Cells of the Morris hepatoma 7777 cultured in vitro have elevated levels of cytoplasmic thymidine kinase similar to those found in vivo. The cell-doubling time is slightly less than 24 hr. The addition of 5-fluorouracil to the culture medium (10 fig/ml) inhibits cell division, stimulates thymidine kinase production, and results in cell death which increases with time. Treated cells release sign...

When (14)C-thymidine labeled only in the ring is administered to Neurospora crassa, the majority of the recovered label is found in the ribonucleic acid (RNA). Three mutants were isolated in which different steps are blocked in the pathway that converts the pyrimidine ring of thymidine to an RNA precursor. Evidence from genetic, nutritional, and accumulation studies with the three mutants shows...

Methods for the synthesis of bromodeoxyuridine-Br s2 and bromodeoxyuridine-H a (BUdR) are described. The incorporation of both thymidine and BUdR into the deoxyribonucleic acid (DNA) of rat bone marrow cells in vitro was markedly influenced by concentrations of thymidine and BUdR, respectively, in the incubation media. At equivalent concentrations of respective substrate, the amount of thymidin...

Mitochondrial (mt) DNA depletion syndromes can arise from genetic deficiencies for enzymes of dNTP metabolism, operating either inside or outside mitochondria. MNGIE is caused by the deficiency of cytosolic thymidine phosphorylase that degrades thymidine and deoxyuridine. The extracellular fluid of the patients contains 10-20 microM deoxynucleosides leading to changes in dTTP that may disturb m...

Adsorption of ultraviolet-inactivated Sendai virus, at high or low multiplicity, to HeLa cells caused a transient increased incorporation of (3)H-thymidine into the cellular deoxyribonucleic acid (DNA). In HeLa cells synchronized by a double-thymidine block, this increased incorporation of thymidine during the S phase lasted from about 30 to 90 min after virus adsorption. The observations that ...

The short term effect of 11.4 mum indoleacetic acid on the incorporation of (methyl-(3)H)thymidine into DNA in vegetative tobacco (Nicotiana tabacum cv. Wis. 38) stem segments has been investigated. In segments that are defoliated, inverted, and kept in the dark for 7 hours, indoleacetic acid very rapidly (about 60 minutes) and strikingly initiates thymidine incorporation into DNA. The time req...

Isolated rat liver mitochondria can incorporate tritiated thymidine into DNA. The addition of deoxyribonucleotides and ATP are necessary. The process of incorporation was found to be inhibited to the extent of 92% by actinomycin D and only 14% by pancreatic deoxyribonuclease. The identification of the labeled product as mitochondrial DNA is supported by its insolubility in acid, resistance to a...

The formation of a soluble H(3)-thymidine derivative pool has been examined in Tetrahymena pyriformis as a function of macronuclear DNA synthesis during the cell life cycle. An autoradiographic technique which allows the detection of water-soluble materials within a cell has shown that these cells do not take up and retain exogenous H(3)-thymidine during G1 or G2. Uptake of H(3)-thymidine is re...

was centrifuged at 20000g for 20min and the supernatant filtered through a column (3.5cmx0.85cm) of Sephadex G-25 (fine grade) to remove all molecules of mol.wt. less than 5000. Cell extracts were incubated at 37°C with [3H]thymidine, ATP and MgClz and the phosphorylated products collected on DE-81 (DEAE-cellulose) filters to be assayed for radioactivity. The assay was shown t o be linear with ...