External polyacrylate-coating as alternative material for preparation of photopolymerized sol-gel monolithic column

Photopolymerized sol-gel monolithic columns for use in capillary electrochromatography were prepared in 125 mu m i.d. polyacrylate-coated fused-silica capillaries. The polyacrylate-coating, unlike the polyimide one, is transparent to the radiation used (approximate to 370 nm), and thus, no coating removal is necessary. This is a very important particularity since intrinsic capillary column characteristics, such as flexibility and mechanical resistance, are unchanged. A mixture containing metacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photoinitiator was irradiated at 370 nm for 20 min inside the capillaries to prepare the columns through sol-gel approach. The versatility and viability of the use of polyacrilate as a new capillary external coating were shown through preparation of two columns under different conditions, which were tested in electrochromatography for separation of standard mixture containing thiourea (marker compound), propylbenzene, phenanthrene and pyrene. (C) 2008 Elsevier B.V. All rights reserved.

Antibacterial activity of root canal filling materials for primary teeth: zinc oxide and eugenol cement, Calen paste thickened with zinc oxide, Sealapex and EndoREZ

This study evaluated in vitro the antibacterial activity of 4 root canal filling materials for primary teeth - zinc oxide and eugenol cement (ZOE), Calen paste thickened with zinc oxide (Calen/ZO), Sealapex sealer and EndoREZ sealer - against 5 bacterial strains commonly found in endodontic infections (Kocuria rhizophila, Enterococcus faecalis, Streptococcus mutans, Escherichia coli and Staphylococcus aureus) using the agar diffusion test (agar-well technique). Calen paste, 1% chlorhexidine digluconate (CHX) and distilled water served as controls. Seven wells per dish were made at equidistant points and immediately filled with the test and control materials. After incubation of the plates at 37oC for 24 h, the diameter of the zones of bacterial growth inhibition produced around the wells was measured (in mm) with a digital caliper under reflected light. Data were analyzed statistically by analysis of variance and Tukey's post-hoc test (?=0.05). There were statistically significant differences (p<0.0001) among the zones of bacterial growth inhibition produced by the different materials against all target microorganisms. K. rhizophila was inhibited more effectively (p<0.05) by ZOE, while Calen/ZO had its highest antibacterial activity against E. faecalis (p<0.05). S. mutans was inhibited by Calen/ZO, Sealapex and ZOE in the same intensity (p>0.05). E. coli was inhibited more effectively (p<0.05) by ZOE, followed by Calen/ZO and Sealapex. Calen/ZO and ZOE were equally effective (p>0.05) against S. aureus, while Sealapex had the lowest antibacterial efficacy (p<0.05) against this microorganism. EndoREZ presented antibacterial activity only against K. rhizophila and S. aureus. The Calen paste and Calen/ZO produced larger zones of inhibition than 1% CHX when the marker microorganism was E faecalis. In conclusion, the in vitro antibacterial activity of the 4 root canal filling materials for primary teeth against bacterial strains commonly found in endodontic infections can be presented in a decreasing order of efficacy as follows: ZOE>Calen/ZO>Sealapex>EndoREZ.

Effect of nitric oxide inhibitor and donor substances on the infammatory process caused by endodontic irrigants

Nitric oxide (NO) has been considered a key molecule in infammation. OBJECTIVE: The aim of this study was to evaluate the effect of treatment with L-NAME and sodium nitroprussiate, substances that inhibit and release NO, respectively, on tissue tolerance to endodontic irrigants. MATERIAL AND METHODS: The vital dye exudation method was used in a rat subcutaneous tissue model. Injections of 2% Evans blue were administered intravenously into the dorsal penial vein of 14 male rats (200-300 g). The NO inhibitor and donor substances were injected into the subcutaneous tissue in the dorsal region, forming two groups of animals: G1 was inoculated with L-NAME and G2 with sodium nitroprussiate. Both groups received injections of the test endodontic irrigants: acetic acid, 15% citric acid, 17% EDTA-T and saline (control). After 30 min, analysis of the extravasated dye was performed by light absorption spectrophotometry (620 nm). RESULTS: There was statistically signifcant difference (p<0.05) between groups 1 and 2 for all irrigants. L-NAME produced a less intense infammatory reaction and nitroprussiate intensifed this process. CONCLUSIONS: Independently of the administration of NO inhibitors and donors, EDTA-T produced the highest irritating potential in vital tissue among the tested irrigating solutions.

