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In A549 cell culture, significant variability was found in sensitivity to actinomycin D. Using limiting dilution, actinomycin D-susceptible (G4S) and -resistant (D3R) subclones were isolated. G4S cells were also susceptible to protein synthesis inhibitors, a redox cycling quinone, and an electrophile with concomitant activation of caspases 3 and 9. D3R cells were resistant to these agents without caspase activation. Antioxidant profiles revealed that D3R cells had significantly higher glutathione and glutathione reductase activity but markedly lower catalase, glutathione peroxidase, and aldehyde reductase activities than G4S cells. Thus A549 cells contain at least two distinct subpopulations with respect to predisposition to cell death and antioxidant profile. Because sensitivities to agents and the antioxidant profile were inconsistent, mechanisms independent of antioxidants, including the apparent inability to activate caspases in D3R cells, may play an important role. Regardless, the results suggest that antioxidant profiles of asymmetrical cell populations cannot predict sensitivity to oxidants and warn that the use of single subclones is advisable for mechanistic studies using A549 or other unstable cell lines. oxidative stress; enzyme; caspase; apoptosis; genetic instability

Muscle wasting accompanies diseases that are associated with chronic elevated levels of circulating inflammatory cytokines and oxidative stress. We previously demonstrated that tumor necrosis factor-[alpha] (TNF-[alpha]) inhibits myogenic differentiation via the activation of nuclear factor-[kappa]B (NF-[kappa]B). The goal of the present study was to determine whether this process depends on the induction of oxidative stress. We demonstrate here that TNF-[alpha] causes a decrease in reduced glutathione (GSH) during myogenic differentiation of [C.sub.2][C.sub.12] cells, which coincides with an elevated generation of reactive oxygen species. Supplementation of cellular GSH with N-acetyl-l-cysteine (NAC) did not reverse the inhibitory effects of TNF-[alpha] on troponin I promoter activation and only partially restored creatine kinase activity in TNF-[alpha]-treated cells. In contrast, the administration of NAC before treatment with TNF-[alpha] almost completely restored the formation of multinucleated myotubes. NAC decreased TNF-[alpha]-induced activation of NF-[kappa]B only marginally, indicating that the redox-sensitive component of the inhibition of myogenic differentiation by TNF-[alpha] occurred independently, or downstream of NF-[kappa]B. Our observations suggest that the inhibitory effects of TNF-[alpha] on myogenesis can be uncoupled in a redox-sensitive component affecting myotube formation and a redox independent component affecting myogenic protein expression. inflammation; glutathione; nuclear factor-[kappa]B; myotube; myogenic differentiation

The authors review the publications on p53 transcription factor activation. The topics of interest include p53 participation in human aging involving DNA damage, telomere shortening and oxidative stress.

This article examines the relationship between endurance training, weight loss, and post-exercise food habits in women. An analysis of energy intake, fat oxidation, and protein metabolism is presented.

Research has been conducted on the radionuclides' and heavy metals' absorption onto iron and manganese oxides. The bioremediative strategy for the stabilization of these radionuclides and heavy metals in reducing environments has been developed and the details are presented.

The authors review the publications on the flavin-dependent enzyme identified by yeast Old Yellow Enzyme. The topics of interest include the flavoproteins' Old Yellow Enzyme family, the mechanism and structure of the Old Yellow Enzyme family and enzymes' biotechnological applications.

Research has been conducted on genes implicated in Streptococcus thermophilus CNRZ368 oxidative stress defense. The identification of these genes has been carried out via insertional mutagenesis and the results indicate that the resulting clones are sensitive to menadione and have altered morphologies and reduced growth rates.

Research has been conducted on the adaptive response to the oxidative stress by gram-negative pathogen Clostridium perfringens which exists in the soil, air, animals and humans. The identification of the genes involved in this response has been carried out and the results are discussed.

Research has been conducted on Escherichia coli oxidative stress response. The physiological and regulatory effects of the aconitase mutations on this response have been investigated and the results indicate that the mutants are hypersensitive to the oxidative stress.

