Search PubMed⌕ Search

Biomedical subjects

A Boveris

Publications and source records attributed to A Boveris.

At least 73 records · Page 4Linked to original sources
PubMed1991

Melanin content and hydroperoxide metabolism in human melanoma cells.

Human melanoma cells were grown to exponential and stationary phases showing melanin contents of 4.2 +/- 0.3 and 11.3 +/- 0.6 micrograms/10(6) cells, respectively. The cells were separated in four subpopulations by a Percoll gradient; the subpopulation of density 1.07 (g/ml) was the most enriched in pigmented cells and produced 28 and 58% of the cells in exponential and stationary phases, respectively. Melanoma cells had similar superoxide dismutase and glutathione peroxidase activities in exponential and stationary phases. Moreover melanoma cells exhibited a higher catalase activity in the stationary phase: whole homogenate and cytosol activities were 7.0 +/- 0.3 and 10.8 +/- 0.6 U/mg protein, whereas in exponential phase the activities were 4.9 +/- 0.1 and 7.6 +/- 0.3 U/mg protein for whole homogenate and cytosol, respectively. The intracellular H2O2 steady-state concentration was 3.3 +/- 0.2 and 2.1 +/- 0.2 microM H2O2 for exponential and stationary phases, respectively. The spontaneous chemiluminescence of the two culture phases was 169 +/- 27 cps/10(6) cells (exponential) and 78 +/- 24 cps/10(6) cells (stationary). The cytotoxicity of H2O2 generated extracellularly by glucose oxidase was determined after 60 min of exposure. IC50 values for exponential and stationary cell cultures were 0.9 and 2.4 mU/ml of glucose oxidase, respectively. The increased catalase activities in the stationary phase as compared with the exponential phase are consistent with the decreased intracellular H2O2, with the decreased spontaneous chemiluminescence, and with the increased resistance to exogenous H2O2.

Catalase↗
PubMed1991

Hydroperoxide-initiated chemiluminescence: an assay for oxidative stress in biopsies of heart, liver, and muscle.

Hydroperoxide-initiated chemiluminescence was standardized as a microassay to evaluate the occurrence of oxidative stress in human biopsies. Samples of 10 to 50 mg of rat liver or heart were homogenized, diluted in reaction medium, added with tert-butyl hydroperoxide, and assayed for chemiluminescence in a liquid scintillation counter in the out-of-coincidence mode. Optimal conditions for the assay were: 0.3 to 1.2 mg/mL of homogenate protein in 120 mM KCl, 30 mM phosphate buffer (pH 7.4), and 3 mM tert-butyl hydroperoxide at 30 degrees C. In these conditions, maximal chemiluminescence values were 550 +/- 30 and 1100 +/- 40 cps/mg protein, for liver and heart homogenates, respectively. Liver and heart homogenates were subjected to in vitro oxidative stresses such as supplementation with organic hydroperoxide or with enzymatic systems generating superoxide anion or hydrogen peroxide. Chemiluminescence was higher in the poststress samples than in the control ones. The ratio: poststress chemiluminescence/control chemiluminescence (B/A) was about 1.4 or higher for both tissues. Human heart biopsies were utilized to investigate the occurrence of oxidative stress after clinical situations associated to ischemia-reperfusion. B/A ratios were 2.1 +/- 0.4, 1.4 +/- 0.1, and 2.8 +/- 0.4 for human heart, liver, and skeletal muscle, respectively.

Animals↗
PubMed1991

Betamethasone effects on paraquat lung toxicity.

1. Betamethasone (1 mg/ml) was administered i.v. to adult Wistar rats 3 h before paraquat injection (30 mg/ml) and various parameters of lung function were studied to determine the effect of an anti-inflammatory drug in paraquat lung toxicity. 2. Rats treated with both drugs showed not only increases in spontaneous lung chemiluminescence (90%), malondialdehyde formation (40%), migration of PMN cells to the lungs (450%) and lung wet wt (20%), but also the survival times were decreased to 25% at day 7. 3. The data indicate that betamethasone exacerbates the toxic effects of paraquat. The mechanism can be explained in terms of inhibition of phospholipase A2 activity, which may increase the accumulation of hydroperoxide, produced by paraquat redox cycling upon lipid membranes.

