Importance of oxygen atmosphere to recover the ZnO-based varistors properties

A methodology to recover the non-ohmic properties of ZnO based varistors after degradation with long and short duration pulses was proposed in this work. The basic idea consists in submitt the degraded ceramics at different temperatures and oxygen flows. Thermal treatment at 900 degrees C for 2 h with oxygen flow of 15 l/h allowed to obtain better non-linear coefficient (alpha= 52.5) compared to the standard sample. Rietveld refinement showed that with the thermal treatment, the oxygen species and the beta-Bi2O3 phase, lost in the degradation process, are recovered in the grain boundary.

Toxicity of ad lib. overfeeding: effects on cardiac tissue

The aim of the present study was to determine the effects of ad lib, overfeeding and of dietary restriction (DR) on oxidative stress in cardiac tissue. Lipoperoxide concentrations ere decreased and antioxidant enzymes ere increased in moderate-DR-fed rats. Severe-DR induced increased lipoperoxide concentrations. Overfeeding increased lipoperoxide levels in cardiac tissue. Total superoxide dismutase (SOD) and Cu-Zn superoxide dismutase (Cu-Zn SOD) activities were decreased in cardiac tissue at 35 days of overfeeding. As no changes in glutathione peroxidase (GSH-Px) ere observed in overfed rats, awhile SOD and Cu-Zn SOD activities were decreased in these animals. it is assumed that superoxide anion is an important intermediate in the toxicity of ad lib, overfeeding. Overfeeding induced alterations in markers of oxidative stress in cardiac tissue. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

TEGDMA-induced oxidative DNA damage and activation of ATM and MAP kinases

The development of strategies for the protection of oral tissues against the adverse effects of resin monomers is primarily based on the elucidation of underlying molecular mechanisms. The generation of reactive oxygen species beyond the capacity of a balanced redox regulation in cells is probably a cause of cell damage. This study was designed to investigate oxidative DNA damage, the activation of ATM, a reporter of DNA damage, and redox-sensitive signal transduction through mitogen-activated protein kinases (MAPKs) by the monomer triethylene glycol dimethacrylate (TEGDMA). TEGDMA concentrations as high as 3-5 mm decreased THP-1 cell viability after a 24 h and 48 h exposure, and levels of 8-oxoguanine (8-oxoG) increased about 3- to 5-fold. The cells were partially protected from toxicity in the presence of N-acetylcysteine (NAC). TEGDMA also induced a delay in the cell cycle. The number of THP-1 cells increased about 2-fold in G1 phase and 5-fold in G2 phase in cultures treated with 3-5 mm TEGDMA. ATM was activated in THP-1 cells by TEGDMA. Likewise, the amounts of phospho-p38 were increased about 3-fold by 3 mm TEGDMA compared to untreated controls after a 24 h and 48 h exposure period, and phospho-ERK1/2 was induced in a very similar way. The activation of both MAPKs was inhibited by NAC. Our findings suggest that the activation of various signal transduction pathways is related to oxidative stress caused by a resin monomer. Signaling through ATM indicates oxidative DNA damage and the activation of MAPK pathways indicates oxidative stress-induced regulation of cell survival and apoptosis. (C) 2008 Elsevier Ltd. All rights reserved.

Irradiance stress responses of gas exchange and antioxidant enzyme contents in pariparoba [Pothomorphe umbellata (L.) Miq.] plants

We evaluated the growth and development of the medicinal species Pothomorphe umbellata ( L.) Miq. under different shade levels ( full sun and 30, 50, and 70 % shade, marked as I(100), I(70), I(50), and I(30), respectively) and their effects on gas exchange and activities of antioxidant enzymes. Photosynthetically active radiation varied from 1 254 mu mol m(-2) s(-1) at I(100) to 285 mu mol m(-2) s(-1) at I(30). Stomatal conductance, net photosynthetic rate, and relative chlorophyll (Chl) content were maximal in I(70) plants. Plants grown under I(100) produced leaves with lower Chl content and signs of chlorosis and necrosis. These symptoms indicated Chl degradation induced by the generation of reactive oxygen species. Stress related antioxidant enzyme activities ( Mn-SOD, Fe-SOD, and Cu/Zn-SOD) were highest in I(100) plants, whereas catalase activity was the lowest. Hence P. umbellata is a shade species ( sciophyte), a feature that should be considered in reforestation programs or in field plantings for production of medicinal constituents.

