Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PEROXIDES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMed2004

Effect of fluoride and 10% carbamide peroxide on the surface roughness of low-fusing and ultra low-fusing porcelain.

STATEMENT OF PROBLEM: The effect of repeated applications of fluoride solutions and 10% carbamide peroxide on the surface roughness of newer dental porcelains is not completely known. PURPOSE: The purpose of this study was to compare the surface roughness of 3 different porcelains when exposed to 2 fluoride solutions, a 10% solution of carbamide peroxide, and distilled water. MATERIAL AND METHODS: Forty discs (10-mm diameter, 2 mm thick) were made of each of the following porcelains: feldspathic porcelain (Ceramco II), low-fusing porcelain (Finesse), and an aluminous porcelain (All-Ceram). Each disc was abraded with a medium-grit diamond bur and auto-glazed. One side of each disc was abraded with a diamond bur and polished using a porcelain polishing kit to simulate a chairside adjustment and polishing. The discs (10 specimens/group) were immersed in 1.23% APF, 0.4% stannous fluoride, 10% carbamide peroxide, and distilled water for 50 seconds (control). The discs in the 10% carbamide peroxide solution were immersed for 48 hours. The surface of each disc was evaluated with surface profilometry (0.1 mm/s speed, 600-microm range). The data were analyzed by factorial analysis of variance and a Tukey multiple comparison test, (alpha=.05). RESULTS: The data showed that the acidulated phosphate fluoride etched the auto-glazed surface of all 3 porcelains. For Finesse specimens, the mean Ra values for the auto-glazed surface were significantly higher than that of the control after immersion in 1.23% APF (mean Ra 0.3 +/- 0.06 microm, P<.031). All-Ceram auto-glazed surface specimens had a significantly higher mean Ra value when immersed in the 3 solutions than the control (1.23% APF, 0.4% stannous fluoride, and 10% carbamide peroxide, 0.245 +/- 0.115 microm, 0.22 +/- 0.104 microm, 0.22 +/- 0.04 microm, respectively; P<.002). Ceramco II specimens were affected by all 3 solutions, with the auto-glazed surface having higher Ra values (1.23% APF, 0.4% stannous fluoride, and 10% carbamide peroxide, with mean Ra values of 0.35 +/- 0.1 microm, 0.26 +/- 0.08 microm, and 0.24 +/-.0.05 microm, respectively, P=.001). Immersion in the 3 solutions had no effect on the polished surfaces of all-ceramic specimens tested. CONCLUSION: Prior to the use of fluoride and 10% carbamide peroxide, dentists should ascertain the type of porcelain restoration present to prevent a roughened surface from occurring.

Acidulated Phosphate Fluoride↗
PubMed1988

Evidence for mitochondrial DNA damage by lipid peroxidation.

When mitochondria of rat liver were incubated in an in vitro system containing NADPH and ferrous chloride, marked lipid peroxidation occurred, as evidenced by the evolution of malonic dialdehyde. DNA isolated from these peroxidized mitochondrial preparations had completely different electrophoretic mobility than DNA isolated from mitochondria protected from peroxidation. Scavengers of superoxide anion, hydrogen peroxide and hydroxyl radicals offered no protection against either lipid peroxidation or DNA damage. However, alpha-tocopherol protected against both lipid peroxidation and damage to the mitochondrial genome. These results support the hypothesis that lipid peroxidation can mediate DNA damage.

Animals↗
PubMed1996

Lipid peroxidation and antioxidants in normal and pre-eclamptic pregnancies.

