Effects of nitroprusside as a nitric oxide donor on anoxia/reoxygenation and D-galactosamine hepatic injuries: a study in perfused hepatocytes

We studied factors affecting survival after the diagnosis of AIDS in a cohort of 1253 patients with hemophilia. The nature of the AIDS-defining condition was found to be as important as age at seroconversion and CD4+ lymphocyte level in predicting survival. A multivariate analysis yielded estimates of median survival for groups defined by age at seroconversion (0 through 15, 16 through 69), CD4+ lymphocyte count (<100 cells/microl versus > or = 100 cells/microl), and 10 AIDS-defining disease groups. Estimates of median survival after a single AIDS-defining condition ranged from 3 to 51 months, depending on the diseases. Median survival after a second AIDS-defining condition was about 1.5- to 2.0-fold shorter than after an initial, isolated AIDS-defining condition. HIV-related neurologic disease (i.e., AIDS dementia complex or multifocal leukoencephalopathy) was a notable exception. It correlated with the shortest estimates of median survival (3 to 9 months), and this poor prognosis was no worse for patients who had a second AIDS-defining condition. The results of this analysis were consistent in most respects with other published analyses of factors affecting survival. These findings may be useful in the clinical care of persons with AIDS and in estimating the number of persons alive who have had a particular AIDS-defining disease.     

Nature and biological significance of free radicals generated during bicarbonate hemodialysis

PURPOSE: The purpose of our study was to determine the significance of the loss of visualization of digitations in the hippocampal head on high-resolution fast spin-echo MR images in the diagnosis of mesial temporal sclerosis (MTS). METHODS: MR examinations of 193 patients with intractable epilepsy were evaluated retrospectively for atrophy and/or T2 signal changes of the hippocampi. On the basis of these two criteria, MTS was diagnosed in 63 hippocampi. Twenty-four patients had surgery, and MTS was confirmed in all cases. A control group included 60 hippocampi in patients with frontal seizures but no MR-detectable abnormalities. In a second step, visibility of digitations in the hippocampal head was evaluated in the two groups of subjects. RESULTS: In the group of 63 hippocampi in which MTS was diagnosed, digitations were not visible in 51 cases, poorly visible in eight, and sharply visible in four. Twenty-two of 24 hippocampi in which MTS was confirmed histologically had no MR-visible digitations. In the control group, digitations were sharply visible in 55 cases and poorly visible in five. Statistical analysis showed a significant difference in the visualization of digitations between hippocampi with MTS and those in the control group. CONCLUSION: With a sensitivity of 92% and a specificity of 100%, the finding of complete loss of digitations in the hippocampal head may be used as a major diagnostic criterion to establish the MR diagnosis of MTS. This morphologic sign may also be useful in the diagnosis of bilateral MTS or to validate the MR diagnosis of MTS when there is no obvious atrophy or changes in signal intensity.     

Cerebral vasospasm and free radicals

The literature implicating free radical reactions in the genesis of cerebral vasospasm following aneurysmal subarachnoid hemorrhage is reviewed. While this condition has features of a prototypical free radical-mediated disease and a plausible theory can be outlined, data to support the theory are limited. An association of lipid peroxidation with vasospasm has been observed, but more sophisticated techniques for detection of free radicals and for detection of free radical damage to arterial wall proteins and nucleic acids have not been used. There are conflicting reports about efficacy of various antioxidant treatments for vasospasm. In these studies, concomitant experiments have usually not confirmed that the treatments have decreased free radicals or lipid peroxides in cerebrospinal fluid. Because smooth muscle contraction is involved in vasospasm, it would be interesting to investigate the actions of free radicals on smooth muscle cells using, for example, isometric tension recordings and patch clamp techniques. Studies of cardiac myocytes indicate that free radicals alter conductances through potassium and calcium channels and through the sodium-calcium exchanger and may result in elevations in intracellular calcium. Few studies have been performed on cerebral smooth muscle cells. In one study, exposure of cerebrovascular smooth muscle cells to free radicals resulted in increased outward currents, decreased membrane resistance, cell contraction, appearance of membrane blebs, and cell death. In summary, more investigations using better experimental techniques are required before free radicals and reactions induced by them can be said with certainty to be the primary cause of vasospasm.     

Pre-eclampsia and oxygenated free radicals

Preeclampsia, clinically defined by arterial hypertension, oedema and proteinuria is a frequently occurred complication of pregnancy. This disease seems to be linked to oxidative stress within placenta. The local accumulation of lipid peroxides, resulting from free radicals production increase altered prostacyclin/thromboxane synthesis. Increased production of lipid peroxides, thromboxane and/or cytokines triggered vascular and organic dysfunctions observed in preeclampsia. Changes in lipoprotein metabolism, namely increase in plasma very low density lipoproteins concentrations (VLDL) and oxidized low density lipoproteins (LDL) concentrations could participate to endothelial dysfunctions observed during preeclampsia.     

