Automatic devices for monitoring environmentally induced auto-oxidative degradation of artistic materials in conservation sites

This paper describes an automatic device for in situ and continuous monitoring of the ageing process occurring in natural and synthetic resins widely used in art and in the conservation and restoration of cultural artefacts. The results of tests carried out under accelerated ageing conditions are also presented. This easy-to-assemble palm-top device, essentially consists of oscillators based on quartz crystal resonators coated with films of the organic materials whose response to environmental stress is to be addressed. The device contains a microcontroller which selects at pre-defined time intervals the oscillators and records and stores their oscillation frequency. The ageing of the coatings, caused by the environmental stress and resulting in a shift in the oscillation frequency of the modified crystals, can be straightforwardly monitored in this way. The kinetics of this process reflects the level of risk damage associated with a specific microenvironment. In this case, natural and artificial resins, broadly employed in art and restoration of artistic and archaeological artefacts (dammar and Paraloid B72), were applied onto the crystals. The environmental stress was represented by visible and UV radiation, since the chosen materials are known to be photochemically active, to different extents. In the case of dammar, the results obtained are consistent with previous data obtained using a bench-top equipment by impedance analysis through discrete measurements and confirm that the ageing of this material is reflected in the gravimetric response of the modified quartz crystals. As for Paraloid B72, the outcome of the assays indicates that the resin is resistant to visible light, but is very sensitive to UV irradiation. The use of a continuous monitoring system, apart from being obviously more practical, is essential to identify short-term (i.e. reversible) events, like water vapour adsorption/desorption processes, and to highlight ageing trends or sudden changes of such trends. (C) 2007 Elsevier B.V. All rights reserved.

Low levels of methylmercury induce DNA damage in rats: protective effects of selenium

In this study we examined the possible antigenotoxic effect of selenium (Se) in rats chronically exposed to low levels of methylmercury (MeHg) and the association between glutathione peroxidase (GSH-Px) activity and DNA lesions (via comet assay) in the same exposed animals. Rats were divided into six groups as follows: (Group I) received water; (Group II) received MeHg (100 mu g/day); (Group III) received Se (2 mg/L drinking water); (Group IV) received Se (6 mg/L drinking water); (Group V) received MeHg (100 mu g/day) and Se (2 mg/L drinking water); (Group VI) received MeHg (100 mu g/day) and Se (6 mg/L drinking water). Total treatment time was 100 days. GSH-Px activity was determined spectrophotometrically and DNA damage was determined by comet assay. Mean GSH-Px activity in groups I, II, III, IV, V and VI were, respectively: 40.19 +/- A 17.21; 23.63 +/- A 6.04; 42.64 +/- A 5.70; 38.50 +/- A 7.15; 34.54 +/- A 6.18 and 41.39 +/- A 11.67 nmolNADPH/min/gHb. DNA damage was represented by a mean score from 0 to 300; the results for groups I, II, III, IV, V and VI were, respectively: 6.87 +/- A 3.27; 124.12 +/- A 13.74; 10.62 +/- A 3.81; 13.25 +/- A 1.76; 86.87 +/- A 11.95 and 76.25 +/- A 7.48. There was a significant inhibition of GSH-Px activity in group II compared with group I (P < 0.05). Groups V and VI did not show a difference in enzyme activity compared with groups III and IV, showing the possible protective action of Se. Comet assay presented a significant difference in DNA migration between group II and group I (P < 0.0001). Groups V and VI showed a significant reduction in MeHg-induced genotoxicity (P < 0.001) when compared with group II. A negative correlation (r = -0.559, P < 0.05) was found between GSH-Px activity and DNA lesion, showing that the greater the DNA damage, the lower the GSH-Px activity. Our findings demonstrated the oxidative and genotoxic properties of MeHg, even at low doses. Moreover, Se co-administration reestablished GSH-Px activity and reduced DNA damage.

