The Use of Membrane Electrical Noise in the Study of Characean Electrophysiology

The technique of examining membrane properties through the useof endogenous electrical noise is applied to the study of Characeanelectrophysiology. The frequency band between 0·1 and1·0 Hz is particularly sensitive to the metabolic stateof the cell. It is concluded that measurements of the powerspectral density function and the low frequency excess noisewill prove a useful adjunct to the normal measurements of restingpotential and membrane resistivity.     

A Multi-Unit Sampling System and Its Use in the Characterization of Ultradian and Infradian Growth in Tetrahymena*

SYNOPSIS. A multi-unit automatic sampling device for investigation of microbial growth under a wide variety of conditions is described. The kinetics of asynchronous population growth for batch cultures of Tetrahymena pyriformis (W) at several temperatures show that there are 2 distinct growth phases: an exponential ultradian growth phase that is strongly temperature dependent and a non-stationary growth phase, the infradian phase, that shows little or no temperature dependence over the range from 15–27 C.