A simple permanent aceto-orcein stain for free cells, cultures and homogenates

Some characteristics of DNA synthesis and the mitotic cycle in Ehrlich ascites tumor cells

In vivo 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.

CYTOLOGICAL STUDIES OF "BALLOON CELLS" OCCURRING IN THE EHRLICH ASCITES CARCINOMA

Anomalous giant cells, termed "balloon cells", were found in a subline of the Ehrlich ascites carcinoma. The balloon cells remained in the supernatant when ascitic fluid was centrifuged at 17,000 r.p.m.The balloon cells were considerably larger than the regular tumor cells, and in their fully developed form the nucleus occupied a completely lateral position, resembling a signet-ring cell. The cytoplasm contained only a small number of lipid granules surrounding the nucleus; no vacuolization of the cytoplasm could be demonstrated. Mucoid substances in the cytoplasm were not accumulated. Mitochondrial activity was localized mainly around the nucleus. The uptake of tritiated thymidine in the nucleus indicated continued DNA synthesis by the balloons. They underwent mitotic division and contributed to the expanding tumor cell population.