Medium chain fatty acids (MCFA) are readily oxidized in the liver. Animal and human studies have shown that the fast rate of oxidation of MCFA leads to greater energy expenditure (EE). Most animal studies have also demonstrated that the greater EE with MCFA relative to long-chain fatty acids (LCFA) results in less body weight gain and decreased size of fat depots after several months of consumption. Furthermore, both animal and human trials suggest a greater satiating effect of medium-chain triglycerides (MCT) compared with long-chain triglycerides (LCT). The aim of this review is to evaluate existing data describing the effects of MCT on EE and satiety and determine their potential efficacy as agents in the treatment of human obesity. Animal studies are summarized and human trials more systematically evaluated because the primary focus of this article is to examine the effects of MCT on human energy metabolism and satiety. Hormones including cholescytokinin, peptide YY, gastric inhibitory peptide, neurotensin and pancreatic polypeptide have been proposed to be involved in the mechanism by which MCT may induce satiety; however, the exact mechanisms have not been established. From the literature reviewed, we conclude that MCT increase energy expenditure, may result in faster satiety and facilitate weight control when included in the diet as a replacement for fats containing LCT. KEY WORDS: * medium-chain triglycerides * satiety * energy expenditure * obesity

Potassium channel openers protect cardiac mitochondria by attenuating oxidant stress at reoxygenation. Am J Physiol Heart Circ Physiol 282: H531-H539, 2002; 10.1152/ajpheart.00552.2001.--[K.sup.+] channel openers have been recently recognized for their ability to protect mitochondria from anoxic injury. Yet the mechanism responsible for mitochondrial preservation under oxidative stress is not fully understood. Here, mitochondria were isolated from rat hearts and subjected to 20-min anoxia, followed by reoxygenation. At reoxygenation, increased generation of reactive oxygen species (ROS) was associated with reduced ADP-stimulated oxygen consumption, blunted ATP production, and disrupted mitochondrial structural integrity coupled with cytochrome c release. The prototype [K.sup.+] channel opener diazoxide markedly reduced mitochondrial ROS production at reoxygenation with a half-maximal effect of 29 [micro]M. Diazoxide also preserved oxidative phosphorylation and mitochondrial membrane integrity, as indicated by electron microscopy and reduced cytochrome c release. The protective effect of diazoxide was reproduced by the structurally distinct [K.sup.+] channel opener nicorandil and antagonized by 5-hydroxydecanoic acid, a short-chain fatty acid derivative and presumed blocker of mitochondrial ATP-sensitive [K.sup.+] channels. Opener-mediated mitochondrial protection was simulated by the free radical scavenger system composed of superoxide dismutase and catalase. However, the effect of openers on ROS production was maintained in nominally [K.sup.+]-free medium in the presence or absence of the [K.sup.+] ionophore valinomycin and was mimicked by malonate, a modulator of the mitochondrial redox state. This suggests the existence of a [K.sup.+] conductance-independent pathway for mitochondrial protection targeted by [K.sup.+] channel openers. Thus the cardioprotecive mechanism of [K.sup.+] channel openers includes direct attenuation of mitochondrial oxidant stress at reoxygenation. diazoxide; nicorandil; anoxia; ATP; reactive oxygen species; cardioprotection; energy metabolism; heart

Research has been conducted on the ferric uptake regulator (fur) gene product which acts as an iron-responsive transcriptional repressor protein. The biological function of the fur homolog in dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 and the possible regulatory role of S. oneidensis MR-1 Fur in energy metabolism have been investigated.

The authors reviews the publications on electron transport through DNA. The topics of interest include hole transfer and hole transport through DNA, excess electron transport through DNA and electric conduction through DNA.

