Biomedical subjects

R Francisco

Publications and source records attributed to R Francisco.

5 recordsLinked to original sources

PubMed2006

The decrease of NAD(P)H has a prominent role in dopamine toxicity.

We characterized dopamine toxicity in human neuroblastoma SH-SY5Y cells as a direct effect of dopamine on cell reductive power, measured as NADH and NADPH cell content. In cell incubations with 100 or 500 microM dopamine, the accumulation of dopamine inside the cell reached a maximum after 6 h. The decrease in cell viability was 40% and 75%, respectively, after 24 h, and was not altered by MAO inhibition with tranylcypromine. Dopamine was metabolized to DOPAC by mitochondrial MAO and, at 500 microM concentration, significantly reduced mitochondrial potential and oxygen consumption. This DA concentration caused only a slight increase in cell peroxidation in the absence of Fe(III), but a dramatic decrease in NADH and NADPH cell content and a concomitant decrease in total cell NAD(P)H/NAD(P)+ and GSH/GSSG and in mitochondrial NADH/NAD+ ratios. Dopaminechrome, a product of dopamine oxidation, was found to be a MAO-A inhibitor and a strong oxidizer of NADH and NADPH in a cell-free system. We conclude that dopamine may affect NADH and NADPH oxidation directly. When the intracellular concentrations of NAD(P)H and oxidized dopamine are similar, NAD(P)H triggers a redox cycle with dopamine that leads to its own consumption. The time-course of NADH and NADPH oxidation by dopamine was assessed in cell-free assays: NAD(P)H concentration decreased at the same time as dopamine oxidation advanced. The break in cell redox equilibrium, not excluding the involvement of free oxygen radicals, could be sufficient to explain the toxicity of dopamine in dopaminergic neurons.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2002

Diversity of chromium-resistant and -reducing bacteria in a chromium-contaminated activated sludge.

AIMS: This study attempts to establish a relationship between the Cr(VI) resistance of the culturable microbial community and the Cr(VI) resistance and Cr(VI)-reducing ability of representative strains of each population, in order to assess whether these are exclusive characteristics of one microbial group or abilities shared among many groups. METHODS AND RESULTS: A group of 48 Cr(VI)-resistant isolates, with different colony types, was isolated from chromium-contaminated activated sludge. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis protein patterns and fatty acid methyl ester analysis identified six populations, representing 54% of the isolated bacteria, as belonging to the genera Acinetobacter and Ochrobactrum. The remaining populations included strains identified as species of the beta-Proteobacteria and high G + C Gram-positive bacteria. The Cr(VI) resistance and reduction ability of the strains were tested. All but two isolates grew in the presence of 1 mmol l(-1) Cr(VI). During enrichment, all isolates were able to survive to 2 mmol l(-1) Cr(VI) and complete Cr(VI) reduction was achieved. Representative strains of each population were able to partially reduce (5.4-39.1%) the Cr(VI) present in the growth medium. CONCLUSIONS: Most of the identified isolates have never been reported to be Cr(VI)-resistant and/or Cr(VI)-reducing strains. The mechanisms of Cr(VI) resistance and reduction may differ from group to group; therefore, it is evident that both Cr(VI) resistance and reduction are shared abilities and not an exclusive characteristic of a single group, possibly reflecting horizontal genetic transfer resulting from selective pressure in this contaminated environment. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first study of a microbial community under chronic chromate stress and, as the success of microbial-based metal remediation technologies requires a better understanding of the microbial community and the population response to metal stress, it may contribute to the implementation of a strategy of bioremediation of chromate-contaminated environments.

Bacteria↗

PubMed2002

Clinical review 145: Pleiotropic effects of statins: lipid reduction and beyond.

There is accumulating evidence that statins have beneficial effects that are independent of their classical actions on lipoproteins. These effects include reductions in inflammation in the vasculature, kidney, and bone. Potential beneficial effects of these agents include enhancement of nitric oxide production in vasculature and the kidney. These agents appear to reduce bone fractures and may improve insulin sensitivity and reduce the likelihood of persons progressing from impaired glucose tolerance to type II diabetes. Potential beneficial pleiotropic effects of statins are covered in this review.

Bone Remodeling↗

PubMed1987

An ultraviolet light sensitive target in nitrate reductase of Escherichia coli K-12.

Ultraviolet light was shown to inactivate purified nitrate reductase in the presence of reduced benzyl viologen. Loss of activity was not complete, reaching 60 to 70%. Photolysis was maximum at 345 nm. The differential spectrum between native and irradiated enzyme exhibited absorption bands at 216, 275, 314 and 365 nm. The photosensitive electron carrier could be extracted by organic solvents. It had the following absorption bands: 225, 275 and 285 nm. It was reduced by Nile blue A but not by methylene blue. The precise nature of this light sensitive molecule could not be determined although the results support the idea that this chromophore might be a naphthoquinone.

Escherichia coli↗

PubMed1977

Monochromatic ophthalmoscopy and fundus photography. The normal fundus.

Anatomical details in the ocular fundus can be seen with increased contrast when appropriate monochromatic illumination is used. This technique permits more accurate visualization and documentation than can be achieved with white light. This article reports the optimal spectral ranges for visualization of the different fundus structures. It describes and illustrates the appearance of individual structures and areas of the fundus under different spectral illuminations. There is a detailed discussion of the optical properties of the fundus layers that provides a background for interpreting the data and a baseline for examination of pathologic conditions.

Adolescent↗