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PubMed1987

A linear method for determining specific activity of tracers in radioimmunoassays.

I describe a rapid and objective method for graphically determining specific activity of radioactive tracers by self-displacement. Two sets of results are plotted on the same graph: total/bound counts vs concentration of unlabeled analyte (for the standard curve results) or quantity of radioactivity (for tracer self-displacement results). Because these plots are linear, not only are the difficulties of curve fitting and the need for numerous data points avoided, but also how well the data fit the lines can be assessed by calculating the standard deviation of the slope of the lines. This method minimizes uncertainty between data points, allows easier interpolation, and often yields more precise results than do previously published procedures.

Half-Life↗
PubMed1990

Contribution of red blood cells to the saturable mechanism of heparin clearance.

The pattern of clearance of intravenously administered heparin suggests the participation of a saturable mechanism which has been ascribed to heparin binding to the endothelium. Another potential site of heparin binding which may contribute to the saturable mechanism is the red blood cells. We have examined this possibility using unfractionated heparin together with a chemically-modified low affinity heparin labelled with tritium as tracer. Unfractionated heparin and the radioactive tracer were added to pooled plasma at a fixed concentration. The heparinized plasma was mixed with red cells to reconstitute whole blood. After centrifugation, the radioactivity, APTT, anti-Xa and anti-IIa activities were measured in the resultant plasmas. No evidence of significant binding to red cells could be detected even when the hematocrits of the reconstituted whole blood were increased. These results are at variance with those of a previously published report. We conclude that red cell binding does not contribute to the saturable mechanism of heparin clearance.

Antithrombin III↗
PubMed1980

The role of the synovial fluid and tendon sheath for flexor tendon nutrition. An experimental tracer study on diffusional pathways in dogs.

Radioactive tracers were used to analyse nutritional mechanisms of flexor tendons of dogs during various experimental conditions. The transport and distribution of methyl glucose in the tendon was analysed 15 min after intravenous injection during the following experimental conditions: (1) normal state--rest; (2) passive mobilization of the tendon; (3) active mobilization of the tendon; (4) exclusion of exposure to synovial fluid-preservation of vascular supply; (5) exclusion of vascular supply--preservation of exposure to synovial fluid. The results indicate that active mobilization gives a significant increase in tracer concentration in the volar part of the tendon, while passive mobilization has no such effect. Diffusional pathways from the synovial fluid plays a major role for transport of tracer into the tendon, while the intrinsic vascular system apparently is of no or minor importance in this respect. The main mechanism for solute transport within the tendon is passive diffusion. Transport of sulphate in the volar part follows a similar pattern as in other avascular tissues and the incorporation of sulphate by the cells is low and comparable to that in articular cartilage. The results support our previous hypothesis that the flexor tendon system physiologically corresponds to a joint, and that the synovial fluid plays an important role for flexor tendon nutrition.

Animals↗
PubMed1981

Particle clearance from the respiratory tract as a test of toxicity: effect of ozone on short and long term clearance.

The ability of the lung to mechanically remove inhaled deposited particles is an important mammalian defense mechanism that can be evaluated in the laboratory. Experiments that measure clearance kinetics have been performed by various investigators using human as well as large and small laboratory animals as subjects. Several agents have been shown to significantly alter clearance phenomena in the lung. This paper describes quantitative clearance experiments that used radioactive tracer particles to assess lung damages after exposure of rats to ozone, a photochemical air-pollutant gas. Radioactively labeled tracer microspheres were inhaled by groups of 30 rats prior to exposure to ozone. Ozone levels studied were 0.4, 0.8, and 1.0 ppm and all exposures were 4 hr in length. These exposures caused a delay in the early (0-50 hr postdeposition) clearance and an acceleration in the late (50-300 hr postdeposition) clearance rate of the tracer particles. Dose response curves show that clearance was affected more by the higher concentrations of ozone.

Aerosols↗
PubMed1986

Determination of human ketone body kinetics using stable-isotope labelled tracers.

