Thymidine , occurrence

Thymidine 5 -(a-D-glucopyranosyl pyrophosphate) (4) and the analogous D-galactose derivative have been isolated from extracts of Pasteurella pseudo tuberculosis.102 The ester of thymidine 5 -pyro-phosphate with a-D-mannopyranose was found in an extract of Strep-tomyces griseus,14,103 and the occurrence of the D-ribosyl ester in the... 

UNSCHEDULED DNA SYNTHESIS (UDS) DNA synthesis that occurs at a stage in the cell cycle other than S incorporation of precursors (e.g., tritiated thymidine) into ENA in the absence of semiconservative replication a manifestation of genetic repair, whose occurrence has been used as an indicator of induced DNA damage. 

Resistant variants owing to thymidine kinase or DNA polymerase mutations can be selected by passage in vitro, but the occurrence of resistance during clinical use is currently low. Thymidine kinase-deficient, acyclovir-resistant herpes viruses are cross-resistant to penciclovir. 

Thymidine, thymine deoxyrtboside the nucleoside of thymine and D-2-deoxyribose. M, 242.33, m. p. 185-186 °C, [a]JJ +32.8 (c = 1.04, IM NaOH). Strictly speaking, it is deoxythymidine, but it is conventionally referred to as thymidine. Its phosphates are designated dTMP, dTDP and dTTP 2 -Hydroxythymidine (not present in RNA, and of only rare occurrence) is known as ribosylthymine. For metabolic importance see Thymidine phosphates. 

Stubblefield considers that the simplest explanation for the occurrence of such [asynchronous] cells was that they resulted from multinucleated cells with asynchronous DNA synthesis. The unlabeled chromosomes came from those nuclei that had finished DNA synthesis prior to the addition of the tritiated thymidine, and the labeled chromosomes came from nuclei that were still replicating DNA after the introduction of the isotopic precursor. He indicates however another possibility, namely that all nuclei may begin DNA synthesis together, but at differing rates, so that the asynchrony may be observed only near the end of the DNA synthesis period. ... 

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