Lipid peroxidation has been suggested as a pathogenetic factor of pre-eclampsia. In this study we measured lipid peroxidation products and the counteracting antioxidant functions in maternal serum and placental tissue in normal pregnancy and pre-eclampsia. Placentae and maternal serum from 15 normal and 15 pre-eclamptic pregnancies were collected. Lipid peroxidation was measured as peroxidation potential, thiobarbituric acid reacting substances (TBARS) and conjugated diene onuble bonds. The antioxidative capacity was measured as the activity of superoxide dismutase, glucose 6-phosphate-dehydrogenase, glutathione peroxidase and glutathione transferase and the concentration of placental vitamin E. Placental lipid peroxidation was higher in pre-eclampsia than in normal pregnancy, when measured by peroxidation potential and TBARS (P = 0.002 and P = 0.027, respectively). The activity of placental superoxide dismutase (P = 0.003) and glucose 6-phosphate-dehydrogenase (P = 0.019) was significantly lower in pre-eclampsia than in normal pregnancy. There were no significant differences in the activity of glutathione peroxidase, glutathione-S-transferase or vitamin E level between the study groups. The peroxyl radical trapping capacity (TRAP) was higher (P = 0.013) in the serum of pre-eclamptic than control patients. Lipid peroxidation is increased and the activity of antioxidant enzymes superoxide dismutase and glucose 6-phosphate-dehydrogenase are decreased in pre-eclamptic placenta. The TRAP is high in the serum of pre-eclamptic patients.

Adult↗
PubMed2003

Hydrogen-peroxide-induced heme degradation in red blood cells: the protective roles of catalase and glutathione peroxidase.

Catalase and glutathione peroxidase (GSHPX) react with red cell hydrogen peroxide. A number of recent studies indicate that catalase is the primary enzyme responsible for protecting the red cell from hydrogen peroxide. We have used flow cytometry in intact cells as a sensitive measure of the hydrogen-peroxide-induced formation of fluorescent heme degradation products. Using this method, we have been able to delineate a unique role for GSHPX in protecting the red cell from hydrogen peroxide. For extracellular hydrogen peroxide, catalase completely protected the cells, while the ability of GSHPX to protect the cells was limited by the availability of glutathione. The effect of endogenously generated hydrogen peroxide in conjunction with hemoglobin autoxidation was investigated by in vitro incubation studies. These studies indicate that fluorescent products are not formed during incubation unless the glutathione is reduced to at least 40% of its initial value as a result of incubation or by reacting the glutathione with iodoacetamide. Reactive catalase only slows down the depletion of glutathione, but does not directly prevent the formation of these fluorescent products. The unique role of GSHPX is attributed to its ability to react with hydrogen peroxide generated in close proximity to the red cell membrane in conjunction with the autoxidation of membrane-bound hemoglobin.

Catalase↗
PubMed1997

Isolation and characterization of a multiple peroxide resistant mutant from Xanthomonas campestris pv. phaseoli.

We have isolated a spontaneous multiple peroxide resistant Xanthamonas campestris pv. phaseoli mutant (XpHr). In the presence of peroxides, the mutant had a higher growth rate than the parent. It also had a greater than 100-fold increase in resistance levels to H2O2 killing but only slightly more resistance to tert-butyl hydroperoxide killing. Increases in activity were detected for the peroxide scavenging enzymes catalase (100-fold) and AhpC (over 30-fold). Also observed was cross-resistance to thermal killing; however, no cross-resistance to other oxidants or chemicals was found. Analysis of protein profiles revealed that proteins with molecular masses of 22 and 58 kDa were accumulated while proteins of 29, 33 and 41 kDa were depressed in the mutant. These results indicate that the mutant may have defect(s) in peroxide regulation, which resulted in high constitutive expression of peroxide scavenging enzymes. Nevertheless, the mutant retained growth phase dependent regulation of peroxide killing. The mutant should be useful in unravelling the nature of a complex peroxide stress regulon.

Bacterial Proteins↗
PubMed1997

Influence of long-term supplementation with alpha-linolenic acid on myocardial lipid peroxidation and antioxidative capacity in spontaneously hypertensive rats.