Participation of neuronal nitric oxide synthase in experimental neuropathic pain induced by sciatic nerve transection

Nerve injury leads to a neuropathic pain state that results from central sensitization. This phenomenom is mediated by NMDA receptors and may involve the production of nitric oxide (NO). In this study, we investigated the expression of the neuronal isoform of NO synthase (nNOS) in the spinal cord of 3-month-old male, Wistar rats after sciatic nerve transection (SNT). Our attention was focused on the dorsal part of L3-L5 segments receiving sensory inputs from the sciatic nerve. SNT resulted in the development of neuropathic pain symptoms confirmed by evaluating mechanical hyperalgesia (Randall and Selitto test) and allodynia (von Frey hair test). Control animals did not present any alteration (sham-animals). The selective inhibitor of nNOS, 7-nitroindazole (0.2 and 2 µg in 50 µL), blocked hyperalgesia and allodynia induced by SNT. Immunohistochemical analysis showed that nNOS was increased (48% by day 30) in the lumbar spinal cord after SNT. This increase was observed near the central canal (Rexed’s lamina X) and also in lamina I-IV of the dorsal horn. Real-time PCR results indicated an increase of nNOS mRNA detected from 1 to 30 days after SNT, with the highest increase observed 1 day after injury (1469%). Immunoblotting confirmed the increase of nNOS in the spinal cord between 1 and 15 days post-lesion (20%), reaching the greatest increase (60%) 30 days after surgery. The present findings demonstrate an increase of nNOS after peripheral nerve injury that may contribute to the increase of NO production observed after peripheral neuropathy.

5-HT1A autoreceptor modulation of locomotor activity induced by nitric oxide in the rat dorsal raphe nucleus

The dorsal raphe nucleus (DRN) is the origin of ascending serotonergic projections and is considered to be an important component of the brain circuit that mediates anxiety- and depression-related behaviors. A large fraction of DRN serotonin-positive neurons contain nitric oxide (NO). Disruption of NO-mediated neurotransmission in the DRN by NO synthase inhibitors produces anxiolytic- and antidepressant-like effects in rats and also induces nonspecific interference with locomotor activity. We investigated the involvement of the 5-HT1A autoreceptor in the locomotor effects induced by NO in the DRN of male Wistar rats (280-310 g, N = 9-10 per group). The NO donor 3-morpholinosylnomine hydrochloride (SIN-1, 150, and 300 nmol) and the NO scavenger S-3-carboxy-4-hydroxyphenylglycine (carboxy-PTIO, 0.1-3.0 nmol) were injected into the DRN of rats immediately before they were exposed to the open field for 10 min. To evaluate the involvement of the 5-HT1A receptor and the N-methyl-D-aspartate (NMDA) glutamate receptor in the locomotor effects of NO, animals were pretreated with the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 8 nmol), the 5-HT1A receptor antagonist N-(2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-2-pyridinyl-cyclohexanecarboxamide maleate (WAY-100635, 0.37 nmol), and the NMDA receptor antagonist DL-2-amino-7-phosphonoheptanoic acid (AP7, 1 nmol), followed by microinjection of SIN-1 into the DRN. SIN-1 increased the distance traveled (mean ± SEM) in the open-field test (4431 ± 306.1 cm; F7,63 = 2.44, P = 0.028) and this effect was blocked by previous 8-OH-DPAT (2885 ± 490.4 cm) or AP7 (3335 ± 283.5 cm) administration (P < 0.05, Duncan test). These results indicate that 5-HT1A receptor activation and/or facilitation of glutamate neurotransmission can modulate the locomotor effects induced by NO in the DRN.

The effects of nitric oxide on the immune response during giardiasis

Nitric oxide (NO) is a free radical synthesized from L-arginine by different isoforms NO-synthases. NO possesses multiple and complex biological functions. NO is an important mediator of homeostasis, and changes in its generation or actions can contribute or not to pathological states. The knowledge of effects of NO has been not only important to our understanding of immune response, but also to new tools for research and treatment of various diseases. Knowing the importance of NO as inflammatory mediator in diverse infectious diseases, we decided to develop a revision that shows the participation/effect of this mediator in immune response induced against Giardia spp. Several studies already demonstrated the participation of NO with microbicidal and microbiostatic activity in giardiasis. On the other hand, some works report that Giardia spp. inhibit NO production by consuming the intermediate metabolite arginine. In fact, studies in vitro showed that G. lamblia infection of human intestinal epithelial cells had reduced NO production. This occurs due to limited offer of the crucial substrate arginine (essential aminoacid for NO production), consequently reducing NO production. Therefore, the balance between giardial arginine consumption and epithelial NO production could contribute to the variability of the duration and severity of infections by this ubiquitous parasite.

