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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a previous study, we reported that fragment Bb of bovine complement factor B activated bovine monocytes, as demonstrated by the uptake of 3H-deoxyglucose. In the present study, the effects of Bb on the production of superoxide anion and hydrogen peroxide by bovine monocytes was investigated. The production of superoxide was measured by the superoxide dismutase inhibitable reduction of cytochrome c. The change in absorbance was determined by a spectrophotometer at a wavelength of 550 nm. Hydrogen peroxide production was measured by the horse-radish peroxidase-dependent oxidation of phenol red. The resulting color change was measured by a spectrophotometer at a wavelength of 620 nm. Fragment Bb (20 micrograms/mL) induced the generation of 0.96 +/- 0.2 (mean +/- SEM) nanomoles of superoxide/2.5 x 10(5) monocytes at 5 min. The production of superoxide peaked at 15 min (1.24 +/- 0.3 nanomoles). The production of hydrogen peroxide was also rapid: 0.195 +/- 0.05 nanomoles/2.5 x 10(5) monocytes at 5 min with a peak at 15 min (0.250 +/- 0.04 nanomoles). These observations show that fragment Bb, which has serine protease activity, induces bovine monocytes to generate reactive oxygen intermediates such as superoxide and hydrogen peroxide.
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PMID:Bb fragment of bovine complement factor B: stimulation of the oxidative burst in bovine monocytes. 217 93

Besides their cytotoxic effects, Tumor necrosis factor (TNF) and Lymphotoxin (LT) were shown to modulate distinct PMN functions. Therefore, in the present study we evaluated the effect of recombinant human TNF and LT on the oxidative metabolism of isolated human PMN. In addition ultrastructural changes upon stimulation were evaluated. For detection of granulocyte activation different assay systems were used: 1) lucigenin-dependent chemiluminescence (CL), 2) superoxide-dismutase (SOD) inhibitable cytochrome C-reduction (superoxide), 3) horseradish peroxidase-mediated oxidation of phenol red (hydrogen peroxide), 4) release of myeloperoxidase, 5) ultrastructural detection of hydrogen peroxide-production, 6) scanning and transmission electron microscopy (SEM and TEM). TNF at concentrations as low as 10(-3) U/ml induced a distinct CL response, whereas LT appeared to be less active. PMN preincubated with TNF or LT for 150 min were completely deactivated to renewed stimulation with TNF, LT, and with GM-CSF, but responded to other triggers of the oxidative burst. Moreover, stimulation with f-met-leu-phe resulted in an enhanced response after preincubation with TNF or LT. The CL response was significantly inhibited by SOD, but not by catalase, D-mannitol, and DMTU, suggesting that mainly .O2- is responsible for the CL signal. The effect on PMN could be completely blocked by antibodies to TNF. Significant release of reactive oxygen species upon stimulation with TNF was also demonstrated by cytochrome C reduction and by detection of H2O2 using functional and ultrastructural assays. Only minimal amounts of peroxidase were released. Activation of PMN could be visualized by SEM and TEM. After addition of TNF at concentrations as low as 10(-1) U/ml PMN adhered to the substratum and were typically polarized within 15 min. Stimulation with LT resulted in comparable results, but based on its biologic activity in the cytotoxicity assay LT, in comparison to TNF, was significantly less active. Based on the data presented LT and, particularly, TNF appear to be potent activators of PMN oxidative metabolism.
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PMID:Human tumor necrosis factor is a potent activator of the oxidative metabolism in human polymorphonuclear neutrophilic granulocytes: comparison with human lymphotoxin. 253 65

We investigated the activity and the content of copper and zinc-containing superoxide dismutase (SOD) and superoxide anion (O2-) production in polymorphonuclear leukocytes (PMN) from healthy term newborn infants, very low birth wt infants, and healthy adults. SOD activity in PMN was measured with nitroblue tetrazolium reduction assay on PAGE, and the SOD content in PMN was determined with an ELISA using a monoclonal antibody against human copper and zinc-containing SOD. The activity and the content of SOD in the term neonatal PMN and VLBW-infants' PMN were significantly lower than those in the adults' PMN (term newborn infants, 6.6 +/- 0.6 U/mg protein and 170.4 +/- 16.3 ng/mg protein, n = 10; VLBW infants, 6.8 +/- 0.9 and 173.0 +/- 16.2, n = 6; adults, 10.3 +/- 0.6 and 241.9 +/- 13.3, n = 10; values were expressed as mean +/- SEM). Both the phorbol myristate acetate- and the N-formyl-methionyl-leucyl-phenylalanine-induced O2- production rates of VLBW-infants' PMN were significantly higher than those of the term neonatal PMN. The phorbol myristate acetate-induced O2- production rate of the term neonatal PMN was significantly lower than that of the adults' PMN. The phorbol myristate acetate-induced H2O2 production rate of the term neonatal PMN was significantly lower than that of the adults' PMN. The conversion rate from O2- to H2O2 of the neonatal PMN was similar to that of the adults' PMN.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Superoxide dismutase in polymorphonuclear leukocytes of term newborn infants and very low birth weight infants. 258 25

