Figure 2.

FM1-43 uptake by Ax2 amoebae grown axenically. (A) Direct method: uptake in the absence (●) or presence of 10 mM azide (○). (B) Indirect methods: uptake at 22°C (▴) or at 0°C (×), followed by formaldehyde fixation; and uptake at 22°C, followed by solubilization in 1% Triton X-100 (▵). The lines represent the data fit to a two-exponent equation (●, ▴, ▵) or to a straight line (○, ×). In A, the uptake of FM1-43 was continued to 180 min; at this time, the level of fluorescence had nearly plateaued and the ratio of total-to-surface fluorescence was ∼2.5. A.U., arbitrary units.