Oxygen Free Radical Activity Research Articles

Anti-oxidant and pro-oxidant effects on nerve conduction velocity, endoneurial blood flow and oxygen tension in non-diabetic and streptozotocin-diabetic rats

Increased oxygen free radical activity, coupled with reduced protection against oxidative stress, could play a role in the aetiology of neurovascular abnormalities in experimental diabetes mellitus. To test this hypothesis, non-diabetic and streptozotocin-diabetic rats were treated with the anti-oxidant probucol or the pro-oxidant primaquine. One-month diabetes caused 21.4% and 13.6% reduction in sciatic motor and saphenous sensory conduction velocity (p < 0.001). These deficits were prevented by probucol treatment (p < 0.001). After 1-month untreated diabetes, conduction velocity deficits were reversed by a further month of probucol treatment (p < 0.001). For non-diabetic rats, primaquine treatment caused a 12.9% reduction in motor conduction velocity (p < 0.001), which was prevented by probucol treatment (p < 0.001). Primaquine treatment did not affect diabetic rats. Sciatic nerve nutritive endoneurial blood flow, measured using microelectrode polarography and hydrogen clearance, was 48.0% reduced by 2-month diabetes (p < 0.001). This was completely prevented by probucol treatment (p < 0.001). Primaquine treatment did not affect blood flow in diabetic rats. However, in non-diabetic rats it caused a 30.0% reduction (p < 0.01) which was prevented by probucol treatment (p < 0.05). Sciatic endoneurial oxygen tensions were also measured by microelectrode polarography. Mean tension was 38.8% reduced by diabetes (p < 0.001). This was prevented by probucol treatment. Non-diabetic rats given primaquine treatment showed a 21.7% reduction in endoneurial oxygen tension (p < 0.01). The data suggest that vascular-mediated nerve dysfunction in diabetes depends on oxidative stress, and that similar effects in non-diabetic rats may be produced by pro-oxidant treatment. This provides evidence for the potentially important role of oxygen free radical activity in diabetic neuropathy.

Free radical activity and loss of plasma antioxidants, vitamin E, and sulfhydryl groups in patients with burns: the 1993 Moyer Award.

This study examines the relationship of burn injury and plasma levels of conjugated dienes, total sulfhydryl groups, and vitamin E in patients with thermal injuries. Plasma neopterin levels were determined as an index of macrophage activity and serine elastase as an index of polymorphonuclear cell activation. Thirteen patients with burns, six survivors and seven nonsurvivors, were studied for the first 4 days, then every other day until postburn day 14. Twelve healthy volunteers served as the control group. Survivors had 56% +/- 4% total body surface area burned, and nonsurvivors had 63.9% +/- % total body surface area burned. The patients with burns, compared with the control group, showed elevated plasma levels of the lipid peroxidation products conjugated dienes (0.767 +/- 0.045 vs 0.269 +/- 0.013 Abs at 233 nm) and reduced levels of the natural scavengers of free radicals, vitamin E (196.2 +/- 12.6 vs 841.1 +/- 22.7 micrograms/dl) and total sulfhydryl groups (54.0 +/- 0.4 vs 15.8 +/- 1.0 mumol/dl). The total sulfhydryl groups/conjugated dienes ratio fell at a greater rate (9.8% +/- 3.2% vs 3.2% +/- 0.7%/day) in nonsurvivors than in survivors (p < 0.05 by Mann-Whitney). The levels of elastase were slightly elevated in the patients with burns, but there was no difference between survivors and nonsurvivors. Normal neopterin levels are 3 to 10 nm/L; peak levels were 119 +/- 48 nm/L in nonsurvivors and 37.4 +/- 10 nm/L in survivors. Patients with burns demonstrated evidence of increased oxygen free radical activity and activation of polymorphonuclear cell and macrophages. Nonsurvivors demonstrated increased consumption of antioxidants compared with survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermal desorption-gas chromatographic determination of ethane and pentane in breath as potential markers of lipid peroxidation.

