Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anatase and rutile are titanium dioxides (TiO2) with different crystal lattices. The particles of TiO2 are considered a "nuisance" dust. It has been reported that rutile can be considered "inert". However, anatase, because of its hemolytic activity in vitro and slow lung clearance, should warrant further research regarding its toxicity. We exposed rats to an aerosol of either anatase or rutile and determined the TiO2 retention in the lung up to 132 days post exposure. Particle clearance from the lung, calculated from the retention data, was similar in both the anatase and the rutile groups with T1/2 of 51 or 53 days, respectively. In addition a pulmonary cell response test was performed on other rats. After intratracheal instillation of anatase and rutile in doses of 0.5 or 5.0 mg/rat, lung lavage was performed and the harvested cells counted. The counts of all cells, alveolar macrophages (AM), peroxidase positive AM, and polymorphonuclear leukocytes were compared. The pulmonary cell response test also yielded similar results for both types of TiO2. Thus there was no indication that the crystal lattices of TiO2 altered the biological effects of TiO2 particles. The evidence suggests that both anatase and rutile are "nuisance" dusts.
...
PMID:Biological effects and toxicity assessment of titanium dioxides: anatase and rutile. 397 97

The enzyme horseradish peroxidase is extensively inactivated by UVA exposure in the presence of TiO2, a common ingredient of sunscreens and cosmetics. The effect is attributed to the generation of reactive oxygen species, as indicated by the inactivation enhancement observed in the presence of air.
...
PMID:Enzyme inactivation by TiO2 photosensitization. 1115 86

Alterations in the hydrophobic status of particle surfaces have been suggested to modify the toxic properties of ultrafine TiO2. We investigated the acute inflammatory responses and cell damage after intratracheal instillation of surface modified (hydrophilic and hydrophobic) fine (180 nm) and ultrafine (20-30 nm) TiO2 particles 16 h at equivalent mass (1 or 6 mg) and surface doses (100, 500, 600 and 3000 cm2) in rats. Inflammatory response and most enzyme levels were significantly related to the administered surface dose. The hydrophobic surface of the TiO2 particles, achieved by methylation, induced a lower total cell number and influx of neutrophils (PMN) compared to rats instilled with the 1 mg of the untreated, fine or ultrafine TiO2 but the outcomes were not statistically significant. No differences were observed between fine/ultrafine and hydophilic/hydrophobic TiO2 at the high dose (6 mg) or surface dose over 600 cm2. The differences in BAL cellularity at the low dose were reflected in changes in the chemokine MIP-2, but no differences were seen in levels of macrophage cytokines. Considering the large influx of PMN little cell damage was seen when studying enzyme leakage in lavage fluid, although PMNs appeared to be activated as suggested by increased myeloperoxidase (MPO) activity in the lavage fluid. We conclude that the surface area rather than the hydrophobic surface determines the acute, pulmonary inflammation induced by both fine and ultrafine TiO2.
...
PMID:The surface area rather than the surface coating determines the acute inflammatory response after instillation of fine and ultrafine TiO2 in the rat. 1204 Sep 22

H2O2 generated and released from TiO2 photocatalysts to the gas phase was detected. A flow-through cell packed with TiO2-coated glass beads was irradiated with UV light, and the gas flowing out of the cell was flushed through a collecting solution containing 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulforic acid) diammonium salt (ABTS) and peroxidase. Oxidative coloration of ABTS was observed only in the absence of catalase, indicating the presence of H2O2 in the gas. The quantum yield of the H2O2 generation was estimated to be > 1 x 10(-7). The detected amount of H2O2 decreased as the TiO2 thickness decreased. H2O2 was not detected when dry air or nitrogen was used.
...
PMID:Detection of H2O2 released from TiO2 photocatalyst to air. 1511 53

