The macronuclear envelope of Tetrahymena pyriformis GL in different physiological states : I. Quantitative structural data

Abstract

The pore diameters and the pore frequencies, i.e. number of pores per square micron, of isolated nuclear envelopes were evaluated in four different physiological states of Tetrahymena pyriformis GL (1. logarithmic phase, 2. stationary phase, 3. heat-synchronized cultures at the end of the heat-synchronization treatment, and 4. heat-synchronized cultures at the division maximum). Evidence is presented that a correlation exists between the pore diameters and the pore frequencies: The smaller the average pore diameter of an envelope piece the higher is its pore frequency. As a consequence of this phenomenon there results a constancy of the ratio of pore area to the nuclear surface for all the four investigated different states. Whereas the pore diameters of the T. pyriformis macronucleus vary within the range reported for other cell material, the pore frequencies reach unusually high values up to 190 pores/μ 2.