free radicals


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free radicals

Highly chemically active atoms or group of atoms capable of free existence, under special conditions, for very short periods, each having at least one unpaired electron in the outer shell. Oxygen free radicals can be very damaging to DNA and proteins and to the fat in cell membranes where a free radical chain reaction can be set up. They are normally mopped up by ANTIOXIDANTS and associated substances such as vitamins E and C, FLAVONOIDS, selenium, copper, zinc, and manganese. Produced in excess, or insufficiently opposed, free radicals are believed to be implicated in the production of ATHEROSCLEROSIS, cancer, RHEUMATOID ARTHRITIS, radiation sickness and many other conditions. They are thought to be responsible for much of the damage to the heart during the reperfusion that follows a coronary thrombosis. They are said to be promoted by many agents including radiation, atmospheric pollutants and smoking. The body's natural antioxidants include superoxide dismutase and vitamins C and E. See also NANOPARTICLES.

free radicals,

n.pl compounds with an unpaired electron, which makes them extremely reactive.
References in periodicals archive ?
Instead of fighting off the virus, the mice exposed to free radicals cranked up an anti-inflammatory signal, interleukin-10, and immune cells called regulatory T cells.
Normally, we can keep pace with the production of free radicals as long as the system isn't overwhelmed, but under certain circumstances our own antioxidants get overpowered.
Excessive amounts of free radicals have an aging effect on cells they come into contact with.
Now researchers report in the August 2005 Journal of Clinical Investigation that even before the immune system cranks up, NADPH oxidases in pollen itself generate a type of free radical known as reactive oxygen species (ROS), which interfere with cell signaling pathways and cause the immune system to overreact.
As well as protecting us from illness by attacking viruses and bacteria free radicals also cause ageing, illness and eventually death.
Other research points to another process linking free radicals to aging.
Finally, the book does not really provide a perspective on free radicals in the context of other mediators in disease states.
During a stroke, free radicals (molecules with unpaired electrons), are released to the clot by toxins in the body, causing even more damage to occur.
Numerous studies have been conducted over the years to determine that antioxidants combat free radicals and the effects of aging.
Antioxidants are a relatively large group of nutrients that help to disarm free radicals in the body.
Gomberg's discovery attracted immediate worldwide attention, and progress in solution phase free radical chemistry up until 1929 concentrated on the preparation of a variety of other stable free radicals, primarily through the efforts of Heinrich Wieland, Wihelm Schlenk, and Karl Ziegler in Germany, and James Bryant Conant and Carl Marvel in the U.
The free radicals are formed after gamma sterilization and subsequently cause degradation of the UHMWPE through oxidation.