The phenomenon of multidrug resistance implies that a wide spectrum of structurally and functionally unrelated chemotherapeutic drugs are recognized and processed by the molecular system which protects multidrug-resistant (MDR) cells against lipophilic cytotoxic drugs. This suggests that lipophilic agents with low toxicity may also be recognized and processed by this molecular system. At high c...

Actinomycin D, at a concentration that inhibits cellular ribonucleic acid (RNA) synthesis, inhibited the production of foot-and-mouth disease virus-induced RNA polymerase in baby hamster kidney cells. Inhibition was proportional to exposure time and reached 85% when actinomycin D was added 90 min before infection. Polymerase production was inhibited to the same extent in growth and minimal medi...

Two DNA hexadecamers containing one central 5'-GC-3' base step have been examined by footprinting methodology in the presence and absence of actinomycin D. The results of these studies, coupled with imino proton NMR measurements indicate that the antitumor drug causes a change in DNA conformation at a distance from the actinomycin intercalation site in a molecule of sequence d[ATATATAGCTATATAT]...

The LD 50 in mice of intact virus-like particles (VLP) from Penicillium stololllferum NRRL 5267 was greater than 240 mg/kg body weight, and their component double-stranded ribonucleic acid (dsRNA) was 34·0 mg/kg. Judged by decreases in LD50 values, administration of sublethal amounts of actinomycin D or cycloheximide simultaneously with sublethal amounts of intact VLP or mycoviral dsRNA enhance...

Rapid killing of Escherichia coli by intact or disrupted rabbit granulocytes or by granulocyte fractions was found to be accompanied by an equally rapid increase in permeability of the E.coli envelope. This increase in permeability was detected by determining entry of substances that normally do not cross E.coli's permeability barrier, namely actinomycin D and o-nitrophenyl-beta-D-galactopyrano...

Spleen colony assays were used to quantitate the cytocidal effect of actinomycin D on leukemic cells and normal hematopoietic stem cells. Different doses of actinomycin D were administered to either normal or leukemia-bearing mice, and the surviving fraction of these cell populations was determined. Following single injections of the drug, the killing of both the normal and leukemic cell popula...

In this report we demonstrate that human immunodeficiency virus type 1 (HIV-1) minus-strand transfer, assayed in vitro and in endogenous reactions, is greatly inhibited by actinomycin D. Previously we showed that HIV-1 nucleocapsid (NC) protein (a nucleic acid chaperone catalyzing nucleic acid rearrangements which lead to more thermodynamically stable conformations) dramatically stimulates HIV-...

Cells were isolated from the somite mesoderm and from the unsegmented (presomite) mesoderm of early chick embryos and exposed to actinomycin D in single cell culture. Actinomycin D inhibited proliferation in cell cultures derived from the unsegmented mesoderm, although the same concentrations of this antibiotic did not inhibit cultures derived from the somite mesoderm. This differential sensiti...

Spleen colony assays were used to quantitate the cytocidal effect of actinomycin D on leukemic cells and normal hematopoietic stem cells. Different doses of actinomycin D were administered to either normal or leukemia-bearing mice, and the surviving fraction of these cell populations was determined. Following single injections of the drug, the killing of both the normal and leukemic cell popula...

Cells were isolated from the somite mesoderm and from the unsegmented (presomite) mesoderm of early chick embryos and exposed to actinomycin D in single cell culture. Actinomycin D inhibited proliferation in cell cultures derived from the unsegmented mesoderm, although the same concentrations of this antibiotic did not inhibit cultures derived from the somite mesoderm. This differential sensiti...