Formation of free radicals and lipoperoxidation occur at the onset of cellular damage. These effects are produced during normal metabolism and in pathological states. The peroxidation of polyunsaturated fatty acids, i.e. linoleic acid and linolenic acid, which are both cellular membrane compounds, induces ethane and pentane formation in pulmonary air exhalation. These two volatile hydrocarbons can be considered as potential lipoperoxidation markers. Methodological difficulties limit the use of these gases for assessment of free oxygen radical activity but we have developed and validated a non-invasive technique. A study was performed with ten healthy volunteers.

Recombinant human-type SOD attenuates circulatory disorders after reperfusion of splanchnic organs in rats.

Oxygen free radicals (OFRs) have been reported to play pivotal roles in the pathogenesis of cell damage induced by ischemia and reperfusion. The efficacy of recombinant human superoxide dismutase (rh-SOD) in the treatment of circulatory disorders after reperfusion of the splanchnic area was investigated in rats. All rats died within 3 hours after release of 60-min superior mesenteric artery occlusion (SMAO) when no treatment was given. Animals which received rh-SOD, 2 mg.100 g(-1)BW, at reperfusion followed by a continuous infusion of rh-SOD 0.67 mg.100 g(-1)BW.hr(-1), exhibited prolonged survival times compared with no treatment rats (231 +/- 35 min and 149 +/- 43 min, respectively). Mean blood pressure in rats treated with rh-SOD was higher than in controls after reperfusion, and was concomitant with improvement in splanchnic perfusion. The results suggest excessive activity of OFRs in reperfused organs and a possible scavenging effect of rh-SOD as a means of eliminating them.

Evidence for increased lipid peroxidation in multiple sclerosis

Pentane and ethane are degradation products of unsaturated fatty acids which are released during lipid peroxidation. In order to assess whether multiple sclerosis is associated with lipid peroxidation, we measured pentane and ethane excretion by 16 patients with multiple sclerosis and compared them to healthy control subjects. Patients with acute exacerbation of multiple sclerosis had significantly higher concentrations of pentane (10.5 +/- 4.2 nmol/l)(p less than 0.01) compared to either patients in remission (4.5 +/- 1.7 nmol/l) or control subjects (4.9 +/- 1.1 nmol/l). The concentrations of ethane were not significantly different among these groups. Of the patients with acute exacerbation who later achieved remission, the pentane excretion also returned to normal (5.6 +/- 0.9 nmol/l). One patient who failed to reachieve clinical remission continued to excrete large amounts of pentane. We conclude that oxygen free radical activity is enhanced during exacerbation of multiple sclerosis.

Increased oxygen free radical activity in patients on cardiopulmonary bypass undergoing aortocoronary bypass surgery

Cardiac dysfunction after cardiopulmonary bypass (CPB) has been reported by various investigators. Oxygen free radicals have been shown to depress cardiac function and contractility. To evaluate the possible role of oxygen free radicals (OFR) in post-pump cardiac dysfunction, measurements of cardiac function, OFR producing activity of polymorphonuclear (PMN) leukocytes (PMN chemiluminescence) and malondialdehyde (MDA), a lipid peroxidation product, in blood were made at induction of anesthesia (T1), before cross clamping of the aorta (T2), after closure of the chest (T3), and 24 hours postoperatively (T4) in 21 patients undergoing aortocoronary bypass surgery. The total OFR-derived chemiluminescence at T1, T2, T3, and T4 was 1590 ± 156, 3169 ± 338, 1972 ± 214, and 2614 ± 366 mv·min·106 PMN−1, respectively. Superoxide dismutase (SOD)-inhibitable chemiluminescence at T1, T2, T3, and T4 was 1214 ± 129, 2674 ± 328, 1752 ± 215, and 2139 ± 292 mv·min·106 PMN−1, respectively. Superoxide anion at T1, T2, T3, and T4 was 0.99 ± 0.14, 1.30 ± 0.17, 1.07 ± 0.14, and 1.19 ± 0.12 nmol·106 PMN−1·30 min−1, respectively. Blood MDA at T1, T2, T3, and T4 was 0.17 ± 0.02, 0.25 ± 0.03, 0.20 ± 0.03, and 0.23 ± 0.02 nmol/ml, respectively. OFR-derived and SOD inhibitable chemiluminescence, superoxide anion, and blood MDA increased significantly during CPB and postoperatively. There were decreases in the blood pressure and stroke volume, and increases in the central venous pressure, capillary wedge pressure, and heart rate during CPB and postoperatively. Cardiac output remained unchanged during this procedure. There was leukopenia during CPB. The hematocrit and hemoglobin content of blood decreased during bypass and remained low postoperatively. These results suggest that an increase in the level of oxygen free radicals in patients on cardiopulmonary bypass undergoing aortocoronary bypass surgery and 24 hours postoperatively was associated with depressed cardiac function. The increased levels of OFR might be responsible for myocardial dysfunction after cardiopulmonary bypass.