Oxygen free radicals and Ca2+ overload have been implicated in the genesis of reperfusion induced arrhythmia and injury. Effects of hydrogen peroxide (H2O2) on action potentials and intracellular Ca2+ concentration ([Ca2+]i) were studied using guinea pig papillary muscles and ventricular myocytes. High concentration of H2O2 (10 mmol.litre-1) caused delayed afterdepolarisations in all six papillary muscles, and induced triggered activity in 3/6 preparations. Pretreatment with ryanodine (1 mumol.litre-1) abolished delayed afterdepolarisations and triggered activity induced by H2O2. [Ca2+]i and morphological changes in isolated ventricular myocytes of guinea pig were measured using fura-2. Quiescent and rod shaped myocytes became shortened and rounded (contracture) after the application of 0.1 and 1 mmol.litre-1 H2O2. [Ca2+]i increased from the control values of 53 (SEM 4) and 62(8) nmol.litre-1 to 110(29) and 105(24) nmol.litre-1 (p less than 0.05 v control) when cells were shortened during perfusion with 0.1 and 1 mmol.litre-1 H2O2, respectively. The values were 130(26) nmol.litre-1 (p less than 0.05 v control) and 100(18) nmol.litre-1 (p less than 0.05 v control) when the cells became rounded during perfusion with 0.1 and 1 mmol.litre-1 H2O2. We suggest that the arrhythmia caused by Ca2+ overload was induced by H2O2, possibly by lipid peroxidation of cell membrane. H2O2 was also shown to shorten cells and cause cell contracture (rounding). The mechanism of cell injury is not likely to be due to the Ca2+ overload, since the increase in [Ca2+]i during perfusion with H2O2 was not large.
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PMID:Effects of hydrogen peroxide on action potentials and intracellular Ca2+ concentration of guinea pig heart. 261 15

As shown previously monocytes upon stimulation with bacterial lipopolysaccharides (LPS) release granulocyte-activating mediator(s) (M-GRAM) which induced a long-lasting chemiluminescence (CL) response in human granulocytes. M-GRAM could be separated from interleukin-1 alpha and beta, interleukin-2, interferon alpha and gamma, granulocyte colony stimulating factor (G-CSF) and macrophage colony stimulating factor (M-CSF), since these cytokines are shown to be unable to induce a significant CL response. In contrast, granulocyte macrophage colony stimulating factor (GM-CSF) and particularly tumor necrosis factor (TNF) are important triggers of the oxidative burst and they are capable of inducing a CL response. TNF activity but not lymphotoxin (LT) activity could be demonstrated in M-GRAM samples. A polyclonal rabbit IgG as well as a monoclonal antibody to recombinant human TNF which neutralized the TNF activity in M-GRAM preparations did not substantially block the CL signal. Furthermore, M-GRAM-induced CL response was not significantly inhibited by a polyclonal calf antiserum to human recombinant GM-CSF. For further functional characterization of M-GRAM-induced granulocyte activation different assays were performed in order to compare GM-CSF and TNF: (a) SOD-inhibitable cytochrome C-reduction (.O2-); (b) horseradish peroxidase-mediated oxidation of phenol red (H2O2); (c) the release of peroxidase; (d) ultrastructural detection of hydrogen peroxide production; and (e) scanning and transmission electron microscopy (SEM and TEM). Significant release of .O2- was induced by M-GRAM, TNF, and GM-CSF, whereas H2O2 production was significantly stimulated only by M-GRAM and TNF, as shown by functional and ultrastructural assays.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Granulocyte-activating mediators (GRAM): III. Further functional characterization of monocyte-derived GRAM. 284 61