Light-Induced Oxidation of Unsaturated Lipids as Sensitized by Flavins

Triplet-excited riboflavin ((3)RF*) was found by laser flash photolysis to be quenched by polyunsaturated fatty acid methyl esters in tert-butanol/water (7:3, v/v) in a second-order reaction with k similar to 3.0 x 10(5) L mol(-1) s(-1) at 25 degrees C for methyl linoleate and 3.1 x 10(6) L mol(-1) s(-1), with Delta H double dagger = 22.6 kJ mol(-1) and Delta S double dagger = -62.3 J K(-1) mol(-1), for methyl linolenate in acetonitrile/water (8:2, v/v). For methyl oleate, k was <10(4) L mol(-1) s(-1). For comparison, beta-casein was found to have a rate constant k similar to 4.9 x 10(8) L mol(-1) s(-1). Singlet-excited flavin was not quenched by the esters as evidenced by insensitivity of steady-state fluorescence to their presence. Density functional theory (DFT) calculations showed that electron transfer from unsaturated fatty acid esters to triplet-excited flavins is endergonic, while a formal hydrogen atom transfer is exergonic (Delta G(HAT)degrees = -114.3, -151.2, and -151.2 kJ mol(-1) for oleate, linoleate, and linolenate, respectively, in acetonitrile). The reaction is driven by acidity of the lipid cation radical for which a pK(a) similar to -0.12 was estimated by DFT calculations. Absence of electrochemical activity in acetonitrile during cyclic voltammetry up to 2.0 V versus NHE confirmed that Delta G(ET)degrees > 0 for electron transfer. Interaction of methyl esters with (3)RF* is considered as initiation of the radical chain, which is subsequently propagated by combination reactions with residual oxygen. In this respect, carbon-centered and alkoxyl radicals were detected using the spin trapping technique in combination with electron paramagnetic resonance spectroscopy. Moreover, quenching of 3RF* yields, directly or indirectly, radical species which are capable of initiating oxidation in unsaturated fatty acid methyl esters. Still, deactivation of triplet-excited flavins by lipid derivatives was slower than by proteins (factor up to 10(4)), which react preferentially by electron transfer. Depending on the reaction environment in biological systems (including food), protein radicals are expected to interfere in the mechanism of light-induced lipid oxidation.

Quantum control of electromagnetically induced transparency dispersion via atomic tunneling in a double-well Bose-Einstein condensate

Electromagnetically induced transparency (EIT) is an important tool for controlling light propagation and nonlinear wave mixing in atomic gases with potential applications ranging from quantum computing to table top tests of general relativity. Here we consider EIT in an atomic Bose-Einstein condensate (BEC) trapped in a double-well potential. A weak probe laser propagates through one of the wells and interacts with atoms in a three-level Lambda configuration. The well through which the probe propagates is dressed by a strong control laser with Rabi frequency Omega(mu), as in standard EIT systems. Tunneling between the wells at the frequency g provides a coherent coupling between identical electronic states in the two wells, which leads to the formation of interwell dressed states. The macroscopic interwell coherence of the BEC wave function results in the formation of two ultranarrow absorption resonances for the probe field that are inside of the ordinary EIT transparency window. We show that these new resonances can be interpreted in terms of the interwell dressed states and the formation of a type of dark state involving the control laser and the interwell tunneling. To either side of these ultranarrow resonances there is normal dispersion with very large slope controlled by g. We discuss prospects for observing these ultranarrow resonances and the corresponding regions of high dispersion experimentally.

Quantitative Analysis of Diepoxybutane Damage within the Chicken β-globin Domain

In industrial polymer and synthetic rubber production facilities, workers are exposed to 1,3-butadiene. This compound is converted in vivo to 1,2,3,4-diepoxybutane (DEB) and has been linked to increased incidences of cancer in these individuals. Carcinogenesis has been attributed to formation of DEB induced DNA interstrand cross-links. Previous studies have demonstrated that DEB cross-links deoxyguanosine residues within 5'-GNC sequences in synthetic DNA, in restriction fragments, and in defined sequence nucleosomes. The current study utilized the polymerase chain reaction (PCR) to examine DEB damage frequencies within nuclear genes, found within "open" regions of chromatin, as compared to regions of unexpressed sequence that reside in tightly packed, "closed" chromatin, to more closely model DEB reactivity in vivo. These initial studies have been performed in chicken liver homogenates. Preliminarily, we have found a dose-dependent DEB lesion-forming response within "open" chromatin. DEB appears to have little-to-no effect upon regions of "closed" chromatin.

An Anisotropic Model of Damage and Unilateral Effect for Brittle Materials

This work deals with the initial applications and formulation of an aniscitropic plastic-damage constitutive model proposed for non-linear analysis of reinforced concrete structures submitted to a loading with change of the sign. The original constitutive model is based on the fundamental hypothesis of energy equivalence between real and continuous medium following the concepts of the Continuum Damage Mechanics. The concrete is assumed as an initial elastic isotropic medium presenting anisotropy, permanent strains and bimodularity (distinct elastic responses whether traction or compression stress states prevail) induced by damage evolution. In order to take into account the bimodularity, two damage tensors governing the rigidity in tension or compression regimes are introduced. Then, some conditions are introduced in the original version of the model in order to simulate the damage unilateral effect. The three-dimensional version of the proposed model is analyzed in order to validate its formulation when compared to micromechanical theory. The one-dimensional version of the model is applied in the analyses of a reinforced concrete beam submitted to a loading with change of the sign. Despite the parametric identification problems, the initial applications show the good performance of the model.

