Macrophage

a special type of cell that forms part of the IMMUNE SYSTEM of vertebrates. Macrophages are derived from MONOCYTES in the blood system and can move to infected or inflamed areas of the body using PSEUDOPODIA. In these areas, they surround, engulf and degrade broken cells and other debris, including microbes, by means of the process called PHAGOCYTOSIS.

Taken from Dictionary of Science

Labelled Compound

a compound used in radioactive tracing, where an atom of the compound is replaced by a radioactive ISOTOPE, which can be followed through a biological or physical system by means of the RADIATION it emits.

Taken from Dictionary of Science
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Chemical compound in which a radioactive isotope is substituted for a stable one. The path taken by such a compound through a system can be followed, for example by measuring the radiation emitted.

This powerful and sensitive technique is used in medicine, chemistry, biochemistry, and industry.

Taken from Tiscali