Animals↗
PubMed1991

Inhibition of microsomal lipid peroxidation by alpha-tocopherol and alpha-tocopherol acetate.

1. The antioxidant effects of alpha-tocopherol and alpha-tocopherol acetate were assayed for the (a) oxygen uptake, (b) chemiluminescence and (c) malondialdehyde formation, of tert-butyl hydroperoxide-supplemented rat liver microsomes. 2. Oxygen uptake was inhibited 60% by both alpha-tocopherol and alpha-tocopherol acetate with the half-maximal effect at 5 nmol tocopherol/mg protein. Chemiluminescence and malondialdehyde formation were equally inhibited 35% by both tocopherols with half-maximal effects at 2 nmol tocopherol/mg protein. 3. The rate of O2 uptake by tocopherol-supplemented microsomes was dependent on O2 concentration. A 60% inhibition by 5 nmol tocopherol/mg protein at 0.2 mM O2 is decreased to 5% inhibition at 0.6 mM O2. 4. The inhibition of O2 uptake, chemiluminescence and malondialdehyde formation indicate that both alpha-tocopherol and alpha-tocopherol acetate have similar effects as free radical traps in the hydrophobic domain of biomembranes. The different inhibition observed at different O2 concentrations indicate competition between vitamin E and O2 by unoxygenated lipid radicals.

Animals↗
PubMed1991

Alcohol-induced oxidative stress in rat liver.

1. Livers from rats treated acutely with ethanol showed increased chemiluminescence, malondialdehyde production, and diene formation. Previous administration of (+)-cyanidanol-3 completely abolished acute ethanol-induced chemiluminescence. 2. Rats fed alcohol liquid diets for 3 weeks showed significant increases in microsomal and mitochondrial malondialdehyde formation, and in microsomal H2O2 and O2-. generation. 3. Rats fed a solid basal diet plus ethanol solution for 12 weeks also showed increased microsomal production of O2-. and increased content of microsomal cytochrome P-450. Hydroperoxide-induced chemiluminescence was higher in homogenates, mitochondria and microsomes from ethanol-treated rats than from controls. Vitamins E and A were more effective inhibitors of hydroperoxide-stimulated chemiluminescence in liver homogenates from ethanol-treated rats than from control animals. 4. Results are consistent with peroxidative stress leading to increased lipid peroxidation in liver of rats fed ethanol both acutely and after long-term dosing.

Animals↗
PubMed1990

Adriamycin effects on hydroperoxide metabolism and growth of human breast tumor cells.

Human breast tumor cells MCF-7 were grown during 5 days in the presence of Adriamycin and the IC50 was 50 nM with the highest sublethal concentration 0.1 microM. At this latter concentration Adriamycin produced a complete inhibition of cell division and a partial reversion to a normal breast epithelial appearance. Similar effects of Adriamycin were observed in cells cultured in the presence of 10% FBS and in a chemically defined medium, with Se-glutathione peroxidase activities of 3.8 and 1.3 U/mg of protein, respectively. Cell size and cell oxygen uptake were increased by 41% and by 50%, respectively, in Adriamycin-treated cells. The spontaneous chemiluminescence of monolayers of intact MCF-7 cells (81 +/- 9 cps/mg protein) was increased by 48% in the Adriamycin-treated cultures (120 +/- 11 cps/mg of protein) in agreement with a 91% higher concentration of malondialdehyde in the same cultures. Adriamycin treatment produced a 71% increase in the steady state concentration of H2O2, which was estimated assuming diffusion equilibrium with the external medium, from 1.38 microM in the control cells to 2.38 microM in the treated cells. Cyanide-insensitive respiration was also higher in the cells exposed to the drug than in the control cells. Adriamycin did not affect the activity of the antioxidant enzymes, Cu-Zn and Mn-superoxide dismutase, Se and non-Se-glutathione peroxidase, and catalase. These results contribute to the current hypothesis that oxygen free radicals produced by Adriamycin redox cycling are responsible for at least part of the cytotoxic effects due to this drug.

