CELL PRODUCTION IN TUMOUR ISOGRAFTS MEASURED USING VINCRISTINE AND COLCEMID

Vincristine sulphate has been found to be a more useful metaphase arrest agent than Colcemid. Metaphase accumulation, in isografts of a CBA mammary adenocarcinoma, was linear with time for at least 10 hr after vincristine administration and also independent of drug dose in the range 1–4 mg/kg body weight. A method for evaluating the cell production rate, in histological sections, of a cell population which forms a heterogeneous component of the tissue has been described. The percentage of each tissue component was determined using the Chalkley point count method and the mean number of metaphases in an arbitrary defined field were evaluated. Corrections for percentage composition and sectioning were applied and the cell production rate defined. This was found to be 15.8 ± 0.6 cells per 1000 cells per hour for this tumour.