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Biomedical subjects

F Reusser

Publications and source records attributed to F Reusser.

At least 55 records · Page 3Linked to original sources
PubMed1971

Mode of action of streptozotocin.

Streptozotocin induces rapid degradation of deoxyribonucleic acid (DNA) in actively dividing or resting Bacillus subtilis cells. Difference spectroscopy showed that the antibiotic interacts specifically with cytosine containing mononucleotides in vitro. This interference occurs only within the very narrow pH range of 5 to 5.5 and is reversed immediately upon lowering or increasing the pH. No measurable interaction was observed between isolated DNA and streptozotocin. The possibility is discussed that interaction of streptozotocin with cytosine residues in cellular DNA, although possibly taking place at a very low frequency, may constitute the primary step inducing DNA strand breakage.

Anti-Bacterial Agents↗
PubMed1971

Mode of action of zorbamycin.

Zorbamycin (U-30,604E) induces rapid degradation of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in Bacillus subtilis cells. DNA degradation is initiated first and is closely followed by the degradation of RNA. No interaction between isolated DNA and zorbamycin is observed. Nucleic acid and protein syntheses are not inhibited by zorbamycin in cell-free systems. Since the initial effect of the antibiotic is expressed at the level of the cellular DNA fraction, we assume that zorbamycin somehow induces a change in the structure or function of the cellular DNA fraction which results in rapid breakdown of this fraction.

Anti-Bacterial Agents↗
PubMed1970

Tirandamycin: inhibition of ribonucleic Acid polymerase.

Tirandamycin acts as a potent inhibitor of ribonucleic acid (RNA) polymerase in bacterial and mammalian cell-free test systems. The antibiotic inhibits the actively synthesizing template-enzyme-nascent RNA complex. Prolonged preincubation of RNA polymerase with tirandamycin prior to assay does not result in a drastic increase of tirandamycin inhibition. Tirandamycin inhibition is not reversed by further addition of deoxyribonucleic acid but is reversed upon further addition of RNA polymerase. Substantial inhibition of RNA polymerase is also obtained when the antibiotic is added at various times after initiation of the reaction. This suggests that tirandamycin interferes with the actively synthesizing template-RNA polymerase complex and inhibits chain elongation rather than chain initiation during RNA synthesis. Tirandamycin also interferes with oxidative phosphorylation in rat liver mitochondria and thus possesses two modes of action.

Journal Article↗
PubMed1970

Tirandamycin: inhibition of oxidative phosphorylation in rat liver mitochondria.

Tirandamycin inhibits respiration and phosphorylation in rat liver mitochondria. An investigation of individual reaction sequences occurring within the respiratory chain showed that the antibiotic stimulates reduced nicotinamide adenine dinucleotide (NADH)- and succinate-linked coenzyme Q reductase. NADH-linked reduction of tetrazolium salts remains unaffected by tirandamycin. Succinotetrazolium salt reductase is inhibited significantly. Reduction of cytochrome c by succinate is blocked by the antibiotic; NADH-cytochrome c reductase is inhibited but not completely blocked. Cytochrome c oxidase remains unaffected. Mitochondrial difference spectra prepared in the presence of tirandamycin indicate that the reduction of cytochrome b is not impaired but no reduction of cytochromes c or a is apparent. These results indicate that tirandamycin interferes with the respiratory chain at a point beyond the cytochrome b and prior to the cytochrome c reduction site. Tirandamycin acts also as a potent inhibitor of ribonucleic acid polymerase as discussed in the foregoing paper.

Journal Article↗
PubMed1969

Mode of action of albocycline, an inhibitor of nicotinate biosynthesis.

The antibiotic albocycline blocks the synthesis of nicotinate or nicotinamide in Bacillus subtilis cells. The inhibitory activity of the agent is fully reversed by nicotinic acid, nicotinamide, and, to a moderate extent, also by quinolinate. This suggests that in B. subtilis the antibiotic interferes with a reaction step occurring prior to the formation of quinolinate within the biosynthetic pathway leading to nicotinate.

Anti-Bacterial Agents↗
PubMed1969

Streptolydigin, an inhibitor of oxidative phosphorylation in rat liver mitochondria.

Streptolydigin interferes with oxidative phosphorylation in rat liver mitochondria. The agent acts primarily as an uncoupler of respiration-associated phosphorylation but also impairs respiration to various degrees depending on the substrate. Streptolydigin partially inhibits electron flow at a point past the cytochrome b and prior to the cytochrome c reduction site. Streptolydigin also inhibits the function of the enzyme ribonucleic acid polymerase in whole bacterial cells and cell-free systems. The streptolydigin concentrations that cause effective inhibition of ribonucleic acid polymerase in cell-free systems are approximately 10 times less than those required to inhibit oxidative phosphorylation in mitochondria.

Anti-Bacterial Agents↗
PubMed1968

Mode of action of melinacidin, an inhibitor of nicotinic acid biosynthesis.

Melinacidin, a new antibacterial agent, blocked the synthesis of nicotinic acid and its amide in Bacillus subtilis cells. The inhibitory activity of the agent was reversed by nicotinic acid, its amide, or nicotinamide adenine dinucleotides, but not by l-kynurenine, l-3-hydroxykynurenine, l-hydroxyanthranilic acid, or quinolinic acid. These properties indicated that the antibiotic interferes with the conversion of quinolinic acid to nicotinate ribonucleotide by the enzyme quinolinate phosphoribosyl-transferase. However, the activity of a purified preparation of this enzyme derived from a Pseudomonas strain was not impaired by the antibiotic. This suggested that, in B. subtilis, melinacidin interferes with a reaction which occurs before the formation of quinolinic acid in the biosynthetic pathway leading to nicotinic acid. Failure of quinolinic acid to reverse melinacidin inhibition in B. subtilis cultures might be due to insufficient penetration of the cell membranes by quinolinate.

Anti-Bacterial Agents↗