The kinetics of [(3)H]thymidine incorporation into the DNA of carrot suspension cultures were investigated. At a thymidine concentration of 0.1 micromolar, incorporation into DNA is not quantitative but ceases after only 14% of the thymidine has been incorporated. Thymidine incorporation into DNA is resumed following addition of a second aliquot of thymidine, which is consistent with substrate ...

The initial rate of thymidine-(3)H incorporation into the acid-soluble pool by cultured Novikoff rat hepatoma cells was investigated as a function of the thymidine concentration in the medium. Below, but not above 2 microM, thymidine incorporation followed normal Michaelis-Menten kinetics at 22 degrees , 27 degrees , 32 degrees , and 37 degrees C with an apparent K(m) of 0.5 microM, and the V(m...

The levels of ribonucleotide reductase, DNA polymerase, thymidine kinase, and labeled thymidine incorporation into DNA were measured in Ehrlich ascites tumor cells as a function of time after inoculation of the tumor in mice. The levels of ribonucleotide reductase and thymidine kinase activities decreased with tumor growth, while the level of DNA polymerase activity did not decrease. Thymidine ...

A study of the metabolic pathways of H(3)-thymidine utilization in buds of Lilium longiflorum and root tips of Vicia faba was undertaken in order to obtain information that might explain the binding of H(3) from H(3)-thymidine in the cytoplasm of these plants. H(3)-thymidine was administered for various periods of time, the tissues were fixed and processed in the manner routinely used in prepar...