The effect of aging on endoneurial blood flow, hyperemic response and oxygen-free radicals in rat sciatic nerve

Electrophysiologic abnormalities and reduced energy metabolic rate develop in aging nerves. We investigated the effects of aging on nerve blood flow (NBF) in Fischer rats aged 2, 12, 24 and 30 months. NBF regressed negatively with increasing age and this decline was associated with an increase in nerve vascular resistance. Twenty minutes of nerve stimulation resulted in an increase in blood flow by about 50% in adult animals and did not decline with increasing age. As indices of oxygen free radical activity, we measured conjugated dienes, hydroperoxides, and norepinephrine from 2 to 30 months. There was a gradual decline with increasing age of all indices. We conclude that NBF declines with aging due to reduced microvascular caliber. These vessels retain their hyperemic response and oxygen free radical activity is less with increasing age.

Aminoguanidine effects on nerve blood flow, vascular permeability, electrophysiology, and oxygen free radicals.

Since advanced glycosylation end products have been suggested to mediate hyperglycemia-induced microvascular atherogenesis and because aminoguanidine (AG) prevents their generation, we examined whether AG could prevent or ameliorate the physiologic and biochemical indices of streptozotocin (STZ)-induced experimental diabetic neuropathy. Four groups of adult Sprague-Dawley rats were studied: group I received STZ plus AG (25 mg.kg-1.day-1), group II received STZ plus AG (50 mg.kg-1.day-1), group III received STZ alone, and group IV was a control. We monitored conduction and action potential amplitudes serially in sciatic-tibial and caudal nerves, nerve blood flow, oxygen free radical activity (conjugated dienes and hydroperoxides), and the product of the permeability coefficient and surface area to 125I-labeled albumin. STZ-induced diabetes (group III) caused a 57% reduction in nerve blood flow and in abnormal nerve conduction and amplitudes and a 60% increase in conjugated dienes. Nerve blood flow was normalized by 8 weeks with AG (groups I and II) and conduction was significantly improved, in a dose-dependent manner, by 16 and 24 weeks in sciatic-tibial and caudal nerves, respectively. The permeability coefficient was not impaired, suggesting a normal blood-nerve barrier function for albumin, and the oxygen free-radical indices were not ameliorated by AG. We suggest that AG reverses nerve ischemia and more gradually improves their electrophysiology by an action on nerve microvessels. AG may have potential in the treatment of diabetic neuropathy.