Screening process for activity determination of conductive oxide electrodes for organic oxidation

A modified method for the calculation of the normalized faradaic charge (q fN) is proposed. The method involves the simulation of an oxidation process, by cyclic voltammetry, by employing potentials in the oxygen evolution reaction region. The method is applicable to organic species whose oxidation is not manifested by a defined oxidation peak at conductive oxide electrodes. The variation of q fN for electrodes of nominal composition Ti/RuX Sn1-X O2 (x = 0.3, 0.2 and 0.1), Ti/Ir0.3Ti0.7O2 and Ti/Ru0.3Ti0.7O2 in the presence of various concentrations of formaldehyde was analyzed. It was observed that electrodes containing SnO2 are the most active for formaldehyde oxidation. Subsequently, in order to test the validity of the proposed model, galvanostatic electrolyses (40 mA cm-2) of two different formaldehyde concentrations (0.10 and 0.01 mol dm-3) were performed. The results are in agreement with the proposed model and indicate that this new method can be used to determine the relative activity of conductive oxide electrodes. In agreement with previous studies, it can be concluded that not only the nature of the electrode material, but also the organic species in solution and its concentration are important factors to be considered in the oxidation of organic compounds.

Cyclic nitroxides inhibit the toxicity of nitric oxide-derived oxidants: mechanisms and implications

The substantial therapeutic potential of tempol (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy) and related cyclic nitroxides as antioxidants has stimulated innumerous studies of their reactions with reactive oxygen species. In comparison, reactions of nitroxides with nitric oxide-derived oxidants have been less frequently investigated. Nevertheless, this is relevant because tempol has also been shown to protect animals from injuries associated with inflammatory conditions, which are characterized by the increased production of nitric oxide and its derived oxidants. Here, we review recent studies addressing the mechanisms by which cyclic nitroxides attenuate the toxicity of nitric oxidederived oxidants. As an example, we present data showing that tempol protects mice from acetaminophen-induced hepatotoxicity and discuss the possible protection mechanism. In view of the summarized studies, it is proposed that nitroxides attenuate tissue injury under inflammatory conditions mainly because of their ability to react rapidly with nitrogen dioxide and carbonate radical. In the process the nitroxides are oxidized to the corresponding oxammonium cation, which, in turn, can be recycled back to the nitroxides by reacting with upstream species, such as peroxynitrite and hydrogen peroxide, or with cellular reductants. An auxiliary protection mechanism may be down-regulation of inducible nitric oxide synthase expression. The possible therapeutic implications of these mechanisms are addressed.

Study of metal oxide-semiconductor capacitors with rf magnetron sputtering TiO(x) and TiO(x)N(y) gate dielectric layer

Metal oxide-semiconductor capacitors with TiO(x) deposited with different O(2) partial pressures (30%, 35%, and 40%) and annealed at 550, 750, and 1000 degrees C were fabricated and characterized. Fourier transform infrared, x-ray near edge spectroscopy, and elipsometry measurements were performed to characterize the TiO(x) films. TiO(x)N(y) films were also obtained by adding nitrogen to the gaseous mixture and physical results were presented. Capacitance-voltage (1 MHz) and current-voltage measurements were utilized to obtain the effective dielectric constant, effective oxide thickness, leakage current density, and interface quality. The results show that the obtained TiO(x) films present a dielectric constant varying from 40 to 170 and a leakage current density (for V(G)=-1 V, for some structures as low as 1 nA/cm(2), acceptable for complementary metal oxide semiconductor circuits fabrication), indicating that this material is a viable, in terms of leakage current density, highk substitute for current ultrathin dielectric layers. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3043537]

Enhanced luminescence of Tb(3+)/Eu(3+) doped tellurium oxide glass containing silver nanostructures

We report on energy transfer studies in terbium (Tb(3+))-europium (Eu(3+)) doped TeO(2)-ZnO-Na(2)O-PbO glass containing silver nanostructures. The samples excitation was made using ultraviolet radiation at 355 nm. Luminescence spectra were recorded from approximate to 480 to approximate to 700 nm. Enhanced Eu(3+) luminescence at approximate to 590 nm (transition (5)D(0)-(7)F(1)) and approximate to 614 nm (transition (5)D(0)-(7)F(2)) are observed. The large luminescence enhancement was obtained due to the simultaneous contribution of the Tb(3+)-Eu(3+) energy transfer and the contribution of the intensified local field on the Eu(3+) ions located near silver nanostructures.

Surface-plasmon-enhanced frequency upconversion in Pr(3+) doped tellurium-oxide glasses containing silver nanoparticles

A frequency upconversion process in Pr(3+) doped TeO(2)-ZnO glasses containing silver nanoparticles is studied under excitation with a nanosecond laser operating at 590 nm, in resonance with the (3)H(4)-->(1)D(2) transition. The excited Pr(3+) ions exchange energy in the presence of the nanoparticles, originating efficient conversion from orange to blue. The enhancement in the intensity of the luminescence at similar to 482 nm, corresponding to the (3)P(0)-->(3)H(4) transition, is due to the influence of the large local field on the Pr(3+) ions, which are located near the metallic nanoparticles. (C) 2008 American Institute of Physics.