Oxidizing agents and free radicals in biomedicine

The reactions which involve oxidants and free radicals species have played an essential role at the beginning of aerobic life, and they are an intrinsic part in the regulation of the cellular processes. However, as a result of the derived toxic effects of these oxidative processes, antioxidants molecules appeared in the very early stages of the evolution and they are able to control the production of these reactants and their dangerous effects. Oxidants and antioxidants have a clear function in the cellular physiology. When this delicate balance change many biochemical and cellular reactions are altered, and that may cause different pathologic diseases. In addition, free radicals of oxygen are thought to play a growing role in the biological process of ageing (1). It is not unusual to find papers about these reactants in every topic of the biomedicine. The main oxidants and free radicals in the organisms are oxygen-related agents, which are globally called reactive oxygen intermediates (ROI). These unavoidable, useful and dangerous biological oxidants are well characterized, although the recent implications they received in some pathologies deserve, in our opinion, a general review.     

Generation of free radicals from hydrogen peroxide and lipid hydroperoxides in the presence of Cr(III)

Free radical generation from H2O2 and lipid hydroperoxides in the presence of Cr(III) was investigated by electron spin resonance (ESR) spin trapping methodology. Incubation of Cr(III) with H2O2 at physiological pH generated hydroxyl (.OH) radical, the yield of which reached saturation level in about 6 min. Deferoxamine reduced the .OH radical yield by only about 20%, diethylenetriamine pentaacetic acid (DTPA) reduced it by about 70%, while cysteine, glutathione, and NADH exhibited no significant effect. The yield of .OH radical formation also depended on the pH being 15 times higher at pH 10 than that at pH 7.2. At pH 3.0, .OH radical generation became nondetectable, and addition of H2O2 to Cr(III) solution did not affect the intensity of the Cr(III) ESR signal while at pH 10, addition of H2O2 reduced the Cr(III) intensity by about 40%, showing that reaction of Cr(III) with H2O2 occurred only at higher pH. Incubation of Cr(III) with the model lipid hydroperoxides, cumene hydroperoxide and t-butyl hydroperoxide, generated lipid hydroperoxide-derived free radicals. Addition of deferoxamine or DTPA had a minor inhibitory effect on that generation. These results show that Cr(III) is capable of producing free radicals from H2O2 and lipid hydroperoxides, which may have significant implications regarding the mechanism of chromium-induced carcinogenesis.     

Generation of hydroxyl radicals by polymorphonuclear neutrophils during exposure to direct current and iron

Human polymorphonuclear neutrophils were exposed to direct output current of 3 or 5 mA at either 300 or 500 V for 1 h in the presence and absence of iron. The current density was 25 or 40 nA/cm2. The formation of free oxygen radicals was measured as breakdown products from deoxyribose and methional. The cells were shown to generate oxygen radicals on electrical stimulation. A physiological concentration of iron enhanced radical formation, but OH. was also formed in the absence of added iron. The most pronounced stimulation was seen at output current 5 mA and 500 V.     

Interaction of free radicals with proteins

This review describe the generation of free radicals in the cells under the influence of exogenously and endogenously acting factors. The interactions of free radicals with proteins and amino acids and the consequences of these effects are also presented.     

Oxygen free radicals and their clinical implications

Reactive oxygen species (ROS) have been implicated in a variety of pathological processes. The generation of highly reactive oxygen metabolites is an integral feature of normal cellular metabolism (mitochondrial respiratory chain, phagocytosis, arachidonic acid metabolism, ovulation and fertilization), however their production can multiply during pathological circumstances. Free oxygen radicals act either on the extracellular matrix or directly upon cellular membranes themselves. The fundamental defense of the organism against ROS include scavenger enzymes (superoxide dismutase, catalase, glutathione peroxidase) and lipid- and water soluble antioxidant compound (ascorbic acid, glutathione, albumin, transferrin, etc.). Their role in ischemia-reperfusion models have now been comprehensively investigated and it has become clear that ROS is to be blamed for the bulk of post-ischemic injuries, hence the basis for newly established antioxidant therapy in such cases. Also more and more studies have concluded a pivotal role of ROS in degenerative and inflammatory conditions, post-radiation processes and aging. Therefore it seems as we are continuously shedding light on the crucial part played by these molecules regarding a wide range of pathologies, we are discovering new therapeutic windows that would clinically assist us in managing such conditions.     

Calcium, free radicals and excitotoxins in neuronal apoptosis

Apoptosis is an active process of cell destruction, characterized by cell shrinkage, chromatin aggregation with extensive genomic fragmentation, and nuclear pyknosis. In contrast, necrosis is characterized by passive cell swelling, intense mitochondrial damage with rapid energy loss, and generalized disruption of internal homeostasis. This swiftly leads to membrane lysis, release of intracellular constituents that evoke a local inflammatory reaction, edema, and injury to the surrounding tissue. In collaboration, our two research laboratories have been defining excitotoxic signals that lead to apoptosis versus necrosis via, among other pathways, Ca2+ signaling mechanisms; this is the subject of this brief review.     

