Some Characteristics of DNA Synthesis and the Mitotic Cycle in Ehrlich Ascites Tumor Cells

Abstract

In ~vo studies of Ehrlich ascites tumor cells during the first ,5 days of growth in peritoneal cavities of mice consisted of the following:1. Determination of growth curves by direct enumeration of cells. 2. Estimation of the duration of each phase of the mitotic cycle based on incidence of cells in different phases.3. Radioautographic studies to determine the proportion of cells in different phases of the mitotic cycle that incorporate tritiated thymidine during a single brief exposure to this precursor of DNA.4. Estimation of the rate of incorporation of tritiated thymidine at different times during the period of DNA synthesis by comparison of mean grain counts over nuclei in radioautographs at different times following exposure to tritiated thymidine.The assumptions underlying these experiments and our observations concerning the duration of the period of DNA synthesis and its relation to the mitotic cycle are discussed. It is concluded that DNA synthesis is continuous, occupying a period of 8.5 hours during the interphase and that the average rate of synthesis is approximately constant.

Studies of Cellular Proliferation in Human Leukemia. I. Estimation of Growth Rates of Leukemic and Normal Hematopoietic Cells in Two Adults with Acute Leukemia Given Single Injections of Tritiated Thymidine *

“…Different results have been reported in different cell types growing in vivo or in vitro under different experimental conditions. In some studies (57)(58)(59)) the rate of thymidine-3H incorporation during DNA synthesis has been almost constant, whereas in others the cells have shown nonuniformity in rate of labeling (60)(61)(62)(63). Significant differences have been noted in the rate of thymidine-3H incorporation among different pairs or groups of human leukemic chromosomes and also between different segments of individual chromosomes (64).…”

Relationship between γ-ray-induced G2/M Delay and Cellular Radiosensitivity

“…In one study radiosensitive AT homozygote cell strains were reported to show a shorter delay in G2 after irradiation as determined by cumulative mitotic indices (CMI) (Zampetti-Bosseler and Scott 1981) . These slow growing cell populations contained a large fraction of G1 cells, since other parts of the cell cycle are relatively constant in cultured mammalian cells (Edwards et al 1960) . The synchronized radiosensitive mutant mouse cell line L5178Ys/s showed an extremely long mitotic delay after doses of , 1 .…”

Cytogenetical Studies on Root Growth Rate in Alloplasmic Rye

“…Knowing the mitotic cycle duration and the partial mitotic index, one can calculate the interphase and mitosis duration. According to EDWARDS et al (1960) and GONZALEZ-FERNANDEZ et al (1966) a correction on mitotic indices must be carried out as follows: y log2 = log(l + R), \V here…”