The ischaemic vulnerability of the heart of spontaneously hypertensive rats (SHR) is enhanced after feeding an alpha-linolenic acid (LNA) enriched diet. Because oxygen radical-induced reactions (e.g. lipid peroxidation) are involved in the ischaemic damage, an increased susceptibility of the SHR heart to such damaging reactions might be the reason. As a sign of the enhanced susceptibility to lipid peroxidation of LNA-fed SHR, we found (measured as TBARS) higher plasma and heart lipid peroxide levels (3.84 +/- 0.50 micromol/l vs 2.98 +/- 0.78 micromol/l and 507 +/- 127 nmol/g prot. vs 215 +/- 80 nmol/g prot., respectively) after feeding LNA. Using Fe2+/Vit. C to induce lipid peroxidation in myocardial tissue homogenates, we demonstrated the enhanced susceptibility to lipid peroxidation of the LNA-fed SHR heart (68 +/- 12 nmol/min x g prot. vs 40 +/- 8 nmol/min x g prot.) also in vitro. The myocardial enrichment of n-3 polyunsaturated fatty acids (PUFA) resulting in a higher peroxidation index (PI 227 vs. 170) and the loss in myocardial activities of the antioxidative enzymes (SOD: 76 +/- 24 U x 10(3)/g prot. vs 235 +/- 150 U x 10(3)/g prot.; GSH-Px: 32 +/- 5 U/g prot. vs 110 +/- 30 U/g prot.) by feeding LNA could be the cause of the increase in myocardial susceptibility to lipid peroxidation of PUFA supplemented SHR.

Animals↗
PubMed2002

Concentration effects in myoglobin-catalyzed peroxidation of linoleate.

The concentration of the free fatty acid anion linoleate was found to be important for the pro-oxidative activity of metmyoglobin, MbFe(III), and for mixtures of metmyoglobin and hydrogen peroxide, MbFe(III)/H(2)O(2), to yield perferrylmyoglobin, (*)MbFe(IV)=O, whereas for ferrylmyoglobin, MbFe(IV)=O, no concentration effect was noted as studied in linoleate emulsions (pH 7.4 and 25 degrees C). Determination of conjugated dienes using second-derivative absorption spectroscopy, changes in Soret band absorbance, and spin-trapping ESR spectroscopy with alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone (POBN) as the spin trap were used to evaluate the pro-oxidative activity of myoglobins. At a linoleate (LA)/heme protein (HP) ratio of 100, no MbFe(III)-induced linoleate peroxidation was observed, as MbFe(III) was converted to its non-pro-oxidative low-spin derivative, hemichrome, independently of the presence of H(2)O(2). At higher LA/HP ratios, linoleate peroxidation was initiated by the addition of MbFe(III), both in the presence and in the absence of H(2)O(2). This proceeded with denaturation of MbFe(III), as followed by changes in Soret absorption band, which most probably release or expose the heme group to the environment and thereby permit hematin-induced lipid peroxidation. The obtained results show that the mechanism by which MbFe(IV)=O initiates linoleate peroxidation is different from MbFe(III)- and MbFe(III)/H(2)O(2)-initiated linoleate peroxidation. The shift in mechanism between heme protein cleavage of lipid hydroperoxides and hematin-induced lipid peroxidation is discussed in relation to oxidative progress in biological systems and muscle-based foods.

Electron Spin Resonance Spectroscopy↗
PubMed2002

Doxorubicin-dependent reduction of ferrylmyoglobin and inhibition of lipid peroxidation: implications for cardiotoxicity of anticancer anthracyclines.

Lipid peroxidation has been proposed to mediate cardiotoxicity induced by doxorubicin (DOX) and other anticancer anthracyclines; however, there have been reports showing that DOX can also inhibit lipid peroxidation. Here we characterized the effects of DOX on the oxo-ferryl moiety [Fe(IV)=O, Mb(IV)] of H(2)O(2)-activated myoglobin, a lipid oxidant likely formed in the heart during treatment with DOX. Mb(IV) was formed in vitro by reacting 100 microM H(2)O(2) with 50 microM horse heart metmyoglobin (Mb(III)). Spectral studies showed that DOX reduced Mb(IV) to Mb(III), half-maximal regeneration of Mb(III) occurring at approximately 18 microM DOX. Comparisons between DOX, its aglycone doxorubicinone, and other approved or investigational anthracyclines or model compounds (daunorubicin, idarubicin, aclarubicin, and naphthazarin), showed that DOX reduced Mb(IV) through the hydroquinone moiety of its tetracyclic ring. DOX inhibited Mb(IV)-dependent peroxidation of arachidonic acid, suppressing the formation of thiobarbituric acid-reactive substances with an IC(50) of approximately 18 microM. Lipid peroxidation was inhibited also by the hydroquinone-containing daunorubicin and idarubicin but not by the hydroquinone-deficient aclarubicin; moreover, neither simple hydroquinone nor other known Mb(IV) reductants (ascorbate, glutathione, and ergothioneine) reached measurable IC(50)s in a micromolar range. DOX-dependent inhibition of lipid peroxidation correlated with its ability to reduce Mb(IV) to Mb(III) in competition with arachidonic acid (r = 0.83, P = 0.029); it did not correlate with its ability to scavenge other free radical species [like e.g., peroxyl radicals generated through the thermal decomposition of 2,2'-azo-bis(2-amidinopropane)]. DOX reduced Mb(IV) and inhibited lipid peroxidation also when H(2)O(2), Mb(III) and arachidonic acid were reacted in cytosol of human myocardial biopsies, a model developed to predict the cardiotoxic mode of action of DOX in patients. These results illustrate "antioxidant" properties of DOX, mediated by reduction of Mb(IV) to Mb(III), and cast doubts on lipid peroxidation as a causative mechanism of anthracycline-induced cardiotoxicity.