The influence of the supplementation of black and white rice outer layer fractions on atherosclerotic plaque formation induced by hypercholesterolemia was investigated in rabbits. Male rabbits (n = 32) were randomly divided into four groups. They were fed nonpurified diet (normal group), a lard (3.5 g/100 g) with high cholesterol (0.5 g/100 g) diet (HC group); the HC diet with 5 g/100 g white rice outer layer fraction (WRF group); or the HC diet with 5 g/100 g black rice outer layer fraction (BRF) for 2 mo. Blood samples were collected for determination of lipid concentration and oxidative and antioxidative status variables, and aortae were taken for the assessment of atherosclerotic plaques. The atherosclerotic plaque area in rabbits fed the BRF diet was 66% lower than that of the HC or WRF rabbits (P < 0.001). Supplementation of the black rice outer layer significantly (P < 0.05) lowered aortic 8-hydroxy-2'-deoxyguanosine (8-OHdG) (-52%, -44%) compared with the WRF or HC diets (P 0.05). There were no differences in aortic 8-OHdG levels between rabbits fed the BRF and normal diets. The BRF diet significantly (P < 0.05) decreased the malondialdehyde (MDA) level of serum (-37%) and aortic artery (-50%) compared with the WRF diet. There were no differences in the concentrations of serum total cholesterol (TC), LDL cholesterol (LDL-C), HDL-C or the ratio of apoprotein (apo)I/apoB among the HC, WRF and BRF groups. Similarly, there were no differences in the serum vitamin E concentration and erythrocyte and aorta superoxide dismutase (SOD) activities among rabbits fed these diets. The serum concentration of most fatty acids except 18:1 did not differ between the WRF and the BRF groups. We conclude that the inhibition of atherosclerotic plaque formation derived from the black rice outer layer fraction in rabbits might be mediated by antioxidative or anti-inflammatory effects. KEY WORDS: * rice * atherosclerosis * oxidative status * lipids * rabbits.

This article discusses the relationship between exercise and glucose and lipid metabolism in the aged. An analysis of glucose production, fat oxidation, and oxygen consumption is presented.

Chen, Ya-Fei, Pin-Lan Li, and Ai-Ping Zou. Oxidative stress enhances the production and actions of adenosine in the kidney. Am J Physiol Regulatory Integrative Comp Physiol281: R1808-R1816, 2001.--The purpose of this study was to determine whether superoxide anions ([O.sub2].) activate 5'-nucleotidase (5'-ND), thereby increasing the production of renal adenosine and regulating renal function. Using HPLC analysis, we found that incubation of renal tissue homogenate with the [O.sup.-.sub.2], donor K[O.sub.2] doubled adenosine production and increased the maximal reaction velocity of 5'-ND from 141 to 192 nmol.[min.sup.-1].mg [protein.sup.-1]. The [O.sup.-.sub.2].-generating system, xanthine/xanthine oxidase increased the maximal reaction velocity of 5'-ND from 122 to 204 nmol .[min.sup.-1].mg [protein.sup.-1]. Superoxide dismutase (SOD) with catalase produced a concentration-dependent reduction of 5'-ND activity in renal tissue homogenate, while the SOD inhibitor diethyl-dithiocarbamic acid significantly increased 5'-ND activity. Inhibition of disulfide bond formation by thioredoxin or thioredoxin reductase significantly decreased xanthine/xanthine oxidase-induced activation of renal 5'-ND. In in vivo experiments, inhibition of SOD by diethyldithiocarbamic acid (0.5 mg.[kg.sup.-1], .[min.sup.-1] iv) enhanced renal vasoconstriction induced by endogenously produced adenosine and increased renal tissue adenosine concentrations under control condition and in ischemia and reperfusion. We conclude that oxidative stress activates 5'-ND and increases adenosine production in the kidney and that this redox regulatory mechanism of adenosine production is important in the control of renal vascular tone and glomerular perfusion. redox signaling; renal hemodynamics; reactive oxygen species; nucleotide Received 5 February 2001; accepted in final form 25 July 2001

Xu, Zhelong, Michael V. Cohen, James M. Downey, Terry L. Vanden Hoek, and Zhenhai Yao. Attenuation of oxidant stress during reoxygenation by AMP 579 in cardiomyocytes. Am J Physiol Heart Circ Physiol 281: H2585-H2589, 2001.--AMP 579, an adenosine [A.sub.1]/[A.sub.2] receptor agonist, has a strong anti-infarct effect when administered just before reperfusion. Because oxidative stress has been proposed to contribute to myocardial reperfusion injury, we tested whether AMP 579 can reduce the production of reactive oxidant species (ROS) during reoxygenation in cultured chick embryonic cardiomyocytes. The intracellular fluorescent probe 2',7'-dichlorofluorescin diacetate (DCFH) was used to detect ROS. The cells were subjected to 60 min of simulated ischemia, followed by either 15 min or 3 h of reoxygenation. AMP 579 (0.5 and 1 [micro]M), when started 10 min before reoxygenation, significantly reduced ROS generation from 4.86 [+ or -] 0.30 (arbitrary units) in untreated cells to 2.72 [+ or -] 0.31 and 1.85 [+ or -] 0.14, respectively (P < 0.05). Cell death that was assessed by propidium iodide uptake was markedly reduced by AMP 579 (49.6 [+ or -] 4.7% of control cells vs. 25.4 [+ or -] 2.4%, P < 0.05). In contrast, adenosine did not alter ROS generation or cell death. Attenuation of ROS production by AMP 579 was completely prevented by simultaneous exposure of cells to the selective adenosine [A.sub.2] antagonist 8-(13-chlorostyryl) caffeine. These results indicate that AMP 579 directly protects cardiomyocytes from reperfusion injury by a mechanism that attenuates intracellular oxidant stress. Furthermore, adenosine could not duplicate these effects. adenosine; cell viability; reperfusion injury; reactive oxygen species Received 16 April 2001; accepted in final form 31 August 2001

