No abstract

Liposomes with phase transitions a few degrees above physiological temperature delivered more than four times as much methotrexate to murine tumors heated to 42 degrees C as to unheated control tumors. Most of the accumulated drug appeared to be intracellular and bound to dihydrofolate reductase, the enzyme blocked by methotrexate in its role as an antineoplastic agent.

A modified plasma radioimmunoassay has been developed that uses a cellulose slurry to separate bound from free insulin. This material, which is commercially available, shelf stable, and simple to prepare, makes it possible to run the entire method in test tubes and to use a low specific activity insulin. Details concerning conditions and materials that determined sensitivity, accuracy, and precision are reported. The method is sensitive to about 10 μU/ml. of plasma and has a reproducibility of approximately ± 15 per cent. This method is proposed for use by those who desire to measure rises in plasma insulin by a simple, rapid and reasonably accurate technic.