Animals↗
PubMed1998

Effects of peroxide on endothelial nitric oxide synthase in coronary arteries.

Reactive oxygen species (ROS) are produced in ischemia and reperfusion. Since endothelial nitric oxide synthase (eNOS) is key to the endothelium-dependent vasodilation, we examined the effects of peroxide on this enzyme. We treated cells cultured from pig coronary artery endothelium with different concentrations of hydrogen peroxide, washed them, solubilized them and measured NOS activity by arginine to citrulline conversion. Hydrogen peroxide inhibited the eNOS activity with an IC50 value of 0.85 +/- 0.39 mM. In another experiment, we perfused arteries with solutions containing 0 or 1 mM hydrogen peroxide, washed them, removed the endothelium using a cotton swab, centrifuged and solubilized the endothelium and monitored its NOS activity. Hydrogen peroxide (1 mM) did not affect the NOS activity significantly (p > 0.05) in this assay. We conclude that the inactivation of eNOS by hydrogen peroxide does not play a major role in the ischemia-reperfusion damage because the peroxide concentrations attained during ischemia-perfusion are much lower than those affecting the eNOS activity.

Animals↗
PubMed1993

Formation of peroxides in amino acids and proteins exposed to oxygen free radicals.

Dilute aqueous solutions of BSA or lysozyme gave positive tests for peroxides after exposure to reactive oxygen species. The reactive species were generated by gamma-irradiation, reduction of H2O2 with Fe2+ ions or thermal decomposition of an azo compound. Peroxides were assayed by an iodometric method. Identification of the new groups as hydroperoxides was confirmed by their ability to oxidize a range of compounds and by the kinetics of their reaction with iodide. The hydroperoxide groups were bound to the proteins and their yields (G values) corresponded to 1.2 -OOH groups per 100 eV of radiation energy absorbed for BSA, and 0.8 for lysozyme. The oxygen free radicals effective in protein peroxidation were the hydroxyl and organic peroxyl, but not superoxide or its protonated form. The efficiency of BSA peroxidation initiated by the hydroxyl radicals was 40%. Protein peroxides decayed spontaneously with a half-life of about 1.5 days at 20 degrees C. Exposure of the common amino acids to hydroxyl free radicals showed that six of them (glutamate, isoleucine, leucine, lysine, proline and valine) were peroxidized with similar efficiency to the proteins, whereas the rest were inert or much less susceptible. These results suggest that some proteins may be peroxidized by a variety of agents in vivo and that their subsequent reactions with protective agents, such as ascorbate or glutathione, may decrease the antioxidant potential of cells and tissues.

Amino Acids↗
PubMed2003

Relationship between tissue lipid peroxidation and peroxidizability index after alpha-linolenic, eicosapentaenoic, or docosahexaenoic acid intake in rats.