Effect of Byrsonima crassa and Phenolic Constituents on Helicobacter pylori-Induced Neutrophils Oxidative Burst

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

In vivo assessment of DNA damage and protective effects of extracts from Miconia species using the comet assay and micronucleus test

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The effects of oral glutamine on cisplatin-induced nephrotoxicity in rats

The antioxidant activity of the amino acid glutamine was investigated to obtain protection against peroxidative damage in rat kidney and nephrotoxicity induced by the treatment with a single dose of the antitumoral cisplatin (5 mg kg(-1) body weight). The animals were divided into four treatment and control groups of six rats each (n = 6). Cisplatin was injected i.p. and glutamine (300 mg kg(-1) body weight) was given by gavage 24 h before the cisplatin injection. After 24 h and 7 days of cisplatin administration, the rats were sacrificed. A single dose of cisplatin resulted in significant reduction in body weight and creatinine clearance, and higher urinary volumes were observed in all groups treated with this antitumor drug (P < 0.05). Renal tissue from cisplatin-treated rats showed an increase in malondialdehyde production and increase in glutathione contents 24 h and 7 days after cisplatin administration. Pretreatment of rats with glutamine substantially inhibited the increase in the levels of renal glutathione induced by cisplatin 24 h after the i.p. injection. The malondialdehyde, in the renal tissues was significantly reduced 7 days after cisplatin treatment. However, the reduction in the peroxidative damage did not reach the value of the control group. The protective effects obtained by glutamine pretreatment in peroxidative alterations were not observed in the other parameters studied. These results suggest that glutamine partially protect against cisplatin-induced lipid peroxidation damage, but it was not enough to inhibit cisplatin-induced nephrotoxicity in rats. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

Comparative effects of acute and subacute lycopene administration on chromosomal aberrations induced by cisplatin in male rats

Lycopene is a natural carotenoid, free radical scavenger, and presents protective effects by inhibiting oxidative DNA damage. The objective of the current study was to investigate the cytogenetic effects of a single acute and four daily gavage administrations of lycopene, and to examine possible protective effects on chromosomal damage induced by the antitumor drug cisplatin (cDDP) in rat bone marrow cells. The animals were divided into treatment groups, with three lycopene doses in the acute treatment (2, 4, and 6 mg/kg b.w.), three lycopene doses in the subacute treatment (0.5, 1.0, and 1.5 mg/kg b.w.) with and without cDDP (5 mg/kg b.w. i.p.), and respective controls. The results indicated that lycopene is neither cytotoxic nor clastogenic when compared with the negative controls (P > 0.01). cDDP-treated animals submitted to acute and subacute treatments with different lycopene doses showed a significant reduction (p < 0.01) in the number of abnormal metaphases when compared with the animals treated only with cDDP. The protective effects of lycopene on cDDP-induced chromosomal damage may be attributed to its antioxidant activity. These results suggest that this carotenoid may prove useful in reducing some of the toxic effects associated with certain classes of chemotherapeutic agents. (c) 2006 Elsevier Ltd. All rights reserved.

Efeito da crioterapia e da laserterapia na resposta ao dano muscular induzido pelo exercício excêntrico: ensaio clínico e randomizado

Exercise-induced muscle damage mainly affects individuals who returned to physical activity after a time without practicing it or had some kind of exhaustive exercise, particularly eccentric exercise. To evaluate the effect of cryotherapy and laser therapy in response to muscle damage induced by eccentric exercise on the biceps muscle. This was a randomized clinical trial consisting of 60 female subjects. All subjects initially underwent an evaluation consisting of perimetry, measurement of pain sensation (via algometry and visual analogue scale), electromyography and dynamometry. Then the subjects performed an exercise protocol on the isokinetic dynamometer consisting of 2 sets of 10 eccentric elbow flexors contraction at 60 °/s. Completed this protocol, an intervention was held according to a previously random group distribution: control group (no intervention), cryotherapy group and laser therapy group. Finally, subjects were re-evaluated immediately and 48 hours after the intervention protocol, except for Visual Analogue Scale (VAS), which was also evaluated 24 hours after exercise. The circumference of the limb, the pain sensation (VAS and algometry), the muscle activation amplitude (via Root Mean Square - RMS), median frequency, peak torque normalized per body weight, average peak torque, power and work were analyzed. The median frequency immediately after the intervention protocol on the cryotherapy group was the only variable that showed inter and intra-group differences; the remaining variables showed only intragroup differences. The perimetry values did not change immediately after the protocol on the groups which underwent cryotherapy and laser therapy, however, there was an increase after 48 hours; algometry values decreased in all groups for 48 hours and the VAS values increased 24 and 48 hours also for all groups. Regarding RMS no significant change was observed. For dynamometry, peak torque normalized per body weight and average peak torque had a similar behavior, with a reduction in the post protocol that has remained after 48 hours. For the power and work, a decrease was observed immediately after the protocol with a further reduction after 48 hours. Cryotherapy and laser therapy does not alter the muscle damage response, except for the perimetry values immediately after exercise.

Photo-Induced Dipole Relaxation Current in Natural Amethyst

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Trypanocidal action of eupomatenoid-5 is related to mitochondrion dysfunction and oxidative damage in Trypanosoma cruzi

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

AT1-receptor mediated vascular damage in myocardium, kidneys and liver in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)