Abstract
Three-week-old male rats of the Wistar strain were given tritiated thymidine, 1 microc/gm body weight, intraperitoneally and were killed at intervals from 0.25 to 72 hours later. Autoradiographs were made from 5 micro sections, stained by the Feulgen method. The replication time and its component intervals were determined from the scoring of the labeling of interphase nuclei as well as of prophase, metaphase, anaphase, and telophase nuclei. Absorption of the intraperitoneally injected label is rapid and is attended by "flash" labeling during interphase. The results show that at any one time about 4 per cent of the liver cells are synthesizing DNA preliminary to cell division. These cells alternate with waves of other cells and it is estimated that about 10 per cent of the liver cell population is engaged in cell duplication. The replication time is about 21.5 hours, and its component intervals occupy the following times: DNA synthesis, 9 hours; post-DNA synthesis gap, 0.50 hour; prophase, 1.3 hours; metaphase, 1.0 hour; anaphase, 0.4 hour; telophase, 0.3 hour; postmitosis gap, 9.0 hours. A group of liver cells has been recorded in at least 3 successive replication cycles.
Highlights
The first prophase curve shows that 23 per cent of these cells are labeled within 0.5 hour
The skewing reflects the variations among the many dividing cells
The replication timc and pattern of the liver cell in the growing rat havc been studied by the use of H3TDR labeling of deoxyribonucleic acid (DNA) and autoradiography
Summary
The estimation of the mitotic intervals from the intercepts of the abscissae yields the following results: prophase, 1.8 minus 0.5 (G2) = 1.3 hours; metaphase, 2.8 minus 1.8 = 1.0 hour; anaphase, 3.2 minus 2.8 = 0.4 hour. Telophase is calculated from the population ratios of anaphase and telophase. The respective population percentages were derived from the distribution of 1729 mitoses scored during the first 9 hours of the first cycle. The respective means and their standard errors are as follows: prophase, 41.0 -4-. 3.1; metaphase, 36.7 4-2.6; anaphase, 13.7 -4- 1.6; and telophase, 9.3 -4- 2.1 From these data the time for telophase is estimated as 0.3 hour
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