Our previous studies have shown that exposure of cultured rabbit lenses to physiological levels of hydrogen peroxide, following inhibition of the glutathione redox cycle, leads to the formation of distinct vacuoles in the anterior region of the lens at the germinative zone between the epithelium and lens fibers. In the present study the ultrastructure of H2O2-induced membrane damage in the intact lens and in cultured lens epithelial cells was examined by scanning and transmission electron microscopy (SEM and TEM), following the inhibition of glutathione reductase with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). Lenses treated with BCNU/H2O2 exhibited swollen epithelial cells which were observed only above the peroxide-induced vacuoles. The apical surface of the swollen cells had membrane blebs which protruded into the underlying vacuolar space. The appearance of the blebs coincided with a change in the organization of the layer of microfilaments which is normally associated with the apical surface of the cell. Cultured lens epithelial cells treated with BCNU/H2O2 showed membrane blebs which increased in size and number with the duration of exposure. Initially, the blebs were seen only on certain regions of the cell surface with other regions appearing normal. TEM revealed a disorganization of microfilaments in the BCNU/H2O2 treated cells. Neither BCNU nor H2O2 alone affected the morphology of intact lenses or of cultured lens epithelial cells. In culture, isolated lens epithelial cells exposed to BCNU/H2O2 were more susceptible to damage than contiguous cells. While the exact mechanism by which H2O2-induced damage leads to bleb formation on the cell surface is not known, the inability of the cells to detoxify H2O2 due to the inhibition of glutathione reductase results in the disturbance of membrane cytoskeleton and a focal weakening of the cell surface. These results indicate a correlation between the active glutathione redox cycle in lens epithelium and maintenance of normal cytoskeletal protein organization.
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PMID:Effect of inhibition of the glutathione redox cycle on the ultrastructure of peroxide-treated rabbit epithelial cells. 292 23

The capacity of human blood monocytes to secrete hydrogen peroxide (H2O2) and superoxide (O2-) was measured as the cells differentiated during 4 wk of culture. Morphologic transformation of monocytes into macrophages, epithelioid cells, and multinucleated giant cells accompanied a steady increase in the content of protein per cell, from 0.77 mg/10(7) cells on days 0 to 11.77 mg/10(7) cells on days 20 to 29. In contrast, secretion of H2O2 by adherent monocytes was 859 +/- 73 nmol/60 min per mg protein (mean +/- SEM, n = 18) on day 0, rose 40% on day 3, and then fell rapidly, remaining below 6% of the initial values after day 10. The decline in capacity to secrete reactive oxygen intermediates was observed whether H2O2 or O2- were measured, whether the cells were challenged with phorbol myristate acetate or with opsonized zymosan, and whether the results were expressed per milligram cell protein or per cell. Superoxide dismutase activity tripled in adherent monocytes from day 0 to day 3, and thereafter remained elevated through at least day 16. In contrast, the activity of myeloperoxidase declined rapidly, catalase and glutathione peroxidase declined more gradually, and glutathione reductase and glutathione remained constant through the period of observation. Thus, the decline in capacity to secrete H2O2 could not be attributed to increases in cellular levels of these antioxidants. On the first day of culture, H2O2 release was enhanced up to fourfold by inclusion of sodium azide or potassium cyanide in the assay medium. This enhancement appeared to be due to inhibition of monocyte myeloperoxidase, rather than catalase. This conclusion was based on the kinetics and dose-response relationships for the effects of azide and cyanide on H2O2 release and on the activities of catalase and myeloperoxidase. Thus, the differentiation of human monocytes into macrophages in vitro is accompanied by an apparent reduction in the capacity to produce H2O2 and O2-. In this regard, the human monocyte-derived macrophage comes to resemble the resting tissue macrophage previously characterized in the mouse peritoneal cavity.
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PMID:Hydrogen peroxide metabolism in human monocytes during differentiation in vitro. 627 9

