Methylxanthines inhibit nucleologenesis in binucleate cells

Abstract

Roots of Zea mays L. were treated for 2 hr with 0.1% solutions of caffeine, isobutylmethylxanthine (IBMX) or 8-ethoxycaffeine (8-EOC) or with 0.01% colchicine. These treatments produced two types of marked cells in which to study nucleologenesis in early interphase, i.e. binucleate cells and mononucleate tetraploid cells. Nucleoli were stained with Fast Green or azure B. The mean sum of nucleolar volumes was similar, at 2 hr, in binucleate and mononucleate tetraploid cells but after a 6 hr recovery period the mean nucleolar volumes had increased much more in tetraploid cells than in binucleate cells. It is suggested that methylxanthines inhibit nucleologenesis: this parallels the inhibition of both cell and nuclear growth by these drugs. Roots of Pisum sativum L. were treated with 0.1% caffeine to induce binucleate cells and incorporation of 3H-uridine in 1 hr was determined. Treatment with 0.01% colchicine for 2 hr before exposure to 3H-uridine resulted in a 21% increase in mean grain count per binucleate cell: colchicine stimulates RNA synthesis in binucleate cells.