Category: N

A culture made from suspected matter that fails to reveal the suspected organism.  

A water-soluble contrast medium whose molecules do not dissociate into cations and anions in solution. These agents tend to have low osmolarity. They decrease the risk of adverse reactions but are costly.  

A collection of membrane-associated proteins that regulate the passage of large molecules between the cytoplasm and the cell nucleus.  

Ectopic cardiac beat originating in the atrioventricular node.  

Leg pain or numbness that occurs with standing or walking and is relieved by sitting or resting with the spine flexed. It is typically caused by lumbar disk disease.  

Deceleration of the rate of an event such as the heartbeat.  

Radiochemistry; the study of changes that take place within the nucleus of an atom, especially when the nucleus is bombarded by electrons, neutrons, or other subatomic particles.  

An area in the central nervous system or in a ganglion that is responsible for certain functions; examples include the motor areas in the frontal lobes of the cerebrum.  

A lymphocyte that is neither a T cell nor a B cell.  

Any cell found in the bone marrow that cannot reconstitute the marrow or give rise to more differentiated blood cells.