In order to avoid the use of radioactive tracers for the determination of human ketone body turnover, we have developed a method using a primed-continuous infusion of 13C-labelled acetoacetate or D-beta-hydroxybutyrate. Determination of the mole percent enrichment of blood acetoacetate and D-beta-hydroxybutyrate was performed by gas chromatography/mass spectrometry. In the post-absorptive state, the mean total ketone body appearance rate, determined in four subjects, was 3.74 mumol X kg-1 X min-1 using [3,4-13C2] acetoacetate and 2.76 mumol X kg-1 X min-1 using [3-13C]D-beta-hydroxybutyrate, values in agreement with those reported in studies with 14C-labelled tracers. In order to evaluate the usefulness of the method for determination of ketone body kinetics in non steady-state conditions, we infused four subjects with natural sodium acetoacetate and calculated the isotopically determined total ketone body appearance rate using a single compartment model (volume of distribution 0.20 l/kg; functional pool fraction: 1). During the tests with [3,4-13C2]-acetoacetate, the actual infusion rates of natural acetoacetate were 7.3 +/- 0.3, 14.6 +/- 0.8, 21.9 +/- 1.2 and 10.9 +/- 0.6 mumol X kg-1 X min-1 whereas the corresponding isotopically determined total ketone body appearance rates were respectively 9.2 +/- 1.0, 16.3 +/- 0.7, 23.1 +/- 1.1 and 10.7 +/- 0.8 mumol X kg-1 X min-1. During the tests with [3-13C]D-beta-hydroxybutyrate, the actual infusion rates were 8.4 +/- 0.5, 16.8 +/- 0.9, 25.2 +/- 1.4 and 12.6 +/- 0.8 mumol X kg-1 X min-1, and the isotopically determined appearance rates respectively 11.1 +/- 0.7, 16.7 +/- 0.7, 25.0 +/- 1.1 and 11.1 +/- 0.7 mumol X kg-1 X min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1977

Non-drug-related residues in tracer studies.

Factors involved in residue studies with radioactive tracers are discussed. Three types of metabolic management of 14C-labeled compounds are described. Intact incorporation into protein of chick muscle is demonstrated with L-O-ethyl-[14C]threonine. Retention of unchanged and quantitatively recoverable parent compound occurred with [14C]thiabendazole sprayed on oranges. The latter drug fed to animals was retained in tissue partly intact, but mostly metabolized to recognizable detoxification products, and ultimately to endogenous tissue components. The latter type of residue was termed a "nonmetabolite" residue. The extreme case of extensive metabolism to products structurally unrelated to the parent compound was illustrated with [14C]ronidazole administered to turkeys.

Animal Feed↗
PubMed1978

Entry of [3H]norepinephrine, [125I]albumin and Evans blue from blood into brain following unilateral osmotic opening of the blood-brain barrier.

The blood-brain barrier in adult rats was opened unilaterally by infusing 1.58 M L (+)-arabinose in 0.9% NaCl solution into the internal carotid artery, via a catheter in the external carotid. The common carotid remained patent during the procedure. Osmotic barrier opening allowed entry into the brain of three intravascularly administered tracers--a visual tracer Evans blue (pulsely injected) and radioactive tracers [3H]norepinephrine (continuously infused) and [125I]albumin (pulsely injected). In osmotically perfused brain tissue, uptake of both 3H and 125I from blood was increased 2-5-fold above control, with maximal increases observed in the caudate nucleus, hippocampus and thalamus. In control brain regions, Evans blue and albumin remained intravascular, whereas norepinephrine was taken up, possibly by sympathetic nerve endings in cerebral vessels, as a function of blood plasma concentration and duration of exposure. The barrier closed within 4 h after intracarotid arabinose infusion, and barrier opening was not associated with edema as measured two days after infusion.

Animals↗
PubMed2002

Localization of extramedullary hematopoiesis with Tc-99m-labeled monoclonal antibodies (BW 250/183).

Extramedullary hematopoiesis is of special interest to physicians because of its relation to hematologic disease. Because it normally remains asymptomatic, sites are typically found by chance. Effective diagnosis involves a specific, reliable, whole-body and low-cost method of screening. Although radiologic methods such as computed tomography and magnetic resonance imaging can only suggest the presence of extramedullary hematopoiesis, apart from invasive and therefore risky biopsy procedures, only scintigraphy can detect and confirm the nature of hematopoietic tissue. Although radioactive tracers commonly in use partly lack the demands for specific diagnosis, Tc-99m-labeled antibodies (NCA-95) seem to combine the advantages of different scintigraphic approaches. Two patients with dyserythropoetic anemia and paravertebrally situated pelvic and thoracic tumor masses were studied for extramedullary hematopoiesis. Planar and SPECT images were obtained 6 and 24 hours after injection of 800 to 850 MBq (22 to 23 mCi) Tc-99m-labeled monoclonal antibodies (BW 250/183). In both patients, tracer accumulated in the masses, thereby revealing hematopoietic tissue. Biopsy confirmed these findings. By using Tc-99m-labeled monoclonal antibodies to detect extramedullary hematopoiesis, the demands of diagnosis were met. As an alternative to invasive diagnostic procedures, this tracer combines the advantages of other radioactive substances previously used, such as radioiron, In-111 chloride, and Tc-99m colloids. This low-cost agent is readily available and when applied, reliable, and delivers whole-body images free of additional uptake in the liver or spleen.