Research has been conducted on the 8-oxoguanine, an oxidized guanine form. Results indicate that the Escherichia coli cells contain proteins binding specifically to RNA molecules that carry this oxoguanine and that the mutants defective in the protein are hyperresistant to the drug inducing oxidative stress.

Research reveals that in Staphylococcus aureus, the superoxide dismutase activity is predominantly of SodA type during all phases of growth and SodM type dismutase manifests under oxidative stress conditions during late exponential and stationary phases of growth. The SodM sequence specifies a 187-amino-acid protein with a 75% homology with SodA.

Results reveal that alphaRT, the fragmentation product of thymine, serves as a substrate for Alka protein, which excises opened form of a pyrimidine. This excision by AlkA is similar to the excision carried out by other two DNA glycosylases, Fpg and Nth proteins.

Research shows that fatty acid oxidation is essential for the polymerization of tau-positive neurofibrillary tangles suggesting a link between oxidative stress mechanism and fibrillar pathology in Alzheimer's disease.

Researchers have discovered D(sub 4)/E(sub 4)-neuroprostanes in brain tissue. These D/E-ring isoprostane-like compounds are formed by the oxidation of docosahexaenoic acid, the most abundant unsaturated fatty acid in the brain. This indicates that oxidative stress occurs in the brain, and may cause some neurological diseases.

Exposure of the white-rot fungus Phanerochaete chrysosporium to pure oxygen causes a loss of cellular ultrastructure. This fungus is usually exposed to pure oxygen to induce lignin peroxidase synthesis.

The effect of dichloroacetate (DCA) infusion on the concentrations of muscle tricarboxylic acid cycle intermediates (TCAI) at rest and during dynamic knee extensor exercise in humans has been studied. Six subjects did moderate leg kicking exercises for 15 min. that was immediately followed by intense exercixe until exhaustion after being given saline or DCA infusions. Results indicate that DCA diminished TCAI pool size at rest by increasing the flux through the pyruvate dehydrogenase and diverting pyruvate away from anaplerotic pathways.

The role of dichloroacetate (DCA) in reducing the reliance on substrate level phosphorylation during the transition from rest to moderate-intensity exercise in humans has been studied. Nine subjects cycled at approximately 65% of maximal oxygen uptake after saline of DCA infusion. Muscle biopsies were taken at rest, 30 sec., 2 and 10 min. of exercise. Results indicate that increased provision of substrate by DCA infusion increases oxidative metabolism during the rest-to-work transition. There is a reduction in the utilization of phosphocreatine and better cellular energy state at the start of exercise.

The 20S proteasome has been shown to be largely responsible for the degradation of oxidatively modified proteins in the cytoplasm. Nuclear proteins are also subject to oxidation, and the nucleus of mammalian cells contains proteasome. In human beings, tumor cells frequently are subjected to oxidation as a consequence of antitumor chemotherapy, and K562 human myelogenous leukemia cells have a higher nuclear proteasome activity than do nonmalignant cells. Adaptation to oxidative stress appears to be one element in the development of long-term resistance to many chemotherapeutic drugs and the mechanisms of inducible tumor resistance to oxidation are of obvious importance. After hydrogen peroxide treatment of K562 cells, degradation of the model proteasome peptide substrate suc-LLVY-MCA and degradation of oxidized histones in nuclei increases significantly within minutes. Both increased proteolytic susceptibility of the histone substrates (caused by modification by oxidation) and activation of the proteasome enzyme complex occur independently during oxidative stress. This rapid upregulation of 20S proteasome activity is accompanied by, and depends on, poly-ADP ribosylation of the proteasome, as shown by inhibitor experiments, 14C-ADP ribose incorporation assays, immunoblotting, in vitro reconstitution experiments, and immunoprecipitation of (activated) proteasome with anti-poly-ADP ribose polymerase antibodies. The poly-ADP ribosylation-mediated activated nuclear 20S proteasome is able to remove oxidatively damaged histones more efficiently and therefore is proposed as an oxidant-stimulatable defense or repair system of the nucleus in K562 leukemia cells.