In a previous study, we found that the extent of dietary n-3 docosahexaenoic acid (DHA)-stimulated tissue lipid peroxidation was less than expected from the relative peroxidizability index of the total tissue lipids in rats with adequate vitamin E nutritional status. This suppression of lipid peroxidation was especially prominent in the liver. To elucidate whether this phenomenon was unique to DHA, we compared the peroxidation effects of n-3 alpha-linolenic acid (alpha-LN) and n-3 eicosapentaeonic acid (EPA) with those of DHA in rats. Either alpha-LN (8.6 % of total energy), EPA (8.2 %), or DHA (8.0 %) and one of two levels of dietary vitamin E (7.5 and 54 mg/kg diet) were fed to rats for 22 d. Levels of conjugated diene, chemiluminescence emission and thiobarbituric acid (TBA)-reactive substance in the liver, kidney, and testis were determined as indicators of lipid peroxidation. In rats fed the DHA diet deficient in vitamin E (7.5 mg/kg diet), TBA values in the liver, kidney, and testis correlated well with the tissues' relative peroxidizability indices. In rats fed the alpha-LN diet with an adequate level of vitamin E (54 mg/kg diet), a close association between relative peroxidizability indices and lipid peroxide levels was observed in all the tissues analysed. However, in rats fed either the EPA diet or the DHA diet with an adequate level of vitamin E, the extent of lipid peroxidation in each tissue was less than expected from the relative peroxidizability index. This suppression was particularly marked in the liver. We concluded that suppression of lipid peroxidation below the relative peroxidizability index was not unique to DHA, but was also seen with EPA, which has five double bonds, in rats with adequate vitamin E nutritional status, but not with alpha-LN, which has three double bonds.

Animals↗
PubMed2003

Dietary docosahexaenoic acid-induced production of tissue lipid peroxides is not suppressed by higher intake of ascorbic acid in genetically scorbutic Osteogenic Disorder Shionogi/Shi-od/od rats.

In previous studies, we showed that docosahexaenoic acid (DHA) ingestion enhanced the susceptibility of rat liver and kidney to lipid peroxidation, but did not increase lipid peroxide formation to the level expected from the relative peroxidizability index (P-index) of the total tissue lipids. The results suggested the existence of some suppressive mechanisms against DHA-induced tissue lipid peroxide formation, as increased tissue ascorbic acid (AsA) and glutathione levels were observed. Therefore, we focused initially on the role of AsA for the suppressive mechanisms. For this purpose, we examined the influence of different levels of dietary AsA (low, moderate, high and excessive levels were 100, 300 (control), 600 and 3000 mg/kg diet respectively) on the tissue lipid peroxide and antioxidant levels in AsA-requiring Osteogenic Disorder Shionogi/Shi-od/od (ODS) rats fed DHA (6.4 % total energy) for 32 or 33 d. Diets were pair-fed to the DHA- and 100 mg AsA/kg diet-fed group. We found that the lipid peroxide concentrations of liver and kidney in the DHA-fed group receiving 100 mg AsA/kg diet were significantly higher or tended to be higher than those of the DHA-fed groups with AsA at more than the usual control level of 300 mg/kg diet. Contrary to this, the liver alpha-tocopherol concentration was significantly lower or tended to be lower in the DHA and 100 mg AsA/kg diet-fed group than those of the other DHA-fed groups. However, tissue lipid peroxide formation and alpha-tocopherol consumption were not suppressed further, even after animals received higher doses of AsA. The present results suggest that higher than normal concentrations of tissue AsA are not necessarily associated with the suppressive mechanisms against dietary DHA-induced tissue lipid peroxide formation.

Animals↗
PubMed1998

Oxidative modification of human low-density lipoprotein by horseradish peroxidase in the absence of hydrogen peroxide.

Heme-peroxidases, such as horseradish peroxidase (HRP), are among the most popular catalysts of low density lipoprotein (LDL) peroxidation. In this model system, a suitable oxidant such as H2O2 is required to generate the hypervalent iron species able to initiate the peroxidative chain. However, we observed that traces of hydroperoxides present in a fresh solution of linoleic acid can promote lipid peroxidation and apo B oxidation, substituting H2O2. Spectral analysis of HRP showed that an hypervalent iron is generated in the presence of H2O2 and peroxidizing linoleic acid. Accordingly, careful reduction of the traces of linoleic acid lipid hydroperoxide prevented formation of the ferryl species in HRP and lipid peroxidation. However, when LDL was oxidized in the presence of HRP, the ferryl form of HRP was not detectable, suggesting a Fenton-like reaction as an alternative mechanism. This was supported by the observation that carbon monoxide, a ligand for the ferrous HRP, completely inhibited peroxidation of LDL. These results are in agreement with previous studies showing that myoglobin ferryl species is not produced in the presence of phospholipid hydroperoxides, and emphasize the relevance of a Fenton-like chemistry in peroxidation of LDL and indirectly, the role of pre-existing lipid hydroperoxides.