Protective effect of nickel chloride on superoxide damage: enhancement of CuZn superoxide dismutase affinity to the oxygen free radical.

The effect of nickel from soluble NiCl2 on Cu-Zn superoxide dismutase (SOD) activity, as well as on rate of nitro blue tetrazolium reduction, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel insoluble compounds, whose toxicity and carcinogenicity are well established. The physical and chemical nature of nickel compounds is one of the key determinations of its toxicity. Soluble nickel freely enter cells, but is just as readily excreted reducing the opportunity for production of lipid damage. Nickel from NiCl2 strongly activated SOD activity. In vitro addition of nickel chloride to a crude lung preparation altered the KM for SOD without changing the Vmax. Nickel chloride produced increased enzyme affinity to the substrate, because decreased (O2-) concentration that yields half-maximal velocity. The combination of nickel and SOD may contribute to stabilization of the particular conformation of SOD responsible for maximal catalytically activity.

Superoxide radical and nephrotoxic effect of cadmium exposure

Pollution and industrial practices result in concentrations of metals and other environmental agents that are related to environmental toxicity. Concentrations of metals are widely related to biochemicals values which are used in disease diagnosis due to environmental toxicity. This work was carried out in order to verify the nephrotoxic effect of cadmium and to clarify the contribution of reactive oxygen species (ROS) in this process. Cadmium chloride was tested for nephrotoxic damage in rats by a single intraperitoneal (i.p.) injection Cd 2+ (2 mg/kg) and oral intake (Cd2 +-100 mg/l-from CdCl 2). The cadmium-induced biochemical alterations included significant increased levels of serum creatinine concentrations, in rats with i.p. injection. Total urinary protein concentrations were only increased in rats with cadmium intake. Lipoperoxide was also increased after 3 and 7 days of the Cd 2+ treatment. No changes were observed in glutathione peroxidase activities. Cadmium-induced damage might be due to superoxide radicals (O 2 -), since Cu-Zn superoxide dismutase activities were decreased by Cd 2+ treatment. This study allows tentative conclusions to be drawn regarding which reactive oxygen metabolites play a role in cadmium nephrotoxicity. We concluded that the superoxide radical may be produced as a mediator of nephrotoxic action of cadmium.

Toxic mechanism of nickel exposure on cardiac tissue

The incidence of cardiovascular disease has increased in the general population, and cardiac damage is indicated as one important cause of mortality. In addition, pollution and metal exposure have increased in recent years. For this reason, toxic effects of metals, such as nickel, and their relation to cardiac damage should be urgently established. Although free radical-mediated cellular damage and reactive oxygen species have been theorized as contributing to the nickel mechanism of toxicity, recent investigations have established that free radicals may be important contributors to cardiac dysfunction. However, there is little information on the effect of nickel exposure on markers of oxidative stress in cardiac tissue. Nickel exposure (Ni2+ 100 mg L-1 from NiSO4) significantly increased lipoperoxide and total lipid concentrations in cardiac tissue. We also observed increased serum levels of cholesterol (59%), lactate dehydrogenase (LDH-64%), and alanine transaminase (ALT-30%) in study animals. The biochemical parameters recovered to the control values with tocopherol intake (0.2 mg 200 g-1). Vitamin E alone significantly decreased the lipoperoxide concentration and increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in the heart. Since no alterations were observed in catalase and GSH-Px activities by nickel exposure while SOD activities were decreased, we conclude that superoxide radical (O2 -) generated by nickel exposure is of primary importance in the pathogenesis of cardiac damage. Tocopherol, by its antioxidant activity, decreased the toxic effects of nickel exposure on heart of rats.

Silibinin attenuates oxidative metabolism and cytokine production by monocytes from preeclamptic women.