Anemia, Dyserythropoietic, Congenital↗
PubMed1992

[Determination of an intrinsic value of diffusion coefficient of active principle in polymeric matrix for the formulation of a controlled release system].

The study of diffusion in a polymeric system often poses difficult experimental problems, notably when the rate of release is determined in a liquid receptor phase which can interact with the system. In this publication, we propose two experimental methods to determine the diffusion coefficient by a gel-gel kinetic release study, in which the receptor is a same gel unloaded initially. The first method is based on the use of radioactive tracers and a multi-channel radioactivity counter to obtain, at different times, the concentration profiles in the diffusion medium. The theoretical model is given for a gel donor with the concentration C0 of diffusing molecules is below or above the solubility Cs. The second method is based on the measurement of the displacement of solubility front during the diffusion within the system in the case C0 > Cs. The theoretical model shows that this displacement is a function of square root of t. For illustration, two experimental determinations of testosterone diffusion coefficient on the one hand in a silisic acid gels and on the other hand in an acrylic acid gels are given.

Immunodiffusion↗
PubMed2002

Diffusion studies in non-oxide ceramics: analytical aspects of the use of ion implanted stable tracers and SIMS.

The physical and chemical properties of complex non-oxide ceramic materials require advanced methods of diffusivity determination. In this study, we present a method based on the high-dose ion implantation of stable tracers in combination with secondary ion mass spectroscopy for depth profiling. The analytical basics, advantages and problems of the method are discussed for two examples of complex materials, the Si-B-C-N precursor ceramics and the Ti-based transition metal diborides. We demonstrate that is possible to measure the temperature dependence of diffusivities, especially for ceramic systems with low diffusivities, for systems that contain elements for which no suitable radioactive tracers exist for extended measurements.

Ceramics↗
PubMed1982

Effect of fatty acids on plasma membrane lipid dynamics and cation permeability in neuroblastoma cells.

In this study the effects of experimental modifications of plasma membrane lipid lateral mobility on the electrical membrane properties and cation transport of mouse neuroblastoma cells, clone Neuro-2A, have been studied. Short-term supplementation of a chemically defined growth medium with oleic acid or linoleic acid resulted in an increase in the lateral mobility of lipids as inferred from fluorescence recovery after photobleaching of the lipid probe 3,3'-dioctadecylindocarbocyanide iodide. These changes were accompanied by a marked depolarization of the membrane potential from -51 mV to -36 mV, 1.5 h after addition, followed by a slow repolarization. Tracer flux studies, using 86Rb+ as a radioactive tracer for K+, demonstrated that the depolarization was not caused by changes in (Na+ + K+)-ATPase-mediated K+ influx or in the transmembrane K+ gradient. The permeability ratio (PNa/PK), determined from electrophysiological measurements, however, increased from 0.10 to 0.27 upon supplementation with oleic acid or linoleic acid. This transient rise of PNa/PK was shown by 24Na+ and 86Rb+ flux measurements to be due to both an increase of the Na+ permeability and a decrease of the K+ permeability. None of these effects occurred upon supplementation of the growth medium with stearic acid.

Animals↗
PubMed1978

Turnover of liver glycogen in the rat foetus.

Incorporation and release of the radioactivity in the liver glycogen of 18.5- and 19.5-day-old rat foetuses were studied after intravenous injection of E11-14C]glycerol. Incorporation occurred during 1 h after injection of the radioactive tracer to the foetus; then, the incorporated radioactivity decreased. Glycogen content in the liver, and glycogen phosphorylase and glycogen synthase were not modified during the experiment. It is therefore postulated that a physiological turnover of glycogen exists in the liver of the rat foetus.

Animals↗
PubMed1982

Bile acid absorption kinetics in Crohn's disease on elemental diet after oral administration of a stable-isotope tracer with chenodeoxycholic-11, 12-d2 acid.

A non-radioactive tracer, deuterium, incorporated in chenodeoxycholic acid, was used to study bile acid absorption kinetics employing gas chromatography-mass fragmentography for its analysis. Eight patients with Crohn's disease and four control volunteers were administered chenodeoxycholic-11, 12-d2 acid. In order to obtain constant dietary conditions, they were fed by an elemental diet during the study. There were significant reductions of the biological half-life of chenodeoxycholic-11, 12-d2 acid, the pool size of chenodeoxycholic acid, and the total bile acid pool size in patients with Crohn's disease as compared with those in normal subjects. There was a marked increase in the relative concentration of ursodeoxycholic acid with a concomitant decrease of deoxycholic acid in patients with Crohn's disease, although such differences did not reach statistical significance. The present study confirms that there are some impairments of enterohepatic circulation of bile acids in patients with Crohn's disease.

Adolescent↗