In vitro penetration of bleaching agents into the pulp chamber

Aim: To investigate pulp chamber penetration of bleaching agents in teeth following restorative procedures. Methodology: Bovine lateral incisors were sectioned 3 mm apical to the cemento-enamel junction and the coronal pulpal tissue was removed. Teeth were divided into six groups (n = 10): G1, G2 and G3 were not submitted to any restorative procedure, while G4, G5 and G6 were submitted to Class V preparations and restored with composite resin. Acetate buffer was placed in the pulp chamber and treatment agents were applied for 60 min at 37°C as follows: G1 and G4, immersion into distilled water; G2 and G5, 10% carbamide peroxide (CP) exposure; G3 and G6, 35% CP bleaching. The buffer solution was removed and transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined spectrophotometrically at 596 nm. A standard curve made with known amounts of hydrogen peroxide was used to convert the optical density values of the coloured samples into microgram equivalents of hydrogen peroxide. Data were submitted to ANOVA and Tukey's test (5%). Results: Amounts of hydrogen peroxide found in the pulp chamber of G2 and G5 specimens (0.1833 ± 0.2003 μg) were significantly lower (P = 0.001) when compared to G3 and G6 specimens (0.4604 ± 0.3981 μg). Restored teeth held significantly higher (P = 0.001) hydrogen peroxide concentrations in the pulp chamber than intact teeth. Conclusion: Higher concentrations of the bleaching agent produced higher levels of hydrogen peroxide in the pulp chamber, especially in restored teeth.

Effect of an acid diet allied to sonic toothbrushing on root dentin permeability: An in vitro study

This study quantified alterations in root dentin permeability after exposure to different acid beverages. Twenty-five third molars were sectioned below the cementoenamel junction, the root segment was collected, and the pulp tissue was removed. The root segments were connected to a hydraulic pressure apparatus to measure the permeability of root dentin after the following sequential steps, with 5 specimens in each: 1) phosphoric acid etching for 30 s (maximum permeability), 2) root planning to create new smear layer, 3) exposure to different acid substances for 5 min (orange, cola drink, vinegar, white wine, lemon juice), 4) toothbrushing with sonic toothbrush for 3 min, 5) toothbrushing with sonic toothbrush plus dentifrice for 3 min. Considering step I as 100%, the data were converted into percentage and each specimen was its own control. Data were analyzed statistically by Kruskal-Wallis and Dunn's post test at 5% significance level. All acidic substances increased dentin permeability significantly after scraping (p<0.05). Toothbrushing after exposure to acid substances decreased dentin permeability and the association with dentifrice accentuated the decrease (p<0.05), except for the specimens treated with cola drink. Thus, it may be concluded that all tested acid fruit juices increased dentin permeability, and toothbrushing with or without dentifrice can decrease root dentin permeability after dentin exposure to acid diet.

Baccharis dracunculifolia, the main source of green propolis, exhibits potent antioxidant activity and prevents oxidative mitochondrial damage

Baccharis dracunculifolia DC (Asteraceae) is the main botanical source used by honeybees to produce Brazilian green propolis whose hepatoprotective properties have been already described. In this work we investigated the protective effects of the glycolic extract of B. dracunculifolia (GEBd) against oxidative stress in isolated rat liver mitochondria (RLM). The GEBd was prepared by fractionated percolation using propylene glycol as solvent. The total phenols and flavonoids, which are substances with recognized antioxidant action, were quantified in GEBd and the phytochemical analysis was carried out by HPLC. GEBd exhibited significant scavenger activity towards DPPH radicals and superoxide anions in a concentration-dependent manner, and also a Fe 2+ chelating activity. GEBd decreased the basal H 2O 2 generation and the Fe 2+- or t-BuOOH-induced ROS production in isolated mitochondria. Lipid oxidation of mitochondrial membranes, protein thiol groups and GSH oxidation were also prevented by GEBd. This shows that B. dracunculifolia exhibit potent antioxidant activity protecting liver mitochondria against oxidative damage and such action probably contribute to the antioxidant and hepatoprotective effects of green propolis. © 2011 Elsevier Ltd.

Structural insights into selectivity and cofactor binding in snake venom l-amino acid oxidases

l-Amino acid oxidases (LAAOs) are flavoenzymes that catalytically deaminate l-amino acids to corresponding α-keto acids with the concomitant production of ammonia (NH 3) and hydrogen peroxide (H 2O 2). Particularly, snake venom LAAOs have been attracted much attention due to their diverse clinical and biological effects, interfering on human coagulation factors and being cytotoxic against some pathogenic bacteria and Leishmania ssp. In this work, a new LAAO from Bothrops jararacussu venom (BjsuLAAO) was purified, functionally characterized and its structure determined by X-ray crystallography at 3.1å resolution. BjsuLAAO showed high catalytic specificity for aromatic and aliphatic large side-chain amino acids. Comparative structural analysis with prokaryotic LAAOs, which exhibit low specificity, indicates the importance of the active-site volume in modulating enzyme selectivity. Surprisingly, the flavin adenine dinucleotide (FAD) cofactor was found in a different orientation canonically described for both prokaryotic and eukaryotic LAAOs. In this new conformational state, the adenosyl group is flipped towards the 62-71 loop, being stabilized by several hydrogen-bond interactions, which is equally stable to the classical binding mode. © 2012 Elsevier Inc.