Apolipoproteins B↗
PubMed2004

Influence of alpha-lipoic acid on lipid peroxidation and antioxidant defence system in blood of insulin-resistant rats.

BACKGROUND: High fructose feeding induces insulin resistance and hyperinsulinaemia in rats. A role for oxidative stress in the occurrence of insulin resistance has been suggested by several workers. AIM: The aim of this study was to investigate the effect of alpha-lipoic acid (LA) on oxidant-antioxidant balance in rats fed on a high-fructose diet that showed characteristic features of insulin resistance. METHODS: Male Wistar rats weighing 150-170 g were divided into seven groups. The control group received the control diet containing starch. The fructose group was given a high-fructose diet (>60% of total calories). The third and fourth groups were given fructose diet and were administered two different doses of LA at a low dose (35 mg/kg body weight) and high dose (70 mg/kg body weight) using olive oil as vehicle. The fifth group received fructose diet and olive oil. The sixth group received control diet and was administered LA (70 mg/kg body weight). And, the seventh group received the control diet and olive oil. Products of lipid peroxidation and activities of enzymic antioxidants, namely superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase, in red blood cells were assayed. Levels of non-enzymic antioxidants alpha-tocopherol, ascorbic acid and reduced glutathione were determined in plasma. RESULTS: The levels of lipid peroxides, diene conjugates and thiobarbituric acid-reactive substances were significantly higher in fructose-fed rats. Inadequate antioxidant system was observed in high-fructose-fed rats. Treatment of fructose rats mitigated the imbalance between peroxidation and antioxidant defence system at both the doses tested. Increases in glucose, triglycerides, free fatty acids, insulin and insulin resistance were observed in fructose-fed rats. LA administration prevented these alterations and improved insulin sensitivity. Significant positive correlations were obtained between insulin resistance and lipid peroxidation indices. CONCLUSIONS: Increased lipid peroxidation and deficient antioxidant system are observed in high-fructose-fed rats. LA administration preserves the antioxidant system and lowers lipid peroxidation. The findings suggest an interrelationship between lipid peroxidation and insulin resistance.

Animals↗
PubMed1982

Peroxidation, vitamin E, and sickle-cell anemia.

In summary, we propose the following scheme (Figure 5) to describe the role of peroxidation in the pathophysiology of SCA. Sickle erythrocytes are more susceptible to peroxidation than are normal erythrocytes. This increased susceptibility to peroxidation is, in part, due to decreased blood vitamin E levels and abnormal membrane phospholipid organization induced by sickling. The peroxidative damage of sickle erythrocytes may accelerate or contribute to loss of cell deformability and to chronic hemolysis. Peroxidative damage can produce abnormal cellular properties, such as potassium leak and reduced filterability, and contribute to formation of ISCs. Increased red cell rigidity can initiate episodes of capillary obstruction, leading to vasoocclusive painful crises and to tissue infarction. Liver dysfunction as well as increased production of bilirubin secondary to hemolysis could result in bile sludging and decreased secretion of bile salts into the intestinal lumen. Reduced bile salt secretion leads to partial fat and vitamin E malabsorption. Vitamin E deficiency enhances red cell susceptibility to peroxidation and promotes a vicious cycle in SCA. Although we have not studied factors that might initiate peroxidative damage, sickle hemoglobin and excess body iron should be considered as potential sources. Our studies suggest that vitamin E supplementation to sickle-cell patients could be of clinical benefit.

Anemia, Sickle Cell↗
PubMed1999

Peroxide-induced membrane blebbing in endothelial cells associated with glutathione oxidation but not apoptosis.

