918 publications from this institution
Abstract The element oxygen (chemical symbol 0) exists in air as a ‘ double’ molecule, two atoms being joined together to give O2 (dioxygen). Oxygen was first isolated and characterized between 1772 and 1774 by the individual skills of three great European scientists— Scheele, Priestley, and Lavoisier. Oxygen appeared in significant amounts in the Earth’s atmosphere some 2.5 × 109 years ago, and geological evidence suggests that this was due to the photosynthetic activity of certain microorganisms, the blue-green algae. As they split water to obtain their essential requirement for hydrogen atoms, blue-greens released tonnes of oxygen into the atmosphere, creating perhaps the worst case of environmental pollution ever recorded on this planet.
Ascorbic acid has a multiplicity of antioxidant properties, but it can exert pro-oxidant effects in vitro, usually by interaction with transition metal ions. It is as yet uncertain that these pro-oxidant effects have any biological relevance: some of the available data are summarized.
No abstract is provided for this article.
Species such as superoxide radical (O2−), hydrogen peroxide (H2O2), hydroxyl radical (·OH), and hypochlorous acid (HOC1) can be formed in vivo, e.g., by activated phagocytic cells. Generation of ·OH from H2O2 in vivo usually involves iron-dependent reactions. Good evidence exists for increased generation of oxidants in vivo in patients with active rheumatoid disease, but the contribution of these oxidants to the disease process is still uncertain. The likelihood that anti-inflammatory drugs used in the treatment of arthritis could act by scavenging oxidants or preventing their formation is discussed.— Halliwell, B.; Hoult, J. R.; Blake, D. R. Oxidants, inflammation, and anti-inflammatory drugs. FASEB J. 2: 2867-2873; 1988.
A free radical is any species capable of independent existence that contains one or more unpaired electrons. Free radicals and other reactive oxygen species are frequently proposed to be involved in the pathology of several neurological disorders. Criteria for establishing such involvement are presented. Development of new methods for measuring oxidative damage should enable elucidation of the precise role of reactive oxygen species in neurological disorders.
No abstract is provided for this article.
Synthetic and natural phenolic compounds are increasingly used in food preservation. Carnosol and carnosic acid (active components of rosemary extract), flavonoids (morin, quercetin, fisetin, myricetin), other plant phenolics (gossypol) and propyl gallate may protect lipids against oxidative damage but have the potential to increase damage to non-lipid constituents of foods, such as carbohydrates and DNA. Thus, in the presence of ferric EDTA and H2O2, they can form highly reactive hydroxyl radicals that can degrade the sugar deoxyribose and/or accelerate DNA degradation by means of a ferricbleomycin complex. Human and bovine serum albumin afford considerable protection against damage to deoxyribose and DNA mediated by the above reactions. It is suggested that, given the fortification of foods with iron and EDTA and the use of phenolic substances as ‘antioxidant’ food additives, the addition of albumin might afford some protection.
Free radicals and other reactive oxygen species (ROS) are constantly formed in the human body, often for useful metabolic purposes.Antioxidant defenses protect against them, but these defenses are not completely adequate, and systems that repair damage by ROS are also necessary.Mild oxidative stress often induces antioxidant defense enzymes, but severe stress can cause oxidative damage to lipids, proteins, and DNA within cells, leading to such events as DNA strand breakage and disruption of calcium ion metabolism.Oxidative stress can result from exposure to toxic agents, and by the process of tissue injury itself.Ozone, oxides of nitrogen, and cigarette smoke can cause oxidative damage; but the molecular targets that they damage may not be the same.-
It is proposed that one of the functions of the mucus layers lining the respiratory tract and gastrointestinal system is the scavenging of highly reactive oxygen-derived species. This would provide anti-oxidant protection to the underlying mucosal epithelial cells.
Abstract The production of O2• ™ and H202 by some types of white blood cell is one example of a useful role for these oxygen-derived species, but it can become a source of tissue damage if their production is too widespread or goes on for too long. Human blood contains large numbers of neutrophils (about 2.5 —7.5 million per ml in healthy subjects), amoeba-like white blood cells whose function is to recognize, engulf, and destroy foreign organisms, such as bacteria and viruses (Figure Al). This process of engulfment is called phagocytosis, and cells which can do it are often called phagocytes. Indeed, infection usually causes a rise in the ‘ white blood cell count’ (number of cells per ml of blood) as the body mobilizes more of these cells to fight the infection.