Signatures of oxygen on Cu(3)Au(100): From isolated impurity to oxide regimes

We analyze the scanning tunneling microscopy (STM) signatures for the O/Cu(3)Au(100) surface from the low-coverage (isolated impurity) to high-coverage (oxide) regimes. First-principles calculations show that oxygen signatures switch from dark to bright spots as the oxygen coverage increases. This behavior is nicely traced back to a change in the oxygen orbital character of the Fermi-level electronic states. Our results allow for the chemical identification by STM of oxygen and copper atoms in the fully ordered O/Cu(3)Au(100)-c(2x2) surface.

Ferromagnetic resonance for the quantification of superparamagnetic iron oxide nanoparticles in biological materials

The aim of the present work is the presentation of a quantification methodology for the control of the amount of superparamagnetic iron oxide nanoparticles (SPIONs) administered in biological materials by means of the ferromagnetic resonance technique (FMR) applied to studies both in vivo and in vitro. The in vivo study consisted in the analysis of the elimination and biodistribution kinetics of SPIONs after intravenous administration in Wistar rats. The results were corroborated by X-ray fluorescence. For the in vitro study, a quantitative analysis of the concentration of SPIONs bound to the specific AC133 monoclonal antibodies was carried out in order to detect the expression of the antigenic epitopes (CD133) in stem cells from human umbilical cord blood. In both studies FMR has proven to be an efficient technique for the SPIONs quantification per volume unit (in vivo) or per labeled cell (in vitro).

Shear Stress Induces Nitric Oxide-Mediated Vascular Endothelial Growth Factor Production in Human Adipose Tissue Mesenchymal Stem Cells

It has been demonstrated that human adipose tissue-derived mesenchymal stem cells (hASCs) enhance vascular density in ischemic tissues, suggesting that they can differentiate into vascular cells or release angiogenic factors that may stimulate neoangiogenesis. Moreover, there is evidence that shear stress (SS) may activate proliferation and differentiation of embryonic and endothelial precursor stem cells into endothelial cells (ECs). In this work, we investigated the effect of laminar SS in promoting differentiation of hASCs into ECs. SS (10 dyn/cm(2) up to 96 h), produced by a cone plate system, failed to induce EC markers (CD31, vWF, Flk-1) on hASC assayed by RT-PCR and flow cytometry. In contrast, there was a cumulative production of nitric oxide (determined by Griess Reaction) and vascular endothelial growth factor (VEGF; by ELISA) up to 96 h of SS stimulation ( NO(2)(-) in nmol/10(4) cells: static: 0.20 +/- 0.03; SS: 1.78 +/- 0.38, n = 6; VEGF in pg/10(4) cells: static: 191.31 +/- v35.29; SS: 372.80 +/- 46.74, n = 6, P < 0.05). Interestingly, the VEGF production was abrogated by 5 mM N(G)-L-nitro-arginine methyl ester (L-NAME) treatment (VEGF in pg/10(4) cells: SS: 378.80 +/- 46.74, n = 6; SS + L-NAME: 205.84 +/- 91.66, n = 4, P < 0.05). The results indicate that even though SS failed to induce EC surface markers in hASC under the tested conditions, it stimulated NO-dependent VEGF production.

Endothelial Nitric Oxide Genotypes and Haplotypes Are Not Associated with End-Stage Renal Disease

The identification of genetic markers associated with chronic kidney disease (CKD) may help to predict its development. Because reduced nitric oxide (NO) bioavailability and endothelial dysfunction are involved in CKD, genetic polymorphisms in the gene encoding the enzyme involved in NO synthesis (endothelial NO synthase [eNos]) may affect the susceptibility to CKD and the development of end-stage renal disease (ESRD). We compared genotype and haplotype distributions of three relevant eNOS polymorphisms (T(-786) C in the promoter region, Glu298Asp in exon 7, and 4b/4a in intron 4) in 110 healthy control subjects and 127 ESRD patients. Genotypes for the T(-786) C and Glu298Asp polymorphisms were determined by TaqMan (R) Allele Discrimination assay and real-time polymerase chain reaction. Genotypes for the intron 4 polymorphism were determined by polymerase chain reaction and fragment separation by electrophoresis. The software program PHASE 2.1 was used to estimate the haplotypes frequencies. We considered significant a probability value of p < 0.05/number of haplotypes (p < 0.05/8 = 0.0063). We found no significant differences between groups with respect to age, ethnicity, and gender. CKD patients had higher blood pressure, total cholesterol, and creatinine levels than healthy control subjects (all p < 0.05). Genotype and allele distributions for the three eNOS polymorphisms were similar in both groups (p > 0.05). We found no significant differences in haplotype distribution between groups (p > 0.05). The lack of significant associations between eNOS polymorphisms and ESRD suggests that eNOS polymorphisms may not be relevant to the genetic component of CKD that leads to ESRD.