The effects of nano-TiO2 (rutile) on the chloroplast aging of spinach under light were studied. The results showed that when the chloroplasts were illuminated for 1, 5, and 10 min with 500 micromol/cm2/min light intensity, respectively, the evolution oxygen rate was rapidly increased; when the chloroplasts were treated for 20, 30, and 40 min with 500 micromol/cm2/min light intensity, respectively, the evolution oxygen rate was gradually decreased. While spinach was treated with 0.25% nano-TiO2, the rate of evolution oxygen of chloroplasts in different illumination times (1, 5, 10, 20, 30, and 40 min) was higher than that of control, and when the illumination time was over 10 min, the reduction of the evolution oxygen rate was lower than that of control. It suggested that nano-TiO2 treatment could protect chloroplasts from aging for long-time illumination. The mechanism researches indicated that nano-TiO2 treatment could significantly increase the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), decrease accumulation of reactive oxygen free radicals and the level of malondialdehyde (MDA), and maintain stability of membrane structure of chloroplast under light.
...
PMID:Influences of nano-TiO2 on the chloroplast aging of spinach under light. 1593 May 94

The photovoltaic effect of titanium dioxide (TiO2) nanoparticles, induced by ultraviolet light, can greatly improve the catalytic activity of hemoglobin as a peroxidase, with the sensitivity increased nearly 3-fold and the detection limit lowered 2 orders, in contrast to the catalytic reactions in the dark, which indicates a possible method to tune the properties of proteins for development of photocontrolled protein-based biosensors.
...
PMID:Hemoglobin-based hydrogen peroxide biosensor tuned by the photovoltaic effect of nano titanium dioxide. 1615 49

Titanate nanotubes (TNT) were proven to be efficient support matrixes for the immobilization of myoglobin (Mb). A comparative study was performed using the corresponding analogue, nanocrystalline anatase TiO2 (TNP). UV-visible absorption and FT-IR spectra show that Mb was not obviously denatured in TNT film in contrast to the significant denaturation of Mb in TNP film. Cyclic voltammetry and square wave voltammetry measurements were carried out using the Mb-TNT or Mb-TNP cast film-covered basal plane pyrolytic graphite electrode. The Mb-TNT film gave a well-defined, nearly reversible redox couple with the apparent formal peak potential (Ep) of -0.239 V (vs Ag/AgCl) in pH 5.5 buffer, whereas a relatively smaller, quais-reversible redox pair with Ep of -0.263 V was observed for the Mb-TNP film. The amounts of electroactive Mb in TNT film and TNP film were 15 and 10%, respectively. Moreover, the Mb-TNT film exerted facile direct electron transfer with the apparent heterogeneous electron-transfer rate constant (kET) of 86+/-7 s-1, almost 4 times the 22+/-5 s-1 value for the Mb-TNP membrane and higher than other Mb-entrapped films reported. Additionally, the Mb-TNT film demonstrates good electrocatalytic reduction of hydrogen peroxide with a detection limit of 0.6 microM, much lower than the 3.0 microM value for the Mb-TNP electrode and other Mb-related film-modified electrodes reported so far. The Mb-TNT film exhibits higher peroxidase-like activity with the apparent Michaelis-Menton constant (KM) of 140 microM, significantly lower than the 1300 microM value for the Mb-TNP film. The functional hydroxyl group and the surface charge as well as tubular morphology of TNT are important factors to stabilize the bound protein.
...
PMID:Direct electrochemistry of myoglobin in titanate nanotubes film. 1635 Nov 57

