| oxygen-18 | A stable oxygen isotope making up 0.20% of natural oxygen; used in mass spectrometry and in NMR studies of tissue. Synonym: heavy oxygen. (05 Mar 2000) |
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| oxygen capacity | The maximum quantity of oxygen that will combine chemically with the haemoglobin in a unit volume of blood; normally it amounts to 1.34 ml of O2 per gm of Hb or 20 ml of O2 per 100 ml of blood. (05 Mar 2000) |
| oxygen compounds | Inorganic compounds that contain oxygen as an integral part of the molecule. (12 Dec 1998) |
| oxygen consumption | The rate at which oxygen is used by a tissue; microliters of oxygen stpd used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (12 Dec 1998) |
| oxygen debt | The extra oxygen (compared with its usual oxygen intake at rest) an organismconsumes after a period of strenouousphysical activity. (09 Oct 1997) |
| oxygen deficit | The difference between oxygen uptake of the body during early stages of exercise and during a similar duration in a steady state of exercise; sometimes considered as the formation of the oxygen debt. (05 Mar 2000) |
| oxygen dependent killing | One of the most important bactericidal mechanisms of mammalian phagocytes involves the production of various toxic oxygen species (hydrogen peroxide, superoxide, singlet oxygen, hydroxyl radicals) through the metabolic burst. Although anaerobic killing is possible, the oxygen dependent mechanism is crucial for normal resistance to infection and a defect in this system is usually fatal within the first decade of life (chronic granulomatous disease). See: myeloperoxidase, chemiluminescence. (18 Nov 1997) |
| oxygen deprivation theory of narcosis | That narcotics inhibit oxidation, which causes the cell to be narcotised. (05 Mar 2000) |
| oxygen derived free radicals | An atom or atom group having an unpaired electron on an oxygen atom, typically derived from molecular oxygen. For example, one-electron reduction of O2 produces the superoxide radical, O2-; other examples include the hydroperoxyl radical (HOO-), the hydroxyl radical (HO-), and nitric oxide (NO-). (05 Mar 2000) |
| oxygen effect | Enhancement of radiosensitivity of cells in a high concentration of oxygen. (05 Mar 2000) |
| oxygen electrode | A sensitive method to detect oxygen consumption, involves a PTFE (Teflon) membrane. (18 Nov 1997) |
| oxygen inhalation therapy | Inhalation of oxygen aimed at restoring toward normal any pathophysiologic alterations of gas exchange in the cardiopulmonary system, as by the use of a respirator, nasal catheter, tent, chamber, or mask. (12 Dec 1998) |
| oxygen isotopes | Stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. O-17 and 18 are stable oxygen isotopes. (12 Dec 1998) |
| oxygen poisoning | A body disturbance resulting from breathing high partial pressures of oxygen; characterised by visual and hearing abnormalities, unusual fatigue while breathing, muscular twitching, anxiety, confusion, incoordination, and convulsions; although the mechanism for development of the condition is obscure, a disruption of enzymatic activity is likely, perhaps as a result of free radical formation. Synonym: oxygen poisoning. (05 Mar 2000) |
| oxygen radical | <chemistry> Any oxygen species that carries an unpaired electron (except free oxygen). Examples are the hydroxyl radical and the superoxide anion. These radicals are very powerful oxidizing agents and cause structural damage to proteins and nucleic acids. They mediate the damaging effects of ionising radiation. (18 Nov 1997) |