Analysis of Variance↗
PubMed1990

Myocardial damage induced by doxorubicins: hydroperoxide-initiated chemiluminescence and morphology.

Doxorubicin (1.2 mg/kg body weight) or 4'-epidoxorubicin (1.7 mg/kg body weight) was injected intravenously to rabbits twice a week during 7 to 8 weeks. Total doses were 17.9 +/- 0.2 mg and 24.4 +/- 0.3 mg, respectively. Heart, liver, muscle, and brain homogenates from treated and control animals were supplemented with 3 mM tert-butyl hydroperoxide and hydroperoxide-initiated chemiluminescence was measured. Heart homogenates from doxorubicin-treated rabbits showed an increased hydroperoxide-initiated chemiluminescence (77.2 +/- 3.9; expressed as cpm/mg protein X 10(-3]; whereas 4'-epidoxorubicin-treated rabbits did not exhibit changes (40.7 +/- 4.6) when both were compared with the untreated animals (41.3 +/- 3.0). Liver, muscle, and brain homogenates from doxorubicin and 4'-epidoxorubicin-treated animals showed a hydroperoxide-initiated chemiluminescence that was similar to the one from control animals. Microscopically, the total extent of the myocardial damage (as percentage of damaged myocytes) was markedly higher in the doxorubicin-treated rabbits (63.0 +/- 8.6) than in the 4'-epidoxorubicin-treated group (34.6 +/- 5.0); being both values higher than the one corresponding to control animals (8.0 +/- 1.1). The subendocardial areas of the septum and of the left ventricle were highly sensitive to doxorubicin damage. Hydroperoxide-initiated chemiluminescence of whole heart homogenate correlated statistically with the microscopic tissue damage in the subendocardial and intramural areas of the right ventricle. It is concluded that chronic administration of doxorubicins lead to oxidative stress of the myocardium and that 4'-epidoxorubicin produces less severe oxidative stress and less extensive myocardial damage than those provoked by lower doses of doxorubicin.

Animals↗
PubMed1990

The photodynamic effect of rose bengal on proteins of the mitochondrial inner membrane.

Photodynamic action promoted by Rose Bengal was evaluated in solutions of unsaturated fatty acids or histidine, and on beef heart submitochondrial particles. Rose Bengal-promoted photooxidation of histidine was mainly due to the opening up of the imidazole ring by singlet oxygen. Photosensitization of polyunsaturated fatty acids (PUFA) resulted in oxygen consumption and thiobarbituric acid-reactive substances (TBARS) formation, the extent of which was linearly related to the increasing degree of unsaturation. Photosensitization of submitochondrial particles caused oxygen consumption and TBARS production. These processes involved two different reaction components: during the first, most of the mitochondrial proteins were inactivated, the most sensitive being succinate dehydrogenase and cytochrome c. The values for the rate ratios of [TBARS] formation/[O2] consumption for the first and second phase were 0.36 and 1.32%, respectively, pointing to a larger contribution of lipid peroxidation during the second phase. The calculation of the rate constants for reaction of singlet oxygen with mitochondrial proteins suggests that singlet oxygen is more reactive towards proteins than to PUFA. The biological role of this selectivity is discussed in terms of the mitochondria as one of the first targets for photosensitized reactions.

Animals↗
PubMed1990

Effect of supplementing cardioplegic solution with deferoxamine on reperfused human myocardium.