Cells under oxidative stress induced by peroxides undergo functional and morphological changes, which often resemble those observed during apoptosis. Peroxides, however, also cause the oxidation of intracellular reduced glutathione (GSH). We investigated the relation between these peroxide-induced effects by using human umbilical vein endothelial cells (HUVEC) and two HUVEC-derived cell lines, ECRF24 and ECV304. With HUVEC, tert-butyl hydroperoxide (tBH) or hydrogen peroxide application in the presence of serum induced, in a dose-dependent way, reorganization of the actin cytoskeleton, membrane blebbing, and nuclear condensation. These processes were accompanied by transient oxidation of GSH. With ECRF24 cells, this treatment resulted in less blebbing and a shorter period of GSH oxidation. However, repeated tBH addition increased the number of blebbing cells and prolonged the period of GSH oxidation. ECV304 cells were even more resistant to peroxide-induced bleb formation and GSH oxidation. Inhibition of glutathione reductase activity potentiated the peroxide-induced blebbing response in HUVEC and ECRF24 cells, but not in ECV304 cells. Neither membrane blebbing nor nuclear condensation in any of these cell types was due to apoptosis, as evidenced by the absence of surface expression of phosphatidylserine or fragmentation of DNA, even after prolonged incubations with tBH, although high tBH concentrations lead to nonapoptotic death. We conclude that, in endothelial cells, peroxide-induced cytoskeletal reorganization and bleb formation correlate with the degree of GSH oxidation but do not represent an early stage of the apoptotic process.

Apoptosis↗
PubMed1995

Role of lipid peroxidation in H2O2-induced renal epithelial (LLC-PK1) cell injury.

The exact sequence of events or mechanisms by which H2O2 induces renal cell injury remains undetermined. Specifically, whether the attendant lipid peroxidation is a cause or an effect remains unclear. Employing H2O2 and LLC-PK1 cells, we tested the hypothesis that lipid peroxidation is a seminal event and that its inhibition is cytoprotective. In a time course study, lipid peroxidation (thiobarbituric acid reaction) and degradation (release of [3H]arachidonic acid) preceded H2O2-induced cytolysis (51Cr and lactate dehydrogenase release). The role of preceding lipid peroxidation in cytolysis was examined with lipid radical scavengers. alpha-Tocopherol and lazaroid compound 2-methyl aminochroman dose-dependently inhibited H2O2-induced lipid peroxidation and prevented cytolysis. 2-Methyl aminochroman cytoprotection was associated with blockade of lipid degradation. 21-Aminosteroid, another lazaroid, also inhibited lipid peroxidation and prevented cytolysis. These findings provide evidence that lipid alterations contribute to H2O2-mediated LLC-PK1 injury and, for the first time, demonstrate the potency of lazaroids in a renal cell line. In vivo studies with lazaroids may define the role of lipid peroxidation in acute renal injury models.

Amitrole↗
PubMedDate not supplied

Susceptibility of enamel surfaces to demineralization after application of fluoridated carbamide peroxide gels.

The aim of the present study was to evaluate the effect of experimental, fluoridated carbamide peroxide gels on formation of erosively induced demineralization of enamel. Seventy-five bovine enamel specimens were polished for microhardness determination and evenly distributed among 5 groups (A-E). The specimens were treated with 10% carbamide peroxide gel (8 h) and subjected twice to remineralization for 2 h in artificial saliva and demineralisation for 90 s in 1% citric acid, pH 2.2. The cycles of treatment with carbamide peroxide and twofold re- and demineralization were repeated three times. The carbamide peroxide gels were different in pH and fluoride content. Gel A (pH 7.0) and gel B (pH 5.7) were fluoridated (0.5% F), gel C (pH 7.0) and gel D (pH 5.7) were not fluoridated. In control group E the samples were not treated with a gel, but stored in 100% humidity for 8 h instead. Knoop microhardness of the specimens was assessed directly after polishing, and after each carbamide peroxide treatment and demineralization. All specimens showed a loss of microhardness at the end of the experiment. After 3 days, the controls revealed a significantly lower hardness loss compared to the specimens treated with the carbamide peroxide gels. Surface softening was significantly lower for the specimens of group A compared to the remaining groups (B-D), which were not significantly different among each other. It is concluded that treatment with either fluoridated or unfluoridated carbamide peroxide gels, at either neutral and acidic pH, renders enamel more susceptible to demineralization. Use of a fluoridated neutral gel decreases the degree of surface softening compared to the other gels investigated.

Analysis of Variance↗