Alberto Jorge Eraso

Pyoverdine Production by Pseudomonas fluorescens in Synthetic Media with Various Sources of Nitrogen

Summary: The influence of the nitrogen source on pyoverdine production by Pseudomonas fluorescens grown in chemostat culture in synthetic media at constant pH was studied. Pigment synthesis was highest in a medium with proline as the nitrogen source; other amino acids were less effective in promoting pigment synthesis. The pH and Fe3+ content of the media affected pyoverdine production. The ratio of pigment to growth was maximal at pH 8. When the Fe3+ concentration was increased from 10 to 200 μg 1-1 in media with the same nitrogen source, pyoverdine synthesis decreased. Since the Fe3+ contents of the synthetic media were different, the amount present was adjusted to a standard concentration to permit comparisons between the various nitrogen sources.

Eriobotrya japonica Counteracts Reactive Oxygen Species and Nitric Oxide Stimulated by Chloramphenicol

Chloramphenicol is a toxic antibiotic used for certain infections, though aplastic anaemia is one of its side-effects. The results of our experiments showed that blood cells suffered oxidative stress in the presence of chloramphenicol, with a significant increase in reactive oxygen species (ROS) detected by luminol-chemiluminescence (CL). The extract of fruits of Eriobotrya japonica markedly decreased ROS in leukocytes and erythrocytes, the oxidative stress caused by this antibiotic. Nitro Blue Tetrazolium (NBT) assay with purified leukocytes demonstrated that the antioxidant action of E. japonica caused an intracellular reduction in ROS, and that the extracts decreased these promoters of oxidative stress to normal levels in the cytoplasm. Determinations of nitric oxide (NO) generation indicated that E. japonica extracts also inhibited the stimuli of NO provoked by chloramphenicol. This study showed that the immediate antioxidant effect of E. japonica could be associated with the action of vitamin A. The protective action of this fruit was seen on mature leukocytes and erythrocytes, beneficial effect on blood cells suggest that its extract could be used as an antioxidant agent complementing the administration of chloramphenicol, as a modern-day extension to its traditional use in Chinese medicine.

Chemiluminescence determination of antioxidant property of Zizyphus mistol and Prosopis alba during oxidative stress generated in blood by Hemolytic Uremic Syndrome‐producing Escherichia coli

This study was undertaken to elucidate the antioxidant effect of Zizyphus mistol and Prosopis alba, with the hypothesis that these fruits can counteract the induction of reactive oxygen species (ROS) caused by toxins produced by Escherichia coli. In the search of nutrients effective against the Hemolytic Uremic Syndrome (HUS), we detected by chemiluminescence a protective role of both plants, due to their natural antioxidants significantly decreasing the levels of ROS induced by toxins from E. coli in blood. The ferric reducing antioxidant power (FRAP) was found to be higher in Z. mistol than in P. alba. The chemical analyses of the phenols and flavonoids present in the fruit extracts indicated that the FRAP correlated with the amount of phenolic compounds, but not with the flavonoids analyzed. Both fruits studied reduce the induction of ROS, and in this way help to prevent the development of complications related to oxidative stress generated in the blood of patients with HUS.