We have investigated the significance of a number of physiological par
ameters in the preparation of cells for experiments on chemokinesis in
Tetrahymena. The study comprises (1) growth state of the cells, (2) c
omposition of the starvation medium, (3) concentration of cells during
starvation, (4) oxygen saturation of the starvation medium, (5) tempe
rature during starvation, and (6) starvation period. By controlling th
e physiological state of the cells, we significantly improved the repr
oducibility of the results obtained in assays for chemokinesis in Tetr
ahymena. In short, cells optimal for chemokinesis at an assay temperat
ure of 28 degrees C should be starved from the exponential growth phas
e in a concentration below 2 X 10(5) cells ml(-1) for 10-20 h. The sur
face-to-volume ratio of the starvation medium-water or Hepes buffer-sh
ould be about 5 cm(-1) (or more) to ensure more than 95% oxygen satura
tion of the starvation medium. Maximal chemosensory responses were obt
ained if the cells were starved at 21 degrees C. The chemokinetic pote
ntial of the cells decreased significantly, as did the levels of the r
atio of ATP to ADP, if cells were starved at higher temperatures. A te
ntative correlation between the ATP level in the cells and the chemose
nsory potential of the cells has been found. We suggest that chemokine
sis is a constant quality of Tetrahymena, because we found no sign tha
t prolonged starvation or other changes applied to the cells produced
an up-regulation of the chemosensory response. Apparently, starvation
is obligatory only to remove the growth medium (which is itself a very
potent attractant), thereby making the cells sensitive to the chemoat
tractants.