Research has been conducted on creatine administration. Results indicate that oral administration of creatine improves motor performance, extends survival in transgenic mice and protects mice from motor neuron and nigra neuron loss and that creatine administration can become a therapeutics for amyotrophic lateral aclerosis treatment.

The physiological chemistry of nitric oxide (NO) and its metabolites and the regulation of inflammatory processes were described and analyzed. The effects of NO on metal nitrosyl complexes, oxidative stress and oxidation states were also discussed. However, observations revealed NO's stimulation of prostaglandin secretions. Moreover, evidences were found which confirmed the regulatory and anti-inflammatory biological functions of NO.

Two unnatural amino acids, o,o'-dityrosine and o-tyrosine, are stable markers of protein oxidation. Experiments were conducted to determine whether assaying these compounds in urine could give a noninvasive method to determine levels of protein oxidation in vivo. Findings showed that in both sedentary rats and exercise-trained rats, antioxidant therapy decreased levels of protein-bound o,0'-dityrosine in skeletal muscle. On the other hand, antioxidant therapy or exercise training had only a slight effect on o-tyrosine levels in this tissue.

The resistance of Vibrio rumoiensis S-1 to hydrogen peroxide has been studied. The strain was isolated from the drain pool of a fish processing plant which uses H2O2 as the bleaching and microbiocidal agent. The effects of H2O2 on the growth and structure on the growth of V. rumoiensis S-1 cells were compared with those of a spontaneous mutant without the catalase activity and other bacterial strains. Results reveal that the mutant strain did not survive in the presence of five mg of H2O2. This finding suggests that catalase is involved in the resistance and survival of V. rumoiensis S-1 in the presence of H2O2.

Experiments were performed to investigate the roles of hemin and sodium nitroprusside in the expression of heme-oxygenase 1 (HO-1) in skeletal muscle cells. The findings showed that the response to hemin stimulation was comparable to other cell types. Moreover, the protective role of HO-1 against oxidative stress and the modification of heme turnover indicate its significance in various pathophysiological skeletal muscle cell conditions.

Chronic oxidative stress may play a critical role in the pathogenesis of many human cancers. Here, we report that mouse embryonic stem (ES) cells deficient in DNA mismatch repair responded abnormally when exposed to low levels of ionizing radiation, a stress known to generate oxidative DNA damage. ES cells derived from mice carrying either one or two disrupted Msh2 alleles displayed an increased survival following protracted exposures to low-level ionizing radiation as compared with wild-type ES cells. The increases in survival exhibited by ES cells deficient in DNA mismatch repair appeared to have resulted from a failure to efficiently execute cell death (apoptosis) in response to radiation exposure. For each of the ES cell types, prolonged low-level radiation treatment generated oxidative genome damage that manifested as an accumulation of oxidized bases in genomic DNA. However, ES cells from [Msh2.sup.+/-] and [Msh2.sup.-/-] mice accumulated more oxidized bases as a consequence of low-level radiation exposure than ES cells from [Msh2.sup.+/+] mice. The propensity for normal cells with mismatch repair enzyme deficiencies, including cells heterozygous for inactivating mismatch repair enzyme gene mutations, to survive promutagenic genome insults accompanying oxidative stresses may contribute to the increased cancer risk characteristic of the hereditary nonpolyposis colorectal cancer syndrome.

