The inhibitory effect of bleomycin on DNA, RNA and protein syntheses of mouse L cells was determined. DNA synthesis was most affected. Protein and RNA syntheses were less affected in this order. Inhibition of DNA synthesis exhibited an upward-concave curve as a function of time of exposure to bleomycin. Analysis of this particular curvature revealed a characteristic interaction between the antibiotic and mammalian cells. Results obtained from the experiments of two pulsed drug treatments showed that (1) when bleomycin was introduced into culture, cell resistance developed with time and was complete within 60 minutes, and (2) the resistance so induced disappeared in approximately 2 hours upon removal of bleomycin. The nature of this resistance was not elucidated. Either an enzyme which inactivates bleomycin or DNA-repair enzymes may be responsible for resistance. The above interaction may have some relevance to bleomycin chemotherapy.
Mixtures of DNA with the three antibiotics zorbamycin, phleomycin or bleomycin were analyzed by UV and circular dichroism measurements. The results indicate that a physical interaction between isolated DNA and each of the three antibiotics occurs and that these antibiotics definitely bind to DNA.
The effects of several methylation inhibitors on fermentations of Streptomyces lincolnensis depend on the composition of the fermentation media, the levels of the metabolic inhibitors added, and the timing of the addition. Of all the compounds screened, it appears that sulfonamides and sulfanilamide in particular inhibit N-methylation, rather selectively, resulting in production of N-demethyllincomycin, in addition to the normally produced lincomycin and 4'-depropyl-4'-ethyllincomycin.
Experiments were carried out in which lymphocytes stimulated by phytohemagglutinin were exposed during 3-day culture to concentrations of bleomycin varying from 0.0 to 300 μg/ml. Inhibition of one hour 3H-thymidine incorporation in these 72-hour cultures increased as the concentration of bleomycin increased from 1.5μg/ml (14.1 % inhibition) to 300μg/ml (96.4% inhibition), and was a linear function when dose and percent control 3H-thymidine uptake were plotted logarithmically. In 3 of 9 experiments, 3H-thymidine uptake at the 1.5μg/ml dose was increased. This increase was not statistically significant, but the possibility of sublethal DNA damage followed by repair was raised. Exposure of resting lymphocytes to bleomycin in the absence of PHA showed no significant increase above baseline thymidine uptake. Addition of bleomycin to cultures at 24 and 48 hours after the addition of PHA produced the same quantitative reduction in uptake of thymidine at 70 hours as the same concentration added at zero time, suggesting that the effect of bleomycin is independent of the initial stimulatory events resulting from the addition of PHA. Evidence of a repair-like process following damage by bleomycin was observed in a different system utilizing isolated hepatic nuclei. A two to five fold increase of thymidine tri-phosphate incorporation was obtained in response to addition of bleomycin in this isolated nuclear system (rat liver nuclei). This process was time and dose related and continued for at least one hour in the presence of bleomycin. These results demonstrate that bleomycin causes dose-dependent reduction of DNA synthesis in PHA-stimulated lymphocytes. Furthermore, they suggest that DNA damage caused by low concentrations of bleomycin may be repaired, and that when damage exceeds the cell's ability to repair, cell death results.
EM 49 is a new basic peptide antibiotic complex produced by a strain of Bacillus circulans. When isolated as the hydrochloride, it has an approximate empirical formula of C49-50H91-98N13O10Cl4. The antibiotic has broad-spectrum antibacterial activity and also displays considerable antifungal and antiprotozoal activities. EM 49 is not cross-resistant with other antibiotics, including those of a peptide nature.
EM 49 is a new, broad-spectrum peptide antibiotic. The products of acid hydrolysis have been identified as 2, 4-diaminobutyric acid, leucine, phenylalanine, and a mixture consisting chiefly of C10- and C11-β-hydroxy fatty acids. The antibiotic is a tetraäcidic base, having four free amino groups, which have been identified as the γ-amino groups of 2, 4-diaminobutyric acid residues. The nonintegral quantities of leucine and phenylalanine and the mixture of fatty acid obtained by acid hydrolysis indicated that EM 49 is a mixture of closely related compounds. That this is so has been verified by the separation of EM 49 by ion-exchange chromatography into four distinct fractions. The analytical properties of the mixture are in good agreement with those predicted from the products of hydrolysis of the individual ion-exchange fractions. We conclude that EM 49 is a complex of cyclic, homodectic octapeptide antibiotics that are monoacylated with β-hydroxy fatty acids.
EM49, a novel peptide antibiotic produced by Bacillus circulans, shows broad-spectrum antibacterial activity in vitro and also has substantial activity against yeasts, fungi, and protozoa. Its high degree of antipseudomonal activity and its greater activity against gram-negative than against gram-positive bacteria are noteworthy. EM49 is rapidly biocidal to populations of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Candida albicans. Even after ten successive subcultures in the presence of EM49, strains of P. aeruginosa, E. coli and S. aureus did not develop any resistance to this compound. The antibiotic was active in vivo upon subcutaneous administration to mice infected with Streptococcus pyogenes C203 or E. coli, but was inactive when given by the oral route. When applied topically at a concentration of 0.5 % in a cream base, EM49 prevented the multiplication of P. aeruginosa in experimentally induced wounds in mice.
A9145 is a new water-soluble antifungal antibiotic produced by a strain of Streptomyces griseolus (NRRL 3739). This basic antibiotic has an apparent molecular weight of about 510, contains adenine and a possible sugar moiety, and forms crystalline organic and inorganic salts. A9145 is active against Candida species, Saccharomyces pastorianus, plant disease fungi, and Trypanosoma species. It has an LD50 (subcutaneous) of 185 mg/kg in mice.
A9145 is a new adenine-containing antifungal antibiotic. A9145 showed weak in vitro activity against Candida albicans in SABOURAUD'S medium, but was strongly inhibitory in a chemically defined medium. Viability counts of C. albicans following extended exposure to A9145 indicated a fungistatic action. Following a 100mg/kg dose, a peak of 64μg/mlof A9145 activity was detected in mouse blood. Administration of 10 mg/kg for 3 days extended the survival time of mice infected with C. albicans 128%; equivalent doses of amphotericin B extended survival time 112%. A total dose of 31.25 mg/kg administered over a 5-day period reduced by 400-fold the number of Candida recovered from kidney homogenates of infected mice. A combination of amphotericin B and A9145 caused a possible synergistic effect against C. albicans in vitro and an additive effect in vivo.
A new antibiotic XK-19-2 is produced by Streptomyces sp. MK-19 and it is a basic peptide antibiotic containing lysine, threonine or serine, arginine, glycine, proline, aspartic acid, histidine, alanine, isoleucine and phenylalanine. This antibiotic has antibacterial activity against gram-positive and gram-negative bacteria, but has no antitumor activity. In this paper, some characteristics of the strain, the isolation and some properties of this antibiotic are reported.