Hydroxyethyl starch macromolecule and superoxide dismutase effects on myocardial reperfusion injury

Myocardial reperfusion injury may be due to biophysical changes (e.g., endothelial cell junctional separations), as well as biochemical mechanisms (e.g., oxygen free radical activity). Superoxide dismutase (SOD), a free radical scavanger, may be effective in reducing chemical injury. Fractions of hydroxyethyl starch (HES-Pz), a large macromolecule, have been shown to decrease microvascular permeability associated with reperfusion-induced biophysical alterations. A comparison of SOD to HES-Pz was performed using a canine model of 1-hour left anterior descending coronary artery (LAD) clamping followed by 24 hours of reperfusion. Amounts of the test solution equal to 10% of the dog's blood volume were administered intraatrially to the animals just before release of the LAD clamp. Six dogs received Ringer's lactate, 7 were given 600,000 IU of SOD, 13 received 6% HES-Pz, and 9 were given SOD and HES-Pz. The ratio of infarct to area at risk was 20 ± 3% in the control dogs receiving Ringer's lactate, 16 ± 4% in animals receiving SOD alone (p = NS), 6 ± 3% in dogs receiving HES-Pz alone (p < 0.05), and 8 ± 3% in dogs given a combination of SOD and HES-Pz (p < 0.05). HES-Pz alone and with SOD significantly reduced reperfusion injury, although addition of SOD to HES-Pz did not have an additive effect. Appropriate-sized macromolecules may act by reducing ischemia-induced microvascular permeability.

OLEIC ACID‐INDUCED INJURIES IN THE GUINEA‐PIG. EFFECTS OF ALLOPURINOL ON CELL DYNAMICS, ERYTHROCYTE‐CATALASE AND URIC ACID PLASMA LEVELS

1. Oleic acid was used to produce adult respiratory distress syndrome-like pulmonary microvascular injuries. The resulting injuries have previously indicated involvement of accumulating neutrophils (Hultkvist et al. 1988). Activated neutrophils release oxygen free radicals that may be possible to detect in the plasma. 2. The dynamics of neutrophils and platelets were studied in the guinea-pig after oleic acid-induced injury (0.03 ml/kg per 10 min). 3. As an indication of oxygen free radical activity, plasma levels of uric acid and red blood cell (RBC)-catalase, were analysed. 4. Allopurinol (10 mg/kg, i.p.) was given prior to oleic acid infusion to block the production of uric acid. 5. The neutropenia, in contrast to the thrombocytopenia seen at 15 min, was significantly inhibited in the allopurinol pretreated group compared with oleic acid and vehicle alone. 6. The blood plasma concentration of uric acid was significantly elevated after 15 min from start of experiment. Allopurinol pretreatment significantly reduced the uric acid plasma level. 7. The RBC catalase activity did not change with time within or between any groups. 8. The results indicate that sequestration of activated neutrophils in the microvasculature are to some extent oxygen free radical dependent.

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.

Stimulatory and Inhibitory Actions of Proteins and Amino Acids On Copper-Catalysed Free Radical Generation in the Bulk Phase

The effect of a variety of proteins and amino acids was investigated on oxygen free radical activity as assessed by copper/hydrogen peroxide induced benzoate hydroxylation as well as copper-catalysed ascorbate autoxidation. Serum albumins from a variety of species (human, bovine and dog) had both inhibitory and stimulatory effects depending on the molar copper to protein ratio; low ratios were inhibitory and high stimulatory. Some other proteins tested (lysozyme, soybean trypsin inhibitor and conalbumin) also had dual (inhibitory and stimulatory) effects, as did both histidine and polyhistidine, but all effects occurred at different molar ratios presumably dependent on the relative affinities for the copper ions. In contrast, metallothionein and caeruloplasmin, proteins specialised to bind copper in vivo had no stimulatory effects. In this paper we show that in addition to their fairly well documented inhibitory effects, under certain conditions some proteins also stimulate radical reactions. The possible role of this phenomenon in vivo is discussed.

Determination of ethane and pentane in free oxygen radical‐induced lipid peroxidation

It has been proposed that ethane and pentane reflect free oxygen radical-induced lipid peroxidation. However, methodological difficulties limit the use of these gases for assessment of free oxygen radical activity. In the present report we describe an improved method for the accurate analysis of picomole quantities (greater than or equal to 1 pmol) of ethane and pentane. They are first quantitatively trapped into an adsorbent and then heat-desorbed directly into a capillary column for gas chromatographic quantitation. During oxidation of linolenic (n-3) and linoleic (n-6) acid, ethane and pentane were formed, respectively. Nonstimulated granulocytes formed pentane. Upon addition of phorbol 13-myristate 12-acetate, the generation of pentane was increased by 540%. Addition of superoxide dismutase plus catalase inhibited lipid peroxidation in both a cell-free system and in isolated cells. The present method is useful in the evaluation of free oxygen radical induced damage.