The cytolytic capacity of monocytes per se and stimulated monocytes has been documented to only a limited extent, and when observed has been ascribed to the generation of a variety of cytolytic molecular entities. In the present study we have examined de novo human monocyte-mediated tumor cytotoxicity and that induced by the agent 12-O-tetradecanoylphorbol-13-acetate (TPA). Cytolytic function was analyzed by reference to the release of [111In] oxine from two prelabeled tumor cell lines, K562 and U937, in a 16-hr assay in the presence of serum to more closely mimic in vivo circumstances. Observed cytolysis was clearly related to TPA concentration and effector cell number. Maximal cytolysis was obtained with TPA at 5 ng/ml, at which specific releases were 43% +/- 6 and 18% +/- 5 (mean +/- 1 SEM) at an effector cell to target cell (E:T) ratio of 2.5:1 and 65% +/- 6, and 41% +/- 12 at an E:T ratio of 20:1, for K562 and U937, respectively. In contrast, unstimulated monocytes expressed minimal cytolytic activity, or at best a low cytotoxic effect at high cellular ratios. When TPA-stimulated monocyte-mediated cytolysis was examined, catalase (2750 U/ml) inhibited K562 and U937 cytolysis by 92% and 84%, respectively; superoxide dismutase (300 U/ml) only inhibited cytotoxicity by 17% and 24%, respectively, implicating a central role of H2O2 rather than superoxide ions. Sodium azide (1 mM), an inhibitor of myeloperoxidase, did not diminish cytolysis; in contrast, it increased K562 and U937 cytolysis by 34% and 57%. This increased cytotoxicity was observed for K562 at low levels of cytotoxicity. These data tend to dismiss an essential role of the H2O2-halide-myeloperoxidase pathway of cytolysis. The OH scavengers, histidine (20 mM) and ethanol (40 mM), did not affect K562 killing; mannitol (50 mM), another OH scavenger, had only a slight inhibitory effect (23%). Finally, H2O2 generated by a glucose-glucose oxidase system directly mediated K562 killing and, to a lesser extent, U937 lysis. These results point strongly towards the role of: 1) a myeloperoxidase-independent mechanism of cytotoxicity, with 2) H2O2 as a key mediator of the cytolytic mechanism, and 3) a limited role of O2.- in synergy with H2O2 in the cytolytic activity of monocytes, and suggest that significant cytolytic function requires an inductive event.
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PMID:Human monocyte-mediated tumor cytotoxicity. I. Demonstration of an oxygen-dependent myeloperoxidase-independent mechanism. 632 94

It has been suggested that oxidants from pulmonary inflammatory cells may contribute to the development of emphysema by (i) direct tissue toxicity and (ii) inhibition of alpha 1-antitrypsin, thus diminishing protection of the lung from proteolytic damage. The extracellular release of hydrogen peroxide (H2O2) by human alveolar macrophages (AM) has been measured. AM were obtained by bronchoalveolar lavage and adherence from 24 smokers and 17 non-smokers. Smokers' AM released significantly more H2O2 (3.83 nmol h-1 micrograms-1 of DNA; SEM 0.44) than those of non-smokers' (2.33 nmol h-1 microgram-1 of DNA; SEM 0.40) (P less than 0.05). AM from donors with a recent lower respiratory tract infection released increased quantities of H2O2 (5.22 nmol h-1 microgram-1 of DNA; SEM 0.72; P less than 0.01) even when allowance was made for smoking habits. These findings are consistent with the hypothesis that H2O2 of AM origin contributes to the development of emphysema in smokers.
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PMID:Extracellular release of hydrogen peroxide by human alveolar macrophages: the relationship to cigarette smoking and lower respiratory tract infections. 662 51

Although several studies have shown that vanadate evokes vasoconstriction whether it elevates cytosolic free calcium, [Ca2+]i, in vascular smooth muscle (VSM) cells has not been investigated. The present study shows that acute additions of low concentrations of vanadate (10-200 microM) to cultured aortic smooth muscle cells (ASMC) produced a rapid and a concentration-dependent increase in [Ca2+]i with an EC50 (mean +/- SEM) value of 42 +/- 11 microM. Inclusion of vanadate (200 microM) led to a significant increase (p < 0.05) in the peak [Ca2+]i level to 190 +/- 23 nM from a basal level of 102 +/- 2 nM. At concentrations > 200 microM, vanadate caused quenching of fura-2 fluorescence. For example, addition of 1 mM vanadate led to an apparent decrease in fluorescence by about 50% (due to a quenching effect), followed by a transient rise. H2O2, which is used in the preparation of peroxide forms of vanadate, pervanadate (PV), also produced a rise in [Ca2+]i. These data suggest that vanadate promotes vascular tone by elevating [Ca2+]i in ASMC. However, [Ca2+]i measurements made with higher concentrations of vanadate and PV, using the fura-2 method, must be interpreted with caution.
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PMID:Vanadate increases cytosolic free calcium in rat aortic smooth muscle cells. 786 26


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