Source:http://linkedlifedata.com/resource/umls/id/C0034289
MSH: A family of 6-membered heterocyclic compounds occurring in nature in a wide variety of forms. They include several nucleic acid constituents (CYTOSINE; THYMINE; and URACIL) and form the basic structure of the barbiturates.,CSP: 6-membered aromatic ring structure with 2 meta nitrogen heteroatoms.,NCI: One of two classes of heterocyclic nitrogenous bases found in the nucleic acids DNA and RNA: in DNA the pyrimidines are cytosine and thymine, in RNA uracil replaces thymine.