Effects of basic fibroblast growth factor on anoxia/reoxygenation injury of rat neonatal cardiomyocytes

The effects of basic fibroblast growth factor (bFGF) on anoxia/reoxygenation (A/R) injury and protein kinase C (PKC) activity were studied on a model of A/R injury of neonatal rat cardiomyocytes to investigate the possibility of its using as a substrate for pharmacological preconditioning. The data indicated that bFGF improved the viability of cardiomyocytes, lowered the deplection of ATP and leakage of intracellular lactate dehydrogenase (LDH) in a concentration-dependent manner. PKC inhibitor, H7, completely abolished the protective effects. It was also found that bFGF directely activated PKC in cardiomyocytes in a time course similar to that in hypoxic preconditioning. The data suggested that the protective effect of bFGF on cardiomyocyte A/R injury might be mediated by PKC.     

Direct measurement of oxygen free radicals during in utero hypoxia in the fetal guinea pig brain

The present study tested the hypothesis that maternal hypoxia induces oxygen free radical generation in the fetal guinea pig brain utilizing techniques of electron spin resonance spectroscopy and alpha-phenyl-tert-butyl nitrone (PBN) spin trapping. Pregnant guinea pigs of 60 days gestation were divided into normoxic and hypoxic groups and exposed to 21% or 7% oxygen for 60 min. Free radical generation was documented by measuring the signal of PBN spin adducts. Fluorescent compounds were determined as an index of lipid peroxidation and the activity of Na+,K+-ATPase was determined as an index of brain cell membrane function. Hypoxic fetal cerebral cortical tissue showed a significant increase in spin adducts (normoxic: 33.8+/-9.3 units/g tissue vs. hypoxic: 57.9+/-9.2 units/g tissue, p<0.01) and fluorescent compounds (normoxic: 0.639+/-0.054 microg quinine sulfate/g brain vs. 0.810+/-0.102 microg quinine sulfate/g brain, p<0.01) and a decrease in Na+,K+-ATPase activity (normoxic: 43.04+/-2.50 micromol Pi/mg protein/h vs. hypoxic: 33. 80+/-3.51 micromol Pi/mg protein/h, p<0.001). These results demonstrate an increased free radical generation during hypoxia in the fetal guinea pig brain. The spectral characteristics of the radicals were consistent with those of alkoxyl radicals. The increased level of fluorescent compounds and decreased activity of Na+,K+-ATPase indicated hypoxia induced brain cell membrane lipid peroxidation and dysfunction, respectively. These results directly demonstrate an increased oxygen free radical generation during hypoxia and suggest that hypoxia-induced increase in lipid peroxidation and decrease in membrane function, as indicated by a decrease in Na+,K+-ATPase activity, are consequences of increased free radicals. The nature of predominantly present alkoxyl radical indicates ongoing lipid peroxidation during hypoxia. The direct demonstration of oxygen free radical generation during hypoxia is the critical missing link in the mechanism of hypoxia-induced brain cell membrane dysfunction and damage.     

Presence of free radicals in pigment gallstone in vivo

OBJECTIVE: To clarify whether free radical, which may play a role in pigment gallstone formation, is present in pigment gallstones in vivo. MATERIALS AND METHODS: Free radical signal of gallstones from 18 patients was detected by electron paramagnetic resonance spectroscopy at 77K under anaerobic condition and in air (control). As soon as the anaerobic determination was finished, the fresh anaerobic sample was exposed to air and stored in a freezer at -20 degrees C. RESULTS: Free radical signal (g = 2.0038) was detected in fresh anaerobic samples containing more than 2% bilirubin compound, and the signal intensity correlated linearly with the content of calcium bilirubinate (r = +0.95, P < 0.0005). During the storage at -20 degrees C and exposure to air, the signal intensity of each anaerobic sample and its control increased gradually, eventually reaching the same stable level. Fe(III) signal intensity was enhanced synchronously and related linearly with free radical signal (r = +0.99, P < 0.0005). CONCLUSIONS: Free radical exists originally in pigment gallstones in vivo, and it may play an important role in pigment gallstone formation. The free radical signal carried by gallstones may be strengthened by the action of oxygen in air on bilirubin. The transition metal ions probably take part in the formation of bilirubin free radical.     

Mitochondrial free calcium regulation in hypoxia and reoxygenation: relation to cellular injury

The role of mitochondria in myocardial ischemic and hypoxic injury is discussed. Increases in mitochondrial Ca content and ionized Ca2+ concentration are observed during and after ischemic and hypoxic exposure and have traditionally been considered to impair mitochondrial function. New data are discussed in which it is shown that increases in mitochondrial [Ca2+] do not necessarily reflect irreversible myocyte injury. Further, it is shown that irreversible cellular injury may occur in hypoxic myocytes in association with increases in mitochondrial [Ca2+] that would ordinarily be considered to fall within a physiologic range. The significance of these observations is considered in context with observations relating to the assessment of post-hypoxic mitochondrial function.