The level of plasma 3-nitrotyrosine in the blood of premature newborns may indicate those at risk for bronchopulmonary dysplasia (BPD). BPD describes premature infants who require supplemental oxygen beyond 36 weeks gestational age. Researchers measured plasma 3-nitrotyrosine levels in 10 premature infants who developed BPD and 16 other infants. Levels were significantly higher in infants who developed BPD, and higher levels were associated with higher concentrations of supplemental oxygen. Plasma 3-nitrotyrosine may indicate the level of oxidative damage in the lungs., Objective. Premature infants are susceptible to bronchopulmonary dysplasia (BPD), a chronic lung disease of infancy that appears to be caused in part by oxidative stress from hyperoxia. To investigate the possible role of nitric oxide-derived oxidants such as peroxynitrite in the etiology of BPD, we measured levels of plasma 3-nitrotyrosine, which is produced by the reaction of peroxynitrite with proteins. Patients and Methods. Ten premature infants who developed BPD, defined as requiring supplemental oxygen beyond 36 weeks&apos; postmenstrual age, were identified retrospectively from a group of subjects enrolled in a clinical trial of antenatal therapy. Serial plasma samples had been collected on these infants during the first month of life as part of the trial. Sixteen comparison premature infants were identified from the same population: 5 had no lung disease, 6 had respiratory distress syndrome that resolved, and 5 had residual lung disease at 28 days of life that resolved by 36 weeks&apos; postmenstrual age. Plasma 3-nitrotyrosine levels were measured using a solid phase immunoradiochemical method. Results. All 3-nitrotyrosine values in infants without BPD were [is less than] 0.25 ng/mg protein, and levels did not change with postnatal age. Plasma 3-nitrotyrosine concentrations were significantly higher in infants with BPD, increasing approximately fourfold during the first month of life. For the 20 infants who had blood samples available at 28 days of life, plasma 3-nitrotyrosine levels correlated with the fraction of inspired oxygen that the infant was receiving (r = 0.7). Conclusion. Plasma 3-nitrotyrosine content is increased during the first month of life in infants who develop BPD. This suggests that peroxynitrite-mediated oxidant stress may contribute to the development of this disease in premature infants and that 3-nitrotyrosine may be useful as an early plasma indicator of infants at risk for developing BPD. Pediatrics 1998;101:870-874; nitrotyrosine, bronchopulmonary dysplasia, premature infant, oxidant stress, peroxynitrite., ABBREVIATIONS. RDS, respiratory distress syndrome; BPD, bronchopulmonary dysplasia; TRH, thyrotropin-releasing hormone; PPHN, persistent pulmonary hypertension of the newborn; [FIO.sub.2], fraction of inspired oxygen. Despite recent advances in antenatal prevention and [...]

The mechanism of arachidonic acid release from vascular smooth muscle during oxidative stress is investigated using hydrogen peroxide. Results reveal that treatment with hydrogen peroxide inhibited the incorporation of arachidonic acid to the lipid component of the cell membrane. This impairment in reesterification is responsible for the accumulation and subsequent release of arachidonic acid during oxidative stress.

Urine tests for 8-epi-prostaglandin F2 alpha (8-epi-PGF2a) appear to be a useful measurement of tissue stress caused by free radical or oxidative injury. Urine levels of 8-epi-PGF2a have been shown to correspond to free radical reactions occurring as an artery is blocked and then unblocked or when smoking or drinking excessive alcohol. These effects appear to be independent of aspirin metabolism. These tests, however, are as yet impractical to use on a widespread basis.

The stimulation of glucose transport, lipogenesis and glycogen synthase activity were analyzed in 3T3-L1 adipocyte cell lines to determine the effects of oxidant stress on adipocyte insulin resistance. Prolonged exposure of 3T3-L1 adipocyte cell lines to glucose oxidase increased the uptake of basal 2-deoxyglucose and enhanced basal lipoxygenase activity. However, basal lipoxygenase activity was significantly reduced by insulin stimulation in a dose-dependent manner.

The role of heat shock and oxidative stress response on the induction of cell apoptosis was analyzed in ECV-304 human endothelial cell lines treated with sodium arsenite. Administration of the sodium arsenite induced cellular apoptosis in ECV-304 cells in a dose-dependent manner. However, administration of proinflammatory mediators such as tumor necrosis factor-alpha and lipopolysaccharide was not sufficient to trigger cellular apoptosis. Furthermore, the induction of apoptosis in ECV-304 cells required a combination of heat shock and oxidative stress responses.

