A new dual-label technique for platelet survival studies with the use of 111indium and 114mindium tropolonate.

A dual-label technique to study the survival of two different populations of platelets within one individual was developed using 111indium and 114mindium. The validity of the technique was demonstrated in seven individuals with an expected equal survival time of two platelet populations and in two persons with an expected difference in platelet survival time. Since the energy spectra of the two indium isotopes are very close, a well-type germanium semiconductor detector was applied. By adaptation of the counting time the effective dose equivalent of the dual-label procedure could be restricted to 1.6 mSv. The dual-label technique provides an instrument for studying the survival of two different populations of platelets simultaneously within one individual.

New possibilities in erythrocyte survival studies with the application of a Well-type germanium semiconductor detector.

The application of a Well-type germanium semiconductor detector creates new possibilities in erythrocyte survival studies. Using 51Cr, the effective dose equivalent in a standard procedure can be reduced from approximately 780 to 2 microSv. The properties of the detector, namely, high efficiency and high energy resolution, also enable the application of two or even more radionuclides within one individual. This is demonstrated by some experiments utilizing a novel dual-label technique with 57Co tropolonate and 58Co tropolonate. Although this new dual-label technique needs further investigation, it underlines the potential possibilities of studying certain unanswered but clinically relevant questions in the field of transfusion medicine with the application of a Well-type germanium semiconductor detector.

Binding of 99mTc(113Sn)-MDP to human serum albumin. The influence of various technetium, tin, and MDP concentrations.

The HSA-binding of 99mTc incubated as 99mTc(113Sn)-MDP depends in vitro on the presence of competing anions normally present in plasma and on the MDP and Tc concentration, but is independent of the Sn concentration. The HSA-binding of 113Sn depends on the MDP and Sn concentration; not on the Tc concentration. 99mTc(Sn)-MDP binds to HSA as a unit. The binding of 99mTc(Sn)-MDP to plasma proteins in vivo is much lower as calculated from in vitro experiments because of competition between 99mTc(Sn)-MDP and endogenous anions for the same binding-sites.

A micro-autoradiographical study of the localization of 99mTc(Sn)-MDP and 99mTc-MDP in undecalcified bone sections.

The localization of 99mTc(Sn)-MDP in bone tissue was compared with 99mTc-MDP by means of microautoradiography of undecalcified bone sections. Sections of good histological quality were obtained by a rapid embedding method in methylmethacrylate. No differences were found in the localization of these radiopharmaceuticals in fetal rat calvariae after incubation in vitro or in rat femora after administration in vivo. In the incubation experiment, hydrolyzed 99mTc was formed. The uptake was high in areas of new bone formation. No uptake was seen in cells or in resorbing areas. In compact bone 99mTc(Sn)-MDP was predominantly taken up in the vicinity of blood vessels.

Bioresorption of ceramic strontium-85-labeled calcium phosphate implants in dog femora. A pilot study to quantitate bioresorption of ceramic implants of hydroxyapatite and tricalcium orthophosphate in vivo.

Ceramic hydroxyapatite and tricalcium orthophosphate were radioactively labeled with their strontium-85 analogs. Porous blocks of these materials (dimensions 2.5 X 1.25 X 0.5 cm) were implanted into surgically created defects in dog femora. The fate of the implants was studied by roentgenography, radioactivity measurements, histology, and microradiography. The radioactivity over the implant site was followed for 22 weeks. Implants were retrieved after 20-25 and 50-55 weeks. Hydroxyapatite implants were not affected by biodegradation processes, while tricalcium orthophosphate implants were subject to extensive bioresorption (25%-30% in 22 weeks). Resorption debris from tricalcium orthophosphate implants was found in mononuclear phagocytes and multinuclear osteoclastlike cells. The supposition is that tricalcium orthophosphate is transformed into hydroxyapatite in a physiologic environment. Labeling of ceramic calcium phosphate implants with strontium-85 analogs offers an adequate technique to quantitate bioresorption in vivo.

Protein-binding and urinary excretion of 99mTc(Sn)-MDP and 99mTc-MDP.

In an incubation experiment the Human Serum Albumin (HSA) binding of 99mTc-MDP (electrolytically labeled) and 99mTc(Sn)-MDP is established. During the incubation some pertechnetate is formed and in the case of 99mTc(Sn)-MDP also some hydrolyzed 99mTc. The HSA binding of 99mTc-MDP is less than the HSA binding of 99mTc(Sn)-MDP as established with gel chromatography, TCA-precipitation, ammonium sulfate precipitation and ultrafiltration. TCA-precipitation seems to be an insufficient method for determining the protein binding of 99mTc(Sn)-MDP. The urinary excretion in rats shows only one 99mTc-compound in both cases. The bone seeking properties of the urine-excreted 99mTc-compound were confirmed in another rat.

Electrolytically labeled [99mTc]MDP: chromatographic pattern, stability and biodistribution in rats.

The labeling of methylene diphosphonate with 99mTc is possible after reduction of pertechnetate by means of controlled potential electrolysis. This results in a [99mTc]MDP complex which differs slightly from 99mTc(Sn)-MDP in paper and gel chromatography. The scintigraphic images of both preparations are comparable in quality. Biodistribution in rats shows a higher bone uptake for the 99mTc(Sn)-MDP complex, whereas [99mTc]MDP shows a higher uptake in the gastric wall.

Urinary oxalate excretion, as determined by isotope dilution and indirect colorimetry.

A simple and reliable method for the determination of urinary oxalate excretion is described. Urinary oxalate is precipitated with calcium chloride, and the oxalate content of the precipitate is measured by an indirect colorimetric method developed by Neas and Guyon in 1972 [1]. For single urine samples, a correction is made for the incompleteness of the precipitation of calcium oxalate by isotope dilution. The range of normal values (5% limits) determined in 52 normal subjects was 0.121-0.325 mmol . 24 h-1 . m-2 for a 1-day collection period and 0.145-0.301 mmol . 24 h-1 . m-2 for a 3-day collection period. The within-assay CV of a control urine with a low oxalate concentration was 9% (n = 7) and the between-assay CV for the same control urine was 12% (n = 6). When the values obtained for oxalate excretion were normalized to body surface area, there was no significant difference between males and females; the main source of variation was the intra-individual variation.