of metabolic studies on Fe, Mo, and Te in man and/or animal. Some fundamental metabolic parameters are extracted by means of compartment analysis. Data on blood serum clearance constants and relative intestinal absorption coefficients are discussed.

Squid Photoreceptors and Retinas: Content of Phosphatidylinositol-Bisphosphate and Inositol Trisphosphate.

Previous articleNext article No AccessARTICLESSquid Photoreceptors and Retinas: Content of Phosphatidylinositol-Bisphosphate and Inositol TrisphosphateE. Z. SzutsE. Z. Szuts Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Biological Bulletin Volume 183, Number 2October 1992 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/BBLv183n2p352 Views: 7Total views on this site Copyright © 1992 by Marine Biological LaboratoryPDF download Crossref reports no articles citing this article.

A method to determine resin flow during curing of composite laminates

AbstractAn experimental method is presented to determine the amount of resin flow within a composite laminate during cure. The method is analogous to the use of radioactive tracers in other applications. Heavier elements such as chlorine and bromine, which may be naturally present in small amounts in epoxy resins are used to follow resin flow and mixing. The presence and the quantity of these “tags” is determined using wavelength dispersive X‐ray analysis in a scanning electron microscope. With the resins in this study, it is shown that it is possible to measure volume fractions of resin with accuracies ranging from ±0.5 to ±3 volume %. By using brominated resin in only one layer of a laminate, the degree of flow and mixing can be followed accurately. The results suggest that there is considerable resin mixing as well as flow.

Biosynthesis of limonoid glucosides in lemon (Citrus limon)

TLC analyses of lemon (Citrus limon (L) Burm f) fruit at various stages of maturity showed that limonoid glucosides were synthesised during the late stages of fruit growth. No limonoid glucosides were found in the stem and leaf. Use of radioactive tracers showed that 14C-nomilin was converted to 14C-nomilin 17-β-D-glucopyranoside in fruit tissues and seeds. Glucosides are indeed the major end products of limonoid metabolism.

Determination of deoxycholic acid pool size and input rate using [24-13C]deoxycholic acid and serum sampling.

We have developed an isotope dilution method for determination of deoxycholic acid pool size and input rate which employs oral administration of 50 mg of [24-13C]deoxycholic acid and serum sampling. The method has been validated by classical isotope dilution technique using [24-14C]deoxycholic acid and bile sampling in five patients with colonic adenomas. Excellent agreement between pool sizes and input rates determined with 13C/12C isotope ratio measurements in serum and 14C measurements in bile was obtained when isotope ratios were measured in the conjugated fraction of deoxycholic acid in serum. We conclude that pool size and input rate of deoxycholic acid can accurately be determined by blood sampling after oral administration of [24-13C]deoxycholic acid, therewith eliminating the use of radioactive tracers and the need for bile sampling.

Microcomputer systems for analysis of radioactive tracers data

Applications of radioactive materials to peaceful uses in Mexico, is the responsibility of the Instituto Nacional de Investigaciones de Nucleares. This paper describes how the Institute monitors one such use of radioactive tracers, namely their application to measuring fluid flow rates and residence time in industrial equipment.

Direct areal density measurement by activation technique for plastic hollow shell implosion experiments

The fuel areal density ρR measurement of imploded plastic hollow shell targets by use of a neutron activation technique is reported. Silicon was doped as an activatable tracer into a hollow shell of tritium-contained deuterated polymer(CDTSi). This target was imploded by 0.53 μm Nd:glass laser light and the induced radioactivity of 28 Al was measured with a β-γ coincidence counting system. The collection efficiency was calibrated by the use of radioactive tracer 24 Na and was verified by comparing the estimated ρR with that simultaneously measured by a knock-on method.

Quinacrine inhibits the calcium-induced calcium release in heavy sacroplasmic reticulum vesicles

Quinacrine is a fluorescence probe useful for studying the effect of local anesthetics. The interaction of quinacrine and sacroplasmic reticulum membranes measured by fluorencence spectroscopy indicates the presence of a saturable binding site. Typical local anesthetics are able to displace quinacrine bound to heavy sacroplasmic reticulum membranes. The effectiveness of that displacement decreases in the order dibucaine > tetracine > benzocaine > procaine > procainamide, indicating that the size and hydrophobicity of quinacrine are major determinants in the binding process. The use of radioactive tracer and a rapid filtration technique reveals that quinacrine interacts, at lower concentrations, with sarcoplasmic reticulum membranes by blocking the Ca 2+-induced Ca 2+ release. Higher quinacrine concentrations also affect the Ca 2+-pump activity.

Use of radioactive tracers for detecting cracks in steel structural welds in seawater: Jones, J.E., Natalie, C.A. and Burns, M.Weld. J. Sept. 1988, 67, (9), 47–53

Microstructural developments were determined on solution-annealed (SA) and cold-worked (CW) JPCA and U.S. PCAs irradiated in the High Flux Isotope Reactor (HFIR) at 300 and 400°C. Irradiation produced damage levels of about 10 and 34 dpa and helium concentrations of around 580 and 2500 appm respectively. High concentrations of fine bubbles and MC precipitates, as well as Frank faulted loops, were observed in both SA and CW PCAs. Mutual stability of the MC particles and associated fine bubbles contributed to the extension of the transient regime of swelling to higher fluence. The irradiation responses of JPCA and U.S.-PCA were similar in the HFIR, despite minor compositional differences (P, B) between the two materials. Useful fusion applications of SA-PCA as well as CW-PCA in the 300 to 400° C temperature range are suggested from these data.

Use of Radioactive Tracers for Studies on Fluidized Cracking Catalytic Plants

In this paper are described the experiments carried out with radioactive tracers on Fluidized Cracking Catalytic (F.C.C.) plants. The tracers used are 41Ar and 79Kr for gas and 140La for the catalyst. Results obtained on different parts of the F.C.C. plant are given.