The effects of long-term propionyl-L-carnitine administration on the overall energy turnover and mechanical function of volume-overloaded hearts were analyzed in rats with chronic aortocaval fistula. The contractile function of rats with mechanically-overloaded hearts was improved by the prolonged administration of propionyl-L-carnitine. The prolongation of isometric contractions in the papillary muscles of pressure-overloaded rat hearts were also attenuated by propionyl-L-carnitine.

The effects of cyanide and azides on cell surface reduction were analyzed in cultured bovine pulmonary endothelial cells to determine the mechanisms that mediate the inhibition of methylene blue uptake. Analysis of the extracellular reduction of methylene blue by cyanide and azide indicated the presence of distinct mechanisms that mediate the reduction of thiazines. Furthermore, cyanide- and azide-insensitive reduction on the endothelial cell surface can be separated from the cyanide- and azide-sensitive oxidation within subcellular organelles.

The role of oxyhemoglobin (oxyHb) redox transformation and O2/H2O2 reduction in triggering the mechanisms of oxidative damage were analyzed in rats exposed to blast overpressure (BOP). Analysis of endogenous levels of methemoglobin (metHb) in lung tissue samples from rats exposed to BOP indicated the role of oxyHb in mediating the formation of metHb by catalyzing the one-electron oxidation of ascorbate and glutathione. Furthermore, endogenous antioxidants played a major role in tissue damage by mediating the redox-cycling of Hb.

The role of mechanical deformation inducing oxidative stress was analyzed in porcine aortic endothelial cells (PAEC) exposed to cyclic strain. Analysis of lipid peroxidation levels based on the accumulation of thiobarbituric acid reactive substances (TBARS) in PAEC during cyclic strain indicated the role of mechanical stress in enhancing lipid peroxidation. Furthermore, oxidative stress due to mechanical deformation induced the formation of reactive oxygen and H2O2.

According to the free radical theory of aging, reactive oxygen species cause oxidative damage, proposed to be an underlying factor of the aging process. In the current study, we have used electron paramagnetic resonance spin labeling, measurements of protein carbonyl content, an index of protein oxidation, and determination of the activity of glutamine synthetase (an oxidatively sensitive enzyme) to report that cortical synaptosomal membranes from the senescence accelerated-prone (SAMP8) mouse showed structural characteristics of free radical oxidative stress relative to the senescence accelerated-resistant (SAMR1) mouse. The SAMP8 mouse exhibited a decrease in the relevant EPR parameter consistent with oxidative stress (P < 0.002), a decreased glutamine synthetase activity (P < 0.05), and an increased protein carbonyl content (P < 0.01) compared with these parameters in the SAMR1 mouse. Further, because free radical trapping compounds have been demonstrated to extend maximum life span and improve cognition in SAMP8 mice, we investigated the protective nature of the known free radical scavenger, N-tert-butyl-[Alpha]-phenylnitrone (PBN), on the physical state of cortical synaptosomal membrane proteins. For 14 days, SAMR1 and SAMP8 mice were injected with 30 mg/kg PBN while the controls were injected with the corresponding volume of saline. Characteristic of less oxidized systems, cortical synaptosomal membranes from the PBN-injected SAMP8 mouse exhibited a return toward normal values of the relevant EPR parameter [the [M.sub.I] = +1 low-field weakly immobilized line/[M.sub.I] = +1 low-field strongly immobilized line (W/S) ratio of a protein-specific spin label] (P < 0.001) compared with that from saline-injected SAMP8 mice. In SAMR1 mice, in contrast to SAMP8, there was no significant change in the conformation of membrane proteins or protein carbonyl content of cortical synaptosomal membranes from the PBN-injected and saline-injected SAMR1 mice, showing that PBN itself did not induce conformational changes in cortical synaptosomal membrane proteins. The results are discussed with reference to the use of free radical scavengers as potential anti-aging agents.

Zinc possesses cardiac cytoprotective qualities and inhibits post ischemic OH formation by entering the cell and displacing site-specifically bound Cu(II). Reactive oxygen intermediates such as .OH inhibit sarcolemmal Ca(2+)-ATPase activity leading to disturbances in cellular metabolism and cardiac contraction. Zinc supplementation in cardiac post-ischemic injury antagonizes metal-mediated oxidative stress by acting as an antioxidant and decreases post-ischemic contracture.