Fourteen randomized patients undergoing myocardial revascularization were divided into group A standard hypothermic cardioplegic solution) and group B (the same cardioplegic solution supplemented with deferoxamine 1000 mg/L). In all patients myocardial biopsy specimens were obtained before ischemia and during reperfusion and were assessed for chemiluminescence (to indirectly determine oxygen-free radical activity) and for electron microscopic studies. Chemiluminescence in group A showed a photoemission of 36.5 +/- 1.5 cpm/mg protein X10(-3) for the preischemia samples and 72 +/- 5.7 cpm/mg protein X10(-3) for the reperfusion samples (p less than 0.01). In the patients who received deferoxime (group B), values for chemiluminescence for preischemia and reperfusion samples were not significantly different. Electron microscopic studies showed a significant increase in grade 4 (severely damaged) mitochondria in reperfusion biopsy specimens from both groups as compared with preischemia samples. However, reperfusion samples from group B showed a better preservation of myocardial cells with marked reduction of grade 4 (severely damaged) mitochondria. These results support the hypothesis that oxygen-free radicals are responsible in part for the production of reperfusion injury in the human heart. They suggest that this mechanism may be at least partially controlled by adding an iron chelating agent such as deferoxime.

Cardioplegic Solutions↗
PubMed1989

Brain chemiluminescence and oxidative stress in hyperthyroid rats.

Newborn Wistar rats were made hyperthyroid by injection of tri-iodothyronine and assayed for survival, brain oxygen uptake, brain chemiluminescence and activity of antioxidant enzymes. Brain chemiluminescence was measured (1) by removing the parietal bones or (2) through the translucid parietal bones. Control animals showed a brain chemiluminescence of 130 +/- 12 c.p.s./cm2 and 99 +/- 10 c.p.s./cm2 for procedures (1) and (2) respectively. Hyperthyroid rats showed increases in the spontaneous brain photoemission of 46 and 70% compared with controls, measured by procedures 1 and 2 respectively. The hyperthyroid state did not modify the oxygen-dependent chemiluminescence of brain homogenates. The hyperthyroid animals showed a 30% increase in the oxygen uptake of brain slices and a dramatic shortening of life-span to about 16 weeks. Superoxide dismutase (the Cu-Zn enzyme), catalase and Se-dependent glutathione peroxidase activities of brain homogenates were increased by 18, 36 and 30% respectively in the hyperthyroid animals. Isolated brain mitochondria produced 0.18-0.20 nmol of H2O2/min per mg of protein in state 4 in the presence of succinate as substrate. No difference was observed between control and hyperthyroid animals. It is concluded that hyperthyroidism leads to hypermetabolism and oxidative stress in the brain. The increased levels of oxygen and peroxyl radicals may contribute to premature ageing in these animals.

Animals↗
PubMed1989

Reduction of reperfusion injury with mannitol cardioplegia.

Forty consecutive patients undergoing myocardial revascularization were divided into two equal groups: group 1 received standard cardioplegic solution, and group 2 received a solution containing mannitol, 59.8 mmol/L. In 6 patients in each group, myocardial biopsies were done before ischemia and at the time of reperfusion. Samples were assessed by chemiluminescence to determine oxidative stress and by electron microscopic studies. A significant reduction in atrial arrhythmias was observed in the mannitol group. Chemiluminescence in group 1 showed a photoemission of 37.6 +/- 3.5 cpm/mg of protein x 10(-3) for the preischemia samples and 74.8 +/- 16 cpm/mg of protein x 10(-3) for the reperfusion samples (p less than 0.001). In group 2, the values for chemiluminescence were 37.7 +/- 3.4 cpm/mg of protein x 10(-3) and 40 +/- 6.1 cpm/mg of protein x 10(-3), respectively (p = not significant). Electron microscopic studies showed, for group 1, increased grades of damaged mitochondria in the reperfusion biopsy specimens compared with the preischemia biopsy specimens (p less than 0.01). In group 2, differences for damaged mitochondria were not significant. These results support the hypothesis that mannitol reperfusate significantly reduces myocardial damage in patients undergoing open heart procedures. They also suggest that this protective effect may be in part secondary to the antioxidant property of mannitol, although other mechanisms may have accounted for or contributed to the improved outcome after ischemia.

