MITOTIC CYCLES IN OXYGEN UPTAKE AND CARBON DIOXIDE OUTPUT IN THE CLEAVING FROG EGG

¹ The Biological Institute of the Carlsberg Foundation, 16 Tagensvej, DK-2200 Copenhagen N, Denmark

Rates of oxygen uptake and of carbon dioxide output of single cleaving frog eggs were measured at short intervals. A Cartesian diver modified for the purpose was used in conjunction with a sensitive manometer. Carbon dioxide outputs were measured as the difference between results obtained with and without absorption of CO₂ in the system.

For both measured parameters reproducible variations were found to accompany the mitotic cycle. Oxygen uptake occurred at minimal rate shortly before the beginning of each new division (cleavage furrow) and at maximal rate halfway between two maxima. Rates of carbon dioxide production varied in an inverse manner and at the same time were more pronounced. Consequently, RQ cycled regularly around a mean (0.6-0.7) and with an amplitude of about 0.1-0.15 units. RQ maxima were at 10-15 min before, minima at 10-20 min after the beginning of furrow formation.