Silibinin is a polyphenolic plant flavonoid with anti-inflammatory properties. The present study investigated the effect of silibinin on oxidative metabolism and cytokine production - tumor necrosis factor-alpha (TNF-α), interleukin (IL)12, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, IL-10, and transforming growth factor beta (TGF-β1) - by peripheral blood monocytes (PBM) from preeclamptic pregnant women. It is a case-controlled study involving women with preeclampsia (PE, n = 30) compared with normotensive pregnant (NT, n = 30) and with non-pregnant (NP, n = 30) women. Monocytes were obtained and cultured with or without silibinin (5 μM or 50 μM) for 18 h. Superoxide anion (O2-) and hydrogen peroxide (H2O2) release were determined by specific assays, and cytokine levels were determined by immunoenzymatic assays (ELISA). Monocytes from preeclamptic women cultured without stimulus released higher levels of O22, H2O2 and TNF-α, and lower levels of IL-10 and TGF-β1 than did monocytes from NT and NP women. Treatment in vitro with silibinin significantly inhibited spontaneous O2- and H2O2 release and TNF-α production by monocytes from preeclamptic women. The main effect of silibinin was obtained at 50 μM concentration. Thus, silibinin exerts anti-oxidative and anti-inflammatory effects on monocytes from preeclamptic pregnant women by inhibiting the in vitro endogenous release of reactive oxygen species and TNF-α production.

Mechanism and effect of esculetin in an experimental animal model of inflammatory bowel disease

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

Diabetes mellitus triggers oxidative stress in the liver of alloxan-treated rats: A mechanism for diabetic chronic liver disease

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biochemical responses in armored catfish (Pterygoplichthys anisitsi) after short-term exposure to diesel oil, pure biodiesel and biodiesel blends

Biodiesel fuel is gradually replacing petroleum-based diesel oil use. Despite the biodiesel being considered friendlier to the environment, little is known about its effects in aquatic organisms. In this work we evaluated whether biodiesel exposure can affect oxidative stress parameters and biotransformation enzymes in armored catfish (Pterygoplichthys anisitsi, Loricariidae), a South American endemic species. Thus, fish were exposed for 2 and 7d to 0.01mLL-1 and 0.1mLL-1 of pure diesel, pure biodiesel (B100) and blends of diesel with 5% (B5) and 20% (B20) biodiesel. Lipid peroxidation (malondialdehyde) levels and the activities of the enzymes glutathione S-transferase, superoxide dismutase, catalase and glutathione peroxidase were measured in liver and gills. Also, DNA damage (8-oxo-7, 8-dihydro-2'-deoxyguanosine) levels in gills and 7-ethoxyresorufin-O-deethylase activity in liver were assessed. Pure diesel, B5 and B20 blends changed most of the enzymes tested and in some cases, B5 and B20 induced a higher enzyme activity than pure diesel. Antioxidant system activation in P. anisitsi was effective to counteract reactive oxygen species effects, since DNA damage and lipid peroxidation levels were maintained at basal levels after all treatments. However, fish gills exposed to B20 and B100 presented increased lipid peroxidation. Despite biodiesel being more biodegradable fuel that emits less greenhouse gases, the increased lipid peroxidation showed that biofuel and its blends also represent hazards to aquatic biota. © 2013 Elsevier Ltd.

Storage of sugarcane stalks (Saccharum officinarum cv. SP 79-1011) in low oxygen atmospheres and the effects on enzymatic browning

Although sugarcane consumption is very popular worldwide there are few studies regarding the postharvest storage of stalks that focus on controlling enzymatic browning. The objective of this study was to evaluate the quality of sugarcane stalks stored at 10±1°C in controlled atmosphere with various oxygen (O2) levels (1kPa, 5kPa, 10kPa, 15kPa, and 21kPa) and to verify the effect of this storage on the activities of polyphenoloxidase (PPO) and peroxidase (POD). At 1kPa and 5kPa O2, the stalks' respiratory rate, POD activity, and reducing sugar content were significantly less (P<0.05) than at higher O2 concentrations. In contrast, low O2 levels did not affect PPO activity or influence cane coloration. These results can be used to guide the choice of plastic films, making it possible to store sugarcane stalks in a controlled atmosphere. © 2013 Elsevier B.V.

Caracterização bioquímica e centesimal das espécies Astrocaryum vulgare Mart. (tucumã) e Endopleura uchi (Huber) Cuatrec. (uxi) nativas da região Amazônica

Pós-graduação em Biotecnologia - IQ

Determinação dos genótipos para o polimorfismo dos receptores de IgG, FcγRlla (H/R131) e FcγRIIIb (NA1/NA2), e estudo do burst oxidativo dos neutrófilos em indivíduos infectados pelo HIV e/ou Mycobacterium tuberculosis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Morfologia e morfometria do arco aórtico de colehos com ateroma induzido e tratados com resveratol, como modelo experimental na prevenção da aterosclerose: perfil lipídico sérico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)