Biomedical subjects

M C Araújo

Publications and source records attributed to M C Araújo.

8 recordsLinked to original sources

PubMed2001

Protective effect of thiourea, a hydroxyl-radical scavenger, on curcumin-induced chromosomal aberrations in an in vitro mammalian cell system.

Natural dietary antioxidants are extensively studied for their ability to protect cells from damage to DNA, protein, and lipids induced by antitumor agents or radiation that leads to the generation of free radical in normal cells in vivo and in vitro. Curcumin is a natural antioxidant known to possess therapeutic properties and has been reported to scavenge free radicals and to inhibit clastogenesis in mammalian cells. However, curcumin has been reported to induce a significant increase in the frequency of chromosomal aberrations in Chinese hamster ovary (CHO) cells. To investigate whether the clastogenic activity of curcumin in CHO cells in culture can be ascribed to a pro-oxidant behavior, mediated by free radical generation, experiments were carried out with the combination of curcumin (15 microg/ml) and thiourea (10, 20, or 40 microg/ml), a potent hydroxyl radical scavenger. The results showed that the clastogenic action of curcumin was statistically decreased in a dose-dependent manner in the presence of thiourea. These data have shown that curcumin-induced chromosomal damage in CHO cells can be mediated by hydroxyl radical generation in the present experimental conditions. Teratogenesis Carcinog. Mutagen. 21:175-180, 2001.

Animals↗

PubMed2000

Effects of the antioxidants curcumin and vitamin C on cisplatin-induced clastogenesis in Wistar rat bone marrow cells.

The use of dietary antioxidants to prevent antitumor agent-induced chromosomal damage in nontumor cells is currently eliciting considerable interest. Curcumin (CMN) is a dietary antioxidant that has been reported to protect against clastogenesis in in vivo and in vitro assays. This study was undertaken to investigate the modulatory effects of CMN on cisplatin-induced chromosomal aberrations in Wistar rat bone marrow cells and whether there is any potentiation of these effects with the combination between CMN and vitamin C (VC), which has been reported to reduce the clastogenic effect of many antitumor agents in in vivo assays. Animals treated with CMN plus a single dose of cisplatin, at 18, 24 or 72 h following treatment, presented a statistically significant reduction in the total amount of chromosomal damage and in the number of abnormal metaphases. The results also indicate that the combination between antioxidants would not be effective in protecting against cisplatin-induced chromosomal damage in animals sacrificed 24 h after cisplatin treatment. Under the present experimental conditions, CMN could prevent cisplatin-induced clastogenesis by acting as a free radical scavenger.

Animals↗

PubMed2000

Modified microelectrodes and multivariate calibration for flow injection amperometric simultaneous determination of ascorbic acid, dopamine, epinephrine and dipyrone.

Flow injection amperometric quantification of ascorbic acid (AA), dopamine (DA), epinephrine (EP) and dipyrone (DI) in mixtures (in the microgram g-1 range) was successfully performed by using an array of microelectrodes with units modified by the electrodeposition of different noble metals, together with multivariate calibration analysis. The four groups of microelectrodes utilized included a pure gold electrode and electrodes modified by electrodeposition of platinum, palladium or a mixture of platinum + palladium. The array of microelectrodes was inserted in a flow cell and the amperometric data acquisition was performed with a four-channel potentiostat. The analysis of the resulting signals was carried out by a multivariate calibration method, using a group of 16 standard mixtures selected by a two-level factorial design. The analysis of synthetic samples and pharmaceutical compounds containing AA and DI led to very similar values to those obtained by the classical iodimetric analysis. The average absolute errors (in microgram g-1) calculated for each analyte were 0.3, 0.2, 0.4 and 0.4 for AA, DA, EP and DI, respectively.

Ascorbic Acid↗

PubMed1999

Modulatory effects of curcumin on the chromosomal damage induced by doxorubicin in Chinese hamster ovary cells.

Curcumin, a natural phenolic compound, is gaining importance as a free radical scavenger. This study was undertaken to investigate the modulatory effects of curcumin on the chromosomal damage induced by the antitumoral doxorubicin (DXR), a known free radical generator, in Chinese hamster ovary cells in culture. Cells were treated with three concentrations of curcumin (2.5, 5, or 10 microg/ml) and then treated with DXR (1.0 microg/ml) during different phases of the cell cycle. The results show that curcumin induces chromosomal damage in CHO at the highest concentration when compared to the untreated control. Neither treatment with curcumin shows a reduction in the clastogenicity of DXR. Instead, a statistically significant increase in the frequency of chromosomal damage was observed when the middle and the highest concentrations of curcumin were associated with DXR during the G1/S, S, and S/G2 phases of the cell cycle. The results clearly indicate the potentiating effect of curcumin on DXR-induced chromosomal damage.

