Acridine orange enhances the uptake of [(3)H]actinomycin D in disrupted and intact human lymphocytes, as measured by liquid scintillation and autoradiography. Proflavine, quinacrine, chloroquine, and ethidium bromide are not effective. In mice, acridine orange increases the capacity of actinomycin to reduce spleen weight. Type II acridine binding to DNA may be a prerequisite for actinomycin enh...

A graded series of drug-resistant Chinese hamster sublines has been examined for biochemical changes accompanying resistance to actinomycin D. The most highly resistant subline, DC-3F/AD X, is maintained at 10 microg/ml of the antibiotic. It was shown that over 250 times more actinomycin D is required to inhibit RNA synthesis in this subline than in the parental DC-3F line. The DC-3F/AD X subli...

The inhibition of flowering of Lemna perpusilla Torr. strain 6746 caused by a light break can be partially reversed by treatment with actinomycin D or 2-thiouracil. Actinomycin D is most active in reversing the response to a light break if the inhibitor is present in the fronds at the time the light break is administered.

Growth of Mycoplasma pneumoniae was completely prevented by 0.06 mug of actinomycin D/ml, and 0.00375 mug/ml caused 90% inhibition. It thus appears that M. pneumoniae is more susceptible to actinomycin D than previously reported. Low concentrations (0.019 mug/ml) of the antibiotic primarily inhibited ribonucleic acid synthesis and high concentrations (20 mug/ml) inhibited both ribonucleic and d...