We describe a simple fluoroimmunoassay for the determination of thyroxine concentrations in serum. The method, "sequential addition, separation fluoroimmunoassay," involves both thyroxine labeled with fluorescein and magnetizable cellulose/iron oxide particles to which antibodies to thyroxine have been covalently linked. Serum sample or standard is incubated with an excess of the solid-phase an...

Suspensions of tadpole liver cells have been developed as a model to further understanding of the biochemical differentiation of this tissue during thyroxine-induced metamorphosis. The cell population is homogeneous and stable; no cell division or DNA synthesis occurs in these isolated cells. RNA synthesis in cell suspensions is stimulated by thyroxine and triiodothyronine. The optimum concentr...

Most procedures used for the separation of thyroxine from other iodinecontaining compounds of the thyroid gland are based on either the method of Harington and Randall (I) or that of Leland and Foster (2). In the former the thyroxine is separated from diiodotyrosine by precipitation in a slightly acid medium, whereas in Leland and Foster’s method thyroxine is extracted with butyl alcohol from a...

Prealbumin was isolated from human plasma by chromatography on columns of diethylaminoethyl Sephadex and Sephadex G-200, followed by preparative polyacrylamide gel electrophoresis. The prealbumin was homogeneous in the analytical ultracentrifuge with an s=z~,~ of 3.7 S and with a molecular weight of about 50,000. Prealbumin formed a protein-protein complex with plasma retinol-binding protein in...

The hormone thyroxine that regulates mammalian metabolism is carried and stored in the blood by thyroxine-binding globulin (TBG). We demonstrate here that the release of thyroxine from TBG occurs by a temperature-sensitive mechanism and show how this will provide a homoeostatic adjustment of the concentration of thyroxine to match metabolic needs, as with the hypothermia and torpor of small ani...

We studied the influence of specially prepared highly diluted thyroxine on the spontaneous tendency of juvenile frogs, which were at the end of thyroxine-controlled metamorphosis, to leave the water and climb onto land. The test dilution with a thyroxine concentration beyond Avogadro's value (dilution thyroxine D30) and the reference (dilution water D30) were prepared according to directions fr...

Markedly increased concentrations of free fatty acids after a fatty meal and heparin injection already have been shown to falsely increase thyroxine values measured by competitive protein-binding techniques, where ethanol extraction in used. We report here the effect of lesser increases. In 10 patients receiving heparin during hemodialysis we found significant increases in serum thyroxine by co...