The risk factors for Alzheimer's disease: a review and a hypothesis.

More than 20 risk factors for Alzheimer's disease (AD) have been proposed in the literature. The evidence for them is examined in this review. Amongst those that appear likely to be true risk factors, an attempt is made to identify a common mechanism to which they might contribute. There is some support for a hypothesis that the formation of amyloid plaques is due to the activity of free oxygen radicals. This would be consistent with the association between AD and late age, a family history of Down's syndrome, vascular dementia, head injury, and exposure to phenacetin, organic solvents or vibrating tools. This hypothesis provides a theory-driven lead in the search for further risk factors; if upheld, it would suggest a strategy for treatment and for prevention.

Phagocytic cell activity in pre-eclampsia.

To compare the immune response in normal and pathological pregnancy, some functions of phagocytic cells were studied in 8 women with pre-eclampsia and 7 healthy women matched for age and parity. Free oxygen radical activity determined by chemiluminescence (CL) of polymorphonuclear leukocytes (PMN) and monocytes (MN) during phagocytosis of preopsonized zymosan, and cell migration measured by tube migration of PMN were studied together during and after pregnancy. CL of MN decreased or remained unchanged during normal pregnancy, but a marked increase was observed in pre-eclampsia. CL of PMN increased, too, in the pre-eclamptic patients, but the difference was not significant. Tube migration was enhanced during pregnancy compared with baseline values, but the values were significantly lower in the pre-eclamptic group. Immuno-globulins (Ig G, Ig M and Ig A) were studied in both groups. A decline in Ig G level from baseline to the 3rd trimester was observed in patients. The complement fractions C3 and C4 were not altered during pregnancy in any group. The study indicates a difference in behavior of phagocytic cells in normal vs. pre-eclamptic pregnancy.

Superoxide Dismutase (Erythrocuprein) and Free Radicals in Clinical Chemistry

Erythrocuprein (superoxide dismutase) has recently been shown to have an enzymic function towards superoxide anions. The discovery of superoxide dismutase, its mode of action, and estimation are reviewed along with a brief introduction to oxygen activation and free-radical chemistry. The formation, activity, and destruction of oxygen free radicals in white blood cells, red blood cells, and subcellular particles are discussed. (a) The production of superoxide anions by white cells during phagocytosis is thought to be advantageous for the overall bactericidal event. (b) Normal red blood cells generate low levels of superoxide anions. Increased levels of free-radical production could play a significant role in accelerating cell ageing (haemolysis). (c) Subcellular particles produce superoxide anions. These as well as organic peroxides have been implicated in drug hydroxylation reactions involving cytochrome P-450.

Fundamental Properties of High Structure Blacks

Abstract The present study reports properties connected with physical and chemical surface reactivity of HAF and ISAF carbon blacks of a wide variation in structural characteristics. Methods used include determination of bound rubber and of crosslink in density in vulcanizates, adsorption of polar material from solution, adsorption and heat of adsorption of polar and nonpolar gases and vapors in the gas phase, retention of adsorbed vapors after temperature increase, electron micrography, chemical characteristics such as hydroquinone, quinone and oxygen contents and free radical activity. The results fail to show any direct connection between physical or chemical reactivity of the surface and structure. It appears that presumed manifestations of enhanced surface reactivity of high structure blacks either are nonexistent or can be explained from secondary effects not directly connected with reactivity of the particle surface. It could be shown that improved reinforcing characteristics of high structure carbon blacks are directly related to particle structure, either through particle fusion (persistent structure) or though van der Waals' type of attractive forces (transient structure).