The epidemiologic association between pulmonary exposure to ambient particulate matter (PM) and cardiovascular dysfunction is well known, but the systemic mechanisms that drive this effect remain unclear. We have previously shown that acute pulmonary exposure to PM impairs or abolishes endothelium-dependent arteriolar dilation in the rat spinotrapezius muscle. The purpose of this study was to further characterize the effect of pulmonary PM exposure on systemic microvascular function and to identify local inflammatory events that may contribute to these effects. Rats were intratracheally instilled with residual oil fly ash (ROFA) or titanium dioxide at 0.1 or 0.25 mg/rat 24 hr before measurement of pulmonary and systemic microvascular responses. In vivo microscopy of the spinotrapezius muscle was used to study systemic arteriolar responses to intraluminal infusion of the Ca2+ ionophore A23187 or iontophoretic abluminal application of the adrenergic agonist phenylephrine (PHE). Leukocyte rolling and adhesion were quantified in venules paired with the studied arterioles. Histologic techniques were used to assess pulmonary inflammation, characterize the adherence of leukocytes to systemic venules, verify the presence of myeloperoxidase (MPO) in the systemic microvascular wall, and quantify systemic microvascular oxidative stress. In the lungs of rats exposed to ROFA or TiO2, changes in some bronchoalveolar lavage markers of inflammation were noted, but an indication of cellular damage was not found. In rats exposed to 0.1 mg ROFA, focal alveolitis was evident, particularly at sites of particle deposition. Exposure to either ROFA or TiO2 caused a dose-dependent impairment of endothelium-dependent arteriolar dilation. However, exposure to these particles did not affect microvascular constriction in response to PHE. ROFA and TiO2 exposure significantly increased leukocyte rolling and adhesion in paired venules, and these cells were positively identified as polymorphonuclear leukocytes (PMNLs). In ROFA- and TiO2-exposed rats, MPO was found in PMNLs adhering to the systemic microvascular wall. Evidence suggests that some of this MPO had been deposited in the microvascular wall. There was also evidence for oxidative stress in the microvascular wall. These results indicate that after PM exposure, the impairment of endothelium-dependent dilation in the systemic microcirculation coincides with PMNL adhesion, MPO deposition, and local oxidative stress. Collectively, these microvascular observations are consistent with events that contribute to the disruption of the control of peripheral resistance and/or cardiac dysfunction associated with PM exposure.
...
PMID:Systemic microvascular dysfunction and inflammation after pulmonary particulate matter exposure. 1650 65

We have shown that pulmonary nanoparticle exposure impairs endothelium dependent dilation in systemic arterioles. However, the mechanism(s) through which this effect occurs is/are unclear. The purpose of this study was to identify alterations in the production of reactive species and endogenous nitric oxide (NO) after nanoparticle exposure, and determine the relative contribution of hemoproteins and oxidative enzymes in this process. Sprague-Dawley rats were exposed to fine TiO2 (primary particle diameter approximately 1 microm) and TiO2 nanoparticles (primary particle diameter approximately 21 nm) via aerosol inhalation at depositions of 4-90 microg per rat. As in previous intravital experiments in the spinotrapezius muscle, dose-dependent arteriolar dilations were produced by intraluminal infusions of the calcium ionophore A23187. Nanoparticle exposure robustly attenuated these endothelium-dependent responses. However, this attenuation was not due to altered microvascular smooth muscle NO sensitivity because nanoparticle exposure did not alter arteriolar dilations in response to local sodium nitroprusside iontophoresis. Nanoparticle exposure significantly increased microvascular oxidative stress by approximately 60%, and also elevated nitrosative stress fourfold. These reactive stresses coincided with a decreased NO production in a particle deposition dose-dependent manner. Radical scavenging, or inhibition of either myeloperoxidase or nicotinamide adenine dinucleotide phosphate oxidase (reduced) oxidase partially restored NO production as well as normal microvascular function. These results indicate that in conjunction with microvascular dysfunction, nanoparticle exposure also decreases NO bioavailability through at least two functionally distinct mechanisms that may mutually increase local reactive species.
...
PMID:Pulmonary nanoparticle exposure disrupts systemic microvascular nitric oxide signaling. 1927 16

We report on a novel amperometric biosensor for detecting phenolic compounds based on the co-immobilization of horseradish-peroxidase (HRP) and methylene blue (MB) with chitosan on Au-modified TiO2 nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then coated onto the TiO2 nanotubes by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO2 nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and amperometry were used to study the proposed electrochemical biosensor. The effect of pH, applied electrode potential and the concentration of H(2)O(2) on the sensitivity of the biosensor have been systemically investigated. The performance of the proposed biosensor was tested using seven different phenolic compounds, showing very high sensitivity; in particular, the linearity of the biosensor for the detection of 3-nitrophenol was observed from 3 x 10(-7) to 1.2 x 10(-4)M with a detection limit of 9 x 10(-8)M (based on the S/N=3).
...
PMID:A novel amperometric biosensor for the detection of nitrophenol. 1937 50


1 2 3 4 Next >>

---