Apocynin: Chemical and biophysical properties of a NADPH oxidase inhibitor

Apocynin is the most employed inhibitor of NADPH oxidase (NOX), a multienzymatic complex capable of catalyzing the one-electron reduction of molecular oxygen to the superoxide anion. Despite controversies about its selectivity, apocynin has been used as one of the most promising drugs in experimental models of inflammatory and neurodegenerative diseases. Here, we aimed to study the chemical and biophysical properties of apocynin. The oxidation potential was determined by cyclic voltammetry (Epa = 0.76V), the hydrophobicity index was calculated (logP = 0.83) and the molar absorption coefficient was determined (ε275nm = 1.1 × 104 M-1 cm-1). Apocynin was a weak free radical scavenger (as measured using the DPPH, peroxyl radical and nitric oxide assays) when compared to protocatechuic acid, used here as a reference antioxidant. On the other hand, apocynin was more effective than protocatechuic acid as scavenger of the non-radical species hypochlorous acid. Apocynin reacted promptly with the non-radical reactive species H2O2 only in the presence of peroxidase. This finding is relevant, since it represents a new pathway for depleting H2O2 in cellular experimental models, besides the direct inhibition of NADPH oxidase. This could be relevant for its application as an inhibitor of NOX4, since this isoform produces H 2O2 and not superoxide anion. The binding parameters calculated by fluorescence quenching showed that apocynin binds to human serum albumin (HSA) with a binding affinity of 2.19 × 104 M -1. The association did not alter the secondary and tertiary structure of HSA, as verified by synchronous fluorescence and circular dichroism. The displacement of fluorescent probes suggested that apocynin binds to site I and site II of HSA. Considering the current biomedical applications of this phytochemical, the dissemination of these chemical and biophysical properties can be very helpful for scientists and physicians interested in the use of apocynin.

Influência da estrutura de corantes azo na cinética de degradação por processo foto-Feton e ferro zero e na toxicidade

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de um biosensor amperométrico para a detecção do vírus da Hepatite C

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Suplementação com creatina, estado redox e metabolismo glicídico muscular de ratos submetidos ao treinamento de caráter aeróbio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da eficiência de produção de peróxido de hidrogênio por naftoquinonas em associação com ácido ascórbico: aplicações como agentes citotóxicos em linhagem de células normal e tumoral

Pós-graduação em Biociências e Biotecnologia Aplicadas à Farmácia - FCFAR

Tratamento de manipueira de fecularia utilizando processos oxidativos com peróxido de hidrogênio, ôzônio e radiação ultravioleta

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Síntese hidrotérmica de nanopartículas de 'TI''O IND.2', de nanocompósitos metal/'TI''O IND.2' e degradação oxidativa de 4-clorofenol em reator membranar fotocatalítico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Enraizamento de Eucalyptus grandis x Eucalyptus urophylla pela ação de peróxido de hidrogênio, quercetina e ácido indolbutírico

Pós-graduação em Ciências Biológicas (Botânica) - IBB

Protonation Pattern, Tautomerism, Conformerism, and Physicochemical Analysis in New Crystal Forms of the Antibiotic Doxycycline

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Apocinina versus diapocinina como inibidor da produção de peróxido de hidrogênio e ácido hipocloroso por neutrófilos ativados

Apocynin has been used as an efficient inhibitor of the multi-enzymatic complex NADPH oxidase in many experimental models involving phagocytic and nonphagocytic cells. The mechanism of inhibition has been linked with the previous activation of apocynin through the action of cellular peroxidases leading to the formation of a dimeric oxidation product, diapocynin. In this study we compared apocynin with pure diapocynin regarding their effects as scavenger of hydrogen peroxide and hypochlorous generated by glucose/glucose oxidase and myeloperoxidase respectively, and as inhibitors of the production of hydrogen peroxide and hypochlorous acid by activated neutrophils. The production of hydrogen peroxide was measured by the oxidation of the fluorescent substance Amplex Red and the production of hypochlorous acid by was measured as taurine-chloramine derivative using the chromogenic substrate 3,3’,5,5’- tetramethylbenzidine (TMB). Neutrophils (1 x106 cells/mL) were pre-incubated in PBS buffer supplemented with 1 mM calcium chloride, 0.5 mM magnesium chloride, 1 mg/mL glucose and 5 mM taurine in the presence or absence of inhibitors. The reactions were triggered by adding the soluble stimulus Forbol Miristate Acetate PMA or zymosan and incubated by additional 30 minutes. We found that pure diapocynin was not better than apocynin regarding its scavenger and inhibitory properties. These results suggest that the formation of diapocynin is not essential for the action of apocynin as inhibitor of NADPH oxidase activation

Oxidation of ethanol and its derivatives on well defined pt single crystal electrodes vicinal to pt(111): a comparative study

The oxidation of ethanol (EtOH) at Pt(111) electrodes is dominated by the 4e path leading to acetic acid. The inclusion of surface defects such as those present on stepped surfaces leads to an increase of the reactivity towards the most desirable 12e path leading to CO2 as final product. This path is also favored when the methyl group is more oxidized, as in the case of ethylene glycol (EG) that spontaneously decomposes to CO on Pt(111) electrodes, thus showing a more effective breaking of the C-C bond. Some trends in reactivity can be envisaged when other derivative molecules are compared at well-ordered electrodes. This strategy was used in the past, but the improvement in the electrode pretreatment and the overall information available on the subject suggest that relevant information is still missing.