Biopsy↗
PubMed1989

Chemiluminescence of ischaemic and reperfused intestine in vivo.

Low level chemiluminescence of exposed rat intestine was measured during occlusive ischaemia and reperfusion. Spontaneous emission of in vivo rat intestine (10 +/- 1 cps/cm2) decreased almost to zero in animals subjected to ischaemia and when the period of ischaemia lasted only two minutes, chemiluminescence increased beyond control levels (39%, three minutes after reperfusion) at intestine deligation. This overshoot did not occur when rats were pretreated with allopurinol (40 + 100 mg/kg bw). The ratio of xanthine dehydrogenase to xanthine oxidase activities was 3.46 in preischaemic intestine samples. The same ratio was changed to 0.35 in samples subjected to two minutes of ischaemia. As chemiluminescence appears to reflect the steady state level of singlet oxygen, which in turn derives from the steady state level of peroxy radicals, these results agree with the view that oxygen radicals derived from the xanthine oxidase reaction are involved in the cellular damage produced after ischaemia and reoxygenation in the intestine.

Allopurinol↗
PubMed1989

On the characteristics of the visible chemiluminescence following free radical lipid peroxidation.

The characteristics of the visible luminescence that follows the lipid peroxidative process were investigated either in the autoxidation of rat brain homogenates or in the azo-bis-amidinopropane initiated lipid peroxidation of erythrocyte plasma membranes and liver microsomes. In these systems the luminescence decay observed after total inhibition of the lipid peroxidation is not an iron-catalyzed process, and follows a complex kinetics comprising fast and slow components. The slow component of the decay lasts for several hours at 27 degrees C and amounts to nearly half of the total intensity measured prior to the inhibition of the oxidative process by propyl gallate. The addition of thiols (diethyldithiocarbamate, penicillamine or dithiothreitol) to a lipid peroxidizing system inhibits the chain oxidation and catalyzes the dark decomposition of one (or several) of the luminescence precursors, following first order kinetics. The effect of temperature on the slow luminescence decay corresponds to an activation energy of 18.5 kcal/mol.

Amidines↗
PubMed1989

[Kinetics of chemoluminiscence of rat intestine during ischemia and reperfusion].

Oxygen free radicals are involved in ischemic and reperfusion tissular injuries. Chemiluminescence of organs reflects the steady state level of peroxy radicals, usually generated by oxygen radicals. In this study, chemiluminescence of intestine has been determined in rats subjected to 2, 5 or 10 min of occlusive ischemia by ligation. During the ischemic period, chemoluminescence tends to decrease. After delegation, a constant response, a chemiluminescence overshoot, can be obtained only in the group of rats subjected to 2 min of ligation. This methodology does not provide constant results with longer periods of ligation. In other groups of rats subjected to 2 min of ligation and then delegated, the kinetics of the organ emission in function of time show a mean overshoot of about 44% after 3 min of reperfusion. This early excess of chemiluminescence is maintained for the first 10 to 20 min after delegation, but not for longer periods. The administration of a free radical scavenger, thioctic acid 100 mg/kg i.p., prevents or reduces the amount of the overshoot previously described during the 20 min postdelegation follow-up period. These data suggest that excessive oxygen radical generation occurs in vivo during the early minutes of reperfusion and may be the consequence of very fast enzymatic changes during the short-term previous hypoxic period. Further studies are needed to demonstrate the subsequent functional alteration and the pathological implication of this phenomenon.

Analysis of Variance↗
PubMed1989

[Neutrophil-dependent inflammatory reactions in systemic lupus erythematosus].