Animals↗

PubMed1999

Potentiation by turmeric and curcumin of gamma-radiation-induced chromosome aberrations in Chinese hamster ovary cells.

The effect of turmeric and curcumin, two natural antioxidants, on the frequencies of chromosome aberrations induced in Chinese hamster ovary (CHO) cells by gamma-radiation was investigated. Cells were treated with three concentrations of each drug, turmeric (100, 250, and 500 microg/ml) and curcumin (2.5, 5, and 10 microg/ml), and then irradiated (2.5 Gy) during different phases of the cell cycle. Turmeric was not clastogenic by itself, whereas curcumin at 10 microg/ml enhanced the chromosomal damage frequency. Neither of the two antioxidants showed protective effect against the clastogenicity of gamma-radiation. Instead, an obvious increase in the frequencies of chromosome aberrations was observed when turmeric at 500 microg/ml was associated with gamma-radiation during G2/S phase, and curcumin at 10 microg/ml plus gamma-radiation during S and G2/S phases of the cell cycle. The results clearly indicate the exacerbated effect of turmeric and curcumin on radiation-induced clastogenicity, suggesting that these antioxidants are also potentiating agents depending on the experimental conditions.

Animals↗

PubMed1997

Mutagenic and cytotoxic activity of an isocoumarin (Paepalantine) isolated from Paepalanthus vellozioides.

A new isocoumarin with antimicrobial activity was isolated from Paepalanthus vellozioides (a native Brazilian plant) and called paepalantine. This study was carried out to assess the mutagenic activity of this new agent in assays with Salmonella typhimurium TA100, TA98, and TA102 and in Chinese hamster ovary (CHO) cell cultures, as well as cytotoxicity to McCoy cells. paepalantine caused a significant dose-dependent increase in the frequency of revertants in the three strains used in the assay, both with and without S9 mix, in concentrations varying from 2 to 128 micrograms/plate. The mutagenicity was confirmed in assays with CHO cells treated in the G1, S, and G2 phases of the cell cycle. There was an increase in the chromosomal aberration frequency, mainly in the G2 phase. Furthermore, the mitotic index of the treated cultures (40,80, and 160 micrograms/ml) was significantly lower, indicating cytotoxicity. The midpoint cytotoxicity values of McCoy cells by the neutral red (NR) and microculture tetrazolium (MTT) techniques resulted in a NR50 and MTT50 of 30 and 38 micrograms/ml, respectively. Alterations to the paepalantine structure are suggested to reduce its mutagenic and cytotoxic activity in investigations for its antineoplastic potential.

Animals↗

PubMed1997

Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canals.

The efficacy of five instrumentation techniques for cleaning the apical third of curved root canals was assessed by histological examination. Mesial root canals of freshly extracted human mandibular molars were prepared by the following instrumentation methods: step-back technique using stainless steel files; step-back technique using nickel-titanium files; ultrasonic technique; balanced force technique; and Canal Master U technique and instruments. The apical portion of the root was histologically processed, and cross-sections were examined for remaining soft tissue, predentin, and debris. The results showed no significant differences among the techniques. Although the five instrumentation methods were effective in removal of major amounts of tissue from the canals, none totally debrided the entire root canal system, especially when variations in the internal anatomy were present.

Dental Alloys↗

PubMed1992

Photosynthetic capacity of leaves of Eucalyptus globulus (Labill.) growing in the field with different nutrient and water supplies.

The effects of water and nutrient availability on photosynthetic capacity of juvenile and adult leaves of Eucalyptus globulus Labill. seedlings were evaluated by measuring oxygen evolution at light and CO(2) saturation. Seedlings supplied with near optimal amounts of water and nutrients had higher growth rates than non-irrigated, unfertilized control seedlings, but photosynthetic capacity was similar in both treatments. Differences in foliar nitrogen concentrations between the two treatments were minor, which largely explains why the growth response to near optimal nutrition was not associated with an increase in photosynthetic capacity per unit leaf area. Nevertheless, the photosynthetic capacity of juvenile leaves decreased from distal to proximal positions in the mid-crown and was positively correlated with leaf nitrogen concentration expressed on a leaf surface area basis. During the dry season, non-irrigated, unfertilized seedlings fixed carbon at lower rates than irrigated seedlings supplied with near optimal nutrition because of stomatal closure even though photosynthetic capacity was unaffected by water deficits. In both treatments, there were differences between the photosynthetic capacity of adult and juvenile leaves that were largely explained by the low specific leaf area of adult leaves.

Journal Article↗