Further investigations on serum ultrafiltrate as medium for tissue respiration in vitro

Serum ultrafiltrate was shown to be able to sustain in vitro the oxygen consumption of various tissue slices, attaining values very close to those reached in vivo. Serum ultrafiltrate also exerted its stimulating effect on homogenate, and maintained this activity for some time, after dilution, after lyophilization and after boiling; finally it was not species-specific. Serum ultrafiltrate was also more efficient than Eagle's Minimum Essential Medium in supporting tissue respiration. Preliminary data, obtained from gel fractionating serum ultrafiltrate, suggested that the metabolic activity should be ascribed to a sum of small single effects due to the single fractions of serum ultrafiltrate.