[Relation between the mitosis-inhibitory activity of a chalone preparation of Ehrlich ascites tumor and its diurnal secretion].

Mitosis inhibitory activity of chalone-containing preparations extracted from cells of Ehrlich's ascites carcinoma (EAC) at varying time of day (9, 13, 17, 21 1, 5 and 9 o'clock) was studied in a temporary suspension culture of EAC. The inhibitory action of the preparations depended on the time of their extraction. This may be indicative of rhythmical alterations of the production or activity of EAC chalone. The maximum activity was demonstrated by the preparations extracted at 5, 9 and 13 o'clock. The activity of the preparations, extracted at 17, 21 and 1 o'clock was considerably less. The degree of mitotic activity inhibition also depends on the dose of duration of action of the chalone-containing preparation.