Potentiation of 5-fluorouracil, chromomycin A3, and bleomycin by amphotericin B or polymyxin B in transformed fibroblastic cells

By using cultured, transformed fibroblastic cells, antitumor agents including cytosine arabinoside, thio-tepa, nitrogen mustard N-oxide, mitomycin C, chromomycin A3, 5-fluorouracil, daunomycin, vinblastine, vincristine, and bleomycin A2 were screened for the potentiation of their activity by amphotericin B or polymyxin B. Among them, the action of 5-fluorouracil and chromomycin A3 on ribonucleic acid synthesis was potentiated in their action by amphotericin B, not by polymyxin B. Bleomycin A2 was potentiated in its action on deoxyribonucleic acid and ribonucleic acid synthesis only by polymyxin B.

Temperature-sensitive mutation in regulation of ribonucleic acid synthesis in Escherichia coli

An Escherichia coli mutant dependent on exogenous transfer ribonucleic acid (RNA) for bulk RNA formation at 42 C has been isolated, starting from a parental strain permeable to RNA. In the absence of added transfer RNA at the high temperature, protein synthesis stopped, and the strain formed little if any ribosomal RNA.