We studied the possible role of polymorphonuclear neutrophil (PMN) aggregation in Systemic Lupus Erythematosus (SLE) by the capacity of sera from 32 lupus patients to induce in vitro normal PMN aggregation. Neutrophil aggregating activity (NAA) in this group was significantly greater than that found in 8 inactive SLE patients and in 8 controls. In patients with SLE, there was a positive correlation between disease severity and the quantitative measure of NAA. High levels of NAA were particularly characteristic of central nervous system SLE. These data suggest that the formation of intravascular leukoaggregates may contribute to morbidity in SLE. Normal PMN increase their spontaneous superoxide anion production (0.21 nmol/min 10(7) PMN) when stimulated with sera from SLE patients. Lupus PMN also show an enhancement of 100% in superoxide production in vitro when stimulated with lupus sera. When N formyl methionine leucyl phenylalanine (FMLP) was used, lupus PMN showed an O2-production of 2.1 nmol/min 10(7) which is 5-fold the response of normal PMN stimulated by FMLP. Our results show the existence of seric factors in SLE patients that can stimulate O2-production by PMN. Lupus neutrophils show an increased response to membrane stimuli such as FMLP, capable of triggering the respiratory burst. Lupus neutrophils appear more responsive membrane stimuli such as FMLP, capable of triggering the respiratory burst. Lupus neutrophils appear more responsive to membrane stimuli. The seric and the cellular factors seem to indicate an increased rate of superoxide production by PMN in SLE patients, which can be relevant to vasculitis and tissue damage.

Adult↗
PubMed1988

Control of leucine transport in yeast by periplasmic binding proteins.

The concentrative inward transport of leucine in Saccharomyces carlsbergensis involves two transport systems (S1 and S2); S1 is a system of high affinity and low translocation velocity, and S2 is a system of low affinity and high translocation velocity. The inward transport process of the amino acid is discriminated into two kinetically defined steps: first, binding to periplasmic proteins and second, translocation across the plasmalemma. When cells were incubated with glucose to increase the metabolic energy charge, we observed that JTmax (maximum flux that each system can exhibit for the translocation step) increased for both systems. This increase in JTmax is due to variations in the parameters defining the initial step (Ks (apparent dissociation constant) and N (concentration of binding sites)): for S1, N1 increases and for S2, KS2 diminishes. Dissipation of the electrochemical proton gradient produced an increase of KS1 and a decrease of N2, resulting in a decrease of JTmax in both systems. Instead, osmotic shock decreases N1 and N2, which suggests that periplasmic components were removed, resulting also in a decrease of JTmax in both systems. These results are consistent with the proposition that the total unidirectional flux of the amino acid proceeds by means of a system of multiple components, with the simultaneous operation of two independent transport processes. We propose that the initial interaction of leucine with components of the cellular envelope might be the essential step for the subsequent translocation of the amino acid across the permeability barrier.

Biological Transport, Active↗
PubMed1988

Assessment of myocardial oxidative stress in patients after myocardial revascularization.

A homogeneous group of six patients, who underwent coronary artery bypass surgery, was studied to determine the presence of oxidative stress caused by oxygen-derived free radicals and its relationship with reperfusion cell damage. Biopsies were performed before ischemia and 10 minutes after reperfusion. The samples were assayed for hydroperoxide-initiated chemiluminescence and histochemical succinic dehydrogenase activity; the specimens were also studied by electron microscopy. The preischemic biopsy specimens showed chemiluminescence of 40 +/- 2 (cpm/mg protein) x 10(3), normal succinic dehydrogenase activity (grade 4), and generally preserved ultrastructure (necrotic/normal cells 5/100). However, the reperfusion biopsy specimens showed an increase in chemiluminescence to 91 +/- 19 (cpm/mg protein) x 10(3) (p less than 0.025), a partial loss of enzymatic activity (grade 2.6), and ultrastructural changes characterized by mitochondrial swelling and focal myofibrillar disorganization (necrotic/normal cells: 15/100; p less than 0.001). These observations seem to indicate the presence of oxidative stress during reoxygenation, a situation that may play a major role in the genesis of reperfusion injury. It appears to be the first observation relating free radical-induced oxidative stress to reperfusion injury in humans.

Adult↗